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Martinez-Canton M, Galvan-Alvarez V, Martin-Rincon M, Calbet JAL, Gallego-Selles A. Unlocking peak performance: The role of Nrf2 in enhancing exercise outcomes and training adaptation in humans. Free Radic Biol Med 2024:S0891-5849(24)00597-5. [PMID: 39151836 DOI: 10.1016/j.freeradbiomed.2024.08.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/30/2024] [Revised: 07/30/2024] [Accepted: 08/10/2024] [Indexed: 08/19/2024]
Abstract
Since the discovery of the nuclear factor erythroid-derived 2-like 2 (Nrf2) transcription factor thirty years ago, it has been shown that it regulates more than 250 genes involved in a multitude of biological processes, including redox balance, mitochondrial biogenesis, metabolism, detoxification, cytoprotection, inflammation, immunity, autophagy, cell differentiation, and xenobiotic metabolism. In skeletal muscle, Nrf2 signalling is primarily activated in response to perturbation of redox balance by reactive oxygen species or electrophiles. Initial investigations into human skeletal muscle Nrf2 responses to exercise, dating back roughly a decade, have consistently indicated that exercise-induced ROS production stimulates Nrf2 signalling. Notably, recent studies employing Nrf2 knockout mice have revealed impaired skeletal muscle contractile function characterised by reduced force output and increased fatigue susceptibility compared to wild-type counterparts. These deficiencies partially stem from diminished basal mitochondrial respiratory capacity and an impaired capacity to upregulate specific mitochondrial proteins in response to training, findings corroborated by inducible muscle-specific Nrf2 knockout models. In humans, baseline Nrf2 expression in skeletal muscle correlates with maximal oxygen uptake and high-intensity exercise performance. This manuscript delves into the mechanisms underpinning Nrf2 signalling in response to acute exercise in human skeletal muscle, highlighting the involvement of ROS, antioxidants and Keap1/Nrf2 signalling in exercise performance. Furthermore, it explores Nrf2's role in mediating adaptations to chronic exercise and its impact on overall exercise performance. Additionally, the influence of diet and certain supplements on basal Nrf2 expression and its role in modulating acute and chronic exercise responses are briefly addressed.
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Affiliation(s)
- Miriam Martinez-Canton
- Department of Physical Education, University of Las Palmas de Gran Canaria, Campus Universitario de Tafira s/n, Las Palmas de Gran Canaria, 35017, Spain; Research Institute of Biomedical and Health Sciences (IUIBS), University of Las Palmas de Gran Canaria, Paseo Blas Cabrera Felipe "Físico" s/n, 35017, Las Palmas de Gran Canaria, Spain
| | - Victor Galvan-Alvarez
- Department of Physical Education, University of Las Palmas de Gran Canaria, Campus Universitario de Tafira s/n, Las Palmas de Gran Canaria, 35017, Spain; Research Institute of Biomedical and Health Sciences (IUIBS), University of Las Palmas de Gran Canaria, Paseo Blas Cabrera Felipe "Físico" s/n, 35017, Las Palmas de Gran Canaria, Spain
| | - Marcos Martin-Rincon
- Department of Physical Education, University of Las Palmas de Gran Canaria, Campus Universitario de Tafira s/n, Las Palmas de Gran Canaria, 35017, Spain; Research Institute of Biomedical and Health Sciences (IUIBS), University of Las Palmas de Gran Canaria, Paseo Blas Cabrera Felipe "Físico" s/n, 35017, Las Palmas de Gran Canaria, Spain
| | - Jose A L Calbet
- Department of Physical Education, University of Las Palmas de Gran Canaria, Campus Universitario de Tafira s/n, Las Palmas de Gran Canaria, 35017, Spain; Research Institute of Biomedical and Health Sciences (IUIBS), University of Las Palmas de Gran Canaria, Paseo Blas Cabrera Felipe "Físico" s/n, 35017, Las Palmas de Gran Canaria, Spain; Department of Physical Performance, The Norwegian School of Sport Sciences, Postboks, 4014 Ulleval Stadion, 0806, Oslo, Norway; School of Kinesiology, Faculty of Education, The University of British Columbia, Vancouver, BC, Canada.
| | - Angel Gallego-Selles
- Department of Physical Education, University of Las Palmas de Gran Canaria, Campus Universitario de Tafira s/n, Las Palmas de Gran Canaria, 35017, Spain; Research Institute of Biomedical and Health Sciences (IUIBS), University of Las Palmas de Gran Canaria, Paseo Blas Cabrera Felipe "Físico" s/n, 35017, Las Palmas de Gran Canaria, Spain
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Beever AT, Zhuang AY, Murias JM, Aboodarda SJ, MacInnis MJ. Effects of acute simulated altitude on the maximal lactate steady state in humans. Am J Physiol Regul Integr Comp Physiol 2024; 327:R195-R207. [PMID: 38842515 DOI: 10.1152/ajpregu.00065.2024] [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: 03/12/2024] [Revised: 05/03/2024] [Accepted: 05/17/2024] [Indexed: 06/07/2024]
Abstract
We sought to determine the effects of acute simulated altitude on the maximal lactate steady state (MLSS) and physiological responses to cycling at and 10 W above the MLSS-associated power output (PO) (MLSSp and MLSSp+10, respectively). Eleven (4 females) participants (means [SD]; 28 [4] yr; V̇o2max: 54.3 [6.9] mL·kg-1·min-1) acclimatized to ∼1,100 m performed 30-min constant PO trials in simulated altitudes of 0 m sea level (SL), 1,111 m mild altitude (MILD), and 2,222 m moderate altitude (MOD). MLSSp, defined as the highest PO with stable (<1 mM change) blood lactate concentration ([BLa]) between 10 and 30 min, was significantly lower in MOD (209 [54] W) compared with SL (230 [56] W; P < 0.001) and MILD (225 [58] W; P = 0.001), but MILD and SL were not different (P = 0.12). V̇o2 and V̇co2 decreased at higher simulated altitudes due to lower POs (P < 0.05), but other end-exercise physiological responses (e.g., [BLa], ventilation [V̇e], heart rate [HR]) were not different between conditions at MLSSp or MLSSp + 10 (P > 0.05). At the same absolute intensity (MLSSp for MILD), [BLa], HR, and V̇E and all perceptual variables were exacerbated in MOD compared with SL and MILD (P < 0.05). Maximum voluntary contraction, voluntary activation, and potentiated twitch forces were exacerbated at MLSSp + 10 relative to MLSSp within conditions (P < 0.05); however, condition did not affect performance fatiguability at the same relative or absolute intensity (P > 0.05). As MLSSp decreased in hypoxia, adjustments in PO are needed to ensure the same relative intensity across altitudes, but common indices of exercise intensity may facilitate exercise prescription and monitoring in hypoxia.NEW & NOTEWORTHY This study demonstrates the power output and metabolic rate associated with the maximal lactate steady-state (MLSS) decline in response to simulated altitude; however, common indices of exercise intensity remained unchanged when cycling was performed at the work rate associated with MLSS at each simulated altitude. These results support previous studies that investigated the effects of hypoxia on alternative measures of the critical intensity of exercise and will inform exercise prescription/monitoring across altitudes.
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Affiliation(s)
- Austin T Beever
- Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada
| | - Andrea Y Zhuang
- Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada
| | - Juan M Murias
- Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada
| | - Saied J Aboodarda
- Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada
| | - Martin J MacInnis
- Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada
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Bertucci DR, de Carvalho CD, Scariot PPM, Kalva-Filho CA, Luches-Pereira G, Arruda TB, Alves IS, Gardim CB, Castiglia M, Riberto M, Gobatto CA, Papoti M. Four-week experimental plus 1-week taper period using live high train low does not alter muscle glycogen content. Eur J Appl Physiol 2024; 124:1795-1805. [PMID: 38231229 DOI: 10.1007/s00421-023-05404-z] [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: 06/23/2023] [Accepted: 12/12/2023] [Indexed: 01/18/2024]
Abstract
This study aimed to investigate the effects of a 4-week live high train low (LHTL; FiO2 ~ 13.5%), intervention, followed by a tapering phase, on muscle glycogen concentration. Fourteen physically active males (28 ± 6 years, 81.6 ± 15.4 kg, 179 ± 5.2 cm) were divided into a control group (CON; n = 5), and the group that performed the LHTL, which was exposed to hypoxia (LHTL; n = 9). The subjects trained using a one-legged knee extension exercise, which enabled four experimental conditions: leg training in hypoxia (TLHYP); leg control in hypoxia (CLHYP, n = 9); leg trained in normoxia (TLNOR, n = 5), and leg control in normoxia (CLNOR, n = 5). All participants performed 18 training sessions lasting between 20 and 45 min [80-200% of intensity corresponding to the time to exhaustion (TTE) reached in the graded exercise test]. Additionally, participants spent approximately 10 h day-1 in either a normobaric hypoxic environment (14.5% FiO2; ~ 3000 m) or a control condition (i.e., staying in similar tents on ~ 530 m). Thereafter, participants underwent a taper protocol consisting of six additional training sessions with a reduced training load. SpO2 was lower, and the hypoxic dose was higher in LHTL compared to CON (p < 0.001). After 4 weeks, glycogen had increased significantly only in the TLNOR and TLHYP groups and remained elevated after the taper (p < 0.016). Time to exhaustion in the LHTL increased after both the 4-week training period and the taper compared to the baseline (p < 0.001). Although the 4-week training promoted substantial increases in muscle glycogen content, TTE increased in LHTL condition.
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Affiliation(s)
- Danilo R Bertucci
- Triângulo Mineiro Federal University (UFTM), Av. Frei Paulino, nº 30, Abadia, Uberaba, MG, Brazil
| | - Carlos Dellavechia de Carvalho
- Ribeirão Preto Medical School, University of São Paulo (FMRP-USP), Avenida Bandeirantes, 3900, Vila Monte Alegre, Ribeirão Prêto, SP, Brazil.
| | - Pedro P M Scariot
- Faculty of Applied Sciences, State University of Campinas (FCA-UNICAMP), R. Pedro Zaccaria, 1300, Limeira, SP, Brazil
| | - Carlos A Kalva-Filho
- Human Movement Research Laboratory (MOVI-LAB), São Paulo State University (UNESP), Av. Eng. Luiz Edmundo C. Coube, nº 14-01, Núcleo Habitacional Presidente Geisel, Bauru, SP, Brazil
| | - Gabriel Luches-Pereira
- School of Physical Education and Sports of Ribeirão Preto, University of São Paulo (EEFERP-USP), Avenida Bandeirantes, 3900, Vila Monte Alegre, Ribeirão Preto, SP, Brazil
| | - Tarine B Arruda
- Ribeirão Preto Medical School, University of São Paulo (FMRP-USP), Avenida Bandeirantes, 3900, Vila Monte Alegre, Ribeirão Prêto, SP, Brazil
| | - Isabela S Alves
- School of Physical Education and Sports of Ribeirão Preto, University of São Paulo (EEFERP-USP), Avenida Bandeirantes, 3900, Vila Monte Alegre, Ribeirão Preto, SP, Brazil
| | - Camila B Gardim
- Ribeirão Preto Medical School, University of São Paulo (FMRP-USP), Avenida Bandeirantes, 3900, Vila Monte Alegre, Ribeirão Prêto, SP, Brazil
| | - Marcelo Castiglia
- Ribeirão Preto Medical School, University of São Paulo (FMRP-USP), Avenida Bandeirantes, 3900, Vila Monte Alegre, Ribeirão Prêto, SP, Brazil
| | - Marcelo Riberto
- Ribeirão Preto Medical School, University of São Paulo (FMRP-USP), Avenida Bandeirantes, 3900, Vila Monte Alegre, Ribeirão Prêto, SP, Brazil
| | - Claudio Alexandre Gobatto
- Faculty of Applied Sciences, State University of Campinas (FCA-UNICAMP), R. Pedro Zaccaria, 1300, Limeira, SP, Brazil
| | - Marcelo Papoti
- Ribeirão Preto Medical School, University of São Paulo (FMRP-USP), Avenida Bandeirantes, 3900, Vila Monte Alegre, Ribeirão Prêto, SP, Brazil
- School of Physical Education and Sports of Ribeirão Preto, University of São Paulo (EEFERP-USP), Avenida Bandeirantes, 3900, Vila Monte Alegre, Ribeirão Preto, SP, Brazil
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Galvan-Alvarez V, Gallego-Selles A, Martinez-Canton M, Perez-Suarez I, Garcia-Gonzalez E, Martin-Rincon M, Calbet JAL. Physiological and molecular predictors of cycling sprint performance. Scand J Med Sci Sports 2024; 34:e14545. [PMID: 38268080 DOI: 10.1111/sms.14545] [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: 09/04/2023] [Revised: 11/15/2023] [Accepted: 11/17/2023] [Indexed: 01/26/2024]
Abstract
The study aimed to identify novel muscle phenotypic factors that could determine sprint performance using linear regression models including the lean mass of the lower extremities (LLM), myosin heavy chain composition (MHC), and proteins and enzymes implicated in glycolytic and aerobic energy generation (citrate synthase, OXPHOS proteins), oxygen transport and diffusion (myoglobin), ROS sensing (Nrf2/Keap1), antioxidant enzymes, and proteins implicated in calcium handling. For this purpose, body composition (dual-energy X-ray absorptiometry) and sprint performance (isokinetic 30-s Wingate test: peak and mean power output, Wpeak and Wmean ) were measured in young physically active adults (51 males and 10 females), from which a resting muscle biopsy was obtained from the musculus vastus lateralis. Although females had a higher percentage of MHC I, SERCA2, pSer16 /Thr17 -phospholamban, and Calsequestrin 2 protein expressions (all p < 0.05), and 18.4% lower phosphofructokinase 1 protein expression than males (p < 0.05), both sexes had similar sprint performance when it was normalized to body weight or LLM. Multiple regression analysis showed that Wpeak could be predicted from LLM, SDHB, Keap1, and MHC II % (R 2 = 0.62, p < 0.001), each variable contributing to explain 46.4%, 6.3%, 4.4%, and 4.3% of the variance in Wpeak , respectively. LLM and MHC II % explained 67.5% and 2.1% of the variance in Wmean , respectively (R 2 = 0.70, p < 0.001). The present investigation shows that SDHB and Keap1, in addition to MHC II %, are relevant determinants of peak power output during sprinting.
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Affiliation(s)
- Victor Galvan-Alvarez
- Department of Physical Education, University of Las Palmas de Gran Canaria, Campus Universitario de Tafira s/n, Las Palmas de Gran Canaria, Spain
- Research Institute of Biomedical and Health Sciences (IUIBS), University of Las Palmas de Gran Canaria, Paseo Blas Cabrera Felipe "Físico" s/n, Las Palmas de Gran Canaria, Spain
| | - Angel Gallego-Selles
- Department of Physical Education, University of Las Palmas de Gran Canaria, Campus Universitario de Tafira s/n, Las Palmas de Gran Canaria, Spain
- Research Institute of Biomedical and Health Sciences (IUIBS), University of Las Palmas de Gran Canaria, Paseo Blas Cabrera Felipe "Físico" s/n, Las Palmas de Gran Canaria, Spain
| | - Miriam Martinez-Canton
- Department of Physical Education, University of Las Palmas de Gran Canaria, Campus Universitario de Tafira s/n, Las Palmas de Gran Canaria, Spain
- Research Institute of Biomedical and Health Sciences (IUIBS), University of Las Palmas de Gran Canaria, Paseo Blas Cabrera Felipe "Físico" s/n, Las Palmas de Gran Canaria, Spain
| | - Ismael Perez-Suarez
- Department of Physical Education, University of Las Palmas de Gran Canaria, Campus Universitario de Tafira s/n, Las Palmas de Gran Canaria, Spain
- Research Institute of Biomedical and Health Sciences (IUIBS), University of Las Palmas de Gran Canaria, Paseo Blas Cabrera Felipe "Físico" s/n, Las Palmas de Gran Canaria, Spain
| | - Eduardo Garcia-Gonzalez
- Department of Physical Education, University of Las Palmas de Gran Canaria, Campus Universitario de Tafira s/n, Las Palmas de Gran Canaria, Spain
- Research Institute of Biomedical and Health Sciences (IUIBS), University of Las Palmas de Gran Canaria, Paseo Blas Cabrera Felipe "Físico" s/n, Las Palmas de Gran Canaria, Spain
| | - Marcos Martin-Rincon
- Department of Physical Education, University of Las Palmas de Gran Canaria, Campus Universitario de Tafira s/n, Las Palmas de Gran Canaria, Spain
- Research Institute of Biomedical and Health Sciences (IUIBS), University of Las Palmas de Gran Canaria, Paseo Blas Cabrera Felipe "Físico" s/n, Las Palmas de Gran Canaria, Spain
| | - Jose A L Calbet
- Department of Physical Education, University of Las Palmas de Gran Canaria, Campus Universitario de Tafira s/n, Las Palmas de Gran Canaria, Spain
- Research Institute of Biomedical and Health Sciences (IUIBS), University of Las Palmas de Gran Canaria, Paseo Blas Cabrera Felipe "Físico" s/n, Las Palmas de Gran Canaria, Spain
- Department of Physical Performance, The Norwegian School of Sport Sciences, Postboks, Oslo, Norway
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Ciarlone GE, Swift JM, Williams BT, Mahon RT, Roney NG, Yu T, Gasier HG. 5-Hydroxymethylfurfural reduces skeletal muscle superoxide production and modifies force production in rats exposed to hypobaric hypoxia. Physiol Rep 2023; 11:e15743. [PMID: 37491570 PMCID: PMC10368650 DOI: 10.14814/phy2.15743] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2023] [Revised: 05/17/2023] [Accepted: 05/25/2023] [Indexed: 07/27/2023] Open
Abstract
Decreased blood-tissue oxygenation at high altitude (HA) increases mitochondrial oxidant production and reduces exercise capacity. 5-Hydroxymethylfurfural (5-HMF) is an antioxidant that increases hemoglobin's binding affinity for oxygen. For these reasons, we hypothesized that 5-HMF would improve muscle performance in rats exposed to a simulated HA of ~5500 m. A secondary objective was to measure mitochondrial activity and dynamic regulation of fission and fusion because they are linked processes impacted by HA. Fisher 344 rats received 5-HMF (40 mg/kg/day) or vehicle during exposure to sea level or HA for 72 h. Right ankle plantarflexor muscle function was measured pre- and post-exposure. Post-exposure measurements included arterial blood gas and complete blood count, flexor digitorum brevis myofiber superoxide production and mitochondrial membrane potential (ΔΨm), and mitochondrial dynamic regulation in the soleus muscle. HA reduced blood oxygenation, increased superoxide levels and lowered ΔΨm, responses that were accompanied by decreased peak isometric torque and force production at frequencies >75 Hz. 5-HMF increased isometric force production and lowered oxidant production at sea level. In HA exposed animals, 5-HMF prevented a decline in isometric force production at 75-125 Hz, prevented an increase in superoxide levels, further decreased ΔΨm, and increased mitochondrial fusion 2 protein expression. These results suggest that 5-HMF may prevent a decrease in hypoxic force production during submaximal isometric contractions by an antioxidant mechanism.
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Affiliation(s)
- Geoffrey E Ciarlone
- Undersea Medicine Department, Naval Medical Research Center, Silver Spring, Maryland, USA
- Department of Military & Emergency Medicine, Uniformed Services University of the Health Sciences, Bethesda, Maryland, USA
| | - Joshua M Swift
- Undersea Medicine Department, Naval Medical Research Center, Silver Spring, Maryland, USA
- Department of Military & Emergency Medicine, Uniformed Services University of the Health Sciences, Bethesda, Maryland, USA
| | - Brian T Williams
- Undersea Medicine Department, Naval Medical Research Center, Silver Spring, Maryland, USA
- The Henry M. Jackson Foundation for the Advancement of Military Medicine, Inc, Bethesda, Maryland, USA
| | - Richard T Mahon
- Undersea Medicine Department, Naval Medical Research Center, Silver Spring, Maryland, USA
- The Henry M. Jackson Foundation for the Advancement of Military Medicine, Inc, Bethesda, Maryland, USA
| | - Nicholas G Roney
- Undersea Medicine Department, Naval Medical Research Center, Silver Spring, Maryland, USA
| | - Tianzheng Yu
- Department of Military & Emergency Medicine, Uniformed Services University of the Health Sciences, Bethesda, Maryland, USA
- The Henry M. Jackson Foundation for the Advancement of Military Medicine, Inc, Bethesda, Maryland, USA
| | - Heath G Gasier
- Department of Military & Emergency Medicine, Uniformed Services University of the Health Sciences, Bethesda, Maryland, USA
- The Duke Center for Hyperbaric Medicine & Environmental Physiology, Duke University, Durham, North Carolina, USA
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The role of exercise and hypoxia on glucose transport and regulation. Eur J Appl Physiol 2023; 123:1147-1165. [PMID: 36690907 DOI: 10.1007/s00421-023-05135-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2022] [Accepted: 01/06/2023] [Indexed: 01/25/2023]
Abstract
Muscle glucose transport activity increases with an acute bout of exercise, a process that is accomplished by the translocation of glucose transporters to the plasma membrane. This process remains intact in the skeletal muscle of individuals with insulin resistance and type 2 diabetes mellitus (T2DM). Exercise training is, therefore, an important cornerstone in the management of individuals with T2DM. However, the acute systemic glucose responses to carbohydrate ingestion are often augmented during the early recovery period from exercise, despite increased glucose uptake into skeletal muscle. Accordingly, the first aim of this review is to summarize the knowledge associated with insulin action and glucose uptake in skeletal muscle and apply these to explain the disparate responses between systemic and localized glucose responses post-exercise. Herein, the importance of muscle glycogen depletion and the key glucoregulatory hormones will be discussed. Glucose uptake can also be stimulated independently by hypoxia; therefore, hypoxic training presents as an emerging method for enhancing the effects of exercise on glucose regulation. Thus, the second aim of this review is to discuss the potential for systemic hypoxia to enhance the effects of exercise on glucose regulation.
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Combined Effects of Hypocapnic Hyperventilation and Hypoxia on Exercise Performance and Metabolic Responses During the Wingate Anaerobic Test. Int J Sports Physiol Perform 2023; 18:69-76. [PMID: 36521190 DOI: 10.1123/ijspp.2022-0121] [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: 03/25/2022] [Revised: 08/25/2022] [Accepted: 09/13/2022] [Indexed: 12/23/2022]
Abstract
Hypoxia during supramaximal exercise reduces aerobic metabolism with a compensatory increase in anaerobic metabolism without affecting exercise performance. A similar response is elicited by preexercise voluntary hypocapnic hyperventilation, but it remains unclear whether hypocapnic hyperventilation and hypoxia additively reduce aerobic metabolism and increase anaerobic metabolism during supramaximal exercise. To address that issue, 12 healthy subjects (8 males and 4 females) performed the 30-second Wingate anaerobic test (WAnT) after (1) spontaneous breathing in normoxia (control, ∼21% fraction of inspired O2 [FiO2]), (2) voluntary hypocapnic hyperventilation in normoxia (hypocapnia, ∼21% FiO2), (3) spontaneous breathing in hypoxia (hypoxia, ∼11% FiO2), or (4) voluntary hypocapnic hyperventilation in hypoxia (combined, ∼11% FiO2). Mean power output during the 30-second WAnT was similar among the control (561 [133] W), hypocapnia (563 [140] W), hypoxia (558 [131] W), and combined (560 [133] W) trials (P = .778). Oxygen uptake during the 30-second WAnT was lower in the hypocapnia (1523 [318] mL/min), hypoxia (1567 [300] mL/min), and combined (1203 [318] mL/min) trials than in the control (1935 [250] mL/min) trial, and the uptake in the combined trial was lower than in the hypocapnia or hypoxia trial (all P < .001). Oxygen deficit, an index of anaerobic metabolism, was higher in the hypocapnia (38.4 [7.3] mL/kg), hypoxia (37.8 [6.8] mL/kg), and combined (40.7 [6.9] mL/kg) trials than in the control (35.0 [6.8] mL/kg) trial, and the debt was greater in the combined trial than in the hypocapnia or hypoxia trial (all P < .003). Our results suggest that voluntary hypocapnic hyperventilation and hypoxia additively reduce aerobic metabolism and increase anaerobic metabolism without affecting exercise performance during the 30-second WAnT.
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High-Intensity Conditioning for Combat Athletes: Practical Recommendations. APPLIED SCIENCES-BASEL 2021. [DOI: 10.3390/app112210658] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Combat sports have been practiced for millennia and today are predominant sports at the Olympic games, with international organizations that host world, continental and national championships at amateur standard. There are also an increasing number of professional combat sports with global audiences. The growing popularity of professional combat sports and their importance at the Olympic games have led to an increase in scientific studies that characterize the physical, physiological, nutritional, biomechanical and training strategies of combat sports athletes. These studies characterize combat sports as high-intensity sports which require training strategies to develop the high-intensity capabilities of athletes. Therefore, the aim of this article is to (i) summarize the physiological demands of combat sports; (ii) present the primary considerations required to program high-intensity conditioning for athletes; (iii) define and present key high-intensity conditioning methods; and (iv) provide guidance for scientists and coaches to help prepare athletes under common but differing circumstances.
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Zagatto AM, Bishop DJ, Antunes BM, Beck WR, Malta ES, de Poli RAB, Cavaglieri CR, Chacon-Mikahil MPT, Castro A. Impacts of high-intensity exercise on the metabolomics profile of human skeletal muscle tissue. Scand J Med Sci Sports 2021; 32:402-413. [PMID: 34706104 DOI: 10.1111/sms.14086] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2021] [Revised: 10/13/2021] [Accepted: 10/25/2021] [Indexed: 01/06/2023]
Abstract
The study aimed to identify and quantify the metabolites profile and metabolic pathways in human muscle tissue engaged during exhaustive high-intensity cycling exercise. Seven healthy physically active men performed a graded exercise test and an exhaustive supramaximal effort at 115% of maximal aerobic power with muscles biopsies performed in rest and immediately after exhaustion for quantifying of muscle metabolites changes by 1 H-NMR spectroscopy. The time until exhaustion (tlim) recorded was 224.7 ± 35.5 s whereas the muscle pH at exhaustion was 6.48 ± 0.05. A total of 54 metabolites were identified and quantified. The most enriched and impacted pathways included: beta oxidation of very long chain fatty acids, mitochondrial electron transport chain, alanine aspartate, and glutamate metabolism, citric acid cycle, arginine biosynthesis, propanoate metabolism, threonine and 2-oxobutanoate degradation and pyruvate metabolism. In addition, the muscle concentrations in Post exercise, compared to Pre increased significantly (p < 0.0398) for fumarate (42.0%), succinate (101.2%), glucose (249.7%), lactate (122.8%), O-acetylcarnitine (164.7%), glycerol (79.3%), AMP (288.2%), 2-oxobutyrate (121.0%), and methanol (58.5%), whereas decreased significantly (p < 0.010) for creatine phosphate (-70.2%), ADP (-56.5%), carnitine (-33.5%), and glutamate (-42.3%). Only the succinate was significantly correlated with tlim (r = -0.76; p = 0.0497). Besides the classical expected contribution of glycolytic and phosphagen energetic pathways, it was demonstrated that the high-intensity exercise is also associated with pathways indicatives of amino acid and fatty acid oxidation metabolisms, highlighting the inverse relation between changes in the intramuscular succinate levels and tlim.
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Affiliation(s)
- Alessandro M Zagatto
- Laboratory of Physiology and Sport Performance (LAFIDE), São Paulo State University (UNESP), Bauru, Brazil
| | - David J Bishop
- Institute for Health and Sport (iHeS), Victoria University, Footscray, Victoria, Australia
| | - Barbara Moura Antunes
- Laboratory of Physiology and Sport Performance (LAFIDE), São Paulo State University (UNESP), Bauru, Brazil
| | - Wladimir R Beck
- Federal University of Sao Carlos (UFSCar), Sao Carlos, Brazil
| | - Elvis S Malta
- Laboratory of Physiology and Sport Performance (LAFIDE), São Paulo State University (UNESP), Bauru, Brazil
| | - Rodrigo A B de Poli
- Laboratory of Physiology and Sport Performance (LAFIDE), São Paulo State University (UNESP), Bauru, Brazil
| | - Claudia R Cavaglieri
- Laboratory of Exercise Physiology, Faculty of Physical Education, University of Campinas (UNICAMP), Campinas, Brazil
| | | | - Alex Castro
- Laboratory of Exercise Physiology, Faculty of Physical Education, University of Campinas (UNICAMP), Campinas, Brazil
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Heden TD, Chow LS, Hughey CC, Mashek DG. Regulation and role of glycophagy in skeletal muscle energy metabolism. Autophagy 2021; 18:1078-1089. [PMID: 34506219 DOI: 10.1080/15548627.2021.1969633] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
Abstract
Glycophagy is the autophagic degradation of glycogen via the lysosomal enzyme GAA/alpha-acid glucosidase. Glycophagy is considered a housekeeping process to degrade poorly branched glycogen particles, but the regulation and role of glycophagy in skeletal muscle metabolism remains enigmatic. Herein, prior muscle contraction promoted glycogen supercompensation 24 and 48 h post contraction, an effect associated with reduced glycophagy. Moreover, NOTCH or cAMP signaling promoted glycophagy, whereas acute glycophagy deficiency rewired cell metabolism by reducing glycolysis and enhancing AMPK and PPAR signaling and fatty acid and glutamine metabolism. These metabolic adaptations were associated with reduced inflammation and triglyceride content but enhanced phosphoinositide 3-kinase (PI3K)-AKT/protein kinase B signaling and insulin action, the latter of which was abolished by exogenous oxidative stress. Collectively, these data suggest glycophagy is dynamically regulated, while the function of glycophagy can be extended beyond a housekeeping process to having an additional role in regulating energy metabolism and insulin action.Abbreviations: AMPK, AMP-activated protein kinase; ASM, acid soluble metabolites; cAMP, cyclic adenosine monophosphate; EPS, electrical pulse stimulation; FCCP, carbonyl cyanide-p-trifluoromethoxyphenylhydrazone; GAA, glucosidase, alpha, acid; mTOR, mechanistic target of rapamycin kinase; NAD, nicotinamide adenine dinucleotide; PARP, poly (ADP-ribose) polymerase family; PI3K, phosphoinositide 3-kinase; PPAR, peroxisome proliferator activated receptor ; PYGM, muscle glycogen phosphorylase; STBD1, starch binding domain 1; TFEB, transcription factor EB.
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Affiliation(s)
- Timothy D Heden
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN, USA
| | - Lisa S Chow
- Department of Medicine, Division of Endocrinology
| | - Curtis C Hughey
- Department of Medicine, Division of Molecular Medicine, University of Minnesota, Minneapolis, MN, USA
| | - Douglas G Mashek
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN, USA.,Department of Medicine, Division of Endocrinology
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11
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Hostrup M, Cairns SP, Bangsbo J. Muscle Ionic Shifts During Exercise: Implications for Fatigue and Exercise Performance. Compr Physiol 2021; 11:1895-1959. [PMID: 34190344 DOI: 10.1002/cphy.c190024] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Exercise causes major shifts in multiple ions (e.g., K+ , Na+ , H+ , lactate- , Ca2+ , and Cl- ) during muscle activity that contributes to development of muscle fatigue. Sarcolemmal processes can be impaired by the trans-sarcolemmal rundown of ion gradients for K+ , Na+ , and Ca2+ during fatiguing exercise, while changes in gradients for Cl- and Cl- conductance may exert either protective or detrimental effects on fatigue. Myocellular H+ accumulation may also contribute to fatigue development by lowering glycolytic rate and has been shown to act synergistically with inorganic phosphate (Pi) to compromise cross-bridge function. In addition, sarcoplasmic reticulum Ca2+ release function is severely affected by fatiguing exercise. Skeletal muscle has a multitude of ion transport systems that counter exercise-related ionic shifts of which the Na+ /K+ -ATPase is of major importance. Metabolic perturbations occurring during exercise can exacerbate trans-sarcolemmal ionic shifts, in particular for K+ and Cl- , respectively via metabolic regulation of the ATP-sensitive K+ channel (KATP ) and the chloride channel isoform 1 (ClC-1). Ion transport systems are highly adaptable to exercise training resulting in an enhanced ability to counter ionic disturbances to delay fatigue and improve exercise performance. In this article, we discuss (i) the ionic shifts occurring during exercise, (ii) the role of ion transport systems in skeletal muscle for ionic regulation, (iii) how ionic disturbances affect sarcolemmal processes and muscle fatigue, (iv) how metabolic perturbations exacerbate ionic shifts during exercise, and (v) how pharmacological manipulation and exercise training regulate ion transport systems to influence exercise performance in humans. © 2021 American Physiological Society. Compr Physiol 11:1895-1959, 2021.
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Affiliation(s)
- Morten Hostrup
- Section of Integrative Physiology, Department of Nutrition, Exercise and Sports, University of Copenhagen, Copenhagen, Denmark
| | - Simeon Peter Cairns
- SPRINZ, School of Sport and Recreation, Auckland University of Technology, Auckland, New Zealand.,Health and Rehabilitation Research Institute, Auckland University of Technology, Auckland, New Zealand
| | - Jens Bangsbo
- Section of Integrative Physiology, Department of Nutrition, Exercise and Sports, University of Copenhagen, Copenhagen, Denmark
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12
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Sumi D, Hayashi N, Yatsutani H, Goto K. Exogenous glucose oxidation during endurance exercise in hypoxia. Physiol Rep 2020; 8:e14457. [PMID: 32652803 PMCID: PMC7354086 DOI: 10.14814/phy2.14457] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2020] [Revised: 04/27/2020] [Accepted: 04/30/2020] [Indexed: 12/22/2022] Open
Abstract
Purpose Endurance exercise in hypoxia promotes carbohydrate (CHO) metabolism. However, detailed CHO metabolism remains unclear. The purpose of this study was to evaluate the effects of endurance exercise in moderate hypoxia on exogenous glucose oxidation at the same energy expenditure or relative exercise intensity. Methods Nine active healthy males completed three trials on different days, consisting of 30 min of running at each exercise intensity: (a) exercise at 65% of normoxic maximal oxygen uptake in normoxia [NOR, fraction of inspired oxygen (FiO2) = 20.9%, 10.6 ± 0.3 km/h], (b) exercise at the same relative exercise intensity with NOR in hypoxia (HYPR, FiO2 = 14.5%, 9.4 ± 0.3 km/h), and (c) exercise at the same absolute exercise intensity with NOR in hypoxia (HYPA, FiO2 = 14.5%, 10.6 ± 0.3 km/h). The subjects consumed 113C‐labeled glucose immediately before exercise, and expired gas samples were collected during exercise to determine 13C‐excretion (calculated by 13CO2/12CO2). Results The exercise‐induced increase in blood lactate was significantly augmented in the HYPA than in the NOR and HYPR (p = .001). HYPA involved a significantly higher respiratory exchange ratio (RER) during exercise compared with the other two trials (p < .0001). In contrast, exogenous glucose oxidation (13C‐excretion) during exercise was significantly lower in the HYPA than in the NOR (p = .03). No significant differences were observed in blood lactate elevation, RER, or exogenous glucose oxidation between NOR and HYPR. Conclusion Endurance exercise in moderate hypoxia caused a greater exercise‐induced blood lactate elevation and RER compared with the running exercise at same absolute exercise intensity in normoxia. However, exogenous glucose oxidation (13C‐excretion) during exercise was attenuated compared with the same exercise in normoxia.
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Affiliation(s)
- Daichi Sumi
- Graduate School of Sports and Health Science, Ritsumeikan University, Kusatsu, Shiga, Japan.,Research Fellow of Japan Society for the Promotion of Science, Chiyodaku, Japan
| | - Nanako Hayashi
- Graduate School of Sports and Health Science, Ritsumeikan University, Kusatsu, Shiga, Japan
| | - Haruka Yatsutani
- Graduate School of Sports and Health Science, Ritsumeikan University, Kusatsu, Shiga, Japan
| | - Kazushige Goto
- Graduate School of Sports and Health Science, Ritsumeikan University, Kusatsu, Shiga, Japan.,Faculty of Sports and Health Science, Ritsumeikan University, Kusatsu, Shiga, Japan
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13
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Handzlik MK, Constantin‐Teodosiu D, Greenhaff PL, Cole MA. Increasing cardiac pyruvate dehydrogenase flux during chronic hypoxia improves acute hypoxic tolerance. J Physiol 2018; 596:3357-3369. [PMID: 29383727 PMCID: PMC6068244 DOI: 10.1113/jp275357] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2017] [Accepted: 01/19/2018] [Indexed: 01/18/2023] Open
Abstract
KEY POINTS The cardiac metabolic reprogramming seen in heart diseases such as myocardial infarction and hypertrophy shares similarities with that seen in chronic hypoxia, but understanding of how the hypoxic heart responds to further hypoxic challenge - hypoxic tolerance - is limited. The pyruvate dehydrogenase complex serves to control irreversible decarboxylation of pyruvate within mitochondria, and is a key regulator of substrate metabolism, potentially regulating hypoxic tolerance. Acute activation of the pyruvate dehydrogenase complex did not improve cardiac function during acute hypoxia; however, simultaneous activation of the pyruvate dehydrogenase complex during chronic hypoxic exposure improved tolerance to subsequent acute hypoxia. Activation of the pyruvate dehydrogenase complex during chronic hypoxia stockpiled cardiac acetylcarnitine, and this was used during acute hypoxia. This maintained cardiac ATP and glycogen, and improved hypoxic tolerance as a result. These findings demonstrate that pyruvate dehydrogenase complex activation can improve cardiac function under hypoxia. ABSTRACT The pattern of metabolic reprogramming in chronic hypoxia shares similarities with that following myocardial infarction or hypertrophy; however, the response of the chronically hypoxic heart to subsequent acute injury, and the role of metabolism is not well understood. Here, we determined the myocardial tolerance of the chronically hypoxic heart to subsequent acute injury, and hypothesised that activation of a key regulator of myocardial metabolism, the pyruvate dehydrogenase complex (PDC), could improve hypoxic tolerance. Mouse hearts, perfused in Langendorff mode, were exposed to 30 min of hypoxia, and lost 80% of pre-hypoxic function (P = 0.001), with only 51% recovery of pre-hypoxic function with 30 min of reoxygenation (P = 0.046). Activation of the PDC with infusion of 1 mm dichloroacetate (DCA) during hypoxia and reoxygenation did not alter function. Acute hypoxic tolerance was assessed in hearts of mice housed in hypoxia for 3 weeks. Chronic hypoxia reduced cardiac tolerance to subsequent acute hypoxia, with recovery of function 22% of pre-acute hypoxic levels vs. 39% in normoxic control hearts (P = 0.012). DCA feeding in chronic hypoxia (per os, 70 mg kg-1 day-1 ) doubled cardiac acetylcarnitine content, and this fell following acute hypoxia. This acetylcarnitine use maintained cardiac ATP and glycogen content during acute hypoxia, with hypoxic tolerance normalised. In summary, chronic hypoxia renders the heart more susceptible to acute hypoxic injury, which can be improved by activation of the PDC and pooling of acetylcarnitine. This is the first study showing functional improvement of the chronically hypoxic heart with activation of the PDC, and offers therapeutic potential in cardiac disease with a hypoxic component.
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Affiliation(s)
- Michal K. Handzlik
- School of Life SciencesUniversity of Nottingham Medical SchoolQueen's Medical CentreNottinghamUK
| | - Dumitru Constantin‐Teodosiu
- School of Life SciencesUniversity of Nottingham Medical SchoolQueen's Medical CentreNottinghamUK
- MRC/Arthritis Research UK Centre for Musculoskeletal Ageing ResearchUK
| | - Paul L. Greenhaff
- School of Life SciencesUniversity of Nottingham Medical SchoolQueen's Medical CentreNottinghamUK
- MRC/Arthritis Research UK Centre for Musculoskeletal Ageing ResearchUK
| | - Mark A. Cole
- School of Life SciencesUniversity of Nottingham Medical SchoolQueen's Medical CentreNottinghamUK
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14
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Morales-Alamo D, Guerra B, Santana A, Martin-Rincon M, Gelabert-Rebato M, Dorado C, Calbet JAL. Skeletal Muscle Pyruvate Dehydrogenase Phosphorylation and Lactate Accumulation During Sprint Exercise in Normoxia and Severe Acute Hypoxia: Effects of Antioxidants. Front Physiol 2018; 9:188. [PMID: 29615918 PMCID: PMC5867337 DOI: 10.3389/fphys.2018.00188] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2017] [Accepted: 02/23/2018] [Indexed: 12/30/2022] Open
Abstract
Compared to normoxia, during sprint exercise in severe acute hypoxia the glycolytic rate is increased leading to greater lactate accumulation, acidification, and oxidative stress. To determine the role played by pyruvate dehydrogenase (PDH) activation and reactive nitrogen and oxygen species (RNOS) in muscle lactate accumulation, nine volunteers performed a single 30-s sprint (Wingate test) on four occasions: two after the ingestion of placebo and another two following the intake of antioxidants, while breathing either hypoxic gas (PIO2 = 75 mmHg) or room air (PIO2 = 143 mmHg). Vastus lateralis muscle biopsies were obtained before, immediately after, 30 and 120 min post-sprint. Antioxidants reduced the glycolytic rate without altering performance or VO2. Immediately after the sprints, Ser293- and Ser300-PDH-E1α phosphorylations were reduced to similar levels in all conditions (~66 and 91%, respectively). However, 30 min into recovery Ser293-PDH-E1α phosphorylation reached pre-exercise values while Ser300-PDH-E1α was still reduced by 44%. Thirty minutes after the sprint Ser293-PDH-E1α phosphorylation was greater with antioxidants, resulting in 74% higher muscle lactate concentration. Changes in Ser293 and Ser300-PDH-E1α phosphorylation from pre to immediately after the sprints were linearly related after placebo (r = 0.74, P < 0.001; n = 18), but not after antioxidants ingestion (r = 0.35, P = 0.15). In summary, lactate accumulation during sprint exercise in severe acute hypoxia is not caused by a reduced activation of the PDH. The ingestion of antioxidants is associated with increased PDH re-phosphorylation and slower elimination of muscle lactate during the recovery period. Ser293 re-phosphorylates at a faster rate than Ser300-PDH-E1α during the recovery period, suggesting slightly different regulatory mechanisms.
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Affiliation(s)
- David Morales-Alamo
- Department of Physical Education, University of Las Palmas de Gran Canaria, Las Palmas de Gran Canaria, Spain.,Research Institute of Biomedical and Health Sciences, Las Palmas de Gran Canaria, Spain
| | - Borja Guerra
- Department of Physical Education, University of Las Palmas de Gran Canaria, Las Palmas de Gran Canaria, Spain.,Research Institute of Biomedical and Health Sciences, Las Palmas de Gran Canaria, Spain
| | - Alfredo Santana
- Research Institute of Biomedical and Health Sciences, Las Palmas de Gran Canaria, Spain.,Clinical Genetics Unit, Complejo Hospitalario Universitario Insular-Materno Infantil de Las Palmas de Gran Canaria, Las Palmas de Gran Canaria, Spain
| | - Marcos Martin-Rincon
- Department of Physical Education, University of Las Palmas de Gran Canaria, Las Palmas de Gran Canaria, Spain.,Research Institute of Biomedical and Health Sciences, Las Palmas de Gran Canaria, Spain
| | - Miriam Gelabert-Rebato
- Department of Physical Education, University of Las Palmas de Gran Canaria, Las Palmas de Gran Canaria, Spain.,Research Institute of Biomedical and Health Sciences, Las Palmas de Gran Canaria, Spain
| | - Cecilia Dorado
- Department of Physical Education, University of Las Palmas de Gran Canaria, Las Palmas de Gran Canaria, Spain.,Research Institute of Biomedical and Health Sciences, Las Palmas de Gran Canaria, Spain
| | - José A L Calbet
- Department of Physical Education, University of Las Palmas de Gran Canaria, Las Palmas de Gran Canaria, Spain.,Research Institute of Biomedical and Health Sciences, Las Palmas de Gran Canaria, Spain
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15
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Kwak MK, Ku M, Kang SO. Inducible NAD(H)-linked methylglyoxal oxidoreductase regulates cellular methylglyoxal and pyruvate through enhanced activities of alcohol dehydrogenase and methylglyoxal-oxidizing enzymes in glutathione-depleted Candida albicans. Biochim Biophys Acta Gen Subj 2018; 1862:18-39. [DOI: 10.1016/j.bbagen.2017.10.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2016] [Revised: 09/30/2017] [Accepted: 10/06/2017] [Indexed: 12/15/2022]
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16
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Morales-Alamo D, Losa-Reyna J, Torres-Peralta R, Martin-Rincon M, Perez-Valera M, Curtelin D, Ponce-González JG, Santana A, Calbet JAL. What limits performance during whole-body incremental exercise to exhaustion in humans? J Physiol 2015; 593:4631-48. [PMID: 26250346 DOI: 10.1113/jp270487] [Citation(s) in RCA: 73] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2015] [Accepted: 07/29/2015] [Indexed: 12/13/2022] Open
Abstract
To determine the mechanisms causing task failure during incremental exercise to exhaustion (IE), sprint performance (10 s all-out isokinetic) and muscle metabolites were measured before (control) and immediately after IE in normoxia (P(IO2) 143 mmHg) and hypoxia (P(IO2): 73 mmHg) in 22 men (22 ± 3 years). After IE, subjects recovered for either 10 or 60 s, with open circulation or bilateral leg occlusion (300 mmHg) in random order. This was followed by a 10 s sprint with open circulation. Post-IE peak power output (W(peak)) was higher than the power output reached at exhaustion during IE (P < 0.05). After 10 and 60 s recovery in normoxia, W(peak) was reduced by 38 ± 9 and 22 ± 10% without occlusion, and 61 ± 8 and 47 ± 10% with occlusion (P < 0.05). Following 10 s occlusion, W(peak) was 20% higher in hypoxia than normoxia (P < 0.05), despite similar muscle lactate accumulation ([La]) and phosphocreatine and ATP reduction. Sprint performance and anaerobic ATP resynthesis were greater after 60 s compared with 10 s occlusions, despite the higher [La] and [H(+)] after 60 s compared with 10 s occlusion recovery (P < 0.05). The mean rate of ATP turnover during the 60 s occlusion was 0.180 ± 0.133 mmol (kg wet wt)(-1) s(-1), i.e. equivalent to 32% of leg peak O2 uptake (the energy expended by the ion pumps). A greater degree of recovery is achieved, however, without occlusion. In conclusion, during incremental exercise task failure is not due to metabolite accumulation or lack of energy resources. Anaerobic metabolism, despite the accumulation of lactate and H(+), facilitates early recovery even in anoxia. This points to central mechanisms as the principal determinants of task failure both in normoxia and hypoxia, with lower peripheral contribution in hypoxia.
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Affiliation(s)
- David Morales-Alamo
- Department of Physical Education, University of Las Palmas de Gran Canaria, Campus Universitario de Tafira s/n, 35017, Las Palmas de Gran Canaria, Spain.,Research Institute of Biomedical and Health Sciences (IUIBS), Las Palmas de Gran Canaria, Spain
| | - José Losa-Reyna
- Department of Physical Education, University of Las Palmas de Gran Canaria, Campus Universitario de Tafira s/n, 35017, Las Palmas de Gran Canaria, Spain.,Research Institute of Biomedical and Health Sciences (IUIBS), Las Palmas de Gran Canaria, Spain
| | - Rafael Torres-Peralta
- Department of Physical Education, University of Las Palmas de Gran Canaria, Campus Universitario de Tafira s/n, 35017, Las Palmas de Gran Canaria, Spain.,Research Institute of Biomedical and Health Sciences (IUIBS), Las Palmas de Gran Canaria, Spain
| | - Marcos Martin-Rincon
- Research Institute of Biomedical and Health Sciences (IUIBS), Las Palmas de Gran Canaria, Spain.,Department of Sports and Informatics, Pablo de Olavide University, Seville, Spain
| | - Mario Perez-Valera
- Department of Physical Education, University of Las Palmas de Gran Canaria, Campus Universitario de Tafira s/n, 35017, Las Palmas de Gran Canaria, Spain.,Research Institute of Biomedical and Health Sciences (IUIBS), Las Palmas de Gran Canaria, Spain
| | - David Curtelin
- Research Institute of Biomedical and Health Sciences (IUIBS), Las Palmas de Gran Canaria, Spain.,Emergency Medicine Department, Complejo Hospitalario Universitario Insular-Materno Infantil de Las Palmas de Gran Canaria, Avenida Marítima del Sur, s/n, 35016, Las Palmas de Gran Canaria, Spain
| | - Jesús Gustavo Ponce-González
- Department of Physical Education, University of Las Palmas de Gran Canaria, Campus Universitario de Tafira s/n, 35017, Las Palmas de Gran Canaria, Spain
| | - Alfredo Santana
- Department of Physical Education, University of Las Palmas de Gran Canaria, Campus Universitario de Tafira s/n, 35017, Las Palmas de Gran Canaria, Spain.,Research Institute of Biomedical and Health Sciences (IUIBS), Las Palmas de Gran Canaria, Spain.,Clinical Genetics Unit, Complejo Hospitalario Universitario Insular-Materno Infantil de Las Palmas de Gran Canaria, Avenida Marítima, del Sur, s/n, 35016, Las Palmas de Gran Canaria, Spain
| | - José A L Calbet
- Department of Physical Education, University of Las Palmas de Gran Canaria, Campus Universitario de Tafira s/n, 35017, Las Palmas de Gran Canaria, Spain.,Research Institute of Biomedical and Health Sciences (IUIBS), Las Palmas de Gran Canaria, Spain
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17
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Torres-Peralta R, Losa-Reyna J, González-Izal M, Perez-Suarez I, Calle-Herrero J, Izquierdo M, Calbet JAL. Muscle activation during exercise in severe acute hypoxia: role of absolute and relative intensity. High Alt Med Biol 2015; 15:472-82. [PMID: 25225839 DOI: 10.1089/ham.2014.1027] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
The aim of this study was to determine the influence of severe acute hypoxia on muscle activation during whole body dynamic exercise. Eleven young men performed four incremental cycle ergometer tests to exhaustion breathing normoxic (FIO2=0.21, two tests) or hypoxic gas (FIO2=0.108, two tests). Surface electromyography (EMG) activities of rectus femoris (RF), vastus medialis (VL), vastus lateralis (VL), and biceps femoris (BF) were recorded. The two normoxic and the two hypoxic tests were averaged to reduce EMG variability. Peak VO2 was 34% lower in hypoxia than in normoxia (p<0.05). The EMG root mean square (RMS) increased with exercise intensity in all muscles (p<0.05), with greater effect in hypoxia than in normoxia in the RF and VM (p<0.05), and a similar trend in VL (p=0.10). At the same relative intensity, the RMS was greater in normoxia than in hypoxia in RF, VL, and BF (p<0.05), with a similar trend in VM (p=0.08). Median frequency increased with exercise intensity (p<0.05), and was higher in hypoxia than in normoxia in VL (p<0.05). Muscle contraction burst duration increased with exercise intensity in VM and VL (p<0.05), without clear effects of FIO2. No significant FIO2 effects on frequency domain indices were observed when compared at the same relative intensity. In conclusion, muscle activation during whole body exercise increases almost linearly with exercise intensity, following a muscle-specific pattern, which is adjusted depending on the FIO2 and the relative intensity of exercise. Both VL and VM are increasingly involved in power output generation with the increase of intensity and the reduction in FIO2.
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Affiliation(s)
- Rafael Torres-Peralta
- 1 Department of Physical Education, University of Las Palmas de Gran Canaria , Campus Universitario de Tafira s/n, Las Palmas de Gran Canaria, Spain
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18
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D'Antona G, Nabavi SM, Micheletti P, Di Lorenzo A, Aquilani R, Nisoli E, Rondanelli M, Daglia M. Creatine, L-carnitine, and ω3 polyunsaturated fatty acid supplementation from healthy to diseased skeletal muscle. BIOMED RESEARCH INTERNATIONAL 2014; 2014:613890. [PMID: 25243159 PMCID: PMC4163371 DOI: 10.1155/2014/613890] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/24/2014] [Revised: 07/19/2014] [Accepted: 08/06/2014] [Indexed: 12/22/2022]
Abstract
Myopathies are chronic degenerative pathologies that induce the deterioration of the structure and function of skeletal muscle. So far a definitive therapy has not yet been developed and the main aim of myopathy treatment is to slow the progression of the disease. Current nonpharmacological therapies include rehabilitation, ventilator assistance, and nutritional supplements, all of which aim to delay the onset of the disease and relieve its symptoms. Besides an adequate diet, nutritional supplements could play an important role in the treatment of myopathic patients. Here we review the most recent in vitro and in vivo studies investigating the role supplementation with creatine, L-carnitine, and ω3 PUFAs plays in myopathy treatment. Our results suggest that these dietary supplements could have beneficial effects; nevertheless continued studies are required before they could be recommended as a routine treatment in muscle diseases.
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Affiliation(s)
- Giuseppe D'Antona
- Department of Molecular Medicine and Laboratory for Motor Activities in Rare Diseases (LUSAMMR), University of Pavia, Via Forlanini 6, 27100 Pavia, Italy
| | - Seyed Mohammad Nabavi
- Applied Biotechnology Research Center, Baqiyatallah University of Medical Sciences, P.O. Box 19395-5487, Tehran, Iran
| | - Piero Micheletti
- Department of Experimental and Forensic Medicine, University of Pavia, Via Forlanini 2, 27100 Pavia, Italy
| | - Arianna Di Lorenzo
- Department of Drug Sciences, Medicinal Chemistry and Pharmaceutical Technology Section, University of Pavia, Via Taramelli 12, 27100 Pavia, Italy
| | - Roberto Aquilani
- Maugeri Foundation IRCCS, Montescano Scientific Institute, Via Per Montescano 31, 27040 Montescano, Italy
| | - Enzo Nisoli
- Center for Study and Research on Obesity, Department of Medical Biotechnology and Translational Medicine, University of Milan, Via Vanvitelli 32, 20129 Milan, Italy
| | - Mariangela Rondanelli
- Human Nutrition Section, Health Sciences Department, University of Pavia, Azienda di Servizi alla Persona, Via Emilia 12, 27100 Pavia, Italy
| | - Maria Daglia
- Department of Drug Sciences, Medicinal Chemistry and Pharmaceutical Technology Section, University of Pavia, Via Taramelli 12, 27100 Pavia, Italy
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19
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Oliveira PF, Martins AD, Moreira AC, Cheng CY, Alves MG. The Warburg effect revisited--lesson from the Sertoli cell. Med Res Rev 2014; 35:126-51. [PMID: 25043918 DOI: 10.1002/med.21325] [Citation(s) in RCA: 125] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Otto Warburg observed that cancerous cells prefer fermentative instead of oxidative metabolism of glucose, although the former is in theory less efficient. Since Warburg's pioneering works, special attention has been given to this difference in cell metabolism. The Warburg effect has been implicated in cell transformation, immortalization, and proliferation during tumorigenesis. Cancer cells display enhanced glycolytic activity, which is correlated with high proliferation, and thus, glycolysis appears to be an excellent candidate to target cancer cells. Nevertheless, little attention has been given to noncancerous cells that exhibit a "Warburg-like" metabolism with slight, but perhaps crucial, alterations that may provide new directions to develop new and effective anticancer therapies. Within the testis, the somatic Sertoli cell (SC) presents several common metabolic features analogous to cancer cells, and a clear "Warburg-like" metabolism. Nevertheless, SCs actively proliferate only during a specific time period, ceasing to divide in most species after puberty, when they become terminally differentiated. The special metabolic features of SC, as well as progression from the immature but proliferative state, to the mature nonproliferative state, where a high glycolytic activity is maintained, make these cells unique and a good model to discuss new perspectives on the Warburg effect. Herein we provide new insight on how the somatic SC may be a source of new and exciting information concerning the Warburg effect and cell proliferation.
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Affiliation(s)
- Pedro F Oliveira
- CICS-UBI, Health Sciences Research Centre, University of Beira Interior, Covilhã, Portugal
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20
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Puype J, Ramaekers M, Van Thienen R, Deldicque L, Hespel P. No effect of dietary nitrate supplementation on endurance training in hypoxia. Scand J Med Sci Sports 2014; 25:234-41. [PMID: 24646076 DOI: 10.1111/sms.12199] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/20/2014] [Indexed: 12/20/2022]
Abstract
We investigated whether dietary nitrate (NO(3)(-)) supplementation enhances the effect of training in hypoxia on endurance performance at sea level. Twenty-two healthy male volunteers performed high-intensity endurance training on a cycle ergometer (6 weeks, 5×30 min/week at 4-6 mmol/L blood lactate) in normobaric hypoxia (12.5% FiO(2)), while ingesting either beetroot juice [0.07 mmol NO(3)(-) /kg body weight (bw)/day; BR, n = 11] or a control drink (CON, n = 11). During the pretest and the posttest, the subjects performed a 30-min simulated time trial (TT) and an incremental VO(2max) test. Furthermore, a biopsy was taken from m. vastus lateralis before and after the TT. Power output during the training sessions in both groups increased by ∼6% from week 1 to week 6 (P < 0.05). Compared with the pretest, VO(2max) in the posttest was increased (P < 0.05) in CON (5%) and BR (9%). Power output corresponding with the 4 mmol/L blood lactate threshold, as well as mean power output during TT increased by ∼16% in both groups (P < 0.05). Muscle phospho-AMP-activated protein kinase, hypoxia inducible factor-1α mRNA content, and glycogen breakdown during the TT were similar between the groups in both the pretest and the posttest. In conclusion, low-dose dietary NO(3)(-) supplementation does not enhance the effects of intermittent hypoxic training on endurance exercise performance at sea level.
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Affiliation(s)
- J Puype
- Exercise Physiology Research Group, Department of Kinesiology, KU Leuven, Belgium
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21
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Ren J, Dean Sherry A, Malloy CR. Noninvasive monitoring of lactate dynamics in human forearm muscle after exhaustive exercise by (1)H-magnetic resonance spectroscopy at 7 tesla. Magn Reson Med 2012. [PMID: 23192863 DOI: 10.1002/mrm.24526] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Despite its importance in energy metabolism, lactate in human skeletal muscle has been difficult to detect by noninvasive (1)H-magnetic resonance spectroscopy mainly due to interference from large water and lipid signals. Long echo-time acquisitions at 7 T effectively attenuates the water and lipid signals in forearm muscle allowing direct observation of both lactate resonances, the methine at 4.09 ppm and the methyl at 1.31 ppm. Using this approach, we were able to monitor lactate dynamics at a temporal resolution of 32 s. While lactate was not detectable at rest, immediately after an acute period of exercise to fatigue the forearm muscle, lactate rose to a level comparable to that of creatine (∼30 mmol/kg wet weight). In a typical (1)H-magnetic resonance spectrum collected using a echo-time of 140 ms, the lactate methine and methyl resonances both appear as doublets with an unusually large splitting of ∼20 Hz due to residual dipolar coupling. During muscle recovery following exercise, the lactate signals decay rapidly with a time constant of t½ = 2.0 ± 0.6 min (n = 12 subjects). This fast and simple lactate detection method may prove valuable for monitoring lactate metabolism in cancer and in sports medicine applications.
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Affiliation(s)
- Jimin Ren
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas, USA; Department of Radiology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
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Christensen PM, Nordsborg NB, Nybo L, Mortensen SP, Sander M, Secher NH, Bangsbo J. Thigh oxygen uptake at the onset of intense exercise is not affected by a reduction in oxygen delivery caused by hypoxia. Am J Physiol Regul Integr Comp Physiol 2012; 303:R843-9. [DOI: 10.1152/ajpregu.00201.2012] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
In response to hypoxic breathing most studies report slower pulmonary oxygen uptake (V̇o2) kinetics at the onset of exercise, but it is not known if this relates to an actual slowing of the V̇o2 in the active muscles. The aim of the present study was to evaluate whether thigh V̇o2 is slowed at the onset of intense exercise during acute exposure to hypoxia. Six healthy male subjects (25.8 ± 1.4 yr, 79.8 ± 4.0 kg, means ± SE) performed intense (100 ± 6 watts) two-legged knee-extensor exercise for 2 min in normoxia (NOR) and hypoxia [fractional inspired oxygen concentration (FiO2) = 0.13; HYP]. Thigh V̇o2 was measured by frequent arterial and venous blood sampling and blood flow measurements. In arterial blood, oxygen content was reduced ( P < 0.05) from 191 ± 5 ml O2/l in NOR to 180 ± 5 ml O2/l in HYP, and oxygen pressure was reduced ( P < 0.001) from 111 ± 4 mmHg in NOR to 63 ± 4 mmHg in HYP. Thigh blood flow was the same in NOR and HYP, and thigh oxygen delivery was consequently reduced ( P < 0.05) in HYP, but femoral arterial-venous oxygen difference and thigh V̇o2 were similar in NOR and HYP. In addition, muscle lactate release was the same in NOR and HYP, and muscle lactate accumulation during the first 25 s of exercise determined from muscle biopsy sampling was also similar (0.35 ± 0.07 and 0.36 ± 0.07 mmol·kg dry wt−1·s−1 in NOR and HYP). Thus the increase in thigh V̇o2 was not attenuated at the onset of intense knee-extensor exercise despite a reduction in oxygen delivery and pressure.
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Affiliation(s)
| | | | - Lars Nybo
- Department of Exercise and Sport Sciences, University of Copenhagen, Denmark
| | | | - Mikael Sander
- The Copenhagen Muscle Research Center and Flight Medicine, Department of Cardiology, Rigshospitalet, Copenhagen, Denmark
| | - Niels H. Secher
- The Copenhagen Muscle Research Center, Department of Anesthesia, Rigshospitaliet, University of Copenhagen, Denmark
| | - Jens Bangsbo
- Department of Exercise and Sport Sciences, University of Copenhagen, Denmark
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A global view of the biochemical pathways involved in the regulation of the metabolism of cancer cells. Biochim Biophys Acta Rev Cancer 2012; 1826:423-33. [PMID: 22841746 DOI: 10.1016/j.bbcan.2012.07.001] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2012] [Revised: 07/09/2012] [Accepted: 07/10/2012] [Indexed: 02/08/2023]
Abstract
Cancer cells increase glucose uptake and reject lactic acid even in the presence of oxygen (Warburg effect). This metabolism reorients glucose towards the pentose phosphate pathway for ribose synthesis and consumes great amounts of glutamine to sustain nucleotide and fatty acid synthesis. Oxygenated and hypoxic cells cooperate and use their environment in a manner that promotes their development. Coenzymes (NAD(+), NADPH,H(+)) are required in abundance, whereas continuous consumption of ATP and citrate precludes the negative feedback of these molecules on glycolysis, a regulation supporting the Pasteur effect. Understanding the metabolism of cancer cells may help to develop new anti-cancer treatments.
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Spencer MD, Murias JM, Grey TM, Paterson DH. Regulation of V̇o2 kinetics by O2 delivery: insights from acute hypoxia and heavy-intensity priming exercise in young men. J Appl Physiol (1985) 2012; 112:1023-32. [PMID: 22194321 DOI: 10.1152/japplphysiol.01215.2011] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
This study examined the separate and combined effects of acute hypoxia (Hypo) and heavy-intensity “priming” exercise (Hvy) on pulmonary O2 uptake (V̇o2p) kinetics during moderate-intensity exercise (Mod). Breath-by-breath V̇o2p and near-infrared spectroscopy-derived muscle deoxygenation {deoxyhemoglobin concentration [HHb]} were monitored continuously in 10 men (23 ± 4 yr) during repetitions of a Mod 1-Hvy-Mod 2 protocol, where each of the 6-min (Mod or Hvy) leg-cycling bouts was separated by 6 min at 20 W. Subjects were exposed to Hypo [fraction of inspired O2 (FiO2) = 15%, Mod 2 + Hypo] or “sham” (FiO2 = 20.9%, Mod 2-N) 2 min following Hvy in half of these repetitions; Mod was also performed in Hypo without Hvy (Mod 1 + Hypo). On-transient V̇o2p and [HHb] responses were modeled as a monoexponential. Data were scaled to a relative percentage of the response (0–100%), the signals were time-aligned, and the individual [HHb]-to-V̇o2 ratio was calculated. Compared with control (Mod 1), τV̇o2p and the O2 deficit (26 ± 7 s and 638 ± 144 ml, respectively) were reduced ( P < 0.05) in Mod 2-N (20 ± 5 s and 529 ± 196 ml) and increased ( P < 0.05) in Mod 1 + Hypo (34 ± 14 s and 783 ± 184 ml); in Mod 2 + Hypo, τV̇o2p was increased (30 ± 8 s, P < 0.05), yet O2 deficit was unaffected (643 ± 193 ml, P > 0.05). The modest “overshoot” in the [HHb]-to-V̇o2 ratio (reflecting an O2 delivery-to-utilization mismatch) in Mod 1 (1.06 ± 0.04) was abolished in Mod 2-N (1.00 ± 0.05), persisted in Mod 2 + Hypo (1.09 ± 0.07), and tended to increase in Mod 1 + Hypo (1.10 ± 0.09, P = 0.13). The present data do not support an “O2 delivery-independent” speeding of τV̇o2p following Hvy (or Hvy + Hypo); rather, this study suggests that local muscle O2 delivery likely governs the rate of adjustment of V̇o2 at τV̇o2p greater than ∼20 s.
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Affiliation(s)
- Matthew D. Spencer
- Canadian Centre for Activity and Aging and
- School of Kinesiology, University of Western Ontario, London, Ontario, Canada
| | - Juan M. Murias
- Canadian Centre for Activity and Aging and
- School of Kinesiology, University of Western Ontario, London, Ontario, Canada
| | - Tyler M. Grey
- School of Kinesiology, University of Western Ontario, London, Ontario, Canada
| | - Donald H. Paterson
- Canadian Centre for Activity and Aging and
- School of Kinesiology, University of Western Ontario, London, Ontario, Canada
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Li Y, Lai N, Kirwan JP, Saidel GM. Computational Model of Cellular Metabolic Dynamics in Skeletal Muscle Fibers during Moderate Intensity Exercise. Cell Mol Bioeng 2011; 5:92-112. [PMID: 22942911 DOI: 10.1007/s12195-011-0210-y] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Human skeletal muscles have different fiber types with distinct metabolic functions and physiological properties. The quantitative metabolic responses of muscle fibers to exercise provide essential information for understanding and modifying the regulatory mechanisms of skeletal muscle. Since in vivo data from skeletal muscle during exercise is limited, a computational, physiologically based model has been developed to quantify the dynamic metabolic responses of many key chemical species. This model distinguishes type I and II muscle fibers, which share the same blood supply. An underlying hypothesis is that the recruitment and metabolic activation of the two main types of muscle fibers differ depending on the pre-exercise state and exercise protocols. Here, activation measured by metabolic response (or enzymatic activation) in single fibers is considered linked but distinct from fiber recruitment characterized by the number (or mass) of each fiber type involved during a specific exercise. The model incorporates species transport processes between blood and muscle fibers and most of the important reactions/pathways in cytosol and mitochondria within each fiber type. Model simulations describe the dynamics of intracellular species concentrations and fluxes in muscle fibers during moderate intensity exercise according to various experimental protocols and conditions. This model is validated by comparing model simulations with experimental data in single muscle fibers and in whole muscle. Model simulations demonstrate that muscle-fiber recruitment and metabolic activation patterns in response to exercise produce significantly distinctive effects depending on the exercise conditions.
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Affiliation(s)
- Yanjun Li
- Center for Modeling Integrated Metabolic Systems, Case Western Reserve University, Cleveland, OH
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Le Moine CMR, Morash AJ, McClelland GB. Changes in HIF-1α protein, pyruvate dehydrogenase phosphorylation, and activity with exercise in acute and chronic hypoxia. Am J Physiol Regul Integr Comp Physiol 2011; 301:R1098-104. [PMID: 21775648 DOI: 10.1152/ajpregu.00070.2011] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Exercise under acute hypoxia elicits a large increase in blood lactate concentration ([La](b)) compared with normoxic exercise. However, several studies in humans show that with the transition to chronic hypoxia, exercise [La](b) returns to normoxic levels. Although extensively examined over the last decades, the muscle-specific mechanisms responsible for this phenomenon remain unknown. To assess the changes in skeletal muscle associated with a transition from acute to chronic hypoxia, CD-1 mice were exposed for 24 h (24H), 1 wk (1WH), or 4 wk (4WH) to hypobaric hypoxia (equivalent to 4,300 m), exercised under 12% O(2), and compared with normoxic mice (N) at 21% O(2). Since the enzyme pyruvate dehydrogenase (PDH) plays a major role in the metabolic fate of pyruvate (oxidation vs. lactate production), we assessed the changes in its activity and regulation. Here we report that when run under hypoxia, 24H mice exhibited the highest blood and intramuscular lactate of all groups, while the 1WH group approached N group values. Concomitantly, the 24H group exhibited the lowest PDH activity, associated with a higher phosphorylation (inactive) state of the Ser(232) residue of PDH, a site specific to PDH kinase-1 (PDK1). Furthermore, protein levels of PDK1 and its regulator, the hypoxia inducible factor-1α (HIF-1α), were both elevated in the 24H group compared with N and 1WH groups. Overall, our results point to a novel mechanism in muscle where the HIF-1α pathway is desensitized in the transition from acute to chronic hypoxia, leading to a reestablishment of PDH activity and a reduction in lactate production by the exercising muscles.
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Mackenzie R, Maxwell N, Castle P, Brickley G, Watt P. Acute hypoxia and exercise improve insulin sensitivity (S(I) (2*)) in individuals with type 2 diabetes. Diabetes Metab Res Rev 2011; 27:94-101. [PMID: 21218513 DOI: 10.1002/dmrr.1156] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
BACKGROUND hypoxia has been shown to increase glucose uptake in skeletal muscle using the contraction-stimulated pathway, independent of the actions of insulin. Yet, the same stress has also been linked with causing insulin resistance and hyperglycaemia. The aim of this study was to examine the effects of acute hypoxia with and without exercise on insulin sensitivity (S(I)(2*) in individuals with type 2 diabetes. METHODS eight type 2 diabetic patients completed 60 min of the following: (1) normoxic rest; (2) hypoxic rest [O(2) = 14.6 (0.4)%]; (3) normoxic exercise and (4) hypoxic exercise [O(2) = 14.6 (0.4)%]. Exercise trials were set at 90% of lactate threshold. Each condition was followed by a labelled intravenous glucose tolerance test to provide estimations of insulin sensitivity (S(I)(2*) and β-cell function. RESULTS Two-compartmental analysis showed that insulin sensitivity (S(I)(2*) was higher following hypoxic rest compared with normoxic rest (p = 0.047). Insulin sensitivity (S(I)(2*) was also higher following hypoxic exercise [4.37 (0.48) × 10(-4) /min (µU/mL)] compared with normoxic exercise [3.24 (0.51) × 10(-4) /min (µU/mL)] (p = 0.048). Acute insulin response to glucose was reduced following hypoxic rest versus normoxic rest (p = 0.014). CONCLUSIONS this study demonstrated that (1) hypoxic-induced improvements in glucose tolerance in the 4 h following exposure can be attributed to improvements in peripheral insulin sensitivity (S( I)(2*) and (2) exercise and hypoxia have an additive effect on insulin sensitivity (S(I)(2*) in type 2 diabetic patients. Acute hypoxia may therefore improve short-term glycaemic control in individuals with type 2 diabetes. The application of these findings in the clinic will require further investigation.
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Affiliation(s)
- Richard Mackenzie
- School of Life Sciences, Department of Human and Health Sciences, University of Westminster, London, United Kingdom.
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28
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Ferreira LM. Cancer metabolism: The Warburg effect today. Exp Mol Pathol 2010; 89:372-80. [DOI: 10.1016/j.yexmp.2010.08.006] [Citation(s) in RCA: 194] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2010] [Revised: 08/22/2010] [Accepted: 08/22/2010] [Indexed: 11/30/2022]
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Green HJ, Burnett ME, Smith IC, Tupling SM, Ranney DA. Failure of hypoxia to exaggerate the metabolic stress in working muscle following short-term training. Am J Physiol Regul Integr Comp Physiol 2009; 297:R593-604. [PMID: 19474386 DOI: 10.1152/ajpregu.91035.2008] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
This study investigated the effects of hypoxia (experiment 1) and the effects of hypoxia following short-term training (experiment 2) on metabolism in working muscle. In experiment 1, eight males with a peak aerobic power (VO2peak) of 45 +/- 1.7 ml x kg(-1) x min(-1) (x +/- SE) cycled for 15 min at 66.1 +/- 2.1% VO2peak while breathing room air [normoxia (N)] or 14% O(2) [hypoxia (H)]. In experiment 2, nine males with a VO2peak of 43.3 +/- 1.6 ml x kg(-1) x min(-1) performed a similar protocol at 60.7 +/- 1.4% VO2peak during N and during H following 5 days of submaximal exercise training (H + T). Tissue samples extracted from the vastus lateralis before exercise and at 1, 3, and 15 min of exercise indicated that compared with N, H resulted in lower (P < 0.05) concentrations (mmol/kg dry wt) of creatine phosphate and higher (P < 0.05) concentrations of creatine, inorganic phosphate, and lactate, regardless of exercise time. When the exercise was performed at H + T and compared with N, no differences were observed in creatine phosphate, creatine, inorganic phosphate, and lactate, regardless of duration. Given the well-documented effects of the short-term training model on elevating VO2 kinetics and attenuating the alterations in high-energy phosphate metabolism and lactate accumulation, it would appear that the mechanism underlying the reversal of these adaptations during H is linked to a more rapid increase in oxidative phosphorylation, mediated by increased oxygen delivery and/or mitochondrial activation.
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Affiliation(s)
- H J Green
- Dept. of Kinesiology, Univ. of Waterloo, Waterloo, ON, N2L3G1, Canada.
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31
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Li Y, Dash RK, Kim J, Saidel GM, Cabrera ME. Role of NADH/NAD+ transport activity and glycogen store on skeletal muscle energy metabolism during exercise: in silico studies. Am J Physiol Cell Physiol 2008; 296:C25-46. [PMID: 18829894 DOI: 10.1152/ajpcell.00094.2008] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Skeletal muscle can maintain ATP concentration constant during the transition from rest to exercise, whereas metabolic reaction rates may increase substantially. Among the key regulatory factors of skeletal muscle energy metabolism during exercise, the dynamics of cytosolic and mitochondrial NADH and NAD+ have not been characterized. To quantify these regulatory factors, we have developed a physiologically based computational model of skeletal muscle energy metabolism. This model integrates transport and reaction fluxes in distinct capillary, cytosolic, and mitochondrial domains and investigates the roles of mitochondrial NADH/NAD+ transport (shuttling) activity and muscle glycogen concentration (stores) during moderate intensity exercise (60% maximal O2 consumption). The underlying hypothesis is that the cytosolic redox state (NADH/NAD+) is much more sensitive to a metabolic disturbance in contracting skeletal muscle than the mitochondrial redox state. This hypothesis was tested by simulating the dynamic metabolic responses of skeletal muscle to exercise while altering the transport rate of reducing equivalents (NADH and NAD+) between cytosol and mitochondria and muscle glycogen stores. Simulations with optimal parameter estimates showed good agreement with the available experimental data from muscle biopsies in human subjects. Compared with these simulations, a 20% increase (or approximately 20% decrease) in mitochondrial NADH/NAD+ shuttling activity led to an approximately 70% decrease (or approximately 3-fold increase) in cytosolic redox state and an approximately 35% decrease (or approximately 25% increase) in muscle lactate level. Doubling (or halving) muscle glycogen concentration resulted in an approximately 50% increase (or approximately 35% decrease) in cytosolic redox state and an approximately 30% increase (or approximately 25% decrease) in muscle lactate concentration. In both cases, changes in mitochondrial redox state were minimal. In conclusion, the model simulations of exercise response are consistent with the hypothesis that mitochondrial NADH/NAD+ shuttling activity and muscle glycogen stores affect primarily the cytosolic redox state. Furthermore, muscle lactate production is regulated primarily by the cytosolic redox state.
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Affiliation(s)
- Yanjun Li
- Center for Modeling Integrated Metabolic Systems, Case Western Reserve University, 11100 Euclid Ave., Cleveland, OH 44106-6011, USA
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32
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Dash RK, Li Y, Kim J, Beard DA, Saidel GM, Cabrera ME. Metabolic dynamics in skeletal muscle during acute reduction in blood flow and oxygen supply to mitochondria: in-silico studies using a multi-scale, top-down integrated model. PLoS One 2008; 3:e3168. [PMID: 18779864 PMCID: PMC2526172 DOI: 10.1371/journal.pone.0003168] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2008] [Accepted: 07/19/2008] [Indexed: 11/18/2022] Open
Abstract
Control mechanisms of cellular metabolism and energetics in skeletal muscle that may become evident in response to physiological stresses such as reduction in blood flow and oxygen supply to mitochondria can be quantitatively understood using a multi-scale computational model. The analysis of dynamic responses from such a model can provide insights into mechanisms of metabolic regulation that may not be evident from experimental studies. For the purpose, a physiologically-based, multi-scale computational model of skeletal muscle cellular metabolism and energetics was developed to describe dynamic responses of key chemical species and reaction fluxes to muscle ischemia. The model, which incorporates key transport and metabolic processes and subcellular compartmentalization, is based on dynamic mass balances of 30 chemical species in both capillary blood and tissue cells (cytosol and mitochondria) domains. The reaction fluxes in cytosol and mitochondria are expressed in terms of a general phenomenological Michaelis-Menten equation involving the compartmentalized energy controller ratios ATP/ADP and NADH/NAD(+). The unknown transport and reaction parameters in the model are estimated simultaneously by minimizing the differences between available in vivo experimental data on muscle ischemia and corresponding model outputs in coupled with the resting linear flux balance constraints using a robust, nonlinear, constrained-based, reduced gradient optimization algorithm. With the optimal parameter values, the model is able to simulate dynamic responses to reduced blood flow and oxygen supply to mitochondria associated with muscle ischemia of several key metabolite concentrations and metabolic fluxes in the subcellular cytosolic and mitochondrial compartments, some that can be measured and others that can not be measured with the current experimental techniques. The model can be applied to test complex hypotheses involving dynamic regulation of cellular metabolism and energetics in skeletal muscle during physiological stresses such as ischemia, hypoxia, and exercise.
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Affiliation(s)
- Ranjan K. Dash
- Center for Modeling Integrated Metabolic Systems, Case Western Reserve University, Cleveland, Ohio, United States of America
- Department of Pediatrics, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Yanjun Li
- Center for Modeling Integrated Metabolic Systems, Case Western Reserve University, Cleveland, Ohio, United States of America
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Jaeyeon Kim
- Center for Modeling Integrated Metabolic Systems, Case Western Reserve University, Cleveland, Ohio, United States of America
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Daniel A. Beard
- Biotechnology and Bioengineering Center, Medical College of Wisconsin, Milwaukee, Wisconsin, United States of America
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin, United States of America
| | - Gerald M. Saidel
- Center for Modeling Integrated Metabolic Systems, Case Western Reserve University, Cleveland, Ohio, United States of America
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Marco E. Cabrera
- Center for Modeling Integrated Metabolic Systems, Case Western Reserve University, Cleveland, Ohio, United States of America
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio, United States of America
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, Ohio, United States of America
- Department of Pediatrics, Case Western Reserve University, Cleveland, Ohio, United States of America
- * E-mail:
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Metabolic control analysis: a tool for designing strategies to manipulate metabolic pathways. J Biomed Biotechnol 2008; 2008:597913. [PMID: 18629230 PMCID: PMC2447884 DOI: 10.1155/2008/597913] [Citation(s) in RCA: 122] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2007] [Revised: 01/16/2008] [Accepted: 03/26/2008] [Indexed: 02/06/2023] Open
Abstract
The traditional experimental approaches used for changing the flux or the concentration of a particular metabolite of a metabolic pathway have been mostly based on the inhibition or over-expression of the presumed rate-limiting step. However, the attempts to manipulate a metabolic pathway by following such approach have proved to be unsuccessful. Metabolic Control Analysis (MCA) establishes how to determine, quantitatively, the degree of control that a given enzyme exerts on flux and on the concentration of metabolites, thus substituting the intuitive, qualitative concept of rate limiting step. Moreover, MCA helps to understand (i) the underlying mechanisms by which a given enzyme exerts high or low control and (ii) why the control of the pathway is shared by several pathway enzymes and transporters. By applying MCA it is possible to identify the steps that should be modified to achieve a successful alteration of flux or metabolite concentration in pathways of biotechnological (e.g., large scale metabolite production) or clinical relevance (e.g., drug therapy). The different MCA experimental approaches developed for the determination of the flux-control distribution in several pathways are described. Full understanding of the pathway properties when is working under a variety of conditions can help to attain a successful manipulation of flux and metabolite concentration.
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Dash RK, Li Y, Kim J, Saidel GM, Cabrera ME. Modeling cellular metabolism and energetics in skeletal muscle: large-scale parameter estimation and sensitivity analysis. IEEE Trans Biomed Eng 2008; 55:1298-318. [PMID: 18390321 DOI: 10.1109/tbme.2007.913422] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Skeletal muscle plays a major role in the regulation of whole-body energy metabolism during physiological stresses such as ischemia, hypoxia, and exercise. Current experimental techniques provide relatively little in vivo data on dynamic responses of metabolite concentrations and metabolic fluxes in skeletal muscle to such physiological stimuli. As a complementary approach to experimental measurements and as a framework for quantitatively analyzing available in vivo data, a physiologically based model of skeletal muscle cellular metabolism and energetics is developed. This model, which incorporates key transport and reaction processes, is based on dynamic mass balances of 30 chemical species in capillary (blood) and tissue (cell) domains. The reaction fluxes in the cellular domain are expressed in terms of a generalized Michaelis?Menten equation involving energy controller ratios ATP/ADP and ATP/ADP and NADH/NAD+ . This formalism introduces a large number of unknown parameters ( approximately 90). Estimating these parameters from in vivo sparse data and evaluating dynamic sensitivities of the model outputs with respect to these parameters is a challenging problem. Parameter estimation is accomplished using an efficient, nonlinear, constraint-based, optimization algorithm that minimizes differences between available experimental data and corresponding model outputs by explicitly utilizing equality constraints on resting fluxes and concentrations. With the estimated parameter values, the model is able to simulate dynamic responses to reduced blood flow (ischemia) of key metabolite concentrations and metabolic fluxes, both measured and nonmeasured. A general parameter sensitivity analysis is carried out to determine and characterize the parameters having the most and least effects on the measured outputs.
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Affiliation(s)
- Ranjan K Dash
- Center for Modeling Integrated Metabolic Systems and Pediatrics, Case Western Reserve University, Cleveland, OH 44106, USA
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35
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Howlett RA, Hogan MC. Effect of hypoxia on fatigue development in rat muscle composed of different fibre types. Exp Physiol 2007; 92:887-94. [PMID: 17545215 DOI: 10.1113/expphysiol.2007.037291] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
This study investigated the relationship between hypoxia and the rate of fatigue development in contracting rat hindlimb muscles composed primarily of different fibre types. Hindlimb muscles of 11 rats were exposed, and the soleus (SOL) and gastrocnemius/plantaris (GP) were each isolated with circulation intact and attached to individual force transducers. Rats were then equilibrated with either normoxic (N; arterial partial pressure of O(2) 87.7 +/- 1.5 mmHg) or hypoxic conditions (H; arterial partial pressure of O(2) 30.0 +/- 2.4 mmHg) using an inspired O(2) fraction of 0.21 and 0.10, respectively. The stimulation protocol consisted of 2 min each at 0.125, 0.25, 0.33 and 0.5 tetanic contractions s(-1) sequentially for both conditions. Following the 8 min stimulation period, relative developed muscle tension (% of maximal) was nearly identical for both H and N in SOL (54.2 +/- 3.5 versus 54.3 +/- 4.2%), but was significantly (P < 0.05) lower in H than N (10.8 +/- 0.9 versus 43.0 +/- 8.9%) in GP, indicating a greater amount of fatigue during hypoxia only in the GP. Soleus phosphocreatine (PCr) content fell to similar levels (24.1 +/- 1.6 versus 21.1 +/- 4.9 mmol (kg dry weight (dw))(-1)) during both H and N, but in the white portion of the gastrocnemius (WG), PCr was significantly lower following H than N (14.3 +/- 1.5 versus 34.0 +/- 6.0 mmol (kg dw)(-1)). Similarly, muscle lactate increased in both fibre types at fatigue, but only in WG was the increase significantly greater with H (SOL 7.1 +/- 2.0 versus 5.3 +/- 1.1 mmol (kg dw)(-1); WG 13.7 +/- 4.5 versus 5.3 +/- 2.2 mmol (kg dw)(-1)). Increases in calculated muscle [H(+)], free ADP and free AMP were similar between N and H in SOL but were significantly greater during H compared with N in WG. These data demonstrate that hypoxia induces greater fatigue and disruption of cellular homeostasis in rat hindlimb muscle composed primarily of fibres with low oxidative capacity compared with those of a more oxidative type.
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Affiliation(s)
- Richard A Howlett
- Department of Medicine, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0623, USA
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Richards JG, Wang YS, Brauner CJ, Gonzalez RJ, Patrick ML, Schulte PM, Choppari-Gomes AR, Almeida-Val VM, Val AL. Metabolic and ionoregulatory responses of the Amazonian cichlid, Astronotus ocellatus, to severe hypoxia. J Comp Physiol B 2007; 177:361-74. [PMID: 17219139 DOI: 10.1007/s00360-006-0135-2] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2006] [Revised: 11/14/2006] [Accepted: 11/24/2006] [Indexed: 11/28/2022]
Abstract
We examined the metabolic and ionoregulatory responses of the Amazonian cichlid, Astronotus ocellatus, to 20 h exposure to severe hypoxia (0.37 +/- 0.19 mg O(2)/l; 4.6% air saturation) or 8 h severe hypoxia followed by 12 h recovery in normoxic water. During 20 h exposure to hypoxia, white muscle [ATP] was maintained at normoxic levels primarily through a 20% decrease in [creatine phosphate] (CrP) and an activation of glycolysis yielding lactate accumulation. Muscle lactate accumulation maintained cytoplasmic redox state ([NAD(+)]/[NADH]) and was associated with an inactivation of the mitochondrial enzyme pyruvate dehydrogenase (PDH). The inactivation of PDH was not associated with significant changes in cytoplasmic allosteric modulators ([ADP(free)], redox state, or [pyruvate]). Hypoxia exposure caused an approximately 65% decrease in gill Na(+)/K(+) ATPase activity, which was not matched by changes in Na(+)/K(+) ATPase alpha-subunit protein abundance indicating post-translational modification of Na(+)/K(+) ATPase was responsible for the decrease in activity. Despite decreases in gill Na(+)/K(+) ATPase activity, plasma [Na(+)] increased, but this increase was possibly due to a significant hemoconcentration and fluid shift out of the extracellular space. Hypoxia caused an increase in Na(+)/K(+) ATPase alpha-subunit mRNA abundance pointing to either reduced mRNA degradation during exposure to hypoxia or enhanced expression of Na(+)/K(+) ATPase alpha-subunit relative to other genes.
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Affiliation(s)
- J G Richards
- Department of Zoology, The University of British Columbia, 6270 University Blvd, Vancouver, BC, Canada V6T 1Z4.
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Zhou H, Saidel GM, Cabrera ME. Multi-organ system model of O2 and CO2 transport during isocapnic and poikilocapnic hypoxia. Respir Physiol Neurobiol 2006; 156:320-30. [PMID: 17188027 DOI: 10.1016/j.resp.2006.11.002] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2006] [Revised: 10/31/2006] [Accepted: 11/01/2006] [Indexed: 11/15/2022]
Abstract
A multi-organ systems model of O(2) and CO(2) transport is developed to analyze the control of ventilation and blood flow during hypoxia. Among the aspects of the control processes that this model addressed are possible mechanisms responsible for the second phase of the ventilatory hypoxic response to mild hypoxia, i.e., hypoxic ventilatory decline (HVD). Species mass transport processes are described by compartmental mass balances in brain, heart, skeletal muscle, and "other tissues" connected in parallel via the circulation. In pulmonary and systemic capillaries and in the vasculature connecting the systemic tissues, species transport processes are represented by a one-dimensional, convection-dispersion model. The effects of bicarbonate acid-base buffering, hemoglobin, and myoglobin on the transport processes are included. The model incorporates feedback control mechanisms through a cardiorespiratory control system in which peripheral and central chemoreceptors sense O(2) and CO(2) partial pressures. Model simulations of the ventilatory responses to isocapnic and poikilocapnic hypoxia show two phases with distinct dynamics. A fast phase is discernable immediately after switching from normoxic to hypoxic conditions, while a delayed slow phase (HVD) typically becomes manifested after several minutes. Model simulations allow quantitative evaluation of several proposed mechanisms to account for HVD. Under isocapnic hypoxia, simulations indicate that an increase in brain blood flow has no effect on HVD, but that HVD can be entirely described by central ventilatory depression (CVD). Under poikilocapnic hypoxia, the hypocapnia caused by hypoxic hyperventilation has no effect on HVD.
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Affiliation(s)
- Haiying Zhou
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, USA
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Szubski C, Burtscher M, Löscher WN. The effects of short-term hypoxia on motor cortex excitability and neuromuscular activation. J Appl Physiol (1985) 2006; 101:1673-7. [PMID: 16902059 DOI: 10.1152/japplphysiol.00617.2006] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The effects of acute hypoxia on motor cortex excitability, force production, and voluntary activation were studied using single- and double-pulse transcranial magnetic stimulation techniques in 14 healthy male subjects. Electrical supramaximal stimulations of the right ulnar nerve were performed, and transcranial magnetic stimulations were delivered to the first dorsal interosseus motor cortex area during short-term hypoxic (HX) and normoxic (NX) condition. M waves, voluntary activation, F waves, resting motor threshold (rMT), recruitment curves (100-140% of rMT), and short-interval intracortical inhibition and intracortical facilitation were measured. Moreover, motor-evoked potentials (MEPs) and cortical silent periods were determined during brief isometric maximum right index finger abductions. Hypoxia was induced by breathing a fraction of inspired oxygen of 12% via a face mask. M waves, voluntary activation, and F waves did not differ between NX and HX. The rMT was significantly lower in HX (55.79 +/- 9.40%) than in NX (57.50 +/- 10.48%) (P < 0.01), whereas MEP recruitment curve, short-interval intracortical inhibition, intracortical facilitation, maximum right index finger abduction, and MEPs were unaffected by HX. In contrast, the cortical silent periods in HX (158.21 +/- 33.96 ms) was significantly shortened compared with NX (169.42 +/- 39.69 ms) (P < 0.05). These data demonstrate that acute hypoxia results in increased cortical excitability and suggest that acute hypoxia alters motor cortical ion-channel function and GABAergic transmission.
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Affiliation(s)
- Christoph Szubski
- Department of Sports Science, University of Innsbruck, Innsbruck, Austria
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Marwood S, Bowtell JL. Effects of glutamine and hyperoxia on pulmonary oxygen uptake and muscle deoxygenation kinetics. Eur J Appl Physiol 2006; 99:149-61. [PMID: 17115180 DOI: 10.1007/s00421-006-0324-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/04/2006] [Indexed: 11/29/2022]
Abstract
The aim of the present study was to determine whether glutamine ingestion, which has been shown to enhance the exercise-induced increase in the tricarboxylic acid intermediate (TCAi) pool size, resulted in augmentation of the rate of increase in oxidative metabolism at the onset of exercise. In addition, the potential interaction with oxygen availability was investigated by completing exercise in both normoxic and hyperoxic conditions. Eight male cyclists cycled for 6 min at 70% VO2max following consumption of a drink (5 ml kg body mass(-1)) containing a placebo or 0.125 g kg body mass(-1) of glutamine in normoxic (CON and GLN respectively) and hyperoxic (HYP and HPG respectively) conditions. Breath-by-breath pulmonary oxygen uptake and continuous, non-invasive muscle deoxygenation (via near infrared spectroscopy: NIRS) data were collected throughout exercise. The time constant of the phase II component of pulmonary oxygen uptake kinetics was unchanged between trials (CON: 21.5 +/- 3.0 vs. GLN: 18.2 +/- 1.3 vs. HYP: 18.9 +/- 2.0 vs. HPG: 18.6 +/- 1.2 s). There was also no alteration of the kinetics of relative muscle deoxygenation as measured via NIRS (CON: 5.9 +/- 0.7 vs. GLN: 7.3 +/- 0.8 vs. HYP: 6.5 +/- 0.9 vs. HPG: 5.2 +/- 0.4 s). Conversely, the mean response time of pulmonary oxygen uptake kinetics was faster (CON: 33.4 +/- 1.2 vs. GLN: 29.8 +/- 2.3 vs. HYP: 33.2 +/- 2.6 vs. HPG: 31.6 +/- 2.6 s) and the time at which muscle deoxygenation increased above pre-exercise values was earlier (CON: 9.6 +/- 0.9 vs. GLN: 8.7 +/- 1.1 vs. HYP: 8.5 +/- 0.8 vs. HPG: 8.4 +/- 0.7 s) following glutamine ingestion. In normoxic conditions, plasma lactate concentration was lower following glutamine ingestion compared to placebo. Whilst the results of the present study provide some support for the present hypothesis, the lack of any alteration in the time constant of pulmonary oxygen uptake and muscle deoxygenation kinetics suggest that the normal exercise induced expansion of the TCAi pool size is not limiting to oxidative metabolism at the onset of cycle exercise at 70% VO2max.
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Affiliation(s)
- Simon Marwood
- Academy of Sport, Physical Activity and Well-being, London South Bank University, 103 Borough Road, London, SE1 0AA, UK.
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Yu F, Lu S, Yu F, Feng S, McGuire PM, Li R, Wang R. Protective effects of polysaccharide from Euphorbia kansui (Euphorbiaceae) on the swimming exercise-induced oxidative stress in mice. Can J Physiol Pharmacol 2006; 84:1071-9. [PMID: 17218972 DOI: 10.1139/y06-052] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The present study examined the effects of derivatives of galactosides and glucosides in a polysaccharide extract from Euphorbia kansui (Euphorbiaceae) on exercise-induced oxidative stress in mice. Exhaustive swimming exercise significantly increases the degree of lipid peroxidation in terms of malondialdehyde content and reduces the antioxidant activities of superoxide dismutase (SOD) and glutathione peroxidase (GPx). Our findings revealed that chronic oral treatment with the extract elevates enzymatic activities of SOD and GPx accompanied by a corresponding decrease in malondialdehyde. The antioxidative activities of these compounds against exercise-induced oxidative stress are correlated with various activities such as reducing the production of superoxide and hydroxyl radicals, inhibiting lipid peroxidation, enhancing antioxidative defenses, and increasing the production of SOD and GPx activity and expression in different tissues. These compounds may be involved in glycogen metabolism to meet the requirement of working skeletal muscles and act as antioxidants by terminating the chain reaction of lipid peroxidation to maintain the morphological stability of mitochondria in spinal motor neurons. These observations suggest that E. kansui has antioxidative and antifatigue properties and can be given as prophylactic and (or) therapeutic supplements for increasing antioxidant enzyme activities and preventing lipid peroxidation during strenuous exercise.
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Affiliation(s)
- Farong Yu
- School of Public Security, Gansu Institute of Political Science and Law, Lanzhou 730070, China.
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41
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Mantovani V, Kennergren C, Goiny M, Ungerstedt U, Lönnroth P, Sala A, Berglin E. Microdialysis for myocardial metabolic surveillance: developing a clinical technique. Clin Physiol Funct Imaging 2006; 26:224-31. [PMID: 16836695 DOI: 10.1111/j.1475-097x.2006.00680.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Metabolic surveillance of the myocardium is of great interest in cardiac surgery. Microdialysis allows sampling of chemical substances from the interstitial fluid for immediate analysis. The two objectives of this study were to develop a technique for simple and safe implantation of a commercially available microdialysis probe (CMA-70) into the myocardium and to obtain reference data for further use and metabolic control. Eighteen pigs were used in an experimental ischaemic heart model where the left anterior descending coronary artery was occluded for 20 min. Microdialysis was performed proximally as well as distally to the arterial occlusion site corresponding to a control and an ischaemic area in the heart. Two techniques were tried for probe implantation, using either a pacemaker wire attached to the probe tip or a needle introducer. Metabolic substrates (glucose, lactate, glycerol and pyruvate) were collected before, during and after ischaemia, for up to 6 h. Both techniques were highly effective in registering metabolic changes due to ischaemia with sharp time resolution, but the needle introducer was superior regarding probe durability. It is concluded that the CMA-70 microdialysis probe implanted with the needle introducer allows for an accurate monitoring of myocardial metabolism during a prolonged period of time. Future studies in the human heart are warranted to further validate the technique.
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Wadley GD, Lee-Young RS, Canny BJ, Wasuntarawat C, Chen ZP, Hargreaves M, Kemp BE, McConell GK. Effect of exercise intensity and hypoxia on skeletal muscle AMPK signaling and substrate metabolism in humans. Am J Physiol Endocrinol Metab 2006; 290:E694-702. [PMID: 16263768 DOI: 10.1152/ajpendo.00464.2005] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We compared in human skeletal muscle the effect of absolute vs. relative exercise intensity on AMP-activated protein kinase (AMPK) signaling and substrate metabolism under normoxic and hypoxic conditions. Eight untrained males cycled for 30 min under hypoxic conditions (11.5% O(2), 111 +/- 12 W, 72 +/- 3% hypoxia Vo(2 peak); 72% Hypoxia) or under normoxic conditions (20.9% O(2)) matched to the same absolute (111 +/- 12 W, 51 +/- 1% normoxia Vo(2 peak); 51% Normoxia) or relative (to Vo(2 peak)) intensity (171 +/- 18 W, 73 +/- 1% normoxia Vo(2 peak); 73% Normoxia). Increases (P < 0.05) in AMPK activity, AMPKalpha Thr(172) phosphorylation, ACCbeta Ser(221) phosphorylation, free AMP content, and glucose clearance were more influenced by the absolute than by the relative exercise intensity, being greatest in 73% Normoxia with no difference between 51% Normoxia and 72% Hypoxia. In contrast to this, increases in muscle glycogen use, muscle lactate content, and plasma catecholamine concentration were more influenced by the relative than by the absolute exercise intensity, being similar in 72% Hypoxia and 73% Normoxia, with both trials higher than in 51% Normoxia. In conclusion, increases in muscle AMPK signaling, free AMP content, and glucose disposal during exercise are largely determined by the absolute exercise intensity, whereas increases in plasma catecholamine levels, muscle glycogen use, and muscle lactate levels are more closely associated with the relative exercise intensity.
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Affiliation(s)
- G D Wadley
- Department of Physiology, The University of Melbourne, Parkville, Victoria, Australia
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Abstract
Studies in athletes have shown that carnitine supplementation may foster exercise performance. As reported in the majority of studies, an increase in maximal oxygen consumption and a lowering of the respiratory quotient indicate that dietary carnitine has the potential to stimulate lipid metabolism. Treatment with L-carnitine also has been shown to induce a significant postexercise decrease in plasma lactate, which is formed and used continuously under fully aerobic conditions. Data from preliminary studies have indicated that L-carnitine supplementation can attenuate the deleterious effects of hypoxic training and speed up recovery from exercise stress. Recent data have indicated that L-carnitine plays a decisive role in the prevention of cellular damage and favorably affects recovery from exercise stress. Uptake of L-carnitine by blood cells may induce at least three mechanisms: 1) stimulation of hematopoiesis, 2) a dose-dependent inhibition of collagen-induced platelet aggregation, and 3) the prevention of programmed cell death in immune cells. As recently shown, carnitine has direct effects in regulation of gene expression (i.e., carnitine-acyltransferases) and may also exert effects via modulating intracellular fatty acid concentration. Thus there is evidence for a beneficial effect of L-carnitine supplementation in training, competition, and recovery from strenuous exercise and in regenerative athletics.
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Affiliation(s)
- Heidrun Karlic
- Ludwig Boltzmann Institute for Leukemia Research and Hematology, Vienna, Austria.
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Bahlmann L, Misfeld M, Klaus S, Leptien A, Heringlake M, Schmucker P, Sievers HH, Ungerstedt U, Kraatz EG. Myocardial redox state during coronary artery bypass grafting assessed with microdialysis. Intensive Care Med 2004; 30:889-94. [PMID: 14985951 DOI: 10.1007/s00134-004-2199-3] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2003] [Accepted: 10/15/2003] [Indexed: 10/26/2022]
Abstract
PURPOSE Microdialysis allows the biochemical analysis of interstitial fluids of nearly every organ as a bedside procedure. This technique could be useful to reveal data about the myocardial metabolism during cardiopulmonary bypass in human coronary artery bypass graft (CABG) surgery. METHODS In 17 patients undergoing CABG a myocardial microdialysis catheter (CMA 70, CMA/Microdialysis AB, Sweden) was inserted in the apical region of the beating heart. Microdialysis measurements were performed at timed intervals before, during, and after cardiopulmonary bypass (CPB). The concentrations of lactate and pyruvate were analyzed semi-continuously. RESULTS During CPB the myocardial lactate-pyruvate-ratio (LPR) rose from an initial 11 (8-15) to 33 (29-41) ( P<0.01). After CPB the LPR decreased to 4 (3-7) at the end of observation ( P<0.05). The pyruvate concentration showed an immediate increase from 34 (30-42) microM at the end of CPB to 181 (147-234) microM after removal of the cross-clamp with subsequent increase during reperfusion ( P<0.01). Plasma lactate and pyruvate showed no essential changes during the study. CONCLUSION Using the microdialysis technique it was possible to analyze myocardial metabolic changes during CABG. The course of myocardial LPR as a sensitive indicator of the myocardial redox state showed profound changes during and after CPB. We propose the microdialysis technique as an additional monitoring tool in CABG.
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Affiliation(s)
- Ludger Bahlmann
- Department of Anesthesiology, Medical University of Lübeck, Ratzeburger Allee 160, 23538 Lübeck, Germany.
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Otterstedt K, Larsson C, Bill RM, Ståhlberg A, Boles E, Hohmann S, Gustafsson L. Switching the mode of metabolism in the yeast Saccharomyces cerevisiae. EMBO Rep 2004; 5:532-7. [PMID: 15071495 PMCID: PMC1299050 DOI: 10.1038/sj.embor.7400132] [Citation(s) in RCA: 149] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2003] [Revised: 02/25/2004] [Accepted: 02/26/2004] [Indexed: 11/08/2022] Open
Abstract
The biochemistry of most metabolic pathways is conserved from bacteria to humans, although the control mechanisms are adapted to the needs of each cell type. Oxygen depletion commonly controls the switch from respiration to fermentation. However, Saccharomyces cerevisiae also controls that switch in response to the external glucose level. We have generated an S. cerevisiae strain in which glucose uptake is dependent on a chimeric hexose transporter mediating reduced sugar uptake. This strain shows a fully respiratory metabolism also at high glucose levels as seen for aerobic organisms, and switches to fermentation only when oxygen is lacking. These observations illustrate that manipulating a single step can alter the mode of metabolism. The novel yeast strain is an excellent tool to study the mechanisms underlying glucose-induced signal transduction.
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Affiliation(s)
- Karin Otterstedt
- Department of Chemistry and Bioscience-Molecular Biotechnology, Chalmers University of Technology, Box 462, SE-405 30, Göteborg, Sweden.
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Abstract
Two billion years of aerobic evolution have resulted in mammalian cells and tissues that are extremely oxygen-dependent. Exposure to oxygen tensions outside the relatively narrow physiological range results in cellular stress and toxicity. Consequently, hypoxia features prominently in many human diseases, particularly those associated with blood and vascular disorders, including all forms of anemia and ischemia. Bioenergetic enzymes have evolved both acute and chronic oxygen sensing mechanisms to buffer changes of oxygen tension; at normal P(O) oxidative phosphorylation is the principal energy supply for eukaryotic cells, but when the P(O) falls below a critical mark metabolic switches turn off mitochondrial electron transport and activate anaerobic glycolysis. Without this switch cells would suffer an immediate energy deficit and death at low P(O). An intriguing feature of the switching is that the same conditions that regulate energy metabolism also regulate bioenergetic genes, so that enzyme activity and transcription are regulated simultaneously, albeit with different time courses and signaling pathways. In this review we explore the pathways mediating hypoxia-regulated glycolytic enzyme gene expression, focusing on their atavistic traits and evolution.
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Affiliation(s)
- Keith A Webster
- Department of Molecular and Cellular Pharmacology, University of Miami Medical Center, Miami, FL 33136, USA.
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Flück M, Hoppeler H. Molecular basis of skeletal muscle plasticity--from gene to form and function. Rev Physiol Biochem Pharmacol 2003; 146:159-216. [PMID: 12605307 DOI: 10.1007/s10254-002-0004-7] [Citation(s) in RCA: 292] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Skeletal muscle shows an enormous plasticity to adapt to stimuli such as contractile activity (endurance exercise, electrical stimulation, denervation), loading conditions (resistance training, microgravity), substrate supply (nutritional interventions) or environmental factors (hypoxia). The presented data show that adaptive structural events occur in both muscle fibres (myofibrils, mitochondria) and associated structures (motoneurons and capillaries). Functional adaptations appear to involve alterations in regulatory mechanisms (neuronal, endocrine and intracellular signalling), contractile properties and metabolic capacities. With the appropriate molecular techniques it has been demonstrated over the past 10 years that rapid changes in skeletal muscle mRNA expression occur with exercise in human and rodent species. Recently, gene expression profiling analysis has demonstrated that transcriptional adaptations in skeletal muscle due to changes in loading involve a broad range of genes and that mRNA changes often run parallel for genes in the same functional categories. These changes can be matched to the structural/functional adaptations known to occur with corresponding stimuli. Several signalling pathways involving cytoplasmic protein kinases and nuclear-encoded transcription factors are recognized as potential master regulators that transduce physiological stress into transcriptional adaptations of batteries of metabolic and contractile genes. Nuclear reprogramming is recognized as an important event in muscle plasticity and may be related to the adaptations in the myosin type, protein turnover, and the cytoplasma-to-myonucleus ratio. The accessibility of muscle tissue to biopsies in conjunction with the advent of high-throughput gene expression analysis technology points to skeletal muscle plasticity as a particularly useful paradigm for studying gene regulatory phenomena in humans.
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Affiliation(s)
- M Flück
- Institute of Anatomy, University of Bern, Bühlstrasse 26, 3000, Bern 9, Switzerland.
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Klaus S, Heringlake M, Gliemroth J, Pagel H, Staubach K, Bahlmann L. Biochemical tissue monitoring during hypoxia and reoxygenation. Resuscitation 2003; 56:299-305. [PMID: 12628561 DOI: 10.1016/s0300-9572(02)00342-8] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Oxygen deficiency during critical illness may cause profound changes in cellular metabolism and subsequent tissue and organ dysfunction. Clinical treatment in these cases targets rapid reoxygenation to avoid a prolonged impaired synthesis of cellular high-energy phosphates (ATP). However, the effect of this therapeutic intervention on tissue metabolism has not been determined yet. Thus the present study was designed to determine the effects of hypoxia and reoxygenation with either room air or 100% oxygen on variables of interstitial metabolism in different tissues using in vivo microdialysis. Twenty-seven adult, male CD-rats (407-487 g; Ivanovas, Kisslegg, Germany) were studied during general anesthesia. Following preparation and randomization, rats were normoventilated for 45 min (FiO(2) 0.21), followed by induction of hypoxia (FiO(2) 0.1, 40 min) and reoxygenated for 50 min either with FiO(2) 1.0 (group 1, n=10) or FiO(2) 0.21 (group 2, n=10). Control animals (n=7) were ventilated with 21% oxygen during the observation period. Additional to invasive haemodynamic parameters, biochemical tissue monitoring was performed using CMA 20 microdialysis probes, inserted into muscle, subcutaneous space, liver, and the peritoneal cavity allowing analyses of lactate and pyruvate at short intervals. Hypoxia induced a significant reduction in mean arterial pressure (MAP) in group 1 and 2 compared with the control group (P<0.05) without any significant differences between both treatment groups. This was accompanied by a significant increase in blood lactate (10.5+/-3.1 mM (group 1) and 12.3+/-4.1 mM (group 2) vs. 1.5+/-0.3 mM (control); P<0.05) and severe metabolic acidosis (base excess (BE): -18.3+/-5 mM (1) and -17.3+/-7 mM (2) vs. -2.6+/-1.8 mM (control), P<0.05). During hypoxia, the interstitial lacate/pyruvate ratio in groups 1 and 2 increased to 455+/-199% (muscle), 468+/-148% (intraperitoneal), 770+/-218% (hepatic) and 855+/-432% (subcutaneous) (P<0.05 vs. control, respectively). No significant inter-organ or inter-group differences in interstitial dialysates were observed in the treatment groups, neither during hypoxia nor during reoxygenation. Our data suggest, that hypoxia induces comparable metabolic alterations in various tissues and that reoxygenation with 100% oxygen is not superior to 21% oxygen in restoring tissue metabolism after critical hypoxia.
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Affiliation(s)
- Stephan Klaus
- Department of Anaesthesiology, Medical University of Lübeck, Ratzeburger Allee 160, 23538 Lübeck, Germany.
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Stellingwerff T, Watt MJ, Heigenhauser GJF, Spriet LL. Effects of reduced free fatty acid availability on skeletal muscle PDH activation during aerobic exercise. Pyruvate dehydrogenase. Am J Physiol Endocrinol Metab 2003; 284:E589-96. [PMID: 12556353 DOI: 10.1152/ajpendo.00418.2002] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
This study investigated the effect of reduced free fatty acid (FFA) availability on pyruvate dehydrogenase activation (PDHa) and carbohydrate metabolism during moderate aerobic exercise. Eight active male subjects cycled for 40 min at 55% Vo(2 peak) on two occasions. During one trial, subjects ingested 20 mg/kg body mass of the antilipolytic drug nicotinic acid (NA) during the hour before exercise to reduce FFA. Nothing was ingested in the control trial (CON). Blood and expired gas measurements were obtained throughout the trials, and muscle biopsy samples were obtained immediately before exercise and at 5, 20, and 40 min of exercise. Plasma FFA were lower in the NA trial (0.13 +/- 0.01 vs. 0.48 +/- 0.03 mM, P < 0.05), and the respiratory exchange ratio (RER) was increased with NA (0.93 +/- 0.01 vs. 0.89 +/- 0.01, P < 0.05), resulting in a 14.5 +/- 1.8% increase in carbohydrate oxidation compared with CON. PDHa increased rapidly in both trials at exercise onset but was approximately 15% higher (P < 0.05) throughout exercise in the NA trial (2.44 +/- 0.19 and 2.07 +/- 0.12 mmol x kg wet muscle(-1) x min(-1) for NA and CON at 40 min). Muscle glycogenolysis was 15.3 +/- 9.6% greater in the NA trial vs. the CON trial but did not reach statistical significance. Glucose 6-phosphate contents were elevated (P < 0.05) in the NA trial at 30 and 40 min of exercise, but pyruvate and lactate contents were unaffected. These data demonstrate that the reduction of exogenous FFA availability increased the activation of PDH and carbohydrate oxidation during moderate aerobic exercise in men. The increased activation of PDH was not explained by changes in muscle pyruvate or the ATP/ADP ratio but may be related to a decrease in the NADH/NAD(+) ratio or an epinephrine-induced increase in calcium concentration.
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Affiliation(s)
- Trent Stellingwerff
- Department of Human Biology and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada
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50
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Van Hall G, Calbet JAL, Sondergaard H, Saltin B. Similar carbohydrate but enhanced lactate utilization during exercise after 9 wk of acclimatization to 5,620 m. Am J Physiol Endocrinol Metab 2002; 283:E1203-13. [PMID: 12388157 DOI: 10.1152/ajpendo.00134.2001] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We hypothesized that reliance on lactate as a means of energy distribution is higher after a prolonged period of acclimatization (9 wk) than it is at sea level due to a higher lactate Ra and disposal from active skeletal muscle. To evaluate this hypothesis, six Danish lowlanders (25 +/- 2 yr) were studied at rest and during 20 min of bicycle exercise at 146 W at sea level (SL) and after 9 wk of acclimatization to 5,260 m (Alt). Whole body glucose Ra was similar at SL and Alt at rest and during exercise. Lactate Ra was also similar for the two conditions at rest; however, during exercise, lactate Ra was substantially lower at SL (65 micro mol. min(-1). kg body wt(-1)) than it was at Alt (150 micro mol. min(-1). kg body wt(-1)) at the same exercise intensity. During exercise, net lactate release was approximately 6-fold at Alt compared with SL, and related to this, tracer-calculated leg lactate uptake and release were both 3- or 4-fold higher at Alt compared with SL. The contribution of the two legs to glucose disposal was similar at SL and Alt; however, the contribution of the two legs to lactate Ra was significantly lower at rest and during exercise at SL (27 and 81%) than it was at Alt (45 and 123%). In conclusion, at rest and during exercise at the same absolute workload, CHO and blood glucose utilization were similar at SL and at Alt. Leg net lactate release was severalfold higher, and the contribution of leg lactate release to whole body lactate Ra was higher at Alt compared with SL. During exercise, the relative contribution of lactate oxidation to whole body CHO oxidation was substantially higher at Alt compared with SL as a result of increased uptake and subsequent oxidation of lactate by the active skeletal muscles.
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Affiliation(s)
- G Van Hall
- Copenhagen Muscle Research Centre, Rigshospitalet section 7652, DK-2100 Copenhagen Ø, Denmark.
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