Circadian Clock and Beta Cell Stress Adaptation

描述（由申请人提供）：昼夜节律紊乱是现代生活方式的祸根，与糖尿病和代谢综合征密切相关。最近的人体研究也暗示b细胞功能障碍是代谢异常的重要组成部分。因此，了解生物钟和胰岛细胞功能调节之间的相互作用以保持胰岛素分泌从而预防糖尿病是非常必要的。我们先前已经表明，在小鼠中，通过缺失非冗余核心时钟基因Bmal 1，生物钟的遗传破坏导致胰岛细胞衰竭和糖尿病，继发于葡萄糖刺激的ATP产生受损、OXPHOS解偶联和葡萄糖刺激的胰岛素分泌受损（GSIS）。然而，对于神经细胞的适应性应激反应是否需要内在的神经细胞时钟，目前还不清楚.在初步的研究中，我们证明了由轮班工作模拟诱导的中枢时钟中断，在诱导未折叠蛋白反应（UPR）中表现为Bmal 1在B12细胞中的遗传中断，促凋亡基因CHOP的上调，暗示了在细胞中不可补救的ER应激。 细胞，并伴有受损的GSIS。重要的是，β细胞中Bmal 1缺失的小鼠由于β细胞衰竭而患糖尿病。令人惊讶的是，Rev-erbα（一种时钟功能的负调节因子和Bmal 1靶基因）的缺失导致了β细胞中类似的未折叠蛋白反应（UPR）诱导。我们还表明，ATF 4，一个关键的转录因子参与UPR，显示昼夜节律的表达，是Bmal 1的直接转录靶点。因此，我们假设内源性内质网细胞时钟调节因子Bmal 1和Rev-erbα通过转录控制其关键成分来协调适应性UPR通路，以减轻内质网应激。其主要目标是通过分子钟的遗传、环境和药理学调节来描述ER应激诱导的胰岛细胞功能障碍中的关键昼夜节律钟调节途径。我们将具体1。测试昼夜节律紊乱是否足以诱导ER应激和β细胞衰竭B，剖析中枢和外周时钟对ER应激和β细胞功能的不同作用。我们还将确定细胞自主作用的分子时钟ER压力在细胞2。确定Bmal 1和Rev-erbα在乳腺癌细胞中UPR和ER应激中的转录靶点。测试生物钟是否调节人类胰岛的ER应激适应性反应和胰岛素分泌反应。我们还将测试分子钟的药理学调节是否可以挽救糖尿病患者胰岛中的适应性应激信号。总的来说，拟议的研究将严格解决如何分子时钟调节ER压力和ER-细胞的稳态，并将导致新的见解昼夜节律钟调节适应性压力途径在ER-细胞。我们设想，这项研究的结果将导致发现靶向疗法，以调节生物钟功能，从而在对抗糖尿病时保护胰岛细胞功能。

DESCRIPTION (provided by applicant): Circadian disruption, the bane of modern lifestyle, has been strongly associated with diabetes and metabolic syndrome. Recent human studies also implicate b-cell dysfunction as a significant component of the metabolic abnormalities. It is, therefore, imperative to understand the interaction between the circadian clock and regulation of ß-cell function for the preservation of insulin secretion to prevent diabetes. We have shown previously that genetic disruption of the circadian clock, by deletion of Bmal1, a non-redundant core clock gene, in mice, leads to ß-cell failure and diabetes, secondary to impaired glucose-stimulated ATP production, uncoupling of OXPHOS and impaired glucose-stimulated insulin secretion (GSIS). However, whether the intrinsic ß-cell clock is required for adaptive stress responses in ß-cells is unknown. In preliminary studies, we demonstrate that central clock disruption induced by shift work simulation, phenocopies genetic disruption of Bmal1 in ß-cells in inducing Unfolded Protein Response (UPR), upregulation of the pro-apoptotic gene CHOP, suggestive of irremediable ER stress in ß-cells, and is accompanied by impaired GSIS. Importantly, mice with a deletion of Bmal1 in ß-cells become diabetic due to ß-cell failure. Surprisingly, deletion of Rev-erbα, a negative regulator of clock function and a Bmal1 target gene, leads to similar induction of unfolded protein response (UPR) in ß-cells. We also show that ATF4, a key transcription factor involved in UPR, displays circadian rhythmicity in expression and is a direct transcriptional target of Bmal1. We, hence, hypothesized that intrinsic ß-cell clock regulators, Bmal1 and Rev-erbα, coordinate the adaptive UPR pathway, through transcriptional control of its key components, to mitigate ER stress. The broad goal is to delineate key circadian clock-regulated pathways in ER stress-induced ß-cell dysfunction through genetic, environmental and pharmacological modulation of the molecular clock. We will specifically 1. Test if circadian disruption is sufficient to induce ER stress and ß-cell failure b dissecting the differential role of the central and peripheral clocks on ER stress and ß-cell function. We will also determine the cell-autonomous role of the molecular clock in ER stress in ß-cells 2. Define the transcriptional targets of Bmal1 and Rev-erbα in UPR and ER stress in ß-cells and 3. Test if the circadian clock regulates ER stress adaptive responses and insulin secretory response in human islets. We will also test if pharmacological modulation of the molecular clock can rescue adaptive stress signaling in diabetic patient islets. Collectively, the proposed studies will critically address how the molecular clock regulates ER stress and ß-cell homeostasis and will lead to novel insights into circadian clock regulated adaptive stress pathways in ß-cells. We envision that the results from this study will lead to discovery of targeted therapies to modulate circadian clock function for the preservation of ß-cell function in combating diabetes.