Metabolically Coupled Ion Channel Interactions in Islets

描述（由申请人提供）：在2型糖尿病（T2DM）及其一级亲属以及该疾病的动物模型中，葡萄糖依赖性胰岛素分泌的脉搏性被破坏。虽然β细胞中功能失调的电和钙振荡可能导致胰岛素分泌不足，但这种振荡功能障碍的性质尚不清楚；正常β细胞振荡的机制也没有完全阐明。先前的研究支持胰岛β细胞固有的电振荡（EO）和代谢振荡（MO）之间复杂的相互作用导致分泌振荡的假设（“双振荡模型”；DOM）。使用新的实验范式获得的试点数据表明，代谢振荡可以主导电振荡器，与其他模型的预测不同，具有独特的时间过程，并且可以与钙解耦。基于这一进展，我们建议：检查EO和MO的性质，阐明EO和MO如何相互作用产生振荡，并测试双振子框架的有效性（目标1）；研究对DOM有贡献的其他离子机制，包括新型离子电流（目标2）；确定胰岛代谢振荡是糖酵解还是线粒体起源，并设计新的FRET探针和质谱方法来测量活胰岛细胞内燃料代谢物（Aim 3）；并确定双振荡器是否解释了正常人类胰岛或缺乏KCNQ1（一种与T2DM相关的β细胞钾通道）的小鼠的振荡特性；目标4)。这些目标的完成将代表迄今为止理解胰岛潜在振荡机制的最全面的努力，并将增加我们对健康和疾病中胰岛功能的了解。

DESCRIPTION (provided by applicant): The pulsatility of glucose-dependent insulin secretion is disrupted in Type 2 diabetics (T2DM) and their first-degree relatives, and in animal models of the disease. Although dysfunctional electrical and calcium oscillations in beta cells likely contribute to insulin secretory deficits, the nature of this oscillatory dysfunction is not known; nor have the mechanisms underlying normal beta cell oscillations been fully elucidated. Research conducted during the previous period supports the hypothesis that oscillations in secretion result from complex interactions between electrical (EO) and metabolic oscillators (MO) intrinsic to islet beta cells (the 'Dual Oscillator Model'; DOM). Pilot data obtained using a new experimental paradigm show that metabolic oscillations can dominate the electrical oscillator, have a distinctive time course unlike the predictions of other models, and can be decoupled from calcium. Building on this progress, we propose to: examine the properties of the EO and MO, elucidate how EO and MO interact to produce oscillations, and test the validity of the dual oscillator framework (Aim 1); investigate additional ionic mechanisms contributing to the DOM, including novel ion currents (Aim 2); determine whether islet metabolic oscillations are glycolytic or mitochondrial in origin, and design novel FRET probes and mass spectrometry approaches to measure intracellular fuel metabolites in living islets (Aim 3); and determine whether the dual oscillator accounts for the oscillatory properties of normal human islets or a mouse lacking KCNQ1, a putative beta cell potassium channel linked to T2DM; Aim 4). Completion of these aims will represent the most comprehensive effort to date to understand the underlying oscillatory mechanisms of pancreatic islets, and will increase our insight into islet function in both health and disease.