Mechanisms of NAT2 Regulation of Insulin Resistance and Mitochondrial Dysfunction

NAT2调节胰岛素抵抗和线粒体功能障碍的机制

• 批准号: 10213015
• 负责人: Joshua Wiley Knowles
• 金额: $ 49.63万
• 依托单位: STANFORD UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-08-01 至 2024-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10213015
• 关键词: Acetylation; Adipocytes; Adipose tissue; Affect; Basal metabolic rate; Binding; Bioenergetics; Biogenesis; Blood Glucose; Body mass index; Bypass; Carcinogens; Cardiovascular Diseases; Cell Respiration; Cells; Clustered Regularly Interspaced Short Palindromic Repeats; Coculture Techniques; Code; Data; Defect; Endocrine; Energy Metabolism; Engineering; Fasting; Fatty acid glycerol esters; Generations; Genes; Genetic; Gluconeogenesis; Glucose Clamp; Grant; Hepatic; Hepatocyte; High Fat Diet; Human; Hypertriglyceridemia; Immune Response Genes; Impairment; In Vitro; Indirect Calorimetry; Insulin; Insulin Resistance; Intervention; Knockout Mice; Label; Link; Lipids; Lipolysis; Liver; Mass Spectrum Analysis; Measures; Mediating; Mediator of activation protein; Medium chain fatty acid; Membrane Potentials; Metabolic; Metabolism; Mitochondria; Molecular; Mus; Myoblasts; NAT1 gene; NMR Spectroscopy; Non-Insulin-Dependent Diabetes Mellitus; Orthologous Gene; Pathogenesis; Patients; Peroxidases; Pharmaceutical Preparations; Pharmacology; Phenotype; Plasma; Protein Acetylation; Publishing; RNA Interference; Reactive Oxygen Species; Resources; Role; Signal Transduction; Skeletal Muscle; Stress; Testing; Thermogenesis; Tissues; Transferase; Triglycerides; Variant; Wild Type Mouse; acylcarnitine; ascorbate; blood glucose regulation; cardiovascular risk factor; dietary; energy balance; exercise capacity; experimental study; fatty acid oxidation; genome wide association study; glucose uptake; in vivo; insulin regulation; insulin sensitivity; knock-down; mitochondrial dysfunction; mitochondrial membrane; novel; novel therapeutics; overexpression; oxidation; pandemic disease; protein protein interaction; risk variant; trait

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.

项目总结/摘要 胰岛素敏感性降低（胰岛素抵抗，IR）是2型糖尿病患者的基本异常， 糖尿病（T2 D）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联合 研究（GWAS）用于直接测量IR，并鉴定了一种新的IR基因，N-乙酰转移酶2（NAT 2）。非 NAT 2的同义编码变异与IR增加相关，与体重指数无关， 以及与IR相关的特征。小鼠直系同源基因Nat 1的敲低和过表达导致葡萄糖水平的变化 脂肪细胞和成肌细胞的内稳态。Nat 1缺陷小鼠（Nat 1 KO）胰岛素敏感性降低， 空腹血糖、胰岛素和甘油三酯升高。Nat 1与关键的线粒体基因高度共调节 基因和RNA干扰介导的Nat 1沉默导致线粒体功能障碍，其特征在于 细胞内活性氧和线粒体碎片增加， 线粒体膜电位、生物发生、质量、细胞呼吸和ATP生成。Nat 1 KO小鼠 基础代谢率和运动能力降低，而产热作用与野生型Nat 1相比没有改变 型（Nat 1 WT）小鼠。Nat 1 KO小鼠的血浆代谢物和脂质也发生变化，如降低 水平的酰基肉毒碱，和间接量热法数据显示，减少利用脂肪的能量，这表明 Nat 1缺乏与脂肪酸氧化受损有关（FAO）。新数据显示， 来自Nat 1缺陷肝细胞的上清液导致脂肪细胞中的IR。我们的总体假设是，Nat 1 结合并调节线粒体功能和肝脏能量平衡的关键介质， 使用我们独特的资源，包括肝脏特异性敲除小鼠（Nat 1 LKO），我们将测试 阐明了Nat 1缺乏引起胰岛素抵抗的机制。nat 1已知 乙酰化某些药物和致癌物，但内源性底物是未知的。目标1中的研究将 鉴定调节能量平衡的Nat 1蛋白-蛋白相互作用和Nat 1乙酰化底物， 新陈代谢.我们的假设是，Nat 1结合线粒体功能的关键调节因子。在目标2中，我们将定义 Nat 1缺陷中的特定线粒体缺陷。我们的假设是，Nat 1缺乏导致受损 FAO，这可以通过增加β-氧化来挽救。在目标3中，我们将定义本地和 Nat 1缺乏的全身性影响。Nat 1在肝脏中高度表达，在肝脏中表达较低。 胰岛素敏感组织。我们认为，肝脏Nat 1介导全身胰岛素敏感性， 通过影响脂肪和骨骼肌的信号传导中间体。我们将证实这一点 通过肝脏特异性Nat 1 KO的详细表型分析，包括正葡萄糖钳夹。我们还将确定 基于我们来自Nat 1的共培养数据，在Nat 1缺乏症中损害胰岛素敏感性的分泌因子 缺乏肝细胞和脂肪细胞。这些目标将确定新的IR基因的病理生理作用 Nat 1，从而增加我们对IR的理解，这是迈向新疗法的必要一步。