Methionine, Homocystine, Choline, Folic Acid and Vitamin B12 in the Nutrition of the Mouse

Abstract

Weanling mice fed a methionine-free, choline-free basal diet, supplemented with homocystine, died or failed to grow when either folic acid or vitamin B₁₂ was added. The addition of both vitamins permitted survival but little growth. Further supplementation with glycine, serine and threonine resulted in 50% of normal growth. The addition of choline alone to the homocystine-supplemented basal diet permitted only slight growth, whereas about 50% of normal growth was obtained with betaine. The addition of folic acid in the presence of either choline or betaine resulted in nearly normal growth. The further addition of vitamin B₁₂ had only a slight effect. Methionine alone permitted nearly normal growth which was improved slightly by the presence of choline, folic acid and vitamin B₁₂. The liver choline oxidase activity was markedly reduced in mice fed the basal diet supplemented with homocystine. The reduction in activity was largely prevented by dietary supplements of folic acid and partially with vitamin B₁₂. Choline was also effective, whereas betaine was ineffective. Liver transmethylase activity was reduced when choline, folic acid, and vitamin B₁₂ were omitted from the basal-homocystine diet. The activity was improved when folic acid and vitamin B₁₂ were added to the diet. When choline was present in the diet, supplements of folic acid permitted normal activity while partial improvement was noted with supplements of vitamin B₁₂. Extremely fatty livers were observed in mice fed the basal-homocystine diet, either in the presence or absence of folic acid and vitamin B₁₂. When choline or betaine was present, the liver fat was greatly reduced. Normal values were obtained when choline, folic acid and vitamin B₁₂ were fed.