Objective: This study examined the relationship between cellular glutathione and vitamin E concentrations and the effect of vitamin E (alpha-tocopherol) supplementation on glutathione and lipid peroxidation product concentrations in the erythrocytes of type 1 diabetic patients.
Research design and methods: We obtained written informed consent to participate in this study from diabetic patients (n = 29) and their age-matched nondiabetic siblings (n = 21) according to the guidelines of the Institutional Review Board on Human Experimentation. Diabetic patients were supplemented with a DL-alpha-tocopherol (vitamin E) capsule (100 IU/orally) or placebo for 3 months in a double-blind clinical trial. Fasting blood samples were collected from each diabetic patient before the start of and after the 3 months of vitamin E or placebo supplementation. Glutathione, malondialdehyde (which is a product of lipid peroxidation), and alpha-tocopherol were determined using high-performance liquid chromatography A total of 5 diabetic patients were excluded after randomization from the data analyses. Data were analyzed statistically using a paired Students t test to compare 12 diabetic patients taking vitamin E with 12 diabetic patients receiving placebo supplementation and to compare diabetic patients with healthy nondiabetic subjects.
Results: Erythrocytes of diabetic patients had 21% higher (P<0.001) malondialdehyde and 15% lower (P<0.05) glutathione concentrations than healthy subjects. Vitamin E in erythrocytes had a significant correlation with the glutathione concentrations in the erythrocytes (r = 0.46, P<0.02). Vitamin E supplementation increased glutathione concentrations by 9% (P<0.01) and lowered concentrations of malondialdehyde by 23% (P<0.001) and of HbA1c by 16% (P<0.02) in erythrocytes of diabetic patients. No differences were evident in these parameters before versus after placebo supplementation.
Conclusions: Glutathione level is significantly related to vitamin E level, and supplementation with vitamin E (100 IU/day) significantly increases glutathione and lowers lipid peroxidation and HbA1c concentrations in the erythrocytes of type 1 diabetic patients.