Who produces a neurotransmitter in the intestine?
Microbes help produce the "happiness hormone" in the intestine
Margarita Paimakova, "Vesti" based on Caltech materials: Microbes Help Produce Serotonin in Gut
Although serotonin is known as a neurotransmitter of the brain, it is estimated that about 90% of its total amount in the body is produced in the gastrointestinal tract.
Changes in the levels of this so-called peripheral serotonin are associated with various diseases, including irritable bowel syndrome, cardiovascular diseases and osteoporosis.
A new study by specialists from the California Institute of Technology has shown that some gut bacteria are of great importance for the production of peripheral serotonin.
"More and more studies show that mice and other model organisms exhibit behavioral changes in response to changes in the microbial composition of their intestines," says Elaine Hsiao, professor of biology and bioengineering and lead author of the study. – We are interested in tracing the relationship between microbes and the nervous system. To begin with, we studied how gut bacteria can affect neurotransmitter levels."
Peripheral serotonin is produced in the gastrointestinal tract by enterochromaffin cells, as well as some types of immune cells and neurons. Xiao and her colleagues first tried to determine whether intestinal microorganisms affect the production of serotonin in the intestine, and if so, in which type of cells. The scientists began by measuring peripheral serotonin levels in mice with a normal composition of intestinal bacteria, as well as in sterile mice deprived of these microscopic residents.
As it turned out, enterochromaffin cells of sterile mice produce about 60% less serotonin than cells of their relatives with the usual composition of intestinal bacteria. When sterile mice were injected with normal microbial colonies, their serotonin levels reached normal (that is, serotonin deficiency can be reversible).
"Enterochromaffin cells are a rich source of serotonin in the intestine," says Jessica Yano, co–author of the study. "What we saw during this experiment shows that their ability to produce serotonin, or at least most of this ability, directly depends on the composition of the intestinal microbial community."
Diagram from the article in Cell – VM
In the future, the researchers decided to find out which specific types of bacteria (or the entire diversity of the intestinal microbiome) interact with enterochromaffin cells during the production of serotonin. After testing various species and groups of known intestinal bacteria, Yano and Xiao noticed that one group of about 20 species of spore-forming bacteria is responsible for the production of serotonin in sterile mice.
Mice injected with this group of microorganisms also showed changes in the activity of platelets, which are known to use serotonin for clotting.
The researchers also managed to identify even a number of specific metabolite molecules that regulate the number of spore-forming bacteria and increase serotonin levels in the culture of embryonic cells.
Previous research in this area has shown that some bacteria can produce the "happiness hormone" by themselves. Nevertheless, this scientific work suggests that most of the serotonin in the body depends on specific bacteria.
Despite the fact that serotonin is important for many aspects of human life, Xiao warns that a lot of additional research needs to be done before the results of this work can be applied to the treatment of people.
"We have identified a group of bacteria responsible for increasing serotonin levels, but there is a possibility that it is responsible for various other effects – we have yet to find out," says the researcher. "In addition, there are situations in which an excess of peripheral serotonin can harm the body."
Details of the work were published in the journal Cell (Yano et al., Indigenous Bacteria from the Gut Microbiota Regulate Host Serotonin Biosynthesis).
Portal "Eternal youth" http://vechnayamolodost.ru16.04.2015