餵食炸油鼠藉活化PPARALPHA 調控其下游基因的表現(3/3)

為探討炸油及其成分藉PPARα調 控脂質代謝相關基因表現情形，本研 究分別以PPARα活化能力分析(體外 實驗)及動物實驗，探討炸油及其區分 物對PPAR 傳訊途徑之效應。實驗一 結果，餵食含5 或20%炸油使鼠肝 Acyl CoA Oxidase(ACO)活性、CYP4A 蛋白質及其mRNA 顯著增加，且炸由 經水解後PPARα活化能力顯著高於未 經油炸支新鮮黃豆油。顯示油炸過程 產生之脂肪酸衍生物，具有較高之活 化能力。實驗二分別以黃豆油、芥花 油及牛脂同樣進行油炸並餵養大鼠， 結果油炸過之三種油均能使鼠肝 CYP4A 蛋白質顯著增加，但芥花炸油 之效應顯著低於另兩種炸油。Acyl CoA Oxidase(ACO)活性亦以餵食黃 豆炸油及油炸過牛脂鼠顯著高於其控 制組，而芥花炸油組則否。經油脂分 析結果，推測炸油上調控鼠肝PPARα 下游基因之能力似與其所帶有之-CO, -OH 官能基關係最密切。實驗三將黃 豆炸油水解以逆向層析管柱區分，發 現PPARα活化能力以高極性區分物較 高，其中極性最高之中短鏈脂肪酸活 化能力低、而極性次高之未斷裂脂肪 酸衍生物活性最高。此區分物經進一 步之管柱層析分離，得到活性最高之 幾種區分物，其中一種被鑑定為 Ricinoleic Acid (12-OH oleic acid)，另 外幾個高活性區分物因量不夠，未繼 續鑑定。將高活性之高極性區分物管 餵小鼠，確可使鼠肝ACO 活性顯著 增高。An in vitro transactivation assay and in vivo rat study were used to characterize the regulation of gene expression through PPARα signaling by dietary frying oil. In Experiment 1, groups of Sprague-Dawley male weanling rats were fed diets containing either high (20 g/100 g, HO and HF) or low (5 g/100 g, LO and LF) levels of oxidized frying soybean oil (HO and LO) or fresh soybean oil (HF and LF) for 6 wk. The OFO sample was prepared by frying wheat dough sheets in soybean oil at 205 ± 5°C for 24 h. OFO dose dependently and significantly increased (P < 0.05) mRNA of acyl-CoA oxidase (ACO) and cytochrome P450 4A1(CYP4A1) in liver of rats. Dietary OFO also dose dependently increased liver microsomal CYP4A protein (P < 0.05). The activity of hepatic ACO of the HO group was sixfold that of the HF group (P < 0.05). In Experiment 2, Sprague-Dawley male rats were fed the eight test diets which contain 15% fat, namely, SB(fresh soybean oil), FSB(frying soybean oil), CO(fresh canola oil), FCO(frying canola oil), BT(fresh beef tallow), FBT(frying beef tallow), A or B (Frying oil from street Vendors). Liver ACO activity of the FSB and FBT groups were 5 and 3.6 folds that of the SB and BTgroups (p<0.05), respectively. However, ACO activity if the FCO group were only 1.4 fold that of the CO group (p>0.05). The Liver CYP 4A1 of FSB and FBT groups were about 9 folds (p