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... A recent study on the efficacy of anamorelin used prophylactically against the adverse effects of gemcitabine and cisplatin combination chemotherapy in mice (31) reported that it attenuated chemotherapy-induced skeletal muscle atrophy and gastric damage via the downregulation of FOXO1/atrogin-1 signaling. Another report described an inhibitory effect of anamorelin on cisplatin-induced emesis in ferrets, suggesting that brain penetration is important for its anti-emetic effect (32). Nevertheless, the association between anamorelin efficacy and chemotherapy-induced adverse events in humans remains unclear. ...
... Adverse events. Comparatively frequent major adverse events in clinical trials and an interim analysis of post-marketing surveillance of anamorelin included hyperglycemia, increases in glycosylated hemoglobin and γ-glutamyltransferase, nausea, first-degree atrioventricular block, and prolonged QRS complex (a measure of ventricular depolarization on electrocardiograms, ECG) (32)(33)(34)(35)(36)(37)51). In the ROMANA 3 study, tolerability of anamorelin over 24 weeks was demonstrated (38). ...
Hironori Fujii Yunami Yamada
Hirotoshi Iihara
Akio Suzuki
Cancer cachexia, a systemic multifactorial syndrome that affects survival prognosis, occurs in 80% of patients with advanced cancer. Patients with cancer cachexia experience progressive functional disability and persistent loss of skeletal muscle mass associated with reduced quality of life. Cancer cachexia requires multidisciplinary early intervention, including drugs, exercise, nutrition, and psychotherapy. Anamorelin is an oral drug with ghrelin-like effects, including significant appetite stimulation, increase in food intake and weight, and stimulation of growth hormone secretion. This review provides an overview of basic drug information and clinical trial data on anamorelin, focusing on its role in the treatment of cancer cachexia, with the aim of achieving more effective anamorelin administration. In several randomized, double-blind, placebo-controlled clinical trials, anamorelin significantly improved lean body mass and appetite in patients with cancer cachexia. However, no improvement was observed in motor function (handgrip strength and 6-minute walk test). Clinical trials of anamorelin have shown approximately consistent trends in efficacy, but decisions on whether or not to approve anamorelin vary internationally. The treatment of cancer cachexia, including with anamorelin, requires consideration of the selection of target patients, burden of treatment on patients, and assessment tools used by healthcare providers that may affect treatment outcomes. Based on several retrospective datasets, the initiation of anamorelin at earlier stages of cancer cachexia, combined with nutritional and exercise therapy, should be considered. However, current evidence is insufficient, and results of future studies are awaited.
Haruto Nishino Hitoshi Kawazoe Mayu Sekiguchi Tomonori Nakamura
Objective: Platinum- and anthracycline-based chemotherapy regimens cause nausea and vomiting in clinical practice, resulting in the deterioration of patients’ QoL, discontinuation of chemotherapy, and reduced therapeutic outcomes. Using pica behavior as an indicator, we aimed to clarify whether anamorelin, an orally active ghrelin receptor agonist, exerts antiemetic effects against cisplatin-induced nausea and vomiting in rats. Materials and Methods: Sprague–Dawley rats were treated with cisplatin (5 mg/kg, i.p.), three-drug or four-drug antiemetics (granisetron [0.3 mg/kg, p.o.], dexamethasone [1.5 mg/kg, p.o.], fosaprepitant [12.5 mg/kg, i.p.], with or without anamorelin [30 mg/kg, p.o.]). Data on kaolin intake, normal food intake, and spontaneous motor activity (SMA) were recorded 1 d before and 5 d after cisplatin administration. Body weight (BW) was measured daily, and the percentage change in BW from baseline was calculated. Results: At the primary endpoint, kaolin intake was significantly higher in the cisplatin-only group than in the pretreatment and vehicle groups (p < 0.05). Additionally, kaolin food intake was not significantly low in cisplatin-treated mice treated with three-drug antiemetics with or without anamorelin. At the secondary endpoints, normal food intake, SMA, and percentage change in BW were significantly lower in the cisplatin-only group than in the vehicle group. Conclusion: Our findings suggest that the prophylactic administration of standard three-drug antiemetics, besides anamorelin, may not improve cisplatin-induced nausea and vomiting. Further studies using methods suitable for evaluating anamorelin levels are required.
Jumpei Taniguchi Sunao Mikura
Katharina Da Silva Lopes
Cancer-related anorexia/cachexia syndrome (CACS) is characterized by anorexia and loss of body weight. Evidence is insufficient to strongly endorse any pharmacologic agent for the treatment of CACS. In this systematic review, we assessed the efficacy of oral anamorelin treatment for patients with CACS. On July 6, 2022, we systematically searched the following databases for randomized controlled trials (RCTs) of adults with CACS comparing oral anamorelin versus placebo: CENTRAL, PubMed, EMBASE, and ICHUSHI. The primary outcomes were total body weight (TBW), patient-reported quality of life (QOL), and adverse events (AEs). Secondary outcomes included lean body mass (LBM), overall survival (OS), non-dominant hand grip strength (HGS), and appetite. We included seven RCTs with a total of 1944 CACS patients. Anamorelin significantly increased TBW (mean difference (MD) 1.73, 95% confidence interval (CI) 1.34–2.13, p < 0.00001), LBM (MD 1.06, 95% CI 0.30–1.81, p = 0.006), and QOL (standardized mean difference (SMD) 0.16, 95% CI 0.04–0.27, p = 0.006) compared with placebo without a significant difference in all AEs, severe AEs, OS, HGS or appetite. Anamorelin may be an effective treatment for CACS patients; however, further studies are needed to confirm the efficacy and safety of this drug.
Di Wu Qi Chen
Xiaojie Chen
Yi Wang
Blood–brain barrier (BBB) is a natural protective membrane that prevents central nervous system (CNS) from toxins and pathogens in blood. However, the presence of BBB complicates the pharmacotherapy for CNS disorders as the most chemical drugs and biopharmaceuticals have been impeded to enter the brain. Insufficient drug delivery into the brain leads to low therapeutic efficacy as well as aggravated side effects due to the accumulation in other organs and tissues. Recent breakthrough in materials science and nanotechnology provides a library of advanced materials with customized structure and property serving as a powerful toolkit for targeted drug delivery. In-depth research in the field of anatomical and pathological study on brain and BBB further facilitates the development of brain-targeted strategies for enhanced BBB crossing. In this review, the physiological structure and different cells contributing to this barrier are summarized. Various emerging strategies for permeability regulation and BBB crossing including passive transcytosis, intranasal administration, ligands conjugation, membrane coating, stimuli-triggered BBB disruption, and other strategies to overcome BBB obstacle are highlighted. Versatile drug delivery systems ranging from organic, inorganic, and biologics-derived materials with their synthesis procedures and unique physio-chemical properties are summarized and analyzed. This review aims to provide an up-to-date and comprehensive guideline for researchers in diverse fields, offering perspectives on further development of brain-targeted drug delivery system.
Rachid Akki
Kawtar Raghay Mohammed Errami
Background Oxidative stress is the result of cellular troubles related to aerobic metabolism. Furthermore, this stress is always associated with biological responses evoked by physical, chemical, environmental, and psychological factors. Several studies have developed many approaches of antioxidant defense to diminish the severity of many diseases. Ghrelin was originally identified from the rat stomach, and it is a potent growth hormone-releasing peptide that has pleiotropic functions. Methods A systematic review was conducted within PubMed, ScienceDirect, MEDLINE, and Scopus databases using keywords such as ghrelin, antioxidant, oxidative stress, and systemic oxidative stress sensor. Results In the last decade, many studies show that ghrelin exhibits protection effects against oxidative stress derived probably from its antioxidant effects. Pieces of evidence demonstrate that systemic oxidative stress increase ghrelin levels in the plasma. The expression of ghrelin and its receptor in ghrelin peripheral tissues and extensively in the central nervous system suggests that this endogenous peptide plays an important role as a systemic oxidative stress sensor Conclusion The current evidence confirms that ghrelin and its derived peptides (Desacyl-ghrelin, obestatin) act as a protective antioxidant agent. Therefore, stressor modality, duration, and intensity are the parameters of oxidative stress that must be taken into consideration to determine the role of ghrelin, Desacyl-ghrelin, and obestatin in the regulation of cell death pathways.
Kush Gupta Rebecca Walton BS S P Kataria
The significant physical and emotional effects of chemotherapy-induced nausea and vomiting (CINV) are experienced by cancer patients. Severe symptoms decrease the patient's quality of life and potentially deters further treatment. The five main forms of CINV (i.e., acute, delayed, anticipatory, breakthrough, and refractory) require different treatment regimens, which often include 5-HT3 receptor antagonists, NK1 receptor antagonists, and corticosteroids. Despite a significant amount of research and development of antiemetic agents, management of CINV remains a great challenge with many needs waiting to be adequately addressed, such as controlling non-acute CINV, developing appropriate CINV treatment protocols for multiple-day chemotherapy patients, and providing options for those prone to CINV despite treatment. Further research is required to optimize CINV management for these patients.
Longlong Tu
Zengbing Lu Man P. Ngan
John A Rudd
Background and Purpose HM01, a novel, orally bioavailable, brain‐penetrating agonist of ghrelin receptors, ameliorates emesis in Suncus murinus. This study compared HM01's activity against motion sickness with that of the less brain‐penetrating ghrelin receptor agonist, HM02. Experimental Approach The potential of HM01 and HM02 to relax isolated mesenteric arteries and to increase feeding was investigated. Radio telemetry was used to record gastric slow waves and body temperature. Plethysmography was used to measure respiratory function. HM01 and HM02 were administered p.o. 1 hr prior to provocative motion, and c‐Fos expression in brain sections was assessed. Key Results HM01 and HM02 both relaxed precontracted arteries, yielding EC50 values of 2.5 ± 0.5 and 3.5 ± 0.4 nM respectively. HM01 increased feeding, but HM02 did not. Both compounds caused hypothermia and bradygastria. Motion induced 123 ± 24 emetic events. HM01, but not HM02, reduced motion‐induced emesis by 67.6%. Motion increased c‐Fos expression in the nucleus tractus solitarius (NTS), dorsal motor nucleus of the vagus (DMNV), medial vestibular nucleus (MVe), central nucleus of the amygdala, and paraventricular hypothalamic nucleus (PVH). HM01 alone increased c‐Fos expression in the area postrema, NTS, DMNV, PVH, and arcuate hypothalamic nucleus; HM02 had a similar pattern except it did not increase c‐Fos in the PVH. Both compounds antagonized the motion‐induced increases in c‐Fos expression in the MVe. Conclusions and Implications HM01 is more effective than HM02 in preventing motion‐induced emesis. The difference in potency may relate to activation of ghrelin receptors in the PVH.
Chia-Shan Wu
Qiong Wei
Hongying Wang Yuxiang Sun
Sarcopenia is the aging-associated progressive loss of skeletal muscle, however the pathogenic mechanism of sarcopenia is not clear. The orexigenic hormone ghrelin stimulates growth hormone secretion, increases food intake, and promotes adiposity. Here we showed that fasting-induced muscle loss was exacerbated in old ghrelin–null (Ghrl-/-) mice, exhibiting decreased expression of myogenic regulator MyoD and increased expression of protein degradation marker MuRF1, as well as altered mitochondrial function. Moreover, acylated ghrelin (AG) and unacylated ghrelin (UAG) treatments significantly increased mitochondrial respiration capacity in muscle C2C12 cells. Consistently, AG and UAG treatments effectively increased myogenic genes and decreased degradation genes in the muscle in fasted old Ghrl-/- mice, possibly by stimulating insulin and AMPK pathways. Furthermore, Ghrl-/- mice showed a profile of pro-inflammatory gut microbiota, exhibiting reduced butyrate-producing bacteria Roseburia and ClostridiumXIVb. Collectively, our results showed that ghrelin has a major role in the maintenance of aging muscle via both muscle-intrinsic and -extrinsic mechanisms. AG and UAG enhanced muscle anabolism and exerted protective effects for muscle atrophy. Since UAG is devoid of the obesogenic side effect seen with AG, it represents an attractive therapeutic option for sarcopenia.
John A Rudd Sze Wa Chan Man P. Ngan
Claudio Pietra
Ghrelin has well-known activity to stimulate appetite and weight gain. Evidence suggests that ghrelin may also have effects in reducing chemotherapy-induced emesis via growth hormone secretagogue receptors (GHS-R1A) in the brain. However, it is not known whether the stimulation of GHS-R1A has broad inhibitory anti-emetic effects. In the present studies, we used Suncus murinus to investigate the potential of the new and novel orally bioavailable brain-penetrating GHS-R1A mimetic, HM01 (1-[(1S)-1-(2,3-dichloro-4-methoxyphenyl)ethyl]-3-methyl-3-[(4R)-1-Methyl-3,3-dimethyl-4-piperidyl]urea), to reduce emesis induced by a variety of emetic challenges. HM01 (1 to 30 mg/kg, p.o.) antagonized emesis induced by cisplatin (30 mg/kg, i.p.) and by motion (4 cm horizontal displacement, 1 Hz) but was ineffective against emesis induced by nicotine (5 mg/kg, s.c.) and copper sulfate (120 mg/kg by intragastric gavage). In other experiments, HM01 (3 mg/kg, p.o.) enhanced the anti-emetic control of a regimen of palonosetron (0.01 mg/kg, p.o.) alone and palonosetron (0.01 mg/kg p.o.) plus netupitant (1 mg/kg, p.o.). HM01 (10 mg/kg, p.o.) also had positive effects in increasing feeding and drinking in nicotine-treated animals, and it shortened the latency to drink in animals treated with cisplatin. These data indicate that brain-penetrating GHS-R1A agonists may have use alone and/or in combination with standard anti-emetic regimens for the treatment of chemotherapy-induced nausea and vomiting and motion sickness. Highlights - The novel orally bioavailable brain-penetrating GHS-R1A agonist, HM01 (1-[(1S)-1-(2,3-dichloro-4-methoxyphenyl)ethyl]-3-methyl-3-[(4R)-1-Methyl-3,3-dimethyl-4-piperidyl]urea), antagonizes motion- and cisplatin-induced emesis. - HM01 did not reduce emesis induced by nicotine or by intragastric copper sulfate. - HM01 has positive effects on food consumption after treatment with nicotine. - HM01 has synergistic effects against cisplatin when combined with palonosetron and palonosetron/netupitant regimens. - It is suggested that GHS-R1A agonists may be protective against chemotherapy-induced nausea and vomiting in combination with traditional anti-emetics and against motion-induced emesis.
Zengbing Lu
Ge Lin Man P. Ngan
John A Rudd
Preclinical studies show that the glucagon-like peptide-1 (GLP-1) receptor antagonist, exendin (9-39), can reduce acute emesis induced by cisplatin. In the present study, we investigate the effect of exendin (9-39) (100 nmol/24 h, i.c.v), on cisplatin (5 mg/kg, i.p.)-induced acute and delayed emesis and changes indicative of ‘nausea’ in ferrets. Cisplatin induced 37.2 ± 2.3 and 59.0 ± 7.7 retches + vomits during the 0-24 (acute) and 24-72 h (delayed) periods, respectively. Cisplatin also increased (P<0.05) the dominant frequency of gastric myoelectric activity from 9.4 ± 0.1 to 10.4 ± 0.41 cpm and decreased the dominant power (DP) during acute emesis; there was a reduction in the % power of normogastria and an increase in the % power of tachygastria; food and water intake was reduced. DP decreased further during delayed emesis, where normogastria predominated. Advanced multifractal detrended fluctuation analysis revealed that the slow wave signal shape became more simplistic during delayed emesis. Cisplatin did not affect blood pressure (BP), but transiently increased heart rate, and decreased heart rate variability (HRV) during acute emesis; HRV spectral analysis indicated a shift to ‘sympathetic dominance’. A hyperthermic response was seen during acute emesis, but hypothermia occurred during delayed emesis and there was also a decrease in HR. Exendin (9-39) did not improve feeding and drinking but reduced cisplatin-induced acute emesis by ~59 % (P<0.05) and antagonised the hypothermic response (P<0.05); systolic, diastolic and mean arterial BP increased during the delayed phase. In conclusion, blocking GLP-1 receptors in the brain reduces cisplatin-induced acute but not delayed emesis. Restoring power and structure to slow waves may represent a novel approach to treat the side effects of chemotherapy.
Neil E. Hill
Kevin Murphy
Saima Saeed
Mervyn Singer
Background Patients with multiple injuries or sepsis requiring intensive care treatment invariably develop a catabolic state with resultant loss of lean body mass, for which there are currently no effective treatments. Recovery can take months and mortality is high. We hypothesise that treatment with the orexigenic and anti-inflammatory gastric hormone, ghrelin may attenuate the loss of body mass following critical illness and improve recovery. Methods Male Wistar rats received an intraperitoneal injection of the fungal cell wall derivative zymosan to induce a prolonged peritonitis and consequent critical illness. Commencing at 48h after zymosan, animals were randomised to receive a continuous infusion of ghrelin or vehicle control using a pre-implanted subcutaneous osmotic mini-pump, and continued for 10 days. Results Zymosan peritonitis induced significant weight loss and reduced food intake with a nadir at Day 2 and gradual recovery thereafter. Supra-physiologic plasma ghrelin levels were achieved in the treated animals. Ghrelin-treated rats ate more food and gained more body mass than controls. Ghrelin increased adiposity and promoted carbohydrate over fat metabolism, but did not alter total body protein, muscle strength nor muscle morphology. Muscle mass and strength remained significantly reduced in all zymosan-treated animals, even at ten days post-insult. Conclusions Continuous infusion of ghrelin increased body mass and food intake, but did not increase muscle mass nor improve muscle function, in a long-term critical illness recovery model. Further studies with pulsatile ghrelin delivery or additional anabolic stimuli may further clarify the utility of ghrelin in survivors of critical illness.
William M. Pardridge
Introduction: There are 2 misconceptions about the cerebrospinal fluid (CSF), the blood-brain barrier (BBB), and brain drug delivery, which date back to the discovery of a barrier between blood and brain over 100 years ago. Misconception 1 is that drug distribution into CSF is a measure of BBB transport. Misconception 2 is that drug injected into the CSF compartment distributes to the inner parenchyma of brain. Areas Covered: Drug distribution into the CSF is a function of drug transport across the choroid plexus, which forms the blood-CSF barrier, and not drug transport across the BBB, which is situated at the microvascular endothelium of brain. Drug injected into CSF undergoes rapid efflux to the blood compartment via bulk flow. Drug penetration into brain parenchyma from the CSF is limited by diffusion and drug concentrations in brain decrease exponentially relative to the CSF concentration. Expert Opinion: The barrier between blood and brain was discovered in 1913, when it was believed that the BBB was localized to the choroid plexus, and that nutrient flow from blood passed through the CSF en route to brain. These misconceptions are still widely held, and hinder progress in the development of technology for BBB drug delivery.
Zengbing Lu Sze Wa Chan
Nathalie Percie du Sert
John A Rudd
Background Rodents are incapable of emesis and consequently the emetic potential of glucagon-like peptide-1 receptor (GLP-1R) agonists in studies designed to assess a potential blood glucose lowering action of the compound was missed. Therefore, we investigated if the ferret, a carnivore with demonstrated translation capability in emesis research, would identify the emetic potential of the GLP-1R agonist, exendin-4, and any associated effects on gastric motor function, appetite and cardiovascular homeostasis.Methods The biological activity of the GLP-1R ligands was investigated in vivo using a glucose tolerance test in pentobarbitone-anesthetised ferrets and in vitro using organ bath studies. Radiotelemetry was used to investigate the effect of exendin-4 on gastric myoelectric activity (GMA) and cardiovascular function in conscious ferrets; behaviour was also simultaneously assessed. Western blot was used to characterize GLP-1R distribution in the gastrointestinal and brain tissues.ResultsIn anesthetised ferrets, exendin-4 (30 nmol/kg, s.c.) reduced experimentally elevated blood glucose levels by 36.3%, whereas the GLP-1R antagonist, exendin (9¿39) (300 nmol/kg, s.c.) antagonised the effect and increased AUC0¿120 by 31.0% when injected alone (P < 0.05). In animals with radiotelemetry devices, exendin-4 (100 nmol/kg, s.c.) induced emesis in 1/9 ferrets, but inhibited food intake and decreased heart rate variability (HRV) in all animals (P < 0.05). In the animal not exhibiting emesis, there was no effect on GMA, mean arterial blood pressure, heart rate, or core body temperature. In the ferret exhibiting emesis, there was a shift in the GMA towards bradygastria with a decrease in power, and a concomitant decrease in HRV. Western blot revealed GLP-1R throughout the gastrointestinal tract but exendin-4 (up to 300 nM) and exendin (9¿39), failed to contract or relax isolated ferret gut tissues. GLP-1R were found in all major brain regions and the levels were comparable those in the vagus nerve.Conclusions Peripherally administered exendin-4 reduced blood glucose and inhibited feeding with a low emetic potential similar to that in humans (11% vs 12.8%). A disrupted GMA only occurred in the animal exhibiting emesis raising the possibility that disruption of the GMA may influence the probability of emesis occurring in response to treatment with GLP-1R agonists.
Claudio Pietra Yasuhiro Takeda N. Tazawa-Ogata
S. Robert Northrup
Background Anamorelin HCl (ANAM) is a novel, orally active, ghrelin receptor agonist in clinical development for the treatment of cancer cachexia. We report in vitro and in vivo studies evaluating the preclinical pharmacologic profile of ANAM. Methods Fluorescent imaging plate reader and binding assays in HEK293 and baby hamster kidney cells determined the agonist and antagonist activity of ANAM, and its affinity for the ghrelin receptor. Rat pituitary cells were incubated with ANAM to evaluate its effect on growth hormone (GH) release. In vivo, rats were treated with ANAM 3, 10, or 30 mg/kg, or control orally, once daily for 6 days to evaluate the effect on food intake (FI) and body weight (BW), and once to assess GH response. In pigs, single (3.5 mg/kg) or continuous (1 mg/kg/day) ANAM doses were administered to assess GH and insulin-like growth factor (IGF-1) response. Results ANAM showed significant agonist and binding activity on the ghrelin receptor, and stimulated GH release in vitro. In rats, ANAM significantly and dose-dependently increased FI and BW at all dose levels compared with control, and significantly increased GH levels at 10 or 30 mg/kg doses. Increases in GH and IGF-1 levels were observed following ANAM administration in pigs. Conclusion ANAM is a potent and highly specific ghrelin receptor agonist with significant appetite-enhancing activity, leading to increases in FI and BW, and a stimulatory effect on GH secretion. These results support the continued investigation of ANAM as a potential treatment of cancer anorexia-cachexia syndrome.
Rosie G Albarran-Zeckler
Roy G Smith
The growth hormone (GH) secretagogue receptor (GHS-R1a) is a G protein-coupled receptor (GPCR) expressed in the brain as well as other areas of the body. In the early 1990s, this receptor was expression cloned in MERCK laboratories by using a group of synthesized small molecules known to increase GH release in humans and other animals. Since its discovery, hundreds of studies have shown the importance of this receptor and its endogenous ligand, ghrelin, in metabolism, neurotransmission, and behavior. Even more relevant are the prospective benefits that will result from pharmacologic manipulation of GHS-R1a. Multiple GHS-R1a agonists and antagonists are available for experimentation, and some have been used in patients with promising results. Studies in rodents have revealed intriguing potential roles for GHS-R1a modulation. Our goal in this chapter is to connect these studies with the inherent advantages of targeting this receptor pharmacologically.
Nathalie Percie du Sert
William M. Pardridge
The human brain has no lymphatic system, but produces over a half-liter each day of cerebrospinal fluid. The cerebrospinal fluid is secreted at the choroid plexus and occupies the cavities of the four ventricles, as well as the cranial and spinal sub-arachnoid space. The cerebrospinal fluid moves over the surfaces of the brain and spinal cord and is rapidly absorbed into the general circulation. The choroid plexus forms the blood-cerebrospinal fluid barrier, and this barrier is functionally distinct from the brain microvascular endothelium, which forms the blood-brain barrier. Virtually all non-cellular substances in blood distribute into cerebrospinal fluid, and drug entry into cerebrospinal fluid is not an index of drug transport across the blood-brain barrier. Drug injected into the cerebrospinal fluid rapidly moves into the blood via bulk flow, but penetrates into brain tissue poorly owing to the limitations of diffusion. Drug transport into cerebrospinal fluid vs. brain interstitial fluid requires knowledge of the relative expression of transporters at the choroid plexus versus the brain microvascular endothelium.
L Jiménez-Reina
Ramón Cañete M.J. de la Torre J. Bernal
The pentapeptide Ipamorelin stimulates growth hormone (GH) release in pigs, sheep, dogs, rats and humans. In order to determine the effects of chronic treatment with Ipamorelin on the in vitro GH response, Ipamorelin was administered daily for 21 days to 60-day old female rats and the effects compared with those of growth hormone-releasing hormone (GHRH) (10 μg/kg body weight). Daily monitoring revealed a higher % weight gain in the Ipamorelin- pretreated group (IPG) and the GHRH-pretreated group (GPG) than in the vehicle-pretreated group (VPG). In 3-day pituitary cell monolayer cultures, basal GH release was greater in IPG and GPG than in VPG. After 3-day culture, basal GH release from individual cells was lower in IPG than in VPG and GPG. The intracellular GH content was lower in IPG and GPG than in VPG (P<0.05). In 3-day monolayer cultures, Ipamorelin (10-8 M) and GHRH (10-8 M) increased GH release in VPG and IPG, but not in GPG. Similarly, Ipamorelin (10-8 M) and GHRH (10-8 M) stimulated individual GH release in VPG and IPG. In conclusion, these data show that chronic administration of Ipamorelin to young female rats is effective in increasing body weight gain and enhancing in vitr o basal and Ipamorelin or GHRH-stimulated GH release. In the same conditions, GHRH increases body weight gain and maintains basal GH at levels similar to those produced by Ipamorelin, but without prompting any in vitro enhancement of the GH response to subsequent stimuli. These results suggest that Ipamorelin does not lead to desensitization of the GH response in young female rats, whilst GHRH produces desensitization of GH release in vitro.
Charles C Horn
Bart C De Jonghe Kathleen Matyas
Ralph Norgren
Anticancer agents, such as cisplatin, stimulate nausea, vomiting, and behaviors indicative of malaise. Rats and mice do not possess a vomiting response, and, therefore, in these species, the ingestion of kaolin clay (a pica response) has been used as an index of malaise. In the rat, cisplatin-induced kaolin intake is inhibited by antiemetic treatments. In addition, cisplatin activates vagal afferent fibers in the gut, and kaolin intake induced by cisplatin is largely dependent on an intact vagus. Nevertheless, little is known about the brain pathways controlling pica. We investigated the role of the lateral parabrachial nucleus (lPBN), a major visceral afferent link between the hindbrain and forebrain, in cisplatin-induced c-Fos expression and pica. Injection of cisplatin (6 mg/kg ip) produced c-Fos expression in the ventrolateral (external) lPBN, a region receiving viscerosensory input. In rats with bilateral ibotenic acid lPBN lesions, cisplatin treatment substantially increased kaolin intake compared with controls ( approximately 30 g vs. approximately 5 g, respectively, over 24 h). Food intake was reduced by cisplatin treatment and by apomorphine, an emetic agent that acts centrally. Unlike cisplatin, however, apomorphine stimulated kaolin intake to a similar degree in both the lesioned and control rats, suggesting that lPBN damage neither produces nonspecific effects nor enhances malaise in general. These data suggest that lPBN-lesioned animals not only demonstrate pica after cisplatin treatment, but, in fact, show an exaggerated response that is greatly in excess of any treatment known to produce kaolin intake in rats.
Kirsten Raun B S Hansen Nils Langeland Johansen
Peter Hongaard Andersen
The development and pharmacology of a new potent growth hormone (GH) secretagogue, ipamorelin, is described. Ipamorelin is a pentapeptide (Aib-His-D-2-Nal-D-Phe-Lys-NH2), which displays high GH releasing potency and efficacy in vitro and in vivo. As an outcome of a major chemistry programme, ipamorelin was identified within a series of compounds lacking the central dipeptide Ala-Trp of growth hormone-releasing peptide (GHRP)-1. In vitro, ipamorelin released GH from primary rat pituitary cells with a potency and efficacy similar to GHRP-6 (ECs) = 1.3+/-0.4nmol/l and Emax = 85+/-5% vs 2.2+/-0.3nmol/l and 100%). A pharmacological profiling using GHRP and growth hormone-releasing hormone (GHRH) antagonists clearly demonstrated that ipamorelin, like GHRP-6, stimulates GH release via a GHRP-like receptor. In pentobarbital anaesthetised rats, ipamorelin released GH with a potency and efficacy comparable to GHRP-6 (ED50 = 80+/-42nmol/kg and Emax = 1545+/-250ng GH/ml vs 115+/-36nmol/kg and 1167+/-120ng GH/ml). In conscious swine, ipamorelin released GH with an ED50 = 2.3+/-0.03 nmol/kg and an Emax = 65+/-0.2 ng GH/ml plasma. Again, this was very similar to GHRP-6 (ED50 = 3.9+/-1.4 nmol/kg and Emax = 74+/-7ng GH/ml plasma). GHRP-2 displayed higher potency but lower efficacy (ED50 = 0.6 nmol/kg and Emax = 56+/-6 ng GH/ml plasma). The specificity for GH release was studied in swine. None of the GH secretagogues tested affected FSH, LH, PRL or TSH plasma levels. Administration of both GHRP-6 and GHRP-2 resulted in increased plasma levels of ACTH and cortisol. Very surprisingly, ipamorelin did not release ACTH or cortisol in levels significantly different from those observed following GHRH stimulation. This lack of effect on ACTH and cortisol plasma levels was evident even at doses more than 200-fold higher than the ED50 for GH release. In conclusion, ipamorelin is the first GHRP-receptor agonist with a selectivity for GH release similar to that displayed by GHRH. The specificity of ipamorelin makes this compound a very interesting candidate for future clinical development.
Holly S Callahan
David E Cummings Margaret Sullivan Pepe David S Weigle
Plasma ghrelin levels rise before meals and fall rapidly afterward. If ghrelin is a physiological meal-initiation signal, then a large oral caloric load should suppress ghrelin levels more than a small caloric load, and the request for a subsequent meal should be predicted by recovery of the plasma ghrelin level. To test this hypothesis, 10 volunteers were given, at three separate sessions, liquid meals (preloads) with widely varied caloric content (7.5%, 16%, or 33% of total daily energy expenditure) but equivalent volume. Preloads were consumed at 0900 h, and blood was sampled every 20 min from 0800 h until 80 min after subjects spontaneously requested a meal. The mean (+/- SE) intervals between ingestion of the 7.5%, 16%, and 33% preloads and the subsequent voluntary meal requests were 247 +/- 24, 286 +/- 20, and 321 +/- 27 min, respectively (P = 0.015), and the nadir plasma ghrelin levels were 80.2 +/- 2.8%, 72.7 +/- 2.7%, and 60.8 +/- 2.7% of baseline (the 0900 h value), respectively (P < 0.001). A Cox regression analysis failed to show a relationship between ghrelin profile and the spontaneous meal request. We conclude that the depth of postprandial ghrelin suppression is proportional to ingested caloric load but that recovery of plasma ghrelin is not a critical determinant of intermeal interval.
Y.-L. Liu N M Malik
Gareth J Sanger P.L.R. Andrews
Chemotherapy treatment may lead to delayed gastric emptying, early satiety, anorexia, nausea and vomiting, described collectively as the cancer-associated dyspepsia syndrome (CADS). We examined the effects of ghrelin in rodent models of CADS induced by treatment with cisplatin. In rats, increased gastric contents and reduced feeding were observed 48 h after injection with cisplatin (6 mg/kg, i.p.). Ghrelin (0.5 mg/kg, i.p.) caused a 16-fold increase in food intake over 1 h in cisplatin/ghrelin-treated rats compared to cisplatin/vehicle-treated rats. A single dose of ghrelin also restored the decreased locomotor activity in rats induced by cisplatin to almost the same level of saline-treated rats. In mice, daily food intake was significantly decreased at 24 h (60%) and 48 h (74%) after cisplatin (20 mg/kg, i.p.). Ghrelin (1 mg/kg, i.p.x2) significantly increased food intake measured at the 48 h time-point in both saline/ghrelin-treated and cisplatin/ghrelin-treated mice, with this effect being most marked in the cisplatin-treated group, where a twofold increase in feeding was observed. In cisplatin-treated mice, delayed gastric emptying was indicated by a 7.7-fold increase in the wet weight of gastric contents and ghrelin improved the gastric emptying index (GEI) by 31% (P < 0.01). Together, these results suggest that it is possible to model cancer chemotherapy-induced dyspepsia in rodents and that ghrelin can greatly alleviate the behaviours associated with this syndrome. Agonists at the ghrelin receptor may, therefore, become a useful human therapeutic for this disorder.
Amanda J Page James A Slattery Catherine Milte
L. Ashley Blackshaw
Ghrelin is a peptide released from gastric endocrine cells that has an orexigenic effect via a vagal pathway. Here we determine the effect of ghrelin on mechanosensitivity of upper-intestinal vagal afferent fibers in ferret and mouse. The responses of gastroesophageal vagal afferents to graded mechanical stimulation were determined in vitro before and during application of ghrelin to their peripheral endings. Three types of vagal afferent were tested: tension receptors responding to circumferential tension, mucosal receptors responding only to mucosal stroking, and tension/mucosal (TM) receptors in ferret esophagus that responded to both stimuli. In the mouse, ghrelin did not significantly affect the response of mucosal receptors to mucosal stroking with calibrated von Frey hairs. However, it significantly reduced responses of tension receptors to circumferential tension (P < 0.005; two-way ANOVA) by up to 40%. This inhibition was reversed by the ghrelin receptor antagonist [d-Lys-3]-growth hormone-releasing peptide (GHRP)-6. In the ferret, ghrelin significantly reduced the response of mucosal and TM receptors to mucosal stroking with calibrated von Frey hairs. Surprisingly, ghrelin did not significantly alter the response to circumferential tension in either tension or TM receptors. RT-PCR analysis indicated that both ghrelin and its receptor are expressed in vagal afferent cell bodies in mouse nodose ganglia. In conclusion, ghrelin selectively inhibits subpopulations of mechanically sensitive gastroesophageal vagal afferents; there is also potential for ghrelin release from vagal afferents. However, the subpopulation of afferents inhibited differs between species. These data have broad implications for ghrelin's role in food intake regulation and reflex control of gastrointestinal function.
Rosario B. Jaime-Lara Tito Borner
Ruby A. Holland
Bart C De Jonghe
Nausea and vomiting are consistently identified among the most distressing side effects of chemotherapy. In recent years, Olanzapine (OLZ) treatment was added to anti-emetic guidelines as a treatment for chemotherapy-induced nausea and vomiting (CINV), despite little available data supporting a mechanism behind the positive benefits of the drug. Here, we examine whether OLZ reduces cisplatin chemotherapy-induced side effects on food intake and pica behavior in rats (i.e., kaolin intake, a proxy for nausea/emesis). Behavioral experiments tested whether systemic or hindbrain administration of OLZ ameliorated cisplatin-induced pica, anorexia, and body weight loss in rats. We also tested whether systemic OLZ reduces cisplatin-induced neuronal activation in the dorsal vagal complex (DVC), a hindbrain region controlling emesis. Lastly, given their role in regulating feeding and emesis, circulating ghrelin levels and central mRNA expression levels of serotonin (HT) receptor subunits, including 5-HT2C, were measured in brain regions that regulate CINV and energy balance in an exploratory analysis to investigate potential mediators of OLZ action. Our results show that both systemic and hindbrain administration of OLZ attenuated cisplatin-induced kaolin intake and body weight loss, but not anorexia. Systemic OLZ decreased cisplatin-induced c-Fos immunofluorescence in the DVC and prevented cisplatin-induced reductions in circulating ghrelin levels. IP OLZ also blocked cisplatin-induced increases in Htr2c expression in DVC and hypothalamic micropunches. These data suggest hindbrain exposure to OLZ is sufficient to induce reductions in cisplatin-induced pica and that central serotonergic signaling, via 5-HT2C, and changes in circulating ghrelin may be potential mediators of olanzapine anti-emetic action.
Alfonso Abizaid
James L Hougland
Ghrelin and the growth hormone secretagogue receptor 1a (GHS-R1a) are important targets for disorders related to energy balance and metabolic regulation. Pharmacological control of ghrelin signaling is a promising avenue to address health issues involving appetite, weight gain, obesity, and related metabolic disorders, and may be an option for patients suffering from wasting conditions like cachexia. In this review, we summarize recent developments in the biochemistry of ghrelin and GHS-R1a signaling. These include unravelling the enzymatic transformations that generate active ghrelin and the discovery of multiple proteins that interact with ghrelin and GHS-R1a to regulate signaling. Furthermore, we propose that harnessing these processes will lead to highly selective treatments to address obesity, diabetes, and other metabolism-linked disorders.
Xingshen Sun
Yaling Yi Bo Liang
Andrew W Norris
Background: Insulin secretion is insufficient in cystic fibrosis (CF), even before diabetes is present, though the mechanisms involved remain unclear. Acyl-ghrelin (AG) can diminish insulin secretion and is elevated in humans with CF. Methods: We tested the hypothesis that elevated AG contributes to reduced insulin secretion and hyperglycemia in CF ferrets. Results: Fasting AG was elevated in CF versus non-CF ferrets. Similar to its effects in other species, AG administration in non-CF ferrets acutely reduced insulin, increased growth hormone, and induced hyperglycemia. During oral glucose tolerance testing, non-CF ferrets had responsive insulin, glucagon like peptide-1 (GLP-1) and gastric inhibitory polypeptide (GIP) levels and maintained normal glucose levels, whereas CF ferrets had insufficient responses and became hyperglycemic. Interestingly in wild-type ferrets, the acyl-ghrelin receptor antagonist [D-Lys3]-GHRP-6 impaired glucose tolerance, and abolished insulin, GLP-1, and GIP responses during glucose tolerance testing. By contrast, in CF ferrets [D-Lys3]-GHRP-6 improved glucose tolerance, enhanced the insulin-to-glucose ratio, but did not impact the already low GLP-1 and GIP levels. Conclusions: These results suggest a mechanism by which elevated AG contributes to CF hyperglycemia through inhibition of insulin secretion, an effect magnified by low GLP-1 and GIP. Interventions that lower ghrelin, ghrelin action, and/or raise GLP-1 or GIP might improve glycemia in CF.
Omar Al-Massadi Rubén Nogueiras
Carlos Dieguez
Jean-Antoine Girault
Food intake is tightly regulated by homeostatic and reward mechanisms and the adequate function of both is necessary for the proper maintenance of energy balance. Ghrelin impacts these two levels to induce feeding. In this review, we present the actions of ghrelin in food reward, including their dependence on other relevant modulators implicated in the motivational aspects of feeding, including dopamine, opioid peptides, and endocannabinoids. We also describe the interaction between brain areas involved in homeostatic regulation of feeding and the reward system, with a special emphasis on the role of arcuate nucleus melanocortins and lateral hypothalamus orexins in ghrelin function. Finally, we briefly discuss the actions of ghrelin in food reward in obesity. We propose that new insights into the mechanism of action of ghrelin in the rewarding and motivational control of food intake will help to understand food-related disorders including obesity and anorexia.
Y-L Gong F. Liu H. Jin F-F Guo
Objective: Ghrelin had been known to promote gastric motility in human and animals previously. We aim to investigate the role of ghrelin in chemotherapy-induced nausea and vomiting. Materials and methods: In the present study, we observed the changes in food intake, kaolin consumption, body weight, plasma ghrelin concentration and expression of ghrelin and its receptor GHS-R1a in the stomach and nucleus tractus solitaries (NTS) in cisplatin-treated rats, and the effects of ghrelin microinjected into NTS on the discharge activity of gastric distension (GD) responsive neurons and gastric motility were also observed. Results: Cisplatin induced the decrease in food intake and the increase in kaolin consumption of rats. In addition, mRNA expression of GHS-R1a in the stomach and NTS increased significantly after cisplatin treatment. The discharge activity of GD excited (GD-E) and GD inhibited (GD-I) neurons in cisplatin-treated rats was weaker than that of saline treatment, while ghrelin administration into NTS excited most of GD-E and GD-I neurons. Cisplatin induced the decrease in gastric contraction while ghrelin administrated into NTS promoted the gastric motility significantly. However, the amplitude and frequency of gastric contraction promoted by ghrelin in NTS of cisplatin-treated rats were lower than that of saline treated rats. The effects of ghrelin could be completely blocked by its receptor antagonist BIM28163. Conclusions: These results indicated that ghrelin in the NTS might participate in the regulation of GD-neurons and gastric motility via its receptor in cisplatin-treated rats.
John Broad
Brid Callaghan
John B Furness
Gareth J Sanger
Ghrelin and motilin are released from gastrointestinal endocrine cells during hunger, to act through G protein-coupled receptors that have closely related amino acid sequences. The actions of ghrelin are more complex than motilin because ghrelin also exists outside the GI tract, it is processed to des-acyl ghrelin which has activity, ghrelin can exist in truncated forms and retain activity, the ghrelin receptor can have constitutive activity and is subject to biased agonism and finally additional ghrelin-like and des-acyl ghrelin receptors are proposed. Both ghrelin and motilin can stimulate gastric emptying, acting via different pathways, perhaps influenced by biased agonism at the receptors, but research is revealing additional pathways of activity. For example, it is becoming apparent that reduction of nausea may be a key therapeutic target for ghrelin receptor agonists and perhaps for compounds that modulate the constitutive activity of the ghrelin receptor. Reduction of nausea may be the mechanism through which gastroparesis symptoms are reduced. Intriguingly, a potential ability of motilin to influence nausea is also becoming apparent. Ghrelin interacts with digestive function through its effects on appetite, and ghrelin antagonists may have a place in treating Prader-Willi syndrome. Unlike motilin, ghrelin receptor agonists also have the potential to treat constipation by acting at the lumbosacral defecation centres. In conclusion, agonists of both ghrelin and motilin receptors hold potential as treatments for specific subsets of digestive system disorders.
P.L.R. Andrews
John A Rudd
The basic pathways inducing vomiting, the brainstem sites of integration and the main motor components had all been described by the early 1950s but relatively little was known about how cancer chemotherapeutic agents induced emesis until research was prompted by the clinical use of cisplatin thirty years later. The acute phase of cisplatin-induced emesis is predominantly driven by 5-hydroxytryptamine released from enterochromaffin cells in the small intestine activating 5-HT3 receptors located on vagal afferent terminals. Other substances such as prostanoids and substance P also interact with receptors on the afferents and are proposed to be involved in local inflammatory responses. Although for the delayed phase of cisplatin-induced emesis a contribution of the vagal afferents driven by an inflammatory response in the gut cannot be excluded, the evidence supports release of an endocrine mediator (unidentified) from the gut but acting on the area postrema to activate central pathways. The potential mechanisms by which cisplatin and other chemotherapeutic agents act on the gut epithelium and enteric neurones are reviewed. The sites and mechanisms of action of 5-HT3 and NK1 receptor antagonists are discussed in relation to the emetic pathways. The biologically significant, aversive, unpleasant sensation of nausea is a focus of the chapter because it impacts on the patient’s quality of life. The potential roles of vasopressin secretion, disturbance of gastric myoelectric activity and central pathways implicated in the genesis of the sensation are discussed in the wider context of the relative efficacy of anti-emetic drugs against nausea as compared to retching and vomiting.
David Beck W. Brian Sweeney
Martin D McCarter
Background: Postoperative ileus is a significant clinical challenge lacking effective management strategies. Ghrelin-receptor stimulation has promotility effects in the upper and lower gastrointestinal tract. Objective: This proof-of-concept, phase 2, randomized study evaluated the safety and efficacy of the ghrelin-receptor agonist ipamorelin in the treatment of postoperative ileus following abdominal surgery (ClinicalTrials.gov NCT00672074). Design: The design was a multicenter, double-blind, placebo-controlled, clinical trial. Settings: The settings include hospital inpatients. Patients: The patients were adults undergoing small and large bowel resection by open or laparoscopic surgery. Intervention: The intervention was intravenous infusions of 0.03-mg/kg ipamorelin vs placebo twice daily, on postoperative day 1 to 7 or hospital discharge. Main outcome measures: Safety was assessed by monitoring adverse events and laboratory tests. The key efficacy endpoint was time from first dose of study drug to tolerance of a standardized solid meal. Results: One hundred seventeen patients were enrolled, of whom 114 patients composed the safety and modified intent-to-treat populations. Demographic and disease characteristics were balanced between groups. Overall incidence of any treatment-emergent adverse events was 87.5 % in the ipamorelin group and 94.8 % in placebo group. Median time to first tolerated meal was 25.3 and 32.6 h in the ipamorelin and placebo groups, respectively (p = 0.15). Limitations: This proof of concept study was small and enrolled patients with a broad range of underlying conditions. Conclusions: Ipamorelin 0.03-mg/kg twice daily for up to 7 days was well tolerated. There were no significant differences between ipamorelin and placebo in the key and secondary efficacy analyses.
David C Currow
Amy P Abernethy
ABSTRACT Anamorelin hydrochloride is an orally active ghrelin receptor agonist in development by Helsinn, for the treatment of non-small cell lung cancer (NSCLC) cachexia. In preclinical and clinical studies, the potent affinity of anamorelin for the ghrelin receptor is associated with significant appetite-enhancing activity and resultant improvements in body weight, lean body mass, and handgrip strength compared with placebo. The accompanying stimulatory effects on growth hormone and IGF-1 are not associated with tumor growth, and overall survival in patients with cancer is not compromised. Anamorelin is well tolerated with no dose-limiting toxicities identified to date. The findings of ongoing Phase III studies are needed to confirm the significant potential of anamorelin to treat NSCLC cachexia.
Yuichiro Hiura Shuji Takiguchi
Kazuyoshi Yamamoto
Yuichiro Doki
Cisplatin reduces plasma ghrelin levels through the 5-hydroxytryptamine (5-HT) receptor. This may cause cisplatin-induced gastrointestinal disorders and hinders the continuation of chemotherapy. The authors of this report conducted a prospective, randomized phase 2 trial to evaluate the effects of exogenous ghrelin during cisplatin-based chemotherapy. Forty-two patients with esophageal cancer who were receiving cisplatin-based neoadjuvant chemotherapy were assigned to either a ghrelin group (n = 21) or a placebo group (n = 21). They received either intravenous infusions of synthetic human ghrelin (3 μg/kg) or saline twice daily for 1 week with cisplatin administration. The primary endpoint was changes in oral calorie intake, and the secondary endpoints were chemotherapy-related adverse events; appetite visual analog scale (VAS) scores; changes in gastrointestinal hormones and nutritional status, including rapid turnover proteins, and quality of life (QoL) estimated with the European Organization for Research and Treatment of Cancer QoL core questionnaire (QLQ-C30). Two patients were excluded from the final analysis: One patient suspended ghrelin administration because of excessive diaphoresis, and another patient in the placebo group failed to monitor the self-questionnaire. Food intake and appetite VAS scores were significantly higher in the ghrelin group than in the placebo group (18.2 ± 5.2 kcal/kg/day vs 12.7 ± 3.4 kcal/kg/day [P = .001] and 6.2 ± 0.9 vs 4.1 ± 0.9 [P < .0001], respectively). Patients in the ghrelin group had fewer adverse events during chemotherapy related to anorexia and nausea than patients in the control group. Significant deterioration was noted after chemotherapy in the placebo group in QoL scores, appetite, nausea and vomiting, and global health status. Short-term administration of exogenous ghrelin at the start of cisplatin-based chemotherapy stimulated food intake and minimized adverse events. Cancer 2012. © 2012 American Cancer Society.
Marisa Ghersi
Sebastián Marcelo Casas Carla Escudero
Susana R de Barioglio
Ghrelin (Ghr) is a peptide produced peripherally and centrally. It participates in the modulation of different biological processes. In our laboratory we have shown that (a) Ghr administration, either intracerebroventricular or directly into the hippocampus enhanced memory consolidation in a step down test in rats (b) the effect of Ghr upon memory decreases in animals pretreated with a serotonin (5-HT) reuptake inhibitor, Fluoxetine, suggesting that Ghr effects in the hippocampus could be related to the availability of 5-HT. It has been demonstrated that Ghr inhibits 5-HT release from rat hypothalamic synaptosomes. Taking in mint these evidences, we studied the release of radioactive 5-HT to the superfusion medium from hippocampal slices treated with two doses of Ghr (0.3 and 3 nm/μl). Ghr inhibited significantly the 5-HT release in relation to those superfused with artificial cerebrospinal fluid (ACSF) (H = 9.48, df = 2, p ≤ 0.05). In another set of experiments, Ghr was infused into the CA1 area of hippocampus of the rats immediately after training in the step down test and the 5-HT release from slices was studied 24h after Ghr injection showing that in this condition also the 5-HT release was inhibited (H = 11.72, df = 1, p ≤ 0.05). In conclusion, results provide additional evidence about the neurobiological bases of Ghr action in hippocampus.
Kalina Venkova
William Mann Richard Nelson
Beverley Greenwood-Van Meerveld
Ghrelin and ghrelin mimetics stimulate appetite and enhance gastric motility. The present study investigates whether ipamorelin, a selective growth hormone secretagogue and agonist of the ghrelin receptor, would accelerate gastrointestinal transit and ameliorate the symptoms in a rodent model of postoperative ileus (POI). Fasted male rats were subjected to laparotomy and intestinal manipulation. At the end of surgery, a dye marker was infused in the proximal colon to evaluate postsurgical colonic transit time, which was the time to the first bowel movement. In addition, fecal pellet output, food intake, and body weight were monitored regularly for 48 h. Ipamorelin (0.01-1 mg/kg), growth hormone-releasing peptide (GHRP)-6 (20 microg/kg), or vehicle (saline) were administered via intravenous bolus infusion after a single dosing or a 2-day repetitive dosing regimen (four doses a day at 3-h intervals). Compared with the vehicle, a single dose of ipamorelin (1 mg/kg) or GHRP-6 (20 microg/kg) decreased the time to the first bowel movement but had no effect on cumulative fecal output, food intake, or body weight gain measured 48 h after the surgery. In contrast, repetitive dosing of ipamorelin (0.1 or 1 mg/kg) significantly increased the cumulative fecal pellet output, food intake, and body weight gain. The results suggest that postsurgical intravenous infusions of ipamorelin may ameliorate the symptoms in patients with POI.
Yoshifumi Torii Masato Mutoh Hiroshi Saito Norio Matsuki
The participation of free radicals in cisplatin-induced emesis was investigated in the house musk shrew, Suncus murinus. Thiobarbituric acid (TBA) values, which indicate the degree of lipid peroxidation, in brain, liver and small intestine were increased significantly 60 min after the treatment with cisplatin (20 mg/kg, i.p.). Moreover, cisplatin (20 mg/kg, i.p.)-induced emesis was prevented by intraperitoneal injection of N-(2-mercaptopropionyl)glycine (MPG), a radical scavenging agent, with ID50 value of 130 mg/kg. However, MPG did not block the emesis induced by copper sulfate (40 mg/kg, p.o.), veratrine (0.5 mg/kg, s.c.) or serotonin (10 mg/kg, i.p.). We also investigated the effects of superoxide dismutase conjugated to polyethylene glycol and catalase, but the number of vomiting episodes and latency did not change significantly when these agents were intraperitoneally injected 30 min prior to or 20 min after the administration of cisplatin. MPG did not affect the antitumor effect of cisplatin tested in vitro. These results suggest that free radicals mediate emesis caused by cisplatin and that radical scavengers may become a new class of prophylactic drug against cancer-chemotherapeutic drug-induced emesis.
R J Naylor
John A Rudd
Cisplatin, 5 mg kg −1 , i.p., administered as a single treatment, induced an acute (day 1) and delayed (days 2 and 3) emetic response in the ferret that was used to investigate the potential anti‐emetic activity of ondansetron and dexamethasone and their interaction over a three day period. Ondansetron, 1 mg kg −1 , i.p., administered three times per day in two experiments, antagonized significantly the retching and vomiting that occurred on days 1 and 2 by 60–76 and 73–84%. On the third day of treatment there was a trend for a 38% reduction in one experiment and a 74% reduction in the other. There was a trend for dexamethasone, 1 mg kg −1 , i.p., administered as a single daily injection for three days, to reduce by 37% the retching and vomiting response that occurred on day 1, the reduction of 77% on day 2 achieved significance and dexamethasone non‐significantly increased the retching and vomiting response by 46% on day 3. However, dexamethasone 1 mg kg −1 i.p. administered three times per day for three days significantly reduced the retching+vomiting reponse by 85, 97 and 86% on days 1, 2 and 3 respectively. The combination of dexamethasone, 1 mg kg −1 , i.p., as single daily injections with ondansetron, 1 mg kg −1 , i.p., administered three times per day improved the control of the retching and vomiting response, significantly reducing the total numbers of retches and vomits by more than 70% over a three day period. The combination of dexamethasone (1.0 mg kg −1 ) and ondansetron (1.0 mg kg −1 ), both administered three times daily, abolished cisplatin‐induced emesis over the three day period. The three times per day administration of ondansetron, 1 mg kg −1 , i.p., plus dexamethasone, 1 mg kg −1 , i.p., administered only on day 1 prevented day 1 emesis but did not modify the retching and vomiting that occurred on days 2 and 3. The present results indicate that ondansetron and dexamethasone significantly reduce cisplatininduced emesis in the ferret during both the acute and delayed phase; drug/co‐treatment can exert an additive action to abolish cisplatin‐induced emesis. The ferret model may be useful to detect anti‐emetic drug action for treatment of chemotherapy‐induced acute and delayed emesis in man.
Hiroshi Hosoda
Yukari Date Kenji Kangawa Masayasu Kojima
Small synthetic molecules called growth-hormone secretagogues (GHSs) stimulate the release of growth hormone (GH) from the pituitary. They act through GHS-R, a G-protein-coupled receptor for which the ligand is unknown. Recent cloning of GHS-R strongly suggests that an endogenous ligand for the receptor does exist and that there is a mechanism for regulating GH release that is distinct from its regulation by hypothalamic growth-hormone-releasing hormone (GHRH). We now report the purification and identification in rat stomach of an endogenous ligand specific for GHS-R. The purified ligand is a peptide of 28 amino acids, in which the serine 3 residue is n-octanoylated. The acylated peptide specifically releases GH both in vivo and in vitro, and O-n-octanoylation at serine 3 is essential for the activity. We designate the GH-releasing peptide 'ghrelin' (ghre is the Proto-Indo-European root of the word 'grow'). Human ghrelin is homologous to rat ghrelin apart from two amino acids. The occurrence of ghrelin in both rat and human indicates that GH release from the pituitary may be regulated not only by hypothalamic GHRH, but also by ghrelin.
Jean-François Ghersi-Egea Nathalie Strazielle
The choroid plexuses (CPs) have the capability to modulate drug delivery to the cerebrospinal fluid (CSF) and to participate in the overall cerebral biodisposition of drugs. The specific morphological properties of the choroidal epithelium and the existence of a CSF pathway for drug distribution to different targets in the central nervous system suggest that the CP-CSF route is more significant than previously thought for brain drug delivery. In contrast to its role in CSF penetration of drugs, CP is also involved in brain protection in that it has the capacity to clear the CSF from numerous potentially harmful CSF-borne exogenous and endogenous organic compounds into the blood. Furthermore, CP harbors a large panel of drug-metabolizing enzymes as well as transport proteins of the multidrug resistance phenotype, which modulate the cerebral bioavailability of drugs and toxins. The use of an in vitro model of the choroidal epithelium suitable for drug transport studies has allowed the demonstration of the choroidal epithelium acting as an effective metabolic blood-CSF barrier toward some xenobiotics, and that a vectorial, blood-facing efflux of conjugated metabolites occurs at the choroidal epithelium. This efflux involves a specific transporter with characteristics similar to those of the multidrug resistance associated protein (MRP) family members. Indeed, at least one member, MRP1, is largely expressed at the CP epithelium, and localizes at the basolateral membrane. These metabolic and transport features of the choroidal epithelium point out the CP as a major detoxification site within the brain.
William A Banks
Matthias Tschöp Sandra M Robinson
Mark Heiman
The novel hormone ghrelin is a potent orexigen that may counterbalance leptin. Ghrelin is the only secreted molecule requiring post-translational acylation with octanoic acid to ensure bioactivity. Ghrelin, predominantly derived from the stomach, may target neuroendocrine networks within the central nervous system (CNS) to regulate energy homeostasis. This would require ghrelin to cross the blood-brain barrier (BBB). In mice, we examined whether ghrelin crosses the BBB and whether its lipophilic side chain is involved in this process. We found that saturable systems transported human ghrelin from brain-to-blood and from blood-to-brain. Mouse ghrelin, differing from human ghrelin by two amino acids, was a substrate for the brain-to-blood but not for the blood-to-brain transporter and so entered the brain to a far lesser degree. des-Octanoyl ghrelin entered the brain by nonsaturable transmembrane diffusion and was sequestered once within the CNS. In summary, we show that ghrelin transport across the BBB is a complex, highly regulated bidirectional process. The direction and extent of passage are determined by the primary structure of ghrelin, defining a new role for the unique post-translational octanoylation.
Masayasu Kojima Kenji Kangawa
Small synthetic molecules called growth hormone secretagogues (GHSs) stimulate the release of growth hormone (GH) from the pituitary. They act through the GHS-R, a G protein-coupled receptor whose ligand has only been discovered recently. Using a reverse pharmacology paradigm with a stable cell line expressing GHS-R, we purified an endogenous ligand for GHS-R from rat stomach and named it "ghrelin," after a word root ("ghre") in Proto-Indo-European languages meaning "grow." Ghrelin is a peptide hormone in which the third amino acid, usually a serine but in some species a threonine, is modified by a fatty acid; this modification is essential for ghrelin's activity. The discovery of ghrelin indicates that the release of GH from the pituitary might be regulated not only by hypothalamic GH-releasing hormone, but also by ghrelin derived from the stomach. In addition, ghrelin stimulates appetite by acting on the hypothalamic arcuate nucleus, a region known to control food intake. Ghrelin is orexigenic; it is secreted from the stomach and circulates in the bloodstream under fasting conditions, indicating that it transmits a hunger signal from the periphery to the central nervous system. Taking into account all these activities, ghrelin plays important roles for maintaining GH release and energy homeostasis in vertebrates.
Takio Kitazawa
Bernardo De Smet
Kristin Verbeke
Tiebe Peeters
The gastroprokinetic activities of ghrelin, the natural ligand of the growth hormone secretagogue receptor (GHS-R), prompted us to compare the effect of ghrelin with that of synthetic peptide (growth hormone releasing peptide 6 (GHRP-6)) and non-peptide (capromorelin) GHS-R agonists both in vivo and in vitro. In vivo, the dose dependent effects (1-150 nmol/kg) of ghrelin, GHRP-6, and capromorelin on gastric emptying were measured by the 14C octanoic breath test which was adapted for use in mice. The effect of atropine, N(G)-nitro-L-arginine methyl ester hydrochloride (L-NAME), or D-Lys3-GHRP-6 (GHS-R antagonist) on the gastroprokinetic effect of capromorelin was also investigated. In vitro, the effect of the GHS-R agonists (1 microM) on electrical field stimulation (EFS) induced responses was studied in fundic strips in the absence and presence of L-NAME. Ghrelin, GHRP-6, and capromorelin accelerated gastric emptying in an equipotent manner, with bell-shaped dose-response relationships. In the presence of atropine or l-NAME, which delayed gastric emptying, capromorelin failed to accelerate gastric emptying. D-Lys3-GHRP-6 also delayed gastric emptying but did not effectively block the action of the GHS-R agonists, but this may be related to interactions with other receptors. EFS of fundic strips caused frequency dependent relaxations that were not modified by the GHS-R agonists. L-NAME turned EFS induced relaxations into cholinergic contractions that were enhanced by ghrelin, GHRP-6, and capromorelin. The 14C octanoic breath test is a valuable technique to evaluate drug induced effects on gastric emptying in mice. Peptide and non-peptide GHS-R agonists accelerate gastric emptying of solids in an equipotent manner through activation of GHS receptors, possibly located on local cholinergic enteric nerves.
John A Rudd Man P. Ngan Man K Wai
Gareth J Sanger
Emesis may be modulated via multiple mechanisms. The actions of ghrelin suggest an ability to couple an induction of hunger with preparation of the stomach for ingestion of food. Such a process might reduce any tendency to vomit, so an anti-emetic activity of ghrelin was investigated in the ferret cisplatin-induced emesis model. In controls, intra-peritoneal cisplatin (10 mg/kg) induced 41.4+/-8.4 episodes of emesis comprising 310.4+/-55.3 retches and 28.8+/-6.9 vomits during the 6h observation; the latency to onset of the first emetic episode was 108.9+/-4.8 min. Intra-peritoneal ghrelin (1mg/kg, split as a 30 min pre- and 30 min-post dose) did not induce a change in behaviour or modify cisplatin-induced emesis (p>0.05). Intracerebroventricular (i.c.v.) administration (third ventricle) was achieved via a pre-implanted cannula. At the first emetic episode following cisplatin, ghrelin or vehicle (20 microl saline) was administered i.c.v. During the 30 min following the initial episode of emesis, control animals exhibited 18.0+/-2.6 emetic episodes comprising 160.3+/-24.1 retches and 13.8+/-2.7 vomits. Ghrelin 10 microg i.c.v. reduced the number of retches by 61.5% (p<0.05) and at a dose of 30 microg i.c.v. ghrelin reduced the number of episodes, individual retches and vomits by 74.4 (p<0.05), 80.4 (p<0.01), and 72.5% (p<0.05), respectively. At subsequent time periods there were no differences between ghrelin- or saline-treated animals (p>0.05). An ability of ghrelin to reduce emesis is consistent with a role in modulating gastro-intestinal functions and identifies a novel approach to the treatment of emesis.
The physiology and pharmacology of postoperative nausea and vomiting
Naylor