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Brain Also Needs a Daily Bath

BrainBath_PPTYou can easily accept the idea that you need to have a daily bath, wash face, and brush teeth every day—we have to clean up our body before go to bed. You won’t want to be a dirty and stinking guy, because chance of having diseases will increase and you’ll be disliked, too.  Now, people have better living conditions and some of us have a bath every day. But would you imagine, our brain also needs a daily bath?

I’m not saying you should split the brain and wash it under the shower nozzle. Nerve cells in brain generates beta amyloid and tau protein—some metabolite and these protein can gather and produce strong neurovirulence that is able to kill brain cells. The notorious Alzheimer disease is related to the gathering of these harmful substances. For our brain, these metabolite are just like foul and dangerous wastes that need to be cleaned on time.

Human has a self-cleaning system. Lymphatic vessel, around venous duct, are in charge of cleaning. The well-known Lymphatic Detox Therapy, is actually facilitate elimination of metabolite by enhancing the flow of Lymphatic fluids. However, there is no such structure like Lymphatic vessel in brain, which is in fact a strange thing—as the most active organ in a human body, how could brain clean up the wastes generated by brain cells?

Don’t worry! As the source of wisdom, brain is not only able to have a bath, but also has its exclusive “bath center”—Glymphatic system.  From “Lymphatic”, we can learn that this system works in a similar way as peripheral lymphatic system, while “G”means Gila, a cell population called gliocyte that can express a kind of protein named as aquaporins—the master valve of inner bath center of brain. When the master valve is on, water in the bath center starts to circulate and wash away those harmful substances produced by brain cells.

In fact, the water that brain uses to have bath is also unusual—the ventricle of brain can continuously generate a liquid called cerebrospinal fluid, which is transported along the ducts in between ventricles and then moved to brain surface. Subsequently, cerebrospinal fluid will flow along arteries on brain surface into brain tissues. During this process, cerebrospinal fluid and brain cells keep exchanging and the fluid carry the wastes—generated by brain cells and exhausted to cell interspace—to cerebral vein space and out of brain. Till this moment, the brain finishes one bath. You think it takes some time to take a bath for brain? Sure it does, and brain spends longer on bathing than woman! Normally, brain bath requires about 8 hours.

8 hours might remind you of something. Right, your brain has a bath when you are resting. A study published on Science [1] suggests that when human is in sleeping, the space between brain cells will increase and cerebrospinal fluid circulates faster than that when one is awake, helping brain exhaust wastes generated when one is awake. Therefore, if you don’t sleep, your brain can’t take a good bath. When you are tired, it’s highly likely that you have too many brain cell wastes and your brain is forcing you to feel tired so you will go to rest.

Staying up late appears to be common for modern people. Indeed, we have to work every day and we also want some entertainment, so it is acceptable to sacrifice some sleep time for entertainment. However, what I’m trying to say is we should sleep on time every day. Do something good to your brain and it can give more back. Taking Grey’s mother in Grey’s Anatomy as an example, she was an outstanding surgeon when she was young. She worked hard and stayed up late often. What’s the result? She suffered early onset Alzheimer’s. Think about it—is it worthwhile?

Reference:   1.  Lulu Xie et al. Sleep Drives Metabolite Clearance from the Adult Brain.Science 342, 373 (2013).