Gegen-Qinlian decoction alleviates metabolic dysfunction-associated steatohepatitis by modulating the microbiota-bile acid axis in mice

Ethnopharmacological relevance: Metabolic dysfunction-associated steatohepatitis (MASH) is the progressive form of metabolic dysfunction-associated steatotic liver disease (MASLD), and is currently the most prevalent chronic liver disease worldwide. Gegen-Qinlian decoction (GQD), a classical Traditional Chinese Medicine (TCM) formula from Treatise on Febrile Diseases, has been historically used to treat heat-dampness syndromes. Recent studies revealed that GQD is effective in treating MASH, but the underlying mechanisms remain unknown. Aim of the study: This study aims to evaluate the therapeutic effect of GQD on MASH and explore the potential mechanisms targeting the gut microbiota-bile acid (BA) axis. Materials and methods: Phytochemical profiling of GQD was performed using UPLC-Q-TOF-MS. MASH was induced in mice via a fructose-, palmitate-, and cholesterol-enriched (FPC) diet, followed by treatment with low-, medium-, or high-dose GQD. H&E and oil red O staining were utilized to examine the histological change, and serum lipids and enzymes were biochemically analyzed. 16SrDNA sequencing was applied to analyze the alteration of the gut microbiota, and the gas chromatography-mass spectrometry technique was introduced to investigate the fecal bile acid (BA) profile. Serum lipopolysaccharide (LPS) concentrations were analyzed by enzyme-linked immunosorbent assay. Intestinal tight junction proteins (ZO1, Occludin) and BA receptors (FXR, TGR5, and VDR) were detected by Western blot and immunofluorescence staining. Results: The quality of GQD was confirmed, and GQD treatment improved hepatic steatosis, reduced the content of liver triglyceride (20-40 % reduction, p < 0.01) and cholesterol (20-25 % reduction, p < 0.01) in FPC-induced MASH mice. High-dose GQD further decreased serum TC (3.97 +/- 1.00 vs 5.51 +/- 1.11, p < 0.05), LDL-c (0.53 +/- 0.18 vs 1.07 +/- 0.28, p < 0.01), ALT (31.90 +/- 6.20 vs 47.90 +/- 12.78, p < 0.05) and ALP (90.83 +/- 13.46 vs 132.90 +/- 23.67, p < 0.05) levels, suggesting the effects of GQD in counteracting metabolic inflammation. GQD treatment restored gut microbiota diversity and reversed gut dysbiosis by decreasing the abundance of pathogenic bacteria, resulting in reduced serum LPS while enhancing intestinal tight junction proteins (ZO1, Occludin). Concurrently, GQD treatment reshaped fecal BA profiles, increased intestinal TGR5/VDR expression, with BA shifts strongly correlating to microbiota changes. Conclusion: GQD alleviated hepatic and metabolic disorders in MASH mice, possibly through reversing gut dysbiosis and modulating BA profile. Targeting the microbiota-BA axis represents a promising pattern for TCM prescriptions in treating MASH.