| Summary: | Docosahexaenoic acid (DHA) is an omega-3 highly unsaturated fatty acid that plays an
important role in fetal brain development. The fetal demand for DHA appears to be met
by placental transport and various maternal physiological adaptations. Estrogen, which is
elevated during pregnancy, is associated with increased DHA biosynthesis, but estrogen
is also implicated in the synthesis of phospholipids, specifically the regulation of
phosphatidyl ethanolamine methyltransferase (PEMT) that methylates phosphatidyl
ethanolamine (PE) to form phosphatidyl choline (PC). PE in various tissues is typically
enriched in DHA relative to PC, but PC is the dominant phospholipid in plasma. The
conversion of PE to PC by PEMT as a potential mechanism to mobilize maternal DHA to
plasma for placental transport was examined in diets that mimic human fatty acid intakes
with and without DHA as well as in a standard rat chow diet low in DHA. Rats were
examined at baseline, day 15 and day 20 of pregnancy, and 7 days post partum. The
accumulation of fatty acids into lipid fractions in maternal plasma and liver were
determined with DHA in PC increasing dramatically at day 20, particularly in plasma.
PEMT mRNA expression was increased at day 15 and PEMT liver protein tended to be
increased at day 20 of pregnancy. In addition, increased dietary DHA appeared to be
associated with increased expression of PEMT suggesting DHA hepatic concentrations
may be upregulating PEMT by a substrate feed forward mechanism. Given the
supporting role of PEMT in mobilizing DHA, and the extent of the increase of DHA in
plasma PC during the last stages of pregnancy, other mechanisms are likely involved that
remain to be elucidated.
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