FMO5 and heart disorder: 2006). ROS can also be actively generated through various oxidases, such as NADPH oxidase, in cardiovascular tissues (Cave et al. 2006). Low/moderate levels of ROS produced by NADPH oxidases have been proven to be essential for normal cardiac growth and function (Prosser et al. 2011). However, excess ROS or a decrease of antioxidant systems leads to oxidative damage (Tsutsui et al. 2011), causing a wide range of damage to macromolecules, and eventually apoptotic or necrotic cell death, which are often associated with human heart diseases (Sawyer et al. 2002).