Aberrant Circadian Regulation of Autophagy in the Heart During Diabetes

已经提出了许多机制作为糖尿病心肌病病因学的促成因素， 从神经体液失衡和细胞外重塑，到内在特性的扰动， 的心肌细胞。在后一种情况下，损害率的不平衡（例如，氧化的）和置换（即， 周转）的细胞成分（例如，蛋白质，线粒体）已经被牵连的发展， 糖尿病期间的心脏功能障碍。尽管许多研究已经调查了氧化应激增加的作用， 由于糖尿病患者的应激反应，人们对糖尿病如何损害受损细胞成分的周转知之甚少。 细胞成分的周转表现出显著的时间依赖性变化，这是由细胞内的 心肌细胞生物钟此外，心脏生物钟的遗传中断暂时中止 这些过程，导致扩张型心肌病的发展。内提出的有力证据 这一应用表明，自噬和线粒体自噬（线粒体的自噬）， 细胞成分的修复/替换在心脏中是昼夜节律调节的。我们的调查 心肌细胞昼夜节律钟进一步揭示了翻译后修饰，蛋白质O-GlcNAc化， 是生物钟机制的组成部分;这种关系的重要性在糖尿病（两种类型） 1和2），当心脏蛋白O-GlcNAc酰化慢性升高（继发于异常葡萄糖 代谢）与心脏内时钟的相移有关。因此，我们假设， 糖尿病期间时钟-O-GlcNAc关系的破坏导致 涉及细胞成分修复/替换的心脏过程。这些研究导致了 T2 DM期间心脏中时钟-O-GlcNAc关系慢性破坏假说 损害自噬/线粒体自噬的时间划分，最终损害细胞成分质量 控制导致收缩功能。为了检验这一假设，提出了三个具体目标。 目的1：证明心肌细胞生物钟调节细胞生物学质量控制， 通过自噬/线粒体自噬的转录和翻译后调节 介质（生理/机械目的）。目的2：证明时钟-O-的慢性中断 T2 DM期间的GlcNAc关系损害了细胞成分的质量控制， 自噬/线粒体自噬的时间划分（病理学目的）。目标3：展示这种行为- 和/或药理学介导的T2 DM期间时钟-O-GlcNAc关系的正常化 减缓心功能障碍的发展（治疗目的）。成功完成 拟议的研究将导致新的基本见解的因果作用，昼夜节律的破坏， 糖尿病性心肌病的病因，并将有助于确定创新的方法，以减少心脏病的风险， 糖尿病患者的功能障碍。

Numerous mechanisms have been proposed as contributing factors in the etiology of diabetic cardiomyopathy, ranging from neurohumoral imbalances and extracellular remodeling, to perturbations in the intrinsic properties of cardiomyocytes. In the latter case, imbalances in rates of damage (e.g., oxidative) and replacement (i.e., turnover) of cellular constituents (e.g., proteins, mitochondria) have been implicated in the development of cardiac dysfunction during diabetes. Although many studies have investigated the role of increased oxidative stress, little is known regarding how diabetes impairs the turnover of damaged cellular constituents. Turnover of cellular constituents exhibits a striking time-of-day-dependent variation, which is governed by the cardiomyocyte circadian clock. Moreover, genetic disruption of the clock in the heart temporally suspends these processes, leading to development of dilated cardiomyopathy. Compelling evidence presented within this application suggests that both autophagy and mitophagy (autophagy of mitochondria), processes critical in the repair/replacement of cellular constituents, are circadian regulated in the heart. Our investigation of the cardiomyocyte circadian clock further revealed that the posttranslational modification, protein O-GlcNAcylation, is integral to the clock mechanism; the importance of this relationship is highlighted during diabetes (both type 1 and 2), when chronic elevation of cardiac protein O-GlcNAcylation (secondary to aberrant glucose metabolism) is associated with a phase shift in the clock within the heart. We postulate therefore that disruption of the clock-O-GlcNAc relationship during diabetes causes temporal misalignment of cardiac processes involved in repair/replacement of cellular constituents. These studies have led to the hypothesis that chronic disruption of the clock-O-GlcNAc relationship in the heart during T2DM impairs temporal partitioning of autophagy/mitophagy, ultimately impairing cellular constituent quality control leading to contractile function. In order to test this hypothesis, three Specific Aims are proposed. Aim 1: Demonstrate that the cardiomyocyte circadian clock modulates quality control of cellular constituents through transcriptional and posttranslational regulation of autophagy/mitophagy mediators (Physiologic/Mechanistic Aim). Aim 2: Demonstrate that chronic disruption of the clock-O- GlcNAc relationship during T2DM impairs quality control of cellular constituents through attenuated temporal partitioning of autophagy/mitophagy (Pathologic Aim). Aim 3: Demonstrate that behavior- and/or pharmacologic- mediated normalization of the clock-O-GlcNAc relationship during T2DM attenuates development of cardiac dysfunction (Therapeutic Aim). Successful completion of the proposed studies will lead to new fundamental insights regarding the causal role of circadian disruption in the etiology of diabetic cardiomyopathy, and will help identify innovative approaches for reducing the risk of cardiac dysfunction in diabetic patients.