Abstract 15119: Remote Ischemic Preconditioning Does Not Affect Skeletal Muscle Energy Metabolism Measured by 31-Phosphorus Magnetic Resonance Spectroscopy: A Randomized Crossover Trial
Background: Remote ischemic preconditioning (RIPC), induced by transient limb ischemia, has been demonstrated to protect organs against ischemia-reperfusion injury and to improve maximal, but not submaximal exercise performance. Nonetheless, the cellular mechanisms remain poorly understood. Phosphocreatinine concentration was recently shown to recover more rapidly during reperfusion in muscle that has undergone local ischemic preconditioning. Therefore, we used 31P-MRS and blood oxygen level dependent MRI (BOLD fMRI) to test the hypothesis that RIPC beneficially modifies muscle metabolism and perfusion during maximal but not submaximal exercise.
Method: Ten healthy subjects, 20 to 27 years, were randomised to RIPC (4 cycles of 5 minutes (min) arm ischemia/5 min reperfusion) or sham procedure, then crossed-over to the other intervention. Each subject performed ten 30 seconds (sec) bouts at 65% of the previously determined maximal work rate each separated by 15 sec of rest. Finally, six of the subjects also performed two bouts of 60 sec of maximal (100%) exercise. 31P-MRS and BOLD fMRI data were obtained before and after every testing protocol.
Results: There were no differences for ATP production (0.3±0.1 RIPC mmol/L, 0.3±0.1 SHAM, p=0.90), phosphocreatinine to inorganic phosphate ratio (0.9±0.8, 1.0±0.7, p=0.78) or in the half-time of phosphocreatinine recovery (27.1±11.8, 24.6±12.8 sec, p=0.66) during submaximal exercise. There were also no differences in BOLD signal amplitude between RIPC and SHAM (279.3 ± 169.3, 276.6 + 135.9, p=0.96) or for BOLD signal intercept (1614.0 + 373.4, 1522.7 + 332.9, p = 0.1), or for the BOLD signal recovery time constant (75.5 + 154.5, 47.3 + 23.6 sec, p=0.34). Similarly for the maximal exercise protocol, we observed no difference in pre vs. post-exercise pH (0.77±0.26, 0.93±0.14, p= 0.29), post-exercise phosphocreatinine and phosphate ratio (1.9±1.5, 2.4±2.4, p=0.70) or in the half-time of phosphocreatinine recovery (23.0±19.5, 20.2±7.3 sec, p=0.67).
Conclusion: The lack of demonstrated effect of RIPC on aerobic and anaerobic energy metabolism, and perfusion, is different than previously shown with local preconditioning and may suggest that different mechanisms play a role in the observed effects of RIPC.
- © 2013 by American Heart Association, Inc.