Genetics and Epigenetics of Eating Disorders

Molecular neuroanatomy of anorexia nervosa

Anorexia nervosa is a complex eating disorder with genetic, metabolic, and psychosocial underpinnings. Using genome-wide methods, recent studies have associated many genes with the disorder. We characterized these genes by projecting them into reference transcriptomic atlases of the prenatal and adult human brain to determine where these genes are expressed in fine detail. We found that genes from an induced stem cell study of anorexia nervosa cases are expressed at higher levels in the lateral parabrachial nucleus. Although weaker, expression enrichment of the adult lateral parabrachial is also found with genes from independent genetic studies. Candidate causal genes from the largest genetic study of anorexia nervosa to date were enriched for expression in the arcuate nucleus of the hypothalamus. We also found an enrichment of anorexia nervosa associated genes in the adult and fetal raphe and ventral tegmental areas. Motivated by enrichment of these feeding circuits, we tested if these genes respond to fasting in mice hypothalami, which highlighted the differential expression of Rps26 and Dalrd3. This work improves our understanding of the neurobiology of anorexia nervosa by suggesting disturbances in subcortical appetitive circuits.

Genetic contributions to the etiology of anorexia nervosa: New perspectives in molecular diagnosis and treatment

Background

Anorexia nervosa is a multifactorial eating disorder that manifests with self‐starvation, extreme anxiety, hyperactivity, and amenorrhea. Long‐term effects include organ failure, disability, and in extreme cases, even death.

Methods

Through a literature search, here we summarize what is known about the molecular etiology of anorexia nervosa and propose genetic testing for this condition.

Results

Anorexia nervosa often has a familial background and shows strong heritability. Various genetic studies along with genome‐wide association studies have identified several genetic loci involved in molecular pathways that might lead to anorexia.

Conclusion

Anorexia nervosa is an eating disorder with a strong genetic component that contributes to its etiology. Various genetic approaches might help in the molecular diagnosis of this disease and in devising novel therapeutic options.

Anorexia nervosa is a multifactorial eating disorder with a strong genetic component that manifests with self‐starvation, extreme anxiety, hyperactivity, and amenorrhea. Through a literature search, here we summarize what is known about the molecular etiology of anorexia nervosa and propose genetic testing for this condition.

Impulsivity and anxiety-related dimensions in adults with bulimic-spectrum disorders differentially relate to eating disordered behaviors

While facets of both anxiety and impulsivity appear central to the development and maintenance of bulimia nervosa (BN), specific BN behaviors may be propagated by differing profiles of risk. The current study examined associations between dimensions of anxiety and impulsivity and BN symptoms (binge eating, vomiting, laxative misuse, driven exercise), both in terms of the presence of such behaviors and their frequency. Two hundred and four women (M_age = 25.7 years) who met DSM-IV criteria for full or subthreshold BN completed self-report measures of perfectionism (Frost Multidimensional Perfectionism Scale), anxiety (Spielberger Trait Anxiety Inventory), impulsivity (Barratt Impulsiveness Scale-11; Impulsive Behavior Scale), eating disordered behaviors (Eating Disorder Examination - Questionnaire), and associated psychiatric symptoms (Michigan Assessment Screening Test/Alcohol-Drug; Maudsley Obsessive-Compulsive Inventory). Factor analysis revealed multidimensional impulsive and anxiety-related traits (5 anxiety-related factors; 7 impulsivity-related factors). In zero-sensitive regression models, different facets of impulsivity evidenced association with the presence of binge eating (risk taking), laxative misuse (impulsive spending), and fasting (difficulty concentrating), along with the frequency of vomiting (long-term planning difficulties). In contrast, anxiety-related dimensions were only associated with driven exercise (high standards) and fasting (concern over mistakes, high standards, parental expectations). Overall, impulsive and anxiety-related factors and symptoms showed distinct associations with specific eating disorder behaviors, even among those with the same diagnosis.

Disordered eating behaviors in adolescents with celiac disease

PURPOSE

Celiac disease (CD) is a chronic immune-mediated systemic disease characterized by inflammation and villous atrophy of the small intestine. A strict, lifelong gluten-free diet (GFD) is the only treatment for CD. Disordered eating behaviors (DEBs) prevail in adolescence and young adulthood, and confer a risk of developing into full-blown eating disorders. The aims of the current study were to assess the incidence and risk factors for DEBs among individuals with CD, and to examine an association between adherence to GFD and DEBs.

METHODS

A cohort of 136 individuals with CD responded to a web-mediated survey that assessed DEBs and adherence to a GFD. The survey included demographic data (gender, age, weight, disease duration) and two self-rating questionnaires: the Eating Attitudes Test-26 and the gluten-free diet questionnaire.

RESULTS

DEBs were found in 19% of female and 7% of male responders. These individuals were characterized by being overweight (p = 0.02), of an older age (p = 0.04) and female sex (p = 0.06). Strict adherence to a GFD was reported by 32% of the responders and was not correlated with age, disease duration, age at diagnosis of CD and with being overweight.

CONCLUSIONS

Caregivers should be aware of the increased occurrence of DEBs in adolescents with CD, especially those who are overweight, older and of a female gender.

LEVEL OF EVIDENCE

Level V, cross-sectional descriptive study.

Evidence for a sex-specific contribution of polygenic load for anorexia nervosa to body weight and prefrontal brain structure in nonclinical individuals

Genetic predisposition and brain structural abnormalities have been shown to be involved in the biological underpinnings of anorexia nervosa (AN). Prefrontal brain regions are suggested to contribute through behavioral inhibition mechanisms to body weight. However, it is unknown if and to which extent biological correlates for AN might be present in individuals without clinical AN symptomatology. We therefore investigated the contribution of polygenic load for AN on body weight and prefrontal brain structure in a sample of n = 380 nonclinical individuals. A polygenic score (PGS) reflecting the individual genetic load for the trait of anorexia nervosa was calculated. Structural MRI data were acquired and preprocessed using the cortical parcellation stream of FreeSurfer. We observed a significant PGS × sex interaction effect on body mass index (BMI), which was driven by a negative correlation between PGS and BMI in female participants. Imaging analyses revealed significant interaction effects of sex  × PGS on surface area of the lateral orbitofrontal cortex (OFC), the pars orbitalis (PO), the rostral middle frontal gyrus (RMF) and the pars triangularis (PT) of the left frontal cortex. The interaction effects were driven by positive correlations between PGS and prefrontal surface areas in female participants and negative correlations in male participants. We furthermore found sex-specific associations between BMI and left RMF surface area as well as between BMI and left PO and left RMF thickness. Our findings demonstrate a sex-specific association between polygenic load for AN, BMI, and prefrontal brain structure in nonclinical individuals. Hence, this study identifies structural abnormalities associated with polygenic load for AN and BMI in brain regions deeply involved in behavioral inhibition and impulse regulation as candidate brain regions for future research.

Cyfip1 Haploinsufficiency Increases Compulsive-Like Behavior and Modulates Palatable Food Intake in Mice: Dependence on Cyfip2 Genetic Background, Parent-of Origin, and Sex

Binge eating (BE) is a heritable trait associated with eating disorders and involves episodes of rapid, large amounts of food consumption. We previously identified cytoplasmic FMR1-interacting protein 2 (Cyfip2) as a genetic factor underlying compulsive-like BE in mice. CYFIP2 is a homolog of CYFIP1 which is one of four paternally-deleted genes in patients with Type I Prader-Willi Syndrome (PWS), a neurodevelopmental disorder whereby 70% of cases involve paternal 15q11-q13 deletion. PWS symptoms include hyperphagia, obesity (if untreated), cognitive deficits, and obsessive-compulsive behaviors. We tested whether Cyfip1 haploinsufficiency (+/-) would enhance compulsive-like behavior and palatable food (PF) intake in a parental origin- and sex-dependent manner on two Cyfip2 genetic backgrounds, including the BE-prone C57BL/6N (Cyfip2N/N) background and the BE-resistant C57BL/6J (Cyfip2J/J) background. Cyfip1+/- mice showed increased compulsive-like behavior on both backgrounds and increased PF intake on the Cyfip2N/N background. In contrast, maternal Cyfip1 haploinsufficiency on the BE-resistant Cyfip2J/J background induced a robust escalation in PF intake in wild-type Cyfip1J/J males while having no effect in Cyfip1J/- males. Notably, induction of behavioral phenotypes in wild-type males following maternal Fmr1+/- has previously been reported. In the hypothalamus, there was a paternally-enhanced reduction in CYFIP1 protein whereas in the nucleus accumbens, there was a maternally-enhanced reduction in CYFIP1 protein. Nochange in FMR1 protein (FMRP) was observed in Cyfip1+/- mice, regardless of parental origin. To summarize, Cyfip1 haploinsufficiency increased compulsive-like behavior and induced genetic background-dependent, sex-dependent, and parent-of-origin-dependent effects on PF consumption and CYFIP1 expression that could have relevance for neurodevelopmental and neuropsychiatric disorders.

Gut-Brain Interactions: Implications for a Role of the Gut Microbiota in the Treatment and Prognosis of Anorexia Nervosa and Comparison to Type I Diabetes

Anorexia nervosa has poor prognosis and treatment outcomes and is influenced by genetic, metabolic, and psychological factors. Gut microbes interact with gut physiology to influence metabolism and neurobiology, although potential therapeutic benefits remain unknown. Type 1 diabetes is linked to anorexia nervosa through energy dysregulation, which in both disease states is related to the gut microbiota, disordered eating, and genetics.

Genome-wide association study identifies eight risk loci and implicates metabo-psychiatric origins for anorexia nervosa

Characterized primarily by a low body-mass index, anorexia nervosa is a complex and serious illness1, affecting 0.9-4% of women and 0.3% of men2-4, with twin-based heritability estimates of 50-60%5. Mortality rates are higher than those in other psychiatric disorders6, and outcomes are unacceptably poor7. Here we combine data from the Anorexia Nervosa Genetics Initiative (ANGI)8,9 and the Eating Disorders Working Group of the Psychiatric Genomics Consortium (PGC-ED) and conduct a genome-wide association study of 16,992 cases of anorexia nervosa and 55,525 controls, identifying eight significant loci. The genetic architecture of anorexia nervosa mirrors its clinical presentation, showing significant genetic correlations with psychiatric disorders, physical activity, and metabolic (including glycemic), lipid and anthropometric traits, independent of the effects of common variants associated with body-mass index. These results further encourage a reconceptualization of anorexia nervosa as a metabo-psychiatric disorder. Elucidating the metabolic component is a critical direction for future research, and paying attention to both psychiatric and metabolic components may be key to improving outcomes.

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.

Prenatal and perinatal risk factors for eating disorders in women: A population cohort study

OBJECTIVE

The fetal programming model hypothesizes that developmental programming in utero and in early life induces adaptations that predetermine the adult phenotype. This study investigated whether prenatal/perinatal complications are associated with lifetime eating disorders in women.

METHOD

Participants included 46,373 adult women enrolled in the Norwegian Mother and Child Cohort Study (den norske Mor & barn-undersøkelsen [MoBa]). MoBa mothers and their mothers (MoBa grandmothers) were the focus of the current study. MoBa mothers with lifetime eating disorders were compared to a referent group.

RESULTS

MoBa mothers who weighed more at birth (birth weight, adjusted odds ratio [OR] = 1.14; 95% confidence interval [CI]: 1.10-1.19) or were born large-for-gestational-age (adjusted OR = 1.39; 95% CI: 1.27-1.52) were more likely to develop binge-eating disorder in later life. MoBa mothers who weighed less at birth were more likely to develop anorexia nervosa (birth weight, adjusted OR = 0.88; 95% CI: 0.81-0.95). Bulimia nervosa and purging disorder (PD) were not significantly predicted by the prenatal and perinatal factors examined.

DISCUSSION

Results of this study, which include the first known investigation of prenatal and perinatal factors in binge-eating disorder and PD, suggest that fetal programming may be relevant to the development of anorexia nervosa and binge-eating disorder. Future genetically informative research is needed to help disentangle whether these associations are a function of genetic influences or a true environmental fetal programming effect.

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.

Trauma-informed care and practice for eating disorders: personal and professional perspectives of lived experiences

BACKGROUND

Learning about the life stories of patients who have experienced a severe eating disorder (ED), but also traumas that led to PTSD, dissociative disorders, and other comorbidities, has great value to clinicians in their efforts to deliver trauma-informed care (TIC). Many investigators have been researching and writing about these issues for years, and strong scientific evidence has emerged, indicating that trauma is a significant risk factor for the development of EDs, particularly in its bulimic forms.

PURPOSE

Peer-reviewed literature contains scarce input from people with "lived experiences". Hearing and "sitting with" such individuals are extremely useful in clinical practice and research. Further, encouraging patients to put words to their pain has recognized therapeutic effects. These lived experiences are often demonstrative of key elements of what professionals need to know about evaluating and treating patients with EDs and co-occurring trauma-related disorders.

METHOD/RESULTS

The principal author invited two courageous recovered ED advocates and writers (June Alexander and Jenni Schaefer), who have gone public about their ED-PTSD experiences, to recount their life stories and treatment experiences (both positive and negative). Dr. Brewerton then offers his professional perspectives on the course of their treatment experiences put in the context of ongoing relevant clinical research.

CONCLUSION

Their and other patients' experiences have great power to guide professionals toward trauma-informed care, more integrated practice, and theoretically improved outcomes.

LEVEL OF EVIDENCE

Level V.

Does it Get Better? Change in Depressive Symptoms from Late-Adolescence to Early-Adulthood, Disordered Eating Behaviors, and Sexual Identity

Sexual minority youth are often described as at-risk for mental health comorbidities, including disordered eating behavior (DEB) and depression. This study assesses differences in late-adolescent DEB and depressive symptoms among gay/lesbian, bisexual, or mostly-heterosexual individuals, and how their symptoms change across early-adulthood. While sexual minority youth were more likely to report DEB and elevated depressive symptoms in late-adolescence relative to exclusively heterosexual peers, gay/lesbian individuals experienced improvement in early-adulthood depressive symptoms. Conversely, bisexual individuals maintained elevated depressive symptoms into early-adulthood, and additional depressive symptoms associated with DEB. DEB may be a unique risk-factor shaping the mental health of bisexual youth.

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.

Immunoglobulin G modulation of the melanocortin 4 receptor signaling in obesity and eating disorders

Melanocortin 4 receptor (MC4R) plays a key role in regulation of appetite activated by its main ligand α-melanocyte-stimulating hormone (α-MSH) in both central and peripheral targets. α-MSH also binds to circulating immunoglobulins (Igs) but the functional significance of such immune complexes (ICs) in MC4R signaling in normal and pathological conditions of altered appetite has remained unknown. To address this question, we analyzed plasma levels, affinity kinetics, and binding epitopes of α-MSH-reactive IgG extracted from plasma samples of female patients with hyperphagic obesity, anorexia nervosa, bulimia nervosa, binge-eating disorder, and healthy controls. Ability of α-MSH/IgG IC to bind and activate human MC4R were studied in vitro and to influence feeding behavior in vivo in rodents. We found that α-MSH-reactive IgG were low in obese but increased in anorectic and bulimic patients and displayed different epitope and kinetics of IC formation. Importantly, while α-MSH/IgG IC from all subjects were binding and activating MC4R, the receptor binding affinity was decreased in obesity. Additionally, α-MSH/IgG IC had lower MC4R-mediated cAMP activation threshold as compared with α-MSH alone in all but not obese subjects. Furthermore, the cellular internalization rate of α-MSH/IgG IC by MC4R-expressing cells was decreased in obese but increased in patients with anorexia nervosa. Moreover, IgG from obese patients prevented central anorexigenic effect of α-MSH. These findings reveal that MC4R is physiologically activated by IC formed by α-MSH/IgG and that different levels and molecular properties of α-MSH-reactive IgG underlie biological activity of such IC relevant to altered appetite in obesity and eating disorders.

Developmental Premorbid Body Mass Index Trajectories of Adolescents With Eating Disorders in a Longitudinal Population Cohort

OBJECTIVE

To examine whether childhood body mass index (BMI) trajectories are prospectively associated with later eating disorder (ED) diagnoses.

METHOD

Using a subsample from the Avon Longitudinal Study of Parents and Children (N = 1,502), random-coefficient growth models were used to compare premorbid BMI trajectories of individuals who later developed anorexia nervosa (n = 243), bulimia nervosa (n = 69), binge-eating disorder (n = 114), and purging disorder (n = 133) and a control group without EDs or ED symptoms (n = 966). BMI was tracked longitudinally from birth to 12.5 years of age and EDs were assessed at 14, 16, and 18 years of age.

RESULTS

Distinct developmental trajectories emerged for EDs at a young age. The average growth trajectory for individuals with later anorexia nervosa veered significantly below that of the control group before 4 years of age for girls and 2 years for boys. BMI trajectories were higher than the control trajectory for all other ED groups. Specifically, the mean bulimia nervosa trajectory veered significantly above that of controls at 2 years for girls, but boys with later bulimia nervosa did not exhibit higher BMIs. The mean binge-eating disorder and purging disorder trajectories significantly diverged from the control trajectory at no older than 6 years for girls and boys.

CONCLUSION

Premorbid metabolic factors and weight could be relevant to the etiology of ED. In anorexia nervosa, premorbid low weight could represent a key biological risk factor or early manifestation of an emerging disease process. Observing children whose BMI trajectories persistently and significantly deviate from age norms for signs and symptoms of ED could assist the identification of high-risk individuals.

Sex Differences in Adolescent Anorexia and Bulimia Nervosa: Beyond the Signs and Symptoms

PURPOSE OF REVIEW

We review research related to sex differences in eating disorders (EDs) in adolescents. Prior work has explored clinical differences; thus, we examine literature in areas identified as playing an etiological or maintenance role in EDs including: genetics, hormones, neurocognitive inefficiencies, and reward circuitry.

RECENT FINDINGS

Sex steroids appear to a play role in the unmasking of genetic risk for development of EDs and puberty may be a heightened period of risk for females. While neurocognitive differences have been well studied in adults with ED, research with adolescents has been less conclusive. Recent work suggests that neural circuitry involved in reward and punishment may play role in development and maintenance of EDs in females. Males are underrepresented in these areas of research. Given known sex differences in healthy adolescents, it is likely there are sex differences in the putative biological etiology/maintenance of EDs. Males should be included in future research.

Hypothesis: Clues From Mammalian Hibernation for Treating Patients With Anorexia Nervosa

This hypothesis is that anorexia nervosa (AN) is a biologically driven disorder, and mammalian hibernation may offer clues to its pathogenesis. Using this approach, this hypothesis offers suggestions for employing heart rate variability as an early diagnostic test for AN; employing the ketogenic diet for refeeding patients, attending to omega 3:6 ratio of polyunsaturated fatty acids (PUFAs) in the refeeding diet; and exploring clinical trials of the endocannabinoid-like agent, palmitoylethanolamde for patients with AN. This hypothesis also explores the role of lipids and autoimmune phenomena in AN, and suggest a lipodomics study to search for antibodies in the serum on patients with AN.

Evolutionary Psychology of Eating Disorders: An Explorative Study in Patients With Anorexia Nervosa and Bulimia Nervosa

Prior research on non-clinical samples has lent support to the sexual competition hypothesis for eating disorders (SCH) where the drive for thinness can be seen as an originally adaptive strategy for women to preserve a nubile female shape, which, when driven to an extreme, may cause eating disorders. Restrictive versus impulsive eating behavior may also be relevant for individual differences in allocation of resources to either mating effort or somatic growth, reflected in an evolutionary concept called “Life History Theory” (LHT). In this study, we aimed to test the SCH and predictions from LHT in female patients with clinically manifest eating disorders. Accordingly, 20 women diagnosed with anorexia nervosa (AN), 20 with bulimia nervosa (BN), and 29 age-matched controls completed a package of questionnaires comprising measures for behavioral features and attitudes related to eating behavior, intrasexual competition, life history strategy, executive functioning and mating effort. In line with predictions, we found that relatively faster life history strategies were associated with poorer executive functioning, lower perceived own mate value, greater intrasexual competition for mates but not for status, and, in part, with greater disordered eating behavior. Comparisons between AN and BN revealed that individuals with BN tended to pursue a “fast” life history strategy, whereas people with AN were more similar to controls in pursuing a “slow” life history strategy. Moreover, intrasexual competition for mates was significantly predicted by the severity of disordered eating behavior. Together, our findings lend partial support to the SCH for eating disorders. We discuss the implications and limitations of our study findings.

Genetic differences in the behavioral organization of binge eating, conditioned food reward, and compulsive-like eating in C57BL/6J and DBA/2J strains

Binge eating (BE) is a heritable symptom of eating disorders associated with anxiety, depression, malnutrition, and obesity. Genetic analysis of BE could facilitate therapeutic discovery. We used an intermittent, limited access BE paradigm involving sweetened palatable food (PF) to examine genetic differences in BE, conditioned food reward, and compulsive-like eating between C57BL/6J (B6J) and DBA/2J (D2J) inbred mouse strains. D2J mice showed a robust escalation in intake and conditioned place preference for the PF-paired side. D2J mice also showed a unique style of compulsive-like eating in the light/dark conflict test where they rapidly hoarded and consumed PF in the preferred unlit environment. BE and compulsive-like eating exhibited narrow-sense heritability estimates between 56 and 73%. To gain insight into the genetic basis, we phenotyped and genotyped a small cohort of 133 B6J × D2J-F₂ mice at the peak location of three quantitative trait loci (QTL) previously identified in F₂ mice for sweet taste (chromosome 4: 156 Mb), bitter taste (chromosome 6: 133 Mb) and behavioral sensitivity to drugs of abuse (chromosome 11: 50 Mb). The D2J allele on chromosome 6 was associated with greater PF intake on training days and greater compulsive-like PF intake, but only in males, suggesting that decreased bitter taste may increase BE in males. The D2J allele on chromosome 11 was associated with an increase in final PF intake and slope of escalation across days. Future studies employing larger crosses and genetic reference panels comprising B6J and D2J alleles will identify causal genes and neurobiological mechanisms.

Food Addiction and Binge Eating: Lessons Learned from Animal Models

The feeding process is required for basic life, influenced by environment cues and tightly regulated according to demands of the internal milieu by regulatory brain circuits. Although eating behaviour cannot be considered "addictive" under normal circumstances, people can become "addicted" to this behaviour, similarly to how some people are addicted to drugs. The symptoms, cravings and causes of "eating addiction" are remarkably similar to those experienced by drug addicts, and both drug-seeking behaviour as eating addiction share the same neural pathways. However, while the drug addiction process has been highly characterised, eating addiction is a nascent field. In fact, there is still a great controversy over the concept of "food addiction". This review aims to summarize the most relevant animal models of "eating addictive behaviour", emphasising binge eating disorder, that could help us to understand the neurobiological mechanisms hidden under this behaviour, and to improve the psychotherapy and pharmacological treatment in patients suffering from these pathologies.

Updates on Genome-Wide Association Findings in Eating Disorders and Future Application to Precision Medicine

Heterogeneity, frequent diagnostic fluctuation across presentations, and global concerns with the absence of effective treatments all encourage science that moves the field toward individualized or precision medicine in eating disorders. We review recent advances in psychiatric genetics focusing on genome-wide association studies (GWAS) in eating disorders. Given that the only eating disorder to be the subject of GWAS to date is anorexia nervosa, we review anorexia GWAS and enumerate the prospects and challenges of a genomics-driven approach towards personalized intervention in eating disorders.

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.

The Role of Working Memory for Cognitive Control in Anorexia Nervosa versus Substance Use Disorder

Prefrontal cortex executive functions, such as working memory (WM) interact with limbic processes to foster impulse control. Such an interaction is referred to in a growing body of publications by terms such as cognitive control, cognitive inhibition, affect regulation, self-regulation, top-down control, and cognitive–emotion interaction. The rising trend of research into cognitive control of impulsivity, using various related terms reflects the importance of research into impulse control, as failure to employ cognitions optimally may eventually result in mental disorder. Against this background, we take a novel approach using an impulse control spectrum model – where anorexia nervosa (AN) and substance use disorder (SUD) are at opposite extremes – to examine the role of WM for cognitive control. With this aim, we first summarize WM processes in the healthy brain in order to frame a systematic review of the neuropsychological, neural and genetic findings of AN and SUD. In our systematic review of WM/cognitive control, we found n = 15 studies of AN with a total of n = 582 AN and n = 365 HC participants; and n = 93 studies of SUD with n = 9106 SUD and n = 3028 HC participants. In particular, we consider how WM load/capacity may support the neural process of excessive epistemic foraging (cognitive sampling of the environment to test predictions about the world) in AN that reduces distraction from salient stimuli. We also consider the link between WM and cognitive control in people with SUD who are prone to ‘jumping to conclusions’ and reduced epistemic foraging. Finally, in light of our review, we consider WM training as a novel research tool and an adjunct to enhance treatment that improves cognitive control of impulsivity.

Risk of being convicted of theft and other crimes in anorexia nervosa and bulimia nervosa: A prospective cohort study in a Swedish female population

OBJECTIVE

We examined epidemiological associations between anorexia nervosa (AN) and bulimia nervosa (BN) and risks of committing theft and other crimes in a nationwide female population.

METHOD

Females born in Sweden during 1979-1998 (N = 957,106) were followed from age 15 for up to 20 years using information on clinically diagnosed AN and BN (exposures), convictions of theft and other crimes (outcomes), psychiatric comorbidities, and familial relatedness from Swedish national registers. We estimated hazard ratios (HRs) of criminality in exposed versus unexposed females using Cox proportional hazards regressions and explored how comorbidities and unmeasured familial factors explained the associations.

RESULTS

The cumulative incidence of convictions of theft (primarily petty theft) and other crimes was higher in exposed females (AN: 11.60% theft, 7.39% other convictions; BN: 17.97% theft, 13.17% other convictions) than in unexposed females (∼5% theft, ∼6% other convictions). The significantly increased risk of being convicted of theft in exposed females (AN: HR = 2.51, 95% confidence interval = [2.29, 2.74], BN: 4.31 [3.68, 5.05]) was partially explained by comorbidities; unmeasured familial factors partially explained the association with convictions of theft in BN but not in AN. Females with BN had a doubled risk of convictions of other crimes, which was partially explained by comorbidities.

DISCUSSION

Individuals with eating disorders had increased risk for convictions of theft and potentially other crimes. Results underscore the importance of regular forensic screening and encourage research on mechanisms underlying the relation between crime and eating disorder psychopathology and efforts to determine how best to address such relation in treatment.

Significant Locus and Metabolic Genetic Correlations Revealed in Genome-Wide Association Study of Anorexia Nervosa

OBJECTIVE

The authors conducted a genome-wide association study of anorexia nervosa and calculated genetic correlations with a series of psychiatric, educational, and metabolic phenotypes.

METHOD

Following uniform quality control and imputation procedures using the 1000 Genomes Project (phase 3) in 12 case-control cohorts comprising 3,495 anorexia nervosa cases and 10,982 controls, the authors performed standard association analysis followed by a meta-analysis across cohorts. Linkage disequilibrium score regression was used to calculate genome-wide common variant heritability (single-nucleotide polymorphism [SNP]-based heritability [h2SNP]), partitioned heritability, and genetic correlations (rg) between anorexia nervosa and 159 other phenotypes.

RESULTS

Results were obtained for 10,641,224 SNPs and insertion-deletion variants with minor allele frequencies >1% and imputation quality scores >0.6. The h2SNP of anorexia nervosa was 0.20 (SE=0.02), suggesting that a substantial fraction of the twin-based heritability arises from common genetic variation. The authors identified one genome-wide significant locus on chromosome 12 (rs4622308) in a region harboring a previously reported type 1 diabetes and autoimmune disorder locus. Significant positive genetic correlations were observed between anorexia nervosa and schizophrenia, neuroticism, educational attainment, and high-density lipoprotein cholesterol, and significant negative genetic correlations were observed between anorexia nervosa and body mass index, insulin, glucose, and lipid phenotypes.

CONCLUSIONS

Anorexia nervosa is a complex heritable phenotype for which this study has uncovered the first genome-wide significant locus. Anorexia nervosa also has large and significant genetic correlations with both psychiatric phenotypes and metabolic traits. The study results encourage a reconceptualization of this frequently lethal disorder as one with both psychiatric and metabolic etiology.

Investigating Direct Links between Depression, Emotional Control, and Physical Punishment with Adolescent Drive for Thinness and Bulimic Behaviors, Including Possible Moderation by the Serotonin Transporter 5-HTTLPR Polymorphism

Objectives: To examine the relationship between psychological and social factors (depression, emotional control, sexual abuse, and parental physical punishment) and adolescent drive for Thinness and Bulimic behaviors in a large community sample, and to investigate possible genetic moderation.

Method: Data were drawn from the Australian Temperament Project (ATP), a population-based cohort study that has followed a representative sample of 2443 participants from infancy to adulthood across 16 waves since 1983. A subsample of 650 participants (50.2% female) of Caucasian descent who provided DNA were genotyped for a serotonin transporter promoter polymorphism (5-HTTLPR). Adolescent disordered eating attitudes and behaviors were assessed using the Bulimia and Drive for Thinness scales of the Eating Disorder Inventory-2 (15–16 years). Depression and emotional control were examined at the same age using the Short Mood and Feelings Questionnaire, and an ATP-devised measure of emotional control. History of sexual abuse and physical punishment were assessed retrospectively (23–24 years) in a subsample of 467 of those providing DNA.

Results: EDI-2 scores were associated with depression, emotional control, and retrospectively reported parental physical punishment. Although there was statistically significant moderation of the relationship between parental physical punishment and bulimic behaviors by 5-HTTLPR (p = 0.0048), genotypes in this subsample were not in Hardy–Weinberg Equilibrium. No other G×E interactions were significant. Conclusion: Findings from this study affirm the central importance of psychosocial processes in disordered eating patterns in adolescence. Evidence of moderation by 5-HTTLPR was not conclusive; however, genetic moderation observed in a subsample not in Hardy–Weinberg Equilibrium warrants further investigation.

Exploration of large, rare copy number variants associated with psychiatric and neurodevelopmental disorders in individuals with anorexia nervosa

Anorexia nervosa (AN) is a serious and heritable psychiatric disorder. To date, studies of copy number variants (CNVs) have been limited and inconclusive because of small sample sizes. We conducted a case-only genome-wide CNV survey in 1983 female AN cases included in the Genetic Consortium for Anorexia Nervosa. Following stringent quality control procedures, we investigated whether pathogenic CNVs in regions previously implicated in psychiatric and neurodevelopmental disorders were present in AN cases. We observed two instances of the well-established pathogenic CNVs in AN cases. In addition, one case had a deletion in the 13q12 region, overlapping with a deletion reported previously in two AN cases. As a secondary aim, we also examined our sample for CNVs over 1 Mbp in size. Out of the 40 instances of such large CNVs that were not implicated previously for AN or neuropsychiatric phenotypes, two of them contained genes with previous neuropsychiatric associations, and only five of them had no associated reports in public CNV databases. Although ours is the largest study of its kind in AN, larger datasets are needed to comprehensively assess the role of CNVs in the etiology of AN.

Molecular bases of anorexia nervosa, bulimia nervosa and binge eating disorder: shedding light on the darkness

Eating-disorders (EDs) consequences to human health are devastating, involving social, mental, emotional, physical and life-threatening aspects, concluding on impairment and death in cases of extreme anorexia nervosa. It also implies that people suffering an ED need to find psychiatric and psychological help as soon as possible to achieve a fully physical and emotional recovery. Unfortunately, to date, there is a crucial lack of efficient clinical treatment to these disorders. In this review, we present an overview concerning the actual pharmacological and psychological treatments, the knowledge of cells, circuits, neuropeptides, neuromodulators and hormones in the human brain- and other organs- underlying these disorders, the studies in animal models and, finally, the genetic approaches devoted to face this challenge. We will also discuss the need for new perspectives, avenues and strategies to be developed in order to pave the way to novel and more efficient therapeutics.

Genome-wide association analysis and functional annotation of positional candidate genes for feed conversion efficiency and growth rate in pigs

Feed conversion efficiency is a measure of how well an animal converts feed into live weight and it is typically expressed as feed conversion ratio (FCR). FCR and related traits like growth rate (e.g. days to 110 kg—D110) are of high interest for animal breeders, farmers and society due to implications on animal performance, feeding costs and environmental sustainability. The objective of this study was to identify genomic regions associated with FCR and D110 in pigs. A total of 952 terminal line boars, showing an individual variation in FCR, were genotyped using 60K SNP-Chips. Markers were tested for associations with estimated breeding values (EBV) for FCR and D110. For FCR, the largest number of associated SNPs was located on chromosomes 4 (30 SNPs), 1 (25 SNPs), X (15 SNPs) and 6 (12 SNPs). The most prominent genomic regions for D110 were identified on chromosomes 15 (10 SNPs), 1 and 4 (both 9 SNPs). The most significantly associated SNPs for FCR and D110 mapped 129.8 Kb from METTL11B (chromosome 4) and 32Kb from MBD5 (chromosome 15), respectively. A list of positional genes, closest to significantly associated SNPs, was used to identify enriched pathways and biological functions related to the QTL for both traits. A number of candidate genes were significantly overrepresented in pathways of immune cell trafficking, lymphoid tissue structure, organ morphology, endocrine system function, lipid metabolism, and energy production. After resequencing the coding region of selected positional and functional candidate genes, six SNPs were genotyped in a subset of boars. SNPs in PRKDC, SELL, NR2E1 and AKRIC3 showed significant associations with EBVs for FCR/D110. The study revealed a number of chromosomal regions and candidate genes affecting FCR/D110 and pointed to corresponding biological pathways related to lipid metabolism, olfactory reception, and also immunological status.

A Comparison of Personality, Life Events, Comorbidity, and Health in Monozygotic Twins Discordant for Anorexia Nervosa

Genetic and environmental factors contribute to the etiology of anorexia nervosa (AN). The co-twin control design is one of the most powerful methods available to evaluate environmental factors that could contribute to differences between monozygotic (MZ) twins who are discordant for AN. Using available data from a unique and rare sample of 22 Swedish female MZ pairs discordant for AN, we compared personality, life events, comorbidity, and health factors. Twins with AN had significantly higher perfectionism scores than unaffected co-twins and reported younger ages at first diet than unaffected co-twins who had dieted. Consistent with previous literature, more twins with AN reported gastrointestinal problems than unaffected co-twins. Although not significant due to low statistical power, more unaffected co-twins reported experiencing emotional neglect than twins with AN. Early dieting may be a harbinger of the development of AN or an early symptom. Higher perfectionism may represent a risk factor, sequela, or both. Sibling perception of neglect is noteworthy given the impact of an ill child with AN on family function and wellbeing. The health and wellbeing of siblings should be addressed clinically when one child in the family suffers from AN.

The tyrosine kinase receptor Tyro3 enhances lifespan and neuropeptide Y (Npy) neuron survival in the mouse anorexia (anx) mutation

Severe appetite and weight loss define the eating disorder anorexia nervosa, and can also accompany the progression of some neurodegenerative disorders such as amyotrophic lateral sclerosis (ALS). Although acute loss of hypothalamic neurons that produce appetite-stimulating neuropeptide Y (Npy) and agouti-related peptide (Agrp) in adult mice or in mice homozygous for the anorexia (anx) mutation causes aphagia, our understanding of the factors that help maintain appetite regulatory circuitry is limited. Here we identify a mutation (C19T) that converts an arginine to a tryptophan (R7W) in the TYRO3 protein tyrosine kinase 3 (Tyro3) gene, which resides within the anx critical interval, as contributing to the severity of anx phenotypes. Our observation that, like Tyro3-/- mice, anx/anx mice exhibit abnormal secondary platelet aggregation suggested that the C19T Tyro3 variant might have functional consequences. Tyro3 is expressed in the hypothalamus and other brain regions affected by the anx mutation, and its mRNA localization appeared abnormal in anx/anx brains by postnatal day 19 (P19). The presence of wild-type Tyro3 transgenes, but not an R7W-Tyro3 transgene, doubled the weight and lifespans of anx/anx mice and near-normal numbers of hypothalamic Npy-expressing neurons were present in Tyro3-transgenic anx/anx mice at P19. Although no differences in R7W-Tyro3 signal sequence function or protein localization were discernible in vitro, distribution of R7W-Tyro3 protein differed from that of Tyro3 protein in the cerebellum of transgenic wild-type mice. Thus, R7W-Tyro3 protein localization deficits are only detectable in vivo Further analyses revealed that the C19T Tyro3 mutation is present in a few other mouse strains, and hence is not the causative anx mutation, but rather an anx modifier. Our work shows that Tyro3 has prosurvival roles in the appetite regulatory circuitry and could also provide useful insights towards the development of interventions targeting detrimental weight loss.

Genetic epidemiology of eating disorders

PURPOSE OF REVIEW

We capture recent findings in the field of genetic epidemiology of eating disorders. As analytic techniques evolve for twin, population, and molecular genetic studies, new findings emerge at an accelerated pace. We present the current status of knowledge regarding the role of genetic and environmental factors that influence risk for eating disorders.

RECENT FINDINGS

We focus on novel findings from twin studies, population studies using genetically informative designs, and molecular genetic studies. Over the past 2 years, research in this area has yielded insights into: comorbidity with other psychiatric and medical disorders and with metabolic traits; developmental factors associated with the emergence of eating disorders; and the molecular genetics of anorexia nervosa.

SUMMARY

Insights from genetic epidemiology provide an important explanatory model for patients with eating disorders, family members, and clinicians. Understanding core biological determinants that explain the severity and persistence of the illnesses, their frequent co-occurrence with other conditions, and their familial patterns raises awareness and increases compassion for individuals living with these disorders. Large-scale genomic studies are currently underway. Ultimately, this domain of research may pave the way to greater understanding of the underlying neurobiology and inform the development of novel and effective interventions.

Prenatal exposure to gestational diabetes mellitus as an independent risk factor for long-term neuropsychiatric morbidity of the offspring

BACKGROUND

The reported rates of gestational diabetes mellitus are constantly escalating and little is known about long-term complications in the offspring. Evidence from the field of epigenetics strongly advocates the need for research on the neuropsychiatric complications in offspring prenatally exposed to gestational diabetes mellitus.

OBJECTIVE

We sought to assess whether in utero exposure to gestational diabetes mellitus increases the risk of long-term neuropsychiatric morbidity in the offspring.

STUDY DESIGN

A population-based cohort study compared the incidence of hospitalizations due to neuropsychiatric disease between singletons exposed and unexposed to gestational diabetes mellitus. Deliveries occurred in the years 1991 through 2014 in a regional tertiary medical center. Perinatal deaths, multiple gestations, mothers with pregestational diabetes or lack of prenatal care, and children with congenital malformations were excluded from the study. A multivariate generalized estimating equation logistic regression model analysis was used to control for confounders and for maternal clusters.

RESULTS

During the study period 231,271 deliveries met the inclusion criteria; 5.4% of the births were to mothers diagnosed with gestational diabetes mellitus (n = 12,642), of these 4.3% had gestational diabetes type A1 (n = 10,076) and 1.1% had gestational diabetes type A2 (n = 2566). During the follow-up period, a significant linear association was noted between the severity of the gestational diabetes (no gestational diabetes, gestational diabetes mellitus A1, gestational diabetes mellitus A2) and neuropsychiatric disease of the offspring (1.02% vs 1.36% vs 1.68%, respectively, P < .001). A Kaplan-Meier curve demonstrated that children born to women with gestational diabetes mellitus had higher cumulative incidence of neuropsychiatric morbidity. Using a generalized estimating equation multivariable logistic regression model, controlling for time-to-event, maternal age, gestational age at delivery, maternal obesity, maternal preeclampsia and fertility treatments, maternal gestational diabetes mellitus was found to be an independent risk factor for long-term neuropsychiatric disease of the offspring (gestational diabetes mellitus A1 [adjusted odds ratio, 1.83; 95% confidence interval, 1.53-2.19] and gestational diabetes mellitus A2 [adjusted odds ratio, 1.64; 95% confidence interval, 1.18-2.27]). Within the limits of our database, our findings also point to a possible association between in utero exposure to gestational diabetes mellitus and autistic spectrum disorder of the offspring (adjusted odds ratio, 4.44; 95% confidence interval, 1.55-12.69), which was found significant also after controlling for time-to-event, maternal age, gestational age at delivery, and offspring weight at birth.

CONCLUSION

Exposure to maternal gestational diabetes mellitus is an independent risk factor for long-term neuropsychiatric morbidity in the offspring.

A Primer on the Genetics of Comorbid Eating Disorders and Substance Use Disorders

Eating disorders (EDs) and substance use disorders (SUDs) frequently co-occur; however, the reasons for this are unclear. We review the current literature on genetic risk for EDs and SUDs, as well as preliminary findings exploring whether these classes of disorders have overlapping genetic risk. Overall, genetic factors contribute to individual differences in liability to multiple EDs and SUDs. Although initial family studies concluded that no shared familial (which includes genetic) risk between EDs and SUDs exists, twin studies suggest a moderate proportion of shared variance is attributable to overlapping genetic factors, particularly for those EDs characterized by binge eating and/or inappropriate compensatory behaviours. No adoption or molecular genetic studies have examined shared genetic risk between these classes of disorders. Research investigating binge eating and inappropriate compensatory behaviours using emerging statistical genetic methods, as well as examining gene-environment interplay, will provide important clues into the aetiology of comorbid EDs and SUDs.

Anorexia nervosa

Anorexia nervosa (AN) is a psychiatric condition characterized by severe weight loss and secondary problems associated with malnutrition. AN predominantly develops in adolescence in the peripubertal period. Without early effective treatment, the course is protracted with physical, psychological and social morbidity and high mortality. Despite these effects, patients are noted to value the beliefs and behaviours that contribute to their illness rather than regarding them as problematic, which interferes with screening, prevention and early intervention. Involving the family to support interventions early in the course of the illness can produce sustained changes; however, those with a severe and/or protracted illness might require inpatient nursing support and/or outpatient psychotherapy. Prevention programmes aim to moderate the overvaluation of 'thinness' and body dissatisfaction as one of the proximal risk factors. The low prevalence of AN limits the ability to identify risk factors and to study the timing and sex distribution of the condition. However, genetic profiles, premorbid features, and brain structures and functions of patients with AN show similarities with other psychiatric disorders and contrast with obesity and metabolic disorders. Such studies are informing approaches to address the neuroadaptation to starvation and the other various physical and psychosocial deficits associated with AN. This Primer describes the epidemiology, diagnosis, screening and prevention, aetiology, treatment and quality of life of patients with AN.

Perceptions of the causes of eating disorders: a comparison of individuals with and without eating disorders

BACKGROUND

In this study, we examined perceptions regarding the causes of eating disorders, both among those with eating disorders as well as those without. By understanding the differences in perceived causes between the two groups, better educational programs for lay people and those suffering from eating disorders can be developed.

METHOD

This study used open-ended questions to assess the beliefs of 57 individuals with self-reported eating disorders and 220 without. Participants responded to the questions, "What do you think was (were) the cause(s) of your eating disorder?" and "What do you think is (are) the cause(s) of eating disorders?".

RESULTS

A list of possible codes for the causes of eating disorders was created based on a thorough review of the literature. A manually-generated set of eight codes was then created from individuals' actual responses. Frequencies and chi square analyses demonstrated differences in rates of endorsement between those with eating disorders and those without. Participants with eating disorders most frequently endorsed psychological/emotional and social problems, with genetics/biology and media/culture ideals least endorsed. Participants without eating disorders most frequently endorsed psychological/emotional problems and media/culture ideals, with traumatic life events and sports/health least endorsed. There was a difference between groups in the endorsement of the media as a cause of eating disorders, suggesting that those without eating disorders may overly attribute the media as the main cause while those with eating disorders may not be fully aware of the media's impact. Additionally, while both groups highly endorsed psychological/emotional problems, there was a noticeable stigma about eating disorders among those without eating disorders.

CONCLUSIONS

There were noteworthy differences between samples; such differences suggest that there is a need for more education on the topic of eating disorders. Furthermore, despite empirical support for the effects of genetics, sports, and family factors, these were infrequently endorsed as causes of eating disorders by both groups. Our results suggest that there is a need for more education regarding the factors associated with eating disorders, in order to reduce the stigma surrounding these disorders and to potentially aid the treatment process.