Exercise training impacts the myocardial metabolism of older individuals in a gender-specific manner

Aging is associated with decreases in aerobic capacity, cardiac function, and insulin sensitivity as well as alterations in myocardial substrate metabolism. Endurance exercise training (EET) improves cardiac function in a gender-specific manner, and EET has been shown to improve whole body glucose tolerance, but its effects on myocardial metabolism are unclear. Accordingly, we studied the effect of EET on myocardial substrate metabolism in older men and women. Twelve healthy older individuals (age: 60-75 yr; 6 men and 6 women) underwent PET with [¹⁵O]water, [¹¹C]acetate, [ ¹¹C]glucose, and [¹¹C]palmitate for the assessment of myocardial blood flow (MBF), myocardial O₂ consumption (MV̇O ₂), myocardial glucose utilization (MGU), and myocardial fatty acid utilization (MFAU), respectively, at rest and during dobutamine infusion (10 μg·kg^-1·min^-1). Measurements were repeated after 11 mo of EET. Maximal O₂ uptake (V̇O _2max) increased (P = 0.005) after EET. MBF was unaffected by training, as was resting MV̇O₂; however, posttraining dobutamine MV̇O₂ was significantly higher (P = 0.05), as was MGU (P < 0.04). Although overall dobutamine MFAU was unchanged, posttraining dobutamine MFAU increased in women (P = 0.01) but decreased in men (P = 0.03). Thus, EET in older individuals improves the catecholamine response of myocardial glucose metabolism. Moreover, gender differences exist in the myocardial fatty acid metabolic response to training. These findings suggest a role for altered myocardial substrate metabolism in modulating the cardiovascular benefits of EET in older individuals.