Bile Derivative T3K Ameliorates Colitis by Regulating the Intestinal Microbiota-Bile Acid Axis

<b>Background/Objectives</b>: The pathogenesis of ulcerative colitis (UC) is complex, and there is an urgent need for effective therapeutic agents with low side effects. Recent studies highlight the critical roles of abnormal bile acid (BA) metabolism and gut microbiota dysbiosis in UC progression. However, there is a significant knowledge gap about the relation between BA and gut microbiota. The BA derivative T3K exerts good anti-UC effect, and its mechanism is still unknown. In this study, we investigate how its anti-UC mechanism is involved in the modulation of the gut microbiota-BA axis and BA metabolism. <b>Methods</b>: Gene expression microarray GSE92415 of UC from the Gene Expression Omnibus was used to analyze BA metabolism. DSS-induced colitis mouse model, Caco-2 and IEC6 cells were used to confirm the anti-UC of T3K using intestinal permeability assay with FITC, Western-blot, immunohistochemical staining, immunofluorescenc and so on in vitro and in vivo. The changes in bile acid and microbiota were measured by 16S rRNA sequencing and bile acid analysis combined with pseudo-germ-free (PGF) models and fecal microbiota transplantation (FMT). <b>Results</b>: T3K demonstrated strong therapeutic effects, including reduced weight loss, lower disease activity index (DAI), and increased colon length. T3K also enhanced the expression of Occludin and Mucin2, and restored gut barrier integrity. Furthermore, T3K improved intestinal dysbiosis and abnormal BA metabolism in colitis mice. Through PGF models and FMT, we confirmed that T3K modulates BA metabolism via the gut microbiota. T3K specifically promotes the growth of beneficial bacteria, such as <i>Akkermansia muciniphila</i>, increases levels of hydrophilic BAs like muricholic acid (MCA), lithocholic acid (LCA) and its derivatives isoLCA and then repairs damaged intestinal mucosa. <b>Conclusions</b>: Bile acid derivative T3K, as a potential anti-UC candidate, effectively restores gut barrier integrity and then ameliorates colitis by improving gut microbiota composition and regulating BA metabolism, including increasing hydrophilic BAs.