Sphingolipids in Diabetic Cardiomyopathy

描述（由申请人提供）：糖尿病患者患心脏病的风险增加，这是由于几个因素，包括与其他风险因素无关的几何和功能变化;这被称为"糖尿病心肌病"。这种疾病的机制尚未完全了解，但越来越多的数据支持异常脂质代谢有助于这种疾病过程的概念。在这些代谢变化中，鞘脂合成受到干扰;我们已经证明，阻断鞘脂合成可以改善糖尿病心肌病的许多方面。鞘脂代谢包括许多酶、途径和产物;分离介导特定过程的特定鞘脂已被证明具有挑战性。此外，这些过程发生的机制一直难以确定。我们最近发表了鞘脂合成的特异性酶神经酰胺合成酶5（CerS5）介导脂质诱导的心肌细胞肥大和自噬。在小鼠高饱和脂肪喂养模型中，导致胰岛素抵抗和肥胖，心脏中的鞘脂生物合成受到干扰。我们观察到鞘脂依赖性细胞肥大，自噬，最重要的是，心脏功能障碍。新的初步数据表明鞘脂参与线粒体损伤和线粒体自噬，并揭示了CerS5引起自噬的分子机制。我们已经观察到CerS5及其产物C14-神经酰胺的1-核积累，2-CerS5依赖的p53在核中的积累，和3-鞘脂依赖的线粒体储备损失，以及线粒体自噬的增加。在这里，我们建议解剖DbCM的机制的基础上，这些初步的研究结果，并使用的策略，包括在体内测定舒张功能障碍的小鼠缺乏CerS5，组件的线粒体自噬途径，组件的macroautophagy途径。如我们最近的出版物所证明的（Russo等人，2012，J. Clin. Invest.; Russo等2013，J. Biol. Chem.），我们非常适合解决这些位于鞘脂生物化学和心脏病学界面的问题。为了促进这项高度转化的工作，我们招募了心脏病学和代谢专家，以补充我们在鞘脂生物化学，信号传导和分析方面的专业知识。这些研究将揭示这些细胞过程在糖尿病心肌病中的作用，解决围绕心脏损伤中自噬性质的争议，特别是它是适应性的还是有害的，提供对鞘脂依赖性线粒体功能障碍的见解，这在糖尿病背景下尤其重要，并最终揭示心脏中鞘脂依赖性脂毒性的细胞，生化和分子机制。

DESCRIPTION (provided by applicant):: Diabetics are at increased risk of heart disease from several factors including geometric and functional changes that occur independently of other risk factor; this is termed 'diabetic cardiomyopathy'. Mechanisms of this disease are not completely understood, but data increasingly support the notion that aberrant lipid metabolism contributes to this disease process. Among these metabolic changes are perturbations in sphingolipid synthesis; others and we have shown that blocking sphingolipid synthesis ameliorates many facets of diabetic cardiomyopathy. Sphingolipid metabolism comprises numerous enzymes, pathways, and products; teasing apart specific sphingolipids that mediate a specific process has proven challenging. Moreover, mechanisms by which these processes occur have been difficult to determine. We recently published that a specific enzyme of sphingolipid synthesis, Ceramide Synthase 5 (CerS5), mediated lipid- induced cardiomyocyte hypertrophy and autophagy. In a high saturated-fat feeding model in mice, which caused insulin resistance and obesity, sphingolipid biosynthesis was perturbed in heart. We observed sphingolipid-dependent cell hypertrophy, autophagy, and most importantly, cardiac dysfunction. New preliminary data implicate sphingolipids in mitochondrial damage and mitophagy, and also shed light on molecular mechanisms by which CerS5 causes autophagy. We have observed 1-nuclear accumulation of CerS5 and its product C14-ceramide, 2-CerS5-dependent accumulation of p53 in the nucleus, and 3- sphingolipid-dependent loss of mitochondrial reserve, and increase in mitophagy. Here we propose to dissect mechanisms for DbCM based on these initial findings, and using a combination of strategies including in vivo determinations o diastolic dysfunction in mice lacking CerS5, components of the mitophagy pathway, components of the macroautophagy pathway. As evidenced by our recent publications (Russo et al. 2012, J. Clin. Invest.; Russo et al 2013, J. Biol. Chem.), we are highly suited to address these questions that lie at the interface of sphingolipid biochemistry and cardiology. To facilitat this highly translational work we have enlisted cardiology and metabolism experts to complement our expertise in sphingolipid biochemistry, signaling, and analysis. These studies will reveal roles of these cell processes in diabetic cardiomyopathy, address the controversy surrounding the nature of autophagy in cardiac injury, specifically whether it is adaptive or deleterious, provide insights into sphingolipid-dependent mitochondrial dysfunction, which is especially important in the diabetic context, and finally reveal cell, biochemical, and molecular mechanisms of sphingolipid-dependent lipotoxicity in the heart.