Diabetes, Vol 46, Issue 8 1336-1340, Copyright © 1997 by American Diabetes Association
Skeletal muscle myosin heavy chain synthesis in type 1 diabetes
MR Charlton, P Balagopal and KS Nair
Department of Medicine, Mayo Clinic and Foundation, Rochester, Minnesota 55905, USA.
Although insulin's anticatabolic effect on protein metabolism in type 1
diabetes has been clearly shown to be related to the inhibition of protein
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 measurements
represent the mean synthesis of several muscle proteins and may miss
changes in the synthesis rates of individual muscle proteins. We measured
the fractional synthesis rates of myosin heavy chain (MHC), the principal
muscle contractile protein, and mixed muscle protein (MMP) in six type 1
diabetic patients during insulin deprivation and insulin treatment.
Comparisons were made with six healthy control subjects. Muscle biopsies
were taken at 2 h and 8 h during a primed continuous infusion of
L-[1-13C]leucine. MHC was purified by a preparative continuous elution gel
electrophoresis, and fractional synthesis rates were calculated. We found
that in type 1 diabetic subjects, the fractional synthesis rates of MHC and
MMP during insulin treatment are similar to those of control subjects.
Acute insulin deprivation did not affect either the synthesis rate or the
ratio of MHC to MMP in type 1 diabetic subjects. In the postabsorptive
state, acute insulin deprivation has no effect on MHC or MMP synthesis in
type 1 diabetic patients.