Modelling the developmental origins of health and disease in the early embryo

The herbicides glyphosate and glufosinate and the cyanotoxin β-N-methylamino-l-alanine induce long-term motor disorders following postnatal exposure: the importance of prior asymptomatic maternal inflammatory sensitization

Background

Prenatal maternal immune activation (MIA) and/or perinatal exposure to various xenobiotics have been identified as risk factors for neurological disorders, including neurodegenerative diseases. Epidemiological data suggest an association between early multi-exposures to various insults and neuropathologies. The "multiple-hit hypothesis" assumes that prenatal inflammation makes the brain more susceptible to subsequent exposure to several kinds of neurotoxins. To explore this hypothesis and its pathological consequences, a behavioral longitudinal procedure was performed after prenatal sensitization and postnatal exposure to low doses of pollutants.

Methods

Maternal exposure to an acute immune challenge (first hit) was induced by an asymptomatic lipopolysaccharide (LPS) dose (0.008 mg/kg) in mice. This sensitization was followed by exposing the offspring to environmental chemicals (second hit) postnatally, by the oral route. The chemicals used were low doses of the cyanotoxin β-N-methylamino-l-alanine (BMAA; 50 mg/kg), the herbicide glufosinate ammonium (GLA; 0.2 mg/kg) or the pesticide glyphosate (GLY; 5 mg/kg). After assessing maternal parameters, a longitudinal behavioral assessment was carried out on the offspring in order to evaluate motor and emotional abilities in adolescence and adulthood.

Results

We showed that the low LPS immune challenge was an asymptomatic MIA. Even though a significant increase in systemic pro-inflammatory cytokines was detected in the dams, no maternal behavioral defects were observed. In addition, as shown by rotarod assays and open field tests, this prenatal LPS administration alone did not show any behavioral disruption in offspring. Interestingly, our data showed that offspring subjected to both MIA and post-natal BMAA or GLA exposure displayed motor and anxiety behavioral impairments during adolescence and adulthood. However, this synergistic effect was not observed in the GLY-exposed offspring.

Conclusion

These data demonstrated that prenatal and asymptomatic immune sensitization represents a priming effect to subsequent exposure to low doses of pollutants. These double hits act in synergy to induce motor neuron disease-related phenotypes in offspring. Thus, our data strongly emphasize that multiple exposures for developmental neurotoxicity regulatory assessment must be considered. This work paves the way for future studies aiming at deciphering cellular pathways involved in these sensitization processes.

Adverse weather during in utero development is linked to higher rates of later-life herpesvirus reactivation in adult European badgers, Meles meles

Maternal immune and/or metabolic conditions relating to stress or nutritional status can affect in utero development among offspring with subsequent implications for later-life responses to infections. We used free-ranging European badgers as a host-pathogen model to investigate how prenatal weather conditions affect later-life herpesvirus genital tract reactivation. We applied a sliding window analysis of weather conditions to 164 samples collected in 2018 from 95 individuals born between 2005-2016. We test if the monthly mean and variation in rainfall and temperature experienced by their mother during the 12 months of delayed implantation and gestation prior to parturition subsequently affected individual herpes reactivation rates among these offspring. We identified four influential prenatal seasonal weather windows that corresponded with previously identified critical climatic conditions affecting badger survival, fecundity and body condition. These all occurred during the pre-implantation rather than the post-implantation period. We conclude that environmental cues during the in utero period of delayed implantation may result in changes that affect an individual's developmental programming against infection or viral reactivation later in life. This illustrates how prenatal adversity caused by environmental factors, such as climate change, can impact wildlife health and population dynamics-an interaction largely overlooked in wildlife management and conservation programmes.

Nutritional Regulation of Embryonic Survival, Growth, and Development

Maternal nutritional status affects conceptus development and, therefore, embryonic survival, growth, and development. These effects are apparent very early in pregnancy, which is when most embryonic losses occur. Maternal nutritional status has been shown to affect conceptus growth and gene expression throughout the periconceptual period of pregnancy (the period immediately before and after conception). Thus, the periconceptual period may be an important "window" during which the structure and function of the fetus and the placenta are "programmed" by stressors such as maternal malnutrition, which can have long-term consequences for the health and well-being of the offspring, a concept often referred to as Developmental Origins of Health and Disease (DOHaD) or simply developmental programming. In this review, we focus on recent studies, using primarily animal models, to examine the effects of various maternal "stressors," but especially maternal malnutrition and Assisted Reproductive Techniques (ART, including in vitro fertilization, cloning, and embryo transfer), during the periconceptual period of pregnancy on conceptus survival, growth, and development. We also examine the underlying mechanisms that have been uncovered in these recent studies, such as effects on the development of both the placenta and fetal organs. We conclude with our view of future research directions in this critical area of investigation.

Programming of Embryonic Development

Assisted reproductive techniques (ART) and parental nutritional status have profound effects on embryonic/fetal and placental development, which are probably mediated via "programming" of gene expression, as reflected by changes in their epigenetic landscape. Such epigenetic changes may underlie programming of growth, development, and function of fetal organs later in pregnancy and the offspring postnatally, and potentially lead to long-term changes in organ structure and function in the offspring as adults. This latter concept has been termed developmental origins of health and disease (DOHaD), or simply developmental programming, which has emerged as a major health issue in animals and humans because it is associated with an increased risk of non-communicable diseases in the offspring, including metabolic, behavioral, and reproductive dysfunction. In this review, we will briefly introduce the concept of developmental programming and its relationship to epigenetics. We will then discuss evidence that ART and periconceptual maternal and paternal nutrition may lead to epigenetic alterations very early in pregnancy, and how each pregnancy experiences developmental programming based on signals received by and from the dam. Lastly, we will discuss current research on strategies designed to overcome or minimize the negative consequences or, conversely, to maximize the positive aspects of developmental programming.

Environmental Alterations during Embryonic Development: Studying the Impact of Stressors on Pluripotent Stem Cell-Derived Cardiomyocytes

Non-communicable diseases (NCDs) sauch as diabetes, obesity and cardiovascular diseases are rising rapidly in all countries world-wide. Environmental maternal factors (e.g., diet, oxidative stress, drugs and many others), maternal illnesses and other stressors can predispose the newborn to develop diseases during different stages of life. The connection between environmental factors and NCDs was formulated by David Barker and colleagues as the Developmental Origins of Health and Disease (DOHaD) hypothesis. In this review, we describe the DOHaD concept and the effects of several environmental stressors on the health of the progeny, providing both animal and human evidence. We focus on cardiovascular diseases which represent the leading cause of death worldwide. The purpose of this review is to discuss how in vitro studies with pluripotent stem cells (PSCs), such as embryonic and induced pluripotent stem cells (ESC, iPSC), can underpin the research on non-genetic heart conditions. The PSCs could provide a tool to recapitulate aspects of embryonic development “in a dish”, studying the effects of environmental exposure during cardiomyocyte (CM) differentiation and maturation, establishing a link to molecular mechanism and epigenetics.

Correlation of methylation status in MTHFR promoter region with recurrent pregnancy loss

Background

DNA methylation is an epigenetic process for modifying transcription factors in various genes. Methylenetetrahydrofolate reductase (MTHFR) stimulates synthesis of methyl radical in the homocysteine cycle and delivers methyl groups needed in DNA methylation. Furthermore, numerous studies have linked gene polymorphisms of this enzyme with a larger risk of recurrent pregnancy loss (RPL), yet scarce information is available concerning the association between epigenetic deviations in this gene and RPL. Hypermethylation at precise DNA sequences can function as biomarkers for a diversity of diseases. We aimed by this study to evaluate the methylation status of the promoter region of MTHFR gene in women with RPL compared to healthy fertile women. It is a case–control study. Hundred RPL patients and hundred healthy fertile women with no history of RPL as controls were recruited. MTHFR C677T was assessed by polymerase chain reaction-restriction fragment length polymorphism (RFLP). Quantitative evaluation of DNA methylation was performed by high-resolution melt analysis by real-time PCR.

Results

The median of percentage of MTHFR promoter methylation in RPL cases was 6.45 [0.74–100] vs. controls was 4.50 [0.60–91.7], P value < 0.001. In the case group, 57 hypermethylated and 43 normo-methylated among RPL patients vs. 40 hypermethylated and 60 normo-methylated among controls, P< 0.005. Frequency of T allele in C677T MTHFR gene among RPL patients was 29% vs. 23% among the control group; C allele vs. T allele: odds ratio (OR) = 1.367 (95% confidence interval (CI) 0.725–2.581).

Conclusion

Findings suggested a significant association between hypermethylation of the MTHFR promoter region in RPL patients compared to healthy fertile women.

Epigenetics of the developing and aging brain: Mechanisms that regulate onset and outcomes of brain reorganization

Brain development is a life-long process that encompasses several critical periods of transition, during which significant cognitive changes occur. Embryonic development, puberty, and reproductive senescence are all periods of transition that are hypersensitive to environmental factors. Rather than isolated episodes, each transition builds upon the last and is influenced by consequential changes that occur in the transition before it. Epigenetic marks, such as DNA methylation and histone modifications, provide mechanisms by which early events can influence development, cognition, and health outcomes. For example, parental environment influences imprinting patterns in gamete cells, which ultimately impacts gene expression in the embryo which may result in hypersensitivity to poor maternal nutrition during pregnancy, raising the risks for cognitive impairment later in life. This review explores how epigenetics induce and regulate critical periods, and also discusses how early environmental interactions prime a system towards a particular health outcome and influence susceptibility to disease or cognitive impairment throughout life.

Interspecific Variation in One-Carbon Metabolism within the Ovarian Follicle, Oocyte, and Preimplantation Embryo: Consequences for Epigenetic Programming of DNA Methylation

One-carbon (1C) metabolism provides methyl groups for the synthesis and/or methylation of purines and pyrimidines, biogenic amines, proteins, and phospholipids. Our understanding of how 1C pathways operate, however, pertains mostly to the (rat) liver. Here we report that transcripts for all bar two genes (i.e., BHMT, MAT1A) encoding enzymes in the linked methionine-folate cycles are expressed in all cell types within the ovarian follicle, oocyte, and blastocyst in the cow, sheep, and pig; as well as in rat granulosa cells (GCs) and human KGN cells (a granulosa-like tumor cell line). Betaine-homocysteine methyltransferase (BHMT) protein was absent in bovine theca and GCs, as was activity of this enzyme in GCs. Mathematical modeling predicted that absence of this enzyme would lead to more volatile S-adenosylmethionine-mediated transmethylation in response to 1C substrate (e.g., methionine) or cofactor provision. We tested the sensitivity of bovine GCs to reduced methionine (from 50 to 10 µM) and observed a diminished flux of 1C units through the methionine cycle. We then used reduced-representation bisulfite sequencing to demonstrate that this reduction in methionine during bovine embryo culture leads to genome-wide alterations to DNA methylation in >1600 genes, including a cohort of imprinted genes linked to an abnormal fetal-overgrowth phenotype. Bovine ovarian and embryonic cells are acutely sensitive to methionine, but further experimentation is required to determine the significance of interspecific variation in BHMT expression.

Differential global and MTHFR gene specific methylation patterns in preeclampsia and recurrent miscarriages: A case-control study from North India

AIM

The purpose of the present study is to evaluate and understand the association of global and MTHFR gene specific methylation in preeclampsia and recurrent miscarriages in light of MTHFR C677T polymorphism.

METHODS

The subjects comprised of recurrent miscarriage cases, their gestation matched controls, preeclampsia cases and matched controls. A set of women at full term were also recruited. Fasting blood sample (~5 ml) was drawn from all the participants followed by DNA extraction, global DNA methylation and MTHFR gene specific methylation. MTHFR C677T polymorphism was analysed by PCR followed by RFLP.

RESULTS HIGHER

Global DNA methylation at maternal front (p = 0.04) and hypomethylation of MTHFR gene at fetal front (p = 0.001) might be a characteristic of preeclampsia. Recurrent miscarriage cases were having significantly (p = 0.002) hyper MTHFR gene specific methylation as compared to controls. Women carrying CT genotype were found to be having significantly (p = 0.001) higher global DNA methylation in PE cases and MTHFR gene specific methylation (p = 0.005) in RM cases. Intergenerational analysis revealed similar patterns of global DNA methylation and MTHFR gene specific methylation among both PE and RM cases at maternal and fetal fronts.

CONCLUSION

The study highlights the importance of global DNA methylation in Preeclampsia and MTHFR gene specific methylation in recurrent miscarriages. MTHFR C677T gene polymorphism in association with global and gene specific methylation seem to play a pivotal role in PE and RM respectively.

Nutritional impact on gene expression and competence of oocytes used to support embryo development and livebirth by cloning procedures in goats

Changes in the nutritional plan have been shown to affect oocyte quality, crucial to oocyte donors animals used in cloning. This study aimed to evaluate the impact of diets with increasing nutritional levels (maintenance diet=M; 1.3M; 1.6M; 1.9M) fed to goats for four weeks on follicular fluid composition, gene expression and oocyte competence used to cloning in goats. Donor females were superovulated for the retrieval of matured oocytes and physical measurements reported. After four weeks, groups receiving diets above maintenance increased thickness of subcutaneous adipose tissue and body weight, with higher values in 1.9M Group (P<0.05). Treatments did not affect follicular density, number of aspirated follicles, retrieved and matured oocytes. Animals from 1.3M group had lower (P<0.05) maturation rate (44.0%) and number of viable oocytes (65.3%) than M (68.8%) and 1.9M (76.0%). Follicular fluid glucose concentrations increased with nutritional levels (P=0.010), with a difference (P<0.05) between groups 1.9M (11.4±2.6mg/dL) and M (2.6±0.5mg/dL). The diet did not affect the expression of GDF9, BMP15, and BAX genes in oocytes, but BCL2 and apoptotic index were significantly higher (P<0.05) in the 1.3M and 1.6M groups than the other groups. Following the transfer of cloned embryos, one fetus was born live of a twin pregnancy in the 1.9M Group. The association between energy intake and oocyte quality suggests better nutritional use by oocytes when the maximum flow was used (1.9M), but the optimal feeding level in cloning still needs refinement.

Nutrition and maternal metabolic health in relation to oocyte and embryo quality: critical views on what we learned from the dairy cow model

Although fragmented and sometimes inconsistent, the proof of a vital link between the importance of the physiological status of the mother and her subsequent reproductive success is building up. High-yielding dairy cows are suffering from a substantial decline in fertility outcome over past decades. For many years, this decrease in reproductive output has correctly been considered multifactorial, with factors including farm management, feed ratios, breed and genetics and, last, but not least, ever-rising milk production. Because the problem is complex and requires a multidisciplinary approach, it is hard to formulate straightforward conclusions leading to improvements on the 'work floor'. However, based on remarkable similarities on the preimplantation reproductive side between cattle and humans, there is a growing tendency to consider the dairy cow's negative energy balance and accompanying fat mobilisation as an interesting model to study the impact of maternal metabolic disorders on human fertility and, more specifically, on oocyte and preimplantation embryo quality. Considering the mutual interest of human and animal scientists studying common reproductive problems, this review has several aims. First, we briefly introduce the 'dairy cow case' by describing the state of the art of research into metabolic imbalances and their possible effects on dairy cow reproduction. Second, we try to define relevant in vitro models that can clarify certain mechanisms by which aberrant metabolite levels may influence embryonic health. We report on recent advances in the assessment of embryo metabolism and meantime critically elaborate on advantages and major limitations of in vitro models used so far. Finally, we discuss hurdles to be overcome to successfully translate the scientific data to the field.

Embryo-maternal communication during the first 4 weeks of equine pregnancy

The first month of equine pregnancy covers a period of rapid growth and development, during which the single-cell zygote metamorphoses into an embryo with a functional circulation and precursors of many important organs, enclosed within extraembryonic membranes responsible for nutrient uptake and gaseous exchange. After exiting the oviduct, the conceptus must influence uterine physiology to ensure adequate nutrition and preparation for implantation, while continued development results in the chorioallantois superseding the yolk sac as the primary interface for maternal interaction and exchange. Throughout the first month, pregnancy maintenance depends absolutely on progesterone secreted by the primary corpus luteum. However, although extension of luteal life span via maternal recognition of pregnancy is clearly essential, it is still not known how the horse conceptus signals its presence. On the other hand, our understanding of how luteolytic prostaglandin F2α release from the endometrium is averted has improved, and we are increasingly aware of the biological and practical significance of various events characteristic of early horse pregnancy, such as selective oviductal transport, the formation and dissolution of the blastocyst capsule, and prolonged intrauterine conceptus migration. It is also increasingly clear that embryo-maternal dialog during the first month is essential not only to conceptus survival but also has more profound and long-lasting implications. In this latter respect, it is now accepted that the maternal environment (e.g., metabolic or health status) may epigenetically alter gene expression capacity of the developing embryo and thereby permanently influence the health of the resulting foal right through adulthood.

Impact of Early Environment on Children's Mental Health: Lessons From DNA Methylation Studies With Monozygotic Twins

Over the past decade, epigenetic analyses have made important contributions to our understanding of healthy development and a wide variety of adverse conditions such as cancer and psychopathology. There is increasing evidence that DNA methylation is a mechanism by which environmental factors influence gene transcription and, ultimately, phenotype. However, differentiating the effects of the environment from those of genetics on DNA methylation profiles remains a significant challenge. Monozygotic (MZ) twin study designs are unique in their ability to control for genetic differences because each pair of MZ twins shares essentially the same genetic sequence with the exception of a small number of de novo mutations and copy number variations. Thus, differences within twin pairs in gene expression and phenotype, including behavior, can be attributed in the majority of cases to environmental effects rather than genetic influence. In this article, we review the literature showing how MZ twin designs can be used to study basic epigenetic principles, contributing to understanding the role of early in utero and postnatal environmental factors on the development of psychopathology. We also highlight the importance of initiating longitudinal and experimental studies with MZ twins during pregnancy. This approach is especially important to identify: (1) critical time periods during which the early environment can impact brain and mental health development, and (2) the specific mechanisms through which early environmental effects may be mediated. These studies may inform the optimum timing and design for early preventive interventions aimed at reducing risk for psychopathology.

Combined parental obesity negatively impacts preimplantation mouse embryo development, kinetics, morphology and metabolism

STUDY QUESTION

Does combined parental obesity, both an obese mother and father, have a greater effect on mouse preimplantation embryo development and quality than single-parent obesity?

SUMMARY ANSWER

Combined parental obesity causes a greater reduction in the blastocyst rate and a greater delay to the timing of key embryonic developmental events than single-parental obesity, as well as altering embryonic characteristics, such as zona pellucida width.

WHAT IS KNOWN ALREADY

Maternal or paternal obesity alone are known to have significant and detrimental impacts on preimplantation embryo development. Furthermore, these early embryonic perturbations can have long-term impacts on both offspring health and further generations. This is one of the first studies to examine the effects of having both an obese mother and an obese father.

STUDY DESIGN, SIZE, DURATION

A cross-sectional control versus treatment mouse study of diet-induced obesity was employed, in which 300 embryos per group were generated and studied from reciprocal matings: (i) control female and control male (Lean Parented Embryos); (ii) control female and obese male (Paternal Obese Parented Embryos); (iii) obese female and control male (Maternal Obese Parented Embryos) and (iv) obese female and obese male (Combined Obese Parented embryos). Assessments of the embryonic development rate, timing of development, morphological characteristics, metabolic gene expression, metabolism and cell lineage allocation were made at selected time points and analysed in relation to parental obesity status.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Three-week-old C57BL6 male and female mice were fed control (7% total fat) or high fat (21% total fat) diets for a minimum of 8 weeks. Females were superovulated, mated, fertilized zygotes recovered and standard mouse in vitro embryo culture performed. Time-lapse monitoring was undertaken to compare developmental timings and morphological characteristics (embryonic area and zona pellucida width) for embryos from all four reciprocal matings. Differential staining identified cell lineage allocation. Real-time quantitative RT-PCR (qRT-PCR) and microfluorescence were used to measure gene expression and metabolism (glucose consumption and lactate production), respectively, in embryos from Lean Parented and Combined Obese Parented matings. This research was completed in a University research laboratory.

MAIN RESULTS AND THE ROLE OF CHANCE

Blastocyst rate was reduced in Combined Obese Parented embryos when compared with both Single Obese (11% decrease for Maternal Obese Parented, P < 0.05; 15% for Paternal Obese Parented, P < 0.05) and Lean Parented embryos (25% decrease, P < 0.01). Time-lapse analysis of developmental kinetics highlighted a delay of 1 h at the 2-3 cell division, extending to 6 h delay by the blastocyst stage for Combined Obese Parented embryos (P < 0.05). A reduction in the total cell number of Combined Obese Parented blastocysts was a further manifestation of this developmental delay (P < 0.05). Zona pellucida width was reduced in Combined Obese Parented embryos (P < 0.05). Glucose consumption was increased in Combined Obese Parented embryos (P < 0.05), which was associated with the up-regulation of Glucose transporter 1 expression (P < 0.05).

LIMITATIONS AND REASON FOR CAUTION

This study was completed in fertile C57BL/6 mice using a well-defined model of diet-induced obesity in which embryos were fertilized in vivo. Human obesity is complex, with many causes and co-morbidities, and therefore, the impact of combined obesity would require further investigation in human settings.

WIDER IMPLICATIONS OF THE FINDINGS

This study demonstrates that combined parental obesity has a detrimental impact on mouse embryo development, a finding consistent with previous studies on individual parent obesity. Of note, the effect of combined parental obesity upon embryo development markers was greater than that of individual parental obesity. Plausibly, human embryos will be similarly impacted. The reduction in the blastocyst rate and delayed time to developmental events confirms that embryos of obese parents differ from those of lean parents. Allowance for this should therefore be incorporated into clinical practice when selecting the best embryo for the transfer of an obese couple.

STUDY FUNDING/COMPETING INTERESTS

Funding was provided by University of Melbourne research monies. M.P.G. currently holds the position of Merck Serono Lecturer of Reproductive Biology. D.K.G. received research funds from Vitrolife AB Sweden. The other authors of this manuscript have nothing to declare and no conflicts of interest.

Considering maternal dietary modulators for epigenetic regulation and programming of the fetal epigenome

Fetal life is characterized by a tremendous plasticity and ability to respond to various environmental and lifestyle factors, including maternal nutrition. Identification of the role of dietary factors that can modulate and reshape the cellular epigenome during development, including methyl group donors (e.g., folate, choline) and bioactive compounds (e.g., polyphenols) is of great importance; however, there is insufficient knowledge of a particular effect of each type of modulator and/or their combination on fetal life. To enhance the quality and safety of food products for proper fetal health and disease prevention in later life, a better understanding of the underlying mechanisms of dietary epigenetic modulators during the critical prenatal period is necessary. This review focuses on the influence of maternal dietary components on DNA methylation, histone modification, and microRNAs, and summarizes current knowledge of the effect and importance of dietary components on epigenetic mechanisms that control the proper expression of genetic information. Evidence reveals that some components in the maternal diet can directly or indirectly affect epigenetic mechanisms. Understanding the underlying mechanisms of how early-life nutritional environment affects the epigenome during development is of great importance for the successful prevention of adult chronic diseases through optimal maternal nutrition.

Both the folate cycle and betaine-homocysteine methyltransferase contribute methyl groups for DNA methylation in mouse blastocysts

The embryonic pattern of global DNA methylation is first established in the inner cell mass (ICM) of the mouse blastocyst. The methyl donor S-adenosylmethionine (SAM) is produced in most cells through the folate cycle, but only a few cell types generate SAM from betaine (N,N,N-trimethylglycine) via betaine-homocysteine methyltransferase (BHMT), which is expressed in the mouse ICM. Here, mean ICM cell numbers decreased from 18-19 in controls to 11-13 when the folate cycle was inhibited by the antifolate methotrexate and to 12-14 when BHMT expression was knocked down by antisense morpholinos. Inhibiting both pathways, however, much more severely affected ICM development (7-8 cells). Total SAM levels in mouse blastocysts decreased significantly only when both pathways were inhibited (from 3.1 to 1.6 pmol/100 blastocysts). DNA methylation, detected as 5-methylcytosine (5-MeC) immunofluorescence in isolated ICMs, was minimally affected by inhibition of either pathway alone but decreased by at least 45-55% when both BHMT and the folate cycle were inhibited simultaneously. Effects on cell numbers and 5-MeC levels in the ICM were completely rescued by methionine (immediate SAM precursor) or SAM. Both the folate cycle and betaine/BHMT appear to contribute to a methyl pool required for normal ICM development and establishing initial embryonic DNA methylation.

Accumulation of advanced glycation end products in the rabbit blastocyst under maternal diabetes

Diabetes mellitus (DM) during pregnancy is one of the leading causes of perinatal morbidity and birth defects. The mechanism by which maternal hyperglycemia, the major teratogenic factor, induces embryonic malformations remains unclear. Advanced glycation end products (AGEs) are known to accumulate during the course of DM and contribute to the development of diabetic complications. Employing a diabetic rabbit model, we investigated the influence of maternal hyperglycemia during the preimplantation period on AGE formation (pentosidine, argpyrimidine, and Nε-carboxymethyllysine (CML)) in the reproductive tract and the embryo itself. As a consequence of type 1 DM, the AGE levels in blood plasma increased up to 50%, correlating closely with an AGE accumulation in the endometrium of diabetic females. Embryos from diabetic mothers had increased protein-bound CML levels and showed enhanced fluorescent signals for AGE-specific fluorescence in the blastocyst cavity fluid (BCF). The quantification of CML by HPLC–mass spectrometry (MS/MS) showed a higher amount of soluble CML in the BCF of blastocysts from diabetic rabbits (0.26±0.05 μmol/l) compared with controls (0.18±0.02 μmol/l). The high amount of AGEs in blastocysts from diabetic mothers correlates positively with an increased AGER (receptor for AGE (RAGE)) mRNA expression. Our study gives alarming insights into the consequences of poorly controlled maternal diabetes for AGE formation in the embryo. Maternal hyperglycemia during the preimplantation period is correlated with an increase in AGE formation in the uterine environment and the embryo itself. This may influence the development of the embryo through increased AGE-mediated cellular stress by RAGEs.

Long-lived crowded-litter mice exhibit lasting effects on insulin sensitivity and energy homeostasis

The action of nutrients on early postnatal growth can influence mammalian aging and longevity. Recent work has demonstrated that limiting nutrient availability in the first 3 wk of life [by increasing the number of pups in the crowded-litter (CL) model] leads to extension of mean and maximal lifespan in genetically normal mice. In this study, we aimed to characterize the impact of early-life nutrient intervention on glucose metabolism and energy homeostasis in CL mice. In our study, we used mice from litters supplemented to 12 or 15 pups and compared those to control litters limited to eight pups. At weaning and then throughout adult life, CL mice are significantly leaner and consume more oxygen relative to control mice. At 6 mo of age, CL mice had low fasting leptin concentrations, and low-dose leptin injections reduced body weight and food intake more in CL female mice than in controls. At 22 mo, CL female mice also have smaller adipocytes compared with controls. Glucose and insulin tolerance tests show an increase in insulin sensitivity in 6 mo old CL male mice, and females become more insulin sensitive later in life. Furthermore, β-cell mass was significantly reduced in the CL male mice and was associated with reduction in β-cell proliferation rate in these mice. Together, these data show that early-life nutrient intervention has a significant lifelong effect on metabolic characteristics that may contribute to the increased lifespan of CL mice.

Sex-specific embryonic origin of postnatal phenotypic variability

Preimplantation developmental plasticity has evolved in order to offer the best chances of survival under changing environments. Conversely, environmental conditions experienced in early life can dramatically influence neonatal and adult biology, which may result in detrimental long-term effects. Several studies have shown that small size at birth, which is associated with a greater risk of metabolic syndrome, is largely determined before the formation of the blastocysts because 70%–80% of variation in bodyweight at birth has neither a genetic nor environmental component. In addition, it has been reported that adult bodyweight is programmed by energy-dependent process during the pronuclear stage in the mouse. Although the early embryo has a high developmental plasticity and adapts and survives to adverse environmental conditions, this adaptation may have adverse consequences and there is strong evidence that in vitro culture can be a risk factor for abnormal fetal outcomes in animals systems, with growing data suggesting that a similar link may be apparent for humans. In this context, male and female preimplantation embryos display sex-specific transcriptional and epigenetic regulation, which, in the case of bovine blastocysts, expands to one-third of the transcripts detected through microarray analysis. This sex-specific bias may convert the otherwise buffered stochastic variability in developmental networks in a sex-determined response to the environmental hazard. It has been widely reported that environment can affect preimplantation development in a sex-specific manner, resulting in either a short-term sex ratio adjustment or in long-term sex-specific effects on adult health. The present article reviews current knowledge about the natural phenotypic variation caused by epigenetic mechanisms and the mechanisms modulating sex-specific changes in phenotype during early embryo development resulting in sex ratio adjustments or detrimental sex-specific consequences for adult health. Understanding the natural embryo sexual dimorphism for programming trajectories will help understand the early mechanisms of response to environmental insults.

Metabolic induction and early responses of mouse blastocyst developmental programming following maternal low protein diet affecting life-long health

Previously, we have shown that a maternal low protein diet, fed exclusively during the preimplantation period of mouse development (Emb-LPD), is sufficient to induce by the blastocyst stage a compensatory growth phenotype in late gestation and postnatally, correlating with increased risk of adult onset cardiovascular disease and behavioural dysfunction. Here, we examine mechanisms of induction of maternal Emb-LPD programming and early compensatory responses by the embryo. Emb-LPD induced changes in maternal serum metabolites at the time of blastocyst formation (E3.5), notably reduced insulin and increased glucose, together with reduced levels of free amino acids (AAs) including branched chain AAs leucine, isoleucine and valine. Emb-LPD also caused reduction in the branched chain AAs within uterine fluid at the blastocyst stage. These maternal changes coincided with an altered content of blastocyst AAs and reduced mTORC1 signalling within blastocysts evident in reduced phosphorylation of effector S6 ribosomal protein and its ratio to total S6 protein but no change in effector 4E-BP1 phosphorylated and total pools. These changes were accompanied by increased proliferation of blastocyst trophectoderm and total cells and subsequent increased spreading of trophoblast cells in blastocyst outgrowths. We propose that induction of metabolic programming following Emb-LPD is achieved through mTORC1signalling which acts as a sensor for preimplantation embryos to detect maternal nutrient levels via branched chain AAs and/or insulin availability. Moreover, this induction step associates with changes in extra-embryonic trophectoderm behaviour occurring as early compensatory responses leading to later nutrient recovery.

Overfeeding and underfeeding have detrimental effects on oocyte quality measured by in vitro fertilization and early embryonic development in sheep

To determine effects of maternal diet on in vitro fertilization (IVF) and early embryonic development, ewes (n = 48) were divided into control, overfed (ad libitum feeding), and underfed (60% of control) nutritional planes for 8 wk before oocyte collection. Follicular development was induced by twice-daily injections of FSH on days 13 and 14 of the estrous cycle, and ovaries and blood samples were collected on day 15 of the estrous cycle. During the 8-wk experiment, for control ewes BW and BCS did not change, but for overfed ewes mean (± SEM) BW and BCS increased (11.8 ± 1.1 kg and 2.0 ± 0.1, respectively) and for underfed ewes decreased (14.2 ± 0.9 kg and 0.7 ± 0.1, respectively). The number of follicles was determined; oocytes were collected and subjected to in vitro maturation and fertilization. After IVF, developing embryos were evaluated throughout the 8-d culture period. The proportion of cleaved oocytes after IVF and developing morula and blastocyst were less (P < 0.0001) in overfed and underfed ewes than in control ewes. However, number of visible follicles, total number of oocytes, number of healthy oocytes, and percentage of healthy oocytes were similar for control, overfed, and underfed ewes. Serum insulin concentration was greater (P < 0.05) in overfed ewes than in underfed ewes, estradiol 17-β (E(2)) concentration was greater (P < 0.05) in underfed ewes than in overfed ewes, but triiodothyronine (T(3)) and thyroxine (T(4)) concentrations were similar in all treatment groups. These data show that inadequate feeding has a negative effect on oocyte quality which results in lower oocyte cleavage after IVF and morula and blastocyst formation; overfeeding increased serum insulin and underfeeding increased serum E(2) but not T(3) or T(4). These data emphasize the importance of diet for reproductive and metabolic functions. Furthermore, the mechanisms through which enhanced or decreased energy in diet affect oocyte quality and serum insulin and E(2) concentrations remain to be elucidated.

Transcriptional differences between rhesus embryonic stem cells generated from in vitro and in vivo derived embryos

Numerous studies have focused on the transcriptional signatures that underlie the maintenance of embryonic stem cell (ESC) pluripotency. However, it remains unclear whether ESC retain transcriptional aberrations seen in in vitro cultured embryos. Here we report the first global transcriptional profile comparison between ESC generated from either in vitro cultured or in vivo derived primate embryos by microarray analysis. Genes involved in pluripotency, oxygen regulation and the cell cycle were downregulated in rhesus ESC generated from in vitro cultured embryos (in vitro ESC). Significantly, several gene differences are similarly downregulated in preimplantation embryos cultured in vitro, which have been associated with long term developmental consequences and disease predisposition. This data indicates that prior to derivation, embryo quality may influence the molecular signature of ESC lines, and may differentially impact the physiology of cells prior to or following differentiation.

Maternal protein restriction induce skeletal muscle changes without altering the MRFs MyoD and myogenin expression in offspring

Stimuli during pregnancy, such as protein restriction, can affect morphophysiological parameters in the offspring with consequences in adulthood. The phenomenon known as fetal programming can cause short- and long-term changes in the skeletal muscle phenotype. We investigated the morphology and the myogenic regulatory factors (MRFs) MyoD and myogenin expression in soleus, SOL; oxidative and slow twitching and in extensor digitorum longus, EDL; glycolytic and fast twitching muscles in the offspring of dams subjected to protein restriction during pregnancy. Four groups of male Wistar offspring rats were studied. Offspring from dams fed a low-protein diet (6 % protein, LP) and normal protein diet (17 % protein, NP) were euthanized at 30 and 112 days old, and their muscles were removed and kept at -80 °C. Muscles histological sections (8 μm) were submitted to a myofibrillar adenosine triphosphatase histochemistry reaction for morphometric analysis. Gene and protein expression levels of MyoD and myogenin were determined by RT-qPCR and western blotting. The major findings observed were distinct patterns of morphological changes in SOL and EDL muscles in LP offspring at 30 and 112 days old without changes in MRFs MyoD and myogenin expression. Our results indicate that maternal protein restriction followed by normal diet after birth induced morphological changes in muscles with distinct morphofunctional characteristics over the long term, but did not alter the MRFs MyoD and myogenin expression. Further studies are necessary to better understand the mechanisms underlying the maternal protein restriction response on skeletal muscle.

Intrafollicular conditions as a major link between maternal metabolism and oocyte quality: a focus on dairy cow fertility

Reduced oocyte and embryo quality are recognised as major factors in the problem of disappointing fertility in high producing dairy cows. This review aims to shed more light on the importance of the intrafollicular environment in the subfertility problem in dairy cows. Metabolic disturbances associated with negative energy balance (NEB) early postpartum are associated with ovarian dysfunction. Changes in the growth pattern of the ovarian follicle during a period of NEB can indirectly affect oocyte quality. Furthermore, a maternal metabolic disorder (linked with NEB or nutritionally induced) may alter the endocrine and biochemical composition of the follicular fluid, the micro-environment of the growing and maturing female gamete. The maturing oocyte is very sensitive to any perturbation in its direct environment and in vitro maturation models revealed that some of these metabolic changes reduce the oocyte’s developmental competence. Also, embryo quality is significantly reduced due to maturation in adverse conditions. Well balanced and timed oocyte metabolism and gene expression are crucial to safeguard an optimal oocyte development. In that perspective, metabolome and transcriptome parameters of the oocyte may serve to predict reproductive success rates. Finally, there is growing evidence that adverse conditions for oocyte growth and maturation may also jeopardise the health and performance of the offspring.

Developmental programming and epigenetics

The ways in which epigenetic modifications fix the effects of early environmental events, ensuring sustained responses to transient stimuli that result in modified gene expression patterns and phenotypes later in life, are a topic of considerable interest. This article focuses on recently discovered mechanisms and calls into question prevailing views about the dynamics, positions, and functions of epigenetic marks. Most epigenetic studies have addressed the long-term effects of environmental stressors on a small number of epigenetic marks, at the global or individual gene level, in humans and in animal models. In parallel, increasing numbers of studies based on high-throughput technologies are revealing additional complexity in epigenetic processes by highlighting the importance of crosstalk between different epigenetic marks in humans and mice. A number of studies focusing on metabolic programming and the developmental origin of health and disease have identified links between early nutrition, epigenetic processes, and long-term illness. The existence of a self-propagating epigenetic cycle has been shown. Moreover, recent studies have shown an obvious sexual dimorphism both for programming trajectories and in response to the same environmental insult. Despite recent progress, however, we are still far from understanding how, when, and where environmental stressors disturb key epigenetic mechanisms. Thus, the need to identify original key marks and monitor the changes they undergo throughout development, during an individual's lifetime, or over several generations remains a challenging issue.

Epigenetic mechanisms involved in developmental nutritional programming

The ways in which epigenetic modifications fix the effects of early environmental events, ensuring sustained responses to transient stimuli, which result in modified gene expression patterns and phenotypes later in life, is a topic of considerable interest. This review focuses on recently discovered mechanisms and calls into question prevailing views about the dynamics, position and functions of epigenetic marks. Most epigenetic studies have addressed the long-term effects on a small number of epigenetic marks, at the global or individual gene level, of environmental stressors in humans and animal models. In parallel, increasing numbers of studies based on high-throughput technologies and focusing on humans and mice have revealed additional complexity in epigenetic processes, by highlighting the importance of crosstalk between the different epigenetic marks. A number of studies focusing on the developmental origin of health and disease and metabolic programming have identified links between early nutrition, epigenetic processes and long-term illness. The existence of a self-propagating epigenetic cycle has been demonstrated. Moreover, recent studies demonstrate an obvious sexual dimorphism both for programming trajectories and in response to the same environmental insult. Despite recent progress, we are still far from understanding how, when and where environmental stressors disturb key epigenetic mechanisms. Thus, identifying the original key marks and their changes throughout development during an individual’s lifetime or over several generations remains a challenging issue.

Disease embryo development network reveals the relationship between disease genes and embryo development genes

A basic problem for contemporary biology and medicine is exploring the correlation between human disease and underlying cellular mechanisms. For a long time, several efforts were made to reveal the similarity between embryo development and disease process, but few from the system level. In this article, we used the human protein-protein interactions (PPIs), disease genes with their classifications and embryo development genes and reconstructed a human disease-embryo development network to investigate the relationship between disease genes and embryo development genes. We found that disease genes and embryo development genes are prone to connect with each other. Furthermore, diseases can be categorized into three groups according to the closeness with embryo development in gene overlapping, interacting pattern in PPI network and co-regulated by microRNAs or transcription factors. Embryo development high-related disease genes show their closeness with embryo development at least in three biological levels. But it is not for embryo development medium-related disease genes and embryo development low-related disease genes. We also found that embryo development high-related disease genes are more central than other disease genes in the human PPI network. In addition, the results show that embryo development high-related disease genes tend to be essential genes compared with other diseases' genes. This network-based approach could provide evidence for the intricate correlation between disease process and embryo development, and help to uncover potential mechanisms of human complex diseases.

Mitochondrial inhibition during preimplantation embryogenesis shifts the transcriptional profile of fetal mouse brain

Environmental stress results in perturbations to mitochondrial function in the preimplantation embryo and hinders subsequent embryo and possibly offspring development. Global gene expression in fetal mouse brain was investigated following targeted mitochondrial inhibition by amino-oxyacetate (AOA) from the 2-cell to the blastocyst stage. Blastocysts were transferred to pseudopregnant recipients and RNA extracted from Day 18 fetal brains for microarray interrogation. Exposure to 5 μM AOA during preimplantation embryo development induced differential expression of 166 genes (>1.25 fold) in the fetal brain, relative to control medium-cultured embryos. Altered expression pathways included carbohydrate metabolism, neurological development, cellular proliferation and death, DNA replication, recombination and repair. Of 28 genes exhibiting the greatest change in expression, qPCR confirmed that 16 were significantly altered. Targeted qPCR assessment of a further 20 genes associated with methylation, acetylation and mitochondrial dysfunction revealed that three were significantly altered (Immp1l, Nars2, Sat2) and Dmap1 exhibited a sex-specific response to AOA exposure. Only 2/48 genes had significantly altered expression by qPCR (Nola3, Timm8b) in fetal brains exposed to 50 μM AOA embryo culture, excluding an AOA dose-dependent response. It was concluded that perturbation of mitochondrial function induced by 5 μM AOA during preimplantation embryo development alters gene expression in the neonatal brain in a manner that suggests that proper brain development may be compromised.

Role of maternal vitamin B12 on the metabolic health of the offspring: a contributor to the diabetes epidemic?

There is increasing evidence, in humans and other mammals, that periconceptional nutritional status influences health in adulthood. This is called ‘foetal programming’ and is likely to be mediated through DNA methylation. Micronutrients, especially B vitamins such as folic acid and vitamin B12 play crucial roles in providing methyl groups for such reactions. This is called epigenetic regulation and may provide some clues to the epidemic of type 2 diabetes and cardiovascular disease. Evidence from mandatory folic acid fortification studies suggests that in the presence of adequate folic acid, neural tube defects due to B12 deficiency have tripled. Such ‘imbalance of high folic acid and low vitamin B12’ in the elderly causes cognitive impairment. A longitudinal study of young women in India showed that children born to those with ‘high folic acid and low B12’ had higher adiposity and insulin resistance. In addition to increased levels of folic acid, B12 deficiency is increasing in countries with mandatory folic acid fortification. Studies on the prevalence of vitamin B12 deficiency during pregnancy and in women of childbearing age, plus the effects of B12 supplementation are therefore urgently needed. This article reviews the role of vitamin B12 during pregnancy on the offspring’s metabolic risk.

Early nutrition and epigenetic programming: chasing shadows

PURPOSE OF REVIEW

The ways in which epigenetic modifications fix the effects of early environmental events, ensuring sustained responses to transient stimuli, which result into modified gene expression patterns and phenotypes later in life, is a topic of considerable interest. This review focuses on recently discovered mechanisms and calls into question prevailing views about the dynamics, positions and functions of relevant epigenetic marks.

RECENT FINDINGS

Animal models, including mice, rats, sheep, pigs and rabbits, remain a vital tool for studying the influence of early nutritional events on adult health and disease. Most epigenetic studies have addressed the long-term effects on a small number of epigenetic marks, at the global or individual gene level, of environmental stressors in humans and animal models. They have demonstrated the existence of a self-propagating epigenetic cycle. In parallel, an increasing number of studies based on high-throughput technologies and focusing on humans and mice have revealed additional complexity in epigenetic processes, by highlighting the importance of crosstalk between the different epigenetic marks. In recent months, a number of studies focusing on the developmental origin of health and disease and metabolic programming have identified links between early nutrition, epigenetic processes and long-term illness.

SUMMARY

Despite recent progress, we are still far from understanding how, when and where environmental stressors disturb key epigenetic mechanisms. Thus, identifying the original key marks and their changes throughout development, during an individual's lifetime or over several generations, remains a challenging issue.

Amino acid metabolism of bovine blastocysts: a biomarker of sex and viability

The ratio of male/female embryos may be modified by environmental factors such as maternal diet in vivo and the composition of embryo culture media in vitro. We have used amino acid profiling, a noninvasive marker of developmental potential to compare the effect of sex on the metabolism of bovine blastocysts conceived in vivo and in vitro. Blastocysts were incubated individually for 24 hr in a close-to-physiological mixture of amino acids and the depletion or appearance of 18 amino acids measured using HPLC. Blastocysts were then sexed by PCR. Amino acid depletion by in vitro-produced blastocysts and expanded blastocysts was higher than in embryos conceived in vivo (P = 0.02). When cultured in vitro, female embryos exhibited increased depletion of arginine, glutamate, and methionine and appearance of glycine, while male embryos displayed increased depletion of phenylalanine, tyrosine, and valine. Overall, in vitro-produced blastocysts exhibited sex-specific differences in metabolic profiles of 7 out of 18 amino acids; in vivo-produced, in 2 out of 18. These differences had disappeared by the expanded blastocyst stages. We have also shown that amino acid metabolism can predict the ability of bovine zygotes to develop to the blastocyst stage, providing "proof of principle" for the use of this technology in clinical IVF to select single embryos for transfer and thereby avoid the problem of multiple births.

Male gamete survival at stake: causes and solutions

Over the years, the development of assisted reproductive technology to bypass male factor infertility has improved drastically. Considered one of the most perplexing disorders in the reproductive field, male factor infertility is prevalent and may be on the rise. Unfortunately, its aetiology remains elusive. One of the main reasons lies in the complex machinery and structure of the hydrodynamic sperm cell. Its polyunsaturated fatty acid cell membrane, the protamines in its genetic material and the absence of antioxidants in its cytoplasm ensure that the spermatozoon is highly susceptible to environmental effects. The spermatozoon's genesis, storage, and transport through the male reproductive tract are also susceptible, genetically and pathologically, to environmental effects. This review aims to include all the possible causes of disruption to this unique cell and their probable solutions, in the hope of clearing up the ambiguity that surrounds male factor infertility.

Blastocyst environment and its influence on offspring cardiovascular health: the heart of the matter

The development of adult-onset diseases such as type II diabetes, obesity and cardiovascular disease is traditionally attributed to adult lifestyle characteristics such as a lack of physical exercise, poor diet and smoking. However, evidence from both human and animal model studies has demonstrated that environmental factors such as an imbalance or reduction in maternal nutrition during gestation can have adverse effects on offspring metabolism and cardiovascular health. The severity and nature of the phenotypic changes induced in offspring is influenced by the period of gestation manipulated. In particular, the mammalian preimplantation embryo in different animal models displays particular sensitivity to environmental factors, either in vivo (maternal diet) or in vitro (embryo culture) that is associated with the onset of cardiovascular dysfunction in adult life. The detailed mechanisms by which environmental conditions can alter postnatal cardiovascular physiology are poorly understood. However, various factors including endothelial function, vascular responsiveness, the renin-angiotensin system, kidney structure and early postnatal growth dynamics have all been recognize as potential contributors. Here, we review the relationship between preimplantation embryo environment and postnatal cardiovascular disease risk, and consider biochemical, molecular, genetic and physiological pathways implicated in this association.

Low protein diet fed exclusively during mouse oocyte maturation leads to behavioural and cardiovascular abnormalities in offspring

Early embryonic development is known to be susceptible to maternal undernutrition, leading to a disease-related postnatal phenotype. To determine whether this sensitivity extended into oocyte development, we examined the effect of maternal normal protein diet (18% casein; NPD) or isocaloric low protein diet (9% casein; LPD) restricted to one ovulatory cycle (3.5 days) prior to natural mating in female MF-1 mice. After mating, all females received NPD for the remainder of gestation and all offspring were litter size adjusted and fed standard chow. No difference in gestation length, litter size, sex ratio or postnatal growth was observed between treatments. Maternal LPD did, however, induce abnormal anxiety-related behaviour in open field activities in male and female offspring (P < 0.05). Maternal LPD offspring also exhibited elevated systolic blood pressure (SBP) in males at 9 and 15 weeks and in both sexes at 21 weeks (P < 0.05). Male LPD offspring hypertension was accompanied by attenuated arterial responsiveness in vitro to vasodilators acetylcholine and isoprenaline (P < 0.05). LPD female offspring adult kidneys were also smaller, but had increased nephron numbers (P < 0.05). Moreover, the relationship between SBP and kidney or heart size or nephron number was altered by diet treatment (P < 0.05). These data demonstrate the sensitivity of mouse maturing oocytes in vivo to maternal protein undernutrition and identify both behavioural and cardiovascular postnatal outcomes, indicative of adult disease. These outcomes probably derive from a direct effect of protein restriction, although indirect stress mechanisms may also be contributory. Similar and distinct postnatal outcomes were observed here compared with maternal LPD treatment during post-fertilization preimplantation development which may reflect the relative contribution of the paternal genome.

DNA methylation, insulin resistance, and blood pressure in offspring determined by maternal periconceptional B vitamin and methionine status

A complex combination of adult health-related disorders can originate from developmental events that occur in utero. The periconceptional period may also be programmable. We report on the effects of restricting the supply of specific B vitamins (i.e., B(12) and folate) and methionine, within normal physiological ranges, from the periconceptional diet of mature female sheep. We hypothesized this would lead to epigenetic modifications to DNA methylation in the preovulatory oocyte and/or preimplantation embryo, with long-term health implications for offspring. DNA methylation is a key epigenetic contributor to maintenance of gene silencing that relies on a dietary supply of methyl groups. We observed no effects on pregnancy establishment or birth weight, but this modest early dietary intervention led to adult offspring that were both heavier and fatter, elicited altered immune responses to antigenic challenge, were insulin-resistant, and had elevated blood pressure-effects that were most obvious in males. The altered methylation status of 4% of 1,400 CpG islands examined by restriction landmark genome scanning in the fetal liver revealed compelling evidence of a widespread epigenetic mechanism associated with this nutritionally programmed effect. Intriguingly, more than half of the affected loci were specific to males. The data provide the first evidence that clinically relevant reductions in specific dietary inputs to the methionine/folate cycles during the periconceptional period can lead to widespread epigenetic alterations to DNA methylation in offspring, and modify adult health-related phenotypes.

Adaptive responses by mouse early embryos to maternal diet protect fetal growth but predispose to adult onset disease

Poor maternal nutrition during pregnancy can alter postnatal phenotype and increase susceptibility to adult cardiovascular and metabolic diseases. However, underlying mechanisms are largely unknown. Here, we show that maternal low protein diet (LPD), fed exclusively during mouse preimplantation development, leads to offspring with increased weight from birth, sustained hypertension, and abnormal anxiety-related behavior, especially in females. These adverse outcomes were interrelated with increased perinatal weight being predictive of later adult overweight and hypertension. Embryo transfer experiments revealed that the increase in perinatal weight was induced within blastocysts responding to preimplantation LPD, independent of subsequent maternal environment during later pregnancy. We further identified the embryo-derived visceral yolk sac endoderm (VYSE) as one mediator of this response. VYSE contributes to fetal growth through endocytosis of maternal proteins, mainly via the multiligand megalin (LRP2) receptor and supply of liberated amino acids. Thus, LPD maintained throughout gestation stimulated VYSE nutrient transport capacity and megalin expression in late pregnancy, with enhanced megalin expression evident even when LPD was limited to the preimplantation period. Our results demonstrate that in a nutrient-restricted environment, the preimplantation embryo activates physiological mechanisms of developmental plasticity to stablize conceptus growth and enhance postnatal fitness. However, activation of such responses may also lead to adult excess growth and cardiovascular and behavioral diseases.