Humans at high altitude: hypoxia and fetal growth

Proteomic analysis of chick embryonic heart in experimental hypoxia

Investigating prenatal hypoxia is difficult in mammals, as there are confounding factors stemming from maternal adaptations and compensatory mechanisms. We have thus established an avian model of hypoxic incubation (starting after 2 days of normoxia, 15% O2, normobaric, until the time of sampling at embryonic day 8) to study embryonic reactions to low oxygen concentration. Our previous studies have shown increased vascularization, oedema, and ventricular wall thinning preceding the lethality at mid-gestation. Analysis of the cardiac proteome after 6 days of hypoxic incubation showed strong upregulation of enzymes involved in anaerobic glycolysis as well as an increase in apoptosis-related proteins, cell adhesion proteins, and secretory activity.

Impaired maternal central hemodynamics precede the onset of vascular disorders of pregnancy at high altitude

Hypertensive disorders of pregnancy represent an escalating global health concern with increasing incidence in low- to middle-income countries and high-income countries alike. The current lack of methods to detect the subclinical stages of preeclampsia (PE) and fetal growth restriction (FGR), two common vascular disorders of pregnancy, limits treatment options to minimize acute- and long-term adverse outcomes for both mother and child. To determine whether impaired maternal cardiovascular or uteroplacental vascular function precedes the onset of PE and/or FGR (PE-FGR), we used noninvasive techniques to obtain serial measurements of maternal cardiac output (CO), stroke volume (SV), systemic vascular resistance (SVR), and uterine and fetal arterial resistance at gestational weeks 10-16, 20-24, and 30-34 for 79 maternal-infant pairs in La Paz-El Alto, Bolivia (3,850 m), where the chronic hypoxia of high altitude increases the incidence of PE and FGR. Compared with controls (n = 55), PE-FGR cases (n = 24) had lower SV, higher SVR, and greater uterine artery resistance at 10-16 wk. In addition, fetuses of women with lower SV and higher SVR at 10-16 wk showed evidence of brain sparing at 30-34 wk and had lower birth weights, respectively. Although the trajectory of SV and SVR across pregnancy was similar between groups, PE-FGR cases had a comparatively blunted rise in CO from the first to the third visit. Impaired maternal central hemodynamics and increased uteroplacental resistance precede PE-FGR onset, highlighting the potential use of such measures for identifying high-risk pregnancies at high altitudes.NEW & NOTEWORTHY In this prospective study of maternal central hemodynamics at high altitude, pregnancies later affected by preeclampsia (PE) and/or fetal growth restriction (FGR) show elevated systemic and uterine vascular resistance and reduced stroke volume as early as 10-16 wk gestation. Maternal hemodynamic assessments could facilitate early detection of high-risk pregnancies, improving resource allocation and reducing adverse outcomes. We propose an integrated model linking maternal cardiovascular performance to placental insufficiency, enhancing the understanding of PE-FGR in high-altitude settings.

To what extent do physiological tolerances determine elevational range limits of mammals?

A key question in biology concerns the extent to which distributional range limits of species are determined by intrinsic limits of physiological tolerance. Here, we use common-garden data for wild rodents to assess whether species with higher elevational range limits typically have higher thermogenic capacities in comparison to closely related lowland species. Among South American leaf-eared mice (genus Phyllotis), mean thermogenic performance is higher in species with higher elevational range limits, but there is little among-species variation in the magnitude of plasticity in this trait. In the North American rodent genus Peromyscus, highland deer mice (Peromyscus maniculatus) have greater thermogenic maximal oxygen uptake (V ̇ O 2 max ${\dot V_{{{\mathrm{O}}_{\mathrm{2}}}{\mathrm{max}}}}$ ) than lowland white-footed mice (Peromyscus leucopus) at a level of hypoxia that matches the upper elevational range limit of the former species. In highland deer mice, the enhanced thermogenicV ̇ O 2 max ${\dot V_{{{\mathrm{O}}_{\mathrm{2}}}{\mathrm{max}}}}$ in hypoxia is attributable to a combination of evolved and plastic changes in physiological pathways that govern the transport and utilization of O2 and metabolic substrates. Experiments with Peromyscus mice also demonstrate that exposure to hypoxia during different stages of development elicits plastic changes in cardiorespiratory traits that improve thermogenicV ̇ O 2 max ${\dot V_{{{\mathrm{O}}_{\mathrm{2}}}{\mathrm{max}}}}$ via distinct physiological mechanisms. Evolved differences in thermogenic capacity provide clues about why some species are able to persist in higher-elevation habitats that lie slightly beyond the tolerable limits of other species. Such differences in environmental tolerance also suggest why some species might be more vulnerable to climate change than others.

Early-life exposures and long-term health: adverse gestational environments and the programming of offspring renal and vascular disease

According to the Developmental Origins of Health and Disease hypothesis, exposure to certain environmental influences during early life may be a key determinant of fetal development and short- and long-term offspring health. Indeed, adverse conditions encountered during the fetal, perinatal, and early childhood stages can alter normal development and growth, as well as put the offspring at elevated risk of developing long-term health conditions in adulthood, including chronic kidney disease and cardiovascular diseases. Of relevance in understanding the mechanistic basis of these long-term health conditions are previous findings showing low glomerular number in human intrauterine growth restriction and low birth weight-indicators of a suboptimal intrauterine environment. In different animal models, the main suboptimal intrauterine conditions studied relate to maternal dietary manipulations, poor micronutrient intake, prenatal ethanol exposure, maternal diabetes, glucocorticoid and chemical exposure, hypoxia, and placental insufficiency. These studies have demonstrated changes in kidney structure, glomerular endowment, and expression of key genes and signaling pathways controlling endocrine, excretion, and filtration function of the offspring. This review aims to summarize those studies to uncover the effects and mechanisms by which adverse gestational environments impact offspring renal and vascular health in adulthood. This is important for identifying agents and interventions that can prevent and mitigate the long-term consequences of an adverse intrauterine environment on the subsequent generation.NEW & NOTEWORTHY Human data and experimental animal data show that suboptimal environments during fetal development increase the risk of renal and vascular diseases in adult-life. This is related to permanent changes in kidney structure, function, and expression of genes and signaling pathways controlling filtration, excretion, and endocrine function. Uncovering the mechanisms by which offspring renal development and function is impacted is important for identifying ways to mitigate the development of diseases that strain health care services worldwide.

Sex-biased regulatory changes in the placenta of native highlanders contribute to adaptive fetal development

Compared with lowlander migrants, native Tibetans have a higher reproductive success at high altitude though the underlying mechanism remains unclear. Here, we compared the transcriptome and histology of full-term placentas between native Tibetans and Han migrants. We found that the placental trophoblast shows the largest expression divergence between Tibetans and Han, and Tibetans show decreased immune response and endoplasmic reticulum stress. Remarkably, we detected a sex-biased expression divergence, where the male-infant placentas show a greater between-population difference than the female-infant placentas. The umbilical cord plays a key role in the sex-biased expression divergence, which is associated with the higher birth weight of the male newborns of Tibetans. We also identified adaptive histological changes in the male-infant placentas of Tibetans, including larger umbilical artery wall and umbilical artery intima and media, and fewer syncytial knots. These findings provide valuable insights into the sex-biased adaptation of human populations, with significant implications for medical and genetic studies of human reproduction.

Magnetic resonance imaging of placental intralobule structure and function in a preclinical nonhuman primate model†

Although the central role of adequate blood flow and oxygen delivery is known, the lack of optimized imaging modalities to study placental structure has impeded our understanding of its vascular function. Magnetic resonance imaging is increasingly being applied in this field, but gaps in knowledge remain, and further methodological developments are needed. In particular, the ability to distinguish maternal from fetal placental perfusion and the understanding of how individual placental lobules are functioning are lacking. The potential clinical benefits of developing noninvasive tools for the in vivo assessment of blood flow and oxygenation, two key determinants of placental function, are tremendous. Here, we summarize a number of structural and functional magnetic resonance imaging techniques that have been developed and applied in animal models and studies of human pregnancy over the past decade. We discuss the potential applications and limitations of these approaches. Their combination provides a novel source of contrast to allow analysis of placental structure and function at the level of the lobule. We outline the physiological mechanisms of placental T2 and T2* decay and devise a model of how tissue composition affects the observed relaxation properties. We apply this modeling to longitudinal magnetic resonance imaging data obtained from a preclinical pregnant nonhuman primate model to provide initial proof-of-concept data for this methodology, which quantifies oxygen transfer and placental structure across and between lobules. This method has the potential to improve our understanding and clinical management of placental insufficiency once validation in a larger nonhuman primate cohort is complete.

Environmental Exposures and Risks During Pregnancy

The Women in Wilderness Medicine Research Committee of the Wilderness Medical Society conducted a narrative review to address considerations for pregnant individuals in wilderness environments. There is limited evidence behind many opinion-based recommendations on the safety of various environmental exposures in pregnancy. The authors reviewed the literature for the best available evidence, including observational studies, case series, limited controlled trials, and extrapolation from physiological data, as well as evaluating expert consensus statements. The benefits of exposure to natural environments include better pregnancy outcomes and improved maternal mental and physical health. Risks are similar to nonpregnant individuals with the added risks associated with maternal-fetal physiology in wilderness environments and difficulties of evacuation. This narrative review discusses pregnancy-specific concerns in extreme environments, including high altitude, hypothermia, hyperthermia, lightning strikes, envenomations, and common outdoor exposures.

Assessing the performance of Moghani crossbred lambs derived from different mating systems with Texel and Booroola sheep

In our ongoing project, which focuses on the introgression of Booroola/FecB gene and the myostatin (MSTN) gene into purebred Moghani sheep, we assessed the performance of second-generation Moghani crossbreds such as second crossbreds (F2) and initial backcross generation (BC1). These crossbreds were generated through different mating systems, including in-breeding, outcrossing, first paternal backcrossing (PBC1), and first maternal backcrossing (MBC1). Notably, F2 strains exhibited lean tail, woolly fleece and a higher percentage of white coat color compared to BC1. The impact of mating systems and birth types on pre-weaning survival rates was found to be statistically significant (P < 0.0001), with singleton offspring resulting from paternal backcross showing a particularly substantial effect. The F2 crossbred lambs carrying the Booroola gene did not show a statistically significant difference in survivability compared to those carrying the MSTN gene, implying the Booroola prolificacy gene had no significant impact on survival outcomes. However, the occurrence of multiple births had a significant negative impact on lamb survival (P < 0.0001). The PBC1 sheep strains, specifically Texel Tamlet ram strains carrying the MSTN mutation, exhibited superior growth rates compared to others (P < 0.05). Interestingly, the MSTN mutation in the homozygous variant genotype significantly impacts growth rate before weaning compared to other genotypes and pure Moghani sheep (P < 0.05). In conclusion, this study objectively underscores the pivotal role of genetic factors, specifically through strategic mating systems like paternal backcrossing, in enhancing desired traits and growth rates in Moghani sheep, thereby contributing valuable insights to the field of sheep breeding programs.

Cold-inducible RNA binding protein alleviates iron overload-induced neural ferroptosis under perinatal hypoxia insult

Cold-inducible RNA binding protein (CIRBP), a stress response protein, protects cells from mild hypothermia or hypoxia by stabilizing specific mRNAs and promoting their translation. Neurons subjected to hypobaric hypoxia insult trigger various cell death programs. One of these is ferroptosis, a novel non-apoptotic form of programmed cell death, which is characterized by excessive iron ion accumulation and lipid peroxidation. Here, we establish that CIRBP can regulate neuronal ferroptosis both in vivo and in vitro. We observe that hypoxia leads to neuronal death via intracellular ferrous iron overload and impaired antioxidant systems, accompanied by suppressed CIRBP expression. Genetic enrichment of CIRBP in hippocampal neurons CIRBPTg mice bred with Emx1-Cre mice attenuates hypoxia-induced cognitive deficits and neuronal degeneration. Mechanistically, CIRBP alleviates neuronal ferroptosis and intracellular ferrous ion accumulation by binding to the mitochondrial ferritin (FTMT) 3'UTR to stabilize mRNA and promote its translation. Our novel study shows the critical role of CIRBP in the progression of ferroptosis, and provides promising therapeutic target for hypoxia-induced neurological diseases.

Hypoxia delays steroid-induced developmental maturation in Drosophila by suppressing EGF signaling

Animals often grow and develop in unpredictable environments where factors like food availability, temperature, and oxygen levels can fluctuate dramatically. To ensure proper sexual maturation into adulthood, juvenile animals need to adapt their growth and developmental rates to these fluctuating environmental conditions. Failure to do so can result in impaired maturation and incorrect body size. Here we describe a mechanism by which Drosophila larvae adapt their development in low oxygen (hypoxia). During normal development, larvae grow and increase in mass until they reach critical weight (CW), after which point a neuroendocrine circuit triggers the production of the steroid hormone ecdysone from the prothoracic gland (PG), which promotes maturation to the pupal stage. However, when raised in hypoxia (5% oxygen), larvae slow their growth and delay their maturation to the pupal stage. We find that, although hypoxia delays the attainment of CW, the maturation delay occurs mainly because of hypoxia acting late in development to suppress ecdysone production. This suppression operates through a distinct mechanism from nutrient deprivation, occurs independently of HIF-1 alpha and does not involve dilp8 or modulation of Ptth, the main neuropeptide that initiates ecdysone production in the PG. Instead, we find that hypoxia lowers the expression of the EGF ligand, spitz, and that the delay in maturation occurs due to reduced EGFR/ERK signaling in the PG. Our study sheds light on how animals can adjust their development rate in response to changing oxygen levels in their environment. Given that hypoxia is a feature of both normal physiology and many diseases, our findings have important implications for understanding how low oxygen levels may impact animal development in both normal and pathological situations.

Evidence that highly canalized fetal traits are sensitive to intergenerational effects of maternal developmental nutrition

OBJECTIVES

Maternal experiences before pregnancy predict birth outcomes, a key indicator of health trajectories, but the timing and pathways for these effects are poorly understood. Here we test the hypothesis that maternal pre-adult growth patterns predict pregnancy glucose and offspring fetal growth in Cebu, Philippines.

METHODS

Using multiple regression and path analysis, gestational age-adjusted birthweight and variables reflecting infancy, childhood, and post-childhood/adolescent weight gain (conditional weights) were used to predict pregnancy HbA1c and offspring birth outcomes among participants in the Cebu Longitudinal Health and Nutrition Survey.

RESULTS

Maternal early/mid-childhood weight gain predicted birth weight, length, and head circumference in female offspring. Late-childhood/adolescent weight gain predicted birth length, birth weight, skinfold thickness, and head circumference in female offspring, and head circumference in male offspring. Pregnancy HbA1c did not mediate relationships between maternal growth and birth size parameters.

DISCUSSION

In Cebu, maternal growth patterns throughout infancy, childhood, and adolescence predict fetal growth via a pathway independent of circulating glucose, with stronger impacts on female than male offspring, consistent with a role of developmental nutrition on offspring fetal growth. Notably, the strength of relationships followed a pattern opposite to what occurs in response to acute pregnancy stress, with strongest effects on head circumference and birth length and weakest on skinfolds. We speculate that developmental sensitivities are reversed for stable, long-term nutritional cues that reflect average local environments. These findings are relevant to public health and life-history theory as further evidence of developmental influences on health and resource allocation across the life course.

Whole exome sequencing of placental chorangioma

INTRODUCTION

Placental chorangioma is a benign non-trophoblastic vascular proliferation of the placental chorion favored to represent hamartoma-like or hyperplastic capillary lesions. As the exact pathophysiology has not been established, we investigated the molecular characteristics of placental chorangiomas using exploratory whole exome sequencing.

METHODS

Three cases were retrospectively selected and whole exome sequencing was performed on macrodissected lesions. DNA extraction, DNA quantification, library preparation and sequencing were performed with IDT xGen™ Exome Hybridization Panel v2 for library capture. Sequencing data was analyzed with an in-house bioinformatics pipeline for single-nucleotide variants and insertions/deletions.

RESULTS

All neonates were delivered at term and had birth weights ranging from 11th-35th percentile for gestational age. All mothers presented with hypertensive disorder during pregnancy. Chorangiomas ranged from 0.7 cm to 5.1 cm and were well-circumscribed near the fetal surface. Case 1 showed a background of chorangiosis and acute subchorionitis, while case 2 had foci of chronic lymphocytic villitis. Whole exome sequencing did not reveal any significant pathologic variants.

DISCUSSIONS

The absence of molecular alteration in placental chorangioma is likely indicative of the reactive/non-neoplastic nature of this lesion. The presence of compromised blood flow in the form of hypertensive disorders in our cases may be one of its underlying pathophysiologic mechanisms.

Effects of heat load and hypobaric hypoxia on cognitive performance: a combined stressor approach

This study investigates how cognitive performance is affected by the combination of two stressors that are operationally relevant for helicopter pilots: heat load and hypobaric hypoxia. Fifteen participants were exposed to (1) no stressors, (2) heat load, (3) hypobaric hypoxia, and (4) combined heat load and hypobaric hypoxia. Hypobaric hypoxia (13,000 ft) was achieved in a hypobaric chamber. Heat load was induced by increasing ambient temperature to ∼28 °C. Cognitive performance was measured using two multitasks, and a vigilance task. Subjective and physiological data (oxygen saturation, heart rate, core- and skin temperature) were also collected. Mainly heat load caused cognitive performance decline. This can be explained by high subjective heat load and increased skin temperature, which takes away cognitive resources from the tasks. Only the arithmetic subtask was sensitive to hypobaric hypoxia, whereby hypobaric hypoxia caused a further performance decline in addition to the decline caused by heat load.Practitioner summary: Little is known about how multiple environmental stressors interact. This study investigates the combined effects of heat load and hypobaric hypoxia on cognitive performance. An additive effect of heat load and hypobaric hypoxia was found on a arithmetic task, which may be attributed to independent underlying mechanisms.

Polygenic adaptation leads to a higher reproductive fitness of native Tibetans at high altitude

The adaptation of Tibetans to high-altitude environments has been studied extensively. However, the direct assessment of evolutionary adaptation, i.e., the reproductive fitness of Tibetans and its genetic basis, remains elusive. Here, we conduct systematic phenotyping and genome-wide association analysis of 2,252 mother-newborn pairs of indigenous Tibetans, covering 12 reproductive traits and 76 maternal physiological traits. Compared with the lowland immigrants living at high altitudes, indigenous Tibetans show better reproductive outcomes, reflected by their lower abortion rate, higher birth weight, and better fetal development. The results of genome-wide association analyses indicate a polygenic adaptation of reproduction in Tibetans, attributed to the genomic backgrounds of both the mothers and the newborns. Furthermore, the EPAS1-edited mice display higher reproductive fitness under chronic hypoxia, mirroring the situation in Tibetans. Collectively, these results shed new light on the phenotypic pattern and the genetic mechanism of human reproductive fitness in extreme environments.

Deep phenotyping of 11,880 highlanders reveals novel adaptive traits in native Tibetans

Tibetans are the ideal population to study genetic adaptation in extreme environments. Here, we performed systematic phenotyping of 11,880 highlanders, covering 133 quantitative traits of 13 organ systems. We provided a comprehensive phenotypic atlas by comparing altitude adaptation and altitude acclimatization. We found the differences between adaptation and acclimatization are quantitative rather than qualitative, with a whole-system "blunted effect" seen in the adapted Tibetans. We characterized twelve different functional changes between adaptation and acclimatization. More importantly, we established a landscape of adaptive phenotypes of indigenous Tibetans, including 45 newly identified Tibetan adaptation-nominated traits, involving specific changes of Tibetans in internal organ state, metabolism, eye morphology, and skin pigmentation. In addition, we observed a sex-biased pattern between altitude acclimatization and adaptation. The generated atlas of phenotypic landscape provides new insights into understanding of human adaptation to high-altitude environments, and it serves as a valuable blueprint for future medical and physiological studies.

Term alpaca placenta glycosylation profile and its correlation with pregnancy maintenance and fetal survival

Alpaca is a South American camelid, particularly present in Peruvian highlands, where oxygen concentration and atmospheric pressure are very low. Due to this fact, gestational physiology has adapted to preserve the conceptus' and mother's health. In this context, several cellular and molecular features play an essential role during and at the end of gestation. Structural carbohydrates act on maternal-fetal communication, recognize exogenous molecules, and contribute to placental barrier selectivity. Therefore, this study aimed to characterize the structural carbohydrate profiles that are present in the term alpaca placenta, kept in their natural habitat of around 4,000 m height. For this propose, 12 term alpaca placentas were collected, and the material was obtained at the time of birth from camelids raised naturally in the Peruvian highlands, in the Cusco region. All placenta samples were processed for histological analysis. A lectin histochemical investigation was performed using 13 biotinylated lectins, allowing us to determine the location of carbohydrates and their intensity on a semi-quantitative scale. Our results demonstrated that during term gestation, the epitheliochorial alpaca placenta shows a high presence of carbohydrates, particularly glucose, α-linked mannose, N-acetylglucosamine β (GlcNAc), galactose (αGal), and N-acetylgalactosamine α (GalNAc), present in the trophoblast, amnion epithelium, and mesenchyme, as well as the presence of sialic acid residues and low affinity for fucose. In fetal blood capillaries, the presence of bi- and tri-antennary complex structures and α-linked mannose was predominated. In conclusion, we characterized the glycosylation profile in the term alpaca placenta. Based on our data, compared to those reported in the bibliography, we suggest that these carbohydrates could participate in the labor of these animals that survive in Peruvian extreme environments.

Evaluation of Escherichia coli Inactivation at High Altitudes Using Solar Water Disinfection

INTRODUCTION

Solar disinfection (SODIS) is an effective method for microbiologic inactivation of contaminated water using ultraviolet rays at low elevations. The aim of this study was to determine the effectiveness of SODIS at higher elevations.

METHODS

The ability of SODIS to inactivate Escherichia coli bacteria was evaluated at an altitude of ≥1600 m using Nalgene bottles, disposable plastic water bottles, and Ziploc plastic bags. Bacterial viability was determined through measurement of colony forming units (CFUs). Decreases in CFUs were determined at each time point relative to those at the baseline, and a multivariable regression analysis was used to assess significant changes in CFUs.

RESULTS

Bacterial CFUs in exposed containers decreased by >5 log after 6 h of exposure to sunlight. In contrast, the CFUs remained nearly unchanged in unexposed containers, showing a mean decrease of 0.3 log. By 2 h, bacterial inactivation at high altitudes was 1.7-fold greater than that at lower altitudes (P<0.05). By 6 h, nearly all bacteria were inactivated at high or low altitudes. At 6 h, no statistical difference was observed in the efficiency of inactivation between elevations. Compared with Nalgene bottles, plastic bottles had a 1.4-fold greater decrease in CFUs (P<0.05). No statistical difference in bacterial inactivation was found between plastic bottles and plastic bags.

CONCLUSIONS

At high altitudes, SODIS is an effective method for inactivating E coli. Further research investigating other microorganisms is warranted to determine whether SODIS is suitable for disinfecting contaminated water at high altitudes.

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.

Evolved reductions in body temperature and the metabolic costs of thermoregulation in deer mice native to high altitude

The evolution of endothermy was instrumental to the diversification of birds and mammals, but the energetic demands of maintaining high body temperature could offset the advantages of endothermy in some environments. We hypothesized that reductions in body temperature help high-altitude natives overcome the metabolic challenges of cold and hypoxia in their native environment. Deer mice (Peromyscus maniculatus) from high-altitude and low-altitude populations were bred in captivity to the second generation and were acclimated as adults to warm normoxia or cold hypoxia. Subcutaneous temperature (Tsub, used as a proxy for body temperature) and cardiovascular function were then measured throughout the diel cycle using biotelemetry. Cold hypoxia increased metabolic demands, as reflected by increased food consumption and heart rate (associated with reduced vagal tone). These increased metabolic demands were offset by plastic reductions in Tsub (approx. 2°C) in response to cold hypoxia, and highlanders had lower Tsub (approx. 1°C) than lowlanders in both environmental treatments. Empirical and theoretical evidence suggested that these reductions could together reduce metabolic demands by approximately 10-30%. Therefore, plastic and evolved reductions in body temperature can help mammals overcome the metabolic challenges at high altitude and may be a valuable energy-saving strategy in some non-hibernating endotherms in extreme environments.

Population history and genome wide association studies of birth weight in a native high altitude Ladakhi population

Pathological low birth weight due to fetal growth restriction (FGR) is an important predictor of adverse obstetric and neonatal outcomes. It is more common amongst native lowlanders when gestating in the hypoxic environment of high altitude, whilst populations who have resided at high altitude for many generations are relatively protected. Genetic study of pregnant populations at high altitude permits exploration of the role of hypoxia in FGR pathogenesis, and perhaps of FGR pathogenesis more broadly. We studied the umbilical cord blood DNA of 316 neonates born to pregnant women managed at the Sonam Norboo Memorial Hospital, Ladakh (altitude 3540m) between February 2017 and January 2019. Principal component, admixture and genome wide association studies (GWAS) were applied to dense single nucleotide polymorphism (SNP) genetic data, to explore ancestry and genetic predictors of low birth weight. Our findings support Tibetan ancestry in the Ladakhi population, with subsequent admixture with neighboring Indo-Aryan populations. Fetal growth protection was evident in Ladakhi neonates. Although no variants achieved genome wide significance, we observed nominal association of seven variants across genes (ZBTB38, ZFP36L2, HMGA2, CDKAL1, PLCG1) previously associated with birthweight.

Clotting factor genes are associated with preeclampsia in high-altitude pregnant women in the Peruvian Andes

Preeclampsia is a multi-organ complication of pregnancy characterized by sudden hypertension and proteinuria that is among the leading causes of preterm delivery and maternal morbidity and mortality worldwide. The heterogeneity of preeclampsia poses a challenge for understanding its etiology and molecular basis. Intriguingly, risk for the condition increases in high-altitude regions such as the Peruvian Andes. To investigate the genetic basis of preeclampsia in a population living at high altitude, we characterized genome-wide variation in a cohort of preeclamptic and healthy Andean families (n = 883) from Puno, Peru, a city located above 3,800 meters of altitude. Our study collected genomic DNA and medical records from case-control trios and duos in local hospital settings. We generated genotype data for 439,314 SNPs, determined global ancestry patterns, and mapped associations between genetic variants and preeclampsia phenotypes. A transmission disequilibrium test (TDT) revealed variants near genes of biological importance for placental and blood vessel function. The top candidate region was found on chromosome 13 of the fetal genome and contains clotting factor genes PROZ, F7, and F10. These findings provide supporting evidence that common genetic variants within coagulation genes play an important role in preeclampsia. A selection scan revealed a potential adaptive signal around the ADAM12 locus on chromosome 10, implicated in pregnancy disorders. Our discovery of an association in a functional pathway relevant to pregnancy physiology in an understudied population of Native American origin demonstrates the increased power of family-based study design and underscores the importance of conducting genetic research in diverse populations.

Hypoxia ameliorates maternal diet-induced insulin resistance during pregnancy while having a detrimental effect on the placenta

Maternal overweight/obesity contributes significantly to the development of gestational diabetes, which causes risks to both mother and fetus and is increasing sharply in prevalence worldwide. Since hypoxia reprograms energy metabolism and can alleviate weight gain, adiposity, insulin resistance (IR), and dyslipidemia, we set out to study the potential of sustained reduced ambient oxygen tension (15% O₂ ) during pregnancy for alleviating the detrimental effects of diet-induced IR in C57Bl/6N mice, taking normal chow-fed and normoxia (21% O₂ ) groups as controls. Our data show that hypoxic intervention reduced maternal weight gain, adiposity, and adipose tissue inflammation, and ameliorated maternal glucose metabolism and IR during gestation in diet-induced IR relative to normoxia. Where diet-induced IR reduced maternal hemoglobin and increased serum erythropoietin levels, hypoxic intervention compensated for these changes. Diet-induced IR reduced fetal growth in normoxia, and even more in hypoxia. Hypoxic intervention reduced liver weight gain during pregnancy in the dams with diet-induced IR, maternal liver weight being positively associated with embryo number. In case of diet-induced IR, the hypoxic intervention compromised placental energy metabolism and vascularization and increased end-pregnancy placental necrosis. Altogether, these data show that although hypoxic intervention mediates several beneficial effects on maternal metabolism, the combination of it with diet-induced IR is even more detrimental to the placental and fetal outcome than diet-induced IR alone.

Fetal growth and spontaneous preterm birth in high-altitude pregnancy: A systematic review, meta-analysis, and meta-regression

OBJECTIVE

To understand the relationship between birth weight and altitude to improve health outcomes in high-altitude populations, to systematically assess the impact of altitude on the likelihood of low birth weight (LBW), small for gestational age (SGA), and spontaneous preterm birth (sPTB), and to estimate the magnitude of reduced birth weight associated with altitude.

METHODS

PubMed, OvidEMBASE, Cochrane Library, Medline, Web of Science, and clinicaltrials.gov were searched (from inception to November 11, 2020). Observational, cohort, or case-control studies were included if they reported a high altitude (>2500 m) and appropriate control population.

RESULTS

Of 2524 studies identified, 59 were included (n = 1 604 770 pregnancies). Data were abstracted according to PRISMA guidelines, and were pooled using random-effects models. There are greater odds of LBW (odds ratio [OR] 1.47, 95% confidence interval [CI] 1.33-1.62, P < 0.001), SGA (OR 1.88, 95% CI 1.08-3.28, P = 0.026), and sPTB (OR 1.23, 95% CI 1.04-1.47, P = 0.016) in high- versus low-altitude pregnancies. Birth weight decreases by 54.7 g (±13.0 g, P < 0.0001) per 1000 m increase in altitude. Average gestational age at delivery was not significantly different.

CONCLUSION

Globally, the likelihood of adverse perinatal outcomes, including LBW, SGA, and sPTB, increases in high-altitude pregnancies. There is an inverse relationship between birth weight and altitude. These findings have important implications for the increasing global population living at altitudes above 2500 m.

Consecutive chorioangiomas in the same pregnancy: A clinical case and review of literature

Background and Aims

Aetiopathogenesis of chorioangioma is already unknown. Among the risk factors, hypoxia, environmental and genetic factors are believed to induce the overexpression of angiogenic cytokines promoting vascular proliferation. We reported a case of prenatally diagnosed 67 mm‐wide placental chorioangioma, which occurred at 32 weeks of gestational age, infarcted, and followed by the onset of a second infarcted chorioangioma at 35 weeks of gestational age. Besides, we discussed the hypothesis of chorioangioma aetiopathogenesis and behavior through a literature summary.

Methods

We carried out a literature search of chorioangioma cases without a time interval. Therefore, we carried out a literature summary on chorioangioma risk factors and etiology, by selecting articles within a time interval from 1995 to 2021.

Results

This is the first case of two consecutive chorioangiomas in the same pregnancy published in the literature. We found a possible genetic predisposition in women developing chorioangioma while infarction may be related to the abnormal structure of tumor vessels. The onset of a second lesion could reflect hypoxic stimuli following infarction and involves hypoxia‐induced factor‐1alpha, vascular endothelial growth factor, transforming growth factor‐beta, and soluble Fms‐like tyrosine kinase‐1 pathways. Chorangiosis can be coexistent and may reflect a mutual etiology in susceptible individuals.

Conclusion

In a predisposed placenta, that previously generated a chorioangioma, infarction of the chorioangioma should not represent a sign for pregnancy termination, but a marker for closer monitoring to early detect the possible onset of a second chorioangioma and a higher risk of umbilical cord thrombosis.

Denisovans and Homo sapiens on the Tibetan Plateau: dispersals and adaptations

Recent archaeological discoveries suggest that both archaic Denisovans and Homo sapiens occupied the Tibetan Plateau earlier than expected. Genetic studies show that a pulse of Denisovan introgression was involved in the adaptation of Tibetan populations to high-altitude hypoxia. These findings challenge the traditional view that the plateau was one of the last places on earth colonized by H. sapiens and warrant a reappraisal of the population history of this highland. Here, we integrate archaeological and genomic evidence relevant to human dispersal, settlement, and adaptation in the region. We propose two testable models to address the peopling of the plateau in the broader context of H. sapiens dispersal and their encounters with Denisovans in Asia.

The Effect of Altitude on Birthweight/Length Ratio: A Population-Based Study Over 36 Years in an Altitude Range from Sea Level to 1,700 m

Klebermass-Schrehof Katrin, Thomas Waldhoer, and Lin Yang. The effect of altitude on birthweight/length ratio: a population-based study over 36 years in an altitude range from sea level to 1,700 m. High Alt Med Biol. 23:90-95, 2022. Objective: The negative effect of altitude on fetal growth has been documented, but it is unknown whether this effect changes over time. We investigated the effect of altitude on infant birthweight/length ratio as well as its potential dependence on gestational age and year of birth in the range from sea level up to 1,700 m (Austria). Materials and Methods: Data on maternal characteristics, infant birthweights, and infant lengths were extracted from all Austrian birth certificates between 1984 and 2019. Results: A total of 2,240,439 birth certificates were identified and analyzed. The effect of altitude on birthweight/length ratio was -2.66 g/cm (95% confidence interval [CI]: -2.77 to -2. 54) per 1,000 m increased altitude in 1984-1986, which decreased to -1.96 g/cm (95% CI: -2.09 to -1.82) in 2017-2019. The effect of altitude on birthweight/length ratio remained constant for preterm infants, which fluctuated around -1.5 g/cm. For term infants, the negative effect of altitude on birthweight/length ratio attenuated from -3 to -1.9 g/cm over time with a stronger decrease for infants born between 41 and 42 compared with those between 37 and 40 weeks of gestation. Conclusion: In summary, our data demonstrate a strong effect of altitude on birthweight/length ratio over 36 years with a smaller effect in recent years and a stronger effect in infants born around term age compared with preterm infants.

Sex differences and shifts in body composition, physical activity, and total energy expenditure across a 3-month expedition

OBJECTIVES

An energetically demanding environment like a wilderness expedition can lead to potent stressors on human physiology and homeostatic balance causing shifts in energy expenditure and body composition. These shifts likely have consequences on overall health and performance and may potentially differ by sex. It is therefore critical to understand the potential differential body composition and energy expenditure changes in response to a novel and challenging environment in both males and female bodies.

METHODS

Data were collected from 75 healthy individuals (female = 41; ages 18-53) throughout a 3-month long expedition in the American Rockies. Body mass, body fat, and lean muscle mass were measured before, during, and after the course. Physical activity intensity and energy expenditure were also measured in a subset of participants using the wGT3X-BT Actigraph wrist monitor and an accompanying Bluetooth heart rate monitor.

RESULTS

Over the 3-month period, individuals initially experienced declines in body mass, body fat percentage, and lean muscle mass. Participants partially rebounded from these deficits to maintain overall body mass with a slight recomposition of body fat and lean muscle mass. Our data also demonstrated that sex moderated total energy expenditure, where females experienced a modest decline whereas males experienced an increase in energy expenditure from the beginning to the end of the course.

CONCLUSIONS

Understanding changes in energy storage in the body and variation in energy expenditure between sexes during a 3-month expedition has critical implications for maintaining health and performance in an energetically demanding environment where resources may be scarce.

Altered erythropoiesis in newborns with congenital heart disease

BACKGROUND

Fetal hypoxia has been implicated in fetal growth restriction in congenital heart disease (CHD) and leads to stress erythropoiesis in utero. The objective is to assess erythropoiesis and its association with growth in newborns with CHD.

METHODS

Fetuses with prenatally diagnosed CHD from 2013 to 2018 were retrospectively reviewed. Pregnancies with multiple gestation, genetic abnormalities, major extra-cardiac anomalies, and placental abruption were excluded. Complete blood count tests at birth were compared to published normative values. Spearman correlation assessed associations of red blood cell (RBC) indices with birth anthropometrics and prenatal Doppler measures.

RESULTS

A total of 160 newborns were included. Median gestational age was 38.3 (37.3, 39.0) weeks. Infants ≥37 weeks gestation had lower hemoglobin (Hgb), hematocrit, and elevated nucleated RBC (nRBC), mean corpuscular volume, and mean corpuscular hemoglobin compared to reference. No differences in RBC indices were observed in infants <34 and 34-37 weeks gestation. There was no difference in Hgb and nRBC between CHD subgroups. Neither Hgb nor nRBC were associated with birth anthropometrics or Doppler patterns.

CONCLUSIONS

Term infants with CHD demonstrated multiple alterations in erythrocyte indices suggesting ineffective stress erythropoiesis in late gestation resulting in lower Hgb at birth. Altered erythropoiesis was not correlated to growth or Doppler patterns.

IMPACT

Newborns with congenital heart disease (CHD) born at term gestation demonstrated altered erythropoiesis. Term newborns with CHD have decreased hemoglobin levels despite having red blood cell indices consistent with stress erythropoiesis, suggesting an incomplete compensatory response to in utero physiologic disturbances associated with CHD. The etiology is unknown; however, it may be influenced by multiple risk factors during pregnancy in the maternal-fetal dyad. Alterations in red blood cell indices were not associated with outcomes of fetal growth.

A systematic review of electrocardiographic changes in healthy high-altitude populations

High-altitude environments are characterized by decreased atmospheric pressures at which individuals exhibit a reduced volume of maximal oxygen uptake and arterial partial pressure of oxygen, both of which lead to hypobaric hypoxia. While acute exposure may temporarily offset cardiovascular homeostasis in sea-level residents, native highlanders have become accustomed to these high-altitude conditions and often exhibit variations in normal ECG parameters. As part of the "Altitude Non-differentiated ECG Study" (ANDES) project, this paper aims to systematically review the available literature regarding ECG changes in healthy highlander populations. After searching the PubMed, Medline, and Embase databases, 286 abstracts were screened, of which 13 full-texts were ultimately included. This process was completed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines. Major ECG deviations in native healthy highlanders include right QRS axis deviation, right ventricular hypertrophy signs, and more prevalent T-wave inversion in the right precordial leads. Notably, they exhibit a prolonged QTc compared to sea-level residents, although within normal limits. Evidence about increased P-wave amplitude or duration, variations in PR interval, or greater prevalence of complete right bundle branch block is not conclusive. This review provides ECG reference standards that can be used by clinicians, who should be aware of the effects of high-altitude residence on cardiovascular health and how these may change according to age, ethnicity, and other factors.

Birth growth curves of neonates in high-altitude areas: A cross-sectional study

BACKGROUND

Since the current commonly used birth growth curves are unsuitable for neonates in high-altitude areas; this study aimed to establish birth growth curves for full-term neonates residing at 2,000-3,000 m.

METHODS

This cross-sectional study retrospectively analyzed the physical measurement data of 1,546 full-term neonates delivered at the Red Cross Hospital of Qinghai province, China, from July 2021 to April 2022. The percentile curves of birth weight, length, and head circumference of neonates of different gestational ages and genders were developed using curve fitting. The newly developed birth-weight percentile reference was compared with the INTERGROWTH-21st Neonatal Growth Curve (International Standard) and the Chinese Neonate Growth Curve (Chinese Standard).

RESULTS

The median birth weight, length, and head circumference of the study population were 3,200 g, 52.0 cm, and 32.8 cm, respectively, except for the group with a gestational age of 37 weeks. The growth indicators of male infants in all groups were higher than those of the female infants (P < 0.05). We found differences between the newly developed birth-weight percentile curves in the high-altitude areas and the International and Chinese Standards.

CONCLUSION

Establishing birth growth curves corresponding to altitude may be more suitable than the existing standards for local medical staff to conduct health assessments of neonates.

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.

Dichotomous responses to chronic fetal hypoxia lead to a predetermined aging phenotype

Hypoxia-induced intrauterine growth restriction increases the risk for cardiovascular, renal and other chronic diseases in adults, representing thus a major public health problem. Still, not much is known about the fetal mechanisms that predispose these individuals to disease. Using a previously validated mouse model of fetal hypoxia and bottom-up proteomics we characterize the response of the fetal kidney to chronic hypoxic stress. Fetal kidneys exhibit a dichotomous response to chronic hypoxia, comprising on the one hand cellular adaptations that promote survival (glycolysis, autophagy, and reduced DNA and protein synthesis), but on the other processes that induce a senescence-like phenotype (infiltration of inflammatory cells, DNA damage, and reduced proliferation). Importantly, chronic hypoxia also reduces the expression of the anti-aging proteins klotho and Sirt6, a mechanism that is evolutionary conserved between mice and humans. Taken together, we uncover that predetermined aging during fetal development is a key event in chronic hypoxia, establishing a solid foundation for Barker's hypothesis of fetal programming of adult diseases. This phenotype is associated with a characteristic biomarker profile in tissue and serum samples, exploitable for detecting and targeting accelerated aging in chronic hypoxic human diseases.

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.

Contemporary biomedical engineering perspective on volitional evolution for human radiotolerance enhancement beyond low-earth orbit

A primary objective of the National Aeronautics and Space Administration (NASA) is expansion of humankind's presence outside low-Earth orbit, culminating in permanent interplanetary travel and habitation. Having no inherent means of physiological detection or protection against ionizing radiation, humans incur capricious risk when journeying beyond low-Earth orbit for long periods. NASA has made large investments to analyze pathologies from space radiation exposure, emphasizing the importance of characterizing radiation's physiological effects. Because natural evolution would require many generations to confer resistance against space radiation, immediately pragmatic approaches should be considered. Volitional evolution, defined as humans steering their own heredity, may inevitably retrofit the genome to mitigate resultant pathologies from space radiation exposure. Recently, uniquely radioprotective genes have been identified, conferring local or systemic radiotolerance when overexpressed in vitro and in vivo. Aiding in this process, the CRISPR/Cas9 technique is an inexpensive and reproducible instrument capable of making limited additions and deletions to the genome. Although cohorts can be identified and engineered to protect against radiation, alternative and supplemental strategies should be seriously considered. Advanced propulsion and mild synthetic torpor are perhaps the most likely to be integrated. Interfacing artificial intelligence with genetic engineering using predefined boundary conditions may enable the computational modeling of otherwise overly complex biological networks. The ethical context and boundaries of introducing genetically pioneered humans are considered.

Uteroplacental nutrient flux and evidence for metabolic reprogramming during sustained hypoxemia

Gestational hypoxemia is often associated with reduced birth weight, yet how hypoxemia controls uteroplacental nutrient metabolism and supply to the fetus is unclear. This study tested the effects of maternal hypoxemia (HOX) between 0.8 and 0.9 gestation on uteroplacental nutrient metabolism and flux to the fetus in pregnant sheep. Despite hypoxemia, uteroplacental and fetal oxygen utilization and net glucose and lactate uptake rates were similar in HOX (n = 11) compared to CON (n = 7) groups. HOX fetuses had increased lactate and pyruvate concentrations and increased net pyruvate output to the utero-placenta. In the HOX group, uteroplacental flux of alanine to the fetus was decreased, as was glutamate flux from the fetus. HOX fetuses had increased alanine and decreased aspartate, serine, and glutamate concentrations. In HOX placental tissue, we identified hypoxic responses that should increase mitochondrial efficiency (decreased SDHB, increased COX4I2) and increase lactate production from pyruvate (increased LDHA protein and LDH activity, decreased LDHB and MPC2), both resembling metabolic reprogramming, but with evidence for decreased (PFK1, PKM2), rather than increased, glycolysis and AMPK phosphorylation. This supports a fetal-uteroplacental shuttle during sustained hypoxemia whereby uteroplacental tissues produce lactate as fuel for the fetus using pyruvate released from the fetus, rather than pyruvate produced from glucose in the placenta, given the absence of increased uteroplacental glucose uptake and glycolytic gene activation. Together, these results provide new mechanisms for how hypoxemia, independent of AMPK activation, regulates uteroplacental metabolism and nutrient allocation to the fetus, which allow the fetus to defend its oxidative metabolism and growth.

Blood pressure and hypertensive disorders of pregnancy at high altitude: a systematic review and meta-analysis

OBJECTIVE

Exposure to high altitude (≥2500 m) is associated with increased arterial blood pressure. During pregnancy, even a mild elevation of maternal blood pressure is associated with reduced birthweight and increased prevalence of pregnancy complications. This study aimed to systematically assess the impact of altitude on maternal blood pressure at term and on the prevalence of hypertensive disorders of pregnancy.

DATA SOURCES

PubMed, Ovid Embase, Cochrane Library, Medline, Web of Science, and ClinicalTrials.gov were searched (inception to November 11, 2020).

STUDY APPRAISAL AND SYNTHESIS METHODS

Observational, cohort, or case-control studies were included if they reported a high-altitude and appropriate control pregnant population. Studies published >50 years ago were excluded; 2 reviewers independently assessed articles for eligibility and risk of bias.

RESULTS

At high altitude, maternal systolic and diastolic blood pressure at term was higher than at low altitude (4.8±1.6 mm Hg; P<.001; 4.0±0.8 mm Hg; P<.001, respectively). Hypertensive disorders of pregnancy were more common at high altitude (odds ratio, 1.31 [1.03-1.65]; P<.05). The prevalence of gestational hypertension was nearly twice as high at high altitude (odds ratio, 1.92 [1.15-3.22]; P<.05) but the prevalence of preeclampsia was half as high (odds ratio, 0.57 [0.46-0.70]; P<.001). The likelihood of stillbirth was increased by 63% in pregnancies at high altitude compared with low altitude (odds ratio, 1.63 [1.12-2.35]; P<.01).

CONCLUSION

Maternal blood pressure is higher at term in pregnancies at high altitude than low altitude, accompanied with an increased risk of gestational hypertension but not preeclampsia. Risk of stillbirth at high altitude is also increased. With a growing population residing at high altitude worldwide, it is essential to clearly define the associated risk of adverse pregnancy outcomes.

Mechanisms linking hypoxia to phosphorylation of insulin-like growth factor binding protein-1 in baboon fetuses with intrauterine growth restriction and in cell culture

Hypoxia increases fetal hepatic insulin-like growth factor binding protein-1 (IGFBP-1) phosphorylation mediated by mechanistic target of rapamycin (mTOR) inhibition. Whether maternal nutrient restriction (MNR) causes fetal hypoxia remains unclear. We used fetal liver from a baboon (Papio sp.) model of intrauterine growth restriction due to MNR (70% global diet of Control) and liver hepatocellular carcinoma (HepG2) cells as a model for human fetal hepatocytes and tested the hypothesis that mTOR-mediated IGFBP-1 hyperphosphorylation in response to hypoxia requires hypoxia-inducible factor-1α (HIF-1α) and regulated in development and DNA-damage responses-1 (REDD-1) signaling. Western blotting (n = 6) and immunohistochemistry (n = 3) using fetal liver indicated greater expression of HIF-1α, REDD-1 as well as erythropoietin and its receptor, and vascular endothelial growth factor at GD120 (GD185 term) in MNR versus Control. Moreover, treatment of HepG2 cells with hypoxia (1% pO₂ ) (n = 3) induced REDD-1, inhibited mTOR complex-1 (mTORC1) activity and increased IGFBP-1 secretion/phosphorylation (Ser101/Ser119/Ser169). HIF-1α inhibition by echinomycin or small interfering RNA silencing prevented the hypoxia-mediated inhibition of mTORC1 and induction of IGFBP-1 secretion/phosphorylation. dimethyloxaloylglycine (DMOG) induced HIF-1α and also REDD-1 expression, inhibited mTORC1 and increased IGFBP-1 secretion/phosphorylation. Induction of HIF-1α (DMOG) and REDD-1 by Compound 3 inhibited mTORC1, increased IGFBP-1 secretion/ phosphorylation and protein kinase PKCα expression. Together, our data demonstrate that HIF-1α induction, increased REDD-1 expression and mTORC1 inhibition represent the mechanistic link between hypoxia and increased IGFBP-1 secretion/phosphorylation. We propose that maternal undernutrition limits fetal oxygen delivery, as demonstrated by increased fetal liver expression of hypoxia-responsive proteins in baboon MNR. These findings have important implications for our understanding of the pathophysiology of restricted fetal growth.

Intrauterine Hypoxia and Epigenetic Programming in Lung Development and Disease

Clinically, intrauterine hypoxia is the foremost cause of perinatal morbidity and developmental plasticity in the fetus and newborn infant. Under hypoxia, deviations occur in the lung cell epigenome. Epigenetic mechanisms (e.g., DNA methylation, histone modification, and miRNA expression) control phenotypic programming and are associated with physiological responses and the risk of developmental disorders, such as bronchopulmonary dysplasia. This developmental disorder is the most frequent chronic pulmonary complication in preterm labor. The pathogenesis of this disease involves many factors, including aberrant oxygen conditions and mechanical ventilation-mediated lung injury, infection/inflammation, and epigenetic/genetic risk factors. This review is focused on various aspects related to intrauterine hypoxia and epigenetic programming in lung development and disease, summarizes our current knowledge of hypoxia-induced epigenetic programming and discusses potential therapeutic interventions for lung disease.

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.

Placental hypoxia: What have we learnt from small animal models?

Intrauterine hypoxia is a feature of pregnancy complications, both at high altitude and sea level. To understand the placental response to reduced oxygen availability, small animal models of maternal inhalation hypoxia (MIH) or reduced uterine perfusion pressure (RUPP) may be utilised. The aim of this review was to compare the findings of those studies to identify the role of oxygen availability in adapting placental structural and functional phenotypes in relation to fetal outcome. It also sought to explore the evidence for the involvement of particular genes and protein signalling pathways in the placenta in mediating hypoxia driven alterations. The data available demonstrate that both MIH and RUPP can induce placental hypoxia, which affects placental structure and vascularity, as well as glucose, amino acid, calcium and possibly lipid transport capacity. In addition, changes have been observed in HIF, VEGF, insulin/IGF2, AMPK, mTOR, PI3K and PPARγ signalling, which may be key in linking together observed phenotypes under conditions of placental hypoxia. Many different manipulations have been examined, with varied outcomes depending on the intensity, timing and duration of the insult. Some manipulations have detrimental effects on placental phenotype, viability and fetal growth, whereas in others, the placenta appears to adapt to uphold fetal growth despite the challenge of low oxygen. Together these data suggest a complex response of the placenta to reduced oxygen availability, which links to changes in fetal outcomes. However, further work is required to explore the role of fetal sex, altered maternal physiology and placental molecular mechanisms to fully understand placental responses to hypoxia and their relevance for pregnancy outcome.

An MRI approach to assess placental function in healthy humans and sheep

KEY POINTS

Human placental function is evaluated using non-invasive Doppler ultrasound of umbilical and uterine artery pulsatility indices as measures of resistance in placental vascular beds, while measurement of placental oxygen consumption ( V O 2 ) is only possible during Caesarean delivery. This study shows the feasibility of using magnetic resonance imaging (MRI) in utero to measure blood flow and oxygen content in uterine and umbilical vessels to calculate oxygen delivery to and V O 2 by the gravid uterus, uteroplacenta and fetus. Normal late gestational human uteroplacental V O 2 by MRI was ∼4 ml min^-1  kg^-1 fetal weight, which was similar to our MRI measurements in sheep and to those previously measured using invasive techniques. Our MRI approach can quantify uteroplacental V O 2 , which involves the quantification of maternal- and fetal-placental blood flows, fetal oxygen delivery and V O 2 , and the oxygen gradient between uterine- and umbilical-venous blood, providing a comprehensive assessment of placental function with clinical potential.

ABSTRACT

It has not been feasible to perform routine clinical measurement of human placental oxygen consumption ( V O 2 ) and in vitro studies do not reflect true metabolism in utero. Here we propose an MRI method to non-invasively quantify in utero placental and fetal oxygen delivery ( D O 2 ) and V O 2 in healthy humans and sheep. Women (n = 20) and Merino sheep (n = 10; 23 sets of measurements) with singleton pregnancies underwent an MRI in late gestation (36 ± 2 weeks and 128 ± 9 days, respectively; mean ± SD). Blood flow (phase-contrast) and oxygen content (T1 and T2 relaxometry) were measured in the major uterine- and umbilical-placental vessels, allowing calculation of uteroplacental and fetal D O 2 and V O 2 . Maternal D O 2 (ml min^-1  kg^-1 fetus) to the gravid uterus was similar in humans and sheep (human = 54 ± 15, sheep = 53 ± 21, P = 0.854), while fetal D O 2 (human = 25 ± 4, sheep = 22 ± 5, P = 0.049) was slightly lower in sheep. Uteroplacental and fetal V O 2 (ml min^-1  kg^-1 fetus; uteroplacental: human = 4.1 ± 1.5, sheep = 3.5 ± 1.9, P = 0.281; fetus: human = 6.8 ± 1.3, sheep = 7.2 ± 1.7, P = 0.426) were similar between species. Late gestational uteroplacental:fetal V O 2 ratio did not change with age (human, P = 0.256; sheep, P = 0.121). Human umbilical blood flow (ml min^-1  kg^-1 fetus) decreased with advancing age (P = 0.008), while fetal V O 2 was preserved through an increase in oxygen extraction (P = 0.046). By contrast, sheep fetal V O 2 was preserved through stable umbilical flow (ml min^-1  kg^-1 ; P = 0.443) and oxygen extraction (P = 0.582). MRI derived measurements of uteroplacental and fetal V O 2 between humans and sheep were similar and in keeping with prior data obtained using invasive techniques. Taken together, these data confirm the reliability of our approach, which offers a novel clinical 'placental function test'.

Impact of resveratrol-mediated increase in uterine artery blood flow on fetal haemodynamics, blood pressure and oxygenation in sheep

NEW FINDINGS

What is the central question of this study? Uterine artery blood flow helps to maintain fetal oxygen and nutrient delivery. We investigated the effects of increased uterine artery blood flow mediated by resveratrol on fetal growth, haemodynamics, blood pressure regulation and oxygenation in pregnant sheep. What is the main finding and its importance? Fetuses from resveratrol-treated ewes were significantly larger and exhibited a haemodynamic profile that might promote peripheral growth. Absolute uterine artery blood flow was positively correlated with umbilical vein oxygen saturation, absolute fetal oxygen delivery and fetal growth. Increasing uterine artery blood flow with compounds such as resveratrol might have clinical significance for pregnancy conditions in which fetal growth and oxygenation are compromised.

ABSTRACT

High placental vascular resistance hinders uterine artery (UtA) blood flow and fetal substrate delivery. In the same group of animals as the present study, we have previously shown that resveratrol (RSV) increases UtA blood flow, fetal weight and oxygenation in an ovine model of human pregnancy. However, the mechanisms behind changes in growth and the effects of increases in UtA blood flow on fetal circulatory physiology have yet to be investigated. Twin-bearing ewes received s.c. vehicle (VEH, n = 5) or RSV (n = 6) delivery systems at 113 days of gestation (term = 150 days). Magnetic resonance imaging was performed at 123-124 days to quantify fetal volume, blood flow and oxygen saturation of major fetal vessels. At 128 days, i.v. infusions of sodium nitroprusside and phenylephrine were administered to study the vascular tone of the fetal descending aorta. Maternal RSV increased fetal body volume (P = 0.0075) and weight (P = 0.0358), with no change in brain volume or brain weight. There was a positive relationship between absolute UtA blood flow and umbilical vein oxygen saturation, absolute fetal oxygen delivery and combined fetal twin volume (all P ≤ 0.05). There were no differences between groups in fetal haemodynamics or blood pressure regulation except for higher blood flow to the lower body in RSV fetuses (P = 0.0170). The observed increase in fetal weight might be helpful in pregnancy conditions in which fetal growth and oxygen delivery are compromised. Further preclinical investigations on the mechanism(s) accounting for these changes and the potential to improve growth in complicated pregnancies are warranted.

Hypoxia and Mitochondrial Dysfunction in Pregnancy Complications

Hypoxia is a common and severe stress to an organism's homeostatic mechanisms, and hypoxia during gestation is associated with significantly increased incidence of maternal complications of preeclampsia, adversely impacting on the fetal development and subsequent risk for cardiovascular and metabolic disease. Human and animal studies have revealed a causative role of increased uterine vascular resistance and placental hypoxia in preeclampsia and fetal/intrauterine growth restriction (FGR/IUGR) associated with gestational hypoxia. Gestational hypoxia has a major effect on mitochondria of uteroplacental cells to overproduce reactive oxygen species (ROS), leading to oxidative stress. Excess mitochondrial ROS in turn cause uteroplacental dysfunction by damaging cellular macromolecules, which underlies the pathogenesis of preeclampsia and FGR. In this article, we review the current understanding of hypoxia-induced mitochondrial ROS and their role in placental dysfunction and the pathogenesis of pregnancy complications. In addition, therapeutic approaches selectively targeting mitochondrial ROS in the placental cells are discussed.

Fetuin-A is a HIF target that safeguards tissue integrity during hypoxic stress

Intrauterine growth restriction (IUGR) is associated with reduced kidney size at birth, accelerated renal function decline, and increased risk for chronic kidney and cardiovascular diseases in adults. Precise mechanisms underlying fetal programming of adult diseases remain largely elusive and warrant extensive investigation. Setting up a mouse model of hypoxia-induced IUGR, fetal adaptations at mRNA, protein and cellular levels, and their long-term functional consequences are characterized, using the kidney as a readout. Here, we identify fetuin-A as an evolutionary conserved HIF target gene, and further investigate its role using fetuin-A KO animals and an adult model of ischemia-reperfusion injury. Beyond its role as systemic calcification inhibitor, fetuin-A emerges as a multifaceted protective factor that locally counteracts calcification, modulates macrophage polarization, and attenuates inflammation and fibrosis, thus preserving kidney function. Our study paves the way to therapeutic approaches mitigating mineral stress-induced inflammation and damage, principally applicable to all soft tissues.

Molecular mechanisms governing offspring metabolic programming in rodent models of in utero stress

The results of different human epidemiological datasets provided the impetus to introduce the now commonly accepted theory coined as 'developmental programming', whereby the presence of a stressor during gestation predisposes the growing fetus to develop diseases, such as metabolic dysfunction in later postnatal life. However, in a clinical setting, human lifespan and inaccessibility to tissue for analysis are major limitations to study the molecular mechanisms governing developmental programming. Subsequently, studies using animal models have proved indispensable to the identification of key molecular pathways and epigenetic mechanisms that are dysregulated in metabolic organs of the fetus and adult programmed due to an adverse gestational environment. Rodents such as mice and rats are the most used experimental animals in the study of developmental programming. This review summarises the molecular pathways and epigenetic mechanisms influencing alterations in metabolic tissues of rodent offspring exposed to in utero stress and subsequently programmed for metabolic dysfunction. By comparing molecular mechanisms in a variety of rodent models of in utero stress, we hope to summarise common themes and pathways governing later metabolic dysfunction in the offspring whilst identifying reasons for incongruencies between models so to inform future work. With the continued use and refinement of such models of developmental programming, the scientific community may gain the knowledge required for the targeted treatment of metabolic diseases that have intrauterine origins.

Long term hypoxia during gestation alters perirenal adipose tissue gene expression in the lamb

We previously reported that following long-term hypoxia (LTH), the ovine foetus exhibits enhanced expression of brown/beige adipose genes. This study was designed to determine if these changes are preserved after birth. Pregnant ewes were divided among three groups, 1) Control, sea level, 2) LTH, high altitude (3,820 m, LTH-HA) from ~ day 40 of gestation through ~14 days post-delivery and 3) LTH from ⁓ day 40 through day 137 of gestation then returned to the laboratory where atory reduced maternal PO₂ was maintained by nitrogen infusion. Following delivery, lambs remained at sea level (LTH-SL). Perirenal adipose tissue was collected at ~day 14, and qRT-PCR was used to quantify mRNA. Uncoupling protein 1 (UCP-1), PPAR gamma coactivator 1 (PGC1α), and deiodinase-2 (DIO2) mRNA levels were significantly lower in both LTH groups while PR domain containing 16 (PRDM16) levels did not differ. Peroxisome proliferator-activated receptor (PPARγ) was maintained in the LTH-HA group and significantly increased in the LTH-SL group, compared to control. Unlike our previous LTH foetal studies, the brown/beige fat phenotype was rapidly lost by day 14 postpartum compared to control, while PPARγ was maintained. This loss of the brown fat phenotype may promote obesity due to decreased energy expenditure, favouring fat deposition.

Evaluation of Linear Growth at Higher Altitudes

IMPORTANCE

Irrespective of their genetic makeup, children living in an ideal home environment that supports healthy growth have similar growth potential. However, whether this potential is true for children residing at higher altitudes remains unknown.

OBJECTIVE

To investigate whether altitude is associated with increased risk of linear growth faltering and evaluate the implications associated with the use of the 2006 World Health Organization growth standards, which have not been validated for populations residing 1500 m above sea level.

DESIGN, SETTINGS, AND PARTICIPANTS

Analysis of 133 nationally representative demographic and health cross-sectional surveys administered in 59 low- and middle-income countries using local polynomial and multivariate regression was conducted. A total of 964 299 height records from 96 552 clusters at altitudes ranging from -372 to 5951 m above sea level were included. Demographic and Health Surveys were conducted between 1992 and 2018.

EXPOSURES

Residence at higher altitudes, above and below 1500 m above sea level, and in ideal home environments (eg, access to safe water, sanitation, and health care).

MAIN OUTCOMES AND MEASURES

The primary outcome was child linear growth deficits expressed in length-for-age/height-for-age z scores (HAZ). Associations between altitude and height among all children and those residing in ideal home environments were assessed. Child growth trajectories above and below 1500 m above sea level were compared and the altitude-mediated height deficits were estimated using multivariable linear regression.

RESULTS

In 2010, a total of 842 million people in the global population (approximately 12%) lived 1500 m above sea level or higher, with 67% in Asia and Africa. Eleven percent of the sample was children who resided 1500 m above sea level or higher. These children were born at shorter length and remained on a lower growth trajectory than children residing in areas less than 1500 m above sea level. The negative association between altitude and HAZ was approximately linear through most part of the altitude distribution, indicating no clear threshold for an abrupt decrease in HAZ. A 1000-m above sea level increase in altitude was associated with a 0.163-unit (95% CI, -0.205 to -0.120 units) decrease in HAZ after adjusting for common risk factors using multivariable linear regressions. The HAZ distribution of children residing in ideal home environments was similar to the 2006 World Health Organization HAZ distribution, but only up to 500 m above sea level.

CONCLUSIONS AND RELEVANCE

The findings of this study suggest that residing at a higher altitude may be associated with child growth slowing even for children living in ideal home environments. Interventions addressing altitude-mediated growth restrictions during pregnancy and early childhood should be identified and implemented.

Gestational Hypoxia Inhibits Pregnancy-Induced Upregulation of Ca2+ Sparks and Spontaneous Transient Outward Currents in Uterine Arteries Via Heightened Endoplasmic Reticulum/Oxidative Stress

Hypoxia during pregnancy profoundly affects uterine vascular adaptation and increases the risk of pregnancy complications, including preeclampsia and fetal intrauterine growth restriction. We recently demonstrated that increases in Ca2+ sparks and spontaneous transient outward currents (STOCs) played an essential role in pregnancy-induced uterine vascular adaptation. In the present study, we hypothesize that gestational hypoxia suppresses Ca2+ sparks/STOCs coupling leading to increased uterine vascular tone via enhanced endoplasmic reticulum (ER)/oxidative stress. Uterine arteries were obtained from nonpregnant and near-term pregnant sheep residing in low altitude or acclimatizing to high-altitude (3801 m) hypoxia for ≈110 days. High-altitude hypoxia suppressed pregnancy-induced upregulation of RyR1 and RyR2 (ryanodine receptor 1 and 2) protein abundance, Ca2+ sparks, and STOCs in uterine arteries. Inhibition of Ca2+ sparks/STOCs with the RyR inhibitor ryanodine significantly increased pressure-dependent myogenic tone in uterine arteries from low-altitude normoxic pregnant animals but not those from high-altitude hypoxic pregnant animals. Gestational hypoxia significantly increased ER/oxidative stress in uterine arteries. Of importance, the hypoxia-mediated suppression of Ca2+ sparks/STOCs and increase in myogenic tone in uterine arteries of pregnant animals were reversed by inhibiting ER/oxidative stress. Of great interest, the impaired sex hormonal regulation of STOCs in high-altitude animals was annulled by scavenging reactive oxygen species but not by inhibiting ER stress. Together, the findings reveal the differential mechanisms of ER and oxidative stresses in suppressing Ca2+ sparks/STOCs and increasing myogenic tone of uterine arteries in hypoxia during gestation, providing new insights into the understanding of pregnancy complications associated with hypoxia.