Effect of oxidized fats on the nutritive value of proteins. V. Liver and plasma lipids in rats fed casein reacted with oxidized ethyl linoleate.

Abstract

Experiments were performed to estimate the effect of casein reacted with oxidized ethyl linoleate (casein: lipid=2:1, w/w, at 50°C and RH 80.4% for 14 days) on the liver and plasma lipids of young rats. The results were compared with those of the ad libitum or pair feeding controls fed the unreacted casein. At a 9 % protein level, feeding the reacted casein resulted in depression of growth and enlargement of liver. Content of liver lipids and glycogen increased, whereas that of liver nitrogen and plasma lipids decreased. The increase in liver lipids was attributable to that of triglyceride. Percentage of stearic and arachidonic acids in liver total lipids of rats fed the reacted casein decreased and that of oleic acid increased. The inverse changes were observed in the composition of plasma lipids. Supplementation of 0.5% Lys or 0.5% Lys and 0.3% Met to the reacted casein exhibited no improvement of the growth and liver and plasma lipids. Further addition of 0.3% Thr showed considerable supplementary effects on the liver and plasma lipids. At a 20% protein level, in contrast to the experiments with a low protein level, the content of liver lipids was decreased: this was mainly attributable to the decrease in phospholipid. In liver lecithin, percentage of arachidonic acid decreased, while that of palmitic and linoleic acids increased. The present and previous experiments indicated that the responses of the liver lipids to the reacted casein or egg albumin markedly differed from each other.