Do Gut Microbes Control Your Personality? | Kathleen McAuliffe | TED

譯者: Lilian Chiu 審譯者: 麗玲 辛

We've been debating the question forever.

我們一直在辯論這個問題。

自由意志真的存在嗎？

Is there such a thing as free will?

我的船由我掌舵嗎？

Am I captain of my ship?

Master of my own destiny?

我能主導我自己的命運嗎？

I'm no philosopher.

我不是哲學家。

Biology is my realm and from where I stand,

我的領域是生物學， 從我的觀點來看，

掌舵的很明顯不只一人。

there is clearly more than one of us at the helm.

I'm referring to the fact

我指的是，

that half the cells in your body do not contain your own DNA.

你體內的細胞有一半 都沒有你自己的 DNA。

They belong to bacteria, protozoa, fungi

它們屬於細菌、原生動物、菌類，

and other unicellular creatures.

及其他單細胞生物。

These tiny tenants, collectively known as our microbiota,

這些小小房客統稱為微生物叢，

are most abundant in the gut,

在腸道中最多，

where they aid in digestion

在那裡，它們能幫助消化 並進行其他重要的功能。

and carry out many other essential functions.

Most amazing, they "talk" to your brain.

最神奇的是，它們 會跟你的大腦「說話」。

They influence your mood,

它們會影響你的心情、

your energy level, your appetite,

你的能量水平、你的食慾、

your memory,

你的記憶力，

perhaps even your personality.

甚至可能影響你的個性。

I can say this with confidence

我能信心滿滿地這樣說， 是因為這種沒有微生物的老鼠。

owing to mice like this, which have no microbes.

They've been dubbed bubble mice

牠們被稱為泡泡老鼠， 因為牠們被養在無菌設施中。

because they're raised in sterile facilities.

Contrast their behavior to that of a normal mouse,

把牠們的行為和正常老鼠做比對，

which is colonized at birth with microbes,

也就是出生時就有 微生物共生的老鼠，

and you'll notice striking differences.

就會發現驚人的差異。

正常的老鼠學習速度快且渴望學習。

A normal mouse is a quick and eager learner.

Show it a novel object, like a napkin ring,

讓牠接觸一個新穎的物體，如餐巾環，

and it will circle and sniff it with great interest.

牠會很有興趣地繞著它、聞聞看。

Place it in a maze and it's keen to explore new passages

把牠放在迷宮裡，牠會 很熱衷去探索新的通道，

and remembers where it's been.

且記住牠走過的路。

A bubble mouse could not be more different.

泡泡老鼠截然不同。

It lacks natural curiosity.

牠缺乏天生的好奇心。

It's slow to learn, quick to forget,

牠的學習速度很慢，很快就忘記。

and just as inclined to favor the familiar

且傾向偏好熟悉的事物，

over what's new, exciting, or different.

而非新奇、有趣，或不同的事物。

Indeed, they don't even protest

實際上，若小時被和母親分開， 牠們甚至也不會抗議，

if separated at a young age from their mothers,

a trauma that in a normal mouse would lead to lifelong skittishness.

換作正常老鼠，這種創傷 會造成一生都很怯懦。

But if you colonize a bubble mouse early in life

但如果在泡泡老鼠小時候就讓牠們

with the normal microbiota for that strain,

和該種正常的微生物叢共生，

guess what happens?

猜猜會如何？

Their behavior normalizes.

牠們的行為會變正常。

We're not mice.

我們不是老鼠。

So does any of this apply to us?

前述的現象也適用於我們嗎？

Actually a mountain of evidence suggests that it does.

事實上，有大量證據證明的確適用。

Consider this.

想想這個狀況：

If I transfer gut bacteria from an overweight twin to bubble mice,

若我把腸道細菌 從體重過重的雙胞胎轉移

給泡泡老鼠，牠們就會胖起來。

the animals fatten up.

Transfer gut bacteria from a thin twin to bubble mice,

把腸道細菌從瘦的雙胞胎 轉移給泡泡老鼠，

feed them the same rat chow and the animals stay thin.

餵牠們吃同樣的老鼠食物， 牠們仍然維持瘦的體態。

Similarly, if I transfer gut bacteria from a depressed person

同樣的，

如果我把腸道細菌 從憂鬱的人轉移給泡泡老鼠，

to a bubble mouse,

the animal will display depressive-like symptoms.

牠們會展現出類似憂鬱的症狀。

For example, if placed in a water tank,

比如，把牠們放在水槽中，

it stops swimming sooner than a mouse that receives gut bacteria

牠們停止游泳的時間會早於

接收來自非憂鬱者腸道細菌的老鼠。

from a non-depressed person.

That mouse will keep trying to escape.

那些老鼠會持續嘗試逃脫， 不會那麼快絕望。

It's not so quick to give in to despair.

How in the world can gut bacteria influence how we feel and act?

到底為什麼腸道細菌 會影響我們的感受和行為？

They have many techniques, actually.

事實上，牠們有很多技能。

But here's one of their coolest.

但以下這點最酷：

Gut bacteria produce hoards of psychoactive compounds,

腸道細菌會產生

大量的精神活性化合物， 包括六種神經傳遞質。

including half a dozen neurotransmitters.

Put simply, gut bacteria can talk to the brain because we,

簡言之，腸道細菌

能和大腦對話，因為我們， 即人體細胞和體內的微生物，

meaning our microbes and human cells,

all speak the same language.

都說同樣的語言。

In fact, some scientists think

事實上，

有些科學家認為這種語言 實際上是由細菌發明的。

this language was actually invented by bacteria.

I should point out that this long-distance conversation

我要強調，這種長程對話

is facilitated by a major nerve cable that runs from your gut to your brain.

是透過一條連結腸道和大腦的 主要神經纜線來進行的。

It's called the vagus nerve,

它叫做迷走神經，

and it can be directly activated by bacteria

細菌可以直接啟動它，

or by the psychoactive compounds they produce.

也可由它們產生的 精神活性化合物來啟動。

Incidentally, about 80 percent of the traffic on this cable

順道一提，這條神經 纜線上約 80% 的訊息

is going from the gut to the brain and not the other way around,

是從腸道傳向大腦，而非 長期以來大家假設的相反方向。

as had long been assumed.

Of course, gut bacteria can also rely on the circulatory system

當然，腸道細菌也可以靠循環系統

to transport their psychoactive compounds upstairs.

把它們的精神活性化合物向上傳送。

And there's one other very important, albeit indirect way

腸道細菌還有一種 間接但很重要的方式，

that gut bacteria signal the brain.

可以把訊息傳遞給大腦，

And that's by misbehaving.

那就是做出不當行為。

When aggressive bacteria invade the gut wall,

當侵略性細菌入侵腸壁時，

immune cells rush to the scene

免疫細胞會趕到現場，

and surprising scientists,

讓科學家很驚訝的是，

those immune cells and related compounds don't always stay localized in the gut,

那些免疫細胞和相關的化合物 不見得都會留在腸道處，

but can travel to the brain

有可能會跑到大腦。

where they trigger inflammation and depression.

在那裡，它們會觸發炎症和憂鬱。

For reasons that are not well understood,

我們尚不了解原因，

inflammation and depression often go hand in hand.

但炎症和憂鬱通常是相伴出現的。

They're a destructive duo.

它們是破壞雙煞。

有趣的是，有種快速發展的 方法可以治療心理障礙，

Interestingly, a rapidly advancing treatment for mental disturbances

is called vagus nerve stimulation, or VNS.

叫做迷走神經刺激（VNS）。

As its name suggests,

顧名思義，

it entails electrically stimulating the vagus nerve

需要透過植入在胸部的電極 對迷走神經進行電刺激。

via an electrode implanted in the chest.

Although this therapy evolved independently of microbiota research,

儘管這種治療法的發展 獨立於微生物叢的研究，

some scientists think

但有些科學家認為，

that the current may actually mimic the effects of gut bacteria

電流實際上可能模仿了 腸道細菌對神經的影響。

on the nerve.

That's speculative, but what is clear is that VNS strengthens the gut barrier,

這只是推測，但可以確定的是 VNS 強化了腸道屏障，

preventing pathogenic bacteria from breaching it

防止致病的細菌突破屏障，

and causing an inflammatory response that spreads to the brain.

造成在大腦中擴散的炎症反應。

Encouragingly, the FDA has already approved VNS

讓人振奮的是，美國食品藥物 管理局已經核准用 VNS

for the treatment of severe epilepsy

來治療用標準療法沒有效果的 嚴重癲癇及憂鬱症。

and depression unresponsive to standard therapy.

What's more, early clinical trials suggest

此外，早期的臨床試驗顯示，

the procedure may also benefit people suffering from ADHD, OCD and PTSD.

VNS 也許可以幫助患有過動症、 強迫症，及創傷後壓力症候群的人。

In parallel with these developments,

在發展這些的同時，

microbiota researchers are attempting to treat mental disturbances

微生物叢研究者 也在試圖治療心理障礙，

by changing the composition of our gut bacteria

做法是改變腸道細菌的組成，

or alternatively,

另一種方法是促進或阻斷

by boosting or blocking the action of the chemicals these organisms make.

這些有機體所製造的 化學物質的影響。

To that end,

在這方面，

they're making exciting progress

他們已有令人興奮的進展，

in pinpointing exactly which bacteria are good or bad actors

確切找出在各種神經精神疾病中，

哪些細菌扮演有益或有害的角色。

in various neuropsychiatric conditions.

People with autism spectrum disorder, for example,

舉例來說，患有自閉症類群障礙的人

often have high amounts of a bacteria molecule in their blood,

血液中通常會有 某種大量的細菌分子，

and in rodents,

在齧齒目動物身上，

this molecule has been shown to raise anxiety

已證明這種分子會造成焦慮，

and even alter brain connectivity.

甚至會改變大腦的連接性。

Axial Therapeutics,

Axial Therapeutics

a company at the forefront of developing microbiota-based treatments,

這家公司在開發以微生物叢 為基礎的治療方面走在很前端，

is now conducting a clinical trial of a drug

該公司目前正在進行 一項藥物的臨床試驗，

designed to prevent this destructive molecule

藥物的目的在預防 這種有害分子進入大腦。

from reaching the brain.

The goal is to treat irritability in children with autism.

目標是要治療自閉症兒童的易怒症狀。

Meanwhile, a bacterium found in yogurt called Lactobacillus reuteri

同時，在優格中發現的洛德乳酸桿菌

has shown to promote social bonding in animal models of autism.

已證實可在自閉症動物模型中 促進社交連結。

Both good and bad bacteria have similarly been linked

好細菌和壞細菌同樣都

to amyotrophic lateral sclerosis, or ALS.

與肌萎縮性脊髓側索 硬化症（ALS）有關。

That's the neurodegenerative disease

那是一種神經退化性疾病，

best known for paralyzing the great baseball player Lou Gehrig

最為人所知的是這種疾病 讓偉大的棒球員盧‧蓋瑞格

at the peak of his career.

在職涯巔峰時癱瘓，

Like him, most patients die within just a few years

和他一樣，

大部分的病人會在被診斷出 該疾病的幾年內過世。

of being diagnosed with the disease.

A small minority live ten years or longer.

有一小部分病人能再活超過十年。

In animal models of ALS,

在 ALS 的動物模型中，

Israeli researchers have recently discovered two bacteria

以色列研究者最近發現了兩種細菌

會加速該疾病，

that accelerate the disease

and another that slows its development.

還有一種則會減緩疾病的發展。

They suspect the benefits of the good bacteria

他們懷疑，好細菌之所以有益，

are due to a vitamin that it produces, called nicotinamide.

是因為它們會產生一種 叫做菸鹼醯胺的維生素。

Microbiota researchers are making even greater progress

微生物叢研究者還有更大的進展，

in unraveling the root causes of Parkinson's disease.

有機會解開帕金森氏症的根本成因。

If you know the actor Michael J. Fox,

如果你知道演員米高‧J‧福克斯，

if you've seen many of his videos,

如果你看過許多他的影片， 就會知道該疾病的症狀包括

you'll know its symptoms are shaking,

顫抖、僵硬，和步伐不穩定。

stiffness and an unsteady gait.

It's long been known that the disease involves the misfolding of a protein

長年以來我們都知道這種疾病 和大腦中這個區域裡的

called alpha-synuclein in this part of the brain.

蛋白質 α—突觸核蛋白 發生錯誤摺疊有關。

As the misfolding spreads, brain cells start to die,

隨著錯誤摺疊的擴散， 大腦細胞會開始死亡，

symptoms worsen.

症狀就會惡化。

The big mystery is, what causes alpha-synuclein,

最大的謎團是：

什麼造成 α—突觸核蛋白， 即帕金森氏症蛋白質，

the Parkinson's protein,

to misfolded in the first place.

在一開始會發生錯誤摺疊？

Several labs have recently converged on one likely culprit.

最近，數個實驗室對於 可能禍首的認定有了共識。

The guts of some people, their research suggests,

他們的研究發現，有一些人的腸道

harbor a strain of E. coli

內有一種大腸桿菌的菌株，

that churns out a misfolded compound very similar to the Parkinson's protein.

它會產生一種錯誤摺疊的化合物，

和帕金森氏症的蛋白質很類似。

And when misfolded variants of this protein

當把這種蛋白質的錯誤摺疊變體

are injected into the guts of susceptible rodents,

注射到易受感染的 齧齒目動物的腸道中，

it causes the normal protein in the intestinal lining

會導致腸道內壁的 正常蛋白質隨之錯誤折疊，

to misfold in turn.

就像倒下的骨牌，

Like falling dominoes,

this wave of misfolding proteins slowly spreads up the vagus nerve,

這波錯誤摺疊蛋白質會緩慢地 沿著迷走神經向上擴散，

and in about two months,

經過大約兩個月，

you see clumped up protein in exactly the part of the brain

就會在大腦中看到凝聚的蛋白質，

正好就在帕金森氏症患者 腦部退化的部分。

that degenerates in Parkinson's patients.

Most importantly,

最重要的是，

these fresh glimpses into the origins of the disease

這些對於疾病起源的新發現

are suggesting new ways of intervening in its progression,

意味著有新方法 可以干預疾病的發展，

a prospect, needless to say, that has experts super excited.

不用說，專家對於 這個前景都感到超級興奮。

Of course, it's early days.

當然，現在還在初期。

We don't yet know

我們尚不知道

whether successful treatments will emerge from this line of research,

是否能從這個研究方向， 找到成功的治療方法，

or, for that matter,

或，就這點來說，

any of the other investigations I've described.

從我先前提到的其他研究裡找到。

But I think you'll agree there's cause for optimism.

但我相信各位都同意， 有保持樂觀的理由。

If nothing else, I hope I've convinced you that your behavior is controlled

我希望我至少已經說服大家， 你們的行為是被控制的，

not just from the top down,

不只是由上而下的控制， 也真的有由下而上的控制。

but quite literally from the bottom up.

In short, the person you call "I" is really "we."

簡言之，各位稱為「我」的那個人

其實應該是「我們」。

Thank you.

謝謝。

(Applause)

（掌聲）