Increase in Energy Intake Leads to a Decrease in Obestatin in Restricting-Type of Anorexia Nervosa

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

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

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

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

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

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

The Role of Ghrelin in Anorexia Nervosa

Ghrelin, a 28-amino acid peptide hormone expressed in X/A-like endocrine cells of the stomach, is the only known peripherally produced and centrally acting peptide that stimulates food intake and therefore attracted a lot of attention with one major focus on the treatment of conditions where an increased energy intake or body weight gain is desired. Anorexia nervosa is an eating disorder characterized by a pronounced reduction of body weight, a disturbed body image and hormonal alterations. Ghrelin signaling has been thoroughly investigated under conditions of anorexia nervosa. The present review will highlight these alterations of ghrelin in anorexia and discuss possible treatment strategies targeting ghrelin signaling. Lastly, gaps in knowledge will be mentioned to foster future research.

Biochemical properties and biological actions of obestatin and its relevence in type 2 diabetes

Obestatin was initially discovered in rat stomach extract, and although it is principally produced in the gastric mucosa, it can be found throughout the gastrointestinal tract. This 23-amino acid C-terminally amidated peptide is derived from preproghrelin and has been ascribed a wide range of metabolic effects relevant to type 2 diabetes. Obestatin reportedly inhibits gastrointestinal motility, reduces food intake and lowers body weight and improves lipid metabolism. Furthermore, it appears to exert actions on the pancreatic β-cell, most notably increasing β-cell mass and upregulating genes associated with insulin production and β-cell regeneration, with relevance to type 2 diabetes. It is becoming evident that obestatin also exerts pleiotropic effects on the cardiovascular system, possibly modulating blood pressure, endothelial function and triggering cardioprotective mechanisms, which may be important in determining cardiovascular outcomes in type 2 diabetes. Furthermore, it seems that like other gut peptides obestatin has neuroprotective properties. This review examines the biochemical properties of the obestatin peptide (its structure, sequence, stability and distribution) and the candidate receptors through which it may act. It provides a balanced examination of the reported pancreatic and extrapancreatic actions of obestatin and evaluates its potential relevance with respect to diabetes therapy, together with discussion of direct evidence linking alterations in obestatin signalling with obesity/diabetes and other diseases.

Obestatin as a key regulator of metabolism and cardiovascular function with emerging therapeutic potential for diabetes

Obestatin is a 23-amino acid C-terminally amidated gastrointestinal peptide derived from preproghrelin and which forms an α helix. Although obestatin has a short biological half-life and is rapidly degraded, it is proposed to exert wide-ranging pathophysiological actions. Whilst the precise nature of many of its effects is unclear, accumulating evidence supports positive actions on both metabolism and cardiovascular function. For example, obestatin has been reported to inhibit food and water intake, body weight gain and gastrointestinal motility and also to mediate promotion of cell survival and prevention of apoptosis. Obestatin-induced increases in beta cell mass, enhanced adipogenesis and improved lipid metabolism have been noted along with up-regulation of genes associated with beta cell regeneration, insulin production and adipogenesis. Furthermore, human circulating obestatin levels generally demonstrate an inverse association with obesity and diabetes, whilst the peptide has been shown to confer protective metabolic effects in experimental diabetes, suggesting that it may hold therapeutic potential in this setting. Obestatin also appears to be involved in blood pressure regulation and to exert beneficial effects on endothelial function, with experimental studies indicating that it may also promote cardioprotective actions against, for example, ischaemia-reperfusion injury. This review will present a critical appraisal of the expanding obestatin research area and discuss the emerging therapeutic potential of this peptide for both metabolic and cardiovascular complications of diabetes.

High unacylated ghrelin levels support the concept of anorexia in infants with prader-willi syndrome

Background

Prader-Willi syndrome (PWS) is a rare genetic neurodevelopmental disorder with different nutritional phases from suckling deficit with failure to thrive to early onset of obesity. Hyperghrelinemia has been described in PWS long before the development of obesity. Ghrelin is found in both acylated (AG) and unacylated (UAG) forms in the circulation. In contrast to AG, UAG has been shown to inhibit food intake and to be elevated in anorexia nervosa. The present project is aiming to determine the underlying mechanisms driving the different nutritional phases in PWS.

Methods

Measurement of at least 4 h-fasting plasma acylated and unacylated ghrelin in 37 infants with a genetic diagnosis of PWS aged from 1 month to 4 years and in 100 age-matched controls without endocrine disorder recruited prior to minor surgery. One blood sampling was analysed for each patient/control and clinical data were recorded. Eleven PWS infants underwent repetitive blood samples at 3 or 6-month intervals during routine visits.

Results

In infants with PWS, AG is not elevated (p = 0.45), UAG is significantly higher (p = 0.0044; confidence interval 1.06;1.33) resulting in a low AG/UAG ratio (p = 0.0056; confidence interval 0.76;0.95) compared to controls.

Conclusion

Unlike children and adults with PWS that have high AG and AG/UAG ratio, infants with PWS have elevated UAG that supports the concept of anorexia in the early phases of the disease. The change in AG/UAG ratio possibly drives the switch from failure to thrive to obesity.

Clinical trial registration

NCT02529085.

Electronic supplementary material

The online version of this article (doi:10.1186/s13023-016-0440-0) contains supplementary material, which is available to authorized users.

Ghrelin Actions on Somatotropic and Gonadotropic Function in Humans

Ghrelin, a 28 amino-acid octanoylated peptide predominantly produced by the stomach, was discovered to be the natural ligand of the type 1a GH secretagogue receptor (GHS-R1a). It was thus considered as a natural GHS additional to GHRH, although later on ghrelin has mostly been considered a major orexigenic factor. The GH-releasing action of ghrelin takes place both directly on pituitary cells and through modulation of GHRH from the hypothalamus; some functional antisomatostatin action has also been shown. However, ghrelin is much more than a natural GH secretagogue. In fact, it also modulates lactotroph and corticotroph secretion in humans as well as in animals and plays a relevant role in the modulation of the hypothalamic-pituitary-gonadal function. Several studies have indicated that ghrelin plays an inhibitory effect on gonadotropin pulsatility, is involved in the regulation of puberty onset in animals, and may regulate spermatogenesis, follicular development and ovarian cell functions in humans. In this chapter ghrelin actions on the GH/IGF-I and the gonadal axes will be revised. The potential therapeutic role of ghrelin as a treatment of catabolic conditions will also be discussed.

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.

Adipocytokine levels in women with anorexia nervosa. Relationship with weight restoration and disease duration

OBJECTIVE

Starvation-induced depletion of fat stores in anorexia nervosa (AN) is known to be accompanied by alterations in some circulating adipocytokines. We analyzed a panel of circulating adipocytokines in women with AN compared with normal-weight controls and their relation with the disease duration and weight restoration.

METHOD

We analyzed circulating adipocytokine levels in 28 patients with AN and in 33 normal-weight controls who were eating healthily. We determined by enzyme-linked immunosorbent assay the circulating levels of total and high molecular weight (HMW) adiponectin, lipocalin-2 (LCN2), leptin, tumor necrosis factor receptor-II (TNFRII), interleukin-6 (IL6), adipocyte fatty acid binding protein-4 (FABP4), ghrelin, and resistin.

RESULTS

The two circulating forms of adiponectin are higher in AN women compared with controls. Both total and HMW adiponectin related negatively to the duration of the disease (r = -0.372, p = 0.033; r = -0.450, p = 0.038, respectively). Furthermore, the lipid binding-proteins LCN2 and FABP4 are lower in AN compared to the control group. Finally, leptin levels are lower in AN against controls and correlated positively with disease duration (r = 0.537, p = 0.007). Resistin, ghrelin, TNFRII, and IL6 have similar values in both groups, although TNFRII and ghrelin related negatively to body mass index variation at the end of treatment (r = -0.456, p = 0.039; r = -0.536, p = 0.015, respectively).

DISCUSSION

These results suggest there is a need to investigate if changes in adipocytokine levels could serve as weight restoration biomarkers. Further studies are warranted to elucidate the specific role of these molecules in the timing of weight restoration.

Obestatin: a new metabolic player in the pancreas and white adipose tissue

Obestatin is a 23 amino acid amidated peptide, member of the preproghrelin gene-derived peptides. Initially, obestatin was reported to exert opposite effects to those of ghrelin on food intake and body weight gain, through interaction with GPR39; however, these findings are still strongly debated and obestatin biological role remains largely unknown. Interestingly, binding of obestatin to the glucagon-like peptide 1 receptor has been recently suggested. Despite being a controversial peptide, recent findings have clearly indicated that obestatin is indeed a multifunctional peptide, exerting a variety of effects, such as stimulation of cell proliferation, survival and differentiation, influence on glucose and lipid metabolism, as well as anti-inflammatory and cardioprotective actions. Its positive effects on glucose and lipid metabolism candidate this peptide as a potential therapeutic tool in pathological conditions such as insulin resistance and diabetes.

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

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

The role of ghrelin, salivary secretions, and dental care in eating disorders

Eating disorders, including anorexia and bulimia nervosa, are potentially life-threatening syndromes characterized by severe disturbances in eating behavior. An effective treatment strategy for these conditions remains to be established, as patients with eating disorders tend to suffer from multiple relapses. Because ghrelin was originally discovered in the stomach mucosa, it has been widely studied over the past decade in an effort to uncover its potential roles; these studies have shed light on the mechanism by which ghrelin regulates food intake. Thus, studying ghrelin in the context of eating disorders could improve our understanding of the pathogenesis of eating disorders, possibly resulting in a promising new pharmacological treatment strategy for these patients. In addition, early detection and treatment of eating disorders are critical for ensuring recovery of young patients. Oral symptoms, including mucosal, dental, and saliva abnormalities, are typically observed in the early stages of eating disorders. Although oral care is not directly related to the treatment of eating disorders, knowledge of the oral manifestations of eating disorder patients may aid in early detection, resulting in earlier treatment; thus, oral care might contribute to overall patient management and prognosis. Moreover, ghrelin has also been found in saliva, which may be responsible for oral hygiene and digestion-related functions. This review discusses the pharmacological potential of ghrelin in regulating food-intake and the role of saliva and oral care in young patients with eating disorders.