Effect of Feeding Egg Yolk on Liver Lipids of Rats

Abstract

The deposition of fat and sterol-ester in the livers of animals fed diets rich in cholesterol has been reported by a number of workers. The following is a report of one of a series of experiments made to determine the influence of other dietary constituents than sterol on this lipid deposition in the livers of rats.

The experimental diet fed contained dried egg yolk powder 25.3%, extracted casein 12.6%, agar 4%, Osborne Mendel salts 3%, starch 55.1% with supplements of yeast and cod liver oil. This represented egg yolk protein 8.4%, egg yolk lipids 16%, of which 1/16 was cholesterol, 1/4 lecithin. For the control diet the egg yolk powder was first extracted with alcohol-ether and the egg yolk lipid replaced by Crisco. Each experimental group consisted of 8 rats, while there were 12 in the control group, littermates of the experimental animals.

The rats were placed on the diet at weaning time. Both experimental and control groups grew extremely well. They were killed after approximately 60 days on the diet. The livers of the experimental animals presented the typical whitish coloration of sterol-fed animals. The average total fatty acid content of the livers was for the males of the experimental group, 9.3%; for the females, 11.7%. For the control groups the corresponding figures were: males 7.5%; females 7.4%. Total cholesterol (digitonid precipitation) for the males of the experimental group was 2.58%; for the females 3.86%. For the control groups the corresponding figures were: males .48%; females .30%. There was very little difference in the free cholesterol in the control and experimental groups. The average for both groups was approximately 0.3%. Likewise the figures for lecithin were not very different, the average for males in both groups being 2.7% and for females in both groups 2.25%. It was noted, however, that the odor of choline, presumably from decomposition of lecithin, was very strong in the tissues of the animals of the experimental group and absent in those of the control group.