Effect of Wakame Containing Diets on Hepatic Gene Expressions in Rat

Wakame is an edible seaweed that is a common constituent in the Japanese diet. Previous studies showed that wakame consumption is associated with prevention of metabolic syndrome; however, the molecular mechanisms of this protective effect are poorly understood. To determine if the expression of hepatic genes is affected by the ingestion of brown seaweed, Undaria pinnatifida (wakame), rats were fed diets containing 0, 0.1, or 1.0 g/100 g dried wakame powder for 28 days. Administration of 1% wakame significantly decreased total serum total cholesterol levels. Hepatic gene expression was investigated using DNA microarray analysis. Microarray analysis showed that wakame suppresses the lipogenic pathway by downregulating SREBF-1. Moreover, bile acid biosynthesis and gluconeogenesis are promoted by upregulation of the PPAR signaling pathway, which leads to a reduction in the accumulation of cholesterol and promotion of β-oxidation. These results provide useful genetic information about various biochemical processes by which wakame regulates energy metabolism. Male Sprague Dawley (SD) rats aged 4 weeks were housed in a temperature-controlled room with a 12-h light-dark cycle (lights on at 08:00 and off at 20:00). Animals were allowed free access to drinking water and were fed a diet prepared according to the recommendations of the American Institute of Nutrition (AIN-93G). After acclimatization to the environment and to investigators for 1 week, rats were fed purified experimental diets. Rats were divided into three groups (n = 6, 3 rats/cage) and fed one of the following synthetic diets: control diet containing 7% fat, 20% casein, 52.9% corn starch, 5% cellulose, 1% vitamins, 3.5% minerals, or wakame diet, consisting of the control diet supplemented with the indicated amount of wakame powder. Animals were fed these diets for 28 days. Food intake was measured every 2–3 days on a per-cage basis. On the final day of the experiment, livers were excised from each animal and submerged in RNALater (Life Technologies, Carlsbad, CA, USA) overnight at 4°C and then stored at -80 °C until RNA isolation. Total RNA was used for microarray analysis. All animal experiments were approved by the Animal Care Committee of Oriental Yeast Co., Ltd. and followed the Committee Guidelines for the Care and Use of Laboratory Animals (11009).