Amelioration of non-alcoholic steatohepatitis by Qushi Huayu decoction is associated with inhibition of the intestinal mitogen-activated protein kinase pathway

Background: Gut microbiota is increasingly recognized as the key participant in the pathogenesis of non-alcoholic fatty liver disease (NAFLD) by translocation of its products, such as lipopolysaccharide (LPS), via the dysfunctional intestinal barrier. Qushi Huayu decoction (QHD), a traditional Chinese medicine, is developed specially for NAFLD and used in clinic in China for more than a decade and previously found to ameliorate nonalcoholic steatohepatitis (NASH) induced by high-fat diet (HFD) in mice accompanied with inhibited metabolic endotoxemia and hepatic LPS signalling. Purpose: To investigate the mechanism of LPS gut-leakage inhibition by QHD in NASH. Methods: Effects of QHD on gut microbioa and intestinal barrier were evaluated in NASH induced by HFD in mice. 16S rRNA sequencing is employed to analyse the gut microbiota composition. To identify the potential signalling pathway responsible for tight junction regulation, the colonic phosphoprotein profile is screened via the Phospho Explorer Antibody Array and verified in NASH, intestinal barrier dysfunctional mouse and Caco-2 cells. Results: HD ameliorates NASH accompanied with regulating the gut microbiota composition, protecting intestinal tight junctions and inhibiting LPS gut-leakage without decreasing the abundance of identified Gram-negative bacteria. The validated data of phosphorylated proteins suggested that mitogen-activated protein kinase (MAPK) pathway is predominantly responsible for the colonic tight junction regulation by QHD. Conclusion: QHD inhibits LPS gut-leakage in NASH, which is associated with downregulation of intestinal MAPK pathway.