Maternal Nutrient Restriction Reduces Concentrations of Amino Acids and Polyamines in Ovine Maternal and Fetal Plasma and Fetal Fluids1

Developmental changes in polyamines and autophagic marker levels in normal and growth-restricted fetal pigs

Polyamines are essential for embryonic and fetal survival, growth, and development. Additionally, polyamines may induce autophagy in mammalian cells. However, little is known about the availability of polyamines or autophagy in the porcine conceptus with intrauterine growth restriction (IUGR). The present study was performed to evaluate the developmental changes of polyamine concentrations in IUGR and normal porcine fetuses as well as autophagic marker levels in the fetal intestinal mucosa during the second half of gestation when most fetal growth occurs. Allantoic fluid (ALF), amniotic fluid (AMF), umbilical vein, and the small-intestinal mucosa were obtained from both IUGR and normal fetal pigs at d 60, 90, and 110 of gestation. Concentrations of polyamines in fetal fluids as well as protein abundances of microtubule-associated protein light chain 3B (LC3B), an autophagic marker, in the fetal small-intestinal mucosa were determined. Concentrations of polyamines varied greatly in different fetal compartments and changed substantially with advancing gestation. Concentrations of polyamines in IUGR fetal fluids and the small-intestinal mucosa were markedly different from those in their normal counterparts at d 60 and 90 of gestation, whereas most of the differences were not detected by late (d 110) gestation. Specifically, polyamine levels were lower in the umbilical vein plasma but higher in ALF and AMF from IUGR fetuses. Furthermore, enhanced levels of an autophagic marker were observed in the small-intestinal mucosa of IUGR fetuses throughout mid and late gestation in association with abnormal spermidine levels in fetal plasma. These findings support the notion that enhanced autophagy may be an important survival mechanism in IUGR fetuses. Collectively, our findings provide a new framework for future studies to define the roles for polyamines in the prevention and treatment of IUGR in both human medicine and animal production.

Role of the Small Intestine in Developmental Programming: Impact of Maternal Nutrition on the Dam and Offspring

Small-intestinal growth and function are critical for optimal animal growth and health and play a major role in nutrient digestion and absorption, energy and nutrient expenditure, and immunological competence. During fetal and perinatal development, the small intestine is affected by the maternal environment and nutrient intake. In ruminants, altered small-intestinal mass, villi morphology, hypertrophy, hyperplasia, vascularity, and gene expression have been observed as a result of poor gestational nutrition or intrauterine growth restriction. Although many of these data come from fetal stages, data have also demonstrated that nutrition during mid- and late gestation affects lamb small-intestinal growth, vascularity, digestive enzyme activity, and gene expression at 20 and 180 d of age as well. The small intestine is known to be a highly plastic tissue, changing with nutrient intake and physiological state even in adulthood, and the maternal small intestine adapts to pregnancy and advancing gestation. In ruminants, the growth, vascularity, and gene expression of the maternal small intestine also adapt to the nutritional plane and specific nutrient intake such as high selenium during pregnancy. These changes likely alter both pre- and postnatal nutrient delivery to offspring. More research is necessary to better understand the role of the offspring and maternal small intestines in whole-animal responses to developmental programming, but programming of this plastic tissue seems to play a dynamic role in gestational nutrition impacts on the whole animal.

Effect of protein or energy restriction during late gestation on hormonal and metabolic status in pregnant goats and postnatal male offspring

The objective of this study was to investigate the effects of maternal protein or energy restriction on hormonal and metabolic status of pregnant goats during late gestation and their postnatal male kids. Forty-five pregnant goats were fed a control (CON), 40% protein-restricted (PR) or 40% energy-restricted (ER) diet from 90 days of gestation until parturition. Plasma of mothers (90, 125 and 145 days of gestation) and kids (6 weeks of age) were sampled to determine metabolites and hormones. Glucose concentration for pregnant goats subjected to PR or ER was less (P < 0.001) than that of CON goats at 125 and 145 days of gestation. However, plasma nonesterified fatty acids concentration was greater (P < 0.01) at 125 and 145 days for PR and ER than CON. Protein restriction increased (P < 0.01) maternal cortisol concentration by 145 days of gestation, and ER decreased (P < 0.01) maternal insulin concentration at 125 days of gestation. Moreover, maternal amino acid (AA) concentrations were affected by nutritional restriction, with greater (P < 0.05) total AA (TAA) and nonessential AA (NEAA) for PR goats but less (P < 0.05) TAA and NEAA for ER goats at 125 days of gestation. After 6 weeks of nutritional recovery, plasma concentrations of most metabolic and hormonal parameters in restricted kids were similar to CON kids, except for reduced (P < 0.05) insulin concentration in ER, and reduced (P < 0.05) Asp concentration in PR and ER kids. These results provide information on potential metabolic mechanisms responsible for fetal programming.

Nitrergic system and plasmatic methylarginines: Evidence of their role in the perinatal programming of cardiovascular diseases

Atherosclerosis, in turn preceded by endothelial dysfunction, underlies a series of important cardiovascular diseases. Reduced bioavailability of endothelial nitric oxide, by increasing vascular tone and promoting platelet aggregation, leukocyte adhesion, and smooth muscle cell proliferation, plays a key role in the onset of the majority of cardiovascular diseases. In addition, high blood levels of asymmetric dimethylarginine, a potent inhibitor of nitric oxide synthesis, are associated with future development of adverse cardiovascular events and cardiac death. Recent reports have demonstrated that another methylarginine, i.e., symmetric dimethylarginine, is also involved in the onset of endothelial dysfunction and hypertension. Almost a decade ago, prematurity at birth and intrauterine growth retardation were first associated with a potential negative influence on the cardiovascular apparatus, thus constituting risk factors or leading to early onset of cardiovascular diseases. This condition is referred to as cardiovascular perinatal programming. Accordingly, cardiovascular morbidity and mortality are higher among former preterm adults than in those born at term. The aim of this paper was to undertake a comprehensive literature review focusing on cellular and biochemical mechanisms resulting in both reduced nitric oxide bioavailability and increased methylarginine levels in subjects born preterm. Evidence of the involvement of these compounds in the perinatal programming of cardiovascular risk are also discussed.

Impacts of Maternal Nutrition on Vascularity of Nutrient Transferring Tissues during Gestation and Lactation

As the demand for food increases with exponential growth in the world population, it is imperative that we understand how to make livestock production as efficient as possible in the face of decreasing available natural resources. Moreover, it is important that livestock are able to meet their metabolic demands and supply adequate nutrition to developing offspring both during pregnancy and lactation. Specific nutrient supplementation programs that are designed to offset deficiencies, enhance efficiency, and improve nutrient supply during pregnancy can alter tissue vascular responses, fetal growth, and postnatal offspring outcomes. This review outlines how vascularity in nutrient transferring tissues, namely the maternal gastrointestinal tract, the utero-placental tissue, and the mammary gland, respond to differing nutritional planes and other specific nutrient supplementation regimes.

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.

Duration of maternal undernutrition differentially alters fetal growth and hormone concentrations

To investigate the impact of duration of maternal undernutrition in twin sheep pregnancies, ewes were either fed 100% (C) or 50% of their nutrient requirements from 28 to 78 d gestational age (dGA) and readjusted to 100% beginning at 79 dGA (LC) or continuously restricted from 28 to 135 dGA (LL). Weights of the fetus, empty carcass, brain, and liver were greater in the LC than LL fetuses at 135 dGA (P ≤ 0.05). Although umbilical vein (UmV) glucose concentrations did not differ, the UmV:umbilical artery (UmA) glucose gradient was smaller (0.26 ± 0.03 vs 0.38 ± 0.03 and 0.39 ± 0.04 mmol L(-1); P ≤ 0.05) in LL than C and LC fetuses, respectively. Umbilical vein concentrations of IGF-1 were less (46.7 ± 5.62 vs 74.3 ± 6.71 ng/mL; P ≤ 0.05) in LL than LC fetuses. Additionally, LL fetuses tended (P ≤ 0.10) to have lower UmA concentrations of insulin (0.24 ± 0.13 vs 0.70 ± 0.15 ng/mL) and IGF-1 (66.6 ± 7.51 vs 91.4 ± 8.97 ng/mL) than LC fetuses. Although most of the observed differences occurred between LC and LL pregnancies, LC fetuses tended (P ≤ 0.10) to have greater UmV and UmA pCO2 than C fetuses. Furthermore, the UmV:UmA O2 content gradient tended to be greater (5.02 ± 0.43 vs 3.41 ± 0.47; P ≤ 0.10) in C than LL fetuses. UmA placental lactogen also tended to be greater (46.6 ± 4.40 vs 31.1 ± 4.69 ng/mL; P ≤ 0.10) in LL than C fetuses. These data suggest that in twin pregnancies, maternal undernutrition followed by realimentation induces a different fetal outcome compared with continuous nutrient restriction, and both may differ physiologically from control fed pregnancies.

Amino acid metabolism in intestinal bacteria and its potential implications for mammalian reproduction

Reproduction is vital for producing offspring and preserving genetic resources. However, incidences of many reproductive disorders (e.g. miscarriage, intrauterine growth restriction, premature delivery and lower sperm quality) have either increased dramatically or remained at high rates over the last decades. Mounting evidence shows a strong correlation between enteral protein nutrition and reproduction. Besides serving as major nutrients in the diet, amino acids (AA) are signaling molecules in the regulation of diverse physiological processes, ranging from spermatogenesis to oocyte fertilization and to embryo implantation. Notably, the numbers of bacteria in the intestine exceed the numbers of host cells by 10 times. Microbes in the small-intestinal lumen actively metabolize large amounts of dietary AA and, therefore, affect the entry of AA into the portal circulation for whole-body utilization. Changes in the composition and abundance of AA-metabolizing bacteria in the gut during pregnancy, as well as their translocation to the uterus, may alter uterine function and epigenetic modifications of maternal physiology and metabolism, which are crucial for pregnancy recognition and fetal development. Thus, the presence of the maternal gut microbiota and AA metabolites in the intrauterine environments (e.g. endometrium and placenta) and breast milk is likely a unique signature for the programming of the whole-body microbiome and metabolism in both the fetus and infant. Dietary intervention with functional AA, probiotics and prebiotics to alter the abundance and activity of intestinal bacteria may ameliorate or prevent the development of metabolic syndrome, while improving reproductive performance in both males and females as well as their offspring.

Environmental factors affecting pregnancy: endocrine disrupters, nutrients and metabolic pathways

Uterine adenogenesis, a unique post-natal event in mammals, is vulnerable to endocrine disruption by estrogens and progestins resulting in infertility or reduced prolificacy. The absence of uterine glands results in insufficient transport of nutrients into the uterine lumen to support conceptus development. Arginine, a component of histotroph, is substrate for production of nitric oxide, polyamines and agmatine and, with secreted phosphoprotein 1, it affects cytoskeletal organization of trophectoderm. Arginine is critical for development of the conceptus, pregnancy recognition signaling, implantation and placentation. Conceptuses of ungulates and cetaceans convert glucose to fructose which is metabolized via multiple pathways to support growth and development. However, high fructose corn syrup in soft drinks and foods may increase risks for metabolic disorders and increase insulin resistance in adults. Understanding endocrine disrupters and dietary substances, and novel pathways for nutrient metabolism during pregnancy can improve survival and growth, and prevent chronic metabolic diseases in offspring.

The effects of diet and arginine treatment on serum metabolites and selected hormones during the estrous cycle in sheep

The aim of this study was to determine the effects of diet and arginine (Arg) treatment on serum concentrations of selected metabolites and metabolic and reproductive hormones in nonpregnant ewes. Sixty days before the onset of estrus (Day 0), Rambouillet ewes were randomly assigned to one of three dietary groups: maintenance control (C; N = 16; 100% National Research Council requirements), overfed (O; N = 16; 2 × C), or underfed (U; N = 16, 0.6 × C) to achieve and maintain three different body conditions during their estrous cycle(s). At Day 0, ewes from each nutritional group were randomly assigned to receive one of two treatments: saline (Sal) or Arg (L-Arg-HCl; 155 μmol Arg per kg of body weight [BW]; intravenous), which was administered three times per day for 21 or 26 days. Blood samples were collected on Days 0, 6, 10, 12, 16, 21, and 26 of Sal or Arg treatment for evaluation of Arg, nitric oxide metabolite, cholesterol, glucose, insulin, insulin-like growth factor 1, leptin, and progesterone. For a time-response trial, blood samples were collected at 0, 1, 2, 4, and 7 hours after Sal or Arg treatment at the mid-luteal phase to determine serum Arg concentrations. During the 11-week study, C maintained body weight, O gained 9.6 ± 0.7 kg, and U lost 13.9 ± 0.1 kg. Overall, serum concentrations of Arg, glucose, insulin, insulin-like growth factor 1, leptin, and progesterone were greater (P < 0.05) in O ewes than C and/or U ewes and were not affected by Arg treatment. Serum Arg concentration increased at 1 and 2 hours and decreased to basal level at 4 and 7 hours after Arg treatment. These data reinforce the importance of diet in regulation of metabolic and endocrine functions, and demonstrated that the dose and duration of Arg treatment used in this study does not alter serum metabolites or hormones in nonpregnant ewes of various nutritional planes.

Maternal endocrine adaptation throughout pregnancy to nutrient manipulation: consequences for sexually dimorphic programming of thyroid hormones and development of their progeny

Maternal nutrient restriction during critical windows of fetal development alters postnatal growth, often in a sexually dimorphic manner. Intrauterine growth restriction is frequently characterized by accelerated growth and increased adiposity in later life. Thyroid hormones are implicated as part of the mechanism involved in this scenario via their actions within the hypothalamic-pituitary-thyroid axis. We fed high (H = 240%) and low (L = 70%) levels of recommended daily crude protein intake during the first and second trimesters of gestation to beef heifers to investigate effects to their progeny's plasma concentrations of free and total triiodothyronine (FT3 and TT3) and thyroxine (FT4 and TT4) from birth until weaning at 191 days of age (n = 68). The study design was a two-by-two factorial. For male progeny, exposure to maternal diets low in protein during the first trimester of gestation resulted in greater FT4 at birth (P < 0.05) which was subsequent to lower concentrations of leptin in maternal plasma at 271 days of gestation compared with their high-protein-exposed counterparts. These same animals went on to have greater milk intake during the latter half of the lactation period (P < 0.05) and exhibited faster rates of average daily gain (ADG) relative to birth weight during this time (P < 0.05). For all progeny, independent of sex, exposure to low-protein maternal diets during the second trimester of gestation resulted in greater FT3 relative to TT3 at birth. Because FT3 at birth and 29 days was positively associated with ADG (P < 0.05) and ADG relative to birth weight (P < 0.05), it is proposed that FT3 plays an integral role in catch-up growth in the bovine as per other species. Protein intake during the first and second trimesters of gestation has a sexually dimorphic effect on progeny plasma thyroid hormone concentrations, and these changes are associated with altered milk intake and postnatal growth pathway.

Maternal low-protein diet affects myostatin signaling and protein synthesis in skeletal muscle of offspring piglets at weaning stage

PURPOSE

We tested the hypothesis that maternal low-protein (LP) diet during gestation and lactation can program myostatin (MSTN) signaling and protein synthesis in skeletal muscle of offspring at weaning stage (35 days).

METHODS

Fourteen Meishan sows were fed either LP or standard-protein diets throughout gestation and lactation, male offspring piglets were killed at weaning stage and longissimus dorsi (LD) muscles were taken. The cross-sectional areas (CSA) of LD muscles were measured by hematoxylin and eosin staining. The levels of free amino acids in plasma were measured by amino acid auto-analyzer. Proteins and mRNA were determined by Western blot and RT-qPCR, respectively.

RESULTS

Body weight, LD muscle weight and the myofiber CSA were significantly decreased (P < 0.05) in LP piglets; meanwhile, the concentration of branched-chain amino acids was also significantly decreased (P < 0.001). MSTN protein content tended to be higher (P = 0.098) in LP piglets, while the expression of MSTN receptors, activin type II receptor-beta and transforming growth factor type-beta type I receptor kinase, was significantly up-regulated (P < 0.05). Furthermore, p38 mitogen-activated protein kinase, the downstream signaling factor of MSTN, was also enhanced significantly (P < 0.05). In addition, key factors of translation initiation, phosphorylated eukaryotic initiation factor 4E and the 70 kDa ribosomal protein S6 kinase, were significantly decreased (P < 0.05) in LP piglets.

CONCLUSIONS

Our results suggest that maternal LP diet during gestation and lactation affects MSTN signaling and protein synthesis in skeletal muscle of offspring at weaning stage.

Maternal protein-energy malnutrition during early pregnancy in sheep impacts the fetal ornithine cycle to reduce fetal kidney microvascular development

This paper identifies a common nutritional pathway relating maternal through to fetal protein-energy malnutrition (PEM) and compromised fetal kidney development. Thirty-one twin-bearing sheep were fed either a control (n=15) or low-protein diet (n=16, 17 vs. 8.7 g crude protein/MJ metabolizable energy) from d 0 to 65 gestation (term, ∼145 d). Effects on the maternal and fetal nutritional environment were characterized by sampling blood and amniotic fluid. Kidney development was characterized by histology, immunohistochemistry, vascular corrosion casts, and molecular biology. PEM had little measureable effect on maternal and fetal macronutrient balance (glucose, total protein, total amino acids, and lactate were unaffected) or on fetal growth. PEM decreased maternal and fetal urea concentration, which blunted fetal ornithine availability and affected fetal hepatic polyamine production. For the first time in a large animal model, we associated these nutritional effects with reduced micro- but not macrovascular development in the fetal kidney. Maternal PEM specifically impacts the fetal ornithine cycle, affecting cellular polyamine metabolism and microvascular development of the fetal kidney, effects that likely underpin programming of kidney development and function by a maternal low protein diet.—Dunford, L. J., Sinclair, K. D., Kwong, W. Y., Sturrock, C., Clifford, B. L., Giles, T. C., Gardner, D. S.. Maternal protein-energy malnutrition during early pregnancy in sheep impacts the fetal ornithine cycle to reduce fetal kidney microvascular development.

Muscle free amino acid profiles are related to differences in skeletal muscle growth between single and twin ovine fetuses near term

Twin sheep fetuses have reduced skeletal muscle weight near birth relative to singles as a result of restricted muscle hypertrophy. Intracellular free amino acids (FAA) are reported to regulate metabolic pathways which control muscle protein accretion, whereby reduced intracellular content of specific FAA may reduce their activation and therefore, muscle hypertrophy. The aim of this study was to determine whether differences in muscle weight between singleton and twin fetuses, under different maternal conditions is associated with reduced concentration of specific FAA. The FAA content in the semitendinosus muscle (ST) in singleton and twin fetuses (rank) at 140 days of gestation from heavy (H) or light (L) ewes fed ad libitum (A) or maintenance (M) level of nutrition was measured. Muscle weight was reduced in twin fetuses compared to singletons in all groups. Reduced concentrations of leucine, threonine and valine, but higher concentrations of methionine, ornithine, lysine and serine were found in twin fetuses compared to singletons. Maternal size and nutrition interaction with rank resulted in reduced glutamine in twins from HM-ewes (H-ewes under M nutrition) compared to their singleton counterparts. Maternal weight interaction with pregnancy rank reduced the concentration of arginine in twins, with a larger effect on H-ewes compared with L-ewes. Maternal size interaction with pregnancy rank resulted in twins from M-ewes to have lower alanine, while twins from A-ewes had lower aspartic acid concentration compared to singletons. The ST muscle weight was positively correlated only with arginine concentration after taking into account rank, size and nutrition. The present results indicate that reduced concentrations of specific intracellular FAA, such as arginine, leucine, valine, glutamine, which are known to play a role in muscle growth, could be acting as limiting factors for muscle hypertrophy in twin fetuses during late gestation. Ewe size and nutrition can influence the concentration of specific FAA in muscle and should be considered in any intervention plan to improve twin fetal muscle growth.

Uterine infusion of melatonin or melatonin receptor antagonist alters ovine feto-placental hemodynamics during midgestation

Dietary melatonin supplementation from mid- to late gestation increases umbilical artery blood flow and causes disproportionate fetal growth. Melatonin receptors have been described throughout the cardiovascular system; however, there is a paucity of data on the function of placental melatonin receptors. The objectives of the current experiment were to determine fetal descending aorta blood flow, umbilical artery blood flow, and placental and fetal development following a 4-wk uterine infusion of melatonin (MEL), melatonin receptor 1 and 2 antagonist (luzindole; LUZ), or vehicle (CON) from Day 62 to Day 90 of gestation. After 4 wk of infusion, umbilical artery blood flow and umbilical artery blood flow relative to placentome weight were increased (P < 0.05) in MEL- versus CON- and LUZ-infused dams. Fetal descending aorta blood flow was increased (P < 0.05) in MEL- versus CON- and LUZ-infused dams, while fetal descending aorta blood flow relative to fetal weight was increased in MEL- versus CON-infused dams and decreased in LUZ- versus CON-infused dams. Following the 4-wk infusion, we observed an increase in placental efficiency (fetal-placentome weight ratio) in MEL- versus LUZ-infused dams. The increase in umbilical artery blood flow due to chronic uterine melatonin infusion is potentiated by an increased fetal cardiac output through the descending aorta. Moreover, melatonin receptor antagonism decreased fetal descending aorta blood flow relative to fetal weight. Therefore, melatonin receptor activation may partially mediate the observed increase in fetal blood flow following dietary melatonin supplementation.

An intercellular polyamine transfer via gap junctions regulates proliferation and response to stress in epithelial cells

Polyamines are essential for mammalian cell growth and proliferation, and their synthesis in cells or transport from the extracellular environment has attracted much attention, especially in cancer research. Here it is shown for the first time that polyamines can be transferred from cell to cell via gap junctions to coordinate cell growth.

In the organism, quiescent epithelial cells have the potential to resume cycling as a result of various stimuli, including wound healing or oxidative stress. Because quiescent cells have a low polyamine level, resuming their growth requires an increase of their intracellular polyamine levels via de novo polyamine synthesis or their uptake from plasma. Another alternative, explored here, is an intercellular exchange with polyamine-rich cycling cells via gap junctions. We show that polyamines promote gap junction communication between proliferating cells by promoting dynamical microtubule plus ends at the cell periphery and thus allow polyamine exchange between cells. In this way, cycling cells favor regrowth in adjacent cells deprived of polyamines. In addition, intercellular interactions mediated by polyamines can coordinate the translational response to oxidative stress through the formation of stress granules. Some putative in vivo consequences of polyamine-mediated intercellular interactions are also discussed regarding cancer invasiveness and tissue regeneration.

Roles of nitric oxide and asymmetric dimethylarginine in pregnancy and fetal programming

Nitric oxide (NO) regulates placental blood flow and actively participates in trophoblast invasion and placental development. Asymmetric dimethylarginine (ADMA) can inhibit NO synthase, which generates NO. ADMA has been associated with uterine artery flow disturbances such as preeclampsia. Substantial experimental evidence has reliably supported the hypothesis that an adverse in utero environment plays a role in postnatal physiological and pathophysiological programming. Growing evidence suggests that the placental nitrergic system is involved in epigenetic fetal programming. In this review, we discuss the roles of NO and ADMA in normal and compromised pregnancies as well as the link between placental insufficiency and epigenetic fetal programming.

Metabolomic profiling in blood from umbilical cords of low birth weight newborns

BACKGROUND

Low birth weight has been linked to an increased risk to develop obesity, type 2 diabetes, and hypertension in adult life, although the mechanisms underlying the association are not well understood. The objective was to determine whether the metabolomic profile of plasma from umbilical cord differs between low and normal birth weight newborns.

METHODS

Fifty healthy pregnant women and their infants were selected. The eligibility criteria were being born at term and having a normal pregnancy. Pairs were grouped according to their birth weight: low birth weight (LBW, birth weight < 10th percentile, n = 20) and control (control, birth weight between the 75th-90th percentiles, n = 30). Nuclear Magnetic Resonance (NMR) was used to generate metabolic fingerprints of umbilical cord plasma samples. Simultaneously, the metabolomic profiles of the mothers were analysed. The resulting data were subjected to chemometric, principal component and partial least squares discriminant analyses.

RESULTS

Umbilical cord plasma from LBW and control newborns displayed a clearly differentiated metabolic profile. Seven metabolites were identified that discriminate the LBW from the control group. LBW newborns had lower levels of choline, proline, glutamine, alanine and glucose than did the control newborns, while plasma levels of phenylalanine and citrulline were higher in LBW newborns (p < 0.05). No significant differences were found between the two groups of mothers.

CONCLUSIONS

Low birth weight newborns display a differential metabolomic profile than those of normal birth weight, a finding not present in the mothers. The meaning and the potential utility of the findings as biomarkers of risk need to be addressed in future studies.

Biological mechanisms for nutritional regulation of maternal health and fetal development

This review paper highlights mechanisms for nutritional regulation of maternal health and fetal development. Malnutrition (nutrient deficiencies or obesity) in pregnant women adversely affects their health by causing or exacerbating a plethora of problems, such as anaemia, maternal haemorrhage, insulin resistance, and hypertensive disorders (e.g. pre-eclampsia/eclampsia). Maternal malnutrition during gestation also impairs embryonic and fetal growth and development, resulting in deleterious outcomes, including intrauterine growth restriction (IUGR), low birthweight, preterm birth, and birth defects (e.g. neural tube defects and iodine deficiency disorders). IUGR and preterm birth contribute to high rates of neonatal morbidity and mortality. Major common mechanisms responsible for malnutrition-induced IUGR and preterm birth include: (i) abnormal growth and development of the placenta; (ii) impaired placental transfer of nutrients from mother to fetus; (iii) endocrine disorders; and (iv) disturbances in normal metabolic processes. Activation of a series of physiological responses leading to premature and sustained contraction of the uterine myometrium also results in preterm birth. Recent epidemiologic studies have suggested a link between IUGR and chronic metabolic disease in children and adults, and the effects of IUGR may be carried forward to subsequent generations through epigenetics. While advanced medical therapies, which are generally unavailable in low-income countries, are required to support preterm and IUGR infants, optimal nutrition during pregnancy may help ameliorate many of these problems. Future studies are necessary to develop effective nutritional interventions to enhance fetal growth and development and alleviate the burden of maternal morbidity and mortality in low- and middle-income countries.

Melatonin supplementation alters uteroplacental hemodynamics and fetal development in an ovine model of intrauterine growth restriction

Using a mid- to late-gestation ovine model of intrauterine growth restriction (IUGR), we examined uteroplacental blood flow and fetal growth during melatonin supplementation as a 2 × 2 factorial design. At day 50 of gestation, 32 ewes were supplemented with 5 mg of melatonin (MEL) or no melatonin (CON) and were allocated to receive 100% [adequate; (ADQ)] or 60% [restricted (RES)] of nutrient requirements until day 130 of gestation. Umbilical artery blood flow was increased from day 60 to day 110 of gestation in MEL vs. CON dams, while umbilical artery blood flow was decreased from day 80 to day 110 of gestation in RES vs. ADQ dams. At day 130 of gestation, uteroplacental hemodynamics, measured under general anesthesia, and fetal growth were evaluated. Uterine artery blood flow was decreased in RES vs. ADQ dams, while melatonin supplementation did not affect uterine artery blood flow. Total placentome weight and placentome number were not different between treatment groups. Fetal weight was decreased by nutrient restriction. Abdominal girth and ponderal index were increased in fetuses from MEL-ADQ dams vs. all other groups. Fetal biparietal distance was decreased in CON-RES vs. CON-ADQ dams, while melatonin supplementation rescued fetal biparietal distance. Fetal kidney length and width were increased by maternal melatonin treatment. Fetal cardiomyocyte area was altered by both maternal melatonin treatment and nutritional plane. In summary, melatonin may negate the consequences of IUGR during specific abnormalities in umbilical blood flow as long as sufficient uterine blood perfusion is maintained during pregnancy.

Programming the offspring through altered uteroplacental hemodynamics: how maternal environment impacts uterine and umbilical blood flow in cattle, sheep and pigs

As placental growth and vascularity precedes exponential fetal growth, not only is proper establishment of the placenta important, but also a continual plasticity of placental function throughout gestation. Inadequate maternal environment, such as nutritional plane, has been documented to alter fetal organogenesis and growth, thus leading to improper postnatal growth and performance in many livestock species. The timing and duration of maternal nutritional restriction appears to influence the capillary vascularity, angiogenic profile and vascular function of the placenta in cattle and sheep. In environments where fetal growth and/or fetal organogenesis are compromised, potential therapeutics may augment placental nutrient transport capacity and improve offspring performance. Supplementation of specific nutrients, including protein, as well as hormone supplements, such as indolamines, during times of nutrient restriction may assist placental function. Current use of Doppler ultrasonography has allowed for repeated measurements of uterine and umbilical blood flow including assessment of uteroplacental hemodynamics in cattle, sheep and swine. Moreover, these variables can be monitored in conjugation with placental capacity and fetal growth at specific time points of gestation. Elucidating the consequences of inadequate maternal intake on the continual plasticity of placental function will allow us to determine the proper timing and duration for intervention.

Circulating and utero-placental adaptations to chronic placental ischemia in the rat

While utero-placental insufficiency is associated with adverse outcomes for both mother and fetus, many of the maternal-fetal adaptations during pregnancy in models of fetal compromise remain unclear. The purpose of this study was to determine if chronically reduced uterine perfusion pressure (RUPP) during days 14-19 of gestation alters feto-placental growth differentially from the cervical to ovarian ends of the uterus and generates metabolic adaptations such as increased blood lactate (BLa) concentrations and lactate transporter expression in the placenta. Fetal growth restriction was evident, placental efficiency (fetal weight/placental weight) decreased (4.7 ± 0.35 vs. 5.9 ± 0.30; P < 0.05) and fetal growth pattern within the uterus was altered in the RUPP compared to the normal pregnant (NP) rats. Blood lactate concentrations were increased (3.3 ± 0.3 vs. 2.1 ± 0.4 mmol/l; P < 0.05) in NP compared to virgin rats, and in RUPP compared to NP (5.0 ± 0.6 vs. 3.3 ± 0.3 mmol/l; P < 0.05). Lactate concentration was increased (10.0 ± 0.6 vs. 7.1 ± 0.8 mmol/l; P < 0.05) in the media from hypoxic compared to normoxic BeWo cells. No changes in expression of placental MCT1, 2, or 4 were observed between RUPP and NP rats. RUPP resulted in decreased plasma leptin (2.0 ± 0.3 vs. 3.1 ± 0.4; P < 0.05) but no change in IGF-1 compared to NP. The present data indicate chronic placental ischemia results in numerous endocrine and metabolic changes during late pregnancy in the rat and that the RUPP model has differential effects on fetal growth depending on uterine position.

Cord blood metabolomic profiling in intrauterine growth restriction

A number of metabolic abnormalities have been observed in pregnancies complicated by intrauterine growth restriction (IUGR). Metabolic fingerprinting and clinical metabolomics have recently been proposed as tools to investigate individual phenotypes beyond genomes and proteomes and to advance hypotheses on the genesis of diseases. Non-targeted metabolomic profiling was employed to study fetal and/or placental metabolism alterations in IUGR fetuses by liquid chromatography high-resolution mass spectrometry (LC-HRMS) analysis of cord blood collected soon after birth. Samples were collected from 22 IUGR and 21 appropriate for gestational age (AGA) fetuses. Birth weight differed significantly between IUGR and AGA fetuses (p < 0.001). Serum samples were immediately obtained and deproteinized by mixing with methanol at room temperature and centrifugation; supernatants were lyophilized and reconstituted in water for analysis. LC-HRMS analyses were performed on an Orbitrap mass spectrometer linked to a Surveyor Plus LC. Samples were injected into a 1.0 × 150-mm Luna C18 column. Spectra were collected in full-scan mode at a resolution of approximately 30,000. Data were acquired over the m/z range of 50-1,000, with measurements performed in duplicate. To observe metabolic variations between the two sets of samples, LC-HRMS data were analyzed by a principal component analysis model. Many features (e.g., ionic species with specific retention times) differed between the two classes of samples: among these, the essential amino acids phenylalanine, tryptophan, and methionine were identified by comparison with available databases. Logistic regression coupled to a receiver-operating characteristic curve identified a cut-off value for phenylalanine and tryptophan, which gave excellent discrimination between IUGR and AGA fetuses. Non-targeted LC-HRMS analysis of cord blood collected at birth allowed the identification of significant differences in relative abundances of essential amino acids between IUGR and AGA fetuses, emerging as a promising tool for studying metabolic alterations.

Polyamines on the reproductive landscape

The polyamines are ubiquitous polycationic compounds. Over the past 40 yr, investigation has shown that some of these, namely spermine, spermidine, and putrescine, are essential to male and female reproductive processes and to embryo/fetal development. Indeed, their absence is characterized by infertility and arrest in embryogenesis. Mammals synthesize polyamines de novo from amino acids or import these compounds from the diet. Information collected recently has shown that polyamines are essential regulators of cell growth and gene expression, and they have been implicated in both mitosis and meiosis. In male reproduction, polyamine expression correlates with stages of spermatogenesis, and polyamines appear to function in promoting sperm motility. There is evidence for polyamine involvement in ovarian follicle development and ovulation in female mammals, and polyamine synthesis is required for steroidogenesis in the ovary. Studies of the embryo indicate a polyamine requirement that can be met from maternal sources before implantation, whereas elimination of polyamine synthesis abrogates embryo development at gastrulation. Polyamines play roles in embryo implantation, in decidualization, and in placental formation and function, and polyamine privation during gestation results in intrauterine growth retardation. Emerging information implicates dietary arginine and dietary polyamines as nutritional regulators of fertility. The mechanisms by which polyamines regulate these multiple and diverse processes are not yet well explored; thus, there is fertile ground for further productive investigation.

Low amino acids affect expression of 11β-HSD2 in BeWo cells through leptin-activated JAK-STAT and MAPK pathways

Maternal protein restriction diminishes placental 11β-hydroxysteroid dehydrogenase type 2 (11β-HSD2) activity and causes fetal growth restriction in mammals. However, it is unknown whether such effect was caused directly by nutrient deficiency, or indirectly through the mediation of maternal hormones. In the present study, a human placental cell line (BeWo) was cultured in F12K as control and F12 as low amino acids (LAA) media for 48 h to investigate the effects of amino acids deficiency on 11β-HSD2 expression and activity. Despite a significant up-regulation of 11β-HSD2 mRNA expression in LAA cells, 11β-HSD2 activity and protein content were decreased by 38 and 54%, respectively (P<0.05), indicating a mechanism of post-transcriptional regulation. Among 5 miRNAs targeting 11β-HSD2, miR-498 was expressed significantly higher in LAA cells. Leptin concentration was significantly lower (P<0.01) in LAA medium. The mRNA expression of both isoforms of leptin receptor was significantly higher in LAA cells, although no difference was detected at protein level. To further clarify whether leptin is involved in mediating the effect of LAA on 11β-HSD2 activity, leptin was supplemented to LAA medium, whereas three specific inhibitors of leptin signaling pathways, WP1066 for JAK-STAT, PD98059 for MAPK and LY294002 for PI3K, respectively were added to control medium. Leptin restored the diminished 11β-HSD2 activity in LAA cells, whereas WP1066 (5 nM) and PD98059 (50 nM) significantly decreased 11β-HSD2 activity in control cells. In conclusion, the present results indicate that LAA diminishes 11β-HSD2 expression and activity in BeWo cells through leptin-activated JAK-STAT and MAPK pathways.

Heifer nutrient intake during early- and mid-gestation programs adult offspring adiposity and mRNA expression of growth-related genes in adipose depots

Changes in maternal nutrient intake during gestation alter IGF receptor abundance and leptin (LEP) mRNA expression in fetal adipose tissue. It is not known whether such changes persist into adult life and whether they are associated with an effect on phenotype. We investigated the effect of high (240%) and low (70%) levels of recommended daily crude protein intake for beef heifers during the first and second trimesters of gestation on singleton progeny (n=68): subcutaneous (SC) adipose tissue depth at rump (P8) and rib (RF) sites from 65 until 657 days of age; plasma leptin concentrations from birth until 657 days and expression of IGF1 and IGF2, their receptors (IGF1R and IGF2R) and LEP mRNA in perirenal (PR), omental (OM) and SC adipose tissue at 680 days of age. High-protein diets during the first trimester increased LEP and IGF1 mRNA in PR of males and females, respectively, compared with low-protein diets, and decreased IGF1R mRNA in SC of all progeny but increased RF depth of males between 552 and 657 days. High-protein diets compared with low-protein diets during the second trimester increased IGF1R mRNA in PR and OM of all progeny; LEP mRNA in PR of males; and IGF2 and IGF2R mRNA in OM of all progeny. Conversely, LEP mRNA in OM and IGF2 mRNA in PR of all progeny were decreased following exposure to high- compared with low-protein diets during the second trimester. Heifer diet during gestation has permanent sex- and depot-specific effects on the expression of adipogenic and adipocytokine genes and offspring adiposity.

Protein intake during gestation affects postnatal bovine skeletal muscle growth and relative expression of IGF1, IGF1R, IGF2 and IGF2R

Expression of insulin-like growth factor (IGF)1 and IGF2 and their receptor (IGF1R and IGF2R) mRNA in fetal skeletal muscle are changed by variations in maternal nutrient intake. The persistence of these effects into postnatal life and their association with phenotype in beef cattle is unknown. Here we report that the cross-sectional areas of longissimus dorsi and semitendinosus (ST) muscles were greater for mature male progeny born to heifers fed low protein diets (70% vs. 240% of recommended) during the first trimester. In ST, this was accompanied by greater IGF1, IGF2 and IGF2R mRNA at 680 d. Females exposed to low protein diets during the first trimester had decreased IGF2 mRNA in ST at 680 d, however this did not result in an effect to phenotype. Exposure to low protein diets during the second trimester increased IGF1R mRNA in ST of all progeny at 680 d. Changes to expression of IGF genes in progeny skeletal muscle resulting from variations to maternal protein intake during gestation may have permanent and sex-specific effect on postnatal skeletal muscle growth.

Correlation of 2nd trimester amniotic fluid amino acid profile with gestational age and estimated fetal weight

OBJECTIVES

Our aim was to identify and quantitate free amino acids in human amniotic fluid (AF) specimens collected during 2nd trimester amniocentesis and determine the correlation between amino acid concentrations, gestational age, and estimated fetal weight.

METHODS

Seventy-eight AF samples were retrieved between 18 and 22 weeks of gestation. Fetal weight estimation was based on fetal biometric measurements.

RESULTS

Twenty-one amino acids were quantified. The concentration of glutamine exhibited the greatest correlation with gestational age (r = 0.477, p < 0.01). Additionally, significant negative correlations were recorded between gestational age and levels of alanine, proline, lysine, valine, taurine, leucine, glutamic acid, tyrosine, phenylalanine, isoleucine, ornithine, methionine, and tryptophane (p < 0.05). After adjusting for maternal age, fetal gender, intervals between consecutive pregnancies, pre-pregnancy body mass index, and smoking during pregnancy the strength of the correlation for proline and lysine decreased. A stepwise multiple linear regression model including gestational age as a first level predictor of fetal weight indicated that lysine and cysteine concentrations were additional predictors.

CONCLUSIONS

Our results suggest that AF amino acids are crucial for fetal growth. Our purpose was not to establish an immediate diagnostic application. However, further exploration is likely to be fruitful, especially in high-risk pregnancies.

Maternal amino acid supplementation for intrauterine growth restriction

Maternal dietary protein supplementation to improve fetal growth has been considered as an option to prevent or treat intrauterine growth restriction. However, in contrast to balanced dietary supplementation, adverse perinatal outcomes in pregnant women who received high amounts of dietary protein supplementation have been observed. The responsible mechanisms for these adverse outcomes are unknown. This review will discuss relevant human and animal data to provide the background necessary for the development of explanatory hypotheses and ultimately for the development therapeutic interventions during pregnancy to improve fetal growth. Relevant aspects of fetal amino acid metabolism during normal pregnancy and those pregnancies affected by IUGR will be discussed. In addition, data from animal experiments which have attempted to determine mechanisms to explain the adverse responses identified in the human trials will be presented. Finally, we will suggest new avenues for investigation into how amino acid supplementation might be used safely to treat and/or prevent IUGR.

Breed differences in fetal and placental development and feto-maternal amino acid status following nutrient restriction during early and mid pregnancy in Scottish Blackface and Suffolk sheep

This study assessed the effect of feeding 0.75 energy requirements between Days 1 and 90 of pregnancy on placental development and feto-placental amino acid status on Day 125 of pregnancy in Scottish Blackface and Suffolk ewes carrying a single fetus. Such moderate nutrient restriction did not affect placental size, placentome number or the distribution of placentome types. Although fetal weight was unaffected by maternal nutrition, fetuses carried by nutrient restricted mothers had relatively lighter brains and gastrocnemius muscles. Suffolk fetuses were heavier and longer with a greater abdominal circumference, relatively lighter brains, hearts and kidneys, but heavier spleens, livers and gastrocnemius muscles than Blackface fetuses. Total placentome weight was greater in Suffolk than Blackface ewes. Ewe breed had a greater effect on amino acid concentrations than nutrition. Ratios of maternal to fetal amino acid concentrations were greater in Suffolk ewes than Blackface ewes, particularly for some essential amino acids. The heavier liver and muscles in Suffolk fetuses may suggest increased amino acid transport across the Suffolk placenta in the absence of breed differences in gross placental efficiency. These data provide evidence of differences in nutrient handling and partitioning between the maternal body and the fetus in the two breeds studied.

Partial contributions of developmental hypoxia and undernutrition to prenatal alterations in somatic growth and cardiovascular structure and function

OBJECTIVE

The objective of the study was to compare and contrast the effects of developmental hypoxia vs undernutrition on fetal growth, cardiovascular morphology, and function.

STUDY DESIGN

On day 15 of gestation, Wistar dams were divided into control, hypoxic (10% O(2)), or undernourished (35% reduction in food intake) pregnancy. On day 20, fetal thoraces were fixed, and the fetal heart and aorta underwent quantitative histological analysis. In a separate group, fetal aortic vascular reactivity was determined via wire myography.

RESULTS

Both hypoxic and undernourished pregnancy was associated with asymmetric fetal growth restriction. Pregnancy complicated by hypoxia promoted fetal aortic thickening without changes in cardiac volumes when expressed as a percentage of total heart volume. In contrast, maternal undernutrition affected fetal cardiac morphology without changes in aortic structure. Fetal aortic vascular reactivity was also differentially affected by hypoxia or undernutrition.

CONCLUSION

Developmental hypoxia or undernutrition in late gestation has differential effects on fetal cardiovascular morphology and function.

Parenteral administration of L-arginine prevents fetal growth restriction in undernourished ewes

Intrauterine growth restriction (IUGR) is a major health problem worldwide that currently lacks an effective therapeutic solution. This study was conducted with an ovine IUGR model to test the hypothesis that parenteral administration of l-arginine (Arg) is effective in enhancing fetal growth. Beginning on d 28 of gestation, ewes were fed a diet providing 100% (control-fed) or 50% (underfed) of NRC-recommended nutrient requirements. Between d 60 of gestation and parturition, underfed ewes received i.v. infusions of saline or 155 micromol Arg-HCl/kg body weight 3 times daily, whereas control-fed ewes received only saline. The birth weights of lambs from saline-infused underfed ewes were 23% lower (P < 0.01) than those of lambs from control-fed dams. Administration of Arg to underfed ewes increased (P < 0.01) concentrations of Arg (69%), ornithine (55%), proline (29%), methionine (37%), leucine (36%), isoleucine (35%), cysteine (19%), and FFA (43%) in maternal serum, decreased maternal circulating levels of ammonia (18%) and triglycerides (32%), and enhanced birth weights of lambs by 21% compared with saline-infused underfed ewes. There was no difference in birth weights of lambs between the control-fed and the Arg-infused underfed ewes. These novel results indicate that parenteral administration of Arg to underfed ewes prevented fetal growth restriction and provide support for its clinical use to ameliorate IUGR in humans. The findings also lay a new framework for studying cellular and molecular mechanisms responsible for the beneficial effects of Arg in regulating conceptus growth and development.

Sildenafil citrate treatment enhances amino acid availability in the conceptus and fetal growth in an ovine model of intrauterine growth restriction

Adequate placental blood flow is essential for the optimal delivery of nutrients from mother to fetus for conceptus growth. Restricted fetal development results from pathophysiological and environmental factors that alter utero-placental blood flow, placental function, and, therefore, nutrient availability in the fetus. To test this hypothesis, 0, 75, or 150 mg/d sildenafil citrate (Viagra) was administered subcutaneously from d 28 to 115 of gestation to either nutrient-restricted [50% of NRC requirements) or adequately-fed ewes (100% of NRC requirements). On d 115, maternal, fetal, and placental tissues and fluids were collected. Concentrations of total amino acids and polyamines in uterine venous and arterial sera, amniotic and allantoic fluids, and fetal umbilical venous serum were lower (P < 0.05) in nutrient-restricted ewes than in adequately fed ewes, as were the ratios of total amino acids in fetal umbilical venous serum to uterine arterial serum. Sildenafil citrate dose-dependently increased (P < 0.05) total amino acids and polyamines in amniotic fluid, allantoic fluid, and fetal serum without affecting values in maternal serum. Fetal weight was lower (P < 0.05) in nutrient-restricted ewes on d 115. Sildenafil citrate treatment dose-dependently increased (P < 0.05) fetal weight in both nutrient-restricted and adequately fed ewes. This study supports the hypothesis that long-term sildenafil citrate treatment enhances fetal growth, at least in part, by increasing the availability of amino acids in the conceptus. These findings may lead to the clinical use of sildenafil citrate in human pregnancies suspected to be at risk for intrauterine fetal growth retardation.