title: Bone morphogenetic protein-3b (BMP-3b) is expressed in adipocytes and inhibits adipogenesis as a unique complex.
abstract: BACKGROUND
  Bone morphogenetic protein-3b (BMP-3b) is a member of the transforming growth factor-β (TGF-β) superfamily. BMP-3b regulates osteogenesis and has critical roles in developing embryos. BMP-3b is expressed not only in the bone and developing embryos but also in adipose tissues. However, the functions of BMP-3b in adipose tissue are still unknown.
  
  
  METHODS
  BMP-3b expression was quantified in various adipose tissues and in the adipose-derived stromal-vascular fraction (SVF) and mature adipocyte fraction (AD.F) of mice. We also used 3T3-L1 preadipocytes to analyze the expression, function and molecular forms of BMP-3b. In order to determine the effects of BMP-3b on the adipogenesis of 3T3-L1 cells, BMP-3b siRNA-mediated knockdown and gene overexpression studies were performed, and a conditioned medium (CM) containing the BMP-3b protein was added to 3T3-L1 cell cultures. Adipocyte differentiation was evaluated by measuring the expression of adipogenic markers or by Oil Red O staining. The molecular form of BMP-3b that was secreted from the 3T3-L1 cells was analyzed by western blotting.
  
  
  RESULTS
  BMP-3b is expressed in all adipose tissues and is expressed at higher levels in preadipocytes than in mature adipocytes. In mesenteric adipose tissue, BMP-3b expression was increased in diet-induced obesity (DIO) mice as compared with that in control mice. BMP-3b was also expressed highly in 3T3-L1 cells. We showed that siRNA-mediated knockdown of endogenous BMP-3b expression in 3T3-L1 cells enhanced adipogenesis. Conversely, overexpressing BMP-3b inhibited adipocyte differentiation. We also showed that addition of CM containing the BMP-3b protein inhibited the differentiation of 3T3-L1 cells, and that this inhibitory effect was abolished by removing BMP-3b with an anti-BMP-3b antibody. Furthermore, BMP-3b was secreted from adipocytes as a unique non-covalent complex.
  
  
  CONCLUSIONS
  These data suggest that BMP-3b is secreted from adipocytes and is involved in adipocyte differentiation.
authors.affiliation: Department of Biochemistry, National Cerebral and Cardiovascular Center Research Institute, 5-7-1 Fujishirodai, Suita, Osaka, Japan.
authors.forename: J
authors.initials: J
authors.lastname: Hino
authors.forename: T
authors.initials: T
authors.lastname: Miyazawa
authors.forename: M
authors.initials: M
authors.lastname: Miyazato
authors.forename: K
authors.initials: K
authors.lastname: Kangawa
mesh_terms: D041721:3T3-L1 Cells / Q000378:metabolism; D017667:Adipocytes / Q000378:metabolism*; D050156:Adipogenesis / Q000235:genetics; D000273:Adipose Tissue / Q000166:cytology / Q000378:metabolism*; D000818:Animals; D015153:Blotting, Western; D055785:Gene Knockdown Techniques; D055413:Growth Differentiation Factor 10 / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015854:Up-Regulation
chemical_list: D055413:Growth Differentiation Factor 10