Moderate altitude exposure induced gut microbiota enterotype shifts impacting host serum metabolome and phenome

BACKGROUND: Consistent patterns of gut microbiota variations, particularly in relative abundance, have been identified in the adult human gut. Enterotype, another general measure of the gut microbiota, is a valuable approach for categorizing the human gut microbiota into distinct clusters. The impact of different enterotypes on human health varies, and the changes induced by moderate altitude exposure remain unclear. This study aimed to conduct a comprehensive investigation of the cascade effects triggered by enterotype shifts following moderate altitude exposure. RESULTS: Using shotgun metagenome sequencing, participants before and after moderate-altitude exposure were classified into cluster BL (dominated by Blautia) and cluster BA (dominated by Bacteroides). Relative to cluster BL, cluster BA consisted predominantly of individuals exposed to moderate altitude. Compared to cluster BL, Cluster BA exhibited rewired metabolism of serum metabolites (i.e., amino acids, fatty acids and bile acids) and gut microbiota, lower inflammatory factor levels (i.e., tumor necrosis factor-α (TNF-α)), and sparser correlations among these parameters. Individuals with baseline BL enterotype who transitioned to the BA enterotype following moderate-altitude exposure showed prominent improvement in fasting blood glucose (FBG) levels, with higher abundance of Bacteroidetes species (e.g., Bacteroides thetaiotaomicron, and Bacteroides uniformis), but lower Proteobacteria species abundance (e.g., Escherichia coli) and decreased L-Glutamic acid levels. Furthermore, fecal microbiota transplantation (FMT) from moderate-altitude exposed individuals to high-fat diet (HFD) fed mice confirmed increased Bacteroides abundance shifts associated with improvements in glucose homeostasis regulation and rewired amino acid metabolism. In addition, significant increases in alanine aminotransferase (ALT) levels but decreased serum creatinine (Scr), arterial oxygen saturation (SaO2), 4-Hydroxyproline, L-Glutamic acid, L-Asparagine, L-Threonine, L-Citrulline, L-Lysine and Isovaleric acid levels were identified as potentially important signals for individuals upon moderate altitude exposure, regardless of the gut microbiota enterotype. CONCLUSIONS: Moderate altitude exposure could induce enterotype switching, and a Bacteroides-dominant enterotype may be a beneficial pattern of the gut microbiome related to host metabolism. Moderate-altitude exposure has potential implications for glycemic control, suggesting new avenues for managing FBG levels in future.