Parenting, Socioeconomic Status Risk, and Later Young Adult Health: Exploration of Opposing Indirect Effects via DNA Methylation

Epigenome-wide association study of incident type 2 diabetes in Black and White participants from the Atherosclerosis Risk in Communities Study

AIMS/HYPOTHESIS

DNA methylation studies of incident type 2 diabetes in US populations are limited and to our knowledge none include individuals of African descent. We aimed to fill this gap by identifying methylation sites (CpG sites) and regions likely influencing the development of type 2 diabetes using data from Black and White individuals from the USA.

METHODS

We prospectively followed 2091 Black and 1029 White individuals without type 2 diabetes from the Atherosclerosis Risk in Communities study over a median follow-up period of 17 years, and performed an epigenome-wide association analysis of blood-based methylation levels with incident type 2 diabetes using Cox regression. We assessed whether significant CpG sites were associated with incident type 2 diabetes independently of BMI or fasting glucose at baseline. We estimated variation in incident type 2 diabetes accounted for by the major non-genetic risk factors and the significant CpG sites. We also examined groups of methylation sites that were differentially methylated. We performed replication of previously discovered CpG sites associated with prevalent and/or incident type 2 diabetes. All analyses were adjusted for batch effects, cell-type proportions and relevant confounders.

RESULTS

At an epigenome-wide threshold (10-7), we detected seven novel diabetes-associated CpG sites, of which the sites at MICOS10 (cg05380846: HR 0.89, p=8.4 × 10-12), ZNF2 (cg01585592: HR 0.88, p=1.6 × 10-9), JPH3 (cg16696007: HR 0.87, p=7.8 × 10-9) and GPX6 (cg02793507: HR 0.85, p=2.7 × 10-8; cg00647063: HR 1.20, p=2.5 × 10-8) were identified in Black adults; chr17q25 (cg16865890: HR 0.8, p=6.9 × 10-8) in White adults; and chr11p15 (cg13738793: HR 1.11, p=7.7 × 10-8) in the meta-analysed group. The JPH3 and GPX6 sites remained epigenome-wide significant on adjustment for BMI, while only the JPH3 site retained significance after adjusting for fasting glucose. We replicated known type 2 diabetes-associated CpG sites, including cg19693031 at TXNIP, cg00574958 at CPT1A, cg16567056 at PLCB2, cg11024682 at SREBF1, cg08857797 at VPS25 and cg06500161 at ABCG1, three of which were replicated in Black adults at the epigenome-wide threshold and all of which had directionally consistent effects. We observed a modest increase in type 2 diabetes variance explained by the significantly associated CpG sites over and above traditional type 2 diabetes risk factors and fasting glucose (26.2% vs 30.5% in Black adults; 36.9% vs 39.4% in White adults). At the Šidák-corrected significance threshold of 5%, our differentially methylated region (DMR) analyses revealed several clusters of significant CpG sites, including a DMR consisting of a previously discovered CpG site at ADCY7 (pBlack=1.8 × 10-4, pWhite=3.6 × 10-3, pAll=1.6 × 10-9) and a DMR consisting of the promoter region of TP63 (pBlack=7.4 × 10-4, pWhite=3.9 × 10-3, pAll=1.4 × 10-5), which were differentially methylated across all racial and ethnic groups.

CONCLUSIONS/INTERPRETATION

This study illustrates improved discovery of CpG sites and regions by leveraging both individual CpG site analysis and DMR analyses in an unexplored population. Our findings include genes linked to diabetes in experimental studies (e.g. GPX6, JPH3 and TP63). The JPH3 and GPX6 sites were likely associated with incident type 2 diabetes independently of BMI. All the CpG sites except that at JPH3 were likely consequences of elevated glucose. Replication in African-descent individuals of CpG sites previously discovered mostly in individuals of European descent indicates that some of these methylation-type 2 diabetes associations are robust across racial and ethnic groups. This study is a first step towards understanding the influence of methylation on the incidence of type 2 diabetes and its disparity in two major racial and ethnic groups in the USA. It paves the way for future studies to investigate causal relationships between type 2 diabetes and the CpG sites and potentially elucidate molecular targets for intervention.

Epigenome-wide association study of incident type 2 diabetes in Black and White participants from the Atherosclerosis Risk in Communities Study

DNA methylation studies of incident type 2 diabetes in US populations are limited, and to our knowledge none included individuals of African descent living in the US. We performed an epigenome-wide association analysis of blood-based methylation levels at CpG sites with incident type 2 diabetes using Cox regression in 2,091 Black and 1,029 White individuals from the Atherosclerosis Risk in Communities study. At an epigenome-wide significance threshold of 10-7, we detected 7 novel diabetes-associated CpG sites in C1orf151 (cg05380846: HR= 0.89, p = 8.4 × 10-12), ZNF2 (cg01585592: HR= 0.88, p = 1.6 × 10-9), JPH3 (cg16696007: HR= 0.87, p = 7.8 × 10-9), GPX6 (cg02793507: HR= 0.85, p = 2.7 × 10-8 and cg00647063: HR= 1.20, p = 2.5 × 10-8), chr17q25 (cg16865890: HR= 0.8, p = 6.9 × 10-8), and chr11p15 (cg13738793: HR= 1.11, p = 7.7 × 10-8). The CpG sites at C1orf151, ZNF2, JPH3 and GPX6, were identified in Black adults, chr17q25 was identified in White adults, and chr11p15 was identified upon meta-analyzing the two groups. The CpG sites at JPH3 and GPX6 were likely associated with incident type 2 diabetes independent of BMI. All the CpG sites, except at JPH3, were likely consequences of elevated glucose at baseline. We additionally replicated known type 2 diabetes-associated CpG sites including cg19693031 at TXNIP, cg00574958 at CPT1A, cg16567056 at PLBC2, cg11024682 at SREBF1, cg08857797 at VPS25, and cg06500161 at ABCG1, 3 of which were replicated in Black adults at the epigenome-wide threshold. We observed modest increase in type 2 diabetes variance explained upon addition of the significantly associated CpG sites to a Cox model that included traditional type 2 diabetes risk factors and fasting glucose (increase from 26.2% to 30.5% in Black adults; increase from 36.9% to 39.4% in White adults). We examined if groups of proximal CpG sites were associated with incident type 2 diabetes using a gene-region specific and a gene-region agnostic differentially methylated region (DMR) analysis. Our DMR analyses revealed several clusters of significant CpG sites, including a DMR consisting of a previously discovered CpG site at ADCY7 and promoter regions of TP63 which were differentially methylated across all race groups. This study illustrates improved discovery of CpG sites/regions by leveraging both individual CpG site and DMR analyses in an unexplored population. Our findings include genes linked to diabetes in experimental studies (e.g., GPX6, JPH3, and TP63), and future gene-specific methylation studies could elucidate the link between genes, environment, and methylation in the pathogenesis of type 2 diabetes.

DNA methylation signatures as biomarkers of socioeconomic position

This review article provides a framework for the use of deoxyribonucleic acid (DNA) methylation (DNAm) biomarkers to study the biological embedding of socioeconomic position (SEP) and summarizes the latest developments in the area. It presents the emerging literature showing associations between individual- and neighborhood-level SEP exposures and DNAm across the life course. In contrast to questionnaire-based methods of assessing SEP, we suggest that DNAm biomarkers may offer an accessible metric to study questions about SEP and health outcomes, acting as a personal dosimeter of exposure. However, further work remains in standardizing SEP measures across studies and evaluating consistency across domains, tissue types, and time periods. Meta-analyses of epigenetic associations with SEP are offered as one approach to confirm the replication of DNAm loci across studies. The development of DNAm biomarkers of SEP would provide a method for examining its impact on health outcomes in a more robust way, increasing the rigor of epidemiological studies.

School Disengagement Predicts Accelerated Aging among Black American Youth: Mediation by Psychological Maladjustment and Moderation by Supportive Parenting

Early experiences of school disengagement may serve as a warning sign for later young adult adjustment difficulties and eventually contribute to accelerated aging among Black American youth. At the same time, supportive parenting may play a protective role. Using longitudinal data from the Family and Community Health Study (FACHS), we examined psychological maladjustment (comprising depression, lack of self-regulation, and low self-esteem) as a mediator of the relationship between school disengagement and accelerated aging. We also examined the effect of supportive parenting in buffering the impact of school disengagement on adulthood outcomes by controlling for covariates. Hypotheses were examined in a sample of 386 (Mean age = 28.68; Females = 62.7%; Males = 37.3%) Black American youth who were followed into young adulthood. Path modeling was used to test hypothesized relationships. We found school disengagement, i.e., problems with school attendance, performance, and engagement, reported across ages 10-18, predicted psychological maladjustment, which, in turn, predicted accelerated aging at age 29. We also found a buffering effect for supportive parenting. No significant gender difference in the indirect effect or buffering effect was found. This study highlights the potential importance of greater attention to school disengagement to identify and potentially influence long-term health trajectories and adult outcomes for Black American youth.

Childhood Neighborhood Disadvantage, Parenting, and Adult Health

INTRODUCTION

Growing up in disadvantaged neighborhoods is associated with poor adult health indicators. Consistent and supportive parenting plays a key role in life-long health, but it is not known whether positive parenting can mitigate the relationship between neighborhood adversity and poor health. This study examines parenting as a moderator of the links between childhood neighborhood characteristics and adult health indicators.

METHODS

A sample of 305 individuals (61% female; 82% African American, 18% Caucasian) were assessed in childhood (T1; age 11 years; 2003‒2004) and adulthood (T2; age 27 years; 2018‒2021). At T1, neighborhood poverty was derived from census data; neighborhood disorder was reported by parents. Children reported on parental harsh discipline, inconsistent discipline, and parental nurturance. At T2, health outcomes included BMI, serum cortisol and C-reactive protein (CRP), and salivary DNA methylation index related to CRP. Regression models predicted T2 health outcomes from T1 neighborhood and parenting variables and their interactions, adjusting for clustering and confounders. Data were analyzed in 2021.

RESULTS

Neighborhood poverty was associated with lower cortisol, whereas neighborhood disorder was linked with CRP‒related DNA methylation. Multiple interactions between neighborhood and parenting variables emerged, indicating that adverse neighborhood conditions were only related to poor adult health when combined with inconsistent discipline and low parental nurturance. By contrast, warm and supportive parenting, consistent discipline, and to a lesser extent harsh discipline buffered children from poor health outcomes associated with neighborhood disadvantage.

CONCLUSIONS

Interventions enhancing consistent and nurturing parenting may help to reduce the long-term associations of neighborhood disadvantage with poor health.

Evaluating the challenges and reproducibility of studies investigating DNA methylation signatures of psychological stress

Psychological stress can increase the risk of a wide range of negative health outcomes. Studies have been completed to determine if DNA methylation changes occur in the human brain because of stress and are associated with long-term effects and disease, but results have been inconsistent. Human candidate gene studies (150) and epigenome-wide association studies (67) were systematically evaluated to assess how DNA methylation is impacted by stress during the prenatal period, early childhood and adulthood. The association between DNA methylation of NR3C1 exon 1F and child maltreatment and early life adversity was well demonstrated, but other genes did not exhibit a clear association. The reproducibility of individual CpG sites in epigenome-wide association studies was also poor. However, biological pathways, including stress response, brain development and immunity, have been consistently identified across different stressors throughout the life span. Future studies would benefit from the increased sample size, longitudinal design, standardized methodology, optimal quality control, and improved statistical procedures.

Early Childhood Socioeconomic Status and Cognitive and Adaptive Outcomes at the Transition to Adulthood: The Mediating Role of Gray Matter Development Across Five Scan Waves

BACKGROUND

Early low socioeconomic status (SES) is associated with poor outcomes in childhood, many of which endure into adulthood. It is critical to determine how early low SES relates to trajectories of brain development and whether these mediate relationships to poor outcomes. We use data from a unique 17-year longitudinal study with five waves of structural brain imaging to prospectively examine relationships between preschool SES and cognitive, social, academic, and psychiatric outcomes in early adulthood.

METHODS

Children (n = 216, 50% female, 47.2% non-White) were recruited from a study of early onset depression and followed approximately annually. Family income-to-needs ratios (SES) were assessed when children were ages 3 to 5 years. Volumes of cortical gray and white matter and subcortical gray matter collected across five scan waves were processed using the FreeSurfer Longitudinal pipeline. When youth were ages 16+ years, cognitive function was assessed using the NIH Toolbox, and psychiatric diagnoses, high-risk behaviors, educational function, and social function were assessed using clinician administered and parent/youth report measures.

RESULTS

Lower preschool SES related to worse cognitive, high-risk, educational, and social outcomes (|standardized B| = 0.20-0.31, p values < .003). Lower SES was associated with overall lower cortical (standardized B = 0.12, p < .0001) and subcortical gray matter (standardized B = 0.17, p < .0001) volumes, as well as a shallower slope of subcortical gray matter growth over time (standardized B = 0.04, p = .012). Subcortical gray matter mediated the relationship of preschool SES to cognition and high-risk behaviors.

CONCLUSIONS

These novel longitudinal data underscore the key role of brain development in understanding the long-lasting relations of early low SES to outcomes in children.

Associations between indicators of socioeconomic position and DNA methylation: a scoping review

BACKGROUND

Socioeconomic position (SEP) is a major determinant of health across the life course. Yet, little is known about the biological mechanisms explaining this relationship. One possibility widely pursued in the scientific literature is that SEP becomes biologically embedded through epigenetic processes such as DNA methylation (DNAm), wherein the socioeconomic environment causes no alteration in the DNA sequence but modifies gene activity in ways that shape health.

METHODS

To understand the evidence supporting a potential SEP-DNAm link, we performed a scoping review of published empirical findings on the association between SEP assessed from prenatal development to adulthood and DNAm measured across the life course, with an emphasis on exploring how the developmental timing, duration, and type of SEP exposure influenced DNAm.

RESULTS

Across the 37 identified studies, we found that: (1) SEP-related DNAm signatures varied across the timing, duration, and type of SEP indicator; (2) however, longitudinal studies examining repeated SEP and DNAm measures are generally lacking; and (3) prior studies are conceptually and methodologically diverse, limiting the interpretability of findings across studies with respect to these three SEP features.

CONCLUSIONS

Given the complex relationship between SEP and DNAm across the lifespan, these findings underscore the importance of analyzing SEP features, including timing, duration, and type. To guide future research, we highlight additional research gaps and propose four recommendations to further unravel the relationship between SEP and DNAm.

We Know Even More Things: A Decade Review of Parenting Research

In this article, we highlight the important ideas that have emerged from research on parenting and adolescent development over the past decade. Beginning with research on authoritative parenting, we examine key elements of this parenting style and its influence across diverse contexts and populations. We turn our attention to four topics that have generated much research in the past decade: (1) how parenting contributes to adolescent peer and romantic relationships; (2) the impact of parenting on adolescent brain development; (3) gene-environment interactions in parenting research; and (4) parents' involvement in adolescents' social media use. We discuss contemporary challenges and ways parents can promote healthy development. We consider the integration of research, practice, and policy that best supports parents and adolescents.

The Impact of Harsh Parenting on the Development of Obesity in Adulthood: An Examination of Epigenetic/Gene Expression Mediators Among African American Youth

Objective: We examined the association of prospectively assessed harsh parenting during adolescence with body mass index (BMI) in young adulthood among African American youth. We also assessed the role of methylation of obesity-related genes and gene expression markers of obesity as mediators of this association, providing a pathway for the biological embedding of early harsh parenting and its long-term impact on young adult health.

Methods: Hypotheses were tested with a sample of 362 African American youth for whom harsh parenting was assessed at ages 10–15, BMI was assessed at age 10 and 29, and both DNA methylation (DNAm) and gene expression of obesity genes were assessed at age 29. Mediational analyses were conducted using bootstrap methods to generate confidence intervals.

Results: Controlling for genetic risk for obesity and health-related covariates, harsh parenting across childhood and adolescence was associated with change in BMI (Δ BMI) from ages 10–29. In addition, we found that the indirect effect of harsh parenting on Δ BMI was mediated through obesity-related DNAm and accounted for 45.3% of the total effect. Further, obesity-related DNAm mediated the effect of harsh parenting on gene expression of obesity-related genes (GEOG), and GEOG, in turn, mediated the impact of obesity-related DNAm on ΔBMI. This pathway accounted for 3.4% of the total effect. There were no gender differences in the magnitude of this indirect effect.

Conclusions: The results suggest that alterations in methylation and gene expression mediate the impact of harsh parenting on change in obesity from childhood to young adulthood, illustrating plausible biological pathways from harsh parenting to obesity and bolstering the hypothesis that harsh parenting in childhood and adolescence can become biologically embedded and contribute to obesity.

Methylation of FKBP5 is associated with accelerated DNA methylation ageing and cardiometabolic risk: replication in young-adult and middle-aged Black Americans

Methylation of FKBP5 is involved in the regulation of the stress response and is influenced by early stress exposure. Two CpG sites, cg20813374 and cg00130530, have been identified as potential reporters of early stress. We examined whether FKBP5 methylation was associated with accelerated DNA methylation ageing and indirectly predicted poorer cardiovascular health among both young adult and middle-aged Black Americans. Four hundred and forty-nine young adults, with a mean age of 28.67 and N = 469 middle-age parents and their current partners with a mean age of 57.21, provided self-reports, biometric assessments, and blood draws. Methylation values were obtained using the Illumina Epic Array. Cardiometabolic risk was calculated by summing the standardized log-transformed scores for the body mass index, mean arterial blood pressure, and HbA1c. We also used a more standard index of risk, the Framingham 10-year cardiometabolic risk index, as an alternative measure of cardiometabolic risk. To measure accelerated ageing, four widely used indices of accelerated, DNA methylation-based ageing were used controlling sex, age, other variation in FKBP5, and cell-type. Exposure to community danger was associated with demethylation of FKBP5. FKBP5 methylation was significantly associated with accelerated ageing for both young-adult and middle-aged samples, with significant indirect effects from FKBP5 methylation to cardiometabolic risk through accelerated ageing for both. Early exposure to danger may influence FKBP5 methylation. In turn, FKBP5 methylation may help explain intrinsic accelerated ageing and elevated cardiometabolic risk in adulthood for Black Americans.

How are social determinants of health integrated into epigenetic research? A systematic review

OBJECTIVE

We systematically review the literature on social epigenetics, examining how empirical research to date has conceptualized and operationalized social determinants of health (SDOH).

METHODS

Using comprehensive search procedures, we identified studies that consider the impact of SDOH on DNA methylation (DNAm), the most common measure of epigenetic change in research on human adult populations. We analyzed the studies to determine: 1) which populations and environments have been investigated in the literature; 2) how SDOH are defined and operationalized; 3) which SDOH have been linked to DNAm; and 4) what lessons from the SDOH literature can be better integrated into future studies exploring the social determinants of health and epigenetic outcomes.

RESULTS

We identified 67 studies, with 39 to 8397 participants. The SDOH most commonly considered were early life socioeconomic exposures and early life trauma or mental health. Our review highlights four broad challenges: a) high dependence on convenience sampling, b) limited racial/ethnic, and geographic diversity in sampling frames, c) overreliance on individual sociodemographic characteristics as proxies for broader stratification processes, and d) a focus on downstream social determinants of health and individualized experiences with social stressors.

CONCLUSIONS

Future social epigenetics research should prioritize larger, more diverse and representative population-based samples and employ the SDOH framework to better inform the conceptualization of research questions and interpretation of findings. In particular, the simplified depiction of race/ethnicity, gender, and socioeconomic status as individual-level characteristics should be updated with an explicit acknowledgement that these characteristics are more accurately interpreted as cues used by society to differentiate subpopulations. Social epigenetics research can then more clearly elucidate the biological consequences of these social exposures for patterns of gene expression, subsequent disease etiology, and health inequities.

Interactions between race/ethnicity, poverty status, and pregnancy cardio-metabolic diseases in prediction of postpartum cardio-metabolic health

Background: Prenatal health disparities exist for African Americans and low socioeconomic status (SES) individuals when compared to non-Hispanic Whites and people of higher SES, particularly in cardio-metabolic diseases. Furthermore, having had a pregnancy-specific cardio-metabolic disease, e.g. preeclampsia, increases risk for future cardio-metabolic disease. Although these factors (race, SES and pregnancy cardio-metabolic disease) are interrelated, studies have rarely considered their combined effect on postpartum cardio-metabolic risk. The purpose of this study was to assess whether SES, race/ethnicity, and prenatal cardio-metabolic disease interact in the prediction of postpartum cardio-metabolic risk. Methods: A sample of 1,753 low-income women of African American, Latina, non-Hispanic White race/ethnicity was recruited after a birth in 5 US sites. Household income was used to categorize poverty status as Poor (< Federal Poverty Level; FPL), near poor (100-200% FPL), or low/middle income (> 200% FPL). Three prenatal cardio-metabolic disease diagnoses (preeclampsia, gestational hypertension, gestational diabetes) were identified from medical records. Four biomarkers (mean arterial pressure, glycosylated haemoglobin, total cholesterol:HDL ratio, and waist-hip ratio) were collected at 6 and 12 months postpartum, and combined into an average postpartum cardio-metabolic risk index. Maternal age, pre-pregnancy body mass index, parity, health behaviors and employment status were covariates. Results: Analyses revealed interactions of race/ethnicity, poverty status, and prenatal cardio-metabolic diseases in the prediction of postpartum cardio-metabolic risk. African American women had higher postpartum cardio-metabolic risk, which was exacerbated following a prenatal cardio-metabolic disease. Low/middle income African American women had higher cardio-metabolic risk compared to poor African American, and all Latina and White women. Conclusions: African American women, and especially those who experienced pregnancy complications, emerged as vulnerable, and greater household income did not appear to confer protection against worse postpartum cardio-metabolic risk for this group. These results highlight the complex interplay between socioeconomic status and race/ethnicity with respect to understanding health disparities.

Scars of childhood socioeconomic stress: A systematic review

Childhood socioeconomic position (SEP) is associated with the development of adult psychological outcomes, with DNA methylation (DNAm) as a mechanism to potentially explain these changes. We present the first systematic review synthesising the literature investigating childhood SEP and DNAm. Thirty-two publications were included. Seventeen studies focused on candidate genes, typically focusing on genes implicated with the stress response and/or development of psychiatric conditions. These studies typically investigated different regions of the genes, which revealed inconsistent results. Six studies calculated epigenetic age, with a small number revealing an elevated significant association with childhood SEP. Epigenome-wide studies revealed altered patterns of DNAm which varied between the nine studies. This research area is emerging and demonstrated great variance in findings with no clear patterns identified across studies. Multiple methodological shortcomings are identified, including at the phenotypic level where construct validity of childhood SEP is highly inconsistent, with studies using a wide range of measures. Larger cohorts will be required with international collaborations to strengthen this research area.

A multi-omics approach to investigate the inflammatory response to life course socioeconomic position

Aim: Inflammation represents a potential pathway through which socioeconomic position (SEP) is biologically embedded. Materials & methods: We analyzed inflammatory biomarkers in response to life course SEP by integrating multi-omics DNA-methylation, gene expression and protein level in 178 European Prospective Investigation into Cancer and Nutrition-Italy participants. Results & conclusion: We identified 61 potential cis acting CpG loci whose methylation levels were associated with gene expression at a Bonferroni correction. We examined the relationships between life course SEP and these 61 cis-acting regulatory methylation sites individually and jointly using several scores. Less-advantaged SEP participants exhibit, later in life, a lower inflammatory methylome score, suggesting an overall increased expression of the corresponding inflammatory genes or proteins, supporting the hypothesis that SEP impacts adult physiology through inflammation.

Epigenome-wide DNA methylation in placentas from preterm infants: association with maternal socioeconomic status

This study evaluated the hypothesis that prenatal maternal socioeconomic status (SES) adversity is associated with DNA methylation in the placenta. SES adversity was defined by the presence of, as well as a summative count of, four factors: less than college education, single marital status, food and nutritional service assistance, and public health insurance. Epigenome-wide DNA methylation was assessed using the Illumina EPIC array in 426 placentas from a sample of infants born < 28 weeks of gestation from the Extremely Low Gestational Age Newborn cohort. Associations between SES adversity and DNA methylation were assessed with robust linear regressions adjusted for covariates and controlled the false discovery rate at < 10%. We also examined whether such associations were sex specific. Indicators of SES adversity were associated with differential methylation at 33 CpG sites. Of the 33 identified CpG sites, 19 (57.6%) displayed increased methylation, and 14 (42.4%) displayed decreased methylation in association with at least one of the SES adversity factors. Sex differences were observed in DNA methylation associated with summative SES score; in which placentas derived from female pregnancies showed more robust differential CpG methylation than placentas from male pregnancies. Maternal SES adversity was associated with differential methylation of genes with key role in gene transcription and placental function, potentially altering immunity and stress response. Further investigation is needed to evaluate the role of epigenetic differences in mediating the association between maternal socioeconomic status during pregnancy and later life health outcomes in children.

Socioeconomic Status, Preeclampsia Risk and Gestational Length in Black and White Women

BACKGROUND

Higher socioeconomic status (SES) has less impact on cardio-metabolic disease and preterm birth risk among Black women compared to White women, an effect called "diminishing returns." No studies have tested whether this also occurs for pregnancy cardio-metabolic disease, specifically preeclampsia, or whether preeclampsia risk could account for race-by-SES disparities in birth timing.

METHODS

A sample of 718,604 Black and White women was drawn from a population-based California cohort of singleton births. Education, public health insurance status, gestational length, and preeclampsia diagnosis were extracted from a State-maintained birth cohort database. Age, prenatal care, diabetes diagnosis, smoking during pregnancy, and pre-pregnancy body mass index were covariates.

RESULTS

In logistic regression models predicting preeclampsia risk, the race-by-SES interaction (for both education and insurance status) was significant. White women were at lower risk for preeclampsia, and higher SES further reduced risk. Black women were at higher risk for preeclampsia, and SES did not attenuate risk. In pathway analyses predicting gestational length, an indirect effect of the race-by-SES interaction was observed. Among White women, higher SES predicted lower preeclampsia risk, which in turn predicted longer gestation. The same was not observed for Black women.

CONCLUSIONS

Compared to White women, Black women had increased preeclampsia risk. Higher SES attenuated risk for preeclampsia among White women, but not for Black women. Similarly, higher SES indirectly predicted longer gestational length via reduced preeclampsia risk among White women, but not for Black women. These findings are consistent with diminishing returns of higher SES for Black women with respect to preeclampsia.

Sensitive Periods for the Effect of Childhood Adversity on DNA Methylation: Results From a Prospective, Longitudinal Study

BACKGROUND

Exposure to early-life adversity is known to predict DNA methylation (DNAm) patterns that may be related to psychiatric risk. However, few studies have investigated whether adversity has time-dependent effects based on the age at exposure.

METHODS

Using a two-stage structured life course modeling approach, we tested the hypothesis that there are sensitive periods when adversity induces greater DNAm changes. We tested this hypothesis in relation to two alternatives: an accumulation hypothesis, in which the effect of adversity increases with the number of occasions exposed, regardless of timing; and a recency model, in which the effect of adversity is stronger for more proximal events. Data came from the Accessible Resource for Integrated Epigenomic Studies, a subsample of mother-child pairs from the Avon Longitudinal Study of Parents and Children (n = 691-774).

RESULTS

After covariate adjustment and multiple testing correction, we identified 38 CpG sites that were differentially methylated at 7 years of age following exposure to adversity. Most loci (n = 35) were predicted by the timing of adversity, namely exposures before 3 years of age. Neither the accumulation nor recency of the adversity explained considerable variability in DNAm. A standard epigenome-wide association study of lifetime exposure (vs. no exposure) failed to detect these associations.

CONCLUSIONS

The developmental timing of adversity explains more variability in DNAm than the accumulation or recency of exposure. Very early childhood appears to be a sensitive period when exposure to adversity predicts differential DNAm patterns. Classification of individuals as exposed versus unexposed to early-life adversity may dilute observed effects.

Biological embedding of neighborhood disadvantage and collective efficacy: Influences on chronic illness via accelerated cardiometabolic age

The present study extends prior research on the link between neighborhood disadvantage and chronic illness by testing an integrated model in which neighborhood characteristics exert effects on health conditions through accelerated cardiometabolic aging. Hypotheses were tested using a sample of 408 African Americans from the Family and Community Health Study. Using four waves of data spanning young adulthood (ages 18-29), we first found durable effects of neighborhood disadvantage on accelerated cardiometabolic aging and chronic illness. Then, we used marginal structural modeling to adjust for potential neighborhood selection effects. As expected, accelerated cardiometabolic aging was the biopsychosocial mechanism that mediated much of the association between neighborhood disadvantage and chronic illness. This finding provides additional support for the view that neighborhood disadvantage can influence morbidity and mortality by creating social contexts that becomes biologically embedded. Perceived neighborhood collective efficacy served to buffer the relationship between neighborhood disadvantage and biological aging, identifying neighborhood-level resilience factor. Overall, our results indicate that neighborhood context serves as a fundamental cause of weathering and accelerated biological aging. Residing in a disadvantaged neighborhood increases biological wear and tear that ultimately leads to onset of chronic illness, but access to perceived collective efficacy buffers the impact of these neighborhood effects. From an intervention standpoint, identifying such an integrated model may help inform future health-promoting interventions.

Associations between body size, nutrition and socioeconomic position in early life and the epigenome: A systematic review

Background

Body size, nutrition and socioeconomic position (SEP) in early life have been associated with a wide range of long-term health effects. Epigenetics is one possible mechanism through which these early life exposures can impact later life health. We conducted a systematic review examining the observational evidence for the impact of body size, nutrition and SEP in early life on the epigenome in humans.

Methods

This systematic review is registered with the PROSPERO database (registration number: CRD42016050193). Three datasets were simultaneously searched using Ovid and the resulting studies were evaluated by at least two independent reviewers. Studies measuring epigenetic markers either at the same time as, or after, the early life exposure and have a measure of body size, nutrition or SEP in early life (up to 12 years), written in English and from a community-dwelling participants were included.

Results

We identified 90 eligible studies. Seventeen of these papers examined more than one early life exposure of interest. Fifty six papers examined body size, 37 nutrition and 17 SEP. All of the included papers examined DNA methylation (DNAm) as the epigenetic marker. Overall there was no strong evidence for a consistent association between these early life variables in DNAm which may be due to the heterogeneous study designs, data collection methods and statistical analyses.

Conclusions

Despite these inconclusive results, the hypothesis that the early life environment can impact DNAm, potentially persisting into adult life, was supported by some studies and warrants further investigation. We provide recommendations for future studies.

When inflammation and depression go together: The longitudinal effects of parent-child relationships

Parent-child relationships have long-term effects on health, particularly later inflammation and depression. We hypothesized that these effects would be mediated by later romantic partner relationships and elevated stressors in young adulthood, helping promote chronic, low grade, inflammation as well as depressive symptoms, and driving their covariation. It has been proposed recently that youth experiencing harsher parenting may also develop a stronger association between inflammation and depressive symptoms in adulthood and altered effects of stressors on outcomes. In the current investigation, we test these ideas using an 18-year longitudinal study of N = 413 African American youth that provides assessment of the parent-child relationship (at age 10), pro-inflammatory cytokine profile and depressive symptoms (at age 28), and potential mediators in early young adulthood (assessed at ages 21 and 24). As predicted, the effect of harsher parent-child relationships (age 10) on pro-inflammatory state and increased depressive symptoms at age 28 were fully mediated through young adult stress and romantic partner relationships. In addition, beyond these mediated effects, parent-child relationships at age 10 moderated the concurrent association between inflammation and depressive symptoms, as well as the prospective association between romantic partner relationships and inflammation, and resulted in substantially different patterns of indirect effects from young adult mediators to outcomes. The results support theorizing that the association of depression and inflammation in young adulthood is conditional on earlier parenting, and suggest incorporating this perspective into models predicting long-term health outcomes.

Household Financial Assets Inequity and Health Disparities Among Young Adults: Evidence from the National Longitudinal Study of Adolescent to Adult Health

INTRODUCTION

Research has established a strong relationship between financial resources and health outcomes. Yet, little is known about the effects of assets disparities on health outcomes, especially during the critical period when adolescents transition to adults. Methods: Using data from the National Longitudinal Study of Adolescent to Adult Health (n = 10,861), this study investigated the relationships between three household total assets value groups (low, moderate, and high assets) and three net worth groups (negative, neutral, and positive) on young adults' general health, obese, and depression.

RESULTS

Both assets and debts were related to young adults' health status, young adults with more assets and positive net worth have higher probability to report a better level of both general health and depression. Young adult's obesity was found to be associated with net worth but not with assets.

CONCLUSIONS AND IMPLICATIONS

Our work connects health promotion with poverty alleviation to address the challenge of health disparity. A better understanding of different forms of financial resources (e.g., income, assets, and debt) and their dynamic relationships with health outcomes will contribute to developing effective asset-based interventions for promoting health status. Particularly, current policy and practice should consider the importance of resolving and clearing debt.

C.7van MeursJoyce8IsaacsAaron9JansenRick10FrankeLude11BoomsmaDorret I.12PoolRené12van DongenJenny12HottengaJouke J.12van GreevenbroekMarleen MJ13StehouwerCoen D. A.13van der KallenCarla J. H.13SchalkwijkCasper G.13WijmengaCisca11FrankeLude11ZhernakovaSasha11TigchelaarEttje F.11SlagboomP. Eline6BeekmanMarian6DeelenJoris6van HeemstDiana14VeldinkJan H.15van den BergLeonard H.15van DuijnCornelia M.9HofmanBert A.16IsaacsAaron9UitterlindenAndré G.8van MeursJoyce8JhamaiP. Mila8VerbiestMichael8SuchimanH. Eka D.6VerkerkMarijn8van der BreggenRuud6van RooijJeroen8LakenbergNico6MeiHailiang17van ItersonMaarten6van GalenMichiel7BotJan18ZhernakovaDasha V.11JansenRick10van’t HofPeter17DeelenPatrick11NoorenIrene18’t HoenPeter A. C.7HeijmansBastiaan T.6MoedMatthijs6FrankeLude11VermaatMartijn7ZhernakovaDasha V.11LuijkRené6BonderMarc Jan11van ItersonMaarten6DeelenPatrick11van DijkFreerk19van GalenMichiel7ArindrartoWibowo17KielbasaSzymon M.20SwertzMorris A.19van ZwetErik W.20JansenRick10HoenPeter-Bram’t7HeijmansBastiaan T.6. DNA methylation signatures of educational attainment

Educational attainment is a key behavioural measure in studies of cognitive and physical health, and socioeconomic status. We measured DNA methylation at 410,746 CpGs (N = 4152) and identified 58 CpGs associated with educational attainment at loci characterized by pleiotropic functions shared with neuronal, immune and developmental processes. Associations overlapped with those for smoking behaviour, but remained after accounting for smoking at many CpGs: Effect sizes were on average 28% smaller and genome-wide significant at 11 CpGs after adjusting for smoking and were 62% smaller in never smokers. We examined sources and biological implications of education-related methylation differences, demonstrating correlations with maternal prenatal folate, smoking and air pollution signatures, and associations with gene expression in cis, dynamic methylation in foetal brain, and correlations between blood and brain. Our findings show that the methylome of lower-educated people resembles that of smokers beyond effects of their own smoking behaviour and shows traces of various other exposures.

From forensic epigenetics to forensic epigenomics: broadening DNA investigative intelligence

Human genetic variation is a major resource in forensics, but does not allow all forensically relevant questions to be answered. Some questions may instead be addressable via epigenomics, as the epigenome acts as an interphase between the fixed genome and the dynamic environment. We envision future forensic applications of DNA methylation analysis that will broaden DNA-based forensic intelligence. Together with genetic prediction of appearance and biogeographic ancestry, epigenomic lifestyle prediction is expected to increase the ability of police to find unknown perpetrators of crime who are not identifiable using current forensic DNA profiling.

An epigenome-wide association study meta-analysis of educational attainment

The epigenome is associated with biological factors, such as disease status, and environmental factors, such as smoking, alcohol consumption and body mass index. Although there is a widespread perception that environmental influences on the epigenome are pervasive and profound, there has been little evidence to date in humans with respect to environmental factors that are biologically distal. Here we provide evidence on the associations between epigenetic modifications-in our case, CpG methylation-and educational attainment (EA), a biologically distal environmental factor that is arguably among the most important life-shaping experiences for individuals. Specifically, we report the results of an epigenome-wide association study meta-analysis of EA based on data from 27 cohort studies with a total of 10 767 individuals. We find nine CpG probes significantly associated with EA. However, robustness analyses show that all nine probes have previously been found to be associated with smoking. Only two associations remain when we perform a sensitivity analysis in the subset of never-smokers, and these two probes are known to be strongly associated with maternal smoking during pregnancy, and thus their association with EA could be due to correlation between EA and maternal smoking. Moreover, the effect sizes of the associations with EA are far smaller than the known associations with the biologically proximal environmental factors alcohol consumption, body mass index, smoking and maternal smoking during pregnancy. Follow-up analyses that combine the effects of many probes also point to small methylation associations with EA that are highly correlated with the combined effects of smoking. If our findings regarding EA can be generalized to other biologically distal environmental factors, then they cast doubt on the hypothesis that such factors have large effects on the epigenome.

Why is parental lifespan linked to children's chances of reaching a high age? A transgenerational hypothesis

Purpose

Transgenerational determinants of longevity are poorly understood. We used data from four linked generations (G0, G1, G2 and G3) of the Uppsala Birth Cohort Multigeneration Study to address this issue.

Methods

Mortality in G1 (N = 9565) was followed from 1961–2015 and analysed in relation to tertiles of their parents’ (G0) age-at-death using Cox regression. Parental social class and marital status were adjusted for in the analyses, as was G1’s birth order and adult social class. For an almost entirely deceased segment of G1 (n = 1149), born 1915–1917, we compared exact age-at-death with G0 parents’ age-at-death. Finally, we explored ‘resilience’ as a potentially important mechanism for intergenerational transmission of longevity, using conscript information from psychological interviews of G2 and G3 men.

Results

G0 men’s and women’s ages-at-death were independently associated with G1 midlife and old age mortality. This association was robust and minimally reduced when G0 and G1 social class were adjusted for. We observed an increased lifespan in all social groups. Median difference in age-at-death for sons compared to fathers was + 3.9 years, and + 6.9 years for daughters compared to mothers.

Parents’ and maternal grandmother’s longevity were associated with resilience in subsequent generations. Resilience scores of G2 men were also associated with those of their G3 sons and with their own mortality in midlife.

Conclusions

The chance of reaching a high age is transmitted from parents to children in a modest, but robust way. Longevity inheritance is paralleled by the inheritance of individual resilience. Individual resilience, we propose, develops in the first part of life as a response to adversity and early experience in general. This gives rise to a transgenerational pathway, distinct from social class trajectories. A theory of longevity inheritance should bring together previous thinking around general susceptibility, frailty and resilience with new insights from epigenetics and social epidemiology.

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Parents’ ages-at-death predict children's midlife and old-age mortality.

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We speculate that these results reflect early programming of resilience.

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Male resilience, measured at age 18, predicts mortality between ages 50 and 65.

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Resilience is transmitted across generations, from fathers to sons.

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Male descendants to long-lived parents are somewhat more resilient than their peers.

Early stress, parental motivation, and reproductive decision-making: applications of life history theory to parental behavior

This review focuses on the impact of parental behavior on child development, as interpreted from an evolutionary-developmental perspective. We employ psychosocial acceleration theory to reinterpret the effects of variation in parental investment and involvement on child development, arguing that these effects have been structured by natural selection to match the developing child to current and expected future environments. Over time, an individual's development, physiology, and behavior are organized in a coordinated manner (as instantiated in 'life history strategies') that facilitates survival and reproductive success under different conditions. We review evidence to suggest that parental behavior (1) is strategic and contingent on environmental opportunities and constraints and (2) influences child life history strategies across behavioral, cognitive, and physiological domains.

The epigenetic impacts of social stress: how does social adversity become biologically embedded?

Epigenetic mechanisms are implicated in the processes through which social stressors erode health in humans and other animals. Here I review progress in elucidating the biological pathways underlying the social gradient in health, with particular emphasis on how behavioral stresses influence epigenomic variation linked to health. The evidence that epigenetic changes are involved in embedding of social status-linked chronic stress is reviewed in the context of current knowledge about behavior within animal dominance hierarchies and the impacts of social position on behaviors that affect health. The roles of epigenetic mechanisms in responses to trauma and the evidence for their involvement in intergenerational transmission of the biological impacts of traumatic stress are also considered. Taken together, the emerging insights have important implications for development of strategies to improve societal health and well-being.

Smoking in young adulthood among African Americans: Interconnected effects of supportive parenting in early adolescence, proinflammatory epitype, and young adult stress

We examined two potentially interacting, connected pathways by which parental supportiveness during early adolescence (ages 1-13) may come to be associated with later African American young adult smoking. The first pathway is between parental supportiveness and young adult stress (age 19), with stress, in turn, predicting increased smoking at age 20. The second pathway is between supportive parenting and tumor necrosis factor (TNF) gene methylation (i.e., TNFm), a proinflammatory epitype, with low levels indicating greater inflammatory potential and forecasting increased risk for smoking in response to young adult stress. In a sample of 382 African American youth residing in rural Georgia, followed from early adolescence (age 10-11) to young adulthood (age 20), supportive parenting indirectly predicted smoking via associations with young adult stress, IE = -0.071, 95% confidence interval [-0.132, -0.010]. In addition, supportive parenting was associated with TNFm measured at age 20 (r = .177, p = .001). Further, lower TNFm was associated with a significantly steeper slope (b = 0.583, p = .003) of increased smoking in response to young adult stress compared to those with higher TNFm (b = 0.155, p = .291), indicating an indirect, amplifying role for supportive parenting via TNFm. The results suggest that supportive parenting in early adolescence may play a role in understanding the emergence of smoking in young adulthood.

Exploring genetic moderators and epigenetic mediators of contextual and family effects: From Gene × Environment to epigenetics

In the current manuscript, we provide an overview of a research program at the University of Georgia's Center for Family Research designed to expand upon rapid and ongoing developments in the fields of genetics and epigenetics. By placing those developments in the context of translational research on family and community determinants of health and well-being among rural African Americans, we hope to identify novel, modifiable environments and biological processes. In the first section of the article, we review our earlier work on genotypic variation effects on the association between family context and mental and physical health outcomes as well as differential responses to family-based intervention. We then transition to discuss our more recent research on the association of family and community environments with epigenetic processes. In this second section of the article, we begin by briefly reviewing terminology and basic considerations before describing evidence that early environments may influence epigenetic motifs that potentially serve as mediators of long-term effects of early family and community environments on longer term health outcomes. We also provide evidence that genotype may sometimes influence epigenetic outcomes. Finally, we describe our recent efforts to use genome-wide characterization of epigenetic patterns to better understand the biological impact of protective parenting on long-term shifts in inflammatory processes and its potential implications for young adult health. As will be clear, research on epigenetics as a mediator of the connections between family/community processes and a range of health outcomes is still in its infancy, but the potential to develop important insights regarding mechanisms linking modifiable environments to biological processes and long-term health outcomes already is coming into view.

Methylation of the oxytocin receptor gene mediates the effect of adversity on negative schemas and depression

Building upon various lines of research, we posited that methylation of the oxytocin receptor gene (OXTR) would mediate the effect of adult adversity on increased commitment to negative schemas and in turn the development of depression. We tested our model using structural equation modeling and longitudinal data from a sample of 100 middle-aged, African American women. The results provided strong support for the model. Analysis of the 12 CpG sites available for the promoter region of the OXTR gene identified four factors. One of these factors was related to the study variables, whereas the others were not. This factor mediated the effect of adult adversity on schemas relating to pessimism and distrust, and these schemas, in turn, mediated the impact of OXTR methylation on depression. All indirect effects were statistically significant, and they remained significant after controlling for childhood trauma, age, romantic relationship status, individual differences in cell types, and average level of genome-wide methylation. These finding suggest that epigenetic regulation of the oxytocin system may be a mechanism whereby the negative cognitions central to depression become biologically embedded.

Introduction to the Special Section on Epigenetics

Epigenetics provides the opportunity to revolutionize our understanding of the role of genetics and the environment in explaining human behavior, although the use of epigenetics to study human behavior is just beginning. In this introduction, the authors present the basics of epigenetics in a way that is designed to make this exciting field accessible to a wide readership. The authors describe the history of human behavioral epigenetic research in the context of other disciplines and graphically illustrate the burgeoning of research in the application of epigenetic methods and principles to the study of human behavior. The role of epigenetics in normal embryonic development and the influence of biological and environmental factors altering behavior through epigenetic mechanisms and developmental programming are discussed. Some basic approaches to the study of epigenetics are reviewed. The authors conclude with a discussion of challenges and opportunities, including intervention, as the field of human behavioral epigenetics continue to grow.

Higher levels of protective parenting are associated with better young adult health: exploration of mediation through epigenetic influences on pro-inflammatory processes

The current investigation was designed to examine the association of parenting during late childhood and early adolescence, a time of rapid physical development, with biological propensity for inflammation. Based on life course theory, it was hypothesized that parenting during this period of rapid growth and development would be associated with biological outcomes and self-reported health assessed in young adulthood. It was expected that association of parenting with health would be mediated either by effects on methylation of a key inflammatory factor, Tumor necrosis factor (TNF), or else by association with a pro-inflammatory shift in the distribution of mononuclear blood cells. Supporting expectations, in a sample of 398 African American youth residing in rural Georgia, followed from age 11 to age 19, parenting at ages 11-13 was associated with youth reports of better health at age 19. We found that parenting was associated with changes in TNF methylation as well as with changes in cell-type composition. However, whereas methylation of TNF was a significant mediator of the association of parenting with young adult health, variation in mononuclear white blood cell types was not a significant mediator of the association of parenting with young adult health. The current research suggests the potential value of examining the health-related effects of parenting in late childhood and early adolescence. Further examination of protection against pro-inflammatory tendencies conferred by parenting appears warranted.