Journal Name:
Lipids
Article Title:
Moderate Dietary Intake of Myristic and Alpha-Linolenic Acids Increases Lecithin-Cholesterol Acyltransferase Activity in Humans
Date Written:
2007
Volume:
42
Number:
0
Page:
717
Author(s):
Vaysse-Boue, C.; Dabadie, H.; Peuchant, E.; Le Ruyet, P.; Mendy, F.; Gin, H.; Combe, N.
Article:
Cholesterol removal from tissues into HDL depends on the activity of the enzyme lecithin-cholesterol acyltransferase (LCAT; E.C. 2.3.1.43) that is associated with lower cardiovascular diseases risk. HDL cholesterol concentration and LCAT activity can be modulated by dietary fatty acids. Original data with substrate models have shown a positive effect of the fatty acid myristic acid (C16:0 - MA) on the esterification rate of cholesterol.
The purpose of the present study was to examine the effect of moderate intakes of MA plus alpha-linolenic acid (ALA) on LCAT activity in humans. Two experimental diets were tested for 3 months each. Diet 1-MA 1.2% of total energy (TE) and ALA 0.9% TE, diet 2-MA 1.8% and ALA 0.9% TE; a control diet (MA 1.2% and ALA 0.4% TE) was given 3 months before diet 1 and diet 2. The study lasted 12 months, with four periods of 3 months: P3,P6,P9 and P12. Twenty-nine monks consumed successively a control diet (i.e. controlled fat intake of habitual diet) (P3), diet 1 (P6), control diet (P9) and finally diet 2 (P12). The control diet provided 32% TE from fat (11% SFA, 1.2% MA), 13% MUFA and 8% PUFA, of which 5.5% LA and 0.4% ALA). Both interventional diets provided the same intake levels of SFA (11–12% TE), oleic acid (11% TE), linoleic acid (LA; 4.5% TE) and ALA (0.9% TE), but MA intakes were different in diet 1 (1.2% TE) and diet 2 (1.8% TE). *The endogenous activity of LCAT was determined at completion of each diet. Compared with the control diet (13.2 ± 3.1 lmol CE/ (L.h)), LCAT activity increased significantly (33.3 ± 7.4 lmol CE/(L.h)); the increase observed with diet 2 was significantly (P < 0.001) greater than that due to diet 1. These results suggest that ALA from canola oil and MA (from dairy fat) favor LCAT activity, by respective increases of 83 and 38%. When the two fatty acids are supplied together, a complementary effect was observed (average increase of 152%). Thus, in vitro rates of cholesterol esterification found in this study show that LCAT activity increases in response to an increase in ALA or MA intake. These findings were associated with a decrease of the ratio of total to HDL-cholesterol.
In response to the experimental diets, fatty acid compositions of plasma phospholipids and cholesterol esters (CE) were modified. Diet 1 was associated with an increase in ALA, EPA, and DHA levels in phospholipids and CE. Diet 2 was associated with an increase in ALA in phospholipids and CE.
The results suggest that ALA and MA do not act on the same level towards LCAT. ALA, because of its incorporation within ‘‘substrate’’ phospholipids of LCAT could improve LCAT affinity for its substrate. In conclusion, this current study suggests there would seem to be a complementary effect between MA and ALA in the sn-2 position of dietary triacylglycerols, within the framework of combined physiological intakes.
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