Gut microbiome balance and behavior


This week we focused on two examples of research highlighting the effects of environmental differences on gut microbiota and its downstream effects on brain function and behavior. Reber and colleagues (2016) used the chronic subordinate stress to explore the effect of stress of gut microbiome and the protective role m.vaccae immunization in those alteration. Results demonstrated that m.vaccae had a protective effect to CSC induced changes in coping response, increased anxiety-like behavior, reduced serotonin expression and reduced microglial density. M.vaccae also prevented colitis resulting from stress. The protective effects of m.vaccae in anxiety-like behavior and colitis were dependent on Treg. The CSC model is especially relevant for disorders like PTSD, which are stress induced, and this research demonstrates that m.vaccae immunization protects again some stress-induced changes in both behavior and neural dynamics. The parallel is not as clear when it comes to the compromised immunoregulation observed in high income regions; a germ-free line would be a more adequate to explore if m.vaccae also has a protective role when gut microbiome is compromised due to reduced exposure associated with high income areas.

The article by Buffington et. al (2016) used a maternal high-fat model to induce gut microbiome dysregulation. MHFD induced alterations in 8 different species of bacteria in offspring. These gut microbiome changes induced social deficits, which were corrected with cohousing with control mice. This rescue of symptoms was found to have a critical period, indicating that the social deficit results from neurodevelopmental alterations resulting from gut microbiome imbalance. L. reuteri was also used to rescue social-deficits and that the effect was likely mediated by increased oxytocin signaling to the VTA. Interestingly, other symptoms associated MHFD were not rescued (e.g. marble burying, anxiety, repetitive behavior). This suggests that those deficits could be associated with earlier stages of development or be mediated by other MHFD induced changes on systems other than the gut microbiome. Together, these articles highlight the reaching effects of gut microbiome disruption. I look forward to seeing longitudinal studies in humans of probiotic use based on articles like these.

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