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

描述(申请人提供)：脂肪组织巨噬细胞(ATM)是脂肪组织基质细胞群的关键组成部分。随着肥胖，自动取款机在内脏脂肪中的数量增加，并在其炎症活动中经历质变。瘦小鼠的自动取款机是由2型自动取款机组成的，这些自动取款机具有低炎症能力，表达抗炎细胞因子IL-10。对于饮食诱导的肥胖，人群转变为以1型ATM为主的人群，这是一种独特的ATM类型，具有高炎症基因表达。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患者发生胰岛素抵抗所必需的。PI的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影响脂肪组织和新陈代谢。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这两种自动取款机。颁奖期间的工作表明，1型和2型自动取款机是由循环单核细胞的不同招募途径产生的。在我们的研究中，我们发现2型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不表达IL-10和MGL1。在初步实验中，我们检查了MGL1缺陷小鼠，并取得了令人惊讶的发现：通过饮食诱导的肥胖，它们可以免受葡萄糖耐量异常和胰岛素抵抗的影响。这种保护与这样一个事实有关，即MGL1在血液中炎性的7/4hi单核细胞上表达，这些单核细胞在肥胖的Mgl1/-小鼠中与对照组相比减少。这些观察表明，MGL1是一种新的受体，类似于CCR2和CX3CR1，调节炎症单核细胞的水平。这项提案的目的是描述MGL1如何调节肥胖症患者的单核细胞功能，以及这如何影响1型和2型ATM之间的平衡。我们将通过解决两个主要目标来阐明MGL1在单核细胞中的作用：(1)评估MGL1如何调节单核细胞在循环中的稳定性和滞留。我们将利用来自野生型和Mgl1-/-小鼠的过继单核细胞移植到瘦小和肥胖的受体中，以解决MGL1是维持血液中炎性单核细胞所必需的假说。单核细胞-内皮细胞黏附的体外模型将评估MGL1介导的细胞-细胞相互作用。(2)确定肥胖患者内脏脂肪组织中的MGL1配体。我们将使用亲和纯化方法，利用MGL1融合蛋白在脂肪组织中鉴定MGL1配体。总体而言，这项建议将在PI的K08奖的基础上扩展一个新的研究方向。R03的资金将支持PI在建立他的研究计划时的独立性。这些研究产生的数据将为更广泛的赠款申请奠定基础。 公共卫生相关性：肥胖症的炎症性变化对胰岛素抵抗和糖尿病的发展具有重要后果。许多这些炎性变化与巨噬细胞和单核细胞的激活有关，巨噬细胞和单核细胞是帮助直接免疫反应的炎性细胞。这项提议旨在扩大我们对一种新分子的理解，该分子指导这些肥胖单核细胞的激活。这项研究的结果可能会导致针对2型糖尿病的新疗法，旨在阻止肥胖引起的炎症。

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.