Effect of folic acid plus glycine supplement on uterine prostaglandin and endometrial granulocyte-macrophage colony-stimulating factor expression during early pregnancy in pigs

Abstract

The objective was to determine the effects of folic acid+glycine supplement on uterine metabolism of prostaglandin and mRNA expression of endometrial granulocyte-macrophage colony-stimulating factor (GM-CSF) in nulliparous (NYL) and multiparous Yorkshire–Landrace (YL) sows, and in multiparous Meishan–Landrace sows (ML). In each of these three groups, sows were randomly assigned to two treatments: 15 ppm folic acid+0.6% glycine or no supplement. The dietary supplement was given from the estrus before mating to slaughter on Day 25 of pregnancy. At slaughter, endometrial tissue was collected to determine endometrial expression levels of GM-CSF mRNA, cyclooxygenase-1 (COX1) and -2 (COX2) and to evaluate in vitro endometrial secretion of prostaglandin E 2 (PGE 2) secretion. Allantoic fluid samples were also collected to determine the concentration of PGE 2, prostaglandin F 2α (PGF 2α), estradiol-17β (E 2), progesterone (P 4), and transforming-growth factor-β 2 (TGF-β 2). The allantoic contents of PGF 2α, E 2 and P 4, and endometrial in vitro secretion of PGE 2 were not significantly influenced by the folic acid+glycine supplement. The folic acid+glycine supplement tended ( P<0.07) to increase allantoic content of PGE 2 and TGF-β 2 in all sows and increased ( P<0.05) endometrial expression of COX2, especially in NYL sows. The endometrial expression of COX1 was decreased ( P<0.05) by folic acid+glycine supplement, especially in multiparous YL sows. The allantoic contents of PGE 2 and PGF 2α were not significantly affected by sow type. However, NYL sows had higher ( P<0.05) endometrial in vitro secretion of PGE 2 and allantoic content of P 4 than multiparous YL and ML sows. The allantoic content of E 2 was also higher ( P<0.05) in NYL sows than in multiparous ML sows only. The allantoic content of TGF-β 2 was lower ( P<0.05) in multiparous ML than in multiparous YL only sows. Finally, in YL and NYL sows, folic acid+glycine supplement decreased ( P<0.05) the endometrial expression of GM-CSF but not in ML sows. In summary, folic acid+glycine supplement altered endometrial expression of GM-CSF and uterine metabolism of prostaglandins during the post-attachment period of porcine embryos but some of these effects were manifest only in Meishan and nulliparous sows.