The Myokine Irisin Modulates Bone Resorption via Stimulation of Osteoclastogenesis

肌动素鸢尾素通过刺激破骨细胞生成调节骨吸收

基本信息

批准号：
10426130
负责人：
Eben Grant Estell
金额：
$ 5.51万
依托单位：
MAINEHEALTH
依托单位国家：
美国
项目类别：
财政年份：
2020
资助国家：
美国
起止时间：
2020-05-05 至 2023-01-31
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/10426130
关键词：
Address Adipose tissue Affect Antibodies Apoptosis Binding Proteins Biochemical Biochemical Markers Biophysics Blood Circulation Bone Resorption Bone remodeling Calcium Cell Line Cell physiology Cells Coculture Techniques Data Development Distal Dose Estrogens Exercise Family Female Fibronectins Gene Expression Gene Proteins Genetic Goals Growth Factor Homeostasis Hormones Hydrogen Peroxide In Vitro Infusion procedures Integrin Binding Integrin alphaV Integrins Knockout Mice Link Liquid substance Maintenance Mechanical Stimulation Mediating Modeling Molecular Profiling Mus Muscle Muscle Cells Musculoskeletal Diseases Nature Organ Osteoblasts Osteoclasts Osteocytes Osteogenesis Osteolysis Osteoporosis Ovariectomy Paracrine Communication Pathway interactions Peptides Physical activity Physiological Play Population Production Proteins Quantitative Reverse Transcriptase PCR Research Role Running Serum Signal Transduction Signaling Protein TNFSF11 gene Testing Vertebral Bone Western Blotting Wild Type Mouse Work antagonist bone bone cell bone health bone loss bone mass cell type cortical bone density deprivation experimental study in vivo insight mRNA Expression male mechanical load mouse genetics novel therapeutics osteoblast differentiation osteoclastogenesis paracrine prevent programs receptor skeletal transcriptome sequencing

项目摘要

ABSTRACT The myokine irisin is a peptide that is proteolyzed from the muscle-bound protein Fndc5 (fibronectin type III domain-containing protein 5) during exercise and enters circulation and induces a thermogenic program in beige adipose tissue1,2. Several studies have suggested a key role for irisin in mediating the effect of exercise on bone, demonstrating that intermittent low dose irisin (0.1 mg/kg once per week) stimulates cortical bone formation and prevents unloading-induced bone loss in vivo, and enhances osteogenesis in vitro3-5. Utilizing the power of mouse genetics, our group has endeavored to further elucidate the role of irisin in skeletal remodeling, demonstrating that forced expression of Fndc5 in muscle markedly reduces bone formation and mass, decreases osteoblast number while increasing osteoclasts, and increasing NF-κB and SOST expression while suppressing serum levels of bone formation markers. Similarly, genetic deletion of Fndc5 led to high vertebral bone volume and complete protection from ovariectomy (OVX)-induced bone loss in female mice, marked by maintenance of osteocyte lacunae density and size, blocked bone resorption, and no increase in RANKL expression despite prolonged estrogen deprivation. Short term irisin infusions in wild type mice resulted in higher serum levels of sclerostin and greater SOST mRNA expression. Irisin treatment of MLOY-4 osteocytes in vitro demonstrated a direct effect on this cell type, inducing gene and protein level expression of sclerostin in a dose dependent manner and preventing hydrogen peroxide-induced apoptosis. Importantly, we identified through biochemical and biophysical means that the αVβ5 integrin is the principal, although possibly not the only, receptor for irisin in osteocytes6. We now have evidence that in addition to its effect on the osteocyte, irisin acts directly on the osteoclast to stimulate differentiation, and this effect is reversed by blocking both αVβ5 and αVβ3 with antibody antagonists. At face value these data would seem to run counter to the prevailing hypothesis that myokines are purely anabolic for bone. However, in a physiologic context irisin might also indirectly stimulate osteoblasts via release of clastokines or matrix-bound growth factors, or it may have a unique role as a counter regulatory hormone to maintain calcium homeostasis by increasing resorption. With the work proposed herein, we will address two specific aims to test the central hypothesis that irisin acts as a key regulating factor in the influence of exercise on bone remodeling; both by direct action on the osteoclast through integrin αVβ5, and by modulation of osteoclast paracrine signaling with osteocytes and osteoblasts. Because this myokine may play a key role in linking physical activity and bone remodeling, this work will focus both on traditional static in vitro culture models as well as address the effect of mechanical loading such as fluid shear on the osteoclast, osteoblast, and osteocyte with specific regard to the influence of irisin on cell mechanosensitivity.

抽象的肌因子鸢尾素是一种肽，由肌肉结合蛋白 Fndc5（纤连蛋白）水解而成。含有 III 型结构域的蛋白质 5) 在运动期间进入循环系统并诱导生热程序一些研究表明，鸢尾素在调节米色脂肪组织的作用中发挥着关键作用。对骨骼的锻炼，证明间歇性低剂量鸢尾素（0.1 毫克/千克，每周一次）刺激皮质骨形成并防止体内卸载引起的骨丢失，并在体外增强成骨作用3-5。利用小鼠遗传学的力量，我们的团队致力于进一步阐明鸢尾素在骨骼重塑，证明肌肉中强制表达 Fndc5 可显着减少骨质形成和质量，减少成骨细胞数量，同时增加破骨细胞，并增加 NF-κB 和 SOST 表达同时抑制骨形成标志物的血清水平，类似地，基因缺失。 Fndc5 导致椎骨量增加，并完全防止卵巢切除术 (OVX) 引起的骨质流失在雌性小鼠中，其特点是维持骨细胞腔隙密度和大小，阻止骨吸收，并且尽管在野外长期缺乏雌激素，但 RANKL 表达没有增加。型小鼠导致较高的血清硬化素水平和较高的 Irisin mRNA 表达。 MLOY-4 骨细胞体外表现出对该细胞类型的直接影响，诱导基因和蛋白质水平以剂量依赖性方式表达硬化蛋白并防止过氧化氢诱导的细胞凋亡。重要的是，我们通过生物化学和生物物理手段确定αVβ5整合素是主要的，尽管可能不是骨细胞中鸢尾素的唯一受体6。我们现在有证据表明，除了对骨细胞有影响外，鸢尾素还直接作用于骨细胞。破骨细胞刺激分化，用抗体阻断 αVβ5 和 αVβ3 可以逆转这种效应从表面上看，这些数据似乎与肌因子是拮抗剂的普遍假设背道而驰。然而，在生理背景下，鸢尾素也可能通过直接刺激成骨细胞。释放 clastokine 或基质结合生长因子，或者它可能具有作为反调节的独特作用通过增加吸收来维持钙稳态的激素通过本文提出的工作，我们将解决两个具体目标，以检验鸢尾素作为关键调节因素的中心假设运动对骨重塑的影响；通过整合素 αVβ5 直接作用于破骨细胞，以及通过破骨细胞旁分泌信号与骨细胞和成骨细胞的调节，因为这种肌因子可能发挥作用。这项工作在连接身体活动和骨重塑方面发挥着关键作用，将重点关注传统的静态体外研究培养模型以及解决机械载荷（例如流体剪切力）对破骨细胞的影响，成骨细胞和骨细胞，特别是鸢尾素对细胞机械敏感性的影响。