SOD1 and diabetes mellitus: Our previous study found that the major endogenous antioxidant enzyme superoxide dismutase (SOD), which plays an important role in balancing ROS generation and the overall tissue antioxidant capacity, was increased in both the plasma and heart tissue of rats at a relatively early stage (4 weeks) of diabetes, but tissue and plasma levels of free 15-F2t-isoprostane, a specific marker of lipid peroxidation, were also increased [6].