EXERCISE REDUCES MUSCLE GLUCOSE-TRANSPORT PROTEIN (GLUT-4) MESSENGER-RNA 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, insuli n dose 44 +/- 4 U/day, glycosylated hemoglobin 7.8 +/- 0.4%) and in ni ne healthy control subjects (34 +/- 1 yr, 25.3 +/- 0.8 kg/m2). Three h ours of cycle ergometer exercise was performed after an overnight fast . A needle biopsy (100-150 mg) was taken from the quadriceps femoris 4 0 min before and immediately after the end of exercise. During exercis e, plasma glucose, insulin, cortisol, and growth hormone concentration s were higher in the diabetic patients than in the control subjects. I n the basal state, GLUT-4 protein and mRNA concentrations were similar in the two groups. During exercise, GLUT-4 mRNA concentration decreas ed by 30-45% in the diabetic patients but remained unchanged in the co ntrol subjects. GLUT-4 protein content remained unchanged in both grou ps. These data suggest an abnormal GLUT-4 mRNA production or degradati on or both in type 1 diabetic patients during physical exercise.