Molecular structure of glycerolipids in rats fed partially hydrogenated triacylglycerols

The positional distribution of acyl moieties was studied in two major classes of glycerolipids, i.e. triacylglycerols and diacylglycerophosphocholines, of liver, heart and serum of rats that were fed either an unhydrogenated soybean oil (control group) or a partially hydrogenated soybean oil (experimental group) containing 12.3% trans-octadecenoic acids. In both groups, most of the fatty acids from dietary triacylglycerols were found to be utilized for the synthesis of tissue triacylglycerols accoring to their dietary availability. Irrespective of the dietary fat, the saturated fatty acids were preferentially esterified at positions 1 and 3 and the unsaturated fatty acids at position 2 of tissue triacylglycerols. In the experimental group, however, very little of the dietary trans-octadecenoic acids was incorporated into either positions 1 or 3 or position 2 of tissue triacylglycerols. In diacylglycerophosphocholines of both groups, the dietary as well as endogenous palmitic and stearic acids were esterified predominantaly at position 1, whereas dietary linoleic acid and the polyunsaturated fatty acids derived therefrom were esterified almost exclusively at position 2. Relatively large proportions of trans-octadecenoic acids were selectively esterified at position 1 of diacylglycerophosphocholines of the experimental group. Reported specificities of enzymes that are involved in the biosynthesis of glycerolipids from sn-glycero-3-phosphate satisfactorily account for the positional distribution of acyl moieties.