You smell with your body, not just your nose | Jennifer Pluznick

譯者: yihui ma 審譯者: 绮丽 罗

Here's a question for you:

我要問你們一個問題：

how many different scents do you think you can smell,

你們知道你可以聞到多少種氣味？

and maybe even identify with accuracy?

甚至精確地辨識出來?

100?

100 種？

300?

300 種？

1,000?

1000 種？

One study estimates that humans can detect up to one trillion different odors.

一個研究估算，人類可以分辨出 高達一兆種不同氣味。

A trillion.

一兆種。

It's hard to imagine,

這個數字很難想像，

but your nose has the molecular machinery to make it happen.

但鼻子所具有的分子機制 能夠使之成爲現實。

Olfactory receptors --

嗅覺接受器──

tiny scent detectors --

微小的氣味探測器──

are packed into your nose,

都聚集在你的鼻子裡，

each one patiently waiting to be activated by the odor,

每一個都耐心等待著氣味來激活它，

or ligand,

也就是被配體激活，

that it's been assigned to detect.

被指定來檢測。

It turns out we humans, like all vertebrates,

事實上我們人類 和所有脊椎動物一樣，

have lots of olfactory receptors.

有很多嗅覺接受器。

In fact, more of our DNA is devoted to genes for different olfactory receptors

事實上，我們的 DNA 中被用來表達 不同的嗅覺接受器的基因數量，

than for any other type of protein.

多於任何其他的蛋白質結構。

Why is that?

為什麽會這樣呢？

Could olfactory receptors be doing something else

難道嗅覺接受器還有別種用途，

in addition to allowing us to smell?

除了讓我們聞到東西？

In 1991, Linda Buck and Richard Axel uncovered the molecular identity

1991 年琳達．巴克 和理察．阿克塞爾發現了

嗅覺接受器的分子識別機制。

of olfactory receptors --

work which ultimately led to a Nobel Prize.

最終得到了諾貝爾獎。

At the time,

當時，

we all assumed that these receptors were only found in the nose.

我們都以為那些接受器 只存在鼻子裡。

However, about a year or so later,

但是，大概一年之後

a report emerged of an olfactory receptor expressed in a tissue

一篇報告顯示嗅覺接受器

也存在於鼻子以外的身體組織。

other than the nose.

接著又有一個類似的報告出現，

And then another such report emerged,

and another.

一個接一個。

We now know that these receptors are found all over the body,

我們現在知道全身上下都可以 找到這些接受器，

including in some pretty unexpected places --

包括那些意想不到的部位──

in muscle,

在肌肉裡，

in kidneys,

在腎臟裡，

lungs

在肺臟裡，

and blood vessels.

在血管裡。

But what are they doing there?

但它們在那裡做什麼？

Well, we know that olfactory receptors act as sensitive chemical sensors

我們知道嗅覺接受器

是鼻子中敏感的化學感測器──

in the nose --

that's how they mediate our sense of smell.

它們傳達我們的嗅覺。

It turns out they also act as sensitive chemical sensors

然而嗅覺接受器 作為敏感的化學感測器，

in many other parts of the body.

也在身體的其他部位起作用。

Now, I'm not saying that your liver can detect the aroma of your morning coffee

我不是說你的肝能聞到 你早晨咖啡的香氣，

as you walk into the kitchen.

當你走進廚房時。

Rather, after you drink your morning coffee,

不如說，你喝了早晨咖啡後，

your liver might use an olfactory receptor

你的肝可能啓用一種嗅覺接受器，

to chemically detect the change in concentration

用化學方式探測

某種在血液中的 化學物其濃度的變化。

of a chemical floating through your bloodstream.

Many cell types and tissues in the body use chemical sensors,

身體裡很多類型的細胞和組織 都會使用化學感測器，

or chemosensors,

或稱為化學受器，

to keep track of the concentration of hormones, metabolites

來追蹤賀爾蒙、代謝物

and other molecules,

及其他分子的濃度，

and some of these chemosensors are olfactory receptors.

而其中一些化學感測器 就是嗅覺受器。

If you are a pancreas or a kidney

假設你是胰腺或腎臟，

and you need a specialized chemical sensor

你需要一種特製的化學感測器，

that will allow you to keep track of a specific molecule,

來幫你追蹤一個特定的分子。

why reinvent the wheel?

那為什麼要浪費時間重複發明呢？

One of the first examples

有一個早期發現 鼻子以外有嗅覺接受器的例子，

of an olfactory receptor found outside the nose

showed that human sperm express an olfactory receptor,

顯示人的精子裡 具有嗅覺接受器結構，

and that sperm with this receptor will seek out the chemical

精子及嗅覺接受器就會找出

會與接受器產生反應化學物質──

that the receptor responds to --

the receptor's ligand.

嗅覺接受器的配體。

That is, the sperm will swim toward the ligand.

也就是說，精子會游向配體。

This has intriguing implications.

這裡頭的含意使人好奇。

Are sperm aided in finding the egg

精子是否被幫助去尋找卵子？

by sniffing out the area with the highest ligand concentration?

通過嗅覺接收器聞出 最高濃度的配體區域？

I like this example because it clearly demonstrates

我喜歡這個例子，是因為這清楚顯示

that an olfactory receptor's primary job is to be a chemical sensor,

嗅覺接受器的主要工作 是化學感測器，

but depending on the context,

但取決於環境，

it can influence how you perceive a smell,

那可能影響你如何感知氣味，

or in which direction sperm will swim,

或影響精子將會游動的方向。

and as it turns out,

實際上，

a huge variety of other processes.

涉及一系列其他多種的程序。

Olfactory receptors have been implicated in muscle cell migration,

嗅覺接收器參與肌肉細胞的移動，

in helping the lung to sense and respond to inhaled chemicals,

來幫助肺去感測被吸進來的 化學物質並產生反應，

and in wound healing.

還有幫助傷口癒合。

Similarly, taste receptors once thought to be found only in the tongue,

同樣，味覺收器曾被認爲 只存在於舌頭上。

are now known to be expressed in cells and tissues throughout the body.

現在味覺接收器表現在 身體許多其它細胞和組織裡。

Even more surprisingly,

甚至更讓人吃驚的是，

a recent study found

在一個最近的研究發現，

that the light receptors in our eyes also play a role in our blood vessels.

在我們眼中的光感接收器在我們的 血液循環系統中也起一定的作用。

In my lab,

在我的實驗室，

we work on trying to understand the roles of olfactory receptors and taste receptors

我們正在試圖去理解 嗅覺和味覺收器

in the context of the kidney.

在腎臟工作中起的作用。

The kidney is a central control center for homeostasis.

腎是我們體內恆定的主要控制中心。

And to us,

對於我們來說，

it makes sense that a homeostatic control center would be a logical place

體內恆定控制中心

運用一系列的化學感應器 是完全合情合理的。

to employ chemical sensors.

We've identified a number of different olfactory and taste receptors

我們已經發現並識別了

在腎的工作中起作用的多種 嗅覺和味覺接收器。

in the kidney,

one of which, olfactory receptor 78,

其中之一是第 78 號嗅覺接收器。

is known to be expressed in cells and tissues

事實上，它在 各種細胞和組織裡表現，

that are important in the regulation of blood pressure.

有控制血壓的重要作用。

When this receptor is deleted in mice,

我們發現把小白鼠體内的 這個嗅覺接收器拿掉，

their blood pressure is low.

小白鼠的血壓變低。

Surprisingly, this receptor was found to respond

令人驚訝的是，這個接收器 對某種化學物質──

to chemicals called short-chain fatty acids

就是短鏈脂肪酸──產生反應，

that are produced by the bacteria that reside in your gut --

它是由生活在 腸道裡的細菌產生的──

your gut microbiota.

腸道菌叢。

After being produced by your gut microbiota,

短鏈脂肪酸被腸道菌叢製作出來後，

these chemicals are absorbed into your bloodstream

這些化學物質被吸收進血液中。

where they can then interact with receptors

由此，再與嗅覺和味覺接收器 互相作用和影響，

like olfactory receptor 78,

例如，嗅覺接收器 78，

meaning that the changes in metabolism of your gut microbiota

也就是説，你的腸道菌叢的 新陳代謝的變化

may influence your blood pressure.

可能會影響你的血壓。

Although we've identified a number of different olfactory and taste receptors

儘管我們辨識了幾種不同的 嗅覺和味覺接收器，

in the kidney,

主要是在腎裡，

we've only just begun to tease out their different functions

我們才剛剛開始試著找出 它們各種不同的功能，

and to figure out which chemicals each of them responds to.

並且找出它們分別對什麽 化學物質發生反應。

Similar investigations lie ahead for many other organs and tissues --

擺在我們前面的工作是對 其他器官和組織開展同樣的研究。

only a small minority of receptors has been studied to date.

目前我們只探究了 非常小部分的接收器。

This is exciting stuff.

這可是令人激動的發展。

It's revolutionizing our understanding of the scope of influence

這些發現革新了 我們對嗅覺影響層面的理解，

for one of the five senses.

而這只是五感覺之一。

And it has the potential to change our understanding

它具有很大潛力改變

of some aspects of human physiology.

人類對人體生理學的某些理解。

It's still early,

雖然這些研究還處於早期階段，

but I think we've picked up on the scent of something we're following.

但是我們認爲我們已經嗅到了 追尋已久的成功的氣味。

(Laughter)

（笑聲）

Thank you.

謝謝。

(Applause)