Absorption of Molecular Forms of Dietary Docosahexaenoic acid (DHA) and Their Potential to Provide DHA to the Brain

Abstract

In this study, we tested the hypothesis that the presence of dietary DHA in the sn‐1 position of phosphatidylcholine (PC) results in greater incorporation of absorbed DHA into the phospholipids of plasma lipoproteins, compared to its presence in triacylglycerol (TG) or in the sn‐2 position of PC, because of the positional specificities of the pancreatic enzymes. Micelle containing the DHA either in lyso PC (LPC) form (surrogate for the dietary sn‐1 DHA PC) or as free fatty acid (surrogate for dietary DHA TG and sn‐2 DHA PC) were infused intraduodenally into lymph fistula rats, and the concentration of DHA in PC and TG of lymph chylomicrons and HDL was determined by GC and LC/MS. The total amount of DHA absorbed was comparable with the two preparations. However the ratio of DHA in PC/TG in lymph was much higher (0.4) after LPC‐DHA infusion, compared to free DHA infusion (0.1). Also, more DHA appeared in HDL fraction of lymph after LPC‐DHA infusion, and more of the HDL DHA was in PC than in TG. Similar results were obtained with CACO‐2 cells grown on micropore membranes in transwell plates. The two types of DHA micelle were added to the apical medium and the lipoproteins in the basolateral medium were analyzed after 24 h. The results showed a 4‐fold higher incorporation of DHA into PC in presence of LPC DHA compared to free DHA. These data indicate that the dietary DHA in the sn‐1 position of PC is potentially more available than the DHA in sn‐2 position of PC (krill oil) or in TG (fish oil) for uptake by the brain since the phospholipid form of DHA, especially from HDL, is transported more efficiently into the brain. Supported by NIH R21 AT008457.