RESUMEN
Alcohol use disorder (AUD) is a highly prevalent public health problem. The ghrelin system has been identified as a potential target for therapeutic intervention for AUD. Previous work showed that systemic administration of the growth hormone secretagogue receptor (GHSR) antagonist DLys reduced alcohol intake and preference in male mice. Yet, it is unclear whether central or peripheral GHSRs mediated these effects. We hypothesized that alcohol consumption is driven by central GHSRs and addressed this hypothesis by testing the effects of central administration of DLys. Male C57BL/6J mice consumed alcohol in a two-bottle choice procedure (10% ethanol versus water). DLys (2â nmol) was administered intracerebroventricularly for 7â days to examine alcohol intake and preference. DLys decreased alcohol intake and preference but had no effect on food intake. The effects on alcohol intake and preference persisted after several administrations, indicating lack of tolerance to DLys' effects. These results suggest that central administration of DLys is sufficient to reduce alcohol drinking and that DLys remains effective after several administrations when given intracerebroventricularly. Moreover, this work suggests that the effects of intracerebroventricularly administered DLys are specific to alcohol and do not generalize to other calorie-driven behaviors.
Asunto(s)
Consumo de Bebidas Alcohólicas , Ratones Endogámicos C57BL , Receptores de Ghrelina , Animales , Masculino , Receptores de Ghrelina/antagonistas & inhibidores , Ratones , Etanol/administración & dosificación , Etanol/farmacología , Inyecciones Intraventriculares , Conducta de Elección/efectos de los fármacos , Ingestión de Alimentos/efectos de los fármacos , Preferencias Alimentarias/efectos de los fármacos , Glicina/análogos & derivados , TriazolesRESUMEN
This study investigated whether ghrelin mimetics, namely anamorelin and ipamorelin, can alleviate weight loss and inhibition of feeding observed during acute and delayed phases of cisplatin-induced emesis in ferrets. The potential of anamorelin to inhibit electrical field stimulation (EFS)-induced contractions of isolated ferret ileum was compared with ipamorelin. In other experiments, ferrets were administered anamorelin (1-3 mg/kg), ipamorelin (1-3 mg/kg), or vehicle intraperitoneally (i.p.) 30 s before cisplatin (5 mg/kg, i.p.) and then every 24 h, and their behaviour was recorded for up to 72 h. Food and water consumption was measured every 24 h. The effect of anamorelin (10 µg) was also assessed following intracerebroventricular administration. Anamorelin and ipamorelin inhibited EFS-induced contractions of isolated ileum by 94.4 % (half-maximal inhibitory concentration [IC50]=14.0 µM) and 54.4 % (IC50=11.7 µM), respectively. Neither of compounds administered i.p. had any effect on cisplatin-induced acute or delayed emesis, but both inhibited associated cisplatin-induced weight loss on the last day of delayed phase (48-72 h) by approximately 24 %. Anamorelin (10 µg) administered intracerebroventricularly reduced cisplatin-induced acute emesis by 60 % but did not affect delayed emesis. It also improved food and water consumption by approximately 20 %-40 % during acute phase, but not delayed phase, and reduced associated cisplatin-induced weight loss during delayed phase by â¼23 %. In conclusion, anamorelin and ipamorelin administered i.p. had beneficial effects in alleviating cisplatin-induced weight loss during delayed phase, and these effects were seen when centrally administered anamorelin. Anamorelin inhibited cisplatin-induced acute emesis following intracerebroventricular but not intraperitoneal administration, suggesting that brain penetration is important for its anti-emetic mechanism of action.
Asunto(s)
Cisplatino , Hurones , Pérdida de Peso , Animales , Pérdida de Peso/efectos de los fármacos , Masculino , Ingestión de Alimentos/efectos de los fármacos , Receptores de Ghrelina/agonistas , Receptores de Ghrelina/antagonistas & inhibidores , Vómitos/inducido químicamente , Vómitos/prevención & control , Vómitos/tratamiento farmacológico , Antieméticos/farmacología , Oligopéptidos/farmacología , Íleon/efectos de los fármacos , Ingestión de Líquidos/efectos de los fármacos , Relación Dosis-Respuesta a DrogaRESUMEN
Ghrelin is an octanoylated peptide acting by the activation of the growth hormone secretagogue receptor, namely, GHS-R1a. The involvement of ghrelin in several physiological processes, including stimulation of food intake, gastric emptying, body energy balance, glucose homeostasis, reduction of insulin secretion, and lipogenesis validates the considerable interest in GHS-R1a as a promising target for the treatment of numerous disorders. Over the years, several GHS-R1a ligands have been identified and some of them have been extensively studied in clinical trials. The recently resolved structures of GHS-R1a bound to ghrelin or potent ligands have provided useful information for the design of new GHS-R1a drugs. This perspective is focused on the development of recent nonpeptide small molecules acting as GHS-R1a agonists, antagonists, and inverse agonists, bearing classical or new molecular scaffolds, as well as on radiolabeled GHS-R1a ligands developed for imaging. Moreover, the pharmacological effects of the most studied ligands have been discussed.
Asunto(s)
Diseño de Fármacos , Ghrelina/agonistas , Ghrelina/antagonistas & inhibidores , Receptores de Ghrelina/agonistas , Receptores de Ghrelina/antagonistas & inhibidores , Bibliotecas de Moléculas Pequeñas , Animales , Ghrelina/genética , Homeostasis , Humanos , Ligandos , Receptores de Ghrelina/genéticaRESUMEN
Growth hormone secretagogue receptor type 1A (GHSR-1A) is a functional receptor of orexigenic peptide ghrelin and is highly expressed in mesolimbic dopaminergic systems that regulate incentive value of artificial reward in substance abuse. Interestingly, GHSR-1A has also shown ligand-independent constitutive activity. Alcohol use disorder (AUD) is one of the growing concerns worldwide as it involves complex neuro-psycho-endocrinological interactions. Positive correlation of acylated ghrelin and alcohol-induced human brain response in the right and left ventral striatum are evident. In the last decade, the beneficial effects of ghrelin receptor (GHSR-1A) antagonism to suppress artificial reward circuitries and induce self-control for alcohol consumption have drawn significant attention from researchers. In this updated review, we summarize the available recent preclinical, clinical, and experimental data to discuss functional, molecular actions of central ghrelin-GHSR-1A signaling in different craving levels for alcohol as well as to promote "GHSR-1A antagonism" as one of the potential therapies in early abstinence.
Asunto(s)
Alcoholismo/metabolismo , Ghrelina/metabolismo , Receptores de Ghrelina/metabolismo , Consumo de Bebidas Alcohólicas , Alcoholismo/terapia , Animales , Encéfalo/metabolismo , Ansia , Modelos Animales de Enfermedad , Humanos , Ligandos , Receptores de Ghrelina/antagonistas & inhibidores , Transducción de Señal/fisiologíaRESUMEN
Much effort has been invested in the investigation of the structural basis of G protein-coupled receptors (GPCRs) activation. Inverse agonists, which can inhibit GPCRs with constitutive activity, are considered useful therapeutic agents, but the molecular mechanism of such ligands remains insufficiently understood. Here, we report a crystal structure of the ghrelin receptor bound to the inverse agonist PF-05190457 and a cryo-electron microscopy structure of the active ghrelin receptor-Go complex bound to the endogenous agonist ghrelin. Our structures reveal a distinct binding mode of the inverse agonist PF-05190457 in the ghrelin receptor, different from the binding mode of agonists and neutral antagonists. Combining the structural comparisons and cellular function assays, we find that a polar network and a notable hydrophobic cluster are required for receptor activation and constitutive activity. Together, our study provides insights into the detailed mechanism of ghrelin receptor binding to agonists and inverse agonists, and paves the way to design specific ligands targeting ghrelin receptors.
Asunto(s)
Receptores de Ghrelina/agonistas , Receptores de Ghrelina/antagonistas & inhibidores , Microscopía por Crioelectrón , Cristalografía por Rayos X , Ghrelina/agonistas , Ghrelina/genética , Humanos , Ligandos , Mutación , Unión Proteica , Receptores de Ghrelina/genéticaRESUMEN
AIMS: During illnesses caused by infectious diseases, a suite of brain-mediated responses called sickness syndrome occurs, triggering behavioral and physiological changes. This study investigated whether ghrelin modulates sickness syndrome induced by systemic administration of lipopolysaccharide (LPS). MAIN METHODS: Male Wistar rats were pretreated with vehicle or [D-lys3]-GHRP-6, a ghrelin receptor GHS-R1 antagonist (20 nmol, i.c.v), 30 min before injection of LPS (200 µg/kg, i.p.) or sterile saline. We investigated the behavioral effects in male rats after LPS administration by screening for depressive-like behavior, locomotor activity alterations, and corticosterone release. Changes in body temperature were measured using a biotelemetry probe preimplanted in the peritoneal cavity to evaluate the effect of ghrelin on the thermoregulatory response during immunological challenge. KEY FINDINGS: Pretreatment with [D-lys3]-GHRP-6 blunted most of the assessed parameters related to sickness syndrome, including social withdrawal, anhedonia, depressive-like behavior, and anorexia, reduced the activation of the HPA axis, but did not alter LPS-induced fever. SIGNIFICANCE: Our findings suggest that ghrelin centrally mediates the sickness behavior and activation of HPA, as a ghrelin receptor antagonist attenuates social withdrawal, anhedonia, depressive-like behavior, anorexia, and HPA activation in response to LPS.
Asunto(s)
Sistema Hipotálamo-Hipofisario/fisiología , Conducta de Enfermedad/efectos de los fármacos , Lipopolisacáridos/toxicidad , Trastornos Mentales/prevención & control , Oligopéptidos/farmacología , Receptores de Ghrelina/antagonistas & inhibidores , Animales , Temperatura Corporal , Sistema Hipotálamo-Hipofisario/efectos de los fármacos , Conducta de Enfermedad/fisiología , Locomoción , Masculino , Trastornos Mentales/inducido químicamente , Trastornos Mentales/metabolismo , Trastornos Mentales/patología , Ratas , Ratas WistarRESUMEN
Studies have shown the anti-seizure properties of the ghrelin hormone in different models of epilepsy. Nevertheless, the role of the endogenous ghrelin is unknown in the electrical kindling model of epilepsy. In this study, we evaluated the effect of the antagonism of the ghrelin receptors in the brain of fully kindled rats. Adult male Wistar rats weighing 300 g were used. Animals were stereotaxically implanted with two uni-polar electrodes in the skull surface and a tri-polar electrode in the basolateral amygdala, and a guide cannula in the left lateral ventricle. Animals underwent a rapid kindling protocol. After showing three consecutive stages of five seizures, the animals were considered fully kindled. D-Lys-3-GHRP-6 (1, 50, and 100 µg/rat) was injected intracerebroventricularly (i.c.v.) in the kindled animals. Each rat was considered as its control and received a single dose of D-Lys-3-GHRP-6. Seizure parameters including after discharge duration (ADD), seizure stage (SS), stage four latency (S4L), and stage five duration (S5D) were recorded. The paired t test indicated a significant increase in seizure induction. D-Lys-3-GHRP-6 (1 µg/rat; i.c.v.) prolonged ADD in the kindled rats, significantly. D-Lys-3-GHRP-6 (50 and 100 µg/rat; i.c.v.) induced spontaneous seizures, which led to status epilepticus in the kindled rats. The results indicate that the antagonism of the ghrelin functional receptors prolongs seizures and induces status epilepticus in the kindling model of epilepsy, and propose that the endogenous ghrelin signaling has crucial antiepileptic properties.
Asunto(s)
Epilepsia , Excitación Neurológica , Receptores de Ghrelina , Estado Epiléptico , Amígdala del Cerebelo , Animales , Masculino , Ratas , Ratas Wistar , Receptores de Ghrelina/antagonistas & inhibidoresRESUMEN
Islet transplantation is a type of cellular replacement therapy for severe diabetes that is limited by compromising effect on engrafted islets. Trials aiming to improve the function of transplanted islets have also been challenging. This study attempted to elucidate whether regulation of growth hormone secretagogue receptor-1a (GHS-R1a), one of the ghrelin receptors, improve the therapeutic effects of islet transplantation using [D-Lys3]-GHRP-6 (DLS), a specific GHS-R1a antagonist. The therapeutic effects of DLS were assessed in terms of the expression/production of endocrine genes/proteins, insulin-releasing function under glucose stimulation of mouse islets, and outcomes of syngeneic murine islet transplantation with systemic DLS administration. DLS treatment promoted insulin production and suppressed somatostatin production, suggesting that cancelation of the binding between ghrelin and GHS-R1a on ß or δ cells improved insulin expression. DLS also promoted the glucose-dependent insulin-releasing function of ß cells. However, the therapeutic effect of DLS in islet transplantation was fractional. In conclusion, the GHS-R1a antagonist showed preferable effects in improving the therapeutic outcomes of islet transplantation, including the promotion of insulin-releasing function.
Asunto(s)
Trasplante de Islotes Pancreáticos , Islotes Pancreáticos/efectos de los fármacos , Islotes Pancreáticos/metabolismo , Oligopéptidos/farmacología , Receptores de Ghrelina/antagonistas & inhibidores , Acilación , Animales , Técnica del Anticuerpo Fluorescente , Regulación de la Expresión Génica/efectos de los fármacos , Inmunohistoquímica , Células Secretoras de Insulina/efectos de los fármacos , Células Secretoras de Insulina/metabolismo , Trasplante de Islotes Pancreáticos/efectos adversos , Trasplante de Islotes Pancreáticos/métodos , Ratones , Oligopéptidos/uso terapéutico , Receptores de Ghrelina/genética , Receptores de Ghrelina/metabolismo , Células Secretoras de Somatostatina/efectos de los fármacos , Células Secretoras de Somatostatina/metabolismoRESUMEN
Liver-expressed antimicrobial peptide 2 (LEAP-2), originally described as an antimicrobial peptide, has recently been recognized as an endogenous blocker of growth hormone secretagogue receptor 1a (GHS-R1a). GHS-R1a, also known as ghrelin receptor, is a G protein-coupled receptor (GPCR) widely distributed on the hypothalamus and pituitary gland where it exerts its major functions of regulating appetite and growth hormone (GH) secretion. The activity of GHS-R1a is controlled by two counter-regulatory endogenous ligands: Ghrelin (activation) and LEAP-2 (inhibition). Ghrelin activates GHS-R1a on the neuropeptide Y/Agouti-related protein (NPY/AgRP) neurons at the arcuate nucleus (ARC) to promote appetite, and on the pituitary somatotrophs to stimulate GH release. On the flip side, LEAP-2, acts both as an endogenous competitive antagonist of ghrelin and an inverse agonist of constitutive GHS-R1a activity. Such a biological property of LEAP-2 vigorously blocks ghrelin's effects on food intake and hormonal secretion. In circulation, LEAP-2 displays an inverse pattern as to ghrelin; it increases with food intake and obesity (positive energy balance), whereas decreases upon fasting and weight loss (negative energy balance). Thus, the LEAP-2/ghrelin molar ratio fluctuates in response to energy status and modulation of this ratio conversely influences energy intake. Inhibiting ghrelin's activity has shown beneficial effects on obesity in preclinical experiments, which sheds light on LEAP-2's anti-obesity potential. In this review, we will analyze LEAP-2's effects from a metabolic point of view with a focus on metabolic hormones (e.g., ghrelin, GH, and insulin), and discuss LEAP-2's potential as a promising therapeutic target for obesity.
Asunto(s)
Péptidos Catiónicos Antimicrobianos/farmacología , Péptidos Antimicrobianos/farmacología , Proteínas Sanguíneas/farmacología , Metabolismo Energético , Ghrelina/antagonistas & inhibidores , Obesidad/tratamiento farmacológico , Receptores de Ghrelina/antagonistas & inhibidores , Pérdida de Peso , Humanos , Obesidad/metabolismo , Obesidad/patologíaRESUMEN
G (1-5)-NH2, G (1-7)-NH2, and G (1-9) are the active fragments of ghrelin. The aim of this study was to investigate the antinociceptive effects, their ability to cross the blood-brain barrier, and the receptor mechanism(s) of these fragments using the tail withdrawal test in male Kunming mice. The antinociceptive effects of these fragments (2, 6, 20, and 60 nmol/mouse) were tested at 5, 10, 20, 30, 40, 50, and 60 min after intravenous (i.v.) injection. These fragments induced dose- and time-related antinociceptive effects relative to saline. Using the near infrared fluorescence imaging experiments, our results showed that these fragments could cross the brain-blood barrier and enter the brain. The antinociceptive effects of these fragments were completely antagonized by naloxone (intracerebroventricular, i.c.v.); however, naloxone methiodide (intraperitoneal, i.p.), which is the peripheral restricted opioid receptor antagonist, did not antagonize these antinociceptive effects. Furthermore, the GHS-R1α antagonist [D-Lys3]-GHRP-6 (i.c.v.) completely antagonized these antinociceptive effects, too. These results suggested that these fragments induced antinociceptive effects through central opioid receptors and GHS-R1α. In conclusion, our studies indicated that these active fragments of ghrelin could cross the brain-blood barrier and enter the brain and induce antinociceptive effects through central opioid receptors and GHS-R1α after intravenous injection.
Asunto(s)
Dolor Agudo/tratamiento farmacológico , Analgésicos/farmacología , Barrera Hematoencefálica/metabolismo , Encéfalo/metabolismo , Ghrelina/administración & dosificación , Ghrelina/farmacocinética , Calor/efectos adversos , Dolor Agudo/etiología , Dolor Agudo/metabolismo , Dolor Agudo/patología , Animales , Animales no Consanguíneos , Barrera Hematoencefálica/efectos de los fármacos , Encéfalo/efectos de los fármacos , Ghrelina/farmacología , Masculino , Ratones , Antagonistas de Narcóticos/farmacología , Receptores de Ghrelina/antagonistas & inhibidores , Receptores de Ghrelina/metabolismo , Receptores Opioides/química , Receptores Opioides/metabolismoRESUMEN
Recent studies have demonstrated that liver-expressed antimicrobial peptide 2 (LEAP2) antagonizes the ghrelin receptor GHSR1a in mammals. However, its antagonistic function in lower vertebrates has not yet been tested. LEAP2 orthologs have been identified from a variety of fish species; however, previous studies all focused on their antimicrobial activity. To test whether LEAP2 functions as a GHSR1a antagonist in the lowest vertebrates, we studied the antagonism of a fish LEAP2 from Latimeria chalumnae, an extant coelacanth that is one of the closest living fish relatives of tetrapods. Using binding assays, we demonstrated that the coelacanth LEAP2 and ghrelin bound to the coelacanth GHSR1a with IC50 values in the nanomolar range. Using activation assays, we demonstrated that the coelacanth ghrelin activated the coelacanth GHSR1a with an EC50 value in the nanomolar range, and this activation effect was efficiently antagonized by a nanomolar range of the coelacanth LEAP2. In addition, we also showed that the human LEAP2 and ghrelin were as effective as their coelacanth orthologs towards the coelacanth GHSR1a; however, the coelacanth peptides had moderately lower activity towards the human GHSR1a. Thus, LEAP2 serves as an endogenous antagonist of the ghrelin receptor GHSR1a in coelacanth and the ghrelin-LEAP2-GHSR1a system has evolved slowly since its emergence in ancient fish.
Asunto(s)
Péptidos Catiónicos Antimicrobianos , Proteínas Sanguíneas , Evolución Molecular , Proteínas de Peces , Peces , Receptores de Ghrelina , Animales , Péptidos Catiónicos Antimicrobianos/genética , Péptidos Catiónicos Antimicrobianos/metabolismo , Proteínas Sanguíneas/genética , Proteínas Sanguíneas/metabolismo , Proteínas de Peces/genética , Proteínas de Peces/metabolismo , Peces/genética , Peces/metabolismo , Células HEK293 , Humanos , Receptores de Ghrelina/antagonistas & inhibidores , Receptores de Ghrelina/genética , Receptores de Ghrelina/metabolismoRESUMEN
Cannabis/cannabinoids are widely used for recreational and therapy purposes, but their risks are largely disregarded. However, cannabinoid-associated use disorders and dependence are alarmingly increasing and an effective treatment is lacking. Recently, the growth hormone secretagogue receptor (GHSR1A) antagonism was proposed as a promising mechanism for drug addiction therapy. However, the role of GHS-R1A and its endogenous ligand ghrelin in cannabinoid abuse remains unclear. Therefore, the aim of our study was to investigate whether the GHS-R1A antagonist JMV2959 could reduce the tetrahydrocannabinol (THC)-induced conditioned place preference (CPP) and behavioral stimulation, the WIN55,212-2 intravenous self-administration (IVSA), and the tendency to relapse. Following an ongoing WIN55,212-2 self-administration, JMV2959 3 mg/kg was administered intraperitoneally 20 min before three consequent daily 120-min IVSA sessions under a fixed ratio FR1, which significantly reduced the number of the active lever-pressing, the number of infusions, and the cannabinoid intake. Pretreatment with JMV2959 suggested reduction of the WIN55,212-2-seeking/relapse-like behavior tested in rats on the twelfth day of the forced abstinence period. On the contrary, pretreatment with ghrelin significantly increased the cannabinoid IVSA as well as enhanced the relapse-like behavior. Co-administration of ghrelin with JMV2959 abolished/reduced the significant efficacy of the GHS-R1A antagonist in the cannabinoid IVSA. Pretreatment with JMV2959 significantly and dose-dependently reduced the manifestation of THC-induced CPP. The THC-CPP development was reduced after the simultaneous administration of JMV2959 with THC during conditioning. JMV2959 also significantly reduced the THC-induced behavioral stimulation in the LABORAS cage. Our findings suggest that GHS-R1A importantly participates in the rewarding/reinforcing effects of cannabinoids.
Asunto(s)
Conducta Animal/efectos de los fármacos , Cannabinoides/farmacología , Condicionamiento Operante/efectos de los fármacos , Condicionamiento Psicológico/efectos de los fármacos , Glicina/análogos & derivados , Receptores de Ghrelina/antagonistas & inhibidores , Triazoles/farmacología , Administración Intravenosa , Animales , Cannabinoides/administración & dosificación , Glicina/farmacología , Masculino , Ratas , Ratas Wistar , Refuerzo en Psicología , AutoadministraciónRESUMEN
Under severe calorie restriction (CR), the ghrelin-growth hormone axis in mice is involved in the maintenance of plasma glucose levels. Ghrelin, a stomach-derived acylated peptide, is up-regulated by the sympathetic nerve in the negative energy status. Central corticotrophin-releasing factor receptor (CRF-R) signalling stimulates the sympathetic tone. The present study aimed to examine the effect of central CRF-R signalling on the maintenance of plasma glucose concentrations in severe calorie-restricted mice with the involvement of ghrelin. Intracerebroventricular injections of urocorin-1 and urocorin-2, which are natural ligands for CRF-R1 and CRF-R2, elevated plasma ghrelin concentrations and ghrelin elevation with an i.c.v. injection of urocorin-1 was cancelled by atenolol (ß1 adrenergic receptor antagonist) administration. We then established a mice model of 60% CR and found that the administration of [d-Lys3]-GHRP-6 (a ghrelin receptor antagonist) in mice under 60% CR reduced the plasma glucose concentration more compared to the vehicle mice. Similarly, the atenolol injection in mice under 60% CR significantly reduced the plasma glucose concentration, which was rescued by the co-administration of ghrelin. An i.c.v. injection of the alpha helical CRH, a non-selective corticotrophin-releasing factor receptor antagonist, in mice under 60% CR significantly reduced the plasma glucose concentration, although the co-administration of α-helical CRH with ghrelin maintained plasma glucose levels. These results suggest that central CRF-R signalling is involved in the maintenance of plasma glucose levels in mice under severe CR via the sympathetic-ghrelin pathway.
Asunto(s)
Glucemia/metabolismo , Restricción Calórica , Ghrelina/fisiología , Receptores de Hormona Liberadora de Corticotropina/fisiología , Transducción de Señal/fisiología , Agonistas Adrenérgicos beta/farmacología , Animales , Atenolol/farmacología , Hormona Liberadora de Corticotropina/farmacología , Ghrelina/metabolismo , Inyecciones Intraventriculares , Masculino , Ratones , Ratones Endogámicos C57BL , Receptores de Hormona Liberadora de Corticotropina/antagonistas & inhibidores , Receptores de Hormona Liberadora de Corticotropina/metabolismo , Receptores de Ghrelina/antagonistas & inhibidores , Transducción de Señal/efectos de los fármacos , Sistema Nervioso Simpático/efectos de los fármacosRESUMEN
The orexigenic peptide ghrelin increases the release of dopamine in the nucleus accumbens (NAc) shell via central ghrelin receptors, especially those located in the ventral tegmental area (VTA). The activity of the VTA dopamine neurons projecting to NAc shell, involves somatodendritic dopamine release within the VTA. However, the effects of ghrelin on the concomitant dopamine release in the VTA and NAc shell is unknown. It is further unknown whether addictive drugs, such as alcohol and amphetamine, enhance the dopamine levels in both these areas via ghrelin receptor dependent mechanisms. Thus, the effects of a ghrelin receptor antagonist, JMV2959, on the ability of i) central ghrelin ii) systemic alcohol or iii) systemic amphetamine to increase the dopamine release in the VTA and in the NAc shell in rats by using in vivo microdialysis was explored. We showed that systemic administration of JMV2959 blocks the ability of central ghrelin to increases dopamine release in the VTA and the NAc shell, and reduces the alcohol- and amphetamine-induced dopamine release in both these areas. Locomotor activity studies was then conducted in an attempt to correlate the ghrelin-induced dopamine release in the VTA to a behavioural outcome. These revealed that local infusion of a dopamine D1 receptor antagonist into the VTA blocks the ability of central ghrelin to cause a locomotor stimulation in mice. Collectively, this study adds to the growing body of evidence indicating that ghrelin signalling modulates the ability of ghrelin, and addictive drugs, to activate the mesoaccumbal dopamine pathway.
Asunto(s)
Anfetamina/farmacología , Dopamina/metabolismo , Etanol/farmacología , Ghrelina/farmacología , Glicina/análogos & derivados , Antagonistas de Hormonas/farmacología , Núcleo Accumbens/efectos de los fármacos , Receptores de Ghrelina/antagonistas & inhibidores , Triazoles/farmacología , Área Tegmental Ventral/efectos de los fármacos , Animales , Conducta Animal/efectos de los fármacos , Glicina/farmacología , Locomoción/efectos de los fármacos , Masculino , Ratones , Núcleo Accumbens/metabolismo , Ratas Wistar , Receptores de Dopamina D1/metabolismo , Receptores de Ghrelina/metabolismo , Recompensa , Área Tegmental Ventral/metabolismoRESUMEN
Diabetic gastroparesis is defined as delayed gastric emptying without mechanical obstruction in the setting of diabetes. Symptoms range from mild bloating to severe vomiting episodes and can result in frequent hospitalizations and poor quality of life. It is suspected that diabetic gastroparesis is underdiagnosed due to its similar presentation to other conditions such as gastroesophageal reflux disease. The pathogenesis of diabetic gastroparesis remains unclear, but proposed mechanisms include vagal dysfunction, hyperglycemia, interstitial cells of Cajal network disturbances, loss of neural nitric oxide synthase expression in the myenteric plexus, and oxidative stress. Current management for diabetic gastroparesis focuses on dietary and lifestyle changes as well as improved glycemic control. Limited options for medical therapies are available that include prokinetic and antiemetic medications. Metoclopramide is the only FDA-approved medication for the treatment of gastroparesis. Metoclopramide improves symptoms of gastroparesis although extended treatment presents challenges such as decreased efficacy over time and increased risks for adverse events. We summarize the current knowledge of the pathophysiology of diabetic gastroparesis and review current and investigational treatments for diabetes gastroparesis.
Asunto(s)
Neuropatías Diabéticas , Gastroparesia , Receptores de Ghrelina/antagonistas & inhibidores , Diabetes Mellitus , Neuropatías Diabéticas/complicaciones , Vaciamiento Gástrico , Gastroparesia/tratamiento farmacológico , Gastroparesia/etiología , Humanos , Metoclopramida/uso terapéutico , Calidad de VidaRESUMEN
The endocannabinoidome (expanded endocannabinoid system, eCBome)-gut microbiome (mBIome) axis plays a fundamental role in the control of energy intake and processing. The liver-expressed antimicrobial peptide 2 (LEAP2) is a recently identified molecule acting as an antagonist of the ghrelin receptor and hence a potential effector of energy metabolism, also at the level of the gastrointestinal system. Here we investigated the role of the eCBome-gut mBIome axis in the control of the expression of LEAP2 in the liver and, particularly, the intestine. We confirm that the small intestine is a strong contributor to the circulating levels of LEAP2 in mice, and show that: (1) intestinal Leap2 expression is profoundly altered in the liver and small intestine of 13 week-old germ-free (GF) male mice, which also exhibit strong alterations in eCBome signaling; fecal microbiota transfer (FMT) from conventionally raised to GF mice completely restored normal Leap2 expression after 7 days from this procedure; in 13 week-old female GF mice no significant change was observed; (2) Leap2 expression in organoids prepared from the mouse duodenum is elevated by the endocannabinoid noladin ether, whereas in human Caco-2/15 epithelial intestinal cells it is elevated by PPARγ activation by rosiglitazone; (3) Leap2 expression is elevated in the ileum of mice with either high-fat diet-or genetic leptin signaling deficiency-(i.e., ob/ob and db/db mice) induced obesity. Based on these results, we propose that LEAP2 originating from the small intestine may represent a player in eCBome- and/or gut mBIome-mediated effects on food intake and energy metabolism.
Asunto(s)
Péptidos Antimicrobianos/genética , Péptidos Antimicrobianos/metabolismo , Endocannabinoides/genética , Microbioma Gastrointestinal/genética , Receptores de Ghrelina/antagonistas & inhibidores , Animales , Células CACO-2 , Dieta Alta en Grasa , Femenino , Glicéridos/metabolismo , Humanos , Intestinos , Hígado , Masculino , Ratones , Ratones Endogámicos C57BL , Modelos Animales , Obesidad , ARN Mensajero/genética , Rosiglitazona/metabolismo , Transducción de Señal , Espectrometría de Masas en TándemRESUMEN
BACKGROUND: Dopamine receptor 2 (DRD2) and ghrelin receptor (GHSR1a) agonists both stimulate defecation by actions at the lumbosacral defecation center. Dopamine is in nerve terminals surrounding autonomic neurons of the defecation center, whereas ghrelin is not present in the spinal cord. Dopamine at D2 receptors generally inhibits neurons, but at the defecation center, its effect is excitatory. METHODS: In vivo recording of defecation and colorectal propulsion was used to investigate interaction between DRD2 and GHSR1a. Localization studies were used to determine sites of receptor expression in rat and human spinal cord. KEY RESULTS: Dopamine, and the DRD2 agonist, quinpirole, directly applied to the lumbosacral cord, caused defecation. The effect of intrathecal dopamine was inhibited by the GHSR1a antagonist, YIL781, given systemically, but YIL781 was not an antagonist at DRD2. The DRD2 agonist, pramipexole, administered systemically caused colorectal propulsion that was prevented when the pelvic nerves were cut. Drd2 and Ghsr were expressed together in autonomic preganglionic neurons at the level of the defecation centers in rat and human. Behaviorally induced defecation (caused by water avoidance stress) was reduced by the DRD2 antagonist, sulpiride. We had previously shown it is reduced by YIL781. CONCLUSIONS AND INFERENCES: Our observations imply that dopamine is a transmitter of the defecation pathways whose actions are exerted through interacting dopamine (D2) and ghrelin receptors on lumbosacral autonomic neurons that project to the colorectum. The results explain the excitation by dopamine agonists and the conservation of GHSR1a in the absence of ghrelin.
Asunto(s)
Defecación/fisiología , Motilidad Gastrointestinal/fisiología , Receptores de Dopamina D2/metabolismo , Receptores de Ghrelina/metabolismo , Médula Espinal/metabolismo , Animales , Defecación/efectos de los fármacos , Dopamina/farmacología , Agonistas de Dopamina/farmacología , Antagonistas de Dopamina/farmacología , Motilidad Gastrointestinal/efectos de los fármacos , Ghrelina/metabolismo , Humanos , Piperidinas/farmacología , Pramipexol/farmacología , Quinazolinonas/farmacología , Quinpirol/farmacología , Ratas , Receptores de Ghrelina/antagonistas & inhibidores , Médula Espinal/efectos de los fármacos , Médula Espinal/fisiología , Asta Lateral de la Médula Espinal/metabolismo , Sulpirida/farmacologíaRESUMEN
Ghrelin is a peptide hormone whose effects are mediated by the growth hormone secretagogue receptor subtype 1a (GHS-R1a), mainly expressed in the brain but also in kidneys. The hypothesis herein raised is that GHS-R1a would be player in the renal contribution to the neurogenic hypertension pathophysiology. To investigate GHS-R1a role on renal function and hemodynamics, we used Wistar (WT) and spontaneously hypertensive rats (SHR). First, we assessed the effect of systemically injected vehicle, ghrelin, GHS-R1a antagonist PF04628935, ghrelin plus PF04628935 or GHS-R1a synthetic agonist MK-677 in WT and SHR rats housed in metabolic cages (24 h). Blood and urine samples were also analyzed. Then, we assessed the GHS-R1a contribution to the control of renal vasomotion and hemodynamics in WT and SHR. Finally, we assessed the GHS-R1a levels in brain areas, aorta, renal artery, renal cortex and medulla of WT and SHR rats using western blot. We found that ghrelin and MK-677 changed osmolarity parameters of SHR, in a GHS-R1a-dependent manner. GHS-R1a antagonism reduced the urinary Na+ and K+ and creatinine clearance in WT but not in SHR. Ghrelin reduced arterial pressure and increased renal artery conductance in SHR. GHS-R1a protein levels were decreased in the kidney and brain areas of SHR when compared to WT. Therefore, GHS-R1a role in the control of renal function and hemodynamics during neurogenic hypertension seem to be different, and this may be related to brain and kidney GHS-R1a downregulation.
Asunto(s)
Encéfalo/metabolismo , Ghrelina/administración & dosificación , Hipertensión/fisiopatología , Imidazoles/administración & dosificación , Indoles/administración & dosificación , Riñón/metabolismo , Receptores de Ghrelina/metabolismo , Compuestos de Espiro/administración & dosificación , Animales , Encéfalo/efectos de los fármacos , Modelos Animales de Enfermedad , Regulación hacia Abajo , Ghrelina/farmacología , Hemodinámica , Hipertensión/metabolismo , Hipertensión/orina , Imidazoles/farmacología , Indoles/farmacología , Riñón/efectos de los fármacos , Riñón/fisiopatología , Pruebas de Función Renal , Masculino , Potasio/orina , Ratas , Ratas Endogámicas SHR , Ratas Wistar , Receptores de Ghrelina/antagonistas & inhibidores , Sodio/orina , Compuestos de Espiro/farmacologíaRESUMEN
Ghrelin is a gastric peptide hormone with important physiological functions. The unique feature of ghrelin is its Serine 3 acyl-modification, which is essential for ghrelin's activity. However, it remains to be elucidated why the acyl-modification of ghrelin is necessary for activity. To address these questions, we solved the crystal structure of the ghrelin receptor bound to antagonist. The ligand-binding pocket of the ghrelin receptor is bifurcated by a salt bridge between E124 and R283. A striking feature of the ligand-binding pocket of the ghrelin receptor is a wide gap (crevasse) between the TM6 and TM7 bundles that is rich in hydrophobic amino acids, including a cluster of phenylalanine residues. Mutagenesis analyses suggest that the interaction between the gap structure and the acyl acid moiety of ghrelin may participate in transforming the ghrelin receptor into an active conformation.
Asunto(s)
Ghrelina/metabolismo , Fenilalanina/metabolismo , Receptores de Ghrelina/metabolismo , Animales , Sitios de Unión/genética , Células CHO , Cricetinae , Cricetulus , Cristalografía por Rayos X , Ghrelina/química , Ghrelina/genética , Células HEK293 , Humanos , Ligandos , Ratones Endogámicos MRL lpr , Mutagénesis Sitio-Dirigida , Fenilalanina/química , Fenilalanina/genética , Unión Proteica , Conformación Proteica , Receptores de Ghrelina/antagonistas & inhibidores , Receptores de Ghrelina/genética , Células Sf9 , SpodopteraRESUMEN
Brain ghrelin plays a role in gastrointestinal functions. Among them, ghrelin acts centrally to stimulate gastrointestinal motility and induce visceral antinociception. Intestinal barrier function, one of important gastrointestinal functions, is also controlled by the central nervous system. Little is, however, known about a role of central ghrelin in regulation of intestinal permeability. The present study was performed to clarify whether brain ghrelin is also involved in regulation of intestinal barrier function and its mechanism. Colonic permeability was estimated in vivo by quantifying the absorbed Evans blue in colonic tissue in rats. Intracisternal injection of ghrelin dose-dependently abolished increased colonic permeability in response to LPS while intraperitoneal injection of ghrelin at the same dose or intracisternal injection of des-acyl-ghrelin failed to block it. Carbachol potently attenuated LPS-induced intestinal hyperpermeability, and atropine or bilateral subdiaphragmatic vagotomy prevented the improvement of intestinal hyperpermeability by central ghrelin. Intracisternal (D-Lys3)-GHRP-6, a selective ghrelin receptor antagonist, significantly blocked improvement of intestinal barrier function by intravenously administered 2-deoxy-d-glucose, central vagal stimulant. Intracisternal injection of orexin 1 receptor antagonist, SB-334867 blocked intracisternal ghrelin-induced improvement of colonic hyperpermeability. These results suggest that exogenously administered or endogenously released ghrelin acts centrally to improve a disturbed intestinal barrier function through orexinergic signaling and the vagal cholinergic pathway. Central ghrelin may be involved in the pathophysiology and be a novel therapeutic option in not only gastrointestinal diseases such as irritable bowel syndrome but also non-gastrointestinal diseases associated with the altered intestinal permeability.