Antimitogenic effect of green tea (-)-epigallocatechin gallate on 3T3-L1 preadipocytes depends on the ERK and Cdk2 pathways.
Green tea catechins, especially (-)-epigallocatechin gallate (EGCG), have been proposed as a chemopreventative for obesity, diabetes, cancer, and cardiovascular diseases. However, relatively little is known about the mechanism of the action of EGCG on fat cell function. This study was designed to investigate the pathways of EGCG's modulation of the mitogenesis of 3T3-L1 preadipocytes. Preadipocyte proliferation as indicated by an increased number of cells and greater incorporation of bromodeoxyuridine (BrdU) was inhibited by EGCG in dose-, time-, and growth phase-dependent manners. Also, EGCG dose and time dependently decreased levels of phospho-ERK1/2, Cdk2, and cyclin D(1) proteins, reduced Cdk2 activity, and increased levels of G(0)/G(1) growth arrest, p21(waf/cip), and p27(kip1), but not p18(ink), proteins and their associations to Cdk2. However, neither MEK1, ERK1/2, p38 MAPK, phospho-p38, JNK, nor phospho-JNK was changed. Increased phospho-ERK1/2 content and Cdk2 activity, respectively, via the transfection of MEK1 and Cdk2 cDNA into preadipocytes prevented EGCG from reducing cell numbers. These data demonstrate the ERK- and Cdk2-dependent antimitogenic effects of EGCG. Moreover, EGCG was more effective than epicatechin, epicatechin gallate, and epigallocatechin in changing the mitogenic signals. The signal of EGCG in reducing growth of 3T3-L1 preadipocytes differed from that of 3T3 fibroblasts. Results of this study may relate to the mechanism by which EGCG modulates body weight.
Hung
Pei-Fang
PF
Dept. of Life Science, College of Science, National Central Univ., Chung-Li City, Taoyuan, Taiwan.
Wu
Bo-Tsung
BT
Chen
Hui-Chian
HC
Chen
Yen-Hang
YH
Chen
Chia-Lin
CL
Wu
Ming-Hua
MH
Liu
Hsien-Chun
HC
Lee
Meng-Jung
MJ
Kao
Yung-Hsi
YH
D041721:3T3-L1 Cells; D017667:Adipocytes / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D042846:CDC2-CDC28 Kinases / Q000378:metabolism*; D002392:Catechin / Q000031:analogs & derivatives* / Q000494:pharmacology*; D002453:Cell Cycle / Q000187:drug effects / Q000502:physiology; D018797:Cell Cycle Proteins / Q000378:metabolism; D049109:Cell Proliferation / Q000187:drug effects*; D019938:Cyclin D1 / Q000378:metabolism; D051357:Cyclin-Dependent Kinase 2; D050763:Cyclin-Dependent Kinase Inhibitor p18; D050759:Cyclin-Dependent Kinase Inhibitor p21; D050760:Cyclin-Dependent Kinase Inhibitor p27; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D016758:Genes, jun / Q000502:physiology; D051379:Mice; D010766:Phosphorylation / Q000187:drug effects; D013662:Tea; D025521:Tumor Suppressor Proteins / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
C493957:Cdkn1a protein, mouse; C493961:Cdkn1b protein, mouse; C493972:Cdkn2c protein, mouse; D018797:Cell Cycle Proteins; D050763:Cyclin-Dependent Kinase Inhibitor p18; D050759:Cyclin-Dependent Kinase Inhibitor p21; D013662:Tea; D025521:Tumor Suppressor Proteins; D019938:Cyclin D1; D050760:Cyclin-Dependent Kinase Inhibitor p27; D002392:Catechin; C045651:epigallocatechin gallate; D042846:CDC2-CDC28 Kinases; C495893:Cdk2 protein, mouse; D051357:Cyclin-Dependent Kinase 2; D048049:Extracellular Signal-Regulated MAP Kinases; D048051:p38 Mitogen-Activated Protein Kinases