title: Beta-cell function during insulin-modified intravenous glucose tolerance test successfully assessed by the C-peptide minimal model.
abstract: The insulin-modified intravenous glucose tolerance test (IM-IVGTT) is increasingly used to measure insulin sensitivity. However, the assessment of beta-cell secretion is usually made using rough indices. The aim here is to evaluate the ability of the minimal model of C-peptide secretion and kinetics recently proposed for the standard IVGTT (S-IVGTT) to also assess beta-cell function during the IM-IVGTT. C-peptide and glucose data from the IM-IVGTT in 15 normal humans were analyzed. The results show that the same rich beta-cell picture from the S-IVGTT can be obtained during an IM-IVGTT. In particular, in each individual, the time course of beta-cell secretion can be reconstructed and the functional indices of glucose control on first-phase (phi1), second-phase (phi2), and basal (phi(b)) insulin secretion can be estimated (phi1 = 191 +/- 29, phi2 = 10.9 +/- 1.4 x 10(-9) x min(-1), and phi(b) = 5.7 +/- 1.0 x 10(-9) x min(-1), mean +/- SE). Finally, the comparison between IM-IVGTT and S-IVGTT phi1, phi2, and phi(b) values suggest they are not affected by insulin administration.
authors.affiliation: Department of Electronics and Informatics, University of Padova, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Toffolo
authors.forename: W T
authors.initials: WT
authors.lastname: Cefalu
authors.forename: C
authors.initials: C
authors.lastname: Cobelli
mesh_terms: D002096:C-Peptide / Q000097:blood* / Q000493:pharmacokinetics; D005951:Glucose Tolerance Test / Q000379:methods*; D006801:Humans; D007328:Insulin / Q000097:blood / Q000494:pharmacology*; D007515:Islets of Langerhans / Q000378:metabolism*; D007700:Kinetics; D008875:Middle Aged; D012680:Sensitivity and Specificity
chemical_list: D002096:C-Peptide; D007328:Insulin