The alteration of bile acids and gut microbiota is associated with intestinal barrier dysfunction and inflammaging in human

Background: The increasing prevalence of age-related chronic diseases, driven by the aging population, poses substantial medical and economic challenges. Emerging researches have underscored the crucial roles of gut microbiota and bile acids (BAs) in metabolic and physiological functions regulation. Methods: 100 elderly and 100 young participants were enrolled in this study. Fecal and serum BAs were quantified by liquid chromatography-tandem mass spectrometry (LC-MS/MS), while gut microbiota composition was assessed through 16S rRNA gene sequencing. Cytokine levels were measured by Enzyme-Linked Immunosorbent Assay (ELISA). Results: Elderly participants exhibited significantly lower levels of primary fecal BAs, particularly cholic acid (CA) and chenodeoxycholic acid (CDCA), alongside an increase in secondary BAs such as lithocholic acid (LCA), leading to a marked reduction in the primary/secondary BAs ratio. Serum showed a decline in both conjugated and unconjugated BAs, primary/secondary BAs ratio, while a notable rise in 12α-OH/non-12α-OH BAs. Furthermore, increased levels of P21, LPS, IL-6, and TNF-α in the elderly were associated with specific BA changes, including reduced fecal unconjugated primary BAs and increased LCA. Significant differences in gut microbiota composition were observed, with the elderly displaying a higher abundance of microbiota capable of 7α-dehydroxylation. Correlations were observed among BAs, gut microbiota alterations, and markers of chronic inflammation and intestinal barrier dysfunction. Conclusion: Aging is associated with significant changes in the BA pool, which are associated with gut microbiota dysbiosis. These alterations may be related to intestinal barrier dysfunction and chronic low-grade inflammation. Modulating BA metabolism presents a potential strategy for mitigating the aging process. Due to the cross-sectional design, causal relationships cannot be established.