Unaltered antioxidant activity of plasma in subjects at increased risk for IDDM

Evidence suggests that free oxygen radicals are involved in the destruction of islet beta-cells in insulin-dependent diabetes mellitus (IDDM). Therefore, we determined the plasma antioxidant activity in 51 healthy unaffected children and adolescents randomly chosen from a study of beta-cell autoimmunity in schoolchildren in northern Finland. Twenty-two subjects tested positive for one or more IDDM-associated autoantibodies and 9 subjects had at least two of the three antibodies tested (antibodies against islet cells, ICA; glutamic acid decarboxylase, GADA; insulin, IAA). There was no significant association of total plasma antioxidant potential, plasma concentrations of alpha-tocopherol, ascorbic acid, protein thiols, or uric acid with the presence of ICA, GADA, or IAA. A reduced first-phase insulin response to intravenous glucose was also not associated with reduced plasma antioxidant activity. These results indicate that the plasma antioxidant activity is not decreased in subjects at increased risk for IDDM. Furthermore, the results suggest that the clinical onset of IDDM is not preceded by signs of increased systemic oxidative stress in plasma.