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INNOVATIVE METHODOLOGY
APPETITE, OBESITY, DIGESTION, AND METABOLISM
School of Veterinary Medicine, University of Pennsylvania, Kennett Square, Pennsylvania
Submitted 16 October 2007 ; accepted in final form 26 January 2008
Dynamics of nonesterified fatty acid (NEFA) metabolism in humans requires quantification if we are to understand the etiology of such diseases as type 1 and 2 diabetes, as well as metabolic syndrome and obesity, or if we are to elucidate the mechanism of action of various interventions. We present a new compartmental model that employs the pattern of plasma glucose concentrations in healthy young adults to predict dynamic changes that occur in plasma NEFA concentrations during either a glucose-only intravenous glucose tolerance test, or an insulin-modified intravenous tolerance test, or a modified protocol during which variable-rate glucose infusions were administered to prevent plasma glucose from declining below 100 mg/dl. The model described all of the major features of NEFA response to an intravenous glucose tolerance test, including an initial latency phase, a phase during which plasma NEFA concentrations plummet to a nadir, and a rebound phase during which plasma NEFA concentrations may rise to a plateau concentration, which may be substantially higher than the initial basal NEFA concentration. This model is consistent with physiological processes and provides seven adjustable parameters that can be used to quantify NEFA production (lipolysis) and utilization (oxidation). When tested on data from the scientific literature, the range in estimated rate of lipolysis was 24–36 µmol·l–1·min–1 and for NEFA oxidation rate was 25–54 µmol·l–1·min–1. All model parameters were well identified and had coefficients of variation < 15% of their estimated values. It is concluded that this model is suitable to describe NEFA kinetics in human subjects.
compartmental model; glucose tolerance test
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R. C. Boston and P. J. Moate NEFA minimal model parameters estimated from the oral glucose tolerance test and the meal tolerance test Am J Physiol Regulatory Integrative Comp Physiol, August 1, 2008; 295(2): R395 - R403. [Abstract] [Full Text] [PDF] |
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