Intrafamilial correspondences on platelet [3H-]paroxetine-binding indices in bulimic probands and their unaffected first-degree relatives

A systematic review of blood-based serotonergic biomarkers in Bulimia Nervosa

Bulimia Nervosa (BN) is a serious eating disorder, which affects 0.8-2.9% of the young population. The etiology is unknown and biomarkers would support in understanding the pathophysiology of BN, and in identifying BN patients that may benefit from medical treatment. This systematic review aims to answer whether (a) BN deviate from healthy controls in terms of serotonin (5-HT) biomarkers in blood, and whether (b) blood-based 5-HT biomarkers could be used to tailor psychopharmacological treatment in BN. A literature search using PubMed, PsycINFO and Embase was done using the following search terms: "Bulimia Nervosa" AND "serotonin" AND "blood" OR "plasma" OR "serum". 32 studies were included in this systematic review. Several biomarkers and challenge tests were identified and all studies described an association with BN and dysregulation of the 5-HT system compared to healthy controls. Several studies pointed to an association also to borderline symptoms in BN. BN deviate from healthy controls in terms of 5-HT biomarkers in blood supporting an abnormal 5-HT system in BN. 5-HT biomarkers and associated methods could be used to tailor treatment in BN although as yet, most tests described are unpractical for bedside use.

Molecular Genetic Studies of Eating Disorders: Current Status and Future Directions

We review association studies that have examined the genetic basis of eating disorders. Overall, findings suggest that serotonin, brain-derived neurotrophic factor, and estrogen genes may be important for the development of the disorders. These neuronal systems influence behavioral and personality characteristics (e.g., anxiety, food intake) that are disrupted in eating disorders. Future studies would benefit from larger sample sizes and inclusion of behavioral and personality covariates in analyses. Consideration of the mechanisms of genetic effects and interactions between genes and environment is also needed to extend conceptualizations of the genetic basis of these disorders.

Research Review: What we have learned about the causes of eating disorders - a synthesis of sociocultural, psychological, and biological research

BACKGROUND

Eating disorders are severe psychiatric disorders with a complex etiology involving transactions among sociocultural, psychological, and biological influences. Most research and reviews, however, focus on only one level of analysis. To address this gap, we provide a qualitative review and summary using an integrative biopsychosocial approach.

METHODS

We selected variables for which there were available data using integrative methodologies (e.g., twin studies, gene-environment interactions) and/or data at the biological and behavioral level (e.g., neuroimaging). Factors that met these inclusion criteria were idealization of thinness, negative emotionality, perfectionism, negative urgency, inhibitory control, cognitive inflexibility, serotonin, dopamine, ovarian hormones. Literature searches were conducted using PubMed. Variables were classified as risk factors or correlates of eating disorder diagnoses and disordered eating symptoms using Kraemer et al.'s (1997) criteria.

FINDINGS

Sociocultural idealization of thinness variables (media exposure, pressures for thinness, thin-ideal internalization, thinness expectancies) and personality traits (negative emotionality, perfectionism, negative urgency) attained 'risk status' for eating disorders and/or disordered eating symptoms. Other factors were identified as correlates of eating pathology or were not classified given limited data. Effect sizes for risk factors and correlates were generally small-to-moderate in magnitude.

CONCLUSIONS

Multiple biopsychosocial influences are implicated in eating disorders and/or disordered eating symptoms and several can now be considered established risk factors. Data suggest that psychological and environmental factors interact with and influence the expression of genetic risk to cause eating pathology. Additional studies that examine risk variables across multiple levels of analysis and that consider specific transactional processes amongst variables are needed to further elucidate the intersection of sociocultural, psychological, and biological influences on eating disorders.

Platelet serotonin transporter function predicts default-mode network activity

Background

The serotonin transporter (5-HTT) is abundantly expressed in humans by the serotonin transporter gene SLC6A4 and removes serotonin (5-HT) from extracellular space. A blood-brain relationship between platelet and synaptosomal 5-HT reuptake has been suggested, but it is unknown today, if platelet 5-HT uptake can predict neural activation of human brain networks that are known to be under serotonergic influence.

Methods

A functional magnetic resonance study was performed in 48 healthy subjects and maximal 5-HT uptake velocity (V_max) was assessed in blood platelets. We used a mixed-effects multilevel analysis technique (MEMA) to test for linear relationships between whole-brain, blood-oxygen-level dependent (BOLD) activity and platelet V_max.

Results

The present study demonstrates that increases in platelet V_max significantly predict default-mode network (DMN) suppression in healthy subjects independent of genetic variation within SLC6A4. Furthermore, functional connectivity analyses indicate that platelet V_max is related to global DMN activation and not intrinsic DMN connectivity.

Conclusion

This study provides evidence that platelet V_max predicts global DMN activation changes in healthy subjects. Given previous reports on platelet-synaptosomal V_max coupling, results further suggest an important role of neuronal 5-HT reuptake in DMN regulation.

Methylation of the glucocorticoid receptor gene promoter in bulimic women: associations with borderline personality disorder, suicidality, and exposure to childhood abuse

OBJECTIVE

To compare levels of methylation of the glucocorticoid receptor (GR) gene (NR3C1) promoter between women with bulimia nervosa (BN) and women with no eating disorder (ED), and also to explore, in women with BN, the extent to which methylation of the GR gene promoter corresponds to childhood abuse, suicidality, or borderline personality disorder (BPD).

METHOD

We measured methylation levels in selected NR3C1 promoter regions using DNA obtained from lymphocytes in 64 women with BN (32 selected as having a history of severe childhood abuse and 32 selected as having no such history) and 32 comparison women with no ED or history of childhood abuse.

RESULTS

Compared to noneating disordered women, women with BN and comorbid BPD (or BN with a history of suicidality) showed significantly more methylation of specific exon 1C sites. There was also a (nonsignificant) result indicative of greater methylation in some 1C sites among women with BN, when compared (as a group) to women with no ED. No parallel effects owing to childhood abuse were observed.

DISCUSSION

Our findings associate BN (when accompanied by BPD or suicidality) with hypermethylation of certain GR exon 1C promoter sites. We discuss theoretical and clinical implications of our findings.

Neurobiological and psychopathological variables related to emotional instability: a study of their capability to discriminate patients with bulimia nervosa from healthy controls

OBJECTIVE

To analyze the capability of a set of neurobiological and psychopathological variables to discriminate bulimia nervosa (BN) patients from healthy controls.

METHOD

Seventy-five female patients with purging BN and 30 healthy controls were compared for psychopathology (impulsivity, borderline personality traits, depressive symptoms and self-defeating personality traits) and neurobiological parameters reflecting hypothalamic-pituitary-adrenal axis activity (morning serum cortisol before and after dexamethasone) and monoamine activity (24-hour urinary excretion of norepinephrine, serotonin, dopamine, and their main metabolites: 3-methoxy-4-hydroxyphenylglycol, 5-hydroxyindoleacetic acid, and homovanillic acid). Furthermore, the relationships between the 2 sets of variables were compared in the 2 samples.

RESULTS

BN patients displayed higher impulsivity, more severe depressive features, and more borderline and self-defeating personality traits than controls. The 4 psychopathological variables were strongly interrelated in patients, whereas only depressive features correlated with self-defeating personality traits in controls. Patients had lower 24-hour excretion of serotonin and dopamine than controls, as well as lower ability to suppress cortisol. The relations between the biochemical and the psychopathological variables were only significant in the BN patients, but not in the control group. When discriminant analysis methods were applied, patients and controls differed for psychopathology (impulsive behaviors and borderline personality traits) and biological parameters (baseline cortisol and dopamine excretion), but when the variables were analyzed together, the differences in neurobiological parameters appeared as mediated by the psychopathological status.

DISCUSSION

Our results suggest that hypothalamic-pituitary-adrenal axis activity, dopamine activity and other biological parameters are worthy of further study as potential dimensional markers of BN, although they seem to depend on the psychopathological status of the patients, in such a way that the psychopathological items associated with emotional instability (impulsivity and borderline personality traits) seem to be more reliable as clinical markers at the time being.

Contributions of the glucocorticoid receptor polymorphism (Bcl1) and childhood abuse to risk of bulimia nervosa

This study evaluated the hypothesis that traumatic stress can increase risk of bulimia nervosa (BN) in individuals who are genetically disposed towards lower modulation of physiological stress reactions. We explored the extent to which childhood abuse (physical or sexual), variants of a main glucocorticoid receptor (GR) polymorphism (Bcl1), or their interaction, differentiated women with and without BN. Women seeking treatment for BN (N=129) and non-eating-disordered comparison women (N=98) provided blood samples for assays of the Bcl1 polymorphism, and completed structured interviews assessing eating symptoms, psychiatric symptoms and childhood abuse. Compared to normal-eaters, bulimic women were significantly more likely to carry the low-function Bcl1 C allele (CC or CG genotypes), to report a history of childhood abuse and, more importantly, to be positive for both factors. We interpret our findings as indicating that traumatic stress, when impacting individuals disposed to lower GR modulation, can be etiological for BN.

Platelet [³H] paroxetine binding in female patients with borderline personality disorder and their sisters

Paroxetine binding could be a vulnerability marker for traits associated with borderline personality disorder (BPD). To study this relationship, we examined [³H] paroxetine binding in female patients with BPD and their sisters. The sample consisted of 54 sibling pairs in which a proband met criteria for BPD. All subjects were given the Diagnostic Interview for Borderlines, revised (DIB-R), the Diagnostic Assessment for Personality Pathology: Brief Questionnaire (DAPP-BQ), the Barratt Impulsivity Scale (BIS), the Affective Lability Scale (ALS), the Hamilton Rating Scale for Anxiety (HAM-A), the Hamilton Rating Scale for Depression (HAM-D), and the Symptom Checklist-90, revised (SCL-90-R). All subjects had platelets assayed for [³H] paroxetine binding. There were no significant differences between probands and sisters, but both groups scored significantly lower than a previously studied control group on B(max). There were no differences on Kd. Neither B(max) nor K(d) was related to most trait or symptomatic measures. Paroxetine binding could reflect endophenotypes common to BPD probands and their first-degree relatives.

Rapid remission of anorexia nervosa and unconscious communication

An alternate framework for thinking about anorexia treatment is presented with a treatment approach that results in prompt remission of anorexia symptoms. Prior treatment of eating disorders using hypnosis is reviewed. A case example illustrating the method is followed by a discussion. The process is described for teaching clients how to nullify the anorexia symptom complex when it is reactivated.

Neural circuits, neurotransmitters, and behavior: serotonin and temperament in bulimic syndromes

In bulimia nervosa (BN), and in related binge-purge syndromes, factors affecting central serotonin (5-hydroxytryptamine, 5-HT) function appear to contribute not only to appetitive dysregulation but also to temperamental and personality manifestations. Drawing upon findings from neurobiological, molecular-genetic, and brain-imaging studies, we present an integrative model of the role of 5-HT function in bulimic syndromes. At the core of our model is a consideration of the ways in which diverse hereditary and environmental influences impact the action of the 5-HT system. We believe that our model helps account for heterogeneous traits seen in the bulimic population, for disproportionate representation of individuals displaying pathological personality traits and exposure to severe environmental stressors, and for interindividual variations as to treatment response.

The possible influence of impulsivity and dietary restraint on associations between serotonin genes and binge eating

Although serotonin (5-HT) genes are thought to be involved in the etiology of bulimia nervosa and binge eating, findings from molecular genetic studies are inconclusive. This may be due to limitations of past research, such as a failure to consider the influence of quantitative traits and gene-environment interactions. The current study investigated these issues by examining whether quantitative traits (i.e., impulsivity) and environmental exposure factors (i.e., dietary restraint) moderate 5-HT gene/binge eating associations in a sample of young women (N = 344). Binge eating was assessed using the Minnesota Eating Behavior Survey and the Dutch Eating Behavior Questionnaire (DEBQ). Impulsivity was assessed with the Barratt Impulsiveness Scale-Version 11. Dietary restraint was measured with a factor score derived from common restraint scales. Saliva samples were genotyped for the 5-HT2a receptor T102C polymorphism and 5-HT transporter promoter polymorphism. As expected, impulsivity and dietary restraint were associated with binge eating. Although the T allele of the 5-HT2a receptor gene and the s allele of the 5-HTT gene were associated with higher levels of impulsivity, there were no main effects of 5-HT genotypes on any binge eating measure, and interactions between genotypes, impulsivity, and dietary restraint were non-significant. In conclusion, we found no evidence to suggest that dietary restraint or impulsivity moderate associations between binge eating and these 5-HT genes. Future research should continue to explore interaction effects by examining larger samples, assessing dietary intake directly, and investigating other genes, traits, and environmental factors that may be related to binge eating and bulimia nervosa.

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.

Association of trait-defined, eating-disorder sub-phenotypes with (biallelic and triallelic) 5HTTLPR variations

CONTEXT

Efforts to classify eating-disordered individuals based on concurrent personality traits have consistently converged on a typology encompassing "over-regulated", "dysregulated", and "low psychopathology" subgroups. In various populations, evidence has associated personality variations of an "over-regulated/dysregulated" type with differences on serotonin-system indices, and specifically, with different loadings of serotonin transporter promoter regulatory region polymorphism (5HTTLPR) genotypes and alleles. We explored the extent to which an empirical, trait-defined typology of eating-disordered individuals coincided systematically with variations in 5HTTLPR, assayed using biallelic and triallelic models.

METHOD

We tested 185 women with a DSM-IV eating disorder (108 with Bulimia Nervosa, 17 Anorexia Nervosa, and 60 an Eating Disorder Not Otherwise Specified) and 93 with no eating disorder on measures reflecting psychopathological traits and 5HTTLPR (biallelic and triallelic) genotypes and alleles.

RESULTS

The highest-function, triallelic (L(A)/L(A)) genotype occurred significantly more frequently among eating-disordered individuals than among controls. However, a more fine-grained analysis suggested that this association was attributable to the fact that, among eating-disordered participants, those displaying an "Inhibited/Compulsive" profile (derived using latent class analysis) were more likely than those of a "Dissocial/Impulsive" or a "Low Psychopathology" group to carry the triallelic 5HTTLPR gain-of-function L(A) allele and to be L(A)/L(A) homozygotes.

DISCUSSION

This study's empirically derived classes coincide with interpretable differences on genetic indices-associating an "Inhibited/Compulsive" group with 5HTTLPR gain-of-function genotypes (and alleles) that have elsewhere been linked to trait compulsivity. The findings, furthermore, suggest that 5HTTLPR, by influencing personality-trait manifestations may, in turn, influence eating-disorder risk and symptom expression.

Genetic epidemiology, endophenotypes, and eating disorder classification

OBJECTIVE

To explore how genetic epidemiology has informed the identification of endophenotypes and how endophenotypes may inform future classification of eating disorders.

METHOD

Literature review and synthesis.

RESULTS

Although a number of endo- and subphenotypes have been suggested for eating disorders, few reach the rigorous definitions developed for candidate endophenotypes.

CONCLUSION

Further study of endophenotypes and subphenotypes for eating disorders may assist with developing a more homogenous classification system that more closely reflects underlying biological mechanisms, and provides a clearer focus for the development of coherent models and treatments.

Neurobiology of addiction. An integrative review

Evidence that psychoactive substance use disorders, bulimia nervosa, pathological gambling, and sexual addiction share an underlying biopsychological process is summarized. Definitions are offered for addiction and addictive process, the latter being the proposed designation for the underlying biopsychological process that addictive disorders are hypothesized to share. The addictive process is introduced as an interaction of impairments in three functional systems: motivation-reward, affect regulation, and behavioral inhibition. An integrative review of the literature that addresses the neurobiology of addiction is then presented, organized according to the three functional systems that constitute the addictive process. The review is directed toward identifying candidate neurochemical substrates for the impairments in motivation-reward, affect regulation, and behavioral inhibition that could contribute to an addictive process.

Phenotypes, endophenotypes, and genotypes in bulimia spectrum eating disorders

OBJECTIVES

To review the main phenomenological variants observed among bulimia spectrum syndromes and the factors believed to act etiologically for them and also to generate an etiologic model that accommodates known heterogeneities within the population suffering bulimic syndromes.

METHOD

Defining bulimic syndromes broadly, we address threshold and subthreshold forms of bulimia nervosa (BN) and also the provisional or newly proposed diagnoses of binge eating disorder (BED) and purging disorder (PD). We review evidence bearing on the validity of these diagnostic entities and on the place of sociocultural, family-developmental, neurobiological, and genetic factors in a multidimensional etiologic model for these classifications.

RESULTS

Available data validate certain bulimic phenotypes and subphenotypes that are characterized by such traits as impulsivity or affective instability. Findings associate subphenotypic, or trait-based, variations with putative endophenotypes, such as reduced serotonin transporter activity, and with candidate genotypes affecting the serotonin system; the data also indicate intriguing correspondences between gene environment interactions and subphenotypic variations along such dimensions as novelty seeking.

CONCLUSIONS

Bulimic syndromes sometimes reflect a primary disruption of controls over mood, impulses, and appetite in individuals showing marked psychopathology; at other times, they reflect a more circumscribed erosion of appetitive controls in relatively intact individuals, following prolonged dieting. We argue that dimensional perspectives involving careful attention to comorbid personality traits and symptoms are needed to accommodate existing heterogeneities within the population suffering from bulimia and to characterize the etiologic roles of familial-developmental, neurobiological, and genetic variables (and of interactions among these variables) in bulimic syndromes.