MODIFIED GLUCAGON TEST ALLOWING SIMULTANEOUS ESTIMATION OF INSULIN-SECRETION AND INSULIN SENSITIVITY - APPLICATION TO OBESITY, INSULIN-DEPENDENT DIABETES-MELLITUS, AND NONINSULIN-DEPENDENT DIABETES-MELLITUS

The aim of this study was to describe an adaptation of the glucagon te st allowing the simultaneous characterization of insulin secretion and sensitivity. A glucagon test (1 mg/m(2)) was performed in healthy sub jects (n = 11), obese patients (n = 5), insulin-dependent diabetics (n = 9), nonobese noninsulin-dependent diabetics (n = 7), and overweight noninsulin-dependent diabetics (n = 8). Previously, they had been con nected to the Biostator, modified for continuous blood collection. End ogenous insulin secretion induced by glucagon was derived from integra ted C-peptide concentrations. An index of insulin sensitivity was obta ined by dividing the rate of decrease in blood glucose by the total am ount of insulin entering the circulation (secreted + infused by the Bi ostator). The indices of insulin sensitivity obtained in the above gro ups of subjects were, respectively, 0.064 +/- 0.006, 0.030 +/- 0.006, 0.037 +/- 0.007, 0.021 +/- 0.006, and 0.016 +/- 0.002 mmol/L.U.min (P < 0.001). The estimated insulin secretion values in the 20 min followi ng glucagon injection were, respectively, 0.38 +/- 0.05, 0.65 +/- 0.08 , 0.05 +/- 0.01, 0.26 +/- 0.15, and 0.30 +/- 0.07 U (P < 0.001). The i nsulin sensitivity index obtained from this test correlated with the g lucose MCR obtained from a euglycemic glucose clamp (r = 0.816; P < 0. 001; n = 12). C-Peptide levels after glucagon administration were also significantly correlated with the estimated endogenous insulin secret ion (r = 0.808; P < 0.001; n = 30). This adaptation of the classical g lucagon test is an efficient and simple method to simultaneously evalu ate insulin secretion and insulin sensitivity.