Glucagon-like peptide-1 secretion in bulimia nervosa

The interplay between leptin, glucocorticoids, and GLP1 regulates food intake and feeding behaviour

Nutritional, endocrine, and neurological signals converge in multiple brain centres to control feeding behaviour and food intake as part of the allostatic regulation of energy balance. Among the several neuroendocrine systems involved, the leptin, glucocorticoid, and glucagon-like peptide 1 (GLP1) systems have been extensively researched. Leptin is at the top hierarchical level since its complete absence is sufficient to trigger severe hyperphagia. Glucocorticoids are key regulators of the energy balance adaptation to stress and their sustained excess leads to excessive adiposity and metabolic perturbations. GLP1 participates in metabolic adaptation to food intake, regulating insulin secretion and satiety by parallel central and peripheral signalling systems. Herein, we review the brain and peripheral targets of these three hormone systems that integrate to regulate food intake, feeding behaviour, and metabolic homeostasis. We examine the functional relationships between leptin, glucocorticoids, and GLP1 at the central and peripheral levels, including the cross-regulation of their circulating levels and their cooperative or antagonistic actions at different brain centres. The pathophysiological roles of these neuroendocrine systems in dysregulated intake are explored in the two extremes of body adiposity - obesity and lipodystrophy - and eating behaviour disorders.

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

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

Gastrointestinal peptides in eating-related disorders

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

Binge-like palatable food intake in rats reduces preproglucagon in the nucleus tractus solitarius

Binge eating involves eating larger than normal quantities of food within a discrete period of time. The neurohormonal controls governing binge-like palatable food intake are not well understood. Glucagon-like peptide-1 (GLP-1), a hormone produced peripherally in the intestine and centrally in the nucleus tractus solitarius (NTS), reduces food intake. Given that the NTS plays a critical role in integrating peripheral and central signals relevant for food intake, as well as the role of GLP-1 in motivated feeding, we tested the hypothesis that expression of the GLP-1 precursor preproglucagon (PPG) would be reduced in the NTS of rats with a history of binge-like palatable food intake. Adult male rats received access to fat for 1 h shortly before lights off, either every day (Daily, D) or only 3d/week (Intermittent, INT). INT rats ate significantly more fat than did D rats in sessions where all rats had fat access. After ~8.5 weeks of diet maintenance, we measured plasma GLP-1 as well as NTS PPG and GLP-1 receptor expression. INT rats had significantly lower NTS PPG mRNA expression compared to D rats. However, plasma GLP-1 was significantly increased in the INT group versus D rats. No significant differences were observed in NTS GLP-1 receptor expression. We also measured plasma insulin levels, fasted blood glucose, and plasma corticosterone but no differences were detected between groups. These results support the hypothesis that binge-like eating reduces NTS GLP-1 expression, and furthermore, demonstrate divergent impacts of binge-like eating on peripheral (plasma) versus central GLP-1.

Liraglutide for psychiatric disorders: clinical evidence and challenges

Obesity and diabetes are both risk factors and consequences of psychiatric disorders. Glucagon like peptide 1 (GLP-1) receptor agonists such as liraglutide are widely used in the treatment of diabetes and obesity. There are considerable amounts of preclinical studies showing the effects of liraglutide on promotion of neurogenesis, while preventing apoptosis and oxidation. Preliminary clinical evidence has suggested that liraglutide could decrease weight gain, improve cognition and prevent cognitive decline. Accordingly, liraglutide has been regarded as a potential candidate for the management of psychiatric disorders. Herein, we will discuss the association between obesity/diabetes and psychiatric disorders, and the emerging use of liraglutide in psychiatry.

Molecular bases of anorexia nervosa, bulimia nervosa and binge eating disorder: shedding light on the darkness

Eating-disorders (EDs) consequences to human health are devastating, involving social, mental, emotional, physical and life-threatening aspects, concluding on impairment and death in cases of extreme anorexia nervosa. It also implies that people suffering an ED need to find psychiatric and psychological help as soon as possible to achieve a fully physical and emotional recovery. Unfortunately, to date, there is a crucial lack of efficient clinical treatment to these disorders. In this review, we present an overview concerning the actual pharmacological and psychological treatments, the knowledge of cells, circuits, neuropeptides, neuromodulators and hormones in the human brain- and other organs- underlying these disorders, the studies in animal models and, finally, the genetic approaches devoted to face this challenge. We will also discuss the need for new perspectives, avenues and strategies to be developed in order to pave the way to novel and more efficient therapeutics.

Preliminary examination of glucagon-like peptide-1 levels in women with purging disorder and bulimia nervosa

OBJECTIVE

This study examined pre- and postprandial glucagon-like peptide 1 (GLP-1) levels in women with bulimia nervosa (BN), purging disorder (PD), and non-eating disorder control women to better understand whether alterations in satiation-related hormones in BN may be linked to binge-eating episodes or other altered ingestive behaviors.

METHOD

Participants included women with BN (n = 19), PD (n = 14), or controls (n = 14). Participants provided subjective ratings for hunger and fullness and plasma samples before and after consumption of a standardized test meal.

RESULTS

As expected, GLP-1 levels increased significantly following test meal consumption; however, participants with BN displayed significantly lower GLP-1 levels compared to PD and control participants both before and after consumption of the test meal. There were no significant differences between PD and control participants in GLP-1 levels, but individuals with PD displayed significantly higher levels of fullness throughout the test meal as compared to both control and BN participants.

DISCUSSION

Our findings provide preliminary evidence that reduced GLP-1 levels in individuals with BN may be associated with binge-eating episodes. Additionally, increased fullness in individuals with PD does not appear to be accounted for by exaggerated postprandial GLP-1 release.

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

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

Role of ghrelin in the pathophysiology of eating disorders: implications for pharmacotherapy

Ghrelin is the only known circulating orexigenic hormone. It increases food intake by interacting with hypothalamic and brainstem circuits involved in energy balance, as well as reward-related brain areas. A heightened gut-brain ghrelin axis is an emerging feature of certain eating disorders such as anorexia nervosa and Prader-Willi syndrome. In common obesity, ghrelin levels are lowered, whereas post-meal ghrelin levels remain higher than in lean individuals. Agents that interfere with ghrelin signalling have therapeutic potential for eating disorders, including obesity. However, most of these drugs are only in the preclinical phase of development. Data obtained so far suggest that ghrelin agonists may have potential in the treatment of anorexia nervosa, while ghrelin antagonists seem promising for other eating disorders such as obesity and Prader-Willi syndrome. However, large clinical trials are needed to evaluate the efficacy and safety of these drugs.

Women with bulimia nervosa exhibit attenuated secretion of glucagon-like peptide 1, pancreatic polypeptide, and insulin in response to a meal

BACKGROUND

The eating disorder bulimia nervosa (BN) is characterized by frequent episodes of binge eating, followed regularly by inappropriate compensatory behavior, such as self-induced vomiting.

OBJECTIVE

The current investigation was designed to examine possible alterations in the secretion of the gastrointestinal satiety peptides glucagon-like peptide 1 (GLP-1) and pancreatic polypeptide (PP) in women with BN.

DESIGN

Twenty-one women with BN and 17 healthy control subjects of comparable age and BMI were recruited. After fasting overnight, the subjects provided blood samples during ingestion of a standardized meal and self-rated their appetite on a visual analog scale. Fasting and meal-related secretion of the incretin GLP-1 and the meal-related feedback signal PP and insulin and glucose as indicators of the metabolic homeostasis were analyzed.

RESULTS

Women with BN had significantly lower fasting and postprandial serum concentrations of GLP-1 (P < 0.01) and PP (P < 0.05) than did the control subjects. Furthermore, both the basal (P < 0.001) and peak (P < 0.05) concentrations of insulin were significantly attenuated in the bulimic subjects, whereas glucose concentrations were normal. As a consequence, the bulimic homeostasis model assessment of insulin index values were also lower (P < 0.001).

CONCLUSIONS

Women with BN secrete abnormally low amounts of GLP-1 and PP, possibly because of the adaption to large meals in the form of enlarged gastric capacity and reduced muscle tone in the gastric wall. Attenuated secretion of these gastrointestinal satiety peptides may play a role in the maintenance of bulimic behavior.

Eating disorders and gastrointestinal peptides

PURPOSE OF REVIEW

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

RECENT FINDINGS

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

SUMMARY

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