Increase of essential amino acids in the bovine uterine lumen during preimplantation development

Amino acids (AAs) are crucial for the developing conceptus prior to implantation. To provide insights into the requirements of the bovine embryo, we determined the AA composition of the uterine fluid. At days 12, 15, and 18 post-estrus, the uteri of synchronized pregnant and non-pregnant Simmental heifers were flushed for the analysis of 41 AAs and their derivatives by liquid chromatography-tandem mass spectrometry. The ipsilateral endometrium was sampled for quantitative PCR. In addition to a pregnancy-dependent increase of the essential AAs (P<0.01), we detected elevated concentrations for most non-essential proteinogenic AAs. Histidine (His) and the expression of the His/peptide transporter solute carrier 15A3 (SLC15A3) were significantly increased at day 18 of pregnancy in vivo. In addition, SLC15A3 was predominantly stimulated by trophoblast-derived interferon-τ in stroma cells of an in vitro co-culture model of endometrial cells. Our results show an increased concentration of AAs most likely to optimally provide the elongating pre-attachment conceptus with nutrients.

Triennial Growth Symposium: important roles for L-glutamine in swine nutrition and production

L-Glutamine (Gln) has traditionally not been considered a nutrient needed in diets for livestock species or even mentioned in classic animal nutrition textbooks. This is due to previous technical difficulties in Gln analysis and the unsubstantiated assumption that animals can synthesize sufficient amounts of Gln to meet their needs. Consequently, the current (1998) version of NRC does not recommend dietary Gln requirements for swine. This lack of knowledge about Gln nutrition has contributed to suboptimal efficiency of global pig production. Because of recent advances in research, Gln is now known to be an abundant AA in physiological fluids and proteins and a key regulator of gene expression. Additionally, Gln can regulate cell signaling via the mammalian target of rapamycin pathway, adenosine monophosphate-activated protein kinase, extracellular signal-related kinase, Jun kinase, mitogen-activated protein kinase, and nitric oxide. The exquisite integration of Gln-dependent regulatory networks has profound effects on cell proliferation, differentiation, migration, metabolism, homeostasis, survival, and function. As a result of translating basic research into practice, dietary supplementation with 1% Gln maintains gut health and prevents intestinal dysfunction in low-birth-weight or early-weaned piglets while increasing their growth performance and survival. In addition, supplementing 1% Gln to a corn- and soybean-meal-based diet between d 90 and 114 of gestation ameliorates fetal growth retardation in gilts and reduces preweaning mortality of piglets. Furthermore, dietary supplementation with 1% Gln enhances milk production by lactating sows. Thus, adequate amounts of dietary Gln, a major nutrient, are necessary to support the maximum growth, development, and production performance of swine.

Proteomic profile of uterine luminal fluid from early pregnant ewes

Embryonic development is a time-sensitive period that requires a synchronized uterine environment, which is created by the secretion of proteins from both the embryo and uterus. Numerous studies have identified uterine luminal proteins and related these to specific adaptations during early pregnancy (EP). However, no study has yet utilized LC-MS/MS to identify the signature profile of proteins in the uterine lumen during EP. In this study, uterine luminal fluid from nonpregnant (NP; n = 3) and EP (n = 3; gestational day 16) ewes were analyzed by LC-MS/MS and validated by Western immunoblotting. We identified a unique signature profile for EP luminal fluid; 15 proteins related to specific aspects of embryonic development including growth and remodeling, immune system regulation, oxidative stress balance, and nutrition were significantly altered (up to 65-fold of NP) in EP profile. Specific uterine remodeling proteins such as transgelin (P = 0.008) and placental proteins like PP9 (P = 0.02) were present in EP luminal fluid but were barely detectable in the NP flushings. Direct correlations (R(2) = 0.84, P = 0.01) were observed between proteomics and immunoblotting. These data provide information on dynamic physiological processes associated with EP at the level of the uterus and conceptus and may potentially demonstrate a signature profile associated with embryonic well-being.

Effect of pregnancy and progesterone concentration on expression of genes encoding for transporters or secreted proteins in the bovine endometrium

The objective of this study was to determine the temporal and spatial expression patterns of genes encoding transporters, as well as selected secreted proteins that may be regulated by progesterone (P4) and/or the presence of the conceptus in the bovine endometrium. Estrus-synchronized beef heifers were randomly assigned to either: 1) pregnant, high P4; 2) pregnant, normal P4; 3) cyclic, high P4; or 4) cyclic, normal P4. Uteri were collected on days 5, 7, 13, and 16 of the estrous cycle or pregnancy. Localization of mRNAs for ANPEP, CTGF, LPL, LTF, and SLC5A1 in the uteri was determined by radioactive in situ hybridization, and expression quantified in the endometria by quantitative real-time PCR. ANPEP localized to luminal (LE) and superficial glandular (sGE) epithelia of all heifers on days 5 and 7 only. SLC5A1 mRNA was detected in the LE and sGE on days 13 and 16 in all heifers, and expression increased on day 16 in pregnant groups. CTGF localized weakly to the LE and GE on days 5 and 7 but increased on days 13 and 16 with an increase ( P < 0.05) in CTGF expression in high P4 ( day 7) and pregnant heifers ( day 16). Both LPL and LTF localized to the GE only on days 5 and 7. In conclusion we have characterized the temporal expression pattern of these genes and modulation of their transcript abundance by P4 ( CTGF, LPL) and/or the conceptus ( CTGF, SLC5A1) likely modifies the uterine microenvironment, enhancing histotroph composition and contributing to advanced conceptus elongation.

Pregnancy recognition and abnormal offspring syndrome in cattle

Development of the post-hatching conceptus in ruminants involves a period of morphological expansion that is driven by complex interactions between the conceptus and its intrauterine environment. As a result of these interactions, endometrial physiology is altered, leading to establishment of the pregnancy and continued development of the placenta. Disruption of normal fetal and placental development can occur when embryos are exposed to manipulations in vitro or when inappropriate endocrine sequencing occurs in vivo during the pre- and peri-implantation periods. The present review addresses the development of the post-hatching bovine conceptus, its interactions with the maternal system and changes in development that can occur as a result of in vivo and in vitro manipulations of the bovine embryo.

Impacts of amino acid nutrition on pregnancy outcome in pigs: mechanisms and implications for swine production

Pigs suffer up to 50% embryonic and fetal loss during gestation and exhibit the most severe naturally occurring intrauterine growth retardation among livestock species. Placental insufficiency is a major factor contributing to suboptimal reproductive performance and reduced birth weights of pigs. Enhancement of placental growth and function through nutritional management offers an effective solution to improving embryonic and fetal survival and growth. We discovered an unusual abundance of the arginine family of AA in porcine allantoic fluid (a reservoir of nutrients) during early gestation, when placental growth is most rapid. Arginine is metabolized to ornithine, proline, and nitric oxide, and these compounds possess a plethora of physiological functions. Nitric oxide is a vasodilator and angiogenic factor, whereas both ornithine and proline are substrates for placental synthesis of polyamines, which are key regulators of protein synthesis and angiogenesis. Additionally, arginine, leucine, glutamine, and proline activate the mammalian target of rapamycin cell-signaling pathway to enhance protein synthesis and cell proliferation in placentae. To translate basic research on AA biochemistry and nutrition into application, dietary supplementation with 0.83% l-arginine to gilts on d 14 to 28 or d 30 to 114 of gestation increased the number and litter birth weight of live-born piglets. In addition, supplementing the gestation diet with 0.4% l-arginine plus 0.6% l-glutamine enhanced the efficiency of nutrient utilization, reduced variation in piglet birth weight, and increased litter birth weight. By regulating syntheses of nitric oxide, polyamines, and proteins, functional AA stimulate placental growth and the transfer of nutrients from mother to embryo or fetus to promote conceptus survival, growth, and development.

Discovery of candidate genes and pathways in the endometrium regulating ovine blastocyst growth and conceptus elongation

Establishment of pregnancy in ruminants requires blastocyst growth to form an elongated conceptus that produces interferon tau, the pregnancy recognition signal, and initiates implantation. Blastocyst growth and development requires secretions from the uterine endometrium. An early increase in circulating concentrations of progesterone (P4) stimulates blastocyst growth and elongation in ruminants. This study utilized sheep as a model to identify candidate genes and regulatory networks in the endometrium that govern preimplantation blastocyst growth and development. Ewes were treated daily with either P4 or corn oil vehicle from day 1.5 after mating to either day 9 or day 12 of pregnancy when endometrium was obtained by hysterectomy. Microarray analyses revealed many differentially expressed genes in the endometria affected by day of pregnancy and early P4 treatment. In situ hybridization analyses revealed that many differentially expressed genes were expressed in a cell-specific manner within the endometrium. The Database for Annotation, Visualization, and Integrated Discovery (DAVID) was used to identify functional groups of genes and biological processes in the endometrium that are associated with growth and development of preimplantation blastocysts. Notably, biological processes affected by day of pregnancy and/or early P4 treatment included lipid biosynthesis and metabolism, angiogenesis, transport, extracellular space, defense and inflammatory response, proteolysis, amino acid transport and metabolism, and hormone metabolism. This transcriptomic data provides novel insights into the biology of endometrial function and preimplantation blastocyst growth and development in sheep.

Comparative aspects of implantation

Uterine receptivity to implantation of blastocysts in mammals includes hatching from zona pellucida, precontact with uterine luminal (LE) and superficial glandular (sGE) epithelia and orientation of blastocyst, apposition between trophectoderm and uterine LE and sGE, adhesion of trophectoderm to uterine LE/sGE, and, in some species, limited or extensive invasion into the endometrial stroma and induction of decidualization of stromal cells. These peri-implantation events are prerequisites for pregnancy recognition signaling, implantation, and placentation required for fetal-placental growth and development through the remainder of pregnancy. Although there is a range of strategies for implantation in mammals, a common feature is the requirement for progesterone (P(4)) to downregulate expression of its receptors in uterine epithelia and P(4) prior to implantation events. P(4) then mediates its effects via growth factors expressed by stromal cells in most species; however, uterine luminal epithelium may express a growth factor in response to P(4) and/or estrogens in species with a true epitheliochorial placenta. There is also compelling evidence that uterine receptivity to implantation involves temporal and cell-specific expression of interferon (IFN)-stimulated genes that may be induced directly by an IFN or induced by P(4) and stimulated by an IFN. These genes have many roles including nutrient transport, cellular remodeling, angiogenesis and relaxation of vascular tissues, cell proliferation and migration, establishment of an antiviral state, and protection of conceptus tissues from challenges by the maternal immune cells.

Amino acids: metabolism, functions, and nutrition

Recent years have witnessed the discovery that amino acids (AA) are not only cell signaling molecules but are also regulators of gene expression and the protein phosphorylation cascade. Additionally, AA are key precursors for syntheses of hormones and low-molecular weight nitrogenous substances with each having enormous biological importance. Physiological concentrations of AA and their metabolites (e.g., nitric oxide, polyamines, glutathione, taurine, thyroid hormones, and serotonin) are required for the functions. However, elevated levels of AA and their products (e.g., ammonia, homocysteine, and asymmetric dimethylarginine) are pathogenic factors for neurological disorders, oxidative stress, and cardiovascular disease. Thus, an optimal balance among AA in the diet and circulation is crucial for whole body homeostasis. There is growing recognition that besides their role as building blocks of proteins and polypeptides, some AA regulate key metabolic pathways that are necessary for maintenance, growth, reproduction, and immunity. They are called functional AA, which include arginine, cysteine, glutamine, leucine, proline, and tryptophan. Dietary supplementation with one or a mixture of these AA may be beneficial for (1) ameliorating health problems at various stages of the life cycle (e.g., fetal growth restriction, neonatal morbidity and mortality, weaning-associated intestinal dysfunction and wasting syndrome, obesity, diabetes, cardiovascular disease, the metabolic syndrome, and infertility); (2) optimizing efficiency of metabolic transformations to enhance muscle growth, milk production, egg and meat quality and athletic performance, while preventing excess fat deposition and reducing adiposity. Thus, AA have important functions in both nutrition and health.

Select nutrients in the ovine uterine lumen. VI. Expression of FK506-binding protein 12-rapamycin complex-associated protein 1 (FRAP1) and regulators and effectors of mTORC1 and mTORC2 complexes in ovine uteri and conceptuses

FRAP1 (FK506-binding protein 12-rapamycin complex-associated protein 1), a component of the nutrient-sensing cell signaling pathway, is critical for cell growth and metabolism. The present study determined expression of FRAP1 and associated members of the mTORC1 and mTORC2 cell signaling pathways in uteri of cyclic and pregnant ewes and conceptuses, as well as effects of pregnancy, progesterone (P4), and interferon tau (IFNT) on their expression. The mRNAs for FRAP1, LST8, MAPKAP1, RAPTOR, RICTOR, TSC1, TSC2, RHEB, and EIF4EBP1 were localized to luminal, superficial glandular, and glandular epithelia and stromal cells of uteri from cyclic and pregnant ewes, as well as trophectoderm and endoderm of conceptuses between Days 13 and 18 of pregnancy. The abundance of FRAP1, RAPTOR, RICTOR, TSC1, and TSC2 mRNAs in endometria was unaffected by pregnancy status or by day of the estrous cycle or pregnancy; however, levels of LST8, MAPKAP1, RHEB, and EIF4EBP1 mRNA increased in endometria during early pregnancy. In ovariectomized ewes, P4 and IFNT stimulated expression of RHEB and EIF4EBP1 in uterine endometria. Total endometrial FRAP1 protein and phosphorylated FRAP1 protein levels were affected by pregnancy status and by day after onset of estrus, and phosphorylated FRAP1 protein was detected in nuclei of uterine epithelia and conceptuses. In endometria of pregnant ewes, increases in abundance of mRNAs for RICTOR, RHEB, and EIF4EBP1, as well as RHEB protein, correlated with rapid conceptus growth and development during the peri-implantation period. These results suggest that the FRAP1 cell signaling pathway mediates interactions between the maternal uterus and peri-implantation conceptuses and that P4 and IFNT affect this pathway by regulating expression of RHEB and EIF4EBP1.