“All of our cells accumulate waste while they are working, and these waste products can be toxic. If they aren’t removed they can build up and kill our cells. Throughout the rest of the body the lymphatic system washes these waste products away, but the brain is cut off from these actions because of the blood-brain barrier.
The team just discovered the brain’s unique trash disposal system last year — the find was published in the journal Science Translational Medicine on Aug. 15, 2012. It works like a plumbing system.
The brain itself is bathed in a special clear liquid called cerebrospinal fluid, which doesn’t mix with the blood and lymph system of the rest of the body. In the study from last year, they found that this fluid travels through special channels and washes the brain out.
There are two types of cells in the brain — the neurons that send signals and the glial that keep them healthy. They found that these glial cells seem to create these cleaning channels around the neurons.
It washes away toxic proteins and removes them from the brain’s circulatory system. They are transferred to the general circulatory system, where the liver can remove them.
By studying this newfound pathway in mice trained to sleep on a microscope, the researchers found that this system was 10 times more active during sleep than it was while the mice were awake.
They injected the mice with colored toxic proteins to see the system at work — when the mice were sleeping, these toxic proteins were removed from the brain twice as quickly as when they were awake.”
“The timely removal of waste from the brain is essential where the unchecked accumulation of toxic proteins such as amyloid-beta can lead to Alzheimer’s disease. In fact, almost every neurodegenerative disease is associated with the accumulation of cellular waste products.
One of the clues hinting that the glymphatic system may be more active during sleep was the fact that the amount of energy consumed by the brain does not decrease dramatically decrease while we sleep. Because pumping CSF demands a great deal of energy, researchers speculated that the process of cleaning may not be compatible with the functions the brain must perform when we are awake and actively processing information.
Through a series of experiments in mice, the researchers observed that the glymphatic system was almost 10-fold more active during sleep and that the sleeping brain removed significantly more amyloid-beta.
“The brain only has limited energy at its disposal and it appears that it must choice between two different functional states - awake and aware or asleep and cleaning up,” said Nedergaard. “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.“”
