Insulin time-dependent effects on the leg exchange of glucose and amino acids in man

Time-dependent effects of insulin on the leg exchange of glucose, lactate, glycerol, free fatty acids (FFA) and amino acids were measured in relation to oxygen uptake (leg and whole body) and whole body glucose assimilation including oxidation. Seven healthy males (58 +/- 3 years of age) were investigated before operation of uncomplicated inguinal hernia or varicose veins. Euglycaemic glucose clamp investigations with systemic hyperinsulinaemia between 100-120 mU1(-1) were used. Metabolic measurements were performed before and during hyperinsulinaemia at 2 and 6 h following the start of glucose clamp to evaluate the time-dependency of insulin actions. Whole body glucose uptake increased continuously for up to 6 h (from 4.7 +/- 0.7 to 8.0 +/- 0.8 mg/kg/min, P less than 0.01) despite stable plasma concentrations of glucose and insulin. This was also true for glucose oxidation. Whole body oxygen uptake did not change significantly during the clamp while the leg exchange of oxygen uptake did (from 5.9 +/- 0.86 mumol/100 g/min to 11.6 +/- 2.4, P less than 0.01). Insulin effect on leg blood flow was time-dependent and increased two-fold (2.3 +/- 0.4 ml/100 g/min to 4.4 +/- 0.9, P less than 0.001) during clamp. The leg production of lactate increased continuously, accounting for approximately 15% of the glucose uptake across the leg, but the rise in arterial lactate did not reach the level of statistical significance. Plasma FFA concentrations decreased in a time-dependent manner during clamp, while the leg exchange of FFA switched rapidly to a stable net uptake.(ABSTRACT TRUNCATED AT 250 WORDS)