大鼠尿液及血漿中維生素E代謝物α-CEHC 對維生素E營養狀況之反應性

Abstract

中文摘要 近年的研究報告指出維生素E之尿中代謝產物乃其支鏈僅剩三個碳之carboxyethyl hydroxychroman(CEHC)，血漿生育醇濃度超過某一閾值，人體尿中才會有顯著之人體尿中α-CEHC排出，暗示尿中α-CEHC可能與維生素E營養狀況有某種關連。 本論文研究以以大鼠作為動物模式，探討維生素 E 營養狀況與α-CEHC生成量之相關性。先餵食 48隻雄性離乳 Wistar 大鼠缺維生素E飼料一週後，隨機分成8組，其中7組分別餵食不同0，5，10，15，25，35，75 mg/kg diet RRR-α-tocopheryl acetate（E0、E5、E10、E15、E25、E35及E75組飼料）之實驗飼料，另一組則餵食102 mg/kg diet all-rac-α-tocopheryl acetate之實驗飼料（EA組飼料）8、10週及13.5週，於第 0、50∼56、64∼70天及第90∼94天起將各組大鼠鼠移至代謝籠，收集每天之 24 小時尿液，記錄各鼠每日攝水量與排尿量。最後，經禁食隔夜後於第94天犧牲。 結果顯示，8組鼠中，只有E0組之血漿Pyruvarte kinase活性顯著較其他各組較高(p＜0.05)，紅血球體外溶血率亦只有E0組顯著較高(p＜0.05)，於8週、10週及13.5週分別達91%、87%及95%。血漿α-tocopherol 濃度方面，E0、E5、E10 、E25、E35、E75為E15組之0.09、0.3、0.63、1.01、1.38、1.61及1.74倍。肝臟α-tocopherol含量方面，E0、E5、E10 、E25、E35、E75分別為E15組之0.09、0.34、0.68、1.21、1.78及3.31倍。副睪脂α-tocopherol 含量方面，E0、E5、E10、 E25、E35、E75分別為E15組之1.4、0.72、1.3、2.83(p＜0.05)、1.46及2.43倍。而EA組與E75皆無顯著差異(p＞0.05)。以上各指標除脂肪組織的α-tocophero外，在飲食維生素E含量0∼75mg/kg diet之範圍內反應皆靈敏，皆和飲食維生素E攝取量呈現高度正相關。尤以肝臟α-tocopherol之相關性最佳。 8組尿液α-CEHC排出量於0週並無顯著差異(p＞0.05)，皆很低。餵食實驗飼料8週後除E0組外均有上升，且隨飲食維生素 E 攝取量增加而顯著提升。於餵食13.5週後，Free α-CEHC方面，E0、E5、E10 、E25、E35、E75分別為E15組之1.14、0.88、 1.03、1.2、1.32及2.66倍(p＜0.05)。Conjugated α-CEHC方面，E0、E5、E10 、E25、E35、E75分別為E15組之0.17、0.42、0.67、1.78、3.78及9.95倍(p＜0.05)。Total α-CEHC方面， E0、E5、E10 E25、E35、E75為E15組之0.14、0.43、0.68、1.77、3.73及8.91倍。而EA組與E75組於13.5週後無顯著差異。血漿中α-CEHC 濃度亦隨飲食維生素 E 攝取量增加而顯著提升。Free α-CEHC方面，E0、E5、E10 、E25、E35、E75分別為E15組之0.17、0.27、0.82、0.86、1.26及1.53倍。Conjugated α-CEHC方面，E0、E5、E10 、E25、E35、E75分別為E15組之0.44、0.79、0.98、2.61、3.24及4.6倍。Total α-CEHC方面， E0、E5、E10 E25、E35、E75為E15組之0.35、0.61、0.93、2.01、2.57及3.55倍。而EA組與E75亦無顯著差異。 將α-CEHC、血漿及組織α-tocopherol含量與飲食維生素E攝入量進行相關性分析，以肝臟α-tocopherol含量與飲食維生素E攝入量相關係數最高(r =0.96, p＜0.0001)，其次是血漿conjugated α-CEHC(r = 0.9, p＜0.0001)及total α-CEHC(r = 0.88, p＜0.0001)，高於血漿α-tocopherol(r = 0.79, p＜0.0001)。尿中conjugated α-CEHC排出量與飲食維生素E攝取量之相關性(r = 0.78, p＜0.0001)與血漿α-tocopherol和飲食維生素攝取量之相關性接近。 總結，於飼料維生素E含量0∼15 mg/kg diet範圍中，血漿和肝臟α-tocopherol與飲食維生素E攝取量反應靈敏。尿液和血漿α-CEHC則於25∼75及0∼25 mg/kg diet之範圍中反應較佳。此外，在0∼75 mg/kg diet之範圍中，尿液α-CEHC與飲食維生素E攝取量之相關性，與血漿α-tocopherol相近，而血漿α-CEHC及肝臟α-tocopherol含量則與飲食維生素E攝取量相關性更高。血漿α-CEHC供為維生素E營養狀況之生化指標的潛力，值得進一步深究。

Abstract 2, 5, 7,8-tetramethyl-2-(2’-carboxyethyl)-6-hydroxychroman (α-CEHC) has been demonstrated to be the urinary metabolite of α-tocopherol. It has been reported that α-CEHC could be detected in the human urine while the plasma α-tocopherol concentration of the subject was higher than a threshold value (Shultz et al., 1995),implying that the urinary α-CEHC excretion might be related to the nutritional status of vitamin E. To characterizing the quantitative relationship between α-CEHC level and dietary α-tocopherol intake, rats were fed diets of which the vitamin E level ranged from 0 to 75 mg/kg diet. The response of α-CEHC in urine and plasma to increasing intake of vitamin E were compared to other biomarkers of vitamin E status. Forty-eight weanling Wistar rats were fed vitamin E-deficient diet for 1 week. They were then randomly assigned to eight groups and respectively fed diets containing 0 (E0), 5 (E5), 10 (E10), 15 (E15), 25 (E25), 35 (E35) or 75 (E75) mg/kg diet of RRR-α-tocopheryl acetate or 102mg/kg diet of all-rac-α-tocopheryl acetate(EA) for 13.5 weeks. Twenty-four hour urine was collected and daily water intake recorded on week 8, 10 and 13.5. After an overnight fasting, rats were sacrificed on day 94. Among the 8 groups, only E0 showed significantly higher plasma pyruvate kinase activity as well as the in vitro RBC hemolysis.(p < 0.05) The plasma α-tocopherol concentration of the E0,E5,E10, E25,E35 and E75 group were respectively 0.09, 0.3, 0.63,1.01, 1.38, 1.61and 1.74 fold that of the E15 group. The liver α-tocopherol content of the E0, E5, E10, E25, E35 and E75 group were 0.09, 0.34, 0.68, 1.21, 1.78 and 3.31 fold that of the E15 group. The EWAT α-tocopherol content of the E0,E5,E10, E25,E35 and E75 group were 1.14, 0.72, 1.3, 2.83, 1.46 and 2.43 fold that of the E15 group. The linear relationship between plasma α-tocopherol and dietary vitamin E level was sharper in the range of 0-15 mg/kg diet than in the range of 25-75 mg/kg diet. The correlation coefficient between α-tocopherol level and vitamin E intake in the range of 0 to 75 mg/kg diet was highest with the liver. The urinary α-CEHC excretion of the 8 groups were not significant different in week 0. After 8 weeks , the urinary α-CEHC excretion markedly increased with the increase of the dietary vitamin E level. The excretion (μg/day) of free α-CEHC of E0,E5,E10, E25,E35 and E75 group were 1.14, 0.88, 1.03, 1.2, 1.32 and 2.66 (p＜0.05)fold that of the E15 group, respectively. The excretion of conjugated α-CEHC of E0,E5,E10, E25,E35 and E75 group were 0.17, 0.42, 0.67,1.78, 3.78 and 9.95 fold that of E15 group, respectively. The excretion of total α-CEHC of E0,E5,E10, E25,E35 and E75 group were0.14, 0.43, 0.68, 1.77, 3.73 and 8.91 fold that of the E15 group, respectively. EA showed significant difference with E75 after 13.5 weeks. The plasma α-CEHC concentration also increased markedly with the increase of dietary vitamin E level. The plasma concentration (μM) of free α-CEHC of E0,E5,E10, E25,E35 and E75 group were 0.17, 0.27, 0.82, 0.86, 1.26 and 1.53 fold that of the E15 group, respectively. The concentration(μM) of conjugated α-CEHC of E0,E5,E10, E25,E35 and E75 group were 0.44, 0.79, 0.98, 2.61, 3.24 and 4.6 fold that of the E15 group, respectively. The concentration (μM) of total α-CEHC of E0,E5,E10, E25,E35 and E75 group were0.35, 0.61, 0.93, 2.01, 2.57 and 3.55 fold that of the E15 group, respectively. EA also showed no significant difference with E75. The correlation of various responder to dietary vitamin intake were found to be highest with the liver α-tocopherol content (r = 0.96, p＜0.000), and the plasma conjugated α-CEHC(r = 0.9, p＜0.000) and total α-CEHC(r = 0.88, p＜0.000) were next to it. In conclusion, the plasma and liverα--tocopherol responded more sharply to dietary vitamin E level in the range between 0-15 mg/kg diet of RRR-α-tocopheryl acetate while plasma and urinary α-CEHC responded more sharply to dietary vitamin E intake in the range between 0-25 and 25-75 mg/kg diet. The results implied the potential of using the plasma α-CEHC as an indicator of dietary vitamin E intake beyond the adequate level.