Probiotic LGG prevents liver fibrosis through inhibiting hepatic bile acid synthesis and enhancing bile acid excretion in mice

: Cholestatic liver disease is characterized by gut dysbiosis and excessive toxic hepatic bile acids (BAs). Modification of gut microbiota and repression of BA synthesis are potential strategies for the treatment of cholestatic liver disease. The purpose of this study was to examine the effects and to understand the mechanisms of the probiotic, Lactobacillus rhamnosus GG (LGG), on hepatic bile acid synthesis, liver injury and fibrosis in bile-duct ligation (BDL) and Mdr2-/- mice. Global and intestinal specific FXR inhibitors were used to dissect the role of FXR. LGG treatment significantly attenuated liver inflammation, injury and fibrosis with a significant reduction of hepatic BAs in BDL mice. Hepatic concentration of T-βMCA, an FXR antagonist, was markedly increased in BDL mice and reduced in LGG-treated mice, while chenodeoxycholic acid (CDCA), an FXR agonist, was decreased in BDL mice and normalized in LGG-treated mice. LGG treatment significantly increased the expression of serum and ileum FGF15 and subsequently reduced hepatic CYP7A1 and BA synthesis in BDL and Mdr2-/- mice. At the molecular level, these changes were reversed by global and intestinal specific FXR inhibitors in BDL mice. In addition, LGG treatment altered gut microbiota, which was associated with increased BA de-conjugation and increased fecal and urine BA excretion both in BDL and Mdr2-/- mice. In vitro studies showed that LGG suppressed the inhibitory effect of T-βMCA on FXR and FGF19 expression in Caco-2 cells. Conclusion: LGG supplementation decreases hepatic BA by increasing intestinal FXR/FGF15 signaling pathway-mediated suppression of BA de novo synthesis and enhances BA excretion, which prevents excessive BA-induced liver injury and fibrosis in mice.