Perturbation of the metabolism of essential fatty acids by dietary partially hydrogenated vegetable oil.

Abstract

Rats were fed purified diets containing (i) partially hydrogenated soybean oil as source ofisomeric octadecenoic acids, (ii) hydrogenated coconut oil as source of saturated fatty acids, and (iii) a low level of corn oil as low-fat control. All diets contained 18% of the linoleate requirement. Rat liver and heart phospholipids were analyzed by gas/liquid chromatography for fatty acids, and liver microsomes were assayed for desaturase (acyl-CoA, hydrogen-donor: oxidoreductase, EC 1.14.99.5) activities. Products of desaturation reactions measured analytically provided more information with greater statistical significance than did the enzymatic assays. Rats fed isomeric octadecenoic acids showed more severe essential fatty acid deficiency than did saturated-fat and control groups. The suppression of linoleate metabolites was largely due to decreased A5 and A6 desaturase activities. At several levels of linoleate, the deficiency was more severe at the higher level ofisomeric octadecenoic acids. Increasing the intake of linoleate to 7.5% of calories did not suppress deposition of isomeric unsaturated acids in tissue lipids.High levels ofpolyunsaturated fatty acids (Pufa) in many dietary vegetable oils make them extremely vulnerable to autoxidation, decreasing their Pufa content and producing objectionable and toxic products. This characteristic limits the useful lifetime in exposure to air and causes problems in distribution and storage. Partial hydrogenation of vegetable oils produces fats of desired physical property, lessens rancidity and off-flavors, increases shelf life, and makes available inexpensive food fats on a large scale, but it diminishes Pufa content, increases saturated acids, and increases ciS and trans positional isomers of monoenoic acids, many of which are rare in nature and whose metabolism is not known. trans isomeric acids are better known because they are more abundant in hydrogenated oils and are more easily measured than the cis isomers that accompany them. trans acids are known to be incorporated into tissue lipids at appreciable levels (1-6), and isomers of common unsaturated fatty acids affect Pufa metabolism (6-10). Dietary fat containing appreciable isomeric 18:1t acids intensifies essential fatty acid (Efa) deficiency and affects desaturase (acyl-CoA, hydrogendonor: oxidoreductase, EC 1.14.99.5) activities assayed in vitro (6). Effects ofisomeric unsaturated acids on Efa metabolism are studied here in greater detail, using an analytical approach to measure metabolic activities at each step in the conversion of dietary Efa to longer and more highly unsaturated acids. This study compares such analyses with enzymatic assays and presents data to evaluate some of the changes in Pufa metabolism attributable to high levels of isomeric octadecenoic acids in dietary fat. MATERIALS AND METHODSMale weanling Sprague-Dawley rats were housed individually and fed semipurified diets and water ad lib. The diets were a modified Efa-deficient diet (6) with fat substitutions made at the expense o...

A Prospective Study ofTrans-Fatty Acid Levels in Blood and Risk of Prostate Cancer

“…Intake of trans fats increased insulin resistance in controlled feeding trials (5, 6) and has been associated to increased risk of type 2 diabetes in observational studies (24). Further, trans-fatty acids can decrease the activity of the D5 and D6 desaturases (25,26), which may also contribute to increased insulin resistance (27).…”

A Prospective Study of Trans Fatty Acids in Erythrocytes and Risk of Coronary Heart Disease

“…2,32 Trans fatty acids may increase the risk of CHD through other pathways, such as an increase in lipoprotein(a) 4,5 and blood triacylglycerol concentrations 6 and interference with essential fatty acids metabolism and eicosanoids balance by inhibition of delta-6-desaturase. 33,34 Furthermore, trans fat intake has been shown to be associated with systemic inflammation, endothelial cell dysfunction, and insulin resistance. 7,8 By their incorporation into the phospholipids in cell membranes, trans fatty acids may also alter the membrane function and decrease the membrane fluidity in a manner similar to saturated fat.…”

The Effects Of Fresh And Thermoxidized Palm Oil Diets On Some Haematological Indices In The Rat

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