Forsythiaside A alleviated carbon tetrachloride-induced liver fibrosis by modulating gut microbiota composition to increase short-chain fatty acids and restoring bile acids metabolism disorder

Liver fibrosis is a chronic and progressive disease with complex pathogenesis related to bile acids (BAs) and gut microbiota. Forsythiaside A (FTA), isolated from the traditional Chinese medicine Forsythiae Fructus (Lian Qiao), is a natural hepatoprotective agent. The purpose of this study was to investigate the protective effect of FTA on carbon tetrachloride (CCl4)-induced liver fibrosis in mice. Liver fibrosis was induced in mice by intraperitoneal injection of 2 mL/kg CCl4 three times a week for 4 weeks. FTA attenuated CCl4-induced liver fibrosis in mice, which was proved by the results of Masson and Sirius red staining, liver hydroxyproline, hyaluronic acid, laminin, type III procollagen, and type IV collagen assays. FTA inhibited hepatic stellate cell activation, and reduced hepatic inflammation and oxidative stress in mice treated with CCl4. What’s more, FTA ameliorated CCl4-induced gut dysbiosis, maintained intestinal barrier function, increased the production of short-chain fatty acids (SCFAs), and improved endotoxemia, as manifested by decreased serum lipopolysaccharide levels and increased expression of ileal tight junction proteins. Besides, FTA can modulate the genes related to bile acid metabolism to alter the distribution of fecal BAs in fibrotic mice. In a word, FTA can improve liver fibrosis by inhibiting inflammation and oxidative stress, regulating gut microbiota and BA metabolism, and increasing the content of SCFAs. The results of this study provided an important reference for the study on the mechanisms by which natural products prevent liver fibrosis.