Induction of GLUT-1 protein in adult human skeletal muscle fibers

Prompted by our recent observations that GLUT-1 is expressed in fetal muscl es, but not in adult muscle fibers, we decided to investigate whether GLUT- 1 expression could be reactivated. We studied different stimuli concerning their ability to induce GLUT-1 expression in mature human skeletal muscle f ibers. Metabolic stress (obesity, non-insulin-dependent diabetes mellitus), contractile activity (training), and conditions of de- and reinnervation ( amyotrophic lateral sclerosis) could not induce GLUT-1 expression in human muscle fibers. However, regenerating muscle fibers in polymyositis expresse d GLUT-1. In contrast to GLUT-1, GLUT-4 was expressed in all investigated m uscle fibers. Although the significance of GLUT-1 in adult human muscle fib ers appears limited, GLUT-1 may be of importance for the glucose supplies i n immature and regenerating muscle.