高脂日粮通过非编码RNAs调控哺乳动物胎盘养分转运的研究进展

胎儿生长发育和生理状况与母体营养水平及胎盘养分转运能力密切相关。在妊娠期给母体饲喂高脂日粮可能影响母体健康和胎儿宫内发育状况,同时对后代长期健康和新陈代谢方面也有重要影响。随着高通量RNA测序(RNA-Seq)技术的兴起,部分非编码RNAs(non-coding RNAs)调控哺乳动物机体细胞增殖与分化等多个生理学过程的机制得以阐明。笔者综述了高脂日粮通过环状RNAs(circRNAs)、长链非编码RNAs(lncRNAs)和微小RNAs(miRNAs)影响母体胎盘养分转运的研究进展,并阐述了circRNAs、lncRNAs及miRNAs在哺乳动物孕期饲喂高脂日粮对胎盘养分转运的具体调控机制,为预防哺乳动物孕期肥胖并促进胎儿健康生长提供一定的理论依据,同时为非编码RNA参与机体生命活动和物质代谢奠定理论基础。     

功能性氨基酸对猪胎盘血管生成及繁殖性能影响的研究进展

胎盘是介于胎儿与母体间的唯一连接器官,对胎猪发育和存活至关重要。妊娠期间胎猪所需的营养物质几乎均要经胎盘循环系统从母体获得,故胎盘血管管脉系统的正常网络化发育是母猪和仔猪之间营养传输的必要前提。胎盘血管发生和血管生成缺乏或受阻会导致养分运输滞后,易引发宫内发育迟缓现象。功能性氨基酸是指不仅可作为蛋白质合成原料,还可通过调节机体的关键代谢通路以影响动物的生长发育、繁殖和免疫等诸多生理活动的氨基酸。已有研究报道功能性氨基酸可作为生物活性分子激活血管生成相关信号通路,促进胎盘血管网络化的形成。本文综述了胎盘血管生成对胎猪发育的影响及其关键调控因子,并且归纳总结了关键信号通路介导功能性氨基酸调控猪胎盘血管生成及繁殖性能的研究进展,旨在为靶向促进胎盘血管发育的功能性氨基酸在母猪生产中的开发利用提供参考。     

反刍动物妊娠期骨骼肌发育及营养调控

反刍动物骨骼肌的生长发育对其生产性能有很大影响,而妊娠期是胎儿骨骼肌发育的重要时期,Wnt、胰岛素样生长因子(IGF)等重要通路/信号因子与胎儿骨骼肌发育密切相关,且母体营养水平在该阶段对胎儿骨骼肌肌纤维发育和脂肪组织生成过程发挥重要的调控作用。因而,本文综述了反刍动物骨骼肌各组分的发育顺序、发生机制以及母体妊娠期营养水平对胎儿骨骼肌发育的影响。     

功能性氨基酸对母猪胎盘功能影响的研究进展北大核心CSCD

功能性氨基酸是指可以通过调节动物机体的关键代谢通路,对人和动物的生长发育、繁殖健康有促进作用,对生命活动起到诸多生理调控作用的氨基酸。一些功能性氨基酸及其产物对母猪胎盘功能有着重要的作用。胎盘是妊娠期间由胚胎胚膜和母体子宫内膜联合长成的母子间组织结合器官,具备物质交换、代谢、防御及激素合成等重要功能。在孕期,胎盘是胎儿和母体之间传递物质的枢纽,它可以从母体运输氧气、二氧化碳、水和一些其他的胎儿生长发育所必需的营养物质,也可以将胎儿的代谢废物等通过母体排出。本文从几个研究较多的功能性氨基酸(精氨酸、脯氨酸、谷氨酰胺和支链氨基酸)入手,分别就其对母猪胎盘功能的影响进行了综述,旨在促进功能性氨基酸在母猪生产中更好地开发利用。     

Wnt信号通路在牛胎盘发育过程中的功能研究进展

胎盘是哺乳动物在妊娠期间胎儿和母体之间的联系枢纽,因此,胎盘发育是否正常在妊娠中起着关键的作用。Wnt信号通路在胚胎发育和胎盘形成的过程中有着重要的作用,作者通过回顾几条已经研究较为清楚的Wnt信号通路和牛早期胚胎和胎盘的形成过程,介绍了Wnt信号通路的组成部分在体细胞核移植（somatic cell nuclear transfer,SCNT）牛和正常人工授精的牛的胚胎早期表达,提出了DKK-1和Fzd4的表达对于早期胎盘形成和发育有特殊的作用。此外,抑制MAP2K和GSK3信号可以激活Wnt信号通路,增加内细胞团和滋养层细胞的数量,加速囊胚的发育。SCNT牛和正常人工授精的牛早期胎盘中E-cadherin和β-catenin蛋白的磷酸化程度相似,所以对于Wnt信号通路在牛胎盘的早期形成和发育中的作用还需进一步的了解和研究。     

胎盘糖代谢对猪宫内发育迟缓的调控作用

宫内发育迟缓（intrauterine growth retardation,IUGR）是指胚胎或其器官在怀孕期间生长和发育受阻,表现为后代生长发育受限或停滞。初生低体重或极低体重是IUGR仔猪的主要特征。IUGR严重影响新生仔猪的存活和后期的生长发育。诱发IUGR的原因包括母体在妊娠期间养分摄入不足、发病、环境应激以及子宫和胎盘功能异常等。猪作为多胎家畜,受IUGR影响最为严重,主要原因在于妊娠期间母猪无法提供足够的养分满足子宫角上所有胎儿正常生长发育的需要。胎盘作为母子之间唯一的联系,胎盘营养物质能否正常转运与代谢是影响胎儿发育的重要因素。碳水化合物是胎儿宫内发育最主要的能量底物,胎盘的糖类转运及代谢异常对IUGR的形成至关重要。在糖代谢的过程中,葡萄糖、磷酸戊糖和果糖可以通过葡萄糖转运蛋白、胎盘滋养层细胞和血管生成等对仔猪宫内发育起到调控作用。文章阐述了胎盘糖代谢对仔猪宫内发育迟缓的调控作用,以期为减少IUGR发生及改善IUGR仔猪的生长发育提供科学依据。     

氨基酸对妊娠母猪繁殖性能的影响及其作用机理(续完)

<正>上期回顾:上期介绍了母猪窝产仔数受影响的因素、养猪生产中胎儿宫内发育迟缓问题、胎盘在胚胎发育中的作用主氨基酸在胎盘生长中的作用。5氨基酸对胎儿肌肉和脂肪组织生长发育的影响研究表明,妊娠期间母体的蛋白质营养会影响出生后仔猪的肌肉生长和肌内脂肪的含量(Rehfeldt等,2004)。肌细胞和脂肪细胞来源于普通的造血前体细胞     

母猪胎盘发育的营养调控北大核心CSCD

胎盘发育是一个复杂且精细的过程,胎盘发育及其功能的完整性是胎儿正常生长发育的首要保障。母猪胎盘功能异常将会导致母胎间养分运输的滞后,从而引发宫内发育迟缓现象。本文综述了几种主要营养物质(氨基酸、脂肪酸、维生素和矿物质)对母猪胎盘发育和功能的影响及机制,为充分发挥母猪繁殖潜能提供营养策略。     

胎盘糖代谢对猪宫内发育迟缓的调控作用

宫内发育迟缓(intrauterine growth retardation,IUGR)是指胚胎或其器官在怀孕期间生长和发育受阻,表现为后代生长发育受限或停滞。初生低体重或极低体重是IUGR仔猪的主要特征。IUGR严重影响新生仔猪的存活和后期的生长发育。诱发IUGR的原因包括母体在妊娠期间养分摄入不足、发病、环境应激以及子宫和胎盘功能异常等。猪作为多胎家畜,受IUGR影响最为严重,主要原因在于妊娠期间母猪无法提供足够的养分满足子宫角上所有胎儿正常生长发育的需要。胎盘作为母子之间唯一的联系,胎盘营养物质能否正常转运与代谢是影响胎儿发育的重要因素。碳水化合物是胎儿宫内发育最主要的能量底物,胎盘的糖类转运及代谢异常对IUGR的形成至关重要。在糖代谢的过程中,葡萄糖、磷酸戊糖和果糖可以通过葡萄糖转运蛋白、胎盘滋养层细胞和血管生成等对仔猪宫内发育起到调控作用。文章阐述了胎盘糖代谢对仔猪宫内发育迟缓的调控作用,以期为减少IUGR发生及改善IUGR仔猪的生长发育提供科学依据。     

NO对胎盘功能和胎儿生长发育的影响

一氧化氮(NO)化学结构简单,性质活跃,广泛参与机体的生理、病理调节。在妊娠期,NO可降低血管对加压物质的反应性,降低外周阻力及血压。目前认为,NO产生减少是妊娠高血压征合征发病的重要原因,是导致母体妊娠期心血管系统发生血容量增加、血压下降、血液重新分布等生理性改变的重要因素,胎盘局部NO及其相关因子对胎盘功能和胎儿的生长发育有直接的影响作用。     

Factors controlling nutrient availability to the developing fetus in ruminants

Inadequate delivery of nutrients results in intrauterine growth restriction (IUGR), which is a leading cause of neonatal morbidity and mortality in livestock. In ruminants, inadequate nutrition during pregnancy is often prevalent due to frequent utilization of exensive forage based grazing systems, making them highly susceptible to changes in nutrient quality and availability. Delivery of nutrients to the fetus is dependent on a number of critical factors including placental growth and development, utero-placental blood flow, nutrient availability, and placental metabolism and transport capacity. Previous findings from our laboratory and others, highlight essential roles for amino acids and their metabolites in supporting normal fetal growth and development, as well as the critical role for amino acid transporters in nutrient delivery to the fetus. The focus of this review will be on the role of maternal nutrition on placental form and function as a regulator of fetal development in ruminants.     

Factors controlling nutrient availability to the developing fetus in ruminants

Inadequate delivery of nutrients results in intrauterine growth restriction(IUGR), which is a leading cause of neonatal morbidity and mortality in livestock. In ruminants, inadequate nutrition during pregnancy is often prevalent due to frequent utilization of exensive forage based grazing systems, making them highly susceptible to changes in nutrient quality and availability. Delivery of nutrients to the fetus is dependent on a number of critical factors including placental growth and development, utero-placental blood flow, nutrient availability, and placental metabolism and transport capacity. Previous findings from our laboratory and others, highlight essential roles for amino acids and their metabolites in supporting normal fetal growth and development, as well as the critical role for amino acid transporters in nutrient delivery to the fetus. The focus of this review will be on the role of maternal nutrition on placental form and function as a regulator of fetal development in ruminants.     

Board-invited review: intrauterine growth retardation: implications for the animal sciences

Intrauterine growth retardation (IUGR), defined as impaired growth and development of the mammalian embryo/fetus or its organs during pregnancy, is a major concern in domestic animal production. Fetal growth restriction reduces neonatal survival, has a permanent stunting effect on postnatal growth and the efficiency of feed/forage utilization in offspring, negatively affects whole body composition and meat quality, and impairs long-term health and athletic performance. Knowledge of the underlying mechanisms has important implications for the prevention of IUGR and is crucial for enhancing the efficiency of livestock production and animal health. Fetal growth within the uterus is a complex biological event influenced by genetic, epigenetic, and environmental factors, as well as maternal maturity. These factors impact on the size and functional capacity of the placenta, uteroplacental blood flows, transfer of nutrients and oxygen from mother to fetus, conceptus nutrient availability, the endocrine milieu, and metabolic pathways. Alterations in fetal nutrition and endocrine status may result in developmental adaptations that permanently change the structure, physiology, metabolism, and postnatal growth of the offspring. Impaired placental syntheses of nitric oxide (a major vasodilator and angiogenic factor) and polyamines (key regulators of DNA and protein synthesis) may provide a unified explanation for the etiology of IUGR in response to maternal undernutrition and overnutrition. There is growing evidence that maternal nutritional status can alter the epigenetic state (stable alterations of gene expression through DNA methylation and histone modifications) of the fetal genome. This may provide a molecular mechanism for the role of maternal nutrition on fetal programming and genomic imprinting. Innovative interdisciplinary research in the areas of nutrition, reproductive physiology, and vascular biology will play an important role in designing the next generation of nutrient-balanced gestation diets and developing new tools for livestock management that will enhance the efficiency of animal production and improve animal well being.     

Effects of a Streptococcus equi infection--mediated nutritional insult during mid-gestation in primiparous Thoroughbred fillies. Part 1: placental and fetal development

REASONS FOR PERFORMING STUDY: There is a paucity of information on factors that influence placental development in the horse. Hypothesis: Changes in nutrition, particularly around the time of proliferative placental growth, can affect development of the placenta and fetal growth. OBJECTIVE: To investigate the effects of 2 planes of nutrition and an unforeseen infection-mediated nutritional insult on placental and fetal development in the mare. METHODS: Twenty maiden Thoroughbred fillies, age 3 or 4 years, mated to one Thoroughbred stallion, were maintained on either High or Moderate food intake throughout pregnancy. In mid-gestation all the mares unexpectedly became infected with Streptococcus equi and suffered varying degrees of weight loss as a consequence. Gross and stereological measurements of the placenta and measurements of foal birthweight, crown-rump length, ponderal index and plasma IGF-1 concentration were made at term. RESULTS: Gains in bodyweight during gestation were significantly higher in the High vs. the Moderate nutrition groups. Placental and fetal growth parameters were not influenced by the plane of nutrition. However, transient weight loss in mid-gestation from acutely reduced food intake resulted in morphological changes to the allantochorion and decreased foal birthweight. CONCLUSIONS: Excessive weight gain during gestation in maiden Thoroughbred fillies does not result in nutrient partitioning to the dam at the expense of the fetus. However, sudden weight loss in mid-gestation has detrimental effects on placental development which results in reduced fetal growth. POTENTIAL RELEVANCE: Clinicians should appreciate the likely effects of maternal infection and resulting weight loss on pregnancy outcome.     

Effects of maternal nutrition and porcine growth hormone (pGH) treatment during gestation on endocrine and metabolic factors in sows, fetuses and pigs, skeletal muscle development, and postnatal growth

Prenatal growth is very complex and a highly integrated process. Both maternal nutrition and the maternal somatotropic axis play a significant role in coordinating nutrient partitioning and utilization between maternal, placental and fetal tissues. Maternal nutrition may alter the nutrient concentrations and in turn the expression of growth regulating factors such as IGFs and IGFBPs in the blood and tissues, while GH acts in parallel via changing IGFs/IGFBPs and nutrient availability. The similarity in the target components implies that maternal nutrition and the somatotropic axis are closely related to each other and may induce similar effects on placental and fetal growth. Severe restriction of nutrients throughout gestation has a permanent negative effect on fetal and postnatal growth, whereas the effects of both temporary restriction and feeding above requirements during gestation seem to be of transitional character. Advantages in fetal growth gained by maternal growth hormone treatment during early to mid-gestation are not maintained to term, whereas treatment during late or greatest part of gestation increases progeny size at birth, which could be of advantage for postnatal growth. This review summarizes the available knowledge on the effects of different maternal feeding strategies and maternal GH administration during pregnancy and their interactions on metabolic and hormonal (especially IGFs/IGFBPs) status in the feto-maternal unit, skeletal muscle development and growth of the offspring in pigs.     

Baggs ewes adapt to maternal undernutrition and maintain conceptus growth by maintaining fetal plasma concentrations of amino acids

Adequate delivery of AA is essential for normal fetal growth and development. Recently, we reported that when ewes from the University of Wyoming flock (farm flock with adequate nutrition) were fed 50% (nutrient-restricted) or 100% (control-fed) of the NRC-recommended nutrient requirements between d 28 and 78 of gestation, fetal weights as well as concentrations of most AA in maternal and fetal blood were substantially reduced in nutrient-restricted vs. control-fed pregnancies. The current study utilized Baggs ewes, which were selected under a markedly different production system (range flock with limited nutrition), to test the hypothesis that adaptation of ewes to nutritional and environmental changes may alter placental efficiency and conceptus nutrient availability in the face of maternal nutrient restriction. Baggs ewes received 50 or 100% of the NRC nutrient requirements between d 28 and 78 of pregnancy. On d 78, maternal uterine arterial and fetal umbilical venous blood samples were obtained, and the ewes were euthanized. Amino acids and their metabolites (ammonia, urea, and polyamines) in plasma were analyzed using enzymatic and HPLC methods. The results showed that maternal plasma concentrations of 9 AA (Asp, Ile, Leu, Lys, Orn, Phe, Thr, Trp, and Val) as well as maternal and fetal plasma concentrations of ammonia and urea were reduced (P < 0.05) in nutrient-restricted compared with control-fed Baggs ewes. However, fetal plasma concentrations of all AA and polyamines did not differ (P = 0.842) between the 2 groups of ewes. Collectively, these findings suggest that Baggs ewes, by adapting to the harsh conditions and limited nutrition under which they were selected, were able to maintain fetal concentrations of AA in the face of a maternal nutrient restriction through augmenting placental efficiency.     

Effect of nutrient intake during pregnancy on fetal and placental growth and vascular development

Remarkable diversity of size and health of offspring exists after normal pregnancies. When pregnancies are complicated by an extrinsic variable such as inappropriate maternal nutrition, birth weight and health of the neonate are substantially affected. The placenta is the organ through which respiratory gases, nutrients, and wastes are exchanged between the maternal and fetal systems. Thus, transplacental exchange provides for all the metabolic demands of fetal growth. Transplacental exchange is dependent upon uterine and umbilical blood flow, and blood flow rates are in turn dependent in large part upon vascularization of the placenta. Therefore, factors that influence placental vascular development will have a dramatic impact on fetal growth and development, and thereby on neonatal mortality and morbidity. Recent work from our laboratories has focused on the effects of nutrient intake during pregnancy on placental growth and vascular development. Both nutrient restriction of the adult dam and overnourishment of the adolescent dam during pregnancy suppress placental cell proliferation and vascularity. Furthermore, placental expression of angiogenic factors and their receptors, factors that are known to affect vascular growth, are perturbed by level of nutrition. Studies in this area will lead to improved methods to manage nutritionally-compromised pregnancies.     

Placentomal differentiation may compensate for maternal nutrient restriction in ewes adapted to harsh range conditions

Maternal nutrient restriction from early to midgestation can lead to fetal growth retardation, with long-term impacts on offspring growth, physiology, and metabolism. We hypothesized that ewes from flocks managed under markedly different environmental conditions and levels of nutrition might differ in their ability to protect their own fetus from a bout of maternal nutrient restriction. We utilized multiparous ewes of similar breeding, age, and parity from 2 flocks managed as 1) ewes adapted to a nomadic existence and year-long, limited nutrition near Baggs, WY (Baggs ewes), and 2) University of Wyoming ewes with a sedentary lifestyle and continuous provision of more than adequate nutrition (UW ewes). Groups of Baggs ewes and UW ewes were fed 50 (nutrient restricted) or 100% (control fed) of National Research Council recommendations from d 28 to 78 of gestation, then necropsied, and fetal and placental data were obtained. Although there was a marked decrease (P < 0.05) in fetal weight and blood glucose concentrations in nutrient-restricted vs. control fed UW ewes, there was no difference in these fetal measurements between nutrient-restricted and control-fed Baggs ewes. Nutrient-restricted and control-fed UW ewes exhibited predominantly type A placentomes on d 78, but there were fewer (P c0.05) type A and greater (P < 0.05) numbers of type B, C, and D placentomes in nutrient-restricted than control-fed Baggs ewes. Placental efficiency (fetal weight/placentomal weight) was reduced (P = 0.04) in d 78 nutrient-restricted UW ewes when compared with control-fed UW ewes. In contrast, nutrient-restricted and control-fed Baggs ewes exhibited similar placental efficiencies on d 78. This is the first report of different placental responses to a nutritional challenge during pregnancy when ewes were selected under different management systems. These data are consistent with the concept that Baggs ewes or their conceptuses, which were adapted to both harsh environments and limited nutrition, initiated conversion of type A placentomes to other placentomal types when subjected to an early to mid-gestational nutrient restriction, whereas this conversion failed to occur in UW ewes. This early placentomal conversion in the Baggs ewes may function to maintain normal nutrient delivery to their developing fetuses during maternal nutrient restriction.     

Ruminant Nutrition Symposium: Optimizing Performance of the Offspring: nourishing and managing the dam and postnatal calf for optimal lactation, reproduction, and immunity

For several mammalian species, it has been shown that fetal and early postnatal nutrition has a role in long-term lipid and glucose metabolism of the offspring, and it thus also may have consequences on milk yield in the dairy cow. For instance, high-energy diets during the last weeks of pregnancy may result in increased glycemia, which in turn, may alter fetal adipose tissue development. However, most research efforts on management and nutrition of dry cows have focused on minimizing metabolic disorders of the postpartum cow without devoting much attention to potential consequences for the offspring. Similarly, nutritional needs for proper placental development and early fetal growth have received little attention, despite the fact that alterations in placental and fetal development may alter expression of genes participating in homeorhesis of the offspring. Therefore, nutrition of the pregnant cow, both while lactating and dry, should also consider aspects of placental and fetal development that may affect health and performance of the progeny. Similarly, newborn calves and young heifers are fed to ensure a particular growth target without compromising mammary development, although data linking postnatal growth targets with future milk yield are scarce. However, milk yield not only depends on mammary development, but also on nutrient partitioning, which is regulated by the endocrine milieu. There are some periods of time during development where nutrition may have long-lasting effects on metabolic function and milk production. For instance, the first months of postnatal life seem to be critical because recent data from both retrospective and controlled studies indicate that increased growth rate or plane of nutrition during this phase is positively associated with future milk production. Postnatal growth rate depends on nutrition (a necessary but not sufficient condition) and management (i.e., grouping strategies and housing systems), and thus optimal rearing programs should be designed considering long-term consequences on milk yield.