Transcriptional Repression of PPARgamma-2 by Glucocorticoid-Induced Leucine Zippe

糖皮质激素诱导的亮氨酸 Zippe 对 PPARgamma-2 的转录抑制

• 批准号: 8034954
• 负责人: XINGMING SHI
• 金额: $ 7.16万
• 依托单位: AUGUSTA UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-03-15 至 2011-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8034954
• 关键词: 3T3-L1 Cells; Address; Adipocytes; Adipose tissue; Aging; Agonist; Arts; Binding; Binding Sites; Biological Assay; Body fat; Bone Marrow; CCAAT-Enhancer-Binding Proteins; Coronary; Coronary heart disease; DNA-Protein Interaction; Data; Diet; Disease; Elements; Family; Fatty acid glycerol esters; Genetic Transcription; Glucocorticoids; Goals; In Vitro; Insulin Resistance; Laboratories; Lead; Leucine; Leucine Zippers; Marrow; Mediating; Molecular; Molecular Biology; Mus; Obesity; Osteoblasts; Osteogenesis; Osteoporosis; PPAR gamma; Pathway interactions; Peroxisome Proliferator-Activated Receptors; Predisposition; Protein Binding; Protein C; Proteins; Public Health; Research; Resistance; Risk; Solutions; Stem cells; Testing; Time; Transactivation; Transgenic Mice; Vascular Diseases; adipocyte differentiation; base; bone; bone loss; bone mass; gene repression; in vivo; lipid biosynthesis; osteoblast differentiation; osteogenic; overexpression; promoter; protein protein interaction; public health relevance; response; rosiglitazone; transcription factor

DESCRIPTION (provided by applicant): Research Goals and Significance: Osteoporosis and obesity are major public health threats in the US. However, the underlying mechanisms, and whether these seemingly unrelated diseases have a common element, are unknown. During aging, bone mass decreases. At the same time, fat builds up in non-adipose tissues such as belly and bone marrow, suggesting that an imbalance may develop between the osteogenic and adipogenic differentiation pathways. PPAR(2, also known as the "master" regulator of adipogenesis, positively regulates adipogenesis but has the opposite effect on osteogenesis. Our long-term goal is to determine the molecular mechanisms by which PPAR(2 controls both adipogenic and osteogenic pathways. The purpose of this research is to address the question of how PPAR(2 expression can be repressed by glucocorticoid-induced leucine zipper (GILZ), a recently identified leucine zipper protein. Since excess belly fat increases the risks of coronary disease and causes insulin resistance, both of which are major public health threats, understanding how PPAR(2 expression can be negatively regulated will provide solutions not only for treating osteoporosis, but obesity and obesity-related disorders as well. Rationale and Hypotheses: We and others have shown that the expression of PPAR(2 is activated by direct binding of the CCAAT/enhancer-binding proteins (C/EBPs) to the PPAR(2 promoter. In contrast, very little is known about how PPAR(2 can be negatively regulated. Our recent studies show that GILZ can suppress PPAR(2 transcription, inhibit adipogenic differentiation, and enhance osteogenic differentiation of bone marrow progenitor cells, the common precursors of fat- and bone-forming adipocytes and osteoblasts. Based on these studies and our recent preliminary data showing that GILZ interacts with the C/EBPs and inhibits C/EBP-mediated PPAR(2 expression, we hypothesize that GILZ represses PPAR(2 transcription by either inhibiting the binding of C/EBPs to the PPAR(2 promoter or by disrupting C/EBP transactivation functions via GILZ-C/EBP interactions. Based on recent evidence that 1) PPAR(2 inhibits Runx2/Cbfa1 expression and osteoblast differentiation; 2) PPAR( agonists induce bone loss and marrow adiposity; and 3) PPAR( insufficiency enhances osteogenesis and increases bone formation, and protects mice against diet- induced obesity and insulin resistance, we also hypothesize that GILZ overexpression in vivo will reduce the level of PPAR(2 expression, thus reducing the susceptibility of mice to PPAR( agonist-induced bone loss and marrow adiposity, and protecting against high-fat diet-induced obesity and insulin resistance. Specific Aims and Approaches: Our Specific Aims are to test the above two hypotheses using state-of-the- art molecular biology approaches, including DNA-protein and protein-protein interactions, transcriptional activities, and knockdown approaches (Aim #1, in vitro studies), and to validate our hypothesis developed in Aim #1 using GILZ transgenic mice that have been recently generated in our laboratory (Aim #2, in vivo studies). PUBLIC HEALTH RELEVANCE: Osteoporosis and obesity are major public health threats in the US. However, the underlying mechanisms, and whether these seemingly unrelated diseases have a common element, are unknown. During aging, bone mass decreases and fat builds up in belly and bone marrow, resulting in osteoporosis and the diseases that are associated with excess body fat, such as insulin resistance and coronary vascular diseases. Peroxisome proliferators-activated receptor-gamma2 (PPAR(2), also known as the "master" regulator of adipogenesis, positively regulates adipocyte differentiation but has the opposite effect on osteoblast differentiation. Thus, understanding how PPAR(2 can be negatively regulated, a focus of this study, may lead to new therapies for treating osteoporosis and obesity.

描述（由申请人提供）：研究目的和意义：骨质疏松症和肥胖症是美国主要的公共卫生威胁。然而，其潜在机制，以及这些看似无关的疾病是否有共同的元素，都是未知的。在衰老过程中，骨量减少。与此同时，脂肪在非脂肪组织如腹部和骨髓中积累，这表明成骨和成脂分化途径之间可能存在不平衡。过氧化物酶体增殖物激活受体β 2，也被称为脂肪生成的“主”调节因子，积极调节脂肪生成，但对骨生成具有相反的作用。我们的长期目标是确定PPAR（2）控制成脂和成骨途径的分子机制。本研究的目的是探讨糖皮质激素诱导的亮氨酸拉链蛋白（GILZ）如何抑制PPAR β 2的表达。由于过多的腹部脂肪会增加冠心病的风险并导致胰岛素抵抗，这两者都是主要的公共卫生威胁，因此了解PPAR β 2表达如何受到负调控不仅可以为治疗骨质疏松症提供解决方案，还可以为肥胖和肥胖相关疾病提供解决方案。 原理和假设：我们和其他人已经表明，通过CCAAT/增强子结合蛋白（C/EBP）与PPAR β 2启动子的直接结合，激活了PPAR β 2的表达。相比之下，人们对PPAR β 2是如何负调控的知之甚少。我们最近的研究表明，GILZ可以抑制PPAR β 2转录，抑制成脂分化，并增强骨髓祖细胞的成骨分化，骨髓祖细胞是脂肪和骨形成脂肪细胞和成骨细胞的共同前体。基于这些研究和我们最近的初步数据显示GILZ与C/EBP相互作用并抑制C/EBP介导的PPAR β 2表达，我们假设GILZ通过抑制C/EBP与PPAR β 2启动子的结合或通过GILZ-C/EBP相互作用破坏C/EBP反式激活功能来抑制PPAR β 2转录。根据最近的证据，1）PPAR（2）抑制Runx 2/Cbfa 1表达和成骨细胞分化;（激动剂诱导骨丢失和骨髓肥胖;和3）PPAR β表达不足增强骨生成并增加骨形成，并保护小鼠免于饮食诱导的肥胖和胰岛素抵抗，我们还假设体内GILZ过表达将降低PPAR β表达水平，从而降低小鼠对PPAR（激动剂诱导的骨丢失和骨髓肥胖）的易感性，并防止高脂饮食诱导的肥胖和胰岛素抵抗。 具体目标和方法：我们的具体目标是使用最先进的分子生物学方法，包括DNA-蛋白质和蛋白质-蛋白质相互作用、转录活性和敲低方法（目标#1，体外研究）来测试上述两个假设，并使用我们实验室最近产生的GILZ转基因小鼠来验证我们在目标#1中开发的假设（目标#2，体内研究）。公共卫生相关性：骨质疏松症和肥胖症是美国主要的公共卫生威胁。然而，其潜在机制，以及这些看似无关的疾病是否有共同的元素，都是未知的。在衰老过程中，骨量减少，脂肪在腹部和骨髓中积聚，导致骨质疏松症和与体内脂肪过多有关的疾病，如胰岛素抵抗和冠状动脉疾病。过氧化物酶体增殖物激活受体-γ 2（PPAR（2）），也被称为脂肪生成的“主”调节因子，积极调节脂肪细胞分化，但对成骨细胞分化有相反的作用。因此，本研究的重点是了解PPAR β 2是如何负调控的，这可能会导致治疗骨质疏松症和肥胖症的新疗法。