Synthesis of muscle glycogen during recovery after prolonged severe exercise in diabetic and non-diabetic subjects

Abstract

Glycogen synthesis rate in skeletal muscle was studied in six juvenile diabetic and six non-diabetic males ingesting a carbohydrate rich diet during 12 h of resting recovery after exhaustive bicycle exercise. The diabetic subjects took their regular insulin. Blood samples and muscle biopsies were obtained at rest prior to exercise, immediately after the cessation of exercise and after 2, 4, 6, 9 and 12 h of recovery. A marked decrease in muscle glycogen content was observed in response to exercise in both groups of subjects. Mean glycogen utilization rate was the same in the two groups. Glycogen synthesis rate during the first 4 h of recovery was 6·4·0·6 mmol glucosyl units/kg w.w./h in the diabetic subjects and 7·2·0·7 mmol glucosyl units/kg w.w./h in the non-diabetic subjects. During the next 8 h glycogen synthesis rate was approximately 1/3 of that being 2·0·0·3 and 2·4·0·5 mmol glucosyl units/kg w.w./h in the two groups respectively. Glycogen synthetase I-activity increased markedly in response to exercise in both groups of subjects. However, no differences were observed between the groups. No significant differences in muscle glucose-6-phosphate concentrations were observed between the two groups. Plasma glucose levels were significantly higher in the diabetic than in the non-diabetic subjects. It is concluded that glycogen synthesis during recovery following prolonged severe exercise can proceed at the same rate in diabetic subjects taking their regular insulin as in non-diabetic subjects.

Key Words:

• diabetes mellitus
• exercise
• glucose
• glucose-6-phosphate
• glycogen
• glycogen synthesis rate
• glycogen synthetase
• insulin
• recovery after exercise
• skeletal muscle