ACE2 and diabetes mellitus: In serum samples, there was a significant increase of ACE2 activity in DB mice at early and late stages of diabetes as compared to CONT (p = 0.0003 and p = 0.0003, respectively) and insulin administration significantly decreased ACE2 activity in DB mice at early and late stages (p = 0.001 and p = 0.001, respectively) (Figure 4a).