The gut microbiota plays a crucial role in maintaining host nutrition, metabolism, and immune homeostasis, particularly in extreme environmental conditions. However, the regulatory mechanisms of the gut microbiota in animal organisms hypobaric hypoxia exposure require further study. We conducted a research by comparing SD rats treated with an antibiotic (ABX) cocktail and untreated SD rats that were housed in a low-pressure oxygen chamber (simulating low pressure and hypoxic environment at 6000 m altitude) for 30 days. After the experiment, blood, feces, and lung tissues from SD rats were collected for analysis of blood, 16S rRNA amplicon sequencing, and non-targeted metabolomics. The results demonstrated that the antibiotic cocktail-treated SD rats exhibited elevated counts of neutrophil (Neu) and monocyte (Mon) cells, an enrichment of sulfate-reducing bacteria (SBC), reduced levels of glutathione, and accumulated phospholipid compounds. Notably, the accumulation of phospholipid compounds, particularly lysophosphatidic acid (LPA), lipopolysaccharide (LPS), and lysophosphatidylcholine (LPC), along with the aforementioned changes, contributed to heightened oxidative stress and inflammation in the organism. In addition, we explored the resistance mechanisms of SD rats in low-oxygen and low-pressure environments and found that increasing the quantity of the Prevotellaceae and related beneficial bacteria (especially Lactobacillus) could reduce oxidative stress and inflammation. These findings offer valuable insights into enhancing the adaptability of low-altitude animals under hypobaric hypoxia exposure.

Ulcerative colitis (UC) is a severe inflammatory bowel disease affecting millions of people worldwide, but the factors driving the condition are poorly understood. In tissue samples from individuals with UC, we found that macrophages were depleted from areas of the colon that did not yet exhibit overt epithelial inflammation. We hypothesized that toxins produced by bacteria could impair macrophages and that this could promote wider inflammation. We isolated a variant of Aeromonas genus from stool samples from UC patients, which we termed macrophage-toxic bacteria (MTB), because aerolysin secreted by MTB caused macrophage death. MTB colonized mice under pathogenic conditions and triggered colitis. Antibodies against aerolysin alleviated colitis induced by Aeromonas in mice. In a cohort, UC patients more frequently tested positive for Aeromonas than healthy controls did.

Prolonged exposure to hypoxic conditions can lead to reduced appetite, stunted growth, systemic inflammation, and pulmonary hypertension. Previous studies have indicated a correlation between gut dysbiosis and the development of hypoxia-related hazards. We designed an experiment to investigate the effect of microbiota on mitigating hypoxic damage. Gut microbiota from high-altitude-adapted species (Ochotona curzoniae) were transplanted into Sprague Dawley (SD) rats, which were then housed in a simulated 6000 m altitude environment for 30 days. After the experiment, we conducted analyses on average daily weight gain (ADG), feed conversion ratio (FCR), mean pulmonary artery pressure (mPAP), gut flora, and fecal metabolism. The results demonstrated that the ADG in the transplantation group (2.98 ± 0.17 g) was significantly higher than in the control groups (2.68 ± 0.19 g and 2.26 ± 0.13 g) (p < 0.05). The FCR was reduced in the transplantation group (6.30 ± 0.33 g) compared to the control groups (8.20 ± 1.15 g and 8.83 ± 0.45 g) (p < 0.05). The mPAP was decreased in the transplantation group (38.1 ± 1.13 mmHg) compared to the control groups (43.4 ± 1.30 mmHg and 43.5 ± 1.22 mmHg) (p < 0.05). Multi-omics analysis revealed that Lachnospiraceae, Desulfovibrionaceae, and specific amino acid metabolic pathways play crucial roles in hypoxia and are associated with both inflammation and nutritional metabolism. This study proposes a novel approach to the treatment of hypoxic pulmonary hypertension and holds potential significance for improving high-altitude developmental potential.

Although mechanical tension from luminal distension is a primary regulator of gut motility, we reveal a parallel chemosensory pathway wherein long-chain unsaturated free fatty acids (LUFFAs) from dietary or enterobacterial sources directly modulate gastrointestinal motor function. Using ex vivo and in vivo contractility assays in human and murine intestinal tissues, we found that LUFFAs, particularly Omega-3 fatty acids, suppressed spontaneous contractions and delayed intestinal transit in a double bond-dependent manner. Mechanistically, selective activation of free fatty acid receptor 1/4 (FFAR1/4) on nitrergic myenteric ganglia triggered a rise in intracellular calcium and nitric oxide release, inducing smooth muscle relaxation independent of epithelial signaling. Genetic ablation of Ffar4 in enteric neurons or defect in enteric nitrergic ganglia abolished LUFFAs-mediated motility suppression and ameliorated colonic dysmotility induced by pathologically elevated LUFFAs levels. Our findings establish nitrergic ganglia as critical chemosensors translating dietary or enterobacterial lipid signals into gut motor responses.