Objectives To determine the gender-specific effects of obesity on myocardial metabolism, work, and efficiency Background Myocardial metabolism abnormalities may contribute to the development of obesity-related heart failure. Increased myocardial oxygen consumption (MVO2) and fatty acid (FA) metabolism and decreased efficiency occur with obesity in women. It is unknown whether similar changes occur with obesity in men. Methods We quantified cardiac work, and efficiency, myocardial blood flow (MBF), MVO2, glucose, and FA metabolism, with echocardiography and positron emission tomography in nonobese and obese men and women (N=86). Results There were significant differences between the obese (N=35) and nonobese (N=51) in age, body composition, plasma lipids, and insulin resistance and differences between the men (N=30) and women (N=56) in body composition and plasma lipids. Female gender independently predicted increased cardiac work (p<.001). Female gender also related to lower efficiency (p<.05). Obesity and female gender independently predicted higher MBF (p<.01, p<.0005, respectively) and MVO2 (p<.0005, p<.0001). Myocardial glucose uptake was not different among the 4 subject groups, but obesity and gender interacted in predicting glucose uptake (p<.05). Lower myocardial glucose utilization was independently predicted by female gender (p<.05), and it independently predicted lower myocardial glucose utilization/plasma insulin (p<.05). Obesity and gender significantly interacted in the determination of glucose utilization/plasma insulin (p=.01). There were no differences in FA uptake among the 4 groups, and although increasing obesity correlated with higher myocardial FA utilization and oxidation; female gender (p<.005, <.01) and plasma triglycerides (p<.05, <.005) were their independent predictors. Conclusions Women’s and men’s myocardial metabolic response to obesity is not exactly the same. Obesity and gender modulate MBF and MVO2, are related to myocardial substrate metabolism, and sometimes interact in its prediction. Gender modifies efficiency. Gender-related differences in myocardial metabolism may affect the development of/adaptation to obesity-related cardiac disease.

With aging, humans exhibit a decline in MFAU and MFAO. Although absolute rates of MGU do not increase, by virtue of the decline in MFAU there is likely an increase in relative contribution of MGU to substrate metabolism. The clinical significance of this metabolic switch awaits further study.

Patients with metabolic syndrome have LV diastolic dysfunction independent of LV mass. These functional abnormalities may partially explain the increased cardiovascular morbidity and mortality associated with metabolic syndrome.