Aaron Shoskes, D.O.’18, explores link between chronic stress and gut bacteria

Aaron Shoskes, D.O.'18, presents his research at the American Urological Association Annual Meeting.
Aaron Shoskes presented his research on the link between stress and the gut microbiome for the AUA.

Aaron Shoskes, D.O.’18, gave a platform presentation titled “A possible link between chronic stress and the microbiome: a metagenomic analysis” at the Society for Infection and Inflammation in Urology as part of the American Urological Association Annual Meeting in New Orleans May 15-19.

Conducted in the lab of LiLian Yuan, Ph.D., associate professor of Physiology and Pharmacology, in collaboration with researchers at Iowa State University, Shoskes’ work concluded that chronic, unpredictable stress alters the environment in your gut. If this association proves causal, it opens up the possibility of using medications, prebiotics and probiotics to manipulate the gut microbiome and influence mental well-being.

What motivated this research?

​This project was created out of Dr. Yuan’s larger project looking at the effects of chronic stress and possible rapid-acting antidepressants in mice. We collaborated with Gregory Phillips, M.A., Ph.D., an Iowa State University microbiologist with an interest in the brain-gut-microbiome and its implications for behavior. As Dr. Yuan’s project was going to be driving mice into a stressed state, we decided to look at their microbiota before and after the period of chronic stress to see what effects it may have.

What were you trying to understand?

Previous research has illustrated the importance of microbes in the gut for a proper stress response in both animals and humans. Microbes are able to send signals from the gut to both the gastrointestinal tract and brain, resulting in changes in behavior. There is evidence to suggest that single, acute exposures to stress can transiently disrupt the homeostatic population of the gut microbiome. We were interested in seeing whether a chronic, longer lasting stressor would have any affect on the gut microbiome and if it would resemble the changes scene in acute stress.

What problems does stress create in the gut microbiome?

Stress changes the phylogenetic abundance of different taxa of the gut microbiome. Starting at the highest hierarchy of bacteria, the phylum, stress caused an increase in Bacteroidetes and a decrease in Firmicutes. Within the phylum Firmicutes, we observed a decrease in the class Bacilli, which is likely responsible for the phylum level decrease.

The most interesting finding was a decrease in the genus Lactobacillus. This genus has several species that are currently being researched for their potential as probiotics due to their anti-inflammatory, anti-oxidant and antimicrobial properties.

How does your research fit into the other research in this area?

Based on other research in the area, our hypothesis suggests that chronic stress leads to changes in the gastrointestinal microenvironment, with increased gut motility, permeability and pH. That results in a change in the microbial diversity, which leads to changes in microbe-host interactions that feed back to the central and enteric nervous systems.

How do you plan to expand on this research?

We are conducting a similar study evaluating the effects of chronic pain — more of a physical stressor — on the gut microbiome to see if there would be any effects and if they are similar. We are also using metagenomic analysis to try to get a more functional answer to how the bacteria of the gut are being influenced and how they are influencing the brain gut axis.

Using a variety of different analytical techniques, we are able to see which genes are expressed at higher and lower levels before and after the stress. By analyzing this data, we hope to better understand which specific enzymes and signaling molecules are being affected by stress and how it all affects the interaction of bacterial species with host (us!) in order to cause behavioral changes.

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