Journal Name:
Annals of Nutrition and Metabolism
Article Title:
Dietary fats and lecithin-cholesterol acyltransferase activity in healthy humans.
Date Written:
1998
Volume:
32
Number:
5
Page:
352
Author(s):
Baudet, M.F.; Jacotot, B.
Article:
Several mechanisms have been proposed to explain the hypocholesterolemic effect of polyunsaturated fatty acids versus the hypercholesterolemic effect of saturated fatty acids. Changes in high density lipoproteins (HDL) can affect the metabolism of cholesterol in peripheral tissues in vitro, with correlations being reported between the capacity of HDL to take up free cholesterol from fibroblasts and the characteristics of the fatty acids found in the phospholipids of these HDL. Most free cholesterol entering the HDL is esterified by the plasma enzyme lecithin-cholesterol acyltransferase (LCAT) which catalyzes the transport of fatty acids between lecithin and cholesterol on the surface of plasma lipoproteins. LCAT plays a central role in cholesterol transport in plasma. The objective of the present study was to determine the effect of dietary fats on plasma LCAT activity.
LCAT activity was assessed in twenty healthy women aged 26-49 years who consumed 6-week diets containing 54% of the calories as carbohydrates, 16% as protein and 30% as fat. The tested fats were low erucic acid rapeseed (canola oil), sunflower oil, peanut oil and milk fats (butter and cream).
The fractional and molar rates of LCAT were higher after sunflower and peanut oil diets and decreased significantly after LEAR oil and milk fat diets. The LCAT activity was independent of the P/S ratio of the diet, but positively correlated with the percentage of linoleic acid in serum phospholipids and cholesteryl esters, and negatively correlated with the percentage of oleic acid in the same fractions. The study results suggest that LCAT activity appeared to depend on the quality of fat, particularly on the relative percentage of linoleic and oleic acids which are characteristically found in the phospholipid lecithin-2 position. Further, LCAT activity was positively correlated with percentage of linoleic acid and negatively correlated with the percentage of oleic acid in HDL lecithin. Linoleic acid was the most favourable substrate for the LCAT reaction. A positive correlation between percentage of linoleic acid and a negative correlation of the percentage of oleic acid, in serum cholesteryl esters, with LCAT activity was confirmed. In healthy women, no relationship between the LCAT activity and the concentration of plasma cholesterol or of plasma triglycerides was found. The plasma cholesterol ester/total cholesterol ratio was unchanged by the tested dietary fats, indicating that the rate of plasma cholesterol esterification did not solely determine that ratio. Further studies are suggested, particularly on cholesteryl ester transfer protein activity.
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