Unlike catalase, both SOD and GPx decreased by the induction of diabetes (P= 0.001 for both enzymes), as observed in group D. However, reduction in the activity of both enzymes was completely prevented by the treatment of the rats using either low or high doses of curcumin and metformin in all treated animals (D + Cur50, D + Cur150, D + Met300, and D + Met500), as shown in Table 4. Here, CAT is linked to diabetes mellitus.