Khaberni - Research indicates that memory decline with aging might not be linked only to the brain, but also to biological processes occurring in the gut.
It was previously known that the microbiome, as a microbial environment coexisting with the body, affects cognitive functions, but the mechanisms of this effect remained unclear.
Experiments on mice, published in the journal Nature, showed that the aging digestive system produces specific molecules that weaken the activity of a main neural pathway connecting the gut to the brain, leading to age-related cognitive decline.
The experiments demonstrated that the aging digestive system produces molecules that inhibit the activity of the vagus nerve, which connects the internal organs to the brain and is responsible for receiving internal signals of the body and visceral perception. With aging, the composition of the microbiome changes.
In the course of the experiments, the microbiome of aged mice was transplanted into young mice, leading their cognitive indicators to deteriorate to the level of aged mice. Antibiotic treatment restored the indicators to normal levels. Mice without a microbiome experienced a slower process of age-related cognitive decline.
The researchers hypothesized that the bacteria named Parabacteroides goldsteinii might be causing this phenomenon, while not ruling out the role of other microbes in it. These bacteria produce medium-chain fatty acids, which activate immune cells in the gut. These cells secrete an inflammatory molecule called Interleukin-1 beta (IL-1β) that disrupts the function of neuronal cells of the vagus nerve headed to the hippocampus (memory center).
In experiments conducted on mice, the researchers were able to reverse memory disorders in mice using the following:
• Antibiotics for the purpose of depleting the microbiome.
• Bacterial phage (virus) specifically targeting P. goldsteinii bacteria.
• Stimulation of the vagus nerve by hormone cholecystokinin (CCK) or drugs like "Ozempic".
This study was conducted on mice, but it indicates similarities in the processes in humans. Vagus nerve stimulation is currently used when treating epilepsy and stroke, and patients notice an improvement in their cognitive abilities. Further studies are needed to explore the links between the gut and dementia and degenerative neurological diseases.
