Nuclear Receptor Control of Glucose and Lipid Metabolism

描述(申请人提供)：心血管疾病是糖尿病患者的主要死因。尽管有大量的流行病学数据将糖尿病和心血管疾病联系在一起，但高血糖促进动脉粥样硬化的分子机制仍然知之甚少。肝X受体(LXRs)是由氧化形式的胆固醇(氧固醇)激活的转录因子，它是细胞内胆固醇过度积累的传感器。LXRs除了在调节胆固醇和脂质稳态方面发挥作用外，还调节葡萄糖代谢中的关键基因的表达。我们最近报道了一项令人惊讶的观察结果，即葡萄糖可以在体内结合LXRs并激活LXR靶基因。它们结合葡萄糖和氧固醇的能力表明，LXRs可能代表了糖尿病高血糖状态和动脉粥样硬化之间的分子联系。这项拟议的研究将在体内测试LXRs作为双重氧固醇-葡萄糖传感器的想法。这种作用的阐明有望加强我们对糖尿病和动脉粥样硬化之间的转录机制的理解。 通过鉴定对这两种生理配体有不同反应的突变体，将有助于评估LXR作为双重氧固醇-葡萄糖传感器的作用。具体目标1是使用模型在基于细胞和生化分析的LXR突变体中分离和表征配体反应改变的突变体。为了了解LXR如何整合来自两种营养素的代谢信号，并使LXR突变体的指导设计成为可能，在特定目标2中，我们将阐明LXR-葡萄糖-氧固醇相互作用的结构基础。在具体目标3中，将在培养的肝细胞中测试具有解离配体反应的LXR突变体调节内源性LXR靶标的能力，并选择突变体用于系统地描述LXR信号对代谢途径的影响。在特定目标4中，将使用配体反应改变的LXR突变体来创建使用基因靶向的动物模型，以剖析LXR在体内葡萄糖和胆固醇代谢中的作用。这些研究的最终目标是使用具有工程突变的动物来测试LXRs在体内作为葡萄糖-氧固醇传感器的作用。未来对表达突变LXR的小鼠的研究将测试LXR作为糖尿病和动脉粥样硬化之间的联系的体内意义。我们希望这项工作能加深我们对糖尿病如何加速动脉粥样硬化的理解，并提出治疗这些疾病的新的治疗方法。 心血管疾病是糖尿病的主要并发症，占糖尿病患者死亡人数的70%以上。糖尿病患者的心血管死亡风险是血清胆固醇水平相近的非糖尿病患者的四倍。这项拟议研究的长期目标是促进我们对糖尿病和心血管疾病之间联系的细胞和分子机制的理解。

DESCRIPTION (provided by applicant): Cardiovascular disease is the principal cause of death in patients with diabetes. In spite of ample epidemiological data linking diabetes and cardiovascular disease, the molecular mechanisms that underlie how hyperglycemia promotes atherosclerosis, remain poorly understood. The Liver X Receptors (LXRs) are transcription factors activated by oxidized forms of cholesterol (oxysterols) that serve as sensors of excessive intracellular cholesterol accumulation. In addition to their role in regulation of cholesterol and lipid homeostasis, the LXRs also modulate expression of key genes in glucose metabolism. We recently reported the surprising observation that glucose can bind the LXRs and activate LXR target genes in vivo. Their ability to bind both glucose and oxysterols hints that LXRs may represent a molecular connection between the diabetic hyperglycemic state and atherosclerosis. The proposed research will test the idea that LXRs act as dual oxysterol-glucose sensors in vivo. Elucidation of such a role is expected to enhance our understanding of the transcriptional mechanisms that link diabetes and atherosclerosis. Evaluation of the role of LXR as a dual oxysterol-glucose sensor will be facilitated by the identification of mutants that respond differentially to these two physiological ligands. Specific Aim 1 is to use modeling to isolate and characterize in cell-based and biochemical assays LXR mutants with altered ligand responses. To understand how LXR integrates metabolic signals from two nutrients, and to enable guided design of LXR mutants, in Specific Aim 2 we will elucidate the structural basis of the LXR-glucose-oxysterol interaction. In Specific Aim 3, the ability of LXR mutants with dissociated ligand responses to regulate endogenous LXR targets will be tested in cultured hepatocytes and selected mutants will be used to systematically profile the impact of LXR signaling on metabolic pathways. In Specific Aim 4, LXR mutants with altered ligand responses will be used to create using gene targeting animal models to dissect the role of LXR in glucose and cholesterol metabolism in vivo. The ultimate goal of these studies is to use animals with engineered mutations to test the role of LXRs as glucose-oxysterol sensors in vivo. Future studies with mice expressing mutant LXRs will test the in vivo significance of LXR as a link between diabetes and atherosclerosis. We expect this work to enhance our understanding of how diabetes accelerates atherosclerosis, and to suggest novel therapeutic approaches to treat these conditions. Cardiovascular disease is a major complication of diabetes that accounts for more than 70% of all deaths in patients with diabetes. The risk of cardiovascular mortality is four times higher in individuals with diabetes than in nondiabetic individuals with similar levels of serum cholesterol. The long term goal of the proposed research is to advance our understanding of the cellular and molecular mechanisms that link diabetes and cardiovascular disease.