探討味噌及烏龍茶藉由調節脂質代謝及腸道菌相抑制高脂飲食誘導肥胖大鼠之作用機制

Abstract

根據世界衛生組織統計，全球肥胖人口持續增加，同時肥胖為罹患第二型糖尿病、非酒精性脂肪肝等疾病的危險因子，嚴重危害人體健康。文獻指出多酚類化合物 (Polyphenols) 具有抗肥胖功效，若能從日常飲食攝取這些機能性物質，透過影響體內代謝機制與腸道菌相，將有助於減緩肥胖與其相關代謝疾病。本次實驗所使用之樣品：烏龍茶和味噌分別富含茶多酚 (Tea polyphenols) 與大豆異黃酮 (Isoflavones)，兩者皆透過發酵製程使其生物活性與生物可利用率改變。本實驗以高脂飲食 (HFD) 誘導Sprague Dawley (SD) 大鼠肥胖模式，探討烏龍茶與味噌的抗肥胖功效與調節腸道菌之功能。從動物實驗結果顯示，在HFD中添加0.5% 烏龍茶萃取粉末 (Oolong tea extract, OTE) 可以抑制大鼠白色脂肪組織中脂質合成 (Lipogenesis) 相關蛋白SREBP1、FASN的表現量，並提高白色脂肪之PGC1α、UCP1蛋白表現量，增加產熱作用 (Thermogenesis)。兩者作用之下，使OTE具有減少大鼠內臟脂肪重量之功效。此外腸道菌相方面，發現OTE可以增加大鼠腸道中的Akkermansia菌屬，以及Lachnospiraceae菌科之下的丁酸生產菌，如：Lachnospiraceae_NK4A136_group和Roseburia，而根據文獻指出，丁酸具有改善腸道上皮屏障，減緩發炎與增加能量代謝的功能。綜合以上，OTE可透過調節脂質代謝、合成作用以及腸道菌相，達到抗肥胖之效果。味噌的實驗結果顯示，HFD添加1% 和2% 味噌對於降低大鼠體重和內臟脂肪重量並無顯著影響，但可以透過活化大鼠肝臟中AMPK路徑，增加PGC1α、CPT1α蛋白表現量，進而提高肝臟的脂肪酸氧化作用，減緩HFD誘導之肝臟脂質蓄積，然而味噌添加比例增加至5%時，其改善肝臟脂質蓄積的效果並不如低濃度顯著。此外，味噌亦可大幅增加益生菌Akkermansia比例，根據文獻指出Akkermansia除了可以改善腸道通透性外，也能調節腸道內分泌，進而增加肝臟的能量代謝。綜合以上結果，味噌可以促進肝臟脂質氧化作用和調節腸道菌相，具有減緩HFD造成之肝臟脂質蓄積之功效，其中又以2% 味噌的效果最為顯著。總結研究結果，烏龍茶與味噌在高脂飲食誘導大鼠肥胖模式中，分別對於降低內臟脂肪和減緩肝臟脂質蓄積有顯著的效果，其機制可能為透過調節大鼠腸道菌相，以及影響脂質代謝分子路徑，而達到抗肥胖與其相關代謝症候群之功效。

According to WHO, obesity has high prevalence in the last few decades. Due to association with many metabolic disorders, such as type-2-diabetes and nonalcoholic fatty liver, obesity become a serious health problem. Many natural compounds like polyphenols and isoflavones have anti-obesity effects. Therefore, the way to intake those functional compounds through daily food is quite important. Oolong tea is rich in polyphenols, and miso is rich in isoflavones. Both of them have different biological activity or better bioavailability through fermenting processing. In this study, we investigated the anti-obesity effects of oolong tea and miso by high-fed diet (HFD)-induced obesity Sprague Dawley (SD) rat model. The results showed that oolong tea extract (OTE) can reduce the weight of white adipose tissue by inhibiting lipogenesis related proteins SREBP1 and FASN expression. Besides, OTE increased PGC1α and UCP1 protein expression which can promote thermogenesis in white adipose tissue. OTE also modulated gut microbiota by increasing Akkermansia, and butyrate-producing bacteria Lachnospiraceae, such as Lachnospiraceae_NK4A136_group and Roseburia. According to previous reports, butyrate has benefits to improve intestinal barrier and promote metabolism. Base on the above results, OTE can modulate lipid metabolism and gut microbiota to improve HFD-induced obesity. Although, miso feed with HFD groups showed no difference in body weight and white adipose tissue weight. We found 1% and 2% miso can decrease in HFD-induced triglycerides accumulation in liver through induced liver fatty acid oxidation by activating AMPK pathway and increasing PGC1α and CPT1α protein expression, but 5% miso didn’t show better effects in hepatic triglycerides accumulation compare with low percentage of miso. About gut microbiota, miso increased Akkermansia largely. Akkermansia is not only famous of improving gut barrier, and also can influence enteroendocrine to increase liver energy metabolism. To sum up, miso could improve HFD-induced fatty liver by activating fatty acid oxidation and modulating gut microbiota. In conclusion, oolong tea reduced body fat, and miso decreased hepatic triglycerides accumulation both in HFD-induced obesity rat model. The mechanism of these effects may be through modulating gut microbiota and affecting lipid metabolize.