Association between 5-HT2A gene promoter polymorphism and anorexia nervosa

Non-Suicidal Self-Injury in Eating and Feeding Disorder Patients: Characteristics and Clinical Implications in a Group of Referred Female Adolescents

BACKGROUND

Non-suicidal self-injury (NSSI) and Feeding or Eating Disorders (FEDs) often coexist during adolescence with reciprocal influences on their clinical picture. The present study aimed to identify differences and similarities in the clinical presentation of young patients with both conditions compared to those with the two non-comorbid disorders.

METHODS

We consecutively recruited forty-five female patients aged between 11 and 18 at our third-level hospital and subdivided them into three groups (NSSI: n = 15; FED: n = 15; NSSI + FED: n = 15). Patients underwent a full clinical assessment.

RESULTS

Based on our results, the NSSI + FED group was characterized by higher rates of binging/purging behaviors, greater prevalence of Cyclothymic Disorder, and a more severe clinical presentation compared to the non-comorbid groups. Moreover, higher levels of suicidal ideation were found in the NSSI + FED group. Pharmacological treatment patterns also differed, with SSRI being prescribed more frequently to NSSI + FED patients while mood stabilizers were prescribed more frequently to NSSI ones. A Principal Component Analysis identified four main dimensions: "Body Image" impairment was more pronounced in NSSI + FED patients, indicating negative attitudes towards their own body; "Metacognition" deficits were higher in NSSI than FED.

CONCLUSIONS

The present study underscores distinctive clinical features in patients with comorbid NSSI and FED, emphasizing the urgent need for tailored intervention strategies focusing on specific symptom domains.

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.

Serotonin 5-HT2A receptor polymorphisms are associated with irritability and aggression in conduct disorder

In childhood and adolescence, overt antisocial and aggressive manifestations are typically diagnosed as conduct disorder (CD). Given that the emerging research has pointed to the influence of 5-HT_2A receptors in the ontogeny of aggression, we aimed to analyze the association of its genetic polymorphisms with CD. The study included 228 male adolescent subjects (120 with and 108 without CD). CD was diagnosed according to Structured Clinical Interview for DSM-IV criteria, while evaluations of aggressive/dissociative behaviors were performed using psychometric questionnaires including the PCL-YV, OAS-M, KADS, and CBCL. Platelet 5-HT concentration was determined by spectrophotofluorometry. Genotyping of 5-HT_2A receptor polymorphisms rs2070040, rs9534511, rs4142900, rs9534512 was performed using TaqMan SNP Genotyping Assays. Subjective irritability, physical aggression toward others, and antisocial behavior were strongly associated with the G allele of rs2070040 and rs4142900, and the C allele of rs9534511 and rs9534512. A significantly increased platelet 5-HT concentration in CD subjects, compared to controls, was lost after the correction according to the smoking status. Our results indicate an association of the studied HTR2A polymorphisms and their haplotypes with irritability and impulsivity traits, which may contribute to the aggressive and antisocial behavior in male adolescents with CD.

Genetics of anorexia nervosa: an overview of genome-wide association studies and emerging biological links

Anorexia nervosa (AN) is a complex disorder with a strong genetic component. Comorbidities are frequent and there is substantial overlap with other disorders. The lack of understanding of the molecular and neuroanatomical causes has made it difficult to develop effective treatments and it is often difficult to treat in clinical practice. Recent advances in genetics have changed our understanding of polygenic diseases, increasing the possibility of understanding better how molecular pathways are intertwined. This review synthetizes the current state of genetic research providing an overview of genome-wide association studies (GWAS) findings in AN as well as overlap with other disorders, traits, pathways, and imaging results. This paper also discusses the different putative global pathways that are contributing to the disease including the evidence for metabolic and psychiatric origin of the disease.

The impact of COMT, BDNF and 5-HTT brain-genes on the development of anorexia nervosa: a systematic review

PURPOSE

The genetic aspect of anorexia nervosa (AN) involving specific genes of the central-nervous-system has not yet been clearly understood. The aim of this systematic review is to assess the impact of three candidate genes of the brain: catechol-O-methyltransferase, brain-derived neurotrophic factor (BDNF) and serotonin transporter protein, on the susceptibility to AN and identify whether a clear connection persists between each of the gene-polymorphisms and AN.

METHODS

A total of 21 articles were selected for this review conforming to the PRISMA guidelines. Detailed keyword combinations were implemented within specific databases such as MEDLINE, SCIENCEDIRECT and PUBMED.

RESULTS

The catechol-O-methyltransferase gene-polymorphism did not show any change in phenotypic variation between AN and control subjects; but the familial association was rather strong with an over-transmission of the H allele. The latter also correlated with several dimensions of the Temperament and Character Inventory (TCI) scale. A notable relation was indicated between BDNF gene-polymorphism and anorexia-restrictive in terms of phenotypic distribution; the Met66-allele also depicted high association with anorexic behavioral traits. The 5-HTTLPR gene-polymorphism was found to be significantly associated with AN susceptibility with an over-transmission of the S-allele from parents to offspring.

CONCLUSION

The systematic review distinctively emphasized the genetic contribution of the brain-genes on the development of AN. Despite significant study findings, no clear and standardized genetic route was determined to be the cause of AN development. Future research is needed on these specific genes to closely monitor the genetic polymorphisms and their mechanism on AN susceptibility.

LEVEL OF EVIDENCE

I, systematic review.

Association of 5-HTR2A -1438A/G polymorphism with anorexia nervosa and bulimia nervosa: A meta-analysis

Although a number of studies have been conducted on the association of -1438A/G polymorphism in serotonin 2A receptor (5-HTR2A) gene with anorexia nervosa (AN) and bulimia nervosa (BN), the results remained inconsistent. We thus performed a meta-analysis to clarify the effects of -1438A/G polymorphism on the risk of AN and BN. PubMed, Embase, the Cochrane Library, CNKI, Weipu and Wanfang databases were searched for eligible studies. Pooled odds ratio (OR) and 95 % confidence interval (CI) were calculated to estimate the strength of the association. Subgroup analysis was also performed by ethnicity. In total, 17 studies were included for the meta-analysis, of which 15 studies containing 2028 cases and 2725 controls were used for AN analysis and 7 studies containing 505 cases and 1129 controls for BN analysis. The results showed -1438A/G polymorphism was significantly associated with the risk of AN in four genetic models (allele model, A vs. G: OR = 1.31, 95 % CI = 1.11-1.64, P = 0.003; recessive model, AA vs. GA + GG: OR = 1.69, 95 % CI = 1.28-2.23, P = 0.000; dominant model, AA + GA vs. GG: OR = 1.35, 95 % CI = 1.02-1.79, P = 0.037; co-dominant model, AA vs. GG: OR = 1.94, 95 % CI = 1.29-2.92, P = 0.002) in Caucasians, but not in Asians. We failed to observe a significant association between -1438A/G polymorphism and the risk of BN either in overall or in Caucasian population. The present meta-analysis indicated that A allele and AA genotype of 5-HTR2A -1438A/G polymorphism may contribute to higher risk of AN, especially in Caucasians. However, this polymorphism was not associated with the susceptibility to BN.

5-HT2AR and BDNF gene variants in eating disorders susceptibility

Evidence from family and twin studies points to a genetic contribution to the etiology of eating disorders (EDs), confirmed by the association of several single nucleotide polymorphisms (SNPs) with this group of disorders. Previous reports have suggested that the serotonin receptor (5-HT2AR) and brain-derived neurotrophic factor (BDNF) genes could be both involved in EDs susceptibility. In order to provide further evidence about such association, we focused our attention on two SNPs located in these genes carrying out a genetic association study on a large Italian cohort composed of 556 ED patients and 355 controls (CTRs). Obtained results confirm the presence of an association between 5-HT2AR and BDNF genes and the susceptibility to EDs.

Association of the 5-HT2A receptor gene promoter polymorphism-1438G/A with anorexia nervosa and psychopathological traits in the Chinese Han population: A preliminary study

OBJECTIVE

The aim of the study was to explore the possible role of the 5-HT_2A -1438G/A polymorphism in the susceptibility to anorexia nervosa (AN) in the Chinese Han population.

METHODS

The -1438G/A polymorphism of 249 female AN patients, 228 matched healthy controls, and 198 trios was genotyped using SNaP shot assay. Psychopathological traits of eating-disordered behaviors in AN subjects were examined using the Chinese version of the Eating Disorder Examination Questionnaire.

RESULTS

Neither the case-control analysis nor the transmission disequilibrium test revealed significant associations between the -1438G/A polymorphism and AN (P > .05). However, AA homozygote patients with AN had lower weight and shape concern scores of the EDE-Q6.0 than those of GA heterozygotes (P < .05).

DISCUSSION

Our findings suggested that female AN patients with 5-HT_2A -1438AA genotype may be characterized by less severe eating-disordered psychopathological traits in the Chinese Han population.

Usual Consumption of Specific Dairy Foods Is Associated with Breast Cancer in the Roswell Park Cancer Institute Data Bank and BioRepository

Background: Dairy foods are complex mixtures which include nutrients and non-nutrient substances that could potentially influence cancer etiology, including breast cancer. Objective: The purpose of this study was to examine associations between the types and quantity of dairy foods consumed and the risk of breast cancer among women participating in the Roswell Park Cancer Institute Data Bank and BioRepository (DBBR) between 2003 and 2014. Methods: Archived clinical and questionnaire data were obtained from the DBBR from 1941 women diagnosed with breast cancer between December 2003 and October 2014, and 1237 control participants. Intakes of dairy foods were queried with a self-administered food-frequency questionnaire and grouped into monthly intakes of total dairy, milk, yogurt, low-fat cheese, other cheese, and sweet dairy. ORs and 95% CIs were estimated with unconditional logistic regression adjusting for age, race, body mass index, menopausal status, energy intake, type of milk usually consumed, cigarette smoking status, and family history of breast cancer. Results: Total dairy intakes were associated with a non-significant 15% reduction in breast cancer risk (P = 0.11). Higher intakes of yogurt were associated with reduced risk of breast cancer (OR: 0.61; 95% CI: 0.46, 0.82) and higher intakes of American, cheddar, and cream cheeses were associated with a marginally significant increased risk (OR: 1.53; 95% CI: 0.99, 2.34; P = 0.05). Associations with dairy foods were mixed when stratified by estrogen receptor (ER) status, and in general reflected those of overall breast cancer. However, we observed positive associations between milk intake and risk of ER- breast cancer (OR: 1.58; 95% CI: 1.05, 2.37) and inverse associations between sweet dairy and ER+ breast cancer (OR: 0.52; 95% CI: 0.29, 0.95). Conclusions: Specific dairy foods may contribute to breast cancer risk in women, although the risk varies by source of dairy. Future studies are warranted to confirm the protective potential of yogurt in this type of cancer.

Paraphilic Sexual Offenders Do Not Differ From Control Subjects With Respect to Dopamine- and Serotonin-Related Genetic Polymorphisms

INTRODUCTION

Rape and pedophilic child molestation are the most commonly convicted sexual offenses in Poland. Recent studies have suggested a possible genetic contribution toward pathologic sexual interests and behaviors.

AIM

To analyze and compare functional polymorphisms of genes associated with the activity of the serotonin and dopamine systems in a group of paraphilic sexual offenders and control subjects.

METHODS

The study sample (n = 97) consisted of two groups: paraphilic sexual offenders (65 pedophilic child molesters and 32 rapists) and controls (n = 76). Genetic polymorphisms previously associated with behavioral control, addictive behaviors, and sexual functions were chosen for analyses. Specifically, functional polymorphisms in dopamine receptors genes (DRD1, DRD2, DRD4), catechol-O-methyltransferase gene (COMT), dopamine transporter gene (DAT), serotonin transporter gene (SLC6A4), serotonin type 2A receptor gene (5HTR2A), tryptophan hydroxylase 2 gene (TPH2), monoamine oxidase A gene (MAOA), and brain-derived neurotrophic factor gene (BDNF) were analyzed.

MAIN OUTCOME MEASURES

An association between a history of sexual offense and the distribution of genotypes and alleles in the analyzed polymorphisms.

RESULTS

Our results found no association between a history of sexual offense and the distribution of genotypes or alleles in the analyzed polymorphisms.

CONCLUSION

Although these results are limited by the small sample and are exploratory, they highlight a novel approach to sample selection in a population that is difficult to access and study. Future research should include larger samples and other relevant polymorphisms to advance this field of study.

Effect of a human serotonin 5-HT2A receptor gene polymorphism on impulsivity: Dependence on cholesterol levels

BACKGROUND

Impulsivity is multidimensional: Low impulse control may result in behavioural disorders, but acting on the spur of moment may also be advantageous. Previous studies have shown negative associations between different facets of impulsivity and serotonergic function. Other investigations have found negative correlations between serum lipid levels and impulsivity.

METHODS

We have investigated whether the functional polymorphism -1438A/G in the serotonin 5-HT_2A receptor gene (HTR2A) is associated with impulsivity levels and whether there is any interaction with serum lipid levels. This analysis was based on data of the population-representative Estonian Children Personality Behaviour and Health Study at age 25. Impulsivity was self-reported with the Adaptive and Maladaptive Impulsivity Scale.

RESULTS

Subjects with the A/A genotype of the HTR2A -1438A/G polymorphism had higher scores of Maladaptive impulsivity, but not Adaptive impulsivity. In females, high LDL and total cholesterol levels increased the genotype effect. In males, in the highest quartile of total or LDL cholesterol the genotype effect was altered, with G/G homozygotes having the highest Maladaptive impulsivity levels.

LIMITATIONS

Only one cohort of the European Youth Heart Study (EYHS) was used in the current study and impulsivity measures were self-reported.

CONCLUSIONS

Our results do not support the notion that low cholesterol levels universally lead to higher impulsivity, but it was found that high total and LDL cholesterol levels moderate the effect of the HTR2A gene promoter polymorphism. This suggests that future studies on impulsivity need to consider the interaction of serotonergic measures with the whole range of cholesterol levels.

Anxiolytic-like effects of leptin on fixed interval responding

Leptin has been shown to affect energy homeostasis, learning and memory, and some models of anxiolytic action. However, leptin has produced inconsistent results in previous non-operant behavioural tests of anxiety. Here, we test the anxiolytic potential of leptin in an operant paradigm that has produced positive results across all classes of anxiolytic so far tested. Rats were tested in the Fixed Interval 60 Seconds (FI60) task following administration of 0/0.5/1.0mg/kg (i.p.) leptin or an active anxiolytic control of 5mg/kg (i.p.) chlordiazepoxide (CDP). By the end of the 14days of testing in the FI60 task, 0.5mg/kg leptin released suppressed responding in a manner similar to CDP, and 1.0mg/kg leptin produced a relative depression in responding, a similar outcome pattern to previously tested 5HT-agonist anxiolytics. This suggests that leptin behaves similarly to established serotonergic anxiolytics such as buspirone and fluoxetine; with the delay in development of effect during testing, and the inverted-U dose-response curve explaining the inconsistent behaviour of leptin in behavioural tests of anxiety, as this type of pattern is common to serotonergic anxiolytics.

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.

Association of schizophrenia with T102C (rs6313) and 1438 A/G (rs6311) polymorphisms of HTR2A gene

OBJECTIVE

The aim of this study is to investigate whether there were any associations between the T102C and 1438 A/G polymorphisms of the 5-HT2A receptor gene and schizophrenia. We conducted a case-control study of the T102C and 1438 A/G polymorphisms in Turkish patients.

METHODS

We compared genotypes and allele frequencies of T102C and 1438 A/G polymorphisms of 5-HT2A receptor gene in 102 patients with schizophrenia diagnosed, according to DSM-IV, and 107 healthy controls. Genotyping was performed by real-time polymerase chain reaction.

RESULTS

We found no significant association between schizophrenia and genotypic or allele frequencies of HTR2A gene 102T/C (rs6313) and 1438 A/G (6311) polymorphisms. However, comparison of HTR2A gene 102 T/C and 1438 A/G polymorphisms in terms of genotypic and allele frequencies between the two patient groups, with or without a family history of schizophrenia, shows that T- and A-allele frequencies were significantly higher (p < 0.05) in the case group that has a history of schizophrenia in their family.

CONCLUSION

In conclusion, our results do not support the hypothesis that the T102C and 1438 A/G polymorphisms in the 5-HT2A receptor gene are associated with schizophrenia, but further studies in a larger sample are needed.

Genetic variations in the serotoninergic system contribute to body-mass index in Chinese adolescents

OBJECTIVE

Obesity has become a worldwide health problem in the past decades. Human and animal studies have implicated serotonin in appetite regulation, and behavior genetic studies have shown that body mass index (BMI) has a strong genetic component. However, the roles of genes related to the serotoninergic (5-hydroxytryptamine,5-HT) system in obesity/BMI are not well understood, especially in Chinese subjects.

SUBJECTS AND DESIGN

With a sample of 478 healthy Chinese volunteers, this study investigated the relation between BMI and genetic variations of the serotoninergic system as characterized by 136 representative polymorphisms. We used a system-level approach to identify SNPs associated with BMI, then estimated their overall contribution to BMI by multiple regression and verified it by permutation.

RESULTS

We identified 12 SNPs that made statistically significant contributions to BMI. After controlling for gender and age, four of these SNPs accounted for 7.7% additional variance of BMI. Permutation analysis showed that the probability of obtaining these findings by chance was low (p = 0.015, permuted for 1000 times).

CONCLUSION

These results showed that genetic variations in the serotoninergic system made a moderate contribution to individual differences in BMI among a healthy Chinese sample, suggesting that a similar approach can be used to study obesity.

Serotonin 2A Receptor Gene Polymorphism in Korean Children with Attention-Deficit/Hyperactivity Disorder

OBJECTIVE

The purpose of this study was to investigate the association between the T102C polymorphism in the serotonin 2A receptor gene and attention-deficit/hyperactivity disorder (ADHD) in Korean patients.

METHODS

A total of 189 Korean children with ADHD as well as both parents of the ADHD children and 150 normal children participated in this study. DNA was extracted from blood samples from all of the subjects, and genotyping was conducted. Based on the allele and genotype information obtained, case-control analyses were performed to compare the ADHD and normal children, and Transmission disequilibrium tests (TDTs) were used for family-based association testing (number of trios=113). Finally, according to the significant finding which was showed in the case-control analyses, the results of behavioral characterastics and neuropsychological test were compared between ADHD children with and without the C allele.

RESULTS

In the case-control analyses, statistically significant differences were detected in the frequencies of genotypes containing the C allele (χ(2)=4.73, p=0.030). In the family-based association study, TDTs failed to detect linkage disequilibrium of the T102C polymorphism associated with ADHD children. In the ADHD children, both the mean reaction time and the standard deviation of the reaction time in the auditory continuous performance test were longer in the group with the C allele compared to the group without the C allele.

CONCLUSION

The results of this study suggest that there is a significant genetic association between the T102C polymorphism in the serotonin 2A receptor gene and ADHD in Korean children.

The ALDH2 and 5-HT2A genes interacted in bipolar-I but not bipolar-II disorder

OBJECTIVE

Clarifying the similarities and differences between the two most common subtypes of bipolar disorder, bipolar-I and bipolar-II, is essential for improving our understanding of them. Because the serotonergic system has been implicated in the pathogenesis of bipolar disorder, it may be important to investigate genes such as the aldehyde dehydrogenase 2 (ALDH2) and serotonin 2A receptor genes, which are involved in metabolizing serotonin and encoding serotonin receptors. We examined the association of the ALDH2 and 5-HT2A-A1438G polymorphisms with bipolar I and II and possible interactions between these genes.

METHODS

One thousand forty-nine participants were recruited: 249 with bipolar-I, 456 with bipolar-II, and 344 healthy controls. The genotypes of the ALDH2 and 5HT2A-A1438G polymorphisms were determined using polymerase chain reactions plus restriction fragment length polymorphism analysis.

RESULTS

Logistic regression analysis showed a significant effect of the ALDH2 and the 5-HT2A-A1438G polymorphisms, and a significant interaction effect for the A/G genotypes of the 5-HT2A-A1438G polymorphism and the ALDH2*1*1 genotypes (p=0.004) discriminated between bipolar-I patients and controls without bipolar disorder. These polymorphisms, however, were not associated with bipolar-II disorder.

LIMITATIONS

The significant differences of age and gender between patients and controls limit the comparison, although statistical adjustments were made for them.

CONCLUSION

Our findings provide initial evidence that the ALDH2 and 5-HT2A genes interact in bipolar-I but not in bipolar-II disorder. Our findings suggest a unique genetic distinction between bipolar-I and bipolar-II.

A debate on current eating disorder diagnoses in light of neurobiological findings: is it time for a spectrum model?

BACKGROUND

Sixty percent of eating disorders do not meet criteria for anorexia- or bulimia nervosa, as defined by the Diagnostic and Statistical Manual version 4 (DSM-IV). Instead they are diagnosed as 'eating disorders not otherwise specified' (EDNOS). Discrepancies between criteria and clinical reality currently hampering eating disorder diagnoses in the DSM-IV will be addressed by the forthcoming DSM-V. However, future diagnoses for eating disorders will rely on current advances in the fields of neuroimaging and genetics for classification of symptoms that will ultimately improve treatment.

DISCUSSION

Here we debate the classification issues, and discuss how brain imaging and genetic discoveries might be interwoven into a model of eating disorders to provide better classification and treatment. The debate concerns: a) current issues in the classification of eating disorders in the DSM-IV, b) changes proposed for DSM-V, c) neuroimaging eating disorder research and d) genetic eating disorder research.

SUMMARY

We outline a novel evidence-based 'impulse control' spectrum model of eating disorders. A model of eating disorders is proposed that will aid future diagnosis of symptoms, coinciding with contemporary suggestions by clinicians and the proposed changes due to be published in the DSM-V.

Eating Disorders: From Twin Studies to Candidate Genes and Beyond

Substantial effort has been put into the exploration of the biological background of eating disorders, through family, twin and molecular genetic studies. Family studies have shown that anorexia (AN) and bulimia nervosa (BN) are strongly familial, and that familial etiologic factors appear to be shared by both disorders. Twin studies often focus on broader phenotypes or subthreshold eating disorders. These studies consistently yielded moderate to substantial heritabilities. In addition, there has been a proliferation of molecular genetic studies that focused on Diagnostic and Statistical Manual of Mental Disorders (4th ed.; DSM-IV; American Psychiatric Association, 1994) AN and BN. Seven linkage regions have been identified in genome-wide screens. Many genetic association studies have been performed, but no consistent association between a candidate gene and AN or BN has been reported. Larger genetic association studies and collaborations are needed to examine the involvement of several candidate genes and biological pathways in eating disorders. In addition, twin studies should be designed to assist the molecular work by further exploring genetic determinants of endophenotypes, evaluating the magnitude of contribution to liability of measured genotypes as well as environmental risk factors related to eating disorders. In this manner twin and molecular studies can move the field forward in a mutually informative way.

Genetic polymorphisms in the serotonergic system and symptom clusters of major depressive disorder

BACKGROUND

It has been suggested that the symptoms of major depressive disorder (MDD) are composed of some clusters, which are linked to distinct genetic mechanisms. The purpose of this study was to examine the associations of genetic polymorphisms in the serotonergic system with three factors of the Montgomery-Åsberg Depression Rating Scale (MADRS), i.e., dysphoria, retardation, and vegetative symptoms.

METHODS

The subjects were 132 Japanese patients of MDD. The genotypes of tryptophan hydroxylase 218A/C, serotonin transporter gene-linked polymorphic region (5HTTLPR), and 5HT2A receptor -1438G/A polymorphisms were determined by PCR methods. Statistical analyses were performed by the multiple regression analysis.

RESULTS

The A allele of 5HT2A polymorphism was associated with higher vegetative scores (p=0.001) and total MADRS scores (p=0.005), while the S allele of 5HTTLPR was related to higher dysphoric scores (p=0.012). The tryptophan hydroxylase genotype was not related to any factor scores or total MADRS scores.

LIMITATIONS

The sample size was relatively small, and the subjects were composed of Japanese only.

CONCLUSION

This study suggests that the genetic polymorphisms in 5HT2A receptor and serotonin transporter are linked to discrete symptom clusters of MDD.

Contemporary thinking about the role of genes and environment in eating disorders

Objective – To review recent literature documenting how family, twin and molecular genetic studies of eating disorders have revolutionized our conceptualizations of anorexia and bulimia nervosa. Methods – We summarized extant litera-ture on genetic epidemiology of eating disorders. Results – Results of extant studies highlight the underlying biological vulnera- bilities associated with these conditions. Genetic research has also opened up new avenues and approaches for exploring how the environment exerts its influence on risk. Conclusions – We discuss state-of-the-science findings in the genetics of eating disorders, explore various mechanisms of gene-environment interplay, and discuss implications of this research for science, practice, families and individuals with eating disorders.

Genetic and environmental factors in complex neurodevelopmental disorders

Complex neurodevelopmental disorders, such as schizophrenia, autism, attention deficit (hyperactivity) disorder, (manic) depressive illness and addiction, are thought to result from an interaction between genetic and environmental factors. Association studies on candidate genes and genome-wide linkage analyses have identified many susceptibility chromosomal regions and genes, but considerable efforts to replicate association have been surprisingly often disappointing. Here, we summarize the current knowledge of the genetic contribution to complex neurodevelopmental disorders, focusing on the findings from association and linkage studies. Furthermore, the contribution of the interaction of the genetic with environmental and epigenetic factors to the aetiology of complex neurodevelopmental disorders as well as suggestions for future research are discussed.

Association of the A-1438G polymorphism in serotonin 2A receptor in migraine with aura among Japanese patients

We investigated the possible association of serotonin (5-HT) 2A receptor gene A-1438G polymorphism in Japanese patients with migraine. Genotyping of 5-HT(2A) A-1438G polymorphism was performed by polymerase chain reaction-restriction fragment length polymorphism in patients with migraine (male 17 : 3 with aura and 14 without aura, female 65 : 17 with aura and 48 without aura) and controls (male 31, female 84). The distribution of 5-HT(2A) A-1438G genotype frequency between migraine patients and controls did not differ. These results suggest that the A-1438G polymorphism of the 5-HT(2A) receptor gene is not a direct risk factor for migraine; however, the incidence of the A/A genotype between migraine with aura (MA) and without aura (MO) was significantly different. The 5-HT(2A) A-1438G polymorphism may be involved in determining the subtypes of migraine in Japanese.

The genetics of eating disorders

The eating disorders anorexia nervosa (AN), bulimia nervosa (BN), binge eating disorder and allied diagnoses such as eating disorder not otherwise specified are common, complex psychiatric disorders with a significant genetic component. Aetiology is unknown, but both phenotypic characteristics and genetic factors appear to be shared across these disorders, and indeed patients often change between diagnostic categories. Molecular studies have attempted to define genetic risk factors for these disorders, including case-control and family-based candidate gene association studies and linkage analysis of multiply affected nuclear families. These have used both clinical diagnoses and eating disorder-related intermediate phenotypes such as drive-for-thinness or body dissatisfaction. Candidate gene studies have focussed on neurotransmitter and neurodevelopmental systems [e.g. serotonergic, opioid, cannabinoid and dopaminergic receptors, and brain-derived neurotrophic factor (BDNF)], appetite regulatory peptides and their receptors [leptin, ghrelin, agouti-related protein (AgRP), melanocortin receptors, neuropeptide Y], energy balance systems (e.g. uncoupling proteins), genes implicated in obesity (e.g. FTO) and sex hormone systems (e.g. oestrogen receptors), either identified on the basis of their function alone or as positional candidates from linkage analysis. Of these studies, linkage analysis implicates 1p33-36 for AN, 1q31.3 for quantitative behavioural traits related to anorexia and 10p14 for BN, as well as other behavioural phenotypes across both disorders. Candidate gene association has implicated BDNF, delta 1 opioid receptor (OPDR1) and AgRP. More recently, with the advent of genome-wide association studies (GWAS), analysis with microsatellite markers has implicated novel candidate loci for AN at 1q41 and 11q22, and further GWAS results are expected in the near future.

Role of 2 common variants of 5HT2A gene in medication overuse headache

OBJECTIVE

The aim of the present study was to evaluate a possible involvement of 2 polymorphisms of the serotonin 5HT2A receptor gene (A-1438G and C516T) as risk factors for medication overuse headache (MOH) and whether the presence of these polymorphic variants might determine differences within MOH patients in monthly drug consumption.

BACKGROUND

Despite a growing scientific interest in the mechanisms underlying the pathophysiology of MOH, few studies have focused on the role of genetics in the development of the disease, as well as on the genetic determinants of the inter-individual variability in the number of drug doses taken per month.

METHODS

Our study was performed by polymerase chain reaction (PCR) and PCR-restriction fragment length polymorphism on genomic DNA extracted from peripheral blood of 227 MOH patients and 312 control subjects. Genotype-specific risks were estimated as odds ratios with associated 95% confidence intervals by unconditional logistic regression and adjusted for age and gender. A stepwise multiple linear regression analysis was employed to identify significant predictors of the number of drug doses taken per month.

RESULTS

No significant association was found between 5HT2A A and 1438G and C516T gene polymorphisms and MOH risk. In contrast, a higher consumption of monthly drug doses was observed among 516T 5HT2A carriers (median 50, range 13-120) compared to 516CC patients (median 30, range 12-128) (Mann-Whitney U-test, P = .018). In the stepwise multiple regression analysis, C516T 5HT2A polymorphism (P = .018) and class of overused drug (P = .047) emerged as significant, independent predictors of the monthly drug consumption in MOH patients.

CONCLUSIONS

Although our results do not support a major role of the A-1438G and C516T polymorphic variants of the 5HT2A gene in the susceptibility of MOH, our findings support an influence of the C516T polymorphism on the number of symptomatic drug doses taken and, possibly, on the drug-seeking behavior in these patients.

Eating disorders: the current status of molecular genetic research

Anorexia nervosa (AN) and bulimia nervosa (BN) are complex disorders characterized by disordered eating behavior where the patient's attitude towards weight and shape, as well as their perception of body shape, are disturbed. Formal genetic studies on twins and families suggested a substantial genetic influence for AN and BN. Candidate gene studies have initially focused on the serotonergic and other central neurotransmitter systems and on genes involved in body weight regulation. Hardly any of the positive findings achieved in these studies were unequivocally confirmed or substantiated in meta-analyses. This might be due to too small sample sizes and thus low power and/or the genes underlying eating disorders have not yet been analyzed. However, some studies that also used subphenotypes (e.g., restricting type of AN) led to more specific results; however, confirmation is as yet mostly lacking. Systematic genome-wide linkage scans based on families with at least two individuals with an eating disorder (AN or BN) revealed initial linkage regions on chromosomes 1, 3 and 4 (AN) and 10p (BN). Analyses on candidate genes in the chromosome 1 linkage region led to the (as yet unconfirmed) identification of certain variants associated with AN. Genome-wide association studies are under way and will presumably help to identify genes and pathways involved in these eating disorders. The elucidation of the molecular mechanisms underlying eating disorders might improve therapeutic approaches.

Genetic findings in anorexia and bulimia nervosa

Anorexia nervosa (AN) and bulimia nervosa (BN) are complex disorders associated with disordered eating behavior. Heritability estimates derived from twin and family studies are high, so that substantial genetic influences on the etiology can be assumed for both. As the monoaminergic neurotransmitter systems are involved in eating disorders (EDs), candidate gene studies have centered on related genes; additionally, genes relevant for body weight regulation have been considered as candidates. Unfortunately, this approach has yielded very few positive results; confirmed associations or findings substantiated in meta-analyses are scant. None of these associations can be considered unequivocally validated. Systematic genome-wide approaches have been performed to identify genes with no a priori evidence for their relevance in EDs. Family-based scans revealed linkage peaks in single chromosomal regions for AN and BN. Analyses of candidate genes in one of these regions led to the identification of genetic variants associated with AN. Currently, an international consortium is conducting a genome-wide association study for AN, which will hopefully lead to the identification of the first genome-wide significant markers.

Molecular mechanisms underlying anorexia nervosa: focus on human gene association studies and systems controlling food intake

Anorexia nervosa (AN) is a complex multi-factorial disease with high heritability. The psychological AN symptoms are poorly connected with specific molecular mechanisms. Here we review the molecular basis of AN with the focus on human genetic association studies; we put these in the experimental biological context with emphasis on molecular systems controlling food intake and body weight in a direct or indirect manner. We systematically searched for human genetic studies related to AN and grouped data into main categories/systems reflecting their major known roles: (1) Systems related to mental disorders (serotonin, brain-derived neurotrophic factor (BDNF), norepinephrine (NE), glutamate (NMDA) receptor and SK3 channel, KCCN3). (2) Hunger regulatory systems (leptin, AGRP, MSH, melanocortin 4 receptor (MC4R), NPY, ghrelin, cholecystokinin (CCK). (3) Feeding motivation- and reward-related systems (opioids, OPRD1, cannabinoids (anandamide (AEA), THC, CBR1), dopamine, DRD2, DRD3, DRD4, catecholamine-O-methyl transferase (COMT). (4) Systems regulating energy metabolism (uncoupling proteins 2 and 3 (UCP2 and UCP3). (5) Neuroendocrine systems with emphasis on sex hormones (estrogen receptor-beta (ESR2). (6) The immune system and inflammatory response (tumor necrosis factor-alpha (TNF-alpha)). Overall, we found that in total 175 association studies have been performed on AN cohorts on 128 different polymorphisms related to 43 genes. We review the strongest associations, identify some genes that have an important role in regulating BMI whose possible relationship to AN has not been investigated and discuss the potential targets for pharmacological interventions.

Genetic variation and effects on human eating behavior

Feeding is a physiological process, influenced by genetic factors and the environment. In recent years, many studies have been performed to unravel the involvement of genetics in both eating behavior and its pathological forms: eating disorders and obesity. In this review, we provide a condensed introduction on the neurological aspects of eating and we describe the current status of research into the genetics of eating behavior, primarily focused on specific traits such as taste, satiation, and hunger. This is followed by an overview on the genetic studies done to unravel the heritable background of obesity and eating disorders. We examine the discussion currently taking place in the field of genetics of complex disorders and phenotypes on how to perform good and powerful studies, with the use of large-scale whole-genome association studies as one of the possible solutions. In the final part of this review, we give our view on the latest developments, including endophenotype approaches and animal studies. Studies of endophenotypes of eating behavior may help to identify core traits that are genetically influenced. Such studies would yield important knowledge on the underlying biological scaffold on which diagnostic criteria for eating disorders could be based and would provide information to influence eating behavior toward healthier living.

HTR2A A-1438G/T102C polymorphisms predict negative symptoms performance upon aripiprazole treatment in schizophrenic patients

RATIONALE

Aripiprazole acts as a partial agonist at dopamine D2 and D3 and serotonin 1A receptors and as an antagonist at serotonin 2A receptors (HTR2A). Since aripiprazole acts as an antagonist at HTR2A, genetic variants of HTR2A may be important in explaining variability in response to aripiprazole.

OBJECTIVES

This study investigated whether the efficacy of aripiprazole can be predicted by functional HTR2A A-1438G/T102C polymorphisms (rs63311/rs6313) as modified by clinical factors in Han Chinese hospitalized patients with acutely exacerbated schizophrenia.

MATERIALS AND METHODS

After hospitalization, the patients (n = 128) were given a 4-week course of aripiprazole. Patients were genotyped for HTR2A A-1438G/T102C polymorphisms via the restriction fragment length polymorphism method. Clinical factors such as gender, age, duration of illness, education level, diagnostic subtype, and medication dosage were noted as well. The researchers measured psychopathology biweekly, using the Positive and Negative Syndrome Scale (PANSS). A mixed model regression approach (SAS Proc MIXED) was used to analyze the effects of genetic and clinical factors on PANSS performance after aripiprazole treatment.

RESULTS

We found that the GG/CC genotype group of HTR2A A-1438G/T102C polymorphisms predicts poor aripiprazole response specifically for negative symptoms. In addition, the clinical factors, including dosage of aripiprazole, age, duration of illness, and diagnostic subtype, were found to influence PANSS performance after aripiprazole treatment.

CONCLUSIONS

The data suggest HTR2A A-1438G/T102C polymorphisms may predict negative symptoms performance upon aripiprazole treatment in schizophrenic patients as modified by clinical factors.

The serotonin 2A receptor gene in alcohol dependence and tobacco smoking

Alcohol and nicotine abuse and dependence are multifactorial traits that frequently co-occur, where 80-90% of alcohol-dependent individuals who seek treatment smoke. Nicotine is the main compound of tobacco and one of its effects is to increase the release of serotonin. Variations in the serotonergic system may influence some aspects of smoking. The serotonin receptor gene HTR2A has been a candidate gene with some evidence for association with alcohol and nicotine dependencies. The polymorphism HTR2A A-1438G is a functional SNP, and the presence of the A allele increases the transcriptional activity of the gene. The aim of the present study was to test for possible associations between the A-1438G polymorphism in the serotonin receptor gene (HTR2A) with tobacco smoking combined or not with alcohol dependence. The polymorphic site was genotyped in three groups of European-derived Brazilians: individuals with co-occurrence of alcohol dependence and tobacco smoking (n=113), non-alcoholic smokers (n=120) and non-smoking controls (n=115). A higher frequency of the A allele was observed in the two groups of smokers than in the non-smoking controls (chi(2)=6.53, p=0.04). Combining these groups in comparison with the control group, the difference is more significant (chi(2)=6.45, p=0.01). These results support previous evidence for association between HTR2A polymorphisms and substance use disorders.

Performance of a neuro-fuzzy model in predicting weight changes of chronic schizophrenic patients exposed to antipsychotics

Artificial intelligence has become a possible solution to resolve the problem of loss of information when complexity of a disease increases. Obesity phenotypes are observable clinical features of drug-naive schizophrenic patients. In addition, atypical antipsychotic medications may cause these unwanted effects. Here we examined the performance of neuro-fuzzy modeling (NFM) in predicting weight changes in chronic schizophrenic patients exposed to antipsychotics. Two hundred and twenty inpatients meeting DSMIV diagnosis of schizophrenia, treated with antipsychotics, either typical or atypical, for more than 2 years, were recruited. All subjects were assessed in the same study period between mid-November 2003 and mid-April 2004. The baseline and first visit's physical data including weight, height and circumference were used in this study. Clinical information (Clinical Global Impression and Life Style Survey) and genotype data of five single nucleotide polymorphisms were also included as predictors. The subjects were randomly assigned into the first group (105 subjects) and second group (115 subjects), and NFM was performed by using the FuzzyTECH 5.54 software package, with a network-type structure constructed in the rule block. A complete learned model trained from merged data of the first and second groups demonstrates that, at a prediction error of 5, 93% subjects with weight gain were identified. Our study suggests that NFM is a feasible prediction tool for obesity in schizophrenic patients exposed to antipsychotics, with further improvements required.

Genetic susceptibility to eating disorders: associated polymorphisms and pharmacogenetic suggestions

Anorexia nervosa (AN), bulimia nervosa (BN) and binge-eating disorder (BED) are characterized by abnormal eating behaviors often resulting in dramatic physical consequences for the patients. The etiology of eating disorders (EDs) is currently unknown; however, a strong genetic contribution is likely to be involved. To date, the majority of genetic studies have focused on candidate genes, and polymorphic variants of genes coding for substances likely to be involved in the etiopathogenesis of EDs have been assessed for association with AN, BN, BED and/or ED-related phenotypic traits. Results have been generally inconsistent and cannot be considered conclusive because of several methodological flaws and differences, such as small sample sizes, ethnic heterogeneity of studied populations, lack of statistical correction for multiple testing, adoption of different diagnostic criteria and population stratification. Although, at present, no convincing evidence for associations of candidate genes with EDs has been provided, the 5-HT2A receptor gene and the BDNF gene seem to be promising candidates for genetic influences on AN, since polymorphic variants of these genes have been found quite consistently, although not specifically, linked to AN restricting subtype in large sample studies. Moreover, pharmacogenetic investigations have suggested a possible role of some gene polymorphisms in predicting the response to treatment with selective serotonin reuptake inhibitors in BN, but results are still preliminary. The heterogeneity of ED phenotypes is believed to represent the most relevant variable responsible for contradictory and not conclusive results. Future studies should focus on more homogeneous subgroups, either relying on specific ED traits or identifying endophenotypes. This will be useful also for prevention and treatment of EDs.

Electrical stimulation in the lateral hypothalamus in rats in the activity-based anorexia model

Object

One quarter of patients with anorexia nervosa have a poor outcome and continue to suffer chronically or die. Electrical brain stimulation may be of therapeutic benefit in some of these patients; however, the brain target for inducing symptom relief is unknown. In this study, the authors evaluated the effects of acute and chronic electrical stimulation in the lateral hypothalamus on food intake, locomotor activity, and survival time in rats in an activity-based anorexia model.

Methods

In an acute experiment, the authors electrically stimulated at 100 Hz and 0, 25, 50 and 75% of the maximal stimulation amplitude (that is, the amplitude leading to severe side effects) in the lateral hypothalamus on consecutive days during 4 test sessions in 10 rats and evaluated food intake and locomotor activity. In a chronic experiment, they compared food intake, wheel revolutions, and survival time between 6 rats that underwent electrical stimulation in the lateral hypothalamus (50% of maximal stimulation amplitude) and 8 rats that did not undergo stimulation.

Results

In the acute experiment, overall electrical stimulation (25, 50, and 75% combined) and stimulation at 75% of the maximal stimulation amplitude significantly decreased the locomotor activity. However, if the authors omitted results of 1 rat, in which the electrode tip was not located in the lateral hypothalamus on one side but rather in the supraoptic chiasm, the remaining results did not yield significance. No other differences were observed.

Conclusions

When the findings of the current study are extrapolated to patients with anorexia nervosa, the authors do not expect major effects on symptoms with electrical stimulation at high frequency in the lateral hypothalamus.

Genetic evaluation of the serotonergic system in chronic fatigue syndrome

Chronic fatigue syndrome (CFS) is a debilitating disorder of unknown etiology with no known lesions, diagnostic markers or therapeutic intervention. The pathophysiology of CFS remains elusive, although abnormalities in the central nervous system (CNS) have been implicated, particularly hyperactivity of the serotonergic (5-hydroxytryptamine; 5-HT) system and hypoactivity of the hypothalamic-pituitary-adrenal (HPA) axis. Since alterations in 5-HT signaling can lead to physiologic and behavioral changes, a genetic evaluation of the 5-HT system was undertaken to identify serotonergic markers associated with CFS and potential mechanisms for CNS abnormality. A total of 77 polymorphisms in genes related to serotonin synthesis (TPH2), signaling (HTR1A, HTR1E, HTR2A, HTR2B, HTR2C, HTR3A, HTR3B, HTR4, HTR5A, HTR6, and HTR7), transport (SLC6A4), and catabolism (MAOA) were examined in 137 clinically evaluated subjects (40 CFS, 55 with insufficient fatigue, and 42 non-fatigued, NF, controls) derived from a population-based CFS surveillance study in Wichita, Kansas. Of the polymorphisms examined, three markers (-1438G/A, C102T, and rs1923884) all located in the 5-HT receptor subtype HTR2A were associated with CFS when compared to NF controls. Additionally, consistent associations were observed between HTR2A variants and quantitative measures of disability and fatigue in all subjects. The most compelling of these associations was with the A allele of -1438G/A (rs6311) which is suggested to have increased promoter activity in functional studies. Further, in silico analysis revealed that the -1438 A allele creates a consensus binding site for Th1/E47, a transcription factor implicated in the development of the nervous system. Electrophoretic mobility shift assay supports allele-specific binding of E47 to the A allele but not the G allele at this locus. These data indicate that sequence variation in HTR2A, potentially resulting in its enhanced activity, may be involved in the pathophysiology of CFS.

Meta-analysis of genome-wide linkage studies in BMI and obesity

OBJECTIVE

The objective was to provide an overall assessment of genetic linkage data of BMI and BMI-defined obesity using a nonparametric genome scan meta-analysis.

RESEARCH METHODS AND PROCEDURES

We identified 37 published studies containing data on over 31,000 individuals from more than >10,000 families and obtained genome-wide logarithm of the odds (LOD) scores, non-parametric linkage (NPL) scores, or maximum likelihood scores (MLS). BMI was analyzed in a pooled set of all studies, as a subgroup of 10 studies that used BMI-defined obesity, and for subgroups ascertained through type 2 diabetes, hypertension, or subjects of European ancestry.

RESULTS

Bins at chromosome 13q13.2- q33.1, 12q23-q24.3 achieved suggestive evidence of linkage to BMI in the pooled analysis and samples ascertained for hypertension. Nominal evidence of linkage to these regions and suggestive evidence for 11q13.3-22.3 were also observed for BMI-defined obesity. The FTO obesity gene locus at 16q12.2 also showed nominal evidence for linkage. However, overall distribution of summed rank p values <0.05 is not different from that expected by chance. The strongest evidence was obtained in the families ascertained for hypertension at 9q31.1-qter and 12p11.21-q23 (p < 0.01).

CONCLUSION

Despite having substantial statistical power, we did not unequivocally implicate specific loci for BMI or obesity. This may be because genes influencing adiposity are of very small effect, with substantial genetic heterogeneity and variable dependence on environmental factors. However, the observation that the FTO gene maps to one of the highest ranking bins for obesity is interesting and, while not a validation of this approach, indicates that other potential loci identified in this study should be investigated further.

Impact of the -1438G>a polymorphism in the serotonin 2A receptor gene on anthropometric profile and obesity risk: a case-control study in a Spanish Mediterranean population

Research into the genetic factors that regulate food intake is arousing great interest. The polymorphism -1438G>A in the serotonin 2A receptor or 5-hydroxytriptamine (5-HT) type 2A receptor (5-HTR2A) gene has been associated with alterations in food intake such as anorexia and bulimia. However, its association with obesity has not been studied to the same extent. Our aim, therefore, was to estimate the association between the -1438G>A polymorphism and obesity risk and related anthropometric variables in a Spanish Mediterranean population. A case-control study including 303 cases and 606 controls paired by gender and age was undertaken. The association between the -1438G>A polymorphism and obesity and other anthropometric measures was studied. No association with obesity risk was observed. However, when only the obese group was analyzed, it was observed that AA subjects presented a lower body mass index (BMI) than G allele carriers (35.2+/-5.3 kg/m2 vs 37.5+/-7.8 kg/m2; P=0.039). Moreover, significant differences were also obtained in waist perimeter that was lower in AA subjects compared to G allele carriers (105+/-11 cm vs 112+/-17 cm; P=0.011). In conclusion, although the -1438G>A polymorphism is not a relevant marker for obesity risk, this variant may play a role in determining BMI in obese subjects.

Hyperkalemia and hyperdopaminemia induced by an obsessive eating of banana in an anorexia nervosa adolescent

Banana is known as a dopamine-rich and potassium-rich food, however no previous data regarding biochemical or psychological alteration induced by excess intake of banana has been reported. We have experienced an adolescent female case of Anorexia nervosa (AN) who denied eating anything but maximum 20 bananas and less than 500 ml mineral water per day for more than two years. During the period of massive banana eating habit, she showed increase of serum potassium (from 4.7 mEq/l to 6.1 mEq/l) and whole blood dopamine (from 11 ng/ml to 210 ng/ml; normal range 0.5-6.2 ng/ml), and obvious dysthymia that is inexplicable only by the pathology of AN. When the patient resumed other food ingestion after 26 months of obsessive and restricted eating of banana, the abnormalities in her blood data and her psychological state were all corrected toward normal. We conclude that in this case, the obsessive and restricted habit of banana ingestion resulted in hyperkalemia, hyperdopaminemia, and psychological change.

Visual hallucinations in Parkinson's disease are not influenced by polymorphisms of serotonin 5-HT2A receptor and transporter genes

Psychiatric disorders are common in Parkinson's disease (PD) and hallucinations are observed in nearly 40% of PD patients. The involvement of dopaminergic system in the pathogenesis of psychosis has been sustained by most of the authors even if several evidences indicate that multiple neurochemical substrates might underlie psychosis in PD. In PD there is an extensive loss of serotoninergic raphe neurons and serotonin dysfunction had been implicated in the pathogenesis of many psychiatric disorders such as depression, schizophrenia, and in psychosis of patients with Alzheimer disease. The association of a serotonin transporter gene-linked polymorphic region (5-HTTLPR) and the 5-HT2A receptor T102C polymorphism with psychosis in a group of patients with PD was investigated. No significant differences in the distribution of allele and genotype frequencies of the 5-HTTLPR (p>0.01) and 5-HT2A T102C (p>0.05) were found between patients and controls as well as between the patients' subgroups without and with psychosis. These data might suggest that 5-HTTLPR and 5-HT2A polymorphisms are not major susceptibility factors of psychotic symptoms in PD patients.

Temporomandibular disorder is associated with a serotonin transporter gene polymorphism in the Japanese population

Aims

Recent genetic studies have linked serotonin-related genetic polymorphisms with diverse disorders characterized by functional somatic symptoms, including chronic fatigue syndrome, irritable bowel syndrome, and premenstrual dysphoric disorder.

Methods

We investigated three serotonin-related genetic polymorphisms by screening genomic DNA of 36 temporomandibular disorder (TMD) patients.

Results

A significant increase of longer alleles (l and xl) was found in the TMD patients compared to the controls both by the genotype-wise and the allele-wise analyses (both p < 0.01 by χ² test and Fisher's exact test).

Conclusion

Genetic factors that involve the serotonergic system may play a role in the pathogenesis of TMD.

Genetics in eating disorders: extending the boundaries of research

OBJECTIVE: To review the recent literature relevant to genetic research in eating disorders and to discuss unique issues which are crucial for the development of a genetic research project in eating disorders in Brazil. METHOD: A computer literature review was conducted in the Medline database between 1984 and may 2005 with the search terms "eating disorders", "anorexia nervosa", "bulimia nervosa", "binge eating disorder", "family", "twin" and "molecular genetic" studies. RESULTS: Current research findings suggest a substantial influence of genetic factors on the liability to anorexia nervosa and bulimia nervosa. Genetic research with admixed populations should take into consideration sample size, density of genotyping and population stratification. Through admixture mapping it is possible to study the genetic structure of admixed human populations to localize genes that underlie ethnic variation in diseases or traits of interest. CONCLUSIONS: The development of a major collaborative genetics initiative of eating disorders in Brazil and South America would represent a realistic possibility of studying the genetics of eating disorders in the context of inter ethnic groups, and also integrate a new perspective on the biological etiology of eating disorders.

Involvement of a polymorphism in the 5-HT2A receptor gene in impulsive behavior

RATIONALE AND OBJECTIVE

Impulsive behavior has been suggested to occur due to a dysfunction of serotonergic 5-HT neurotransmission. After evaluation by a self-reporting measure, a polymorphism in the promoter of the 5-HT2A receptor gene has been proposed to underlie the impulsive behavior; however, this hypothesis is not convincing. In this study, we examined whether this 5-HT2A receptor gene polymorphism is involved in impulsive aggression by evaluating a behavioral task (go/no-go task) in normal volunteers.

MATERIALS AND METHODS

The polymorphism of the 5-HT2A receptor gene promoter was analyzed by polymerase chain reaction using lymphocytes from 71 volunteers. Impulsivity was defined as the number of commission errors (responding when one should not) made during a go/no-go task (a larger number of commission errors indicates greater difficulty in inhibiting the behavior).

RESULTS

The subjects in the group with the A-1438A allele of the 5-HT2A receptor gene (A-1438A group) made more commission errors under the punishment-reward condition in a go/no-go task than those in the G-1438G group.

CONCLUSIONS

These results suggest the possible involvement of the A-1438A polymorphism of the 5-HT2A receptor gene in impulsive behavior; this was evaluated using a behavioral task measure that can directly reveal the traits of human impulsive behavior.

Allele C-specific methylation of the 5-HT2A receptor gene: evidence for correlation with its expression and expression of DNA methylase DNMT1

Differential DNA methylation has been suggested to contribute to differential activity of alleles C and T and thereby to genetic associations between the C/T(102) polymorphism in the 5-HT2A receptor gene (5HT2AR) and psychiatric disorders. We surveyed methylation in two CpG sites, which are specific to allele C. The majority of allele C-specific CpG sites were methylated in human temporal cortex and peripheral leukocytes and levels of methylation varied between individuals. Levels of methylation in the promoter correlated significantly with the expression of 5HT2AR. Methylation of allele C-specific CpG sites in the first exon correlated significantly with the expression of DNA methylase 1 (DNMT1) but not S-adenosylhomocysteine hydrolase (AHCY). These findings support the hypothesis that allele-specific DNA methylation is involved in regulation of 5HT2AR expression, influencing expression differences between alleles C and T.