<i>Panax notoginseng</i> Saponins Alleviate Inflammatory Bowel Disease via Alteration of Gut Microbiota–Bile Acid Metabolism

Bile acid metabolism mediated by gut microbiota is significantly related to immunity regulation that plays an important role in the development and treatment of inflammatory bowel disease (IBD). Our previous study has demonstrated that <i>Panax notoginseng</i> saponins (PNS) alleviate colitis due to the regulation of T helper 17/Regulatory T cells (Th17/Treg) balance via gut microbiota. However, the effects and mechanism of PNS on colitis pertinent to bile acid metabolism mediated by gut microbiota remain elusive. This study aims to investigate the anti-colitis mechanism of PNS by regulating the Th17/Treg balance pertinent to gut microbiota-bile acid metabolism. Results showed that PNS significantly decreased the relative abundance of <i>Allobaculum</i>, <i>Dubosiella</i>, <i>Muribaculum</i>, and <i>Alistipes</i>, and up-regulated the relative contents of conjugated bile acids, such as TCA and TCDCA. Fecal microbiota transplantation (FMT) showed that the gut microbiota remodeled by PNS had a regulatory effect on bile acid metabolism, and up-regulated the relative contents of TCA and TCDCA, which alleviated IBD and promoted Treg cell expression <i>in</i> <i>vivo</i> and <i>in vitro</i>. Taken together, PNS could reshape the profiling of gut microbiota to generate more TCA and TCDCA, which improve the balance of Th17/Treg to exert anti-IBD effects.