Effects of intensity of acute-resistance exercise on rates of protein synthesis in moderately diabetic rats.

Abstract

These studies determined whether increases in rates of protein synthesis observed in skeletal muscle after moderate or severe acute-resistance exercise were blunted by insulinopenia. Rats (n = 6-9 per group) were made insulin deficient by partial pancreatectomy or remained nondiabetic. Groups either remained sedentary or performed acute-resistance exercise 16 h before rates of protein synthesis were measured in vivo. Exercise required 50 repetitions of standing on the hindlimbs with either 0.6 g backpack wt/g body wt (moderate exercise) or 1.0 g backpack wt/g body wt (severe exercise). Insulin-deficient rats had a mean blood glucose concentration >15 mM and reduced insulin concentrations in the plasma. Rates of protein synthesis in gastrocnemius muscle were not different in all sedentary groups. The moderate-exercised nondiabetic group (192 +/- 12 nmol phenylalanine incorporated. g muscle-1. h-1) and moderate-exercised diabetic group (215 +/- 18) had significantly (P < 0.05, ANOVA) higher rates of protein synthesis than did respective sedentary groups. In contrast, diabetic rats that performed severe-resistance exercise had rates of protein synthesis (176 +/- 12) that were not different (P > 0.05) from diabetic sedentary rats (170 +/- 9), whereas nondiabetic rats that performed severe exercise had higher (212 +/- 24) rates compared with nondiabetic sedentary rats (178 +/- 10) P < 0.05. The present data in combination with previous studies [J. D. Fluckey, T. C. Vary, L. S. Jefferson, and P. A. Farrell. Am. J. Physiol. 270 (Endocrinol. Metab. 33): E313-E319, 1996] show that the amount of insulin required for an in vivo permissive effect of insulin on rates of protein synthesis can be quite low after moderate-intensity resistance exercise. However, severe exercise in combination with low insulin concentrations can ablate an anabolic response.