Environmental obesogens reduce Thy1 expression and promote obesity

描述（由申请人提供）：在过去的30年里，肥胖人数急剧上升。仅在美国，就有6000万人被诊断为临床肥胖。尤其令人担忧的是儿童肥胖几乎是流行病。肥胖的发生是由于过度的脂肪形成（脂肪细胞的形成）或由于既定脂肪细胞大小的增加。被称为肥胖源的环境毒物会破坏内分泌系统，增加脂肪生成。三丁基锡（TBT）、二氯二苯基二氯乙烯（DDE）、双酚- a二缩水甘油酯醚（BADGE）和四溴双酚- a （TBBPA）已被报道会增加肥胖。外源性致肥因子干扰内分泌系统和增加肥胖率的机制需要积极研究。我们的工作重点是表面糖蛋白Thy1 （CD90）。Thy1是一种糖磷脂酰肌醇（GPI）锚定的膜蛋白，在神经元、干细胞和其他细胞类型的亚群上表达。我们发现成纤维细胞表达Thy1是异质的，只有Thy1+的成纤维细胞才能分化成瘢痕形成的肌成纤维细胞，只有Thy1-/低的成纤维细胞才能分化成脂肪细胞。在这个R21应用中，我们假设Thy1在预防脂肪形成中有直接作用。我们的支持数据表明，Thy1的缺失增加了脂肪的形成，而Thy1的过表达则损害了脂肪的形成。这些数据支持这样一个概念，即Thy1不仅仅是一个标记，而且Thy1可以改变细胞命运。我们还发现，暴露于TBBPA、BADGE和TBT后，人和小鼠多能基质细胞（MSCs）中的Thy1表达均降低。重要的是，致肥因子可能发挥作用的一种机制是对MSCs的表观遗传密码进行重编程，从而改变生理机能。Thy1基因座包含多个CpG岛，这些岛可以通过表观遗传控制，可能是致肥因子的关键靶点。发育暴露于致肥源可能会在暴露后很长一段时间内重编程Thy1表达水平并改变生理。因此，我们假设环境致肥因子改变Thy1的表达，从而增加脂肪形成和肥胖。为了调查这一假设，我们制定了以下目标。目的1：验证环境致肥因子降低多能基质细胞中Thy1的表达和活性从而增加脂肪形成的假设。目的2：验证体内发育暴露于肥胖源降低Thy1表达并增加脂肪形成和肥胖的假设。这些研究结果将首次表明，环境致肥因子会降低Thy1的表达，而这种降低是致肥因子增加脂肪形成和肥胖的关键机制。

DESCRIPTION (provided by applicant): Obesity has risen dramatically over the last 30 years. In the U.S. alone, 60 million people are defined as clinically obese. Especially concerning is the nearly epidemic rate of childhood obesity. Obesity occurs through excessive adipogenesis (formation of adipocytes) or through increases in established adipocyte size. Environmental toxicants termed obesogens disrupt the endocrine system and can increase adipogenesis. Tributyltin (TBT), dichlorodiphenyl-dichloroethylene (DDE), bisphenol-A diglycidyl ether (BADGE), and tetrabromobisphenol-A (TBBPA), have been reported to increase obesity. The mechanism(s) by which xenobiotic obesogens function to disrupt the endocrine system and increase rates of obesity requires active investigation. Our work focuses on the surface glycoprotein, Thy1 (CD90). Thy1 is an glycophosphatidylinositol (GPI)-anchored membrane protein expressed on subsets of neurons, stem cells and other cell types. We discovered that fibroblasts are heterogeneous for expression of Thy1 and that only Thy1+ fibroblasts can differentiate into scar-forming myofibroblasts and only Thy1-/low fibroblasts can differentiate int adipocytes. In this R21 application, we hypothesize that there is a direct role for Thy1 in preventing adipogenesis. Our supporting data show that depletion of Thy1 increases adipogenesis while over- expression of Thy1 impairs adipogenesis. These data support the concept that Thy1 is more than a marker and that Thy1 can function to modify cell fate. We also discovered that Thy1 expression is reduced in both human and mouse multipotent stromal cells (MSCs) after exposure to TBBPA, BADGE and TBT. Importantly, one mechanism by which obesogens may function is to reprogram the epigenetic code of MSCs to alter physiology. The Thy1 locus contains multiple CpG islands that can be controlled epigenetically and may be key targets of obesogens. Developmental exposure to obesogens may reprogram Thy1 expression levels and modify physiology long after exposure. Therefore, we hypothesize that environmental obesogens alter Thy1 expression to increase adipogenesis and obesity. To investigate this hypothesis we have developed the following aims. Aim 1: Test the hypothesis that environmental obesogens diminish Thy1 expression and activity in multipotent stromal cells to increase adipogenesis. Aim 2: Test the hypothesis that developmental exposure to obesogens reduces Thy1 expression and increases adipogenesis and obesity in vivo. The results of these studies will show for the first time that Thy1 expression is reduced by environmental obesogens and this reduction is key to the mechanism whereby obesogens increase adipogenesis and obesity.