Effects of polyunsaturated fatty acids on factors related to cardiovascular disease.

Dietary fats play a critical role in atherogenesis and thrombosis. Both the amount of fat consumed and its composition affect various events associated with coronary artery disease. Dietary unsaturated fatty acids appear to reduce the incidence of these events, in particular polyunsaturated fatty acids (PUFAs), which exert markedly different effects on risk factors related to heart disease. The omega-3 (n-3) PUFAs, at high levels of dietary intake, significantly reduce hyperlipidemia and the production of the prothrombotic substance thromboxane, and they enhance the production of the platelet-antiaggregatory substance prostacyclin. Data from clinical trials indicate a significant reduction of levels of very low density lipoprotein (VLDL). The n-3 PUFAs also depress hepatic fatty acid and triglyceride synthesis and VLDL secretion. The n-3 PUFAs of fish oils displace arachidonic acid from tissue phospholipids and concomitantly increase n-3 PUFA levels, which inhibit thromboxane synthesis. Most significantly, in human subjects the antiaggregatory prostacyclin PGI3 is also synthesized and the net effect is enhanced antiaggregatory/antiadhesive activity. In addition, the chemotactic platelet adhesion-promoting substance leukotriene B4 is suppressed. These composite effects reduce atherogenesis and thrombosis. Fish oil n-3 PUFAs may also reduce blood pressure and blood viscosity. Through the combined vasodilatory effects via prostacyclin (PGI2 and PGI3), fish oils may improve peripheral circulation and thereby facilitate VLDL removal. The n-3 PUFAs of fish oils, by altering membrane fluidity in a specific manner, alter the activities of membrane-bound enzymes and may change receptor activity, specificity and signal transduction. Overall, these data indicate a beneficial role for n-3 PUFAs as part of a dietary approach to minimizing coronary artery disease.