Circadian disruption-induced mitochondrial dysfunction in diabetes

昼夜节律紊乱与糖尿病和代谢综合征密切相关。最近的人类研究 提示β细胞功能障碍是昼夜节律性糖尿病风险增加的潜在机制， 破坏因此，必须了解生物钟和调节之间的相互作用， β细胞功能，以预防糖尿病。我们以前已经表明，生物钟的遗传破坏， 在小鼠中，非冗余核心时钟基因Bmal 1的缺失导致β细胞衰竭和糖尿病，继发于 葡萄糖刺激的ATP产生、解偶联和葡萄糖刺激的胰岛素分泌受损 （GSIS）。通常，β细胞需要“代谢灵活”，能够在能量底物之间切换 生产然而，尚不清楚生物钟是否调节β细胞中的这种代谢灵活性。我们的初步 数据表明，昼夜节律的破坏，即使是短期的，通过上调Pdk（丙酮酸 脱氢酶激酶），限制丙酮酸进入线粒体进行氧化，并诱导代谢 胰腺β细胞对葡萄糖的利用受损，导致糖尿病。总体 这一建议的假设是，生物钟协调β细胞中的代谢途径，以确保 有效的刺激-分泌偶联。我们实验室的新数据表明，昼夜节律紊乱会导致代谢紊乱， 在β-细胞中的不稳定性，其中它不能有效地利用葡萄糖。因此，我们假设昼夜节律 破坏导致线粒体功能受损，导致底物利用、代谢 导致β-细胞衰竭和糖尿病。我们将使用环境手段来诱导昼夜节律紊乱 在小鼠中，辅以诱导型和β细胞特异性基因缺失和分子过度表达模型， 时钟（Bmal 1和Rev-erb α）沿着分子时钟的药理学和遗传学调节， 提出的靶向途径，包括人类和小鼠胰岛中的Pdk，以测试β- 细胞衰竭与昼夜节律的破坏，特别是当它涉及到底物氧化。我们将使用 针对特定中断途径的药理学干预，以恢复昼夜节律中的代谢灵活性 破坏β细胞。该提案的具体目标是：（1）测试昼夜节律中断是否会导致线粒体 使用环境和遗传昼夜节律破坏模型， 并研究Rev-erb α-Pdk轴是否介导β细胞底物利用的昼夜节律调节。（二） 描述正常人β细胞中线粒体功能的昼夜节律钟调节和 使用正常人和糖尿病患者分子钟的功能丧失和获得研究的糖尿病状态 小岛(3)测试靶向药物干预以逆转昼夜节律破坏诱导的β细胞 线粒体功能障碍这项提案将破译β细胞衰竭的潜在机制与昼夜节律 破坏小鼠模型，测试它们在人类胰岛中的适用性，并研究靶向特定途径， 改善β细胞功能，从而导致预防和治疗糖尿病的疗法。

Circadian disruption has been strongly associated with diabetes and metabolic syndrome. Recent human studies implicate β-cell dysfunction as a potential mechanism underlying the increased risk for diabetes with circadian disruption. It is, therefore, imperative to understand the interaction between the circadian clock and regulation of β-cell function 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 β-cell failure and diabetes, secondary to impaired glucose-stimulated ATP production, uncoupling and impaired glucose-stimulated insulin secretion (GSIS). β-cells, normally, need to be “metabolically flexible” in being able to switch between substrates for energy production. However, it is unknown if circadian clock regulates this metabolic flexibility in β-cells. Our preliminary data suggests that circadian disruption, even for short periods, via an upregulation of Pdk (pyruvate dehydrogenase kinase), restricts pyruvate entry into mitochondria for oxidation and induces metabolic inflexibility, and impairment in glucose utilization by the pancreatic β-cells leading to diabetes. The overarching hypothesis for this proposal is that the circadian clock orchestrates the metabolic pathways in β-cells to ensure efficient stimulus-secretion coupling. New data from our lab indicates that circadian disruption leads to metabolic inflexibility in the β-cell wherein it is unable to utilize glucose effectively. We hence hypothesize that circadian disruption leads to impaired mitochondrial function resulting in impaired substrate utilization, metabolic inflexibility leading to β-cell failure and diabetes. We will use environmental means to induce circadian disruption in mice, complemented by inducible and β-cell specific genetic deletion and overexpression models of molecular clock (Bmal1 and Rev-erb alpha) along with pharmacological and genetic modulation of the molecular clock and the proposed target pathways including Pdk in human and mouse islets, to test mechanisms underlying the β- cell failure seen with circadian disruption, especially as it relates to substrate oxidation. We will use pharmacological interventions to target specific disrupted pathways to restore metabolic flexibility in circadian disrupted β-cells. The specific aims of the proposal are: (1) To test if circadian disruption leads to mitochondrial dysfunction and metabolic inflexibility in β-cells, using environmental and genetic circadian disruption models and investigate if Rev-erb alpha-Pdk axis mediate the circadian regulation of substrate utilization in β-cells. (2) To delineate circadian clock regulation of mitochondrial function in normal human β-cells and alteration in diabetic state using loss-of and gain-of-function studies of the molecular clock in normal and diabetic human islets. (3) Test targeted pharmacological interventions to reverse circadian disruption-induced β-cell mitochondrial dysfunction. This proposal will decipher the underlying mechanisms of β-cell failure with circadian disruption in mouse models, test their applicability in human islets and look at targeting specific pathways to improve β-cell function that lead to therapies to prevent and treat diabetes.