The Role of Autoantibody and Antioxidant Enzymes in Patients with Type I Diabetes

To determine autoantibodies and antioxidant enzymes as well as the correlation between them.
This study included 80 individuals, 40 patients with type 1 diabetes and 40 healthy individuals without diabetes (as a control group). The study was carried out during the period from December 2010 to the end of December 2012 at Al-Tahreer General Hospital, Al-Basra Maternity and Pediatric Hospital, and Al-Sader Teaching Hospital. Laboratory investigations were performed to estimate glutamic acid decarboxylase antibody (GADA) and islet cell antigen-2 antibody (IA-2A) by enzyme-linked immunosorbent assay (ELISA), antioxidant enzymes (glutathione peroxidase [GPX] and superoxide dismutase [SOD]), and glycosylated hemoglobin (HbA1c) (as a marker of glycemic control) for these patient and control groups.
The high prevalence of GADA and IA-2A had been demonstrated among patients with type 1 diabetes, which was significantly higher (P < 0.001) (72.5%) in comparison to 0% in the control group. These results are suggestive of the autoimmune characteristic of type 1 diabetes.
The age of onset of type 1 diabetes is found to affect the frequency of these autoantibodies. The frequency was significantly higher in patients who developed the disease in early childhood (91.7% for GADA and 58.3% for IA-2A) in comparison with those who developed the disease later on (40% for GADA and 20% for IA-2A); this probably occurred due to genetic and non-genetic factors.
Although the statistical analysis of the correlation between gender and autoantibodies showed no significant difference, female patients with type 1 diabetes were found to be more affected than male patients.
The frequency of these autoantibodies was found to decrease as the duration of type 1 diabetes increased. The prevalence of GADA and IA-2A in patients with duration of disease less than 5 years was 78.3% and 43.5%, respectively, and began to decrease to 0% for GADA and IA-2A in those with disease duration more than 12 years. These results are attributed to the depletion of islet cell autoantibodies with time.
Additionally, HbA1c levels were significantly higher in islet cell autoantibodies–positive patients than in islet cell autoantibodies–negative patients (P < 0.001). The difficulty in achieving glycemic control despite oral hypoglycemic drug and insulin therapy is attributed to the fact that the pathogenesis of disease in developing type 1 diabetes and latent autoimmune diabetes (LADA) in adults is due to -cell destruction rather than insulin resistance as in classical type 2 diabetes.
The mean activity of both antioxidant enzymes (SOD and GPX) in red blood cells (RBCs) was significantly lower than the control (P < 0.001). Also the lower mean activity of both antioxidant enzymes (SOD and GPX) in RBCs showed a higher significant value in patients who had uncontrolled diabetes (HbA1c level > 8%) (P < 0.001).
Patients with LADA who were tested positive for GAD and IA-2A showed a significant decrease in the mean activity of SOD and GPX in comparison to patients with type 2 diabetes who were tested negative to autoantibodies; most of the patients with LADA also had a higher HbA1c level > 8% (P< 0.001).
There is a strong evidence of the role of autoimmunity in the pathogenesis of type 1 diabetes. The oxidative stress SOD and GPX are depleted as well. The correlation reflects the more oxidative stress with poor diabetic patients may progress the complications.