Impacts of the Plateau Environment on the Gut Microbiota and Blood Clinical Indexes in Han and Tibetan Individuals

Notoginsenoside R1 treatment facilitated Nrf2 nuclear translocation to suppress ferroptosis via Keap1/Nrf2 signaling pathway to alleviated high-altitude myocardial injury

High-altitude myocardial injury (HAMI) represents a critical form of altitude illness for which effective drug therapies are generally lacking. Notoginsenoside R1, a prominent constituent derived from Panax notoginseng, has demonstrated various cardioprotective properties in models of myocardial ischemia/reperfusion injury, sepsis-induced cardiomyopathy, cardiac fibrosis, and myocardial injury. The potential utility of notoginsenoside R1 in the management of HAMI warrants prompt investigation. Following the successful construction of a HAMI model, a series of experimental analyses were conducted to assess the effects of notoginsenoside R1 at dosages of 50 mg/Kg and 100 mg/Kg. The results indicated that notoginsenoside R1 exhibited protective effects against hypoxic injury by reducing levels of CK, CK-MB, LDH, and BNP, leading to improved cardiac function and decreased incidence of arrhythmias. Furthermore, notoginsenoside R1 was found to enhance Nrf2 nuclear translocation, subsequently regulating the SLC7A11/GPX4/HO-1 pathway and iron metabolism to mitigate ferroptosis, thereby mitigating cardiac inflammation and oxidative stress induced by high-altitude conditions. In addition, the application of ML385 has confirmed the involvement of Nrf2 nuclear translocation in the therapeutic approach to HAMI. Collectively, the advantageous impacts of notoginsenoside R1 on HAMI have been linked to the suppression of ferroptosis via Nrf2 nuclear translocation signaling.

Characterizations of gut bacteriome, mycobiome, and virome of healthy individuals living in sea-level and high-altitude areas

BACKGROUND

The contribution of gut microbiota to human high-altitude adaptation remains inadequately understood.

METHODS

Here a comparative analysis of gut microbiota was conducted between healthy individuals living at sea level and high altitude using deep whole-metagenome shotgun sequencing, to investigate the adaptive mechanisms of gut microbiota in plateau inhabitants.

RESULTS

The results showed the gut bacteriomes in high-altitude individuals exhibited greater within-sample diversity and significant alterations in both bacterial compositional and functional profiles when compared to those of sea-level individuals, indicating the potential selection of unique bacteria associated with high-altitude environments. The strain-level investigation revealed enrichment of Collinsella aerofaciens and Akkermansia muciniphila in high-altitude populations. The characteristics of gut virome and gut mycobiome were also investigated. Compared to sea-level subjects, high-altitude subjects exhibited a greater diversity in their gut virome, with an increased number of viral operational taxonomic units (vOTUs) and unique annotated genes. Finally, correlation analyses revealed 819 significant correlations between 42 bacterial species and 375 vOTUs, while no significant correlations were observed between bacteria and fungi or between fungi and viruses.

CONCLUSION

The findings have significantly contributed to an enhanced comprehension of the mechanisms underlying the high-altitude geographic adaptation of the human gut microbiota.

Lactobacillus delbrueckii subsp. bulgaricus Alleviates Acute Injury in Hypoxic Mice

Acute mountain sickness (AMS) is a common ailment in high-altitude areas caused by the body's inadequate adaptation to low-pressure, low-oxygen environments, leading to organ edema, oxidative stress, and impaired intestinal barrier function. The gastrointestinal tract, being the first to be affected by ischemia and hypoxia, is highly susceptible to injury. This study investigates the role of Lactobacillus delbrueckii subsp. bulgaricus in alleviating acute hypoxic-induced intestinal and tissue damage from the perspective of daily consumed lactic acid bacteria. An acute hypoxia mouse model was established to evaluate tissue injury, oxidative stress, inflammatory responses, and intestinal barrier function in various groups of mice. The results indicate that strain 4L3 significantly mitigated brain and lung edema caused by hypoxia, improved colonic tissue damage, and effectively increased the content of tight junction proteins in the ileum, reducing ileal permeability and alleviating mechanical barrier damage in the intestines due to acute hypoxia. Additionally, 4L3 helped to rebalance the intestinal microbiota. In summary, this study found that Lactobacillus delbrueckii subsp. bulgaricus strain 4L3 could alleviate acute intestinal damage caused by hypoxia, thereby reducing hypoxic stress. This suggests that probiotic lactic acid bacteria that exert beneficial effects in the intestines may alleviate acute injury under hypoxic conditions in mice, offering new insights for the prevention and treatment of AMS.

Impact of high-altitude acclimatization and de-acclimatization on the intestinal microbiota of rats in a natural high-altitude environment

Introduction

Intestinal microorganisms play an important role in the health of both humans and animals, with their composition being influenced by changes in the host's environment.

Methods

We evaluated the longitudinal changes in the fecal microbial community of rats at different altitudes across various time points. Rats were airlifted to high altitude (3,650 m) and acclimatized for 42 days (HAC), before being by airlifted back to low altitude (500 m) and de-acclimatized for 28 days (HADA); meanwhile, the control group included rats living at low altitude (500 m; LA). We investigated changes in the gut microbiota at 12 time points during high-altitude acclimatization and de-acclimatization, employing 16S rRNA gene sequencing technology alongside physiological indices, such as weight and daily autonomous activity time.

Results

A significant increase in the Chao1 index was observed on day 14 in the HAC and HADA groups compared to that in the LA group, indicating clear differences in species richness. Moreover, the principal coordinate analysis revealed that the bacterial community structures of HAC and HADA differed from those in LA. Long-term high-altitude acclimatization and de- acclimatization resulted in the reduced abundance of the probiotic Lactobacillus. Altitude and age significantly influenced intestinal microbiota composition, with changes in ambient oxygen content and atmospheric partial pressure being considered key causal factors of altitude-dependent alterations in microbiota composition. High-altitude may be linked to an increase in anaerobic bacterial abundance and a decrease in non-anaerobic bacterial abundance.

Discussion

In this study, the hypobaric hypoxic conditions at high-altitude increased the abundance of anaerobes, while reducing the abundance of probiotics; these changes in bacterial community structure may, ultimately, affect host health. Overall, gaining a comprehensive understanding of the intestinal microbiota alterations during high-altitude acclimatization and de-acclimatization is essential for the development of effective prevention and treatment strategies to better protect the health of individuals traveling between high- and low-altitude areas.

Cold exposure, gut microbiota and health implications: A narrative review

Temperature has been recognized as an important environmental factor affecting the composition and function of gut microbiota (GM). Although research on high-temperature impacts has been well studied, knowledge about the effect of cold exposure on GM remains limited. This narrative review aims to synthesize the latest scientific findings on the impact of cold exposure on mammalian GM, and its potential health implications. Chronic cold exposure could disrupt the α-diversity and the composition of GM in both experimental animals and wild-living hosts. Meanwhile, cold exposure could impact gut microbial metabolites, such as short-chain fatty acids. We also discussed plausible biological pathways and mechanisms by which cold-induced changes may impact host health, including metabolic homeostasis, fitness and thermogenesis, through the microbiota-gut-brain axis. Intriguingly, alterations in GM may provide a tool for favorably modulating the host response to the cold temperature. Finally, current challenges and future perspectives are discussed, emphasizing the need for translational research in humans. GM could be manipulated by utilizing nutritional strategies, such as probiotics and prebiotics, to deal with cold-related health issues and enhance well-being in populations living or working in cold environments.

Comparative analysis of the vaginal bacteriome and virome in healthy women living in high-altitude and sea-level areas

The vaginal microbiota plays an important role in the health of the female reproductive tract and is closely associated with various pregnancy outcomes and sexually transmitted diseases. Plenty of internal and external factors have strong influence on the changes in a woman's vaginal microbiome. However, the effect of a high-altitude on female vaginal microbiota has not been described. In this study, we characterized the vaginal bacteriome and virome of 13 and 34 healthy women living in high-altitude and sea-level areas, using whole-metagenome shotgun sequencing of their vaginal mucus samples. The results revealed that the vaginal bacteriomes of high-altitude individuals are featured by a significant increase of species diversity, depletion of Lactobacillus crispatus, and more abundant of some anaerobic bacteria, such as Chlamydia trachomatis, Mageeibacillus indolicus, Dialister micraerophilus, and Sneathia amnii). In addition, the vagina samples of sea-level subjects harbor more Lactobacillus strains, whereas the anaerobic bacteroidetes strains mostly appeared in high-altitude subjects. Identified and assembled 191 virus operational taxonomic units (vOTUs), there were significant differences in the abundance of 107 vOTUs between the two groups. Together, the results of this study raised the understanding of bacteriome and virome in the vagina of women at different elevations, and demonstrated that the vaginal microbiome is related to the high-altitude geographic adaptation.

Stachyose in combination with L. rhamnosus GG ameliorates acute hypobaric hypoxia-induced intestinal barrier dysfunction through alleviating inflammatory response and oxidative stress

High altitude is closely related to intestinal mucosal damage and intestinal microbiota imbalance, and there is currently no effective prevention and treatment measures. In this study, the effects of stachyose (STA), L. rhamnosus GG (LGG) and their combination on inflammatory response, oxidatve stress and intestinal barrier function in mice exposed to acute hypobaric hypoxia were investigated. Our results indicated the combination of STA and LGG could more effectively regulate intestinal microbiota disorders caused by hypobaric hypoxia than STA or LGG alone. When mice were administered with STA + LGG, the content of short chain fatty acids (SCFAs) especially butyric acid significantly increased, which helped intestinal cells to form tight connections, improve the level of anti-inflammatory cytokine (TGF-β) and antioxidant enzymes (SOD, CAT, GSH-Px), and decrease the expression of pro-inlammatory cytokines and hypoxia-inducing factors (IFN-γ, IL-1β, IL-6, TNF-α and HIF-1α), thereby enhance the strong intestinal barrier function. Furthermore, the synbiotics significantly reduced the ratio of Firmicutes to Bacteroidetes, while significantly increased the relative abundance of Rikenella, Bacteroides, Odoribacter, Ruminiclostridium_5 and Gordonibacter, which were correlated with production of SCFAs and anti-inflammatory role. Correlation analysis showed that the protective effect of synbiotics on intestinal barrier function was associated with its anti-inflammatory activity and antioxidant capacity. It provided a strong foundation for further research on the role of STA and LGG in maintaining normal intestinal function at high altitude. Our study has identified and demonstrated a new synbiotic that may be one of the ideal intervention measures for preventing and treating intestinal dysfunction at high altitude.

Meta-analysis identifying gut microbial biomarkers of Qinghai-Tibet Plateau populations and the functionality of microbiota-derived butyrate in high-altitude adaptation

The extreme environmental conditions of a plateau seriously threaten human health. The relationship between gut microbiota and human health at high altitudes has been extensively investigated. However, no universal gut microbiota biomarkers have been identified in the plateau population, limiting research into gut microbiota and high-altitude adaptation. 668 16s rRNA samples were analyzed using meta-analysis to reduce batch effects and uncover microbiota biomarkers in the plateau population. Furthermore, the robustness of these biomarkers was validated. Mendelian randomization (MR) results indicated that Tibetan gut microbiota may mediate a reduced erythropoietic response. Functional analysis and qPCR revealed that butyrate may be a functional metabolite in high-altitude adaptation. A high-altitude rat model showed that butyrate reduced intestinal damage caused by high altitudes. According to cell experiments, butyrate may downregulate hypoxia-inducible factor-1α (HIF-1α) expression and blunt cellular responses to hypoxic stress. Our research found universally applicable biomarkers and investigated their potential roles in promoting human health at high altitudes.

Research Progress on the Mechanism of Intestinal Barrier Damage and Drug Therapy in a High Altitude Environment

The plateau is a typical extreme environment with low temperature, low oxygen and high ultraviolet rays. The integrity of the intestinal barrier is the basis for the functioning of the intestine, which plays an important role in absorbing nutrients, maintaining the balance of intestinal flora, and blocking the invasion of toxins. Currently, there is increasing evidence that high altitude environment can enhance intestinal permeability and disrupt intestinal barrier integrity. This article mainly focuses on the regulation of the expression of HIF and tight junction proteins in the high altitude environment, which promotes the release of pro-inflammatory factors, especially the imbalance of intestinal flora caused by the high altitude environment. The mechanism of intestinal barrier damage and the drugs to protect the intestinal barrier are reviewed. Studying the mechanism of intestinal barrier damage in high altitude environment is not only conducive to understanding the mechanism of high altitude environment affecting intestinal barrier function, but also provides a more scientific medicine treatment method for intestinal damage caused by the special high altitude environment.

Coping with extremes: Alternations in diet, gut microbiota, and hepatic metabolic functions in a highland passerine

In wild animals, diet and gut microbiota interactions are critical moderators of metabolic functions and are highly contingent on habitat conditions. Challenged by the extreme conditions of high-altitude environments, the strategies implemented by highland animals to adjust their diet and gut microbial composition and modulate their metabolic substrates remain largely unexplored. By employing a typical human commensal species, the Eurasian tree sparrow (Passer montanus, ETS), as a model species, we studied the differences in diet, digestive tract morphology and enzyme activity, gut microbiota, and metabolic energy profiling between highland (the Qinghai-Tibet Plateau, QTP; 3230 m) and lowland (Shijiazhuang, Hebei; 80 m) populations. Our results showed that highland ETSs had enlarged digestive organs and longer small intestinal villi, while no differences in key digestive enzyme activities were observed between the two populations. The 18S rRNA sequencing results revealed that the dietary composition of highland ETSs were more animal-based and less plant-based than those of the lowland ones. Furthermore, 16S rRNA sequencing results suggested that the intestinal microbial communities were structurally segregated between populations. PICRUSt metagenome predictions further indicated that the expression patterns of microbial genes involved in material and energy metabolism, immune system and infection, and xenobiotic biodegradation were strikingly different between the two populations. Analysis of liver metabolomics revealed significant metabolic differences between highland and lowland ETSs in terms of substrate utilization, as well as distinct sex-specific alterations in glycerophospholipids. Furthermore, the interplay between diet, liver metabolism, and gut microbiota suggests a dietary shift resulting in corresponding changes in gut microbiota and metabolic functions. Our findings indicate that highland ETSs have evolved to optimize digestion and absorption, rely on more protein-rich foods, and possess gut microbiota tailored to their dietary composition, likely adaptive physiological and ecological strategies adopted to cope with extreme highland environments.

Structural variants involved in high-altitude adaptation detected using single-molecule long-read sequencing

Structural variants (SVs), accounting for a larger fraction of the genome than SNPs/InDels, are an important pool of genetic variation, enabling environmental adaptations. Here, we perform long-read sequencing data of 320 Tibetan and Han samples and show that SVs are highly involved in high-altitude adaptation. We expand the landscape of global SVs, apply robust models of selection and population differentiation combining SVs, SNPs and InDels, and use epigenomic analyses to predict enhancers, target genes and biological functions. We reveal diverse Tibetan-specific SVs affecting the regulatory circuitry of biological functions, including the hypoxia response, energy metabolism and pulmonary function. We find a Tibetan-specific deletion disrupts a super-enhancer and downregulates EPAS1 using enhancer reporter, cellular knock-out and DNA pull-down assays. Our study expands the global SV landscape, reveals the role of gene-regulatory circuitry rewiring in human adaptation, and illustrates the diverse functional roles of SVs in human biology.

Distinctive biochemistry profiles associated with hyperuricemia between Tibetans and Hans in China

Purpose

We sought to identify distinct risk factors for hyperuricemia in native Tibetan and immigrant Han populations in Tibet, China.

Methods

Three cohorts of male participants aged between 20 and 40 years were enrolled in this study. Biochemical parameters including serum uric acid (UA), fasting plasma glucose, insulin, lactate dehydrogenase (LDH), thyroxin, blood cell count, aminotransferase, and lipid profiles were analyzed. The association of risk factors with UA levels was evaluated using a multivariable line regression model. The effect of UA level on the biochemical parameters between the Hans and Tibetans was evaluated by two-way ANOVA.

Results

The prevalence of hyperuricemia (≥420 μmol/L) was 24.8% (62/250) in the Hans, similar to 23.8% (29/136) in the Tibetans. In the regression analysis, the risk factors that were significantly associated with UA in Hans did not apply to Tibetans. Tibetans had higher fasting insulin (P<0.05) and LDH (P<0.01) levels, in contrast with lower levels of triglycerides (P<0.05), total cholesterol (P<0.01), and low-density lipoprotein-cholesterol (P<0.01) than Hans in normal UA populations. Biochemistry analysis revealed lower albumin levels (P<0.001) and higher levels of all aminotransaminase and especially alkaline phosphatase (P<0.01) in Tibetans than in Hans in both populations. Compared with Hans, Tibetans had lower serum levels of urea, creatinine, and electrolytes in the normal UA population, which were further exacerbated in the high UA population. Tibetans had comparable white blood cell counts as Hans in both normal and high UA populations. In contrast, the red blood cell count and hemoglobin concentration were much lower in Tibetans than in Hans under high UA conditions.

Conclusions

The distinctive biochemistry between Tibetans and Hans may underlie the different etiologies of hyperuricemia in Tibet, China.

Structure and Metabolic Characteristics of Intestinal Microbiota in Tibetan and Han Populations of Qinghai-Tibet Plateau and Associated Influencing Factors

Residents of the Qinghai-Tibet Plateau might experience shifts in their gut microbiota composition as a result of the plateau environment. For example, high altitudes can increase the abundance of obligate anaerobic bacteria, decrease the number of aerobic bacteria and facultative anaerobic bacteria, increase probiotics, and decrease pathogenic bacteria. This study aimed to determine the structure and metabolic differences in intestinal microbial communities among the Tibetan and Han populations on the Qinghai-Xizang Plateau and shed light on the factors that influence the abundance of the microbial communities in the gut. The structural characteristics of intestinal microorganisms were detected from blood and fecal samples using 16S rRNA sequencing. Metabolic characteristics were detected using gas chromatography-time-of-flight mass spectrometry (GC-TOFMS). The influencing factors were analyzed using Spearman's correlation analysis. Bacteroides and Bifidobacterium were dominant in the intestinal tract of the Han population, while Bacteroides and Prevotella were dominant in that of the Tibetan population, with marked differences in Pseudomonas, Prevotella, and other genera. Ferulic acid and 4-methylcatechol were the main differential metabolites between the Tibetan and Han ethnic groups. This may be the reason for the different adaptability of Tibetan and Han nationalities to the plateau. Alanine aminotransferase and uric acid also have a high correlation with different bacteria and metabolites, which may play a role. These results reveal notable disparities in the compositions and metabolic characteristics of gut microbial communities in the Tibetan and Han people residing on the Qinghai-Tibet Plateau and may provide insights regarding the mechanism of plateau adaptability.

Oxygen enrichment protects against intestinal damage and gut microbiota disturbance in rats exposed to acute high-altitude hypoxia

Acute high-altitude hypoxia can lead to intestinal damage and changes in gut microbiota. Sustained and reliable oxygen enrichment can resist hypoxic damage at high altitude to a certain extent. However, it remains unclear whether oxygen enrichment can protect against gut damage and changes in intestinal flora caused by acute altitude hypoxia. For this study, eighteen male Sprague-Dawley rats were divided into three groups, control (NN), hypobaric hypoxic (HH), and oxygen-enriched (HO). The NN group was raised under normobaric normoxia, whereas the HH group was placed in a hypobaric hypoxic chamber simulating 7,000 m for 3 days. The HO group was exposed to oxygen-enriched air in the same hypobaric hypoxic chamber as the HH group for 12 h daily. Our findings indicate that an acute HH environment caused a fracture of the crypt structure, loss of epithelial cells, and reduction in goblet cells. Additionally, the structure and diversity of bacteria decreased in richness and evenness. The species composition at Phylum and Genus level was characterized by a higher ratio of Firmicutes and Bacteroides and an increased abundance of Lactobacillus with the abundance of Prevotellaceae_NK3B31_group decreased in the HH group. Interestingly, after oxygen enrichment intervention, the intestinal injury was significantly restrained. This was confirmed by an increase in the crypt depth, intact epithelial cell morphology, increased relative density of goblet cells, and higher evenness and richness of the gut microbiota, Bacteroidetes and Prevotellaceae as the main microbiota in the HO group. Finally, functional analysis showed significant differences between the different groups with respect to different metabolic pathways, including Amino acid metabolism, energy metabolism, and metabolism. In conclusion, this study verifies, for the first time, the positive effects of oxygen enrichment on gut structure and microbiota in animals experiencing acute hypobaric hypoxia.

Serum metabolomics of hyperbilirubinemia and hyperuricemia in the Tibetan plateau has unique characteristics

Few studies have provided data on the metabolomics characteristics of metabolic diseases such as hyperuricemia and hyperbilirubinemia in the Tibetan plateau. In the current study, we sought to investigate the serum metabolomics characteristics of hyperbilirubinemia and hyperuricemia in the Tibetan plateau, with the aim to provide a basis for further research on their pathogenesis, prevention, and treatment. The study participants were born in low-altitude areas below 1000 m and had no prior experience living in a high-altitude area before entering Golmud, Tibet (average elevation: 3000 m) and Yushu, Qinghai (average elevation: 4200 m). Thirty-four participants with hyperbilirubinemia (18 in Golmud and 16 in Yushu), 24 participants with hyperuricemia, and 22 healthy controls were enrolled. The serum samples of subjects were separated and then sent to a local tertiary hospital for biochemical examination. Serum widely targeted technology, based on the ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) platform, was used to detect serum metabolites and differential metabolites. Compared to the healthy controls, hyperbilirubinemia patients from Golmud showed 19 differential metabolites, hyperbilirubinemia patients from Yushu showed 12 differential metabolites, and hyperuricemia patients from Yushu showed 23 differential metabolites. Compared to the hyperbilirubinemia patients from Golmud that is at a low altitude, the Yushu groups had 33 different metabolites. Differential metabolites are primarily classified into amino acids and their derivatives, nucleotides and their derivatives, organic acids and their derivatives, and lipids/fatty acids. These are related to metabolic pathways such as caffeine metabolism, arachidonic acid metabolism, and tyrosine metabolism. Hyperbilirubinemia and hyperuricemia in the Tibetan plateau have unique serum metabolomics characteristics. Glycine derivatives and arachidonic acid and its derivatives were associated with plateau hyperbilirubinemia, and vanillic acid and pentadecafluorooctanoic acid were associated with plateau hyperuricemia.

Citrus tangerine pith extract alleviates hypoxia-induced ileum damage in mice by modulating intestinal microbiota

Visitors to high altitude are susceptible to hypoxia-induced acute intestinal mucosal barrier injury and severe gastrointestinal disorders, which are life-threatening. Citrus tangerine pith extract (CTPE) is rich in pectin and flavonoids and has been proved to enhance intestinal health and improve gut dysbiosis. In this study, we aim to explore the protective effect of CTPE on ileum injury induced by intermittent hypobaric hypoxia in a mouse model. Balb/c mice were divided into blank normoxia (BN), blank hypobaric hypoxia (BH), hypobaric hypoxia plus CTPE (TH), and hypobaric hypoxia plus Rhodiola extract (RH) groups. From the 6th day of gavage, mice in BH, TH, and RH groups were transferred into a hypobaric chamber at a simulated elevation of 6000 m for 8 hours per day for 10 days. Then half the mice were tested for small intestine movement, and others were used to evaluate intestinal physical barrier function, inflammation, and gut microbiota. Results showed that CTPE reversed the increase of intestinal peristalsis, effectively attenuated impaired structural integrity of ileum, improved the mRNA and protein expression levels of tight junction proteins, and reduced serum D-LA content in mice to alleviate hypoxia-induced mucosal barrier damage. Moreover, CTPE supplementation ameliorated hypoxia-induced intestinal inflammation response by significantly downregulating the proinflammatory cytokines IL-6, TNF-α and IFN-γ. By 16S rDNA gene sequencing of gut microbiota, CTPE significantly increased the abundance of probiotic Lactobacillus, suggesting that CTPE may be used as a prebiotic to regulate ecology of intestinal microorganisms. In addition, Spearman rank correlation analysis revealed that changed gut microbiota were significantly correlated with alteration of intestinal barrier function indexes. Taken together, these results indicate that CTPE effectively alleviates hypoxia-induced intestinal injury in mice and enhances intestinal integrity and barrier function by altering intestinal microbiota composition.

Exploring the links between gut microbiome changes and irritable bowel syndrome in Han populations in the Tibetan Plateau

The gut microbiome shows changes under a plateau environment, while the disbalance of intestinal microbiota plays an important role in the pathogenesis of irritable bowel syndrome (IBS); however, the relationship between the two remains unexplored. In this work, we followed up a healthy cohort for up to a year before and after living in a plateau environment and performed 16S ribosomal RNA (rRNA) sequencing analysis of their fecal samples. Through evaluating the participants' clinical symptoms, combined with an IBS questionnaire, we screened the IBS sub-population in our cohort. The sequencing results showed that a high-altitude environment could lead to changes in the diversity and composition of gut flora. In addition, we found that the longer the time volunteers spent in the plateau environment, the more similar their gut microbiota composition and abundance became compared to those before entering the plateau, and IBS symptoms were significantly alleviated. Therefore, we speculated that the plateau may be a special environment that induces IBS. The taxonomic units g_Alistipes, g_Oscillospira, and s_Ruminococcus_torques, which had been proved to play important roles in IBS pathogenesis, were also abundant in the IBS cohort at high altitudes. Overall, the disbalance of gut microbiota induced by the plateau environment contributed to the high frequency of IBS and the psychosocial abnormalities associated with IBS. Our results prompt further research to elucidate the relevant mechanism.

Microbial Enterotypes Shape the Divergence in Gut Fermentation, Host Metabolism, and Growth Rate of Young Goats

Enterotypes can be useful tools for studying the gut microbial community landscape, which is thought to play a crucial role in animal performance. However, few studies have been carried out to identify enterotypes and their associations with growth performance in young goats. In this study, two enterotypes were categorized in 76 goats: cluster 1 (n = 39) and cluster 2 (n = 37). Compared to cluster 2, cluster 1 had greater growth rates, the concentrations of acetate, propionate, valerate, and total volatile fatty acids (VFA) in the gut. Several serum glycolipid metabolism parameters, including glucose, total cholesterol, high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C), were also increased in cluster 1, while serum IgG was decreased in cluster 1. Using α-diversity analysis, we found a microbiome with lower richness and diversity in cluster 1. Some gut bacteria, including Succinivibrio and several members of the Prevotellaceae family, were enriched in cluster 1, while Christensenellaceae R-7 group, Romboutsia, and Clostridium sensu stricto 1 were enriched in cluster 2. A co-occurrence network analysis revealed that the differential interaction patterns existed in two enterotypes, and microbial function prediction suggested that some nutrient metabolism-related pathways, including amino acid biosynthesis and starch and sucrose metabolism, were enriched in cluster 1. Furthermore, a correlation analysis showed that enterotype-related bacteria were closely correlated with gut fermentation, serum biochemistry, and growth rate. Overall, our data provide a new perspective for understanding enterotype characteristics in goats, offering insights into important microbial interaction mechanisms for improving the growth performance of ruminant animals. IMPORTANCE The intricate relationships between a host animal and its resident gut microbiomes provide opportunities for dealing with energy efficiency and production challenges in the livestock industry. Here, we applied the enterotype concept to the gut microbiome in young goats and found that it can be classified into two enterotypes which are apparently associated with divergences in gut fermentation, blood biochemistry, and goat growth rates. The microbial co-occurrence networks and function predictions differed between the two enterotypes, suggesting that the formation of host phenotype may be modified by different bacterial features and complex bacterial interactions. The characteristics of enterotypes related to growth performance in young goats may enable us to improve long-term production performance in goat industry by modulating the gut microbiome during early life.

Changes in the Gut Microbiota of Rats in High-Altitude Hypoxic Environments

This study was conducted to investigate the effects of high-altitude hypoxic environments on the gut microbiota. Male Sprague-Dawley rats were randomly divided into three groups, namely, the plain, moderate-altitude hypoxic, and high-altitude hypoxic groups. On the 3rd, 7th, 15th, and 30th days of exposure, fecal samples were collected and analyzed via 16S rRNA gene sequencing technology. Fecal microbiota transplantation (FMT) experiments were also performed. The results showed significant differences between the gut microbiota structure and diversity of rats in the high-altitude hypoxic group and those of rats in the other groups. Further, compared with that of rats in the plain group, the gut microbiota of rats in the two hypoxic groups showed the most significant changes on day 7. Furthermore, the gut microbiota of the rats in the FMT groups exhibited changes and became increasingly similar to those of the rats in the hypoxic groups. We also identified the phylum Firmicutes, genus Akkermansia, and genus Lactobacillus as the core microbiota under hypoxic conditions. Phenotypic analysis indicated a decrease in the proportion of aerobic bacteria and an increase in that of anaerobic bacteria, possibly owing to the high-altitude hypoxic environment. Additionally, functional analysis showed significant differences between the different groups with respect to different metabolic pathways, including carbohydrate metabolism, energy metabolism, glycan biosynthesis, and metabolism. These findings indicated significant changes in gut microbiota structure and diversity under high-altitude hypoxia, establishing a foundation for further research on the pathogenesis and development of diseases, as well as drug metabolism, under high-altitude hypoxia. IMPORTANCE In this study, we investigated the effects of high-altitude hypoxic environments with low oxygen levels on the gut microbiota characteristics of rats. We observed that high-altitude hypoxia is an important environmental factor that can affect gut microbiota structure and diversity, thereby affecting homeostasis in the host intestinal environment. These findings provide a basis for further studies on disease initiation and development, as well as drug metabolism, in high-altitude hypoxic environments.

Review of the relationship and underlying mechanisms between the Qinghai-Tibet plateau and host intestinal flora

The intestinal microbial community is the largest ecosystem in the human body, in which the intestinal flora plays a dominant role and has a wide range of biological functions. However, it is vulnerable to a variety of factors, and exposure to extreme environments at high altitudes, as seen on the Qinghai-Tibet plateau, may cause changes in the structure and function of the host intestinal flora. Conversely, the intestinal flora can help the host adapt to the plateau environment through a variety of ways. Herein, we review the relationship and underlying mechanism between the host intestinal flora and the plateau environment by discussing the characteristics of the plateau environment, its influence on the intestinal flora, and the important role of the intestinal flora in host adaptation to the plateau environment. This review aimed to provide a reference for maintaining the health of the plateau population.

Analysis of the gut microbiome in obese native Tibetan children living at different altitudes: A case-control study

Objective

To explore the relationship between intestinal flora and obesity in Tibetan children at different altitudes.

Methods

Using16S rRNA gene sequencing results and blood lipid metabolism indexes to study the characteristics of the intestinal flora present in faeces and changes in blood lipid metabolism in obese children in Tibet who reside at different altitudes and to study correlations between blood lipid metabolism indicators and the intestinal flora composition.

Results

The results showed the following. (a) The triglyceride (TG) and low-density lipoprotein cholesterol (LDL-C) levels in the obesity groups were higher than those in the normal-weight groups, and those in the high-altitude obesity groups were lower than those in the low-altitude obesity groups. (b) The 16S rRNA gene sequencing results showed that altitude affected the composition and relative abundance of the gut microbiota. These parameters were basically the same among the low-altitude groups, while they were significantly lower in the high-altitude groups than in the low-altitude groups. (c) Groups that lived at different altitudes and had different body weights had different dominant bacterial genera. Megamonas was closely related to obesity, and its relative abundance in the low-altitude groups was higher than that in the high-altitude groups. Prevotella was associated with altitude, and its relative abundance in the high-altitude groups was higher than that in the low-altitude groups. In addition, Prevotella elicited changes in the abundance of Escherichia-Shigella. The lower prevalence of obesity and incidence of intestinal inflammation in those living at high altitudes were related to the abundance of Prevotella. (d) There were correlations between the gut microbiota composition and lipid metabolism indicators. The abundance of Romboutsia was positively correlated with TG and LDL-C levels but negatively correlated with high-density lipoprotein cholesterol (HDL-C) levels. The abundance of Akkermansia was negatively correlated with LDL-C levels, and the abundance of Blautia was negatively correlated with body mass index (BMI) and LDL-C levels.

Conclusions

The intestinal flora diversity varied by body weight and altitude, with lower diversity in those at higher altitudes and with lower body weights. Prevotella likely plays a role in suppressing obesity at high altitudes.

Lactobacillus johnsonii YH1136 plays a protective role against endogenous pathogenic bacteria induced intestinal dysfunction by reconstructing gut microbiota in mice exposed at high altitude

Background

Intestinal microbiota plays an important role in maintaining the microecological balance of the gastrointestinal tract in various animals. Disturbances in the intestinal microbiota may lead to the proliferation of potentially pathogenic bacteria that become the dominant species, leading to intestinal immune disorders, intestinal inflammation, and other intestinal diseases. Numerous studies have been confirmed that high-altitude exposure affects the normal function of the intestine and the composition of the intestinal microbiota. However, it is still necessary to reveal the changes in intestinal microbiota in high-altitude exposure environments, and clarify the relationship between the proliferation of potentially pathogenic bacteria and intestinal injury in this environment. In addition, explored probiotics that may have preventive effects against intestinal diseases.

Methods and results

C57BL/6 mice were randomly divided into three groups, a high-altitude group (HA), control group (C), and high-altitude probiotic group (HAP). The HA and HAP groups were subjected to hypoxia modeling for 14 days in a low-pressure oxygen chamber with daily gavage of 0.2 mL of normal saline (HA) and Lactobacillus johnsonii YH1136 bacterial fluid (HAP), while the control group was fed normally. L. johnsonii YH1136 was isolated from feces of a healthy Tibetan girl in Baingoin county, the Nagqu region of the Tibet Autonomous Region, at an altitude of 5000 meters. Our observations revealed that gavage of YH1136 was effective in improving the damage to the intestinal barrier caused by high-altitude exposure to hypoxic environments and helped to reduce the likelihood of pathogenic bacteria infection through the intestinal barrier. It also positively regulates the intestinal microbiota to the extent of Lactobacillus being the dominant microbiome and reducing the number of pathogenic bacteria. By analyzing the expression profile of ileal microRNAs and correlation analysis with intestinal microbiota, we found that Staphylococcus and Corynebacterium1 cooperated with miR-196a-1-3p and miR-3060-3p, respectively, to play a regulatory role in the process of high-altitude hypoxia-induced intestinal injury.

Conclusion

These findings revealed the beneficial effect of L. johnsonii YH1136 in preventing potential endogenous pathogenic bacteria-induced intestinal dysfunction in high-altitude environments. The mechanism may be related to the regulation of intestinal injury from the perspective of the gut microbiota as well as miRNAs.

Dynamics of the gut microbiota in rats after hypobaric hypoxia exposure

Background

Gut microbiota plays an important role in host health and is influenced by multiple factors. Hypobaric hypoxia usually existing at high altitude conditions can adversely affect normal physiological functions. However, the dynamic changes of gut microbiota influenced by hypobaric hypoxia have not been elucidated.

Methods

In this study, we collected fecal samples from seven rats at 14 time points from entering the hypobaric chamber (eight time points) to leaving the chamber (six time points) and five rats served as normoxic controls. Metagenome sequencing was performed on all samples and the dynamics of taxa and functions were analyzed.

Results

We found that the α-diversity was changed in the first 5 days after entering or leaving the hypobaric chamber. The β-diversity analysis revealed that gut microbiota structure was significantly separated among 14 time points. After entering the chamber, the relative abundance of Bacteroides decreased and the most abundant genus turned into Prevotella. The abundance of Firmicutes and Bacteroidetes showed an opposite trend and both have a significant change within 5 days after entering or leaving the hypobaric hypoxia chamber. Some obligate anaerobic bacteria belonging to Desulfovibrio and Alistipes were significantly enriched after entering the chamber for 5 weeks, whereas Probiotics like Bifidobacterium and Lactococcus, and short-chain fatty acids producers like Butyrivibrio and Pseudobutyrivibrio were significantly enriched after leaving the chamber for 3 weeks. Microbial functions like 'Two-component regulatory system', 'beta-carotene biosynthesis' and 'Fatty acid biosynthesis' were significantly enriched after entering the chamber for 5 weeks. Hypobaric hypoxia conditions could deeply affect the diversity and structure of gut microbiota. The alterations of abundance of dominant taxa (Firmicutes and Bacteroidetes), increased anaerobes and decreased probiotics induced by hypobaric hypoxia conditions might affect the host health.

Alterations in gut microbiota and metabolites associated with altitude-induced cardiac hypertrophy in rats during hypobaric hypoxia challenge

The gut microbiota is involved in host responses to high altitude. However, the dynamics of intestinal microecology and their association with altitude-related illness are poorly understood. Here, we used a rat model of hypobaric hypoxia challenge to mimic plateau exposure and monitored the gut microbiome, short-chain fatty acids (SCFAs), and bile acids (BAs) over 28 d. We identified weight loss, polycythemia, and pathological cardiac hypertrophy in hypoxic rats, accompanied by a large compositional shift in the gut microbiota, which is mainly driven by the bacterial families of Prevotellaceae, Porphyromonadaceae, and Streptococcaceae. The aberrant gut microbiota was characterized by increased abundance of the Parabacteroides, Alistipes, and Lactococcus genera and a larger Bacteroides to Prevotella ratio. Trans-omics analyses showed that the gut microbiome was significantly correlated with the metabolic abnormalities of SCFAs and BAs in feces, suggesting an interaction network remodeling of the microbiome-metabolome after the hypobaric hypoxia challenge. Interestingly, the transplantation of fecal microbiota significantly increased the diversity of the gut microbiota, partially inhibited the increased abundance of the Bacteroides and Alistipes genera, restored the decrease of plasma propionate, and moderately ameliorated cardiac hypertrophy in hypoxic rats. Our results provide an insight into the longitudinal changes in intestinal microecology during the hypobaric hypoxia challenge. Abnormalities in the gut microbiota and microbial metabolites contribute to the development of high-altitude heart disease in rats.

Microarray-Based Prediction of Polycythemia after Exposure to High Altitudes

In high-altitude environments, the prevalence of high-altitude polycythemia (HAPC) ranges between 5 and 18 percent. However, there is currently no effective treatment for this condition. Therefore, disease prevention has emerged as a critical strategy against this disease. Here, we looked into the microarray profiles of GSE135109 and GSE29977, linked to either short- or long-term exposure to the Qinghai Tibet Plateau (QTP). The results revealed inhibition in the adaptive immune response during 30 days of exposure to QTP. Following a gene set enrichment analysis (GSEA) discovered that genes associated with HAPC were enriched in Cluster1, which showed a dramatic upregulation on the third day after arriving at the QTP. We then used GeneLogit to construct a logistic prediction model, which allowed us to identify 50 genes that classify HAPC patients. In these genes, LRRC18 and HCAR3 were also significantly altered following early QTP exposure, suggesting that they may serve as hub genes for HAPC development. The in-depth study of a combination of the datasets of transcriptomic changes during exposure to a high altitude and whether diseases occur after long-term exposure in Hans can give us some inspiration about genes associated with HAPC development during adaption to high altitudes.

Correlation between adipocyte fatty acid binding protein and glucose dysregulation is closely associated with obesity and metabolic syndrome: A cohort of Han Chinese population from Yunnan plateau

The present study investigated the correlation of plasma A-FABP with glucose dysregulation under different body mass index (BMI) and metabolic states in a Han Chinese population from Yunnan plateau. We cross-sectionally analyzed data from the China Multi Ethnic Cohort, Yunnan province. Participants were divided into two groups. Group A contained 297 obese individuals with metabolic syndrome (MetS). Group B contained 326 age-, sex-, and region-matched normal BMI subjects without MetS. Glucose dysregulation was defined as elevated fasting plasma glucose (FPG) (FPG ≥ 5.6 mmol/L or current use of oral hypoglycemic agents or insulin). Circulating A-FABP were assayed by ELISA method. Binary and multiple regression analyses were preformed to evaluate the correlation between A-FABP and glucose dysregulation. Plasma A-FABP level was significantly higher in group A compared with group B (p < 0.001). Plasma A-FABP level correlated positively with elevated FPG in group A (r = 0.120, p = 0.039), but negatively with elevated FPG in group B (r = -0.115, p = 0.039). Multiple logistic regression analysis revealed that A-FABP was an independent predictor for elevated FPG in group A (β, 0.028; 95% CI, 1.001-1.056; p < 0.05), but not in group B (β, -0.008; 95% CI, 0.882-1.117; p > 0.05). In this study, A-FABP was an independent risk factor for glucose dysregulation in obese individuals with MetS living in the Yunnan plateau, but not for those without obesity and MetS.

Yak Gut Microbiota: A Systematic Review and Meta-Analysis

The yak (Bos grunniens) is closely related to common cows (Bos taurus), but is clearly a distinct species. Yaks are of substantial importance to food and leather production in certain high-altitude regions of Asia. The animal is increasing elsewhere as well, mainly because of the perceived health benefits of its milk. Like all ruminants, the animal harbors a complex community of microbial cells in its gut, crucial for its physiology. Despite yaks being important domestic animals, the composition of its gut microbiota and how the composition is guided by its specific high-altitude environment remains largely uncategorized. Hence, online databases (Embase, Medline ALL, Web of Science Core Collection, Cochrane Central Register of Controlled Trials, and Google Scholar) were searched for articles on yak intestinal microbiota. The pooled taxonomic abundance was compared between regions, sexes, different age groups, and feeding patterns. The gut microbiota distribution across different yak intestinal segments was established through pooled average taxonomic abundance. A total of 34 studies met the inclusion criteria and yielded information on 982 unique yak gut microbiota samples. An analysis of overall pooled microbiota revealed a segmented microbial community composition of the yak gut. Yak rumen microbiota was significantly influenced by difference in region, sex, and feeding patterns, the latter factor being dominant in this respect. Yak microbiome is shaped by the feeding strategy and provides an obvious avenue for improving health and productivity of the animal. More generally, the current segmental description of physiological gut microbiome provides insight into how the microbiology of this animal has adapted itself to help comping yaks with its high-altitude habitat.

Proteomic and clinical biomarkers for acute mountain sickness in a longitudinal cohort

Ascending to high-altitude by non-high-altitude natives is a well-suited model for studying acclimatization to extreme environments. Acute mountain sickness (AMS) is frequently experienced by visitors. The diagnosis of AMS mainly depends on a self-questionnaire, revealing the need for reliable biomarkers for AMS. Here, we profiled 22 AMS symptom phenotypes, 65 clinical indexes, and plasma proteomic profiles of AMS via a combination of proximity extension assay and multiple reaction monitoring of a longitudinal cohort of 53 individuals. We quantified 1069 proteins and validated 102 proteins. Via differential analysis, machine learning, and functional association analyses. We found and validated that RET played an important role in the pathogenesis of AMS. With high-accuracies (AUCs > 0.9) of XGBoost-based models, we prioritized ADAM15, PHGDH, and TRAF2 as protective, predictive, and diagnostic biomarkers, respectively. Our findings shed light on the precision medicine for AMS and the understanding of acclimatization to high-altitude environments.

Potential acute mountain sickness diagnostic, predictive, protective biomarkers are established using plasma proteomic, clinical and symptom phenotype data with machine learning approaches in a longitudinal cohort of 53 individuals.

Role of gene regulation and inter species interaction as a key factor in gut microbiota adaptation

Gut microbiota is a class of microbial flora present in various eukaryotic multicellular complex animals such as human beings. Their community's growth and survival are greatly influenced by various factors such as host-pathogen, pathogen-environment and genetic regulation. Modern technologies like metagenomics have particularly extended our capacity to uncover the microbial treasures in challenging conditions like communities surviving at high altitude. Molecular characterizations by newly developed sequencing tools have shown that this complex interaction greatly influences microbial adaptation to the environment. Literature shows that gut microbiota alters the genetic expression and switches to an alternative pathway under the influence of unfavorable conditions. The remarkable adaptability of microbial genetic regulatory networks enables them to survive and expand in tough and energy-limited conditions. Variable prevalence of species in various regions has strengthened this initial evidence. In view of the interconnection of the world in the form of a global village, this phenomenon must be explored more clearly. In this regard, recently there has been significant addition of knowledge to the field of microbial adaptation. This review summarizes and shed some light on mechanisms of microbial adaptation via gene regulation and species interaction in gut microbiota.

Gut microbiota imbalance mediates intestinal barrier damage in high-altitude exposed mice

The environmental conditions in high-altitude areas can induce gastrointestinal disorders and changes in gut microbiota. The gut microbiota is closely related to a variety of gastrointestinal diseases, although the underlying pathogenic mechanisms are not well-identified. The present study aimed to investigate the regulatory effect of high altitude on intestinal dysfunction via gut microbiota disturbance. Forty C57BL/6J mice were divided into four groups: one plain control group (CON) and three high-altitude exposure groups (HAE) (altitude: 4000 m a.s.l.; oxygen content: 12.7%; 1-, 2- and 4-week exposure). Another set of 40 mice was divided into two CON and two HAE subgroups. Antibiotic cocktails were administered to one CON and HAE groups and autoclaved water was administered to the second CON and HAE groups for 4 weeks, respectively. In the fecal microbiota transplantation experiment, there were four transplantation groups, which received, respectively: phosphate-buffered saline for 2 weeks, feces from CON for 2 weeks, feces from HAE-4W for 2 weeks, and HAE-4W for 4 weeks. Hematoxylin and eosin staining, periodic acid-Schiff staining, a terminal deoxynucleotidyl transferase dUTP nick end labeling assay and a quantitative reverse transcriptase-polymerase chain reaction were applied to detect changes in intestinal cellular structure, morphology, apoptosis and intestinal inflammatory response. Fecal microbiota was analyzed using 16S rDNA amplicon sequencing. A high-altitude environment changed the ecological balance of gut microbiota in mice and caused damage to the intestinal structure and mucosal barrier. Interestingly, similar damage, which was inhibited by antibiotic cocktails at high altitude, was observed in mice transplanted with fecal microbiota from HAE. A high-altitude environment contributes to dyshomeostasis of gut microbiota, thereby impairing the intestinal mucosal barrier, eventually inducing and exacerbating intestinal damage.

Hypoxia Improves Endurance Performance by Enhancing Short Chain Fatty Acids Production via Gut Microbiota Remodeling

Hypoxia environment has been widely used to promote exercise capacity. However, the underlying mechanisms still need to be further elucidated. In this study, mice were exposed to the normoxia environment (21% O₂) or hypoxia environment (16.4% O₂) for 4 weeks. Hypoxia-induced gut microbiota remodeling characterized by the increased abundance of Akkermansia and Bacteroidetes genera, and their related short-chain fatty acids (SCFAs) production. It was observed that hypoxia markedly improved endurance by significantly prolonging the exhaustive running time, promoting mitochondrial biogenesis, and ameliorating exercise fatigue biochemical parameters, including urea nitrogen, creatine kinase, and lactic acid, which were correlated with the concentrations of SCFAs. Additionally, the antibiotics experiment partially inhibited hypoxia-induced mitochondrial synthesis. The microbiota transplantation experiment demonstrated that the enhancement of endurance capacity induced by hypoxia was transferable, indicating that the beneficial effects of hypoxia on exercise performance were partly dependent on the gut microbiota. We further identified that acetate and butyrate, but not propionate, stimulated mitochondrial biogenesis and promoted endurance performance. Our results suggested that hypoxia exposure promoted endurance capacity partially by the increased production of SCFAs derived from gut microbiota remodeling.

Gut Microbiota as the Potential Mechanism to Mediate Drug Metabolism Under High-Altitude Hypoxia

BACKGROUND

The characteristics of pharmacokinetics and the activity and expression of drug-metabolizing enzymes and transporters significantly change under a high-altitude hypoxic environment. Gut microbiota is an important factor affecting the metabolism of drugs through direct or indirect effects, changing the bioavailability, biological activity, or toxicity of drugs and further affecting the efficacy and safety of drugs in vivo. A high-altitude hypoxic environment significantly changes the structure and diversity of gut microbiota, which may play a key role in drug metabolism under a high-altitude hypoxic environment.

METHODS

An investigation was carried out by reviewing published studies to determine the role of gut microbiota in the regulation of drug-metabolizing enzymes and transporters. Data and information on expression change in gut microbiota, drug-metabolizing enzymes and transporters under a high-altitude hypoxic environment were explored and proposed.

RESULTS

High-altitude hypoxia is an important environmental factor that can adjust the structure of the gut microbiota and change the diversity of intestinal microbes. It was speculated that the gut microbiota could regulate drug-metabolizing enzymes through two potential mechanisms, the first being through direct regulation of the metabolism of drugs in vivo and the second being indirect, i.e., through the regulation of drug-metabolizing enzymes and transporters, thereby affecting the activity of drugs.

CONCLUSION

This article reviews the effects of high-altitude hypoxia on the gut microbiota and the effects of these changes on drug metabolism.

Challenging traditional carbohydrate intake recommendations for optimizing performance at high altitude

PURPOSE OF REVIEW

To highlight emerging evidence challenging traditional recommendations to increase carbohydrate intake to optimize performance at high altitude.

RECENT FINDINGS

Several studies have now clearly demonstrated that, compared with sea level, exogenous carbohydrate oxidation during aerobic exercise is blunted in lowlanders during initial exposure to high altitude. There is also no apparent ergogenic effect of ingesting carbohydrate during aerobic exercise on subsequent performance at high altitude, either initially after arriving or even after up to 22 days of acclimatization. The inability to oxidize and functionally benefit from exogenous carbohydrate intake during exercise after arriving at high altitude coincides with hyperinsulinemia, accelerated glycogenolysis, and reduced peripheral glucose uptake. Collectively, these responses are consistent with a hypoxia-mediated metabolic dysregulation reflective of insulin resistance. Parallel lines of evidence have also recently demonstrated roles for the gut microbiome in host metabolism, bioenergetics, and physiologic responses to high altitude, implicating the gut microbiome as one potential mediator of hypoxia-mediated metabolic dysregulation.

SUMMARY

Identification of novel and well tolerated nutrition and/or pharmacological approaches for alleviating hypoxia-mediated metabolic dysregulation and enhancing exogenous carbohydrate oxidation may be more effective for optimizing performance of lowlanders newly arrived at high altitude than traditional carbohydrate recommendations.

The Correlation between Gut Microbiota and Serum Metabolomic in Elderly Patients with Chronic Heart Failure

OBJECTIVE

Chronic heart failure (CHF) refers to a state of persistent heart failure that can be stable, deteriorated, or decompensated. The mechanism and pathogenesis of myocardial remodeling remain unknown. Based on 16S rDNA sequencing and metabolomics technology, this study analyzed the gut microbiota and serum metabolome in elderly patients with CHF to provide new insights into the microbiota and metabolic phenotypes of CHF.

METHODS

Blood and fecal samples were collected from 25 elderly patients with CHF and 25 healthy subjects. The expression of inflammatory factors in blood was detected by ELISA. 16S rDNA sequencing was used to analyze the changes in microorganisms in the samples. The changes of small molecular metabolites in serum samples were analyzed by LC-MS/MS. Spearman correlation coefficients were used to analyze the correlation between gut microbiota and serum metabolites.

RESULTS

Our results showed that the IL-6, IL-8, and TNF-α levels were significantly increased, and the IL-10 level was significantly decreased in the elderly patients with CHF compared with the healthy subjects. The diversity of the gut microbiota was decreased in the elderly patients with CHF. Moreover, Escherichia Shigella was negatively correlated with biocytin and RIBOFLAVIN. Haemophilus was negatively correlated with alpha-lactose, cellobiose, isomaltose, lactose, melibiose, sucrose, trehalose, and turanose. Klebsiella was positively correlated with bilirubin and ethylsalicylate. Klebsiella was negatively correlated with citramalate, hexanoylcarnitine, inosine, isovalerylcarnitine, methylmalonate, and riboflavin.

CONCLUSION

The gut microbiota is simplified by the disease, and serum small-molecule metabolites evidently change in elderly patients with CHF. Serum and fecal biomarkers could be used for elderly patients with CHF screening.

Ocular microbial diversity, community structure, and function at high altitude

PURPOSE

To investigate the composition and function of ocular surface microbiome in healthy people from different altitudes.

METHODS

Thirty-two healthy people living in a high altitude region and 30 sex- and age-matched individuals living in a low altitude region were enrolled. Samples were collected from the lower conjunctival sac of one randomly chosen eye for each participant. 16S rRNA sequencing was conducted to study the bacterial community composition and predict gene function using PICRUSt software.

RESULTS

Microbial diversity and richness was significantly decreased in samples from highlanders as calculated by Abundance-based Coverage Estimator (ACE) index, Chao1 index, and observed-species index (all p < 0.01). Principle coordinate analysis (PCoA) suggested significantly distinct clustering of the conjunctival sac bacterial communities between two groups (p = 0.03), especially the dominant genera. The relative abundances of Corynebacterium, Staphylococcus, and Anaerococcus were significantly enriched in highlanders, while those of Pseudomonas and Massilia were significantly decreased as compared with lowlanders (p < 0.01). In the functional annotation analysis, we found that 74 gene pathways, mainly in metabolism, differed in abundance. Pathways related to immune system diseases and infectious diseases were also enriched in highlanders.

CONCLUSION

The composition and function of ocular surface microbiome in highlanders were distinct from those of lowlanders and our study may provide a reference catalog of the healthy conjunctival microbiome in highlanders.

Migration effects on the intestinal microbiota of Tibetans

BACKGROUND

Diet, environment, and genomic context have a significant impact on humans' intestinal microbiota. Moreover, migration may be accompanied by changes in human eating habits and living environment, which could, in turn, affect the intestinal microbiota. Located in southwestern China, Tibet has an average altitude of 4,000 meters and is known as the world's roof. Xianyang is situated in the plains of central China, with an average altitude of about 400 meters.

METHODS

To understand the association between intestinal microbiota and population migration, we collected the fecal samples from 30 Tibetan women on the first day (as TI1st), six months (as TI2nd), and ten months (as TI3rd) following migration from Tibet to Xianyang. Fecal samples were collected from 29 individuals (belonging to the Han women) as a control. The dietary information of the Tibetan women and the Han women was gathered. We performed a 16S rRNA gene survey of the collected fecal samples using Illumina MiSeq sequencing.

RESULTS

Following the migration, the alpha and beta diversity of Tibetan women's intestinal microbiota appeared unaffected. Linear discriminant analysis effect size (LEfSe) analysis showed that Klebsiella, Blautia, and Veillonella are potential biomarkers at TI1st, while Proteobacteria and Enterobacteriaceae were common in TI3rd. Finally, functional prediction by phylogenetic investigation of communities by reconstruction of unobserved states (PICRUSt) found no significant up-regulation or down-regulation gene pathway in the intestinal microbiota of Tibetan women after migration. The present study reveals that the higher stability in Tibetan women's intestinal microbiota was less affected by the environment and diet, indicating that Tibetan women's intestinal microbiota is relatively stable. The main limitations of the study were the small sample size and all volunteers were women.

Distinguishing feature of gut microbiota in Tibetan highland coronary artery disease patients and its link with diet

The prevalence of coronary artery disease (CAD) in Tibetan Highlanders is lower than that in plain-living individuals, but the mechanism still unclear. Gut microbiota (GM) disorder is considered one of the potential factors involved in the pathogenesis of CAD, but the GM characteristics of Tibetan Highlanders suffering from CAD are unknown. We sequenced the V3-V4 region of the 16S ribosomal RNA of gut bacteria from fecal samples from Tibetan and Han CAD patients and healthy individuals inhabiting the Qinghai-Tibet Plateau, as well as from Han CAD patients and healthy individuals living at sea level, and we analyzed the GM characteristics of these subjects by bioinformatics analysis. The results showed that Tibetan Highlanders suffering from CAD had higher GM α-diversity, with differently distributed cluster compared with healthy Tibetan Highlanders and Han CAD patients living at high and low altitudes. Genera Catenibacterium, Clostridium_sensu_stricto, Holdemanella, and Ruminococcus 2 were enriched in Tibetan Highlanders suffering from CAD compared with healthy Tibetan Highlanders and Han CAD patients living at high- and low-altitudes. Prevotella was enriched in Tibetan Highlanders suffering from CAD compared with Han CAD patients living at high- and low-altitudes. Moreover, Catenibacterium was positively correlated with Prevotella. Additionally, Catenibacterium, Holdemanella, and Prevotella were positively correlated with fermented dairy product, carbohydrate and fiber intake by the subjects, while Clostridium_sensu_stricto was negatively correlated with protein intake by the subjects. In conclusion, our study indicated that Tibetan Highlanders suffering from CAD showed distinct GM, which was linked to their unique dietary characteristics and might associated with CAD.

Recent progress in research on the gut microbiota and highland adaptation on the Qinghai-Tibet Plateau

Microbial communities that inhabit the host's intestine influence many aspects of the host's health and bear the adaptive potential to alterations in harsh environments and diets. The Qinghai-Tibet Plateau represents one of the harshest environments in the world. Preliminary progress has been made in identifying the communities of gut microbes in Indigenous Tibetans and non-human animals. However, due to the complexity of microbial communities, the effects of gut microbes on the host's health and high-plateau adaptation remain unexplained. Herein, we review the latest progress in identifying factors affecting the gut microbiota of native Tibetans and non-human animals and highlight the complex interactions between the gut microbiota, health and highland adaptation, which provides a basis for exploring the correlations between the gut microbiota and clinical indexes in native highland residents and travellers, as well as developing microbiota-based strategies to mitigate health risks for tourists and treatments for mountain sickness during high-altitude travel in the future.

[Betelnut polyphenols provide protection against high-altitude hypoxia in rats]

OBJECTIVE

To investigate the protective effects of betelnut polyphenols on the vital organs against high-altitude hypoxia in rats.

OBJECTIVE

We compared low-, medium-, and high- dose betelnut polyphenols (400, 800, and 1600 mg/kg, respectively) and rhodiola the effects of against high-altitude hypoxia in Wistar rats. The rats were kept in normal condition and given the drugs daily for 3 days before transfer to a facility at the altitude of 4010 m, where the rats were kept for 5 consecutive days for hypoxic exposure. The rats were then euthanized for measuring arterial blood gas and assessing liver, lung, brain and cardiac pathologies with HE staining. SOD activity, MDA content and GSH content in the organs were measured, and serum levels of inflammatory factors were detected using a protein microarray.

OBJECTIVE

Acute exposure to hypoxia significantly reduced blood oxygen saturation of the rats (P < 0.05), caused damages in the liver, lung, brain and myocardium, lowered SOD activity and GSH content and increased MDA content in the vital organs, and increased serum levels of TIMP-1, MCP-1, ICAM-1, and L-selectin (P < 0.05). Treatment with betelnut polyphenols significantly improved blood oxygen saturation, alleviated organ damages, decreased MDA content and increased SOD activity and GSH content in the tissues, and significantly lowered serum levels of inflammatory cytokines in rats with acute exposure to high-altitude hypoxia (P < 0.05).

OBJECTIVE

Betelnut polyphenols provides protection of the vital organs against acute high-altitude hypoxia in rats by enhancing the antioxidant capacity and reducing inflammatory response.

Effects of altitude on human oral microbes

Human oral microbes play a vital role maintaining host metabolic homeostasis. The Qinghai-Tibet Plateau is mainly characterized by a high altitude, dry, cold, and hypoxic environment. The oral microbiota is subject to selective pressure from the plateau environment, which affects oral health. Only a few studies have focused on the characteristics of oral microbiota in high-altitude humans. We collected saliva samples from 167 Tibetans at four altitudes (2800 to 4500 m) in Tibet to explore the relationship between the high altitude environment and oral microbiota. We conducted a two (high- and ultra-high-altitude) group analysis based on altitude, and adopted the 16S rRNA strategy for high-throughput sequencing. The results show that the alpha diversity of the oral microbiota decreased with altitude, whereas beta diversity increased with altitude. A LEfSe analysis revealed that the oral microbial biomarker of the high-altitude group (< 3650 m) was Streptococcus, and the biomarker of the ultra-high-altitude group (> 4000 m) was Prevotella. The relative abundance of Prevotella increased with altitude, whereas the relative abundance of Streptococcus decreased with altitude. A network analysis showed that the microbial network structure was more compact and complex, and the interaction between the bacterial genera was more intense in the high altitude group. Gene function prediction results showed that the amino acid and vitamin metabolic pathways were upregulated in the ultra-high-altitude group. These result show that altitude is an important factor affecting the diversity and community structure of the human oral microbiota.

Beet on Alps: Time-course changes of plasma nitrate and nitrite concentrations during acclimatization to high-altitude

Nitric oxide seems to be involved in the altitude acclimatization process due to its ability to regulate pulmonary, cardiovascular and muscular responses to hypoxia. In this study, we investigated the plasma nitrate (NO₃^-) and nitrite (NO₂^-) response to hypobaric hypoxia in two groups of lowlanders exposed at different altitudes. For seven days, fourteen subjects were evaluated at Casati Hut (3269 m a.s.l. M.CEVEDALE) and eleven individuals were studied at Capanna Regina Margherita (4554 m a.s.l. M.ROSA). Before expeditions and at different time points during high-altitude sojourn, plasma NO₃^- and NO₂^- concentrations were measured by chemiluminescence. Resting peripheral arterial oxygen saturation (SpO₂), heart rate (HR) and mean arterial blood pressure (MAP) were monitored during the experimental period. Possible confounding factors such as dietary NO₃^- intake, physical activity and altitude changes were controlled. Sea level plasma NO₃^- and NO₂^- concentrations significantly increased at altitude in both M.CEVEDALE group (+26.2 μM, p ≤ 0.0001, 95% CI [+17.6, +34.8] and +559.2 nM, p ≤ 0.0001, [+332.8, +785.6]) and M.ROSA group (+18.7 μM, p ≤ 0.0001, [+10.8, +26.5] and +463.7 nM, p ≤ 0.0001, [+314.3, +613.0]). Average peak value in NO metabolites concentration occurred earlier in M.CEVEDALE group vs M.ROSA group (NO₃^-, day 3 vs day 5, p = 0.007; NO₂^-, day 3 vs day 5, p = 0.019). In both groups, resting SpO₂, HR and MAP values changed according to altitude levels. This study shows that exposure to hypobaric hypoxia affects nitric oxide metabolites, resulting in a significant increase in plasma NO₃^- and NO₂^- concentrations from sea level values. Interestingly, the higher the altitude reached, the longer the time taken to reach a peak in plasma concentrations of nitric oxide metabolites.

Distinct Features of Gut Microbiota in High-Altitude Tibetan and Middle-Altitude Han Hypertensive Patients

Indigenous animals show unique gut microbiota (GM) in the Tibetan plateau. However, it is unknown whether the hypertensive indigenous people in plateau also have the distinct gut bacteria, different from those living in plains. We sequenced the V3-V4 region of the gut bacteria 16S ribosomal RNA (rRNA) gene of feces samples among hypertensive patients (HPs) and healthy individuals (HIs) from 3 distinct altitudes: Tibetans from high altitude (3600-4500 m, n = 38 and 34), Hans from middle altitude (2260 m, n = 49 and 35), and Hans from low altitude (13 m, n = 34 and 35) and then analyzed the GM composition among hypertensive and healthy subgroups using the bioinformatics analysis, respectively. The GM of high-altitude Tibetan and middle-altitude Han HPs presented greater α- and β-diversities, lower ratio of Firmicutes/Bacteroidetes (F/B), and higher abundance of beneficial Verrucomicrobia and Akkermansia than the low-altitudes HPs did. The GM of high-altitude Tibetan and middle-altitude HIs showed greater α-diversity and lower ratio of F/B than the low-altitudes HIs did. But, β-diversity and abundance of Verrucomicrobia and Akkermansia among different subgroups of HIs did not show any differences. Conclusively, the high-altitude Tibetan and middle-altitude Han HPs have a distinct feature of GM, which may be important in their adaptation to hypertension in the plateau environments.

Comparative analysis of oral microbiome from Zang and Han populations living at different altitudes

OBJECTIVES

The aim of this study was to obtain greater insight into the environmental and genetic factors affecting the oral microbiome.

DESIGN

To this end, we investigated the oral microbiome composition in Han and Zang populations living at different altitudes. The saliva microbiome in 115 individuals from Zang and Han populations living at different altitudes was analyzed using the 16 s rRNA gene sequencing method on the Illumina MiSeq platform. The dominant species in the oral microbiome were verified by quantitative real-time polymerase chain reaction (qPCR) analysis.

RESULTS

The Han population, living at an altitude of 500 m, had higher microbiome diversity than the Zang population living at altitudes of 3000-4000 m. People living at 3000 m had a higher relative abundance of Leptothrix genus, but people living at 500 m had a higher relative abundance of Capnocytophaga genus according to Lefse difference analysis (P < 0.05). Compared to the Zang population, the Han population had higher relative abundances of Porphyromonas and Treponema genus organisms, especially Porphyromonas (P < 0.001). qPCR analysis confirmed that people living at high altitudes had the highest relative abundance of Porphyromonas gingivalis (P < 0.01).

CONCLUSIONS

This study showed that both genetics and the environment had significant influences on the oral microbiome composition. The study proposed a meaningful research direction to explore the relationship between different ethnic and altitude groups and oral diseases, such as periodontal diseases.