Decreased insulin-stimulated GLUT-4 translocation in glycogen-supercompensated muscles of exercised rats

It was recently found that the effect of an exercise-induced increase in mu scle GLUT-4 on insulin-stimulated glucose transport is masked by a decrease d responsiveness to insulin in glycogen-supercompensated muscle. We evaluat ed the role of hexosamines in this decrease in insulin responsiveness and f ound that UDP-N-acetyl hexosamine concentrations were not higher in glycoge n-supercompensated muscles than in control muscles with a low glycogen cont ent. We determined whether the smaller increase in glucose transport is due to translocation of fewer GLUT-4 to the cell surface with the 2-N-4-(1-azi -2,2,2-trifluroethyl)-benzoyl-1,3-bis(D-mannose-4-yloxy)-2-propylamine (ATB -[2-H-3]BMPA) photolabeling technique. The insulin-induced increase in GLUT -4 at the cell surface was no greater in glycogen-supercompensated exercise d muscle than in muscles of sedentary controls and only 50% as great as in exercised muscles with a low glycogen content. We conclude that the decreas ed insulin responsiveness of glucose transport in glycogen-supercompensated muscle is not due to increased accumulation of hexosamine biosynthetic pat hway end products and that the smaller increase in glucose transport is med iated by translocation of fewer GLUT-4 to the cell surface.