Plasma D9-PC and D3-PC metabolism in response to D9-choline supplements
PC is the major carrier for the plasma transport of long-chain polyunsaturated fatty acids (LC-PUFA), mainly arachidonic (ARA) and docosahexaenoic acid (DHA) to organs, via lipoproteins [In general, the formation of betaine, and its D9-enrichment correlated with the plasma concentrations of D3-PC (see supplementary Figure s5A). In this context, the lower increase in plasma D9-betaine and, subsequently, in D3-PC in response to D9-POPC, compared to its water-soluble D9-choline analogues, may be important for the homeostasis of methyl groups. In response to the ingestion of D9-POPC, compared to that of D9-choline chloride, D9-GPC and D9-phosphocholine, the generation of free D9-choline, D9-betaine and D6-dimethylglycine was decreased and, instead, (D9-PO)PC was used by the enterocytes via (D9-) lyso-PC re-acylation to PC for chylomicron formation. In line with this, D9-PC concentrations in plasma rapidly increase and maximal concentrations are highest after (D9-PO)PC as a choline supplement. Whilst D9-POPC resulted in lower plasma concentrations of free D9-choline, D9-betaine and D6-dimethylglycine (D6-DMG), it should be noticed that the administration of any water-soluble components not only normalises plasma choline concentrations, but may increase plasma betaine above physiological values [