Clinical effects of probiotics on the functioning of the gut-brain axis in children

Abstract

The gut microbiota is a complex collection of bacteria, viruses, protozoa, archaea, and fungi colonising the human gastrointestinal (GI) tract. The microbiota plays a fundamental role in keeping the body healthy and the development of various diseases, including mental ones. Clinical studies have showed that there exists a bidirectional communication between the gut, microbiota and brain within the brain-gut-microbiome axis. It is understood that gut microbes play a role in many mental disorders and may be a potential therapeutic target. The nervous system and GI tract communicate through a bidirectional signalling network that includes multiple pathways, among which are the vagus nerve, the immune system, the hypothalamic-pituitary-adrenal axis, some transmitters, and bacterial metabolites. The available data indicate the mutual influence of the microbiota and the activation of inflammatory processes in the brain. Psychobiotics have been increasingly used for the management of the microbiota in case of injury of this pathway. The term that was used for the first time in 2013 defined psychobiotics as probiotics, which have a positive effect on mental health provided that they are taken orally at adequate doses.Afterwards they were included in the definition, given the proven benefit of prebiotics. Thus, psychobiotics are beneficial bacteria (probiotics) or auxiliary substances for such bacteria (prebiotics) that affect the communication and interactions between bacteria and the brain. Following ingestion, probiotic bacteria concentrate mainly in the intestinal epithelium, providing the host with nutrients and influencing the immune system, as well as producing neuroactive substances that act on the brain-gut axis. This review is devoted to the new interesting area that correlates the gut microbiota with nervous system diseases and its possible treatment with psychobiotics.