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Tell Me More about Telomeres

Categories: genomics

Researchers, journalists, and inquiring minds want to know more about telomeres, which seem to hold clues to human aging and age-related diseases. Could telomeres provide an answer to questions like “How long will I live?” or “Will I get cancer?”

What are telomeres?

Telomeres are structures at the ends of chromosomes  that contain repetitive stretches of DNA. They “seal” chromosomes at the tips, preventing them from unraveling or sticking together. Telomeres also protect a chromosome’s DNA sequence as it is being copied during cell division. Because the enzymes that copy DNA aren’t able to continue to the very end of the sequence, a bit of DNA is lost each time the chromosome is copied. Telomeres provide a buffer that grows shorter every time a cell divides. 

telomere

   Over time, telomeres become so short that cell division stops and the cell dies. This mechanism is thought to restrict the lifespan of cells to a limited number of divisions, making telomere length a measure of aging at the cellular level.

Telomeres and stress

Environmental stress can accelerate telomere shortening. Studies have implicated cigarette smoking, radiation, poor diet, and even psychological stress as causes. A newly published study  reported that children who spent a large proportion of their early lives in institutions had shorter telomeres on average than children who received high-quality foster care as part of an intervention study. Previous studies have found telomere shortening in adults who were maltreated as children.  

Telomeres and disease

Chromosomes that have lost their telomeres can rearrange or fuse together; these abnormal chromosomes are often observed in cancer cells. In some families, inheritance of exceptionally short telomeres is linked to specific diseases, such as pulmonary fibrosis or bone marrow failure.

Several epidemiologic studies have found that shorter telomeres tend to be associated with diseases that become more frequent with age, including heart disease and cancer.  Telomere shortening and chronic diseases could be caused by the same cell-damaging processes, such as oxidative stress and inflammation.    

Telomeres and aging

Is telomere length a biomarker for aging? According to a systematic review published last year, the evidence is equivocal. On average, older people have shorter telomeres; however, there is a great deal of variation among individuals. It isn’t clear whether shorter telomeres are just a sign of aging, or whether they contribute to it.    

Studies of telomere length and mortality have found mixed results. Very few studies have actually followed people over time to see how changes in telomere length correlated with survival. Several such studies now underway should shed more light on this question.

Telomeres and immortality

Germ cells (eggs and sperm) and stem cells contain an enzyme, telomerase, that restores telomere length. Although it is normally inactive in most other cells in the body, telomerase is activated in cancer cells, making them “immortal.” Although activating telomerase to immortalize normal cells is a theoretical possibility, its feasibility isn’t known. 

Testing for telomeres

Research on telomeres is still at an early stage but some entrepreneurs see human curiosity as an untapped market. Last week, a company in the UK announced that it would soon be offering a test of “biological age” based on telomere length to the public for approximately $700 (US). Given the state of the science, it doesn’t sound like a good deal.  

Most of the 2,000 or so genetic tests currently available for clinical use are for diagnosing rare disorders, like cystic fibrosis. Many other tests are being developed and marketed directly to the public via the Internet and other media. Tests that are based on very limited scientific information may not be valid or useful. Let the buyer beware!  telomere

Learn more about telomeres

Telmeres in Disease, The Scientist, May 1, 2012.

Genetic Science Learning Center. “Are Telomeres the Key to Aging and Cancer?” Learn.Genetics. May 25, 2011.   

Learn more about genetic tests

Public Health Genomics. “Genetic Testing.” Centers for Disease Control and Prevention. May 25, 2011. 

Learn more about genetics

For definitions of genetic terms, see this glossary developed by the National Human Genome Research Institute (NHGRI) for learners at any level:

Talking Glossary of Genetic Terms 

For links to additional information resources on the Web, see the CDC Office of Public Health Genomics website:

Genomic Resources

Public Comments

Comments listed below are posted by individuals not associated with CDC, unless otherwise stated. These comments do not represent the official views of CDC, and CDC does not guarantee that any information posted by individuals on this blog is correct, and disclaims any liability for any loss or damage resulting from reliance on any such information. Read more about our comment policy ».

  1. July 8, 2011 at 12:20 pm ET  -   Maria A. Blasco, Jerry W. Shay and Stephen J. Matlin

    We write to clarify for your readers some points regarding your article published on June 9th, “Tell me more about telomeres” and specifically about the following opinion that you expressed in that article:

    “Research on telomeres is still at an early stage but some entrepreneurs see human curiosity as an untapped market. Last week, a company in the UK announced that it would soon be offering a test of “biological age” based on telomere length to the public for approximately $700 (US). Given the state of the science, it doesn’t sound like a good deal.”

    To begin, Life Length is a Spanish company and a spin-off of the prestigious Spanish National Cancer Research Centre, backed by Dr. María Blasco, one of the world’s leading experts in telomeres, together with the financial backing of Spain’s largest foundation, the Botín Foundation and Matlin Associates, an investment bank based in Madrid. As such, Life Length has been set up with the highest standards of scientific rigour.

    Life Length does not claim to offer a test that indicates how long a specific individual has left to live. Instead, we offer a unique test that only we possess to measure the percentage of “critically short” telomeres (that is, telomeres which have become so short that normal cellular division is impaired) which allows us with great precision to estimate the degree of telomere shortening of a given individual. There is solid genetic evidence in humans and mice that telomere length and in particular the abundance of “critically short” telomeres (those telomeres which represent a persistent damage to the cell) are relevant for aging and the development of age-associated diseases. There are a number of epidemiological studies that also indicate that individuals with shorter telomeres have a higher risk of developing cardiovascular disease, and infections while certain life habits are known to accelerate the rate of telomere erosion with aging such as obesity, stress, and smoking. In contrast, other habits (exercise, meditation, nutritional supplements) have been shown to improve telomere maintenance with age.

    This is analogous to the test for cholesterol which has proven that people with lower cholesterol have a lesser risk for heart attack. This is statistically true for large numbers of people but it is perfectly possible for a particular person with low cholesterol to have a heart attack while an individual with high cholesterol may never develop any problem. Therefore, while there is strong evidence that presence of short telomeres may indicate that a person is at a higher risk of disease and probably should revise her/his life habits and check her/his health status, this does not mean that it will estimate longevity.

    The utility of Life Length’s test is to provide:

    - An excellent indicator of a person’s overall general health status.
    - An estimate of the biological age of their telomeres.
    - Contribute to the growing concept of “personalized medicine” by allowing physicians to provide treatments and care that are based on their patients’ biological age.
    - A diagnostic tool. We believe that our test will open the door to further incentivize the development of drugs that may allow us to slow the aging of our telomeres and live longer if not healthier lives.
    - Our test has great utility for the pharmaceutical industry in helping in the development of treatment and medicine for such important and critical fields as oncology, neurological diseases and infertility.

    Our test materially advances mankind’s scientific knowledge of aging and our natural quest that we all share to live longer, healthier lives.

    Sincerely,

    Maria A. Blasco, PhD (Chief Scientific Advisor, Life Length)
    Jerry W. Shay, PhD (Scientific Advisor, Life Length)
    Stephen J. Matlin (CEO, Life Length)

    Link to this comment

  2. August 9, 2011 at 5:46 pm ET  -   Nancee Kemper

    Thanks for your interesting information. I have been reading a lot lately about telomeres and telomerase and their effect on human aging. Two particular articles caught my eye, one in Popular Science on Bill Andrews, who currently holds 35 US Patents for his extensive research on telomerase, and one – no kidding – in Elle magazine about the two women who won the Nobel Prize in 2009 for their research on telomeres. Although Elle is not exactly viewed as a scientific journal, it was actually enlightening!

    Link to this comment

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