Friday, May 27, 2016

Loss of Y Chromosome in Men Tied to Alzheimer’s Risk

Men who lose Y chromosomes from their blood cells as they age may have an increased risk of developing Alzheimer’s disease, a new study suggests.

The study of more than 3,200 men found those who already had Alzheimer’s were nearly three times more likely to show a loss of the Y chromosome in some of the blood cells. What’s more, older men with that “loss of Y” faced a higher risk of developing Alzheimer’s over the next eight years.

Experts said the study doesn’t prove that loss of the Y chromosome directly contributes to Alzheimer’s disease. But it adds to evidence tying loss of the Y to disease risk, said study co-author Lars Forsberg.

It also raises the possibility of one day testing men’s blood for loss of Y, to predict their risk of developing Alzheimer’s, said Forsberg, a researcher at Uppsala University in Sweden.

The findings were reported online May 23 in the American Journal of Human Genetics.

Men have an X and a Y chromosome, while women have two X chromosomes. Researchers used to think that the Y did little more than determine male sex and ensure normal sperm production.

But recent studies have shown that the Y chromosome contains a large number of genes, whose jobs are not fully understood yet.

Similarly, researchers have long known that as men age, they can lose the Y chromosome form some of their body cells. It was seen as a normal part of aging. Some recent studies, however, have suggested otherwise.

In a 2014 study, for example, Forsberg and his team found that older men with a loss of Y had a higher cancer risk and shorter lives than other men.

Dr. Luca Giliberto, a neurologist and researcher with the Feinstein Institute for Medical Research, in Manhasset, N.Y., who was not involved with the study, said the researchers accounted for other factors tied to Alzheimer’s risk – inducing older age, education levels, high blood pressure and diabetes.

“It seems that the loss of Y is, per se, an independent risk factor for Alzheimer’s disease,” Giliberto said.

My Take – This study has far reaching implications. First and foremost, the fact that the loss of Y appears to be independent of metabolic syndrome makes it an important marker for multiple disease processes. Second, the Y chromosome can be readily measured from a routine blood draw. I believe the cost of such testing will be reasonable.

The study goes on to say that it is yet to be determined at what age men begin to lose Y; the earlier the loss, the more significant the marker. For example, I am seeing the hemoglobin A1c elevate in patients in their late 20s to early 30s; many years prior to the diagnosis of diabetes. Early detection and intervention is the key. I suspect this will be the next area of research for Forsberg and his team.

The Bottom Line:
Look for the RBC Y chromosome test to become readily available in the next few years. I will start running the test on my patients (and myself) as soon as it comes to the market.

By the way, the concept of “junk DNA” is junk science. The human body is not wasteful. Just because we do not yet know what purpose most of our DNA serves, does not mean it has no purpose.

Source: May 23, 2016 National Institutes of Health

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