Role of gut/liver metabolites and gut microbiota in liver fibrosis caused by cholestasis

Aim of the study: Cholestasis induces severe liver injury and subsequent liver fibrosis. However, a comprehensive understanding of the relationships between liver fibrosis and cholestasis-induced changes in metabolites in the gut and fibrotic liver tissue and in the gut microbiota is insufficient. Methods: Common bile duct ligation (BDL) was employed to establish a cholestatic liver fibrosis model in mice for 26 days. Fibrotic liver tissue and the gut contents were collected. Untargeted metabolomics was conducted for the determination of metabolites in the gut contents and liver tissues. Metagenomics was adopted to explore the gut microbiota. Results: The metabolites in the gut contents and liver tissues between normal and cholestatic liver fibrosis mice were highly distinct. Beta-alanine metabolism and glutathione metabolism were downregulated in the gut of the BDL group. Galactose metabolism, biosynthesis of unsaturated fatty acids, and ABC transporters were upregulated in the gut and downregulated in the liver of the BDL group. Arginine biosynthesis, taurine and hypotaurine metabolism, arginine and proline metabolism, and primary bile acid biosynthesis were downregulated in the gut and upregulated in the liver of the BDL group. Metagenomic analysis revealed that the alpha diversity of the microbiota in the BDL group decreased. The altered structure of the gut microbiota in the BDL group led to the hypofunction of important metabolic pathways (such as folate biosynthesis, histidine metabolism, thiamine metabolism, biotin metabolism, and phenylalanine, tyrosine and tryptophan biosynthesis) and enzymes (such as NADH, DNA helicase, and DNA-directed DNA polymerase). Correlation analyses indicated that certain gut microbes were associated with gut and liver metabolites. Conclusions: Untargeted metabolomics and metagenomics provided comprehensive information on gut and liver metabolism and gut microbiota in mice with cholestatic liver fibrosis. Therefore, significantly altered bacteria and metabolites may help provide some targets against cholestatic liver fibrosis in the future.