Models for the Estimation of Glucose Fluxes in Non-Steady State from Concentration Measurements

Abstract

Abstract Glucose concentration in blood is the final result o-f the balance of the rate of its release into the circulation and its removal by tissues. These rates need to be measured in order to characterize the glucoregulatory system. Unfortunately, these fluxes are not directly accessible and indirect model-based measurement must be employed. This is a difficult task, especially in the so-called non-steady state, i.e. when a perturbation induces changes in the masses and fluxes of the system. This paper discusses experimental methods and models for determining glucose fluxes in the intact organism out of steady-state. Emphasis is on tracers and on models for describing their kinetics in non-steady state. Widely used approximate models which have been proposed as tools of general use are critically evaluated. An alternative physiological modeling strategy based on multiple steady state tracer experiments is discussed and exemplified on a specific problem of physiological interest