Posted with permission from STEAM Register

Lola Gayle, STEAM Register

COLUMBIA, MO: Probiotics are beneficial microorganisms that are said to provide numerous health benefits by interacting with our gut microbes after being ingested.

While most studies have focused on the physical health benefits of these live bacteria, researchers at the University of Missouri (MU) are focusing on the mental health benefits of probiotics. Specifically, they found that a common probiotic found in supplements and yogurt may help to decrease stress-related behavior and anxiety.

But before you immediately run out and stock up on probiotics, let me make a disclaimer: this specific research is based on a zebrafish model, which is quite common in studies of vertebrate development and gene function. In this case, it was used to gain a better understanding of how probiotics may affect the central nervous system in humans.

"Zebrafish are an emerging model species for neurobehavioral studies and their use is well-established in drug-screening," Aaron Ericsson, director of the MU Metagenomics Center and a research assistant professor in the Department of Veterinary Pathobiology, said in a statement. "Our study has shown that simple probiotics that we normally use to keep our digestive tract in sync, could be beneficial to reducing our stress levels as well."

The researchers conducted several tests where they gave doses of Lactobacillus plantarum to zebrafish in the lab. In the first study, the bacteria was added to zebrafish tanks, while fish in control tanks were given no probiotics. The fish we then subjected to environmental stressors, such as draining small amounts of water from the tank and overcrowding.

NOTE: Lactobacillus plantarum is a member of the genus Lactobacillus, commonly found in many fermented food products and anaerobic plant matter. It is also found in saliva (from which it was first isolated). It has the ability to liquefy gelatin, has one of the largest genomes known among the lactic acid bacteria, and is a very flexible and versatile species.

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"Each day we introduced a different stressor - tests that are validated by other researchers and cause higher anxiety among zebrafish," said Elizabeth Bryda, professor of veterinary pathobiology in the MU College of Veterinary Medicine. "These are common environmental stress patterns, such as isolation stress and temperature change, so it made the tests relevant to humans as well."

Afterwards, the researchers analyzed the gene pathways of both groups of fish, finding that fish in the supplement-provided tanks showed a reduction in the metabolic pathways associated with stress.

"By measuring the genes associated with stress and anxiety, our tests were able to predict how this common probiotic is able to benefit behavioral responses in these fish," said Daniel Davis, assistant director of the MU Animal Modeling Core. "Essentially, bacteria in the gut altered the gene expression associated with stress- and anxiety-related pathways in the fish allowing for increased signaling of particular neurotransmitters."

In a second study, the researchers measured the movements of fish in their tanks using sophisticated computer measuring and imaging tools. Previous research has found that stressed fish prefer to spend more time at the bottom of their tanks. During this study, the stressed fish on probiotics spent more time near the top of their tanks, indicating they were less stressed and anxious than their control group counterparts.

Results of this work are published in Scientific Reports. Funding was provided by the Missouri-Columbia College of Veterinary Medicine.

NOTE: √Člie Metchnikoff first suggested the possibility of colonizing the gut with beneficial flora in the early 20th century. He suggested in 1907 that "the dependence of the intestinal microbes on the food makes it possible to adopt measures to modify the flora in our bodies and to replace the harmful microbes by useful microbes."

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