Role of 12-lipoxygenase and 12-HETE signaling in beta-cell dysfunction

在1型和2型糖尿病的背景下，胰岛β细胞功能和/或质量的缺陷是从葡萄糖耐量受损向明显糖尿病转变的中心。脂氧合酶（LOX）代表催化细胞多不饱和脂肪酸的氧合以在β细胞中形成脂质炎症介质的酶家族。12-LOX活性的类二十烷酸产物12-羟基二十碳四烯酸（12-HETE）在β细胞内施加炎症和氧化应激。然而，脂氧合酶生物学中的一个挑战是人类和小鼠在β细胞中表达不同的12-LOX同种型（分别由ALOX 12和Alox 15编码），每种同种型表现出不同的活性位点特征。该应用程序的优势在于多PI Drs. R。Mirmira（胰岛炎症通路专家）和R。Kulkarni（胰岛生长因子信号传导专家）和共同研究者J. Nadler（类花生酸生物学专家），他们将共同带来他们的专业知识和独特的试剂-包括敲除和人类基因敲入小鼠模型，显示人类同种型激活，人类12-LOX选择性抑制剂和原代人类细胞-承担12-LOX及其炎症产物的生物学。我们假设在胰岛素抵抗期间，β细胞中12-LOX的活化通过其下游产物12-HETE的受体介导的信号传导促进β细胞功能障碍。为了验证这一假设，我们提出了以下具体目标：目的1：阐明β细胞胰岛素抵抗与12-LOX活性和细胞功能障碍之间的分子机制。目的2：确定体内胰岛素抵抗背景下12-LOX活性对β细胞功能障碍的贡献。目的3：确定12-HETE受体GPR 31在介导12-LOX下游β细胞功能障碍中的作用。到目前为止，还没有研究人类12-LOX和12-HETE生物学的工具和试剂。该提案的主要影响将是为治疗靶向胰岛素抵抗/β细胞功能障碍中的人12-LOX途径的预期奠定基础，并确定12-HETE G蛋白偶联受体GPR 31中的潜在新靶点。

Deficiencies in islet β-cell function and/or mass are central in the transition from impaired glucose tolerance to frank diabetes in the setting of both type 1 and type 2 diabetes. The lipoxygenases (LOXs) represent a family of enzymes that catalyzes the oxygenation of cellular poly-unsaturated fatty acids to form lipid inflammatory mediators in β-cells. The eicosanoid product of 12-LOX activity, 12-hydoxyeicosatetraenoic acid (12-HETE), imposes inflammatory and oxidative stress within β cells. A challenge in lipoxygenase biology, however, is that humans and mice express different isoforms of 12-LOX in β cells (encoded by ALOX12 and Alox15, respectively), with each isoform exhibiting different active-site characteristics. The strength of this application is the collaborative effort between Multi-PIs Drs. R. Mirmira (an expert in islet inflammation pathways) and R. Kulkarni (an expert in growth factor signaling in the islet), and coinvestigator J. Nadler (an expert in eicosanoid biology), who will collectively bring their expertise and unique reagents—including knockout and human gene knock-in mouse models that show human isoform activation, human 12-LOX-selective inhibitors, and primary human cells—to bear on the biology of 12-LOX and its inflammatory products. We hypothesize that during insulin resistance the activation of 12-LOX in β-cells promotes β cell dysfunction through receptor-mediated signaling by its downstream product 12-HETE. To test this hypothesis, we propose the following specific aims: Aim 1: Elucidate the molecular mechanisms linking β-cell insulin resistance to 12-LOX activity and cellular dysfunction. Aim 2: Determine the contribution of 12-LOX activity to β cell dysfunction in the setting of insulin resistance in vivo. Aim 3: Determine the role of the 12-HETE receptor GPR31 in mediating β-cell dysfunction downstream of 12-LOX. Until now, tools and reagents to interrogate the biology of human 12-LOX and 12-HETE did not exist. The primary impact of this proposal will be to set the stage for the expectations of therapeutically targeting the human 12-LOX pathway in insulin resistance/β-cell dysfunction, and to identify a potential new target in the 12-HETE G protein-coupled receptor GPR31.