Department of Biochemistry, National Cerebral and Cardiovascular Center Research Institute, 5-7-1 Fujishirodai, Suita, Osaka, Japan.
Int J Obes (Lond). 2012 May;36(5):725-34. doi: 10.1038/ijo.2011.124. Epub 2011 Jun 28.
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.
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.
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.
These data suggest that BMP-3b is secreted from adipocytes and is involved in adipocyte differentiation.
骨形态发生蛋白 3b（BMP-3b）是转化生长因子-β（TGF-β）超家族的一员。BMP-3b 调节成骨作用，并在胚胎发育中起关键作用。BMP-3b 不仅在骨骼和发育中的胚胎中表达，而且在脂肪组织中也表达。然而，BMP-3b 在脂肪组织中的功能尚不清楚。
定量分析了各种脂肪组织以及小鼠脂肪组织源性基质血管部分（SVF）和成熟脂肪细胞部分（AD.F）中的 BMP-3b 表达。我们还使用 3T3-L1 前体脂肪细胞分析 BMP-3b 的表达、功能和分子形式。为了确定 BMP-3b 对 3T3-L1 细胞脂肪生成的影响，进行了 BMP-3b siRNA 介导的敲低和基因过表达研究，并向 3T3-L1 细胞培养物中添加含有 BMP-3b 蛋白的条件培养基（CM）。通过测量脂肪生成标记物的表达或通过油红 O 染色来评估脂肪细胞分化。通过 Western blot 分析从 3T3-L1 细胞分泌的 BMP-3b 的分子形式。
BMP-3b 在所有脂肪组织中表达，并在前体脂肪细胞中表达水平高于成熟脂肪细胞。在肠系膜脂肪组织中，与对照小鼠相比，饮食诱导肥胖（DIO）小鼠的 BMP-3b 表达增加。BMP-3b 在 3T3-L1 细胞中也高表达。我们表明，3T3-L1 细胞中内源性 BMP-3b 表达的 siRNA 介导敲低增强了脂肪生成。相反，过表达 BMP-3b 抑制脂肪细胞分化。我们还表明，添加含有 BMP-3b 蛋白的 CM 抑制了 3T3-L1 细胞的分化，并且用抗 BMP-3b 抗体去除 BMP-3b 可消除这种抑制作用。此外，BMP-3b 作为独特的非共价复合物从脂肪细胞中分泌。
这些数据表明，BMP-3b 从脂肪细胞中分泌，并参与脂肪细胞分化。
