Obesity affects myocardial vasoreactivity and coronary flow response to insulin.

OBJECTIVE: Obesity is associated with increased risk for cardiovascular diseases and peripheral endothelial dysfunction. We examined whether myocardial vasoreactivity and coronary-flow response to insulin stimulation are altered in obesity. RESEARCH METHODS AND PROCEDURES: Myocardial blood flow was quantitated in 10 obese men (body mass index, 33.6 +/- 1.9 kg/m(2)) and 10 healthy matched non-obese men (body mass index, 24.2 +/- 1.9 kg/m(2)), using positron emission tomography and oxygen-15-labeled water. The measurements were performed basally and during adenosine infusion (140 microg/kg per minute), with or without simultaneous physiological (1 mU/kg per minute) and supraphysiological (5 mU/kg per minute) hyperinsulinemia.
RESULTS: Basal myocardial blood flow was not significantly different between obese and non-obese subjects. Adenosine-stimulated flow was blunted in obese (3.2 +/- 0.6 mL/g per minute) when compared with non-obese subjects (4.0 +/- 1.1 mL/g per minute, p < 0.05). Simultaneous physiological hyperinsulinemia increased adenosine-stimulated myocardial flow significantly in both groups (to 4.03 +/- 1.24 and 4.85 +/- 1.04 mL/g per minute in obese and non-obese men, respectively; p < 0.05 vs. adenosine). Supraphysiological hyperinsulinemia further enhanced the adenosine-stimulated flow in non-obese subjects (to 5.56 +/- 0.98 mL/g per minute; p < 0.05) but not in obese subjects. DISCUSSION: Young obese, healthy men have reduced myocardial vasoreactivity, which may represent an early precursor of future coronary artery disease. Additionally, insulin-induced enhancement of myocardial blood flow is blunted in obesity. Thus, endothelial dysfunction seems to also characterize myocardial vasculature of obese subjects.