Dietary fats containing concentrates of cis or trans octadecenoates and the patterns of polyunsaturated fatty acids of liver phosphatidylcholine and phosphatidylethanolamine.

The effects of the mixed cis- 18:1 isomers and mixed trans- 18:1 isomers present in partially hydrogenated soybean oil (PHSO) upon the patterns of polyunsaturated fatty acids (PUFA) in liver phosphatidylcholine (PC) and phosphatidylethanolamine (PE) were studied in rats fed concentrates of cis- 18:1 or trans- 18:1 isomers isolated as triacylglycerides from PHSO. The cis- 18:1 and trans- 18:1 concentrates were fed at levels equal to those present in PHSO fed at 17.9% of the diet. All diets contained the required amounts of both linoleic and linolenic acids. The trans- 18:1 concentrate was found to suppress the levels of 20:4 omega 6 and 20:3 omega 9, and to increase the levels of 18:2 omega 6 and 20:5 omega 3 in PC and PE. The cis- 18:1 concentrate suppressed 20:4 omega 6 in PC, 20:5 omega 3 in PC and PE, and 18:2 omega 6 in PC, but increased the levels of 20:4 omega 6 in PE, and 20:3 omega 9 in PC and PE. The cis- 18:1 concentrate was more effective than the trans concentrate in suppressing 22:6 omega 3. The trans- 18:1 concentrate was more effective in suppressing 20:4 omega 6. The trans- 18:1 isomers appear to modify PUFA metabolism by inhibition of PUFA synthesis, whereas the cis- 18:1 isomers appear to complete with 2-position fatty acyl transfer and to inhibit omega 3 PUFA acylation.