Direct vascular antiatherogenic effects of oleic acid: a clue to the cardioprotective effects of the Mediterranean diet.

Atherosclerosis, the main cause of ischemic heart disease, is a process with relevant inflammatory components, in which LDL-cholesterol, largely emphasized in the last years as a "causal" factor following the improvement in prognosis with cholesterol-lowering agents, is only one of the culprits. Despite the use of new cholesterol-lowering drugs, atherosclerotic vascular disease will likely continue to be the main cause of death in Western countries. Furthermore, the statistical relationship between cholesterol and cardiovascular mortality only explains a relatively minor component of differences in mortality among diverse countries. For these reasons, the interest in preventive approaches complementary or alternative to cholesterol reduction should be one of the main objectives of cardiovascular research in the years to come. Already in the '70s the very low incidence of atherosclerotic diseases in Mediterranean countries (Greece and Southern Italy) and the importance of the "dietary factor" in such protection were noticed. Diets for people in these countries are, among other components, very rich in oleic acid, the main constituent of olive oil, with about 29% of daily caloric intake derived from monounsaturated fatty acids. Oleic acid, besides exerting relatively minor effects on the quantitative and qualitative regulation of cholesterol levels, appears to interfere directly with the inflammatory response that characterizes early atherogenesis. The endothelial expression of adhesion molecules for circulating monocytes, induced by inflammatory cytokines, minimally oxidized LDL and the advanced glycation end-products present in diabetes, substantially contributes to the onset and early progression of atherosclerosis. In an in vitro model of early atherogenesis based on cultured endothelial cells stimulated by cytokines, we observed that the incorporation of oleic acid in total cell lipids--mostly at the expenses of saturated fatty acids--decreases the expression of several endothelial leukocyte adhesion molecules, among which vascular cell adhesion molecule-1, involved in the selective monocyte recruitment in the arterial intima. Oleic acid also determines a parallel reduction in messenger RNA for this molecule, interfering with the activation of the most important transcription factor controlling endothelial activation, nuclear factor-kappa B. Thus, possibly in concert with other more highly unsaturated fatty acids, oleic acid may contribute to the prevention of atherosclerosis also through a modulation of gene expression for endothelial leukocyte adhesion molecules. This series of investigations emphasizes the possibility of preventive interventions in atherosclerosis based on the modulation of vascular response to classical "triggers" (cholesterol, advanced glycation end-products of diabetes), an intervention strategy fundamentally different from--and thereby complementary to--those now more in fashion.