Background: Glycated proteins present new immunological epitopes on their surface against which autoantibodies are generated that have a possible role in immunopathogenesis in diabetic complications. Methods: In the present study, in vitro glycation- and reactive oxygen species (ROS)-modified human serum albumin (HSA) has been studied by different spectroscopic techniques (UV and fluorescence) and thermal denaturation profiles. The binding characteristics of circulating autoantibodies in diabetic patients and diabetic patients with secondary complications against native HSA (N-HSA) and ROS-modified glycated HSA (RG-HSA) were assessed by direct and competition enzyme-linked immunosorbent assay (ELISA). In another approach, antibodies against RG-HSA (RG-HSA-Abs) induced in experimental animals were used as an immunochemical probe for the detection of gluco-oxidative lesions in blood proteins of patients (n = 8) with diabetic retinopathy. Results: Modified RG-HSA showed marked structural changes. High recognition of RG-HSA was shown by diabetic serum autoantibodies. Diabetic patients with retinopathy, nephropathy and atherosclerosis showed significantly (p < 0.001) stronger binding to RG-HSA over N-HSA. Normal human sera exhibited negligible binding with either antigen. Competitive inhibition ELISA results show significantly high binding of RG-HSA-Abs to albumin, immunoglobulin G and red blood cell membrane isolated from diabetic retinopathic patients. Conclusion: In conclusion, these results suggest that hyperglycemia together with ROS may contribute to the immunopathogenesis of diabetes-associated complications.

Keywords:
Autoantibodies, Diabetes, Diabetes-associated complications, Enzyme-linked immunosorbent assay, Gluco-oxidation, Reactive oxygen species-modified glycated human serum albumin
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