High levels of fatty acids delay the recovery of intracellular pH and cardiac efficiency in post-ischemic hearts by inhibiting glucose oxidation

OBJECTIVES This study was designed to determine if the fatty acid-induced increase in H+ production from glycolysis uncoupled from glucose oxidation delays the recovery, of intracellular pH (pH(i)) during reperfusion of ischemic hearts. BACKGROUND High rates of fatty acid oxidation inhibit glucose oxidation and impair the recovery, of mechanical function and cardiac efficiency during reperfusion of ischemic hearts. METHODS pH(i) was measured by P-31 nuclear magnetic resonance spectroscopy in isolated working rat hearts perfused in the absence (5.5 mmol/l glucose) or presence of 1.2 mmol/l palmitate (glucose+palmitate). Glycolysis and glucose oxidation were measured using [5-H-3/U-C-14]glucose. RESULTS When glucose+palmitate hearts were subjected to 20 min of no-flow ischemia, recoveries of mechanical function and cardiac efficiency were significantly, impaired compared with glucose hearts. Glucose oxidation rates were significantly lower in glucose+palmitate hearts during reperfusion compared with glucose hearts, whereas glycolysis rates were unchanged. This resulted in an increase in H+ production from uncoupled glucose metabolism, and a decreased rate of recovery of pH(i) in glucose+palmitate hearts during reperfusion compared with glucose-perfused hearts. Dichloroacetate (3 mmol/l) given at reperfusion to glucose+palmitate hearts resulted in a 3.2-fold increase in glucose oxidation, a 35% +/- 3% decrease in H+ production from glucose metabolism, a 1.7-fold increase in cardiac efficiency and a 2.2-fold increase in the rate of pH(i) recovery during reperfusion. CONCLUSIONS A high level of fatty acid delays the recovery of pH(i) during reperfusion of ischemic hearts because of an increased H+ production from glycolysis uncoupled from glucose oxidation. Improving the coupling of glucose metabolism by stimulating glucose oxidation accelerates the recovery of pH(i) and improves both mechanical function and cardiac efficiency. (C) 2002 by the American College of Cardiology.