NUTRITIONAL REGULATION OF GLUCOSE TRANSPORTER IN MUSCLE AND ADIPOSE-TISSUE OF WEANED RATS

The role of glucose transporters GLUT-1 and GLUT-4 in the development of insulin sensitivity at weaning in rat skeletal muscles and adipose tissue was studied in relation to the nutritional changes when suckling rats shift from a high-fat (HF) to a high-carbohydrate (HCHO) diet. Insulin stimulated the translocation of GLUT-4 protein from an intracellular pool to the plasma membrane in adipocytes from suckling and HCHO- or HF-weaned rats. The GLUT-4 protein and the insulin stimulation were threefold higher in adipocytes from HCHO-weaned rats than in suckling or HF-weaned rats. GLUT-4 mRNA and protein were low in adipose tissue and skeletal muscles of suckling rats and increased two- to threefold in HCHO-weaned rats. This increase was prevented in HF-weaned rats. GLUT-1 mRNA was not affected in both tissues by the developmental stage or the nutritional environment. After feeding HCHO to a suckling rat, GLUT-4 mRNA was threefold increased in 6 days and reached a peak after 4 days in both tissues. The insulin sensitivity of glucose transport in rats at weaning might be conferred by an enhanced expression of GLUT-4, which can be induced within a few hours after feeding a HCHO diet.