Revealing the Causal Relationship of the Gut‐Liver Axis in MASH : A Study Based on Mendelian Randomization and Multi‐Omics

ABSTRACT Metabolic dysfunction‐associated steatohepatitis (MASH) is a serious chronic liver disease. Its pathogenesis is complex, involving lipid metabolism disorders, inflammation, and intestinal microbiota imbalance, but the specific mechanism and causal relationship remain unclear. This study aims to explore the causal relationship between the gut microbiota and MASH, and to further clarify the regulatory mechanism of liver metabolites and targets. The causal association of gut microbiota with MASH was screened using Mendelian randomization (MR) analysis. Subsequently, mice were fed a 12‐week choline‐deficient, l‐amino acid‐defined, high‐fat diet (CDAHFD) to establish the MASH model. Hematoxylin and eosin (H&E) and Masson staining were performed to assess liver pathology. Fecal microbiota was analyzed using 16S rRNA sequencing technology, and bacteria consistent with the MR analysis results were screened. Liver metabolites were detected by metabolomics technology. Spearman correlation analysis was applied to clarify gut microbes associated with the metabolites. The targets of differential metabolites were predicted by bioinformatics methods and validated by Western blot. MR analysis identified 11 gut microbes that were causally linked to MASH. MASH mice exhibited dysbiosis of the intestinal microbiota and alterations of liver metabolites. Correlation analysis indicated that intestinal microbiota were closely related to unsaturated fatty acids and their derivatives. The function of differential metabolites was enriched in fatty acid metabolism. Molecular experiments showed that PPARα and PPARγ were effective targets. Gut microbiota and liver metabolites showed significant correlations. Further acting on the PPAR signaling pathway, they played a crucial role in the pathogenesis of MASH.