DOC2B-based therapeutics for prevention/remediation of type 2 diabetes

2型糖尿病(T2D)困扰着近10%的美国人口；令人震惊的是，还有8600万人患有前驱糖尿病，并显示出糖耐量受损的迹象。使这一问题雪上加霜的是，由于严重的健康并发症，某些胰岛素敏感型药物正在全球市场暂停销售，使糖尿病前期患者和T2D患者的治疗选择更少。由于多组织功能障碍导致糖尿病前期和发展为T2D，预防或逆转这些疾病需要多管齐下的方法。具体地说，胰腺β细胞功能障碍和骨骼肌胰岛素抵抗是人类糖尿病前期和T2D的主要特征。DOC2B是胞吐蛋白的关键调节因子，对于正常的胰岛素分泌(从胰岛β细胞)和外周胰岛素敏感性(在骨骼肌中)是必需的；DOC2B丰度的丧失与人和啮齿动物的胰岛和骨骼肌中的糖尿病前期和T2D有关，并且DOC2B+/-小鼠更容易受到糖耐量受损的影响。因此，长期目标是了解如何操纵囊泡胞吐机制来预防和/或逆转前驱糖尿病并阻止进展为T2D。最近发现的DOC2B在胞吐作用中的新功能，加上靶向DOC2B丰度和/或利用其组织特异性功能来控制血糖失调的新方法，为疾病干预提供了一个诱人的、尚未开发的机会。这项应用的目的是在体内和分子水平上确定DOC2B富集物如何在人体组织中增强β细胞胰岛素分泌和骨骼肌胰岛素敏感性。初步数据显示，β细胞中DOC2B的上调增加了人T2D胰岛的功能，减少了细胞因子诱导的细胞凋亡，并保护小鼠免受糖尿病刺激。此外，DOC2B在骨骼肌中的功能是增加胞吐蛋白之间重要的复合体的形成，DOC2B的一个肽片段可以概括这一功能。核心假设是DOC2B对β细胞的胰岛素释放和骨骼肌的葡萄糖摄取分别是必不可少的，并且DOC2B的上调可以改善胰岛素/葡萄糖调节，以预防或逆转糖尿病前期。这项拟议研究的基本原理是，一旦知道DOC2B浓缩是如何保护葡萄糖稳态的，就可以操纵DOC2B来预防或逆转糖尿病前期。我们设计了两个特定的目的来测试这一点：1)评估DOC2B在预防/逆转糖尿病刺激诱导的β细胞功能障碍和死亡中的作用，以及2)描述DOC2B在骨骼肌中的丰富如何促进胰岛素敏感性。我们将使用创新的可诱导的β细胞和骨骼肌特异的DOC2B转基因小鼠进行机械发现。我们还将在人类细胞/组织中使用活细胞成像生物传感器和生化分析来测试提高DOC2B表达和功能的翻译方法。这一结果将对改善糖尿病前期的努力产生积极影响，因为已确定的机制极有可能提供新的治疗策略。

Type 2 diabetes (T2D) plagues nearly 10% of the US population; a shocking 86 million more have prediabetes, and show signs of impaired glucose tolerance. Compounding this problem, certain insulin-sensitizing drugs are undergoing global market suspensions due to severe health complications, leaving prediabetic and T2D patients with fewer treatment options. Because multi-tissue dysfunction contributes to prediabetes and progression to T2D, prevention or reversal of these diseases requires a multi-pronged approach. Specifically, pancreatic β-cell dysfunction and skeletal muscle insulin resistance are primary features of human prediabetes and T2D. DOC2B, a key regulator of exocytosis proteins, is required for normal insulin secretion (from islet β-cells) and peripheral insulin sensitivity for normal glucose uptake (in skeletal muscle); loss of DOC2B abundance is associated with prediabetes and T2D in human and rodent islets and skeletal muscle, and DOC2B+/- mice are more susceptible to impaired glucose tolerance. Thus, the long-term goal is to understand how vesicle exocytosis mechanisms can be manipulated to prevent and/or reverse prediabetes and halt the progression to T2D. Recent discoveries of new functions of DOC2B in exocytosis, plus new methods to target DOC2B abundance and/or capitalize on its tissue-specific functions to control glycemic dysregulation, offer an enticing and untapped opportunity for disease intervention. The objective of this application is to determine how DOC2B enrichment enhances β-cell insulin secretion and skeletal muscle insulin sensitivity in human tissues, in vivo, and at the molecular level. Preliminary data show that DOC2B upregulation in β-cells increases the function of human T2D islets, diminishes cytokine-induced apoptosis, and protects mice from diabetogenic stimuli. Moreover, DOC2B functions in skeletal muscle to increase vital complex formation amongst exocytosis proteins, and a peptide fragment of DOC2B can recapitulate this function. The central hypothesis is that DOC2B is essential for insulin release and glucose uptake in β-cells and skeletal muscle, respectively, and that DOC2B upregulation can improve insulin/glucose regulation to prevent or reverse prediabetes. The rationale for the proposed research is that once it is known how DOC2B enrichment protects glucose homeostasis, DOC2B can be manipulated to prevent or reverse prediabetes. Two Specific Aims are designed to test this: 1) Evaluate DOC2B enrichment in the prevention/reversal of diabetogenic stimuli-induced β-cell dysfunction and demise, and 2) Delineate how DOC2B enrichment in skeletal muscle promotes insulin sensitivity. We will use innovative inducible β-cell- and skeletal muscle-specific DOC2B transgenic mice for mechanistic discovery. We will also test translational approaches for increasing DOC2B expression and function, using live-cell imaging biosensors paired with biochemical assays in human cells/tissues. The results will positively impact efforts to ameliorate prediabetes as the identified mechanisms are highly likely to provide new therapeutic strategies.