Role of monocyte/macrophage lectin receptors in obesity-induced inflammation

描述（由申请人提供）：脂肪组织巨噬细胞（ATMs）是脂肪组织基质细胞群的关键组成部分。随着肥胖，内脏脂肪中的atm数量增加，其炎症活性也发生质变。瘦小鼠的atm由低炎症能力的2型atm组成，表达IL-10，一种抗炎细胞因子。随着饮食引起的肥胖，人群转变为1型ATM占主导地位，这是一种具有高炎症基因表达的独特ATM类型。这些ATM亚型之间的平衡很重要，因为巨噬细胞介导的炎症已被证明是肥胖症胰岛素抵抗发展所必需的。PI K08奖的目标是研究1型和2型atm之间的平衡如何通过IL-10影响脂肪组织和代谢。在这些研究中，我们开发了新的技术，使我们能够区分和研究两种ATM类型。研究表明，1型和2型atm是由循环单核细胞的不同募集途径产生的。在我们的研究中，我们发现2型常驻atm同时表达IL-10和MGL1（巨噬细胞半乳糖型c型凝集素1），而1型atm则不表达。在初步实验中，我们检查了MGL1缺陷小鼠，并发现了令人惊讶的发现，即它们可以免受饮食性肥胖引起的葡萄糖耐受不良和胰岛素抵抗。这种保护作用与MGL1在血液中的炎性7/4hi单核细胞上表达有关，与对照组相比，肥胖MGL1 -/-小鼠的这些单核细胞减少。这些观察结果表明MGL1是一种新的受体，可以调节炎症单核细胞的水平，类似于CCR2和CX3CR1。本研究的目标是描述MGL1如何调节肥胖中的单核细胞功能，以及它如何影响1型和2型atm之间的平衡。我们将通过解决两个主要目的来阐明MGL1如何在单核细胞中发挥作用：(1)评估MGL1如何调节单核细胞在循环中的稳定性和保留。我们将利用野生型和Mgl1-/-小鼠的单核细胞过继转移到瘦型和肥胖受体，以解决Mgl1是维持血液中炎症单核细胞所必需的假设。单核细胞-内皮细胞粘附的体外模型将评估MGL1介导的细胞间相互作用。(2)肥胖症患者内脏脂肪组织中MGL1配体的鉴定。我们将使用亲和纯化方法，利用MGL1融合蛋白鉴定脂肪组织中的MGL1配体。总的来说，该提案将在PI的K08奖的基础上扩展一个新的研究方向。来自R03的资金将支持PI建立他的研究项目的独立性。从这些研究中产生的数据将为更广泛的拨款申请奠定基础。

DESCRIPTION (provided by applicant): Adipose tissue macrophages (ATMs) are a key component of the adipose tissue stromal cell population. With obesity, ATMs increase in number in visceral fat and also undergo qualitative changes in their inflammatory activity. ATMs in lean mice are comprised of Type 2 ATMs with low inflammatory capacity that express IL-10, an anti-inflammatory cytokine. With diet-induced obesity, the populations shifts to one where Type 1 ATMs predominates, a distinct ATM type with high inflammatory gene expression. The balance between these ATM subtypes is important since macrophage-mediated inflammation has been shown to be required for the develop insulin resistance in obesity. The goal of the PI's K08 award is to examine how the balance between Type 1 and Type 2 ATMs influences adipose tissue and metabolism via IL-10. During these studies, we developed novel techniques that allowed us to distinguish and study the two ATM types. Work during the award showed that Type 1 and Type 2 ATMs are generated by distinct recruitment pathways from circulating monocytes. In our studies, we discovered that Type 2 resident ATMs express both IL-10 and MGL1 (macrophage galactose-type c-type lectin 1) and Type 1 ATMs do not. In preliminary experiments, we examined MGL1 deficient mice and made the surprising finding that they are protected from glucose intolerance and insulin resistance with diet induced obesity. This protection is related to the fact that MGL1 is expressed on inflammatory 7/4hi monocytes in the blood and that these monocytes are decreased in obese Mgl1-/- mice compared to controls. These observations identify MGL1 as a novel receptor that regulates the levels of inflammatory monocytes similar to CCR2 and CX3CR1. The goal of this proposal is to delineate how MGL1 regulates monocyte function in obesity and how this influences the balance between Type 1 and Type 2 ATMs. We will elucidate how MGL1 functions in monocytes by addressing two primary aims: (1) To assess how MGL1 regulates monocyte stability and retention in the circulation. We will utilize adoptive transfer of monocytes from wild type and Mgl1-/- mice into lean and obese recipients to address the hypothesis that MGL1 is required for the maintenance of inflammatory monocytes in the blood. In vitro models of monocyte-endothelial cells adhesion will evaluate MGL1 mediated cell-cell interactions. (2) To identify MGL1 ligands in visceral adipose tissue in obesity. We will use affinity purification approaches to identify MGL1 ligands in adipose tissue using MGL1 fusion proteins. Overall, this proposal will expand upon a new research direction that has extended from the PI's K08 award. Funds from the R03 will support the independence of the PI as he builds his research program. Data generated from these studies will set the stage for a more expansive grant application. PUBLIC HEALTH RELEVANCE: Inflammatory changes in obesity have important consequences on the development of insulin resistance and diabetes. Many of these inflammatory changes relate to the activation of macrophages and monocytes, inflammatory cells that help direct immune responses. This proposal seeks to expand our understanding of a novel molecule that directs the activation of these monocytes with obesity. Results of this study could potentially lead to novel therapies for type 2 diabetes that are directed towards blocking obesity-induced inflammation.