過氧小體增殖活化受體(peroxisome proliferator-activated receptors；PPARs) 包括三種不同的細胞核荷爾蒙受體，主要的弁酮O參與調節脂質的平衡、脂蛋白的代謝及葡萄糖的衡定等。PPARs和發炎反應的控制機制具有相關連性，且與動脈粥狀硬化早期形成之機轉有關。
本研究之目的是構築含有GAL4 DNA結合區域(DNA binding domain；DBD) 及PPARs配位體結合區域(ligand binding domain；LBD) 的chimeric 表現載體，以建立PPARs 促效劑(agonist)的篩選平台。
本論文首先利用RT-PCR選殖構築了pSV-GAL4-PPAR及pSV-GAL4-PPAR兩個載體。接著將構築好的載體、pFR-Luc報告載體及pSV--galactosidase對照載體三者共同轉染到CHO-K1細胞，並以已知的PPAR及PPAR促效劑，利用luciferase活性及-galactosidase活性的比值，確認 PPARs促效劑的篩選平台的建立。
接著利用此系統探討三萜類及類黃酮是否具活化PPARs的活性。結果顯示，oleanolic acid及hederagenin具有顯著活化PPAR的效果，EC50分別為21.83 ± 1.38 M及6.09 ± 0.77 M，而18-glycyrrhetinic acid methylester也具有較弱的活化PPAR的效果，綜合以上可以證實oleanolic acid、hederagenin及18-glycyrrhetinic acid methylester可為PPAR促效劑。另外，結果顯示luteolin-7-glucoside 具有顯著活化PPAR的效果，其EC50為38.20 ± 2.04M，可以推論luteolin-7-glucoside為PPAR的促效劑。 In mammals, the peroxisome proliferator-activated receptor (PPAR) family of nuclear hormone receptors consists of three subtypes encoded by separate genes: PPAR? PPARβ (δ) and PPARγ. PPARs regulate lipid homeostasis, lipoprotein metabolism and glucose homeostasis.
The aim of this study is to identify potential natural PPAR ligands using transactivation system. Two chimeric plasmids, pSV-GAL4-PPARandpSV-GAL4-PPARwhichcontain GAL4 DNA binding domain (DBD) and PPARs ligand binding domain (LBD) were constructed via RT-PCR. Three plasmids, pSV-GAL4-PPARs, pFR-Luc trans-reporter plasmid and pSV--galactosidase control plasmid, were co-transfected into CHO-K1 cells. The commercial PPARs agonists were employed and the activities of luciferase and -galactosidase were analyzed for the validity of the cell-based transactivation system.
Using the system, we found that oleanolic acid and hederagenin were potent PPARagonists with EC50 21.83 ± 1.38 M and 6.09 ± 0.77 M, respectively. Another triterpenoids, 18--glycyrrhetinic acid methylester, was a weak PPAR agonist. On the other hand, luteolin-7-glucoside was a PPAR agonist.
