Fat mass and obesity-associated gene (FTO) in eating disorders: evidence for association of the rs9939609 obesity risk allele with bulimia nervosa and anorexia nervosa

Relationship of Genetic Polymorphisms and Microbial Composition with Binge Eating Disorder: A Systematic Review

Humans are the result of an evolutionary process, and because of this, many biological processes are interconnected with each other. The intestine-brain axis consists of an intricately connected neuronal-neuroendocrine circuit that regulates the sensation of hunger and satiety. Genetic variations and the consumption of unnatural diets (ultra-processed foods, high contents of sugars, etc.) can override this circuit and cause addiction to certain foods and/or the inability to feel satiety in certain situations. The patients who come to consultations (mainly psychology or nutrition) in an attempt to resolve this problem sometimes fail, which leads to them looking for new strategies based on biological predisposition. This investigation aims to evaluate the genetic studies regarding the microbiota carried out in the last 12 years in humans to try to determine which genes and microbes that have been recently studied are related to patients diagnosed with binge eating disorder or compulsive eating (presenting obesity or not). The protocol followed the PRISMA statement, and the following databases were searched from 2012 until the present day: PubMed, PsycINFO, SCOPUS, and Web of Science. Twenty-four international articles were analyzed, including cross-sectional or exploratory studies; five of them referred to the microbial composition, and in nineteen, the existence of genetic polymorphisms present in binge eating disorder or in compulsive eating could be observed: DRD2, OPRM1, COMT, MC4R, BNDF, FTO, SLC6A3, GHRL, CARTPT, MCHR2, and LRP11. Even though there is still much to investigate on the subject, it must be highlighted that, in the last 4 years, a two-fold increase has been observed in potential markers and in studies related to the matter, also highlighting the importance of different analyses in relation to psychosocial factors and their interaction with the genetic and microbial factors, for which research on the matter must be continued.

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.

Unexpected identification of obesity-associated mutations in LEP and MC4R genes in patients with anorexia nervosa

Mutations leading to a reduced or loss of function in genes of the leptin-melanocortin system confer a risk for monogenic forms of obesity. Yet, gain of function variants in the melanocortin-4-receptor (MC4R) gene predispose to a lower BMI. In individuals with reduced body weight, we thus expected mutations leading to an enhanced function in the respective genes, like leptin (LEP) and MC4R. Therefore, we have Sanger sequenced the coding regions of LEP and MC4R in 462 female patients with anorexia nervosa (AN), and 445 healthy-lean controls. In total, we have observed four and eight variants in LEP and MC4R, respectively. Previous studies showed different functional in vitro effects for the detected frameshift and non-synonymous variants: (1) LEP: reduced/loss of function (p.Val94Met), (2) MC4R: gain of function (p.Val103Ile, p.Ile251Leu), reduced or loss of function (p.Thr112Met, p.Ser127Leu, p.Leu211fsX) and without functional in vitro data (p.Val50Leut). In LEP, the variant p.Val94Met was detected in one patient with AN. For MC4R variants, one patient with AN carried the frameshift variant p.Leu211fsX. One patient with AN was heterozygous for two variants at the MC4R (p.Val103Ile and p.Ser127Leu). All other functionally relevant variants were detected in similar frequencies in patients with AN and lean individuals.

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.

The Advent of Nutrigenomics: A Narrative Review with an Emphasis on Psychological Disorders

A new research field is emerging that combines nutrition and genetics at the molecular level, namely nutrigenomics. Several aspects of nutrigenomics are examined in this review, with a particular focus on psychological disorders. The origin of this field in the 20th century and its modern developments have been investigated. Various studies have reported the impact of genetic factors and diet on various chronic disorders, elucidating how the deficiency of several macronutrients results in significant ailments, including diabetes, cancer, cardiovascular disorders, and others. Furthermore, the application of nutrigenomics to diet and its impact on the global disease rate and quality of life have been discussed. The relationship between diet and gene expression can facilitate the classification of diet-gene interactions and the diagnosis of polymorphisms and anomalies. Numerous databases and research tools for the study of nutrigenomics are essential to the medical application of this field. The nutrition-gene interrelationships can be utilized to study brain development, impairment, and diseases, which could be a significant medical breakthrough. It has also been observed that psychological conditions are exacerbated by the interaction between gut microbes and the prevalence of malnutrition. This article focuses on the impact of nutrition on genes involved in various psychological disorders and the potential application of nutrigenomics as a revolutionary treatment method.

A review on association and correlation of genetic variants with eating disorders and obesity

Background

Now, eating disorders and obesity and their correlations are danger signal in worldwide which is caused by multifactor and associated with significant mortality and morbidity.

Main body

Every aspect of a patient’s life is influenced by eating disorders and obesity and their correlations. Due to frequent seeing of obese patients, eating disorders have been included in the review as they can sometimes be associated with obesity. However, it should be noted that most patients having eating disorder are at risk to be obese or overweight. This research explores the risk factors for the two disorders, as well as the assessment of medical complications and treatment recommendations for the disorders. In these two disorders, there is also a correlation. The essential consideration is that eating disorders are impulse-control disorders which are similar to addictive behaviors in some aspects. So it is a crying need to treat a patient with obesity and eating disorders simultaneously to ensure success. Genome-wide association studies (GWASs) have increased our knowledge of the pathophysiology of eating disorders (EDs) and obesity and their correlation.

Conclusion

This review enlightens on the summary of eating disorder, obesity, genotypic traits, molecular relations, interaction, correlation, and effect of eating disorder and obesity which outline potential future directions and clinical implications for patients with EDs and obesity.

The Significance of the FTO Gene for Weight and Body Composition in Swedish Women With Severe Anorexia Nervosa During Intensive Nutrition Therapy

OBJECTIVE

The aim of this prospective study was to investigate the potential influence of the fat mass and obesity-associated gene (FTO), SNP rs9939609, on body mass index (BMI) and body composition in women with anorexia nervosa (AN) undergoing intensive nutrition therapy.

METHOD

Twenty-five female patients with AN (20.1 ± 2.3 years; BMI, 15.5 ± 0.9 kg/m²) were included for 12 weeks of treatment with a high-energy diet. FTO was genotyped and body composition parameters were assessed by dual-energy X-ray absorptiometry and peripheral quantitative computed tomography at baseline and after 12 weeks.

RESULTS

The distribution of the different FTO genotypes were as follows: AA, 24%; TA, 48%; and TT, 28%. Patients gained a median of 9.8 kg (range, 5.5-17.0 kg) and BMI increased to 19.0 ± 0.9 kg/m². The increase in BMI, fat mass, and the quotient fat/muscle area was significant for the TT and TA genotype groups. Total lean mass was stable in all genotype groups. We could not demonstrate any difference among the 3 FTO genotypes related to the increases in BMI during nutrition therapy when the additive, dominant, and recessive models of inheritance were applied.

CONCLUSIONS

Irrespective of the FTO genotype, there was no difference in weight response during nutrition therapy. Hence, in this small study there was limited support for individualized nutrition therapy for AN based on FTO genotype.

Associations between FTO rs9939609 polymorphism, serum vitamin D, mental health, and eating behaviors in overweight adults

Background: Despite the significant role of the Fat Mass and Obesity-Associated (FTO) gene in obesity, the underlying mechanisms are not fully elucidated. Besides, vitamin D deficiency and obesity are mostly seen together, and it can be hypothesized that this nutrient may have an impact in the role of FTO genotype in adiposity.Objective: Thus, this study aimed to investigate the association of FTO rs9939609 gene polymorphism with eating behaviors, eating disorders, and general mental health in overweight adults, considering their vitamin D intake as a mediate confounding factor.Methods: This cross-sectional study was carried out on 197 overweight adults in Shiraz, Iran. Genotyping was performed through amplification refractory mutation system polymerase chain reaction (ARMS PCR). Mental health, vitamin D intake, eating behaviors and disorders were assessed by the validated questionnaires.Results: The risk allele of the FTO rs9939609 polymorphism (A) was significantly associated with a higher risk of eating behavior and mental health disorders (all P < 0.05). After considering vitamin D intake, the AA genotype carriers had significantly higher risks for poorer eating behavior (P = 0.002), mental health (P = 0.007), and general mental health (P = 0.039) compared with the TT carriers if they had insufficient vitamin D intake.Conclusion: In conclusion, these results indicated that the A-allele of the FTO rs9939609 polymorphism may be associated with poorer eating behaviors, mental health, and higher risk of eating disorders. It was also identified that the effect of FTO rs9939609 A risk allele on eating behavior and mental health may be limited to people with insufficient vitamin D intake.

Psychiatric Comorbidity in Mexican Adolescents with a Diagnosis of Eating Disorders Its Relationship with the Body Mass Index

The prevalence of comorbid psychiatric disorders among patients with eating disorders (ED) is higher than the general population. Individuals diagnosed with eating disorders have changes in their body mass index which could promote severe metabolic disruptions. This study aimed (1) to report the prevalence of comorbid psychiatric disorders among a Mexican adolescent sample diagnosed with eating disorders, (2) to compare our results with the prevalence of psychiatric disorders reported from a national survey of mental health of adolescents, (3) to compare the presence of psychiatric comorbidities between ED diagnoses, and (4) to explore the relationship of these comorbidities with the body mass index. In the study, we included 187 Mexican adolescents diagnosed with eating disorders. The psychiatric comorbidities were evaluated using the Mini International Neuropsychiatric Interview for children/adolescents, and a revised questionnaire on eating and weight patterns. We found that 89% of the Mexican adolescents diagnosed with ED had another psychiatric comorbidity. Major depressive disorder (52.40%) and suicide risk (40%) were the most prevalent comorbidities. Attention and deficit hyperactivity disorder (ADHD) prevalence was different between ED diagnosis, and adolescents with binge-eating disorder and ADHD had the higher body mass index. Our results showed that in this sample of Mexican adolescents, the presence of comorbidities could impact body mass index. This emphasizes the importance that clinicians take into consideration the presence of psychiatric comorbidities to achieve an integrative treatment for adolescents diagnosed with ED.

Variants in the Obesity-Linked FTO gene locus modulates psychopathological features of patients with Anorexia Nervosa

Our aim was to determine whether variability in the fat mass obesity (FTO) gene locus, consistently related to obesity, affects the risk of eating disorders (ED) and/or the psychopathology displayed by these patients. We analyzed 26 tag-single nucleotide polymorphisms (SNPs) that capture FTO variability in 352 ED patients [233 with Anorexia Nervosa (AN) and 119 with binge-eating] and 396 controls. Psychopathological symptoms and traits were evaluated by the Eating Disorders Inventory Test 2 (EDI-2) and Symptoms Checklist 90 Revised (SCL-90R) questionnaires. No associations were found for ED risk. The rs7205987 CC genotype correlated with higher scores in all but one of the EDI-2 scales in the AN group. Associations with Bulimia (p = 0.0019) and Interoceptive Awareness (p = 0.00007) retained significance after False Discovery Rate (FDR) correction for multiple testing. A 3-SNP sliding window analysis showed that FTO haplotypes were again highly associated with Interoceptive Awareness (rs9921255/rs6499662/rs7205987 haplotype; FDR-q = 0.04), Bulimia (rs1125338/rs2192872/rs708258; FDR-q = 0.00037), and Maturity Fears (rs708258/rs12599672/rs11076017; FDR-q = 0.041). In addition, a distal region of the gene between rs9924877 (position 53947509) and rs2192872 (54040715) was linked to Anxiety, Depression and Phobic Anxiety in AN patients, with FDR-q values ranging from 0.023 to 0.045. The results suggest that the FTO gene might be an important locus regarding traits and psychopathological symptoms often displayed by AN patients.

Interaction of FTO rs9939609 and the native American-origin ABCA1 p.Arg230Cys with circulating leptin levels in Mexican adolescents diagnosed with eating disorders: Preliminary results

Eating disorders (ED) are characterized by disruption of eating behaviour and alteration of food intake. Leptin, is one of the main hormones that modulate food intake and are altered in individuals diagnosed with ED. Genetic risk variants for obesity, like those reported inFTO and ABCA1, have also been associated to ED disorders. The present study aimed to analysed leptin circulating levels and the interaction between obesity-risk variants in FTO and ABCA1, in adolescents diagnosed with ED. A total of 99 individuals diagnosed with ED were genotype using Taqman probes for FTO (rs9939609) and ABCA1 (p.Arg230Cys, rs9282541). Commercial enzyme-linked immunosorbent assays were utilized to determined circulating leptin. Differences in leptin concentration were analysed by t-Student or ANOVA test. Gene-gene interaction were analysed using general estimation equations. Circulating leptin levels differed between the three diagnostic groups, lead by individuals diagnosed with binge eating-disorder. In individuals with more than 3 of episodes of binge-eating per week having the highest leptin levels. Also, we found that carriers of both risk alleles had the highest leptin levels. Our observations found an interaction between FTO rs9969609 and the native American-origin ABCA1 p.Arg230Cys to modulate circulating leptin levels in Mexican adolescents diagnosed with eating-disorders.

Clinical phenotype and genetic risk factors for bipolar disorder with binge eating: an update

Introduction: Clinical and genetic study of psychiatric conditions has underscored the co-occurrence of complex phenotypes and the need to refine them. Bipolar Disorder (BD) and Binge Eating (BE) behavior are common psychiatric conditions that have high heritability and high co-occurrence, such that at least one quarter of BD patients have BE (BD + BE). Genetic studies of BD alone and of BE alone suggest complex polygenic risk models, with many genetic risk loci yet to be identified. Areas covered: We review studies of the epidemiology of BD+BE, its clinical features (cognitive traits, psychiatric comorbidity, and role of obesity), genomic studies (of BD, eating disorders (ED) defined by BE, and BD + BE), and therapeutic implications of BD + BE. Expert opinion: Subphenotyping of complex psychiatric disorders reduces heterogeneity and increases statistical power and effect size; thus, it enhances our capacity to find missing genetic (and other) risk factors. BD + BE has a severe clinical picture and genetic studies suggests a distinct genetic architecture. Differential therapeutic interventions may be needed for patients with BD + BE compared with BD patients without BE. Recognizing the BD + BE subphenotype is an example of moving towards more precise clinical and genetic entities.

Differential effects on neurodevelopment of FTO variants in obesity and bipolar disorder suggested by in silico prediction of functional impact: An analysis in Mexican population

INTRODUCTION

Several studies indicate that polygenic obesity is linked to fat-mass and obesity-associated (FTO) genetic variants. Nevertheless, the link between variants in FTO and mental disorders has been barely explored. The present work aims to determine whether FTO genetic variants are associated with bipolar disorder and obesity, and to perform an in silico prediction of variant-dependent functional impact on the developing brain transcriptome.

METHODS

Four hundred and forty-six Mexican mestizos were included in a genetic association analysis. SNP-sequence kernel association test and linear mixed models were implemented for genetic association assessment. For functional impact prediction, we analyzed the mapping of regulatory elements, the modification of binding sites of transcription factors and the expression of transcription factors in the brain developing transcriptome, searching on different databases.

RESULTS

In the set-based analysis, we found different associated regions to BD (bipolar disorder) and obesity. The promoter flanking region of FTO intron 1 was associated with differential effects on BMI, while intron 2 of RPGRIP1L and FTO upstream regions were associated with BD. The prediction analysis showed that FTO BD-associated variants disturb binding sites of SP1 and SP2; obesity-associated variants, on the other hand, disturb binding sites of FOXP1, which are transcription factors highly expressed during prenatal development stages of the brain.

CONCLUSION

Our results suggest a possible effect of FTO variants on neurodevelopment in obesity and bipolar disorder, which gives new insights into the molecular mechanism underlying this association.

Role of eating disorders-related polymorphisms in obesity pathophysiology

Human biological system provides innumerable neuroendocrine inputs for food intake control, with effects on appetite's modulation and the satiety signs. Its regulation is very complex, engaging several molecular interactions with many tissues, hormones, and neural circuits. Thus, signaling molecules that control food intake are critical for normal energy homeostasis and a deregulation of these pathways can lead to eating disorders and obesity. In line of this, genetic factors have a significantly influence of the regulation of neural circuits controlling the appetite and satiety pathways, as well as the regulation of brain reward systems. Single Nucleotide Polymorphisms (SNPs) in genes related to hypothalamic appetite and satiety mechanisms, further in multiple neurotransmitter systems may contribute to the development of major Eating Disorders (EDs) related to obesity, among them Binge Eating Disorder (BED) and Bulimia Nervosa (BN), which are discussed in this review.

Association study of variants in genes FTO, SLC6A4, DRD2, BDNF and GHRL with binge eating disorder (BED) in Portuguese women

A population based case-control study was conducted in Portuguese women with overweight/obesity to investigate the possible association of variants in genes FTO, SLC6A4, DRD2, BDNF and GHRL with binge eating disorder (BED). The distribution of seven polymorphisms was evaluated in 31 BED patients and 62 controls. No significant associations were found between polymorphisms and BED. Of interest, a markedly lower frequency of the FTO rs9939609 obesity risk A-allele was found in BED patients (0.290) in relation to the control group (0.402). Contrasting with anorexia nervosa and bulimia nervosa, our data suggest that rs9939609 A-allele has no potential role in BED.

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.

Genetic Markers in Psychiatry

Psychiatric disorders such as addiction (substance use and addictive disorders), depression, eating disorders, schizophrenia, and post-traumatic stress disorder (PTSD) are severe, complex, multifactorial mental disorders that carry a high social impact, enormous public health costs, and various comorbidities as well as premature morbidity. Their neurobiological foundation is still not clear. Therefore, it is difficult to uncover new set of genes and possible genetic markers of these disorders since the understanding of the molecular imbalance leading to these disorders is not complete. The integrative approach is needed which will combine genomics and epigenomics; evaluate epigenetic influence on genes and their influence on neuropeptides, neurotransmitters, and hormones; examine gene × gene and gene × environment interplay; and identify abnormalities contributing to development of these disorders. Therefore, novel genetic approaches based on systems biology focused on improvement of the identification of the biological underpinnings might offer genetic markers of addiction, depression, eating disorders, schizophrenia, and PTSD. These markers might be used for early prediction, detection of the risk to develop these disorders, novel subtypes of the diseases and tailored, personalized approach to therapy.

Influence of TFAP2B and KCTD15 genetic variability on personality dimensions in anorexia and bulimia nervosa

INTRODUCTION

TFAP2B and KCTD15 are obesity-related genes that interact to regulate feeding behavior. We hypothesize that variability in these loci, isolated or in combination, could also be related to the risk of eating disorders (ED) and/or associated psychological traits.

METHODS

We screened 425 participants (169 ED patients, 75 obese subjects, and 181 controls) for 10 clinically relevant and tag single-nucleotide polymorphisms (SNPs) in KCTD15 and TFAP2B by the Sequenom MassARRAY platform and direct sequencing. Psychometric evaluation was performed with EDI-2 and SCL-90R inventories.

RESULTS

The KCTD15 rs287103 T variant allele was associated with increased risk of bulimia nervosa (BN) (OR = 4.34 [1.47-29.52]; p = .003) and with scores of psychopathological scales of these patients. Haplotype *6 in KCTD15 was more frequent in controls (OR = 0.40 [0.20-0.80], p = .009 for anorexia nervosa), while haplotype *4 in TFAP2B affected all three scales of the SCL-90R inventory in BN patients (p ≤ .01). Epistasis analyses revealed relevant interactions with body mass index of BN patients (p < .001). Genetic profiles in obese patients did not significantly differ from those found in ED patients.

CONCLUSIONS

This is the first study that evaluates the combined role of TFAP2B and KCTD15 genes in ED. Our preliminary findings suggest that the interaction of genetic variability in these loci could influence the risk for ED and/or anthropometric and psychological parameters.

Effects of single genetic variants and polygenic obesity risk scores on disordered eating in adolescents - The HUNT study

PURPOSE

Improving the understanding of the role of genetic risk on disordered eating (DE).

METHODS

A case-control study including 1757 (F: 979, M: 778) adolescents (aged 13-19 years) from the Nord-Trøndelag Health Study (HUNT), an ethnically homogenous Norwegian population based study. Cases and controls were defined using a shortened version of the Eating Attitude Test. Logistic regression was employed to test for associations between DE phenotypes and 24 obesity and eating disorder susceptibility SNPs, and the joint effect of a subset of these in a genetic risk score (GRS).

RESULTS

COMT was shown to be associated with poor appetite/undereating (OR: 0.6, CI 95%: 0.43-0.83, p = 0.002). Independent of obesity associations, the weighted GRS was associated to overeating in 13-15 year old females (OR: 2.07, CI 95%: 1.14-3.76, p = 0.017). Additionally, a significant association was observed between the GRS and loss of control over eating in the total sample (OR: 1.62, CI 95%: 1.01-2.61, p = 0.046).

CONCLUSIONS

The COMT variant (rs4680) was associated with poor appetite/undereating. Our study further confirms prior findings that obesity risk also confers risk for loss of control over eating; and overeating amongst girls.

Fat mass and obesity-associated gene (FTO) is associated to eating disorders susceptibility and moderates the expression of psychopathological traits

Eating Disorders (EDs) show a multifactorial etiopathogenesis including environmental, psychological and biological factors. In the present study, we propose a model of interactions between genetic vulnerability-represented by Fat Mass and Obesity-Associated (FTO) gene-and stable psychopathological traits, such as bodily disorders and emotion dysregulation for EDs patients. The distribution of a polymorphism of the FTO (rs9939609 T>A) was evaluated in a series of 250 EDs patients and in a group of 119 healthy control subjects. Clinical data were collected through a face-to-face interview and several self-reported questionnaires were applied, including the Emotional Eating Scale and the IDentity and EAting disorders (IDEA) questionnaire for bodily disorders and self-identity. The A-allele was associated with an increased vulnerability to EDs (AA+AT genotypes frequency 72.8% in EDs vs. 52.9% in controls). The presence of the A-allele was associated with binge eating behavior, higher emotional eating and higher IDEA scores. Finally, the FTO rs9939609 SNP was found to influence the relationship between these variables, as an association between disorder of corporeality and emotional eating was found only in A-allele carriers. A-allele seems to represent a potential additive risk factor for EDs persons, with bodily disorders to develop emotional eating and binge eating behaviors.

Genome-wide association study of body mass index in subjects with alcohol dependence

Outcomes related to disordered metabolism are common in alcohol dependence (AD). To investigate alterations in the regulation of body mass that occur in the context of AD, we performed a genome-wide association study (GWAS) of body mass index (BMI) in African Americans (AAs) and European Americans (EAs) with AD. Subjects were recruited for genetic studies of AD or drug dependence and evaluated using the Semi-structured Assessment for Drug Dependence and Alcoholism. We investigated a total of 2587 AAs and 2959 EAs with DSM-IV AD diagnosis. In the stage 1 sample (N = 4137), we observed three genome-wide significant (GWS) single-nucleotide polymorphism associations, rs200889048 (P = 8.98 * 10-12 ) and rs12490016 (P = 1.44 * 10-8 ) in EAs and rs1630623 (P = 5.14 * 10-9 ) in AAs and EAs meta-analyzed. In the stage 2 sample (N = 1409), we replicated 278, 253 and 168 of the stage 1 suggestive loci (P < 5*10-4 ) in AAs, EAs, and AAs and EAs meta-analyzed, respectively. A meta-analysis of stage 1 and stage 2 samples (N = 5546) identified two additional GWS signals: rs28562191 in EAs (P = 4.46 * 10-8 ) and rs56950471 in AAs (P = 1.57 * 10-9 ). Three of the GWS loci identified (rs200889048, rs12490016 and rs1630623) were not previously reported by GWAS of BMI in the general population, and two of them raise interesting hypotheses: rs12490016-a regulatory variant located within LINC00880, where there are other GWAS-identified variants associated with birth size, adiposity in newborns and bulimia symptoms, which also interact with social stress in relation to birth size; rs1630623-a regulatory variant related to ALDH1A1, a gene involved in alcohol metabolism and adipocyte plasticity. These loci offer molecular insights regarding the regulatory mechanisms of body mass in the context of AD.

Contributions of mindful eating, intuitive eating, and restraint to BMI, disordered eating, and meal consumption in college students

PURPOSE

Mindful eating and intuitive eating are promoted as means to circumvent potentially maladaptive dietary restraint while maintaining a healthy weight. Although theoretically related, no studies have examined the correlations between intuitive eating, mindful eating, and restraint in the same sample. This study sought to examine these constructs and their correlations with body mass index (BMI), eating-disordered behaviors, and meal consumption in a college sample.

METHODS

Participants (N = 125) completed a laboratory taste-test meal and measures of each eating-related construct using the EDDS, IES, MEQ, and TFEQ-Restraint Subscale.

RESULTS

Mindful eating, intuitive eating, and restraint were not strongly correlated. Hierarchical multiple regression analyses indicated that restraint and intuitive eating accounted for significant variance in disordered eating and BMI. Elevated restraint was associated with increased BMI and disordered eating; elevated intuitive eating was associated with decreased BMI and disordered eating. Mindful eating did not correlate with any outcome variables. Follow-up analyses suggested that specific intuitive eating subscales accounted for unique variance in the relation between intuitive eating and disordered eating. Intuitive eating was the only construct that was significantly associated with meal consumption.

CONCLUSIONS

Intuitive eating and restraint appear to be only weakly correlated, and each is differentially associated with meal consumption. Mindful eating does not appear to relate to outcome variables.

Machine learning derived risk prediction of anorexia nervosa

Background

Anorexia nervosa (AN) is a complex psychiatric disease with a moderate to strong genetic contribution. In addition to conventional genome wide association (GWA) studies, researchers have been using machine learning methods in conjunction with genomic data to predict risk of diseases in which genetics play an important role.

Methods

In this study, we collected whole genome genotyping data on 3940 AN cases and 9266 controls from the Genetic Consortium for Anorexia Nervosa (GCAN), the Wellcome Trust Case Control Consortium 3 (WTCCC3), Price Foundation Collaborative Group and the Children’s Hospital of Philadelphia (CHOP), and applied machine learning methods for predicting AN disease risk. The prediction performance is measured by area under the receiver operating characteristic curve (AUC), indicating how well the model distinguishes cases from unaffected control subjects.

Results

Logistic regression model with the lasso penalty technique generated an AUC of 0.693, while Support Vector Machines and Gradient Boosted Trees reached AUC’s of 0.691 and 0.623, respectively. Using different sample sizes, our results suggest that larger datasets are required to optimize the machine learning models and achieve higher AUC values.

Conclusions

To our knowledge, this is the first attempt to assess AN risk based on genome wide genotype level data. Future integration of genomic, environmental and family-based information is likely to improve the AN risk evaluation process, eventually benefitting AN patients and families in the clinical setting.

Electronic supplementary material

The online version of this article (doi:10.1186/s12920-016-0165-x) contains supplementary material, which is available to authorized users.

Overlap in Eating Disorders and Obesity in Adolescence

While eating disorders and obesity have traditionally been conceptualized as separate conditions, recent research suggests important overlap in several areas including etiology, comorbidity, risk factors, and prevention approaches. Examining the commonality among these conditions is particularly important as adolescents who present with both eating disorder symptomology and obesity demonstrate poorer outcomes within weight control treatments and are at greater risk for future development of full threshold eating disorders and additional weight gain. The purpose of this paper is to review the research examining the overlap in prevalence rates for eating disorders and obesity in adolescents, as well as shared etiology, risk factors, and psychiatric and medical comorbidities. Current preventive and treatment approaches also will be discussed, while highlighting the need for more integrated assessment, prevention, and treatment efforts that focus on maladaptive eating and activity patterns shared by both eating disorders and obesity.

Are obesity risk genes associated with binge eating in adolescence?

OBJECTIVE

Cognitions and behaviors characteristic of binge eating are associated with a polymorphism in the FTO gene, robustly related to body mass index (BMI) and obesity risk. We investigated the association between binge eating and the individual and combined effect of 32 SNPs robustly associated with BMI in a population-based sample. We hypothesized that higher BMI and binge eating might share a common genetic etiology.

METHODS

Binge eating was assessed in adolescents from the Avon Longitudinal Study of Parents and Children at age 14 (n = 5,958) and 16 years (n = 4,948). We tested associations between 32 BMI-related SNPs and binge eating in crude and BMI-, age-, and gender-adjusted regression models.

RESULTS

Crude analyses showed an association between binge eating and rs1558902 (FTO) that persisted after adjustment for BMI (OR = 1.20, P = 8 × 10(-3) ). A weighted allelic score consisting of all 32 BMI-related SNPs was associated with binge eating (P = 8 × 10(-4) ); this association attenuated (P = 0.08) when rs1558902 was removed from the weighted allelic score.

CONCLUSIONS

BMI-related genes are associated with adolescent binge eating, in particular an FTO polymorphism. Although replication is needed, our findings have biological plausibility and are consistent with a postulated effect of FTO on appetite and food intake. Future studies should aim to understand the mechanisms underlying the relationship between FTO, binge eating, and obesity.

Discussing the putative role of obesity-associated genes in the etiopathogenesis of eating disorders

In addition to the identification of mutations clearly related to Mendelian forms of obesity; genome-wide association studies and follow-up studies have in the last years pinpointed several loci associated with BMI. These genetic alterations are located in or near genes expressed in the hypothalamus that are involved in the regulation of eating behavior. Accordingly, it seems plausible that these SNPs, or others located in related genes, could also help develop aberrant conduct patterns that favor the establishment of eating disorders should other susceptibility factors or personality dimensions be present. However, and somewhat surprisingly, with few exceptions such as BDNF, the great majority of the genes governing these pathways remain untested in patients with anorexia nervosa, bulimia nervosa or binge-eating disorder. In the present work, we review the few existing studies, but also indications and biological concepts that point to these genes in the CNS as good candidates for association studies with eating disorder patients.

Association between the oxytocin receptor gene polymorphism (rs53576) and bulimia nervosa

OBJECTIVE

Oxytocin circuits are implicated in the regulation of appetite and weight. Variants in the oxytocin receptor (OXTR) gene have been associated with bulimic behaviour. This study aimed to investigate the association between the OXTR gene and eating disorders.

METHOD

We genotyped six single nucleotide polymorphisms, rs53576, rs237879, rs2228485, rs13316193, rs2254298 and rs1042778, located within the OXTR gene in Korean patients with eating disorders using the single-base extension method. We studied a total of 262 women, including 69 patients with anorexia nervosa, 90 patients with bulimia nervosa (BN), and 103 healthy women.

RESULTS

We found a positive association between the G allele of OXTR rs53576 and BN. In the BN group, the G carriers showed a high score on the behavioural inhibition system.

CONCLUSIONS

These findings suggest the involvement of the oxytocinergic system in the mechanism that underlies BN.

Genetics and Epigenetics of Eating Disorders

Eating disorders (EDs) are serious psychiatric conditions influenced by biological, psychological, and sociocultural factors. A better understanding of the genetics of these complex traits and the development of more sophisticated molecular biology tools have advanced our understanding of the etiology of EDs. The aim of this review is to critically evaluate the literature on the genetic research conducted on three major EDs: anorexia nervosa (AN), bulimia nervosa (BN), and binge eating disorder (BED). We will first review the diagnostic criteria, clinical features, prevalence, and prognosis of AN, BN, and BED, followed by a review of family, twin, and adoption studies. We then review the history of genetic studies of EDs covering linkage analysis, candidate gene association studies, genome-wide association studies, and the study of rare variants in EDs. Our review also incorporates a translational perspective by covering animal models of ED-related phenotypes. Finally, we review the nascent field of epigenetics of EDs and a look forward to future directions for ED genetic research.

The 'Fat Mass and Obesity Related' (FTO) gene: Mechanisms of Impact on Obesity and Energy Balance

A cluster of single nucleotide polymorphisms (SNPs) in the first intron of the fat mass and obesity related (FTO) gene were the first common variants discovered to be associated with body mass index and body fatness. This review summarises what has been later discovered about the biology of FTO drawing together information from both human and animal studies. Subsequent work showed that the 'at risk' alleles of these SNPs are associated with greater food intake and increased hunger/lowered satiety, but are not associated with altered resting energy expenditure or low physical activity in humans. FTO is an FE (II) and 2-oxoglutarate dependent DNA/RNA methylase. Contrasting the impact of the SNPs on energy balance in humans, knocking out or reducing activity of the Fto gene in the mouse resulted in lowered adiposity, elevated energy expenditure with no impact on food intake (but the impact on expenditure is disputed). In contrast, overexpression of the gene in mice led to elevated food intake and adiposity, with no impact on expenditure. In rodents, the Fto gene is widely expressed in the brain including hypothalamic nuclei linked to food intake regulation. Since its activity is 2-oxoglutarate dependent it could potentially act as a sensor of citrate acid cycle flux, but this function has been dismissed, and instead it has been suggested to be much more likely to act as an amino acid sensor, linking circulating AAs to the mammalian target of rapamycin complex 1. This may be fundamental to its role in development but the link to obesity is less clear. It has been recently suggested that although the obesity related SNPs reside in the first intron of FTO, they may not only impact FTO but mediate their obesity effects via nearby genes (notably RPGRIP1L and IRX3).

A genome-wide association study of anorexia nervosa

Anorexia nervosa (AN) is a complex and heritable eating disorder characterized by dangerously low body weight. Neither candidate gene studies nor an initial genome-wide association study (GWAS) have yielded significant and replicated results. We performed a GWAS in 2907 cases with AN from 14 countries (15 sites) and 14 860 ancestrally matched controls as part of the Genetic Consortium for AN (GCAN) and the Wellcome Trust Case Control Consortium 3 (WTCCC3). Individual association analyses were conducted in each stratum and meta-analyzed across all 15 discovery data sets. Seventy-six (72 independent) single nucleotide polymorphisms were taken forward for in silico (two data sets) or de novo (13 data sets) replication genotyping in 2677 independent AN cases and 8629 European ancestry controls along with 458 AN cases and 421 controls from Japan. The final global meta-analysis across discovery and replication data sets comprised 5551 AN cases and 21 080 controls. AN subtype analyses (1606 AN restricting; 1445 AN binge-purge) were performed. No findings reached genome-wide significance. Two intronic variants were suggestively associated: rs9839776 (P=3.01 × 10(-7)) in SOX2OT and rs17030795 (P=5.84 × 10(-6)) in PPP3CA. Two additional signals were specific to Europeans: rs1523921 (P=5.76 × 10(-)(6)) between CUL3 and FAM124B and rs1886797 (P=8.05 × 10(-)(6)) near SPATA13. Comparing discovery with replication results, 76% of the effects were in the same direction, an observation highly unlikely to be due to chance (P=4 × 10(-6)), strongly suggesting that true findings exist but our sample, the largest yet reported, was underpowered for their detection. The accrual of large genotyped AN case-control samples should be an immediate priority for the field.

Impact of NEGR1 genetic variability on psychological traits of patients with eating disorders

Genetics variants in the NEGR1 gene, strongly expressed in the brain, have been reported to affect the neuronal control of food intake therefore inducing obesity. With the same rationale, we hypothesized that this genetic variability may be associated with psychological traits commonly displayed by eating disorder (ED) patients and/or with the risk for the disorder. We analyzed 21 tag-single-nucleotide polymorphisms (SNPs) in the coding sequence and adjacent regions of the NEGR1 gene. A total of 169 ED patients (106 with anorexia nervosa (AN) and 63 with bulimia nervosa (BN)) and 312 healthy subjects were genotyped. Personality traits and general psychopathological symptoms were assessed by the Eating Disorders Inventory Test-2 (EDI-2) and Symptom Checklist 90 Revised inventories. None of the SNPs or haplotypes analyzed were associated with a greater risk of ED or correlated with anthropometric parameters. However, in patients with BN, four SNPs (rs12740031, rs10789322, rs6659202 and rs591540) correlated with the scores in Drive for Thinness (DT), Ineffectiveness (I) and Interoceptive Awareness (IA) (Bonferroni-P<0.05 in all instances). The first two SNPs along with rs954299 and rs2422021 formed a haplotype block, which showed a consistent association with the EDI-2 score in BN patients (Bonferroni-P=0.01). A subsequent three-SNP sliding-window approach identified a central area, encompassing both the haplotype block and the individually relevant SNPs that strongly correlated with the scores of BN patients in DT, I, IA and Bulimia. No associations were identified in the AN group. These preliminary results indicate that NEGR1 could be an important locus influencing certain personality dimensions in BN patients.

Genetics of eating disorders

Disordered eating behavior is the core symptom of the complex disorders anorexia nervosa and bulimia nervosa. Twin and family studies derive high heritability estimates. Hence, substantial genetic influences on the etiology can be assumed for both. Initially, candidate gene studies pertaining to the monoaminergic neurotransmitter systems and to body weight regulation comprised the core of the genetic analyses. Unfortunately, confirmed, solid findings substantiated in meta-analyses are rare, so that eventually none of these associations is unequivocal. Thus, systematic, genome-wide approaches emerged to identify genes with no a priori evidence for their involvement in eating disorders. Genome-wide association studies have hinted to formerly unknown genetic regions. However, significant genome-wide findings have not yet been reported.

The genetics of eating disorders

Over the past decade, considerable advances have been made in understanding genetic influences on eating pathology. Eating disorders aggregate in families, and twin studies reveal that additive genetic factors account for approximately 40% to 60% of liability to anorexia nervosa (AN), bulimia nervosa (BN), and binge eating disorder (BED). Molecular genetics studies have been undertaken to identify alterations in deoxyribonucleic acid sequence and/or gene expression that may be involved in the pathogenesis of disordered eating behaviors, symptoms, and related disorders and to uncover potential genetic variants that may contribute to variability of treatment response. This article provides an in-depth review of the scientific literature on the genetics of AN, BN, and BED including extant studies, emerging hypotheses, future directions, and clinical implications.

A genome-wide association study on common SNPs and rare CNVs in anorexia nervosa

Anorexia nervosa (AN) is a mental illness with high mortality that most commonly afflicts adolescent female individuals. Clinical symptoms include chronic food refusal, weight loss and body image distortions. We carried out a genome-wide association study on 1033 AN cases and 3733 pediatric control subjects, all of whom were of European ancestry and were genotyped on the Illumina HumanHap610 platform (Illumina, San Diego, CA, USA). We confirmed that common single-nucleotide polymorphisms (SNPs) within OPRD1 (rs533123, P=0.0015) confer risk for AN, and obtained suggestive evidence that common SNPs near HTR1D (rs7532266, P=0.04) confer risk for restricting-type AN specifically. However, no SNPs reached genome-wide significance in our data, whereas top association signals were detected near ZNF804B, CSRP2BP, NTNG1, AKAP6 and CDH9. In parallel, we performed genome-wide analysis on copy number variations (CNVs) using the signal intensity data from the SNP arrays. We did not find evidence that AN cases have more CNVs than control subjects, nor do they have over-representation of rare or large CNVs. However, we identified several regions with rare CNVs that were only observed in AN cases, including a recurrent 13q12 deletion (1.5 Mb) disrupting SCAS in two cases, and CNVs disrupting the CNTN6/CNTN4 region in several AN cases. In conclusion, our study suggests that both common SNPs and rare CNVs may confer genetic risk to AN. These results point to intriguing genes that await further validation in independent cohorts for confirmatory roles in AN.