Paracrine Signaling by Kupffer Cells in Hepatic Insulin Resistance

 描述（由申请人提供）：该项目的总体长期目标是了解肥胖症中产生脂肪肝和肝脏胰岛素抵抗的机制，以及这两种现象之间的分子关系。我们试图解开的悖论，即肝脂肪变性是密切相关的胰岛素抵抗在人类，而这些途径可以清楚地在实验模型中分离。我们假设，这一矛盾可能会解决调查库普弗细胞作为介导的胰岛素抵抗在邻近肝细胞通过释放炎症细胞因子响应先天免疫受体和脂质传感器CD36和Msr1清道夫受体。新的证据表明，这些脂质传感器激活库普弗细胞中的炎性小体和NFkB通路，这提供了一种合理的机制，即肥胖症中的营养过剩可能导致肝脏炎症的激活。为了解决这个问题，我们开发了一种独特的葡聚糖封装的siRNA（GeRP）递送方法，以选择性地沉默巨噬细胞和枯否细胞中的基因，这些细胞特异性地存在于肝脏中，同时使其他组织中的肝细胞和巨噬细胞不受影响。用这种方法，我们可以选择性地探测库普弗细胞的贡献，肝细胞功能在体内的各种小鼠模型的肥胖。使用这种方法，我们将选择性地沉默枯否细胞NFkB p65、Nlrp3、TLR4共受体CD14、CD36和Msr1以及其他靶标，单独或组合，以破坏体内炎性因子的释放。将对这些小鼠进行代谢分析（葡萄糖耐量、胰岛素耐量、全身胰岛素敏感性、肝葡萄糖输出和其他代谢参数），以评估沉默枯否细胞炎症的全身效应。然后，我们将测试的假设，枯否细胞因子，调节全身代谢这样做的旁分泌信号，以邻近的肝细胞。我们还试图发现新的枯否细胞因子，破坏肝脏胰岛素敏感性使用深度测序，蛋白质组学和脂质组学方法。最后，我们将确定肝细胞内的哪些细胞内途径导致受损的肝细胞胰岛素信号传导，以响应枯否细胞因子。将在体内Kupffer细胞中GeRP介导的炎症通路沉默后评价候选物，如DAG、神经酰胺、JNK以及在无偏筛选中发现的新型信号传导组分。

 DESCRIPTION (provided by applicant): The overall long term goal of this project is to understand the mechanisms that generate fatty liver and hepatic insulin resistance in obesity, and the molecular relationships between these two phenomena. We seek to unravel the paradox whereby hepatic steatosis is tightly correlated with insulin resistance in humans, whereas these pathways can be clearly dissociated in experimental models. We hypothesize that this paradox may be solved by investigating Kupffer cells as mediators of insulin resistance in neighboring hepatocytes through their release of inflammatory cytokines in response to innate immune receptors and lipid sensors CD36 and Msr1 scavenger receptor. New evidence that these lipid sensors activate inflammasome and NFkB pathways in Kupffer cells provides a plausible mechanism whereby over-nutrition in obesity can lead to activation of liver inflammation. In order to attack this problem, we developed a unique glucan encapsulated siRNA (GeRP) delivery method to silence genes selectively in macrophages and Kupffer cells that reside specifically in liver, while leaving hepatocytes and macrophages in other tissues unaffected. With this method we can selectively probe Kupffer cell contributions to hepatocyte function in vivo in various mouse models of obesity. Using this approach we shall selectively silence Kupffer cell NFkB p65, Nlrp3, TLR4 co-receptor CD14, CD36 and Msr1 and other targets, alone and in combinations, to disrupt release of inflammatory factors in vivo. Metabolic profiling will be performed on these mice (glucose tolerance, insulin tolerance, systemic insulin sensitivity, hepatic glucose output and other metabolic parameters) to assess systemic effects of silencing Kupffer cell inflammation. We will then test the hypothesis that Kupffer cell factors that modulate whole body metabolism do so by paracrine signaling to neighboring hepatocytes. We also seek to discover novel Kupffer cell factors that disrupt hepatic insulin sensitivity using deep sequencing, proteomics and lipidomics approaches. Finally, we shall identify which intracellular pathways within hepatocytes cause impaired hepatocyte insulin signaling in response to Kupffer cell factors. Candidates such as DAG, ceramides, JNK as well as novel signaling components found in unbiased screens will be evaluated following GeRP-mediated silencing of inflammatory pathways in Kupffer cells in vivo.