Objective: Diabetes-associated oxidative stress is a consequence of both increased production of free radicals and reduced capacity of antioxidative defense. Prolonged hyperglycemia is the major factor in the pathogenesis of atherosclerosis in diabetes which can lead to cardiovascular complications. The aim of this study was to test the parameters of antioxidative defense in type 2 diabetic patients.
Methods: A total of 117 type 2 diabetics with and without cardiovascular complications were examined in order to find out the influence of hyperglycemia, type and duration of complications and duration of diabetes on the extent of disorder of antioxidative parameter values: superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), glutathione reductase (GR) and total antioxidant status (TAS).
Results: Compared to healthy control subjects, type 2 diabetic patients with cardiovascular complications (CVC) had significantly lower SOD (P<0.0001), GSH-Px (P<0.0001), GR ( P = 0.0002) and TAS values (P<0.0001). In type 2 diabetic subjects with CVC, males had significantly lower SOD (778.7+/-103.2 U/gHb, P<0.01) and GR activities (52.2+/-8.9 U/L, P<0.001) compared to females (839.3+/-94.9 U/gHb; 58.5+/-9.1 U/L). Significant and positive correlation was found between glucose levels and SOD (r = 0.375 for P<0.05) and GSH-Px (r = 0.384, P<0.05 ) activity in the group of complications-free diabetics, while significant negative correlation between glucose and GSH-Px values (r = -0.382, P<0.05) was found in the group of type 2 diabetics with coronary artery disease (CAD) and hypertension (HTA) and with CAD and acute myocardial infarction (AMI) (r = -0.860 P<0.05), and highly negative correlation between glucose and SOD levels (r = -0.590, P<0.05) in the group of diabetic subjects with CAD, AMI and HTA. Likewise, there was highly significant negative correlation of SOD (r = -0.949, P<0.05) and TAS (r = -0.393 for P = 0.038) with duration of diabetes in the group of diabetics with CAD and HTA.
Conclusion: Our results confirm the hypothesis that there is reduced antioxidative defense in type 2 diabetics with prominent cardiovascular complications, which negatively correlates with glucose concentrations and duration of diabetes and cardiovascular complications.