Insulin sensitivity and glucose effectiveness: minimal model analysis of regular and insulin-modified ivgtt. Pacini, Giovanni, Giancarlo Tonolo, Maria Sambataro, Mario Maioli, Milco Ciccarese, Enrico Brocco, Angelo Avogaro, and Romano Nosadini. Institute of Systems Science and Biomedical Engineering, Italian National Research, Council, 35127 Padova; Institute of Clinical Medicine, University of Sassari, 07100 Sassari; Institute of Internal Medicine, and Department of Clinical and Experimental Medicine, University of Padova, 35128 Padova, Italy.
APStracts 4:0282E, 1997.
The minimal model is widely used to evaluate insulin action on glucose disappearance from frequently sampled intravenous glucose tolerance tests (FSIGT). The common protocols are regular (rFSIGT: single injection of 0.3 g/kg of glucose) and insulin-modified test (mFSIGT: with an additional insulin administration at 20 min). This study compared the insulin sensitivity index, SI, and glucose effectiveness, SG, obtained in the same individual (16 normal subjects) with the two tests. SI was 7.11+/-0.80 10-4min-1/([mu]U/ml) in rFSIGT and 6.96+/-0.83 in mFSIGT (p=0.656), regression: r=0.92, p<0.0001; SG was 0.0260+/-0.0028 min- 1 and 0.0357+/-0.0052, respectively, statistically different (p=0.013) but still with a good regression (r=0.66, p=0.0051). SG and insulin amount during the early period correlated (r=0.6, p=0.015 in rFSIGT, and r=0.76, p=0.0006 in mFSIGT). In summary, both FSIGTs with minimal model analysis provide the same SI, which is a very robust index. SG was different by 28% due probably to the relationship between SG and the amount of circulating insulin. In studies comparing groups, the simpler rFSIGT can still be used with the advantage of accounting for endogenous insulin, thus offering the possibility of direct inferences on the beta cell activity. 

Received 2 September 1997; accepted in final form 16 December
1997.
APS Manuscript Number E415-7.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 7 January 1998