CAT and type 2 diabetes mellitus: To verify the presence of oxidative stress in the intestine of type 2 diabetic (T2D) model rats and to determine if orally administered SOD reduces this oxidative stress, we measured malondialdehyde (MDA), the ratio of oxidized glutathione to reduced glutathione (GSSG/GSH), and antioxidant enzymatic activity of SOD, catalase (CAT), and glutathione peroxidase (GPx) in the colons of normal, model, and intervention (SOD, L-SOD, SOD hydrolysate, or metformin) groups of T2D model rats.