Mechanisms of NAT2 Regulation of Insulin Resistance and Mitochondrial Dysfunction

项目摘要/摘要 胰岛素敏感性降低(胰岛素抵抗，IR)是2型患者的基本异常 糖尿病(T2D)和心血管疾病(CVD)的主要危险因素。我们领导了一个全基因组的联合 并鉴定了一个新的IR基因--N-乙酰转移酶2(NAT2)。非- NAT2中的同义编码变体与IR增加相关，独立于体重指数，因为 以及与IR相关的特征。小鼠直系同源基因Nat1的敲除和过表达导致血糖变化 脂肪细胞和成肌细胞的动态平衡。Nat1缺陷小鼠(Nat1 KO)胰岛素敏感性降低， 空腹血糖、胰岛素和甘油三酯升高。Nat1与关键线粒体高度协同调节 基因和RNA干扰介导的Nat1沉默导致线粒体功能障碍 细胞内活性氧和线粒体碎裂增加以及减少 线粒体膜电位，生物发生，质量，细胞呼吸和三磷酸腺苷生成。Nat1KO小鼠 在基础代谢率和运动能力没有改变的情况下，与Nat1 Wild相比 (Nat1WT)型小鼠。Nat1KO小鼠也有血浆代谢物和血脂的变化，如 脂酰肉碱水平和间接量热法数据显示脂肪的能量利用率降低，这表明 Nat1缺乏与脂肪酸氧化受损有关(粮农组织)。新的数据表明， Nat1缺陷性肝细胞的上清液可导致脂肪细胞的IR。我们的总体假设是Nat1 最终结合并调节肝脏中线粒体功能和能量平衡的关键介质 导致IR。利用我们独特的资源，包括肝脏特异性基因敲除小鼠(Nat1 LKO)，我们将测试 这一假说并阐明了Nat1缺乏引起胰岛素抵抗的机制。Nat1已知 对某些药物和致癌物进行乙酰化，但内源性底物/S未知。目标1中的研究将 确定Nat1蛋白-蛋白质相互作用和Nat1乙酰化底物，调节能量平衡和 新陈代谢。我们的假设是，Nat1结合了线粒体功能的关键调节因子。在目标2中，我们将定义 Nat1缺乏症的特异性线粒体缺陷。我们的假设是，Nat1缺乏会导致身体受损 粮农组织认为，这可以通过加强β氧化来挽救。在目标3中，我们将定义本地和 纳豆素1缺乏症的系统效应。Nat1在肝脏中高度表达，在肝脏中表达较弱 胰岛素敏感组织。我们认为肝脏Nat1特异性地介导全身胰岛素敏感性。 通过对脂肪和骨骼肌起作用的信号中间体。我们会确认这一点的 通过肝脏特异性Nat1 KO的详细表型，包括正常血糖钳夹。我们还将确定 基于我们的Nat1共培养数据，在Nat1缺乏症患者中影响胰岛素敏感性的分泌因素 缺乏肝细胞和脂肪细胞。这些目的将定义新的IR基因的病理生理作用 Nat1，从而增加了我们对IR的理解，这是迈向新疗法的必要一步。

PROJECT SUMMARY/ABSTRACT Decreased insulin sensitivity (insulin resistance, IR) is a fundamental abnormality in patients with type 2 diabetes (T2D), and a major risk factor for cardiovascular disease (CVD). We led a genome wide association study (GWAS) for direct measures of IR and identified a novel IR gene, N-acetyl transferase 2 (NAT2). Non- synonymous coding variants in NAT2 were associated with increased IR independently of body mass index as well as IR-related traits. Knockdown and overexpression of the mouse ortholog Nat1 led to changes in glucose homeostasis in adipocytes and myoblasts. Nat1 deficient mice (Nat1 KO) had decreased insulin sensitivity and elevations in fasting blood glucose, insulin and triglycerides. Nat1 is highly co-regulated with key mitochondrial genes and RNA-interference mediated silencing of Nat1 leads to mitochondrial dysfunction characterized by increased intracellular reactive oxygen species and mitochondrial fragmentation as well as decreased mitochondrial membrane potential, biogenesis, mass, cellular respiration and ATP generation. Nat1 KO mice have a decrease in basal metabolic rate and exercise capacity without altered thermogenesis versus Nat1 wild type (Nat1 WT) mice. Nat1 KO mice also have changes in plasma metabolites and lipids, such as decreased levels of acylcarnitines, and indirect calorimetry data shows decreased utilization of fats for energy, suggesting that Nat1 deficiency is associated with an impaired fatty acid oxidation (FAO). New data indicate that supernatant from Nat1 deficient liver cells results in IR in adipocytes. Our overall hypothesis is that Nat1 binds to and regulates key mediators of mitochondrial function and energy balance in the liver ultimately leading to IR. Using our unique resources including a liver specific knockout mouse (Nat1 LKO), we will test this hypothesis and elucidate the mechanisms of insulin resistance caused by Nat1 deficiency. Nat1 is known to acetylate certain drugs and carcinogens but the endogenous substrate/s are unknown. Studies in Aim 1 will identify Nat1 protein-protein interactions and Nat1 acetylation substrates that regulate energy balance and metabolism. Our hypothesis is that Nat1 binds key regulators of mitochondrial function. In Aim 2 we will define the specific mitochondrial defects in Nat1 deficiency. Our hypothesis is that Nat1 deficiency causes impaired FAO and that this can be rescued by augmenting β-oxidation. In Aim 3 we will define mediators of local and systemic effects of Nat1 deficiency. Nat1 is highly expressed in the liver with more modest expression in insulin-sensitive tissues. We believe that hepatic Nat1 mediates whole body insulin sensitivity specifically through signaling intermediates that act through effects on adipose and skeletal muscle. We will confirm this through detailed phenotyping, including euglycemic clamp, of liver specific Nat1 KO. We will also identify secreted factors that impair insulin sensitivity in Nat1 deficiency building on our co-culture data from Nat1 deficient liver cells and adipocytes. These aims will define the pathophysiological role of the novel IR gene Nat1, thereby increasing our understanding of IR, which is a necessary step towards new therapies.