Journal Name:
J. Nutr.
Article Title:
Dietary mono- and polyunsaturated fatty acids similarly affect LDL size in healthy men and women.
Date Written:
2002
Volume:
132
Number:
4
Page:
715
Author(s):
Kratz, M.; Gülbahçe, E.; Von Eckardstein, A.; Cullen, P.; Cignarella, A.; Assmann, G.
Article:
Research has shown that low density lipoprotein (LDL) are very different in size, density and composition. Small, dense LDL subclass are associated with an increased risk of coronary heart disease (CHD). Hypercholesterolemic mice with predominantly small, dense LDL develop more atherosclerosis than mice with similar cholesterol levels but large, buoyant LDL particles. Small, dense LDL have a reduced affinity for the LDL receptor which results in a longer plasma half-life, and an increased affinity for receptor-independent cell-surface binding sites. Small, dense LDL have also been associated with impaired endothelial function in vivo and are more susceptible to oxidative modification. In humans, the relationship between LDL subclasses and cardiovascular diseases is not fully understood. LDL particle size and subclass pattern may be influenced by dietary fat in that low fat diets lead to a decrease in mean LDL size compared with high fat diets.
The purpose of this study was to investigate the effect of dietary fatty acids on LDL peak particle diameter in healthy volunteers. This study was designed to determine the effect of refined olive oil (rich in monounsaturated fats - MUFA), canola/rapeseed oil [rich in MUFA and (n-3)-polyunsaturated fats - PUFA], and sunflower oil [rich in (n-6)-PUFA] on LDL susceptibility to oxidation.
LDL size was measured by gradient gel electrophoresis in 56 (30 men, 26 women) participants. First, all participants received a baseline diet rich in saturated fat (SFA) for 2 weeks and then were randomly assigned to one of three dietary treatments for 4 weeks. The results showed that diets rich in MUFA (olive oil), (n-6)-PUFA (sunflower oil), or MUFA and (n-3)-PUFA (canola/rapeseed oil) had similar effects on the LDL peak particle diameter. Given the wide differences in the fatty acid compositions of the diets, the observed changes and differences were small.
In subjects that consumed the canola/rapeseed oil diet, the amount of linoleic acid in LDL remained constant, whereas the amount of n-3 alpha-linolenic acid and eicosapentaenoic acid increased. In subjects that consumed the sunflower oil diet, the amount of linoleic acid increased further. These findings suggest that dietary PUFA decrease LDL size by being incorporated into the particle. Individual PUFA appear to effect the expression or activity of enzymes such as cholesterol ester transfer protein, lecithin cholesterol acyltransferase, lipoprotein lipase or hepatic lipase. The activities of these proteins have been reported to be influenced by the content of MUFA and PUFA in the diet and the activities of these enzymes have been associated with the LDL subclass pattern. Changing the type of dietary fat had only a small effect on LDL size and the results do not determine whether such changes would have any clinical implications.
In conclusion, changing the quality of dietary fat from saturated to unsaturated fat slightly reduced the LDL peak particle diameter, with no significant difference between diets rich in MUFA, (n-6)-PUFA and (n-3)-PUFA. It is not clear whether such a small decrease in LDL size has any effect on CHD risk. The authors conclude that the small magnitude of this reduction suggests that the composition of dietary fat is not a major factor affecting LDL size.
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