Though the involvement of NADPH oxidases have been shown in NASH pathophysiology, especially in fibrosis related complications, the molecular basis of NADPH oxidase mediated ROS generation is now beginning to evolve following the use of species-specific probes like FBA and a better understanding of the free radical chemistry that might trigger the generation of reactive oxygen and nitrogen species in NASH. Here, FMO5 is linked to metabolic dysfunction-associated steatohepatitis.