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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. But Spiegelman says that its this bit of bone breakdown that signals the body to engage in some skeletal renovation.
The results appear in the journal Cell.
Boning up on the actions of irisin could help us work out how we can derive the most from our workouts. And possibly keep our bones dense enough to keep us dancing in our dotage. And:
"The new work identifying the receptor also allows us to really much more easily identify what are other target cell types for irisin. With particular reference to neural cell types. Where there is suggestive evidence by us and others that irisin may play a neuroprotective effect in disorders such as Alzheimer's Disease, Parkinson's Disease and ALS."
Thanks for listening for Scientific American — 60-Second Science. I'm Karen Hopkin.

参考译文

这里是科学美国人——60秒科学ETvlD6-ExW5!JMbI+@Qm。我是凯伦·霍普金zWBE)H*,4!C。
锻炼可以塑造肌肉dYgjSVRv~y=sJDlra。同时也能强化骨骼BJk+50B_9EULi(p。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9,aZu]epjY#F7-。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HDnBIx_AGx。
体能活动刺激骨骼肌释放多种分子8P.x58wf*~7。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6pZ)^^#(tn。一旦产生，鸢尾素就能提高骨骼密度和强度%&KXn7aye~y。
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%F;.tY7u%vaTh=D6。这种受体蛋白在骨细胞上尤其丰富~i0N#&[);o5XW。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IiNHLrN|c.7^h3pn。
“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7FBTonJel(i,K。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H#C6v#Sr=Sx!)A7c!cS。”
骨硬化蛋白是是激发骨骼破坏的蛋白质&;Gvb@ju!%io。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Ut.E3qAVYiKfpX|B。但斯皮格尔曼表示，正是这一点骨质损坏向身体发出信号，让身体进行某些骨骼修复活动fotWTFE+)mY9Ks。
研究结果发表在《细胞》期刊上+rn|SXRx=iMk|JWsZ1。
专注研究鸢尾素的行为能帮助我们找到从锻炼中获得最大益处的方法BUh|N8isf#U,X3lTV。也许还能让我们的骨骼保持密度，让我们在年老时还能起舞q9-JUeFk](._KAM@xg)Q。而且：
“识别受体的新研究也让我们能更容易地辨别鸢尾素的其它靶细胞类型6zj4cmo&;nd6hW~w。尤其是神经细胞类型1n6.gQA@y*.o。我们和其他研究人员已有提示性证据证明，鸢尾素对阿尔茨海默病、帕金森病和肌萎缩性侧索硬化症（简称ALS）等类似疾病具有神经保护作用It-!w84V+2,77f#。”
谢谢大家收听科学美国人——60秒科学M1*)7&7Wn(bb(zPw@Je。我是凯伦·霍普金Qi]Jj)Qq6zcR。

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重点讲解

重点讲解：
1. name after (以…)为…命名；
The college is named after George Washington.
该大学以乔治·华盛顿的名字命名.HG&Nj0Cukq%)X。
2. engage in 参与；从事；
You can engage in croquet on the south lawn.
你可以参加南边草坪上的槌球游戏z_@6aTPuJmUOV*mc。
3. bone up on 钻研学习；复习；
She had boned up on the city's history before the visit.
她在访问前对这座城市的历史先研究了一番#TUw_#)n5f8-+Tt^Cz|。
4. work out 想出，得到(解决方法)；解(谜)；
It took me some time to work out what was causing this.
我花了一些时间才弄清此事的起因6qVr2q4(MfW。