Understanding the effect of Mild Traumatic Brain Injury on gut microbial diversity in rats

Studies on the role of the gut-brain-microbiome axis in mental health and disease have gained reasonable attention in the past decade. The perturbations in the microbial communities are linked to a multitude of disorders including co-morbid intestinal ailments and neuropsychological disorders. Traumatic stress is known to culminate in co-morbid conditions such as intestinal bowel disease (IBD) and anxiety-like symptoms. The current study analyses the gut microbiome of trauma-exposed animals and its possible link to intestinal health and psychiatric manifestations. The rats were subjected to repeated mild traumatic brain injury (MTBI) by using the weight-drop method, and their gut microbial composition was studied after 6 hours, 48 hours, and 30 days. Significant reduction in the bacterial diversity (alpha) was observed in the MTBI-exposed animals at all time points, which could be linked to the altered gut motility and anxiety-like behaviours. The inter- sample diversity (beta) was evaluated using principal coordinate analysis based on weighted UniFrac distances, which indicated significant differences in gut microbial diversity and abundances in trauma groups as compared to sham controls. Moreover the population of Proteobacteria increased significantly (p value < 0.05) after traumatic stress, whereas Firmicutes were decreased at all the time points (p value < 0.05). At genus level, Helicobacter and Campylobacter dominated in trauma-exposed rats indicating profound dysbiosis from the healthy state of gut microbiome. Future studies are warranted to discern the link between specific microbial entities with the phenotypic outcome as a result of trauma.