Posts Tagged ‘Glymphatic system’

One Drink a Day Might Be Enough to Stop Dementia by Flushing the Brain

August 10, 2018

The title of this post is identical to the title of an article by Clare Wilson in the News section of the 4 August 2018 issue of the New Scientist. The article begins, “Light drinking helps prevent dementia, and now we may know why it revs up the brain’s waste disposal system. Brain cells are surrounded by a network of ultra-thin tubes that flush toxins and cell waste products away. Work in mice shows that low levels of alcohol stimulate this system, while higher amounts hinder it.

If the findings apply to people, the low levels would be equivalent to about two units of alcohol, which is about a pint of beer or a medium glass of beer. This study still needs to be replicated in people, but it is still clear that large levels of alcohol are unhealthy. In the UK, the recommendation is that both men and women are advised to stick to 14 units or fewer a week.

Total abstention from alcohol carries a slightly higher risk than low to moderate drinking. This is the finding, but it had been unclear as to why. According to the article the reason may be the brain’s waste disposal system, known as the glymphatic system. The glymphatic system ramps up its activity during sleep. Among the toxins it clears is a protein called beta-amyloid, which makes up the sticky plaques found in the brains of people with Alzheimer’s disease. Some studies have suggested that long-term sleep disruption may contribute to Alzheimer’s by causing amyloid build up.

Iben Lundgaard and her colleagues at the University of Rochester looked at the effects of alcohol on this network by injecting alcohol into mouse brains then removing them half an hour later to see how much had got into the tubes. Low doses of alcohol boosted the amount cleared by 40% compared with mice that had no alcohol. Intermediate and high doses had the opposite effect, cutting it by about 30%.

Roxanna Carare of the University of Southhmpton, UK says that the reason a low doses of alcohol have this effect may be because they raised the heart rate, and the pumping of blood helps drive fluid through the glymphatic system.

Readers of the healthy memory should be aware that many people have died with their brains filled with neurofibrillary tangles and amyloid plaque, yet who never had any of the behavioral or cognitive symptoms of Alzheimer’s. The reason given for this is that these individuals, through cognitive activities had built up a cognitive reserve.

To build up this cognitive reserve, the healthy memory blog recommends growth mindsets and meditation along with a healthy lifestyle that includes sleep, a healthy diet, and physical exercise.

© Douglas Griffith and healthymemory.wordpress.com, 2018. Unauthorized use and/or duplication of this material without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Douglas Griffith and healthymemory.wordpress.com with appropriate and specific direction to the original content.

Sleep, the Brain, and Alzheimer’s

November 24, 2013

Sleep has always presented a problem for science. It is an activity in which we humans spend approximately one-third of our lives. So there must be some justification, but what is it? Dreaming is an important area of study. The healthymemory blog has a substantial number of posts on dreaming, which will not be reviewed here (to find them, enter “dreaming” into the search block of the healthymemory blog). Recent research has identified how waste materials are removed from the brain, and how this removal increases when we sleep. A healthymemory blog reader has led me to some of this research and I do thank him for his assistance.

For most of the body there is a complex system of lymphatic vessels that cleanse tissues of potentially harmful metabolic waste products, accumulations of soluble proteins and excess interstitial fluid. Unfortunately, the central nervous system lacks a lymphatic vasculature, so the problem was to identify how waste products are removed from the brain. Research by Maiken Nedergaard and her research group at the University of Rochester has appeared to have solved this problem.1 This finding is especially important as the breakdown of the brain’s innate clearance system might underlie the pathogenesis of neurodegenerative disorders such as Alzheimer’s, Parkinson’s, and Huntington’s disease, as well as ALS and chronic traumatic encephalopathy.

The research team injected fluorescent tracers into the brains of living mice, and then imaged the movement of the tracers using two-photon microscopy in real time. They were able to identify a complete anatomical pathway, which they dubbed the “glymphatic system” due to its dependence on glial cells performing a “lymphatic” cleansing of the brain interstitial fluid. (enter “glial” into the healthymemory blog search block to learn more about glial cells).

“During sleep, the cerbrospinal fluid flushed through the brain very quickly and broadly,” said Rochester neuropharmacologist Lulu Xi/”2. Another experiment revealed that sleep causes the space between cells to increase by 60%, allowing the flow to increase. When the mouse was awakened, the flow in the brain was greatly constrained.

“Brain cells shrink when we sleep, allowing fluid to enter and flush out the brain,” Nedergaard said. “It’s like opening and closing a faucet.”3 The research also found that beta-amyloid protein cleans out of the brain twice as fast in a sleeping rodent as in one who is awake.

This research once again underscores the importance of getting enough sleep. It also suggests that failures in this cleansing system might contribute to neurodegenerative disorders such as Alzheimer’s, Parkinson’s, and Huntington’s disease, as well as ALS and chronic traumatic encephalopathy. So this research opens up new research avenues for studying and, possibly curing or remediating these diseases.

2Kim, M. (2013). During sleep, the brain clears up. The Washington Post, October 20, p. A5.

3ibid.