SKELETAL-MUSCLE MYOSIN HEAVY-CHAIN SYNTHESIS IN TYPE-1 DIABETES

Although insulin's anticatabolic effect on protein metabolism in type 1 diabetes has been clearly shown to be related to the inhibition of p rotein breakdown, insulin's effect on muscle protein synthesis remains controversial. Cross-limb studies and measurements of synthesis rates of mixed muscle protein have yielded conflicting results. These measu rements represent the mean synthesis of several muscle proteins and ma y miss changes in the synthesis rates of individual muscle proteins. W e measured the fractional synthesis rates of myosin heavy chain (MHC), the principal muscle contractile protein, and mixed muscle protein (M MP) in six type 1 diabetic patients during insulin deprivation and ins ulin treatment. Comparisons were made with six healthy control subject s. Muscle biopsies were taken at 2 h and 8 h during a primed continuou s infusion of L-[1-C-13]leueine. MHC was purified by a preparative con tinuous elution gel electrophoresis, and fractional synthesis rates we re calculated. We found that in type 1 diabetic subjects, the fraction al synthesis rates of MHC and MMP during insulin treatment are similar to those of control subjects. Acute insulin deprivation did not affec t either the synthesis rate or the ratio of MHC to MMP in type 1 diabe tic subjects. In the postabsorptive state, acute insulin deprivation h as no effect on MHC or MMP synthesis in type 1 diabetic patients.