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

'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.

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.

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.

Change over time in brain serotonin transporter binding in major depression: effects of therapy measured with [(123) I]-ADAM SPECT

Several studies have reported low brain serotonin transporter (SERT) binding in individuals with major depression. We hypothesized that the SERT standardized uptake ratio (SUR) values using [(123) I]-ADAM single photon emission computed tomography would increase in depressed subjects who responded to cognitive behavior therapy (CBT) compared to CBT nonresponders. [(123) I]-ADAM scans were acquired before and after 12 weeks of CBT from 20 depressed subjects and on two occasions 12 weeks apart from 10 nondepressed, healthy volunteers. The primary outcome measure was change over time in SUR values in the midbrain, medial temporal lobe, and basal ganglia regions. Depressed subjects demonstrated low pretreatment mean SUR values that significantly increased over time in the midbrain (P = .011), right medial temporal lobe (P = .008), and left medial temporal lobe (P = .000) regions. Treatment responders showed a significant increase over time in SUR values in left medial temporal lobe (P = .029) and right medial temporal lobe (P = .007) regions. Partial and nonresponder subjects also showed a significant increase over time in SUR values in the left medial temporal region (P = .040) (vs. healthy volunteers), but to a lesser degree. The findings suggest that low pretreatment SERT binding may increase over time in some depressed individuals who experience symptom improvement.

Personality features of obese women in relation to binge eating and night eating

Personality traits can affect eating behaviors, the development of obesity, and obesity treatment failure. We investigated the personality characteristics and their relation with disordered eating in 586 obese women consecutively seeking treatment at eight Italian medical centers (age, 47.7±9.8 years) and 185 age-matched, normal weight women without symptoms of eating disorders (Eating Attitude Test<20). The assessment included anthropometry, the Temperament and Character Inventory (TCI), the Binge Eating Scale (BES) and the Night Eating Questionnaire (NEQ). Logistic regression analyses were carried out in different models with BES score≥27 and NEQ≥30 as dependent variables and TCI scores as independent factors. Personality traits of obese individuals included significantly lower self-directedness and cooperativeness on TCI. BES and NEQ scores were higher in obese women, and values above the defined cut-offs were present in 77 and 18 cases (14 with high BES), respectively. After controlling for age and BMI, high BES values were associated with high novelty seeking and harm avoidance and low self-directedness, the last two scales being also associated with high NEQ. We conclude that personality traits differ between obese patients seeking treatment and controls, and the presence of disordered eating is associated with specific personality characteristics.

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.

Key players in major and bipolar depression--a retrospective analysis of in vivo imaging studies

In the present study, we evaluated the contribution of the individual synaptic constituents of all assessed neurotransmitter systems by subjecting all available in vivo imaging studies on patients with unipolar major depressive disorder (MDD) and bipolar depression (BD) to a retrospective analysis. In acute MDD, findings revealed significant increases of prefrontal and frontal DA synthesis, decreases of thalamic and midbrain SERT, increases of insular SERT, decreases of midbrain 5-HT(1A) receptors and decreases of prefrontal, frontal, occipital and cingulate 5-HT(2A) receptors, whereas, in remission, decreases of striatal D₂ receptors, midbrain SERT, frontal, parietal, temporal, occipital and cingulate 5-HT(1A) receptors and parietal 5-HT(2A) receptors were observed. In BD, findings indicated a trend towards increased striatal D₂ receptors in depression and mania, decreased striatal DA synthesis in remission and decreased frontal D₁ receptors in all three conditions. Additionally, there is some evidence that ventrostriatal and hippocampal SERT may be decreased in depression, whereas in remission and mania elevations of thalamic and midbrain SERT, respectively, were observed. Moreover, in depression, limbic 5-HT(1A) receptors were elevated, whereas in mania a decrease of both cortical and limbic 5-HT(2A) receptor binding was observed. Furthermore, in depression, prefrontal, frontal, occipital and cingulate M2 receptor binding was found to be reduced. From this, a complex pattern of dysregulations within and between neurotransmitter systems may be derived, which is likely to be causally linked not only with the subtype and duration of disease but also with the predominance of individual symptoms and with the kind and duration of pharmacological treatment(s).

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.

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.

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.