Diet reduction to requirements in obese/overfed ewes from early gestation prevents glucose/insulin dysregulation and returns fetal adiposity and organ development to control levels

The influence of maternal prepregnancy weight and gestational weight gain on the umbilical cord blood metabolome: a case-control study

BACKGROUND

Maternal overweight/obesity and excessive gestational weight gain (GWG) are frequently reported to be risk factors for obesity and other metabolic disorders in offspring. Cord blood metabolites provide information on fetal nutritional and metabolic health and could provide an early window of detection of potential health issues among newborns. The aim of the study was to explore the impact of maternal prepregnancy overweight/obesity and excessive GWG on cord blood metabolic profiles.

METHODS

A case control study including 33 pairs of mothers with prepregnancy overweight/obesity and their neonates, 30 pairs of mothers with excessive GWG and their neonates, and 32 control mother-neonate pairs. Untargeted metabolomic profiling of umbilical cord blood samples were performed using UHPLC‒MS/MS.

RESULTS

Forty-six metabolites exhibited a significant increase and 60 metabolites exhibited a significant reduction in umbilical cord blood from overweight and obese mothers compared with mothers with normal body weight. Steroid hormone biosynthesis and neuroactive ligand‒receptor interactions were the two top-ranking pathways enriched with these metabolites (P = 0.01 and 0.03, respectively). Compared with mothers with normal GWG, in mothers with excessive GWG, the levels of 63 metabolites were increased and those of 46 metabolites were decreased in umbilical cord blood. Biosynthesis of unsaturated fatty acids was the most altered pathway enriched with these metabolites (P < 0.01).

CONCLUSIONS

Prepregnancy overweight and obesity affected the fetal steroid hormone biosynthesis pathway, while excessive GWG affected fetal fatty acid metabolism. This emphasizes the importance of preconception weight loss and maintaining an appropriate GWG, which are beneficial for the long-term metabolic health of offspring.

Maternal hepatic adaptations during obese pregnancy encompass lobe-specific mitochondrial alterations and oxidative stress

Maternal obesity (MO) is rising worldwide, affecting half of all gestations, constituting a possible risk-factor for some pregnancy-associated liver diseases (PALD) and hepatic diseases. PALD occur in approximately 3% of pregnancies and are characterized by maternal hepatic oxidative stress (OS) and mitochondrial dysfunction. Maternal hepatic disease increases maternal and fetal morbidity and mortality. Understanding the role of MO on liver function and pathophysiology could be crucial for better understanding the altered pathways leading to PALD and liver disease, possibly paving the way to prevention and adequate management of disease. We investigated specific hepatic metabolic alterations in mitochondria and oxidative stress during MO at late-gestation. Maternal hepatic tissue was collected at 90% gestation in Control and MO ewes (fed 150% of recommended nutrition starting 60 days before conception). Maternal hepatic redox state, mitochondrial respiratory chain (MRC), and OS markers were investigated. MO decreased MRC complex-II activity and its subunits SDHA and SDHB protein expression, increased complex-I and complex-IV activities despite reduced complex-IV subunit mtCO1 protein expression, and increased ATP synthase ATP5A subunit. Hepatic MO-metabolic remodeling was characterized by decreased adenine nucleotide translocator 1 and 2 (ANT-1/2) and voltage-dependent anion channel (VDAC) protein expression and protein kinase A (PKA) activity (P<0.01), and augmented NAD+/NADH ratio due to reduced NADH levels (P<0.01). MO showed an altered redox state with increased OS, increased lipid peroxidation (P<0.01), decreased GSH/GSSG ratio (P=0.005), increased superoxide dismutase (P=0.03) and decreased catalase (P=0.03) antioxidant enzymatic activities, lower catalase, glutathione peroxidase (GPX)-4 and glutathione reductase protein expression (P<0.05), and increased GPX-1 abundance (P=0.03). MO-related hepatic changes were more evident in the right lobe, corroborated by the integrative data analysis. Hepatic tissue from obese pregnant ewes showed alterations in the redox state, consistent with OS and MRC and metabolism remodeling. These are hallmarks of PALD and hepatic disease, supporting MO as a risk-factor and highlighting OS and mitochondrial dysfunction as mechanisms responsible for liver disease predisposition.

Made in the Womb: Maternal Programming of Offspring Cardiovascular Function by an Obesogenic Womb

Obesity incidence has been increasing at an alarming rate, especially in women of reproductive age. It is estimated that 50% of pregnancies occur in overweight or obese women. It has been described that maternal obesity (MO) predisposes the offspring to an increased risk of developing many chronic diseases in an early stage of life, including obesity, type 2 diabetes, and cardiovascular disease (CVD). CVD is the main cause of death worldwide among men and women, and it is manifested in a sex-divergent way. Maternal nutrition and MO during gestation could prompt CVD development in the offspring through adaptations of the offspring's cardiovascular system in the womb, including cardiac epigenetic and persistent metabolic programming of signaling pathways and modulation of mitochondrial metabolic function. Currently, despite diet supplementation, effective therapeutical solutions to prevent the deleterious cardiac offspring function programming by an obesogenic womb are lacking. In this review, we discuss the mechanisms by which an obesogenic intrauterine environment could program the offspring's cardiovascular metabolism in a sex-divergent way, with a special focus on cardiac mitochondrial function, and debate possible strategies to implement during MO pregnancy that could ameliorate, revert, or even prevent deleterious effects of MO on the offspring's cardiovascular system. The impact of maternal physical exercise during an obesogenic pregnancy, nutritional interventions, and supplementation on offspring's cardiac metabolism are discussed, highlighting changes that may be favorable to MO offspring's cardiovascular health, which might result in the attenuation or even prevention of the development of CVD in MO offspring. The objectives of this manuscript are to comprehensively examine the various aspects of MO during pregnancy and explore the underlying mechanisms that contribute to an increased CVD risk in the offspring. We review the current literature on MO and its impact on the offspring's cardiometabolic health. Furthermore, we discuss the potential long-term consequences for the offspring. Understanding the multifaceted effects of MO on the offspring's health is crucial for healthcare providers, researchers, and policymakers to develop effective strategies for prevention and intervention to improve care.

Maternal Exposure to Oxidized Soybean Oil Impairs Placental Development by Modulating Nutrient Transporters in a Rat Model

INTRODUCTION

As an exogenous food contaminant, dietary oxidized lipid impairs growth and development, and triggers chronic diseases in humans or animals. This study explores the effects of soybean oil with different oxidative degree on the placental injury of gestational rats.

METHODS AND RESULTS

Thirty-two female adult rats are randomly assigned to four groups. The control group is fed the purified diet with fresh soybean oil (FSO), and the treatment groups are fed purified diets with lipid content replaced by oxidized soybean oil (OSO) at 200, 400, and 800 mEqO2 kg-1 from conception until delivery. On day 20 of gestation, OSO decreased placental and embryonic weights as the oxidative degree increased linearly and quadratically. The expression of Bax showed a linear increase, and Bcl-2 decreased as the oxidative degree increased. The expression of Fosl1 and Esx1 is linearly and quadratically decreased in OSO-treated groups than FSO group. OSO decreased the level of IL-10 but increased expression of IL-1β in placenta and plasma. OSO remarkably upregulates levels of Fatp1 and Glut1 and decreases expression of Snat2 and Glut3.

CONCLUSION

OSO aggravates placental injury by modulating nutrient transporters and apoptosis-related genes, impedes placental growth and development, and ultimately leads to the decrease of fetal weight.

The Impact of Maternal Body Composition and Dietary Fat Consumption upon Placental Lipid Processing and Offspring Metabolic Health

The proportion of women of reproductive age who are overweight or obese is increasing globally. Gestational obesity is strongly associated in both human studies and animal models with early-onset development of adult-associated metabolic diseases including metabolic syndrome in the exposed offspring. However, animal model studies have suggested that gestational diet in obese pregnancies is an independent but underappreciated mediator of offspring risk for later life metabolic disease, and human diet consumption data have highlighted that many women do not follow nutritional guidelines prior to and during pregnancy. Thus, this review will highlight how maternal diet independent from maternal body composition impacts the risk for later-life metabolic disease in obesity-exposed offspring. A poor maternal diet, in combination with the obese metabolic state, are understood to facilitate pathological in utero programming, specifically through changes in lipid handling processes in the villous trophoblast layer of the placenta that promote an environment associated with the development of metabolic disease in the offspring. This review will additionally highlight how maternal obesity modulates villous trophoblast lipid processing functions including fatty acid transport, esterification and beta-oxidation. Further, this review will discuss how altering maternal gestational diet may ameliorate these functional changes in lipid metabolic processes in the obese placenta.

A heretical view: rather than a solely placental protective function, placental 11β hydroxysteroid dehydrogenase 2 also provides substrate for fetal peripheral cortisol synthesis in obese pregnant ewes

Exposure to glucocorticoid levels higher than appropriate for current developmental stages induces offspring metabolic dysfunction. Overfed/obese (OB) ewes and their fetuses display elevated blood cortisol, while fetal Adrenocorticotropic hormone (ACTH) remains unchanged. We hypothesized that OB pregnancies would show increased placental 11β hydroxysteroid dehydrogenase 2 (11β-HSD2) that converts maternal cortisol to fetal cortisone as it crosses the placenta and increased 11β-HSD system components responsible for peripheral tissue cortisol production, providing a mechanism for ACTH-independent increase in circulating fetal cortisol. Control ewes ate 100% National Research Council recommendations (CON) and OB ewes ate 150% CON diet from 60 days before conception until necropsy at day 135 gestation. At necropsy, maternal jugular and umbilical venous blood, fetal liver, perirenal fat, and cotyledonary tissues were harvested. Maternal plasma cortisol and fetal cortisol and cortisone were measured. Fetal liver, perirenal fat, cotyledonary 11β-HSD1, hexose-6-phosphate dehydrogenase (H6PD), and 11β-HSD2 protein abundance were determined by Western blot. Maternal plasma cortisol, fetal plasma cortisol, and cortisone were higher in OB vs. CON (p < 0.01). 11β-HSD2 protein was greater (p < 0.05) in OB cotyledonary tissue than CON. 11β-HSD1 abundance increased (p < 0.05) in OB vs. CON fetal liver and perirenal fat. Fetal H6PD, an 11β-HSD1 cofactor, also increased (p < 0.05) in OB vs. CON perirenal fat and tended to be elevated in OB liver (p < 0.10). Our data provide evidence for increased 11β-HSD system components responsible for peripheral tissue cortisol production in fetal liver and adipose tissue, thereby providing a mechanism for an ACTH-independent increase in circulating fetal cortisol in OB fetuses.

Effect of maternal obesity on fetal and postnatal baboon (Papio species) early life phenotype

BACKGROUND

Non-human primate models of developmental programming by maternal obesity (MO) are needed for translation to human programming outcomes. We present baboon offspring (F1) morphometry, blood cortisol, and adrenocorticotropic hormone (ACTH) from 0.9 gestation to 0-2 years.

METHODS

Control mothers ate chow; MO mothers ate high-fat high-energy diet pre-pregnancy through lactation.

RESULTS

Maternal obesity mothers weighed more than controls pre-pregnancy. Maternal obesity gestational weight gain was lower with no correlation with fetal or placenta weights. At 0.9 gestation, MO and control F1 morphometry and ACTH were similar. MO-F1 0.9 gestation male cortisol was lower, rising slower from 0-2 years vs control-F1. At birth, male MO-F1 and control-F1 weights were similar, but growth from 0-2 years was steeper in MO-F1; newborn female MO-F1 weighed more than control-F1 but growth from 0-2 years was similar. ACTH did not change in either sex.

CONCLUSIONS

Maternal obesity produced sexually dimorphic fetal and postnatal growth and hormonal phenotypes.

Pregnancy and Lactation: A Window of Opportunity to Improve Individual Health

Human and animal studies indicate that obesity during pregnancy adversely impacts both maternal health and offspring phenotype predisposing them to chronic diseases later in life including obesity, dyslipidemia, type 2 diabetes mellitus, and hypertension. Effective interventions during human pregnancy and/or lactation are needed to improve both maternal and offspring health. This review addresses the relationship between adverse perinatal insults and its negative impact on offspring development and presents some maternal intervention studies such as diet modification, probiotic consumption, or maternal exercise, to prevent or alleviate the negative outcomes in both the mother and her child.

Rapid Communication: Reduced maternal nutrition during early- to mid-gestation elevates newborn lamb plasma cortisol concentrations and eliminates the neonatal leptin surge

Human epidemiological and animal studies show that maternal nutrient reduction (MNR) and maternal overnutrition/obesity (MO) alter fetal growth and development, predisposing offspring (F1) to endocrine and appetite dysregulation. Compared to F1 of control-fed ewes, F1 of MO ewes display hypercortisolemia at birth and fail to exhibit the neonatal leptin surge implicated in lifelong appetite regulation. Here, we determined if MNR also elevates newborn lamb plasma cortisol and eliminates the neonatal leptin surge. Starting 30 d prior to conception, nulliparous control (CON, n = 6) ewes ate 100% NRC recommendations through parturition. Nutrient-reduced (NR, n = 6) ewes ate a CON diet through day 27 of gestation. From gestational days 28 to 78, NR ewes ate 50% of the CON diet before realimentation to 100% NRC recommendations. Jugular blood was collected daily from lambs from birth (day 0) through postnatal day 10, to determine plasma cortisol and leptin. Newborn NR plasma cortisol concentrations were increased (P < 0.0001) vs. CON and were similar to concentrations in MO lambs. Plasma leptin concentrations were similar between groups through postnatal day 7. The leptin surge, seen in CON lambs on postnatal days 8 to 10 was not present in NR lambs. These data show that, similar to MO lambs, early pregnancy MNR elevates newborn lamb plasma cortisol and eliminates the neonatal leptin surge. In the light of the similar elevation of neonatal cortisol in MNR and MO lambs, we conclude that cortisol plays a central role in regulating the neonatal lamb leptin surge.

Maternal obesity impairs fetal cardiomyocyte contractile function in sheep

Obesity is a major public health problem worldwide. In the United States, one-third of women of reproductive age are obese. Human studies show that maternal obesity (MO) predisposes offspring to cardiovascular disease. However, the underlying mechanisms remain unclear. Given the similarities between pregnancy in sheep and humans, we studied sheep to examine the impact of MO on fetal cardiomyocyte contractility at term. We observed that MO impaired cardiomyocyte contractility by reducing peak shortening and shortening/relengthening velocity, prolonging time to relengthening. MO disrupted Ca²⁺ homeostasis in fetal cardiomyocytes, increasing intracellular Ca²⁺ and inducing cellular Ca²⁺ insensitivity. The Ca²⁺-release channel was impaired, but Ca²⁺ uptake was unaffected by MO. The upstream kinases that phosphorylate the Ca²⁺-release channel-ryanodine receptor-2, PKA, and calmodulin-dependent protein kinase II-were activated in MO fetuses. Contractile dysfunction was associated with an increased ratio of myosin heavy chain (MHC)-β to MHC-α and upregulated cardiac troponin (cTn)-T and tropomyosin, as well as cTn-I phosphorylation. In summary, this is the first characterization of the effects of MO on fetal cardiomyocyte contractility. Our findings indicate that MO impairs fetal cardiomyocyte contractility through altered intracellular Ca²⁺ handling, overloading fetal cardiomyocyte intracellular Ca²⁺ and aberrant myofilament protein composition. These mechanisms may contribute to developmental programming by MO of offspring cardiac function and predisposition to later life cardiovascular disease in the offspring.-Wang, Q., Zhu, C., Sun, M., Maimaiti, R., Ford, S. P., Nathanielsz, P. W., Ren, J., Guo, W. Maternal obesity impairs fetal cardiomyocyte contractile function in sheep.

Effects of maternal obesity on maternal and fetal plasma concentrations of adiponectin and expression of adiponectin and its receptor genes in cotyledonary and adipose tissues at mid- and late-gestation in sheep

Adiponectin potentially influences fetal weight by altering insulin signaling and trans-placental amino acid and glucose transporters. The objective of this study was to determine how maternal obesity influences maternal and fetal plasma concentrations of adiponectin, expression of fetal adiponectin, its receptors, and adipogenic genes at mid- and late-gestation. Blood samples and tissues were collected from obese and control multiparous pregnant ewes at day 75 or 135 of gestation. Although day of gestation or maternal obesity did not influence (P >  0.6) maternal plasma concentrations of adiponectin, fetal weight was increased (P <  0.001) and adiponectin tended to decrease (P =  0.10) at mid-gestation in fetuses from obese ewes. Differences were not apparent at late-gestation (P > 0.70). Relative abundance of adiponectin (P =  0.01), AdipoR2 (P =  0.04) and PPARγ (P =  0.01) mRNA was less at mid-gestation in fetal adipose tissue from obese mothers. By late gestation, maternal obesity tended to associated with a decrease in relative abundance of adiponectin (P =  0.09) and SREBF1 (P =  0.10) mRNA in fetal adipose tissue. Maternal obesity did not influence (P ≥  0.20) the relative abundance of adiponectin, AdipoR1 and AdipoR2 mRNA in cotyledonary tissue at mid or late- gestation. In conclusion, maternal obesity in sheep influences relative abundance of fetal adipose tissue mRNA for adiponectin and adipogenic, as well as plasma concentrations of total adiponectin. Although adiposity in pregnant ewes did not influence maternal adiponectin, maternal obesity potentially influenced fetal adipogenesis by altering the abundance of adiponectin, PPARγ and SREBF1 mRNA in fetal adipose tissue.

Maternal obesity in the ewe increases cardiac ventricular expression of glucocorticoid receptors, proinflammatory cytokines and fibrosis in adult male offspring

Obesity during human pregnancy predisposes offspring to obesity and cardiovascular disease in postnatal life. In a sheep model of maternal overnutrition/obesity we have previously reported myocardial inflammation and fibrosis, as well as cardiac dysfunction in late term fetuses, in association with chronically elevated blood cortisol. Significant research has suggested a link between elevated glucocorticoid exposure in utero and hypertension and cardiovascular disease postnatally. Here we examined the effects of maternal obesity on myocardial inflammation and fibrosis of their adult offspring. Adult male offspring from control (CON) mothers fed 100% of National Research Council (NRC) recommendations (n = 6) and male offspring from obese mothers (MO) fed 150% NRC (n = 6), were put on a 12-week ad libitum feeding challenge then necropsied. At necropsy, plasma cortisol and left and right ventricular thickness were markedly increased (P<0.05) in adult male MO offspring. Myocardial collagen content and collagen-crosslinking were greater (P<0.05) in MO offspring compared to CON offspring in association with increased mRNA and protein expression of glucocorticoid receptors (GR). No group difference was found in myocardial mineralocorticoids receptor (MR) protein expression. Further, mRNA expression for the proinflammatory cytokines: cluster of differentiation (CD)-68, transforming growth factor (TGF)-β1, and tumor necrosis factor (TNF)-α were increased (P < 0.05), and protein expression of CD-68, TGF-β1, and TNF-α tended to increase (P<0.10) in MO vs. CON offspring. These data provide evidence for MO-induced programming of elevated plasma cortisol and myocardial inflammation and fibrosis in adult offspring potentially through increased GR.

Effects of maternal nutrient restriction during early or mid-gestation without realimentation on maternal physiology and foetal growth and development in beef cattle

The aim of this study is to determine the effects of early and mid-gestation nutrient restriction on maternal metabolites and foetal growth. Primiparous Angus cows were synchronized and inseminated with semen from one sire. Dietary treatments were: control to gain 1 kg/week (CON) or 0.55% maintenance energy and CP requirements (nutrient restricted; NR). A subset of dams was fed NR (n=8) or CON (n=8) from days 30 to 110 of gestation. Another group was fed CON (n=8), days 30 to 190; NR (n=7), days 30 to 110 followed by CON days 110 to 190; or CON, (n=7) days 30 to 110 followed by NR days 110 to 190. Cows were harvested at days 110 or 190 of gestation, when foetal measurements and samples were collected. Cows that were NR during days 30 to 110 or 110 to 190 of gestation lost significant BW and body condition score (P<0.001), this was associated with reduced plasma glucose during NR (P<0.002). Foetal weights, empty foetal weights, abdominal and thoracic circumferences were all reduced (P<0.03) in day 110 NR animals. Foetal perirenal adipose as a percentage of empty foetal weight was increased (P=0.01) in NR day 110 female foetuses compared with CON foetus. Maternal serum triglycerides at day 110 of gestation were decreased (P<0.05) in NR dams, whereas foetal serum triglycerides were increased (P<0.05) in response to maternal NR. Foetal weights tended to be reduced (P=0.08) in NR/CON and CON/NR v. CON/CON cattle at day 190 of gestation. Empty foetal weights, abdominal and thoracic circumferences were reduced (P⩽0.03) in NR/CON and CON/NR v. CON/CON cattle. Brain weight as a percentage of empty foetal weight was increased (P<0.001) in NR/CON and CON/NR v. CON/CON cattle. Foetal perirenal adipose as a percentage of empty foetal weight was increased (P=0.003) in NR/CON and CON/NR v. CON/CON cattle. Maternal serum triglycerides at day 190 of gestation were decreased (P<0.05) in association with maternal NR. Foetal serum triglycerides at day 190 of gestation were increased (P<0.05) in response to maternal NR during early gestation but decreased by NR in mid gestation compared with CON foetuses. The data show that maternal nutrient restriction during early or mid-gestation cause's asymmetrical foetal growth restriction, regardless if the restriction is preceded or followed by a period of non-restriction.

Placental phenotype and the insulin-like growth factors: resource allocation to fetal growth

The placenta is the main determinant of fetal growth and development in utero. It supplies all the nutrients and oxygen required for fetal growth and secretes hormones that facilitate maternal allocation of nutrients to the fetus. Furthermore, the placenta responds to nutritional and metabolic signals in the mother by altering its structural and functional phenotype, which can lead to changes in maternal resource allocation to the fetus. The molecular mechanisms by which the placenta senses and responds to environmental cues are poorly understood. This review discusses the role of the insulin-like growth factors (IGFs) in controlling placental resource allocation to fetal growth, particularly in response to adverse gestational environments. In particular, it assesses the impact of the IGFs and their signalling machinery on placental morphogenesis, substrate transport and hormone secretion, primarily in the laboratory species, although it draws on data from human and other species where relevant. It also considers the role of the IGFs as environmental signals in linking resource availability to fetal growth through changes in the morphological and functional phenotype of the placenta. As altered fetal growth is associated with increased perinatal morbidity and mortality and a greater risk of developing adult-onset diseases in later life, understanding the role of IGFs during pregnancy in regulating placental resource allocation to fetal growth is important for identifying the mechanisms underlying the developmental programming of offspring phenotype by suboptimal intrauterine growth.

Expression of epigenetic machinery genes is sensitive to maternal obesity and weight loss in relation to fetal growth in mice

BACKGROUND

Maternal obesity impacts fetal growth and pregnancy outcomes. To counteract the deleterious effects of obesity on fertility and pregnancy issue, preconceptional weight loss is recommended to obese women. Whether this weight loss is beneficial/detrimental for offspring remains poorly explored. Epigenetic mechanisms could be affected by maternal weight changes, perturbing expression of key developmental genes in the placenta or fetus. Our aim was to investigate the effects of chronic maternal obesity on feto-placental growth along with the underlying epigenetic mechanisms. We also tested whether preconceptional weight loss could alleviate these effects.

RESULTS

Female mice were fed either a control diet (CTRL group), a high-fat diet (obese (OB) group), or a high-fat diet switched to a control diet 2 months before conception (weight loss (WL) group). At mating, OB females presented an obese phenotype while WL females normalized metabolic parameters. At embryonic day 18.5 (E18.5), fetuses from OB females presented fetal growth restriction (FGR; -13 %) and 28 % of the fetuses were small for gestational age (SGA). Fetuses from WL females normalized this phenotype. The expression of 60 epigenetic machinery genes and 32 metabolic genes was measured in the fetal liver, placental labyrinth, and junctional zone. We revealed 23 genes altered by maternal weight trajectories in at least one of three tissues. The fetal liver and placental labyrinth were more responsive to maternal obesity than junctional zone. One third (18/60) of the epigenetic machinery genes were differentially expressed between at least two maternal groups. Interestingly, genes involved in the histone acetylation pathway were particularly altered (13/18). In OB group, lysine acetyltransferases and Bromodomain-containing protein 2 were upregulated, while most histone deacetylases were downregulated. In WL group, the expression of only a subset of these genes was normalized.

CONCLUSIONS

This study highlights the high sensitivity of the epigenetic machinery gene expression, and particularly the histone acetylation pathway, to maternal obesity. These obesity-induced transcriptional changes could alter the placental and the hepatic epigenome, leading to FGR. Preconceptional weight loss appears beneficial to fetal growth, but some effects of previous obesity were retained in offspring phenotype.

Prenatal origins of postnatal variation in growth, development and productivity of ruminants

This review provides an update on recent research into the effects of maternal nutrition on fetal biology and the growth, development and productivity of progeny in postnatal life of ruminant livestock. Evidence is summarised for effects on postnatal growth and body composition, feed intake and efficiency, carcass characteristics and meat quality, wool production, reproduction and lactation performance. In general, these demonstrated effects are not large in relation to the effects of postnatal nutrition and other environmental influences. The mechanisms underpinning the above production outcomes are briefly discussed in terms of systemic endocrine and metabolic responses, and cellular and molecular effects in skeletal muscle, bone, adipose tissue, wool follicles and brain of fetal, neonatal and adult progeny. Treatments observed to elicit tissue responses include maternal under- and overnutrition at various stages of pregnancy and placental insufficiency caused by increased litter size, chronic maternal heat stress and premating carunclectomy in sheep. The as yet meagre evidence for epigenetic mediation of intergenerational effects in ruminants is considered, as is the likelihood that other, more conventional explanations may suffice in some cases. Finally, evidence is summarised for the proposition that the placenta is not merely a passive conduit for nutrient transfer from dam to fetus, but plays an active role in buffering the effects of variations in maternal nutrition on fetal growth and development, and thence, postnatal outcomes.

Why primate models matter

Research involving nonhuman primates (NHPs) has played a vital role in many of the medical and scientific advances of the past century. NHPs are used because of their similarity to humans in physiology, neuroanatomy, reproduction, development, cognition, and social complexity-yet it is these very similarities that make the use of NHPs in biomedical research a considered decision. As primate researchers, we feel an obligation and responsibility to present the facts concerning why primates are used in various areas of biomedical research. Recent decisions in the United States, including the phasing out of chimpanzees in research by the National Institutes of Health and the pending closure of the New England Primate Research Center, illustrate to us the critical importance of conveying why continued research with primates is needed. Here, we review key areas in biomedicine where primate models have been, and continue to be, essential for advancing fundamental knowledge in biomedical and biological research.