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Saturday, October 19, 2013

12:31 AM 0


"The brain only has limited energy at its disposal and it appears that it must [choose] between two different functional states - awake and aware or asleep and cleaning up. You can think of it like having a house party. You can either entertain the guests or clean up the house, but you can't really do both at the same time."


When you sleep, your brain undergoes a mop-up process that removes waste products linked to Alzheimer’s and dementia, according to new research published yesterday in the online version of Science.



A Team of researchers at the University of Rochester Medical Center (URMC) used high-tech imaging to look deep into the brains of mice and discovered that the brain functions differently while asleep than awake, ridding itself of accumulated proteins at a much faster rate. (In mice, that is – but researchers use mouse brains because they’re considered surprisingly similar to human brains.)


Nedergaard and her team coined the term “glymphatic system” last year, when they used new imaging technology known as two-photon microscopy to discover a scrubbing process taking place around brain cells, known as glial cells. The mechanism of this cleanup process is fascinating: Nedergaard and colleagues found that cerebrospinal fluid flows through the spaces between neurons, flushing proteins and other neural waste into the circulatory system and away.Led by Maiken Nedergaard, M.D., who co-directs the URMC’s Center for Translational Neuromedicine, the researchers discovered that a waste-draining system they call the “glymphatic system” is ten times more active during sleep than while awake. This nocturnal cleaning system removes proteins called amyloid-beta, which accumulate into the plaques that contribute to Alzheimer’s disease and dementia. 

In this year’s research, they discovered that not only does the “glymphatic system” kick into high gear only during sleep, but it also mops up significantly more of the toxic protein amyloid-beta, considered a primary culprit in Alzheimer’s disease. Again using two-photon microscopy, the researchers looked at the timing of this flushing process and discovered that brain cells contract noticeably during sleep, thus expanding the areas between brain cells by as much as 60 percent. With brain cells smaller and the space between them larger, there’s more room for the cerebrospinal fluid to move freely. 

Likening the changes during sleep to “turning on a faucet,” Nedergaard says it appears that a sleep state is necessary for this “active clearance of the by-products of neural activity” to take place. This would offer a convincing explanation of why sleep has such an essential restorative function, she says. 


The discovery of the brain’s nocturnal cleaning service, coupled with previous research out of Washington University showing that levels of beta-amyloid drop during sleep, could open up new avenues of prevention and treatment for Alzheimer’s and dementia, experts say. Previous research found that depriving mice of sleep led to accumulation of amyloid-beta protein, also in mice. A few years ago, aNew York Times report suggested that new insights into how some people’s brains hold on to beta-amyloid plaques more than others offered new hope for Alzheimer’s disease breakthroughs. 


I’ve written before about the dangerous effects of sleep loss on your health, including elevated risk of stroke. Now we’ll need to add the possibility that sleep loss – and possibly sleep problems such as apnea – could increase your risk of Alzheimer’s and dementia.

"Understanding precisely how and when the brain activates the glymphatic system and clears waste is a critical first step in efforts to potentially modulate this system and make it work more efficiently."

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