| 摘要: | 共軛亞麻油酸(Conjugated linoleic acid, CLA)為一群含 18 個碳，具共軛雙鍵的脂肪酸，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(c9, t11)和trans-10, cis-12 CLA (t10, c12)兩種型式為主。本實驗室於先前研究發現小鼠以 CLA 餵食四週後會提升血漿、肝臟和週邊組織的 α-生育醇濃度及肝臟 α-生育醇轉移蛋白(α-Tocopherol transfer protein,α-TTP)表現量。因此本研究目的欲藉由實驗一了解短期餵食 CLA (一週)是否即對維生素 E (VE)營養狀況有所影響。實驗二則進一步確認 CLA 是否藉由影響肝臟 α-生育醇分泌速率進而影響血漿 α-生育醇的濃度。由於不同形式之 CLA 異構物對脂質代謝的影響各自有很大的專一性，故由實驗三來探討不同形式之 CLA 異構物對鼠體組織 α-生育醇含量的影響。實驗一：18隻7週大 C57BL/6J 雄性小鼠，依飼料不同分成三大組：對照組 (CC組，5% 大豆油)、CLA組 (1% CLA + 4% 大豆油)、VE組 (5% 大豆油 + 3750 ppm?生育醇)，飼養一週後犧牲。實驗二：26隻7週大 C57BL/6J 雄性小鼠，分成兩大組對照組 (CC組) 和 CLA 組(飼料成分同實驗一)每組又因飼養期長短分兩小組 (1wk 及4wk)。於犧牲當日收集 LPL 抑制劑(Triton-1339)注射前與注射後4小時之血液，血漿經三酸甘油酯、α-生育醇濃度分析並以公式計算肝臟分泌速率。實驗三：28隻7週大 C57BL/6J 雄性小鼠，依飼料不同分成四大組：分成對照組(CC組，5% 大豆油)、1% CLA組 (1% CLA + 4% 大豆油)、C9t11組 (0.5% cis-9, trans-11 CLA + 4.5% 大豆油) 以及 T10c12組 (0.5% trans-10, cis-12 CLA + 4.5% 大豆油)，飼養期為四週。實驗一結果顯示，小鼠餵食CLA一週後，其肝臟、腎臟和副睪脂肪 (EP) 的 α-生育醇濃度顯著提高約為控制組的2.5～6倍。VE組則提高了肝臟、腎臟、脾臟及 EP 的 α-生育醇濃度 (p<0.05)。肝臟 α-TTP 蛋白質含量及血漿 α-生育醇的濃度於三組間皆並無顯著差異，CLA 降低血漿及肝臟 TG 含量及抗氧化酵素 CAT 和 GPx 活性 (p<0.05)，而 VE 組皆無顯著影響。實驗二結果顯示，注射Triton-1339 四小時後，血漿中三酸甘油酯和 α-生育醇濃度皆隨時間增加而累積增加。經公式換算成肝臟分泌速率後，不管一週或四週餵食 CLA，肝臟α-生育醇分泌速率皆顯著增加，但 TG 分泌速率則顯著下降(p<0.05)。實驗三結果發現，CLA mixture 組和 t10, c12 組與 CC 組比皆會顯著提升肝臟中 α-TTP 蛋白質含量與血漿、肝臟及週邊組織 α-生育醇濃度(p<0.05)，但餵食 c9, t11 則無此等影響。抗氧化酵素方面，CLA mixture 與 t10, c12 降低肝臟 CAT 和 GPx 活性，c9, t11降低 CAT 活性。綜合上述，CLA 於短期作用下即會改變小鼠體內維生素 E 的營養狀況。且 CLA 可能是透過 t10, c12 此異構物形式影響肝臟中 α-TTP 蛋白質含量與 α-生育醇分泌速率以及肝臟抗氧化酵素活性之調控，進而影響小鼠肝臟脂質代謝及體內維生素 E 的營養。
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 (c9, t11) and trans-10, cis-12 CLA (t10, c12)are the two predominant forms of CLA. Many studies have shown that the CLA possess antioxidant activites, we also found the α-tocopherol levels of plasma, liver and peripheral tissues increased when in mice with fed CLA for four weeks in the previous study. Therefore, in experiment 1 we aimed to determine wether the α-tocopherol status is affected by CLA in short-term feeding. In experiment 2, we further confirm whether the hepatic secretion rates of α-tocopherol and triglyceride are influenced by CLA when mice fed one week and four weeks. Since different CLA isomers show different function in animal, in experiment 3, we would like to clarify the effect of CLA isomers (c9, t11 and t10, c12) on the vitamin E status in mice. Experiment 1: Eighteen seven-week-old C57BL/6J male 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 α-tocopherol, equal in common feed vitamin E content 50 times) The feeding period is 1 wk. Experiment 2 : twenty-six seven-week-old C57BL/6J male mice were divided into control group and the CLA group (the same feed ingredients as exp 1). The hepatic secretion rates of α-tocopherol and triglyceride (TG) were measured with Triton-WR1339 injection after 1 wk or 4wk feeding. Experiment 3 : twenty-eight seven-week-old C57BL/6J male mice were divided into 4 groups：according to the diet for 4 wks. CC group : containing 5 % soybean oil, CLA group : containing 4 % soybean oil + 1 % CLA, c9t11 CLA group : containing 4.5 % soybean oil + 0.5 % cis-9, trans-11 CLA , and t10c12 CLA group : containing 4.5 % soybean oil + 0.5 % trans-10, cis-12 CLA. Results from exp 1 showed that the α-tocopherol levels of liver, kidney and epididymal adipose tissue (EP) in the CLA group were significantly higher than that in the CC group. The α-tocopherol concentrations of liver, kidney, spleen and EP of vitamin E supplementation (VE group) was significantly increased. The α-TTP protein content of liver and plasma α-tocopherol levels showed no significant difference in the three groups, however, CLA significantly decreased the triglyceride levels in plasma and liver. The activities of antioxidative enzymes (CAT, GPx) in liver were decreased by CLA feeding, but didn’t change by Vitamin E supplementation. In experiment 2, the results showed that CLA significantly increased the α-tocopherol secretion rate both in the one week or four weeks feeding groups. In contrast, the triglyceride secretion rate was significantly decreased in CLA group when compared with CC group. Experiment 3: The α-tocopherol levels in plasma and tissue significantly increased in CLA group and t10c12 group. The α-TTP protein contents in liver were also elevated by CLA and t10c12 group. Feeding of c9, t11 CLA showed no influence in those parameter. The activities of antioxidative enzymes (CAT, GPx) in liver were decreased by feeding of mixture, c9, t11 CLA and t10, c12 CLA. In conclusion, CLA increased the VE status in one week feeding. The elevation of α-TTP protein levels and the hepatic secretion rate of α-tocopherol by CLA seems to be the major reasons for alteration of VE status in mice. Moreover, t10, c12 CLA isomers is the most active form in the regulation of VE status. |
