Myotubes from lean and severely obese subjects with and without type 2 diabetes respond differently to an in vitro model of exercise

Exercise improves insulin sensitivity and oxidative capacity in skeletal muscles. However, the effect of exercise on substrate oxidation is less clear in obese and type 2 diabetic subjects than in lean subjects. We investigated glucose and lipid metabolism and gene expression after 48 h with low-frequency electrical pulse stimulation (EPS), as an in vitro model of exercise, in cultured myotubes established from lean nondiabetic subjects and severely obese subjects (BMI ≥ 40 kg/m2) with and without type 2 diabetes. EPS induced an increase in insulin sensitivity but did not improve lipid oxidation in myotubes from severely obese subjects. Thus, EPS-induced increases in insulin sensitivity and lipid oxidation were positively and negatively correlated to BMI of the subjects, respectively. EPS enhanced oxidative capacity of glucose in myotubes from all subjects. Furthermore, EPS reduced mRNA expression of slow fiber-type marker (MYH7) in myotubes from diabetic subjects; however, the protein expression of this ...