Abstract 2199: The Myocardium of Young Obese Men in the Resting Fasted State is More Insulin-Resistant but not less Efficient than Nonobese Men
Objectives: To determine if obesity in men 1) has effects on myocardial blood flow (MBF), oxygen consumption (MVO2), efficiency, fatty acid utilization (MFAU), oxidation (MFAO), the % of MFAU oxidized (%MFAO), glucose utilization (MGU) and 2) makes the myocardium more insulin-resistant.
Background: Obese women’s myocardium has a higher MVO2, MFAU, MFAO, and lower efficiency than nonobese women’s. Whether obese young men’s myocardium shows similar changes, and whether it is resistant to insulin’s effects (increasing glucose utilization, suppressing the %MFAO) are not clear.
Methods: We prospectively studied 22 nondiabetic, nonhypertensive men in the resting, fasted state (8 obese [age 34± 6yrs, body mass index 37± 2kg/m2], 14 nonobese [27± 7 yrs, 24± 3kg/m2]). All (except 1 who dropped) underwent positron emission tomography (PET) imaging for quantification of MBF, MVO2, MGU, MFAU, MFAO, and %MFAO. Plasma substrate and insulin levels and echocardiographically-determined cardiac structure and function were quantified during the PET. HOMA quantified insulin resistance. Tissue Doppler imaging quantified load-independent systolic (Sm) and diastolic (Em) function. Efficiency = cardiac work/MVO2.
Results: Obese men were older (p = .02), had a worse metabolic and hemodynamic profile, and lower Em (p = .0003). LV mass, ejection fraction, Sm, MBF, MVO2, and efficiency were not different between groups. Body mass index was not related to MVO2 or efficiency.
Conclusions: Myocardium of young obese men in the resting, fasted state is more resistant to effects of insulin on MGU and %MFAO, but not less efficient than nonobese men. Further studies are needed to determine whether the myocardium in obese men adapts as well as that of nonobese men to superimposed conditions that require a shift towards glucose use (e.g., ischemia).