FMO5 and brain ischemia: To address the underlying molecular mechanism, we examined the effect of linagliptin on cerebral claudin-5 and gp91phox levels in cerebral ischemia-subjected diabetic mice, since claudin-5 [36, 37] is a main cerebral endothelial tight junction protein which plays a major role in blood-brain barrier function and gp91phox is a major subunit of NADPH oxidase, the main oxidative stress-generating enzyme.