Why do we age? Researchers have yet to unravel the mysteries that control human lifespan, but a number of theories on ageing have attempted to explain the process. These days, much discussion revolves around the role of telomeres.
What are telomeres?
Telomeres are the repeated short, non-coding sequences of DNA at each end of a chromosome. If you recall from high school biology, cells contain our genetic code or DNA (deoxyribonucleic acid), which is organised into long structures called chromosomes. Telomeres protect the chromosomes from damage, but they shorten each time a cell divides.
As telomeres shorten, a critical threshold is reached at which the cell no longer replicates and starts to decline and eventually dies.
How are they associated with ageing? Telomeres are an important aspect in the stem cell theory of ageing, according to Taylor Mitchell, a doctoral candidate working with Dr Xu-Dong Zhu, associate professor of biology at McMaster University in Ontario, Canada.
We have a given number of adult stem cells, he explains, and they are unique in that they can differentiate into a number of different cell types, able to replenish older and dying tissues.
“If you make unhealthy lifestyle choices that cause you to have a higher rate of cell turnover, you are going to need to replace dying cells more often, and in turn, you are depleting your stem cell population at a faster rate”, Mitchell says.
Can cells be rejuvenated?
Yet all cells appear capable of rejuvenation. Scientists Elizabeth Blackburn, Carol Greider and Jack Szostak discovered that the ends of the chromosomes are protected by telomeres and that they are built by an enzyme, telomerase. These important advances earned them the prestigious Nobel Prize in 2009.
Understanding the mechanism by which telomeres can be restored has excited researchers in the antiageing field, and as a result, a large body of knowledge is growing around the factors that influence telomere length and telomerase activation.
What they found is that although cells have the capacity for restoration through telomerase, most human cells lack sufficient stores of the enzyme to maintain telomeres. Certain cells, such as stem cells, have this capacity, but we only have so many of them.
What influences telomere length? Researchers have learned that genetics, prenatal conditions and early adversity all contribute to adult telomere length.
Dr Peter Lansdorp, a scientist at the British Columbia Cancer Agency and a professor at the University of British Columbia in Canada, says stress plays a critical role.
“There’s good data from the laboratory to support the theory that stress, and other oxidative, damage, also damages telomeres and increases the rate by which telomeres shorten”, says Lansdorp.
Other lifestyle behaviours also have an effect. Studies show a sedentary lifestyle (in addition to smoking, high body mass index and low socioeconomic status) has an effect on telomere length and may even accelerate the ageing process.
“Living a healthy lifestyle by not smoking, lowering stress levels, exercising and healthy eating are thought to slow the rate of telomere loss”, says Mitchell, “but I don’t think we can undo what is already done.”
But can we restore telomeres?
This is a matter of discussion and controversy. In recent years, supplements said to activate telomerase have become popular.
A molecule from the extract of the dried root of Astragalus membranaceus, a plant commonly used in traditional Chinese medicine, has been shown to increase telomerase activity in cells.
While some scientists dismiss these “telomerase activators” as snake oil, others glow about its potential. Celebrity Suzanne Somers’ newest book, Bombshell (Crown Archetype, 2012), devotes an entire chapter to the supplement.
But the fountain of youth doesn’t come cheap. A Canadian distributor is advertising on its website a 30-capsule bottle for over $200.
Telomere length tests are also now available commercially and are being actively marketed to the medical profession.
Why do we need to know?
Physicians looking after patients with specific diseases find the test results very useful, as they give information that helps with treatment options, according to Lansdorp. The tests are also available to the public, but he isn’t encouraging average healthy people to get their telomeres measured. “There’s not much point”, he says. And besides, “They would need help in the assessment.”
However, some would argue that a telomere length measurement test can serve as a “wake up” call. If telomere length is a biomarker of general health, the test may offer information of interest. For example, if one finds out her biological age is significantly above chronological age, it may serve as a tap on the shoulder to change some lifestyle behaviours.
Can telomere research unlock the mysteries of ageing? While we may not be able to stop cell ageing, at least not yet, we can adopt lifestyle modifications such as avoiding excessive stress and maintaining an ideal weight.
Healthy living is our best defence in slowing down the signs and symptoms of ageing.
Life extension through diet
If life extension is what you’re after, “one of the best ways to increase lifespan is to eat less than the body wants”, says Lansdorp. “The effects of being overweight are well known.”
While calorie restriction may not appeal to many, there are supplements that may mimic the effects. Studies show that when mice were fed a high-fat-and-calorie diet supplemented with resveratrol, the mice experienced not only a number of health benefits but also the effects of calorie restriction.