Integration of reward signalling and appetite regulating peptide systems in the control of food-cue responses

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.

Orexins in apoptosis: a dual regulatory role

The orexins, also referred to as hypocretins, are neuropeptides that originate from the lateral hypothalamus (LH) region of the brain. They are composed of two small peptides, orexin-A, and orexin-B, which are broadly distributed throughout the central and peripheral nervous systems. Orexins are recognized to regulate diverse functions, involving energy homeostasis, the sleep-wake cycle, stress responses, and reward-seeking behaviors. Additionally, it is suggested that orexin-A deficiency is linked to sleepiness and narcolepsy. The orexins bind to their respective receptors, the orexin receptor type 1 (OX1R) and type 2 (OX2R), and activate different signaling pathways, which results in the mediation of various physiological functions. Orexin receptors are widely expressed in different parts of the body, including the skin, muscles, lungs, and bone marrow. The expression levels of orexins and their receptors play a crucial role in apoptosis, which makes them a potential target for clinical treatment of various disorders. This article delves into the significance of orexins and orexin receptors in the process of apoptosis, highlighting their expression levels and their potential contributions to different diseases. The article offers an overview of the existing understanding of the orexin/receptor system and how it influences the regulation of apoptosis.

Soy-Based High-Protein Spheric Foods with the Appearance of Familiar Sugary Snacks

Excessive consumption of sugary foods increases the likelihood of obesity, as well as the preventable risk of lifestyle illnesses such as diabetes and cardiovascular diseases. Frequent intake of sweet snacks is considered to increase the risk of overweight/obesity in industrial nations. However, we cannot stop snacking against our better judgment. Therefore, in this study, we sought to develop high-protein, low-carb "mock snacks" to satisfy snack lovers' appetites and nutrition. Soy protein-based, ball-shaped food products with 57.7% (w/w) protein and 3.6% sugar have been developed. The addition of canola oil made them melty in the mouth without sacrificing their crispiness. Moreover, evaluation of the surface topography of the "soy balls" by 3D laser scanning demonstrated their high degree of sphericity. Conclusively, the snacks developed here may be one of the healthy alternatives for the current sugary ones.

Vagal Stimulation Ameliorates Non-Alcoholic Fatty Liver Disease in Rats

BACKGROUND

The harmful consequences of non-alcoholic fatty liver disease (NAFLD) are posing an increasing threat to public health as the incidence of diabetes and obesity increases globally. A non-invasive treatment with a range of autonomic and metabolic benefits is transcutaneous vagus nerve stimulation (tVNS).

AIM OF THE STUDY

To investigate the possible preventive impacts of VNS against adult rats' NAFLD caused by a high-fat diet (HFD) and to clarify the underlying mechanisms.

METHODS

A total of thirty-two adult male rats were split into two groups: the HFD-induced NAFLD group (n = 24) and the control normal group (n = 8). The obesogenic diet was maintained for 12 weeks to induce hepatic steatosis. The HFD-induced NAFLD group (n = 24) was separated into three groups: the group without treatment (n = 8), the group with sham stimulation (n = 8), and the group with VNS treatment (n = 8). VNS was delivered for 30 min per day for 6 weeks after the establishment of NAFLD using a digital TENS device. The subsequent assessments included hepatic triglyceride, cholesterol content, serum lipid profile, and liver function testing. In this context, inflammatory biomarkers (TNF-α, IL-6) and hepatic oxidative stress (MDA, SOD, and GPx) were also assessed. To clarify the possible mechanisms behind the protective benefits of VNS, additional histological inspection and immunohistochemistry analysis of TNF-α and Caspase-3 were performed.

RESULTS

In the NAFLD-affected obese rats, VNS markedly decreased the rats' body mass index (BMI) and abdominal circumference (AC). Liver function markers (albumin, ALT, and AST) and the serum lipid profile-which included a notable decrease in the amounts of hepatic triglycerides and cholesterol-were both markedly improved. Additionally, oxidative stress and inflammatory indicators showed a considerable decline with VNS. Notably, the liver tissues examined by histopathologists revealed that there is evidence of the protective impact of VNS on the oxidative and inflammatory states linked to HFD-induced NAFLD while maintaining the architectural and functional condition of the liver.

CONCLUSIONS

Our findings suggest that VNS may represent a promising therapeutic candidate for managing NAFLD induced by obesity. It can be considered to be an effective adjuvant physiological intervention for the obese population with NAFLD to spare the liver against obesity-induced deleterious injury.

The energy content of meals with a similar macronutrient distribution may have a greater impact on appetite sensations than food preferences in adolescents with obesity: A secondary analysis

PURPOSE

The energy and macronutrient composition of a meal has been shown to influence postprandial appetitive responses, but it is not clear how energy content independent of macronutrient distribution affects postprandial appetite in adolescents with obesity. Extracting data from a primary study testing the effect of energy turnover on appetite, this secondary analysis assessed how fixed meals varying in energy content with similar macronutrient distributions influences postprandial appetite sensations and food reward.

METHODS

Using a randomised, counterbalanced crossover design, N = 14 adolescents with obesity (Mage = 12.71, SDage = 0.99; 10 female) consumed fixed lunch meals with similar macronutrient content starting at 750 kcal in energy and progressively increasing by 250 kcal on three different test days. Liking and wanting for food images varying in fat and taste were assessed at baseline and immediately after meal consumption. Appetite sensations were assessed in half-hour intervals from baseline to 1-h post-meal.

RESULTS

The area under the curve for subjective hunger (p < .001, ω = 0.36), desire to eat (p < .001, ω = 0.54), and prospective food consumption (p = .004, ω = 0.32) were significantly lower after consumption of the higher calorie meals relative to the lowest. Explicit wanting for sweet foods increased after intake of the intermediate calorie meal yet decreased after the highest calorie meal (p = .014, ω = 0.09). Conversely, implicit wanting sweet bias increased after consumption of the test meal independent of energy content (p < .001, ω = 0.15).

CONCLUSION

The consumption of additional calories without a meaningful change in macronutrient distribution may affect appetite sensations more reliably than hedonic responses to energy-dense foods in adolescents with obesity.

Neural correlates of naturalistic single-trial appetitive conditioning

BACKGROUND

Prior research suggests naturalistic single-trial appetitive conditioning may be a potent phenomenon in humans, capable of modulating both motivation and attention. In this study, we aimed to characterise the neural correlates of this phenomenon using functional Magnetic Resonance Imaging (fMRI) paradigms METHODS: Twenty-three healthy adults (12 males) underwent conditioning during which they ate a novel 3D object made from white chocolate (CS+) and handled a similar object made from plastic (CS-). Brain activity was recorded before and after conditioning during a passive viewing paradigm RESULTS: A naturalistic CS+ was rated as more highly craved, better-liked and elicited greater expectancies for chocolate than the CS- after conditioning. An exploration of the interaction between time (pre- and post-conditioning) and CS type (CS+, CS-) during the passive viewing task suggested enhanced activation from pre- to post-conditioning in the right superior frontal gyrus (R.SFG) in response to the CS-.

CONCLUSION

Results reveal neural correlates of single-trial appetitive conditioning and highlight a possible role of response inhibition during learning about non-rewards, perhaps optimizing motivated behaviour. These findings contribute to our understanding of the neural mechanisms underpinning rapid reward and non-reward learning, and may inform development of behavioural interventions for reward-driven overeating.

Sucralose Targets the Insulin Signaling Pathway in the SH-SY5Y Neuroblastoma Cell Line

Sucralose is widely used as a non-nutritive sweetener (NNS). However, in order to justify its use as a non-nutritive food additive, sucralose would have to be metabolically neutral. The aim of this study was to examine whether sucralose altered the insulin signaling pathway in an in vitro cell model of Parkinson's disease (PD)-the dopaminergic differentiated cell line SH-SY5Y. Cells were exposed to sucralose alone and in combination with either insulin or levodopa. Activation of the insulin signaling pathway was assessed by quantifying protein kinase B (AKT) and glycogen synthase kinase 3 (GSK3), as well as the phosphorylated forms of insulin-like growth factor 1 receptor (IGF1-R). Metabolic effects were assayed using MALDI-TOF MS analysis. In the cell viability test, 2 mM sucralose had a negative effect, and levodopa in all combinations had a positive effect. Sucralose treatment alone suppressed GSK3 and IGF1-R phosphorylation in a dose-dependent manner. This treatment also altered the metabolism of fatty acids and amino acids, especially when combined with insulin and levodopa. Suppression of the insulin signaling pathway and sucralose-induced changes in the metabolic profile could underlie a diet-acquired insulin resistance, previously associated with neurodegeneration, or may be an altered response to insulin or levodopa medical therapy.

Effects of Essential Oils and Fragrant Compounds on Appetite: A Systematic Review

Appetite dysregulation is one of the factors contributing to anorexia, bulimia nervosa, obesity, and diabetes. Essential oils or fragrant compounds have been proven to regulate food intake and energy expenditure; hence, this study aimed to summarize their effects on appetite and the underlying mechanisms. The PubMed and Web of Science databases were searched until July 2022. Only two of the 41 studies were performed clinically, and the remaining 39 used animal models. Oral administration was the most common route, and a dosage range of 100-2000 mg/kg for mice or 2-32 mg/kg for rats was applied, with a duration of 12 days to 4 weeks, followed by inhalation (10^-6-10^-3 mg/cage or 10^-9-10^-2 mg/cm³ within 1 h). Approximately 11 essential oil samples and 22 fragrant compounds were found to increase appetite, while 12 essential oils and seven compounds decreased appetite. These fragrant components can exert appetite-regulating effects via leptin resistance, the activity of sympathetic/parasympathetic nerves, or the mRNA expression of neuropeptide Y (NPY)/agouti-related protein (AgRP), cocaine- and amphetamine-regulated transcript (CART)/proopiomelanocortin (POMC) in the hypothalamus. Fragrance memory and cognitive processes may also play roles in appetite regulation. The findings of this study accentuate the potential of essential oils and fragrant compounds to regulate appetite and eating disorders.

Food memory circuits regulate eating and energy balance

In mammals, learning circuits play an essential role in energy balance by creating associations between sensory cues and the rewarding qualities of food. This process is altered by diet-induced obesity, but the causes and mechanisms are poorly understood. Here, we exploited the relative simplicity and wealth of knowledge about the D. melanogaster reinforcement learning network, the mushroom body, in order to study the relationship between the dietary environment, dopamine-induced plasticity, and food associations. We show flies that are fed a high-sugar diet cannot make associations between sensory cues and the rewarding properties of sugar. This deficit was caused by diet exposure, not fat accumulation, and specifically by lower dopamine-induced plasticity onto mushroom body output neurons (MBONs) during learning. Importantly, food memories dynamically tune the output of MBONs during eating, which instead remains fixed in sugar-diet animals. Interestingly, manipulating the activity of MBONs influenced eating and fat mass, depending on the diet. Altogether, this work advances our fundamental understanding of the mechanisms, causes, and consequences of the dietary environment on reinforcement learning and ingestive behavior.

The Role of Molecular and Hormonal Factors in Obesity and the Effects of Physical Activity in Children

Obesity and overweight are defined as abnormal fat accumulations. Adipose tissue consists of more than merely adipocytes; each adipocyte is closely coupled with the extracellular matrix. Adipose tissue stores excess energy through expansion. Obesity is caused by the abnormal expansion of adipose tissue as a result of adipocyte hypertrophy and hyperplasia. The process of obesity is controlled by several molecules, such as integrins, kindlins, or matrix metalloproteinases. In children with obesity, metabolomics studies have provided insight into the existence of unique metabolic profiles. As a result of low-grade inflammation in the system, abnormalities were observed in several metabolites associated with lipid, carbohydrate, and amino acid pathways. In addition, obesity and related hormones, such as leptin, play an instrumental role in regulating food intake and contributing to childhood obesity. The World Health Organization states that physical activity benefits the heart, the body, and the mind. Several noncommunicable diseases, such as cardiovascular disease, cancer, and diabetes, can be prevented and managed through physical activity. In this work, we reviewed pediatric studies that examined the molecular and hormonal control of obesity and the influence of physical activity on children with obesity or overweight. The purpose of this review was to examine some orchestrators involved in this disease and how they are related to pediatric populations. A larger number of randomized clinical trials with larger sample sizes and long-term studies could lead to the discovery of new key molecules as well as the detection of significant factors in the coming years. In order to improve the health of the pediatric population, omics analyses and machine learning techniques can be combined in order to improve treatment decisions.

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.

CD36 and GPR120 mediated orogustatory perception of dietary lipids and its physiological implication in the pygmy mouse Mus booduga

Fat taste perception has long been concerned in the regulation of dietary fat intake. Substantial experimental evidence defends fat as a sixth taste modality, but its allied peripheral mechanisms are not yet well established. The present study aimed to analyse the diet-induced changes in fat taste perception and its associated physiological variations in Mus booduga. Four groups of animals were used for the present study and were fed any one of the following diet; normal diet (10% fat), low-fat diet (4% fat), high-fat diet (36% fat), or high-fat diet (HFD) (36% fat) + rapeseed oil (HFRDO) (14%) for 9 weeks. The animals were then subjected to metabolic tolerance, fat preference, and conditioned taste aversion studies. Diet-induced alterations in the expression of genes associated with lipogenesis, inflammation, and fat taste (CD36 and GPR120) were analysed. Capacitative calcium signalling induced by both linoleic acid and grifolic acid in taste bud cells (TBCs) was also analysed. In result, both the HFD and HFDRO groups revealed deterioration in glucose homoeostasis and displayed decreased preference scores for fatty acids, which are associated with lower CD36 expression and increased GPR120 expression in TBCs. Furthermore, change in [Ca²⁺ ]i induced by LA was also compromised in CD36 positive TBCs along with elevated systemic inflammatory and lipidemic responses in both these obese groups. Overall, for the first time, our results support that chronic HFD feeding alters the CD36 and GPR120 mediated fat taste perception in M. booduga.

Anti-obesity weight loss medications: Short-term and long-term use

As obesity prevalence increases, more and more drugs that assist with weight loss have been developed. Numerous weight loss drugs had been approved, but many have also been withdrawn based on their lack of efficacy as well as safety concerns. Initial approaches in developing weight loss drugs was by increasing physiological energy expenditure and suppressing the appetite. Subsequently, as more physiological mechanisms for weight gain has been unearthed, drugs targeting newly discovered receptors and/or enzymes have been introduced with improved safety profiles and fewer psychological adverse events. Additionally, drugs targeting hunger or satiety signaling have been actively studied, and have shown increased adoption by physicians. Studies have also evaluated drugs that target metabolic tissues-such as adipose tissue or muscle-to promote weight loss, however to-date nothing has carried on into clinical practice. Starting with a brief history of early obesity treatments, this review evaluates current weight loss pharmaceutical options based on their duration of therapy status.

Metabolic hormones mediate cognition

Recent biochemical and behavioural evidence indicates that metabolic hormones not only regulate energy intake and nutrient content, but also modulate plasticity and cognition in the central nervous system. Disruptions in metabolic hormone signalling may provide a link between metabolic syndromes like obesity and diabetes, and cognitive impairment. For example, altered metabolic homeostasis in obesity is a strong determinant of the severity of age-related cognitive decline and neurodegenerative disease. Here we review the evidence that eating behaviours and metabolic hormones-particularly ghrelin, leptin, and insulin-are key players in the delicate regulation of neural plasticity and cognition. Caloric restriction and antidiabetic therapies, both of which affect metabolic hormone levels can restore metabolic homeostasis and enhance cognitive function. Thus, metabolic hormone pathways provide a promising target for the treatment of cognitive decline.

Identification of an endocannabinoid gut-brain vagal mechanism controlling food reward and energy homeostasis

The regulation of food intake, a sine qua non requirement for survival, thoroughly shapes feeding and energy balance by integrating both homeostatic and hedonic values of food. Unfortunately, the widespread access to palatable food has led to the development of feeding habits that are independent from metabolic needs. Among these, binge eating (BE) is characterized by uncontrolled voracious eating. While reward deficit seems to be a major contributor of BE, the physiological and molecular underpinnings of BE establishment remain elusive. Here, we combined a physiologically relevant BE mouse model with multiscale in vivo approaches to explore the functional connection between the gut-brain axis and the reward and homeostatic brain structures. Our results show that BE elicits compensatory adaptations requiring the gut-to-brain axis which, through the vagus nerve, relies on the permissive actions of peripheral endocannabinoids (eCBs) signaling. Selective inhibition of peripheral CB1 receptors resulted in a vagus-dependent increased hypothalamic activity, modified metabolic efficiency, and dampened activity of mesolimbic dopamine circuit, altogether leading to the suppression of palatable eating. We provide compelling evidence for a yet unappreciated physiological integrative mechanism by which variations of peripheral eCBs control the activity of the vagus nerve, thereby in turn gating the additive responses of both homeostatic and hedonic brain circuits which govern homeostatic and reward-driven feeding. In conclusion, we reveal that vagus-mediated eCBs/CB1R functions represent an interesting and innovative target to modulate energy balance and counteract food-reward disorders.

Satiety Associated with Calorie Restriction and Time-Restricted Feeding: Central Neuroendocrine Integration

This review focuses on summarizing current knowledge on how time-restricted feeding (TRF) and continuous caloric restriction (CR) affect central neuroendocrine systems involved in regulating satiety. Several interconnected regions of the hypothalamus, brainstem, and cortical areas of the brain are involved in the regulation of satiety. Following CR and TRF, the increase in hunger and reduction in satiety signals of the melanocortin system [neuropeptide Y (NPY), proopiomelanocortin (POMC), and agouti-related peptide (AgRP)] appear similar between CR and TRF protocols, as do the dopaminergic responses in the mesocorticolimbic circuit. However, ghrelin and leptin signaling via the melanocortin system appears to improve energy balance signals and reduce hyperphagia following TRF, which has not been reported in CR. In addition to satiety systems, CR and TRF also influence circadian rhythms. CR influences the suprachiasmatic nucleus (SCN) or the primary circadian clock as seen by increased clock gene expression. In contrast, TRF appears to affect both the SCN and the peripheral clocks, as seen by phasic changes in the non-SCN (potentially the elusive food entrainable oscillator) and metabolic clocks. The peripheral clocks are influenced by the primary circadian clock but are also entrained by food timing, sleep timing, and other lifestyle parameters, which can supersede the metabolic processes that are regulated by the primary circadian clock. Taken together, TRF influences hunger/satiety, energy balance systems, and circadian rhythms, suggesting a role for adherence to CR in the long run if implemented using the TRF approach. However, these suggestions are based on only a few studies, and future investigations that use standardized protocols for the evaluation of the effect of these diet patterns (time, duration, meal composition, sufficiently powered) are necessary to verify these preliminary observations.

Cocaine-induced neural adaptations in the lateral hypothalamic melanin-concentrating hormone neurons and the role in regulating rapid eye movement sleep after withdrawal

Sleep abnormalities are often a prominent contributor to withdrawal symptoms following chronic drug use. Notably, rapid eye movement (REM) sleep regulates emotional memory, and persistent REM sleep impairment after cocaine withdrawal negatively impacts relapse-like behaviors in rats. However, it is not understood how cocaine experience may alter REM sleep regulatory machinery, and what may serve to improve REM sleep after withdrawal. Here, we focus on the melanin-concentrating hormone (MCH) neurons in the lateral hypothalamus (LH), which regulate REM sleep initiation and maintenance. Using adult male Sprague-Dawley rats trained to self-administer intravenous cocaine, we did transcriptome profiling of LH MCH neurons after long-term withdrawal using RNA-sequencing, and performed functional assessment using slice electrophysiology. We found that 3 weeks after withdrawal from cocaine, LH MCH neurons exhibit a wide range of gene expression changes tapping into cell membrane signaling, intracellular signaling, and transcriptional regulations. Functionally, they show reduced membrane excitability and decreased glutamatergic receptor activity, consistent with increased expression of voltage-gated potassium channel gene Kcna1 and decreased expression of metabotropic glutamate receptor gene Grm5. Finally, chemogenetic or optogenetic stimulations of LH MCH neural activity increase REM sleep after long-term withdrawal with important differences. Whereas chemogenetic stimulation promotes both wakefulness and REM sleep, optogenetic stimulation of these neurons in sleep selectively promotes REM sleep. In summary, cocaine exposure persistently alters gene expression profiles and electrophysiological properties of LH MCH neurons. Counteracting cocaine-induced hypoactivity of these neurons selectively in sleep enhances REM sleep quality and quantity after long-term withdrawal.

Decoding the Role of Gut-Microbiome in the Food Addiction Paradigm

Eating behaviour is characterised by a solid balance between homeostatic and hedonic regulatory mechanisms at the central level and highly influenced by peripheral signals. Among these signals, those generated by the gut microbiota have achieved relevance in recent years. Despite this complex regulation, under certain circumstances eating behaviour can be deregulated becoming addictive. Although there is still an ongoing debate about the food addiction concept, studies agree that patients with eating addictive behaviour present similar symptoms to those experienced by drug addicts, by affecting central areas involved in the control of motivated behaviour. In this context, this review tries to summarise the main data regarding the role of the gut microbiome in eating behaviour and how a gut dysbiosis can be responsible for a maladaptive behaviour such as “food addiction”.

Advertising Influences Food Choices of University Students With ADHD

Objective: Previous research in adults with ADHD showed high rates of obesity and unhealthy food choices. There is evidence that contextual cues, for example, advertisements, influence food choices. This study assessed the sensitivity of university students with ADHD to advertised food. Method: University students (N = 457) with and without ADHD participated in a cafeteria field experiment. Food choices were examined in periods of advertising either healthy or unhealthy sandwiches. Results: Students with ADHD (a) chose less healthy food items, (b) were more influenced by advertising, (c) showed the same overall healthy food choices as controls when exposed to healthy advertising. Conclusion: Students with ADHD chose unhealthier foods at the cafeteria but were also more influenced by advertising. Healthy food advertisements raised their healthy food choices. As this population has strong association with unhealthy dietary patterns, it is important to investigate the influence of food cues on their eating habits.

Predictors of weight loss in participants with obesity following bariatric surgery - A prospective longitudinal fMRI study

Prevalence rates of overweight and obesity are increasing worldwide and are amongst the leading causes of death. Participants with obesity also suffer from poorer mental health with a concomitant reduced quality of life. Bariatric surgery outperforms other existing weight optimization approaches. However, hitherto, it was not possible to identify factors predicting weight loss following surgery. Therefore, we aimed at investigating neural and behavioral predictors of weight loss, as well as the neurological underpinnings of food cue-induced craving before and after bariatric surgery. The total sample consisted of 26 participants with obesity (17 females and 9 males, mean age 41 ± 12 years, mean BMI 46 ± 6 kg/m2, 21 received Roux-en-Y gastric bypass and 5 sleeve gastrectomy). Participants with obesity were prospectively assessed using functional magnetic resonance imaging two weeks before, as well as eight and 24 weeks after surgery. Imaging data were available for 11 individuals; 10 received Roux-en-Y gastric bypass and one sleeve gastrectomy. Subjective cue-induced food craving correlated positively with brain activation in the amygdala, the parahippocampal gyrus, and hippocampus, and negatively with brain activation in frontal brain regions. In the total sample (N = 26), perceived feeling of hunger and YFAS sum score explained 50.6% of the variance (R² = 0.506, F_(1,23) = 10.759, p < 0.001) and in the imaging sample, cue-induced food craving at baseline before surgery explained 49.6% of the variance (R² = 0.496, F_(1,23) = 7.862, p = 0.023) of % total weight loss (%TWL). In other words, with respect to %TWL, bariatric surgery was most efficient in candidates characterized by high cue-induced food craving, high-perceived feeling of hunger and a low YFAS sum score.

Effects of exercise and diet intervention on appetite-regulating hormones associated with miRNAs in obese children

AIMS

This study investigated the effects of exercise and diet intervention on appetite-regulating hormones and subjective appetite changes in obese children and examined expressions of specific key microRNAs (miRNA, miR).

METHODS

16 obese children were included in a training program consisting of exercise and diet intervention for 6 weeks. Before and after the intervention, fasting blood was collected to determine appetite-regulating hormones (leptin, ghrelin, and orexin) and miRNA (miR-103a-3p and miR-200a-3p) levels; eating behavior of the children was reported using the Children Eating Behavior Questionnaire (CEBQ).

RESULTS

The level of orexin was significantly decreased (P < 0.05), while ghrelin was significantly enhanced (P < 0.05) after 6 weeks. The scores of food responsiveness (FR) and enjoyment of food (EF) of the CEBQ were significantly decreased (P < 0.05) after intervention. The changes of leptin and that of SR were significantly correlated (r = - 0.455, P < 0.05), and the correlation between the alterations of orexin and that of EF was moderate with significance (r = 0.625, P < 0.05). miR-103a-3p expression was not statistically changed, while miR-200a-3p was significantly inhibited after 6-week intervention (P < 0.05). The correlation between relative changes of miR-103a-3p and that of leptin and orexin were both with significant difference (r = 0.413, P < 0.05; r = 0.409, P < 0.05), whereas the alterations of miR-200a-3p were not correlative with hormones or appetite sensation.

CONCLUSION

Exercise combined with diet intervention for 6 weeks was effective in regulating appetite sensations and hormones in obese children, and miR-103a-3p and miR-200a-3p might provide a foundation for target biomarkers of appetite trait in modulating the energy balance control by exercise and dietary intervention.

LEVEL OF EVIDENCE

Level III, case-control analytic study.

TRIAL REGISTRATION

The trial was registered in ClinicalTrials.gov (NCT03762629).

Appetite self-regulation declines across childhood while general self-regulation improves: A narrative review of the origins and development of appetite self-regulation

This narrative review discusses the origins and development of appetite self-regulation (ASR) in childhood (from infancy to age 6 or 7 years). The origins, or foundations, are the biological infrastructure associated with appetite regulation and appetite self-regulation. Homeostatic regulation in infancy is examined and then evidence about developmental change in components of ASR. The main ASR-related components covered are: delay-of-gratification, caloric compensation, eating in the absence of hunger, food responsiveness/hedonics and fussy eating. The research included behavioral measures, parent-reports of appetitive traits and fMRI studies. There were two main trends in the evidence: a decline across childhood in the components of ASR associated with food approach (and therefore an increase in disinhibited eating), and wide individual differences. The decline in ASR contrasts with general self-regulation (GSR) where the evidence is of an improvement across childhood. For many children, bottom-up automatic reactive processes via food reward/hedonics or food avoidance as in fussy eating, appear not to be matched by improvements in top-down regulatory capacities. The prominence of bottom-up processes in ASR could be the main factor in possible differences in developmental paths for GSR and ASR. GSR research is situated in developmental science with its focus on developmental processes, theory and methodology. In contrast, the development of ASR at present does not have a strong developmental tradition to access and there is no unifying model of ASR and its development. We concluded (1) outside of mean-level or normative changes in the components of ASR, individual differences are prominent, and (2) there is a need to formulate models of developmental change in ASR together with appropriate measurement, research designs and data analysis strategies.

Possibilities for Maintaining Appetite in Recovering COVID-19 Patients

COVID-19 and sequelae thereof are known to cause chemosensory dysfunction, posing a risk for intake and adequate nutrition for recovery. The overall objective of this study was to investigate the subjective strategies for maintaining appetite applied by patients recovering from COVID-19. The study included 19 in-depth interviews, focusing on patients suffering from long-term effects of COVID-19. The results were analysed using a thematic analysis for qualitative data. Results on strategies for maintaining appetite included four key themes: (1) a focus on well-functioning senses, (2) a focus on familiar foods, (3) a focus on the eating environment, and (4) a focus on post-ingestive well-being. It was found that factors prior to, during and after food intake, as well as the context, could influence desire to eat and pleasure related to food intake. As ageusia and anosmia make characterization of food difficult, being able to recognize and memorize its flavour was important to engage in consumption. Under normal circumstances, the hedonic value of food relies predominantly on the flavour of foods. When suffering from chemosensory dysfunction, shifting focus towards the texture of food, including trigeminal stimulation during consumption, were beneficial for maintaining appetite and food-related pleasure. Furthermore, a focus on the holistic satisfying feelings of choosing healthy food, as well as a focus on other people’s enjoyment during meals were reported to boost well-being around food intake. The study elaborated our understanding of the complex consequences of COVID-19, and can be applied in health promoting initiatives targeted patients recovering from COVID-19.

BDNF influences neural cue-reactivity to food stimuli and food craving in obesity

There is increasing evidence that brain-derived neurotrophic factor (BDNF) impacts on the development of obesity. We are the first to test the hypothesis that BDNF levels might be associated with neural reactivity to food cues in patients suffering from obesity and healthy controls. We assessed visual food cue-induced neural response in 19 obese patients and 20 matched controls using functional magnetic resonance imaging and analyzed the associations between BDNF levels, food cue-reactivity and food craving. Whole-brain analysis in both groups revealed that food cues elicited higher neural activation in clusters of mesolimbic brain areas including the insula (food > neutral). Patients suffering from obesity showed a significant positive correlation between plasma BDNF levels and visual food cue-reactivity in the bilateral insulae. In addition, patients suffering from obesity with positive food cue-induced insula activation also reported significantly higher food craving than those with low cue-reactivity-an effect that was absent in normal weight participants. The present findings implicate that BDNF levels in patients suffering from obesity might be involved in food craving and obesity in humans. This highlights the importance to consider BDNF pathways when investigating obesity and obesity treatment.

The orexinergic neural pathway from the lateral hypothalamus to the nucleus accumbens and its regulation of palatable food intake

OBJECTIVE

To explore the orexinergic pathway from the lateral hypothalamus (LHA) to the nucleus accumbens (NAc) and its regulation on the palatable food intake.

METHODS

Fluorescent gold retrograde tracing combined with fluoro-immunohistochemical staining were used to observe the projection of orexinergic neurons from LHA to NAc. The orexin-A expression in LHA and c-Fos in NAc were studied after electrical stimulation of LHA. The firing rates of neurons were monitored by single-unit extracellular electric discharge recording and the palatable food intake were measured after orexin microinjection in NAc or electrical stimulation of LHA.

RESULTS

(1) Fluorescent gold retrograde tracing combined with fluoro-immunohistochemical staining showed some orexinergic neural projection from the LHA to the NAc shell. (2) Electrical stimulation of LHA significantly enhanced the expression of orexin-A in LHA and the expression of c-Fos in NAc (P < .05). (3) The results of single-unit extracellular discharge recording showed that the microinjection of orexin in NAc or electrical stimulation of LHA significantly increased the discharge activity of gastric distension responsive neurons in NAc, and the effect could be partly blocked by pretreatment of orexin-A receptor inhibitor SB334867 in NAc (P < .05). (4) Microinjection orexin-A in NAc or electrical stimulation of LHA significantly increased the palatable food intake in rats, and the effect also was partly inhibited by pretreatment of SB334867 in NAc (P < .05).

CONCLUSION

There is an orexinergic pathway from LHA to NAc, which may have potential regulatory effects on food reward and obesity.

Change in eating pattern as a contributor to energy intake and weight gain during the winter holiday period in obese adults

Background/Objectives:

The winter holiday season in the US, which spans mid-November to mid-January, contributes to over half of annual body weight gain. Although self-reported data has linked this weight change to both increased energy intake and reduced physical activity, objective techniques have never been used and thus the actual cause of holiday weight gain is controversial. Here, we aimed to determine changes in components of energy balance leading to the holiday weight gain.

Methods:

Body weight change was compared between the pre-holiday (mid-September to mid-November) and the holiday period (mid-November to early January). Total energy expenditure (TEE) was measured using doubly labeled water during holiday time (early to mid-December). Subjective (ratings) and physiological (appetite-regulating hormones) measures of appetite, eating-away-from-home frequency, and incentive salience of food pictures were also evaluated.

Results:

In 23 obese adults (87% female), body weight change during the holidays (0.41 ± 0.42 kg) was significantly higher (P=0.02) than the body weight change during the pre-holiday period (−0.86 kg ± 0.42 kg). The TEE was unchanged during the two periods, suggesting no role of energy expenditure on weight gain. However, participants reported lower satisfaction after a meal pre-load which was significantly correlated with increased body weight during the holiday period. An increase in number of episodes of eating at sit-down restaurants was also reported during that period. Overall, these changing behaviors were supported by a non-significant increase in energy intake (+80 kcal/day, P=0.07) observed during the study holiday period.

Conclusion:

We conclude that a decrease in energy expenditure does not result in the weight increase, but that an increase in food intake is the more likely cause. Our data imply that compromised internal satiety mechanisms in presence of external food cues and diet related behavioral variables during the holidays may influence this weight gain.

"Food" and "non-food" self-regulation in childhood: a review and reciprocal analysis

BACKGROUND

In developmental science, there is an extensive literature on non-food related self-regulation in childhood, where several domains relating to emotions, actions and cognitions have been identified. There is now growing attention to food related self-regulation in childhood, especially difficulties with ASR, and the consequences for weight gain and adiposity. The aim of this narrative review was to conduct a reciprocal analysis of self-regulation in the food and non-food domains in childhood (referred to as appetite self-regulation (ASR) and general self-regulation (GSR) respectively). The focus was on commonalities and differences in key concepts and underpinning processes.

METHODS

Databases and major journals were searched using terms such as self-regulation, appetite self-regulation, or self-regulation of energy intake, together with associated constructs (e.g., Executive Function, Effortful Control, delay-of-gratification). This was followed by backward and forward snowballing.

RESULTS AND DISCUSSION

The scholarship on GSR in childhood has had a focus on the role of the cognitively-oriented Executive Function (EF), the temperamentally-based Effortful Control (EC) and the recursive interplay between bottom-up (reactive, emotion driven, approach or avoidance) and top-down (cognitive, conscious decision-making) processes. "Hot" and "cool/cold" EF and self-regulation situations have been distinguished. There were some parallels between GSR and ASR in these areas, but uncertainty about the contribution of EF and EC to ASR in young children. Possible differences between the contribution to ASR-related outcomes of delay-of-gratification in food and non-food tasks were apparent. Unique elements of ASR were identified; associated with psychological, biological and neurological responses to food and bottom-up processes. A diverse number of situations or elements connected to ASR exist: for example, energy balance homeostasis, caloric compensation, hunger regulation, satiation, satiety, energy density of food, eating in the absence of hunger, emotional eating, etc. CONCLUSIONS: Self-regulation in food and non-food domains are amenable to a reciprocal analysis. We argue that self-regulation of appetite should be added as a domain under the umbrella of self-regulation in childhood along with the other non-food related domains. This could lead to a broader understanding of self-regulation in childhood, and generate novel lines of enquiry.

An examination of children's eating behaviours as mediators of the relationship between parents' feeding practices and early childhood body mass index z-scores

OBJECTIVE

Parent's use of restrictive feeding practices is associated with child weight. Similarly, the literature shows that children's eating behaviours are also associated with child weight. Given this interrelationship between children's eating behaviours, restrictive feeding practices and child weight, examination of possible mediator relationships is warranted. This study aimed to examine the relationships between overt restriction and covert restriction with child body mass index z-scores (BMIz) and determine if children's eating behaviours (satiety responsiveness and food responsiveness) act as mediators.

METHOD

Parents of Australian children (n = 977) 2.0-5.0 years of age (49.4% male) provided data in an online survey on child eating behaviours, parent's restrictive feeding practices and child anthropometrics (modified z-scores were created to screen for biologically implausible values). Correlation analysis was used to determine variables to include in mediation models. Hayes' PROCESS macros in spss was used to examine mediation, controlling for covariates of child BMIz.

RESULTS

Overt restriction was the only parent feeding practice related to child BMIz (B = 0.132, P = 0.04). Mediation analysis showed that the indirect effect of overt restriction on child BMIz (controlling for child age, gender, parent BMI and income) became non-significant when controlling for food responsiveness, thus suggesting full mediation, explaining 5.75% of the relation.

CONCLUSION

Overt restriction and covert restriction have distinctly different relationships with children's eating behaviours. Food responsiveness appears an important intermediary in the relationship between overt restriction and child BMIz.

Aetiology of eating behaviours: A possible mechanism to understand obesity development in early childhood

Childhood obesity is an issue of public health concern that is understood to emerge due to disequilibrium in energy homeostasis. This commentary explores literature regarding neuro-biological mechanisms of energy homeostasis and the relationship between subjective measures of children's eating behaviours and objective measures of appetite, in order to better understand the aetiology of childhood obesity. Early life influences, such as in utero exposure, breastfeeding, and general disadvantage, appear to have an important influence on neuro-biological mechanisms of appetite and may contribute to inequitable distributions of obesity within the population. Subject measures of eating behaviours appear to capture various aspects of neuro-biologically driven (objective) appetite systems, however, these systems are complex, interdependent and not yet fully understood. Future research focusing attention on early life influences on appetite and eating behaviours is warranted to increase understanding of differences in rates of obesity within the population, to determine opportunities for targeted obesity prevention initiatives, and to explore the potential to measure change in eating behaviours as a marker of appetite and obesity risk.

Incubation of feeding behavior is regulated by neuromedin U receptor 2 in the paraventricular nucleus of the hypothalamus

A diet of energy-dense food, characterized mainly as a high-fat diet, leads to a persistent excessive consumption defined as overeating. According to the National Institute of Health, more than 2 in 3 adults in the United States are overweight or obese, straining our healthcare system with epidemic proportions. Diets that include abstaining from high-fat foods, ironically, result in an increase in motivation and craving for said high-fat foods, defined as an incubation effect because the behavior aids in developing overeating. Previously, we have shown that modulation of neuromedin U receptor 2 (NMUR2) in the paraventricular nucleus of the hypothalamus (PVN) results in increased food intake and motivation for energy-dense foods. Here, we continue our focus on NMUR2 in the PVN, but in relation to the incubation effect on craving for high-fat food. We employed a model for incubation of craving by having rats abstain from high-fat foods for 30 days before undergoing intake of fatty food on fixed ratio and progressive ratio schedules of reinforcement, and then assess their response to reactivity to cues. Using this model, we compared the feeding behaviors of rats that underwent an mRNA knockdown of the NMUR2 in the PVN to controls after both underwent a 30-day abstinence from high-fat foods. Our results show knockdown of NMUR2 in the PVN blocks the incubation of feeding behavior for food-related cues and high-fat foods.

Food Addiction and Binge Eating: Lessons Learned from Animal Models

The feeding process is required for basic life, influenced by environment cues and tightly regulated according to demands of the internal milieu by regulatory brain circuits. Although eating behaviour cannot be considered "addictive" under normal circumstances, people can become "addicted" to this behaviour, similarly to how some people are addicted to drugs. The symptoms, cravings and causes of "eating addiction" are remarkably similar to those experienced by drug addicts, and both drug-seeking behaviour as eating addiction share the same neural pathways. However, while the drug addiction process has been highly characterised, eating addiction is a nascent field. In fact, there is still a great controversy over the concept of "food addiction". This review aims to summarize the most relevant animal models of "eating addictive behaviour", emphasising binge eating disorder, that could help us to understand the neurobiological mechanisms hidden under this behaviour, and to improve the psychotherapy and pharmacological treatment in patients suffering from these pathologies.

Systemic Administration of Orexin a Loaded Liposomes Potentiates Nucleus Accumbens Shell Dopamine Release by Sucrose Feeding

Orexin neurons originate in the lateral and dorsomedial hypothalamus and perifornical area and produce two different neuropeptides: orexin A (OxA) and orexin B (OxB), which activate OxR1 and OxR2 receptors. In the lateral hypothalamus (LH) orexin neurons are involved in behavior motivated by natural rewards such as palatable food (sugar, high-fat food) and it has been demonstrated similarly that the orexin signaling in the ventral tegmental area (VTA) is implicated in the intake of high-fat food. The VTA is an important area involved in reward processing. Given the involvement of nucleus accumbens (NAc) shell dopamine (DA) in motivation for food, we intended to investigate the effect of OxA on the basal and feeding-activated DA transmission in the NAc shell. OxA is a large peptide and does not cross the blood-brain barrier and for this reason was loaded on two kinds of liposomes: anti-transferrin-monoclonal antibodies (OX26-mAb) and lactoferrin-modified stealth liposomes. The effect of IV administration of both OxA liposomes on NAc shell DA was studied by microdialysis in freely moving rats. OxA, administered using both kinds of liposomes, produced a delayed and transitory increase in dialysate DA in the NAc shell, strongly and lastingly potentiated the increase in dialysate DA elicited by sucrose pellet consumption and increased the number of eaten pellets. These effects of OxA on DA transmission and feeding were prevented by the OxR1 antagonist SB 334867. Hence, OxA acting on VTA OxR1 can facilitate sucrose-stimulated NAc shell DA transmission directly by increasing the basal activity of VTA DA neurons that send their projections to the NAc shell.

Palatable Hyper-Caloric Foods Impact on Neuronal Plasticity

Neural plasticity is an intrinsic and essential characteristic of the nervous system that allows animals “self-tuning” to adapt to their environment over their lifetime. Activity-dependent synaptic plasticity in the central nervous system is a form of neural plasticity that underlies learning and memory formation, as well as long-lasting, environmentally-induced maladaptive behaviors, such as drug addiction and overeating of palatable hyper-caloric (PHc) food. In western societies, the abundance of PHc foods has caused a dramatic increase in the incidence of overweight/obesity and related disorders. To this regard, it has been suggested that increased adiposity may be caused at least in part by behavioral changes in the affected individuals that are induced by the chronic consumption of PHc foods; some authors have even drawn attention to the similarity that exists between over-indulgent eating and drug addiction. Long-term misuse of certain dietary components has also been linked to chronic neuroimmune maladaptation that may predispose individuals to neurodegenerative conditions such as Alzheimer’s disease. In this review article, we discuss recent evidence that shows how consumption of PHc food can cause maladaptive neural plasticity that converts short-term ingestive drives into compulsive behaviors. We also discuss the neural mechanisms of how chronic consumption of PHc foods may alter brain function and lead to cognitive impairments, focusing on prenatal, childhood and adolescence as vulnerable neurodevelopmental stages to dietary environmental insults. Finally, we outline a societal agenda for harnessing permissive obesogenic environments.

Reward-Induced Eating: Therapeutic Approaches to Addressing Food Cravings

The homeostatic controls over eating are inextricably linked to the reward aspects of eating. The result is an integrated response that coordinates the internal milieu with the prevailing environment. Thus, appetite, which reflects a complex interaction among the external environment, behavioral profile, and subjective states as well as the storage and metabolism of energy, has an important role in the regulation of energy balance. In the prevailing food environment which offers an abundance of food choices it is likely that the motivation to consume from a wide range of delectable foods plays a greater role in contributing to overeating than in the past when the motivation to eat was largely governed by metabolic need. The response to food-related cues can promote strong desires to eat known as cravings by activating the mesocorticolimbic dopamine neurocircuitry. Cravings are associated with subsequent eating and weight-related outcomes. Being able to control food cravings is a determinant of success at adhering to an energy-restricted diet regimen. Increased understanding of the neurocircuitry of appetite regulation, especially reward-related eating behavior, has provided potential targets for therapeutic anti-obesity agents specifically directed at reward mechanisms. The naltrexone-bupropion combination and lorcaserin, which are both approved by the US Food and Drug Administration (FDA) for long-term weight management, have shown promise in addressing craving-related eating behavior. Phentermine and liraglutide are approved as monotherapies for weight management. Preliminary research suggests that liraglutide, as well as phentermine alone or in combination with lorcaserin, may be effective in targeting food cravings. Food components such as thylakoid membranes have also been shown to influence food cravings. This review explores the concepts related to appetite and reward-induced eating behavior, as well as the pharmacological options and food-derived components that may be used to address food cravings.

Disorders of gastrointestinal hypomotility

Ingestion and digestion of food as well as expulsion of residual material from our gastrointestinal tract requires normal propulsive, i.e. motor, function. Hypomotility refers to inherited or acquired changes that come with decreased contractile forces or slower transit. It not only often causes symptoms but also may compromise nutritional status or lead to other complications. While severe forms, such as pseudo-obstruction or ileus, may have a tremendous functional impact, the less severe forms of hypomotility may well be more relevant, as they contribute to common disorders, such as functional dyspepsia, gastroparesis, chronic constipation, and irritable bowel syndrome (IBS). Clinical testing can identify changes in contractile activity, defined by lower amplitudes or abnormal patterns, and the related effects on transit. However, such biomarkers show a limited correlation with overall symptom severity as experienced by patients. Similarly, targeting hypomotility with pharmacological interventions often alters gut motor function but does not consistently improve symptoms. Novel diagnostic approaches may change this apparent paradox and enable us to obtain more comprehensive information by integrating data on electrical activity, mechanical forces, patterns, wall stiffness, and motions with information of the flow of luminal contents. New drugs with more selective effects or more specific delivery may improve benefits and limit adverse effects. Lastly, the complex regulation of gastrointestinal motility involves the brain-gut axis as a reciprocal pathway for afferent and efferent signaling. Considering the role of visceral input in emotion and the effects of emotion on visceral activity, understanding and managing hypomotility disorders requires an integrative approach based on the mind-body continuum or biopsychosocial model of diseases.

Integration of reward signalling and appetite regulating peptide systems in the control of food-cue responses

Understanding the neurobiological substrates that encode learning about food-associated cues and how those signals are modulated is of great clinical importance especially in light of the worldwide obesity problem. Inappropriate or maladaptive responses to food-associated cues can promote over-consumption, leading to excessive energy intake and weight gain. Chronic exposure to foods rich in fat and sugar alters the reinforcing value of foods and weakens inhibitory neural control, triggering learned, but maladaptive, associations between environmental cues and food rewards. Thus, responses to food-associated cues can promote cravings and food-seeking by activating mesocorticolimbic dopamine neurocircuitry, and exert physiological effects including salivation. These responses may be analogous to the cravings experienced by abstaining drug addicts that can trigger relapse into drug self-administration. Preventing cue-triggered eating may therefore reduce the over-consumption seen in obesity and binge-eating disorder. In this review we discuss recent research examining how cues associated with palatable foods can promote reward-based feeding behaviours and the potential involvement of appetite-regulating peptides including leptin, ghrelin, orexin and melanin concentrating hormone. These peptide signals interface with mesolimbic dopaminergic regions including the ventral tegmental area to modulate reactivity to cues associated with palatable foods. Thus, a novel target for anti-obesity therapeutics is to reduce non-homeostatic, reward driven eating behaviour, which can be triggered by environmental cues associated with highly palatable, fat and sugar rich foods.