Human Genetic Adaptation to High Altitude: Evidence from the Andes

Oxidative potential of particulate matter and its association to respiratory health endpoints in high-altitude cities in Bolivia

Exposure to particulate matter (PM) pollution is a significant health risk, driving the search for innovative metrics that more accurately reflect the potential harm to human health. Among these, oxidative potential (OP) has emerged as a promising health-based metric, yet its application and relevance across different environments remain to be further explored. This study, set in two high-altitude Bolivian cities, aims to identify the most significant sources of PM-induced oxidation in the lungs and assess the utility of OP in assessing PM health impacts. Utilizing two distinct assays, OPDTT and OPDCFH, we measured the OP of PM samples, while also examining the associations between PM mass, OP, and black carbon (BC) concentrations with hospital visits for acute respiratory infections (ARI) and pneumonia over a range of exposure lags (0-2 weeks) using a Poisson regression model adjusted for meteorological conditions. The analysis also leveraged Positive Matrix Factorization (PMF) to link these health outcomes to specific PM sources, building on a prior source apportionment study utilizing the same dataset. Our findings highlight anthropogenic combustion, particularly from traffic and biomass burning, as the primary contributors to OP in these urban sites. Significant correlations were observed between both OPDTT and PM2.5 concentration exposure and ARI hospital visits, alongside a notable association with pneumonia cases and OPDTT levels. Furthermore, PMF analysis demonstrated a clear link between traffic-related pollution and increased hospital admissions for respiratory issues, affirming the health impact of these sources. These results underscore the potential of OPDTT as a valuable metric for assessing the health risks associated with acute PM exposure, showcasing its broader application in environmental health studies.

Work at high altitude and non-fatal cardiovascular disease associated with unfitness to work: Prospective cohort observation

INTRODUCTION

Mining at high altitude exposes workers to hypoxic environment and cold climate in addition to conventional hazards in mining, but very little is known on how to define fitness to work in prospective candidates with pre-existing conditions. The aim of the current study was to define the incidence of cardiovascular diseases leading to unfitness to work as well as their predictors in a prospective observation.

METHODS

A total of 569 prospective employees (median age 34 (interquartile range (IQR) 28;40) years, 95% men 85% mid-altitude residents) for a high-altitude gold mine in Kyrgyzstan operating at 3800-4500 meters above sea level were screened at pre-employment in 2009-2012 and followed by January 2022. Cox regression was used to quantify the association of baseline demographics and physiological variables with newly diagnosed cardiovascular diseases (CVD) leading to unfitness to work, expressed as hazard ratios (HRs) with 95% confidence intervals (CI).

RESULTS

With 5190 person-years of observation, 155 (27%) workers have left work, of whom 23 had a newly identified CVD leading to unfitness to work (cumulative incidence 4%) with no difference between drivers and other occupations, despite greater blood pressure and body mass index (BMI) in the former at baseline. Age (HR 1.13 (95% CI 1.06;1.22) and BMI (HR 1.18 (95% CI 1.04;1.34)) were associated with a greater chance of having CVD, adjusted for lung function, baseline diagnoses, year of employment and baseline blood pressure. Narrowing the analysis to only men, drivers, smokers and even middle-altitude residents did not change the effect.

CONCLUSION

These findings confirmed high efficacy of pre-employment screening limiting access of workers with advanced conditions to work which later yielded low CVD incidence. In addition to conventional contraindications to work at high altitude, age and high BMI should be considered when a decision is made.

Critical pregnancy at altitude: A look at Latin America

Critical pregnancy at high altitudes increases morbidity and mortality from 2500 m above sea level. In addition to altitude, there are other influential factors such as social inequalities, cultural, prehospital barriers, and lack the appropriate development of healthcare infrastructure. The most frequent causes of critical pregnancy leading to admission to Intensive Care Units are pregnancy hypertensive disorders (native residents seem to be more protected), hemorrhages and infection/sepsis. In Latin America, there are 32 Intensive Care Units above 2500 m above sea level. Arterial blood gases at altitude are affected by changes in barometric pressure. The analysis of their values provides very useful information for the management of obstetric emergencies at very high altitude, especially respiratory and metabolic pathologies.

Low- and moderate-intensity aerobic exercise improves the physiological acclimatization of lowlanders on the Tibetan plateau

This study investigates whether exercise as a strategy for improving physical fitness at sea level also offers comparable benefits in the unique context of high altitudes (HA), considering the physiological challenges of hypoxic conditions. Overall, 121 lowlanders who had lived on the Tibetan Plateau for >2 years and were still living at HA during the measurements were randomly classified into four groups. Each individual of the low-intensity (LI), moderate-intensity (MI), and high-intensity (HI) groups performed 20 sessions of aerobic exercise at HA (3680 m) over 4 weeks, while the control group (CG) did not undergo any intervention. Physiological responses before and after the intervention were observed. The LI and MI groups experienced significant improvement in cardiopulmonary fitness (0.27 and 0.35 L/min increases in peak oxygen uptake [V ˙ $\dot{\mathrm{V}}$ O2peak], both p < 0.05) after exercise intervention, while the hematocrit (HCT) remained unchanged (p > 0.05). However, HI exercise was less efficient for cardiopulmonary fitness of lowlanders (0.02 L/min decrease inV ˙ $\dot{\mathrm{V}}$ O2peak, p > 0.05), whereas both the HCT (1.74 %, p < 0.001) and glomerular filtration rate (18.41 mL/min, p < 0.001) increased with HI intervention. Therefore, LI and MI aerobic exercise, rather than HI, can help lowlanders in Tibet become more acclimated to the HA by increasing cardiopulmonary function and counteracting erythrocytosis.

Waist Reduction through Conversion from False to Floating Ribs

Background

Waist reduction by ultrasound-guided monocortical fracture (RibXcar), usually performed on floating ribs, may show limitations when performed on false ribs (9 and 10) because of the stress force exerted on the anterior fixation point (cartilage union to sternum). Hence, we introduced a procedure for conversion from false to floating ribs to improve the final result of the treatment of false ribs through a rib treatment scheme.

Methods

Forty-nine female patients undergoing rib surgery were recruited. Waist measurements and angular variations were compared between two groups of patients, the first (26 patients) consisting of patients who underwent RibXcar with conversion surgery (ribs 9 and 10) and the second (23 patients) consisting of patients who underwent RibXcar without conversion surgery (ribs 9 and 10).

Results

The waist measurements taken after 6 months showed a mean decrease of 8.70 cm in the group where only RibXcar was performed, whereas a statistically significant mean reduction of 17.04 cm was observed in the group where RibXcar was performed with rib conversion surgery.

Conclusions

The false-to-floating-rib conversion technique combined with RibXcar demonstrated more reduction in waist circumference and a more efficient rib angulation compared with RibXcar alone.

The Precision and Power of Population Branch Statistics in Identifying the Genomic Signatures of Local Adaptation

Population branch statistics, which estimate the branch lengths of focal populations with respect to two outgroups, have been used as an alternative to FST-based genome-wide scans for identifying loci associated with local selective sweeps. In addition to the original population branch statistic (PBS), there are subsequently proposed branch rescalings: normalized population branch statistic (PBSn1), which adjusts focal branch length with respect to outgroup branch lengths at the same locus, and population branch excess (PBE), which also incorporates median branch lengths at other loci. PBSn1 and PBE have been proposed to be less sensitive to allele frequency divergence generated by background selection or geographically ubiquitous positive selection rather than local selective sweeps. However, the accuracy and statistical power of branch statistics have not been systematically assessed. To do so, we simulate genomes in representative large and small populations with varying proportions of sites evolving under genetic drift or background selection (approximated using variable Ne), local selective sweeps, and geographically parallel selective sweeps. We then assess the probability that local selective sweep loci are correctly identified as outliers by FST and by each of the branch statistics. We find that branch statistics consistently outperform FST at identifying local sweeps. When background selection and/or parallel sweeps are introduced, PBSn1 and especially PBE correctly identify local sweeps among their top outliers at a higher frequency than PBS. These results validate the greater specificity of rescaled branch statistics such as PBE to detect population-specific positive selection, supporting their use in genomic studies focused on local adaptation.

Hypertension subtypes at high altitude in Peru: Analysis of the Demographic and Family Health Survey 2016-2019

BACKGROUND

The prevalence of hypertension in Peru has increased over the years. Approximately one third of the Peruvian population lives at high altitudes. This population presents particular physiological, genetic and environmental characteristics that could be related to the prevalence of hypertension and its subtypes.

OBJECTIVE

To assess the association between altitude and hypertension in the Peruvian population through an analysis of a nationally representative survey.

METHODS

We conducted a cross-sectional analysis of the Demographic and Family Health Survey for the period 2016-2019. We included 122,336 individuals aged 18 years and older. Hypertension was defined according to the JNC-7 guidelines. High-altitude location was defined as a residential cluster located above 2,500 meters above sea level. We utilized generalized linear models from the Poisson family with a log-link function to assess the magnitude of the association between high altitude and hypertension. Additionally, we employed multinomial regression models to analyze the association between high altitude and subtypes of hypertension, including isolated systolic hypertension (ISH), isolated diastolic hypertension (IDH), and systolic-diastolic hypertension (SDH).

RESULTS

In the adjusted Poisson regression model, we found that the prevalence of hypertension among participants living at high altitudes was lower compared to those living at low altitudes (aPR: 0.89; 95% CI: 0.86-0.93). In the adjusted multinomial regression model, we observed a lower prevalence rate of ISH among participants residing at high altitudes (aRPR: 0.68; 95% CI: 0.61-0.73) and a higher prevalence rate of IDH among participants residing at high altitudes (aRPR: 1.60; 95% CI: 1.32-1.94).

CONCLUSIONS

Residents at high altitudes in Peru have a lower prevalence rate of ISH and a higher prevalence rate of IDH compared to those living at low altitudes. Further studies are needed to determine the influence of other biological, environmental, and healthcare access factors on this relationship.

Adaptation to Living at High Altitude in Patients with COPD. Comparative Study of Exercise Capacity and Ventilatory Variables between Patients Residing at High and Low Altitudes in the Andes

González-García, Mauricio and Luis Ernesto Téllez. Adaptation to living at high altitude in patients with COPD. Comparative study of exercise capacity and ventilatory variables between patients residing at high and low altitudes in the Andes. High Alt Med Biol. 00:000-000, 2024. Introduction: Although some variables related to oxygen transport and utilization such as ventilation, pulmonary vascular responses to hypoxia, heart rate (HR), cardiac output, hemoglobin (Hb), and oxygen saturation (SpO2) are used to compare adaptation to altitude between populations, peak oxygen consumption (VO2) constitutes an integrative measure of total oxygen transport that may reflect successful adaptation to altitude. We designed this study to make a direct comparison of VO2 in a cardiopulmonary exercise test (CPET) between chronic obstructive pulmonary disease (COPD) patients residing at high altitude (Bogotá, Colombia: 2,640 m) (COPD-HA) and those living at low altitude (Bucaramanga, Colombia: 959 m) (COPD-LA). Methods: All patients performed a CPET with measurements of VO2, minute ventilation (VE), HR, oxygen pulse (VO2/HR), ventilatory equivalents (VE/VCO2), and SpO2. Unpaired T-test or Mann-Whitney U test were used for comparisons between COPD-HA and COPD-LA. Results: We included 71 patients with COPD, 53 COPD-HA, and 18 COPD-LA. There were no differences between groups in age, sex, or forced expiratory volume in 1 second. The means ± SD of Hb, g/dl was slightly higher in COPD-HA (15.9 ± 1.9 vs. 14.7 ± 1.8, p = 0.048), without differences in VO2, % pred (71.6 ± 17.9 vs. 69.0 ± 17.0, p = 0.584), VO2/HR, % pred (92.1 ± 22.0 vs. 89.7 ± 19.8, p = 0.733) or VE/MVV, % (75.5 ± 14.1 vs. 76.5 ± 14.3, p = 0.790) at peak exercise between groups. Median (IQR) of VE/VCO2 nadir [38.0 (37.0-42.0) vs. 32.5 (31.0-39.0), p = 0.005] was significantly higher, and SpO2, % at rest [88.0 (86.0-91.0) vs. 95.0 (94.0-96.0), p < 0.001] and at peak exercise [84.0 (77.0-90.0) vs. 93.0 (92.0-95.0), p < 0.001] were significantly lower in COPD-HA. Conclusions: Despite higher desaturation at rest and during exercise in COPD-HA, there were no differences in VO2 peak between COPD-HA and COPD-LA, suggesting a potential altitude adaptation in those patients chronically exposed to hypoxia.

A new algorithm DEtectS critical Congenital Heart Disease at different altitudes: ANDES-CHD study

BACKGROUND

Neonatal pulse oximetry screening (POS) algorithms for critical congenital heart disease (CCHD) have contributed towards decreasing neonatal mortality but cannot be applied at high altitudes. New POS algorithms at high altitudes are needed.

METHODS

This observational, prospective study included newborns born at different altitudes from 0 to 4380 meters above the sea level in Peru. Healthy newborns underwent neonatal preductal and postductal oximetry, echocardiography and telephonic follow-up up to 12 months of age. Newborns with CCHD underwent preductal and postductal oximetry at the time of telemedicine evaluation while located at the high-altitude hospital where they were born, and their diagnoses were confirmed with echocardiography locally or after arriving to the referral center. Two new algorithms were designed using clinically accepted neonatal oximetry cutoffs or the 5th and 10th percentiles for preductal and postductal oximetry values.

RESULTS

A total of 502 healthy newborns and 15 newborns with CCHD were enrolled. Echocardiography and telephonic follow-up were completed in 227 (45%) and 330 healthy newborns (65%), respectively. The algorithm based on clinically accepted cutoffs had a sensitivity of 92%, specificity of 73% and false positive rate of 27% The algorithm based on the 5th and 10th percentiles had a sensitivity of 80%, specificity of 88% and false positive rate of 12%.

CONCLUSIONS

Two algorithms that detect CCHD at different altitudes had adequate performance but high false positive rates.

Hypoxia Inducible Factor pathway proteins in high-altitude mammals

Humans and other mammals inhabit hypoxic high-altitude locales. In many of these species, genes under positive selection include ones in the Hypoxia Inducible Factor (HIF) pathway. One is PHD2 (EGLN1), which encodes for a key oxygen sensor. Another is HIF2A (EPAS1), which encodes for a PHD2-regulated transcription factor. Recent studies have provided insights into mechanisms for these high-altitude alleles. These studies have (i) shown that selection can occur on nonconserved, unstructured regions of proteins, (ii) revealed that high altitude-associated amino acid substitutions can have differential effects on protein-protein interactions, (iii) provided evidence for convergent evolution by different molecular mechanisms, and (iv) suggested that mutations in different genes can complement one another to produce a set of adaptive phenotypes.

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.

Fetal hypoxia expose caused autophagy in ovary granulosa cells via PI3K/Akt/FoxO1 pathway and mitigated by melatonin subheading

INTRODUCTION

Fetal hypoxia has long-term effects on postnatal reproductive functions and the mitochondrial impairments of ovarian granulosa cells may be one of the causes. Melatonin applied to mitigate mitochondrial dysfunction and autophagy in mammalian cells has been reported. However, the potential mechanisms by which fetal hypoxia damages reproductive function in neonatal female mice and the melatonin effects on this problem remain unclear.

OBJECTIVES

This research aimed to explore the mechanism that fetal hypoxia damages reproductive function in neonatal female mice and attempt to improve the reproductive function by treating with melatonin in vivo and in vitro.

METHODS

We established a fetal hypoxia model and confirmed that fetal hypoxia affects ovarian function by inducing GC excessive autophagy. Transcriptomic analysis, gene interference, cell immunofluorescence, immunohistochemistry and western blot were conducted to explore and verify the underlying mechanisms in mice GCs and KGN cells. Finally, melatonin treatment was executed on hypoxia-treated mice GCs and KGN cells and melatonin injection to fetal-hypoxia-treated mice to determine its effect.

RESULTS

The results of in vitro experiments found that fetal hypoxia led to mitochondrial dysfunction in ovarian GCs causing autophagic cell death. And the PI3K/Akt/FoxO pathway mediated the occurrence of this process by transcriptome analysis of ovarian GCs from normal and fetal hypoxia mice, which was further verified in mice GCs and KGN cells. Additionally, melatonin administration prevented autophagic injuries and mitochondrial impairments in hypoxia-treated mice GCs and KGN cells. Meanwhile, in vivo experiments by melatonin injection ameliorated oxidative stress of ovary in fetal-hypoxia-treated mice and improved their low fertility.

CONCLUSION

Our data found that fetal hypoxia causes ovarian GCs excessive autophagy leading to low fertility in neonatal female mice and mitigated by melatonin. These results provide a potential therapy for hypoxic stress-related reproductive disorders.

Arterial blood analysis of healthy residents in Huamachuco, Peru (3,164 m): a cross-sectional study

Background: Given that arterial blood gas is affected by altitude and ethnicity, establishing reliable reference standards for these values requires analysis of arterial blood at different elevations and locations. Our objective was to measure the arterial blood gases of healthy young volunteers in Huamachuco, Peru, at 3,164 m above sea level. This is likely the first study of arterial blood gas analysis of healthy Northern Peruvians living at high altitude. Methods: Healthy residents of Huamachuco were recruited for this cross-sectional convenience sample study and arterial blood was drawn by standard procedures. People with obesity, diabetes, high levels of physical activity and a history of using selected substances were excluded. The samples were analyzed on-site in less than 15 minutes using a Stat Profile Prime CCS analyzer (Nova Biomedical). Results: Data from 46 participants (17 male, 29 female) were included in the study. The median values for arterial blood pH, oxygen, carbon dioxide, ionized calcium, glucose, lactate, hematocrit, oxygen saturation, and bicarbonate were 7.42, 9.3 kPa (70 mmHg), 4.5 kPa (33.5 mmHg), 1.04 mM, 5.19 mM, 1.8 mM, 50 %, 94 %, and 21.6 mM, respectively. We also found a lower prevalence of diabetes among highlanders compared to the Peruvian population. Conclusions: The results determined here were comparable to other results determined at different altitudes in the Americas, although arterial blood oxygen was slightly higher than predicted. These results indicate that Northern Peruvians have an Andean-style adaptation to high altitude.

The Effectiveness of L-arginine in Clinical Conditions Associated with Hypoxia

The review summarises the data of the last 50 years on the effectiveness of the amino acid L-arginine in therapeutic practice in conditions accompanied by different-origin hypoxia. The aim of this review was to analyse the literature and our research data on the role of nitric oxide in the modulation of individual physiological reactivity to hypoxia. The review considers the possibility of eliminating methodological conflicts in the case of L-arginine, which can be solved by taking into account individual physiological reactivity (or the hypoxia resistance factor). Considerable attention is paid to genetic and epigenetic mechanisms of adaptation to hypoxia and conditions of adaptation in different models. The article presents data on the clinical effectiveness of L-arginine in cardiovascular system diseases (hypertension, atherosclerosis, coronary heart disease, etc.) and stress disorders associated with these diseases. The review presents a generalised analysis of techniques, data on L-arginine use by athletes, and the ambiguous role of NO in the physiology and pathology of hypoxic states shown via nitric oxide synthesis. Data on the protective effects of adaptation in the formation of individual high reactivity in sportsmen are demonstrated. The review demonstrates a favourable effect of supplementation with L-arginine and its application depending on mitochondrial oxidative phosphorylation processes and biochemical indices in groups of individuals with low and high capacity of adaptation to hypoxia. In individuals with high initial anti-hypoxic reserves, these favourable effects are achieved by the blockade of NO-dependent biosynthesis pathways. Therefore, the methodological tasks of physiological experiments and the therapeutic consequences of treatment should include a component depending on the basic level of physiological reactivity.

Time-course effects and mechanisms of hypobaric hypoxia on nervous system in mice

OBJECTIVE

The aim of this study was to investigate the effect of time course on neurological impairment after acute hypobaric hypoxia exposure in mice and clarify the mechanism of acclimatization, so as to provide a suitable mice model and identify potential target against hypobaric hypoxia for further drug research.

METHOD

Male C57BL/6J mice were exposed to hypobaric hypoxia at a simulated altitude of 7000 m for 1, 3, and 7 days (1HH, 3HH and 7HH respectively). The behavior of the mice was evaluated by novel object recognition (NOR) and morris water maze test (MWM), then, the pathological changes of mice brain tissues were observed by H&E and Nissl staining. In addition, RNA sequencing (RNA-Seq) was performed to characterize the transcriptome signatures, and enzyme-linked immunosorbent assay (ELISA), Real-time polymerase chain reaction (RT-PCR), and western blot (WB) were used to verify the mechanisms of neurological impairment induced by hypobaric hypoxia.

RESULT

The hypobaric hypoxia condition resulted in impaired learning and memory, decreased new object cognitive index, and increased escape latency to the hidden platform in mice, with significant changes seen in the 1HH and 3HH groups. Bioinformatic analysis of RNA-seq results of hippocampal tissue showed that 739 differentially expressed genes (DEGs) appeared in the 1HH group, 452 in the 3HH group, and 183 in the 7HH group compared to the control group. There were 60 key genes overlapping in three groups which represented persistent changes and closely related biological functions and regulatory mechanisms in hypobaric hypoxia-induced brain injuries. DEGs enrichment analysis showed that hypobaric hypoxia-induced brain injuries were associated with oxidative stress, inflammatory responses, and synaptic plasticity. ELISA and WB results confirmed that these responses occurred in all hypobaric hypoxic groups while attenuated in the 7HH group. VEGF-A-Notch signaling pathway was enriched by DEGs in hypobaric hypoxia groups and was validated by RT-PCR and WB.

CONCLUSION

The nervous system of mice exposed to hypobaric hypoxia exhibited stress followed by gradual habituation and thus acclimatization over time, which was reflected in the biological mechanism involving inflammation, oxidative stress, and synaptic plasticity, and accompanied by activation of the VEGF-A-Notch pathway.

"What We Know and What We Do Not Know about Evolutionary Genetic Adaptation to High Altitude Hypoxia in Andean Aymaras"

Three well-studied populations living at high altitudes are Tibetans, Andeans (Aymaras and Quechuas), and Ethiopians. Unlike Tibetans and Ethiopians who have similar hemoglobin (Hb) levels as individuals living at sea level, Aymara Hb levels increase when living at higher altitudes. Our previous whole genome study of Aymara people revealed several selected genes that are involved in cardiovascular functions, but their relationship with Hb levels was not elucidated. Here, we studied the frequencies of known evolutionary-selected variants in Tibetan and Aymara populations and their correlation with high Hb levels in Aymara. We genotyped 177 Aymaras at three different altitudes: 400 m (Santa Cruz), 4000 m (La Paz), and 5000 m (Chorolque), and correlated the results with the elevation of residence. Some of the Tibetan-selected variants also exist in Aymaras, but at a lower prevalence. Two of 10 Tibetan selected variants of EPAS1 were found (rs13005507 and rs142764723) and these variants did not correlate with Hb levels. Allele frequencies of 5 Aymara selected SNPs (heterozygous and homozygous) at 4000 m (rs11578671_BRINP3, rs34913965_NOS2, rs12448902_SH2B1, rs10744822_TBX5, and rs487105_PYGM) were higher compared to Europeans. The allelic frequencies of rs11578671_BRINP3, rs34913965_NOS2, and rs10744822_SH2B1 were significantly higher for Aymaras living at 5000 m than those at 400 m elevation. Variant rs11578671, close to the BRINP3 coding region, correlated with Hb levels in females. Variant rs34913965 (NOS2) correlated with leukocyte counts. Variants rs12448902 (SH2B1) and rs34913965 (NOS2) associated with higher platelet levels. The correlation of these SNPs with blood cell counts demonstrates that the selected genetic variants in Aymara influence hematopoiesis and cardiovascular effects.

Genotyped indigenous Kiwcha adults at high altitude are lighter and shorter than their low altitude counterparts

Background

Anthropometric measures have been classically used to understand the impact of environmental factors on the living conditions of individuals and populations. Most reference studies on development and growth in which anthropometric measures were used were carried out in populations that are located at sea level, but there are few studies carried out in high altitude populations.

Objective

The objective of this study was to evaluate the anthropometric and body composition in autochthonous Kiwcha permanently living at low and high altitudes.

Methodology

A cross-sectional study of anthropometric and body composition between genetically matched lowland Kiwcha from Limoncocha (n = 117), 230 m in the Amazonian basin, and high-altitude Kiwcha from Oyacachi (n = 95), 3800 m in Andean highlands. Student’s t-test was used to analyze the differences between continuous variables, and the chi-square test was performed to check the association or independence of categorical variables. Fisher’s exact test or Spearman’s test was used when the variable had evident asymmetries with histograms prior to the selection of the test.

Results

This study shows that high altitude men are shorter than their counterparts who live at low altitude, with p = 0.019. About body muscle percentage, women at high altitudes have less body muscle percentage (− 24.8%). In comparison, men at high altitudes have significantly more muscle body mass percentage (+ 13.5%) than their lowland counterparts. Body fat percentage was lower among low altitude women (− 15.5%), and no differences were found among men.

Conclusions

This is the first study to be performed in two genotyped controlled matching populations located at different altitudes to our best knowledge. The anthropometric differences vary according to sex, demonstrating that high altitude populations are, in general, lighter and shorter than their low altitude controls. Men at high altitude have more muscled bodies compared to their lowland counterparts, but their body age was older than their actual age.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40101-022-00280-6.

Effect of hypobaric hypoxia on hematological parameters related to oxygen transport, blood volume and oxygen consumption in adolescent endurance-training athletes

Objective

To analyze the effect of altitude on hematological and cardiorespiratory variables in adolescent athletes participating in aerobic disciplines.

Methods

21 females and 89 males participated in the study. All were adolescent elite athletes engaged in endurance sports (skating, running and cycling) belonging to two groups: permanent residents in either low altitude (LA, 966 m) or moderate altitude (MA, 2640 m). Hematocrit (Hct), hemoglobin concentration ([Hb]), total hemoglobin mass (Hbt), blood, plasma and erythrocyte volumes (BV, PV and EV), VO₂peak and other cardiorespiratory parameters were evaluated.

Results

Sex differences were evident both in LA and HA skating practitioners, the males having higher significant values than the females in oxygen transport-related hematological parameters and VO₂peak. The effect of altitude residence was also observed in Hct, [Hb], Hbt and EV with increased (14%–18%) values in the hematological parameters and higher EV (5%–24%). These results matched the significantly higher values of VO₂peak measured in MA residents. However, BV and PV did not show differences between LA and MA residents in any case. Sports discipline influenced neither the hematological variables nor most of the cardiorespiratory parameters.

Conclusions

LA and MA adolescent skaters showed sex differences in hematological variables. Endurance-trained male adolescent residents at MA had an increased erythropoietic response and a higher VO₂peak compared to their counterparts residing and training at LA. These responses are similar in the three aerobic sports studied, indicating that the variables described are highly sensitive to hypoxia irrespective of the sports discipline.

The impact of COVID-19 on populations living at high altitude: Role of hypoxia-inducible factors (HIFs) signaling pathway in SARS-CoV-2 infection and replication

Cases of coronavirus disease 2019 (COVID-19) have been reported worldwide. However, one epidemiological report has claimed a lower incidence of the disease in people living at high altitude (&gt;2,500 m), proposing the hypothesis that adaptation to hypoxia may prove to be advantageous with respect to SARS-CoV-2 infection. This publication was initially greeted with skepticism, because social, genetic, or environmental parametric variables could underlie a difference in susceptibility to the virus for people living in chronic hypobaric hypoxia atmospheres. Moreover, in some patients positive for SARS-CoV-2, early post-infection ‘happy hypoxia” requires immediate ventilation, since it is associated with poor clinical outcome. If, however, we accept to consider the hypothesis according to which the adaptation to hypoxia may prove to be advantageous with respect to SARS-CoV-2 infection, identification of the molecular rational behind it is needed. Among several possibilities, HIF-1 regulation appears to be a molecular hub from which different signaling pathways linking hypoxia and COVID-19 are controlled. Interestingly, HIF-1α was reported to inhibit the infection of lung cells by SARS-CoV-2 by reducing ACE2 viral receptor expression. Moreover, an association of the rs11549465 variant of HIF-1α with COVID-19 susceptibility was recently discovered. Here, we review the evidence for a link between HIF-1α, ACE2 and AT1R expression, and the incidence/severity of COVID-19. We highlight the central role played by the HIF-1α signaling pathway in the pathophysiology of COVID-19.

Fertility Impairment after Trekking at High Altitude: A Proof of Mechanisms on Redox and Metabolic Seminal Changes

Many authors described negative but reversible effects of high-altitude hypoxic exposure on animal and human fertility in terms of sperm concentration, function, and biochemical alterations. The aim of this study was to evaluate the acute and chronic effects of high-altitude exposure on classical sperm parameters, redox status, and membrane composition in a group of travellers. Five healthy Italian males, all lowlanders not accustomed to the altitude, were evaluated after 19 days-trekking through low, moderate, and high altitudes in the Himalayas. Sperm samples were collected before (Pre), 10 days after (Post), and 70 days after the end of the expedition (Follow-up). Sperm concentration, cholesterol and oxysterol membrane content, and redox status were measured. Hypoxic trek led to a significant reduction in sperm concentration (p < 0.001, η2p = 0.91), with a reduction from Pre to Post (71.33 ± 38.81 to 60.65 ± 34.63 × 106/mL) and a further reduction at Follow-up (to 37.13 ± 39.17 × 106/mL). The seminal volume was significantly affected by the hypoxic trek (p = 0.001, η2p = 0.75) with a significant reduction from Pre to Post (2.86 ± 0.75 to 1.68 ± 0.49 mL) and with partial recovery at Follow-up (to 2.46 ± 0.45 mL). Moreover, subjects had an increase in ROS production (+86%), and a decrease in antioxidant capacity (−37%) in the Post period with partial recovery at Follow-up. These results integrated the hormonal response on thyroid function, hypothalamus−pituitary−gonadal axis, and the prolactin/cortisol pathways previously reported. An uncontrolled ROS production, rather than a compromised antioxidant activity, was likely the cause of impaired sperm quality. The reduction in fertility status observed in this study may lie in an evolutionary Darwinian explanation, i.e., limiting reproduction due to the “adaptive disadvantage” offered by the combined stressors of high-altitude hypoxia and daily physical exercise.

Effect of High Altitude on the Survival of COVID-19 Patients in Intensive Care Unit: A Cohort Study

Purpose: The effect of high altitude ( ≥ 1500 m) and its potential association with mortality by COVID-19 remains controversial. We assessed the effect of high altitude on the survival/discharge of COVID-19 patients requiring intensive care unit (ICU) admission for mechanical ventilation compared to individuals treated at sea level. Methods: A retrospective cohort multi-center study of consecutive adults patients with a positive RT-PCR test for COVID-19 who were mechanically ventilated between March and November 2020. Data were collected from two sea-level hospitals and four high-altitude hospitals in Ecuador. The primary outcome was ICU and hospital survival/discharge. Survival analysis was conducted using semi-parametric Cox proportional hazards models. Results: Of the study population (n = 670), 35.2% were female with a mean age of 58.3 ± 12.6 years. On admission, high-altitude patients were more likely to be younger (57.2 vs. 60.5 years old), presented with less comorbidities such as hypertension (25.9% vs. 54.9% with p-value <.001) and diabetes mellitus (20.5% vs. 37.2% with p-value <.001), less probability of having a capillary refill time > 3 sec (13.7% vs. 30.1%, p-value <.001), and less severity-of-illness condition (APACHE II score, 17.5 ± 8.1 vs. 20 ± 8.2, p < .01). After adjusting for key confounders high altitude is associated with significant higher probabilities of ICU survival/discharge (HR: 1.74 [95% CI: 1.46-2.08]) and hospital survival/discharge (HR: 1.35 [95% CI: 1.18-1.55]) than patients treated at sea level. Conclusions: Patients treated at high altitude at any time point during the study period were 74% more likely to experience ICU survival/discharge and 35% more likely to experience hospital survival/discharge than to the sea-level group. Possible reasons for these findings are genetic and physiological adaptations due to exposure to chronic hypoxia.

Feature selection reveal peripheral blood parameter's changes between COVID-19 infections patients from Brazil and Ecuador

The investigation of conventional complete blood-count (CBC) data for classifying the SARS-CoV-2 infection status became a topic of interest, particularly as a complementary laboratory tool in developing and third-world countries that financially struggled to test their population. Although hematological parameters in COVID-19-affected individuals from Asian and USA populations are available, there are no descriptions of comparative analyses of CBC findings between COVID-19 positive and negative cases from Latin American countries. In this sense, machine learning techniques have been employed to examine CBC data and aid in screening patients suspected of SARS-CoV-2 infection. In this work, we used machine learning to compare CBC data between two highly genetically distinguished Latin American countries: Brazil and Ecuador. We notice a clear distribution pattern of positive and negative cases between the two countries. Interestingly, almost all red blood cell count parameters were divergent. For males, neutrophils and lymphocytes are distinct between Brazil and Ecuador, while eosinophils are distinguished for females. Finally, neutrophils, lymphocytes, and monocytes displayed a particular distribution for both genders. Therefore, our findings demonstrate that the same set of CBC features relevant to one population is unlikely to apply to another. This is the first study to compare CBC data from two genetically distinct Latin American countries.

Conserved and convergent mechanisms underlying performance-life-history trade-offs

Phenotypic trade-offs are inevitable in nature, but the mechanisms driving them are poorly understood. Movement and oxygen are essential to all animals, and as such, the common ancestor to all living animals passed on mechanisms to acquire oxygen and contract muscle, sometimes at the expense of other activities or expression of traits. Nevertheless, convergent pathways have also evolved to deal with critical trade-offs that are necessary to survive ubiquitous environmental challenges. We discuss how whole-animal performance traits, such as locomotion, are important to fitness, yet costly, resulting in trade-offs with other aspects of the phenotype via specific conserved and convergent mechanistic pathways across all animals. Specifically, we discuss conserved pathways involved in muscle structure and signaling, insulin/insulin-like signaling, sirtuins, mitochondria and hypoxia-inducible factors, as well as convergent pathways involved in energy regulation, development, reproductive investment and energy storage. The details of these mechanisms are only known from a few model systems, and more comparative studies are needed. We make two main recommendations as a framework for future studies of animal form and function. First, studies of performance should consider the broader life-history context of the organism, and vice versa, as performance expression can require a large portion of acquired resources. Second, studies of life histories or mechanistic pathways that measure performance should do so in meaningful and standardized ways. Understanding proximate mechanisms of phenotypic trade-offs will not only better explain the phenotypes of the organisms we study, but also allow predictions about phenotypic variation at the evolutionary scale.

Optimism and Health Self-Perception-Related Differences in Indigenous Kiwchas of Ecuador at Low and High Altitude: A Cross-Sectional Analysis

Ortiz-Prado, Esteban, Katherine Simbaña-Rivera, Diego Duta, Israel Ochoa, Juan S. Izquierdo-Condoy, Eduardo Vasconez, Kathia Carrasco, Manuel Calvopiña, Ginés Viscor, and Clara Paz. Optimism and health self-perception-related differences in indigenous Kiwchas of Ecuador at low and high altitude: a cross-sectional analysis. High Alt Med Biol 00:000-000, 2021. Background: Living at high altitude causes adaptive responses at every physiological and molecular level within the human body. Emotional and psychological short- or long-term consequences, including mood changes, higher mental overload, and depression prevalence, as well as increased risk to commit suicide have been reported among highlanders. The objective of this report is to explore the differences in self-reported dispositional optimism and health perception among sex-, age-, and genotype-controlled indigenous Kiwcha natives living at two different altitudes. Methods: A cross-sectional analysis of the comparison of means of subscales and summary scores of the 36-item short-form health survey (SF-36) self-reported questionnaire and the Life Orientation Test-Revised was conducted among 219 adults Kiwchas living at low (230 m) and high altitude (3,800 m) in Ecuador. Results: High-altitude dwellers presented lower scores in all the studied dimensions of SF-36 and the total score. Differences were found for the role limitation sphere due to vitality (p = 0.005), mental health (p = 0.002), and social functioning (p = 0.005). In all the cases, participants living at low altitudes scored higher than those living at high altitudes. Lowland women were more optimistic than their high-altitude counterparts. Conclusions: We observe that populations located at high altitudes have more unfavorable self-reported health states. Although our results depict the existence of significant differences in the health status of indigenous peoples living at different altitudes, further studies are needed to explain in depth the sociodemographic and/or environmental factors that might underlie these differences.

Socioeconomic impacts on Andean adolescents’ growth

Background/Objectives

We evaluated potential socioeconomic contributors to variation in Andean adolescents’ growth between households within a peri-urban community undergoing rapid demographic and economic change, between different community types (rural, peri-urban, urban) and over time. Because growth monitoring is widely used for assessing community needs and progress, we compared the prevalences of stunting, underweight, and overweight estimated by three different growth references.

Methods

Anthropometrics of 101 El Alto, Bolivia, adolescents (Alteños), 11.0–14.9 years old in 2003, were compared between households (economic status assessed by parental occupations); to one urban and two rural samples collected in 1983/1998/1977, respectively; and to the WHO growth reference, a representative sample of Bolivian children (MESA), and a region-wide sample of high-altitude Peruvian children (Puno).

Results

Female Alteños’ growth was positively associated with household and maternal income indices. Alteños’ height averaged ∼0.8SD/∼0.6SD/∼2SDs greater than adolescents’ height in urban and rural communities measured in 1983/1998/1977, respectively. Overweight prevalence was comparable to the WHO, and lower than MESA and Puno, references. Stunting was 8.5/2.5/0.5 times WHO/MESA/Puno samples, respectively.

Conclusions/Implications

Both peri-urban conditions and temporal trends contributed to gains in Alteños’ growth. Rural out-migration can alleviate migrants’ poverty, partly because of more diverse economic options in urbanized communities, especially for women. Nonetheless, Alteños averaged below WHO and MESA height and weight medians. Evolved biological adaptations to environmental challenges, and the consequent variability in growth trajectories, favor using multiple growth references. Growth monitoring should be informed by community- and household-level studies to detect and understand local factors causing or alleviating health disparities.

Influence of motor activity and polymorphism I/D of ACE on the affinity of oxygen for hemoglobin

The influence of rs4646994 polymorphism of the ACE gene on the affinity of oxygen for hemoglobin among young men with different levels of physical activity has been studied. 245 young men aged 20-22 years were included in the study. All young men were divided into three groups depending on their motor activity: low (LMA), average (AMA) and high (HMA). SatO2, pO2, pCO2, p50 and HbO2 were analyzed in capillary blood of all examined young men. It was found out that I/I genotype of the ACE gene is associated with a decrease in the affinity of oxygen for hemoglobin both in LMA (p=0.022) and in HMA (p=0.000096). The intensification of physical activity among I/D and D/D genotypes is accompanied by an increase in the level of hemoglobin oxygenation in blood, while the I/I genotype with part of HbO2 does not change depending on motor activity. These features can be explained by the shift of the oxygen dissociation curve to the left among young men with the *D allele genotype, with an increase in physical activity. On the contrary, the I/I genotype of the ACE gene have efficient oxygen extraction to tissues, regardless of the level of motor activity compared to the D/D genotype.

High Altitude Pregnancies and Vascular Dysfunction: Observations From Latin American Studies

An estimated human population of 170 million inhabit at high-altitude (HA, above 2,500 m). The potential pathological effects of HA hypobaric hypoxia during gestation have been the focus of several researchers around the world. The studies based on the Himalayan and Central/South American mountains are particularly interesting as these areas account for nearly 70% of the HA world population. At present, studies in human and animal models revealed important alterations in fetal development and growth at HA. Moreover, vascular responses to chronic hypobaria in the pregnant mother and her fetus may induce marked cardiovascular impairments during pregnancy or in the neonatal period. In addition, recent studies have shown potential long-lasting postnatal effects that may increase cardiovascular risk in individuals gestated under chronic hypobaria. Hence, the maternal and fetal adaptive responses to hypoxia, influenced by HA ancestry, are vital for a better developmental and cardiovascular outcome of the offspring. This mini-review exposes and discusses the main determinants of vascular dysfunction due to developmental hypoxia at HA, such as the Andean Mountains, at the maternal and fetal/neonatal levels. Although significant advances have been made from Latin American studies, this area still needs further investigations to reveal the mechanisms involved in vascular dysfunction, to estimate complications of pregnancy and postnatal life adequately, and most importantly, to determine potential treatments to prevent or treat the pathological effects of being developed under chronic hypobaric hypoxia.

Regional Features and Spatial Distribution of Fifty-Eight Ethnic Groups in Southwest China

Eco-environmental variability was the basis of ethnic diversity with a persistent influence on the regional development. The unique geographic conditions and multi-ethnic characteristics in southwest China were valuable for exploring sustainable development of ethnic regions. In this study, the regional features of distribution areas of ethnic groups in southwest China were analysed, and it was found that average altitude, slope, water coverage and water form ratio of each ethnic group differed apparently. Additionally, regional features of southern minorities were relatively stable, while those of northern minorities changed evidently from 1990 to 2010. Furthermore, taking the spatial coordinates and regional features as parameters, fifty-eight ethnic groups were clustered into six categories via spatial cluster analysis. Moreover, based on the county-level population data, the ethnic similarities in southwest China were identified by correlation analysis, and the results were in accordance with those of spatial cluster analysis but more detailed. In addition, the eco-environmental adaptability of various ethnic groups was discussed in terms of living and production as well as regional sustainable development. This research was of referential meaning for population settlement, natural resources utilization and biodiversity conservation in multi-ethnic regions.

Influence of geographic conditions on body length of male newborns in Kyrgyzstan

Newborn length has been reported by many researchers to be reduced at high altitudes. However, many of these studies lacked adequate control of the ethnic group which may be confounding the altitude differences. In addition, few studies have examined the sources of variation in birth weight at high altitudes that may be related to ethnic group adaptation to the stresses of this hypoxic environment. In our study, we tested the hypotheses that the effect of altitude differences in newborn length depends on ethnic variation. Samples of 3359 healthy male newborns from different areas in Kyrgyzstan between the years 2003 and 2011 were analyzed for altitude and ethnic variation on male newborn length. Our results indicate significant decrease in male newborn length as a latitude increase. It is concluded that ethnic group difference in pregnancy outcome reflects a better state of adaptation to high altitude in this healthy indigenous population and that long-term genetic selection may be the most plausible explanation for these ethnic differences.

Evaluation of Buccal Bone Wall Thickness of Anterosuperior Teeth and Nasopalatine Duct Morphology in Cone Beam Computed Tomography of Patients Living at Different Altitudes: A Two-Year Retrospective Study

AIM

To evaluate the buccal bone wall thickness of anterosuperior teeth and the dimension and morphology of the nasopalatine duct in cone beam computed tomography (CBCT) of patients treated in two cities at different altitudes.

MATERIALS AND METHODS

In this retrospective analytical study, 79 CBCT scans were selected from a total of 347 in Juliaca, Peru (3824 m a.s.l.) and 171 CBCT scans were selected from a total of 622 in Lima, Peru (154 m a.s.l.). The buccal bone wall thickness of anterosuperior teeth was measured at 1 mm, 3 mm, and 5 mm from the alveolar crest. For the nasopalatine duct, its length and diameter were measured, and its anatomical shape was determined in coronal view. Descriptive statistical data such as mean and standard deviation were used, and Mann-Whitney U test was used for bivariate analysis.

RESULTS

When comparing the CBCT scans from both cities, significant differences were observed in buccal bone wall thickness at 3 mm and 5 mm from the alveolar crest (P < 0.01 and P < 0.01, respectively); for men, at 1 mm and 3 mm (P = 0.04 and P = 0.04); for the age group from 33 to 47 years, at 3 mm and 5 mm (P < 0.01 and P < 0.01); and for the age group from 48 to 77 years, at 1 mm (P = 0.02). Regarding the nasopalatine duct, significant differences were observed in women in relation to length and nasal opening diameter (P < 0.01 and P < 0.01) and for men, in length (P < 0.01); for the age group from 18 to 32 years, in all three levels (P < 0.01); for the age group from 33 to 47 years, in length and diameter of the oral opening (P < 0.01 and P < 0.01); and for the age group from 48 to 77 years, in length and diameter of the nasal opening (P < 0.01 and P < 0.01). The most frequent nasopalatine duct shape was a single canal with more than 66% of cases, according to sex and age group.

CONCLUSION

Patients living at different altitudes presented significant differences in buccal bone wall thickness according to sex and age; however, there were no differences related to dental inclination. Significant differences were found in the length and diameter of the nasopalatine duct at the nasal opening. In addition, the most frequent shape of the nasopalatine duct was the simple canal.

Hematological Parameters, Lipid Profile, and Cardiovascular Risk Analysis Among Genotype-Controlled Indigenous Kiwcha Men and Women Living at Low and High Altitudes

Introduction: Human adaptation to high altitude is due to characteristic adjustments at every physiological level. Differences in lipid profile and cardiovascular risk factors in altitude dwellers have been previously explored. Nevertheless, there are no reports available on genotype-controlled matches among different altitude-adapted indigenous populations.

Objective: To explore the possible differences in plasma lipid profile and cardiovascular risk among autochthonous Kiwcha people inhabitants of low and high-altitude locations.

Methodology: A cross-sectional analysis of plasmatic lipid profiles and cardiovascular risk factors in lowland Kiwchas from Limoncocha (230 m) and high-altitude Kiwchas from Oyacachi (3,800 m).

Results: In the low altitude group, 66% were women (n = 78) and 34% (n = 40) were men, whereas in the high altitude group, 59% (n = 56) were women and 41% (n = 41%) were men. We found the proportion of overweight and obese individuals to be higher among low altitude dwellers (p < 0.05). Red blood cells (RBCs), hemoglobin concentration, and SpO₂% were higher among high altitude dwellers and the erythrocyte size was found to be smaller at high altitude. The group located at low altitude also showed lower levels of plasma cholesterol, low-density lipoprotein (LDL), and high-density lipoprotein (HDL), but most of these differences are not influenced by gender or elevation.

Conclusions: Living at an altitude elicits well-known adaptive physiological changes such as erythrocyte count, hemoglobin concentration, hematocrit level, and serum glucose level. We also report clinical differences in the plasma lipid profile, with higher levels of cholesterol, HDL, and LDL in inhabitants of the Andes Mountain vs. their Amazonian basin peers. Despite this, we did not find significant differences in cardiovascular risk.

A sex-specific evolutionary interaction between ADCY9 and CETP

Pharmacogenomic studies have revealed associations between rs1967309 in the adenylyl cyclase type 9 (ADCY9) gene and clinical responses to the cholesteryl ester transfer protein (CETP) modulator dalcetrapib, however, the mechanism behind this interaction is still unknown. Here, we characterized selective signals at the locus associated with the pharmacogenomic response in human populations and we show that rs1967309 region exhibits signatures of positive selection in several human populations. Furthermore, we identified a variant in CETP, rs158477, which is in long-range linkage disequilibrium with rs1967309 in the Peruvian population. The signal is mainly seen in males, a sex-specific result that is replicated in the LIMAA cohort of over 3400 Peruvians. Analyses of RNA-seq data further suggest an epistatic interaction on CETP expression levels between the two SNPs in multiple tissues, which also differs between males and females. We also detected interaction effects of the two SNPs with sex on cardiovascular phenotypes in the UK Biobank, in line with the sex-specific genotype associations found in Peruvians at these loci. We propose that ADCY9 and CETP coevolved during recent human evolution due to sex-specific selection, which points toward a biological link between dalcetrapib’s pharmacogene ADCY9 and its therapeutic target CETP.

Methamphetamine exacerbates pathophysiology of traumatic brain injury at high altitude. Neuroprotective effects of nanodelivery of a potent antioxidant compound H-290/51

Military personnel are often exposed to high altitude (HA, ca. 4500-5000m) for combat operations associated with neurological dysfunctions. HA is a severe stressful situation and people frequently use methamphetamine (METH) or other psychostimulants to cope stress. Since military personnel are prone to different kinds of traumatic brain injury (TBI), in this review we discuss possible effects of METH on concussive head injury (CHI) at HA based on our own observations. METH exposure at HA exacerbates pathophysiology of CHI as compared to normobaric laboratory environment comparable to sea level. Increased blood-brain barrier (BBB) breakdown, edema formation and reductions in the cerebral blood flow (CBF) following CHI were exacerbated by METH intoxication at HA. Damage to cerebral microvasculature and expression of beta catenin was also exacerbated following CHI in METH treated group at HA. TiO2-nanowired delivery of H-290/51 (150mg/kg, i.p.), a potent chain-breaking antioxidant significantly enhanced CBF and reduced BBB breakdown, edema formation, beta catenin expression and brain pathology in METH exposed rats after CHI at HA. These observations are the first to point out that METH exposure in CHI exacerbated brain pathology at HA and this appears to be related with greater production of oxidative stress induced brain pathology, not reported earlier.

Exposomes to Exosomes: Exosomes as Tools to Study Epigenetic Adaptive Mechanisms in High-Altitude Humans

Humans on earth inhabit a wide range of environmental conditions and some environments are more challenging for human survival than others. However, many living beings, including humans, have developed adaptive mechanisms to live in such inhospitable, harsh environments. Among different difficult environments, high-altitude living is especially demanding because of diminished partial pressure of oxygen and resulting chronic hypobaric hypoxia. This results in poor blood oxygenation and reduces aerobic oxidative respiration in the mitochondria, leading to increased reactive oxygen species generation and activation of hypoxia-inducible gene expression. Genetic mechanisms in the adaptation to high altitude is well-studied, but there are only limited studies regarding the role of epigenetic mechanisms. The purpose of this review is to understand the epigenetic mechanisms behind high-altitude adaptive and maladaptive phenotypes. Hypobaric hypoxia is a form of cellular hypoxia, which is similar to the one suffered by critically-ill hypoxemia patients. Thus, understanding the adaptive epigenetic signals operating in in high-altitude adjusted indigenous populations may help in therapeutically modulating signaling pathways in hypoxemia patients by copying the most successful epigenotype. In addition, we have summarized the current information about exosomes in hypoxia research and prospects to use them as diagnostic tools to study the epigenome of high-altitude adapted healthy or maladapted individuals.

Seeding drug discovery: Telomeric tankyrase as a pharmacological target for the pathophysiology of high-altitude hypoxia

Cellular exposure to extreme environments leads to the expression of multiple proteins that participate in pathophysiological manifestations. Hypobaric hypoxia at high altitude (HA) generates reactive oxygen species (ROS) that can damage telomeres. Tankyrase (TNKS) belongs to multiple telomeric protein complexes and is actively involved in DNA damage repair. Although published research on TNKS indicates its possible role in cancer and other hypoxic diseases, its role in HA sicknesses remains elusive. Understanding the roles of telomeres, telomerase, and TNKS could ameliorate physiological issues experienced at HA. In addition, telomeric TNKS could be a potential biomarker in hypoxia-induced sicknesses or acclimatization. Thus, a new research avenue on TNKS linked to HA sickness might lead to the discovery of drugs for hypobaric hypoxia.

Is a higher altitude associated with shorter survival among at-risk neonates?

INTRODUCTION

We hypothesize that high altitudes could have an adverse effect on neonatal health outcomes, especially among at-risk neonates. The current study aims to assess the association between higher altitudes on survival time among at-risk neonates.

METHODS

Retrospective survival analysis. Setting: Ecuadorian neonates who died at ≤28 days of life. Patients: We analyzed the nationwide dataset of neonatal deaths from the Surveillance System of Neonatal Mortality of the Ministry of Public Health of Ecuador, registered from 126 public and private health care facilities, between January 2014 to September 2017. Main outcome measures: We retrospectively reviewed 3016 patients. We performed a survival analysis by setting the survival time in days as the primary outcome and fixed and mixed-effects Cox proportional hazards models to estimate hazard ratios (HR) for each altitude stratum of each one of the health care facilities in which those neonates were attended, adjusting by individual variables (i.e., birth weight, gestational age at birth, Apgar scale at 5 minutes, and comorbidities); and contextual variables (i.e., administrative planning areas, type of health care facility, and level of care).

RESULTS

Altitudes of health care facilities ranging from 80 to <2500 m, 2500 to <2750m, and ≥2750 m were associated respectively with 20% (95% CI: 1% to 44%), 32% (95% CI:<1% to 79%) and 37% (95% CI: 8% to 75%) increased HR; compared with altitudes at <80 m.

CONCLUSION

Higher altitudes are independently associated with shorter survival time, as measured by days among at-risk neonates. Altitude should be considered when assessing the risk of having negative health outcomes during neonatal period.

Enhanced Placental Mitochondrial Respiration in Tibetan Women at High Altitude

Living at high altitudes is extremely challenging as it entails exposure to hypoxia, low temperatures, and high levels of UV radiation. However, the Tibetan population has adapted to such conditions on both a physiological and genetic level over 30,000–40,000 years. It has long been speculated that fetal growth restriction is caused by abnormal placental development. We previously demonstrated that placentas from high-altitude Tibetans were protected from oxidative stress induced by labor compared to those of European descent. However, little is known about how placental mitochondria change during high-altitude adaptation. In this study, we aimed to uncover the mechanism of such adaptation by studying the respiratory function of the placental mitochondria of high-altitude Tibetans, lower-altitude Tibetans, and lower-altitude Chinese Han. We discovered that mitochondrial respiration was greater in high-altitude than in lower-altitude Tibetans in terms of OXPHOS via complexes I and I+II, ETS_max capacity, and non-phosphorylating respiration, whereas non-ETS respiration, LEAK/ETS, and OXPHOS via complex IV did not differ. Respiration in lower-altitude Tibetans and Han was similar for all tested respiratory states. Placentas from high-altitude Tibetan women were protected from acute ischemic/hypoxic insult induced by labor, and increased mitochondrial respiration may represent an acute response that induces mitochondrial adaptations.

Newborn anthropometry, maternal capital, and altitude in the highland population from the province of Jujuy, Argentina

OBJECTIVE

To analyze variability in newborn (NB) anthropometry among Jujenean NBs as a function of geographic altitude (500 m to ≈4000 masl), maternal anthropometry and other maternal characteristics within the maternal capital framework.

MATERIALS AND METHODS

Data obtained from 41,371 mother/child pairs recorded in the Jujuy Perinatal Information System (SIP) between 2009 and 2014, including: NB and maternal weight, length/height and BMI; gestational age (corrected); maternal age, educational level, nutritional status, and marital status; birth interval; and planned pregnancy. Based on the declared place of residence, the prevalence of unsatisfied basic needs (% UBN) was determined and the data was split into two altitudinal groups: highlands (HL, >2500 masl) and lowlands (LL, <2500 masl). ANOVA, Chi-squared and Pearson tests were applied as needed. Statistical associations between the response variables-NB weight, length and BMI-and maternal and environmental variables were tested using a Generalized Additive Mixed Model (GAMM).

RESULTS

All NB and maternal anthropometric variables were lower in HL compared to LL; they also presented negative correlations with altitude, except NB length. Apart from gestational age and birth interval, HL and LL presented statistically significant differences in all study variables. GAMM results showed that maternal anthropometry was the main influence on NB weight and length.

DISCUSSION

Of all the maternal capital features examined, only maternal anthropometric variables were found to protect offspring against the negative impact of HL environments.

Perinatal Hypoxemia and Oxygen Sensing

The development of the control of breathing begins in utero and continues postnatally. Fetal breathing movements are needed for establishing connectivity between the lungs and central mechanisms controlling breathing. Maturation of the control of breathing, including the increase of hypoxia chemosensitivity, continues postnatally. Insufficient oxygenation, or hypoxia, is a major stressor that can manifest for different reasons in the fetus and neonate. Though the fetus and neonate have different hypoxia sensing mechanisms and respond differently to acute hypoxia, both responses prevent deviations to respiratory and other developmental processes. Intermittent and chronic hypoxia pose much greater threats to the normal developmental respiratory processes. Gestational intermittent hypoxia, due to maternal sleep-disordered breathing and sleep apnea, increases eupneic breathing and decreases the hypoxic ventilatory response associated with impaired gasping and autoresuscitation postnatally. Chronic fetal hypoxia, due to biologic or environmental (i.e. high-altitude) factors, is implicated in fetal growth restriction and preterm birth causing a decrease in the postnatal hypoxic ventilatory responses with increases in irregular eupneic breathing. Mechanisms driving these changes include delayed chemoreceptor development, catecholaminergic activity, abnormal myelination, increased astrocyte proliferation in the dorsal respiratory group, among others. Long-term high-altitude residents demonstrate favorable adaptations to chronic hypoxia as do their offspring. Neonatal intermittent hypoxia is common among preterm infants due to immature respiratory systems and thus, display a reduced drive to breathe and apneas due to insufficient hypoxic sensitivity. However, ongoing intermittent hypoxia can enhance hypoxic sensitivity causing ventilatory overshoots followed by apnea; the number of apneas is positively correlated with degree of hypoxic sensitivity in preterm infants. Chronic neonatal hypoxia may arise from fetal complications like maternal smoking or from postnatal cardiovascular problems, causing blunting of the hypoxic ventilatory responses throughout at least adolescence due to attenuation of carotid body fibers responses to hypoxia with potential roles of brainstem serotonin, microglia, and inflammation, though these effects depend on the age in which chronic hypoxia initiates. Fetal and neonatal intermittent and chronic hypoxia are implicated in preterm birth and complicate the respiratory system through their direct effects on hypoxia sensing mechanisms and interruptions to the normal developmental processes. Thus, precise regulation of oxygen homeostasis is crucial for normal development of the respiratory control network. © 2021 American Physiological Society. Compr Physiol 11:1653-1677, 2021.

High altitude and cancer: An old controversy

Ecological studies have found that individuals that live at high altitude regions and in places where ultraviolet radiation is maximal, have lower rates of different types of cancer. However, there is evidence that in these same regions, genetic mutations that are prooncogenic, develop, as they are needed to increase human adaptability to hypoxic environments. Debate has arisen between researchers who consider high altitude environments as suitable for human longevity because of its protective effects against malignancies, and scientists that have reported an increased incidence of different type of cancers in these same regions. Evidence is presented that altitude is related to the development of genetic alterations in micro RNAs, p53 protein, lymphocyte activity, decrease in Fas Ligand and other proapoptotic molecules, as well as increase in prometastatic VGEF an HIF. Notwithstanding, higher vitamin D and ultraviolet B levels, and a better metabolic profile, taken together with lower pollution levels hves been related to lower incidence and mortality rates from malignancies in a series of epidemiological studies.

The correlation of altitude with gingival status among adolescents in western China: a cross-sectional study

Periodontal disease is common in Chinese adolescents. There is little information about the effect of different altitudes on gingival health. This study aimed to investigate the gingival status at different altitudes and to identify relative factors that affect adolescents' gingival status. A total of 1033 adolescents aged 12-14 years were included in this cross-sectional study in Ganzi (plateau, 1400 m, 2560 m, 3300 m) and Suining (plain, 300 m). Gingival status was assessed by the presence of gingival bleeding on probing (BOP) and dental calculus (DC). Demographic variables, socioeconomic status, dairy habits and oral health-related knowledge, attitudes and behaviors were obtained via questionnaire. Univariate and multivariate binary logistic regression analyses were performed to identify potential relative factors. A total of 64.09% and 77.15% of adolescents had BOP and DC, respectively. The prevalence rates of BOP and DC were higher in the plateau than the plain (P < 0.05). After adjusting for all other factors and interaction terms, residence altitudes of 2560 m [300 m as reference: P < 0.001, odds ratio (OR) = 4.072] and 3300 m (300 m as reference: P = 0.002, OR = 4.053) were significant relative factors of BOP, and an altitude of 2560 m (300 m as reference: P = 0.001, OR = 3.866, 1400 m as reference: P = 0.001, OR = 3.944) was an important relative factor of DC. Gingival bleeding and calculus deposits were common at different altitudes. High altitude was a significant relative factor of gingival bleeding and calculus deposits.

High-altitude Illnesses and Air Travel: Pediatric Considerations

Healthy children may present acute mountain sickness (AMS) within a few hours after arrival at high altitudes. In few cases, serious complications may occur, including high-altitude pulmonary edema and rarely high-altitude cerebral edema. Those with preexisting conditions especially involving hypoxia and pulmonary hypertension shall not risk travelling to high altitudes. Newborn from low altitude mothers may have prolonged time to complete postnatal adaptation. The number of children and adolescents traveling on commercial aircrafts is growing, and this poses a need for their treating physicians to be aware of the potential risks of hypoxia while air traveling.

[Adaption to chronic hypoxaemia by populations living at high altitude]

Permanent life at high altitude induces important physiological stresses linked to the exposure to chronic hypoxia. Various strategies have been adopted by diverse populations living in the Andes, Tibet or East Africa. The main mechanism is an increase in red blood cell production, more marked in Andeans than in Tibetans or Ethiopians. Other changes are observed in the cardiovascular or respiratory systems, as well as in the utero-placental circulation. Sometimes, a de-adaptation process to hypoxia develops, when erythrocytosis becomes excessive and leads to haematological, vascular and cerebral complications (Monge's disease or chronic mountain sickness). Pulmonary hypertension may also appear. Therapeutic options are available but not sufficiently used. Genetic studies have recently been undertaken to try to better understand the evolution of the human genome in populations living in various high altitude regions of the world, as well as the genetic risk factors for chronic diseases. A new model has appeared, intermittent chronic hypoxia, due to the development of economic activities (mainly mining) in desert regions of the Altiplano.

Feeding Your Himalayan Expedition: Nutritional Signatures and Body Composition Adaptations of Trekkers and Porters

High-altitude exposure leads to many physiological challenges, such as weight loss and dehydration. However, little attention has been posed to the role of nutrition and ethnic differences. Aiming to fulfill this gap, five Italian trekkers and seven Nepalese porters, all males, recorded their diet in diaries during a Himalayan expedition (19 days), and the average daily intake of micro and macro-nutrients were calculated. Bioimpedance analysis was performed five times during the trek; muscle ultrasound was performed before and after the expedition, only for the Italians. The Nepalese group consumed a lot of rice and only Italians consumed cheese. Water intake was slightly over 3000 g/d for both groups. Nepalese diet had a higher density of dietary fibre and lower density of riboflavin, vitamins A, K, and B12. Intake of calcium was lower than recommended levels. Body mass index, waist circumference, fat-free mass, and total body water decreased in both groups, whereas resistance (Rz) increased. Italians reactance (Xc) increased at day 9, whereas that of Nepalese occurred at days 5, 9, and 16. The cross-sectional area of the Vastus lateralis was reduced after the expedition. Specific nutritional and food-related risk factors guidance is needed for diverse expedition groups. Loss of muscle mass and balance of fluids both deserve a particular focus as concerns altitude expeditions.

Adaptations of the human placenta to hypoxia: opportunities for interventions in fetal growth restriction

BACKGROUND

The placenta is the functional interface between the mother and the fetus during pregnancy, and a critical determinant of fetal growth and life-long health. In the first trimester, it develops under a low-oxygen environment, which is essential for the conceptus who has little defense against reactive oxygen species produced during oxidative metabolism. However, failure of invasive trophoblasts to sufficiently remodel uterine arteries toward dilated vessels by the end of the first trimester can lead to reduced/intermittent blood flow, persistent hypoxia and oxidative stress in the placenta with consequences for fetal growth. Fetal growth restriction (FGR) is observed in ∼10% of pregnancies and is frequently seen in association with other pregnancy complications, such as preeclampsia (PE). FGR is one of the main challenges for obstetricians and pediatricians, as smaller fetuses have greater perinatal risks of morbidity and mortality and postnatal risks of neurodevelopmental and cardio-metabolic disorders.

OBJECTIVE AND RATIONALE

The aim of this review was to examine the importance of placental responses to changing oxygen environments during abnormal pregnancy in terms of cellular, molecular and functional changes in order to highlight new therapeutic pathways, and to pinpoint approaches aimed at enhancing oxygen supply and/or mitigating oxidative stress in the placenta as a mean of optimizing fetal growth.

SEARCH METHODS

An extensive online search of peer-reviewed articles using PubMed was performed with combinations of search terms including pregnancy, placenta, trophoblast, oxygen, hypoxia, high altitude, FGR and PE (last updated in May 2020).

OUTCOMES

Trophoblast differentiation and placental establishment are governed by oxygen availability/hypoxia in early pregnancy. The placental response to late gestational hypoxia includes changes in syncytialization, mitochondrial functions, endoplasmic reticulum stress, hormone production, nutrient handling and angiogenic factor secretion. The nature of these changes depends on the extent of hypoxia, with some responses appearing adaptive and others appearing detrimental to the placental support of fetal growth. Emerging approaches that aim to increase placental oxygen supply and/or reduce the impacts of excessive oxidative stress are promising for their potential to prevent/treat FGR.

WIDER IMPLICATIONS

There are many risks and challenges of intervening during pregnancy that must be considered. The establishment of human trophoblast stem cell lines and organoids will allow further mechanistic studies of the effects of hypoxia and may lead to advanced screening of drugs for use in pregnancies complicated by placental insufficiency/hypoxia. Since no treatments are currently available, a better understanding of placental adaptations to hypoxia would help to develop therapies or repurpose drugs to optimize placental function and fetal growth, with life-long benefits to human health.

The genetic structure and adaptation of Andean highlanders and Amazonians are influenced by the interplay between geography and culture

Western South America was one of the worldwide cradles of civilization. The well-known Inca Empire was the tip of the iceberg of an evolutionary process that started 11,000 to 14,000 years ago. Genetic data from 18 Peruvian populations reveal the following: 1) The between-population homogenization of the central southern Andes and its differentiation with respect to Amazonian populations of similar latitudes do not extend northward. Instead, longitudinal gene flow between the northern coast of Peru, Andes, and Amazonia accompanied cultural and socioeconomic interactions revealed by archeology. This pattern recapitulates the environmental and cultural differentiation between the fertile north, where altitudes are lower, and the arid south, where the Andes are higher, acting as a genetic barrier between the sharply different environments of the Andes and Amazonia. 2) The genetic homogenization between the populations of the arid Andes is not only due to migrations during the Inca Empire or the subsequent colonial period. It started at least during the earlier expansion of the Wari Empire (600 to 1,000 years before present). 3) This demographic history allowed for cases of positive natural selection in the high and arid Andes vs. the low Amazon tropical forest: in the Andes, a putative enhancer in HAND2-AS1 (heart and neural crest derivatives expressed 2 antisense RNA1, a noncoding gene related to cardiovascular function) and rs269868-C/Ser1067 in DUOX2 (dual oxidase 2, related to thyroid function and innate immunity) genes and, in the Amazon, the gene encoding for the CD45 protein, essential for antigen recognition by T and B lymphocytes in viral-host interaction.