Hormonal and neural mechanisms of food reward, eating behaviour and obesity

Exploring the Shared Genetic Architecture Between Obstructive Sleep Apnea and Body Mass Index

Purpose

The reciprocal comorbidity of obstructive sleep apnea (OSA) and body mass index (BMI) has been observed, yet the shared genetic architecture between them remains unclear. This study aimed to explore the genetic overlaps between them.

Methods

Summary statistics were acquired from the genome-wide association studies (GWASs) on OSA (Ncase = 41,704; Ncontrol = 335,573) and BMI (Noverall = 461,460). A comprehensive genome-wide cross-trait analysis was performed to quantify global and local genetic correlation, infer the bidirectional causal relationships, detect independent pleiotropic loci, and investigate potential comorbid genes.

Results

A positive significant global genetic correlation between OSA and BMI was observed (r g = 0.52, P = 2.85e-122), which was supported by three local signal. The Mendelian randomization analysis confirmed bidirectional causal associations. In the meta-analysis of cross-traits GWAS, a total of 151 single-nucleotide polymorphisms were found to be pleiotropic between OSA and BMI. Additionally, we discovered that the genetic association between OSA and BMI is concentrated in 12 brain regions. Finally, a total 134 expression-tissue pairs were observed to have a significant impact on both OSA and BMI within the specified brain regions.

Conclusion

Our comprehensive genome-wide cross-trait analysis indicates a shared genetic architecture between OSA and BMI, offering new perspectives on the possible mechanisms involved.

Amylin Modulates a Ventral Tegmental Area-to-Medial Prefrontal Cortex Circuit to Suppress Food Intake and Impulsive Food-Directed Behavior

BACKGROUND

A better understanding of the neural mechanisms regulating impaired satiety to palatable foods is essential to treat hyperphagia linked with obesity. The satiation hormone amylin signals centrally at multiple nuclei including the ventral tegmental area (VTA). VTA-to-medial prefrontal cortex (mPFC) projections encode food reward information to influence behaviors including impulsivity. We hypothesized that modulation of VTA-to-mPFC neurons underlies amylin-mediated decreases in palatable food-motivated behaviors.

METHODS

We used a variety of pharmacological, behavioral, genetic, and viral approaches (n = 4-16/experiment) to investigate the anatomical and functional circuitry of amylin-controlled VTA-to-mPFC signaling in rats.

RESULTS

To first establish that VTA amylin receptor (calcitonin receptor) activation can modulate mPFC activity, we showed that intra-VTA amylin decreased food-evoked mPFC cFos. VTA amylin delivery also attenuated food-directed impulsive behavior, implicating VTA amylin signaling as a regulator of mPFC functions. Palatable food activates VTA dopamine and mPFC neurons. Accordingly, dopamine receptor agonism in the mPFC blocked the hypophagic effect of intra-VTA amylin, and VTA amylin injection reduced food-evoked phasic dopamine levels in the mPFC, supporting the idea that VTA calcitonin receptor activation decreases dopamine release in the mPFC. Surprisingly, calcitonin receptor expression was not found on VTA-to-mPFC projecting neurons but was instead found on GABAergic (gamma-aminobutyric acidergic) interneurons in the VTA that provide monosynaptic inputs to this pathway. Blocking intra-VTA GABA signaling, through GABA receptor antagonists and DREADD (designer receptor exclusively activated by designer drugs)-mediated GABAergic neuronal silencing, attenuated intra-VTA amylin-induced hypophagia.

CONCLUSIONS

These results indicate that VTA amylin signaling stimulates GABA-mediated inhibition of dopaminergic projections to the mPFC to mitigate impulsive consumption of palatable foods.

Associations of parental preconception and maternal pregnancy urinary phthalate biomarker and bisphenol-a concentrations with child eating behaviors

BACKGROUND

Eating behaviors are controlled by the neuroendocrine system. Whether endocrine disrupting chemicals have the potential to affect eating behaviors has not been widely studied in humans. We investigated whether maternal and paternal preconception and maternal pregnancy urinary phthalate biomarker and bisphenol-A (BPA) concentrations were associated with children's eating behaviors.

METHODS

We used data from mother-father-child triads in the Preconception Environmental exposure And Childhood health Effects (PEACE) Study, an ongoing prospective cohort study of children aged 6-13 years whose parent(s) previously enrolled in a fertility clinic-based prospective preconception study. We quantified urinary concentrations of 11 phthalate metabolites and BPA in parents' urine samples collected preconceptionally and during pregnancy. Parents rated children's eating behavior using the Child Eating Behavior Questionnaire (CEBQ). Using multivariable linear regression, accounting for correlation among twins, we estimated covariate-adjusted associations of urinary phthalate biomarkers and BPA concentrations with CEBQ subscale scores.

RESULTS

This analysis included 195 children (30 sets of twins), 160 mothers and 97 fathers; children were predominantly non-Hispanic white (84%) and 53% were male. Paternal and maternal preconception monobenzyl phthalate (MBzP) concentrations and maternal preconception mono-n-butyl phthalate (MnBP) were positively associated with emotional overeating, food responsiveness, and desire to drink scores in children (β's= 0.11 [95% CI: 0.01, 0.20]-0.21 [95% CI: 0.10, 0.31] per loge unit increase in phthalate biomarker concentration). Paternal preconception BPA concentrations were inversely associated with scores on food approaching scales. Maternal pregnancy MnBP, mono-isobutyl phthalate (MiBP) and MBzP concentrations were associated with increased emotional undereating scores. Maternal pregnancy monocarboxy-isononyl phthalate concentrations were related to decreased food avoiding subscale scores.

CONCLUSIONS

In this cohort, higher maternal and paternal preconception urinary concentrations of some phthalate biomarkers were associated with increased food approaching behavior scores and decreased food avoiding behavior scores, which could lead to increased adiposity in children.

Satiety: a gut-brain-relationship

Many hormones act on the hypothalamus to control hunger and satiety through various pathways closely associated with several factors. When food is present in the gastro intestinal (GI) tract, enteroendocrine cells (EECs) emit satiety signals such as cholecystokinin (CCK), glucagon like peptide-1 (GLP-1) and peptide YY (PYY), which can then communicate with the vagus nerve to control food intake. More specifically, satiety has been shown to be particularly affected by the GLP-1 hormone and its receptor agonists that have lately been acknowledged as a promising way to reduce weight. In addition, there is increasing evidence that normal flora is also involved in the peripheral, central, and reward system that impact satiety. Moreover, neurologic pathways control satiety through neurotransmitters. In this review, we discuss the different roles of each of the GLP-1 hormone and its agonist, gut microbiomes, as well as neurotransmitters and their interconnected relation in the regulation of body's satiety homeostasis.

Effects of Bradykinin B2 Receptor Ablation from Tyrosine Hydroxylase Cells on Behavioral and Motor Aspects in Male and Female Mice

The kallikrein-kinin system is a versatile regulatory network implicated in various biological processes encompassing inflammation, nociception, blood pressure control, and central nervous system functions. Its physiological impact is mediated through G-protein-coupled transmembrane receptors, specifically the B1 and B2 receptors. Dopamine, a key catecholamine neurotransmitter widely distributed in the CNS, plays a crucial role in diverse physiological functions including motricity, reward, anxiety, fear, feeding, sleep, and arousal. Notably, the potential physical interaction between bradykinin and dopaminergic receptors has been previously documented. In this study, we aimed to explore whether B2R modulation in catecholaminergic neurons influences the dopaminergic pathway, impacting behavioral, metabolic, and motor aspects in both male and female mice. B2R ablation in tyrosine hydroxylase cells reduced the body weight and lean mass without affecting body adiposity, substrate oxidation, locomotor activity, glucose tolerance, or insulin sensitivity in mice. Moreover, a B2R deficiency in TH cells did not alter anxiety levels, exercise performance, or motor coordination in female and male mice. The concentrations of monoamines and their metabolites in the substantia nigra and cortex region were not affected in knockout mice. In essence, B2R deletion in TH cells selectively influenced the body weight and composition, leaving the behavioral and motor aspects largely unaffected.

Cluster analysis in gambling disorder based on sociodemographic, neuropsychological, and neuroendocrine features regulating energy homeostasis

BACKGROUND

The heterogeneity of gambling disorder (GD) has led to the identification of different subtypes, mostly including phenotypic features, with distinctive implications on the GD severity and treatment outcome. However, clustering analyses based on potential endophenotypic features, such as neuropsychological and neuroendocrine factors, are scarce so far.

AIMS

This study firstly aimed to identify empirical clusters in individuals with GD based on sociodemographic (i.e., age and sex), neuropsychological (i.e., cognitive flexibility, inhibitory control, decision making, working memory, attention, and set-shifting), and neuroendocrine factors regulating energy homeostasis (i.e., leptin, ghrelin, adiponectin, and liver-expressed antimicrobial peptide 2, LEAP-2). The second objective was to compare the profiles between clusters, considering the variables used for the clustering procedure and other different sociodemographic, clinical, and psychological features.

METHODS

297 seeking-treatment adult outpatients with GD (93.6% males, mean age of 39.58 years old) were evaluated through a semi-structured clinical interview, self-reported psychometric assessments, and a protocolized neuropsychological battery. Plasma concentrations of neuroendocrine factors were assessed in peripheral blood after an overnight fast. Agglomerative hierarchical clustering was applied using sociodemographic, neuropsychological, and neuroendocrine variables as indicators for the grouping procedure. Comparisons between the empirical groups were performed using Chi-square tests (χ2) for categorical variables, and analysis of variance (ANOVA) for quantitative measures.

RESULTS

Three-mutually-exclusive groups were obtained, being neuropsychological features those with the greatest weight in differentiating groups. The largest cluster (Cluster 1, 65.3%) was composed by younger males with strategic and online gambling preferences, scoring higher on self-reported impulsivity traits, but with a lower cognitive impairment. Cluster 2 (18.2%) and 3 (16.5%) were characterized by a significantly higher proportion of females and older patients with non-strategic gambling preferences and a worse neuropsychological performance. Particularly, Cluster 3 had the poorest neuropsychological performance, especially in cognitive flexibility, while Cluster 2 reported the poorest inhibitory control. This latter cluster was also distinguished by a poorer self-reported emotion regulation, the highest prevalence of food addiction, as well as a metabolic profile characterized by the highest mean concentrations of leptin, adiponectin, and LEAP-2.

CONCLUSIONS

To the best of our knowledge, this is the first study to identify well-differentiated GD clusters using neuropsychological and neuroendocrine features. Our findings reinforce the heterogeneous nature of the disorder and emphasize a role of potential endophenotypic features in GD subtyping. This more comprehensive characterization of GD profiles could contribute to optimize therapeutic interventions based on a medicine of precision.

Treatment of obesity by acupuncture combined with medicine based on pathophysiological mechanism: A review

Obesity is a complex, multifactorial disease. The incidence of overweight and obesity has doubled worldwide since 1980, and nearly one-third of the world population is now classified as overweight or obese. Obesity rates are increasing in all age groups and for both sexes, regardless of geographic region, race, or socioeconomic status, although they are generally higher in older adults and women. Although the absolute prevalence of overweight and obesity varies widely, this trend is similar across different regions and countries. In some developed countries, the prevalence of obesity has levelled off over the past few years. However, obesity has become a health problem that cannot be ignored in low- and middle-income countries. Although the drug treatment model of modern medicine has a significant therapeutic effect in the treatment of obesity, its adverse effects are also obvious. Acupuncture combined with Chinese medicine treatment of obesity has prominent advantages in terms of clinical efficacy, and its clinical safety is higher, with fewer adverse reactions. The combination of acupuncture and medicine in the treatment of obesity is worth exploring.

Identification and quantification of kukoamine A and kukoamine B as novel μ-opioid receptor agonists in potato and other solanaceous plants

Activation of the µ-opioid receptor (µOR) by food components could lead to reward effects or to the modulation of motor functions in the gastrointestinal tract. In an unbiased search for novel µOR agonists in food, a three-step virtual-screening process selected 22 promising candidates with potential to interact with the µOR. Radioligand binding studies showed that ten of these substances indeed bind to the receptor. Functional assays identified kukoamine A as a full agonist (EC50 = 5.6 µM) and kukoamine B as a partial agonist (EC50 = 8.7 µM) to µOR. After extraction, both kukoamines were analyzed by LC-MS/MS in potato, tomato, pepper, and eggplant. Depending on the potato variety, up to 16 µg of kukoamine A and 157 µg of kukoamine B per gram dry weight could be determined in the whole tuber, mainly concentrated in the potato peel. Cooking did not influence the kukoamine contents.

The effects of Spirulina platensis on behavior in adolescent rats fed a high-fat diet

In recent years, childhood overweight and obesity have become a universal public health problem. Obesity may lead to cognitive disorders, depression and anxiety by affecting neuronal processes. Spirulina platensis (SP), a species of microalgae from the Chlorophyceae green algae class, has neuroprotective effects and may reduce body weight. In this study, we aimed to investigate the effects of SP on behavior alongside the role of leptin and Sirtuin-1 in fed with high-fat diet (HFD) adolescent rats. Four-week-old Sprague Dawley male rats were divided into four groups: control, HFD, HFD + SP150 (150 mg/kg/day SP, orally), HFD + SP450 (450 mg/kg/day SP, orally). Rats except for the control group exposed to 60% HFD along 12 weeks. Last 6 weeks SP or vehicle administered. After the behavioral tests, leptin and Sirtuin-1 levels in prefrontal cortex and hippocampus regions were evaluated. SP150 significantly reduced body weight compared with HFD group. The time spent in the center of open field increased significantly in SP150-treated rats compared with HFD. SP150 and SP450 significantly decreased immobility time in forced swim test compared with HFD. Leptin levels in HFD group were significantly lower in prefrontal cortex compared to control group. Leptin levels of the HFD + SP450 group were significantly higher than HFD group in the hippocampus. There was no significant difference between groups in Sirtuin-1 levels. In conclusion, SP supplementation in adolescence period might positively affect chronic high fat-induced anxiety-like and depressive-like behavior by partially affecting brain leptin levels and without affecting Sirtuin-1 levels.

Phase-shifting the circadian glucocorticoid profile induces disordered feeding behaviour by dysregulating hypothalamic neuropeptide gene expression

Here we demonstrate, in rodents, how the timing of feeding behaviour becomes disordered when circulating glucocorticoid rhythms are dissociated from lighting cues; a phenomenon most commonly associated with shift-work and transmeridian travel 'jetlag'. Adrenalectomized rats are infused with physiological patterns of corticosterone modelled on the endogenous adrenal secretory profile, either in-phase or out-of-phase with lighting cues. For the in-phase group, food intake is significantly greater during the rats' active period compared to their inactive period; a feeding pattern similar to adrenal-intact control rats. In contrast, the feeding pattern of the out-of-phase group is significantly dysregulated. Consistent with a direct hypothalamic modulation of feeding behaviour, this altered timing is accompanied by dysregulated timing of anorexigenic and orexigenic neuropeptide gene expression. For Neuropeptide Y (Npy), we report a glucocorticoid-dependent direct transcriptional regulation mechanism mediated by the glucocorticoid receptor (GR). Taken together, our data highlight the adverse behavioural outcomes that can arise when two circadian systems have anti-phasic cues, in this case impacting on the glucocorticoid-regulation of a process as fundamental to health as feeding behaviour. Our findings further highlight the need for development of rational approaches in the prevention of metabolic dysfunction in circadian-disrupting activities such as transmeridian travel and shift-work.

Immunometabolic regulation during the presence of microorganisms and parasitoids in insects

Multicellular organisms live in environments containing diverse nutrients and a wide variety of microbial communities. On the one hand, the immune response of organisms can protect from the intrusion of exogenous microorganisms. On the other hand, the dynamic coordination of anabolism and catabolism of organisms is a necessary factor for growth and reproduction. Since the production of an immune response is an energy-intensive process, the activation of immune cells is accompanied by metabolic transformations that enable the rapid production of ATP and new biomolecules. In insects, the coordination of immunity and metabolism is the basis for insects to cope with environmental challenges and ensure normal growth, development and reproduction. During the activation of insect immune tissues by pathogenic microorganisms, not only the utilization of organic resources can be enhanced, but also the activated immune cells can usurp the nutrients of non-immune tissues by generating signals. At the same time, insects also have symbiotic bacteria in their body, which can affect insect physiology through immune-metabolic regulation. This paper reviews the research progress of insect immune-metabolism regulation from the perspective of insect tissues, such as fat body, gut and hemocytes. The effects of microorganisms (pathogenic bacteria/non-pathogenic bacteria) and parasitoids on immune-metabolism were elaborated here, which provide guidance to uncover immunometabolism mechanisms in insects and mammals. This work also provides insights to utilize immune-metabolism for the formulation of pest control strategies.

Hyperphagia, Growth, and Puberty in Children with Angelman Syndrome

Angelman Syndrome (AS) is a rare genetic disorder caused by lack of maternal UBE3A protein due to a deletion of the chromosome 15q11.2-q13 region, uniparental paternal disomy, imprinting center defect, or pathogenic variant in the UBE3A gene. Characteristics are developmental delay, epilepsy, behavioral, and sleep problems. There is some evidence for hyperphagia, shorter stature, and higher BMI compared to neurotypical children, but longitudinal studies on growth are lacking. In this study, we analyzed prospectively collected data of 145 children with AS, who visited the ENCORE Expertise Center between 2010 and 2021, with a total of 853 visits. Children showed an elevated mean score of 25 on the Dykens Hyperphagia questionnaire (range 11-55) without genotype association. Higher scores were significantly associated with higher body mass index (BMI) standard deviation scores (SDS) (p = 0.004). Mean height was -1.2 SDS (SD 1.3), mean BMI-SDS was 0.6 (SD 1.7); 43% had a BMI-SDS > 1 and 20% had a BMI-SDS > 2. Higher BMI-SDS was significantly associated with non-deletion genotype (p = 0.037) and walking independently (p = 0.023). Height SDS decreased significantly with age (p < 0.001) and BMI-SDS increased significantly with age (p < 0.001. Onset of puberty was normal. In conclusion, children with AS showed moderate hyperphagia, lower height SDS, and higher BMI-SDS compared to norm data, with increasing deviation from the norm with age. It is uncertain how loss of maternal UBE3A function may influence growth. Attention to diet, exercise, and hyperphagia from an early age is recommended to prevent obesity and associated health problems.

Higher body weight-dependent neural activation during reward processing

Obesity is associated with alterations in brain structure and function, particularly in areas related to reward processing. Although brain structural investigations have demonstrated a continuous association between higher body weight and reduced gray matter in well-powered samples, functional neuroimaging studies have typically only contrasted individuals from the normal weight and obese body mass index (BMI) ranges with modest sample sizes. It remains unclear, whether the commonly found hyperresponsiveness of the reward circuit can (a) be replicated in well-powered studies and (b) be found as a function of higher body weight even below the threshold of clinical obesity. 383 adults across the weight spectrum underwent functional magnetic resonance imaging during a common card-guessing paradigm simulating monetary reward. Multiple regression was used to investigate the association of BMI and neural activation in the reward circuit. In addition, a one-way ANOVA model comparing three weight groups (normal weight, overweight, obese) was calculated. Higher BMI was associated with higher reward response in the bilateral insula. This association could no longer be found when participants with obesity were excluded from the analysis. The ANOVA revealed higher activation in obese vs. lean, but no difference between lean and overweight participants. The overactivation of reward-related brain areas in obesity is a consistent finding that can be replicated in large samples. In contrast to brain structural aberrations associated with higher body weight, the neurofunctional underpinnings of reward processing in the insula appear to be more pronounced in the higher body weight range.

Leptin, but not ghrelin, is associated with food addiction scores in a population-based subject sample

BACKGROUND

Ghrelin and leptin are both peptide hormones and act as opposing players in the regulation of hunger, satiety and energy expenditure. Leptin reduces appetite and feelings of hunger and is secreted mainly by adipocytes, while ghrelin increases appetite and food intake and reduces metabolic rate. Both hormones have been implicated in addictive disorders. Ghrelin was shown to have pro-addictive effects while leptin's role in addiction yields more conflicting results. Their involvement in the regulation of both food intake and addictive behaviors make them interesting candidates when investigating the regulation of food addiction. However, only few human studies have been performed and large-scale studies are lacking to date. We aimed to investigate the association between total ghrelin and leptin serum levels with scores in the Yale Food Addiction Scale (YFAS).

METHODS

Subjects were recruited in the LIFE Adult cohort. 909 subjects were included in the analysis and we performed univariate multiple linear regression models, adjusted for age, sex (in total group analyses only), alcohol consumption, smoking status, BMI scores, cortisol concentrations, Center for Epidemiological Studies Depression Scale (CES-D) and the 7-item Generalized Anxiety Disorder Scale (GAD-7) sum scores. The dependent variable was the YFAS score.

RESULTS

In men, leptin serum levels showed a significant positive association (standardized β = 0.146; p = 0.012) with the YFAS score. This finding was confirmed in an extreme-group comparison: men in the highest quartile of leptin levels had significantly higher YFAS sum scores than men in the lowest quartile (1.55 vs. 1.18; p = 0.00014). There was no association with YFAS sum score in the total group (standardized β = -0.002; p = 0.974) or in women (standardized β = -0.034; p = 0.674). Total serum ghrelin showed no association with YFAS sum score neither in the total group (standardized β = -0.043; p = 0.196) nor in men (n = 530; standardized β = -0.063; p = 0.135) or women (n = 379; standardized β = -0.035; p = 0.494).

CONCLUSION

Our findings are in line with previous literature and suggest that total ghrelin serum levels are not associated with food addiction scores. Leptin had been previously shown to be associated with food addiction and we confirmed this finding for men in a large, population-based approach.

Metabolic Hormone Action in the VTA: Reward-Directed Behavior and Mechanistic Insights

Dysfunctional signaling in midbrain reward circuits perpetuates diseases characterized by compulsive overconsumption of rewarding substances such as substance abuse, binge eating disorder, and obesity. Ventral tegmental area (VTA) dopaminergic activity serves as an index for how rewarding stimuli are perceived and triggers behaviors necessary to obtain future rewards. The evolutionary linking of reward with seeking and consuming palatable foods ensured an organism's survival, and hormone systems that regulate appetite concomitantly developed to regulate motivated behaviors. Today, these same mechanisms serve to regulate reward-directed behavior around food, drugs, alcohol, and social interactions. Understanding how hormonal regulation of VTA dopaminergic output alters motivated behaviors is essential to leveraging therapeutics that target these hormone systems to treat addiction and disordered eating. This review will outline our current understanding of the mechanisms underlying VTA action of the metabolic hormones ghrelin, glucagon-like peptide-1, amylin, leptin, and insulin to regulate behavior around food and drugs of abuse, highlighting commonalities and differences in how these five hormones ultimately modulate VTA dopamine signaling.

Seeking the Psilocybiome: Psychedelics meet the microbiota-gut-brain axis

Moving towards a systems psychiatry paradigm embraces the inherent complex interactions across all levels from micro to macro and necessitates an integrated approach to treatment. Cortical 5-HT2A receptors are key primary targets for the effects of serotonergic psychedelics. However, the therapeutic mechanisms underlying psychedelic therapy are complex and traverse molecular, cellular, and network levels, under the influence of biofeedback signals from the periphery and the environment. At the interface between the individual and the environment, the gut microbiome, via the gut-brain axis, plays an important role in the unconscious parallel processing systems regulating host neurophysiology. While psychedelic and microbial signalling systems operate over different timescales, the microbiota-gut-brain (MGB) axis, as a convergence hub between multiple biofeedback systems may play a role in the preparatory phase, the acute administration phase, and the integration phase of psychedelic therapy. In keeping with an interconnected systems-based approach, this review will discuss the gut microbiome and mycobiome and pathways of the MGB axis, and then explore the potential interaction between psychedelic therapy and the MGB axis and how this might influence mechanism of action and treatment response. Finally, we will discuss the possible implications for a precision medicine-based psychedelic therapy paradigm.

Food addiction, hormones and blood biomarkers in humans: A systematic literature review

BACKGROUND

Food addiction may play a role in rising obesity rates in connection with obesogenic environments and processed food availability, however the concept of food addiction remains controversial. While animal studies show evidence for addictive processes in relation to processed foods, most human studies are psychologically focussed and there is a need to better understand evidence for biological mechanisms of food addiction in humans. Several key hormones are implicated in models of food addiction, due to their key roles in feeding, energy metabolism, stress and addictive behaviours. This systematic literature review examines evidence for relationships between food addiction, hormones and other blood biomarkers.

METHODS

A series of literature searches was performed in Scopus, PsychInfo, MedLine, ProQuest, CINAHL and Web of Science. A total of 3111 articles were found, of which 1045 were duplicates. Articles were included if they contained a psychometric measurement of food addiction, such as the Yale Food Addiction Scale, as well as addressed the association between FA and hormones or blood biomarkers in humans. Articles were assessed for eligibility by two independent reviewers.

RESULTS

Sixteen studies were identified that examined relationships between food addiction and blood biomarkers, published between 2015 and 2021. Significant findings were reported for leptin, ghrelin, cortisol, insulin and glucose, oxytocin, cholesterol, plasma dopamine, thyroid stimulating hormone (TSH), haemoglobin A1c (HbA1c), triglyceride (TG), amylin, tumour necrosis factor alpha (TNF- α) and cholecystokinin (CCK). Methodological issues included small sample sizes and variation in obesity status, sex and mental health-related comorbidities. Due to methodological limitations, definite connections between FA, hormones and other blood biomarkers cannot yet be determined.

CONCLUSION

This systematic review identified preliminary evidence linking FA symptoms to hormones and other blood biomarkers related to feeding, addiction, and stress. However, due to the small number of studies and methodological limitations, further research is needed to evaluate biopsychosocial models of FA and to resolve controversies.

Glucocorticoids, stress and eating: The mediating role of appetite-regulating hormones

Disrupted hormonal appetite signaling plays a crucial role in obesity as it may lead to uncontrolled reward-related eating. Such disturbances can be induced not only by weight gain itself but also by glucocorticoid overexposure, for example, due to chronic stress, disease, or medication use. However, the exact pathways are just starting to be understood. Here, we present a conceptual framework of how glucocorticoid excess may impair hormonal appetite signaling and, consequently, eating control in the context of obesity. The evidence we present suggests that counteracting glucocorticoid excess can lead to improvements in appetite signaling and may therefore pose a crucial target for obesity prevention and treatment. In turn, targeting hormonal appetite signals may not only improve weight management and eating behavior but may also decrease detrimental effects of glucocorticoid excess on cardio-metabolic outcomes and mood. We conclude that gaining a better understanding of the relationship between glucocorticoid excess and circulating appetite signals will contribute greatly to improvements in personalized obesity prevention and treatment.

Insulin sensitivity in mesolimbic pathways predicts and improves with weight loss in older dieters

Central insulin is critically involved in the regulation of hedonic feeding. Insulin resistance in overweight has recently been shown to reduce the inhibitory function of insulin in the human brain. How this relates to effective weight management is unclear, especially in older people, who are highly vulnerable to hyperinsulinemia and in whom neural target systems of insulin action undergo age-related changes. Here, 50 overweight, non-diabetic older adults participated in a double-blind, placebo-controlled, pharmacological functional magnetic resonance imaging study before and after randomization to a 3-month caloric restriction or active waiting group. Our data show that treatment outcome in dieters can be predicted by baseline measures of individual intranasal insulin (INI) inhibition of value signals in the ventral tegmental area related to sweet food liking as well as, independently, by peripheral insulin sensitivity. At follow-up, both INI inhibition of hedonic value signals in the nucleus accumbens and peripheral insulin sensitivity improved with weight loss. These data highlight the critical role of central insulin function in mesolimbic systems for weight management in humans and directly demonstrate that neural insulin function can be improved by weight loss even in older age, which may be essential for preventing metabolic disorders in later life.

Gut microbes and food reward: From the gut to the brain

Inappropriate food intake behavior is one of the main drivers for fat mass development leading to obesity. Importantly the gut microbiota-mediated signals have emerged as key actors regulating food intake acting mainly on the hypothalamus, and thereby controlling hunger or satiety/satiation feelings. However, food intake is also controlled by the hedonic and reward systems leading to food intake based on pleasure (i.e., non-homeostatic control of food intake). This review focus on both the homeostatic and the non-homeostatic controls of food intake and the implication of the gut microbiota on the control of these systems. The gut-brain axis is involved in the communications between the gut microbes and the brain to modulate host food intake behaviors through systemic and nervous pathways. Therefore, here we describe several mediators of the gut-brain axis including gastrointestinal hormones, neurotransmitters, bioactive lipids as well as bacterial metabolites and compounds. The modulation of gut-brain axis by gut microbes is deeply addressed in the context of host food intake with a specific focus on hedonic feeding. Finally, we also discuss possible gut microbiota-based therapeutic approaches that could lead to potential clinical applications to restore food reward alterations. Therapeutic applications to tackle these dysregulations is of utmost importance since most of the available solutions to treat obesity present low success rate.

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.

Influence of the Gut Microbiome on Feed Intake of Farm Animals

With the advancement of microbiome research, the requirement to consider the intestinal microbiome as the “last organ” of an animal emerged. Through the production of metabolites and/or the stimulation of the host’s hormone and neurotransmitter synthesis, the gut microbiota can potentially affect the host’s eating behavior both long and short-term. Based on current evidence, the major mediators appear to be short-chain fatty acids (SCFA), peptide hormones such as peptide YY (PYY) and glucagon-like peptide-1 (GLP-1), as well as the amino acid tryptophan with the associated neurotransmitter serotonin, dopamine and γ-Aminobutyrate (GABA). The influence appears to extend into central neuronal networks and the expression of taste receptors. An interconnection of metabolic processes with mechanisms of taste sensation suggests that the gut microbiota may even influence the sensations of their host. This review provides a summary of the current status of microbiome research in farm animals with respect to general appetite regulation and microbiota-related observations made on the influence on feed intake. This is briefly contrasted with the existing findings from research with rodent models in order to identify future research needs. Increasing our understanding of appetite regulation could improve the management of feed intake, feed frustration and anorexia related to unhealthy conditions in farm animals.

Brain regulation of hunger and motivation: The case for integrating homeostatic and hedonic concepts and its implications for obesity and addiction

Obesity and other eating disorders are marked by dysregulations to brain metabolic, hedonic, motivational, and sensory systems that control food intake. Classic approaches in hunger research have distinguished between hedonic and homeostatic processes, and have mostly treated these systems as independent. Hindbrain structures and a complex network of interconnected hypothalamic nuclei control metabolic processes, energy expenditure, and food intake while mesocorticolimbic structures are though to control hedonic and motivational processes associated with food reward. However, it is becoming increasingly clear that hedonic and homeostatic brain systems do not function in isolation, but rather interact as part of a larger network that regulates food intake. Incentive theories of motivation provide a useful route to explore these interactions. Adapting incentive theories of motivation can enable researchers to better how motivational systems dysfunction during disease. Obesity and addiction are associated with profound alterations to both hedonic and homeostatic brain systems that result in maladaptive patterns of consumption. A subset of individuals with obesity may experience pathological cravings for food due to incentive sensitization of brain systems that generate excessive 'wanting' to eat. Further progress in understanding how the brain regulates hunger and appetite may depend on merging traditional hedonic and homeostatic concepts of food reward and motivation.

The dopamine system: insights between kidney and brain

BACKGROUND

Chronic kidney disease (CKD) is one of the most common diseases in adult age and it is typical of older adults. Recent data suggest that almost half of the elders have CKD. It is now clear that CKD is accompanied, in the early stages, by cognitive impairment, together with depression and subtle abnormalities in motor control (such as gait and balance alterations).

SUMMARY

Several data suggest a link between brain dopamine and kidney diseases. Metabolic syndrome and diabetes can affect dopamine neuron survival (leading to Parkinson's Disease). Several uremic toxins in CKD (uric acid, indoxyl sulphate) and trace elements accumulating in CKD (aluminium, manganese) can also modify the dopaminergic system. Hormones produced by the kidney such as vitamin D are neuroprotective for dopamine neurons. Dopaminergic drugs are useful for the treatment of a common sleep disorder in CKD, the restless legs syndrome. However, experiments on animal models of CKD show conflicting results regarding a modification of dopamine neurons.

KEY MESSAGES

Several observations suggest a limited relevance of the dopaminergic system in CKD-related cognitive impairment. However, a common sleep disturbance in CKD, the restless leg syndrome, improves with dopaminergic drugs. Therefore, it remains to be established the role of the dopamine system in subtle motor dysfunction observed in CKD, such as tremors, gait alterations, and central sleep apnea.

Brain circuits for promoting homeostatic and non-homeostatic appetites

As the principal means of acquiring nutrients, feeding behavior is indispensable to the survival and well-being of animals. In response to energy or nutrient deficits, animals seek and consume food to maintain energy homeostasis. On the other hand, even when animals are calorically replete, non-homeostatic factors, such as the sight, smell, and taste of palatable food, or environmental cues that predict food, can stimulate feeding behavior. These homeostatic and non-homeostatic factors have traditionally been investigated separately, but a growing body of literature highlights that these factors work synergistically to promote feeding behavior. Furthermore, recent breakthroughs in cell type-specific and circuit-specific labeling, recording, and manipulation techniques have markedly accelerated the discovery of well-defined neural populations underlying homeostatic and non-homeostatic appetite control, as well as overlapping circuits that contribute to both types of appetite. This review aims to provide an update on our understanding of the neural circuit mechanisms for promoting homeostatic and non-homeostatic appetites, focusing on the function of recently identified, genetically defined cell types.

Research on the neural circuit mechanisms underlying feeding behaviors is critical to identifying therapeutic targets for food-related disorders like obesity and anorexia. Sung-Yon Kim and colleagues at Seoul National University, South Korea, reviewed the current understanding of neural circuits promoting feeding behavior, which is regulated by homeostatic and non-homeostatic appetites. In response to deficits in energy (caloric) or nutrients, specific populations of neurons sensitive to hormones leptin and ghrelin generate homeostatic appetite and promote feeding. In addition, diverse neural populations stimulate non-homeostatic appetite in the absence of immediate internal needs and are thought to drive overconsumption in the modern obesogenic environment. These appetites extensively interact through overlapping neural circuits to jointly promote feeding behaviors.

The Opioid System in Rainbow Trout Telencephalon Is Probably Involved in the Hedonic Regulation of Food Intake

We hypothesize that opioids are involved in the regulation of food intake in fish through homeostatic and hedonic mechanisms. Therefore, we evaluated in rainbow trout (Oncorhynchus mykiss) hypothalamus and telencephalon changes in precursors, endogenous ligands and receptors of the opioid system under different situations aimed to induce changes in the homeostatic (through fasted/fed/refed fish) and hedonic (through feeding fish a control or a palatable high-fat diet) regulation of food intake. No major changes occurred in parameters assessed related with the nutritional condition of fish (fasted/fed/refed), allowing us to suggest that the opioid system seems not to have an important role in the homeostatic regulation of food intake in rainbow trout. The responses observed in telencephalon of rainbow trout fed the palatable high-fat diet included a decrease in mRNA abundance of the opioid precursor penka, in a way similar to that known in mammals, and increased mRNA abundance of the opioid receptors oprd1 and oprk1 supporting a role for telencephalic opioid system in the hedonic regulation of food intake in fish.

Disrupted stepwise functional brain organization in overweight individuals

Functional hierarchy establishes core axes of the brain, and overweight individuals show alterations in the networks anchored on these axes, particularly in those involved in sensory and cognitive control systems. However, quantitative assessments of hierarchical brain organization in overweight individuals are lacking. Capitalizing stepwise functional connectivity analysis, we assess altered functional connectivity in overweight individuals relative to healthy weight controls along the brain hierarchy. Seeding from the brain regions associated with obesity phenotypes, we conduct stepwise connectivity analysis at different step distances and compare functional degrees between the groups. We find strong functional connectivity in the somatomotor and prefrontal cortices in both groups, and both converge to transmodal systems, including frontoparietal and default-mode networks, as the number of steps increased. Conversely, compared with the healthy weight group, overweight individuals show a marked decrease in functional degree in somatosensory and attention networks across the steps, whereas visual and limbic networks show an increasing trend. Associating functional degree with eating behaviors, we observe negative associations between functional degrees in sensory networks and hunger and disinhibition-related behaviors. Our findings suggest that overweight individuals show disrupted functional network organization along the hierarchical axis of the brain and these results provide insights for behavioral associations.

Antipsychotic-Associated Weight Gain and Clinical Improvement Under Clozapine Treatment

BACKGROUND

Antipsychotic-associated weight gain is a common adverse effect with several negative outcomes in the clinical evolution of patients, which might also affect patients' self-identity from physical appearance and imply treatment discontinuation. However, recent research has drawn attention to an unexpected clinical improvement associated with weight gain, mostly in patients under treatment with clozapine or olanzapine.

METHODS

Twenty-three treatment-resistant psychosis patients initiating clozapine were evaluated. Longitudinal psychopathological assessment through the Positive and Negative Syndrome Scale (PANSS) and anthropometric evaluation were performed at baseline, week 8, and 18.

RESULTS

Body mass index (BMI) change during clozapine treatment was associated with clinical improvement measured with PANSS total score at week 8 (P = 0.021) while showed a trend at week 18 (P = 0.058). The PANSS general score was also associated with weight gain at week 8 (P = 0.022), whereas negative subscale score showed a trend at week 8 (P = 0.088) and was associated between week 8 and 18 (P = 0.018). Sex differences applied at week 8 for PANSS total score, where clinical improvement was significantly associated with BMI in male subjects (P = 0.024). We also stratified for time to initiate clozapine, finding significant associations in negative symptom at week 8 (P = 0.023) and week 18 (P = 0.003) for subjects, which started clozapine after 3 years of illness.

CONCLUSIONS

Our results suggest that in subjects initiating clozapine, clinical improvement is associated with BMI increase, mostly in negative symptom and in patients after 3 years of antipsychotic use. Our findings were already described in the preantipsychotic era, suggesting some pathophysiological mechanism underlying both conditions.

IgG antibodies reacting with ghrelin and leptin are correlated with body composition and appetitive traits in young subjects

Appetitive traits are important behavioural characteristics affecting eating and body composition. Ghrelin and leptin are two key hormones regulating appetite and metabolism. Recent studies have reported the presence of autoantibodies (autoAbs) directed to ghrelin and leptin in healthy individuals as well as affinity alterations in eating disorders such as anorexia nervosa and hyperphagic obesity. Nevertheless, the relationship of these autoAbs with appetitive traits is unknown. The goals of this exploratory study were to analyze circulating IgG autoAbs reacting to ghrelin and leptin and evaluate their relationship with body composition parameters and appetitive traits. This cross-sectional study included 180 young subjects (20 ± 2 years) that underwent body composition evaluation. Seven appetitive traits were assessed with AEBQ-Esp and were classified as low-score or high-score. A validated in-house ELISA test was performed to measure IgG ghrelin and leptin-reactive autoAbs in its free, total, and immune complexes fractions. Free IgG ghrelin-reactive were significantly higher in women than in men. Immune complexes of IgG-ghrelin were positively correlated with waist-hip ratio in the total cohort. In women, free IgG leptin-reactive were positively correlated with body fat percentage and waist-hip ratio, whereas in men, immune complexes of IgG-leptin were positively correlated with body fat percentage. Women with a low-score for 'enjoyment of food', exhibited higher levels of IgG ghrelin-reactive autoAbs on its free form than the high-score group. Men with a high-score for 'emotional undereating' had higher levels of free IgG leptin-reactive autoAbs than the low-score group. The correlation of these autoAbs with anthropometric parameters and appetitive traits in young subjects support its role as carriers and modulators of the biologic functions of ghrelin and leptin and suggest a novel role in eating behaviour through appetitive traits.

Enhancing mask activity in dopaminergic neurons extends lifespan in flies

Dopaminergic neurons (DANs) are essential modulators for brain functions involving memory formation, reward processing, and decision‐making. Here I demonstrate a novel and important function of the DANs in regulating aging and longevity. Overexpressing the putative scaffolding protein Mask in two small groups of DANs in flies can significantly extend the lifespan in flies and sustain adult locomotor and fecundity at old ages. This Mask‐induced beneficial effect requires dopaminergic transmission but cannot be recapitulated by elevating dopamine production alone in the DANs. Independent activation of Gα_s in the same two groups of DANs via the drug‐inducible DREADD system also extends fly lifespan, further indicating the connection of specific DANs to aging control. The Mask‐induced lifespan extension appears to depend on the function of Mask to regulate microtubule (MT) stability. A structure–function analysis demonstrated that the ankyrin repeats domain in the Mask protein is both necessary for regulating MT stability (when expressed in muscles and motor neurons) and sufficient to prolong longevity (when expressed in the two groups of DANs). Furthermore, DAN‐specific overexpression of Unc‐104 or knockdown of p150^Glued, two independent interventions previously shown to impact MT dynamics, also extends lifespan in flies. Together, these data demonstrated a novel DANs‐dependent mechanism that, upon the tuning of their MT dynamics, modulates systemic aging and longevity in flies.

Crosstalk between dopamine and insulin signaling in growth control of the oyster

Neuroendocrine hormones such as dopamine and insulin/insulin-like peptides play indispensable roles in growth regulation of animals, while the interplay between dopamine and insulin signaling pathways remains largely unknown in invertebrates. In the present study, we showed that tyrosine hydroxylase (TH), the rate-limiting enzyme of dopamine synthesis, was highly expressed in all tissues of the fast-growing oysters, and gradually increased with the development, which indicated the potential role of dopamine in growth regulation. Incubated with dopamine hydrochloride and insulin-like peptide recombinant proteins in vitro induced the expression of TH, suggesting a mutual regulatory relationship between insulin and dopamine signaling. Fasting and re-feeding experiments confirmed the role of TH in food intake regulation, also provide a clue about the potential regulatory relationship between the FoxO and TH. Further luciferase assay experiment confirmed that FoxO was involved in transcriptional regulation of TH gene through binding to its specific promoter region. This work provided insights into the crosstalk between dopamine and insulin signaling in growth control of mollusks.

The response to prolonged fasting in hypothalamic serotonin transporter availability is blunted in obesity

BACKGROUND AND AIMS

Serotonergic and dopaminergic systems in the brain are essential for homeostatic and reward-associated regulation of food intake and systemic energy metabolism. It is largely unknown how fasting influences these systems or if such effects are altered in humans with obesity. We therefore aimed to evaluate the effects of fasting on hypothalamic/thalamic serotonin transporter (SERT) and striatal dopamine transporter (DAT) availability in lean subjects and subjects with obesity.

METHODS

In this randomized controlled cross-over trial, we assessed the effects of 12 vs 24 h of fasting on SERT and DAT availability in the hypothalamus/thalamus and striatum, respectively, using SPECT imaging in 10 lean men and 10 men with obesity.

RESULTS

As compared with the 12-h fast, a 24-h fast increased hypothalamic SERT availability in lean men, but not in men with obesity. We observed high inter-individual variation in the effects of fasting on thalamic SERT and striatal DAT, with no differences between lean men and those with obesity. In all subjects, fasting-induced increases in circulating free fatty acid (FFA) concentrations were associated with an increase in hypothalamic SERT availability and a decrease in striatal DAT availability. Multiple regression analysis showed that changes in plasma insulin and FFAs together accounted for 44% of the observed variation in striatal DAT availability.

CONCLUSION

Lean men respond to prolonged fasting by increasing hypothalamic SERT availability, whereas this response is absent in men with obesity. Inter-individual differences in the adaptations of the cerebral serotonergic and dopaminergic systems to fasting may, in part, be explained by changes in peripheral metabolic signals of fasting, including FFAs and insulin.

Weight Loss by Low-Calorie Diet Versus Gastric Bypass Surgery in People With Diabetes Results in Divergent Brain Activation Patterns: A Functional MRI Study

OBJECTIVE

Weight loss achieved with very-low-calorie diets (VLCDs) can produce remission of type 2 diabetes (T2D), but weight regain very often occurs with reintroduction of higher calorie intakes. In contrast, bariatric surgery produces clinically significant and durable weight loss, with diabetes remission that translates into reductions in mortality. We hypothesized that in patients living with obesity and prediabetes/T2D, longitudinal changes in brain activity in response to food cues as measured using functional MRI would explain this difference.

RESEARCH DESIGN AND METHODS

Sixteen participants underwent gastric bypass surgery, and 19 matched participants undertook a VLCD (meal replacement) for 4 weeks. Brain responses to food cues and resting-state functional connectivity were assessed with functional MRI pre- and postintervention and compared across groups.

RESULTS

We show that Roux-en-Y gastric bypass surgery (RYGB) results in three divergent brain responses compared with VLCD-induced weight loss: 1) VLCD resulted in increased brain reward center food cue responsiveness, whereas in RYGB, this was reduced; 2) VLCD resulted in higher neural activation of cognitive control regions in response to food cues associated with exercising increased cognitive restraint over eating, whereas RYGB did not; and 3) a homeostatic appetitive system (centered on the hypothalamus) is better engaged following RYGB-induced weight loss than VLCD.

CONCLUSIONS

Taken together, these findings point to divergent brain responses to different methods of weight loss in patients with diabetes, which may explain weight regain after a short-term VLCD in contrast to enduring weight loss after RYGB.

Inter-individual body mass variations relate to fractionated functional brain hierarchies

Variations in body mass index (BMI) have been suggested to relate to atypical brain organization, yet connectome-level substrates of BMI and their neurobiological underpinnings remain unclear. Studying 325 healthy young adults, we examined associations between functional connectivity and inter-individual BMI variations. We utilized non-linear connectome manifold learning techniques to represent macroscale functional organization along continuous hierarchical axes that dissociate low level and higher order brain systems. We observed an increased differentiation between unimodal and heteromodal association networks in individuals with higher BMI, indicative of a disrupted modular architecture and hierarchy of the brain. Transcriptomic decoding and gene enrichment analyses identified genes previously implicated in genome-wide associations to BMI and specific cortical, striatal, and cerebellar cell types. These findings illustrate functional connectome substrates of BMI variations in healthy young adults and point to potential molecular associations.

The impact of overweight/obesity on monetary reward processing: A systematic review

OBJECTIVE

Converging evidence suggests abnormalities in monetary reward processing may underlie the shared pathophysiology between major depressive disorder and obesity. As such, there is a need to parse deficits in specific subcomponents of monetary reward functioning (i.e., valuation, learning and anticipation).

METHODS

PsycINFO, Google Scholar and PubMed databases were searched for English-language articles published between database inception to June 6th, 2020. Studies were identified using the following medical search heading (MeSH) terms and search strings: (reward (valuation OR motivation OR anticipation OR learning OR functioning OR decision-making OR reinforcement)) AND ((obesity OR overweight OR obese).

RESULTS

Findings were reviewed from 11 studies evaluating the association between obesity and monetary reward processing. Four studies found significant differences in reward learning in individuals with obesity compared to normal-weight participants. Five studies found body mass index (BMI) to be predictive of willingness to expend effort (i.e., valuation) for a monetary reward. Three studies found changes in neural activations in the ventral striatum during anticipatory phases preceding receipt of a monetary reward in participants with obesity.

CONCLUSIONS

Participants with obesity demonstrated significantly poorer performance in task-based measures of reward learning, valuation, and anticipation, resulting in lower monetary reward outcomes across all studies compared to healthy controls. Notably, participants with obesity and comorbid depression performed worse than participants with no comorbid depression.

LIMITATIONS

There persists heterogeneity between studies with regards to inclusion of mood disorder populations and exclusion of psychiatric comorbidities in groups with obesity.

Negative Modulation of the Metabotropic Glutamate Receptor Type 5 as a Potential Therapeutic Strategy in Obesity and Binge-Like Eating Behavior

Obesity is a multifactorial disease, which in turn contributes to the onset of comorbidities, such as diabetes and atherosclerosis. Moreover, there are only few options available for treating obesity, and most current pharmacotherapy causes severe adverse effects, while offering minimal weight loss. Literature shows that metabotropic glutamate receptor 5 (mGluR5) modulates central reward pathways. Herein, we evaluated the effect of VU0409106, a negative allosteric modulator (NAM) of mGluR5 in regulating feeding and obesity parameters. Diet-induced obese C57BL/6 mice were treated for 14 days with VU0409106, and food intake, body weight, inflammatory/hormonal levels, and behavioral tests were performed. Our data suggest reduction of feeding, body weight, and adipose tissue inflammation in mice treated with high-fat diet (HFD) after chronic treatment with VU0409106. Furthermore, a negative modulation of mGluR5 also reduces binge-like eating, the most common type of eating disorder. Altogether, our results pointed out mGluR5 as a potential target for treating obesity, as well as related disorders.

Ageing alters the lipid sensing process in the hypothalamus of Wistar rats. Effect of food restriction

INTRODUCTION

Lipids regulate a wide range of biological processes. The mechanisms by which fatty acids (FA) and its metabolites influence the hypothalamic regulation of energy homeostasis have been highly studied. However, the effect of ageing and food restriction (FR) on this process is unknown.

METHODS

Herein, we analyzed the gene expression, protein and phosphorylation levels of hypothalamic enzymes and transcription factors related to lipid metabolism. Experiments were performed in male Wistar rats of 3-, 8- and 24-month-old Wistar rats fed ad libitum (AL), as ageing model. Besides, 5- and 21-month-old rats were subjected to a moderate FR protocol (equivalent to ≈ 80% of normal food intake) for three months before the sacrifice.

RESULTS

Aged Wistar rats showed a situation of chronic lipid excess as a result of an increase in de novo FA synthesis and FA levels that reach the brain, contributing likely to the development of central leptin and insulin resistance. We observe a hypothalamic downregulation of AMP-activated protein kinase (AMPK) and stearoyl-CoA desaturase (SCD1) and an increase of carnitine palmitoyltransferase-1c (CPT1c) expression.

DISCUSSION

Our results suggest an impairment in the physiological lipid sensing system of aged Wistar rats, which would alter the balance of the intracellular mobilization and trafficking of lipids between the mitochondria and the Endoplasmic Reticulum (ER) in the hypothalamus, leading probably to the development of neurolipotoxicity in aged rats. Lastly, FR can only partially restore this imbalance.Schematic representation of the fate of LCFA-CoA in the hypothalamus of young and old rats. Blood circulating LCFAs in young Wistar rats reach the hypothalamus, where they are esterified to LCFA-CoA. Into glial cells or neurons, LCFA-CoA are driven to mitochondria (CPT1a) or ER (CPT1c) where could be desaturated by SDC1 and, thereby, converted into structural and signaling unsaturated lipids as oleic acid, related with neuronal myelinization and differentiation. However, the excess of LCFA that reach to the hypothalamus in old animals, could generate an increase in LCFA-CoA, which together with an increase in CPT1c levels, could favor the capture of LCFA-CoA to the ER. The decrease in the levels of SCD1 in old rats would decrease FA unsaturation degree that could trigger lipotoxicity process and neurodegeneration, both related to the development of neurodegenerative diseases linked to age.

Physiological Responses of Post-Dietary Effects: Lessons from Pre-Clinical and Clinical Studies

Dieting regimens such as calorie restriction (CR) are among the most commonly practiced interventions for weight management and metabolic abnormalities. Due to its independence from pharmacological agents and considerable flexibility in regimens, many individuals turn to dieting as a form of mitigation and maintenance of metabolic health. While metabolic benefits of CR have been widely studied, weight loss maintenance and metabolic benefits are reported to be lost overtime when the diet regimen has been terminated—referred to as post-dietary effects. Specifically, due to the challenges of long-term adherence and compliance to dieting, post-dietary repercussions such as body weight regain and loss of metabolic benefits pose as major factors in the efficacy of CR. Intermittent fasting (IF) regimens, which are defined by periodic energy restriction, have been deemed as more flexible, compliant, and easily adapted diet interventions that result in many metabolic benefits which resemble conventional CR diets. Many individuals find that IF regimens are easier to adhere to, resulting in fewer post-dietary effects; therefore, IF may be a more effective intervention. Unfortunately, there is a severe gap in current research regarding IF post-dietary effects. We recognize the importance of understanding the sustainability of dieting; as such, we will review the known physiological responses of CR post-dietary effects and its potential mechanisms through synthesizing lessons from both pre-clinical and clinical studies. This review aims to provide insight from a translational medicine perspective to allow for the development of more practical and effective diet interventions. We suggest more flexible and easily practiced dieting regimens such as IF due to its more adaptable and practical nature.

Nicotine exposure during lactation causes disruption of hedonic eating behavior and alters dopaminergic system in adult female rats

Tobacco smoke during gestation is associated with increased consumption of palatable foods by the offspring in humans and rats. Postpartum relapse is observed in lactating women who quit smoking during pregnancy, putting their children at risk of adverse health outcomes caused by secondhand smoke. Nicotine is transferred through milk and alters the dopaminergic reward system of adult male rats, reducing dopamine action in the nucleus accumbens (NAc) and hypothalamic arcuate nucleus. Here, we evaluated the long-term effects of nicotine-only exposure during lactation on eating behavior, anxiety, locomotion, dopaminergic system, hypothalamic leptin signaling and nicotinic receptor in the adult female rat progeny. Two days after birth (PN2), Wistar rat dams were separated into control and nicotine (Nic) groups for implantation of osmotic minipumps that released respectively saline or 6 mg/kg nicotine. Lactating dams were kept with 6 pups. After weaning (PN21; nicotine withdrawal), only the female offspring were studied. Euthanasia occurred at PN180. Nic females showed hyperphagia, preference for a high-sucrose diet, increased anxiety-like behavior, lower tyrosine hydroxylase (TH), lower dopamine transporter and higher dopamine receptor (Drd2) in NAc; lower Drd1 in prefrontal cortex and lower TH in dorsal striatum (DS). These animals showed changes that can explain their hyperphagia, such as: lower leptin signaling pathway (Lepr^b, pJAK2, pSTAT3) and Chrna7 expression in hypothalamus. Neonatal nicotine exposure affects the brain reward system of the female progeny differently from males, mainly decreasing dopamine production in NAc and DS. Therefore, Nic females are more susceptible to develop food addiction and obesity.

Microbiota-gut-brain axis as a regulator of reward processes

Our gut harbours trillions of microorganisms essential for the maintenance of homeostasis and host physiology in health and disease. In the last decade, there has been a growing interest in understanding the bidirectional pathway of communication between our microbiota and the central nervous system. With regard to reward processes there is accumulating evidence from both animal and human studies that this axis may be a key factor in gating reward valence. Focusing on the mesocorticolimbic pathway, we will discuss how the intestinal microbiota is involved in regulating brain reward functions, both in natural (i.e. eating, social or sexual behaviours) and non-natural reinforcers (drug addiction behaviours including those relevant to alcohol, psychostimulants, opioids and cannabinoids). We will integrate preclinical and clinical evidence suggesting that the microbiota-gut-brain axis could be implicated in the development of disorders associated with alterations in the reward system and how it may be targeted as a promising therapeutic strategy. Cover Image for this issue: https://doi.org/10.1111/jnc.15065.

Imperial Satiety Protocol: A new non-surgical weight-loss programme, delivered in a health care setting, produces improved clinical outcomes for people with obesity

'Imperial Satiety Protocol' (I-SatPro) is a new multifaceted approach to weight loss for people with obesity (PwO), encompassing dietary advice, time-restricted eating, physical activity and coaching to support behaviour change. Participants (n = 84) attended fortnightly I-SatPro group sessions for 30 weeks, with 70% of participants completing. On completion at 30 weeks, the mean weight loss was 15.2 ± 1.1 kg (13.2 ± 0.8% from baseline, P < .0001), which was maintained to 52 weeks (16.6 ± 1.5 kg, 14.1 ± 1.2%, P < .0001). Weight loss was not associated with reduced energy expenditure. In participants with type 2 diabetes and pre-diabetes (n = 16), glycated haemoglobin fell from 50 to 43 mmol/mol (P < .01). Systolic blood pressure fell by 12 mmHg (P < .0001). Triglycerides fell by 0.37 mmol/L (P < .01) and high-density lipoprotein rose by 0.08 mmol/L (P < .01). Short Form-36 (SF-36) functioning and wellbeing scores increased in all domains post I-SatPro intervention. For selected PwO, I-SatPro delivers clinically meaningful weight loss, and the potential for long-term health and wellbeing improvements.

Leptin at birth and at age 7 in relation to appetitive behaviors at age 7 and age 10

Leptin contributes to the control of food intake and energy balance. However, its association with appetitive behaviors during childhood is not well understood. We aimed to investigate the association between leptin, assessed at birth and at 7 years of age (y), and appetitive behaviors assessed at 7 and 10 y. Children from a Portuguese cohort with assessment of leptin levels at birth from umbilical cord blood (n = 645) and at 7 y from venous blood samples (n = 587), were included. The Children's Eating Behavior Questionnaire assessed appetitive behaviors at 7 and 10 y. Weight and height were measured at 7 and 10 y to derive BMI z-scores (BMIz). A series of Generalized Linear Models tested relationships between leptin and appetitive behaviors, adjusting for potential confounders (maternal age, education, pre-pregnancy BMI, smoking during pregnancy, child physical activity and child BMIz), and interaction terms for child sex and child BMIz. At 7 y, 116 boys and 118 girls were classified as having overweight/obesity, and these children had higher leptin levels. Cross-sectional analyses using the 7 y data produced the strongest results. Higher leptin at 7 y was significantly associated with lower scores on Satiety Responsiveness, Food Fussiness and Slowness in Eating, and higher scores on Food Responsiveness, Enjoyment of Food and Emotional Overeating at 7 y. Only the association with Emotional Overeating remained when adjusting for child BMIz. Significant interaction effects between child sex and leptin were found for appetite at 7 y, such that higher leptin was associated with higher Food Responsiveness (p < 0.001) and lower Slowness in Eating (p < 0.001) to a greater extent among boys. Umbilical cord blood leptin was not associated with appetitive behaviors at 7 or 10 y. Our results show that leptin levels are positively associated with food approach and negatively with food avoidant behaviors. Associations were more consistent in cross-sectional analyses (at 7 y), were largely dependent on child weight, and tended to be stronger among boys. Our findings support a role for leptin in affecting appetite, with potential consequences for current weight status and future weight gain.

Whole-brain functional connectivity correlates of obesity phenotypes

Dysregulated neural mechanisms in reward and somatosensory circuits result in an increased appetitive drive for and reduced inhibitory control of eating, which in turn causes obesity. Despite many studies investigating the brain mechanisms of obesity, the role of macroscale whole‐brain functional connectivity remains poorly understood. Here, we identified a neuroimaging‐based functional connectivity pattern associated with obesity phenotypes by using functional connectivity analysis combined with machine learning in a large‐scale (n ~ 2,400) dataset spanning four independent cohorts. We found that brain regions containing the reward circuit positively associated with obesity phenotypes, while brain regions for sensory processing showed negative associations. Our study introduces a novel perspective for understanding how the whole‐brain functional connectivity correlates with obesity phenotypes. Furthermore, we demonstrated the generalizability of our findings by correlating the functional connectivity pattern with obesity phenotypes in three independent datasets containing subjects of multiple ages and ethnicities. Our findings suggest that obesity phenotypes can be understood in terms of macroscale whole‐brain functional connectivity and have important implications for the obesity neuroimaging community.

Effect of Supplementation with Hydroethanolic Extract of Campomanesia xanthocarpa (Berg.) Leaves and Two Isolated Substances from the Extract on Metabolic Parameters of Mice Fed a High-Fat Diet

There are still controversies regarding the correlation between the beneficial effects for health and the administration of isolated compounds or crude extracts in therapeutic applications. Campomanesia xanthocarpa, found in the Brazilian Cerrado, demonstrated beneficial effects in metabolic disorders associated with obesity. We investigated the effects of Campomanesia xanthocarpa hydroethanolic extract and two isolated substances from the extract (S1 and S2) in a diet-induced obesity (DIO) model. Male Swiss mice were divided into five groups: (1) American Institute of Nutrition (AIN-93M) diet, (2) high-fat diet (HF), (3) HF supplemented with C. xanthocarpa hydroethanolic leaf extract at 100 mg/kg (HFE), (4) HF supplemented with S1 at 1 mg/kg (HFS1) and (5) HF supplemented with S2 at 1 mg/kg (HFS2). The HFS1, HFS2 and HFE groups did not present decreasing body weight or visceral adiposity gain. No differences in glycemic and lipid parameters, or in the expression of protein content in two cytokines, interleukin-6 (IL-6) and anti-inflammatory (IL-10), were observed. Only the HFS1 group displayed decreased food intake. Even though substantial effects such as an improvement in obesity features or the metabolic and histological parameters promoted by S1, S2 and the extract were not observed, further investigations are necessary to evaluate the principal genes and protein expressions involved in regulating food behavior promoted by S1.

The effect of underweight on female and male reproduction

Chronic energy deficiency can impair the hypothalamic-pituitary-gonadal (HPG) axis and lead to hypothalamic anovulation in underweight women. This review presents the syndromes related to underweight status that are associated with infertility, summarizes the underlying mechanisms, and reviews the available treatment options. Eating disorders, such as anorexia nervosa (AN), constitute the most common cause of infertility in underweight women, who, in addition, experience miscarriages, and sexual dysfunction. The relative energy deficiency in sports (RED-S; former terminology: athlete's triad) involves menstrual dysfunction due to low energy availability, which results in anovulation. Moreover, lipodystrophies, malnutrition, starvation, systematic illnesses (malignancies, endocrinopathies, infectious diseases, advanced chronic diseases, neurologic illnesses), and the utilization of drugs can cause excessive weight loss. They may result in fertility problems due to the loss of adipose tissue and the subsequent hormonal disturbances. Each of these conditions requires multidisciplinary management. Nutritional counseling should target the restoration of energy balance by increasing intake and reducing output. Medical treatment, recommended only for patients who did not respond to standard treatment, may include antipsychotics, antidepressants, or leptin administration. Finally, psychiatric treatment is considered an integral part of the standard treatment.

Bidirectional relationships between appetitive behaviours and body mass index in childhood: a cross-lagged analysis in the Generation XXI birth cohort

PURPOSE

Appetitive behaviours have been associated with body mass index (BMI). However, existing data were largely derived from cross-sectional studies and cannot provide insight into the direction of associations. We aimed to explore the bidirectionality of these associations in school-age children.

METHODS

Participants are from the Generation XXI birth cohort, assessed at both 7 and 10 years of age (n = 4264; twins excluded). The Children's Eating Behaviour Questionnaire (CEBQ) was used to measure appetitive behaviours (8 subscales). Anthropometrics were measured and WHO BMI z-score was calculated. Cross-lagged analyses were performed to compare the magnitude and direction of the associations (behaviours at 7 years to BMI z-score at 10 years and the reverse) (covariates: child's sex, physical exercise, maternal age and education; plus BMI z-score at age 7 or, in the reverse direction, the subscale score).

RESULTS

In cross-lagged analyses, appetitive behaviours at 10 years of age (apart from emotional undereating) were shown to be reactive to the child BMI z-score at 7 years of age. Only slowness in eating was significantly related to subsequent BMI. However, the strongest association was from the child BMI z-score to the behaviour (β_standardized = - 0.028 compared with β_standardized = - 0.103, likelihood ratio test p < 0.001).

CONCLUSIONS

BMI at age 7 was related to appetitive behaviours at 10 years of age, rather than the reverse. This suggests that children with a higher BMI in middle childhood are at increased risk of developing an avid appetite over time.