Regulation of adipocyte differentiation and metabolism

描述（由申请人提供）：在过去的资助期内，我们进行了新的研究，证明Wnt信号作为培养的前脂肪细胞和转基因小鼠中脂肪形成的抑制剂具有重要作用。我们的研究表明，Wnt 10 b在前脂肪细胞和基质血管细胞中表达，并在诱导脂肪形成时迅速减少。此外，我们发现Wnt 10 b通过抑制C/EBPalpha和PPARgamma调节脂肪形成，并且用中和抗血清抑制内源性Wnt 10 b刺激培养的前脂肪细胞的脂肪形成。在脂肪组织中表达Wnt 10 b的转基因小鼠脂肪组织减少。食用高脂肪饮食的FABP 4-Wnt 10 b小鼠对饮食诱导的和遗传性肥胖具有抗性，并且这些小鼠比对照组更耐葡萄糖和胰岛素敏感。我们的研究还将Wnt 10 b的作用从简单的抑制前脂肪细胞分化扩展到调节多能干细胞的命运。因此，FABP 4-Wnt 10 b小鼠的骨小梁增加了4倍。这似乎是Wnt 10 b刺激骨髓中常驻间充质祖细胞的成骨细胞生成和减少脂肪生成的直接作用。Wnt 10 b在控制间充质前体命运中的关键作用的进一步支持来自我们的观察，即Wnt 10 b-/-小鼠的骨小梁减少约30%，血清成骨细胞标志物相应减少。虽然我们在Wnt信号对脂肪形成的影响的研究中取得了相当大的进展，但培养细胞和脂肪组织中的自分泌和旁分泌信号如何调节内源性Wnt信号仍然是未知的。在DK 51563的这种竞争性更新中，我们提出实验来测试以下假设：前体细胞中的Wnt活性由前脂肪细胞和脂肪细胞中的多个Wnt和分泌的卷曲相关蛋白（sFRP）的竞争性贡献组成，并且Wnt信号通过抑制PPARgamma的表达和/或活性来抑制脂肪形成。因此，本授权申请的具体目标是：具体目标1：研究Wnt信号分子（包括Wnt、Fzd和sFRPs）的活性和调节。具体目标2：研究Wnt信号传导抑制PPARgamma表达的机制。这些具体目标的成功完成将为脂肪细胞分化和代谢提供重要的见解，并为肥胖和II型糖尿病这两个美国主要健康风险的医学问题提供见解。

DESCRIPTION (provided by applicant): In the past funding period, we have performed novel studies demonstrating an important role for Wnt signaling as an inhibitor of adipogenesis in cultured preadipocytes and in transgenic mice. Our studies have demonstrated that Wnt10b is expressed in preadipocytes and stromal vascular cells and decreases rapidly upon induction of adipogenesis. Further, we found that Wnt10b regulates adipogenesis through suppression of C/EBPalpha and PPARgamma and that inhibition of endogenous Wnt10b with neutralizing antisera stimulates adipogenesis of cultured preadipocytes. Transgenic mice expressing Wnt10b in adipose tissue have reduced adipose tissue. FABP4-Wnt10b mice consuming a high fat diet are resistant to diet-induced and genetic-obesity, and these mice are more glucose-tolerant and insulin-sensitive than controls. Our studies have also expanded the role for Wnt10b from simple inhibition of preadipocyte differentiation to modulating fate of multipotent stem cells. Thus, FABP4-Wnt10b mice have a four-fold increase in trabecular bone. This appears to be a direct effect of Wnt10b to stimulate osteoblastogenesis and decrease adipogenesis of resident mesenchymal progenitor cells in marrow. Further support for a critical role for Wnt10b in governing fate of mesenchymal precursors comes from our observations that Wnt10b -/- mice have approximately 30% less trabecular bone and a corresponding decrease in serum osteoblast markers. Although we have made considerable progress in our studies on the effects of Wnt signaling on adipogenesis, how autocrine and paracrine signals in cultured cells and adipose tissue regulate endogenous Wnt signaling remains unknown. In this competitive renewal of DK51563, we propose experiments to test the hypotheses that Wnt activity in precursor cells is comprised of competing contributions from multiple Wnts and secreted frizzled-related proteins (sFRP) in preadipocytes and adipocytes, and that Wnt signaling inhibits adipogenesis by repressing the expression and/or activity of PPARgamma. Thus, the specific aims of this grant application are to: Specific Aim 1: Investigate activity and regulation of Wnt signaling molecules including Wnts, Fzd, and sFRPs. Specific Aim 2: Investigate mechanisms whereby Wnt signaling inhibits expression of PPARgamma. Successful completion of these specific aims will provide important insight into fat cell differentiation and metabolism, and provide insight into the medical problems of obesity and type II diabetes, two major health risks in the United States.