Effects of ghrelin receptor agonist, relamorelin, on gastric motor functions and satiation in healthy volunteers

Resolution of severe gastroparesis induced by parasympathetic surge following facial trauma: a case report

BACKGROUND

Gastroparesis is a condition that affects the motility of the gastrointestinal (GI) tract, causing a delay in the emptying process and leading to nausea, vomiting, bloating, and upper abdominal pain. Motility treatment along with symptom management can be done using antiemetics or prokinetics. This study highlights the diagnostic and therapeutic challenges of gastroparesis and suggests a potential link between facial trauma and symptom remission, indicating the need for further investigation.

CASE PRESENTATION

A 46-year-old Hispanic man with hypertension, type 2 diabetes (T2D), and hyperlipidemia on amlodipine 10 mg, lisinopril 5 mg, empagliflozin 25 mg, and insulin glargine presented with a diabetic foot ulcer with probable osteomyelitis. During hospitalization, the patient developed severe nausea and vomiting. The gastroenterology team advised continuing antiemetic medicine and trying very small sips of clear liquids. However, the patient didn't improve. Therefore, the gastroenterology team was contacted again. They advised having stomach emptying tests to rule out gastroparesis as the source of emesis. In addition, they recommended continuing metoclopramide, and starting erythromycin due to inadequate improvement. Studies found a 748-min stomach emptying time. Normal is 45-90 min. An uneventful upper GI scope was done. Severe gastroparesis was verified, and the gastroenterology team advised a percutaneous jejunostomy or gastric pacemaker for gastroparesis. Unfortunately, the patient suffered a mechanical fall resulting in facial trauma. After the fall, the patient's nausea eased, and emesis stopped. He passed an oral liquids trial after discontinuation of erythromycin and metoclopramide.

CONCLUSION

This case exemplifies the difficulties in diagnosing and treating gastroparesis. An interesting correlation between parasympathetic surges and recovery in gastroparesis may be suggested by the surprising remission of symptoms following face injuries.

Prokinetics-safety and efficacy: The European Society of Neurogastroenterology and Motility/The American Neurogastroenterology and Motility Society expert review

BACKGROUND

Prokinetics are a class of pharmacological drugs designed to improve gastrointestinal (GI) motility, either regionally or across the whole gut. Each drug has its merits and drawbacks, and based on current evidence as high-quality studies are limited, we have no clear recommendation on one class or other. However, there remains a large unmet need for both regionally selective and/or globally acting prokinetic drugs that work primarily intraluminally and are safe and without systemic side effects.

PURPOSE

Here, we describe the strengths and weaknesses of six classes of prokinetic drugs, including their pharmacokinetic properties, efficacy, safety and tolerability and potential indications.

Effects of corticotropin-releasing hormone on gastric electrical activity and sensorimotor function in healthy volunteers: a double-blinded crossover study

Biopsychosocial factors are associated with disorders of gut-brain interaction (DGBI) and exacerbate gastrointestinal symptoms. The mechanisms underlying pathophysiological alterations of stress remain unclear. Corticotropin-releasing hormone (CRH) is a central regulator of the hormonal stress response and has diverse impact on different organ systems. The aim of the present study was to investigate the effects of peripheral CRH infusion on meal-related gastrointestinal symptoms, gastric electrical activity, and gastric sensorimotor function in healthy volunteers (HVs). In a randomized, double-blinded, placebo-controlled, crossover study, we evaluated the effects of CRH on gastric motility and sensitivity. HVs were randomized to receive either peripheral-administered CRH (100 µg bolus + 1 µg/kg/h) or placebo (saline), followed by at least a 7-day washout period and assignment to the opposite treatment. Tests encompassed saliva samples, gastric-emptying (GE) testing, body surface gastric mapping (BSGM, Gastric Alimetry; Alimetry) to assess gastric myoelectrical activity with real-time symptom profiling, and a gastric barostat study to assess gastric sensitivity to distention and accommodation. Twenty HVs [13 women, mean age 29.2 ± 5.3 yr, body mass index (BMI) 23.3 ± 3.8 kg/m2] completed GE tests, of which 18 also underwent BSGM measurements during the GE tests. The GE half-time decreased significantly after CRH exposure (65.2 ± 17.4 vs. 78.8 ± 24.5 min, P = 0.02) with significantly increased gastric amplitude [49.7 (34.7-55.6) vs. 31.7 (25.7-51.0) µV, P < 0.01], saliva cortisol levels, and postprandial symptom severity. Eleven HVs also underwent gastric barostat studies on a separate day. However, the thresholds for discomfort during isobaric distensions, gastric compliance, and accommodation did not differ between CRH and placebo.NEW & NOTEWORTHY In healthy volunteers, peripheral corticotropin-releasing hormone (CRH) infusion accelerates gastric-emptying rate and increases postprandial gastric response, accompanied by a rise in symptoms, but does not alter gastric sensitivity or meal-induced accommodation. These findings underscore a significant link between stress and dyspeptic symptoms, with CRH playing a pivotal role in mediating these effects.

Physiological characterization of gastric emptying using high-resolution antropyloroduodenal manometry

Delayed gastric emptying (GE) has been associated with antral and pyloric dysmotility. We aimed to characterize differences in the antral, duodenal, and pyloric motility profiles associated with delayed GE, using high-resolution antropyloroduodenal manometry (HR-ADM). Patients referred for HR-ADM for dyspeptic symptoms performed a concurrent GE breath test (NCT01519180 and NCT04918329). HR-ADM involved 36 sensors 1 cm apart, placed across the pylorus. Interdigestive and postprandial periods were identified. Antral, pyloric, and duodenal motor profiles were analyzed recording the frequency, amplitude, and propagative nature of contractions for each period. Plots of patients with normal and delayed GE were compared. Sixty patients underwent both HR-ADM and GE tests. Twenty-five and 35 patients had delayed and normal GE, respectively. Antral and duodenal motor profiles were not different between the two groups during the interdigestive period. During the postprandial period, a lower frequency of antral contractions was associated with delayed GE (2.22 vs. 1.39 contractions/min; P = 0.002), but no difference in mean contraction amplitude was observed. The pyloric region was identified in all the patients and pylorospasms, defined as 3 min of repeated isolated pyloric contractions, were more frequent in patients with delayed GE (32.0% vs. 5.7%; P = 0.02) during the postprandial period. No difference in duodenal contraction profiles was observed. Manometric profile alterations were observed in 72% of the patients with delayed GE, with 56% having a low frequency of antral contractions. Using HR-ADM, patients with delayed GE displayed different postprandial antropyloric motility as compared with patients with normal GE.NEW & NOTEWORTHY High-resolution antropyloroduodenal manometry (HR-ADM) allows precise characterization of antral, pyloric, and duodenal motility, although its association with gastric emptying (GE) has been poorly investigated. Concurrent HR-ADM with GE measurement showed a lower frequency of antral postprandial contractions and an increased frequency of postprandial pylorospasms in patients with delayed GE. HR-ADM could, therefore, be useful in the future to better select patients for treatments targeting the pylorus.

Ten controversies in gastroparesis and a look to the future

BACKGROUND

Gastroparesis is a complex, challenging gastrointestinal disorder presenting with upper gastrointestinal symptoms, especially nausea and vomiting, with significant impact on patients' quality of life. After ruling out mechanical obstruction, it is essential to identify delay in gastric emptying for definitive diagnosis. The most common causes are idiopathic (no identified etiology), diabetes mellitus, and postsurgical status. Management of gastroparesis focuses on dietary modifications and treatment directed to symptom relief. Unfortunately, approximately one-third of patients are refractory to pharmacological therapy, and the effectiveness of the few nonpharmacological options has been questioned.

PURPOSE

Extensive review of the literature identifies several uncertainties or controversies regarding the differential diagnosis based on the spectrum of symptoms, the lack of availability of reliable diagnostic test, and questions regarding effective therapeutic options. In this review, we discuss ten controversies regarding gastroparesis: clinical presentation, diagnosis, overlap syndromes, pathophysiology, etiology, as well as pharmacological and nonpharmacological therapeutic options. In addition, we briefly review studies exploring pathological, inflammatory, and molecular disturbances affecting the intrinsic neuromuscular elements that may be involved in the pathophysiology of gastroparesis and may constitute possible therapeutic targets in the future. Finally, we tabulate future research opportunities to resolve these controversies in the management of patients with gastroparesis.

Comprehensive characterization of antral and pyloric contractions by high resolution manometry: applied physiology in suspected gastroparesis

Delayed gastric emptying may result from diverse pathophysiological mechanisms including antral hypomotility and pylorospasm. With increasing use of gastric peroral endoscopic myotomy and preliminary evidence of efficacy, our aim was to assess the motor functions of the distal antrum and pylorus in patients with symptoms of gastroparesis using high-resolution antropyloroduodenal manometry (HR-ADM). Sixteen patients with symptoms suggestive of gastroparesis underwent HR-ADM with 13 sensors, 1 cm apart, placed across the antropyloroduodenal (APD) junction and 2 sensors, 10 cm apart, in descending and distal duodenum. The 1-h postprandial motility was quantitated as contraction frequency/minute, average amplitude, and motility index (MI). Six healthy volunteers served as controls. In the patient group, the HR-ADM identified postprandial antral hypomotility, isolated pyloric pressure waves, and tonic elevation of baseline pressure in pylorus. Patients had significantly reduced frequency of the full-hour postprandial antral contractions/minute compared with healthy volunteers [1.52 (0.97, 1.67) vs. 2.04 (1.70, 2.67), P = 0.005], as well as reduced MI [9.65 (8.29, 10.31) vs. 11.04 (10.65, 11.63), P = 0.002]. The average contraction amplitude was numerically, but not significantly reduced [51.9 (21.9, 74.9) vs. 73.0 (59.8, 82.7), P = 0.14]. Bland-Altman plots showed similar distribution of antral contraction frequency and MI during the first and second postprandial 30-min periods for both patients and controls. High-resolution ADM can characterize a variety of postprandial antral contractile and pyloric motility dysfunctions. This technique shows promise to provide guidance for the selection of optimal treatment of patients with gastroparesis.NEW & NOTEWORTHY Current selection of different treatments for patients with gastroparesis is empiric or based on trial and error, though pyloric distensibility and diameter may predict response to pyloric interventions. High-resolution antropyloroduodenal manometry (HR-ADM) can characterize a variety of postprandial antral contractile and pyloric motility dysfunctions in patients with suspected gastroparesis. HR-ADM shows promise to provide guidance for selection and individualization of treatments such as prokinetic agents or pyloric interventions for patients with gastroparesis based on documented pathophysiology.

[Gastrointestinal motility disorders in critically ill patients]

The gastrointestinal tract is one of the most complex organ systems of the human body. On the one hand, it forms the absorption surface for nutrients, but on the other hand it is also a barrier for toxins, food components and against up to 10¹⁴ commensal microorganisms. The complexity of the interplay between absorption, motility and immune functions of the gastrointestinal tract is particularly evident in critically ill patients. In this article, we review the latest updates on pathogenic relationships of motility disorders and diagnostic algorithms in intensive care patients. In addition to established therapies, new developments in the treatment of hypomotility are outlined.

Gastroparesis

Gastroparesis is characterized by symptoms suggestive of, and objective evidence of, delayed gastric emptying in the absence of mechanical obstruction. This review addresses the normal emptying of solids and liquids from the stomach and details the myogenic and neuromuscular control mechanisms, including the specialized function of the pyloric sphincter, that result in normal emptying, based predominantly on animal research. A clear understanding of fundamental mechanisms is necessary to comprehend derangements leading to gastroparesis, and additional research on human gastric muscles is needed. The section on pathophysiology of gastroparesis considers neuromuscular diseases that affect nonsphincteric gastric muscle, disorders of the extrinsic neural control, and pyloric dysfunction that lead to gastroparesis. The potential cellular basis for gastroparesis is attributed to the effects of oxidative stress and inflammation, with increased pro-inflammatory and decreased resident macrophages, as observed in full-thickness biopsies from patients with gastroparesis. Predominant diagnostic tests involving measurements of gastric emptying, the use of a functional luminal imaging probe, and high-resolution antral duodenal manometry in characterizing the abnormal motor functions at the gastroduodenal junction are discussed. Management is based on supporting nutrition; dietary interventions, including the physical reduction in particle size of solid foods; pharmacological agents, including prokinetics and anti-emetics; and interventions such as gastric electrical stimulation and pyloromyotomy. These are discussed briefly, and comment is added on the potential for individualized treatments in the future, based on optimal gastric emptying measurement and objective documentation of the underlying pathophysiology causing the gastroparesis.

Management of Gastroparesis

Gastroparesis is a gastrointestinal motility disorder characterized by nausea, vomiting, early satiation, postprandial fullness, bloating, and upper abdominal pain. The diagnosis requires documented delay in gastric emptying with an optimal test such as scintigraphy or stable isotope gastric emptying breath test in the absence of mechanical obstruction. The pathophysiologic mechanisms of gastroparesis are multifactorial, including antroduodenal hypomotility, pylorospasm, impaired gastric accommodation, and visceral hypersensitivity. The etiologies of gastroparesis are broad, but the most common subtypes are idiopathic, diabetic, and postsurgical. Less frequent etiologies are neurodegenerative disorder (Parkinson disease), myopathies (scleroderma, amyloidosis), and neoplastic syndrome. Symptoms of gastroparesis can be refractory and challenging to manage, leading to reduced quality of life and significant health care expenditure. This article introduces the epidemiology, clinical presentation, diagnosis, and differential diagnoses of gastroparesis, followed by a focused discussion on its management, including nutritional support, prokinetic and antiemetic agents, and emerging interventions directed at the pylorus. Robust sham-controlled trials are needed to evaluate the long-term efficacy of gastric peroral endoscopic myotomy. A multidisciplinary approach with individualized strategies based on characterization of the patho-physiology is deemed necessary to enhance clinical outcomes.

New Developments in Prokinetic Therapy for Gastric Motility Disorders

Prokinetic agents amplify and coordinate the gastrointestinal muscular contractions to facilitate the transit of intra-luminal content. Following the institution of dietary recommendations, prokinetics are the first medications whose goal is to improve gastric emptying and relieve symptoms of gastroparesis. The recommended use of metoclopramide, the only currently approved medication for gastroparesis in the United States, is for a duration of less than 3 months, due to the risk of reversible or irreversible extrapyramidal tremors. Domperidone, a dopamine D2 receptor antagonist, is available for prescription through the FDA's program for Expanded Access to Investigational Drugs. Macrolides are used off label and are associated with tachyphylaxis and variable duration of efficacy. Aprepitant relieves some symptoms of gastroparesis. There are newer agents in the pipeline targeting diverse gastric (fundic, antral and pyloric) motor functions, including novel serotonergic 5-HT₄ agonists, dopaminergic D_2/3 antagonists, neurokinin NK₁ antagonists, and ghrelin agonist. Novel targets with potential to improve gastric motor functions include the pylorus, macrophage/inflammatory function, oxidative stress, and neurogenesis. In the current review, we discuss the use of pharmacological approaches with potential to enhance motor functions in the management of gastroparesis.

Association of gastric emptying with postprandial appetite and satiety sensations in obesity

OBJECTIVE

Satiety, defined as the duration of the sensation of fullness, is usually measured by validated visual analog scales (VAS) for appetite. Gastric function plays a key role in food intake regulation. However, the association between gastric emptying (GE) and VAS appetite is unknown.

METHODS

In this cross-sectional study, 134 participants (mean [SEM] age = 39 [0.8] years, mean [SEM] BMI = 38 [0.5] kg/m² , 67% females) completed simultaneous measurements of GE and VAS appetite. After a 320-kcal meal, GE was measured by scintigraphy and appetite by validated 100-mm VAS for 240 minutes. Satiation was defined as calories consumed to terminate meal and was measured by an ad libitum meal. GE, VAS, and ad libitum meal tests were measured on the same day. Percent of meal retention in the stomach, VAS area under curve (AUC_{0-240 min} ), and overall appetite score (OAS) were calculated. Pearson correlation (ρ) determined the association of GE with VAS appetite and satiation. Appetite components were also analyzed by quartiles based on GE_{120 min} .

RESULTS

GE_{120 min} was correlated with sensation of VAS hunger_{AUC(0-240 min)} (ρ = 0.24, p = 0.004), fullness_{AUC(0-240 min)} (ρ = 0.16, p = 0.05), and OAS_{AUC(0-240 min)} (ρ = 0.20, p = 0.02). Patients with rapid GE_{120 min} had a mean increase in VAS hunger_{AUC(0-240 min)} by 32 mm/min (15.62%, p = 0.03) compared with normal/slow GE_{120 min} .

CONCLUSIONS

GE is associated with the sensations of appetite, and rapid GE is associated with increased appetite, which may contribute to weight gain.

Gastric accommodation influences proximal gastric and total gastric emptying in concurrent measurements conducted in healthy volunteers

Gastric emptying and gastric accommodation play a role in generation of upper gastrointestinal symptoms. Although both functions have been measured simultaneously using MRI or ^99mTc SPECT methodology, the correlation of these two functions has not been evaluated simultaneously using a solid and liquid meal. To study relationships of whole or proximal stomach volumes to emptying, we concurrently measured postprandial gastric accommodation and emptying (over 4 h) of a ¹¹¹In-labeled mixed solid and liquid meal. A semiautomated method allowing selection of a segmentation threshold based on a grayscale image was used to measure volume of the proximal half of the stomach, defined as the top half of axial slices along the vertical length of the stomach. A correction factor derived from phantom studies was applied for upscatter from the ^99mTc to the ¹¹¹In window. Relationships of time to emptying 10%, 25%, 50%, and 75% of the meal to fasting and postprandial gastric volumes were evaluated using Spearman correlation. Whole stomach fed and accommodation volumes were significantly correlated with all gastric emptying times (10%, 25%, and 50%). Proximal stomach fed volumes were similarly associated with 50% and 75% proximal gastric emptying. Fed proximal gastric volume was associated with 50% and 75% whole gastric emptying. Fed proximal accommodation volume was associated with 50% gastric emptying. Fasting gastric volumes were not significant determinants of emptying rates. In conclusion, postprandial gastric accommodation is significantly associated with the rate of gastric emptying, with higher gastric volumes associated with prolongation of emptying. Novel methods to measure proximal gastric accommodation and correct for radioisotope upscatter are described.NEW & NOTEWORTHY In vivo human studies evaluated concurrently the volume of the stomach during fasting and after a solid and liquid meal using a new SPECT-based method. Although fasting gastric volumes did not impact the rates of gastric emptying, both postprandial and accommodation volumes of the whole and proximal stomach were significantly correlated with gastric emptying. Larger stomach volumes were associated with slower gastric emptying.

Gastric Sensory and Motor Functions and Energy Intake in Health and Obesity-Therapeutic Implications

Sensory and motor functions of the stomach, including gastric emptying and accommodation, have significant effects on energy consumption and appetite. Obesity is characterized by energy imbalance; altered gastric functions, such as rapid gastric emptying and large fasting gastric volume in obesity, may result in increased food intake prior to reaching usual fullness and increased appetite. Thus, many different interventions for obesity, including different diets, anti-obesity medications, bariatric endoscopy, and surgery, alter gastric functions and gastrointestinal motility. In this review, we focus on the role of the gastric and intestinal functions in food intake, pathophysiology of obesity, and obesity management.

Gastroparesis in the Hospital Setting

Gastroparesis (GP) is commonly seen in hospitalized patients. Refractory vomiting and related dehydration, electrolyte abnormalities, and malnutrition are indications for hospital admission. In addition, tube feeding intolerance is a common sign of gastric dysmotility in critically ill patients. The diagnosis and management of GP in the hospital setting can be quite challenging. Diagnostic tests are often deferred because of patient intolerance of the oral meal for standard scintigraphy or severity of the primary disease. The diagnosis of GP is often established on the basis of clinical scenario and risk factors for gastric motor dysfunction. Medical therapy in GP is directed toward controlling nausea and vomiting by prokinetic and antinausea medications and correcting nutrition risks or treating malnutrition with nutrition therapy. Enteral nutrition is the preferred nutrition intervention for patients with GP. Delayed gastric emptying in critically ill patients has a negative impact on the timely delivery of enteral feeding and meeting the energy and protein goals. Measures to improve gastric tolerance or provide feeding beyond the stomach are often needed, since early enteral nutrition has been an important target of therapy for critically ill patients. This review will address the current understanding of the mechanisms of GP and feeding intolerance in critical illness, diagnostic workup, drug therapies, and interventions to improve the provision of enteral nutrition in hospital settings when gastric dysmotility is present or suspected.

Overall safety of relamorelin in adults with diabetic gastroparesis: Analysis of phase 2a and 2b trial data

BACKGROUND

Relamorelin, a pentapeptide ghrelin receptor agonist, accelerated gastric emptying significantly and improved symptoms in adults with diabetic gastroparesis in phase 2 trials.

AIM

To assess the safety and tolerability of relamorelin across phase 2 trials.

METHODS

Safety assessments in patients aged 18-75 years (weight, adverse events [AEs] and laboratory tests) from two randomised, double-blind phase 2 trials (NCT01571297, NCT02357420; results published previously) were reviewed descriptively. Analysis of covariance assessed treatment effect on glycated haemoglobin (HbA1c) and blood glucose post hoc. Phase 2a and 2b trial durations were, respectively, 4 weeks (relamorelin 10 µg once or twice daily [b.d.] or placebo b.d.) and 12 weeks (relamorelin 10, 30 or 100 µg or placebo b.d.) with 1- and 2-week, single-blind placebo run-ins.

RESULTS

Among 204 phase 2a and 393 phase 2b patients, respectively, 67% and 62% were female, and 88% and 89% had type 2 diabetes. Proportions of patients reporting serious AEs were similar across treatment groups, as were those with ≥1 treatment-emergent AE (TEAE). TEAE-related discontinuations were proportionally higher in relamorelin groups than placebo. Of 12 serious TEAEs in phase 2a, none occurred in >1 patient. In phase 2b, five serious TEAEs were reported in >1 patient, and one (100 µg) died (urosepsis), all unrelated to relamorelin. In phase 2b, increased HbA1c and fasting blood glucose levels were dose-related (P < 0.0001 and P = 0.0043, respectively).

CONCLUSIONS

Relamorelin showed acceptable safety and tolerability in phase 2 trials. Relamorelin may elevate blood glucose: this should be managed proactively in relamorelin-treated patients.

Gastroparesis in the 2020s: New Treatments, New Paradigms

PURPOSE OF REVIEW

This review highlights recent work that will lead to near-term advances in the understanding and treatment of gastroparesis (Gp).

RECENT FINDINGS

Major current advancements in the pathophysiology of Gp, include recognition of the SIP syncytium as the pacemaking unit rather than ICC alone and that Gp may be part of a pan-enteric autoimmune and/or autonomic disorder with macrophage imbalance. The development of newer techniques to assess gastric emptying (gastric emptying breath test and wireless motility capsule) and pyloric distensibility (EndoFLIP®) are allowing clinicians better characterization of their patients. In addition to pharmaceutical compounds in the pipeline, neuromodulation and endosurgical techniques, such as G-POEM, may help address refractory Gp. We expect that the 2020 decade will witness exciting developments. Treatments targeting gastrointestinal motility, immunological dysfunction, and inflammatory mediators will be evaluated. We anticipate future studies will be guided by biomarkers correlated with patient outcomes and therapeutic efficacy to establish new paradigms in the management of Gp.

Pharmacological Approaches to Diabetic Gastroparesis: A systematic review of randomised clinical trials

Pharmacological interventions of diabetic gastroparesis (DG) constitute an essential element of a patient’s management. This article aimed to systematically review the available pharmacological approaches of DG, including their efficacy and safety. A total of 24 randomised clinical trials (RCTs) that investigated the efficacy and/or safety of medications targeting DG symptoms were identified using several online databases. Their results revealed that metoclopramide was the only approved drug for accelerating gastric emptying and improving disease symptoms. However, this medication may have several adverse effects on the cardiovascular and nervous systems, which might be resolved with a new intranasal preparation. Acceptable alternatives are oral domperidone for patients without cardiovascular risk factors or intravenous erythromycin for hospitalised patients. Preliminary data indicated that relamorelin and prucalopride are novel candidates that have proven to be effective and safe. Future RCTs should be conducted based on unified guidelines using universal diagnostic modalities to reveal reliable and comprehensive outcomes.

[Ghrelin Physiology and Pathophysiology: Focus on the Cardiovascular System]

Ghrelin is a multifunctional peptide hormone, mainly synthesized by P / D1 cells of the stomach fundus mucosa. Its basic effect, which is realized via GHS-R1 α receptor in the arcuate and the ventromedial nucleuses of hypothalamus, is stimulation of the synthesis of pituitary hormones. Ghrelin is involved in control of appetite and energy balance, regulation of carbohydrate and lipid metabolism, cell proliferation and apoptosis, as well as modulation of functioning of gastrointestinal, cardiovascular, pulmonary and immune systems. It was found that cardiomyocytes are able to synthesize ghrelin. High concentrations of GHS-R1α in the heart and major blood vessels evidence for its possible participation in functioning of cardiovascular system. Ghrelin inhibits apoptosis of cardiomyocytes and endothelial cells, and improves the functioning of the left ventricle (LV) after injury of ischemia-reperfusion mechanism. In rats with heart failure (HF) ghrelin improves LV function and attenuates development of cardiac cachexia. In addition, ghrelin exerts vasodilatory effects in humans, improves cardiac function and reduces peripheral vascular resistance in patients with chronic HF. The review contains of the predictive value of ghrelin in the development and prevention of cardiovascular disease.

Gastrointestinal hormones and regulation of gastric emptying

PURPOSE OF REVIEW

This review examines the hormonal regulation of gastric emptying, a topic of increasing relevance, given the fact that medications that are analogs of some of these hormones or act as agonists at the hormonal receptors, are used in clinical practice for optimizing metabolic control in the treatment of type 2 diabetes and in obesity.

RECENT FINDINGS

The major effects on gastric emptying result from actions of incretins, particularly gastric inhibitory polypeptide, glucagon-like peptide-1, and peptide tyrosine-tyrosine, the duodenal and pancreatic hormones, motilin, glucagon, and amylin, and the gastric orexigenic hormones, ghrelin and motilin. All of these hormones delay gastric emptying, except for ghrelin and motilin which accelerate gastric emptying. These effects on gastric emptying parallel the effects of the hormones on satiation (by those retarding emptying) and increase appetite by those that accelerate emptying. Indeed, in addition to the effects of these hormones on hypothalamic appetite centers and glycemic control, there is evidence that some of their biological effects are mediated through actions on the stomach, particularly with the glucagon-like peptide-1 analogs or agonists used in treating obesity.

SUMMARY

Effects of gastrointestinal hormones on gastric emptying are increasingly recognized as important mediators of satiation and postprandial glycemic control.

Parkinson's Disease and Current Treatments for Its Gastrointestinal Neurogastromotility Effects

PURPOSE OF REVIEW

Gastrointestinal disturbances are seen in nearly all patients with Parkinson's disease and lead to impaired quality of life, affect drug pharmacodynamics, and potentially worsen patient's existing motor fluctuations, leading to further disability. Recent evidence links abnormal accumulations of α-synuclein aggregates in the periphery (gut) as seen in the cortex which causes dysfunctions impacting every level of the gastrointestinal tract from the esophagus, to the stomach, small bowel, colon, and rectum and can even predate the onset of the central neurologic disorder itself. Many treatments exist for the clinical phenotypes that result from the autonomic dysfunction and neuropathy involved in this neurodegenerative disorder. The treatments for the gut dysfunction seen in Parkinson's disease (PD) depend on the specific area of the gastrointestinal tract affected. For dysphagia, behavioral therapies with speech pathology, neuromuscular electrical stimulation, or botulinum toxin injection may be helpful. For gastroparesis, domperidone may serve as an antiemetic while also blunting the hypotensive potential of Levodopa while new treatments such as ghrelin agonists may prove beneficial to help appetite, satiety, gastric emptying in those with constipation, and even improve constipation. Antibiotics such as rifaximin with poor systemic absorption may be used to treat small bacterial overgrowth also found in those with PD while the benefits of probiotics is yet to be determined. Finally, constipation in PD can be a reflection of pelvic floor dyssynergia, slow transit constipation, or both, thus treatments targeting the specific anorectal dysfunction is necessary for better outcomes.

Ghrelin, a gastrointestinal hormone, regulates energy balance and lipid metabolism

Ghrelin, an acylated peptide hormone of 28 amino acids, is an endogenous ligand of the released growth hormone secretagogue receptor (GHSR). Ghrelin has been isolated from human and rat stomach and is also detected in the hypothalamic arcuate nucleus. Ghrelin receptor is primarily located in the neuropeptide Y and agouti-related protein neurons. Many previous studies have shown that ghrelin and GHSR are involved in the regulation of energy homeostasis, and its administration can increase food intake and body weight gain. AMP-activated protein kinase is activated by ghrelin in the hypothalamus, which contributes to lower intracellular long-chain fatty acid level. Ghrelin appears to modulate the response to food cues via a neural network involved in the regulation of feeding and in the appetitive response to food cues. It also increases the response of brain areas involved in visual processing, attention, and memory to food pictures. Ghrelin is also an important factor linking the central nervous system with peripheral tissues that regulate lipid metabolism. It promotes adiposity by the activation of hypothalamic orexigenic neurons and stimulates the expression of fat storage-related proteins in adipocytes. Meanwhile, ghrelin exerts direct peripheral effects on lipid metabolism, including increase in white adipose tissue mass, stimulation of lipogenesis in the liver, and taste sensitivity modulation.

New developments in the treatment of gastroparesis and functional dyspepsia

Functional dyspepsia (FD) and gastroparesis are frequent causes of upper gastrointestinal symptoms such as postprandial fullness, early satiation, epigastric pain or burning, upper abdominal bloating, bothersome belching, nausea and vomiting. The underlying pathophysiological mechanisms are heterogeneous and involved mechanisms such as abnormal gastric motility (accommodation, emptying), visceral hypersensitivity, low grade mucosal inflammation and cellular changes in enteric nerves, muscle or interstitial cells of Cajal. Patient-reported outcomes for evaluating treatment efficacy in these conditions were recently developed and validated. Prokinetic agents, which enhance gastric motility, are used for treating both gastroparesis and FD. In FD, besides acid suppressive therapy and Helicobacter pylori eradication, neuromodulators and drugs that enhance gastric accommodation can be applied. In gastroparesis, anti-emetics may also provide symptom relief. Novel approaches under evaluation in these conditions are the fundus relaxing agents acotiamide and buspirone and the antidepressant mirtazapine in FD. For gastroparesis, recently studied agents include the prokinetic ghrelin agonist relamorelin, the prokinetic serotonergic agents velusetrag and prucalopride, the anti-emetic aprepitant and per-endoscopic pyloric myotomy procedures.

Chronic nausea and vomiting: evaluation and treatment

Nausea is an uneasy feeling in the stomach while vomiting refers to the forceful expulsion of gastric contents. Chronic nausea and vomiting represent a diverse array of disorders defined by 4 weeks or more of symptoms. Chronic nausea and vomiting result from a variety of pathophysiological processes, involving gastrointestinal and non-gastrointestinal causes. The prevalence of chronic nausea and vomiting is unclear, although the epidemiology of specific conditions, such as gastroparesis and cyclic vomiting syndrome, is better understood. The economic impact of chronic nausea and vomiting and effects on quality of life are substantial. The initial diagnostic evaluation involves distinguishing gastrointestinal causes of chronic nausea and vomiting (e.g., gastroparesis, cyclic vomiting syndrome) from non-gastrointestinal causes (e.g., medications, vestibular, and neurologic disorders). After excluding anatomic, mechanical and biochemical causes of chronic nausea and vomiting, gastrointestinal causes can be grouped into two broad categories based on the finding of delayed, or normal, gastric emptying. Non-gastrointestinal disorders can also cause chronic nausea and vomiting. As a validated treatment algorithm for chronic nausea and vomiting does not exist, treatment should be based on a thoughtful discussion of benefits, side effects, and costs. The objective of this monograph is to review the evaluation and treatment of patients with chronic nausea and vomiting, emphasizing common gastrointestinal causes.

Capromorelin: a ghrelin receptor agonist and novel therapy for stimulation of appetite in dogs

Ghrelin is a hormone, secreted from cells in the stomach, which is important in the regulation of appetite and food intake in mammals. It exerts its action by binding to a specific G-protein-coupled receptor, the growth hormone secretagogue receptor 1a (GHS-R1a) which is found in areas of the brain associated with the regulation of food intake. Ghrelin causes a release of growth hormone (GH) through binding to GHS-R1a in the hypothalamus and pituitary gland. A class of compounds known as growth hormone secretagogues, or ghrelin receptor agonists, were developed for therapeutic use in humans for the stimulation of GH in the frail elderly, and have subsequently been studied for their effects on increasing appetite and food intake, increasing body weight, building lean muscle mass, and treating cachexia. Subsequent research has shown that ghrelin has anti-inflammatory and immunomodulatory effects. This article reviews the basic physiology of ghrelin and the ghrelin receptor agonists, including the available evidence of these effects in vitro and in vivo in rodent models, humans, dogs and cats. One of these compounds, capromorelin, has been FDA-approved for the stimulation of appetite in dogs (ENTYCE ®). The data available on the safety and effectiveness of capromorelin is reviewed, along with a discussion of the potential clinical applications for ghrelin receptor agonists in both human and veterinary medicine.

Functional dyspepsia and gastroparesis

PURPOSE OF REVIEW

This review summarizes recent progress in the epidemiology, pathophysiology and treatment of functional dyspepsia and gastroparesis.

RECENT FINDINGS

The definition of functional dyspepsia and its subgroups has been revised in the recent Rome IV consensus. In gastroparesis, the symptom pattern and its similarities and differences from functional dyspepsia have been a focus of recent research. In functional dyspepsia, pathophysiological research continued to evaluate gastric sensorimotor dysfunctions, but low-grade inflammatory changes and loss of mucosal integrity in the duodenum is a new topic of intense research. Treatment advances include new prokinetics such as acotiamide and the ghrelin receptor agonist relamorelin. The efficacy of tricyclic antidepressants was recently reviewed and mirtazapine is a new agent used in the treatment of functional dyspepsia and gastroparesis. In gastroparesis, research has focused on the role of macrophages in loss of interstitial cells of Cajal, and on the role of pyloric resistance as a target for therapy, using botulinum toxin injection and gastric per-endoscopic pyloric myotomy.

SUMMARY

The functional dyspepsia definition and subgrouping were updated in the Rome IV consensus. Research focuses on duodenal mucosal alterations in functional dyspepsia and pyloric resistance in gastroparesis. New treatments include novel prokinetics and pylorus-directed interventions.

Efficacy and Safety of Relamorelin in Diabetics With Symptoms of Gastroparesis: A Randomized, Placebo-Controlled Study

BACKGROUND & AIMS

Gastroparesis is a complication of diabetes with few treatment options. Relamorelin (also referred to as RM-131) is a selective, prokinetic agonist of ghrelin. We aimed to evaluate the efficacy of relamorelin on symptoms and gastric emptying (GE) in a 12-week, phase 2B study of diabetic patients with moderate to severe gastroparesis symptoms (DG).

METHODS

We performed a study of 393 patients with DG (37.7% male; 9.9% with type 1 diabetes; median age, 58.2 years [range 20-76]; median body mass index, 31.4 kg/m2 [range, 18.2-60.1]; HbA1c level, 7.6%, [range, 5.2-11.0]). All participants had 13C-spirulina GE breath test T1/2 values of 79 minutes or more (with 89.8% delayed relative to 90th %ile of normal, 85.75 minutes), recent vomiting, and gastroparesis cardinal symptom index-daily diary scores of 2.6 or more. Patients were randomly assigned to groups given placebo (n=104) or relamorelin (10 μg [n=98], 30 μg [n=109], or 100 μg [n=82] twice daily) for 12 weeks, following a 2-week, single-blind, placebo run-in period. Patient-reported outcomes were determined from DG Symptom Severity daily e-diaries, in which patients recorded vomiting frequency and symptom scores (nausea, abdominal pain, postprandial fullness, and bloating) on a 0-10 scale. Endpoints were change from baseline in vomiting frequency, composite DG Symptom Severity score, GE, and safety. We performed longitudinal, mixed-effects model analysis using repeated measures, with baseline and baseline-by-week interaction values as covariates.

RESULTS

Patients given relamorelin had a 75% reduction in vomiting frequency compared with baseline, but this difference was not significant compared with the placebo group. All 4 symptoms of DG (composite or individual symptoms) were significantly reduced over the 12-week study period in all 3 relamorelin dose groups compared with the placebo group (all P < .05, based on longitudinal analysis over 12 weeks). Relamorelin significantly accelerated GE from baseline compared with placebo (by 12%, P < .05 for the 10 μg and 30 μg groups; P = .051 for the 100 μg group). Dose-related worsening of glycemic control was noted in 14.5% of patients who received relamorelin; some required insulin or other diabetes drug dosage adjustments.

CONCLUSIONS

In a phase 2B randomized trial of patients with moderate to severe DG, relamorelin significantly reduced core symptoms of DG and overall composite score compared with placebo, accelerated GE, and was generally safe and well tolerated. ClinicalTrials.gov Identifier: NCT02357420.

Prokinetics in the Management of Functional Gastrointestinal Disorders

PURPOSE OF REVIEW

The goal of this review is to review the current status of prokinetics and to place it in historical context. Impaired motility and thus propulsion have long been thought to play important roles in the pathogenesis of a number of gastrointestinal disorders including gastroesophageal reflux disease (GERD), gastroparesis, chronic idiopathic pseudo-obstruction, and constipation. Historically, disordered motility was also thought to contribute to a number of functional gastrointestinal disorders such as functional dyspepsia (FD) and irritable bowel syndrome (IBS).

RECENT FINDINGS

As we learn more of the pathophysiology of FD, IBS, GERD, constipation, and gastroparesis, the limitations of a therapeutic strategy based on the stimulation of motility (i.e., the use of a prokinetic) have become apparent and the disappointments of the past explained. The development of prokinetic drugs has also been hampered by the non-selective nature of many of the agents studied to date which resulted in some unexpected side effects. There is still an unmet need for an effective and safe prokinetic, but drug development in this area must be mindful of the challenges of the area and the need for selectivity for a given target receptor.

Gastroparesis: Medical and Therapeutic Advances

Gastroparesis is a chronic, bothersome, and often disabling neuromuscular disorder of the upper gastrointestinal tract. The most frequently reported symptoms of gastroparesis include nausea, vomiting, epigastric pain, early satiety, and unintentional weight loss. Etiologies of gastroparesis include diabetes, connective tissue disorders, prior infection, mesenteric ischemia, and post-surgical complications. The largest category of gastroparesis patients is comprised of those in whom no definitive cause can be identified (idiopathic gastroparesis). The individual and societal burden of gastroparesis is substantial. It considerably reduces patients' quality of life accompanied by a significant negative impact to the healthcare system. The current treatments of gastroparesis are less than ideal. Dietary modification may improve symptoms in patients with mild disease. Metoclopramide is the only medication currently approved for the treatment of gastroparesis; however, it is associated with adverse effects in a sizable proportion of patients. Other medications are frequently employed to treat symptoms of nausea and vomiting, although technically all are used off-label since they are not FDA approved for the treatment of gastroparesis. These data highlight the need to identify novel, more effective treatment options for this disabling disease. This review will provide a brief synopsis on the epidemiology, etiology, and impact of gastroparesis, discussing new therapeutic advances.

Relamorelin for the treatment of gastrointestinal motility disorders

INTRODUCTION

Current treatments for gastroparesis are limited. Chronic idiopathic constipation (CIC) has more treatment options, but none are efficacious for severe cases. Areas covered: Molecular targets to accelerate GI motility are being identified, and relamorelin, a synthetic ghrelin analog, has been promising. In humans, relamorelin increases growth hormone levels and accelerates gastric emptying. Relamorelin was superior to placebo for symptom relief in phase IIA studies for diabetic gastroparesis (DG) and CIC. In phase IIB studies in DG, relamorelin did not significantly reduce vomiting frequency when compared to placebo, but it reduced four symptoms of DG (nausea, fullness, bloating and abdominal pain) and accelerated gastric emptying. To date, relamorelin has been well tolerated and safe in humans without cardiac or neurologic adverse effects. It is still in clinical trial stages and not yet approved by the Food and Drug Administration. Phase III studies are underway. Expert opinion: Relamorelin shows promise in treating DG, with a reduction in core symptoms. Relative to available treatments, it appears to be efficacious and well tolerated. The absence of neurological or cardiovascular adverse effects places it at an advantage over other available therapies. Once approved, it will likely become the drug of first choice for DG.

Small Bowel Motility

PURPOSE OF REVIEW

Small bowel motility disorders constitute a relatively small but important segment of clinical gastroenterology. Presenting features encompass a broad range of symptom manifestations and severity: from chronic functional-type complaints to life-threatening nutritional impairment. Diagnostic assessment of patients with suspected intestinal motility disorders is often hampered by the complexity of measuring intestinal contractile activity in humans. In this review, we describe and critically comment the main current and forthcoming methodologies.

RECENT FINDINGS

Beyond conventional small bowel manometry, radiological methods, and intestinal transit tests that have been available for several decades, now we focus on novel methodologies such as high-resolution manometry, magnetic resonance methodology, and endoluminal capsule image analysis. Gradual introduction of new approaches to diagnostic investigation of patients with suspected intestinal motility disorders should facilitate a less invasive and more accurate characterization of disturbed motor function. Enhanced understanding of the pathophysiological basis of clinical conditions should allow better application of therapeutic approaches that are also highlighted in this review.

Future Treatment of Constipation-associated Disorders: Role of Relamorelin and Other Ghrelin Receptor Agonists

There is an unmet need for effective pharmacological therapies for constipation, a symptom that significantly deteriorates patients’ quality of life and impacts health care. Ghrelin is an endogenous ligand for the growth hormone secretagogue receptor and has been shown to exert prokinetic effects on gastrointestinal (GI) motility via the vagus and pelvic nerves. The pharmacological potential of ghrelin is hampered by its short half-life. Ghrelin receptor (GRLN-R) agonists with enhanced pharmacokinetics were thus developed. Centrally penetrant GRLN-R agonists stimulate defecation and improve impaired lower GI transit in animals and humans. This review summarizes the current knowledge on relamorelin, a potent ghrelin mimetic, and other GRLN-R analogs which are in preclinical or clinical stages of development for the management of disorders with underlying GI hypomotility, like constipation.

A randomized trial of relamorelin for constipation in Parkinson's disease (MOVE-PD): Trial results and lessons learned

BACKGROUND

Bowel dysfunction, including both slow transit constipation and defecatory dysfunction, is a frequent and often troubling nonmotor manifestation of Parkinson's disease (PD). A variety of agents are employed for the treatment of constipation in PD, but dissatisfaction with available treatment approaches is common. Relamorelin is a synthetic ghrelin agonist that has demonstrated prokinetic properties within the gastrointestinal tract.

METHODS

We carried out a multi-center, randomized, double-blind, placebo-controlled study of relamorelin in patients with PD experiencing chronic, inadequately controlled constipation.

RESULTS

Only 18 of an intended 56 subjects completed the trial, in part because of the unexpected occurrence of multiple partially complete bowel movements in constipated PD patients, which made many subjects ineligible for participation.

CONCLUSIONS

Although recruitment goals were not met, which precluded demonstration of any potential beneficial effect of relamorelin, unique and important insights with regard to the nature of constipation in PD were recognized, which hopefully will lead to more effective clinical trials in the future. It is clear that what PD patients understand as constipation may be more complex than previously realized and does not appear to be characterized by decreased stool frequency alone.

Investigational drug therapies for the treatment of gastroparesis

INTRODUCTION

Gastroparesis is defined by nausea, vomiting, pain, early satiety and bloating, and characterized by delayed gastric emptying without obvious structural abnormalities. Metoclopramide is widely used, increasing gastric emptying and inhibiting nausea and vomiting. Other drugs are available in certain countries and some are used 'off-label' because they increase gastric emptying or inhibit emesis. However, correlation between gastroparesis symptoms and rates of gastric emptying is poor. For anti-emetic drugs, dose-ranging and Phase III trials in gastroparesis are lacking. Areas covered: Gastric motility may still be disordered, leading to nausea, even though gastric emptying is unchanged. One hypothesis is that interstitial cells of Cajal (ICC) are damaged by diabetes leading to gastric dysrhythmia and nausea. Novel approaches to treatment of nausea also include the use of ghrelin receptor agonists, highlighting a link between appetite and nausea. Expert opinion: There is an urgent need to diversify away from historical drug targets. In particular, there is a need to control nausea by regulating ICC functions and/or by facilitating appetite via ghrelin receptor agonists. It is also important to note that different upper gastrointestinal disorders (gastroparesis, chronic unexplained nausea and vomiting, functional dyspepsia) are difficult to distinguish apart, suggesting wider therapeutic opportunity.

Newest Drugs for Chronic Unexplained Nausea and Vomiting

OPINION STATEMENT

Chronic unexplained nausea and vomiting (CUNV) refers to a symptom complex defined by nausea and/or vomiting with normal diagnostic testing, including anatomic assessments (including upper endoscopy) and measures of upper gut function (e.g., gastric emptying testing). Nausea and vomiting in this condition are postulated to result from aberrant peripheral or central neurohumoral activity. A substantial subset of patients satisfies this diagnosis as more than half of individuals referred for scintigraphic testing exhibit normal gastric emptying rates. No randomized, placebo-controlled trials of any medication treatment have been performed in CUNV. However, agents with potential therapeutic benefits in CUNV include antiemetic drugs, neuromodulatory treatments which are proposed to act by reducing gastric sensitivity, and medications with prokinetic action to stimulate upper gut propulsion. Recently approved drugs with antiemetic capability include serotonin antagonists with novel modes of delivery and neurokinin antagonists with or without additional serotonergic blocking capabilities. Existing neuroleptics and pain-modifying neuromodulatory therapies with fortuitous antiemetic benefits are being considered for their benefits in this disorder. Furthermore, current investigations will define potential therapeutic actions of agents that stimulate gastric emptying via action on gastroduodenal serotonin, motilin, and ghrelin receptors. This current research may broaden the treatment options for refractory cases of unexplained nausea and vomiting.