High-throughput DNA methylation analysis in anorexia nervosa confirms TNXB hypermethylation

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.

DNA methylation in people with anorexia nervosa: Epigenome-wide patterns in actively ill, long-term remitted, and healthy-eater women

OBJECTIVES

Recent studies have reported altered methylation levels at disorder-relevant DNA sites in people who are ill with Anorexia Nervosa (AN) compared to findings in people with no eating disorder (ED) or in whom AN has remitted. The preceding implies state-related influences upon gene expression in people with AN. This study further examined this notion.

METHODS

We measured genome-wide DNA methylation in 145 women with active AN, 49 showing stable one-year remission of AN, and 64 with no ED.

RESULTS

Comparisons revealed 205 differentially methylated sites between active and no ED groups, and 162 differentially methylated sites between active and remitted groups (Q < 0.01). Probes tended to map onto genes relevant to psychiatric, metabolic and immune functions. Notably, several of the genes identified here as being differentially methylated in people with AN (e.g. SYNJ2, PRKAG2, STAT3, CSGALNACT1, NEGR1, NR1H3) have figured in previous studies on AN. Effects also associated illness chronicity and lower BMI with more pronounced DNA methylation alterations, and remission of AN with normalisation of DNA methylation.

CONCLUSIONS

Findings corroborate earlier results suggesting reversible DNA methylation alterations in AN, and point to particular genes at which epigenetic mechanisms may act to shape AN phenomenology.

Candidate Biological Markers for Social Anxiety Disorder: A Systematic Review

Social anxiety disorder (SAD) is a common psychiatric condition associated with a high risk of psychiatric comorbidity and impaired social/occupational functioning when not promptly treated. The identification of biological markers may facilitate the diagnostic process, leading to an early and proper treatment. Our aim was to systematically review the available literature about potential biomarkers for SAD. A search in the main online repositories (PubMed, ISI Web of Knowledge, PsychInfo, etc.) was performed. Of the 662 records screened, 61 were included. Results concerning cortisol, neuropeptides and inflammatory/immunological/neurotrophic markers remain inconsistent. Preliminary evidence emerged about the role of chromosome 16 and the endomannosidase gene, as well as of epigenetic factors, in increasing vulnerability to SAD. Neuroimaging findings revealed an altered connectivity of different cerebral areas in SAD patients and amygdala activation under social threat. Some parameters such as salivary alpha amylase levels, changes in antioxidant defenses, increased gaze avoidance and QT dispersion seem to be associated with SAD and may represent promising biomarkers of this condition. However, the preliminary positive correlations have been poorly replicated. Further studies on larger samples and investigating the same biomarkers are needed to identify more specific biological markers for SAD.

Immunoinflammatory processes: Overlapping mechanisms between obesity and eating disorders?

Obesity and eating disorders are conditions that involve eating behaviors and are sometimes comorbid. Current evidence supports alterations in immunoinflammatory processes in both obesity and eating disorders. A plausible hypothesis is that immunoinflammatory processes may be involved in the pathophysiology of obesity and eating disorders. The aim of this review is to highlight the link between obesity and eating disorders, with a particular focus on immunoinflammatory processes. First, the relation between obesity and eating disorders will be presented, followed by a brief review of the literature on their association with immunoinflammatory processes. Second, developmental factors will be discussed to clarify the link between obesity, eating disorders, and immunoinflammatory processes. Genetic and epigenetic risk factors as well as the potential roles of stress pathways and early life development will be presented. Finally, implications of these findings for future research are discussed. This review highlighted biological and developmental aspects that overlap between obesity and EDs, emphasizing the need for biopsychosocial research approaches to advance current knowledge and practice in these fields.

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.

Prenatal metal exposure, cord blood DNA methylation and persistence in childhood: an epigenome-wide association study of 12 metals

BACKGROUND

Prenatal exposure to essential and non-essential metals impacts birth and child health, including fetal growth and neurodevelopment. DNA methylation (DNAm) may be involved in pathways linking prenatal metal exposure and health. In the Project Viva cohort, we analyzed the extent to which metals (As, Ba, Cd, Cr, Cs, Cu, Hg, Mg, Mn, Pb, Se, and Zn) measured in maternal erythrocytes were associated with differentially methylated positions (DMPs) and regions (DMRs) in cord blood and tested if associations persisted in blood collected in mid-childhood. We measured metal concentrations in first-trimester maternal erythrocytes, and DNAm in cord blood (N = 361) and mid-childhood blood (N = 333, 6-10 years) with the Illumina HumanMethylation450 BeadChip. For each metal individually, we tested for DMPs using linear models (considered significant at FDR < 0.05), and for DMRs using comb-p (Sidak p < 0.05). Covariates included biologically relevant variables and estimated cell-type composition. We also performed sex-stratified analyses.

RESULTS

Pb was associated with decreased methylation of cg20608990 (CASP8) (FDR = 0.04), and Mn was associated with increased methylation of cg02042823 (A2BP1) in cord blood (FDR = 9.73 × 10-6). Both associations remained significant but attenuated in blood DNAm collected at mid-childhood (p < 0.01). Two and nine Mn-associated DMPs were identified in male and female infants, respectively (FDR < 0.05), with two and six persisting in mid-childhood (p < 0.05). All metals except Ba and Pb were associated with ≥ 1 DMR among all infants (Sidak p < 0.05). Overlapping DMRs annotated to genes in the human leukocyte antigen (HLA) region were identified for Cr, Cs, Cu, Hg, Mg, and Mn.

CONCLUSIONS

Prenatal metal exposure is associated with DNAm, including DMRs annotated to genes involved in neurodevelopment. Future research is needed to determine if DNAm partially explains the relationship between prenatal metal exposures and health outcomes.

Genetics of eating disorders in the genome-wide era

Enabled by advances in high throughput genomic sequencing and an unprecedented level of global data sharing, molecular genetic research is beginning to unlock the biological basis of eating disorders. This invited review provides an overview of genetic discoveries in eating disorders in the genome-wide era. To date, five genome-wide association studies on eating disorders have been conducted - all on anorexia nervosa (AN). For AN, several risk loci have been detected, and ~11-17% of the heritability has been accounted for by common genetic variants. There is extensive genetic overlap between AN and psychological traits, especially obsessive-compulsive disorder, and intriguingly, with metabolic phenotypes even after adjusting for body mass index (BMI) risk variants. Furthermore, genetic risk variants predisposing to lower BMI may be causal risk factors for AN. Causal genes and biological pathways of eating disorders have yet to be elucidated and will require greater sample sizes and statistical power, and functional follow-up studies. Several studies are underway to recruit individuals with bulimia nervosa and binge-eating disorder to enable further genome-wide studies. Data collections and research labs focused on the genetics of eating disorders have joined together in a global effort with the Psychiatric Genomics Consortium. Molecular genetics research in the genome-wide era is improving knowledge about the biology behind the established heritability of eating disorders. This has the potential to offer new hope for understanding eating disorder etiology and for overcoming the therapeutic challenges that confront the eating disorder field.

Dissection of the Genetic Association between Anorexia Nervosa and Obsessive-Compulsive Disorder at the Network and Cellular Levels

Anorexia nervosa (AN) and obsessive-compulsive disorder (OCD) exhibit a high co-morbidity rate, similar symptoms, and a shared genetic basis. However, an understanding of the specific underlying mechanisms of these commonalities is currently limited. Here, we collected Genome-Wide Association Analysis results for AN and OCD, and obtained genes hit by the top SNPs as the risk genes. We then carried out an integrative coexpression network analysis to explore the convergence and divergence of AN and OCD risk genes. At first, we observed that the AN risk genes were enriched in coexpression modules that involved extracellular matrix functions and highly are expressed in the postnatal brain, limbic system, and non-neuronal cell types, while the OCD risk genes were enriched in modules of synapse function, the prenatal brain, cortex layers, and neurons. Next, by comparing the expressions from the eating disorder and OCD postmortem patient brain tissues, we observed both disorders have similar prefrontal cortex expression alterations influencing the synapse transmission, suggesting that the two diseases could have similar functional pathways. We found that the AN and OCD risk genes had distinct functional and spatiotemporal enrichment patterns but carried similar expression alterations as a disease mechanism, which may be one of the key reasons they had similar but not identical clinical phenotypes.

DNA methylation differences associated with social anxiety disorder and early life adversity

Social anxiety disorder (SAD) is a psychiatric disorder characterized by extensive fear in social situations. Multiple genetic and environmental factors are known to contribute to its pathogenesis. One of the main environmental risk factors is early life adversity (ELA). Evidence is emerging that epigenetic mechanisms such as DNA methylation might play an important role in the biological mechanisms underlying SAD and ELA. To investigate the relationship between ELA, DNA methylation, and SAD, we performed an epigenome-wide association study for SAD and ELA examining DNA from whole blood of a cohort of 143 individuals using DNA methylation arrays. We identified two differentially methylated regions (DMRs) associated with SAD located within the genes SLC43A2 and TNXB. As this was the first epigenome-wide association study for SAD, it is worth noting that both genes have previously been associated with panic disorder. Further, we identified two DMRs associated with ELA within the SLC17A3 promoter region and the SIAH3 gene and several DMRs that were associated with the interaction of SAD and ELA. Of these, the regions within C2CD2L and MRPL28 showed the largest difference in DNA methylation. Lastly, we found that two DMRs were associated with both the severity of social anxiety and ELA, however, neither of them was found to mediate the contribution of ELA to SAD later in life. Future studies are needed to replicate our findings in independent cohorts and to investigate the biological pathways underlying these effects.

Is there a hypothalamic basis for anorexia nervosa?

The hypothalamus has long been known to control food intake and energy metabolism through a complex network of primary and secondary neurons and glial cells. Anorexia nervosa being a complex disorder characterized by abnormal feeding behavior and food aversion, it is thus quite surprising that not much is known concerning potential hypothalamic modifications in this disorder. In this chapter, we review the recent advances in the fields of genetics, epigenetics, structural and functional imaging, and brain connectivity, as well as neuroendocrine findings and emerging animal models, which have begun to unravel the importance of hypothalamic adaptive processes to our understanding of the pathology of eating disorders.

Applying epigenetic science to the understanding of eating disorders: a promising paradigm for research and practice

PURPOSE OF REVIEW

Studies indicate that environmental factors, acting at various moments throughout the life cycle, can result in epigenetically mediated alterations in gene expression. In this article, we review recent findings on the role of epigenetic factors in eating disorders, address methodological issues that need to be considered when interpreting research findings, and comment on possible clinical applications.

RECENT FINDINGS

Evidence suggests that eating disorders implicate alterations of methylation in genes involved in the mental status, metabolism, anthropometric features and immunity. Furthermore, some research in individuals with anorexia nervosa suggests the presence of reversible, malnutrition-induced epigenetic alterations that 'reset' as patients recover.

SUMMARY

Epigenetic studies in the eating disorders corroborate the idea that eating disorder cause is multifactorial, and identify markers that could help inform our understanding of illness staging and subtyping that may explain the commonly progressive course of these disorders, and that may provide insights towards the development of novel interventions. Already, there is evidence to suggest that, in people with eating disorders, epigenetically informed interventions help reduce stigma and shame, and increase self-acceptance and hopes of recovery. Although findings are intriguing, further research is required as, to date, studies apply modest sample sizes and disparate methodologies.

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.

Behavioral Alterations in Mice Carrying Homozygous HDAC4 A778T Missense Mutation Associated With Eating Disorder

Eating disorders (EDs) are serious mental illnesses thought to arise from the complex gene-environment interactions. DNA methylation patterns in histone deacetylase 4 (HDAC4) locus have been associated with EDs and we have previously identified a missense mutation in the HDAC4 gene (HDAC4^A786T) that increases the risk of developing an ED. In order to evaluate the biological consequences of this variant and establish a useful mouse model of EDs, here we performed behavioral characterization of mice homozygous for Hdac4^A778T (corresponding to human HDAC4^A786T) that were further backcrossed onto C57BL/6 background. When fed high-fat diet, male, but not female, homozygous mice showed a trend toward decreased weight gain compared to their wild-type littermates. Behaviorally, male, but not female, homozygous mice spent less time in eating and exhibited reduced motivation to work for palatable food and light phase-specific decrease in locomotor activity. Additionally, homozygous Hdac4^A778T female, but not male, mice display social subordination when subjected to a tube dominance test. Collectively, these results reveal a complex sex- and circadian-dependent role of ED-associated Hdac4^A778T mutation in affecting mouse behaviors. Homozygous Hdac4^A778T mice could therefore be a useful animal model to gain insight into the neurobiological basis of EDs.

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.

Twin Registries Moving Forward and Meeting the Future: A Review

Twin registries have developed as a valuable resource for the study of many aspects of disease and society over the years in many different countries. A number of these registries include large numbers of twins with data collected at varying information levels for twin cohorts over the past several decades. More recent expansion of twin datasets has allowed for the collection of genetic data, together with many other levels of 'omic' information along with multiple demographic, physiological, health outcomes and other measures typically used in epidemiologic research. Other twin data sources outside these registries reflect research interests in particular aspects of disease or specific phenotypic assessment. Twin registries have the potential to play a key role in many aspects of the artificial intelligence/machine learning-driven projects of the future and will continue to keep adapting to the changing research landscape.

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.

Genetic risk factors for eating disorders: an update and insights into pathophysiology

Genome-wide-association studies (GWASs), epigenetic, gene-expression and gene-gene interaction projects, nutritional genomics and investigations of the gut microbiota have increased our knowledge of the pathophysiology of eating disorders (EDs). However, compared with anorexia nervosa, genetic studies in patients with bulimia nervosa and binge-eating disorder are relatively scarce, with the exception of a few formal genetic and small-sized candidate-gene-association studies. In this article, we review important findings derived from formal and molecular genetics in order to outline a genetics-based pathophysiological model of EDs. This model takes into account environmental and nutritional factors, genetic factors related to the microbiome, the metabolic and endocrine system, the immune system, and the brain, in addition to phenotypical traits of EDs. Shortcomings and advantages of genetic research in EDs are discussed against the historical background, but also in light of potential future treatment options for patients with EDs.

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.

Homocysteine levels associate with subtle changes in leukocyte DNA methylation: an epigenome-wide analysis

AIM

Homocysteine (Hcy) is a sensitive marker of one-carbon metabolism. Higher Hcy levels have been associated with global DNA hypomethylation. We investigated the association between plasma Hcy and epigenome-wide DNA methylation in leukocytes.

METHODS

Methylation was measured using Illumina 450 k arrays in 2035 individuals from six cohorts. Hcy-associated differentially methylated positions and regions were identified using meta-analysis.

RESULTS

Three differentially methylated positions cg21607669 (SLC27A1), cg26382848 (AJUBA) and cg10701000 (KCNMA1) at chromosome 19, 14 and 10, respectively, were significantly associated with Hcy. In addition, we identified 68 Hcy-associated differentially methylated regions, the most significant of which was a 1.8-kb spanning domain (TNXB/ATF6B) at chromosome 6.

CONCLUSION

We identified novel epigenetic loci associated with Hcy levels, of which specific role needs to be further validated.