Altering n-3 to n-6 polyunsaturated fatty acid ratios affects prostaglandin production by ovine uterine endometrium.

Consumption of n-3 polyunsaturated fatty acids (PUFAs) is considered beneficial to health but effects on fertility remain uncertain. This study investigated the effect of n-3 PUFA supplementation on endometrial prostaglandin (PG) production. Ovine uterine endometrial cells were cultured to confluence in DMEM/F12 medium containing 10% foetal bovine serum. Stromal and epithelial cell populations were confirmed by immunocytochemistry. Cultures were supplemented with 0, 20 or 100 µM of α-linolenic acid (ALA), stearidonic acid (SDA), eicosapentaenoic acid (EPA) with lipopolysaccharide (LPS) at 0 and 0.1 µg/ml, or different combinations of EPA with arachidonic acid (AA) in serum-free medium for 24h. PGs were quantified using radioimmunoassay and PG-endoperoxide synthase (PTGS) isoforms, PGE and PGF synthase (microsomal PGES1 and PGFS) mRNAs by qPCR. LPS increased PGE2 production significantly without changing PGF2α production, causing increased PGE2:PGF2α ratios. ALA and SDA increased PGE2, PGF2α and PGE2:PGF2α ratios (P<0.05-0.01) while EPA alone did not affect PG generation. AA significantly stimulated PTGS1 and PTGS2 mRNA expression and PGE2 and PGF2α production (P<0.01). The stimulatory effect of AA was attenuated by up to 80% (P<0.05) when AA was combined with EPA. The PGE2:PGF2α ratio was not affected by AA or EPA alone, but increased when these two PUFAs were combined (P<0.05). SDA and EPA decreased PTGS1 mRNA expression (P<0.05) but did not alter PTGS2 expression. EPA and AA up-regulated mPGES1 expression (P<0.05) without affecting PGFS expression. Since AA is preferentially incorporated in uterine endometrium to produce 2-series PGs, alteration of PG production by EPA may affect many reproductive processes.

The effect of supplementation with n-6 polyunsaturated fatty acids on 1-, 2- and 3-series prostaglandin F production by ovine uterine epithelial cells.

Linoleic acid (LA, 18:2n-6) has variously been found to increase or inhibit synthesis of 2-series prostaglandins (PGs), derived from arachidonic acid (AA, 20:4n-6). gamma-linolenic acid (GLA, 18:3n-6) containing oils are promoted to women for a variety of reproductive problems. Little is known concerning their actual effects on reproduction. We investigated the effects of LA, GLA and AA supplementation (25-100 microM) on basal and oxytocin (OT) stimulated production of 1-, 2- and-3 series PGs by uterine epithelial cells isolated from non-pregnant ewes, used as a model system to study endometrial PG production. PGF isomers were measured using radioimmunoassays following separation by high performance chromatography (HPLC). OT challenge increased the proportion of PGF2alpha in relation to PGF1alpha and PGF3alpha in control medium. LA supplementation decreased all PGF isomer production and reduced responsiveness to OT. GLA increased both absolute and proportional PGF1alpha production and slightly enhanced PGF2alpha generation. AA increased PGF2alpha generation and raised its isometric proportion. Both GLA and AA increased overall PGF output significantly but prevented the cells from responding to OT. These results suggest that consumption of LA and GLA are likely to differentially alter both uterine PG metabolism and responsiveness to OT. This may have implications for the control of a variety of reproductive processes.

The effect of dietary supplementation with linoleic acid to late gestation ewes on the fatty acid composition of maternal and fetal plasma and tissues and the synthetic capacity of the placenta for 2-series prostaglandins.

Linoleic acid (18:2n-6) is metabolised to arachidonic acid (20:4n-6), the precursor for 2-series prostaglandins (PGs). Increased consumption of 18:2n-6 during pregnancy may thus modify PG synthesis during labour. We have investigated whether increased 18:2n-6 composition during gestation altered the fatty acid consumption and PG synthesis of maternal and fetal tissues in the sheep. Ewes were fed a control diet or a diet providing 40% more 18:2n-6 from 96 days gestation. Half of each group received dexamethasone on day 136 to up-regulate the PG synthetic pathways promoting parturition. Maternal and fetal tissues were collected at 138 days. The 18:2n-6 diet significantly increased the 20:4n-6 content of maternal plasma, fetal plasma and allantochorion (51-81%) phosphatidylcholine, and fetal liver (40%) and maternal caruncular endometrium (57%) phosphatidylethanolamine. Increased 18:2n-6 intake increased production of PGF(2alpha) and PGE(2) in all placental tissues (maternal caruncular and intercaruncular endometrium and fetal allantochorion) by 23-98%, whereas dexamethasone increased it by 32-142%. This suggests that consumption of an 18:2n-6-enriched diet in late pregnancy enhanced placental PG production by increasing the supply of 20:4n-6. Variations in the extent to which the diet altered the polyunsaturated fatty acid (PUFA) content of the different tissues indicated complex interactions between nutrient availability and metabolic adaptation.

Roles for prostaglandins in the steroidogenic response of human granulosa cells to high-density lipoproteins.

In human granulosa-lutein cells, high-density lipoproteins (HDL) can stimulate progesterone synthesis. The objective of the present study was to establish whether prostaglandins (PGs) participate in the steroidogenic response to HDL. Both HDL and apolipoprotein AI (ApoAI) stimulated concentration-dependent increases in PGE2, cAMP and progesterone accumulation. The minimum concentrations of HDL and ApoAI required to elevate PGE2 production were the same as those required to stimulate cAMP accumulation and progesterone synthesis. Concentrations of PGE2 were elevated within 10 min in cells exposed to HDL and rose progressively over 24 h, whereas cAMP and progesterone were only increased significantly after 24 h of treatment with HDL. Co-treatment with prostaglandin H synthase inhibitors (meclofenamic acid and indomethacin) abolished the cAMP and progesterone responses to both HDL and ApoAI. Hence, the ability of HDL to stimulate progesterone synthesis can be mimicked by ApoAI and appears to involve increased generation of one or more luteotrophic PGs, possibly acting via cAMP.

Ovarian modulators of 11beta-hydroxysteroid dehydrogenase (11beta HSD) activity in follicular fluid from bovine and porcine large antral follicles and spontaneous ovarian cysts.

In the ovary, cortisol is oxidized to cortisone by 11beta-hydroxysteroid dehydrogenase (11betaHSD). The present study investigated whether follicular fluid (FF) from large antral follicles and spontaneous ovarian cysts, isolated from bovine and porcine ovaries, contained modulators of 11betaHSD activity. Whereas FF from antral follicles had no significant effect over 1 h on NADP+-dependent 11betaHSD activity in rat kidney homogenates, enzyme activity was inhibited by FF from bovine and porcine ovarian cysts (80.5% +/- 2.3% and 72.8% +/- 3.4% of control, respectively). Following C18 reverse-phase chromatography, the hydrophilic fractions of FF from bovine and porcine antral follicles stimulated NADP+-dependent 11betaHSD activities (111.5% +/- 21.6% and 55.2% +/- 5.7% respectively). Hydrophobic compounds inhibited NADP+-dependent cortisol oxidation by 58.2% +/- 5.1% (bovine) and 45.7% +/- 2.0% (porcine). In both species, FF from ovarian cysts appeared to contain less of the hydrophilic stimuli to 11betaHSD activity and more of the hydrophobic inhibitors. The FF from antral follicles and ovarian cysts, and the C18 fractions thereof, had no significant effect on NAD+-dependent cortisol oxidation. The ovarian modulators of NADP+-dependent 11betaHSD activities did not coelute with cortisol, cortisone, estradiol, testosterone, progesterone, pregnenolone, and cholesterol. However, the 11betaHSD stimuli in porcine FF from both antral follicles and cysts coeluted with prostaglandin (PG) E2 and PGF2alpha. We conclude that large antral follicles and spontaneous ovarian cysts, in both the cow and the pig, contain ovarian modulators of the NADP+-dependent 11betaHSD activity. Moreover, FF from spontaneous ovarian cysts, because of decreased content of the 11betaHSD stimulus accompanied by increased content of the 11betaHSD inhibitors, exerts a net inhibitory effect on 11betaHSD activity.