Adipocytes and cardiac remodeling

 产品描述（由申请方提供）：罗格列酮（RSG）是核激素过氧化物酶体激活受体（PPAR-R）的合成激动剂，已成功用于2型糖尿病的临床治疗，作为胰岛素增敏剂。然而，不良的心脏副作用严重阻碍了其临床应用。现有的实验模型的证据表明，RSG导致心脏肥大，这可能导致心力衰竭。目前，RSG诱导心肌肥大的分子机制尚不清楚。脂肪组织是过氧化物酶体增殖物激活受体（PPAR-binding protein，PPAR-binding protein，PPAR-binding protein）表达和功能的主要部位.我们的初步数据表明，在共培养体系中，RSG激活脂肪细胞中的过氧化物酶体增殖物激活受体，导致心肌细胞肥大。此外，脂肪细胞中的PPAR-mRNA的消融在体内减弱了RSG诱导的心脏肥大。这些数据表明脂肪和心脏组织之间的功能相互作用，调节心脏肥大。脂肪组织作为一种内分泌器官起着重要的作用，并分泌细胞因子来调节全身的稳态和其他器官的功能。有趣的是，最近的筛选以及我们的初步数据显示，脂肪细胞能够释放microRNA（miR）。miR是高度保守的小（~22个核苷酸）非编码RNA家族，其通过降解或抑制其靶mRNA的翻译来转录后抑制基因表达。血清中循环细胞外miR的发现表明它们可能在介导细胞-细胞通讯中发挥新的作用。外泌体是分泌型miR的主要转运囊泡，允许miR在细胞之间转移和遗传交换。我们的初步研究表明，RSG刺激脂肪细胞中的PPAR-γ信号传导导致miR-200 a/B/429簇的上调，以及外泌体中成熟miR-200 a的分泌。生物信息学分析和实验研究表明，miR-200 a可以靶向调节心肌肥大的mTOR通路的组分。此外，我们发现miR-200 a在饮食诱导的肥胖相关心肌病模型中上调。上述提示我们的总体假设是miR-200 a/B/429簇的循环成员介导脂肪和心脏组织之间的通讯，从而在两种不同的心肌病模型中不利地影响心脏重塑。本项目的总体目标是阐明脂肪组织诱导的不良心脏重塑的分子机制，并提供对脂肪和心脏组织之间的新型外泌体miR介导的途径的见解。因此，我们的具体目标是：1。检查miR-200 a/B/429簇的所有成员是否在外泌体中从脂肪细胞转运到心肌细胞，并确定其体外潜在的功能后果; 2.通过脂肪细胞特异性基因敲除小鼠模型，阐明miR-200 a和miR-200 a/B/429簇在RSG介导的体内心脏肥大中的作用; 3.使用脂肪细胞特异性敲除小鼠，了解miR-200 a和miR-200 a/B/429簇在肥胖相关心肌病小鼠模型中的病理生理学作用。

 DESCRIPTION (provided by applicant): Rosiglitazone (RSG) is a synthetic agonist of the nuclear hormone Peroxisome Proliferator-Activated Receptor-  (PPAR-) and has been successfully used in the clinic for type 2 diabetes as an insulin-sensitizer. However, adverse cardiac side effects have seriously hindered its clinical application. Existing evidence from experimental models revealed that RSG results in cardiac hypertrophy, which may lead to heart failure. Currently, molecular mechanisms underlying RSG-induced cardiac hypertrophy remain unclear. Adipose tissue is a major site of PPAR- expression and function. Our preliminary dat showed that activation of PPAR- by RSG in adipocytes in a co-culture system resulted in cardiomyocyte hypertrophy. Furthermore, ablation of PPAR- in adipocytes attenuated RSG-induced cardiac hypertrophy in vivo. These data imply a functional interplay between adipose and cardiac tissue that regulates cardiac hypertrophy. Adipose tissue plays a critical role as an endocrine organ, and secretes cytokines that regulate systemic homeostasis and the function of other organs. Interestingly, a recent screen as well as our preliminary data revealed that adipocytes are able to release microRNAs (miRs). miRs are a family of highly conserved, small (~22 nucleotide) noncoding RNAs that post-transcriptionally repress gene expression by degrading or inhibiting translation of their target mRNA. The discovery of circulating extracellula miRs in serum suggests they may play a novel role in mediating cell-cell communication. Exosomes are the major transport vesicle of secretory miRs, allowing miR transfer and genetic exchange between cells. Our preliminary studies demonstrated that RSG stimulation of PPAR- signaling in adipocytes leads to upregulation of the miR-200a/b/429 cluster, and secretion o mature miR-200a in exosomes. Bioinformatics analysis and experimental investigation demonstrated that miR-200a can target components of the mTOR pathway, which regulates cardiac hypertrophy. In addition, we found that miR-200a was upregulated in a diet-induced obesity-associated cardiomyopathy model. The aforementioned suggest our overall hypothesis is that circulating members of the miR-200a/b/429 cluster mediate communication between adipose and cardiac tissue to adversely affect cardiac remodeling in two distinct models of cardiomyopathy. The overall goal of this project is to elucidate molecular mechanisms underlying adverse cardiac remodeling induced by adipose tissue, and provide insights into a novel exosomal miR-mediated pathway between adipose and cardiac tissue. Accordingly, our Specific Aims are: 1. To examine whether all members of the miR-200a/b/429 cluster are transported from adipocytes to cardiomyocytes in exosomes and to determine potential functional consequences of this in vitro; 2. To elucidate the role of miR-200a and the miR-200a/b/429 cluster in RSG-mediated cardiac hypertrophy in vivo by using adipocyte-specific knockout mouse models; and 3. To understand pathophysiological effects of miR-200a and the miR-200a/b/429 cluster in a mouse model of obesity-associated cardiomyopathy using adipocyte-specific knockout mice.