Expression of mitochondrial superoxide dismutase in polymorphonuclear leukocytes from patients with type 1 diabetes with and without microvascular complications

INTRODUCTION One of the causes of impaired antioxidant response in patients with type 1 diabetes might be decreased expression of mitochondrial manganese superoxide dismutase (MnSOD).
OBJECTIVES The aim of this study was to evaluate the expression of MnSOD on transcript and protein levels in polymorphonuclear leukocytes (PMNLs) from patients with type 1 diabetes and analyze its association with microvascular complications.
PATIENTS AND METHODS The MnSOD expression was assessed in PMNLs from 46 patients with type 1 diabetes and 12 age- and sex -matched healthy subjects. The study group was divided into 2 subgroups: with and without microvascular complications. The MnSOD expression on the transcript level was evaluated by real -time quantitative polymerase chain reaction, while that on the protein level by Western blot analysis.
RESULTS A significant increase in the MnSOD transcript level was observed in all patients with diabetes with and without microvascular complications (P = 0.01, P = 0.02, respectively). The MnSOD protein level was higher in patients without microvascular complications compared with those with complications and the control group (P = 0.05, P = 0.03, respectively). The MnSOD expression was positively correlated with fasting plasma glucose and total cholesterol levels both at the transcript level (r = 0.4, P <0.05 for both correlations) and at the protein level (r = 0.3 and r = 0.4, respectively, P <0.05).
CONCLUSIONS Although an increased MnSOD transcript level in patients with type 1 diabetes suggests enhanced antioxidant mobilization in all diabetic patients, decreased levels of the MnSOD protein in PMNLs from patients with microvascular complications compared with those without complications indicates that patients with microvascular complications may have impaired antioxidant response.