Insulin treatment increases skeletal muscle fibre area in patients with diabetes mellitus type 2

The effects of insulin treatment on skeletal muscle characteristics were st udied in 18 patients (62 +/- 11 years) with poorly controlled diabetes mell itus type 2 (mean duration 7.5 +/- 6 years). Skeletal muscle biopsy samples were taken from the lateral portion of the quadriceps muscle before and af ter a period of insulin treatment of 40 +/- 14 days. Enzyme activities (pho sphofructokinase, 3-hydroxyacyl-CoA dehydrogenase, citrate synthase, lactat e dehydrogenase and creatine kinase) and myoglobin content were assessed. I n a subgroup of 11 patients (60 +/- 11 years), skeletal muscle fibre type c omposition (type I, IIA, IIB and IIC) and fibre type cross-sectional area w ere also analysed. Following insulin treatment there were 32 and 38% increa ses, respectively, in the cross-sectional areas of type IIA and IIB fast-tw itch fibres (P < 0.02). The fibre type distribution did not change. The myo globin content in muscle decreased by 20% (P < 0.01). Of the enzymes tested , the 3-hydroxyacyl-CoA dehydrogenase activity decreased by 10% (P < 0.04). Serum glucose, HbA1(C) and serum triglyceride levels decreased (P < 0.001) and body weight and arm muscle circumference increased (P < 0.02). In conc lusion, insulin treatment of patients with poorly controlled non-insulin-de pendent diabetes mellitus increased the fast-twitch fibre area, reduced myo globin levels and decreased muscle enzyme activity related to fatty acid ox idation.