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: 10228556
• 负责人: Eben Grant Estell
• 金额: $ 6.73万
• 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 2023-05-04
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10228556
• 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; Cleaved cell; 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; 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.

摘要 肌因子鸢尾素是一种肽，其是从肌肉结合蛋白Fndc 5（纤连蛋白）蛋白水解而来的 含III型结构域的蛋白质5）在运动期间进入循环并诱导产热程序 在米色脂肪组织中1，2.几项研究表明，鸢尾素在介导抗肿瘤作用中起关键作用。 在骨骼上运动，证明间歇性低剂量鸢尾素（0.1mg/kg每周一次）刺激皮质 骨形成和防止体内卸载诱导的骨丢失，并增强体外骨生成3 -5。 利用小鼠遗传学的力量，我们的研究小组致力于进一步阐明鸢尾素在以下方面的作用： 骨骼重塑，表明Fndc 5在肌肉中的强制表达显著降低了骨 形成和质量，减少成骨细胞数量，同时增加破骨细胞，增加NF-κB和 SOST表达，同时抑制骨形成标志物的血清水平。同样，基因缺失 Fndc 5导致高椎体骨体积和完全保护免受卵巢切除术（OVX）诱导的骨丢失 在雌性小鼠中，以维持骨细胞陷窝密度和大小为标志，阻止骨吸收， 尽管长期雌激素剥夺，但RANKL表达未增加。野生动物短期输注鸢尾素 型小鼠导致更高的血清硬化素水平和更大的SOST mRNA表达。Irisin治疗 体外培养的MLOY-4骨细胞表现出对该细胞类型、诱导基因和蛋白水平的直接影响 sclerostin以剂量依赖性方式表达并阻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鉴定出αVβ5整合素是主要的， 尽管可能不是唯一的，骨细胞中鸢尾素的受体6。 我们现在有证据表明，除了对骨细胞的作用外，鸢尾素还直接作用于 破骨细胞刺激分化，这种作用可以通过用抗体阻断αVβ5和αVβ3来逆转 对手。从表面上看，这些数据似乎与肌因子是 纯合成代谢的骨骼。然而，在生理学背景下，鸢尾素也可能间接刺激成骨细胞， 断裂因子或基质结合生长因子的释放，或者它可能具有作为反调节因子的独特作用。 激素通过增加再吸收来维持钙稳态。通过本文提出的工作，我们将 解决两个具体的目标，以测试中心假设，即鸢尾素作为一个关键的调节因素， 运动对骨重建的影响;通过整合素αVβ5直接作用于破骨细胞， 用骨细胞和成骨细胞调节破骨细胞旁分泌信号。因为这个肌细胞因子可能会 这项工作在联系身体活动和骨骼重塑方面发挥着关键作用，将重点关注传统的体外静态研究 培养模型以及解决机械负荷如流体剪切对破骨细胞的影响， 成骨细胞和骨细胞，特别是关于鸢尾素对细胞机械敏感性的影响。