INSULIN-STIMULATED GLUCOSE-UPTAKE IS ENHANCED IN SEDENTARY AND ENDURANCE-TRAINED LOW INSULIN RESPONDERS

The mechanisms by which healthy sedentary subjects with low insulin response (LIR; 5-min insulin response to glucose load within lowest quartile of healthy population) maintain a normal glucose tolerance are not clear. We studied glucose uptake and hepatic glucose production in LIR, in healthy subjects with high insulin response (HIR; two highest quartiles of insulin response) matched for weight and physical fitness, and in endurance-trained subjects (ET). For this purpose, we performed hyperinsulinemic euglycemic clamps using the ''hot-GINF'' method with high-pressure liquid chromatography purified [6-H-3]glucose. Ah groups had a similar basal glucose appearance rate (R(a)). During clamps, plasma insulin levels were doubled to 169 +/- 9 pmol/l, whereas R(a) decreased similarly in all groups. Glucose utilization rate increased more in LIR and ET than in HIR (to 20.9 +/- 1.5 mu mol . kg(-1). min(-1) in LIR, P < 0.001 vs. HIR; 27.4 +/- 3.6 in ET, P < 0.01 vs. HIR and LIR; and 14.3 +/- 0.6 in HIR). In conclusion, the present study demonstrates increased insulin sensitivity in LIR and ET with respect to glucose uptake but not glucose production.