Action Mechanism of Main Components from Glycyrrhizae Radix et Rhizoma in Improving Insulin Resistance in L6 Rat Myoblasts / 中国实验方剂学杂志

ABSTRACT

Objective:To determine whether the main components of Glycyrrhizae Radix et Rhizoma can improve insulin resistance by regulating glycogen synthesis, glycolysis pathway and fatty acid synthesis in myoblasts of L6 rat myoblasts. Method:Insulin resistance (IR) model of L6 rat myoblasts was established through incubation with 0.05 mmol·L-1 palmitic acid (PA) for 9 hours. Normal group, model group, glycyrrhizic acid (GA, 25 μmol·L-1) group, 18β-glycyrrhetinic acid (18β-GA, 25 μmol·L-1) group, isoliquiritigenin (ILG, 25 μmol·L-1) group and isoliquiritin (ILQ, 25 μmol·L-1) group were set up, glucose content in supernatant of cell culture medium was detected by glucose kit, myoblasts glycogen content was determined by glycogen detection kit, protein expression levels of Sterol regulatory element binding protein-1c(SREBP-1c), fatty acid synthetase (FAS) and glycogen synthase kinase3β(GSK3β) were detected by Western blot, and the mRNA expressions of key enzymes in glycolysis were detected by quantitative real-time fluorescence polymerase chain reaction(Real-time PCR). Result:Compared with those in the normal group, the glucose consumption rate was significantly down-regulated in model group (P<0.01), the glycogen content was decreased (P<0.05), the protein expressions of Sterol regulatory element binding protein-1c (SREBP-1c) and fatty acid synthase (FAS) were decreased (P<0.05, P<0.01), the mRNA expressions of fructose phosphate kinase 1 (PFK1), pyruvate kinase (PK) and hexokinase (HK) were down-regulated (P<0.05), and the protein expression of glycogen synthase kinase 3 (GSK3β) protein was increased (P<0.05). Compared with model group, GA, 18β-GA and ILG could significantly increase glycogen content in myoblasts of IR-L6 rats (P<0.05, P<0.01). GA, 18β-GA and ILQ could significantly increase the expression of SREBP-1c (P<0.05, P<0.01), and GA, 18β-GA, ILG and ILQ could significantly increase the expression of FAS (P<0.05, P<0.01), the mRNA expressions of PFK1, PK and HK (P<0.05, P<0.01), and down-regulate the protein expression of GSK3β (P<0.05). Conclusion:The main components of licorice improve the insulin resistance by promoting glycolysis and glycogen synthesis and regulating fatty acid synthesis.