Abstract
The microbiota–gut–brain axis is a bidirectional communication pathway that enables the gut microbiota to communicate with the brain through direct and indirect signaling pathways to influence brain physiology, function, and even behavior. Research has shown that probiotics can improve several aspects of health by changing the environment within the gut, and several lines of evidence now indicate a beneficial effect of probiotics on mental and brain health. Such evidence has prompted the arrival of a new term to the world of biotics research: psychobiotics, defined as any exogenous influence whose effect on mental health is bacterially mediated. Several taxonomic changes in the gut microbiota have been reported in neurodevelopmental disorders, mood disorders such as anxiety and depression, and neurodegenerative disorders such as Alzheimer’s disease. While clinical evidence supporting the role of the gut microbiota in mental and brain health, and indeed demonstrating the beneficial effects of probiotics is rapidly accumulating, most of the evidence to date has emerged from preclinical studies employing different animal models. The purpose of this review is to focus on the role of probiotics and the microbiota–gut–brain axis in relation to mood disorders and to review the current translational challenges from preclinical to clinical research.
Highlights
The gut microbiota constitute a so-called virtual organ consisting of a complex ecosystem involving around one hundred trillion microorganisms, mostly consisting of bacteria, and including viruses, fungi, and protozoa [1,2]
Neurotransmission, i.e., the process driving the transfer of information between neurons and their targets, can be influenced by the gut microbiota, which have been shown to produce a range of major neurotransmitters such as dopamine, norepinephrine, serotonin, γ-aminobutyric acid (GABA), nitric oxide (NO), melatonin, histamine, and acetylcholine (Ach)
It is evident from the preclinical research that specific bacterial strains play a role in ameliorating depressive-like behaviors, and certain clinical studies have demonstrated a role for probiotics towards alleviating symptoms of depression; the exact bacterial species and/or strains and mechanisms underpinning their beneficial effects remain unclear
Summary
The gut microbiota constitute a so-called virtual organ consisting of a complex ecosystem involving around one hundred trillion microorganisms, mostly consisting of bacteria, and including viruses, fungi, and protozoa [1,2]. The microbiota of the intestinal lumen affect the CNS activities of the host, such as cognition and the stress response, and likewise the activity of the brain affects microbial composition. Recent advances in research have described the importance of the gut microbiota in influencing these interactions; the microbiota–gut–brain axis is a more relevant term to describe this bi-directional communication pathway [9]. The balance between the human microbiome and the development of psychopathologies is interesting, since the gut microbiota can be altered through external factors such as diet, probiotics, prebiotics, and antibiotics, all of which have been demonstrated to affect brain functions and behavior. This review will focus on the role of probiotics in modulating the microbiota–gut–brain axis to impact mood and behavior, as well as the translational challenges moving from preclinical to clinical intervention studies, published up to December 2021
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
