Where does our ‘brain waste’ go? Scientists think they have discovered it and can use it to treat Alzheimer’s disease

Scientists are beginning to better understand how the brain gets rid of waste to stay healthy and ward off neurological diseases.

Two teams of Washington scientists have discovered signs that a slow wave of electricity pulsing through the brain during sleep pushes waste products, including the protein closely linked to Alzheimer’s disease, from deep within the brain to the surface.

A vein that runs through the brain then acts as a pipe to carry waste products out through the barrier that separates the brain and the rest of the body. This causes them to enter the bloodstream and be filtered out by the kidneys.

But when the elimination system stops working properly, which can happen with aging, traumatic brain injury, and chronic stress, these waste products can build up in the brain.

It can also cause immune cells to invade the organ, leading to inflammation associated with degenerative brain diseases.

The study was conducted in mice, but researchers believe their findings are consistent with research into possible causes of Alzheimer’s disease and other forms of dementia.

In February, scientists led by Dr. Jonathan Kipnis, a neurologist at Washington University in St. Louis, answered the question of how the brain removes waste through its rigid protective barrier without using the body’s lymphatic system, a network that drains fluids throughout the body.

The brain is not part of that system and the waste disposal pathway is known as the glymphatic system. It clears away waste generated by energy-consuming metabolic processes (all the chemical processes that constantly work in the body to keep it functioning properly), such as carbon dioxide, damaged proteins and dead cells.

Scientists have uncovered points in the brain where cerebrospinal fluid, which transports waste, flowed into the thick membrane surrounding the brain and spinal cord and into the bloodstream, where the body’s lymphatic vessels took over to clean it up.

A few weeks later, that group of scientists expanded on these findings and showed how the waste-laden fluid ends up at those exit points.

They reported that while the brain sleeps, neurons fire inward synchronized, rhythmic waves that generate force to flush cerebrospinal fluid through the brain and past the blood-brain barrier.

Dr. Li-Feng Jiang-Xie, a researcher at Washington University and lead author of the second study, said: ‘These neurons are miniature pumps. Synchronized neural activity drives fluid flow and debris removal from the brain.

‘If we can build on this process, there is the potential to slow or even prevent neurological diseases, including Alzheimer’s and Parkinson’s, where excess waste – such as metabolic waste and junk proteins – build up in the brain and lead to lead to neurodegeneration.’

In that same issue of Naturea team led by scientists at the Massachusetts Institute of Technology has expanded the evidence that a slow wave of waste washes away.

They tested mice that had developed Alzheimer’s disease and found evidence that exposure to flickering lights and clicking sounds at the same brain rhythm frequency caused pulsating signals in the brain that moved cerebral fluid from the organ.

That cerebrospinal fluid contained amyloid protein, which accumulates in the brains of people with Alzheimer’s disease.

Dr. Jiang-Xie said, “We think the brain cleaning process is similar to washing dishes.

‘For example, you start with a big, slow, rhythmic sweeping motion to clean up the soluble waste that splashes across the board.

‘You then reduce the range of motion and increase the speed of these movements to remove particularly sticky food waste on the plate.

‘Despite the varying amplitude and rhythm of your hand movements, the overarching goal remains consistent: removing different types of waste from the dishes.

‘Maybe the brain adapts its cleaning method depending on the type and amount of waste.’

However, as we age, the glymphatic system decays and waste products such as amyloid proteins and tau tangles accumulate. These contribute to cognitive decline and memory loss, as well as Alzheimer’s disease and dementia.

Changes in sleep patterns can also disrupt the normal waste disposal process. CSF flows more freely between cells while we sleep, and the entire glymphatic process is optimized during sleep.

Without adequate sleep, the flow of CSF is impaired, as is the elimination of waste products associated with neurodegenerative diseases.