[Studies of the effects of cis, cis and trans, trans-octadecadienoic acids on lipid metabolism in essential fatty acid deficient rats (author's transl)].

The effect of an essential fatty acid [EFA] deficiency in male Sprague-Dawley rats and its excerbation by inclusion of trans fatty acids in the diet were observed from the level and composition of serum lipoproteins. Male Sprague-Dawley rats were fed from weaning diet containing all essential nutrients and 10% of a fat supplement as safflower oil (SAFF] or hydrogenated coconut oil [HCO] for 28 weeks. At the end of 28 weeks, the blood was withdrawn from the retro-ocular plexes of 4 animals of each group, and lipoprotein lipid and fatty acids were analyzed. Another 5 animals of each group were switched to a 5% supplement of ethyl linolelaidate [TRANS]. In addition, the remaining 5 animals of HCO group were switched to SAFF diet. Lipoprotein lipid and fatty acid analyses were performed on the pooled serum in each group at 3, 7 and 14 days after switching the diet, and after 21 days serum was analyzed on the individual animal of each group. The results obtained were as follows: [1] With the development of an EFA deficiency in HCO group, there was a decrease in the high density lipoprotein [HDL] and increase in the very low density lipoprotein [VLDL] plus low density lipoprotein [LDL] fraction. [2] In a switching group from the SAFF to the TRANS supplement, the level of arachidonate in the serum lipid was decreased with a corresponding decrease in HDL, whereas linoleate, at least for the initial 3 weeks, decreased only in triglyceride fraction. [3] In a EFA deficient rat [HCO group] after switched to the TRANS supplement, HDL was further decreased and increase o VLDL-LDL was progressed. Consequently, the HDL: VLDL-LDL ratio was lowered strikingly. These changes in the EFA deficiency were accompanied by a large increase in monoenoic acids and a decrease in eicosatrienoic acid converted from oleic acid. [4] The administration of SAFF diet to the EFA deficient group induced a rapid increase in arachidonate in HDL, and decrease in eicosatrienoic acid and oleic acid. These changes were accompanied by a marked decrease in VLDL-LDL. It is suggested that the normal HDL might play an important role on catabolism of VLDL-LDL. These results suggest that polyunsaturated fatty acid, especially arachidonic acid rather than linoleic acid is essential to the formation and the function of HDL in the rats.