Writing in Nature Scientific Reports the team from Missouri-Columbia College of Veterinary Medicine added Lactobacillus plantarum (L. plantarum) to certain water tanks housing zebrafish while other zebrafish populations received no probiotics.
They then began stressing the animal’s environment by draining small amounts of water from the tank and overcrowding it.
Zebrafish given the supplements showed a minor reduction in the metabolic pathways linked with stress patterns.
In a second study the team began recording the movements of fish in their tanks. The findings indicated that those supplemented with probiotics tended to spend more time toward the top of the tanks. This behaviour modification was deemed an indicator of less stress or anxiousness.
Previous studies of fish behaviour have found that fish that are stressed tend to spend more time at the bottom of their tanks.
“Common environmental stress patterns, such as isolation stress and temperature change, made the tests relevant to humans as well," explained Elizabeth Bryda, professor of veterinary pathobiology in the MC College of Veterinary Medicine.
“Essentially, bacteria in the gut altered the gene expression associated with stress- and anxiety-related pathways in the fish allowing for increased signalling of particular neurotransmitters," added Daniel Davis, assistant director of the MU Animal Modeling Core.
Probiotics’ role in oxidative stress
The results of this study point to the effects changes to the gut microbiota can have on the chemical processes that involve metabolites.
L. plantarum in particular, appears to enhance the metabolic pathways involved in vitamin biosynthesis.
Referring to previous studies, folic acid biosynthesis was predicted to be enriched with L. plantarum supplementation, along with the production of antioxidant vitamins such as folic acid (vitamin B9), riboflavin (vitamin B2), and vitamin B12.
Nutrients such as vitamins, amino acids or dietary fibres that are ingested by the host are assimilated and converted into other metabolites by microbes within the gastrointestinal tract.
These products include short-chain fatty acids (SCFAs), biogenic amines, or other amino acid-derived compounds such as serotonin or GABA.
Many of these neuroactive compounds that can be produced by the gut microbiota have previously shown an ability to alter neurological function and behaviour.
“Probiotics are often used to correct dysbiotic states of the gut microbiota,” the study commented. “However, only minor stress-induced changes occurred in zebrafish with probiotic supplementation.”
“Microbiota structural alterations were accompanied by predicted functional metabolic changes. In particular it was shown that stress-induced downregulation of riboflavin biosynthesis occurred in stressed fish not supplemented with L. plantarum.”
Source: Nature Scientific Reports
Published online ahead of print, doi:10.1038/srep33726
“Lactobacillus plantarum attenuates anxiety-related behavior and protects against stress-induced dysbiosis in adult zebrafish.”
Authors: Aaron Ericsson & Elizabeth Bryda et al.
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