常动肠年轻

Marathon Microbes

肠道菌群让我们保持健康,增强免疫力,促进新陈代谢。其实,细菌不仅能助我们一臂之力,还能助我们两腿之力,让我们跑得又快又久。一项新研究发现,喂食了从优秀运动员身上分离出的细菌的老鼠比只喂食酸奶中的细菌的老鼠在跑步机上跑得更久。这项研究结果发表在自然医学杂志上。

亚历山大科斯蒂奇是哈佛医学院的菌群学家,他最初的研究方向是,糖尿病人与没有糖尿病的人,他们的肠道菌群是否不同,改变菌群是不是有助于治疗糖尿病。他后来发现,我们还可以从另一个角度提高整体健康水平,研究的方向变成了:一个完全健康的人,肠道菌群有何独特之处?我们能不能将这种健康者体内特有的菌群转移到其他人身上,让他们变得健康?

要研究肠道菌群,查大便是个好方法。于是,科斯蒂奇和团队找了十五名二零一五年波士顿马拉松选手,请他们提供从赛前一周直到赛后一周的每日大便样本。团队还收集了另外十个明显更爱久坐的人的大便样本。然后团队对所有人的细菌进行统计。拿到统计结果后,他们意外发现:有一种细菌我们还没有很好研究,那就是韦荣氏菌。他们发现,在跑完马拉松之后,肠道中的韦荣氏菌数量显著增加。不仅如此,在优秀的马拉松运动员体内发现这种细菌的频率要比在普通人中高得多。

为了判定这种菌群是否有利于运动员,他们给了老鼠喂了一些,然后让它们跑起来。结果发现,与携带乳杆菌的老鼠相比,携带韦荣氏菌的老鼠在跑步机上跑得更久,时间延长了百分之十三。不管是耐力型运动员,还是普通运动员都会告诉你,百分之十三的增幅是相当可观的。

有趣的是,韦荣氏菌以乳酸为食,乳酸是由于肌肉疲劳而产生的一种化学物质。韦荣氏菌消耗乳酸,将其转化为一种叫丙酸的脂肪酸。研究人员通过极小的灌肠剂将丙酸注入老鼠体内,模仿肠道细菌释放丙酸的过程,同样延长了老鼠在跑步机上的时间。所以说这是一种良性循环。运动产生乳酸,乳酸提供养分,使韦荣氏菌大量繁殖,韦荣氏菌产生丙酸,丙酸又能提高耐力,至少能提高跑步机上老鼠的耐力。难怪优秀马拉松运动员身上韦荣氏菌那么富集。这也意味着,大便里的肠道菌群可能是提高耐力预防疲惫的秘密武器。

原文

The microbes in our intestines help keep us healthy, strengthening our immune systems and promoting metabolism. But they may also give us a leg up when it comes to moving our legs up - and down again, rapidly and repeatedly - because a new study finds that mice that are fed bacteria isolated from elite athletes log more time on the treadmill than other mice that are treated only to bacteria found in yogurt. The results appear in the journal Nature Medicine.

Aleksandar Kostic, a microbiologist at Harvard Medical School, was initially interested in how the gut microbes of people with diabetes might differ from folks without the condition - the idea being that tweaking the microbiome might help to treat the disease. But the question of enhancing overall health and fitness can also come from the other direction: "Here the question was more, what's unique in the gut microbiome of someone who is supremely healthy? And can we use that feature of the microbiome to transfer into other people to potentially make them healthier?"

And a handy window into the gut is poop. So Kostic and his crew asked 15 runners who competed in the Boston Marathon in 2015 to provide daily stool samples from a week before the race to a week after. They also collected samples from 10 people who are decidedly more sedentary, and they tallied the bacteria present in each. "And when we looked at this data, there was really one thing that jumped out at us, and it was this genus of bacteria that isn't so well studied: Veillonella. We found it was very significantly higher in abundance in the gut after the marathon. But not only that, it was found much more frequently in elite marathon runners than in the general population."

To see whether this microbe might provide the athletes with any benefit, they gave some to mice and then let the little rodents run. And they found that the mice loaded with Veillonella spent more time on the treadmill than those that got Lactobacillus. "And this was an increase of 13 percent. I think any endurance athlete or any athlete in general will tell you that a 13 percent increase is pretty significant."

Now, the interesting thing about Veillonella is that they thrive on lactate, which is a chemical produced by fatigued muscle. The bacteria consume lactate and convert it into a fatty acid called proprionate. And mice that were treated to proprionate, which was delivered via teeny tiny enemas to mimic its release by gut bacteria, similarly extended their treadmill time. "So this creates a kind of a positive feedback loop and helps us to understand why Veillonella might be enriched in elite athletes in the first place." Exercise produces lactate, which feeds Veillonella. Veillonella produces proprionate, which somehow promotes endurance, at least in treadmill-trotting mice. Which means that gut microbes may hold the secret to extending that workout - without getting pooped.

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