Nuclear Receptor Control of Glucose and Lipid Metabolism

描述（由申请方提供）：心血管疾病是糖尿病患者死亡的主要原因。尽管有大量的流行病学数据将糖尿病和心血管疾病联系起来，但高血糖如何促进动脉粥样硬化的分子机制仍然知之甚少。肝脏X受体（LXR）是由胆固醇的氧化形式（氧化固醇）激活的转录因子，其充当细胞内胆固醇过度积累的传感器。除了它们在胆固醇和脂质稳态调节中的作用之外，LXR还调节葡萄糖代谢中的关键基因的表达。我们最近报道了令人惊讶的观察结果，即葡萄糖可以结合LXR并在体内激活LXR靶基因。它们结合葡萄糖和氧固醇的能力提示LXR可能代表糖尿病高血糖状态和动脉粥样硬化之间的分子联系。拟议的研究将测试LXR在体内充当双重氧固醇-葡萄糖传感器的想法。阐明这种作用有望增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反应不同的突变体，将有助于评价LXR作为双氧固醇-葡萄糖传感器的作用。具体目标1是使用建模在基于细胞的生化测定中分离和表征配体反应改变的LXR突变体。为了了解LXR如何整合来自两种营养素的代谢信号，并能够指导LXR突变体的设计，在具体目标2中，我们将阐明LXR-葡萄糖-氧固醇相互作用的结构基础。在特定目标3中，将在培养的肝细胞中检测具有解离配体应答的LXR突变体调节内源性LXR靶点的能力，并将使用选定的突变体系统性分析LXR信号传导对代谢途径的影响。在特定目标4中，具有改变的配体反应的LXR突变体将用于使用基因靶向动物模型来创建，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LXR作为体内葡萄糖-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联系的体内意义。我们希望这项工作能提高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，占糖尿病患者死亡总数的70%以上。在血清胆固醇水平相似的情况下，糖尿病患者的心血管死亡风险比非糖尿病患者高4倍。这项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.