SOD1 and type 2 diabetes mellitus: In agreement with previous experiments, our study found that the T2DM model induced the decrease of the SOD, GSH-Px, and CAT levels in the liver, and increased the MDA level, whereas complementing with OP (400 mg/kg) could increase the levels of SOD, GSH-Px, and CAT while lowering the level of MDA in the T2DM mice (Table 2).