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

在1型和2型糖尿病患者中，胰岛β细胞功能和/或质量的缺陷是从糖耐量受损向普通糖尿病转变的核心。脂氧合酶(LOX)是一类催化细胞内多不饱和脂肪酸氧化，在β细胞中形成脂质炎症介质的酶家族。12-脂氧合酶活性的二十烷类产物，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，人和小鼠在β细胞中表达不同的12-LOX亚型(分别由ALOX12和ALOX15编码)，每种亚型都表现出不同的活性部位特征。这项应用的优势是多PI Dr.R.Mirmira博士(胰岛炎症途径专家)和R.Kulkarni博士(胰岛生长因子信号转导专家)和合作研究员J.Nadler(二十烷类生物学专家)的合作努力，他们将共同带来他们的专业知识和独特的试剂-包括显示人类异构体激活的基因敲除和人类基因敲入小鼠模型、人类12-LOX选择性抑制物，以及原代人类细胞-来研究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的激活通过其下游产物12-HETE的受体介导的信号转导促进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：探讨12-脂氧合酶活性在体内胰岛素抵抗时β细胞功能障碍中的作用。目的3：确定12-羟色胺受体GPR31在介导12-LOX下游β细胞功能障碍中的作用。到目前为止，还没有工具和试剂来询问人类12-LOX和12-HETE的生物学。这项提议的主要影响将是为预期在治疗上靶向人类12-LOX途径治疗胰岛素抵抗/β细胞功能障碍奠定基础，并在12-HETE G蛋白偶联受体GPR31中确定一个潜在的新靶点。

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.