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Birol A, Aras D, Akalan C, Aldhahi MI, Gülü M. Three sessions of repeated sprint training in normobaric hypoxia improves sprinting performance. Heliyon 2024; 10:e27607. [PMID: 38496896 PMCID: PMC10944258 DOI: 10.1016/j.heliyon.2024.e27607] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2023] [Revised: 03/01/2024] [Accepted: 03/04/2024] [Indexed: 03/19/2024] Open
Abstract
The objective of the present study was to evaluate the impacts of three-session repeated sprint training conducted in normobaric hypoxia with 48-h intervals on sprint performance, arterial oxygen saturation (SpO2), and rating of perceived exertion (RPE) scores. A total of 27 moderately trained male university students voluntarily took part in this study. In this single-blind placebo-controlled study, subjects were assigned into normobaric hypoxia (FiO2: 13.6%; HYP), normobaric normoxia (FiO2: 20.9%; PLA), and control group (CON). The HYP and PLA groups underwent three repeated sprint training sessions (a total of four sets of five times 5-s sprints with a 5-min rest between sets and a 30-s rest between each sprint) on a cycle ergometer in normobaric hypoxia or normoxia conditions. Pre- and post-tests were performed 72 h before and after the training period. Three participants were excluded from the study, and the data from twenty-four participants were analyzed. Contrary to what was observed in the pre and post tests, no time and condition interactions were observed in the relative peak power output (PPO), mean power output (MPO), percentage of sprint decrement score (Sdec%), and RPE parameters. Time effect was found in all observed variables respectively; relative PPO (F = 5.784, p = 0.045, η2 = 0.74), relative MPO (F = 3.927, p = 0.042, η2 = 0.66) and large time effect found for Sdec% (F = 11.430, p = 0.046, 0.83), and RPE (F = 14.990, p = 0.008, η2 = 0.96). A notable increase in relative peak power output (PPO) and mean power output (MPO) was observed in the post-test in comparison to the pre-test values, indicating statistical significance. The increase in PPO was in HYP 13.44% (p = 0.006), in PLA 7.48% (p = 0.264) and in CON 2.66% (p = 0.088). The decrease in Sdec% was in HYP -13.34%% (p = 0.048), PLA -10.54 (p = 0.577) and CON -4.83 (p = 0.644) at post-test. The results show that although there were no statistical differences between the groups, notable differences in performance-related variables were observed in the HYP group after 3 sessions of repetitive sprint training in hypoxia.
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Affiliation(s)
- Abdulkadir Birol
- Graduate School of Health Sciences, Ankara University, Ankara, Türkiye
- Department of Coaching Education, Faculty of Sport Sciences, Trabzon University, Trabzon, Türkiye
| | - Dicle Aras
- Department of Coaching Education, Faculty of Sport Sciences, Ankara University, Ankara, Türkiye
- Performance Analysis in Sports Application and Research Center, Ankara University, Türkiye
| | - Cengiz Akalan
- Department of Coaching Education, Faculty of Sport Sciences, Ankara University, Ankara, Türkiye
| | - Monira I. Aldhahi
- Department of Rehabilitation Sciences, College of Health and Rehabilitation Sciences, Princess Nourah Bint Abdulrahman University (PNU), Riyadh, Saudi Arabia
| | - Mehmet Gülü
- Department of Sports Management, Faculty of Sport Sciences, Kırıkkale University, Kırıkkale, Türkiye
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2
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Simpson LL, Stembridge M, Siebenmann C, Moore JP, Lawley JS. Mechanisms underpinning sympathoexcitation in hypoxia. J Physiol 2024. [PMID: 38533641 DOI: 10.1113/jp284579] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2023] [Accepted: 02/28/2024] [Indexed: 03/28/2024] Open
Abstract
Sympathoexcitation is a hallmark of hypoxic exposure, occurring acutely, as well as persisting in acclimatised lowland populations and with generational exposure in highland native populations of the Andean and Tibetan plateaus. The mechanisms mediating altitude sympathoexcitation are multifactorial, involving alterations in both peripheral autonomic reflexes and central neural pathways, and are dependent on the duration of exposure. Initially, hypoxia-induced sympathoexcitation appears to be an adaptive response, primarily mediated by regulatory reflex mechanisms concerned with preserving systemic and cerebral tissue O2 delivery and maintaining arterial blood pressure. However, as exposure continues, sympathoexcitation is further augmented above that observed with acute exposure, despite acclimatisation processes that restore arterial oxygen content (C a O 2 ${C_{{\mathrm{a}}{{\mathrm{O}}_{\mathrm{2}}}}}$ ). Under these conditions, sympathoexcitation may become maladaptive, giving rise to reduced vascular reactivity and mildly elevated blood pressure. Importantly, current evidence indicates the peripheral chemoreflex does not play a significant role in the augmentation of sympathoexcitation during altitude acclimatisation, although methodological limitations may underestimate its true contribution. Instead, processes that provide no obvious survival benefit in hypoxia appear to contribute, including elevated pulmonary arterial pressure. Nocturnal periodic breathing is also a potential mechanism contributing to altitude sympathoexcitation, although experimental studies are required. Despite recent advancements within the field, several areas remain unexplored, including the mechanisms responsible for the apparent normalisation of muscle sympathetic nerve activity during intermediate hypoxic exposures, the mechanisms accounting for persistent sympathoexcitation following descent from altitude and consideration of whether there are sex-based differences in sympathetic regulation at altitude.
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Affiliation(s)
- Lydia L Simpson
- Department of Sport Science, Performance Physiology and Prevention, Universität Innsbruck, Innsbruck, Austria
| | - Mike Stembridge
- Cardiff School of Sport and Health Sciences, Cardiff Metropolitan University, Cardiff, UK
| | | | - Jonathan P Moore
- School of Psychology and Sport Science, Institute of Applied Human Physiology, Bangor University, Bangor, UK
| | - Justin S Lawley
- Department of Sport Science, Performance Physiology and Prevention, Universität Innsbruck, Innsbruck, Austria
- Institute of Mountain Emergency Medicine, EURAC Research, Bolzano, Italy
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3
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Liu B, Yuan M, Yang M, Zhu H, Zhang W. The Effect of High-Altitude Hypoxia on Neuropsychiatric Functions. High Alt Med Biol 2024; 25:26-41. [PMID: 37815821 DOI: 10.1089/ham.2022.0136] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/11/2023] Open
Abstract
Liu, Bo, Minlan Yuan, Mei Yang, Hongru Zhu, and Wei Zhang. The effect of high-altitude hypoxia on neuropsychiatric functions. High Alt Med Biol. 25:26-41, 2024. Background: In recent years, there has been a growing popularity in engaging in activities at high altitudes, such as hiking and work. However, these high-altitude environments pose risks of hypoxia, which can lead to various acute or chronic cerebral diseases. These conditions include common neurological diseases such as acute mountain sickness (AMS), high-altitude cerebral edema, and altitude-related cerebrovascular diseases, as well as psychiatric disorders such as anxiety, depression, and psychosis. However, reviews of altitude-related neuropsychiatric conditions and their potential mechanisms are rare. Methods: We conducted searches on PubMed and Google Scholar, exploring existing literature encompassing preclinical and clinical studies. Our aim was to summarize the prevalent neuropsychiatric diseases induced by altitude hypoxia, the potential pathophysiological mechanisms, as well as the available pharmacological and nonpharmacological strategies for prevention and intervention. Results: The development of altitude-related cerebral diseases may arise from various pathogenic processes, including neurovascular alterations associated with hypoxia, cytotoxic responses, activation of reactive oxygen species, and dysregulation of the expression of hypoxia inducible factor-1 and nuclear factor erythroid 2-related factor 2. Furthermore, the interplay between hypoxia-induced neurological and psychiatric changes is believed to play a role in the progression of brain damage. Conclusions: While there is some evidence pointing to pathophysiological changes in hypoxia-induced brain damage, the precise mechanisms responsible for neuropsychiatric alterations remain elusive. Currently, the range of prevention and intervention strategies available is primarily focused on addressing AMS, with a preference for prevention rather than treatment.
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Affiliation(s)
- Bo Liu
- Mental Health Center and Psychiatric Laboratory, West China Hospital of Sichuan University, Chengdu, China
- Zigong Mental Health Center, Zigong, China
| | - Minlan Yuan
- Mental Health Center and Psychiatric Laboratory, West China Hospital of Sichuan University, Chengdu, China
| | - Mei Yang
- State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, West China School of Basic Medical Sciences and Forensic Medicine, Chengdu, Sichuan
| | - Hongru Zhu
- Mental Health Center and Psychiatric Laboratory, West China Hospital of Sichuan University, Chengdu, China
| | - Wei Zhang
- Mental Health Center and Psychiatric Laboratory, West China Hospital of Sichuan University, Chengdu, China
- West China Biomedical Big Data Center, West China Hospital, Sichuan University, Chengdu, China
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4
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Lees RM, Bianco IH, Campbell RAA, Orlova N, Peterka DS, Pichler B, Smith SL, Yatsenko D, Yu CH, Packer AM. Standardised Measurements for Monitoring and Comparing Multiphoton Microscope Systems. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.01.23.576417. [PMID: 38328224 PMCID: PMC10849699 DOI: 10.1101/2024.01.23.576417] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/09/2024]
Abstract
The goal of this protocol is to enable better characterisation of multiphoton microscopy hardware across a large user base. The scope of this protocol is purposefully limited to focus on hardware, touching on software and data analysis routines only where relevant. The intended audiences are scientists using and building multiphoton microscopes in their laboratories. The goal is that any scientist, not only those with optical expertise, can test whether their multiphoton microscope is performing well and producing consistent data over the lifetime of their system.
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Affiliation(s)
- Robert M Lees
- Science and Technology Facilities Council, Octopus imaging facility, Research Complex at Harwell, Harwell Campus, Oxfordshire, UK
| | - Isaac H Bianco
- Department of Neuroscience, Physiology & Pharmacology, University College London, UK
| | | | | | - Darcy S Peterka
- Mortimer B. Zuckerman Mind Brain Behavior Institute, Columbia University, New York, NY 10027, USA
| | - Bruno Pichler
- Independent NeuroScience Services INSS Ltd, Lewes, East Sussex, UK
| | - Spencer LaVere Smith
- Department of Electrical and Computer Engineering, University of California Santa Barbara, USA
| | | | - Che-Hang Yu
- Department of Electrical and Computer Engineering, University of California Santa Barbara, USA
| | - Adam M Packer
- Department of Physiology, Anatomy, and Genetics, University of Oxford, Oxford, UK
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5
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Siebenmann C, Roche J, Schlittler M, Simpson LL, Stembridge M. Regulation of haemoglobin concentration at high altitude. J Physiol 2023. [PMID: 38051656 DOI: 10.1113/jp284578] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2023] [Accepted: 11/21/2023] [Indexed: 12/07/2023] Open
Abstract
Lowlanders sojourning for more than 1 day at high altitude (HA) experience a reduction in plasma volume (PV) that increases haemoglobin concentration and thus restores arterial oxygen content. If the sojourn extends over weeks, an expansion of total red cell volume (RCV) occurs and contributes to the haemoconcentration. While the reduction in PV was classically attributed to an increased diuretic fluid loss, recent studies support fluid redistribution, rather than loss, as the underlying mechanism. The fluid redistribution is presumably driven by a disappearance of proteins from the circulation and the resulting reduction in oncotic pressure exerted by the plasma, although the fate of the disappearing proteins remains unclear. The RCV expansion is the result of an accelerated erythropoietic activity secondary to enhanced renal erythropoietin release, but a contribution of other mechanisms cannot be excluded. After return from HA, intravascular volumes return to normal values and the normalisation of RCV might involve selective destruction of newly formed erythrocytes, although this explanation has been strongly challenged by recent studies. In contrast to acclimatised lowlanders, native highlanders originating from the Tibetan and the Ethiopian plateaus present with a normal or only mildly elevated haemoglobin concentration. Genetic adaptations blunting the erythropoietic response to HA exposure have been proposed as an explanation for the absence of more pronounced haemoconcentration in these populations, but new evidence also supports a contribution of a larger than expected PV. The functional significance of the relatively low haemoglobin concentration in Tibetan and Ethiopian highlanders is incompletely understood and warrants further investigation.
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Affiliation(s)
| | - Johanna Roche
- Institute of Mountain Emergency Medicine, EURAC Research, Bolzano, Italy
| | - Maja Schlittler
- AO Research Institute Davos, Regenerative Orthopaedics Program, Davos, Switzerland
| | - Lydia L Simpson
- Department of Sport Science, Division of Performance Physiology and Prevention, Universität Innsbruck, Innsbruck, Austria
| | - Mike Stembridge
- Cardiff School of Sport and Health Sciences, Cardiff Metropolitan University, Cardiff, UK
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Hu M, Kim I, Morán I, Peng W, Sun O, Bonnefond A, Khamis A, Bonas-Guarch S, Froguel P, Rutter GA. Multiple genetic variants at the SLC30A8 locus affect local super-enhancer activity and influence pancreatic β-cell survival and function. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.07.13.548906. [PMID: 37502937 PMCID: PMC10369998 DOI: 10.1101/2023.07.13.548906] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/29/2023]
Abstract
Variants at the SLC30A8 locus are associated with type 2 diabetes (T2D) risk. The lead variant, rs13266634, encodes an amino acid change, Arg325Trp (R325W), at the C-terminus of the secretory granule-enriched zinc transporter, ZnT8. Although this protein-coding variant was previously thought to be the sole driver of T2D risk at this locus, recent studies have provided evidence for lowered expression of SLC30A8 mRNA in protective allele carriers. In the present study, combined allele-specific expression (cASE) analysis in human islets revealed multiple variants that influence SLC30A8 expression. Epigenomic mapping identified an islet-selective enhancer cluster at the SLC30A8 locus, hosting multiple T2D risk and cASE associations, which is spatially associated with the SLC30A8 promoter and additional neighbouring genes. Deletions of variant-bearing enhancer regions using CRISPR-Cas9 in human-derived EndoC-βH3 cells lowered the expression of SLC30A8 and several neighbouring genes, and improved insulin secretion. Whilst down-regulation of SLC30A8 had no effect on beta cell survival, loss of UTP23, RAD21 or MED30 markedly reduced cell viability. Although eQTL or cASE analyses in human islets did not support the association between these additional genes and diabetes risk, the transcriptional regulator JQ1 lowered the expression of multiple genes at the SLC30A8 locus and enhanced stimulated insulin secretion.
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Affiliation(s)
- Ming Hu
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology and Metabolism, Department of Metabolism, Digestion and Reproduction, Faculty of Medicine, Imperial College London, Du Cane Road, London W12 0NN, UK
| | - Innah Kim
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology and Metabolism, Department of Metabolism, Digestion and Reproduction, Faculty of Medicine, Imperial College London, Du Cane Road, London W12 0NN, UK
| | - Ignasi Morán
- Life Sciences Department, Barcelona Supercomputing Center (BSC-CNS), 08034 Barcelona, Spain
| | - Weicong Peng
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology and Metabolism, Department of Metabolism, Digestion and Reproduction, Faculty of Medicine, Imperial College London, Du Cane Road, London W12 0NN, UK
| | - Orien Sun
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology and Metabolism, Department of Metabolism, Digestion and Reproduction, Faculty of Medicine, Imperial College London, Du Cane Road, London W12 0NN, UK
| | - Amélie Bonnefond
- Department of Metabolism, Digestion, and Reproduction, Imperial College London, Hammersmith Hospital Campus, Du Cane Road, London W12 0NN, UK
- Inserm U1283, CNRS UMR 8199, EGID, Institut Pasteur de Lille, F-59000, France
- University of Lille, Lille University Hospital, Lille, F-59000, France.France
| | - Amna Khamis
- Department of Metabolism, Digestion, and Reproduction, Imperial College London, Hammersmith Hospital Campus, Du Cane Road, London W12 0NN, UK
- Inserm U1283, CNRS UMR 8199, EGID, Institut Pasteur de Lille, F-59000, France
- University of Lille, Lille University Hospital, Lille, F-59000, France.France
| | - Silvia Bonas-Guarch
- Department of Metabolism, Digestion, and Reproduction, Imperial College London, Hammersmith Hospital Campus, Du Cane Road, London W12 0NN, UK
- Center for Genomic Regulation (CRG), C/ Dr. Aiguader, 88, PRBB Building, 08003 Barcelona, Spain
- Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Spain
| | - Philippe Froguel
- Department of Metabolism, Digestion, and Reproduction, Imperial College London, Hammersmith Hospital Campus, Du Cane Road, London W12 0NN, UK
- Inserm U1283, CNRS UMR 8199, EGID, Institut Pasteur de Lille, F-59000, France
- University of Lille, Lille University Hospital, Lille, F-59000, France.France
| | - Guy A. Rutter
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology and Metabolism, Department of Metabolism, Digestion and Reproduction, Faculty of Medicine, Imperial College London, Du Cane Road, London W12 0NN, UK
- Centre de Recherche du CHUM, Faculté de Médicine, Université de Montréal, Montréal, QC, Canada
- Lee Kong Chian Imperial Medical School, Nanyang Technological University, Singapore
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Bourdillon N, Subudhi AW, Fan JL, Evero O, Elliott JE, Lovering AT, Roach RC, Kayser B. AltitudeOmics: effects of 16 days acclimatization to hypobaric hypoxia on muscle oxygen extraction during incremental exercise. J Appl Physiol (1985) 2023; 135:823-832. [PMID: 37589059 PMCID: PMC10642515 DOI: 10.1152/japplphysiol.00100.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2023] [Revised: 07/11/2023] [Accepted: 08/03/2023] [Indexed: 08/18/2023] Open
Abstract
Acute altitude exposure lowers arterial oxygen content ([Formula: see text]) and cardiac output ([Formula: see text]) at peak exercise, whereas O2 extraction from blood to working muscles remains similar. Acclimatization normalizes [Formula: see text] but not peak [Formula: see text] nor peak oxygen consumption (V̇o2peak). To what extent acclimatization impacts muscle O2 extraction remains unresolved. Twenty-one sea-level residents performed an incremental cycling exercise to exhaustion near sea level (SL), in acute (ALT1) and chronic (ALT16) hypoxia (5,260 m). Arterial blood gases, gas exchange at the mouth and oxy- (O2Hb) and deoxyhemoglobin (HHb) of the vastus lateralis were recorded to assess arterial O2 content ([Formula: see text]), [Formula: see text], and V̇o2. The HHb-V̇o2 slope was taken as a surrogate for muscle O2 extraction. During moderate-intensity exercise, HHb-V̇o2 slope increased to a comparable extent at ALT1 (2.13 ± 0.94) and ALT16 (2.03 ± 0.88) compared with SL (1.27 ± 0.12), indicating increased O2 extraction. However, the HHb/[Formula: see text] ratio increased from SL to ALT1 and then tended to go back to SL values at ALT16. During high-intensity exercise, HHb-V̇o2 slope reached a break point beyond which it decreased at SL and ALT1, but not at ALT16. Increased muscle O2 extraction during submaximal exercise was associated with decreased [Formula: see text] in acute hypoxia. The significantly greater muscle O2 extraction during maximal exercise in chronic hypoxia is suggestive of an O2 reserve.NEW & NOTEWORTHY During incremental exercise muscle deoxyhemoglobin (HHb) and oxygen consumption (V̇o2) both increase linearly, and the slope of their relationship is an indirect index of local muscle O2 extraction. The latter was assessed at sea level, in acute and during chronic exposure to 5,260 m. The demonstrated presence of a muscle O2 extraction reserve during chronic exposure is coherent with previous studies indicating both limited muscle oxidative capacity and decrease in motor drive.
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Affiliation(s)
- Nicolas Bourdillon
- Institute of Sports Sciences, University of Lausanne, Lausanne, Switzerland
| | - Andrew W Subudhi
- Hybl Sports Medicine and Performance Center, Department of Human Physiology and Nutrition, University of Colorado, Colorado Springs, Colorado, United States
| | - Jui-Lin Fan
- Department of Physiology, Faculty of Medical & Health Sciences, Manaaki Manawa-The Centre for Heart Research, University of Auckland, Auckland, New Zealand
| | - Oghenero Evero
- Altitude Research Center, Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, Colorado, United States
| | - Jonathan E Elliott
- Department of Human Physiology, University of Oregon, Eugene, Oregon, United States
| | - Andrew T Lovering
- Department of Human Physiology, University of Oregon, Eugene, Oregon, United States
| | - Robert C Roach
- Altitude Research Center, Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, Colorado, United States
| | - Bengt Kayser
- Institute of Sports Sciences, University of Lausanne, Lausanne, Switzerland
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8
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Paul S, Jain S, Gangwar A, Mohanty S, Khan N, Ahmad Y. Quantifying systemic molecular networks affected during high altitude de-acclimatization. Sci Rep 2023; 13:14768. [PMID: 37679378 PMCID: PMC10484924 DOI: 10.1038/s41598-023-40576-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2022] [Accepted: 08/13/2023] [Indexed: 09/09/2023] Open
Abstract
High altitude acclimatization and disease have been the centerpiece of investigations concerning human health at high altitude. Almost all investigations have focused on either understanding and ameliorating high altitude disease or finding better methods of acclimatization/training at high altitude. The aspect of altitude de-induction/de-acclimatization has remained clouded despite the fact that it was documented since the first decade of twentieth century. A few recent studies, particularly in China, have stated unanimously that high altitude de-acclimatization involved multiple observable clinical symptoms ranging from headache to abdominal distention. These symptoms have been collectively referred to as "high altitude de-acclimatization syndrome" (HADAS). However, computational omics and network biology centric investigations concerning HADAS are nascent. In this study, we focus on the quantitative proteo-informatics, especially network biology, of human plasma proteome in individuals who successfully descended from high altitude areas after a stay of 120 days. In brief, the protein list was uploaded into STRING and IPA to compute z-score based cut-offs which were used to analyze the directionality and significance of various identified protein networks as well as the proteins within them. Relevant upstream regulators extracted using computational strategies were also validated. Time-points till the 180th day of de-induction have been investigated to comparatively assess the changes in the plasma proteome and protein pathways of such individuals since the 7th day of arrival at altitude. Our investigation revealed extensive effects of de-induction on lipid metabolism, inflammation and innate immune system as well as coagulation system. This novel study provides a conceptual framework for formulating therapeutic strategies to ease the symptoms of HADAS during de-acclimatization. Such strategies should focus on normalization of lipid metabolism, inflammatory signaling and coagulation systems.
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Affiliation(s)
- Subhojit Paul
- Peptide & Proteomics Division, Defence Institute of Physiology & Allied Sciences (DIPAS), Defence R&D Organization (DRDO), Timarpur, New Delhi, 110054, India
| | - Shikha Jain
- Peptide & Proteomics Division, Defence Institute of Physiology & Allied Sciences (DIPAS), Defence R&D Organization (DRDO), Timarpur, New Delhi, 110054, India
| | - Anamika Gangwar
- Peptide & Proteomics Division, Defence Institute of Physiology & Allied Sciences (DIPAS), Defence R&D Organization (DRDO), Timarpur, New Delhi, 110054, India
| | - Swaraj Mohanty
- Peptide & Proteomics Division, Defence Institute of Physiology & Allied Sciences (DIPAS), Defence R&D Organization (DRDO), Timarpur, New Delhi, 110054, India
| | - Nilofar Khan
- Peptide & Proteomics Division, Defence Institute of Physiology & Allied Sciences (DIPAS), Defence R&D Organization (DRDO), Timarpur, New Delhi, 110054, India
| | - Yasmin Ahmad
- Peptide & Proteomics Division, Defence Institute of Physiology & Allied Sciences (DIPAS), Defence R&D Organization (DRDO), Timarpur, New Delhi, 110054, India.
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9
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Patrician A, Willie C, Hoiland RL, Gasho C, Subedi P, Anholm JD, Tymko MM, Ainslie PN. Manipulation of iron status on cerebral blood flow at high altitude in lowlanders and adapted highlanders. J Cereb Blood Flow Metab 2023; 43:1166-1179. [PMID: 36883428 PMCID: PMC10291452 DOI: 10.1177/0271678x231152734] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/31/2022] [Revised: 01/27/2023] [Accepted: 12/05/2022] [Indexed: 03/09/2023]
Abstract
Cerebral blood flow (CBF) increases during hypoxia to counteract the reduction in arterial oxygen content. The onset of tissue hypoxemia coincides with the stabilization of hypoxia-inducible factor (HIF) and transcription of downstream HIF-mediated processes. It has yet to be determined, whether HIF down- or upregulation can modulate hypoxic vasodilation of the cerebral vasculature. Therefore, we examined whether: 1) CBF would increase with iron depletion (via chelation) and decrease with repletion (via iron infusion) at high-altitude, and 2) explore whether genotypic advantages of highlanders extend to HIF-mediated regulation of CBF. In a double-blinded and block-randomized design, CBF was assessed in 82 healthy participants (38 lowlanders, 20 Sherpas and 24 Andeans), before and after the infusion of either: iron(III)-hydroxide sucrose, desferrioxamine or saline. Across both lowlanders and highlanders, baseline iron levels contributed to the variability in cerebral hypoxic reactivity at high altitude (R2 = 0.174, P < 0.001). At 5,050 m, CBF in lowlanders and Sherpa were unaltered by desferrioxamine or iron. At 4,300 m, iron infusion led to 4 ± 10% reduction in CBF (main effect of time p = 0.043) in lowlanders and Andeans. Iron status may provide a novel, albeit subtle, influence on CBF that is potentially dependent on the severity and length-of-stay at high altitude.
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Affiliation(s)
- Alexander Patrician
- Centre for Heart, Lung, & Vascular Health, School of Health and Exercise Sciences, University of British Columbia – Okanagan, Kelowna, BC, Canada
| | - Christopher Willie
- Centre for Heart, Lung, & Vascular Health, School of Health and Exercise Sciences, University of British Columbia – Okanagan, Kelowna, BC, Canada
| | - Ryan L Hoiland
- Centre for Heart, Lung, & Vascular Health, School of Health and Exercise Sciences, University of British Columbia – Okanagan, Kelowna, BC, Canada
- Department of Anesthesiology, Pharmacology and Therapeutics, Faculty of Medicine, Vancouver General Hospital, University of British Columbia, Vancouver, BC, Canada
- Department of Cellular and Physiological Sciences, Faculty of Medicine, University of British Columbia, Vancouver, BC, Canada
- International Collaboration on Repair Discoveries (ICORD), University of British Columbia, Vancouver, British Columbia, Canada
| | - Christopher Gasho
- Pulmonary/Critical Care Section, VA Loma Linda Healthcare System and Department of Medicine, Loma Linda University, Loma Linda, CA, USA
| | - Prajan Subedi
- Pulmonary/Critical Care Section, VA Loma Linda Healthcare System and Department of Medicine, Loma Linda University, Loma Linda, CA, USA
| | - James D Anholm
- Pulmonary/Critical Care Section, VA Loma Linda Healthcare System and Department of Medicine, Loma Linda University, Loma Linda, CA, USA
| | - Michael M Tymko
- Centre for Heart, Lung, & Vascular Health, School of Health and Exercise Sciences, University of British Columbia – Okanagan, Kelowna, BC, Canada
| | - Philip N Ainslie
- Centre for Heart, Lung, & Vascular Health, School of Health and Exercise Sciences, University of British Columbia – Okanagan, Kelowna, BC, Canada
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10
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Ruggiero L, McNeil CJ. UBC-Nepal Expedition: Motor Unit Characteristics in Lowlanders Acclimatized to High Altitude and Sherpa. Med Sci Sports Exerc 2023; 55:430-439. [PMID: 36730980 DOI: 10.1249/mss.0000000000003070] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
INTRODUCTION With acclimatization to high altitude (HA), adaptations occur throughout the nervous system and at the level of the muscle, which may affect motor unit (MU) characteristics. However, despite the importance of MUs as the final common pathway for the control of voluntary movement, little is known about their adaptations with acclimatization. METHODS Ten lowlanders and Sherpa participated in this study 7 to 14 d after arrival at HA (5050 m), with seven lowlanders repeating the experiment at sea level (SL), 6 months after the expedition. The maximal compound muscle action potential (M max ) was recorded from relaxed biceps brachii. During isometric elbow flexions at 10% of maximal torque, a needle electrode recorded the MU discharge rate (MUDR) and MU potential (MUP) characteristics of single biceps brachii MUs. RESULTS Compared with SL, acclimatized lowlanders had ~10% greater MUDR, ~11% longer MUP duration, as well as ~18% lower amplitude and ~6% greater duration of the first phase of the M max (all P < 0.05). No differences were noted between SL and HA for variables related to MUP shape (e.g., jitter, jiggle; P > 0.08). Apart from lower near-fiber MUP area for Sherpa than acclimatized lowlanders ( P < 0.05), no M max or MU data were different between groups ( P > 0.10). CONCLUSIONS Like other components of the body, MUs in lowlanders adapt with acclimatization to HA. The absence of differences between acclimatized lowlanders and Sherpa suggests that evolutionary adaptations to HA are smaller for MUs than components of the cardiovascular or respiratory systems.
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Affiliation(s)
| | - Chris J McNeil
- Integrated Neuromuscular Physiology Laboratory, Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, BC, CANADA
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11
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Sun Y, Zhang C, He B, Wang L, Tian D, Kang Z, Guo Y, Zhang Y, Dingda D, Zhang Q, Gao F. 7.0T cardiac magnetic resonance imaging of right ventricular function in rats with high-altitude deacclimatization. ANNALS OF TRANSLATIONAL MEDICINE 2023; 11:116. [PMID: 36819537 PMCID: PMC9929826 DOI: 10.21037/atm-22-5991] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/30/2022] [Accepted: 01/10/2023] [Indexed: 01/31/2023]
Abstract
Background High-altitude deacclimatization syndrome (HADAS) is a severe public health issue. The study of the changes in right ventricular function caused by high-altitude deacclimatization (HADA) is of great significance for the prevention and treatment of HADAS. Methods Six-week-old, male Sprague Dawley (SD) rats were randomly divided into the plain, plateau and the HADA group. Rats in the plateau and plain group were exposed to altitudes of 3,850 and 360 m, respectively, for 12 weeks. Rats in HADA group were exposed to the plateau altitude of 3,850 m for 12 weeks and subsequently transported to the plain altitude of 360 m for 4 weeks. Right ventricular ejection fraction (RVEF), end-diastolic volume (EDV), end-systolic volume (ESV), stroke volume (SV), and myocardial strain parameters, including the global longitudinal strain (GLS), global radial strain (GRS), and global circumferential strain (GCS), were evaluated by 7.0T cardiac magnetic resonance (CMR). The levels of red blood cell (RBC), hemoglobin (HGB), and hematocrit (HCT) in the blood were measured, and hematoxylin-eosin (HE) staining was used to observe the pathological changes in the myocardium. Results In rats in the plateau group, the right ventricular fibrous space was slightly widened, and partial focal steatosis were observed. However, in the HADA group, only a few focal steatoses were found. Rats in the plateau group had elevated levels of RBC, HGB and HCT, increased right ventricular end-diastolic volume (RVEDV), right ventricular end-systolic volume (RVESV) and right ventricular stroke volume (RVSV), and decreased right ventricular global longitudinal strain (RVGLS), right ventricular global circumferential strain (RVGCS), and right ventricular global radial strain (RVGRS) compared to rats in the plain group (P<0.001). The RVEDV, RVGCS, and RVGRS in the HADA group basically returned to the plain state. Interestingly, the RVESV in the HADA group was higher, while the RVSV, RVEF, and RVGLS were lower than those in the other two groups. Conclusions After 12 weeks of exposure to high-altitude environment, there were some pathological changes and the whole contractile strain of the right ventricle was observed. Some pathological changes in the myocardial tissue and stroma recovered after returning to the plain for 4 weeks. However, the right ventricular systolic function and strain did not recover completely.
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Affiliation(s)
- Yanqiu Sun
- Department of Radiology, Qinghai Provincial People’s Hospital, Xining, China
| | - Chenhong Zhang
- Department of Radiology, Qinghai Provincial People’s Hospital, Xining, China
| | - Bo He
- Department of Radiology, West China Hospital of Sichuan University, Chengdu, China
| | - Lei Wang
- Department of Radiology, West China Hospital of Sichuan University, Chengdu, China
| | - Dengfeng Tian
- Department of Radiology, Qinghai Provincial People’s Hospital, Xining, China
| | - Zhiqiang Kang
- Department of Radiology, Qinghai Provincial People’s Hospital, Xining, China
| | - Yong Guo
- Department of Radiology, Yushu People’s Hospital, Yushu, China
| | - Yonghai Zhang
- Department of Radiology, The Fifth People’s Hospital of Qinghai Province, Xining, China
| | - Duojie Dingda
- Department of Radiology, Yushu People’s Hospital, Yushu, China
| | - Qiang Zhang
- Department of Neurosurgery, Qinghai Provincial People’s Hospital, Xining, China
| | - Fabao Gao
- Department of Radiology, West China Hospital of Sichuan University, Chengdu, China
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12
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Rytz CL, Pun M, Mawhinney JA, Mounsey CA, Mura M, Martin A, Pialoux V, Hartmann SE, Furian M, Rawling JM, Lopez I, Soza D, Moraga FA, Lichtblau M, Bader PR, Ulrich S, Bloch KE, Frise MC, Poulin MJ. Differential Effects of High-Altitude Exposure on Markers of Oxidative Stress, Antioxidant Capacity and Iron Profiles. Am J Physiol Regul Integr Comp Physiol 2022; 323:R445-R456. [PMID: 35938686 DOI: 10.1152/ajpregu.00321.2021] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
High altitude (HA) exposure may stimulate significant physiological and molecular changes, resulting in HA-related illnesses. HA may impact oxidative stress, antioxidant capacity and iron homeostasis, yet it is unclear how both repeated exposure and HA acclimatization may modulate such effects. Therefore, we assessed the effects of weeklong repeated daily HA exposure (2,900m to 5,050m) in altitude-naïve individuals (n=21, 13 females, mean ± SD, 25.3 ± 3.7 years) to mirror the working schedule of HA workers (n=19, all males, 40.1 ± 2.1 years) at the Atacama Large Millimeter Array (ALMA) Observatory (San Pedro de Atacama, Chile). Markers of oxidative stress, antioxidant capacity and iron homeostasis were measured in blood plasma. Levels of protein oxidation (p<0.001) and catalase activity (p=0.023) increased and serum iron (p<0.001), serum ferritin (p<0.001) and transferrin saturation (p<0.001) levels decreased with HA exposure in both groups. HA workers had lower levels of oxidative stress, and higher levels of antioxidant capacity, iron supply and hemoglobin concentration as compared to altitude-naïve individuals. Upon a second week of daily HA exposure, changes in levels of protein oxidation, glutathione peroxidase and nitric oxide metabolites were lower as compared to the first week in altitude-naïve individuals. These results indicate that repeated exposure to HA may significantly alter oxidative stress and iron homeostasis, and the degree of such changes may be dependent on if HA is visited naïvely or routinely. Further studies are required to fully elucidate differences in HA-induced changes in oxidative stress and iron homeostasis profiles amongst visitors of HA.
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Affiliation(s)
- Chantal L Rytz
- Libin Cardiovascular Institute, Calgary, Canada.,Cumming School of Medicine, University of Calgary, Calgary, Canada
| | - Matiram Pun
- Cumming School of Medicine, University of Calgary, Calgary, Canada.,Hotchkiss Brain Institute, University of Calgary, Calgary, Canada
| | - Jamie A Mawhinney
- Department of Plastic Surgery, Queen Alexandra Hospital, Portsmouth University Hospital NHS Foundation Trust, UK
| | | | - Mathilde Mura
- Univ Lyon, University Lyon 1, Team "Atherosclerosis, Thrombosis and Physical Activity", Lyon, France
| | - Agnès Martin
- Univ Lyon, University Lyon 1, Team "Atherosclerosis, Thrombosis and Physical Activity", Lyon, France
| | - Vincent Pialoux
- Univ Lyon, University Lyon 1, Team "Atherosclerosis, Thrombosis and Physical Activity", Lyon, France
| | - Sara E Hartmann
- Cumming School of Medicine, University of Calgary, Calgary, Canada.,Department of Physiology and Pharmacology, University of Calgary, Calgary, Canada.,Hotchkiss Brain Institute, University of Calgary, Calgary, Canada
| | - Michael Furian
- Pulmonary Division, Sleep Disorders Centre and Pulmonary Hypertension Clinic, University Hospital Zurich, Zurich, Switzerland
| | - Jean M Rawling
- Department of Family Medicine at the University of Calgary, Calgary, Canada
| | - Ivan Lopez
- Safety Group, Atacama Large Millimeter Submillimeter Array, Calama, Chile
| | - Daniel Soza
- Safety Group, Atacama Large Millimeter Submillimeter Array, Calama, Chile
| | - Fernando A Moraga
- Laboratorio de Fisiología, Hipoxia y Función Vascular, Departamento de Ciencias Biomédicas, Facultad de Medicina, Universidad Católica del Norte, Coquimbo, Chile
| | - Mona Lichtblau
- Pulmonary Division, Sleep Disorders Centre and Pulmonary Hypertension Clinic, University Hospital Zurich, Zurich, Switzerland
| | - Patrick R Bader
- Pulmonary Division, Sleep Disorders Centre and Pulmonary Hypertension Clinic, University Hospital Zurich, Zurich, Switzerland
| | - Silvia Ulrich
- Pulmonary Division, Sleep Disorders Centre and Pulmonary Hypertension Clinic, University Hospital Zurich, Zurich, Switzerland
| | - Konrad E Bloch
- Pulmonary Division, Sleep Disorders Centre and Pulmonary Hypertension Clinic, University Hospital Zurich, Zurich, Switzerland
| | - Matthew C Frise
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK; Intensive Care Unit, Royal Berkshire Hospitals NHS Foundation Trust, Reading, UK
| | - Marc J Poulin
- Libin Cardiovascular Institute, Calgary, Canada.,Cumming School of Medicine, University of Calgary, Calgary, Canada.,Department of Physiology and Pharmacology, University of Calgary, Calgary, Canada.,Hotchkiss Brain Institute, University of Calgary, Calgary, Canada.,Faculty of Kinesiology, University of Calgary, Calgary, Canada
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13
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Williams AM, Levine BD, Stembridge M. A change of heart: mechanisms of cardiac adaptation to acute and chronic hypoxia. J Physiol 2022; 600:4089-4104. [PMID: 35930370 PMCID: PMC9544656 DOI: 10.1113/jp281724] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Accepted: 07/21/2022] [Indexed: 11/20/2022] Open
Abstract
Over the last 100 years, high‐altitude researchers have amassed a comprehensive understanding of the global cardiac responses to acute, prolonged and lifelong hypoxia. When lowlanders are exposed to hypoxia, the drop in arterial oxygen content demands an increase in cardiac output, which is facilitated by an elevated heart rate at the same time as ventricular volumes are maintained. As exposure is prolonged, haemoconcentration restores arterial oxygen content, whereas left ventricular filling and stroke volume are lowered as a result of a combination of reduced blood volume and hypoxic pulmonary vasoconstriction. Populations native to high‐altitude, such as the Sherpa in Asia, exhibit unique lifelong or generational adaptations to hypoxia. For example, they have smaller left ventricular volumes compared to lowlanders despite having larger total blood volume. More recent investigations have begun to explore the mechanisms underlying such adaptive responses by combining novel imaging techniques with interventions that manipulate cardiac preload, afterload, and/or contractility. This work has revealed the contributions and interactions of (i) plasma volume constriction; (ii) sympathoexcitation; and (iii) hypoxic pulmonary vasoconstriction with respect to altering cardiac loading, or otherwise preserving or enhancing biventricular systolic and diastolic function even amongst high altitude natives with excessive erythrocytosis. Despite these advances, various areas of investigation remain understudied, including potential sex‐related differences in response to high altitude. Collectively, the available evidence supports the conclusion that the human heart successfully adapts to hypoxia over the short‐ and long‐term, without signs of myocardial dysfunction in healthy humans, except in very rare cases of maladaptation.
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Affiliation(s)
- Alexandra M Williams
- Department of Cellular and Physiological Sciences, Faculty of Medicine, University of British Columbia, Vancouver, BC, Canada.,International Collaboration on Repair Discoveries, University of British Columbia, Vancouver, BC, Canada
| | - Benjamin D Levine
- Institute for Exercise and Environmental Medicine, The University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Mike Stembridge
- Cardiff School of Sport and Health Sciences, Cardiff Metropolitan University, Cardiff, UK
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14
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Baker J, Safarzadeh MA, Incognito AV, Jendzjowsky NG, Foster GE, Bird JD, Raj SR, Day TA, Rickards CA, Zubieta-DeUrioste N, Alim U, Wilson RJA. Functional optical coherence tomography at altitude: retinal microvascular perfusion and retinal thickness at 3,800 meters. J Appl Physiol (1985) 2022; 133:534-545. [PMID: 35771223 DOI: 10.1152/japplphysiol.00132.2022] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Cerebral hypoxia is a serious consequence of several cardiorespiratory illnesses. Measuring the retinal microvasculature at high altitude provides a surrogate for cerebral microvasculature, offering potential insight into cerebral hypoxia in critical illness. Additionally, while sex-specific differences in cardiovascular diseases are strongly supported, few have focused on differences in ocular blood flow. We evaluated the retinal microvasculature in males (n=11) and females (n=7) using functional optical coherence tomography at baseline (1,130m) (Day 0), following rapid ascent (Day 2) and prolonged exposure (Day 9) to high altitude (3,800m). Retinal vascular perfusion density (rVPD; an index of total blood supply), retinal thickness (RT; reflecting vascular and neural tissue volume) and arterial blood were acquired. As a group, rVPD increased on Day 2 vs. Day 0 (p<0.001) and was inversely related to PaO2 (R2=0.45; p=0.006). By Day 9, rVPD recovered to baseline, but was significantly lower in males vs. females (p=0.007). RT was not different on Day 2 vs. Day 0 (p>0.99) but was reduced by Day 9 relative to Day 0 and Day 2 (p<0.001). RT changes relative to Day 0 were inversely related to changes in PaO2 on Day 2 (R2=0.6; p=0.001) and Day 9 (R2=0.4; p=0.02). RT did not differ between sexes. These data suggest differential time course and regulation of the retina during rapid ascent and prolonged exposure to high altitude and are the first to demonstrate sex-specific differences in rVPD at high altitude. The ability to assess intact microvasculature contiguous with the brain has widespread research and clinical applications.
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Affiliation(s)
- Jacquie Baker
- Libin Cardiovascular Institute, Department of Cardiac Sciences, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada.,Department of Physiology and Pharmacology, University of Calgary, Calgary, Alberta, Canada
| | - Mohammad Amin Safarzadeh
- Department of Physiology and Pharmacology, University of Calgary, Calgary, Alberta, Canada.,Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada.,Alberta Children's Hospital Research Institute, University of Calgary, Calgary, Alberta, Canada
| | - Anthony V Incognito
- Department of Physiology and Pharmacology, University of Calgary, Calgary, Alberta, Canada.,Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada.,Alberta Children's Hospital Research Institute, University of Calgary, Calgary, Alberta, Canada
| | - Nicholas G Jendzjowsky
- Division of Respiratory and Critical Care Physiology and Medicine, The Lundquist Institute for Biomedical Innovation at Harbor-UCLA Medical Center, Torrance, California, United States
| | - Glen Edward Foster
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, BC, Canada
| | - Jordan D Bird
- Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, Alberta, Canada
| | - Satish R Raj
- Libin Cardiovascular Institute, Department of Cardiac Sciences, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Trevor A Day
- Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, Alberta, Canada
| | - Caroline A Rickards
- Department of Physiology and Anatomy, University of North Texas Health Science Center, Fort Worth, Texas, United States
| | - Natalia Zubieta-DeUrioste
- Department of Physiology and Pharmacology, University of Calgary, Calgary, Alberta, Canada.,Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada.,High Altitude Pulmonary and Pathology Institute (HAPPI - IPPA), La Paz, Bolivia
| | - Usman Alim
- Department of Computer Science, University of Calgary, Calgary, Alberta, Canada
| | - Richard J A Wilson
- Department of Physiology and Pharmacology, University of Calgary, Calgary, Alberta, Canada.,Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada.,Alberta Children's Hospital Research Institute, University of Calgary, Calgary, Alberta, Canada
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15
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Erythrocyte transglutaminase-2 combats hypoxia and chronic kidney disease by promoting oxygen delivery and carnitine homeostasis. Cell Metab 2022; 34:299-316.e6. [PMID: 35108516 PMCID: PMC9380699 DOI: 10.1016/j.cmet.2021.12.019] [Citation(s) in RCA: 30] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/10/2021] [Revised: 09/29/2021] [Accepted: 12/21/2021] [Indexed: 02/03/2023]
Abstract
Due to lack of nuclei and de novo protein synthesis, post-translational modification (PTM) is imperative for erythrocytes to regulate oxygen (O2) delivery and combat tissue hypoxia. Here, we report that erythrocyte transglutminase-2 (eTG2)-mediated PTM is essential to trigger O2 delivery by promoting bisphosphoglycerate mutase proteostasis and the Rapoport-Luebering glycolytic shunt for adaptation to hypoxia, in healthy humans ascending to high altitude and in two distinct murine models of hypoxia. In a pathological hypoxia model with chronic kidney disease (CKD), eTG2 is critical to combat renal hypoxia-induced reduction of Slc22a5 transcription and OCNT2 protein levels via HIF-1α-PPARα signaling to maintain carnitine homeostasis. Carnitine supplementation is an effective and safe therapeutic approach to counteract hypertension and progression of CKD by enhancing erythrocyte O2 delivery. Altogether, we reveal eTG2 as an erythrocyte protein stabilizer orchestrating O2 delivery and tissue adaptive metabolic reprogramming and identify carnitine-based therapy to mitigate hypoxia and CKD progression.
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16
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Stembridge M, Hoiland RL, Williams AM, Howe CA, Donnelly J, Dawkins TG, Drane A, Tymko MM, Gasho C, Anholm J, Simpson LL, Moore JP, Bailey DM, MacLeod DB, Ainslie PN. The influence of hemoconcentration on hypoxic pulmonary vasoconstriction in acute, prolonged, and lifelong hypoxemia. Am J Physiol Heart Circ Physiol 2021; 321:H738-H747. [PMID: 34448634 DOI: 10.1152/ajpheart.00357.2021] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Hemoconcentration can influence hypoxic pulmonary vasoconstriction (HPV) via increased frictional force and vasoactive signaling from erythrocytes, but whether the balance of these mechanism is modified by the duration of hypoxia remains to be determined. We performed three sequential studies: 1) at sea level, in normoxia and isocapnic hypoxia with and without isovolumic hemodilution (n = 10, aged 29 ± 7 yr); 2) at altitude (6 ± 2 days acclimatization at 5,050 m), before and during hypervolumic hemodilution (n = 11, aged 27 ± 5 yr) with room air and additional hypoxia [fraction of inspired oxygen ([Formula: see text])= 0.15]; and 3) at altitude (4,340 m) in Andean high-altitude natives with excessive erythrocytosis (EE; n = 6, aged 39 ± 17 yr), before and during isovolumic hemodilution with room air and hyperoxia (end-tidal Po2 = 100 mmHg). At sea level, hemodilution mildly increased pulmonary artery systolic pressure (PASP; +1.6 ± 1.5 mmHg, P = 0.01) and pulmonary vascular resistance (PVR; +0.7 ± 0.8 wu, P = 0.04). In contrast, after acclimation to 5,050 m, hemodilution did not significantly alter PASP (22.7 ± 5.2 vs. 24.5 ± 5.2 mmHg, P = 0.14) or PVR (2.2 ± 0.9 vs. 2.3 ± 1.2 wu, P = 0.77), although both remained sensitive to additional acute hypoxia. In Andeans with EE at 4,340 m, hemodilution lowered PVR in room air (2.9 ± 0.9 vs. 2.3 ± 0.8 wu, P = 0.03), but PASP remained unchanged (31.3 ± 6.7 vs. 30.9 ± 6.9 mmHg, P = 0.80) due to an increase in cardiac output. Collectively, our series of studies reveal that HPV is modified by the duration of exposure and the prevailing hematocrit level. In application, these findings emphasize the importance of accounting for hematocrit and duration of exposure when interpreting the pulmonary vascular responses to hypoxemia.NEW & NOTEWORTHY Red blood cell concentration influences the pulmonary vasculature via direct frictional force and vasoactive signaling, but whether the magnitude of the response is modified with duration of exposure is not known. By assessing the pulmonary vascular response to hemodilution in acute normobaric and prolonged hypobaric hypoxia in lowlanders and lifelong hypobaric hypoxemia in Andean natives, we demonstrated that a reduction in red cell concentration augments the vasoconstrictive effects of hypoxia in lowlanders. In high-altitude natives, hemodilution lowered pulmonary vascular resistance, but a compensatory increase in cardiac output following hemodilution rendered PASP unchanged.
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Affiliation(s)
- Mike Stembridge
- Cardiff School of Sport and Health Sciences, Cardiff Metropolitan University, Cardiff, United Kingdom
| | - Ryan L Hoiland
- Centre for Heart, Lung and Vascular Health, University of British Columbia Okanagan, Kelowna, British Columbia, Canada.,Department of Anesthesiology, Pharmacology, and Therapeutics, Vancouver General Hospital, University of British Columbia, Vancouver, British Columbia, Canada
| | - Alexandra M Williams
- Centre for Heart, Lung and Vascular Health, University of British Columbia Okanagan, Kelowna, British Columbia, Canada.,Faculty of Medicine, Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, British Columbia, Canada
| | - Connor A Howe
- Centre for Heart, Lung and Vascular Health, University of British Columbia Okanagan, Kelowna, British Columbia, Canada
| | - Joseph Donnelly
- Department of Anaesthesiology, University of Auckland, Auckland, New Zealand
| | - Tony G Dawkins
- Cardiff School of Sport and Health Sciences, Cardiff Metropolitan University, Cardiff, United Kingdom
| | - Aimee Drane
- Cardiff School of Sport and Health Sciences, Cardiff Metropolitan University, Cardiff, United Kingdom
| | - Michael M Tymko
- Centre for Heart, Lung and Vascular Health, University of British Columbia Okanagan, Kelowna, British Columbia, Canada.,Neurovascular Health Laboratory, Faculty of Kinesiology, Sport, and Recreation, University of Alberta, Edmonton, Alberta, Canada
| | - Christopher Gasho
- Division of Pulmonary and Critical Care, School of Medicine, Loma Linda University, Loma Linda, California
| | - James Anholm
- Division of Pulmonary and Critical Care, School of Medicine, Loma Linda University, Loma Linda, California
| | - Lydia L Simpson
- Extremes Research Group, School of Sport, Health and Exercise Sciences, Bangor University, Wales, United Kingdom
| | - Jonathan P Moore
- Extremes Research Group, School of Sport, Health and Exercise Sciences, Bangor University, Wales, United Kingdom
| | - Damian M Bailey
- Neurovascular Research Laboratory, Faculty of Life Sciences and Education, University of South Wales, Pontypridd, United Kingdom
| | - David B MacLeod
- Human Pharmacology and Physiology Laboratory, Department of Anesthesiology, Duke University Medical Center, Durham, North Carolina
| | - Philip N Ainslie
- Centre for Heart, Lung and Vascular Health, University of British Columbia Okanagan, Kelowna, British Columbia, Canada
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17
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Koivisto-Mørk AE, Svendsen IS, Skattebo Ø, Hallén J, Paulsen G. Impact of baseline serum ferritin and supplemental iron on altitude-induced hemoglobin mass response in elite athletes. Scand J Med Sci Sports 2021; 31:1764-1773. [PMID: 33908091 DOI: 10.1111/sms.13982] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2021] [Revised: 03/26/2021] [Accepted: 04/16/2021] [Indexed: 01/05/2023]
Abstract
The present study explored the impact of pre-altitude serum (s)-ferritin and iron supplementation on changes in hemoglobin mass (ΔHbmass) following altitude training. Measures of Hbmass and s-ferritin from 107 altitude sojourns (9-28 days at 1800-2500 m) with world-class endurance athletes (males n = 41, females n = 25) were analyzed together with iron supplementation and self-reported illness. Altitude sojourns with a hypoxic dose [median (range)] of 1169 (912) km·h increased Hbmass (mean ± SD) 36 ± 38 g (3.7 ± 3.7%, p < 0.001) and decreased s-ferritin -11 (190) µg·L-1 (p = 0.001). Iron supplements [27 (191) mg·day-1 ] were used at 45 sojourns (42%), while only 11 sojourns (10%) were commenced with s-ferritin <35 µg/L. Hbmass increased by 4.6 ± 3.7%, 3.4 ± 3.3%, 4.2 ± 4.3%, and 2.9 ± 3.4% with pre-altitude s-ferritin ≤35 µg·L-1 , 36-50 µg·L-1 , 51-100 µg·L-1 , and >100 µg·L-1 , respectively, with no group difference (p = 0.400). Hbmass increased by 4.1 ± 3.9%, 3.0 ± 3.0% and 3.7 ± 4.7% without, ≤50 mg·day-1 or >50 mg·day-1 supplemental iron, respectively (p = 0.399). Linear mixed model analysis revealed no interaction between pre-altitude s-ferritin and iron supplementation on ΔHbmass (p = 0.906). However, each 100 km·h increase in hypoxic dose augmented ΔHbmass by an additional 0.4% (95% CI: 0.1-0.7%; p = 0.012), while each 1 g·kg-1 higher pre-altitude Hbmass reduced ΔHbmass by -1% (-1.6 to -0.5; p < 0.001), and illness lowered ΔHbmass by -5.7% (-8.3 to -3.1%; p < 0.001). In conclusion, pre-altitude s-ferritin or iron supplementation were not related to the altitude-induced increase in Hbmass (3.7%) in world-class endurance athletes with clinically normal iron stores.
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Affiliation(s)
- Anu Elisa Koivisto-Mørk
- Norwegian Olympic Sports Centre, Norwegian Olympic and Paralympic Committee and Confederation of Sports, Oslo, Norway
| | - Ida Siobhan Svendsen
- Norwegian Olympic Sports Centre, Norwegian Olympic and Paralympic Committee and Confederation of Sports, Oslo, Norway
| | - Øyvind Skattebo
- Department of Physical Performance, Norwegian School of Sport Sciences, Oslo, Norway
| | - Jostein Hallén
- Department of Physical Performance, Norwegian School of Sport Sciences, Oslo, Norway
| | - Gøran Paulsen
- Norwegian Olympic Sports Centre, Norwegian Olympic and Paralympic Committee and Confederation of Sports, Oslo, Norway.,Department of Physical Performance, Norwegian School of Sport Sciences, Oslo, Norway
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18
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DeLoughery TG. Clinician's Corner: Anemia at Altitude-Iron Deficiency and Other Acquired Anemias. High Alt Med Biol 2021; 22:245-248. [PMID: 33945328 DOI: 10.1089/ham.2021.0041] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
DeLoughery, Thomas G. Clinician's corner: Anemia at altitude-Iron deficiency and other acquired anemias. High Alt Med Biol. 22:000-000, 2021.-Acquired anemias are common throughout the world. This article will discuss iron deficiency and other acquired causes of anemia such as inflammation and renal disease. Iron deficiency with or without anemia can detract from performance and may be a risk factor for altitude sickness. Anyone considering going to altitude should be screened for iron deficiency with a serum ferritin if they have risk factors for iron deficiency. The effects of other acquired anemias are less well defined. Several other diseases can also lead to anemia, and altitude challenges are more related to the underlying disease than to anemia.
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Affiliation(s)
- Thomas G DeLoughery
- Division of Hematology/Medical Oncology, Department of Medicine, Oregon Health and Science University, Portland, Oregon, USA.,Division of Laboratory Medicine, Department of Pathology, Oregon Health and Science University, Portland, Oregon, USA
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19
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Willie CK, Patrician A, Hoiland RL, Williams AM, Gasho C, Subedi P, Anholm J, Drane A, Tymko MM, Nowak-Flück D, Plato S, McBride E, Varoli G, Binsted G, Eller LK, Reimer RA, MacLeod DB, Stembridge M, Ainslie PN. Influence of iron manipulation on hypoxic pulmonary vasoconstriction and pulmonary reactivity during ascent and acclimatization to 5050 m. J Physiol 2021; 599:1685-1708. [PMID: 33442904 DOI: 10.1113/jp281114] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2020] [Accepted: 12/16/2020] [Indexed: 12/11/2022] Open
Abstract
KEY POINTS Iron acts as a cofactor in the stabilization of the hypoxic-inducible factor family, and plays an influential role in the modulation of hypoxic pulmonary vasoconstriction. It is uncertain whether iron regulation is altered in lowlanders during either (1) ascent to high altitude, or (2) following partial acclimatization, when compared to high-altitude adapted Sherpa. During ascent to 5050 m, the rise in pulmonary artery systolic pressure (PASP) was blunted in Sherpa, compared to lowlanders; however, upon arrival to 5050 m, PASP levels were comparable in both groups, but the reduction in iron bioavailability was more prevalent in lowlanders compared to Sherpa. Following partial acclimatization to 5050 m, there were differential influences of iron status manipulation (via iron infusion or chelation) at rest and during exercise between lowlanders and Sherpa on the pulmonary vasculature. ABSTRACT To examine the adaptational role of iron bioavailability on the pulmonary vascular responses to acute and chronic hypobaric hypoxia, the haematological and cardiopulmonary profile of lowlanders and Sherpa were determined during: (1) a 9-day ascent to 5050 m (20 lowlanders; 12 Sherpa), and (2) following partial acclimatization (11 ± 4 days) to 5050 m (18 lowlanders; 20 Sherpa), where both groups received an i.v. infusion of either iron (iron (iii)-hydroxide sucrose) or an iron chelator (desferrioxamine). During ascent, there were reductions in iron status in both lowlanders and Sherpa; however, Sherpa appeared to demonstrate a more efficient capacity to mobilize stored iron, compared to lowlanders, when expressed as a Δhepcidin per unit change in either body iron or the soluble transferrin receptor index, between 3400-5050 m (P = 0.016 and P = 0.029, respectively). The rise in pulmonary artery systolic pressure (PASP) was blunted in Sherpa, compared to lowlanders during ascent; however, PASP was comparable in both groups upon arrival to 5050 m. Following partial acclimatization, despite Sherpa demonstrating a blunted hypoxic ventilatory response and greater resting hypoxaemia, they had similar hypoxic pulmonary vasoconstriction when compared to lowlanders at rest. Iron-infusion attenuated PASP in both groups at rest (P = 0.005), while chelation did not exaggerate PASP in either group at rest or during exaggerated hypoxaemia ( P I O 2 = 67 mmHg). During exercise at 25% peak wattage, PASP was only consistently elevated in Sherpa, which persisted following both iron infusion or chelation. These findings provide new evidence on the complex interplay of iron regulation on pulmonary vascular regulation during acclimatization and adaptation to high altitude.
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Affiliation(s)
- Christopher K Willie
- Centre for Heart, Lung, & Vascular Health, School of Health and Exercise Sciences, University of British Columbia - Okanagan, Kelowna, British Columbia, Canada
| | - Alexander Patrician
- Centre for Heart, Lung, & Vascular Health, School of Health and Exercise Sciences, University of British Columbia - Okanagan, Kelowna, British Columbia, Canada
| | - Ryan L Hoiland
- Centre for Heart, Lung, & Vascular Health, School of Health and Exercise Sciences, University of British Columbia - Okanagan, Kelowna, British Columbia, Canada.,Department of Anaesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, British Columbia, Canada
| | - Alexandra M Williams
- Department of Cellular and Physiological Sciences, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
| | - Christopher Gasho
- Pulmonary/Critical Care Section, VA Loma Linda Healthcare System and Department of Medicine, Loma Linda University, Loma Linda, CA, USA
| | - Prajan Subedi
- Pulmonary/Critical Care Section, VA Loma Linda Healthcare System and Department of Medicine, Loma Linda University, Loma Linda, CA, USA
| | - James Anholm
- Pulmonary/Critical Care Section, VA Loma Linda Healthcare System and Department of Medicine, Loma Linda University, Loma Linda, CA, USA
| | - Aimee Drane
- Cardiff School of Sport and Health Sciences, Cardiff Metropolitan University, Cardiff, UK
| | - Michael M Tymko
- Centre for Heart, Lung, & Vascular Health, School of Health and Exercise Sciences, University of British Columbia - Okanagan, Kelowna, British Columbia, Canada.,Neurovascular Health Laboratory, University of Alberta, Edmonton, Alberta, Canada
| | - Daniela Nowak-Flück
- Centre for Heart, Lung, & Vascular Health, School of Health and Exercise Sciences, University of British Columbia - Okanagan, Kelowna, British Columbia, Canada
| | - Sawyer Plato
- Centre for Heart, Lung, & Vascular Health, School of Health and Exercise Sciences, University of British Columbia - Okanagan, Kelowna, British Columbia, Canada
| | - Emily McBride
- Centre for Heart, Lung, & Vascular Health, School of Health and Exercise Sciences, University of British Columbia - Okanagan, Kelowna, British Columbia, Canada
| | - Giovanfrancesco Varoli
- Centre for Heart, Lung, & Vascular Health, School of Health and Exercise Sciences, University of British Columbia - Okanagan, Kelowna, British Columbia, Canada
| | - Gordon Binsted
- Centre for Heart, Lung, & Vascular Health, School of Health and Exercise Sciences, University of British Columbia - Okanagan, Kelowna, British Columbia, Canada
| | - Lindsay K Eller
- Faculty of Kinesiology and Cumming School of Medicine, University of Calgary, Alberta, Canada
| | - Raylene A Reimer
- Faculty of Kinesiology and Cumming School of Medicine, University of Calgary, Alberta, Canada
| | - David B MacLeod
- Human Pharmacology & Physiology Lab, Department of Anesthesiology, Duke University Medical Center, Durham, NC, USA
| | - Michael Stembridge
- Cardiff School of Sport and Health Sciences, Cardiff Metropolitan University, Cardiff, UK
| | - Philip N Ainslie
- Centre for Heart, Lung, & Vascular Health, School of Health and Exercise Sciences, University of British Columbia - Okanagan, Kelowna, British Columbia, Canada
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20
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Simpson LL, Steinback CD, Stembridge M, Moore JP. A sympathetic view of blood pressure control at high altitude: new insights from microneurographic studies. Exp Physiol 2020; 106:377-384. [PMID: 33345334 PMCID: PMC7898382 DOI: 10.1113/ep089194] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2020] [Accepted: 12/09/2020] [Indexed: 02/06/2023]
Abstract
NEW FINDINGS What is the topic of the review? Sympathoexcitation and sympathetic control of blood pressure at high altitude. What advances does it highlight? Sustained sympathoexcitation is fundamental to integrative control of blood pressure in humans exposed to chronic hypoxia. The largest gaps in current knowledge are in understanding the complex mechanisms by which central sympathetic outflow is regulated at high altitude. ABSTRACT High altitude (HA) hypoxia is a potent activator of the sympathetic nervous system, eliciting increases in sympathetic vasomotor activity. Microneurographic evidence of HA sympathoexcitation dates back to the late 20th century, yet only recently have the characteristics and underpinning mechanisms been explored in detail. This review summarises recent findings and highlights the importance of HA sympathoexcitation for the regulation of blood pressure in lowlanders and indigenous highlanders. In addition, this review identifies gaps in our knowledge and corresponding avenues for future study.
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Affiliation(s)
- Lydia L Simpson
- Institute for Sport Science, Division of Physiology, Innsbruck University, Innsbruck, Austria
| | - Craig D Steinback
- Neurovascular Health Laboratory, Faculty of Kinesiology, Sport, and Recreation, University of Alberta, Edmonton, Canada
| | - Mike Stembridge
- Cardiff School of Sport and Health Sciences, Cardiff Metropolitan University, Cardiff, UK
| | - Jonathan P Moore
- Extremes Research Group, School of Sport, Health and Exercise Sciences, Bangor University, Bangor, UK
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21
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Nutrition and Altitude: Strategies to Enhance Adaptation, Improve Performance and Maintain Health: A Narrative Review. Sports Med 2020; 49:169-184. [PMID: 31691928 PMCID: PMC6901429 DOI: 10.1007/s40279-019-01159-w] [Citation(s) in RCA: 53] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Training at low to moderate altitudes (~ 1600-2400 m) is a common approach used by endurance athletes to provide a distinctive environmental stressor to augment training stimulus in the anticipation of increasing subsequent altitude- and sea-level-based performance. Despite some scientific progress being made on the impact of various nutrition-related changes in physiology and associated interventions at mountaineering altitudes (> 3000 m), the impact of nutrition and/or supplements on further optimization of these hypoxic adaptations at low-moderate altitudes is only an emerging topic. Within this narrative review we have highlighted six major themes involving nutrition: altered energy availability, iron, carbohydrate, hydration, antioxidant requirements and various performance supplements. Of these issues, emerging data suggest that particular attention be given to the potential risk for poor energy availability and increased iron requirements at the altitudes typical of elite athlete training (~ 1600-2400 m) to interfere with optimal adaptations. Furthermore, the safest way to address the possible increase in oxidative stress associated with altitude exposure is via the consumption of antioxidant-rich foods rather than high-dose antioxidant supplements. Meanwhile, many other important questions regarding nutrition and altitude training remain to be answered. At the elite level of sport where the differences between winning and losing are incredibly small, the strategic use of nutritional interventions to enhance the adaptations to altitude training provides an important consideration in the search for optimal performance.
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22
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Tymko MM, Hoiland RL, Tremblay JC, Stembridge M, Dawkins TG, Coombs GB, Patrician A, Howe CA, Gibbons TD, Moore JP, Simpson LL, Steinback CD, Meah VL, Stacey BS, Bailey DM, MacLeod DB, Gasho C, Anholm JD, Bain AR, Lawley JS, Villafuerte FC, Vizcardo-Galindo G, Ainslie PN. The 2018 Global Research Expedition on Altitude Related Chronic Health (Global REACH) to Cerro de Pasco, Peru: an Experimental Overview. Exp Physiol 2020; 106:86-103. [PMID: 32237245 DOI: 10.1113/ep088350] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2019] [Accepted: 03/26/2020] [Indexed: 12/18/2022]
Abstract
NEW FINDINGS What is the central question of this study? Herein, a methodological overview of our research team's (Global REACH) latest high altitude research expedition to Peru is provided. What is the main finding and its importance? The experimental objectives, expedition organization, measurements and key cohort data are discussed. The select data presented in this manuscript demonstrate the haematological differences between lowlanders and Andeans with and without excessive erythrocytosis. The data also demonstrate that exercise capacity was similar between study groups at high altitude. The forthcoming findings from our research expedition will contribute to our understanding of lowlander and indigenous highlander high altitude adaptation. ABSTRACT In 2016, the international research team Global Research Expedition on Altitude Related Chronic Health (Global REACH) was established and executed a high altitude research expedition to Nepal. The team consists of ∼45 students, principal investigators and physicians with the common objective of conducting experiments focused on high altitude adaptation in lowlanders and in highlanders with lifelong exposure to high altitude. In 2018, Global REACH travelled to Peru, where we performed a series of experiments in the Andean highlanders. The experimental objectives, organization and characteristics, and key cohort data from Global REACH's latest research expedition are outlined herein. Fifteen major studies are described that aimed to elucidate the physiological differences in high altitude acclimatization between lowlanders (n = 30) and Andean-born highlanders with (n = 22) and without (n = 45) excessive erythrocytosis. After baseline testing in Kelowna, BC, Canada (344 m), Global REACH travelled to Lima, Peru (∼80 m) and then ascended by automobile to Cerro de Pasco, Peru (∼4300 m), where experiments were conducted over 25 days. The core studies focused on elucidating the mechanism(s) governing cerebral and peripheral vascular function, cardiopulmonary regulation, exercise performance and autonomic control. Despite encountering serious logistical challenges, each of the proposed studies was completed at both sea level and high altitude, amounting to ∼780 study sessions and >3000 h of experimental testing. Participant demographics and data relating to acid-base balance and exercise capacity are presented. The collective findings will contribute to our understanding of how lowlanders and Andean highlanders have adapted under high altitude stress.
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Affiliation(s)
- Michael M Tymko
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia - Okanagan, Kelowna, British Columbia, Canada.,Faculty of Kinesiology, Sport, and Recreation, University of Alberta, Edmonton, Alberta, Canada
| | - Ryan L Hoiland
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia - Okanagan, Kelowna, British Columbia, Canada.,Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, BC, Canada
| | - Joshua C Tremblay
- Cardiovascular Stress Response Laboratory, School of Kinesiology and Health Studies, Queen's University, Kingston, Ontario, Canada
| | - Mike Stembridge
- Cardiff School of Sport and Health Sciences, Cardiff Metropolitan University, Cardiff, UK
| | - Tony G Dawkins
- Cardiff School of Sport and Health Sciences, Cardiff Metropolitan University, Cardiff, UK
| | - Geoff B Coombs
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia - Okanagan, Kelowna, British Columbia, Canada
| | - Alexander Patrician
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia - Okanagan, Kelowna, British Columbia, Canada
| | - Connor A Howe
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia - Okanagan, Kelowna, British Columbia, Canada
| | - Travis D Gibbons
- School of Physical Education, Sport & Exercise Science, University of Otago, Dunedin, New Zealand
| | - Jonathan P Moore
- School of Sport, Health and Exercise Sciences, Bangor University, Bangor, UK
| | - Lydia L Simpson
- School of Sport, Health and Exercise Sciences, Bangor University, Bangor, UK
| | - Craig D Steinback
- Faculty of Kinesiology, Sport, and Recreation, University of Alberta, Edmonton, Alberta, Canada
| | - Victoria L Meah
- Faculty of Kinesiology, Sport, and Recreation, University of Alberta, Edmonton, Alberta, Canada
| | - Benjamin S Stacey
- Neurovascular Research Laboratory, Faculty of Life Sciences and Education, University of South Wales, Glamorgan, UK
| | - Damian M Bailey
- Neurovascular Research Laboratory, Faculty of Life Sciences and Education, University of South Wales, Glamorgan, UK
| | - David B MacLeod
- Human Pharmacology & Physiology Lab, Duke University Medical Center, Durham, NC, USA
| | - Christopher Gasho
- Department of Medicine, Division of Pulmonary and Critical Care, Loma Linda University School of Medicine, Loma Linda, CA, USA
| | - James D Anholm
- Department of Medicine, Division of Pulmonary and Critical Care, Loma Linda University School of Medicine, Loma Linda, CA, USA
| | - Anthony R Bain
- Department of Integrative Physiology, University of Colorado, Boulder, NC, USA.,Faculty of Human Kinetics, University of Windsor, Windsor, Ontario, Canada
| | - Justin S Lawley
- Department of Sport Science, University of Innsbruck, Innsbruck, Austria
| | - Francisco C Villafuerte
- Laboratorio de Fisiología Comparada/Fisiología del Transporte de Oxígeno, Facultad de Ciencias y Filosofía, Universidad Peruana Cayetano Heredia, Lima, Perú
| | - Gustavo Vizcardo-Galindo
- Laboratorio de Fisiología Comparada/Fisiología del Transporte de Oxígeno, Facultad de Ciencias y Filosofía, Universidad Peruana Cayetano Heredia, Lima, Perú
| | - Philip N Ainslie
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia - Okanagan, Kelowna, British Columbia, Canada
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23
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Hematological status and endurance performance predictors after low altitude training supported by normobaric hypoxia: a double-blind, placebo controlled study. Biol Sport 2020; 36:341-349. [PMID: 31938005 PMCID: PMC6945048 DOI: 10.5114/biolsport.2019.88760] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2019] [Revised: 07/04/2019] [Accepted: 09/25/2019] [Indexed: 11/20/2022] Open
Abstract
The benefits of altitude/hypoxic training for sea level performance are still under debate. This study examined the effects of low altitude training supported by normobaric hypoxia on hematological status and endurance performance predictors in elite female cyclists. Twenty-two female cyclists trained for 3 weeks at low altitude (<1100 m) and 2 weeks near sea level. During the first 3 weeks, 15 subjects stayed in hypoxic rooms simulating an altitude of 2200 m (+NH group, n = 8) or 1000 m (placebo group, n = 7), and 7 (control group) stayed in regular rooms. Significant increases in total hemoglobin mass (tHb-mass: p = 0.008, p = 0.025), power at 4 mmol·l-1 lactate (PAT4: p = 0.004, p = 0.005) (in absolute and relative values, respectively) and maximal power (PF: p = 0.034) (in absolute values) were observed. However, these effects were not associated with normobaric hypoxia. Changes in tHb-mass were not associated with initial concentrations of ferritin or transferrin receptor, whereas changes in relative tHb-mass (r = -0.53, p = 0.012), PF (r = -0.53, p = 0.01) and PAT4 (r = -0.65, p = 0.001) were inversely correlated with initial values. Changes in tHb-mass and PAT4 were positively correlated (r = 0.50, p = 0.017; r = 0.47, p = 0.028). Regardless of normobaric hypoxia application, low altitude training followed by sea-level training might improve hematological status in elite female cyclists, especially with relatively low initial values of tHb-mass, which could translate into enhanced endurance performance.
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24
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Efficacy of Shenqi Pollen Capsules for High-Altitude Deacclimatization Syndrome via Suppression of the Reoxygenation Injury and Inflammatory Response. J Immunol Res 2019; 2019:4521231. [PMID: 31828172 PMCID: PMC6881745 DOI: 10.1155/2019/4521231] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2019] [Accepted: 08/29/2019] [Indexed: 11/25/2022] Open
Abstract
High-altitude deacclimatization syndrome (HADAS) is involved in hypoxia-reoxygenation injury and inflammatory response, induced a series of symptoms, and has emerged as a severe public health issue. Here, we investigated the mechanism as well as potential means to prevent HADAS using Shenqi pollen capsules (SPCs) in subjects with HADAS in a multicenter, double-blinded, randomized, placebo-controlled study. All subjects were at the same high altitude (3650 m) for 4-8 months before returning to lower altitudes. Subjects (n = 288) in 20 clusters were diagnosed with mild or moderate HADAS on the third day of the study. We randomly allocated 20 clusters of subjects (1 : 1) to receive SPCs or a placebo for 7 weeks, and they were then followed up to the 14th week. The primary endpoints were subjects' HADAS scores recorded during the 14 weeks of follow-up. Compared with the placebo, SPC treatment significantly decreased the subjects' HADAS scores and reduced the incidence of symptom persistence. SPC therapy also reduced the serum levels of CK, CK-MB, LDH, IL-17A, TNF-α, and miR-155 and elevated IL-10 and miR-21 levels. We thus demonstrate that SPCs effectively ameliorated HADAS symptoms in these subjects via suppression of the hypoxia-reoxygenation injury and inflammatory response.
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25
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Howe CA, Ainslie PN, Tremblay JC, Carter HH, Patrician A, Stembridge M, Williams A, Drane AL, Delorme E, Rieger MG, Tymko MM, Gasho C, Santoro A, MacLeod DB, Hoiland RL. UBC-Nepal Expedition: Haemoconcentration underlies the reductions in cerebral blood flow observed during acclimatization to high altitude. Exp Physiol 2019; 104:1963-1972. [PMID: 31410899 DOI: 10.1113/ep087663] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2019] [Accepted: 08/13/2019] [Indexed: 12/16/2022]
Abstract
NEW FINDINGS What is the central question of this study? The aim was to evaluate the degree to which increases in haematocrit alter cerebral blood flow and cerebral oxygen delivery during acclimatization to high altitude. What is the main finding and its importance? Through haemodilution, we determined that, after 1 week of acclimatization, the primary mechanism contributing to the cerebral blood flow response during acclimatization is an increase in haemoglobin and haematocrit. The remaining contribution to the cerebral blood flow response during acclimatization is likely to be attributable to ventilatory acclimatization. ABSTRACT At high altitude, an increase in haematocrit (Hct) is achieved through altitude-induced diuresis and erythropoiesis, both of which result in increased arterial oxygen content. Given the impact of alterations in Hct on oxygen content, haemoconcentration has been hypothesized to mediate, in part, the attenuation of the initial elevation in cerebral blood flow (CBF) at high altitude. To test this hypothesis, healthy men (n = 13) ascended to 5050 m over 9 days without the aid of prophylactic acclimatization medications. After 1 week of acclimatization at 5050 m, participants were haemodiluted by rapid saline infusion (2.10 ± 0.28 l) to return Hct towards pre-acclimatization values. Arterial blood gases, Hct, global CBF (duplex ultrasound) and haemodynamic variables were measured after initial arrival at 5050 m and after 1 week of acclimatization at high altitude, before and after the haemodilution protocol. After 1 week at 5050 m, the Hct increased from 42.5 ± 2.5 to 49.6 ± 2.5% (P < 0.001), and it was subsequently reduced to 45.6 ± 2.3% (P < 0.001) after haemodilution. Global CBF decreased from 844 ± 160 to 619 ± 136 ml min-1 (P = 0.033) after 1 week of acclimatization and increased to 714 ± 204 ml min -1 (P = 0.045) after haemodilution. Despite the significant changes in Hct, and thus oxygen content, cerebral oxygen delivery was unchanged at all time points. Furthermore, these observations occurred in the absence of any changes in mean arterial blood pressure, cardiac output, arterial blood pH or oxygen saturation pre- and posthaemodilution. These data highlight the influence of Hct in the regulation of CBF and are the first to demonstrate experimentally that haemoconcentration contributes to the reduction in CBF during acclimatization to altitude.
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Affiliation(s)
- Connor A Howe
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia - Okanagan Campus, Kelowna, BC, Canada
| | - Philip N Ainslie
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia - Okanagan Campus, Kelowna, BC, Canada
| | - Joshua C Tremblay
- Cardiovascular Stress Response Laboratory, School of Kinesiology and Health Studies, Queen's University, Kingston, ON, Canada
| | - Howard H Carter
- Department of Nutrition, Exercise and Sports, University of Copenhagen, Copenhagen, Denmark
| | - Alex Patrician
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia - Okanagan Campus, Kelowna, BC, Canada
| | - Mike Stembridge
- Cardiff Centre for Exercise and Health, Cardiff Metropolitan University, Cardiff, UK
| | - Alex Williams
- International Collaboration on Repair Discoveries, University of British Columbia, Vancouver, BC, Canada
| | - Aimee L Drane
- Cardiff Centre for Exercise and Health, Cardiff Metropolitan University, Cardiff, UK
| | - Eric Delorme
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia - Okanagan Campus, Kelowna, BC, Canada
| | - Mathew G Rieger
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia - Okanagan Campus, Kelowna, BC, Canada
| | - Michael M Tymko
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia - Okanagan Campus, Kelowna, BC, Canada
| | - Chris Gasho
- VA Loma Linda Healthcare System and Loma Linda University School of Medicine, Loma Linda, CA, USA
| | - Antoinette Santoro
- Department of Anesthesiology, Duke University Medical Center, Durham, NC, USA
| | - David B MacLeod
- Department of Anesthesiology, Duke University Medical Center, Durham, NC, USA
| | - Ryan L Hoiland
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia - Okanagan Campus, Kelowna, BC, Canada
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26
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Hoiland RL, Howe CA, Carter HH, Tremblay JC, Willie CK, Donnelly J, MacLeod DB, Gasho C, Stembridge M, Boulet LM, Niroula S, Ainslie PN. UBC‐Nepal expedition: phenotypical evidence for evolutionary adaptation in the control of cerebral blood flow and oxygen delivery at high altitude. J Physiol 2019; 597:2993-3008. [DOI: 10.1113/jp277596] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Accepted: 04/09/2019] [Indexed: 01/26/2023] Open
Affiliation(s)
- Ryan L. Hoiland
- Centre for Heart, Lung and Vascular HealthUniversity of British Columbia–Okanagan Campus, School of Health and Exercise Sciences 3333 University Way Kelowna British Columbia Canada V1V 1V7
| | - Connor A. Howe
- Centre for Heart, Lung and Vascular HealthUniversity of British Columbia–Okanagan Campus, School of Health and Exercise Sciences 3333 University Way Kelowna British Columbia Canada V1V 1V7
| | - Howard H. Carter
- Department of Nutrition, Exercise and SportsUniversity of Copenhagen Nørre Allé 51 DK‐2200 Copenhagen Denmark
| | - Joshua C. Tremblay
- Cardiovascular Stress Response Laboratory, School of Kinesiology and Health StudiesQueen's University 28 Division Street Kingston Ontario Canada K7L 3N6
| | - Chris K. Willie
- Centre for Heart, Lung and Vascular HealthUniversity of British Columbia–Okanagan Campus, School of Health and Exercise Sciences 3333 University Way Kelowna British Columbia Canada V1V 1V7
| | - Joseph Donnelly
- Brain Physics Laboratory, Division of Neurosurgery, Department of Clinical NeurosciencesCambridge Biomedical Campus, University of Cambridge Cambridge CB2 0QQ UK
| | - David B. MacLeod
- Human Pharmacology and Physiology Lab, Department of AnesthesiologyDuke University Medical Center Durham NC 27708 USA
| | - Chris Gasho
- VA Loma Linda Healthcare System and Loma Linda University School of Medicine Loma Linda CA USA
| | - Mike Stembridge
- Cardiff Centre for Exercise and HealthCardiff Metropolitan University Cyncoed Road Cardiff CF23 6XD UK
| | - Lindsey M. Boulet
- Centre for Heart, Lung and Vascular HealthUniversity of British Columbia–Okanagan Campus, School of Health and Exercise Sciences 3333 University Way Kelowna British Columbia Canada V1V 1V7
| | | | - Philip N. Ainslie
- Centre for Heart, Lung and Vascular HealthUniversity of British Columbia–Okanagan Campus, School of Health and Exercise Sciences 3333 University Way Kelowna British Columbia Canada V1V 1V7
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27
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Iron considerations for the athlete: a narrative review. Eur J Appl Physiol 2019; 119:1463-1478. [PMID: 31055680 DOI: 10.1007/s00421-019-04157-y] [Citation(s) in RCA: 113] [Impact Index Per Article: 22.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2019] [Accepted: 05/02/2019] [Indexed: 02/07/2023]
Abstract
Iron plays a significant role in the body, and is specifically important to athletes, since it is a dominant feature in processes such as oxygen transport and energy metabolism. Despite its importance, athlete populations, especially females and endurance athletes, are commonly diagnosed with iron deficiency, suggesting an association between sport performance and iron regulation. Although iron deficiency is most common in female athletes (~ 15-35% athlete cohorts deficient), approximately 5-11% of male athlete cohorts also present with this issue. Furthermore, interest has grown in the mechanisms that influence iron absorption in athletes over the last decade, with the link between iron regulation and exercise becoming a research focus. Specifically, exercise-induced increases in the master iron regulatory hormone, hepcidin, has been highlighted as a contributing factor towards altered iron metabolism in athletes. To date, a plethora of research has been conducted, including investigation into the impact that sex hormones, diet (e.g. macronutrient manipulation), training and environmental stress (e.g. hypoxia due to altitude training) have on an athlete's iron status, with numerous recommendations proposed for consideration. This review summarises the current state of research with respect to the aforementioned factors, drawing conclusions and recommendations for future work.
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28
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Simpson LL, Busch SA, Oliver SJ, Ainslie PN, Stembridge M, Steinback CD, Moore JP. Baroreflex control of sympathetic vasomotor activity and resting arterial pressure at high altitude: insight from Lowlanders and Sherpa. J Physiol 2019; 597:2379-2390. [PMID: 30893472 DOI: 10.1113/jp277663] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2019] [Accepted: 03/18/2019] [Indexed: 01/23/2023] Open
Abstract
KEY POINTS Hypoxia, a potent activator of the sympathetic nervous system, is known to increase muscle sympathetic nerve activity (MSNA) to the peripheral vasculature of native Lowlanders during sustained high altitude (HA) exposure. We show that the arterial baroreflex control of MSNA functions normally in healthy Lowlanders at HA, and that upward baroreflex resetting permits chronic activation of basal sympathetic vasomotor activity under this condition. The baroreflex MSNA operating point and resting sympathetic vasomotor outflow both are lower for highland Sherpa compared to acclimatizing Lowlanders; these lower levels may represent beneficial hypoxic adaptation in Sherpa. Acute hyperoxia at HA had minimal effect on baroreflex control of MSNA in Lowlanders and Sherpa, raising the possibility that mechanisms other than peripheral chemoreflex activation contribute to vascular sympathetic baroreflex resetting and sympathoexcitation. These findings provide a better understanding of sympathetic nervous system activation and the control of blood pressure during the physiological stress of sustained HA hypoxia. ABSTRACT Exposure to high altitude (HA) is characterized by heightened muscle sympathetic neural activity (MSNA); however, the effect on arterial baroreflex control of MSNA is unknown. Furthermore, arterial baroreflex control at HA may be influenced by genotypic and phenotypic differences between lowland and highland natives. Fourteen Lowlanders (12 male) and nine male Sherpa underwent haemodynamic and sympathetic neural assessment at low altitude (Lowlanders, low altitude; 344 m, Sherpa, Kathmandu; 1400 m) and following gradual ascent to 5050 m. Beat-by-beat haemodynamics (photoplethysmography) and MSNA (microneurography) were recorded lying supine. Indices of vascular sympathetic baroreflex function were determined from the relationship of diastolic blood pressure (DBP) and corresponding MSNA at rest (i.e. DBP 'operating pressure' and MSNA 'operating point'), as well as during a modified Oxford baroreflex test (i.e. 'gain'). Operating pressure and gain were unchanged for Lowlanders during HA exposure; however, the operating point was reset upwards (48 ± 16 vs. 22 ± 12 bursts 100 HB-1 , P = 0.001). Compared to Lowlanders at 5050 m, Sherpa had similar gain and operating pressure, although the operating point was lower (30 ± 13 bursts 100 HB-1 , P = 0.02); MSNA burst frequency was lower for Sherpa (22 ± 11 vs. 30 ± 9 bursts min-1 P = 0.03). Breathing 100% oxygen did not alter vascular sympathetic baroreflex function for either group at HA. For Lowlanders, upward baroreflex resetting promotes heightened sympathetic vasoconstrictor activity and maintains blood pressure stability, at least during early HA exposure; mechanisms other than peripheral chemoreflex activation could be involved. Sherpa adaptation appears to favour a lower sympathetic vasoconstrictor activity compared to Lowlanders for blood pressure homeostasis.
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Affiliation(s)
- Lydia L Simpson
- Extremes Research Group, School of Sport, Health and Exercise Sciences, Bangor University, Bangor, Wales, UK
| | - Stephen A Busch
- Neurovascular Health Laboratory, Faculty of Kinesiology, Sport and Recreation, University of Alberta, Edmonton, Alberta, Canada
| | - Samuel J Oliver
- Extremes Research Group, School of Sport, Health and Exercise Sciences, Bangor University, Bangor, Wales, UK
| | - Philip N Ainslie
- Centre for Heart, Lung, and Vascular Health, University of British Columbia Okanagan, BC, Kelowna, Canada
| | - Mike Stembridge
- Cardiff School of Sport and Health Sciences, Cardiff Metropolitan University, Cardiff, Wales, UK
| | - Craig D Steinback
- Neurovascular Health Laboratory, Faculty of Kinesiology, Sport and Recreation, University of Alberta, Edmonton, Alberta, Canada
| | - Jonathan P Moore
- Extremes Research Group, School of Sport, Health and Exercise Sciences, Bangor University, Bangor, Wales, UK
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Stembridge M, Levine B. Cardiac performance with chronic hypoxia: mechanisms regulating stroke volume. CURRENT OPINION IN PHYSIOLOGY 2019. [DOI: 10.1016/j.cophys.2018.12.007] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Ahlgrim C, Birkner P, Seiler F, Grundmann S, Baumstark MW, Bode C, Pottgiesser T. Applying the Optimized CO Rebreathing Method for Measuring Blood Volumes and Hemoglobin Mass in Heart Failure Patients. Front Physiol 2018; 9:1603. [PMID: 30483155 PMCID: PMC6240604 DOI: 10.3389/fphys.2018.01603] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2018] [Accepted: 10/25/2018] [Indexed: 11/13/2022] Open
Abstract
Introduction: Determination of blood volume, red cell volume, and plasma volume contributes to the understanding of the pathophysiology in heart failure, especially concerning anemia and volume load. The optimized carbon monoxide (CO)-rebreathing method (oCORM) is used to determine these parameters and hemoglobin mass (Hbmass) in exercise physiology. The applicability of oCORM to determine the intravascular volumes and Hbmass in heart failure patients is currently undetermined because assumptions concerning CO kinetics with oCORM rely on healthy subjects with a normal ejection fraction. Therefore, the aim of the present study is to determine the applicability and the systematic error of oCORM arising from a reduced EF when oCORM is used for measurement of intravascular volumes and Hbmass in heart failure patients. Methods: oCORM was performed in 21 patients with heart failure and a reduced ejection fraction (EF) of < 30% (EFsev) and 25 controls (CONT). CO kinetics in capillary blood was studied 3-15 min after commencement of CO rebreathing. Differences in CO kinetics between the groups were assessed using a generalized linear model. The systematic error for determination of Hbmass with oCORM arising from differences in CO kinetics was assessed using the Monte Carlo method. Results: The CO kinetics was significantly different between EFsev and CONT. In both groups, exposure to CO led to a COHb increase to 6.0 ± 1.0% 3 min after CO rebreathing. There were no CO related side effects or any clinical symptoms. Monte Carlo simulation quantifies the systematic error for determination of Hbmass arising from an impaired ejection fraction to be -0.88%. Conclusion: Our results indicate an impaired vascular mixing of CO when EF is severely reduced. When Hbmass is determined using the original oCORM protocol in heart failure patients with a reduced EF, the systematic underestimation of about 1% should be considered. However, the error arising from this impaired vascular mixing appears small and clinically negligible. Furthermore, application of oCORM was safe and not related to any side effects resulting from CO exposure. In conclusion, oCORM can be used for assessing intravascular volumes and Hbmass in patients with a reduced EF.
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Affiliation(s)
- Christoph Ahlgrim
- Center for Medicine, Institute for Exercise and Occupational Medicine, Medical Center - University of Freiburg, Freiburg, Germany.,Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Philipp Birkner
- Department of Cardiology and Angiology I, Heart Center Freiburg University, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Florian Seiler
- Department of Cardiology and Angiology I, Heart Center Freiburg University, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Sebastian Grundmann
- Department of Cardiology and Angiology I, Heart Center Freiburg University, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Manfred W Baumstark
- Center for Medicine, Institute for Exercise and Occupational Medicine, Medical Center - University of Freiburg, Freiburg, Germany.,Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Christoph Bode
- Department of Cardiology and Angiology I, Heart Center Freiburg University, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Torben Pottgiesser
- Department of Cardiology and Angiology I, Heart Center Freiburg University, Faculty of Medicine, University of Freiburg, Freiburg, Germany
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Willie CK, Stembridge M, Hoiland RL, Tymko MM, Tremblay JC, Patrician A, Steinback C, Moore J, Anholm J, Subedi P, Niroula S, McNeil CJ, McManus A, MacLeod DB, Ainslie PN. UBC-Nepal Expedition: An experimental overview of the 2016 University of British Columbia Scientific Expedition to Nepal Himalaya. PLoS One 2018; 13:e0204660. [PMID: 30379823 PMCID: PMC6209169 DOI: 10.1371/journal.pone.0204660] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2018] [Accepted: 09/12/2018] [Indexed: 01/04/2023] Open
Abstract
The University of British Columbia Nepal Expedition took place over several months in the fall of 2016 and was comprised of an international team of 37 researchers. This paper describes the objectives, study characteristics, organization and management of this expedition, and presents novel blood gas data during acclimatization in both lowlanders and Sherpa. An overview and framework for the forthcoming publications is provided. The expedition conducted 17 major studies with two principal goals—to identify physiological differences in: 1) acclimatization; and 2) responses to sustained high-altitude exposure between lowland natives and people of Tibetan descent. We performed observational cohort studies of human responses to progressive hypobaric hypoxia (during ascent), and to sustained exposure to 5050 m over 3 weeks comparing lowlander adults (n = 30) with Sherpa adults (n = 24). Sherpa were tested both with (n = 12) and without (n = 12) descent to Kathmandu. Data collected from lowlander children (n = 30) in Canada were compared with those collected from Sherpa children (n = 57; 3400–3900m). Studies were conducted in Canada (344m) and the following locations in Nepal: Kathmandu (1400m), Namche Bazaar (3440m), Kunde Hospital (3480m), Pheriche (4371m) and the Ev-K2-CNR Research Pyramid Laboratory (5050m). The core studies focused on the mechanisms of cerebral blood flow regulation, the role of iron in cardiopulmonary regulation, pulmonary pressures, intra-ocular pressures, cardiac function, neuromuscular fatigue and function, blood volume regulation, autonomic control, and micro and macro vascular function. A total of 335 study sessions were conducted over three weeks at 5050m. In addition to an overview of this expedition and arterial blood gas data from Sherpa, suggestions for scientists aiming to perform field-based altitude research are also presented. Together, these findings will contribute to our understanding of human acclimatization and adaptation to the stress of residence at high-altitude.
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Affiliation(s)
- Christopher K. Willie
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia – Okanagan, Kelowna, British Columbia, Canada
| | - Michael Stembridge
- Cardiff Centre for Exercise and Health, Cardiff School of Sport, Cardiff Metropolitan University, Cardiff, United Kingdom
| | - Ryan L. Hoiland
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia – Okanagan, Kelowna, British Columbia, Canada
| | - Michael M. Tymko
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia – Okanagan, Kelowna, British Columbia, Canada
| | - Joshua C. Tremblay
- Cardiovascular Stress Response Laboratory, School of Kinesiology and Health Studies, Queen’s University, Kingston, Ontario, Canada
| | - Alexander Patrician
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia – Okanagan, Kelowna, British Columbia, Canada
| | | | - Jonathan Moore
- Bangor University, School of Sport, Health & Exercise Sciences, Gwynedd, Wales, United Kingdom
| | - James Anholm
- Pulmonary/Critical Care Section, VA Loma Linda Healthcare System, Loma Linda, California, United States of America
| | - Prajan Subedi
- Paloma Medical Group, San Juan Capistrano, California, United States of America
| | | | - Chris J. McNeil
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia – Okanagan, Kelowna, British Columbia, Canada
| | - Ali McManus
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia – Okanagan, Kelowna, British Columbia, Canada
| | - David B. MacLeod
- Human Pharmacology & Physiology Lab, Duke University Medical Center, Durham, North Carolina, United States of America
| | - Philip N. Ainslie
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia – Okanagan, Kelowna, British Columbia, Canada
- * E-mail:
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Tremblay JC, Hoiland RL, Carter HH, Howe CA, Stembridge M, Willie CK, Gasho C, MacLeod DB, Pyke KE, Ainslie PN. UBC-Nepal expedition: upper and lower limb conduit artery shear stress and flow-mediated dilation on ascent to 5,050 m in lowlanders and Sherpa. Am J Physiol Heart Circ Physiol 2018; 315:H1532-H1543. [PMID: 30168724 DOI: 10.1152/ajpheart.00345.2018] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The study of conduit artery endothelial adaptation to hypoxia has been restricted to the brachial artery, and comparisons with highlanders have been confounded by differences in altitude exposure, exercise, and unknown levels of blood viscosity. To address these gaps, we tested the hypothesis that lowlanders, but not Sherpa, would demonstrate decreased mean shear stress and increased retrograde shear stress and subsequently reduced flow-mediated dilation (FMD) in the upper and lower limb conduit arteries on ascent to 5,050 m. Healthy lowlanders (means ± SD, n = 22, 28 ± 6 yr) and Sherpa ( n = 12, 34 ± 11 yr) ascended over 10 days, with measurements taken on nontrekking days at 1,400 m (baseline), 3,440 m ( day 4), 4,371 m ( day 7), and 5,050 m ( day 10). Arterial blood gases, blood viscosity, shear stress, and FMD [duplex ultrasound of the brachial and superficial femoral arteries (BA and SFA, respectively)] were acquired at each time point. Ascent decreased mean and increased retrograde shear stress in the upper and lower limb of lowlanders and Sherpa. Although BA FMD decreased in lowlanders from 7.1 ± 3.9% to 3.8 ± 2.8% at 5,050 versus 1,400 m ( P < 0.001), SFA FMD was preserved. In Sherpa, neither BA nor SFA FMD were changed upon ascent to 5,050 m. In lowlanders, the ascent-related exercise may favorably influence endothelial function in the active limb (SFA); selective impairment in FMD in the BA in lowlanders is likely mediated via the low mean or high oscillatory baseline shear stress. In contrast, Sherpa presented protected endothelial function, suggesting a potential vascular aspect of high-altitude acclimatization/adaptation. NEW & NOTEWORTHY Upper and lower limb arterial shear stress and flow-mediated dilation (FMD) were assessed on matched ascent from 1,400 to 5,050 m in lowlanders and Sherpa. A shear stress pattern associated with vascular dysfunction/risk manifested in both limbs of lowlanders and Sherpa. FMD was impaired only in the upper limb of lowlanders. The findings indicate a limb-specific impact of high-altitude trekking on FMD and a vascular basis to acclimatization wherein endothelial function is protected in Sherpa on ascent.
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Affiliation(s)
- Joshua C Tremblay
- Cardiovascular Stress Response Laboratory, School of Kinesiology and Health Studies, Queen's University , Kingston, Ontario , Canada
| | - Ryan L Hoiland
- Centre for Heart, Lung, and Vascular Health, University of British Columbia-Okanagan, Kelowna, British Columbia, Canada
| | - Howard H Carter
- Department of Nutrition, Exercise and Sports, University of Copenhagen , Copenhagen , Denmark
| | - Connor A Howe
- Centre for Heart, Lung, and Vascular Health, University of British Columbia-Okanagan, Kelowna, British Columbia, Canada
| | - Mike Stembridge
- Cardiff Centre for Exercise and Health, Cardiff Metropolitan University , Cardiff , United Kingdom
| | - Christopher K Willie
- Centre for Heart, Lung, and Vascular Health, University of British Columbia-Okanagan, Kelowna, British Columbia, Canada
| | - Christopher Gasho
- Division of Pulmonary, Critical Care, Hyperbaric and Sleep Medicine, Loma Linda University School of Medicine , Loma Linda, California
| | - David B MacLeod
- Human Pharmacology and Physiology Laboratory, Department of Anesthesiology, Duke University Medical Center , Durham, North Carolina
| | - Kyra E Pyke
- Cardiovascular Stress Response Laboratory, School of Kinesiology and Health Studies, Queen's University , Kingston, Ontario , Canada
| | - Philip N Ainslie
- Centre for Heart, Lung, and Vascular Health, University of British Columbia-Okanagan, Kelowna, British Columbia, Canada
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Trudel G, Uhthoff HK, Laneuville O. Hemolysis during and after 21 days of head-down-tilt bed rest. Physiol Rep 2018; 5:5/24/e13469. [PMID: 29263114 PMCID: PMC5742697 DOI: 10.14814/phy2.13469] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2017] [Revised: 09/12/2017] [Accepted: 09/14/2017] [Indexed: 12/22/2022] Open
Abstract
Hemoconcentration is observed in bed rest studies, descent from altitude, and exposure to microgravity. Hemoconcentration triggers erythrocyte losses to subsequently normalize erythrocyte concentration. The mechanisms of erythrocyte loss may involve enhanced hemolysis, but has never been measured directly in bed rest studies. Steady‐state hemolysis was evaluated by measuring two heme degradation products, endogenous carbon monoxide concentration [CO] and urobilinogen in feces, in 10 healthy men, before, during, and after two campaigns of 21 days of 6° head‐down‐tilt (HDT) bed rest. The subjects were hemoconcentrated at 10 and 21 days of bed rest: mean concentrations of hemoglobin (15.0 ± 0.2 g/L and 14.6 ± 0.1 g/L, respectively) and erythrocytes (5.18 ± 0.06E6/μL and 5.02 ± 0.06E6/μL, respectively) were increased compared to baseline (all Ps < 0.05). In contrast, mean hemoglobin mass (743 ± 19 g) and number of erythrocytes (2.56 ± 0.07E13) were decreased at 21 days of bed rest (both Ps < 0.05). Indicators of hemolysis mean [CO] (1660 ± 49 ppb and 1624 ± 48 ppb, respectively) and fecal urobilinogen concentration (180 ± 23 mg/day and 199 ± 22 mg/day, respectively) were unchanged at 10 and 21 days of bed rest compared to baseline (both Ps > 0.05). A significant decrease in [CO] (−505 ppb) was measured at day 28 after bed rest. HDT bed rest caused hemoconcentration in parallel with lower hemoglobin mass. Circulating indicators of hemolysis remained unchanged throughout bed rest supporting that enhanced hemolysis did not contribute significantly to erythrocyte loss during the hemoconcentration of bed rest. At day 28 after bed rest, decreased hemolysis accompanied the recovery of erythrocytes, a novel finding.
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Affiliation(s)
- Guy Trudel
- The Ottawa Hospital Rehabilitation Centre, Ottawa, Ontario, Canada .,University of Ottawa, Faculty of Medicine, Department of Medicine, Ottawa, Ontario, Canada.,Ottawa Hospital Research Institute, Clinical Epidemiology Program, Ottawa, Ontario, Canada
| | - Hans K Uhthoff
- Faculty of Medicine, University of Ottawa, Ottawa, Ontario, Canada
| | - Odette Laneuville
- Department of Biology, Faculty of Science, University of Ottawa, Ottawa, Ontario, Canada
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Zhao Y, Wang X, Noviana M, Hou M. Nitric oxide in red blood cell adaptation to hypoxia. Acta Biochim Biophys Sin (Shanghai) 2018; 50:621-634. [PMID: 29860301 DOI: 10.1093/abbs/gmy055] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2018] [Indexed: 12/28/2022] Open
Abstract
Nitric oxide (NO) appears to be involved in virtually every aspect of cardiovascular biology. Most attention has been focused on the role of endothelial-derived NO in basal blood flow regulation by relaxing vascular smooth muscle; however, it is now known that NO derived from red blood cells (RBCs) plays a fundamental role in vascular homeostasis by enhancing oxygen (O2) release at the cellular and physiological level. Hypoxia is an often seen problem in diverse conditions; systemic adaptations to hypoxia permit people to adjust to the hypoxic environment at high altitudes and to disease processes. In addition to the cardiopulmonary and hematologic adaptations that support systemic O2 delivery in hypoxia, RBCs assist through newly described NO-based mechanisms, in line with their vital role in O2 transport and delivery. Furthermore, to increase the local blood flow in proportion to metabolic demand, NO regulates membrane mechanical properties thereby modulating RBC deformability and O2 carrying-releasing function. In this review article, we focus on the effect of NO bioactivity on RBC-based mechanisms that regulate blood flow and RBC deformability. RBC adaptations to hypoxia are summarized, with particular attention to NO-dependent S-nitrosylation of membrane proteins and hemoglobin (S-nitrosohemoglobin). The NO/S-nitrosylation/RBC vasoregulatory cascade contributes fundamentally to the molecular understanding of the role of NO in human adaptation to hypoxia and may inform novel therapeutic strategies.
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Affiliation(s)
- Yajin Zhao
- Key Laboratory of Biorheological Science and Technology, Ministry of Education, College of Bioengineering, Chongqing University, Chongqing, China
| | - Xiang Wang
- Key Laboratory of Biorheological Science and Technology, Ministry of Education, College of Bioengineering, Chongqing University, Chongqing, China
| | - Milody Noviana
- Key Laboratory of Biorheological Science and Technology, Ministry of Education, College of Bioengineering, Chongqing University, Chongqing, China
| | - Man Hou
- Key Laboratory of Biorheological Science and Technology, Ministry of Education, College of Bioengineering, Chongqing University, Chongqing, China
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35
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Stembridge M, Ainslie PN, Boulet LM, Anholm J, Subedi P, Tymko MM, Willie CK, Cooper SM, Shave R. The independent effects of hypovolaemia and pulmonary vasoconstriction on ventricular function and exercise capacity during acclimatisation to 3800 m. J Physiol 2018; 597:1059-1072. [PMID: 29808473 DOI: 10.1113/jp275278] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2017] [Accepted: 04/17/2018] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS We sought to determine the isolated and combined influence of hypovolaemia and hypoxic pulmonary vasoconstriction on the decrease in left ventricular (LV) function and maximal exercise capacity observed under hypobaric hypoxia. We performed echocardiography and maximal exercise tests at sea level (344 m), and following 5-10 days at the Barcroft Laboratory (3800 m; White Mountain, California) with and without (i) plasma volume expansion to sea level values and (ii) administration of the pulmonary vasodilatator sildenafil in a double-blinded and placebo-controlled trial. The high altitude-induced reduction in LV filling and ejection was abolished by plasma volume expansion but to a lesser extent by sildenafil administration; however, neither intervention had a positive effect on maximal exercise capacity. Both hypovolaemia and hypoxic pulmonary vasoconstriction play a role in the reduction of LV filling at 3800 m, but the increase in LV filling does not influence exercise capacity at this moderate altitude. ABSTRACT We aimed to determine the isolated and combined contribution of hypovolaemia and hypoxic pulmonary vasoconstriction in limiting left ventricular (LV) function and exercise capacity under chronic hypoxaemia at high altitude. In a double-blinded, randomised and placebo-controlled design, 12 healthy participants underwent echocardiography at rest and during submaximal exercise before completing a maximal test to exhaustion at sea level (SL; 344 m) and after 5-10 days at 3800 m. Plasma volume was normalised to SL values, and hypoxic pulmonary vasoconstriction was reversed by administration of sildenafil (50 mg) to create four unique experimental conditions that were compared with SL values: high altitude (HA), Plasma Volume Expansion (HA-PVX), Sildenafil (HA-SIL) and Plasma Volume Expansion with Sildenafil (HA-PVX-SIL). High altitude exposure reduced plasma volume by 11% (P < 0.01) and increased pulmonary artery systolic pressure (19.6 ± 4.3 vs. 26.0 ± 5.4, P < 0.001); these differences were abolished by PVX and SIL respectively. LV end-diastolic volume (EDV) and stroke volume (SV) were decreased upon ascent to high altitude, but were comparable to sea level in the HA-PVX trial. LV EDV and SV were also elevated in the HA-SIL and HA-PVX-SIL trials compared to HA, but to a lesser extent. Neither PVX nor SIL had a significant effect on the LV EDV and SV response to exercise, or the maximal oxygen consumption or peak power output. In summary, at 3800 m both hypovolaemia and hypoxic pulmonary vasoconstriction contribute to the decrease in LV filling, but restoring LV filling does not confer an improvement in maximal exercise performance.
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Affiliation(s)
- Mike Stembridge
- Cardiff Centre for Exercise and Health, Cardiff Metropolitan University, Cardiff, UK
| | - Philip N Ainslie
- Centre for Heart Lung and Vascular Health, University of British Columbia, Kelowna, BC, Canada
| | - Lindsey M Boulet
- Centre for Heart Lung and Vascular Health, University of British Columbia, Kelowna, BC, Canada
| | - James Anholm
- VA Loma Linda Healthcare System and Loma Linda University School of Medicine, Loma Linda, CA, USA
| | - Prajan Subedi
- VA Loma Linda Healthcare System and Loma Linda University School of Medicine, Loma Linda, CA, USA
| | - Michael M Tymko
- Centre for Heart Lung and Vascular Health, University of British Columbia, Kelowna, BC, Canada
| | - Christopher K Willie
- Centre for Heart Lung and Vascular Health, University of British Columbia, Kelowna, BC, Canada
| | - Stephen-Mark Cooper
- Cardiff Centre for Exercise and Health, Cardiff Metropolitan University, Cardiff, UK
| | - Rob Shave
- Cardiff Centre for Exercise and Health, Cardiff Metropolitan University, Cardiff, UK.,Centre for Heart Lung and Vascular Health, University of British Columbia, Kelowna, BC, Canada
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36
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Mairbäurl H. Neocytolysis: How to Get Rid of the Extra Erythrocytes Formed by Stress Erythropoiesis Upon Descent From High Altitude. Front Physiol 2018; 9:345. [PMID: 29674976 PMCID: PMC5896414 DOI: 10.3389/fphys.2018.00345] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2017] [Accepted: 03/20/2018] [Indexed: 01/18/2023] Open
Abstract
Neocytolysis is the selective destruction of those erythrocytes that had been formed during stress-erythropoiesis in hypoxia in order to increase the oxygen transport capacity of blood. Neocytolysis likely aims at decreasing this excess amount of erythrocytes and hemoglobin (Hb) when it is not required anymore and to decrease blood viscosity. Neocytolysis seems to occur upon descent from high altitude. Similar processes seem to occur in microgravity, and are also discussed to mediate the replacement of erythrocytes containing fetal hemoglobin (HbF) with those having adult hemoglobin (HbA) after birth. This review will focus on hypoxia at high altitude. Hemoglobin concentration and total hemoglobin in blood increase by 20-50% depending on the altitude (i.e., the degree of hypoxia) and the duration of the sojourn. Upon return to normoxia hemoglobin concentration, hematocrit, and reticulocyte counts decrease faster than expected from inhibition of stress-erythropoiesis and normal erythrocyte destruction rates. In parallel, an increase in haptoglobin, bilirubin, and ferritin is observed, which serve as indirect markers of hemolysis and hemoglobin-breakdown. At the same time markers of progressing erythrocyte senescence appear even on reticulocytes. Unexpectedly, reticulocytes from hypoxic mice show decreased levels of the hypoxia-inducible factor HIF-1α and decreased activity of the BCL2/adenovirus E1B 19 kDa protein-interacting protein 3 (BNIP3), which results in elevated mitochondrial activity in these cells. Furthermore, hypoxia increases the expression of miR-21, which inhibits the expression of catalase and thus decreases one of the most important mechanisms protecting against oxygen free radicals in erythrocytes. This unleashes a series of events which likely explain neocytolysis, because upon re-oxygenation systemic and mitochondrial oxygen radical formation increases and causes the selective destruction of those erythrocytes having impaired anti-oxidant capacity.
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Affiliation(s)
- Heimo Mairbäurl
- Medical Clinic VII, Sports Medicine, Translational Lung Research Center, German Center for Lung Research, University Hospital Heidelberg, Heidelberg, Germany
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37
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Ventilatory and cerebrovascular regulation and integration at high-altitude. Clin Auton Res 2018; 28:423-435. [PMID: 29574504 DOI: 10.1007/s10286-018-0522-2] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2017] [Accepted: 03/09/2018] [Indexed: 01/17/2023]
Abstract
Ascent to high-altitude elicits compensatory physiological adaptations in order to improve oxygenation throughout the body. The brain is particularly vulnerable to the hypoxemia of terrestrial altitude exposure. Herein we review the ventilatory and cerebrovascular changes at altitude and how they are both implicated in the maintenance of oxygen delivery to the brain. Further, the interdependence of ventilation and cerebral blood flow at altitude is discussed. Following the acute hypoxic ventilatory response, acclimatization leads to progressive increases in ventilation, and a partial mitigation of hypoxemia. Simultaneously, cerebral blood flow increases during initial exposure to altitude when hypoxemia is the greatest. Following ventilatory acclimatization to altitude, and an increase in hemoglobin concentration-which both underscore improvements in arterial oxygen content over time at altitude-cerebral blood flow progressively decreases back to sea-level values. The complimentary nature of these responses (ventilatory, hematological and cerebral) lead to a tightly maintained cerebral oxygen delivery while at altitude. Despite this general maintenance of global cerebral oxygen delivery, the manner in which this occurs reflects integration of these physiological responses. Indeed, ventilation directly influences cerebral blood flow by determining the prevailing blood gas and acid/base stimuli at altitude, but cerebral blood flow may also influence ventilation by altering central chemoreceptor stimulation via central CO2 washout. The causes and consequences of the integration of ventilatory and cerebral blood flow regulation at high altitude are outlined.
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Gangwar A, Paul S, Ahmad Y, Bhargava K. Competing trends of ROS and RNS-mediated protein modifications during hypoxia as an alternate mechanism of NO benefits. Biochimie 2018; 148:127-138. [PMID: 29571702 DOI: 10.1016/j.biochi.2018.03.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2018] [Accepted: 03/16/2018] [Indexed: 01/01/2023]
Abstract
Hypoxia, especially altitude associated hypoxia is known to cause severe physiological alterations and life-threatening conditions. Impaired redox balance along with oxidative stress, protein carbonylation and instigation of apoptotic events are common sub-cellular events that follow the hypoxic insult. The role of nitric oxide (NO) is very dynamic and versatile in preventing the ill effects of hypoxia vis-a-vis reacting with oxidative species and causing protein nitrosylation. Although several mechanisms of NO-mediated cytoprotection are known during hypoxic insult, limited pieces of evidence are available to support the relationship between two downstream events of oxidative stress, protein carbonylation (caused by carbonyl; CO radical) and protein nitrosylation/nitration (caused by NO/peroxynitrite; ONOO radical). In this study, we investigated an entirely new aspect of NO protection in hypoxia involving crosstalk between carbonylation and nitrosylation. Using standard NO inhibitor l-NAME and simulated hypoxic conditions in hypoxia-sensitive cell line H9c2, we evaluated the levels of radicals, cell death, mitochondrial membrane potential, levels of protein nitrosylation, protein nitration and carbonylation and glutathione content. The results were then carefully analyzed in light of NO bioavailability. Our study shows that reducing NO during hypoxia caused cell death via the increased degree of carbonylation in proteins. This provides a new aspect of NO benefits which furthers opens new possibilities to explore potential mechanisms and effects of cross-talk between nitrosylation, protein nitration and carbonylation, especially through some common antioxidant mediators such as glutathione and thioredoxin.
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Affiliation(s)
- Anamika Gangwar
- Peptide and Proteomics Division, Defence Institute of Physiology and Allied Sciences, Defence Research and Development Organization, Lucknow Road, Timarpur, Delhi, 110054, India
| | - Subhojit Paul
- Peptide and Proteomics Division, Defence Institute of Physiology and Allied Sciences, Defence Research and Development Organization, Lucknow Road, Timarpur, Delhi, 110054, India
| | - Yasmin Ahmad
- Peptide and Proteomics Division, Defence Institute of Physiology and Allied Sciences, Defence Research and Development Organization, Lucknow Road, Timarpur, Delhi, 110054, India
| | - Kalpana Bhargava
- Peptide and Proteomics Division, Defence Institute of Physiology and Allied Sciences, Defence Research and Development Organization, Lucknow Road, Timarpur, Delhi, 110054, India.
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Twomey R, Wrightson J, Fletcher H, Avraam S, Ross E, Dekerle J. Exercise-induced Fatigue in Severe Hypoxia after an Intermittent Hypoxic Protocol. Med Sci Sports Exerc 2018; 49:2422-2432. [PMID: 28708702 DOI: 10.1249/mss.0000000000001371] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
PURPOSE Exercise-induced central fatigue is alleviated after acclimatization to high altitude. The adaptations underpinning this effect may also be induced with brief, repeated exposures to severe hypoxia. The purpose of this study was to determine whether (i) exercise tolerance in severe hypoxia would be improved after an intermittent hypoxic (IH) protocol and (ii) exercise-induced central fatigue would be alleviated after an IH protocol. METHODS Nineteen recreationally active men were randomized into two groups who completed ten 2-h exposures in severe hypoxia (IH: partial pressure of inspired O2 82 mm Hg; n = 11) or normoxia (control; n = 8). Seven sessions involved cycling for 30 min at 25% peak power (W˙peak) in IH and at a matched heart rate in normoxia. Participants performed baseline constant-power cycling to task failure in severe hypoxia (TTF-Pre). After the intervention, the cycling trial was repeated (TTF-Post). Before and after exercise, responses to transcranial magnetic stimulation and supramaximal femoral nerve stimulation were obtained to assess central and peripheral contributions to neuromuscular fatigue. RESULTS From pre- to postexercise in TTF-Pre, maximal voluntary contraction (MVC), cortical voluntary activation (VATMS), and potentiated twitch force (Qtw,pot) decreased in both groups (all P < 0.05). After IH, TTF-Post was improved (535 ± 213 s vs 713 ± 271 s, P < 0.05) and an additional isotime trial was performed. After the IH intervention only, the reduction in MVC and VATMS was attenuated at isotime (P < 0.05). No differences were observed in the control group. CONCLUSIONS Whole-body exercise tolerance in severe hypoxia was prolonged after a protocol of IH. This may be related to an alleviation of the central contribution to neuromuscular fatigue.
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Affiliation(s)
- Rosie Twomey
- 1Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, AB, CANADA; 2Centre for Sport and Exercise Science and Medicine, University of Brighton, Eastbourne, UNITED KINGDOM; and 3English Institute of Sport, Bisham Abbey National Sports Centre, Marlow, UNITED KINGDOM
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Beidleman BA, Fulco CS, Cadarette BS, Cymerman A, Buller MJ, Salgado RM, Posch AM, Staab JE, Sils IV, Yurkevicius BR, Luippold AJ, Welles AP, Muza SR. Is normobaric hypoxia an effective treatment for sustaining previously acquired altitude acclimatization? J Appl Physiol (1985) 2017; 123:1214-1227. [PMID: 28705998 DOI: 10.1152/japplphysiol.00344.2017] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2017] [Revised: 07/06/2017] [Accepted: 07/06/2017] [Indexed: 12/25/2022] Open
Abstract
This study examined whether normobaric hypoxia (NH) treatment is more efficacious for sustaining high-altitude (HA) acclimatization-induced improvements in ventilatory and hematologic responses, acute mountain sickness (AMS), and cognitive function during reintroduction to altitude (RA) than no treatment at all. Seventeen sea-level (SL) residents (age = 23 ± 6 yr; means ± SE) completed in the following order: 1) 4 days of SL testing; 2) 12 days of HA acclimatization at 4,300 m; 3) 12 days at SL post-HA acclimatization (Post) where each received either NH (n = 9, [Formula: see text] = 0.122) or Sham (n = 8; [Formula: see text] = 0.207) treatment; and 4) 24-h reintroduction to 4,300-m altitude (RA) in a hypobaric chamber (460 Torr). End-tidal carbon dioxide pressure ([Formula: see text]), hematocrit (Hct), and AMS cerebral factor score were assessed at SL, on HA2 and HA11, and after 20 h of RA. Cognitive function was assessed using the SynWin multitask performance test at SL, on HA1 and HA11, and after 4 h of RA. There was no difference between NH and Sham treatment, so data were combined. [Formula: see text] (mmHg) decreased from SL (37.2 ± 0.5) to HA2 (32.2 ± 0.6), decreased further by HA11 (27.1 ± 0.4), and then increased from HA11 during RA (29.3 ± 0.6). Hct (%) increased from SL (42.3 ± 1.1) to HA2 (45.9 ± 1.0), increased again from HA2 to HA11 (48.5 ± 0.8), and then decreased from HA11 during RA (46.4 ± 1.2). AMS prevalence (%) increased from SL (0 ± 0) to HA2 (76 ± 11) and then decreased at HA11 (0 ± 0) and remained depressed during RA (17 ± 10). SynWin scores decreased from SL (1,615 ± 62) to HA1 (1,306 ± 94), improved from HA1 to HA11 (1,770 ± 82), and remained increased during RA (1,707 ± 75). These results demonstrate that HA acclimatization-induced improvements in ventilatory and hematologic responses, AMS, and cognitive function are partially retained during RA after 12 days at SL whether or not NH treatment is utilized.NEW & NOTEWORTHY This study demonstrates that normobaric hypoxia treatment over a 12-day period at sea level was not more effective for sustaining high-altitude (HA) acclimatization during reintroduction to HA than no treatment at all. The noteworthy aspect is that athletes, mountaineers, and military personnel do not have to go to extraordinary means to retain HA acclimatization to an easily accessible and relevant altitude if reexposure occurs within a 2-wk time period.
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Affiliation(s)
- Beth A Beidleman
- Biophysics and Biomedical Modeling Division, U.S. Army Research Institute of Environmental Medicine, Natick, Massachusetts;
| | - Charles S Fulco
- Thermal and Mountain Medicine Division, U.S. Army Research Institute of Environmental Medicine, Natick, Massachusetts
| | - Bruce S Cadarette
- Thermal and Mountain Medicine Division, U.S. Army Research Institute of Environmental Medicine, Natick, Massachusetts
| | - Allen Cymerman
- Thermal and Mountain Medicine Division, U.S. Army Research Institute of Environmental Medicine, Natick, Massachusetts
| | - Mark J Buller
- Biophysics and Biomedical Modeling Division, U.S. Army Research Institute of Environmental Medicine, Natick, Massachusetts
| | - Roy M Salgado
- Thermal and Mountain Medicine Division, U.S. Army Research Institute of Environmental Medicine, Natick, Massachusetts
| | - Alexander M Posch
- Thermal and Mountain Medicine Division, U.S. Army Research Institute of Environmental Medicine, Natick, Massachusetts
| | - Janet E Staab
- Military Performance Division, U.S. Army Research Institute of Environmental Medicine, Natick, Massachusetts; and
| | - Ingrid V Sils
- Thermal and Mountain Medicine Division, U.S. Army Research Institute of Environmental Medicine, Natick, Massachusetts
| | - Beau R Yurkevicius
- Thermal and Mountain Medicine Division, U.S. Army Research Institute of Environmental Medicine, Natick, Massachusetts
| | | | - Alexander P Welles
- Biophysics and Biomedical Modeling Division, U.S. Army Research Institute of Environmental Medicine, Natick, Massachusetts
| | - Stephen R Muza
- Scientifc Strategic Management Office, U.S. Army Research Institute of Environmental Medicine, Natick, Massachusetts
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Siebenmann C, Robach P, Lundby C. Regulation of blood volume in lowlanders exposed to high altitude. J Appl Physiol (1985) 2017; 123:957-966. [PMID: 28572493 DOI: 10.1152/japplphysiol.00118.2017] [Citation(s) in RCA: 65] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2017] [Revised: 05/18/2017] [Accepted: 05/31/2017] [Indexed: 12/21/2022] Open
Abstract
Humans ascending to high altitude (HA) experience a reduction in arterial oxyhemoglobin saturation and, as a result, arterial O2 content ([Formula: see text]). As HA exposure extends, this reduction in [Formula: see text] is counteracted by an increase in arterial hemoglobin concentration. Initially, hemoconcentration is exclusively related to a reduction in plasma volume (PV), whereas after several weeks a progressive expansion in total red blood cell volume (RCV) contributes, although often to a modest extent. Since the decrease in PV is more rapid and usually more pronounced than the expansion in RCV, at least during the first weeks of exposure, a reduction in circulating blood volume is common at HA. Although the regulation of hematological responses to HA has been investigated for decades, it remains incompletely understood. This is not only related to the large number of mechanisms that could be involved and the complexity of their interplay but also to the difficulty of conducting comprehensive experiments in the often secluded HA environment. In this review, we present our understanding of the kinetics, the mechanisms and the physiological relevance of the HA-induced reduction in PV and expansion in RCV.
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Affiliation(s)
- Christoph Siebenmann
- The Centre for Physical Activity Research, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark; and
| | - Paul Robach
- National School for Mountain Sports, Site of the National School for Skiing and Mountaineering (ENSA), Chamonix, France
| | - Carsten Lundby
- The Centre for Physical Activity Research, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark; and
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Song A, Zhang Y, Han L, Yegutkin GG, Liu H, Sun K, D'Alessandro A, Li J, Karmouty-Quintana H, Iriyama T, Weng T, Zhao S, Wang W, Wu H, Nemkov T, Subudhi AW, Jameson-Van Houten S, Julian CG, Lovering AT, Hansen KC, Zhang H, Bogdanov M, Dowhan W, Jin J, Kellems RE, Eltzschig HK, Blackburn M, Roach RC, Xia Y. Erythrocytes retain hypoxic adenosine response for faster acclimatization upon re-ascent. Nat Commun 2017; 8:14108. [PMID: 28169986 PMCID: PMC5309698 DOI: 10.1038/ncomms14108] [Citation(s) in RCA: 67] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2016] [Accepted: 11/29/2016] [Indexed: 12/19/2022] Open
Abstract
Faster acclimatization to high altitude upon re-ascent is seen in humans; however, the molecular basis for this enhanced adaptive response is unknown. We report that in healthy lowlanders, plasma adenosine levels are rapidly induced by initial ascent to high altitude and achieved even higher levels upon re-ascent, a feature that is positively associated with quicker acclimatization. Erythrocyte equilibrative nucleoside transporter 1 (eENT1) levels are reduced in humans at high altitude and in mice under hypoxia. eENT1 deletion allows rapid accumulation of plasma adenosine to counteract hypoxic tissue damage in mice. Adenosine signalling via erythrocyte ADORA2B induces PKA phosphorylation, ubiquitination and proteasomal degradation of eENT1. Reduced eENT1 resulting from initial hypoxia is maintained upon re-ascent in humans or re-exposure to hypoxia in mice and accounts for erythrocyte hypoxic memory and faster acclimatization. Our findings suggest that targeting identified purinergic-signalling network would enhance the hypoxia adenosine response to counteract hypoxia-induced maladaptation. Humans that reach high altitude soon after the first ascent show faster adaptation to hypoxia. Song et al. show that this adaptive response relies on decreased red blood cell uptake of plasma adenosine due to reduced levels of nucleoside transporter ENT1 resulting from coordinated adenosine generation by ectonucleotidase CD73 and activation of A2B receptors.
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Affiliation(s)
- Anren Song
- Department of Biochemistry and Molecular Biology, The University of Texas Health Science Center at Houston, Houston, Texas 77030, USA
| | - Yujin Zhang
- Department of Biochemistry and Molecular Biology, The University of Texas Health Science Center at Houston, Houston, Texas 77030, USA
| | - Leng Han
- Department of Biochemistry and Molecular Biology, The University of Texas Health Science Center at Houston, Houston, Texas 77030, USA
| | | | - Hong Liu
- Department of Biochemistry and Molecular Biology, The University of Texas Health Science Center at Houston, Houston, Texas 77030, USA.,Graduate School of Biomedical Sciences, University of Texas Health Science Center at Houston, Houston, Texas 77030, USA
| | - Kaiqi Sun
- Department of Biochemistry and Molecular Biology, The University of Texas Health Science Center at Houston, Houston, Texas 77030, USA.,Graduate School of Biomedical Sciences, University of Texas Health Science Center at Houston, Houston, Texas 77030, USA
| | - Angelo D'Alessandro
- Department of Biochemistry and Molecular Genetics, University of Colorado, Aurora, Colorado 80045, USA
| | - Jessica Li
- Department of Biochemistry and Molecular Biology, The University of Texas Health Science Center at Houston, Houston, Texas 77030, USA
| | - Harry Karmouty-Quintana
- Department of Biochemistry and Molecular Biology, The University of Texas Health Science Center at Houston, Houston, Texas 77030, USA
| | - Takayuki Iriyama
- Department of Biochemistry and Molecular Biology, The University of Texas Health Science Center at Houston, Houston, Texas 77030, USA.,Department of Obstetrics and Gynecology, Faculty of Medicine, The University of Tokyo, Tokyo 113-8655, Japan
| | - Tingting Weng
- Department of Biochemistry and Molecular Biology, The University of Texas Health Science Center at Houston, Houston, Texas 77030, USA
| | - Shushan Zhao
- Department of Biochemistry and Molecular Biology, The University of Texas Health Science Center at Houston, Houston, Texas 77030, USA.,Department of Orthopedics, Xiangya Hospital, Central South University, Changsha, 410008 Hunan, China
| | - Wei Wang
- Department of Biochemistry and Molecular Biology, The University of Texas Health Science Center at Houston, Houston, Texas 77030, USA.,Department of Nephrology, Xiangya Hospital, Central South University, Changsha, 410008 Hunan, China
| | - Hongyu Wu
- Department of Biochemistry and Molecular Biology, The University of Texas Health Science Center at Houston, Houston, Texas 77030, USA
| | - Travis Nemkov
- Altitude Research Center, Department of Emergency Medicine University of Colorado School of Medicine, Aurora, Colorado 80045, USA
| | - Andrew W Subudhi
- Altitude Research Center, Department of Emergency Medicine University of Colorado School of Medicine, Aurora, Colorado 80045, USA
| | - Sonja Jameson-Van Houten
- Altitude Research Center, Department of Emergency Medicine University of Colorado School of Medicine, Aurora, Colorado 80045, USA
| | - Colleen G Julian
- Altitude Research Center, Department of Emergency Medicine University of Colorado School of Medicine, Aurora, Colorado 80045, USA
| | - Andrew T Lovering
- Altitude Research Center, Department of Emergency Medicine University of Colorado School of Medicine, Aurora, Colorado 80045, USA
| | - Kirk C Hansen
- Department of Biochemistry and Molecular Genetics, University of Colorado, Aurora, Colorado 80045, USA
| | - Hong Zhang
- Department of Pathology, MD Anderson Cancer Center, Houston, Texas 77030, USA
| | - Mikhail Bogdanov
- Department of Biochemistry and Molecular Biology, The University of Texas Health Science Center at Houston, Houston, Texas 77030, USA
| | - William Dowhan
- Department of Biochemistry and Molecular Biology, The University of Texas Health Science Center at Houston, Houston, Texas 77030, USA
| | - Jianping Jin
- Department of Biochemistry and Molecular Biology, The University of Texas Health Science Center at Houston, Houston, Texas 77030, USA
| | - Rodney E Kellems
- Department of Biochemistry and Molecular Biology, The University of Texas Health Science Center at Houston, Houston, Texas 77030, USA.,Graduate School of Biomedical Sciences, University of Texas Health Science Center at Houston, Houston, Texas 77030, USA
| | - Holger K Eltzschig
- Organ Protection Program, Department of Anesthesiology, University of Colorado School of Medicine, Aurora, Colorado 80045, USA
| | - Michael Blackburn
- Department of Biochemistry and Molecular Biology, The University of Texas Health Science Center at Houston, Houston, Texas 77030, USA.,Graduate School of Biomedical Sciences, University of Texas Health Science Center at Houston, Houston, Texas 77030, USA
| | - Robert C Roach
- Altitude Research Center, Department of Emergency Medicine University of Colorado School of Medicine, Aurora, Colorado 80045, USA
| | - Yang Xia
- Department of Biochemistry and Molecular Biology, The University of Texas Health Science Center at Houston, Houston, Texas 77030, USA.,Graduate School of Biomedical Sciences, University of Texas Health Science Center at Houston, Houston, Texas 77030, USA.,Department of Nephrology, Xiangya Hospital, Central South University, Changsha, 410008 Hunan, China
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Leone RJ, Lalande S. Intermittent hypoxia as a means to improve aerobic capacity in type 2 diabetes. Med Hypotheses 2017; 100:59-63. [PMID: 28236850 DOI: 10.1016/j.mehy.2017.01.010] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2016] [Revised: 12/15/2016] [Accepted: 01/21/2017] [Indexed: 11/18/2022]
Abstract
Physical inactivity and a low maximal aerobic capacity (VO2max) strongly predict morbidity and mortality in patients with type 2 diabetes (T2D). Patients with T2D have a reduced VO2max when compared with healthy individuals of similar age, weight, and physical activity levels, and this lower aerobic capacity is usually attributed to a reduced oxygen delivery to the working muscles. The oxygen carrying capacity of the blood, as well as increases in cardiac output and blood flow, contribute to the delivery of oxygen to the active muscles during exercise. Hemoglobin mass (Hb mass), a key determinant of oxygen carrying capacity, is suggested to be reduced in patients with T2D following the observation of a lower blood volume (BV) in combination with normal hematocrit levels in this population. Therefore, a lower Hb mass, in addition to a reported lower BV and impaired cardiovascular response to exercise, likely contributes to the reduced oxygen delivery and VO2max in patients with T2D. While exercise training increases Hb mass, BV, and consequently VO2max, the majority of patients with T2D are not physically active, highlighting the need for alternative methods to improve VO2max in this population. Exposure to hypoxia triggers the release of erythropoietin, the hormone regulating red blood cell production, which increases Hb mass and consequently BV. Exposure to mild intermittent hypoxia (IH), characterized by few and short episodes of hypoxia at a fraction of inspired oxygen ranging between 10 and 14% interspersed with cycles of normoxia, increased red blood cell volume, Hb mass, and plasma volume in patients with coronary artery disease or chronic obstructive pulmonary disease, which resulted in an improved VO2max in both populations. We hypothesize that 12 exposures to mild IH over a period of 4weeks will increase Hb mass, BV, cardiac function, and VO2max in patients with T2D. Therefore, exposures to mild IH may increase oxygen delivery and VO2max without the need to perform exercise in patients with T2D.
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Affiliation(s)
- R J Leone
- School of Exercise and Rehabilitation Sciences, College of Health and Human Services, University of Toledo, Toledo, OH, USA.
| | - S Lalande
- School of Exercise and Rehabilitation Sciences, College of Health and Human Services, University of Toledo, Toledo, OH, USA
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D'Alessandro A, Nemkov T, Sun K, Liu H, Song A, Monte AA, Subudhi AW, Lovering AT, Dvorkin D, Julian CG, Kevil CG, Kolluru GK, Shiva S, Gladwin MT, Xia Y, Hansen KC, Roach RC. AltitudeOmics: Red Blood Cell Metabolic Adaptation to High Altitude Hypoxia. J Proteome Res 2016; 15:3883-3895. [PMID: 27646145 DOI: 10.1021/acs.jproteome.6b00733] [Citation(s) in RCA: 85] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Red blood cells (RBCs) are key players in systemic oxygen transport. RBCs respond to in vitro hypoxia through the so-called oxygen-dependent metabolic regulation, which involves the competitive binding of deoxyhemoglobin and glycolytic enzymes to the N-terminal cytosolic domain of band 3. This mechanism promotes the accumulation of 2,3-DPG, stabilizing the deoxygenated state of hemoglobin, and cytosol acidification, triggering oxygen off-loading through the Bohr effect. Despite in vitro studies, in vivo adaptations to hypoxia have not yet been completely elucidated. Within the framework of the AltitudeOmics study, erythrocytes were collected from 21 healthy volunteers at sea level, after exposure to high altitude (5260 m) for 1, 7, and 16 days, and following reascent after 7 days at 1525 m. UHPLC-MS metabolomics results were correlated to physiological and athletic performance parameters. Immediate metabolic adaptations were noted as early as a few hours from ascending to >5000 m, and maintained for 16 days at high altitude. Consistent with the mechanisms elucidated in vitro, hypoxia promoted glycolysis and deregulated the pentose phosphate pathway, as well purine catabolism, glutathione homeostasis, arginine/nitric oxide, and sulfur/H2S metabolism. Metabolic adaptations were preserved 1 week after descent, consistently with improved physical performances in comparison to the first ascendance, suggesting a mechanism of metabolic memory.
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Affiliation(s)
- Angelo D'Alessandro
- Department of Biochemistry and Molecular Genetics, University of Colorado Denver , Anschutz Medical Campus, Aurora, Colorado 80045, United States
| | - Travis Nemkov
- Department of Biochemistry and Molecular Genetics, University of Colorado Denver , Anschutz Medical Campus, Aurora, Colorado 80045, United States
| | - Kaiqi Sun
- Department of Biochemistry and Molecular Biology, The University of Texas Health Science Center at Houston , Houston, Texas, United States
| | - Hong Liu
- Department of Biochemistry and Molecular Biology, The University of Texas Health Science Center at Houston , Houston, Texas, United States
| | - Anren Song
- Department of Biochemistry and Molecular Biology, The University of Texas Health Science Center at Houston , Houston, Texas, United States
| | - Andrew A Monte
- Altitude Research Center, Department of Emergency Medicine, University of Colorado , Anschutz Medical Campus, Aurora, Colorado, United States
| | - Andrew W Subudhi
- Altitude Research Center, Department of Emergency Medicine, University of Colorado , Anschutz Medical Campus, Aurora, Colorado, United States.,Department of Biology, University of Colorado Colorado Springs , Colorado Springs, Colorado, United States
| | - Andrew T Lovering
- Department of Human Physiology, University of Oregon , Eugene, Oregon, United States
| | - Daniel Dvorkin
- Altitude Research Center, Department of Emergency Medicine, University of Colorado , Anschutz Medical Campus, Aurora, Colorado, United States
| | - Colleen G Julian
- Altitude Research Center, Department of Emergency Medicine, University of Colorado , Anschutz Medical Campus, Aurora, Colorado, United States
| | - Christopher G Kevil
- Department of Pathology, Centre for Cardiovascular Diseases and Sciences, LSU Health , Shreveport, Louisiana, United States
| | - Gopi K Kolluru
- Department of Pathology, Centre for Cardiovascular Diseases and Sciences, LSU Health , Shreveport, Louisiana, United States
| | - Sruti Shiva
- Department of Medicine, University of Pittsburgh , Pittsburgh, Pennsylvania, United States
| | - Mark T Gladwin
- Department of Medicine, University of Pittsburgh , Pittsburgh, Pennsylvania, United States
| | - Yang Xia
- Department of Biochemistry and Molecular Biology, The University of Texas Health Science Center at Houston , Houston, Texas, United States
| | - Kirk C Hansen
- Department of Biochemistry and Molecular Genetics, University of Colorado Denver , Anschutz Medical Campus, Aurora, Colorado 80045, United States
| | - Robert C Roach
- Altitude Research Center, Department of Emergency Medicine, University of Colorado , Anschutz Medical Campus, Aurora, Colorado, United States
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Duke JW, Davis JT, Ryan BJ, Elliott JE, Beasley KM, Hawn JA, Byrnes WC, Lovering AT. Decreased arterial PO2, not O2 content, increases blood flow through intrapulmonary arteriovenous anastomoses at rest. J Physiol 2016; 594:4981-96. [PMID: 27062157 DOI: 10.1113/jp272211] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2016] [Accepted: 03/23/2016] [Indexed: 12/25/2022] Open
Abstract
KEY POINTS The mechanism(s) that regulate hypoxia-induced blood flow through intrapulmonary arteriovenous anastomoses (QIPAVA ) are currently unknown. Our previous work has demonstrated that the mechanism of hypoxia-induced QIPAVA is not simply increased cardiac output, pulmonary artery systolic pressure or sympathetic nervous system activity and, instead, it may be a result of hypoxaemia directly. To determine whether it is reduced arterial PO2 (PaO2) or O2 content (CaO2) that causes hypoxia-induced QIPAVA , individuals were instructed to breathe room air and three levels of hypoxic gas at rest before (control) and after CaO2 was reduced by 10% by lowering the haemoglobin concentration (isovolaemic haemodilution; Low [Hb]). QIPAVA , assessed by transthoracic saline contrast echocardiography, significantly increased as PaO2 decreased and, despite reduced CaO2 (via isovolaemic haemodilution), was similar at iso-PaO2. These data suggest that, with alveolar hypoxia, low PaO2 causes the hypoxia-induced increase in QIPAVA , although where and how this is detected remains unknown. ABSTRACT Alveolar hypoxia causes increased blood flow through intrapulmonary arteriovenous anastomoses (QIPAVA ) in healthy humans at rest. However, it is unknown whether the stimulus regulating hypoxia-induced QIPAVA is decreased arterial PO2 (PaO2) or O2 content (CaO2). CaO2 is known to regulate blood flow in the systemic circulation and it is suggested that IPAVA may be regulated similar to the systemic vasculature. Thus, we hypothesized that reduced CaO2 would be the stimulus for hypoxia-induced QIPAVA . Blood volume (BV) was measured using the optimized carbon monoxide rebreathing method in 10 individuals. Less than 5 days later, subjects breathed room air, as well as 18%, 14% and 12.5% O2 , for 30 min each, in a randomized order, before (CON) and after isovolaemic haemodilution (10% of BV withdrawn and replaced with an equal volume of 5% human serum albumin-saline mixture) to reduce [Hb] (Low [Hb]). PaO2 was measured at the end of each condition and QIPAVA was assessed using transthoracic saline contrast echocardiography. [Hb] was reduced from 14.2 ± 0.8 to 12.8 ± 0.7 g dl(-1) (10 ± 2% reduction) from CON to Low [Hb] conditions. PaO2 was no different between CON and Low [Hb], although CaO2 was 10.4%, 9.2% and 9.8% lower at 18%, 14% and 12.5% O2 , respectively. QIPAVA significantly increased as PaO2 decreased and, despite reduced CaO2, was similar at iso-PaO2. These data suggest that, with alveolar hypoxia, low PaO2 causes the hypoxia-induced increase in QIPAVA . Whether the low PO2 is detected at the carotid body, airway and/or the vasculature remains unknown.
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Affiliation(s)
- Joseph W Duke
- Ohio University, Division of Exercise Physiology, Athens, OH, USA
| | - James T Davis
- University of Oregon, Department of Human Physiology, Eugene, OR, USA
| | - Benjamin J Ryan
- University of Colorado at Boulder, Department of Integrative Physiology, Boulder, CO, USA
| | | | - Kara M Beasley
- University of Oregon, Department of Human Physiology, Eugene, OR, USA
| | - Jerold A Hawn
- Oregon Heart and Vascular Institute, Springfield, OR, USA
| | - William C Byrnes
- University of Colorado at Boulder, Department of Integrative Physiology, Boulder, CO, USA
| | - Andrew T Lovering
- University of Oregon, Department of Human Physiology, Eugene, OR, USA
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Ryan BJ, Goodrich JA, Schmidt WF, Stothard ER, Wright KP, Byrnes WC. Haemoglobin mass alterations in healthy humans following four-day head-down tilt bed rest. Exp Physiol 2016; 101:628-40. [PMID: 26914389 PMCID: PMC4851582 DOI: 10.1113/ep085665] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2015] [Accepted: 02/19/2016] [Indexed: 02/01/2023]
Abstract
NEW FINDINGS What is the central question of this study? Is haemoglobin mass (Hbmass) decreased following 4 days of head-down tilt bed rest (HDTBR), and does increased red blood cell (RBC) destruction mediate this adaptation? What is the main finding and its importance? Haemoglobin mass was increased immediately following HDTBR, before decreasing below baseline 5 days after return to normal living conditions. The transient increase in Hbmass might be the result of decreased RBC destruction, but it is also possible that spleen contraction after HDTBR contributed to this adaptation. Our data suggest that the decreased Hbmass 5 days following HDTBR resulted from decreased RBC production, not increased RBC destruction. Rapid decreases in haemoglobin mass (Hbmass) have been reported in healthy humans following spaceflight and descent from high altitude. It has been proposed that a selective increase in the destruction of young red blood cells (RBCs) mediates these decreases, but conclusive evidence demonstrating neocytolysis in humans is lacking. Based on the proposed triggers and time course of adaptation during spaceflight, we hypothesized that Hbmass would be reduced after 4 days of -6 deg head-down tilt bed rest (HDTBR) and that this would be associated with evidence for increased RBC destruction. We assessed Hbmass in seven healthy, recreationally active men before (PRE), 5 h after (POST) and 5 days after (POST5) 4 days of HDTBR. The concentration of erythropoietin decreased from 7.1 ± 1.8 mIU ml(-1) at PRE to 5.2 ± 2.8 mIU ml(-1) at POST (mean ± SD; P = 0.028). Contrary to our hypothesis, Hbmass was increased from 817 ± 135 g at PRE to 849 ± 141 g at POST (P = 0.014) before decreasing below PRE to 789 ± 139 g at POST5 (P = 0.027). From PRE to POST, the concentration of haptoglobin increased from 0.54 ± 0.32 to 0.68 ± 0.28 g l(-1) (P = 0.013) and the concentration of bilirubin decreased from 0.50 ± 0.24 to 0.32 ± 0.11 mg dl(-1) (P = 0.054), suggesting that decreased RBC destruction might have contributed to the increased Hbmass. However, it is possible that spleen contraction following HDTBR also played a role in the increase in Hbmass at POST, but as the transient increase in Hbmass was unexpected, we did not collect data that would provide direct evidence for or against spleen contraction. From PRE to POST5, the concentration of soluble transferrin receptor decreased from 20.7 ± 3.9 to 17.1 ± 3.3 nmol l(-1) (P = 0.018) but the concentrations of ferritin, haptoglobin and bilirubin were not significantly altered, suggesting that the decrease in Hbmass was mediated by decreased RBC production rather than increased RBC destruction. Peak oxygen uptake decreased by 0.31 ± 0.16 l min(-1) from PRE to POST (P = 2 × 10(-4) ) but was not significantly altered at POST5 compared with PRE. Overall, these findings indicate that 4 days of HDTBR does not increase RBC destruction and that re-examination of the time course and mechanisms of Hbmass alterations following short-term spaceflight and simulated microgravity is warranted.
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Affiliation(s)
- Benjamin J. Ryan
- Department of Integrative Physiology, University of Colorado Boulder, Boulder, CO, USA
| | - Jesse A. Goodrich
- Department of Integrative Physiology, University of Colorado Boulder, Boulder, CO, USA
| | - Walter F. Schmidt
- Department of Sports Medicine/Sports Physiology, University of Bayreuth, Bayreuth, Germany
| | - Ellen R. Stothard
- Department of Integrative Physiology, University of Colorado Boulder, Boulder, CO, USA
| | - Kenneth P. Wright
- Department of Integrative Physiology, University of Colorado Boulder, Boulder, CO, USA
| | - William C. Byrnes
- Department of Integrative Physiology, University of Colorado Boulder, Boulder, CO, USA
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Integrative Conductance of Oxygen During Exercise at Altitude. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2016; 903:395-408. [PMID: 27343110 DOI: 10.1007/978-1-4899-7678-9_26] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
In the oxygen (O2) cascade downstream steps can never achieve higher flows of O2 than the preceding ones. At the lung the transfer of O2 is determined by the O2 gradient between the alveolar space and the lung capillaries and the O2 diffusing capacity (DLO2). While DLO2 may be increased several times during exercise by recruiting more lung capillaries and by increasing the oxygen carrying capacity of blood due to higher peripheral extraction of O2, the capacity to enhance the alveolocapillary PO2 gradient is more limited. The transfer of oxygen from the alveolar space to the hemoglobin (Hb) must overcome first the resistance offered by the alveolocapillary membrane (1/DM) and the capillary blood (1/θVc). The fractional contribution of each of these two components to DLO2 remains unknown. During exercise these resistances are reduced by the recruitment of lung capillaries. The factors that reduce the slope of the oxygen dissociation curve of the Hb (ODC) (i.e., lactic acidosis and hyperthermia) increase 1/θVc contributing to limit DLO2. These effects are accentuated in hypoxia. Reducing the size of the active muscle mass improves pulmonary gas exchange during exercise and reduces the rightward shift of the ODC. The flow of oxygen from the muscle capillaries to the mitochondria is pressumably limited by muscle O2 conductance (DmcO2) (an estimation of muscle oxygen diffusing capacity). However, during maximal whole body exercise in normoxia, a higher flow of O2 is achieved at the same pressure gradients after increasing blood [Hb], implying that in healthy humans exercising in normoxia there is a functional reserve in DmcO2. This conclusion is supported by the fact that during small muscle exercise in chronic hypoxia, peak exercise DmcO2 is similar to that observed during exercise in normoxia despite a markedly lower O2 pressure gradient driving diffusion.
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Siebenmann C, Cathomen A, Hug M, Keiser S, Lundby AK, Hilty MP, Goetze JP, Rasmussen P, Lundby C. Hemoglobin mass and intravascular volume kinetics during and after exposure to 3,454-m altitude. J Appl Physiol (1985) 2015; 119:1194-201. [DOI: 10.1152/japplphysiol.01121.2014] [Citation(s) in RCA: 73] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2014] [Accepted: 02/25/2015] [Indexed: 01/14/2023] Open
Abstract
High altitude (HA) exposure facilitates a rapid contraction of plasma volume (PV) and a slower occurring expansion of hemoglobin mass (Hbmass). The kinetics of the Hbmass expansion has never been examined by multiple repeated measurements, and this was our primary study aim. The second aim was to investigate the mechanisms mediating the PV contraction. Nine healthy, normally trained sea-level (SL) residents (8 males, 1 female) sojourned for 28 days at 3,454 m. Hbmass was measured and PV was estimated by carbon monoxide rebreathing at SL, on every 4th day at HA, and 1 and 2 wk upon return to SL. Four weeks at HA increased Hbmass by 5.26% (range 2.5-11.1%; P < 0.001). The individual Hbmass increases commenced with up to 12 days of delay and reached a maximal rate of 4.04 ± 1.02 g/day after 14.9 ± 5.2 days. The probability for Hbmass to plateau increased steeply after 20–24 days. Upon return to SL Hbmass decayed by −2.46 ± 2.3 g/day, reaching values similar to baseline after 2 wk. PV, aldosterone concentration, and renin activity were reduced at HA ( P < 0.001) while the total circulating protein mass remained unaffected. In summary, the Hbmass response to HA exposure followed a sigmoidal pattern with a delayed onset and a plateau after ∼3 wk. The decay rate of Hbmass upon descent to SL did not indicate major changes in the rate of erythrolysis. Moreover, our data support that PV contraction at HA is regulated by the renin-angiotensin-aldosterone axis and not by changes in oncotic pressure.
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Affiliation(s)
- C. Siebenmann
- Center for Integrative Human Physiology, Institute of Physiology, University of Zürich, Zürich, Switzerland
- Department of Environmental Physiology, School of Technology and Health, Royal Institute of Technology, Solna, Sweden
| | - A. Cathomen
- Institute of Human Movement Sciences and Sport, ETH Zürich, Zürich, Switzerland
| | - M. Hug
- Center for Integrative Human Physiology, Institute of Physiology, University of Zürich, Zürich, Switzerland
| | - S. Keiser
- Center for Integrative Human Physiology, Institute of Physiology, University of Zürich, Zürich, Switzerland
| | - A. K. Lundby
- Center for Integrative Human Physiology, Institute of Physiology, University of Zürich, Zürich, Switzerland
| | - M. P. Hilty
- Intensive Care Unit, University Hospital of Zürich, Zürich, Switzerland
| | - J. P. Goetze
- Department of Clinical Biochemistry, Copenhagen, and Aarhus University, Aarhus, Denmark
| | | | - C. Lundby
- Center for Integrative Human Physiology, Institute of Physiology, University of Zürich, Zürich, Switzerland
- Food and Nutrition and Sport Science, Gothenburg University, Gothenburg, Sweden
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Stembridge M, Ainslie PN, Shave R. Mechanisms underlying reductions in stroke volume at rest and during exercise at high altitude. Eur J Sport Sci 2015; 16:577-84. [DOI: 10.1080/17461391.2015.1071876] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Govus AD, Garvican-Lewis LA, Abbiss CR, Peeling P, Gore CJ. Pre-Altitude Serum Ferritin Levels and Daily Oral Iron Supplement Dose Mediate Iron Parameter and Hemoglobin Mass Responses to Altitude Exposure. PLoS One 2015; 10:e0135120. [PMID: 26263553 PMCID: PMC4532405 DOI: 10.1371/journal.pone.0135120] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2014] [Accepted: 07/17/2015] [Indexed: 11/18/2022] Open
Abstract
PURPOSE To investigate the influence of daily oral iron supplementation on changes in hemoglobin mass (Hbmass) and iron parameters after 2-4 weeks of moderate altitude exposure. METHODS Hematological data collected from 178 athletes (98 males, 80 females) exposed to moderate altitude (1,350-3,000 m) were analysed using linear regression to determine how altitude exposure combined with oral iron supplementation influenced Hbmass, total iron incorporation (TII) and blood iron parameters [ferritin and transferrin saturation (TSAT)]. RESULTS Altitude exposure (mean ± s: 21 ± 3 days) increased Hbmass by 1.1% [-0.4, 2.6], 3.3% [1.7, 4.8], and 4.0% [2.0, 6.1] from pre-altitude levels in athletes who ingested nil, 105 mg and 210 mg respectively, of oral iron supplement daily. Serum ferritin levels decreased by -33.2% [-46.9, -15.9] and 13.8% [-32.2, 9.7] from pre-altitude levels in athletes who supplemented with nil and 105 mg of oral iron supplement daily, but increased by 36.8% [1.3, 84.8] in athletes supplemented with 210 mg of oral iron daily. Finally, athletes who ingested either 105 mg or 210 mg of oral iron supplement daily had a greater TII compared with non-supplemented athletes (0 versus 105 mg: effect size (d) = -1.88 [-2.56, -1.17]; 0 versus 210 mg: effect size (d) = -2.87 [-3.88, -1.66]). CONCLUSION Oral iron supplementation during 2-4 weeks of moderate altitude exposure may enhance Hbmass production and assist the maintenance of iron balance in some athletes with low pre-altitude iron stores.
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Affiliation(s)
- Andrew D. Govus
- Centre for Exercise and Sports Science Research, School of Exercise and Health Science, Edith Cowan University, Joondalup, WA, Australia
- * E-mail:
| | - Laura A. Garvican-Lewis
- Department of Physiology, Australian Institute of Sport, Bruce, ACT, Australia
- Research Institute for Sport and Exercise, University of Canberra, Bruce, ACT, Australia
| | - Chris R. Abbiss
- Centre for Exercise and Sports Science Research, School of Exercise and Health Science, Edith Cowan University, Joondalup, WA, Australia
| | - Peter Peeling
- School of Sport Science, Exercise & Health, University of Western Australia, Crawley, WA, Australia
| | - Christopher J. Gore
- Department of Physiology, Australian Institute of Sport, Bruce, ACT, Australia
- Exercise Physiology Laboratory, Flinders University, Bedford Park, SA, Australia
- Research Institute for Sport and Exercise, University of Canberra, Bruce, ACT, Australia
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