Macrophage AMPK, Inflammation, and Atherosclerosis

描述（由申请人提供）：代谢综合征是一系列代谢异常的集合，包括肥胖、胰岛素抵抗和动脉粥样硬化，慢性炎症是导致代谢异常的潜在机制。肥胖的炎症反应可由营养代谢的改变（如过量的脂质和修饰的脂蛋白颗粒）激活。本文提出的研究旨在确定营养代谢与炎症、动脉粥样硬化和胰岛素抵抗之间的细胞机制。amp活化蛋白激酶（AMPK）是一种进化保守的细胞能量传感器，调节脂质、胆固醇和葡萄糖代谢的代谢途径。在炎症刺激和营养丰富的条件下，如暴露于脂多糖（LPS）、游离脂肪酸（FFAs）、氧化低密度脂蛋白（oxLDL）颗粒和饮食诱导的肥胖，巨噬细胞和脂肪组织中的AMPK信号和表达会下调。此外，激活巨噬细胞AMPK信号显著抑制LPS、FFAs和oxldl诱导的炎症，以及巨噬细胞趋化和粘附，这是动脉粥样硬化发展的重要过程。这种作用主要通过巨噬细胞中的11AMPK亚型发挥作用。因此，总体假设是巨噬细胞AMPK是连接细胞营养代谢与炎症反应的关键信号分子，激活巨噬细胞AMPK可以通过抑制巨噬细胞炎症来预防动脉粥样硬化和胰岛素抵抗。巨噬细胞特异性过表达显性负（功能丧失）或组成性活性（功能获得）11AMPK（分别为DN-11和CA-11）的小鼠已被新生成，并将用于特异性确定巨噬细胞AMPK在对抗肥胖诱导的炎症、动脉粥样硬化和胰岛素抵抗中的作用。特异性目的1将利用巨噬细胞特异性CA-11或DN-11小鼠与LDL受体（LDLR）敲除小鼠杂交，确定巨噬细胞AMPK对动脉粥样硬化的保护作用。动脉粥样硬化的发展和巨噬细胞在早期和晚期疾病阶段对动脉粥样硬化病变的浸润将在这些小鼠的致动脉粥样硬化饮食中确定。特异性目的2将利用巨噬细胞特异性CA-11或DN-11小鼠，确定巨噬细胞AMPK对肥胖诱导的炎症和胰岛素抵抗的保护作用。胰岛素敏感性和脂肪组织炎症将被测定在这些小鼠中，无论是在食物或高脂肪饮食。完成这些研究将为肥胖及相关代谢综合征的研究提供新的视角。也就是说，AMPK作为细胞营养代谢和炎症之间的信号通路；激活巨噬细胞AMPK可显著抑制肥胖巨噬细胞炎症，对动脉粥样硬化和胰岛素抵抗均有保护作用；AMPK减少动脉粥样硬化和胰岛素抵抗的治疗作用可能是通过减少肥胖引起的炎症。

DESCRIPTION (provided by applicant): The metabolic syndrome is a collection of metabolic abnormalities, including obesity, insulin resistance and atherosclerosis, with chronic inflammation as a causative underlying mechanism. Inflammatory responses in obesity can be activated by altered nutrient metabolism (e.g. excess lipids and modified lipoprotein particles). The studies proposed here aim to determine cellular mechanisms linking nutrient metabolism to inflammation, atherosclerosis and insulin resistance. AMP-activated protein kinase (AMPK) is an evolutionally conserved cellular energy sensor that regulates metabolic pathways in lipid, cholesterol and glucose metabolism. AMPK signaling and expression are down-regulated in macrophages and adipose tissue by inflammatory stimuli and in nutrient-rich conditions, such as exposure to lipopolysaccharide (LPS), free fatty acids (FFAs), oxidized low- density lipoprotein (oxLDL) particles, and in diet-induced obesity. In addition, activation of macrophage AMPK signaling significantly suppresses LPS-, FFAs- and oxLDL-induced inflammation, as well as macrophage chemotaxis and adhesion, important processes in the development of atherosclerosis. This effect is exerted primarily through the 11AMPK isoform in macrophages. Therefore, the overall hypothesis is that macrophage AMPK is a key signaling molecule linking cellular nutrient metabolism to inflammatory responses, and activating macrophage AMPK protects against both atherosclerosis and insulin resistance through suppression of macrophage inflammation. Mice with macrophage-specific over-expression of dominant negative (loss-of- function) or constitutively active (gain-of-function) 11AMPK (DN-11 and CA-11, respectively) have been newly generated and will be used to determine specifically the role of macrophage AMPK in antagonizing obesity- induced inflammation, atherosclerosis and insulin resistance. Specific aim 1 will determine the protective effects of macrophage AMPK against atherosclerosis using macrophage-specific CA-11 or DN-11 mice crossed with LDL receptor (LDLR) knockout mice. The development of atherosclerosis and the infiltration of macrophages into atherosclerotic lesions at both early and more advanced disease stages will be determined in these mice on an atherogenic diet. Specific aim 2 will determine the protective effects of macrophage AMPK against obesity-induced inflammation and insulin resistance using macrophage-specific CA-11 or DN-11 mice. The insulin sensitivity and adipose tissue inflammation will be determined in these mice on either chow or high fat diet. Completing these studies will provide novel perspectives in the studying of obesity and associated metabolic syndrome. That is, AMPK serves as a signaling link between cellular nutrient metabolism and inflammation; activating macrophage AMPK significantly suppresses macrophage inflammation in obesity, which have protective effects on both atherosclerosis and insulin resistance; and the therapeutic effects of AMPK to reduce atherosclerosis and insulin resistance may be through reduction of obesity-induced inflammation.