Appetite and gastrointestinal motility: role of ghrelin-family peptides

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.

Roles of Adipokines in Digestive Diseases: Markers of Inflammation, Metabolic Alteration and Disease Progression

Adipose tissue is a highly dynamic endocrine tissue and constitutes a central node in the interorgan crosstalk network through adipokines, which cause pleiotropic effects, including the modulation of angiogenesis, metabolism, and inflammation. Specifically, digestive cancers grow anatomically near adipose tissue. During their interaction with cancer cells, adipocytes are reprogrammed into cancer-associated adipocytes and secrete adipokines to affect tumor cells. Moreover, the liver is the central metabolic hub. Adipose tissue and the liver cooperatively regulate whole-body energy homeostasis via adipokines. Obesity, the excessive accumulation of adipose tissue due to hyperplasia and hypertrophy, is currently considered a global epidemic and is related to low-grade systemic inflammation characterized by altered adipokine regulation. Obesity-related digestive diseases, including gastroesophageal reflux disease, Barrett's esophagus, esophageal cancer, colon polyps and cancer, non-alcoholic fatty liver disease, viral hepatitis-related diseases, cholelithiasis, gallbladder cancer, cholangiocarcinoma, pancreatic cancer, and diabetes, might cause specific alterations in adipokine profiles. These patterns and associated bases potentially contribute to the identification of prognostic biomarkers and therapeutic approaches for the associated digestive diseases. This review highlights important findings about altered adipokine profiles relevant to digestive diseases, including hepatic, pancreatic, gastrointestinal, and biliary tract diseases, with a perspective on clinical implications and mechanistic explorations.

Pharmacological manipulation of the ghrelin system and alcohol hangover symptoms in heavy drinking individuals: Is there a link?

Ghrelin, an orexigenic peptide synthesized in the stomach, is a key player in the gut-brain axis. In addition to its role in regulating food intake and energy homeostasis, ghrelin has been shown to modulate alcohol-related behaviors. Alcohol consumption frequently results in hangover, an underexplored phenomenon with considerable medical, psychological, and socioeconomic consequences. While the pathophysiology of hangover is not clear, contributions of mechanisms such as alcohol-induced metabolic/endocrine changes, inflammatory/immune response, oxidative stress, and gut dysbiosis have been reported. Interestingly, these mechanisms considerably overlap with ghrelin's physiological functions. Here, we investigated whether pharmacological manipulation of the ghrelin system may affect alcohol hangover symptoms. Data were obtained from two placebo-controlled laboratory studies. The first study tested the effects of intravenous (IV) ghrelin and consisted of two experiments: a progressive-ratio IV alcohol self-administration (IV-ASA) and a fixed-dose IV alcohol clamp. The second study tested the effects of an oral ghrelin receptor inverse agonist (PF-5190457) and included a fixed-dose oral alcohol administration experiment. Alcohol hangover data were collected the morning after each alcohol administration experiment using the Acute Hangover Scale (AHS). IV ghrelin, compared to placebo, significantly reduced alcohol hangover after IV-ASA (p = 0.04) and alcohol clamp (p = 0.04); PF-5190457 had no significant effect on AHS scores. Females reported significantly higher hangover symptoms than males following the IV-ASA experiment (p = 0.04), but no gender × drug condition (ghrelin vs. placebo) effect was found. AHS total scores were positively correlated with peak subjective responses, including 'stimulation' (p = 0.08), 'sedation' (p = 0.009), 'feel high' (p = 0.05), and 'feel intoxicated' (p = 0.03) during the IV-ASA. IV ghrelin blunted the positive association between alcohol sedation and hangover as shown by trend-level drug × sedation effect (p = 0.08). This is the first study showing that exogenous ghrelin administration, but not ghrelin receptor inverse agonism, affects hangover symptoms. Future research should investigate the potential mechanism(s) underlying this effect.

Change of appetite in patients with functional digestive disorder. Association with psychological disorders: A cross-sectional study

BACKGROUND AND AIMS

Changes in appetite are a frequent complaint in patients with functional gastrointestinal disorders (FGIDs). The aims of this study are to evaluate whether the changes in appetite are associated with specific FGIDs and to explore associations of these changes with symptoms of anxiety or depression.

METHODS

This study included 1009 consecutive FGID patients (71% female), aged 48.9 years who all filled out a Rome III questionnaire for the evaluation of FGIDs, submitted to a psychological evaluation of symptoms of anxiety, and completed the Beck Depression Inventory questionnaire. The patients were classified according to their appetite change using a 7-point grading scale and split into three groups: those with appetite loss, those with no change in appetite, and those with increased appetite.

RESULTS

Among the 1009, 496 patients (49%) reported a change in appetite, of which 332 (33%) patients reported a decrease in appetite and 164 (16%) patients reported an increase in appetite. Appetite was not affected in 51% of patients. Changes in appetite depended on gender, body mass index and psychometric evaluation scores. Increased appetite did not have specific FGIDs associations, while decreased appetite was associated with esophageal, gastroduodenal, bowel, and anorectal symptoms. The presence of depressive symptoms was also a predictor for the majority of FGIDs in decreased appetite, while anxiety trait was significant for globus and dysphagia.

CONCLUSIONS

Decreased appetite was associated with FGIDs, especially in the presence of depressive symptoms. A reduced appetite would help to predict psychological disorders associated with FGIDs.

FINANCIAL DISCLOSURE

None declared.

LEGAL REGISTRATION

This study was a registered study in the French National Drug Agency (ANSM, Agence Nationale de Securité du Medicamentet des produits de santé, Study Number 2016-A01120-51).

COMPETING INTERESTS

Michel Bouchoucha, Marinos Fysekidis, Florence Mary, Gheorghe Airinei, Cyriaque Bon, and Robert Benamouzig have no competitive interests.

The Role of the Ghrelin System in Drug Addiction

In the past years, a significant volume of research has implicated the appetitive hormone ghrelin in the mechanisms underlying drug use and addiction. From a neuroscientific standpoint, ghrelin modulates both reward and stress pathways, two key drivers of substance use behaviors. Previous investigations support a connection between the ghrelin system and alcohol, stimulants, and tobacco use in both animals and humans, while the research on opioids and cannabis is scarce. In general, upregulation of the ghrelin system seems to enhance craving for drugs as well as substances use. On the other hand, acute and chronic exposure to drugs of abuse influences the ghrelin system at different levels. This chapter summarizes the literature on the relationship between the ghrelin system and substance-related behaviors. We also review recent work investigating the ghrelin system as a potential pharmacological target for treating substance use disorders and discuss the need for additional research.

Ghrelin, Amylin, Gastric Inhibitory Peptide and Cognition in Middle-Aged HIV-Infected and Uninfected Women: The Women's Interagency HIV Study

OBJECTIVE

To explore the gut-brain axis by examining gut hormone levels and cognitive test scores in women with (HIV+) and without (HIV-) HIV infection.

DESIGN/METHODS

Participants included 356 women (248 HIV+, 108 at risk HIV-) in the Brooklyn Women's Interagency HIV Study (WIHS) with measured levels of ghrelin, amylin and gastric inhibitory peptide (GIP), also known as glucose-dependent insulinotropic polypeptide. Cross-sectional analyses using linear regression models estimated the relationship between gut hormones and Trails A, Trails B, Stroop interference time, Stroop word recall, Stroop color naming and reading, and Symbol Digit Modalities Test (SDMT) with consideration for age, HIV infection status, Wide Range Achievement Test score (WRAT), CD4 count, insulin resistance, drug use, and race/ethnicity.

RESULTS

Among women at mid-life with chronic (at least 10 years) HIV infection or among those at risk, ghrelin, amylin and GIP were differentially related to cognitive test performance by cognitive domain. Better performance on cognitive tests was generally associated with higher ghrelin, amylin and GIP levels. However, the strength of association varied, as did significance level by HIV status.

CONCLUSION

Previous analyses in WIHS participants have suggested that higher BMI, waist, and WHR are associated with better cognitive function among women at mid-life with HIV infection. This study indicates that higher gut hormone levels are also associated with better cognition. Gut hormones may provide additional mechanistic insights regarding the association between obesity and Type 2 diabetes and cognition in middle-aged HIV+ and at risk HIV- women. In addition, measuring these hormones longitudinally would add to the understanding of mechanisms of actions of these hormones and their use as potential clinical tools for early identification and intervention on cognitive decline in this vulnerable population.

Exercise-trained men and women: role of exercise and diet on appetite and energy intake

The regulation of appetite and energy intake is influenced by numerous hormonal and neural signals, including feedback from changes in diet and exercise. Exercise can suppress subjective appetite ratings, subsequent energy intake, and alter appetite-regulating hormones, including ghrelin, peptide YY, and glucagon-like peptide 1(GLP-1) for a period of time post-exercise. Discrepancies in the degree of appetite suppression with exercise may be dependent on subject characteristics (e.g., body fatness, fitness level, age or sex) and exercise duration, intensity, type and mode. Following an acute bout of exercise, exercise-trained males experience appetite suppression, while data in exercise-trained women are limited and equivocal. Diet can also impact appetite, with low-energy dense diets eliciting a greater sense of fullness at a lower energy intake. To date, little research has examined the combined interaction of exercise and diet on appetite and energy intake. This review focuses on exercise-trained men and women and examines the impact of exercise on hormonal regulation of appetite, post-exercise energy intake, and subjective and objective measurements of appetite. The impact that low-energy dense diets have on appetite and energy intake are also addressed. Finally, the combined effects of high-intensity exercise and low-energy dense diets are examined. This research is in exercise-trained women who are often concerned with weight and body image issues and consume low-energy dense foods to keep energy intakes low. Unfortunately, these low-energy intakes can have negative health consequences when combined with high-levels of exercise. More research is needed examining the combined effect of diet and exercise on appetite regulation in fit, exercise-trained individuals.

Stomach--key player in the regulation of metabolism

Although the stomach is often perceived as a crude, food-grinding, muscular bag, scientific breakthroughs have shown us that in the case of the stomach there is more than meets the eye. The endocrine function of the stomach is mainly exerted through the actions of ghrelin, an acylated peptide hormone that is the first known and so far most extensively studied endogenous orexigenic substance. The satiety-hunger balance is kept in check by many anorexigenic gut hormones among which is the deacylated form of ghrelin--desacyl ghrelin. The interplay of gut hormones affects the brain directly, as most gut hormones cross the blood-brain barrier and bind to their respective receptors in the central nervous system. Other hormones like obestatin and nesfatin are secreted from the stomach along with ghrelin, yet their physiological function is to be elucidated. The importance of the satiety-hunger balance can be seen in its most typical derangement--obesity. Some studies imply that ghrelin, along with other gut hormones, plays an important part in the pathophysiology of obesity. More importantly, it seems that the mechanisms by which bariatric surgery procedures induce weight loss are primarily based on changing the gut hormone levels, including ghrelin. If proven, ghrelin antagonists could be the renaissance of pharmacological obesity treatment.

Effects of ghrelin on gastric distension sensitive neurons and gastric motility in the lateral septum and arcuate nucleus regulation

BACKGROUND

Ghrelin is an endogenous ligand for the growth hormone secretagogue receptor (GHS-R) and a peptide hormone that promotes food intake and gastric motility. Our aims are to explore the effects of ghrelin on gastric distension (GD) sensitive neurons in the lateral septum, and the possible regulation of gastric motility by ghrelin through the hypothalamic arcuate nucleus (ARC).

METHODS

Single-unit discharges were recorded, extracellularly, and the gastric motility was monitored by the administration of ghrelin in the lateral septum. The projection of nerve fiber and expression of ghrelin were observed by retrograde tracer and fluo-immunohistochemistry staining. The expression of GHS-R and ghrelin was determined by real-time polymerase chain reaction and western blotting analysis.

RESULTS

There were GD neurons in the lateral septum. The administration of ghrelin could excite both GD-excitatory (GD-E) and GD-inhibitory (GD-I) neurons in the lateral septum. Gastric motility was significantly enhanced by the administration of ghrelin in the lateral septum in a dose-dependent manner. Pretreatment with [D-Lys-3]-GHRP-6, however, could completely abolish the ghrelin-induced effects. Electrical stimulation of the ARC could significantly excite the response of GD neurons to ghrelin, increase ghrelin protein expression in the lateral septum and promote gastric motility. Nevertheless, these effects could be mitigated by pretreatment of [D-Lys-3]-GHRP-6. Electrical lesion of the lateral septum resulted in decreased gastric motility. The GHS-R and Ghrelin/FG-double labeled neurons were observed in the lateral septum and ARC, respectively.

CONCLUSIONS

It is suggested that the lateral septum may receive afferent information from the gastrointestinal tract and promote gastric motility. Ghrelin plays an important role in promoting gastric motility in the lateral septum. The ARC may be involved in the regulation of the lateral septum's influence on gastric motility.

Central nesfatin-1 influences the excitability of ghrelin-responsive gastric distension neurons in the arcuate nucleus and reduces gastric motility in rats

Although the novel satiety peptide nesfatin-1 has been shown to regulate gastric motility, the underlying mechanisms have yet to be elucidated. The study aimed to explore the effects of nesfatin-1 on ghrelin-responsive gastric distension (GD) neurons in the arcuate nucleus (Arc), and potential regulation mechanisms of gastric motility by the paraventricular nucleus (PVN). Single-unit discharges in the Arc were recorded extracellularly, and gastric motility in conscious rats was monitored during the administration of nesfatin-1 to the Arc or electrical stimulation of the PVN. Retrograde tracing and fluo-immunohistochemistry staining were used to determine NUCB2/nesfatin-1 neuronal projections. Nesfatin-1 inhibited most of the ghrelin-responsive GD-excitatory neurons, but excited ghrelin-responsive GD-inhibitory neurons in the Arc. Gastric motility was significantly reduced by nesfatin-1 administration to the Arc in a dose-dependent manner. The firing activity in the Arc and changes to gastric motility were partly reduced by SHU9119, an antagonist of melanocortin 3/4 receptors. Electrical stimulation of PVN excited most of the ghrelin-responsive GD neurons in the Arc and promoted gastric motility. Nonetheless, pretreatment with an anti-NUCB2/nesfatin-1 antibody in the Arc further increased the firing rate of most of the ghrelin-responsive GD-excitatory neurons and decreased the ghrelin-responsive GD-inhibitory neurons following electrical stimulation of the PVN. Gastric motility was enhanced by pretreatment with an anti-NUCB2/nesfatin-1 antibody in the Arc following PVN stimulation. Furthermore, NUCB2/nesfatin-1/fluorogold double-labeled neurons were detected in the PVN. These results suggest that nesfatin-1 could serve as an inhibitory factor in the Arc to regulate gastric motility via the melanocortin pathway. The PVN could be involved in the regulation of the Arc in gastric activity.

Ghrelin induces gastric cancer cell proliferation, migration, and invasion through GHS-R/NF-κB signaling pathway

This study aims to investigate the roles of ghrelin signaling in human gastric carcinoma cell lines AGS and SGC7901. Effects of ghrelin signaling on CDK6, P53, NF-κB/P65 and MMP2 mRNA and/or protein expression were determined by real-time PCR and western blot. MTT method and flow cytometry were performed to assess the gastric cancer cell proliferation. The SGC7901 cells overexpressing ghrelin were inoculated into nude mice to produce tumors which were measured later. The wound-healing assay and cell invasion assay were used to test the cell migration and invasive ability of gastric cancer. Ghrelin signaling promotes the oncogene CDK6 gene expression and represses the tumor suppressor gene P53 gene expression in gastric cancer. Ghrelin activates NF-κB/P65 signaling pathway through GHS-R in gastric cancer. Ghrelin upregulates the metastasis factor MMP2 expression via GHS-R/NF-κB signaling pathway in gastric cancer cells and promotes tumor cells migration and invasion, suggesting that ghrelin signaling is a critical pathway in cancer metastasis. Ghrelin induces cell proliferation, migration and invasion via GHS-R/NF-κB signaling pathway in gastric cancer cells. Ghrelin treatment must be avoided for gastric cancer patients.

Conformation propensities of des-acyl-ghrelin as probed by CD and NMR

Des-acyl-ghrelin is a 28 amino acid peptide secreted by both human and rat stomach. Together with ghrelin and obestatin, it is obtained by post-translational modification of a 117 aminoacid prepropeptide mainly expressed in distinct endocrine cell type in the stomach. Although its receptor has not been unambiguously identified so far, des-acyl-ghrelin is considered one of the strongest antagonists of ghrelin in activating the growth hormone secretagogue receptor (GHS-R). Here the secondary structure of des-acyl-ghrelin in different experimental conditions has been investigated and compared with that of obestatin, a bioactive peptide having similar biological functions. CD and NMR techniques have been combined for gaining the desired conformational features. The obtained structures support a steady alpha-helix structure spanning residues from 7 to 14, very similar to that observed for obestatin at the same experimental conditions, leading to suggest that a similar secondary structure can be associated with the similar biological role.

Ghrelin, acylated ghrelin, leptin and PYY-3 levels in hyperemesis gravidarum

OBJECTIVE

To assess the serum levels of gut and adipocyte-derived metabolic hormones that control appetite, adipocity, weight gain and energy hemostasis, namely total ghrelin (TG), acylated ghrelin (AG), leptin and PYY-3 in hyperemesis gravidarum (HG).

METHODS

Plasma samples of 86 women in their first trimester pregnancies with HG (n = 30), morning sickness of pregnancy (MSP) (n = 34) and control (n = 22) groups were obtained. Serum levels of TG, AG, leptin and PYY-3 were compared between the groups, and the correlations with severity of symptoms using modified PUQE (Pregnancy Unique Quantification of Emesis) scoring, BMI, E2, hCG and TSH were calculated.

RESULTS

Levels of TG, AG, PYY-3 and the TG/leptin ratio were significantly higher in HG group compared to MSP and the control groups (p ≤ 0.017). AG/TG ratio was significantly lower in the HG group compared to both MSP and control groups (p ≤ 0.017). There were either weak or no significant statistical correlations between the gut and adipose-related hormones and the modified PUQE scores, BMI, E2, hCG and TSH.

CONCLUSION

Gut-derived metabolic hormones ghrelin, AG and PYY-3 may be involved in the HG pathophysiology.

Bariatric embolization for suppression of the hunger hormone ghrelin in a porcine model

PURPOSE

To prospectively test in a porcine model the hypothesis that bariatric embolization with commercially available calibrated microspheres can result in substantial suppression of systemic ghrelin levels and affect weight gain over an 8-week period.

MATERIALS AND METHODS

The institutional animal care and use committee approved this study. Twelve healthy growing swine (mean weight, 38.4 kg; weight range, 30.3-47.0 kg) were evaluated. Bariatric embolization was performed by infusion of 40-μm calibrated microspheres selectively into the gastric arteries that supply the fundus. Six swine underwent bariatric embolization, while six control animals underwent a sham procedure with saline. Weight and fasting plasma ghrelin and glucose levels were obtained in animals at baseline and at weeks 1-8. Statistical testing for differences in serum ghrelin levels and weight at each time point was performed with the Wilcoxon signed rank test for intragroup differences and the Wilcoxon rank sum test for intergroup differences.

RESULTS

The pattern of change in ghrelin levels over time was significantly different between control and experimental animals. Weekly ghrelin levels were measured in control and experimental animals as a change from baseline ghrelin values. Average postprocedure ghrelin values increased by 328.9 pg/dL ± 129.0 (standard deviation) in control animals and decreased by 537.9 pg/dL ± 209.6 in experimental animals (P = .004). The pattern of change in weight over time was significantly different between control and experimental animals. The average postprocedure weight gain in experimental animals was significantly lower than that in control animals (3.6 kg ± 3.8 vs 9.4 kg ± 2.8, respectively; P = .025).

CONCLUSION

Bariatric embolization can significantly suppress ghrelin and significantly affect weight gain. Further study is warranted before this technique can be used routinely in humans.

Molecular identification of GHS-R and GPR38 in Suncus murinus

We previously identified ghrelin and motilin genes in Suncus murinus (suncus), and also revealed that motilin induces phase III-like strong contractions in the suncus stomach in vivo, as observed in humans and dogs. Moreover, repeated migrating motor complexes were found in the gastrointestinal tract of suncus at regular 120-min intervals. We therefore proposed suncus as a small laboratory animal model for the study of gastrointestinal motility. In the present study, we identified growth hormone secretagogue receptor (GHS-R) and motilin receptor (GPR38) genes in the suncus. We also examined their tissue distribution throughout the body. The amino acids of suncus GHS-R and GPR38 showed high homology with those of other mammals and shared 42% amino acid identity. RT-PCR showed that both the receptors were expressed in the hypothalamus, medulla oblongata, pituitary gland and the nodose ganglion in the central nervous system. In addition, GHS-R mRNA expressions were detected throughout the stomach and intestine, whereas GPR38 was expressed in the gastric muscle layer, lower intestine, lungs, heart, and pituitary gland. These results suggest that ghrelin and motilin affect gut motility and energy metabolism via specific receptors expressed in the gastrointestinal tract and/or in the central nervous system of suncus.

Des-acyl ghrelin exhibits pro-anabolic and anti-catabolic effects on C2C12 myotubes exposed to cytokines and reduces burn-induced muscle proteolysis in rats

Although ghrelin and GHRP-2 have been shown to inhibit skeletal muscle proteolysis in rats with burn injury, the effects of des-acyl ghrelin (DAG) have not been reported. In this paper, we demonstrate that continuous 24h administration of DAG attenuated burn-induced EDL muscle proteolysis, and normalized elevated TNFα mRNA. Combined treatment of cultured C2C12 myotubes with TNFα and IFN-γ (TNF+IFN) inhibited protein synthesis and increased protein breakdown; DAG abolished both effects. PI3 kinase inhibition by LY294002 and mTOR inhibition by rapamycin blocked the reversal of the anti-anabolic effects of TNF+IFN-treated myotubes by DAG. DAG also reversed or attenuated the TNF+IFN-induced reduction in phosphorylation of Akt, FOXO1, 4E-BP-1, and GSK-3β in myotubes. Furthermore, DAG attenuated the atrophy signal, phospho-NF-κB, and the mRNA expression of MAFbx and MuRF1, upregulated by TNF+IFN in C2C12 myotubes. We conclude that DAG reduces muscle cachexia produced by injury and proinflammatory cytokines, and that DAG or DAG-based compounds may be useful in treating wasting disorders.

Structures and molecular forms of the ghrelin-family peptides

Ghrelin is an acylated peptide hormone produced mainly from the stomach. The major active products of the ghrelin gene in the stomach of rats, mice and humans are 28-amino acid peptides acylated at the serine-3 position with an n-octanoyl group (C8:0), called simply ghrelin. However, recent studies have revealed that the ghrelin gene can generate a variety of bioactive molecules besides ghrelin. These include acyl forms of ghrelin other than C8:0-ghrelin (i.e., n-decanoyl ghrelin or n-decenoyl ghrelin), des-acyl ghrelin, obestatin and ghrelin-associated peptides originated from the ghrelin gene. This review surveys the structures of the ghrelin peptides and molecular forms of ghrelin gene-derived products, and summarizes the knowledge about the functions of these peptides, with an emphasis on the acyl forms of the ghrelin peptide.

Contribution of anorexia to tissue wasting in cachexia

PURPOSE OF REVIEW

Anorexia is a severe debilitating symptom characterizing the clinical course of several chronic diseases. It negatively impacts on patient outcome by contributing to weight loss, lean body mass catabolism and adipose tissue wasting. Although disease-associated anorexia may stand alone as a clinically relevant symptom, it is now considered as a component of the cachexia syndrome. The present review discusses experimental and clinical data indicating that the pathogenic mechanisms of anorexia may also suggest a neural control of tissue wasting in cachexia.

RECENT FINDINGS

Consistent data show that selective melanocortin receptor antagonism modulates food intake and reduces wasting in experimental models of chronic disease. Consequently, ghrelin administration, whose prophagic effects are related to melanocortin antagonism, has been tested both in animal studies and human trials, with promising effects, although restoration of lean body mass has been not achieved. More interest is driven by the use of small molecules selectively antagonising hypothalamic melanocortin receptors.

SUMMARY

The 'brain-muscle axis' coordinated by the hypothalamus seems to mediate the onset of not only anorexia but also tissue wasting in cachexia, by centrally influencing energy homeostasis and the balance between anabolism and catabolism.

Endogenous gastric mediators: patho-physiological role and measurements

The protocols described in this unit are designed to present the major endogenous gastric mediators involved in the control of gastric acid secretion, namely gastrin and histamine, and in the regulation of gastric motility, which include motilin and ghrelin, under physiological and pathological conditions. The measurement of these mediators in plasma or serum of humans and animals by radioimmunoassay are described and their pathophysiological role is discussed.