Metformin alleviates liver fibrosis in mice by enriching Lactobacillus sp. MF-1 in the gut microbiota.

BACKGROUND: Liver fibrosis is associated with gut dysbiosis. Metformin administration has emerged as a promising method for the treatment of organ fibrosis. We aimed to investigate whether metformin ameliorates liver fibrosis by enhancing the gut microbiota in mice with carbon tetrachloride (CCl4 )-induced liver fibrosis and the underlying mechanism.

MATERIALS AND METHODS: A liver fibrosis mouse model was established, and the therapeutic effects of metformin were observed. We administered antibiotic treatment and performed fecal microbiota transplantation (FMT), and 16S rRNA-based microbiome analysis to evaluate the effects of the gut microbiome on metformin-treated liver fibrosis. We isolated the bacterial strain preferably enriched by metformin and assessed its antifibrotic effects.

RESULTS: Metformin treatment repaired the gut integrity of the CCl4 -treated mice. It reduced the number of bacteria in colon tissues and reduced the portal vein lipopolysaccharide (LPS) levels. The FMT performed on the metformin-treated CCl4 mice alleviated their liver fibrosis and reduced their portal vein LPS levels. The markedly changed gut microbiota was screened out from the feces and named Lactobacillus sp. MF-1 (L. sp. MF-1). In the CCl4 -treated mice, daily gavage of L. sp. MF-1 maintained gut integrity, inhibited bacterial translocation, and reduced liver fibrosis. Mechanistically, metformin or L. sp. MF-1 inhibited the apoptosis of intestinal epithelial cells and restored CD3+ intestinal intraepithelial lymphocytes in the ileum and CD4+ Foxp3+ lamina propria lymphocytes in the colon.

CONCLUSIONS: Metformin and its enriched L. sp. MF-1 can reinforce the intestinal barrier to alleviate liver fibrosis by restoring immune function.