Allo-lithocholic acid, a microbiome derived secondary bile acid, attenuates liver fibrosis

Secondary bile acids, lithocholic acid and deoxycholic acid (LCA and DCA), are dehydroxylated derivatives of primary bile acids. However, in addition to LCA and DCA the intestinal microbiota produced a variety of poorly characterized metabolites. Allo-LCA, a LCA metabolite, acts as a dual GPBAR1 agonist and RORγt inverse agonist and modulates intestinal immunity, although is not yet known whether allo-LCA exerts regulatory functions outside the intestine. In the present study we have therefore investigated whether administration of allo-LCA, 10 mg/kg/day, to mice administered a high fat/high fructose diet (HFD-F) and carbon tetrachloride (Ccl4), a model for metabolic dysfunction-associated steatohepatitis (MASH), protects from development of liver damage. In vitro allo-LCA functions as GPBAR1 agonist and RORγt inverse agonist and prevents macrophages M1 polarization and Th17 polarization of CD4 cells. In vivo studies, while exposure to a HFD-F/Ccl4 promoted insulin resistance and development of a pro-atherogenic lipid profile and liver steatosis and fibrosis, allo-LCA reversed this pattern by improving insulin sensitivity and liver lipid accumulation. The liver transcriptomic profile demonstrated that allo-LCA reversed the dysregulation of multiple pathways associated with immunological, inflammatory and metabolic signaling. Allo-LCA also restored bile acid homeostasis, reversing HFD/Ccl4-induced shifts in bile acid pool composition and restored adipose tissue histopathology and function by reducing the expression of leptin and resistin, two pro-inflammatory adipokines, and restored a healthier composition of the intestinal microbiota. In conclusion, present results expand on the characterization of entero-hepatic signaling and suggest that allo-LCA, a microbial metabolite, might have therapeutic potential in liver diseases.