SERUM GAD65 AS A BIOMARKER OF ISLET INJURY, INSULITIS AND TRANSPLANT REJECTION

描述（由申请人提供）：自身免疫性糖尿病之前可能有一段长时间的沉默胰岛β细胞破坏。自身抗体检测有助于诊断和预测1型糖尿病，但不能确认或评估持续的胰岛细胞损伤。代谢试验仅显示广泛的胰岛损伤或移植后胰岛组织的免疫排斥反应。简而言之，仍然迫切需要持续的胰岛损伤和炎症（胰岛炎）的生物标志物。通过对比，在临床症状发作之前和之后对其他器官的损伤可以通过对排出的蛋白质的血清测定来检测和监测。针对GAD 65酶的自身抗体通常先于自身免疫性糖尿病的发作，有时提前许多年。GAD 65从培养的应激胰岛中释放。本申请的中心假设是β-细胞蛋白GAD 65的血浆测定将首次提供检测和监测进行中的β-细胞损伤的手段，所述进行中的β-细胞损伤例如发生在患有自身免疫性糖尿病的个体、患有无症状胰岛炎的个体和胰岛移植的接受者中。在初步工作的过程中，以测试这一假设，我们已经开发了什么是，据我们所知，唯一的生物标志物检测能够检测正在进行的胰岛损伤在体内。该项目的目的是表征GAD 65作为胰岛损伤的循环标志物的新发现的作用，并确定排出的GAD 65是否可以作为1型糖尿病胰岛炎和自身免疫的生物标志物。具体目标是：1.测定用高剂量和多个低剂量链脲佐菌素治疗的大鼠和糖尿病易感BB大鼠中糖尿病发作之前和发作时的循环GAD 65水平;和2.检验1型糖尿病受试者在疾病发作时或之前血浆GAD 65水平相对于对照组升高的假设。这些研究产生的数据将构成监测GAD 65出院的时间过程、触发因素和临床效用的进一步研究的基础。我们的长期目标是确定胰岛损伤的循环生物标志物，这将成为糖尿病相关研究和临床护理的重要工具。与公共卫生的相关性：能够检测糖尿病相关β细胞损伤的血清测定对于各种应用将是非常宝贵的，包括帮助识别预防性治疗的候选者，监测对研究性治疗的反应，评估胰岛毒性的药物，监测移植胰岛的排斥反应，以及研究人类和动物模型中胰岛损伤和自身免疫的触发因素和发病机制。

DESCRIPTION (provided by applicant): Autoimmune diabetes is likely preceded by an extended period of silent islet beta-cell destruction. Autoantibody assays aid in the diagnosis and prediction of type 1 diabetes but do not enable confirmation or assessment of ongoing islet cell damage. Metabolic tests reveal only extensive islet damage or immunological rejection of transplanted islet tissue after the fact. In short, there remains a critical need for biomarkers of ongoing islet injury and inflammation (insulitis). By way of contrast, damage to other organs, both prior to and after the onset of clinical symptoms, can be detected and monitored by serum assays for discharged proteins. Autoantibodies against the enzyme GAD65 often precede, sometimes by many years, the onset of autoimmune diabetes. GAD65 is released from cultured, stressed islets. The central hypothesis of this application is that a plasma assay for the beta-cell protein GAD65 will provide, for the first time, a means to detect and monitor ongoing beta-cell damage such as occurs in individuals with autoimmune diabetes, in individuals with asymptomatic insulitis, and in recipients of islet transplants. In the course of preliminary work to test this hypothesis, we have developed what is, to the best of our knowledge, the only biomarker assay capable of detecting ongoing islet damage in vivo. The objective of the project proposed here is to characterize the newly-found role of GAD65 as a circulating marker of islet injury and determine whether discharged GAD65 can serve as a biomarker of insulitis and autoimmunity in type 1 diabetes. The specific aims are: 1. To determine circulating GAD65 levels prior to and at the onset of diabetes in rats treated with high dose and multiple low-doses of streptozotocin and in diabetes-prone BB rats; and 2. To test the hypothesis that subjects with type 1 diabetes have increased plasma GAD65 levels relative to controls at the time of or prior to disease onset. Data generated by these studies will form the basis of further studies of the time-course, triggers and clinical utility of monitoring GAD65 discharge. Our long term objective is identification of circulating biomarkers of islet damage that will become important tools for diabetes-related research and clinical care. Relevance to Public Health: A serum assay capable of detecting diabetes-associated beta cell damage would be invaluable for a variety of applications, including helping identify candidates for preventative therapies, monitoring the response to investigational therapies, assessing drugs for islet toxicity, monitoring transplanted islets for rejection, and investigating the triggers and pathogenesis of islet damage and autoimmunity both in humans and in animal models.