ABSTRACT
Objective To investigate the effects of recombinant adeno-associated virus-mediated myostatin propeptide (MPRO) on uptake and oxidation of glucose,and glycogen synthesis in C2C12 myotubes,as well as the associated molecular mechanism.Methods Mature C2C12 myotubes were assigned to the following 6 groups:control,insulin,green fluorescent protein (GFP),insulin + GFP,MPRO,and insulin + MPRO groups.Glucose uptake,glucose oxidation,and glycogen synthesis were detected by counting radioactivity of 14CO2 or 14C labeled glycogen derived from 2-deoxy-[1-14 C] glucose.The activity of insulin signal pathway was evaluated by Western blot.Results Compared with control group,glucose uptake and glycogen synthesis were significantly increased in insulin and insulin+GFP groups,and further increased in insulin+MPRO group as compared with insulin alone(all P＜ O.05).However,MPRO and insulin had no effect on glucose oxidation.The phosphorylations of insulin receptor (IR) β,insulin receptor substrate 1 (IRS-1),protein kinase B (Akt),glycogen synthase kinase-3 β (GSK-3β),and the expressions of phosphatidylinositol 3-kinase (PI3K) and glucose transporter 4 (Glut4) in membrane were significantly increased in insulin and insulin+GFP groups compared with control group(all P＜0.05),and were further increased after MPRO transfection (all P ＜ 0.05).Conclusion MPRO may increase insulin-stimulated glucose uptake and glycogen synthesis in C2C12 cells by activating the IRS/PI3K/Akt signal pathway.