Study: Sleep-wake cycle affects levels of protein tied to Alzheimer's disease

Feb. 10 (UPI) -- Healthy sleep habits could help prevent Alzheimer's disease, a new study indicates.

That's because the brain's ability to process a protein closely linked with the disease relies on the body's circadian cycle, a study published Thursday by PLOS Genetics found.

In laboratory experiments, production of immune cells that help the brain clear the protein amyloid-beta fluctuated with circadian rhythms, the data showed.

Circadian rhythms are the natural, internal process that regulates the sleep-wake cycle, which repeats roughly every 24 hours, according to the Sleep Foundation.

As a result of these changes in immune cells, the body's levels of amyloid-beta, which accumulates in the brain and adversely affects its nerve and cell function, causing Alzheimer's, also fluctuate with the sleep-wake cycle, study co-author Jennifer Hurley said in a press release.

"This tells us a healthy sleep pattern might be important to alleviate some of the symptoms in Alzheimer's disease," said Hurley, an expert in circadian rhythms, and associate professor of biological science at Rensselaer Polytechnic Institute in Troy, N.Y.

The circadian system is composed of a core set of clock proteins that anticipate the day-night cycle by causing changes in the levels of enzymes and hormones in the body.

This process affects everything from body temperature to immune response, and its disruption has been linked with conditions such as heart disease, diabetes and certain types of cancer, as well as dementia, research suggests.

"Clumps" of amyloid-beta protein in the brain called plaques, as seen on magnetic resonance imaging scans, are a telltale sign of Alzheimer's disease, according to the Alzheimer's Association.

Macrophages, or microglia as they are called when they reside in the brain, are immune cells that seek and destroy unwanted material, including amyloid-beta, Hurley and her colleagues said.

Using a technique they developed in earlier research, she and her team were able to see how macrophage production was affected by the circadian cycle, they said.

Levels of enzymes involved in the production of macrophages appeared to fluctuate during the sleep-wake cycle, the data showed.

As a result, the amount of amyloid-beta ingested by healthy macrophages changes with a daily circadian rhythm, the researchers said.

That pattern did not occur in macrophages without a circadian clock, according to the researchers.

In addition to highlighting the potential benefits of healthy sleep, this relationship could be used to develop therapies that would encourage greater amyloid-beta clearance, perhaps by boosting the daily changes in macrophage production, which tend to diminish with age, they said.

"What's clear is that this is all timed by the circadian clock," Hurley said.

"In theory, if we could boost that rhythm, perhaps we could increase the clearance of amyloid-beta and prevent damage to the brain," she said.