Epigenetic profiling of ADHD symptoms trajectories: a prospective, methylome-wide study.

Attention-deficit/hyperactivity disorder (ADHD) is a prevalent developmental disorder, associated with a range of long-term impairments. Variation in DNA methylation, an epigenetic mechanism, is implicated in both neurobiological functioning and psychiatric health. However, the potential role of DNA methylation in ADHD symptoms is currently unclear. In this study, we examined data from the Avon Longitudinal Study of Parents and Children (ALSPAC)-specifically the subsample forming the Accessible Resource for Integrated Epigenomics Studies (ARIES)-that includes (1) peripheral measures of DNA methylation (Illumina 450k) at birth (n=817, 49% male) and age 7 (n=892, 50% male) and (2) trajectories of ADHD symptoms (7-15 years). We first employed a genome-wide analysis to test whether DNA methylation at birth associates with later ADHD trajectories; and then followed up at age 7 to investigate the stability of associations across early childhood. We found that DNA methylation at birth differentiated ADHD trajectories across multiple genomic locations, including probes annotated to SKI (involved in neural tube development), ZNF544 (previously implicated in ADHD), ST3GAL3 (linked to intellectual disability) and PEX2 (related to perixosomal processes). None of these probes maintained an association with ADHD trajectories at age 7. Findings lend novel insights into the epigenetic landscape of ADHD symptoms, highlighting the potential importance of DNA methylation variation in genes related to neurodevelopmental and peroxisomal processes that play a key role in the maturation and stability of cortical circuits.

Maternal depression symptoms, unhealthy diet and child emotional-behavioural dysregulation.

BACKGROUND: Maternal depression and unhealthy diet are well-known risk factors for adverse child emotional-behavioural outcomes, but their developmental relationships during the prenatal and postnatal periods are largely uncharted. This study sought to examine the inter-relationships between maternal depression symptoms and unhealthy diet (assessed during pregnancy and postnatal periods) in relation to child emotional-behavioural dysregulation (assessed at the ages of 2, 4 and 7 years). METHOD: In a large prospective birth cohort of 7814 mother-child pairs, path analysis was used to examine the independent and inter-related associations of maternal depression symptoms and unhealthy diet with child dysregulation. RESULTS: Higher prenatal maternal depression symptoms were prospectively associated with higher unhealthy diet, both during pregnancy and the postnatal period, which, in turn, was associated with higher child dysregulation up to the age of 7 years. In addition, during pregnancy, higher maternal depression symptoms and unhealthy diet were each independently associated with higher child dysregulation up to the age of 7 years. These results were robust to other prenatal, perinatal and postnatal confounders (such as parity and birth complications, poverty, maternal education, etc.). CONCLUSIONS: Maternal depression symptoms and unhealthy diet show important developmental associations, but are also independent risk factors for abnormal child development.

Environmental risk, Oxytocin Receptor Gene (OXTR) methylation and youth callous-unemotional traits: a 13-year longitudinal study.

Youth with high callous-unemotional traits (CU) are at risk for early-onset and persistent conduct problems. Research suggests that there may be different developmental pathways to CU (genetic/constitutional vs environmental), and that the absence or presence of co-occurring internalizing problems is a key marker. However, it is unclear whether such a distinction is valid. Intermediate phenotypes such as DNA methylation, an epigenetic modification regulating gene expression, may help to clarify etiological pathways. This is the first study to examine prospective inter-relationships between environmental risk (prenatal/postnatal) and DNA methylation (birth, age 7 and 9) in the prediction of CU (age 13), for youth low vs high in internalizing problems. We focused on DNA methylation in the vicinity of the oxytocin receptor (OXTR) gene as it has been previously implicated in CU. Participants were 84 youth with early-onset and persistent conduct problems drawn from the Avon Longitudinal Study of Parents and Children. For youth with low internalizing problems (46%), we found that (i) OXTR methylation at birth associated with higher CU (age 13) as well as decreased experience of victimization during childhood (evocative epigenetic-environment correlation; birth-age 7), (ii) higher prenatal parental risks (maternal psychopathology, criminal behaviors, substance use) associated with higher OXTR methylation at birth and (iii) OXTR methylation levels were more stable across time (birth-age 9). In contrast, for youth with high internalizing problems, CU were associated with prenatal risks of an interpersonal nature (that is, intimate partner violence, family conflict) but not OXTR methylation. Findings support the existence of distinct developmental pathways to CU.

The duration and timing of maternal depression as a moderator of the relationship between dependent interpersonal stress, contextual risk and early child dysregulation.

BACKGROUND: Risk factors that are associated with depression in the mother also negatively affect the child. This research sought to extend current knowledge by examining the duration and timing of maternal depression as a moderator of: (1) the impact of dependent interpersonal stress (DIS), such as partner conflict or low social support, and contextual risk (e.g. poverty) on child dysregulation; and (2) continuity in early child dysregulation. METHOD: Mother-child pairs (n = 12 152) who participated in the Avon Longitudinal Study of Parents and Children (ALSPAC) were examined between pregnancy and age 4 years. Data on maternal depression were collected five times between pregnancy and 33 months postpartum; on DIS and contextual risk three times between pregnancy and 33 months; and on child dysregulation at age 2 and 4 years. RESULTS: Longitudinal latent class analysis identified a class of mothers (10%) who evinced a chronic level of depression between pregnancy and 33 months. For chronic-depressed versus non-depressed mothers, the results indicate that: (1) DIS predicted higher child dysregulation if experienced between pregnancy and age 2; (2) contextual risk had a differential effect on child dysregulation if experienced during pregnancy; and (3) children had higher continuity in dysregulation between age 2 and age 4. CONCLUSIONS: Assessing the impact of the timing and duration of maternal depression, and different types of co-occurring risk factors, on child well-being is important. Maternal depression and associated DIS, in comparison to contextual risk, may be more responsive to intervention.

Intergenerational transmission of maltreatment and psychopathology: the role of antenatal depression.

BACKGROUND: Maternal experience of childhood maltreatment and maternal antenatal depression are both associated with offspring childhood maltreatment and offspring adjustment problems. We have investigated the relative impact of maternal childhood maltreatment and exposure to depression in utero on offspring maltreatment and psychopathology. METHOD: The sample included 125 families from the South London Child Development Study. A prospective longitudinal design was used. Data on maternal childhood maltreatment, maternal antenatal depression (36 weeks of pregnancy), offspring childhood maltreatment (age 11 years) and offspring adolescent antisocial behaviour and depression (ages 11 and 16 years) were obtained from parents and offspring through clinical interview. RESULTS: Mothers who experienced childhood maltreatment were significantly more likely to be depressed during pregnancy [odds ratio (OR) 10.00]. Offspring of mothers who experienced only childhood maltreatment or only antenatal depression were no more at risk of being maltreated or having psychopathology; however, offspring of mothers who experienced both maternal childhood maltreatment and antenatal depression were exposed to significantly greater levels of childhood maltreatment and exhibited significantly higher levels of adolescent antisocial behaviour compared with offspring not so exposed. Furthermore, maternal childhood maltreatment accounted for a significant proportion of the variance in offspring childhood maltreatment in only those offspring exposed to depression in utero. CONCLUSIONS: Maternal childhood maltreatment and maternal antenatal depression are highly associated. The co-occurrence of both insults significantly increases the risk of offspring adversity. The antenatal period is an optimum period to identify vulnerable women and to provide interventions.

Differences and similarities in the serotonergic diathesis for suicide attempts and mood disorders: a 22-year longitudinal gene-environment study.

To investigate similarities and differences in the serotonergic diathesis for mood disorders and suicide attempts, we conducted a study in a cohort followed longitudinally for 22 years. A total of 1255 members of this cohort, which is representative of the French-speaking population of Quebec, were investigated. Main outcome measures included (1) mood disorders (bipolar disorder and major depression) and suicide attempts by early adulthood; (2) odds ratios and probabilities associated with 143 single nucleotide polymorphisms in 11 serotonergic genes, acting directly or as moderators in gene-environment interactions with childhood sexual or childhood physical abuse (CPA), and in gene-gene interactions; (3) regression coefficients for putative endophenotypes for mood disorders (childhood anxiousness) and suicide attempts (childhood disruptiveness). Five genes showed significant adjusted effects (HTR2A, TPH1, HTR5A, SLC6A4 and HTR1A). Of these, HTR2A variation influenced both suicide attempts and mood disorders, although through different mechanisms. In suicide attempts, HTR2A variants (rs6561333, rs7997012 and rs1885884) were involved through interactions with histories of sexual and physical abuse whereas in mood disorders through one main effect (rs9316235). In terms of phenotype-specific contributions, TPH1 variation (rs10488683) was relevant only in the diathesis for suicide attempts. Three genes contributed exclusively to mood disorders, one through a main effect (HTR5A (rs1657268)) and two through gene-environment interactions with CPA (HTR1A (rs878567) and SLC6A4 (rs3794808)). Childhood anxiousness did not mediate the effects of HTR2A and HTR5A on mood disorders, nor did childhood disruptiveness mediate the effects of TPH1 on suicide attempts. Of the serotonergic genes implicated in mood disorders and suicidal behaviors, four exhibited phenotype-specific effects, suggesting that despite their high concordance and common genetic determinants, suicide attempts and mood disorders may also have partially independent etiological pathways. To identify where these pathways diverge, we need to understand the differential, phenotype-specific gene-environment interactions such as the ones observed in the present study, using suitably powered samples.

ADHD symptoms and body composition changes in childhood: a longitudinal study evaluating directionality of associations.

BACKGROUND: Attention-deficit/hyperactivity disorder (ADHD) is linked to increased risk of overweight/obesity among children and adults. Studies have also implicated obesity as a risk factor for ADHD. However, no studies have evaluated bidirectional, longitudinal associations between childhood fat mass and ADHD symptom severity. OBJECTIVES: We investigate bidirectional associations between ADHD symptoms and measures of body composition between ages 1.5 and 9. We further examine effects of specific eating patterns linked to ADHD on associations between symptom severity and body composition. METHODS: The study utilized data from children (N = 3903) participating in the Generation R cohort (Netherlands). Children were enrolled at birth and retained regardless of ADHD symptoms over time. Cross-lagged and change models examined bidirectional associations between body composition (body mass index/dual-energy X-ray absorptiometry) and ADHD symptoms at four time points in childhood. RESULTS: A child with a clinically concerning ADHD symptom z-score two standard deviations above the mean at age 6 would be expected to experience about 0.22 kg greater fat mass gain measured via dual-energy x-ray absorptiometry between ages 6 and 9, even if they displayed healthy eating patterns (95% CI: 0.11 - 0.28, p < 0.001). Conversely, fat mass at any age did not predict worse ADHD symptoms later. CONCLUSIONS: Beginning in early childhood, more ADHD symptoms predict higher fat mass at later ages. We did not find evidence of a reverse association. Based on these and prior findings, lifestyle counselling during treatment for children with a diagnosis of ADHD should be considered, even if they are diagnosed in early childhood and do not yet have a body mass index of clinical concern.

DNA methylation and substance-use risk: a prospective, genome-wide study spanning gestation to adolescence.

Epigenetic processes have been implicated in addiction; yet, it remains unclear whether these represent a risk factor and/or a consequence of substance use. Here, we believe we conducted the first genome-wide, longitudinal study to investigate whether DNA methylation patterns in early life prospectively associate with substance use in adolescence. The sample comprised of 244 youth (51% female) from the Avon Longitudinal Study of Parents and Children (ALSPAC), with repeated assessments of DNA methylation (Illumina 450k array; cord blood at birth, whole blood at age 7) and substance use (tobacco, alcohol and cannabis use; age 14-18). We found that, at birth, epigenetic variation across a tightly interconnected genetic network (n=65 loci; q<0.05) associated with greater levels of substance use during adolescence, as well as an earlier age of onset amongst users. Associations were specific to the neonatal period and not observed at age 7. Key annotated genes included PACSIN1, NEUROD4 and NTRK2, implicated in neurodevelopmental processes. Several of the identified loci were associated with known methylation quantitative trait loci, and consequently likely to be under significant genetic control. Collectively, these 65 loci were also found to partially mediate the effect of prenatal maternal tobacco smoking on adolescent substance use. Together, findings lend novel insights into epigenetic correlates of substance use, highlight birth as a potentially sensitive window of biological vulnerability and provide preliminary evidence of an indirect epigenetic pathway linking prenatal tobacco exposure and adolescent substance use.

The stimulation of glucose absorption and metabolism in rat jejunum by bradykinin: dependence on the composition of commercial diets.

Rats were maintained on one of two standard commercial chow diets, Oxoid modified 41B or Bantin & Kingman rat and mouse diet, which differ in that linoleic acid comprises 27% and 44% of their total fatty acid content, respectively: the effects of bradykinin on the absorption, transmural transport and metabolism of glucose (5 mM) were then measured by the perfusion of isolated jejunal loops in vitro. With intestine from rats fed the Oxoid diet, bradykinin (100 nM in the serosal medium) caused significant increases in the rates of glucose absorption (34%, P less than 0.01) and lactate production (69%, P less than 0.01). These bradykinin-stimulated rates were the same, within experimental error, as those observed in the absence of bradykinin with intestine taken from rats fed the Bantin & Kingman diet and on which bradykinin had no effect. It is concluded that feeding rats with different commercial brands of apparently similar laboratory chow diets may result in significantly altered steady-states of glucose homeostasis in rat small intestine and in quite different sensitivities of glucose homeostasis to bradykinin. The possibility is considered that the differences in absorption might result in part from differences in the proportion of linoleic acid, which is known to enhance glucose absorption.

The effect of vanadate on glucose transport and metabolism in rat small intestine.

The effect of sodium orthovanadate on the absorption, transmural transport and metabolism of glucose was studied by perfusion of isolated loops of rat jejunum in vitro. The presence of 1 mM vanadate in the serosal medium diminished absorption from 539 +/- 19 (n = 12) to 246 +/- 19 (P less than 0.001) mumol/h per g dry weight and transmural transport from 333 +/- 17 to 14 +/- 19 (P less than 0.001) mumol/h per g dry weight, whereas glucose utilisation was unaffected. The rate of release of lactate into the serosal medium was also diminished from 168 +/- 14 to 75 +/- 5 mumol/h per g dry weight (P less than 0.001). The observed rates were linear with respect to time and vanadate was effective within 5 min. In contrast, the rate of release of lactate into the luminal perfusate was strongly enhanced. Moreover, the progress curve showed a positive transient with an apparent lag time of 18.0 +/- 0.3 min, during which the rate increased to a value 9.2-times that of the control. Under the final steady-state conditions, the ratio of mucosal to serosal lactate production was 5.2 +/- 0.2 compared with 0.25 +/- 0.06 for the control, so that the effect of vanadate was to reverse the vectorial disposition of lactate. The concentration dependence of the effect of vanadate on absorption and metabolism was similar to that observed for the inhibition by vanadate of Na+/K+-ATPase activity in mucosal homogenates. The results are discussed in terms of the dissipation of transmembrane Na+ gradients as a result of the inhibition of the Na+/K+-ATPase.

Effect of nordihydroguaiaretic acid on glucose absorption, metabolism and (Na(+)+K+)-ATPase activity in rat jejunum.

A regulatory role of endogenously synthesized eicosanoids on the absorption, transmural transport and metabolism of glucose in perfused, isolated loops of jejunum in vitro was investigated using the lipoxygenase/cyclooxygenase inhibitor, nordihydroguaiaretic acid (NDGA). NDGA diminished glucose absorption over the range 100-500 microM: maximal inhibition at 500 microM NDGA was 52 +/- 9 and 64 +/- 9% (mean +/- SE, P < 0.001) for jejuna from fed rats and rats maintained on glucose water for 48 hr, respectively. In each instance, transmural transport was effectively abolished. The vectorial disposition of lactate release was also changed such that the ratio of luminal to serosal production was increased from 0.19 +/- 0.02 to 1.72 +/- 0.12 (P < 0.001) in fed rats, indicating inhibition of the Na+ pump. NDGA inhibited (Na(+)+K+)-ATPase activity in whole mucosal homogenates with a concentration dependence similar to that observed for glucose absorption. However, NDGA also inhibited Mg(2+)-ATPase activity in whole homogenates and purified rabbit skeletal muscle phosphofructokinase under the same conditions. The results are discussed in terms of the dissipation of the transmembrane Na+ gradient via direct inhibition of the (Na(+)+K+)-ATPase by NDGA. Inhibition of the ATPase precludes the use of NDGA as a suitable drug with which to investigate the role of endogenously synthesized eicosanoids in the regulation of intestinal function.