Intergenerational consequences of fetal programming by in utero exposure to glucocorticoids in rats

General health and social outcomes 50 years after exposure to antenatal betamethasone: follow-up of a randomised controlled trial

BACKGROUND

Antenatal corticosteroids are recommended for women at risk of preterm birth from 24 to 34 weeks' gestation as they reduce neonatal morbidity and mortality, but evidence regarding their long-term effects on offspring is limited. This study assessed general health and social outcomes 50 years after antenatal exposure to corticosteroids.

METHODS

We assessed 424 adult offspring of women who participated in the first randomised, double-blind, placebo-controlled trial of antenatal betamethasone for the prevention of neonatal respiratory distress syndrome. The first 717 mothers received two intramuscular injections of betamethasone (6 mg betamethasone sodium phosphate and 6 mg betamethasone acetate) or placebo given 24 h apart and the subsequent 398 received two injections of double dose betamethasone (12 mg betamethasone sodium phosphate and 12 mg betamethasone acetate) or equivalent volume of placebo. Follow-up included a health questionnaire and consent for access to administrative data sources. Outcome categories included mental health (depression, anxiety, bipolar affective disorder, schizophrenia and treatment or hospital admission for any mental health disorder), general health (chronic kidney disease, cancer diagnosis, bone fracture, oral health, allergies, functional difficulties and physical activity) and social outcomes (educational attainment, employment and criminal convictions). Investigators remained blinded to treatment allocation. Analyses were adjusted for gestational age at entry, sex and clustering.

RESULTS

We assessed 424 adult offspring (46% of survivors; mean [SD] age 49.3 [1.0] years; 212 [50%] female). There was no difference in mental health, general health and social outcomes between those exposed to betamethasone and those exposed to placebo, with the exception that osteoporotic site fracture in adulthood was more likely to have occurred in the betamethasone group compared with placebo (adjusted relative risk 1.57, 95% CI 1.00, 2.48, p = 0.05). No dose-effect relationship was evident and there was no difference in the proportion with at least one fracture. Follow-up rate and lack of in-person assessments were the main limitations.

CONCLUSIONS

There is no evidence that antenatal corticosteroids have clinically important effects on general health and social outcomes up to 50 years of age.

Cardiovascular outcomes 50 years after antenatal exposure to betamethasone: Follow-up of a randomised double-blind, placebo-controlled trial

BACKGROUND

Antenatal corticosteroids for women at risk of preterm birth reduce neonatal morbidity and mortality, but there is limited evidence regarding their effects on long-term health. This study assessed cardiovascular outcomes at 50 years after antenatal exposure to corticosteroids.

METHODS AND FINDINGS

We assessed the adult offspring of women who participated in the first randomised, double-blind, placebo-controlled trial of antenatal betamethasone for the prevention of neonatal respiratory distress syndrome (RDS) (1969 to 1974). The first 717 mothers received 2 intramuscular injections of 12 mg betamethasone or placebo 24 h apart and the subsequent 398 received 2 injections of 24 mg betamethasone or equivalent volume of placebo. Follow-up included a health questionnaire and consent to access administrative data sources. The co-primary outcomes were the prevalence of cardiovascular risk factors (any of hypertension, hyperlipidaemia, diabetes mellitus, gestational diabetes mellitus, or prediabetes) and age at first major adverse cardiovascular event (MACE) (cardiovascular death, myocardial infarction, coronary revascularisation, stroke, admission for peripheral vascular disease, and admission for heart failure). Analyses were adjusted for gestational age at entry, sex, and clustering. Of 1,218 infants born to 1,115 mothers, we followed up 424 (46% of survivors; 212 [50%] female) at mean (standard deviation) age 49.3 (1.0) years. There were no differences between those exposed to betamethasone or placebo for cardiovascular risk factors (159/229 [69.4%] versus 131/195 [67.2%]; adjusted relative risk 1.02, 95% confidence interval [CI] [0.89, 1.18;]; p = 0.735) or age at first MACE (adjusted hazard ratio 0.58, 95% CI [0.23, 1.49]; p = 0.261). There were also no differences in the components of these composite outcomes or in any of the other secondary outcomes. Key limitations were follow-up rate and lack of in-person assessments.

CONCLUSIONS

There is no evidence that antenatal corticosteroids increase the prevalence of cardiovascular risk factors or incidence of cardiovascular events up to 50 years of age. Established benefits of antenatal corticosteroids are not outweighed by an increase in adult cardiovascular disease.

Effects of prenatal dexamethasone exposure on adult C57BL/6J mouse metabolism and oxidative stress

Prenatal glucocorticoid exposure has been shown to alter hypothalamic-pituitary-adrenal axis function resulting in altered fetal development that can persist through adulthood. Fetal exposure to excess dexamethasone, a synthetic glucocorticoid, has been shown to alter adult behaviour and metabolism. This study investigated the effects prenatal dexamethasone exposure had on adult offspring cardiac and liver metabolism and oxidative stress. Pregnant C57BL/6 mice received a dose of 0.4 mg/kg dexamethasone on gestational days 15-17. Once pups were approximately 7 months old, glucose uptake was determined using positron emission tomography and insulin resistance (IR) was determined by homeostatic model assessment (HOMA) IR calculation. Oxidative stress was assessed by measuring 4-hydroxynonenal protein adduct formation and total reactive oxygen species. Female dexamethasone group had significantly increased glucose uptake when insulin stimulated compared to vehicle-treated mice. HOMA IR revealed no evidence of IR in either male or female offspring. There was also no change in oxidative stress markers in either cardiac or liver tissues of male or female offspring. These data suggest that prenatal dexamethasone exposure in male mice does not alter oxidative stress or metabolism. However, prenatal dexamethasone exposure increased glucocorticoids, cardiac glucose uptake, and pAkt signaling in female heart tissues in adult mice, suggesting there are sex differences in prenatal dexamethasone exposure.

Unaltered hepatic wound healing response in male rats with ancestral liver injury

The possibility that ancestral environmental exposure could result in adaptive inherited effects in mammals has been long debated. Numerous rodent models of transgenerational responses to various environmental factors have been published but due to technical, operational and resource burden, most still await independent confirmation. A previous study reported multigenerational epigenetic adaptation of the hepatic wound healing response upon exposure to the hepatotoxicant carbon tetrachloride (CCl4) in male rats. Here, we comprehensively investigate the transgenerational effects by repeating the original CCl4 multigenerational study with increased power, pedigree tracing, F2 dose-response and suitable randomization schemes. Detailed pathology evaluations do not support adaptive phenotypic suppression of the hepatic wound healing response or a greater fitness of F2 animals with ancestral liver injury exposure. However, transcriptomic analyses identified genes whose expression correlates with ancestral liver injury, although the biological relevance of this apparent transgenerational transmission at the molecular level remains to be determined. This work overall highlights the need for independent evaluation of transgenerational epigenetic inheritance paradigms in mammals.

The Legacy of Parental Obesity: Mechanisms of Non-Genetic Transmission and Reversibility

While a dramatic increase in obesity and related comorbidities is being witnessed, the underlying mechanisms of their spread remain unresolved. Epigenetic and other non-genetic mechanisms tend to be prominent candidates involved in the establishment and transmission of obesity and associated metabolic disorders to offspring. Here, we review recent findings addressing those candidates, in the context of maternal and paternal influences, and discuss the effectiveness of preventive measures.

Metabolic Consequences of Glucocorticoid Exposure before Birth

Glucocorticoids have an important role in development of the metabolic phenotype in utero. They act as environmental and maturational signals in adapting feto-placental metabolism to maximize the chances of survival both before and at birth. They influence placental nutrient handling and fetal metabolic processes to support fetal growth, fuel storage and energy production with respect to nutrient availability. More specifically, they regulate the transport, utilization and production of a range of nutrients by the feto-placental tissues that enables greater metabolic flexibility in utero while minimizing any further drain on maternal resources during periods of stress. Near term, the natural rise in fetal glucocorticoid concentrations also stimulates key metabolic adaptations that prepare tissues for the new energy demanding functions after birth. Glucocorticoids, therefore, have a central role in the metabolic communication between the mother, placenta and fetus that optimizes offspring metabolic phenotype for survival to reproductive age. This review discusses the effects of maternal and fetal glucocorticoids on the supply and utilization of nutrients by the feto-placental tissues with particular emphasis on studies using quantitative methods to assess metabolism in rodents and sheep in vivo during late pregnancy. It considers the routes of glucocorticoid overexposure in utero, including experimental administration of synthetic glucocorticoids, and the mechanisms by which these hormones control feto-placental metabolism at the molecular, cellular and systems levels. It also briefly examines the consequences of intrauterine glucocorticoid overexposure for postnatal metabolic health and the generational inheritance of metabolic phenotype.

Prenatal caffeine exposure induced renal developmental toxicity and transgenerational effect in rat offspring

Epidemiological studies revealed that prenatal caffeine exposure (PCE) is associated with adverse gestational outcomes and susceptibility to chronic diseases in offspring, yet the effects of PCE on glomerulosclerosis susceptibility in adult female offspring and its intergenerational transmission remain to be further investigated. Here, we found that PCE caused fetal kidney dysplasia and glomerulosclerosis of the female offspring. Besides, the kidney of F1 offspring in PCE group exhibited the "low expressional programming of AT2R" and "GC-IGF1 programming" alteration. Intergenerational genetic studies revealed that the renal defect and GC-IGF1 programming alteration was inherited to F2 adult female offspring derived from the female germ line, but Low expression of AT2R did not extend to the F2 female offspring. Taken together, PCE caused renal dysplasia and adult glomerulosclerosis in the F1 female offspring, which might be mediated by renal AT2R low expressional programming and GC-IGF1 axis alteration. Furthermore, PCE induced transgenerational toxicity on kidney, and GC-IGF1 programming alteration might be the potential molecular mechanism. This study provided experimental evidence for the mechanism study of the intergenerational inheritance of kidney developmental toxicity caused by PCE.

Maternal low protein diet and fetal programming of lean type 2 diabetes

Maternal nutrition is found to be the key factor that determines fetal health in utero and metabolic health during adulthood. Metabolic diseases have been primarily attributed to impaired maternal nutrition during pregnancy, and impaired nutrition has been an immense issue across the globe. In recent years, type 2 diabetes (T2D) has reached epidemic proportion and is a severe public health problem in many countries. Although plenty of research has already been conducted to tackle T2D which is associated with obesity, little is known regarding the etiology and pathophysiology of lean T2D, a variant of T2D. Recent studies have focused on the effects of epigenetic variation on the contribution of in utero origins of lean T2D, although other mechanisms might also contribute to the pathology. Observational studies in humans and experiments in animals strongly suggest an association between maternal low protein diet and lean T2D phenotype. In addition, clear sex-specific disease prevalence was observed in different studies. Consequently, more research is essential for the understanding of the etiology and pathophysiology of lean T2D, which might help to develop better disease prevention and treatment strategies. This review examines the role of protein insufficiency in the maternal diet as the central driver of the developmental programming of lean T2D.

Epigenetic Mechanisms Responsible for the Transgenerational Inheritance of Intrauterine Growth Restriction Phenotypes

A poorly functioning placenta results in impaired exchanges of oxygen, nutrition, wastes and hormones between the mother and her fetus. This can lead to restriction of fetal growth. These growth restricted babies are at increased risk of developing chronic diseases, such as type-2 diabetes, hypertension, and kidney disease, later in life. Animal studies have shown that growth restricted phenotypes are sex-dependent and can be transmitted to subsequent generations through both the paternal and maternal lineages. Altered epigenetic mechanisms, specifically changes in DNA methylation, histone modifications, and non-coding RNAs that regulate expression of genes that are important for fetal development have been shown to be associated with the transmission pattern of growth restricted phenotypes. This review will discuss the subsequent health outcomes in the offspring after growth restriction and the transmission patterns of these diseases. Evidence of altered epigenetic mechanisms in association with fetal growth restriction will also be reviewed.

Three-Generation Study of Male Rats Gestationally Exposed to High Butterfat and Bisphenol A: Impaired Spermatogenesis, Penetrance with Reduced Severity

Gestational high butterfat (HFB) and/or endocrine disruptor exposure was previously found to disrupt spermatogenesis in adulthood. This study addresses the data gap in our knowledge regarding transgenerational transmission of the disruptive interaction between a high-fat diet and endocrine disruptor bisphenol A (BPA). F0 generation Sprague-Dawley rats were fed diets containing butterfat (10 kcal%) and high in butterfat (39 kcal%, HFB) with or without BPA (25 µg/kg body weight/day) during mating and pregnancy. Gestationally exposed F1-generation offspring from different litters were mated to produce F2 offspring, and similarly, F2-generation animals produced F3-generation offspring. One group of F3 male offspring was administered either testosterone plus estradiol-17β (T + E2) or sham via capsule implants from postnatal days 70 to 210. Another group was naturally aged to 18 months. Combination diets of HFB + BPA in F0 dams, but not single exposure to either, disrupted spermatogenesis in F3-generation adult males in both the T + E2-implanted group and the naturally aged group. CYP19A1 localization to the acrosome and estrogen receptor beta (ERbeta) localization to the nucleus were associated with impaired spermatogenesis. Finally, expression of methyl-CpG-binding domain-3 (MBD3) was consistently decreased in the HFB and HFB + BPA exposed F1 and F3 testes, suggesting an epigenetic component to this inheritance. However, the severe atrophy within testes present in F1 males was absent in F3 males. In conclusion, the HFB + BPA group demonstrated transgenerational inheritance of the impaired spermatogenesis phenotype, but severity was reduced in the F3 generation.

Effects of maternal obesity in an ovine model on metabolic outcomes in F2 adults and F3 neonates

Accumulating evidence suggests that indications of metabolic syndrome can be inherited through the germline as a result of maternal obesity. We hypothesized that diet-induced maternal obesity during gestation would program metabolic consequences for multiple generations of offspring, even when first, second, and third generation offspring (F1, F2, F3, respectively) were fed only to requirements. Control (CON) and obese (OB) ewes (generation 0; F0) were bred to a single ram to produce the first generation of offspring (F1). From 60 d prior to conception through term, CONF0 ate 100% National Research Council recommendations (NRC), while OBF0 ewes ate 150% NRC. All F1, F2, and F3 ate 100% NRC after weaning. All mature F1 ewes were bred to a single ram to generate CONF2 (n = 6) and OBF2 (n = 10). All mature F2 ewes were bred to a single ram to produce CONF3 (n = 6) and OBF3 (n = 10). OBF2 ewes exhibited greater (P < 0.0001) plasma cortisol than CONF2 throughout gestation. A glucose tolerance test at 90% gestation revealed OBF2 ewes had higher (P < 0.05) insulin response with similar glucose, resulting in greater (P < 0.05) insulin resistance. OBF3 neonates had similar weight, lean mass, and body fat mass to CONF3 neonates. These data suggest that multigenerational programming of adverse metabolic phenotypes occur in association with F0 maternal obesity, yet adiposity may return to CON levels in F3 neonates.

Metabolic and Epigenetics Action Mechanisms of Antiobesity Medicinal Plants and Phytochemicals

Ever-growing research efforts are demonstrating the potential of medicinal plants and their phytochemicals to prevent and manage obesity, either individually or synergistically. Multiple combinations of phytochemicals can result in a synergistic activity that increases their beneficial effects at molecular, cellular, metabolic, and temporal levels, offering advantages over chemically synthesized drug-based treatments. Herbs and their derived compounds have the potential for controlling appetite, inhibiting pancreatic lipase activity, stimulating thermogenesis and lipid metabolism, increasing satiety, promoting lipolysis, regulating adipogenesis, and inducing apoptosis in adipocytes. Furthermore, targeting adipocyte life cycle using various dietary bioactives that affect different stages of adipocyte life cycle represents also an important target in the development of new antiobesity drugs. In this regard, different stages of adipocyte development that are targeted by antiobesity drugs can include preadipocytes, maturing preadipocytes, and mature adipocytes. Various herbal-derived active compounds, such as capsaicin, genistein, apigenin, luteolin, kaempferol, myricetin, quercetin, docosahexaenoic acid, quercetin, resveratrol, and ajoene, affect adipocytes during specific stages of development, resulting in either inhibition of adipogenesis or induction of apoptosis. Although numerous molecular targets that can be used for both treatment and prevention of obesity have been identified, targeted single cellular receptor or pathway has resulted in limited success. In this review, we discuss the state-of-the-art knowledge about antiobesity medicinal plants and their active compounds and their effects on several cellular, molecular, and metabolic pathways simultaneously with multiple phytochemicals through synergistic functioning which might be an appropriate approach to better management of obesity. In addition, epigenetic mechanisms (acetylation, methylation, miRNAs, ubiquitylation, phosphorylation, and chromatin packaging) of phytochemicals and their preventive and therapeutic perspective are explored in this review.

Protective role of Allium cepa Linn (onion) juice on maternal dexamethasone induced alterations in reproductive functions of female offspring of Wistar rats

Maternal treatment with dexamethasone induces oxidative stress in the reproductive structures of offspring. Consumption of Allium cepa Linn improves antioxidant status. This study was designed to evaluate the protective role of Allium cepa Linn juice on maternal dexamethasone induced alterations in reproductive functions of the female offspring of Wistar rats. Twenty lactating dams (180-200 ​g) were randomly assigned into four groups (n ​= ​5) on the day of parturition and treated as follows during lactation for 21 days: Control (5 ​ml/kg BW distilled water); Dexamethasone (60 ​μg/kg BW); Allium cepa (5 ​ml/kg BW); Dexamethasone ​+ ​Allium cepa (60 ​μg/kg BW ​+ ​5 ​ml/kg BW). The female offspring were separated at birth. Days of vaginal opening and first oestrus cycle, length and frequency of estrous cycle as well as serum hormonal profiles were assessed as measure of reproductive functions. Ovarian superoxide dismutase (SOD) activity, catalase activity and malondialdehyde (MDA) level were measured as indices of oxidative stress. Oestrous cycle length, frequencies of diestrus as well as the Ovarian MDA were significantly increased (p ​< ​0.05) in dexamethasone (DEX) group relative to control group. Serum 17β-oestradiol and corticosterone level in addition to SOD and catalase activities were significantly reduced (p ​< ​0.05) in DEX group relative to control. Co-administration of Dex with Allium cepa Linn juice reduced the oestrous length, frequency of diestrous as well as ovarian MDA. There was also a significant increase in serum 17β-oestradiol, ovarian SOD and catalase activity. The results suggest that Allium cepa could protect against alterations in reproductive functions of offspring induced by maternal treatment with dexamethasone during lactation in Wistar rats. The flavonoid constituent of onion may also help in reducing oxidative stress in the offspring.

Cardinal role of the environment in stress induced changes across life stages and generations

The stress response in rodents and humans is exquisitely dependent on the environmental context. The interactive element of the environment is typically studied by creating laboratory models of stress-induced plasticity manifested in behavior or the underlying neuroendocrine mediators of the behavior. Here, we discuss three representative sets of studies where the role of the environment in mediating stress sensitivity or stress resilience is considered across varying windows of time. Collectively, these studies testify that environmental variation at an earlier time point modifies the relationship between stressor and stress response at a later stage. The metaplastic effects of the environment on the stress response remain possible across various endpoints, including behavior, neuroendocrine regulation, region-specific neural plasticity, and regulation of receptors. The timescale of such variation spans adulthood, across stages of life history and generational boundaries. Thus, environmental variables are powerful determinants of the observed diversity in stress response. The predominant role of the environment suggests that it is possible to promote stress resilience through purposeful modification of the environment.

Intergenerational health impact of adverse environment in utero under civil conflict: evidence from Cambodia

Purpose

This study aims to empirically examine how the Khmer Rouge regime (1975–1979) in Cambodia continues to affect the health of the second generation.

Design/methodology/approach

The 2000 and 2005 Cambodia Demographic and Health Surveys were used in the analysis. The study sample were women with a child/children in 2000/2005. The sample population was identified according to whether the person was in utero “91 months or earlier before the Khmer Rouge regime,” “46–90 months before the Khmer Rouge regime” and “1–45 months before the Khmer Rouge regime” and during the Khmer Rouge regime. The authors then regressed the size of babies of the targeted population on the timing of the mothers being in utero.

Findings

Mothers who were in utero during the regime had a higher likelihood of giving birth to smaller-than-average babies. Additionally, mothers born in the areas that had a higher probability of death of children aged five or under during the regime were at risk of giving birth to smaller-than-average babies if they were in utero during that time.

Originality/value

This is the first paper to assess the impact of the Khmer Rouge regime on the health of the second generation.

Impact of maternal prenatal stress by glucocorticoids on metabolic and cardiovascular outcomes in their offspring: A systematic scoping review

BACKGROUND

"Stress" is an emerging problem in our society, health care system as well as patient care, worldwide. Especially by focusing on pre-gestational, gestational but also lactation phases "stress" is to be considered as an own trans-generational risk factor which is associated with adverse metabolic as well cardiovascular outcomes in mothers and their children. Hence, the maternal hypothalamic-pituitary-adrenotrophic (HPA) axis may be stimulated by various "stress" mechanisms as well as risk factors leading to an adverse in utero environment, e.g. by excess exposure of glucocorticoids, contributing to cardio-metabolic disorders in mothers and their offspring.

OBJECTIVE

To review the evidence of in utero programming by focusing on the impact of maternal "stress", on adverse cardio-metabolic outcomes on their offspring later in life, by identifying underlying (patho-) physiological mechanisms (1) as well as adverse short and long-term cardio-metabolic outcomes (2).

METHODS

We conducted a systematic scoping review to identify publications systematically including reviews, interventional, observational, experimental studies as well as human and animal model studies. MEDLINE (PubMed) and EMBASE databases and reference lists were searched. Peer-reviewed articles from January 2000 until August 2020 were included.

RESULTS

Overall, n = 2.634 citations were identified, n = 45 eligible studies were included and synthesized according to their key findings. In brief, maternal hypothalamic-pituitary-adrenotrophic (HPA) axis might play a key role modifying in utero milieu leading to cardio-metabolic diseases in the offspring later in life. However, maternal risk factor "stress", is clearly linked to adverse cardio-metabolic offspring outcomes, postnatally, such as obesity, hyperglycemia, insulin resistance, diabetes mellitus (DM), Metabolic Syndrome (MetS), cardiovascular disease (CD), hypertension, restricted fetal growth as well as reduced birth, adrenal, and pancreas weights.

CONCLUSIONS

Women who experienced "stress" as risk factor, as well as their offspring, clearly have a higher risk of adverse short- as well as long-term cardio-metabolic outcomes. Future research work is needed to understand complex transgenerational mechanisms.

Molecular mechanisms governing offspring metabolic programming in rodent models of in utero stress

The results of different human epidemiological datasets provided the impetus to introduce the now commonly accepted theory coined as 'developmental programming', whereby the presence of a stressor during gestation predisposes the growing fetus to develop diseases, such as metabolic dysfunction in later postnatal life. However, in a clinical setting, human lifespan and inaccessibility to tissue for analysis are major limitations to study the molecular mechanisms governing developmental programming. Subsequently, studies using animal models have proved indispensable to the identification of key molecular pathways and epigenetic mechanisms that are dysregulated in metabolic organs of the fetus and adult programmed due to an adverse gestational environment. Rodents such as mice and rats are the most used experimental animals in the study of developmental programming. This review summarises the molecular pathways and epigenetic mechanisms influencing alterations in metabolic tissues of rodent offspring exposed to in utero stress and subsequently programmed for metabolic dysfunction. By comparing molecular mechanisms in a variety of rodent models of in utero stress, we hope to summarise common themes and pathways governing later metabolic dysfunction in the offspring whilst identifying reasons for incongruencies between models so to inform future work. With the continued use and refinement of such models of developmental programming, the scientific community may gain the knowledge required for the targeted treatment of metabolic diseases that have intrauterine origins.

Developmental programming of insulin resistance: are androgens the culprits?

Insulin resistance is a common feature of many metabolic disorders. The dramatic rise in the incidence of insulin resistance over the past decade has enhanced focus on its developmental origins. Since various developmental insults ranging from maternal disease, stress, over/undernutrition, and exposure to environmental chemicals can all program the development of insulin resistance, common mechanisms may be involved. This review discusses the possibility that increases in maternal androgens associated with these various insults are key mediators in programming insulin resistance. Additionally, the intermediaries through which androgens misprogram tissue insulin sensitivity, such as changes in inflammatory, oxidative, and lipotoxic states, epigenetic, gut microbiome and insulin, as well as data gaps to be filled are also discussed.

Allium cepa Linn juice protect against alterations in reproductive functions induced by maternal dexamethsone treatment during lactation in male offspring of Wistar rats

Treatment with dams with dexamethasone during lactation has been reported to induce oxidative stress in the testis of the offspring. Allium cepa L (Red Onion) is known to be a potent free radical scavenger. The protective role of Allium cepa against oxidative stress induced in testis following treatment with dexamehasone during lactation in Wistar rats was assessed. Twenty female rats were assigned into four groups (n = 5) during lactation and they were treated as follows: Group 1 serve as Control (distilled water), Group 2, 3, and four were admistered dexamethasone (60 μg/kg), Allium cepa (5 ml/kg) and dexamethasone + Allium cepa respectively. Testicular descent, pubertal age, sperm quality indices, and serum hormonal profile were assessed as indices of reproductive function. Testicular malondialdehyde (MDA) reduced glutathione (GSH) as well as superoxide dismutase (SOD) and catalase activities were assessed as measures of oxidative stress. Results obtained showed that dexamethasone caused significant (P < 0.05) reduction in testes weights, indices of sperm quality, serum testosterone, FSH, LH levels and testicular antioxidant enzyme activities. There was significant delay (P < 0.05) in days of testes descent, preputial separation and increase in testicular MDA. However, maternal treatment with Allium cepa Linn juice significantly (P < 0.05) improved both indices of reproductive function and testicular antioxidant enzymes. These findings suggest that Allium cepa Linn has a protective effect against testicular oxidative stress and reproductive dysfunction following treatment of dams with dexamethasone during lactation.

Glucocorticoids as Mediators of Adverse Outcomes of Prenatal Stress

A number of prenatal experiences are associated with adverse outcomes after birth, ranging from cardiovascular problems to psychiatric disease. Prenatal stress is associated with neurodevelopmental alterations that persist after birth and manifest at the behavioral level, for example, increased fearfulness, and at the physiological one, that is, brain structural and functional changes. Understanding the mechanisms that drive these lasting effects may help in preventing long-term negative outcomes of prenatal stress. Elevated glucocorticoid signaling in utero may be one of the key mediators of prenatal stress effects on the offspring. In this review, we summarize how prenatal glucocorticoids may impact the activity of the fetal hypothalamic-pituitary-adrenal (HPA) axis, disrupt neurodevelopmental processes and alter the epigenetic landscape of the fetus. We also discuss the need to take into consideration the interaction of these processes with the offspring's genetic landscape.

Non-genetic inheritance via the male germline in mammals

Numerous studies in humans and in animal models have demonstrated that exposure to adverse environmental conditions in early life results in long-term structural and functional changes in an organism, increasing the risk of cardiometabolic, neurobehavioural and reproductive disorders in later life. Such effects are not limited to the first generation offspring but may be transmitted to a second or a number of subsequent generations, through non-genomic mechanisms. While the transmission of ‘programmed’ effects through the maternal line could occur as a consequence of multiple influences, for example, altered maternal physiology, the inheritance of effects through the male line is more difficult to explain and there is much interest in a potential role for transgenerational epigenetic inheritance. In this review, we will discuss the mechanisms by which induced effects may be transmitted through the paternal lineage, with a particular focus on the role of epigenetic inheritance.

This article is part of the theme issue ‘Developing differences: early-life effects and evolutionary medicine’.

Early-life programming of adipose tissue

Worldwide obesity is increasing at an alarming rate in children and adolescents, with the consequent emergence of co-morbidities. Moreover, the maternal environment during pregnancy plays an important role in obesity, contributing to transgenerational transmission of the same and metabolic dysfunction. White adipose tissue represents a prime target of metabolic programming induced by maternal milieu. In this article, we review adipose tissue physiology and development, as well as maternal influences during the perinatal period that may lead to obesity in early postnatal life and adulthood. First, we describe the adipose tissue cell composition, distribution and hormonal action, together with the evidence of hormonal factors participating in fetal/postnatal programming. Subsequently, we describe the critical periods of adipose tissue development and the relationship of gestational and early postnatal life with healthy fetal adipose tissue expansion. Furthermore, we discuss the evidence showing that adipose tissue is an important target for nutritional, hormonal and epigenetic signals to modulate fetal growth. Finally, we describe nutritional, hormonal, epigenetic and microbiome changes observed in maternal obesity, and whether their disruption alters fetal growth and adiposity. The presented evidence supports the developmental origins of health and disease concept, which proposes that the homeostatic system is affected during gestational and postnatal development, impeding the ability to regulate body weight after birth, thereby resulting in adult obesity. Consequently, we anticipate that promoting a healthy early-life programming of adipose tissue and increasing the knowledge of the mechanisms by which maternal factors affect the health of future generations may offer novel strategies for explaining and addressing worldwide health problems such as obesity.

The 3G Multigenerational Cohort of Nova Scotian women and their mothers and offspring

BACKGROUND

The negative impact of exposures such as maternal obesity, excessive gestational weight gain, and hypertension in pregnancy on the health of the next generation has been well studied. Evidence from animal studies suggests that the effects of in utero exposures may persist into the second generation, but the epidemiological literature on the influence of pregnancy-related exposures across three generations in humans is sparse.

OBJECTIVES

This cohort was established to investigate associations between antenatal and perinatal exposures and health outcomes in women and their offspring.

POPULATION

The cohort includes women who were born and subsequently had their own pregnancies in the Canadian province of Nova Scotia from 1980 onward.

DESIGN

Intergenerational linkage of data in the Nova Scotia Atlee Perinatal Database was used to establish a population-based dynamic retrospective cohort.

METHODS

The cohort has prospectively collected information on sociodemographics, maternal health and health behaviours, pregnancy health and complications, and obstetrical and neonatal outcomes for two generations of women and their offspring.

PRELIMINARY RESULTS

As of October 2018, the 3G cohort included 14 978 grandmothers (born 1939-1986), 16 766 mothers or cohort women (born 1981-2003), and 28 638 children (born 1996-2018). The cohort women were generally younger than Nova Scotian women born after 1980, and as a result, characteristics associated with pregnancy at a younger age were more frequently seen in the cohort women; sampling weights will be created to account for this design effect. The cohort will be updated annually to capture future deliveries to women who are already in the cohort and women who become eligible for inclusion when they deliver their first child.

CONCLUSIONS

The 3G Multigenerational Cohort is a population-based cohort of women and their mothers and offspring, spanning a time period of 38 years, and provides the opportunity to study inter- and transgenerational associations across the maternal line.

Antenatal Corticosteroids for Fetal Lung Maturity - Too Much of a Good Thing?

BACKGROUND

Between 5-15% of babies are born prematurely worldwide, with preterm birth defined as delivery before 37 completed weeks of pregnancy (term is at 40 weeks of gestation). Women at risk of preterm birth receive antenatal corticosteroids as part of standard care to accelerate fetal lung maturation and thus improve neonatal outcomes in the event of delivery. As a consequence of this treatment, the entire fetal organ system is exposed to the administered corticosteroids. The implications of this exposure, particularly the long-term impacts on offspring health, are poorly understood.

AIMS

This review will consider the origins of antenatal corticosteroid treatment and variations in current clinical practices surrounding the treatment. The limitations in the evidence base supporting the use of antenatal corticosteroids and the evidence of potential harm to offspring are also summarised.

RESULTS

Little has been done to optimise the dose and formulation of antenatal corticosteroid treatment since the first clinical trial in 1972. International guidelines for the use of the treatment lack clarity regarding the recommended type of corticosteroid and the gestational window of treatment administration. Furthermore, clinical trials cited in the most recent Cochrane Review have limitations which should be taken into account when considering the use of antenatal corticosteroids in clinical practice. Lastly, there is limited evidence regarding the long-term effects on the different fetal organ systems exposed in utero, particularly when the timing of corticosteroid administration is sub-optimal.

CONCLUSION

Further investigations are urgently needed to determine the most safe and effective treatment regimen for antenatal corticosteroids, particularly regarding the type of corticosteroid and optimal gestational window of administration. A clear consensus on the use of this common treatment could maximise the benefits and minimise potential harms to offspring.

Intergenerational Influence of Antenatal Betamethasone on Growth, Growth Factors, and Neurological Outcomes in Rats

Antenatal steroids suppress growth in the fetus and newborn. Although weight deficits are regained by weaning, studies show that intrauterine growth restriction with postnatal "catch-up" growth is a risk factor for hypertension, insulin resistance, and ischemic heart disease in adult life, with multigenerational consequences. We tested the hypothesis that fetal exposure to betamethasone suppresses fetal growth in the F1 pups and their untreated F2 offspring. Timed pregnant rats received a single two-dose course of intramuscular betamethasone (0.25 mg/kg/day) on days 17 and 18 of gestation. Matched controls received equivalent volumes sterile normal saline. The first-generation (F1) offspring were studied at term, P21, and P70, or mated at P60 to produce the following subgroups: (1) saline male/saline female (SM/SF), (2) betamethasone (B) male/BFemale (BM/BF), (3) BM/SF, and (4) SM/BF. The unexposed second-generation (F2) offspring were examined at birth and P70. Growth, neurological outcomes, and growth factors were determined. At birth, the F1 pups exposed to B were significantly growth suppressed compared with the controls, with correspondingly lower blood glucose, insulin, IGF-I, corticosterone, and leptin levels and delayed neurological outcomes. Catchup growth occurred at P21, surpassing that of the control group. By P70, growth was comparable, but glucose was higher, insulin was lower, and memory was retarded in the B group, and transmitted to the unexposed F2 offspring of B-exposed rats. Antenatal betamethasone has sustained metabolic and neurological effects that may impact the unexposed offspring. Whether these intergenerational effects reverse in future generations remain to be determined.

Transgenerational inheritance: how impacts to the epigenetic and genetic information of parents affect offspring health

BACKGROUND

A defining feature of sexual reproduction is the transmission of genomic information from both parents to the offspring. There is now compelling evidence that the inheritance of such genetic information is accompanied by additional epigenetic marks, or stable heritable information that is not accounted for by variations in DNA sequence. The reversible nature of epigenetic marks coupled with multiple rounds of epigenetic reprogramming that erase the majority of existing patterns have made the investigation of this phenomenon challenging. However, continual advances in molecular methods are allowing closer examination of the dynamic alterations to histone composition and DNA methylation patterns that accompany development and, in particular, how these modifications can occur in an individual’s germline and be transmitted to the following generation. While the underlying mechanisms that permit this form of transgenerational inheritance remain unclear, it is increasingly apparent that a combination of genetic and epigenetic modifications plays major roles in determining the phenotypes of individuals and their offspring.

OBJECTIVE AND RATIONALE

Information pertaining to transgenerational inheritance was systematically reviewed focusing primarily on mammalian cells to the exclusion of inheritance in plants, due to inherent differences in the means by which information is transmitted between generations. The effects of environmental factors and biological processes on both epigenetic and genetic information were reviewed to determine their contribution to modulating inheritable phenotypes.

SEARCH METHODS

Articles indexed in PubMed were searched using keywords related to transgenerational inheritance, epigenetic modifications, paternal and maternal inheritable traits and environmental and biological factors influencing transgenerational modifications. We sought to clarify the role of epigenetic reprogramming events during the life cycle of mammals and provide a comprehensive review of how the genomic and epigenomic make-up of progenitors may determine the phenotype of its descendants.

OUTCOMES

We found strong evidence supporting the role of DNA methylation patterns, histone modifications and even non-protein-coding RNA in altering the epigenetic composition of individuals and producing stable epigenetic effects that were transmitted from parents to offspring, in both humans and rodent species. Multiple genomic domains and several histone modification sites were found to resist demethylation and endure genome-wide reprogramming events. Epigenetic modifications integrated into the genome of individuals were shown to modulate gene expression and activity at enhancer and promoter domains, while genetic mutations were shown to alter sequence availability for methylation and histone binding. Fundamentally, alterations to the nuclear composition of the germline in response to environmental factors, ageing, diet and toxicant exposure have the potential to become hereditably transmitted.

WIDER IMPLICATIONS

The environment influences the health and well-being of progeny by working through the germline to introduce spontaneous genetic mutations as well as a variety of epigenetic changes, including alterations in DNA methylation status and the post-translational modification of histones. In evolutionary terms, these changes create the phenotypic diversity that fuels the fires of natural selection. However, rather than being adaptive, such variation may also generate a plethora of pathological disease states ranging from dominant genetic disorders to neurological conditions, including spontaneous schizophrenia and autism.

Pregnancy drugs, fetal germline epigenome, and risks for next-generation pathology: A call to action

Drugs taken during pregnancy can affect three generations at once: the gestating woman (F0), her exposed fetus (F1), and the fetal germ cells that confer heritable information for the grandchildren (F2). Unfortunately, despite growing evidence for connections between F0 drug exposures and F2 pathology, current approaches to risk assessment overlook this important dimension of risk. In this commentary, we argue that the unique molecular vulnerabilities of the fetal germline, particularly with regard to global epigenomic reprogramming, combined with empirical evidence for F2 effects of F1 in utero drug and other exposures, should change the way we consider potential long-term consequences of pregnancy drugs and alter toxicology's standard somatic paradigm. Specifically, we (1) suggest that pregnancy drugs common in the postwar decades should be investigated as potential contributors to the "missing heritability" of many pathologies now surging in prevalence; (2) call for inclusion of fetal germline risks in pregnancy drug safety assessment; and (3) highlight the need for intensified research to ascertain generational impacts of diethylstilbestrol, a vanguard question of human germline toxicity. Only by fully addressing this important dimension of transplacental exposure can we responsibly evaluate safety of drug exposures during pregnancy and convey the full scope of risks, while also retrospectively comprehending the generational legacy of recent history's unprecedented glut of evolutionarily novel intrauterine exposures. Environ. Mol. Mutagen. 60:445-454, 2019. © 2019 Wiley Periodicals, Inc.

Maternal effects obscure condition-dependent sex allocation in changing environments

Climate change increases environmental fluctuations which thereby impact population demography. Species with temperature-dependent sex determination may experience more extreme sex ratio skews, but this has not been considered in species with chromosomally determined sex. However, anticipatory maternal effects cause lifelong physiological changes impacting sex ratios. Here we show, in mice, that more sons were born to mothers in good condition when their breeding environment matched their gestational environment, consistent with theoretical predictions, but mothers in mismatched environments have no condition-sex ratio relationship. Thus, the predicted effect of condition on sex ratio was obscured by maternal effects when the environment changed. This may explain extreme sex ratio skews in reintroduced or translocated populations, and sex ratio skews may become more common and less predictable with accelerating environmental change.

Treadmill Exercise Ameliorates Depression-Like Behavior in the Rats With Prenatal Dexamethasone Exposure: The Role of Hippocampal Mitochondria

Prenatal exposure to synthetic glucocorticoids (sGCs) can increase the risk of affective disorders, such as depression, in adulthood. Given that exercise training can ameliorate depression and improve mitochondrial function, we sought to investigate whether exercise can ameliorate depression-like behavior induced by prenatal sGC exposure and mitochondria function contributes to that behavior. At first, we confirmed that prenatal dexamethasone (Dex) administration in late pregnancy resulted in depression-like behavior and elevated level of circulatory corticosterone in adult offspring. We then found that mRNA and protein expression of a number of mitochondrial genes was changed in the hippocampus of Dex offspring. Mitochondria in the hippocampus showed abnormal morphology, oxidative stress and dysfunction in Dex offspring. Intracerebroventricular (ICV) injection of the mitochondrial superoxide scavenger mitoTEMPO significantly alleviated depression-like behavior but did not significantly affect circulatory corticosterone level in Dex offspring. The adult Dex offspring treated with treadmill exercise starting at four-weeks of age showed ameliorated depressive-like behavior, improved mitochondrial morphology and function and reduced circulatory corticosterone level. Our data suggest mitochondria dysfunction contributes to depression-like behavior caused by prenatal sGC exposure. Intervention with exercise training in early life can reverse depression caused by prenatal Dex exposure, which is associated with improvement of mitochondrial function in the hippocampus.

The epigenetics of the hypothalamic-pituitary-adrenal axis in fetal development

The hypothalamic-pituitary-adrenal (HPA) axis is an important hormonal mechanism of the human body and is extremely programmable during embryonic and fetal development. Analyzing its development in this period is the key to understanding in fact how vulnerabilities of congenital diseases occur and any other changes in the phenotypic and histophysiological aspects of the fetus. The environment in which the mother is exposed during the gestational period can influence this axis. Knowing this, our objective was to analyze in recent research the possible impact of epigenetic programming on the HPA axis and its consequences for fetal development. This review brought together articles from two databases: ScienceDirect and PUBMED researched based on key words such as "epigenetics, HPA axis, cardiovascular disease, and circulatory problems" where it demonstrated full relevance in experimental and scientific settings. A total of 101 articles were selected following the criteria established by the researchers. Thus, it was possible to verify that the development of the HPA axis is directly related to changes that occur in the cardiovascular system, to the cerebral growth and other systems depending on the influence that it receives in the period of fetal formation.

Prenatal exposure to bisphenol-A altered miRNA-224 and protein expression of aromatase in ovarian granulosa cells concomitant with elevated serum estradiol levels in F1 adult offspring

This study was aimed to predict bisphenol-A (BPA)-responsive miRNA's using an in silico approach and to study their expression in granulosa cells of animals exposed prenatally to BPA. Pregnant Wistar rats were exposed to BPA through water (25 μg/L, 250 μg/L, and 2.5 mg/L) during gestation. The expression of miRNA-133b, miRNA-378 and miRNA-224 were analyzed in ovarian granulosa cells. BPA affected the postnatal developmental landmarks such as weight of the pups at birth and reduced anogenital distance. BPA exposed animals showed elevated serum estradiol (E2) levels, while follicle-stimulating hormone levels were reduced. The expression of miRNA-224 and aromatase protein levels were found to be increased. This preliminary finding reveals the impact of early life exposure to BPA on the long-term ovarian functions that may be mediated through miRNA-based granulosa cell response. Besides, it is also a compelling indicator for the subclinical response that could have important consequences on female fertility.

Genome-wide epigenetic signatures of childhood adversity in early life: Opportunities and challenges

Maternal adversity and fetal glucocorticoid exposure has long-term effects on cardiovascular, metabolic and behavioral systems in offspring that can persist throughout the lifespan. These data, along with other environmental exposure data, implicate epigenetic modifications as potential mechanisms for long-term effects of maternal exposures on adverse health outcomes in offspring. Advances in microarray, sequencing and bioinformatic approaches have enabled recent studies to examine the genome-wide epigenetic response to maternal adversity. Studies of maternal exposures to xenobiotics such as arsenic and smoking have been performed at birth to examine fetal epigenomic signatures in cord blood relating to adult health outcomes. However, there have been no epigenomic studies examining these effects in animal models. On the other hand, to date, only a few studies of the effects of maternal psychosocial stress have been performed in human infants, and the majority of animal studies have examined epigenomic outcomes in adulthood. In terms of maternal exposure to excess glucocorticoids by synthetic glucocorticoid treatment, there has been no epigenetic study performed in humans and only a few studies undertaken in animal models. This review emphasizes the importance of examining biomarkers of exposure to adversity throughout development to identify individuals at risk and to target interventions. Thus, research performed at birth will be reviewed. In addition, potential subject characteristics associated with epigenetic modifications, technical considerations, the selection of target tissues and combining human studies with animal models will be discussed in relation to the design of experiments in this field of study.

Exploring the effect of antenatal depression treatment on children's epigenetic profiles: findings from a pilot randomized controlled trial

Background

Children prenatally exposed to maternal depression more often show behavioral and emotional problems compared to unexposed children, possibly through epigenetic alterations. Current evidence is largely based on animal and observational human studies. Therefore, evidence from experimental human studies is needed. In this follow-up of a small randomized controlled trial (RCT), DNA-methylation was compared between children of women who had received cognitive behavioral therapy (CBT) for antenatal depression and children of women who had received treatment as usual (TAU). Originally, 54 women were allocated to CBT or TAU. A beneficial treatment effect was found on women’s mood symptoms.

Findings

We describe DNA methylation findings in buccal swab DNA of the 3–7-year-old children (CBT(N) = 12, TAU(N) = 11), at a genome-wide level at 770,668 CpG sites and at 729 CpG sites spanning 16 a priori selected candidate genes, including the glucocorticoid receptor (NR3C1). We additionally explored associations with women’s baseline depression and anxiety symptoms and offspring DNA methylation, regardless of treatment. Children from the CBT group had overall lower DNA methylation compared to children from the TAU group (mean ∆β = − 0.028, 95% CI − 0.035 to − 0.022). Although 68% of the promoter-associated NR3C1 probes were less methylated in the CBT group, with cg26464411 as top most differentially methylated CpG site (p = 0.038), mean DNA methylation of all NR3C1 promoter-associated probes did not differ significantly between the CBT and TAU groups (mean ∆β = 0.002, 95%CI − 0.010 to 0.011). None of the effects survived correction for multiple testing. There were no differences in mean DNA methylation between the children born to women with more severe depression or anxiety compared to children born to women with mild symptoms of depression or anxiety at baseline (mean ∆β (depression) = 0.0008, 95% CI − 0.007 to 0.008; mean ∆β (anxiety) = 0.0002, 95% CI − 0.004 to 0.005).

Conclusion

We found preliminary evidence of a possible effect of CBT during pregnancy on widespread methylation in children’s genomes and a trend toward lower methylation of a CpG site previously shown by others to be linked to depression and child maltreatment. However, none of the effects survived correction for multiple testing and larger studies are warranted.

Trial registration

Trial registration of the original RCT: ACTRN12607000397415. Registered on 2 August 2007.

Mother or Father: Who Is in the Front Line? Mechanisms Underlying the Non-Genomic Transmission of Obesity/Diabetes via the Maternal or the Paternal Line

Extensive epidemiological and experimental evidence have shown that exposure to an adverse intrauterine environment as observed in offspring of pregnancies complicated by obesity or diabetes, can program susceptibility to metabolic, endocrine and cardiovascular disorders later in life. Although most studies have concentrated on the maternal environment, it is also becoming evident that paternal exposure to obesity or diabetes can result in the later development of metabolic disorders in the offspring. Such programmed effects might not be limited to the first directly exposed generation, but could be transmitted to subsequent generations. This suggests the existence of mechanisms by which metabolic changes in parental phenotype are transmissible to offspring. The mechanisms which underpin the transmission of the programmed effects across generations are still unclear. However, epigenetic regulation of transcription has emerged as a strong candidate for mediating the heritability of metabolic diseases. Here, we review the most relevant evidence from human and animal studies showing transmission of programming effects of obesity or diabetes across generations, and the current mechanisms underlying either maternal or paternal influences on the metabolic status of offspring.

Grandmaternal high-fat diet primed anxiety-like behaviour in the second-generation female offspring

The health consequences of maternal obesity during pregnancy are disturbing as they may contribute to mental disorders in subsequent generations. We examine the influence of suboptimal grandmaternal diet on potential metabolic and mental health outcome of grand-progenies with a high-fat diet (HFD) manipulation in adulthood in a rat HFD model. Grandmaternal exposure to HFD exacerbated granddaughter's anxiety-like phenotype. Grandmaternal exposure to HFD led to upregulated corticotropin-releasing hormone receptor 2 mRNA expression involved in the stress axis in the male F₂ offspring. Thus, we demonstrate that suboptimal grandmaternal diet prior to and during pregnancy and lactation may persist across subsequent generations. These findings have important implications for understanding both individual rates of metabolic and mental health problems and the clinical impact of current global trends towards comorbidity of obesity and depression and anxiety. In conclusion, the effect of grandmaternal HFD consumption during pregnancy on stress axis function and mental disorders may be transmitted to future generations.

Epigenetic changes of hepatic glucocorticoid receptor in sheep male offspring undernourished in utero

The aim of this study was to characterise the effects of maternal undernutrition during gestation on hepatic gluconeogenic enzyme gene expression and to determine whether such effects are mediated through epigenetic changes in the glucocorticoid receptor (GR). Pregnant ewes were fed a 50% nutrient-restricted diet from Day 0 to 30 (R1) or from Day 31 to 100 of gestation (R2) or a 100% diet throughout gestation (Control). After parturition lambs were fed to appetite. At 10 months of age offspring were euthanised and livers were removed. Maternal undernutrition did not affect offspring bodyweight at birth or at 10 months of age. However, liver weight of males of the R2 group was lower (P<0.05) in relation to other groups. A significant (P<0.05) hypomethylation of the hepatic GR promoter was revealed in males of the R2 group and a tendency towards the same in the R1 group, along with increased (P<0.001) GR gene expression in both restricted groups. A significant increase (P<0.05) in hepatic phosphoenolpyruvate carboxykinase (PEPCK) gene expression was found in male lambs of both undernourished groups, accompanied by increased (P<0.01) protein levels, while no differences were detected for glucose-6-phosphatase (G6Pase) mRNA abundance and protein levels. In female lambs, no differences between groups were observed for any parameter studied. These data represent potential mechanisms by which insults in early life may lead to persistent physiological changes in the offspring.

Human and animal evidence of potential transgenerational inheritance of health effects: An evidence map and state-of-the-science evaluation

BACKGROUND

An increasing number of reports suggest early life exposures result in adverse effects in offspring who were never directly exposed; this phenomenon is termed "transgenerational inheritance." Given concern for public health implications for potential effects of exposures transmitted to subsequent generations, it is critical to determine how widespread and robust this phenomenon is and to identify the range of exposures and possible outcomes.

OBJECTIVES

This scoping report examines the evidence for transgenerational inheritance associated with exposure to a wide range of stressors in humans and animals to identify areas of consistency, uncertainty, data gaps, and to evaluate general risk of bias issues for the transgenerational study design.

METHODS

A protocol was developed to collect and categorize the literature into a systematic evidence map for transgenerational inheritance by health effects, exposures, and evidence streams following the Office of Health Assessment and Translation (OHAT) approach for conducting literature-based health assessments.

RESULTS

A PubMed search yielded 63,758 unique records from which 257 relevant studies were identified and categorized into a systematic evidence map by evidence streams (46 human and 211 animal), broad health effect categories, and exposures. Data extracted from the individual studies are available in the Health Assessment Workspace Collaborative (HAWC) program. There are relatively few bodies of evidence where multiple studies evaluated the same exposure and the same or similar outcomes. Studies evaluated for risk of bias generally had multiple issues in design or conduct.

CONCLUSIONS

The evidence mapping illustrated that risk of bias, few studies, and heterogeneity in exposures and endpoints examined present serious limitations to available bodies of evidence for assessing transgenerational effects. Targeted research is suggested to addressed inconsistencies and risk of bias issues identified, and thereby establish more robust bodies of evidence to critically assess transgenerational effects - particularly by adding data on exposure-outcome pairs where there is some evidence (i.e., reproductive, metabolic, and neurological effects).

Increased H3K27ac level of ACE mediates the intergenerational effect of low peak bone mass induced by prenatal dexamethasone exposure in male offspring rats

Prenatal dexamethasone exposure (PDE) induces developmental toxicities of multiple organs in offspring. Here, we verified the intergenerational effect of low peak bone mass induced by PDE and investigated its intrauterine programming mechanism. Pregnant rats were injected subcutaneously with 0.2 mg/kg/d dexamethasone from gestation day (GD) 9 to 20. Some pregnant rats were killed for the fetuses on GD20, and the rest went on to spontaneous labor to produce the first-generation (F1) offspring. The adult F1 male offspring were mated with normal females to produce the F2 offspring. In vivo, PDE leads to low peak bone mass in F1 male offspring rats at postnatal week (PW) 28. Furthermore, PDE reduced the bone mass in F1 male offspring from GD20 to PW12. Meanwhile, the osteogenic differentiation was suppressed and the local renin–angiotensin system (RAS) was activated continuously by PDE. Moreover, the histone 3 lysine 27 acetylation (H3K27ac) level in angiotensin-converting enzyme (ACE) promoter region was increased by PDE from GD20 to PW12. Likewise, PDE induced the low peak bone mass and the activated local RAS in F2 male offspring. Meaningfully, the H3K27ac level of ACE was increased by PDE in the F2 offspring. In vitro, dexamethasone inhibited bone marrow mesenchymal stem cells (BMSCs) osteogenic differentiation and promoted RAS activation. Furthermore, dexamethasone recruited CCAAT/enhancer-binding protein α and p300 into the BMSCs nucleus by activating glucocorticoid receptor, which cooperatively increased the H3K27ac level in the ACE promoter region. In conclusion, PDE induced the low peak bone mass and its intergenerational effect, which was mediated by sustained activation of RAS via increasing H3K27ac level of ACE.

Investigation into the role of the germline epigenome in the transmission of glucocorticoid-programmed effects across generations

Background

Early life exposure to adverse environments affects cardiovascular and metabolic systems in the offspring. These programmed effects are transmissible to a second generation through both male and female lines, suggesting germline transmission. We have previously shown that prenatal overexposure to the synthetic glucocorticoid dexamethasone (Dex) in rats reduces birth weight in the first generation (F1), a phenotype which is transmitted to a second generation (F2), particularly through the male line. We hypothesize that Dex exposure affects developing germ cells, resulting in transmissible alterations in DNA methylation, histone marks and/or small RNA in the male germline.

Results

We profile epigenetic marks in sperm from F1 Sprague Dawley rats expressing a germ cell-specific GFP transgene following Dex or vehicle treatment of the mothers, using methylated DNA immunoprecipitation sequencing, small RNA sequencing and chromatin immunoprecipitation sequencing for H3K4me3, H3K4me1, H3K27me3 and H3K9me3. Although effects on birth weight are transmitted to the F2 generation through the male line, no differences in DNA methylation, histone modifications or small RNA were detected between germ cells and sperm from Dex-exposed animals and controls.

Conclusions

Although the phenotype is transmitted to a second generation, we are unable to detect specific changes in DNA methylation, common histone modifications or small RNA profiles in sperm. Dex exposure is associated with more variable 5mC levels, particularly at non-promoter loci. Although this could be one mechanism contributing to the observed phenotype, other germline epigenetic modifications or non-epigenetic mechanisms may be responsible for the transmission of programmed effects across generations in this model.

Electronic supplementary material

The online version of this article (10.1186/s13059-018-1422-4) contains supplementary material, which is available to authorized users.

CRH/CRHR1 mediates prenatal synthetic glucocorticoid programming of depression-like behavior across 2 generations

Pregnant women at risk of preterm labor usually receive synthetic glucocorticoids (sGCs) to promote fetal lung development. Emerging evidence indicates that antenatal sGC increases the risk of affective disorders in offspring. Data from animal studies show that such disorders can be transmitted to the second generation. However, the molecular mechanisms underlying the intergenerational effects of prenatal sGC remain largely unknown. Here we show that prenatal dexamethasone (Dex) administration in late pregnancy induced depression-like behavior in first-generation (F1) offspring, which could be transmitted to second-generation (F2) offspring with maternal dependence. Moreover, corticotropin-releasing hormone (CRH) and CRH receptor type 1 (CRHR1) expression in the hippocampus was increased in F1 Dex offspring and F2 offspring from F1 Dex female rats. Administration of a CRHR1 antagonist to newborn F1 Dex offspring alleviated depression-like behavior in these rats at adult. Furthermore, we demonstrated that increased CRHR1 expression in F1 and F2 offspring was associated with hypomethylation of CpG islands in Crhr1 promoter. Our results revealed that prenatal sGC exposure could program Crh and Crhr1 gene expression in hippocampus across 2 generations, thereby leading to depression-like behavior. Our study indicates that prenatal sGC can cause epigenetic instability, which increases the risk of disease development in the offspring's later life.-Xu, Y.-J., Sheng, H., Wu, T.-W., Bao, Q.-Y., Zheng, Y., Zhang, Y.-M., Gong, Y.-X., Lu, J.-Q., You, Z.-D., Xia, Y., Ni, X. CRH/CRHR1 mediates prenatal synthetic glucocorticoid programming of depression-like behavior across 2 generations.

Prenatal Glucocorticoid Exposure Modifies Endocrine Function and Behaviour for 3 Generations Following Maternal and Paternal Transmission

Fetal exposure to high levels of glucocorticoids programs long-term changes in the physiologic stress response and behaviours. However, it is not known whether effects manifest in subsequent generations of offspring following maternal (MT) or paternal (PT) transmission. We treated pregnant guinea pigs with three courses of saline or synthetic glucocorticoid (sGC) at a clinically relevant dose. Altered cortisol response to stress and behaviours transmitted to juvenile female and male F2 and F3 offspring from both parental lines. Behavioural effects of sGC in F1-F3 PT females associated with altered expression of genes in the prefrontal cortex and hypothalamic paraventricular nucleus (PVN). Exposure to sGC programmed large transgenerational changes in PVN gene expression, including type II diabetes, thermoregulation, and collagen formation gene networks. We demonstrate transgenerational programming to F3 following antenatal sGC. Transmission is sex- and generation-dependent, occurring through both parental lines. Paternal transmission to F3 females strongly implicates epigenetic mechanisms of transmission.

The placenta and neurodevelopment: sex differences in prenatal vulnerability

Prenatal insults, such as maternal stress, are associated with an increased neurodevelopmental disease risk and impact males significantly more than females, including increased rates of autism, mental retardation, stuttering, dyslexia, and attention deficit/hyperactivity disorder (ADHD). Sex differences in the placenta, which begin with sex chromosomes, are likely to produce sex-specific transplacental signals to the developing brain. Our studies and others have identified X-linked genes that are expressed at higher levels in the female placenta. Through a genome-wide screen after maternal stress in mice, we identified the X-linked gene O-linked N-acetylglucosamine transferase (OGT) and demonstrated its causality in neurodevelopmental programming producing a male-specific stress phenotype. Elucidating the sex-specific molecular mechanisms involved in transplacental signals that impact brain development is key to understanding the sex bias in neurodevelopmental disorders and is expected to yield novel insight into disease risk and resilience.

Grandmaternal stress during pregnancy and DNA methylation of the third generation: an epigenome-wide association study

Stress during pregnancy may impact subsequent generations, which is demonstrated by an increased susceptibility to childhood and adulthood health problems in the children and grandchildren. Although the importance of the prenatal environment is well reported with regards to future physical and emotional outcomes, little is known about the molecular mechanisms that mediate the long-term consequences of early stress across generations. Recent studies have identified DNA methylation as a possible mediator of the impact of prenatal stress in the offspring. Whether psychosocial stress during pregnancy also affects DNA methylation of the grandchildren is still not known. In the present study we examined the multigenerational hypothesis, that is, grandmaternal exposure to psychosocial stress during pregnancy affecting DNA methylation of the grandchildren. We determined the genome-wide DNA methylation profile in 121 children (65 females and 56 males) and tested for associations with exposure to grandmaternal interpersonal violence during pregnancy. We observed methylation variations of five CpG sites significantly (FDR<0.05) associated with the grandmother's report of exposure to violence while pregnant with the mothers of the children. The results revealed differential methylation of genes previously shown to be involved in circulatory system processes (FDR<0.05). This study provides support for DNA methylation as a biological mechanism involved in the transmission of stress across generations and motivates further investigations to examine prenatal-dependent DNA methylation as a potential biomarker for health problems.

Epigenetics, nutrition and mental health. Is there a relationship?

Many aspects of human development and disease are influenced by the interaction between genetic and environmental factors. Understanding how our genes respond to the environment is central to managing health and disease, and is one of the major contemporary challenges in human genetics. Various epigenetic processes affect chromosome structure and accessibility of deoxyribonucleic acid (DNA) to the enzymatic machinery that leads to expression of genes. One important epigenetic mechanism that appears to underlie the interaction between environmental factors, including diet, and our genome, is chemical modification of the DNA. The best understood of these modifications is methylation of cytosine residues in DNA. It is now recognized that the pattern of methylated cytosines throughout our genomes (the 'methylome') can change during development and in response to environmental cues, often with profound effects on gene expression. Many dietary constituents may indirectly influence genomic pathways that methylate DNA, and there is evidence for biochemical links between nutritional quality and mental health. Deficiency of both macro- and micronutrients has been associated with increased behavioural problems, and nutritional supplementation has proven efficacious in treatment of certain neuropsychiatric disorders. In this review we examine evidence from the fields of nutrition, developmental biology, and mental health that supports dietary impacts on epigenetic processes, particularly DNA methylation. We then consider whether such processes could underlie the demonstrated efficacy of dietary supplementation in treatment of mental disorders, and whether targeted manipulation of DNA methylation patterns using controlled dietary supplementation may be of wider clinical value.