Characterizing the Dedifferentiating Beta Cell in Diabetes

项目摘要 在过去的几年里，肥胖和II型糖尿病的全球发病率惊人地上升。 几十年世界卫生组织现在估计有3.47亿人患有糖尿病，糖尿病- 在未来10年内，相关死亡人数将增加50%，成为第七大死亡原因。 糖尿病是胰腺β细胞衰竭，其中β细胞不能分泌足够的胰岛素来维持胰岛素分泌。 正常许多机制被认为是这种失败的原因，但最近， 去分化已被确定为小鼠、灵长类动物和人类的共同致病机制 糖尿病靶向去分化作为治疗措施是特别有吸引力的，因为去分化 理论上β细胞应该能够“再分化”。然而，去分化的原因 仍然未知。拟议的项目旨在研究细胞色素b5还原酶亚型3是否 （Cyb 5 r3）可以在这个过程中发挥作用。Cyb 5 r3被鉴定为在大肠杆菌中差异表达的转录本。 去分化β细胞此外，Cyb 5 r3的缺失与FoxO 1功能的降低有特异性联系， β细胞去分化的标志。最后，已知小鼠中相关同种型Cyb 5 r4的缺失导致 与胰岛素抵抗无关的早发性糖尿病。我的初步工作已经确定， Cyb 5 r3是FoxO 1的直接转录靶点，并且它是维持线粒体DNA完整性所必需的。 基础呼吸和葡萄糖刺激的体外胰岛素分泌。我假设Cyb 5 r3对正常的 β细胞在体内的功能，其损失有助于β细胞去分化。 因此，我将描述两个具体目标，旨在进一步描述Cyb 5 r3在以下方面的作用： β细胞首先，我建议通过建立Cyb 5 r3功能获得模型来证实我的初步数据， 我预测这将部分逆转糖尿病小鼠胰岛的胰岛素分泌缺陷。我也会研究如何 Cyb 5 r3功能丧失通过检测线粒体呼吸和胰岛素分泌来损害线粒体呼吸和胰岛素分泌 复杂函数第二，我正在培育缺乏Cyb 5 r3的小鼠，特别是在β细胞中， 命名为B-Cyb 5 r3 B-Cyb 5 r3小鼠将经历彻底的代谢表型（例如葡萄糖和胰岛素 耐受性试验、高血糖钳夹研究）以及胰岛的组织病理学和功能评估 和β细胞，我们希望这将揭示β细胞特异性的胰岛素分泌缺陷。总之，这 一套全面的实验不仅将大大有助于我作为一个科学家的发展， 也可能被证明对糖尿病的治疗有价值。

PROJECT SUMMARY The worldwide incidence of obesity and type II diabetes has risen alarmingly over the past few decades. The World Health Organization now estimates that 347 million people are diabetic, and that diabetes- related deaths will rise by 50% over the next 10 years, making it the 7th leading cause of death.1 A hallmark of diabetes is pancreatic beta cell failure, wherein beta cells are unable to secrete enough insulin to maintain normoglycemia. Many mechanisms have been suggested as the cause of this failure, but more recently, dedifferentiation has been identified as a common pathogenic mechanism in murine, primate, and human diabetes. Targeting dedifferentiation as a therapeutic measure is particularly attractive since dedifferentiating beta cells should theoretically be amenable to “redifferentiation.” However, the causes of dedifferentiation remain unknown. The proposed project seeks to examine whether cytochrome b5 reductase isoform 3 (Cyb5r3) can play a role in this process. Cyb5r3 was identified as a differentially expressed transcript in dedifferentiating beta cells. Moreover, loss of Cyb5r3 was specifically linked to decreased FoxO1 function, a hallmark of beta cell dedifferentiation. Finally, loss of the related isoform Cyb5r4 in mice is known to cause early-onset diabetes independent of insulin resistance. My preliminary work has already established that Cyb5r3 is a direct transcriptional target of FoxO1, and that it is required for the maintenance of mitochondrial basal respiration and glucose-stimulated insulin secretion in vitro. I hypothesize that Cyb5r3 is critical to normal beta cell function in vivo, and that its loss contributes to beta cell dedifferentiation. I will therefore describe two Specific Aims that seek to further characterize the role of Cyb5r3 in beta cells. First, I propose to corroborate my preliminary data by establishing a Cyb5r3 gain-of-function model, which I predict will partially reverse insulin secretory defects in diabetic mouse islets. I will also study how Cyb5r3 loss-of-function impairs mitochondrial respiration and insulin secretion by examining mitochondrial complex function. Second, I am generating mice lacking Cyb5r3 specifically in beta cells, a model I have termed “B-Cyb5r3.” The B-Cyb5r3 mice will undergo thorough metabolic phenotyping (e.g. glucose and insulin tolerance tests, hyperglycemic clamp studies), as well as histopathological and functional assessment of islets and beta cells, which we expect will reveal a beta cell-specific defect in insulin secretion. In summary, this comprehensive set of experiments will not only contribute significantly to my development as a scientist but may also prove valuable to the treatment of diabetes.