Variation in the ESR1 and ESR2 genes and genetic susceptibility to anorexia nervosa

Brain-based sex differences in autism spectrum disorder across the lifespan: A systematic review of structural MRI, fMRI, and DTI findings

Females with autism spectrum disorder (ASD) have been long overlooked in neuroscience research, but emerging evidence suggests they show distinct phenotypic trajectories and age-related brain differences. Sex-related biological factors (e.g., hormones, genes) may play a role in ASD etiology and have been shown to influence neurodevelopmental trajectories. Thus, a lifespan approach is warranted to understand brain-based sex differences in ASD. This systematic review on MRI-based sex differences in ASD was conducted to elucidate variations across the lifespan and inform biomarker discovery of ASD in females We identified articles through two database searches. Fifty studies met criteria and underwent integrative review. We found that regions expressing replicable sex-by-diagnosis differences across studies overlapped with regions showing sex differences in neurotypical cohorts. Furthermore, studies investigating age-related brain differences across a broad age-span suggest distinct neurodevelopmental patterns in females with ASD. Qualitative comparison across youth and adult studies also supported this hypothesis. However, many studies collapsed across age, which may mask differences. Furthermore, accumulating evidence supports the female protective effect in ASD, although only one study examined brain circuits implicated in "protection." When synthesized with the broader literature, brain-based sex differences in ASD may come from various sources, including genetic and endocrine processes involved in brain "masculinization" and "feminization" across early development, puberty, and other lifespan windows of hormonal transition. Furthermore, sex-related biology may interact with peripheral processes, in particular the stress axis and brain arousal system, to produce distinct neurodevelopmental patterns in males and females with ASD. Future research on neuroimaging-based sex differences in ASD would benefit from a lifespan approach in well-controlled and multivariate studies. Possible relationships between behavior, sex hormones, and brain development in ASD remain largely unexamined.

The influence of microsatellite polymorphisms in sex steroid receptor genes ESR1, ESR2 and AR on sex differences in brain structure

The androgen receptor (AR), oestrogen receptor alpha (ESR1) and oestrogen receptor beta (ESR2) play essential roles in mediating the effect of sex hormones on sex differences in the brain. Using Voxel-based morphometry (VBM) and gene sizing in two independent samples (discovery n ​= ​173, replication ​= ​61), we determine the common and unique influences on brain sex differences in grey (GM) and white matter (WM) volume between repeat lengths (n) of microsatellite polymorphisms AR(CAG)n, ESR1(TA)n and ESR2(CA)n. In the hypothalamus, temporal lobes, anterior cingulate cortex, posterior insula and prefrontal cortex, we find increased GM volume with increasing AR(CAG)n across sexes, decreasing ESR1(TA)n across sexes and decreasing ESR2(CA)n in females. Uniquely, AR(CAG)n was positively associated with dorsolateral prefrontal and orbitofrontal GM volume and the anterior corona radiata, left superior fronto-occipital fasciculus, thalamus and internal capsule WM volume. ESR1(TA)n was negatively associated with the left superior corona radiata, left cingulum and left inferior longitudinal fasciculus WM volume uniquely. ESR2(CA)n was negatively associated with right fusiform and posterior cingulate cortex uniquely. We thus describe the neuroanatomical correlates of three microsatellite polymorphisms of steroid hormone receptors and their relationship to sex differences.

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Microsatellite polymorphisms in sex hormone receptor genes influence volume in regions of brain sex difference

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AR(CAG)n repeat length is positively associated with grey and white matter volume across males and females

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ESR1(TA)n repeat length is negatively associated with grey and white matter volume across males and females

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ESR2(CA)n repeat length is negatively associated with grey matter volume in females but not in males

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Repeat length was associated with volume in the hypothalamus, insula, temporal cortices, prefrontal cortices, inferior and superior longitudinal fasciculi in the three genes.

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These regions were largely replicated in an independent cohort acquired on a separate scanner.

Interaction of estrogen receptor β and negative life events in susceptibility to major depressive disorder in a Chinese Han female population

BACKGROUND

Both genetic and environmental factors as well as their interaction contribute to the etiology of major depressive disorder (MDD). Estrogen receptor β (ESR2) may play a vital role in the development of MDD in females. The aim of this study is to analyze ESR2 gene polymorphisms and the interaction of ESR2 gene variation and negative life events concerning the risk of developing MDD in females, especially during menopausal stage.

METHODS

Genotyping was performed by Taqman allelic discrimination assay among 191 female MDD patients and 200 healthy females. Life Events Scale and the generalized multifactor dimensionality reduction method were employed to assess the frequency and severity of negative life events and gene-environment interaction (G×E), respectively. All subjects were regrouped into reproductive and menopausal group based on age. Logistic regression was used to evaluate the set of risk factors.

RESULTS

No association of ESR2 G×E interaction with MDD was found in the reproductive group. However, in menopausal females, significant G×E interactions between negative life events and allelic variation of rs1256049 and rs4986938 were observed. Individuals with the A⁺ allele of rs1256049 and rs4986938 were susceptible to MDD when exposed to low negative life events.

LIMITATION

Assessment of negative life events was influenced by subjective interpretation.

CONCLUSIONS

ESR2 may modify the interaction between negative life events and MDD in the Chinese Han menopausal females. To our knowledge, this study is the first to report an effect modification between negative life events and ESR2 variations in female MDD patients.

Synaptic changes in the hippocampus of adolescent female rodents associated with resilience to anxiety and suppression of food restriction-evoked hyperactivity in an animal model for anorexia nervosa

Anorexia nervosa is a mental illness that emerges primarily during early adolescence, with mortality rate that is 200 times higher than that of suicide. The illness is characterized by intense fear of gaining weight, heightened anxiety, obstinate food restriction, often accompanied by excessive exercise, in spite of mounting hunger. The illness affects females nine times more often than males, suggesting an endocrine role in its etiology. Its relapse rate exceeds 25%, yet there are no accepted pharmacological treatments to prevent this. Here, we summarize studies from this laboratory that have used adolescent female rodents in activity-based anorexia (ABA), an animal model of anorexia nervosa, with the goal of identifying neurobiological underpinnings of this disease. We put forth a hypothesis that a GABAergic mechanism within the hippocampus is central to regulating an individual׳s anxiety which, in turn, strongly influences the individual׳s resilience/vulnerability to ABA. In particular, we propose that ionotropic GABAA receptors containing the subunits alpha4 and delta, are at play for exerting shunting inhibition upon hippocampal pyramidal neurons that become more excitable during ABA. Since these receptors confer insensitivity to benzodiazepines, this pharmacological profile of ABA fits with lack of report indicating efficacy of benzodiazepines in reducing the anxiety experienced by individuals with anorexia nervosa. The idea that the GABAergic system of the hippocampus regulates resilience/vulnerability to anorexia nervosa complements current opinions about the important roles of the prefrontal cortex, amygdala, striatum, gustatory pathways and feeding centers of the hypothalamus and of the neuromodulators, serotonin and dopamine, in the etiology of the disease. This article is part of a Special Issue entitled SI: Adolescent plasticity.

Eating Disorders and Epigenetics

Eating disorders (EDs) are characterized by intense preoccupation with shape and weight and maladaptive eating practices. The complex of symptoms that characterize EDs often arise through the activation of latent genetic potentials by environmental exposures, and epigenetic mechanisms are believed to link environmental exposures to gene expression. This chapter provides an overview of genetic factors acting in the etiology of EDs. It then provides a background to the hypothesis that epigenetic mechanisms link stresses such as obstetric complications and childhood abuse as well as effects of malnutrition to eating disorders (EDs). The chapter then summarizes the emerging body of literature on epigenetics and EDs-mainly studies on DNA methylation in samples of anorexia and bulimia. The available evidence base suggests that an epigenetically informed perspective contributes in valuable ways to the understanding of why people develop EDs.

Memory impairment is associated with the loss of regular oestrous cycle and plasma oestradiol levels in an activity-based anorexia animal model

OBJECTIVES

Patients with anorexia nervosa (AN) suffer from neuropsychological deficits including memory impairments. Memory partially depends on 17β-oestradiol (E2), which is reduced in patients with AN. We assessed whether memory functions correlate with E2 plasma levels in the activity-based anorexia (ABA) rat model.

METHODS

Nine 4-week-old female Wistar rats were sacrificed directly after weight loss of 20-25% (acute starvation), whereas 17 animals had additional 2-week weight-holding (chronic starvation). E2 serum levels and novel object recognition tasks were tested before and after starvation and compared with 21 normally fed controls.

RESULTS

Starvation disrupted menstrual cycle and impaired memory function, which became statistically significant in the chronic state (oestrous cycle (P < 0.001), E2 levels (P = 0.011) and object recognition memory (P = 0.042) compared to controls). E2 reduction also correlated with the loss of memory in the chronic condition (r = 0.633, P = 0.020).

CONCLUSIONS

Our results demonstrate that starvation reduces the E2 levels which are associated with memory deficits in ABA rats. These effects might explain reduced memory capacity in patients with AN as a consequence of E2 deficiency and the potentially limited effectiveness of psychotherapeutic interventions in the starved state. Future studies should examine whether E2 substitution could prevent cognitive deficits and aid in earlier readiness for therapy.

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.

Genetics and Epigenetics of Eating Disorders

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

Estrogen receptor 2 gene polymorphism in idiopathic scoliosis

STUDY DESIGN

A genetic association study of estrogen receptor 2 gene (ESR2) polymorphisms in idiopathic scoliosis (IS).

OBJECTIVE

To investigate association of the ESR2 polymorphisms with either predisposition to or progression of IS in Central European population.

SUMMARY OF BACKGROUND DATA

In ESR2 the rs1256120 polymorphism was described to be associated with predisposition to and severity of IS in Chinese population. This observation has not been confirmed in Japanese population. The ESR2 rs4986938 and rs1256049 polymorphisms were described to present association with breast cancer, rheumatoid arthritis, and bone mineral density, however the association with IS has not been evaluated.

METHODS

Case-control study of 248 females with IS and 243 healthy females was performed. Three single-nucleotide polymorphisms were studied using polymerase chain reaction-restriction fragments length polymorphism technique with the restriction enzymes: AlwNI (C/T rs1256120), AluI (A/G rs4986938), and RsaI (A/G rs1256049). The patients' medical history was evaluated, Cobb angle was measured and surgery rate established. The patients were analyzed in 3 subgroups according to curve progression velocity.

RESULTS

Neither the genotypes nor alleles distribution showed significant differences between patients with IS and healthy controls. There was no significant difference in genotype or allele frequency. In the AluI site polymorphism a significant difference in mean Cobb angle between genotypes was found: (AA, 31.9° ± 14.2°; AG, 43.2° ± 17.8°; and GG, 38.9° ± 19.0°), P = 0.002. There was significant difference in genotype distribution between patients with moderate (<40°) versus severe (≥40°) scoliosis, P = 0.0011; the minor allele frequency (AA) in recessive model of penetration was over-represented in patients with Cobb angle below 40°, P = 0.0075, odds ratio = 3.65.

CONCLUSION

No association between ESR2 polymorphism and predisposition to IS was found in Caucasian females. None of the previously reported associations of AlwNI site polymorphism could be confirmed. ESR2 AluI site polymorphism may be associated with curve severity.

LEVEL OF EVIDENCE

N/A.

Association study of the estrogen receptor I gene (ESR1) in anorexia nervosa and eating disorders: no replication found

OBJECTIVE

The female preponderance and onset around puberty in the majority of eating disorders (EDs) suggest that sex hormones, like estrogens, may be involved in the onset of these disorders. An eight-SNP haplotype at the estrogen receptor I (ESR1) gene was found to be associated with anorexia nervosa (AN) (Versini et al., Neuropsychopharmacology, 35, 1818-1825, 2010) and three SNPs from this haplotype (rs726281, rs2295193, and rs3798577) were associated with AN and/or EDs. Our objective was to replicate these findings in an independent cohort of 520 patients with an eating disorder, of whom 244 had AN (142 restricting type) from the GenED study and 2,810 random women from the Netherlands Twin Registry.

METHOD

The frequencies of the eight-SNP haplotype and three ESR1 SNPs were compared between patients with an eating disorder, with AN (restricting type), with bulimia nervosa (BN), and the control women.

RESULTS

Neither the haplotype nor the three ESR1 SNPs were associated with EDs, BN, AN, or restricting type AN.

DISCUSSION

Despite sufficient statistical power, the associations reported by Versini et al. (Neuropsychopharmacology, 35, 1818-1825, 2010) were not replicated.

Estrogen receptor 1 gene rs2295193 polymorphism and anorexia nervosa: new data and meta-analysis

INTRODUCTION

Estrogen plays essential roles in the regulation of food intake, adiposity, and body weight control. The estrogen alpha receptor, encoded by estrogen receptor 1 gene (ESR1), has been implicated with anorexia nervosa (AN). A previous study indicated that the rs2295193 polymorphism in ESR1 may confer a genetic susceptibility to AN.

METHODS

In a case-control study, we assessed 195 AN probands and 93 healthy controls; 99 trios were studied in a family-based association analysis through genotyping the rs2295193 polymorphism in ESR1. Additionally, we carried out a meta-analysis of the combined sample groups.

RESULTS

There were no significant differences in the genotype or allele frequencies of the rs2295193 polymorphism between the AN and control groups (Ps > 0.05). In the transmission disequilibrium test (TDT) analyses, there was no evidence for biased transmission of the G allele of rs2295193 polymorphism (P = 0.32). In female-only samples, no significant association was observed between the rs2295193 polymorphism and AN in either case-control or transmission disequilibrium test analyses (Ps > 0.05). The meta-analysis revealed that no excess of transmission of the G allele in AN families (pooled odds ratio = 1.10, P = 0.79).

DISCUSSION

Meta-analytically combined evidence from the present genotyping and the literature showed that rs2295193 polymorphism in ESR1 is not a major genetic susceptibility factor in AN.

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.

Association between a common CYP17A1 haplotype and anxiety in female anorexia nervosa

Dehydroepiandrosterone (DHEA), the main brain neurosteroid, has been implicated in various psychiatric disorders especially those including gender differences. We studied genetic variability in the DHEA-producing enzyme CYP17A1 in relation to anorexia nervosa (AN) susceptibility and AN-related co-morbidities. We performed analysis of 100 Israeli AN family trios accounting for CYP17A1 haplotypes characteristic of populations of European origin and studied genotype-phenotype relationships using correlation analyses and transmission disequilibrium test. Although our analysis revealed no evidence of association between CYP17A1 and AN per se, it revealed an association between specific CYP17A1 haplotypes and AN co-morbidity, specifically anxiety. We found that a common CYP17A1 haplotype (H1) was associated with higher anxiety in AN patients (Clinical Global Impression; CGI-anxiety ≥4). Moreover, H1 homozygotes were at higher risk for expressing high CGI-anxiety levels (OR = 3.7), and H1 was preferentially transmitted to AN patients with high CGI-anxiety levels (P = 0. 037). We suggest that CYP17A1 H1 haplotype may contribute to genetic predisposition to higher CGI-anxiety levels in AN patients and that this predisposition may be mediated by reduced CYP17A1 enzymatic activity and corresponding lower DHEA production.

Sex differences in the physiology of eating

Hypothalamic-pituitary-gonadal (HPG) axis function fundamentally affects the physiology of eating. We review sex differences in the physiological and pathophysiological controls of amounts eaten in rats, mice, monkeys, and humans. These controls result from interactions among genetic effects, organizational effects of reproductive hormones (i.e., permanent early developmental effects), and activational effects of these hormones (i.e., effects dependent on hormone levels). Male-female sex differences in the physiology of eating involve both organizational and activational effects of androgens and estrogens. An activational effect of estrogens decreases eating 1) during the periovulatory period of the ovarian cycle in rats, mice, monkeys, and women and 2) tonically between puberty and reproductive senescence or ovariectomy in rats and monkeys, sometimes in mice, and possibly in women. Estrogens acting on estrogen receptor-α (ERα) in the caudal medial nucleus of the solitary tract appear to mediate these effects in rats. Androgens, prolactin, and other reproductive hormones also affect eating in rats. Sex differences in eating are mediated by alterations in orosensory capacity and hedonics, gastric mechanoreception, ghrelin, CCK, glucagon-like peptide-1 (GLP-1), glucagon, insulin, amylin, apolipoprotein A-IV, fatty-acid oxidation, and leptin. The control of eating by central neurochemical signaling via serotonin, MSH, neuropeptide Y, Agouti-related peptide (AgRP), melanin-concentrating hormone, and dopamine is modulated by HPG function. Finally, sex differences in the physiology of eating may contribute to human obesity, anorexia nervosa, and binge eating. The variety and physiological importance of what has been learned so far warrant intensifying basic, translational, and clinical research on sex differences in eating.

Shared genetic effects between age at menarche and disordered eating

PURPOSE

An early age at menarche is associated with disordered eating in women. However, it is unclear whether they share genetic factors. The goal of the current study was to delineate the genetic correlation between age at menarche and disordered eating.

METHODS

Participants included 427 monozygotic and 329 dizygotic 16-17-year-old female twins from the Swedish Twin Study of Child and Adolescent Development. Disordered eating was assessed with the Eating Disorder Inventory-2. Age at menarche was assessed through self-report. A bivariate correlated factors model was used to delineate the genetic correlation between age at menarche and disordered eating.

RESULTS

The analysis revealed a negative genetic correlation of -.18 in the best-fit model, indicating that the genetic factors that influence younger age at menarche are associated with increased liability for disordered eating.

CONCLUSIONS

Future research should examine possible causes for this correlation, such as the estrogen system and gene-environment interactions.

Adolescent female rats exhibiting activity-based anorexia express elevated levels of GABA(A) receptor α4 and δ subunits at the plasma membrane of hippocampal CA1 spines

Activity-based anorexia (ABA) is an animal model for anorexia nervosa that has revealed genetic links to anxiety traits and neurochemical characteristics within the hypothalamus. However, few studies have used this animal model to investigate the biological basis for vulnerability of pubertal and adolescent females to ABA, even though the great majority of the anorexia nervosa cases are females exhibiting the first symptoms during puberty. GABAergic inhibition of the hippocampus strongly regulates anxiety as well as plasticity throughout life. We recently showed that the hippocampal CA1 of female mice undergo a dramatic change at puberty onset--from expressing virtually none of the nonsynaptic α4βδ GABA(A) receptors (GABARs) prepubertally to expressing these GABARs at ~7% of the CA1 dendritic spine membranes at puberty onset. Furthermore, we showed that this change underlies the enhanced modulation of anxiety, neuronal excitability, and NMDA receptor-dependent synaptic plasticity in the hippocampus by the stress neurosteroid, THP (3α-OH-5α[β]-pregnan-20-one or [allo]pregnanolone). Here, we used quantitative electron microscopy to determine whether ABA induction in female rats during adolescence also elevates the expression of α4 and δ subunits of α4βδ GABARs, as was observed at puberty onset for mice. Our analysis revealed that rats also exhibit a rise of α4 and δ subunits of α4βδ GABARs at puberty onset, in that these subunits are detectable at ~6% of the dendritic spine membranes of CA1 pyramidal cells at puberty onset (postnatal day 32-36; P32-36) but this drops to about 2% by P40-P44. The levels of α4 and δ subunits at the CA1 spines remained low following exposure of females to either of the two environmental factors needed to generate ABA--food restriction and access to a running wheel for 4 days--from P40 to P44. This pattern contrasted greatly from those of ABA animals, for which the two environmental factors were combined. Within the hippocampus of ABA animals, 12% of the spine profiles were labeled for α4, reflecting a sixfold increase, relative to hippocampi of age-matched (P44) control females (p < 0.005). Concurrently, 7% of the spine profiles were labeled for δ, reflecting a 130% increase from the control values of 3% (p = 0.01). No measurable change was detected for spine size. The observed magnitude of increase in the α4 and δ subunits at spines is sufficient to increase both tonic inhibition of hippocampus and anxiety during stress, thereby likely to exacerbate hyperactivity and weight loss.

The diversity of sex steroid action: regulation of metabolism by estrogen signaling

The metabolic syndrome is a complex condition characterized by obesity, insulin resistance, decreased high-density lipoproteins, and hypertension associated with high risk of developing type 2 diabetes and cardiovascular disease. A major increase in the incidence of developing metabolic syndrome and related diseases is observed worldwide in association with a change toward a less active lifestyle and increased food consumption. Estrogen and the estrogen receptors (ERs) are well-known regulators of several aspects of metabolism, including glucose and lipid metabolism, and impaired estrogen signaling is associated with the development of metabolic diseases. This review will describe the key effects of estrogen signaling in metabolic and glucose sensing tissues, including the liver, pancreatic β cells, adipose tissue, and skeletal muscle. The impact on metabolic processes of impaired estrogen signaling and knock out of each ER subtype will also be discussed.

Association between co-twin sex and eating disorders in opposite sex twin pairs: evaluations in North American, Norwegian, and Swedish samples

OBJECTIVE

These three studies examined the hypothesis that prenatal exposure to sex hormones influences twins' risk for eating disorders based on co-twin sex, such that individuals with a female co-twin would be more likely than individuals with a male co-twin to meet diagnostic criteria for an eating disorder.

METHODS

Male and female twins from the United States (N=2607), Norway (N=2796) and Sweden (N=16,458) with known co-twin sex and zygosity were assessed for eating disorders.

RESULTS

In the U.S. and Swedish samples, sex was significantly associated with eating disorder diagnoses, and although co-twin sex was not associated with eating disorders overall, it was associated with broadly defined bulimia nervosa in the Swedish sample. The effects for bulimia were not sustained when monozygotic twins were excluded, suggesting that the effects of prenatal sex hormones play a minor role in influencing eating disorders. Sex and co-twin sex were not associated with eating disorders in the Norwegian sample.

CONCLUSION

The prenatal sex hormone hypothesis, which proposes that prenatal hormone exposure is associated with later eating disorder symptomatology, was not supported in these three population-based twin samples.

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.

A systematic review of the relationship between polymorphic sites in the estrogen receptor-beta (ESR2) gene and breast cancer risk

The estrogen signal is mediated by the estrogen receptor (ER). The specific role of ER-beta, a second ER, in breast carcinogenesis is not known. A number of association studies have been carried out to investigate the relationship between polymorphic sites in the ESR2 gene and breast cancer risk, however, the results are inconsistent. We searched PubMed, Medline, and Web of Science database (updated to 10 January 2010) and identified 13 relevant case-control studies, and approximately 28 single-nucleotide polymorphisms (SNPs) and one micro-satellite marker were reported in the literature. The median number of study subjects was 776 (range 158-13,550). Three genetic variants [(CA)n, rs2987983, and rs4986938] showed significant overall associations with breast cancer, and rs4986938 was reported twice. Because rs4986938 and rs1256049 were the most extensively studied polymorphisms, we subsequently conducted a meta-analysis to evaluate their relationship with breast cancer risk (9 studies of 10,837 cases and 16,021 controls for rs4986938; 8 studies of 11,652 cases and 15,726 controls for rs1256049). For rs4986938, the women harboring variant allele seemed to be associated with a decreased risk either in the dominant model [pooled OR = 0.944, 95% confidence interval (95% CI) 0.897-0.993, fixed-effects] or in the co-dominant model (AG vs. GG) (OR = 0.944, 95% CI 0.895-0.997, fixed-effects). rs1256049 was not associated with breast cancer risk in any model. Five studies had investigated the effect of haplotypes in the ESR2 gene on breast cancer risk, and four of them had positive outcomes. In summary, the present systematic review suggests that SNP rs4986938 as well as haplotypes in the ESR2 gene might be associated with breast cancer. The need for additional studies examining these issues seems of vital importance.

Genetic variability in estrogen disposition: Potential clinical implications for neuropsychiatric disorders

Variability in the physiological levels of neuroactive estrogens is widely believed to play a role in predisposition to several disorders of the central nervous system. Local biosynthesis of estrogens in the brain as well as their circulating serum levels are known to contribute to this pool of neuroactive steroids. It has been well accepted that estrogens modulate neuronal functions by affecting genesis, differentiation, excitability, and degeneration of nerve cells. These actions of estrogens appear to be more prominent in females with higher concentrations and marked variability of circulating serum levels occurring over a woman's lifetime. However, our knowledge regarding the variability of neuroactive steroid levels is very limited. Furthermore, several studies have recently reported differences in the synchronization of circulating and neuronal levels of estradiol. In the absence of reliable circulating steroid levels, knowledge of genetic variability in estrogen disposition may play a determining factor in predicting altered susceptibility or severity of neuropsychiatric disorders in women. Over the past decade, several genetic variants have been linked to both differential serum estrogen levels and predisposition to diverse types of neuropsychiatric disorders in women. Polymorphisms in genes encoding estrogen-metabolizing enzymes as well as estrogen receptors may account for this phenotypic variability. In this review, we attempt to show the contribution of genetics in determining estrogenicity in females with a particular emphasis on the central nervous system. This knowledge will further provide a driving force for unearthing the novel field of "Estrogen Pharmacogenomics." © 2010 Wiley-Liss, Inc.

ERbeta: recent understanding of estrogen signaling

The discovery of a second estrogen receptor, ERbeta, and the finding that 5alpha-androstane-3beta,17beta-diol (3betaAdiol) strongly binds to ERbeta, have opened up a new aspect of estrogen signaling. Some of the major shifts in our understanding come from finding ERbeta in tissues which do not express ERalpha but are estrogen-responsive; these were called sites of 'indirect estrogen action'. Two key sites that fall into this category are the brain and the prostate. Studies of ERbeta in the past 10 years have led us to hypothesize that estrogen signaling depends on the balance between ERalpha and ERbeta, and that inadequate predominance of one or the other isoform could lead to disease.

Estrogen receptor 1 gene (ESR1) is associated with restrictive anorexia nervosa

Anorexia nervosa (AN) is a highly heritable young-onset psychiatric illness the etiology of which remains unknown. Estrogen alpha and beta receptors, encoded by ESR1 and ESR2 genes, are involved in food intake regulation and eating behavior, and may have a potential role in AN. We performed a family-based association study of 17 single-nucleotide polymorphisms (SNPs) encompassing ESR1 and ESR2 genes in a cohort of 321 French AN families. We attempted to replicate this finding in a cohort of 41 restrictive AN (RAN) families and in a population-based study of 693 young women. Using the transmission disequilibrium test, a significant over-transmission was detected between AN and ESR1 rs726281 and rs2295193. These SNPs and another among ESR1 were more specifically associated with the RAN subtype (rs726281, p=0.005, odds ratio (OR)=2.1, 95% confidence interval (95% CI)=1.2-3.6; rs3798577, p=0.021, OR=1.6, 95% CI=1.1-2.3; and rs2295193, p=0.007, OR=1.7, 95% CI=1.2-2.5). A large eight-SNPs haplotype of ESR1 gene was also associated with AN (p<0.0001, OR=3.1, 95% CI=1.8-5.1). Association of ESR1 SNPs and RAN was driven by paternal over-transmissions (p<0.0001, OR=3.7, 95% CI=1.9-7.3). Furthermore, we confirmed the preferential paternal over-transmission of the ESR1 rs726281 on the independent German sample of 41 RAN trios (p=0.025, OR=3, 95% CI=1.1-8.3). Finally, rs3798577 was associated with eating disorders in a population-based sample of 693 women (p<0.01). Our findings are strongly in favor of an association between ESR1 polymorphisms and AN. In particular, ESR1 gene confers a high risk of vulnerability to the restrictive subtype of AN, and suggests that the estrogen pathway has to be further analyzed in AN.

Association of estrogen and aromatase gene polymorphisms with systemic lupus erythematosus

Experimental and animal studies suggested that estrogens play an important role in the development of systemic lupus erythematosus (SLE) through a variety of mechanisms involved in the regulation of the immune system. The objective of this study was to investigate the association between genetic variations in estrogen metabolic pathway genes, including estrogen receptor alpha (ESR1), estrogen receptor beta (ESR2), and aromatase (CYP19A1), and risk of SLE. We performed a genetic study of SLE among 46 medical record-confirmed female SLE cases and 102 female controls participating in an Internet-based case-control study of SLE. Polymorphisms analysed included: ESR1 PvuII, XbaI, and GT repeat; ESR2 RsaI, AluI, and CA repeat; and CYP19A1 RsaI, SfaN1, and TTTA repeat. We found significant association of the ESR1 PvuII (PP vs. pp, odds ratio (OR): 3.1, 95% confidence interval (CI): 1.1-9.3) and XbaI (XX vs. xx, adjusted OR: 3.4, 95% CI: 1.1-10.5) with SLE. Carrying the PPXX genotype conferred the highest risk (PPXX vs. ppxx, OR: 4.6, 95% CI: 1.3-15.9). We also found an association of SLE with the ESR2 CA repeat (SS vs. LL, OR: 2.8, 95% CI: 1.0-8.0). Our results support a role of estrogen in pathogenesis of SLE and suggested that genetic variants in the estrogen receptor genes might influence susceptibility.

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.

Do Estrogen Receptor beta Polymorphisms Play A Role in the Pharmacogenetics of Estrogen Signaling?

Estrogen hormones play critical roles in the regulation of many tissue functions. The effects of estrogens are primarily mediated by the estrogen receptors (ER) alpha and beta. ERs are ligand-activated transcription factors that regulate a complex array of genomic events that orchestrate cellular growth, differentiation and death. Although many factors contribute to their etiology, estrogens are thought to be the primary agents for the development and/or progression of target tissue malignancies. Many of the current modalities for the treatment of estrogen target tissue malignancies are based on agents with diverse pharmacology that alter or prevent ER functions by acting as estrogen competitors. Although these compounds have been successfully used in clinical settings, the efficacy of treatment shows variability. An increasing body of evidence implicates ERalpha polymorphisms as one of the contributory factors for differential responses to estrogen competitors. This review aims to highlight the recent findings on polymorphisms of the lately identified ERbeta in order to provide a functional perspective with potential pharmacogenomic implications.

Haplotypes of the estrogen receptor beta gene and breast cancer risk

Exposure to exogenous (oral contraceptives, postmenopausal hormone therapy) and endogenous (number of ovulatory cycles, adiposity) steroid hormones is associated with breast cancer risk. Breast cancer risk associated with these exposures could hypothetically be modified by genes in the steroid hormone synthesis, metabolism and signaling pathways. Estrogen receptors are the first step along the path of signaling cell growth and development upon stimulation with estrogens. The National Cancer Institute Breast and Prostate Cancer Cohort Consortium has systematically selected haplotype tagging SNPs in genes along the steroid hormone synthesis, metabolism and binding pathways, including the estrogen receptor beta (ESR2) gene. Four htSNPs tag the 6 major (>5% frequency) haplotypes of the ESR2 gene. These polymorphisms have been genotyped in 5,789 breast cancer cases and 7,761 controls nested within the American Cancer Society Cancer Prevention Study II, European Prospective Investigation into Cancer and Nutrition, Multiethnic Cohort, Nurses' Health Study and Women's Health Study cohorts. None of the SNPs were independently associated with breast cancer risk. One haplotype of the ESR2 gene was associated with breast cancer risk before correction for multiple testing (OR 1.17, 95% CI 1.07-1.28, p = 0.0007). This haplotype remained associated with breast cancer risk after adjustment for multiple testing using a permutation procedure. There was no statistically significant heterogeneity in SNP or haplotype odds ratios across cohorts. These data suggest that inherited variants in ESR2 (while possibly conferring a small increased risk of breast cancer) are not associated with appreciable (OR > 1.2) changes in breast cancer risk among Caucasian women.

Impact of estrogen receptor gene polymorphisms and mRNA levels on obesity and lipolysis--a cohort study

Background

The estrogen receptors α and β (ESR1, ESR2) have been implicated in adiposity, lipid metabolism and feeding behaviour. In this report we analyse ESR1 and ESR2 gene single nucleotide polymorphisms (SNPs) for association with obesity. We also relate adipose tissue ESR1 mRNA levels and ESR1 SNPs to adipocyte lipolysis and lipogenesis phenotypes.

Methods

23 ESR1 and 11 ESR2 tag-SNPs, covering most of the common haplotype variation in each gene according to HAPMAP data, were analysed by Chi² for association with obesity in a cohort comprising 705 adults with severe obesity and 402 lean individuals. Results were replicated in a cohort comprising 837 obese and 613 lean subjects. About 80% of both cohorts comprised women and 20% men. Adipose tissue ESR1 mRNA was quantified in 122 women and related to lipolysis and lipogenesis by multiple regression. ESR1 SNPs were analysed for association with adipocyte lipolysis and lipogenesis phenotypes in 204 obese women by simple regression.

Results

No ESR1 SNP was associated with obesity. Five ESR2 SNPs displayed nominal significant allelic association with obesity in women and one in men. The two ESR2 SNPs associated with obesity with nominal P value < 0.01 were genotyped in a second cohort where no association with obesity was observed. There was an inverse correlation between ESR1 mRNA levels in abdominal subcutaneous (sc) adipose tissue and basal lipolysis, as well as responsiveness to adrenoceptor agonists independent of age and BMI (P value 0.009–0.045). ESR1 rs532010 was associated with lipolytic sensitivity to noradrenaline (nominal P value 0.012), and ESR1 rs1884051 with responsiveness to the non-selective beta-adrenoceptor agonist isoprenaline (nominal P value 0.05). These associations became non-significant after Bonferroni correction.

Conclusion

ESR1 gene alleles are unlikely to be a major cause of obesity in women. A minor importance of ESR2 on severe obesity cannot be excluded. The inverse correlation between ESR1 mRNA levels and lipolytic responsiveness to adrenoceptor agonists implies that low adipose tissue ESR1 levels attenuate catecholamine resistance in sc fat cells of obese women hereby contributing to loss of sc and gain of visceral fat. There is no evidence for a genetic impact of ESR1 on lipolysis or lipogenesis.

Eating disorders: an overview of treatment responses and the potential impact of vulnerability genes and endophenotypes

Anorexia nervosa (AN), bulimia nervosa (BN) and binge-eating disorder (BED) are the three main eating disorders. Antidepressants, antipsychotics, anticonvulsants, prokinetic agents, opiate antagonists, appetite suppressants, tetrahydrocannabinol, cyproheptadine, zinc and ondansetron have been tested, and are frequently associated with psychological treatment. Selective serotonin reuptake inhibitors have a proven efficacy in BN and binge eating disorder. Other treatments, such as atypical antipsychotics in AN, anticonvulsants in BN and BED, and naltrexone and ondansetron in BN, may be promising, but lack the appropriate trials. The development of genetic researches in eating disorders may help the clinician to choose the most appropriate treatment in forthcoming years, using genetic polymorphisms of vulnerability genes, those linked to endophenotypes, or genes implicated in the metabolism of the drug treatment.

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.

Reduced levels of oestrogen receptor beta mRNA in Swedish patients with chronic fatigue syndrome

BACKGROUND

Chronic fatigue syndrome (CFS) is an illness with unknown aetiology and pathophysiology. The difference in incidence by sex observed for CFS indicates a role for oestrogen and oestrogen receptors in disease development. Furthermore, an immunomediated pathogenesis has been suggested for CFS, providing an additional connection to oestrogen, which displays immunomodular functions.

AIMS

To investigate a possible association of oestrogen receptor (ER) mRNAs and two ERbeta single-nucleotide polymorphisms (SNPs) with CFS.

METHODS

Messenger RNA levels of ERalpha, ERbeta wt and ERbeta cx were investigated in peripheral blood mononuclear cells from 30 patients with CFS and 36 healthy controls by quantitative real-time polymerase chain reaction. Two ERbeta SNPs were scored in the same material.

RESULTS

The CFS group showed significantly lower mRNA expression levels of ERbeta wt compared with the healthy control group. No differences were observed for ERalpha or ERbeta cx between patients and controls. There were no significant differences in frequency for the investigated ERbeta SNPs between cases and controls.

CONCLUSIONS

The reduced ERbeta wt expression level observed in this study is consistent with an immune-mediated pathogenesis of CFS. Additionally, the observation that ERbeta wt expression is decreased in CFS could provide an entry point to identify interesting, potentially disease-causing, candidate molecules for further study. A possible connection between oestrogen, oestrogen receptors and CFS should be evaluated further.

Combined estrogen receptor α and estrogen receptor β genotypes influence the age of menarche

BACKGROUND

Age at menarche has a strong genetic influence. We reported recently an association between the XbaI (351A-->C)and PvuII (397T-->C) polymorphisms of the estrogen receptor (ER)alpha gene with the age of menarche in Greek adolescents. In the present study, we examined whether ERbeta genotypes alone, or in combination with ERalpha genotypes, may also influence onset of menarche.

METHODS

We performed genotyping for the single nucleotide polymorphisms 1730A-->G and 1082G-->A of the ERbeta gene and examined their association with the age of menarche in the same cohort of 145 Greek girls. We then looked for a possible effect of combined ERalpha and beta genotypes on the age of menarche.

RESULTS

Menarche occurred 7 months later in girls with the AA genotype of the 1730A-->G polymorphism than in girls with the AG genotype (mean +/- SD: 13.23 +/- 1.24 versus 12.66 +/- 1.26 years, respectively; P = 0.005). The 1082G-->A polymorphism was not detected in any of the girls examined. A significant effect of combined ERalpha and beta genotypes was also apparent. Menarche occurred 11 months later in girls bearing the AA/TT,AA (ERalpha, ERbeta) genotypes compared with girls with the CC/CC,AG genotype (13.30 +/- 1.27 nersus 12.41 +/- 1.28 years; P = 0.042). The difference remained significant after adjusting for body mass index (P = 0.034).

CONCLUSION

Combined ERalpha and ERbeta polymorphisms may influence the age of menarche.

Single nucleotide polymorphisms in the leptin receptor gene: studies in anorexia nervosa

Anorexia nervosa is an eating disorder of unknown aetiology. There is significant evidence for a genetic component in the pathogenesis of this disorder. A region on chromosome 1 has been identified as a susceptibility locus. The leptin receptor has been mapped to a similar region, further upstream of this susceptibility locus. Leptin and its receptor are known to be important factors in the control and regulation of body weight. Single nucleotide polymorphisms (SNPs) in the leptin receptor are associated with measures of body weight. In the present study, SNPs in the coding region of the leptin receptor were analysed and their possible association with anorexia nervosa was investigated. Two cohorts of young women, 176 Caucasian anorexia nervosa patients and 152 normal Caucasian females, were genotyped for three SNPs in the leptin receptor. There was no significant difference in allele or genotype frequency, for any SNP, between the normal controls and the cohort of anorexia subjects. There were no significant associations with any genotype and body mass index in either the control or anorexic cohorts. When the anorexic cohort was subdivided into restricting and bingeing/purging behaviours, we found no significant association with any genotype. Analysis of haplotypes showed no significant evidence of association with anorexia. In summary, leptin receptor SNPs do not appear to be important factors in the regulation of body weight in young, pre-menopausal women or have any significant association with anorexia nervosa.

Estrogen receptor 2 and progesterone receptor gene polymorphisms and lipid levels in women with different hormonal status

Sex steroid hormones have multiple effects on lipid metabolism. We investigated the association between two common single nucleotide polymorphisms of the estrogen receptor 2 gene (ESR2), 1082G>A and 1730A>G, and PROGINS polymorphism of the progesterone receptor gene (PGR) with lipoprotein levels in a cross-sectional study with 472 women of European descent. The women were classified into three subgroups according to hormonal status, premenopausal women (n=187; mean age=34+/-9.7 years), postmenopausal women exposed to hormone replacement therapy (HRT) (n=118; 56+/-6.7 years) and postmenopausal women unexposed to HRT (n=167; 58+/-9.8 years). The premenopausal and postmenopausal women exposed to HRT, both carriers of G/A genotype, exhibited LDL-C (P=0.027 and 0.001, respectively) and T-chol levels (P=0.035 and 0.001, respectively) lower than carriers of G/G genotype. This association was not observed in postmenopausal women unexposed to HRT. These results suggest that ESR2 1082G>A genotype may influence LDL-C levels in women with abundant estrogen levels, due to either endogenous or exogenous sources.

Association between the estrogen receptor beta gene and age of onset of Parkinson's disease

The purpose of this study was to investigate the potential contribution of genetic variants in the estrogen receptor beta gene to the aetiology of Parkinson's disease (PD). Several lines of evidence from human and animal studies suggest a protective role for estrogen in PD. Recently the estrogen receptor beta subtype was reported to be an important mediator of estrogen actions in the nigrostriatal dopamine system. Two single nucleotide polymorphisms at position 1730 and 1082 in the ER beta gene were genotyped, using pyrosequencing, in 260 patients with PD and 308 controls recruited from the Swedish population. Neither of the two estrogen receptor beta polymorphisms was associated with an increased risk for PD. However, the G allele of the A1730G polymorphism was more frequent in patients with an early age of onset than in patients with a late age of onset of PD (P = 0.006). Patients carrying the GG genotype had an odds ratio of 2.2 for having an early onset of PD compared to non-carriers. In conclusion, our results indicate that genetic variation in the estrogen receptor beta gene may influence the age of onset of PD.

Genetics in eating disorders: state of the science

Eating disorders have been viewed as psychiatric illnesses that are strongly influenced by societal pressures towards thinness and attractiveness. Although the environmental context of these disorders must not be neglected, recent research in the area of genetic epidemiology suggests a substantial influence of genetic factors on liability to eating disorders. This review presents a synthesis of current knowledge about genetic factors implicated in the etiology of eating disorders.

Association study of cannabinoid receptor gene (CNR1) alleles and anorexia nervosa: differences between restricting and binging/purging subtypes

Anorexia nervosa (AN) is a severe and disabling psychiatric disorder, characterized by profound weight loss and body image disturbance. Family and twin studies indicate a significant genetic contribution to this disorder although no genetic mutation has yet been identified. The endocannabinoid system has recently been implicated in many physiological functions including appetite regulation. We, therefore, undertook a family based study to test the hypothesis whether a polymorphism of the CNR1 gene, which encodes human CB1 receptor, a subclass of the central cannabinoid receptor, contributes to the susceptibility to AN. Fifty two families (parents with one or two affected siblings) were genotyped for the (AAT) trinucleotide repeat of CNR1 gene. Using the haplotype relative risk (HRR) method, the distribution of alleles transmitted to the patients was not found to be significantly different from the non-transmitted parental alleles. However, upon dividing the samples to restricting and binging/purging subtypes of AN, the extended transmission disequilibrium test (ETDT) revealed that there is preferential transmission of different alleles in each of the subtypes. The 14 repeat allele was preferentially transmitted in the binging/purging AN group (P = 0.05) but not in the restricting AN group, whereas the 13 repeat allele was preferentially transmitted in the restricting AN group (almost significant, P = 0.07) but not in the binging/purging AN group. Our study suggests that restricting AN and binging/purging AN may be associated with different alleles of the CNR1 gene.

Genetic Risk Factors in Eating Disorders

Eating disorders such as anorexia nervosa and bulimia nervosa involve complex and interacting mechanisms. Formal genetic studies suggest that there is a substantial genetic influence for these disorders. Animal models of eating disorders are scarce. Candidate gene studies have initially focused on the serotonergic and other central neurotransmitter systems and on genes involved in body weight regulation. Most of the studies, including meta-analysis, have yielded negative results; only a single positive finding has been replicated independently. Recently, systematic genome-wide scans based on families with two or more individuals with an eating disorder (anorexia nervosa or bulimia nervosa) revealed initial linkage regions on chromosomes 1, 3, and 4 (anorexia nervosa) and 10p (bulimia nervosa). Fine mapping of one of these regions led to the identification of genes where an association with anorexia nervosa was detected. Currently treatment of patients with eating disorders can not rely on results of molecular genetic studies.

Refinement of behavioural traits in animals for the genetic dissection of eating disorders

Both twin and family studies have revealed the involvement of genetic factors in disorders that affect the regulation of body weight, such as obesity and anorexia nervosa. However, pinpointing the genes that contribute to these human disorders has not yet been very successful. In contrast, genetic studies in animals have been basic for the identification of many genes involved in the regulation of various physiological processes of energy metabolism. We thus plan to review here ways in which findings from animal studies and what is known about behavioural diversity in the human population with eating disorders can be combined. This would probably optimise phenotype-based candidate gene analysis in humans.

Dieting, body weight, body image and self-esteem in young women: doctors' dilemmas

Many young women feel that body image and exercise are important for their self-esteem, want to lose weight, are afraid they might gain weight, and feel fat. Interventions that improve self-esteem, encourage communication and help adolescents to be supportive of each other may prevent some of these women from developing eating disorders. If an eating disorder is suspected, it may be useful for physicians to ask about fear of loss of control over the body, eating, weight and shape; and preoccupation with food, eating, nutrition, body weight and shape, as these issues may differentiate those at greater risk.

A practice guideline for treatment of eating disorders in children and adolescents

Eating disorders are diseases of both the body and the psyche. Early treatment focuses on restoration of nutritional status and somatic health, including psycho-educational counselling and support offered to the patient and his/her family. Diagnosis and treatment require a multidisciplinary approach. Psychological factors related to the condition should be assessed. The most severe weight loss should be reversed before psychotherapeutic treatment. Nutritional counselling is recommended, and the benefits of individual and/or family therapy are considered in accordance with the patient's age, development, symptomatology and comorbid psychiatric disorders. Medication is useful in the treatment of bulimia nervosa and certain comorbid symptoms of anorexia nervosa. Early admission to treatment and active therapy are associated with a more favourable prognosis.

The physiological-psychological dichotomy in the study of food intake

Human food intake is driven by necessity. We eat to live, but as Brillat-Savarin and others have noted throughout history, in affluent societies eating is a pleasure and becomes more than a means to an end. Eating signifies lifestyle choice and it has considerable meaning in our society beyond the acquisition of essential energy and nutrients. Thus, it is that the study of human food intake, particularly food choice, in contrast to food intake in other animals, tends to be skewed towards measures of behavioural, social and environmental influences rather than on precise physiological processes reflecting metabolism and nutrient partitioning. The dichotomy between physiological and psychological measures is a false one, since all behaviours are necessarily expressed through physiological systems. However, in the field of human food intake research the dichotomy refers to the divergent strands of interest in either psychological or physiological processes underlying intake and appetite. The present review considers both psychological and physiological measures in promoting our understanding of the human appetite system. The overall conclusion is that the burgeoning interest in identifying appetite suppressant drugs to combat obesity and in genotyping alongside behavioural phenotyping will close the gap between psychological and physiological perspectives on human food intake.