Mechanisms of decreased bone formation with aging

随年龄增长骨形成减少的机制

• 批准号: 10707568
• 负责人: Maria Jose Almeida
• 金额: $ 45.53万
• 依托单位: UNIV OF ARKANSAS FOR MED SCIS
• 依托单位国家: 美国
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-09-22 至 2024-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10707568
• 关键词: Adult; Age; Age-Months; Age-Related Bone Loss; Aging; Attenuated; Bone Formation Stimulation; Cell Lineage; Cells; Coenzymes; Consumption; Cyclic ADP-Ribose; Development; Enzymes; FOXO1A gene; Funding; Gene Expression; Genetic Transcription; Homeostasis; Human; In Vitro; Incidence; Knowledge; Mediating; Mesenchymal; Metabolism; Mitochondria; Mus; Nicotinamide adenine dinucleotide; Osteoblasts; Osteocytes; Osteogenesis; Osteoporosis; Osteoporotic; Oxidation-Reduction; Pathology; Pathway interactions; Pharmaceutical Preparations; Phenotype; Poly(ADP-ribose) Polymerases; Production; Proteins; Reaction; Reactive Oxygen Species; Role; SIRT1 gene; Seminal; Signal Pathway; Signal Transduction; Sirtuins; Skeleton; Testing; Tissues; Transgenes; WNT Signaling Pathway; Work; aged; aging population; attenuation; base; beta catenin; bone; bone loss; bone mass; catalase; cofactor; dentin matrix protein 1; fracture risk; functional decline; healthspan; human old age (65+); in vivo; inhibitor; mitochondrial dysfunction; nicotinamide phosphoribosyltransferase; nicotinamide-beta-riboside; osteoporosis with pathological fracture; osteoprogenitor cell; overexpression; postnatal; prevent; progenitor; skeletal; targeted treatment; therapy development; transcription factor

Project Summary/Abstract Loss of bone mass is the seminal pathology underlying the increased incidence of osteoporotic fractures in the aged population. The cellular changes in the skeleton of aged mice are similar to those observed in aged humans. A decrease in osteoblast number and bone formation are major contributors to skeletal aging in both humans and mice, however the underlying mechanisms remain unclear. A reduction in the levels of coenzyme NAD+ contributes to the functional decline of multiple tissues with age due to mitochondria dysfunction and attenuation of the activity of NAD-dependent enzymes such as the sirtuins (SIRTs) and poly(ADP-ribose) polymerases (PARPs). Sirt1 and Parp5 can promote the activity of the Wnt/β-catenin pathway, which is indispensable for osteoblast formation. We have shown that osteoblast progenitor number and proliferation are reduced in aged mice and that these changes correlate with lower levels of NAD+ and expression of nicotinamide phosphoribosyltransferase (Nampt) – a critical enzyme in the NAD+ salvage pathway. In contrast, the levels of the NAD+ consuming enzyme CD38 are increased with aging. Administration of the NAD precursor molecule nicotinamide riboside (NR) to aging mice counteracts the loss of osteoblast progenitors and bone mass. Moreover, heterozygous deletion of Nampt in cells of the mesenchymal lineage using Prx1-Cre mimics skeletal aging. We have also obtained evidence to suggest that the deleterious effects of NAD depletion on bone mass are mediated by mitochondrial reactive oxygen species (ROS) and the FoxO transcription factors. Notably, the protein levels of β-catenin and stimulation of the canonical Wnt signaling in osteoblastic cells are greatly dependent on NAD+. We hypothesize that a decline in the NAD+ salvage pathway with old age decreases Wnt signaling and thereby osteoblast number, via FoxO-dependent and -independent mechanisms. In Aim 1 we will elucidate the contribution of the NAD+ salvage pathway in cells of the osteoblast lineage and CD38 to skeletal homeostasis in young and old mice. To do this, we will examine the effects of Nampt deletion or overexpression in osteoblast lineage cells, as well as the impact of CD38 in skeletal aging. In Aim 2 we will determine the contribution of mitochondrial ROS or FoxOs in osteoprogenitors to the adverse skeletal effects of NAD+ depletion. In Aim 3 we will investigate the effects of NAD+ on Wnt signaling by deleting Nampt and overexpressing Wnt1. We will also examine whether the NAD+ stimulatory actions on β-catenin are dependent on Parp5a and Parp5b. Successful completion of these studies should help us understand the mechanisms mediating the decrease in NAD with aging and unravel how the NAD salvage pathway in osteoblast lineage cells promotes bone formation. This work should also elucidate the interaction, or lack thereof, between ROS and NAD+ and may suggest more targeted therapeutic approaches to slowing or preventing skeletal aging.

项目摘要/摘要 骨骼质量的损失是骨质疏松骨折入射增加的第二种病理 人口老年。老年小鼠骨骼的细胞变化与老年人观察到的细胞变化相似 人类。成骨细胞数量和骨形成的减少是两者中骨骼衰老的主要因素 人类和小鼠，但是基本机制尚不清楚。辅酶的水平降低 NAD+有助于多个时间因线粒体功能障碍和 NAD依赖性酶的活性衰减，例如Sirtuins（Sirts）和Poly（ADP-核糖） 聚合酶（PARPS）。 SIRT1和PARP5可以促进Wnt/β-catenin途径的活性，这是 对于成骨细胞形成不可或缺的。我们已经表明成骨细胞祖细胞数和增殖是 老年小鼠的减少，这些变化与较低水平的NAD+和烟酰胺的表达相关 磷酸贝糖基转移酶（NAMPT） - NAD+打捞途径中的关键酶。相反， NAD+消耗酶CD38随着衰老而增加。 NAD前体分子的给药 尼古丁酰胺核糖剂（NR）对老化小鼠的衰老会抵消成骨细胞祖细胞和骨骼质量的损失。 此外，使用prx1-cre模拟骨骼的细胞谱系细胞中NAMPT的杂合缺失 老化。我们还获得了证据表明NAD部署对骨骼质量的删除影响 由线粒体活性氧（ROS）和FOXO转录因子介导。值得注意的是 蛋白质水平的β-catenin和成骨细胞中规范Wnt信号的刺激很棒 取决于NAD+。我们假设NAD+救助途径的下降，老年有所下降 Wnt信号传导以及成骨细胞数，通过FOXO依赖性和非依赖性机制。在 AIM 1我们将阐明成骨细胞谱系和CD38细胞中NAD+打捞途径的贡献 为此，我们将研究NAMPT删除的影响或 成骨细胞谱系细胞中的过表达以及CD38在骨骼老化中的影响。在目标2中，我们将 确定线粒体ROS或FOXOS在骨基因生成剂中的贡献 NAD+耗尽。在AIM 3中，我们将通过删除NAMPT和 过表达WNT1。我们还将检查NAD+刺激作用是否依赖于β-catenin 在PARP5A和PARP5B上。这些研究的成功完成应该有助于我们了解机制 通过衰老和解开成骨细胞中的NAD挽救途径的介导NAD的下降 促进骨形成。这项工作还应阐明ROS和ROS之间的相互作用或缺乏互动 NAD+，并可能建议采用更靶向的治疗方法来减慢或预防骨骼衰老。