The papers for this week focused on the relationship between the gut and the brain, known as the gut-brain axis. This is a topic that interests me because I am currently taking Microbiology and we often discuss effects of a healthy and diverse human microbiome. It is commonly said that what you eat affects how you think and feel, but I was interested to explore some of the evidence behind this anecdote and the gut-brain connection. These papers as well as others demonstrate that the microbiome has influence over brain function and behavior, but it is clear that there is still a lot to be learned about this relationship.
The first paper, Reber et al., studied how injecting mice with a heat-killed preparation
Of M. vaccae, a non-pathogenic bacterium that lives in soil, protects against various negative stress-related outcomes. The researchers concluded that the immunization reduced the stress response, inflammation, and subordinate responses to a dominant aggressor in mice. I thought the data in this study was convincing and their tests were thorough. However, I would have liked some more factors included in the social-defeat paradigm they used. Testing females, investigating the levels of other hormones besides testosterone, comparing the effects of chronic stress versus cute stress, and genetically predisposing the mice to anxiety are some of the ways to increase the possible clinical applications of the study. That being said, I thought this research has the potential to be very clinically impactful for people suffering from IBS, Crohn’s disease, and other GI inflammatory disorders. I thought the “Old Friend’s” hypothesis was interesting and makes me wonder what other bacteria or strains of M. vaccae has similar effects on improving stress, allergies, or the human system in general. Research on the gut-brain axis is something that most people probably find interesting and relatable as almost everyone has probably experienced a stress-induced digestive issue. It’s exciting to think about where this research will take us and who will have axis to possible “stress reducing” vaccines.
The second paper, Buffington et al, explored the relationship between maternal obesity during pregnancy and increased risk of ASD in offspring. They built their research off of previous studies showing that maternal obesity heightens the risk of neuropsychiatric/ social deficits in offspring, and that treatment with L. reuteri, a probiotic bacterium found in the GI tract of many animals, selectively restores the social behavior. One thing that stood out to me in the article was how it emphasizes a comparison to ASD, but I was not convinced that the social deficits seen in the MHFD mice were more comparable to ASD than social anxiety, for example. What intrigued me most about this paper was the link between L. reuteri and oxytocin. Since MHFD offspring have social deficits, and oxytocin is known to improve social behaviors, I was curious as to why the paper didn’t mention or test the natural ways one can increase oxytocin in an offspring (licking, physical touch, specific herbs, vitamins). On that note, I would be interested in seeing if estrogen levels in MHFD or offspring have any affect on social deficits in the offspring, since estrogen increases the synthesis of oxytocin. Additionally, this is not directly related to the research, but since L. reuteri is found in breast milk, I would be interest in studying if mothers with higher amounts of L. reuteri who breast feed are less likely to have children with social deficits, or if creating formula with L. reuteri supplements would be beneficial for the child.
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