GSR and metabolic syndrome: Another important factor that contributes to the development of insulin resistance in MetS is the increased production of reactive oxygen species (ROS) due to an increased activity of prooxidant enzymes such as NADPH oxidases (NOX) and/or decreased activity of antioxidant enzymes, such as superoxide dismutase (SOD), glutathione reductase (GSR), or glutathione peroxidase (GPX) [10].