Why does insulin resistance develop during maturation?
We compared skeletal muscle glucose uptake between young and mature rats. Hindlimb perfusions at insulin concentrations of 0, 100, 250, or 10,000 microU/mL were performed on male Sprague-Dawley rats at 5 weeks or 4 months of age. Basal glucose uptake, and glucose uptake at all insulin concentrations were significantly lower in the 4-month-old mature rats (p < .05). This difference was most pronounced at maximally stimulating insulin concentrations. Skeletal muscle insulin receptor binding, autophosphorylation, and tyrosine kinase activity did not differ between young and mature rats. Surprisingly, GLUT-4 glucose transporter content was significantly higher in several muscles of the mature rats (p < .05). Therefore, the decline in insulin-stimulated glucose uptake in hindlimbs of mature rats cannot be explained by decreased activity of these steps in the glucose transport system.
Reed
M J
MJ
Department of Medicine, Stanford University School of Medicine, California.
Reaven
G M
GM
Mondon
C E
CE
Azhar
S
S
D000375:Aging / Q000502:physiology*; D000818:Animals; D005947:Glucose / Q000378:metabolism; D051275:Glucose Transporter Type 4; D006614:Hindlimb; D007328:Insulin / Q000378:metabolism / Q000494:pharmacology; D007333:Insulin Resistance; D008297:Male; D009004:Monosaccharide Transport Proteins / Q000378:metabolism; D009124:Muscle Proteins; D009132:Muscles / Q000378:metabolism; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D011972:Receptor, Insulin / Q000378:metabolism
D051275:Glucose Transporter Type 4; D007328:Insulin; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; C495694:Slc2a4 protein, rat; D011505:Protein-Tyrosine Kinases; D011972:Receptor, Insulin; D005947:Glucose