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

• 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
• 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

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 肌动物虹膜蛋白是一种从肌肉结合的蛋白FNDC5（纤连蛋白）蛋白水解的胡椒粉（纤连蛋白 含III型结构域的蛋白质5）在运动过程中并进入循环并诱导热程序 在米色脂肪组织中1,2。几项研究表明，虹膜蛋白在介导的作用中起着关键作用 骨骼运动，证明间歇性低剂量虹膜蛋白（每周一次0.1 mg/kg）刺激皮质 骨形成并防止体内卸载引起的骨质损失，并在体外增强成骨3-5。 利用小鼠遗传学的力量，我们的小组已努力进一步阐明虹膜蛋白在 骨骼重塑，证明在肌肉中强迫FNDC5表达显着减少骨骼 形成和质量会减少成骨细胞数，同时增加破骨细胞，并增加NF-κB和 在抑制骨形成标记的血清水平的同时表达较高的表达。同样，遗传缺失的 FNDC5导致高椎骨体积，并完全保护卵巢切除术（OVX）诱导的骨质流失 在雌性小鼠中，以维持骨细胞的密度和大小为特征 RANKL表达目的地没有增加延长雌激素剥夺。野生中的短期虹膜蛋白输注 类型小鼠导致血清硬化素水平较高和更高的SOST mRNA表达。虹膜蛋白治疗 MLOY-4体外骨细胞对这种细胞类型，诱导基因和蛋白质水平有直接影响 硬化蛋白以剂量依赖性的方式表达，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的方法确定αVβ5整合素是主要的， 虽然不是唯一的，但在骨细胞中的虹膜蛋白的受体6。 现在，我们有证据表明，除了对骨细胞的影响外，虹膜蛋白还直接作用于 刺激分化的破骨细胞，通过用抗体阻断αVβ5和αVβ3来逆转这种效果 从表面上看，这些数据似乎与普遍的假设相反，即肌动物是 纯合成代谢骨骼。但是，在生理环境中，虹膜蛋白也可能通过 释放clastokines或矩阵结合的生长因子，或者它可能具有与反调节性的独特作用 马酮通过增加分辨率来维持钙稳态。在本文提议的工作中，我们将 解决了两个具体的目的，以检验虹膜蛋白作为关键调节剂的中心假设 运动对骨骼重塑的影响；通过直接通过整联蛋白αVβ5对破骨细胞的直接作用，以及 用骨细胞和成骨细胞调节破骨细胞旁分泌信号传导。因为这个肌动物可能会玩 这项工作在连接体育锻炼和骨骼重塑方面的关键作用将重点放在传统的静态体外 培养模型以及解决机械载荷（例如流体剪切对破骨细胞）的影响， 成骨细胞和骨细胞，对虹膜蛋白对细胞机理的影响具有特定的考虑。