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Four groups of rats were fed diets containing 15% (w/w) high-oleic safflower oil (SFO, rich in cis-18:1 acids), a mixture of 80% partially hydrogenated soybean oil plus 20% corn oil (H + CO, rich in trans-18:1 acids), lard (L, rich in saturated fatty acids) and corn oil (Co, rich in 18:2 omega 6). Fatty acid composition of liver microsomes and activities of the delta 5, delta 6 and delta 9 desaturases were determined. Microsomal delta 6 desaturase activity and arachidonic acid were lower in the H + CO group compared with SFO of L. No difference was found in the delta 5 or delta 6 desaturase activity of CO and SFO groups. Thus, the oleic-acid level of the SFO diet had no effect on the metabolism of 18:2 omega 6. Fluorescent polarization studies, using trans-parinaric acid as a probe, showed no differences between the physical states of phospholipid vesicles made from lipids isolated from each group. We concluded that the trans-18:1 acids in partially hydrogenated soybean oil have a more inhibitory effect than saturated acids on EFA metabolism, even in the presence of adequate amounts of essential fatty acid.

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Our model indicated that a diet inadequate in magnesium combined with trans fat may increase the risk of calcification of endothelial cells.

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Experimental Mg2+ deficiency was induced in a group of rats by feeding them a Mg2+-deficient diet for 23 days. They were pair-fed to compare with a control group of rats fed a Mg2+-sufficient diet. In the Mg2+-deficient group the plasma total cholesterol and triglyceride levels were increased while HDL-cholesterol was decreased. In the Mg2+-deficient group the plasma level of thiobarbituric acid reacting substances (TBARS) used as a measure for lipid peroxidation was increased. The increase was attributed to the increased cytosolic Ca2+ in Mg2+-deficiency which can cause: 1) increase of hydro and endoperoxide levels as a consequence of the increase of arachidonic acid release and eicosanoid synthesis in Mg2+-deficiency, and 2) inhibition of the mitochondrial respiratory activity and activation of Ca2+-dependent proteases which may activate the conversion of xanthine dehydrogenase to xanthine oxidase which generates active O2 species. In the Mg2+-deficient group, the fatty acid composition of the liver microsomes indicated a slower rate of conversion of linoleic acid to arachidonic acid which was consistent with the decrease of delta 6 desaturase activity in liver microsomes of Mg2+-deficient rats as measured in vitro. The decrease of delta 6 desaturase activity was attributed to the lower concentration of actual enzyme molecules as a result of the decreased rate of protein synthesis in Mg2+-deficiency. The possible effects of the increased catecholamine release in Mg2+-deficiency are discussed.