This study was designed to examine whether n-3 and n-6 polyunsaturated fatty acids at a very low dietary level (about 0.2%) would alter liver activities in respect to fatty acid oxidation. Obese Zucker rats were used because of their low level of fatty acid oxidation, which would make increases easier to detect. Zucker rats were fed diets containing different oil mixtures (5%, w/w) with the same ratio of n-6/n-3 fatty acids supplied either as fish oil or arachidonic acid concentrate. Decreased hepatic triacylglycerol levels were observed only with the diet containing fish oil. In mitochondrial outer membranes, which support carnitine palmitoyltransferase I activity, cholesterol content was similar for all diets, while the percentage of 22:6n-3 and 20:4n-6 in phospholipids was enhanced about by 6 and 3% with the diets containing fish oil and arachidonic acid, respectively. With the fish oil diet, the only difference found in activities related to fatty acid oxidation was the lower sensitivity of carnitine palmitoyltransferase I to malonyl-CoA inhibition. With the diet containing arachidonic acid, peroxisomal fatty acid oxidation and carnitine palmitoyltransferase I activity were markedly depressed. Compared with the control diet, the diets enriched in fish oil and in arachidonic acid gave rise to a higher specific activity of aryl-ester hydrolase in microsomal fractions. We suggest that slight changes in composition of n-3 or n-6 polyunsaturated fatty acids in mitochondrial outer membranes may alter carnitine palmitoyltransferase I activity.

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A method is described for the determination of molecular species of oil triacylglycerols. The method is based on the analytical separation of the enantiomeric sn-l,2-and sn-2,3-diacylglycerols, derived from triacylglycerols, by high-performance liquid-chromatography (HPLC) on a chiral column containing N-(R)-l-(a-naphthyl)ethylaminocarbonyl-(S)-valine as stationary phase. Model triacylglycerol molecules comprising three known fatty acids were isolated from peanut oil and cottonseed oil by a combination of argentation-TLC and reversed-phase HPLC and submitted to partial chemical deacylation. The derived sn-l,2(2,3)-diacylglycerols were analyzed and fractionated as 3,5-dinitrophenyl urethane derivatives by reversed-phase HPLC according to chalnlength and unsaturation. From the sn-l,2(2,3)-diacylglycerol composition and the diacylglycerol sn-l,2-and sn-2,3-enantiomer composition, the individual molecular species of four peanut oil triacylglycerols and one cottonseed oil triacylglycerol were identified and quantitated. The method can be applied to triacylglycerols of any other oil or fat.In stereospecific analysis of oil triacylglycerols, representative diacylglycerols should be produced by enzymatic or chemical partial deacylation and studied for fatty acid distribution (1). In the previous methods, the enantiomeric sn-l,2(2,3)-diacylglycerols, isolated by preparative thinlayer chromatography (TLC), were transformed into phospholipid-like molecules. The two enantiomeric synthetic phospholipids were then differentiated by the stereospecific action of phospholipase A (2) or phospholipase C (3). The diacylglycerol enantiomers are preferentially separated by high-performance liquid chromatography (HPLC) either as diastereomers on a classical silica column (4,5), or more currently as 3,5-dinitrophenylurethane (DNPU) derivatives on a chiral column (6-8}.In a previous study (9), we submitted pure peanut oil triacylglycerols isolated by argentationTLC and reversedphase HPLC to partial chemical deacylation, and we fractionated the pure enantiomeric diacylglycerols as DNPU derivatives by reversed-phase HPLC. The diacylglycerol enantiomers were consecutively separated by chiral-phase HPLC (8).The present study reports the determination of molecular species of the major peanut oil diacid-and triacidtriacylglycerols from the data previously obtained. These results complete those of another study on triacylglycerol structure of an African peanut oil of the same origin (10).

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