Why do our bodies age? - Monica Menesini

譯者: Crystal Yip 審譯者: 旻霏 郭

In 1997, a French woman named Jeanne Calment

在 1997 年，一位法國女士 雅娜・卡爾曼特

passed away after 122 years and 164 days on this Earth,

在世上活了 122 年 又 164 天後與世長辭

making her the oldest known person in history.

她是史上最長壽的人

Her age was so astounding

由於她的年齡十分驚人

that a millionaire pledged $1 million to anyone who could break her record.

甚至有位百萬富翁願意付一百萬元 給打破她記錄的人

But in reality, living to this age or beyond

但事實上，活到那個歲數 或甚至更長壽

is a feat that very few, maybe even no humans,

是十分少數人，甚至沒有人

are likely to accomplish.

可以達成的目標

Human bodies just aren't built for extreme aging.

人類的身體本來就不是 適合極度老化的

Our capacity is set at about 90 years.

我們大約能活到 90 歲

But what does aging really mean

但是衰老究竟代表什麼

and how does it counteract the body's efforts to stay alive?

還有這如何與身體 維持生命的力量抗衡

We know intuitively what it means to age.

我們直覺上知道衰老是什麼意思

For some, it means growing up,

對於某些人來說，衰老就是成長

while for others, it's growing old.

而其他人則認為衰老就是變老

Yet finding a strict scientific definition of aging is a challenge.

但想找到衰老的 嚴謹科學定義是一個挑戰

What we can say is that aging occurs when intrinsic processes

我們能說的是衰老發生 在內在過程

and interactions with the environment, like sunlight,

以及與環境的互動，例如陽光

and toxins in the air, water, and our diets,

和空氣、水、我們日常膳食中的毒素

cause changes in the structure

引致結構上的改變

and function of the body's molecules and cells.

以及體內分子和細胞功能的改變

Those changes in turn drive their decline,

這些改變進而導致它們的衰退

and subsequently, the failure of the whole organism.

然後是整個生物的衰竭

The exact mechanisms of aging are poorly understood.

我們對衰老的確實機制認識很淺

But recently, scientists have identified nine physiological traits,

但近來，科學家辨識了九種生理特徴

ranging from genetic changes

範圍由基因變化

to alterations in a cell's regenerative ability

至細胞再生能力的變異

that play a central role.

均扮演了重要角色

Firstly, as the years pass, our bodies accumulate genetic damage

首先，隨年月過去， 我們的身體累積了基因損傷

in the form of DNA lesions.

以 DNA 損傷的形式出現

These occur naturally when the body's DNA replicates,

這些在身邊 DNA 複製時自然發生

but also in non-dividing cells.

但也會在非分裂細胞內發生

Organelles called mitochondria are especially prone to this damage.

稱為「粒線體」的細胞器 特別容易因此受損

Mitochondria produce adenosine triphosphate,

粒線體製造三磷酸腺苷

or ATP,

或簡稱為 ATP

the main energy source for all cellular processes,

是所有細胞過程的主要能量來源

plus mitochondria regulate many different cell activities

而且調節很多不同的細胞活動

and play an important role in programmed cell death.

並在預設的細胞死亡中 扮演重要角色

If mitochondrial function declines,

如果粒線體的功能衰退

then cells and, later on, whole organs, deteriorate, too.

那麼細胞，繼而整個器官， 都會隨之惡化

Other changes are known to occur in the expression patterns of genes,

其他變化已知是發生在 基因的表現模式

also known as epigenetic alterations,

或稱為「表觀基因改變」

that affect the body's tissues and cells.

影響身體組織和細胞

Genes silenced or expressed only at low levels in newborns

新生嬰兒時，靜默 或只作低程度表現的基因

become prominent in older people,

在較年長的人變得顯著

leading to the development of degenerative diseases,

發展出退化性疾病

like Alzheimer's, which accelerate aging.

例如阿滋海默氏症，加速衰老

Even if we could avoid all these harmful genetic alterations,

即使我們能夠避免 這些有害的基因變異

not even our own cells could save us.

我們自己的細胞也不能拯救我們

The fact remains that cellular regeneration,

事實仍是，細胞再生

the very stuff of life,

這生命的基本

declines as we age.

會隨我們年長而衰退

The DNA in our cells is packaged within chromosomes,

細胞內的 DNA 包裹於染色體內

each of which has two protective regions at the extremities called telomeres.

每個染色體的兩個末端 各有保護性區域，稱為「端粒」

Those shorten every time cells replicate.

每次細胞複製時，那些區域會變短

When telomeres become too short,

當端粒變得太短

cells stop replicating and die,

細胞便會停止複製並死亡

slowing the body's ability to renew itself.

減慢身體更新自己的能力

With age, cells increasingly grow senescent, too,

細胞也會隨時間逐漸衰老

a process that halts the cell cycle in times of risk,

這過程是當有風險時 便停止細胞週期

like when cancer cells are proliferating.

例如當癌細胞增生時

But the response also kicks in more as we age,

但當我們年紀愈大 愈容易有這樣的反應

halting cell growth and cutting short their ability to replicate.

停止細胞生長，減低它們複製的能力

Aging also involves stem cells that reside in many tissues

衰老也闗乎幹細胞 它們在很多身體組織內

and have the property of dividing without limits to replenish other cells.

並有無限分裂的特性 能補充其他細胞

As we get older, stem cells decrease in number

當我們年歲漸長，幹細胞數目減少

and tend to lose their regenerative potential,

並傾向失去它們再生的潛能

affecting tissue renewal and maintenance of our organs original functions.

影響細胞組織的更新 和器官原有功能的維持

Other changes revolve around cells' ability to function properly.

其他變化則圍繞細胞正常運作的能力

As they age, they stop being able to do quality control on proteins,

當它們老化，不能再有效控制蛋白質

causing the accumulation of damaged and potentially toxic nutrients,

導致受損並潛有毒素的營養堆積

leading to excessive metabolic activity that could be fatal for them.

進而引致過多的新陳代謝活動 這可讓細胞死亡

Intercellular communication also slows,

另外，細胞間的溝通減慢

ultimately undermining the body's functional ability.

最終削弱身體運作的能力

There's a lot we don't yet understand about aging.

對於衰老，我們還有 很多不瞭解的地方

Ultimately, does longer life as we know it come down to diet,

歸根究底，壽命較長是因為日常膳食

exercise,

運動

medicine,

藥物

or something else?

抑或其他？

Will future technologies, like cell-repairing nanobots,

將來的科技 例如細胞修復奈米機械人

or gene therapy,

或基因療法

artificially extend our years?

會否人為地延長我們的壽命？

And do we want to live longer than we already do?

而我們是否希望比現在更長壽？

Starting with 122 years as inspiration,

以 122 歲作為想像起點

there's no telling where our curiosity might take us.

沒人能說準

我們的好奇心會帶我們到何處