10 Feb DUKE-NUS Study Supports Link Between Gut Microbiome and Anxiety Behaviors
MedicalResearch.com Interview with:
Shawn Je
Associate Professor Shawn Je
Neuroscience and Behavioural Disorders Programme,
Duke-NUS Medical School
MedicalResearch.com: What is the background for this study? What questions were you trying to address?
Response: The project started in 2013 when I met Professor Sven Petterson, then a visiting professor from the Karolinska Institute, during his time at the National Cancer Centre Singapore (NCCS) in Singapore.
At the time, our lab was studying autism, and we discovered that many children with autism also had gastrointestinal problems. This sparked my interest in the relationship between gut microbiota and brain disorders.
Professor Petterson had already established a germ-free facility at NCCS to study the link between cancer and gut microbiota. I asked him if he could create germ-free C57BL/6 mice, a strain often used to study learning, memory and brain disorders. After developing the mice, we subjected them to behavioural testing at the Duke-NUS Behavioural Phenotyping Facility to assess their emotional responses (fear, anxiety, depression), cognitive abilities (learning and memory), and social interactions.
We were surprised to find that the germ-free C57BL/6 mice exhibited increased anxiety, although no significant changes in social behaviours typical of autism were observed.
Anxiety was assessed using tests in which mice were placed in an elevated arena with open and closed sections, and the time spent in each area was measured. The increased anxiety in these germ-free mice had not been reported before, so we repeated the tests several times to confirm the findings.
Interestingly, other researchers had observed hyperactivity in germ-free mice of different strains, but our C57BL/6 mice showed unusual anxious behaviour, even though this strain typically has lower anxiety.
This led us to investigate the underlying mechanisms behind the increased anxiety in these mice, with the goal of discovering why this particular strain exhibited such pronounced anxiety.
MedicalResearch.com: What was your main challenge when conducting this study?
Response: The first major challenge we faced was maintaining consistent access to aseptic facilities, which were relocated several times within Singapore. This made it difficult to ensure a steady supply of germ-free mice for our research, contributing to the lengthy timeline—it took over a decade to publish our findings.
Additionally, conducting behavioural tests in a sterile, germ-free environment (the “bubble”) added complexity to the experiments, as we had to carefully manage the conditions to avoid contamination.
The second challenge was identifying the specific neural changes in different parts of the brain that contribute to anxiety-related behaviours. While we know that multiple brain regions are involved in anxiety, we used a technique called whole-brain activity mapping to precisely pinpoint which neurons are responsible for these behaviours. This allowed us to focus on the exact brain regions and cells affected by the absence of microbiota.
MedicalResearch.com: What are your main findings?
Response: Our main finding was identifying the types of neurons and mechanisms that underlie anxiety behaviour in germ-free mice. The absence of microbiota in these mice has broad effects, but it specifically alters ion channels in a brain region called the amygdala, which is key to regulating emotions such as fear and anxiety.
We also found that we could reverse anxiety-like behaviour in germ-free mice by reintroducing microbes or microbial-derived metabolites. This suggests a promising potential for therapeutic approaches that involve restoring the gut microbiota to treat anxiety-related disorders.
MedicalResearch.com: What are the implications of these findings? How can this potentially lead to new therapies to improve mental health?
Response: First, it opens the therapeutic potential of targeting the gut-brain axis to treat anxiety-related disorders by restoring the microbial composition through dietary supplementation with indoles or by introducing indole-producing gut microbes as probiotics.
Second, studies such as this illustrate the close hereditary relationship that exists between our indigenous microbes and the higher complexity of life.
MedicalResearch.com: What should readers take away from your report?
Response: This study highlights the important role the gut microbiota plays in influencing brain function, particularly in anxiety-related behaviours.
The findings suggest that an imbalance or absence of gut microbes can lead to changes in the brain’s neural circuits, specifically in areas like the amygdala, which is crucial for emotional regulation.
The study strengthens the concept of the “gut-brain axis,” showing how the state of our gut microbiota can impact emotional and cognitive health. It emphasises that mental health might not only be influenced by the brain’s functioning but also by the microbial environment within our digestive system.
MedicalResearch.com: What’s the next step for your research?
Response: We still don’t fully understand why a specific ion channel, the small conductance potassium channel (SK2), is affected in the absence of microbiota.
We suspect that the lack of microbiota may lead to epigenetic changes that silence the SK2 gene during neurodevelopment, but we are still investigating how this affects specific cells in specific brain regions.
In addition, while we have seen that indole treatment can help reverse anxiety-like behaviours even in the absence of microbiota, we don’t yet know exactly how this works.
Our next steps include exploring other microbiota-derived metabolites and determining which specific types of microbiota might influence different brain-related behaviours.
MedicalResearch.com: What recommendations do you have for future research as a results of this study?
Response: While our research is promising, there are still mixed reports on how microbiota influence behaviour through the gut-brain axis.
To improve consistency and reliability, it’s important to standardise the species used in studies, define clear protocols for standard pathogen-free conditions, and ensure reproducible methods for conventionalisation.
In addition, while animal models provide valuable insights, it is critical to translate these findings to other animals, companion animals, and ultimately humans.
Citation:
Yu W, Xiao Y, Jayaraman A, Yen YC, Lee HU, Pettersson S, Je HS. Microbial metabolites tune amygdala neuronal hyperexcitability and anxiety-linked behaviors. EMBO Mol Med. 2025 Feb 5. doi: 10.1038/s44321-024-00179-y. Epub ahead of print. PMID: 39910348.
https://www.embopress.org/doi/full/10.1038/s44321-024-00179-y
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Last Updated on February 10, 2025 by Marie Benz MD FAAD