title: (-)-Epigallocatechin gallate inhibits thyroid hormone-stimulated osteocalcin synthesis in osteoblasts.
abstract: It is recognized that catechin possesses beneficial properties for bone metabolism. We previously revealed that triiodothyronine (T₃)-activated p38 mitogen-activated protein (MAP) kinase, but not p44/p42 MAP kinase, is involved in the synthesis of osteocalcin in osteoblast-like MC3T3-E1 cells. In the present study, we investigated the effect of (-)-epigallocatechin gallate (EGCG), the predominant green tea polyphenol, on the synthesis of osteocalcin in MC3T3-E1 cells. EGCG significantly suppressed T₃-stimulated osteocalcin synthesis. The inhibitory effect of EGCG was dose-dependent in the range of 3 to 30 µM. On the other hand, T₃-induced phosphorylation of p38 MAP kinase was not affected by EGCG. EGCG profoundly inhibited T₃-stimulated transcriptional activity. These results strongly suggest that EGCG suppresses T3-stimulated osteocalcin synthesis upstream of the transcriptional level in osteoblast-like MC3T3-E1 cells.
authors.affiliation: Department of Orthopedic Surgery, Nagoya City University Graduate School of Medical Sciences, Nagoya 467-8601, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Kato
authors.forename: Takanobu
authors.initials: T
authors.lastname: Otsuka
authors.forename: Seiji
authors.initials: S
authors.lastname: Adachi
authors.forename: Rie
authors.initials: R
authors.lastname: Matsushima-Nishiwaki
authors.forename: Hideo
authors.initials: H
authors.lastname: Natsume
authors.forename: Osamu
authors.initials: O
authors.lastname: Kozawa
authors.forename: Haruhiko
authors.initials: H
authors.lastname: Tokuda
mesh_terms: D000818:Animals; D002392:Catechin / Q000031:analogs & derivatives* / Q000494:pharmacology; D002460:Cell Line; D051379:Mice; D010006:Osteoblasts / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism*; D015675:Osteocalcin / Q000096:biosynthesis*; D010766:Phosphorylation / Q000187:drug effects; D020218:Response Elements / Q000235:genetics; D015533:Transcriptional Activation / Q000187:drug effects / Q000235:genetics; D014284:Triiodothyronine / Q000494:pharmacology*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D014284:Triiodothyronine; D015675:Osteocalcin; D002392:Catechin; C045651:epigallocatechin gallate; D048051:p38 Mitogen-Activated Protein Kinases