Department of Chemistry, Tsinghua University and Key Laboratory of Biological Organic Phosphorus and Chemical Biology, Ministry of Education, Beijing 100084, China.
Hunan Provincial Key Laboratory of Crop Germplasm Innovation and Utilization and Key Laboratory of Tea Science, Ministry of Education, Hunan Agricultural University, Changsha, Hunan 410128, China.
Proteome Sci. 2013 Jul 18;11(1):32. doi: 10.1186/1477-5956-11-32.
(-)-Epigallocatechin-3-gallate (EGCG), the most abundant catechin found in green tea, effectively reduces body weight and tissue and blood lipid accumulation. To explore the mechanism by which EGCG inhibits cellular lipid accumulation in free fatty acid (FFA) induced HepG2 cell culture, we investigated the proteome change of FFA-induced HepG2 cells exposed to EGCG using two-dimensional gel electrophoresis and mass spectrometry.
In this study, 36 protein spots showed a significant change in intensity by more than 1.5-fold from the control group to the FFA group and from the FFA group to the FFA + EGCG group. Among them, 24 spots were excised from gels and identified by LC-MS/MS. In total, 18 proteins were successfully identified. All identified proteins were involved in lipid metabolism, glycometabolism, antioxidant defense, respiration, cytoskeleton organization, signal transduction, DNA repair, mRNA processing, iron storage, or were chaperone proteins. This indicated that these physiological processes may play roles in the mechanism of inhibition of lipid accumulation by EGCG in FFA-induced HepG2 cells. Western blotting analysis was used to verify the expression levels of differentially expressed proteins, which agree with the proteomic results.
From the proteomic analysis, we hypothesized that EGCG reduced cellular lipid accumulation in FFA-induced HepG2 cells through the activation of AMP-activated protein kinase (AMPK) resulting from the generation of reactive oxygen species (ROS). The induction of ROS may be a result of EGCG regulation of the antioxidant defense system. Activation of AMPK shifted some FFA toward oxidation, away from lipid and triglyceride storage, and suppressed hepatic gluconeogenesis. The findings of this study improve our understanding of the molecular mechanisms of inhibition of lipid accumulation by EGCG in HepG2 cells.
（-）-表没食子儿茶素没食子酸酯（EGCG）是绿茶中含量最丰富的儿茶素，能有效降低体重和组织及血液脂质堆积。为了探讨 EGCG 抑制游离脂肪酸（FFA）诱导的 HepG2 细胞培养中细胞脂质积累的机制，我们使用二维凝胶电泳和质谱法研究了 EGCG 处理 FFA 诱导的 HepG2 细胞的蛋白质组变化。
在这项研究中，有 36 个蛋白点的强度与对照组相比，FFA 组和 FFA+EGCG 组分别增加了 1.5 倍以上。其中，从凝胶中切取 24 个斑点并用 LC-MS/MS 进行鉴定。共成功鉴定出 18 种蛋白质。所有鉴定出的蛋白质均参与脂质代谢、糖代谢、抗氧化防御、呼吸、细胞骨架组织、信号转导、DNA 修复、mRNA 加工、铁储存或作为伴侣蛋白。这表明这些生理过程可能在 EGCG 抑制 FFA 诱导的 HepG2 细胞中脂质积累的机制中发挥作用。Western 印迹分析用于验证差异表达蛋白的表达水平，与蛋白质组学结果一致。
从蛋白质组学分析中，我们假设 EGCG 通过生成活性氧（ROS）激活 AMP 激活的蛋白激酶（AMPK），从而减少 FFA 诱导的 HepG2 细胞中的细胞脂质积累。ROS 的诱导可能是 EGCG 调节抗氧化防御系统的结果。AMPK 的激活使一些 FFA 向氧化方向转化，远离脂质和甘油三酯储存，并抑制肝糖异生。本研究的结果提高了我们对 EGCG 抑制 HepG2 细胞中脂质积累的分子机制的理解。
