α-Tocopherol levels in plasma in new-onset, insulin-dependent diabetes mellitus

Diabetic complications have been related to increased oxidative stress. Plasma antioxidant levels may be affected by hyperglycemia-induced oxidative stress as well as by insulin therapy. We evaluated the immediate effect of insulin treatment and improved metabolic control on the important antioxidant α-tocopherol plasma (vitamin E) levels in new-onset, insulin-dependent diabetes mellitus. The study was performed in 15 consecutive patients, aged 20-67 years, with new-onset diabetes mellitus requiring acute insulin treatment. Plasma α-tocopherol levels were measured before the start of intensive insulin treatment and monthly for 6 months thereafter. Simultaneously, we studied plasma malondialdehyde (MDA) as a reflection of lipid peroxidation. In addition, comparisons were made to a nondiabetic reference group. Baseline α-tocopherol levels did not differ from those in nondiabetic subjects. α-Tocopherol decreased significantly, from 33.5±12.1 μmol/l before treatment to 28.11±6.85 μmol/l (-16%) after 1 month of insulin therapy (p<0.04) to 26.6±7.03 μmol/l (-20%) after 3 months of insulin therapy (p<0.02). This trend did not change after adjusting for variations in cholesterol levels. After 6 months, α-tocopherol was no longer decreased compared to baseline levels (29.6±7.4 μmol/l). MDA concentrations at baseline were significantly higher in the diabetic patients (3.79±2.91 μmol/l) than in the nondiabetic subjects (1.57±0.21 μmol/l, p=0.006). MDA concentrations decreased significantly following the start of insulin treatment. Patients with new-onset, insulin-dependent diabetes mellitus have α-tocopherol levels that are similar to those in normal subjects. Insulin treatment and/or improved metabolic control cause a significant decrease in α-tocopherol levels during the first months.