Green tea (-)-epigallocatechin gallate suppresses IGF-I and IGF-II stimulation of 3T3-L1 adipocyte glucose uptake via the glucose transporter 4, but not glucose transporter 1 pathway.
This study investigated the pathways involved in EGCG modulation of insulin-like growth factor (IGF)-stimulated glucose uptake in 3T3-L1 adipocytes. EGCG inhibited IGF-I and IGF-II stimulation of adipocyte glucose uptake with dose and time dependencies. EGCG at 20μM for 2h decreased IGF-I- and IGF-II-stimulated glucose uptake by 59% and 64%, respectively. Pretreatment of adipocytes with antibody against the EGCG receptor (also known as the 67-kDa laminin receptor; 67LR), prevented the effects of EGCG on IGF-increased glucose uptake, but pretreatment with normal rabbit immunoglobulin did not. This suggests that the 67LR mediates the anti-IGF effect of EGCG on adipocyte glucose uptake. Further analysis indicated EGCG, IGF-I, and IGF-II did not alter total levels of GLUT1 or GLUT4 protein. However, EGCG prevented the IGF-increased GLUT4 levels in the plasma membrane and blocked the IGF-decreased GLUT4 levels in low-density microsomes. Neither EGCG nor its combination with IGF altered GLUT1 protein levels in the plasma membrane and low-density microsomes. EGCG also suppressed the IGF-stimulated phosphorylation of IGF signaling molecules, PKCζ/λ, but not AKT and ERK1/2, proteins. This study suggests that EGCG suppresses IGF stimulation of 3T3-L1 adipocyte glucose uptake through inhibition of the GLUT4 translocation, but not through alterations of the GLUT1 pathway.
Department of Life Sciences, National Central University, 300 Jhongda Road, Jhongli, Taoyuan 320, Taiwan.
Hui-Chen
HC
Ku
Taoyuan Armed Forces General Hospital, Longtan, Taoyuan 325, Taiwan.
Yi-Wei
YW
Tsuei
Taoyuan Armed Forces General Hospital, Longtan, Taoyuan 325, Taiwan.
Chung-Cheng
CC
Kao
Department of Life Sciences, National Central University, 300 Jhongda Road, Jhongli, Taoyuan 320, Taiwan; Taoyuan Armed Forces General Hospital, Longtan, Taoyuan 325, Taiwan.
Jueng-Tsueng
JT
Weng
Department of Life Sciences, National Central University, 300 Jhongda Road, Jhongli, Taoyuan 320, Taiwan; Taoyuan Armed Forces General Hospital, Longtan, Taoyuan 325, Taiwan.
Li-Jane
LJ
Shih
Department of Life Sciences, National Central University, 300 Jhongda Road, Jhongli, Taoyuan 320, Taiwan.
Hsin-Huei
HH
Chang
Department of Life Sciences, National Central University, 300 Jhongda Road, Jhongli, Taoyuan 320, Taiwan.
Chi-Wei
CW
Liu
Cathay General Hospital, Taipei, Taiwan.
Shu-Wei
SW
Tsai
Taiwan Landseed Hospital, Taoyuan, Taiwan.
Yow-Chii
YC
Kuo
Department of Life Sciences, National Central University, 300 Jhongda Road, Jhongli, Taoyuan 320, Taiwan. Electronic address: ykao@cc.ncu.edu.tw.
Yung-Hsi
YH
Kao
D041721:3T3-L1 Cells; D000111:Acetylcysteine / Q000494:pharmacology; D017667:Adipocytes / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D000906:Antibodies / Q000378:metabolism; D002392:Catechin / Q000031:analogs & derivatives* / Q000494:pharmacology; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D003593:Cytoplasm / Q000187:drug effects / Q000378:metabolism; D005947:Glucose / Q000378:metabolism*; D051272:Glucose Transporter Type 1 / Q000378:metabolism*; D051275:Glucose Transporter Type 4 / Q000378:metabolism*; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D007335:Insulin-Like Growth Factor II / Q000378:metabolism*; D051379:Mice; D010766:Phosphorylation / Q000187:drug effects; D021381:Protein Transport; D017474:Receptors, Laminin / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D013662:Tea / Q000737:chemistry*
D000906:Antibodies; D051272:Glucose Transporter Type 1; D051275:Glucose Transporter Type 4; D017474:Receptors, Laminin; C495677:SLC2A1 protein, human; D013662:Tea; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II; D002392:Catechin; C045651:epigallocatechin gallate; D005947:Glucose; D000111:Acetylcysteine
Adipocyte glucose uptake; Epigallocatechin gallate; Glucose transporter; Green tea; Insulin-like growth factor