Effects of an essential fatty acid deficiency on serum lipoproteins in the rat

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Abstract
Studies are reported on the effect of an essential fatty acid (EFA) deficiency in male Sprague‐Dawley rats and its exacerbation by inclusion oftrans fatty acids in the diet on the level and composition of serum lipoproteins. Weanling male Sprague‐Dawley rats were fed diets containing all essential nutritients and a 5% fat supplement of safflower oil (SAFF) or hydrogenated coconut oil (HCO) in 2 experiments, one for 31 wk and the other for 17 wk. For the final 3 wk of each experiment, animals were switched from each group to a 5% supplement of a concentrate of ethyl linolelaidate (TRANS). In addition, a group of animals fed the HCO diet in the first experiment were also switched to the SAFF Diet. With the development of an EFA deficiency in the HCO group, there was a decrease in the high density lipoprotein (HDL) and an increase in the very low density plus the low density (VL‐LDL) lipoprotein fractions separated by heparin‐manganese precipitation. Switching animals of the HCO group to the TRANS supplement exaggerated this effect and produced a very low ratio of HDL‐to‐VL‐LDL. Analysis of the serum lipoproteins by polyacrylamide disc gel electrophoresis showed that an EFA deficiency produced a marked alternation of the HDL fraction. Changes also appeared to be produced in the VL‐LDL fraction by an EFA deficiency and particularly upon switching EFA‐deficient animals to the TRANS supplemented diet. Switching animals of the SAFF group to the TRANS supplement brough about an immediate reduction in HDL with a corresponding decrease in serum arachidonic acid. The data suggested a general relationship between arachidonic acid and the level and composition of HDL on the one hand, and 18∶1 and VL‐LDL on the other. Accordingly, the ratio of HDL‐to‐VL‐LDL appears to provide a sensitive biochemical index of the EFA status of the rat.