Dopamine-related frontostriatal abnormalities in obesity and binge-eating disorder: emerging evidence for developmental psychopathology

Operant Training for Highly Palatable Food Alters Translating Messenger RNA in Nucleus Accumbens D2 Neurons and Reveals a Modulatory Role of Ncdn

BACKGROUND

Highly palatable food triggers behavioral responses including strong motivation. These effects involve the reward system and dopamine neurons, which modulate neurons in the nucleus accumbens (NAc). The molecular mechanisms underlying the long-lasting effects of highly palatable food on feeding behavior are poorly understood.

METHODS

We studied the effects of 2-week operant conditioning of mice with standard or isocaloric highly palatable food. We investigated the behavioral responses and dendritic spine modifications in the NAc. We compared the translating messenger RNA in NAc neurons identified by the type of dopamine receptors they express, depending on the kind of food and training. We tested the consequences of invalidation of an abundant downregulated gene, Ncdn.

RESULTS

Operant conditioning for highly palatable food increased motivation for food even in well-fed mice. In wild-type mice, free choice between regular and highly palatable food increased weight compared with access to regular food only. Highly palatable food increased spine density in the NAc. In animals trained for highly palatable food, translating messenger RNAs were modified in NAc neurons expressing dopamine D2 receptors, mostly corresponding to striatal projection neurons, but not in neurons expressing D1 receptors. Knockout of Ncdn, an abundant downregulated gene, opposed the conditioning-induced changes in satiety-sensitive feeding behavior and apparent motivation for highly palatable food, suggesting that downregulation may be a compensatory mechanism.

CONCLUSIONS

Our results emphasize the importance of messenger RNA alterations in D2 striatal projection neurons in the NAc in the behavioral consequences of highly palatable food conditioning and suggest a modulatory contribution of Ncdn downregulation.

Distinct Topological Properties of the Reward Anticipation Network in Preadolescent Children With Binge Eating Disorder Symptoms

OBJECTIVE

Few studies have considered the neural underpinnings of binge eating disorder (BED) in children, despite clinical and subclinical symptom presentation occurring in this age group. Symptom presentation at this age is of clinical relevance, as early onset of binge eating is linked to negative health outcomes. Studies in adults have highlighted dysfunction in the frontostriatal reward system as a potential candidate for binge eating pathophysiology, although the exact nature of such dysfunction is currently unclear.

METHOD

Data from 83 children (mean age 9.9 years, SD = 0.60) with symptoms of BED (57% girls) and 123 control participants (mean age 10.0 years, SD = 0.60) (52% girls) were acquired from the 4.0 baseline release of the Adolescent Brain Cognitive Development Study. Task-based graph theoretic techniques were used to analyze data from anticipation trials of the monetary incentive delay task. Network and nodal properties were compared between groups.

RESULTS

The BED-S group showed alterations in topological properties associated with the frontostriatal subnetwork, such as reduced nodal efficiency in the superior frontal gyrus, nucleus accumbens, putamen, and in normal sex-difference patterns of these properties, such as diminished girls-greater-than-boys pattern of betweenness-centrality in nucleus accumbens observed in controls.

CONCLUSION

Distinct network properties and sex-difference patterns in preadolescent children with BED-S suggest dysregulation in the reward system compared to those of matched controls. For the first time, these results quantify this dysregulation in terms of systems-level properties during anticipation of monetary reward and significantly inform the early and sex-related brain markers of BED symptoms.

Laser Scribing Turns Plastic Waste into a Biosensor via the Restructuration of Nanocarbon Composites for Noninvasive Dopamine Detection

The development of affordable and compact noninvasive point-of-care (POC) dopamine biosensors for the next generation is currently a major and challenging problem. In this context, a highly sensitive, selective, and low-cost sensing probe is developed by a simple one-step laser-scribing process of plastic waste. A flexible POC device is developed as a prototype and shows a highly specific response to dopamine in the real sample (urine) as low as 100 pmol/L in a broad linear range of 10-10-10-4 mol/L. The 3D topological feature, carrier kinetics, and surface chemistry are found to improve with the formation of high-density metal-embedded graphene-foam composite driven by laser irradiation on the plastic-waste surface. The development of various kinds of flexible and tunable biosensors by plastic waste is now possible thanks to the success of this simple, but effective, laser-scribing technique, which is capable of modifying the matrix's electronic and chemical composition.

Operant training for highly palatable food alters translating mRNA in nucleus accumbens D2 neurons and reveals a modulatory role of Neurochondrin

BACKGROUND

Highly palatable food triggers behavioral alterations reminiscent of those induced by addictive drugs. These effects involve the reward system and dopamine neurons, which modulate neurons in the nucleus accumbens (NAc). The molecular mechanisms underlying the effects of highly palatable food on feeding behavior are poorly understood.

METHODS

We studied the effects of 2-week operant conditioning of mice with standard or isocaloric highly palatable food. We investigated the behavioral effects and dendritic spine modifications in the NAc. We compared the translating mRNA in NAc neurons identified by the type of dopamine receptors they express, depending on the type of food and training. We tested the consequences of invalidation of an abundant downregulated gene, Ncdn (Neurochondrin).

RESULTS

Operant conditioning for highly palatable food increases motivation for food even in well-fed mice. In control mice, free access to regular or highly palatable food results in increased weight as compared to regular food only. Highly palatable food increases spine density in the NAc. In animals trained for highly palatable food, translating mRNAs are modified in NAc dopamine D2-receptor-expressing neurons, mostly corresponding to striatal projection neurons, but not in those expressing D1-receptors. Knock-out of Ncdn, an abundant down-regulated gene, opposes the conditioning-induced changes in satiety-sensitive feeding behavior and apparent motivation for highly palatable food, suggesting down-regulation may be a compensatory mechanism.

CONCLUSIONS

Our results emphasize the importance of mRNA alterations D2 striatal projection neurons in the NAc in the behavioral consequences of highly palatable food conditioning and suggest a modulatory contribution of Ncdn downregulation.

Binge eating, depressive symptoms and suicidal ideation in obese candidates for bariatric surgery

PURPOSE

The aim of the present study was to determine possible associations between binge eating, depressive symptoms and suicidal ideation in obese candidates for bariatric surgery.

METHODS

A cross-sectional study was conducted with 254 obese patients recruited from the general surgery service for bariatric procedures at the hospital affiliated with the Federal University of Pernambuco, Brazil. Evaluations were performed using the Binge Eating Scale (BES), Beck Depression Inventory, Beck Scale for Suicidal Ideation (BSSI) and a questionnaire addressing sociodemographic characteristics.

RESULTS

Most patients were women (82%), 48% had a moderate binge eating disorder, 42% a severe binge eating disorder, 32% had symptoms suggestive of mild, moderate or severe depression and 6% had suicidal ideation. Severe binge eating was positively associated with depressive symptoms (p < 0.001) and suicidal ideation (p < 0.05). Cases of severe binge eating were more frequent in young adults, but not necessarily associated with symptoms of depression or suicidal ideation in this portion of the sample.

CONCLUSIONS

The present findings underscore the need for psychological and psychiatric follow-up of obese candidates for bariatric surgery using appropriate assessment scales to guide therapeutic approaches.

LEVEL III

Evidence obtained from cross-sectional study.

A literature review of dopamine in binge eating

OBJECTIVE

Binge eating, a core diagnostic symptom in binge eating disorder and bulimia nervosa, increases the risk of multiple physiological and psychiatric disorders. The neurotransmitter dopamine is involved in food craving, decision making, executive functioning, and impulsivity personality trait; all of which contribute to the development and maintenance of binge eating. The objective of this paper is to review the associations of dopamine levels/activities, dopamine regulator (e.g., dopamine transporter, degrading enzymes) levels/activities, and dopamine receptor availability/affinity with binge eating.

METHODS

A literature search was conducted in PubMed and PsycINFO to obtain human and animal studies published since 2010.

RESULTS

A total of 31 studies (25 human, six animal) were included. Among the human studies, there were 12 case-control studies, eight randomized controlled trials, and five cross-sectional studies. Studies used neuroimaging (e.g., positron emission tomography), genetic, and pharmacological (e.g., dopamine transporter inhibitor) techniques to describe or compare dopamine levels/activities, dopamine transporter levels/activities, dopamine degrading enzyme (e.g., catechol-O-methyltransferase) levels/activities, and dopamine receptor (e.g., D1, D2) availability/affinity among participants with and without binge eating. Most human and animal studies supported an altered dopaminergic state in binge eating (26/31, 83.9%); however, results were divergent regarding whether the altered state was hyperdopaminergic (9/26, 34.6%) or hypodopaminergic (17/26, 65.4%). The mixed findings may be partially explained by the variability in sample characteristics, study design, diagnosis criteria, and neuroimaging/genetic/pharmacological techniques used. However, it is possible that instead of being mutually exclusive, the hyperdopaminergic and hypodopaminergic state may co-exist, but in different stages of binge eating or in different individual genotypes.

CONCLUSIONS

For future studies to clarify the inconsistent findings, a homogenous sample that controls for confounders that may influence dopamine levels (e.g., psychiatric diseases) is preferable. Longitudinal studies are needed to evaluate whether the hyper- and hypo-dopaminergic states co-exist in different stages of binge eating or co-exist in individual phenotypes. Binge eating is characterized by eating a large amount of food in a short time and a feeling of difficulty to stop while eating. Binge eating is the defining symptom of binge eating disorder and bulimia nervosa, both of which are associated with serious health consequences. Studies have identified several psychological risk factors of binge eating, including a strong desire for food, impaired cognitive skills, and distinct personality traits (e.g., quick action without careful thinking). However, the physiological markers of binge eating remain unclear. Dopamine is a neurotransmitter that is heavily involved in feeding behavior, human motivation, cognitive ability, and personality. Therefore, dopamine is believed to play a critical role in binge eating. This review synthesized study findings related to the levels and activities of dopamine, dopamine regulators, and dopamine receptors in the context of binge eating. The primary finding is that most studies that used neuroimaging, genetic, or drug techniques found an altered dopaminergic state related to binge eating. However, the literature is inconsistent concerning the direction of the alteration. Considering the mixed findings and the limitations in study design, future studies, especially those that include repeated measurements, are needed to clarify the role of dopamine in binge eating.

Molecular Engineered Carbon-Based Sensor for Ultrafast and Specific Detection of Neurotransmitters

In the quest for designing affordable diagnostic devices with high performance, precisely functionalized carbon-based materials with high accuracy and selectivity are required. Every material has its own unique ability to interact with the analyte, and its performance can be enhanced by probing the interaction mechanism. Herein, p-aminophenol (PAP)-functionalized reduced graphene oxide (rGO) nanoscale material is developed by a one-step synthetic route as an all-organic-based sensor. As the PAP molecules are precisely covalently interacted with the rGO at the basal plane and form a wrinkled-paper-like structure, the functionalized material exhibits an outstanding sensing ability (7.5 nM neurotransmitter dopamine (DA) at a wide linear range, 0.01-100 μM) with fast electrical transduction (<3 s) and good recyclability (∼10 cycles) in a real sample. Combining various analytical and density functional theory (DFT) calculation methods, physicochemical properties and the interaction mechanism of analyte-materials transduction are discussed exclusively. Besides, the potential application of the well-dispersed rGO-PAP gravure ink in flexible-printed electronics fields is explored. This study not only provides new insights into the surface/interface chemistry and working principle of this unique anchoring of PAP on rGO but also offers a new pathway for developing other forms of metal-free/organic functionalized biosensors with high efficiency.

Therapeutic Potential of TAAR1 Agonists in Schizophrenia: Evidence from Preclinical Models and Clinical Studies

Trace amine-associated receptor 1 (TAAR1) has emerged as a promising therapeutic target for neuropsychiatric disorders due to its ability to modulate monoaminergic and glutamatergic neurotransmission. In particular, agonist compounds have generated interest as potential treatments for schizophrenia and other psychoses due to TAAR1-mediated regulation of dopaminergic tone. Here, we review unmet needs in schizophrenia, the current state of knowledge in TAAR1 circuit biology and neuropharmacology, including preclinical behavioral, imaging, and cellular evidence in glutamatergic, dopaminergic and genetic models linked to the pathophysiology of psychotic, negative and cognitive symptoms. Clinical trial data for TAAR1 drug candidates are reviewed and contrasted with antipsychotics. The identification of endogenous TAAR1 ligands and subsequent development of small-molecule agonists has revealed antipsychotic-, anxiolytic-, and antidepressant-like properties, as well as pro-cognitive and REM-sleep suppressing effects of TAAR1 activation in rodents and non-human primates. Ulotaront, the first TAAR1 agonist to progress to randomized controlled clinical trials, has demonstrated efficacy in the treatment of schizophrenia, while another, ralmitaront, is currently being evaluated in clinical trials in schizophrenia. Coupled with the preclinical findings, this provides a rationale for further investigation and development of this new pharmacological class for the treatment of schizophrenia and other psychiatric disorders.

Detecting Cognitive Impairment in Idiopathic Intracranial Hypertension Using Ocular Motor and Neuropsychological Testing

Objective: To determine whether cognitive impairments in patients with Idiopathic Intracranial Hypertension (IIH) are correlated with changes in visual processing, weight, waist circumference, mood or headache, and whether they change over time.

Methods: Twenty-two newly diagnosed IIH patients participated, with a subset assessed longitudinally at 3 and 6 months. Both conventional and novel ocular motor tests of cognition were included: Symbol Digit Modalities Test (SDMT), Stroop Colour and Word Test (SCWT), Digit Span, California Verbal Learning Test (CVLT), prosaccade (PS) task, antisaccade (AS) task, interleaved antisaccade-prosaccade (AS-PS) task. Patients also completed headache, mood, and visual functioning questionnaires.

Results: IIH patients performed more poorly than controls on the SDMT (p< 0.001), SCWT (p = 0.021), Digit Span test (p< 0.001) and CVLT (p = 0.004) at baseline, and generated a higher proportion of AS errors in both the AS (p< 0.001) and AS-PS tasks (p = 0.007). Further, IIH patients exhibited prolonged latencies on the cognitively complex AS-PS task (p = 0.034). While weight, waist circumference, headache and mood did not predict performance on any experimental measure, increased retinal nerve fibre layer (RNFL) was associated with AS error rate on both the block [F_{(3, 19)}=3.22, B = 0.30, p = 0.022] and AS-PS task [F_{(3, 20)} = 2.65, B = 0.363, p = 0.013]. Unlike ocular motor changes, impairments revealed on conventional tests of cognition persisted up to 6 months.

Conclusion: We found multi-domain cognitive impairments in IIH patients that were unrelated to clinical characteristics. Marked ocular motor inhibitory control deficits were predicted by RNFL thickness but remained distinct from other cognitive changes, underscoring the significance of visual processing changes in IIH.

Converging vulnerability factors for compulsive food and drug use

Highly palatable foods and substance of abuse have intersecting neurobiological, metabolic and behavioral effects relevant for understanding vulnerability to conditions related to food (e.g., obesity, binge eating disorder) and drug (e.g., substance use disorder) misuse. Here, we review data from animal models, clinical populations and epidemiological evidence in behavioral, genetic, pathophysiologic and therapeutic domains. Results suggest that consumption of highly palatable food and drugs of abuse both impact and conversely are regulated by metabolic hormones and metabolic status. Palatable foods high in fat and/or sugar can elicit adaptation in brain reward and withdrawal circuitry akin to substances of abuse. Intake of or withdrawal from palatable food can impact behavioral sensitivity to drugs of abuse and vice versa. A robust literature suggests common substrates and roles for negative reinforcement, negative affect, negative urgency, and impulse control deficits, with both highly palatable foods and substances of abuse. Candidate genetic risk loci shared by obesity and alcohol use disorders have been identified in molecules classically associated with both metabolic and motivational functions. Finally, certain drugs may have overlapping therapeutic potential to treat obesity, diabetes, binge-related eating disorders and substance use disorders. Taken together, data are consistent with the hypotheses that compulsive food and substance use share overlapping, interacting substrates at neurobiological and metabolic levels and that motivated behavior associated with feeding or substance use might constitute vulnerability factors for one another. This article is part of the special issue on 'Vulnerabilities to Substance Abuse'.

Exploring Neural Mechanisms Related to Cognitive Control, Reward, and Affect in Eating Disorders: A Narrative Review of FMRI Studies

Studies using functional magnetic resonance imaging (fMRI) have contributed to our understanding of possible neural abnormalities among individuals with eating disorders. Many of these studies have focused on three domains: 1) cognitive control, 2) reward processing, and 3) affective processing. This review attempts to summarize the recent fMRI findings across these domains among the most well-characterized eating disorders: anorexia nervosa (AN), bulimia nervosa (BN), and binge eating disorder (BED). Though the literature is a bit murky, a few major themes have emerged. Cognitive control systems are affected among individuals across eating disorder diagnoses, but effects seem least pronounced in AN. Specifically, individuals with all eating disorders appear to show decreased prefrontal activation during cognitive control, but there is less evidence in AN linking decreased prefrontal activation with behavior. There is some evidence that the reinforcing value of food is reduced in AN, but individuals with BN and BED show hyperactivation to rewarding food-related stimuli, suggesting the reinforcing value of food may be enhanced. However, more complex reward processing paradigms show that individuals with BN and BED exhibit hypoactivation to reward anticipation and provide mixed results with regards to reward receipt. There are fewer neuroimaging findings related to affective processing, yet behavioral findings suggest affective processing is important in understanding eating disorders. Though the extant literature is complicated, these studies represent a foundation from which to build and provide insight into potential neurobiological mechanisms that may contribute to the pathophysiology of eating disorders.

Objective aerobic fitness level and neuropsychological functioning in healthy adolescents and emerging adults: Unique sex effects

Objective

Research suggests positive relationships between aerobic fitness and cognition in older adults; however, limited research has adequately investigated the relationship between objectively measured aerobic fitness and broad cognitive functioning in healthy adolescents and young adults without psychiatric or physical health disorders. Further, studies to date have disproportionately examined males and failed to examine sex differences. Here we examine the relationship between aerobic fitness and neuropsychological functioning in physically healthy youth and whether sex moderates these findings.

Design

Sixty-four healthy emerging adults (16-25 years-old; 32 female) underwent measurement of objective aerobic fitness (VO2 max) and neuropsychological assessment. Exclusion criteria included: left-handedness, prenatal medical issues or alcohol/illicit drug exposure, Axis-I psychiatric disorders, major medical disorders including metabolic conditions such as diabetes, hypertension, hyperlipidemia, major neurologic disorders, LOS greater than 2 min, intellectual disability or learning disability, regular substance use (e.g., greater than biweekly use of cannabis) or positive drug toxicology testing.

Method

Multiple regressions examined VO2 max, sex, sex*VO2interaction in relation to neurocognition, controlling for objectively measured body fat percentage.

Results

Prior to including body fat percentage, higher VO2 max related to improved working memory (Letter-Number Sequencing; p = .03) and selective attention (CPT-II hit response time standard error; p = .03). Aerobic fitness significantly interacted with sex, as higher-fit males had better performance on two sustained attention tasks while females did not demonstrate this pattern (CPT-II variability standard error, p = .047; Ruff 2&7 Total Speed, p = .02). Body fat percentage was positively slower cognitive flexibility (D-KEFS color-word switching/inhibition, p = .046).

Conclusions

VO2 independently predicted better working memory and selective attention. Increased aerobic fitness level related to increased performance on sustained attention tasks in males but not females. Therefore, aerobic fitness may be positively related to better cognitive functioning in physically healthy adolescents and emerging adults without metabolic conditions. Further research into factors (e.g., intensity or type of activity) that may relate to beneficial outcomes by sex are needed.

Relating goal-directed behaviour to grazing in persons with obesity with and without eating disorder features

BACKGROUND

Both obesity and eating disorders (ED) have been associated with reductions in purposeful, flexible goal-directed behaviour, and with an overreliance on more rigid habitual behaviour. It is currently unknown whether grazing, an eating style which is common in both conditions, is related to goal-directed behaviour. The current study therefore aimed to relate grazing to goal-directed behaviour in a group of participants with obesity with and without ED features, compared to a healthy-weight control group.

METHODS

Participants (N = 87; 67.8% women, mean age 28.57 years), of whom 19 had obesity and significant eating disorder features, 25 had obesity but without marked eating disorder features, and 43 were age- and sex-matched healthy-weight controls, completed two instrumental learning tasks assessing action-outcome contingency sensitivity and devaluation sensitivity, as well as demographic and eating disorder-related questionnaires. Gamma and Ordinary Least Squares regressions were performed to examine the effect of group and grazing on goal-directed behaviour.

RESULTS

Lower action-outcome contingency sensitivity was found in the group with obesity and with eating disorder features than in the group with obesity but without eating disorder features or in healthy controls. No group differences in devaluation sensitivity were found. A small but significant relationship was found between grazing severity and contingency sensitivity in the group with obesity and eating disorder features, such that increasing grazing severity was associated with less diminished contingency sensitivity.

CONCLUSIONS

There is some indication that in persons with obesity and eating disorder features instrumental behaviour is less flexible and adaptive; furthermore, within this group grazing may represent a goal-directed behaviour, despite unhelpful long-term implications of grazing.

Eating disorders: Do PET and SPECT have a role? A systematic review of the literature

A systematic review was implemented according to PRISMA guidelines on Pubmed, Psychinfo, Medline, Embase to fill the existing literature gap on the effectiveness of using Positron Emission Tomography (PET) and Single Photon Emission Computed Tomography (SPECT) in Anorexia Nervosa (AN), Bulimia Nervosa (BN) and Binge Eating Disorder (BED). Twenty-two articles were included. Four studies reported an increased density in 5-hydroxytryptamine receptor (5-HT_1A) in fronto-temporo-parietal regions in both affected and recovered AN as well as in BN. The 5-HT transporter (5-HTT) binding was increased or diminished in different specific cortical areas and in relation to Eating Disorder (ED) subtypes. Some evidences of blunted Dopamine (DA) release in the putamen in BN patients suggest that their DA function might be impaired as in addictive behaviours. Studies estimating the regional Cerebral Blood Flow (rCBF) with SPECT demonstrated that temporal areas seem to play a key role in ED corroborating the hypothesis of a cingulate-temporal cortical dysfunction in AN. In addition, alterations of both parietal and prefrontal cortex provide a possible common neural substrate in AN. Studies included in this review are heterogeneous preventing robust conclusions, however, our findings add knowledge on some of the neurotransmitters involved in ED.

Effects of hunger on mood and affect reactivity to monetary reward in women with obesity - A pilot study

Worldwide, nearly 3 million people die every year because of being overweight or obese. Although obesity is a metabolic disease, behavioral aspects are important in its etiology. Hunger changes the rewarding potential of food in normal-weight controls. In obesity, impairments related to reward processing are present, but it is not clear whether these are due to mental disorders more common among this population. Therefore, in this pilot study, we aimed at investigating whether fasting influence mood reactivity to reward in people with obesity. Women with obesity (n = 11, all mentally healthy) and normal weight controls (n = 17) were compared on a computerized monetary reward task (the wheel of fortune), using self-reports of mood and affect (e.g., PANAS and mood evaluation during the task) as dependent variables. This task was done in 2 satiety conditions, during fasting and after eating. Partially, in line with our expectation of a reduced affect and mood reactivity to monetary reward in participants with obesity accentuated by fasting, our results indicated a significant within-group difference across time (before and after the task), with monetary gains significantly improving positive affect in healthy controls (p>0.001), but not in individuals with obesity (p = 0.32). There were no significant between-group differences in positive affect before (p = 0.328) and after (p = 0.70) the task. In addition, women with obesity, compared to controls, reported more negative affect in general (p < 0.05) and less mood reactivity during the task in response to risky gains (p < 0.001) than healthy controls. The latter was independent of the level of satiety. These preliminary results suggest an impairment in mood reactivity to monetary reward in women with obesity which is not connected to the fasting state. Increasing the reinforcing potential of rewards other than food in obesity may be one target of intervention in order to verify if that could reduce overeating.

Circulating Triglycerides Gate Dopamine-Associated Behaviors through DRD2-Expressing Neurons

Energy-dense food alters dopaminergic (DA) transmission in the mesocorticolimbic (MCL) system and can promote reward dysfunctions, compulsive feeding, and weight gain. Yet the mechanisms by which nutrients influence the MCL circuitry remain elusive. Here, we show that nutritional triglycerides (TGs), a conserved post-prandial metabolic signature among mammals, can be metabolized within the MCL system and modulate DA-associated behaviors by gating the activity of dopamine receptor subtype 2 (DRD2)-expressing neurons through a mechanism that involves the action of the lipoprotein lipase (LPL). Further, we show that in humans, post-prandial TG excursions modulate brain responses to food cues in individuals carrying a genetic risk for reduced DRD2 signaling. Collectively, these findings unveil a novel mechanism by which dietary TGs directly alter signaling in the reward circuit to regulate behavior, thereby providing a new mechanistic basis by which energy-rich diets may lead to (mal)adaptations in DA signaling that underlie reward deficit and compulsive behavior.

Hypothalamic Fatty Acids and Ketone Bodies Sensing and Role of FAT/CD36 in the Regulation of Food Intake

The obesity and type-2 diabetes epidemic is escalating and represents one of the costliest biomedical challenges confronting modern society. Moreover, the increasing consumption of high fat food is often correlated with an increase in body mass index. In people predisposed to be obese or already obese, the impaired ability of the brain to monitor and respond to alterations in fatty acid (FA) metabolism is increasingly recognized as playing a role in the pathophysiological development of these disorders. The brain senses and regulates metabolism using highly specialized nutrient-sensing neurons located mainly in the hypothalamus. The same neurons are able to detect variation in the extracellular levels of glucose, FA and ketone bodies as a way to monitor nutrient availability and to alter its own activity. In addition, glial cells such as astrocytes create major connections to neurons and form a tight relationship to closely regulate nutrient uptake and metabolism. This review will examine the different pathways by which neurons are able to detect free fatty acids (FFA) to alter its activity and how high fat diet (HFD)-astrocytes induced ketone bodies production interplays with neuronal FA sensing. The role of HFD-induced inflammation and how FA modulate the reward system will also be investigated here.

Effect of lisdexamfetamine on emotional network brain dysfunction in binge eating disorder

We examined the effects of lisdexamfetamine (LDX) treatment on ventral prefrontal cortex (VPFC) and striatal brain activation in binge eating disorder (BED). We hypothesized that participants with BED have an abnormal brain response to palatable food cues, and that VPFC and striatal regions would respond to such cues after LDX treatment. Twenty women with moderate to severe BED consented to a 12-week, open-label trial of LDX with fMRI before and after treatment. Twenty obese women without BED served as healthy controls and received one fMRI. LDX was started at 30 mg/d with a target of 70 mg/d at week 12. At baseline, women with BED showed greater activation in ventrolateral prefrontal cortex (VLPFC), striatum, and globus pallidus to food pictures and brain activation to food pictures predicted clinical outcome at 12 weeks. After 12 weeks of LDX treatment, BED women showed significant reductions in globus pallidus activation. Reductions in ventromedial prefrontal cortex (VMPFC) and thalamus activation specifically correlated with binge eating and obsessive-compulsive symptom reductions, respectively. Results suggest that BED is characterized by an abnormally large VPFC-subcortical brain response to palatable foods that LDX treatment helps modify. Moreover, VPFC-subcortical activation at baseline is a potential biomarker of LDX response.

Effect of the catechol-O-methyltransferase Val 158 Met polymorphism on theory of mind in obesity

Obesity is often accompanied with psychosocial adjustment problems, such as difficulties in social interactions and social withdrawal. A key aspect of social cognition is theory of mind, which allows inferring mental states, feelings, motivations, and beliefs of others and to use this information to predict their future behaviour. Theory of mind is highly dependent on prefrontal dopaminergic neurotransmission, which is regulated by catechol-O-methyltransferase (COMT) activity. We aimed at determining whether theory of mind is altered in obesity and if this ability is modulated by COMT. Fifty patients with obesity and 47 normal-weight individuals underwent the Reading the Mind in the Eyes Test, the Wisconsin Card Sorting Test, and the Vocabulary subscale of the Wechsler Adult Intelligence Scale. The genotype for the COMT Val ¹⁵⁸ Met functional polymorphism was determined for all subjects. Patients with obesity obtained significantly lower scores in the negative items of the Reading the Mind in the Eyes Test than normal-weight subjects. Further, an interaction effect was observed between group and COMT genotype. Specifically, the presence of the Met allele was associated to a better identification of negative mental states only in patients with obesity. Our results indicate that obesity is accompanied with difficulties in theory of mind and that this ability is influenced by the COMT genotype.

Understanding the neural mechanisms of lisdexamfetamine dimesylate (LDX) pharmacotherapy in Binge Eating Disorder (BED): a study protocol

BACKGROUND

The efficacy and safety of Lisdexamfetamine dimesylate (LDX) in the treatment of moderate to severe binge eating disorder (BED) has been demonstrated in multiple randomised clinical trials. Despite this, little is known about how LDX acts to improve binge eating symptoms. This study aims to provide a comprehensive understanding of the neural mechanisms by which LDX improves symptoms of BED. We hypothesise that LDX will act by normalising connectivity within neural circuits responsible for reward and impulse control, and that this normalisation will correlate with reduced binge eating episodes.

METHODS

This is an open-label Phase 4 clinical trial of LDX in adults with moderate to severe BED. Enrolment will include 40 adults with moderate to severe BED aged 18-40 years and Body Mass Index (BMI) of 20-45 kg/m², and 22 healthy controls matched for age, gender and BMI. Clinical interview and validated scales are used to confirm diagnosis and screen for exclusion criteria, which include comorbid anorexia nervosa or bulimia nervosa, use of psychostimulants within the past 6 months, and current use of antipsychotics or noradrenaline reuptake inhibitors. Baseline assessments include clinical symptoms, multimodal neuroimaging, cognitive assessment of reward sensitivity and behavioural inhibition, and an (optional) genetic sample. A subset of these assessments are repeated after eight weeks of treatment with LDX titrated to either 50 or 70 mg. The primary outcome measures are resting-state intrinsic connectivity and the number of binge eating episodes. Analyses will be applied to resting-state fMRI data to characterise pharmacological effects across the functional connectome, and assess correlations with symptom measure changes. Comparison of neural measures between controls and those with BED post-treatment will also be performed to determine whether LDX normalises brain function.

DISCUSSION

First enrolment was in May 2018, and is ongoing. This study is the first comprehensive investigation of the neurobiological changes that occur with LDX treatment in adults with moderate to severe BED.

TRIAL REGISTRATION

ACTRN12618000623291, Australian and New Zealand Clinical Trials Registry URL: https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=374913&isReview=true. Date of Registration: 20 April 2018.

Trace Amines and Their Receptors

Trace amines are endogenous compounds classically regarded as comprising β-phenylethyalmine, p-tyramine, tryptamine, p-octopamine, and some of their metabolites. They are also abundant in common foodstuffs and can be produced and degraded by the constitutive microbiota. The ability to use trace amines has arisen at least twice during evolution, with distinct receptor families present in invertebrates and vertebrates. The term "trace amine" was coined to reflect the low tissue levels in mammals; however, invertebrates have relatively high levels where they function like mammalian adrenergic systems, involved in "fight-or-flight" responses. Vertebrates express a family of receptors termed trace amine-associated receptors (TAARs). Humans possess six functional isoforms (TAAR1, TAAR2, TAAR5, TAAR6, TAAR8, and TAAR9), whereas some fish species express over 100. With the exception of TAAR1, TAARs are expressed in olfactory epithelium neurons, where they detect diverse ethological signals including predators, spoiled food, migratory cues, and pheromones. Outside the olfactory system, TAAR1 is the most thoroughly studied and has both central and peripheral roles. In the brain, TAAR1 acts as a rheostat of dopaminergic, glutamatergic, and serotonergic neurotransmission and has been identified as a novel therapeutic target for schizophrenia, depression, and addiction. In the periphery, TAAR1 regulates nutrient-induced hormone secretion, suggesting its potential as a novel therapeutic target for diabetes and obesity. TAAR1 may also regulate immune responses by regulating leukocyte differentiation and activation. This article provides a comprehensive review of the current state of knowledge of the evolution, physiologic functions, pharmacology, molecular mechanisms, and therapeutic potential of trace amines and their receptors in vertebrates and invertebrates.

Eating behavior and body composition across childhood: a prospective cohort study

Background

Although many cross-sectional studies reported that children with overweight or obesity show more food approaching and less food avoidant eating behaviors, there is a lack of replication in longitudinal studies. Therefore, the question remains whether healthcare professionals should target eating behaviors in childhood obesity interventions and prevention. We aimed to examine the longitudinal and possible bi-directional associations between eating behavior and body composition across childhood.

Methods

Data was included from 3331 children participating in the Generation R Study. At 4 and 10 years, mothers reported on the Child Eating Behavior Questionnaire including the subscales Food Responsiveness, Enjoyment of Food, Emotional Overeating and Satiety Responsiveness, and children’s BMI was measured. Body composition, consisting of Fat Mass Index and Fat Free Mass Index was measured at 6 and 10 years with Dual-energy-X-ray-Absorptiometry scans.

Results

Cross-lagged models including both directions of the BMI – eating behavior association showed that a higher BMI at the age of 4 years predicted more food responsiveness and enjoyment of food and less satiety responsiveness at 10 years (e.g. satiety responsiveness:β = − 0.10, 95% CI = − 0.14, − 0.07), but no associations were found in the opposite direction. For emotional overeating, however, a bi-directional association was found with BMI predicting more emotional eating and vice versa. Multivariable linear regression analyses showed that associations were stronger for Fat Mass Index than for Fat Free Mass Index.

Conclusions

Results showed that a higher BMI, and particularly higher fat mass, at pre-school age predicted more food approaching and less food avoidant eating behaviors at the age of 10 years, rather than the hypothesized reverse direction. This suggests that increased adiposity in early childhood might upregulate appetite and related eating behaviors.

Electronic supplementary material

The online version of this article (10.1186/s12966-018-0725-x) contains supplementary material, which is available to authorized users.

Restrictive Diet Control as a Means of Child Abuse

We have recently encountered a series of cases where an obese caretaker is juxtaposed to a severely starved, malnourished dependent. The cases described all share a common characteristic: that the primary perpetrator was an obese caretaker who tried to exert absolute control over their victim's daily life in a way that included either a severe restriction or complete denial of food. Because the pathophysiology of both child abuse and obesity are incredibly complex and multifactorial, these cases are presented to encourage further discussion and more rigorous investigation into the validity of a hypothesis that has been derived from this set of cases: that the obesity of a child's caretaker may be an additional risk factor for child maltreatment by starvation.

Machine Learning Based Classification of Deep Brain Stimulation Outcomes in a Rat Model of Binge Eating Using Ventral Striatal Oscillations

Neuromodulation-based interventions continue to be evaluated across an array of appetitive disorders but broader implementation of these approaches remains limited due to variable treatment outcomes. We hypothesize that individual variation in treatment outcomes may be linked to differences in the networks underlying these disorders. Here, Sprague-Dawley rats received deep brain stimulation separately within each nucleus accumbens (NAc) sub-region (core and shell) using a within-animal crossover design in a rat model of binge eating. Significant reductions in binge size were observed with stimulation of either target but with significant variation in effectiveness across individuals. When features of local field potentials (LFPs) recorded from the NAc were used to classify the pre-defined stimulation outcomes (response or non-response) from each rat using a machine-learning approach (lasso), stimulation outcomes could be classified with greater accuracy than expected by chance (effect sizes: core = 1.13, shell = 1.05). Further, these LFP features could be used to identify the best stimulation target for each animal (core vs. shell) with an effect size = 0.96. These data suggest that individual differences in underlying network activity may relate to the variable outcomes of circuit based interventions, and measures of network activity could have the potential to individually guide the selection of an optimal stimulation target to improve overall treatment response rates.

The Trace Amine-Associated Receptor 1 Agonist RO5256390 Blocks Compulsive, Binge-like Eating in Rats

Compulsive, binge eating of highly palatable food constitutes a core feature of some forms of obesity and eating disorders, as well as of the recently proposed disorder of food addiction. Trace amine-associated receptor 1 (TAAR1) is a highly conserved G-protein-coupled receptor bound by endogenous trace amines. TAAR1 agonists have been shown to reduce multiple behavioral effects of drugs of abuse through their actions on the mesocorticolimbic system. In this study, we hypothesized that TAAR1 may have a role in compulsive, binge-like eating; we tested this hypothesis by assessing the effects of a TAAR1 agonist, RO5256390, in multiple excessive feeding-related behaviors induced by limiting access to a highly palatable diet in rats. Our results show that RO5256390 blocked binge-like eating in rats responding 1 h per day for a highly palatable sugary diet. Consistent with a palatability-selective effect, drug treatment selectively reduced the rate and regularity of palatable food responding, but it did not affect either baseline intake or food restriction-induced overeating of the standard chow diet. Furthermore, RO5256390 fully blocked compulsive-like eating when the palatable diet was offered in an aversive compartment of a light/dark conflict box, and blocked the conditioned rewarding properties of palatable food, as well as palatable food-seeking behavior in a second-order schedule of reinforcement. Drug treatment had no effect on either anxiety-like or depressive-like behavior, and it did not affect control performance in any of the tests. Importantly, rats exposed to palatable food showed decreased TAAR1 levels in the medial prefrontal cortex (mPFC), and RO5256390 microinfused into the infralimbic, but not prelimbic, subregion of the mPFC-reduced binge-like eating. Altogether, these results provide evidence for TAAR1 agonism as a novel pharmacological treatment for compulsive, binge eating.

Core, social and moral disgust are bounded: A review on behavioral and neural bases of repugnance in clinical disorders

Disgust is a multifaceted experience that might affect several aspects of life. Here, we reviewed research on neurological and psychiatric disorders that are characterized by abnormal disgust processing to test the hypothesis of a shared neurocognitive architecture in the representation of three disgust domains: i) personal experience of 'core disgust'; ii) social disgust, i.e., sensitivity to others' expressions of disgust; iii) moral disgust, i.e., sensitivity to ethical violations. Our review provides some support to the shared neurocognitive hypothesis and suggests that the insula might be the "hub" structure linking the three domains of disgust sensitivity, while other brain regions may subserve specific facets of the multidimensional experience. Our review also suggests a role of serotonin core and moral disgust, supporting "neo-sentimentalist" theories of morality, which posit a causal role of affect in moral judgment.

Pilot clinical observations between food and drug seeking derived from fifty cases attending an eating disorder clinic

Background The reward deficiency syndrome hypothesis posits that genes are responsible for reward dependence and related behaviors. There is evidence that both bulimia and anorexia nervosa, especially in women, have been linked to a lifetime history of substance use disorder (SUD). There are difficulties in accepting food as an addiction similar to drugs; however, increasingly neuroimaging studies favor such an assertion. Case presentations We are reporting the evidence of comorbidity of eating disorders with SUD found within these case presentations. We show 50 case reports derived from two independent treatment centers in Florida that suggest the commonality between food and drug addictions. In an attempt to provide data from this cohort, many participants did not adequately respond to our questionnaire. Discussion We propose that dopamine agonist therapy may be of common benefit. Failure in the past may reside in too powerful D2 agonist activity leading to D2 receptor downregulation, while the new methodology may cause a reduction of "dopamine resistance" by inducing "dopamine homeostasis." While this is not a definitive study, it does provide some additional clinical evidence that these two addictions are not mutually exclusive. Conclusion Certainly, it is our position that there is an overlap between food- and drug-seeking behavior. We propose that the studies focused on an effort to produce natural activation of dopaminergic reward circuitry as a type of common therapy may certainly be reasonable. Additional research is warranted.

α2A adrenergic receptors highly expressed in mesoprefrontal dopamine neurons

α2 adrenoreceptors (α2-ARs) play a key role in the control of noradrenaline and dopamine release in the medial prefrontal cortex (mPFC). Here, using UV-laser microdissection-based quantitative mRNA expression in individual neurons we show that in hTH-GFP rats, a transgenic line exhibiting intense and specific fluorescence in dopaminergic (DA) neurons, α2A adrenoreceptor (α2A-AR) mRNA is expressed at high and low levels in DA cells in the ventral tegmental area (VTA) and substantia nigra compacta (SNc), respectively. Confocal microscopy fluorescence immunohistochemistry revealed that α2A-AR immunoreactivity colocalized with tyrosine hydroxylase (TH) in nearly all DA cells in the VTA and SNc, both in hTH-GFP rats and their wild-type Sprague-Dawley (SD) counterparts. α2A-AR immunoreactivity was also found in DA axonal projections to the mPFC and dorsal caudate in the hTH-GFP and in the anterogradely labeled DA axonal projections from VTA to mPFC in SD rats. Importantly, the α2A-AR immunoreactivity localized in the DA cells of VTA and in their fibers in the mPFC was much higher than that in DA cells of SNc and their fibers in dorsal caudate, respectively. The finding that α2A-ARs are highly expressed in the cell bodies and axons of mesoprefrontal dopaminergic neurons provides a morphological basis to the vast functional evidence that somatodendritic and nerve-terminal α2A-AR receptors control dopaminergic activity and dopamine release in the prefrontal cortex. This finding raises the question whether α2A-ARs might function as autoreceptors in the mesoprefrontal dopaminergic neurons, replacing the lack of D2 autoreceptors.

Dietary triglycerides as signaling molecules that influence reward and motivation

The reinforcing and motivational aspects of food are tied to the release of the dopamine in the mesolimbic system (ML). Free fatty acids from triglyceride (TG)-rich particles are released upon action of TG-lipases found at high levels in peripheral oxidative tissue (muscle, heart), but also in the ML. This suggests that local TG-hydrolysis in the ML might regulate food seeking and reward. Indeed, evidence now suggests that dietary TG directly target the ML to regulate amphetamine-induced locomotion and reward seeking behavior. Though the cellular mechanisms of TG action are unresolved, TG act in part through ML lipoprotein lipase, upstream of dopamine 2 receptor (D₂R), and show desensitization in conditions of chronically elevated plasma TG as occur in obesity. TG sensing in the ML therefore represents a new mechanism by which chronic consumption of dietary fat might lead to adaptations in the ML and dysregulated feeding behaviors.

Presynaptic D1 heteroreceptors and mGlu autoreceptors act at individual cortical release sites to modify glutamate release

The aim of this work was to study release of glutamic acid (GLU) from one-axon terminal or bouton at-a-time using cortical neurons grown in vitro to study the effect of presynaptic auto- and heteroreceptor stimulation. Neurons were infected with release reporters SypHx2 or iGluSnFR at 7 or 3 days-in-vitro (DIV) respectively. At 13-15 DIV single synaptic boutons were identified from images obtained from a confocal scanning microscope before and after field electrical stimulation. We further stimulated release by raising intracellular levels of cAMP with forskolin (10µM). Forskolin-mediated effects were dependent on protein kinase A (PKA) and did not result from an increase in endocytosis, but rather from an increase in the size of the vesicle readily releasable pool. Once iGluSnFR was confirmed as more sensitive than SypHx2, it was used to study the participation of presynaptic auto- and heteroreceptors on GLU release. Although most receptor agonizts (carbamylcholine, nicotine, dopamine D2, BDNF) did not affect electrically stimulated GLU release, a significant increase was observed in the presence of metabotropic D1/D5 heteroreceptor agonist (SKF38393 10µM) that was reversed by PKA inhibitors. Interestingly, stimulation of group II metabotropic mGLU2/3 autoreceptors (LY379268 50nM) induced a decrease in GLU release that was reversed by the specific mGLU2/3 receptor antagonist (LY341495 1µM) and also by PKA inhibitors (KT5720 200nM and PKI14-22 400nM). These changes in release probability at individual release sites suggest another level of control of the distribution of transmitter substances in cortical tissue.

Genetic Similarities between Compulsive Overeating and Addiction Phenotypes: A Case for "Food Addiction"?

There exists a continuous spectrum of overeating, where at the extremes there are casual overindulgences and at the other a 'pathological' drive to consume palatable foods. It has been proposed that pathological eating behaviors may be the result of addictive appetitive behavior and loss of ability to regulate the consumption of highly processed foods containing refined carbohydrates, fats, salt, and caffeine. In this review, we highlight the genetic similarities underlying substance addiction phenotypes and overeating compulsions seen in individuals with binge eating disorder. We relate these similarities to findings from neuroimaging studies on reward processing and clinical diagnostic criteria based on addiction phenotypes. The abundance of similarities between compulsive overeating and substance addictions puts forth a case for a 'food addiction' phenotype as a valid, diagnosable disorder.

Overview of the treatment of binge eating disorder

We performed a qualitative review of treatment studies of binge eating disorder (BED), focusing on randomized clinical trials (RCTs). Limited effectiveness has been demonstrated for self-help strategies, and substantial effectiveness has been shown for cognitive behavioral therapy (CBT) and interpersonal therapy (IPT). CBT and IPT may each be more effective than behavior weight loss therapy (BWLT) for reducing binge eating over the long term. The stimulant pro-drug lisdexamfetamine dimesylate (LDX) is the only drug approved by the FDA for the treatment of BED in adults based on 2 pivotal RCTs. Topiramate also decreases binge eating behavior, but its use is limited by its adverse event profile. Antidepressants may be modestly effective over the short term for reducing binge eating behavior and comorbid depressive symptoms, but are not associated with clinically significant weight loss. A RCT presented in abstract form suggests that intranasal naloxone may decrease time spent binge eating. There is no RCT of obesity surgery in BED, but many patients with BED seek and receive such surgery. While some studies suggest patients with BED and obesity do just as well as patients with obesity alone, other studies suggest that patients with BED have more post-operative complications, less weight loss, and more weight regain. This evidence suggests that patients with BED would benefit from receiving highly individualized treatment.

The epidemiology and genetics of binge eating disorder (BED)

This narrative review provides an overview of the epidemiology of binge eating disorder (BED), highlighting the medical history of this disorder and its entry as an independent condition in the Feeding and Eating Disorders section of the recently published Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition. Estimates of prevalence are provided, as well as recognition that the female to male ratio is lower in BED than in other eating disorders. Evidence is also provided of the most common comorbidities of BED, including mood and anxiety disorders and a range of addiction disorders. In addition, discussion of the viewpoint that BED itself may be an addiction - at least in severe cases - is presented. Although the genetic study of BED is still in its infancy, current research is reviewed with a focus on certain neurotransmitter genes that regulate brain reward mechanisms. To date, a focal point of this research has been on the dopamine and the μ-opioid receptor genes. Preliminary evidence suggests that a predisposing risk factor for BED may be a heightened sensitivity to reward, which could manifest as a strong dopamine signal in the brain's striatal region. Caution is encouraged, however, in the interpretation of current findings, since samples are relatively small in much of the research. To date, no genome-wide association studies have focused exclusively on BED.

Nucleus accumbens deep brain stimulation in a rat model of binge eating

Binge eating (BE) is a difficult-to-treat behavior with high relapse rates, thus complicating several disorders including obesity. In this study, we tested the effects of high-frequency deep brain stimulation (DBS) in a rodent model of BE. We hypothesized that BE rats receiving high-frequency DBS in the nucleus accumbens (NAc) core would have reduced binge sizes compared with sham stimulation in both a 'chronic BE' model as well as in a 'relapse to chronic BE' model. Male Sprague-Dawley rats (N=18) were implanted with stimulating electrodes in bilateral NAc core, and they received either active stimulation (N=12) or sham stimulation (N=6) for the initial chronic BE experiments. After testing in the chronic BE state, rats did not engage in binge sessions for 1 month, and then resumed binge sessions (relapse to chronic BE) with active or sham stimulation (N=5-7 per group). A significant effect of intervention group was observed on binge size in the chronic BE state, but no significant difference between intervention groups was observed in the relapse to chronic BE experiments. This research, making use of both a chronic BE model as well as a relapse to chronic BE model, provides data supporting the hypothesis that DBS of the NAc core can decrease BE. Further research will be needed to learn how to increase the effect size and decrease deep brain stimulation-treatment outcome variability across the continuum of BE behavior.

Dietary triglycerides act on mesolimbic structures to regulate the rewarding and motivational aspects of feeding

Circulating triglycerides (TGs) normally increase after a meal but are altered in pathophysiological conditions, such as obesity. Although TG metabolism in the brain remains poorly understood, several brain structures express enzymes that process TG-enriched particles, including mesolimbic structures. For this reason, and because consumption of high-fat diet alters dopamine signaling, we tested the hypothesis that TG might directly target mesolimbic reward circuits to control reward-seeking behaviors. We found that the delivery of small amounts of TG to the brain through the carotid artery rapidly reduced both spontaneous and amphetamine-induced locomotion, abolished preference for palatable food and reduced the motivation to engage in food-seeking behavior. Conversely, targeted disruption of the TG-hydrolyzing enzyme lipoprotein lipase specifically in the nucleus accumbens increased palatable food preference and food-seeking behavior. Finally, prolonged TG perfusion resulted in a return to normal palatable food preference despite continued locomotor suppression, suggesting that adaptive mechanisms occur. These findings reveal new mechanisms by which dietary fat may alter mesolimbic circuit function and reward seeking.

The interaction effect between BDNF val66met polymorphism and obesity on executive functions and frontal structure

The prevalence of obesity is increasing worldwide. Previous research has shown a relationship between obesity and both executive functioning alterations and frontal cortex volume reductions. The Brain Derived Neurotrophic Factor val66met polymorphism, involved in eating behavior, has also been associated with executive functions and prefrontal cortex volume, but to date it has not been studied in relation to obesity. Our aim is to elucidate whether the interaction between the Brain Derived Neurotrophic Factor val66met polymorphism and obesity status influences executive performance and frontal-subcortical brain structure. Sixty-one volunteers, 34 obese and 27 controls, age range 12-40, participated in the study. Participants were assigned to one of two genotype groups (met allele carriers, n = 16, or non-carriers, n = 45). Neuropsychological assessment comprised the Trail Making Test, the Stroop Test and the Wisconsin Card Sorting Test, all tasks that require response inhibition and cognitive flexibility. Subjects underwent magnetic resonance imaging in a Siemens TIM TRIO 3T scanner and images were analyzed using the FreeSurfer software. Analyses of covariance controlling for age and intelligence showed an effect of the obesity-by-genotype interaction on perseverative responses on the Wisconsin Card Sorting Test as well as on precentral and caudal middle frontal cortical thickness: obese met allele carriers showed more perseverations on the Wisconsin Card Sorting Test and lower frontal thickness than obese non-carriers and controls. In conclusion, the Brain Derived Neurotrophic Factor may play an important role in executive functioning and frontal brain structure in obesity.

A systematic review of the effects of neuromodulation on eating and body weight: evidence from human and animal studies

BACKGROUND

Eating disorders (ED) are chronic and sometimes deadly illnesses. Existing treatments have limited proven efficacy, especially in the case of adults with anorexia nervosa (AN). Emerging neural models of ED provide a rationale for more targeted, brain-directed interventions.

AIMS

This systematic review has examined the effects of neuromodulation techniques on eating behaviours and body weight and assessed their potential for therapeutic use in ED.

METHOD

All articles in PubMed, PsychInfo and Web of Knowledge were considered and screened against a priori inclusion/exclusion criteria. The effects of repetitive transcranial magnetic stimulation (rTMS), transcranial direct current stimulation, vagus nerve stimulation (VNS) and deep brain stimulation (DBS) were examined across studies in ED samples, other psychiatric and neurological disorders, and animal models.

RESULTS

Sixty studies were identified. There is evidence for ED symptom reduction following rTMS and DBS in both AN and bulimia nervosa. Findings from studies of other psychiatric and neurological disorders and from animal studies demonstrate that increases in food intake and body weight can be achieved following DBS and that VNS has potential value as a means of controlling eating and inducing weight loss.

CONCLUSIONS

Neuromodulation tools have potential for reducing ED symptomatology and related behaviours, and for altering food intake and body weight. In response to such findings, and emerging neural models of ED, treatment approaches are highly unlikely to remain 'brainless'. More research is required to evaluate the potential of neuromodulation procedures for improving long-term outcomes in ED.

Neurocognitive correlates of obesity and obesity-related behaviors in children and adolescents

Childhood obesity rates have risen dramatically over the past few decades. Although obesity has been linked to poorer neurocognitive functioning in adults, much less is known about this relationship in children and adolescents. Therefore, we conducted a systematic review to examine the relationship between obesity and obesity-related behaviors with neurocognitive functioning in youth. We reviewed articles from 1976 to 2013 using PsycInfo, PubMed, Medline and Google Scholar. Search terms included cognitive function, neurocognitive function/performance, executive function, impulsivity, self-regulation, effortful control, cognitive control, inhibition, delayed gratification, memory, attention, language, motor, visuo-spatial, academic achievement, obesity, overweight, body mass index, waist-hip ratio, adiposity and body fat. Articles were excluded if participants had health problems known to affect cognitive functioning, the study used imaging as the only outcome measure, they were non-peer-reviewed dissertations, theses, review papers, commentaries, or they were non-English articles. Sixty-seven studies met inclusion criteria for this review. Overall, we found data that support a negative relationship between obesity and various aspects of neurocognitive functioning, such as executive functioning, attention, visuo-spatial performance, and motor skill. The existing literature is mixed on the effects among obesity, general cognitive functioning, language, learning, memory, and academic achievement. Executive dysfunction is associated with obesity-related behaviors, such as increased intake, disinhibited eating, and less physical activity. Physical activity is positively linked with motor skill. More longitudinal research is needed to determine the directionality of such relationships, to point towards crucial intervention time periods in the development of children, and to inform effective treatment programs.