返老还童美梦成真？！

开始神话

美国科学家最近成功实现了在动物体上逆转年龄老化进程的工作。这项研究工作发表在Cell上去，研究人员成功使小鼠的肌肉细胞从相当于60岁状态逆转到20岁水平。不过却未能增强肌肉强度。来自哈佛医学院的研究人员是通过对细胞中的一种名为NAD（烟酰胺腺嘌呤二核苷酸）的化学物质进行调控来达到这一目的。细胞中的NAD水平会随着年龄的增长而降低，这一变化会导致线粒体的产能水平降低并进而导致细胞衰老。研究人员通过加入一种能够在细胞内转化为NAD的化学物质来增加衰老细胞中的NAD含量，并最终完成了以上发现。

然而不幸的是，这种方法可能永远无法完成我们返老还童的梦想，因为这种方法并不能使细胞所有的状态获得逆转，如无法恢复端粒以及修复DNA因年龄老化而产生的损伤。这项研究的参与者之一Dr Gomes也承认，老化是一个多因素控制的进程，单一条件的改变并不足以完全逆转所有的细胞衰老状态。

详细英文报道：

US scientists have performed a dramatic reversal of the ageing process in animal studies.

They used a chemical to rejuvenate muscle in mice and said it was the equivalent of transforming a 60-year-old's muscle to that of a 20-year-old - but muscle strength did not improve.

Their study, in the journal Cell, identified an entirely new mechanism of ageing and then reversed it.

Other researchers said it was an "exciting finding".

Ageing is considered a one-way street, but now researchers at Harvard Medical School have shown that some aspects can be reversed.

Their research focused on a chemical called NAD. Its levels naturally drop in all cells of the body with age.

The team showed this disrupted the function of the cell's in-built powerstations, mitochondria, leading to lower energy production and ageing.

Experiments showed that boosting NAD levels, by giving mice a chemical which they naturally convert into NAD, could reverse the sands of time.

One week of youth-medication in two-year-old mice meant their muscles became akin to those of a six-month-old in terms of mitochondrial function, muscle wastage, inflammation and insulin resistance.

Dr Ana Gomes, from the department of genetics at Harvard Medical School, said: "We believe this is quite an important finding."

She argues muscle strength may return with a longer course of treatment.

A cure?

However, this could never be a cure-all for ageing. Other aspects such as shortening of telomeres or damage to DNA would not be reversed.

Dr Gomes told the BBC: "Ageing is multi-factorial, it's not just one component we can fix, so it's hard to target the whole thing.

"I believe there is a lot of cross-talk in cells and energy is very important in a cell and likely to be a very big component of ageing that might cause some of the other things that happen with ageing."

The research group wants to begin clinical trials in 2015.

Dr Gomes said human therapies were a distant prospect but: "From what we know so far we don't think you'd have to take it from 20 years until we die.

"It seems we can start when we're already old, but not too old that we're already damaged.

"If started at 40 you would probably have a much nicer window of health ageing - but I would guess that, we have to do clinical trials."

Prof Tim Spector, from Kings College London, commented: "This is an intriguing and exciting finding that some aspects of the ageing process are reversible.

开始神话

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"It is however a long and tough way to go from these nice mouse experiments to showing real anti-ageing effects in humans without side effects."
Dr Ali Tavassoli, from the University of Southampton argued: "It is important to note, that they did not see any changes in the mouse itself.
"This could be for one of two reasons. Either they need to treat for longer so that the changes occurring in the cells have time to affect the whole organism, or alternatively, the biochemical changes by themselves are not sufficient to reverse the physical changes associated with ageing in the mouse.
"More experiments are necessary to see which of these cases are true."