ELEVATED GLUT-1 LEVEL IN CRUDE MUSCLE MEMBRANES FROM DIABETIC ZUCKER RATS DESPITE A NORMAL GLUT 1 LEVEL IN PERINEURIAL SHEATHS

Recently, we demonstrated that approximately 60% of GLUT 1 in a crude membrane fraction of rat skeletal muscle originates from perineurial s heaths. To study the in vivo regulation of GLUT 1 expression in differ ent tissues in muscles, we measured the level of GLUT 1 in crude muscl e membranes and in perineurial sheaths in diabetic (fa/fa) Zucker rats and lean controls, with and without metformin treatment. The GLUT 1 c oncentration in perineurial sheaths was identical in all four groups o f rats, both when measured by quantitative immunofluorescence and by i mmunoblotting and densitometry. In a fraction of crude membranes of so leus muscles GLUT 1 expression was more than two-fold higher in (fa/fa ) rats than in lean controls (p < 0.005). Metformin treatment signific antly elevated GLUT 1 in control rats (p < 0.05) and tended to decreas e GLUT 1 in diabetic rats (p < 0.075). The expressions of GLUT 1 and G LUT 4 in crude muscle membranes were inversely correlated (p < 0.01), and GLUT 1 expression correlated positively with fasting glucose (p < 0.05). In conclusion, GLUT 1 expression in perineurial sheaths is unaf fected by alterations in glucose homeostasis and by the genes responsi ble for obesity and diabetes in the Zucker rat. GLUT 1 expression in a crude membrane fraction of soleus muscle is increased in the diabetic animals, likely due to an increased expression in muscle cells proper .