The effect of creatine supplementation on glucose uptake in rat skeletal muscle.

Glucose transport in muscle is a function of the muscle metabolic state, as evidenced by the increase in glucose transport which occurs with conditions of altered aerobic metabolism such as hypoxia or contractile activity. The energy state of the muscle can be determined by the muscle phosphocreatine concentration. Dietary supplementation of creatine has been shown to increase both phosphocreatine (PCr) and creatine (TCr) levels in muscle, although not in the same proportion, so that the PCr/TCr ratio falls suggesting an altered energy state in the cell. The purpose of this study was to determine the effect of increased creatine content on glucose uptake in muscle. PCr and TCr were determined in plantaris muscles from rats following five weeks of dietary supplementation of creatine monohydrate (300 mg/kg/day). (3)H-2-deoxyglucose uptake was measured in epitrochlearis muscles incubated in the presence or absence of a maximally stimulating dose of insulin. Despite a significant increase in creatine content in muscle, neither basal nor insulin-stimulated glucose uptake was altered in creatine supplemented rats. Since PCr levels were not increased with creatine supplementation, these results suggest that the actual concentration of PCr is a more important determinant of glucose uptake than the PCr/TCr ratio.