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 肌动蛋白是一种从肌肉结合蛋白FNDC5(纤维连接蛋白)中分解而来的多肽 III型含结构域蛋白5)在运动过程中，并进入循环并诱导生热程序 在米色脂肪组织中，1，2。几项研究表明，淫羊藿素在调节 在骨骼上锻炼，表明间歇性小剂量淫羊藿素(0.1 mg/kg，每周一次)刺激皮质 在体内形成骨和防止卸载导致的骨丢失，并在体外3-5促进成骨。 利用小鼠遗传学的力量，我们小组努力进一步阐明淫羊藿素在 骨骼重塑，表明FNDC5在肌肉中的强制表达显著减少骨骼 形成和质量，减少成骨细胞数量，增加破骨细胞，增加NF-κB和 在抑制血清骨形成标志物水平的同时，减少骨形成标志物的表达。同样，基因缺失也会导致 FNDC5可增加椎体骨体积，完全防止卵巢摘除(OVX)所致的骨丢失 在雌性小鼠中，以维持骨细胞陷窝密度和大小为特征，阻止骨吸收，以及 尽管长时间的雌激素剥夺，RANKL的表达没有增加。野生短期注射淫羊藿素 各型小鼠血清硬化素水平较高，Sost基因表达较高。淫羊藿素治疗慢性萎缩性胃炎 体外培养的MLOY-4骨细胞直接作用于该细胞类型、诱导基因和蛋白水平 以剂量依赖的方式表达硬化素，并防止过氧化氢诱导的细胞凋亡。 重要的是，我们通过生化和生物物理手段确定了αVβ5整合素是主要的， 尽管可能不是骨细胞中唯一的虹膜蛋白受体。 我们现在有证据表明，除了对骨细胞的影响外，淫羊藿素还直接作用于 破骨细胞刺激分化，这种作用通过用抗体阻断αVβ5和αVβ3而被逆转 对抗者。从表面上看，这些数据似乎与肌肉激动素的普遍假设背道而驰 纯合成代谢的骨骼。然而，在生理学方面，淫羊藿素也可能通过间接刺激成骨细胞。 释放碎裂因子或与基质结合的生长因子，或者它可能作为一种反调节因子具有独特的作用 通过增加吸收来维持钙动态平衡的激素。通过这里提出的工作，我们将 阐述两个具体的目的，以检验虹膜蛋白作为关键调节因子在体内的中心假说 运动对骨重建的影响；既通过整合素αVβ5直接作用于破骨细胞，又通过 破骨细胞旁分泌信号与骨细胞和成骨细胞的调节。因为这个myokine可能会玩 作为联系体力活动和骨重建的关键角色，这项工作将重点放在传统的静态体外研究上 培养模型以及诸如流体剪切等机械载荷对破骨细胞的影响， 成骨细胞，和骨细胞，特别是关于淫羊藿素对细胞机械敏感性的影响。