Partial inhibition of fatty acid oxidation increases regional contractile power and efficiency during demand-induced ischemia.

OBJECTIVE: Clinical trials in patients with stable angina show that drugs that partially inhibit myocardial fatty acid oxidation reduce the symptoms of demand-induced ischemia, presumably by reducing lactate production and improving regional systolic function. We tested the hypothesis that partial inhibition of fatty acid oxidation with oxfenicine (a carnitine palmitoyl transferase-I inhibitor) reduces lactate production and increases regional myocardial power during demand-induced ischemia. METHODS: Demand-induced ischemia was produced in anesthetized open-chest swine by reducing flow by 20% in the left anterior descending coronary artery and increasing heart rate and contractility with dobutamine (15 microg kg(-1) min(-1) i.v.) for 20 min. Glucose and fatty acid oxidation were measured with an intracoronary infusion of [U-14C] glucose and [9,10-3H] oleate, and hearts were treated with oxfenicine (2 mmol l(-1); n=7) or vehicle (n=7). Regional anterior wall power was assessed from the left ventricular pressure-anterior free wall segment length loops. RESULTS: During demand-induced ischemia, the oxfenicine group had a higher rate of glucose oxidation (6.9+/-1.1 vs. 4. 7+/-0.8 micromol min(-1); P<0.05), significantly lower fatty acid uptake, but no change in total or active PDH activity. The oxfenicine group had significantly lower lactate output integrals (1.11+/-0.23 vs. 0.60+/-0.11 mmol) and glycogen depletion (66+/-6 vs. 43+/-8%), and higher anterior wall power index (0.95+/-0.17 vs. 1.30+/-0.11%) and anterior wall energy efficiency index (91+/-17 vs. 129+/-10%). CONCLUSIONS: Partial inhibition of fatty acid oxidation reduced non-oxidative glycolysis and improved regional contractile power and efficiency during demand-induced ischemia.

Effect of hyperglycemia and fatty acid oxidation inhibition during aerobic conditions and demand-induced ischemia.

Metabolic interventions improve performance during demand-induced ischemia by reducing myocardial lactate production and improving regional systolic function. We tested the hypotheses that 1) stimulation of glycolysis would increase lactate production and improve ventricular wall motion, and 2) the addition of fatty acid oxidation inhibition would reduce lactate production and further improve contractile function. Measurements were made in anesthetized open-chest swine hearts. Three groups, hyperglycemia (HG), HG + oxfenicine (HG + Oxf), and control (CTRL), were treated under aerobic conditions and during demand-induced ischemia. During demand-induced ischemia, HG resulted in greater lactate production and tissue lactate content but had no significant effect on glucose oxidation. HG + Oxf significantly lowered lactate production and increased glucose oxidation compared with both the CTRL and HG groups. Myocardial energy efficiency was greater in the HG and HG + Oxf groups under aerobic conditions but did not change during demand-induced ischemia. Thus enhanced glycolysis resulted in increased energy efficiency under aerobic conditions but significantly enhanced lactate production with no further improvement in function during demand-induced ischemia. Partial inhibition of free fatty acid oxidation in the presence of accelerated glycolysis increased energy efficiency under aerobic conditions and significantly reduced lactate production and enhanced glucose oxidation during demand-induced ischemia.