Men lose Y chromosomes as they age. It may be harming their hearts

Men don't just lose their hair, they also lose their muscles. Y chromosomes are lost from their cells. The evidence has been circumstantial but scientists have linked this to diseases and a higher risk of death. The Y chromosomes were removed from male mice and they died earlier than their Y-carrying counterparts.

John Perry, a human geneticist at the University of Cambridge, says that this is the best evidence to date that the Y chromosome is bad for health. One of the biggest studies on the incidence of Y chromosomes loss in men was led by Perry.

The Y chromosome has less genes than the X chromosome but it's still a macho one. It is possible that the chromosomes don't get passed on when a cell splits. The easiest way to detect the loss of Y is by analyzing blood samples, and researchers have found that at least 40% of 70 and 93 year olds have the Y missing. Most of the cells in older men can be short.

Men who don't have the Y in their cells are more likely to suffer from heart disease, cancer, Alzheimer's disease, and other aging related ailments. According to Kenneth Walsh of the University of Virginia, the condition could be a reason why men die earlier than women.

Walsh and colleagues performed bone marrow transplants on 38 mice to see if removing the Y chromosomes harms health. Young male mice whose bone marrow had been removed were inserted with altered cells after they were deleted from mouse bone marrow cells. The swap did not remove the Y chromosomes from the recipients, but it removed the Y chromosomes from the white blood cells. The control mice received transplants but retained their Y chromosomes.

The researchers followed two groups of animals. The Y-lacking rodents were more likely to die than the control rodents after the transplant.

The mice that lost their Y chromosomes had less strength in their hearts. The contraction strength of the heart had fallen by 20%. In addition, the hearts of mice without the Y chromosome were filled with tough tissue. The heart is stiffened and can't pump as much blood.

The transplants on the mice did not remove the Y chromosomes from the heart muscle cells. There are white blood cells in the heart. The scientists found that many of the cells in the heart were stimulated by the lack of the Y chromosomes in mice.

It's possible that something similar is happening in humans. The UK Biobank contains survival information for more than 15,000 men. The team found that men who lost at least 40% of their Y chromosomes were more likely to die from diseases related to the circulatory system. The causes of death that correlated with the Y chromosome's absence were identified by the scientists.

Losing the Y chromosome leads to heart failure and an earlier death. Walsh says that researchers have downplayed the Y chromosome's health impact because it sports so few genes, but the evidence suggests that it leads to a lot of years of life lost.

Mitchell Machiela of the National Cancer Institute was not connected to the study. Amy Bradshaw of the Medical University of South Carolina says the discovery that macrophages in the Y-lacking mice change their "personality" makes sense. A lot of the fibrosis in the heart is caused by this switch.

The Albert Einstein College of Medicine cautions that there is no proof that increased fibrosis is killing the mice. He says that the fibrosis is subtle in the animals that are missing the Y chromosomes. The weakened heart of the rodents would not be fatal. There is a possibility that the mice are dying from something related to the heart. The study could have a big impact on how we view heart failure.