Treatment of atherosclerosis in the new millennium: is there a role for vitamin E?
Oxidative stress appears to be of fundamental relevance to diseases as diverse as atherosclerosis, cancer, and Alzheimer's disease. Observational data in humans have suggested that antioxidant vitamin intake is associated with reduced cardiovascular disease. Animal studies are largely consistent with the concept that dietary supplementation with antioxidant vitamins reduces the progression of atherosclerosis. However, recent prospective, controlled clinical trials of vitamin E, including the Cardiovascular Disease, Hypertension and Hyperlipidemia, Adult-Onset Diabetes, Obesity, and Stroke (CHAOS) study, the Heart Outcomes Prevention Evaluation (HOPE) trial, Gruppo Italiano per lo Studio della Sopravvivvenza nell'Infarto Miocardico (GISSI)-Prevenzione trial, the Secondary Prevention with Antioxidants of Cardiovascular Disease in End Stage Renal Disease (SPACE) trial, and the Heart Protection Study (HPS) present a confused picture. The various possibilities that have been advanced to explain this discrepancy are discussed in this review. A striking feature of these and other trials of antioxidants is the absence of a biochemical basis for patient inclusion or, indeed, dose selection. Patients with high levels of oxidant stress or depletion of natural antioxidant defense systems may be the most likely to benefit from antioxidant therapy. If this is the case, then reliable, quantitative indices of in vivo oxidant stress such as urinary isoprostane levels should be considered as an inclusion criterion for patient selection. Future trials of antioxidant therapy in cardiovascular disease should then be targeted toward such patients with high levels of oxidant stress or patients with depletion of natural antioxidant defense systems. Furthermore, the dose of antioxidant should be chosen based on a surrogate readout that is a reliable, reproducible, and easily obtainable in vivo measure of oxidant stress. In the interim, although the safety of vitamin E up to doses of 800 IU/day has been determined, the conflicting nature of the results published to date encourages us to avoid making premature recommendations with respect to vitamin E supplementation in the prevention and treatment of cardiovascular disease.
Center for Experimental Therapeutics and Department of Medicine, University of Pennsylvania, 9055 West Gates Pavilion, 3400 Spruce Street, Philadelphia, PA 19104, USA.
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Meagher
D000818:Animals; D000975:Antioxidants / Q000627:therapeutic use; D003324:Coronary Artery Disease / Q000188:drug therapy* / Q000503:physiopathology; D019317:Evidence-Based Medicine / Q000639:trends*; D006801:Humans; D018384:Oxidative Stress / Q000187:drug effects / Q000502:physiology; D014810:Vitamin E / Q000502:physiology / Q000627:therapeutic use
D000975:Antioxidants; D014810:Vitamin E