Disruption of the Clock O-GlcNAc axis in diabetic cardiomyopathy

描述（由申请人提供）：糖尿病仍然是缺血性和非缺血性心血管疾病（CVD）发展的主要风险因素;然而，尽管临床治疗有所改善，但我们对糖尿病相关CVD的分子基础知识了解甚少。与大多数心血管生理学一样，病理性心血管事件在发病和对疾病进展的影响方面表现出时间依赖性，我们已经证明心肌细胞生物钟直接影响心脏对特定应激源的反应方式。重要的是，我们已经证明糖尿病诱导心肌细胞生物钟的相移。因此，心肌细胞生物钟的不同步可能是糖尿病心肌病病因学的一个重要的和以前未被认识的贡献者。蛋白质O-GlcNAc酰化是一种代谢调节的翻译后修饰，可迅速影响蛋白质功能，越来越多地被认为是心脏生理学和病理学（包括糖尿病的不良反应）的关键调节因子。我们最近报道，心肌细胞生物钟直接影响心脏O-GlcNAc水平，至少有两个生物钟成分是O-GlcNAc修饰的，O-GlcNAc水平的急性增加使时钟发生相移，类似于糖尿病期间在心脏中看到的情况。我们还观察到在非活动期心脏中蛋白质合成增加，此时蛋白质O-GlcNAc化较低。这使我们假设蛋白质O-GlcNAc化可能是心肌细胞生物钟在时间上协调心脏中受损蛋白质修复/替换的关键机制。总的来说，这些观察结果支持了这一提议的总体假设，即蛋白质O-GlcNAc化的失调是一个关键的调节因子。 糖尿病是导致心肌细胞生物钟改变的重要因素，心肌细胞生物钟失调是糖尿病相关心功能不全的关键机制。为了验证这一假设，我们将追求3个具体目标：1）确定心肌细胞生物钟与蛋白质O-GlcNAc化之间的分子基础，并确定这种关系在糖尿病期间是如何改变的; 2）确定O-GlcNAc化在生物钟介导的蛋白质周转中的作用，并阐明这种关系在糖尿病期间是如何改变的; 3）确定糖尿病期间心肌细胞生物钟的重新排列是否减弱心肌病的发展。成功完成拟议的研究将导致关于异常昼夜节律功能在糖尿病相关心脏病发展中的作用的分子机制的新的基本见解，并将有助于确定降低糖尿病患者CVD风险的新方法。

DESCRIPTION (provided by applicant): Diabetes remains a major risk factor for the development of both ischemic and non-ischemic cardiovascular disease (CVD); however, despite improvements in clinical treatments, our knowledge of the molecular underpinnings of diabetes-associated CVD is poorly understood. As with the majority of cardiovascular physiology, pathologic cardiovascular events exhibit a time-of-day-dependence, with regards to both onset and impact on disease progression and we have shown that the cardiomyocyte circadian clock directly influences the manner with which the heart responds to specific stressors. Importantly, we have shown that diabetes induces a phase shift in the cardiomyocyte circadian clock. Thus dysynchrony of the cardiomyocyte circadian clock may be an important and previously unrecognized contributor to the etiology of diabetic cardiomyopathy. Protein O-GlcNAcylation, a metabolically regulated post-translational modification that rapidly influences protein function, is increasingly recognized as a key regulator of both cardiac physiology and pathology including the adverse effects of diabetes. We recently reported that the cardiomyocyte circadian clock directly influences cardiac O-GlcNAc levels, that at least two circadian clock components are O-GlcNAc modified, and those acute increases in O-GlcNAc levels phase shifts the clock similarly to that seen in the heart during diabetes. We have also observed increased protein synthesis in the heart during the inactive phase, a time when protein O-GlcNAcylation is low. This has led us to postulate that protein O- GlcNAcylation may be a key mechanism by which the cardiomyocyte circadian clock temporally coordinates repair/replacement of damaged proteins in the heart. Collectively, these observations support the overall hypothesis of this proposal that dysregulation of protein O-GlcNAcylation is a critical factor contributing to diabetes-induced alterations of the cardiomyocyte circadian clock, and that misalignment of the cardiomyocyte circadian clock represents a key mechanism underlying diabetes-related cardiac dysfunction. To test this hypothesis we will pursue 3 specific aims: 1) Determine the molecular underpinnings linking the cardiomyocyte circadian clock with protein O-GlcNAcylation, and identify how this relationship is altered during diabetes; 2) Determine the role of O-GlcNAcylation in circadian clock mediated protein turnover, and elucidate how this relationship is modified during diabetes; 3) Determine whether re-alignment of the cardiomyocyte circadian clock during diabetes attenuates cardiomyopathy development. Successful completion of the proposed studies will lead to new fundamental insights regarding the molecular mechanisms underlying the role of aberrant circadian function in the development of diabetes-related cardiac disease and will help identify new approaches for reducing the risk of CVD in diabetic patients.