Regular exercise is associated with a protective metabolic phenotype in the rat heart

1 James Hogg/iCAPTUR 4 E Centre for Cardiovascular and Pulmonary Research, Department of Pathology and Laboratory Medicine, University of British Columbia-St. Paul's Hospital, Vancouver, British Columbia V6Z 1Y6; 2 Division of Sports Medicine, Departments of Zoology and Radiology, the University of British Columbia, Vancouver, British Columbia V6T 1Z4; 3 Department of Human Biology and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada N1G 2W1; 4 Faculté des Sciences, Université de Paris XII, Creteil Cedex 94010, France; 5 Department of Pharmacology, Southern Illinois University School of Medicine, Springfield, Illinois 62794; and 6 Department of Biochemistry and Molecular Genetics, University of Alabama, Birmingham, Alabama 35294 Submitted 1 October 2003 ; accepted in final form 14 April 2004 Adaptation of myocardial energy substrate utilization may contribute to the cardioprotective effects of regular exercise, a possibility supported by evidence showing that pharmacological metabolic modulation is beneficial to ischemic hearts during reperfusion. Thus we tested the hypothesis that the beneficial effect of regular physical exercise on recovery from ischemia-reperfusion is associated with a protective metabolic phenotype. Function, glycolysis, and oxidation of glucose, lactate, and palmitate were measured in isolated working hearts from sedentary control (C) and treadmill-trained (T: 10 wk, 4 days/wk) female Sprague-Dawley rats submitted to 20 min ischemia and 40 min reperfusion. Training resulted in myocardial hypertrophy (1.65 ± 0.05 vs. 1.30 ± 0.03 g heart wet wt, P < 0.001) and improved recovery of function after ischemia by nearly 50% ( P < 0.05). Glycolysis was 25–30% lower in T hearts before and after ischemia ( P < 0.05), whereas rates of glucose oxidation were 45% higher before ischemia ( P < 0.01). As a result, the fraction of glucose oxidized before and after ischemia was, respectively, twofold and 25% greater in T hearts ( P < 0.05). Palmitate oxidation was 50–65% greater in T than in C before and after ischemia ( P < 0.05), whereas lactate oxidation did not differ between groups. Alteration in content of selected enzymes and proteins, as assessed by immunoblot analysis, could not account for the reduction in glycolysis or increase in glucose and palmitate oxidation observed. Combined with the studies on the beneficial effect of pharmacological modulation of energy metabolism, the present results provide support for a role of