Investigation of peptide YY and ghrelin responses to a test meal in bulimia nervosa

From gut microbiota to brain: implications on binge eating disorders

The prevalence of eating disorders has been increasing over the last 50 years. Binge eating disorder (BED) and bulimia nervosa (BN) are two typical disabling, costly and life-threatening eating disorders that substantially compromise the physical well-being of individuals while undermining their psychological functioning. The distressing and recurrent episodes of binge eating are commonly observed in both BED and BN; however, they diverge as BN often involves the adoption of inappropriate compensatory behaviors aimed at averting weight gain. Normal eating behavior is coordinated by a well-regulated trade-off between intestinal and central ingestive mechanism. Conversely, despite the fact that the etiology of BED and BN remains incompletely resolved, emerging evidence corroborates the notion that dysbiosis of gastrointestinal microbiome and its metabolites, alteration of gut-brain axis, as well as malfunctioning central circuitry regulating motivation, execution and reward all contribute to the pathology of binge eating. In this review, we aim to outline the current state of knowledge pertaining to the potential mechanisms through which each component of the gut-brain axis participates in binge eating behaviors, and provide insight for the development of microbiome-based therapeutic interventions that hold promise in ameliorating patients afflicted with binge eating disorders.

Gut hormones, adipokines, and pro- and anti-inflammatory cytokines/markers in loss of control eating: A scoping review

Loss of control (LOC) eating is the defining feature of binge-eating disorder, and it has particular relevance for bariatric patients. The biomarkers of LOC eating are unclear; however, gut hormones (i.e., ghrelin, cholecystokinin [CCK], peptide YY [PYY], glucagon-like peptide 1 [GLP-1], and pancreatic polypeptide [PP]), adipokines (i.e., leptin, adiponectin), and pro- and anti-inflammatory cytokines/markers (e.g., high-sensitivity C-reactive protein [hsCRP]) are candidates due to their involvement in the psychophysiological mechanisms of LOC eating. This review aimed to synthesize research that has investigated these biomarkers with LOC eating. Because LOC eating is commonly examined within the context of binge-eating disorder, is sometimes used interchangeably with subclinical binge-eating, and is the latent construct underlying disinhibition, uncontrolled eating, and food addiction, these eating behaviors were included in the search. Only studies among individuals with overweight or obesity were included. Among the identified 31 studies, 2 studies directly examined LOC eating and 4 studies were conducted among bariatric patients. Most studies were case-control in design (n = 16) and comprised female-dominant (n = 13) or female-only (n = 13) samples. Studies generally excluded fasting total ghrelin, fasting CCK, fasting PYY, and fasting PP as correlates of the examined eating behaviors. However, there was evidence that the examined eating behaviors were associated with lower levels of fasting acyl ghrelin (the active form of ghrelin) and adiponectin, higher levels of leptin and hsCRP, and altered responses of postprandial ghrelin, CCK, and PYY. The use of GLP-1 analog was able to decrease binge-eating. In conclusion, this review identified potential biomarkers of LOC eating. Future studies would benefit from a direct focus on LOC eating (especially in the bariatric population), using longitudinal designs, exploring potential mediators and moderators, and increased inclusion of the male population.

Gastrointestinal peptides in eating-related disorders

Food intake is tightly controlled by homeostatic signals sensitive to metabolic need for the regulation of body weight. This review focuses on the peripherally-secreted gastrointestinal peptides (i.e., ghrelin, cholecystokinin, glucagon-like peptide 1, and peptide tyrosine tyrosine) that contribute to the control of appetite and discusses how these peptides or the signals arising from their release are disrupted in eating-related disorders across the weight spectrum, namely anorexia nervosa, bulimia nervosa, and obesity, and whether they are normalized following weight restoration or weight loss treatment. Further, the role of gut peptides in the pathogenesis and treatment response in human weight conditions as identified by rodent models are discussed. Lastly, we review the incretin- and hormone-based pharmacotherapies available for the treatment of obesity and eating-related disorders.

The regulation of gastric ghrelin secretion

Ghrelin is a gastric hormone with multiple physiological functions, including the stimulation of food intake and adiposity. It is well established that circulating ghrelin levels are closely associated with feeding patterns, rising strongly before a meal and lowering upon food intake. However, the mechanisms underlying the modulation of ghrelin secretion are not fully understood. The purpose of this review is to discuss current knowledge on the circadian oscillation of circulating ghrelin levels, the neural mechanisms stimulating fasting ghrelin levels and peripheral mechanisms modulating postprandial ghrelin levels. Furthermore, the therapeutic potential of targeting the ghrelin pathway is discussed in the context of the treatment of various metabolic disorders, including obesity, type 2 diabetes, diabetic gastroparesis and Prader-Willi syndrome. Moreover, eating disorders including anorexia nervosa, bulimia nervosa and binge-eating disorder are also discussed.

Current Aspects of the Role of Autoantibodies Directed Against Appetite-Regulating Hormones and the Gut Microbiome in Eating Disorders

The equilibrium and reciprocal actions among appetite-stimulating (orexigenic) and appetite-suppressing (anorexigenic) signals synthesized in the gut, brain, microbiome and adipose tissue (AT), seems to play a pivotal role in the regulation of food intake and feeding behavior, anxiety, and depression. A dysregulation of mechanisms controlling the energy balance may result in eating disorders such as anorexia nervosa (AN) and bulimia nervosa (BN). AN is a psychiatric disease defined by chronic self-induced extreme dietary restriction leading to an extremely low body weight and adiposity. BN is defined as out-of-control binge eating, which is compensated by self-induced vomiting, fasting, or excessive exercise. Certain gut microbiota-related compounds, like bacterial chaperone protein Escherichia coli caseinolytic protease B (ClpB) and food-derived antigens were recently described to trigger the production of autoantibodies cross-reacting with appetite-regulating hormones and neurotransmitters. Gut microbiome may be a potential manipulator for AT and energy homeostasis. Thus, the regulation of appetite, emotion, mood, and nutritional status is also under the control of neuroimmunoendocrine mechanisms by secretion of autoantibodies directed against neuropeptides, neuroactive metabolites, and peptides. In AN and BN, altered cholinergic, dopaminergic, adrenergic, and serotonergic relays may lead to abnormal AT, gut, and brain hormone secretion. The present review summarizes updated knowledge regarding the gut dysbiosis, gut-barrier permeability, short-chain fatty acids (SCFA), fecal microbial transplantation (FMT), blood-brain barrier permeability, and autoantibodies within the ghrelin and melanocortin systems in eating disorders. We expect that the new knowledge may be used for the development of a novel preventive and therapeutic approach for treatment of AN and BN.

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.

Plasma Peptide Concentrations and Peptide-Reactive Immunoglobulins in Patients with Eating Disorders at Inclusion in the French EDILS Cohort (Eating Disorders Inventory and Longitudinal Survey)

Eating disorders (EDs) are increasingly frequent. Their pathophysiology involves disturbance of peptide signaling and the microbiota–gut–brain axis. This study analyzed peptides and corresponding immunoglobulin (Ig) concentrations in groups of ED. In 120 patients with restrictive (R), bulimic (B), and compulsive (C) ED, the plasma concentrations of leptin, glucagon-like peptide-1 (GLP-1), peptide YY (PYY), and insulin were analyzed by Milliplex and those of acyl ghrelin (AG), des-acyl ghrelin (DAG), and α-melanocyte-stimulating hormone (α-MSH) by ELISA kits. Immunoglobulin G (in response to an antigen) concentrations were analyzed by ELISA, and their affinity for the respective peptide was measured by surface plasmon resonance. The concentrations of leptin, insulin, GLP-1, and PYY were higher in C patients than in R patients. On the contrary, α-MSH, DAG, and AG concentrations were higher in R than in C patients. After adjustment for body mass index (BMI), differences among peptide concentrations were no longer different. No difference in the concentrations of the IgG was found, but the IgG concentrations were correlated with each other. Although differences of peptide concentrations exist among ED subtypes, they may be due to differences in BMI. Changes in the concentration and/or affinity of several anti-peptide IgG may contribute to the physiopathology of ED or may be related to fat mass.

Meal-Related Acyl and Des-Acyl Ghrelin and Other Appetite-Related Hormones in People with Obesity and Binge Eating

OBJECTIVE

Potential mechanisms of abnormal food intake, such as dysregulation of meal-related appetite hormones, including acyl ghrelin (AG) and des-acyl ghrelin (DAG), were investigated among men and women with obesity, with and without binge eating (BE).

METHODS

Participants (n = 42: 19 female, 23 male) were assigned to a liquid meal and water condition in counterbalanced order, and blood samples for measuring hormones were obtained before and after these conditions.

RESULTS

Participants with BE had significantly lower fasting and postingestive AG concentrations than participants without BE in both conditions. During the meal condition, postprandial decreases in AG concentrations were significantly smaller for the BE group than for the non-BE group. There were no significant differences in DAG by BE group. Leptin increased significantly less after meals for those with BE compared with those without BE. There were no differences in other hormones by BE group. Fasting and postmeal hunger ratings were significantly higher for those with BE than for those without BE.

CONCLUSIONS

In individuals with BE, lower fasting AG may be due to downregulation by habitual overeating, and a smaller postmeal decline in AG may contribute to overeating. Lower postmeal leptin concentrations may also contribute to overeating.

Disturbance of gut satiety peptide in purging disorder

OBJECTIVE

Little is known about biological factors that contribute to purging after normal amounts of food-the central feature of purging disorder (PD). This study comes from a series of nested studies examining ingestive behaviors in bulimic syndromes and specifically evaluated the satiety peptide YY (PYY) and the hunger peptide ghrelin in women with PD (n = 25), bulimia nervosa-purging (BNp) (n = 26), and controls (n = 26). Based on distinct subjective responses to a fixed meal in PD (Keel, Wolfe, Liddle, DeYoung, & Jimerson, ), we tested whether postprandial PYY response was significantly greater and ghrelin levels significantly lower in women with PD compared to controls and women with BNp.

METHOD

Participants completed structured clinical interviews, self-report questionnaires, and laboratory assessments of gut peptide and subjective responses to a fixed meal.

RESULTS

Women with PD demonstrated a significantly greater postprandial PYY response compared to women with BNp and controls, who did not differ significantly. PD women also endorsed significantly greater gastrointestinal distress, and PYY predicted gastrointestinal intestinal distress. Ghrelin levels were significantly greater in PD and BNp compared to controls, but did not differ significantly between eating disorders. Women with BNp endorsed significantly greater postprandial hunger, and ghrelin predicted hunger.

DISCUSSION

PD is associated with a unique disturbance in PYY response. Findings contribute to growing evidence of physiological distinctions between PD and BNp. Future research should examine whether these distinctions account for differences in clinical presentation as this could inform the development of specific interventions for patients with PD.

Emerging Treatments in Eating Disorders

Eating disorders (EDs), including anorexia nervosa, bulimia nervosa, and binge-eating disorder, constitute a class of common and deadly psychiatric disorders. While numerous studies in humans highlight the important role of neurobiological alterations in the development of ED-related behaviors, the precise neural substrate that mediates this risk is unknown. Historically, pharmacological interventions have played a limited role in the treatment of eating disorders, typically providing symptomatic relief of comorbid psychiatric issues, like depression and anxiety, in support of the standard nutritional and psychological treatments. To date there are no Food and Drug Administration-approved medications or procedures for anorexia nervosa, and only one Food and Drug Administration-approved medication each for bulimia nervosa (fluoxetine) and binge-eating disorder (lisdexamfetamine). While there is little primary interest in drug development for eating disorders, postmarket monitoring of medications and procedures approved for other indications has identified several novel treatment options for patients with eating disorders. In this review, I utilize searches of the PubMed and ClinicalTrials.gov databases to highlight emerging treatments in eating disorders.

Systemic administration of anorexic gut peptide hormones impairs hedonic-driven sucrose consumption in mice

A number of reports suggest that gut hormones such as cholecystokinin (CCK), glucagon-like peptide 1 (GLP-1), and peptide YY(3-36) (PYY_3-36), which are released postprandially, suppress homeostatic food intake and result in satiety and the termination of feeding. However, it remains unclear whether these peptide hormones also suppress non-homeostatic consumption of palatable foods or fluids. To examine whether gut hormones reduce hedonically motivated sugar consumption, we assessed the effects of intraperitoneal administration of these gut hormones on the consumption of a highly palatable sucrose solution, using a mouse model we previously established for binge-like sucrose overconsumption (Yasoshima and Shimura, 2015). To reduce homeostatic hunger, chow was available at nighttime prior to testing. After a limited-access training procedure for 10days, during which access to both sucrose and chow were controlled, on the test day, control mice injected with saline consumed significantly more sucrose than during the pre-training period. In contrast, sucrose consumption on the test day in the mice injected with CCK-8 (2 and 4μg/kg), GLP-1 (500 and 1000nmol/kg), or PYY_3-36 (12.5 and 25nmol/kg) was significantly less than that in saline-injected mice. In a separate cohort of mice, the higher doses of CCK-8 and GLP-1 and a greater dose of PYY_3-36 (50nmol/kg) did not produce conditioned taste aversion to saccharin, suggesting that the doses of exogenous hormones in the present study do not cause aversive visceral distress. The present findings suggest that the systemic administration of these three gut hormones suppresses hedonic-driven sugar consumption due to the anorexic, but not aversive-visceral, effects of these hormones.

Different effects of cholestyramine on postprandial secretions of cholecystokinin and peptide YY in women with bulimia nervosa

OBJECTIVE

Patients with bulimia nervosa (BN) are reported to have decreased postprandial levels of cholecystokinin (CCK) and peptide YY (PYY). Fatty nutrients are the most powerful stimulus for releasing these peptides. Cholestyramine is an anion exchanger which adsorbs bile salts and reduces the digestion of lipids, affecting the secretion of both CCK and PYY. To further characterise the physiology of these peptides in BN, we aimed to investigate the effects of cholestyramine (12 g, per os) or placebo administered with a high-fat meal on CCK and PYY secretions in bulimic versus healthy women.

RESULTS

Postprandial CCK levels significantly increased in both healthy and bulimic women after placebo + the high-fat meal, without any significant difference between the two groups. Cholestyramine administration significantly increased postprandial CCK responses in both healthy and bulimic women; however, significantly lower CCK levels were observed in BN. Postprandial PYY levels significantly increased after placebo administration in healthy women after the high-fat meal, whereas no significant changes were found in bulimic women. Cholestyramine, administered with the high-fat meal, significantly reduced postprandial PYY response in healthy women, but not in bulimic women. Finally, there was a negative correlation of the area under the curve with respect to the increase of PYY (after placebo administration) with binge frequency in the bulimic women.

CONCLUSION

In BN an altered postprandial secretion of CCK may be evidenced when cholestyramine is combined with a high-fat meal. Instead, the postprandial secretion of PYY is significantly blunted and not affected by cholestyramine administration.

Stress-induced release of GUT peptides in young women classified as restrained or unrestrained eaters

Basal release of GUT peptides has been found to be altered in restrained eaters. Stress-induced secretion, however, has not yet been described, but could be a biological basis of overeating that exposes restrained eaters to a higher risk of becoming obese. The aim of the present study was to compare restrained and unrestrained eaters with respect to stress-induced release of the GUT peptides ghrelin and PYY. 46 young women were studied. Blood sampling for peptides was done before and after the Trier Social Stress Test. Ghrelin secretion after stress was significantly elevated in the restrained eaters, whereas no significant differences were detected for PYY. Stress-induced release of GUT peptides can be interpreted as a cause as well as a consequence of restrained eating.

Ghrelin in psychiatric disorders - A review

Ghrelin is a 28-amino-acid peptide hormone, first described in 1999 and broadly expressed in the organism. As the only known orexigenic hormone secreted in the periphery, it increases hunger and appetite, promoting food intake. Ghrelin has also been shown to be involved in various physiological processes being regulated in the central nervous system such as sleep, mood, memory and reward. Accordingly, it has been implicated in a series of psychiatric disorders, making it subject of increasing investigation, with knowledge rapidly accumulating. This review aims at providing a concise yet comprehensive overview of the role of ghrelin in psychiatric disorders. Ghrelin was consistently shown to exert neuroprotective and memory-enhancing effects and alleviated psychopathology in animal models of dementia. Few human studies show a disruption of the ghrelin system in dementia. It was also shown to play a crucial role in the pathophysiology of addictive disorders, promoting drug reward, enhancing drug seeking behavior and increasing craving in both animals and humans. Ghrelin's exact role in depression and anxiety is still being debated, as it was shown to both promote and alleviate depressive and anxiety-behavior in animal studies, with an overweight of evidence suggesting antidepressant effects. Not surprisingly, the ghrelin system is also implicated in eating disorders, however its exact role remains to be elucidated. Its widespread involvement has made the ghrelin system a promising target for future therapies, with encouraging findings in recent literature.

Appetite regulatory hormones in women with anorexia nervosa: binge-eating/purging versus restricting type

OBJECTIVE

Anorexia nervosa is a psychiatric illness characterized by low weight, disordered eating, and hallmark neuroendocrine dysfunction. Behavioral phenotypes are defined by predominant restriction or bingeing/purging; binge-eating/purging type anorexia nervosa is associated with poorer outcome. The pathophysiology underlying anorexia nervosa types is unknown, but altered hormones, known to be involved in eating behaviors, may play a role.

METHOD

To examine the role of anorexigenic hormones in anorexia nervosa subtypes, we examined serum levels of peptide YY (PYY; total and active [3-36] forms), brain-derived neurotrophic factor (BDNF), and leptin as primary outcomes in women with DSM-5 restricting type anorexia nervosa (n = 50), binge-eating/purging type anorexia nervosa (n = 25), and healthy controls (n = 22). In addition, women completed validated secondary outcome measures of eating disorder psychopathology (Eating Disorder Examination-Questionnaire) and depression and anxiety symptoms (Hamilton Rating Scales for Depression [HDRS] and Anxiety [HARS]). The study samples were collected from May 22, 2004, to February 7, 2012.

RESULTS

Mean PYY 3-36 and leptin levels were lower and BDNF levels higher in binge-eating/purging type anorexia nervosa than in restricting type anorexia nervosa (all P values < .05). After controlling for body mass index, differences in PYY and PYY 3-36 between anorexia nervosa types were significant (P < .05) and differences in BDNF were at the trend level (P < .10). PYY 3-36 was positively (r = 0.27, P = .02) and leptin was negatively (r = -0.51, P < .0001) associated with dietary restraint; BDNF was positively associated with frequency of purging (r = 0.21, P = .04); and leptin was negatively associated with frequency of bingeing (r = -0.29, P = .007) and purging (r = -0.31, P = .004).

CONCLUSIONS

Among women with anorexia nervosa, the anorexigenic hormones PYY, BDNF, and leptin are differentially regulated between the restricting and binge/purge types. Whether these hormone pathways play etiologic roles with regard to anorexia nervosa behavioral types or are compensatory merits further study.

Central and peripheral peptides regulating eating behaviour and energy homeostasis in anorexia nervosa and bulimia nervosa: a literature review

A large body of literature suggests the occurrence of a dysregulation in both central and peripheral modulators of appetite in patients with anorexia nervosa (AN) and bulimia nervosa (BN), but at the moment, the state or trait-dependent nature of those changes is far from being clear. It has been proposed, although not definitively proved, that peptide alterations, even when secondary to malnutrition and/or to aberrant eating behaviours, might contribute to the genesis and the maintenance of some symptomatic aspects of AN and BN, thus affecting the course and the prognosis of these disorders. This review focuses on the most significant literature studies that explored the physiology of those central and peripheral peptides, which have prominent effects on eating behaviour, body weight and energy homeostasis in patients with AN and BN. The relevance of peptide dysfunctions for the pathophysiology of eating disorders is critically discussed.

Reduction in total plasma ghrelin levels following catecholamine depletion: relation to bulimic and depressive symptoms

There is increasing preclinical and clinical evidence of the important role played by the gastric peptide hormone ghrelin in the pathogenesis of symptoms of depression and eating disorders. To investigate the role of ghrelin and its considered counterpart, peptide tyrosine tyrosine (PYY), in the development of bulimic and depressive symptoms induced by catecholamine depletion, we administered the tyrosine hydroxylase inhibitor alpha-methyl-paratyrosine (AMPT) in a randomized, double-blind, placebo-controlled crossover, single-site experimental trial to 29 healthy controls and 20 subjects with fully recovered bulimia nervosa (rBN). We found a decrease between preprandial and postprandial plasma ghrelin levels (p<0.0001) and a postprandial rise in plasma PYY levels (p<0.0001) in both conditions in the entire study population. Plasma ghrelin levels decreased in the entire study population after treatment with AMPT compared to placebo (p<0.006). AMPT-induced changes in plasma ghrelin levels were negatively correlated with AMPT-induced depressive symptoms (p<0.004). Plasma ghrelin and plasma PYY levels were also negatively correlated (p<0.05). We did not observe a difference in ghrelin or PYY response to catecholamine depletion between rBN subjects and healthy controls, and there was no correlation between plasma ghrelin and PYY levels and bulimic symptoms induced by catecholamine depletion. These findings suggest a relationship between catecholamines and ghrelin with depressive symptoms.

Dysfunctions of leptin, ghrelin, BDNF and endocannabinoids in eating disorders: beyond the homeostatic control of food intake

A large body of literature documents the occurrence of alterations in the physiology of both central and peripheral modulators of appetite in acute patients with anorexia nervosa (AN) and bulimia nervosa (BN). Until more recently the role of most of the appetite modulators in the control of eating behavior was conceptualized solely in terms of their influence on homeostatic control of energy balance. However, it is becoming more and more evident that appetite modulators also affect the non-homeostatic cognitive, emotional and rewarding component of food intake as well as non food-related reward, and, recently, AN and BN have been pathophysiologically linked to dysfunctions of reward mechanisms. Therefore, the possibility exists that observed changes in appetite modulators in acute AN and BN may represent not only homeostatic adaptations to malnutrition, but also contribute to the development and/or the maintenance of aberrant non-homeostatic behaviors, such as self-starvation and binge eating. In the present review, the evidences supporting a role of leptin, ghrelin, brain-derived neurotrophic factor and endocannabinoids in the homeostatic and non-homeostatic dysregulations of patients with AN and BN will be presented. The reviewed literature is highly suggestive that changes in the physiology of these modulators may play a pivotal role in the pathophysiology of eating disorders by providing a possible link between motivated behaviors, reward processes, cognitive functions and energy balance.

Ghrelin and eating disorders

There is growing evidence supporting a multifactorial etiology that includes genetic, neurochemical, and physiological components for eating disorders above and beyond the more conventional theories based on psychological and sociocultural factors. Ghrelin is one of the key gut signals associated with appetite, and the only known circulating hormone that triggers a positive energy balance by stimulating food intake. This review summarizes recent findings and several conflicting reports on ghrelin in eating disorders. Understanding these findings and inconsistencies may help in developing new methods to prevent and treat patients with these disorders.

The role of "mixed" orexigenic and anorexigenic signals and autoantibodies reacting with appetite-regulating neuropeptides and peptides of the adipose tissue-gut-brain axis: relevance to food intake and nutritional status in patients with anorexia nervosa and bulimia nervosa

Eating disorders such as anorexia (AN) and bulimia nervosa (BN) are characterized by abnormal eating behavior. The essential aspect of AN is that the individual refuses to maintain a minimal normal body weight. The main features of BN are binge eating and inappropriate compensatory methods to prevent weight gain. The gut-brain-adipose tissue (AT) peptides and neutralizing autoantibodies play an important role in the regulation of eating behavior and growth hormone release. The mechanisms for controlling food intake involve an interplay between gut, brain, and AT. Parasympathetic, sympathetic, and serotoninergic systems are required for communication between brain satiety centre, gut, and AT. These neuronal circuits include neuropeptides ghrelin, neuropeptide Y (NPY), peptide YY (PYY), cholecystokinin (CCK), leptin, putative anorexigen obestatin, monoamines dopamine, norepinephrine (NE), serotonin, and neutralizing autoantibodies. This extensive and detailed report reviews data that demonstrate that hunger-satiety signals play an important role in the pathogenesis of eating disorders. Neuroendocrine dysregulations of the AT-gut-brain axis peptides and neutralizing autoantibodies may result in AN and BN. The circulating autoantibodies can be purified and used as pharmacological tools in AN and BN. Further research is required to investigate the orexigenic/anorexigenic synthetic analogs and monoclonal antibodies for potential treatment of eating disorders in clinical practice.

From disordered eating to addiction: the "food drug" in bulimia nervosa

The high prevalence of substance abuse in individuals with bulimia nervosa (BN) and the pervasive symptom substitution in many types of drug addiction suggest that a number of substances--including food--can impair an individual's self-control, even in the presence of negative consequences. Nonetheless, the neurobiological similarities between BN and drug addiction are not clearly established. This review explores how the specific eating patterns seen in BN (binge eating and purging, with intermittent dietary restriction) are particularly addictive and differentiate BN from other eating disorders and obesity. A number of peripheral and central biological aberrations seen in BN may result in altered reward sensitivity in these individuals, particularly through effects on the dopaminergic system. Neurobiological findings support the notion that BN is an addictive disorder, which has treatment implications for therapy and pharmacological manipulations.

Gastric emptying and symptoms of bulimia nervosa: effect of a prokinetic agent

OBJECTIVE

Previous studies have suggested that delayed gastric emptying and abnormal postprandial release of hormones that influence satiation, particularly cholecystokinin (CCK), may play an important role in the pathophysiology of bulimia nervosa (BN). This study was designed to test these hypotheses as well as the efficacy of the prokinetic agent erythromycin in patients with BN.

METHOD

Thirty-two normal-weight women with BN and 24 control participants consumed a large liquid test meal. Gastric emptying and pre- and postprandial release of CCK, peptide YY (PYY), and ghrelin were determined. Participants with BN were then recruited for double-blind treatment with erythromycin up to 500 mg three times daily vs. placebo for 6 weeks, following which they consumed a repeat test meal with gastric emptying and appetitive hormone measurements.

RESULTS

CCK release at 15 min following the meal was marginally lower (p=0.1) in BN than in control participants. Rate of gastric emptying and postprandial hormone release were similar in BN and controls. BN patients assigned to erythromycin compared to those assigned to placebo had more rapid gastric emptying following treatment, but there were no differences in release of CCK, PYY, or ghrelin following the post-treatment test meal. Moreover, treatment with erythromycin was not associated with clinical response.

DISCUSSION

The current study does not support the clinical utility of moderate dose erythromycin in treating BN. Furthermore, the findings suggest that a modest increase in gastric emptying rate is associated neither with altered postprandial hormonal release nor with clinical benefit in these patients. While providing no evidence for the effectiveness of prokinetic agents in this setting, our findings do not preclude the possibility that a greater increase in gastric emptying rate might prove beneficial.

Eating disorders and gastrointestinal peptides

PURPOSE OF REVIEW

Disturbances in gastrointestinal hormones have been implicated in the pathogenesis of eating disorders such as anorexia nervosa and bulimia nervosa. However, the contribution of these hormonal changes to the onset and maintenance of eating disorder remains unclear. We focus our review on a selective number of gastrointestinal hormones that are known to play a role in the regulation of short-term or long-term energy balance and examine their association with eating disorder in recently published literature.

RECENT FINDINGS

Several new studies reported differential changes of ghrelin isoforms during fasting and following nutrient ingestion. New findings on other appetite-regulating hormones (peptide YY, cholecystokinin, incretin hormones and pancreatic polypeptide) at different nutritional states and disease stage have also been reported in subtypes of eating disorder. Most of the changes in peripheral hormones disappeared or partially recovered after the restoration of weight with nutritional and behavioral therapy.

SUMMARY

Dysregulation of gastrointestinal hormones is more likely to contribute to the maintenance of the disordered eating behavior and related metabolic outcomes as well as the clinical course rather than causing them. A better understanding of this relationship also carries implications for developing targeted hormone-base treatment for eating disorder.

Psychobiology of purging disorder: reduction in circulating leptin levels in purging disorder in comparison with controls

OBJECTIVE

Purging disorder (PD), a recently recognized eating disorder syndrome, is differentiated from bulimia nervosa (BN) based on the absence of objectively large binge episodes. BN has been associated with low serum leptin levels. This study examined whether PD is also characterized by low serum leptin.

METHOD

Participants included women with PD (n = 20) or BN (n = 37), and non-eating disorder controls (n = 33). Blood samples for measurement of leptin and total ghrelin were obtained after overnight fast.

RESULTS

In comparison with control values, leptin levels were significantly decreased in PD (p < .01), as well as in BN (p < .02). Plasma ghrelin levels did not differ significantly across groups.

DISCUSSION

These results provide the first evidence that PD is associated with alteration in a neurobiological pathway influencing eating patterns and body weight. Further research is needed to assess whether low leptin levels in PD and BN are associated with restrained eating and weight suppression.

Impact of exercise and dietary fatty acid composition from a high-fat diet on markers of hunger and satiety

To compare the effects of both dietary fatty acid composition and exercise vs. sedentary conditions on circulating levels of hunger and satiety hormones. Eight healthy males were randomized in a 2 × 2 crossover design. The four treatments were 3 days of HF diets (50% of energy) containing high saturated fat (22% of energy) with exercise (SE) or sedentary (SS) conditions, and high monounsaturated fat (30% of energy) with exercise (UE) or sedentary (US) conditions. Cycling exercise was completed at 45% of VO(2)max for 2h daily. On the third HF day, 20 blood samples were drawn over a 24h period for each hormone (leptin, insulin, ghrelin, and peptide YY (PYY)). A visual analog scale (VAS) was completed hourly between 0800 and 2200. Average 24h leptin and insulin levels were lower while 24h PYY was higher during exercise vs. sedentary conditions. FA composition did not differentially affect 24h hormone values. VAS scores for hunger and fullness did not differ between any treatment but did correlate with ghrelin, leptin, and insulin. High saturated or unsaturated fat diets did not differ with respect to markers of hunger or satiety. Exercise decreased 24h leptin and insulin while increasing PYY regardless of FA composition.

Tratamento nutricional da bulimia nervosa

A bulimia nervosa é um transtorno alimentar caracterizado por compulsões alimentares e métodos compen-satórios recorrentes. Os pacientes apresentam ingestão alimentar inadequada e comportamentos alimentares disfuncionais. O adequado tratamento do transtorno requer uma equipe multiprofissional e terapia nutricional especializada. Compreender as características desse transtorno, os padrões de consumo e o comportamento alimentar, bem como atentar para as atitudes alimentares dos pacientes, é fundamental para o planejamento e para a adequada condução da abordagem nutricional. A terapia nutricional para esse transtorno é diferenciada, exigindo do nutricionista maiores habilidades de aconselhamento nutricional. Educação nutricional e acon-selhamento nutricional, com ênfase na abordagem de atitudes alimentares e insatisfação corporal, são o foco da terapia nutricional. Para o atendimento eficaz desses pacientes e o sucesso no tratamento nutricional, é importante que o profissional se mantenha atualizado sobre nutrição e transtornos alimentares e procure especialização e experiência nessa área do conhecimento.

Ghrelin and obestatin circadian levels differentiate bingeing-purging from restrictive anorexia nervosa

CONTEXT

Anorexia nervosa (AN) patients present with restrictive food behavior (AN-R). Some of them develop episodes of bulimia (AN-BP) without any clear pathophysiological explanation to date. Their clinical differentiation is important but not easily performed. Orexigenic/anorexigenic peptides measurements could provide some clues for that matter.

OBJECTIVE

The objective of the study was to determine whether the circadian profile of total and acylated ghrelin, obestatin, and peptide YY (PYY) levels is different in AN-R subjects when compared with AN-BP patients.

DESIGN AND SETTINGS

This was a cross-sectional study in an endocrinological unit.

PATIENTS AND CONTROL SUBJECTS

Four groups of age-matched young women: 22 AN-R, 10 AN-BP, 16 normal-weight bulimia nervosa (BN), and nine controls.

MAIN OUTCOME MEASURES

Twelve-point circadian profiles of plasma total and acylated ghrelin, obestatin, and PYY were measured.

RESULTS

Total and acylated ghrelin and obestatin circadian levels were increased in AN-R when compared with controls but decreased in both AN-BP and BN groups (P < 0.001). PYY was decreased in all groups with eating disorders. Acylated to total ghrelin ratio was decreased in AN-BP and BN (P < 0.001), whereas obestatin to acylated ghrelin and PYY to acylated ghrelin ratios were increased in both groups with bingeing-purging behavior (P < 0.0001).

CONCLUSIONS

Patients with AN-associated bingeing-purging behavior present a very different profile of appetite regulatory peptides when compared with the pure restrictive type. The assessment of ghrelin (and eventually obestatin) could be of particular interest for differential diagnosis. Very low ghrelin levels and increased anorexigenic to orexigenic peptide ratios suggest either a lack of adaptation to a starvation state or a higher facility to cope with undernutrition.

Ghrelin gene products and the regulation of food intake and gut motility

A breakthrough using "reverse pharmacology" identified and characterized acyl ghrelin from the stomach as the endogenous cognate ligand for the growth hormone (GH) secretagogue receptor (GHS-R) 1a. The unique post-translational modification of O-n-octanoylation at serine 3 is the first in peptide discovery history and is essential for GH-releasing ability. Des-acyl ghrelin, lacking O-n-octanoylation at serine 3, is also produced in the stomach and remains the major molecular form secreted into the circulation. The third ghrelin gene product, obestatin, a novel 23-amino acid peptide identified from rat stomach, was found by comparative genomic analysis. Three ghrelin gene products actively participate in modulating appetite, adipogenesis, gut motility, glucose metabolism, cell proliferation, immune, sleep, memory, anxiety, cognition, and stress. Knockdown or knockout of acyl ghrelin and/or GHS-R1a, and overexpression of des-acyl ghrelin show benefits in the therapy of obesity and metabolic syndrome. By contrast, agonism of acyl ghrelin and/or GHS-R1a could combat human anorexia-cachexia, including anorexia nervosa, chronic heart failure, chronic obstructive pulmonary disease, liver cirrhosis, chronic kidney disease, burn, and postsurgery recovery, as well as restore gut dysmotility, such as diabetic or neurogenic gastroparesis, and postoperative ileus. The ghrelin acyl-modifying enzyme, ghrelin O-Acyltransferase (GOAT), which attaches octanoate to serine-3 of ghrelin, has been identified and characterized also from the stomach. To date, ghrelin is the only protein to be octanylated, and inhibition of GOAT may have effects only on the stomach and is unlikely to affect the synthesis of other proteins. GOAT may provide a critical molecular target in developing novel therapeutics for obesity and type 2 diabetes.

Ghrelin and peptide YY in postpartum lactating and nonlactating women

BACKGROUND

Epidemiologic studies suggest that childbearing is an important contributor to the development of obesity in many women and that breastfeeding may be protective. Ghrelin and peptide YY (PYY) are gut hormones involved in appetite regulation and energy homeostasis and are biological neuroendocrine signals that potentially affect body weight and adiposity.

OBJECTIVE

This study evaluated whether fasting or postprandial ghrelin or PYY is different between lactating and nonlactating postpartum women matched for age, body weight, and adiposity.

DESIGN

Ten postpartum lactating women (mean + or - SD: 28.1 + or - 4.9 y of age, 69.2 + or - 11.3 kg, 35.4 + or - 6.6% body fat) and 8 nonlactating women (28.8 + or - 7.6 y of age, 75.6 + or - 13.7 kg, 37.5 + or - 6.5% body fat) at 4-5 wk postpartum underwent measurements of body weight, body composition, and ghrelin and PYY responses to a standardized meal (350 kcal). Seven never-pregnant women served as control subjects (29.7 + or - 4.1 y of age, 60.4 + or - 4.8 kg, 25.5 + or - 2.0% body fat).

RESULTS

Ghrelin concentrations decreased, whereas PYY concentrations increased significantly (P < 0.05) in response to the meal, but fasting or meal-induced changes were not significantly different between lactating and nonlactating women. The fasting ghrelin concentration correlated with body mass index (r = -0.53, P < 0.05) and was significantly lower in postpartum than in control women (894.9 + or - 247.7 compared with 1316.9 + or - 241.0 pg/mL), even after adjustment for body mass index.

CONCLUSIONS

Our data do not support the notion that ghrelin, PYY, or both are plausible neuroendocrine signals that influence body weight regulation during lactation. They suggest, however, that ghrelin may change with increased adiposity in the postpartum state and may potentially play a role in body weight regulation after child birth.

Enhanced ghrelin secretion in the cephalic phase of food ingestion in women with bulimia nervosa

In humans, the cephalic phase response to food ingestion consists mostly of vagal efferent activation, which promotes the secretion of entero-pancreatic hormones, including ghrelin. Since symptomatic patients with bulimia nervosa (BN) are characterized by increased vagal tone, we hypothesized an enhanced ghrelin secretion in the cephalic phase of vagal stimulation. Therefore, we investigated ghrelin response to modified sham feeding (MSF) in both BN and healthy women. Six drug-free BN women and 7 age-matched healthy females underwent MSF with initially seeing and smelling a meal, and then chewing the food without swallowing it. Blood samples were drawn immediately before and after MSF for hormone assay. Circulating ghrelin increased after MSF in both groups with BN individuals exhibiting a greater ghrelin increase, which positively correlated with the patients' weekly frequency of binge-purging. These results show for the first time an increased ghrelin secretion in the cephalic phase of vagal stimulation in symptomatic BN patients, likely resulting in a potentiation of the peripheral hunger signal, which might contribute to their aberrant binge-purging behavior.

New frontiers in endocrinology of eating disorders

Alterations of both central and peripheral feeding regulatory substances occur in the acute phases of anorexia nervosa (AN) and bulimia nervosa (BN) and, generally, reverse after recovery. Some of these alterations are believed not only to sustain the altered eating behavior but also to contribute to certain psychopathological aspects and/or etiopathogenetic processes of eating disorders (EDs). It has been suggested that EDs are clinical conditions linked to reward-related mechanisms leading to a kind of addiction to self-starvation and/or overeating. Most of the feeding regulatory substances, which are dysregulated in EDs, are also implicated in the modulation of reward, emotional, and cognitive functions, thus representing possible links between altered nutritional regulation, motivated behaviors and reward processes. In this chapter, the ED literature dealing with ghrelin, brain-derived neurotrophic factor, opioid peptides, and endocannabinoids, which have prominent effects on eating behavior, body weight, reward, emotional, and cognitive functions, is reviewed in view of the above suggested links. Moreover, the potential therapeutics of new medications developed on the basis of neuroendocrine aberrations found in EDs is also presented.

Systematic review and meta-analysis of the baseline concentrations and physiologic responses of gut hormones to food in eating disorders

BACKGROUND

Disturbances in gastrointestinal hormones have been widely identified in persons with eating disorders (EDs) and have been implicated in their clinical pathologies.

OBJECTIVE

The objective was to identify, critically examine, and summarize studies investigating the short-term response of gastrointestinal hormones to food in persons with an ED, including the subtypes anorexia nervosa and bulimia nervosa.

DESIGN

A priori inclusion and exclusion criteria were set and included a procedure in which a test meal or glucose load was given and blood hormone concentrations measured. All studies included a healthy control group for comparison. The outcome variable was defined as the mean difference between fasting plasma hormone concentrations and the maximum postprandial peak or nadir. The difference in baseline values between groups was also examined. Pooled standardized mean differences were calculated and analyzed where possible.

RESULTS

A total of 28 studies were identified, including sufficient studies to perform a meta-analysis for ghrelin, peptide YY, cholecystokinin, insulin, and pancreatic polypeptide. Persons with an ED had higher baseline concentrations of ghrelin (large effect), peptide YY (medium effect), and cholecystokinin (medium effect for ED, large effect for anorexia nervosa). The response of insulin to food was decreased in persons with an ED (medium effect). No further differences were found in the release of gut peptides to a standardized test meal.

CONCLUSIONS

All of the studies had low power for the different subtypes of EDs. High heterogeneity among the studies was observed, and limitations are discussed. The findings suggest that the physiologic changes observed in patients with EDs are highly variable and subject to multiple confounding factors.

Appetite-Related Gut Peptides in Obesity and Binge Eating Disorder

The worldwide increase in obesity prevalence is a result of positive energy balance, with energy intake exceeding expenditure. The eating behavior in obesity ranges from mild passive overconsumption to excessive overeating with loss of control observed in binge eating disorder (BED). The signaling systems that underlie appetite control in BED are complex and, at this point, not well understood. The present review highlights the current knowledge of key components of the gut peptide system and examines evidence of defects in signaling that differentiate obese binge eaters from obese non-binge eaters. The signaling network underlying hunger, satiety, and metabolic status includes leptin and insulin from energy stores and cholecystokinin, glucagon-like peptide-1, peptide YY(3-36), and ghrelin from the gastrointestinal tract. Of the many gastrointestinal peptides, ghrelin is the only established appetite-stimulating one, whereas cholecystokinin, glucagon-like peptide-1, and peptide YY(3-36) promote satiety. Adipose tissue provides hormonal signals via leptin and insulin to the brain about energy stores and likely from adiponectin and resistin. Binge eating has been related to a dysfunction in the ghrelin signaling system. Moreover, the larger gastric capacity observed in BED may further reduce satiety signals and contribute to overeating.

Neuroendocrine dysregulation of food intake in eating disorders

Anorexia nervosa (AN) and bulimia nervosa (BN) are psychiatric disorders characterized by abnormal eating behaviors and imbalance of energy homeostasis. Changes of both central and peripheral neuroendocrine substances involved in the modulation of food intake and energy expenditure have been described in acutely ill patients with eating disorders. This review selectively focuses on the most recent findings supporting abnormal changes in the physiology of some peripheral adipokines and gut-secreted peptides, brain-derived neurotrophic factor and endocannabinoids in patients with AN or BN. Literature data do suggest a dysregulation of these neuroendocrine feeding regulators but, at the moment, they do not allow to establish the state or trait-dependent nature of those aberrations. It has been proposed, although not definitively proved, that neuroendocrine alterations, even when secondary to malnutrition and/or to aberrant eating behaviors, might contribute to the genesis and the maintenance of some symptomatic aspects of AN and BN, thus affecting the course and the prognosis of these disorders. Future studies should clarify whether neuroendocrine alterations are part of the genetically transmitted biological vulnerability to eating disorders.

The diagnostic validity of the criteria for binge eating disorder

OBJECTIVE

This paper considers whether the criteria currently used to classify the diagnosis of binge eating disorder (BED) are valid and appropriate.

METHOD

We review evidence that reflects on the validity of the current criteria for binge eating episodes and BED, using literature retrieved through major psychology and psychiatry search engines (e.g., PsycInfo, PubMed).

RESULTS

Evidence from experimental research points to the relative importance of episode frequency, the amount of food consumed at episodes, the subjective sense of loss of control over eating, and several additional criteria associated with binge episodes in BED. Evidence on the differences in psychopathology between BED and bulimia nervosa and between BED and obesity without binge eating, as related to diagnostic criteria, is reviewed.

CONCLUSION

Although evidence concerning the diagnostic criteria of BED is mixed, broadening certain diagnostic criteria for binge eating episodes and BED might more accurately reflect the research literature and increase the number of individuals eligible for inclusion in treatment programs.

The 3111T/C polymorphism of the CLOCK gene confers a predisposition to a lifetime lower body weight in patients with anorexia nervosa and bulimia nervosa: a preliminary study

Feeding is subjected to circadian regulation; therefore, changes in the components of the endogenous oscillator regulating circadian rhythms may be involved in disordered rhythmicity of eating behavior as it occurs in anorexia nervosa (AN) and bulimia nervosa (BN). We investigated whether the 3111T/C polymorphism of the CLOCK gene, which is part of the endogenous oscillator system, was associated to AN and/or BN. A total of 241 women, including 90 healthy controls, 60 patients with AN and 91 patients with BN, participated into the study. The frequencies of 3111T/C genotypes and alleles did not significantly differ among the groups. In both the AN and BN group, subjects carrying one copy of the C allele had a lifetime body weight significantly lower than those carrying the T/T genotype. These findings, although preliminary, suggest that the 3111T/C polymorphism of the CLOCK gene does not play a major role in the genetic vulnerability to AN and BN, but it seems to predispose eating disorders (EDs) patients to a more severe lifetime body weight loss.

Loss of control over eating reflects eating disturbances and general psychopathology

This study examined the clinical significance of the loss of control over eating as a key component of eating disorders. It investigated the association of eating-related psychopathology and general psychopathology with objective bulimic episodes (OBEs; experiencing a loss of control while consuming large amounts of food) and subjective bulimic episodes (SBEs; experiencing a loss of control while consuming small/moderate amounts). A community sample of 81 women with a range of disordered eating was recruited: binge-eating disorder, bulimia nervosa, subclinical eating disturbances, or no eating disorders. They were interviewed using the Eating Disorder Examination and completed measures of eating-related and general psychopathology. Both OBE and SBE frequencies correlated significantly with measures of eating-related and general psychopathology, and no significant differences were found between the magnitudes of the correlations with either binge episode type. SBE frequency significantly and independently predicted global eating disorder psychopathology. The loss of control over eating, without consuming large amounts of food, was as closely associated with specific eating disorder psychopathology and general mental health as were traditionally defined OBEs. SBEs may be an important target of treatment and should be considered for future diagnostic classifications of eating disorders.

Cannabinoids in eating disorders and obesity

Cannabinoid system is a crucial mechanism in regulating food intake and energy metabolism. It is involved in central and peripheral mechanisms regulating such behavior, interacting with many other signaling systems with a role in metabolic regulation. Cannabinoid agonists promote food intake, and soon a cannabinoid antagonist, rimonabant, will be marketed for the treatment of obesity. It not only causes weight loss, but also alleviates metabolic syndrome. We present a review of current knowledge on this subject, along with data from our own research: genetic studies on this system in eating disorders and obesity and studies locating cannabinoid receptors in areas related to food intake. Such studies suggest cannabinoid hyperactivity in obesity, and this excessive activity may have prognostic implications.

Peptide YY release in anorectic patients after liquid meal

Fasting and postprandial levels of human peptide YY (PYY) were recently found to be lower in obesity. To investigate whether PYY levels are correspondingly high in patients with anorexia nervosa, PYY concentrations were analyzed under basal conditions and in response to a liquid meal. We investigated PYY plasma levels in 16 female anorectic (BMI 15.2+/-0.3 kg/m2) and seven lean subjects (BMI 21.3+/-0.6 kg/m2) before and after ingestion of a liquid meal (250 kcal; 15% protein, 55% carbohydrates, and 30% fat). PYY levels were analyzed using PYY ELISA (DSL, USA). Values are given as mean+/-SEM. Basal PYY levels in anorectic patients (89.0+/-14.4 pg/mL) were not significantly different from lean subjects (64.1+/-12.1 pg/mL). Postprandial PYY levels in healthy volunteers increased significantly after 20 and 60 min (80.4+/-12.7 and 96.0+/-19.9 pg/mL, respectively). In anorectic women PYY was increased at 20 min (137.9+/-19.5 pg/mL) and at 60 min (151.3+/-19.2 pg/mL). No difference was found between both groups. We conclude that basal and postprandial PYY levels in normal weight women are not different from anorectic patients. We could not confirm the recently published blunted postprandial PYY response in anorexia, a finding that merits further study.

The Leu72Met polymorphism of the ghrelin gene is significantly associated with binge eating disorder

OBJECTIVES

The pathophysiological mechanisms underlying binge eating disorder are poorly understood. Evidence exists for the fact that abnormalities in peptides involved in the regulation of appetite, including ghrelin, may play a role in binge eating behavior. Genes involved in the ghrelin physiology may therefore contribute to the biological vulnerability to binge eating disorder.

METHODS

We examined whether two polymorphisms of the ghrelin gene, the G152A (Arg51Gln) and C214A (Leu72Met), were associated with binge eating disorder. Ninety obese or nonobese women with binge eating disorder and 119 normal weight women were genotyped at the ghrelin gene.

RESULTS

Statistical analyses showed that the Leu72Met ghrelin gene variant was significantly more frequent in binge eating disorder patients (chi2=5.940; d.f.=1, P=0.01) and was associated with a moderate, but significant risk to develop binge eating disorder (odds ratio=2.725, 95% confidence interval: 1.168-6.350).

CONCLUSIONS

Although these data should be regarded as preliminary because of the small sample size, they suggest that the Leu72Met ghrelin gene variant may contribute to the genetic susceptibility to binge eating disorder.

Phenotypes, endophenotypes, and genotypes in bulimia spectrum eating disorders

OBJECTIVES

To review the main phenomenological variants observed among bulimia spectrum syndromes and the factors believed to act etiologically for them and also to generate an etiologic model that accommodates known heterogeneities within the population suffering bulimic syndromes.

METHOD

Defining bulimic syndromes broadly, we address threshold and subthreshold forms of bulimia nervosa (BN) and also the provisional or newly proposed diagnoses of binge eating disorder (BED) and purging disorder (PD). We review evidence bearing on the validity of these diagnostic entities and on the place of sociocultural, family-developmental, neurobiological, and genetic factors in a multidimensional etiologic model for these classifications.

RESULTS

Available data validate certain bulimic phenotypes and subphenotypes that are characterized by such traits as impulsivity or affective instability. Findings associate subphenotypic, or trait-based, variations with putative endophenotypes, such as reduced serotonin transporter activity, and with candidate genotypes affecting the serotonin system; the data also indicate intriguing correspondences between gene environment interactions and subphenotypic variations along such dimensions as novelty seeking.

CONCLUSIONS

Bulimic syndromes sometimes reflect a primary disruption of controls over mood, impulses, and appetite in individuals showing marked psychopathology; at other times, they reflect a more circumscribed erosion of appetitive controls in relatively intact individuals, following prolonged dieting. We argue that dimensional perspectives involving careful attention to comorbid personality traits and symptoms are needed to accommodate existing heterogeneities within the population suffering from bulimia and to characterize the etiologic roles of familial-developmental, neurobiological, and genetic variables (and of interactions among these variables) in bulimic syndromes.

Recent progress in PYY research--an update report for 8th NPY meeting

PYY(3-36) is a gut regulatory peptide which has recently been found to reduce appetite. Variability of this effect across different experimental conditions has led to confusion and polarization of opinion on its potential as an anti-obesity treatment. This review summarizes recent progress in this area. The basic anorexigenic effect leading to weight loss in rodents has now been confirmed by several groups. Anorexia has also been confirmed in human studies although optimal route and dosing remain to be defined. Gastric bypass causes PYY levels to rise, which may in part mediate the weight loss occurring after this surgery, and levels have been found to be normal or low in obese people. The straightforward ARC model of mechanism, involving inhibition and activation, respectively, of NPY and POMC neurons, is giving way to a more complicated system involving vagal afferent signals.

CONCLUSION

It works, but not how we thought it did.

A lesser postprandial suppression of plasma ghrelin in Prader-Willi syndrome is associated with low fasting and a blunted postprandial PYY response

OBJECTIVE

Ghrelin and polipeptide YY (PYY) are involved in the regulation of food intake. We evaluated these two peptides and their possible relationship in adult patients with Prader-Willi syndrome (PWS).

PATIENTS

Seven patients with PWS, 16 age-sex-BMI matched obese and 42 age-sex matched lean subjects.

DESIGN AND MEASUREMENTS

Fasting plasma PYY and ghrelin levels were measured in all subjects and, postprandially until 6 h, in seven matched subjects of each group.

RESULTS

Fasting ghrelin levels were higher in PWS than in the other two groups. Fasting PYY levels were lower in patients with PWS than in lean subjects but similar to those in obese subjects. The postprandial decrease in ghrelin concentrations was lower in PWS as compared to the other two groups and therefore the 6-h-postprandial area under the curve (AUC) for ghrelin was higher in PWS than in obese subjects. PYY response after the meal was blunted in patients with PWS, but not in the other two groups that showed a peak at 60 min The AUC for PYY was lower in PWS as compared to the other two groups. Fasting PYY levels correlated negatively with fasting ghrelin levels and with ghrelin AUC and they were the only predictor for ghrelin AUC (beta = -0.464, P = 0.034). The increase in PYY correlated negatively with the decrease in ghrelin at times 60 min and 120 min in PWS.

CONCLUSIONS

In PWS, the low decrease in postprandial ghrelin levels could be related to the low fasting PYY concentrations and their blunted postprandial response.

Changes in appetite related gut hormones in intensive care unit patients: a pilot cohort study

Introduction

The nutritional status of patients in the intensive care unit (ICU) appears to decline not only during their stay in the ICU but also after discharge from the ICU. Recent evidence suggests that gut released peptides, such as ghrelin and peptide YY (PYY) regulate the initiation and termination of meals and could play a role in the altered eating behaviour of sick patients. The aim of this study was to assess the patterns of ghrelin and PYY levels during the stay of ICU patients in hospital.

Methods

Sixteen ICU patients (60 ± 4.7 years, body mass index (BMI) 28.1 ± 1.7 kg/m² (mean ± standard error of the mean)) underwent fasting blood sample collections on days 1, 3, 5, 14, 21 and 28 of their stay at Hammersmith and Charing Cross Hospitals. Changes in appetite and biochemical and anthropometric markers of nutritional status were recorded. A comparison was made to a group of 36 healthy volunteers matched for age and BMI (54.3 ± 2.9 years, p = 0.3; BMI 25.8 ± 0.8 kg/m² p = 0.2).

Results

Compared to healthy subjects, ICU patients exhibited a significantly lower level of ghrelin (day one 297.8 ± 76.3 versus 827.2 ± 78.7 pmol/l, p < 0.001) during their stay in the ICU. This tended to rise to the normal level during the last three weeks of hospital stay. Conversely, ICU patients showed a significantly higher level of PYY (day one 31.5 ± 9.6 versus 11.3 ± 1.0 pmol/l, p < 0.05) throughout their stay in the ICU and on the ward, with a downward trend to the normal level during the last three weeks of stay.

Conclusions

Results from our study show high levels of PYY and low levels of ghrelin in ICU patients compared to healthy controls. There appears to be a relationship between the level of these gut hormones and nutritional intake.

Early tolerance to the hypophagic effect of the cannabinoid receptor antagonist SR141716 does not impede blockade of an orexigenic stimulus

The cannabinoid CB1 receptor antagonist SR141716 (Rimonabant) is known to reduce food intake by central and peripheral mechanisms. Recently, SR141716 has been reported to block the orexigenic effect of ghrelin, a potent orexigenic peptide produced by the stomach. This study investigated whether in rats, made tolerant to the hypophagic effect of SR141716, the drug was still capable to block the orexigenic activity of another non-natural (hypothalamic) peptide, i.e., the growth hormone releasing peptide (GHRP) hexarelin, a ghrelin mimetic. In the acute experiments, each dose of SR141716 (1, 5 and 10 mg/kg i.p.) reduced food intake with respect to vehicle-treated rats, whereas hexarelin (160 microg/kg s.c.) markedly stimulated feeding. All doses of SR141716 were capable to reduce the orexigenic effect of the GHRP. A 15-day administration of SR141716 (10 mg/kg i.p.) reduced both food intake and body weight. Tolerance to the hypophagic effect of SR141716 developed within 5 days, but in contrast, body weight remained markedly below that of vehicle-treated group throughout the entire treatment period. Interestingly, despite development of tolerance to its hypophagic effect, SR141716 was capable to suppress the orexigenic effect of repeated hexarelin challenge tests performed throughout the chronic experiments. In conclusion, the results of the present study confirm and broaden the existence of a functional relationship between ghrelin and endocannabinoids in the control of food intake, and bespeak the ability of a CB1 receptor antagonist to suppress orexia caused by stimuli alien to direct stimulation of the cannabinoid system.

Obese subjects respond to the stimulatory effect of the ghrelin agonist growth hormone-releasing peptide-2 on food intake

OBJECTIVE

The administration of the growth hormone (GH) secretagogue GH-releasing peptide (GHRP)-2, like ghrelin, increases food intake (FI) in lean healthy men. The aim of this study was to investigate whether this effect occurs in obese subjects and whether it is dose-dependent.

RESEARCH METHODS AND PROCEDURES

Nineteen subjects (10 lean and nine obese), all healthy and weight stable, received a double-blind randomized subcutaneous infusion of GHRP-2 at high dose (HD; 1 mug/kg per hour), low dose (0.1 microg/kg per hour), or placebo for 270 minutes over three study visits. Blood for hormone assays was collected through an intravenous forearm catheter. Hunger and fullness were rated on visual analog scales before and after a fixed breakfast (320 kcal at 120 minutes) and a buffet lunch at 240 minutes. Before lunch, subjects received taped instructions to eat as much as they wanted.

RESULTS

GHRP-2 infusion significantly increased ad libitum FI in a dose-dependent manner by 10.2 +/- 3.9% at low dose (p = 0.011) and by 33.5 +/- 5.8% at HD (p = 0.000) compared with placebo. Obesity status did not influence the effect of GHRP-2 on FI. All subjects had greater ratings of appetite before but similar levels of fullness after the meal with the HD GHRP-2. Serum GH levels increased dose dependently in all subjects.

DISCUSSION

The dual stimulatory effect of GHRP-2 on FI and human GH is dose dependent. Obese individuals retain their ability to respond to GHRP-2 both in terms of FI and human GH.

No association of the Arg51Gln and Leu72Met polymorphisms of the ghrelin gene with anorexia nervosa or bulimia nervosa

Genetic factors likely contribute to the biological vulnerability to anorexia nervosa (AN) and bulimia nervosa (BN). We investigated whether the Arg51Gln and/or the Leu72Met gene polymorphisms of the human ghrelin, a peptide involved in the regulation of eating behavior, were associated to AN and/or BN. Two-hundred-ninety-two Caucasian women (114 with BN, 59 with AN and 119 healthy controls) participated into the study. No significant differences were found in the frequencies of the Arg51Gln and the Leu72Met ghrelin gene variants among patients with AN or BN and healthy controls. Moreover, no significant differences emerged in eating-related phenotypic variables between patients carrying the Leu72Met genotype as compared to those with the Leu72Leu genotype. These results suggest that the Arg51Gln and the Leu72Met polymorphisms of the human ghrelin gene do not contribute to the genetic susceptibility to AN and BN.