Osteoporosis and Molecular Targets of Vitamin D

骨质疏松症和维生素 D 的分子靶标

• 批准号: 8976989
• 负责人: SYLVIA S CHRISTAKOS
• 金额: $ 15.81万
• 依托单位: RBHS-NEW JERSEY MEDICAL SCHOOL
• 依托单位国家: 美国
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-09-30 至 2017-12-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8976989
• 关键词: Affect; Age; Age-Related Bone Loss; Aging; Biological Assay; Biomedical Research; Bone Diseases; Calcium; Calcium Channel; Calcium-Binding Proteins; Catabolism; ChIP-seq; Clinical Research; Complex; Confocal Microscopy; Deterioration; Development; Diffusion; Electrophysiology (science); Endocrine system; Epigenetic Process; Epithelial; Equilibrium; Event; Fracture; Gene Expression; Gene Targeting; Genes; Genetic Transcription; Goals; Health; Homeostasis; Intestines; Kidney; Lead; Mediating; Methyltransferase; Modeling; Molecular; Molecular Target; Mus; Osteopenia; Osteoporosis; Pathway interactions; Process; Protein Methyltransferases; Proteins; Regulation; Resistance; Risk; Risk Factors; Role; Testing; Time; Vitamin D; Vitamin D Analog; Vitamin D3 Receptor; Work; age related; calbindin; calcium absorption; coactivator-associated arginine methyltransferase 1; cofactor; epigenetic regulation; epigenomics; genome-wide; histone methylation; insight; methylation pattern; new therapeutic target; novel; novel therapeutics; prevent; receptor function; response; tool; treatment strategy

DESCRIPTION (provided by applicant): Vitamin D and calcium deficiencies are risk factors for age-related bone loss and increased fracture risk. Decreased intestinal calcium absorption (which correlates with decreased expression of TRPV6 and calbindin-D9k, the two major molecular targets of 1,25(OH)2D3 in the intestine) combined with an increase in the catabolism of 1,25(OH)2D3 by 24(OH)ase contribute to age related bone loss. Although a principal action of 1,25(OH)2D3 is intestinal calcium absorption, we are far from understanding the mechanisms involved in vitamin D induced transport of calcium. In addition, the mechanisms by which inadequate vitamin D status contributes to osteoporosis are not yet known. The unifying hypothesis of this exploratory study is that basic mechanisms involved in 1,25(OH)2D3 mediated intestinal calcium absorption remain to be defined, that a complex of cofactors, including those associated with epigenetic regulation, are involved in vitamin D receptor (VDR) mediated events involved in maintaining calcium homeostasis and that there is a deterioration in this process with aging. To test this hypothesis in the first specific aim we propose to examine the functional interrelationship between calbindin and TRPV6. In initial studies using double KO mice we found that intestinal calcium absorption in response to low calcium or 1,25(OH)2D3 is least efficient in the absence of both calbindin-D9k and TRPV6 (compared to WT and single KO mice), suggesting that TRPV6 and calbindin-D9k (which are co-localized in the intestine) act together to affect calcium absorption. We hypothesize that calbindin-D9k is not a facilitator of calcium diffusion (thus challenging the traditional model of vitamin D mediated transcellular calcium absorption) but rather a modulator of calcium influx via TRPV6. Studies are proposed (using confocal microscopy, co-ip., GST pull down assays and electrophysiology) that will enable us to understand for the first time the functional interrelationship between calbindin-D9k and TRPV6 and thus their role in 1,25(OH)2D3 regulated intestinal calcium transport. Findings from these studies may lead to the development of pharmacological tools to enhance intestinal calcium absorption and thus help to maintain calcium responsiveness during aging. In specific aim 2 we propose to examine mechanisms by which 1,25(OH)2D3 acts to maintain calcium homeostasis and changes in vitamin D regulation that occur with aging . Besides the functional significance of target proteins it is also important to understand the molecular mechanisms by which 1,25(OH)2D3 controls calcium homeostasis. Epigenomic control is a new and rapidly evolving field and my lab has obtained the first evidence that specific protein methyltransferases cooperate with the p160 coactivator GRIP1 in regulating 1,25(OH)2D3 target gene expression. We will examine the role of CARM1 methyltransferase and cooperating cofactors in the regulation of key 1,25(OH)2D3 target genes including TRPV6 and 24(OH)ase and how the function of VDR, VDR associated factors and epigenetic regulation of VDR function are altered with age. In addition we will analyze by ChIP seq genome wide changes in histone methylation patterns and co-occurrence of regulatory cofactors in response to 1,25(OH)2D3 in VDR regulated genes (novel as well as known) in kidney and intestine and changes that occur with aging. VDR coactivators are master regulators of 1,25(OH)2D3 action. Understanding altered recruitment by 1,25(OH)2D3 of VDR and coactivators and epigenetic changes may be the key to understanding dysregulation of calcium homeostasis and altered responsiveness to vitamin D that occurs with aging. The long term goal is to define molecular pathways of vitamin D action in order to reveal new therapeutic strategies to sustain calcium balance. Identifying the most effective vitamin D analog to prevent or reverse deterioration of calcium homeostasis through transcriptional and epigenetic mechanisms could have long range implications for how bone diseases, particularly osteoporosis and osteopenia, are treated. This application is appropriate for an R21 since it "involves considerable risk but may lead to a breakthrough that could have a major impact on a field of biomedical or clinical research".

描述（由申请人提供）：维生素D和钙缺乏症是与年龄相关的骨质流失和骨折风险增加的风险因素。肠道钙吸收的降低（与TRPV6和Calbindin-D9K的表达降低相关，这是肠中1,25（OH）2d3的两个主要分子靶标与1,25（OH）2d3的分解代谢增加24（OH）的增加，这是对年龄相关的年龄相关的1,25（OH）2D3。尽管1,25（OH）2d3的主要作用是肠道钙的吸收，但我们远非了解维生素D诱导钙转运所涉及的机制。另外，尚不清楚维生素D状态不足导致骨质疏松症的机制。这项探索性研究的统一假设是，涉及1,25（OH）2d3介导的肠钙吸收的基本机制尚待定义，包括与表观遗传调节的复合体有关维生素D受体（VDR）介导的事件涉及维持钙稳态和该钙化型的辅助事件。为了在第一个特定目的中检验这一假设，我们建议检查Calbindin和TRPV6之间的功能相互关系。 In initial studies using double KO mice we found that intestinal calcium absorption in response to low calcium or 1,25(OH)2D3 is least efficient in the absence of both calbindin-D9k and TRPV6 (compared to WT and single KO mice), suggesting that TRPV6 and calbindin-D9k (which are co-localized in the intestine) act together to affect calcium absorption.我们假设Calbindin-D9K不是钙扩散的促进剂（因此挑战了维生素D介导的跨细胞钙吸收的传统模型），而是通过TRPV6的钙涌入的调节剂。提出了研究（使用共聚焦显微镜，co-IP。，GST下拉测定和电生理学），这将使我们能够首次理解Calbindin-D9K和TRPV6之间的功能相互关系，从而在1,25（OH）2d3调节的肠骨转运中的作用。这些研究的发现可能导致药理学工具的开发，以增强肠道钙的吸收，从而有助于在衰老过程中维持钙的反应性。在特定的目标2中，我们建议研究1,25（OH）2D3行为以维持钙稳态和随着衰老而发生的维生素D调节变化的机制。除了靶蛋白的功能意义外，了解1,25（OH）2d3控制钙稳态的分子机制也很重要。表观基因组对照是一个新的迅速发展的领域，我的实验室获得了第一个证据，表明特定蛋白甲基转移酶与P160共激活因子GRIP1在调节1,25（OH）2D3靶基因表达时合作。我们将研究CARM1甲基转移酶和合作辅助因子在关键1,25（OH）2D3靶基因（包括TRPV6和24（OH）ASE）的调节中的作用，以及VDR，VDR相关因素和VDR功能的表观遗传调节的功能如何随着年龄而改变。此外，我们还将通过芯片SEQ基因组的大广泛变化的组蛋白甲基化模式变化，并在VDR调节基因（肾脏和肠道中的新颖）中对1,25（OH）2d3的响应，响应1,25（OH）2d3，以及随着衰老而发生的变化。 VDR共激活因子是1,25（OH）2D3动作的主调节器。了解VDR的1,25（OH）2d3的募集改变以及表观遗传变化可能是了解钙稳态失调以及随着衰老而发生的对维生素D的反应性的关键。长期目标是定义维生素D作用的分子途径，以揭示维持钙平衡的新治疗策略。通过转录和表观遗传机制鉴定最有效的维生素D类似物，以防止或逆转钙稳态的恶化，可能对如何治疗骨骼疾病，尤其是骨质疏松症和骨质疏松症具有长期影响。该应用适用于R21，因为它“涉及很大的风险，但可能会导致突破，这可能会对生物医学或临床研究领域产生重大影响”。

项目成果

Vitamin D, calcium homeostasis and aging.

• DOI: 10.1038/boneres.2016.41
• 发表时间: 2016
• 期刊: BONE RESEARCH
• 影响因子: 12.7
• 作者: Veldurthy, Vaishali;Wei, Ran;Oz, Leyla;Dhawan, Puneet;Jeon, Yong Heui;Christakos, Sylvia
• 通讯作者: Christakos, Sylvia

Mechanisms Underlying the Regulation of Innate and Adaptive Immunity by Vitamin D.

• DOI: 10.3390/nu7105392
• 发表时间: 2015-09-24
• 期刊: Nutrients
• 影响因子: 5.9
• 作者: Wei R;Christakos S
• 通讯作者: Christakos S