Effect of ingestion of purple grape juice on endothelial function in patients with coronary heart disease.

T “French Paradox” refers to the observation that the coronary heart disease mortality rate is lower in France than in other industrialized countries with similar prevalences of coronary risk factors.1,2 This paradox has been attributed to frequent consumption of alcohol-containing beverages, which increase highdensity lipoprotein (HDL) cholesterol levels and inhibit platelet function.1–7 Several epidemiologic studies suggest that ingestion of red wine, which contains several hundred different types of flavonoids, is more cardioprotective than beer or spirits.1–4 Indeed, the flavonoids found in red wine and purple grape juice (GJ) also inhibit platelet aggregation, and in 1 study, were shown to be powerful antioxidants that improved endothelial function.8–10 In that study, however, most subjects were taking vitamin E, so it is unclear if the observed results were due solely to the flavonoids in GJ or a combination of vitamin E and GJ.10 Furthermore, a high dose of GJ was administered (approximately 8 ml/kg/day) for only 2 weeks. The purpose of this study was to assess the endothelial function and antioxidant effects of 2 doses of purple GJ alone and in combination with vitamin E for 8 weeks. • • • The institutional review board of the University of Wisconsin Medical School approved this study. All subjects provided informed consent before participation. Twenty-two adults with angiographically documented coronary artery disease were recruited for this study. Subjects were not allowed to take vitamin supplements for 4 weeks before enrollment or during this study, except as prescribed by the research protocol. Subjects also were prohibited from consuming fruit products, tea, or alcoholic beverages during this study. Medications could not be changed during the study. All subjects ingested purple GJ (Welch’s 100% Concord Grape, Concord, Massachusetts) for 56 days. The first 11 subjects were instructed to drink 8.0 ml/kg of GJ, twice daily. For an average 80-kg person, this was approximately 640 ml/day (21 ounces) of GJ, which contained approximately 112 g of carbohydrate. The next 11 subjects were instructed to drink 4.0 ml/kg of purple GJ, once daily (low-dose group). After 28 days, subjects added vitamin E (d,l-a-tocopheryl) 400 IU to their daily intake of GJ. Subjects’ diaries indicated .90% compliance with GJ and vitamin E. Endothelial function was evaluated by measuring flow-mediated vasodilation (FMD) of the brachial artery using B-mode ultrasound. Studies were performed at baseline and at subsequent visits on the morning of phlebotomy, after a 12-hour fast. Subjects were instructed to drink their daily dose of GJ at least 2 hours before testing. Brachial artery diameters and blood flows were measured with a 7.5-MHz linear array vascular ultrasound transducer and an Agilent Technologies 5500 Sonos ultrasound system (Palo Alto, California). Increased forearm blood flow was induced by inflating a blood pressure tourniquet around the widest part of the forearm to a systolic blood pressure of 250 mm Hg for 4.5 minutes. Repeat brachial artery diameter and blood flow scans were obtained immediately and 1 minute after deflation of the tourniquet. Resting brachial artery diameter and blood flow scans were repeated 15 minutes later. Sublingual nitroglycerin (400 mg) was administered and final scans were performed after 3 minutes. The brachial artery was imaged in longitudinal sections 2 to 15 cm above the elbow. Images were recorded using the digital storage and retrieval software of the ultrasound system. Vessel diameters were measured in triplicate using digital calipers (Freeland Systems, Westfield, Indiana). Measurements were performed and interpreted by investigators who were blinded to subject information and study date. The brachial artery diameter was measured at end-diastole, using intima-media interfaces, or if they could not be visualized, media-adventitia interfaces, as landmarks. FMD was calculated as the ratio of the brachial artery diameter after reactive hyperemia to the baseline diameter, expressed as a percent change. Nitroglycerinmediated vasodilation was calculated in an analogous fashion. In this laboratory, intraobserver reliability for measurement of the brachial artery diameter is 0.987, reflecting an interclass correlation coefficient across all readings and conditions.10 Lipid and glucose levels were measured using enzymatic techniques on a Hitachi 747 analyzer (Tokyo, Japan) using standard reagents (Roche, Mannheim, Germany). Insulin levels were measured by radioimmunoassay. Low-density lipoprotein (LDL) particles were isolated from serum by sequential density ultracentrifugation between densities of 1.006 and 1.063 g/ml using a Beckman Optima ultracentrifuge (Fullerton, California) at 100,000 rpm (.400,000 g). The LDL-containing fraction was desalted with a 2-ml column of preswollen 12% cellulose and 0.1 mol/L From the University of Wisconsin Medical School, Madison, Wisconsin. This study was supported by an unrestricted grant from Welch’s Foods, Inc., Concord, Massachusetts. Dr. Stein’s address is: Section of Cardiovascular Medicine, University of Wisconsin Medical School, 600 Highland Avenue, H6/315 CSC (MC 3248), Madison, Wisconsin 53792. E-mail: jhs@medicine.wisc.edu. Manuscript received February 21, 2001; revised manuscript received and accepted April 10, 2001.