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Nicholls et al. (1) found an increased expression of adhesion molecules intracellular adhesion molecule (ICAM)-1 and vascular cell adhesion molecule (VCAM)-1 in human umbilical vein endothelial cells incubated with high-density lipoprotein taken from subjects eating a meal rich in coconut oil and a decreased expression of these molecules in cells incubated with high-density lipoprotein taken from subjects eating a meal rich in safflower oil (1). The authors attributed this effect to the fatty acid composition of the oils; since the oils used were unrefined, however (D. Celermajer and J. Harmer, personal communication, August 2006), a possible role for constituents other than fatty acids must be considered.
Compared to coconut oil per unit mass, safflower oil contains 77 times the alpha-tocopherol, more than 100 times the gamma-tocopherol, and 73 times the total tocopherol (2).
Vitamin E down-regulates the expression of ICAM-1 (3). Fan et al. (4) found that the incubation of human umbilical vein endothelial cells with alpha-tocopherol, gamma-tocopherol, or mixed tocopherols inhibited the induction of ICAM-1 expression by oxidized low-density lipoprotein in a dose-dependent manner, although it did not inhibit the induction of ICAM-1 expression by recombinant human C-reactive protein (4). Vitamin E suppressed ICAM-1 and VCAM-1 levels in a rabbit model of hypercholesterolemia (5) and in a rat model of heart transplantation (6). The effect on VCAM-1, however, was statistically significant only in the rat model and not in the rabbit model.
The respective vitamin E concentrations of the oils may therefore have contributed to their observed differential effects on ICAM-1 and VCAM-1 expression. Future research should investigate the relative contribution of fatty acid composition and micronutrient composition to this effect.
- American College of Cardiology Foundation