C3 and diabetes mellitus: Western blotting of the serum samples identified a slight but statistically insignificant increase in total C3 in PDR and NPDR compared to the no-DM samples (PDR vs. no-DM: 1.69 ± 0.58, p = 0.7, NPDR vs. no-DM: 1.38 ± 0.24, p = 0.7 and PDR vs. NPDR: 1.19 ± 0.23, p = 0.9).