Calculus Bovis ameliorates primary sclerosing cholangitis via a dual-pronged mechanism restoring bile acid and lipid homeostasis in the gut-liver axis

Objective: Primary sclerosing cholangitis (PSC) is a progressive cholestatic liver disease lacking FDA-approved therapy. Calculus Bovis (CB), a traditional medicine derived from animal gallstones, has been historically used for treating hepatobiliary diseases, but its therapeutic potential and mechanisms in PSC remain unexplored. This study aimed to investigate the efficacy of CB in an experimental PSC model and elucidate its underlying mechanisms.

Methods: A PSC mouse model was induced by a 0.1% 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC) diet for 4 weeks. Mice were treated with CB (50,100, 150 mg/kg/day) or ursodeoxycholic acid (UDCA, 100 mg/kg/day). Liver injury, fibrosis, intestinal barrier integrity, bile acid (BA) profiles, and lipid levels were assessed. Hepatic and intestinal gene/protein expression related to BA and lipid metabolism was analyzed. Integrated transcriptomics, network pharmacology, and in vitro serum pharmacology were employed to elucidate the underlying mechanisms.

Results: CB administration significantly alleviated liver injury, fibrosis, and intestinal barrier damage in DDC-induced mice. It restored BA homeostasis across the gut-liver axis, normalizing aberrant BA profiles in serum and liver while increasing BA excretion in feces. CB also ameliorated dyslipidemia, reducing hepatic and serum lipid levels. Mechanistically, CB and its bioactive BA components exerted their effects through a dual-pronged mechanism: (1) activation of the SIRT1-PGC-1α axis to transcriptionally upregulate the expression of nuclear receptors FXR and PPARα in the liver and intestine, and (2) direct ligand-dependent activation of FXR and PPARα protein functions. This concerted activation enhanced the transcription of genes involved in BA detoxification, transport, and fatty acid β-oxidation. Inhibition of SIRT1 or antagonism of FXR/PPARα attenuated these protective effects in vitro.

Conclusion: CB attenuates experimental PSC by modulating BA and lipid homeostasis via the gut-liver axis, mediated through a novel dual mechanism involving SIRT1-PGC-1α pathway activation and direct receptor agonism. These findings not only highlight CB as a promising multi-target agent for PSC treatment, but also provide novel insights into the therapeutic modulation of metabolism in the gut-liver axis.