The effect of vitamin E on blood pressure in individuals with type 2 diabetes: a randomized, double-blind, placebo-controlled trial.
OBJECTIVE
Oxidative stress has been suggested to play a role in the development of diabetes, hypertension and vascular dysfunction. Vitamin E, a major lipid-soluble dietary antioxidant, has two major dietary forms, alpha-tocopherol and gamma-tocopherol. The potential importance of gamma-tocopherol has largely been overlooked. Our aim was to investigate the effect of alpha-tocopherol and gamma-tocopherol supplementation on 24-h ambulatory blood pressure (BP) and heart rate, vascular function and oxidative stress in individuals with type 2 diabetes.


METHODS
Fifty-eight individuals with type 2 diabetes were randomized in a double-blind, placebo-controlled trial. Participants were randomized to a daily dose of 500 mg/day RRR-alpha-tocopherol, 500 mg/day mixed tocopherols (60% gamma-tocopherol) or placebo for 6 weeks. Primary endpoints were 24-h ambulatory BP and heart rate, endothelium-dependent and independent vasodilation and plasma and urinary F2-isoprostanes.


RESULTS
Treatment with alpha-tocopherol significantly increased systolic BP [7.0 (5.2, 8.8) mmHg, P < 0.0001], diastolic BP [5.3 (4.0, 6.5) mmHg, P < 0.0001], pulse pressure [1.8 (0.6, 3.0) mmHg, P < 0.005] and heart rate [2.0 (0.6, 3.3) bpm, P < 0.005] versus placebo. Treatment with mixed tocopherols significantly increased systolic BP [6.8 (4.9, 8.6) mmHg, P < 0.0001], diastolic BP [3.6 (2.3, 4.9) mmHg, P < 0.0001], pulse pressure [3.2 (2.0, 4.4) mmHg, P < 0.0001] and heart rate [1.8 (0.5, 3.2) bpm, P < 0.01] versus placebo. Treatment with alpha-tocopherol or mixed tocopherols significantly reduced plasma F2-isoprostanes versus placebo, but had no effect on urinary F2-isoprostanes. Endothelium-dependent and independent vasodilation was not affected by either treatment.


CONCLUSIONS
In contrast to our initial hypothesis, treatment with either alpha- or mixed tocopherols significantly increased BP, pulse pressure and heart rate in individuals with type 2 diabetes.
Ward
Natalie C
NC
School of Medicine and Pharmacology, University of Western Australia, Perth, Australia. nward@cyllene.uwa.edu.au
Wu
Jason H Y
JH
Clarke
Michael W
MW
Puddey
Ian B
IB
Burke
Valerie
V
Croft
Kevin D
KD
Hodgson
Jonathan M
JM
D000975:Antioxidants / Q000494:pharmacology / Q000627:therapeutic use*; D001794:Blood Pressure / Q000187:drug effects*; D018660:Blood Pressure Monitoring, Ambulatory; D001916:Brachial Artery / Q000187:drug effects / Q000503:physiopathology; D003924:Diabetes Mellitus, Type 2 / Q000188:drug therapy* / Q000378:metabolism / Q000503:physiopathology; D019587:Dietary Supplements; D004311:Double-Blind Method; D004359:Drug Therapy, Combination; D004730:Endothelium, Vascular / Q000187:drug effects / Q000503:physiopathology; D028441:F2-Isoprostanes / Q000378:metabolism; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D008297:Male; D008875:Middle Aged; D018384:Oxidative Stress / Q000187:drug effects; D013997:Time Factors; D016896:Treatment Outcome; D014664:Vasodilation / Q000187:drug effects; D014810:Vitamin E / Q000494:pharmacology / Q000627:therapeutic use*; D014904:Western Australia; D024502:alpha-Tocopherol / Q000627:therapeutic use; D024504:gamma-Tocopherol / Q000627:therapeutic use
D000975:Antioxidants; D028441:F2-Isoprostanes; D014810:Vitamin E; D024504:gamma-Tocopherol; D024502:alpha-Tocopherol