高脂肪飲食小鼠模式Pioglitazone對肝臟庫佛氏細胞脂解作用的調控

The Regulation of Lipolysis in Kupffer Cells by Pioglitazone in a High-Fat Diet Mice Model

李佳蓁(Chia-Chen Lee)

指導教授 ： 辛錫璋 教授

高雄醫學大學/醫學院/醫學遺傳學研究所/碩士(2010年)

https://doi.org/10.6832/KMU.2010.00043

摘要

脂肪肝是由於大量三酸甘油酯堆積於肝臟細胞所造成的脂肪變性，隨症狀加重會導致肝硬化發生。而肝硬化為WHO於西元2004年所公佈全球前二十大死因之一。目前所知造成脂肪肝的因素很多，包括飲酒、肥胖、脂肪代謝障礙等。在人體研究報告指出pioglitazone (PPARgamma agonist)用來治療第2型糖尿病，也可改善肝臟脂肪變性。然而pioglitazone如何調控肝臟脂解作用來改善脂肪變性，其機轉仍未清楚。庫佛氏細胞(Kupffer cells)為肝臟內特異性巨噬細胞，可將外來物質吞噬送入細胞內溶小體(lysosome)後進行消化分解。而在溶小體中約含有四十多種的酵素，lysosomal-acid lipase(LAL)為其中一種存在於溶小體內參與脂解作用的酵素。Pioglitazone是為一種PPARgamma agonist，而PPARgamma 的活化促進巨噬細胞對脂肪代謝等生理作用的進行。
本實驗利用高脂肪飲食的小鼠模式，分成對照組、高脂肪飲食組及高脂肪飲食併pioglitazone藥物組，在研究中我們檢測血清生化值，並進行即時螢光定量聚合酶連鎖反應(real-time PCR)、西方點墨法(western blotting)及肝臟組織切片染色等實驗，觀察蛋白質與基因表現。結果顯示本實驗中三組小鼠的體重及肝臟重量無顯著變化。在高脂肪飲食組與對照組相比可發現血清中游離脂肪酸及三酸甘油酯的含量是較為增加的，而這些由脂肪新陳代謝而來的產物會被肝臟再吸收可合成肝臟內三酸甘油酯，被儲存或作為能量利用。另外，在高脂肪飲食組的肝臟組織染色可見有白色脂肪空泡的出現，同時可偵測到庫佛氏細胞的增生指數上升與LAL的表現趨勢一致。給予pioglitazone後，肝臟內三酸甘油酯的量減少，血清中高密度脂蛋白膽固醇的含量增加。由組織免疫染色也可觀察到LAL在藥物給予下在庫佛氏細胞相對位置的表現量增強，同時肝臟組織型態改善，白色空泡減少。因此我們推論pioglitazone可能與庫佛氏細胞中LAL的活化有關，進而調控肝臟內的脂解作用，改善肝臟內脂肪變性並減緩脂肪肝的進展。

關鍵字

吡格列酮 ； 脂解作用 ； 庫佛氏細胞 ； 溶小體酸脂解酶

並列摘要

Fatty liver is due to excess triglyceride accumulations in hepatocyte resulting in hepatic steatosis. It will lead to liver cirrhosis which is one of the world's top 20 leading causes of death in 2004 (WHO). As we know that fatty liver is caused by numerous factors including alcohol, obesity, impaired fat metabolism and other reasons. According to humans studies that pioglitazone which is used for Type 2 diabetes treatment can also improve hepatic steatosis. However, the mechanism is still unclear. The Kupffer cell is the specific macrophage in the liver which can swallow foreign substances into the lysosome and digests them via phagocytosis. There are about forty types of enzymes in the lysosome. Lysosomal-acid lipase (LAL) is one kind of enzymes in the lysosome relating to lipolysis. Pioglitazone is a PPARgamma agonist. The activation of PPARgamma can stimulate macrophages to promote the fat metabolism. Therefore we hypothesize that pioglitazone might be related to the activation of LAL in Kupffer cells to regulate lipolysis in the liver and to prevent the fatty liver progression.
We used the high-fat diet mice model. Mice were divided into three groups: the chow diet group, the high-fat diet group, and the high-fat diet with pioglitazone group. The serum biochemistry, the real-time PCR, the western blotting, and the liver section staining had been done in this study. The results showed that the mice body weight and the mice liver weight had no significant difference among the three groups of mice. The biochemistry data revealed that serum NEFA and triglycerides levels were higher in the high-fat diet group compared with that in the chow diet group. These products of lipid metabolism might reverse to liver for hepatic triglycerides synthesis, storage, or energy consumption. In high-fat diet group, we found that lipid vacuoles appeared in hepatic tissue. At the same time we also noted that the macrophage hyperplasia index is consistent with the increased expression of LAL. After pioglitazone treatment, the hepatic triglycerides decreased; plasma cholesterol and HDL-C significantly increased. From IHC staining, we observe the expression of LAL in Kupffer cells which might be activated by pioglitazone, and the hepatic tissue morphology improved, there is no obvious fat vacuoles exist. Thus we deduce pioglitazone possibly regulate the lipolysis in the liver via activating LAL in the Kupffer cell to improve hepatic steatosis and to slow down the fatty liver progression.

並列關鍵字

pioglitazone ； lipolysis ； Kupffer cells ； lysosomal acid lipase

參考文獻

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