Intestinal bacteria responsible for brain cell death and cognitive decline with age found

(ORDO NEWS) — A group of American researchers have discovered a molecule produced by bacteria in the intestinal microbiome (including humans) that can enter the brain, causing the death of neurons and other brain cells.

The effect is especially noticeable with age, when the number of these bacteria increases markedly, which can lead to a decrease in cognitive functions such as learning and memory.

The gut microbiome is the totality of all microorganisms that inhabit the gastrointestinal tract and live in an essentially mutually beneficial relationship with the host organism.

For example, intestinal bacteria help us digest and assimilate various substances (the same fiber) and play an important role in the synthesis of B and K vitamins. In the process of life, the microbiome releases many molecules, some of which can be harmful to the host organism.

The authors of a new study published in the journal Cell Host & Microbe were convinced of this . They studied the bacterial family Ruminococcaceae, which inhabits the intestines of mice (but also occurs in humans), and the small molecule they secrete is isoamylamine (IAA).

The scientists found that the older the mouse became, the more these bacteria were in its intestinal microbiome, and, as a result, the content of IAA increased.

The IAA molecule interested researchers even more when it was found that it was able to cross the blood-brain barrier, a defense system that normally prevents any unwanted molecules and microorganisms from entering the brain from the bloodstream. Next, the scientists determined the role of the IAA molecule in the brain.

Intestinal bacteria responsible for brain cell death and cognitive decline with age found 2
Brief description of the principle and effect of the isoamylamine (IAA) molecule on brain microglia

It turned out that it affects microglia – auxiliary cells of the central nervous system involved in the formation and maintenance of contacts between nerve cells, as well as the destruction of various kinds of “garbage”, such as damaged neurons or other brain cells.

IAA activates a special gene S100A8, which contributes to excessive activation of microglia (as in an inflammatory process), which can lead to the death of neurons and other brain cells due to an autoimmune process (microglia attack even intact and healthy cells).

To find out the consequences of getting IAA into the brain, the authors of the work orally (through the mouth) administered a preparation containing IAA to young healthy mice and observed the reaction.

As a result of several behavioral and cognitive tests, it turned out that exposure to IAA led to a loss of cognitive function: rodents began to learn to navigate the maze and recognize objects worse.

The opposite effect was observed when the scientists blocked the effect of IAA on microglia in older mice, resulting in improved memory and spatial learning.

Thus, the researchers were able to establish the presence and mechanism of action of a molecule produced by an intestinal bacterium on brain cells and cognitive functions using mice as an example.

However, scientists acknowledge that more research is needed to determine whether these findings apply to humans and whether blocking the action of IAAs can prevent cognitive decline as people age or in some neurodegenerative diseases.


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