CAT and diabetes mellitus: To study the hypoglycemic effect, the activity of antioxidant enzymes (catalase, superoxide dismutase, and glutathione peroxidase) and markers of oxidative stress (malondialdehyde and 8-hydroxy-2-desoxyguanosine) were evaluated in the model of diabetes mellitus induced by nicotinamide and streptozotocin in rats.