Impact of aging on myocardial metabolic response to dobutamine

Abstract

of aging on myocardial metabolic response to dobutamine. Am J Physiol Heart Circ Physiol 285: H2158-H2164, 2003. First published July 24, 2003 10.1152/ajpheart.00086. 2003.-In humans, under resting conditions there is an agerelated decrease in myocardial fatty acid utilization (MFAU) and oxidation (MFAO) and a relative increase in myocardial glucose utilization (MGU). The impact of age on an individual's myocardial metabolic response to catecholamines is not well defined. Sixteen younger (mean age, 26 Ϯ 5 yr) and 14 older (mean age, 69 Ϯ 4 yr) volunteers underwent positron emission tomography to measure myocardial blood flow, myocardial oxygen consumption (MV O2), MFAU, MFAO, and MGU both under resting conditions and during dobutamine infusion. In response to dobutamine administration, the ratepressure product, myocardial blood flow, and MV O2 measurements increased by similar amounts in both groups. No age-related differences were noted in the responses of plasma insulin, glucose, fatty acid, or lactate levels to dobutamine. With dobutamine infusion, MFAU and MFAO increased by a similar extent in both younger and older volunteers (age/ dobutamine interactions, P ϭ 0.62 and 0.75, respectively). In contrast, MGU increased with dobutamine administration in the younger (from 149 Ϯ 71 to 209 Ϯ 78 nmol ⅐ g Ϫ1 ⅐ min Ϫ1 ; P ϭ 0.04) but not in the older (from 235 Ϯ 147 to 176 Ϯ 84 nmol ⅐ g Ϫ1 ⅐ min Ϫ1 ; P ϭ 0.23; age/dobutamine interaction, P ϭ 0.03) group. With dobutamine infusion, hearts in both younger and older volunteers responded by increasing their MFAU and MFAO values. Whereas younger hearts also responded with an increase in MGU, older hearts did not. Although the clinical significance of these findings awaits further study, these results may partially explain the impaired contractile reserve and the increased incidence of cardiovascular disease in older individuals. fatty acids; glucose; oxidation; heart; catecholamine CARDIOVASCULAR DISEASE IS a primary cause of death and disability in Americans 65 yr of age or older (2). The prevalence of a variety of cardiac disorders including atherosclerosis, atrial fibrillation, heart failure, and hypertension increases with age (1). Moreover, because of the effects of aging on the heart, the clinical manifestations of these disorders are more pronounced in older patients than in younger ones. Consequently, it is important to better delineate the effects of aging on the heart to potentially reduce both the incidence and the impact of various disorders that are specific to the cardiovascular system.Aging has numerous deleterious effects on the heart. For example, with increasing age there is impairment in left ventricular systolic reserve capacity and in diastolic filling (34) as well as blunted inotropic and chronotropic responses to certain ␤-adrenergic agonists (26). A decline in myocardial vasodilator capacity, predominantly through endothelial-dependent mechanisms that are distinct from epicardial involvement by coronary atherosclerosis, is present in both experime...

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