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Regioisomers of Phosphatidylcholine Containing DHA and Their Potential to Deliver DHA to the Brain: Role of Phospholipase Specificities
Author(s) -
Chen Su,
Subbaiah Papasani V.
Publication year - 2013
Publication title -
lipids
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.601
H-Index - 120
eISSN - 1558-9307
pISSN - 0024-4201
DOI - 10.1007/s11745-013-3791-5
Subject(s) - phosphatidylcholine , docosahexaenoic acid , structural isomer , biochemistry , phospholipase , chemistry , phospholipase a2 , fatty acid , enzyme , biology , stereochemistry , phospholipid , polyunsaturated fatty acid , membrane
Because neurons cannot synthesize docosahexaenoic acid (DHA), a dietary supplement of DHA in the form of phospholipids is recommended for maintaining proper brain functions. A model for delivering dietary sn ‐ 2 ‐DHA phosphatidylcholine (PtdCho) to the brain involves phospholipase A 2 based deacylation/reacylation cycle followed by delivery of DHA through high‐density lipoproteins that bind to the brain capillary endothelial cells in the blood–brain barrier (BBB). Our previous study demonstrated preference of endothelial lipase (EL) for PtdCho species that contain sn ‐2‐DHA, resulting in production of sn ‐2‐DHA lysoPtdCho that is preferentially taken up by the brain. However, since CoA‐dependent reacylation of lysoPtdCho with DHA at the sn ‐2 position is not favored in vivo, we proposed that sn ‐1‐DHA PtdCho in the diet may be a superior source of DHA for the brain. To test this hypothesis, DHA PtdCho regioisomers were prepared, and their hydrolysis by physiologically relevant phospholipases was determined. The data presented here show that: (1) group X secretory PLA 2 (sPLA 2 ) is about threefold more active than group V sPLA 2 in releasing sn ‐2 fatty acids from DHA regioisomers, and (2) EL shows its specificity for DHA PtdCho species in a concentration independent manner, suggesting that the enzyme could play a major role in generating free sn ‐1‐DHA or/and sn ‐2‐DHA lysoPtdCho from the regioisomers in the BBB. We propose that PtdCho species containing sn ‐1‐DHA may have the advantages of both “preserving” DHA in deacylation/reacylation cycle and releasing free DHA in the BBB for uptake by the brain.