Epigenetics as the mediator of fetal programming of adult onset disease: what is the evidence?

YTHDF3 modulates the Cbln1 level by recruiting BTG2 and is implicated in the impaired cognition of prenatal hypoxia offspring

The "Fetal Origins of Adult Disease (FOAD)" hypothesis holds that adverse factors during pregnancy can increase the risk of chronic diseases in offspring. Here, we investigated the effects of prenatal hypoxia (PH) on brain structure and function in adult offspring and explored the role of the N6-methyladenosine (m6A) pathway. The results suggest that abnormal cognition in PH offspring may be related to the dysregulation of the m6A pathway, specifically increased levels of YTHDF3 in the hippocampus. YTHDF3 interacts with BTG2 and is involved in the decay of Cbln1 mRNA, leading to the down-regulation of Cbln1 expression. Deficiency of Cbln1 may contribute to abnormal synaptic function, which in turn causes cognitive impairment in PH offspring. This study provides a scientific clues for understanding the mechanisms of impaired cognition in PH offspring and provides a theoretical basis for the treatment of cognitive impairment in offspring exposed to PH.

Intrauterine androgen exposure impairs gonadal adipose tissue functions of adult female rats

Prenatal androgen exposure induces fetal programming leading to alterations in offspring health and phenotypes that resemble those seen in women with Polycystic Ovary Syndrome. It has been described that prenatal androgenization affects the reproductive axis and leads to metabolic and endocrine disorders. Adipose tissue plays a crucial role in all these functions and is susceptible to programming effects. Particularly, gonadal adipose tissue is involved in reproductive functions, so dysfunctions in this tissue could be related to fertility alterations. We aimed to investigate the extent to which prenatal hyperandrogenization is able to alter the functionality of gonadal adipose tissue in female adult rats, including lipid metabolism, adipokines expression, and de novo synthesis of steroids. Pregnant rats were treated with 1 mg of testosterone from day 16 to day 19 of pregnancy, and female offspring were followed until 90 days of age, when they were euthanized. The prenatally hyperandrogenized (PH) female offspring displayed two phenotypes: irregular ovulatory (PHiov) and anovulatory (PHanov). Regarding lipid metabolism, both PH groups displayed disruptions in the main lipid pathways with altered levels of triglyceride and increased lipid peroxidation levels. In addition, we found that Peroxisome Proliferator-Activated Receptors (PPARs) alpha protein expression was decreased in both PH phenotypes (p < 0.05), but no changes were found in PPARγ protein levels. Furthermore, regarding adipokines, no changes were found in Leptin and Adiponectin protein levels, but Chemerin protein levels were decreased in the PHiov group (p < 0.05). Regarding de novo synthesis of steroids, the PHanov group showed increased protein levels of Cyp17a1 and Cyp19, while the PHiov group only showed decreased protein levels of Cyp19 (p < 0.05). These results suggest that prenatal androgen exposure affects females' gonadal adipose tissue in adulthood, disturbing different lipid pathways, Chemerin expression, and de novo synthesis of steroids.

Childhood adverse events and BDNF promoter methylation in later-life

Studies have shown that the effects of early-life stress and trauma can be enduring, with long-term negative effects on health. Epigenetics, including DNA methylation, have been implicated as a potential mechanism for these effects. Brain-derived neurotropic factor (BDNF) is a neurotransmitter involved in learning and memory, and altered BDNF promoter methylation measured in peripheral tissue has been found with early-life stress. However, whether such methylation differences remain stable into later life, is unknown. This study aimed to investigate the association between childhood adversity and BDNF promoter methylation in adults aged 65 years and over. Data came from a large study of older community-dwelling individuals in France (ESPRIT). Information on three major childhood adverse events, namely abuse/maltreatment, war/natural disaster, and financial difficulties/poverty, was obtained by retrospective reporting from participants of ESPRIT study. BDNF promoter I and IV methylation was assessed in blood and buccal tissue. Linear regression analysis was performed, adjusting for age, sex, education, depression, and morbidity. Among 927 participants, there was no strong evidence that childhood abuse/maltreatment or financial difficulties/poverty were associated with BDNF methylation in older individuals. For war/natural disaster, differential methylation at four of twenty-nine CpG sites was observed, however, these would not have remained significant after correction for multiple testing. Together, these findings do not support a long-term association between adverse childhood events and BDNF methylation in older age, but further large prospective studies are needed, which do not target specific genes, but consider DNA methylation across the genome.

Sex-differential RXRα gene methylation effects on mRNA and protein expression in umbilical cord of the offspring rat exposed to maternal obesity

Maternal obesity (MO) induces negative consequences in the offspring development. Adiposity phenotype is associated with maternal diet at early pregnancy and DNA methylation marks in the RXRα promotor at birth. Glucocorticoids play an important role in the regulation of metabolism through the activation of nuclear hormone receptors such as the RXRα protein. The aim of the study was to analyze steroid hormone changes at the end of pregnancy in the obese mother and RXRα gene methylation in the umbilical cord. For this purpose, in a well-established MO model, female Wistar rats were fed either standard chow (controls: C) or high-fat obesogenic diet (MO) before and during pregnancy to evaluate at 19 days of gestation (19 dG): 1) maternal concentration of circulating steroid hormones in MO and C groups, 2) maternal and fetal weights, 3) analysis of correlation between hormones concentration and maternal and fetal weights, 4) DNA methylation status of a single locus of RXRα gene near the early growth response (EGR-1) protein DNA binding site, and 5) RXRα mRNA and protein expressions in umbilical cords. Our results demonstrate that at 19 dG, MO body weight before and during pregnancy was higher than C; MO progesterone and corticosterone serum concentrations were higher and estradiol lower than C. There were not differences in fetal weight between male and female per group, therefore averaged data was used; MO fetal weight was lower than C. Positive correlations were found between progesterone and corticosterone with maternal weight, and estradiol with fetal weight, while negative correlation was observed between corticosterone and fetal weight. Additionally, male umbilical cords from MO were hypermethylated in RXRα gene compared to male C group, without differences in the female groups; mRNA and protein expression of RXRα were decreased in F1 male but not in female MO compared to C. In conclusion, MO results in dysregulation of circulating steroid hormones of the obese mothers and low fetal weight in the F1, modifying DNA methylation of RXRα gene as well as RXRα mRNA and protein expression in the umbilical cord in a sex-dependent manner.

DNA methylation: a potential mediator between air pollution and metabolic syndrome

Given the global increase in air pollution and its crucial role in human health, as well as the steep rise in prevalence of metabolic syndrome (MetS), a better understanding of the underlying mechanisms by which environmental pollution may influence MetS is imperative. Exposure to air pollution is known to impact DNA methylation, which in turn may affect human health. This paper comprehensively reviews the evidence for the hypothesis that the effect of air pollution on the MetS is mediated by DNA methylation in blood. First, we present a summary of the impact of air pollution on metabolic dysregulation, including the components of MetS, i.e., disorders in blood glucose, lipid profile, blood pressure, and obesity. Then, we provide evidence on the relation between air pollution and endothelial dysfunction as one possible mechanism underlying the relation between air pollution and MetS. Subsequently, we review the evidence that air pollution (PM, ozone, NO2 and PAHs) influences DNA methylation. Finally, we summarize association studies between DNA methylation and MetS. Integration of current evidence supports our hypothesis that methylation may partly mediate the effect of air pollution on MetS.

Hypo-Hydroxymethylation of Nobox is Associated with Ovarian Dysfunction in Rat Offspring Exposed to Prenatal Hypoxia

Prenatal hypoxia (PH) is a common feature of a suboptimal intrauterine environment affecting the development of fetuses. Whether PH leads to abnormal ovary development is not yet clear. This study investigated ovarian function in offspring exposed to PH and the potential underlying molecular mechanisms. SD female rats (n = 12 per group) at 9 weeks of age were housed in individual cages (21% O2). After the pregnant rats were exposed to hypoxia (10.5% oxygen) from embryonic day (E) 5 to E21, PH offspring were generated. All animals maintained normoxia during lactation. The number of follicles was counted in female offspring at 3 months under an optical microscope. The expression of Nobox, Gdf9, and Tets was detected by quantitative real-time polymerase chain reaction (PCR) and Western blot. Global DNA hydroxymethylation was measured by dot blot. The hydroxymethylation level of the Nobox gene was evaluated with an NGS-based multiple targeted CpG hydroxymethylation analysis method. Body weight and ovary weight were significantly decreased in the PH group compared with the control group. PH offspring have abnormal estrous cycle, decreased serum anti-Mullerian hormone (AMH), and increased serum follicle-stimulating hormone (FSH), and follicular atresia, which are consistent with the clinical manifestations in patients with ovarian dysfunction. In terms of mechanism, the expression of Nobox was significantly decreased in the PH group. Subsequent high-throughput sequencing results showed that the level of hydroxymethylation in the candidate region of the Nobox gene was reduced. Cultured cells treated with hypoxia exhibited lower levels of both 5hmC and Nobox, while vitamin C, a coactivator of Tets, rescued hypo-hydroxymethylation and increased the expression level of Nobox. This study indicated that PH could cause hypo-hydroxymethylation of Nobox through epigenetic regulation and may consequently contribute to ovarian dysfunction in adult rat offspring.

Maternal and neonatal one-carbon metabolites and the epigenome-wide infant response

Maternal prenatal status, as encapsulated by that to which a mother is exposed through diet and environment, is a key determinant of offspring health and disease. Alterations in DNA methylation (DNAm) may be a mechanism through which suboptimal prenatal conditions confer disease risk later in life. One-carbon metabolism (OCM) is critical to both fetal development and in supplying methyl donors needed for DNAm. Plasma concentrations of one-carbon metabolites across maternal first trimester (M1), maternal term (M3), and infant cord blood (CB) at birth were tested for association with DNAm patterns in CB from the Michigan Mother and Infant Pairs (MMIP) pregnancy cohort. The Illumina Infinium MethylationEPIC BeadChip was used to quantitatively evaluate DNAm across the epigenome. Global and single-site DNAm and metabolite models were adjusted for infant sex, estimated cell type proportions, and batch as covariates. Change in mean metabolite concentration across pregnancy (M1 to M3) was significantly different for S-adenosylhomocysteine (SAH), S-adenosylmethionine (SAM), betaine, and choline. Both M1 SAH and CB SAH were significantly associated with the global distribution of DNAm in CB, with indications of a shift toward less methylation. M3 SAH and CB SAH also displayed significant associations with locus-specific DNAm in infant CB (FDR<0.05). Our findings underscore the role of maternal one-carbon metabolites in shifting the global DNAm pattern in CB and emphasizes the need to closely evaluate how dietary status influences cellular methylation potential and ultimately offspring health.

Fetal programming by androgen excess impairs liver lipid content and PPARg expression in adult rats

It is known that prenatal hyperandrogenization induces alterations since early stages of life, contributing to the development of polycystic ovary syndrome affecting the reproductive axis and the metabolic status, thus promoting others associated disorders, such as dyslipidemia, insulin resistance, liver dysfunction, and even steatosis. In this study, we aimed to evaluate the effect of fetal programming by androgen excess on the hepatic lipid content and metabolic mediators at adult life. Pregnant rats were hyperandrogenized with daily subcutaneous injections of 1 mg of free testosterone from days 16 to 19 of pregnancy. The prenatally hyperandrogenized (PH) female offspring displayed two phenotypes: irregular ovulatory phenotype (PHiov) and anovulatory phenotype (PHanov), with different metabolic and endocrine features. We evaluated the liver lipid content and the main aspect of the balance between fatty acid (FA) synthesis and oxidation. We investigated the status of the peroxisomal proliferator-activated receptors (PPARs) alpha and gamma, which act as lipid mediators, and the adipokine chemerin, one marker of liver alterations. We found that prenatal hyperandrogenization altered the liver lipid profile with increased FAs levels in the PHanov phenotype and decreased cholesterol content in the PHiov phenotype. FA metabolism was also disturbed, including decreased mRNA and protein PPARgamma levels and impaired gene expression of the main enzymes involved in lipid metabolism. Moreover, we found low chemerin protein levels in both PH phenotypes. In conclusion, these data suggest that prenatal hyperandrogenization exerts a negative effect on the liver and alters lipid content and metabolic mediators' expression at adult age.

Shifting epigenetic contexts influence regulatory variation and disease risk

Epigenetic shifts are a hallmark of aging that impact transcriptional networks at regulatory level. These shifts may modify the effects of genetic regulatory variants during aging and contribute to disease pathomechanism. However, these shifts occur on the backdrop of epigenetic changes experienced throughout an individual's development into adulthood; thus, the phenotypic, and ultimately fitness, effects of regulatory variants subject to developmental- versus aging-related epigenetic shifts may differ considerably. Natural selection therefore may act differently on variants depending on their changing epigenetic context, which we propose as a novel lens through which to consider regulatory sequence evolution and phenotypic effects. Here, we define genomic regions subjected to altered chromatin accessibility as tissues transition from their fetal to adult forms, and subsequently from early to late adulthood. Based on these epigenomic datasets, we examine patterns of evolutionary constraint and potential functional impacts of sequence variation (e.g., genetic disease risk associations). We find that while the signals observed with developmental epigenetic changes are consistent with stronger fitness consequences (i.e., negative selection pressures), they tend to have weaker effects on genetic risk associations for aging-related diseases. Conversely, we see stronger effects of variants with increased local accessibility in adult tissues, strongest in young adult when compared to old. We propose a model for how epigenetic status of a region may influence the effects of evolutionary relevant sequence variation, and suggest that such a perspective on gene regulatory networks may elucidate our understanding of aging biology.

Impact of maternal hypertensive disorders of pregnancy on brain volumes at term-equivalent age in preterm infants: A voxel-based morphometry study

OBJECTIVES

Infants born to mothers with hypertensive disorders of pregnancy (HDP) reportedly have negative behavioral and neurodevelopmental outcomes. However, the effects of maternal HDP on infant brain growth have not been fully evaluated. We aimed to evaluate brain volumes and brain injury in preterm infants born to mothers with HDP using magnetic resonance (MR) imaging at term-equivalent age.

STUDY DESIGN

In this cohort study, MR imaging was performed for 94 preterm infants born before 34 weeks of gestation at Nagoya University Hospital between 2010 and 2018. Twenty infants were born to mothers with HDP and 74 to mothers without HDP.

MAIN OUTCOME MEASURES

Total brain volumes and regional volumetric alterations were assessed by voxel-based morphometry, and brain injury was evaluated using the Kidokoro global brain abnormality score. Developmental quotient was assessed at a corrected age of 1.5 years in 59 infants (HDP, n = 11; non-HDP, n = 48).

RESULTS

No significant differences were observed in the gray and white matter volumes of the two groups (HDP: 175 ± 24 mL, 137 ± 13 mL, respectively; non-HDP: 172 ± 24 mL, 142 ± 13 mL, respectively). Additionally, no regional volumetric alterations were observed between the two groups after covariate adjustment (gestational age and infant sex). The total Kidokoro score and developmental quotient were similar in both groups.

CONCLUSIONS

No significant differences in the global and regional brain volumes were observed. Further research is needed to confirm our findings at different time points of MR imaging and in different populations.

Birth weight and body fat mass in adults assessed by bioimpedance in the ELSA-Brasil study

Intrauterine life is a critical period for the development of body fat and metabolic risk. This study investigated associations between birth weight and total and truncal body fat in adults. To do so, we analyzed data on 10,011 adults participating in the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil) who self-reported birth weight as < 2.5kg, 2.5-4.0kg, or > 4.0kg at baseline (2008-2010) and underwent bioimpedance in the next follow-up visit (2012-2014). Greater mean total and truncal fat mass were seen in those with high birth weight compared with adequate birth weight (p < 0.001) in both sexes (total fat: 25.2 vs. 23.1kg in men and 31.4 vs. 27.7kg in women, and truncal fat: 13.5 vs. 12.4kg in men and 15.9 vs. 14.2kg in women). U-shaped patterns were observed in restricted cubic-spline analyses in the subset of 5,212 individuals reporting exact birth weights, although statistically significant only for those with high birth weight. In the whole sample, in comparing high to adequate birth weight, the latter predicted having a large (> 85 percentile) total and truncal fat mass, respectively: OR = 1.76, 95%CI: 1.37-2.25 (men) and OR = 1.86, 95%CI: 1.42-2.44 (women); OR = 1.68, 95% CI: 1.31-2.16 (men) and OR = 1.73, 95%CI: 1.31-2.28 (women). However, low birth weight predicted having a large (> 85 percentile) % truncal fat only in women (OR = 1.40, 95%CI: 1.03-1.91). In conclusion, in these men and women born in a period in which fetal malnutrition was prevalent, birth weight showed complex, frequently non-linear associations with adult body fat, highlighting the need for interventions to prevent low and high birth weight during pregnancy.

Lower insulin sensitivity remains a feature of children born very preterm

BACKGROUND

The first report of children born very preterm (<32 weeks of gestation) having insulin resistance was made 16 years ago. However, neonatal care has improved since. Thus, we aimed to assess whether children born very preterm still have lower insulin sensitivity than term controls.

METHODS

Participants were prepubertal children aged 5 to 11 years born very preterm (<32 weeks of gestation; n = 51; 61% boys) or at term (37-41 weeks; n = 50; 62% boys). Frequently sampled intravenous glucose tolerance tests were performed, and insulin sensitivity was calculated using Bergman's minimal model. Additional clinical assessments included anthropometry, body composition using whole-body dual-energy X-ray absorptiometry scans, clinic blood pressure, and 24-hour ambulatory blood pressure monitoring.

RESULTS

Children born very preterm were 0.69 standard deviation score (SDS) lighter (P < .001), 0.53 SDS shorter (P = .003), and had body mass index 0.57 SDS lower (P = .003) than children born at term. Notably, children born very preterm had insulin sensitivity that was 25% lower than term controls (9.4 vs 12.6 × 10^-4 minutes^-1 ·[mU/L]; P = .001). Other parameters of glucose metabolism, including fasting insulin levels, were similar in the two groups. The awake systolic blood pressure (from 24-hour monitoring) tended to be 3.1 mm Hg higher on average in children born very preterm (P = .054), while the clinic systolic blood pressure was 5.4 mm Hg higher (P = .002).

CONCLUSIONS

Lower insulin sensitivity remains a feature of children born very preterm, despite improvements in neonatal intensive care. As reported in our original study, our findings suggest the defect in insulin action in prepubertal children born very pretermis primarily peripheral and not hepatic.

Maternal and Cord Blood 25-Hydroxyvitamin D3 Are Associated with Increased Cord Blood and Naive and Activated Regulatory T Cells: The Barwon Infant Study

Vitamin D has shown immune-modulatory effects but mostly in in vitro and animal studies. Regulatory T cells (Treg) are important for a balanced immune system. The relationship between vitamin D on the number of circulating neonatal Treg is unclear. We sought to investigate the association between maternal and neonatal vitamin D metabolites and cord blood (CB) Treg subsets. In a cohort of Australian infants (n = 1074), recruited using an unselected antenatal sampling frame, 158 mother-infant pairs had data on the following: 1) 25-hydroxyvitamin D₃ (25(OH)D₃) measures in both maternal peripheral blood (28- to 32-wk gestation) and infant CB; 2) proportions (percentage of CD4⁺ T cells) of CB Treg subsets (CD4⁺CD45RA⁺ FOXP3^low naive Treg, and CD4⁺CD45RA^- FOXP3^high activated Treg [aTreg]); and 3) possible confounders, including maternal personal UV radiation. Multiple regression analyses were used. The median 25(OH)D₃ was 85.4 and 50.7 nmol/l for maternal and CB samples, respectively. Higher maternal 25(OH)D₃ levels were associated with increased CB naive Treg (relative adjusted mean difference [AMD] per 25 nmol/l increase: 5%; 95% confidence interval [CI]: 1-9%), and aTreg (AMD per 25 nmol/l increase: 17%; 95% CI: 6-28%). Furthermore, a positive association between CB 25(OH)D₃ levels and CB aTreg (AMD per 25 nmol/l increase: 29%; 95% CI: 13-48%) was also evident. These results persisted after adjustment for other factors such as maternal personal UV radiation and season of birth. 25(OH)D_3, may play a role in the adaptive neonatal immune system via induction of FOXP3⁺ Tregs. Further studies of immune priming actions of antenatal 25(OH)D₃ are warranted.

Maternal low birth weight and hypertensive disorders of pregnancy

OBJECTIVES

To investigate the association between maternal own low birth weight (<2500 g) and subsequent risks for hypertensive disorders of pregnancy (HDP) and preeclampsia.

STUDY DESIGN

A multicenter retrospective study was conducted using clinical data from 12 primary maternity care units from 2012 to 2018. A total of 17,119 women with information about their own birth weight, who delivered at term, were subdivided into four groups according to maternal birth weights [(<2500, 2500-3499, 3500-3999, and ≥4000) g].

MAIN OUTCOME MEASURES

Multivariate regression analyses were conducted to evaluate the risks for HDP and preeclampsia among women born with low birth weight compared with women born with a birth weight of 2500-3499 g. We evaluated these risks, stratified by pre-pregnancy BMI or their infants' birth weight categories.

RESULTS

Maternal low birth weight was an independent risk factor for HDP after adjustment for several covariates, but not for preeclampsia. A 100-g increase in maternal birth weight was associated with a 3% risk reduction for HDP. Additionally, women born with low birth weight had the highest risk for HDP among those with a pre-pregnancy BMI of ≥25 kg/m². Conversely, women born with high birth weight (≥4000 g) had the highest risk for preeclampsia if they complicate with fetal growth restrictions.

CONCLUSION

Women born with low birth weight had an increased risk for HDP. Collection of information on maternal birth weight may facilitate the prediction of HDP and patients' self-awareness of such risk, allowing the modification of lifestyle factors associated with HDP.

DNA methylation at the crossroads of gene and environment interactions

DNA methylation is an epigenetic mark involved in regulating genome function and is critical for normal development in mammals. It has been observed that the developmental environment can lead to permanent changes in gene expression and DNA methylation, at least at 'metastable epialleles'. These are defined as regions of the genome that show a variable epigenetic state that is established early in development and maintained through subsequent cell divisions. However, the majority of the known genome does not behave in this manner. Here, we use the developmental origins of adult disease hypothesis to understand environmental epigenomics. Some challenges to studying how DNA methylation is influenced by the environment include identifying DNA methylation changes associated with an environmental exposure in tissues with a complex cellular composition and at genomic regions for which DNA methylation is dynamically regulated in a cell-type specific manner. We also offer a perspective of how emerging technologies may be useful for dissecting the functional contribution of exposure-associated epigenetic changes and highlight recent evidence that suggests that genomic regions that are absent from genome assemblies may be unappreciated hotspots for environmental modulation of the epigenetic state.

Sex Differences Across the Lifespan: A Focus on Cardiometabolism

Women's health and sex differences research remain understudied. In 2016, to address the topic of sex differences, the Center for Women' s Health Research (CWHR) at the University of Colorado (cwhr@ucdenver.edu) held its inaugural National Conference, "Sex Differences Across the Lifespan: A Focus on Metabolism" and published a report summarizing the presentations. Two years later, in 2018, CWHR organized the 2nd National Conference. The research presentations and discussions from the 2018 conference also addressed sex differences across the lifespan with a focus on cardiometabolism and expanded the focus by including circadian physiology and effects of sleep on cardiometabolic health. Over 100 participants, including basic scientists, clinicians, policymakers, advocacy group leaders, and federal agency leadership participated. The meeting proceedings reveal that although exciting advances in the area of sex differences have taken place, significant questions and gaps remain about women's health and sex differences in critical areas of health. Identifying these gaps and the subsequent research that will result may lead to important breakthroughs.

Fetal programming in dairy cows: Effect of heat stress on progeny fertility and associations with the hypothalamic-pituitary-adrenal axis functions

Ambient temperatures that result in body temperatures beyond those of the thermo-neutral zone for dairy cattle can lead to reduced reproductive efficiencies that have negative effects on economic and productive efficiencies of dairy farms. In addition, in pregnant cows, ambient temperature-induced heat stress leads to modifications in the epigenome of the developing embryo, which, in turn, could lead to phenotypic variations in the sexually mature animal and its offspring. In the mammalian response to stress, adrenocorticotropic hormone stimulates the synthesis and secretion of glucocorticoids, which may have detrimental effects on the hypothalamic-pituitary-gonadal axis and the female estrous cycle. The aim of this review is to describe the effects of ambient heat stress on the reproductive system of dairy cattle and its potential trans-generational effects. There are many heat stress occurrences in dairy cattle during a large portion of the year in many countries and there is an increase in incidence with the onset of global warming. These heat stress conditions make it possible that the embryo/fetus of cows may be affected when heat stress conditions prevail in ways that there is impaired fertility of the sexually mature cows that develop from these embryos/fetuses. This is the outcome because of molecular changes in ovarian glucocorticoid response caused by epigenetic modifications established during fetal development.

Epigenome- and Transcriptome-wide Changes in Muscle Stem Cells from Low Birth Weight Men

Background: Being born with low birth weight (LBW) is a risk factor for muscle insulin resistance and type 2 diabetes (T2D), which may be mediated by epigenetic mechanisms programmed by the intrauterine environment. Epigenetic mechanisms exert their prime effects in developing cells. We hypothesized that muscle insulin resistance in LBW subjects may be due to early differential epigenomic and transcriptomic alterations in their immature muscle progenitor cells.Results: Muscle progenitor cells were obtained from 23 healthy young adult men born at term with LBW, and 15 BMI-matched normal birth weight (NBW) controls. The cells were subsequently cultured and differentiated into myotubes. DNA and RNA were harvested before and after differentiation for genome-wide DNA methylation and RNA expression measurements.After correcting for multiple comparisons (q ≤ 0.05), 56 CpG sites were found to be significantly, differentially methylated in myoblasts from LBW compared with NBW men, of which the top five gene-annotated CpG sites (SKI, ARMCX3, NR5A2, NEUROG, ESRRG) previously have been associated to regulation of cholesterol, fatty acid and glucose metabolism and muscle development or hypertrophy. LBW men displayed markedly decreased myotube gene expression levels of the AMPK-repressing tyrosine kinase gene FYN and the histone deacetylase gene HDAC7. Silencing of FYN and HDAC7 was associated with impaired myotube formation, which for HDAC7 reduced muscle glucose uptake.Conclusions: The data provides evidence of impaired muscle development predisposing LBW individuals to T2D is linked to and potentially caused by distinct DNA methylation and transcriptional changes including down regulation of HDAC7 and FYN in their immature myoblast stem cells.

One-Carbon Metabolism and Nonalcoholic Fatty Liver Disease: The Crosstalk between Nutrients, Microbiota, and Genetics

The prevalence of nonalcoholic fatty liver disease (NAFLD) is increasing worldwide. Its etiology includes nutritional, genetic, and lifestyle factors. Several mechanisms may link one-carbon metabolism - the associated metabolic pathways of folate, methionine, and choline - to the onset of NAFLD. In this review, we attempted to assess how choline, folate, methionine, and betaine affect NAFLD development, mainly through their role in the secretion of very low-density lipoproteins (VLDL) from the liver. We also reviewed recent articles that have described the relation between microbiota metabolism and NAFLD progression. Moreover, we describe the effect of single-nucleotide polymorphisms (SNP) in genes related to one-carbon metabolism and disease prevalence. We additionally seek SNP identified by genome-wide associations that may increase the risk of this disease. Even though the evidence available is not entirely consistent, it seems that the concentrations of choline, methionine, folate, and betaine may affect the progression of NAFLD. Since there is no effective therapy for NAFLD, further investigations into the link between nutrition, gut microbiota, genetic factors, and NAFLD are still necessary, with a particular emphasis on methyl donors.

Nutrition, epigenetic markers and growth in preterm infants

Background and aim: Maternal diet and early nutrition of newborns may affect the phenotype later in adulthood. Susceptibility of epigenetic mechanisms to the nutritional environment is a critical element in neonatal development. Epigenetic mechanisms could be considered as a bridge between environmental stimuli and long lasting phenotype. IC2, a key region on 11p15, is involved in the control of growth and regulates CDKN1C, PHLDA2 and KCNQ1, growth inhibitor genes. Our aim was to investigate the relationship between epigenetic markers, nutrition and postnatal growth.Methods: We enrolled 37 newborns (gestational age at birth was <34 weeks) admitted to Neonatal Intensive Care Unit at University Hospital of Pisa.Results: We observed a relationship between reduced protein and lipid intake and IC2 hypermethylation (p = .003 and p = .001 respectively) and we also investigated the correlation between growth pattern and IC2 methylation.Conclusion: The reduced growth, in part related to a reduced intake of nutrients (lipids and proteins), might be due to IC2 hypermethylation, causing an increased expression of growth inhibitor genes. IC2 hypermethylation could be a marker of reduced infants' growth and may guides us to nutritional interventional strategies for a precocious prevention of extrauterine growth restriction (EUGR).

Influence of pre-pregnancy body mass index (p-BMI) and gestational weight gain (GWG) on DNA methylation and protein expression of obesogenic genes in umbilical vein

Understanding the regulatory mechanisms that affect obesogenic genes expression in newborns is essential for early prevention efforts, but they remain unclear. Our study aimed to explore whether the maternal p-BMI and GWG were associated with regulatory single-locus DNA methylation in selected obesogenic genes. For this purpose, DNA methylation was assayed by Methylation-Sensitive High Resolution Melting (MS-HRM) technique and Sanger allele-bisulfite sequencing in fifty samples of umbilical vein to evaluate glucosamine-6-phosphate deaminase 2 (GNPDA2), peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC1α), and leptin receptor (LEPR) genes. Correlations between DNA methylation levels and indicators of maternal nutritional status were carried out. Western blotting was used to evaluate protein expression in extracts of the same samples. Results indicated that GNPDA2 and PGC1α genes have the same level of DNA methylation in all samples; however, a differential DNA methylation of LEPR gene promoter was found, correlating it with GWG and this correlation is unaffected by maternal age or unhealthy habits. Furthermore, leptin receptor (Lep-Rb) was upregulated in samples that showed the lowest levels of DNA methylation. This study highlights the association between poor GWG and adjustments on obesogenic genes expression in newborn tissues with potential consequences for development of obesity in the future.

Effects of birth weight on body composition and overweight/obesity at early school age

OBJECTIVES

The prevalence of childhood obesity has increased substantially. We aimed to characterize the effect of birth weight on body composition and overweight/obesity at early school age.

STUDY DESIGN

A total of 1669 children with available birth records from a double-blind cluster-randomized controlled trial exploring micronutrient supplementation during pregnancy were included. Data regarding school-aged body composition, social-demographic factors and health behaviours were prospectively collected.

RESULT

s: The study population consisted of 1004 boys and 665 girls aged between 7 and 10 years. The prevalence of overweight/obesity (>85th age-sex-specific percentiles) was 7.4% for boys and 5.0% for girls. Generalized estimating equation models were used to account for the cluster nature of the data. A significant upward trend across quintiles of birth weight was observed for fat mass index (boys: P for trend 0.002; girls: P for trend <0.001), fat-free mass index (boys: P for trend <0.001; girls: P for trend <0.001), and percentage of body fat (boys: P for trend 0.003; girls: P for trend <0.001). A birth weight in the higher three quintiles could increase the risk ratios [RRs (95% CI) third quintile: 2.88, (1.13, 7.32); fourth quintile: 2.40, (0.87, 6.66); top quintile: 2.31, (0.92, 5.80)] of overweight/obesity at early school age compared with the RRs of the reference group (the second quintile of birth weight) among boys.

CONCLUSIONS

Higher birth weight could increase the risk of being overweight/obese among 7- to 10-year-old boys in rural western China. Sex differences in this association need to be considered when planning interventions.

RESEARCH REGISTRATION

This trial was registered at www.isrctn.com with the identifier ISRCTN08850194.

Maternal and Early Life Iron Intake and Risk of Childhood Type 1 Diabetes: A Danish Case-Cohort Study

BACKGROUND

Iron overload has been associated with diabetes. Studies on iron exposure during pregnancy and in early life and risk of childhood type 1 diabetes (T1D) are sparse. We investigated whether iron supplementation during pregnancy and early in life were associated with risk of childhood T1D.

METHODS

In a case-cohort design, we identified up to 257 children with T1D (prevalence 0.37%) from the Danish National Birth Cohort through linkage with the Danish Childhood Diabetes Register. The primary exposure was maternal pure iron supplementation (yes/no) during pregnancy as reported in interview two at 30 weeks of gestation (n = 68,497 with iron supplement data). We estimated hazard ratios (HRs) using weighted Cox regression adjusting for multiple confounders. We also examined if offspring supplementation during the first 18 months of life was associated with later risk of T1D.

RESULTS

Maternal iron supplementation was not associated with later risk of T1D in the offspring HR 1.05 (95% CI: 0.76⁻1.45). Offspring intake of iron droplets during the first 18 months of life was inversely associated with risk of T1D HR 0.74 (95% CI: 0.55⁻1.00) (ptrend = 0.03).

CONCLUSIONS

Our large-scale prospective study demonstrated no harmful effects of iron supplementation during pregnancy and in early life in regard to later risk of childhood T1D in the offspring.

Maternal vitamin D deficiency and developmental origins of health and disease (DOHaD)

Vitamin D is an essential nutrient that is metabolized in the body to generate an active metabolite (1,25(OH)2D) with hormone-like activity and highly diverse roles in cellular function. Vitamin D deficiency (VDD) is a prevalent but easily preventable nutritional disturbance. Emerging evidence demonstrates the importance of sufficient vitamin D concentrations during fetal life with deficiencies leading to long-term effects into adulthood. Here, we provide a detailed review and perspective of evidence for the role of maternal VDD in offspring long term health, particularly as it relates to Developmental Origins of Health and Disease (DOHaD). We focus on roles in neurobehavioral and cardiometabolic disorders in humans and highlight recent findings from zebrafish and rodent models that probe potential mechanisms linking early life VDD to later life health outcomes. Moreover, we explore evidence implicating epigenetic mechanisms as a mediator of this link. Gaps in our current understanding of how maternal VDD might result in deleterious offspring outcomes later in life are also addressed.

Folate and choline absorption and uptake: Their role in fetal development

SCOPE

In this review, we attempt to assess how choline and folate transporters affect fetal development. We focus on how the expression of these transporters in response to choline and folate intake affects transport effectiveness. We additionally describe allelic variants of the genes encoding these transporters and their phenotypic effects.

METHODS AND RESULTS

We made an extensive review of recent articles describing role of choline and folate - with particularly emphasize on their transporters - in fetal development. Folate and choline are necessary for the proper functioning of the cell and body. During pregnancy, the requirements of these nutrients increase because of elevated maternal demand and the rapid division of fetal cells. The concentrations of folate and choline in cells depend on food intake, the absorption of nutrients, and the cellular transport system, which is tissue-specific and developmentally regulated. Relatively few studies have investigated the role of choline transporters in fetal development.

CONCLUSIONS

In this review we show relations between functioning of folate and choline transporters and fetal development.

Diabetes in Pregnancy and MicroRNAs: Promises and Limitations in Their Clinical Application

Maternal diabetes is associated with an increased risk of complications for the mother and her offspring. The latter have an increased risk of foetal macrosomia, hypoglycaemia, respiratory distress syndrome, preterm delivery, malformations and mortality but also of life-long development of obesity and diabetes. Epigenetics have been proposed as an explanation for this long-term risk, and microRNAs (miRNAs) may play a role, both in short- and long-term outcomes. Gestation is associated with increasing maternal insulin resistance, as well as β-cell expansion, to account for the increased insulin needs and studies performed in pregnant rats support a role of miRNAs in this expansion. Furthermore, several miRNAs are involved in pancreatic embryonic development. On the other hand, maternal diabetes is associated with changes in miRNA both in maternal and in foetal tissues. This review aims to summarise the existing knowledge on miRNAs in gestational and pre-gestational diabetes, both as diagnostic biomarkers and as mechanistic players, in the development of gestational diabetes itself and also of short- and long-term complications for the mother and her offspring.

DNA methylation in cord blood as mediator of the association between prenatal arsenic exposure and gestational age

Prenatal arsenic exposure is associated with adverse birth outcomes and disease risk later in life, which could be mediated through epigenetic dysregulation. We evaluated the association between arsenic and gestational age (GA) that was mediated through DNA methylation (DNAm) using data from a Bangladeshi birth cohort. Arsenic exposure was measured in maternal drinking water at ≤16 weeks GA and maternal toenails collected ≤1 month postpartum. Cord blood DNAm was measured using Infinium HumanMethylation450 arrays (n = 44, discovery phase). Top loci identified in the discovery phase were then pyrosequenced in a second group (n = 569, validation phase). Structural equation models (SEM) evaluated the direct and indirect effects of arsenic and DNAm on GA. In the discovery phase, arsenic was associated with differential DNAm of 139 loci that were associated with GA (P < 1.10X10-6; |β regression|>0.10). Each doubling in water arsenic concentration decreased GA by 2 days, which was fully mediated through the main principal component of the top-ten CpGs (P < 0.001). In the validation phase, there were direct and indirect effects of miR214-3 and MCC DNAm on GA. In an adjusted SEM model, mediation of the association between arsenic and GA by miR124-3 was borderline significant (P = 0.061). This study therefore identified DNAm at specific loci in cord blood that mediated the effect of arsenic exposure on GA. Specifically, prenatal arsenic exposure was associated with lower methylation of miR124-3 that mediated the exposure-response of arsenic on GA. Future research should evaluate if these epigenetic changes are persistent and associated with disease risk.

Developmental programming of the female neuroendocrine system by steroids

Developmental programming refers to processes that occur during early life that may have long-term consequences, modulating adult health and disease. Complex diseases, such as diabetes, cancer and cardiovascular disease, have a high prevalence in different populations, are multifactorial, and may have a strong environmental component. The environment interacts with organisms, affecting their behaviour, morphology and physiology. This interaction may induce permanent or long-term changes, and organisms may be more susceptible to environmental factors during certain developmental stages, such as the prenatal and early postnatal periods. Several factors have been identified as responsible for inducing the reprogramming of various reproductive and nonreproductive tissues. Among them, both natural and synthetic steroids, such as endocrine disruptors, are known to have either detrimental or positive effects on organisms depending on the dose of exposure, stage of development and biological sexual background. The present review focuses on the action of steroids and endocrine disruptors as agents involved in developmental programming and on their modulation and effects on female neuroendocrine functions.

Caloric restriction can affect one-carbon metabolism during pregnancy in the rat: A transgenerational model

One-carbon metabolism is critical to pregnancy outcomes, because it determines the availability of nutrients involved in cell divisions and DNA methylation. The aim of this study was to analyze how 50% prenatal calorie restriction affected one-carbon metabolism in pregnant Wistar rats of the F0 to F2 generations. Mean choline (p < 0.001), betaine (p < 0.001), and S-adenosylmethionine (SAM) (p < 0.05) concentrations were respectively about 40%, 45%, and 20% lower in the F0_R (R - restricted diet) than in the F0_C (C - control diet). Homocysteine, S-adenosylhomocysteine (SAH), and trimethylamine oxide concentrations were unaffected. In the F1_R, the SAM-to-SAH ratio was 25% higher (p < 0.05) than in the F1_C. No differences between the C and R groups were observed in the F2 generation. The SAM concentrations in the F1_R were higher than in the F0_R and the F2_R (p < 0.01). The relative transcript levels of Mat1a, Bhmt, Cbs, Pemt, and Mthfr were only slightly affected by the diet, with changes of less than a factor of 2.0. Cbs activity in the F2_R was significantly higher than in the F2_C (p < 0.001). Food deprivation may affect one-carbon metabolism in pregnant rats, but it does not stimulate persistent metabolic changes that can be observed during the pregnancy of their progeny of the F1 or F2 generations.

Methylation-reprogrammed Wnt/β-catenin signalling mediated prenatal hypoxia-induced brain injury in foetal and offspring rats

Prenatal hypoxia (PH) is a common pregnancy complication, harmful to brain development. This study investigated whether and how PH affected Wnt pathway in the brain. Pregnant rats were exposed to hypoxia (10.5% O₂) or normoxia (21% O₂; Control). Foetal brain weight and body weight were decreased in the PH group, the ratio of brain weight to body weight was increased significantly. Prenatal hypoxia increased mRNA expression of Wnt3a, Wnt7a, Wnt7b and Fzd4, but not Lrp6. Activated β‐catenin protein and Fosl1 expression were also significantly up‐regulated. Increased Hif1a expression was found in the PH group associated with the higher Wnt signalling. Among 5 members of the Sfrp family, Sfrp4 was down‐regulated. In the methylation‐regulating genes, higher mRNA expressions of Dnmt1 and Dnmt3b were found in the PH group. Sodium bisulphite and sequencing revealed hyper‐methylation in the promoter region of Sfrp4 gene in the foetal brain, accounting for its decreased expression and contributing to the activation of the Wnt‐Catenin signalling. The study of PC12 cells treated with 5‐aza further approved that decreased methylation could result in the higher Sfrp4 expression. In the offspring hippocampus, protein levels of Hif1a and mRNA expression of Sfrp4 were unchanged, whereas Wnt signal pathway was inhibited. The data demonstrated that PH activated the Wnt pathway in the foetal brain, related to the hyper‐methylation of Sfrp4 as well as Hif1a signalling. Activated Wnt signalling might play acute protective roles to the foetal brain in response to hypoxia, also would result in disadvantageous influence on the offspring in long‐term.

Physiological adaptation of the growth-restricted fetus

The growth-restricted fetus in utero is exposed to a hostile environment and suffers undernutrition and hypoxia. To cope with the stress, the fetus changes its physiological functions. These adaptive changes aid intrauterine survival; however, they can lead to permanent functional and structural changes that can contribute to the development of serious chronic diseases later in life. Epigenetic mechanisms are an important part of the pathophysiological processes behind this "developmental origin of adult diseases." The dominant cardiovascular adaptive change is the redistribution of blood flow in hypoxic fetuses, with preferential supply of blood to the fetal brain, myocardium, and adrenal glands. The proportion of blood from the umbilical vein to the ductus venosus and foramen ovale increases, which increases the cardiac output of the left heart ventricle. The increased perfusion of fetal brain can be followed with Doppler ultrasound as increased diastolic velocities and decreased pulsatility index in the middle cerebral artery.

Interpregnancy interval, maternal age, and offspring's BMI and blood pressure at 7 years of age

Interpregnancy interval and maternal age are associated with birth outcomes. However, it is unknown regarding their long-term effects on child health. We aim to assess the associations between interpregnancy interval and offspring’s body mass index (BMI) and blood pressure (BP) at age of 7 years and to examine the role of maternal age in the associations. A secondary analysis was performed among 2604 mother-infant pairs in the prospective National Collaborative Perinatal Project, in which the children were followed up until 7 yrs of age. Interpregnancy interval was positively associated with offspring’s diastolic BP at 7 yrs (β = 0.053, 95% CI: 0.004–0.102) after adjusting for maternal and perinatal characteristics, feeding pattern, rapid weight gain in the first year of life, and current BMI z score and height z score. The inclusion of maternal age in the model did not change the effect size. Maternal age was independently associated with offspring’s BMI z score at 7 yrs (β = 0.014, 95% CI: 0.001–0.027). An interaction between interpregnancy interval and maternal age was present in the association with diastolic BP (P = 0.019), and the increasing maternal age aggravated the effects of long interpregnancy interval. Our finding suggests long interpregnancy interval is a risk factor for higher diastolic BP of the offspring. Increasing maternal age could amplify the impact. Our study challenges the current WHO recommendation for ideal interpregnancy interval, and we would suggest lowering the recommendation to <24 months and even shorter for women of advanced age.

Fetal programming of the metabolic syndrome

Prenatal development is currently recognized as a critical period in the etiology of human diseases. This is particularly so when an unfavorable environment interacts with a genetic predisposition. The fetal programming concept suggests that maternal nutritional imbalance and metabolic disturbances may have a persistent and intergenerational effect on the health of offspring and on the risk of diseases such as obesity, diabetes, and cardiovascular diseases.

Interaction between prenatal pesticide exposure and a common polymorphism in the PON1 gene on DNA methylation in genes associated with cardio-metabolic disease risk-an exploratory study

BACKGROUND

Prenatal environmental conditions may influence disease risk in later life. We previously found a gene-environment interaction between the paraoxonase 1 (PON1) Q192R genotype and prenatal pesticide exposure leading to an adverse cardio-metabolic risk profile at school age. However, the molecular mechanisms involved have not yet been resolved. It was hypothesized that epigenetics might be involved. The aim of the present study was therefore to investigate whether DNA methylation patterns in blood cells were related to prenatal pesticide exposure level, PON1 Q192R genotype, and associated metabolic effects observed in the children.

METHODS

Whole blood DNA methylation patterns in 48 children (6-11 years of age), whose mothers were occupationally unexposed or exposed to pesticides early in pregnancy, were determined by Illumina 450 K methylation arrays.

RESULTS

A specific methylation profile was observed in prenatally pesticide exposed children carrying the PON1 192R-allele. Differentially methylated genes were enriched in several neuroendocrine signaling pathways including dopamine-DARPP32 feedback (appetite, reward pathways), corticotrophin releasing hormone signaling, nNOS, neuregulin signaling, mTOR signaling, and type II diabetes mellitus signaling. Furthermore, we were able to identify possible candidate genes which mediated the associations between pesticide exposure and increased leptin level, body fat percentage, and difference in BMI Z score between birth and school age.

CONCLUSIONS

DNA methylation may be an underlying mechanism explaining an adverse cardio-metabolic health profile in children carrying the PON1 192R-allele and prenatally exposed to pesticides.

Does maternal mental well-being in pregnancy impact the early human epigenome?

There is considerable interest in the potential nongenetic transmission of a suite of mental health conditions across generations, with epigenetics emerging as a candidate mediator of such effects. This review summarizes findings from 22 studies measuring candidate gene DNA methylation and seven epigenome-wide association studies of offspring epigenetic profile in women with adverse mental wellbeing measures (stress, depression or anxiety) in pregnancy. Despite some compelling evidence to suggest an association, there is a lack of reproducible findings, potentially linked to a number of limitations to this research and the field more broadly. Large cohorts with well characterized exposures across pregnancy are now needed. There is exciting potential that epigenetics may help explain some of the link between maternal wellbeing and child health outcomes, thereby informing novel interventions, but future studies must address current limitations to advance translational knowledge in this area.

Sex-specific associations of birth weight with measures of adiposity in mid-to-late adulthood: the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil)

BACKGROUND/OBJECTIVES

To investigate sex-specific associations of birth weight with body mass index (BMI), waist circumference (WC) and waist-to-hip ratio (WHR) in mid-to-late adulthood.

SUBJECTS/METHODS

ELSA-Brasil is a multicenter cohort study of adults aged 35-74 years affiliated with universities or research institutions of six capital cities in Brazil. After exclusions, we investigated 11 636 participants. Socio-demographic factors and birth weight were obtained by interview. All anthropometry was directly measured at baseline. We categorized birth weight as low (⩽2.5 kg); normal (2.5-4 kg) and high (⩾4 kg). We performed analysis of covariance (ANCOVA) for continuous outcomes and ordinal logistic regression for categorical adiposity outcomes. We examined interaction on the multiplicative scale by sex and by race.

RESULTS

High birth weight uniformly predicted greater overall and central obesity in men and women. However, low (vs normal) birth weight, in ANCOVA models adjusted for participant age, family income, race, education, maternal education, and maternal and paternal history of diabetes, was associated with lower BMI, WC and WHR means for men, but not for women (Pinteraction=0.01, <0.0001 and <0.0001, respectively). In similarly adjusted ordinal logistic regression models, odds of obesity (odds ratio (OR)=0.65, 0.46-0.90) and of being in the high (vs low) tertile of WC (OR=0.66, 0.50-0.87) and of WHR (OR=0.79, 0.60-1.03) were lower for low (vs normal) birth weight men, but trended higher (BMI: OR=1.18, 0.92-1.51; WC: OR=1.21, 0.97-1.53; WHR: OR=1.44, 1.15-1.82) for low (vs normal) birth weight women.

CONCLUSIONS

In this Brazilian sample of middle-aged and elderly adults who have lived through a rapid nutritional transition, low birth weight was associated with adult adiposity in a sex-specific manner. In men, low birth weight was associated with lower overall and central adult adiposity, while in women low birth weight was generally associated with greater central adiposity.

In Utero Origins of Hypertension: Mechanisms and Targets for Therapy

The developmental origins of health and disease theory is based on evidence that a suboptimal environment during fetal and neonatal development can significantly impact the evolution of adult-onset disease. Abundant evidence exists that a compromised prenatal (and early postnatal) environment leads to an increased risk of hypertension later in life. Hypertension is a silent, chronic, and progressive disease defined by elevated blood pressure (>140/90 mmHg) and is strongly correlated with cardiovascular morbidity/mortality. The pathophysiological mechanisms, however, are complex and poorly understood, and hypertension continues to be one of the most resilient health problems in modern society. Research into the programming of hypertension has proposed pharmacological treatment strategies to reverse and/or prevent disease. In addition, modifications to the lifestyle of pregnant women might impart far-reaching benefits to the health of their children. As more information is discovered, more successful management of hypertension can be expected to follow; however, while pregnancy complications such as fetal growth restriction, preeclampsia, preterm birth, etc., continue to occur, their offspring will be at increased risk for hypertension. This article reviews the current knowledge surrounding the developmental origins of hypertension, with a focus on mechanistic pathways and targets for therapeutic and pharmacologic interventions.

Race-specific Association of Caesarean-Section Delivery with Body Size at Age 2 Years

OBJECTIVE

African American children are at higher risk of obesity than White children and African American women are more likely to undergo caesarean-section (CS) delivery than White women. CS is associated with childhood obesity; however, little is known whether this relationship varies by race. We examined if the association of CS with obesity at age 2 years varied by race.

DESIGN

Longitudinal birth cohort.

SETTING

Birth cohort conducted in a health care system in metropolitan Detroit, Michigan with follow-up at age 2 years.

PARTICIPANTS

639 birth cohort participants; 367 children (57.4%) were born to African American mothers and 230 (36.0%) children were born via CS.

MAIN OUTCOME MEASURES

Obesity defined as body mass index ≥95th percentile at age 2 years.

RESULTS

Slightly more children of African American (n=37; 10.1%) than non-African American mothers (n=18; 6.6%) were obese (P=.12). There was evidence of effect modification between race and delivery mode with obesity at age 2 years (interaction P=.020). In children of African American mothers, CS compared to vaginal birth was associated with a significantly higher odds of obesity (aOR=2.35 (95% CI: 1.16, 4.77), P=.017). In contrast, delivery mode was not associated with obesity at age 2 years in children of non-African American mothers (aOR=.47 (95% CI: .13, 1.71), P=.25).

CONCLUSIONS

There is evidence for a race-specific effect of CS on obesity at age 2 years; potential underlying mechanisms may be racial differences in the developing gut microbiome or in epigenetic programming. Future research is needed to determine if this racial difference persists into later childhood.

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

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

Developmental origins of health and disease: a paradigm for understanding disease cause and prevention

PURPOSE OF REVIEW

Although diseases may appear clinically throughout the lifespan, it is clear that many diseases have origins during development. Altered nutrition, as well as exposure to environmental chemicals, drugs, infections, or stress during specific times of development, can lead to functional changes in tissues, predisposing those tissues to diseases that manifest later in life. This review will focus on the role of altered nutrition and exposures to environmental chemicals during development in the role of disease and dysfunction.

RECENT FINDINGS

The effects of altered nutrition or exposure to environmental chemicals during development are likely because of altered programming of epigenetic marks, which persist across the lifespan. Indeed some changes can be transmitted to future generations.

SUMMARY

The evidence in support of the developmental origins of the health and disease paradigm is sufficiently robust and repeatable across species, including humans, to suggest a need for greater emphasis in the clinical area. As a result of these data, obesity, diabetes, cardiovascular morbidity, and neuropsychiatric diseases can all be considered pediatric diseases. Disease prevention must start with improved nutrition and reduced exposure to environmental chemicals during development.

Epigenetics and Metabolism

The molecular signatures of epigenetic regulation and chromatin architectures are fundamental to genetically determined biological processes. Covalent and post-translational chemical modification of the chromatin template can sensitize the genome to changing environmental conditions to establish diverse functional states. Recent interest and research focus surrounds the direct connections between metabolism and chromatin dynamics, which now represents an important conceptual challenge to explain many aspects of metabolic dysfunction. Several components of the epigenetic machinery require intermediates of cellular metabolism for enzymatic function. Furthermore, changes to intracellular metabolism can alter the expression of specific histone methyltransferases and acetyltransferases conferring widespread variations in epigenetic modification patterns. Specific epigenetic influences of dietary glucose and lipid consumption, as well as undernutrition, are observed across numerous organs and pathways associated with metabolism. Studies have started to define the chromatin-dependent mechanisms underlying persistent and pathophysiological changes induced by altered metabolism. Importantly, numerous recent studies demonstrate that gene regulation underlying phenotypic determinants of adult metabolic health is influenced by maternal and early postnatal diet. These emerging concepts open new perspectives to combat the rising global epidemic of metabolic disorders.

Mendelian randomization supports causality between maternal hyperglycemia and epigenetic regulation of leptin gene in newborns

Leptin is an adipokine that acts in the central nervous system and regulates energy balance. Animal models and human observational studies have suggested that leptin surge in the perinatal period has a critical role in programming long-term risk of obesity. In utero exposure to maternal hyperglycemia has been associated with increased risk of obesity later in life. Epigenetic mechanisms are suspected to be involved in fetal programming of long term metabolic diseases. We investigated whether DNA methylation levels near LEP locus mediate the relation between maternal glycemia and neonatal leptin levels using the 2-step epigenetic Mendelian randomization approach. We used data and samples from up to 485 mother-child dyads from Gen3G, a large prospective population-based cohort. First, we built a genetic risk score to capture maternal glycemia based on 10 known glycemic genetic variants (GRS10) and showed it was an adequate instrumental variable (β = 0.046 mmol/L of maternal fasting glucose per additional risk allele; SE = 0.007; P = 7.8 × 10(-11); N = 467). A higher GRS10 was associated with lower methylation levels at cg12083122 located near LEP (β = -0.072 unit per additional risk allele; SE = 0.04; P = 0.05; N = 166). Direction and effect size of association between the instrumental variable GRS10 and methylation at cg12083122 were consistent with the negative association we observed using measured maternal glycemia. Lower DNA methylation levels at cg12083122 were associated with higher cord blood leptin levels (β = -0.17 log of cord blood leptin per unit; SE = 0.07; P = 0.01; N = 170). Our study supports that maternal glycemia is part of causal pathways influencing offspring leptin epigenetic regulation.