Dysbacteriosis and the Dysregulation of the Brain-Gut Axis as Pathophysiological Mechanisms of Neuropsychiatric Disorders

Abstract

The central nervous system (CNS) and the gastrointestinal tract (GIT) form numerous connections that are often referred to in the scientific literature as the brain-gut axis. It includes structures from the enteric nervous system, the sympathetic nervous system and the spinal nerves, the vagus nerve and the endocrine system. A number of neurotransmitters and hormones take part in the formation of the nexuses of the brain-gut axis, one of them being serotonin (5-hydroxytryptamine, 5-HT). 5-HT is a neurotransmitter synthesized from tryptophan in the serotonergic neurons of the CNS (10%) and the enterochromaffin cells of the GIT (90%). A number of publications point to the contribution of the intestinal microflora—in particular anaerobic bacteria, such as Turicibacter sanguinis, Akkermansia muciniphila, Lactobacillus plantarum, Lactobacillus Rhamnosus, and other bacteria of the normal gut microbiome, in the regulation of the levels of 5-HT in the GIT and the brain-gut axis. The colonization of the GIT with pathogenic bacteria and dysbacteriosis can cause dysregulation in the brain gut-axis, which in turn can affect the function of the CNS. Research shows that such dysregulations take part in the pathogenesis of a number of gastrointestinal diseases (inflammatory bowel disease) and neuropsychiatric disorders (depression, anxiety and panic disorders, autism and multiple sclerosis). The aim of our research is to review the existing scientific literature on this topic and to clarify the role of dysbacteriosis as a pathophysiological mechanism in neuropsychiatric disorders. The constant increase in the cases of people with depression, anxiety, and panic disorders predetermines the need of researching the connections between the intestinal microbiome and the 5-HT levels in the CNS in hopes of finding new ways to prevent and treat these disorders.