Beta Cell Adaptation to Stress in Baboon Pancreas After Partial Pancreatectomy

描述(申请人提供)：胰岛淀粉样胰多肽(IAPP)在朗格汉斯的胰岛沉积是人类2型糖尿病胰腺的特征，但代表着很早以前就开始的过程的最后阶段。最近的证据表明，淀粉样多肽的细胞毒性不是在光学显微镜下可见的沉积中产生的，而是来自细胞内的纤维聚集体和作为非选择性离子通道的可溶低聚物。有毒的IAPP纤维和寡聚体与阿尔茨海默病(AD)相关的淀粉样蛋白(A)纤维和寡聚体具有共同的结构，表明2型糖尿病(T2 DM)和AD的发病机制相似。此外，胰腺细胞表达高水平的AD相关多肽，T2 DM经常与AD相关。非人灵长类动物是研究致淀粉样多肽在细胞失代偿中作用的理想模型，因为非人类灵长类动物会自发发生胰岛淀粉样变性和T2 DM，这与人类非常相似。我们的具体目标是：(1)研究胰岛素敏感(IS)和胰岛素抵抗(IR)狒狒的细胞功能、形态和超微结构；(2)检测胰岛素分泌需求急剧增加(通过部分胰腺切除(PPX)实现的)对正常糖耐量(NGT)和IR狒狒的细胞功能、形态和超微结构(尤其是IAPP和A)的影响；(3)观察不同治疗干预措施对防止PPX诱导的细胞失代偿的影响；(4)检验A代谢和谷氨酸转运体(GLT-1)活性异常可能导致 (5)研究IAPP和A在体内(PPX前和PPX后)、体外细胞系和离体猴胰岛诱导的细胞毒作用的分子机制。重点将放在淀粉样变和内质网(ER)应激、胰岛素信号(胰岛素受体底物-2，IRS-2)和降解(胰岛素降解酶，IDE)，以及谷氨酸运输(GLT-1)和代谢(产生-氨基丁酸，GABA)；(6)研究埃塞那肽在体内和体外有益于细胞扩张/新生和存活的分子机制，特别是IAPP-和 A？诱导的细胞毒性和内质网应激，胰岛素信号和降解，以及谷氨酸运输和代谢。了解狒狒体内淀粉样蛋白沉积和细胞死亡的分子机制可以为新的治疗方法提供理论基础。与公共卫生相关：我们的项目旨在：1)阐明在一种新型的非人灵长类肥胖和2型糖尿病动物模型--狒狒中，胰岛素产生的胰腺细胞适应增加的代谢需求的生理和分子机制，以及旨在保护胰岛素产生细胞的新疗法的效果；2)阐明朗格汉斯和贝塔细胞系的狒狒胰岛中产生胰岛素的胰腺异常蛋白质沉积和细胞死亡的细胞和分子机制，以及旨在防止这种现象的新疗法的效果。鉴于这种非人类灵长类动物与人类具有极高的遗传相似性，以及剖析产生胰岛素的细胞死亡的新分子机制以及一些药物可以防止它的机制的可能性，这些研究将使我们能够发现新的治疗方法，以防止受2型糖尿病影响的患者产生胰岛素的胰腺细胞丢失。

DESCRIPTION (provided by applicant): Deposition of islet amyloid pancreatic polypeptide (IAPP) in the islets of Langerhans is the characteristic feature of human type 2 diabetic pancreas but represents the final stage of a process started long before. Recent evidence suggests that ¿-cell toxicity of amyloidogenic peptides results, not in the deposits visible by light microscopy, but rather from intracellular fibril aggregates and soluble oligomers that act as non-selective ion channels. Toxic IAPP fibrils and oligomers share a common structure with Alzheimer Disease (AD)-related ¿-amyloid (A¿) fibrils and oligomers, suggesting a similar pathogenesis of type 2 diabetes mellitus (T2DM) and AD. Moreover, pancreatic ¿-cells express high levels of AD-related peptides, and T2DM is frequently associated with AD. Non human primates (NHPs) represent ideal models to study the role of amyloidogenic peptides in ¿-cell decompensation, because NHPs spontaneously develop islet amyloidosis and T2DM very similarly to humans. Our specific aims are: (1) to study ¿-cell function, morphology, and ultrastructure in insulin sensitive (IS) and insulin resistant (IR) baboons; (2) to examine the effects of an acute increase in insulin secretory demand (achieved by partial pancreatectomy, PPx) on ¿-cell function, morphology and ultrastructure (with particular emphasis on IAPP and A¿) in normal glucose tolerant (NGT) IS and IR baboons; (3) to examine the effects of different therapeutic interventions aimed at preventing PPx-induced ¿-cell decompensation; (4) to test the hypothesis that abnormal A¿ metabolism and glutamate transporter (GLT-1) activity may induce ¿-cell death; (5) to study the molecular mechanisms responsible for IAPP- and A¿-induced cytotoxicity in vivo in the baboon pancreas (prior and after PPx) and in vitro in ¿-cells lines and isolated baboon islets. Particular emphasis will be placed in amyloidogenesis, and endoplasmic reticulum (ER) stress, insulin signaling (insulin receptor substrate-2, IRS-2) and degradation (insulin degrading enzyme, IDE), and glutamate transport (GLT- 1) and metabolism (production of ?-aminobutyric acid, GABA); (6) to study the molecular mechanisms responsible for the beneficial effect of Exenatide on ¿-cell expansion/neogenesis and survival in vivo and in vitro with particular emphasis on IAPP- and A¿-induced cytotoxicity and ER stress, insulin signaling and degradation, and glutamate transport and metabolism. Understanding the molecular mechanisms of amyloid deposition and ¿-cell death in the baboon could provide the rationale for the novel therapeutic approaches. PUBLIC HEALTH RELEVANCE: Our project is aimed at: 1) Clarifying the physiological and molecular mechanisms of adaptation to increased metabolic demand of insulin-producing pancreatic cell in a novel non-human primate model of obesity and type 2 diabetes, the baboon, and the effect of new therapies aimed at the protection of insulin producing cells, 2) clarifying the cellular and molecular mechanisms underlying abnormal protein deposition and cell death in insulin-producing pancreatic in baboon islets of Langerhans and beta cell lines and the effect of new therapies aimed at preventing this phenomenon. Given the extremely high genetic similarity of this non human primate to humans and the possibility to dissect novel molecular mechanisms of insulin producing cell death as well as the mechanisms by which some drugs could prevent it, these studies will allow us to discover new treatments to prevent the loss of insulin-producing pancreatic cells in patients affected by type 2 diabetes mellitus.