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2015年9月21日讯 /生物谷BIOON/ --近日一项研究发现运动之后由肌肉产生的一种分子能够增加骨密度，这项研究由美国和意大利的科学家共同完成，发表在国际学术期刊PNAS上。 虽然大家都知道运动是促进新骨形成的一个重要因素，并且肌肉与骨还是靠得很近的'邻居'，但是人们对于肌肉究竟如何与骨进行'对话'一直不是很了解。 在这项研究中，研究人员选取了年轻的雄性小鼠作为研究对象，主要因为在年轻小鼠体内更容易观察到骨质沉积。之后他们给小鼠注射了一种叫做Irisin的物质，Irisin是一种来源于骨骼肌的蛋白分子，因此也是一种肌肉因子，之前有研究表明Irisin在身体脂肪调节方面发挥重要作用。在注射Irisin之后，研究人员观察到小鼠的骨含量和强度都得到显著增强，特别是占身体骨骼重量80%的高密度紧实型骨组织--皮质骨。而骨小梁以及松质骨等成分基本不会受到影响。 这项研究表明Irisin是肌肉与骨之间'对话'的物质基础，它能够直接刺激成骨细胞促进新骨形成，从而将运动带来的促骨骼合成代谢作用'翻译'出来。 身体活动量下降会导致骨的不断流失并增加骨折风险，比如宇航员在太空中骨质流失的速度是绝境早期女性的10倍还多，植物人以及脊柱损伤病人发生脆性骨折的风险非常高，因此失重情况以及缺乏运动都会导致急性，快速同时非常严重的骨质流失。 这项研究发现运动后肌肉产生的Irisin可以增加骨质含量，或对未来治疗衰老导致的肌肉减少症以及骨质疏松症具有重要意义。（生物谷Bioon.com） 本文系生物谷原创编译整理。欢迎转载！转载请注明来源并附原文链接。更多资讯请下载生物谷资讯APP。  The myokine irisin increases cortical bone mass Graziana Colaiannia,1, Concetta Cuscitoa,1, Teresa Mongellia, Paolo Pignataroa, Cinzia Buccolieroa, Peng Liub, Ping Lub, Loris Sartinic, Mariasevera Di Comitea, Giorgio Morid, Adriana Di Benedettod, Giacomina Brunettia, Tony Yuenb, Li Sunb, Janne E. Reselande, Silvia Coluccia, Maria I. Newb,2, Mone Zaidib,2, Saverio Cintic, and Maria Grano It is unclear how physical activity stimulates new bone synthesis. We explored whether irisin, a newly discovered myokine released upon physical activity, displays anabolic actions on the skeleton. Young male mice were injected with vehicle or recombinant irisin (r-irisin) at a low cumulative weekly dose of 100 ?g kg?1. We observed significant increases in cortical bone mass and strength, notably in cortical tissue mineral density, periosteal circumference, polar moment of inertia, and bending strength. This anabolic action was mediated primarily through the stimulation of bone formation, but with parallel notable reductions in osteoclast numbers. The trabecular compartment of the same bones was spared, as were vertebrae from the same mice. Higher irisin doses (3,500 ?g kg?1 per week) cause browning of adipose tissue; this was not seen with low-dose r-irisin. Expectedly, low-dose r-irisin modulated the skeletal genes, Opn and Sost, but notUcp1 or Pparγ expression in white adipose tissue. In bone marrow stromal cell cultures, r-irisin rapidly phosphorylated Erk, and up-regulated Atf4, Runx2, Osx, Lrp5, β-catenin, Alp, and Col1a1; this is consistent with a direct receptor-mediated action to stimulate osteogenesis. We also noted that, although the irisin precursor Fndc5 was expressed abundantly in skeletal muscle, other sites, such as bone and brain, also expressed Fndc5, albeit at low levels. Furthermore, muscle fibers from r-irisin-injected mice displayed enhanced Fndc5 positivity, and irisin induced Fdnc5 mRNA expression in cultured myoblasts. Our data therefore highlight a previously unknown action of the myokine irisin, which may be the molecular entity responsible for muscle-bone connectivity. |
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