MECHANISMS OF CARDIOVASCULAR DISEASE IN OBESITY

关于促进高凝状态和增加人类肥胖心血管疾病风险的分子机制的信息很少。尽管纤溶酶原激活物抑制剂1 （PAI-1）在肥胖者血浆中持续且显著升高，并且是动脉粥样硬化性疾病的已知危险因素，但其在肥胖中表达的起源和调控机制仍有待明确。我们对肥胖小鼠和培养脂肪细胞的研究表明，血浆PAI-1升高是由于脂肪细胞对肿瘤坏死因子- α和胰岛素的反应而增加的合成，并且脂肪细胞可能在人类肥胖的止血基因表达中起着核心的和以前未被认识到的作用。以下观察结果为肥胖中脂肪细胞和PAI-1的生物合成提供了新的见解，并形成了该应用的基础：(1)转化生长因子β (tgf - β) mRNA在肥胖小鼠的脂肪组织中长期升高，是脂肪细胞中PAI-1的强大诱导剂；(2)就PAI-1而言，脂肪细胞是主要的胰岛素应答细胞；(3)胰岛素在代谢胰岛素抵抗型脂肪细胞和小鼠中持续诱导PAI-1。我们假设肥胖中tgf - β和高胰岛素血症的增加改变了脂肪细胞的生物合成活性，并增加了与此相关的心血管风险。在Aim 1中，我们将研究tgf - β在肥胖和脂肪形成过程中的表达调控及其后果。tgf - β改变脂肪前细胞生长和分化以及脂肪细胞基因表达、葡萄糖稳态和胰岛素抵抗的可能性将在体内和体外使用特异性tgf - β抑制剂进行探索。在Aim 2中，我们将研究小鼠肥胖的其他模型，以确定胰岛素对PAI-1影响的普遍性和组织特异性。我们还将利用胰岛素信号传导抑制剂来确定控制PAI-1基因表达的途径，并验证在脂肪细胞中，葡萄糖稳态和PAI-1基因表达受不同途径调节的假设。这些研究应该提供关于tgf - β和胰岛素的新信息，以及它们各自在健康和疾病中调节脂肪细胞中PAI-1的作用。

Little information is available about the molecular mechanisms that promote the hypercoagulable state and increased risk for cardiovascular disease in human obesity. Although plasminogen activator inhibitor 1 (PAI-1) is consistently and significantly elevated in the plasma of obese humans and is a known risk factor for atherothrombolic disease, the origin and regulatory mechanism(s) that control its expression in obesity remain to be defined. Our studies of obese mice and cultured adipocytes suggest that elevated plasma PAI-1 results from increased synthesis by adipocytes in response to tumor necrosis factor-alpha and insulin, and that the adipocyte may play a central and previously unrecognized role in hemostatic gene expression in human obesity. The following observations provide additional novel insights into adipocytes and PAI-1 biosynthesis in obesity and form the basis of this application: (1) transforming growth factor beta (TGF-beta) mRNA is chronically elevated in adipose tissue of obese mice and is a powerful inducer of PAI-1 in adipocytes; (2) the adipocyte is the primary insulin-responsive cell in terms of PAI-1; and (3) insulin continues to induce PAI-1 in metabolically insulin-resistant adipocytes and mice. We hypothesize that the increased TGF-beta and hyperinsulinemia in obesity alters the biosynthetic activity of adipocytes and promotes the cardiovascular risk associated with this condition. In Aim 1, we will investigate the regulation and consequences of TGF-beta expression in obesity and during adipogenesis. The possibility that TGF-beta alters preadipocyte growth and differentiation as well as adipocyte gene expression, glucose homeostasis, and insulin-resistance will be explored in vivo and in vitro using specific inhibitors of TGF-beta. In Aim 2, we will examine additional models of murine obesity to determine the generality and tissue specificity of the effects of insulin on PAI-1. We will also employ inhibitors of insulin-signaling to define the pathways that control PAI-1 gene expression, and to test the hypothesis that in adipocytes, glucose homeostasis and PAI-1 gene expression are regulated by different pathways. These studies should provide novel information about TGF-beta and insulin and their respective roles in the regulation of PAI-1 in adipocytes in health and disease.