Hypoxia-Induced Oxidative Stress Modulation with Physical Activity

Altitude and COVID-19: Friend or foe? A narrative review

Recent reports suggest that high-altitude residence may be beneficial in the novel coronavirus disease (COVID-19) implicating that traveling to high places or using hypoxic conditioning thus could be favorable as well. Physiological high-altitude characteristics and symptoms of altitude illnesses furthermore seem similar to several pathologies associated with COVID-19. As a consequence, high altitude and hypoxia research and related clinical practices are discussed for potential applications in COVID-19 prevention and treatment. We summarize the currently available evidence on the relationship between altitude/hypoxia conditions and COVID-19 epidemiology and pathophysiology. The potential for treatment strategies used for altitude illnesses is evaluated. Symptomatic overlaps in the pathophysiology of COVID-19 induced ARDS and high altitude illnesses (i.e., hypoxemia, dyspnea…) have been reported but are also common to other pathologies (i.e., heart failure, pulmonary embolism, COPD…). Most treatments of altitude illnesses have limited value and may even be detrimental in COVID-19. Some may be efficient, potentially the corticosteroid dexamethasone. Physiological adaptations to altitude/hypoxia can exert diverse effects, depending on the constitution of the target individual and the hypoxic dose. In healthy individuals, they may optimize oxygen supply and increase mitochondrial, antioxidant, and immune system function. It is highly debated if these physiological responses to hypoxia overlap in many instances with SARS-CoV-2 infection and may exert preventive effects under very specific conditions. The temporal overlap of SARS-CoV-2 infection and exposure to altitude/hypoxia may be detrimental. No evidence-based knowledge is presently available on whether and how altitude/hypoxia may prevent, treat or aggravate COVID-19. The reported lower incidence and mortality of COVID-19 in high-altitude places remain to be confirmed. High-altitude illnesses and COVID-19 pathologies exhibit clear pathophysiological differences. While potentially effective as a prophylactic measure, altitude/hypoxia is likely associated with elevated risks for patients with COVID-19. Altogether, the different points discussed in this review are of possibly some relevance for individuals who aim to reach high-altitude areas. However, due to the ever-changing state of understanding of COVID-19, all points discussed in this review may be out of date at the time of its publication.

Dietary Adjustments to Altitude Training in Elite Endurance Athletes; Impact of a Randomized Clinical Trial With Antioxidant-Rich Foods

Background: Altitude training stresses several physiological and metabolic processes and alters the dietary needs of the athletes. International Olympic Committee (IOC)'s Nutrition Expert Group suggests that athletes should increase intake of energy, carbohydrate, iron, fluid, and antioxidant-rich foods while training at altitude. Objective: We investigated whether athletes adjust their dietary intake according to the IOC's altitude-specific dietary recommendations, and whether an in-between meal intervention with antioxidant-rich foods altered the athletes' dietary composition and nutrition-related blood parameters (mineral, vitamin, carotenoid, and hormone concentrations). Design: The dietary adjustments to altitude training (3 weeks at 2,320 m) were determined for 31 elite endurance athletes (23 ± 5 years, 23 males, 8 females) by six interviewer-administered 24-h dietary recalls on non-consecutive days; three before and during the altitude camp. The additional effect of in -between meal intervention with eucaloric antioxidant-rich or control snacks (1,000 kcal/day) was tested in a randomized controlled trial with parallel design. Results: At altitude the athletes increased their energy intake by 35% (1,430 ± 630 kcal/day, p < 0.001), the provided snacks accounting for 70% of this increase. Carbohydrate intake increased from 6.5 ± 1.8 g/kg body weight (BW) (50 E%) to 9.3 ± 2.1 g/kg BW (53 E%) (p < 0.001), with no difference between the antioxidant and control group. Dietary iron, fluid, and antioxidant-rich food intake increased by 37, 38, and 104%, respectively, in the whole cohort. The intervention group had larger increases in polyunsaturated fatty acids (PUFA), ω3 PUFA (n-3 fatty acids), ω6 PUFA (n-6 fatty acids), fiber, vitamin C, folic acid, and copper intake, while protein intake increased more among the controls, reflecting the nutritional content of the snacks. Changes in the measured blood minerals, vitamins, and hormones were not differentially affected by the intervention except for the carotenoid; zeaxanthin, which increased more in the intervention group (p < 0.001). Conclusions: Experienced elite endurance athletes increased their daily energy, carbohydrate, iron, fluid, and antioxidant-rich food intake during a 3-week training camp at moderate altitude meeting most of the altitude-specific dietary recommendations. The intervention with antioxidant-rich snacks improved the composition of the athletes' diets but had minimal impact on the measured nutrition-related blood parameters. Clinical Trial Registry Number: NCT03088891 (www.clinicaltrials.gov), Norwegian registry number: 626539 (https://rekportalen.no/).

Cerebral Small Vessel Disease

Cerebral small vessel disease (CSVD) represents a cluster of various vascular disorders with different pathological backgrounds. The advanced vasculature net of cerebral vessels, including small arteries, capillaries, arterioles and venules, is usually affected. Processes of oxidation underlie the pathology of CSVD, promoting the degenerative status of the epithelial layer. There are several classifications of cerebral small vessel diseases; some of them include diseases such as Binswanger’s disease, leukoaraiosis, cerebral microbleeds (CMBs) and lacunar strokes. This paper presents the characteristics of CSVD and the impact of the current knowledge of this topic on the diagnosis and treatment of patients.

Coal Dust-Induced Systematic Hypoxia and Redox Imbalance among Coal Mine Workers

Continuous inhalation of coal dust among coal workers leads to a variety of disorders. The present study aims to evaluate the potential oxidative stress associated with coal dust generated from coal mining activities among exposed workers through the antioxidant enzyme system, including superoxide dismutase (SOD), catalase (CAT), and glutathione (GSH). In this study cohort, intensive coal mine workers were assessed for antioxidant variations. Blood samples were collected from dust-exposed workers (engaged in different activities at coal mines; n = 311) and residents of the same city (nonexposed, control group; n = 50). The workers' exposure to coal dust was categorized based on working area (administrative group, surface workers, underground workers), working hours (up to 8 h and more than 8 h), and time of service. The results showed significantly altered activities of SOD, CAT, and GSH among the whole exposed group and its categories compared to the control group. A significant difference was also observed between high- and low-exposure groups. Statistical analysis revealed a negative correlation between antioxidant activity (catalase and SOD) and coal dust levels. Besides, coal exposure was associated with the time of service, smoking status, and dietary habits. The findings of this study reveal higher oxidative stress among highly exposed coal mine workers (underground workers > surface workers > administrative group > nonexposed group), and longer working hours have more pronounced adverse effects on workers' health.

Increased Antioxidant Capacity and Pro-Homeostatic Lipid Mediators in Ocular Hypertension-A Human Experimental Model

The main risk factor for primary open-angle glaucoma (POAG) is increased intraocular pressure (IOP). It is of interest that about half of the patients have an IOP within the normal range (normal-tension glaucoma, NTG). Additionally, there is a group of patients with a high IOP but no glaucomatous neurodegeneration (ocular hypertension, OHT). Therefore, risk factors other than IOP are involved in the pathogenesis of glaucoma. Since the retina has a very high oxygen-demand, decreased autoregulation and a fluctuating oxygen supply to the retina have been linked to glaucomatous neurodegeneration. To assess the significance of these mechanisms, we have utilized a human experimental model, in which we stress participants with a fluctuating oxygen supply. Levels of oxidative stress molecules, antioxidants, and lipid mediators were measured in the plasma. Patients with NTG, OHT, and control subjects were found to have similar levels of oxidative stress markers. In contrast, patients with OHT had a higher level of total antioxidant capacity (TAC) and pro-homeostatic lipid mediators. Thus, we suggest that OHT patients manage fluctuating oxygen levels more efficiently and, thus, are less susceptible to glaucomatous neurodegenerations, due to enhanced systemic antioxidant protection.

Effects of physical exercise on the prevention of stem cells senescence

Regular physical activity is essential for maintaining wellbeing; physical inactivity, on the contrary, is considered by the World Health Organization (WHO) as one of the most important risk factors for global mortality. During physical exercise different growth factors, cytokines and hormones are released, which affect positively the functions of heart, bone, brain and skeletal muscle. It has been reported that physical activity is able to stimulate tissue remodeling. Therefore, in this scenario, it is important to deepen the topic of physical activity-induced effects on stem cells.

Hypoxia-mediated regulation of mitochondrial transcription factors in renal epithelial cells: implications for hypertensive renal physiology

Kidneys have a high resting metabolic rate and low partial pressure of oxygen due to enhanced mitochondrial oxygen consumption and ATP production needed for active solute transport. Heightened mitochondrial activity leads to progressively increasing hypoxia from the renal cortex to the renal medulla. Renal hypoxia is prominent in hypertensive rats due to increased sodium reabsorption within the nephrons, which demands higher energy production by oxidative phosphorylation (OXPHOS). Consequently, spontaneously hypertensive rats (SHR) display greater oxygen deficiency (hypoxia) than normotensive Wistar Kyoto rats (WKY). Here, we sought to investigate the expression of key proteins for mitochondrial biogenesis in SHR and WKY, and study the regulation of mitochondrial transcription factors (mtTFs) under in vitro hypoxic conditions in renal epithelial cells. We report that renal expressions of hypoxia-inducible factor-1-alpha (HIF-1α), peroxisome proliferator-activated receptor-gamma coactivator-1-alpha (PGC-1α), mtTFs, and OXPHOS proteins are elevated in SHR compared to WKY. In addition, our experiments in cultured kidney cells demonstrate that acute hypoxia augments the expression of these genes. Furthermore, we show that the transcripts of HIF-1α and mtTFs are positively correlated in various human tissues. We reveal, for the first time to our knowledge, that HIF-1α transactivates mtTF genes by direct interaction with their promoters in rat kidney epithelial cells (NRK-52E) under acute hypoxia. Concomitant increases in the mitochondrial DNA and RNA, and OXPHOS proteins are observed. Taken together, this study suggests that hypoxia within the renal epithelial cells may enhance mitochondrial function to meet the energy demand in proximal tubular cells during prehypertensive stages in kidneys of young SHR.

Cardiovascular and metabolic responses to passive hypoxic conditioning in overweight and mildly obese individuals

Although severe intermittent hypoxia (IH) is well known to induce deleterious cardiometabolic consequences, moderate IH may induce positive effects in obese individuals. The present study aimed to evaluate the effect of two hypoxic conditioning programs on cardiovascular and metabolic health status of overweight or obese individuals. In this randomized single-blind controlled study, 35 subjects (54 ± 9.3 yr, 31.7 ± 3.5 kg/m²) were randomized into three 8-wk interventions (three 1-h sessions per week): sustained hypoxia (SH), arterial oxygen saturation ([Formula: see text]) = 75%; IH, 5 min [Formula: see text] = 75% - 3 min normoxia; normoxia. Ventilation, heart rate, blood pressure, and tissue oxygenation were measured during the first and last hypoxic conditioning sessions. Vascular function, blood glucose and insulin, lipid profile, nitric oxide metabolites, and oxidative stress were evaluated before and after the interventions. Both SH and IH increased ventilation in hypoxia (+1.8 ± 2.1 and +2.3 ± 3.6 L/min, respectively; P < 0.05) and reduced normoxic diastolic blood pressure (-12 ± 15 and -13 ± 10 mmHg, respectively; P < 0.05), whereas changes in normoxic systolic blood pressure were not significant (+3 ± 9 and -6 ± 13 mmHg, respectively; P > 0.05). IH only reduced heart rate variability (e.g., root-mean-square difference of successive normal R-R intervals in normoxia -21 ± 35%; P < 0.05). Both SH and IH induced no significant change in body mass index, vascular function, blood glucose, insulin and lipid profile, nitric oxide metabolites, or oxidative stress, except for an increase in superoxide dismutase activity following SH. This study indicates that passive hypoxic conditioning in obese individuals induces some positive cardiovascular and respiratory improvements despite no change in anthropometric data and even a reduction in heart rate variability during IH exposure.

Nutrition and Altitude: Strategies to Enhance Adaptation, Improve Performance and Maintain Health: A Narrative Review

Training at low to moderate altitudes (~ 1600-2400 m) is a common approach used by endurance athletes to provide a distinctive environmental stressor to augment training stimulus in the anticipation of increasing subsequent altitude- and sea-level-based performance. Despite some scientific progress being made on the impact of various nutrition-related changes in physiology and associated interventions at mountaineering altitudes (> 3000 m), the impact of nutrition and/or supplements on further optimization of these hypoxic adaptations at low-moderate altitudes is only an emerging topic. Within this narrative review we have highlighted six major themes involving nutrition: altered energy availability, iron, carbohydrate, hydration, antioxidant requirements and various performance supplements. Of these issues, emerging data suggest that particular attention be given to the potential risk for poor energy availability and increased iron requirements at the altitudes typical of elite athlete training (~ 1600-2400 m) to interfere with optimal adaptations. Furthermore, the safest way to address the possible increase in oxidative stress associated with altitude exposure is via the consumption of antioxidant-rich foods rather than high-dose antioxidant supplements. Meanwhile, many other important questions regarding nutrition and altitude training remain to be answered. At the elite level of sport where the differences between winning and losing are incredibly small, the strategic use of nutritional interventions to enhance the adaptations to altitude training provides an important consideration in the search for optimal performance.

Physical exercise: An inducer of positive oxidative stress in skeletal muscle aging

Oxidative stress is the core of most pathological situations, and its attribution toward disease conversion is not yet well established. The adaptive capacity of a cell can overcome ROS-induced pathology. However, when a cell fails to extend its maximum adaptive capacity against oxidative stress, it could lead a cell to misbehave or defunct from its normal functions. Any type of physical activity can increase the cells' maximum adaptive capacity, but aging can limit this. However, whether aging is the initiating point of reducing cells' adaptive capacity against oxidative stress or oxidative stress can induce the aging process is a mystery, and it could be the key to solving several uncured diseases. Paradoxically, minimum ROS is needed for cellular homeostasis. Nevertheless, finding factors that can limit or nullify the production of ROS for cellular homeostasis is a million-dollar question. Regular physical exercise is considered to be one of the factors that can limit the production of ROS and increase the ROS-induced benefits in the cells through inducing minimum oxidative stress and increasing maximum adapting capacity against oxidative stress-induced damages. The type and intensity of exercise that can produce such positive effects in the cells remain unclear. Therefore, this review discusses how physical exercise can help to produce minimal positive oxidative stress in preventing skeletal muscle aging.

Hypoxia-Induced Degenerative Protein Modifications Associated with Aging and Age-Associated Disorders

Aging is an inevitable time-dependent decline of various physiological functions that finally leads to death. Progressive protein damage and aggregation have been proposed as the root cause of imbalance in regulatory processes and risk factors for aging and neurodegenerative diseases. Oxygen is a modulator of aging. The oxygen-deprived conditions (hypoxia) leads to oxidative stress, cellular damage and protein modifications. Despite unambiguous evidence of the critical role of spontaneous non-enzymatic Degenerative Protein Modifications (DPMs) such as oxidation, glycation, carbonylation, carbamylation, and deamidation, that impart deleterious structural and functional protein alterations during aging and age-associated disorders, the mechanism that mediates these modifications is poorly understood. This review summarizes up-to-date information and recent developments that correlate DPMs, aging, hypoxia, and age-associated neurodegenerative diseases. Despite numerous advances in the study of the molecular hallmark of aging, hypoxia, and degenerative protein modifications during aging and age-associated pathologies, a major challenge remains there to dissect the relative contribution of different DPMs in aging (either natural or hypoxia-induced) and age-associated neurodegeneration.

Effect of pre-term birth on oxidative stress responses to normoxic and hypoxic exercise

Pre-term birth is a major health concern that occurs in approximately 10% of births worldwide. Despite high incidence rate, long-term consequences of pre-term birth remain unclear. Recent evidence suggests that elevated oxidative stress observed in pre-term born infants could persist into adulthood. Given that oxidative stress is known to play an important role in response to physical activity and hypoxia, we investigated whether oxidative stress responses to acute exercise in normoxia and hypoxia may be differently modulated in pre-term vs. full-term born adults. Twenty-two pre-term born and fifteen age-matched full-term born controls performed maximal incremental cycling tests in both normoxia (FiO2: 0.21) and normobaric hypoxia (FiO2: 0.13; simulated altitude of 3800 m) in blinded and randomized manner. Plasma levels of oxidative stress (advanced oxidation protein products [AOPP] and malondialdehyde), antioxidant (ferric reducing antioxidant power, glutathione peroxidase, catalase [CAT] and superoxide dismutase [SOD]) and nitrosative stress markers (nitrotyrosine, nitrite and total nitrite and nitrate [NOx]) were measured before and immediately after each test. AOPP (+24%, P<0.001), CAT (+38%, P<0.001) and SOD (+12%, P=0.018) and NOx (+17%, P=0.024) significantly increased in response to exercise independently of condition and birth status. No difference in response to acute exercise in normoxia was noted between pre-term and full-term born adults in any of measured markers. Hypoxic exposure during exercise resulted in significant increase in AOPP (+45%, P=0.008), CAT (+55%, P=0.019) and a trend for an increase in nitrite/nitrate content (+35%, P=0.107) only in full-term and not pre-term born individuals. These results suggest that prematurely born adult individuals exhibit higher resistance to oxidative stress response to exercise in hypoxia.

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Oxidative stress and antioxidant activity are increased in full-term and pre-term adults following normoxic exercise.

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Plasma AOPP, catalase and NOx levels are not increased in pre-term adults following an acute exercise in hypoxia.

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Oxidative stress is differently regulated in pre-term adults during acute physical exercise under hypoxic condition.

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Pre-term birth may have long term consequences concerning oxidative stress regulation especially during these conditions.

Redox Homeostasis in Humans Exposed to Intermittent Hypoxia-Normoxia and to Intermittent Hypoxia-Hyperoxia

Aim: Exposure to hypoxia is known to increase oxidative stress and to impair antioxidant defenses in humans. The aim of the study was to measure oxidative stress and antioxidant capacity in healthy humans after being acutely exposed to both intermittent hypoxia-normoxia (IHN) and intermittent hypoxia-hyperoxia (IHH). Methods: Twenty-one healthy, young male participants were exposed to both IHN and IHH (fraction of inspired oxygen [FIO₂] 0.11 for up to 7 minutes followed by 3-5 minutes of exposure to normoxia (room air) or hyperoxia, FIO₂ 0.3-0.35) in a crossover design study. In each participant, oxidative stress and antioxidant capacity were measured before and after each exposure in both experimental conditions. Results: After IHN, compared with baseline, neither oxidative stress (289.1 ± 63.2 vs. 262.2 ± 85.2 UCarr) nor antioxidant capacity (2376.1 ± 452.9 vs. 2525.0 ± 400.7 UCor) was significantly different. After IHH, neither oxidative stress (285.1 ± 94.2 vs. 277.5 ± 86.7 UCarr) nor antioxidant capacity (2653.6 ± 492.7 vs. 2568.4 ± 427.4 UCor) was significantly different compared with baseline. When the two studied exposure modalities were compared, there was no significant difference between groups with respect to both oxidative stress and antioxidant capacity. Conclusions: These data suggest that exposing healthy individuals to short-term IHN and IHH does not increase oxidative stress and it does not impair antioxidant defenses.

NANDROLONE DECANOATE IS PROOXIDANT IN THE MYOCARDIUM OF EXERCISED OR SEDENTARY RATS

ABSTRACT Introduction: Nandrolone decanoate is a synthetic testosterone analogue considered one of the most widely used anabolic androgenic steroids (AAS) among adolescents and athletes. Chronic ingestion of AAS increases the incidence of cardiovascular abnormalities in athletes, but the mechanism that causes these changes remains unknown. Objectives: The purpose of this study is to verify the possible effects of the use of anabolic androgenic steroids (AAS) on the morphology and oxidative metabolism of the heart in exercised and sedentary rats. Methods: This is a comparative prospective level II study. Twenty-four Wistar rats were distributed in groups that performed voluntary (TG) and sedentary (SG) running exercises, and used AAS: the Anabolic Training Group (ATG), and the Anabolic Sedentary Group (ASG). During the three months of the running protocol, the animals received an intramuscular injection of 5 mg/kg b.p. of AAS. After the training period, the rats were euthanized and the hearts were removed for evaluation of lipid peroxidation and antioxidant capacity, and for morphometric analysis. Results: The anabolic groups, ASG (0.3072 ± 0.0531) and ATG (0.2732 ± 0.0413), presented higher lipid peroxidation when compared to the non-anabolic groups SG (0.1705 ± 0.0224) and TG (0.1785 ± 0.0340). Conclusion: There was no change in total antioxidant capacity or in the thickness of the interventricular septum and left ventricular wall. Thus, the use of anabolic androgenic steroids did not cause morphological changes in the myocardium. However it did alter the oxidative metabolism. It was also verified that aerobic exercise had no protective effect against lipid peroxidation in the myocardium caused by the use of AAS. Level of evidence II; Prospective comparative study.

Saliva panel of protein candidates: A comprehensive study for assessing high altitude acclimatization

Altitude acclimatization describes the processes whereby lowland humans respond to decreased partial pressure of oxygen. It refers to the changes seen as beneficial and involves a series of physiological adjustments that compensate for reduced ambient PO₂, as opposed to changes that are pathological. Although numerous reports document the physiological effects of exposure to hypobaric hypoxia of varying durations but an interesting aspect overlooked by many researchers is that of acclimatization related studies. As proteome, a dynamic entity responds immediately to external stimuli, protein markers and their trends can be studied to assess acclimatization status of an individual. Compared to blood, the use of saliva is advantageous because sample collection and processing are easy, minimally invasive, low cost and better tolerated by individuals. In this study, we employed iTRAQ based LC-MS/MS technique for comparing saliva samples from humans exposed to hypobaric hypoxia from 7 to 120 days with normoxic controls followed by analysis using Ingenuity Pathway Analysis software and validation by immunoassays. Nearly 67 proteins were found to be differentially expressed in the exposed groups as compared to normoxia indicating modulated canonical pathways as lipid metabolism; acute phase response signalling and proteins as carbonic anhydrase 6, alpha-enolase, albumin, and prolactin inducible protein. Collectively, this study provides the proof of concept for the non-invasive assessment of high altitude acclimatization.

Physical Activity Prevents Cartilage Degradation: A Metabolomics Study Pinpoints the Involvement of Vitamin B6

Osteoarthritis (OA) is predominantly characterized by the progressive degradation of articular cartilage, the connective tissue produced by chondrocytes, due to an imbalance between anabolic and catabolic processes. In addition, physical activity (PA) is recognized as an important tool for counteracting OA. To evaluate PA effects on the chondrocyte lineage, we analyzed the expression of SOX9, COL2A1, and COMP in circulating progenitor cells following a half marathon (HM) performance. Therefore, we studied in-depth the involvement of metabolites affecting chondrocyte lineage, and we compared the metabolomic profile associated with PA by analyzing runners’ sera before and after HM performance. Interestingly, this study highlighted that metabolites involved in vitamin B6 salvage, such as pyridoxal 5′-phosphate and pyridoxamine 5′-phosphate, were highly modulated. To evaluate the effects of vitamin B6 in cartilage cells, we treated differentiated mesenchymal stem cells and the SW1353 chondrosarcoma cell line with vitamin B6 in the presence of IL1β, the inflammatory cytokine involved in OA. Our study describes, for the first time, the modulation of the vitamin B6 salvage pathway following PA and suggests a protective role of PA in OA through modulation of this pathway.

The interactive effects of acute exercise and hypoxia on cognitive performance: A narrative review

Acute moderate intensity exercise has been shown to improve cognitive performance. In contrast, hypoxia is believed to impair cognitive performance. The detrimental effects of hypoxia on cognitive performance are primarily dependent on the severity and duration of exposure. In this review, we describe how acute exercise under hypoxia alters cognitive performance, and propose that the combined effects of acute exercise and hypoxia on cognitive performance are mainly determined by interaction among exercise intensity and duration, the severity of hypoxia, and duration of exposure to hypoxia. We discuss the physiological mechanism(s) of the interaction and suggest that alterations in neurotransmitter function, cerebral blood flow, and possibly cerebral metabolism are the primary candidates that determine cognitive performance when acute exercise is combined with hypoxia. Furthermore, acclimatization appears to counteract impaired cognitive performance during prolonged exposure to hypoxia although the precise physiological mechanism(s) responsible for this amelioration remain to be elucidated. This review has implications for sporting, occupational, and recreational activities at terrestrial high altitude where cognitive performance is essential. Further studies are required to understand physiological mechanisms that determine cognitive performance when acute exercise is performed in hypoxia.

Effects of Whole-Body Vibration Training Combined With Cyclic Hypoxia on Bone Mineral Density in Elderly People

Prevention and treatment of osteoporosis are an issue of great concern in public health so that the increase/maintenance of whole-body bone mineral density (BMD) is clinically relevant and could reduce the financial burden. Whole-body vibration (WBV) has been recently proposed as a potential alternative to bone stimulation, which combined with therapies, could provide a new treatment for osteoporosis prevention. In this sense, moderate cyclic hypoxia protocols may help to restrain osteoclastic activity and/or stimulate osteoblastic activity, enhance the effects of whole-body vibration alone. So, the present study investigated the effects of cyclic hypoxic exposure combined with WBV training on BMD of the elderly. Healthy elderly persons (n = 30) were randomly assigned to a (1) Hypoxia-Whole Body Vibration group (HWBV; n = 10), (2) Normoxic-Whole Body Vibration group (NWBV; n = 10) or (3) Control group (CON; n = 10). During 18 weeks, HWBV performed WBV treatment under normobaric hypoxic conditions (16.1% FiO₂). A vibration session included 4 bouts of 30 s (12.6 Hz–4 mm) with 1 min rest between bouts. NWBV performed the same vibration treatment as HWBV but under normoxic conditions. Whole-body and proximal femur BMD (g⋅cm⁻²) were measured using dual-energy X-ray absorptiometry. Two-way ANOVA indicated a borderline significant (p = 0.07) time x group interaction for total BMD; post hoc analysis revealed a slight but significant (p = 0.021) increase of BMD after treatment in the HWBV group. In conclusion, 18-week WBV training with hypoxic stimuli has shown positive effects for the participants of the current study. As changes did not differ significantly between groups, future large-scale studies will be necessary to confirm these findings.

Effects of antioxidant-rich foods on altitude-induced oxidative stress and inflammation in elite endurance athletes: A randomized controlled trial

Background

Various altitude training regimes, systematically used to improve oxygen carrying capacity and sports performance, have been associated with increased oxidative stress and inflammation. We investigated whether increased intake of common antioxidant-rich foods attenuates these processes.

Methods

In a randomized controlled trial, 31 elite endurance athletes (23 ± 5 years), ingested antioxidant-rich foods (n = 16), (> doubling their usual intake), or eucaloric control foods (n = 15) during a 3-week altitude training camp (2320 m). Fasting blood and urine samples were collected 7 days pre-altitude, after 5 and 18 days at altitude, and 7 days post-altitude. Change over time was compared between the groups using mixed models for antioxidant capacity [uric acid-free (ferric reducing ability of plasma (FRAP)], oxidative stress (8-epi-PGF_2α) and inflammatory biomarkers (IFNγ, IL1α, IL1RA, IL1β, IL2, IL5, IL6, IL7, IL10, IL12p70, IL13, IL17, TNFα, MCP-1 and micro-CRP). The cytokine response to a stress-test (VO_2max ramp test or 100 m swimming) was assessed at pre- and post-altitude.

Results

FRAP increased more in the antioxidant compared to the control group (p = 0.034). IL13 decreased in the antioxidant group, while increasing in the controls (p = 0.006). A similar trend was seen for IL6 (p = 0.062). A larger decrease in micro-CRP was detected in the antioxidant group compared to controls (β: -0.62, p = 0.02). We found no group differences for the remaining cytokines. 8-epi-PGF_2α increased significantly in the whole population (p = 0.033), regardless group allocation. The stress response was significantly larger post-altitude compared with pre-altitude for IL1β, IL6, IL7, IL13, IL12p70 and TNFα, but we found no group differences.

Conclusions

Increased intake of antioxidant-rich foods elevated the antioxidant capacity and attenuated some of the altitude-induced systemic inflammatory biomarkers in elite athletes. The antioxidant intervention had no impact on the altitude-induced oxidative stress or changes in acute cytokine responses to exercise stress-tests.

Exercise Overrides Blunted Hypoxic Ventilatory Response in Prematurely Born Men

Purpose

Pre-term birth provokes life-long anatomical and functional respiratory system sequelae. Although blunted hypoxic ventilatory response (HVR) is consistently observed in pre-term infants, it remains unclear if it persists with aging and, moreover, if it influences hypoxic exercise capacity. In addition, it remains unresolved whether the previously observed prematurity-related alterations in redox balance could contribute to HVR modulation.

Methods

Twenty-one prematurely born adult males (gestational age = 29 ± 4 weeks], and 14 age matched controls born at full term (gestational age = 39 ± 2 weeks) underwent three tests in a randomized manner: (1) hypoxia chemo-sensitivity test to determine the resting and exercise poikilocapnic HVR and a graded exercise test to volitional exhaustion in (2) normoxia (F_iO₂ = 0.21), and (3) normobaric hypoxia (F_iO₂ = 0.13) to compare the hypoxia-related effects on maximal aerobic power (MAP). Selected prooxidant and antioxidant markers were analyzed from venous samples obtained before and after the HVR tests.

Results

Resting HVR was lower in the pre-term (0.21 ± 0.21 L ⋅ min^-1 ⋅ kg^-1) compared to full-term born individuals (0.47 ± 0.23 L ⋅ min^-1 ⋅ kg^-1; p < 0.05). No differences were noted in the exercise HVR or in any of the measured oxidative stress markers before or after the HVR test. Hypoxia-related reduction of MAP was comparable between the groups.

Conclusion

These findings indicate that blunted resting HVR in prematurely born men persists into adulthood. Also, active adults born prematurely seem to tolerate hypoxic exercise well and should, hence, not be discouraged to engage in physical activities in hypoxic environments. Nevertheless, the blunted resting HVR and greater desaturation observed in the pre-term born individuals warrant caution especially during prolonged hypoxic exposures.

Bioinspired Small-Molecule Tools for the Imaging of Redox Biology

The availability of electrons to biological systems underpins the mitochondrial electron transport chain (ETC) that powers living cells. It is little wonder, therefore, that the sufficiency of electron supply is critical to cellular health. Considering mitochondrial redox activity alone, a lack of oxygen (hypoxia) leads to impaired production of adenosine triphosphate (ATP), the major energy currency of the cell, whereas excess oxygen (hyperoxia) is associated with elevated production of reactive oxygen species (ROS) from the interaction of oxygen with electrons that have leaked from the ETC. Furthermore, the redox proteome, which describes the reversible and irreversible redox modifications of proteins, controls many aspects of biological structure and function. Indeed, many major diseases, including cancer and diabetes, are now termed "redox diseases", spurring much interest in the measurement and monitoring of redox states and redox-active species within biological systems. In this Account, we describe recent efforts to develop magnetic resonance (MR) and fluorescence imaging probes for studying redox biology. These two classes of molecular imaging tools have proved to be invaluable in supplementing the structural information that is traditionally provided by MRI and fluorescence microscopy, respectively, with highly sensitive chemical information. Importantly, the study of biological redox processes requires sensors that operate at biologically relevant reduction potentials, which can be achieved by the use of bioinspired redox-sensitive groups. Since oxidation-reduction reactions are so crucial to modulating cellular function and yet also have the potential to damage cellular structures, biological systems have developed highly sophisticated ways to regulate and sense redox changes. There is therefore a plethora of diverse chemical structures in cells with biologically relevant reduction potentials, from transition metals to organic molecules to proteins. These chemical groups can be harnessed in the development of exogenous molecular imaging agents that are well-tuned to biological redox events. To date, small-molecule redox-sensitive tools for oxidative stress and hypoxia have been inspired from four classes of cellular regulators. The redox-sensitive groups found in redox cofactors, such as flavins and nicotinamides, can be used as reversible switches in both fluorescent and MR probes. Enzyme substrates that undergo redox processing within the cell can be modified to provide fluorescence or MR readout while maintaining their selectivity. Redox-active first-row transition metals are central to biological homeostasis, and their marked electronic and magnetic changes upon oxidation/reduction have been used to develop MR sensors. Finally, redox-sensitive amino acids, particularly cysteine, can be utilized in both fluorescent and MR sensors.

Significance of malondialdehyde, superoxide dismutase and endotoxin levels in Budd-Chiari syndrome in patients and a rat model

Budd-Chiari syndrome (BCS) is a rare clinical syndrome caused by the obstruction of hepatic venous outflow. In theory, hepatic congestion and hypoxia induce pathological damage and changes in the liver. However, at present, laboratory evidence supporting this theory is lacking. The aim of the present study was to assess the expression and significance of the hypoxia-associated indicators malondialdehyde (MDA), superoxide dismutase (SOD) and endotoxin (ET) in the liver and serum of subjects with BCS. An animal model of BCS was established by partial ligation of the inferior vena cava (IVC) in rats. The levels of MDA, SOD and ET in the serum of BCS patients, as well as in the liver and serum of rats with BCS, were detected and analyzed. In human patients with BCS, the serum levels of MDA, ET and SOD were significantly different from those in healthy control subjects. In the animal model, similar trends were observed regarding the MDA, ET and SOD levels in liver homogenate and serum (P<0.05), the degree of which was more pronounced in the liver homogenate than in the serum. At 6 weeks after the surgery, these indicators reached peak/valley levels in the experimental group and were at least partially restored by week 12. A negative correlation between MDA and SOD, a positive correlation between MDA and ET, and a negative correlation between SOD and ET was identified. In conclusion, the levels of hypoxia-associated indicators significantly changed with BCS progression, suggesting that hypoxia is a major factor in the pathogenesis of BCS.

Impact of high altitude on key determinants of female reproductive health: a review

Imperishable research work was done on females visiting high-altitude (HA) areas for recreational activities or job purposes as well as on female HA natives. Hypoxia at HA is an unavoidable condition that affects the determinants of female reproductive functions like, the age of menarche and menopause, whole reproductive span, hormone synthesis, and fertility. This review will emphasize whether HA hypoxia is a threat to women: residents or visitors by analyzing these proximate determinants. Delayed menarcheal and advanced menopausal age was found to shorten the reproductive span in some HA populations, whereas in some cases, menstrual cycle was also reported to be irregular. In addition, the completed fertility rate (CFR) was increased when people migrated to lower altitude. Altered stress hormones and reproductive hormones were observed in sea-level females exposed to HA. Oxidative stress (OS) at HA was also reviewed to explain the probable reasons for the observed changes in these determinants because disturbed redox homeostasis may be a connecting link, affecting the reproductive functions. In conclusion, HA hypoxia plays a crucial role on various determinants of female reproductive health and this review will be helpful for more precise study along with the probable underlying mechanisms responsible for the changes in female reproductive functions at HA.

A Personalized Physical Activity Program With Activity Trackers and a Mobile Phone App for Patients With Metastatic Breast Cancer: Protocol for a Single-Arm Feasibility Trial

BACKGROUND

About 5% of breast cancer cases are metastatic at diagnosis, and 20%-30% of localized breast cancer cases become secondarily metastatic. Patients frequently report many detrimental symptoms related to metastasis and treatments. The physical, biological, psychological, and clinical benefits of physical activity during treatment in patients with localized breast cancer have been demonstrated; however, limited literature exists regarding physical activity and physical activity behavior change in patients with metastatic breast cancer.

OBJECTIVE

The primary objective of this study is to assess the feasibility of a 6-month physical activity intervention with activity trackers in patients with metastatic breast cancer (the Advanced stage Breast cancer and Lifestyle Exercise, ABLE Trial). Secondary objectives are to examine the effects of physical activity on physical, psychological, anthropometrics, clinical, and biological parameters.

METHODS

We plan to conduct a single-center, single-arm trial with 60 patients who are newly diagnosed with metastatic breast cancer. Patients will receive an unsupervised and personalized 6-month physical activity program that includes an activity tracker Nokia Go and is based on the physical activity recommendation. Patients will be encouraged to accumulate at least 150 minutes per week of moderate-to-vigorous intensity physical activity. Baseline and 6-month assessments will include anthropometric measures, functional tests (eg, 6-minute walk test and upper and lower limb strength), blood draws, patient-reported surveys (eg, quality of life and fatigue), and clinical markers of tumor progression (eg, Response Evaluation Criteria In Solid Tumors criteria).

RESULTS

Data collection occurred between October 2016 and January 2018, and the results are expected in August 2018.

CONCLUSIONS

The ABLE Trial will be the first study to assess the feasibility and effectiveness of an unsupervised and personalized physical activity intervention performed under real-life conditions with activity trackers in patients with metastatic breast cancer.

TRIAL REGISTRATION

ClinicalTrials.gov NCT03148886; https://clinicaltrials.gov/ct2/show/NCT03148886 (Accessed by WebCite at http://www.webcitation.org/71yabi0la).

REGISTERED REPORT IDENTIFIER

RR1-10.2196/10487.

Effects of Hypoxia and Bed Rest on Markers of Cardiometabolic Risk: Compensatory Changes in Circulating TRAIL and Glutathione Redox Capacity

In chronic diseases, hypoxia and physical inactivity are associated with atherosclerosis progression. In contrast, a lower mortality from coronary artery disease and stroke is observed in healthy humans residing at high altitude in hypoxic environments. Eleven young, male volunteers completed the following 10-day campaigns in a randomized order: hypoxic ambulatory, hypoxic bed rest and normoxic bed rest. Before intervention, subjects were evaluated in normoxic ambulatory condition. Normobaric hypoxia was achieved in a hypoxic facility simulating 4000 m of altitude. Following hypoxia, either in bed rest or ambulatory condition, markers of cardiometabolic risk shifted toward a more atherogenic pattern consisting of: (a) lower levels of total HDL cholesterol and HDL2 sub-fraction and decreased hepatic lipase; (b) activation of systemic inflammation, as determined by C-reactive protein and serum amyloid A; (c) increased plasma homocysteine; (d) decreased delta-5 desaturase index in cell membrane fatty acids, a marker of insulin sensitivity. Bed rest and hypoxia additively decreased total HDL and delta-5 desaturase index. In parallel to the pro-atherogenic effects, hypoxia activated selected anti-atherogenic pathways, consisting of increased circulating TNF-related apoptosis-inducing ligand (TRAIL), a protective factor against atherosclerosis, membrane omega-3 index and erythrocyte glutathione availability. Hypoxia mediated changes in TRAIL concentrations and redox glutathione capacity (i.e., GSH/GSSG ratio) were greater in ambulatory conditions (+34 ± 6% and +87 ± 31%, respectively) than in bed rest (+17 ± 7% and +2 ± 27% respectively). Hypoxia-induced cardiometabolic risk is blunted by moderate level of physical activity as compared to bed rest. TRAIL and glutathione redox capacity may contribute to the positive interaction between physical activity and hypoxia.

Highlights:

– Hypoxia and bed rest activate metabolic and inflammatory markers of atherogenesis.

– Hypoxia and physical activity activate selected anti-atherogenic pathways.

– Hypoxia and physical activity positive interaction involves TRAIL and glutathione.

Hypobaric hypoxia induced renal damage is mediated by altering redox pathway

Systemic hypobaric hypoxia is reported to cause renal damage; nevertheless the exact pathophysiological mechanisms are not completely understood. Therefore, the present study aims to explore renal pathophysiology by using proteomics approach under hypobaric hypoxia. Six to eight week old male Sprague Dawley rats were exposed to hypobaric hypoxia equivalent to altitude of 7628 metres (pO₂-282mmhg) at 28°C and 55% humidity in decompression chamber for different time intervals; 1, 3, and7 days. Various physiological, proteomic and bioinformatic studies were carried out to examine the effect of chronic hypobaric hypoxia on kidney. Our data demonstrated mild to moderate degenerative tubular changes, altered renal function, injury biomarkers and systolic blood pressure with increase in duration of hypobaric hypoxia exposure. Renal proteomic analysis showed 38 differential expressed spots, out of which 25 spots were down regulated and 13 were up regulated in 7 dayhypobarichypoxic exposure group of rats as compared to normoxia control. Identified proteins were involved in specific molecular changes pertinent to endogenous redox pathways, cellular integrity and energy metabolism. The study provides an empirical evidence of renal homeostasis under hypobaric hypoxia by investigating both physiological and proteomics changes. The identification of explicit key proteins provides a valuable clue about redox signalling mediated renal damage under hypobaric hypoxia.

Killing Many Birds With Two Stones: Hypoxia and Fibrosis Can Generate Ectopic Beats in a Human Ventricular Model

During cardiac diseases many types of anatomical and functional remodeling of cardiac tissue can occur. In this work, we focus on two conditions: hypoxia and fibrosis, which are part of complex pathological modifications that take place in many cardiac diseases (hypertrophic cardiomyopathy, hypertensive heart disease, and recurrent myocardial infarction) and respiratory diseases (obstructive pulmonary disease, obstructive sleep apnea, and cystic fibrosis). Using computational models of cardiac electrophysiology, we evaluate if the interplay between hypoxia and fibrosis is sufficient to trigger cardiac arrhythmia. We study the mechanisms behind the generation of ectopic beats, an arrhythmic trigger also known as premature ventricular contractions (PVCs), in regions with high hypoxia and fibrosis. First, we modify an electrophysiological model of myocytes of the human left ventricle to include the effects of hypoxia. Second, diffuse fibrosis is modeled by randomly replacing cardiac myocytes by non-excitable and non-conducting cells. The Monte Carlo method is used to evaluate the probability of a region to generate ectopic beats with respect to different levels of hypoxia and fibrosis. In addition, we evaluate the minimum size of three-dimensional slabs needed to sustain reentries for different stimulation protocols. The observed mechanism behind the initiation of ectopic beats is unidirectional block, giving rise to sustained micro-reentries inside the region with diffuse fibrosis and hypoxia. In summary, our results suggest that hypoxia and fibrosis are sufficient for the creation of a focal region in the heart that generates PVCs.

Association of 150-kDa oxygen-regulated protein with vascular endothelial growth factor in proliferative diabetic retinopathy

PURPOSE

150-kDa oxygen-regulated protein (ORP150), a member of heat-shock protein family located in endoplasmic reticulum (ER), has a critical role in secretion of vascular endothelial growth factor (VEGF). We investigated expression levels of ORP150 and correlated these levels with VEGF and total vitreous antioxidant capacity (TAC) in proliferative diabetic retinopathy (PDR). We also examined expression of ORP150 in retinas of diabetic rats and in human retinal microvascular endothelial cells (HRMEC).

METHODS

Vitreous samples from 40 PDR and 20 non-diabetic patients, epiretinal membranes from 14 patients with PDR, retinas of rats and HRMEC were studied by enzyme-linked immunosorbent assay, immunohistochemistry and Western blot analysis.

RESULTS

We showed a significant increase in expression of VEGF and ORP150 in vitreous samples from PDR patients compared with controls (p < 0.0001 for both comparisons). Total vitreous antioxidant capacity (TAC) levels were significantly lower in patients with PDR than those in controls (p < 0.0001). Vascular endothelial growth factor (VEGF) and ORP150 levels in PDR with active neovascularization were significantly higher than that in inactive PDR (p = 0.016; p = 0.011, respectively). A significant positive correlation was observed between levels of ORP150 and levels of VEGF (r = 0.42; p = 0.001). In epiretinal membranes, ORP150 was expressed in vascular endothelial cells and stromal cells. We also demonstrated colocalization of the nuclear cell proliferation marker Ki67 and ORP150 in endothelial cells of pathologic new blood vessels. 150-kDa oxygen-regulated protein (ORP150) levels were significantly increased in rat retinas after induction of diabetes. Vascular endothelial growth factor (VEGF) and the pro-inflammatory cytokines interleukin-6 (IL-6) and tumour necrosis factor-α (TNF-α) induced upregulation of ORP150 in HRMEC.

CONCLUSION

These results suggest a role for ORP150 in PDR angiogenesis.

Antioxidant-rich foods and response to altitude training: A randomized controlled trial in elite endurance athletes

High doses of isolated antioxidant supplements such as vitamin C and E have demonstrated the potential to blunt cellular adaptations to training. It is, however, unknown whether intake of high doses of antioxidants from foods has similar effects. Hence, the aim of the study was to investigate whether intake of antioxidant-rich foods affects adaptations to altitude training in elite athletes. In a randomized controlled trial, 31 national team endurance athletes (23 ± 5 years) ingested antioxidant-rich foods (n = 16) or eucaloric control foods (n = 15) daily during a 3-week altitude training camp (2320 m). Changes from baseline to post-altitude in hemoglobin mass (Hb_mass ; optimized CO rebreathing), maximal oxygen uptake (VO_2max ; n = 16) or 100 m swimming performance (n = 10), and blood parameters were compared between the groups. The antioxidant group significantly increased total intake of antioxidant-rich foods (~118%) compared to the control group during the intervention. The total study population improved VO_2max by 2.5% (1.7 mL/kg/min, P = .006) and Hb_mass by 4.7% (48 g, P < .001), but not 100 m swimming performance. No difference was found between the groups regarding changes in Hb_mass , VO_2max or swimming performance. However, hemoglobin concentration increased more in the antioxidant group (effect size = 0.7; P = .045) with a concomitantly larger decrease in plasma and blood volumes compared to control group. Changes in ferritin and erythropoietin from pre- to post-altitude did not differ between the groups. Doubling the intake of antioxidant-rich foods was well tolerated and did not negatively influence the adaptive response to altitude training in elite endurance athletes.

Characteristic profiles of DNA epigenetic modifications in colon cancer and its predisposing conditions-benign adenomas and inflammatory bowel disease

Background

Active demethylation of 5-methyl-2'-deoxycytidine (5-mdC) in DNA occurs by oxidation to 5-(hydroxymethyl)-2'-deoxycytidine (5-hmdC) and further oxidation to 5-formyl-2'-deoxycytidine (5-fdC) and 5-carboxy-2'-deoxycytidine (5-cadC), and is carried out by enzymes of the ten-eleven translocation family (TETs 1, 2, 3). Decreased level of epigenetic DNA modifications in cancer tissue may be a consequence of reduced activity/expression of TET proteins. To determine the role of epigenetic DNA modifications in colon cancer development, we analyzed their levels in normal colon and various colonic pathologies. Moreover, we determined the expressions of TETs at mRNA and protein level.The study included material from patients with inflammatory bowel disease (IBD), benign polyps (AD), and colorectal cancer (CRC). The levels of epigenetic DNA modifications and 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) in examined tissues were determined by means of isotope-dilution automated online two-dimensional ultraperformance liquid chromatography with tandem mass spectrometry (2D-UPLC-MS/MS). The expressions of TET mRNA were measured with RT-qPCR, and the expressions of TET proteins were determined immunohistochemically.

Results

IBD was characterized by the highest level of 8-oxodG among all analyzed tissues, as well as by a decrease in 5-hmdC and 5-mdC levels (at a midrange between normal colon and CRC). AD had the lowest levels of 5-hmdC and 5-mdC of all examined tissues and showed an increase in 8-oxodG and 5-(hydroxymethyl)-2'-deoxyuridine (5-hmdU) levels. CRC was characterized by lower levels of 5-hmdC and 5-mdC, the lowest level of 5-fdC among all analyzed tissues, and relatively high content of 5-cadC. The expression of TET1 mRNA in CRC and AD was significantly weaker than in IBD and normal colon. Furthermore, CRC and AD showed significantly lower levels of TET2 and AID mRNA than normal colonic tissue.

Conclusions

Our findings suggest that a complex relationship between aberrant pattern of DNA epigenetic modification and cancer development does not depend solely on the transcriptional status of TET proteins, but also on the characteristics of premalignant/malignant cells. This study showed for the first time that the examined colonic pathologies had their unique epigenetic marks, distinguishing them from each other, as well as from normal colonic tissue. A decrease in 5-fdC level may be a characteristic feature of largely undifferentiated cancer cells.

Heat and Hypoxic Acclimation Increase Monocyte Heat Shock Protein 72 but Do Not Attenuate Inflammation following Hypoxic Exercise

Acclimation to heat or hypoxic stress activates the heat shock response and accumulation of cytoprotective heat shock proteins (HSPs). By inhibiting the NF-κB pathway HSP72 can preserve epithelial function and reduce systemic inflammation. The aim of this study was to determine the time course of mHSP72 accumulation during acclimation, and to assess intestinal barrier damage and systemic inflammation following hypoxic exercise. Three groups completed 10 × 60-min acclimation sessions (50% normoxic VO₂peak) in control (n = 7; 18°C, 35% RH), hypoxic (n = 7; F_iO₂ = 0.14, 18°C, 35% RH), or hot (n = 7; 40°C, 25% RH) conditions. Tumor necrosis factor-α (TNF-α), interleukin 6 (IL-6), interleukin 10 (IL-10), and intestinal fatty acid binding protein (I-FABP) were determined at rest and following a cycling normoxic stress test (NST; ~2 weeks before acclimation), pre-acclimation hypoxic stress test (HST1; F_iO₂ = 0.14, both at 50% normoxic VO₂peak; ~1 week before acclimation) and post-acclimation HST (48 h; HST2). Monocyte HSP72 (mHSP72) was determined before and after exercise on day 1, 3, 5, 6, and 10 of acclimation. Accumulation of basal mHSP72 was evident from day 5 (p < 0.05) of heat acclimation and increased further on day 6 (p < 0.01), and day 10 (p < 0.01). In contrast, basal mHSP72 was elevated on the final day of hypoxic acclimation (p < 0.05). Following the NST, plasma TNF-α (–0.11 ± 0.27 ng^.mL⁻¹), IL-6 (+0.62 ± 0.67 ng^.mL⁻¹) IL-10 (+1.09 ± 9.06 ng^.mL⁻¹) and I-FABP (+37.6 ± 112.8 pg^.mL⁻¹) exhibited minimal change. After HST1, IL-6 (+3.87 ± 2.56 ng^.mL⁻¹), IL-10 (+26.15 ± 26.06 ng^.mL⁻¹) and I-FABP (+183.7 ± 182.1 pg^.mL⁻¹) were elevated (p < 0.01), whereas TNF-α was unaltered (+0.08 ± 1.27; p > 0.05). A similar trend was observed after HST2, with IL-6 (+3.09 ± 1.30 ng^.mL⁻¹), IL-10 (+23.22 ± 21.67 ng^.mL⁻¹) and I-FABP (+145.9 ±123.2 pg^.mL⁻¹) increased from rest. Heat acclimation induces mHSP72 accumulation earlier and at a greater magnitude compared to matched work hypoxic acclimation, however neither acclimation regime attenuated the systemic cytokine response or intestinal damage following acute exercise in hypoxia.

Hypoxic Air Inhalation and Ischemia Interventions Both Elicit Preconditioning Which Attenuate Subsequent Cellular Stress In vivo Following Blood Flow Occlusion and Reperfusion

Ischemic preconditioning (IPC) is valid technique which elicits reductions in femoral blood flow occlusion mediated reperfusion stress (oxidative stress, Hsp gene transcripts) within the systemic blood circulation and/or skeletal muscle. It is unknown whether systemic hypoxia, evoked by hypoxic preconditioning (HPC) has efficacy in priming the heat shock protein (Hsp) system thus reducing reperfusion stress following blood flow occlusion, in the same manner as IPC. The comparison between IPC and HPC being relevant as a preconditioning strategy prior to orthopedic surgery. In an independent group design, 18 healthy men were exposed to 40 min of (1) passive whole-body HPC (FiO₂ = 0.143; no ischemia. N = 6), (2) IPC (FiO₂ = 0.209; four bouts of 5 min ischemia and 5 min reperfusion. n = 6), or (3) rest (FiO₂ = 0.209; no ischemia. n = 6). The interventions were administered 1 h prior to 30 min of tourniquet derived femoral blood flow occlusion and were followed by 2 h subsequent reperfusion. Systemic blood samples were taken pre- and post-intervention. Systemic blood and gastrocnemius skeletal muscle samples were obtained pre-, 15 min post- (15PoT) and 120 min (120PoT) post-tourniquet deflation. To determine the cellular stress response gastrocnemius and leukocyte Hsp72 mRNA and Hsp32 mRNA gene transcripts were determined by RT-qPCR. The plasma oxidative stress response (protein carbonyl, reduced glutathione/oxidized glutathione ratio) was measured utilizing commercially available kits. In comparison to control, at 15PoT a significant difference in gastrocnemius Hsp72 mRNA was seen in HPC (−1.93-fold; p = 0.007) and IPC (−1.97-fold; p = 0.006). No significant differences were observed in gastrocnemius Hsp32 and Hsp72 mRNA, leukocyte Hsp72 and Hsp32 mRNA, or oxidative stress markers (p > 0.05) between HPC and IPC. HPC provided near identical amelioration of blood flow occlusion mediated gastrocnemius stress response (Hsp72 mRNA), compared to an established IPC protocol. This was seen independent of changes in systemic oxidative stress, which likely explains the absence of change in Hsp32 mRNA transcripts within leukocytes and the gastrocnemius. Both the established IPC and novel HPC interventions facilitate a priming of the skeletal muscle, but not leukocyte, Hsp system prior to femoral blood flow occlusion. This response demonstrates a localized tissue specific adaptation which may ameliorate reperfusion stress.