Associations of FPG, A1C and disease duration with protein markers of oxidative damage and antioxidative defense in type 2 diabetes and diabetic retinopathy

Abstract

Purpose To investigate the role of protein oxidative damage and antioxidant defense in relationship to hyperglycemia measured as fasting plasma glucose (FPG), glycated hemoglobin (A1C), and duration of disease in type 2 diabetes mellitus (DM) and diabetic retinopathy (DR).MethodsThis study recruited 23 non-diabetic subjects, 16 DM patients without any complications and 18 DR patients. The serum ischemia modified albumin (IMA) and glutathione (GSH) levels were measured. The IMA results were corrected for serum albumin. Between-group differences were studied by analysis of variance and between-variable associations were studied by Spearman's and partial correlations.ResultsIMA and cIMA values were elevated, whereas GSH was decreased in both patient groups vs controls (P<0.05), and the increase in IMA formation is not related to serum albumin changes. DR patients have much severe oxidative stress (OS) status with high IMA and cIMA, and low GSH than in the DM group (P<0.05). Both FPG and A1C levels were positively associated with IMA in DM group, while in the DR group, duration of disease too had a positive association with IMA. The antioxidant GSH had negative correlations with FPG (r=-0.52, P=0.02) and IMA (r=-0.49, P=0.03) in the DR group. Partial correlation analyses predicted mutual or independent associations among parameters.ConclusionsSevere OS in DR has been associated with increased FPG, A1C, and disease duration. Both hyperglycemia and elevated oxidative damage detected as IMA are collectively associated with depleted GSH status. Our study unravels the need for monitoring of OS in addition to standard glycemic management in DR.