title: Proteomic analysis of the inhibitory effect of epigallocatechin gallate on lipid accumulation in human HepG2 cells.
abstract: BACKGROUND
  (-)-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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: 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.|National Research Center of Engineering & Technology for Utilization of Botanical Functional Ingredients, Changsha, Hunan 410128, China.
authors.forename: Zhonghua
authors.initials: Z
authors.lastname: Liu
authors.affiliation: 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.|National Research Center of Engineering & Technology for Utilization of Botanical Functional Ingredients, Changsha, Hunan 410128, China.
authors.forename: Qin
authors.initials: Q
authors.lastname: Li
authors.affiliation: 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.
authors.forename: Jianan
authors.initials: J
authors.lastname: Huang
authors.affiliation: Department of Chemistry, Tsinghua University and Key Laboratory of Biological Organic Phosphorus and Chemical Biology, Ministry of Education, Beijing 100084, China.
authors.forename: Qionglin
authors.initials: Q
authors.lastname: Liang
authors.affiliation: National Research Center of Engineering & Technology for Utilization of Botanical Functional Ingredients, Changsha, Hunan 410128, China.
authors.forename: Yujun
authors.initials: Y
authors.lastname: Yan
authors.affiliation: National Research Center of Engineering & Technology for Utilization of Botanical Functional Ingredients, Changsha, Hunan 410128, China.
authors.forename: Haiyan
authors.initials: H
authors.lastname: Lin
authors.affiliation: National Research Center of Engineering & Technology for Utilization of Botanical Functional Ingredients, Changsha, Hunan 410128, China.
authors.forename: Wenjun
authors.initials: W
authors.lastname: Xiao
authors.affiliation: National Research Center of Engineering & Technology for Utilization of Botanical Functional Ingredients, Changsha, Hunan 410128, China.
authors.forename: Yong
authors.initials: Y
authors.lastname: Lin
authors.affiliation: National Research Center of Engineering & Technology for Utilization of Botanical Functional Ingredients, Changsha, Hunan 410128, China.
authors.forename: Sheng
authors.initials: S
authors.lastname: Zhang
authors.affiliation: National Research Center of Engineering & Technology for Utilization of Botanical Functional Ingredients, Changsha, Hunan 410128, China.
authors.forename: Bin
authors.initials: B
authors.lastname: Tan
authors.affiliation: Department of Chemistry, Tsinghua University and Key Laboratory of Biological Organic Phosphorus and Chemical Biology, Ministry of Education, Beijing 100084, China.
authors.forename: Guoan
authors.initials: G
authors.lastname: Luo