Systems-level computational modeling demonstrates fuel selection switching in high capacity running and low capacity running rats
Fig 13
HCR and LCR transient and steady-state fuel utilization with normalized exercise.
(A) Data only: Transient respiratory quotient (JCO2/JO2) data obtained from HCR (blue connected circles) and LCR (red connected circles) rats during the previously described treadmill exercise protocol [30] are plotted as a function of %VO2max. Steady-state respiratory quotient HCR (blue diamond) and LCR (red diamond) data obtained at 75% VO2max are also plotted in panel A. (B) Transient data with transient simulations: HCR and LCR parameter set families, transitioned from a resting state parameter set, were used to simulate transient normalized exercise intensity (described in Methods), as a function of %VO2max. HCR data are shown as blue circles (as in panel A) while the simulations are shown as blue lines. LCR data are shown as red circles (as in panel A) while the simulations are shown as red lines. Transient simulations were conducted by simulating exercise for 2 min at each %VO2max, as is the case with HCR and LCR transient data. (C) Steady-state data with steady-state simulation: Lines are simulated as in panel B except with 60 minutes of simulation time to mimic steady-state exercise data. HCR data are shown as blue diamonds while the HCR simulations are shown as blue lines. LCR data are shown as red diamonds while the LCR simulations are shown as red lines. LCR was also simulated without an additional reduction in FAO enzyme and FA transport activities (red dashed line), to better match the LCR steady-state data. (D) Simulated HCR % fuel utilization: HCR fuel utilization percentages with both transient (dashed lines) and steady-state (solid lines), normalized exercise intensity. FA (Fatty acid) percentages are shown as circles and carbohydrate are shown as squares. (E) Simulated LCR % fuel utilization: LCR fuel utilization percentages with both transient (dashed lines) and steady-state exercise (solid lines). FA percentages are shown as circles and carbohydrate are shown as squares. (F) Simulated steady-state HCR and LCR %fuel utilization only: Steady-state fuel utilization percentage estimates from panel D and E for HCR (blue) and LCR (red) are re-plotted in this panel for comparison.