A Novel Tool to Understand Insulin Production and Failure in Pancreatic beta-Cell

随着糖尿病患病率的增加，认识疾病进展的主要细胞和分子过程的需要变得更加迫切。越来越清楚的是，在2型糖尿病患者中，P细胞无法完全补偿以随时间推移维持正常。 3-细胞缺乏之前是一段时间，在这段时间中β-细胞仍然存活，但表现出胰岛素储存/分泌缺陷。内质网（ER）变得充满胰岛素原，而正常胰岛素的产生下降。在p细胞死亡之前的这个“黄金时期”特别令人感兴趣，因为它可能突出了可以在科学和治疗上攻击的可逆过程。目前流行的假说是胰岛素原错误折叠加剧3细胞功能障碍，最终降低胰腺胰岛素含量和3细胞质量。在秋田小鼠中，胰岛素原的点突变改变了其折叠，导致持续性先天性糖尿病，尽管从野生型等位基因（常染色体显性遗传）可获得丰富的非突变胰岛素原。在K99年，我开发了一种新的方法来研究活动物的胰岛素含量和3细胞质量，以及探索正常和错误折叠的胰岛素原之间的潜在相互作用。用中间区域绿色荧光蛋白（GFP）标记的人胰岛素原可以模拟细胞系以及称为hProins-CpepGFP的转基因小鼠系中天然胰岛素原的正常折叠、运输、加工和分泌。在ROO基金中，我正在研究一种新的模型，其中秋田突变直接引入hProins-CpepGFP转基因（顺式），以研究错误折叠的胰岛素原的命运。我还开发了携带GFP标记的秋田胰岛素原的新转基因小鼠系，其还携带消除配偶体（B7）游离巯基的额外点突变，以监测显性阴性糖尿病的发展。我计划针对瘦素受体缺陷db-/-小鼠培育hProinsC（A7）Y-CpepGFP系，以检查胰岛素原错误折叠和增加的胰岛素分泌需求之间的致病协同作用。这些研究将探索导致2型糖尿病的潜在可逆途径。

As the prevalence of Diabetes Mellitus increases, the need for recognizing the major cellular and molecular processes that underlie progression of the disease becomes more urgent. It is becoming increasingly clear that in patients with type 2 diabetes, P-cells are unable to fully compensate to maintain euglycemia overtime. 3-cell deficiency is preceded by a period in which p-cells are still viable but exhibit defective insulin storage/secretion. The endoplasmic reticulim (ER) becomes packed with proinsulin while production of normal insulin declines. This "golden period" before p-cell demise is of particular interest since it may highlight reversible processes that could be attacked both scientifically and therapeutically. A currently favored hypothesis is that proinsulin misfolding exacerbates 3-cell dysfunction, ultimately decreasing pancreatic insulin content and 3-cell mass. As in the Akita mouse, point mutations in proinsulin that alter its folding result in persistent congenital diabetes despite abundant nonmutant proinsulin available from wild-type alleles (autosomal dominant inheritance). In the K99 years, I have developed a novel approach to study insulin content and 3-cell mass in live animals, as well as to explore potential interactions between normal and misfolded proinsulin. Human proinsulin labeled with mid-region green fluorescent protein (GFP) can mimic the normal folding, trafficking, processing, and secretion of the native proinsulin in cell lines as well as in a transgenic mouse line called hProins-CpepGFP. In the ROO grant I am working on a new model in which the Akita mutation is introduced directly into the hProins-CpepGFP transgene (in cis) to study the fate of the misfolded proinsulin. I have also developed a new transgenic mouse line bearing GFP tagged Akita proinsulin that also bears an additional point mutation eliminating the partner (B7) free thiol group to be monitored for development of dominant negative diabetes. I plan to breed the hProinsC(A7)Y-CpepGFP line against Leptin receptor deficient db-/- mice in order to examine pathogenic synergies between proinsulin misfolding and increased insulin secretory demand. These studies will explore potentially reversible pathways leading to type 2 diabetes.