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Published on: July 5, 2017
Elevated skeletal muscle glucose transporter levels in exercise-trained middle-aged men
J A Houmard1, P C Egan, P D Neufer
1Human Performance Laboratory, School of Medicine, East Carolina University, Greenville, North Carolina 27858.
The American Journal of Physiology
|October 1, 1991
Summary
Regular exercise training enhances insulin sensitivity in middle-aged men by increasing glucose transporter type 4 (GLUT-4) protein levels in skeletal muscle. This adaptation may explain how exercise improves glucose metabolism.
Area of Science:
- Exercise Physiology
- Metabolic Health
- Skeletal Muscle Biology
Background:
- Exercise training is known to improve whole-body insulin sensitivity.
- This improvement is hypothesized to involve post-receptor adaptations in skeletal muscle.
- The role of specific proteins like glucose transporter type 4 (GLUT-4) remains an area of investigation.
Purpose of the Study:
- To investigate the association between exercise training, insulin sensitivity, and muscle glucose transporter type 4 (GLUT-4) protein levels in middle-aged men.
- To compare GLUT-4 protein content and insulin sensitivity in trained versus sedentary individuals.
- To explore acute effects of exercise on GLUT-4 levels and glucose tolerance.
Main Methods:
- Compared age-matched trained and sedentary middle-aged men (n=11).
- Assessed muscle GLUT-4 protein content via Western blotting.
- Evaluated insulin sensitivity using an oral glucose tolerance test (OGTT).
- Examined acute exercise effects in sedentary subjects.
Main Results:
- Trained men exhibited significantly lower plasma insulin levels during OGTT (P<0.01) but similar glucose responses compared to sedentary men.
- Muscle GLUT-4 protein content was approximately twofold higher in trained men (2.41 ± 0.17 vs. 1.36 ± 0.11 µg standard, P<0.001).
- Acute exercise did not alter OGTT responses or GLUT-4 levels in sedentary subjects within 15-18 hours.
Conclusions:
- Chronically exercise-trained middle-aged men demonstrate increased skeletal muscle GLUT-4 protein levels.
- Elevated GLUT-4 levels are associated with enhanced insulin sensitivity in this population.
- Increased GLUT-4 may represent a key mechanism underlying exercise-induced improvements in insulin sensitivity.
