A healthy intestinal flora makes an important contribution to protection against infections, allergies and other diseases. But when it is destroyed, for example by antibiotics, the memory also suffers. German researchers have now found that out.
Healthy intestinal flora can protect the brain
It has long been known that an intact intestinal flora makes an important contribution to protection against infections, allergies and other diseases. But it may also keep the brain healthy, as German researchers reported last summer in the renowned journal "Nature Neuroscience". The bacterial composition in the human intestine therefore influences immune cells in the brain. Now scientists from the Max Delbrück Center for Molecular Medicine in the Helmholtz Association (MDC) have reported that a special type of immune cell mediates between the intestinal flora and the brain. "The findings are important for the consequences of long-term use of antibiotics, but could also help to alleviate the symptoms of psychiatric conditions," the MDC wrote in a press release.
Gut and brain "talk" to each other
As the message says, the gut and brain “talk” to each other. Through hormones, metabolic products or direct nerve connections. Another link is a certain population of immune cells from the group of monocytes, like Dr. Susanne Wolf from the MDC research group led by Prof. Helmut Kettenmann together with colleagues from the University of Magdeburg, the Charité - Universitätsmedizin Berlin and the US National Institutes of Health (NIH). The experts have now published their results in the "Cell Reports" journal.
Microbiome with antibiotics turned off
To get to their knowledge, the researchers switched off the microbiome, the bacteria of the intestinal flora, with an antibiotic cocktail in mice. When they compared rodents to untreated animals, they observed significantly fewer newly formed nerve cells in the hippocampal region of the brain. According to the researchers, the memory of the mice also deteriorated, because this formation of new brain cells - called "neurogenesis" - is important for certain memory functions. When the microbiome was switched off, the number of a certain immune cell population in the brain, that of the Ly6Chi monocytes, decreased significantly together with the neurogenesis.
Experimental animals cured with different strategies
When Wolf and her team only removed these cells from the mice, the neurogenesis decreased. If they administered Ly6Chi monocytes to the animals treated with antibiotics, the neurogenesis increased again. According to their own statements, the scientists cured the antibiotic-treated animals using two different strategies. If the mice took a mixture of selected strains of bacteria or did voluntary training in the mouse impeller, the negative effects of the antibiotics were reversed. The monocyte count recovered, as did memory and neurogenesis. According to the experts, restoration of the intestinal flora with the microbiome of untreated animals was unsuccessful.
Consequences for the treatment of mentally ill people
According to Wolf, the hitherto unknown mediator function of the immune cells is of particular scientific interest. "With the Ly6Chi monocytes, we may have discovered a new general communication path from the periphery to the brain." Applied to humans, the results do not mean that all antibiotics interfere with brain function, because the combination of drugs used was extremely strong. "However, similar effects can be expected with antibiotic therapy over a long period of time," says Wolf. The antibiotics also have a direct effect on the neurogenesis via the intestinal flora, as further results from the research team show. Furthermore, the new work also has consequences for the treatment of psychiatrically ill people, such as schizophrenia or depression patients with impaired neurogenesis, explained Susanne Wolf: "In addition to medication and sports, probiotic preparations may also help these patients. In order to check this, we would like to conduct clinical pilot studies together with the Charité. ”(Ad)