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Article Title

EXPONENTIAL MODELING OF VO2 KINETICS IN ENDURANCE-TRAINED DIABETIC MICE

Abstract

Rodent models of type 2 diabetes mellitus (T2DM) are often used to study aerobic exercise training (AET) in diabetes. However, it is not known how T2DM affects oxygen consumption (VO2) kinetics in rodents, or whether rodent fitness is improvedby the same low- to moderate-intensity exercise that is prescribed for humans with T2DM. PURPOSE: The purpose of this study was to determine the effects of T2DM and exercise on VO2 kinetic parameters in mice. METHODS: Non-diabetic (C57) and genetically type 2 diabetic (db/db; DB) mice were treadmill trained for eight weeks. Mice completed maximal exercise tests in a metabolic modular treadmill at baseline, week 4, and week 8. Weekly exercise progressed from 40-70% of the peak workload achieved in these tests. VO2 data were smoothed using LOWESS regression and fitted to a one-component (1C) and a 2C exponential kinetic model. RESULTS: After eight weeks of training, absolute VO2 was significantly increased from baseline in both DB (239 ± 14 ml/min vs 189 ± 6, PDB mice was 83% lower than C57 mice. A 1C exponential model showed that the VO2 intercept for weeks 0, 4, and 8 was significantly lower in DB mice than C57 mice (P2max when fitted to the whole exercise protocol and the on-transient of exercise, respectively. CONCLUSION: These data provide reference values for VO2max in DB mice, and show that a 1C exponential model is more useful than a 2C model for determining τ in diabetic mice. Low- to moderate-intensity exercise training increased absolute VO2max in both DB and C57 mice without changing τ, suggesting that cardiovascular fitness can improve independent of VO2 kinetics in these mice.

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