Disentangling Organ-Specific Roles of Farnesoid X Receptor in Bile Acid and Glucolipid Metabolism.

Background And Aims: The farnesoid X receptor (FXR) is an attractive pharmaceutical target for metabolic dysfunction-associated steatotic liver disease (MASLD). However, its tissue-specific roles in energy metabolism remain controversial, hindering the development of effective therapies. To address this, new approaches are required.

Methods: A novel mouse model was developed to facilitate the re-expression of endogenous FXR in specific tissues on a global FXR-null background. Liver-specific and gut-specific FXR re-expression models were generated. Mice were subjected to a high-fat diet (HFD) for 12 weeks, after which metabolic indices, bile acid (BA) profiles, and gut microbiota composition were analysed. Antibiotic treatment was used to mimic germ-free conditions.

Results: The resistance of FXR-null mice to MASLD and most HFD-induced metabolic disorders, including increased body weight, adiposity, hepatic triglyceride (TG) accumulation, and hyperglycemia, was reversed by liver, but not gut, FXR re-expression. Gut FXR re-expression restored the increased intestinal TG absorption in FXR-null mice by limiting 12OH BA synthesis and inhibiting intestinal microsomal triglyceride transfer protein (MTTP). Moreover, gut FXR activity was essential for gut microbiota-driven promotion of diet-induced obesity (DIO) and MASLD.

Conclusions: Our study overcomes the limitations of traditional tissue-specific knockout models, providing a more comprehensive understanding of FXR's complex roles in metabolic homeostasis, encouraging the development of organ-specific FXR targeting strategy.