Stress as a possible influence on gut motility- related changes in the composition of gut microbiota

Depression is a complex mental disorder affecting up to 7% of the population. Though scientists have a better understanding of the etiology of the disorder than in the past, there is much to be discovered about its specific causes and aggravating factors. Recently, it was discovered that the composition of the gut microbiome, the collection of microorganisms in the digestive tract, can play a role in the development of depression. Depressed mice were found to have decreased levels of the bacteria Lactobacillus and consequently increased levels of kynurenine, a metabolite associated with depression.1 We are exploring the mechanism by which stress decreases levels of Lactobacillus, hypothesizing it is related to gut motility, specifically the composition of mucins. Mucins are glycoproteins that lubricate and protect organs, forming the foundation for the mucus in the gut where much of the microbiota live. To test this hypothesis, we are using a mouse model of anxiety and depression by supplementing mice with corticosterone via drinking water. Using various anxiety and depression behavioral tests, such as nestlet- shredding and sucrose preference, we will access their depression and anxiety phenotypes. Additionally, we will quantify mucin levels by quantitative polymerase chain reaction (qPCR). We expect to see changes in mucin levels in response to increased levels of depression. If this is observed, it would provide a more thorough view of how stress is associated with the composition of the gut, which could have large implications on how we view and treat depression and anxiety.