As Y Chromosomes Vanish With Age, Heart Risks May Grow

A new paper, published in the journal Science, found that when the Y chromosome was gone from blood cells in male mice genetically engineered to lose their Y chromosomes, scar tissue built up in the heart, leading to heart failure and a shortened life span. The New York Times reports: Because there was a direct cause-and-effect relationship between the loss of Y and ailments of aging in the mice, the study bolsters the notion that the same thing can happen in human males. Researchers have documented an increase in risk for chronic diseases like heart disease and cancer related to loss of the Y chromosome in many studies over the years, including the new one, which used data from a large genetic study of the British population. The loss of Y could even account for some of the difference between the life spans of men and women, the authors of the Science study say.

At least 40 percent of males lose the Y chromosome from some of their blood cells by age 70. And by age 93, at least 57 percent have lost some of it. The chromosome is lost sporadically from blood cells during cell division, when it is kicked out of some cells and then disintegrates. The result is what researchers call a mosaic loss of Y. There is no way, other than to stop smoking, to reduce the risk of losing the Y chromosome. And the condition is unrelated to men having lower levels of testosterone in their bodies as they age. Taking testosterone supplements would have no effect, nor would it reverse the consequences.

It is too soon to say what men should do -- other than to stop smoking -- to protect themselves from losing their Y chromosomes or to alleviate the consequences. Those in [the researcher's] group found they could protect the hearts of the mice without Y chromosomes by blocking TGF-beta, a key molecule involved in the production of scar tissue. Dr. Stephen Chanock, the director of the division of cancer epidemiology and genetics at the National Cancer Institute, said the mouse study was 'really cool.' But he noted that there was no evidence yet that drugs to block TGF-beta would be effective in men who lost their Y. And, for now, there is little point in testing men for loss of Y, Dr. Chanock said, adding, 'the over-interpretation of these data for monetary purposes worries me deeply.'

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