Exercise reduces muscle glucose transport protein (GLUT-4) mRNA in type 1 diabetic patients

We examined the effect of acute exercise on muscle glucose transporter (GLUT-4) protein and mRNA concentrations in nine male type 1 diabetic patients (age 31 ± 3 yr, body mass index 23.6 ± 0.7 kg/m², insulin dose 44 ± 4 U/day, glycosylated hemoglobin 7.8 ± 0.4%) and in nine healthy control subjects (34 ± 1 yr, 25.3 ± 0.8 kg/m²). Three hours of cycle ergometer exercise was performed after an overnight fast. A needle biopsy (100-150 mg) was taken from the quadriceps femoris 40 min before and immediately after the end of exercise. During exercise, plasma glucose, insulin, cortisol, and growth hormone concentrations were higher in the diabetic patients than in the control subjects. In the basal state, GLUT-4 protein and mRNA concentrations were similar in the two groups. During exercise, GLUT-4 mRNA concentration decreased by 30-45% in the diabetic patients but remained unchanged in the control subjects. GLUT-4 protein content remained unchanged in both groups. These data suggest an abnormal GLUT-4 mRNA production or degradation or both in type 1 diabetic patients during physical exercise.