Research in mice suggests for the first time that physical activity significantly reduces the amount of protein deposits in the brain, which are characteristic of Alzheimer's disease
Physical activity helps in maintaining body health and preventing diseases that characterize Western society such as cancer and cardiovascular diseases. Now it turns out that it may also induce changes in the brain that slow down Alzheimer's disease. Researchers from several universities in the US found that an environment rich in activities, especially physical activity, caused in mice a decrease in protein deposits in the brain that characterize Alzheimer's disease. This is the first time that experimental evidence shows that an external environment reduces pathological signs of the disease.
The deposits are of beta amyloid - a protein that is produced and secreted by the body's cells and whose function is unknown. In healthy people it is found in a soluble state and does not cause harm, but in Alzheimer's patients it is formed in large quantities, accumulates and sinks in the brain in clusters (plaques) that look like wires twisted together. Alzheimer's researchers are still divided on the question of whether the beta amyloid deposits cause the disease or are its products. What is clear is that the appearance of deposits and their accumulation in the brain is one of the main symptoms of Alzheimer's; The deposits appear in the patients at the same time as a sharp decrease in the number of nerve cells in the brain, memory impairment and a decrease in cognitive functions.
In recent years, circumstantial evidence has been discovered that an environment enriched with intellectual stimulation reduces the risk of Alzheimer's disease. Other studies have shown that different areas of the brain of adults, especially those related to cognition and memory, can change depending on external environmental conditions. Additional studies have indicated that an environment rich in stimuli significantly improves memory functions. The improvement in memory functions was associated with noticeable structural changes in the networks of nerve cells and the creation of new nerve cells and new blood vessels in the brain.
The team of researchers, led by Sam Sisodia of the University of Chicago, built on these studies. "The studies made us think that an enriched environment could play an important role in preventing Alzheimer's," the researchers wrote in the journal "Cell", where their research was published last month. Since the amyloid deposits are related to the disease, "we decided to test the hypothesis that the beta amyloid deposits in Alzheimer's patients are also affected by the external environment". A positive answer, the researchers thought, would verify the circumstantial estimates regarding the connection between the environment and Alzheimer's and give them experimental validity.
The researchers took two groups of one-month-old mice that were implanted with a gene that causes them to get Alzheimer's. One group of mice was placed in an enriched environment - large cages with "treadmills" on which the mice could run, colorful tunnels to wander through, and a selection of toys. The researchers placed a second group of mice in standard cages without any means of enrichment.
The activity of the mice was recorded daily for five months, and at the end of the period their brains were examined. "We saw that the mice raised in the enriched environment had much less beta amyloid deposits compared to the mice raised in standard conditions," the researchers wrote. They also found in the brains of the "enriched" mice a significant increase in the activity of the enzymes that break down these deposits and changes in the activity of certain genes that can increase the lifespan of nerve cells and increase learning and memory processes.
The experiments showed that the longer the mice spent on the treadmill, the lower the amount of beta amyloid deposits in their brains. "From this point of view, it can be assumed that exercises and physical training can delay processes related to aging, induce structural changes in the brain, cause recovery of memory problems and brain injuries, and improve cognitive functions in the elderly and Alzheimer's patients," the researchers conclude. "However, since the finding linking running to a decrease in the accumulation of amyloid deposits is provocative, it is necessary to test this in large groups of animals and isolate the exercise exercises from the other stimuli given to the mice before reaching an unequivocal conclusion about the unique role of physical activity in lowering amyloid deposits" .
"The relationship between the enriched environment and physical activity and the decrease measured in precipitation can certainly indicate a positive, and perhaps even preventive, effect of physical activity," says Prof. Danny Michaelson, an Alzheimer's researcher from Tel Aviv University. Michaelson and doctoral student Ofir Levy examined another aspect of the connection between an enriched environment and Alzheimer's. They asked if such an environment might help all patients or only some of them. To this end, they created an environment rich in stimuli and in it they examined two groups of mice - one group with a hereditary risk factor for Alzheimer's, and a second group without a risk factor.
"About six years ago, it was discovered that a molecule called APOE can be found in the body in two genetically determined versions," Michaelson explains. "In the 'bad' version (called APOE4) it increases the risk of getting Alzheimer's compared to people who carry the 'good' version (APOE3). The 'bad' version of the molecule is known to be the most distinct genetic risk factor for the disease."
Michaelson and his team tested whether the two groups of mice responded similarly to an enriched environment. "We found that in mice that carried the 'good' version of the molecule and were placed in an enriched environment, the volume of the brain increased, the connections between nerve cells multiplied, new nerve cells were formed and they learned and remembered better," says Michaelson. "In contrast, in the mice carrying the 'bad' version, no changes occurred in the brain - they could not take advantage of the enriched environment. The ability to benefit from the enriched environment, both in the development and functioning of the brain and in reducing the risk of Alzheimer's, therefore depends on the hereditary background and is not the same for everyone."
