Gut–brain axis biochemical signalling from the gastrointestinal tract to the central nervous system: gut dysbiosis and altered brain function

Abstract Background The gut–brain axis facilitates a critical bidirectional link and communication between the brain and the gut. Recent studies have highlighted the significance of interactions in the gut–brain axis, with a particular focus on intestinal functions, the nervous system and the brain. Furthermore, researchers have examined the effects of the gut microbiome on mental health and psychiatric well-being. The present study reviewed published evidence to explore the concept of the gut–brain axis. Aims This systematic review investigated the relationship between human brain function and the gut–brain axis. Methods To achieve these objectives, peer-reviewed articles on the gut–brain axis were identified in various electronic databases, including PubMed, MEDLINE, CIHAHL, Web of Science and PsycINFO. Results Data obtained from previous studies showed that the gut–brain axis links various peripheral intestinal functions to brain centres through a broad range of processes and pathways, such as endocrine signalling and immune system activation. Researchers have found that the vagus nerve drives bidirectional communication between the various systems in the gut–brain axis. In humans, the signals are transmitted from the liminal environment to the central nervous system. Conclusions The communication that occurs in the gut–brain axis can alter brain function and trigger various psychiatric conditions, such as schizophrenia and depression. Thus, elucidation of the gut–brain axis is critical for the management of certain psychiatric and mental disorders.