Life-long echoes--a critical analysis of the developmental origins of adult disease model

Prenatal determinants of anxiety symptoms in middle childhood. Evidence from Growing Up in New Zealand

BACKGROUND

Early life environments can have long-lasting impacts on future health and wellbeing. Maternal health during pregnancy, including experiencing stress or mood disorders, has been associated with psychopathology in later life. Anxiety disorders are one of the most prevalent mental health conditions, affecting approximately 7 % of children and adolescents globally, with a lifetime prevalence of 15-20 %. Identifying prenatal risk factors can support future and current public health interventions and maternity care.

METHODS

Data were obtained from the Growing Up in New Zealand longitudinal study of child development. Prenatally, mothers provided sociodemographic information as well as data on their mental health, potential teratogens, and lifestyle factors such as supplement intake and exercise levels. At 8-years old, 4922 children self-completed the PROMIS-SF anxiety measure. Bivariate analyses and backward stepwise regression were used to determine the best multivariable model.

RESULTS

Significant prenatal predictors of anxiety symptoms at 8-years old included elevated maternal depression symptoms, body mass index in the overweight/obese range, exercise patterns, and paracetamol, anti-inflammatory and alcohol intake.

LIMITATIONS

Sample attrition from baseline to 8-year may have affected statistical power. To further untangle the effect of timing and duration of the exposures reported in this study, larger sample sizes would be required.

CONCLUSIONS

Prenatal mental health and wellbeing was significantly associated with child anxiety symptoms at 8-years of age. This study highlights the importance of supporting expectant mothers' health and wellbeing during pregnancy to ensure children have the best opportunity to have good mental health.

Fetal Growth Trajectories and Measures of Insulin Resistance in Young Adults

CONTEXT

Events during gestation greatly influence the risk of cardiometabolic diseases including diabetes in offspring during later life.

OBJECTIVE

This study aimed to investigate relationships between serial ultrasound-derived fetal growth trajectories and markers of insulin resistance in young adults in the Raine Study, an Australian pregnancy cohort.

METHODS

Linear mixed modeling examined the relationship between fetal growth trajectory groups, constructed using serial ultrasound-based abdominal circumference (AC), femur length (FL), and head circumference (HC) from 1333 mother-fetal pairs, and offspring Homeostatic Model Assessment of Insulin Resistance (HOMA-IR), as a marker of diabetes risk, at 20 (n = 414), 22 (n = 385), and 27 (n = 431) years. Analyses were adjusted for age, sex, ethnicity, socioeconomic status, adult lifestyle factors, and maternal factors during pregnancy.

RESULTS

The study identified 7 AC, 5 FL, and 5 HC growth trajectory groups. Compared to the average-stable (reference) group, a low-falling AC growth trajectory (26%; P = .005) and 2 low HC growth trajectories (20%; P = .006% and 8%; P = .021) were associated with higher adult HOMA-IR. Trajectories representing a high-stable FL and a rising HC were associated with 12% (P = .002) and 9% (P = .021) lower adult HOMA-IR, respectively, compared to the reference group.

CONCLUSION

Restricted fetal HC and AC from early pregnancy are associated with higher relative insulin resistance in the offspring during adulthood. These data strengthen our understanding of the importance of the intrauterine environment and its effect on the risk of predisposition to adult diabetes and related metabolic disorders.

Developmental origins of health and disease: Impact of paternal nutrition and lifestyle

Most epidemiological and experimental studies have focused on maternal influences on offspring's health. The impact of maternal undernutrition, overnutrition, hypoxia, and stress is linked to adverse offspring outcomes across a range of systems including cardiometabolic, respiratory, endocrine, and reproduction among others. During the past decade, it has become evident that paternal environmental factors are also linked to the development of diseases in offspring. In this article, we aim to outline the current understanding of the impact of male health and environmental exposure on offspring development, health, and disease and explore the mechanisms underlying the paternal programming of offspring health. The available evidence suggests that poor paternal pre-conceptional nutrition and lifestyle, and advanced age can increase the risk of negative outcomes in offspring, via both direct (genetic/epigenetic) and indirect (maternal uterine environment) effects. Beginning at preconception, and during utero and the early life after birth, cells acquire an epigenetic memory of the early exposure which can be influential across the entire lifespan and program a child's health. Potentially not only mothers but also fathers should be advised that maintaining a healthy diet and lifestyle is important to improve offspring health as well as the parental health status. However, the evidence is mostly based on animal studies, and well-designed human studies are urgently needed to verify findings from animal data.

Birth weight in the feline species: Description and factors of variation in a large population of purebred kittens

Birth weight is one of the earliest health parameters with short (neonatal period) and long term (adulthood) implications for an individual. The present work was conducted on the domestic cat, with the objective of determining factors affecting kitten birth weight. Data voluntarily shared by 139 French breeders allowed building a large dataset of purebred kittens (n = 3,547) from 15 breeds. A linear mixed model with queen and cattery as random terms was used to investigate variation factors of kitten birth weight such as breed, litter size, season of birth, age of the queen, presence of stillborn in the litter, sex of the kitten. The most important factor was breed which explained 25% of the variation in birth weight observed in the study population. The five other parameters were also significant but explained only a small additional part of the variance (less than 3% each). Analyses showed that kitten birth weight increased with the age of the queen, was higher in males than females and in litters without stillbirth than in litters with at least one stillborn. In addition, lower birth weights were recorded in summer and autumn compared to other seasons, and birth weight values decreased as the number of kittens in the litter increased. In order to group feline breeds according to their average birth weights and litter sizes, a K-means algorithm was used to identify three clusters among the 15 breeds represented (Group 1: small litter sizes/low birth weights; Group 2: large litter sizes/intermediate birth weights; Group 3: large litter sizes/high birth weights). This study, based on a large dataset established at the national scale, provides reference values of feline birth weights for breeders and veterinarians. The next step could be to explore the relationship between birth weight and neonatal mortality to help identify neonates requiring specific care.

Are Brain and Cognitive Reserve Shaped by Early Life Circumstances?

When growing older, many people are faced with cognitive deterioration, which may even amount to a form of dementia at some point in time. Although neuropathological signs of dementia disorders can often be demonstrated in brains of patients, the degree to which clinical symptoms are present does mostly not accurately reflect the amount of neuropathology that is present. Sometimes existent pathology even goes without any obvious clinical presentation. An explanation for this phenomenon may be found in the concept of reserve capacity. Reserve capacity refers to the ability of the brain to effectively buffer changes that are associated with normal aging processes and to cope with pathological damage. A larger reserve capacity has been suggested to increase resilience against age-associated cognitive deterioration and dementia disorders. Traditionally, a division has been made between brain reserve, which is based on morphological characteristics of the brain, and cognitive reserve, which is based on functional characteristics of the brain. The present review discusses the premises that brain and cognitive reserve capacity are shaped by prenatal and early postnatal factors. Evidence is accumulating that circumstances during the first 1,000 days of life are of the utmost importance for the lifelong health of an individual. Cognitive deterioration and dementia disorders may also have their origin in early life and a potentially important pathway by which the early environment affects the risk for neurodegenerative diseases is by developmental programming of the reserve capacity of the brain. The basic idea behind developmental programming of brain and cognitive reserve is explained and an overview of studies that support this idea is presented. The review is concluded by a discussion of potential mechanisms, synthesis of the evidence and relevance and future directions in the field of developmental origins of reserve capacity.

Epidemiologists’ ambivalence towards the epigenetics of social adversity

This article studies how social epidemiologists get involved in research carried out on rodent models to explore the biological pathways underpinning exposure to social adversity in early life. We analyze their interdisciplinary exchanges with biologists in a social epigenetics project—i.e., in the experimental study of molecular alterations following social exposures. We argue that social epidemiologists are ambivalent regarding the use of non-human animal models on two levels: first, in terms of whether such models provide scientific evidence useful to social epidemiology, and second, regarding whether such models help promote their conception of public health. While they maintain expectations towards rodent experiments by elevating their functional value over their representational potential, they fear that their research will contribute to a public health approach that focuses on individual responsibility rather than the social causes of health inequalities. This interdisciplinary project demonstrates the difficulties encountered when research in social epigenetics engages with the complexities of laboratory experiments and social environments, as well as the conflicting sociopolitical projects stemming from such research.

Parasite intensity drives fetal development and sex allocation in a wild ungulate

An understanding of the mechanisms influencing prenatal characteristics is fundamental to comprehend the role of ecological and evolutionary processes behind survival and reproductive success in animals. Although the negative influence of parasites on host fitness is undisputable, we know very little about how parasitic infection in reproductive females might influence prenatal factors such as fetal development and sex allocation. Using an archival collection of Dall’s sheep (Ovis dalli dalli), a capital breeder that depends on its body reserves to overcome the arctic winter, we investigated the direct and indirect impacts of the parasite community on fetal development and sex allocation. Using partial least squares modelling, we observed a negative effect of parasite community on fetal development, driven primarily by the nematode Marshallagia marshalli. Principal component analysis demonstrated that mothers with low parasite burden and in good body condition were more likely to have female versus male fetuses. This association was primarily driven by the indirect effect of M. marshalli on ewe body condition. Refining our knowledge of the direct and indirect impact that parasite communities can have on reproduction in mammals is critical for understanding the effects of infectious diseases on wildlife populations. This can be particularly relevant for species living in ecosystems sensitive to the effects of global climate change.

The developmental support hypothesis: adaptive plasticity in neural development in response to cues of social support

Across mammals, cues of developmental support, such as touching, licking or attentiveness, stimulate neural development, behavioural exploration and even overall body growth. Why should such fitness-related traits be so sensitive to developmental conditions? Here, we review what we term the 'developmental support hypothesis', a potential adaptive explanation of this plasticity. Neural development can be a costly process, in terms of time, energy and exposure. However, environmental variability may sometimes compromise parental care during this costly developmental period. We propose this environmental variation has led to the evolution of adaptive plasticity of neural and behavioural development in response to cues of developmental support, where neural development is stimulated in conditions that support associated costs. When parental care is compromised, offspring grow less and adopt a more resilient and stress-responsive strategy, improving their chances of survival in difficult conditions, similar to existing ideas on the adaptive value of early-life programming of stress. The developmental support hypothesis suggests new research directions, such as testing the adaptive value of reduced neural growth and metabolism in stressful conditions, and expanding the range of potential cues animals may attend to as indicators of developmental support. Considering evolutionary and ecologically appropriate cues of social support also has implications for promoting healthy neural development in humans. This article is part of the theme issue 'Life history and learning: how childhood, caregiving and old age shape cognition and culture in humans and other animals'.

Sexually dimorphic behavioral effects of maternal separation in anorexic rats

Exposure to negative events during the neonatal period is one of the leading factors contributing to the development of psychiatric disorders, including anorexia nervosa. In this study, we investigated the effects of maternal separation (MS) on the development of anorexia in rodents using the mild-stress form of the activity-based anorexia (ABA) model (2 hr of free access to a running wheel and a 1-hr feeding test) in both male and female rats. We assessed anxiety-like and locomotor behavior and hyperactivity with the open field and elevated plus maze tests. Our results showed that ABA rats of both sexes displayed hyperactive behavior associated with reduced anxiety-like behavior when compared to controls. However, a sexually dimorphic effect of MS emerged in anorexic rats: while the females exposed to MS + ABA were hyperactive with diminished anxiety-related behaviors compared to females of the ABA group, MS in males attenuated or did not alter the effects of the ABA protocol. In conclusion, our data reveal that the synergistic effects of MS and ABA on physical activity and anxiety-like behavior act in opposite directions in the two sexes.

Developmental Trajectories of Early Life Stress and Trauma: A Narrative Review on Neurobiological Aspects Beyond Stress System Dysregulation

Early life stressors display a high universal prevalence and constitute a major public health problem. Prolonged psychoneurobiological alterations as sequelae of early life stress (ELS) could represent a developmental risk factor and mediate risk for disease, leading to higher physical and mental morbidity rates in later life. ELS could exert a programming effect on sensitive neuronal brain networks related to the stress response during critical periods of development and thus lead to enduring hyper- or hypo-activation of the stress system and altered glucocorticoid signaling. In addition, alterations in emotional and autonomic reactivity, circadian rhythm disruption, functional and structural changes in the brain, as well as immune and metabolic dysregulation have been lately identified as important risk factors for a chronically impaired homeostatic balance after ELS. Furthermore, human genetic background and epigenetic modifications through stress-related gene expression could interact with these alterations and explain inter-individual variation in vulnerability or resilience to stress. This narrative review presents relevant evidence from mainly human research on the ten most acknowledged neurobiological allostatic pathways exerting enduring adverse effects of ELS even decades later (hypothalamic-pituitary-adrenal axis, autonomic nervous system, immune system and inflammation, oxidative stress, cardiovascular system, gut microbiome, sleep and circadian system, genetics, epigenetics, structural, and functional brain correlates). Although most findings back a causal relation between ELS and psychobiological maladjustment in later life, the precise developmental trajectories and their temporal coincidence has not been elucidated as yet. Future studies should prospectively investigate putative mediators and their temporal sequence, while considering the potentially delayed time-frame for their phenotypical expression. Better screening strategies for ELS are needed for a better individual prevention and treatment.

Nutrition and Ageing

The ageing trajectory is plastic and can be slowed down by lifestyle factors, including good nutrition, adequate physical activity and avoidance of smoking. In humans, plant-based diets such as the Mediterranean dietary pattern are associated with healthier ageing and lower risk of age-related disease, whereas obesity accelerates ageing and increases the likelihood of most common complex diseases including CVD, T2D, dementia, musculoskeletal diseases and several cancers. As yet, there is only weak evidence in humans about the molecular mechanisms through which dietary factors modulate ageing but evidence from cell systems and animal models suggest that it is probable that better dietary choices influence all 9 hallmarks of ageing. It seems likely that better eating patterns retard ageing in at least two ways including (i) by reducing pervasive damaging processes such as inflammation, oxidative stress/redox changes and metabolic stress and (ii) by enhancing cellular capacities for damage management and repair. From a societal perspective, there is an urgent imperative to discover, and to implement, cost-effective lifestyle (especially dietary) interventions which enable each of us to age well, i.e. to remain physically and socially active and independent and to minimise the period towards the end of life when individuals suffer from frailty and multi-morbidity.

Prenatal Exposure to Endocrine Disruptors and Reprogramming of Adipogenesis: An Early-Life Risk Factor for Childhood Obesity

Obesity is a global health problem. It is characterized by excess adipose tissue that results from either increase in the number of adipocytes or increase in adipocytes size. Adipocyte differentiation is a highly regulated process that involves the activation of several transcription factors culminating in the removal of adipocytes from the cell cycle and induction of highly specific proteins. Several other factors, including hormones, genes, and epigenetics, are among the most important triggers of the differentiation process. Although the main contributing factors to obesity are high caloric intake, a sedentary lifestyle, and genetic predisposition, strong evidence supports a role for life exposure to environmental pollutants. Endocrine-disrupting chemicals are exogenous, both natural and man-made, chemicals that disrupt the body signaling processes, thus interfering with the endocrine system. Several studies have shown that prenatal exposure to endocrine disruptors modulates the mechanisms, by which multipotent mesenchymal stem cells differentiate into adipocytes. This review discusses adipocytes differentiation and highlights the possible mechanisms of prenatal exposure to endocrine disruptors in reprogramming of adipogenesis and induction of obesity later in life. Therefore, this review provides knowledge that reduction of early life exposure to these chemicals could open the door for new strategies in the prevention of obesity, especially during childhood.

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.

The impact of life stress on adult depression and anxiety is dependent on gender and timing of exposure

There is debate about the relative importance of timing of stressful events prenatally and over the life course and risk for subsequent depressive/anxious illness. The aim of this study was to examine the relative roles of prenatal stress and postnatal stress trajectories in predicting depression and anxiety in early adulthood in males and females. Exposure to life stress events was examined in the Western Australian Pregnancy Cohort (Raine) Study during pregnancy and ages 1, 2, 3, 5, 8, 10, 14, and 17 years. At age 20, offspring completed the Depression Anxiety Stress Scale. Prenatal stress and trajectories of stress events from age 1 to 17 were analyzed in linear regression analyses. Five postnatal stress trajectories were identified. In females, medium to high chronic stress exposure or exposure during puberty/adolescence predicted depression and anxiety symptoms while low or reduced stress exposure over the life course did not, after adjustment for relevant confounders. High stress early in pregnancy contributed to male depression/anxiety symptoms independent of postnatal stress trajectory. In females, postnatal stress trajectory was more important than prenatal stress in predicting depression/anxiety symptoms. Interventions focused on reducing and managing stress events around conception/pregnancy and exposure to chronic stress are likely to have beneficial outcomes on rates of depression and anxiety in adults.

Organ-Specific Gene Expression Changes in the Fetal Liver and Placenta in Response to Maternal Folate Depletion

Growing evidence supports the hypothesis that the in utero environment can have profound implications for fetal development and later life offspring health. Current theory suggests conditions experienced in utero prepare, or "programme", the fetus for its anticipated post-natal environment. The mechanisms responsible for these programming events are poorly understood but are likely to involve gene expression changes. Folate is essential for normal fetal development and inadequate maternal folate supply during pregnancy has long term adverse effects for offspring. We tested the hypothesis that folate depletion during pregnancy alters offspring programming through altered gene expression. Female C57BL/6J mice were fed diets containing 2 mg or 0.4 mg folic acid/kg for 4 weeks before mating and throughout pregnancy. At 17.5 day gestation, genome-wide gene expression was measured in male fetal livers and placentas. In the fetal liver, 989 genes were expressed differentially (555 up-regulated, 434 down-regulated) in response to maternal folate depletion, with 460 genes expressed differentially (250 up-regulated, 255 down-regulated) in the placenta. Only 25 differentially expressed genes were common between organs. Maternal folate intake during pregnancy influences fetal gene expression in a highly organ specific manner which may reflect organ-specific functions.

Impact of Life History on Fear Memory and Extinction

Behavioral profiles are strongly shaped by an individual's whole life experience. The accumulation of negative experiences over lifetime is thought to promote anxiety-like behavior in adulthood (“allostatic load hypothesis”). In contrast, the “mismatch hypothesis” of psychiatric disease suggests that high levels of anxiety-like behavior are the result of a discrepancy between early and late environment. The aim of the present study was to investigate how different life histories shape the expression of anxiety-like behavior and modulate fear memory. In addition, we aimed to clarify which of the two hypotheses can better explain the modulation of anxiety and fear. For this purpose, male mice grew up under either adverse or beneficial conditions during early phase of life. In adulthood they were further subdivided in groups that either matched or mismatched the condition experienced before, resulting in four different life histories. The main results were: (i) Early life benefit followed by late life adversity caused decreased levels of anxiety-like behavior. (ii) Accumulation of adversity throughout life history led to impaired fear extinction learning. Late life adversity as compared to late life benefit mainly affected extinction training, while early life adversity as compared to early life benefit interfered with extinction recall. Concerning anxiety-like behavior, the results do neither support the allostatic load nor the mismatch hypothesis, but rather indicate an anxiolytic effect of a mismatched early beneficial and later adverse life history. In contrast, fear memory was strongly affected by the accumulation of adverse experiences over the lifetime, therefore supporting allostatic load hypothesis. In summary, this study highlights that anxiety-like behavior and fear memory are differently affected by specific combinations of adverse or beneficial events experienced throughout life.

The hepatic transcriptome of young suckling and aging intrauterine growth restricted male rats

Intrauterine growth restriction leads to the development of adult onset obesity/metabolic syndrome, diabetes mellitus, cardiovascular disease, hypertension, stroke, dyslipidemia, and non-alcoholic fatty liver disease/steatohepatitis. Continued postnatal growth restriction has been shown to ameliorate many of these sequelae. To further our understanding of the mechanism of how intrauterine and early postnatal growth affects adult health we have employed Affymetrix microarray-based expression profiling to characterize hepatic gene expression of male offspring in a rat model of maternal nutrient restriction in early and late life. At day 21 of life (p21) combined intrauterine and postnatal calorie restriction treatment led to expression changes in circadian, metabolic, and insulin-like growth factor genes as part of a larger transcriptional response that encompasses 144 genes. Independent and controlled experiments at p21 confirm the early life circadian, metabolic, and growth factor perturbations. In contrast to the p21 transcriptional response, at day 450 of life (d450) only seven genes, largely uncharacterized, were differentially expressed. This lack of a transcriptional response identifies non-transcriptional mechanisms mediating the adult sequelae of intrauterine growth restriction. Independent experiments at d450 identify a circadian defect as well as validate expression changes to four of the genes identified by the microarray screen which have a novel association with growth restriction. Emerging from this rich dataset is a portrait of how the liver responds to growth restriction through circadian dysregulation, energy/substrate management, and growth factor modulation.

Low-grade inflammation, diet composition and health: current research evidence and its translation

The importance of chronic low-grade inflammation in the pathology of numerous age-related chronic conditions is now clear. An unresolved inflammatory response is likely to be involved from the early stages of disease development. The present position paper is the most recent in a series produced by the International Life Sciences Institute's European Branch (ILSI Europe). It is co-authored by the speakers from a 2013 workshop led by the Obesity and Diabetes Task Force entitled ‘Low-grade inflammation, a high-grade challenge: biomarkers and modulation by dietary strategies’. The latest research in the areas of acute and chronic inflammation and cardiometabolic, gut and cognitive health is presented along with the cellular and molecular mechanisms underlying inflammation–health/disease associations. The evidence relating diet composition and early-life nutrition to inflammatory status is reviewed. Human epidemiological and intervention data are thus far heavily reliant on the measurement of inflammatory markers in the circulation, and in particular cytokines in the fasting state, which are recognised as an insensitive and highly variable index of tissue inflammation. Potential novel kinetic and integrated approaches to capture inflammatory status in humans are discussed. Such approaches are likely to provide a more discriminating means of quantifying inflammation–health/disease associations, and the ability of diet to positively modulate inflammation and provide the much needed evidence to develop research portfolios that will inform new product development and associated health claims.

Birth weight and polycystic ovary syndrome in adult life: is there a causal link?

Objectives

Several studies have demonstrated associations of birth weight with metabolic and reproductive abnormalities in adults. The aim of this study was to investigate the birth weight in women with PCOS and its correlation with clinical and biochemical characteristics of the syndrome.

Materials and Methods

We studied 288 women with PCOS according to the NIH criteria and 166 women with normal cycle and without clinical hyperandrogenism. Birth weight and anthropometric characteristics were recorded, and levels of serum androgens, SHBG, insulin and fasting glucose were measured.

Results

Birth weight data were available for 243/288 women with PCOS and age- and BMI-matched 101/166 controls. No differences were found (p> 0.05) in birth weight among women with PCOS and normal controls. Birth weight of PCOS women was negatively correlated with DHEAS levels (p = 0.031, r = -0.143) and positively correlated with waist circumference (p <0.001, r = 0.297) and body mass index (BMI) (p = 0.040, r = 0.132). Birth weight of controls was negatively correlated with SHBG levels (p = 0.021, r = -0.234). Women from both groups were further divided in 6 categories according to birth weight (A. <2.500 gr, B. 2.501-3.000 gr, C. 3.001-3.500 gr, D. 3.501-4.000 gr, E. 4.001-4.500 gr, F. > 4.500 gr). No statistically significant differences were observed in the distribution percentages between PCOS women and controls. (A. 7% vs 7.9%, B. 26.8% vs 20.8%, C. 39.1% vs 48.5%, D. 21.4% vs 20.8%, E. 4.9% vs 2%, F. 0.8% vs 0%), (in all comparisons, p> 0.05).

Conclusions

Women with PCOS do not differ from controls in birth weight distribution. However, birth weight may contribute to subtypes of the syndrome that are characterized by adrenal hyperandrogenism and central obesity.

Benefits of adversity?! How life history affects the behavioral profile of mice varying in serotonin transporter genotype

Behavioral profiles are influenced by both positive and negative experiences as well as the genetic disposition. Traditionally, accumulating adversity over lifetime is considered to predict increased anxiety-like behavior (“allostatic load”). The alternative “mismatch hypothesis” suggests increased levels of anxiety if the early environment differs from the later-life environment. Thus, there is a need for a whole-life history approach to gain a deeper understanding of how behavioral profiles are shaped. The aim of this study was to elucidate the effects of life history on the behavioral profile of mice varying in serotonin transporter (5-HTT) genotype, an established mouse model of increased anxiety-like behavior. For this purpose, mice grew up under either adverse or beneficial conditions during early phases of life. In adulthood, they were further subdivided so as to face a situation that either matched or mismatched the condition experienced so far, resulting in four different life histories. Subsequently, mice were tested for their anxiety-like and exploratory behavior. The main results were: (1) Life history profoundly modulated the behavioral profile. Surprisingly, mice that experienced early beneficial and later escapable adverse conditions showed less anxiety-like and more exploratory behavior compared to mice of other life histories. (2) Genotype significantly influenced the behavioral profile, with homozygous 5-HTT knockout mice displaying highest levels of anxiety-like and lowest levels of exploratory behavior. Our findings concerning life history indicate that the absence of adversity does not necessarily cause lower levels of anxiety than accumulating adversity. Rather, some adversity may be beneficial, particularly when following positive events. Altogether, we conclude that for an understanding of behavioral profiles, it is not sufficient to look at experiences during single phases of life, but the whole life history has to be considered.

Grandmother's smoking when pregnant with the mother and asthma in the grandchild: the Norwegian Mother and Child Cohort Study

BACKGROUND

A trans-generational influence of prenatal tobacco smoke exposure on asthma development has been proposed but the evidence remains sparse.

METHODS

We examined the grandmother's smoking when pregnant with the mother in relation to asthma outcomes in the grandchild (current asthma at 36 months (N=53 169, cases=3013), current asthma at 7 years (N=25 394, cases=1265) and dispensed asthma medications at 7 years in the Norwegian Prescription Database (N=45 607, cases=1787)) within the Norwegian Mother and Child Cohort Study (MoBa). We calculated adjusted RR (adj. RR) and 95% CIs using log binomial regression.

RESULTS

A total of 23.5% of mothers reported that their mother smoked when pregnant with them. The grandmother's smoking when pregnant with the mother was positively associated with asthma at 36 months (adj. RR 1.15 (95% CI 1.06 to 1.24)), asthma at 7 years (adj. RR 1.21 (95% CI 1.07 to 1.37)) and dispensed asthma medications at 7 years (adj. RR 1.15 (95% CI 1.04 to 1.26)). This positive association did not differ significantly by the mother's smoking status when pregnant with the child (p values for multiplicative interaction >0.1).

CONCLUSIONS

The grandmother's smoking when pregnant with the mother increased the risk of asthma in the grandchild independent of the mother's smoking status. However, given limited information on the grandmother's socioeconomic status, asthma status and other factors, unmeasured confounding may be present.

Human placental transcriptome shows sexually dimorphic gene expression and responsiveness to maternal dietary n-3 long-chain polyunsaturated fatty acid intervention during pregnancy

Background

Previously we have examined the effect of maternal dietary n-3 long-chain polyunsaturated fatty acid (LCPUFA) supplementation during pregnancy on offspring fat mass. Considering the involvement of the placenta in fetal programming, we aimed to analyze the sex-specific gene expression in human term placenta and its response to the n-3 LCPUFA intervention, as well as their correlations to offspring adiposity.

Results

Placental gene expression was assessed in a control and n-3 LCPUFA intervention group by DNA microarrays, biological pathway analyses and RT-qPCR validation. Expression data were correlated with sex steroid hormone levels in placenta and cord plasma, and offspring anthropometric data. Transcriptome data revealed sexually dimorphic gene expression in control placentas per se, whereas in intervention placentas sex-specific expression changed, and more n-3 LCPUFA-regulated genes were found in female than male placentas. Sexually dimorphic gene expression and n-3 LCPUFA-responsive genes were enriched in the pathway for cell cycle and its associated modulator pathways. Significant mRNA expression changes for CDK6, PCNA, and TGFB1 were confirmed by RT-qPCR. CDK6 and PCNA mRNA levels correlated with offspring birth weight and birth weight percentiles. Significantly reduced placental estradiol-17β/testosterone ratio upon intervention found in female offspring correlated with mRNA levels for the 'Wnt signaling' genes DVL1 and LRP6.

Conclusions

Overall, human placentas show sexually dimorphic gene expression and responsiveness to maternal n-3 LCPUFA intervention during pregnancy with more pronounced effects in female placentas. The absence of correlations of analyzed placental gene expression with offspring adipose tissue growth in the first year is not mutually exclusive with programming effects, which may manifest later in life, or in other physiological processes.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2164-15-941) contains supplementary material, which is available to authorized users.

The chromosome 3q25 locus associated with fetal adiposity is not associated with childhood adiposity

Increased newborn adiposity is associated with later adverse metabolic outcomes. Previous genome-wide association studies (GWAS) demonstrated strong association of a locus on chromosome 3 (3q25.31) with newborn sum of skinfolds, a measure of overall adiposity. Whether this locus is associated with childhood adiposity is unknown. Genotype and sum of skinfolds data were available for 293 children at birth and age 2, and for 350 children at birth and age 6 from a European cohort (Belfast, UK) who participated in the Hyperglycemia and Adverse Pregnancy Outcome GWAS. We examined single nucleotide polymorphisms (SNPs) at the 3q25.31 locus associated with newborn adiposity. Linear regression analyses under an additive genetic model adjusting for maternal body mass index were performed. In both cohorts, a positive association was observed between all SNPs and sum of skinfolds at birth (P=2.3 × 10⁻⁴, β=0.026 and P=4.8 × 10⁻⁴, β=0.025). At the age of 2 years, a non-significant negative association was observed with sum of skinfolds (P=0.06; β =−0.015). At the age of 6 years, there was no evidence of association (P=0.86; β=0.002). The 3q25.31 locus strongly associated with newborn adiposity had no significant association with childhood adiposity suggesting that its impact may largely be limited to fetal fat accretion.

Factors associated with growth patterns from birth to 18 months in a Beninese cohort of children

The aim of this study was to analyze factors influencing the growth pattern of children from birth to 18 months. A longitudinal prospective study was conducted in three maternity wards in Southern Benin. Inclusion took place between June 2007 and July 2008; children were followed-up until 18 months of age. Height-for-age and weight-for-height Z-scores were computed using the newborn's anthropometric measurements taken at delivery, every month up to 6 months and then quarterly. Infant and young child feeding (IYCF) practices and malarial morbidity were recorded. Gestational age was estimated using the Ballard method; William's sex-specific reference curve of birth weight-for-gestational-age was used to determine intrauterine growth retardation (IUGR). Analyses were performed on 520 children using a linear mixed model. Low birth weight (coef=-0.43; p=0.002), IUGR (coef=-0.49; p<0.001), maternal short stature (coef=-0.25; p=0.001) and maternal low weight status (coef=-0.19; p=0.006) were significantly associated with growth impairment. Only LBW (coef=-0.28; p=0.05) and maternal low weight status (coef=-0.23; p=0.004) were associated with wasting. A good IYCF score was positively associated with weight gain (coef=0.14; p<0.001) whereas we found a paradoxical association with length (coef=-0.18; p<0.001). Malaria morbidity was not associated with growth. LBW, IUGR and maternal low weight status and height were important determinants of children's growth. These results reinforce and justify continuing public health initiatives to fight IUGR and LBW and break the intergenerational cycle of malnutrition.

Developmental cigarette smoke exposure: hippocampus proteome and metabolome profiles in low birth weight pups

Exposure to cigarette smoke during development is linked to neurodevelopmental delays and cognitive impairment including impulsivity, attention deficit disorder, and lower IQ. However, brain region specific biomolecular alterations induced by developmental cigarette smoke exposure (CSE) remain largely unexplored. In the current molecular phenotyping study, a mouse model of 'active' developmental CSE (serum cotinine > 50 ng/mL) spanning pre-implantation through third trimester-equivalent brain development (gestational day (GD) 1 through postnatal day (PD) 21) was utilized. Hippocampus tissue collected at the time of cessation of exposure was processed for gel-based proteomic and non-targeted metabolomic profiling with partial least squares-discriminant analysis (PLS-DA) for selection of features of interest. Ingenuity pathway analysis was utilized to identify candidate molecular and metabolic pathways impacted within the hippocampus. CSE impacted glycolysis, oxidative phosphorylation, fatty acid metabolism, and neurodevelopment pathways within the developing hippocampus.

Developmental programming of offspring obesity, adipogenesis, and appetite

A newly recognized primary cause of the obesity epidemic is the developmental programming effects of infants born to mothers with obesity or gestational diabetes, intrauterine growth-restricted newborns, and offspring exposed to environmental toxins including bisphenol A. The mechanisms which result in offspring obesity include the programming of the hypothalamic appetite pathway and adipogenic signals regulating lipogenesis. Processes include nutrient sensors, epigenetic modifications, and alterations in stem cell precursors of both appetite/satiety neurons and adipocytes which are modulated to potentiate offspring obesity. Future strategies for the prevention and therapy of obesity must address programming effects of the early life environment.

Metabolic effects of a high-fat diet post-weaning after low maternal dietary folate during pregnancy and lactation

SCOPE

Investigate the influence of low-folate supply during pregnancy and lactation on obesity and markers of the metabolic syndrome in offspring, and how provision of a high-fat diet post weaning may exacerbate the resultant phenotype.

METHODS AND RESULTS

Female C57Bl/6 mice were randomized to low or normal folate diets (0.4 or 2 mg folic acid/kg diet) prior to and during pregnancy and lactation. At 4 wk of age, offspring were randomized to high- or low-fat diets, weighed weekly and food intake assessed at 9 and 18 wk old. Adiposity was measured at 3 and 6 months. Plasma glucose and triacylglycerol (TAG) concentrations were measured at 6 months. Maternal folate supply did not influence adult offspring body weight or adiposity. High-fat feeding post weaning increased body weight and adiposity at 3 and 6 months (p > 0.001). Maternal low folate lowered plasma glucose (p = 0.010) but increased plasma TAG (p = 0.048). High-fat feeding post weaning increased plasma glucose and TAG (p = 0.023, p = 0.049 respectively). Offspring from folate-depleted (but not folate-adequate) dams had 30% higher TAG concentration when fed the high-fat diet from weaning (p = 0.005 for interaction).

CONCLUSION

Inadequate maternal folate intake has long-term effects on offspring metabolism, manifested as increased circulating TAG, particularly in offspring with high-fat intake post weaning.

Maternal Prepregnancy Body Mass Index and Their Children’s Blood Pressure and Resting Cardiac Autonomic Balance at Age 5 to 6 Years

Adverse intrauterine conditions can program hypertension. Because one of the underlying mechanisms is thought to be cardiac autonomic balance, we investigated the association between prepregnancy body mass index (BMI) and blood pressure and indicators of the autonomic balance in the child at age 5 to 6 years. Also investigated was whether these associations were mediated by standardized birth weight and child BMI. Pregnant women (n=3074) participating in the Amsterdam Born Children and their Development study completed a questionnaire at gestational week 14. At age 5 to 6 years, offspring’s sympathetic drive (pre-ejection period), parasympathetic drive (respiratory sinus arrhythmia), and heart rate were measured by electrocardiography and impedance cardiography at rest. Blood pressure was assessed simultaneously. After adjusting for possible maternal/offspring confounders, prepregnancy BMI was positively linearly associated with diastolic blood pressure (β=0.11 mm Hg; 95% confidence interval, 0.05–0.17), systolic blood pressure (β=0.14 mm Hg; 95% confidence interval, 0.07–0.21), but not with heart rate, sympathetic or parasympathetic drive. After adding birth weight and child BMI to the model, the independent effect size of prepregnancy body mass index on systolic blood pressure (β=0.07 mm Hg; 95% confidence interval, 0.00–0.14) and diastolic blood pressure (β=0.07 mm Hg; 95% confidence interval, 0.01–0.13) decreased by ≈50%. Birth weight did not mediate these relationships, but was independently and negatively associated with blood pressure. Child BMI was positively associated with blood pressure and partly mediated the association between prepregnancy BMI and blood pressure. In conclusion, higher prepregnancy BMI is associated with higher blood pressure in the child (aged 5–6 years) but does not seem to be attributable to early alterations in resting cardiac autonomic balance. Child BMI, but not birth weight, mediated the association between prepregnancy BMI and blood pressure.

Pregnancy Complications and the Risk of Metabolic Syndrome for the Offspring

Metabolic syndrome is a growing problem globally, and is a contributor to non-communicable diseases such as type II diabetes and cardiovascular disease. The risk of developing specific components of the metabolic syndrome such as obesity, hyperlipidemia, hypertension, and elevated fasting blood sugar has been largely attributed to environmental stressors including poor nutrition, lack of exercise, and smoking. However, large epidemiologic cohorts and experimental animal models support the "developmental origins of adult disease" hypothesis, which posits that a significant portion of the risk for adult metabolic conditions is determined by exposures occurring in the perinatal period. Maternal obesity and the rate of complications during pregnancy such as preterm birth, preeclampsia, and gestational diabetes continue to rise. As our ability to reduce perinatal morbidity and mortality improves the long-term metabolic consequences remain uncertain, pointing to the need for further research in this area.

Physiopathology of intrauterine growth retardation: from classic data to metabolomics

It is well known that adverse conditions during intrauterine life, such as intrauterine growth restriction (IUGR), can result in permanent changes in the physiology and metabolism of the newborn, which in turn leads to an increased risk of disease in adulthood (fetal origin of adult disease hypothesis). In the first part of this review the epidemiological studies in which a correlation between low birth weight and chronic pathologies in adulthood was observed are reported. The second part of the review is focused on metabolomics studies that have revealed an altered metabolism in IUGR patients compared to controls. Together with more classic biomarkers of IUGR, such as endothelin-1, leptin, protein S100B and visfatin, the new holistic metabolomics approach has assumed a crescent role in the identification of disorders in the neonatal metabolic profile, determined by the interconnection of the different processes.

Developmental origins of obesity: programmed adipogenesis

The metabolic syndrome epidemic, including a marked increase in the prevalence of obesity and gestational diabetes mellitus (GDM) among pregnant women, represents a significant public health problem. There is increasing recognition that the risk of adult obesity is clearly influenced by prenatal and infant environmental exposures, particularly nutrition. This tenet is the fundamental basis of developmental programming. Low birth weight, together with infant catch-up growth, is associated with a significant risk of adult obesity. Exposure to maternal obesity, with or without GDM, or having a high birth weight also represents an increased risk for childhood and adult obesity. Animal models have replicated human epidemiologic findings and elucidated potential programming mechanisms that include altered organ development, cellular signaling responses, and epigenetic modifications. Prenatal care has made great strides in optimizing maternal, fetal, and neonatal health, and now has the opportunity to begin interventions which prevent or reduce childhood/adult obesity. Guidelines that integrate optimal pregnancy nutrition and weight gain, management of GDM, and newborn feeding strategies with long-term consequences on adult obesity, remain to be elucidated.

A multidisciplinary reconstruction of Palaeolithic nutrition that holds promise for the prevention and treatment of diseases of civilisation

Evolutionary medicine acknowledges that many chronic degenerative diseases result from conflicts between our rapidly changing environment, our dietary habits included, and our genome, which has remained virtually unchanged since the Palaeolithic era. Reconstruction of the diet before the Agricultural and Industrial Revolutions is therefore indicated, but hampered by the ongoing debate on our ancestors' ecological niche. Arguments and their counterarguments regarding evolutionary medicine are updated and the evidence for the long-reigning hypothesis of human evolution on the arid savanna is weighed against the hypothesis that man evolved in the proximity of water. Evidence from various disciplines is discussed, including the study of palaeo-environments, comparative anatomy, biogeochemistry, archaeology, anthropology, (patho)physiology and epidemiology. Although our ancestors had much lower life expectancies, the current evidence does neither support the misconception that during the Palaeolithic there were no elderly nor that they had poor health. Rather than rejecting the possibility of 'healthy ageing', the default assumption should be that healthy ageing posed an evolutionary advantage for human survival. There is ample evidence that our ancestors lived in a land-water ecosystem and extracted a substantial part of their diets from both terrestrial and aquatic resources. Rather than rejecting this possibility by lack of evidence, the default assumption should be that hominins, living in coastal ecosystems with catchable aquatic resources, consumed these resources. Finally, the composition and merits of so-called 'Palaeolithic diets', based on different hominin niche-reconstructions, are evaluated. The benefits of these diets illustrate that it is time to incorporate this knowledge into dietary recommendations.

Transcriptome changes affecting Hedgehog and cytokine signalling in the umbilical cord: implications for disease risk

BACKGROUND

Babies born at lower gestational ages or smaller birthweights have a greater risk of poorer health in later life. Both the causes of these sub-optimal birth outcomes and the mechanism by which the effects are transmitted over decades are the subject of extensive study. We investigated whether a transcriptomic signature of either birthweight or gestational age could be detected in umbilical cord RNA.

METHODS

The gene expression patterns of 32 umbilical cords from Singaporean babies of Chinese ethnicity across a range of birthweights (1698-4151 g) and gestational ages (35-41 weeks) were determined. We confirmed the differential expression pattern by gestational age for 12 genes in a series of 127 umbilical cords of Chinese, Malay and Indian ethnicity.

RESULTS

We found that the transcriptome is substantially influenced by gestational age; but less so by birthweight. We show that some of the expression changes dependent on gestational age are enriched in signal transduction pathways, such as Hedgehog and in genes with roles in cytokine signalling and angiogenesis. We show that some of the gene expression changes we report are reflected in the epigenome.

CONCLUSIONS

We studied the umbilical cord which is peripheral to disease susceptible tissues. The results suggest that soma-wide transcriptome changes, preserved at the epigenetic level, may be a mechanism whereby birth outcomes are linked to the risk of adult metabolic and arthritic disease and suggest that greater attention be given to the association between premature birth and later disease risk.

Fetal programming of adult disease: implications for prenatal care

The obesity epidemic, including a marked increase in the prevalence of obesity among pregnant women, represents a critical public health problem in the United States and throughout the world. Over the past two decades, it has been increasingly recognized that the risk of adult health disorders, particularly metabolic syndrome, can be markedly influenced by prenatal and infant environmental exposures (ie, developmental programming). Low birth weight, together with infant catch-up growth, is associated with a significant risk of adult obesity and cardiovascular disease, as well as adverse effects on pulmonary, renal, and cerebral function. Conversely, exposure to maternal obesity or high birth weight also represents an increased risk for childhood and adult obesity. In addition, fetal exposure to select chemicals (eg, phytoestrogens) or environmental pollutants (eg, tobacco smoke) may affect the predisposition to adult disease. Animal models have confirmed human epidemiologic findings and provided insight into putative programming mechanisms, including altered organ development, cellular signaling responses, and epigenetic modifications (ie, control of gene expression without modification of DNA sequence). Prenatal care is transitioning to incorporate goals of optimizing maternal, fetal, and neonatal health to prevent or reduce adult-onset diseases. Guidelines regarding optimal pregnancy nutrition and weight gain, management of low- and high-fetal-weight pregnancies, use of maternal glucocorticoids, and newborn feeding strategies, among others, have yet to fully integrate long-term consequences on adult health.

The estrogenic endocrine disrupting chemical bisphenol A (BPA) and obesity

There is increasing experimental and epidemiological evidence that fetal programming of genetic systems is a contributing factor in the recent increase in adult obesity and other components of metabolic syndrome. In particular, there is evidence that epigenetic changes associated with the use of manmade chemicals may interact with other factors that influence fetal and postnatal growth in contributing to the current obesity epidemic. The focus of this review is on the developmental effects of estrogenic endocrine disrupting chemicals (EDCs), and more specifically on effects of exposure to the estrogenic EDC bisphenol A (BPA), on adipocytes and their function, and the ultimate impact on adult obesity; BPA exposure also results in impaired reproductive capacity. We discuss the interaction of EDCs with other factors that impact growth during fetal and neonatal life, such as placental blood flow and nutrient transport to fetuses, and how these influence fetal growth and abnormalities in homeostatic control systems required to maintain normal body weight throughout life.

Periconceptional maternal micronutrient supplementation is associated with widespread gender related changes in the epigenome: a study of a unique resource in the Gambia

In addition to the genetic constitution inherited by an organism, the developmental trajectory and resulting mature phenotype are also determined by mechanisms acting during critical windows in early life that influence and establish stable patterns of gene expression. This is the crux of the developmental origins of health and disease hypothesis that suggests undernutrition during gestation and infancy predisposes to ill health in later life. The hypothesis that periconceptional maternal micronutrient supplementation might affect fetal genome-wide methylation within gene promoters was explored in cord blood samples from offspring of Gambian women enrolled into a unique randomized, double blind controlled trial. Significant changes in the epigenome in cord blood DNA samples were further explored in a subset of offspring at 9 months. Gender-specific changes related to periconceptional nutritional supplementation were identified in cord blood DNA samples, some of which showed persistent changes in infant blood DNA samples. Significant effects of periconceptional micronutrient supplementation were also observed in postnatal samples which were not evident in cord blood. In this Gambian population, the increased death rate of individuals born in nutritionally poor seasons has been related to infection and it is of interest that we identified differential methylation at genes associated with defence against infection and immune response. Although the sample size was relatively small, these pilot data suggest that periconceptional nutrition in humans is an important determinant of newborn whole genome methylation patterns but may also influence postnatal developmental patterns of gene promoter methylation linking early with disease risk.

Obesity and the developmental origins of health and disease

The concept that environmental stimuli imparted on a developing organism have the potential to affect both its short- and long-term developmental profiles is intuitively appealing and, more importantly, supported by a growing body of experimental and observational evidence. A number of groups have posited model hypotheses in tandem with experimental data, linking extrinsic factors to the development of a host of human diseases. Here, we review the evolution of 'the developmental origins of health and disease' as a concept and discuss recent advances in the association of specific stimuli to obesity, an epidemic cause of human morbidity and mortality.

Mismatch or cumulative stress: toward an integrated hypothesis of programming effects

This paper integrates the cumulative stress hypothesis with the mismatch hypothesis, taking into account individual differences in sensitivity to programming. According to the cumulative stress hypothesis, individuals are more likely to suffer from disease as adversity accumulates. According to the mismatch hypothesis, individuals are more likely to suffer from disease if a mismatch occurs between the early programming environment and the later adult environment. These seemingly contradicting hypotheses are integrated into a new model proposing that the cumulative stress hypothesis applies to individuals who were not or only to a small extent programmed by their early environment, while the mismatch hypothesis applies to individuals who experienced strong programming effects. Evidence for the main effects of adversity as well as evidence for the interaction between adversity in early and later life is presented from human observational studies and animal models. Next, convincing evidence for individual differences in sensitivity to programming is presented. We extensively discuss how our integrated model can be tested empirically in animal models and human studies, inviting researchers to test this model. Furthermore, this integrated model should tempt clinicians and other intervenors to interpret symptoms as possible adaptations from an evolutionary biology perspective.

A common cause for a common phenotype: the gatekeeper hypothesis in fetal programming

Sub-optimal nutrition during pregnancy has been shown to have long-term effects on the health of offspring in both humans and animals. The most common outcomes of such programming are hypertension, obesity, dyslipidaemia and insulin resistance. This spectrum of disorders, collectively known as metabolic syndrome, appears to be the consequence of nutritional insult during early development, irrespective of the nutritional stress experienced. For example, diets low in protein diet, high in fat, or deficient in iron are all associated with programming of cardiovascular and metabolic disorders when fed during rat pregnancy. In this paper, we hypothesise that the nutritional stresses act on genes or gene pathways common to all of the insults. We have termed these genes and/or gene pathways the “gatekeepers” and hence developed the “gatekeeper hypothesis”. In this paper, we examine the background to the hypothesis and postulate some possible mechanisms or pathways that may constitute programming gatekeepers.

Gene expression profiling in the Cynomolgus macaque Macaca fascicularis shows variation within the normal birth range

Background

Although an adverse early-life environment has been linked to an increased risk of developing the metabolic syndrome, the molecular mechanisms underlying altered disease susceptibility as well as their relevance to humans are largely unknown. Importantly, emerging evidence suggests that these effects operate within the normal range of birth weights and involve mechanisms of developmental palsticity rather than pathology.

Method

To explore this further, we utilised a non-human primate model Macaca fascicularis (Cynomolgus macaque) which shares with humans the same progressive history of the metabolic syndrome. Using microarray we compared tissues from neonates in the average birth weight (50-75^th centile) to those of lower birth weight (5-25^th centile) and studied the effect of different growth trajectories within the normal range on gene expression levels in the umbilical cord, neonatal liver and skeletal muscle.

Results

We identified 1973 genes which were differentially expressed in the three tissue types between average and low birth weight animals (P < 0.05). Gene ontology analysis identified that these genes were involved in metabolic processes including cellular lipid metabolism, cellular biosynthesis, cellular macromolecule synthesis, cellular nitrogen metabolism, cellular carbohydrate metabolism, cellular catabolism, nucleotide and nucleic acid metabolism, regulation of molecular functions, biological adhesion and development.

Conclusion

These differences in gene expression levels between animals in the upper and lower percentiles of the normal birth weight range may point towards early life metabolic adaptations that in later life result in differences in disease risk.

Stress, vulnerability and resilience, a developmental approach

BACKGROUND

The origins of mental disorders arise often in childhood. Early life is a period of unique sensitivity with long lasting effects on mental health. However, the mechanisms for these effects remain unclear.

OBJECTIVE

This thesis describes a variety of studies using a developmental framework to promote greater understanding of the influence of nature (genotypes) and nurture (e.g., environmental risk and protective factors) on outcomes later in childhood.

METHOD

The aim of this thesis is to investigate gene and environmental influences on behavioural, emotional, and cognitive outcomes in different samples from the Netherlands and Singapore, most derived from the general population. We assessed early life influences from a neurobiological, social, and a psychological perspective by using a biopsychosocial framework.

RESULTS

Our studies support the hypothesis that all experiences during life, including early experiences in utero, will influence the expression of genes and in the end the mental health of individuals. However, genotypes influencing stress responses are found to be "plastic," which implies that they can be modulated by environmental experiences during life. In line with this, patterns of resilience are found to be context-dependent too.

CONCLUSIONS

The model of "epigenetic programming" suggests the predictive power of the environment in utero and early childhood on mental health later in life. This association is probably determined by a neurodevelopmental pathway with individual differences in neural and endocrine responses to stress.

Maternal folate supply and sex influence gene-specific DNA methylation in the fetal gut

SCOPE

Epidemiological evidence supports the developmental origins of health and disease hypothesis that developmental under/over-nutrition increases adulthood disease risk. Epigenetic markings are one potential mechanism mediating these effects. Altered folate supply may influence methyl group availability for DNA methylation. We reported low folate supply in utero was associated with reduced global DNA methylation in the murine small intestine of adult offspring. We hypothesised that aberrant methylation would be observed during early development.

METHODS AND RESULTS

Female C57BL/6J mice were fed diets containing 2 mg folic acid/kg or 0.4 mg folic acid/kg 4 wk before mating and during pregnancy. At 17.5 day gestation, gene methylation in fetal gut was analysed by Pyrosequencing(®) . Low folate reduced overall methylation of Slc394a by 3.4% (p=0.038) but did not affect Esr1 or Igf2 differentially methylated region (DMR) 1. There were sex-specific differences in Slc394a and Esr1 methylation (2.4% higher in females (p=0.002); 4% higher in males (p=0.0014), respectively).

CONCLUSION

This is the first study reporting causal effects of maternal folate depletion on gene-specific methylation in fetal gut. These observations support reports that altered methyl donor intake during development affects DNA methylation in the offspring. The consequences of epigenetic changes for health throughout the life course remain to be investigated.

Effect of maternal and post-weaning folate supply on gene-specific DNA methylation in the small intestine of weaning and adult apc and wild type mice

Increasing evidence supports the developmental origins of adult health and disease hypothesis which argues for a causal relationship between adverse early life nutrition and increased disease risk in adulthood. Modulation of epigenetic marks, e.g., DNA methylation and consequential altered gene expression, has been proposed as a mechanism mediating these effects. Via its role as a methyl donor, dietary folate supply may influence DNA methylation. As aberrant methylation is an early event in colorectal cancer (CRC) pathogenesis, we hypothesized low maternal and/or post-weaning folate intake may influence methylation of genes involved in CRC development. We investigated the effects of maternal folate depletion during pregnancy and lactation on selected gene methylation in the small intestine of wild type (WT) and Apc(+/Min) mice at weaning and as adults. We also investigated the effects of folate depletion post-weaning on gene methylation in adult mice. Female C57Bl6/J mice were fed low or normal folate diets from mating with Apc(+/Min) males to the end of lactation. A sub-set of offspring were killed at weaning. Remaining offspring were weaned on to low or normal folate diets, resulting in four treatment groups of Apc(+/Min) and WT mice. p53 was more methylated in weaning and adult WT compared with Apc(+/Min) mice (p > 0.001). Igf2 and Apc were hypermethylated in adult Apc(+/Min) compared with WT mice (p = 0.004 and 0.012 respectively). Low maternal folate reduced p53 methylation in adults (p = 0.04). Low post-weaning folate increased Apc methylation in Apc(+/Min) mice only (p = 0.008 for interaction). These observations demonstrate that folate depletion in early life can alter epigenetic marks in a gene-specific manner. Also, the differential effects of altered folate supply on DNA methylation in WT and Apc(+/Min) mice suggest that genotype may modulate epigenetic responses to environmental cues and may have implications for the development of personalized nutrition.

Maternal undernutrition significantly impacts ovarian follicle number and increases ovarian oxidative stress in adult rat offspring

BACKGROUND

We have shown recently that maternal undernutrition (UN) advanced female pubertal onset in a manner that is dependent upon the timing of UN. The long-term consequence of this accelerated puberty on ovarian function is unknown. Recent findings suggest that oxidative stress may be one mechanism whereby early life events impact on later physiological functioning. Therefore, using an established rodent model of maternal UN at critical windows of development, we examined maternal UN-induced changes in offspring ovarian function and determined whether these changes were underpinned by ovarian oxidative stress.

METHODOLOGY/PRINCIPAL FINDINGS

Our study is the first to show that maternal UN significantly reduced primordial and secondary follicle number in offspring in a manner that was dependent upon the timing of maternal UN. Specifically, a reduction in these early stage follicles was observed in offspring born to mothers undernourished throughout both pregnancy and lactation. Additionally, antral follicle number was reduced in offspring born to all mothers that were UN regardless of whether the period of UN was restricted to pregnancy or lactation or both. These reductions were associated with decreased mRNA levels of genes critical for follicle maturation and ovulation. Increased ovarian protein carbonyls were observed in offspring born to mothers UN during pregnancy and/or lactation and this was associated with peroxiredoxin 3 hyperoxidation and reduced mRNA levels; suggesting compromised antioxidant defence. This was not observed in offspring of mothers UN during lactation alone.

CONCLUSIONS

We propose that maternal UN, particularly at a time-point that includes pregnancy, results in reduced offspring ovarian follicle numbers and mRNA levels of regulatory genes and may be mediated by increased ovarian oxidative stress coupled with a decreased ability to repair the resultant oxidative damage. Together these data are suggestive of maternal UN potentially contributing to premature ovarian ageing in offspring.