Image: Finches
Paul Jerem
Young, middle-aged and old zebra finches show obvious age-related changes in coloration and condition. Scientists have found that the length of segments on the end of chromosomes during early life was predictive of how long the finches would live.
By Senior writer
updated 1/9/2012 8:32:22 PM ET 2012-01-10T01:32:22

The signs of aging show up in our genes as the protective caps on the ends of packets of our DNA, called chromosomes, gradually wear away over time.

Now, scientists have found that the length of these caps, called telomeres, measured early in life, can predict life span.

Using 99 zebra finches, a small bird also popular as a pet, a team of researchers in the United Kingdom measured the lengths of the telomeres found in the birds' red blood cells over the course of their lives.

They found that the length of the telomeres at the first measurement, made 25 days after the birds hatched, was the strongest predictor of how long the birds actually lived.

In addition, the birds with the longest telomeres early in life, and throughout the study, were the ones most likely to live into old age, up to 8.7 years old — a "ripe old age" for a finch, said study researcher Britt Heidinger, a postdoctoral researcher at the University of Glasgow.

For relatively long-lived vertebrates, such as zebra finches and humans, aging and telomere loss appear to go hand-in-hand. And while it seems reasonable that telomere length early on could predict life span in humans, too, it's not yet certain, since no similar study has been completed in humans, according to Heidinger.

The basics of aging and telomeres
Chromosomes are threadlike strands of protein and DNA (deoxyribonucleic acid), which contain the instructions to make a living thing. Each of our cells contains chromosomes, capped by telomeres, and when our cells divide — a necessary part of growth and the maintenance of our bodies — these chromosomes must be duplicated.

Telomeres serve as markers for the ends of the chromosomes. They naturally become shorter over time, because when the cell's machinery copies its chromosomes it misses the very tip of the telomere. So, every time the chromosomes are copied, the telomere shrinks a little.

Eventually, with age, the telomeres shorten to a point where the cell can no longer divide, and most normal cells cease to function. Previous studies have suggested this process contributes to the deterioration associated with aging.

There is also a cancer connection. Telomeres prevent the uncontrolled cell division characteristic of cancer, but cells with short telomeres can become cancerous by evading this limit, according to Pat Monaghan, the senior researcher and a professor at the University of Glasgow.

Telomere length can vary greatly between individuals of the same age. Genetic inheritance appears to play some role, as do environmental factors, which are linked to the oxidative stress that occurs when the body produces more reactive oxygen molecules than it can neutralize.

Cause of death
In order to complete the study, the birds were allowed to live out their natural lives, with blood samples taken when they were 25 days old, then 1 year old, and periodically afterward. Telomere length measured at other times during the birds' lives did not have the same strong correlation to life span as the initial measurement.

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The researchers did not track the birds' eventual cause of death, but they know these did not include accidents, predators, starvation or infection.

Many other factors — damage elsewhere in the DNA, accumulating damage to biologically important molecules, reduced capacity to replace lost cells, and so on — are also implicated in aging.

The loss of telomeres may ultimately contribute to death by causing body systems to fail, but which systems and when are likely to vary, resulting in different causes of death for different individuals, they write in a study published on Monday in the journal Proceedings of the National Academy of Sciences.

"This is one piece that we have measured, there are many, many things that contribute to aging in individuals," Heidinger said. "It could be multifaceted and there could be many different causes, we are not saying (loss of) telomeres are the only cause of death."

It's not clear why youthful telomere length — measured when the birds were 25 days old, still juveniles that had not yet reached sexual maturity — appears to predict their life span, Monaghan said. 

You can followLiveSciencesenior writer Wynne Parry on Twitter @Wynne_Parry. Follow LiveScience for the latest in science news and discoveries on Twitter @livescience  and on Facebook.

© 2012 LiveScience.com. All rights reserved.

Video: Could people soon be living forever?

  1. Closed captioning of: Could people soon be living forever?

    >>> back now at 7:48 with the latest discovery that has some scientists asking if it is possible to live forever . nbc's michelle kosinski 's here with details. hey, michelle, good morning.

    >> hi, good morning, ann. you know, you talk to some top researchers, microbiologists, molecular geneticists, and it's hard to believe what they're saying is real and not science fiction . there's a growing group of scientists that sees aging not necessarily as an inevitability, but a problem that they believe can be fixed. in science labs around the world, right now the race is heating up to reverse human aging. you heard right. not slow it down or fix it up, but turn it around, by things like regenerating tissues and organs, using stem cells , computers. there's a printer that makes blood vessels, mice that regrow intestines.

    >> what would excite me is that i'm working on the world's biggest, oldest problem.

    >> reporter: there's someone alive today who could live for thousands of years?

    >> i don't think there is any limit. there is nothing that would stop people intrinsically from people living thousands of years.

    >> reporter: at 1,000-year-old cambridge university , where back then people hardly lived past their 20s, they're spearheading research, gathering experts to end aging. they see it not at all as a necessity, but a problem, a build-up of damage and gunk in ourselves. he just isolated an enzyme in bacteria that fixes that and might work in human cells , too.

    >> when we get these therapies, the world is going to be very different.

    >> reporter: there are all kinds of ideas out there -- implanted computer chips to operate mechanical body parts --

    >> here, why don't you take these?

    >> reporter: and a supplement created by american geneticist bill andrews , that he says shortens our tell meres, which is a main reason why we age.

    >> the main reason i want to live forever , it's fun to be alive.

    >> yes.

    >> reporter: inspired by his dad, who challenged him as a child to become a doctor and cure aging.

    >> the literature tells us that i would say 95% certain or better that if we can find ways to lengthen the telomeres, we will reverse aging.

    >> reporter: there are doubters, but some believe real breakthrough in lifespan are possible, soon. there is a book on why society believes we could live to 100 or 1,000. if there's reason to live , you might eat more potato chips on the couch.

    >> you might. the idea of a longer lifespan gives you more opportunity to try new things and be more adventurous.

    >> reporter: these scientists pushing their mortal minds to the limit.

    >> would you hurry up?

    >> yeah.

    >> i promised that i would reach 150.

    >> reporter: to, as they put it, cure aging or die trying . and it's not just about extending lifespan, it's about extending health. and it's funny to hear them talk about this as if it was a car, that if you keep replacing the parts, theoretically, it could last forever. but you know, this research is in the very early stages. there's not a lot of funding and no human has ever lived past 125.

    >> 125 is pretty good, but boy, wouldn't it be something, matt, to live further? what would we do with our time?

    >> what's your definition of soon that they're going to come up with this stuff? is this going to help me?

    >> 10 years, 20 years?

    >> yeah, you're going to live forever as a 70-year-old, how

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