DNA testing companies offer telomere testing, but what do they say about aging and the risk of disease?

In recent years, consumer genetic testing and extracting information from the DNA of your chromosomes have become popular. Through a simple cheek, saliva collection or finger prick, companies offer the opportunity to learn more about your family tree, ancestry or the risk of developing diseases such as than Alzheimer's disease or even some cancers. More recently, some companies are offering tests to measure the ends of chromosomes, called telomeres, to learn more about aging.

But what exactly are the telomeres, what are telomere tests and what companies claim they can tell you? The age of your birthday compared to your "telomere age"?

Telomeres play an important role in preserving our chromosomes and our bodies, even though they represent only a tiny fraction of our total DNA. The Greek origins of the word telomere indicate where to find them. "Telo" means "end" while "simple" means "part". Telomeres cover both ends of the 46 chromosomes of each cell and protect the chromosomes from loss of genetic material. They are often compared to plastic tips at the ends of the laces that prevent fraying.

We are molecular biologists studying how chemicals, environmental agents and metabolism damage telomeres and affect their length and function, as well as the effects of damaged telomeres on the health of our cells and our cells. genome. The idea of ​​proposing telomere length as part of a genetic test is intriguing because telomeres protect our genetic material. But to equate the telomere length with something as complex as aging seemed to be delicate and overly simplistic.

Link between telomere length and human diseases

Telomeres are important for human health and, despite their protective function, they are not indestructible. Telomeres get shorter each time a cell divides and shorten gradually as we get older.

When the telomeres become too short or lost, the ends of the chromosomes are no longer protected and become sticky. This can cause chromosome fusion. To prevent further shortening and chromosome fusions, cells enter senescence, a state in which they can no longer divide. Although they lose the ability to rejuvenate tissues, senescent cells can still promote inflammation and secrete factors that promote the growth of nearby precancerous or cancerous cells.

Unfortunately, our lifestyle can actually speed up the shortening. Environmental exposures such as sunlight, air pollution, cigarette smoke and even inflammation or poor nutrition can damage cellular components, including DNA. They do this by generating unstable oxygen molecules, or free radicals. Telomeres are particularly likely to be damaged by free radicals.

In collaboration with chemist Marcel Bruchez, we have developed a new tool that only damages telomeres. Using this tool, we have found that oxidative damage to telomeres is sufficient to not only accelerate their shortening, but also to cause telomere loss.

In previous laboratory experiments, scientists have discovered that the elimination of senescent mouse cells causes the delay or prevention of diseases and conditions associated with aging, including heart disease, diabetes, osteoporosis, and osteoporosis. pulmonary fibrosis. This has led to the pursuit of new drugs called senolytics that could eliminate senescent cells in humans.

Is longer longer better?

As short telomeres cause cell senescence, this makes them attractive targets for healthy, disease-free aging. Moreover, as telomeres get shorter with age, regardless of exposure to toxins, telomere length can provide information about a person's "true" biological age.

Commercial tests typically measure telomere lengths or amounts of telomeric DNA in a blood sample. Companies are comparing your telomeres to the telomeres of people of the same age to try to determine the biological age of your blood cells.

However, just like people of the same age, their size and weight vary, telomeres too. If a child falls in the 40th percentile for height, that means that, compared to 100 girls of her age, she is over 40 years old. For this reason, diagrams similar to child growth charts have been generated for telomeres.

Individuals whose telomere length is less than the first percentile are at risk of developing specific diseases, including anemia, immune deficiency and pulmonary fibrosis, possibly due to a gene mutation that interferes with maintenance. of the telomere.

In contrast, individuals with gene mutations leading to very long telomeres above the 99th percentile are at increased risk of developing hereditary forms of melanoma and brain cancers. Longer telomeres allow a cell to divide more times and, at each division, it is possible that an error during genome duplication produces a mutation that promotes cancer. The telomeres follow in a way the principle of Goldilock. Telomeres that are too short or too long are not optimal.

Can telomere length predict health outcomes?

But what about lengths of telomeres between extremes? Large studies involving hundreds or even thousands of participants show shorter overall telomere associations with an increased risk of some age-related diseases, including heart disease, while longer telomeres are associated with an increased risk of certain types of cancer.

But it is difficult to translate these population studies into forecasts of the lifespan and health of individuals. For example, as a group, men are taller than women, but that does not mean that all men are taller than women. Similarly, some people with shorter telomeres do not develop heart disease in these population studies. More studies are needed to fully understand what telomere length means for its health and aging.

While large population studies show that a healthy diet is associated with longer telomeres, reports published on specific supplements claiming to support telomere health are lacking.

If such a product could extend the telomeres, would it be safe? Or would it increase the risk of developing cancer due to long telomeres? Can protecting telomeres or slowing their shortening promote disease-free aging? We do not have answers to these questions yet.

Given the uncertainty and the risk of misinterpretation, should you have your telomeres measured? Perhaps, if the results motivate healthy lifestyle changes. For now, a safer bet for healthy aging would be to spend money on exercise programs and nutritious foods.

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