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

描述（由申请人提供）：自身免疫性糖尿病可能之前有一段较长时间的沉默的胰岛β细胞破坏。自身抗体检测有助于1型糖尿病的诊断和预测，但不能确认或评估正在进行的胰岛细胞损伤。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（胰岛素炎）的生物标志物。相比之下，在临床症状出现之前和之后，其他器官的损伤都可以通过对排出蛋白的血清测定来检测和监测。抗GAD65酶的自身抗体通常先于自身免疫性糖尿病的发病，有时早于多年。GAD65从培养的应激胰岛中释放。这项应用的中心假设是，血浆检测β细胞蛋白GAD65将首次提供一种检测和监测β细胞损伤的方法，例如发生在自身免疫性糖尿病患者、无症状胰岛素患者和胰岛移植患者中的β细胞损伤。在测试这一假设的初步工作过程中，据我们所知，我们开发了唯一一种能够检测体内正在进行的胰岛损伤的生物标志物测定方法。本项目的目的是表征GAD65作为胰岛损伤循环标志物的新发现，并确定排出的GAD65是否可以作为1型糖尿病胰岛素炎和自身免疫的生物标志物。具体目标是：1。在接受高剂量和多次低剂量链脲佐菌素治疗的大鼠和易患糖尿病的BB大鼠中，测定糖尿病发病前和发病时的循环GAD65水平；和2。为了验证1型糖尿病患者在发病时或发病前血浆GAD65水平相对于对照组升高的假设。这些研究产生的数据将为进一步研究监测GAD65排放的时间过程、触发因素和临床应用奠定基础。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的β细胞损伤的血清分析对于各种应用将是无价的，包括帮助确定预防性治疗的候选方案，监测对研究性治疗的反应，评估胰岛毒性药物，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.