Alteration of small intestinal microbiota in diet-induced steatohepatitis mice.

OBJECTIVE

Dysbiosis is an important factor that exacerbate metabolic dysfunction-associated steatohepatitis (MASH) via the gut-liver axis. The alterations in the small intestinal microbiota and their contribution to MASH pathogenesis remain largely unexplored. The present study aimed to clarify the alteration of small intestinal microbiota and the gene expression in a diet-induced mouse model of MASH.

METHODS

C57BL6/J mice were fed a choline-deficient L-amino acid-defined high-fat diet (CDAHFD) to induce MASH. qRT-PCR was performed to evaluate the gene expression in liver and ileal tissues. Gut microbiota analysis of small intestinal contents was conducted by 16 S rRNA gene sequencing. The profiles of lamina propria mononuclear cells in the ileum were investigated by flow cytometry analysis. Intestinal mucosal permeability and epithelial expression of Zonula occludens-1 (ZO-1) protein were analyzed by FITC-dextran assay and immunofluorescence, respectively.

RESULTS

Significant fat accumulation was observed at 3 weeks after the start of CDAHFD, and clusters of F4/80-positive cells were observed at 6 weeks. Three weeks of CDAHFD feeding significantly altered the composition of the intestinal microbiota, characterized by a decrease in the abundance of Lactobacillus and Candidatus Arthromitus. Concurrently, mRNA expression of IL-10 and IL-17 A was significantly downregulated in the ileum, accompanied by a reduction in lamina propria IL-17 A+ T cells. At 6 weeks, the mucosal permeability was significantly increased, and the epithelial ZO-1 expression was decreased.

CONCLUSION

Dysbiosis and impaired gut immune system occur in the small intestine during the early phase of MASH development. Small intestinal dysbiosis may be a promising therapeutic target for the progression of MASH.