DNA strands get shorter and shorter with every cell division. So, how do our cells have any DNA left at all? Enter telomeres. Telomeres consist of the same sequence of six nucleotides repeated over and over again, and all this repetition makes them somewhat disposable. They protect the rest of the DNA, as they can gradually get shorter and shorter over time without the loss of any other important genetic information.
In other cells, telomerase is less active, leading to the gradual shortening of telomeres over time. This shortening is thought to be one of several factors that causes cells to age. This cell division limit is called the Hayflick Limit , after researcher Leonard Hayflick found that normal human cells divide roughly 50 times before stopping.
The individuals in the shortest telomere group were three times more likely to develop cancer than the longest telomere group within the ten year observation period!
A similar correlation between long telomeres and less disease also exists for cardiovascular disease. Blackburn was quick to point out that these correlations do not necessarily mean that there is a direct cause and effect relationship. In fact, increasing telomerase levels ought to lengthen telomeres but in the case of cancer, too much telomerase can be just as bad as too little telomeres.
Too much telomerase can help confer immortality onto cancer cells and actually increase the likelihood of cancer, whereas too little telomerase can also increase cancer by depleting the healthy regenerative potential of the body. To reduce the risk of cancer we need an ideal level of telomerase, with not a whole lot of room for error. Why is that telomere lengths are such good predictors of longevity, but too much telomerase can be bad for you? The answer is probably that telomere lengths measured in the white blood cells reflect a broad range of factors, such as our genetic makeup but also the history of a cell.
Some of us may be lucky because we are genetically endowed with a slightly higher telomerase activity or longer telomeres, but the environment also plays a major role in regulating telomeres. If our cells are exposed to a lot of stress and injury — even at a young age — then they are forced to divide more often and shorten their telomeres. The telomere length measurements which predict health and longevity are snapshots taken at a certain point in time and cannot distinguish between inherited traits which confer the gift of longer telomeres to some and the lack of environmental stressors which may have allowed cells to maintain long telomeres.
What are the stressors which can affect cellular aging and shortening of telomeres? Blackburn listed a few of them such as stress hormones, oxidative stress and inflammatory stress.
All of these stressors cause stress on a molecular level, which means they can damage proteins and other essential components of a cell. Oxidative stress, the excess production of reactive oxygen species oxidizes proteins, disrupting their structure and function to the extent that oxidized proteins become either useless or even harmful.
Inflammatory stress refers to excessive inflammation which transcends the normal inflammatory response of cells from which they can recover. Prolonged inflammation, for example, can cause cells to activate a cell-death program. Recent studies in mice have shown that activation of inflammation pathways in the brain can suppress cognitive function, muscle strength and overall longevity. Blackburn also pointed out that stressors are often interconnected.
If the action of telomerase in these cells can be inhibited by drugs during cancer therapy, then the cancerous cells could potentially be stopped from further division. The ends of the chromosomes pose a problem during DNA replication as polymerase is unable to extend them without a primer. Telomerase, an enzyme with a built-in RNA template, extends the ends by copying the RNA template and extending one end of the chromosome.
In this way, the ends of the chromosomes are protected. This is important as evidence indicates telomere length may play a role in regulating cell division and the process of aging. Improve this page Learn More. Skip to main content. Search for:. In Summary: Telomeres The ends of the chromosomes pose a problem during DNA replication as polymerase is unable to extend them without a primer.
Try It. These women had shorter telomeres, reduced telomerase activity, and more oxidative stress when compared to a group of women caring for healthy children. A study evaluated men and women who were exposed to stressors. Those who responded with an increase in cortisol, the main stress hormone, had increased telomere shortening for several years. Regardless of whether it reduces telomere shortening, stress management is a crucial part of feeling your best.
Not convinced? See how stress affects your body. A study involving thousands of men and women in the United States looked at the connection between exercise and telomere length. Those who participated in high levels of activity had significantly longer telomeres than those who did low or medium levels of activity. Another study involving a group of young adults found that those who participated in high levels of aerobic fitness and had more muscle endurance had longer telomeres.
Here are 10 aerobic exercises to add to your workout. Telomeres help protect your chromosomes from damage. In the process, your telomeres shorten, which is associated with aging and disease development. But recent research suggests that there may be ways to hack this process through diet, stress management, and exercise. While these findings are all very preliminary, we already know that an active lifestyle, along with a nutritious diet and stress management techniques, provide a multitude of other health benefits as well.
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