Dietary supplementation with 0.4% L-arginine between days 14 and 30 of gestation enhances NO and polyamine syntheses and water transport in porcine placentae

Abstract

Background Most embryonic loss in pigs occurs before d 30 of gestation. Dietary supplementation with L-arginine (Arg) during early gestation can enhance the survival and development of conceptuses (embryo/fetus and its extra-embryonic membranes) in gilts. However, the underlying mechanisms remain largely unknown. Methods Between d 14 and 30 of gestation, each gilt was fed daily 2 kg of a corn- and soybean-meal based diet (12% crude protein) supplemented with either 0.4% Arg (as Arg-HCl) or an isonitrogenous amount of L-alanine (Control). There were 10 gilts per treatment group. On d 30 of gestation, gilts were fed either Arg-HCl or L-alanine 30 min before they were hysterectomized, followed by the collection of placentae, embryos, fetal membranes, and fetal fluids. Amniotic and allantoic fluids were analyzed for nitrite and nitrate [NOx; stable oxidation products of nitric oxide (NO)], polyamines, and amino acids. Placentae were analyzed for syntheses of NO and polyamines, water and amino acid transport, concentrations of amino acid-related metabolites, and the expression of angiogenic factors and aquaporins (AQPs). Results Compared to the control group, Arg supplementation increased (P < 0.05) the number of viable fetuses by 1.9 per litter, the number and diameter of placental blood vessels (+ 25.9% and + 17.0% respectively), embryonic survival (+ 18.5%), total placental weight (+ 36.5%), the total weight of viable fetuses (+ 33.5%), fetal crown-to-rump length (+ 4.7%), and total allantoic and amniotic fluid volumes (+ 44.6% and + 75.5% respectively). Compared to control gilts, Arg supplementation increased (P < 0.05) placental activities of GTP cyclohydrolase-1 (+ 33.1%) and ornithine decarboxylase (+ 29.3%); placental syntheses of NO (+ 26.2%) and polyamines (+ 28.9%); placental concentrations of NOx (+ 22.5%), tetrahydrobiopterin (+ 21.1%), polyamines (+ 20.4%), cAMP (+ 27.7%), and cGMP (+ 24.7%); total amounts of NOx (+ 61.7% to + 96.8%), polyamines (+ 60.7% to + 88.7%), amino acids (+ 39% to + 118%), glucose (+ 60.5% to + 62.6%), and fructose (+ 41.4% to + 57.0%) in fetal fluids; and the placental transport of water (+ 33.9%), Arg (+ 78.4%), glutamine (+ 89.9%), and glycine (+ 89.6%). Furthermore, Arg supplementation increased (P < 0.05) placental mRNA levels for angiogenic factors [VEGFA120 (+ 117%), VEGFR1 (+ 445%), VEGFR2 (+ 373%), PGF (+ 197%), and GCH1 (+ 126%)] and AQPs [AQP1 (+ 280%), AQP3 (+ 137%), AQP5 (+ 172%), AQP8 (+ 165%), and AQP9 (+ 127%)]. Conclusion Supplementing 0.4% Arg to a conventional diet for gilts between d 14 and d 30 of gestation enhanced placental NO and polyamine syntheses, angiogenesis, and water and amino acid transport to improve conceptus development and survival.

Dietary supplementation with L-citrulline improves placental angiogenesis and embryonic survival in gilts

“…41 This necessitates the placental transport of water from mother to fetus. We reported that porcine placentae expressed AQPs 1, 2, 3, 4, 5, 8, 9, and 11, but not AQP 10, on Day 25 of gestation 15,42,43 and that AQPs 1, 5, 8, and 10 were localized to specific cell types within both the endometrium and placenta. 44 Thus, pigs appear to use AQPs 1, 5, 8, and 9 to transport water from maternal blood across the utero-placental interface into the allantoic sac as allantoic fluid.…”

“…After the abdomen was opened and the uterus was removed, the number of CL in ovaries, the number of live fetuses, placental weight, fetal body weight, fetal crown-to-rump length (the distance from the crown of the head to the base of the tail), volumes of amniotic and allantoic fluid in viable conceptuses, and the number and diameter of placental blood vessels were determined, as we described previously. 13,15 Rates of embryonic survival, expressed as a percentage, were calculated as the number of live fetuses divided by the number of CL present on the ovaries at the time of necropsy. Samples of placentae were snap-frozen in liquid nitrogen.…”

“…18 Sequences of primers used for the quantitative RT-qPCR were the same as we described previously. 15 Tubulin was used as the housekeeping gene. 15 Data for target genes were normalized on the basis of the tubulin mRNA levels.…”

“…Experimental Biology and Medicine 2023; 248: 702-711. DOI: 10.1177/15353702231157943 by 26% (based on the number of blood vessels 15 ), and the number of viable fetuses per litter by about 2. 13 Arg stimulates placental protein synthesis, inhibits placental protein degradation, 16 promotes the placental production of nitric oxide (NO) by tetrahydrobiopterin (BH4)-dependent NO synthase, and increases the expression of angiogenic factors, 15,[17][18][19] thereby enhancing placental growth (including vascular growth) and development.…”

“…We have conducted research to enhance conceptus survival and growth in swine through improving maternal L-arginine (Arg) nutrition. 9–12 Notably, dietary supplementation with 0.4% Arg to gilts between Days 14 and 25 of gestation increased placental growth by 34%, 13 folding at the uterine–placental interface by 28%, 14 placental angiogenesis by 26% (based on the number of blood vessels 15 ), and the number of viable fetuses per litter by about 2. 13 Arg stimulates placental protein synthesis, inhibits placental protein degradation, 16 promotes the placental production of nitric oxide (NO) by tetrahydrobiopterin (BH4)-dependent NO synthase, and increases the expression of angiogenic factors, 15,17–19 thereby enhancing placental growth (including vascular growth) and development.…”