We're living longer than ever before, which is great,

ヒトはかつてないほど長生きに なり、それはすごいことだが、

but an unforeseen consequence of this is that we also spend a larger and larger portion of our lives being sick.

予期せぬ結果として、人生の長い 部分を病気とともに過ごすようになった

Getting old currently means spending more time in pain.

今や長生きは、長い病気を 意味するようになってしまった

So scientists are trying to shift the attention of the medical community from optimizing lifespans to optimizing healthspans,

そこで、科学者は医学界に対して

the part of our lives during which we're disease free.

単なる寿命ではなく、健康寿命を 最適化するように働きかけている

To do this, we need to attack the root cause of almost all bodily defects: aging itself.

健康寿命とは、病気をしないで 過ごせる期間のことだ

Unbeknown to most people, the science of aging has made enormous progress In the last few years,

そのためには、すべての身体的疾患の根幹、 つまり老化そのものに対処する必要がある

with human trials about to begin in the near future.

ここ数年、老化の科学は 長足の進歩を遂げ、

Let's look at three examples of discoveries that might benefit people who are alive right now

ヒトへの応用も近い将来に 始まろうとしている

INTRO

今生きている人が恩恵を受けられる かもしれない発見を3つ紹介しよう

1: senescent cells.

00:01:02,780 --> 00:01:04,780 1: 老化細胞

Your cells have an expiration date.

ヒトの細胞には寿命がある

Each time one of your cells divides, it copies its chromosomes.

細胞が分裂する時、 染色体が複製されるが、

Because of the way this works, they lose a tiny bit of DNA at the ends.

その時、染色体の末端の DNAの小さな部分が失われる

This could be catastrophic, so to protect themselves we have long segments of DNA called telomeres

それでは困るので、末端はテロメアと 呼ばれる長いDNAの区間で守られている

that sort of act like the stiff bits at the end of shoelaces, but they shrink with every cell division.

靴ひもの先の 硬い部分みたいなものだ

In some cells, after a number of divisions the telomeres are gone, and the cell becomes a zombie, a senescent cell.

でも分裂のたびに 短くなるので、

Senescent cells stay around and don't die. The older you get the more of them are inside you.

何度も分裂した細胞の中には、 テロメアを失い、ゾンビになるものがある

They harmed tissue around them and are linked to many diseases that accompany old age like diabetes and kidney failure.

それが老化細胞だ

But what if you could kill them off?

老化細胞は死なず、 存在し続けるので、

Scientists genetically engineered mice so that they could destroy their senescent cells as they pleased.

歳を取るほど増えてゆく

Older mice without senescent cells were more active. Their hearts and kidneys worked better, and they were less prone to cancer.

老化細胞は周囲の組織を傷つけ、 糖尿病や腎不全などを引き起こす

Overall, they lived up to 30 percent longer and in better health than average mice.

しかし老化細胞を 殺せるとしたらどうだろう?

Since we can't genetically engineer all the cells in the human body, we need to find another way to get rid of our senescent cells.

科学者は老化細胞を自ら破壊できる マウスを遺伝子工学的に作った

But how do we kill them without harming healthy cells?

老化細胞がないマウスは より活動的で、

Most cells in the body commit a programmed cell suicide when they're damaged, but senescent cells don't.

心臓や腎臓も丈夫で、 がんにもかかりにくく、

It turns out that they underproduce a protein that tells them when it's time to die.

ふつうのマウスより最大30% 長生きで健康だった

So in a late 2016 study, mice were given an injection of this protein.

人体の全細胞を遺伝子操作する ことはできないので、

It killed 80 % of all their senescent cells, while causing almost no harm to healthy cells.

老化細胞を除去する 別の方法を見つける必要がある

The treated mice became generally healthier and even regrew lost hair.

でも健康な細胞を傷つけずに、 老化細胞だけを殺す方法は?

As a result, there are a number of new companies looking at treatments involving senescent cells and the first human trials will start soon.

ほとんどの体細胞は傷つくと プログラム死するが、

2: NAD+

老化細胞は違う

Cells are made of hundreds of millions of parts.

老化細胞ではプログラム死を知らせる タンパクの産生が少ないことがわかった

They're the structures, machines, messages, and the catalysts that make reactions happen.

そこで、そのタンパクをマウスに 注射する実験が2016年に行なわれた

All these parts constantly need to be destroyed, cleaned up, and rebuilt.

老化細胞の80%が死に、 健康な細胞にはほとんど害がなかった

As we age, this process becomes less effective and so parts become crumpled, bunched up,

処置を受けたマウスは より健康になり、脱毛も改善した

or are removed slower, or they are no longer produced in the quantities we need.

その結果、多くの企業が着目し、 人間への応用すぐに始まりそうだ

One of these parts is NAD+, a coenzyme that tells ourselves to look after themselves.

2: NAD+

At age 50, we only have about half as much in our bodies as we do at age 20.

細胞は何億というパーツで できている

Low amounts of it are linked to a whole bunch of diseases from skin cancer to Alzheimer's, cardiovascular disease, and multiple sclerosis.

細胞骨格や機械、メッセージ、 反応を起こす触媒などだ

But NAD+ can't enter cells so we can't get it as a pill.

それらのパーツはつねに分解され、 綺麗にして再組み立てされる必要がある

But scientists notice that other more flexible substances could enter cells and would then turn into an NAD+ inside.

ところが歳を取ると、この過程は劣化し、 パーツはくたびれてダンゴになったり、

In 2016, multiple trials on mice showed that they boosted the multiplication of skin, brain, and muscle stem cells.

除去が間に合わなかったり、 不足したりするようになる

They were rejuvenated, had a higher ability to repair their DNA, and had a slightly increased lifespan,

そうしたパーツのひとつがNAD+で、 身体の修復に関する補酵素だ

This even got NASA interested,

50歳になると、20歳の時の半分になる

which is looking for a way to minimize the DNA damage astronauts would be exposed to from cosmic radiation on Mars missions.

これが不足すると、皮膚がんやアルツハイマー病、 心血管疾患、多発性硬化症など、多くの疾患が起こる

There are human trials being planned right now,

しかしNAD+は細胞膜を通過できないので、 飲み薬では摂取できない

but it's too soon to say if this will boost our healthspan or even lifespan.

科学者は、細胞膜を通過したあとで NAD+に変化する物質に注目している

But NAD+ is a serious candidate and could become the first human anti-aging pill.

2016年のマウスでの多くの実験の結果、 皮膚や、脳、筋肉の幹細胞の増殖を促すことが示された

3: stem cells

マウスは元気になり、DNAの修復能が 改善し、わずかに寿命が伸びた

Stem cells are like cell blueprints that sit at various places in the body and copy themselves to produce a steady flow of fresh young cells,

NASAも興味を示した

but they decline as we age and so we decline too.

火星で放射線にさらされる飛行士の、 DNA損傷を最小限にできるかも

Without new parts, human bodies break.

ヒトへの試験が すでに計画されているが、

In mice, scientists observed that as the stem cells in their brains disappeared, they started to develop diseases

それが人間の健康寿命などを 改善するかどうかはまだ分からない

So they took stem cells from baby mice brains and injected them directly into the brains of middle-aged mice,

しかしNAD+は最初の抗老化薬の 最有力候補だ

more specifically the hypothalamus, a polyp that's involved in regulating a lot of bodily functions.

3: 幹細胞

The fresh stem cells reinvigorated older brain cells by secreting micro RNAs that regulated their metabolism.

幹細胞は細胞の青写真で身体のあちこちにいて、 自らを複製して若々しい細胞の流れを作っている

After 4 months, brain and muscles worked better than those of untreated mice and on average, they lived ten percent longer.

ところがこれも加齢とともに減少し、 我々も衰弱する

Another study took stem cells from mice embryos and injected them directly into the hearts of older mice.

新しいパーツがないと 人体は壊れてしまう

As a consequence, they had improved heart function, could exercise 20% longer, and weirdly enough their hair regrew faster.

マウスでは脳から幹細胞が 消えるに従い病気が進展した

Conclusion

そこで赤ん坊のマウスの脳の幹細胞を 中年のマウスの脳に直接注射したところ

What all of this tells us is that there is not a single magic bullet with which to cure aging.

特にさまざまな身体機能を司っている 視床下部において、

It requires a complex array of different therapies.

代謝を調節するマイクロRNAを分泌することで 幹細胞は老化した脳細胞を再活性化した

We can kill off senescent cells to clear away the junk,

4ヶ月後、脳と筋肉の働きが改善し、 未処置の群に比べて平均10%長生きした

give ourselves fresh new stem cells to fill the gap, all while regulating the metabolism of the other cells using medication.

別の研究では、マウスの胚由来の幹細胞を 歳取ったマウスの心臓に注射した

This video comes with a big caveat. After all, these studies have been carried out on mice.

その結果、心臓の機能が改善し、 20%長く運動でき、毛の再生が速くなった

There's no guarantee the same therapies would work in us to the same extent, but they are proof of concepts.

結論

To learn more about how we can modify our own healthspan, we need human trials.

これらのことから分かるのは、老化を 治療する単一の特効薬はなく

We've only covered a tiny part of the research that's being done right now, and only scratched the surface of these ideas.

いくつもの治療法の組み合わせが 必要になるということだ

The field of healthspan extension needs more attention and funding.

くずを取り除くために 老化細胞を死滅させ、

If it gets it, all of us might enjoy growing old without pain

隙間をうめるために 新鮮な幹細胞を加え、

If you now want to support the research on aging directly, you can do so at lifespan.io,

その他の細胞の代謝を 調節するのには薬剤を用いる

a community of people actively supporting the scientists working to cure aging.

この動画には大きな警告がある 以上の研究はすべてマウスに関するもので

Check them out to learn about the latest advances and visit their blog or group on Facebook.

同じ治療が我々にも同程度に 効果があるという保証はない

The lifespan team also kindly supported the creation of this video with a donation and their expertise.

とはいえ概念の裏付けにはなる

If you want to help us make more of our videos, you can do so on patreon.com.

我々自身の健康寿命を改善する 方法を知るにはヒトでの研究が必要だ