Trans fatty acids are found mainly in processed foods. It has been shown that when their intake is high, total cholesterol, LDL-cholesterol and triacylglycerols are elevated, while HDL-cholesterol decreases. To evaluate a possible effect of these compounds, even in low amounts, C57Bl/6J mice were fed for 7 weeks a diet containing 13·6 % energy as partially hydrogenated rapeseed oil-enriched diet (Trans diet). The Trans diet contained 3 % energy as trans 18 : 1 fatty acid (elaidic acid). Control mice were on an isologous diet containing native rapeseed oil (Rapeseed diet) in which trans fatty acids were undetectable. Total, free and HDL-cholesterol as well as reverse cholesterol transport did not change. However, plasma triacylglycerol and VLDL levels increased. Hepatic gene expression in the Trans v. Rapeseed diet were compared using quantitative RT-PCR. The Trans diet produced a 2-3-fold elevation in mRNA of fatty acid synthase and microsomal transfer protein mRNA, explaining (at least in part) the observed increase in triacylglycerols and VLDL. In addition, mice on the Trans diet developed a deficiency in plasma vitamin E accompanied by a higher concentration of F2-isoprostanes, indicative of increased oxidative stress. The 78 kDa glucose-related protein (GRP78) mRNA expression increased 3-4-fold in liver, suggesting that a response against apoptosis was provoked by lipid peroxidation.Trans fatty acids: Hepatic triacylglycerol production: Reverse cholesterol transport: Oxidative stress Trans fatty acids (TFA) are steric isomers of the common cis unsaturated fatty acids containing at least one double bond in the trans configuration. TFA are found in meat and dairy products at significant levels since they are intermediates in fatty acid b-oxidation, and also formed in the rumen by bacterial hydrogenation. But they are present at much higher levels in processed fried foods and cookies often made with hydrogenated vegetable oils (shortening). Evidence that use of TFA in food represents a risk for health has accumulated, and very recently a campaign has been launched by a US nutritional group to eliminate them from processed food recipes. TFA have already been cutdown in Denmark where guidelines issued by the government fix the maximal amount tolerated in foods. TFA intake has been associated with an increased risk of CHD. This correlated to increased plasma concentrations of total cholesterol, LDL-cholesterol, triacylglycerols, and decreased levels of HDL-cholesterol, which could explain their effect on CHD (Mensink & Katan, 1990;Ascherio et al. 1999). These biochemical alterations appear to be somewhat proportional to intake (Lichtenstein et al. 1999). However, most of these studies were done with rather high concentrations of TFA and little is known about the possible impact on health of lower dietary intake of TFA as observed in Mediterranean countries. A better understanding of the effect of low levels of TFA on plasma lipoproteins and other biomarkers of CHD risk would provide insight into better prevention ...

In humans, diets rich in fish oil (containing n-3 FA) decrease the incidence of coronary artery diseases. This is thought to be caused by the induction in liver and skeletal muscle of genes involved in lipid oxidation, and to the repression in liver and adipose tissue of genes responsible for lipogenesis. n-3 FA are known to reduce the synthesis of FA and TG in the liver, resulting in a decrease of plasma concentrations of TG-rich lipoproteins. On the other hand, little is known of a possible effect of n-3 FA on HDL metabolism. To investigate this question, female C57Bl/6J mice were fed an n-3 FA-enriched diet for 16 wk. As expected from previous studies, we found that total cholesterol, TG, and phospholipids were reduced in the plasma of treated mice. We also found that HDL-cholesterol decreased after this treatment and that the in vivo fractional catabolic rate of HDL-cholesteryl ester was significantly higher in treated mice than in control mice fed a standard diet. Consistent with these results, treated mice exhibited increased uptake of HDL-cholesteryl ester in the liver. Moreover, quantitative reverse transcriptase-PCR analysis showed a two- to threefold increase in scavenger receptor B-1 gene expression. Taken together, these results suggest that an n-3 FA-enriched diet stimulates one step in the reverse cholesterol transport in mice, probably by increasing the amount of the scavenger receptor class B-1. These effects of n-3 FA on HDL metabolism may contribute to their beneficial effects on the vasculature.

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Objective: Increased HDL-cholesterol (HDL-C) concentrations have been associated with lower coronary heart disease risk. On the other hand, dietary fats are known to influence the fatty acid profile of plasma lipids, including phospholipids that are substrates of lecithin cholesterol acyltransferase (LCAT), an important enzyme in HDL metabolism. The purpose of this study was to examine the association between the saturated fatty acid (SFA) intake and LCAT activity. Design: An interventional study was performed in a monk community of 25 men. Setting: A French monk community, South West of France. Subjects and interventions: The basal diet of the study cohort contained SFA in a proportion of 13.5% of their total energy intake (TEI). They were submitted to two experimental isocaloric diets containing either 8.4% of the TEI in SFA (diet A) or 11% (diet B), each lasting 5 weeks. Results: The elevation of SFA in diet B was mainly obtained by decreasing carbohydrates. The only significant difference among total fats between diets A and B was the myristic acid content (0.6 and 1.2% of TEI, respectively). The elevation in SFA in diet B resulted in a significant increase of HDL-C (Po0.04), while plasma apo A-I concentration and LCAT activity both decreased (Po0.02). Conclusion: Altogether, these results are consistent with a negative effect of SFA on reverse cholesterol transport.

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