Failure of GLP-1(7-36)amide to affect glycogenesis in rat skeletal muscle.

Glucagon-like peptide-1(7-36)amide has been described as exerting potent glycogenic action and as stimulating glycolysis in skeletal muscle. We exposed isolated rat soleus muscle strips to various concentrations of glucagon-like peptide-1(7-36) amide (10(-11) - 10(-6) mol/l) or insulin (10(-10) - 10(-7) mol/l) and determined the respective effects on glucose metabolism. Insulin markedly increased the rate of glucose incorporation into glycogen with a maximal effect at 10(-8) mol/l insulin (348 +/- 46% of intraindividual control experiment, p < 0.005), while glucagon-like peptide-1(7-36)amide was without an effect (e.g. 10(-11) mol/l, 96 +/- 10%; 10(-9) mol/l, 104 +/- 9%; 10(-7) mol/l, 121 +/- 13%; not significant). Likewise, glucagon-like peptide-1(7-36)amide did not affect the rate of 3H-2-deoxy-glucose transport or glycogen content of soleus muscle strips. The rates of aerobic or anaerobic glycolysis were also not increased. The findings were independent of peptide source and of employed muscle size. Our results do not suggest any effect of glucagon-like peptide-1(7-36)amide on skeletal muscle glucose metabolism and, hence, are in contrast to data derived from similar experiments by others.