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.

项目总结/摘要 骨量丢失是导致老年人股骨干骨折发生率增加的根本原因。 老年人口。老年小鼠骨骼中的细胞变化与老年小鼠骨骼中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骨骼老化的主要原因。 人类和小鼠，但潜在的机制仍不清楚。辅酶水平的降低 由于线粒体功能障碍，NAD+导致多种组织的功能随着年龄的增长而下降， NAD依赖性酶如沉默调节蛋白（SIRT）和聚（ADP-核糖）的活性减弱 聚合酶（PARP）。Sirt 1和Parp 5可以促进Wnt/β-catenin通路的活性， 是成骨细胞形成所必需的。我们已经证明成骨细胞祖细胞的数量和增殖是 在老年小鼠中减少，这些变化与较低水平的NAD+和烟酰胺表达相关。 磷酸核糖转移酶（Nampt）-NAD+补救途径中的关键酶。相比之下， NAD+消耗酶CD 38随增龄而增加。NAD前体分子的施用 烟酰胺核苷（NR）对衰老小鼠的作用抵消了成骨细胞祖细胞和骨量的损失。 此外，使用Prx 1-Cre的间充质谱系细胞中Nampt的杂合缺失模拟骨骼肌细胞中Nampt的表达。 衰老我们还获得了证据表明，NAD耗竭对骨量的有害影响， 由线粒体活性氧（ROS）和FoxO转录因子介导。特别是 成骨细胞中β-连环蛋白的蛋白质水平和经典Wnt信号的刺激在很大程度上是 依赖于NAD+。我们假设随着年龄的增长，NAD+补救途径的减少 Wnt信号传导，从而成骨细胞数量，通过FoxO依赖性和非依赖性机制。在 目的1：我们将阐明NAD+补救途径在成骨细胞系和CD 38细胞中的作用。 对年轻和年老老鼠的骨骼稳态的影响。为此，我们将研究Nampt删除或 成骨细胞系细胞中的过度表达，以及CD 38在骨骼衰老中的影响。在目标2中， 确定骨祖细胞中线粒体ROS或FoxOs对 NAD+耗竭。在目标3中，我们将通过删除Nampt和Nampt来研究NAD+对Wnt信号传导的影响。 过量表达Wnt 1。我们还将研究NAD+对β-连环蛋白的刺激作用是否依赖于 在Parp 5a和Parp 5 b上。这些研究的成功完成将有助于我们理解 介导NAD随着衰老而减少，并阐明成骨细胞谱系细胞中NAD补救途径 促进骨骼形成。这项工作还应该阐明ROS与细胞内的蛋白质之间的相互作用，或缺乏这种相互作用。 NAD+和可能建议更有针对性的治疗方法来减缓或预防骨骼衰老。