龍眼花水萃物之乙酸乙酯區分層對高果糖誘發大鼠代謝症候群之改善功效

Ethyl Acetate Fraction of Longan (Dimocarpus longan Lour.) Flower Water Extract Attenuates Metabolic Syndrome in Fructose-Fed Rats

黃潔妤(Chieh-Yu Huang)

指導教授 ： 孫璐西

共同指導教授 ： 吳亮宜

國立臺灣大學/生物資源暨農學院/食品科技研究所/碩士(2009年)

https://doi.org/10.6342/NTU.2009.01649

摘要

代謝症候群因與許多重大之慢性疾病(如:糖尿病及心血管疾病等) 間有密切相關性，為近年來日益受到重視之健康議題，其危險因子包含腹部肥胖、高血糖、血脂異常及高血壓等。本研究室於先前之研究已發現龍眼 (Dimocarpus longan Lour.) 花在體外試驗中具有很好的抗氧化活性，且在高果糖動物模式中證實龍眼花水萃物具有改善代謝症候群諸多症狀之功效。因此本研究之目的為評估龍眼花不同極性區分層對高果糖誘發代謝症候群之改善功效，以便日後尋找龍眼花中之有效成分。
本研究分為兩階段進行，第一階段為急性灌食試驗，用以觀察龍眼花水萃物及其區分層對大鼠葡萄糖耐受能力之影響。在此部分之試驗中，使用正常之Sprague-Dawley雄性大鼠，隨機分成五組，分別灌食龍眼花水萃物、乙酸乙酯區分層、正丁醇區分層、水區分層及去離子水後，進行口服葡萄糖耐受性試驗，觀察各組血糖變化情形。其結果顯示，乙酸乙酯區分層及水區分層皆具改善葡萄糖耐受能力的作用，因此同時選擇此二樣品進入第二階段之試驗。
第二階段則為長效期試驗，採高果糖飲食誘發大鼠代謝症候群之動物模式進行，用以觀察龍眼花水萃物及其區分層改善代謝症候群之功效。此部分試驗同樣選用Sprague-Dawley大鼠，並隨機分為五組：基礎值組 (B) 每日灌食去離子水並給予標準飼料；控制組 (C) 每日灌食去離子水並給予高果糖飼料；龍眼花水萃物組 (LFWE) 每日灌食龍眼花水萃物250 mg/ml/kgBW並給予高果糖飼料；龍眼花水萃物之乙酸乙酯區分層組 (EA) 每日灌食乙酸乙酯區分層36.3 mg/ml/kg BW並給予高果糖飼料；以及龍眼花水萃物之水區分層組 (W) 每日灌食水區分層147.5 mg/ml/kg BW並給予高果糖飼料。實驗期共16週。結果顯示，C組大鼠之禁食血漿葡萄糖、胰島素、三酸甘油酯、膽固醇濃度與血壓皆顯著上升，顯示長期餵飼高果糖飼料已顯著誘發出代謝症候群之症狀。
龍眼花水萃物於本實驗中，具有顯著改善腹部脂肪堆積、禁食血漿葡萄糖、胰島素、三酸甘油酯、總膽固醇濃度上升及高血壓等功效，有顯著改善胰島素阻抗之現象。而其效果可能來自於減少大鼠體內氧化壓力及提高IR、IRS-1、Akt、GLUT4等蛋白質之表現量。
在龍眼花水萃物之乙酸乙酯區分層部分，發現其與龍眼花水萃物具有許多相似之功效：顯著改善腹部脂肪堆積、禁食血漿葡萄糖、胰島素、三酸甘油酯濃度、高血壓及胰島素阻抗之現象。而在體內抗氧化壓力方面，也同樣具有改善血漿TBARS濃度，及增加肝臟抗氧化酵素Glutathione reductase之活性等功效，並且在胰島素訊息傳遞相關蛋白之表現量亦有上升的情形。
在龍眼花水萃物之水區分層部分，則具有顯著降低禁食血漿葡萄糖、總膽固醇濃度的作用，並同樣具有減少腹部脂肪堆積、降低肝中三酸甘油酯濃度等功效；但對胰島素阻抗與高三酸甘油酯血症並無顯著改善的功效。
綜合以上結果，乙酸乙酯區分層在改善代謝症候群之諸多症狀上皆類似於龍眼花水萃物，因此推測龍眼花水萃物中改善代謝症候群之有效成分應存在於乙酸乙酯區分層當中。

關鍵字

龍眼花 ； 代謝症候群 ； 乙酸乙酯區分層 ； 胰島素阻抗

並列摘要

Metabolic syndrome becomes an important issue recently. It has strong correlation with several chronic disease, for instance, diabetes and cardiovascular disease. The risk factors of metabolic syndrome contain abdominal obesity, hyperglycemia, dyslipidemia and hypertension. Previous study in our laboratory has shown that Longan (Dimocarpus Longan Lour.) flower had strong antioxidant activity in vitro. Furthermore, we also have demonstrated that Longan flower water extract (LFWE) can improve the symptoms of the metabolic syndrome in animal model. Therefore, the purpose of this study was to investigate the effect of each fraction of Longan flower water extract on metabolic syndrome. We expect to find effective compound in Longan flower in the future.
The study was carried out into two parts. The first part was an acute study to examine the effects of LFWE and its fractions on glucose tolerance in rats. Male Sprague-Dawley rats were randomly divided into five groups, administered LFWE, ethyl acetate fraction, n-butanol fraction, water fraction and ddH2O by gavage respectly. Results of oral glucose tolerance test (OGTT) in rats showed that both EA and W fraction can improve glucose tolerance. Therefore, we choose these two fractions to do the following study.
The following study was to investigate the effect of long-term treatment of EA and W fraction on rats with metabolic syndrome induced by high fructose diet. Male Sprague-Dawley rats were randomly divided into five groups: group B, fed with standard Purina chow; group C, fed with high fructose diet ; group LFWE, fed with high fructose diet plus LFWE 250 mg/ml/kg BW per day by gavage ; group EA, fed with high fructose diet plus EA 36.3 mg/ml/kg BW per day by gavage ; group W, fed with high fructose diet plus W 147.5 mg/ml/kg BW per day by gavage. The dietary manipulation lasted for 16 weeks. Results of this study showed that, high fructose feeding cause significant increase in abdominal fat mass, fasting plasma glucose, insulin, triglyceride, cholesterol levels and systolic blood pressure. These results indicated that fructose-rich diet could cause a cluster of disorders in metabolic syndrome.
Treatment with LFWE significantly improved abdominal fat accumulation, hypertriglyceridemia, hyperinsulinemia, hyperglycemia, hypercholesterolemia, hypertension and insulin resistance. To further evaluated the possible mechanism of LFWE, we found that the rats showed decreased oxidative stress and increased expression of insulin signaling pathway related protein, including insulin receptor (IR), insulin receptor substrate-1 (IRS-1), Akt and glucose transporter Ⅳ(GLUT4).
The supplement of EA fraction showed many similar efficacies as LFWE on abdominal fat, fasting glucose, insulin, triacylglyceride, hypertension and insulin resistance. EA fraction also showed the ability to decrease plasma TBARS and enhance glutathione reductase activity in fructose-fed rats. And the expressions of insulin signaling pathway related protein were also enhanced.
W fraction significantly decreased fasting glucose, total cholesterol, abdominal fat and liver triacylglycerol accumulation. But it shown no effects on insulin resistance and hypertriglyceridemia induced by high fructose diet instead. According to these finding, we suggested the effective components for ameliorating metabolic syndrome should be in the ethyl acetate fraction.

並列關鍵字

Longan flower ； metabolic syndrome ； ethyl acetate fraction ； insulin resistance

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