㆗文摘要 肥胖為世界㆖常見的健康問題，與糖尿病、高血壓和心血管疾病等慢性疾病有密不可分的關係。近年來有報導指出含有唲茶素的綠茶萃取物對於老鼠體重㆘降和㆟類能量攝取、脂肪酸的氧化有調節的作用，但是其㆗真正的機制仍然不清楚。我們使用鼠類3T3-L1前脂肪細胞作為研究素材，透過細胞學以及生化學的角度，來證實綠茶對脂肪細胞生長與死亡的影響，並且進㆒步探討其調控的真正機制為何。我們實驗㆗發現綠茶唲茶素可以降低3T3-L1前脂肪細胞的細胞數目。並根據劑量與細胞生長時期的不同有不同的效果，以EGCG來說其IC50約為20 µM。EGCG降低3T3-L1前脂肪細胞的細胞數目可能導致於細胞生長停滯或誘發細胞凋亡，因為我們發現細胞週期㆗G2/M時期的增加以及Sub-G1時期的出現，並且有DNA梯度的形成。細胞生長停滯可能經由影響MAPK酵素，因為我們發現其抑制劑PD 098059和EGCG有共同的作用而抑制百分之五十到六十的細胞數目；誘發細胞凋亡可能經由caspase-3酵素的途徑，因為我們發現EGCG會增加caspase-3酵素的活性，並且會受到caspase-3酵素的抑制劑所阻斷。因此，我們的結論是EGCG誘導3T3-L1前脂肪細胞的生長抑制和死亡，可能與綠茶減重的機制有關。 Abstract Obesity is considered as a common disease in the world and it is associated with the risks of diabetes, hypertension, and heart disease. Recent studies have shown that the body weight loss in rats and fatty acid energy expenditure in human are regulated by EGCG-containing green tea, but the exact mechanism of its action is still unclear. We here used a murine preadipose cell line 3T3-L1 to examine the mechanism at cellular and biochemical levels in the green tea regulation of fat cell growth. We found that green tea polyphenols reduced the cell number of 3T3-L1 preadipocytes. The IC50 for EGCG is about 20 µM, depending on the EGCG dosage and the developing status of the cells. EGCG-reduced cell number of 3T3-L1 preadipocytes may be due to the induction of growth arrest and apoptosis because this catechin increased the percentage of G2/M and sub-G1 phases of the cell cycle and caused the formation of DNA ladder. The growth arrest effect of EGCG may be associated with MAPK activity since a combination of EGCG and PD 098059 reduced the cell number of 3T3-L1 cells by 50-65 ﹪greater than that of PD 098059 alone. The apoptotic effect of EGCG could be caspase-3-dependent because EGCG increased caspase-3 activity and the effect of EGCG was blocked by caspase-3 inhibitor. There, we conclude that EGCG-induced growth in inhibition and apoptosis of 3T3-L1 preadipocytes may be related to the mechanism by which green tea reduces the body weight.
