The gut microbiota has been implicated in important roles in the brain in alteration of microglial activity and neurobehavioral functions in health and disease. Short-chain fatty acids (SCFAs) are gut-derived metabolites that are speculated to have a key role in microbiota–gut–brain axis. However, the mechanisms underlying how SCFAs directly or indirectly impact innate and adaptive immunity and brain homeostasis is currently unknown. In our previous reports, we demonstrated that antibiotic-induced gut microbial dysbiosis after traumatic brain injury (TBI) showed increased microglia activation, decreased T cell infiltration into the brain, a reduction in neurogenesis and, decreased of SCFA levels in plasma and stool. After SCFA supplementation for 7 days after TBI, we found an increase of neurogenesis, less activated microglia, and an increase of T regulatory and T helper 1 cells infiltration in the brain. In addition, we also observed how SCFA boosted T cells trafficking from the intestines to the injured brain. Together these data show that SCFAs may alter T cells differentiation and trafficking impacting gut-brain interaction after brain trauma.
