Acute effects of insulin on skeletal muscle growth and differentiation genes in men with type 2 diabetes

Aims: Insulin has anabolic effects on skeletal muscle. However, there is limited understanding of the molecular mechanisms underlying this effect in humans. We evaluated whethe r the skeletal muscle expression of satellite cell activator fibroblast growth factor 2 (FGF2) and muscle growth an d differentiation factors are modulated acutely by insulin during euglycemic-hyperinsulinemic clamp (EHC). Design and methods: This is a secondary investigation and analysis of samples obta ined from a previously completed trial investigating the effect of testosterone replacement in ma les with hypogonadotropic hypogonadism and type 2 diabetes. Twenty men with type 2 diabetes underwent quadriceps muscle biopsies before and after 4 h of EHC. Results: The infusion of insulin during EHC raised the expression of my ogenic growth factors, myogenin (by 72 ± 20%) and myogenin differentiation protein (MyoD; by 81 ± 22%). Insulin reduced the expression of muscle hypertrophy suppressor, myogenic regulatory factor 4 (MRF4) by 34 ± 14%. In addition, there was an increase in expression of FGF receptor 2, but not FGF2, following EHC. The expression of myos tatin did not change. Conclusions: Insulin has an acute potent effect on expression of genes that can stimulate muscle differentiation and growth.