Amino acid sensing mechanisms in beta and alpha cells

项目总结/摘要 2型糖尿病（T2 D）的发病机制主要与β细胞缺陷有关，但也有证据表明， 指出胰高血糖素和α细胞功能在这种疾病中的主要贡献。小鼠中的累积数据 模型和人类表明，几种氨基酸（AAs），包括支链氨基酸（BCAA）和 芳香族氨基酸，已被报道与T2 D的风险有关。这些AA的增加是 与胰岛素分泌减少、胰岛素抵抗和胰岛素抵抗相关。在一起，这 有证据表明，支链氨基酸的升高可能提供了肥胖/胰岛素抵抗之间的机制联系， 以及β细胞和α细胞的适应性反应。然而，AA如何作用于代谢活性组织以增加 糖尿病的风险还不完全清楚。而AA对胰岛素和胰岛素受体的代谢偶联机制， 尽管已经探索了胰高血糖素分泌，但在理解细胞内AA传感如何 这些机制控制由AA在餐后或在胰岛素抵抗中诱导的β和α细胞应答。的 这个项目的长期目标是解开AA传感机制在β和α细胞中的作用， 和病理条件。实验数据已经确定，亮氨酸传感器Sestrin和精氨酸传感器 Castor会聚在GATOR 2复合物中以诱导mTORC 1信号传导的Rag依赖性激活。使用小鼠 通过在β和α中缺失Wdr 24（该复合物的组成部分）来破坏GATOR 2复合物 细胞证明GATOR 2在β和α细胞稳态中起关键作用，并调节胰岛素和 胰高血糖素分泌。这表明，在体内由GATOR 2途径介导的AA传感机制， 对协调β和α细胞中的AA反应至关重要。该应用程序的目标是建立在这些 观察和确定AA传感依赖途径如何调节生理学中的β和α细胞 和病理状态。我们假设AA对体内β和α细胞质量和功能的影响 主要由GATOR 2介导。为了验证这一假设，我们将确定AA传感机制 使用体内和体外研究的遗传方法调节β和α细胞的质量和功能， 小鼠和人类胰岛。在这些研究结束时，我们将有一个更好的了解如何AA可用性 调节β和α细胞的质量和功能，并决定GATOR 2发挥功能的程度 在体内仅作为亮氨酸和精氨酸传感机制。这些研究还将确定新的 在高血糖或高氨基酸血症状态下对营养过剩的适应机制。最后 目前的工作将提供更好的见解AA，特别是支链氨基酸如何增加糖尿病的风险。 了解β细胞和α细胞中AA传感的分子基础将对以下方面产生根本性的影响： 糖尿病，并提供可用于扩大糖尿病药物开发机会的信息。

Project Summary/Abstract The pathogenesis of type 2 diabetes (T2D) has been primarily linked to defects in beta-cells, but evidence also points to a major contribution of glucagon and alpha-cell function in this disease. Cumulative data in mouse models and humans show that several amino acids (AAs), including branched-chain amino acids (BCAAs) and aromatic amino acids, have been reported to be associated with the risk of T2D. The increase in these AAs is associated with reduced insulin secretion, insulin resistance, and glycemia in human cohorts. Together, this evidence suggests that elevation in BCAAs could provide a mechanistic link between obesity/insulin resistance and beta- and alpha- cell adaptive responses. However, how AAs act on metabolically active tissues to increase diabetes risk is not completely understood. While the metabolic coupling mechanisms of AAs on insulin and glucagon secretion have been explored, there is a gap in understanding of how intracellular AA sensing mechanisms control beta and alpha-cell responses induced by AAs after a meal or in insulin resistance. The long-term goal of this project is to unravel the role of AA sensing mechanisms in beta and alpha cells in normal and pathologic conditions. Experimental data have identified that the leucine sensor Sestrin and arginine sensor Castor converge in the GATOR2 complex to induce Rag-dependent activation of mTORC1 signaling. Using mice with disruption of GATOR2 complex by deletion of Wdr24 (integral component of this complex) in beta and alpha cell demonstrates that GATOR2 plays a key role in beta and alpha cell homeostasis and regulates insulin and glucagon secretion. This suggests that AA sensing mechanisms mediated by GATOR2 pathways in vivo are crucial for coordinating AA responses in beta and alpha cells. The objective of this application is to build on these observations and determine how AA sensing dependent pathways regulate beta and alpha cells in physiology and pathological states. We hypothesize that the effects of AAs on beta and alpha cell mass and function in vivo are mediated mainly by GATOR2. To test this hypothesis, we will determine how AA sensing mechanisms regulate beta and alpha-cell mass and function using genetic approaches in vivo as well as ex vivo studies in mouse and human islets. At the end of these studies we will have a better understanding of how AA availability regulates beta and alpha cell mass and function and determine the extent to which GATOR2 functions exclusively as a leucine and arginine sensing mechanism in vivo. These studies will also identify novel mechanisms of adaptation to nutrient excess in states of hyperglycemia or hyper aminoacidemia. Finally, the current work will provide better insights into how AAs and in particular BCAAs increase diabetic risk. Understanding the molecular basis for AA sensing in beta and alpha cells will have a fundamental impact in diabetes and provide information that can be used to expand drug development opportunities for diabetes.