Coronary blood flow regulation in the prediabetic metabolic syndrome

Abstract.   This study tested whether the pre-diabetic metabolicsyndrome impairs coronary blood ow control sufciently to alterthe balance between coronary blood ow and myocardialmetabolism. Experiments were conducted in dogs instrumented withcatheters in the aorta, coronary sinus, and left ventricle andwith ow transducers around the circumex coronary artery andaorta. Coronary blood ow, myocardial oxygen consumption(MVO2), cardiac output, aortic pressure,left ventricular pressure and heart rate were measured at restand during treadmill exercise in normal, control and high fatfed dogs. High fat feeding for ~ six weeks increased body weight15%, increased aortic blood pressure 10%, and induced insulinresistance. Fasting plasma insulin levels were increased2.4-fold while plasma glucose concentration was unchangedrelative to controls (5.0 ± 0.3 mM). The cardiac index increasedwith exercise but was not altered by high fat feeding. Themetabolic syndrome reduced the slope of the relationship betweencoronary blood ow and MVO2 (P < 0.0001) and decreased coronaryvenous PO2 at a given level ofMVO2 (P < 0.05). These ndings indicatethat the metabolic syndrome impairs the balance betweenmyocardial oxygen delivery and metabolism by tonicallyvasoconstricting the coronary circulation.