Increased brain response to appetitive tastes in the insula and amygdala in obese compared with healthy weight children when sated

Exposure to gestational diabetes mellitus in utero impacts hippocampal functional connectivity in response to food cues in children

OBJECTIVES

Intrauterine exposure to gestational diabetes mellitus (GDM) increases the risk of obesity in the offspring, but little is known about the underlying neural mechanisms. The hippocampus is crucial for food intake regulation and is vulnerable to the effects of obesity. The purpose of the study was to investigate whether GDM exposure affects hippocampal functional connectivity during exposure to food cues using functional magnetic resonance imaging (fMRI).

METHODS

Participants were 90 children age 7-11 years (53 females) who underwent an fMRI-based visual food cue task in the fasted state. Hippocampal functional connectivity (FC) was examined using generalized psychophysiological interaction in response to food versus non-food cues. Hippocampal FC was compared between children with and without GDM exposure, while controlling for possible confounding effects of age, sex and waist-to-hip ratio. In addition, the influence of childhood and maternal obesity were investigated using multiple regression models.

RESULTS

While viewing high caloric food cues compared to non-food cure, children with GDM exposure exhibited higher hippocampal FC to the insula and striatum (i.e., putamen, pallidum and nucleus accumbens) compared to unexposed children. With increasing BMI, children with GDM exposure had lower hippocampal FC to the somatosensory cortex (i.e., postcentral gyrus).

CONCLUSIONS

Intrauterine exposure to GDM was associated with higher food-cue induced hippocampal FC especially to reward processing regions. Future studies with longitudinal measurements are needed to clarify whether altered hippocampal FC may raise the risk of the development of metabolic diseases later in life.

Functional alterations in overweight/obesity: focusing on the reward and executive control network

Overweight (OW) and obesity (OB) have become prevalent issues in the global public health arena. Serving as a prominent risk factor for various chronic diseases, overweight/obesity not only poses serious threats to people's physical and mental health but also imposes significant medical and economic burdens on society as a whole. In recent years, there has been a growing focus on basic scientific research dedicated to seeking the neural evidence underlying overweight/obesity, aiming to elucidate its causes and effects by revealing functional alterations in brain networks. Among them, dysfunction in the reward network (RN) and executive control network (ECN) during both resting state and task conditions is considered pivotal in neuroscience research on overweight/obesity. Their aberrations contribute to explaining why persons with overweight/obesity exhibit heightened sensitivity to food rewards and eating disinhibition. This review centers on the reward and executive control network by analyzing and organizing the resting-state and task-based fMRI studies of functional brain network alterations in overweight/obesity. Building upon this foundation, the authors further summarize a reward-inhibition dual-system model, with a view to establishing a theoretical framework for future exploration in this field.

Prolonged latency of the gustatory evoked potentials for sucrose solution in subjects living with obesity compared with normal-weight subjects

OBJECTIVES

A difference in cortical treatment of taste information could alter food intake promoting the development of obesity. The main purpose was to compare, in subjects living with obesity (OB) and normal-weight subjects (NW), the characteristics of gustatory evoked potentials (GEP) for sucrose solution (10 g.100 mL-1) before and after a standard lunch. The secondary objective was to evaluate the correlations between GEP and the plasmatic levels of acylated ghrelin, leptin, insulin and serotonin.

METHODS

Each subject had 2 randomized sessions spaced by an interval of 2 days. During one session, subjects were fasting and during the other, subjects took a lunch low in sugar. In each session, subjects had a blood test before a first GEP recording followed by a second GEP recording either after a lunch (feeding session) or no lunch (fasting session).

RESULTS

Twenty-eight OB (BMI: 38.6 ± 9.0 kg.m-2) were matched to 22 NW (BMI: 22.3 ± 2.2 kg.m-2). GEP latencies were prolonged in OB regardless the sessions and the time before and after lunch, compared with NW (in Cz at the morning: 170 ± 33 ms vs 138 ± 25 ms respectively; p < 0.001). The increase in latency observed in NW after lunch was not observed in OB. Negative or positive correlations were noted in all participants between GEP latencies and ghrelin, leptin, insulin plasmatic levels (P1Cz, r = -0.38, r = 0.33, r = 0.37 respectively, p < 0.0001).

CONCLUSIONS

This study highlights a slower activation in the taste cortex in OB compared with NW.

Associations of radiologic characteristics of the neonatal hypothalamus with early life adiposity gain

BACKGROUND

The mediobasal hypothalamus (MBH) is a key brain area for regulation of energy balance. Previous neuroimaging studies suggest that T2-based signal properties indicative of cellular inflammatory response (gliosis) are present in adults and children with obesity, and predicts greater adiposity gain in children at risk of obesity.

OBJECTIVES/METHODS

The current study aimed to extend this concept to the early life period by considering if, in full-term healthy neonates (up to n = 35), MRI evidence of MBH gliosis is associated with changes in early life (neonatal to six months) body fat percentage measured by DXA.

RESULTS

In this initial study, neonatal T2 signal in the MBH was positively associated with six-month changes in body fat percentage.

CONCLUSION

This finding supports the notion that underlying processes in the MBH may play a role in early life growth and, by extension, childhood obesity risk.

Influence of insulin sensitivity on food cue evoked functional brain connectivity in children

Objective

Insulin resistance during childhood is a risk factor for developing type 2 diabetes and other health problems later in life. Studies in adults have shown that insulin resistance affects regional and network activity in the brain which are vital for behavior, e.g. ingestion and metabolic control. To date, no study has investigated whether brain responses to food cues in children are associated with peripheral insulin sensitivity.

Methods

We included 53 children (36 girls) between the age of 7-11 years, who underwent an oral Glucose Tolerance Test (oGTT) to estimate peripheral insulin sensitivity (ISI). Brain responses were measured using functional magnetic resonance imaging (fMRI) before and after glucose ingestion. We compared food-cue task-based activity and functional connectivity (FC) between children with low and high ISI, adjusted for age and BMIz.

Results

Independent of prandial state (i.e., glucose ingestion), children with lower ISI showed higher FC between the anterior insula and caudate and lower FC between the posterior insula and mid temporal cortex than children with higher ISI. Sex differences were found based on prandial state and peripheral insulin sensitivity in the insular FC. No differences were found on whole-brain food-cue reactivity.

Conclusions

Children with low peripheral insulin sensitivity showed differences in food cue evoked response particularly in insula functional connectivity. These differences might influence eating behavior and future risk of developing diabetes.

Neural correlates of appetite in adolescents

Appetitive characteristics are associated with child adiposity, but their biological underpinnings are unclear. We sought to investigate the neural correlates of psychometric and behavioral measures of appetitive characteristics in youth. Adolescents (14-18y; 39F, 37M) varying in familial obesity risk and body weight (20% with overweight, 24% with obesity) viewed pictures of high energy-density (ED) foods, low-ED foods and non-foods during fMRI scanning on two separate days. On one day participants consumed a 474 ml preload of water (0 kcal, fasted) and on another (counter-balanced) 474 ml milkshake (480 kcal, fed), before scanning. A multi-item ad libitum meal (ALM) followed scanning. Parents completed Child Eating Behavior Questionnaire (CEBQ) sub-scales assessing food approach and food self-regulation. Caloric compensation was calculated as the percentage of preload intake compensated for by down-regulation of ALM intake in the fed vs. fasted condition. Analyses correcting for multiple comparisons demonstrated that, for the fasted condition, higher CEBQ Food Responsiveness scores were associated with greater activation to high-ED (vs. low-ED) foods in regions implicated in food reward (insula, rolandic operculum, putamen). In addition, higher caloric compensation was associated with greater fed vs. fasted activations in response to foods (vs. non-foods) in thalamus and supramarginal gyrus. Uncorrected analyses provided further support for associations of different measures of appetitive characteristics with brain responses to food cues in each condition. Measures of appetitive characteristics demonstrated overlapping and distinct associations with patterns of brain activation elicited by food cues in fasted and fed states. Understanding the neural basis of appetitive characteristics could aid development of biobehaviorally-informed obesity interventions.

A paraventricular thalamus to insular cortex glutamatergic projection gates "emotional" stress-induced binge eating in females

It is well-established that stress and negative affect trigger eating disorder symptoms and that the brains of men and women respond to stress in different ways. Indeed, women suffer disproportionately from emotional or stress-related eating, as well as associated eating disorders such as binge eating disorder. Nevertheless, our understanding of the precise neural circuits driving this maladaptive eating behavior, particularly in women, remains limited. We recently established a clinically relevant model of 'emotional' stress-induced binge eating whereby only female mice display binge eating in response to an acute "emotional" stressor. Here, we combined neuroanatomic, transgenic, immunohistochemical and pathway-specific chemogenetic approaches to investigate whole brain functional architecture associated with stress-induced binge eating in females, focusing on the role of Vglut2 projections from the paraventricular thalamus (PVTVglut2+) to the medial insular cortex in this behavior. Whole brain activation mapping and hierarchical clustering of Euclidean distances revealed distinct patterns of coactivation unique to stress-induced binge eating. At a pathway-specific level, PVTVglut2+ cells projecting to the medial insular cortex were specifically activated in response to stress-induced binge eating. Subsequent chemogenetic inhibition of this pathway suppressed stress-induced binge eating. We have identified a distinct PVTVglut2+ to insular cortex projection as a key driver of "emotional" stress-induced binge eating in female mice, highlighting a novel circuit underpinning this sex-specific behavior.

Biobehavioral susceptibility for obesity in childhood: Behavioral, genetic and neuroimaging studies of appetite

Modern food environments are conducive to overeating and weight gain, but not everyone develops obesity. One reason for this may be that individuals differ in appetitive characteristics, or traits, that manifest early in life and go on to influence their behavioral susceptibility to gain and maintain excess weight. Classic studies showing that eating behavior in children can be measured by behavioral paradigms such as tests of caloric compensation and eating in the absence of hunger inspired the development and validation of psychometric instruments to assess appetitive characteristics in children and infants. A large body of evidence now suggests that food approach traits increase obesity risk, while food avoidant traits, such as satiety responsiveness, decrease obesity risk. Twin studies and genetic association studies have demonstrated that appetitive characteristics are heritable, consistent with a biological etiology. However, family environment factors are also influential, with mounting evidence suggesting that genetic and environmental risk factors interact and correlate with consequences for child eating behavior and weight. Further, neuroimaging studies are revealing that individual differences in responses to visual food cues, as well as to small tastes and larger amounts of food, across a number of brain regions involved in reward/motivation, cognitive control and other functions, may contribute to individual variation in appetitive behavior. Growing evidence also suggests that variation on psychometric measures of appetite is associated with regional differences in brain structure, and differential patterns of resting state functional connectivity. Large prospective studies beginning in infancy promise to enrich our understanding of neural and other biological underpinnings of appetite and obesity development in early life, and how the interplay between genetic and environmental factors affects appetitive systems. The biobehavioral susceptibility model of obesity development and maintenance outlined in this narrative review has implications for prevention and treatment of obesity in childhood.

Obesity-mediated Lipoinflammation Modulates Food Reward Responses

Accumulation of white adipose tissue (WAT) during obesity is associated with the development of chronic low-grade inflammation, a biological process known as lipoinflammation. Systemic and central lipoinflammation accumulates pro-inflammatory cytokines including IL-6, IL-1β and TNF-α in plasma and also in brain, disrupting neurometabolism and cognitive behavior. Obesity-mediated lipoinflammation has been reported in brain regions of the mesocorticolimbic reward circuit leading to alterations in the perception and consumption of ultra-processed foods. While still under investigation, lipoinflammation targets two major outcomes of the mesocorticolimbic circuit during food reward: perception and motivation ("Wanting") and the pleasurable feeling of feeding ("Liking"). This review will provide experimental and clinical evidence supporting the contribution of obesity- or overnutrition-related lipoinflammation affecting the mesocorticolimbic reward circuit and enhancing food reward responses. We will also address neuroanatomical targets of inflammatory profiles that modulate food reward responses during obesity and describe potential cellular and molecular mechanisms of overnutrition linked to addiction-like behavior favored by brain lipoinflammation.

Paediatric obesity and metabolic syndrome associations with cognition and the brain in youth: Current evidence and future directions

Obesity and components of the metabolic syndrome (MetS) are associated with differences in brain structure and function and in general and food-related cognition in adults. Here, we review evidence for similar phenomena in children and adolescents, with a focus on the implications of extant research for possible underlying mechanisms and potential interventions for obesity and MetS in youth. Current evidence is limited by a relative reliance on small cross-sectional studies. However, we find that youth with obesity and MetS or MetS components show differences in brain structure, including alterations in grey matter volume and cortical thickness across brain regions subserving reward, cognitive control and other functions, as well as in white matter integrity and volume. Children with obesity and MetS components also show some evidence for hyperresponsivity of food reward regions and hyporesponsivity of cognitive control circuits during food-related tasks, altered brain responses to food tastes, and altered resting-state connectivity including between cognitive control and reward processing networks. Potential mechanisms for these findings include neuroinflammation, impaired vascular reactivity, and effects of diet and obesity on myelination and dopamine function. Future observational research using longitudinal measures, improved sampling strategies and study designs, and rigorous statistical methods, promises to further illuminate dynamic relationships and causal mechanisms. Intervention studies targeted at modifiable biological and behavioural factors associated with paediatric obesity and MetS can further inform mechanisms, as well as test whether brain and behaviour can be altered for beneficial outcomes.

Binge-Eating Precursors in Children and Adolescents: Neurodevelopment, and the Potential Contribution of Ultra-Processed Foods

Binge-eating disorder (BED) is a highly prevalent disorder. Subthreshold BED conditions (sBED) are even more frequent in youth, but their significance regarding BED etiology and long-term prognosis is unclear. A better understanding of brain findings associated with BED and sBED, in the context of critical periods for neurodevelopment, is relevant to answer such questions. The present narrative review starts from the knowledge of the development of emotional self-regulation in youth, and the brain circuits supporting emotion-regulation and eating behaviour. Next, neuroimaging studies with sBED and BED samples will be reviewed, and their brain-circuitry overlap will be examined. Deficits in inhibition control systems are observed to precede, and hyperactivity of reward regions to characterize, sBED, with overlapping findings in BED. The imbalance between reward/inhibition systems, and the implication of interoception/homeostatic processing brain systems should be further examined. Recent knowledge of the potential impact that the high consumption of ultra-processed foods in paediatric samples may have on these sBED/BED-associated brain systems is then discussed. There is a need to identify, early on, those sBED individuals at risk of developing BED at neurodevelopmental stages when there is a great possibility of prevention. However, more neuroimaging studies with sBED/BED pediatric samples are needed.

Relation of Overweight/Obesity to Reward Region Response to Food Reward and the Moderating Effects of Parental History of Eating Pathology in Adolescent Females

OBJECTIVE

To test whether overweight/obesity is associated with an elevated reward region response to milkshake cues and a low reward region response to milkshake receipt. To test whether the risk for eating pathology moderates the effects of weight status on the neural response to milkshake cues and milkshake receipt.

METHOD

The current study used functional magnetic resonance imaging (fMRI) to examine the neuronal responses of female adolescents (n = 80; M age = 14.6 ± 0.9; M BMI = 21.9 ± 3.6; 41% with a biological parental history of eating pathology) during a food receipt paradigm.

RESULTS

Females with overweight/obesity showed a greater ventromedial prefrontal cortex (vmPFC), and ventral anterior cingulate (ACC) response to milkshake cues and a greater ventral striatum, subgenual ACC, and dorsomedial prefrontal cortex response to milkshake receipt than those with a healthy weight. Females with overweight/obesity plus a parental history of eating pathology showed a greater vmPFC/medial orbitofrontal cortex response to milkshake cues than those without a parental history of eating pathology and those with a healthy weight. Females with overweight/obesity and without a parental history of eating pathology showed a greater thalamus and striatum response to milkshake receipt.

CONCLUSIONS

Overweight/obesity is associated with an elevated reward region response to palatable food cues and food receipt. A risk for eating pathology enhances the reward region response to food cues in those with excess weight.

Associations between eating in the absence of hunger and executive functions in adolescents with binge-eating disorder: An experimental study

Eating in the absence of hunger (EAH) is one of the key behavioral features of binge-eating disorder (BED) in youth. Although preliminary evidence revealed that adolescent BED co-occurs with deficits in executive functions (EFs), it is unclear whether EFs are related to EAH. Thus, this study experimentally examined whether deficits in EFs predict EAH in adolescents with and without BED. Adolescents (12-20 years) with BED (n = 28) and age-, sex-, and weight-matched controls (n = 28) underwent an EAH paradigm in the laboratory, where they were offered snacks ad libitum after having established satiety during a lunch meal. Cognitive interference, cognitive flexibility, decision making, and EFs in daily life were assessed by neuropsychological tests and self-report. The BED group showed a significantly higher food intake in gram during the EAH trial than controls with medium effect, but no significant group differences in EFs emerged. Dysfunctional decision making in terms of risky decision making, but no other EFs, predicted increased EAH (g, kcal) in the total sample. Although increases in risky decision making over adolescence are well known, this study uniquely revealed that general decision-making abilities driven by short-term reward may account for disinhibited eating behavior. Interventions targeting decision making with focus on reward sensitivity should be evaluated for their efficacy in preventing and reducing disinhibited eating behavior in adolescents.

Factors Associated with Eating in the Absence of Hunger among Children and Adolescents: A Systematic Review

Eating in the absence of hunger (EAH) has been extensively studied over the past two decades and has been associated with excess body weight and the development of obesity. However, determinants of EAH remain uncertain. This systematic review aims to identify individual, familial, and environmental factors associated with EAH among children and adolescents. We included studies with a measure of EAH in participants aged 3-17 years old and including ≥1 factor associated with EAH. Our search identified 1494 articles. Of these, we included 81 studies: 53 cross-sectional, 19 longitudinal and nine intervention studies. In childhood (≤12 years old), EAH increases with age, it is greater in boys compared to girls, and it is positively associated with adiposity. Moreover, EAH development seems to be influenced by genetics. In adolescence, the number of studies is limited; yet, studies show that EAH slightly increases or remains stable with age, is not clearly different between sexes, and findings for overweight or obesity are less consistent across studies in adolescence. For familial factors, parental restrictive feeding practices are positively associated with EAH during childhood, mostly for girls. Studies assessing environmental factors are lacking and robust longitudinal studies spanning from early childhood to adolescence are needed.

Food cue reactivity: Neurobiological and behavioral underpinnings

The modern obesogenic environment contains an abundance of food cues (e.g., sight, smell of food) as well cues that are associated with food through learning and memory processes. Food cue exposure can lead to food seeking and excessive consumption in otherwise food-sated individuals, and a high level of food cue responsivity is a risk factor for overweight and obesity. Similar food cue responses are observed in experimental rodent models, and these models are therefore useful for mechanistically identifying the neural circuits mediating food cue responsivity. This review draws from both experimental rodent models and human data to characterize the behavioral and biological processes through which food-associated stimuli contribute to overeating and weight gain. Two rodent models are emphasized - cue-potentiated feeding and Pavlovian-instrumental transfer - that provide insight in the neural circuits and peptide systems underlying food cue responsivity. Data from humans are highlighted that reveal physiological, psychological, and neural mechanisms that connect food cue responsivity with overeating and weight gain. The collective literature identifies connections between heightened food cue responsivity and obesity in both rodents and humans, and identifies underlying brain regions (nucleus accumbens, amygdala, orbitofrontal cortex, hippocampus) and endocrine systems (ghrelin) that regulate food cue responsivity in both species. These species similarities are encouraging for the possibility of mechanistic rodent model research and further human research leading to novel treatments for excessive food cue responsivity in humans.

Decreased excitability of leptin-sensitive anterior insula pyramidal neurons in a rat model of compulsive food demand

Compulsive eating is an overlapping construct with binge eating that shares many characteristics with substance use disorders. Compulsive eating may impact millions of Americans; presenting in some cases of binge eating disorders, overweight/obesity, and among individuals who have not yet been diagnosed with a recognized eating disorder. To study the behavioral and neurobiological underpinnings of compulsive eating, we employ a published rodent model using cyclic intermittent access to a palatable diet to develop a self-imposed binge-withdrawal cycle. Here, we further validated this model of compulsive eating in female Wistar rats, through the lens of behavioral economic analyses and observed heightened demand intensity, inelasticity and essential value as well as increased food-seeking during extinction. Using electrophysiological recordings in the anterior insular cortex, a region previously implicated in modulating compulsive-like eating in intermittent access models, we observed functional adaptations of pyramidal neurons. Within the same neurons, application of leptin led to further functional adaptations, suggesting a previously understudied, extrahypothalamic role of leptin in modulating feeding-related cortical circuits. Collectively, the findings suggest that leptin may modulate food-related motivation or decision-making via a plastic cortical circuit that is influenced by intermittent access to a preferred diet. These findings warrant further study of whether behavioral economics analysis of compulsive eating can impact disordered eating outcomes in humans and of the translational relevance of a leptin-sensitive anterior insular circuit implicated in these behaviors.

Human Primary Olfactory Amygdala Subregions Form Distinct Functional Networks, Suggesting Distinct Olfactory Functions

Three subregions of the amygdala receive monosynaptic projections from the olfactory bulb, making them part of the primary olfactory cortex. These primary olfactory areas are located at the anterior-medial aspect of the amygdala and include the medial amygdala (MeA), cortical amygdala (CoA), and the periamygdaloid complex (PAC). The vast majority of research on the amygdala has focused on the larger basolateral and basomedial subregions, which are known to be involved in implicit learning, threat responses, and emotion. Fewer studies have focused on the MeA, CoA, and PAC, with most conducted in rodents. Therefore, our understanding of the functions of these amygdala subregions is limited, particularly in humans. Here, we first conducted a review of existing literature on the MeA, CoA, and PAC. We then used resting-state fMRI and unbiased k-means clustering techniques to show that the anatomical boundaries of human MeA, CoA, and PAC accurately parcellate based on their whole-brain resting connectivity patterns alone, suggesting that their functional networks are distinct, relative both to each other and to the amygdala subregions that do not receive input from the olfactory bulb. Finally, considering that distinct functional networks are suggestive of distinct functions, we examined the whole-brain resting network of each subregion and speculated on potential roles that each region may play in olfactory processing. Based on these analyses, we speculate that the MeA could potentially be involved in the generation of rapid motor responses to olfactory stimuli (including fight/flight), particularly in approach/avoid contexts. The CoA could potentially be involved in olfactory-related reward processing, including learning and memory of approach/avoid responses. The PAC could potentially be involved in the multisensory integration of olfactory information with other sensory systems. These speculations can be used to form the basis of future studies aimed at clarifying the olfactory functions of these under-studied primary olfactory areas.

Multimodal brain predictors of current weight and weight gain in children enrolled in the ABCD study ®

Multimodal neuroimaging assessments were utilized to identify generalizable brain correlates of current body mass index (BMI) and predictors of pathological weight gain (i.e., beyond normative development) one year later. Multimodal data from children enrolled in the Adolescent Brain Cognitive Development Study® at 9-to-10-years-old, consisted of structural magnetic resonance imaging (MRI), diffusion tensor imaging (DTI), resting state (rs), and three task-based functional (f) MRI scans assessing reward processing, inhibitory control, and working memory. Cross-validated elastic-net regression revealed widespread structural associations with BMI (e.g., cortical thickness, surface area, subcortical volume, and DTI), which explained 35% of the variance in the training set and generalized well to the test set (R2 = 0.27). Widespread rsfMRI inter- and intra-network correlations were related to BMI (R2train = 0.21; R2test = 0.14), as were regional activations on the working memory task (R2train = 0.20; (R2test = 0.16). However, reward and inhibitory control tasks were unrelated to BMI. Further, pathological weight gain was predicted by structural features (Area Under the Curve (AUC)train = 0.83; AUCtest = 0.83, p < 0.001), but not by fMRI nor rsfMRI. These results establish generalizable brain correlates of current weight and future pathological weight gain. These results also suggest that sMRI may have particular value for identifying children at risk for pathological weight gain.

Developmental Changes in Food Perception and Preference

Food choices are a key determinant of dietary intake, with brain regions, such as the mesolimbic and prefrontal cortex maturing at differential rates into adulthood. More needs to be understood about developmental changes in healthy and unhealthy food perceptions and preference. We investigated how food perceptions and preference vary as a function of age and how food attributes (taste and health) impact age-related changes. One hundred thirty-nine participants (8–23 years, 60 females) completed computerized tasks to rate high-calorie and low-calorie food cues for taste, health, and liking (preference), followed by 100 binary food choices based on each participant’s ratings. Dietary self-control was considered successful when the healthier (vs. tastier) food was chosen. Self-control success ratio was the proportion of success trials over total number of choices. Beta-weights for health (β-health) and taste (β-taste) were calculated as each attribute’s influence on food preference. Adiposity measurements included BMI z-score and waist-to-height ratio (WHtR). High-calorie foods were rated more tasty and less healthy with increasing age. Older participants liked high-calorie foods more (vs. younger participants), and β-taste was associated with age. Significant age-by-WHtR interactions were observed for health and taste ratings of high-calorie foods, β-taste, and marginally for preference of high-calorie foods. Stratifying by WHtR (high, low), we found age-related increases in taste and preference ratings of high-calorie foods in the high WHtR group alone. In contrast, age-related decreases in health ratings of high-calorie foods were significant in the low WHtR group alone. Age and β-taste were significantly associated in the high WHtR group and only marginally significant with low WHtR. Although participants rated low-calorie foods as less tasty and less healthy with increasing age, there was no association between age and preference for low-calorie foods. Participants made faster food choices with increasing age regardless of WHtR, with a significant age-by-WHtR interaction on reaction time (RT). There were no age-related effects in self-control success ratio and β-health. These results suggest that individual differences in age and central adiposity play an important role in preference for high-calorie foods, and a higher importance of food tastiness in food choice may contribute to greater preference for high-calorie foods with increasing age.

The Effect of Food Composition and Behavior on Neurobiological Response to Food: a Review of Recent Research

PURPOSE OF REVIEW

Controversy surrounds the construct of food addiction. The current review examines neurobiological evidence for the existence of food addiction as a valid diagnosis.

RECENT FINDINGS

Recent neuroimaging studies suggest significant overlap in the areas of the brain that are activated in relation to both food and drug addiction. Specifically, areas of the brain implicated in executive functioning (e.g., attention, planning, decision-making, inhibition), pleasure and the experience of reward, and sensory input and motor functioning display increased activation among individuals with symptoms of both food and drug addiction. Proposed symptoms of food addiction mirror those comprising other substance use disorder diagnoses, with similar psychological and behavioral sequelae. Results of neuroimaging studies suggest significant overlap in the areas of the brain that are activated in relation to both food and drug addiction, providing support for continued research into the construct of food addiction.

Associations Between Exposure to Gestational Diabetes Mellitus In Utero and Daily Energy Intake, Brain Responses to Food Cues, and Adiposity in Children

OBJECTIVE

Children exposed to gestational diabetes mellitus (GDM) or maternal obesity in utero have an increased propensity to develop obesity. Little is known about the mechanisms underlying this phenomenon. We aimed to examine relationships between exposure to GDM or maternal obesity and daily energy intake (EI), brain responses to food cues within reward regions, and adiposity in children.

RESEARCH DESIGN AND METHODS

Participants were 159 children ages 7-11 years. Repeated 24-h recalls were conducted to assess mean daily EI. A subset of children (n = 102) completed a food cue task in the MRI scanner. A priori regions of interest included the orbital frontal cortex (OFC), insula, amygdala, ventral striatum, and dorsal striatum. Adiposity measurements, BMI z-scores, percent body fat, waist-to-height ratio (WtHR), and waist-to-hip ratio (WHR) were assessed.

RESULTS

Exposure to GDM was associated with greater daily EI, and children exposed to GDM diagnosed before 26 weeks gestation had greater OFC food cue reactivity. Children exposed to GDM also had larger WHR. Results remained significant after adjusting for child's age and sex, maternal education and race/ethnicity, maternal prepregnancy BMI, and child's physical activity levels. Furthermore, children who consumed more daily calories had greater WHR, and the relationship between GDM exposure and WHR was attenuated after adjustment for daily EI. Prepregnancy BMI was not significantly related to daily EI or food cue reactivity in reward regions. However, prepregnancy BMI was significantly related to all adiposity measurements; results remained significant for BMI z-scores, WtHR, and WHR after controlling for child's age and sex, maternal education and race/ethnicity, maternal GDM exposure, and child's physical activity levels.

CONCLUSIONS

Exposure to GDM in utero, in particular before 26 weeks gestation, is associated with increased EI, enhanced OFC food cue reactivity, and increased WHR. Future study with longitudinal follow-up is merited to assess potential pathways of daily EI and food cue reactivity in reward regions on the associations between GDM exposure and childhood adiposity.

Acute after-school screen time in children decreases impulse control and activation toward high-calorie food stimuli in brain regions related to reward and attention

The purpose of this study was to examine the effects of after-school sedentary screen time on children's brain activation in reward and cognitive control regions in response to pictures of high- and low-calorie foods. Thirty-two children participated in a randomized crossover study with counterbalanced treatment conditions. Conditions took place on separate days after school and included three hours of active or sedentary play. After each condition, neural activation was assessed using functional magnetic resonance imaging (fMRI) while participants completed a go/no-go task involving pictures of high- and low-calorie foods. General response inhibition was also measured using the Stroop task. Hunger was measured upon arrival to the testing facility and just prior to fMRI scans. Mixed effects models were used to evaluate main effects and interactions. Significant stimulus by condition interactions were found in the right superior parietal cortex, and left anterior cingulate cortex (Ps ≤ 0.05). High-calorie pictures elicited significantly more activation bilaterally in the orbitofrontal cortex compared to low-calorie pictures (Ps ≤ 0.05). Stroop task performance diminished significantly following the sedentary condition compared to the active (P ≤ 0.05). Subjective feelings of hunger were not different between conditions at any point. Sedentary screen time was associated with significantly decreased response inhibition and a reversed brain activation pattern to pictures of high- and low-calorie foods compared to active play, in areas of the brain important to the modulation of food intake. Decreased attention, and impulse control following sedentary screen time may contribute to disinhibited eating that can lead to overweight and obesity.

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'.

Neonatal amygdala microstructure mediates the relationship between gestational glycemia and offspring adiposity

INTRODUCTION

To determine if variations in the neonatal amygdala mediate the association between maternal antenatal glycemia and offspring adiposity in early childhood.

RESEARCH DESIGN AND METHODS

123 non-obese pregnant women with no pregnancy complications aside from gestational diabetes underwent a 75 g 2-hour oral glucose tolerance test at 26-28 weeks' gestation. Volume and fractional anisotropy (FA) of the neonatal amygdala (5-17 days old) were measured by MRI. The Body Mass Index (BMI) z-scores and sum of skinfold thickness (subscapular and triceps) of these children were tracked up to 60 months of age (18, 24, 36, 48, 54 and 60 months).

RESULTS

Maternal fasting glucose levels were positively associated with the offspring's sum of skinfold thickness at age 48 months (β=3.12, 95% CI 0.18 to 6.06 mm) and 60 months (β=4.14, 95% CI 0.46 to 7.82 mm) and BMI z-scores at 48 months (β=0.94, 95% CI 0.03 to 1.85), 54 months (β=0.74, 95% CI 0.12 to 1.36) and 60 months (β=0.74, 95% CI 0.08 to 1.39). Maternal fasting glucose was negatively associated with the offspring's FA of the right amygdala (β=-0.019, 95% CI -0.036 to -0.003). Right amygdala FA was negatively associated with the sum of skinfold thickness in the offspring at age 48 months (β=-56.95, 95% CI -98.43 to -15.47 mm), 54 months (β=-46.18, 95% CI -88.57 to -3.78 mm), and 60 months (β=-53.69, 95% CI -105.74 to -1.64 mm). The effect sizes mediated by right amygdala FA between fasting glucose and sum of skinfolds were estimated at β=5.14 (95% CI 0.74 to 9.53) mm (p=0.022), β=4.40 (95% CI 0.08 to 8.72) (p=0.049) mm and β=4.56 (95% CI -0.17 to 9.29) mm (p=0.059) at 48, 54 and 60 months, respectively.

CONCLUSIONS

In the offspring of non-obese mothers, gestational fasting glucose concentration is negatively associated with neonatal right amygdala FA and positively associated with childhood adiposity. Neonatal right amygdala FA may be a potential mediator between maternal glycemia and childhood adiposity.

A systematic review of neural correlates of dysregulated eating associated with obesity risk in youth

Dysregulated eating among children and adolescents is associated with a wide range of negative mental and physical health outcomes, including obesity. However, less is known regarding underlying neural mechanisms underlying such behaviors. Therefore, the present manuscript systematically reviewed neuroimaging research examining dysregulated eating behavior linked to excess weight in children and adolescents. A systematic literature search identified 23 eligible studies, the majority of which were cross-sectional functional magnetic resonance imaging (fMRI) studies and excluded participants with psychiatric disorders. Dysregulated eating was captured by measures of eating styles and eating self-regulation, eating disorder behaviors, food addiction, objective measures of non-homeostatic eating and caloric restriction. While preliminary, findings suggested eating dysregulation was related to aberrant functioning within the frontostriatal and frontoparietal regions involved in self-regulatory processes, as well as regions involved in satiety signaling and interoception. This heterogeneous body of research is continually growing and may have potential to inform future prevention and intervention approaches. Results also identified several important limitations to consider and highlight key areas for future research.

Impact of High Fat Diet and Ethanol Consumption on Neurocircuitry Regulating Emotional Processing and Metabolic Function

The prevalence of psychiatry disorders such as anxiety and depression has steadily increased in recent years in the United States. This increased risk for anxiety and depression is associated with excess weight gain, which is often due to over-consumption of western diets that are typically high in fat, as well as with binge eating disorders, which often overlap with overweight and obesity outcomes. This finding suggests that diet, particularly diets high in fat, may have important consequences on the neurocircuitry regulating emotional processing as well as metabolic functions. Depression and anxiety disorders are also often comorbid with alcohol and substance use disorders. It is well-characterized that many of the neurocircuits that become dysregulated by overconsumption of high fat foods are also involved in drug and alcohol use disorders, suggesting overlapping central dysfunction may be involved. Emerging preclinical data suggest that high fat diets may be an important contributor to increased susceptibility of binge drug and ethanol intake in animal models, suggesting diet could be an important aspect in the etiology of substance use disorders. Neuroinflammation in pivotal brain regions modulating metabolic function, food intake, and binge-like behaviors, such as the hypothalamus, mesolimbic dopamine circuits, and amygdala, may be a critical link between diet, ethanol, metabolic dysfunction, and neuropsychiatric conditions. This brief review will provide an overview of behavioral and physiological changes elicited by both diets high in fat and ethanol consumption, as well as some of their potential effects on neurocircuitry regulating emotional processing and metabolic function.

NIH Workshop Report: sensory nutrition and disease

In November 2019, the NIH held the "Sensory Nutrition and Disease" workshop to challenge multidisciplinary researchers working at the interface of sensory science, food science, psychology, neuroscience, nutrition, and health sciences to explore how chemosensation influences dietary choice and health. This report summarizes deliberations of the workshop, as well as follow-up discussion in the wake of the current pandemic. Three topics were addressed: A) the need to optimize human chemosensory testing and assessment, B) the plasticity of chemosensory systems, and C) the interplay of chemosensory signals, cognitive signals, dietary intake, and metabolism. Several ways to advance sensory nutrition research emerged from the workshop: 1) refining methods to measure chemosensation in large cohort studies and validating measures that reflect perception of complex chemosensations relevant to dietary choice; 2) characterizing interindividual differences in chemosensory function and how they affect ingestive behaviors, health, and disease risk; 3) defining circuit-level organization and function that link and interact with gustatory, olfactory, homeostatic, visceral, and cognitive systems; and 4) discovering new ligands for chemosensory receptors (e.g., those produced by the microbiome) and cataloging cell types expressing these receptors. Several of these priorities were made more urgent by the current pandemic because infection with sudden acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and the ensuing coronavirus disease of 2019 has direct short- and perhaps long-term effects on flavor perception. There is increasing evidence of functional interactions between the chemosensory and nutritional sciences. Better characterization of this interface is expected to yield insights to promote health, mitigate disease risk, and guide nutrition policy.

Prefrontal Cortex and Amygdala Subregion Morphology Are Associated With Obesity and Dietary Self-control in Children and Adolescents

A prefrontal control system that is less mature than the limbic reward system in adolescence is thought to impede self-regulatory abilities, which could contribute to poor dietary choices and obesity. We, therefore, aimed to examine whether structural morphology of the prefrontal cortex (PFC; involved in cognitive control) and the amygdala (a key brain region for reward-related processing) are associated with dietary decisions and obesity in children and adolescents. Seventy-one individuals between the ages of 8-22 years (17.35 ± 4.76 years, 51% female, 56% were overweight or obese) participated in this study; each participant completed a computer-based food choice task and a T1- and T2-weighted structural brain scans. Two indices of obesity were assessed, including age- and sex-specific body mass index (BMIz) and waist-to-height ratio (WHtR). The behavioral task included rating 60 food stimuli for tastiness, healthiness, and liking. Based on each participant's self-ratings, 100 binary food choices were then made utilizing a computer mouse. Dietary "self-control" was calculated as the proportion of trials where the individual chose the healthier food item (vs. the tastier food item) over the total number of trials. Cortical thickness and amygdala subnuclei volumes were quantified using FreeSurfer 6.0 and CIT168 atlas, respectively. We found that WHtR was negatively associated with the thickness of bilateral superior frontal, left superior temporal, right insula, and right inferior temporal regions (p < 0.05, corrected for multiple comparisons). We also found WHtR to be positively associated with the volume of the central nucleus (CEN) region of the amygdala (p = 0.006), after adjusting for the hemisphere, age, sex, and intracranial volumes. A similar data pattern was observed when BMIz was used. Moreover, we found that across all participants, thinner right superior frontal cortex and larger left CEN volumes predicted lower dietary self-control. These results suggest that differential development of the PFC and amygdala relate to obesity and dietary self-control. Further longitudinal studies are merited to determine causal relationships among altered PFC to amygdala neural circuitry, dietary self-control, and obesity.

Chemogenetic silencing of hippocampus and amygdala reveals a double dissociation in periadolescent obesogenic diet-induced memory alterations

In addition to numerous metabolic comorbidities, obesity is associated with several adverse neurobiological outcomes, especially learning and memory alterations. Obesity prevalence is rising dramatically in youth and is persisting in adulthood. This is especially worrying since adolescence is a crucial period for the maturation of certain brain regions playing a central role in memory processes such as the hippocampus and the amygdala. We previously showed that periadolescent, but not adult, exposure to obesogenic high-fat diet (HFD) had opposite effects on hippocampus- and amygdala-dependent memory, impairing the former and enhancing the latter. However, the causal role of these two brain regions in periadolescent HFD-induced memory alterations remains unclear. Here, we first showed that periadolescent HFD induced long-term, but not short-term, object recognition memory deficits, specifically when rats were exposed to a novel context. Using chemogenetic approaches to inhibit targeted brain regions, we then demonstrated that recognition memory deficits are dependent on the activity of the ventral hippocampus, but not the basolateral amygdala. On the contrary, the HFD- induced enhancement of conditioned odor aversion specifically requires amygdala activity. Taken together, these findings suggest that HFD consumption throughout adolescence impairs long-term object recognition memory through alterations of ventral hippocampal activity during memory acquisition. Moreover, these results further highlight the bidirectional effects of adolescent HFD on hippocampal and amygdala functions.

Associations Between Body Weight, Hippocampal Volume, and Tissue Signal Intensity in 12- to 18-Year-Olds

OBJECTIVE

The hippocampus is a key structure in feeding behaviors and weight regulation. Obesity may lead to disruptions in hippocampal structure. In animals, obesity-related factors (e.g., high-fat/sugar foods) are associated with hippocampal insult (e.g., alterations in the blood brain barrier). In humans, individuals with obesity, relative to healthy weight, have smaller hippocampal volumes. Few studies have examined the association between body weight and the hippocampus during adolescence, a critical brain development period. This study examined hippocampal volume and tissue signal intensity in adolescents across the weight spectrum.

METHODS

Structural magnetic resonance imaging and anthropomorphic data were available for 102 12- to 18-year-old adolescents (53% female; 15.07 [SD 1.84] years; standardized BMI [BMIz] scores using the Centers for Disease Control and Prevention growth charts: 0.54 [SD 1.17]) from the Pediatric Imaging, Neurocognition, and Genetics database. Linear regression models controlling for age, sex, genetic ancestry, scanner, and household income examined the relationship between BMIz, hippocampal volume, and T2-weighted hippocampal signal intensity.

RESULTS

BMIz was negatively associated with T2-weighted hippocampal signal intensity in the left (t = -3.05; P = 0.003; r = -0.21) and right (t = -2.50; P = 0.01; r = -0.36) hippocampi. BMIz was not significantly associated with hippocampal volume.

CONCLUSIONS

BMIz is associated with hippocampal tissue characteristics during adolescence, which could impact later brain development.

Appetitive traits as targets for weight loss: The role of food cue responsiveness and satiety responsiveness

Individuals with overweight or obesity (OW/OB) are at increased risk for significant physical and psychological comorbidities. The current treatment for OW/OB is behavioral weight loss, which provides psychoeducation on nutrition and physical activity, as well as behavior therapy skills. However, behavioral weight loss is not effective for the majority of the individuals who participate. Research suggests that overeating, or eating past nutritional needs, is one of the leading causes of weight gain. Accumulating evidence suggests that appetitive traits, such as food cue responsiveness and satiety responsiveness, are associated with overeating and weight in youth and adults. The following review presents the current literature on the relationship between food cue responsiveness, satiety responsiveness, overeating, and OW/OB. Research suggests that higher food cue responsiveness and lower satiety responsiveness are associated with overeating and OW/OB cross-sectionally and longitudinally. Emerging data suggest that food cue responsiveness and satiety responsiveness may exist along the same continuum and can be targeted to manage overeating and reduce weight. We have developed a treatment model targeting food cue responsiveness and satiety responsiveness to reduce overeating and weight and have preliminary feasibility, acceptability, and efficacy data, with testing currently being conducted in larger trials. Through programs targeting appetitive traits we hope to develop an alternative weight loss model to assist individuals with a propensity to overeat.

Hunger and BMI modulate neural responses to sweet stimuli: fMRI meta-analysis

OBJECTIVE

Consuming sweet foods, even when sated, can lead to unwanted weight gain. Contextual factors, such as longer time fasting, subjective hunger, and body mass index (BMI), may increase the likelihood of overeating. Nevertheless, the neural mechanisms underlying these moderating influences on energy intake are poorly understood.

METHODS

We conducted both categorical meta-analysis and meta-regression of factors modulating neural responses to sweet stimuli, using data from 30 functional magnetic resonance imaging (fMRI) articles incorporating 39 experiments (N = 995) carried out between 2006 and 2019.

RESULTS

Responses to sweet stimuli were associated with increased activity in regions associated with taste, sensory integration, and reward processing. These taste-evoked responses were modulated by context. Longer fasts were associated with higher posterior cerebellar, thalamic, and striatal activity. Greater self-reported hunger was associated with higher medial orbitofrontal cortex (OFC), dorsal striatum, and amygdala activity and lower posterior cerebellar activity. Higher BMI was associated with higher posterior cerebellar and insular activity.

CONCLUSIONS

Variations in fasting time, self-reported hunger, and BMI are contexts associated with differential sweet stimulus responses in regions associated with reward processing and homeostatic regulation. These results are broadly consistent with a hierarchical model of taste processing. Hunger, but not fasting or BMI, was associated with sweet stimulus-related OFC activity. Our findings extend existing models of taste processing to include posterior cerebellar regions that are associated with moderating effects of both state (fast length and self-reported hunger) and trait (BMI) variables.

Insula to ventral striatal projections mediate compulsive eating produced by intermittent access to palatable food

Compulsive eating characterizes many binge-related eating disorders, yet its neurobiological basis is poorly understood. The insular cortex subserves visceral-emotional functions, including taste processing, and is implicated in drug craving and relapse. Here, via optoinhibition, we implicate projections from the anterior insular cortex to the nucleus accumbens as modulating highly compulsive-like food self-administration behaviors that result from intermittent access to a palatable, high-sucrose diet. We identified compulsive-like eating behavior in female rats through progressive ratio schedule self-administration and punishment-resistant responding, food reward tolerance and escalation of intake through 24-h energy intake and fixed-ratio operant self-administration sessions, and withdrawal-like irritability through the bottle brush test. We also identified an endocrine profile of heightened GLP-1 and PP but lower ghrelin that differentiated rats with the most compulsive-like eating behavior. Measures of compulsive eating severity also directly correlated to leptin, body weight and adiposity. Collectively, this novel model of compulsive-like eating symptoms demonstrates adaptations in insula-ventral striatal circuitry and metabolic regulatory hormones that warrant further study.

Role of appetitive phenotype trajectory groups on child body weight during a family-based treatment for children with overweight or obesity

OBJECTIVE

Emerging evidence suggests that individual appetitive traits may usefully explain patterns of weight loss in behavioral weight loss treatments for children. The objective of this study was to identify trajectories of child appetitive traits and the impact on child weight changes over time.

METHODS

Secondary data analyses of a randomized noninferiority trial conducted between 2011 and 2015 evaluated children's appetitive traits and weight loss. Children with overweight and obesity (mean age = 10.4; mean BMI z = 2.0; 67% girls; 32% Hispanic) and their parent (mean age = 42.9; mean BMI = 31.9; 87% women; 31% Hispanic) participated in weight loss programs and completed assessments at baseline, 3, 6,12, and 24 months. Repeated assessments of child appetitive traits, including satiety responsiveness, food responsiveness and emotional eating, were used to identify parsimonious grouping of change trajectories. Linear mixed-effects models were used to identify the impact of group trajectory on child BMIz change over time.

RESULTS

One hundred fifty children and their parent enrolled in the study. The three-group trajectory model was the most parsimonious and included a high satiety responsive group (HighSR; 47.4%), a high food responsive group (HighFR; 34.6%), and a high emotional eating group (HighEE; 18.0%). Children in all trajectories lost weight at approximately the same rate during treatment, however, only the HighSR group maintained their weight loss during follow-ups, while the HighFR and HighEE groups regained weight (adjusted p-value < 0.05).

CONCLUSIONS

Distinct trajectories of child appetitive traits were associated with differential weight loss maintenance. Identified high-risk subgroups may suggest opportunities for targeted intervention and maintenance programs.

Changes in brain activity after weight loss

OBJECTIVES

The importance of the regulatory role of the brain in directing glucose homeostasis, energy homeostasis, eating behaviour, weight control and obesity is increasingly recognized. Brain activity in (sub)cortical neuronal networks involved in homeostatic control and hedonic responses is generally increased in persons with obesity. Currently, it is not known if these functional changes can be affected by dieting. The aim of the current study was to investigate whether prolonged fasting and/or weight loss influences neuronal brain activity in obese persons.

METHODS

Fourteen participants with obesity were included (two male participants and 12 female participants, body mass index 35.2 ± 1.2 kg m-2). Whole-brain resting-state functional magnetic resonance imaging was performed after an overnight fast, after a prolonged 48-h fast and after an 8-week weight loss intervention.

RESULTS

An 8-week weight loss intervention decreased BOLD signal in areas of the brain involved in salience, sensory motor and executive control. BOLD signal in these areas correlated with leptin levels and body mass index.

CONCLUSIONS

Weight loss decreased activity in brain areas involved in feeding behaviour and reward processing. These results indicate that these obesity-associated alterations in neuronal activity are related to excessive body weight and might change after weight loss.

Of mice and men: incretin actions in the central nervous system

Incretins have risen to the forefront of therapies for obesity and related metabolic complications, primarily because of their efficacy and relatively few side effects. Importantly, their efficacy in altering energy balance and decreasing body weight is apparently through actions in the central nervous system (CNS); the latter may have implications beyond obesity per se, i.e. in other disease states associated with obesity including CNS-related disorders. Here, we first describe the role of the CNS in energy homeostasis and then the current state of knowledge in terms of incretin physiology, pathophysiology and efficacy in preclinical and clinical studies. In the future, more clinical studies are needed to fully map mechanistic pathways underlying incretin actions and outcomes in the human CNS. Additionally, future research will likely lead to the discovery of additional novel incretins and/or more efficacious medications with less side effects through the improvement of current compounds with properties that would allow them to have more favorable pharmacokinetic and pharmacodynamic profiles and/or by combining known and novel incretins into safe and more efficacious combination therapies leading ultimately to more tangible benefits for our patients.

Taste loss with obesity in mice and men

BACKGROUND

Our sense of taste is critical in defining our food choices and habits. Located primarily in our tongue, taste buds are small assemblies of constantly renewing sensory cells, tasked with evaluating oral stimuli before the food we eat is consumed.

METHODS

Using both mice and a free-living human population, we tracked taste papilla abundancy with weight gain, to test for deficiencies in the taste system of obese mice and humans with increased adiposity.

RESULTS

Mice fed a high-fat diet for 8 weeks expressed markers for all subtypes of taste cells at a lower level than chow-fed counterparts. This came alongside the loss of markers for taste cell proliferation (Ki-67) and development (β-catenin), as well as lower fungiform papillae density, consistent with earlier results showing lower circumvallate taste bud abundance in obese mice. Likewise, in a population of college students tracked through 4 years of college attendance, the change in density of fungiform papillae, which house taste buds in the anterior tongue, was negatively correlated with change in neck circumference, a marker of adiposity.

CONCLUSIONS

These results highlight changes in taste during weight gain as a potentially important consideration in the study of obesity.

Eating in the absence of hunger in young children is related to brain reward network hyperactivity and reduced functional connectivity in executive control networks

BACKGROUND

Recent work has implicated disinhibited eating behaviours (DEB) as a potential pathway toward obesity development in children. However, the underlying neurobiology of disinhibited eating behaviours in young, healthy weight children, prior to obesity development, remains unknown.

OBJECTIVES

This study tested the relationship between DEB and intrinsic neuronal activity and connectivity in young children without obesity.

METHODS

Brain networks implicated in overeating including reward, salience and executive control networks, and the default mode network were investigated. DEB was measured by the eating in the absence of hunger (EAH) paradigm with postlunch kilocalories consumed from highly palatable foods (EAH kcal) used as the predictor. Intrinsic neuronal activity within and connectivity between specified networks were measured via resting-state functional magnetic resonance imaging. Eighteen typically developing children (mean age = 5.8 years) were included.

RESULTS

EAH kcal was positively associated with activity of the nucleus accumbens, a major reward network hub (P < 0.05, corrected). EAH kcal was negatively associated with intrinsic prefrontal cortex connectivity to the striatum (P < 0.01, corrected).

CONCLUSIONS

These results suggest that neural aspects of DEB are detectable in young children without obesity, providing a potential tool to better understand the development of obesity in this population.

Neural processing of food cues in pre-pubertal children

BACKGROUND/OBJECTIVES

Neuroimaging investigations of brain pathways involved in reward and motivation have primarily focused on adults. This study sought to identify brain responses to visual food cues and explore its relationships with adiposity and sex in pre-pubertal children.

METHODS

Brain responses to palatable food vs. non-food cues were measured in 53 children (age: 8.18 ± .66 years; sex: 22 boys, 31 girls) after an overnight fast. Whole-brain analysis (cluster-correction Z > 2.3, P < .05) was performed to examine brain food cue reactivity and its relationships with adiposity and sex.

RESULTS

Greater brain activity in response to food vs. non-food cues was observed in regions implicated in reward (orbital frontal cortex, striatum), taste (insula, postcentral gyrus), appetite (hypothalamus), emotion (amygdala), memory (hippocampus), visual processing (occipital cortex) and attention (parietal cortex). A negative association was found between percent body fat and food cue reactivity in the medial prefrontal cortex and lateral orbital frontal cortex adjusting for age and sex. Boys compared with girls had increased food cue reactivity in right hippocampus and visual cortex.

CONCLUSIONS

These data suggest that body fat and sex are important moderators of brain food cue reactivity in children.

Food or money? Children's brains respond differently to rewards regardless of weight status

BACKGROUND

Brain responses to both food and monetary rewards have been linked to weight gain and obesity in adults, suggesting that general sensitivity to reward contributes to overeating. However, the relationship between brain reward response and body weight in children is unclear.

OBJECTIVE

The objective of this study was to assess the brain's response to multiple rewards and the relationship to body weight in children.

METHODS

We tested this by performing functional magnetic resonance imaging while children (7- to 11-years-old; healthy weight [n = 31], overweight/obese [n = 30]) played a modified card-guessing task to assess blood-oxygen-level-dependent (BOLD) response to anticipating and winning food and money rewards. Functional magnetic resonance imaging data were analysed using a region of interest and exploratory whole-brain approach.

RESULTS

Region of interest results demonstrated increased BOLD response in the striatum to anticipating food vs. neutral (control) and winning money vs. neutral. Whole-brain data showed that winning money vs. food was associated with increased activation in the striatum, as well as regions associated with cognitive control and emotion. Notably, for both approaches, these effects were independent of child weight status. Additionally, children's reported food responsiveness and emotional overeating were negatively correlated with the BOLD response in the left cingulate gyrus for winning food vs. money.

CONCLUSION

Overall, findings from this study show that regions associated with reward, cognitive control and emotion may play a role in the brain's response to food and money rewards, independently of how much the child weighs. These findings provide insight into reward sensitivity in children, which may have implications for understanding overeating and the development of obesity.

Oxytocin and Prader-Willi Syndrome

In the chapter, we explore the relationship between the peptide hormone, oxytocin (OT), and behavioral and metabolic disturbances observed in the genetic disorder Prader-Willi Syndrome (PWS). Phenotypic and genotypic characteristics of PWS are described, as are the potential implications of an abnormal OT system with respect to neural development including the possible effects of OT dysfunction on interactions with other regulatory mediators, including neurotransmitters, neuromodulators, and hormones. The major behavioral characteristics are explored in the context of OT dysfunction, including hyperphagia, impulsivity, anxiety and emotion dysregulation, sensory processing and interoception, repetitive and restrictive behaviors, and dysfunctional social cognition. Behavioral overlaps with autistic spectrum disorders are discussed. The implications of OT dysfunction on the mechanisms of reward and satiety and their possible role in informing behavioral characteristics are also discussed. Treatment implications and future directions for investigation are considered.

Percepción del gusto como factor de riesgo para obesidad infantil

Objetivo. Describir el papel de la percepción del gusto como factor de riesgo para el desarrollo de obesidad en niños. Material y métodos. Se realizó una búsqueda inicial de artículos científicos publicados en PubMed entre el 1 de enero de 2011 y el 20 de marzo de 2016 para el tema sobrepeso y obesidad en niños de entre 0 y 12 años. Los algoritmos utilizados fueron (Obesity OR Overweight) AND Taste perception, Satiation, Satiety response, Appetite, Appetite regulation, Habitua­tion, Taste receptors [MeSH] y PROP phenotype. En búsquedas subsecuentes se incluyeron artículos previos y posteriores a la fecha de la búsqueda general (hasta mayo 2018). Re­sultados. Las preferencias por los sabores inician desde la gestación, por lo que los niños que son expuestos a sabores dulces en etapas tempranas de la infancia aumentan su riesgo de habituación a éstos. Asimismo, las experiencias hedónicas dadas por la ingestión de alimentos y bebidas dulces refuerzan el consumo de estos alimentos, lo que propicia la selección de productos o bebidas de sabor dulce en etapas posteriores. Estas preferencias se han asociado con el desarrollo de obe­sidad en los niños. Las variantes genéticas relacionadas con la percepción del gusto también pueden contribuir a la selección de cierto tipo de alimentos. Sin embargo, su relación con una mayor ingestión de energía, así como con un mayor peso corporal, ha sido poco explorada y ha mostrado resultados inconsistentes. Conclusiones. Se requiere más evidencia para entender las interacciones ambientales y genéticas de la percepción del gusto, a fin de considerarlo un factor más en las intervenciones de política pública.

Decision Making Deficits in Relation to Food Cues Influence Obesity: A Triadic Neural Model of Problematic Eating

In this review article we propose a model of the brain systems, the deficiency of which may underlie problematic eating. This integrative model is based on studies that have focused on discrete brain components involved in problematic eating, combined with insights from studies on the neurocognitive basis of other addictive and problematic behaviors. The model includes: (a) a hyper-functioning reward anticipation and processing system (amygdala-striatum dependent) in response to food-related cues; (b) a hypo-functioning reflective and inhibitory control system (prefrontal cortex dependent), that fails to anticipate and properly weigh future outcomes; and (c) an altered interoceptive awareness system (insular cortex dependent) that translates homeostatic violation signals into a strong consumption desire that hijacks the inhibitory system and excites the reward system. We posit that when the abovementioned systems are imbalanced in such a way that the dopamine axis is hyperactive in relation to food cues and the inhibitory system is weak, and this is further aggravated by an altered interoceptive awareness system, people may experience loss of control or inability to resist tempting/rewarding foods. This loss of control over food consumption can explain, at least in part, the development of excess weight and contribute to the obesity epidemic.

Response in taste circuitry is not modulated by hunger and satiety in women remitted from bulimia nervosa

Individuals with bulimia nervosa (BN) engage in episodes of binge eating, marked by loss of control and eating despite fullness. Does altered reward and metabolic state contribute to BN pathophysiology? Normally, hunger increases (and satiety decreases) reward salience to regulate eating. We investigated whether BN is associated with an abnormal response in a neural circuit involved in translating taste signals into motivated behavior, when hungry and fed. Twenty-six women remitted from BN (RBN) and 22 control women (CW) were administered water and sucrose during 2 counterbalanced fMRI visits, following a 16-hr fast or a standardized breakfast. Significant Group × Condition interactions were found in the left putamen, insula, and amygdala. Post hoc analyses revealed CW were significantly more responsive to taste stimuli when hungry versus fed in the left putamen and amygdala. In contrast, RBN response did not differ between conditions. Further, RBN had greater activation in the left amygdala compared with CW when fed. Findings suggest that RBN neural response to rewarding stimuli may not be modulated by metabolic state. Data raise the possibility that disinhibited eating in BN could result from a failure to devalue food reward when fed, resulting in an exaggerated response. (PsycINFO Database Record

Hippocampal atrophy and altered brain responses to pleasant tastes among obese compared with healthy weight children

OBJECTIVE

The hippocampus is a key structure implicated in food motivation and intake. Research has shown that the hippocampus is vulnerable to the consumption of a western diet (i.e., high saturated fat and simple carbohydrates). Studies of patients with obesity (OB), compared with healthy weight (HW), show changes in hippocampal volume and response to food cues. Moreover, evidence suggests that OB children, relative to HW, have greater hippocampal response to taste. However, no study has examined the association of hippocampal volume with taste functioning in children. We hypothesized that OB children, relative to HW, would show a significant reduction in hippocampal volume and that decreased volume would be significantly associated with greater activation to taste. Finally, we explored whether hippocampal activation would be associated with measures on eating and eating habits.

SUBJECTS

Twenty-five 8-12-year-old children (i.e., 13 HW, 12 OB) completed a magnetic resonance imaging scan while participating in a taste paradigm (i.e., 1 ml of 10% sucrose or ionic water delivered pseudorandomly every 20 s).

RESULTS

Children with OB, relative to HW, showed reduced left hippocampal volume (t=1.994, P=0.03, 95% confidence interval (CI)=-40.23,  755.42), and greater response to taste in three clusters within the left hippocampus (z=3.3, P=0.001, 95% CI=-0.241, -0.041; z=3.3, P=0.001, 95% CI=-0.2711, -0.0469; z=2.7, P=0.007, 95% CI=-0.6032, -0.0268). Activation within the hippocampus was associated with eating in the absence of hunger (EAH%; t=2.408, P=0.025, 95% CI= 1.751708, 23.94109) and two subscales on a measure of eating behaviors (Food responsiveness, t=2.572, P=0.017, 95% CI= 0.9565195, 9.043440; Food enjoyment, t=2.298, P=0.032, 95% CI=0.2256749, 4.531298).

CONCLUSION

As hypothesized, OB children, relative to HW, had significantly reduced hippocampal volume, and greater hippocampal activation to taste. Moreover, hippocampal activation was associated with measures of eating. These results contribute to research on the relationship between OB, overeating and cognitive impairment.

Functional neuroimaging in obesity

PURPOSE OF REVIEW

This review examines recent advances in the use of functional neuroimaging to study human obesity, a field that is rapidly expanding and continues to be of paramount importance for a better understanding of the pathogenesis of this condition. With rising levels of obesity worldwide and limited therapeutic options, there is a great need for the development of new solutions that can benefit patients.

RECENT FINDINGS

Studies that utilize functional neuroimaging are beginning to shed light on the nature of behavioral and neurocognitive dysfunctions previously identified in individuals with obesity. Significant progress has occurred in the study of reward-related processes, cognition-reward interactions, mechanisms of weight loss, genetic influences and the case of obesity in children and adolescents. Research findings confirm that obesity and its related overeating behaviors are strongly associated with the brain, both at a regional level and a large-scale network level.

SUMMARY

Functional neuroimaging studies bring unprecedented levels of detail to examine the brain basis of obesity and show promise for the development of future brain-based biomarkers and interventions in this condition.

Functional neuroimaging in obesity

PURPOSE OF REVIEW

The review examines recent advances in the use of functional neuroimaging to study human obesity, a field that is rapidly expanding and continues to be of paramount importance for a better understanding of the pathogenesis of this condition. With rising levels of obesity worldwide and limited therapeutic options, there is a great need for the development of new solutions that can benefit patients.

RECENT FINDINGS

Studies that utilize functional neuroimaging are beginning to shed light on the nature of behavioral and neurocognitive dysfunctions previously identified in individuals with obesity. Significant progress has occurred in the study of reward-related processes, cognition-reward interactions, mechanisms of weight loss, genetic influences, and the case of obesity in children and adolescents. Research findings confirm that obesity and its related overeating behaviors are strongly associated with the brain, both at a regional level and a large-scale network level.

SUMMARY

Functional neuroimaging studies bring unprecedented levels of detail to examine the brain basis of obesity, and show promise for the development of future brain-based biomarkers and interventions in this condition.