Them1-Mediated Metabolic Regulation and Pathogenic Role in NAFLD

项目摘要/摘要 肥胖引起的胰岛素抵抗是非酒精性脂肪性肝病(NAFLD)发病机制的核心。 这项研究提案解决了一个悬而未决的问题，即正常情况下 促进节能，变得不适应，并为NAFLD做出贡献。这样做的长期目标是 研究是为了了解细胞脂分子和新陈代谢之间的调节关系， 尤其是当它们提供治疗机会的时候。这项研究的目的是了解 能量平衡和营养代谢调节的基本机制。我们的中央 假设Them1通过限制棕色和米色脂肪组织的产热来节约能量 通过它作为一种降低脂肪酸氧化速率的脂调节酶和作为一种 转录辅助调节因子。在肥胖症中，我们假设Them1变得不适应。除了限制 生热脂肪组织能量消耗，高脂饮食诱导肝脏Them1上调 脂肪变性和过度的糖异生以及白色脂肪组织中的炎症和胰岛素抵抗。这个 这项拟议研究的理由是，Them1限制能源支出的机制，而 促进肝脏脂肪变性和胰岛素抵抗，将揭示治疗高血压的具体新靶点 NAFLD。在广泛的初步数据的指导下，中心假设将在三个具体目标下进行检验：1) 定义Them1促进肥胖和NAFLD的适应不良机制；2)确定 Them1抑制产热的细胞机制；3)阐明Them1的调控 活性由脂质结合的起始域决定。在目标1中，基因工程小鼠将被用于测试 假设白色脂肪组织中Them1表达增加会促进炎症，从而导致 胰岛素抵抗、肝脏炎症和内质网应激，在米色脂肪组织中减少 生热作用。目标2将验证棕色脂肪组织中的Them1组织成膜的假设- 较少的细胞器(点状)，通过抑制脂肪酸氧化来节省能量，但在能量峰值期间除外 需求，当Them1被定向到细胞核，通过抑制生脂基因来支持产热 表情。我们将用三维电子显微镜显示斑点，并阐明相变 促进它们的形成，并将表征Them1介导的转录调控。目标3将测试 假设脂类结合到起始结构域以变构方式调节酶结构域。我们的方法 将包括使用互补生物物理对Them1脂结合和催化的详细结构分析 方法，以及小分子抑制剂的开发，这也可能被证明是 非酒精性脂肪肝的治疗价值。总体而言，这一提议将阐明Them1介导的代谢调节，它 意义重大，因为在以下情况下，在健康中节约能量的机制可能会促进疾病 营养过剩。这些研究有望确定治疗非酒精性脂肪肝的机会。

PROJECT SUMMARY/ABSTRACT Insulin resistance due to obesity is central to the pathogenesis of non-alcoholic fatty liver disease (NAFLD). This research proposal addresses the unanswered question of how molecular mechanisms that normally promote energy conservation become maladaptive and contribute to NAFLD. The long-term goal of this research is to understand the regulatory relationships between cellular lipid molecules and metabolism, particularly as they present therapeutic opportunities. The objective of this research is to understand fundamental mechanisms for the regulation of energy homeostasis and nutrient metabolism. Our central hypothesis is that Them1 conserves energy by limiting thermogenesis in brown and beige adipose tissue through its functions both as a lipid-regulated enzyme that reduces rates of fatty acid oxidation and as a transcriptional coregulator. In obesity, we postulate that Them1 becomes maladaptive. In addition to limiting energy expenditure in thermogenic adipose tissue, high fat diet-induced Them1 upregulation in liver leads to steatosis and excess gluconeogenesis and in white adipose tissue to inflammation and insulin resistance. The rationale for the proposed research is that the mechanisms by which Them1 limits energy expenditure, while promoting hepatic steatosis and insulin resistance, will reveal specific new targets for the management of NAFLD. Guided by extensive preliminary data, the central hypothesis will be tested in three specific aims: 1) To define the maladaptive mechanisms whereby Them1 promotes obesity and NAFLD; 2) To determine the cellular mechanisms for suppression of thermogenesis by Them1; and 3) To elucidate regulation of Them1 activity by the lipid-binding START domain. In Aim 1, genetically engineered mice will be used to test the hypothesis that increased Them1 expression in white adipose tissue promotes inflammation, which leads to insulin resistance, hepatic inflammation and endoplasmic reticulum stress, and in beige adipose tissue reduces thermogenesis. Aim 2 will test the hypothesis that Them1 in brown adipose tissue organizes into membrane- less organelles (puncta) that conserve energy by suppressing fatty acid oxidation, except during peak energy demand, when Them1 is directed to the nucleus to support thermogenesis by suppressing lipogenic gene expression. We will visualize puncta by 3-D electron microscopy and elucidate the phase transition that promotes their formation, and will characterize Them1-mediated transcriptional regulation. Aim 3 will test the hypothesis that lipids bound to the START domain allosterically regulate the enzymatic domains. Our approach will include detailed structural analysis of Them1 lipid-binding and catalysis using complementary biophysical approaches, along with the development of small molecule inhibitors, which could also prove to be of therapeutic value in NAFLD. Overall, this proposal will elucidate Them1-mediated metabolic regulation, which is significant because mechanisms that conserve energy in health may promote disease under conditions of overnutrition. These studies are expected to identify therapeutic opportunities for the management of NAFLD.