Serotonin and bulimia nervosa

Brain and gut microbiota disorders in the psychopathology of anorexia nervosa

Studies of pathophysiological mechanisms involved in eating disorders (EDs) have intensified over the past several years, revealing their unprecedented and unanticipated complexity. Results from many articles highlight critical aspects in each member of ED family. Notably, anorexia nervosa (AN) is a disorder due to undefined etiology, frequently associated with symptoms of depression, anxiety, obsessive-compulsiveness, accompanied by endocrine alterations, altered immune response, increased inflammation, and dysbiosis of the gut microbiota. Hence, an advanced knowledge of how and why a multisystem involvement exists is of paramount importance to understand the pathogenetic mechanisms of AN. In this review, we describe the change in the brain structure/function focusing on hypothalamic endocrine disorders and the disequilibrium of gut microbiota in AN that might be responsible for the psychopathological complication.

Physiological and psychosocial age-related changes associated with reduced food intake in older persons

Dietary intake changes during the course of aging. Normally an increase in food intake is observed around 55 years of age, which is followed by a reduction in food intake in individuals over 65 years of age. This reduction in dietary intake results in lowered levels of body fat and body weight, a phenomenon known as anorexia of aging. Anorexia of aging has a variety of consequences, including a decline in functional status, impaired muscle function, decreased bone mass, micronutrient deficiencies, reduced cognitive functions, increased hospital admission and even premature death. Several changes during lifetime have been implicated to play a role in the reduction in food intake and the development of anorexia of aging. These changes are both physiological, involving peripheral hormones, senses and central brain regulation and non-physiological, with differences in psychological and social factors. In the present review, we will focus on age-related changes in physiological and especially non-physiological factors, that play a role in the age-related changes in food intake and in the etiology of anorexia of aging. At the end we conclude with suggestions for future nutritional research to gain greater understanding of the development of anorexia of aging which could lead to earlier detection and better prevention.

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.

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.

The genetics of anorexia nervosa

Anorexia nervosa is a perplexing illness marked by low body weight and persistent fear of weight gain. Anorexia nervosa has the highest mortality rate of any psychiatric disease. Historically, anorexia nervosa was viewed as a disorder primarily influenced by sociocultural factors; however, over the past decade, this perception has been challenged. Family studies have consistently demonstrated that anorexia nervosa runs in families. Twin studies have underscored the contribution of additive genetic factors to the observed familial aggregation. With these bodies of literature as a starting point, we evaluate critically the current state of research on molecular genetic studies of anorexia nervosa and provide guidance for future research.

Self-injurious behavior and eating disorders: the extent and nature of the association

We have reviewed the literature on the association between self-injurious behaviors (SIB) and eating disorders from the psychological-behavioral perspective. Our aims were to investigate the extent and possible reasons for the association. A literature search was conducted using the following electronic databases (1989-2005): Medline, PsychInfo and EMBASE. References in identified articles were also screened. The reported occurrence of SIB in eating disorder patients ranged between 25.4% and 55.2%. The figures for occurrence of eating disorders in SIB patients ranged between 54% and 61%. These figures indicate that there is a strong association between these disorders. Impulsivity, obsessive-compulsive characteristics, affect dysregulation, dissociation, self-criticizing cognitive style and need for control were identified as potential factors involved in the association. Early trauma such as childhood sexual abuse and possibly certain characteristics of early family environment might contribute to the development of these factors. We present a hypothetical model which includes these factors and argue that the co-existence of eating disorders and SIB in patients results from several factors being present. SIB and eating disorder symptoms may provide a means whereby patients can deal with each factor simultaneously. The clinical implications of the findings are discussed.

Effects of a novel method of acute tryptophan depletion on plasma tryptophan and cognitive performance in healthy volunteers

RATIONALE

Disorders associated with low levels of serotonin (5-HT) are characterized by mood and cognitive disturbances. Acute tryptophan depletion (ATD) is an established method for lowering 5-HT levels and an important tool to study the effects of reduced 5-HT on mood and cognition in human subjects. The traditional ATD method, i.e., administration of separate amino acids (AAs), has several disadvantages. The AA mixture is costly, unpalatable and associated with gastrointestinal discomfort.

OBJECTIVES

The University of Maastricht developed a new and inexpensive method for ATD: a natural collagen protein (CP) mixture with low tryptophan (TRP) content. The reductions in plasma TRP after taking this CP mixture were compared with the reductions achieved taking the traditional AA mixture, and effects on memory and reversal learning were studied.

METHODS

Fifteen healthy young volunteers participated in a double-blind, counterbalanced within-subject study. Reversal learning, verbal memory and pattern recognition were assessed at baseline and 3-4 h after taking the CP mixture.

RESULTS

The new ATD method significantly reduced plasma TRP by 74% and the ratio between TRP and the other large AAs (TRP/LNAA) by 82%. The placebo mixture did not change these measures. Delayed recognition reaction time on the verbal learning task was increased following ATD. No other cognitive effects were found.

CONCLUSIONS

The CP mixture was shown to be an efficient tool for lowering plasma TRP in humans. The validity of this method with regard to behavioral changes remains to be established in healthy, vulnerable and clinical populations.

Is there a timing synergy during multi-finger production of quick force pulses?

We studied whether characteristics of individual finger force profiles covaried across repetitions of a quick force pulse production task to stabilize the required magnitude and timing of the peak force. Subjects produced series of quick force pulses by pressing with all four fingers of the right hand on force sensors under the instruction to keep the magnitude of the peak of total force at 15 N and reach the force peaks at prescribed times. Individual finger force pulses were then reshuffled across trials to create a surrogate data set. The surrogate data set showed a lower average peak force with a larger dispersion. This finding has been interpreted as pointing at predominantly negative covariation among finger force pulses in the actual data that stabilized the required magnitude of the total force, a force synergy. The difference between the actual and surrogate data sets was significant early into the pulse time, starting about 40 ms after the pulse initiation. This finding points at a central nature of the negative covariation without a major role played by visual or proprioceptive feedback. In contrast,the surrogate data set showed smaller dispersion of the timing of the total peak force, suggesting positive covariation of the timings of individual finger force pulses in the actual data interpreted as the lack of a timing synergy. These results have been confirmed with principal component (PC) analysis. The first PC for the timing of the individual finger peak forces accounted for over 90% of the total variance for the actual data set and for under 40% of the total variance for the surrogate data set. The fourth PC for the magnitudes of the finger forces accounted for under 4% of the total variance for the actual data set and for over 15% of the variance for the surrogate data set. The data are interpreted within the uncontrolled manifold hypothesis; they support the hierarchical control scheme suggested by Schöner.

Thyroid indices and treatment outcome in bulimia nervosa

OBJECTIVE

This study examined the thyroxine (T4) and free T4 (FT4) status of women with bulimia nervosa and its value as a predictor of outcome.

METHOD

A total of 135 women with bulimia nervosa underwent 12-weeks cognitive behavioral therapy treatment. Prior to and at 3-year follow-up patients completed psychiatric assessments and serumT4 and FT4 were measured.

RESULTS

At 3-year follow-up, 71% had no eating disorder and 29% met criteria for any eating disorder diagnosis. Mean T4 and FT4 concentrations were within normal ranges. Pre-treatment T4 and FT4 concentrations were inversely associated with food restriction and purging frequency, respectively. Compared with women with no eating disorder, those with any eating disorder at follow-up had lower pretreatment T4 concentrations. When pre-treatment food restriction, oral contraceptive use and binge frequency where controlled for, low T4 concentration was the only predictor of eating disorder diagnosis at follow-up.

CONCLUSION

Low T4 concentrations at pretreatment may be a predictor of poor outcome in bulimia nervosa.

Etiologia dos transtornos alimentares: aspectos biológicos, psicológicos e sócio-culturais

Os transtornos alimentares possuem uma etiologia multifatorial, composta de predisposições genéticas, socioculturais e vulnerabilidades biológicas e psicológicas. Entre os fatores predisponentes, destacam-se a história de transtorno alimentar e (ou) transtorno do humor na família, os padrões de interação presentes no ambiente familiar, o contexto sociocultural, caracterizado pela extrema valorização do corpo magro, disfunções no metabolismo das monoaminas centrais e traços de personalidade. A dieta é o comportamento precursor que geralmente antecede a instalação de um transtorno alimentar. Contudo, a presença isolada da dieta não é suficiente para desencadear o transtorno alimentar, tornando-se necessária uma interação entre os fatores de risco e outros eventos precipitantes. Por último, o curso transitório ou crônico de um transtorno alimentar está relacionado à persistência de distorções cognitivas, à ocorrência de eventos vitais significativos e a alterações secundárias ao estado de desnutrição.

Nutritional interventions for individuals with bulimia nervosa

Many physical and psychological effects of bulimia nervosa are caused by the patient's partial starvation and chaotic nutritional cycle. Attention should thus be initially directed to correcting nutritional deficiencies and abnormal eating patterns, and providing dietary counselling. Nevertheless, very little has been written about the nutritional management of this eating disorder. Nutritional counselling for bulimia patients is reviewed in this paper. Current knowledge about nutritional therapy and its efficacy, goals and objectives is presented, along with recommendations used in treatment programmes. Lastly, the key steps of nutritional management are summarised.

Disordered eating behaviors and reward sensitivity

This research evaluated the extent to which reward sensitivity demonstrated associations with binge and purge behavior frequency. A verbal operant conditioning task designed to assess conditionability to reward cues was administered to a sample of 34 women who exhibited disordered eating patterns for at least I month prior to study participation. Reward sensitivity significantly correlated with the average weekly frequency of purge (r = 0.44) but not binge behaviors. These findings suggest that reward sensitivity has some associations with aspects of disordered eating and therefore may have relevance for theories on the maintenance of some forms of eating disorder-related behavior.

Clinical implications of brain imaging in eating disorders

Imaging studies have greatly improved the understanding of the pathology and physiology of psychiatric disorders, such as schizophrenia, affective disorders, obsessive-compulsive disorder, and Tourette syndrome. In the past few years, several neuroimaging studies have concentrated on patients with eating disorders. Although the number of studies is small compared with studies of other psychiatric disorders, the results are beginning to highlight potential areas in the brain that may lead to a better understanding of these disorders. Much research still is needed, and replication of results across centers is needed. The brain is an extremely complex organ; that eating disorders are a result of abnormalities in one specific area of the brain is unlikely. More likely is that several components of the brain have a role, including cortex and subcortical regions and involvement of several neurochemical pathways and circuits within the brain. Further studies are needed in this exciting development of research about eating disorders.

Food craving and food "addiction": a critical review of the evidence from a biopsychosocial perspective

Although certain commonalities exist between eating and drug use (mood effects, external cue-control of appetites, reinforcement, etc. ), it is argued that the vast majority of cases of (self-reported) food craving and food "addiction" should not be viewed as addictive behavior. An explanation is proposed that instead gives a prominent role to the psychological processes of ambivalence and attribution, operating together with normal mechanisms of appetite control, the hedonic effects of certain foods, and socially and culturally determined perceptions of appropriate intakes and uses of those foods. Ambivalence (e.g., "nice but naughty") about foods such as chocolate arises from the attitude that it is highly palatable but should be eaten with restraint. Attempts to restrict intake, however, cause the desire for chocolate to become more salient, an experience that is then labelled as a craving. This, together with a need to provide a reason for why resisting eating chocolate is difficult and sometimes fails, can, in turn, lead the individual to an explanation in terms of addiction (e.g., "chocoholism"). Moreishness ("causing a desire for more") occurs during, rather than preceding, an eating episode, and is experienced when the eater attempts to limit consumption before appetite for the food has been sated.

Effects of acute tryptophan depletion on mood in bulimia nervosa

BACKGROUND

The present study investigated the role of serotonin in the pathophysiology of bulimia nervosa (BN) by studying the affective and appetitive responses of women ill with BN to an acute tryptophan depletion (ATD) paradigm.

METHODS

Twenty-two women with BN and 16 healthy control women (CW) were studied on 2 separate days during the follicular stage of the menstrual cycle. Participants drank a control mix of essential amino acids (100 g + 4.6 g tryptophan) on one day and a tryptophan deficient (100 g - 4.6 g tryptophan) mixture (ATD) on the other in a double-blind fashion. Mood/appetite ratings and blood samples were taken at baseline and at intervals up to 420 minutes. Participants were then presented with an array of foods and were allowed to binge and vomit if they desired.

RESULTS

CW and BN women had a similar and significant reduction in plasma tryptophan levels and the tryptophan: LNAA ratio after ATD. After ATD, the BN women had a significantly greater increase in peak (minus baseline) depression, mood lability, sadness and desire to binge compared to the CW. BN subjects and CW had similar peak changes in mood after the control amino acid mixture. BN subjects and CW consumed similar amounts of food after the two amino acid treatments.

CONCLUSIONS

Women with BN seem more vulnerable to the mood lowering effects of ATD, suggesting they have altered modulation of central 5-HT neuronal systems.

Complete recovery from intractable bulimia nervosa by the surgical cure of primary hyperparathyroidism

We document here the first case of bulimia nervosa associated with primary hyperparathyroidism. The binge eating and self-induced vomiting that occurred for more than 10 years disappeared completely after the surgical cure of primary hyperparathyroidism. Depressive and anxiety symptoms also improved dramatically. The possible influence of derangement in calcium metabolism on the neurobiochemical mechanism of bulimia nervosa is discussed.

Physiological changes in Pachinko players; beta-endorphin, catecholamines, immune system substances and heart rate

Pachinko is a popular form of recreation in Japan. However, in recent years, along with Pachinko's popularity, "Pachinko dependence" has become topical news. The purpose of this study was to investigate beta-endorphin, catecholamines, immune system responses and heart rate during the playing of Pachinko. The following significant results were observed. (1) Plasma concentration of beta-endorphin increased before playing Pachinko and while in the Pachinko-center (p < 0.05). (2) Beta-endorphin and norepinephrine increased when the player began to win (i.e. at "Fever-start") compared to baseline (p < 0.05). (3) Beta-endorphin, norepinephrine and dopamine increased when the winning streak finished (i.e. at "Fever-end") compared to baseline (p < 0.05-0.01). (4) Norepinephrine increased past 30 minutes after "Fever-end" compared to baseline (p < 0.05). (5) Heart rate increased before "Fever-start" compared to baseline, peaked at "Fever-start" and rapidly decreased to match rates measured at rest. But the increase was observed from 200 seconds after "Fever-start" (p < 0.05-0.001). (6) There was a positive correlation between the number of hours subjects played Pachinko in a week and the differences between beta-endorphin levels at "Fever-start" and those at rest (p < 0.05). (7) The number of T-cells decreased while the number of NK cells increased at "Fever-start" compared to baseline (p < .05). These results suggest that intracerebral substances such as beta-endorphin and dopamine are involved in the habit-forming behavior associated with Pachinko.

Visceral protein and hematological status of women with bulimia nervosa and depressed controls

Serum visceral protein and hematological indices and their behavioral and clinical correlates were determined in women with bulimia nervosa and depressed controls. One hundred and fifty-two women who met DSM-IV criteria for bulimia nervosa and 68 women with DSM-IV major depression completed a structured clinical interview and had blood samples drawn prior to admission to outpatient treatment programs. Albumin and prealbumin concentrations were lower in the depressed women, possibly due to recent weight loss. Elevated transferrin values suggested mild iron deficiency in nearly one-fifth of women with bulimia nervosa. Of women with bulimia nervosa, the 10.7% who had hemoglobin and 5.1% who had vitamin B12 levels below the normal range were not distinguishable on measures of body mass index, binge eating, vomiting, or restriction frequency. The 4.3% with low prealbumin levels experienced significantly more episodes of binge eating and vomiting in the prior fortnight than those with normal values. Frequency of vomiting was also inversely associated with albumin concentration. Hamilton Depression Rating Scale scores were inversely and linearly related to serum vitamin B12. Lower B12 levels in those with alcohol abuse/dependence did not explain the association between B12 and HDRS scores. No hematological indices were related to body mass index, binge eating or restriction frequency, or restriction intensity. In summary, women with bulimia nervosa do not appear to be at greater risk of visceral protein or hematological abnormalities than psychiatric controls. It is suggested that a high frequency of vomiting and alcohol abuse/dependence, increases the risk of subclinical malnutrition in women with bulimia nervosa, and that poor vitamin B12 nutriture may interfere with the functioning of the serotonergic or catecholaminergic systems and contribute to depressive symptoms in bulimia nervosa.

Eating behavior of bulimics, self-identified binge eaters, and non-eating-disordered individuals: what differentiates these populations?

This article reviews and critiques the eating behavior literature comparing the binge and non-binge-eating episodes of three populations of normal-weight women: bulimics, self-identified binge eaters, and non-eating-disordered women. The specific behaviors evaluated are number of calories consumed during different types of eating episodes, frequency of binge eating, number of eating episodes, rate of food consumption, the macronutrient composition of the food ingested, and context and duration of eating. Differences in these populations' eating behavior are analyzed in terms of their theoretical contribution. It is concluded that differences in the observed behavior of these groups are consistent with restraint theory, purge opportunity, and the forbidden foods hypothesis. Conversely, results do not support carbohydrate craving theory or a deficit in the satiety mechanisms of bulimics. Suggestions for future research are presented.

Hypothalamic serotonin in control of eating behavior, meal size, and body weight

Serotonin (5-HT) has been implicated in the control of eating behavior and body weight. Stimulants of this monoamine reduce food intake and weight gain and increase energy expenditure, both in animals and in humans. This article reviews evidence that supports a role for hypothalamic serotonergic receptor mechanisms in the mediation of these effects. A variety of studies in rodents indicate that, at low doses, 5-HT or drugs that enhance the release of this neurotransmitter preferentially inhibit the ingestion of carbohydrate, more than fat or protein. This phenomenon is mediated, in part, by 5-HT receptors located in various medial hypothalamic nuclei. A negative feedback loop exists between the consumption of this macronutrient and the turnover of 5-HT in the hypothalamus. That is, carbohydrate ingestion enhances the synthesis and release of hypothalamic 5-HT, which in turn serves to control the size of carbohydrate-rich meals. A model is described that proposes the involvement of circulating hormones and glucose in this feedback process. These hormones, including insulin, corticosterone, and the adipose tissue-derived hormone, leptin, have impact on serotonergic function as well as satiety. This model further suggests that 5-HT exerts its strongest effect on appetite at the start of the natural feeding cycle, when carbohydrate is normally preferred. Clinical studies provide evidence that is consistent with the proposed model and that implicates 5-HT in disturbances of eating and body weight disorders.

Common biological pathways in eating disorders and obesity

The purpose of this article is to summarize briefly potential biological pathways that are common among anorexia nervosa, bulimia nervosa, and obesity. We conclude that data on serotonergic and beta-endorphin regulatory systems provide the most promising leads for potential trait-based etiological theories. We then discuss the contribution of current data to a better understanding of the etiology and maintenance of eating disorders. Finally, we comment on how the exploration for common biological mechanisms highlights problems in nosological diagnosis (i.e., the lack of symptom specificity among disorders) and obscures the etiological significance of social stressors and cultural factors.

Biological correlates of binge eating

Eating disorders are associated with numerous biological perturbations; however, sorting out cause from effect is difficult. Neuroendocrine and metabolic abnormalities are seen in both anorexia nervosa and bulimia nervosa, but they have not been described in binge eating disorder, in which neither starvation nor compensatory behaviors are present. Although these findings may reflect biologic differences among subgroups of binge eaters, an alternative explanation is that many of the biological correlates of binge eating are the result of metabolic derangement secondary to starvation and/or purging. The identification of binge eating disorder provides an opportunity to study the causes and concomitants of binge eating in the absence of compensatory behaviors.