The Role of Ghrelin in Anorexia Nervosa

Structural alterations of individual hypothalamic nuclei in young females with obesity and anorexia nervosa: an in vivo 7-T MRI study

BACKGROUND

The hypothalamus (HT) plays a crucial role in regulating eating behaviors. Disruptions in its function have been linked to the development of weight-related disorders. Nevertheless, its characterization remains a challenge.

OBJECTIVES

We assessed the structural alterations of individual HT nuclei related to eating behaviors in patients with weight-related disorders, and their association with body mass index (BMI) and severity of eating disorders.

METHODS

Forty-four young females with normal weight (HC, n = 21), restrictive anorexia nervosa (AN, n = 13), and living with obesity (OB, n = 10) were explored in vivo using 7-T high-resolution (0.6 mm isotropic voxel) T1 quantitative magnetic resonance imaging (MRI). Volumes and quantitative T1 values of individual HT nuclei were compared after whole-brain normalization using nonparametric tests (corrected for multiple comparisons for groups and regions). We investigated the parameters associated with BMI and eating disorders, such as MRI parameters of HT nuclei, ghrelin and leptin levels, depression, and anxiety using multivariate nonlinear partial least square (NIPALS).

RESULTS

Both AN and OB showed higher volumes of HT relative to HC (Zscores: 0.78 ± 1.06; 1.43 ± 1.51). AN showed significantly higher volumes and T1 values of the right paraventricular nucleus (PaVN) (volume Zscore: 1.82 ± 1.45; T1 Zscore: 3.76 ± 4.67), and higher T1 values of the left PaVN (Zscore: 2.25 ± 2.37) and right periventricular nuclei (Zscore: 3.73 ± 4.81). NIPALS models showed that lower BMI in AN was associated with structural alterations of the bilateral PaVN, right anterior commissure, and left fornix (FX). Higher BMI in OB was associated with structural alterations within the right PaVN, bilateral FX, left posterior hypothalamic nucleus, right lateral HT, and right anterior hypothalamic area. Finally, the severity of eating disorders was associated with larger structural alterations within the bilateral PaVN, bilateral arcuate hypothalamic nuclei, right bed nucleus of stria terminalis, left medial preoptic nucleus, and right tubero-mammillary hypothalamic nucleus.

CONCLUSIONS

Weight-related disorders are associated with significant micro and macrostructural alterations in HT nuclei involved in eating behaviors.

Gut-derived appetite regulating hormones across the anorexia nervosa spectrum

BACKGROUND

Appetite-regulating hormones are implicated in anorexia nervosa (AN) pathophysiology, however, data are limited for appetite-regulating hormones across the AN weight spectrum. We aimed to investigate fasting and post-prandial concentrations of appetite-regulating hormones - peptide YY (PYY), cholecystokinin (CCK), and ghrelin - among adolescent and young adult females across the AN weight spectrum, specifically those with AN and Atypical AN, and healthy controls (HC).

METHODS

Participants (N = 95; ages 11-22 years) included 33 with AN, 25 with Atypical AN, and 37 HC. AN was differentiated from Atypical AN by BMI < 10th percentile for age and sex (if <18 years) or < 18.5 kg/m2(if ≥18 years). Blood samples were collected fasting and 30, 60 and 120 minutes following a standardized meal to assess total PYY, CCK, and total ghrelin concentrations.

RESULTS

Median fasting and post-prandial PYY concentrations were significantly higher in AN vs. HC with medium differences (p = .001-.006, r = .34-.43). Atypical AN had significantly higher PYY concentrations compared to HC at T-0 (p = .027, r = .29) only, and did not significantly differ from concentrations in AN (p = .105-.413, r = .11-.22). Area under the curve (AUC; p = .001; r = .41) and peak PYY concentrations (p = .003; r = .41) were also significantly higher in AN vs. HC with medium differences. There were no significant differences in fasting (p = .885) or post-prandial (p = .846-.993) CCK concentrations across groups. AN and Atypical AN each had significantly higher ghrelin concentrations than HC with small to medium effect (AN vs HC p = .004-.025, r = .27-.36; Atypical AN vs HC p = .004-.033; r = .28-.28).

CONCLUSIONS

Higher peak postprandial concentrations of anorexigenic PYY in AN (compared to HC) may facilitate dietary restriction and contribute to maintenance of lower weight. Lack of CCK suppression in AN is maladaptive in the context of undernutrition. Despite continued restriction, ghrelin is adaptively higher in AN overall and may not be differentiated by weight status.

LEAP2 in Physiology-A Narrative Review

Liver Enriched Antimicrobial Peptide 2 (LEAP2) is a fascinating peptide that has gained significant attention since its discovery in 2003. Initially identified as an antimicrobial peptide, LEAP2 has more recently been found to play a key role in the regulation of energy metabolism. One of the most notable functions of LEAP2 is its interaction with the ghrelin hormone, which is known for stimulating hunger. LEAP2 acts as an inhibitor of ghrelin, thereby reducing food intake and influencing energy balance. The physiological roles of LEAP2 extend beyond appetite suppression. Studies have shown that LEAP2 has an impact on insulin secretion, suggesting its potential involvement in glucose metabolism and possibly insulin sensitivity, which is crucial in managing conditions like type 2 diabetes. Moreover, LEAP2 levels appear to fluctuate based on factors such as gender, developmental stage, and even interventions like bariatric surgery, which is known for its role in managing obesity and diabetes. Given these findings, LEAP2 shows potential as a therapeutic target, particularly for addressing obesity and metabolic diseases such as type 2 diabetes. Its ability to influence food intake and energy balance makes it a promising candidate for further research into therapies aimed at weight regulation and glycemic control. In the future, LEAP2 could become an important agent in the development of treatments aimed at curbing obesity and its associated metabolic disorders.

Trajectory of ghrelin and PYY around a test meal in males and females with avoidant/restrictive food intake disorder versus healthy controls

Disruptions in appetite-regulating hormones may contribute to the development and/or maintenance of avoidant/restrictive food intake disorder (ARFID). No study has previously assessed fasting levels of orexigenic ghrelin or anorexigenic peptide YY (PYY), nor their trajectory in response to food intake among youth with ARFID across the weight spectrum. We measured fasting and postprandial (30, 60, 120 minutes post-meal) levels of ghrelin and PYY among 127 males and females with full and subthreshold ARFID (n = 95) and healthy controls (HC; n = 32). We used latent growth curve analyses to examine differences in the trajectories of ghrelin and PYY between ARFID and HC. Fasting levels of ghrelin did not differ in ARFID compared to HC. Among ARFID, ghrelin levels declined more gradually than among HC in the first hour post meal (p =.005), but continued to decline between 60 and 120 minutes post meal, whereas HC plateaued (p =.005). Fasting and PYY trajectory did not differ by group. Findings did not change after adjusting for BMI percentile (M(SD)ARFID = 37(35); M(SD)HC = 53(26); p =.006) or calories consumed during the test meal (M(SD)ARFID = 294(118); M(SD)HC = 384 (48); p <.001). These data highlight a distinct trajectory of ghrelin following a test meal in youth with ARFID. Future research should examine ghrelin dysfunction as an etiological or maintenance factor of ARFID.

Genes Involved in Susceptibility to Obesity and Emotional Eating Behavior in a Romanian Population

Obesity, a significant public health concern with high prevalence in both adults and children, is a complex disorder arising from the interaction of multiple genes and environmental factors. Advances in genome-wide association studies (GWAS) and sequencing technologies have identified numerous polygenic causes of obesity, particularly genes involved in hunger, satiety signals, adipocyte differentiation, and energy expenditure. This study investigates the relationship between six obesity-related genes (CLOCK, FTO, GHRL, LEP, LEPR, MC4R) and their impact on BMI, WC, HC, WHR, and emotional eating behavior in 220 Romanian adults. Emotional eating was assessed using the validated Emotional Eating Questionnaire (EEQ). Our analysis revealed significant variability in obesity-related phenotypes and emotional eating behaviors across different genotypes. Specifically, CLOCK/CC, FTO/AA, and LEP/AA genotypes were strongly associated with higher obesity metrics and emotional eating scores, while GHRL/TT and MC4R/CC were linked to increased BMI and WHR. The interplay between genetic predisposition and emotional eating behavior significantly influenced BMI and WHR, indicating a complex relationship between genetic and behavioral factors. This study, the first of its kind in Romania, provides a foundation for targeted interventions to prevent and reduce obesity and suggests potential strategies for gene expression modulation to mitigate the effects of emotional eating. Adopting a 'One Health' approach by creating an evidence base derived from both human and animal studies is crucial for understanding how to control obesity.

Hypothalamic subregion alterations in anorexia nervosa and obesity: Association with appetite-regulating hormone levels

OBJECTIVE

Anorexia nervosa (AN) and obesity are weight-related disorders with imbalances in energy homeostasis that may be due to hormonal dysregulation. Given the importance of the hypothalamus in hormonal regulation, we aimed to identify morphometric alterations to hypothalamic subregions linked to these conditions and their connection to appetite-regulating hormones.

METHODS

Structural magnetic resonance imaging (MRI) was obtained from 78 patients with AN, 27 individuals with obesity and 100 normal-weight healthy controls. Leptin, ghrelin, and insulin blood levels were measured in a subsample of each group. An automated segmentation method was used to segment the hypothalamus and its subregions. Volumes of the hypothalamus and its subregions were compared between groups, and correlational analysis was employed to assess the relationship between morphometric measurements and appetite-regulating hormone levels.

RESULTS

While accounting for total brain volume, patients with AN displayed a smaller volume in the inferior-tubular subregion (ITS). Conversely, obesity was associated with a larger volume in the anterior-superior, ITS, posterior subregions (PS), and entire hypothalamus. There were no significant volumetric differences between AN subtypes. Leptin correlated positively with PS volume, whereas ghrelin correlated negatively with the whole hypothalamus volume in the entire cohort. However, appetite-regulating hormone levels did not mediate the effects of body mass index on volumetric measures.

CONCLUSION

Our results indicate the importance of regional structural hypothalamic alterations in AN and obesity, extending beyond global changes to brain volume. Furthermore, these alterations may be linked to changes in hormonal appetite regulation. However, given the small sample size in our correlation analysis, further analyses in a larger sample size are warranted.

PUBLIC SIGNIFICANCE

Using an automated segmentation method to investigate morphometric alterations of hypothalamic subregions in AN and obesity, this study provides valuable insights into the complex interplay between hypothalamic alterations, hormonal appetite regulation, and body weight, highlighting the need for further research to uncover underlying mechanisms.

The role of dysregulated ghrelin/LEAP-2 balance in anorexia nervosa

LEAP-2 is a ghrelin antagonist with an anorexigenic drive. This study investigates the evolution of plasma ghrelin and LEAP-2 concentrations in 29 patients with anorexia nervosa (AN) before and after refeeding and compares it to physiological adaptations during fasting in healthy controls or to mouse model of chronic food restriction and refeeding. Acute and chronic food restriction decrease LEAP-2 and increase ghrelin concentrations in both humans and mice, while patients with AN displayed higher ghrelin and LEAP-2 concentrations before than after refeeding (p = 0.043). After 6 months follow-up, patients with unstable weight gain (n = 17) had significantly decreased LEAP-2 concentrations after refeeding (p = 0.044), in contrast to patients with stable weight gain (n = 12). We provide evidence that the ghrelin/LEAP-2 system is not regulated according to the nutritional status in AN, in contrast to what is physiologically expected when coping with food restriction.

Male mice engaging differently in emotional eating present distinct plasmatic and neurological profiles

Objective: Stressed individuals tend to turn to calorie-rich food, also known as 'comfort food' for the temporary relief it provides. The emotional eating drive is highly variable among subjects. Using a rodent model, we explored the plasmatic and neurobiological differences between 'high and low emotional eaters' (HEE and LEE).Methods: 40 male mice were exposed for 5 weeks to a protocol of unpredictable chronic mild stress. Every 3 or 4 days, they were submitted to a 1-h restraint stress, immediately followed by a 3-h period during which a choice between chow and chocolate sweet cereals was proposed. The dietary intake was measured by weighing. Plasmatic and neurobiological characteristics were compared in mice displaying high vs low intakes.Results: Out of 40 mice, 8 were considered as HEE because of their high post-stress eating score, and 8 as LEE because of their consistent low intake. LEE displayed higher plasma corticosterone and lower levels of NPY than HEE, but acylated and total ghrelin were similar in both groups. In the brain, the abundance of NPY neurons in the arcuate nucleus of the hypothalamus was similar in both groups, but was higher in the ventral hippocampus and the basal lateral amygdala of LEE. The lateral hypothalamus LEE had also more orexin (OX) positive neurons. Both NPY and OX are orexigenic peptides and mood regulators.Discussion: Emotional eating difference was reflected in plasma and brain structures implicated in emotion and eating regulation. These results concur with the psychological side of food consumption.

Ghrelin as a Biomarker of "Immunometabolic Depression" and Its Connection with Dysbiosis

Ghrelin, a gastrointestinal peptide, is an endogenous ligand of growth hormone secretagogue receptor 1a (GHSR1a), which is mainly produced by X/A-like cells in the intestinal mucosa. Beyond its initial description as a growth hormone (GH) secretagogue stimulator of appetite, ghrelin has been revealed to have a wide range of physiological effects, for example, the modulation of inflammation; the improvement of cardiac performance; the modulation of stress, anxiety, taste sensation, and reward-seeking behavior; and the regulation of glucose metabolism and thermogenesis. Ghrelin secretion is altered in depressive disorders and metabolic syndrome, which frequently co-occur, but it is still unknown how these modifications relate to the physiopathology of these disorders. This review highlights the increasing amount of research establishing the close relationship between ghrelin, nutrition, microbiota, and disorders such as depression and metabolic syndrome, and it evaluates the ghrelinergic system as a potential target for the development of effective pharmacotherapies.

Mechanism of gastrointestinal injury in COVID-19 and potential use of ghrelin therapy

In Corona Virus Disease 2019 (COVID-19), the most obvious symptoms occur in the respiratory and digestive systems, posing a serious threat to the health of patients. Decreased appetite is the most common digestive system symptom and is an important predictor of mortality. A large number of patients have decreased appetite after infection and do not show obvious organic disease characteristics. Currently, no drugs can directly alleviate such symptom. In order to reduce the number of severe and critically ill patients and decrease the hospitalization rate, it is very important to understand the pathogenic mechanism of appetite loss caused by COVID-19 and manage such symptom. Ghrelin is a key gastric hormone that has anti-inflammatory, neuroprotective, and antidepressant effects. In this paper, we will review the progress in the understanding of the mechanism of appetite loss associated with COVID-19, and introduce a potential therapeutic drug, ghrelin.

Valproate-Induced Metabolic Syndrome

Valproic acid (VPA) and its salts (sodium calcium magnesium and orotic) are psychotropic drugs that are widely used in neurology and psychiatry. The long-term use of VPA increases the risk of developing adverse drug reactions (ADRs), among which metabolic syndrome (MetS) plays a special role. MetS belongs to a cluster of metabolic conditions such as abdominal obesity, high blood pressure, high blood glucose, high serum triglycerides, and low serum high-density lipoprotein. Valproate-induced MetS (VPA-MetS) is a common ADR that needs an updated multidisciplinary approach to its prevention and diagnosis. In this review, we consider the results of studies of blood (serum and plasma) and the urinary biomarkers of VPA-MetS. These metabolic biomarkers may provide the key to the development of a new multidisciplinary personalized strategy for the prevention and diagnosis of VPA-MetS in patients with neurological diseases, psychiatric disorders, and addiction diseases.

Progress on traditional Chinese medicine in treatment of ischemic stroke via the gut-brain axis

Ischemic stroke is a common issue that severely affects the human health. Between the central nervous system and the enteric system, the " Gut-Brain " axis, the bidirectional connection involved in the neuro-immuno-endocrine network, is crucial for the occurrence and development of ischemic stroke. Ischemic stroke can lead to change in the gut microbiota and gastrointestinal hormones, which will then reversely affect the disease development. Traditional Chinese Medicine (TCM) has unique advantages with reference to the treatment for ischemic stroke. The latest research revealed that a significant portion of medicines and prescriptions of TCM exert their therapeutic effects by improving the gut microbiota and regulating the secretion of gastrointestinal hormones. The present review summarized the Chinese medicines that play a therapeutic role in cerebral ischemia through regulating the "Gut-Brain" axis and described the corresponding mechanisms. This study attempts to provide reference for clinical selection of Chinese medicines and helps better understand the relevant mechanisms of action.

Macronutrient intake: Hormonal controls, pathological states, and methodological considerations

A plethora of studies to date has examined the roles of feeding-related peptides in the control of food intake. However, the influence of these peptides on the intake of particular macronutrient constituents of food - carbohydrate, fat, and protein - has not been as extensively addressed in the literature. Here, the roles of several feeding-related peptides in controlling macronutrient intake are reviewed. Next, the relationship between macronutrient intake and diseases including diabetes mellitus, obesity, and eating disorders are examined. Finally, some key considerations in macronutrient intake research are discussed. We hope that this review will shed light onto this underappreciated topic in ingestive behavior research and will help to guide further scientific investigation in this area.

Brain and gut microbiota disorders in the psychopathology of anorexia nervosa

Studies of pathophysiological mechanisms involved in eating disorders (EDs) have intensified over the past several years, revealing their unprecedented and unanticipated complexity. Results from many articles highlight critical aspects in each member of ED family. Notably, anorexia nervosa (AN) is a disorder due to undefined etiology, frequently associated with symptoms of depression, anxiety, obsessive-compulsiveness, accompanied by endocrine alterations, altered immune response, increased inflammation, and dysbiosis of the gut microbiota. Hence, an advanced knowledge of how and why a multisystem involvement exists is of paramount importance to understand the pathogenetic mechanisms of AN. In this review, we describe the change in the brain structure/function focusing on hypothalamic endocrine disorders and the disequilibrium of gut microbiota in AN that might be responsible for the psychopathological complication.

Anti-hypothalamus autoantibodies in anorexia nervosa: a possible new mechanism in neuro-physiological derangement?

PURPOSE

Anorexia nervosa (AN) is a serious and complex mental disorder affecting mainly young adult women. AN patients are characterized by low body weight in combination with self-induced starvation, intense fear of gaining weight, and distortion of body image. AN is a multifactorial disease, linked by recent evidence to a dysregulation of the immune system.

METHODS

In this pilot study, 22 blood serums from AN patients were tested for the presence of autoantibodies against primate hypothalamic periventricular neurons by immunofluorescence and by a home-made ELISA assay. Cellular fluorescence suggests the presence of autoantibodies which are able to recognize these neurons (both to body cell and fiber levels). By means of ELISA, these autoantibodies are quantitatively evaluated. In addition, orexigenic and anorexigenic molecules were measured by ELISA. As control, 18 blood serums from healthy age matched woman were analysed.

RESULTS

All AN patients showed a reactivity against hypothalamic neurons both by immunofluorescence and ELISA. In addition, ghrelin, pro-opiomelanocortin (POMC), and agouti-related peptide (AGRP) were significantly higher than in control serums (p < 0.0001). In contrast, leptin was significantly lower in AN patients than controls (p < 0.0001).

CONCLUSIONS

Immunoreaction and ELISA assays on AN blood serum suggest the presence of autoantibodies AN related. However, it is not easy to determine the action of these antibodies in vivo: they could interact with specific ligands expressed by hypothalamic cells preventing their physiological role, however, it is also possible that they could induce an aspecific stimulation in the target cells leading to an increased secretion of anorexigenic molecules. Further studies are needed to fully understand the involvement of the immune system in AN pathogenesis.

LEVEL OF EVIDENCE

V, descriptive study.

Ghrelin and Obestatin in Adolescent Patients with Anorexia Nervosa: Is There an Association with Disordered Eating, Depression, and Obsessive-Compulsive Symptoms?

Anorexia nervosa (AN) is an eating disorder characterized by restrictive eating and significant weight loss. In the course of AN, changes are observed in appetite regulation, including orexigenic ghrelin and potentially anorexigenic obestatin. The study aimed to determine if any changes in serum ghrelin and obestatin levels during treatment of AN are observed, while investigating the correlations between these peptides and the severity of disturbed eating attitudes, depression, and anxiety. Thirty adolescent inpatients with AN (examined twice: before hospitalization treatment AN-BT and after treatment AN-AT) and thirty healthy age- and height-matched girls (CG) participated in the study. Anthropometric, serum ghrelin and obestatin concentrations and psychometric evaluations (Eating Attitudes Test 26 Item-EAT-26, Beck Depression Inventory-BDI, Hamilton Depression Rating Scale-HDRS, and Yale Brown Obsessive-Compulsive Scale-Y-BOCS) were performed. The study revealed significantly higher ghrelin and obestatin levels in AN-BT than in AN-AT. A trend toward lower levels during treatment provided partial normalizations. Analyzing correlations in the AN-BT vs. CG group, correlations of peptides with EAT-26, BDI, and HDRS scores were detected. These results suggest a potential role for ghrelin and obestatin in the context of defense mechanisms regulating appetite and body weight in the course of AN and in terms of psychopathological changes co-occurring with this eating disorder.

Diverse and Complementary Effects of Ghrelin and Obestatin

Ghrelin and obestatin are two "sibling proteins" encoded by the same preproghrelin gene but possess an array of diverse and complex functions. While there are ample literature documenting ghrelin's functions, the roles of obestatin are less clear and controversial. Ghrelin and obestatin have been perceived to be antagonistic initially; however, recent studies challenge this dogma. While they have opposing effects in some systems, they function synergistically in other systems, with many functions remaining debatable. In this review, we discuss their functional relationship under three "C" categories, namely complex, complementary, and contradictory. Their functions in food intake, weight regulation, hydration, gastrointestinal motility, inflammation, and insulin secretion are complex. Their functions in pancreatic beta cells, cardiovascular, muscle, neuroprotection, cancer, and digestive system are complementary. Their functions in white adipose tissue, thermogenesis, and sleep regulation are contradictory. Overall, this review accumulates the multifaceted functions of ghrelin and obestatin under both physiological and pathological conditions, with the intent of contributing to a better understanding of these two important gut hormones.

White matter integrity is disrupted in adolescents with acute anorexia nervosa: A diffusion tensor imaging study

Anorexia nervosa (AN) is a highly debilitating mental illness with multifactorial etiology. It oftentimes begins in adolescence, therefore understanding the pathophysiology in this period is important. Few studies investigated the possible impact of the acute state of illness on white matter (WM) tissue properties in the developing adolescent brain. The present study expands our understanding of the implications of AN and starvation on WM integrity. 67 acutely ill adolescent patients suffering from AN restricting type were compared with 32 healthy controls using diffusion tensor imaging assessing fractional anisotropy (FA) and mean diffusivity (MD). We found widespread alterations in the vast majority of the WM regions with significantly decreased FA and increased MD in the AN group. In this highly selective sample in the acute stage of AN, the alterations are likely to be the consequence of starvation. Still, we cannot rule out that some of the affected regions might play a key role in AN-specific psychopathology.

Associations of Stress and Appetite Hormones with Binge Eating in Females with Anorexia Nervosa after Weight Restoration: A Longitudinal Study

Binge eating is a transdiagnostic eating disorder symptom that can occur in patients with anorexia nervosa (AN), persisting after weight restoration, and impeding their recovery. However, little is known about the biological predictors of binge eating after AN weight restoration. The goals of this exploratory study of 73 females with AN were: (1) to examine changes in cortisol, the adrenocorticotropic hormone, norepinephrine, ghrelin (total and active), and leptin levels across the admission, discharge, and 3 months post-discharge from the inpatient AN weight restoration; and (2) to determine whether the target hormones were associated with objective or subjective binge eating (OBE or SBE). The participants completed the self-reported Eating Disorder Examination Questionnaire, Beck Anxiety Inventory, and Beck Depression Inventory-II, and provided fasting whole blood samples for hormone assays. The results showed significant changes in body mass index (BMI), cortisol, total ghrelin, and leptin levels over the three time points. The cortisol levels at admission and discharge were significantly associated with the number of SBE episodes at 3 months post-discharge. Findings suggest the need to replicate and confirm the role of cortisol in predicting the emergence of SBE and uncover the mechanisms underlying SBE and cortisol to prevent SBE and its negative consequences.

Exocrine Pancreatic Function in Girls with Anorexia Nervosa

OBJECTIVES

To assess pancreatic exocrine function in patients with anorexia nervosa using a breath test with 13C-labeled mixed triglycerides (MTG-BT) and to determine the relationship between the test results and selected biochemical and hormonal parameters.

MATERIAL AND METHODS

Anthropometric measurements, biochemical and hormonal parameters (serum leptin, soluble leptin receptor (sLR), acylated and desacylated ghrelin, free leptin index (FLI)), and MTG-BT were performed in a group of 31 girls with the restrictive type of AN, as well as 38 healthy girls (C).

RESULTS

The average cumulative dose of 13C-triglycerides recovered with exhaled air (%CD) was similar in both study groups, while the average time from 13C-triglycerides administration to peak 13CO2 excretion in expired air (time to peak (TTP)) was significantly longer in patients with AN compared to C. In both groups, %CD correlated negatively with FLI. TTP correlated negatively with sLR and FLI in the AN and with serum insulin and HOMA-IR values in the C.

CONCLUSIONS

In girls with AN, the pancreatic efficiency of lipase secretion was found to be normal, while the kinetics of this enzyme secretion were disturbed. These changes may result from disorders in the functioning of the adipose-insular and islet-acinar axes.

Altered Serum Immunological and Biochemical Parameters and Microbiota Composition in Patients With AN During Realimentation

Anorexia nervosa (AN) is a life-threatening psychiatric disorder with not well-described pathogenesis. Besides the genetic and sociological factors, autoimmunity is also considered to take part in AN pathogenesis. We evaluated general serological factors showing the physiological state of 59 patients with AN at hospital admission and their discharge. We detected the altered levels of some general biochemical and immunological parameters. We also detected decreased levels of appetite-regulating alpha-melanocyte stimulating hormone (α-MSH) in patients at hospital admission. Moreover, elevated anti-α-MSH IgM levels and decreased anti-α-MSH IgA levels were observed in patients with AN. Therefore, we analyzed the gut microbiota composition with special focus on α-MSH antigen-mimetic containing microbes from the Enterobacteriaceae family. We correlated gut bacterial composition with anti-α-MSH Ig levels and detected decreasing IgG levels with increasing alpha diversity. The upregulation of pro-inflammatory cytokines IL-6, IL-17, and TNF-α were detected in patients with AN both prior and after hospitalization. We also evaluated the treatment outcome and improvement was observed in the majority of patients with AN. We provide new data about various serum biochemical parameters and their changes during the patients' hospitalization, with emphasis on the immune system, and its possible participation in AN pathogenesis.

Deoxynivalenol (Vomitoxin)-Induced Anorexia Is Induced by the Release of Intestinal Hormones in Mice

Deoxynivalenol (DON), also known as vomitoxin, is a mycotoxin that can cause antifeeding and vomiting in animals. However, the mechanism of DON inducing anorexia is complicated. Studies have shown that intestinal hormones play a significant part in the anorexia caused by DON. We adopted the “modeling of acute antifeeding in mice” as the basic experimental model, and used two methods of gavage and intraperitoneal injection to explore the effect of intestinal hormones on the antifeedant response induced by DON in mice. We found that 1 and 2.5 mg/kg·bw of DON can acutely induce anorexia and increase the plasma intestinal hormones CCK, PYY, GIP, and GLP-1 in mice within 3 h. Direct injection of exogenous intestinal hormones CCK, PYY, GIP, and GLP-1 can trigger anorexia behavior in mice. Furthermore, the PYY receptor antagonist JNJ-31020028, GLP-1 receptor antagonist Exendin(9-39), CCK receptor antagonist Proglumide, GIP receptor antagonist GIP(3-30)NH₂ attenuated both intestinal hormone and DON-induced anorectic responses. These results indicate that intestinal hormones play a critical role in the anorexia response induced by DON.

Ghrelin and PYY in low-weight females with avoidant/restrictive food intake disorder compared to anorexia nervosa and healthy controls

BACKGROUND

Avoidant/restrictive food intake disorder (ARFID) is characterized by restrictive eating and failure to meet nutritional needs but is distinct from anorexia nervosa (AN) because restriction is not motivated by weight/shape concerns. We examined levels of orexigenic ghrelin and anorexigenic peptide YY (PYY) in young females with ARFID, AN and healthy controls (HC).

METHODS

94 females (22 low-weight ARFID, 40 typical/atypical AN, and 32 HC ages 10-22 years) underwent fasting blood draws for total ghrelin and total PYY. A subset also provided blood 30, 60 and 120 min after a standardized meal.

RESULTS

Females with ARFID ate less than those with AN or HC (ps<0.012); were younger (14.4 ± 3.2 years) than those with AN (18.9 ± 3.1 years) and HC (17.4 ± 3.1 years) (ps<0.003) and at a lower Tanner stage (3.1 ± 1.5) than AN (4.5 ± 1.1;) and HC (4.4 ± 1.1; ps<0.005), but did not differ in BMI percentiles or BMI Z-scores from AN (ps>0.44). Fasting and postprandial ghrelin were lower in ARFID versus AN (ps≤.015), but not HC (ps≥0.62). Fasting and postprandial PYY did not differ between ARFID versus AN or HC (ps≥0.13); ARFID did not demonstrate the sustained high PYY levels post-meal observed in those with AN and HC. Secondary analyses controlling age or Tanner stage and calories consumed showed similar results. Exploratory analyses suggest that the timing of the PYY peak in ARFID is earlier than HC, showing a peak PYY level 30 min post-meal (p = .037).

CONCLUSIONS

ARFID and AN appear to have distinct patterns of secretion of gut-derived appetite-regulating hormones that may aid in differential diagnosis and provide new treatment targets.

Appetite- and weight-inducing and -inhibiting neuroendocrine factors in Prader-Willi syndrome, Bardet-Biedl syndrome and craniopharyngioma versus anorexia nervosa

Obesity is reaching an epidemic state and has a major impact on health and economy. In most cases, obesity is caused by lifestyle factors. However, the risk of becoming obese differs highly between people. Individual's differences in lifestyle, genetic, and neuroendocrine factors play a role in satiety, hunger and regulation of body weight. In a small percentage of children and adults with obesity, an underlying hormonal or genetic cause can be found. The aim of this review is to present and compare data on the extreme ends of the obesity and undernutrition spectrum in patients with Prader-Willi syndrome (PWS), Bardet-Biedl syndrome (BBS), acquired hypothalamic obesity in craniopharyngioma patients, and anorexia nervosa. This may give more insight into the role of neuroendocrine factors and might give direction for future research in conditions of severe obesity and underweight.

Ghrelin as a possible biomarker and maintaining factor in patients with eating disorders reporting childhood traumatic experiences

OBJECTIVE

The recent conceptualization of ghrelin as a stress hormone suggested that its chronic alterations may have a role in maintaining overeating behaviors in subjects with eating disorders (EDs) reporting childhood traumatic experiences. The aim of this study was to investigate the alterations of ghrelin levels in patients with EDs, their associations with early trauma, binge and emotional eating, and possible moderation/mediation models.

METHOD

Sixty-four patients with EDs and 42 healthy controls (HCs) had their plasma ghrelin levels measured and completed questionnaires evaluating general and ED-specific psychopathology, emotional eating, and childhood traumatic experiences.

RESULTS

Participants with anorexia nervosa had higher ghrelin levels than HCs in body mass index (BMI)-adjusted comparisons. Moreover, patients reporting a history of childhood trauma had higher ghrelin levels. Childhood sexual abuse (CSA), BMI, and self-induced vomiting were independent predictors of ghrelin levels. Moderation analyses showed that ghrelin levels were associated with binge and emotional eating only for higher levels of childhood trauma. Elevated ghrelin was a significant mediator for the association of CSA with binge eating.

CONCLUSIONS

These results support the hypothesis that chronic alterations in ghrelin levels following childhood traumatic experiences could represent a neurobiological maintaining factor of pathological overeating behaviors in EDs.

A Systematic Review and Meta-Analysis Finds Increased Blood Levels of All Forms of Ghrelin in Both Restricting and Binge-Eating/Purging Subtypes of Anorexia Nervosa

Anorexia nervosa (AN) is a severe psychiatric condition associated with high mortality and chronicity. The hunt for state, trait, subtyping, and prognostic biomarkers is ongoing and the orexigenic hormone ghrelin and its different forms, acyl ghrelin and desacyl ghrelin, have been proposed to be increased in AN, especially in the restrictive subtype. A systematic literature search was performed using established databases up to 30 November 2020. Forty-nine studies met inclusion criteria for cross-sectional and longitudinal meta-analyses on total ghrelin, acyl ghrelin, and desacyl ghrelin. All forms of ghrelin were increased in the acute stage of anorexia nervosa during fasting compared to healthy controls. Previous notions on differences in ghrelin levels between AN subtypes were not supported by current data. In addition, a significant decrease in total ghrelin was observed pre-treatment to follow-up. However, total ghrelin levels at follow-up were still marginally elevated compared to healthy controls, whereas for acyl ghrelin, no overall effect of treatment was observed. Due to heterogeneity in follow-up designs and only few data on long-term recovered patients, longitudinal results should be interpreted with caution. While the first steps towards a biomarker in acute AN have been completed, the value of ghrelin as a potential indicator of treatment success or recovery status or its use in subtype differentiation are yet to be established.

Systemic Delivery of hGhrelin Derivative by Lyophilizate for Dry Powder Inhalation System in Monkeys

Ghrelin is the peptide that increases the hunger sensation and food intake and is expected to be clinically applied for treatment of diseases such as cachexia and anorexia nervosa. In the clinical application of ghrelin, injections are problematic in that they are invasive and inconvenient. Thus, we aimed to develop a formulation that can eliminate the need for injections and can be applied clinically. We prepared formulations of an hGhrelin derivative, in which the octanoyl group essential for expression of activity is modified to avoid rapid des-acylation, using lyophilizate for a dry powder inhalation (LDPI) system. The formulation of hGhrelin derivative was optimized by the addition of phenylalanine, of which the fine particle fraction of 5 µm or less was 41.7 ± 3.8%. We also performed pharmacokinetic/pharmacodynamic tests in monkeys using the optimum formulation that can be applied clinically. The absolute bioavailability of inhaled hGhrelin derivative with respect to that intravenously injected was 16.9 ± 2.6%. An increase in growth hormone was shown as an effect of the inhaled hGhrelin derivative similar to intravenous injection. The LDPI formulation can deliver the hGhrelin derivative systemically, and it is expected to be applied clinically as a substitute for injections.

Is Serum BDNF Altered in Acute, Short- and Long-Term Recovered Restrictive Type Anorexia Nervosa?

Brain-derived neurotrophic factor (BDNF), a neurotrophin involved in the regulation of food intake and body weight, has been implicated in the development and maintenance of Anorexia nervosa (AN). The majority of previous studies reported lower BDNF levels in acutely underweight AN patients (acAN) and increasing levels after weight rehabilitation. Here, we investigated serum BDNF concentrations in the largest known AN sample to date, both before and after weight restoration therapy. Serum BDNF was measured in 259 female volunteers: 77 in-patient acAN participants of the restrictive type (47 reassessed after short-term weight rehabilitation), 62 individuals long-term recovered from AN, and 120 healthy controls. We validated our findings in a post-hoc mega-analysis in which we reanalyzed combined data from the current sample and those from our previous study on BDNF in AN (combined sample: 389 participants). All analyses carefully accounted for known determinants of BDNF (age, sex, storage time of blood samples). We further assessed relationships with relevant clinical variables (body-mass-index, physical activity, symptoms). Contrary to our hypotheses, we found zero significant differences in either cross-sectional or longitudinal comparisons and no significant relationships with clinical variables. Together, our study suggests that BDNF may not be a reliable state- or trait-marker in AN after all.

Alterations in B cell subsets correlate with body composition parameters in female adolescents with anorexia nervosa

Anorexia nervosa (AN) is a severe eating disorder and often associated with altered humoral immune responses. However, distinct B cell maturation stages in peripheral blood in adolescents with AN have not been characterized. Treatment effects and the relationship between clinical and B cell parameters are also not fully understood. Here we investigated the phenotype of circulating B cell subsets and the relationship with body composition in adolescents with AN before (T0, n = 24) and after 6 weeks (T1, n = 20) of treatment. Using multi-parameter flow cytometry, we found increased percentages of antigen-experienced B cells and plasmablasts in patients with AN compared to healthy controls (n = 20). In contrast, percentages of CD1d⁺CD5⁺ B cells and transitional B cells with immunoregulatory roles were reduced at T0 and T1. These B cell frequencies correlated positively with fat mass, fat mass index (FMI), free fat mass index, and body mass index standard deviation score. In addition, scavenger-like receptor CD5 expression levels were downregulated on transitional B cells and correlated with fat mass and FMI in AN. Our findings that regulatory B cell subgroups were reduced in AN and their strong relationship with body composition parameters point toward an impact of immunoregulatory B cells in the pathogenesis of AN.

The Utility of Animal Models for Studying the Metabo-Psychiatric Origins of Anorexia Nervosa

Anorexia nervosa (AN) is a severe eating disorder that primarily affects young women and girls, and is characterized by abnormal restrictive feeding and a dangerously low body-mass index. AN has one of the highest mortality rates of any psychiatric disorder, and no approved pharmacological treatments exist. Current psychological and behavioral treatments are largely ineffective, and relapse is common. Relatively little basic research has examined biological mechanisms that underlie AN compared to other major neuropsychiatric disorders. A recent large-scale genome-wide association study (GWAS) revealed that the genetic architecture of AN has strong metabolic as well as psychiatric origins, suggesting that AN should be reconceptualized as a metabo-psychiatric disorder. Therefore, identifying the metabo-psychiatric mechanisms that contribute to AN may be essential for developing effective treatments. This review focuses on animal models for studying the metabo-psychiatric mechanisms that may contribute to AN, with a focus on the activity-based anorexia (ABA) paradigm. We also highlight recent work using modern circuit-dissecting neuroscience techniques to uncover metabolic mechanisms that regulate ABA, and encourage further work to ultimately identify novel treatment strategies for AN.

Diagnostic Accuracy of Plasma Ghrelin Concentrations in Pediatric Sepsis-Associated Acute Respiratory Distress Syndrome: A Single-Center Cohort Study

Background: Ghrelin is the endogenous ligand of growth hormone secretagogue receptor 1a, which plays a role in regulating immunity and inflammation. The aim of this study is to assess the diagnostic value of plasma ghrelin in sepsis-associated pediatric acute respiratory distress syndrome (PARDS). Methods: We recruited patients who were admitted to the pediatric ICU (PICU) of the Children's Hospital of Chongqing Medical University between January 2019 and January 2020 and met the diagnostic criteria for sepsis. Data on clinical variables, laboratory indicators, plasma ghrelin concentrations, and inflammatory factors were collected and evaluated, and patients were followed up for 28 days. The area under the receiver-operating characteristic curves (AUROC) were determined using logistic regression to calculate and test cut-off values for ghrelin as a diagnostic indicator of sepsis-associated PARDS. The log-rank test was used to compare survival according to ghrelin levels. Main results: Sixty-six PICU patients (30 with ARDS and 36 without ARDS) who met the diagnostic criteria of sepsis were recruited. The ghrelin level was significantly higher in the ARDS group than in the non-ARDS group. The AUROC of ghrelin was 0.708 (95% confidence interval: 0.584-0.833) and the positivity cutoff value was 445 pg/mL. Sensitivity, specificity, positive predictive value, negative predictive value, positive likelihood ratio, and negative likelihood ratio of plasma ghrelin for the diagnosis of PARDS-associated sepsis were 86.7, 50.0, 59.1, 81.8, 1.734, and 0.266%, respectively. The survival rate of sepsis patients were significantly improved when the ghrelin level was >445 pg/mL. Conclusions: Ghrelin plasma levels were higher in sepsis-associated PARDS, and accompanied by increased levels of inflammatory factors. High ghrelin levels are a positive predictor of ICU survival in sepsis patients. Yet, there is no evidence to prove that elevated ghrelin is a promising diagnostic indicator of sepsis-associated PARDS. Trial registration: Clinicaltrials, ChiCTR1900023254. Registered 1 December 2018 - Retrospectively registered, http://www.clinicaltrials.gov/ChiCTR1900023254.

Role of Neuroendocrine, Immune, and Autonomic Nervous System in Anorexia Nervosa-Linked Cardiovascular Diseases

Anorexia nervosa represents a severe mental disorder associated with food avoidance and malnutrition. In patients suffering from anorexia nervosa, cardiovascular complications are the main reason leading to morbidity and mortality. However, the origin and pathological mechanisms leading to higher cardiovascular risk in anorexia nervosa are still unclear. In this aspect, the issue of exact pathological mechanisms as well as sensitive biomarkers for detection of anorexia nervosa-linked cardiovascular risk are discussed. Therefore, this review synthesised recent evidence of dysfunction in multiple neuroendocrine axes and alterations in the immune system that may represent anorexia nervosa-linked pathological mechanisms contributing to complex cardiovascular dysregulation. Further, this review is focused on identification of non-invasive biomarkers for the assessment of increased cardiovascular risk in anorexia nervosa that can be linked to a clinical application. Complex non-invasive assessment of cardiovascular autonomic regulation—cardiac vagal control (heart rate variability), sympathetic vascular activity (blood pressure variability), and cardiovascular reflex control (baroreflex sensitivity)—could represent a promising tool for early diagnosis, personalized therapy, and monitoring of therapeutic interventions in anorexia nervosa particularly at a vulnerable adolescent age.

Developmental stage-dependent relationships between ghrelin levels and hippocampal white matter connections in low-weight anorexia nervosa and atypical anorexia nervosa

INTRODUCTION

Disruptions in homeostatic and hedonic food motivation are proposed to underlie anorexia nervosa (AN) and atypical AN, restrictive eating disorders which commonly onset in puberty. Ghrelin, a neuroprotective hormone that drives hedonic eating is increased in AN and is expressed in the hippocampus. White matter (WM) undergoes significant change during puberty in regions involved in food motivation, particularly WM tracts connected with the hippocampus. The association between ghrelin and WM region of interest (ROI) with hippocampal connections in restrictive eating disorders, particularly in adolescence during key neurodevelopmental growth, is unknown.

METHODS

We evaluated fasting plasma ghrelin and WM microstructure (measured by free-water corrected fractional anisotropy (FA-t)) in WM ROIs with hippocampal connections - the fornix and the hippocampal portion of the cingulum - in 56 adolescent females (age range: 11.9 - 22.1 y; mean: 19.0 y) with low-weight eating disorders including AN and atypical AN (N = 36) and healthy controls (N = 20).

RESULTS

FA-t in the fornix or hippocampal portion of the fornix did not differ between groups. Ghrelin was higher in AN/atypical AN vs. HC and was positively correlated with puberty stage in the AN/atypical AN group, but not the HC group. The correlation between ghrelin and FA-t in the fornix was significantly different in females with AN/atypical AN compared to controls. In AN/atypical AN, pubertal stage moderated the relation between fasting plasma ghrelin and FA-t in the fornix: higher fasting ghrelin was associated with lower FA-t in the fornix in late-post-puberty, but was not associated with FA-t in the early to mid stages of puberty.

CONCLUSIONS

In post-pubertal females with low-weight AN/atypical AN, higher levels of ghrelin are associated with lower FA-t in the fornix. This relationship is not evident in the early to mid stages of puberty in AN/atypical AN or in HC, and may reflect a lack of possible neuroprotective effects of ghrelin in late-post puberty only. Understanding the effects of ghrelin on WM microstructure longitudinally and following recovery from AN/Atypical AN and how this differs across pubertal stages will be an important next step. These findings could ultimately inform treatment staging and aid in diagnosis and detection of AN/atypical AN.

Backstage of Eating Disorder-About the Biological Mechanisms behind the Symptoms of Anorexia Nervosa

Anorexia nervosa (AN) represents a disorder with the highest mortality rate among all psychiatric diseases, yet our understanding of its pathophysiological components continues to be fragmentary. This article reviews the current concepts regarding AN pathomechanisms that focus on the main biological aspects involving central and peripheral neurohormonal pathways, endocrine function, as well as the microbiome-gut-brain axis. It emerged from the unique complexity of constantly accumulating new discoveries, which hamper the ability to look at the disease in a more comprehensive way. The emphasis is placed on the mechanisms underlying the main symptoms and potential new directions that require further investigation in clinical settings.

Metabolic state and value-based decision-making in acute and recovered female patients with anorexia nervosa

BACKGROUND

Patients with anorexia nervosa forgo eating despite emaciation and severe health consequences. Such dysfunctional decision-making might be explained by an excessive level of self-control, alterations in homeostatic and hedonic regulation, or an interplay between these processes. We aimed to understand value-based decision-making in anorexia nervosa and its association with the gut hormone ghrelin. Besides its homeostatic function, ghrelin has been implicated in the hedonic regulation of appetite and reward via the modulation of phasic dopamine signalling.

METHODS

In a cross-sectional design, we studied acutely underweight (n = 94) and recovered (n = 37) patients with anorexia nervosa of the restrictive subtype, as well as healthy control participants (n = 119). We assessed plasma concentrations of desacyl ghrelin and parameters of delay discounting, probability discounting for gains and losses, and loss aversion.

RESULTS

Recovered patients displayed higher risk aversion for gains, but we observed no group differences for the remaining decision-making parameters. Desacyl ghrelin was higher in acutely underweight and recovered participants with anorexia nervosa relative to healthy controls. Moreover, we found a significant group × desacyl ghrelin interaction in delay discounting, indicating that in contrast to healthy controls, acutely underweight patients with anorexia nervosa who had high desacyl ghrelin concentrations preferably chose the delayed reward option.

LIMITATIONS

We probed decision-making using monetary rewards, but patients with anorexia nervosa may react differently to disorder-relevant stimuli. Furthermore, in contrast to acyl ghrelin, the functions of desacyl ghrelin are unclear. Therefore, the interpretation of the results is preliminary.

CONCLUSION

The propensity for risk aversion as found in recovered patients with anorexia nervosa could help them successfully complete therapy, or it could reflect sequelae of the disorder. Conversely, ghrelin findings might be related to a mechanism contributing to disease maintenance; that is, in acutely underweight anorexia nervosa, a hungry state may facilitate the ability to forgo an immediate reward to achieve a (dysfunctional) long-term goal.

Changes in appetite-regulating hormones following food intake are associated with changes in reported appetite and a measure of hedonic eating in girls and young women with anorexia nervosa

BACKGROUND

Females with anorexia nervosa (AN) have higher ghrelin and peptide YY (PYY) and lower brain-derived neurotropic factor (BDNF) levels than controls, and differ in their perception of hunger cues. Studies have not examined appetite-regulating hormones in the context of homeostatic and hedonic appetite in AN.

OBJECTIVE

To examine whether alterations in appetite-regulating hormones following a standardized meal are associated with homeostatic and hedonic appetite in young females with AN vs. controls.

METHODS

68 females (36 AN, 32 controls) 10-22 years old were enrolled. Ghrelin, PYY and BDNF levels were assessed before, and 30, 60 and 120 min following a 400-kilocalorie standardized breakfast. Visual Analog Scales (VAS) assessing prospective food consumption, hunger, satiety, and hedonic appetite were administered before and 20 min after breakfast. A Cookie Taste Test (CTT) was conducted after a snack as a measure of hedonic eating behavior ∼3 h after breakfast.

RESULTS

AN had higher fasting ghrelin and PYY, and lower fasting BDNF (p = 0.001, 0.002 and 0.044 respectively) than controls. Following breakfast (over 120 min), ghrelin and PYY area under the curve (AUC) were higher, while BDNF AUC was lower in AN vs. controls (p = 0.007, 0.017 and 0.020 respectively). Among AN (but not controls), reductions in ghrelin and increases in PYY in the first 30-minutes following breakfast were associated with reductions in VAS scores for prospective food consumption. AN consumed fewer calories during the CTT vs. controls (p < 0.0001). In AN (particularly AN-restrictive subtype), BDNF AUC was positively associated with kilocalories consumed during the CTT CONCLUSIONS: In young females with AN, changes in ghrelin and PYY following food intake are associated with reductions in a prospective measure of food consumption, while reductions in BDNF are associated with reduced hedonic food intake. Further studies are necessary to better understand the complex interplay between appetite signals and eating behaviors in AN.

Longitudinal study on novel neuropeptides phoenixin, spexin and kisspeptin in adolescent inpatients with anorexia nervosa - association with psychiatric symptoms

OBJECTIVES

It is hypothesized that novel neuropeptides such as phoenixin (PNX), spexin (SPX), and kisspeptin (KISS) are involved in the pathogenesis of eating disorders. The study presented here analyzed neuropeptide concentrations during the course of anorexia nervosa (AN) and aimed to correlate those values with anthropometric and psychometric measurements.

METHODS

A longitudinal study was carried outin 30 AN adolescent patients and 15 age-matched healthy female controls. Selected neuroprotein serum levels were analyzed in malnourished patients (accAN) and following partial weight recovery (norAN), and these values were compared with the control group.

RESULTS

In accAN patients, decreased serum PNX levels were detected while SPX serum concentrations were lower in the accAN and norAN patients. No differences were observed in KISS concentrations in all studied groups.

CONCLUSIONS

In malnourished adolescent inpatients with AN, serum PNX and SPX level were decreased. The partial weight recovery normalized PNX concentrations but failed to normalize SPX levels. Therefore these two neuropeptides might be crucial for the etiology and course of the AN. The KISS levels did not change in the course of AN. The PNX levels were associated with some symptoms of eating disorders which may indicate its potential contribution in the regulation of emotions and behaviors in AN.

Brain accessibility delineates the central effects of circulating ghrelin

Ghrelin is a hormone produced in the gastrointestinal tract that acts via the growth hormone secretagogue receptor. In the central nervous system, ghrelin signalling is able to recruit different neuronal targets that regulate the behavioural, neuroendocrine, metabolic and autonomic effects of the hormone. Notably, several studies using radioactive or fluorescent variants of ghrelin have found that the accessibility of circulating ghrelin into the mouse brain is both strikingly low and restricted to some specific brain areas. A variety of studies addressing central effects of systemically injected ghrelin in mice have also provided indirect evidence that the accessibility of plasma ghrelin into the brain is limited. Here, we review these previous observations and discuss the putative pathways that would allow plasma ghrelin to gain access into the brain together with their physiological implications. Additionally, we discuss some potential features regarding the accessibility of plasma ghrelin into the human brain based on the observations reported by studies that investigate the consequences of ghrelin administration to humans.

Activity Based Anorexia as an Animal Model for Anorexia Nervosa-A Systematic Review

Anorexia nervosa (AN) is a severe eating disorder affecting around 1 per 100 persons. However, the knowledge about its underlying pathophysiology is limited. To address the need for a better understanding of AN, an animal model was established early on in the late 1960's: the activity-based anorexia (ABA) model in which rats have access to a running wheel combined with restricted food access leading to self-starving/body weight loss and hyperactivity. Both symptoms, separately or combined, can also be found in patients with AN. The aim of this systematic review was to compile the current knowledge about this animal model as well as to address gaps in knowledge. Using the data bases of PubMed, Embase and Web of science 102 publications were identified meeting the search criteria. Here, we show that the ABA model mimics core features of human AN and has been characterized with regards to brain alterations, hormonal changes as well as adaptations of the immune system. Moreover, pharmacological interventions in ABA animals and new developments, such as a chronic adaptation of the ABA model, will be highlighted. The chronic model might be well suited to display AN characteristics but should be further characterized. Lastly, limitations of the model will be discussed.