Creatine supplementation increases glycogen storage but not GLUT-4 expression in human skeletal muscle

Abstract

It has been speculated that creatine supplementation affects muscle glucose metabolism in humans by increasing muscle glycogen storage and up-regulating GLUT-4 protein expression. In the present study, we assessed the effects of creatine loading and prolonged supplementation on muscle glycogen storage and GLUT-4 mRNA and protein content in humans. A total of 20 subjects participated in a 6-week supplementation period during which creatine or a placebo was ingested. Muscle biopsies were taken before and after 5 days of creatine loading (20 g · day-1) and after 6 weeks of continued supplementation (2 g · day-1). Fasting plasma insulin concentrations, muscle creatine, glycogen and GLUT-4 protei..