Secondary Prevention with Antioxidants

Cambridge Heart Antioxidant Study DATATOR Deprenyl and Tocopherol Antioxidative Therapy of Rarkinsonism FMC, Finnish Mobile Clinic Health Examination Survey GISSI, Gruppo Italiano Studio Soprawivenza Infarto HOPE, Heart Outcome Prevention Evaluation HPFS, Health Professional Follow-up Study NHS, Nurses Health Study PPR Primary Prevention Project SPACE, Secondary Prevention with Antioxidants of Cardiovascular disease in End-stage renal disease VEAPS, Vitamin E Atherosclerosis Prevention Study VECAT Vitamin E Cataract Age-related maculopathy Trial. 

Boaz M, Smetana S, Weinstein T et al. Secondary prevention with antioxidants of cardiovascular disease in endstage renal disease (SPACE) randomised placebo-controlled trial. Lancet 2000 356 1213-1218. 

The ability of a-tocopherol supplementation to prevent cardiovascular events in different populations was tested in four larger prospective clinical trials The a-Tocopherol, yS-Carotene Cancer Prevention (ATBC) study, the Cambridge Heart Antioxidant Study (CHAOS), the Gruppo Italiano per lo studio della Sopravvivenza nell Infarto Miocar-dito (GISSI) trial, and the Heart Outcome Prevention Evaluation (HOPE) study. In addition, at least two smaller prospective clinical trials have been completed the Secondary Prevention with... 

If primary antioxidants compete with free radicals for hydrogen abstraction from the polymer and then scavenge another free radical (Eqs. 15.3 and 15.4), secondary antioxidants directly decompose unstable hydroperoxides (Eq. 15.6), thereby preventing with free radicals formation (Eq. 15.7) ... 

The detection and quantification of one or more of the above lipid peroxidation produas (primary and/or secondary) in appropriate biofluids and tissue samples serves to provide indices of lipid peroxidation both in ntro and in vivo. However, it must be stressed that it is absolutely essential to ensure that the products monitored do not arise artifactually, a very difiScult task since parameters such as the availability of catalytic trace metal ions and O2, temperature and exposure to light are all capable of promoting the oxidative deterioration of PUFAs. Indeed, one sensible precaution involves the treatment of samples for analysis with sufficient levels of a chainbreaking antioxidant [for example, butylated hydroxy-toluene (BHT)] immediately after collection to retard or prevent peroxidation occurring during periods of storage or preparation. 

Secondary antioxidants, i.e., sequestrants or chelators, are important compounds in the prevention of lipid oxidation. The effect of chelators tested varied with the different compounds. Of those chelators tested, ethylenediaminetetraacetic acid (EDTA, tetrasodium salt) and sodium phytate were the most effective inhibitors of lipid oxidation (so indicated by low hexanal and TEARS values) and MFD (as seen by high CBB and low PIT and CBD intensity values), see Table 5. Sodium phytate was previously shown to chelate iron and thus, was proposed as a food antioxidant(7J). Sodium citrate at a concentration of 500... 

Two principal classes of antioxidant are effective in thermal oxidation. Chainbreaking or primary antioxidants limit the rate of the chain propagation steps (Eqs. 3-2 and 3-3) by trapping carbon- or oxygen-centered free radicals. Hydroperoxide decomposing or secondary antioxidants prevent chain initiation by interfering with ROOH. Photoantioxidants protect plastics exposed to photo-oxidation. 

Secondary antioxidants are also classified as preventive or class II antioxidants. They offer their antioxidant activity through various mechanisms to slow the rate of oxidation reactions. The main difference with primary antioxidants is that the... 

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