Ghrelin administration affects circulating pituitary and gastro-entero-pancreatic hormones in acromegaly

Gastrointestinal symptoms in acromegaly: A case control study

BACKGROUND

Acromegaly is a chronic disease caused by a pituitary somatotroph adenoma resulting in excess secretion of growth hormone, which leads to excess secretion of Insulin like growth factor 1 from the liver, causing abnormal soft tissue growth. There is increasing awareness that diseases affecting connective tissue are associated with an increase in functional gastrointestinal symptoms. Data was collected from patients with a confirmed diagnosis of acromegaly to evaluate the intensity, variety and impact of abdominal symptoms in comparison with a control group who were healthy participants recruited from the local fracture clinic.

AIM

To evaluate the frequency type and burden of abdominal symptoms in acromegaly in comparison with a control group.

METHODS

Medical documentation of patients with a diagnosis of acromegaly treated in one tertiary medical centre between 2010 and 2017 has been analysed. Data was collected from patients with confirmed acromegaly, using the Short Form Health Survey (SF36) and Rome IV Diagnostic questionnaire for Functional Gastrointestinal Disorders in Adults (R4DQ) and compared to a sex- and age-matched control group, to assess the burden of abdominal symptoms. Microsoft Excel and IBM SPSS v 25 were used for data analysis.

RESULTS

Fifty patients with acromegaly (24 male and 26 females; age range 23-64 years, mean 43) and 200 controls (96 male and 104 females; age range 18-84, mean 42.4) were recruited. 92% (46 out of 50) of patients with acromegaly reported abdominal symptoms and 78% (39 out of 50) had at least one functional gastrointestinal disorder according to the Rome IV diagnostic criteria, compared to 16% of controls (OR > 1, P < 0.0001). The most commonly reported symptom was constipation (69% acromegaly vs 21% of controls OR > 1, P < 0.0001, 95%CI: 4.4–15.8). 34 out of 50 (68%) respondents met the criteria for functional constipation according to Rome IV. Upper gastrointestinal disorders were also more prevalent in the acromegaly group. There was no statistically significant difference in the prevalence of biliary and anorectal symptoms between the two groups. Patients in acromegaly group scored lower on the mean scores of the eight parameters of SF36 Quality of Life questionnaire (mean scores 60.04 vs 71.23, 95%CI: -13.6829 to -8.6971, OR > 1, P < 0.001) as compared to the control group.

CONCLUSION

Upper and lower functional gastrointestinal tract disorders (defined by Rome IV diagnostic criteria) are significantly more prevalent in patients with acromegaly compared with healthy age and sex matched controls in our study. Functional constipation is the most commonly reported problem. Poorer quality of life may in part be attributable to the increased prevalence of abdominal symptoms.

Clinical review: The human experience with ghrelin administration

CONTEXT

Ghrelin is an endogenous stimulator of GH and is implicated in a number of physiological processes. Clinical trials have been performed in a variety of patient populations, but there is no comprehensive review of the beneficial and adverse consequences of ghrelin administration to humans.

EVIDENCE ACQUISITION

PubMed was utilized, and the reference list of each article was screened. We included 121 published articles in which ghrelin was administered to humans.

EVIDENCE SYNTHESIS

Ghrelin has been administered as an infusion or a bolus in a variety of doses to 1850 study participants, including healthy participants and patients with obesity, prior gastrectomy, cancer, pituitary disease, diabetes mellitus, eating disorders, and other conditions. There is strong evidence that ghrelin stimulates appetite and increases circulating GH, ACTH, cortisol, prolactin, and glucose across varied patient populations. There is a paucity of evidence regarding the effects of ghrelin on LH, FSH, TSH, insulin, lipolysis, body composition, cardiac function, pulmonary function, the vasculature, and sleep. Adverse effects occurred in 20% of participants, with a predominance of flushing and gastric rumbles and a mild degree of severity. The few serious adverse events occurred in patients with advanced illness and were not clearly attributable to ghrelin. Route of administration may affect the pattern of adverse effects.

CONCLUSIONS

Existing literature supports the short-term safety of ghrelin administration and its efficacy as an appetite stimulant in diverse patient populations. There is some evidence to suggest that ghrelin has wider ranging therapeutic effects, although these areas require further investigation.

Ghrelin inhibits insulin release by regulating the expression of inwardly rectifying potassium channel 6.2 in islets

INTRODUCTION

The objective is to investigate the influence of ghrelin administration on both the insulin secretion and the expression of ATP-sensitive K(+) channels in islet.

METHODS

Ghrelin and [D-Lys] growth hormone releasing peptide-6 were administered via intraperitoneal injection in Wistar rats at the doses 10 and 10 μmol/kg/d for 2 weeks, respectively. Then glucose tolerance tests were performed and plasma insulin concentrations were measured. Islets were isolated for insulin release experiments. Single β cells were isolated for electrophysiological experiments. Determination of the Kir6.2 and SUR1 mRNA and protein expression levels in islets was performed by polymerase chain reaction and western blotting.

RESULTS

Intraperitoneal administration of exogenous ghrelin significantly (P < 0.05) increased blood glucose concentrations, attenuated insulin responses during glucose tolerance tests, reduced insulin release from the isolated islets induced by 11.1 and 16.7 mmol/L glucose, hyperpolarized the resting membrane potential and increased the Kir6.2 mRNA and protein expression levels. In contrast, counteraction of ghrelin by intraperitoneal injection of [D-Lys(3)] growth hormone releasing peptide-6 significantly (P < 0.05) attenuated the aforementioned changes. SUR1 expression levels were not altered in this study.

CONCLUSIONS

Ghrelin via pancreatic growth hormone secretagogue receptor up-regulates the Kir6.2 expression in islet by hyperpolarizing the resting membrane potential which results in the inhibition of insulin release.

Interactions of gastrointestinal peptides: ghrelin and its anorexigenic antagonists

Food intake behaviour and energy homeostasis are strongly regulated by a complex system of humoral factors and nerval structures constituting the brain-gut-axis. To date the only known peripherally produced and centrally acting peptide that stimulates food intake is ghrelin, which is mainly synthesized in the stomach. Recent data indicate that the orexigenic effect of ghrelin might be influenced by other gastrointestinal peptides such as cholecystokinin (CCK), bombesin, desacyl ghrelin, peptide YY (PYY), as well as glucagon-like peptide (GLP). Therefore, we will review on the interactions of ghrelin with several gastrointestinal factors known to be involved in appetite regulation in order to elucidate the interdependency of peripheral orexigenic and anorexigenic peptides in the control of appetite.

Ghrelin inhibits the development of acute pancreatitis and nuclear factor kappaB activation in pancreas and liver

OBJECTIVES

To investigate the influence of ghrelin on the development of severe acute pancreatitis (SAP) and the expression of nuclear factor kappaB (NF-kappaB) p65 in the pancreas and liver.

METHODS

Severe acute pancreatitis was induced in rat by sodium taurocholate injection in the pancreaticobiliary duct. Ghrelin was administrated twice at the dose 10 or 20 nmol/kg per injection, respectively. Then, serum amylase activity; serum tumor necrosis factor alpha, interleukin 1beta, and interleukin 6 concentrations; and morphological signs of pancreatitis and hepatic damage were measured. Meanwhile, determination of pancreatic and hepatic NF-kappaB p65 expression was performed by Western blotting and immunohistochemistry.

RESULTS

The serumal parameters increased, and morphological damages were observed in the pancreas and liver in SAP rats. Nuclear factor kappaB p65 expression was significantly higher in the pancreas and liver than sham-operated rats (P < 0.05). Treatment with ghrelin attenuated the morphological damages, and reduced the serumal parameters. Nuclear factor kappaB p65 expression was also significantly reduced by ghrelin (P < 0.05), both in the pancreas and liver.

CONCLUSIONS

Ghrelin inhibits the development of acute pancreatitis induced by sodium taurocholate. It exerts the therapeutic effects through inhibiting NF-kappaB expression, thereby blocks the inflammatory signal transduction pathway and reduces the release of inflammatory media and cytokines.

Ghrelin in pathological conditions

The recently identified gastric hormone ghrelin was initially described as a natural Growth Hormone Secretagogue Receptor ligand. Apart from ghrelin's first discovered action, which was the stimulation of Growth Hormone release, implications for many other functions have been reported. It seems that ghrelin exhibits an important role in conditions related to processes regulating nutrition, body composition and growth, as well as heart, liver, thyroid or kidney dysfunction. In this review, current available knowledge about ghrelin's role in various pathological conditions is presented.

Tuning inflammation with anti-inflammatory neuropeptides

The immune system is confronted with the daunting task of defending the organism against invading pathogens while at the same time remaining self-tolerant to the body's own constituents and preserving its integrity. The loss of immune tolerance stemming from an unbalance in pro-inflammatory factors versus anti-inflammatory cytokines, or of autoreactive/inflammatory T helper 1 cells versus regulatory/suppressive T cells, results in the breakdown of immune homeostasis and the subsidiary appearance of exacerbated inflammatory and autoimmune diseases. Some neuropeptides have been shown to have anti-inflammatory properties and to participate in maintaining immune tolerance. Here the authors examine the most recent developments in this field and highlight the effectiveness of using neuropeptides in treating several inflammatory and autoimmune disorders.

Ghrelin in neuroendocrine organs and tumours

Ghrelin is a 28 amino-acid hormone with multiple functions. It is predominantly produced by the stomach but has also been detected in other organs, including the small intestine, pancreas, hypothalamus and pituitary, as well as in the immune system and almost every other normal human tissue examined. It is also present in neuroendocrine tumours, pituitary adenomas, endocrine tumours of the pancreas, breast tumours, and thyroid and medullary thyroid carcinomas. Ghrelin is a brain-gut peptide with growth hormone-releasing and appetite-inducing activities, and is the endogenous ligand of the G protein-coupled growth hormone secretagogue receptor (GHS-R). In this review we comprehensively summarize the available data regarding (a) the expression of ghrelin and the GHS-R in normal endocrine tissues and in pituitary adenomas and neuroendocrine tumours, (b) the levels of circulating ghrelin in patients with pituitary adenomas and neuroendocrine tumours and (c) the effects of ghrelin administration in these patients on the levels of other hormones and on the rate of proliferation of the tumour. It is clear that ghrelin has many more functions and is involved in many more processes than was initially postulated, and its endocrine, paracrine and autocrine effects play a role in its physiological and pathophysiological functions.

Cortistatin-17 and somatostatin-14 display the same effects on growth hormone, prolactin, and insulin secretion in patients with acromegaly or prolactinoma

CONTEXT

Cortistatin binds all somatostatin receptor subtypes but also has particular central actions; moreover, a specific cortistatin receptor has also been discovered.

OBJECTIVE

We compared the endocrine effects of cortistatin-17 with those of somatostatin-14 in patients with acromegaly (ACRO) or prolactinoma (PRLOMA). Normal subjects (NS) were studied as control group.

DESIGN

All subjects underwent the following tests: 1) saline, 2) somatostatin-14 (2.0 microg/kg.h iv, 0-120 min) and 3) cortistatin-17 (2.0 microg/kg.h iv, 0-120 min) infusion.

RESULTS

Cortistatin-17 and somatostatin-14 inhibited GH secretion to the same extent in ACRO (P < 0.05) and NS (P < 0.01). Cortistatin-17 and somatostatin-14 inhibited PRL secretion in PRLOMA (P < 0.05), to some extent in ACRO (P value not significant), but not in NS. Insulin secretion was inhibited by both cortistatin-17 and somatostatin-14 to the same extent in all groups (P < 0.05).

CONCLUSIONS

Cortistatin-17 and somatostatin-14 display the same effects on GH, PRL, and insulin secretion in patients with ACRO or PRLOMA.

Acute psychological stress raises plasma ghrelin in the rat

Ghrelin is produced by the A-like cells of the stomach and mobilized by food deprivation. It was reported recently that acute psychological stress increases ghrelin gene expression in rat oxyntic mucosa. The aim of this study was to examine the effect of such stress on circulating ghrelin levels. To this end, we measured plasma ghrelin in Wistar Kyoto (WKY) rats (a high-anxiety strain) and Sprague-Dawley (SPD) rats (a low-anxiety strain), exposed to water avoidance stress for 60 min. Blood was collected before and after the stress. Acute stress increased the plasma ACTH concentration approximately 5-fold (p<0.01) in both strains of rats, while plasma ghrelin increased by 85% (p<0.01) in the SPD rats and by 40% (p<0.001) in the WKY rats. Ghrelin levels after acute stress were higher (p<0.05) in the SPD rats than in the WKY rats. Sham stress did not affect plasma ghrelin. We conclude that acute psychological stress mobilizes ghrelin and that the SPD rats respond with a higher plasma ghrelin concentration than the WKY rats.

Effects of central infusion of ghrelin on food intake and plasma levels of growth hormone, luteinizing hormone, prolactin, and cortisol secretion in sheep

Ghrelin is an endogenous ligand for the GH secretagogue/ghrelin receptor (GHS-R) and stimulates feeding behavior and GH levels in rodents and humans. A preprandial increase in plasma ghrelin levels is seen in sheep on programmed feeding, followed by a postprandial rise in plasma GH levels, but effects on food intake and endocrine function are not defined in this ruminant species. We administered ghrelin to female sheep in various modes and measured effects on voluntary food intake (VFI) and plasma levels of GH, LH, prolactin, and cortisol. Whether administered intracerebroventricularly or iv, ghrelin consistently failed to stimulate VFI. On the other hand, ghrelin invariably increased plasma GH levels and alpha,beta-diaminopropanoic acid-octanoyl3 human ghrelin was more potent than ovine ghrelin. Bolus injection of ghrelin into the third cerebral ventricle reduced plasma LH levels but did not affect levels of prolactin or cortisol. These findings suggested that the preprandial rise in plasma ghrelin that is seen in sheep on programmed feeding does not influence VFI but is likely to be important in the postprandial rise in GH levels. Thus, ghrelin does not appear to be a significant regulator of ingestive behavior in this species of ruminant but acts centrally to indirectly regulate GH and LH secretion.

Differential effects of sham feeding and meal ingestion on ghrelin and pancreatic polypeptide levels: evidence for vagal efferent stimulation mediating ghrelin release

Ghrelin has been suggested to function as an appetite-stimulating signal from the gastrointestinal tract to the brain acting through a vagal afferent pathway. Ghrelin levels rise before meals and fall after meal ingestion. The purpose of this study was to investigate factors which regulate ghrelin release into the circulation by determining changes in systemic ghrelin concentrations after sham feeding and meal ingestion.

METHODS

Fifteen normal subjects underwent sham feeding of a bacon and cheese toasted sandwich. Serial blood samples were obtained before and every 5 min for another 30 min during sham feeding and for 30 min after actual meal ingestion. Radioimmunoassay was used to measure plasma ghrelin and pancreatic polypeptide concentrations.

RESULTS

During sham feeding, plasma ghrelin concentration increased from 1730+/-237 to 1917+/-269 pg/mL (P<0.05) and plasma pancreatic polypeptide increased from 417+/-50 to 841+/-97 pg/mL (P<0.01). Subsequent meal ingestion was characterized by an increase in pancreatic polypeptide from 782+/-88 to 1710+/-119 pg/mL (P<0.01), but no significant change in ghrelin levels.

CONCLUSIONS

Plasma ghrelin and pancreatic polypeptide concentrations increase with sham feeding. This suggests a vagal efferent pathway mediating ghrelin release. In contrast to pancreatic polypeptide which rises with actual meal ingestion, ghrelin levels did not change.