. A new study published online in Cell may help explain the gender gap – and offer clues to new treatments for helping patients of both sexes fight back.
Researchers zeroed in on a gene named USP11, found on the X chromosome. People assigned female at birth have two X chromosomes, while people assigned male at birth have one X and one Y. So while all males have one copy of USP11, females have two.
The body’s trash collection system
In the normal course of events, the brain creates waste that must be removed lest it becomes toxic. One waste product is the protein tau. Too little tau can damage nerve cells, explained researchers David Kang, PhD, and Jung-A “Alexa” Woo, PhD, who led the study. But too much becomes toxic and can lead to neurodegenerative diseases such as Alzheimer’s disease. In fact, new research suggests that testing for changes in tau may someday help doctors diagnose Alzheimer’s disease earlier.
To manage tau, the brain uses a regulatory protein called ubiquitin to “tag” or signal the body that extra tau should be removed.
USP11’s job is to give instructions to make an enzyme that removes the ubiquitin tag to maintain balance. But if too much of the enzyme is present, too much tau gets untagged – and not enough of it gets cleared.
“Our study showed USP11 is higher in females than males in both humans and in mice,” Dr. Kang said. “That’s already true before the onset of dementia. But once someone has Alzheimer’s disease, USP11 is much higher – regardless of sex.”
The study adds to a growing body of evidence that shows that women may be more vulnerable than men to higher levels of tau, possibly explaining why women are affected by the disease more often than men.
But what if there was a way to “turn off” or deactivate the USP11 gene? Might that help prevent Alzheimer’s disease? And could it be done safely?
What happened when the gene was eliminated?
To examine these questions, researchers used a method of gene manipulation to completely delete the USP11 gene in mice. They then examined the mice for changes. The result? The mice seemed fine.
“The mice bred well. Their brains looked fine,” Dr. Woo said.
It would not be possible – or ethical – to remove a gene from humans. But when a medical condition makes a certain gene unhelpful, that gene can be partially blocked or expression of the gene can be reduced with medication. In fact, medications targeting enzymes are common. Examples include statins for cardiovascular disease or HIV treatments that inhibit protease enzymes.
“If we are able to identify some type of medicine that would inhibit USP11, our study suggests it would be well tolerated and benefit women,” Dr. Woo said.
Dr. Kang also cautions that the process for creating such a therapy takes at least 10-15 years. The researchers said they’d like to shorten the timeline and plan to study currently approved FDA medications to see if any might work to target USP11 gene activity – and hopefully bring forth a new treatment for Alzheimer’s disease sooner.
A version of this article first appeared on WebMD.com.