On the other hand, leptin plays a crucial role in obesity-induced OS by activating nicotinamide adenine dinucleotide phosphate (NADPH) oxidase and increasing the production of reactive species such as hydrogen peroxide and hydroxyl radicals, thereby amplifying OS in the body by stimulating the production of ROS and reducing the activity of antioxidants [116,128,129]. The gene discussed is LEP; the disease is obesity due to melanocortin 4 receptor deficiency.