Intervention of Shugan Xiaozhi Decoction on Nonalcoholic Fatty Liver Disease via Mediating Gut-Liver Axis

Nonalcoholic fatty liver disease (NAFLD) is a chronic liver disease with an increasing incidence rate but few therapies. Shugan Xiaozhi decoction (SX) has demonstrated beneficial effects in treating NAFLD with an unclear mechanism. This study was aimed at investigating the therapeutic mechanism of SX on high-fat diet-induced NAFLD rats via the gut-liver axis. Hepatic steatosis and integrity of intestinal mucosa in NAFLD rats were assessed by histopathological staining. The level of lipid and inflammation were estimated by enzyme-linked immunosorbent assay. Western Blotting was used to detect apolipoprotein (apo) B48 expression. 16S rRNA analysis was used to measure the changes of gut microbial composition after SX treatment. The expressions of zona occludens 1 protein (ZO-1), occludin, and secretory immunoglobulin A (sIgA) in the colon were detected by immunostaining to investigate the intestinal barrier function. Our study found that SX reduced hepatic steatosis, the levels of alanine aminotransferase, aspartate aminotransferase, total cholesterol, and triglyceride and apoB48 expression but increased peroxisome proliferator activated receptor alpha (PPAR alpha) level. Moreover, SX altered the diversity of gut microbiota, upregulating the relative abundance of f_Prevotellaceae, while downregulating f_Bacteroidales_ S24-7, f_Lachnospiraceae, f_Ruminococcaceae, f_Erysipelotrichaceae, and f_Desulfovibrionaceae. By increasing the expression of ZO-1 and occludin and decreasing the level of proinflammatory factors, including sIgA, lipopolysaccharide, tumor necrosis factor-alpha, interleukin-1 beta, monocyte chemotactic protein-1, and transforming growth factor-beta 1, SX improved intestinal mucosal integrity and barrier function. Our study illustrated that the gut-liver axis was a potential way for SX to ameliorate NAFLD, that is, by regulating the expression of PPAR alpha, apoB48, and modulating gut microbiota to protect the intestinal barrier function, and thus alleviate lipid deposition and inflammatory response in the liver.