Effect of olive and sunflower oils on low density lipoprotein level, composition, size, oxidation and interaction with arterial proteoglycans

The atherogenicity of low density lipoproteins (LDL) may be modulated by its serum levels, structure and affinity for components of the intima, all properties that can be altered by diet. Linoleic acid-rich diets (n-G, 18:2) reduce the levels of LDL whereas those rich in oleic (n-9, 18:1) are considered 'neutral'. However, LDL enriched in linoleic acid have been reported to be more vulnerable to free radical-mediated oxidation than those enriched in oleic, a potentially atherogenic property. The effect of dietary fats on other properties of LDL that may also modulate atherogenesis, such as size and capacity to interact with intima components, are not well established. We explored here how a change from an olive oil-rich diet (OO) to a sunflower oil-rich one (SFO) affects these parameters in a community with a traditional Mediterranean diet. Eighteen free-living volunteers were placed for 3 weeks on a diet with 31% of caloric intake as sunflower oil and then shifted for an additional 3 weeks to a diet in which OO provided 30.5% of the calories. The LDL after SFO had a fatty acids ratio of (18:2 + 18:3 + 20:4) to (16:0 + 16:1 + 18:0 + 18:1) of 1.06 +/- 0.11 compared to 0.73 +/- 0.06 after the OO period. Serum LDL was significantly lower after SFO than after OO. Unexpectedly, copper-catalyzed oxidation of LDL from the SFO period was significantly less than that of the particles from the OO period. The resistance to oxidation of LDL of the SFO and OO period related to alterations in content of the antioxidants alpha-tocopherol, beta-carotene and retinol, in addition to changes in size and fatty acids composition. In vitro binding of LDL to human arterial proteoglycans was also significantly lower for the SFO-LDL than the OO-LDL, a result that can also be attributed to the larger size of the SFO-LDL. Therefore, three properties of LDL: circulating levels, oxidizability, and affinity with intima proteoglycans, that may modulate its atherogenicity, were shifted in a favorable direction by diets rich in linoleic acid and natural antioxidants.