Watermelon Supplementation and Arterial Stiffness

The purpose of the study is to examine the effect of 12 weeks of L-citrulline/L-arginine in the form of watermelon supplementation on arterial function and autonomic neural control of the heart rate and blood pressure in older overweight/obese men and women with pre- and stage 1- hypertension. The specific aims of the study are: 1. To investigate the extent to which daily consumption of watermelon supplementation containing L-citrulline/L-arginine (4/2 g) will reduce BP and arterial stiffness. This aim will examine the working hypothesis that watermelon supplementation will reduce BP and improve arterial function. This aim will be tested by measuring brachial and central (aortic and carotid) BP at rest and during physiological stress (head-up tilt test and cold pressor test), and by evaluating arterial stiffness using pulse wave velocity of the aorta and legs as primary variables. 2. To determine the effect of watermelon supplementation on endothelial function. There is evidence that watermelon improves endothelial function in rats. Hence, we postulate that watermelon in part exerts its vascular protective effects by modulating indices of endothelial function. This aim will be tested by measuring flow-mediated dilation using vascular ultrasound and circulating levels of vasodilators, vasoconstrictors, and markers of vascular inflammation (adiponectin, leptin, endothelin-1, angiotensin II, prostaglandin F2α, sVCAM-1, sICAM-1, and 8-isoprostane). 3. To determine whether watermelon supplementation will improve the autonomic control of BP and heart rate in individuals with high abdominal obesity and BP. There is evidence that food high in L-arginine improves baroreflex sensitivity (BRS) in individuals with pre-hypertension. This aim will examine the working hypothesis that watermelon will improve cardiovascular autonomic control of BP by measuring heart rate variability, BP variability and BRS at rest and during physiological stress as secondary variables.