Bacterial Neuroactive Compounds Produced by Psychobiotics

Abstract

We recently coined the phrase 'psychobiotics' to describe an emerging class of probiotics of relevance to psychiatry [Dinan et al., Biol Psychiatry 2013;74(10):720-726]. Such "mind-altering" probiotics may act via their ability to produce various biologically active compounds, such as peptides and mediators normally associated with mammalian neurotransmission. Several molecules with neuroactive functions such as gamma-aminobutyric acid (GABA), serotonin, catecholamines and acetylcholine have been reported to be microbially-derived, many of which have been isolated from bacteria within the human gut. Secreted neurotransmitters from bacteria in the intestinal lumen may induce epithelial cells to release molecules that in turn modulate neural signalling within the enteric nervous system and consequently signal brain function and behaviour of the host. Consequently, neurochemical containing/producing probiotic bacteria may be viewed as delivery vehicles for neuroactive compounds and as such, probiotic bacteria may possibly have the potential as a therapeutic strategy in the prevention and/or treatment of certain neurological and neurophysiological conditions.

A wide diversity of bacteria from the human gut produces and degrades biogenic amines

“…One obvious limitation of our current study is that we did not examine these isolates for their ability to secrete catecholamines and serotonin, which are important neurotransmitters. However, recent studies by others have clearly shown the presence and importance of these metabolites from gut-associated microbes, including the bidirectional character of microbiota–host interactivity via neuromediators including BAs [37,38]. …”

Gut Microbiota Dysfunction as Reliable Non-invasive Early Diagnostic Biomarkers in the Pathophysiology of Parkinson's Disease: A Critical Review

“…are known to produce dopamine and gut microbiota accounts for almost half of the dopamine production in the body. 69,70 Cyanobacteria, present in minute quantities in the GI tract, is believed to produce β-N-methyl amino-L-alanine (BMAA) which has been found to be increased in the brain of PD, Alzheimer's disease, and amyotrophic lateral sclerosis patients. BMAA is an excitotoxin which activates metabotropic glutamate receptor 5 that causes reduction in the levels of glutathione, a major antioxidant.…”

Gut Microbiota: The Conductor in the Orchestra of Immune–Neuroendocrine Communication

“…77,96 Dopamine is also produced in large quantities by a variety of bacteria including E coli, Bacillus cereus, Bacillus subtilis, and Staphylococcus aureus. 97 However, the host produces enzymes that degrade these bacterial neurochemicals. For example, dopamine is silenced by the host-produced enzyme monoamine oxidase.…”