title: Tea catechins modulate the glucose transport system in 3T3-L1 adipocytes.
abstract: In this study, we investigated the effects of tea catechins on the translocation of glucose transporter (GLUT) 4 in 3T3-L1 adipocytes. We found that the ethyl acetate fraction of green tea extract, containing abundant catechins, most decreased insulin-induced glucose uptake activity in 3T3-L1 cells. When the cells were treated with 50 μM catechins in the absence or presence of insulin for 30 min, nongallate-type catechins increased glucose uptake activity without insulin, whereas gallate-type catechins decreased insulin-induced glucose uptake activity. (-)-Epicatechin (EC) and (-)-epigallocatechin (EGC), nongallate-type catechins, increased glucose uptake activity in the dose- and time-dependent manner, whereas (-)-catechin 3-gallate (Cg) and (-)-epigallocatechin 3-gallate (EGCg), gallate-type catechins, decreased insulin-induced glucose uptake activity in the dose- and time-dependent manner. When the cells were treated with 50 μM catechins for 30 min, EC and EGC promoted GLUT4 translocation, whereas Cg and EGCg decreased the insulin-induced translocation in the cells. EC and EGC increased phosphorylation of PKCλ/ζ without phosphorylation of insulin receptor (IR) and Akt. Wortmannin and LY294002, inhibitors for phosphatidylinositol 3'-kinase (PI3K), decreased EC- and EGC-induced glucose uptake activity in the cells. Cg and EGCg decreased phosphorylation of PKCλ/ζ in the presence of insulin without affecting insulin-induced phosphorylation of IR, and Akt. Therefore, EC and EGC promote the translocation of GLUT4 through activation of PI3K, and Cg and EGCg inhibit insulin-induced translocation of GLUT4 by the insulin signaling pathway in 3T3-L1 cells.
authors.affiliation: Department of Agrobioscience, Graduate School of Agricultural Science, Kobe University, Kobe 657-8501, Japan.
authors.forename: Manabu
authors.initials: M
authors.lastname: Ueda
authors.forename: Takashi
authors.initials: T
authors.lastname: Furuyashiki
authors.forename: Kayo
authors.initials: K
authors.lastname: Yamada
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Aoki
authors.forename: Iwao
authors.initials: I
authors.lastname: Sakane
authors.forename: Itsuko
authors.initials: I
authors.lastname: Fukuda
authors.forename: Ken-Ichi
authors.initials: K
authors.lastname: Yoshida
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Ashida
mesh_terms: D041721:3T3-L1 Cells; D017667:Adipocytes / Q000187:drug effects* / Q000378:metabolism*; D000818:Animals; D002392:Catechin / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology; D005947:Glucose / Q000493:pharmacokinetics*; D051272:Glucose Transporter Type 1 / Q000378:metabolism; D051275:Glucose Transporter Type 4 / Q000378:metabolism*; D007328:Insulin / Q000378:metabolism; D051379:Mice; D010766:Phosphorylation / Q000187:drug effects; D010936:Plant Extracts / Q000378:metabolism / Q000494:pharmacology*; D015398:Signal Transduction / Q000187:drug effects; D013662:Tea / Q000737:chemistry*
chemical_list: D051272:Glucose Transporter Type 1; D051275:Glucose Transporter Type 4; D007328:Insulin; D010936:Plant Extracts; C495678:Slc2a1 protein, mouse; C495693:Slc2a4 protein, mouse; D013662:Tea; D002392:Catechin; C057580:gallocatechol; D005947:Glucose