Abstract 10736: Elevated Myocardial Creatine Protects Against Ischemia/Reperfusion Injury by Improving Cardiac Energetics
Creatine is phosphorylated by creatine kinase to form phosphocreatine (PCr), a major energy storage molecule in the heart available for regeneration of ATP during ischemia or high workload. We hypothesised that moderate elevation of intracellular creatine [Cr] would bolster energy storage as PCr and protect against ischemia/reperfusion injury in mice over-expressing the creatine transporter (CrT-OE). In vivo myocardial injury - CrT-OE mice had 45 min of coronary artery ligation then 24 h reperfusion. Hearts were excised and perfused with phthalocyanine blue to delineate the area-at-risk (AAR), then sliced and stained with TTC to quantify area-of-necrosis (AON). Mean myocardial [Cr] was 64 ± 11 in WT and 112 ± 11 nmol/mg protein in CrT-OE mice. CrT-OE mice had 27% less myocardial necrosis: AON/AAR 23 ± 10% (n = 22) vs 32 ± 9% in controls (n = 11, P = 0.02), a reduction comparable to ischemic post-conditioning. Creatine levels negatively correlated with AON/AAR suggesting that protection was dose-dependent (r = -0.39, p = 0.027). Ex vivo functional recovery - Hearts from CrT-OE mice and WT controls (n=9) were perfused in Langendorff mode and 31P-NMR spectra were acquired on a Bruker Avance 500 spectrometer at 11.7 T. Hearts were subjected to 10 min baseline perfusion, 20 min global no-flow ischemia, then 30 min reperfusion. At baseline CrT-OE hearts had similar function, but significantly higher [PCr] compared to WT (21.1 ± 1.6 vs. 14.2 ± 0.6 mM, P<0.01). Loss of function with onset of ischemia was slower in CrT-OE hearts (time to 10% 77 ± 6s vs. 111 ± 11s, p < 0.05). Upon reperfusion CrT-OE hearts made a more complete and sustained functional recovery (max rate pressure product, RPP 59% of baseline vs. 29% for WT, P < 0.05). PCr recovered quicker and to higher levels in CrT-OE, mirroring lower inorganic phosphate (P = 0.02), while ATP recovery did not differ. Throughout the reperfusion period, the free energy of ATP hydrolysis, deltaGATP, was higher in CrT-OE (P = 0.04), increasing the energy available for intracellular ATPases.
Conclusion: Elevation of myocardial [Cr] by 20-100% improved cardiac energetics, reduced in vivo ischemia/reperfusion injury, and improved functional recovery ex vivo, suggesting a new therapeutic principle for cardiac protection.
- © 2011 by American Heart Association, Inc.