Incorporation and Metabolism of Dietary Trans Isomers of Linolenic Acid Alter the Fatty Acid Profile of Rat Tissues

To study the influence on lipid metabolism and platelet aggregation of the fatty acid isomerization that occurs during heat treatment, weanling rats were fed for 8 wk a diet enriched with 5% isomerized (experimental group) or normal (control group) canola oil. Geometrical isomers of [Alpha]-linolenic acid representing 0.2 g/100 g of the experimental diet were incorporated into liver, platelets, aorta and heart, at the expense of their cis homologue and of 18:2(n-6). The major isomer, 9c,12c,15t-18:3, was also metabolized to 5c, 8c, 11c, 14c, 17t-20:5 and to an unknown compound, found in liver, platelets and aorta, which has been identified tentatively as 7c, 10c, 13c, 16c, 19t-22:5. The greater 20:4(n-6)/18:2(n-6) ratio in the liver, platelets and heart of the experimental group than the control group indicated an enhancement of desaturation activities. This induced a higher content of long-chain (n-6) fatty acids in the experimental group. Platelet aggregation tended to be slightly higher (P = 0.065) in the experimental group. We conclude that 0.2 g of trans isomers of [Alpha]-linolenic acid per 100 g of diet was sufficient to be incorporated and metabolized, thus altering the fatty acid profile of rat tissues. J. Nutr. 130: 2550-2555, 2000. KEY WORDS: * dietary trans [Alpha]-linolenic acid * trans 22:5 * platelet aggregation * rats