123I-ADAM SPECT imaging of serotonin transporter binding in patients with night eating syndrome: a preliminary report

Serotonin transporter imaging agent as a probe for β-cells of pancreas

OBJECTIVE

Diabetes mellitus (DM) is one of the major diseases in the world. Nuclear medicine imaging may be able to detect functional status of pancreatic β cells in vivo, which might elucidate the pathological mechanisms of diabetes and develop individualized treatment plans. In this study, we evaluated the ability of [125I]ADAM, a serotonin transporter (SERT) imaging agent, as a probe for detecting pancreatic β-cell mass (BCM).

METHODS

In vitro cell studies were evaluated in INS-1 cells (rat islet β cell line). Biodistribution studies were performed in male normal Sprague-Dawley rats and alloxan-induced type 1 diabetes mellitus (T1DM) rats. Distribution and expression of SERT protein in pancreas of rats were also measured by immunofluorescence staining and Western blot.

RESULTS

In vitro cell studies showed that the concentration of [125I]ADAM associated with the INS-1 cells was increased gradually with incubation time, and the SERT specific inhibitor, escitalopram, exhibited the inhibitory effect on this interaction. Biodistribution studies also showed that the uptake of [125I]ADAM in the pancreas of normal rats was decreased in the presence of escitalopram. However, in the T1DM rat model with a significant β cells reduction, the uptake of pancreas was increased when compared with the control. Through immunofluorescence staining and Western blot, it was found that both the endocrine and exocrine cells of the normal pancreas expressed SERT protein, and the level of SERT protein in the exocrine cells was higher than islets. In the diabetic state, the expression of SERT in the exocrine cells was further increased.

CONCLUSIONS

The SERT imaging agent, [125I]ADAM, at the present form will not be suitable for imaging β cells, specifically because there were extraordinarily high non-specific signals contributing from the exocrine cells of pancreas. In addition, we noticed that the level of SERT expression was abnormally elevated in the diabetic state, which might provide an unexpected target for studying the pathological mechanisms of diabetes.

Radiotracers for the Central Serotoninergic System

This review lists the most important radiotracers described so far for imaging the central serotoninergic system. Single-photon emission computed tomography and positron emission tomography radiotracers are reviewed and critically discussed for each receptor.

Diagnosing a nocturnal eating disorder in an average-weight man

A middle-aged man of average weight presented to the sleep medicine clinic for multiple episodes of nocturnal eating during night-time awakenings for the past several months. His symptoms were more characteristic of night eating syndrome rather than sleep-related eating disorder because of his recollection of the eating episodes and intake of edible substances during these episodes. He was treated with a low dose of sertraline with an initial improvement of symptoms followed by a relapse that was controlled with an increased dose. A year after initiation of therapy, his symptoms have resolved.

'In the night kitchen': A scoping review on the night eating syndrome

BACKGROUND

First described in 1955, night eating syndrome refers to an abnormal eating behavior clinically defined by the presence of evening hyperphagia (>25% of daily caloric intake) and/or nocturnal awaking with food ingestion occurring ⩾ 2 times per week.

AIMS

Although the syndrome is frequently comorbid with obesity, metabolic and psychiatric disorders, its etiopathogenesis, diagnosis, assessment and treatment still remain not fully understood.

METHODS

This review was conducted according to PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines; PubMed database was searched until 31 October 2020, using the key terms: 'Night Eating Syndrome' AND 'complications' OR 'diagnosis' OR 'drug therapy' OR 'epidemiology' OR 'etiology' OR 'physiology' OR 'physiopathology' OR 'psychology' OR 'therapy'.

RESULTS

From a total of 239 citations, 120 studies assessing night eating syndrome met the inclusion criteria to be included in the review.

CONCLUSION

The inclusion of night eating syndrome into the Diagnostic and Statistical Manual of Mental Disorders-5 'Other Specified Feeding or Eating Disorders' category should drive the attention of clinician and researchers toward this syndrome that is still defined by evolving diagnostic criteria. The correct identification and assessment of NES could facilitate the detection and the diagnosis of this disorder, whose bio-psycho-social roots support its multifactorial nature. The significant rates of comorbid illnesses associated with NES and the overlapping symptoms with other eating disorders require a focused clinical attention. Treatment options for night eating syndrome include both pharmacological (selective serotonin reuptake inhibitors, topiramate and melatonergic drugs) and non-pharmachological approaches; the combination of such strategies within a multidisciplinary approach should be addressed in future, well-sized and long-term studies.

Sleep Quality and Eating Disorder-Related Psychopathologies in Patients with Night Eating Syndrome and Binge Eating Disorders

Night eating syndrome (NES) is an eating disorder (ED) characterized by nocturnal ingestion (NI), evening hyperphagia, morning anorexia, as well as mood and sleep disturbances. This study compared subjective and objective sleep quality and ED-related psychopathologies in patients seeking treatment for ED. Method: The sample was composed of 170 women, aged 18–68, who were referred for an ED assessment from 2011 to 2020. The participants were divided into three subgroups: NES-NI only (n = 30), NES+ binge eating (BE) (including binge eating disorders or bulimia nervosa (n = 52), and BE-only (n = 88). The measures consisted of a psychiatric evaluation, objective sleep monitoring measured by an actigraph for 1 week, a subjective sleep self-report, and ED-related psychopathology questionnaires. Results: Objective sleep monitoring revealed significant group differences, with higher sleep efficiency in participants with BE-only and longer sleep durations for the NES-NI only group. Subjectively, the BE-only group described a significantly lower sleep quality than either the NES-NI only or the NES+BE groups. ED-related psychopathology was lower in the NES-NI-only group. A stepwise linear regression revealed that general psychopathology (the brief symptom inventory total score) was a significant predictor of subjective sleep quality. Conclusion: NES-NI-only was correlated with less psychopathology, but with more subjective and objective sleep disturbances. These results lend weight to the supposition that NES lies on a continuum of ED psychopathologies, and that NES-NI-only appears to be a separate entity from NES+BE and BE-only in terms of its psychopathology.

Depression symptoms and night eating in young adulthood

PURPOSE

We estimated cross-sectional and longitudinal associations between depression symptoms and night eating in young adults.

METHODS

Data were drawn from a longitudinal investigation of students age 12-13 years at inception in 1999-2000, in Montreal, Canada. Depression symptoms were measured with the Depressive Symptoms Scale (DSS) 20 times from age 12 to 17, and with the Major Depression Inventory (MDI) post-high school at ages 20 and 24. Night eating was measured at age 24. The association between depression symptoms and night eating was estimated in multivariable logistic regression models adjusted for sex, age and mother university-educated.

RESULTS

9% of 829 participants (n = 77) reported night eating. In cross-sectional analysis, the adjusted odds ratio (OR) estimate for MDI scores (range 0-50) was 1.04 (1.01, 1.07). In longitudinal analyses, the OR estimates were 1.75 (1.20, 2.55) for DSS scores (range 1-4) and 1.03 (1.002, 1.06) for the MDI.

CONCLUSIONS

Depression symptoms are associated with night eating in young adults cross-sectionally and possibly longitudinally. Treatment of depression symptoms may be important in preventing night eating, a core symptom of the Night Eating Syndrome.

LEVEL OF EVIDENCE

Level III, cohort analytic study.

Night-Eating Syndrome and Depressive Symptoms in College Freshmen: Fitness Improvement Tactics in Youths (FITYou) Project

Background

Emerging evidence has shown that night-eating syndrome is correlated to depressive symptoms. However, these studies were mainly small-scale investigations.

Purpose

This study aimed to examine the association of night-eating syndrome with depressive symptoms among college students using a large-scale sample.

Methods

A cross-sectional study, which was a part of the Fitness Improvement Tactics in Youth Project, was conducted in 2017. The current study included 3278 college freshmen from Shenyang, China. They completed self-administered questionnaires and provided their sociodemographic and lifestyle information. Night-eating syndrome was assessed using the night-eating questionnaire (NEQ). Depressive symptoms were measured using the Self-rating Depression Scale (SDS).

Results

Of participants, 5.4% had night-eating syndrome (NEQ score ≥30), and 21.3% had depressive symptoms (SDS score ≥53). Prevalence of night-eating syndrome was higher in male than female students (p = 0.006). Logistic regression analysis indicated that students with night-eating syndrome had a higher prevalence of depressive symptoms than those without the syndrome after adjusting covariates (odds ratios [95% CI]: 3.28 [2.40, 4.48], p < 0.001). Consistent results were found when night-eating syndrome was defined as NEQ score ≥25. In addition, analysis of covariance showed a significant association between NEQ quartiles and SDS score (mean [95% CI]: Q1, 44.4 [43.8, 45.0]; Q2, 43.4 [42.7, 44.0]; Q3, 44.4 [43.7, 45.1]; Q4, 47.5 [46.9, 48.2], p < 0.001 for linear and quadratic trend).

Conclusion

This study showed an association between night-eating syndrome and depressive symptoms among Chinese college freshmen.

Serotonin transporter density in binge eating disorder and pathological gambling: A PET study with [11C]MADAM

Behavioral addictions, such as pathological gambling (PG) and binge eating disorder (BED), appear to be associated with specific changes in brain dopamine and opioid function, but the role of other neurotransmitter systems is less clear. Given the crucial role of serotonin in a number of psychiatric disorders, we aimed to compare brain serotonergic function among individuals with BED, PG and healthy controls. Seven BED patients, 13 PG patients and 16 healthy controls were scanned with high-resolution positron emission tomography (PET) using the serotonin transporter (SERT) tracer [¹¹C]MADAM. Both region-of-interest and voxel-wise whole brain analyses were performed. Patients with BED showed increased SERT binding in the parieto-occipital cortical regions compared to both PG and healthy controls, with parallel decreases in binding in the nucleus accumbens, inferior temporal gyrus and lateral orbitofrontal cortex. No differences between PG patients and controls were observed. None of the subjects were on SSRI medications at the time of imaging, and there were no differences in the level of depression between PG and BED patients. The results highlight differences in brain SERT binding between individuals with BED and PG and provide further evidence of different neurobiological underpinnings in behavioral addictions that are unrelated to the co-existing mood disorder. The results aid in the conceptualization of behavioral addictions by characterizing the underlying serotonin changes and provide a framework for additional studies to examine syndrome-specific pharmaceutical treatments.

New Trends and Current Status of Positron-Emission Tomography and Single-Photon-Emission Computerized Tomography Radioligands for Neuronal Serotonin Receptors and Serotonin Transporter

The critical role of serotonin (5-hydroxytryptamine; 5-HT) and its receptors (5-HTRs) in the pathophysiology of diverse neuropsychiatric and neurodegenerative disorders render them attractive diagnostic and therapeutic targets for brain disorders. Therefore, the in vivo assessment of binding of 5-HT receptor ligands under a multitude of physiologic and pathologic scenarios may support more-accurate identification of disease and its progression and the patient's response to therapy as well as the screening of novel therapeutic strategies. The present Review aims to focus on the current status of radioligands used for positron-emission tomography (PET) and single-photon-emission computerized tomography (SPECT) imaging of human brain serotonin receptors. We further elaborate upon and emphasize the attributes that qualify a radioligand for theranostics on the basis of its frequency of use in clinics, its benefit to risk assessment in humans, and its continuous evolution, along with the major limitations.

Albert J. Stunkard: His Research on Obesity and Its Psychological Impact

Albert J. ("Mickey") Stunkard, MD, was a leader in the field of obesity research, with his work spanning more than five decades. He published several groundbreaking findings on the psychosocial influences of obesity, the genetics of obesity, and the relationship between obesity and factors such as socioeconomic status, stigma, and mood. He also helped establish two eating disorders associated with obesity-binge eating disorder and night eating syndrome. This paper highlights his work and its implications for the field.

Serotonin, a possible intermediate between disturbed circadian rhythms and metabolic disease

It is evident that eating in misalignment with the biological clock (such as in shift work, eating late at night and skipping breakfast) is associated with increased risk for obesity and diabetes. The biological clock located in the suprachiasmatic nucleus dictates energy balance including feeding behavior and glucose metabolism. Besides eating and sleeping patterns, glucose metabolism also exhibits clear diurnal variations with higher blood glucose concentrations, glucose tolerance and insulin sensitivity prior to waking up. The daily variation in plasma glucose concentrations in rats, is independent of the rhythm in feeding behavior. On the other hand, feeding itself has profound effects on glucose metabolism, but differential effects occur depending on the time of the day. We here review data showing that a disturbed diurnal eating pattern results in alterations in glucose metabolism induced by a disrupted circadian clock. We first describe the role of central serotonin on feeding behavior and glucose metabolism and subsequently describe the effects of central serotonin on the circadian system. We next explore the interaction between the serotonergic system and the circadian clock in conditions of disrupted diurnal rhythms in feeding and how this might be involved in the metabolic dysregulation that occurs with chronodisruption.

Optimal management of night eating syndrome: challenges and solutions

Night Eating Syndrome (NES) is a unique disorder characterized by a delayed pattern of food intake in which recurrent episodes of nocturnal eating and/or excessive food consumption occur after the evening meal. NES is a clinically important disorder due to its relationship to obesity, its association with other psychiatric disorders, and problems concerning sleep. However, NES often goes unrecognized by both health professionals and patients. The lack of knowledge regarding NES in clinical settings may lead to inadequate diagnoses and inappropriate treatment approaches. Therefore, the proper diagnosis of NES is the most important issue when identifying NES and providing treatment for this disorder. Clinical assessment tools such as the Night Eating Questionnaire may help health professionals working with populations vulnerable to NES. Although NES treatment studies are still in their infancy, antidepressant treatments and psychological therapies can be used for optimal management of patients with NES. Other treatment options such as melatonergic medications, light therapy, and the anticonvulsant topiramate also hold promise as future treatment options. The purpose of this review is to provide a summary of NES, including its diagnosis, comorbidities, and treatment approaches. Possible challenges addressing patients with NES and management options are also discussed.

Small-animal single-photon emission computed tomographic imaging of the brain serotoninergic systems in wild-type and mdr1a knockout rats

The pharmacokinetic properties of radiotracers are crucial for successful in vivo single-photon emission computed tomographic (SPECT) imaging. Our goal was to determine if MDR1A-deficient animals could allow better SPECT imaging outcomes than wild-type (WT) animals for a selection of serotoninergic radioligands. Thus, we compared the performances of 123I-p-MPPI, 123I-R91150, 123I-SB207710, and 123I-ADAM radioligands, for imaging of their respective targets (5-hydroxytryptamine [5-HT]1A, 5-HT2A, 5-HT4, and serotonin transporter [SERT]), in WT and Mdr1a knockout (KO) rats. With 123I-SB207710, virtually no SPECT signal was recorded in the brain of WT or KO animals. For 123I-p-MPPI, low nondisplaceable binding potentials (BPND, mean ± SD) were observed in WT (0.49 ± 0.25) and KO (0.89 ± 0.52) animals. For 123I-ADAM, modest imaging contrast was observed in WT (1.27 ± 0.02) and KO (1.31 ± 0.09) animals. For 123I-R91150, the BPND were significantly higher in Mdr1a KO (3.98 ± 0.65) animals compared to WT animals (1.22 ± 0.26). The pharmacokinetics of 123I-SB207710 and 123I-p-MPPI do not make them ideal tracers for preclinical SPECT neuroimaging. 123I-ADAM showed adequate brain uptake regardless of Mdr1a expression and appeared suitable for preclinical SPECT neuroimaging in both animal strains. The use of Mdr1a KO animals significantly improved the brain penetration of 123I-R91150, making this animal strain an interesting option when considering SPECT neuroimaging of 5-HT2A receptors in rat.

Using the Neuroscience of Obesity, Eating Behavior, and Sleep to Inform the Neural Mechanisms of Night Eating Syndrome

The development and maintenance of night eating syndrome (NES) is likely influenced by physiological, psychological, and social factors. Within the physiological domain, neural mechanisms (e.g., neurotransmitters and specific brain region functioning) remain understudied in contrast to other eating disorders and obesity. The serotonin system has been hypothesized to contribute to NES based on one single photon emission computed tomography (SPECT) study and supportive pharmacologic treatment outcome findings, but additional neural models are plausible. Functional magnetic resonance imaging (fMRI) is a brain imaging tool that is increasingly being used to study obesity, eating behavior, and sleep. Converging data from these literatures using food motivation and decision making fMRI paradigms suggest that the prefrontal and limbic brain systems might also play a role in the development and/or maintenance of NES. We use these data to support a new neural model of NES for future testing and validation.

Characterization of FlipIDAM as a SERT-selective SPECT imaging agent

INTRODUCTION

Biological evaluation of ([(125)I]4), a new single-photon emission computed tomography (SPECT) radioligand for imaging the serotonin transporter (SERT) which displayed improved in vivo kinetics for mapping SERT binding sites in the brain.

METHODS

In vitro binding studies of [(125)I]4 were performed with membrane homogenates of LLC-PK1 cells stably transfected and overexpressing one of the monoamine transporter (SERT, DAT or NET) and rat cortical homogenates. Biodistribution and ex vivo autoradiography studies were carried out in rats. In vivo competition experiments were evaluated to determine the SERT selectivity of [(125)I]4 vs. ([(125)I]1).

RESULTS

In vitro binding studies of 4 showed excellent binding affinity (Ki,SERT=0.90 ± 0.05 nM) and excellent selectivity over the other monoamine transporters (100 fold and >4000 fold for NET and DAT respectively). Scatchard analysis of saturation binding of [(125)I]4 to rat cortical homogenates gave a Kd value of 0.5 ± 0.09 nM and a Bmax value of 801.4 ± 58.08 fmol/mg protein. The biodistribution study showed rapid high brain uptake (3.09 ± 0.11% dose/organ at 2 min) and a good target to non-target ratio (hypothalamus to cerebellum) at 30 min (2.62) compared to [(125)I]1 (2.19). Ex vivo autoradiography showed that FlipIDAM localizes in accordance with SERT distribution patterns in the brain. In vivo and ex vivo competition experiments with specific and non-specific SERT compounds also showed that [(125)I]4 binds specifically to SERT rich regions.

CONCLUSIONS

The biological evaluation of [(125)I]4 demonstrates that [(123)I]4 would be a good candidate for SPECT imaging of SERT.

Night eating syndrome: implications for severe obesity

Night eating syndrome (NES) was first identified in 1955 by Stunkard, a psychiatrist specialising in eating disorders (ED). Over the last 20 years considerable progress has been made in defining NES as a significant clinical entity in its own right and it has now been accepted for inclusion in the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) due for publication in 2013. NES is considered a dysfunction of circadian rhythm with a disassociation between eating and sleeping. Core criteria include a daily pattern of eating with a significantly increased intake in the evening and/or night time, as manifested by one or both of the following: at least 25% of food intake is consumed after the evening meal or at least two episodes of nocturnal eating per week. An important recent addition to core criteria includes the presence of significant distress and/or impairment in functioning. Stunkard's team recommend further investigation on the pathogenesis of NES, in particular its relationship with traumatic life events, psychiatric comorbidity, the age of onset of NES and course of NES over time. The relationship between NES and other ED also requires further clarification as night-eaters exhibit some features of other ED; previous guidance to separate NES from other ED may have hindered earlier characterisation of NES. Evidence from European and American studies suggests NES features strongly in populations with severe obesity. The complex interplay between depression, impaired sleep and obesity-related comorbidity in severely obese individuals makes understanding NES in this context even more difficult. This review examines evidence to date on the characterisation of NES and concludes by examining the applicability of current NES criteria to individuals with severe obesity.

The night-eating syndrome and obesity

The rising prevalence of obesity is a global concern. Eating behaviour and circadian rhythm are proving to be important factors in the aetiology of obesity. The night-eating syndrome (NES) is characterized by increased late-night eating, insomnia, a depressed mood and distress. It is evident that prevalence is higher among weight-related populations than the general community. The exact relationship between this syndrome and obesity remains unclear. The reasons for the discrepancies found in the literature likely include varying diagnostic criteria and a wide range of study population characteristics. NES does not always lead to weight gain in thus certain individuals may be susceptible to night-eating-related weight gain. Weight loss through surgical and behavioural treatments has shown success in diminishing symptoms. The increasing literature associating obesity with circadian imbalances strengthens the link between the NES and obesity. Circadian genes may play a role in this syndrome. This review will examine different aspects of obesity in the context of the NES.

Night eating syndrome: a critical review of the literature

Clinical psychologists are increasingly called to participate in the treatment of obesity, a condition that affects about one-third of adults in the United States. A disorder gaining increased recognition for its role in the development and maintenance of obesity is Night Eating Syndrome (NES), a relatively novel disorder involving morning anorexia, evening hyperphagia and/or nocturnal ingestions, and insomnia. NES affects men and women from various racial groups and tends to run in families. NES tends to co-occur with mood, anxiety, eating, sleep, and substance use disorders and may have implications for weight and diabetes management. Relatively little is known about the successful treatment of NES. Limited evidence suggests that serotonergic-based pharmacological treatments may be beneficial. Psychological interventions, such as psychoeducation, eating modification, relaxation strategies, sleep hygiene, cognitive restructuring, physical activity, and social support facilitation may also yield beneficial results. The purpose of the present paper is to provide an introduction to NES, including diagnosis, clinical presentation, assessment, comorbidities, clinical implications, and pharmacological and psychological treatment approaches. Areas for further study and development are discussed. NES is an emerging area for clinical description, evaluation, and intervention.

Night eating syndrome: an overview

Objectives

The purpose of this review is to outline the nosographic characteristics of NES and the most reliable ethiopathogenetic theories in relation to the most recent evidence in the literature.

Key findings

The night eating syndrome (NES) is a disorder occurring at the stated time, that does not meet the criteria for any specific eating disorder. NES is characterized by a reduced feeding during the day, evening hyperphagia accompanied by frequent nocturnal awakenings associated with conscious episodes of compulsive ingestion of food and abnormal circadian rhythms of food and other neuroendocrine factors. Frequently it is associated with obesity and depressed mood. We highlight the therapeutic possibilities of some drugs, especially selective serotonin re-uptake inhibitors (SSRIs), which reduce the hyperactivity of the serotonin transporter in NES and significantly improve the clinical picture of this disease.

Conclusions

Night eating syndrome is of importance clinically because of its association with obesity. The recognition and effective treatment of NES may be an increasingly important way to treat a subset of the obese population. Treatment of the syndrome, however, is still in its infancy. One clinical trial has reported efficacy with the SSRI sertraline. Other treatments, such as the anticonvulsant topiramate, phototherapy, and other SSRIs, may also offer future promise. Particularly useful would be studies involving brain scans (magnetic resonance imaging or single-photon emission computed tomography) of patients with NES compared with the healthy population, to investigate more thoroughly the possible alterations involved in the pathogenesis of NES.

5-HT radioligands for human brain imaging with PET and SPECT

The serotonergic system plays a key modulatory role in the brain and is the target for many drug treatments for brain disorders either through reuptake blockade or via interactions at the 14 subtypes of 5-HT receptors. This review provides the history and current status of radioligands used for positron emission tomography (PET) and single photon emission computerized tomography (SPECT) imaging of human brain serotonin (5-HT) receptors, the 5-HT transporter (SERT), and 5-HT synthesis rate. Currently available radioligands for in vivo brain imaging of the 5-HT system in humans include antagonists for the 5-HT(1A), 5-HT(1B), 5-HT(2A), and 5-HT(4) receptors, and for SERT. Here we describe the evolution of these radioligands, along with the attempts made to develop radioligands for additional serotonergic targets. We describe the properties needed for a radioligand to become successful and the main caveats. The success of a PET or SPECT radioligand can ultimately be assessed by its frequency of use, its utility in humans, and the number of research sites using it relative to its invention date, and so these aspects are also covered. In conclusion, the development of PET and SPECT radioligands to image serotonergic targets is of high interest, and successful evaluation in humans is leading to invaluable insight into normal and abnormal brain function, emphasizing the need for continued development of both SPECT and PET radioligands for human brain imaging.

Night eating patterns of individuals with eating disorders: implications for conceptualizing the night eating syndrome

The prevalence, correlates, and symptom coherence of night eating syndrome (NES) in individuals seeking inpatient treatment for eating disorders were assessed. Inpatients (n=68; M age=29.8 years; % female=94.1; % diagnosed with anorexia nervosa [AN]=47.1; % diagnosed with bulimia nervosa [BN]=47.1) were interviewed with the Night Eating Syndrome History and Inventory. Additionally, medical charts were reviewed and participants completed measures of eating behavior and quality of life. NES was diagnosed in 25% of patients; significantly more patients diagnosed with BN meet criteria for NES compared to those diagnosed with AN. In general, patients with NES did not differ from patients without NES on eating behaviors, attitudes, or quality of life; symptoms of NES frequently co-occurred. This study supports previous research finding that night eating behavior is common in individuals diagnosed with eating disorders.

SPECT imaging with the serotonin transporter radiotracer [123I]p ZIENT in nonhuman primate brain

INTRODUCTION

Serotonin dysfunction has been linked to a variety of psychiatric diseases; however, an adequate SPECT radioligand to probe the serotonin transporter system has not been successfully developed. The purpose of this study was to characterize and determine the in vivo selectivity of iodine-123-labeled 2beta-carbomethoxy-3beta-(4'-((Z)-2-iodoethenyl)phenyl)nortropane, [(123)I]p ZIENT, in nonhuman primate brain.

METHODS

Two ovariohysterectomized female baboons participated in nine studies (one bolus and eight bolus to constant infusion at a ratio of 9.0 h) to evaluate [(123)I]p ZIENT. To evaluate the selectivity of [(123)I]p ZIENT, the serotonin transporter blockers fenfluramine (1.5, 2.5 mg/kg) and citalopram (5 mg/kg), the dopamine transporter blocker methylphenidate (0.5 mg/kg) and the norepinephrine transporter blocker nisoxetine (1 mg/kg) were given at 8 h post-radiotracer injection.

RESULTS

In the bolus to constant infusion studies, equilibrium was established by 4-8 h. [(123)I]p ZIENT was 93% and 90% protein bound in the two baboons and there was no detection of lipophilic radiolabeled metabolites entering the brain. In the high-density serotonin transporter regions (diencephalon and brainstem), fenfluramine and citalopram resulted in 35-71% and 129-151% displacement, respectively, whereas methylphenidate and nisoxetine did not produce significant changes (<10%).

CONCLUSION

These findings suggest that [(123)I]p ZIENT is a favorable compound for in vivo SPECT imaging of serotonin transporters with negligible binding to norepinephrine and dopamine transporters.

Rapid changes in night eating: considering mechanisms

This paper considers possible mechanisms for the Night Eating Syndrome (NES). NES is a disorder characterized by a delay in the circadian rhythm of meals and of several neuroendocrine factors. The disorder occurs in genetically vulnerable people when exposed to stress. No convincing mechanism of the NES has been reported until now. To search for the mechanisms of NES, the long term treatment of two highly perceptive patients with rapid onset of the disorder are described. Disruption of three neuroendocrine systems compatible with these histories are discussed: the glucocorticoid system, the melanocortin [corrected] system, and the serotonergic system. Current evidence favors the serotonergic system and this view is strongly supported by the great effectiveness of selective serotonin reuptake inhibitors (SSRIs) in the treatment of NES.

A biobehavioural model of the night eating syndrome

This paper will propose a biobehavioral mechanism for the Night Eating Syndrome (NES), a disorder characterized by a delayed circadian rhythm of food intake and neuroendocrine function. Food intake consists of at least 25% of daily caloric intake after the evening meal and/or at least two nighttime awakenings with ingestions per week. This will be explored by reviewing neuroimaging of brain serotonin transporters (SERT) and treatment with selective serotonin reuptake inhibitors (SSRIs). SERT binding is elevated in the midbrain of night eaters, causing dysregulation of the circadian rhythm of both food intake and neuroendocrine function. The administration of SSRIs blocks the reuptake of serotonin and restores the circadian rhythm of both food intake and neuroendocrine function. This hypothesis implies that reduction of SERT activity should increase postsynaptic serotonin transmission and relieve NES. This is precisely the effect of SSRIs. NES is a function of elevated SERT, and blocking of SERT with an SSRI resolves NES. This model of NES attests to the validity of the diagnosis of NES and the criteria by which it is identified, and it provides an explanation of the mechanism.

Biological rhythms, higher brain function, and behavior: Gaps, opportunities, and challenges

Increasing evidence suggests that disrupted temporal organization impairs behavior, cognition, and affect; further, disruption of circadian clock genes impairs sleep-wake cycle and social rhythms which may be implicated in mental disorders. Despite this strong evidence, a gap in understanding the neural mechanisms of this interaction obscures whether biological rhythms disturbances are the underlying causes or merely symptoms of mental disorder. Here, we review current understanding, emerging concepts, gaps, and opportunities pertinent to (1) the neurobiology of the interactions between circadian oscillators and the neural circuits subserving higher brain function and behaviors of relevance to mental health, (2) the most promising approaches to determine how biological rhythms regulate brain function and behavior under normal and pathological conditions, (3) the gaps and challenges to advancing knowledge on the link between disrupted circadian rhythms/sleep and psychiatric disorders, and (4) the novel strategies for translation of basic science discoveries in circadian biology to clinical settings to define risk, prevent or delay onset of mental illnesses, design diagnostic tools, and propose new therapeutic strategies. The review is organized around five themes pertinent to (1) the impact of molecular clocks on physiology and behavior, (2) the interactions between circadian signals and cognitive functions, (3) the interface of circadian rhythms with sleep, (4) a clinical perspective on the relationship between circadian rhythm abnormalities and affective disorders, and (5) the pre-clinical models of circadian rhythm abnormalities and mood disorders.

Development of criteria for a diagnosis: lessons from the night eating syndrome

Criteria for inclusion of diagnoses of Axis I disorders in the forthcoming Diagnostic and Statistical Manual (DSM-V) of the American Psychiatric Association are being considered. The 5 criteria that were proposed by Blashfield et al as necessary for inclusion in DSM-IV are reviewed and are met by the night eating syndrome (NES). Seventy-seven publications in refereed journals in the last decade indicate growing recognition of NES. Two core diagnostic criteria have been established: evening hyperphagia (consumption of at least 25% of daily food intake after the evening meal) and/or the presence of nocturnal awakenings with ingestions. These criteria have been validated in studies that used self-reports, structured interviews, and symptom scales. Night eating syndrome can be distinguished from binge eating disorder and sleep-related eating disorder. Four additional features attest to the usefulness of the diagnosis of NES: (1) its prevalence, (2) its association with obesity, (3) its extensive comorbidity, and (4) its biological aspects. In conclusion, research on NES supports the validity of the diagnosis and its inclusion in DSM-V.

Circadian rhythm profiles in women with night eating syndrome

Night eating syndrome (NES) is characterized by evening hyperphagia and frequent awakenings accompanied by food intake. Patients with NES display a delayed circadian pattern of food intake but retain a normal sleep-wake cycle. These characteristics initiated the current study, in which the phase and amplitude of behavioral and neuroendocrine circadian rhythms in patients with NES were evaluated. Fifteen women with NES (mean age +/- SD, 40.8 +/- 8.7 y) and 14 control subjects (38.6 +/- 9.5 y) were studied in the laboratory for 3 nights, with food intake measured daily. Blood also was collected for 25 h (every 2 h from 0800 to 2000 h, and then hourly from 2100 to 0900 h) and assayed for glucose and 7 hormones (insulin, ghrelin, leptin, melatonin, cortisol, thyroid-stimulating hormone [TSH] and prolactin). Statistical analyses utilized linear mixed-effects cosinor analysis. Control subjects displayed normal phases and amplitudes for all circadian rhythms. In contrast, patients with NES showed a phase delay in the timing of meals, and delayed circadian rhythms for total caloric, fat, and carbohydrate intake. In addition, phase delays of 1.0 to 2.8 h were found in 2 food-regulatory rhythms-leptin and insulin-and in the circadian melatonin rhythm (with a trend for a delay in the circadian cortisol rhythm). In contrast, circulating levels of ghrelin, the primary hormone that stimulates food intake, were phase advanced by 5.2 h. The glucose rhythm showed an inverted circadian pattern. Patients with NES also showed reduced amplitudes in the circadian rhythms of food intake, cortisol, ghrelin, and insulin, but increased TSH amplitude. Thus, patients with NES demonstrated significant changes in the timing and amplitude of various behavioral and physiological circadian markers involved in appetite and neuroendocrine regulation. As such, NES may result from dissociations between central (suprachiasmatic nucleus) timing mechanisms and putative oscillators elsewhere in the central nervous system or periphery, such as the stomach or liver. Considering these results, chronobiologic treatments for NES such as bright light therapy may be useful. Indeed, bright light therapy has shown efficacy in reducing night eating in case studies and should be evaluated in controlled clinical trials.

Differences in serotonin transporter binding affinity in patients with major depressive disorder and night eating syndrome

OBJECTIVE

We examined serotonin transporter (SERT) binding affinity using single photon emission computed tomography (SPECT) in patients with major depressive disorder (MDD) and night eating syndrome (NES). There are similarities between MDD and NES in affective symptoms, appetite disturbance, nighttime awakenings, and, particularly, response to selective serotonin reuptake inhibitors (SSRIs).

METHODS

Six non-depressed patients with NES and seven patients with MDD underwent SPECT brain imaging with 123I-ADAM, a radiopharmaceutical agent selective for SERT sites. Uptake ratios of 123I-ADAM SERT binding were obtained for the midbrain, basal ganglia, and temporal lobe regions compared to the cerebellum reference region.

RESULTS

Patients with NES had significantly greater SERT uptake ratios (effect size range 0.64-0.84) in the midbrain, right temporal lobe, and left temporal lobe regions than those with MDD whom we had previously studied.

CONCLUSIONS

Pathophysiological differences in SERT uptake between patients with NES and MDD suggest these are distinct clinical syndromes.

Psychopathology and treatment of night eating syndrome: a review

The article reviews the international literature about psychopathological aspects and treatments of Night Eating Syndrome (NES). Studies were found using Medline; data from recent international books and conferences about ED are included, but single case descriptions are not included in the study. NES seems to be consistently related to mood disorders and anxiety. There is a low overlap between other eating disorders, including binge eating disorder (BED), and NES. The relationship between the syndrome and substance abuse is unclear and needs further study. Sleep architecture seems not to be severely altered among those with NES. A limited number of treatment studies for NES have been published or presented. Most of the literature focuses on pharmacological treatment, with fewer psychotherapeutic approaches reported at this time. Larger, multi-site treatment studies would serve to confirm the findings of this first wave of clinical trials.