Effect of diet on insulin binding and glucose transport in rat sarcolemmal vesicles.
The purpose of this study was to compare the effects of a high-fat, high-sucrose diet (HFS) and a low-fat, high-complex carbohydrate diet (LFC) on glucose tolerance, insulin binding, and glucose transport in rat skeletal muscle. During the intravenous glucose tolerance test, peak glucose values at 5 min were significantly higher in the HFS group; 0-, 20-, and 60-min values were similar. Insulin values were significantly higher in the HFS group at all time points (except 60 min), indicating whole-body insulin resistance. Skeletal muscle was responsible, in part, for this insulin resistance, because specific D-glucose transport in isolated sarcolemmal (SL) vesicles under basal conditions was similar between LFC and HFS rats (35 +/- 5 vs. 32 +/- 4 pmol/mg protein), despite the higher plasma insulin levels. Scatchard analyses of insulin binding curves to sarcolemmal vesicles revealed that the Ka of the high-affinity binding sites was significantly reduced by the HFS diet (0.63 +/- 0.09 vs. 0.35 +/- 0.05 X 10(9) M-1); no other binding changes were noted. Specific D-glucose transport in SL vesicles after maximum insulin stimulation (1 U/kg) was significantly depressed in the HFS group (87 +/- 7 vs. 58 +/- 7 pmol/mg protein), indicating that HFS feeding also caused a postbinding defect. These results indicate that the insulin resistance in skeletal muscle associated with a HFS diet is due to both a decrease in the Ka of the high-affinity insulin receptors and a postbinding defect.
D000818:Animals; D001692:Biological Transport; D001786:Blood Glucose / Q000378:metabolism; D004032:Diet; D004040:Dietary Carbohydrates / Q000378:metabolism; D004041:Dietary Fats / Q000378:metabolism; D005947:Glucose / Q000378:metabolism*; D066298:In Vitro Techniques; D007328:Insulin / Q000378:metabolism*; D009132:Muscles / Q000378:metabolism*; D051381:Rats; D011972:Receptor, Insulin / Q000378:metabolism; D012508:Sarcolemma / Q000378:metabolism*
D001786:Blood Glucose; D004040:Dietary Carbohydrates; D004041:Dietary Fats; D007328:Insulin; D011972:Receptor, Insulin; D005947:Glucose