Objective: In diabetes, the persistence of hyperglycemia has been reported to cause increased production of oxygen free radicals through glucose autooxidation and nonenzymatic glycation. The aim of this study was to determine whether oxidative cellular damage occurs at the clinical onset of diabetes and in later stages of the disease in young patients.

Research design and methods: Indicative parameters of lipoperoxidation, protein oxidation, and changes in the status of antioxidant defense systems were evaluated in single blood samples from 54 diabetic children, adolescents, and young adults and 60 healthy age- and sex-matched control subjects.

Results: Malondialdehyde and protein carbonyl group levels in plasma were progressively higher in diabetic children and adolescents than in control subjects (P < 0.0001). The highest erythrocyte superoxide dismutase (SOD) activity was found in diabetic children at onset of clinical diabetes. In diabetic adolescents, SOD was also significantly higher (P < 0.0001) than in control subjects. Erythrocyte glutathione peroxidase was significantly lower in diabetic children and adolescents compared with control subjects (P < 0.002). A significant decline in blood glutathione content at the recent onset of diabetes was found (P < 0.0001). Furthermore, our results demonstrated progressive glutathione depletion during diabetes evolution. The plasma alpha-tocopherol/total lipids ratio and beta-carotene levels during diabetes development (P < 0.001) were low.

Conclusions: This cross-sectional study in young diabetic patients showed that systemic oxidative stress is present upon early onset of type 1 diabetes and is increased by early adulthood. Decreased antioxidant defenses may increase the susceptibility of diabetic patients to oxidative injury. Appropriate support for enhancing antioxidant supply in these young diabetic patients may help prevent clinical complications during the course of the disease.