According to the latest INSEE figures, women live to be 85.4 years old, compared to 79.3 years for men. But how can such differences be explained? Beyond socio-economic factors, lifestyle and social status, Swedish and American researchers have found that the Y-chromosome could be in question. They shared their finding in the journal Science this Thursday, July 14. (source 1)
The chromosomes are made up of DNA that carries genes. Women have two X chromosomes (XX) while men have one X chromosome and one Y chromosome (XY). Nevertheless, as men age, they lose their Y chromosome, mainly in blood cells. This increasingly well-known phenomenon is called mosaic loss of the Y chromosome in the blood (or mLOY). The team of scientists decided to study this occurrence to find out if it affected life expectancy.
The loss of the Y chromosome, the origin of heart problems?
The researchers started by consulting the UK BioBank database which contains the medical and genetic information of more than 500,000 Britons. They found that the men who participated in the study and who had lost a significant portion of Y chromosomes (in over 40% of their blood cells) fared worse in subsequent years.
In fact, they were 41% more likely to die within the next seven years compared to men without chromosome loss. Specifically, they were approximately two to three times more likely to die heart failure or disease.
Next, the scientists genetically modified mice to study the effects of mLOY. Again, the loss of the Y chromosome led to health issues.
“In the mouse models used in the study, the mouse Y chromosome was knocked out to mimic the human mLOY condition and we analyzed the direct consequences of this. Examination of mice with mLOY disease showed increased scarring of the heart, known as myocardial fibrosis.We find that mLOY disease causes fibrosis which leads to a decline in heart function”, explained Lars Forsberg, co-director of the study, in a press release. (source 2)
The loss of the Y chromosome is very frequented and detected in at least 20% of 60-year-olds and 40% of 70-year-old men. Without being the only cause, it could be one of the reasons why men live shorter than women.
