Schisandra polysaccharide inhibits hepatic lipid accumulation by downregulating expression of SREBPs in NAFLD mice

Background: Hepatoprotective effects of Chinese herbal medicine Schisandra Chinensis (Schisandra) have been widely investigated. However, most studies were focused on its lignan extracts. We investigated the effects of Schisandra polysaccharide (SCP) in a mouse model of non-alcoholic fatty liver disease (NAFLD), and studied its effect on sterol regulatory element binding proteins (SREBPs) and the related genes. Methods: The mouse model of NAFLD was established by feeding mice with a high-fat diet for 16 weeks. Effect of SCP-treatment (100 mg/kg, once daily for 12 weeks) on biochemical parameters and liver histopathology was assessed. Relative levels of sterol regulatory element-binding proteins (SREBPs) and their gene expressions were determined by quantitative real-time polymerase chain reaction and Western Blot. Results: SCP significantly reduced the liver index by 12.0%. Serum levels of triglycerides (TG), total cholesterol (TC), low-density lipoprotein cholesterol, alanine aminotransferase and aspartate aminotransferase were decreased by 31.3, 28.3, 42.8, 20.1 and 15.5%, respectively. Serum high-density lipoprotein cholesterol was increased by 26.9%. Further, SCP lowered hepatic TC and TG content by 27.0% and 28.3%, respectively, and alleviated fatty degeneration and necrosis of liver cells. A significant downregulation of mRNA and protein expressions of hepatic lipogenesis genes, SREBP-1c, fatty acid synthase and acetyl-CoA carboxylase, and the mRNA expression of liver X receptor alpha (LXR alpha) was observed in NAFLD mice treated with SCP. SCP also significantly reduced the hepatic expression of SREBP-2 and 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGCR). Conclusion: These findings demonstrate the hepatoprotective effects of SCP in a mouse model of NAFLD; the effects may be mediated via downregulation of LXRa/SREBP-1c/FAS/ACC and SREBP-2/HMGCR signaling pathways in the liver.