Effect of low methionine, choline deficient diets upon major unsaturated phosphatidyl choline fractions of rat liver and plasma

Abstract

To see how the metabolism of specific phosphatidyl choline fractions might be affected when only a limited source of methyl groups was available, rats were fed for 7 days a low methionine, choline-deficient diet or one supplemented with either choline or methionine. Prior to killing, they were injected with -14C-methyl methionine and liver and plasma phosphatidyl choline isolated and separated by argentation chromatography into 3 major unsaturated fractions. Fatty acid composition and radioactivity of the fractions were determined. Deficient rats had reduced total liver phosphatidyl choline when compared with the supplemented groups, but the proportions of 20:4 and 22:6 fatty acids in the total phosphatidyl choline were unchanged. Plasma phosphatidyl choline also was reduced sharply by the deficiency, as was its proportion of 20:4 fatty acid. Specific activities of the liver 22:6, 20:4, and 18:2 phosphatidyl choline fractions showed that deficient rats had less radioactivity in their 20:4 and 18:2 phosphatidyl choline than did the supplemented animals. Plasma phosphatidyl choline fractions presented a similar pattern. Feeding methionine or choline nearly doubled radioactive methyl group incorporation into the 20:4 phosphatidyl choline fraction of liver and plasma, while incorporation into the 22:6 phosphatidyl choline was reduced or unchanged. The results suggested that, in the rat, limited availability of methyl groups altered the metabolism of liver and plasma phosphatidyl choline fractions. Methionine, as a source of labile methyl groups, appears necessary for the normal synthesis of certain unsaturated phosphatidyl choline fractions (particularly 20:4 phosphatidyl choline). Transmethylation of phosphatidyl ethanolamine molecular species to the corresponding phosphatidyl choline species may be an important reaction in normal lipid metabolism and transport. Relative affinities for incorporation of the labeled methyl groups into the phosphatidyl choline fractions of either deficient or supplemented rats were: 22:6 less than 20:4 less than 18:2.

Effect of Dietary Methionine, Arginine and Ornithine on the Metabolism and Accumulation of Polyamines, S-Adenosylmethionine and Macromolecules in Rat Liver and Skeletal Muscle

“…Adequate dietary methionine supply seems to be required to maintain normal hepatic concentrations of riboflavins [22] and coenzyme A [23] as well as interme diates of serine metabolism [24], If methio nine deprivation results in or is accompa nied by a deficiency in methyl groups, which may occur in rapidly growing animals, marked structural changes in the composi tion of membranes are likely to take place [25]. On the other hand, some mammalian systems seem to be equipped with adaptable methionine salvage pathways that are effi cient enough to render the nutritional essen tiality of methionine unlikely in the presence of adequate methyl donors [3].…”

Effects of a methyl-deficient diet on rat liver phosphatidylcholine biosynthesis

“…In a similar manner, it is disputed througl~out the literature as to whether methylation sf PtdEtn increases (41,6,(14)(15)(16)(17)(18)(19)(20)(21)(22) or decreases (3,7,13,(23)(24)(25)(26)(27) during choline deficiency. Specifically, a significant increase in PtdEtn methylation during choline and (or) methisnine deficiency is consistently observed by in vitro analysis (4,14,15,(20)(21)(22) ; however, incorporation of [methyl-14C]methionine (1 3, 17-20, 26, 271, [ I T ] -ethanslamine (23-25), or 13,16,17) has resulted in conflicting interpretations.…”

Changes in long‐chain fatty acid composition of milk fat globule membrane and expression of mammary lipogenic genes in dairy cows fed sunflower seeds and rumen‐protected choline

“…Although choline can be synthesized endogenously from methionine, high yielding dairy cows use methionine for milk protein synthesis; therefore, priority to use methionine for milk protein synthesis may result in suboptimal choline availability (Baldi & Pinotti, 2006). Studies in rats show that methionine and choline deficiency alters the incorporation of polyunsaturated fatty acids into phosphatidylcholine secreted into milk (Lyman, Giotas, Medwadowski, & Miljanich, 1975).…”