Recombinant insulin-like growth factor I normalizes expression of renal glucose transporters in diabetic rats

By immunocytochemistry we have studied the effect of recombinant human insulin-like growth factor I (rhIGF-I) on expression of renal GLUT-1, -2, and -5 in rats with streptozotocin (STZ)-induced diabetes. In the renal tubules of these rats, expression of GLUT-1 was reduced and that of GLUT-2 was increased. GLUT-1 expression was restored, and GLUT-2 expression was normalized by 2-wk administration of rhIGF-I. We have shown that GLUT-5 was expressed at the brush-border membrane of the proximal convoluted tubules (PCT) of the cortex and at the glomerular mesangial cells (GMC) in normal rat kidney. In the diabetic rats, GLUT-5 expression was increased at both sites, along with an increase of GLUT-2 expression at the basolateral membrane of PCT, and was decreased to normal level at both sites by treatment with rhIGF-I. Thus, like GLUT-2, GLUT-5 is suggested to regulate glucose reabsorption in PCT. The relationship between overexpression of GLUT-5 in GMC and accumulation of sorbitol and advanced glycosylation end products are discussed. Regulation of GLUT expression may play an important role on renal glucose homeostasis.