Ends of a chromosome favor severe Covid-19

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Researchers from the Saint-Luc and UCLouvain University Clinics have shown, in a study published in the American journal Aging, that a large proportion of patients hospitalized for severe forms of Covid-19 have telomeres (ends of the chromosome) shorter than the general population.

A second investigation has just been launched to evaluate the link between telomere size and the extent of sequelae in the lungs, Saint-Luc university clinics announced Wednesday.

In charge of a Covid unit during the first wave, Antoine Froidure, a pulmonologist at Saint-Luc and a professor at UCLouvain, was interested in measuring the length of telomeres in his patients with pulmonary fibrosis, that is, having scar tissue that interferes with function. respiratory tract of the lungs. For this reason, he launched a study on the size of telomeres in hospitalized patients, in collaboration with Anabelle Decottignies epigenetics laboratory, the only laboratory in Belgium that works, and this for 10 to 15 years, on these DNA fragments to end of chromosomes that protects genetic material and shrinks as cells divide. The field of study is still young: in 2009 the Nobel Prize in Medicine awarded the first discoveries about telomeres.

In two years, 491 people of all ages have participated in the formation of a reference panel on the size of telomeres in the general population.

Telomere length decreases with age, but it is also determined by genetic characteristics and can be altered by environment and lifestyle.

Seventy COVID patients aged 27 to 96 years (63 on average) hospitalized between April 7 and May 27 (33 intensive care follow-ups and 18 deaths) underwent the test. "The first risk factor for Covid, by far quickly identified, was age," notes Antoine Froidure. "It was a first clue to the telomere link because we know that the immune system of the elderly works a little less. It causes white blood cells to multiply to defend ourselves during an infection and we can imagine that if we have shorter telomeres, we have potential poorer defense against a pathogen.

In the blood tests of patients with severe Covid, they often have lymphopenia, lack of lymphocytes and people with short telomeres also tend to have lymphopenia ”, explains the pulmonologist.

The analyzes showed that 40% of the Covid patients tested had shorter telomeres than 90% of the people in their age group in the control group. "Having short telomeres predisposes to developing more severe forms of the disease", concludes Anabelle Decottignies. "The length of telomeres decreases with age, but it is also determined by genetic characteristics and can be altered by environment and lifestyle." Behind age, obesity, diabetes or hypertension have also been identified as aggravating factors of Covid.

"This research is one of the first to try to demonstrate a mechanism by which people develop severe forms," adds Antoine Froidure. "It partly explains why older people are at higher risk, due to shorter telomeres with age, but also partly variations in risk in younger people."

Anabelle Decottignies points out that "analyzes in the lungs of deceased patients have shown that those with very short telomeres had signs of tissue aging". This is the beginning of the second study on the evaluation of sequelae. According to Antoine Froidure, "the lungs of people with very short telomeres regenerate worse and have a higher risk of sequelae".

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