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Serotonin-modulating Probiotics

By Prof. Gene Bruno, MS, MHS, RH(AHG)
Huntington College of Health Sciences

Research on probiotic has exploded over the past decade. Certainly, probiotics have been shown to have a positive impact on digestion1-3  and immune function,4-6 but beyond that research has demonstrated that probiotics can also impact other aspects of our biochemistry and health. One such area is serotonin modulation.

According to Wall et al,7 the term “psychobiotics” was coined to describe an emerging class of probiotics with relevance to psychiatry. These 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, including serotonin, have been reported to be microbial-derived and 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 signaling within the enteric nervous system and consequently signal brain function and behavior 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.

Examples of Serotonin-modulating Probiotics
For example, in animal research oral ingestion of Bifidobacteria infantis increased plasma levels of tryptophan, precursor to serotonin, suggesting that commensal bacteria have the ability to influence tryptophan metabolism and could potentially act as antidepressants.8 Another example is a study in which Caco-2 cells and mice intestinal tissues were examined after treatment with Lactobacillus rhamnosus GG. Results showed that serotonin transporter (SERT) mRNA and serotonin transporter protein (SERT-P) were higher than those in the control 24 h after treatment. This research clearly demonstrated that Lactobacillus rhamnosus GG can upregulate SERT mRNA and SERT-P levels in intestinal epithelial cells and mice intestinal tissues.

Potential for Appetite Control
In addition to its relevance to psychiatry, serotonin-modulating probiotics may also have value with regard to appetite control. Gastrointestinal hormone release and the regulation of appetite and body weight are thought to be dysbalanced in obesity. Researchers studiedthe expression of the serotonergic system in stomach tissue and serum of obese and non-obese individuals. The results were that serum serotonin was reduced (p < 0.05) in obese compared with non-obese individuals. Given the established role of serotonin in appetite control, improving its expression via supplementation with probiotics may prove to be effective in promoting healthy serotonin levels.

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3 Hojsak I, Abdović S, Szajewska H, Milošević M, Krznarić Ž, Kolaček S. Lactobacillus GG in the Prevention of Nosocomial Gastrointestinal and Respiratory Tract Infections. Pediatrics 2010;125: e1171–e1177.
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5 Cosenza L, Nocerino R, Di Scala C, di Costanzo M, Amoroso A, Leone L, Paparo L, Pezzella C, Aitoro R, Berni Canani R. Bugs for atopy: the Lactobacillus rhamnosus GG strategy for food allergy prevention and treatment in children. Benef Microbes. 2015;6(2):225-32.
6 Ashraf R, Shah NP. Immune system stimulation by probiotic microorganisms. Crit Rev Food Sci Nutr. 2014;54(7):938-56.
7 Wall R, Cryan JF, Ross RP, Fitzgerald GF, Dinan TG, Stanton C. Bacterial neuroactive compounds produced by psychobiotics. Adv Exp Med Biol. 2014;817:221-39.
8 Patterson E, Cryan JF, Fitzgerald GF, Ross RP, Dinan TG, Stanton C. Gut microbiota, the pharmabiotics they produce and host health. Proc Nutr Soc. 2014 Nov;73(4):477-89.
9 Ritze Y, Schollenberger A, Hamze Sinno M, Bühler N, Böhle M, Bárdos G, Sauer H, Mack I, Enck P, Zipfel S, Meile T, Königsrainer A, Kramer M, Bischoff SC.Gastric ghrelin, GOAT, leptin, and leptinR expression as well as peripheral serotonin are dysregulated in humans with obesity. Neurogastroenterol Motil. 2016 Jun;28(6):806-15.

Gene Bruno

Professor Gene Bruno, MS, MHS, the Provost for Huntington College of Health Sciences, is a nutritionist, herbalist, writer and educator. For more than 37 years he has educated and trained natural product retailers and health care professionals, has researched and formulated natural products for dozens of dietary supplement companies, and has written articles on nutrition, herbal medicine, nutraceuticals and integrative health issues for trade, consumer magazines and peer-reviewed publications. He can be reached at gbruno@hchs.edu.