Metabolic crosstalks in regulation of beta-cell stress response and adaptation

摘要 葡萄糖代谢产生重要的信号，调节β细胞健康的几个方面，包括胰岛素 分泌、增殖、存活和分化。我们发现TCA循环酶丙酮酸 羧化酶（PC）促进调节胰岛素分泌的代谢信号， 通过促进尿素循环活性和从头谷胱甘肽（GSH）在β细胞应激缓解中的未被认可的作用 合成.这些PC导向的途径可以促进双重防御机制，从而一氧化氮（NO） 精氨酸的合成减少，因为精氨酸用于尿素生成，抗氧化能力增加 通过在面对糖尿病相关的应激刺激时重新合成GSH。这两条路径都接收来自 葡萄糖通过PC活性，并通过磷酸化的BAD，GK结合和激活蛋白调节 驱动着广泛的β细胞保护程序。 这项更新申请解决了源于这些发现的关键问题： 这种PC驱动的β细胞保护程序的机制组成部分，以及它们如何有助于β- 细胞团动力学我们将从两个方面来探讨这些问题。首先，我们将解剖下游 β-细胞保护所需的尿素循环途径的效应物。我们的预测是除了改变 尿素和NO产生之间的平衡，尿素循环活化提供生物合成中间体， 促进生长，包括鸟氨酸和多胺。我们还将研究葡萄糖是如何与这些 利用代谢组学和代谢追踪研究结合遗传学和药理学 这些途径的干扰。同样，我们将研究葡萄糖合成GSH的途径，以及这是如何发生的。 抗氧化机制因素PC介导的保护。然后我们将测试这些途径的相关性 在边缘团块胰岛移植模型中保护供体胰岛（目的1）。第二，我们将测试 这些途径对β细胞质量适应的贡献，以响应高脂饮食（HFD），使用两种 互补方法;用HFD治疗的β细胞特异性PC敲除小鼠模型，并评估其在小鼠体内的表达。 供体胰岛移植物对移植小鼠的（HFD）处理的反应（目的2）。 这些研究将提供连接磷酸化BAD，GK和PC激活的途径的综合图片 对β细胞应激反应和适应的影响。随着时间的推移，理解这些联系将产生 对捕获和模拟葡萄糖保护作用的最有效策略的宝贵见解 用于保存/恢复功能性β细胞团的信号传导。

Abstract Glucose metabolism generates important signals that regulate several facets of β-cell health, including insulin secretion, proliferation, survival, and differentiation. We have found that the TCA cycle enzyme pyruvate carboxylase (PC), which promotes metabolic signals that regulate insulin secretion, has previously unappreciated roles in β-cell stress mitigation by promoting urea cycle activity and de novo glutathione (GSH) synthesis. These PC-directed pathways can promote a dual defense mechanism, whereby nitric oxide (NO) synthesis from arginine is reduced as arginine is utilized for ureagenesis and antioxidant capacity is increased by de novo GSH synthesis in the face of diabetes-related stress stimuli. Both pathways receive input from glucose through PC activity and are modulated by phosphorylation of BAD, a GK binding and activating protein that drives a broad β-cell protective program. This renewal application addresses key questions that stem from these findings: What are the molecular mechanistic components of this PC-driven β-cell protective program and how do they contribute to β- cell mass dynamics? We will address these questions in two aims. First, we will dissect the downstream effectors of the urea cycle pathway that are required for β-cell protection. Our prediction is that beyond changing the balance between urea and NO production, urea cycle activation provides biosynthetic intermediates that promote growth, including ornithine and polyamines. We will also examine how glucose is connected to these pathways using metabolomics and metabolic tracing studies combined with genetic and pharmacologic perturbations of these pathways. Similarly, we will examine the route for glucose to GSH synthesis and how this antioxidant mechanism factors into PC-mediated protection. We will then test the relevance of these pathways in protecting donor islets in a marginal mass islet transplantation model (Aim 1). Second, we will test the contributions of these pathways to β-cell mass adaptation in response to high fat diet (HFD) using two complementary approaches; a β-cell-specific PC knockout mouse model treated with HFD and assessing the response of donor islet grafts to (HFD) treatment of transplanted mice (Aim 2). These studies will provide an integrated picture of the pathways connecting phospho-BAD, GK and PC activation to β-cell stress response and adaptation. In the fullness of time, understanding these connections will yield valuable insights into the most effective strategies to capture and mimic the protective aspects of glucose signaling for preservation/restoration of functional β-cell mass.