The Journal of nutrition | 2021
Supplemental Watermelon Juice Attenuates Acute Hyperglycemia-Induced Macro-and Microvascular Dysfunction in Healthy Adults.
Abstract
BACKGROUND\nAcute hyperglycemia reduces NO bioavailability and causes macro- and microvascular dysfunction. Watermelon juice (WMJ) is a natural source of the amino acid citrulline, which is metabolized to form arginine for the NO cycle and may improve vascular function.\n\n\nOBJECTIVES\nWe examined the effects of 2 weeks of WMJ compared to a calorie-matched placebo (PLA) to attenuate acute hyperglycemia-induced vascular dysfunction.\n\n\nMETHODS\nIn a randomized, placebo-controlled, double-blind, crossover trial, 6 men and 11 women (aged 21-25; BMI, 23.5\xa0± 3.2\xa0kg/m2) received 2 weeks of daily WMJ (500\xa0mL) or a PLA drink followed by an oral-glucose-tolerance test. Postprandial flow-mediated dilation (FMD) was measured by ultrasound (primary outcome), while postprandial microvascular blood flow (MVBF) and ischemic reperfusion were measured by near-infrared spectroscopy (NIRS) vascular occlusion test (VOT).\n\n\nRESULTS\nThe postprandial FMD area AUC was higher after WMJ supplementation compared to PLA supplementation (838\xa0± 459% · 90\xa0min compared with 539\xa0± 278% · 90\xa0min; P\xa0=\xa00.03). The postprandial MVBF (AUC) was higher (P\xa0=\xa00.01) following WMJ supplementation (51.0\xa0± 29.1\xa0mL blood · 100\xa0mL tissue-1 · min-1 · 90\xa0min) compared to the PLA (36.0\xa0± 20.5\xa0mL blood · 100\xa0mL tissue-1 · min-1 · 90\xa0min; P\xa0=\xa00.01). There was a significant treatment effect (P\xa0=\xa00.048) for WMJ supplementation (71.2\xa0± 1.5%) to increase baseline tissue oxygen saturation (StO2%) when compared to PLA (65.9\xa0± 1.7%). The ischemic-reperfusion slope was not affected by WMJ treatment (P\xa0=\xa00.83).\n\n\nCONCLUSIONS\nTwo weeks of daily WMJ supplementation improved FMD and some aspects of microvascular function (NIRS-VOT) during experimentally induced acute hyperglycemia in healthy adults. Preserved postprandial endothelial function and enhanced skeletal muscle StO2% are likely partially mediated by increased NO production (via citrulline conversion into arginine) and by the potential antioxidant effect of other bioactive compounds in WMJ.