Role and Mechanism of Action of Ksr2, an Obesity and Type 2 Diabetes Gene, in Bone Metabolism

肥胖和2型糖尿病基因Ksr2在骨代谢中的作用和机制

基本信息

批准号：
10541191
负责人：
SUBBURAMAN MOHAN
金额：
$ 32.23万
依托单位：
LOMA LINDA VETERANS ASSN RESEARCH & EDUC
依托单位国家：
美国
项目类别：
财政年份：
2003
资助国家：
美国
起止时间：
2003-08-01 至 2025-12-31
项目状态：
未结题

来源：
https://reporter.nih.gov/project-details/10541191
关键词：
Adipocytes Adipose tissue Adult Affect Age Months Animal Model Applications Grants Automobile Driving Basal metabolic rate Biochemical Body Weight Body fat Bone Density Bone Formation Stimulation Bone Marrow Breeding Cardiovascular Diseases Cell Lineage Cells Characteristics Chemicals Chronic Disease Clinical Data Code Complex Data Disease Distal Drug Targeting Energy Intake Energy Metabolism Exhibits Fatty acid glycerol esters Feeding behaviors Female Femur Fracture Funding Gene Expression General Population Generations Genes Goals HIF1A gene Health Histology Hormone Responsive Human Hypothalamic structure Hypoxia Immunohistochemistry Individual Insulin Resistance KSR gene Knock-out Knockout Mice Link LoxP-flanked allele MAP Kinase Gene MEKs Malignant Neoplasms Mechanics Mediating Metabolic Metabolic Diseases Metaphysis Modeling Molecular Morbidity - disease rate Mus Mutate Mutation Non-Insulin-Dependent Diabetes Mellitus Obesity Orthologous Gene Osteoblasts Osteogenesis Osteoporosis Pathogenesis Pathway interactions Patients Phenotype Phosphorylation Phosphotransferases Physiologic Ossification Physiological Physiology Prevalence Prevention approach Proliferating Proteins Public Health Publishing Ras/Raf Regulation Reverse Transcriptase Polymerase Chain Reaction Risk Factors Role Scaffolding Protein Signal Pathway Signal Transduction Societies Study models Susceptibility Gene Testing Therapeutic Thyroid Hormone Receptor Thyroid Hormones Time United States Variant Western Blotting aging population bone bone epiphysis bone health bone mass bone metabolism conditional knockout cost diabetic early-onset obesity energy balance feeding fracture risk genome wide association study improved in vivo inhibitor knock-down lipid metabolism long bone mTOR protein microCT novel novel therapeutic intervention obese person osteoblast differentiation osteogenic osteoporosis with pathological fracture precursor cell preventable death ras Proteins scaffold skeletal substantia spongiosa

项目摘要

Abstract In an increasingly aging and obese population, type 2 diabetes (T2DM) and osteoporotic fractures are major public health concerns. Affecting more than 1 in 3 adults in the United States, obesity is the most important risk factor for T2DM. It is now well established that obesity and T2DM have effects on fracture risk, and fractures in T2DM are associated with greater morbidity than in the general population. Although bone density is generally known to be increased in obese and T2DM patients, the underpinning causes that contribute to increased fracture risk in T2DM/obese subjects remain to be established. Therefore, understanding the interactions of obesity, T2DM and fracture is becoming a pressing need to reduce the societal and individual costs of fracture. Our efforts to identify control molecules and their signaling pathways that delineate a link between T2DM, osteoporosis and obesity led to the exciting discovery that targeted disruption of kinase suppressor of Ras 2 (Ksr2), an obesity and T2DM gene, led to a >2-fold increase in trabecular bone mass at the distal femur of 4-month-old mice besides inducing obesity and T2DM. By contrast, disruption of a closely related Ksr1 gene had no significant effect on bone or obese phenotypes. KSR1 and 2 were discovered as scaffolding proteins that orchestrate the assembly of Raf, MEK and ERK in the canonical Ras-Raf-MAPKs pathway. While a central role for Ksr2 expressed in hypothalamus has been implicated in the control of feeding behavior and energy balance and, thereby obesity, we have new exciting preliminary data that suggest that KSR2 expressed in osteoblasts acts locally in a cell autonomous fashion to regulate its functions. Based on our preliminary data and published data, we propose a novel hypothesis that KSR2 regulates osteoblast differentiation and bone formation via regulating mTORC1 signaling and its downstream hypoxia signaling. In this competitive renewal RO1 application, we will test this model of KSR2 action as follows: 1) To test the hypothesis that KSR2 acts in a cell autonomous fashion to regulate trabecular bone formation, we will generate osteoblast-specific Ksr2 conditional knockout mice and characterize its skeletal phenotype by micro-CT, histology, mechanical testing and gene expression. 2) To test the hypothesis that KSR2 effects on osteoblasts are mediated via its regulation of mTORC1 signaling, we will determine the functional consequence of KSR2/mTORC1 pathway interactions by evaluating if knockdown of Raptor in osteoblasts abolishes the increased anabolic functions of Ksr2 knockdown osteoblasts. 3) To test the hypothesis that KSR2/mTORC1 effects on osteoblasts are mediated via HIF1α signaling, we will evaluate changes in hypoxia signaling in osteoblasts with conditional disruption of Ksr2 and/or Raptor. We will also determine if disruption of Hif1α expression in osteoblasts rescues the skeletal phenotype in osteoblast-specific Ksr2 conditional knockout mice. Successful completion of our proposed studies will provide important information on the pathway/s by which KSR2 regulates osteoblast and bone marrow adipocyte functions and could lead to improved understanding of the mechanisms linking obesity and a high bone mass phenotype.

抽象的在越来越老化和肥胖的人群中，2型糖尿病（T2DM）和骨质疏松性骨折是主要的公共卫生关注。在美国影响超过三分之一的成年人，肥胖是T2DM的最重要危险因素。这是现在确定肥胖和T2DM对骨折风险有影响，T2DM的断裂与更大的骨折有关发病率比普通人群。尽管通常已知骨骼密度在肥胖和T2DM中增加患者，尚待确定T2DM/肥胖受试者骨折风险增加的基础原因。因此，了解肥胖，T2DM和断裂的相互作用正在成为减少社会的迫切需求和个人骨折成本。我们为识别控制分子及其信号通路的努力，以描绘链接在T2DM，骨质疏松和肥胖症之间，引起了令人兴奋的发现，它针对RAS的激酶抑制剂的破坏 2（KSR2），肥胖和T2DM基因，导致小梁骨质量在4个月大的股骨远端增加> 2倍小鼠除了诱导肥胖和T2DM。相比之下，密切相关的KSR1基因的破坏没有显着影响在骨骼或肥胖表型上。 KSR1和2被发现为脚手架蛋白质，这些蛋白质策划了RAF的组装， Mek和Erk在规范的Ras-Raf-Mapks Pathway中。虽然在下丘脑中表达的KSR2的核心作用具有我们被暗示地控制了喂养行为和能量平衡，因此，肥胖症我们有了新的兴奋初步数据表明，成骨细胞中的KSR2以细胞自主的方式作用以调节其本地作用功能。基于我们的初步数据和发布的数据，我们提出了一个新的假设，可以调节成骨细胞通过调节MTORC1信号传导及其下游缺氧信号传导的分化和骨形成。在这个竞争性更新RO1应用，我们将测试此KSR2动作模型，如下所示：1）测试以下假设： KSR2以细胞自主的方式起作用，以调节小梁骨形成，我们将生成成骨细胞特异性的KSR2 有条件的敲除小鼠，并通过微CT，组织学，机械测试和基因来表征其骨骼表型表达。 2）测试KSR2对成骨细胞的影响的假设是通过调节MTORC1信号传导的调节来介导的，，我们将通过评估是否敲低来确定KSR2/MTORC1途径相互作用的功能结果成骨细胞中的猛禽废除了KSR2敲低成骨细胞的合成代谢功能的增加。 3）检验假设 KSR2/MTORC1对成骨细胞的影响是通过HIF1α信号传导介导的，我们将评估缺氧信号传导的变化在成骨细胞中，有条件地破坏KSR2和/或猛禽。我们还将确定HIF1α表达的破坏是否破坏在成骨细胞中，挽救了成骨细胞特异性KSR2条件敲除小鼠中的骨骼表型。成功完成我们提出的研究将提供有关KSR2调节成骨细胞和骨骼的途径的重要信息骨髓脂肪细胞功能，可能会提高人们对连接肥胖和高骨的机制的理解质量表型。