Hunger in humans induced by MK-329, a specific peripheral-type cholecystokinin receptor antagonist

Appetite- and Weight-Regulating Neuroendocrine Circuitry in Hypothalamic Obesity

Since hypothalamic obesity (HyOb) was first described over 120 years ago by Joseph Babinski and Alfred Fröhlich, advances in molecular genetic laboratory techniques have allowed us to elucidate various components of the intricate neurocircuitry governing appetite and weight regulation connecting the hypothalamus, pituitary gland, brainstem, adipose tissue, pancreas, and gastrointestinal tract. On a background of an increasing prevalence of population-level common obesity, the number of survivors of congenital (eg, septo-optic dysplasia, Prader-Willi syndrome) and acquired (eg, central nervous system tumors) hypothalamic disorders is increasing, thanks to earlier diagnosis and management as well as better oncological therapies. Although to date the discovery of several appetite-regulating peptides has led to the development of a range of targeted molecular therapies for monogenic obesity syndromes, outside of these disorders these discoveries have not translated into the development of efficacious treatments for other forms of HyOb. This review aims to summarize our current understanding of the neuroendocrine physiology of appetite and weight regulation, and explore our current understanding of the pathophysiology of HyOb.

The uncovering and characterization of a CCKoma syndrome in enteropancreatic neuroendocrine tumor patients

OBJECTIVE

Neuroendocrine tumors in the pancreas and the gastrointestinal tract may secrete hormones which cause specific syndromes. Well-known examples are gastrinomas, glucagonomas, and insulinomas. Cholecystokinin-producing tumors (CCKomas) have been induced experimentally in rats, but a CCKoma syndrome in man has remained unknown until now.

MATERIAL AND METHODS

Using a panel of immunoassays for CCK peptides and proCCK as well as for chromogranin A, we have examined plasma samples from 284 fasting patients with gastroenteropancreatic neuroendocrine tumors. In hyperCCKemic samples, plasma CCK was further characterized by chromatography.

RESULTS

One of the patients displayed gross hyperCCKemia. She was a 58-year old woman with a pancreatic endocrine tumor, liver metastases, 500-1000-fold elevated basal CCK concentration in plasma, diarrhea, severe weight loss, recurrent peptic ulcer and bilestone attacks from a contracted gallbladder. The CCK concentrations in plasma were not affected by resection of the pancreatic tumor, but decreased to normal after hemihepatectomy with removal of the metastases.

CONCLUSION

A CCKoma syndrome with severe hypersecretion of CCK exists in man. The duodenal ulcer disease and diarrhea with permanently low gastrin in plasma suggest that CCKomas may mimic gastrinoma-like symptoms, because CCK peptides are full agonists of the gastrin/CCK-B receptor.

Critical review evaluating the pig as a model for human nutritional physiology

The present review examines the pig as a model for physiological studies in human subjects related to nutrient sensing, appetite regulation, gut barrier function, intestinal microbiota and nutritional neuroscience. The nutrient-sensing mechanisms regarding acids (sour), carbohydrates (sweet), glutamic acid (umami) and fatty acids are conserved between humans and pigs. In contrast, pigs show limited perception of high-intensity sweeteners and NaCl and sense a wider array of amino acids than humans. Differences on bitter taste may reflect the adaptation to ecosystems. In relation to appetite regulation, plasma concentrations of cholecystokinin and glucagon-like peptide-1 are similar in pigs and humans, while peptide YY in pigs is ten to twenty times higher and ghrelin two to five times lower than in humans. Pigs are an excellent model for human studies for vagal nerve function related to the hormonal regulation of food intake. Similarly, the study of gut barrier functions reveals conserved defence mechanisms between the two species particularly in functional permeability. However, human data are scant for some of the defence systems and nutritional programming. The pig model has been valuable for studying the changes in human microbiota following nutritional interventions. In particular, the use of human flora-associated pigs is a useful model for infants, but the long-term stability of the implanted human microbiota in pigs remains to be investigated. The similarity of the pig and human brain anatomy and development is paradigmatic. Brain explorations and therapies described in pig, when compared with available human data, highlight their value in nutritional neuroscience, particularly regarding functional neuroimaging techniques.

Immunoglobulin-like domain containing receptor 1 mediates fat-stimulated cholecystokinin secretion

Cholecystokinin (CCK) is a satiety hormone produced by discrete enteroendocrine cells scattered among absorptive cells of the small intestine. CCK is released into blood following a meal; however, the mechanisms inducing hormone secretion are largely unknown. Ingested fat is the major stimulant of CCK secretion. We recently identified a novel member of the lipoprotein remnant receptor family known as immunoglobulin-like domain containing receptor 1 (ILDR1) in intestinal CCK cells and postulated that this receptor conveyed the signal for fat-stimulated CCK secretion. In the intestine, ILDR1 is expressed exclusively in CCK cells. Orogastric administration of fatty acids elevated blood levels of CCK in wild-type mice but not Ildr1-deficient mice, although the CCK secretory response to trypsin inhibitor was retained. The uptake of fluorescently labeled lipoproteins in ILDR1-transfected CHO cells and release of CCK from isolated intestinal cells required a unique combination of fatty acid plus HDL. CCK secretion secondary to ILDR1 activation was associated with increased [Ca2+]i, consistent with regulated hormone release. These findings demonstrate that ILDR1 regulates CCK release through a mechanism dependent on fatty acids and lipoproteins and that absorbed fatty acids regulate gastrointestinal hormone secretion.

Gastrointestinal targets of appetite regulation in humans

The aim of this paper is to describe and discuss relevant aspects of the assessment of physiological functions - and related biomarkers - implicated in the regulation of appetite in humans. A short introduction provides the background and the present state of biomarker research as related to satiety and appetite. The main focus of the paper is on the gastrointestinal tract and its functions and biomarkers related to appetite for which sufficient data are available in human studies. The first section describes how gastric emptying, stomach distension and gut motility influence appetite; the second part describes how selected gastrointestinal peptides are involved in the control of satiety and appetite (ghrelin, cholecystokinin, glucagon-like peptide, peptide tyrosin-tyrosin) and can be used as potential biomarkers. For both sections, methodological aspects (adequacy, accuracy and limitation of the methods) are described. The last section focuses on new developments in techniques and methods for the assessment of physiological targets involved in appetite regulation (including brain imaging, interesting new experimental approaches, targets and markers). The conclusion estimates the relevance of selected biomarkers as representative markers of appetite regulation, in view of the current state of the art.

Cholecystokinin, glucose dependent insulinotropic peptide and glucagon-like peptide 1 secretion in children with anorexia nervosa and simple obesity

Cholecystokinin (CCK), glucose dependent insulinotropic peptide (GIP), and glucagon-like peptide 1 (GLP-1) regulate satiety as enterogastrons and incretins. They also directly affect the satiety centers. Therefore, these peptides may participate in the pathogenesis of eating disorders. CCK, GIP, and GLP-1 secretion were studied in 13 adolescent girls suffering from simple obesity, 13 girls with anorexia nervosa, and 10 healthy girls. Each girl was subjected to an oral glucose tolerance test (OGTT) and standard meal test. Blood was collected before stimulation and at 15, 30, 60, and 120 min. The concentrations of all peptides were determined by RIA commercial kits. Fasting and postprandial levels of these peptides as well as integrated outputs were measured. High postprandial levels of CCK observed in the girls with anorexia may aggravate the course of this disease by intensifying nausea and vomiting. Low postprandial level of GLP-1 in girls with simple obesity may be responsible for excessive ingestion of food and weaker inhibition of gastric emptying, which also leads to obesity.

Association of cholecystokinin 1 receptor and beta3-adrenergic receptor polymorphisms with midlife weight gain

We investigated the relationship of polymorphisms in the cholecystokinin 1 receptor [CCK1R; G to T (n-128), A to G (n-81)] and the beta3-adrenergic receptor (beta3-AR; Trp64Arg) with midlife weight gain. The participants were 1012 Japanese men and women (40 to 59 years of age). Their weight at 18 years old was obtained from a questionnaire. Weight change was defined as the current weight minus the weight at 18 years old. Subjects were grouped into four categories by these genotypes: W/W=noncarriers, W/H=Arg64 carriers of the beta3-AR, H/W=T (n-128) or G (n-81) carriers of the CCK1R, H/H=T (n-128) or G (n-81) and Arg64 carriers. In men, the interaction between the CCK1R and beta3-AR polymorphisms was significant (two-way ANOVA, p < 0.05), but neither the CCK1R nor the beta3-AR was individually associated with weight gain. The H/H group showed a higher possibility of weight gain of 10 kg or more compared with the W/W group in men. The odds ratio for weight gain (> or =10 kg) of H/H was 2.54 (95% confidence interval: 1.50 to 4.30) compared with W/W. In women, neither main effect nor interaction was significant. These results suggest that the combination of CCK1R and the beta3-AR polymorphisms is a contributing factor for midlife weight gain in men.

Biomarkers of satiation and satiety

This review's objective is to give a critical summary of studies that focused on physiologic measures relating to subjectively rated appetite, actual food intake, or both. Biomarkers of satiation and satiety may be used as a tool for assessing the satiating efficiency of foods and for understanding the regulation of food intake and energy balance. We made a distinction between biomarkers of satiation or meal termination and those of meal initiation related to satiety and between markers in the brain [central nervous system (CNS)] and those related to signals from the periphery to the CNS. Various studies showed that physicochemical measures related to stomach distension and blood concentrations of cholecystokinin and glucagon-like peptide 1 are peripheral biomarkers associated with meal termination. CNS biomarkers related to meal termination identified by functional magnetic resonance imaging and positron emission tomography are indicators of neural activity related to sensory-specific satiety. These measures cannot yet serve as a tool for assessing the satiating effect of foods, because they are not yet feasible. CNS biomarkers related to satiety are not yet specific enough to serve as biomarkers, although they can distinguish between extreme hunger and fullness. Three currently available biomarkers for satiety are decreases in blood glucose in the short term (<5 min), which have been shown to be involved in meal initiation; leptin changes during longer-term (>2-4 d) negative energy balance; and ghrelin concentrations, which have been implicated in both short-term and long-term energy balance. The next challenge in this research area is to identify food ingredients that have an effect on biomarkers of satiation, satiety, or both. These ingredients may help consumers to maintain their energy intake at a level consistent with a healthy body weight.

Elevated plasma cholecystokinin and appetitive ratings after consumption of a liquid meal in humans

OBJECTIVE

This study had two objectives. The first was to evaluate the possibility that, in a previous study, a soup preload augmented the reduction of food intake in a test meal induced by an exogenous infusion of cholecystokinin (CCK) because the soup also endogenously released CCK. The second was to compare CCK release by soup between men and women to determine whether the increased satiating effectiveness of soup in women as opposed to men could have been partly attributable to differences in CCK release.

METHODS

By using a bioassay that measures all of its known isoforms, we determined plasma CCK levels at baseline and at several times postprandially in eight healthy, non-obese men and women (four of each sex). Each subject ingested 800 g of tomato soup, which was followed 30 min later by 300 g of a yogurt shake. Appetitive ratings were also collected and related to CCK levels.

RESULTS

Ingestion of tomato soup significantly increased plasma CCK levels by 3.81 pmol/L (+/- 1.21 standard error, P = 0.016) over baseline within 30 min in all subjects combined. When CCK concentrations at 5 min after soup and 5 min after yogurt were averaged, the women's mean averaged concentration was 5.58 pmol/L (+/- 1.994, t = 2.80, P = 0.0073) higher than the men's. The elevated levels persisted but did not rise further upon consumption of the yogurt shake. Hunger ratings declined and fullness ratings increased after eating, although patterns of ratings did not match exactly patterns of CCK release.

CONCLUSIONS

A large quantity of tomato soup stimulates significant CCK release; therefore, some of the satiating effects of soup preloads could have been mediated by an elevation in endogenous CCK.

The effects of a peripherally acting cholecystokinin1 receptor antagonist on food intake in rats: implications for the cholecystokinin-satiety hypothesis

The observation that systemic administration of the peptide cholecystokinin (CCK) inhibits food intake in mammalian species has led to the hypothesis that endogenous peripheral CCK released from the small intestine during a meal acts as a satiety factor. It was predicted that if CCK does play an important role in satiety, then systemic administration of a specific CCK receptor antagonist should block the effects of the endogenous peptide released during a meal and increase food intake. The present study was undertaken to test the hypothesis by investigating the effects of the cholecystokinin(1) (CCK(1)) receptor antagonist N-alpha-3'-quinolinoyl-D-Glu-N,N-dipentylamide dicyclohexylammonium (A70104), which is unlikely to cross the blood-brain barrier, on food intake in rats. A70104 (20-200 microg/kg, i.p.) had no any significant effect on the intake of a test meal in rats under different experimental conditions. However, pretreatment of rats with A70104 (50 microg/kg, i.p.) abolished the inhibitory effects of exogenous peripheral CCK (5 microg/kg, i.p.) on food intake. The findings that A70104 had no effect on food intake when administered on its own, but abolishes the suppressant effect of exogenous peripheral CCK, suggest that endogenously released peripheral CCK does not play an important role as a satiety factor in rats.

Phenotypes of mice with invalidation of cholecystokinin (CCK(1) or CCK(2)) receptors

Cholecystokinin (CCK) is a peptide originally discovered in the gastrointestinal tract, but also found in high density in the mammalian brain. This peptide has been shown to be involved in numerous physiological functions such as feeding behavior, central respiratory control and cardiovascular tonus, vigilance states, memory processes, nociception, emotional and motivational responses. CCK interacts with nanomolar affinites with two different receptors designated CCK(1) and CCK(2). Primarily, the functional role of these binding sites in the brain and the periphery has been investigated thanks to the development of potent and selective CCK receptor antagonists and agonists. However, several studies have yielded conflicting data. Knockout mice provide unique opportunities to analyse diverse aspects of gene function in vivo. This review highlights recent progress in our understanding of the role of CCK(1) and CCK(2) receptors obtained by using mice with genetic invalidation of CCK(1) or CCK(2) receptors or natural CCK receptors mutants. The limits of this approach is discussed and some results were compared to those obtained by pharmacological blockade of CCK receptors by selective antagonists.

The gut and food intake: an update for surgeons

Food intake is the simplest and most obvious measure of gastrointestinal function, yet it rarely receives more than cursory attention from surgeons. In this review we cover recent findings on relationships between gut function and appetite regulation mediated via neuropeptides influenced by afferent and efferent vagal activity. Evidence from the new discipline known as neurogastroenterology elucidates gastric and intestinal signals involved in the elicitation of hunger, satiety, and aversion. Discovery of the adipose-tissue-derived hormone, leptin, has energized the field of metabolism spawning increasing numbers of publications related to interactions between leptin and insulin release and glucose disposal, as well as appetitive behavior. Peptides such as cholecystokinin (CCK), the proglucagon-derived peptides, glucagon-like peptides 1 and 2 (GLP-1 and GLP-2), and the recently identified powerful intake-stimulating molecule, orexin, are examples of potential targets for drug development and studies of surgical pathophysiology. A major conclusion of this work is that the considerable redundancy and overlap between mediators of caloric intake subserving survival of the species, while beneficial after foregut surgery, contribute to the complexity of treating the global epidemic of obesity. Possibly knowledge derived from basic research in neurogastroenterology can translate into advances in surgical treatment of obesity.

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.

Loxiglumide, a CCK-A receptor antagonist, stimulates calorie intake and hunger feelings in humans

Exogenous cholecystokinin (CCK) induces early satiety when infused into humans. Whether alimentary CCK (CCK-A) receptor blockade stimulates food intake in humans is, however, uncertain. The aim of the present investigation was, therefore, to establish the effect of CCK-A receptor blockade on satiety and eating behavior in healthy volunteers. To further explore the role of endogenous CCK, the effects of the specific CCK-A receptor antagonist loxiglumide (Lox; 22 micromol. kg(-1). h(-1)) on satiety and eating behavior were investigated in healthy men and compared with saline infusions (as placebo) in a series of randomized, double-blind, placebo-controlled, crossover studies. Lox produced a slight (7%), but not significant (P = 0.104), increase in food intake that was accompanied by a modest (10%), but significant (P < 0.004), increase in calorie intake. Fluid ingestion was not affected by Lox. Subjects experienced more hunger and delayed fullness during Lox infusion than during saline infusion (P < 0.05). This study provides further evidence that CCK is an endogenous physiological satiety signal acting through CCK-A receptor-mediated mechanisms. Repeated-dose studies comparing hunger and satiety responses after CCK-A receptor blockade in healthy subjects and patients with eating disorders may help clarify the possible involvement of endogenous CCK in these conditions.

Interaction between CCK and a preload on reduction of food intake is mediated by CCK-A receptors in humans

Cholecystokinin (CCK) interacts with neural signals to induce satiety in several species, but the mechanisms are unclear. We therefore tested the hypothesis that alimentary CCK (CCK-A) receptors mediate the interaction of CCK with an appetizer on food intake in humans. CCK octapeptide (CCK-8, 0.75 microgram infused over 10 min) or saline (placebo) with concomitant infusions of saline (placebo) or loxiglumide, a specific CCK-A antagonist, was infused into 16 healthy men with use of a double-blind, four-period design. All subjects received a standard 400-ml appetizer (amounting to 154 kcal) but were free to eat and drink thereafter as much as they wished. The effect of these infusions on feelings of hunger and satiety and on food intake was quantified. CCK-8 induced a reduction in calorie intake (P < 0.05) compared with saline. Furthermore, a decrease in hunger feelings (P < 0.05, saline-CCK-8 vs. all other treatments) and an increase in fullness were observed. These effects were antagonized for hunger and fullness by loxiglumide. We conclude that CCK-8 interacts with an appetizer to modulate satiety in humans. These effects are mediated by CCK-A receptors.

Inhibition of food intake in response to intestinal lipid is mediated by cholecystokinin in humans

Intraduodenal fat inhibits gastric emptying and exerts early satiation in animals and humans, but it is not clear whether the effects are mediated by cholecystokinin (CCK) in humans. Here, we tested whether CCK-A receptors mediate the inhibition of fat on food intake. Two sequential, double-blind, crossover studies were performed in 24 male subjects. First, subjects received either intraduodenal fat or saline together with a preload of either water or banana shake. Second, 12 subjects received either intraduodenal fat or saline perfusion plus a concomitant infusion of saline or loxiglumide, a specific CCK-A receptor antagonist, together with a preload of banana shake. In both studies, subjects were free to eat and drink as much as they wished. Fat induced a reduction in calorie intake (P < 0.05) compared with controls. Furthermore, a decrease in hunger feelings was observed. Infusion of loxiglumide abolished the effects of fat. Duodenal fat interacts with an appetizer to modulate energy intake in humans. This effect is mediated by CCK-A receptors.

The cholecystokinin-A receptor mediates inhibition of food intake yet is not essential for the maintenance of body weight

Food intake and body weight are determined by a complex interaction of regulatory pathways. To elucidate the contribution of the endogenous peptide cholecystokinin, mice lacking functional cholecystokinin-A receptors were generated by targeted gene disruption. To explore the role of the cholecystokinin-A receptor in mediating satiety, food intake of cholecystokinin-A receptor-/- mice was compared with the corresponding intakes of wild-type animals and mice lacking the other known cholecystokinin receptor subtype, cholecystokinin-B/gastrin. Intraperitoneal administration of cholecystokinin failed to decrease food intake in mice lacking cholecystokinin-A receptors. In contrast, cholecystokinin diminished food intake by up to 90% in wild-type and cholecystokinin-B/gastrin receptor-/- mice. Together, these findings indicate that cholecystokinin-induced inhibition of food intake is mediated by the cholecystokinin-A receptor. To explore the long-term consequences of either cholecystokinin-A or cholecystokinin-B/gastrin receptor absence, body weight as a function of age was compared between freely fed wild-type and mutant animals. Both cholecystokinin-A and cholecystokinin-B/gastrin receptor-/- mice maintained normal body weight well into adult life. In addition, each of the two receptor-/- strains had normal pancreatic morphology and were normoglycemic. Our results suggest that although cholecystokinin plays a role in the short-term inhibition of food intake, this pathway is not essential for the long-term maintenance of body weight.

Untangling the effects of hunger, anxiety, and nausea on energy intake during intravenous cholecystokinin octapeptide (CCK-8) infusion

Infusions of cholecystokinin (CCK) may exert their effects on appetite by inducing feelings of nausea or anxiety. In this double blind, placebo controlled crossover study, the impact of these effects on appetite were examined. Fifteen male subjects received a 20 min i.v. infusion of cholecystokinin octapeptide (CCK-8) (4 ng/kg/min) or saline. The infusion commenced 20 min after a soup preload and 10 min before an ad libitum test meal. Visual analogue scales of appetite and mood were measured over 3 h, and subjects were instructed to report any other sensations they experienced over this time. CCK-8 significantly reduced premeal hunger, elevated premeal anxiety, and reduced energy intake at the ad libitum test meal. Meal duration and rate of eating (kcal/min) were also significantly reduced after CCK-8. After the smaller meal with CCK-8, hunger rose quickly to a higher level than with placebo. The return of hunger was commensurate with the smaller amount of energy consumed and indicated that CCK did not exert an enduring effect on hunger suppression. A significant correlation was found between the reduction in energy intake and hunger (r = 0.75 p < 0.01), but not with anxiety (r = 0.15 not significant). Analyses were performed separately on subjects who did (n = 8), or did not (n = 7) report gastrointestinal disturbance. Energy intake was reduced by 56.6% and 44.6%, respectively. These results indicate that, although feelings of anxiety and nausea may accompany CCK infusions, they are not necessary for the effects of CCK on appetite. These data provide support for a role of CCK in satiety.

Relationship between hunger-satiety feelings and various metabolic parameters in women with obesity during controlled weight loss

OBJECTIVE

Satiety plays an important role in weight control. The meaning of fasting hormone levels and satiety feelings, and how post-absorptive changes after meals high in carbohydrate regulate appetite remains to be demonstrated.

RESEARCH METHODS AND PROCEDURES

Prospective metabolic study with 25 non-diabetic obese women at the Energy Metabolism Research Unit of the Department of Nutrition Sciences, University of Alabama at Birmingham. We analyzed fasting and postprandial ratings of hunger-satiety and values of various metabolic parameters (serum glucose and insulin, plasma cholecystokinin, respiratory quotient) during controlled weight loss. The postprandial measures were assessed following a test meal providing 320 kcal and yielding a food quotient of 0.89.

RESULTS

In the fasting state, there was no correlation between hunger-satiety ratings and any of the measured metabolic parameters. Under postprandial conditions, satiety was positively related to glucose (p=0.002) and insulin (p=0.002) responses to the test meal. In multivariate analysis including glucose, insulin, cholecystokinin, hunger-satiety ratings and respiratory quotient, insulin was the only independent predictor of satiety in the postprandial state.

DISCUSSION

These data suggest an association between the endogenous insulin response and feelings of postprandial satiety. Insulin's satiation properties, which could well be mediated by other hormones, may represent a primary factor of food intake regulation after meals relatively high in carbohydrate.

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.

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.

Nonpeptide antagonists of neuropeptide receptors: tools for research and therapy

The recent development of selective and highly potent nonpeptide antagonists for peptide receptors has constituted a major breakthrough in the field of neuropeptide research. Following the discovery of the first nonpeptide antagonists for peptide receptors ten years ago, numerous other antagonists have been developed for most neuropeptide families. These new, metabolically stable compounds, orally active and capable of crossing the blood-brain barrier, offer clear advantages over the previously available peptide antagonists. Nonpeptide antagonists have provided valuable tools to investigate peptide receptors at the molecular, pharmacological and anatomical levels, and have considerably advanced our understanding of the pathophysiological roles of peptides in the CNS and periphery. Evidence from animal and clinical studies suggests that nonpeptide antagonists binding to peptide receptors could be useful for the treatment of disease states associated with high levels of neuropeptides. In this article Catalina Batancur, Mounia Azzi and William Rostène will address the recent developments in nonpeptide antagonists for neuropeptide receptors, with a particular focus on their CNS actions.

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.

Devazepide increases food intake in male but not female Zucker rats

The genetically obese Zucker rat (fa/fa) is hyperphagic compared to lean controls (Fa/?). This hyperphagia is characterized by increased meal size. Cholecystokinin (CCK) has been shown to decrease meal size in many species including humans. In the present study we investigated the role of endogenous CCK in mediating the hyperphagia of male and female obese Zucker rats. CCKA-type receptors were blocked with the specific antagonist, devazepide, and test meal size was measured. Male obese and lean rats significantly increased food intake following devazepide. Neither obese nor lean female rats significantly increased food intake following devazepide. This is the first demonstration of a gender difference in endogenous CCK-mediated satiety. These results have implications for the higher incidence of eating disorders in females.

Human pharmacokinetics and tolerability of L-365,260, a novel cholecystokinin-B antagonist

A study was conducted to examine the tolerability and pharmacokinetics of single and multiple oral doses of L-365,260, a novel antagonist for type B cholecystokinin (CCK) receptors and to quantify effects of selective blockade of type B CCK receptors through treatment with L-365,260 on measures of anxiety, hunger, and cognitive performance. Healthy volunteers were given single oral doses of up to 50 mg of L-365,260 and multiple oral doses of up to 25 mg every 6 hours for 10 days. Plasma concentrations of L-365,260 were quantified by means of high-performance liquid chromatography. Anxiety and hunger were assessed by visual analog scale and the Spielberger State Anxiety Index. Cognitive testing was used to evaluate attention level and short-term memory. L-365,260 was rapidly absorbed and a biphasic pattern of elimination was demonstrated with a terminal half-life (t1/2) of 8 to 12 hours. The mean (n = 6) values for peak plasma concentration (C(max)) and time to peak concentration (t(max)) of L-365,260 were 503 ng/mL and 1.25 hours, respectively, after a single 50-mg oral dose. Accumulation of L-365,260 plasma concentrations was seen after the prescribed multiple-dose regimens. Steady state was achieved after 3 days of oral administration. L-365,260 had an acceptable tolerability profile after oral administration. No changes in measures of anxiety, hunger, or short-term memory were observed at doses of L-365,260 shown to have antagonist activity at the CCK-B receptor.

2-Naphthalenesulphanyl-L-aspartyl-2-(phenethyl) amide (2-NAP) and food intake in rats: evidence that endogenous peripheral CCK does not play a major role as a satiety factor

1. The demonstration that systemic administration of the CCKA receptor antagonist, devazepide, increases food intake in rats has provided the strongest support for the hypothesis that endogenous peripherally released cholecystokinin (CCK) acts as a satiety factor. However, interpretation of these results has been confounded by the fact that devazepide can enter the brain from the systemic circulation and may increase food intake by a central action. The present study was therefore undertaken to confirm the hypothesis that endogenous peripheral CCK is a satiety factor by investigating the effects of a novel CCKA receptor antagonist, 2-NAP, which is unlikely to cross the blood brain barrier, on food intake in rats. 2. 2-NAP (1-16 mg kg-1, i.p.) had no significant effects on the intake of a test meal in rats. 3. Pretreatment of rats with 2-NAP (2 mg kg-1, s.c.) abolished the inhibitory effects of exogenous peripheral CCK (5 micrograms kg-1, i.p.) on food intake. 4. In agreement with previous results, devazepide (50-200 micrograms kg-1, i.p.) significantly increased the intake of a test meal in rats. 5. The observations that 2-NAP, which is unlikely to penetrate the blood brain barrier, had no effect on food intake, but that 2-NAP abolished the suppressant effect of exogenous peripheral CCK, suggest that endogenously released peripheral CCK is not important as a satiety factor in rats.

Satiety effects of the type A CCK receptor antagonist loxiglumide in lean and obese women

Several studies have demonstrated that administration of cholecystokinin (CCK) reduces food intake in several species, including humans. In animal studies CCK-receptor antagonists have been reported to increase food intake, suggesting a physiological satiety effect of CCK in these animals. In a double-blind, placebo-controlled study, we investigated the effect of the specific CCK-A receptor antagonist loxiglumide on food intake (carbohydrate-rich meal) and on subjective hunger feelings scored with visual analogue scales and food selection lists in seven healthy obese women and in seven healthy lean women. Loxiglumide was administered intravenously in a dose of 10 mg/kg ideal weight/h. For the whole group, food intake during loxiglumide (359 +/- 39 g) was not significantly different from food intake during saline infusion (333 +/- 31 g). Also, when the lean and obese subgroups were analyzed separately, no significant influence of loxiglumide on food intake was found. In addition, no significant differences in satiety scores were seen using the food selection lists or visual analogue scales. In conclusion, in the present study during infusing the CCK-A receptor antagonist loxiglumide we found no increase in preprandial satiety nor in food intake of a carbohydrate-rich meal nor in postprandial satiety in lean and obese women.

Satiety effects of a physiological dose of cholecystokinin in humans

Cholecystokinin 33 (CCK) was infused intravenously to eight healthy obese women and 10 healthy lean women of the same age, in doses that elicited plasma cholecystokinin concentrations in the physiological range. The effect of these infusions after a standardised banana 'shake' (preload) on food intake and satiety signals was compared with the effect of saline infusions in the same subjects. For the whole group food intake (mean (SEM)) (282 (29 g)) was significantly less during CCK than during saline (346 (31) g, p < 0.05). Hunger feelings tended to be less during CCK infusions. Examination of the separate subgroups showed no differences between lean and obese subjects in the satiety effects of CCK. In conclusion, under the conditions of this study, CCK significantly decreases food intake in humans, and this effect is similar for lean and obese subjects.

Adaptation to high-fat diets: effects on eating behaviour and plasma cholecystokinin

Twelve male subjects took part in a study to investigate the effects of overfeeding a high-fat diet (19.17 MJ/d; 58% energy from fat) for 2 weeks on plasma cholecystokinin (CCK) levels, food intake, and subjective feelings of hunger and fullness. Before and after the diet, subjects completed a 2-week weighed dietary inventory, formal measurements of food intake from a pre-selected appetizing evening meal were carried out, and blood samples were taken after a standard breakfast for measurement of CCK. Hunger and fullness were rated on visual analogue scales before and after each of these meals and at evening meals during the diet period. Following the high-fat diet there was a small non-significant increase in food intake from the pre-selected meal (6919 (SE 615) kJ v. 6405 (SE 540) kJ; P = 0.1) and a significant increase in the average daily food consumption measured from the diaries (10.25 (SE 0.49) MJ/d v. 9.59 (SE 0.62) MJ/d; P = 0.05). Corresponding trends of increasing feelings of hunger and declining fullness also occurred over the study period. Plasma CCK responses to the standard breakfast were raised following the diet (1285 (SE 153) v. 897 (SE 78) pM min; 3 h integrated CCK production post v. pre diet; P < 0.01) with the major differences observed at 90 and 120 min following the meal. These results suggest that the increase in food intake may be related to a down-regulation in putative CCK receptors responsible for food intake. Elevated CCK levels might suggest a corresponding down-regulation in CCK receptors responsible for feedback inhibition of CCK release.

Satiety effects of cholecystokinin in humans

BACKGROUND/AIMS

Cholecystokinin (CCK) inhibits gastric emptying and may exert satiety effects in several species, including humans. Because the effects of physiological doses of CCK on satiety in humans is unclear, the satiety effects of CCK-33 in physiological levels in lean and obese subjects were studied.

METHODS

CCK-33 was infused intravenously to 32 healthy men or women (14 obese, all women; 18 lean, 4 men and 14 women) in doses that elicited plasma CCK concentrations in the physiological range. The effects of these infusions on feelings of hunger, wish to eat, fullness, and prospective feeding intentions were measured on visual analogue scales and compared with saline during a 1-hour infusion period.

RESULTS

The CCK infusions induced significant decreases in hunger feelings, wish to eat, and prospective feeding intentions (P < 0.05), whereas fullness tended to be increased (P = 0.054). No clear differences between lean and obese subjects were observed apart from a more marked decrease in fullness and increase in prospective feeding intentions during the 1-hour saline infusion in the lean group (P < 0.05).

CONCLUSIONS

CCK infusion leading to physiological plasma levels significantly increases satiety in humans.

Effects of the CCK receptor antagonist MK-329 on food intake in broiler chickens

The cholecystokinin (CCK) receptor antagonist MK-329 (previously L-364,718) was administered intraperitoneally to free-feeding broiler chickens and tested for conditioning effects using the colored food paradigm. The 8.0, 16.0, and 32.0 micrograms/kg doses of MK-329 did not exert any effect on food intake and failed to condition a color preference or aversion. When higher doses were used (90, 180, and 360 micrograms/kg) MK-329 caused a significant increase in food intake during the 2-h test period. Intravenously injected MK-329 (70, 140, and 280 micrograms/kg) produced an increase in food intake, with maximum increases occurring at a dose of 70 micrograms/kg. CCK (14 micrograms/kg) caused a reduction in feeding, and this effect was not blocked by pretreatment with intraperitoneal injection of MK-329 (32, 90, 180, and 360 micrograms/kg). The results question the role of endogenous CCK in satiety in chickens.

Effect of a low dose of intraduodenal fat on satiety in humans: studies using the type A cholecystokinin receptor antagonist loxiglumide

Satiation, the process that brings eating to an end, and satiety, the state of inhibition over further eating, may be influenced by cholecystokinin (CCK). In animal and human studies, it has been shown that infusion of exogenous CCK decreases food intake, but the doses given may well have led to supraphysiological plasma concentrations. This study was done to discover if a low dose of intraduodenal fat releasing physiological amounts of endogenous cholecystokinin exerts satiation or satiety effects, or both and if these effects could be inhibited by the CCK receptor antagonist loxiglumide. In 10 healthy lean volunteers (5 F, 5 M, mean age 26) three tests were performed in a randomised blind fashion. Intralipid 20% (6 g/h) (experiments A and C) or saline (experiment B) were given intraduodenally from 1030 until 1300. The subjects received saline (experiments A and B) or loxiglumide (experiment C) a specific CCK-receptor antagonist (10 mg/kg/h) intravenously from 0930 until 1300. At 1200 a meal was served. At regular time intervals hunger feelings were measured using visual analogue scales and food selection lists and plasma CCK was measured by radioimmunoassay. Food intake (mean (SEM)) during intraduodenal fat (206(35)g) was lower than in the control study (269(37)g, p = 0.09). Loxiglumide largely prevented the inhibitory effect of intraduodenal fat on food intake (245(30)g). From 1030 until the meal at 1200 there was a significant satiating effect of intraduodenal fat compared with the control and loxiglumide experiments according to the food selection lists, which was because of the satiating effect for the fat rich items (p<0.05). Also feelings of fullness were significantly higher during intraduodenal fat than in the control or loxiglumide experiments (p<0.05). During intraduodenal fat there was a significant increase of plasma CCK from 2.4(0.3) to 4.8(0.4) pM (p<0.001). Loxiglumide led to an exaggerated CCK release to a peak concentration of 16(2.4) pM before the meal. This study shows that in humans low dose intraduodenal fat increases satiety and satiation, mainly through the effect of CCK.

Reduced serum cholecystokinin response to food intake in female athletes

Strenuous training in women has been shown to cause menstrual dysfunction and decreased bone mineral density. These endocrine and metabolic complications are associated with an insufficient dietary intake and decreased body fat content in female athletes. The present investigation was undertaken to study serum levels of cholecystokinin (CCK), insulin, gastrin, and cortisol in 14 female long-distance runners and 15 sex- and age-matched control subjects during intake of a standardized meal (500 kcal). The athletes showed a decreased response of the "satiety peptide" CCK to the meal and reported increased hunger compared with the control group. Meal-related insulin response was also decreased in the athletes, whereas gastrin levels were comparable to those of controls. Basal levels of glucose were increased in the athletes, but there was no difference in postprandial levels between the groups. Cortisol levels were clearly elevated in the female runners. We conclude that insufficient food intake in female athletes cannot be explained by increased CCK secretion and satiety. Since the athletes reported a larger caloric intake of a normal daily breakfast than the control subjects, the decreased CCK response may instead be explained by an adaptation to increased food intake. The decreased meal-related insulin response may be a reflection of increased insulin sensitivity as an adaptation to physical exercise. However, an impaired peptide secretion cannot be excluded. The role of elevated cortisol levels in the gastrointestinal hormone response needs further investigation.

The role of the gut in regulating food intake in man

In addition to various psychosocial and metabolic factors, food intake is also influenced by gastrointestinal mechanisms that trigger both the initiation and termination of eating behaviors. Although gastric distension is one of the most obvious signs of "fullness" and clearly plays a role in controlling food intake, its effects are only temporary and are distinct from the feelings of satiety generally associated with a meal. Such postprandial sensations appear to be related to the activation of intestinal chemoreceptors. Other evidence indicates that the release of cholecystokinin and perhaps other transmitters as well may contribute to satiety. Although the stomach probably does not expand or shrink in response to different levels of food intake, nutrient receptors in the small intestine probably do adapt to changes in food intake. Intestinal adaptation also occurs in response to thyroid hormone, insulin, and cortisol as well as to obesity, pregnancy, and illness, which all may have an important bearing on changes in eating behavior in these situations.

Biological actions of cholecystokinin

Cholecystokinin (CCK) has emerged as an important mammalian neuropeptide, localized in peripheral organs and in the central nervous system. This review presents an overview of the molecular aspects of CCK peptides and CCK receptors, the anatomical distribution of CCK, the neurophysiological actions of CCK, release of CCK and effects of CCK on release of other neurotransmitters, and the actions of CCK on digestion, feeding, cardiovascular function, respiratory function, neurotoxicity and seizures, cancer cell proliferation, analgesia, sleep, sexual and reproductive behaviors, memory, anxiety, and dopamine-mediated exploratory and rewarded behaviors. Human clinical studies of CCK in feeding disorders and panic disorders are described. New findings are presented on potent, nonpeptide CCK antagonists, selective for the two CCK receptor subtypes, which demonstrate that endogenous CCK has biologically important effects on physiology and behavior.

Cholecystokinin in human cerebrospinal fluid: concentrations, dynamics, molecular forms and relationship to fasting and feeding in health, depression and alcoholism

Very little is known about the physiologic significance of the gut-brain hormone cholecystokinin (CCK) in the human central nervous system, although the hormone has been hypothesized to be involved in the regulation of both appetite and anxiety. We continuously collected lumbar cerebrospinal fluid (CSF) via indwelling subarachnoid catheters in ten normal volunteers, ten patients with major depression and five abstinent alcoholic humans, while fasting and after eating. Five other healthy subjects were fasted throughout the experiment. We quantified CSF immunoreactive cholecystokinin (IR-CCK) and glucose concentrations at 10-min intervals from 11.00 to 17.00 h. No difference in CSF IR-CCK concentration, half-life or rhythm was observed between normal volunteers and either depressed or alcoholic patients. Fasting CSF IR-CCK concentrations were 1.3 +/- 0.18, 1.3 +/- 0.21 and 1.2 +/- 0.21 fmol/ml (mean +/- S.E.M.) in normal volunteers, depressed patients and alcoholic patients, respectively. After eating, CSF IR-CCK concentrations rose to 1.5 +/- 0.21, 1.5 +/- 0.24 and 1.4 +/- 0.26 fmol/ml, respectively. Normal volunteers who did not eat had similar basal CSF IR-CCK concentrations (1.1 +/- 0.1 fmol/ml) which similarly rose to 1.4 +/- 0.13 fmol/ml during the sampling interval. In contrast, CSF glucose concentrations rose only in the subjects who ate, beginning to rise after about 1 h and remaining elevated for at least 3 h after eating. These data suggest the existence of a diurnal rhythm of IR-CCK release into CSF, as opposed to a response to feeding. The disappearance half-time of CCK in human CSF is less than 13 min.(ABSTRACT TRUNCATED AT 250 WORDS)

Metabolic correlates of behaviour in the newborn infant

Twenty-four infants were submitted to behavioural observation 0.5 and 3.5 h after birth. Blood samples were collected from the umbilical cord and from the infant immediately following observation, for the determination of glucose, insulin, cholecystokinin (CCK), and free fatty acids (FFA). It was found that 88% of the infants were awake and 83% performed sucking movements 0.5 h after birth; these findings were associated to a decrease in the plasma glucose concentration (p = 0.05). Eighty-eight percent of the infants were asleep and only 12% exhibited sucking movements 3.5 h after birth; at this time point there was an increase in the plasma concentrations of both CCK (p = 0.05) and FFA (p = 0.01). The infants' plasma insulin concentrations remained unchanged during the time course. It is suggested that the initial behavioural pattern of the newborn, characterized by the appearance of sucking movements, may be due to the rapid decrease of the circulating glucose concentration. The successive increase in the blood concentrations of both CCK and FFA might be two of the factors contributing to the cessation of sucking and to the establishment of a sleeping state.

MK-329 blocks the inhibition of alcohol intake by CCK-8

Peripheral administration of sulfated cholecystokinin octapeptide (CCK-8) potently reduces alcohol intake, preference, and blood levels in rats. MK-329 (L-364,718 or Devazepide) acts at peripheral cholecystokinin (CCKA) receptors to antagonize CCK-8's physiological and behavioral effects, such as pancreatic stimulation and inhibition of feeding. We determined whether CCKA receptor blockade would also prevent CCK-8's alcohol satiety effect. Water-deprived female and male rats (n = 7 for each) received randomized combinations of intraperitoneal injections of MK-329 (0, 100, 200, or 400 micrograms/kg) followed by CCK-8 (0 or 4 micrograms/kg). Rats were then given access to 5% w/v ethanol for 30 min, followed by 30-min access to water, with food ad lib. MK-329 at all doses significantly (p < 0.05) reduced the suppression of alcohol intake and food intake by CCK-8. MK-329 alone increased alcohol intake at 400 micrograms/kg, and increased food intake, in females and males at 100 and 200 micrograms/kg, respectively. We concluded that CCK-8's alcohol and food satiation effects depend on specific, peripheral CCKA receptors, and satiation of alcohol consumption and drinking-associated feeding reflect an endogenous functional interaction of CCK-8 with CCKA receptors.

Role of gastrointestinal factors in hunger and satiety in man

There is, we feel, a strong case to be made for a major influence of gastrointestinal factors in the control of eating behaviour in humans. Moreover, the findings suggest that satiety and hunger are controlled by different gastrointestinal mechanisms. Gastric distension is perhaps the most important factor that stops people eating, but a true feeling of satiety also requires the presence of nutrients in the small intestine. Hunger appears to be little influenced by the amount of food in the stomach and appears to be more dependent on the nutrient load in the small intestine. I do not mean by this to suggest that the gastrointestinal mechanisms are the only mechanisms controlling eating behaviour in humans or even the most important. Nevertheless they constitute an important and fundamental control system that links with the post-absorptive mechanisms and a plethora of social and conditioning factors to influence what we eat.

Role of circulating cholecystokinin in control of fat-induced inhibition of food intake in humans

Cholecystokinin (CCK) has been proposed to serve as a satiety signal in animals and humans. To further explore the role of CCK in humans, the effect on satiety and eating behavior of a specific CCK-receptor antagonist, loxiglumide, that preferentially inhibits peripheral (CCK-A) receptors was investigated. In a randomized, blind, four-period latin square design, 10 subjects received intravenous saline (placebo) or loxiglumide (10 mg/kg per hour) with concomitant intrajejunal perfusions of isotonic saline or fat (containing 50% corn oil and 3% albumin). Food intake and plasma CCK concentrations were assessed, and subjects scored their feelings of hunger and fullness in paired experiments. In placebo-treated subjects, the duration of the meal was shorter during fat perfusion (30 +/- 2 minutes vs. 35 +/- 2 minutes; P less than 0.01; mean +/- SEM). The amount of food intake was reduced (361 +/- 31 g vs. 454 +/- 35 g; P less than 0.05), and fluid ingestion was inhibited (490 +/- 31 mL vs. 625 +/- 38 mL; P less than 0.01). Loxiglumide did not affect any parameter and did not change the pattern of responses. In loxiglumide-treated subjects there was a 4-5-fold elevation in plasma CCK levels. These results confirm that jejunal infusion of lipid reduces the size of the meal and stimulates early satiety. The data imply that these effects are not mediated through peripheral endogenous CCK under these conditions.

Disturbed cholecystokinin secretion in patients with eating disorders

It has been shown that the gastrointestinal hormone cholecystokinin (CCK) induces satiety and reduces food intake in laboratory animals and humans. In the light of this evidence we studied CCK release in patients suffering from eating disorders. The secretion of CCK into the general circulation was measured in 10 anorectic, in 7 bulimic patients, and in 8 healthy controls before and after a high-caloric liquid testmeal. Baseline CCK values were similar in controls (0.6 +/- 0.2 pmol/l) and bulimics (0.6 +/- 0.1 pmol/l) and were significantly increased in the anorectic group (1.8 +/- 0.4 pmol/l) (p less than or equal to 0.005). After eating peak plasma levels increased to 6.1 +/- 0.9 pmol/l in the anorectic, to 3.8 +/- 0.5 pmol/l in the bulimic and to 2.7 +/- 0.6 pmol/l in the control group. All postprandial CCK values were significantly higher in the anorectic group. The secretion of CCK-8-S, an important peptide in the CCK family, was significantly elevated, too. This disturbed CCK secretion in patients suffering from anorexia nervosa, even if it is a secondary, diet-induced defect, may perpetuate this disorder.