Regulation of adipocyte differentiation and metabolism

描述(由申请人提供)：在过去的资助期间，我们进行了新的研究，证明Wnt信号在培养的前脂肪细胞和转基因小鼠中作为脂肪生成抑制因子具有重要作用。我们的研究表明，WNT10b在前脂肪细胞和间质血管细胞中表达，并在诱导成脂后迅速减少。此外，我们发现WNT10b通过抑制C/EBPalpha和PPARGamma来调节脂肪的生成，并且用中和血清抑制内源性WNT10b可以刺激培养的前脂肪细胞的脂肪生成。在脂肪组织中表达Wnt10b的转基因小鼠脂肪组织减少。食用高脂肪饮食的FABP4-WNT10b小鼠对饮食诱导和遗传性肥胖具有抵抗力，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WNT10b的作用从简单的抑制前脂肪细胞分化扩展到调节多潜能干细胞的命运。因此，FABP4-WNT10b小鼠的骨小梁增加了四倍。这似乎是WNT10b刺激成骨细胞生成和减少骨髓中常驻间充质祖细胞的脂肪生成的直接作用。进一步支持WNT10b在控制间充质前体命运中的关键作用来自我们的观察，WNT10b-/-小鼠的骨小梁减少了大约30%，血清成骨细胞标志物也相应减少。尽管我们对Wnt信号在脂肪形成中的作用的研究已经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信号仍不清楚。在DK51563的这一竞争性更新中，我们提议通过实验来检验以下假设：前体细胞中的WNT活性是由多个WNT以及前脂肪细胞和脂肪细胞中分泌的卷曲相关蛋白(SFRP)的竞争贡献组成的，以及Wnt信号通过抑制PPARGamma的表达和/或活性来抑制脂肪形成。因此，这项资助申请的具体目的是：具体目标1：研究Wnt信号分子的活性和调节，包括Wnts、Fzd和sFRPs。具体目的2：研究Wnt信号抑制PPARGamma表达的机制。这些特定目标的成功完成将提供对脂肪细胞分化和新陈代谢的重要洞察，并提供对肥胖和II型糖尿病这两个美国主要健康风险的医学问题的洞察。

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.