Unravelling the regulatory mechanisms of rhythmic insulin secretion: A physiological role for UCP2?

在24小时周期内的葡萄糖耐量显示每日变化，这是由于胰岛细胞分泌胰岛素的能力的稳健和可预测的波动。目前，对24小时周期内节律性胰岛素分泌能力的调节知之甚少。我的研究的长期目标是确定调节胰岛素分泌的每日波动和最终24小时内葡萄糖稳态的机制途径，特别关注将代谢与胰岛素控制相结合的因素。解偶联蛋白2（UCP 2）在胰岛细胞中的表达与葡萄糖刺激的胰岛素分泌（GSIS）减少和基础胰岛素分泌（BIS）升高有关。虽然已经出现了一些关于UCP 2在胰岛细胞中的功能的假设，但这些研究中的大多数都使用了应激/疾病状态或超生理条件来评估UCP 2在胰岛细胞中的功能。UCP 2在健康胰岛细胞中的生理相关功能仍有待阐明。本发现基金的短期目标是通过检查UCP 2在调节胰岛素分泌的每日节律中的作用来确定UCP 2在健康胰岛细胞中的生理功能，确定UCP 2有助于控制胰岛素分泌的每日节律的机制，并探索驱动UCP 2表达的每日节律的生物节律。一般科学方法：我们的总体假设是，UCP 2在胰岛细胞中是动态的，并且是节律性胰岛素分泌和最终24小时内葡萄糖稳态的重要调节剂。将利用完善的基于细胞的和小鼠模型系统（分别为MIN 6细胞和UCP 2特异性敲除小鼠）进行研究，以确定胰岛素分泌能力的24小时节律、线粒体生物能量学、基因表达分析、葡萄糖耐量、血浆激素水平和活性氧类信号传导谱。将使用这些技术探讨UCP 2对GSIS和BIS每日周期的机制贡献。生物钟和摄食节律对UCP 2节律的影响也将被探索，以确定UCP 2每日节律背后的驱动力。预期意义：这项研究将使我们能够首次定义UCP 2在细胞中的相关生理功能，同时也为HQP创造了极好的训练机会。预计从本研究中获得的知识将为未来的研究铺平道路，以确定其他新的节律性胰岛素分泌调节剂，并最终扩大我们对胰岛素分泌调节和葡萄糖稳态的基本机制的理解，重要的是，允许追求我的研究计划的长期目标。

Glucose tolerance over a 24hr cycle displays daily variations due to robust and predictable fluctuations in the capacity of the ß cell to secrete insulin. Currently, very little is known about the regulation of rhythmic insulin secretory capacity over 24hr cycles. The LONG-TERM OBJECTIVES OF MY RESEARCH PROGRAM are define the mechanistic pathways that regulate daily fluctuations in insulin secretion and ultimately glucose homeostasis over 24hrs, with a particular focus on the factors that couple metabolism to the control of insulin. Uncoupling protein 2 (UCP2) expression in the ß cell is associated with reduced glucose-stimulated insulin secretion (GSIS) and elevated basal insulin secretion (BIS). While some hypotheses have emerged regarding the function of UCP2 in the ß cell, the majority of these studies have used either stressed/diseased states or supra-physiological conditions to assess UCP2 function in the ß cell. A physiologically relevant function for UCP2 in the healthy ß cells remains to be elucidated. The SHORT-TERM OBJECTIVES OF THIS DISCOVERY GRANT are to define a physiological function for UCP2 in healthy ß cells by examining its role in the regulation of daily rhythms of insulin secretion, to define a mechanism by which UCP2 contributes to the control of daily rhythms of insulin secretion, and to explore the biological rhythms that drive daily rhythms of UCP2 expression. GENERAL SCIENTIFIC APPROACH: Our overall HYPOTHESIS is that UCP2 in the ß cell is dynamic and is an important regulator of rhythmic insulin secretion and ultimately glucose homeostasis over 24hrs. Studies utilizing well-established cell-based and mouse model systems (MIN6 cells and a ß cell-specific UCP2 knockout mouse, respectively) will be performed to determine 24hr rhythms of insulin secretion capacities, mitochondrial bioenergetics, gene expression analyses, glucose tolerance, plasma hormone levels and reactive oxygen species signalling profiles. The mechanistic contribution of UCP2 to daily cycles of GSIS and BIS will be explored using these techniques. The impact of the circadian clock and feeding rhythms on rhythmic UCP2 will also be explored to determine the driving force behind daily rhythms of UCP2. EXPECTED SIGNIFICANCE: This study will allow us to define, for the first time, a relevant physiological function for UCP2 in the ß cell, while also creating excellent training opportunities for HQP. It is anticipated that the knowledge gained from this study will pave the way for future studies to define other novel regulators of rhythmic insulin secretion and ultimately broaden our understanding of the fundamental mechanisms of insulin secretion regulation and glucose homeostasis, and importantly, allowing pursuit of the long-term objectives of my research program.