Notch1-FoxO1 interaction in regulation of hepatic gluconeogenesis

描述(由申请人提供)： 肝脏葡萄糖产生(HGP)在空腹状态下提供对低血糖的暂时保护，因此，是一种适应性的生理机制，以满足无法以糖原形式储存足够能量的器官(即大脑)的葡萄糖需求。然而，过量的HGP是2型糖尿病患者胰岛素抵抗状态的病理标志，并导致高血糖。HGP是由含有Forkhead Box的亚家族O蛋白1(FoxOI)诱导的葡萄糖产生限速酶、葡萄糖-6磷酸酶(G6Pase)和磷酸烯醇式丙酮酸羧酸激酶(PEPCK)的转录所介导的。我们实验室以前的工作已经证明，FoxOI在物理上和功能上与RBP-JK相互作用，RBP-JK是Notch受体信号转导的转录效应器，在营养可获得性(Ins/FoxOI)和分化途径(Notch/RBP-JK)之间架起桥梁。在分化过程中，Notch家族的跨膜受体在配体依赖的细胞命运决定中的作用是众所周知的，但在发育的肝脏中，Notch信号的特征相对较少。我们的实验室已经证明，FoxOI是Notchi介导的分化诱导所必需的，这种诱导方式依赖于RBP和JK。我们假设类似的相互作用调节FoxOI依赖的代谢功能。在目标1中，我们将产生FoxOI/Notchi双杂合小鼠(F/N小鼠)，以避免Foxol或Notchi纯合子突变对胚胎的致死性。我们假设F/N小鼠将表现出基础胰岛素敏感性的增强和对饮食诱导的代谢紊乱的抵抗力，这可能是由于相对无法增加G6Pase和PEPCK的表达。在AIM2中，我们建议通过产生出生后肝脏特异的RBP-JK敲除，功能性地阻断Notch依赖的转录，来阐明Notch信号在成年肝组织中的代谢作用。 相关性：了解胰岛素抵抗的机制对于为越来越多面临与2型糖尿病相关的重大健康风险的患者开发新的治疗方案至关重要。通过对小鼠Notch通路的基因操作，我们希望提供证据表明抑制肝脏中的Notch信号可以改善血糖控制。

DESCRIPTION (provided by applicant): Hepatic glucose production (HGP) provides temporary protection from hypoglycemia in the fasted state, and as such, is an adaptive physiologic mechanism to provide for glucose needs of organs that are unable to store sufficient energy in the form of glycogen (ie, brain). Nevertheless, excessive HGP is a pathologic hallmark ofthe insulin-resistant state encountered in patients with type 2 diabetes and leads to hyperglycemia. HGP is mediated by Forkhead Box-containing, sub-family O protein 1 (FoxOI)-induced transcription of the rate-limiting enzymes in glucose production, glucose-6 phosphatase (G6Pase) and phosphoenolpyruvate carboxykinase (PEPCK). Previous work in our laboratory has demonstrated that FoxOI physically and functionally interacts with Rbp-Jk, the transcriptional effector of Notch receptor signalling, bridging nutrient availability (insulin/FoxOI) and differentiation pathways (Notch/Rbp-Jk) in a natural coupling. The role of the Notch family of transmembrane receptors in ligand-dependent cell-fate decisions during differentiation is well-established, but Notch signaling in developed liver is relatively uncharacterized. Our laboratory has shown that FoxOI is necessary for Notchi-mediated induction of differentiation, in a Rbp^Jk-dependent manner. We hypothesize that similar interactions regulate FoxOI dependent metabolic functions. In Aim 1, we will generate FoxOI/Notchi double-heterozygous mice (F/N mice) in order to circumvent the embryonic lethality of homozygous mutation of either Foxol or Notchi. We hypothesize that F/N mice will demonstrate increased basal insulin sensitivity and resistance to diet-induced metabolic derangements, likely due to a relative inability to increase G6Pase and PEPCK expression. In Aim2, we propose to elucidate the metabolic role of Notch signaling in adult liver tissue by generating a post-natal liver-specific knockout of Rbp-Jk, functionally ablating Notch-dependent transcription. Relevance: Understanding the mechanism of insulin resistance is critical to developing novel therapeutic options for the increasing numbers of patients who are at risk for the substantial health risks associated with type 2 diabetes. Through genetic manipulation ofthe Notch pathway in mice, we hope to provide evidence that inhibition of Notch signaling in liver can lead to improved glycemic control.