綠茶唲茶素對於前脂肪細胞分化的影響

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题名:	綠茶唲茶素對於前脂肪細胞分化的影響
作者:	張欣蕙;Shin-Huei Chang
贡献者:	生命科學研究所
关键词:	唲茶素;脂肪細胞;分化;catechin;adipocyte;differentiation
日期:	2003-07-08
上传时间:	2009-09-22 10:17:25 (UTC+8)
出版者:	國立中央大學圖書館
摘要:	脂質的積聚反映出前脂肪細胞分化為脂肪細胞，這過程受許多基因、賀爾蒙(例如胰島素)以及營養因子(如維他命)所調節。本篇論文針對綠茶唲茶素(曾被視為維他命P)對分化中脂肪細胞的影響及作用機制加以探討。我們發現綠茶中的EGCG 在前脂肪細胞分化前期對於降低胰島素- MIX (1-methyl-3-isobutylxanthine)-DEX (dexamethasone)誘發的前脂肪細胞數目比其他結構相近的綠茶唲茶素如EGC、ECG、EC 效果明顯，且其抑制作用具有劑量效應和時間效應。此外，EGCG 改變C/EBPβ、C/EBPα、PPARγ等能有效刺激前脂肪細胞脂肪合成(adipogenesis)的分化相關轉錄因子之蛋白表現，也減少細胞內和培養液中的三酸甘油酯總量。進一步研究發現，單獨給予MIX 刺激造成PPARγ蛋白量顯著的增加，但此結果在綠茶唲茶素中受 EGCG 專一地以劑量相關作用抑制。H-89，一種蛋白激酶A(protein kinase A) 的抑制劑，並不能阻斷EGCG 抑制MIX 刺激的PPARγ表現，此結果支持EGCG 的作用並非經由蛋白激酶A 相關途徑(protein kinase A-associated pathway)。由以上的結果，我們得到的結論為，EGCG 可能經由控制脂肪生成相關的轉錄因子來調節前脂肪細胞的分化。 Lipid accumulation reflects the process of preadipocytes differentiating into adipocytes and such process is regulated by genetic, hormonal (i.e., insulin) and nutritional cues (i.e., vitamins). In this study, we examined the effect of green tea catechins, having been considered as vitamin P, on differentiation of 3T3-L1 preadipocytes and investigated how they work. We found that green tea EGCG was more effective than structurally-related EC, EGC or ECG to reduce insulin-dexamethasone-1-methyl-3-isobutylxanthine (IDM)-induced increases in cell number of preadipocytes during their initial differentiation to adipocytes. The EGCG effect varied with dose administration and with time course. However, EGCG altered the protein amount of C/EBPβ, C/EBPα, or PPARγ transcriptional factors, which were enabling to stimulate adipogenesis of preadipocytes, as well as reduced total triglyceride accumulation in the cells and medium. Further study showed that treatment of preadipocytes with MIX alone, but neither insulin nor dexamethasone, caused a significant increase in the protein amount of PPARγ and such stimulation was decreased by EGCG in the manner of dose dependency or catechin specificity. H-89, a selective protein kinase A inhibitor, could not block the EGCG inhibition of MIX-stimulated PPARγ, suggesting that EGCG effect is independent of protein kinase A-associated pathway. We conclude that green tea EGCG may modulate differentiation of preadipocytes to adipocytes through altering adipogenesis-controlling transcriptional factors.
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