Arachidonic Acid Predominates in the Membrane Phosphoglycerides of the Early and Term Human Placenta

Abstract

The aim of this study was to determine whether the high concentration of arachidonic acid (AA) in term placentae accumulates during pregnancy or is an inherent characteristic of placental lipids. We investigated the lipid content and fatty acid composition of the human placental phospholipids at 2 gestational periods, early in pregnancy (8-14 wk, n = 48) and at term (38-41 wk of gestation, n = 19). The subjects were healthy, normotensive, and free of medical and obstetric complications. The lipid concentration of placentae increased from 0.8% in early gestation to 1.4% at term (P < 0.0001). The mean proportions of AA were lower in the choline (P < 0.05), inositol (P < 0.0001), and ethanolamine (P < 0.0001) phosphoglycerides of the term compared with the early placenta. In contrast, the proportions of the immediate precursor of AA, dihomo-gamma-linolenic acid (DGLA), were higher in the term placenta, particularly in the inositol and serine phosphoglycerides (P < 0.0001). In sphingomyelin, the percentage of lignoceric acid was increased and that of nervonic acid was reduced at term (P < 0.01). The dominance of AA, particularly in the early placenta, suggests that it has an important role for placental development, i.e., organogenesis and vascularization. There was no evidence of an accumulation of AA in the placenta toward term, which might be a trigger for parturition. In contrast, the increased proportion of DGLA (precursor of the vasorelaxant and anticoagulant prostaglandin E(1)) at term is more consistent with a profile favoring optimal blood flow to nourish the fetal growth spurt.

Gestational diabetes mellitus enhances arachidonic and docosahexaenoic acids in placental phospholipids

“…In addition, there was no difference in either of the two FA between the Asian, African, and Caucasian subjects in the control group. This is consistent with our previous study (31), which showed that ethnicity had no significant effect on placental AA and DHA.…”

“…First, the human placenta is a vascular organ rich in phospholipids (28)(29)(30), which in turn are rich in PUFA, particularly AA (31). Second, the placenta lacks desaturase activity (13), and is thought to be primarily dependent on maternal circulation for the supply of these vital FA.…”

Fatty Acids as Biocompounds: Their Role in Human Metabolism, Health and Disease - A Review. Part 2: Fatty Acid Physiological Roles and Applications in Human Health and Disease

“…Also, LA and DGLA (n-6 PUFA) are found in higher levels compared to placental LC n-3 PUFA (ref. 72,74,75 ). In relation to this, AA-derived PG are related to the maintenance of pregnancy and initiation of labor 76 .…”

Background Paper on Fat and Fatty Acid Requirements during Pregnancy and Lactation

“…Placental unsaturated phospholipids are dominated by AA, which appear at a several-fold greater concentration than DHA and other PUFA. AA precursors linoleic acid (LA) and di homo-␥-linolenic acid (DGLA) are also at higher concentrations than n-3 precursors [Bitsanis et al, 2005]. Biosynthesis of AA from its primary dietary precursor LA is thought to be rapid because the 3 enzymatic steps ( ⌬ 6-desaturation, elongation, ⌬ 5-desaturation) are usually considered to be rapid compared to the 7 steps involving 2 organelles in the accepted pathway for DHA biosynthesis.…”