Genetic susceptibility to eating disorders: associated polymorphisms and pharmacogenetic suggestions

The BDNF Val66Met polymorphism serves as a potential marker of body weight in patients with psychiatric disorders

Brain-derived neurotrophic factor (BDNF) is a predominant neurotrophic factor in the brain, indispensable for neuronal growth, synaptic development, neuronal repair, and hippocampal neuroplasticity. Among its genetic variants, the BDNF Val66Met polymorphism is widespread in the population and has been associated with the onset and aggravation of diverse pathologies, including metabolic conditions like obesity and diabetes, cardiovascular ailments, cancer, and an array of psychiatric disorders. Psychiatric disorders constitute a broad category of mental health issues that influence mood, cognition, and behavior. Despite advances in research and treatment, challenges persist that hinder our understanding and effective intervention of these multifaceted conditions. Achieving and maintaining stable body weight is pivotal for overall health and well-being, and the relationship between psychiatric conditions and body weight is notably intricate and reciprocal. Both weight gain and loss have been linked to varying mental health challenges, making the disentanglement of this relationship critical for crafting holistic treatment strategies. The BDNF Val66Met polymorphism's connection to weight fluctuation in psychiatric patients has garnered attention. This review investigated the effects and underlying mechanisms by which the BDNF Val66Met polymorphism moderates body weight among individuals with psychiatric disorders. It posits the polymorphism as a potential biomarker, offering prospects for improved monitoring and therapeutic approaches for mental illnesses.

Similarities and differences between eating disorders and obsessive-compulsive disorder in childhood and adolescence: a systematic review

Background

The developmental age, comprising childhood and adolescence, constitutes an extremely important phase of neurodevelopment during which various psychiatric disorders can emerge. Obsessive-Compulsive Disorder (OCD) and Eating Disorders (ED) often manifest during this critical developmental period sharing similarities but also differences in psychopathology, neurobiology, and etiopathogenesis. The aim of this study is to focus on clinical, genetic and neurobiological similarities and differences in OCD and ED.

Methods

This study is based on a PubMed/MEDLINE and Cochrane Central Register for Controlled Trial (CENTRAL). The research adhered to the guidelines outlined in the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA).

Results

The aforementioned search yielded an initial collection of 335 articles, published from 1968 to September 2023. Through the application of inclusion and exclusion criteria, a total of 324 articles were excluded, culminating in a final selection of 10 articles.

Conclusions

Our findings showed both differences and similarities between OCD and ED. Obsessive-compulsive (OC) symptoms are more prevalent in ED characterized by a binge/purge profile than in those with a restrictive profile during developmental age. OC symptomatology appears to be a common dimension in both OCD and ED. When presents, OC symptomatology, exhibits transversal characteristic alterations in the anterior cingulate cortex and poorer cognitive flexibility. These correlations could be highlighted by genetic overlaps between disorders. A comprehensive definition, integrating psychopathological and neurobiological aspects could significantly aid treatment selection and thereby influence the prognosis of these patients.

Association of serotonin receptor gene polymorphisms with anorexia nervosa: a systematic review and meta-analysis

PURPOSE

Several studies have investigated the association between anorexia nervosa and polymorphisms of genes regulating serotonin neurotransmission, with a focus on the rs6311 polymorphism of 5-HTR2A. However, inconsistent results of these studies and conflicting conclusions of existing meta-analyses complicate the understanding of a possible association. We have updated these results and evaluated the involvement of other serotonin receptor gene polymorphisms in anorexia nervosa.

METHODS

Adhering to PRISMA guidelines, we have searched studies on anorexia nervosa and serotonin-regulating genes published from 1997 to 2022, selected those concerning receptor genes and meta-analyzed the results from twenty candidate gene studies on the 5-HTR2A rs6311 polymorphism and the 5-HTR2C rs6318 polymorphism.

RESULTS

Present analyses reveal an association for the 5-HTR2A rs6311 polymorphism, with G and A alleles, across eighteen studies (2049 patients, 2877 controls; A vs. G allele, Odds Ratio = 1.24; 95% Confidence Interval = 1.06-1.47; p = 0.009). However, after geographic subgrouping, an association emerged only in a Southern European area, involving five studies (722 patients, 773 controls; A vs. G allele, Odds Ratio = 1.82; 95% Confidence Interval = 1.41-2.37; p < 0.00001). No association was observed for the 5-HTR2C rs6318 polymorphism across three studies.

CONCLUSIONS

To date, the involvement in the pathophysiology of anorexia nervosa of the 5-HTR2A rs6311 polymorphism appears limited to a specific genetic and/or environmental context, while that of the 5-HTR2C rs6318 polymorphism seems excluded. Genome-wide association studies and epigenetic studies will likely offer deeper insights of genetic and environmental factors possibly contributing to the disorder.

LEVEL OF EVIDENCE

III Evidence obtained from well-designed cohort or case-control analytic studies. Clinical trial registration PROSPERO registration number: CRD42021246122.

Eating Disorder Risk and Pathogenic Behaviors Among Collegiate Student-Athletes

CONTEXT

Eating disorders (EDs) are a cluster of behavioral conditions characterized by uneasy thoughts and behaviors that grow into severe or persistent eating disturbances. The demands on student-athletes may create mental and physical stressors that increase the likelihood of EDs and disordered eating.

OBJECTIVE

To examine the ED risk through eating attitudes and behaviors in male and female student-athletes and across various sport types (endurance, aesthetic, power, ball or team, or technical sports).

DESIGN

Cross-sectional study.

SETTING

Collegiate athletics.

PATIENTS OR OTHER PARTICIPANTS

National Collegiate Athletic Association Division I and II student-athletes (n = 2054; males = 631; females = 1423) from 40 institutions.

MAIN OUTCOME MEASURE(S)

Participants completed a web-based demographic survey and the Eating Attitudes Test-26 (EAT-26). Multiple χ2 analyses examined participants classified as at risk for EDs. Independent-samples t tests and a 1-way analyses of variance compared sex and sport type across EAT-26 totals and subscale (Dieting, Bulimia, and Oral Control) scores.

RESULTS

Overall, 25.3% (n = 520/2054) of student-athletes were classified as at risk for EDs. Differences were found between sex and ED risk (χ21,2054 = 32.9, P ≤ .01; 17.3% [n = 109/631] males, 28.9% [n = 411/1423] females) and across ED risk and sport type (χ24,2054 = 13.4, P = .01). When examining females only, we observed differences across ED risk and sport type (χ24,1423 = 13.4, P ≤ .01). No differences were evident across ED risk and sport type for males. Differences were seen between sex and binge eating (χ21,2054 = 6.8, P = .009), sex and diet pill use (χ21,2054 = 19.6, P ≤ .01), and sport type and diet pill use (χ24,2054= 12.2, P = .016), excessive exercise (χ24,2054 = 32.1, P ≤ .01), and losing more than 20 lb (9 kg) in the last 6 months (χ24,2054 = 10.2, P ≤ .037).

CONCLUSIONS

Student-athletes in the collegiate setting are at risk for EDs. Medical professionals, such as athletic trainers, need to be educated on the potential risk factors that may lead to EDs. Protocols for prevention, screening and recognition, and referral should be developed for student-athletes at risk for EDs.

Gut microbiota metabolites mediate the interplay between childhood maltreatment and psychopathology in patients with eating disorders

Eating disorders (EDs) are syndromes with a multifactorial etiopathogenesis, involving childhood traumatic experiences, as well as biological factors. Human microbiome has been hypothesised to play a fundamental role, impacting on emotion regulation, as well as with eating behaviours through its metabolites such as short chain fatty acids (SCFAs). The present study investigated the interactions between psychopathology of EDs, the gut microbiome and SCFAs resulting from bacterial community metabolic activities in a population of 47 patients with Anorexia Nervosa, Bulimia Nervosa, and Binge Eating Disorder and in healthy controls (HCs). Bacterial gut microbiota composition differences were found between subjects with EDs and HCs, especially in association with different pathological behaviours (binge-purge vs restricting). A mediation model of early trauma and ED-specific psychopathology linked reduction of microbial diversity to a typical microbiota-derived metabolite such as butyric acid. A possible interpretation for this model might be that childhood trauma represents a risk factor for gut dysbiosis and for a stable modification of mechanisms responsible for SCFAs production, and that this dysfunctional community is inherited in the passage from childhood to adulthood. These findings might open the way to novel interventions of butyric acid-like compounds as well as faecal transplant.

Variability in cannabinoid receptor genes is associated with psychiatric comorbidities in anorexia nervosa

PURPOSE

The endocannabinoid system plays a key role in eating behavior regulating appetite and reward mechanisms, but the impact of its genetic variability has been scarcely studied in Anorexia Nervosa (AN). We aimed to analyze the association of genetic variants in cannabinoid receptors with the risk for AN and with psychiatric comorbidities that are commonplace in these patients.

METHODS

We screened 221 AN patients and 396 controls for 14 tag-SNPs in the CNR1 and CNR2 genes, coding for cannabinoids receptors CB1 and CB2, respectively. Patients were diagnosed according to DSM-5 criteria and interviewed with the SCL-90R and the EDI-2 inventories to identify AN-coupled and general psychopathology.

RESULTS

None of the tag-SNPs was significantly related to AN risk. However, the rs806369-TT genotype and haplotype rs806368/rs1049353/rs806369 of CNR1 were respectively associated with lower weight (mean difference = - 4.92 kg, FDR-q = 0.044) and BMI (FDR-q = 0.042) in AN patients. CNR1 rs806374-TT and CNR2 rs3003335-AA and rs6658703-GG genotypes correlated with higher scores in the Positive Symptom Distress Index (PSDI, FDR-q = 0.011 and 0.009, respectively). These three genotypes were also linked to increased Hostility in the patients (FDR-q < 0.05). Remarkably, a proximal area of the CNR1 gene locus (positions 88,143,916-88,149,832) correlated with PSDI, Hostility, Asceticism and EDI-2 total scores after correcting by multiple testing (FDR-q < 0.05 in all instances). Finally, significant CNR1/CNR2 epistasis was observed in relation to Hostility (p < 0.01) and Maturity Fears (p < 0.001).

CONCLUSION

The CNR1 and CNR2 genes, coding for cannabinoid receptors, may constitute important loci regarding psychiatric comorbidities in AN patients.

LEVEL III

Evidence obtained from well-designed cohort or case-control analytic studies.

Regulation of adenosine A2A receptor gene expression in a model of binge eating in the amygdaloid complex of female rats

BACKGROUND

Pharmacological treatment approaches for eating disorders, such as binge eating disorder and bulimia nervosa, are currently limited.

METHODS AND AIMS

Using a well-characterized animal model of binge eating, we investigated the epigenetic regulation of the A_2A Adenosine Receptor (A_2AAR) and dopaminergic D2 receptor (D2R) genes.

RESULTS

Gene expression analysis revealed a selective increase of both receptor mRNAs in the amygdaloid complex of stressed and restricted rats, which exhibited binge-like eating, when compared to non-stressed and non-restricted rats. Consistently, pyrosequencing analysis revealed a significant reduction of the percentage of DNA methylation but only at the A_2AAR promoter region in rats showing binge-like behaviour compared to the control animals. Focusing thus on A_2AAR agonist (VT 7) administration (which inhibited the episode of binge systemically at 0.1 mg/kg or intra-central amygdala (CeA) injection at 900 ng/side) induced a significant increase of A_2AAR mRNA levels in restricted and stressed rats when compared to the control group. In addition, we observed a significant decrease in A_2AAR mRNA levels in rats treated with the A_2AAR antagonist (ANR 94) at 1 mg/kg. Consistent changes in the DNA methylation status of the A_2AAR promoter were found in restricted and stressed rats after administration of VT 7 or ANR 94.

CONCLUSION

We confirm the role of A_2AAR in binge eating behaviours, and we underline the importance of epigenetic regulation of the A_2AAR gene, possibly due to a compensatory mechanism to counteract the effect of binge eating. We suggest that A_2AAR activation, inducing receptor gene up-regulation, could be relevant to reduction of food consumption.

Environmental Enrichment During Adulthood Reduces Sucrose Binge-Like Intake in a High Drinking in the Dark Phenotype (HD) in C57BL/6J Mice

Repetitive binge episodes favor transition to binge-eating disorders. Experimental evidence points to positive influence of environmental enrichment (EE) on drug/food addiction, although far less is known regarding EE effects over binge-like consumption. Here, we evaluate the following: (1) whether switching from nonenriched standard environment (SE) to EE housing conditions during adulthood alters a stable pattern of voluntary sucrose (10% w/v) binge-like intake in high (HD) vs. low (LD) drinking phenotypes under a drinking in the dark (DID) schedule; and (2) sucrose binge-like intake in a DID task in response to a pharmacological challenge with an OXr1 antagonist in HD/LD subpopulations after long-term exposure to SE or EE conditions. Adolescent (postnatal day 21; PND21) mice were housed in SE conditions. At PND65, all animals were long-term exposed to sucrose DID. On the first episode of DID (PND65), animals were divided into HD vs. LD subpopulations according to their sucrose intake. On PND85, an OXr1 antagonist test was conducted on HD and LD mice with SB-334867 (SB) administration. On PND95, HD and LD subpopulations were again randomly allocated into two subgroups, resulting in the following experimental conditions: HD-SE, HD-EE, LD-SE and LD-EE. Sucrose binge-like intake continued until PND116, when a second SB test was conducted. The main findings are: (1) a single 2 h episode of sucrose binge drinking in a DID procedure consistently segregates two behavioral subpopulations, HD and LD; (2) when adult mice in standard conditions and long-term exposed to sucrose DID were switched to EE conditions, an immediate reduction in sucrose binge-like intake was observed in HD mice, pointing to a therapeutic role of EE exposure; and (3) administration of the OXr1 antagonist caused an acute reduction in sucrose binge-like intake in HD and LD mice exposed to SE conditions. Importantly, exposure to EE conditions blunted the inhibitory effect of SB on sucrose binge consumption in both behavioral phenotypes, indirectly suggesting a potential EE/OXr1 signaling interaction. We propose the hypothesis that EE might regulate OX-dependent anxiety/compulsivity brain systems, which might secondarily modulate sucrose binge-like intake.

Transcriptional regulation of the endocannabinoid system in a rat model of binge-eating behavior reveals a selective modulation of the hypothalamic fatty acid amide hydrolase gene

OBJECTIVE

Binge-eating episodes are recurrent and are defining features of several eating disorders. Thus binge-eating episodes might influence eating disorder development of which exact underlying mechanisms are still largely unknown.

METHODS

Here we focused on the transcriptional regulation of the endocannabinoid system, a potent regulator of feeding behavior, in relevant rat brain regions, using a rat model in which a history of intermittent food restriction and a frustration stress induce binge-like palatable food consumption.

RESULTS

We observed a selective down-regulation of fatty acid amide hydrolase (faah) gene expression in the hypothalamus of rats showing the binge-eating behavior with a consistent reduction in histone 3 acetylation at lysine 4 of the gene promoter. No relevant changes were detected for any other endocannabinoid system components in any brain regions under study, as well as for the other epigenetic mechanisms investigated (DNA methylation and histone 3 lysine 27 methylation) at the faah gene promoter.

DISCUSSION

Our findings suggest that faah transcriptional regulation is a potential biomarker of binge-eating episodes, with a relevant role in the homeostatic regulation of food intake.

[Genetics factors in pathogenesis and clinical genetics of binge eating disorder]

Genetic studies have shown that binge eating disorder (ВЕD) aggregates in families, heritability was estimated as about 60% and additive genetic influences on BED up to 50%. Using a genetic approach has proved useful for verifying the diagnostic categories of BED using DSM-IV criteria and supporting the validity of considering this pathology as a separate nosological category. The results confirmed the genetic and pathogenic originality of BED as a separate psychopathological phenomenon, but not a subtype of obesity. It seems fruitful to considerate BED as a disease with hereditary predisposition with significant genetic influence and a complex psychopathological syndrome, including not only eating disorders, but also depressive and addictive component. A possible mechanism of pathogenesis of BED may be the interaction of the neuroendocrine and neurotransmitters systems including the active involvement of the reward system in response to a variety of chronic stress influences with the important modulatory role of specific personality traits. The high level of genetic influence on the certain clinical manifestations of BED confirms the ability to identify the subphenotypes of BED on genetic basis involving clinical criteria. It can not only contribute to further genetic studies, taking into account more homogeneous samples, but also help in finding differentiated therapeutic approaches.

Genetics of Anorexia Nervosa

PURPOSE OF REVIEW

Genetic factors contribute to the etiology of anorexia nervosa (AN). This review synthesizes the current state of knowledge about the genetic etiology of AN, provides directions for future research, and discusses clinical implications for this research.

RECENT FINDINGS

Candidate gene meta-analyses indicate serotonin genes may be involved in the genetic etiology of AN. Three genome-wide association studies have been conducted and one genome-wide significant locus was identified. Cross-disorder analyses suggest shared genetic risk between AN and several psychiatric, educational, and medical phenotypes. Much has been learned about the genetic etiology of AN over the past 3 decades. However, to fully understand the genetic architecture, we must consider all aspects including common variation, cross-disorder analysis, rare variation, copy number variation, and gene-environment interplay. Findings have important implications for the development of treatment and prevention approaches and for how AN, and psychiatric and medical diseases in general, are conceptualized.

Contemporary views on the genetics of anorexia nervosa

Anorexia nervosa (AN) is a serious mental illness characterized by severe dietary restriction that leads to high rates of morbidity, chronicity, and mortality. Unfortunately, effective treatment is lacking and few options are available. High rates of familial aggregation and significant heritability suggested that the complex etiology of AN is affected by both genetic and environmental factors. In this paper, we review studies that reported common and rare genetic variation that influence susceptibility of AN through candidate gene studies, genome-wide association studies, and sequencing-based studies. We also discuss gene expression, methylation, imaging genetics, and pharmacogenetics to demonstrate that these studies have collectively advanced our knowledge of how genetic variation contributes to AN susceptibility and clinical course. Lastly, we highlight the importance of gene by environment interactions (G×E) and share our enthusiasm for the use of nutritional genomic approaches to elucidate the interaction among nutrients, metabolic intermediates, and genetic variation in AN. A deeper understanding of how nutrition alters genome stability, how genetic variation influences uptake and metabolism of nutrients, and how response to food components affects disordered eating, will lead to personalized dietary interventions and effective nutraceutical and pharmacological treatments for AN.

[Genetic aspects of binge eating disorder Part 2. Molecular genetics and pharmacogenetic approaches]

Genetic risk of binge eating disorder (ВЕD) is a consequence of joint participation of many genes, the contribution of each one is small, but the total (additive) effect is significant and greatly influences the age at onset, clinical dynamics and the level of treatment resistance. It is assumed that the carriers of different polymorphic variants of genes and their combinations have different levels of genetic risk. No Genom Wide Association studies of ВЕD has been performed and the analysis of the results of candidate genes studies gives reason to believe that pathogenetically substantiated panel of genes, including serotonin system, BDNF and, especially dopamine and endogenous opioid system, would be most useful, taking into account the mechanism of action of drugs for the ВЕD treatment. Genetic studies with this panel if using evidence-based design, detailed and quantitative analysis of the family history of binge eating can give good results for: 1) assessment of the genetic risk of ВЕD for primary prevention programs; 2) identification of the specific clinical forms of development and course of ВЕD with significant genetic influence; 3) identification of the specific genetic variants that increase the effectiveness of personalized pharmacotherapy of ВЕD within pharmacogenetic approach.

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.

The BDNF gene Val66Met polymorphism as a modifier of psychiatric disorder susceptibility: progress and controversy

Brain-derived neurotrophic factor (BDNF) has a primary role in neuronal development, differentiation and plasticity in both the developing and adult brain. A single-nucleotide polymorphism in the proregion of BDNF, termed the Val66Met polymorphism, results in deficient subcellular translocation and activity-dependent secretion of BDNF, and has been associated with impaired neurocognitive function in healthy adults and in the incidence and clinical features of several psychiatric disorders. Research investigating the Val66Met polymorphism has increased markedly in the past decade, and a gap in integration exists between and within academic subfields interested in the effects of this variant. Here we comprehensively review the role and relevance of the Val66Met polymorphism in psychiatric disorders, with emphasis on suicidal behavior and anxiety, eating, mood and psychotic disorders. The cognitive and molecular neuroscience of the Val66Met polymorphism is also concisely reviewed to illustrate the effects of this genetic variant in healthy controls, and is complemented by a commentary on the behavioral neuroscience of BDNF and the Val66Met polymorphism where relevant to specific disorders. Lastly, a number of controversies and unresolved issues, including small effect sizes, sampling of allele inheritance but not genotype and putative ethnicity-specific effects of the Val66Met polymorphism, are also discussed to direct future research.

Eating disorders in women

Eating disorders, especially anorexia nervosa and bulimia nervosa have been classically described in young females in Western population. Recent research shows that they are also seen in developing countries including India. The classification of eating disorders has been expanded to include recently described conditions like binge eating disorder. Eating disorders have a multifactorial etiology. Genetic factor appear to play a major role. Recent advances in neurobiology have improved our understanding of these conditions and may possibly help us develop more effective treatments in future. Premorbid personality appears to play an important role, with differential predisposition for individual disorders. The role of cultural factors in the etiology of these conditions is debated. Culture may have a pathoplastic effect leading to non-conforming presentations like the non fat-phobic form of anorexia nervosa, which are commonly reported in developing countries. With rapid cultural transformation, the classical forms of these conditions are being described throughout the world. Diagnostic criteria have been modified to accommodate for these myriad presentations. Treatment of eating disorders can be quite challenging, given the dearth of established treatments and poor motivation/insight in these conditions. Nutritional rehabilitation and psychotherapy remains the mainstay of treatment, while pharmacotherapy may be helpful in specific situations.

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.

The 5-HTTLPR confers susceptibility to anorexia nervosa in Han Chinese: evidence from a case-control and family-based study

Accumulating evidence has implied that serotonin system dysfunction may be involved in the etiology of anorexia nervosa (AN). Serotonin-transporter-linked promoter region (5-HTTLPR) polymorphism is the genetic variant coding for the serotonin transporter and has a modulatory effect on its expression. This study aimed to investigate the possible association between the 5-HTTLPR and the susceptibility and severity of AN in Han Chinese using a case-control (255 patients and 351 controls) and family based study (198 trios). Eating disorder examination was used to measure the severity of AN behavioral symptoms. For the case-control study, the 5-HTTLPR showed significant association with AN in our sample (genotypic P = 0.03). The frequency of S allele was significantly higher in patients than that in controls (OR = 1.38, 95%CI: 1.06–1.79, P = 0.017). For the family-based study, the S allele of 5-HTTLPR was preferentially transmitted rather than non-transmitted from the parents to affected offspring (P = 0.013). The results of ANCOVA test revealed no significant association between the 5-HTTLPR polymorphism and severity of AN. Our findings suggested that 5-HTTLPR is able to confer susceptibility to AN in Han Chinese.

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.

BDNF genetic variability modulates psychopathological symptoms in patients with eating disorders

The brain-derived neurotrophic factor (BDNF) gene may influence eating behavior, body weight and cognitive impairments. We aimed to investigate whether BDNF genetic variability may affect anthropometric and psychological parameters in patients with anorexia or bulimia nervosa (AN, BN) and/or modulate the risk for the disorder. A total of 169 unrelated female patients and 312 healthy controls were genotyped for two common BDNF single-nucleotide polymorphisms (SNPs), Val66Met and C-270T, and several selected tag-SNPs. Associated personality characteristics and psychopathological symptoms were assessed by the EDI-2 and SCL-90R inventories, respectively. No single SNP or haplotype played a relevant role in the risk for AN or BN. The rs16917237 TT genotype was significantly associated with increased weight (74.63 ± 16.58 vs. 57.93 ± 13.02) and body mass index (28.94 ± 6.22 vs. 22.23 ± 4.77) in the BN group after correcting for multiple testing. Haplotype analyses using a sliding window approach with three adjacent SNPs produced four loci of interest. Locus 3 (rs10835210/rs16917237/C-270T) showed a broad impact on the measured psychopathological symptoms. Haplotypes CGC and CGT in this locus correlated with scores in all three scales of the SCL-90R inventory, both in AN and BN patients. In contrast, the results of the EDI-2 inventory were largely unaffected. These preliminary results suggest that variability in the BDNF gene locus may contribute to anthropometric characteristics and also psychopathological symptoms that are common but not exclusive of ED patients.

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.

Identification of hypothalamic neuron-derived neurotrophic factor as a novel factor modulating appetite

Disruption of finely coordinated neuropeptide signals in the hypothalamus can result in altered food intake and body weight. We identified neuron-derived neurotrophic factor (NENF) as a novel secreted protein through a large-scale screen aimed at identifying novel secreted hypothalamic proteins that regulate food intake. We observed robust Nenf expression in hypothalamic nuclei known to regulate food intake, and its expression was altered under the diet-induced obese (DIO) condition relative to the fed state. Hypothalamic Nenf mRNA was regulated by brain-derived neurotrophic factor (BDNF) signaling, itself an important regulator of appetite. Delivery of purified recombinant BDNF into the lateral cerebral ventricle decreased hypothalamic Nenf expression, while pharmacological inhibition of trkB signaling increased Nenf mRNA expression. Furthermore, recombinant NENF administered via an intracerebroventricular cannula decreased food intake and body weight and increased hypothalamic Pomc and Mc4r mRNA expression. Importantly, the appetite-suppressing effect of NENF was abrogated in obese mice fed a high-fat diet, demonstrating a diet-dependent modulation of NENF function. We propose the existence of a regulatory circuit involving BDNF, NENF, and melanocortin signaling. Our study validates the power of using an integrated experimental and bioinformatic approach to identify novel CNS-derived proteins with appetite-modulating function and reveals NENF as an important central modulator of food intake.

Antipsychotic agents in the treatment of anorexia nervosa: neuropsychopharmacologic rationale and evidence from controlled trials

The search for an effective psychopharmacologic strategy in the treatment of anorexia nervosa (AN) has been elusive for decades and has run the gamut from reserpine to typical antipsychotics, to lithium, to tetrahydrocannabinol, to growth hormone, to anticonvulsants, to antidepressants, to atypical antipsychotics. Only recently has there arisen a potential "diamond in the rough" in the form of the atypical antipsychotic agent, olanzapine, which, in four randomized clinical trials, has shown superiority to placebo (two studies), chlorpromazine (one study), and aripiprazole (one study) in terms of weight gain and/or reduction in obsessional symptoms. The pharmacologic profile of olanzapine and other antipsychotic medications is discussed in light of the known pathophysiology of AN involving serotonin and dopamine systems, as well as brain-derived neurotrophic factor.

Association between serotonin transporter gene polymorphism and eating disorders outcome: a 6-year follow-up study

Eating disorder patients show different long-term outcomes, and trait-related alterations of serotonergic function, which might be related with the serotonin transporter (5-HTT) gene. We studied the relationships between 5-HTTLPR polymorphism, eating specific and general psychopathology and the long-term outcome of anorexia nervosa (AN) and bulimia nervosa (BN) patients. We evaluated the distribution of the functional 5-HTTLPR polymorphism in a series of 201 Italian, Caucasian, eating disorder patients (113 with AN and 88 with BN binge/purging (BP subtype) and in 150 Caucasian unrelated controls. Prior to starting an individual cognitive behavior therapy, a clinical assessment was performed by means of the structured clinical interview for DSM-IV axis I disorders and several self-report questionnaires. This assessment was repeated at the end of treatment, 3 years after the end of treatment and 3 years after the first follow-up. Diagnostic changes between AN and BN were frequent (28.3%), and the presence of depressive disorders was associated with a higher rate of diagnostic crossover during the follow-up period. The S-allele of the 5-HTTLPR genotype increases the risk susceptibility for both depressive comorbidity (OR = 4.23; 95% CI, 1.45-12.37) and diagnostic crossover during the follow-up period in AN patients (OR = 5.04; 95% CI, 1.69-14.98). Logistic regression analyses confirmed these findings, when the interaction between genotype and psychiatric comorbidity as predictors of diagnostic instability in AN patients were taken into account. No significant association was found between 5-HTTLPR genotype and recovery. The S-allele of the 5-HTTLPR genotype increases the risk for depressive disorders comorbidity, and moderates the long-term outcome of anorectic patients.

Olanzapine, but not fluoxetine, treatment increases survival in activity-based anorexia in mice

Anorexia nervosa (AN) is an eating disorder characterized by extreme hypophagia, hyperactivity, and fear of weight gain. No approved pharmacological treatments exist for AN despite high mortality rates. The activity-based anorexia (ABA) phenomenon models aspects of AN in rodents, including progressive weight loss, reduced food intake, and hyperactivity. First, we optimized the ABA paradigm for mice. We compared mouse strains (Balb/cJ, A/J) for susceptibility with ABA, and evaluated the effects of different food access durations (2, 4, 6, 8, and 10 h) on ABA parameters. Balb/cJ mice exhibited significantly shorter survival time (days until 25% bodyweight loss) in the ABA paradigm compared with A/J mice. Furthermore, 6 h of food access reduced survival in mice housed with wheels without reducing survival in mice housed without wheels. We then evaluated the effects of chronic treatment with fluoxetine (4 weeks) or subchronic treatment with olanzapine (OLZ) (1 week) on ABA in BALB/cJ mice. OLZ (12 mg/kg/day) significantly increased survival and reduced food anticipatory activity (FAA). However, OLZ did not alter food intake or running wheel activity during ad-lib feeding (baseline) or restriction conditions, or in mice housed without wheels. Fluoxetine (18 mg/kg/day) increased food intake and reduced FAA, but did not alter survival. Here, we report for the first time that OLZ, but not fluoxetine, reduces ABA in mice. Our findings indicate further need for clinical investigations into the effects of OLZ, but not selective serotonin reuptake inhibitors, on core features of AN.

Serotonin receptor 2A -1438G/A promoter polymorphism in relation to obesity and response to sibutramine

AIMS

Serotonin has been related to appetite and body weight control. The aim of this study was to investigate a possible association of the -1438 /A promoter polymorphism of the serotonin 2A receptor (5HT2AR) gene with obesity-related variables and response to sibutramine.

PATIENTS/METHODS

We examined the potential impact of this polymorphism on obesity and related metabolic traits in a cohort of 234 overweight/obese and 103 lean Greek subjects. Additionally, we examined whether the 5HT2AR 1438A/G polymorphism influences weight reduction and change in body composition among 106 out of these subjects, who were treated with 15 g sibutramine. Genotyping was carried out by polymerase chain reaction and restriction enzyme analysis.

RESULTS

Body mass index, fat mass, and waist circumference were not significantly different across the 5HT2AR 1438A/G genotype groups in overweight/obese women. Polymorphic G allele was associated with higher triglyceride and insulin levels but not with other biochemical and metabolic parameters. Distribution of genotypes and alleles was not different between responders and nonresponders (weight loss >5 or <5 g).

CONCLUSIONS

Based on these results, it seems unlikely that the 5HT2AR 1438 /A polymorphism has a major impact on obesity and related traits or the response to sibutramine in Greek overweight/obese subjects.

Illness perception in bulimia nervosa

The study was designed to extend our understanding of illness perceptions in patients with bulimia nervosa (BN). Seventy-eight participants with BN or BN-type Eating Disorder Not Otherwise Specified (EDNOS-BN) completed the Revised Illness Perception Questionnaire (IPQ-R) ( Moss-Morris et al., 2002 ). Clinical variables were also assessed. Participants experienced their ED as chronic, with serious consequences and high associated levels of anxiety and depression. The disorder was attributed primarily to psychological causes. The results indicate the perceived severity of BN, and high level of associated distress. These findings highlight the potential for targeting illness perceptions in treatment.

The 5-HTTLPR polymorphism and eating disorders: a meta-analysis

OBJECTIVE

Eating disorders are influenced by both environmental factors and genes. The 5-HTTLPR polymorphism of serotonin transporter gene has been suggested as a good candidate. This meta-analysis was undertaken: (1) to investigate the association between 5-HTTLPR and eating disorders considered as a whole, including anorexia (AN), bulimia (BN), and binge eating disorder (BED); (2) to extend recently reported findings on the association between 5-HTTLPR and AN-BN.

METHOD

PubMed, ISI, and PsycINFO databases were searched for studies published until October 2009. Fifteen studies have been included. Data were analyzed with the Cochrane Collaboration Review Manager Software. Quality of studies and publication bias were assessed.

RESULTS

An association between S allele and eating disorders, in particular AN, has been found.

DISCUSSION

To be carrier of the 5-HTTLPR S allele seem to represent a risk factor for eating disorders, especially for AN. However, considering the reported high between-study heterogeneity, future studies should focus on more homogeneous endophenotype.

Eating disorders, gene-environment interactions and epigenetics

This review describes the various subtypes of eating disorders and examines factors associated with the risk of illness. It considers evidence that the development and maintenance of eating disorders is due to gene-environment interactions (GxE) that alter genetic expression via epigenetic processes. It describes how environmental factors such as those associated with nutrition and/or stress may cause epigenetic changes which have transcriptional and phenotypic effects, which, in turn, alter the long term risk of developing an eating disorder. It reviews theoretical and practical issues associated with epigenetic studies in psychiatry and how these are relevant to eating disorders. It examines the limited number of epigenetic studies which have been conducted in eating disorders and suggests directions for further research. Understanding the relationship between epigenetic processes and the risk of an eating disorder opens possibilities for preventive and/or therapeutic interventions. For example, epigenetic changes associated with diet and weight may be reversible and those associated with cognitive processes may be accessible to pharmacological interventions.

Conceptualizing the role of estrogens and serotonin in the development and maintenance of bulimia nervosa

Serotonergic dysregulation is thought to underlie much of the pathology in bulimia nervosa (BN). The purpose of this review is to expand the serotonergic model by incorporating specific and nonspecific contributions of estrogens to the development and maintenance of bulimic pathology in order to guide research from molecular genetics to novel therapeutics for BN. Special emphasis is given to the organizing theory of general brain arousal which allows for integration of specific and nonspecific effects of these systems on behavioral endpoints such as binge eating or purging as well as arousal states such as fear, novelty seeking, or sex. Regulation of the serotonergic system by estrogens is explored, and genetic, epigenetic, and environmental estrogen effects on bulimic pathology and risk factors are discussed. Genetic and neuroscientific research support this two-system conceptualization of BN with both contributions to the developmental and maintenance of the disorder. Implications of an estrogenic-serotonergic model of BN are discussed as well as guidelines and suggestions for future research and novel therapeutic targets.

Development of a new genotyping assay for detection of the BDNF Val66Met polymorphism using melting-curve analysis

Brain-derived neurotrophic factor (BDNF) plays a critical role in the growth, differentiation and survival of neurons in the CNS. Recent research has suggested that BDNF may be implicated in the etiology of mood disorders and schizophrenia, as well as in the therapeutic action of some drugs, such as antidepressants and antipsychotics. This study aimed to develop a simple, fast and accurate new method for detecting the Val66Met polymorphism of the BDNF gene in schizophrenia patients using melting-curve analysis and a DNA-specific dye, SYBR Green I. A group of 30 schizophrenia patients were analyzed to detect the BDNF Val66Met polymorphism (rs6265) using the new genotyping method based on the analysis of fluorescence melting curves of PCR products that were labeled with SYBR Green I. The genotype results were confirmed for all 30 samples using the specific BDNF TaqMan allele discrimination assay. This new method allows the analysis of both alleles in the same reaction tube using SYBR Green I, with no need for additional steps. The addition of a GC clamp makes this method universally applicable, since the melting temperature of one allele can be adjusted as necessary to give the distinctive separation of melting curves. Therefore, this new method is simple, fast and accurate for determining the presence of the BDNF Val66Met polymorphism. It may also be useful for the analysis of other SNPs in pharmacogenetic studies.