Effects of a high concentration of hydrogen on neurological function after traumatic brain injury in diabetic rats

•Diabetic rats have a greater loss of neurological function.•A high concentration of hydrogen plays a stronger biological role.•Hydrogen improve neurological function via antioxidant and anti-apoptotic pathways. Reactive oxygen species, inflammation, and apoptosis are major contributors to secondary injuries that follow traumatic brain injury (TBI) in diabetic patients. Hydrogen (H2) can selectively neutralize reactive oxygen species and downregulate inflammatory and apoptotic factors. Therefore, we investigated the effects of inhaled high and low concentrations of hydrogen on neurological function after TBI in diabetic rats and the potential mechanism. We found that the inhalation of high concentrations of H2 significantly improved outcomes following TBI in diabetic rats. The inhalation of 42% H2 for one hour per day for 48 h significantly reduced brain edema, decreased the extravasation of sodium fluorescein, and reduced oxidative stress markers (p