Effect of ω-3 supplementation on placental lipid metabolism in overweight and obese women

Abstract

Background: The placentas of obese women accumulate lipids that may alter fetal lipid exposure. The long-chain omega-3 fatty acids (n–3 FAs) docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) alter FA metabolism in hepatocytes, although their effect on the placenta is poorly understood.

Objective: We aimed to investigate whether n–3 supplementation during pregnancy affects lipid metabolism in the placentas of overweight and obese women at term.

Design: A secondary analysis of a double-blind randomized controlled trial was conducted in healthy overweight and obese pregnant women who were randomly assigned to DHA plus EPA (2 g/d) or placebo twice a day from early pregnancy to term. Placental FA uptake, esterification, and oxidation pathways were studied by measuring the expression of key genes in the placental tissue of women supplemented with placebo and n–3 and in vitro in isolated trophoblast cells in response to DHA and EPA treatment.

Results: Total lipid content was significantly lower in the placentas of overweight and obese women supplemented with n–3 FAs than in those supplemented with placebo (14.14 ± 1.03 compared with 19.63 ± 1.45 mg lipid/g tissue; P < 0.05). The messenger RNA expression of placental FA synthase (FAS) and diacylglycerol O-acyltransferase 1 (DGAT1) was negatively correlated with maternal plasma enrichment in DHA and EPA (P < 0.05). The expression of placental peroxisome proliferator–activated receptor γ (r = −0.39, P = 0.04) and its target genes DGAT1 (r = −0.37, P = 0.02) and PLIN2 (r = −0.38, P = 0.04) significantly decreased, with an increasing maternal n–3:n–6 ratio (representing the n–3 status) near the end of pregnancy. The expression of genes that regulate FA oxidation or uptake was not changed. Birth weight and length were significantly higher in the offspring of n–3-supplemented women than in those in the placebo group (P < 0.05), but no differences in the ponderal index were observed. Supplementation of n–3 significantly decreased FA esterification in isolated trophoblasts without affecting FA oxidation.

Conclusion: Supplementing overweight and obese women with n–3 FAs during pregnancy inhibited the ability of the placenta to esterify and store lipids. This trial was registered at clinicaltrials.gov as NCT00957476.

FIGURE 1

Quantification of total lipid in the placentas of women supplemented with placebo or n–3 FAs. Total lipid was extracted with the use of the Folch method and normalized to tissue weight (placebo: n = 16; n–3 FAs: n = 17). Data are means ± SEMs. **P < 0.01 compared with placebo by Student’s t test. FA, fatty acid.

FIGURE 2

Effect of maternal n–3 supplementation during pregnancy on mRNA expression of placental genes involved in FA transport/uptake (A), FA oxidation (B), and FA esterification (C). Data (means ± SEMs) are expressed as the ratio of gene of interest:reference gene (L19). None of the genes studied was significantly different between groups by Student’s t test (placebo: n = 16; n–3 FAs: n = 17). ACC, acetyl-CoA carboxylase; AMPK-α, AMP-activated protein α AU, arbitrary unit; CD36, fatty acid translocase; CPT1b, carnitine palmitoyltransferase 1b; DGAT, diacylglycerol O-acyltransferase; EL, endothelial lipase; FA, fatty acid; FABPpm, plasma membrane fatty acid–binding protein; FABP-4, fatty acid–binding protein 4; FAS, fatty acid synthase; LPL, lipoprotein lipase; mRNA, messenger RNA; PLIN2, peripilin 2; PPAR, peroxisome proliferator-activated receptor; SCD, steroyl-CoA desaturase; SREBP1c, sterol regulatory element binding transcription factor 1.

FIGURE 3

Correlations between placental FAS, DGAT1 mRNA expression, and maternal plasma enrichment (Δ, calculated as visit 2 – visit 1) of DHA (A and B) and EPA (C and D) (placebo: n = 16; n–3 FAs: n = 17). Pearson’s correlation coefficients (r) are shown. P < 0.05 was considered statistically significant. AU, arbitrary unit; DGAT1, diacylglycerol O-acyltransferase 1; FA, fatty acid; FAS, fatty acid synthase; mRNA, messenger RNA.

FIGURE 4

Correlations between the maternal plasma n–3:n–6 ratio after supplementation (visit 2) and placental mRNA expression of PPAR-γ (A), DGAT1 (B), and PLIN2 (C) (placebo: n = 16; n–3 FAs: n = 17). Pearson’s correlation coefficients (r) are shown. P < 0.05 was considered statistically significant. AU, arbitrary unit; DGAT1, diacylglycerol O-acyltransferase 1; FA, fatty acid; mRNA, messenger RNA; PLIN2, peripilin 2; PPAR-γ, peroxisome proliferator-activated receptor-γ.

FIGURE 5

Representative Western blot of PPAR-γ in the placentas of obese and overweight women supplemented with n–3 FAs or placebo during pregnancy (A). Placental PPAR-γ/β-actin protein expression was negatively correlated with a maternal plasma n–3:n–6 ratio after supplementation (visit 2) (B) (placebo: n = 7; n–3 FAs: n = 7). Pearson’s correlation coefficient (r) is shown. P < 0.05 was considered statistically significant. FA, fatty acid; PPAR-γ, peroxisome proliferator-activated receptor-γ.

FIGURE 6

Fatty acid esterification and oxidation in trophoblasts isolated from obese women. [³H]PA esterification was significantly reduced in isolated trophoblast cells after treatment with 50 μM DHA, 50 μM EPA, and 50 μM DHA + 50 μM EPA for 18 h (A). [³H]PA oxidation was not significantly affected by any of the treatments (B). Data were calculated as a percentage of control ([³H]PA alone) for each independent experiment in triplicate and are expressed as means ± SEMs of 12 experiments (DHA + EPA, n = 5). *P < 0.05 compared with PA control by 1-factor ANOVA with Dunnett’s multiple comparison test. PA, palmitate.