Habitual binge/purge behavior influences circulating ghrelin levels in eating disorders

Microbiota in anorexia nervosa: potential for treatment

Anorexia nervosa (AN) is characterised by the restriction of energy intake in relation to energy needs and a significantly lowered body weight than normally expected, coupled with an intense fear of gaining weight. Treatment of AN is currently based on psychological and refeeding approaches, but their efficacy remains limited since 40% of patients after 10 years of medical care still present symptoms of AN. The intestine hosts a large community of microorganisms, called the "microbiota", which live in symbiosis with the human host. The gut microbiota of a healthy human is dominated by bacteria from two phyla: Firmicutes and, majorly, Bacteroidetes. However, the proportion in their representation differs on an individual basis and depends on many external factors including medical treatment, geographical location and hereditary, immunological and lifestyle factors. Drastic changes in dietary intake may profoundly impact the composition of the gut microbiota, and the resulting dysbiosis may play a part in the onset and/or maintenance of comorbidities associated with AN, such as gastrointestinal disorders, anxiety and depression, as well as appetite dysregulation. Furthermore, studies have reported the presence of atypical intestinal microbial composition in patients with AN compared with healthy normal-weight controls. This review addresses the current knowledge about the role of the gut microbiota in the pathogenesis and treatment of AN. The review also focuses on the bidirectional interaction between the gastrointestinal tract and the central nervous system (microbiota-gut-brain axis), considering the potential use of the gut microbiota manipulation in the prevention and treatment of AN.

Increased plasma asprosin levels are associated with overeating and loss of control in drug-free bulimia nervosa

PURPOSE

Abnormalities in appetite hormones have been implicated in bulimia nervosa (BN). Orexigenic hormone asprosin has been reported to be associated with food intake and weight gain, but no relevant studies have yet been reported in BN. This study investigated asprosin concentrations and their association with eating disorder symptoms in patients with BN.

METHODS

This study recruited a total of 26 BN patients and 23 healthy controls (HC). Symptom severity for eating disorders, depression, and anxiety was determined by the Eating Disorder Examination Questionnaire 6.0, Beck Depression Inventory, Version 2, and Beck Anxiety Inventory, respectively. In addition, the study employed sandwich enzyme-linked immunoassay technology to determine plasma asprosin and glucose concentrations in all participants.

RESULTS

The results revealed that plasma asprosin concentrations were significantly higher in BN patients than in HC (P = 0.037), but the difference disappeared after adjusting for the covariate BMI (F = 2.685, P = 0.108). Correlation analysis showed that asprosin concentration was positively correlated with overeating (r = 0.451, P = 0.021) and eating loss of control (r = 0.483, P = 0.012) in BN patients. Linear regression analysis indicated that an increase in asprosin concentration was associated with an increase in the times of overeating (F = 6.303, P = 0.019, R² = 0.208). Multiple linear regression showed that increases in asprosin concentration and BDI-II total score could explain the frequent eating loss of control (F = 5.766, P = 0.009, R² = 0.334).

CONCLUSIONS

The present study is the first report of plasma asprosin concentration in BN patients and found that overeating and eating loss of control increased with the increase of asprosin concentration. Additionally, asprosin level and degree of depression may explain the frequency of loss of control.

LEVEL OF EVIDENCE

Level III: Evidence obtained from case-control studies.

Gastrointestinal peptides in eating-related disorders

Food intake is tightly controlled by homeostatic signals sensitive to metabolic need for the regulation of body weight. This review focuses on the peripherally-secreted gastrointestinal peptides (i.e., ghrelin, cholecystokinin, glucagon-like peptide 1, and peptide tyrosine tyrosine) that contribute to the control of appetite and discusses how these peptides or the signals arising from their release are disrupted in eating-related disorders across the weight spectrum, namely anorexia nervosa, bulimia nervosa, and obesity, and whether they are normalized following weight restoration or weight loss treatment. Further, the role of gut peptides in the pathogenesis and treatment response in human weight conditions as identified by rodent models are discussed. Lastly, we review the incretin- and hormone-based pharmacotherapies available for the treatment of obesity and eating-related disorders.

Assessing the role of ghrelin and the enzyme ghrelin O-acyltransferase (GOAT) system in food reward, food motivation, and binge eating behavior

The peripheral peptide hormone ghrelin is a powerful stimulator of food intake, which leads to body weight gain and adiposity in both rodents and humans. The hormone, thus, increases the vulnerability to obesity and binge eating behavior. Several studies have revealed that ghrelin's functions are due to its interaction with the growth hormone secretagogue receptor type 1a (GHSR1a) in the hypothalamic area; besides, ghrelin also promotes the reinforcing properties of hedonic food, acting at extra-hypothalamic sites and interacting with dopaminergic, cannabinoid, opioid, and orexin signaling. The hormone is primarily present in two forms in the plasma and the enzyme ghrelin O-acyltransferase (GOAT) allows the acylation reaction which causes the transformation of des-acyl-ghrelin (DAG) to the active form acyl-ghrelin (AG). DAG has been demonstrated to show antagonist properties; it is metabolically active, and counteracts the effects of AG on glucose metabolism and lipolysis, and reduces food consumption, body weight, and hedonic feeding response. Both peptides seem to influence the hypothalamic-pituitary-adrenal (HPA) axis and the corticosterone/cortisol level that drive the urge to eat under stressful conditions. These findings suggest that DAG and inhibition of GOAT may be targets for obesity and bingeing-related eating disorders and that AG/DAG ratio may be an important potential biomarker to assess the risk of developing maladaptive eating behaviors.

Ghrelin as a possible biomarker and maintaining factor in patients with eating disorders reporting childhood traumatic experiences

OBJECTIVE

The recent conceptualization of ghrelin as a stress hormone suggested that its chronic alterations may have a role in maintaining overeating behaviors in subjects with eating disorders (EDs) reporting childhood traumatic experiences. The aim of this study was to investigate the alterations of ghrelin levels in patients with EDs, their associations with early trauma, binge and emotional eating, and possible moderation/mediation models.

METHOD

Sixty-four patients with EDs and 42 healthy controls (HCs) had their plasma ghrelin levels measured and completed questionnaires evaluating general and ED-specific psychopathology, emotional eating, and childhood traumatic experiences.

RESULTS

Participants with anorexia nervosa had higher ghrelin levels than HCs in body mass index (BMI)-adjusted comparisons. Moreover, patients reporting a history of childhood trauma had higher ghrelin levels. Childhood sexual abuse (CSA), BMI, and self-induced vomiting were independent predictors of ghrelin levels. Moderation analyses showed that ghrelin levels were associated with binge and emotional eating only for higher levels of childhood trauma. Elevated ghrelin was a significant mediator for the association of CSA with binge eating.

CONCLUSIONS

These results support the hypothesis that chronic alterations in ghrelin levels following childhood traumatic experiences could represent a neurobiological maintaining factor of pathological overeating behaviors in EDs.

A Systematic Review and Meta-Analysis Finds Increased Blood Levels of All Forms of Ghrelin in Both Restricting and Binge-Eating/Purging Subtypes of Anorexia Nervosa

Anorexia nervosa (AN) is a severe psychiatric condition associated with high mortality and chronicity. The hunt for state, trait, subtyping, and prognostic biomarkers is ongoing and the orexigenic hormone ghrelin and its different forms, acyl ghrelin and desacyl ghrelin, have been proposed to be increased in AN, especially in the restrictive subtype. A systematic literature search was performed using established databases up to 30 November 2020. Forty-nine studies met inclusion criteria for cross-sectional and longitudinal meta-analyses on total ghrelin, acyl ghrelin, and desacyl ghrelin. All forms of ghrelin were increased in the acute stage of anorexia nervosa during fasting compared to healthy controls. Previous notions on differences in ghrelin levels between AN subtypes were not supported by current data. In addition, a significant decrease in total ghrelin was observed pre-treatment to follow-up. However, total ghrelin levels at follow-up were still marginally elevated compared to healthy controls, whereas for acyl ghrelin, no overall effect of treatment was observed. Due to heterogeneity in follow-up designs and only few data on long-term recovered patients, longitudinal results should be interpreted with caution. While the first steps towards a biomarker in acute AN have been completed, the value of ghrelin as a potential indicator of treatment success or recovery status or its use in subtype differentiation are yet to be established.

Body composition in anorexia nervosa: Meta-analysis and meta-regression of cross-sectional and longitudinal studies

OBJECTIVE

Clinically, anorexia nervosa (AN) presents with altered body composition. We quantified these alterations and evaluated their relationships with metabolites and hormones in patients with AN longitudinally.

METHOD

In accordance with PRISMA guidelines, we conducted 94 meta-analyses on 62 samples published during 1996-2019, comparing up to 2,319 pretreatment, posttreatment, and weight-recovered female patients with AN with up to 1,879 controls. Primary outcomes were fat mass, fat-free mass, body fat percentage, and their regional distribution. Secondary outcomes were bone mineral density, metabolites, and hormones. Meta-regressions examined relationships among those measures and moderators.

RESULTS

Pretreatment female patients with AN evidenced 50% lower fat mass (mean difference [MD]: -8.80 kg, 95% CI: -9.81, -7.79, Q = 1.01 × 10-63 ) and 4.98 kg (95% CI: -5.85, -4.12, Q = 1.99 × 10-28 ) lower fat-free mass, with fat mass preferentially stored in the trunk region during early weight restoration (4.2%, 95% CI: -2.1, -6.2, Q = 2.30 × 10-4 ). While the majority of traits returned to levels seen in healthy controls after weight restoration, fat-free mass (MD: -1.27 kg, 95% CI: -1.79, -0.75, Q = 5.49 × 10-6 ) and bone mineral density (MD: -0.10 kg, 95% CI: -0.18, -0.03, Q = 0.01) remained significantly altered.

DISCUSSION

Body composition is markedly altered in AN, warranting research into these phenotypes as clinical risk or relapse predictors. Notably, the long-term altered levels of fat-free mass and bone mineral density suggest that these parameters should be investigated as potential AN trait markers.

RESUMENOBJETIVO

Clínicamente, la anorexia nervosa (AN) se presenta con alteraciones en la composición corporal. Cuantificamos estas alteraciones y evaluamos longitudinalmente su relación con metabolitos y hormonas en pacientes con AN. MÉTODO: De acuerdo con las pautas PRISMA, realizamos 94 meta-análisis en 62 muestras publicadas entre 1996-2019, comparando hasta 2,319 pacientes mujeres en pre-tratamiento, post-tratamiento, y recuperadas en base al peso con hasta 1,879 controles. Las principales medidas fueron masa grasa, masa libre de grasa, porcentaje de grasa corporal y su distribución regional. Las medidas secundarias fueron densidad mineral ósea, metabolitos y hormonas. Las meta-regresiones examinaron las relaciones entre esas medidas y moderadores.

RESULTADOS

Las pacientes femeninas con AN pre-tratamiento mostraron un 50% menos de masa grasa (MD: -8.80 kg, CI 95%: -9.81, -7.79, Q = 1.01 × 10-63 ) y 4.98 kg (CI 95%: -5.85, -4.12, Q = 1.99 × 10-28 ) menos de masa libre de grasa, con masa grasa preferentemente almacenada en la región del tronco durante la recuperación temprana del peso (4.2%, CI 95%: -2.1, -6.2, Q = 2.30 × 10-4 ). Aunque la mayoría de los rasgos regresaron a los niveles vistos en los controles sanos después de la restauración del peso, la masa libre de grasa (MD: -1.27 kg, CI 95%: -1.79, -0.75, Q = 5.49 × 10-6 ) y la densidad mineral ósea (MD: -0.10 kg, CI 95%: -0.18, -0.03, Q = 0.01) permanecieron significativamente alteradas. DISCUSIÓN: La composición corporal es marcadamente alterada en la AN, lo que garantiza la investigación en estos fenotipos como predictores de riesgo clínico o de recaída. Notablemente, la alteración a largo plazo de los niveles de masa libre de grasa y densidad mineral ósea sugieren que estos parámetros debe ser investigados como potenciales rasgos indicadores de AN.

Examining weight suppression as a transdiagnostic factor influencing illness trajectory in bulimic eating disorders

Recent research indicates that weight suppression (WS: defined as the difference between highest lifetime and current weight) prospectively predicts illness trajectory across eating disorders characterized by binge eating, including AN binge-purge subtype (ANbp), bulimia nervosa (BN), and binge eating disorder (BED), collectively referred to as bulimic eating disorders. Through a series of studies, we have developed a model to explain the link between WS and illness trajectory in bulimic eating disorders. Our model posits that WS contributes to reduced circulating leptin, which leads to reduced postprandial glucagon-like peptide 1 (GLP-1) response. Diminished leptin and GLP-1 function contribute to alterations in two reward-related constructs in the Research Domain Criteria (RDoC): reward value/effort and reward satiation. Respectively, these changes increase drive/motivation to consume food and decrease ability for food consumption to lead to a state of satiation/satisfaction. Combined, these alterations increase risk for experiencing large, out-of-control binge-eating episodes. The following review presents evidence that contributed to the development of this model as well as preliminary findings from an on-going project funded to test this model.

The Role of Ghrelin in Anorexia Nervosa

Ghrelin, a 28-amino acid peptide hormone expressed in X/A-like endocrine cells of the stomach, is the only known peripherally produced and centrally acting peptide that stimulates food intake and therefore attracted a lot of attention with one major focus on the treatment of conditions where an increased energy intake or body weight gain is desired. Anorexia nervosa is an eating disorder characterized by a pronounced reduction of body weight, a disturbed body image and hormonal alterations. Ghrelin signaling has been thoroughly investigated under conditions of anorexia nervosa. The present review will highlight these alterations of ghrelin in anorexia and discuss possible treatment strategies targeting ghrelin signaling. Lastly, gaps in knowledge will be mentioned to foster future research.

Hedonic Eating and the "Delicious Circle": From Lipid-Derived Mediators to Brain Dopamine and Back

Palatable food can be seductive and hedonic eating can become irresistible beyond hunger and negative consequences. This is witnessed by the subtle equilibrium between eating to provide energy intake for homeostatic functions, and reward-induced overeating. In recent years, considerable efforts have been devoted to study neural circuits, and to identify potential factors responsible for the derangement of homeostatic eating toward hedonic eating and addiction-like feeding behavior. Here, we examined recent literature on “old” and “new” players accountable for reward-induced overeating and possible liability to eating addiction. Thus, the role of midbrain dopamine is positioned at the intersection between selected hormonal signals involved in food reward information processing (namely, leptin, ghrelin, and insulin), and lipid-derived neural mediators such as endocannabinoids. The impact of high fat palatable food and dietary lipids on endocannabinoid formation is reviewed in its pathogenetic potential for the derangement of feeding homeostasis. Next, endocannabinoid signaling that regulates synaptic plasticity is discussed as a key mechanism acting both at hypothalamic and mesolimbic circuits, and affecting both dopamine function and interplay between leptin and ghrelin signaling. Outside the canonical hypothalamic feeding circuits involved in energy homeostasis and the notion of “feeding center,” we focused on lateral hypothalamus as neural substrate able to confront food-associated homeostatic information with food salience, motivation to eat, reward-seeking, and development of compulsive eating. Thus, the lateral hypothalamus-ventral tegmental area-nucleus accumbens neural circuitry is reexamined in order to interrogate the functional interplay between ghrelin, dopamine, orexin, and endocannabinoid signaling. We suggested a pivotal role for endocannabinoids in food reward processing within the lateral hypothalamus, and for orexin neurons to integrate endocrine signals with food reinforcement and hedonic eating. In addition, the role played by different stressors in the reinstatement of preference for palatable food and food-seeking behavior is also considered in the light of endocannabinoid production, activation of orexin receptors and disinhibition of dopamine neurons. Finally, type-1 cannabinoid receptor-dependent inhibition of GABA-ergic release and relapse to reward-associated stimuli is linked to ghrelin and orexin signaling in the lateral hypothalamus-ventral tegmental area-nucleus accumbens network to highlight its pathological potential for food addiction-like behavior.

Psychotherapy for transdiagnostic binge eating: A randomized controlled trial of cognitive-behavioural therapy, appetite-focused cognitive-behavioural therapy, and schema therapy

Cognitive-behavioural therapy (CBT) is the recommended treatment for binge eating, yet many individuals do not recover, and innovative new treatments have been called for. The current study compares traditional CBT with two augmented versions of CBT; schema therapy, which focuses on early life experiences as pivotal in the history of the eating disorder; and appetite-focused CBT, which emphasises the role of recognising and responding to appetite in binge eating. 112 women with transdiagnostic DSM-IV binge eating were randomized to the three therapies. Therapy consisted of weekly sessions for six months, followed by monthly sessions for six months. Primary outcome was the frequency of binge eating. Secondary and tertiary outcomes were other behavioural and psychological aspects of the eating disorder, and other areas of functioning. No differences among the three therapy groups were found on primary or other outcomes. Across groups, large effect sizes were found for improvement in binge eating, other eating disorder symptoms and overall functioning. Schema therapy and appetite-focused CBT are likely to be suitable alternative treatments to traditional CBT for binge eating.

Relationships Between Fasting Serum Amylase and Ghrelin or Peptide YY3-36 Levels in Healthy Men

OBJECTIVES

Appetite and carbohydrate metabolism are important contributors to the development of obesity. Recently, low serum amylase was shown to be associated with obesity and metabolic disorder. We investigated the relationship between amylase and ghrelin or peptide YY (PYY) levels in healthy men.

METHODS

Twenty-one men were enrolled in this cross-sectional study; all subjects were asymptomatic with no medical history. Fasting serum amylase, ghrelin, PYY3-36, anthropometry, and nutritional intake were measured. Linear regression analyses were performed to examine associations between amylase and ghrelin or PYY3-36.

RESULTS

The mean (SD) age and waist circumference of the subjects were 51.5 (10.9) years and 87.0 (4.4) cm, respectively. Amylase was found to be correlated with waist circumference (r = -0.438, P = 0.054), ghrelin (r = 0.533, P = 0.015), and PYY3-36 (r = -0.511, P = 0.021). Multivariate linear regression analysis revealed a negative association between amylase and PYY3-36 (β = -0.428, P = 0.045) but a nonsignificantly positive association between amylase and ghrelin (β = 0.260, P = 0.146).

CONCLUSIONS

Amylase levels were found to be associated with ghrelin and PYY3-36 in healthy men. Amylase, ghrelin, and PYY3-36 may play a role in obesity; further research is required to identify the underlying mechanism.

Ghrelin Actions on Somatotropic and Gonadotropic Function in Humans

Ghrelin, a 28 amino-acid octanoylated peptide predominantly produced by the stomach, was discovered to be the natural ligand of the type 1a GH secretagogue receptor (GHS-R1a). It was thus considered as a natural GHS additional to GHRH, although later on ghrelin has mostly been considered a major orexigenic factor. The GH-releasing action of ghrelin takes place both directly on pituitary cells and through modulation of GHRH from the hypothalamus; some functional antisomatostatin action has also been shown. However, ghrelin is much more than a natural GH secretagogue. In fact, it also modulates lactotroph and corticotroph secretion in humans as well as in animals and plays a relevant role in the modulation of the hypothalamic-pituitary-gonadal function. Several studies have indicated that ghrelin plays an inhibitory effect on gonadotropin pulsatility, is involved in the regulation of puberty onset in animals, and may regulate spermatogenesis, follicular development and ovarian cell functions in humans. In this chapter ghrelin actions on the GH/IGF-I and the gonadal axes will be revised. The potential therapeutic role of ghrelin as a treatment of catabolic conditions will also be discussed.

The dopamine antagonist flupentixol does not alter ghrelin-induced food intake in rats

It has been shown that dopamine antagonists suppress the ghrelin-induced increased motivation to work for food. The aim of this study was to investigate the influence of the dopamine antagonist flupentixol on ghrelin-induced food intake. Ad libitum fed male Sprague-Dawley (SD) rats were injected intraperitoneally (ip) with vehicle plus vehicle, vehicle plus ghrelin (13 μg/kg), 0.25mg/kg or 0.5mg/kg flupentixol plus ghrelin, or 0.25mg/kg or 0.5 mg/kg flupentixol plus vehicle. In a second experiment, intracerebroventricularly (icv) cannulated rats received an ip injection of vehicle (0.15M NaCl) or flupentixol (0.25mg/kg) and 20 min later an icv injection of vehicle or ghrelin (1 μg/rat). Both experiments were performed twice: first, rats were offered only standard chow, while in the second experiment they could choose between standard chow and a palatable/preferred chow. Cumulative light phase food intake was assessed for 7h. Ip as well as icv injected ghrelin reliably increased intake of standard chow. Flupentixol did not affect ghrelin-induced intake of standard chow. Ip injected ghrelin failed to increase the intake of palatable chow, whereas icv injected ghrelin did. This effect was not blocked by ip flupentixol. In summary, ip administered ghrelin did not increase the intake of chow the rats preferred; whereas icv injected ghrelin further stimulated the intake of preferred chow suggesting a direct central mediation of this effect. Our results show that the dopamine antagonist flupentixol does not influence ghrelin-induced feeding in our choice paradigm.

Central and peripheral peptides regulating eating behaviour and energy homeostasis in anorexia nervosa and bulimia nervosa: a literature review

A large body of literature suggests the occurrence of a dysregulation in both central and peripheral modulators of appetite in patients with anorexia nervosa (AN) and bulimia nervosa (BN), but at the moment, the state or trait-dependent nature of those changes is far from being clear. It has been proposed, although not definitively proved, that peptide alterations, even when secondary to malnutrition and/or to aberrant eating behaviours, might contribute to the genesis and the maintenance of some symptomatic aspects of AN and BN, thus affecting the course and the prognosis of these disorders. This review focuses on the most significant literature studies that explored the physiology of those central and peripheral peptides, which have prominent effects on eating behaviour, body weight and energy homeostasis in patients with AN and BN. The relevance of peptide dysfunctions for the pathophysiology of eating disorders is critically discussed.

Ghrelin as a starvation signal

SUMMARY

Ghrelin, a gastrointestinal hormone, functions as an endogenous ligand for the growth hormone secretagogue receptor (GHS-R). It comprises 28 amino acids, of which the Ser-3 residue is post-translationally modified by the addition of octanoyl acid. Ghrelin stimulates feeding and the secretion of growth hormone; it is also thought to function in energy conservation. Here, we provide an overview of the discovery of ghrelin, its pathophysiological significance, and the mechanism of ghrelin-induced feeding.:

Reduction in total plasma ghrelin levels following catecholamine depletion: relation to bulimic and depressive symptoms

There is increasing preclinical and clinical evidence of the important role played by the gastric peptide hormone ghrelin in the pathogenesis of symptoms of depression and eating disorders. To investigate the role of ghrelin and its considered counterpart, peptide tyrosine tyrosine (PYY), in the development of bulimic and depressive symptoms induced by catecholamine depletion, we administered the tyrosine hydroxylase inhibitor alpha-methyl-paratyrosine (AMPT) in a randomized, double-blind, placebo-controlled crossover, single-site experimental trial to 29 healthy controls and 20 subjects with fully recovered bulimia nervosa (rBN). We found a decrease between preprandial and postprandial plasma ghrelin levels (p<0.0001) and a postprandial rise in plasma PYY levels (p<0.0001) in both conditions in the entire study population. Plasma ghrelin levels decreased in the entire study population after treatment with AMPT compared to placebo (p<0.006). AMPT-induced changes in plasma ghrelin levels were negatively correlated with AMPT-induced depressive symptoms (p<0.004). Plasma ghrelin and plasma PYY levels were also negatively correlated (p<0.05). We did not observe a difference in ghrelin or PYY response to catecholamine depletion between rBN subjects and healthy controls, and there was no correlation between plasma ghrelin and PYY levels and bulimic symptoms induced by catecholamine depletion. These findings suggest a relationship between catecholamines and ghrelin with depressive symptoms.

Dysfunctions of leptin, ghrelin, BDNF and endocannabinoids in eating disorders: beyond the homeostatic control of food intake

A large body of literature documents the occurrence of alterations in the physiology of both central and peripheral modulators of appetite in acute patients with anorexia nervosa (AN) and bulimia nervosa (BN). Until more recently the role of most of the appetite modulators in the control of eating behavior was conceptualized solely in terms of their influence on homeostatic control of energy balance. However, it is becoming more and more evident that appetite modulators also affect the non-homeostatic cognitive, emotional and rewarding component of food intake as well as non food-related reward, and, recently, AN and BN have been pathophysiologically linked to dysfunctions of reward mechanisms. Therefore, the possibility exists that observed changes in appetite modulators in acute AN and BN may represent not only homeostatic adaptations to malnutrition, but also contribute to the development and/or the maintenance of aberrant non-homeostatic behaviors, such as self-starvation and binge eating. In the present review, the evidences supporting a role of leptin, ghrelin, brain-derived neurotrophic factor and endocannabinoids in the homeostatic and non-homeostatic dysregulations of patients with AN and BN will be presented. The reviewed literature is highly suggestive that changes in the physiology of these modulators may play a pivotal role in the pathophysiology of eating disorders by providing a possible link between motivated behaviors, reward processes, cognitive functions and energy balance.

The role of "mixed" orexigenic and anorexigenic signals and autoantibodies reacting with appetite-regulating neuropeptides and peptides of the adipose tissue-gut-brain axis: relevance to food intake and nutritional status in patients with anorexia nervosa and bulimia nervosa

Eating disorders such as anorexia (AN) and bulimia nervosa (BN) are characterized by abnormal eating behavior. The essential aspect of AN is that the individual refuses to maintain a minimal normal body weight. The main features of BN are binge eating and inappropriate compensatory methods to prevent weight gain. The gut-brain-adipose tissue (AT) peptides and neutralizing autoantibodies play an important role in the regulation of eating behavior and growth hormone release. The mechanisms for controlling food intake involve an interplay between gut, brain, and AT. Parasympathetic, sympathetic, and serotoninergic systems are required for communication between brain satiety centre, gut, and AT. These neuronal circuits include neuropeptides ghrelin, neuropeptide Y (NPY), peptide YY (PYY), cholecystokinin (CCK), leptin, putative anorexigen obestatin, monoamines dopamine, norepinephrine (NE), serotonin, and neutralizing autoantibodies. This extensive and detailed report reviews data that demonstrate that hunger-satiety signals play an important role in the pathogenesis of eating disorders. Neuroendocrine dysregulations of the AT-gut-brain axis peptides and neutralizing autoantibodies may result in AN and BN. The circulating autoantibodies can be purified and used as pharmacological tools in AN and BN. Further research is required to investigate the orexigenic/anorexigenic synthetic analogs and monoclonal antibodies for potential treatment of eating disorders in clinical practice.

Ghrelin: central and peripheral implications in anorexia nervosa

Increasing clinical and therapeutic interest in the neurobiology of eating disorders reflects their dramatic impact on health. Chronic food restriction resulting in severe weight loss is a major symptom described in restrictive anorexia nervosa (AN) patients, and they also suffer from metabolic disturbances, infertility, osteopenia, and osteoporosis. Restrictive AN, mostly observed in young women, is the third largest cause of chronic illness in teenagers of industrialized countries. From a neurobiological perspective, AN-linked behaviors can be considered an adaptation that permits the endurance of reduced energy supply, involving central and/or peripheral reprograming. The severe weight loss observed in AN patients is accompanied by significant changes in hormones involved in energy balance, feeding behavior, and bone formation, all of which can be replicated in animals models. Increasing evidence suggests that AN could be an addictive behavior disorder, potentially linking defects in the reward mechanism with suppressed food intake, heightened physical activity, and mood disorder. Surprisingly, the plasma levels of ghrelin, an orexigenic hormone that drives food-motivated behavior, are increased. This increase in plasma ghrelin levels seems paradoxical in light of the restrained eating adopted by AN patients, and may rather result from an adaptation to the disease. The aim of this review is to describe the role played by ghrelin in AN focusing on its central vs. peripheral actions. In AN patients and in rodent AN models, chronic food restriction induces profound alterations in the « ghrelin » signaling that leads to the development of inappropriate behaviors like hyperactivity or addiction to food starvation and therefore a greater depletion in energy reserves. The question of a transient insensitivity to ghrelin and/or a potential metabolic reprograming is discussed in regard of new clinical treatments currently investigated.

Concomitant release of ventral tegmental acetylcholine and accumbal dopamine by ghrelin in rats

Ghrelin, an orexigenic peptide, regulates energy balance specifically via hypothalamic circuits. Growing evidence suggest that ghrelin increases the incentive value of motivated behaviours via activation of the cholinergic-dopaminergic reward link. It encompasses the cholinergic afferent projection from the laterodorsal tegmental area (LDTg) to the dopaminergic cells of the ventral tegmental area (VTA) and the mesolimbic dopamine system projecting from the VTA to nucleus accumbens (N.Acc.). Ghrelin receptors (GHS-R1A) are expressed in these reward nodes and ghrelin administration into the LDTg increases accumbal dopamine, an effect involving nicotinic acetylcholine receptors in the VTA. The present series of experiments were undertaken directly to test this hypothesis. Here we show that ghrelin, administered peripherally or locally into the LDTg concomitantly increases ventral tegmental acetylcholine as well as accumbal dopamine release. A GHS-R1A antagonist blocks this synchronous neurotransmitter release induced by peripheral ghrelin. In addition, local perfusion of the unselective nicotinic antagonist mecamylamine into the VTA blocks the ability of ghrelin (administered into the LDTg) to increase N.Acc.-dopamine, but not VTA-acetylcholine. Collectively our data indicate that ghrelin activates the LDTg causing a release of acetylcholine in the VTA, which in turn activates local nicotinic acetylcholine receptors causing a release of accumbal dopamine. Given that a dysfunction in the cholinergic-dopaminergic reward system is involved in addictive behaviours, including compulsive overeating and alcohol use disorder, and that hyperghrelinemia is associated with such addictive behaviours, ghrelin-responsive circuits may serve as a novel pharmacological target for treatment of alcohol use disorder as well as binge eating.

Serum leptin is not correlated with body fat in severe food restriction

Leptin is an adipose-derived hormone with established roles in energy balance that can impact the response to refeeding after malnutrition. Although the amount of circulating leptin has traditionally been associated with the amount of adipose tissue, controversy exists as to whether this relationship is constant in both humans and animals and over a wide range of body composition. Our objective was to evaluate whether the leptin - body fat ratio is constant in the range of healthy to low body mass in female Wistar rats. Eight ad libitum fed (C) and eight food-restricted (FR) rats were compared over a period of four weeks. FR rats attained the target 75% of baseline body mass after the first two weeks, which was maintained for the remaining two weeks. Serum leptin and IGF-1 (ELISA) and body composition (DXA) were measured at baseline (t(0)) and once weekly for the remainder of the study (t(1)-t(4)). The leptin - body fat ratio was reduced during the two-week period of weight loss (t(0) = 0.036 ± 0.016 (ng·mL(-1))·g(-1) vs. t(1) = 0.010 ± 0.004 (ng·mL(-1))·g(-1) and t(2) = 0.015 ± 0.007 (ng·mL(-1))·g(-1), p < 0.05). Leptin concentration plateaued at its nadir (~0.24 (ng·mL(-1))·g(-1)) at fat mass < 22 g. IGF-1 was correlated with lean mass (r = 0.45, p < 0.05) and fat mass (r = 0.58, p < 0.05), regardless of body mass. We concluded that the leptin - body fat ratio was reduced early in food restriction and the correlation between these two variables was absent at low body fat.

The role of ghrelin, salivary secretions, and dental care in eating disorders

Eating disorders, including anorexia and bulimia nervosa, are potentially life-threatening syndromes characterized by severe disturbances in eating behavior. An effective treatment strategy for these conditions remains to be established, as patients with eating disorders tend to suffer from multiple relapses. Because ghrelin was originally discovered in the stomach mucosa, it has been widely studied over the past decade in an effort to uncover its potential roles; these studies have shed light on the mechanism by which ghrelin regulates food intake. Thus, studying ghrelin in the context of eating disorders could improve our understanding of the pathogenesis of eating disorders, possibly resulting in a promising new pharmacological treatment strategy for these patients. In addition, early detection and treatment of eating disorders are critical for ensuring recovery of young patients. Oral symptoms, including mucosal, dental, and saliva abnormalities, are typically observed in the early stages of eating disorders. Although oral care is not directly related to the treatment of eating disorders, knowledge of the oral manifestations of eating disorder patients may aid in early detection, resulting in earlier treatment; thus, oral care might contribute to overall patient management and prognosis. Moreover, ghrelin has also been found in saliva, which may be responsible for oral hygiene and digestion-related functions. This review discusses the pharmacological potential of ghrelin in regulating food-intake and the role of saliva and oral care in young patients with eating disorders.

From disordered eating to addiction: the "food drug" in bulimia nervosa

The high prevalence of substance abuse in individuals with bulimia nervosa (BN) and the pervasive symptom substitution in many types of drug addiction suggest that a number of substances--including food--can impair an individual's self-control, even in the presence of negative consequences. Nonetheless, the neurobiological similarities between BN and drug addiction are not clearly established. This review explores how the specific eating patterns seen in BN (binge eating and purging, with intermittent dietary restriction) are particularly addictive and differentiate BN from other eating disorders and obesity. A number of peripheral and central biological aberrations seen in BN may result in altered reward sensitivity in these individuals, particularly through effects on the dopaminergic system. Neurobiological findings support the notion that BN is an addictive disorder, which has treatment implications for therapy and pharmacological manipulations.

Role of ghrelin in the pathophysiology of eating disorders: implications for pharmacotherapy

Ghrelin is the only known circulating orexigenic hormone. It increases food intake by interacting with hypothalamic and brainstem circuits involved in energy balance, as well as reward-related brain areas. A heightened gut-brain ghrelin axis is an emerging feature of certain eating disorders such as anorexia nervosa and Prader-Willi syndrome. In common obesity, ghrelin levels are lowered, whereas post-meal ghrelin levels remain higher than in lean individuals. Agents that interfere with ghrelin signalling have therapeutic potential for eating disorders, including obesity. However, most of these drugs are only in the preclinical phase of development. Data obtained so far suggest that ghrelin agonists may have potential in the treatment of anorexia nervosa, while ghrelin antagonists seem promising for other eating disorders such as obesity and Prader-Willi syndrome. However, large clinical trials are needed to evaluate the efficacy and safety of these drugs.

Ghrelin receptor (GHS-R1A) antagonism suppresses both operant alcohol self-administration and high alcohol consumption in rats

The mechanisms involved in alcohol use disorders are complex. It has been shown that ghrelin is an important signal for the control of body weight homeostasis, preferably by interacting with hypothalamic circuits, as well as for drug reward by activating the mesolimbic dopamine system. The ghrelin receptor (GHS-R1A) has been shown to be required for alcohol-induced reward. Additionally, ghrelin increases and GHR-R1A antagonists reduce moderate alcohol consumption in mice, and a single nucleotide polymorphism in the GHS-R1A gene has been associated with high alcohol consumption in humans. However, the role of central ghrelin signaling in high alcohol consumption is not known. Therefore, the role of GHS-R1A in operant self-administration of alcohol in rats as well as for high alcohol consumption in Long-Evans rats and in alcohol preferring [Alko alcohol (AA)] rats was studied here. In the present study, the GHS-R1A antagonist, JMV2959, was found to reduce the operant self-administration of alcohol in rats and to decrease high alcohol intake in Long-Evans rats as well as in AA rats. These results suggest that the ghrelin receptor signaling system, specifically GHS-R1A, is required for operant self-administration of alcohol and for high alcohol intake in rats. Therefore, the GHS-R1A may be a therapeutic target for treatment of addictive behaviors, such as alcohol dependence.

Ghrelin and anorexia nervosa: a psychosomatic perspective

Anorexia nervosa (AN) is a serious medical illness associated with gastrointestinal, metabolic, and psychological complications, and there are no effective pharmacologic treatments for the condition. Recent studies have suggested that the regulatory peptides, including ghrelin, are involved in the pathologic feeding behavior of AN. Previous studies have indicated that plasma total ghrelin and acyl ghrelin levels in patients with AN are higher than in controls, and the ratio of des-acyl ghrelin to acyl ghrelin in AN tend to be higher than in controls. In addition, ghrelin has been reported to stimulate appetite and food intake in various diseases, including chronic heart failure, chronic obstructive pulmonary disease, and cancer. Because it is speculated that difficulties in resolving the underlying psychological condition preclude reversal of the pathologic feeding behavior in AN, ghrelin is expected to be applied in a clinical setting as a new treatment. In this review, we describe the role of ghrelin in the pathophysiology and potential treatment of AN along the gut-brain axis.

Serum amylase in bulimia nervosa and purging disorder: differentiating the association with binge eating versus purging behavior

OBJECTIVE

Elevated serum amylase levels in bulimia nervosa (BN), associated with increased salivary gland size and self-induced vomiting in some patients, provide a possible marker of symptom severity. The goal of this study was to assess whether serum hyperamylasemia in BN is more closely associated with binge eating episodes involving consumption of large amounts of food or with purging behavior.

METHOD

Participants included women with BN (n=26); women with "purging disorder" (PD), a subtype of EDNOS characterized by recurrent purging in the absence of objectively large binge eating episodes (n=14); and healthy non-eating disorder female controls (n=32). There were no significant differences in age or body mass index (BMI) across groups. The clinical groups reported similar frequency of self-induced vomiting behavior and were free of psychotropic medications. Serum samples were obtained after overnight fast and were assayed for alpha-amylase by enzymatic method.

RESULTS

Serum amylase levels were significantly elevated in BN (60.7±25.4 international units [IU]/liter, mean±sd) in comparison to PD (44.7±17.1 IU/L, p<.02) and to Controls (49.3±15.8, p<.05).

CONCLUSION

These findings provide evidence to suggest that it is recurrent binge eating involving large amounts of food, rather than self-induced vomiting, which contributes to elevated serum amylase values in BN.

Serum amylase and risk of the metabolic syndrome in Korean adults

BACKGROUND

Serum amylase has recently been shown to be associated with ghrelin and adiponectin as well as obesity. We investigated the relationship between total amylase and metabolic syndrome in adults.

METHODS

4495 adults were enrolled. All subjects denied any medical history or status of a disorder that could influence their serum amylase. Anthropometry, metabolic risk factors and total amylase concentration were measured. Each participant was categorized into one of 4 subgroups according to their total amylase concentration. Multiple logistic regression analysis was used to assess the independent association between amylase concentration and metabolic syndrome. Receiver-operating characteristics (ROC) curves analyses were used for comparison of the diagnostic value of amylase and other biomarkers for metabolic syndrome.

RESULTS

The prevalence of metabolic syndrome by the National Cholesterol Education Program criteria was 13.4%, 15.3%, 19.3%, and 24.2% of those in the fourth, third, second, and lowest quartile of amylase concentration (P for trend <0.001). After adjusting for age, sex, and body mass index, the odds ratios of the lower quartiles were significantly higher compared to the fourth quartile for the presence of metabolic syndrome. In ROC curve analysis, amylase was similar to uric acid as a significant diagnostic indicator for metabolic syndrome, but it had lower diagnostic value than alanine aminotransferase, γ-glutamyltransferase or C-reactive protein.

CONCLUSIONS

Lower amylase concentration is associated with an increased prevalence of metabolic syndrome. Amylase may contribute to identifying metabolic syndrome, although further research is needed to understand the mechanism behind these associations.

The role of the central ghrelin system in reward from food and chemical drugs

Here we review recent advances that identify a role for the central ghrelin signalling system in reward from both natural rewards (such as food) and artificial rewards (that include alcohol and drugs of abuse). Whereas ghrelin emerged as a stomach-derived hormone involved in energy balance, hunger and meal initiation via hypothalamic circuits, it now seems clear that it also has a role in motivated reward-driven behaviours via activation of the so-called "cholinergic-dopaminergic reward link". This reward link comprises a dopamine projection from the ventral tegmental area (VTA) to the nucleus accumbens together with a cholinergic input, arising primarily from the laterodorsal tegmental area. Ghrelin administration into the VTA or LDTg activates the "cholinergic-dopaminergic" reward link, suggesting that ghrelin may increase the incentive value of motivated behaviours such as reward-seeking behaviour ("wanting" or "incentive motivation"). Further, direct injection of ghrelin into the brain ventricles or into the VTA increases the consumption of rewarding foods as well as alcohol in mice and rats. Studies in rodents show beneficial effects of ghrelin receptor (GHS-R1A) antagonists to suppress the intake of palatable food, to reduce preference for caloric foods, to suppress food reward and motivated behaviour for food. They have also been shown to reduce alcohol consumption, suppress reward induced by alcohol, cocaine and amphetamine. Furthermore, variations in the GHS-R1A and pro-ghrelin genes have been associated with high alcohol consumption, smoking and increased weight gain in alcohol dependent individuals as well as with bulimia nervosa and obesity. Thus, the central ghrelin signalling system interfaces neurobiological circuits involved in reward from food as well as chemical drugs; agents that directly or indirectly suppress this system emerge as potential candidate drugs for suppressing problematic over-eating that leads to obesity as well as for the treatment of substance use disorder.

Ghrelin in eating disorders

Ghrelin is the only known circulating hormone that acts on peripheral and central targets to increase food intake and promote adiposity. The present review focuses on the possible clinical relevance of ghrelin in the regulation of human feeding behavior in individuals with obesity and other eating disorders such as Prader-Willi syndrome, anorexia nervosa, bulimia nervosa and binge-eating.

Eating disorders and gastrointestinal peptides

PURPOSE OF REVIEW

Disturbances in gastrointestinal hormones have been implicated in the pathogenesis of eating disorders such as anorexia nervosa and bulimia nervosa. However, the contribution of these hormonal changes to the onset and maintenance of eating disorder remains unclear. We focus our review on a selective number of gastrointestinal hormones that are known to play a role in the regulation of short-term or long-term energy balance and examine their association with eating disorder in recently published literature.

RECENT FINDINGS

Several new studies reported differential changes of ghrelin isoforms during fasting and following nutrient ingestion. New findings on other appetite-regulating hormones (peptide YY, cholecystokinin, incretin hormones and pancreatic polypeptide) at different nutritional states and disease stage have also been reported in subtypes of eating disorder. Most of the changes in peripheral hormones disappeared or partially recovered after the restoration of weight with nutritional and behavioral therapy.

SUMMARY

Dysregulation of gastrointestinal hormones is more likely to contribute to the maintenance of the disordered eating behavior and related metabolic outcomes as well as the clinical course rather than causing them. A better understanding of this relationship also carries implications for developing targeted hormone-base treatment for eating disorder.

Psychobiology of purging disorder: reduction in circulating leptin levels in purging disorder in comparison with controls

OBJECTIVE

Purging disorder (PD), a recently recognized eating disorder syndrome, is differentiated from bulimia nervosa (BN) based on the absence of objectively large binge episodes. BN has been associated with low serum leptin levels. This study examined whether PD is also characterized by low serum leptin.

METHOD

Participants included women with PD (n = 20) or BN (n = 37), and non-eating disorder controls (n = 33). Blood samples for measurement of leptin and total ghrelin were obtained after overnight fast.

RESULTS

In comparison with control values, leptin levels were significantly decreased in PD (p < .01), as well as in BN (p < .02). Plasma ghrelin levels did not differ significantly across groups.

DISCUSSION

These results provide the first evidence that PD is associated with alteration in a neurobiological pathway influencing eating patterns and body weight. Further research is needed to assess whether low leptin levels in PD and BN are associated with restrained eating and weight suppression.

Ghrelin gene products and the regulation of food intake and gut motility

A breakthrough using "reverse pharmacology" identified and characterized acyl ghrelin from the stomach as the endogenous cognate ligand for the growth hormone (GH) secretagogue receptor (GHS-R) 1a. The unique post-translational modification of O-n-octanoylation at serine 3 is the first in peptide discovery history and is essential for GH-releasing ability. Des-acyl ghrelin, lacking O-n-octanoylation at serine 3, is also produced in the stomach and remains the major molecular form secreted into the circulation. The third ghrelin gene product, obestatin, a novel 23-amino acid peptide identified from rat stomach, was found by comparative genomic analysis. Three ghrelin gene products actively participate in modulating appetite, adipogenesis, gut motility, glucose metabolism, cell proliferation, immune, sleep, memory, anxiety, cognition, and stress. Knockdown or knockout of acyl ghrelin and/or GHS-R1a, and overexpression of des-acyl ghrelin show benefits in the therapy of obesity and metabolic syndrome. By contrast, agonism of acyl ghrelin and/or GHS-R1a could combat human anorexia-cachexia, including anorexia nervosa, chronic heart failure, chronic obstructive pulmonary disease, liver cirrhosis, chronic kidney disease, burn, and postsurgery recovery, as well as restore gut dysmotility, such as diabetic or neurogenic gastroparesis, and postoperative ileus. The ghrelin acyl-modifying enzyme, ghrelin O-Acyltransferase (GOAT), which attaches octanoate to serine-3 of ghrelin, has been identified and characterized also from the stomach. To date, ghrelin is the only protein to be octanylated, and inhibition of GOAT may have effects only on the stomach and is unlikely to affect the synthesis of other proteins. GOAT may provide a critical molecular target in developing novel therapeutics for obesity and type 2 diabetes.

New frontiers in endocrinology of eating disorders

Alterations of both central and peripheral feeding regulatory substances occur in the acute phases of anorexia nervosa (AN) and bulimia nervosa (BN) and, generally, reverse after recovery. Some of these alterations are believed not only to sustain the altered eating behavior but also to contribute to certain psychopathological aspects and/or etiopathogenetic processes of eating disorders (EDs). It has been suggested that EDs are clinical conditions linked to reward-related mechanisms leading to a kind of addiction to self-starvation and/or overeating. Most of the feeding regulatory substances, which are dysregulated in EDs, are also implicated in the modulation of reward, emotional, and cognitive functions, thus representing possible links between altered nutritional regulation, motivated behaviors and reward processes. In this chapter, the ED literature dealing with ghrelin, brain-derived neurotrophic factor, opioid peptides, and endocannabinoids, which have prominent effects on eating behavior, body weight, reward, emotional, and cognitive functions, is reviewed in view of the above suggested links. Moreover, the potential therapeutics of new medications developed on the basis of neuroendocrine aberrations found in EDs is also presented.

The validity and utility of subtyping bulimia nervosa

OBJECTIVE

To review the evidence for the validity and utility of subtyping bulimia nervosa (BN) into a purging (BN-P) and a nonpurging subtype (BN-NP), and of distinguishing BN-NP from binge eating disorder (BED), by comparing course, complications, and treatment.

METHOD

A literature search of psychiatry databases for studies published in peer-reviewed journals that used the DSM-definitions of BN and BED, and included both individuals with BN-NP and individuals with BN-P and/or BED.

RESULTS

Twenty-three studies compared individuals with BN-NP (N = 671) to individuals with BN-P (N = 1795) and/or individuals with BED (N = 1921), two of which reported on course, 12 on comorbidity and none on treatment response-the indicators for validity and clinical utility. The differences found were mainly quantitative rather than qualitative, suggesting a gradual difference in severity from BN-P (most severe) through BN-NP to BED (least severe).

DISCUSSION

None of the comparisons provided convincing evidence for the validity or utility of the BN-NP diagnosis. Three options for the position of BN-NP in DSM-V were suggested: (1) maintaining the BN-NP subtype, (2) dropping nonpurging compensatory behavior as a criterion for BN, so that individuals currently designated as having BN-NP would be designated as having BED, and (3) including BN-NP in a broad BN category.

Repeated binge access to a palatable food alters feeding behavior, hormone profile, and hindbrain c-Fos responses to a test meal in adult male rats

Repetitive cycles of palatable food access and chronic calorie restriction alter feeding behaviors and forebrain neural systems. The purpose of this study was to determine the behavioral, endocrine, and meal-related hindbrain neural activation in adult male Sprague-Dawley rats exposed to a binge-access feeding schedule. The binge-access schedule consisted of repeated twice-per-week episodes of acute calorie restriction (to one-third of the previous day's intake) followed by 2 h of concurrent access to high-calorie palatable food (sweetened fat: 90% vegetable shortening-10% sucrose) and chow. The binge-access rats consumed more calories during the "binge" period than rats with continuous access to sweetened fat (continuous-access group) or subjected to repeated acute calorie restriction only (chow-restricted group). The binge-access group also exhibited a approximately 25% increase in sweetened fat intake from week 1 to week 6. Persistence of the binge phenotype in the binge-access animals was demonstrated 2 wk, but not 4 wk, after ad libitum chow. The binge-access and chow-restricted groups maintained a similar normal body composition and hormonal profiles, whereas the continuous-access animals developed an obese phenotype. Terminal ghrelin levels were significantly higher in the binge-access group than in the continuous-access group. Consumption of a standardized meal resulted in more c-Fos-positive cells along the anterior-posterior nucleus of the solitary tract regions in the binge-access group than in naive controls. These results suggest that repeated cycles of acute calorie restriction followed by palatable food produce physiological alterations that may facilitate overconsumption of a highly palatable food during limited-access periods.

Leptin, ghrelin, and endocannabinoids: potential therapeutic targets in anorexia nervosa

Anorexia nervosa (AN) has the highest mortality rate between psychiatric disorders, and evidence for managing it is still very limited. So far, pharmacological treatment has focused on a narrow range of drugs and only a few controlled studies have been performed. Furthermore, the studies have been of short duration and included a limited number of subjects, often heterogenic with regard to stage and acute nutritive status. Thus, novel approaches are urgently needed. Body weight homeostasis is tightly regulated throughout life. With the discovery of orexigenic and anorectic signals, an array of new molecular targets to control eating behavior has emerged. This review focuses on recent advances in three important signal systems: leptin, ghrelin, and endocannabinoids toward the identification of potential therapeutical breakthroughs in AN. Our review of the current literature shows that leptin may have therapeutic potentials in promoting restoration of menstrual cycles in weight restored patients, reducing motor restlessness in severely hyperactive patients, and preventing osteoporosis in chronic patients. Ghrelin and endocannabinoids exert orexigenic effects which may facilitate nutritional restoration. Leptin and endocannabinoids may exert antidepressive and anxiolytic effects. Finally, monitoring serum concentration of leptin may be useful in order to prevent refeeding syndrome.

Plasma obestatin, ghrelin, and ghrelin/obestatin ratio are increased in underweight patients with anorexia nervosa but not in symptomatic patients with bulimia nervosa

INTRODUCTION

Peptides of the gut-brain axis have a pivotal role in the regulation of energy homeostasis. Obestatin, a sibling of ghrelin derived from preproghrelin, is thought to oppose ghrelin effects on food intake. Because changes in ghrelin levels have been associated with anorexia nervosa (AN) and bulimia nervosa (BN), the investigation of obestatin production may further contribute to understanding the role of peripheral peptides in patients with eating disorders.

METHODS

In the present study, we measured circulating blood levels of obestatin and ghrelin and assessed their relationships with anthropometric and clinical measures in 20 AN patients, 21 BN patients, and 20 appropriate healthy controls.

RESULTS

Compared with healthy women, patients with BN showed no significant differences in plasma obestatin and ghrelin concentrations and in the ghrelin/obestatin ratio, whereas underweight AN patients displayed significantly increased circulating levels of both obestatin (P<0.009) and ghrelin (P<0.002) and an increased ghrelin/obestatin ratio (P<0.04). Moreover, in AN women, positive correlations emerged between the ghrelin/obestatin ratio and current body weight and body mass index.

CONCLUSIONS

Underweight AN patients are characterized by increased concentrations of ghrelin and obestatin and a higher ghrelin to obestatin ratio. No changes in circulating ghrelin or obestatin as well as in ghrelin to obestatin ratio seem to occur in acutely ill patients with BN. Although those changes likely reflect the physiological state of symptomatic AN individuals, they may also contribute to the pathophysiology of the disorder.

Ghrelin in pathological conditions

The recently identified gastric hormone ghrelin was initially described as a natural Growth Hormone Secretagogue Receptor ligand. Apart from ghrelin's first discovered action, which was the stimulation of Growth Hormone release, implications for many other functions have been reported. It seems that ghrelin exhibits an important role in conditions related to processes regulating nutrition, body composition and growth, as well as heart, liver, thyroid or kidney dysfunction. In this review, current available knowledge about ghrelin's role in various pathological conditions is presented.

Neuroendocrine dysregulation of food intake in eating disorders

Anorexia nervosa (AN) and bulimia nervosa (BN) are psychiatric disorders characterized by abnormal eating behaviors and imbalance of energy homeostasis. Changes of both central and peripheral neuroendocrine substances involved in the modulation of food intake and energy expenditure have been described in acutely ill patients with eating disorders. This review selectively focuses on the most recent findings supporting abnormal changes in the physiology of some peripheral adipokines and gut-secreted peptides, brain-derived neurotrophic factor and endocannabinoids in patients with AN or BN. Literature data do suggest a dysregulation of these neuroendocrine feeding regulators but, at the moment, they do not allow to establish the state or trait-dependent nature of those aberrations. It has been proposed, although not definitively proved, that neuroendocrine alterations, even when secondary to malnutrition and/or to aberrant eating behaviors, might contribute to the genesis and the maintenance of some symptomatic aspects of AN and BN, thus affecting the course and the prognosis of these disorders. Future studies should clarify whether neuroendocrine alterations are part of the genetically transmitted biological vulnerability to eating disorders.

No differences are seen in the regional cerebral blood flow in the restricting type of anorexia nervosa compared with the binge eating/purging type

AIMS

Anorexia nervosa (AN) is subdivided into the restricting type (AN-R) and the binge-eating/purging type (AN-BP), but differences in cerebral blood flow between patients with these types of AN and healthy controls have not been investigated.

METHODS

The present study was designed to elucidate any such differences using resting single photon emission computed tomography (SPECT) studies to compare the differences in cerebral perfusion among both types of AN and a healthy control group. Resting regional cerebral blood flow was assessed using SPECT with technetium-99m hexamethylpropyleneamine oxime in 13 female AN-R patients, 13 female AN-BP patients, and 10 healthy women as controls with 3-D stereotactic surface projections.

RESULTS

The analytic program of the SPECT images showed bilateral decreased perfusion of the subcallosal gyrus (SCG), midbrain and posterior cingulate gyrus (PCG) in both AN-R and AN-BP patients, as compared with the controls. There were no clear differences between the AN-R and AN-BP groups. There were no significant differences in cerebral blood flow between patients with AN-R and AN-BP.

CONCLUSIONS

Abnormalities of the neuronal circuits containing the SCG, midbrain and PCG are possibly relevant to trait-related AN.

Meal-induced compositional changes in blood and saliva in persons with bulimia nervosa

BACKGROUND

Binge eating episodes in persons with bulimia nervosa may to some extent be a result of disturbed sensations of hunger and satiety. It has been hypothesized that abnormal appetite sensations may be due to bulimia nervosa-related alterations in the release of hormones that are known to be involved in the physiologic regulation of appetite and metabolism.

OBJECTIVE

The objective was to investigate whether circulating concentrations of the appetite-regulating peptides leptin and ghrelin and markers of metabolism (glucose and insulin) are different in persons with bulimia nervosa than in controls before and after intake of a meal and whether these changes may be reflected in saliva.

DESIGN

Twenty women with bulimia nervosa and 20 age- and sex-matched healthy controls participated. After an overnight fast, the subjects ate a standardized carbohydrate-rich breakfast. Whole saliva and blood were collected, and visual analogue scales for hunger and satiety were completed once before and continuously for 5 h after the breakfast.

RESULTS

A lower pre- and postprandial whole saliva flow rate was found in subjects with bulimia nervosa, which might have been attributable to a concomitant intake of potentially xerogenic medication. Subjects with bulimia nervosa experienced reduced hunger, which could not be explained by pre- or postprandial alterations in circulating ghrelin, leptin, insulin, or glucose concentrations.

CONCLUSIONS

There were no apparent differences in the composition of blood and saliva between bulimia nervosa and control subjects, and meal-induced compositional changes in blood were not directly mirrored in saliva composition.

Elevated ghrelin level in women of normal weight with amenorrhea is related to disordered eating

OBJECTIVE

To determine whether women of normal weight with hypothalamic amenorrhea have elevated ghrelin levels when compared with controls matched for metabolic parameters and whether this elevation is related to disordered eating patterns.

DESIGN

Controlled clinical study.

SETTING

Healthy volunteers in an academic research environment.

PATIENT(S)

Twelve subjects of normal weight with functional hypothalamic amenorrhea, 22 exercising controls, and 5 sedentary controls.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Ghrelin level and eating behavior.

RESULT(S)

The group with functional hypothalamic amenorrhea did not differ from the exercising control group or the sedentary control group with respect to body weight, body fat, and leptin levels. However, ghrelin level showed a significant positive correlation with Eating Attitudes Test (EAT)-40 scores (r = 0.475) at an EAT score > or =10 in all three groups. Eighty-three percent of patients with functional hypothalamic amenorrhea had EAT-40 levels >10.

CONCLUSION(S)

Elevated EAT scores associated with high ghrelin level may represent dietary behaviors that perpetuate reproductive dysfunction. Thus ghrelin may act as a restraining metabolic signal preventing a return to cyclicity in women with disordered eating and of normal weight and body fat.

Incomplete restoration of the secretion of ghrelin and PYY compared to insulin after food ingestion following weight gain in anorexia nervosa

BACKGROUND

In humans, ghrelin has been found to stimulate appetite while PYY3-36 to reduce it; these orexigenic and anorexigenic peptides play significant roles in appetite control. We investigated pre- and postprandial responses of ghrelin and PYY in anorexia nervosa (AN) and the influence of weight gain.

METHODS

Plasma ghrelin, PYY3-36, glucose and insulin responses after ingestion of a 400 kcal standard meal were measured in 14 patients with restricting type of AN and 12 controls. The AN patients were evaluated before therapy and after inpatient therapy. Psychometry was performed by the use of Eating Disorders Inventory.

RESULTS

Ghrelin was suppressed during the meal test, while PYY3-36 was increased in all of the groups. Before therapy, AN patients had significantly increased levels of ghrelin and PYY3-36 compared to the control (P<0.01). After therapeutic intervention, as the nutritional status of AN patients improved, the secretion of these hormones were increased (P<0.05), but not normalized as in psychological testing. In contrast, insulin and glucose responses were normalized after inpatient therapy.

CONCLUSIONS

We found that both ghrelin and PYY3-36 increased in AN patients and these changes were not normalized in contrast to insulin after treatment. The increase in both orexigenic ghrelin and anorexigenic PYY3-36 may have a role in pathological eating behavior in AN.

Ghrelin and leptin levels in patients with obsessive-compulsive disorder

To examine the importance of ghrelin and leptin in the pathogenesis of obsessive-compulsive disorder (OCD), we measured serum ghrelin and leptin levels, lipid profile and body mass index (BMI) in 43 patients with OCD and 20 healthy controls. The patients were divided into two subgroups according to whether DSM-IV OCD was accompanied with major depressive disorder (MDD) (OCD+MDD) or not (OCD-MDD). There was no statistically significant difference in ghrelin and leptin levels between groups. The OCD+MDD group had a trend of higher ghrelin levels and lower leptin levels than the OCD-MDD and control groups. There was a negative correlation between change in serum ghrelin and leptin levels only in the OCD+MDD group. Neither ghrelin nor leptin showed any correlation with severity of MDD and OCD. In conclusion, our results suggest that OCD is not associated with leptin or ghrelin levels. More comprehensive and detailed studies are needed to decipher the exact role of ghrelin and leptin in OCD.