Intestinal FXR deficiency uncouples steatosis protection from liver inflammation and fibrosis in MASH-diet fed mice.

The Farnesoid X Receptor (FXR), a nuclear bile acid (BA) receptor highly expressed in the liver and intestine, is a potential pharmacological target for Metabolic dysfunction-Associated SteatoHepatitis (MASH). While intestinal FXR inhibition reduces high-fat diet (HFD)-induced hepatic steatosis, its role in MASH progression remains unclear. This study investigates the impact of intestinal FXR-deficiency on MASH development in a diet-induced murine model. Intestinal FXR-deficient (intFXR KO) and control mice were fed a high-fat, sucrose, and cholesterol-enriched diet (HFSC) for 24 weeks. Intestinal immune phenotyping, microarray, 16 S rRNA sequencing, bile acid quantification and liver assessments (histology, biochemistry and single-cell RNA sequencing (scRNA-seq)) were performed. intFXR KO mice were protected against HFSC diet-induced obesity and hepatic steatosis but exhibited altered expression of intestinal barrier-associated genes, with increased cytotoxic CD8+ T-lymphocytes. Microbiota composition and bile acid profiles were altered, including reduced Lachnospiraceae species correlating negatively with liver hyocholic acid levels. Despite a protection against hepatic steatosis, liver inflammation and fibrosis were unchanged in intFXR KO mice. Transcriptomic and Immune cell scRNA-seq analysis revealed alteration in immune-related pathways with an increased neutrophil proportion and higher cDC1:cDC2 and CD4:CD8 T cell ratios. Thus, intestinal FXR-deficiency limits steatosis but promote a distinct hepatic immune-inflammatory response and does not prevent progression to MASH.