Development in Minimal Modelling of IVGTT: The Measurement of Glucose Production

Abstract

The minimal modelling approach has been widely applied to assess insulin sensitivity in vivo from intravenous glucose tolerance test (IVGTT) data (Bergman et al., 1985). This technique yields a measurement of the effect that insulin exerts in the disposition of the injected glucose, by simultaneously enhancing its tissue utilisation, Rd(t), and inhibiting its liver production, Ra(t). Standard IVGTT data, that is, glucose and insulin plasma concentration time course following a bolus injection of cold gluccose, do not allow the separate estimation of the contribution of each of those two factors. The use of tracer seems therefore the best candidate for solving this problem. In a previous study (Cobelli et al., 1986) we have developed a minimal model for the analysis of IVGTT data when tracer was injected along with cold glucose. From the estimated insulin effect on labelled glucose disappearance, we were able to evaluate, in quantita-tive terms, the true insulin effect on glucose disposal. This was possible since tracer allowed the segregation of the confounding effect of insulin on glucose production. Therefore, the natural pursuance of this study will be the assessment of insulin effect on liver glucose production. To achieve this goal, the cold glucose must also be included in the data set to be analysed by means of the minimal model developed for labelled IVGTT.