含白色蔬果之高脂飲食對ICR小鼠大腸黏膜基因表現的影響

Abstract

大腸直腸癌盛行於已開發國家，近年來國內大腸直腸癌發生率逐年攀升，已成為國人發生人數最多的癌症。研究指出大腸直腸癌的發生與飲食型態有密切關係，目前主要的保健飲食建議為降低脂質及增加蔬果攝取量。蔬菜與水果富含多種膳食纖維、維生素、礦物質及植化素，大部分研究認為高蔬果飲食可降低罹患大腸直腸癌風險。考量國人近年飲食西化，脂質攝取量明顯增加，因此本研究以預防之觀點，透過微陣列分析於高脂飲食下個別探討攝食國人常食用之白色蔬果對小鼠大腸黏膜基因表現之影響，藉由基因表現差異評估對腸道保健之可能效益。實驗動物選用非近親交配品系雄性ICR小鼠，依照飼料組成分為六組：高脂組（HF）、高脂荔枝組（HFL）、高脂龍眼組（HFO）、高脂芭樂組（HFG）、高脂冬瓜組（HFW）及Chow diet組（Chow），高脂飼料提供脂質熱量百分比為30%，高脂蔬果組則於高脂飼料中添加10%蔬果乾粉。各組餵食四週後犧牲，採集大腸黏膜總RNA進行微陣列分析與執行Q-PCR加以驗證；採集血液與肝臟分析三酸甘油酯、膽固醇與維生素C濃度。高脂冬瓜組之體重增加與肝臟三酸甘油酯濃度低於高脂組與高脂水果組，然而高脂組與高脂蔬果組於攝食量無顯著差異。微陣列分析結果顯示，與低脂Chow組比較，高脂組小鼠大腸黏膜中於參與免疫反應、反應氧化壓力、細胞增生、細胞凋亡及脂質代謝相關等基因之表現量增加；與高脂組相比，高脂蔬果組小鼠大腸黏膜中於參與免疫反應、反應氧化壓力、細胞增生、細胞凋亡及脂質代謝相關等基因之表現量減少。Q-PCR驗證可見，高脂組大腸組織中發炎指標cyclooxygenase-2（COX-2）、細胞增生指標Ki-67基因表現量高於Chow組與高脂蔬果組。攝食高脂飲食會增加小鼠大腸環境中之免疫反應、細胞增生、細胞凋亡、脂質代謝與反應氧化壓力相關基因表現，顯示高脂飲食對大腸健康具較負面影響；於高脂飲食下攝取白色蔬果則與高脂飲食基因表現呈現相反結果，顯示攝取白色蔬果可改變高脂影響的趨勢，其中以冬瓜最具潛力。

Colorectal cancer (CRC) has become especially prevalent in developed countries. CRC has the highest incidence since 2006 in Taiwan and now is the 3rd leading cause of cancer death. Study evidence has suggested a close association between development of CRC and dietary patterns. To reduce the risk, dietary recommendations emphasize that low-fat and high-fruits and vegetables diet. In general, fruits and vegetables contain abundant mixture of disease-preventing substances including vitamins, minerals, dietary fiber and phytochemicals and the majority of epidemiological evidence supporting the high-fruits and vegetables diet is related to decreased risk of CRC. In recent years, human dietary pattern will incline to be more westernized, especially higher intake of fat. Therefore, we investigated the effect high-fat diets containing white fruits and vegetable on gene expression of colonic mucosa in ICR mice using DNA microarray technology. Male ICR mice of outbred strain were purchased from BioLASCO Taiwan Co., Ltd. They were randomized by body weight into six experiment groups：a high-fat 93G (HF), a high-fat litchi group (HFL), a high-fat longan group (HFO), a high-fat guava group (HFG), a high-fat wax gourd group (HFW), and chow diet (Chow). A high fat basal diet (14.4% oil, 30 % Kcal from fat) was modified from AIN-93G. Fruits and vegetable experimental diets were prepared by adding lyophilized food powder to basal diet at 10% wt and adjusting the macronutrient contents to reach similar energy density.After feeding for four weeks, mice were killed by CO2 asphyxiation. Total RNA of colonic mucosa was extracted from each mice and pooled RNA sample corresponding to experiment group were subjected to Agilent Mouse Whole Genome Oligo Microarray assay using One-color Microarray hybridization protocol. Then, Q-PCR was used to validate the microarray results. The liver and serum was collected for analysis of triglyceride, cholesterol and vitamin C. The W group had lower weight gain and liver triglyceride level than HF93G and high-fat fruits groups. However, daily food intakes, estimated energy intake showed no significant difference among the HF93G and high-fat fruits and vegetable groups. Gene expression were increased in HF93G compared to Chow group, including related function to immune response, oxidative stress response, cell proliferation, cell apoptosis, and lipid metabolism. Gene expression were decreased in high-fat fruits and vegetable groups compared to HF93G group, including related function to immune response, oxidative stress response, cell proliferation, cell apoptosis, and lipid metabolism. Cyclooxygenase-2 (COX-2) and ki67 gene expression of individual mice was measured by Q-PCR and showed HF93G group had higher than Chow and high-fat fruits and vegetable groups. Collectively, these data suggest that consumption of a high-fat diet interferes with biological function involving colonic immune response, oxidative stress response, cell proliferation, cell apoptosis, and lipid metabolism, and may exert a proinflammatory stimulus in the colon.The white fruits and vegetables may be beneficial in decreasing adverse effect of high-fat diet.