How Gut Bacteria and Acute Stress Are Linked

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Scientific Frontline: "At a Glance" Summary: How Gut Bacteria and Acute Stress Are Linked

• Main Discovery: In healthy adults, the diversity of gut bacteria and their capacity to produce specific metabolites are directly associated with acute stress reactivity, meaning higher microbial diversity correlates with stronger hormonal and perceived stress responses.
• Methodology: Researchers administered a standardized stress test or a comparative stress-free task to healthy participants. They measured stress hormones, specifically cortisol, in saliva and assessed subjective stress levels, while simultaneously analyzing stool samples to determine gut microbiome composition and short-chain fatty acid production capacity.
• Key Data: Higher microbial diversity and elevated butyrate production capacity were linked to increased stress reactivity, whereas a higher capacity for propionate production correlated with lower stress reactivity.
• Significance: A stronger acute stress response supported by high microbial diversity is not inherently detrimental; rather, it indicates a stable, functionally flexible microbial ecosystem that facilitates appropriate biological adaptation to challenges and threats.
• Future Application: Targeted modulation of the gut microbiome's composition and its short-chain fatty acid metabolites through diet and specific lifestyle interventions may provide novel therapeutic strategies for managing acute stress responses and treating stress-related conditions.
• Branch of Science: Microbiology, Psychology, Neurobiology
• Additional Detail: The findings underscore that the relationship between microbial metabolites and stress regulation is multifaceted and cannot be generalized, as different short-chain fatty acids exert opposing influences on the body's physiological stress reactivity.

The gut microbiome influences numerous physiological processes. Researchers at the University of Vienna have now demonstrated for the first time that, in healthy adults, the diversity of gut bacteria and their capacity to produce certain metabolites are associated with the acute stress response - particularly stress reactivity. Higher microbial diversity was associated with stronger hormonal and subjectively perceived stress reactivity. The results suggest that the gut microbiome may play a role in regulating the acute stress response. The study was published in Neurobiology of Stress. 

The gut microbiome comprises all microorganisms living in the gut, which, among other things, perform important functions in metabolism and the immune system and are also connected to the brain through various pathways. Research suggests that they can modulate stress responses. However, it has remained unclear until now whether differences in the human gut microbiome are associated with acute stress reactivity. 

The latest findings by researchers Thomas Karner, Isabella Wagner, David Berry, and Paul Forbes from the Faculty of Psychology and the Center for Microbiology and Environmental Systems Sciences (CeMESS) at the University of Vienna provide new evidence that the gut microbiome, and thus potentially also diet and lifestyle, is associated with how our bodies respond to stress. In the long term, targeted modulation of gut microbial composition and its metabolites, particularly short-chain fatty acids, could represent a possible avenue for new strategies to related to acute stress responses, stress-related conditions and improve well-being. 

Stress tests, saliva samples, and more provide insight into the association 

In the study, healthy participants either underwent a standardized stress test or performed a comparable, stress-free task. Stress hormones (cortisol) in saliva and subjective stress levels were measured. In addition, the gut microbiome was analyzed using stool samples. Both the composition of the microbiome and the estimated production capacity of short-chain fatty acids were examined. The results show that higher microbial diversity was associated with higher hormonal and subjective stress reactivity. Greater microbial diversity is often associated with a more stable and resilient microbial ecosystem and with greater functional flexibility, which may contribute to the appropriate regulation of stress responses. 

"A stronger acute stress response is not necessarily detrimental. Appropriate activation of the stress system enables flexible adaptation to challenge and threats. A greater diversity of gut bacteria, as well as certain metabolic products, could play a supportive role in this process," explains study leader and psychologist Thomas Karner. 

Complex relationship between microbial metabolites and stress reactivity 

Furthermore, stress reactivity was associated with gut bacteria’s capacity to produce different metabolic products: a higher estimated capacity for butyrate production was associated with higher stress reactivity, whereas higher propionate production was associated with lower reactivity. Butyrate and propionate are short-chain fatty acids produced by gut bacteria that are involved in metabolic and immune processes and can also affect the brain. This suggests that the relationship between microbial metabolites and the acute stress response is more complex and cannot be reduced to a single direction. 

The results provide new insights into possible biological mechanisms of stress regulation and underscore the role of the gut microbiome and its metabolites as potential factors influencing the stress system and the acute stress response in humans. 

Reference material: What Is: Human Microbiome

Published in journal: Neurobiology of Stress

Title: Gut microbial diversity and inferred capacity to produce short-chain fatty acids are associated with acute stress reactivity in healthy adults

Authors: Thomas Karner, Paul A.G. Forbes, David Berry, and Isabella C. Wagner

Source/Credit: Universität Wien

Reference Number: mcb041626_01

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