Background: Increased rate of oxidative stress have important role in diabetic nephropathy. Oxidative stress induces the synthesis of antioxidant enzymes. One of them, Extracellular- SOD (EC–SOD) is a major anti-oxidative enzyme and the only one that neutralizes superoxide ion, a precursor of reactive oxygen species (ROS). The aim of this study was to evaluate the correlation between diabetes- associated oxidative stress and antioxidative defense in macroalbuminuric type 2 diabetic patients.

Methods: One hundred and thirty three patients (74 women, 59 men) with type 2 diabetes were studied during 1385-86. According to level of urinary protein, two groups of patients; normoalbuminuric (urinary protein excertion below 30mg/24h) and macroalbuminuric (urinary protein excretion more than 300mg/24) were recognized. In each group serum level of oxidized- LDL and EC-SOD were measured.

Results: The mean age of patients and the mean duration of diabetes was 59.09±8.26 years and 137.92±65.91 months, respectively. The plasma oxidized-LDL level and extracellular- superoxide dimutase level were significantly higher in macroalbuminuric than normoalbuminuric group (88.57±33.36 versus 78.24±27.59u/l, p=0.039 for oxidized-LDL and 87.60±21.18 versus 76.25±16.25mu/l, p<0.001 for EC-SOD). Oxidized- LDL was significantly correlated to EC-SOD in macroalbuminuric patients (r=0.425, p<0.0001). Oxidized-LDL and EC-SOD does not correlate to Fasting Plasma Glucose and HbA1c in each two groups.
Conclusion: The significantly elevated plasma oxidized-LDL in patients with macroalbuminuria suggests that, oxidized-LDL may play an important role in the progression of diabetic nephropathy. Besides severity of oxidative stress in macroalbuminuic patients, increase level of EC-SOD enzyme could be a compensatory mechanism to prevent tissue damage.