Received on July 20, 2006
Accepted on December 29, 2006

Endocrinology and Metabolism

Effects of -Tocopherol and Mixed Tocopherol Supplementation on Markers of Oxidative Stress and Inflammation in Type 2 Diabetes

¹ School of Medicine and Pharmacology, University of Western Australia, Crawley, Western Australia, Australia
² Centre for Clinical Immunology and Biomedical Statistics, Royal Perth Hospital and Murdoch University, Perth, Western Australia, Australia

^* To whom correspondence should be addressed. E-mail: kcroft{at}cyllene.uwa.edu.au.

Background: Vitamin E isomers may protect against atherosclerosis. The aim of this study was to compare the effects of supplementation with either -tocopherol (T) or mixed tocopherols rich in -tocopherol (T) 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) T, (b) mixed tocopherols, or (c) placebo for 6 weeks. Cellular tocopherols, plasma and urine F₂-isoprostanes, erythrocyte antioxidant enzyme activities, plasma inflammatory markers, and ex vivo assessment of eicosanoid synthesis were analyzed pre- and postsupplementation.

Results: Neutrophil T and T increased (both P <0.001) with mixed tocopherol supplementation, whereas T (P <0.001) increased and T decreased (P <0.005) after T supplementation. Both T and mixed tocopherol supplementation resulted in reduced plasma F₂-isoprostanes (P <0.001 and P = 0.001, respectively) but did not affect 24-h urinary F₂-isoprostanes or erythrocyte antioxidant enzyme activities. Neither T nor mixed tocopherol supplementation affected plasma C-reactive protein, interleukin 6, tumor necrosis factor-, or monocyte chemoattractant protein-1. Stimulated neutrophil leukotriene B₄ production decreased significantly in the mixed tocopherol group (P = 0.02) but not in the T 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 T or mixed tocopherols rich in T is unlikely to confer further benefits in reducing inflammation.