探討紅甘藷葉對餵食炸油老鼠結直腸癌化生成之效應
Effect of purple sweet potato leaf on the colorectal carcinogenesis of oxidized frying oil-fed F344 rats
中文摘要
本研究之目的乃在探討多酚類含量豐富之紅甘藷葉，對餵食炸油和腹腔注射 DMH (1,2-dimethylhydrazine)之 F344 大鼠，所引發結直腸細胞之保護作用。DMH 為專一誘發結腸癌之致癌物，已有許多研究將 DMH 作為誘發結腸癌形成之 initiator。本實驗所使用之炸油為黃豆油經 24 小時，200±5℃油炸馬鈴薯而成。
自國家動物中心購入，54 隻 5～6 週雄性 F344 大白鼠，其中 27 隻經腹腔注射 30 mg DMH/kg BW，每週一次，連續注射六週，再隨機分成 3 組 (n=9)，分別餵食 含 20%新鮮油之 FD0 組、20%炸油之 OD0 組及含有 20%炸油及添加 2.5%紅甘藷 葉粉末之 OD2.5 組；對照組則分別為注射生理食鹽水之 FS0、OS0、OS2.5。 大 鼠餵食 32 週後予以犧牲，取出其肝臟、結腸組織、血漿進行分析。結果顯示，
經 24 小時油炸之炸油其酸價及紫外光吸收值皆高於新鮮油，顯示油脂已有裂解 和酸敗的現象。當給予高量炸油飲食 (OS0 組) 之後大鼠體內之脂質過氧化物 (TBARS) 顯著高於等量新鮮油飲食組 (FS0)，然而其總抗氧化力 (TAS) 及抗氧 化物—Vitamin E 則低於新鮮油飲食組；當餵予含紅甘藷葉之炸油飼料 (OS2.5 組) 後，TBARS 顯著降低，同時 TAS 也有顯著的增加，並有節省 Vitamin E 消耗之 作用。飼料中所添加紅甘藷葉之多酚類含量為 37.95 mgGAE/g，血漿中所測得之 多酚類含量 OS2.5、OD2.5 顯著地高於 OS0、OD0 組，但在肝臟中所測得之多酚 類並無顯著差異。在結直腸部位腫瘤之發生情形顯示，對照組皆無腫瘤之生成，
於注射 DMH 的各組中，則發現腫瘤發生率於 FD0、OD0、OD2.5 組分別為 66.7%、50% 、44.5%。在結直腸癌之前病灶 Aberrant crypt foci (ACF) 及結直腸 細胞增殖之生化指標 Ornithine decarboxylase (ODC) 方面，發現 ACF 於三組間並 無顯著差異，但攝食紅甘藷葉後 (OD2.5 組)，可減少老鼠結直腸中 ODC 及 COX-2 蛋白質的表現量。由結果可知，飼料中添加紅甘藷葉可以改善餵食炸油所帶來老 鼠體內之氧化壓力，並具有降低結直腸細胞病變之潛在效應。
英文摘要
The aim of this study was to investigate the effect of purple sweet potato leaf and oxidized frying oil (OFO) on colorectal carcinoma of F344 rats treated with DMH (1,2-dimethylhydrazine). Twenty-seven male F344 rats received 30mg/kg body weight DMH by intraperitoneal injection, once weekly for 6 weeks. Vehicle-treated groups received an equal volume of normal saline. Rats were assigned to 6 groups which diets containing 20% fresh soybean oil (FO): FS0 and FD0, 20% OFO: OS0 and OD0, 20% OFO with 2.5% purple sweet potato leaf: OS2.5 and OD2.5. Rats were
sacrificed after feeding with experimental diets for 32 weeks; liver were examined for quinone reductase (QR)、cytochrome P450 (CYP450), colon for the measurements of Aberrant crypt foci (ACF)、Ornithine decarboxylase (ODC)、cycloxygenase-2 (COX-2), and plasma for total antioxidant status (TAS)
thiobarbituric-acid-reactive-substances (TBARS). The results showed that CYP450 activity were elevated by OFO feeding. TAS was elevated and TBARS was decreased after feeding purple sweet potato leaf. Aberrant crypt foci had no significant
difference in both OD0 and OD2.5. The results of ODC and COX-2 protein expression were lower in OD2.5 group. In conclusion, fed rats with purple sweet potato leaf could lower phase I enzyme activity, increase antioxidant activity, and decreased ODC and COX-2 protein expression.
Keywords: purple sweet potato, colon cancer, Aberrant crypt foci , oxidized frying oil, 1,2-dimethylhydrazine
