Telomere Shortening: The Secret to Aging?

Can telomeres explain aging?

Elderly man looking out window
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The discovery telomeres completely changed the way researchers study longevity and the process of aging. In fact, the researchers who discovered telomeres won the Nobel Prize in Physiology or Medicine in 2009. Telomeres are bits of "junk DNA," if you will, that are located at the ends of chromosomes. They protect your real DNA every time a cell divides.

Each time a cell divides, the DNA unwraps and the information within is copied.

Because of how cells divide, that very last bit of a chromosome - the telomere - cannot be completely copied. A little bit has to be cut off. It is thought that, as a cell divides, the telomeres become shorter and shorter each time until they are gone. At this point, the so-called "real" DNA cannot be copied anymore, and the cell simply ages and is no longer able to replicate.

What Research Tells Us About Telomere Shortening & Aging

In population level studies, researchers have found that older people have shorter telomeres. Eventually, the cells with shorter telomeres can no longer replicate. This affects more and more cells over time, leading to tissue damage and the dreaded signs of again.

Most cells can replicate approximately 50 times before the telomeres become too short. Some researchers believe that telomeres are the supposed "secret to longevity" and that there are circumstances in which telomeres will not shorten.

For example, cancer cells don't die (which is the main problem) because they activate an enzyme called telomerase that adds on to the telomeres when cells divide.

All cells in the body have the capacity to produce telomerase, but only certain cells - including stem cells, sperm cells, and white blood cells - need to produce the enzyme.

Telomere shortening doesn't affect these cells because they need to replicate more than 50 times within a lifetime.

Shorter telomeres are not only associated with age, but with disease, too. In fact, shorter telomere length and low telomerase activity are associated with several chronic, completely preventable diseases. These include hypertension, cardiovascular disease, insulin resistance, type 2 diabetes, depression, osteoporosis, and obesity.

Does It Happen to Everyone?

No. And that’s a big surprise. Researchers in Sweden discovered that some people’s telomeres do not necessarily get shorter over time. In fact, they found that some people’s telomeres can even get longer. This variation at the individual level was undetectable by prior studies that averaged results over a large population.

In the study, 959 individuals donated blood twice, 9 to 11 years apart. On average, the second samples had shorter telomeres than the first. However, approximately 33 percent of those studied had either a stable or increasing telomere length over a period of about 10 years.

What does this mean? It's unclear. It could be that those people have an amazing cellular anti-aging mechanism; it could be that they have an early sign of cancer (researchers tried to rule this out), or it could be fairly meaningless. What we do know for sure is that aging is a lot more complicated than simply looking at the shortening of telomeres.

See Also

Sources:

Nordfjäll K, Svenson U, Norrback K-F, Adolfsson R, Lenner P, Roos G. The individual blood cell telomere attrition rate is telomere length dependent. PLoS Genetics, February 13, 2009 DOI: 10.1371/journal.pgen.1000375[/sun]

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