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Estimation of glucose production during exercise with a one-compartment variable-volume model
D T Finegood1, P D Miles, H L Lickley
1Department of Medicine, University of Alberta, Edmonton, Canada.
Journal of Applied Physiology (Bethesda, Md. : 1985)
|June 1, 1992
Summary
Estimating endogenous glucose production (Ra) during exercise is more accurate using variable-volume models or improved fixed-volume models with step increases in tracer infusion, especially when Ra changes rapidly.
Area of Science:
- Physiology
- Metabolic Research
- Animal Models
Background:
- Accurate estimation of endogenous glucose production (Ra) is crucial for understanding glucose metabolism, particularly during physiological stress like exercise.
- Traditional fixed-volume models with constant tracer infusion may not capture dynamic changes in Ra during exercise.
- D-[3-3H]glucose tracer is commonly used to study glucose kinetics.
Purpose of the Study:
- To evaluate the efficacy of a variable-volume model and modified fixed-volume models for estimating endogenous glucose production (Ra) during moderate exercise in dogs.
- To determine if step increases in tracer infusion rate improve the accuracy of Ra estimation compared to constant infusion.
- To assess the impact of dynamic changes in Ra on model accuracy.
Main Methods:
- Utilized a variable-volume one-compartment model of glucose kinetics in dogs undergoing moderate exercise.
- Administered a primed infusion of D-[3-3H]glucose with tracer infusion rates held constant or increased 1.5- to 5-fold at exercise onset.
- Employed a regression method to estimate Ra and effective distribution volume dynamically over time.
Main Results:
- Dynamic changes in Ra were revealed by the variable-volume model, which were not apparent with constant infusion and a fixed-volume model.
- The fixed-volume model, when applied with a two- or three-fold step increase in tracer, showed the smallest deviation from the regression method's results.
- Step increases in tracer infusion enriched plasma specific activity, improving Ra estimation accuracy.
Conclusions:
- Variable-volume models, enhanced by step increases in tracer infusion, accurately capture dynamic endogenous glucose production (Ra) during exercise.
- Fixed-volume models can provide improved Ra estimates during rapid metabolic changes by incorporating a single step increase in tracer infusion.
- These refined modeling approaches offer more accurate Ra measurements during rapid endogenous glucose production fluctuations, such as at exercise onset, compared to standard methods.