Oxidative protein damage in plasma of type 2 diabetic patients

In this study, we evaluated protein oxidation in 84 patients with Type 2 di abetes with no complications and in 61 healthy volunteers who formed the co ntrol group, whose ages matched those of the patients. We determined plasma carbonyl and plasma thiol levels as markers of oxidative protein damage an d erythrocyte glutathione, plasma ceruloplasmin and transferrin as markers of free radical scavengers. The concentrations (mean +/- SD) of both of pla sma carbonyl (1.24 +/- 0.46 vs. 0.72 +/- 0.17 nmole/mg protein; p < 0.0001) and lipid hydroperoxides (1.8 +/- 0.63 vs. 1.3 +/- 0.21 mu mole/l; p < 0.0 001) were increased, and the concentration of plasma transferrin (3.85 +/- 0.65 vs, 4.59 +/- 0.79 g/l; p < 0.05) was decreased, respectively, in Type 2 diabetic patients compared with those of the controls. There were no sign ificant differences in the concentrations of plasma thiol (0.0064 +/- 0.001 vs. 0.0068 +/- 0.001 mu mole/mg protein), erythrocyte glutathione (2.54 +/ - 0.57 vs. 2.65 +/- 0.56 mg/g Hb), plasma ceruloplasmin (548 +/- 107.30 vs. 609 +/- 93.34 mg/l) between the patients and the controls. These changes o bserved in diabetic patients contribute to the imbalance in the redox statu s of the plasma. We attribute this imbalance to oxidative protein damage in Type 2 diabetic patients clinically free of complications.