En español | If there were a test that could predict your vulnerability to disease and how quickly you will age, would you take it?
This year, several companies will be selling tests — available through doctors — that measure telomeres, key genetic markers that researchers have linked to health and longevity. The science behind them is so tantalizing that some have touted the tests as the key to understanding mortality. But a number of researchers contend that the science is still far too young for test results to be truly revealing. Tests should not be used, they argue, outside a research setting.
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Even two of the scientists who shared the 2009 Nobel Prize for their telomere research differ on whether a telomere test can currently be used to predict long-term health. Although both believe that analyzing telomeres will become an important medical tool over the next 10 to 20 years, they split over whether we know enough about these structures now to use them to gauge health and aging.
One of the Nobel Prize winners, Elizabeth H. Blackburn of the University of California, San Francisco, has cofounded a company — Telome Health — to offer a telomere test to the public. The other, Carol Greider of Johns Hopkins University, says a lot more research is needed to understand the relationship between telomeres and disease.
So what are telomeres and should you have yours measured?
Telomeres are the protective caps on the ends of the chromosomes that keep them from fraying when cells divide. Scientists know that telomeres shorten as people age, and that eventually telomeres become so short that the cells cannot reproduce, and they die. Also, certain diseases that cause rapid, repeated cell division are known to shorten telomeres. Studies have linked increasing numbers of short telomeres to a shorter life span and to the development of age-related diseases, including lung disease, heart disease, diabetes and cancer.
Scientists are years away from being able to lengthen telomeres in humans, but some research in mice shows promise. In 2010 Harvard-affiliated scientists genetically engineered mice to age quickly by turning off the enzyme that maintains telomeres. When they reactivated that enzyme, it led to dramatic reversals in age-related diseases. The researchers expected the aging process to slow or even stop, but the experiment actually reversed the aging process. The mice began to regrow tissue in the spleen, testes and brain.
"It was akin to a Ponce de Leon effect," senior researcher Ronald DePinho, who is now president of the University of Texas MD Anderson Cancer Center, told the Harvard Gazette. Scientists may have not found the mythical Fountain of Youth, but the possibilities that telomere research holds are intriguing.
"This unique biomarker might help people think more about prevention of disease and monitoring their health earlier in life," says Elissa Epel, a researcher at the University of California, San Francisco, who cofounded Telome Health. She says the goal of the tests is to monitor this marker, and individuals should view their results as simply "a risk factor just like any other risk factor."
But many experts hold that until large, careful studies are done over many years, scientists won't be able to put firm numbers on risk factors for disease or longevity. For starters, there's no consensus yet on how best to measure telomeres or serve up the results. Indeed, two of the companies that have developed tests — Telome Health and Life Length, based in Madrid — will provide different types of results. Life Length says its $700 blood test, which is now available to consumers in the United States, compares your actual and "biologic" ages by measuring the percentage of short telomeres. Telome Health, by contrast, uses your saliva to measure the average length of your telomeres and compare that to others. (Company representatives say they haven't yet set a price for the test.)
Another issue: People are born with varying lengths of telomeres, making it difficult to get a handle on relative shrinkage, says Peter Hornsby, a physiology professor at the Barshop Institute for Longevity and Aging Studies at the University of Texas Health Science Center in San Antonio. "We have no evidence that telomere length is a health predictor — there is always a possibility that this could change in the future but I do not see this happening," he wrote in an email.
Currently, no one knows with any certainty just what constitutes a normal-length telomere at different ages, in different types of people, says Greider. There's simply too much variation within age groups. "If you sent me a telomere sample from a 40-year-old I couldn't tell whether that person was 15 or 70," she says.
And despite the link between telomeres and age-related diseases, only a very small segment of the population has telomeres so short that it's possible to say for certain they have a high risk of a disease, she says. "We have strong data from families with inherited short telomeres showing they are at risk for pulmonary fibrosis and bone marrow failure," she says. But 99 percent of people are not in that group. "Right now we can't tell that 99 percent very much," she says.
Moreover, while science points to a link between short telomeres and disease, it hasn't shown that one causes the other, says Judith Campisi, an expert on aging and a professor at the Buck Institute for Research on Aging in Novato, Calif. She's also concerned that telomere tests could provoke needless anxiety.
Stephen Matlin, Life Length's chief executive officer, says the company's test results include comparisons with people of similar ages and backgrounds, along with information about the test's limitations.
Studies that measure telomeres of large groups of people of various backgrounds and ages will be very important to advancing our understanding of these structures, Greider says. But this work should be done in a scientific setting where the findings are shared and discussed, and where one study builds on another to add to our total knowledge.
Charlotte Huff is a freelance writer in Fort Worth, Texas, who reports on medical issues.
Also of interest: Slow aging and prevent disease.
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