THE ROLE OF GUT BACTERIAL AND IMMUNE COMMUNITIES IN DEPRESSION

Depression is a heterogenous neuropsychiatric disease, affecting 280 million people as stated by the World Health Organization. Current treatments for depression are ineffective for many patients and the search for alternative treatments is an essential focus for research. Utilization and/or modification of the microbes that populate the intestine is emerging as a new potential avenue to treat psychiatric disorders. Moreover, the crosstalk between intestinal bacteria and different immune components seems to have a key role on mental health as well. We performed a metagenomic analysis on the microbiota present in three regions of the gut of stressed and non-stressed mice: proximal (1) and distal (2) regions of the small intestine and colon (3). We found that community composition was different in all three of them, and between stressed and non-stressed mice. Furthermore, when the microbial populations from those regions were introduced in microbiota-depleted mice, we found that animals who were given the bacteria corresponding to regions 2 and 3 were able to recover their original microbiota. Interestingly, those given bacteria from region 1 were unable to do that, and showed more depressive symptoms compared to those treated with microbiota from regions 2 and 3. Moreover, levels of inflammatory markers showed that treatment with regions 2 and 3 also affected the immune response. These results might serve to identify new therapeutic immune targets and bacterial combinations to treat depression and reduce the clinical and societal burden of this psychiatric condition.