Improvement and Mechanism of Ganoderma lucidum Polysaccharides and Its Flora Metabolites on Insulin Resistance in HepG2 Cells

Objective: To investigate the effects of Ganoderma lucidum polysaccharides and its flora metabolites on the insulin resistance status of HepG2 cells and its mechanisms. Methods: Insulin resistant HepG2 (IR-HepG2) model was established with the combination of insulin (10⁻³ µmol/L) and dexamethasone (10 µmol/L). The cytotoxicity of Ganoderma lucidum polysaccharides (GLP) and Ganoderma lucidum polysaccharide flora metabolite (GLP-F) was evaluated using the CCK-8 method. The effects of GLP and GLP-F on glucose consumption and glycogen synthesis in IR-HepG2 cells were evaluated using the glucose kit and glycogen kit methods. Western blot assay was used to detect the effects of GLP and GLP-F on the phosphorylation or expression of IRS-1, AKT, GSK-3β, GLUT2, and PEPCK, key proteins in the insulin signaling cascade in IR-HepG2 cells. Results: Both GLP and GLP-F significantly increased glucose uptake and glycogen synthesis in IR-HepG2 cells (P<0.05). GLP-F promoted glucose consumption in IR-HepG2 cells significantly more than GLP (P<0.05). Western blot experiments showed that both GLP and GLP-F promoted IR-HepG2 cells IRS-1, P-AKT, P-GSK-3β, GLUT2 protein expression and inhibited PEPCK protein expression, and the inhibitory utility of GLP-F on PEPCK was significantly higher than that of GLP (P<0.05). Conclusions: GLP and its metabolism by intestinal flora-mediated production of GLP-F have the same biological effect of alleviating hepatic insulin resistance, and GLP-F has a more significant effect than GLP in promoting glucose consumption in IR-HepG2 cells and inhibiting their gluconeogenic rate-limiting enzyme activity.