Role of SIRT3 in alcoholic heart muscle disease

描述(申请人提供)：酒精滥用是一个主要的公共卫生问题，导致过早死亡，损害医院恢复，以及多器官系统的功能障碍。酒精性心肌病(Ahmd.)是持续酗酒的标志，相关的心肌病在那些长期酗酒的人中有近三分之一被诊断出来。导致AHMD的机制无疑是多因素的，涉及心肌细胞和成纤维细胞。尽管迄今为止对AHMD的研究主要涉及心肌本身的改变，但随着时间的推移，胶原和细胞外基质(ECM)在心脏中的积累可能是导致发病的主要机制。因此，阐明长期饮酒后心肌成纤维细胞转化和激活的细胞和分子机制具有重要的临床意义。我们的长期目标是阐明AHMD的病因和发病机制。我们的初步数据表明，小鼠长期(24周)饮酒为心脏成纤维细胞向肌成纤维细胞(MyoFBs)的转分化提供了确凿的证据，这是一种与胶原沉积增加(例如纤维化)和心脏收缩功能障碍相关的细胞转变。酒精喂养小鼠的心脏也显示sirtuin(SIRT)-3的减少，sirtuin(SIRT)-3是一种蛋白质脱乙酰酶，已成为调节细胞转化和代谢的蛋白质家族的重要成员。最后，我们发现长期饮酒会增加心肌细胞肌球蛋白重链(MHC)的比例。因此，根据这些初步数据和文献中的信息，我们假设Ahmd是由SIRT3的减少引起的。我们推测，这种变化随后刺激心脏成纤维细胞向肌纤维细胞转化，从而促进胶原沉积和间质纤维化，最终损害心脏功能。为了解决这一假说中隐含的问题，拟议的研究有以下具体目的：(1)描述酒精引起的心脏SIRT3的减少是否与ECM周转和Ahmd的介体有关；(2)确定SIRT3在体内的激活是否阻止Ahmd的发展。我们的应用利用了心脏特异性SIRT3过度表达的小鼠模型的可用性，并得到了令人兴奋的初步数据的支持。我们对最先进的活体方法的关注使我们能够明确地将生理重要性分配给我们的观察。为了保持目前应用的重点，没有特别建议进行体外研究。然而，有初步数据表明，酒精还可以降低培养的人心脏成纤维细胞的SIRT3，增加ECM的产生，这表明酒精对这种细胞类型有直接影响。预期的研究结果将有助于提供有关SIRT3代谢影响的基础知识，并为HAMD的临床重要病理提供开创性的机械学见解，从而为我们的研究重点和治疗开发的潜力提供广泛的翻译基础。

DESCRIPTION (provided by applicant): Alcohol abuse is a major public health problem leading to premature death, impaired hospital recovery, and the dysfunction of multiple organ systems. Alcoholic heart muscle disease (AHMD.) is a hallmark of sustained alcohol abuse and the associated cardiomyopathy is diagnosed in nearly a third of those individuals who chronically abuse alcohol. The mechanisms leading to AHMD are undoubtedly multifactorial, involving both cardiac myocytes and fibroblasts. Whereas the preponderance of research to date on AHMD has involved changes in cardiac muscle per se, over time the accumulation of collagen and extracellular matrix (ECM) in the heart may represent a central mechanism contributing to pathogenesis. As such, elucidation of the cellular and molecular mechanisms regulating cardiac myofibroblast conversion and activation in response to prolonged alcohol intake is of clinical significance. Our long-term goal is to elucidate the etiology and pathogenesi of AHMD.. Our preliminary data indicate that chronic (24 wk) alcohol consumption in mice produces definitive evidence for the transdifferentiation of cardiac fibroblasts to myofibroblasts (myoFBs), a cellular transition associated with increased collagen deposition (e.g., fibrosis) and cardiac contractile dysfunction. Hearts from alcohol-fed mice also show a decrease in sirtuin (SIRT)-3, a protein deacetylase which has emerged as an important member of a protein family regulating cell transformation and metabolism. Finally, we have discovered chronic alcohol consumption increases the ¿- to ¿-myosin heavy chain (MHC) ratio in cardiomyocytes. Therefore, based on these preliminary data and information present in the literature, we hypothesize that AHMD is caused by a decrease in SIRT3. We posit this change subsequently stimulates the transformation of cardiac fibroblasts to myoFBs, thereby enhancing collagen deposition and interstitial fibrosis, which ultimately impairs cardiac function. To address the questions implicit in this hypothesis, the proposed research has the following specific aims: (1) To delineate whether the alcohol-induced decrease in cardiac SIRT3 is causally related to ECM turnover and a mediator of AHMD.; and (2) To determine whether in vivo activation of SIRT3 prevents the development of AHMD.. Our application exploits the availability of a murine model of cardiac-specific SIRT3 over-expression and is supported by exciting preliminary data. Our focus on state-of-the-art in vivo approaches permits us to definitively assign physiological importance to our observations. To maintain the focus of the current application, in vitro studies are not specifically proposed. However, preliminary data are available indicating that alcohol also decreases SIRT3 and increases ECM production in cultured human cardiac fibroblasts, suggesting a direct effect of alcohol on this cell type. The expected research outcomes will contribute fundamental knowledge pertaining to the metabolic effects of SIRT3 and provide seminal mechanistic insights into the clinically significant pathology of AHMD., thereby providing a broad translational basis for our research focus and the potential for therapeutic development.