今冬最强寒潮来袭！本轮寒潮影响范围广、降温剧烈，全国大部分地区都将开启冰冻模式。


今冬以来最强寒潮正影响我国 图源：中国天气

随着气温断崖式下降，你有没有被冻得瑟瑟发抖呢？如果答案是“没有”，没准你就是天选“不怕冷星人”！ 6park.com
科学研究发现，全球约有五分之一的人由于基因突变，体内缺乏α-辅肌动蛋白-3（protein α-actinin-3），而更能忍受寒冷。



人的骨骼肌由快缩肌纤维和慢缩肌纤维组成，前者易疲劳，而后者更耐疲劳。 6park.com
Skeletal muscle comprises fast-twitch muscle fibres that fatigue quickly and slow-twitch muscle fibres that are more resistant to fatigue.

▪ skeletal: /ˈskelət(ə)l/ adj. 骨骼的

两种肌纤维的作用不同，快缩肌纤维负责跳跃、冲刺等快速运动，而慢缩肌纤维则负责缓慢的有氧运动。比如，爆发型运动员有很高比例的快缩肌纤维，反之，耐力型运动员则慢缩肌纤维较多。


短跑选手含较高比例的快缩肌纤维 图源：Pediaa

α-辅肌动蛋白-3是一种只存在于快缩肌纤维内的蛋白质。由于基因突变，全球近20%的人（约15亿人）体内完全没有这种蛋白质。 6park.com
The protein α-actinin-3, which is found only in fast-twitch muscle fibres, is absent in almost 20 percent of people — almost 1.5 billion individuals — due to a mutation in the gene that codes for it.

▪ mutation: /mjuːˈteɪʃn/ n. 变异，突变


图源：The American Journal of Human Genetics

来自瑞典卡罗林斯卡学院的研究人员表示，这些人的骨骼肌更多由慢缩肌纤维构成。与快缩肌纤维相比，这一肌纤维更加持久，所需能量较少，而且对低温的忍耐力更强。该研究结果发表于《美国人类遗传学杂志》（The American Journal of Human Genetics）。 6park.com
Researchers at Karolinska Institutet in Sweden now show that more of the skeletal muscle of these individuals comprises slow-twitch muscle fibres, which are more durable and energy-efficient and provide better tolerance to low temperatures than fast-twitch muscle fibres. The results are published in the scientific journal The American Journal of Human Genetics. 6park.com
他们猜测，从进化的角度来看，这一基因突变主要是在人类从非洲迁徙到中欧、北欧等较冷区域时发生的。



卡罗林斯卡学院生理学和药理学系的细胞肌肉生理学教授霍坎·维斯特布拉表示：“这表明缺乏α-辅肌动蛋白-3的人更擅长保暖，能够在极端天气中调节自身能量。但此前我们并没有发现直接的实验证据。” 6park.com
"This suggests that people lacking α-actinin-3 are better at keeping warm and, energy-wise, at enduring a tougher climate, but there hasn't been any direct experimental evidence for this before," says Håkan Westerblad, professor of cellular muscle physiology at the Department of Physiology and Pharmacology, Karolinska Institutet.


图源：Getty Images

研究团队通过实验证实了缺乏这种蛋白质的人会有“突出的抗寒能力” （superior cold resilience）。 6park.com
在实验时，42名年龄在18岁至40岁之间的健康男性被要求坐在14℃的冷水中，一直持续到他们的体温下降至35.5℃。 6park.com
For the study, 42 healthy men between the ages of 18 and 40 were asked to sit in cold water (14 °C) until their body temperature had dropped to 35.5 °C.



在浸入冷水的过程中，研究人员用肌电图（electromyography, EMG）测量受试者的肌电活动。另外他们还进行了肌肉活检（muscle biopsies）以研究蛋白质含量和纤维类型组成。 6park.com
During cold water immersion, researchers measured muscle electrical activity with electromyography (EMG) and took muscle biopsies to study the protein content and fibre-type composition.


图源：Getty Images

结果显示，这些缺乏α-辅肌动蛋白-3的人的骨骼肌中含有较大比例的慢缩肌纤维。在降温实验中，这些人能够通过保存能量来维持自身的体温。快缩肌纤维会靠颤抖来对抗低温，而这些人则是通过增加肌肉收缩（肌紧张），激活慢缩肌纤维来产生热量。 6park.com
The results showed that the skeletal muscle of people lacking α-actinin-3 contains a larger proportion of slow-twitch muscle fibres. On cooling, these individuals were able to maintain their body temperature in a more energy-efficient way. Rather than activating fast-twitch muscle fibres, which results in overt shivering, they increased the activation of slow-twitch muscle fibers that produce heat by increasing baseline contraction (tonus).

▪ baseline: /ˈbeɪslaɪn/ n. 基准 6park.com
▪ contraction: /kənˈtrækʃ(ə)n/ n. 收缩 6park.com
▪ tonus: /ˈtəʊnəs/ n. 肌紧张

维斯特布拉说：“慢缩肌纤维能够有效地产生热量。缺乏α-辅肌动蛋白-3的人在寒冷环境下不会发抖，而是通过肌肉收缩储存能量。” 6park.com
"Slow-twitch muscle fibers generate heat effectively. People with an actinin-3 deficiency do not shiver during cold exposure. Instead, they save energy by increasing their muscle tone," says Westerblad.



然而，在不怕冷基因的背后，也存在着一定的健康隐患。 6park.com
维斯特布拉说：“这一基因突变很可能是为了满足向寒冷地域迁徙的进化需要。但在现代社会中，这种储存能量的能力反而会增加患多种疾病的风险，这是我们目前需要关注的问题。” 6park.com
"The mutation probably gave an evolutionary advantage during the migration to a colder climate, but in today's modern society this energy-saving ability might instead increase the risk of diseases of affluence, which is something we now want to turn our attention to," says Westerblad. 6park.com
一方面，这一人群仅凭借极少的能量就能维持体温，而另一方面，这也意味着他们肌肉消耗的能量更少。 6park.com
来自立陶宛体育大学的科学家马吕斯·布雷扎伊蒂斯（Marius Brazaitis）说：“我们目前推测，具有这种变异基因的人会摄入更多的卡路里，同时还缺乏锻炼，这可能会增加患肥胖症、2型糖尿病及其它代谢紊乱的风险。” 6park.com
"It is our hypothesis or assumption at this point that people with the gene variant who consume more calories and are physically inactive could be at a higher risk of obesity, type-2 diabetes, and other metabolic disorders," says Marius Brazaitis, a scientist at the Lithuanian Sports University.

▪ metabolic: /ˌmɛtəˈbɒlɪk/ adj. 新陈代谢的

不管是不是“不怕冷星人”，面对寒潮，还是添衣防寒更保险哦！