Hypoxia, energy balance, and obesity: An update

Changes in appetite during acute passive intermittent and continuous hypoxemia in postprandial and fasting states: A combined analysis of four laboratory-based randomized crossover trials

Hypoxemia occurs during exposure to high altitude (continuous hypoxemia) or in the context of breathing disorders such as obstructive sleep apnea (OSA; intermittent hypoxemia). Growing evidence demonstrates that hypoxemia induces an anorexigenic effect on appetite; however, few studies have assessed hypoxemia-related reductions in appetite during acute passive exposures and during intermittent hypoxemia. This study thus pooled together four same-single-site randomized crossover trials using simulated models of high altitude (fraction of inspired oxygen = 0.1200, ∼5000 m) and moderate OSA (∼15 hypoxemic cycles per hour, ∼85 oxyhemoglobin saturation). Changes in appetite were evaluated during 6 h of passive normoxia and intermittent or continuous hypoxemia in postprandial or fasting states among healthy young adults (n = 40) and middle-aged individuals living with OSA (n = 7). Our results demonstrate that (1) acute passive intermittent hypoxemia leads to statistically significant, but likely not clinically significant reductions in appetite in the postprandial state, (2) the anorexigenic effect of acute passive hypoxemia on appetite is not consistent across hypoxemic methods and nutritional states, and (3) variations in individual factors may influence appetite responses during normoxia and hypoxemia. These findings indicate that the effect of acute passive hypoxemia on appetite is heterogeneous, particularly across different hypoxemic methods and nutritional states.

Intermittent normobaric hypoxia alters substrate partitioning and muscle oxygenation in individuals with obesity: implications for fat burning

This single-blind, crossover study aimed to measure and evaluate the short-term metabolic responses to continuous and intermittent hypoxic patterns in individuals with obesity. Indirect calorimetry was used to quantify changes in resting metabolic rate (RMR), carbohydrate (CHOox, %CHO), and fat oxidation (FATox, %FAT) in nine individuals with obesity pre and post: 1) breathing normoxic air [normoxic sham control (NS-control)], 2) breathing continuous hypoxia (CH), or 3) breathing intermittent hypoxia (IH). A mean peripheral oxygen saturation ([Formula: see text]) of 80-85% was achieved over a total of 45 min of hypoxia. Throughout each intervention, pulmonary gas exchanges, oxygen consumption (V̇o2) carbon dioxide production (V̇co2), and deoxyhemoglobin concentration (Δ[HHb]) in the vastus lateralis were measured. Both RMR and CHOox measured pre- and postinterventions were unchanged following each treatment: NS-control, CH, or IH (all P > 0.05). Conversely, a significant increase in FATox was evident between pre- and post-IH (+44%, P = 0.048). Although the mean Δ[HHb] values significantly increased during both IH and CH (P < 0.05), the greatest zenith of Δ[HHb] was achieved in IH compared with CH (P = 0.002). Furthermore, there was a positive correlation between Δ[HHb] and the shift in FATox measured pre- and postintervention. It is suggested that during IH, the increased bouts of muscle hypoxia, revealed by elevated Δ[HHb], coupled with cyclic periods of excess posthypoxia oxygen consumption (EPHOC, inherent to the intermittent pattern) played a significant role in driving the increase in FATox post-IH.

Epigenetics in obesity: Mechanisms and advances in therapies based on natural products

Obesity is a major risk factor for morbidity and mortality because it has a close relationship to metabolic illnesses, such as diabetes, cardiovascular diseases, and some types of cancer. With no drugs available, the mainstay of obesity management remains lifestyle changes with exercise and dietary modifications. In light of the tremendous disease burden and unmet therapeutics, fresh perspectives on pathophysiology and drug discovery are needed. The development of epigenetics provides a compelling justification for how environmental, lifestyle, and other risk factors contribute to the pathogenesis of obesity. Furthermore, epigenetic dysregulations can be restored, and it has been reported that certain natural products obtained from plants, such as tea polyphenols, ellagic acid, urolithins, curcumin, genistein, isothiocyanates, and citrus isoflavonoids, were shown to inhibit weight gain. These substances have great antioxidant potential and are of great interest because they can also modify epigenetic mechanisms. Therefore, understanding epigenetic modifications to target the primary cause of obesity and the epigenetic mechanisms of anti-obesity effects with certain phytochemicals can prove rational strategies to prevent the disease and develop novel therapeutic interventions. Thus, the current review aimed to summarize the epigenetic mechanisms and advances in therapies for obesity based on natural products to provide evidence for the development of several potential anti-obesity drug targets.

Resistance and endurance training in intermittent hypoxia reduce body fat mass and blood pressure

BACKGROUND

Hypoxia is an environmental condition that occurs in sports performed at high altitude. Adaptation to hypoxia is accompanied by changes in body composition and cardiac function that could impair sport performance in altitude. These changes concern mainly to a reduction in muscle mass and an increased heart rate. In this context, a resistance training protocol in a normobaric hypoxia chamber has been implemented. Therefore, the aim of this study was to study the changes in body composition and cardiovascular variables after a training period in intermittent hypoxia.

METHODS

A single-blind experimental study was carried out for 3 weeks. Thirty-two participants were distributed in a control group resistance training in normoxia (N) at sea level and an experimental group resistance training in intermittent hypoxia (IH) between a simulated 5100-5800m during 15 sessions with a controlled diet. Anthropometry according to ISAK was used to determine body composition. Systolic and diastolic blood pressures and other cardiovascular parameters were monitored.

RESULTS

IH showed a reduction in body fat (from 8.9±1.9% to 8.2±1.7%) compared to N (from 8.4±1.5% to 8.1±1.4%) (P<0.001). In addition, significant changes in blood pressure were observed at the end compared to the beginning of the intervention in the IH (from 124.7±10.2 to 116.9±8.3 mmHg and 68.3±8.8 to 62.4±5.7 mmHg in systolic a diastolic blood pressure respectively). In addition, resting heart rate was significantly reduced in IH. However, partial oxygen saturation displayed no changes in both groups.

CONCLUSIONS

Altogether, the training protocol in intermittent hypoxia performed in the present report allowed to adjust body weight through fat mass reduction but maintaining muscle mass. In addition, a decrease in blood pressure and basal heart rate was observed.

Obesity and COVID-19 Pandemics: Epidemiology, Mechanisms, and Management

Obesity is a principle causative factor of various metabolic dysfunctions, chronic inflammation, and multi-organ impairment. The global epidemic of obesity has constituted the greatest threat to global health. Emerging evidence has associated obesity with an increased risk of severe infection and poor outcomes from coronavirus disease 2019 (COVID-19). During current COVID-19 pandemic, the interaction between COVID-19 and obesity has exaggerated the disease burden of obesity more than ever before. Thus, there is an urgent need for consideration of universal measures to reduce the risk of complications and severe illness from severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) in obesity population. In this review, we first summarized the clinical evidence on the effect of obesity on susceptibility, severity, and prognosis of COVID-19. Then we discussed and the underlying mechanisms, including respiratory pathophysiology of obesity, dysregulated inflammation, upregulated angiotensin-converting enzyme 2 (ACE2) expression, hyperglycemia, and adipokines. Finally, we proposed recommendations on how to reduce the spread and pandemic of SARS-CoV-2 infection by prevention and treatment of obesity.

From a toxin to an obesogen: a review of potential obesogenic roles of acrylamide with a mechanistic approach

Obesity and obesity-related disorders such as cancer, type 2 diabetes, and fatty liver have become a global health problem. It is well known that the primary cause of obesity is positive energy balance. In addition, obesity is the consequence of complex gene and environment interactions that result in excess calorie intake being stored as fat. However, it has been revealed that there are other factors contributing to the worsening of obesity. The presence of nontraditional risk factors, such as environmental endocrine-disrupting chemicals, has recently been associated with obesity and comorbidities caused by obesity. The aim of this review was to examine the evidence and potential mechanisms for acrylamide having endocrine-disrupting properties contributing to obesity and obesity-related comorbidities. Recent studies have suggested that exposure to environmental endocrine-disrupting obesogens may be a risk factor contributing to the current obesity epidemic, and that one of these obesogens is acrylamide, an environmental and industrial compound produced by food processing, particularly the processing of foods such as potato chips, and coffee. In addition to the known harmful effects of acrylamide in humans and experimental animals, such as neurotoxicity, genotoxicity, and carcinogenicity, acrylamide also has an obesogenic effect. It has been shown in the literature to a limited extent that acrylamide may disrupt energy metabolism, lipid metabolism, adipogenesis, adipocyte differentiation, and various signaling pathways, and may exacerbate the disturbances in metabolic and biochemical parameters observed as a result of obesity. Acrylamide exerts its main potential obesogenic effects through body weight increase, worsening of the levels of obesity-related blood biomarkers, and induction of adipocyte differentiation and adipogenesis. Additional mechanisms may be discovered. Further experimental studies and prospective cohorts are needed, both to supplement existing knowledge about acrylamide and its effects, and to clarify its established relationship with obesity and its comorbidities.

Normobaric hypoxia shows enhanced FOXO1 signaling in obese mouse gastrocnemius muscle linked to metabolism and muscle structure and neuromuscular innervation

Skeletal muscle relies on mitochondria for sustainable ATP production, which may be impacted by reduced oxygen availability (hypoxia). Compared with long-term hypoxia, the mechanistic in vivo response to acute hypoxia remains elusive. Therefore, we aimed to provide an integrated description of the Musculus gastrocnemius response to acute hypoxia. Fasted male C57BL/6JOlaHsd mice, fed a 40en% fat diet for six weeks, were exposed to 12% O2 normobaric hypoxia or normoxia (20.9% O2) for six hours (n = 12 per group). Whole-body energy metabolism and the transcriptome response of the M. gastrocnemius were analyzed and confirmed by acylcarnitine determination and Q-PCR. At the whole-body level, six hours of hypoxia reduced energy expenditure, increased blood glucose and tended to decreased the respiratory exchange ratio (RER). Whole-genome transcriptome analysis revealed upregulation of forkhead box-O (FOXO) signalling, including an increased expression of tribbles pseudokinase 3 (Trib3). Trib3 positively correlated with blood glucose levels. Upregulated carnitine palmitoyltransferase 1A negatively correlated with the RER, but the significantly increased in tissue C14-1, C16-0 and C18-1 acylcarnitines supported that β-oxidation was not regulated. The hypoxia-induced FOXO activation could also be connected to altered gene expression related to fiber-type switching, extracellular matrix remodeling, muscle differentiation and neuromuscular junction denervation. Our results suggest that a six-hour exposure of obese mice to 12% O2 normobaric hypoxia impacts M. gastrocnemius via FOXO1, initiating alterations that may contribute to muscle remodeling of which denervation is novel and warrants further investigation. The findings support an early role of hypoxia in tissue alterations in hypoxia-associated conditions such as aging and obesity.

Endocrine, genetic, and microbiome nexus of obesity and potential role of postbiotics: a narrative review

Obesity is a public health crisis, presenting a huge burden on health care and the economic system in both developed and developing countries. According to the WHO's latest report on obesity, 39% of adults of age 18 and above are obese, with an increase of 18% compared to the last few decades. Metabolic energy imbalance due to contemporary lifestyle, changes in gut microbiota, hormonal imbalance, inherent genetics, and epigenetics is a major contributory factor to this crisis. Multiple studies have shown that probiotics and their metabolites (postbiotics) supplementation have an effect on obesity-related effects in vitro, in vivo, and in human clinical investigations. Postbiotics such as the SCFAs suppress obesity by regulating metabolic hormones such as GLP-1, and PPY thus reducing feed intake and suppressing appetite. Furthermore, muramyl di-peptides, bacteriocins, and LPS have been tested against obesity and yielded promising results in both human and mice studies. These insights provide an overview of targetable pharmacological sites and explore new opportunities for the safer use of postbiotics against obesity in the future.

Prevalence of hypertension in adults living at altitude in Latin America and the Caribbean: A systematic review and meta-analysis

OBJECTIVE

The objective of this systematic review and meta-analysis was to assess the prevalence of hypertension in populations living at altitude in Latin America and the Caribbean.

METHODS

We conducted a systematic search from January 1, 2000 to January 10, 2023 in Web of Science (WoS)/Core Collection, WoS/Medline, WoS/Scielo, Scopus, PubMed and Embase databases. We included studies that assessed the prevalence of hypertension in altitude populations (>1500 m.a.s.l.) and these were meta-analyzed using a random-effects model. To assess the sources of heterogeneity, we performed subgroup and meta-regression analyses.

RESULTS

Thirty cross-sectional studies (117 406 participants) met the inclusion criteria. Studies used different cut-off points. The prevalence of hypertension in the studies that considered the cut-off point of ≥ 140/90 mmHg in the general population was 19.1%, ≥ 130/85 mmHg was 13.1%, and ≥ 130/80 mmHg was 43.4%. There was a tendency for the prevalence of hypertension to be higher in men. In meta-regression analyses, no association was found between altitude, mean age, year of publication, risk of bias and prevalence of hypertension.

CONCLUSION

The prevalence of hypertension in the altitude population of Latin America and the Caribbean is lower than that reported in populations living at sea level and lower than other altitude populations such as Tibetans.

PROSPERO

CRD42021275229.

Effect of Hypoxia Conditioning on Body Composition in Middle-Aged and Older Adults: A Systematic Review and Meta-Analysis

BACKGROUND

The effects of hypoxia conditioning, which involves recurrent exposure to hypoxia combined with exercise training, on improving body composition in the ageing population have not been extensively investigated.

OBJECTIVE

This meta-analysis aimed to determine if hypoxia conditioning, compared to similar training near sea level, maximizes body composition benefits in middle-aged and older adults.

METHODS

A literature search of PubMed, EMBASE, Web of Science, Scopus and CNKI (China National Knowledge Infrastructure) databases (up to 27th November 2022) was performed, including the reference lists of relevant papers. Three independent reviewers extracted study characteristics and health outcome measures. Search results were limited to original studies of the effects of hypoxia conditioning on body composition in middle-aged and older adults.

RESULTS

Twelve studies with a total of 335 participants were included. Hypoxia conditioning induced greater reductions in body mass index (MD = -0.92, 95%CI: -1.28 to -0.55, I2 = 0%, p < 0.00001) and body fat (SMD = -0.38, 95%CI: -0.68 to -0.07, I2 = 49%, p = 0.01) in middle-aged and older adults compared with normoxic conditioning. Hypoxia conditioning improved lean mass with this effect not being larger than equivalent normoxic interventions in either middle-aged or older adults (SMD = 0.07, 95%CI -0.12 to 0.25, I2 = 0%, p = 0.48). Subgroup analysis showed that exercise in moderate hypoxia (FiO2 > 15%) had larger effects than more severe hypoxia (FiO2 ≤ 15%) for improving body mass index in middle-aged and older adults. Hypoxia exposure of at least 60 min per session resulted in larger benefits for both body mass index and body fat.

CONCLUSION

Hypoxia conditioning, compared to equivalent training in normoxia, induced greater body fat and body mass index improvements in middle-aged and older adults. Adding hypoxia exposure to exercise interventions is a viable therapeutic solution to effectively manage body composition in ageing population.

Factors Associated with Normal-Weight Abdominal Obesity Phenotype in a Representative Sample of the Peruvian Population: A 4-Year Pooled Cross-Sectional Study

To examine factors associated with abdominal obesity among normal-weight individuals from the Demographic and Health Survey of Peru (2018-2021). Cross-sectional analytical study. The outcome variable was abdominal obesity defined according to JIS criteria. Crude (cPR) and adjusted prevalence ratios (aPR) were estimated for the association between sociodemographic and health-related variables and abdominal obesity using the GLM Poisson distribution with robust variance estimates. A total of 32,109 subjects were included. The prevalence of abdominal obesity was 26.7%. The multivariate analysis showed a statistically significant association between abdominal obesity and female sex (aPR: 11.16; 95% CI 10.43-11.94); categorized age 35 to 59 (aPR: 1.71; 95% CI 1.65-1.78); 60 to 69 (aPR: 1.91; 95% CI 1.81-2.02); and 70 or older(aPR: 1.99; 95% CI 1.87-2.10); survey year 2019 (aPR: 1.22; 95% CI 1.15-1.28); 2020 (aPR: 1.17; 95% CI 1.11-1.24); and 2021 (aPR: 1.12; 95% CI 1.06-1.18); living in Andean region (aPR: 0.91; 95% CI 0.86-0.95); wealth index poor (aPR: 1.26; 95% CI 1.18-1.35); middle (aPR: 1.17; 95% CI 1.08-1.26); rich (aPR: 1.26; 95% CI 1.17-1.36); and richest (aPR: 1.25; 95% CI 1.16-1.36); depressive symptoms (aPR: 0.95; 95% CI 0.92-0.98); history of hypertension (aPR: 1.08; 95% CI 1.03-1.13), type 2 diabetes (aPR: 1.13; 95% CI 1.07-1.20); and fruit intake 3 or more servings/day (aPR: 0.92; 95% CI 0.89-0.96). Female sex, older ages, and low and high income levels increased the prevalence ratio for abdominal obesity, while depressive symptoms, living in the Andean region, and fruit intake of 3 or more servings/day decreased it.

Hypoxia induces food leaving in C. elegans

Hypoxia alters eating behavior in different animals. In C. elegans , hypoxia induces a strong food leaving response. We found that this behavior was independent of the known O 2 response mechanisms including acute O 2 sensation and HIF-1 signaling of chronic hypoxia response. Mutating egl-3 and egl-21 , encoding the neuropeptide pro-protein convertase and carboxypeptidase, led to defects in hypoxia induced food leaving, suggesting that neuropeptidergic signaling was required for this response. However, we failed to identify any neuropeptide mutants that were severely defective in hypoxia induced food leaving, suggesting that multiple neuropeptides act redundantly to modulate this behavior.

Epigenetic regulation in metabolic diseases: mechanisms and advances in clinical study

Epigenetics regulates gene expression and has been confirmed to play a critical role in a variety of metabolic diseases, such as diabetes, obesity, non-alcoholic fatty liver disease (NAFLD), osteoporosis, gout, hyperthyroidism, hypothyroidism and others. The term 'epigenetics' was firstly proposed in 1942 and with the development of technologies, the exploration of epigenetics has made great progresses. There are four main epigenetic mechanisms, including DNA methylation, histone modification, chromatin remodelling, and noncoding RNA (ncRNA), which exert different effects on metabolic diseases. Genetic and non-genetic factors, including ageing, diet, and exercise, interact with epigenetics and jointly affect the formation of a phenotype. Understanding epigenetics could be applied to diagnosing and treating metabolic diseases in the clinic, including epigenetic biomarkers, epigenetic drugs, and epigenetic editing. In this review, we introduce the brief history of epigenetics as well as the milestone events since the proposal of the term 'epigenetics'. Moreover, we summarise the research methods of epigenetics and introduce four main general mechanisms of epigenetic modulation. Furthermore, we summarise epigenetic mechanisms in metabolic diseases and introduce the interaction between epigenetics and genetic or non-genetic factors. Finally, we introduce the clinical trials and applications of epigenetics in metabolic diseases.

Protective effect and mechanism of lactoferrin combined with hypoxia against high-fat diet induced obesity and non-alcoholic fatty liver disease in mice

Obesity is a global epidemic, it can induce glucose and lipid metabolism disorder and non-alcoholic fatty liver disease (NAFLD). This study explored a new way to control weight and improve fatty liver, namely, living in hypoxia environment and supplement with lactoferrin (Lf). Sixty male C57BL/6J mice were divided into six groups, namely, control, hypoxia, high-fat diet, hypoxia + high-fat diet, hypoxia + high-fat diet + low dose Lf intervention, and hypoxia + high-fat diet + high-dose Lf intervention. Mice in the hypoxia treatment groups were treated with approximately 11.5 % oxygen for 6 h every day for 8 weeks. Results showed that interventions combining Lf and hypoxia treatments showed better effect against obesity and NAFLD than hypoxia treatment alone. The interventions controlled weight gain in mice, improved glucolipid metabolism in mice. The combination intervention reduced cholesterol absorption by reducing the level of hydrophobic bile acids, and elevating the level of hydrophilic bile acids. Gut microbiota analysis revealed that the combination intervention considerably elevated short chain fatty acids (SCFAs)-producing bacteria level, and reduced the Desulfovibrionaceae_unclassified level. Thus, Lf combined with hypoxia intervention effectively prevents obesity and NAFLD by restoring gut microbiota composition and bile acid profile.

Changes in body mass, appetite-related hormones, and appetite sensation in women during 4 days of hypobaric hypoxic exposure equivalent to 3,500-m altitude

Altitude exposure may suppress appetite and hence provide a viable weight-loss strategy. While changes in food intake and availability as well as physical activity may contribute to altered appetite at altitude, herein we aimed to investigate the isolated effects of hypobaric hypoxia on appetite regulation and sensation. Twelve healthy women (age: 24.0 ± 4.2 years, body mass: 60.6 ± 7.0 kg) completed two 4-day sojourns in a hypobaric chamber, one in normoxia [P_B = 761 mmHg, 262 m (NX)] and one in hypobaric hypoxia [P_B = 493 mmHg (HH)] equivalent to 3,500-m altitude. Energy intake was standardized 4 days prior and throughout both sojourns. Plasma concentrations of leptin, acylated ghrelin, cholecystokinin (CCK), and cytokine growth differentiation factor 15 (GDF15) were determined every morning. Before and after breakfast, lunch, and dinner, appetite was assessed using visual analog scales. Body mass was significantly decreased following HH but not NX (-0.71 ± 0.32 kg vs. -0.05 ± 0.54 kg, condition: P < 0.001). Compared to NX, acylated ghrelin decreased throughout the HH sojourn (condition × time: P = 0.020), while leptin was higher throughout the entire HH sojourn (condition: P < 0.001). No differences were observed in CCK and GDF15 between the sojourns. Feelings of satiety and fullness were higher (condition: P < 0.001 and P = 0.013, respectively), whereas prospective food consumption was lower in HH than in NX (condition: P < 0.001). Our findings suggest that hypoxia exerts an anorexigenic effect on appetite-regulating hormones, suppresses subjective appetite sensation, and can induce weight loss in young healthy women. Among the investigated hormones, acylated ghrelin and leptin most likely explain the observed HH-induced appetite suppression.NEW & NOTEWORTHY This study investigated the effects of hypoxia on appetite regulation in women while strictly controlling for diet, physical activity, menstrual cycle, and environmental conditions. In young women, 4 days of altitude exposure (3,500 m) decreases body weight and circulating acylated ghrelin levels while preserving leptin concentrations. In line with the hormonal changes, altitude exposure induces alterations in appetite sensation, consisting of a decreased feeling of hunger and prospective food intake and an increased feeling of fullness and satiety.

Intermittent hypoxia conditioning as a potential prevention and treatment strategy for ischemic stroke: Current evidence and future directions

Ischemic stroke (IS) is the leading cause of disability and death worldwide. Owing to the aging population and unhealthy lifestyles, the incidence of cerebrovascular disease is high. Vascular risk factors include hypertension, diabetes, dyslipidemia, and obesity. Therefore, in addition to timely and effective reperfusion therapy for IS, it is crucial to actively control these risk factors to reduce the incidence and recurrence rates of IS. Evidence from human and animal studies suggests that moderate intermittent hypoxia (IH) exposure is a promising therapeutic strategy to ameliorate common vascular risk factors and comorbidities. Given the complex pathophysiological mechanisms underlying IS, effective treatment must focus on reducing injury in the acute phase and promoting repair in the recovery phase. Therefore, this review discusses the preclinical perspectives on IH conditioning as a potential treatment for neurovascular injury and highlights IH pre and postconditioning strategies for IS. Hypoxia conditioning reduces brain injury by increasing resistance to acute ischemic and hypoxic stress, exerting neuroprotective effects, and promoting post-injury repair and regeneration. However, whether IH produces beneficial effects depends not only on the hypoxic regimen but also on inter-subject differences. Therefore, we discuss the factors that may influence the effectiveness of IH treatment, including age, sex, comorbidities, and circadian rhythm, which can be used to help identify the optimal intervention population and treatment protocols for more accurate, individualized clinical translation. In conclusion, IH conditioning as a non-invasive, non-pharmacological, systemic, and multi-targeted intervention can not only reduce brain damage after stroke but can also be applied to the prevention and functional recovery of IS, providing brain protection at different stages of the disease. It represents a promising therapeutic strategy. For patients with IS and high-risk groups, IH conditioning is expected to develop as an adjunctive clinical treatment option to reduce the incidence, recurrence, disability, and mortality of IS and to reduce disease burden.

Hypoxia as a Double-Edged Sword to Combat Obesity and Comorbidities

The global epidemic of obesity is tightly associated with numerous comorbidities, such as type II diabetes, cardiovascular diseases and the metabolic syndrome. Among the key features of obesity, some studies have suggested the abnormal expansion of adipose-tissue-induced local endogenous hypoxic, while other studies indicated endogenous hyperoxia as the opposite trend. Endogenous hypoxic aggravates dysfunction in adipose tissue and stimulates secretion of inflammatory molecules, which contribute to obesity. In contrast, hypoxic exposure combined with training effectively generate exogenous hypoxic to reduce body weight and downregulate metabolic risks. The (patho)physiological effects in adipose tissue are distinct from those of endogenous hypoxic. We critically assess the latest advances on the molecular mediators of endogenous hypoxic that regulate the dysfunction in adipose tissue. Subsequently we propose potential therapeutic targets in adipose tissues and the small molecules that may reverse the detrimental effect of local endogenous hypoxic. More importantly, we discuss alterations of metabolic pathways in adipose tissue and the metabolic benefits brought by hypoxic exercise. In terms of therapeutic intervention, numerous approaches have been developed to treat obesity, nevertheless durability and safety remain the major concern. Thus, a combination of the therapies that suppress endogenous hypoxic with exercise plans that augment exogenous hypoxic may accelerate the development of more effective and durable medications to treat obesity and comorbidities.

Effects of exercise training in hypoxia versus normoxia on fat-reducing in overweight and/or obese adults: A systematic review and meta-analysis of randomized clinical trials

Objective: Fat loss theory under various oxygen conditions has been disputed, and relevant systematic review studies are limited. This study is a systematic review and meta-analysis to assess whether hypoxic exercise training (HET) leads to superior fat-reducing compared with normoxic exercise training (NET).

Methods: We searched PubMed, Web of Science, CNKI, ProQuest, Google Scholar, Cochrane Library, and EBSCOhost from inception to June 2022 for articles comparing the effects of hypoxic and normoxic exercise on body composition indicators, glycometabolism, and lipometabolism indicators in obese and overweight adults. Only randomized controlled trials (RCTs) were included. The effect sizes were expressed as standardized mean difference (SMD) and 95% confidence intervals (CI). Between-study heterogeneity was examined using the I² test and evaluated publication bias via Egger’s regression test. The risk of bias assessment was performed for each included trial using Cochrane Evaluation Tool second generation. The meta-analysis was performed by using R 4.1.3 and RevMan 5.3 analytic tools.

Results: A total of 19 RCTs with 444 subjects were analyzed according to the inclusion and exclusion criteria. Among them, there were 14 English literature and five Chinese literature. No significant difference in body composition (SMD -0.10, 95% CI -0.20 to -0.01), glycometabolism and lipid metabolism (SMD -0.01, 95% CI -0.13 to -0.10) has been observed when comparing the HET and NET groups. We only found low heterogeneity among trials assessing glycometabolism and lipometabolism (I² = 20%, p = 0.09), and no publication bias was detected.

Conclusion: The effects of HET and NET on fat loss in overweight or obese people are the same. The application and promotion of HET for fat reduction need further exploration.

Healthy worker survival effect at a high-altitude mine: prospective cohort observation

Very little is known about the factors of healthy worker survival effect at high-altitude mines. We conducted this cohort observation of the new hires for a high-altitude gold mine in Kyrgyzstan with the aim to ascertain predictors of survival at work. All new hires in 2009 through 2012 for a high-altitude gold mine (3600–4500 m above sea level) were followed up to January 2022. We tested the association of demographic, physiological predictors and diagnoses at the pre-employment screening with non-survival at work in Cox proportional hazards yielding hazard ratios (HR) with their 95% confidence intervals (CI). The cumulative observation time was 5190 person-years. Blood pressure at pre-employment, lung function, the diagnoses of essential hypertension, chronic obstructive pulmonary disease (COPD) or any other analyzed physiological variables were not associated with non-survival at work. However, smoking (HR 1.55; 95% CI 1.10; 2.17) increased the likelihood of non-survival at work, independent of any diagnosis or lowland residence (HR 1.95; 95% CI 1.31; 2.90). Adjusted for covariates and all diagnoses, having chronic rheumatic fever (HR 10.95; 95% CI 2.92; 33.92), hemorrhoids (HR 1.32; 95% CI 1.01; 3.75), adhesive otitis (HR 1.74; 95% CI 1.05; 2.89) or obesity (HR 1.71; 95% CI 1.01; 2.88) were associated with non-survival at work with time. This prospective observation of new hires for a high-altitude mining operation demonstrated that selected diagnoses, smoking and lowland residence elevated the risk of early exit in prospective workers.

Acute physiological response to a normobaric hypoxic exposure: sex differences

Although preliminary studies suggested sex-related differences in physiological responses to altitude/hypoxia, controlled studies from standardised exposures to normobaric hypoxia are largely lacking. Hence, the goals of this study were to provide information on cardiorespiratory responses to a 7-h normobaric hypoxia exposure and to explore potential differences between men and women. In this crossover study, a total of 15 men and 14 women were subjected to a 7-h exposure in normoxia (FiO₂: 21%) and normobaric hypoxia (FiO₂: 15%). Values of peripheral oxygen saturation, heart rate, systolic and diastolic blood pressure and respiratory gases were recorded every hour (8 time points), and oxygen saturation every 30 min (15 time points). Compared to normoxia, exposure to hypoxia significantly increased minute ventilation from baseline to hour 7 in males (+ 71%) and females (+ 40%), significantly greater in men (p < 0.05). A steeper decrease in peripheral oxygen saturation until 2.5 h in hypoxia was seen in females compared to males (p < 0.05). In conclusion, the ventilatory response to hypoxia was more pronounced in men compared to women. Moreover, during the first hours in hypoxia, peripheral oxygen saturation dropped more markedly in women than in men, likely due an initially lower and/or less efficient ventilatory response to moderate hypoxia. Those findings should be considered when performing interventions for therapy or prevention in normobaric hypoxia. Nevertheless, further large-scaled and well-controlled studies are needed.

Astaxanthin From Haematococcus pluvialis Prevents High-Fat Diet-Induced Hepatic Steatosis and Oxidative Stress in Mice by Gut-Liver Axis Modulating Properties

Scope

Evidence is mounting that astaxanthin (ATX), a xanthophyll carotenoid, used as a nutritional supplement to prevent chronic metabolic diseases. The present study aims to identify the potential function of ATX supplementation in preventing steatohepatitis and hepatic oxidative stress in diet-induced obese mice.

Methods and Results

In this study, ATX as dose of 0.25, 0.5, and 0.75% have orally administered to mice along with a high-fat diet (HFD) to investigate the role of ATX in regulating liver lipid metabolism and gut microbiota. The study showed that ATX dose-dependently reduces body weight, lipid droplet formation, hepatic triglycerides and ameliorated hepatic steatosis and oxidative stress. 0.75% ATX altered the levels of 34 lipid metabolites related to hepatic cholesterol and fatty acid metabolism which might be associated with downregulation of lipogenesis-related genes and upregulation of bile acid biosynthesis-related genes. The result also revealed that ATX alleviates HFD-induced gut microbiota dysbiosis by significantly inhibiting the growth of obesity-related Parabacteroides and Desulfovibrio while promoting the growth of Allobaculum and Akkermansia.

Conclusion

The study results suggested that dietary ATX may prevent the development of hepatic steatosis and oxidative stress with the risk of metabolic disease by gut-liver axis modulating properties.

Intermittent Hypoxia as a Therapeutic Tool to Improve Health Parameters in Older Adults

Aging is associated with metabolic alterations, and with a loss of strength, muscle and bone mass. Moderate intermittent hypoxia has been proposed as a new tool to enhance health-related function. The aim of this study was to evaluate the effect of moderate intermittent hypoxia exposures on parameters related to cardiovascular and bone health in older adults. A total of 38 healthy older adults (aged 65-75 years) were divided into two groups: control group (C), and hypoxia group (H) that was subjected to an intermittent hypoxia exposure (at simulated altitude of 2500 m asl) during a 24-week period (3 days/week). Body composition, blood pressure, metabolic parameters (Cholesterol, triglycerides and glucose), C-reactive protein (CRP), vascular cell adhesion molecule-1 (VCAM-1), interleukin 8 (IL-8), interleukin 10 (IL-10), N-terminal propeptide of type I procollagen (PINP) and beta C-terminal telopeptide of collagen bone formation (b-CTX) were analyzed before and after the intervention. A repeated measures analysis of variance was performed to evaluate between-group differences. The results showed that the hypoxia group achieved after the intervention a decrease in fat mass, CRP (pro-inflammatory biomarker) and b-CTX (bone resorption biomarker), as well as an increase in PINP (bone formation biomarker). In conclusion, the intermittent hypoxia might be a useful therapeutic tool to deal with problems associated with aging, such as the increase in body fat, the loss of bone mass or low-grade inflammation.

Differences in the prevalence of physical activity and cardiovascular risk factors between people living at low (<1,001 m) compared to moderate (1,001-2,000 m) altitude

Living at moderate altitude (up to about 2,000 m) was shown to be associated with distinct health benefits, including lower mortality from cardiovascular diseases and certain cancers. However, it remains unclear, whether those benefits are mainly due to environmental conditions (e.g., hypoxia, temperature, solar ultra-violet radiation) or differences in lifestyle behavior, including regular physical activity levels. This study aims to compare altitude-related differences in levels of physical activity and the prevalence of cardiovascular risk factors such as obesity, hypertension, hypercholesterolemia, and diabetes in an Alpine country. We interrogated the Austrian Health Interview Survey (ATHIS) 2019, a nationally representative study of persons aged over 15 years living in private Austrian households. The results confirm a higher prevalence of hypertension (24.2% vs. 16.8%) in men living at low (<1,001 m) compared to those at moderate (1,001 to 2,000 m) altitude. Women living above 1,000 m tend to have a lower prevalence of hypercholesterolemia (14.8% vs. 18.8%) and diabetes (3.2% vs. 5.6%) than their lower living peers. Both sexes have lower average body mass index (BMI) when residing at moderate altitude (men: 25.7, women: 23.9) compared to those living lower (26.6 and 25.2). Severe obesity (BMI > 40) is almost exclusively restricted to low altitude dwellers. Only men report to be more physically active on average when living higher (1,453 vs. 1,113 weekly MET minutes). These novel findings confirm some distinct benefits of moderate altitude residence on heath. Beside climate conditions, differences in lifestyle behavior, i.e., physical activity, have to be considered when interpreting those health-related divergences, and consequently also mortality data, between people residing at low and moderate altitudes.

The Effects of Intermittent Hypoxic-Hyperoxic Exposures on Lipid Profile and Inflammation in Patients With Metabolic Syndrome

Background: Patients with metabolic syndrome (MS) tend to suffer from comorbidities, and are often simultaneously affected by obesity, dysglycemia, hypertension, and dyslipidemia. This syndrome can be reversed if it is timely diagnosed and treated with a combination of risk factors-reducing lifestyle changes and a tailored pharmacological plan. Interval hypoxic-hyperoxic training (IHHT) has been shown as an effective program in reducing cardiovascular risk factors in patients with MS even in the absence of exercise. However, the influence of IHHT on the lipid profile and inflammation in this clinical population remains relatively unknown.

Methods: A prospective, single-center, randomized controlled trial was conducted on 65 (33 men) patients with MS aged 29–74 years, who were randomly allocated to the IHHT or control (sham) experimental groups. The IHHT group completed a 3-week, 5 days/week intermittent exposure to hypoxia and hyperoxia. The control (sham) group followed the same protocol but was breathing room air instead. The primary endpoints were the lipid profile (concentrations of total cholesterol [TC], low-density lipoprotein [LDL], high-density lipoprotein [HDL], and triglycerides [TG]) and the inflammatory factors such as high-sensitivity C-reactive protein (hs-CRP), galectin-3, heat shock proteins (Hsp70). The secondary endpoints were alanine aminotransferase (ALT), aspartate aminotransferase (AST), N-terminal pro-hormone of brain natriuretic peptide level (NTproBNP), transforming growth factor beta-1 (TGF-beta1), heart-type fatty acid-binding protein (H-FABP), and nitric oxide synthase 2 (NOS2).

Results: There were no differences between the two groups but the different baseline values have affected these results. The IHHT group demonstrated pre-post decrease in total cholesterol (p = 0.001), LDL (p = 0.001), and TG levels (p = 0.001). We have also found a decrease in the CRP-hs (p = 0.015) and Hsp70 (p = 0.006) in IHHT-group after intervention, and a significant decrease in pre-post (delta) differences of NTproBNP (p < 0.0001) in the IHHT group compared to the control group. In addition, the patients of the IHHT group showed a statistically significant decrease in pre-post differences of ALT and AST levels in comparison with the control group (p = 0.001). No significant IHHT complications or serious adverse events were observed.

Conclusions: The IHHT appears to improve lipid profile and anti-inflammatory status. It is a safe, well-tolerated procedure, and could be recommended as an auxiliary treatment in patients suffering from MS, however, the experiment results were limited by the baseline group differences.

Clinical Trial Registration:ClinicalTrials.gov, identifier [NCT04791397]. Evaluation of the effect of IHHT on vascular stiffness and elasticity of the liver tissue in patients with MS.

Phenotypic differences between highlanders and lowlanders in Papua New Guinea

OBJECTIVES

Altitude is one of the most demanding environmental pressures for human populations. Highlanders from Asia, America and Africa have been shown to exhibit different biological adaptations, but Oceanian populations remain understudied [Woolcock et al., 1972; Cotes et al., 1974; Senn et al., 2010]. We tested the hypothesis that highlanders phenotypically differ from lowlanders in Papua New Guinea, as a result of inhabiting the highest mountains in Oceania for at least 20,000 years.

MATERIALS AND METHODS

We collected data for 13 different phenotypes related to altitude for 162 Papua New Guineans living at high altitude (Mont Wilhelm, 2,300-2,700 m above sea level (a.s.l.) and low altitude (Daru, <100m a.s.l.). Multilinear regressions were performed to detect differences between highlanders and lowlanders for phenotypic measurements related to body proportions, pulmonary function, and the circulatory system.

RESULTS

Six phenotypes were significantly different between Papua New Guinean highlanders and lowlanders. Highlanders show shorter height (p-value = 0.001), smaller waist circumference (p-value = 0.002), larger Forced Vital Capacity (FVC) (p-value = 0.008), larger maximal (p-value = 3.20e -4) and minimal chest depth (p-value = 2.37e -5) and higher haemoglobin concentration (p-value = 3.36e -4).

DISCUSSION

Our study reports specific phenotypes in Papua New Guinean highlanders potentially related to altitude adaptation. Similar to other human groups adapted to high altitude, the evolutionary history of Papua New Guineans appears to have also followed an adaptive biological strategy for altitude.