Synthesis of muscle glycogen during recovery after prolonged severe exercise in diabetic subjects. Effect of insulin deprivation

Abstract

The effect of insulin deprivation on muscle glycogen resynthesis during 12 h of resting recovery after exhaustive exercise was studied in five young juvenile diabetic subjects. The subjects were given a carbohydrate rich diet but no insulin during the recovery period. Muscle biopsies and blood samples were taken at rest before exercise, immediately after exercise and after 2, 4, 6, 9 and 12 h of recovery. The results are compared with those obtained in a similar study in which the subjects took their regular insulin injections during recovery (control study). In response to exercise muscle glycogen content decreased to 20% of the pre-exercise level in both studies. After 4 h of recovery muscle glycogen had increased to 66% and 53% of the pre-exercise value in the control and insulin deprivation studies, respectively. The difference was not statistically significant. During the last 8 h of the recovery period muscle glycogen concentration further increased to 95% of the pre-exercise value in the control study, while no further increase was observed in the insulin deprivation study. During recovery the mean values for glycogen synthetase I were higher in the control study than in the insulin deprivation study. Also a higher synthetase I activity for a given glycogen concentration was found in the control experiments than in the insulin deprivation experiments. Plasma glucose concentration was significantly higher during the last 6 h of recovery in the insulin deprivation experiments than in the control experiments and was in both studies well above the level at rest before exercise. It is concluded that in diabetic subjects insulin administration is required to obtain a normal muscle glycogen resynthesis during recovery after exercise.