Glucose uptake and glucose transporter proteins in skeletal muscle from undernourished rats.
Undernutrition in rats impairs secretion of insulin but maintains glucose normotolerance, because muscle tissue presents an increased insulin-induced glucose uptake. We studied glucose transporters in gastrocnemius muscles from food-restricted and control anesthetized rats under basal and euglycemic hyperinsulinemic conditions. Muscle membranes were prepared by subcellular fractionation in sucrose gradients. Insulin-induced glucose uptake, estimated by a 2-deoxyglucose technique, was increased 4- and 12-fold in control and food-restricted rats, respectively. Muscle insulin receptor was increased, but phosphotyrosine-associated phosphatidylinositol 3-kinase activity stimulated by insulin was lower in undernourished rats, whereas insulin receptor substrate-1 content remained unaltered. The main glucose transporter in the muscle, GLUT-4, was severely reduced albeit more efficiently translocated in response to insulin in food-deprived rats. GLUT-1, GLUT-3, and GLUT-5, minor isoforms in skeletal muscle, were found increased in food-deprived rats. The rise in these minor glucose carriers, as well as the improvement in GLUT-4 recruitment, is probably insufficient to account for the insulin-induced increase in the uptake of glucose in undernourished rats, thereby suggesting possible changes in other steps required for glucose metabolism.
Agote
M
M
Instituto de Bioquímica, Centro Mixto Consejo Superior Investigaciones Científicas Universidad Complutense de Madrid, Facultad Farmacia, Universidad Complutense, Ciudad Universitaria, 28040 Madrid, Spain.
Goya
L
L
Ramos
S
S
Alvarez
C
C
Gavete
M L
ML
Pascual-Leone
A M
AM
Escrivá
F
F
D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D001835:Body Weight; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D005260:Female; D005508:Food Deprivation; D005947:Glucose / Q000378:metabolism*; D015309:Glucose Clamp Technique; D051272:Glucose Transporter Type 1; D051274:Glucose Transporter Type 3; D051275:Glucose Transporter Type 4; D051296:Glucose Transporter Type 5; D007328:Insulin / Q000097:blood / Q000494:pharmacology; D009004:Monosaccharide Transport Proteins / Q000235:genetics / Q000378:metabolism*; D009124:Muscle Proteins; D018482:Muscle, Skeletal / Q000187:drug effects / Q000378:metabolism*; D009419:Nerve Tissue Proteins; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017208:Rats, Wistar; D011972:Receptor, Insulin / Q000378:metabolism
D001786:Blood Glucose; D051272:Glucose Transporter Type 1; D051274:Glucose Transporter Type 3; D051275:Glucose Transporter Type 4; D051296:Glucose Transporter Type 5; D007328:Insulin; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; D009419:Nerve Tissue Proteins; D012333:RNA, Messenger; C495679:Slc2a1 protein, rat; C495690:Slc2a3 protein, rat; C495694:Slc2a4 protein, rat; D011972:Receptor, Insulin; D005947:Glucose