title: Integrated model of hepatic and peripheral glucose regulation for estimation of endogenous glucose production during the hot IVGTT.
abstract: We have developed a new model to describe endogenous glucose kinetics during a labeled (hot) intravenous glucose tolerance test (IVGTT) to derive a time profile of endogenous glucose production (EGP). We reanalyzed data from a previously published study (P. Vicini, J. J. Zachwieja, K. E. Yarasheski, D. M. Bier, A. Caumo, and C. Cobelli. Am J Physiol Endocrinol Metab 276: E285-E294, 1999), in which insulin-modified [6,6-2H2]glucose-labeled IVGTTs (0.33 g/kg glucose) were performed in 10 normal subjects. In addition, a second tracer ([U-13C]glucose) was infused in a variable rate to clamp the endogenous glucose tracer-to-tracee ratio (TTR). Our new model describing endogenous glucose kinetics was incorporated into the two-compartment hot minimal-model structure. The model gave estimates of glucose effectiveness [1.54 +/- 0.31 (SE) ml x kg(-1) x min(-1)], insulin sensitivity (37.74 +/- 5.23 10(4) dl x kg(-1) x min(-1) x microU(-1) x ml), and a new parameter describing the sensitivity of EGP to the inhibitory effect of insulin (IC50 = 0.0195 +/- 0.0046 min(-1)). The model additionally provided an estimate of the time course of EGP showing almost immediate inhibition, followed by a secondary inhibitory effect caused by infusion of insulin, and a large overshoot as EGP returns to its basal value. Our estimates show very good agreement with those obtained via deconvolution and the model-independent TTR clamp technique. These results suggest that the new integrated model can serve as a simple one-step approach to obtain metabolic indexes while also providing a parametric description of EGP.
authors.affiliation: Resource Facility for Population Kinetics, Department of Bioengineering, Box 352255, University of Washington, Seattle, WA 98195-2255, USA.
authors.forename: Kevin M
authors.initials: KM
authors.lastname: Krudys
authors.forename: Michael G
authors.initials: MG
authors.lastname: Dodds
authors.forename: Stephanie M
authors.initials: SM
authors.lastname: Nissen
authors.forename: Paolo
authors.initials: P
authors.lastname: Vicini
mesh_terms: D001786:Blood Glucose / Q000032:analysis*; D003198:Computer Simulation; D003936:Diagnosis, Computer-Assisted / Q000379:methods*; D005947:Glucose / Q000378:metabolism*; D005951:Glucose Tolerance Test / Q000379:methods*; D006801:Humans; D007333:Insulin Resistance / Q000502:physiology*; D007700:Kinetics; D008099:Liver / Q000378:metabolism*; D008657:Metabolic Clearance Rate; D008954:Models, Biological; D011865:Radioisotope Dilution Technique; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D001786:Blood Glucose; D005947:Glucose