A comparison of the metabolism of elaidic, oleic, palmitic, and stearic acids in the rat.

SUMMARY A comparison has been made of the metabolism of l-C'4-labeled oleic, elaidic, palmitic, and stearic acids in the rat. Each acid was fed as a component of randomly rearranged soybean oil. All the acids were more than 96% absorbed. The rate of catabolism and the extent to which elaidic acid was ex-creted in the respiratory CO, were essentially the same as those of oleic acid and both of these acids were similar to pal-mitic acid. Oleic, elaidic, and palmitic acids were catabolized to COZ to a greater extent than was stearic acid. Elaidic acid seemed to be incorporated into the lymph phospholipids to a slightly greater extent than was oleic acid during the peak of absorption; otherwise, elaidic acid was similar to oleic acid in its absorption and distribution among the lymph lipids. Stearic acid was incorporated into the lymph phospholipids to a considerably greater degree (-8%) than were the other acids (-2-3%). The major transport of each fatty acid was via the lymph glycerides, being-907" for stearic acid and ~ 9 7 7 ~ for the other aci6s. THE METABOLISM of the saturated fatty acids has been thoroughly studied and the catabolic fate of the carbon chain of these acids is known. However, the metabolism of the unsaturated fatty acids has not been studied as completely. For example, the effect of the geometry of the double bond in the unsaturated acids upon the catabolic fate of that acid in vivo has not been studied The evidence is clear that the animal is capable of metabolizing trans fatty acids such as elaidic acid. Early work by Sinclair (1, 2) and Barbour (3) has shown that dietary elaidic acid can be absorbed and incorporated into the body tissues. A later report by Johnston et al. (4) confirmed these findings. I t was also shown by these investigators (1, 3, 4) that, once incorporated, the isomeric acids disappear from the tissues on cessation of their incorporation into the diet. Also, Dhopeshwarkar and Mead (5) have reported the direct reduction of fully. elaidic acid to stearic acid in vivo. That animal tissues possess the metabolic machinery for catabolizing a trans fatty acid, elaidic acid, was shown by Kennedy and Lehninger (6) , who demonstrated that elaidic acid could be oxidized by rat liver mitochondria. However, the specific behavior of the trans fatty acids in vivo is unknown. Therefore, an investigation was initiated …