Child health, developmental plasticity, and epigenetic programming

Epigenetic and epistatic interactions between serotonin transporter and brain-derived neurotrophic factor genetic polymorphism: insights in depression

Epidemiological studies have shown significant results in the interaction between the functions of brain-derived neurotrophic factor (BDNF) and 5-HT in mood disorders, such as major depressive disorder (MDD). The latest research has provided convincing evidence that gene transcription of these molecules is a target for epigenetic changes, triggered by stressful stimuli that starts in early childhood and continues throughout life, which are subsequently translated into structural and functional phenotypes culminating in depressive disorders. The short variants of 5-HTTLPR and BDNF-Met are seen as forms which are predisposed to epigenetic aberrations, which leads individuals to a susceptibility to environmental adversities, especially when subjected to stress in early life. Moreover, the polymorphic variants also feature epistatic interactions in directing the functional mechanisms elicited by stress and underlying the onset of depressive disorders. Also emphasized are works which show some mediators between stress and epigenetic changes of the 5-HTT and BDNF genes, such as the hypothalamic-pituitary-adrenal (HPA) axis and the cAMP response element-binding protein (CREB), which is a cellular transcription factor. Both the HPA axis and CREB are also involved in epistatic interactions between polymorphic variants of 5-HTTLPR and Val66Met. This review highlights some research studying changes in the epigenetic patterns intrinsic to genes of 5-HTT and BDNF, which are related to lifelong environmental adversities, which in turn increases the risks of developing MDD.

Fluoxetine treatment ameliorates depression induced by perinatal arsenic exposure via a neurogenic mechanism

Several epidemiological studies have reported an association between arsenic exposure and increased rates of psychiatric disorders, including depression, in exposed populations. We have previously demonstrated that developmental exposure to low amounts of arsenic induces depression in adulthood along with several morphological and molecular aberrations, particularly associated with the hippocampus and the hypothalamic-pituitary-adrenal (HPA) axis. The extent and potential reversibility of this toxin-induced damage has not been characterized to date. In this study, we assessed the effects of fluoxetine, a selective serotonin reuptake inhibitor antidepressant, on adult animals exposed to arsenic during development. Perinatal arsenic exposure (PAE) induced depressive-like symptoms in a mild learned helplessness task and in the forced swim task after acute exposure to a predator odor (2,4,5-trimethylthiazoline, TMT). Chronic fluoxetine treatment prevented these behaviors in both tasks in arsenic-exposed animals and ameliorated arsenic-induced blunted stress responses, as measured by corticosterone (CORT) levels before and after TMT exposure. Morphologically, chronic fluoxetine treatment reversed deficits in adult hippocampal neurogenesis (AHN) after PAE, specifically differentiation and survival of neural progenitor cells. Protein expression of BDNF, CREB, the glucocorticoid receptor (GR), and HDAC2 was significantly increased in the dentate gyrus of arsenic animals after fluoxetine treatment. This study demonstrates that damage induced by perinatal arsenic exposure is reversible with chronic fluoxetine treatment resulting in restored resiliency to depression via a neurogenic mechanism.

Early-life nutritional programming of longevity

Available data from both experimental and epidemiological studies suggest that inadequate diet in early life can permanently change the structure and function of specific organs or homoeostatic pathways, thereby ‘programming’ the individual’s health status and longevity. Sufficient evidence has accumulated showing significant impact of epigenetic regulation mechanisms in nutritional programming phenomenon. The essential role of early-life diet in the development of aging-related chronic diseases is well established and described in many scientific publications. However, the programming effects on lifespan have not been extensively reviewed systematically. The aim of the review is to provide a summary of research findings and theoretical explanations that indicate that longevity can be influenced by early nutrition.

Transgenerational epigenetic inheritance: myths and mechanisms

Since the human genome was sequenced, the term "epigenetics" is increasingly being associated with the hope that we are more than just the sum of our genes. Might what we eat, the air we breathe, or even the emotions we feel influence not only our genes but those of descendants? The environment can certainly influence gene expression and can lead to disease, but transgenerational consequences are another matter. Although the inheritance of epigenetic characters can certainly occur-particularly in plants-how much is due to the environment and the extent to which it happens in humans remain unclear.

The intergenerational effects of Indian Residential Schools: implications for the concept of historical trauma

The current paper reviews research that has explored the intergenerational effects of the Indian Residential School (IRS) system in Canada, in which Aboriginal children were forced to live at schools where various forms of neglect and abuse were common. Intergenerational IRS trauma continues to undermine the well-being of today's Aboriginal population, and having a familial history of IRS attendance has also been linked with more frequent contemporary stressor experiences and relatively greater effects of stressors on well-being. It is also suggested that familial IRS attendance across several generations within a family appears to have cumulative effects. Together, these findings provide empirical support for the concept of historical trauma, which takes the perspective that the consequences of numerous and sustained attacks against a group may accumulate over generations and interact with proximal stressors to undermine collective well-being. As much as historical trauma might be linked to pathology, it is not possible to go back in time to assess how previous traumas endured by Aboriginal peoples might be related to subsequent responses to IRS trauma. Nonetheless, the currently available research demonstrating the intergenerational effects of IRSs provides support for the enduring negative consequences of these experiences and the role of historical trauma in contributing to present day disparities in well-being.

Methylation potential associated with diet, genotype, protein, and metabolite levels in the Delta Obesity Vitamin Study

Micronutrient research typically focuses on analyzing the effects of single or a few nutrients on health by analyzing a limited number of biomarkers. The observational study described here analyzed micronutrients, plasma proteins, dietary intakes, and genotype using a systems approach. Participants attended a community-based summer day program for 6-14 year old in 2 years. Genetic makeup, blood metabolite and protein levels, and dietary differences were measured in each individual. Twenty-four-hour dietary intakes, eight micronutrients (vitamins A, D, E, thiamin, folic acid, riboflavin, pyridoxal, and pyridoxine) and 3 one-carbon metabolites [homocysteine (Hcy), S-adenosylmethionine (SAM), and S-adenosylhomocysteine (SAH)], and 1,129 plasma proteins were analyzed as a function of diet at metabolite level, plasma protein level, age, and sex. Cluster analysis identified two groups differing in SAM/SAH and differing in dietary intake patterns indicating that SAM/SAH was a potential marker of nutritional status. The approach used to analyze genetic association with the SAM/SAH metabolites is called middle-out: SNPs in 275 genes involved in the one-carbon pathway (folate, pyridoxal/pyridoxine, thiamin) or were correlated with SAM/SAH (vitamin A, E, Hcy) were analyzed instead of the entire 1M SNP data set. This procedure identified 46 SNPs in 25 genes associated with SAM/SAH demonstrating a genetic contribution to the methylation potential. Individual plasma metabolites correlated with 99 plasma proteins. Fourteen proteins correlated with body mass index, 49 with group age, and 30 with sex. The analytical strategy described here identified subgroups for targeted nutritional interventions.

Obesity and lifespan health--importance of the fetal environment

A marked increase in the frequency of obesity at the population level has resulted in an increasing number of obese women entering pregnancy. The increasing realization of the importance of the fetal environment in relation to chronic disease across the lifespan has focused attention on the role of maternal obesity in fetal development. Previous studies have demonstrated that obesity during adolescence and adulthood can be traced back to fetal and early childhood exposures. This review focuses on factors that contribute to early developmental events, such as epigenetic modifications, the potential for an increase in inflammatory burden, early developmental programming changes such as the variable development of white versus brown adipose tissue, and alterations in organ ontogeny. We hypothesize that these mechanisms promote an unfavorable fetal environment and can have a long-standing impact, with early manifestations of chronic disease that can result in an increased demand for future health care. In order to identify appropriate preventive measures, attention needs to be placed both on reducing maternal obesity as well as understanding the molecular, cellular, and epigenetic mechanisms that may be responsible for the prenatal onset of chronic disease.

Decreased glutathione and elevated hair mercury levels are associated with nutritional deficiency-based autism in Oman

Genetic, nutrition, and environmental factors have each been implicated as sources of risk for autism. Oxidative stress, including low plasma levels of the antioxidant glutathione, has been reported by numerous autism studies, which can disrupt methylation-dependent epigenetic regulation of gene expression with neurodevelopmental consequences. We investigated the status of redox and methylation metabolites, as well as the level of protein homocysteinylation and hair mercury levels, in autistic and neurotypical control Omani children, who were previously shown to exhibit significant nutritional deficiencies in serum folate and vitamin B12. The serum level of glutathione in autistic subjects was significantly below control levels, while levels of homocysteine and S-adenosylhomocysteine were elevated, indicative of oxidative stress and decreased methionine synthase activity. Autistic males had lower glutathione and higher homocysteine levels than females, while homocysteinylation of serum proteins was increased in autistic males but not females. Mercury levels were markedly elevated in the hair of autistic subjects vs. control subjects, consistent with the importance of glutathione for its elimination. Thus, autism in Oman is associated with decreased antioxidant resources and decreased methylation capacity, in conjunction with elevated hair levels of mercury.

Lifecourse health development: past, present and future

During the latter half of the twentieth century, an explosion of research elucidated a growing number of causes of disease and contributors to health. Biopsychosocial models that accounted for the wide range of factors influencing health began to replace outmoded and overly simplified biomedical models of disease causation. More recently, models of lifecourse health development (LCHD) have synthesized research from biological, behavioral and social science disciplines, defined health development as a dynamic process that begins before conception and continues throughout the lifespan, and paved the way for the creation of novel strategies aimed at optimization of individual and population health trajectories. As rapid advances in epigenetics and biological systems research continue to inform and refine LCHD models, our healthcare delivery system has struggled to keep pace, and the gulf between knowledge and practice has widened. This paper attempts to chart the evolution of the LCHD framework, and illustrate its potential to transform how the MCH system addresses social, psychological, biological, and genetic influences on health, eliminates health disparities, reduces chronic illness, and contains healthcare costs. The LCHD approach can serve to highlight the foundational importance of MCH, moving it from the margins of national debate to the forefront of healthcare reform efforts. The paper concludes with suggestions for innovations that could accelerate the translation of health development principles into MCH practice.

Lifecourse health development: past, present and future

During the latter half of the twentieth century, an explosion of research elucidated a growing number of causes of disease and contributors to health. Biopsychosocial models that accounted for the wide range of factors influencing health began to replace outmoded and overly simplified biomedical models of disease causation. More recently, models of lifecourse health development (LCHD) have synthesized research from biological, behavioral and social science disciplines, defined health development as a dynamic process that begins before conception and continues throughout the lifespan, and paved the way for the creation of novel strategies aimed at optimization of individual and population health trajectories. As rapid advances in epigenetics and biological systems research continue to inform and refine LCHD models, our healthcare delivery system has struggled to keep pace, and the gulf between knowledge and practice has widened. This paper attempts to chart the evolution of the LCHD framework, and illustrate its potential to transform how the MCH system addresses social, psychological, biological, and genetic influences on health, eliminates health disparities, reduces chronic illness, and contains healthcare costs. The LCHD approach can serve to highlight the foundational importance of MCH, moving it from the margins of national debate to the forefront of healthcare reform efforts. The paper concludes with suggestions for innovations that could accelerate the translation of health development principles into MCH practice.

Maternal tract factors contribute to paternal seminal fluid impact on metabolic phenotype in offspring

Paternal characteristics and exposures influence physiology and disease risks in progeny, but the mechanisms are mostly unknown. Seminal fluid, which affects female reproductive tract gene expression as well as sperm survival and integrity, provides one potential pathway. We evaluated in mice the consequences for offspring of ablating the plasma fraction of seminal fluid by surgical excision of the seminal vesicle gland. Conception was substantially impaired and, when pregnancy did occur, placental hypertrophy was evident in late gestation. After birth, the growth trajectory and metabolic parameters of progeny were altered, most profoundly in males, which exhibited obesity, distorted metabolic hormones, reduced glucose tolerance, and hypertension. Altered offspring phenotype was partly attributable to sperm damage and partly to an effect of seminal fluid deficiency on the female tract, because increased adiposity was also evident in adult male progeny when normal two-cell embryos were transferred to females mated with seminal vesicle-excised males. Moreover, embryos developed in female tracts not exposed to seminal plasma were abnormal from the early cleavage stages, but culture in vitro partly alleviated this. Absence of seminal plasma was accompanied by down-regulation of the embryotrophic factors Lif, Csf2, Il6, and Egf and up-regulation of the apoptosis-inducing factor Trail in the oviduct. These findings show that paternal seminal fluid composition affects the growth and health of male offspring, and reveal that its impact on the periconception environment involves not only sperm protection but also indirect effects on preimplantation embryos via oviduct expression of embryotrophic cytokines.

Epigenetic programming and risk: the birthplace of cardiovascular disease?

Epigenetics, through control of gene expression circuitries, plays important roles in various physiological processes such as stem cell differentiation and self renewal. This occurs during embryonic development, in different tissues, and in response to environmental stimuli. The language of epigenetic program is based on specific covalent modifications of DNA and chromatin. Thus, in addition to the individual identity, encoded by sequence of the four bases of the DNA, there is a cell type identity characterized by its positioning in the epigenetic "landscape". Aberrant changes in epigenetic marks induced by environmental cues may contribute to the development of abnormal phenotypes associated with different human diseases such as cancer, neurological disorders and inflammation. Most of the epigenetic studies have focused on embryonic development and cancer biology, while little has been done to explore the role of epigenetic mechanisms in the pathogenesis of cardiovascular disease. This review highlights our current knowledge of epigenetic gene regulation and the evidence that chromatin remodeling and histone modifications play key roles in the pathogenesis of cardiovascular disease through (re)programming of cardiovascular (stem) cells commitment, identity and function.

Epigenetics in adipose tissue, obesity, weight loss, and diabetes

Given the role that diet and other environmental factors play in the development of obesity and type 2 diabetes, the implication of different epigenetic processes is being investigated. Although it is well known that external factors can cause cell type-dependent epigenetic changes, including DNA methylation, histone tail modifications, and chromatin remodeling, the regulation of these processes, the magnitude of the changes and the cell types in which they occur, the individuals more predisposed, and the more crucial stages of life remain to be elucidated. There is evidence that obese and diabetic people have a pattern of epigenetic marks different from nonobese and nondiabetic individuals. The main long-term goals in this field are the identification and understanding of the role of epigenetic marks that could be used as early predictors of metabolic risk and the development of drugs or diet-related treatments able to delay these epigenetic changes and even reverse them. But weight gain and insulin resistance/diabetes are influenced not only by epigenetic factors; different epigenetic biomarkers have also been identified as early predictors of weight loss and the maintenance of body weight after weight loss. The characterization of all the factors that are able to modify the epigenetic signatures and the determination of their real importance are hindered by the following factors: the magnitude of change produced by dietary and environmental factors is small and cumulative; there are great differences among cell types; and there are many factors involved, including age, with multiple interactions between them.

Immune dysregulation in autism spectrum disorder

Autism spectrum disorder (ASD) is a common and severe neuro-developmental disorder in early childhood which is defined by social and communication deficits and repetitive and stereotypic behaviours. The aetiology of ASD remains poorly understood. Susceptibility to development of ASD has significant environmental components, in addition to the profound genetic heritability. Few genes have been associated to the risk for ASD development. There is substantial evidence implicating chronic neurological inflammation and immune dysregulation leading to upregulation of inflammatory cytokines in the ASD brain, probably due to altered blood-brain barrier function. The immune system is characterized by excessive and skewed cytokine responses, modulated T cell reactivity, decreased regulation and production of immunosuppressive cytokines, modified NK function and increased autoantibody production.

CONCLUSION

The perinatal environment generates vulnerability to chronic neuro-inflammation in the brain associated with profound modulation and dysregulation in the immune system leading to the rapid development of ASD in genetically susceptible children.

Epigenetics and primary care

Epigenetics, the study of functionally relevant chemical modifications to DNA that do not involve a change in the DNA nucleotide sequence, is at the interface between research and clinical medicine. Research on epigenetic marks, which regulate gene expression independently of the underlying genetic code, has dramatically changed our understanding of the interplay between genes and the environment. This interplay alters human biology and developmental trajectories, and can lead to programmed human disease years after the environmental exposure. In addition, epigenetic marks are potentially heritable. In this article, we discuss the underlying concepts of epigenetics and address its current and potential applicability for primary care providers.

Genetics of nonsyndromic obesity

PURPOSE OF REVIEW

Common obesity is widely regarded as a complex, multifactorial trait influenced by the 'obesogenic' environment, sedentary behavior, and genetic susceptibility contributed by common and rare genetic variants. This review describes the recent advances in understanding the role of genetics in obesity.

RECENT FINDINGS

New susceptibility loci and genetic variants are being uncovered, but the collective effect is relatively small and could not explain most of the BMI heritability. Yet-to-be identified common and rare variants, epistasis, and heritable epigenetic changes may account for part of the 'missing heritability'. Evidence is emerging about the role of epigenetics in determining obesity susceptibility, mediating developmental plasticity, which confers obesity risk from early life experiences. Genetic prediction scores derived from selected genetic variants, and also differential DNA methylation levels and methylation scores, have been shown to correlate with measures of obesity and response to weight loss intervention. Genetic variants, which confer susceptibility to obesity-related morbidities like nonalcoholic fatty liver disease, were also discovered recently.

SUMMARY

We can expect discovery of more rare genetic variants with the advent of whole exome and genome sequencing, and also greater understanding of epigenetic mechanisms by which environment influences genetic expression and which mediate the gene-environment interaction.

Pubertal supplementation of lipotropes in female rats reduces mammary cancer risk by suppressing histone deacetylase 1

PURPOSE

The time from puberty to the first pregnancy is known to be important for a woman's life-time breast cancer risk. Recent studies suggest that epigenetic mechanisms may involve pubertal maturation processes, which can affect the risk of breast cancer in later life. Epigenetic alterations are related to lipotropes (methionine, choline, folate, and vitamin B12), which are methyl donors and cofactors. However, the effects of pubertal supplementation of lipotropes in breast cancer remain largely unknown.

METHODS

Twenty female Sprague-Dawley rats, aged 6 weeks, were divided into two groups and fed a normal control diet or a lipotrope-fortified diet formulated to provide five times basal levels of lipotropes during puberty. All rats were injected intraperitoneally with N-nitroso-N-methylurea at 50 days of age to induce mammary tumors.

RESULTS

Tumor multiplicity and tumor volume decreased significantly as a result of lipotrope supplementation. Interestingly, quantitative RT-PCR revealed significantly decreased expression of histone deacetylase 1 (Hdac1) and DNA methyltransferase 1 (Dnmt1) genes in tumor tissues of the rats supplemented with lipotrope-fortified diet, suggesting that reduced risk of breast cancer can be attributed, at least in part, to decreased expression of these two genes.

CONCLUSIONS

This study demonstrates that supplementation of lipotrope-fortified diet during puberty suppresses tumor growth, potentially through down-regulating Hdac1 and Dnmt1 gene expression. Our findings suggest that pubertal methyl diet plays an important role in the etiology of breast cancer, and further studies are warranted to develop preventative strategies against breast cancer.

Towards identification of molecular mechanisms of short stature

Growth evaluations are among the most common referrals to pediatric endocrinologists. Although a number of pathologies, both primary endocrine and non-endocrine, can present with short stature, an estimated 80% of evaluations fail to identify a clear etiology, leaving a default designation of idiopathic short stature (ISS). As a group, several features among children with ISS are suggestive of pathophysiology of the GH–IGF-1 axis, including low serum levels of IGF-1 despite normal GH secretion. Candidate gene analysis of rare cases has demonstrated that severe mutations of genes of the GH–IGF-1 axis can present with a profound height phenotype, leading to speculation that a collection of mild mutations or polymorphisms of these genes can explain poor growth in a larger proportion of patients. Recent genome-wide association studies have identified ~180 genomic loci associated with height that together account for approximately 10% of height variation. With only modest representation of the GH–IGF-1 axis, there is little support for the long-held hypothesis that common genetic variants of the hormone pathway provide the molecular mechanism for poor growth in a substantial proportion of individuals. The height-associated common variants are not observed in the anticipated frequency in the shortest individuals, suggesting rare genetic factors with large effect are more plausible in this group. As we advance towards establishing a molecular mechanism for poor growth in a greater percentage of those currently labeled ISS, we highlight two strategies that will likely be offered with increasing frequency: (1) unbiased genetic technologies including array analysis for copy number variation and whole exome/genome sequencing and (2) epigenetic alterations of key genomic loci. Ultimately data from subsets with similar molecular etiologies may emerge that will allow tailored interventions to achieve the best clinical outcome.

Effects of antenatal synthetic glucocorticoid on glucocorticoid receptor binding, DNA methylation, and genome-wide mRNA levels in the fetal male hippocampus

The endogenous glucocorticoid (GC) surge in late gestation plays a vital role in maturation of several organ systems. For this reason, pregnant women at risk of preterm labor are administered synthetic glucocorticoids (sGCs) to promote fetal lung development. Animal studies have shown that fetal sGC exposure can cause life-long changes in endocrine and metabolic function. We have previously shown that antenatal sGC treatment is associated with alterations in global DNA methylation and modifications to the hippocampal methylome and acetylome. In this study, we hypothesized that: 1) there are changes in the transcriptional landscape of the fetal hippocampus in late gestation, associated with the endogenous cortisol surge; 2) fetal sGC exposure alters genome-wide transcription in the hippocampus; and 3) these changes in transcription are associated with modified glucocorticoid receptor (GR) DNA binding and DNA methylation. sGC was administered as 2 courses on gestational days (GD) 40, 41, 50, and 51, and the hippocampi of fetal guinea pigs were examined before (GD52) and after (GD65) the endogenous cortisol surge (Term ∼GD67). We also analyzed fetal hippocampi 24 hours and 14 days following maternal sGC injections (n = 3-4/group). Genome-wide modification of transcription and GR DNA binding occurred in late gestation, in parallel with the normal GC surge. Further, sGC exposure had a substantial impact on the hippocampal transcriptome, GR-DNA binding, and DNA methylation at 24 hours and 14 days following the final sGC treatment. These data support the hypothesis that GC exposure in late gestation plays a significant role in modifying the transcriptional and epigenetic landscape of the developing fetal hippocampus and that substantial effects are evident for at least 2 weeks after sGC exposure.

BDNF promoter methylation and suicidal behavior in depressive patients

INTRODUCTION

Suicide is a major health problem, and depression is a major psychiatric cause of suicide. Suicide is influenced by the multifactorial interaction of many risk factors. Therefore, epigenetic research may lead to understandings that are applicable to suicide. This study investigated whether epigenetic changes are associated with suicidal behavior and evaluated the treatment outcome of suicidal ideation in depressive patients.

METHODS

In 108 patients with major depression, the promoter methylation of the gene encoding brain-derived neurotrophic factor (BDNF) was measured. Sociodemographic and clinical characteristics including a history of previous depressive episodes, age at onset, duration of illnesses, family history of depression, and number of stressful life events as well as subjective perception of stress and assessment scales for depression (HAMD), anxiety (HAMA), function (SOFAS), disability (WHODAS-12), and quality of life (WHOQOL-BREF) were evaluated at baseline. Suicidal behavior was ascertained using a semistructured clinical interview with questions about severity and intent. Beck Scale for Suicide Ideation (BSS) was administered during 12 weeks of treatment with antidepressants.

RESULTS

A higher BDNF promoter methylation status was significantly associated with a previous suicidal attempt history, suicidal ideation during treatment, and suicidal ideation at last evaluation as well as with higher BSS scores and poor treatment outcomes for suicidal ideation.

LIMITATIONS

Methylation status was investigated with limited area of the BDNF gene and sample size was relatively small.

CONCLUSIONS

BDNF methylation status could be a proxy marker for previous suicidal attempts and a clinical biomarker for poor treatment outcomes of suicidal ideation in depression.

Adequate but not supplemental folic acid combined with soy isoflavones during early life improves bone health at adulthood in male mice

Previous investigations from our laboratory have demonstrated that neonatal exposure to soy isoflavones (ISO) improves bone outcomes in CD-1 mice at adulthood with greater benefits in females than males. This study determined whether early-life exposure to supplemental folic acid (FA) - that may enhance DNA methylation of target genes - in combination with ISO provides greater benefits to male bone development than ISO alone. CD-1 dams were randomized to a low (0 mg/kg diet), adequate (2 mg/kg diet) or supplemental (8 mg/kg diet) level of FA during pregnancy and lactation. Offspring received corn oil or ISO (7 mg/kg of body weight per day) from postnatal day 1-10. From weaning, males were fed adequate FA and studied to age 4 months. Offspring exposed to adequate FA+ISO had multiple benefits to bone health: higher (P<.05) bone mineral density (BMD) and greater (P<.05) resistance to fracture at the femur and lumbar spine than mice exposed to adequate FA alone. Exposure to supplemental FA+ISO resulted in higher (P<.05) serum osteoprotegerin (OPG), and a higher ratio of OPG to receptor activator for nuclear factor κβ ligand (RANKL) but did not result in greater BMD or strength at the femur or lumbar spine than supplemental FA alone. In conclusion, early-life exposure to adequate FA+ISO provided functional benefits to male bone development, while improvements induced by supplemental FA+ISO were limited to a higher level of serum OPG. Mechanistic studies are needed to better understand how FA and ISO improve bone development in male offspring.

Lessons from the one-carbon metabolism: passing it along to the next generation

During development, a fetus and its placenta must respond to a changing maternal environment to ensure normal growth is achieved and survival is maintained. The mechanisms behind developmental programming involve complex interactions between epigenetic and physiological processes, which are not well understood. Importantly, when programming goes awry, it puts the fetus at risk for disease later in life and may, in some instances, affect subsequent generations via epigenetic processes including DNA methylation. The one-carbon metabolism, which includes the folate, methionine and choline pathways, provides methyl groups necessary for DNA methylation and a normal epigenetic landscape. Accordingly, disruptions in this pathway affect placental development and function leading to altered fetal programming. Remarkably, recent studies have revealed that abnormal folate metabolism causes transgenerational effects probably through epigenetic inheritance. The epigenetic mechanisms behind this phenomenon are not well understood but they have important implications for the influence of the metabolic environment on epigenetic stability and non-genetic inheritance of disease. Importantly, there are increasing concerns that assisted reproductive technologies cause aberrant epigenetic profiles in embryos leading to abnormal fetal programming. How the negative epigenetic consequences of assisted reproduction treatment affect subsequent generations requires further investigation.

Powerline bioactivity - more than magnetism

BACKGROUND

Previous work on the possible public health impact of electricity utilization has mostly considered low frequency electromagnetic fields, particularly those associated with high voltage overhead powerlines, but no generally accepted biological mechanism has been proposed. The present study seeks to expand the area of debate to include airborne electroactivity.

FINDINGS

From a literature survey it is concluded that there is statistically significant published evidence consistent with the involvement of airborne electroactive agents in the powerline proximity modulation of some cytokine activity. Attention is drawn to overhead line fault associated corona discharge action as a source of potentially bioactive agents deserving careful study in view of the widespread close residential proximity to overhead power distribution lines in many countries. Particular attention is given to the role of electricity access associated faults as a possible explanation for the high childhood leukaemia rates in certain districts of Mexico City.

CONCLUSIONS

Despite more than 30 years research worldwide there is no generally accepted biological mechanism to explain the adverse health impact of overhead powerline residential proximity. Expanding the area of consideration to include airborne electroactivity may provide the basis for a plausible outline model of such a mechanism. More attention should be given to this research area.

The prenatal environment and type 1 diabetes

There is ample evidence that environmental factors are involved in the aetiology of type 1 diabetes, but the nature and timing of the interactions are poorly understood. The intrauterine environment is known to play a role in the later development of type 2 diabetes, and this review considers a possible role in type 1 diabetes. Autoimmune type 1 diabetes is rare in those diagnosed before 6 months of age, but endogenous autoantibodies predictive of future type 1 diabetes may be detectable by 6-12 months of age, suggesting that environmental factors may operate before this age in some cases. Indirect evidence of a protective effect for the intrauterine environment comes from the observation that mothers with type 1 diabetes are less likely than affected fathers to transmit diabetes to their offspring, although the precise role (if any) is unclear. The risk of childhood-onset type 1 diabetes increases with maternal age at delivery, and with high birthweight, but these associations are weak and heterogeneous, and these factors are unlikely to be directly causally related to type 1 diabetes. No firm conclusion can be drawn from studies of maternal enteroviral infection or from various nutritional exposures. The birth process itself may play a role, as suggested by the slightly increased risk in children born by Caesarean section; lack of contact with maternal bacteria is one suggested mechanism. In sum, there is circumstantial evidence, but no proof of principle, that maternal or intrauterine conditions may modulate genetic risk of type 1 diabetes. The disease process culminating in type 1 diabetes typically begins in early life, but it is not clear whether the trail begins before or after birth.

Parental height and child growth from birth to 2 years in the WHO Multicentre Growth Reference Study

Linear growth from birth to 2 years of children enrolled in the World Health Organization Multicentre Growth Reference Study was similar despite substantial parental height differences among the six study sites. Within-site variability in child length attributable to parental height was estimated by repeated measures analysis of variance using generalized linear models. This approach was also used to examine relationships among selected traits (e.g. breastfeeding duration and child morbidity) and linear growth between 6 and 24 months of age. Differences in intergenerational adult heights were evaluated within sites by comparing mid-parental heights (average of the mother's and father's heights) to the children's predicted adult height. Mid-parental height consistently accounted for greater proportions of observed variability in attained child length than did either paternal or maternal height alone. The proportion of variability explained by mid-parental height ranged from 11% in Ghana to 21% in India. The average proportion of between-child variability accounted for by mid-parental height was 16% and the analogous within-child estimate was 6%. In the Norwegian and US samples, no significant differences were observed between mid-parental and children's predicted adult heights. For the other sites, predicted adult heights exceeded mid-parental heights by 6.2-7.8 cm. To the extent that adult height is predicted by height at age 2 years, these results support the expectation that significant community-wide advances in stature are attainable within one generation when care and nutrition approximate international recommendations, notwithstanding adverse conditions likely experienced by the previous generation.

The role of early life nutrition in programming of reproductive function

Accumulating evidence suggest that the concept of programming can also be applied to reproductive development and function, representing an ever expanding research area. Recently issues such as peri- or even preconceptional nutrition, transgenerational effects and underlying mechanisms have received considerable attention. The present chapter presents the existed evidence and reviews the available data from numerous animal and human studies on the effects of early life nutritional environment on adult reproductive function. Specific outcomes depend on the severity, duration and stage of development when nutritional perturbations are imposed, while sex-specific effects are also manifested. Apart from undernutrition, effects of relative overnutrition as well as the complex interactions between pre- and postnatal nutrition is of high importance, especially in the context of our days obesity epidemic. Mechanisms underlying reproductive programming are yet unclear, but may include a role for epigenetic modifications. Epigenetic modulation of critical genes involved in the control of reproductive function and potential intergenerational effects represent an exciting area of interdisciplinary research toward the development of new nutritional approaches during pre- and postnatal periods to ensure reproductive health in later life.

Permanent and plastic epigenesis in neuroendocrine systems

The emerging area of neuroepigenetics has been linked to numerous mental health illnesses. Importantly, a large portion of what we know about early gene×environment interactions comes from examining epigenetic modifications of neuroendocrine systems. This review will highlight how neuroepigenetic mechanisms during brain development program lasting differences in neuroendocrine systems and how other neuroepigenetic processes remain plastic, even within the adult brain. As epigenetic mechanisms can either be stable or plastic, elucidating the mechanisms involved in reversing these processes could aid in understanding how to reverse pathological epigenetic programming.

Dietary soy effects on mammary gland development during the pubertal transition in nonhuman primates

While epidemiologic studies suggest that soy intake early in life may reduce breast cancer risk, there are also concerns that exposure to soy isoflavones during childhood may alter pubertal development and hormonal profiles. Here, we assessed the effect of a high-soy diet on pubertal breast development, sex hormones, and growth in a nonhuman primate model. Pubertal female cynomolgus monkeys were randomized to receive a diet modeled on a typical North American diet with one of two protein sources for approximately 4.5 years: (i) casein/lactalbumin (CL, n = 12, as control) or (ii) soy protein isolate with a human equivalent dose of 120 mg/d isoflavones (SOY, n = 17), which is comparable to approximately four servings of soy foods. Pubertal exposure to the SOY diet did not alter onset of menarche, indicators of growth and pubertal progression, or circulating estradiol and progesterone concentrations. Greater endometrial area was seen in the SOY group on the first of four postmenarchal ultrasound measurements (P < 0.05). There was a subtle effect of diet on breast differentiation whereby the SOY group showed higher numbers of differentiated large-sized lobular units and a lower proportion with immature ducts following menarche (P < 0.05). Numbers of small lobules and terminal end buds and mammary epithelial cell proliferation did not differ by diet. Expression of progesterone receptor was lower in immature lobules of soy-fed animals (P < 0.05). Our findings suggest that consumption of soy starting before menarche may result in modest effects consistent with a more differentiated breast phenotype in adulthood.

One-carbon metabolism, fetal growth and long-term consequences

One-carbon metabolism, or methyl transfer, is critical for metabolism in all cells, is involved in the synthesis of purines, pyrimidines, in the methylation of numerous substrates, proteins, DNA and RNA, and in the expression of a number of genes. Serine is the primary endogenous methyl donor to the one carbon pool. Perturbations in methyl transfer due to nutrient and hormonal changes can have profound effect on cell function, growth and proliferation. It is postulated that at critical stages in development, nutrient and environmental influences by their effect on methyl transfer can impair fetal growth, reprogram metabolism and cause long-term morbidity in the offspring. The potential for their effects is underscored by the unique gestation-related changes in methyl transfer in healthy women, the late expression of transsulfuration cascade in the fetus and the unique metabolism of glycine and serine in the fetus. Dietary protein restriction in animal models and protein malnutrition in humans causes remarkable changes in the methyl transfer in vivo. Although the specific consequences of perturbation in maternal and fetal methyl transfer remain to be determined, a profound influence is suggested by the demonstrated relationship between maternal folate and B12 insufficiency and metabolic programming.

A longitudinal study of BDNF promoter methylation and genotype with poststroke depression

INTRODUCTION

Brain derived neurotrophic factor (BDNF) has been shown to play an important role in the pathophysiology of mood disorders including poststroke depression (PSD). BDNF secretion is influenced by epigenetic and genetic profiles. This study aimed to investigate whether BDNF gene promoter methylation status and val66met polymorphism were associated with depression ascertained at two weeks and one year after stroke.

METHODS

A total of 286 patients were evaluated two weeks after stroke, and 222 (78%) were followed one year later. Depression (major or minor depressive disorder) was diagnosed according to DSM-IV criteria, and classified into prevalent, persistent, and incident PSD according to presence at the two examinations. Depression severity was assessed by the Hospital Anxiety and Depression Scale-depression subscale and the Hamilton Depression Rating Scale. The effects of BDNF methylation status and genotype on PSD status were investigated using multivariate logistic regression models. The associations of BDNF methylation status and genotype with score on depression assessment scales were estimated using partial correlation tests and general linear models, respectively.

RESULTS

Higher BDNF methylation status was independently associated with prevalent, persistent and particularly with incident PSD, and with worsening depressive symptoms over follow-up but not with baseline severity. The BDNF val66met polymorphism was independently associated with prevalent PSD, but not with persistent and incident PSD nor with depressive symptoms severity. No significant methylation-genotype interactions were found.

LIMITATIONS

Methylation status was investigated with limited area of the BDNF gene and sample size was relatively small.

CONCLUSIONS

A role for BDNF in PSD was supported, and associations with BDNF gene methylation status may represent a target for drug development.

Association of SLC6A4 methylation with early adversity, characteristics and outcomes in depression

Childhood adversities have been associated with onset and worse clinical presentations of depression. Epigenetic changes may reflect childhood adversities, while their effects on clinical characteristics of depression are unknown. This study aimed to investigate whether epigenetic changes were associated with childhood adversities, pretreatment characteristics, and treatment outcomes in depressive patients. In 108 patients with major depressive disorders, the methylation status in the promoter of gene encoding serotonin transporter (SLC6A4) was measured. Childhood adversities, socio-demographic and clinical characteristics including assessment scales for depression (Hamilton Depression Rating Scale, HAMD), anxiety (Hamilton Anxiety Rating Scale, HAMA), functioning (Social and Occupational Functioning Assessment Scale, SOFAS), disability (World Health Organization Disability Assessment Schedule-12, WHODAS-12), and quality of life (World Health Organization Quality of Life-Abbreviated form, WHOQOL-BREF) were evaluated at baseline. After a 12-week treatment with antidepressants, the assessment scales were reevaluated. To avoid type I error by multiple comparisons, Bonferroni corrections were applied. Higher SLC6A4 promoter methylation status was significantly associated with childhood adversities, worse clinical presentation (family history of depression, higher perceived stress, and more severe psychopathology assessed by SOFAS, WHODAS-12, and WHOQOL-BREF), but was not associated with treatment outcomes after considering multiple comparisons. SLC6A4 methylation status could be a proxy marker for childhood adversities and a clinical biomarker for certain presentations of depression.

Prenatal sensitization of a postnatal trigger for metabolic disease

Intrahepatic cholestasis of pregnancy (ICP), marked by elevated maternal serum bile acid levels, occurs in late pregnancy and is often associated with poor perinatal outcomes. In this issue of the JCI, Papacleovoulou et al. analyze the long-term consequences of ICP and find that teens born to mothers with ICP exhibit enhanced characteristics of metabolic syndrome relative to controls. The authors also used a new ICP mouse model to support and extend these findings, demonstrating that in utero exposure to bile acids induces persistent epigenetic alterations and abnormal placental lipogenesis,setting the stage for later metabolic dysfunction.

Protecting children from toxic chemicals: putting it on Australia's public health agenda

The high volume and widespread use of industrial chemicals, the backlog of internationally untested chemicals, the uptake of synthetic chemicals found in babies in utero, cord blood, and in breast milk, and the lack of a unified and comprehensive regulatory framework all necessitate developing policies that protect the most vulnerable in our society - our children. Australia's failure to do so raises profound intergenerational ethical issues. This article tells a story of international policy, and where Australia is falling down. It demonstrates that we can learn from countries already taking critical steps to reduce the toxic chemical exposure, and that the development of a comprehensive, child-centered chemical regulation framework is central to turning around Australia's failure.

Developmental and environmental epigenetic programming of the endocrine pancreas: consequences for type 2 diabetes

The development of the endocrine pancreas is controlled by a hierarchical network of transcriptional regulators. It is increasingly evident that this requires a tightly interconnected epigenetic "programme" to drive endocrine cell differentiation and maintain islet function. Epigenetic regulators such as DNA and histone-modifying enzymes are now known to contribute to determination of pancreatic cell lineage, maintenance of cellular differentiation states, and normal functioning of adult pancreatic endocrine cells. Persistent effects of an early suboptimal environment, known to increase risk of type 2 diabetes in later life, can alter the epigenetic control of transcriptional master regulators, such as Hnf4a and Pdx1. Recent genome-wide analyses also suggest that an altered epigenetic landscape is associated with the β cell failure observed in type 2 diabetes and aging. At the cellular level, epigenetic mechanisms may provide a mechanistic link between energy metabolism and stable patterns of gene expression. Key energy metabolites influence the activity of epigenetic regulators, which in turn alter transcription to maintain cellular homeostasis. The challenge is now to understand the detailed molecular mechanisms that underlie these diverse roles of epigenetics, and the extent to which they contribute to the pathogenesis of type 2 diabetes. In-depth understanding of the developmental and environmental epigenetic programming of the endocrine pancreas has the potential to lead to novel therapeutic approaches in diabetes.

The EPIIC hypothesis: intrapartum effects on the neonatal epigenome and consequent health outcomes

There are many published studies about the epigenetic effects of the prenatal and infant periods on health outcomes. However, there is very little knowledge regarding the effects of the intrapartum period (labor and birth) on health and epigenetic remodeling. Although the intrapartum period is relatively short compared to the complete perinatal period, there is emerging evidence that this time frame may be a critical formative phase for the human genome. Given the debates from the National Institutes of Health and World Health Organization regarding routine childbirth procedures, it is essential to establish the state of the science concerning normal intrapartum epigenetic physiology. EPIIC (Epigenetic Impact of Childbirth) is an international, interdisciplinary research collaboration with expertise in the fields of genetics, physiology, developmental biology, epidemiology, medicine, midwifery, and nursing. We hypothesize that events during the intrapartum period - specifically the use of synthetic oxytocin, antibiotics, and cesarean section - affect the epigenetic remodeling processes and subsequent health of the mother and offspring. The rationale for this hypothesis is based on recent evidence and current best practice.

Evo-devo of human adolescence: beyond disease models of early puberty

Despite substantial heritability in pubertal development, much variation remains to be explained, leaving room for the influence of environmental factors to adjust its phenotypic trajectory in the service of fitness goals. Utilizing evolutionary development biology (evo-devo), we examine adolescence as an evolutionary life-history stage in its developmental context. We show that the transition from the preceding stage of juvenility entails adaptive plasticity in response to energy resources, other environmental cues, social needs of adolescence and maturation toward youth and adulthood. Using the evolutionary theory of socialization, we show that familial psychosocial stress fosters a fast life history and reproductive strategy rather than early maturation being just a risk factor for aggression and delinquency. Here we explore implications of an evolutionary-developmental-endocrinological-anthropological framework for theory building, while illuminating new directions for research.

Effects of breastfeeding on body composition and maturational tempo in the rat

BACKGROUND

Features of life history are subject to environmental regulation in the service of reproductive fitness goals. We have previously shown that the infant-to-childhood transition reflects the adaptive adjustment of an individual's size to the prevailing and anticipated environment.

METHODS

To evaluate effects of weaning age on life-history traits in rats, we repeatedly measured length and body mass index (BMI), as well as physiological development and sexual maturation in pups weaned early (d16), normally (d21) or late (d26). Males were bred to females of the same weaning age group for four generations.

RESULTS

Here, we show that the age at weaning from lactation regulates a rat's life history, growth, body composition and maturational tempo. We show that early-weaned rats developed faster than normal- or late-weaned rats; they are leaner and longer than late-weaned ones who are heavier and shorter. Early-weaned progeny develop more rapidly (that is, fur budding, pinnae detachment, eye opening); females show earlier vaginal opening and estrous and males show earlier onset of testicular growth. In generations 3 and 4, early-weaned rats bear larger litter sizes and heavier newborn pups. The entire traits complex is transmitted to subsequent generations from the paternal side.

CONCLUSIONS

The findings presented here lend support to the proposition that the duration of infancy, as indexed by weaning age, predicts and perhaps programs growth, body composition, and the tempo of physiological development and maturation, as well as litter size and parity and, thereby, reproductive strategy.

Maternal obesity and diabetes induces latent metabolic defects and widespread epigenetic changes in isogenic mice

Intrauterine nutrition can program metabolism, creating stable changes in physiology that may have significant health consequences. The mechanism underlying these changes is widely assumed to involve epigenetic changes to the expression of metabolic genes, but evidence supporting this idea is limited. Here we have performed the first study of the epigenomic consequences of exposure to maternal obesity and diabetes. We used a mouse model of natural-onset obesity that allows comparison of genetically identical mice whose mothers were either obese and diabetic or lean with a normal metabolism. We find that the offspring of obese mothers have a latent metabolic phenotype that is unmasked by exposure to a Western-style diet, resulting in glucose intolerance, insulin resistance and hepatic steatosis. The offspring show changes in hepatic gene expression and widespread but subtle alterations in cytosine methylation. Contrary to expectation, these molecular changes do not point to metabolic pathways but instead reside in broadly developmental ontologies. We propose that, rather than being adaptive, these changes may simply produce an inappropriate response to suboptimal environments; maladaptive phenotypes may be avoidable if postnatal nutrition is carefully controlled.

The epigenetics of maternal cigarette smoking during pregnancy and effects on child development

The period of in utero development is one of the most critical windows during which adverse intrauterine conditions and exposures can influence the growth and development of the fetus as well as the child's future postnatal health and behavior. Maternal cigarette smoking during pregnancy remains a relatively common but nonetheless hazardous in utero exposure. Previous studies have associated prenatal smoke exposure with reduced birth weight, poor developmental and psychological outcomes, and increased risk for diseases and behavioral disorders later in life. Researchers are now learning that many of the mechanisms whereby maternal smoke exposure may affect key pathways crucial for proper fetal growth and development are epigenetic in nature. Maternal cigarette smoking during pregnancy has been associated with altered DNA methylation and dysregulated expression of microRNA, but a deeper understanding of the epigenetics of maternal cigarette smoking during pregnancy as well as how these epigenetic changes may affect later health and behavior remain to be elucidated. This article seeks to explore many of the previously described epigenetic alterations associated with maternal cigarette smoking during pregnancy and assess how such changes may have consequences for both fetal growth and development, as well as later child health, behavior, and well-being. We also outline future directions for this new and exciting field of research.

Long-term health consequences of early-life exposure to substance abuse: an epigenetic perspective

A growing body of evidence highlights the importance of the nutritional or other environmental stimuli during critical periods of development in the long-term programming of organ systems and homeostatic pathways of the organism. The adverse influences early in development and particularly during intrauterine life have been shown to programme the risks for adverse health outcomes in adult life. The mechanisms underlying developmental programming remain still unclear. However, increasing evidence has been accumulated indicating the important role of epigenetic regulation including DNA methylation, histone modifications and non-coding RNAs in the developmental programming of late-onset pathologies, including cancer, neurodegenerative diseases, and type 2 diabetes. The maternal substance abuse during pregnancy, including smoking, drinking and psychoactive drug intake, is one of the important factors determining the process of developmental programming in modern human beings. The impact of prenatal drug/substance exposure on infant and early childhood development is currently in the main focus. The long-term programming effects of such exposures on aging and associated pathologies, however, have been reported only rarely. The purpose of this review is to provide a summary of recent research findings which indicate that maternal substance abuse during pregnancy and/or neonatal period can programme not only a child's health status, but also can cause long-term or even life-long health outcomes via mechanisms of epigenetic memory.