Denervation provokes greater reductions in insulin-stimulated glucose transport in muscle than severe diabetes

We have examined the independent and combined effects of insulin insufficiency (streptozotocin (STZ)-induced diabetes, 85 mg/kg i.p.) and reduced muscle activity (denervation) (7 days) on basal, insulin-stimulated and contraction-stimulated glucose transport in rat muscles (soleus, red and white gastrocnemius). There were four treatments: control, denervated, diabetic, and denervated + diabetic muscles. Contraction-stimulated glucose transport was lowered (~ 50%) (p < 0.05) to the same extent in all experimental groups. In contrast, there was a much smaller reduction insulin-stimulated glucose transport in muscles from diabetic animals (18-24% reduction, p < 0.05) than in denervated muscles (40-60% reduction, p < 0.05) and in denervated + diabetic muscles (40-60% reduction, p < 0.05). GLUT-4 mRNA reduction was greatest in denervated + diabetic muscles (~ -75%, p < 0.05). GLUT-4 protein was decreased (p < 0.05) to a similar extent in all three experimental conditions (~ -30-40%). In conclusion, (1) muscle inactivity (denervation) and STZ-induced diabetes had similar effects on reducing contraction-stimulated glucose transport, but (2) muscle inactivity (denervation), rather than severe diabetes, produced a 2-fold greater impairment in skeletal muscle insulin-stimulated glucose transport.