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Mixed tocopherols inhibit platelet aggregation in humans: potential mechanisms
Meilin Liu1, Agneta Wallmon, Caroline Olsson-Mortlock
1Department of Surgical Sciences, Section of Forensic Medicine, University of Uppsala, Sweden.
The American Journal of Clinical Nutrition
|February 26, 2003
Summary
Mixed tocopherols, unlike alpha-tocopherol alone, significantly reduced platelet aggregation. This effect is linked to increased nitric oxide release and endothelial nitric-oxide synthase activation, suggesting benefits for cardiovascular health.
Area of Science:
- Cardiovascular Research
- Nutritional Science
- Biochemistry
Background:
- Epidemiologic studies suggest a link between high dietary vitamin E intake and reduced acute coronary events.
- Recent clinical trials with alpha-tocopherol alone have yielded conflicting results regarding cardiovascular benefits.
- The absence of other tocopherol forms in prior studies may explain these discrepancies.
Purpose of the Study:
- To compare the effects of mixed tocopherols (rich in gamma-tocopherol) versus alpha-tocopherol on human platelet aggregation.
- To investigate the underlying mechanisms, including nitric oxide (NO) pathways and protein kinase C (PKC) activation.
Main Methods:
- Forty-six subjects were randomized into three groups: alpha-tocopherol, mixed tocopherols, or control.
- Platelet aggregation, NO release, endothelial constitutive nitric-oxide synthase (ecNOS) and PKC activation, and protein levels of ecNOS, superoxide dismutase (SOD), and PKC were measured.
- Measurements were taken before and after 8 weeks of tocopherol administration.
Main Results:
- Mixed tocopherols significantly decreased ADP-induced platelet aggregation, while alpha-tocopherol alone did not.
- Both tocopherol groups showed increased NO release, ecNOS activation, and SOD protein content.
- PKC activation was reduced in both tocopherol groups; mixed tocopherols showed greater potency in modulating NO release and ecNOS activation.
Conclusions:
- Mixed tocopherols are more effective than alpha-tocopherol alone in preventing platelet aggregation.
- The cardiovascular benefits of mixed tocopherols may be mediated by enhanced NO release, ecNOS activation, and SOD protein levels in platelets.