The Circulatory and Metabolic Responses to Hypoxia in Humans - With Special Reference to Adipose Tissue Physiology and Obesity

Hypoxic compound exercise improves cardiac function in Drosophila high fructose diet via KHK

Overconsumption of fructose has been linked to the development of systemic metabolic and cardiac diseases, yet few studies have focused on the link between cardiac fructose metabolism and the development of heart disease. Low-oxygen complex exercise is considered an effective means of treating and preventing metabolic diseases and improving cardiac function, however, it is unclear, the link between low-oxygen complex exercise and high-fructose-induced heart disease. Therefore, the aim of this study was to investigate the effect of hypoxic complex exercise on heart disease on a high fructose diet. The results of the study found that hypoxic compound exercise improved the upregulation of inflammatory factor Upd3 and systemic fat accumulation in the heart induced by high fructose diet by inhibiting the expression of KHK gene in the heart; and it improved the impaired cardiac rhythmic function and pumping function, improved the disorder of myofilament fiber arrangement, reduced the level of cardiac oxidative stress, and reduced cardiac collagen deposition. In addition, cardiac KHK-specific knockdown had the same effect on high fructose diet hearts. Compared with single KHK cardiac-specific knockdown or hypoxic combination exercise, hypoxic combination exercise combined with KHK cardiac-specific knockdown was superior in improving the high-fructose diet-induced increase in arrhythmia index, systolic and diastolic dysfunction, and decrease in fractional shortening. Therefore, we conclude that hypoxic complex exercise improved high-fructose diet-induced cardiac rhythmic function and pumping dysfunction by reducing KHK expression.

The Impact of Exercise Training in a Hypobaric/Normobaric Hypoxic Environment on Cardiometabolic Health in Adults with Overweight or Obesity: A Systematic Review and Meta-Analysis

This systematic review and meta-analysis aims to comprehensively evaluate the effects of hypoxic training (HT) versus normoxic training (NT) on cardiometabolic health parameters in overweight or obese adults. Searches were performed in PubMed, Web of Science, Embase, Scopus, and the Cochrane Library. A meta-analysis was performed using Stata 18 and RevMan 5.4 software. Seventeen randomized controlled studies involving 517 participants were included. HT significantly improved cardiorespiratory fitness (CRF) and reduced systolic blood pressure (SBP) and diastolic blood pressure (DBP). Compared with NT, HT demonstrated a significant difference in CRF, but no significant differences were observed in SBP and DBP. The subgroup analysis of CRF revealed that HT significantly outperformed NT in six aspects: participants aged < 45 years (Hedges' g = 0.50), an intervention duration of 8 weeks (Hedges' g = 0.43), three sessions per week (Hedges' g = 0.40), each session lasting < 45 min (Hedges' g = 0.23), FiO2 levels > 15% (Hedges' g = 0.69), and high-load-intensity exercise (Hedges' g = 0.57). HT demonstrated favorable effects in improving cardiometabolic health among overweight or obese adults. Compared with NT, this advantage was primarily reflected in CRF while the impacts on SBP and DBP were similar.

Retinal vessel analysis to assess microvascular function in the healthy eye: A systematic review on the response to acute physiological and pathological stressors

The retina allows noninvasive in vivo assessment of the microcirculation. Autoregulation of the retinal microvasculature meets the changing requirements of local metabolic demand and maintains adequate blood flow. Analysis of the retinal vascular reactivity contributes to the understanding of regulatory physiology and its relationship to the systemic microcirculation. We conducted a literature review on the effect of different acute stimuli onto the retinal vasculature was conducted in accordance with the PRISMA guidelines. A literature search between 1-1-2005 and 17-10-2022 was performed in Medline, Embase, Web of Science and the Cochrane Library. We report the retinal vascular behavior of healthy individuals in response to both physiological and pathological stressors in 106 included articles. We provide ables of methodological characteristics for each stressor. Hypoxia, hypercapnia, high altitude, flicker light stimulation, rise of core temperature, blood pressure lowering, and the condition immediately after endurance exercise associate with larger retinal vessels. Hyperoxia, hypocapnia, blood pressure rise (Bayliss effect), and the condition during isometric exercise associate with smaller retinal vessels. The retinal vasculature is highly reactive to physiological and pathological stressors. This autoregulatory capacity is hypothesized to be a source of biomarkers for vascular health. Dynamic and static retinal vessel analysis are noninvasive methods to assess this (micro)vascular function. Exploring its diagnostic potential and application into clinical practice requires the development of standardized assessment methods, for which some recommendations are made.

Intramuscular blood flow and muscle oxygenation of the vastus lateralis response to intermittent incremental muscle contractions

Power Doppler ultrasonography is used to measure blood flow within a given muscle, otherwise known as intramuscular blood flow. However, it is not fully understood how intramuscular blood flow and muscle oxygenation change with repetitive muscle contraction. The present study was conducted to assess changes in intramuscular blood flow and muscle oxygenation of the vastus lateralis (VL) during intermittent and incremental contractions. Fifteen healthy male subjects (21.7 ± 2.6 years) performed intermittent (5 s contraction, 5 s relaxation) and incremental isometric knee extensions at 30%, 40%, 50%, 60% and 70% of maximal voluntary contraction (MVC) until task failure. Intramuscular blood flow and muscle oxygen saturation (S t O 2 ${{S}_{{\mathrm{t}}{{{\mathrm{O}}}_2}}}$ ) were simultaneously measured using power Doppler ultrasonography and near-infrared spectroscopy, respectively, from the right VL of the mid-thigh. Intramuscular blood flow was increased from 0.5 ± 0.5% at rest to 13.9 ± 9.5% at task failure. Intramuscular blood flow significantly increased from rest to 30% and 40% MVC (P = 0.001), andS t O 2 ${{S}_{{\mathrm{t}}{{{\mathrm{O}}}_2}}}$ significantly decreased from 30% to 70% MVC (P = 0.004). These results indicate that intramuscular blood flow andS t O 2 ${{S}_{{\mathrm{t}}{{{\mathrm{O}}}_2}}}$ show different patterns of change, suggesting that the contribution of intramuscular blood flow to oxygen supply decreases within the VL at moderate and higher exercise intensities.

Antarctic Expeditions: A Systematic Review of the Physiological, Nutritional, Body Composition and Psychological Responses to Treks Across the Continental Ice

BACKGROUND

Antarctic expeditions, although supported by scientific knowledge, face various challenges, with little research conducted to explore the physical demands that explorers experience.

OBJECTIVE

To summarise physiological, psychological, body composition and nutritional changes faced during trek expeditions in the Antarctic's continental portion.

DESIGN

Systematic review.

INFORMATION SOURCES

We used PubMed, SPORTDiscus, PsycINFO, Scopus, Cochrane databases, CINAHL and Medline Ovid to search for studies published up to January 2023.

ELIGIBILITY CRITERIA

We included original articles or case reports published in English and in peer-reviewed journals, involving both sexes, using both quantitative and qualitative approaches, that considered Antarctic continent expedition, as well as solo exploration/group exploration. Animal studies, in vitro studies, explorers < 18 years of age, overwintering at research stations, tourist/organized visits to Antarctica or the South Pole, not sleeping on the ice, and ultraendurance events were excluded. The JBI critical appraisal checklist for case studies was used for quality assessment.

RESULTS

A total of 12 studies met the eligibility criteria. The main findings are reversible changes in bone density and mineral content. Despite high-calorie intake (5000 kcal/day or more), participants experienced body weight loss and a decrease in appetite-regulating hormones. Motivation and goal orientation, positive interpersonal communication and support are important skills during polar expeditions. Multidisciplinary research revealed various physiological and cognitive responses, disrupted sleep patterns and mood changes.

CONCLUSION

Prolonged hypobaric hypoxia reduces aerobic capacity and increases anaerobic metabolism, while bone density changes are reversible and weight loss occurs despite high-calorie intake. Effective decision-making, teamwork and personal growth are crucial for Antarctic explorers. Future studies need to investigate strategies on how to improve physiological functions while maintaining homeostasis.

REGISTRATION

PROSPERO-CRD42022382609.

Evaluation of Retinal and Posterior Segment Vascular Changes Due to Systemic Hypoxia Using Optical Coherence Tomography Angiography

Background/Objectives: Retinal vascular occlusions are a significant cause of visual impairment in older adults, resulting in ischemic retinal damage and sudden vision loss. This study evaluates the retinal, optic nerve head (ONH), and choroidal capillary networks in chronic and acute-on-chronic hypoxia compared to normal controls using optical coherence tomography angiography (OCT-A). Methods: We evaluated a prospective study including twenty patients in the hypoxic group (mean age 61.2 ± 10.2) in two phases, chronic hypoxia and acute-on-chronic hypoxia, and 21 control subjects (mean age 59 ± 9.4 years). All patients underwent a comprehensive eye examination, OCT, and OCT-A imaging. The data were analyzed using OCT-A analysis software (Zeiss OCT-A software 2.1.0.55513) and Fiji software (1.51a). Vascular density of the retina and ONH, choriocapillaries, and foveal avascular zone (FAZ) size were measured. Results: The superficial peripapillary vascular density was higher for the control group (0.387 ± 0.03) compared to the hypoxic patients with (0.383 ± 0.03) and without O2 supplementation (0.383 ± 0.03; p = 0.018). No retinal angiographic differences were identified between the two study groups. The ganglion cell layer (GCL) was thinner in the hypoxic group. Both hypoxic subgroups demonstrated denser choriocapillaries (mean 13,073 ± 1812 and 12,689 ± 1815, with and without O2 supplementation, respectively) compared to the control group (mean 9749 ± 2881, p < 0.001 for both groups). Hypoxic patients demonstrated increased area size of choriocapillaries (+O2 supplementation-mean 44,347 ± 10,563; -O2 supplementation-mean 46,984 ± 12,822) compared to the control group (mean 30,979 ± 9635; p < 0.01 and p < 0.001, respectively). Conclusions: Chronic and acute-on-chronic hypoxia did not affect the retinal vascular network, most probably due to the strong autoregulation of vascular function of the retina. However, compared to the control group, GCL, ONH vasculature density, and most choriocapillaries indices were significantly altered among hypoxic patients.

Exploring the Impact of Resistance Training at Moderate Altitude on Metabolic Cytokines in Humans: Implications for Adipose Tissue Dynamics

Hypobaric hypoxia (HH) limits oxygen supply to tissues and increases metabolic demands, especially during exercise. We studied the influence of HH exposure on the subcutaneous adipose tissue (SAT) thickness and circulating metabolic-related cytokines levels after a resistance training (RT) program. Twenty trained men participated in a traditional hypertrophy RT for 8 weeks (three sessions/week) under intermittent terrestrial HH (2320 m) or normoxia (N, 690 m) conditions. Before, at week 6, and after the RT, SAT, and vastus lateralis (VL) muscle thickness were measured by ultrasound. Blood samples were taken to analyse serum cytokines (IL-6, IL-15, irisin, and myostatin) by multiplex immunoassay. Our findings revealed a moderate reduction in IL-6 and irisin in HH following the RT (ES < -0.64; p < 0.05). Additionally, RT in HH promoted serum IL-15 release (ES = 0.890; p = 0.062), which exhibited a trivial inverse association with the reductions observed on SAT (-17.69%; p < 0.001) compared with N. RT in HH explained ~50% of SAT variance (p < 0.001). These results highlight the benefit of stressor factors linked to RT in HH on SAT through the modulation of serum metabolic cytokine profiles, suggesting a potential effect on overall body composition.

Identifying the Causes of Unexplained Dyspnea at High Altitude Using Normobaric Hypoxia with Echocardiography

Exposure to high altitude results in hypobaric hypoxia, leading to physiological changes in the cardiovascular system that may result in limiting symptoms, including dyspnea, fatigue, and exercise intolerance. However, it is still unclear why some patients are more susceptible to high-altitude symptoms than others. Hypoxic simulation testing (HST) simulates changes in physiology that occur at a specific altitude by asking the patients to breathe a mixture of gases with decreased oxygen content. This study aimed to determine whether the use of transthoracic echocardiography (TTE) during HST can detect the rise in right-sided pressures and the impact of hypoxia on right ventricle (RV) hemodynamics and right to left shunts, thus revealing the underlying causes of high-altitude signs and symptoms. A retrospective study was performed including consecutive patients with unexplained dyspnea at high altitude. HSTs were performed by administrating reduced FiO2 to simulate altitude levels specific to patients' history. Echocardiography images were obtained at baseline and during hypoxia. The study included 27 patients, with a mean age of 65 years, 14 patients (51.9%) were female. RV systolic pressure increased at peak hypoxia, while RV systolic function declined as shown by a significant decrease in the tricuspid annular plane systolic excursion (TAPSE), the maximum velocity achieved by the lateral tricuspid annulus during systole (S' wave), and the RV free wall longitudinal strain. Additionally, right-to-left shunt was present in 19 (70.4%) patients as identified by bubble contrast injections. Among these, the severity of the shunt increased at peak hypoxia in eight cases (42.1%), and the shunt was only evident during hypoxia in seven patients (36.8%). In conclusion, the use of TTE during HST provides valuable information by revealing the presence of symptomatic, sustained shunts and confirming the decline in RV hemodynamics, thus potentially explaining dyspnea at high altitude. Further studies are needed to establish the optimal clinical role of this physiologic method.

Decoding the Influence of Obesity on Prostate Cancer and Its Transgenerational Impact

In recent decades, the escalating prevalence of metabolic disorders, notably obesity and being overweight, has emerged as a pressing concern in public health. Projections for the future indicate a continual upward trajectory in obesity rates, primarily attributable to unhealthy dietary patterns and sedentary lifestyles. The ramifications of obesity extend beyond its visible manifestations, intricately weaving a web of hormonal dysregulation, chronic inflammation, and oxidative stress. This nexus of factors holds particular significance in the context of carcinogenesis, notably in the case of prostate cancer (PCa), which is a pervasive malignancy and a leading cause of mortality among men. A compelling hypothesis arises from the perspective of transgenerational inheritance, wherein genetic and epigenetic imprints associated with obesity may wield influence over the development of PCa. This review proposes a comprehensive exploration of the nuanced mechanisms through which obesity disrupts prostate homeostasis and serves as a catalyst for PCa initiation. Additionally, it delves into the intriguing interplay between the transgenerational transmission of both obesity-related traits and the predisposition to PCa. Drawing insights from a spectrum of sources, ranging from in vitro and animal model research to human studies, this review endeavors to discuss the intricate connections between obesity and PCa. However, the landscape remains partially obscured as the current state of knowledge unveils only fragments of the complex mechanisms linking these phenomena. As research advances, unraveling the associated factors and underlying mechanisms promises to unveil novel avenues for understanding and potentially mitigating the nexus between obesity and the development of PCa.

Serum vascular endothelial growth factor is a potential biomarker for acute mountain sickness

Background: Acute mountain sickness (AMS) is the most common disease caused by hypobaric hypoxia (HH) in high-altitude (HA) associated with high mortality when progressing to high-altitude pulmonary edema (HAPE) and/or high-altitude cerebral edema (HACE). There is evidence for a role of pro- and anti-inflammatory cytokines in development of AMS, but biological pathways and molecular mechanisms underlying AMS remain elusive. We aimed to measure changes in blood cytokine levels and their possible association with the development of AMS.

Method: 15 healthy mountaineers were included into this prospective clinical trial. All participants underwent baseline normoxic testing with venous EDTA blood sampling at the Bangor University in United Kingdom (69 m). The participants started from Beni at an altitude of 869 m and trekked same routes in four groups the Dhaulagiri circuit in the Nepali Himalaya. Trekking a 14-day route, the mountaineers reached the final HA of 5,050 m at the Hidden Valley Base Camp (HVBC). Venous EDTA blood sampling was performed after active ascent to HA the following morning after arrival at 5,050 m (HVBC). A panel of 21 cytokines, chemokines and growth factors were assessed using Luminex system (IL-1β, IL-2, IL-4, IL-6, IL-8, IL-10, IL-12p40, IL-1ra, sIL-2Rα, IFN-γ, TNF-α, MCP-1, MIP-1α, MIP-1β, IP-10, G-CSF, GM-CSF, EGF, FGF-2, VEGF, and TGF-β1).

Results: There was a significant main effect for the gradual ascent from sea-level (SL) to HA on nearly all cytokines. Serum levels for TNF-α, sIL-2Rα, G-CSF, VEGF, EGF, TGF-β1, IL-8, MCP-1, MIP-1β, and IP-10 were significantly increased at HA compared to SL, whereas levels for IFN-γ and MIP-1α were significantly decreased. Serum VEGF was higher in AMS susceptible versus AMS resistant subjects (p &lt; 0.027, main effect of AMS) and increased after ascent to HA in both AMS groups (p &lt; 0.011, main effect of HA). Serum VEGF increased more from SL values in the AMS susceptible group than in the AMS resistant group (p &lt; 0.049, interaction effect).

Conclusion: Cytokine concentrations are significantly altered in HA. Within short interval after ascent, cytokine concentrations in HH normalize to values at SL. VEGF is significantly increased in mountaineers suffering from AMS, indicating its potential role as a biomarker for AMS.

Maternal nano-titanium dioxide inhalation alters fetoplacental outcomes in a sexually dimorphic manner

The placenta plays a critical role in nutrient-waste exchange between the maternal and fetal circulations, thus functioning as an interface that profoundly impacts fetal growth and development. The placenta has long been considered an asexual organ, but, due to its embryonic origin it shares the same sex as the fetus. Exposures to toxicant such as diesel exhaust, have been shown to result in sexually dimorphic outcomes like decreased placental mass in exposed females. Therefore, we hypothesize that maternal nano-TiO2 inhalation exposure during gestation alters placental hemodynamics in a sexually dimorphic manner. Pregnant Sprague-Dawley rats were exposed from gestational day 10-19 to nano-TiO2 aerosols (12.17 ± 1.69 mg/m3) or filtered air (sham-control). Dams were euthanized on GD20, and fetal tissue was collected based on fetal sex: whole placentas, placental junctional zone (JZ), and placental labyrinth zone (LZ). Fetal mass, placental mass, and placental zone percent areas were assessed for sex-based differences. Exposed fetal females were significantly smaller compared to their exposed male counterparts (2.65 ± 0.03 g vs 2.78 ± 0.04 g). Nano-TiO2 exposed fetal females had a significantly decreased percent junctional zone area compared to the sham-control females (24.37 ± 1.30% vs 30.39 ± 1.54%). The percent labyrinth zone area was significantly increased for nano-TiO2 females compared to sham-control females (75.63 ± 1.30% vs 69.61 ± 1.54%). Placental flow and hemodynamics were assessed with a variety of vasoactive substances. It was found that nano-TiO2 exposed fetal females only had a significant decrease in outflow pressure in the presence of the thromboxane (TXA2) mimetic, U46619, compared to sham-control fetal females (3.97 ± 1.30 mm Hg vs 9.10 ± 1.07 mm Hg) and nano-TiO2 fetal males (9.96 ± 0.66 mm Hg). Maternal nano-TiO2 inhalation exposure has a greater effect on fetal female mass, placental zone mass and area, and adversely impacts placental vasoreactivity. This may influence the female growth and development later in life, future studies need to further study the impact of maternal nano-TiO2 inhalation exposure on zone specific mechanisms.

Mechanisms for Combined Hypoxic Conditioning and Divergent Exercise Modes to Regulate Inflammation, Body Composition, Appetite, and Blood Glucose Homeostasis in Overweight and Obese Adults: A Narrative Review

Obesity is a major global health issue and a primary risk factor for metabolic-related disorders. While physical inactivity is one of the main contributors to obesity, it is a modifiable risk factor with exercise training as an established non-pharmacological treatment to prevent the onset of metabolic-related disorders, including obesity. Exposure to hypoxia via normobaric hypoxia (simulated altitude via reduced inspired oxygen fraction), termed hypoxic conditioning, in combination with exercise has been increasingly shown in the last decade to enhance blood glucose regulation and decrease the body mass index, providing a feasible strategy to treat obesity. However, there is no current consensus in the literature regarding the optimal combination of exercise variables such as the mode, duration, and intensity of exercise, as well as the level of hypoxia to maximize fat loss and overall body compositional changes with hypoxic conditioning. In this narrative review, we discuss the effects of such diverse exercise and hypoxic variables on the systematic and myocellular mechanisms, along with physiological responses, implicated in the development of obesity. These include markers of appetite regulation and inflammation, body conformational changes, and blood glucose regulation. As such, we consolidate findings from human studies to provide greater clarity for implementing hypoxic conditioning with exercise as a safe, practical, and effective treatment strategy for obesity.

Cross-Sectional Associations of Body Adiposity, Sedentary Behavior, and Physical Activity with Hemoglobin and White Blood Cell Count

BACKGROUND

This study examined whether hemoglobin (Hb) and white blood cell count (WBC) associate with body adiposity and other cardiometabolic risk factors, as well as accelerometer-measured sedentary behavior (SB) and physical activity (PA), when adjusted for body mass index (BMI).

METHODS

The cross-sectional analysis included 144 participants (42 men) with a mean age of 57.0 years and a mean BMI of 31.7 kg/m². SB and standing time, breaks in sedentary time and PA were measured during four consecutive weeks with hip-worn accelerometers. A fasting blood sample was collected from each participant during the 4-week measurement period and analyzed using Sysmex XN and Cobas 8000 c702 analyzers. Associations of WBC, Hb and other red blood cell markers with cardiometabolic risk factors and physical activity were examined by Pearson's partial correlation coefficient test and with linear mixed regression models.

RESULTS

In sex- and age-adjusted correlation analyses both BMI and waist circumference correlated positively with Hb, WBC, red blood cell count (RBC), and hematocrit. Hb was also positively correlated with systolic blood pressure, insulin resistance scores, liver enzymes, LDL, and triglyceride levels. Sedentary time correlated positively with WBC, whereas standing time correlated negatively with WBC. Lying time correlated positively with WBC, RBC, hematocrit, and Hb. Regarding SB and PA measures, only the association between lying time and RBC remained significant after adjustment for the BMI.

CONCLUSION

We conclude that body adiposity, rather than components of SB or PA, associates with Hb levels and WBC, which cluster with general metabolic derangement.

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.

Therapeutic approach for digestive system cancers and potential implications of exercise under hypoxia condition: what little is known? a narrative review

BACKGROUND

Cancer, like other chronic pathologies, is associated with the presence of hypoxic regions due to the uncontrolled cell growth. Under this pathological hypoxic condition, various molecular signaling pathways are activated to ensure cell survival, such as those that govern angiogenesis, erythropoiesis, among others. These molecular processes are very similar to the physiological response caused by exposure to altitude (natural hypobaric systemic hypoxia), the use of artificial hypoxia devices (systemic normobaric simulated hypoxia) or the delivery of vascular occlusion to the extremities (also called local hypoxia by the blood flow restriction technique). "Tumor hypoxia" has gained further clinical importance due to its crucial role in both tumor progression and resistance to treatment. However, the ability to manipulate this pathway through physical exercise and systemic hypoxia-mediated signaling pathways could offer an important range of therapeutic opportunities that should be further investigated.

METHODS

This review is focused on the potential implications of systemic hypoxia combined with exercise in digestive system neoplasms prognosis. Articles included in the review were retrieved by searching among the three main scientific databases: PubMed, Scopus, and Embase.

FINDINGS

The findings of this review suggest that exercise performed under systemic hypoxic conditions could have a positive impact in prognosis and quality of life of the population with digestive system cancers.

CONCLUSIONS

Further studies are needed to consider this paradigm as a new potential intervention in digestive oncological population.

Repeated Ischemic Preconditioning Effects on Physiological Responses to Hypoxic Exercise

INTRODUCTION: Repeated ischemic preconditioning (IPC) can improve muscle and pulmonary oxygen on-kinetics, blood flow, and exercise efficiency, but these effects have not been investigated in severe hypoxia. The aim of the current study was to evaluate the effects of 7 d of IPC on resting and exercising muscle and cardio-pulmonary responses to severe hypoxia.METHODS: A total of 14 subjects received either: 1) 7 d of repeated lower-limb occlusion (4 × 5 min, 217 ± 30 mmHg) at limb occlusive pressure (IPC) or SHAM (4 × 5 min, 20 mmHg). Subjects were tested for resting limb blood flow, relative microvascular deoxyhemoglobin concentration ([HHB]), and pulmonary oxygen (Vo_2p) responses to steady state and incremental exercise to exhaustion in hypoxia (fractional inspired O₂ = 0.103), which was followed by 7 d of IPC or SHAM and retesting 72 h post-intervention.RESULTS: There were no effects of IPC on maximal oxygen consumption, time to exhaustion during the incremental test, or minute ventilation and arterial oxygen saturation. However, the IPC group had higher delta efficiency based on pooled results and lower steady state Δ[HHB] (IPC ∼24% vs. SHAM ∼6% pre to post), as well as slowing the [HHB] time constant (IPC ∼26% vs. SHAM ∼3% pre to post) and reducing the overshoot in [HHB]: Vo₂ ratio during exercise onset.CONCLUSIONS: Collectively, these results demonstrate that muscle O₂ efficiency and microvascular O₂ distribution can be improved by repeated IPC, but there are no effects on maximal exercise capacity in severe hypoxia.Chopra K, Jeffries O, Tallent J, Heffernan S, Kilduff L, Gray A, Waldron M. Repeated ischemic preconditioning effects on physiological responses to hypoxic exercise. Aerosp Med Hum Perform. 2022; 93(1):13-21.

Impact of chronic sub-lethal methylparaben exposure on cardiac hypoxia and alterations in neuroendocrine factors in zebrafish model

BACKGROUND

Endocrine-disrupting chemicals have been shown to cause toxicity in different systems of the body including the endocrine, cardiovascular and nervous systems. This study aims to analyze the adverse effects of Methylparaben (MP) on cardiac functions, neurodevelopment, and behavior of zebrafish.

METHODS AND RESULTS

Adult male and female zebrafish were exposed to MP for 30 days to study the toxicity effects. Zebrafish were grouped into control, solvent control, 1/10th (110 ppb), 1/100th, and 1/1000th (1 ppb) lethal concentration 50 of MP. Neurobehavioral assays, acetylcholinesterase (AChE) activity, serotonin levels, and expression of genes-Hypoxia-inducible factor 1 alpha, Neurotrophic Receptor Tyrosine Kinase, Paired box protein Pax-6, and tnnt2 were investigated in zebrafish. Results of the study showed more anxiety-like behavior in MP-treated female zebrafish when compared to males on chronic exposure. There was a dose-dependent reduction of AChE activity in both male and female zebrafish. Female zebrafish showed a dose-dependent increase in serotonin level on MP exposure while male zebrafish showed a dose-independent decrease in serotonin level. On MP exposure, there was also a dose-dependent dysregulation in the expression of cardiac hypoxia and neuronal differentiation-related genes in female zebrafish while a dose-independent change was observed in male zebrafish.

CONCLUSION

Chronic MP exposure affects cardiac functions, neuronal functions, and behavior of zebrafish by exhibiting changes in AChE activity, serotonin levels, and altering the expression of genes related to cardiac hypoxia and neuronal differentiation even at sub-lethal doses.

Cardiovascular system and coronavirus disease-2019 (COVID-19): mutual injuries and unexpected outcomes

BACKGROUND

Cardiovascular system involvement in coronavirus disease-2019 (COVID-19) has gained great interest in the scientific community.

MAIN BODY

Several studies reported increased morbidity and mortality among COVID-19 patients who had comorbidities, especially cardiovascular diseases like hypertension and acute coronary syndrome (ACS). COVID-19 may be associated with cardiovascular complications as arrhythmia, myocarditis, and thromboembolic events. We aimed to illustrate the interactions of COVID-19 disease and the cardiovascular system and the consequences on clinical decision as well as public health.

CONCLUSIONS

COVID-19 has negative consequences on the cardiovascular system. A high index of suspicion should be present to avoid poor prognosis of those presenting with unusual presentation.

Transcriptome Profiling Reveals the Endogenous Sponging Role of LINC00659 and UST-AS1 in High-Altitude Induced Thrombosis

BACKGROUND

 The pathophysiology of deep vein thrombosis (DVT) is considered as multifactorial, where thrombus formation is an interplay of genetic and acquired risk factors. Little is known about the expression profile and roles of long noncoding RNAs (lncRNAs) in human subjects developing DVT at high altitude.

METHODS

 Using RNAseQ, we compared peripheral blood mRNA and lncRNA expression profile in human high-altitude DVT (HA-DVT) patients with high-altitude control subjects. We used DESeq to identify differentially expressed (DE) genes. We annotated the lncRNAs using NONCODE 3.0 database. In silico putative lncRNA-miRNA association study unravels the endogenous miRNA sponge associated with our candidate lncRNAs. These findings were validated by small-interfering RNA (siRNA) knockdown assay of the candidate lncRNAs conducted in primary endothelial cells.

RESULTS

 We identified 1,524 DE mRNAs and 973 DE lncRNAs. Co-expressed protein-coding gene analysis resulted in a list of 722 co-expressed protein-coding genes with a Pearson correlation coefficients >0.7. The functional annotation of co-expressed genes and putative proteins revealed their involvement in the hypoxia, immune response, and coagulation cascade. Through its miRNA response elements to compete for miR-143 and miR-15, lncRNA-LINC00659 and UXT-AS1 regulate the expression of prothrombotic genes. Furthermore, in vitro RNA interference (siRNA) simultaneously suppressed lncRNAs and target gene mRNA level.

CONCLUSION

 This transcriptome profile describes novel potential mechanisms of interaction between lncRNAs, the coding genes, miRNAs, and regulatory transcription factors that define the thrombotic signature and may be used in establishing lncRNAs as a biomarker in HA-DVT.

Acute psycho-physiological responses to perceptually regulated hypoxic and normoxic interval walks in overweight-to-obese adults

OBJECTIVES

We investigated psycho-physiological responses to perceptually regulated interval walks in hypoxia versus normoxia in obese individuals.

DESIGN

Within-participants repeated measures.

METHODS

Ten obese adults (BMI=32±3kg/m^-2) completed a 60-min interval session (15×2min walking at a rating of perceived exertion of 14 on the 6-20 Borg scale with 2min of rest) either in hypoxia (FiO₂=13.0%, HYP) or normoxia (NOR). A third trial replicating the HYP speed pattern was carried out in normoxia as a control (CON). Exercise responses were analysed comparing the average of 1st to 3rd exercise bouts to those of the 4th-6th, 7th-9th, 10th-12th and 13th-15th exercise bouts (block 1 versus 2, 3, 4 and 5).

RESULTS

Treadmill speed was slower during block 4 (6.14±0.67 versus 6.24±0.73km/h^-1) and block 5 (6.12±0.64 versus 6.25±0.75km/h^-1) in HYP compared to NOR or CON (p=0.009). Compared to NOR and CON, heart rate was +6-10% higher (p=0.001), whilst arterial oxygen saturation (-12-13%) was lower (p<0.001) in HYP. Perceived limb discomfort was lower in HYP and CON versus NOR (-21±4% and -34±6%; p=0.004).

CONCLUSIONS

In overweight-to-obese adults, perceptually regulated interval walks in hypoxia versus normoxia leads to progressively slower speeds along with lower limb discomfort and larger physiological stress than normoxia. Walking at the speed adopted in hypoxia produces similar psycho-physiological responses at the same absolute intensity in normoxia.

Physiological and oxidative stress responses to intermittent hypoxia training in Sprague Dawley rats

AIM

Rapid ascent to high altitude and inability to acclimatize lead to high-altitude illnesses. Intermittent hypoxia (IH) conditioning has been hypothesized as a non-pharmacological strategy aiming to improve adaptive responses during high altitude ascent. In the recent years, IH training (IHT) has become increasingly popular among recreational and professional athletes owing to its ability to mitigate high altitude related problems. This study aimed at exploring the role of IHT in altitude acclimatization.

METHODS

Male Sprague Dawley rats were subjected to IHT for 4 h consecutively for 5 days at 12% FiO₂ under normobaric conditions. To assess the effect of IHT in hypoxic acclimatization, animals were further exposed to extreme hypoxia (EH) at 8% FiO₂. Oxygen saturation (SpO₂), respiratory rate and heart rate were recorded during the exposure. Oxidative stress (ROS, MDA, and 4-HNE) and histopathological examinations were studied in the lung tissue sections. Hypoxia biomarkers, HIF-1α, EPO, VEGF, and BPGM were evaluated through western blotting in the lung tissue.

RESULTS

Assessment of the IHT showed that SpO₂ levels were found to be higher in the IH trained rats with a statistical difference of p < 0.01 in the first hour of hypoxia exposure as compared to the untrained rats. There was a significantly higher (p < 0.001) generation of ROS and MDA in the untrained rats as compared to the trained rats. Lipid peroxidation markers and systemic inflammatory marker were found to be expressed at much higher level in the untrained rats. There was a higher expression of HIF-1α (1.24-fold ↑), VEGF (1.14-fold ↑) and decrease in EPO (1.43-fold ↓) in the untrained rats as compared to trained rats.

CONCLUSIONS

Preconditioning with IHT resulted in the reduction in hypoxia induced oxidative stress during extreme hypoxia exposure and thus, maintaining redox balance as well as adjustment in the physiological changes in rats.

Effects of acute hypobaric hypoxia on thermoregulatory and circulatory responses during cold air exposure

Background

The thermoregulatory responses during simultaneous exposure to hypoxia and cold are not well understood owing to the opposite reactions of vasomotor tone in these two environments. Therefore, the purpose of this study was to investigate the influences of hypobaric hypoxia on various thermoregulatory responses, including skin blood flow (SkBF) during cold exposure.

Methods

Ten subjects participated in two experimental conditions: normobaric normoxia with cold (NC, barometric pressure (P_B) = 760 mmHg) and hypobaric hypoxia with cold (HC, P_B = 493 mmHg). The air temperature was maintained at 28 °C for 65 min and gradually decreased to 19 °C for both conditions. The total duration of the experiment was 135 min.

Results

The saturation of percutaneous oxygen (SpO₂) was maintained at 98–99% in NC condition, but decreased to around 84% in HC condition. The rectal and mean skin temperatures showed no significant differences between the conditions; however, the forehead temperature was higher in HC condition than in NC condition. The pulse rate increased in HC condition, and there was a strong negative relationship between SpO₂ and pulse rate (r = − 0.860, p = 0.013). SkBF and blood pressure showed no significant differences between the two conditions.

Conclusion

These results suggest that hypobaric hypoxia during cold exposure did not alter the overall thermoregulatory responses. However, hypobaric hypoxia did affect pulse rate regardless of cold exposure.

Explaining the Inverse Association between Altitude and Obesity

PURPOSE

To better understand the inverse association between altitude and adult obesity.

METHODS

An ecological study design was used, involving 3,108 counties in the contiguous United States. Data were from several national sources, and assessment involved various statistical techniques, including multiple regression analysis.

RESULTS

Living in counties at higher altitude is associated with lower adult obesity. Compared with counties <500 meters, the percent of adult obesity decreases by 5.18% at 500-999 meters, 9.69% at 1,000-1,499 meters, 16.77% at 1,500-1,999 meters, 24.14% at 2,000-2,499 meters, and 35.28% at ≥2,500 meters. After adjusting for physical inactivity, smoking, and other variables, corresponding decreases in adult obesity with higher altitude groupings are 3.87%, 5.64%, 8.03%, 11.41%, and 17.54%, respectively. Various mechanisms are presented as possible explanations for the association between higher altitude and lower obesity. In addition, altitude may indirectly influence adult obesity, primarily through its relationship with physical inactivity and smoking. In an adjusted regression model, adult obesity was most strongly associated with physical inactivity followed by adult smoking and then altitude. Together they explain 39.04% of the variation in adult obesity. After accounting for these variables, sunlight, precipitation, ambient air temperature, education, income, food insecurity, limited access to healthy foods, race, sex, and rural living explain an additional 4.68% of the variation in adult obesity.

CONCLUSIONS

The inverse association between altitude and adult obesity remains significant after adjustment for several variables.

Changes in the Paradigm of Traditional Exercise in Obesity Therapy and Application of a New Exercise Modality: A Narrative Review Article

BACKGROUND

Obesity is recognized as an important global health problem that increases the risk of all-cause death. It is a major risk factor for various cardiovascular and metabolic diseases.

METHODS

We conducted this review through searching the related literature plus internet links.

RESULTS

Recently, many researchers have been applying various efficient alternative exercise paradigms for treating obesity, such as high-intensity interval training, whole-body vibration training, and hypoxic therapy. Compared with moderate-intensity continuous training, high-intensity interval training involves a shorter exercise time but higher energy expenditure and excess post-exercise oxygen consumption via a higher exercise intensity and is effective for treating obesity. Whole-body vibration training effectively reduces the rate of fat production and accumulation through passive vibration of the whole body and improving the body composition, muscle function, and cardiovascular function of the obese population. Hypoxic therapy has been reported to improve obesity and obesity-related diseases through appetite loss, reduced dietary intake, increased energy consumption, improved glycogen storage and fatty acid oxidation, angiogenesis and left ventricle remodeling, decreased mechanical load, and reduced sarcopenia progression due to aging.

CONCLUSION

The new therapeutic exercise modalities, namely, high-intensity interval training, whole-body vibration training, and hypoxic therapy, are practical, useful, and effective for improving obesity and various metabolic and cardiovascular diseases induced by obesity.

Psycho-physiological responses to perceptually-regulated interval runs in hypoxia and normoxia

We investigated whether perceptually-regulated high-intensity intervals in hypoxia are associated with slower running velocities versus normoxia, when physiological responses and exercise-related sensations remain the same. Nineteen trained runners (33.4 ± 9.1 years) completed a high-intensity interval running protocol (4 × 4-min intervals at a clamped perceived rating exertion of 16 on the 6-20 Borg scale, 3-min passive recoveries) in either hypoxic (HYP; FiO₂ 15.0%) or normoxic (NOR; FiO₂ 20.9%) conditions. Participants adjusted to a progressively slower running velocity from interval 1-4 (-7.0%), and more so in HYP vs. NOR for intervals 2, 3 and 4 (-4.6%, -6.4% and - 7.9%, respectively; p < .01). Heart rate increased from interval 1-4 (+4.8%; p < .01), independent of condition. Arterial oxygen saturation was lower in HYP vs. NOR (86.0% vs. 94.8%; p < .01). Oxyhemoglobin (-23.7%) and total hemoglobin (-77.0%) decreased, whilst deoxyhemoglobin increased (+44.9%) from interval 1-4 (p < .01), independent of condition. Perceived recovery (-41.6%) and motivation (-21.8%) were progressively lower from interval 1-4, and more so in HYP vs. NOR for intervals 2, 3 and 4 (recovery: -8.8%, -24.2% and - 29.3%; motivation: -5.3%, -20.3% and - 22.4%, respectively; p < .01). Perceived breathlessness (+18.6%), limb discomfort (+44.0%) and pleasure (-32.2%) changed from interval 1-4, with significant differences (+21.8%, +11.3% and - 31.3%, respectively) between HYP and NOR (p < .01). Slower interval running velocities in hypoxia achieve similar heart rate and muscle oxygenation responses to those observed in normoxia when perceptually-regulated, yet at the expense of less favourable exercise-related sensations.

Identification of lncRNAs and Genes Responsible for Fatness and Fatty Acid Composition Traits between the Tibetan and Yorkshire Pigs

Tibetan pigs from the Tibetan Plateau are characterized with a significant phenotypic difference relative to lowland pigs. In this study, a significant difference of the fatness and fatty acid composition traits was observed between the Tibetan and Yorkshire pigs. To uncover the involved mechanism, the expression profile of long noncoding RNAs (lncRNAs) and genes was compared between them. After serial filtered steps, 1,964 lncRNAs were obtained through our computational pipeline. In total, 63 and 715 lncRNAs and genes were identified to be differentially expressed. Evidence from cis- and trans-targeting analysis of lncRNAs demonstrated that some lncRNAs, such as MSTRG.14097 and MSTRG.8034, played important roles in the fatness and fatty acid composition traits. Bioinformatics analysis revealed that many candidate genes were responsible for the two traits. Of these, FASN, ACACA, SCD, ME3, PDHB, ACSS1, ACSS2, and ACLY were identified, which functioned in regulating the level of hexadecanoic acid, hexadecenoic acid, octadecenoic acid, and monounsaturated fatty acid. And LPGAT1, PDK4, ACAA1, and ADIPOQ were associated with the content of stearic acid, octadecadienoic acid, and polyunsaturated fatty acid. Candidate genes, which were responsible for fatness trait, consisted of FGF2, PLAG1, ADIPOQ, IRX3, MIF, IL-34, ADAM8, HMOX1, Vav1, and TLR8. In addition, association analysis also revealed that 34 and 57 genes significantly correlated to the fatness and fatty acid composition trait, respectively. Working out the mechanism caused by these lncRNAs and candidate genes is proven to be complicated but is invaluable to our understanding of fatness and fatty acid composition traits.

Additive stress of normobaric hypoxic conditioning to improve body mass loss and cardiometabolic markers in individuals with overweight or obesity: A systematic review and meta-analysis

We performed a systematic review and meta-analysis to determine if hypoxic conditioning, compared to similar training near sea level, maximizes body mass loss and further improves cardiometabolic markers in overweight and obese individuals. A systematic search of PubMed, Web of Science and the Cochrane Library databases (up to January 2019) was performed. This analysis included randomized controlled trials with humans with overweight or obesity assessing the effects of HC on body mass loss or cardiometabolic markers. A subgroup analysis was performed to examine if HC effects differed between individuals with overweight or obesity. 13 articles (336 participants) qualified for inclusion. HC significantly decreased body mass (p = .01), fat mass (p = .04), waist/hip ratio (p < .001), waist (p < .001), LDL (p = .01), diastolic (p < .01) and systolic blood pressure (p < .01) with these effects not being larger than equivalent normoxic interventions. There were trends towards higher triglycerides decrement (p = .06) and higher muscle mass gain in hypoxic (p = .08) compared with normoxic condition. Also, the two BMI categories displayed no difference in the magnitude of the responses. Compared to normoxic equivalent, HC provides greater reductions in triglycerides and greater muscle growth, while body mass changes are similar. In addition, HC responses were essentially similar between individuals with overweight or obesity.

Body Composition and Body Weight Changes at Different Altitude Levels: A Systematic Review and Meta-Analysis

Changes in body composition and weight loss frequently occur when humans are exposed to hypoxic environments. The mechanisms thought to be responsible for these changes are increased energy expenditure resulting from increased basal metabolic rate and/or high levels of physical activity, inadequate energy intake, fluid loss as well as gastrointestinal malabsorption. The severity of hypoxia, the duration of exposure as well as the level of physical activity also seem to play crucial roles in the final outcome. On one hand, excessive weight loss in mountaineers exercising at high altitudes may affect performance and climbing success. On the other, hypoxic conditioning is presumed to have an important therapeutic potential in weight management programs in overweight/obese people, especially in combination with exercise. In this regard, it is important to define the hypoxia effect on both body composition and weight change. The purpose of this study is to define, through the use of meta-analysis, the extent of bodyweight -and body composition changes within the three internationally classified altitude levels (moderate altitude: 1500–3500 m; high altitude: 3500–5300 m; extreme altitude: >5300 m), with emphasis on physical activity, nutrition, duration of stay and type of exposure.

Daily Intermittent Normobaric Hypoxia Over 2 Weeks Reduces BDNF Plasma Levels in Young Adults - A Randomized Controlled Feasibility Study

Background: The results from animal and human research indicate that acute intermittent hypoxia can enhance brain-derived neurotrophic factor (BDNF) plasma levels and gene expression. As BDNF is known to promote the differentiation of new neurons and the formation of synapses, it has been proposed to mediate adult neuroplasticity. Thus, the present study aimed to analyze the long-term effects of daily intermittent exposure to normobaric hypoxia (simulating high altitude exposure at approximately 4000–5000 m) over 2 weeks on BDNF levels in young adults.

Methods: Twenty-eight young adults (age: 19–33 years) were randomized into a hypoxic intervention group (N = 14) or the control group (N = 14). Participants in the intervention group breathed intermittent normobaric hypoxic air at resting conditions (5 min intervals, 80–85% SpO₂ measured via a finger pulse oximeter, 12 sessions for 60 min/day for 2 weeks) via a hypoxic generator. BDNF plasma and serum levels were determined at baseline and at 2 weeks after intervention using sandwich ELISAs.

Results: After 2 weeks of daily intermittent hypoxic treatment (IHT), we found a significant group x time interaction effect for BDNF plasma levels based on a significant decrease in BDNF levels in the hypoxia group.

Conclusion: Our results demonstrate that daily intermittent administration of hypoxic air has a significant effect on BDNF regulation in healthy young adults. Contrary to other results reporting an increase in BDNF levels under hypoxic conditions, the present data suggest that hypoxic treatment using intensive IHT can reduce BDNF plasma levels for at least 2 weeks. This finding indicates that the daily application of hypoxic air is too frequent for the aimed physiological response, namely, an increase in BDNF levels.

Effects of heat and cold on health, with special reference to Finnish sauna bathing

Environmental stress such as extremely warm or cold temperature is often considered a challenge to human health and body homeostasis. However, the human body can adapt relatively well to heat and cold environments, and recent studies have also elucidated that particularly heat stress might be even highly beneficial for human health. Consequently, the aim of the present brief review is first to discuss general cardiovascular and other responses to acute heat stress, followed by a review of beneficial effects of Finnish sauna bathing on general and cardiovascular health and mortality as well as dementia and Alzheimer's disease risk. Plausible mechanisms included are improved endothelial and microvascular function, reduced blood pressure and arterial stiffness, and possibly increased angiogenesis in humans, which are likely to mediate the health benefits of sauna bathing. In addition to heat exposure with physiological adaptations, cold stress-induced physiological responses and brown fat activation on health are also discussed. This is important to take into consideration, as sauna bathing is frequently associated with cooling periods in cold(er) environments, but their combination remains poorly investigated. We finally propose, therefore, that possible additive effects of heat- and cold-stress-induced adaptations and effects on health would be worthy of further investigation.

High-Intensity Interval Training in Normobaric Hypoxia Leads to Greater Body Fat Loss in Overweight/Obese Women than High-Intensity Interval Training in Normoxia

A moderate hypoxic stimulus is considered a promising therapeutic modality for several pathological states including obesity. There is scientific evidence suggesting that when hypoxia and physical activity are combined, they could provide benefits for the obese population. The aim of the present study was to investigate if exposure to hypoxia combined with two different protocols of high-intensity interval exercise in overweight/obese women was more effective compared with exercise in normoxia. Study participants included 82 overweight/obese women, who started a 12 week program of 36 sessions, and were randomly divided into four groups: (1) aerobic interval training in hypoxia (AitH; FiO₂ = 17.2%; n = 13), (2) aerobic interval training in normoxia (AitN; n = 15), (3) sprint interval training in hypoxia (SitH; n = 15), and (4) sprint interval training in normoxia (SitN; n = 18). Body mass, body mass index, percentage of total fat mass, muscle mass, basal metabolic rate, fat, and carbohydrate oxidation, and fat and carbohydrate energy were assessed. Outcomes were measured at baseline (T1), after 18 training sessions (T2), 7 days after the last session (T3), and 4 weeks after the last session (T4). The fat mass in the SitH group was significantly reduced compared with the SitN group from T1 to T3 (p < 0.05) and from T1 to T4 (p < 0.05) and muscle mass increased significantly from T1 to T4 (p < 0.05). Fat mass in the AitH group decreased significantly (p < 0.01) and muscle mass increased (p = 0.022) compared with the AitN group from T1 to T4. All training groups showed a reduction in the percentage of fat mass, with a statistically significant reduction in the hypoxia groups (p < 0.05). Muscle mass increased significantly in the hypoxia groups (p < 0.05), especially at T4. While fat oxidation tended to increase and oxidation of carbohydrates tended to decrease in both hypoxia groups, the tendency was reversed in the normoxia groups. Thus, high-intensity interval training under normobaric intermittent hypoxia for 12 weeks in overweight/obese women seems to be promising for reducing body fat content with a concomitant increase in muscle mass.

Cardiovascular adaptation to hypoxia and the role of peripheral resistance

Systemic vascular pressure in vertebrates is regulated by a range of factors: one key element of control is peripheral resistance in tissue capillary beds. Many aspects of the relationship between central control of vascular flow and peripheral resistance are unclear. An important example of this is the relationship between hypoxic response in individual tissues, and the effect that response has on systemic cardiovascular adaptation to oxygen deprivation. We show here how hypoxic response via the HIF transcription factors in one large vascular bed, that underlying the skin, influences cardiovascular response to hypoxia in mice. We show that the response of the skin to hypoxia feeds back on a wide range of cardiovascular parameters, including heart rate, arterial pressures, and body temperature. These data represent the first demonstration of a dynamic role for oxygen sensing in a peripheral tissue directly modifying cardiovascular response to the challenge of hypoxia.

A vicious circle in chronic lymphoedema pathophysiology? An adipocentric view

Chronic lymphoedema is a disease caused by a congenital or acquired damage to the lymphatic system and characterized by complex chains of pathophysiologic events such as lymphatic fluid stasis, chronic inflammation, lymphatic vessels impairment, adipose tissue deposition and fibrosis. These events seem to maintain and reinforce themselves through a positive feedback loop: regardless of the initial cause of lymphatic stasis, the dysfunctional adipose tissue and its secretion products can worsen lymphatic vessels' function, aggravating lymph leakage and stagnation, which can promote further adipose tissue deposition and fibrosis, similar to what may happen in obesity. In addition to the current knowledge about the tight and ancestral interrelation between immunity system and metabolism, there is evidence for similarities between obesity-related and lymphatic damage-induced lymphoedema. Together, these observations indicate strong reciprocal relationship between lymphatics and adipose tissue and suggest a possible key role of the adipocyte in the pathophysiology of chronic lymphoedema's vicious circle.

Normobaric hypoxic conditioning to maximize weight loss and ameliorate cardio-metabolic health in obese populations: a systematic review

Normobaric hypoxic conditioning (HC) is defined as exposure to systemic and/or local hypoxia at rest (passive) or combined with exercise training (active). HC has been previously used by healthy and athletic populations to enhance their physical capacity and improve performance in the lead up to competition. Recently, HC has also been applied acutely (single exposure) and chronically (repeated exposure over several weeks) to overweight and obese populations with the intention of managing and potentially increasing cardio-metabolic health and weight loss. At present, it is unclear what the cardio-metabolic health and weight loss responses of obese populations are in response to passive and active HC. Exploration of potential benefits of exposure to both passive and active HC may provide pivotal findings for improving health and well being in these individuals. A systematic literature search for articles published between 2000 and 2017 was carried out. Studies investigating the effects of normobaric HC as a novel therapeutic approach to elicit improvements in the cardio-metabolic health and weight loss of obese populations were included. Studies investigated passive (n = 7; 5 animals, 2 humans), active (n = 4; all humans) and a combination of passive and active (n = 4; 3 animals, 1 human) HC to an inspired oxygen fraction ([Formula: see text]) between 4.8 and 15.0%, ranging between a single session and daily sessions per week, lasting from 5 days up to 8 mo. Passive HC led to reduced insulin concentrations (-37 to -22%) in obese animals and increased energy expenditure (+12 to +16%) in obese humans, whereas active HC lead to reductions in body weight (-4 to -2%) in obese animals and humans, and blood pressure (-8 to -3%) in obese humans compared with a matched workload in normoxic conditions. Inconclusive findings, however, exist in determining the impact of acute and chronic HC on markers such as triglycerides, cholesterol levels, and fitness capacity. Importantly, most of the studies that included animal models involved exposure to severe levels of hypoxia ([Formula: see text] = 5.0%; simulated altitude >10,000 m) that are not suitable for human populations. Overall, normobaric HC demonstrated observable positive findings in relation to insulin and energy expenditure (passive), and body weight and blood pressure (active), which may improve the cardio-metabolic health and body weight management of obese populations. However, further evidence on responses of circulating biomarkers to both passive and active HC in humans is warranted.

Comparative and Experimental Studies on the Genes Altered by Chronic Hypoxia in Human Brain Microendothelial Cells

Background : Hypoxia inducible factor 1 alpha (HIF1A) is a master regulator of acute hypoxia; however, with chronic hypoxia, HIF1A levels return to the normoxic levels. Importantly, the genes that are involved in the cell survival and viability under chronic hypoxia are not known. Therefore, we tested the hypothesis that chronic hypoxia leads to the upregulation of a core group of genes with associated changes in the promoter DNA methylation that mediates the cell survival under hypoxia. Results : We examined the effect of chronic hypoxia (3 days; 0.5% oxygen) on human brain micro endothelial cells (HBMEC) viability and apoptosis. Hypoxia caused a significant reduction in cell viability and an increase in apoptosis. Next, we examined chronic hypoxia associated changes in transcriptome and genome-wide promoter methylation. The data obtained was compared with 16 other microarray studies on chronic hypoxia. Nine genes were altered in response to chronic hypoxia in all 17 studies. Interestingly, HIF1A was not altered with chronic hypoxia in any of the studies. Furthermore, we compared our data to three other studies that identified HIF-responsive genes by various approaches. Only two genes were found to be HIF dependent. We silenced each of these 9 genes using CRISPR/Cas9 system. Downregulation of EGLN3 significantly increased the cell death under chronic hypoxia, whereas downregulation of ERO1L, ENO2, adrenomedullin, and spag4 reduced the cell death under hypoxia. Conclusions : We provide a core group of genes that regulates cellular acclimatization under chronic hypoxic stress, and most of them are HIF independent.

High-Intensity Interval Training in Normobaric Hypoxia Improves Cardiorespiratory Fitness in Overweight Chinese Young Women

Previous studies have investigated the effects of high-intensity interval training (HIIT) on cardiorespiratory fitness and body composition in overweight populations. However, the additive effect of HIIT and hypoxia on health parameters is not clear. This study compared the effects of HIIT under hypoxic conditions on cardiometabolic function with that under normoxia in overweight Chinese young women.

Methods: A double-blind randomized controlled experimental design was applied. Twenty-four sedentary overweight Chinese young women (weight: 68.8 ± 7.0 kg, BMI: 25.8 ± 2.3 kg·m⁻²) participated in the HIIT under either normoxia (NORM, n = 13, PIO₂: 150 mmHg, FIO₂: 0.21) or normobaric hypoxia (HYP, n = 11, PIO₂: 117 mmHg, FIO₂: 0.15) for 5 weeks. HIIT was composed of 60 repetitions of 8 s maximal cycling effort interspersed with 12-s recovery per day, for 4 days per week. Cardiorespiratory fitness [peak oxygen uptake (V·O_2peak), and peak oxygen pulse (peak O₂ pulse)], serum lipid profile [triglycerides (TG), total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C)], and body composition (regional and whole-body), were assessed at pre- and post-intervention during the days beyond the self-reported menstrual phase of the participants. Habitual physical activity and diary behavior were maintained during the intervention period.

Results: With similar daily energy intake and physical activity, the increases in V·O_2peak [NORM: 0.26 ± 0.37 L·min⁻¹ (+11.8%) vs. HYP: 0.54 ± 0.34 L·min⁻¹ (+26.1%)] and peak O₂ pulse (NORM: +13.4% vs. HYP: +25.9%) for HYP were twice-larger than for NORM (p < 0.05). Although the 5-wk HIIT led to significant improvements in the ratios of TC/HDL-C (p = 0.035) and TG/HDL-C (p = 0.027), no significant group effects were found on the serum variables. Further, no significant changes in body composition or serum fasting leptin were observed in either group.

Conclusion: 5-wk of HIIT improved cardiorespiratory fitness and blood lipids in overweight Chinese young females, while the additive effect of the HIIT under normobaric hypoxia solely enhanced cardiorespiratory fitness, but not body composition or serum lipid profile.