Duodenal-jejunal bypass ameliorates MASLD in rats by regulating gut microbiota and bile acid metabolism through FXR pathways.

Background: Although bariatric and metabolic surgical methods, including duodenal-jejunal bypass (DJB), were shown to improve metabolic dysfunction-associated steatotic liver disease (MASLD) in clinical trials and experimental rodent models, their underlying mechanisms remain unclear. The present study therefore evaluated the therapeutic effects and mechanisms of action of DJB in rats with MASLD.

Methods: Rats with MASLD were randomly assigned to undergo DJB or sham surgery. Rats were orally administered a broad-spectrum antibiotic cocktail (Abx) or underwent fecal microbiota transplantation to assess the role of gut microbiota in DJB-induced improvement of MASLD. Gut microbiota were profiled by 16S rRNA gene sequencing and metagenomic sequencing, and bile acids (BAs) were analyzed by BA-targeted metabolomics.

Results: DJB alleviated hepatic steatosis and insulin resistance in rats with diet-induced MASLD. Abx depletion of bacteria abrogated the ameliorating effects of DJB on MASLD. Fecal microbiota transplantation from rats that underwent DJB improved MASLD in high-fat diet-fed recipients by reshaping the gut microbiota, especially by significantly reducing the abundance of Clostridium. This, in turn, suppressed secondary BA biosynthesis and activated the hepatic BA receptor, farnesoid X receptor. Inhibition of farnesoid X receptor attenuated the ameliorative effects of post-DJB microbiota on MASLD.

Conclusions: DJB ameliorates MASLD by regulating gut microbiota and BA metabolism through hepatic farnesoid X receptor pathways.