Differential methylation of the oxytocin receptor gene in patients with anorexia nervosa: a pilot study

Potential mechanisms underlying the association between feeding and eating disorders and autism

There is a reliable association between autism and Feeding and Eating Disorders. Concerningly, where these two conditions co-occur, clinical outcomes of Feeding and Eating Disorders are significantly worse, and treatment less effective, than when the Feeding and Eating Disorders occur in neurotypical individuals. Problematically, the reason for the association between autism and Feeding and Eating Disorders is poorly understood, which constrains advances in clinical care. This paper outlines several possible mechanisms that may underlie the observed association and suggests ways in which they may be empirically tested. Mechanisms are split into those producing an artefactual association, and those reflecting a genuine link between conditions. Artefactual associations may be due to conceptual overlap in both diagnostic criteria and measurement, Feeding and Eating Disorders causing transient autistic traits, or the association being non-specific in nature. A genuine association between autism and Feeding and Eating Disorders may be due to common causal factors, autism directly or indirectly causing Feeding and Eating Disorders, and Feeding and Eating Disorders being a female manifestation of autism.

Epigenetic alterations in patients with anorexia nervosa-a systematic review

Anorexia nervosa (AN) is a complex metabolic and psychological disorder that is influenced by both heritable genetic components and environmental factors. Exposure to various environmental influences can lead to epigenetically induced changes in gene expression. Epigenetic research in AN is still in its infancy, and studies to date are limited in determining clear, valid links to disease onset and progression are limited. Therefore, the aim of this systematic review was to compile and critically evaluate the available results of epigenetic studies specifically in AN and to provide recommendations for future studies. In accordance with the PRISMA guidelines, a systematic literature search was performed in three different databases (PubMed, Embase, and Web of Science) through May 2023. Twenty-three original papers or conference abstracts on epigenetic studies in AN were collected. Epigenome-wide association studies (EWASs), which analyze DNA methylation across the genome in patients with AN and identify potential disease-relevant changes in promoter/regulatory regions of genes, are the most promising for future research. To date, five EWASs on AN have been published, suggesting a potential reversibility of malnutrition-induced epigenetic changes once patients recover. Hence, determining differential DNA methylation levels could serve as a biomarker for disease status or early diagnosis and might be involved in disease progression or chronification. For future research, EWASs with a larger sample size, longitudinal study design and uniform methods should be performed to contribute to the understanding of the pathophysiology of AN, the development of individual interventions and a better prognosis for affected patients.

Inclusion of the severe and enduring anorexia nervosa phenotype in genetics research: a scoping review

BACKGROUND

Anorexia nervosa has one of the highest mortality rates of all mental illnesses. For those who survive, less than 70% fully recover, with many going on to develop a more severe and enduring phenotype. Research now suggests that genetics plays a role in the development and persistence of anorexia nervosa. Inclusion of participants with more severe and enduring illness in genetics studies of anorexia nervosa is critical.

OBJECTIVE

The primary goal of this review was to assess the inclusion of participants meeting the criteria for the severe enduring anorexia nervosa phenotype in genetics research by (1) identifying the most widely used defining criteria for severe enduring anorexia nervosa and (2) performing a review of the genetics literature to assess the inclusion of participants meeting the identified criteria.

METHODS

Searches of the genetics literature from 2012 to 2023 were performed in the PubMed, PsycINFO, and Web of Science databases. Publications were selected per the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR). The criteria used to define the severe and enduring anorexia nervosa phenotype were derived by how often they were used in the literature since 2017. The publications identified through the literature search were then assessed for inclusion of participants meeting these criteria.

RESULTS

most prevalent criteria used to define severe enduring anorexia nervosa in the literature were an illness duration of ≥ 7 years, lack of positive response to at least two previous evidence-based treatments, a body mass index meeting the Diagnostic and Statistical Manual of Mental Disorders-5 for extreme anorexia nervosa, and an assessment of psychological and/or behavioral severity indicating a significant impact on quality of life. There was a lack of consistent identification and inclusion of those meeting the criteria for severe enduring anorexia nervosa in the genetics literature.

DISCUSSION

This lack of consistent identification and inclusion of patients with severe enduring anorexia nervosa in genetics research has the potential to hamper the isolation of risk loci and the development of new, more effective treatment options for patients with anorexia nervosa.

Omega-3 as an adjuvant in the treatment eating and psychological symptoms in patients with anorexia nervosa: a systematic review and meta-analyses

BACKGROUND

This study was carried out to assess the effects of omega-3 supplementation as an adjunct treatment for eating and psychological symptoms in patients with anorexia nervosa.

METHODS

We conducted a systematic review of the literature using the terms 'anorexia nervosa' AND 'Fatty Acids, Omega-3'. Five randomised controlled trials with a total of 144 participants, published between 2003 and 2022, were included.

RESULTS

The effects of supplementation of omega-3 on anxiety were standardised mean difference (SMD) 0.79, 95% confidence interval (CI) -0.08 to 1.66; p = 0.08; I² = 3%; two studies, 33 participants; moderate quality of evidence. For depression, the supplementation of omega-3 was SMD: 0.22, 95% CI: -0.50 to 0.93; p = 0.18; I² = 45%; two studies, 33 participants; moderate quality of evidence. For obsessive-compulsive disorder, the supplementation of omega-3 was SMD: -0.22, 95% CI: -0.70 to 2.25; p = 0.36; I² = 0%; three studies, 32 participants; low quality of evidence.

CONCLUSION

This research showed that regardless of dose, time or, if associated with other components, the use of omega-3 supplementations as an adjuvant treatment showed no evidence of effect in eating and psychological symptoms in patients with anorexia nervosa.

Genetic and epigenetic signatures associated with plasma oxytocin levels in children and adolescents with autism spectrum disorder

Oxytocin (OT), the brain's most abundant neuropeptide, plays an important role in social salience and motivation. Clinical trials of the efficacy of OT in autism spectrum disorder (ASD) have reported mixed results due in part to ASD's complex etiology. We investigated whether genetic and epigenetic variation contribute to variable endogenous OT levels that modulate sensitivity to OT therapy. To carry out this analysis, we integrated genome-wide profiles of DNA-methylation, transcriptional activity, and genetic variation with plasma OT levels in 290 participants with ASD enrolled in a randomized controlled trial of OT. Our analysis identified genetic variants with novel association with plasma OT, several of which reside in known ASD risk genes. We also show subtle but statistically significant association of plasma OT levels with peripheral transcriptional activity and DNA-methylation profiles across several annotated gene sets. These findings broaden our understanding of the effects of the peripheral oxytocin system and provide novel genetic candidates for future studies to decode the complex etiology of ASD and its interaction with OT signaling and OT-based interventions. LAY SUMMARY: Oxytocin (OT) is an abundant chemical produced by neurons that plays an important role in social interaction and motivation. We investigated whether genetic and epigenetic factors contribute to variable OT levels in the blood. To this, we integrated genetic, gene expression, and non-DNA regulated (epigenetic) signatures with blood OT levels in 290 participants with autism enrolled in an OT clinical trial. We identified genetic association with plasma OT, several of which reside in known autism risk genes. We also show statistically significant association of plasma OT levels with gene expression and epigenetic across several gene pathways. These findings broaden our understanding of the factors that influence OT levels in the blood for future studies to decode the complex presentation of autism and its interaction with OT and OT-based treatment.

OXTR DNA methylation differentiates men on the obesity spectrum with and without binge eating disorder

BACKGROUND

The neuropeptide oxytocin (OXT) plays a role in the regulation of eating behavior and metabolism. OXT functioning is altered in patients with eating and weight disorders, and a variant of the oxytocin receptor gene (OXTR) has been associated with impulsive eating behavior as it is seen in patients with binge eating disorder (BED). Gene × environment interactions could play a role in BED. One mechanism mediating this interaction is the epigenetic alteration of gene expression. We therefore investigated if DNA methylation of the OXTR differs between individuals with obesity depending on a comorbid BED. We analyzed DNA methylation of the OXTR in peripheral blood of 227 individuals on the obesity spectrum (mean age: 40.3 ± 13.1 yrs; mean BMI: 38.6 ± 7.3 kg/m²), 130 of which were diagnosed with BED.

RESULTS

There were no overall differences in OXTR methylation between participants with and those without BED (p > 0.05), while both subgroups were comparable regarding age and body mass index (BMI), but significantly differed in sex distribution (p = 0.035). We found no relationship between mean DNA methylation and BMI or self-reported eating disorder (ED) pathology. Analyzing potential sex differences revealed a significantly lower OXTR DNA methylation in male participants with BED as compared to those without BED (p = 0.017). No such difference was found in the female subsample (p > 0.05).

CONCLUSIONS

Clinically significant binge eating pathology might be associated with lower OXTR DNA methylation exclusively in males. The differential DNA methylation of OXTR in males with BED supports the view that BED represents a phenotype within the obesity spectrum that is characterized by specific vulnerability factors. A better understanding of the epigenetic underpinnings of the OXT system might contribute to the refinement of OXT administration approaches as potential interventions in eating and weight disorders.

Oxytocin: An Old Hormone, A Novel Psychotropic Drug And Possible Use In Treating Psychiatric Disorders

BACKGROUND

Oxytocin is a nonapeptide synthesized in the paraventricular and supraoptic nuclei of the hypothalamus. Historically, this molecule has been involved as a key factor in the formation of infant attachment, maternal behavior and pair bonding and, more generally, in linking social signals with cognition, behaviors and reward. In the last decades, the whole oxytocin system has gained a growing interest as it was proposed to be implicated in etiopathogenesis of several neurodevelopmental and neuropsychiatric disorders.

METHODS

With the main goal of an in-depth understanding of the oxytocin role in the regulation of different functions and complex behaviors as well as its intriguing implications in different neuropsychiatric disorders, we performed a critical review of the current state of art. We carried out this work through PubMed database up to June 2021 with the search terms: 1) "oxytocin and neuropsychiatric disorders"; 2) "oxytocin and neurodevelopmental disorders"; 3) "oxytocin and anorexia"; 4) "oxytocin and eating disorders"; 5) "oxytocin and obsessive-compulsive disorder"; 6) "oxytocin and schizophrenia"; 7) "oxytocin and depression"; 8) "oxytocin and bipolar disorder"; 9) "oxytocin and psychosis"; 10) "oxytocin and anxiety"; 11) "oxytocin and personality disorder"; 12) "oxytocin and PTSD".

RESULTS

Biological, genetic, and epigenetic studies highlighted quality and quantity modifications in the expression of oxytocin peptide or in oxytocin receptor isoforms. These alterations would seem to be correlated with a higher risk of presenting several neuropsychiatric disorders belonging to different psychopathological spectra. Collaterally, the exogenous oxytocin administration has shown to ameliorate many neuropsychiatric clinical conditions.

CONCLUSION

Finally, we briefly analyzed the potential pharmacological use of oxytocin in patient with severe symptomatic SARS-CoV-2 infection due to its anti-inflammatory, anti-oxidative and immunoregulatory properties.

Distinct promoter regions of the oxytocin receptor gene are hypomethylated in Prader-Willi syndrome and in Prader-Willi syndrome associated psychosis

Prader-Willi syndrome (PWS) is a rare neurodevelopmental disorder caused by a loss of usually paternally expressed, maternally imprinted genes located on chromosome 15q11-q13. Individuals with PWS display a specific behavioral phenotype and have a higher susceptibility than the general population for certain psychiatric conditions, especially psychosis. An impairment of the oxytocin system has been described in Prader-Willi syndrome, but has not yet been investigated in detail on the epigenetic level. Recent studies have pointed out altered methylation patterns of the oxytocin receptor gene (OXTR) in various psychiatric disorders, including psychosis. In this study, we investigated methylation rates of CpG dinucleotides in the promoter region of the oxytocin receptor gene via bisulfite-sequencing using DNA extracted from peripheral blood samples of 31 individuals with PWS and 14 controls matched for age, sex, and BMI. Individuals with PWS show significantly lower methylation in the intron 1 region of the OXTR than neurotypical controls (p = 0.012). Furthermore, male PWS subjects with psychosis show significantly lower methylation of the OXTR exon 1 region than those without psychosis (p = 0.002). Transcription factor binding site analysis revealed E2F1 as a transcription factor potentially binding to the exon 1 region. E2F1 is physiologically regulated by Necdin, an anti-apoptotic protein whose corresponding gene is located within the PWS locus. This study provides evidence of a disruption of the Oxytocin system on an epigenetic level in PWS in general and in individuals with PWS and psychosis.

Genome-wide DNA methylation profiling in anorexia nervosa discordant identical twins

Up until now, no study has looked specifically at epigenomic landscapes throughout twin samples, discordant for Anorexia nervosa (AN). Our goal was to find evidence to confirm the hypothesis that epigenetic variations play a key role in the aetiology of AN. In this study, we quantified genome-wide patterns of DNA methylation using the Infinium Human DNA Methylation EPIC BeadChip array ("850 K") in DNA samples isolated from whole blood collected from a group of 7 monozygotic twin pairs discordant for AN. Results were then validated performing a genome-wide DNA methylation profiling using DNA extracted from whole blood of a group of non-family-related AN patients and a group of healthy controls. Our first analysis using the twin sample revealed 9 CpGs associated to a gene. The validation analysis showed two statistically significant CpGs with the rank regression method related to two genes associated to metabolic traits, PPP2R2C and CHST1. When doing beta regression, 6 of them showed statistically significant differences, including 3 CpGs associated to genes JAM3, UBAP2L and SYNJ2. Finally, the overall pattern of results shows genetic links to phenotypes which the literature has constantly related to AN, including metabolic and psychological traits. The genes PPP2R2C and CHST1 have both been linked to the metabolic traits type 2 diabetes through GWAS studies. The genes UBAP2L and SYNJ2 have been related to other psychiatric comorbidity.

Review of eating disorders and oxytocin receptor polymorphisms

BACKGROUND AND AIMS

Oxytocin, a nine amino acid peptide synthesised in the hypothalamus, has been widely recognised for its role in anxiolysis, bonding, sociality, and appetite. It binds to the oxytocin receptor (OXTR)-a G-protein coupled receptor-that is stimulated by the actions of oestrogen both peripherally and centrally. Studies have implicated OXTR genotypes in conferring either a risk or protective effect in autism, schizophrenia, and eating disorders (ED). There are numerous DNA variations of this receptor, with the most common DNA variation being in the form of the single nucleotide polymorphisms (SNPs). Two OXTR SNPs have been most studied in relation to ED: rs53576 and rs2254298. Each SNP has the same allelic variant that produces genotypes AA, AG, and GG. In this critical review we will evaluate the putative role of rs53576 and rs2254298 SNPs in ED. Additionally, this narrative review will consider the role of gene-environment interactions in the development of ED pathology.

FINDINGS

The OXTR SNPs rs53576 and rs2254298 show independent associations between the A allele and restrictive eating behaviours. Conversely, the G allele of the OXTR rs53576 SNP is associated with binging behaviours, findings that were also evident in neuroanatomy. One study found the A allele of both OXTR SNPs to confer risk for more severe ED symptomatology while the G allele conferred some protective effect. An interaction between poor maternal care and rs2254298 AG/AA genotype conferred increased risk for binge eating and purging in women.

CONCLUSIONS

Individual OXTR SNP are unlikely in themselves to explain complex eating disorders but may affect the expression of and/or effectiveness of the OXTR. A growing body of G x E work is indicating that rs53576G homozygosity becomes disadvantageous for later mental health under early adverse conditions but further research to extend these findings to eating pathology is needed. The GWAS approach would benefit this area of knowledge.

Individuals Diagnosed with Binge-Eating Disorder Have DNA Hypomethylated Sites in Genes of the Metabolic System: A Pilot Study

Binge-eating disorder, recently accepted as a diagnostic category, is differentiated from bulimia nervosa in that the former shows the presence of binge-eating episodes and the absence of compensatory behavior. Epigenetics is a conjunct of mechanisms (like DNA methylation) that regulate gene expression, which are dependent on environmental changes. Analysis of DNA methylation in eating disorders shows that it is reduced. The present study aimed to analyze the genome-wide DNA methylation differences between individuals diagnosed with BED and BN. A total of 46 individuals were analyzed using the Infinium Methylation EPIC array. We found 11 differentially methylated sites between BED- and BN-diagnosed individuals, with genome-wide significance. Most of the associations were found in genes related to metabolic processes (ST3GAL4, PRKAG2, and FRK), which are hypomethylated genes in BED. Cg04781532, located in the body of the PRKAG2 gene (protein kinase AMP-activated non-catalytic subunit gamma 2), was hypomethylated in individuals with BED. Agonists of PRKAG2, which is the subunit of AMPK (AMP-activated protein kinase), are proposed to treat obesity, BED, and BN. The present study contributes important insights into the effect that BED could have on PRKAG2 activation.

Genetic, epigenetic, and environmental factors controlling oxytocin receptor gene expression

BACKGROUND

The neuropeptide oxytocin regulates mammalian social behavior. Disruptions in oxytocin signaling are a feature of many psychopathologies. One commonly studied biomarker for oxytocin involvement in psychiatric diseases is DNA methylation at the oxytocin receptor gene (OXTR). Such studies focus on DNA methylation in two regions of OXTR, exon 3 and a region termed MT2 which overlaps exon 1 and intron 1. However, the relative contribution of exon 3 and MT2 in regulating OXTR gene expression in the brain is currently unknown.

RESULTS

Here, we use the prairie vole as a translational animal model to investigate genetic, epigenetic, and environmental factors affecting Oxtr gene expression in a region of the brain that has been shown to drive Oxtr related behavior in the vole, the nucleus accumbens. We show that the genetic structure of Oxtr in prairie voles resembles human OXTR. We then studied the effects of early life experience on DNA methylation in two regions of a CpG island surrounding the Oxtr promoter: MT2 and exon 3. We show that early nurture in the form of parental care results in DNA hypomethylation of Oxtr in both MT2 and exon 3, but only DNA methylation in MT2 is associated with Oxtr gene expression. Network analyses indicate that CpG sites in the 3' portion of MT2 are most highly associated with Oxtr gene expression. We also identify two novel SNPs in exon 3 of Oxtr in prairie voles and a novel alternative transcript originating from the third intron of the gene. Expression of the novel alternative transcript is associated with genotype at SNP KLW2.

CONCLUSIONS

These results identify putative regulatory features of Oxtr in prairie voles which inform future studies examining OXTR in human social behaviors and disorders. These studies indicate that in prairie voles, DNA methylation in MT2, particularly in the 3' portion, is more predictive of Oxtr gene expression than DNA methylation in exon 3. Similarly, in human temporal cortex, we find that DNA methylation in the 3' portion of MT2 is associated with OXTR expression. Together, these results suggest that among the CpG sites studied, DNA methylation of MT2 may be the most reliable indicator of OXTR gene expression. We also identify novel features of prairie vole Oxtr, including SNPs and an alternative transcript, which further develop the prairie vole as a translational model for studies of OXTR.

Oxytocin, eating behavior, and metabolism in humans

The hypothalamic peptide oxytocin has been increasingly recognized as a hormone and neurotransmitter with important effects on energy intake, metabolism, and body weight and is under investigation as a potential novel therapeutic agent for obesity. The main neurons producing oxytocin and expressing the oxytocin receptor are strategically located in brain areas known to be critically involved in homeostatic energy balance as well as hedonic and motivational aspects of eating behavior. In this chapter, we will review the central and peripheral physiology of oxytocin and the interaction of oxytocin with key hormones and neural circuitries that affect food intake and metabolism. Next, we will synthesize the available data on endogenous oxytocin levels related to caloric intake, body weight, and metabolic status. We will then review the effects of exogenous oxytocin administration on eating behavior, body weight, and metabolism in humans, including in healthy individuals as well as specific populations with suspected perturbations involving oxytocin pathways. Finally, we will address the promise and fundamental challenges of translating this line of research to clinical care.

Chronic stress and adipose tissue in the anorexic state: endocrine and epigenetic mechanisms

Although adipose tissue metabolism in obesity has been widely studied, there is limited research on the anorexic state, where the endocrine system is disrupted by reduced adipose tissue mass and there are depot-specific changes in adipocyte type and function. Stress exposure at different stages of life can alter the balance between energy intake and expenditure and thereby contribute to the pathogenesis of anorexia nervosa. This review integrates information from human clinical trials to describe endocrine, genetic and epigenetic aspects of adipose tissue physiology in the anorexic condition. Changes in the hypothalamus-pituitary-thyroid, -adrenal, and -gonadal axes and their relationships to appetite regulation and adipocyte function are discussed. Because of the role of stress in triggering or magnifying anorexia, and the dynamic but also persistent nature of environmentally-induced epigenetic modifications, epigenetics is likely the link between stress and long-term changes in the endocrine system that disrupt homoeostatic food intake and adipose tissue metabolism. Herein, we focus on the adipocyte and changes in its function, including alterations reinforced by endocrine disturbance and dysfunctional adipokine regulation. This information is critical because of the poor understanding of anorexic pathophysiology, due to the lack of suitable research models, and the complexity of genetic and environmental interactions.

DNA methylation of ghrelin and leptin receptors in underweight and recovered patients with anorexia nervosa

Epigenetic mechanisms, which modulate gene expression, are becoming increasingly important in the research on anorexia nervosa (AN). Patients with AN have difficulties with the perception of hunger even though hormones like high ghrelin and low leptin signal the need for energy intake. Given the prominent role of the growth hormone secretagogue receptor (GHS-R1a) and the leptin receptor (LEPR) in appetite regulation, a dysregulation of the receptors' expression levels, possibly resulting from altered DNA promoter methylation, may contribute to the pathophysiology of AN. Such alterations could be secondary effects of undernutrition (state markers) or biological processes that may play an antecedent, possibly causal, role in the pathophysiology (trait markers). Therefore, the objective of this study was to examine DNA promoter methylation of the GHS-R1a and LEPR gene promoter regions and investigate whether methylation levels are associated with AN symptoms. We studied medication-free underweight patients with acute AN as well as weight-recovered patients and normal-weight, healthy female control subjects. While DNA methylation of the LEPR gene was similar across groups, GHS-R1a promoter methylation was increased in underweight AN compared to healthy controls - a finding which can be interpreted within the framework of the "ghrelin-resistance" hypothesis in AN. The results of the current study suggest for the first time a potential epigenetic mechanism underlying altered GHS-R1a sensitivity or altered ghrelin signaling in acutely underweight AN. If a ghrelin-centered model of AN can be verified, a next step could be the search for a dietary or psychopharmacological modulation at the ghrelin receptor, potentially via epigenetic mechanisms.

Potential shortcomings in current studies on the effect of intranasal oxytocin in Anorexia Nervosa and healthy controls - A systematic review and meta-analysis

RATIONALE

The psychopathology of anorexia nervosa (AN) includes altered social cognition and information processing of fear and anxiety. Oxytocin, a neuromodulating hormone, may influence these functions and could be valuable for the treatment of AN.

OBJECTIVE

The current study aimed at reviewing the effect of intranasal oxytocin (IN-OT) on attentional bias (AB) and emotion recognition (ER) in AN.

METHODS

A systematic literature review was done for free-text and the MeSH-terms: anorexia nervosa, feeding and eating disorders, and oxytocin. Six publications, reporting from 4 unique clinical trials, were included in this review. A meta-analysis was conducted to examine the effects of IN-OT on AB towards food images and ER on healthy controls (HC) and patients with AN.

RESULTS

Overall, IN-OT did not influence AB towards food images (effect size = 0.20 [- 0.16, 0.57], p = 0.28) and had no effect on ER (effect size = - 0.01 [- 0.27, 0.26], p = 0.97) in patients with AN and healthy control (HC) subjects collectively. Assessing HC and AN separately in subgroup analyses did not show any significant effect on AB and ER in neither of the subgroups. All tests were done between 15 and 55 min post-administration of IN-OT, while peak concentration in the cerebrospinal fluid has been determined to be at 75 min.

CONCLUSION

The current level of evidence is moderate showing no effect of IN-OT on AB or ER in AN. However, brain exposure may not have been sufficient which future studies with IN-OT need to ensure by considering dose and dose-to-task interval.

Eating Disorders, Heredity and Environmental Activation: Getting Epigenetic Concepts into Practice

Epigenetic mechanisms are believed to link environmental exposures to alterations in gene expression, and in so doing, to provide a physical substrate for the activation of hereditary potentials by life experiences. In keeping with this idea, accumulating data suggest that epigenetic processes are implicated in eating-disorder (ED) etiology. This paper reviews literature on putative links between epigenetic factors and EDs, and examines ways in which epigenetic programming of gene expression could account for gene-environment interactions acting in the EDs. The paper also presents evidence suggesting that epigenetic processes link malnutrition and life stresses (gestational, perinatal, childhood, and adult) to risk of ED development. Drawing from empirical evidence and clinical experience, we propose that an epigenetically informed understanding of ED etiology can benefit patients, caregivers, and clinicians alike, in the sense that the perspective can reduce judgmental or blameful attitudes on the part of clinicians and caregivers, and increase self-acceptance and optimism about recovery on the part of those affected.

Epigenetic regulation of the cannabinoid receptor CB1 in an activity-based rat model of anorexia nervosa

OBJECTIVE

Both environmental and genetic factors are known to contribute to the development of anorexia nervosa (AN), but the exact etiology remains poorly understood. Herein, we studied the transcriptional regulation of the endocannabinoid system, an interesting target for body weight maintenance and the control of food intake and energy balance.

METHOD

We used two well-characterized animal models of AN: (a) the activity-based anorexia (ABA) model in which rats, housed with running wheels and subjected to daily food restriction, show reductions in body weight and increase in physical activity; (b) the genetic anx/anx mouse displaying the core features of AN: low food intake and emaciation.

RESULTS

Among the evaluated endocannabinoid system components, we observed a selective and significant down-regulation of the gene encoding for the type 1 cannabinoid receptor (Cnr1) in ABA rats' hypothalamus and nucleus accumbens and, in the latter area, a consistent, significant and correlated increase in DNA methylation at the gene promoter. No changes were evident in the anx/anx mice except for a down-regulation of Cnr1, in the prefrontal cortex.

DISCUSSION

Our findings support a possible role for Cnr1 in the ABA animal model of AN. In particular, its regulation in the nucleus accumbens appears to be triggered by environmental cues due to the consistent epigenetic modulation of the promoter. These data warrant further studies on Cnr1 regulation as a possible target for treatment of AN.

Methylation of the OXTR gene in women with anorexia nervosa: Relationship to social behavior

DNA methylation allows for the environmental regulation of gene expression and is believed to link environmental stressors to psychiatric disorder phenotypes, such as anorexia nervosa (AN). The oxytocin receptor (OXTR) gene is epigenetically regulated, and studies have shown associations between OXTR and social behaviours in various samples, including women with AN. The present study examined differential levels of methylation at various CG sites of the OXTR gene in 69 women with active AN (AN-Active), 21 in whom AN was in remission (AN-Rem) and 35 with no eating disorder (NED). Within each group, we explored the correlation between methylation and measures of social behaviour such as insecure attachment and social avoidance. Hypermethylation of a number of CG sites was seen in AN-Active participants as compared with AN-Rem and NED participants. In the AN-Rem sample, methylation at CG27501759 was significantly positively correlated with insecure attachment (r = .614, p = .003, permutation Q = 0.008) and social avoidance (r = .588, p = .005, permutation Q = 0.0184). Our results highlight differential methylation of the OXTR gene among women with AN, those in remission from AN, and those who never had AN and provide some evidence of associations between OXTR methylation and social behaviour in women remitted from AN.

Eating disorder animal model

PURPOSE OF REVIEW

The aim of this review is to describe animal models that simulate the features of eating disorders. The literature pertaining to animal models that are of relevance for clinical eating disorders and the possible underpinning mechanisms was reviewed using PubMed, Ovid database and Google Scholar.

RECENT FINDINGS

New refinements of the circuits regulated by neurotransmitters and neuropeptides which instigate eating behaviours and the various feedback pathways which monitor acute and chronic nutrient status continue to be discovered. Moreover, work with the animal models that simulate the behavioural features and risk factors related to eating disorders is flourishing and providing new insights into possible causal mechanisms. For example, rodents develop binge-eating behaviours if they are intermittently exposed to processed, palatable foods and/or sugar adulterated drinks. This led to the controversial conceptualization of binge eating as a form of food addiction. Self-starvation taken to a fatal consequence such as occurs in anorexia nervosa can emerge in rodents exposed to triggers like social exclusion and/or the opportunity to exercise.

SUMMARY

There are plausible animal models for both anorexia nervosa and binge-eating disorders. These can be used to elaborate the theoretical models to explain the mechanisms underpinning eating disorders.

Histone deacetylase 4 (HDAC4): a new player in anorexia nervosa?

Anorexia nervosa (AN) and other eating disorders continue to constitute significant challenges for individual and public health. AN is thought to develop as a result of complex interactions between environmental triggers, psychological risk factors, sociocultural influences, and genetic vulnerability. Recent research developments have highlighted a novel potentially relevant component in the AN etiology-activity of the histone deacetylase 4 (HDAC4) gene that has emerged in several recent studies related to AN. HDAC4 is a member of the ubiquitously important family of epigenetic modifier enzymes called histone deacetylases and has been implicated in processes related to the formation and function of the central nervous system (CNS), bone, muscle, and metabolism. In a family affected by eating disorders, a missense mutation in HDAC4 (A786T) was found to segregate with the illness. The relevance of this mutation in eating-related behaviors was further confirmed with mouse models. Despite  the fact that HDAC4 has not been identified as a significant signal in genome-wide association studies in AN, several studies have found significant or near-significant methylation differences in HDAC4 locus in peripheral tissues of actively ill AN patients in comparison with different control groups. Limitations of these studies include a lack of understanding of to what extent the changes in methylation are predictive of AN as such changes might also occur as a consequence of the disease. It remains to be determined how methylation in peripheral tissues correlates with that in the CNS and how different methylation patterns affect HDAC4 expression. The present review discusses the findings and potential roles of HDAC4 in AN. Its emerging roles in learning and neuroplasticity may be specific and relevant for the etiology of AN and potentially lead to novel therapeutic approaches.

Induced Pluripotent Stem Cells; New Tools for Investigating Molecular Mechanisms in Anorexia Nervosa

Anorexia nervosa (AN) is a dramatic psychiatric disorder characterized by dysregulations in food intake and reward processing, involving molecular and cellular changes in several peripheral cell types and central neuronal networks. Genomic and epigenomic analyses have allowed the identification of multiple genetic and epigenetic modifications highlighting the complex pathophysiology of AN. Behavioral and genetic rodent models have been used to recapitulate and investigate, with some limitations, the cellular and molecular changes that potentially underlie eating disorders. In the last 5 years, the use of induced pluripotent stem cells (IPSCs), combined with CRISPR-Cas9 technology, has led to the generation of specific neuronal cell subtypes engineered from human somatic samples, representing a powerful tool to complement observations made in human samples and data collected from animal models. Systems biology using IPSCs has indeed proved to be a valuable approach for the study of metabolic disorders, in addition to neurodevelopmental and psychiatric disorders. The manuscript, while reviewing the main findings related to the genetic, epigenetic, and cellular bases of AN, will present how new studies published, or to be performed, in the field of IPSC-derived cells should improve our current understanding of the pathophysiology of AN and provide potential therapeutic strategies addressing specific endophenotypes.

Interaction between polymorphisms of the oxytocinergic system genes and emotion perception in inpatients with anorexia nervosa

OBJECTIVE

The empirical literature describes the role of the oxytocinergic system in emotion perception (EP). Variants in the oxytocin (OXT) and oxytocin receptor genes have been associated with mental disorders, including anorexia nervosa (AN), that are characterized by difficulties in socioemotional functioning. Our study aimed to examine whether variability within the genes related to OXT pathways may play a role in facial EP in inpatients with AN.

METHOD

Single nucleotide polymorphisms (SNPs) of the following genes: oxytocin receptor (rs2254298, rs53576), OXT (rs6133010), OXT-arginine-vasopressin (rs2740204), CD38 (rs6449197, rs3796863), and human leucyl/cystinylaminopeptidase (rs4869317) were genotyped in 60 AN female inpatients and 60 healthy control females (HCs). Associations between genetic polymorphisms and EP as well as clinical symptoms were examined.

RESULTS

The AN group showed decreased EP abilities compared with HCs. SNPs of rs2740204, rs6133010, and rs53576 were associated with differences in EP in women with AN and in HCs. The SNP of rs4869317 was associated with the level of eating disorders symptoms in HCs.

CONCLUSIONS

The OXT system may be involved in EP difficulties in AN. SNPs within genes related to OXT pathways may influence EP abilities. The leucyl/cystinylaminopeptidase rs4869317 SNP may be involved in the development of eating disorders psychopathology.

Epigenetics in eating disorders: a systematic review

Eating disorders are complex heritable conditions influenced by both genetic and environmental factors. Given the progress of genomic discovery in anorexia nervosa, with the identification of the first genome-wide significant locus, as well as animated discussion of epigenetic mechanisms in linking environmental factors with disease onset, our goal was to conduct a systematic review of the current body of evidence on epigenetic factors in eating disorders to inform future directions in this area. Following PRISMA guidelines, two independent authors conducted a search within PubMed and Web of Science and identified 18 journal articles and conference abstracts addressing anorexia nervosa (n = 13), bulimia nervosa (n = 6), and binge-eating disorder (n = 1), published between January 2003 and October 2017. We reviewed all articles and included a critical discussion of field-specific methodological considerations. The majority of epigenetic analyses of eating disorders investigated methylation at candidate genes (n = 13), focusing on anorexia and bulimia nervosa in very small samples with considerable sample overlap across published studies. Three studies used microarray-based technologies to examine DNA methylation across the genome of anorexia nervosa and binge-eating disorder patients. Overall, results were inconclusive and were primarily exploratory in nature. The field of epigenetics in eating disorders remains in its infancy. We encourage the scientific community to apply methodologically sound approaches using genome-wide designs including epigenome-wide association studies (EWAS), to increase sample sizes, and to broaden the focus to include all eating disorder types.

A longitudinal, epigenome-wide study of DNA methylation in anorexia nervosa: results in actively ill, partially weight-restored, long-term remitted and non-eating-disordered women

Background

This study explored state-related tendencies in DNA methylation in people with anorexia nervosa.

Methods

We measured genome-wide DNA methylation in 75 women with active anorexia nervosa (active), 31 women showing stable remission of anorexia nervosa (remitted) and 41 women with no eating disorder (NED). We also obtained post-intervention methylation data from 52 of the women from the active group.

Results

Comparisons between members of the active and NED groups showed 58 differentially methylated sites (Q < 0.01) that corresponded to genes relevant to metabolic and nutritional status (lipid and glucose metabolism), psychiatric status (serotonin receptor activity) and immune function. Methylation levels in members of the remitted group differed from those in the active group on 265 probes that also involved sites associated with genes for serotonin and insulin activity, glucose metabolism and immunity. Intriguingly, the direction of methylation effects in remitted participants tended to be opposite to those seen in active participants. The chronicity of Illness correlated (usually inversely, at Q < 0.01) with methylation levels at 64 sites that mapped onto genes regulating glutamate and serotonin activity, insulin function and epigenetic age. In contrast, body mass index increases coincided (at Q < 0.05) with generally increased methylation-level changes at 73 probes associated with lipid and glucose metabolism, immune and inflammatory processes, and olfaction.

Limitations

Sample sizes were modest for this type of inquiry, and findings may have been subject to uncontrolled effects of medication and substance use.

Conclusion

Findings point to the possibility of reversible epigenetic alterations in anorexia nervosa, and suggest that an adequate pathophysiological model would likely need to include psychiatric, metabolic and immune components.

Epigenetic modification of the oxytocin receptor gene is associated with emotion processing in the infant brain

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First developmental neuroimaging epigenetics study with human infants.

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Oxytocin receptor gene methylation (OXTRm) assessed in a large sample of infants.

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OXTRm predicts inferior frontal brain responses to emotional faces using fNIRS.

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Higher OXTRm linked to enhanced brain responses to angry and fearful faces.

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OXTRm contributes to variability in social brain function early in ontogeny.

The neural capacity to discriminate between emotions emerges early in development, though little is known about specific factors that contribute to variability in this vital skill during infancy. In adults, DNA methylation of the oxytocin receptor gene (OXTRm) is an epigenetic modification that is variable, predictive of gene expression, and has been linked to autism spectrum disorder and the neural response to social cues. It is unknown whether OXTRm is variable in infants, and whether it is predictive of early social function. Implementing a developmental neuroimaging epigenetics approach in a large sample of infants (N = 98), we examined whether OXTRm is associated with neural responses to emotional expressions. OXTRm was assessed at 5 months of age. At 7 months of age, infants viewed happy, angry, and fearful faces while functional near-infrared spectroscopy was recorded. We observed that OXTRm shows considerable variability among infants. Critically, infants with higher OXTRm show enhanced responses to anger and fear and attenuated responses to happiness in right inferior frontal cortex, a region implicated in emotion processing through action-perception coupling. Findings support models emphasizing oxytocin’s role in modulating neural response to emotion and identify OXTRm as an epigenetic mark contributing to early brain function.

Prevention of Early Substance Use Mediates, and Variation at SLC6A4 Moderates, SAAF Intervention Effects on OXTR Methylation

The Strong African American Family (SAAF) program has been shown to have a variety of short and long-term benefits for participating youth and families. However, biological mechanisms potentially influencing long-term effects on resilience in young adulthood have not been examined. In the current investigation, we examine the effects of SAAF on methylation of the OXTR gene in young adulthood, focusing on a regulatory region previously identified to be both responsive to stress and implicated in resilience. Using the subsample of participants from the original study for whom methylation data was available (N = 388), we replicated the previously reported G × E effect on prevention of early substance use and then examined whether there would also be a moderated effect on OXTR methylation in early adulthood, with "s" allele carriers, but not "LL" participants, showing a significant indirect effect of SAAF on OXTR methylation. Results suggest that for susceptible youth (i.e., "s" allele carriers), preventive intervention may "get under the skin," in a manner potentially beneficial for long-term outcomes. Implications for examination of OXTR methylation in future prevention research are discussed.

DNA Methylation and Hydroxymethylation and Behavior

Environmentally sensitive molecular mechanisms in the brain, such as DNA methylation, have become a significant focus of neuroscience research because of mounting evidence indicating that they are critical in response to social situations, stress, threats, and behavior. The recent identification of 5-hydroxymethylcytosine (5hmC), which is enriched in the brain (tenfold over peripheral tissues), raises new questions as to the role of this base in mediating epigenetic effects in the brain. The development of genome-wide methods capable of distinguishing 5-methylcytosine (5mC) from 5hmC has revealed that a growing number of behaviors are linked to independent disruptions of 5mC and 5hmC levels, further emphasizing the unique importance of both of these modifications in the brain. Here, we review the recent links that indicate DNA methylation (both 5mC and 5hmC) is highly dynamic and that perturbations in this modification may contribute to behaviors related to psychiatric disorders and hold clinical relevance.

MECHANISMS IN ENDOCRINOLOGY: Anorexia nervosa and endocrinology: a clinical update

Anorexia nervosa is a syndrome, that is collections of symptoms, which is not defined by its etiology. The severe cases are intractable. The syndrome is associated with multiple, profound endocrine alterations which may be adaptive, reactive or etiologic. Adaptive changes potentially may be inappropriate in clinical settings such as inpatient intensive re-nutrition or in a setting with somatic comorbidity. Electrolyte levels must be closely monitored during the refeeding process, and the need for weight gain must be balanced against potentially fatal refeeding complications. An important focus of clinical research should be to identify biomarkers associated with different stages of weight loss and re-nutrition combined with psychometric data. Besides well-established peripheral endocrine actions, several hormones also are released directly to different brain areas, where they may exert behavioral and psychogenic actions that could offer therapeutic targets. We need reliable biomarkers for predicting outcome and to ensure safe re-nutrition, however, first of all we need them to explore the metabolism in anorexia nervosa to open new avenues with therapeutic targets. A breakthrough in our understanding and treatment of this whimsical disease remains. Considering this, the aim of the present review is to provide an updated overview of the many endocrine changes in a clinical perspective.

Association of Leptin Gene DNA Methylation With Diagnosis and Treatment Outcome of Anorexia Nervosa

Epigenetic alterations are increasingly implicated in the pathophysiology of anorexia nervosa (AN) but are as yet poorly understood. We investigated possible associations between the leptin gene (LEP) and the leptin receptor gene (LEPR) DNA promoter methylation and (1) a diagnosis of AN and (2) outcome after a 10 months psychotherapeutic outpatient treatment. 129 (LEPR: n = 135) patients with AN were investigated during the large scale psychotherapeutic Anorexia Nervosa Treatment Outpatient Study (ANTOP) trial, compared to 117 (LEPR: n = 119) age and height matched, normal-weight healthy controls. Blood samples were taken at baseline, the end of therapy (40 weeks) and the 12-months follow-up and compared to controls. Methylation was measured in whole blood via bisulfite sequencing. Within the promoter region 32 (LEP) and 39 CpG sites (LEPR) were analyzed. Two key findings were observed. First, LEP and LEPR methylation at baseline were lower in patients compared to controls (LEP: [%] AN: 30.94 ± 13.2 vs. controls: 34.53 ± 14.6); LEPR ([%] AN: 3.73 ± 5.4 vs. controls: 5.22 ± 8.3, mixed linear models: both P < 0.001). Second, lower DNA methylation of the LEP promoter, with a dynamic upregulation during treatment, was associated with a full recovery in AN patients (% change from baseline to follow-up in full recovery patients: +35.13% (SD: 47.56); mixed linear model: P < 0.0001). To test for potential predictive properties of mean LEP DNA methylation a LEP DNA methylation cut-off (31.25% DNA methylation) was calculated, which significantly discriminated full recovery vs. full syndrome AN patients. This cut-off was then tested in a group of previously unclassified patients (missing follow-up data of the Structured Interview for Anorexic and Bulimic disorders; n = 33). Patients below the cut-off (31.25% LEP DNA methylation) showed an increase in BMI over time, while those above the cut-off had a decrease in BMI (ANOVA at the 12-months follow-up: P = 0.0142). To our knowledge, this is the first study investigating epigenetic alterations in AN over time. Our findings indicate that LEP DNA methylation might be involved in the disease course of AN.

Oxytocin Receptor Polymorphism Decreases Midline Neural Activations to Social Stimuli in Anorexia Nervosa

Oxytocin is a neurotransmitter related to both feeding and social behavior; anorexia nervosa is a psychiatric illness defined by reduced food intake, weight loss, and problems in social perceptions. Oxytocin receptor single nucleotide polymorphisms rs2254298 or rs53576 and neural responses to social stimuli were evaluated in adult women with or recovered from anorexia nervosa using functional magnetic resonance imaging. Carriers of the A allele for OXTR rs2254298 (2 AA and 10 AG) showed significantly reduced activation of portions of the posterior cingulate cortex and medial prefrontal cortex for social stimuli as well as greater negative connectivity between the posterior cingulate and the occipital lobe relative to the GG subjects for rs2254298. Differences in the other OXTR SNP, rs53576, did not result in detectable neural differences in either whole brain or region of interest analyses. Development of a mechanistic, biological model of how social behavior is impacted by mental illness requires linking genes to functional brain activations in disease. This pilot study suggests that in anorexia nervosa, differences related to OXTR SNP rs2254298 may alter neural responses to social stimuli and disrupt the engagement and disengagement of the default mode network.

The Neuropeptide Hormone Oxytocin in Eating Disorders

PURPOSE OF REVIEW

The neurohormone oxytocin (OXT) impacts food intake as well as cognitive, emotional, and social functioning-all of which are central to eating disorder (ED) pathology across the weight spectrum. Here, we review findings on endogenous OXT levels and their relationship to ED pathology, the impact of exogenous OXT on mechanisms that drive ED presentation and chronicity, and the potential role of genetic predispositions in the OXT-ED link.

RECENT FINDINGS

Current findings suggest a role of the OXT system in the pathophysiology of anorexia nervosa. In individuals with bulimia nervosa, endogenous OXT levels were comparable to those of healthy controls, and exogenous OXT reduced food intake. Studies in other ED are lacking. However, genetic studies suggest a broad role of the OXT system in influencing ED pathology. Highlighting findings on why OXT represents a potential biomarker of and treatment target for ED, we advocate for a systematic research approach spanning the entire ED spectrum.

Epigenetic Modification of OXTR is Associated with Openness to Experience

Oxytocin is a neuropeptide known to influence social and cognitive processing across several mammalian species. There currently exists a mixed and controversial pattern of evidence that oxytocin pathway genes confer individual differences in social cognition and personality in humans. Inconsistencies across studies may in part be explained by the presence of intermediary, epigenetic, variables that exist between genotype and phenotype. This study was designed to investigate the association between epigenetic modification of the Oxytocin Receptor Gene (OXTR), via DNA methylation, and Big-5 personality traits. Genetic data were collected via saliva samples and analyzed to quantify DNA methylation within the promoter region of OXTR. The results indicate that Openness to Experience is associated with OXTR DNA methylation, while controlling for the remaining Big-5 personality dimensions (Neuroticism, Extraversion, Agreeableness, and Conscientiousness) and sex and age. This finding provides additional support for models associating oxytocin with individual differences in personality and identity in humans.

Epigenetic regulation of the oxytocin receptor is associated with neural response during selective social attention

Aberrant attentional biases to social stimuli have been implicated in a number of disorders including autism and social anxiety disorder. Oxytocin, a naturally-occurring mammalian hormone and neuromodulator involved in regulating social behavior, has been proposed to impact basic biological systems that facilitate the detection of and orientation to social information. Here, we investigate a role for naturally-occurring variability in the endogenous oxytocinergic system in regulating neural response during attention to social information. Participants performed a selective social attention task while undergoing fMRI, provided a blood sample for epigenetic analysis, and completed self-report measures of social functioning. We find that a functional epigenetic modification to the oxytocin receptor, OXTR methylation, is associated with increased neural response within and decreased functional coupling between regions of the salience and attentional control networks during selective social attention. We also show that subclinical variability in autistic and social anxiety traits moderates this epigenetic regulation of neural response. These data offer a mechanistic explanation to a growing literature associating social behavior and disorder with epigenetic modification to OXTR by suggesting that OXTR methylation reflects a decrease in the extent to which social information automatically captures attention. We highlight the importance that treatment efficacy be considered in relation to individual differences in molecular makeup, and that future studies aimed at uncovering biomarkers of disorder carefully consider measurement at both the biological and phenotypic level.

The role of oxytocin receptor gene (OXTR) DNA methylation (DNAm) in human social and emotional functioning: a systematic narrative review

BACKGROUND

The neuropeptide Oxytocin (OXT) plays a central role in birthing, mother-infant bonding and a broad range of related social behaviours in mammals. More recently, interest has extended to epigenetic programming of genes involved in oxytocinergic neurotransmission. This review brings together early findings in a rapidly developing field of research, examining relationships between DNA methylation (DNAm) of the Oxytocin Receptor Gene (OXTR) and social and emotional behaviour in human populations.

METHOD

A systematic search across Web of Knowledge/Science, Scopus, Medline and EMBASE captured all published studies prior to June 2017 examining the association between OXTR DNAm and human social and emotional outcomes. Search terms included 'oxytocin gene' or 'oxytocin receptor gene' and 'epigenetics' or 'DNA methylation'. Any article with a focus on social and emotional functioning was then identified from this set by manual review.

RESULTS

Nineteen studies met eligibility criteria. There was considerable heterogeneity of study populations, tissue samples, instrumentation, measurement, and OXTR site foci. Only three studies examined functional consequences of OXTR DNAm on gene expression and protein synthesis. Increases in OXTR DNAm were associated with callous-unemotional traits in youth, social cognitive deficits in Autistic Spectrum Disorder (ASD), rigid thinking in anorexia nervosa, affect regulation problems, and problems with facial and emotional recognition. In contrast, reductions in DNAm were associated with perinatal stress, postnatal depression, social anxiety and autism in children.

CONCLUSIONS

Consistent with an emerging field of inquiry, there is not yet sufficient evidence to draw conclusions about the role of OXTR DNAm in human social and emotional behaviour. However, taken together, findings point to increased OXTR DNAm in general impairments in social, cognitive and emotional functioning, and decreased OXTR DNAm in specific patterns of impairment related to mood and anxiety disorders (but not in all). Future progress in this field would be enhanced by adequately powered designs, greater phenotypic precision, and methodological improvements including longitudinal studies with multiple time-points to facilitate causal inference.

DNA Methylation and Psychiatric Disorders

DNA methylation has been an important area of research in the study of molecular mechanism to psychiatric disorders. Recent evidence has suggested that abnormalities in global methylation, methylation of genes, and pathways could play a role in the etiology of many forms of mental illness. In this article, we review the mechanisms of DNA methylation, including the genetic and environmental factors affecting methylation changes. We report and discuss major findings regarding DNA methylation in psychiatric patients, both within the context of global methylation studies and gene-specific methylation studies. Finally, we discuss issues surrounding data quality improvement, the limitations of current methylation analysis methods, and the possibility of using DNA methylation-based treatment for psychiatric disorders in the future.

Maternal depression, antidepressant use and placental oxytocin receptor DNA methylation: Findings from the MPEWS study

The aim of this study was to investigate placental DNA methylation of the oxytocin receptor gene (OXTR) in women with depression in pregnancy. We also explored the role of antidepressant medication in pregnancy on placental OXTR methylation. Data were obtained from 239 women in the Mercy Pregnancy and Emotional Wellbeing Study (MPEWS), a selected pregnancy cohort. Current depressive disorders were diagnosed using the Structured Clinical Interview for Diagnostic and Statistical Manual of Mental Disorders (SCID-IV). Depressive symptoms were measured during the third trimester in pregnancy using the Edinburgh Postnatal Depression Scale (EPDS). Plasma levels of antidepressant drugs were measured in maternal and cord blood obtained at delivery. OXTR DNA methylation was measured in placenta samples. Depressive symptoms in pregnancy were not associated with significant changes in DNA methylation of OXTR in the placenta. Cord plasma antidepressant levels were more strongly associated than maternal antidepressant dose or circulating blood antidepressant levels with increased DNA methylation of a specific unit within the promotor region of OXTR. This study provides preliminary data to suggest that antidepressant use during pregnancy can alter OXTR methylation in placental tissue. Our findings also indicate that the way exposures are measured in pregnancy can influence the direction and strength of findings. Future studies should investigate whether altered OXTR methylation might mediate the impacts of maternal antidepressant treatment on pregnancy and offspring outcomes.

Associations between oxytocin receptor gene (OXTR) methylation, plasma oxytocin, and attachment across adulthood

The neuropeptide oxytocin (OT) has been implicated in a wide range of affiliative processes. OT exerts its functions via OT receptors, which are encoded by the oxytocin receptor gene (OXTR). Epigenetic modification of OXTR through the process of DNA methylation has been associated with individual differences in behavioral phenotypes. Specifically, lower levels of OXTR methylation have been linked to better social and affective functioning. However, research on epigenetic mechanisms of OXTR is scarce in non-clinical populations, and even less is known about epigenetic variability across adulthood. The present study assessed methylation levels at OXTR CpG site -934 and plasma OT levels in 22 young (20-31 years, M = 23.6) and 34 older (63-80 years, M = 71.4) participants. Lower levels of OXTR methylation and higher plasma OT levels were associated with less self-reported attachment anxiety in young but not older participants, with largely independent contributions of OXTR methylation and plasma OT levels. In contrast, in the overall sample, lower levels of OXTR methylation were associated with higher self-reported attachment avoidance. Age analysis suggested that these results were largely driven by young adults. Plasma OT levels were unrelated to attachment avoidance. Taken together, these findings support the emerging notion in the literature that epigenetic properties of OXTR, in addition to endogenous OT levels, are related to adult attachment. Further, the age effects observed in the associations between OXTR methylation, plasma OT, and adult attachment emphasize the importance of adopting a developmental perspective when studying properties of the OT system and their relation to affiliative processes. Findings contribute to growing evidence suggesting that epigenetic modification of genes regulating OT pathways and endogenous OT levels are associated with the way people form and maintain intimate social relationships.

Oxytocin and Eating Disorders: A Narrative Review on Emerging Findings and Perspectives

BACKGROUND

The hypothalamic neuropeptide oxytocin regulates reproductive behavior and mother-infant interaction, and conclusive studies in humans indicate that oxytocin is also a potent modulator of psychosocial function. Pilot experiments have yielded first evidence that this neuropeptide moreover influences eating behavior.

METHODS

We briefly summarize currently available studies on the involvement of the oxytocin system in the pathophysiology of eating disorders, as well as on the effects of oxytocin administration in patients with these disorders.

RESULTS

Brain administration of oxytocin in animals with normal weight, but also with diet-induced or genetically induced obesity, attenuates food intake and reduces body weight. In normal-weight and obese individuals, acute intranasal oxytocin delivery curbs calorie intake from main dishes and snacks. Such effects might converge with the poignant social and cognitive impact of oxytocin to also improve dysfunctional eating behavior in the therapeutic context. This assumption has received support in first studies showing that oxytocin might play a role in the disease process of anorexia nervosa. In contrast, respective experiments in patients with bulimia nervosa and binge eating disorder are still scarce.

CONCLUSIONS

We propose a framework of oxytocin's role and its therapeutic potential in eating disorders that aims at integrating social and metabolic aspects of its pharmacological profile, and ponder perspectives and limitations of oxytocin use in the clinical setting.

Investigation of differential HDAC4 methylation patterns in eating disorders

The objective of this study was to investigate the relationship between methylation patterns of the histone deacetylase 4 gene and eating disorders in a site previously associated with anorexia nervosa (AN). Women with AN (N=28) or bulimia nervosa (BN) (N=19) were age-matched and sex-matched to controls (N=45). We obtained saliva-derived DNA and use bisulfite pyrosequencing to examine region-specific methylation differences between cases and controls. The region assayed includes 15 CpGs. We found no significant association between the previously implicated CpG and either AN or BN. We found that three CpGs were nominally associated with AN (P=0.02-0.03); the largest difference was a 9% hypermethylation in AN. One CpG was nominally associated with BN (P=0.04), with 4% hypomethylation. None of these results remained significant after correction for multiple testing. We did not replicate previous findings, though through expanded coverage, we identified additional CpGs that were nominally associated with eating disorders.

The effects of DNA methylation on human psychology

DNA methylation is a fundamental epigenetic modification in the human genome; pivotal in development, genomic imprinting, X inactivation, chromosome stability, gene expression and methylation aberrations are involved in an array of human diseases. Methylation at promoters is associated with transcriptional repression, whereas gene body methylation is generally associated with gene expression. Extrinsic factors such as age, diets and lifestyle affect DNA methylation which consequently alters gene expression. Stress, anxiety, depression, life satisfaction, emotion among numerous other psychological factors also modify DNA methylation patterns. This correlation is frequently investigated in four candidate genes; NR3C1, SLC6A4, BDNF and OXTR, since regulation of these genes directly impact responses to social situations, stress, threats, behaviour and neural functions. Such studies underpin the hypothesis that DNA methylation is involved in deviant human behaviour, psychological and psychiatric conditions. These candidate genes may be targeted in future to assess the correlation between methylation, social experiences and long-term behavioural phenotypes in humans; and may potentially serve as biomarkers for therapeutic intervention.

The Science Behind the Academy for Eating Disorders' Nine Truths About Eating Disorders

OBJECTIVE

In 2015, the Academy for Eating Disorders collaborated with international patient, advocacy, and parent organizations to craft the 'Nine Truths About Eating Disorders'. This document has been translated into over 30 languages and has been distributed globally to replace outdated and erroneous stereotypes about eating disorders with factual information. In this paper, we review the state of the science supporting the 'Nine Truths'.

METHODS

The literature supporting each of the 'Nine Truths' was reviewed, summarized and richly annotated.

RESULTS

Most of the 'Nine Truths' arise from well-established foundations in the scientific literature. Additional evidence is required to further substantiate some of the assertions in the document. Future investigations are needed in all areas to deepen our understanding of eating disorders, their causes and their treatments.

CONCLUSIONS

The 'Nine Truths About Eating Disorders' is a guiding document to accelerate global dissemination of accurate and evidence-informed information about eating disorders. Copyright © 2017 John Wiley & Sons, Ltd and Eating Disorders Association.

Associations among oxytocin receptor gene (OXTR) DNA methylation in adulthood, exposure to early life adversity, and childhood trajectories of anxiousness

Recent models propose deoxyribonucleic acid methylation of key neuro-regulatory genes as a molecular mechanism underlying the increased risk of mental disorder associated with early life adversity (ELA). The goal of this study was to examine the association of ELA with oxytocin receptor gene (OXTR) methylation among young adults. Drawing from a 21-year longitudinal cohort, we compared adulthood OXTR methylation frequency of 46 adults (23 males and 23 females) selected for high or low ELA exposure based on childhood socioeconomic status and exposure to physical and sexual abuse during childhood and adolescence. Associations between OXTR methylation and teacher-rated childhood trajectories of anxiousness were also assessed. ELA exposure was associated with one significant CpG site in the first intron among females, but not among males. Similarly, childhood trajectories of anxiousness were related to one significant CpG site within the promoter region among females, but not among males. This study suggests that females might be more sensitive to the impact of ELA on OXTR methylation than males.

Emerging Treatments in Eating Disorders

Eating disorders (EDs), including anorexia nervosa, bulimia nervosa, and binge-eating disorder, constitute a class of common and deadly psychiatric disorders. While numerous studies in humans highlight the important role of neurobiological alterations in the development of ED-related behaviors, the precise neural substrate that mediates this risk is unknown. Historically, pharmacological interventions have played a limited role in the treatment of eating disorders, typically providing symptomatic relief of comorbid psychiatric issues, like depression and anxiety, in support of the standard nutritional and psychological treatments. To date there are no Food and Drug Administration-approved medications or procedures for anorexia nervosa, and only one Food and Drug Administration-approved medication each for bulimia nervosa (fluoxetine) and binge-eating disorder (lisdexamfetamine). While there is little primary interest in drug development for eating disorders, postmarket monitoring of medications and procedures approved for other indications has identified several novel treatment options for patients with eating disorders. In this review, I utilize searches of the PubMed and ClinicalTrials.gov databases to highlight emerging treatments in eating disorders.

Eating Disorders and Epigenetics

Eating disorders (EDs) are characterized by intense preoccupation with shape and weight and maladaptive eating practices. The complex of symptoms that characterize EDs often arise through the activation of latent genetic potentials by environmental exposures, and epigenetic mechanisms are believed to link environmental exposures to gene expression. This chapter provides an overview of genetic factors acting in the etiology of EDs. It then provides a background to the hypothesis that epigenetic mechanisms link stresses such as obstetric complications and childhood abuse as well as effects of malnutrition to eating disorders (EDs). The chapter then summarizes the emerging body of literature on epigenetics and EDs-mainly studies on DNA methylation in samples of anorexia and bulimia. The available evidence base suggests that an epigenetically informed perspective contributes in valuable ways to the understanding of why people develop EDs.

Epigenetic evidence for involvement of the oxytocin receptor gene in obsessive-compulsive disorder

Background

Obsessive–compulsive disorder (OCD) is a chronic neurodevelopmental disorder that affects up to 3% of the general population. Although epigenetic mechanisms play a role in neurodevelopment disorders, epigenetic pathways associated with OCD have rarely been investigated. Oxytocin is a neuropeptide involved in neurobehavioral functions. Oxytocin has been shown to be associated with the regulation of complex socio-cognitive processes such as attachment, social exploration, and social recognition, as well as anxiety and other stress-related behaviors. Oxytocin has also been linked to the pathophysiology of OCD, albeit inconsistently. The aim of this study was to investigate methylation in two targets sequences located in the exon III of the oxytocin receptor gene (OXTR), in OCD patients and healthy controls. We used bisulfite sequencing to quantify DNA methylation in peripheral blood samples collected from 42 OCD patients and 31 healthy controls.

Results

We found that the level of methylation of the cytosine-phosphate-guanine sites in two targets sequences analyzed was greater in the OCD patients than in the controls. The higher methylation in the OCD patients correlated with OCD severity. We measured DNA methylation in the peripheral blood, which prevented us from drawing any conclusions about processes in the central nervous system.

Conclusion

To our knowledge, this is the first study investigating DNA methylation of the OXTR in OCD. Further studies are needed to evaluate the roles that DNA methylation and oxytocin play in OCD.

Low Fasting Oxytocin Levels Are Associated With Psychopathology in Anorexia Nervosa in Partial Recovery

OBJECTIVE

Anorexia nervosa (AN), a psychiatric disorder characterized by restriction of food intake despite severe weight loss, is associated with increased comorbid anxiety and depression. Secretion of oxytocin, an appetite-regulating neurohormone with anxiolytic and antidepressant properties, is abnormal in AN. The link between oxytocin levels and psychopathology in AN has not been well explored.

METHODS

We performed a cross-sectional study of 79 women aged 18-45 years (19 AN, 26 AN in partial recovery [ANPR], and 34 healthy controls [HC]) investigating the relationship between basal oxytocin levels and disordered eating psychopathology, anxiety, and depressive symptoms. AN diagnoses were based on DSM-5 criteria. Data acquisition took place between December 2008 and March 2014. Fasting serum oxytocin levels were obtained, and the following self-report measures were used to assess psychopathology: Eating Disorder Examination Questionnaire, State-Trait Anxiety Inventory, and Beck Depression Inventory-II.

RESULTS

Fasting oxytocin levels were low in ANPR compared to HC (P = .0004). In ANPR but not AN, oxytocin was negatively associated with disordered eating psychopathology (r = -0.39, P = .0496) and anxiety symptoms (state anxiety: r = -0.53, P = .006; trait anxiety: r = -0.49, P = .01). Furthermore, ANPR with significant disordered eating psychopathology, anxiety symptoms, or depressive symptoms had lower oxytocin levels compared to those with minimal or no symptoms (P = .04, .02, and .007, respectively).

CONCLUSIONS

We speculate that a dysregulation of oxytocin pathways may contribute to persistent psychopathology after partial weight recovery from anorexia nervosa.