Mechanisms of the cardioprotective effect of a diet enriched with ω-3 polyunsaturated fatty acids

Abstract

The review presents current views of metabolic conversions of class ω-3 polyunsaturated fatty acids (ω-3 PUFA) and their effects on the heart function. The role of these compounds in regulation of the membrane lipid composition is discussed. Within the organism, ω-3 PUFA incorporate more effectively into membrane phospholipids of the myocardium in comparison with other organs. In animals kept on a ω-3 PUFA-enriched diet, the intramembrane concentration of ω-6 PUFA, in the first place, of arachidonic acid, decreases. Substitution of ω-3 PUFA for arachidonic acid in the metabolic system of eicosanoid synthesis initiates the synthesis of prostaglandins and thromboxanes possessing lowered biological activity, thus minimizing the risk of clot formation in the cardiovascular system. As ω-3 PUFA are direct substrates for lipid peroxidation, any rise in ω-3 PUFA concentration sharply activates free-radical oxidation in the membranes of internal organs particularly in the liver. Original data are presented that in rats kept on ω-3 PUFA-enriched diets, the kinetic parameters of the Ca2+ transport system do not change. However, the resistance of the system to free radical oxidation increases considerably. This may increase myocardial resistance to free-radical-dependent injuries. A rise in the intramembrane ω-3 PUFA content which brings about structural rearrangements within lipids and changes the activity of membrane-bound enzymes in vitro, has no effect in vivo. This finding points to the existence of a mechanism compensating for changes in the fatty acid composition of foods. Data from literature analysis suggest that one of the most active participants in the compensatory system is α-tocopherol, a lipid peroxidation inhibitor and a structural stabilizer of biomembranes. With a rise in ω-3 PUFA concentration, α-tocopherol is released from the liver and blood flow and accumulated in the body (predominantly in myocardial membranes). Whereas potent chemical antioxidants display an ability to inhibit physiologically important free-radical reactions occurring in the organism, vitamin E is without side effects even when used at high concentrations. In case of long-term application of ω-3 PUFA-enriched diets, α-tocopherol must be added to the diet.