Moderate altitude exposure impacts host fasting blood glucose and serum metabolome by regulation of the intestinal flora

Gut opportunistic pathogens contribute to high-altitude pulmonary edema by elevating lysophosphatidylcholines and inducing inflammation

Gut microbiota have been found to promote hypoxia-induced intestinal injury. However, the role of gut microbiota in high-altitude pulmonary edema (HAPE), the preventive effect of synbiotic on HAPE, and the mechanisms by which they might work remain unknown. In this study, we aimed to investigate the role of gut microbiota in the pathogenesis of HAPE and to explore the underlying mechanisms involved. We performed a fecal microbiome analysis and found a significant decrease in intestinal Klebsiella and Escherichia-Shigella, along with a notable increase in intestinal Bifidobacterium and Lactobacillus, as volunteers recovered from acute mountain sickness (AMS). Gavage colonization with Klebsiella pneumoniae and Escherichia coli induced plasma inflammation, increased plasma lysophosphatidylcholine (LPC) levels, and contributed to HAPE in rats at a simulated altitude of 6,500 m. Conversely, a synbiotic containing Bifidobacterium, Lactiplantibacillus, fructooligosaccharides, and isomaltose-oligosaccharides significantly reduced the severity of HAPE. Cellular experiments and molecular dynamics simulations revealed that LPCs can cause damage and permeability to human pulmonary microvascular endothelial cell (HPMEC) and human pulmonary alveolar epithelial cell (HPAEpiC) monolayers under hypoxic conditions by disrupting cell membrane integrity. In addition, tail vein injection of LPCs promoted HAPE in mice at a simulated altitude of 6,500 m. In conclusion, this study describes a gut microbiota-LPCs/inflammation-HAPE axis, an important new insight into HAPE that will help open avenues for prevention and treatment approaches.

IMPORTANCE

The role of the gut microbiota in high-altitude pulmonary edema (HAPE) is currently unknown. This study found that intestinal Klebsiella pneumoniae and Escherichia coli contribute to HAPE by inducing inflammation and increasing lysophosphatidylcholine (LPC) levels under hypoxic conditions. Conversely, a synbiotic containing Bifidobacterium, Lactiplantibacillus, fructooligosaccharides, and isomaltose-oligosaccharides significantly reduced the severity of HAPE. Further investigation revealed that LPCs can cause damage and permeability to human pulmonary microvascular endothelial cell (HPMEC) and human pulmonary alveolar epithelial cell (HPAEpiC) monolayers under hypoxic conditions by disrupting cell membrane integrity. These findings contribute to the understanding of the pathogenesis of HAPE and will benefit populations living at high altitude or traveling from low to high altitude.

Serum metabolomic profiling uncovered metabolic shifts in individuals upon moderate-altitude exposure and identified the potentiality of beta-alanine to ameliorate hyperuricemia

BACKGROUND

High-altitude exposure has been associated with an increased risk of hyperuricemia (HU) and gout, though the underlying mechanisms remain poorly understood.

METHODS

We conducted a comprehensive analysis of the serum metabolome and phenome in both discovery and validation cohorts of Han Chinese individuals who underwent long-term moderate-altitude exposure (∼12 months), as well as in an independent cohort consisting of local Han Chinese and Tibetans residing in Nyingchi (>5 years). Beta-Alanine intervention was applied in hypoxanthine and potassium oxonate-induced in vitro and in vivo experiments.

RESULTS

Individuals exposed to moderate altitude exhibited elevated serum urate and an increase in overall medium-chain fatty acids (MCFAs), coupled with a decrease in overall amino acids (AAs) and short-chain fatty acids (SCFAs). Rmcorr correlation analysis revealed a significant negative association between Beta-Alanine and serum urate, whereas nonanoic acid was in versa, potentially driving lower serum urate in long-term exposed residents. Both in vitro and in vivo experiments demonstrated that Beta-Alanine inhibited xanthine oxidase (XOD) and reversed the HU phenotype in human hepatocytes and mice induced by hypoxanthine (HX) and potassium oxonate (PO), with a urate-lowering effect in mice. Hepatic pathology and transcriptome analysis of HU mice treated with Beta-Alanine indicated that the mechanisms involved the inhibition of XOD, amelioration of the inflammation phenotype in hepatocytes, and promotion of renal urate excretion. Furthermore, the 10-fold cross-validation random forest classification (RFC) predictive modeling based on selected metabolites and phenotypes achieved an area under receiver operating characteristic (ROC) curve (AUC) value of 0.93 (95 % confidence interval (CI): 0.85-1.00) and 0.79 (95 % CI: 0.59-0.98) for distinguishing individuals with high risk of asymptomatic HU (AHU) in the training dataset and validation dataset, respectively.

CONCLUSIONS

This study reveals serum urate and metabolome altered in moderate-altitude exposed individuals and Beta-Alanine intervention could ameliorate hyperuricemia. Our findings suggest that targeting the circulating metabolome may pave novel avenues to counter diseases associated with HU.

Dietary and environmental factors affecting the dynamics of the gut bacteria in Tibetan Awang sheep (Ovis aries) across divergent breeding models

Introduction

Tibetan Awang sheep (Ovis aries), indigenous to the Qinghai-Tibet Plateau, are highly adapted to high-altitude environment. However, knowledge regarding their gut bacterial composition remains limited.

Methods

A comprehensive 16S rRNA highthroughput sequencing was performed on fecal samples from 15 Awang sheep under pure grazing, semi-captivity, and full captivity breeding models.

Results

Our results revealed that Firmicutes and Bacteroidetes were the most abundant bacterial phyla, while Christensenellaceae_R-7_group, Romboutsia, Rikenellaceae_RC9_gut_group, Ruminococcus, and Bacteroides were prevalent genera in the gut microbiota of Awang sheep. Meanwhile, the predominant presence of Bacteroides with increasing altitude of breeding locations indirectly demonstrates its crucial role in mediating energy acquisition among Awang sheep at high altitudes. Furthermore, PCoA and ANOSIM analysis exhibited significant differences in bacterial composition across all breeding models (r > 0.6, p < 0.001). Christensenellaceae_R-7_group, Romboutsia, and Ruminococcus were significantly abundant in the pure grazing breeding model, while Rikenellaceae_RC9_gut_group and Bacteroides were more abundant in the semi-captivity breeding model. An abnormally high abundance of Acinetobacter indicated a potential risk of Acinetobacter infection in the fully captive group. The environmental association analysis exhibited that meadows diet (R 2 = 0.938, Pr[>r] = 0.001) and altitude (R 2 = 0.892, Pr[>r] = 0.001) had significant effects on the dominant genera, explaining a substantial proportion of the total variation in community composition.

Discussion

Our study indicated that breeding conditions significantly impact the gut microbiota of Awang sheep. The environmental association analysis underscores the importance of diet and altitude in shaping the gut microbiota of Awang sheep. The present findings provide insights into the microbiota dynamics of Awang sheep and offer guidance for their scientific husbandry management.

The Role of the Intestinal Flora and Its Derivatives in Neurocognitive Disorders: A Narrative Review from Surgical Perspective

Perioperative neurocognitive dysfunction is a significant concern for population health, impacting postoperative recovery and increasing the financial burden on patients. With an increasing number of surgical procedures being performed, the prevention and management of perioperative neurocognitive dysfunction have garnered significant attention. While factors such as age, lifestyle, genetics, and education are known to influence the development of cognitive dysfunction, recent research has highlighted the role of the gut microbiota in neurological health. An increased abundance of pro-inflammatory gut microbiota can trigger and worsen neuroinflammation, neuronal cell damage, and impaired cellular autophagy. Moreover, the inflammation-promoting gut microbiota can disrupt immune function, impair neuroautophagy, and affect the production and circulation of extracellular vesicles and neurotransmitters. These factors collectively play a role in the onset and advancement of cognitive impairment. This narrative review delves into the molecular mechanisms through which gut microbiota and their derivatives contribute to cognitive impairment, focusing on the impact of anesthesia surgery, changes in gut microbial populations, and perioperative cognitive impairment associations. The study suggests that alterations in the abundance of various bacterial species and their metabolites pre- and post-surgery may be linked to postoperative cognitive impairment. Furthermore, the potential of probiotics or prebiotics in addressing cognitive impairment is discussed, offering a promising avenue for investigating the treatment of perioperative neurocognitive disorders.

Multi-omics reveals immune response and metabolic profiles during high-altitude mountaineering

The physiological perturbations induced by high-altitude exposure in mountain climbers, manifesting as immunological and metabolic deviations, have been previously reported but are not fully understood. In this study, we obtain multi-omic profiles of climbers' blood samples, including single-cell transcriptomic analysis of 375,722 immune cells, and plasma metabolomics and lipidomics. Longitudinal analysis reveals dynamic immune response profiles, during the acclimatization period, characterized by the downregulation of inflammatory responses in myeloid cell subsets and by the enhancement of immune effector processes in cytotoxic CD8+ T, γδT, and CD16+ natural killer cells. In contrast, during extreme-altitude mountaineering, the activation of inflammatory responses and impairment of immune effector function are observed, concomitant with an increased cellular response to hypoxia and oxidative stress pathways. Furthermore, glycolysis and antioxidant gene expression are upregulated during extreme-altitude mountaineering. Plasma metabolic analysis reveals significant alterations, involving enhanced glutamine and fatty acid metabolism.

Cognitive Impairment Mechanisms in High-Altitude Exposure: Proteomic and Metabolomic Insights

High-altitude exposure can adversely affect neurocognitive functions; however, the underlying mechanisms remain elusive. Why and how does high-altitude exposure impair neurocognitive functions, particularly sleep? This study seeks to identify the molecular markers and mechanisms involved, with the goal of forming prevention and mitigation strategies for altitude sickness. Using serum proteomics and metabolomics, we analyzed blood samples from 23 Han Chinese plain dwellers before and after six months of high-altitude work in Tibet. The correlation analysis revealed biomarkers associated with cognitive alterations. Six months of high-altitude exposure significantly compromised cognitive function, notably, sleep quality. The key biomarkers implicated include SEPTIN5, PCBP1, STIM1, UBE2L3/I/N, amino acids (l/d-aspartic acid and l-glutamic acid), arachidonic acid, and S1P. Immune and neural signaling were suppressed, with sex-specific differences observed. This study innovatively identified GABA, arachidonic acid, l-glutamic acid, 2-arachidonoyl glycerol, and d-aspartic acid as biomarkers and elucidated the underlying mechanisms contributing to high-altitude-induced neurocognitive decline with a particular focus on sleep disruption. These findings pave the way for developing preventive measures and enhancing adaptation strategies. This study underscores the physiological significance of high-altitude adaptation, raising new questions about sex-specific responses and long-term consequences. It sets the stage for future research exploring individual variability and intervention efficacy.

[Adaptive Regulation of Glucose Metabolism and Diseases in High-Altitude Areas]

High-altitude regions, characterized by their elevated altitude, are subject to a complex set of environmental conditions including intense ultraviolet radiation, low oxygen levels, low temperatures, and low humidity. These distinctive environmental features lead to unique dietary patterns, lifestyles, and physiological adaptations. Notably, individuals who have just moved into high-altitude areas and those who live there on a long-term basis undergo specific adaptive adjustments in glucose metabolism. Typically, newcomers experience transient elevations in blood glucose levels, which gradually decline after prolonged residence at high altitudes to levels even lower than those found at low altitudes. In general, current findings of observational studies generally suggest a decreased risk of diabetes mellitus among populations inhabiting high-altitude regions. However, the glucose metabolism varies among populations from different high-altitude regions across the world, which indicates that the reshaping of glucose metabolism induced by high altitudes is a complicated phenomenon. This article provides an overview of the impact of various components of high-altitude environment, characteristic lifestyle factors, and socioeconomic development levels on glucose metabolism and the related diseases and the potential mechanisms involved. The aim is to offer valuable insights for researchers investigating glucose metabolism in high-altitude settings.

Gut Microbiota Dysbiosis, Oxidative Stress, Inflammation, and Epigenetic Alterations in Metabolic Diseases

Gut dysbiosis, resulting from an imbalance in the gut microbiome, can induce excessive production of reactive oxygen species (ROS), leading to inflammation, DNA damage, activation of the immune system, and epigenetic alterations of critical genes involved in the metabolic pathways. Gut dysbiosis-induced inflammation can also disrupt the gut barrier integrity and increase intestinal permeability, which allows gut-derived toxic products to enter the liver and systemic circulation, further triggering oxidative stress, inflammation, and epigenetic alterations associated with metabolic diseases. However, specific gut-derived metabolites, such as short-chain fatty acids (SCFAs), lactate, and vitamins, can modulate oxidative stress and the immune system through epigenetic mechanisms, thereby improving metabolic function. Gut microbiota and diet-induced metabolic diseases, such as obesity, insulin resistance, dyslipidemia, and hypertension, can transfer to the next generation, involving epigenetic mechanisms. In this review, we will introduce the key epigenetic alterations that, along with gut dysbiosis and ROS, are engaged in developing metabolic diseases. Finally, we will discuss potential therapeutic interventions such as dietary modifications, prebiotics, probiotics, postbiotics, and fecal microbiota transplantation, which may reduce oxidative stress and inflammation associated with metabolic syndrome by altering gut microbiota and epigenetic alterations. In summary, this review highlights the crucial role of gut microbiota dysbiosis, oxidative stress, and inflammation in the pathogenesis of metabolic diseases, with a particular focus on epigenetic alterations (including histone modifications, DNA methylomics, and RNA interference) and potential interventions that may prevent or improve metabolic diseases.

Integrated Microbiome and Serum Metabolome Analysis Reveals Molecular Regulatory Mechanisms of the Average Daily Weight Gain of Yorkshire Pigs

The average daily weight gain (ADG) is considered a crucial indicator for assessing growth rates in the swine industry. Therefore, investigating the gastrointestinal microbiota and serum metabolites influencing the ADG in pigs is pivotal for swine breed selection. This study involved the inclusion of 350 purebred Yorkshire pigs (age: 90 ± 2 days; body weight: 41.20 ± 4.60 kg). Concurrently, serum and fecal samples were collected during initial measurements of blood and serum indices. The pigs were categorized based on their ADG, with 27 male pigs divided into high-ADG (HADG) and low-ADG (LADG) groups based on their phenotype values. There were 12 pigs in LADG and 15 pigs in HADG. Feces and serum samples were collected on the 90th day. Microbiome and non-targeted metabolomics analyses were conducted using 16S rRNA sequencing and liquid chromatography-mass spectrometry (LC-MS). Pearson correlation, with Benjamini-Hochberg (BH) adjustment, was employed to assess the associations between these variables. The abundance of Lactobacillus and Prevotella in LADG was significantly higher than in HADG, while Erysipelothrix, Streptomyces, Dubosiella, Parolsenella, and Adlercreutzia in LADG were significantly lower than in HADG. The concentration of glutamine, etiocholanolone glucuronide, and retinoyl beta-glucuronide in LADG was significantly higher than in HADG, while arachidonic acid, allocholic acid, oleic acid, phenylalanine, and methyltestosterone in LADG were significantly lower than in HADG. The Lactobacillus-Streptomyces networks (Lactobacillus, Streptomyces, methyltestosterone, phenylalanine, oleic acid, arachidonic acid, glutamine, 3-ketosphingosine, L-octanoylcarnitine, camylofin, 4-guanidinobutyrate 3-methylcyclopentadecanone) were identified as the most influential at regulating swine weight gain. These findings suggest that the gastrointestinal tract regulates the daily weight gain of pigs through the network of Lactobacillus and Streptomyces. However, this study was limited to fecal and serum samples from growing and fattening boars. A comprehensive consideration of factors affecting the daily weight gain in pig production, including gender, parity, season, and breed, is warranted.