Effect of Wakame Containing Diets on Hepatic Gene Expressions in Rat. Rattus norvegicus

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. Overall design: 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).

裙带菜（wakame）是一种可食用海藻，为日本膳食中的常见组分。既往研究显示，摄入裙带菜与代谢综合征的预防存在相关性，但该保护效应的分子机制尚不明晰。为明确褐藻裙带菜（Undaria pinnatifida，wakame）的摄入是否会影响肝脏基因表达，研究者将大鼠分为三组，喂食分别添加0、0.1或1.0 g/100 g干燥裙带菜粉的饲料，持续喂养28天。喂食1%剂量裙带菜粉可显著降低大鼠血清总胆固醇水平。采用DNA微阵列（DNA microarray）分析检测肝脏基因表达情况。微阵列分析结果显示，裙带菜可通过下调SREBF-1的表达抑制脂肪生成通路。此外，裙带菜可通过上调过氧化物酶体增殖物激活受体（PPAR）信号通路，促进胆汁酸生物合成与糖异生过程，进而减少胆固醇蓄积并增强β-氧化作用。本研究结果为阐明裙带菜调控能量代谢的各类生化过程提供了极具价值的遗传学信息。
整体实验设计：4周龄雄性Sprague Dawley（SD）大鼠饲养于温度可控的环境中，采用12小时明暗循环制度（光照时段为08:00至20:00）。所有大鼠可自由饮用净水，并喂食符合美国营养学会（AIN-93G）推荐配方的基础饲料。经过1周的环境与实验人员适应期后，大鼠开始喂食纯化的实验饲料。将大鼠分为三组（每组n=6，每笼饲养3只），分别喂食以下三种合成饲料：对照组饲料（含7%脂肪、20%酪蛋白、52.9%玉米淀粉、5%纤维素、1%维生素、3.5%矿物质），以及添加了指定剂量裙带菜粉的裙带菜饲料。大鼠持续喂食上述饲料28天。每2至3天以笼为单位测量单笼食物摄入量。实验结束当日，处死所有大鼠并摘取肝脏，将肝脏组织浸没于RNALater（Life Technologies，卡尔斯巴德，加利福尼亚州，美国）中，4℃静置过夜后，于-80℃保存直至RNA提取。提取的总RNA用于微阵列分析。所有动物实验均经东方酵母有限公司（Oriental Yeast Co., Ltd.）动物护理委员会批准，并严格遵循《实验动物护理与使用委员会指南》（11009）执行。