Rice Bran Fractions Improve Blood Pressure, Lipid Profile, and Glucose Metabolism in Stroke-Prone Spontaneously Hypertensive Rats ARDIANSYAH,* ,² HITOSHI SHIRAKAWA, ² TAKUYA KOSEKI, ‡ KOUSAKU OHINATA, ² KATSUMI HASHIZUME, ‡ AND MICHIO KOMAI ² Laboratory of Nutrition, Department of Science of Food Function and Health, Graduate School of Agricultural Science, Tohoku University, 1-1 Tsutsumidori-Amamiyamachi, Aoba-ku, Sendai 981-8555, Japan, and National Research Institute of Brewing (NRIB), 3-7-1 Kagamiyama, Higashihiroshima, Hiroshima 739-0046, Japan Effect of dietary supplementation of two types of rice bran fraction on blood pressure (BP), lipid profile, and glucose metabolism in stroke-prone spontaneously hypertensive rats was studied. Male 4-week- old rats were divided into one group fed the AIN-93M-based control (C) diet and two groups fed diet supplemented with 60 g/kg of Driselase and ethanol fractions (DF and EF, respectively) of rice bran. After 8 weeks feeding, the BP decreased in the DF and EF groups in comparison with the C group (p < 0.01). Plasma ACE inhibitory activity, BUN, BUN/creatinine ratio, albumin, triglyceride, and glucose levels were lower in the DF and EF groups than in the C group (p < 0.01). Plasma nitric oxide and urinary 8-hydroxy-2′-deoxyguanosine levels were lower in the DF and EF groups than in the C group (p < 0.01). Rice bran fractions appear to have a beneficial dietary component that improves hypertension, hyperlipidemia, and hyperglycemia. KEYWORDS: Rice bran; Driselase fraction; ethanol fraction; blood pressure; nitric oxide; ACE inhibitory activity; 8-OHdG; lipid profile; glucose level. INTRODUCTION Hypertension, a manifestation of cardiovascular disease, has continued to be a major cause of morbidity and death. Pharmacological treatment using drugs such as enalapril, losartan, and ramipril has shown that these agents have the capability to act as antihypertensive drugs (1-3). Their anti- hypertensive actions are due to their ability to inhibit the angiotensin-1-converting enzyme (ACE). Presently, much effort is being invested in detecting bioactive components in foods that can contribute to a decreased risk of cardiovascular diseases. There is an increasing interest in the use of dietary antioxidants, including vitamin E, vitamin C, carotenoids, and polyphenols, in the prevention of cardiovascular diseases and their risk factors (4). Consumption of various edible plants, including vegetables, fruits, and cereals, has been regarded as a preventive factor against these chronic diseases, and antioxidative constituents present in these foods are important because of their scavenging property. Among these edibles, rice bran is a byproduct of the rice milling process, and it contains various antioxidants that impart beneficial effects on human health. It is well-known that a major rice bran fraction contains 12-13% oil and highly unsaponi- fiable components (4.3%). This fraction contains tocotrienol, γ-oryzanol, and -sitosterol; all of these constituents may contribute to the lowering of the plasma levels of the various parameters of the lipid profile (5-7). Rice bran also contains a high level of dietary fibers (-glucan, pectin, and gum) (8). In addition, it also contains 4-hydroxy-3-methoxycinnamic acid (ferulic acid), which may also be a component of the structure of nonlignified cell walls. Ferulic acid is a unique bifunctional element that can cross-link heteroxylans in cereal tissues (9). Various studies have indicated that purified ferulic acid has a protective effect against -amyloidal peptide toxicity (10); this has been described as a photoprotective (11) or antioxidative effect (12). It also decreases the blood glucose levels in streptozotocin-induced diabetic rats (13) and reduces the blood pressure (BP) in spontaneously hypertensive rats (SHR) (14). A recent report showed that the outer layer fraction of black rice inhibited atherosclerotic plaque formation, lowered the aortic 8-hydroxy-2′-deoxyguanosine (8-OHdG), and decreased malondialdehyde levels in serum and aorta that were induced by hypercholesterolemia in rabbits (15). The present experiment was conducted to determine whether rice bran supplementation has physiological effects on spontaneous hypertension from the viewpoint of dietary manipulation by using naturally occurring foods. We used two types of rice bran fraction as a dietary component in the prevention or treatment of hypertension in * To whom correspondence should be addressed. E-mail: ardy@biochem.tohoku.ac.jp. ² Tohoku University. ‡ National Research Institute of Brewing (NRIB). 1914 J. Agric. Food Chem. 2006, 54, 1914-1920 10.1021/jf052561l CCC: $33.50 © 2006 American Chemical Society Published on Web 01/27/2006 Downloaded by TOHOKU UNIV on July 3, 2009 Published on January 27, 2006 on http://pubs.acs.org | doi: 10.1021/jf052561l