Impaired cholecystokinin secretion in bulimia nervosa

Sex and cognitive dietary restraint influence cholecystokinin release and satiety in response to preloads varying in fatty acid composition and content

The aim of the study was to evaluate the effect of preloads differing in fatty acid composition, content, and delivery form on acute behavioral, subjective, and biological outcomes of satiety. Four energy- and volume-matched preloads were tested in normal weight men and women (n = 12 and 13, respectively), using a random, crossover design. Preloads were semisolid shakes differing in fat source [walnut or safflower (SAFF)], delivery [ground walnuts (WNT) or walnut oil (WOL)] or content [39% fat energy (SAFF, WNT, WOL) or 4% low-fat control (LFC)]. Blood was collected and subjective satiety assessed at 0 (fasting), 15, 30, and 45 min after preload consumption. Lunch (test meal) was provided thereafter. Energy intake at lunch was not affected by preload; however, subjects selected more carbohydrate, fiber-rich foods at the test meal lunch after walnut preloads than after LFC or SAFF preloads. Compared with the LFC preload, appetite satisfaction was significantly greater after SAFF and WNT, but not after WOL. Women were hungrier after SAFF than after WOL, whereas men were less hungry after SAFF and LFC than after WOL or WNT. Plasma cholecystokinin (CCK) concentrations reflected preload fat content and availability, particularly among men; CCK was higher after WOL and SAFF preloads than after LFC or WNT preloads. Plasma insulin was higher after LFC and SAFF preloads, corresponding to hunger suppression in men. Dietary restraint was associated with a blunted CCK response to preloads, whereas insulin was not affected by restraint. The results indicate that test meal energy intake after preloads containing approximately 40% walnut or safflower fat or 4% fat did not differ; however, walnut consumption may promote food patterns consistent with consuming diets higher in fiber.

Plasma Ghrelin Concentrations Are Lower in Binge-Eating Disorder

Binge-eating disorder (BED), characterized by binge meals without purging afterward, is found in about 30% of obese individuals seeking treatment. The study objective was to ascertain abnormalities in hormones influencing appetite in BED, especially ghrelin, an appetite-stimulating peptide, which was expected to be elevated. Measurements were made of plasma insulin, leptin, glucagon, cholecystokinin, and ghrelin, as well as glucose following an overnight 12-h fast, prior to and after ingestion (from 0 to 5 min) of a nutritionally complete liquid meal (1254 kJ) at 0830 h, at -15, 0, 5, 15, 30, 60, 90, and 120 min. Appetite ratings including hunger and fullness were also obtained. An acetaminophen tracer was used to assess gastric emptying rate. Three groups of comparably obese women (BMI = 35.9 +/- 5.5; % body fat = 44.9 +/- 4.7) participated: 12 nonbinge eating normals (NB), 14 subthreshold BED, and 11 BED. The BED subjects, compared to NB subjects, had lower baseline ghrelin concentrations prior to the meal, a lower area under the curve (AUC), with lower levels at 5, 15, 30, 90, and 120 min, and a smaller decline in ghrelin postmeal (all P < 0.03). The other blood values did not differ among groups, and neither did gastric emptying rate nor ratings of fullness. The BED subjects were then randomly assigned to treatment with cognitive-behavior therapy and diet (n = 5) or to a wait-list control (n = 4). Baseline ghrelin (P = 0.01) and AUC increased (P = 0.02), across both conditions, in which most subjects (7 of 9) stopped binge eating. The lower fasting and postmeal plasma ghrelin levels in BED are consistent with lower ghrelin levels in obese compared to lean individuals and suggests downregulation by binge eating.

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

BACKGROUND

Gut-derived peptides, such as peptide YY (PYY) and ghrelin that regulate the initiation and termination of meals, could play a role in the altered eating behavior of patients with bulimia nervosa (BN). Therefore, we aimed to assess plasma PYY and ghrelin responses to a test meal in symptomatic bulimics.

METHODS

Ten healthy women and nine women with BN underwent blood sample collections before and after the ingestion of a test meal of 1300 Kcal (with 15% carbohydrates, 10% proteins, and 75% fat) at 12:00 noon. Plasma total PYY, ghrelin, insulin, and glucose were assayed.

RESULTS

As compared with healthy women, bulimics exhibited a significantly blunted increase of circulating PYY (p < .007) and a significantly reduced suppression of plasma ghrelin (p < .0004) after the test meal. No significant differences emerged in food-induced plasma insulin and glucose changes between the two groups. Plasma ghrelin suppression after the meal was significantly correlated with plasma PYY increase.

CONCLUSIONS

We replicated our previous findings of an altered ghrelin response to food ingestion in people with BN and showed for the first time a blunted PYY increase after food consumption in these patients. These findings support the occurrence in BN of a profound dysregulation of some peripheral regulatory mechanisms involved in the short-term regulation of feeding behavior that might be involved in the pathophysiology of their binge eating behavior.

Altered ghrelin and peptide YY responses to meals in bulimia nervosa

OBJECTIVE

In recent years great advances have been made in our understanding of the peripheral signals produced within the gastrointestinal tract that regulate appetite, such as ghrelin and peptide YY (PYY). While ghrelin elicites hunger signals, PYY elicites satiety. Therefore, alterations in hormone physiology may play a role in the pathogenesis of bulimia nervosa (BN). In this study, we investigated the postprandial profile of ghrelin and PYY levels in patients with BN.

DESIGN AND PATIENTS

Postprandial plasma ghrelin and PYY levels and insulin and glucose responses were measured in 10 patients with BN and 12 control patients in response to a standard 400 kcal meal.

RESULTS

Basal ghrelin levels present in BN subjects (265.0 +/- 25.5 pmol/l) were significantly higher than those in healthy controls (199.3 +/- 18.4 pmol/l, P < 0.05), while basal PYY levels were equivalent in BN (14.6 +/- 1.3 pmol/l) and control (12.8 +/- 1.1 pmol/l, P = 0.30) subjects. Postprandial ghrelin suppression (decremental ghrelin area under the curve) was significantly attenuated in BN patients, compared to controls (-96.3 +/- 26.8 pmol/l x 3 h vs. -178.2 +/- 25.7 pmol/l x 3 h, P < 0.05). After a meal, the incremental PYY area under the curve in BN patients was significantly blunted from that observed in controls (9.2 +/- 2.6 pmol/l x 3 h vs. 26.8 +/- 3.2 pmol/l x 3 h, P < 0.01). Glucose and insulin responses to meals were similar between the two groups.

CONCLUSIONS

BN patients exhibit elevated ghrelin levels before meals with reduced ghrelin suppression after eating. In bulimia nervosa subjects, the rise in PYY levels after meals is also blunted. A gut-hypothalamic pathway involving peripheral signals, such as ghrelin and PYY, may be involved in the pathophysiology of BN.

Is the control of fat ingestion sexually differentiated?

Sexual differentiation is a fundamental aspect of human physiology [Wizemann TM, Pardue M-L, editors. Exploring the biological contributions to human health: does sex matter? Washington DC, National Academy Press, 2001]. Therefore, this review considers whether the physiological control of eating, as related to dietary fat, is sexually differentiated. The effects of dietary fat are considered from the perspective of stimuli controlling eating that arise from oral, gastric, intestinal, hepatic, and adipose sites. The data reviewed provide substantial support for hypothesis that many such controls of fat ingestion are sexually differentiated in both humans and laboratory animals. Because as yet little is established definitively, however, the apparently most promising questions and methodologies for future work are emphasized.

Binge eating and satiety in bulimia nervosa and binge eating disorder: effects of macronutrient intake

OBJECTIVE

The current study tested the hypothesis that supplemental dietary protein would reduce binge eating frequency and test meal intake in women with bulimia nervosa (BN) or binge eating disorder (BED).

METHOD

Eighteen women with BN or BED ingested high-carbohydrate or high-protein supplements (280 kcal) three times daily over two 2-week periods. On the morning after each period, participants were given a high-protein or high-carbohydrate supplement (420 kcal) 3 hr before an ad libitum meal.

RESULTS

Binge eating episodes occurred less frequently during protein supplementation (1.12 episodes per week) than during carbohydrate supplementation (2.94 episodes per week) or baseline (3.01 episodes per week). Participants reported less hunger and greater fullness, and consumed less food at test meals, after protein than after carbohydrate (673 vs. 856 kcal).

DISCUSSION

Adding protein to the diets of women with BN and BED reduced food intake and binge eating over a 2-week period. These findings may have implications for the longer-term treatment of these disorders.

Clinical endocrinology and metabolism. Cholecystokinin

Cholecystokinin (CCK) is a peptide hormone discovered in the small intestine. Together with secretin and gastrin, CCK constitutes the classical gut hormone triad. In addition to gallbladder contraction, CCK also regulates pancreatic enzyme secretion and growth, intestinal motility, satiety signalling and the inhibition of gastric acid secretion. CCK is, however, also a transmitter in central and intestinal neurons. Notably, CCK is the most abundant neuropeptide in the human brain. Owing to difficulties in developing accurate assays, knowledge about CCK secretion in disease is limited. Available data indicate, however, that proCCK is expressed in certain neuroendocrine tumours and sarcomas, whereas the secretion of CCK is impaired in celiac disease and bulimia nervosa. Stimulation with exogenous CCK has proved useful in diagnostic tests of gallbladder and pancreatic diseases, as well as medullary thyroid carcinomas.

Peripheral and central signals in the control of eating in normal, obese and binge-eating human subjects

The worldwide increase in the incidence of obesity is a consequence of a positive energy balance, with energy intake exceeding expenditure. The signalling systems that underlie appetite control are complex, and the present review highlights our current understanding of key components of these systems. The pattern of eating in obesity ranges from over-eating associated with binge-eating disorder to the absence of binge-eating. The present review also examines evidence of defects in signalling that differentiate these sub-types. The signalling network underlying hunger, satiety and metabolic status includes the hormonal signals leptin and insulin from energy stores, and cholecystokinin, glucagon-like peptide-1, ghrelin and peptide YY3-36 from the gastrointestinal tract, as well as neuronal influences via the vagus nerve from the digestive tract. This information is routed to specific nuclei of the hypothalamus and brain stem, such as the arcuate nucleus and the solitary tract nucleus respectively, which in turn activate distinct neuronal networks. Of the numerous neuropeptides in the brain, neuropeptide Y, agouti gene-related peptide and orexin stimulate appetite, while melanocortins and alpha-melanocortin-stimulating hormone are involved in satiety. Of the many gastrointestinal peptides, ghrelin is the only appetite-stimulating hormone, whereas cholecystokinin, glucagon-like peptide-1 and peptide YY3-36 promote satiety. Adipose tissue provides signals about energy storage levels to the brain through leptin, adiponectin and resistin. Binge-eating has been related to a dysfunction in the ghrelin signalling system. Moreover, changes in gastric capacity are observed, and as gastric capacity is increased, so satiety signals arising from gastric and post-gastric cues are reduced. Understanding the host of neuropeptides and peptide hormones through which hunger and satiety operate should lead to novel therapeutic approaches for obesity; potential therapeutic strategies are highlighted.

Eating disorders: clinical features and pathophysiology

Anorexia nervosa (AN) and bulimia nervosa (BN) are disorders of eating and weight-related behavior that together afflict some 1-3% of women in the United States. One of the remarkable features about each of the eating disorders is how persistent the disordered eating behavior becomes once it has begun. Substantial psychological, social, and physiological disturbances are associated with eating disorders, and it has been very difficult to disentangle those factors that may result from the disturbed behavior from the factors that may have predisposed individuals to, or precipitated the development of, the disorder. This article will briefly review the definitions, phenomenology, and identified risk factors for development of each of the major eating disorders. Pathophysiology will be discussed, with a particular focus on candidate factors that might sustain disordered eating behavior, as informed by clinical and basic science research. Future research directions will be suggested.

Behavioral models of binge-type eating

PURPOSE

To describe and evaluate behavioral models of binge-type eating.

DATA IDENTIFICATION

Studies were identified using Medline and hand searches of bibliographies of identified articles.

STUDY SELECTION

Isomorphic studies were selected that were judged to have some measure of construct validity.

DATA EXTRACTION

Face and construct validity were assessed, as well as simplicity and cost of use.

RESULTS OF DATA SYNTHESIS

Several different models of binge-type eating exist, each with different strengths of validity and use. These include models using sham feeding, restriction/refeeding cycles and/or stress, limited access (LA) to optional foods, and eating induced by operant schedules of behavior.

CONCLUSIONS

We concur with Harry Harlow, who was quoted by Gerry Smith as saying: "You'd be crazy to use animal models, but you'd also be crazy not to use them."

Impaired cholecystokinin secretion and disturbed appetite regulation in women with polycystic ovary syndrome

Increased amount of abdominal fat and obesity are common in polycystic ovary syndrome (PCOS). A higher prevalence of bulimia nervosa and greater cravings for sweets have also been reported in these patients. The present study aimed to compare meal-related appetite and secretion of the 'satiety peptide' cholecystokinin (CCK) and glucose regulatory hormones in PCOS women and controls. Sixteen pairs of women with PCOS and controls matched for age and body mass index participated in the study. After an overnight fast, blood samples were collected during ingestion of a standardized meal. We determined basal and postprandial blood levels of CCK, insulin, C-peptide, glucagon, cortisol, growth hormone and glucose. Self-ratings of appetite were assessed by a visual analog scale. PCOS women had a significantly lower meal-related CCK response (p < 0.05) with no association with satiety, as in the controls (r = 0.64). There was a tendency to higher ratings of craving for sweets in PCOS women (p = 0.07) but no correlation with insulin, as in the controls (r = 0.50). Within the PCOS group, ratings of craving for sweets were inversely related to testosterone (r = - 0.60) and the CCK response was positively correlated with levels of free testosterone (r = 0.50). We conclude that women with PCOS have reduced postprandial CCK secretion and deranged appetite regulation associated with increased levels of testosterone. Impaired CCK secretion may play a role in the greater frequency of binge eating and overweight in women with PCOS.

Leptin functioning in eating disorders

Leptin is an adipocyte-derived hormone, which is involved predominantly in the long-term regulation of body weight and energy balance by acting as a hunger suppressant signal to the brain. Leptin is also involved in the modulation of reproduction, immune function, physical activity, and some endogenous endocrine axes. Since anorexia nervosa (AN) and bulimia nervosa (BN) are characterized by abnormal eating behaviors, dysregulation of endogenous endocrine axes, alterations of reproductive and immune functions, and increased physical activity, extensive research has been carried out in the last decade in order to ascertain a role of this hormone in the pathophysiology of these syndromes. In this article, we review the available data on leptin physiology in patients with eating disorders. These data support the idea that leptin is not directly involved in the etiology of AN or BN. However, malnutrition-induced alterations in its physiology may contribute to the genesis and/or the maintenance of some clinical manifestations of AN and BN and may have an impact on the prognosis of AN.

Neuropeptides in eating disorders

The past decade has witnessed a dramatic acceleration in research on the role of the neuropeptides in the regulation of eating behavior and body weight homeostasis. This expanding research focus has been driven in part by increasing public health concerns related to obesity and the eating disorders anorexia nervosa (AN) and bulimia nervosa (BN). Preclinical advances have been facilitated by the development of new molecular and behavioral research methodologies. With a focus on clinical investigations in AN and BN, this article reviews research on selected hypothalamic and gut-related peptide systems with prominent effects on eating behavior. Studies of the orexigenic peptides neuropeptide Y and the opioid peptides have shown state-related abnormalities in patients with eating disorders. With respect to gut-related peptides, there appears to be substantial evidence for blunting in the meal-related release of the satiety promoting peptide cholecystokinin in BN. Fasting plasma levels of the orexigenic peptide ghrelin have been found to be elevated in patients with AN. As discussed in this review, additional studies will be needed to assess the role of nutritional and body weight changes in neuropeptide alterations observed in symptomatic eating disorder patients, and to identify stable trait-related abnormalities in neuropeptide regulation that persist in individuals who have recovered from an eating disorder.

Gastric pacing for morbid obesity: plasma levels of gastrointestinal peptides and leptin

OBJECTIVE

A gastric pacemaker has been developed to treat morbid obesity. Patients experience increased satiety, the ability to reduce food intake, and a resultant weight loss. However, the mechanism behind the changed eating behavior in paced patients is still under investigation.

RESEARCH METHODS AND PROCEDURES

This study was performed on 11 morbidly obese patients (mean BMI, 46.0 kg/m2) treated with gastric pacing. The peripheral blood levels of satiety signals of cholecystokinin (CCK), somatostatin, glucagon-like peptide-1 (GLP-1), and leptin were studied 1 month before gastric pacer implantation, 1 month after implantation, and 6 months after activation of electrical stimulation. Blood samples were drawn 12 hours after fasting and in response to a hypocaloric meal (270 kcal). Patients were followed monthly for vital signs and weight level.

RESULTS

Gastric pacing resulted in a significant weight loss of a mean of 10.4 kg (4.4 BMI units). No negative side effects or complications were observed during the treatment. After activation of the pacemaker, meal-related response of CCK and somatostatin and basal levels of GLP-1 and leptin were significantly reduced (p < 0.05) compared with the tests before gastric pacing. The weight loss correlated significantly with a decrease of leptin levels (R = 0.79, p < 0.01).

DISCUSSION

Gastric pacing is a novel and promising therapy for morbid obesity. Activation of the gastric pacer was associated with a decrease in plasma levels of CCK, somatostatin, GLP-1, and leptin. More studies are necessary to elucidate the correlations between satiety, weight loss, and digestive neuro-hormone changes.

The future of research on eating disorders

In the last several decades, research on the eating disorders has yielded important new knowledge, especially regarding the clinical characteristics and the treatment of individuals with Bulimia Nervosa. Challenging issues now confronting the field include how the eating disorders should be categorized, what factors underlie their development and persistence, and how they are best treated. New efforts based on the analysis of genetic factors, on the use of brain imaging and on the detailed analysis of behavioral disturbances hold promise for significantly advancing our understanding of these disorders in the next decade.

Peripheral signals in the control of satiety and hunger

PURPOSE OF REVIEW

Food intake is critical for survival and is a complex behavior with multiple levels of control. Short-term, meal-related signals arise from many sources including the gastrointestinal tract, the environment, and higher centers in the brain. As described in this review, inputs from the gastrointestinal tract can exert potent effects on meal initiation, meal termination, and meal frequency. The complex array of signals generated from the gastrointestinal system and from adipose tissue, which participate in the regulation of food intake, and specifically how these signals relate to satiety and hunger, is the focus of this review.

RECENT FINDINGS

Literature on the role of the well-studied gastrointestinal peptide, cholecystokinin, in satiety, in addition to its interaction with long-term adiposity signals in mediating food intake will be reviewed. In addition, literature on the gastrointestinal hormones glucagon-like-peptide 1, apolipoprotein A-IV and peptide YY, and how they may act to regulate satiety, is described. Finally, the newly discovered hormone, ghrelin, and how it relates to meal initiation and hunger is discussed.

SUMMARY

A better understanding of these systems and how they relate to body adiposity will prove to have important clinical applications. The available data suggest that interventions directed at multiple targets in the energy homeostasis system may be necessary to achieve and maintain weight loss.

A disturbance of gastric function in bulimia nervosa

BACKGROUND

Because the stomach plays an important role in the development of satiety, gastric function was examined in bulimia nervosa (BN).

METHODS

Sixteen patients with BN and 16 controls swallowed an inflatable bag, which was positioned in the proximal stomach. Minimal distending pressure (MDP), the pressure needed to overcome intraabdominal pressure, was determined. Gastric volume was recorded after subjects drank a liquid meal.

RESULTS

MDP was similar in patient and control groups (7.56 +/- 2.13 vs. 7.13 +/- 2.06 mmHg; t =.57, df = 30, p =.58). Average postmeal gastric relaxation was significantly lower in the patient group (29.7 +/- 97.8 vs. 105.1 +/- 103.3 mL; t = 2.13, df = 30, p =.042).

CONCLUSIONS

Stomach relaxation following food consumption is significantly diminished in patients with BN. Physiologic abnormalities of stomach function in BN may contribute to the perpetuation of disturbances in behavior in this disorder.

Eating disorders

Eating disorders rank among the most debilitating psychiatric disturbances that affect young women. Knowledge has increased in recent years about the two major eating disorders, anorexia nervosa (AN) and bulimia nervosa (BN); however, much remains unknown. This review article will provide an overview of the epidemiology, proposed risk factors and clinical features of AN, and BN, as well as current recommendations for evaluation and treatment of these disorders.

Involvement of cholecystokinin/gastrin-related peptides and their receptors in clinical gastrointestinal disorders

In this paper the possible roles of cholecystokinin (CCK), gastrin, or gastrin-related peptides and their receptors in human gastrointestinal diseases are reviewed. For CCK/CCK(A) receptors (CCK(A)-R), the evidence for their proposed involvement in diseases caused by impaired CCK release or CCK(A)-R mutations, pancreatic disorders (acute/chronic pancreatitis), gastrointestinal motility disorders (gallbladder disease, irritable bowel syndrome), pancreatic tumor growth and satiety disorders, is briefly reviewed. The evidence that has established the involvement of gastrin/CCK(B)-R in mediating the action of hypergastrinaemic disorders, mediating hypergastrinaemic effects on the gastric mucosa (ECL hyperplasia, carcinoids, parietal cell mass), and acid-peptic diseases, is reviewed. The evidence for their possible involvement in mediating growth of gastric and pancreatic tumours and possible involvement of gastrin-related peptides in colon cancers, is reviewed briefly.

Binge size increases with body mass index in women with binge-eating disorder

OBJECTIVE

To determine whether meal size is related to body mass index (BMI) in obese subjects with binge-eating disorder (BED).

RESEARCH METHODS AND PROCEDURES

Five groups of subjects each consumed two laboratory-test meals on nonconsecutive days. Forty-two women, categorized by BMI and BED diagnosis, were instructed to "binge" during one meal and to eat "normally" during another. Eighteen women had BMI values >38 kg/m(2) (more-obese) and 17 had BMI values between 28 to 32 kg/m(2) (less-obese). Twelve of the more-obese and nine of the less-obese individuals met Diagnostic and Statistical Manual (DSM)-IV criteria for BED. Seven normal-weight women also participated as controls.

RESULTS

Subjects with BED ate significantly more in both meals than subjects without BED. Binge meals were significantly larger than normal meals only among subjects with BED. The more-obese subjects with BED ate significantly more than the less-obese subjects with BED, but only when they were asked to binge. Intake of the binge meal was significantly, positively correlated with BMI among subjects with BED. Subjects with BED reported significantly higher satiety ratings after the binge than after the normal meal, but subjects without BED reported similar ratings after both meals. Regardless of instructions and diagnosis, obese subjects consumed a significantly higher percentage of energy from fat (38.5%) than did normal-weight subjects (30.8%).

DISCUSSION

During binge meals, the energy intake of subjects with BED is greater than that of individuals of similar body weight without BED and is positively correlated with BMI.

A new animal model of binge eating: key synergistic role of past caloric restriction and stress

Dieting and stress are important in the etiology and maintenance of eating disorders, and dieting strongly predicts stress-induced overeating in humans. We hypothesized that caloric restriction and stress interact in a unique manner to promote binge eating. To test this hypothesis, a group of young female rats were cycled through a restriction period (4 days of 66% of control food intake) followed by 6 days of free feeding prior to being stressed by acute foot shock. After three of these cycles, the food intake of rats exposed only to restriction (R), or only to stress (S), did not differ from controls. However, R+S rats that were restricted and refed, despite normal body weight and food intake after free feeding, engaged in a powerful bout of hyperphagia when stressed (Experiment 1). The R + S effect was replicated in an older group of rats (Experiment 2). The hyperphagia was characteristically binge-like, it constituted a 40% selective increase in highly palatable (HP) food (P < .001) over a discrete period of time (within 24 h post-stress), and reflected feeding for reward (higher HP:chow ratio) over metabolic need as occurred after restriction (higher chow:HP ratio). Subsequent experiments revealed that binge eating did not occur if only chow was available (Experiment 3) or if restriction-refeeding (R-R) did not proximally precede stress (Experiment 4). Experiment 5 revealed that a history of R-R cycles followed by only one stress episode was sufficient to increase intake to 53% above controls as early as 2 h after stress (P < .001). This animal model of binge eating should facilitate investigations into the neurochemical changes induced by dieting and environmental stress to produce disordered eating and provide a preclinical tool to test preventive strategies and treatments more relevant to bulimia nervosa, multiple cases of binge eating disorder (BED) and binge-purge type anorexia nervosa.

Aetiopathogenesis and pathophysiology of bulimia nervosa: biological bases and implications for treatment

Bulimia nervosa is an eating disorder characterised by recurrent episodes of binge eating and associated efforts to purge the ingested calories through self-induced vomiting, laxative or diuretic abuse, fasting or intensive exercise. The aetiopathogenesis and pathophysiology of the disorder are currently unclear. Biological bases have been proposed repeatedly, based on several lines of evidence: hunger, satiety and food choice are regulated by neurotransmitters and neuropeptides, and impairment of eating habits may be related to alterations in the secretion of these chemicals; genetic studies suggest that these neurotransmitter systems are dysfunctional in individuals with bulimia nervosa; and the frequent comorbidity of bulimia nervosa with major depressive and obsessive-compulsive disorders, conditions in which multiple alterations of brain biochemical functions have been demonstrated. Data in the literature suggest that levels of noradrenaline (norepinephrine) and serotonin (5-hydroxytryptamine; 5-HT) are lower in individuals with bulimia nervosa than in healthy controls. Levels of dopamine are similar to, or lower than, those in controls. After remission of the disorder, noradrenergic function returns to that seen in controls, whereas dopaminergic and serotonergic function rebound to levels higher than in controls. Among the neuropeptides, alterations in the levels of neuropeptide Y, peptide YY, beta-endorphin, corticotrophin-releasing hormone, somatostatin, cholecystokinin and vasopressin have been found in the symptomatic phase of bulimia nervosa, with a return to levels seen in controls after remission. Pharmacological treatment of bulimia nervosa that is directed at correction of the neurochemical alterations observed is difficult because of the complexity of the impairments. However, such treatment is necessary and should be continued long after symptomatic remission to ensure reinstitution of cerebral biochemical homeostasis.

Eating behavior in anorexia nervosa--an excess of both orexigenic and anorexigenic signalling?

Anorexia nervosa (AN) is a disorder characterized by abnormal eating behavior, weight regulation, and disturbances in attitudes and perceptions toward body weight and shape. Although progress has been made in the treatment of AN, a substantial portion of patients have a limited response to treatment. Multiple endocrine and metabolic changes occur after prolonged starvation, conserving energy and protein. A number of the endocrine findings in patients with AN may be secondary to adaptive mechanisms. However, AN differs from simple starvation in that excess of both feeding-stimulatory (orexigenic) and feeding-inhibitory (anorexigenic) signalling is characteristic, producing the "mixed" signal about satiety and desire to feed. This leads to a failure of the adaptive feeding response that is initiated by a decrease in leptin, an adiposity signal from fat tissue, and the resultant increase and decrease of orexigenic and anorexigenic signalling, respectively. The hypothesis of unbalanced shift of feeding-regulatory circuitry places anorexigenic corticotropin-releasing factor and orexigenic neuropeptide Y in the final common neurobiological substrate for AN. Therapeutic intervention using such receptor antagonists may lead to more successful and targeted psychopharmacological treatment.

Gastric capacity in normal, obese, and bulimic women

One function of the stomach is as a reservoir for food; hence, the stomach's capacity may limit the amount of food ingested. A stomach with a large capacity has been associated with bigger test meals. We compared the stomach capacity of three groups of women: normal (n=10), obese (n=11), and bulimic (n=10). Following an overnight fast, gastric capacity was estimated by filling a gastric balloon with water at 100 ml/min, with pauses for measuring intragastric pressure. One estimate was based on the maximum volume the subject could tolerate as indicated by a maximal rating of abdominal discomfort. Another estimate was based on the volume required to produce a given rise of intragastric pressure, 5 cm H(2)O. A third related measure was based on a maximal rating of fullness. Based on these estimates, the gastric capacity of the bulimics was the largest, with the obese subjects intermediate. We then separated the obese subjects according to whether they reported binge eating (n=6) or not (n=5). The gastric capacity of the binge-eating subset was similar to the bulimics, and the nonbinge-eating subset was similar to the normals. Thus, gastric capacity appears more related to binge eating behavior than to body weight.

The effect of cholecystokinin in controlling appetite and food intake in humans

The present review of the satiating effect of cholecystokinin in humans has revealed that cholecystokinin is a physiological satiety factor in humans. The results demonstrate the efficacy of the satiating actions of exogenous and endogenous CCK in humans. The therapeutic potential of CCK analogues cannot be estimated until further studies are performed that demonstrate the efficacy of CCK analogues for decreasing body weight, and the safety of CCK when administered repetitively for prolonged periods.

Estradiol, CCK and satiation

Estradiol has long been known to inhibit feeding in animals, but the mechanism(s) mediating its effects have not been clear. Demonstrations that estradiol's feeding effects are expressed as decreases in meal size coupled with the emerging consensus that cholecystokinin (CCK) released from the small intestines during meals is a physiological negative-feedback signal controlling meal size (i.e. satiation) suggested a new approach to the problem of the mechanisms of estradiol's inhibitory effect on feeding. Progress on this approach is reviewed here. Experimental manipulations of exogenous and endogenous CCK and estradiol have produced converging evidence that estradiol cyclically increases the activity of the CCK satiation-signaling pathway so that meal size and food intake decrease during the ovulatory or estrus phase of the ovarian cycle. This is a striking example of the modulation of the operation of a control of meal size by the physiological context in which the meal occurs. Estradiol also produces a tonic decrease in meal size, but this apparently does not involve the CCK satiation-signaling pathway. Where and how estradiol acts to increase the potency of the CCK satiating-signaling pathway are not known. Several possible sites are suggested by the observations that estradiol treatment increases feeding- and CCK-induced expression of c-Fos in ovariectomized animals in brain areas including the nucleus tractus solitarius, paraventricular nucleus of the hypothalamus, and central nucleus of the amygdala. Tests with null mutation mice indicate that estrogen receptor-alpha is necessary for estradiol's feeding effects. Finally, the possibilities that estradiol exerts important influences on normal or disordered eating in women are discussed. It is concluded that estradiol exerts a biologically significant action on CCK satiation in animals. Further research to determine whether this action of estradiol has a role in the pathogenesis, course, or treatment of disordered eating in women is indicated.

Ondansetron attenuates CCK induced satiety and c-fos labeling in the dorsal medulla

Serotonin 5-HT(3) antagonists have been suggested for treatment of several disorders involving altered gastrointestinal (GI) function. CCK also has well documented GI actions on both food intake and vago-vagal reflexes. To evaluate potential interactions, the effect of a 5-HT(3) antagonist, ondansetron, on exogenous CCK induced satiety and c-fos activation was determined. Ondansetron reduced both actions of CCK by approximately 50%. The reduction in c-fos was localized to a specific subregion of the dorsal medulla, suggesting that a distinct subpopulation of CCK receptive fibers are modulated by 5-HT(3) ligands. Treatments using 5-HT(3) antagonists also may affect endogenous CCK functions.

Dysfunctional eating in the eating disorders

Aberrant eating patterns in the eating disorders have been observed across various laboratory-based and clinical studies. It is now clear that problems in experiencing and expressing hunger, appetite, and satiety in anorexia and bulimia nervosa are likely to perpetuate the disorders once established. Whether problems in appetite regulation are primary or secondary to the development of the disorders is unknown. In studies examining indices of appetite regulation after treatment, there still remain significant levels of eating abnormality. This suggests that the main goals of treatment, including restoration of body weight in anorexia nervosa, abstaining from dieting in anorexia or bulimia nervosa, and reducing or abstaining from binge eating, do not correct some features of abnormal eating. The efficacy of nutritional counseling and specific nutritional management programs have been tested, and these seem to produce positive outcomes in improving eating behavior. Direct behavioral interventions to change eating patterns also have been examined, and these too seem to produce benefits that may be incorporated into CBT. Greater collaboration and cooperation between researchers and clinicians in addressing dysfunctional eating in the eating disorders will highlight improvements in treatment for identifiable eating abnormalities and will further the understanding of the human appetite system.

Cognitive-behavioral therapy and nutritional counseling in the treatment of bulimia nervosa and binge eating

The goals of manual-based cognitive-behavioral therapy (CBT) and nutritional counseling for eating disorders are similar, namely, eliminating dysfunctional patterns of eating. Modifying these behaviors requires specific therapeutic expertise in the principles and procedures of behavior change that is not typically part of the training of nutritionists and dieticians or mental health professionals without specific expertise. We discuss ways in which principles of behavior change can be applied to eating disorders by non-CBT experts. Specific nutritional rehabilitation programs have the potential to augment CBT in addressing the array of appetitive abnormalities present in eating disorder patients. The dysfunctional appetitive, hedonic, and metabolic characteristics of patients with bulimia nervosa (BN) and binge eating disorder are reviewed. These abnormalities constitute potential target areas that might be more fully addressed by nutritional interventions designed to restore normal appetitive function.

Cerebrospinal fluid monoamines in Prader-Willi syndrome

BACKGROUND

The behavioral phenotype of Prader-Willi syndrome (PWS) suggests hypothalamic dysfunction and altered neurotransmitter regulation. The purpose of this study was to examine whether there was any difference in the concentrations of monoamine metabolites in the cerebrospinal fluid (CSF) in PWS and non-PWS comparison cases.

METHODS

The concentration of monoamine metabolites in CSF was determined in 13 children and adolescents with PWS diagnosed on clinical and genetic criteria. The concentrations were compared with those from 56 comparison cases in healthy and other contrast groups.

RESULTS

The concentrations of dopamine and particularly serotonin metabolites were increased in the PWS group. The differences were most prominent for 5-hydroxyindoleacetic acid. The increased concentrations were found in all PWS cases independently of age, body mass index, and level of mental retardation.

CONCLUSIONS

The findings implicate dysfunction of the serotonergic system and possibly also of the dopamine system in PWS individuals, and might help inform future psychopharmacologic studies.

Functional gastrointestinal disorders and eating disorders. Relevance of the association in clinical management

BACKGROUND

As functional gastrointestinal disorders (FGID) are common in eating disorder patients, we aimed to assess past eating disorders in patients referred for current FGID.

METHODS

One hundred and twenty-seven consecutive FGID outpatients and 163 patients with gallstone disease (GD) were enrolled. All patients were interviewed to detect GI symptoms (by means of the GI Symptom Rating Scale), lifetime eating disorders (on the basis of DSM-IV criteria), and current psychologic distress (on the Hospital Anxiety and Depression Scale).

RESULTS

Past eating disorders were significantly more prevalent in FGID (15.7%) than in GD patients (3.1%) (chi-square = 14.6, P < 0.001). FGID patients with past eating disorders were significantly younger, more educated, more psychologically distressed, more dyspeptic, and more were women than FGID patients without past eating disorders.

CONCLUSIONS

This study confirms the previously found association between functional GI symptoms and eating disorders and shows that functional GI symptoms may still persist even after the recovery from eating disorders, particularly in psychologically distressed patients.

Hormonal regulation of appetite and food intake

Several clinical disorders are strongly influenced by hormones involved in appetite and weight regulation. Obesity and eating disorders are of major importance, because they are associated with severe morbidity and considered to be among the greatest health problems in the Western world today. This review describes recent findings in hormonal regulation of food intake by substances acting both centrally, such as corticotropin-releasing factor, neuropeptide Y and leptin, and peripherally, such as cholecystokinin and somatostatin. Sex hormones and glucocorticoids play an important role in long-term regulation of metabolism. The role of these hormones in appetite and weight changes during life as well as during pregnancy and lactation is discussed. Furthermore, the development of obesity and eating disorders is influenced, in particular, by steroid hormones. Treatment with sex hormones, as in hormone replacement therapy, affects appetite and weight and may have beneficial effects in preventing android obesity. Currently, there is great effort in developing endogenous neurohumoral substances into effective drugs for the treatment of obesity and eating disorders. Leptin and neuropeptide Y analogues are of interest as potential antiobesity agents.

Fluoxetine normalizes increased cardiac vagal tone in bulimia nervosa

Patients with bulimia nervosa have been reported to respond to treatment with the serotonin uptake inhibitor fluoxetine. In a preliminary study, which had a small sample size, women with bulimia nervosa were reported to have elevated cardiac vagal tone. We investigated cardiac vagal tone in women with bulimia nervosa before and after treatment with fluoxetine. At baseline, resting cardiac vagal tone, deduced from the respiratory component of heart rate variability, was quantified in 41 healthy volunteer women and in 25 women with bulimia nervosa. The bulimic women received in a parallel-group design, double blind, either placebo or fluoxetine 60 mg/24 hr for 8 weeks. All patients participated in behavioral therapy. Resting cardiac vagal tone was measured again at the end of the treatment. Women with bulimia nervosa had higher cardiac vagal tone than age-matched healthy volunteer women. Placebo had no effect on cardiac vagal tone. Fluoxetine reduced cardiac vagal tone among the women with bulimia nervosa to a level similar to the healthy volunteer women. Women with bulimia nervosa have elevated resting cardiac vagal tone. Fluoxetine normalized the elevated resting cardiac vagal tone among the women with bulimia nervosa. At both the central and peripheral levels, vagal neurons are endowed with serotonin-3 receptors. In vitro, fluoxetine desensitizes or blocks serotonin-3 receptors. A controlled trial of serotonin-3 receptor blockers is warranted in bulimia nervosa.

Sulfated cholecystokinin (26-33) induces mild taste aversion conditioning in rats when administered by three different routes

We investigated the ability of sulfated cholecystokinin (26-33) (CCK-8) and cholecystokinin (30-33) (CCK-4) to induce taste aversion or avoidance conditioning (TAC) in a one-bottle testing paradigm after either intravenous (i.v.), intracerebroventricular (i.c.v.), or intraperitoneal (i.p.) administration. Significant TAC was induced by i.p. administration of CCK-8 at 0.1 but not at 0.025, 0.5, or 1.0 micromol/kg; the TAC was not robust and, in this case, not even dose related. I.p. administration of CCK-4 at 0.05, 0.1, 0.5, or 1.0 micromol/kg did not induce TAC, replicating other studies from our lab. Mild but significant TAC was also induced by i.v. administration of CCK-8 (at 0.025 and 1.0 but not 0.1 or 0.5 micromol/kg) but not by i.v. administration of CCK-4 (at 0.05, 0.1, 0.5, or 1.0 micromol/kg). Finally, mild but significant TAC was induced by i.c.v. (i.e., lateral ventricular) administration of CCK-8 (at 0.0015 but not at 0.015 micromol/brain) but not by i.c.v. administration of CCK-4 (at 0.005 or 0.010 micromol/brain). Because CCK-4 failed to induce TAC, CCK-8 apparently induced TAC via all three routes by an action at a CCK(a), not CCK(B), receptor mechanism. Because i.c.v. or i.v. administrations of CCK-8 were not more efficacious than i.p. administration, the taste avoidance induced by i.p. administration of CCK-8 was not so mild simply because it failed to reach a critical central locus adequately or because it failed to be delivered at a critical speed (i.e., via i.v. injections). We demonstrate that CCK-8 can induce mild TAC at either peripheral or central sites and suggest that these effects of CCK-8 may be independent and may be a sign of salience but not necessarily of toxicosis.

Eating disorders

The eating disorders remain perplexing treatment challenges. These disorders are best understood through the clustering of their symptoms and with a multidimensional model. Treatment must follow from the observed symptoms and cannot always follow a standardized course as is done in other psychiatric disorders. CBT is the most efficacious treatment for both AN and BN.

Effects of preloads of differing energy and macronutrient content on eating behavior in bulimia nervosa

Evidence suggests that bulimics demonstrate blunted satiety possibly due to repeated episodes of overeating. This suggestion was tested further by comparing responses to yogurt preloads differing in carbohydrate and fat relative to a lower energy control yogurt in 12 bulimics and 12 age- and weight-matched controls. Participants were tested on three occasions at lunchtime. On each occasion, appetite and mood were rated before and after receiving a lunch of raspberry yogurt (350 g). Covert manipulation of energy and nutrient content was achieved by matching the yogurts on sensory properties and formulating a control yogurt (161 kcal), a high-fat version (357 kcal: 65% calories from fat), and a high-carbohydrate version (357 kcal: 81% calories from carbohydrate). Although there were no differential effects of the preloads on intake of an ad libitum test meal given 5 hr later in either the control or bulimic groups, there were significant differences in test meal energy intake between groups. On average and with all conditions combined, bulimics ate significantly fewer calories (775 +/- 167 kcal) than controls (1182 +/- 94 kcal) and consumed a greater percentage of calories from carbohydrate than controls. Bulimics restricted their intake relative to controls, and chose foods low in fat. This study provides further evidence of restricted eating in bulimia nervosa when the opportunity to purge is not available. Furthermore, the present study suggests that intake by bulimics is not influenced by nutrient content per se but by consideration of the caloric value of foods and the consequences of eating certain foods for weight control.

Reduced meal-related gastrointestinal hormone response to adrenocorticotropic hormone stimulation test in female athletes

This study was undertaken to elucidate the impact of hypercortisolism in meal-related gastrointestinal hormone secretion and appetite in female endurance athletes. Thirteen elite runners and seven sedentary women participated on two occasions, either receiving intravenous injection of 250 micrograms synthetic adrenocorticotropic hormone (ACTH) 1-24 or saline. Blood samples were collected before and after the injection, and then in connection with a standardized meal. Serum concentrations of cortisol, cholecystokinin (CCK), gastrin, insulin and glucose were analyzed. Self-ratings of appetite were assessed by visual analog scales. Elevated basal levels of cortisol and glucose were found in the athletes. ACTH-induced cortisol response was comparable between groups, but a negative correlation between basal cortisol levels and the ACTH-induced response was found. In sedentary women, ACTH challenge enhanced meal-related CCK and gastrin responses, whereas athletes showed a blunted response of these hormones combined with decreased satiety and reduced levels of insulin. Blunted meal-related response of gastrointestinal hormones and decreased satiety in female runners after ACTH stimulation compared to sedentary women are probably due to difference in the effect of cortisol, which could be explained by cortisol insensitivity as a result of basal hypercortisolism in the athletes. Decreased CCK response and satiety in female athletes may reflect increased nutritional requirements.

The controls of fat intake

OBJECTIVE

To present evidence on the control of the size of fatty meals in the context of the result of interactions of orosensory positive-feedback and postingestive negative-feedback mechanisms activated by fat stimuli in rodent models of feeding and of obesity.

METHOD

We examined the effects of orosensory stimuli and postingestive stimuli in Sprague-Dawley rats, and in the genetically obese Zucker (fa/fa) rat. We used the sham feeding rat preparation to isolate the orosensory stimulating and postingestive satiating properties of oils. The negative-feedback satiating properties of fats were elicited by intestinal infusions of fats. The Zucker rat is an animal model of obesity with abnormal control of meal size and increased intake of fats. Using this model we further examined the interaction of orosensory and postingestive stimuli in the control of meal size.

RESULTS

The orosensory properties of fats are sufficient to drive sham feeding and are not dependent on the postabsorptive metabolic consequences of oils in normal and Zucker rats. The satiating action of fats must act at preabsorptive sites because reduction of intake occurs before absorption of fat. The satiating potency of fats is dependent upon their specific chemical conformation and is mediated by endogenous cholecystokinin and afferent fibers of the abdominal vagus. We have found that oils produce significantly more orosensory positive feedback in obese Zucker rats than in lean rats in experimental tests of preference. This is probably the major abnormal mechanism responsible for the increased preference for fats that is characteristic of obese rats because we have not identified any significant decrease in the postingestive satiating potency of fats in obese Zucker rats.

CONCLUSIONS

Fat intake is controlled by both orosensory and postingestive stimuli in normal and genetically obese rodents. In the Zucker rat the investigation of this model of genetic obesity has produced data that is congruent with the preference for high fat foods in obese people and suggests further experiments directed toward a deeper understanding of the controls of fat intake and how they are disordered.

Common biological pathways in eating disorders and obesity

The purpose of this article is to summarize briefly potential biological pathways that are common among anorexia nervosa, bulimia nervosa, and obesity. We conclude that data on serotonergic and beta-endorphin regulatory systems provide the most promising leads for potential trait-based etiological theories. We then discuss the contribution of current data to a better understanding of the etiology and maintenance of eating disorders. Finally, we comment on how the exploration for common biological mechanisms highlights problems in nosological diagnosis (i.e., the lack of symptom specificity among disorders) and obscures the etiological significance of social stressors and cultural factors.

The hormonal response to intravenous 5-hydroxytryptophan in bulimia nervosa

In recent years evidence has accumulated to implicate a disturbance in serotonin function in the eating disorder bulimia nervosa. This study employs a neuroendocrine technique to assess the effect of intravenous 5-hydroxytryptophan, the immediate precursor to serotonin, on peripheral hormones in bulimia nervosa subjects and controls. Blunted prolactin and growth hormone responses were observed among bulimia nervosa subjects; the possible pathophysiology and implications of the findings are discussed.