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，并表现出糖耐量受损的迹象。使这一问题更加复杂的是，某些胰岛素致敏药物由于严重的健康并发症正在全球市场上暂停，使糖尿病前期和T2D患者的治疗选择更少。由于多组织功能障碍有助于糖尿病前期和进展为T2D，预防或逆转这些疾病需要多管齐下的方法。具体而言，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是胞外分泌蛋白的关键调节因子，是正常胰岛素分泌（胰岛β细胞）和正常葡萄糖摄取（骨骼肌）的外周胰岛素敏感性所必需的；DOC2B丰度的丧失与人类和啮齿动物胰岛和骨骼肌的糖尿病前期和T2D有关，DOC2B+/-小鼠更容易出现糖耐量受损。因此，长期目标是了解如何控制囊泡胞吐机制来预防和/或逆转前驱糖尿病并阻止其发展为T2D。最近发现的DOC2B在胞吐中的新功能，加上针对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和未开发的机会。本应用的目的是确定DOC2B富集如何在体内和分子水平上增强人体组织中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的上调可提高人T2D胰岛的功能，减少细胞因子诱导的凋亡，并保护小鼠免受糖尿病性刺激。此外，DOC2B在骨骼肌中发挥作用，增加胞吐蛋白之间重要复合物的形成，DOC2B的肽片段可以概括这一功能。核心假设是DOC2B分别对β细胞和骨骼肌中的胰岛素释放和葡萄糖摄取至关重要，并且DOC2B上调可以改善胰岛素/葡萄糖调节以预防或逆转前驱糖尿病。这项研究的基本原理是，一旦知道DOC2B富集如何保护葡萄糖稳态，就可以操纵DOC2B来预防或逆转前驱糖尿病。我们设计了两个特定目的来验证这一点：1)评估DOC2B富集在预防/逆转糖尿病刺激诱导的β细胞功能障碍和死亡中的作用；2)描述DOC2B富集在骨骼肌中如何促进胰岛素敏感性。我们将使用创新的诱导β细胞和骨骼肌特异性DOC2B转基因小鼠进行机制发现。我们还将测试增加DOC2B表达和功能的翻译方法，使用活细胞成像生物传感器与人体细胞/组织中的生化测定相结合。该结果将积极影响改善前驱糖尿病的努力，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.