Tetramethylpyrazine ameliorates metabolic dysfunction-associated steatohepatitis by modulating gut microbiota dysbiosis and restoring intestinal barrier integrity.

Abstract

Background and purpose: This study investigated the therapeutic effects and gut-liver axis-related mechanisms of tetramethylpyrazine (TMP) in metabolic dysfunction-associated steatohepatitis (MASH).

Experimental approach: Male C57BL/6 mice were fed a methionine- and choline-deficient (MCD) diet for 6 weeks to establish MASH. TMP or pioglitazone was administered during the final 3 weeks. Hepatic injury, intestinal barrier integrity, gut microbiota, bile acids (BAs), short-chain fatty acids (SCFAs) and faecal metabolomics were assessed using histology, biochemical assays, RT-qPCR, western blotting, 16S rDNA sequencing and metabolomics. Faecal microbiota transplantation (FMT) and lipopolysaccharide (LPS)-stimulated Caco-2 cells were used to evaluate microbiota-dependent and direct intestinal protective effects of TMP.

Key results: TMP alleviated hepatic steatosis, inflammation and fibrosis in MCD-fed mice. TMP decreased hepatic macrophage infiltration and inflammatory cytokines, including TNF-α, IL-1β and IL-6. In the intestine, TMP restored epithelial structure, increased faecal sIgA, reduced serum LPS, D-lactate, zonulin and TNF-α and up-regulated Claudin-1, ZO-1 and Occludin. TMP improved gut microbial diversity, suppressed proinflammatory bacteria and enriched beneficial taxa. FMT from TMP-treated donors partially reproduced the hepatoprotective effects in recipient mice. TMP further restored BA and SCFA homeostasis, regulated the FXR/FGF15/CYP7A1 axis and remodelled faecal metabolic profiles associated with lipid peroxidation and inflammation. In Caco-2 cells, TMP attenuated LPS-induced IL-1β and IL-6 expression and restored Occludin expression.

Conclusion and implications: TMP exerts protective effects against MCD diet-induced MASH by improving hepatic pathology and restoring gut-liver axis homeostasis, including intestinal barrier integrity, gut microbiota composition, BA and SCFA metabolism and faecal metabolic balance.