A novel use of the hyperinsulinemic-euglycemic clamp technique to estimateinsulin sensitivity of systemic lipolysis

The aim of the present study was to assess whether a standard hyperinsuline mic-euglycemic clamp can provide an estimate for the antilipolytic insulin sensitivity. For this purpose, we infused 9 non-obese, healthy volunteers w ith [H-2(5)]glycerol and used the glycerol rate of appearance (Ra) in plasm a as an index for systemic lipolysis during a standard (1 mU/kg (.) min, 12 0 min) and a 3-step (0.1, 0.25, 1.0 mU/kg min) hyperinsulinemic-euglycemic clamp. The insulin concentration, which half-maximally suppressed lipolysis (EC50) in the three-step clamp, was considered to be the gold standard for the antilipolytic insulin sensitivity. Glycerol Ra decreased from 1.53 +/- 0.11 mu mol/kg min to 0.60 +/- 0.09 mu mol/kg min (p < 0.001) during the s tandard clamp. The decrease in Ra at most time points during the standard c lamp significantly correlated with the EC50. The highest correlation for th e % decrease of glycerol Ra from baseline was found at 60 min (r = 0.96, p < 0.001) malting this parameter a useful index for the antilipoytic insulin sensitivity. Neither plasma glycerol nor plasma free fatty acid (FFA) conc entrations were significantly correlated with the EC50. In conclusion, the standard hyperinsulinemic-euglycemic clamp in combination with isotopic det ermination of glycerol Ra provides a reasonable estimate for the antilipoly tic insulin sensitivity. In healthy subjects, the parameter best suited to estimate the insulin EC50 (by linear correlation) was the percentage decrea se of glycerol Ra at 60 min.