Gut microbiota: neurosecretion, modulation by psychobiotics and bacteriocins, and mechanisms of action thereof

点击翻译按钮获取中文摘要

Recent scientific studies have reported that intestinal microbiota, with its structure and metabolism, may be a major contributory factor to the neurobiological and physiological function of the nervous system. Psychobiotics are beneficial bacteria (probiotics) or support for such bacteria (prebiotics) that can positively modulate microbiota–gut–brain interactions. Microbiota–brain communication channels through which psychobiotics exert effects include the enteric nervous system and the immune system. Despite some studies, the mechanisms by which these probiotics are able to exert these beneficial effects on the digestive tract and to modulate the intestinal microbiota are far from being elucidated and remain very hypothetical. We hypothesize that reported effects may be through a microbial endocrinology-based mechanism (i.e. probiotic production of a neurochemical). Commensal gut bacteria, through metabolism of non-digestible fibers, produce a range of neurotransmitters including γ-aminobutyric acid (GABA) by Bifidobacteria, GABA and acetylcholine by Lactobacilli, dopamine and noradrenalin by Bacillus, serotonin by Enterococcus and Streptococcus, and noradrenalin and serotonin by Escherichia. Some of these neurotransmitters could regulate many intestinal physiological functions, including intestinal fluid secretion, blood circulation and ulceration. The GABA receptor has been shown to regulate motility in the small intestine and colon by modulating the release of acetylcholine from enteric neurons. In vivo GABA production by intestinal bacteria may impact the microbiota–gut–brain axis, and could have potential health benefits. It is not yet clear as to why certain bacteria harbour genes responsible for the production of neuroactive molecules. Therefore, there is still a limited understanding of the extent to which specific bacterial strains orchestrate the microbiota-gut-brain axis. In addition, the mechanistic understanding of this microbiota–nervous system crosstalk and how theses microbes impact neurobiological functions is still lacking. We hypothesize that gut microbiota and probiotics have a neurosecretory role with a potential impact on the nervous system. The project aims to (i) establish the exo-neuroendocrine role of microbiota as a key biological function in human gut, (ii) investigate the impact of psychobiotics and their bacteriocins on the gut microbiota diversity, metabolism and neurosecretory function and (iii) develop and perform proof-of-concept analysis of next-generation probiotics with neuro-biological function. Understanding the impact, mechanisms, and biological effects of psychobiotics on gut microbiota architecture, metabolism and function could lead to better comprehension of microbiota–gut–brain communication.