Effects of alpha-tocopherol and mixed tocopherol supplementation on markers of oxidative stress and inflammation in type 2 diabetes

Abstract

Background: Vitamin E isomers may protect against atherosclerosis. The aim of this study was to compare the effects of supplementation with either alpha-tocopherol (alphaT) or mixed tocopherols rich in gamma-tocopherol (gammaT) on markers of oxidative stress and inflammation in patients with type 2 diabetes.

Methods: In a double-blind, placebo-controlled trial, 55 patients with type 2 diabetes were randomly assigned to receive (500 mg/day) (a) alphaT, (b) mixed tocopherols, or (c) placebo for 6 weeks. Cellular tocopherols, plasma and urine F(2)-isoprostanes, erythrocyte antioxidant enzyme activities, plasma inflammatory markers, and ex vivo assessment of eicosanoid synthesis were analyzed pre- and postsupplementation.

Results: Neutrophil alphaT and gammaT increased (both P <0.001) with mixed tocopherol supplementation, whereas alphaT (P <0.001) increased and gammaT decreased (P <0.005) after alphaT supplementation. Both alphaT and mixed tocopherol supplementation resulted in reduced plasma F(2)-isoprostanes (P <0.001 and P = 0.001, respectively) but did not affect 24-h urinary F(2)-isoprostanes or erythrocyte antioxidant enzyme activities. Neither alphaT nor mixed tocopherol supplementation affected plasma C-reactive protein, interleukin 6, tumor necrosis factor-alpha, or monocyte chemoattractant protein-1. Stimulated neutrophil leukotriene B(4) production decreased significantly in the mixed tocopherol group (P = 0.02) but not in the alphaT group (P = 0.15).

Conclusions: The ability of tocopherols to reduce systemic oxidative stress suggests potential benefits of vitamin E supplementation in patients with type 2 diabetes. In populations with well-controlled type 2 diabetes, supplementation with either alphaT or mixed tocopherols rich in gammaT is unlikely to confer further benefits in reducing inflammation.