Impact of obesity on coronary microvascular function in the Zucker rat

Objective: To test the hypothesis that vasomotor control is impaired in the coronary circulation of prediabetic obese (OZR) relative to lean Zucker rats (LZR). Methods: Cardiac function was assessed with in vivo measures of cardiac output and microvascular structure and function was assessed in vitro using videomicroscopic techniques. Results: OZR showed a marked hyperdynamic circulation with an increased cardiac output and elevated stroke volume. Contrary to the stated hypothesis, the authors found no diminution of vasodilator function and no augmentation of vasoconstriction. Indeed, dilation to acetylcholine was potentiated and vasoconstriction to endothelin was reduced in OZR compared to LZR. Structural characteristics of small coronary arteries were similar between LZR and OZR. Conclusions: Taken together, these results indicate that obesity, as manifested in the prediabetic OZR, does not impair coronary vasomotor control. This lack of dysfunction in the presence of the same risk factors that affect other beds may reflect a reversal of vascular injury by the increased metabolism and coronary blood flow caused by hyperdynamic cardiac function early in obesity.