Relationship between carbohydrate oxidation and G-1,6-P2 in human skeletal muscle during euglycemic hyperinsulinemia.
Euglycemic (approximately 5.5 mM) hyperinsulinemic clamps were performed on normoglycemic insulin-sensitive (NIS) men and men who were normoglycemic but insulin resistant (NIR) and hyperglycemic and insulin resistant (HIR) (i.e., noninsulin-dependent diabetes mellitus). Insulin was infused at successive rates of 40 and 400 mU.m-2.min-1, and biopsies were obtained from the quadriceps femoris muscles before and after insulin and analyzed for regulators of phosphofructokinase, a rate-limiting enzyme for glycolysis. Glucose disposal and whole body carbohydrate oxidation were markedly lower in NIR and HIR vs. NIS (P less than 0.001 for disposal and oxidation). The alpha-D-glucose 1,6-bisphosphate (G-1,6-P2) content increased almost twofold during the 40-mU insulin infusion (P less than 0.001) without any further change during the 400-mU infusion in NIS men. The increase in G-1,6-P2 in NIR and HIR was only approximately 25 and 50% of the increase observed in NIS during the 40- and 400-mU infusions, respectively. The mean content of G-1,6-P2 was strongly related to the mean rate of carbohydrate oxidation (r = 0.99; P less than 0.001). Because during euglycemic hyperinsulinemia approximately 90% of the glucose utilization is accounted for by skeletal muscle (J. Clin. Invest. 76: 149, 1985), it is likely that whole body carbohydrate oxidation is proportional to carbohydrate oxidation and glycolysis in muscle. The different rates of carbohydrate oxidation between NIS and insulin-resistant men could not be associated with differences in fructose 6-phosphate, fructose 1,6-bisphosphate, fructose 2,6-bisphosphate, Pi, free ADP and free AMP (activators of phosphofructokinase), or ATP and citrate (inhibitors of phosphofructokinase).
Katz
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Department of Kinesiology, University of Illinois, Urbana 61801.
Bogardus
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D000328:Adult; D000818:Animals; D050260:Carbohydrate Metabolism; D005947:Glucose / Q000378:metabolism / Q000494:pharmacology; D019298:Glucose-6-Phosphate / Q000031:analogs & derivatives*; D005958:Glucosephosphates / Q000378:metabolism*; D006801:Humans; D006946:Hyperinsulinism / Q000378:metabolism*; D007262:Infusions, Intravenous; D007328:Insulin / Q000494:pharmacology; D007333:Insulin Resistance / Q000502:physiology; D008297:Male; D009132:Muscles / Q000378:metabolism*; D010084:Oxidation-Reduction; D010732:Phosphofructokinase-1 / Q000378:metabolism
D005958:Glucosephosphates; D007328:Insulin; D019298:Glucose-6-Phosphate; C016473:glucose-1,6-bisphosphate; D010732:Phosphofructokinase-1; D005947:Glucose