THE EFFECTS OF IMMOBILIZATION AND SUBSEQUENT EXERCISE ON HUMAN MUSCLE GLUT4 mRNA LEVELS 1311

Abstract

Muscle glucose transporter GLUT4 plays an important role in maintaining glucose homeostasis. Previous studies have shown that exercise increases muscle GLUT4 gene expression and protein level in animal models. The purpose of this study was to investigate the human skeletal muscle GLUT4 mRNA levels before and after immobilization and subsequent exercise. Four human subjects were immobilized with a full cast on the left leg for 3 weeks followed by 12 weeks of resistance exercise training. Total RNA was isolated from biopsy samples of the vastus lateralis muscle of the immobilized leg. Ribonuclease protection assay was used to measure the mRNA levels of GLUT4 transporter. Immobilization decreased GLUT4 mRNA levels to 60% of control(p<0.05). Subsequent resistance exercise training on the immobilized leg induced a 2.0-fold increase in GLUT4 mRNA levels vs immobilization(p<0.05). The results of this study suggest that human skeletal muscle glucose transporter GLUT4 can be regulated at the pre-translational level by immobilization and exercise.