Circadian Regulation of Myocardial Insulin Signaling

描述（由申请人提供）：尽管临床治疗有所改善，但心血管疾病（CVD）仍然是美国死亡的主要原因。与多种常见疾病一样，CVD是复杂的基因-环境相互作用的产物，其中遗传信息内在地影响个体对环境刺激/应激的反应性。我们最近强调了心肌细胞昼夜节律钟作为细胞自主分子机制，其促进对各种刺激/应激的时间适当的心脏反应（例如，肾上腺素、脂肪酸、促肥大刺激）。生物钟机制的破坏，通过遗传（例如，时钟组分基因中的多态性）或环境（例如，轮班工作，睡眠和饮食行为调节）意味着，与人类CVD风险增加有关。最近，我们观察到扩张型心肌病（和寿命缩短）的发展，在小鼠心肌细胞限制性删除的昼夜节律钟转录因子BMAL 1（称为CBK小鼠）。转录组和生物信息学方法（在心脏病理学之前的年轻小鼠中）鉴定了9个推定的直接BMAL 1靶基因。随后的验证研究证实，BMAL 1直接与Pik 3r 1（PI 3 K的p85 β调节亚基）启动子中的多个E盒结合，导致对照心脏（而不是CBK）中该胰岛素信号传导组分的mRNA和蛋白水平的时间依赖性振荡。我们的初步研究还表明心肌细胞生物钟中断后心肌胰岛素信号传导受损，并且在Zucker糖尿病脂肪大鼠心脏（肥胖和2型糖尿病模型）中观察到的生物钟功能障碍通过一天中的时间依赖性限制喂养部分正常化。总的来说，这些观察使我们假设心肌细胞生物钟以一种时间依赖性的方式调节心肌胰岛素敏感性（通过调节p85 β），并且饮食诱导的肥胖症后生物钟功能障碍会破坏心肌胰岛素信号传导，从而导致收缩功能障碍。以下具体目的将检验该假设：1）确定心肌细胞昼夜节律钟是否调节心肌胰岛素信号传导和关键的胰岛素介导的过程（例如，代谢，自噬）; 2）通过测试功能障碍继发于p85 β降低的假设来确定BMAL 1缺陷心脏中心肌病的机制;和3）确定心肌细胞昼夜节律钟的正常化是否会减弱胰岛素抵抗小鼠模型中的心脏收缩功能障碍（即，饮食诱导的肥胖症）。这些研究的成功完成将有可能将心肌细胞生物钟确定为调节心肌胰岛素敏感性的一种新的内在机制，并为未来的转化研究提供基础 靶向心肌细胞生物钟用于预防和/或治疗肥胖症/糖尿病性心肌病。

DESCRIPTION (provided by applicant): Despite improvements in clinical treatments, cardiovascular disease (CVD) remains the primary cause of mortality in the United States. CVDs, as with multiple common diseases, are the product of a complex gene- environment interaction, wherein genetic information intrinsically influences the responsiveness of an individual to environmental stimuli/stresses. We have recently highlighted the cardiomyocyte circadian clock as a cell autonomous molecular mechanism that facilitates temporally-appropriate cardiac responses to various stimuli/stresses (e.g., epinephrine, fatty acids, pro-hypertrophic stimuli). Disruption of the circadian clock mechanism, through either genetic (e.g., polymorphisms in clock component genes) or environmental (e.g., shift work, sleep and eating behavior modulation) means, is associated with increased CVD risk in humans. Recently, we have observed development of dilated cardiomyopathy (and reduced lifespan) in mice following cardiomyocyte-restricted deletion of the circadian clock transcription factor BMAL1 (termed CBK mice). Transcriptome and bioinformatic approaches (in young mice, prior to cardiac pathology) identified 9 putative direct BMAL1 target genes. Subsequent validation studies confirmed that BMAL1 directly binds to multiple E- boxes in the Pik3r1 (p85� regulatory subunit of PI3K) promoter, resulting in time-of-day-dependent oscillations in mRNA and protein levels of this insulin signaling component in control, but not CBK, hearts. Our preliminary studies also suggest impaired myocardial insulin signaling following cardiomyocyte circadian clock disruption, and that circadian clock dysfunction observed in Zucker Diabetic Fatty rat hearts (an obesity and type 2 diabetes model) is partially normalized through time-of-day-dependent restricted feeding. Collectively, these observations have led us to hypothesize that the cardiomyocyte circadian clock modulates myocardial insulin sensitivity in a time-of-day-dependent manner (through regulation of p85�), and that dysfunction of the clock following diet-induced obesity disrupts myocardial insulin signaling, thereby contributing to contractile dysfunction. The following specific aims will test this hypothesis: 1) Determine whether the cardiomyocyte circadian clock modulates myocardial insulin signaling and critical insulin- mediated processes (e.g., metabolism, autophagy) in a time-of-day-dependent manner; 2) Determine the mechanism for cardiomyopathy in BMAL1 deficient hearts by testing the hypothesis that dysfunction is secondary to decreased p85�; and 3) Determine if normalization of the cardiomyocyte circadian clock will attenuate cardiac contractile dysfunction in a mouse model of insulin resistance (i.e., diet-induced obesity). Successful completion of the proposed studies will likely identify the cardiomyocyte circadian clock as a novel intrinsic mechanism that modulates myocardial insulin sensitivity, and provide a foundation for future translational studies targeting the cardiomyocyte circadian clock for obesity/diabetic cardiomyopathy prevention and/or treatment.