PPARgamma Deacetylation in the Restoration of Metabolic Homeostasis

PPARgamma 脱乙酰化在恢复代谢稳态中的作用

• 批准号: 10064620
• 负责人: Li Qiang
• 金额: $ 40万
• 依托单位: COLUMBIA UNIVERSITY HEALTH SCIENCES
• 依托单位国家: 美国
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-12-01 至 2022-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10064620
• 关键词: Acetylation; Address; Adipocytes; Adipose tissue; Adverse effects; Adverse event; Affect; Agonist; Antidiabetic Drugs; Arginine; Biological Assay; Blood Vessels; Body Weight; Bone Marrow; Bone remodeling; Cardiac; Cardiovascular system; Cells; Central obesity; Clinical; Complement Factor D; Data; Deacetylation; Diabetes Mellitus; Drug Industry; Endocrine; Energy Metabolism; Fatty acid glycerol esters; Fluid Balance; Genes; Genetic Transcription; Goals; Heart Hypertrophy; Homeostasis; In Vitro; Inflammation; Insulin Resistance; Knock-in; Knock-in Mouse; Knockout Mice; Ligand Binding; Liquid substance; Lysine; Mediating; Medical; Mesenchymal Stem Cells; Metabolic; Modeling; Molecular; Mus; Mutation; Myocardial dysfunction; Non-Insulin-Dependent Diabetes Mellitus; Nuclear Receptors; Obesity; Osteogenesis; PPAR gamma; Physiological; Play; Post-Translational Protein Processing; Prevention; Process; Property; Regulation; Reporter; Reporting; Repression; Research; Role; Specificity; Testing; Thiazolidinediones; Ursidae Family; Visceral fat; Weight Gain; Work; adipocyte biology; adipocyte differentiation; blood glucose regulation; bone; bone loss; bone turnover; cofactor; genetic corepressor; genetic signature; improved; in vivo; in vivo evaluation; insight; insulin sensitivity; insulin sensitizing drugs; lipid metabolism; loss of function; mimetics; mouse model; mutant; novel; novel therapeutic intervention; prevent; programs; promoter; release factor; response; restoration; side effect; success; transcription factor

The research proposed in this application aims to leverage basic discoveries in obesity and diabetes to develop novel approaches for the therapy of these conditions. PPARγ is the master regulator of adipocyte biology and also plays crucial roles in regulating lipid metabolism, glucose homeostasis, inflammation, and other responses. It represents a key target for insulin sensitization. The PI has discovered that deacetylation of PPARγ on lysine K268 and K293 promotes the transformation of energy-storing white adipocytes into energy-dissipating brown-like adipocytes, a process called “browning” or “beiging”. To establish the physiological significance of PPARγ deacetylation, the PI generated deacetylation-mimetic PPARγ K268R/K293R mutant knock-in mice (2KR). As reported in the preliminary data, 2KR mice have increased energy expenditure and are protected from obesity, particularly visceral obesity. Strikingly, when 2KR mice are treated with thiazolidinediones (TZDs), they show a robust insulin-sensitizing response but fail to develop the cardiac and bone loss effects that have limited the clinical utilization of TZD. In this application, he proposes to define the mechanisms underlying the two most compelling effects of PPARγ deacetylation, increased beiging, and prevention of TZD-induced bone loss. In Aim 1, he will determine whether PPARγ deacetylation affects adipocyte beiging in an adipocyte cell-autonomous fashion by ex vivo adipocyte differentiation studies. Next, he will dissect the fat-specific functions of 2KR by employing an adipocyte conditional knock-in model. In Aim 2, using the prototypical white adipocyte gene Adipsin as a target, he will employ ChIP, reporter, and promoter pull-down assays to identify acetylation-responsive co-repressor that mediate the effects of 2KR. To demonstrate the feasibility of the approach, the PI shows that they identified transcription factor Osr1 as an acetylation-dependent PPARγ cofactor. He will test whether the 2KR mutant represses the white adipose program by preventing Osr1-mediated Adipsin expression. In Aim 3, the PI hypothesizes that the 2KR mutant regulates bone turnover by repressing Adipsin. He will first establish the role of Adipsin in osteogenesis and bone remodeling using ex vivo differentiation of bone marrow mesenchymal progenitor cells and Adipsin knockout mice. Next, he will determine whether repression of Adipsin is the mechanism by which the 2KR mutant is protected against TZD-induced bone loss using Adipsin gain- or loss-of-function studies in 2KR mice. The proposed studies will advance the field by elucidating the selective regulation of PPARγ through deacetylation and provide mechanistic insight to dissociate the insulin-sensitizing function of PPARγ activation from its adverse effects.

本申请中提出的研究旨在利用肥胖和糖尿病的基本发现来开发治疗这些疾病的新方法。PPARγ是脂肪细胞生物学的主要调节因子，并且在调节脂质代谢、葡萄糖稳态、炎症和其他反应中也起关键作用。它是胰岛素致敏的关键靶点。PI发现，赖氨酸K268和K293上的PPARγ脱乙酰化促进了能量储存的白色脂肪细胞转化为能量耗散的棕色样脂肪细胞，这一过程称为“布朗宁”或“褐变”。为了确定PPARγ去乙酰化的生理学意义，PI产生了去乙酰化模拟的PPARγ K268 R/K293 R突变体敲入小鼠（2KR）。如初步数据中所报道的，2KR小鼠具有增加的能量消耗并且免受肥胖，特别是内脏肥胖。引人注目的是，当用噻唑烷二酮（TZD）治疗2KR小鼠时，它们显示出强烈的胰岛素增敏反应，但未能产生限制TZD临床应用的心脏和骨丢失作用。在本申请中，他提出定义两种最引人注目的PPARγ脱乙酰化作用的机制，增加beiging和预防TZD诱导的骨丢失。在目标1中，他将通过离体脂肪细胞分化研究来确定PPARγ去乙酰化是否以脂肪细胞自主的方式影响脂肪细胞的形成。接下来，他将通过采用脂肪细胞条件性敲入模型来剖析2KR的脂肪特异性功能。在目标2中，使用原型白色脂肪细胞基因Adipsin作为靶点，他将采用ChIP、报告基因和启动子下拉测定来鉴定介导2 KR效应的乙酰化响应性辅抑制子。为了证明该方法的可行性，PI显示他们将转录因子Osr 1鉴定为乙酰化依赖性PPARγ辅因子。他将测试2KR突变体是否通过阻止Osr 1介导的Adipsin表达来抑制白色脂肪程序。在目的3中，PI假设2KR突变体通过抑制Adipsin调节骨转换。他将首先使用骨髓间充质祖细胞和Adipsin基因敲除小鼠的体外分化来建立Adipsin在骨生成和骨重建中的作用。接下来，他将在2KR小鼠中使用Adipsin功能获得或丧失研究来确定Adipsin的抑制是否是2KR突变体保护免受TZD诱导的骨丢失的机制。拟开展的研究将通过阐明通过去乙酰化对PPARγ的选择性调节来推进该领域，并提供将PPARγ活化的胰岛素增敏功能与其不良反应分离的机制见解。