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This is Scientific American ― 60-Second Science. I'm Karen Hopkin.
Exercise builds muscle. But it also strengthens bones.
Exactly how exercise boosts bone strength is a matter of debate ― and a subject of scientific scrutiny.
Now, a new study in mice shows how a hormone secreted by active muscle cells triggers bone remodeling.
Physical activity stimulates the release of multiple molecules from skeletal muscle.
Take irisin, for example. This hormone, named after the Greek messenger goddess Iris,
is produced by running rodents ― and by us humans when we do high-intensity aerobic training.
Once it's generated, irisin improves bone density and strength.
To find out how, Bruce Spiegelman and his colleagues at the Dana Farber Cancer Institute and Harvard Medical School
took cultured bone cells and located the receptor to which irisin binds.
This receptor protein is particularly abundant on cells called osteocytes.
These cells are the master regulator of bone remodeling and the most abundant cell type in bone.
"What we found interesting in this paper is
the magnitude of the effects we get in terms of irisin acting to stimulate osteocytes and preventing their death in culture.
Also, their ability to make a key protein, sclerostin, under the stimulation of irisin."
Sclerostin is a protein that actually stimulates the breakdown of bone.
That irisin, which builds bone, would promote the production of sclerostin, which destroys it, may seem counterintuitive.
这里是科学美国人――60秒科学。我是凯伦・霍普金。
锻炼可以塑造肌肉。同时也能强化骨骼。
锻炼究竟是如何强化骨骼的?这是一个有争议的问题,也是科学审查的一项课题。
现在,一项在老鼠身上进行的新研究揭示了活跃肌肉细胞分泌的激素是如何触发骨骼重塑的。
体能活动刺激骨骼肌释放多种分子。
以鸢尾素为例,这种以希腊信使彩虹女神命名的激素,
是啮齿动物在奔跑时和我们人类在进行高强度有氧运动时产生的物质。
一旦产生,鸢尾素就能提高骨骼密度和强度。
为了弄清改善方式,布鲁斯・斯皮格尔曼和他在达纳法伯癌症研究所以及哈佛医学院的同事
提取了培养骨细胞,并定位了鸢尾素结合的受体。
这种受体蛋白在骨细胞上尤其丰富。
这些细胞是骨骼重塑的主控因子,也是骨骼中最丰富的细胞种类。
“我们发现这篇论文令人感兴趣的地方在于,
鸢尾素在刺激骨细胞并防止其在培养过程中死亡上发挥了重大作用。
还有,在鸢尾素的刺激下,骨细胞产生关键蛋白骨硬化蛋白的能力。”
骨硬化蛋白是是激发骨骼破坏的蛋白质。
而能生成骨骼的鸢尾素,竟然会促进会破坏骨骼的骨硬化蛋白的产生,这似乎违反常理。
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