Triterpenic acids-enriched fraction from Cyclocarya paliurus attenuates insulin resistance and hepatic steatosis via PI3K/Akt/GSK3β pathway

Background: Non-alcoholic fatty liver disease (NAFLD) is the most prevalent form of chronic liver diseases. Cyclocarya paliurus (C. paliurus), an edible and medicinal plant in Chinese folk, has been demonstrated to ameliorate diabetes, obesity and lipid metabolism disorders. However, its effects on NAFLD and its potential molecular mechanism have not been clearly expounded. Purpose: The present study was designed to explore the therapeutic potential of triterpenic acids-enriched fraction from C. paliurus (CPT), as well as its underlying mechanism in vivo and in vitro models of NAFLD. Methods: The metabolic effects and possible molecular mechanism of CPT were examined using HepG2 cells and primary hepatocytes (isolated from C57BL/6 J mice) models of fatty liver induced by palmitic acid (PA) and a high fat diet mouse model. Results: In high fat diet-induced C57BL/6 J mice, CPT significantly reduced liver weight index, serum alanine transaminase (ALT), aspartate transaminase (AST), triacylglycerol (TG), total cholesterol (TC) and hepatic TG, TC levels. Moreover, CPT dramatically decreased the contents of blood glucose, insulin, and insulin resistance (HOMA-IR) index. Meanwhile, CPT significantly increased the tyrosine phosphorylation level of IRS and the uptake of 2-deoxyglucose (2DG) in PA-induced HepG2 cells and primary hepatocytes fatty liver models. Furthermore, in PA-induced HepG2 cells and primary hepatocytes, CPT significantly decreased the number of lipid droplets and intracellular TG content. In addition, mechanism investigation showed that CPT increased the phosphorylation of phosphoinositide 3-kinase (PI3K), protein kinase B (Akt) and glycogen synthase-3 beta (GSK beta) in vivo and in vitro models, which were abrogated by PI3K inhibitor LY294002 in vitro models. Conclusion: These findings indicate that CPT may exert the therapeutic effects on NAFLD via regulating PI3K/Akt/GSK3 beta pathway.