| 摘要: | 共軛亞麻油酸 (Conjugated linoleic acid, CLA) 是指一群含有 18 個碳，具有共軛雙鍵的脂肪酸，為 ω-6 必需脂肪酸亞麻油酸的立體異構物，其中主要以 cis-9, trans-11 CLA 和 trans-10, cis-12 CLA 兩種型式為主。前人實驗發現 CLA 可提升老鼠血漿及肝臟維生素 E 營養狀況，但其影響機制不明，此外，CLA 對其周邊組織維生素 E 營養狀況之影響為何，亦未見有文獻探討。因此本研究之目的在探討 CLA 對小鼠組織維生素 E 含量之影響及可能機制。將 24 隻 7 週大 C57BL / 6J 雄性小鼠，依飼料不同分成三組：控制組 (CC，5 % Soybean oil)、CLA 組 (CLA，1 % CLA + 4 % Soybean oil)、維生素 E 補充組 (VE，5 % Soybean oil + 3750 ppm alpha-tocopherol, 相當於一般飼料維生素 E 含量的 50 倍)，飼養四週。結果顯示 CLA 組各組織中之 alpha-生育醇濃度幾乎與 VE 組相當，兩組皆顯著高於 CC 組 (p<0.05)。肝臟 alpha-TTP 蛋白質及 mRNA 含量以 CLA 組顯著高於 CC 組 (p<0.05)。但是 CLA 組的維生素 E 吸收率、血漿及肝臟 alpha-CEHC 含量皆與 CC 組無顯著差異。肝臟、脾臟及心臟 TBARS 濃度以 VE 組顯著低於CC 組 (p<0.05)，而 CLA 組與 CC 組則無顯著差異。腎臟、睪丸、肺臟、副睪脂肪及腹腔脂肪的 TBARS 濃度則以 CLA 組和 VE 組兩組顯著低於 CC 組 (p<0.05)。與 CC 組相比，CLA 可提升肺臟、副睪脂肪與腹腔脂肪的 GSH 含量，腎臟 GSH 含量則反而下降，然而脾臟的 GSH 含量則不受 CLA 所影響。在抗氧化酵素方面，CLA 組會顯著降低肝臟中 CAT 與 GPx 兩酵素活性，但是 VE 組反而顯著提升 CAT 之酵素活性。顯示 CLA 與 VE 對於肝臟酵素活性之影響情形有所不同。腎臟中 CAT 活性 CLA 組顯著較低，但 GPx 活性則顯著最高 (p<0.05)，此現象與肝臟完全不同。肝腎 SOD 活性、抗氧化酵素 CAT、GPx 蛋白質含量以及肝臟三種抗氧化酵素 mRNA 的表現量於三組間並無顯著差異。CLA 會活化肝臟 PPAR-gamma mRNA 之表現量，並抑制 PPAR-alpha mRNA 的表現量；而維生素 E 的補充會增加肝臟 ROR-alpha mRNA 之表現量。綜上所述，CLA 可顯著提升小鼠肝臟以及周邊組織 alpha-生育醇濃度，且其提升程度與補充 50 倍維生素 E 組相當。CLA 可藉由提升肝臟中 alpha-TTP 蛋白質及 mRNA 含量，進而提升血漿 alpha-生育醇濃度。維生素 E 吸收及代謝並未受 CLA 所影響，因此並非導致 CLA 組維生素 E 累積之原因。由於 CLA 對於肝、腎抗氧化酵素活性 (CAT, GPx) 以及腎、脾、脂肪等組織 GSH 濃度之影響情形與維生素 E 補充組不同，因此認為 CLA 對組織抗氧化酵素活性之影響並非透過組織所累積之維生素 E 所達成。本論文指出 CLA具有調節抗氧化酵素活性與 alpha-TTP、PPAR-alpha 等 mRNA 表現之弁遄ACLA 藉由這些調控機制以減少組織對維生素 E 的消耗，進而使組織大量累積維生素 E。
Conjugated linoleic acid (CLA) refers to a group of positional and geometric isomers of the omega-6 essential fatty acid linoleic acid that with 18 carbon atoms and conjugated double bonds. In nature, cis-9, trans-11 CLA and trans-10, cis-12 CLA are the two predominant forms of CLA. Previous studies have shown that rodents fed CLA could elevate vitamin E level of plasma and liver, but the mechanism is still unknown. Moreover, how the vitamin E levels in peripheral tissues are influenced by CLA has not been reported. The purpose of this study was to investigate the possible mechanisms that involved in the regulation of tissue vitamin E content in mice fed CLA. Twenty-four seven-week-old male C57BL/6J mice were assigned to three groups: control group (CC, containing 5 % soybean oil), CLA group (CLA, containing 4 % soybean oil + 1 % CLA ), and vitamin E supplemented group (VE, containing 5 % soybean oil + 3750 ppm alpha-TOH, equal in common feed vitamin E content 50 times) were fed experimental diets for 4 wk. The results showed that alpha-TOH levels of various tissues in CLA group were almost equal to the VE group, and the concentrations of alpha-TOH in these two groups were significantly higher than the CC group. The levels of alpha-TTP protein and mRNA in liver were significantly higher in the CLA group when compared with the other two groups. The absorption of vitamin E and the amounts of alpha-CEHC in plasma and liver showed no significant difference between the CC and CLA groups. The concentrations of TBARS in liver, spleen and heart were significantly lower in the VE group than that in the CC group, but not in the CLA group. In the CLA and VE groups, the concentrations of TBARS in kidney, testis, lung, epididymal fat and retroperitoneal fat were significantly lower than that in the CC group. When compared with the CC group, CLA caused a significant increase GSH levels in lung, epididymal fat and retroperitoneal fat, but decrease GSH level in kidney, while having no effect on spleen GSH level. The activities of CAT and GPx in liver were significantly lower in the CLA group, but CAT activity was significantly higher in the VE group. The results showed that CLA differs from vitamin E supplementation on the effect of antioxidative enzymes activities in liver. In kidney, the CAT activity of the CLA group was significant lower than the other groups, whereas, reverse result was shown on the GPx activity. This situation compared with liver was completely different. The activity of SOD, the contents of CAT and GPx protein in liver and kidney, as well as the contents of antioxidative enzymes mRNA in liver were not significantly different among the three groups. Mice fed CLA diet could induce PPAR-gamma but inhibit PPAR-alpha mRNA expression in liver, whereas supplementation with vitamin E could activate hepatic ROR-alpha mRNA expression. In conclusion, mice fed 1 % CLA resulted in significantly higher alpha-TOH levels in liver and peripheral tissues which had similar efficiency with supplementation of vitamin E for 50-fold. CLA induced liver alpha-TTP protein and mRNA contents which may elevate the level of alpha-TOH in plasma. This study demonstrated that the accumulation of vitamin E in tissues by the CLA diet was not due to the changes of vitamin E absorption and metabolism. CLA and vitamin E supplementation showed different effects on the activities of antioxidative enzymes (CAT, GPx) in liver and kidney, as well as the levels of GSH in kidney, spleen and adipose tissues in mice. Thus, the affect of tissues antioxidative enzymes activities by CLA did not mediated via vitamin E accumulation in tissues. This study indicated that CLA could regulate antioxidative enzymes activities, hepatic alpha-TTP and PPAR-alpha mRNA which may reduce the demand for vitamin E and contribute to the accumulation of vitamin E in tissues. |
