Effect of Dietary Supplements of Cystine upon Growth, Liver Fat and Choline Biosynthesis in the Choline-deficient Rat

Abstract

Evidence to support an explanation for the antilipotropic effect of supplementary dietary cystine in choline-deficient rats was presented. The results of these studies showed that supplementary cystine aggravates a choline deficiency under dietary conditions where cystine does not improve the nutritional state of the animal. This was accomplished by using, as the sole dietary protein, isolated soy protein which has been shown not to be limiting in cystine. These experimental results are in conflict with the prevailing hypothesis that cystine acts by improving the nutritional state of the animal which causes an increase in the animal's requirement for methionine and choline. Under these same conditions, supplementary cystine caused a decrease in the synthesis of choline in the liver, thus supporting an hypothesis that cystine increases the dietary requirement for choline by limiting its biosynthesis through an inhibition of methionine transmethylation.