米食對C57BL/6JNarl及ICR小鼠肝臟抗氧化系統與大腸組織之影響

Abstract

長久以來，稻米一直是亞洲許多國家與台灣的主要糧食來源，亦為重要的經濟作物。稻米含有許多抗氧化與抗發炎的物質，主要存在糙米的糠層與胚芽中。流行病學研究指出，攝食較多含有抗氧化成分的食物與降低多種人類疾病的發病率與死亡率有關。所以，若以全穀類米食取代普遍較常食用的精白米，作為膳食中的主食來源，應具有促進健康之潛力。本研究探討攝食米食對於小鼠肝臟與大腸抗氧化能力之影響，實驗動物採用兩種不同品系的小鼠：近交系C57BL/6JNarl雄性小鼠（國家實驗動物中心）與遠交系ICR雄性小鼠（樂斯科生技公司）。依實驗飼料組成分成五組：AIN-93G組（93G）、高蛋白質AIN-93G組（modified AIN-93G, M93G）、Chow diet（Chow）組、高蛋白質白米組（polished rice, PR）與高蛋白質米糠加糙米組（brown rice enriched with rice bran, RB）。實驗期間給予各組小鼠配方飼料並定期記錄攝食量與體重，飼養四週後犧牲。分析項目：肝臟與近端大腸抗氧化酵素、大腸長度與遠端大腸組織免疫染色。抗氧化酵素包括榖胱甘肽過氧化酶、榖胱甘肽還原酶、榖胱甘肽硫基轉移酶、超氧歧化酶與過氧化氫酶；組織免疫染色以Ki-67作為遠端大腸黏膜上皮細胞增生指標。結果顯示，在相同飼養條件下，不同鼠種的反應不盡相同：C57BL/6JNarl雄性小鼠各組平均體重差異大，而肝臟抗氧化酵素比活性組間差異較小；ICR雄性小鼠則是各組平均體重差異小，肝臟抗氧化酵素比活性組間差異較明顯。遠端大腸黏膜上皮細胞增生能力則在二鼠種間有相似之趨勢：93G組與M93G組有較低之增生能力。白米與米糠加糙米飼料使小鼠有較重體重，且攝食chow diet與米糠加糙米飼料，有助提升C57BL/6JNarl雄性小鼠肝臟抗氧化能力與ICR雄性小鼠肝臟及近端大腸抗氧化能力。因此，米食與非精製之飲食，具有提升組織抗氧化能力與疾病預防之潛力。

Rice has been the staple food and an important cash crop for Asians, including Taiwanese for a long time. There are abundant antioxidants and anti-inflammation substances in rice, most of them exist in the bran layer and the germ. According to the epidemiological studies, the more intake of those foods containing antioxidant substances, the less morbidity and mortality of human diseases. Therefore, replacing the polished rice with the whole grain rice diet should be a pro-health dietary pattern. Different from other studies using extracts from rice bran, this study used rice diet to investigate the effects on the antioxidant capacity of liver and colon tissue of mice. Forty-five male inbred C57BL/6JNarl mice were obtained from the National Laboratory Animal Center and forty-five male outbred ICR mice were obtained from the BioLasco Taiwan Co., Ltd. Mice were assigned to 5 dietary groups: an AIN-93G group (93G), a modified high protein AIN-93G group (M93G), a chow diet group (Chow), a polished rice high protein group (PR), and a bran-enriched brown rice high protein group (RB). The mice were fed with the experimental diets and the body weight and food intake were recorded routinely during the experiment. Mice were sacrificed after 4-week fed with experimental diets. Liver tissues were collected for analysis of the antioxidant related enzymes, such as glutathione peroxidase (GPx), glutathione reductase (GR), glutathione S-transferase (GST), superoxide dismutase (SOD) and catalase (CAT). Colon tissues were collected for analysis of glutathione (GSH) and the antioxidant enzymes, and immunochemistry assays of cell proliferation marker, Ki-67. The results show the 2 mouse strains had different responses to the same rearing condition. The body weight of male C57BL/6JNarl mice had obvious difference, but most of the liver antioxidant enzymes had no significant differences. However, male ICR mice had converse results. The cell proliferation capacity in the mucosa epithelial cells of distal colon had a similar trend: the 93G group and M93G group had lower Ki-67 expression. The mice of both strains fed with the PR and RB diet were heavier than others. Chow diet and RB diet enhanced liver antioxidant enzymes specific activity of the 2 mouse strains, and so did in the proximal colon of male ICR mice. In conclusion, these results indicate rice diets and non-refined diets can increase tissue antioxidant capacity and have a great possibility to prevent disease.