The intestinal microbiota is a critical point in our well-being and our health. We know that many pathologies or discomforts can result when this one is unbalanced.
It is also accepted that the intestines and the brain are closely linked. The gut microbiota is a major player in ensuring the good communication between these two organs.
We also know the involvement of intestines and intestinal microbiota in immunity : nearly 70% of immune cells are hosted by our intestines ; and a healthy microbiota limits the proliferation of harmful agents in our body.
Do you know that the intestinal microbiota can impact immune cells’ functions in the brain ?
Our brain is not only made of neurons, but also microglia. These dynamic, small star-shaped immune cells are related to macrophages that resides in our brain. Microglia are the first defense line. After probing their environment and detecting a bacterial lesion or infection, they gather and migrate to the dysfunction where they will digest microorganisms, debris and dead neurons. Microglia also contribute to the development and functioning of the brain by regulating the establishment, maintenance and survival of nerve connections.
Nevertheless, disturbed microglia are associated with developmental and neurogenerative pathologies such as autism spectrum disorder, schizophrenia, Parkinson’s disease, Alzheimer’s disease and autoimmune diseases such as the multiple sclerosis. The gut microbiota would affect these diseases.
This is demonstrated by Thion and his collaborators.
Indeed, after analysis of mice fetal microglia, it has been demonstrated that the absence of microbiota in the mother modifies the genes expression and decreases the protective effect of these cells.
Another surprising fact, according to the sexual identity and the stage of life, the immune cells of the brain were impacted differently. Microglia of male embryos were highly disturbed in contrast to female microglia ; and conversely, at the adult stage, where disturbances preferentially affected females to males. These observations were also visible on microglies from human tissues.
These results suggest the effects on microglia are therefore reversible and they are able to recover depending on the environment ; there are differences from the fetal stage following a disturbance of the gut microbiota resulting in a different interpretation of the signals (while in many studies, researchers considered that there was no difference between genders at this stage).
This study could help us to better understand the gut microbiota impact on certain diseases and help us to find answers to the following questions : « why are men more likely to be affected by schizophrenia or autism » or « why are women more prone to multiple sclerosis » ?
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