The impact of the microbiota on mental health
Not only the intestinal tract of the host itself, but also the microbiota present can influence the function of the central nervous system. The bidirectional interaction between the gut and the brain via the brain-gut-microbiota axis involves neuronal, hormonal and immunological communication. The microbiota interacts with the vagus nerve, which connects the brain to the entire gastrointestinal tract. The afferent fibers of the vagus can sense signals from the microbiota via bacterial compounds and metabolites produced by dietary components such as SCFAs, secondary bile acids and tryptophan metabolites. These molecules signal by interacting with enteroendocrine and enterochromaffin cells of the digestive tract. Gut microbes also influence immune cells and possible inflammation, which can indirectly affect the brain. In addition, bacteria can produce neuroactive compounds such as γ-aminobutyric acid (GABA), serotonin, dopamine, acetylcholine and noradrenaline, which act locally on the enteric nervous system. Neurotransmitters can pass through the intestinal mucosa and enter the bloodstream, but are generally unable to cross the blood-brain barrier and have a more indirect effect on the enteric nervous system. Microbiota-free animals provide compelling evidence of a link between the microbiota and the brain, as the brain and the entire central nervous system show deviations from normal development. An altered microbiome can therefore influence mental health, stress, anxiety and depression.
The effect of neuroactive compounds on the enteric nervous system
Since diet is one of the most important factors shaping the composition of the gut microbiome, it is not surprising that people with eating disorders such as anorexia nervosa, bulimia nervosa or psychogenic overeating have an altered composition of the gut microbiome. The differences in the composition of the gut microbiome in people with anorexia nervosa are a consequence of starvation, where microorganisms equipped with mechanisms to grow at lower energy levels survive and dominate the competitive situation in the gut. Altered composition of the gut microbiome due to diet and stress can lead to impaired gut barrier function, passage of microbial components through the gut barrier and into the bloodstream, and subsequent activation of the immune system and inflammatory response.
Intestinal microbiota and the pathogenesis of food intake disorders
In our lab, we aim to elucidate the role of the gut microbiota in the development and maintenance of eating disorders and identify the mechanisms of action of specific relevant microorganisms, as the gut microbiota and its influence on human physical and mental health may be a missing element in understanding the etiology of eating disorders.
