AJP - Endocrinology and Metabolism, Vol 263, Issue 6 E1134-E1143, Copyright © 1992 by American Physiological Society
Effect of training on insulin-mediated glucose uptake in human muscle
F. Dela, K. J. Mikines, M. von Linstow, N. H. Secher and H. Galbo
Institute of Medical Physiology B, Panum Institute, University of Copenhagen, Denmark.
During insulin stimulation whole body glucose uptake is increased in
trained compared with untrained humans. However, it is not known which
tissue is responsible. Seven young male subjects bicycle trained one leg
for 10 wk at 70% of maximal O2 consumption (VO2max). Sixteen hours after
last exercise bout, a three-step euglycemic hyperinsulinemic clamp (clamp
1) was performed (insulin levels, means +/- SE: 9 +/- 1, 53 +/- 3, 174 +/-
5, and 2,323 +/- 80 was microU/ml), with measurement of arteriovenous
differences and blood flow in both legs. After 6 days of detraining
subjects were restudied, having exercised the untrained leg 16 h before.
VO2max for trained (T) and untrained (UT) legs was 52 +/- 2 vs. 44 +/- 2
ml.min-1.kg-1 (P < 0.05). In clamp 1 glucose uptake in T and UT legs was
1.0 +/- 0.2 vs. 0.5 +/- 0.1 mg.min-1.kg-1 (basal), 9.7 +/- 2.3 vs. 6.7 +/-
1.7 (P < 0.05) (step I), 19.2 +/- 2.8 vs. 14.3 +/- 2.0 (P < 0.05)
(step II), and 22.8 +/- 2.3 vs. 18.6 +/- 2.2 (P < 0.05) (step III).
During insulin infusion lactate release (P < 0.05) [8.9 +/- 1.8 vs. 2.9
+/- 0.9 mumol.min-1.kg-1 (step I), 24.6 +/- 3.1 vs. 12.5 +/- 2.6 (step
III)] and glycogen storage (P < 0.1) calculated by indirect calorimetry
[6.7 +/- 2.3 vs. 5.0 +/- 1.7 mg.min-1.kg-1 (step I), 16.8 +/- 2.1 vs. 14.1
+/- 1.8 (step III)] were always higher in T than in UT legs. Release of
glycerol, free fatty acids, and tyrosine and clearance of insulin were not
influenced by training. Insulin-mediated glucose uptake was not increased
after detraining or a single bout of exercise. In conclusion, training
increases sensitivity and responsiveness of insulin-mediated glucose uptake
in human muscle by local mechanisms. Glycolysis and glycogen storage are
equally enhanced. The training effect represents a genuine adaptation to
repeated exercise but is short lived. Insulin clearance in muscle is not
influenced by training.
