肥胖已成為全球重要的健康議題，且與脂肪細胞數量增加及脂肪細胞內脂質累積密切相關。肥胖的發生與脂肪細胞功能受到細胞自噬及綠茶主要兒茶素成分表沒食子兒茶素沒食子酸酯(EGCG)的調控。本論文旨在比較 EGCG 對前脂肪細胞與成熟脂肪細胞自噬作用的影響差異。以 3T3-L1 及 C3H10T1/2 白色脂肪細胞作為實驗模型，研究結果發現EGCG 能降低前脂肪細胞及成熟脂肪細胞的細胞數量。此外，EGCG 可抑制脂肪細胞脂質累積，並以總三酸甘油酯（triglyceride）含量下降作為證據。進一步利用西方點墨法分析顯示，EGCG 會改變 3T3-L1 及 C3H10T1/2 前脂肪細胞與成熟脂肪細胞中自噬相關蛋白（autophagy-related proteins， ATGs）的表現量。在 3T3-L1 前脂肪細胞中，高濃度EGCG 傾向於降低 ATG-3 ATG-5 及 ATG7 蛋白表現，而對 pAMPK Beclin-1 VTI1A及 LC3β 蛋白則無顯著影響。在成熟脂肪細胞中，EGCG 可降低 ATG-3 ATG-5 ATG7及 LC3β 蛋白表現量，對 Beclin-1 無顯著影響，並傾向提高 pAMPK 及 VTI1A 蛋白表現。於 C3H10T1/2 前脂肪細胞及成熟脂肪細胞中，也觀察到 EGCG 對 ATG 蛋白具有類似的影響。綜合上述結果顯示，EGCG 可能透過調控 ATG 訊號傳遞途徑來影響脂肪細胞的生長，而其對細胞自噬過程的調控作用會隨脂肪細胞發育階段的不同而有所差異。本研究結果亦有助於闡明含有 EGCG 之綠茶發揮抗肥胖作用的分子機制，特別是在調控脂肪細胞相關肥胖形成方面的作用。;Obesity has become a major global health issue， and it is associated with fat cell number and adipocyte lipid accumulation. Development of obesity and fat cell functions can be regulated by autophagy and green tea epigallocatechin gallate (EGCG). The objective of the present thesis was designed to compare the effects of EGCG on autophagy between preadipocytes and adipocytes. Using 3T3-L1 and C3H10T1/2 white fat cells， EGCG was found to reduce the number of preadipocytes and adipocytes. Also， EGCG inhibited adipocyte lipid accumulation， as evidenced by decreased total triglyceride accumulation. Further Western blot analysis indicated that EGCG altered the levels of autophagy-related proteins (ATGs) in 3T3-L1 and C3H10T1/2 preadipocytes and adipocytes. In 3T3-L1 preadipocytes， high concentrations of EGCG tended to reduce ATG-3， ATG-5， and ATG7 protein levels and had no significant effects on pAMPK， Beclin-1， VTI1A， and LC3β proteins. In adipocytes， EGCG reduced levels of ATG-3， ATG-5， ATG7 and LC3β proteins， had no significant effects on Beclin-1， and tended to increase pAMPK and VTI1A proteins. Similar effects of EGCG on ATG proteins on C3H10T1/2 preadipocytes and adipocytes were observed. These results suggest that EGCG may regulate the growth of fat cells through modulations of ATG signaling pathways and such a regulation of the autophagy process may vary with developmental stages of fat cells. Results of this study may also help the mechanisms by which the EGCG-containing green tea exerts its effects on fat cell-associated obesity.
