The effect of ghrelin on bursa and cecal tonsils of chickens infected with an attenuated virus strain of infectious bursal disease virus.

Infectious bursal disease (IBD) significantly affects the poultry industry, causing substantial economic losses. This study aimed to investigate the effects of ghrelin on chicks infected with an attenuated virus strain of IBDV (aIBDV). Chicks were divided into 3 groups: a control group (group I), an aIBDV infection group (group II), and a ghrelin + aIBDV infection group (group III). Mice in groups II and III were fed until they reached 19 d of age and then inoculated with aIBDV to establish a subclinical infection model. Group III received an intraperitoneal injection of 0.5 nmol/100 g ghrelin from d 17 to 23. The present study utilized paraffin sectioning, H&E staining, and immunohistochemical staining to examine the effects of ghrelin on the bursa of fabricius and cecum tonsils in aIBDV-infected chicks. The results indicated that at 3 d postinfection (dpi), the average body weight of group III was significantly greater than that of group II (P < 0.05). At 3 and 7 dpi, the proportion of large lymphoid follicles in the bursa of fabricius in group III was notably greater than that in group II (P < 0.05). aIBDV infection resulted in bleeding, edema, and fibrosis in the cecal mucosal layer of chicks, but ghrelin administration mitigated these pathological changes. At 3 and 7 dpi, the thickness of the lamina propria in the cecal tonsils of group III was significantly lower than that in the cecal tonsils of group II (P < 0.05). Additionally, the percentage of large lymphoid follicles in the cecal tonsils of group III was significantly greater than that in group II at 3 and 5 dpi (P < 0.05). There were significantly fewer macrophages in the cecal tonsils of group III than in those of group II at 1, 3, and 5 dpi (P < 0.05). In conclusion, ghrelin supplementation improved performance and mitigated bursal atrophy in aIBDV-infected chicks. It also reduced histological lesions and immune responses in the cecum tonsil. Notably, the reduction in macrophages in the cecum tonsil following ghrelin administration may decrease the risk of aIBDV spread.

Ghrelin decreases sensitivity to negative feedback and increases prediction-error related caudate activity in humans, a randomized controlled trial.

The stomach-derived hormone ghrelin plays not only a role in feeding, starvation, and survival, but it has been suggested to also be involved in the stress response, in neuropsychiatric conditions, and in alcohol and drug use disorders. Mechanisms related to reward processing might mediate ghrelin's broader effects on complex behaviors, as indicated by animal studies and mostly correlative human studies. Here, using a within-subject double-blind placebo-controlled design with intravenous ghrelin infusion in healthy volunteers (n = 30), we tested whether ghrelin alters sensitivity to reward and punishment in a reward learning task. Parameters were derived from a computational model of participants' task behavior. The reversal learning task with monetary rewards was performed during functional brain imaging to investigate ghrelin effects on brain signals related to reward prediction errors. Compared to placebo, ghrelin decreased punishment sensitivity (t = -2.448, p = 0.021), while reward sensitivity was unaltered (t = 0.8, p = 0.43). We furthermore found increased prediction-error related activity in the dorsal striatum during ghrelin administration (region of interest analysis: t-values ≥ 4.21, p-values ≤ 0.044). Our results support a role for ghrelin in reward processing that extends beyond food-related rewards. Reduced sensitivity to negative outcomes and increased processing of prediction errors may be beneficial for food foraging when hungry but could also relate to increased risk taking and impulsivity in the broader context of addictive behaviors.

[A study of the anti-fibrotic effect of ghrelin on mice with nonalcoholic steatohepatitis].

Objective: To study the anti-fibrotic effect of ghrelin on high-fat diet-induced non-alcoholic steatohepatitis (NASH) in mice. Methods: 24 male C57BL/6 mice were randomly divided into a normal diet group, a normal diet + ghrelin group, a high-fat diet group, and the high-fat diet + ghrelin group. The HFD and HFD+ghrelin groups were fed high-fat diet for 16 weeks to induce non-alcoholic steatohepatitis. Among them, the NCD+ghrelin group and HFD+ghrelin group were continuously given ghrelin intervention (11nmol·kg(-1)·d(-1)) for 2 weeks after feeding for 14 weeks. 16 mice were euthanized on weekends. The plasma levels of alanine aminotransferase (ALT) and hyaluronic acid (HA) were measured in mice. The content of hydroxyproline (Hyp) was determined in liver tissue. RT-qPCR was used to detect the mRNA expression levels of transforming growth factor ß1 (TGF-ß1) and collagen types I, III, and IV in liver tissue. A Western blot was used to detect the expression level of the α-smooth muscle actin (α-SMA) protein in liver tissue. HE staining was used to observe the morphological changes in liver tissue. VG staining was used to observe the fibrotic condition in liver tissue. Results: Compared with the NCD group, plasma ALT (266.80±146.80)U/L, HA (219.00±39.47) ng/ml levels, Hyp content (0.35±0.05)µg/mg prot (P < 0.05), mRNA expression levels of transforming growth factor ß1 (TGF-ß1) and collagen types I, III, IV (P < 0.05), and the expression level of α-SMA protein in the HFD group were significantly increased (P < 0.05), with congestion in the hepatic central lobular veins, hepatocytes swelling, and deposition of a large amount of collagen fibers in liver tissue. Compared with the HFD group, plasma ALT (57.17±20.88)U/L, HA (75.68±8.40)µg/mg levels, Hyp content (0.19±0.07)µg/mg prot, mRNA expression levels of transforming growth factor ß1 (TGF-ß1) and collagen types I, III, IV (P < 0.05), and the expression level of α-SMA protein in the HFD+ghrelin mice group was significantly reduced (P < 0.05), with only mild sinusoidal congestion in the liver tissue but significant improvement and reduction in liver injury and collagen fiber deposition. Conclusion: Ghrelin has a significant improvement effect on liver fibrosis in NASH mice.

El consumo regular de un caldo funcional enriquecido con fosfofructooligosacáridos aumenta los niveles de las hormonas relacionadas con la saciedad en las personas sanas. Ensayo clínico aleatorizado y controlado / Regular consumption of a functional broth enriched with phospho-fructooligosaccharides increases the levels of hormones related to satiety in healthy people. A randomized, controlled clinical trial

Introducción: el exceso de peso representa un problema de salud pública debido a los factores de riesgo asociados. El sedentarismo, una alimentación inadecuada o una disminución de la sensación de saciedad son algunas de sus causas. Objetivos: evaluar las propiedades saciantes del consumo de un caldo ibérico funcional enriquecido con fosfofructooligosacáridos (FOS) en personas sanas a través de la concentración plasmática de las hormonas involucradas en el apetito. Material y métodos: ensayo clínico nutricional, agudo, cruzado, aleatorizado, doble ciego y controlado, llevado a cabo en 18 participantes aleatorizados en dos secuencias de tratamiento (caldo funcional (CF) compuesto de 5,6 g de FOS/100 g y caldo de control (CC), con 0,4 g de maltodextrina/100 g) con 14 días de lavado entre ellas. Se midieron parámetros relacionados con la saciedad (glucosa, insulina, leptina, ghrelina, GLP-1, PYY) y escalas analógicas visuales (EAV). Resultados: el porcentaje de grasa corporal disminuyó en los que tomaron el CF (-0,15 ± 0,32 vs. 0,09 ± 0,52) (p < 0,05). La concentración de leptina fue superior con el CF (p < 0,001), mostrándose dicho aumento en los tiempos -30 (p < 0,001), 0 (p < 0,001), 30 (p = 0,026) y 120 (p = 0,049) con respecto al CC. Las áreas bajo la curva (AUC) de GLP-1 (p = 0,0033) y PYY (p = 0,022) fueron superiores con el CF en comparación con el CC. Conclusión: el consumo de un caldo ibérico enriquecido con FOS mejora la concentración plasmática de las hormonas involucradas en el control de la saciedad y reduce la cantidad de grasa corporal. Dichos resultados podrían tener efectos beneficiosos para la prevención y el tratamiento del exceso de peso corporal (AU)

Introduction: excess weight represents a public health problem due to its associated risk factors. A sedentary lifestyle, an inadequate diet or a decrease in the feeling of satiety are some of the causes. Objetives: to evaluate the satiating properties of the consumption of a functional Iberian broth enriched with phospho-fructooligosaccharides (FOS) in healthy people through the plasma concentration of hormones involved in appetite. Material and methods: acute, crossover, randomized, double-blind and controlled nutritional clinical trial carried out in 18 randomized participants in two treatment sequences (functional broth (CF), composed of 5.6 g POS/100 g and control broth (CC), with 0.4 g of maltodextrin/100 g) with 14 days of washing in between. Satiety-related parameters (glucose, insulin, leptin, ghrelin, GLP-1, PYY) and visual analog scales (VAS) were measured. Results: the percentage of body fat decreased in those who took the CF (-0.15 ± 0.32 vs 0.09 ± 0.52) (p < 0.05). Leptin concentration was higher with CF (p < 0.001), which was shown at time points -30 (p < 0.001), 0 (p < 0.001), 30 (p = 0.026) and 120 (p = 0.049) when compared to CC. The areas under the curve (AUC) for GLP-1 (p = 0.0033) and PYY (p = 0.022) were higher for CF as compared to CC. Conclusion: consumption of an Iberian broth enriched with POS improves the plasma concentration of hormones involved in the control of satiety, and reduces the amount of body fat. This result could have beneficial effects for the prevention and treatment of overweight (AU)

Ghrelin signaling in dCA1 suppresses neuronal excitability and impairs memory acquisition via PI3K/Akt/GSK-3ß cascades.

Ghrelin is a circulating peptide hormone that promotes feeding and regulates metabolism in humans and rodents. The action of ghrelin is mediated by the growth hormone secretagogue receptor type 1a (GHSR-1a) that is widely distributed in the brain, including the hippocampus. Studies have demonstrated the critical role of hippocampal ghrelin/GHS-R1a signaling in synaptic physiology and memory. However, those findings are controversial, and the mechanism underlying ghrelin modulation of learning and memory is uncertain. Here, we report that micro-infusion of ghrelin in the CA1 region of the dorsal hippocampus during training specifically impairs memory acquisition. The activation of GHS-R1a and the subsequent PI3K/Akt/GSK3ß signaling cascades are involved in this process. Moreover, we report that bath application of ghrelin suppresses the intrinsic excitability of dCA1 pyramidal neurons through activating GHS-R1a, and PI3K inhibitor LY294002 blocks ghrelin's effect. However, LY294002 fails to rescue ghrelin-induced LTP impairment. Our findings support an adverse effect of ghrelin-dependent activation of GHS-R1a on memory acquisition, and suggest that PI3K/Akt/GSK3ß signaling-dependent repression of neuronal intrinsic excitability is an important novel mechanism underlying memory inhibition of ghrelin in the hippocampus.

Differential effects of intra-ventral tegmental area ghrelin and glucagon-like peptide-1 on the stimulatory action of D-amphetamine and cocaine-induced ethanol intake in male Sprague Dawley rats.

In order to further elucidate the role of mesolimbic peptides in the expression of ethanol reward, the present study investigated the effects of ghrelin and glucagon-like peptide-1 (GLP-1) on ethanol intake, in addition to ethanol intake stimulated by systemic d-amphetamine or cocaine treatment. While a number of studies suggest that ghrelin plays an important role in mesolimbic reward, emerging data now indicate that GLP-1 receptor mechanisms inhibit reward signaling, possibly by directly or indirectly inhibiting ghrelinergic activity within the mesolimbic system. In the present study all rats were initially habituated to a 6% ethanol solution. We then demonstrated that intraperitoneal injections of d-amphetamine and cocaine increased ethanol intake compared to the vehicle condition. In subsequent testing we examined the effects of ventral tegmental area (VTA) ghrelin or vehicle paired with a fixed dose of d-amphetamine or vehicle. In separate rats we then investigated the impact of the GLP-1 agonist exendin-4 (Ex-4), injected into the VTA, on ethanol intake alone, or when Ex-4 was co-administered with d-amphetamine or cocaine. Our results indicated that VTA ghrelin significantly increased ethanol intake, and most importantly, potentiated the effect of d-amphetamine and cocaine on ethanol consumption. Conversely, VTA Ex-4 inhibited ethanol intake and antagonized the stimulatory effect of d-amphetamine and cocaine on ethanol consumption. In a final study we further demonstrated that VTA Ex-4 treatment significantly inhibited the combined stimulatory effects of ghrelin paired with d-amphetamine or ghrelin paired with cocaine. Overall our findings are consistent with a critical role for both ghrelin and GLP-1 receptor mechanisms in mesolimbic ethanol reward circuitry. Moreover, our results further suggest that ghrelin and GLP-1 modulate the stimulatory effect of psychostimulants on ethanol intake.

Ghrelin Ameliorates Diabetic Retinal Injury: Potential Therapeutic Avenues for Diabetic Retinopathy.

Ghrelin has anti-inflammatory, antioxidant, and antiapoptotic effects, and it may be beneficial for the treatment of many ophthalmic diseases, such as cataract, uveitis, and glaucoma. Our previous work proved that ghrelin pretreatment reduced the apoptosis of lens epithelial cells induced by hydrogen peroxide, reduced the accumulation of reactive oxygen species (ROS), and effectively maintained the transparency of lens tissue. However, no study has yet investigated the effect of ghrelin on retina. In this study, we conducted in vitro and in vivo experiments to explore the effect of ghrelin on high-glucose- (HG-) induced ARPE-19 cell damage and diabetic retinopathy in streptozotocin-induced diabetic rats. ARPE-19 cells were incubated in a normal or an HG (30 mM glucose) medium with or without ghrelin. Cell viability was measured by 3-(4, 5-dimethylthiazol-3-yl)-2,5-diphenyl tetrazolium bromide assay, and apoptosis was detected by the Hoechst-PI staining assay. Intracellular reactive oxygen species (ROS) production levels within cells were measured using 2',7'-dichlorofluorescein diacetate staining, and the contents of superoxide dismutase and malondialdehyde were measured using relevant detection kits. The expression levels of IL-1ß and IL-18 were measured using an enzyme-linked immunosorbent assay, and those of NLRP3, IL-1ß, and IL-18 were measured using Western blotting. The rat diabetes models were induced using a single intraperitoneal injection of streptozotocin (80 mg/kg). The morphological and histopathological changes in the retinal tissues were examined. The results indicated that ghrelin reduced ROS generation, inhibited cell apoptosis and the activation of NLRP3 inflammasome, inhibited the apoptosis of retinal cells in diabetic rats, and protected the retina against HG-induced dysfunction. In conclusion, ghrelin may play a role in the treatment of ocular diseases involving diabetic retinopathy.

Effects of exogenous ghrelin on the tissue structure and somato-statin secretion in the pancreas of African ostrich chicks / Efectos de la grelina exógena en la estructura del tejido y la secreción de somato-estatinas en el páncreas de los polluelos de avestruz africanos

SUMMARY: This study aimed to investigate the effect of exogenous ghrelin on pancreatic growth and development in African ostrich chicks. Sixteen 40-day-old African ostrich chicks (male or female) were randomly divided into four groups and injected intravenously metatarsal vein with saline (control) or ghrelin (10, 50, and 100 μg/kg) for 6 days. Body and pancreas weight were determined, structural characteristics were observed using HE staining, somatostatin-immunopositive cells were detected using immunohistochemistry. The results were as follows: 1. The 50 and 100 μg/kg groups showed lower relative pancreas weight than the control group (P 0.05. Moreover, compared with the control, the islet cells in treatment groups were loosely arranged and showed reduced cytoplasm. In the exocrine pancreas, the volume of acinar cells in the 10, 50, and 100 μg/kg groups all decreased to varying degrees. 3. Somatostatin immunopositive cells were mainly located around the periphery of the islets and sporadically distributed in the center. The density of the somatostatin immunopositive cells in the 10, 50, and 100 μg/kg groups was higher than that in the control (P < 0.05). These findings suggest that exogenous ghrelin increases the area and number of islets and number of somatostatin immunopositive cells but reduces relative pancreas weight and effects the morphological and structural development of the pancreas, which may inhibit the pancreatic growth and development in African ostrich chicks.

RESUMEN: Este estudio tuvo como objetivo investigar el efecto de la grelina exógena sobre el crecimiento y desarrollo del páncreas en polluelos de avestruz africana. Dieciséis pollos de avestruz africana de 40 días (machos o hembras) se dividieron al azar en cuatro grupos y se inyectaron por vía intravenosa con solución salina (control) o grelina (10, 50 y 100 μg / kg) durante 6 días. determinadas, se observaron las características estructurales mediante tinción Hematoxilina-Eosina, se detectaron células inmunopositivas a somatostatina mediante inmunohistoquímica. Los resultados fueron los siguientes: ¨Los grupos de 50 y 100 μg / kg mostraron un menor peso relativo del páncreas que el grupo de control (P <0,05). El área de islotes por unidad de área del páncreas fue mayor en los grupos de 10, 50 y 100 μg / kg grupos que en el grupo de control (P <0,05). El número de islotes por unidad de área del páncreas fue menor en el grupo de 10 μg / kg que en el control (P <0,05). Además, en comparación con el control, las células de los islotes en los grupos de tratamiento estaban dispuestas de forma holgada y mostraban un citoplasma reducido. En el páncreas exocrino, el volumen de células acinares en los grupos de 10, 50 y 100 μg / kg disminuyó en diversos grados. Las células inmunopositivas de somatostatina se ubicaron principalmente alrededor de la periferia de los islotes y se distribuyeron esporádicamente en el centro. La densidad de las células inmunopositivas a la somatostatina en los grupos de 10, 50 y 100 μg / kg fue mayor que la del control (P <0,05). Estos hallazgos sugieren que la grelina exógena aumenta el área y el número de islotes y el número de células inmunopositivas a la somatostatina, pero reduce el peso relativo del páncreas, lo que puede inhibir el crecimiento y desarrollo pancreático en los polluelos de avestruz africana.

The active fragments of ghrelin cross the blood-brain barrier and enter the brain to produce antinociceptive effects after systemic administration.

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.

Effect of intravenous ghrelin administration, combined with alcohol, on circulating metabolome in heavy drinking individuals with alcohol use disorder.

BACKGROUND: Ghrelin may influence several alcohol-related behaviors in animals and humans by modulating central and/or peripheral biological pathways. The aim of this exploratory analysis was to investigate associations between ghrelin administration and the human circulating metabolome during alcohol exposure in nontreatment seeking, heavy drinking individuals with alcohol use disorder (AUD). METHODS: We used serum samples from a randomized, crossover, double-blind, placebo-controlled human laboratory study with intravenous (IV) ghrelin or placebo infusion in two experiments. During each session, participants received a loading dose (3 µg/kg) followed by continuous infusion (16.9 ng/kg/min) of acyl ghrelin or placebo. The first experiment included an IV alcohol self-administration (IV-ASA) session and the second experiment included an IV alcohol clamp (IV-AC) session, both with the counterbalanced infusion of ghrelin or placebo. Serum metabolite profiles were analyzed from repeated blood samples collected during each session. RESULTS: In both experiments, ghrelin infusion was associated with an altered serum metabolite profile, including significantly increased levels of cortisol (IV-ASA q-value = 0.0003 and IV-AC q < 0.0001), corticosterone (IV-ASA q = 0.0202 and IV-AC q < 0.0001), and glycochenodeoxycholic acid (IV-ASA q = 0.0375 and IV-AC q = 0.0013). In the IV-ASA experiment, ghrelin infusion increased levels of cortisone (q = 0.0352) and fatty acids 18:1 (q = 0.0406) and 18:3 (q = 0.0320). Moreover, in the IV-AC experiment, ghrelin infusion significantly increased levels of glycocholic acid (q < 0.0001) and phenylalanine (q = 0.0458). CONCLUSION: IV ghrelin infusion, combined with IV alcohol administration, was associated with increases in the circulating metabolite levels of corticosteroids and glycine-conjugated bile acids, among other changes. Further research is needed to understand the role that metabolomic changes play in the complex interaction between ghrelin and alcohol.

LEAP2 deletion in mice enhances ghrelin's actions as an orexigen and growth hormone secretagogue.

OBJECTIVE: The hormone liver-expressed antimicrobial peptide-2 (LEAP2) is a recently identified antagonist and an inverse agonist of the growth hormone secretagogue receptor (GHSR). GHSR's other well-known endogenous ligand, acyl-ghrelin, increases food intake, body weight, and GH secretion and is lowered in obesity but elevated upon fasting. In contrast, LEAP2 reduces acyl-ghrelin-induced food intake and GH secretion and is found elevated in obesity but lowered upon fasting. Thus, the plasma LEAP2/acyl-ghrelin molar ratio could be a key determinant modulating GHSR signaling in response to changes in body mass and feeding status. In particular, LEAP2 may serve to dampen acyl-ghrelin action in the setting of obesity, which is associated with ghrelin resistance. Here, we sought to determine the metabolic effects of genetic LEAP2 deletion. METHODS: We generated the first known LEAP2-KO mouse line. Food intake, GH secretion, and cellular activation (c-fos induction) in different brain regions following s.c. acyl-ghrelin administration in LEAP2-KO mice and wild-type littermates were determined. LEAP2-KO mice and wild-type littermates were submitted to a battery of tests (such as measurements of body weight, food intake, and body composition; indirect calorimetry, determination of locomotor activity, and meal patterning while housed in metabolic cages) over the course of 16 weeks of high-fat diet and/or standard chow feeding. Fat accumulation was assessed in hematoxylin & eosin-stained and oil red O-stained liver sections from these mice. RESULTS: LEAP2-KO mice were more sensitive to s.c. ghrelin. In particular, acyl-ghrelin acutely stimulated food intake at a dose of 0.5 mg/kg BW in standard chow-fed LEAP2-KO mice while a 2× higher dose was required by wild-type littermates. Also, acyl-ghrelin stimulated food intake at a dose of 1 mg/kg BW in high-fat diet-fed LEAP2-KO mice while not even a 10× higher dose was effective in wild-type littermates. Acyl-ghrelin induced a 90.9% higher plasma GH level and 77.2-119.7% higher numbers of c-fos-immunoreactive cells in the arcuate nucleus and olfactory bulb, respectively, in LEAP2-KO mice than in wild-type littermates. LEAP2 deletion raised body weight (by 15.0%), food intake (by 18.4%), lean mass (by 6.1%), hepatic fat (by 42.1%), and body length (by 1.7%) in females on long-term high-fat diet as compared to wild-type littermates. After only 4 weeks on the high-fat diet, female LEAP2-KO mice exhibited lower O2 consumption (by 13%), heat production (by 9.5%), and locomotor activity (by 49%) than by wild-type littermates during the first part of the dark period. These genotype-dependent differences were not observed in high-fat diet-exposed males or female and male mice exposed for long term to standard chow diet. CONCLUSIONS: LEAP2 deletion sensitizes lean and obese mice to the acute effects of administered acyl-ghrelin on food intake and GH secretion. LEAP2 deletion increases body weight in females chronically fed a high-fat diet as a result of lowered energy expenditure, reduced locomotor activity, and increased food intake. Furthermore, in female mice, LEAP2 deletion increases body length and exaggerates the hepatic fat accumulation normally associated with chronic high-fat diet feeding.

Ghrelin restores memory impairment following olfactory bulbectomy in mice by activating hippocampal NMDA1 and MAPK1 gene expression.

Ghrelin (Ghrl) is an orexigenic peptide with potential roles in the modulation of anxiety- and depressive-like symptoms induced by bilateral olfactory bulbectomy (OB) in rodents. In the present work, we assessed whether intrahippocampal Ghrl could reverse OB-induced depressive-like and amnesic effects by regulating molecular mechanisms related to neuroplasticity. Adult female albino Swiss mice were divided into sham and OB groups, and infused with saline (S) or Ghrl 0.03 nmol/µl, 0.3 nmol/µl, or 3 nmol/µl into the hippocampus before exposition to open-field test (OFT) and tail suspension test (TST) or immediately after training in the object recognition test (ORT). After test phase in ORT, animals were euthanized and their hippocampi were dissected to study the expression of genes related to memory. The OB-S animals presented hyperlocomotion in OFT, increased immobility in TST and memory impairment compared to sham-S (p < 0.05), but acute intrahippocampal infusion of Ghrl 0.3 nmol/µl produced an improvement on these parameters in OB animals (p < 0.05). In addition, this dose of Ghrl reversed OB-induced low expression of NMDA1 and MAPK1 iso1 and up-regulated the expression of CaMKIIa iso1 and iso2, and MAPK1 iso2 (p < 0.05). These results extend the existing literature regarding OB-induced behavioral and neurochemical changes, and provide mechanisms that could underlie the antidepressant effect of Ghrl in this model.

Fetal Programming Effects of a Mild Food Restriction During Pregnancy in Mice: How Does It Compare to Intragestational Ghrelin Administration?

To explore in mice if a 15% food restriction protocol during pregnancy programs the offspring postnatal development, with emphasis on reproductive function, and to assess if ghrelin (Ghrl) administration to mouse dams exerts effects that mimic those obtained under mild caloric restriction. Mice were 15% food-restricted, injected with 4 nmol/animal/day of Ghrl, or injected with the vehicle (control) thorough pregnancy. After birth, the pups did not receive further treatment. Pups born from food-restricted dams (FR pups) were lighter than Ghrl pups at birth, but reached normal weight at adulthood. Ghrl pups were heavier at birth and gained more weight than control pups (C pups). This effect was not associated with plasma IGF-1. FR pups showed a delay in pinna detachment and eye opening, while an advance was observed in Ghrl pups. FR pups showed also impairment in the surface-righting reflex. In both female FR and Ghrl pups, there was an advance in vaginal opening and, in adulthood, FR pups showed a significant decrease in their own litter size and plasma progesterone, and an increase in embryo loss. A delay in testicular descent was evident in male Ghrl pups. Changes in puberty onset were not associated with differences in the expression of Kiss1 in hypothalamic nuclei. Finally, in adulthood, FR pups showed a significant decrease in sperm quality. In conclusion, a mild food restriction thorough gestation exerted programming effects on the offspring, affecting also their reproductive function in adulthood. These effects were not similar to those of intragestational Ghrl administration.

Genetic deletion of the ghrelin receptor (GHSR) impairs growth and blunts endocrine response to fasting in Ghsr-IRES-Cre mice.

OBJECTIVE: The orexigenic hormone ghrelin exerts its physiological effects by binding to and activating the growth hormone secretagogue receptor (GHSR). The recent development of a Ghsr-IRES-Cre knock-in mouse line has enabled to genetically access GHSR-expressing neurons. Inserting a Cre construct using a knock-in strategy, even when following an upstream internal ribosome entry site (IRES) can, however, interfere with expression of a targeted gene, with consequences for the phenotype emerging. This study aimed to phenotype, both physically and metabolically, heterozygous and homozygous Ghsr-IRES-Cre mice, with a view to discovering the extent to which the ghrelin signalling system remains functional in these mice. METHODS: We assessed feeding and arcuate nucleus (Arc) Fos activation in wild-type, heterozygous and homozygous Ghsr-IRES-Cre mice in response to peripherally-administered ghrelin. We also characterised their developmental and growth phenotypes, as well as their metabolic responses upon an overnight fast. RESULTS: Insertion of the IRES-Cre cassette into the 3'-untranslated region of the Ghsr gene led to a gene-dosage GHSR depletion in the Arc. Whereas heterozygotes remained ghrelin-responsive and more closely resembled wild-types, ghrelin had reduced orexigenic efficacy and failed to induce Arc Fos expression in homozygous littermates. Homozygotes had a lower body weight accompanied by a shorter body length, less fat tissue content, altered bone parameters, and lower insulin-like growth factor-1 levels compared to wild-type and heterozygous littermates. Moreover, both heterozygous and homozygous Ghsr-IRES-Cre mice lacked the usual fasting-induced rise in growth hormone (GH) and displayed an exaggerated drop in blood glucose and insulin compared to wild-types. Unexpectedly, fasting acyl-ghrelin levels were allele-dependently increased. CONCLUSIONS: Our data suggest that (i) heterozygous but not homozygous Ghsr-IRES-Cre mice retain the usual responsiveness to administered ghrelin, (ii) the impact of fasting on GH release and glucose homeostasis is altered even when only one copy of the Ghsr gene is non-functional (as in heterozygous Ghsr-IRES-Cre mice) and (iii) homozygous Ghsr-IRES-Cre mice exhibit growth retardation. Of the many transgenic models of suppressed ghrelin signalling, Ghsr-IRES-Cre mice emerge as best representing the full breadth of the expected phenotype with respect to body weight, growth, and metabolic parameters.

Ghrelin attenuate cerebral microvascular leakage by regulating inflammation and apoptosis potentially via a p38 MAPK-JNK dependent pathway.

Ghrelin is a peptide hormone with strong anti-inflammatory properties. In fact, Ghrelin was reported to improve endothelial dysfunction caused by excessive fat. However, its role in preserving the integrity of brain microvascular, under conditions of lipid dysregulation and inflammation, is not known. The objective of this study is to characterize the role of Ghrelin in the protection of cerebral microvascular integrity, during atherosclerosis, and uncover its underlying molecular mechanism. Our results demonstrated that an atherosclerotic condition, brought on by a high fat diet (HFD), can produce massive increases in serum inflammatory factors, blood lipids, cerebral microvascular leakage, and activation of the p38 mitogen-activated protein kinase (MAPK) and c-Jun N-terminal kinase (JNK) (p38 MAPK-JNK) pathway. It also produced significantly damaged pericytes morphology, resulting in pericyte decrease. Ghrelin treatment, on the other hand, protected against cerebral microvascular leakage and pericytes damage. Ghrelin effectively downregulated the expression of pro-inflammatory cytokines, and it also suppressed the p38 MAPK-JNK signaling pathway. Additionally, in isolated mouse cerebral microvascular pericytes, ox-LDL lead to increased apoptosis and secretion of inflammatory factors, along with an elevation in phosphorylated p38 MAPK-JNK proteins. Alternately, Ghrelin administration markedly lowered expression of inflammatory factors, suppressed the p38 MAPK-JNK signaling path, and halted cell apoptosis. However, pretreatment of Hesperetin, a p38 MAPK-JNK agonist, abrogated the Ghrelin-mediated suppression of inflammation and apoptosis in pericytes. Taken together, these results suggest that Ghrelin restored cerebral microvascular integrity and reduced vascular leakage in atherosclerosis mice, in part, by its regulation of inflammatory and apoptotic signaling pathways in pericytes.

Activation of central adenosine A2B receptors mediate brain ghrelin-induced improvement of intestinal barrier function through the vagus nerve in rats.

Leaky gut that is a condition reflecting intestinal barrier dysfunction has been attracting attention for its relations with many diseases such as irritable bowel syndrome or Alzheimer dementia. We have recently demonstrated that ghrelin acts in the brain to improve leaky gut via the vagus nerve. In the present study, we tried to clarify the precise central mechanisms by which ghrelin improves intestinal barrier function through the vagus nerve. Colonic permeability was estimated in vivo by quantifying the absorbed Evans blue in colonic tissue in rats. Adenosine receptor antagonist, 1,3-dipropyl-8-cyclopentylxanthine (DPCPX), blocked the intracisternal ghrelin-induced improvement of intestinal hyperpermeability while dopamine, cannabinoid or opioid receptor antagonist failed to prevent it. Since DPCPX can block adenosine A1 and adenosine A2B receptors, we examined which subtype is involved in the mechanism. Intracisternal injection of adenosine A2B agonist but not adenosine A1 agonist improved colonic hyperpermeability, while peripheral injection of adenosine A2B agonist failed to improve it. Intracisternal adenosine A2B agonist-induced improvement of colonic hyperpermeability was blocked by vagotomy. Adenosine A2B specific antagonist, alloxazine blocked the ghrelin- or central vagal stimulation by 2-deoxy-d-glucose-induced improvement of intestinal hyperpermeability. These results suggest that activation of adenosine A2B receptors in the central nervous system is capable of improving intestinal barrier function through the vagal pathway, and the adenosine A2B receptors may mediate the ghrelin-induced improvement of leaky gut in a vagal dependent fashion. These findings may help us understand the pathophysiology in not only gastrointestinal diseases but also non-gastrointestinal diseases associated with the altered intestinal permeability.

The effect of ghrelin injection in the CA1 region of hippocampus on the MK801- induced memory impairment in wistar rats.

N-Methyl-D-Aspartate (NMDA) receptors are critically involved in the learning and memory formation and dizocilpine (MK-801) is an antagonist of NMDA receptor. Ghrelin plays a crucial role in learning and memory processes. The present study was conducted to the evaluation of ghrelin effect on passive avoidance memory impairment induced by MK801. In this experimental study, 24 male wistar rats were randomly distributed into 3 groups of 8 each. Passive avoidance tests of animals were evaluated using Shuttle Box apparatus. One week after the surgery, ghrelin (3 nmol) was injected intra-hippocampally, 5 min before the MK-801administration. MK-801 (0.15 mg/kg) was injected intraperitoneally (i.p.), 10 min before the test session. Pre-test injection of MK-801 significantly decreased STL (step through latency) at 24 h and 48 h (P < 0.001) and 10 days (P < 0.01) and increased TDC (time spent in dark compartment) at 24 h, 48 h and 10 days (P < 0.001) after training in comparison with control group. Pre-test injection of ghrelin + MK-801 significantly increased STL at 24 h (P < 0.01), 48 h and 10 days (P < 0.001) and decreased TDC at 24 h, 48 h and 10 days (P < 0.001) after training in comparison with MK-801 received group. It is concluded that pre-test injection of MK-801 impaired passive avoidance memory. Administration of ghrelin before MK-801 ameliorated memory impairment induced by MK-801. It is assumed that this compensative effect of ghrelin was mediated by NMDA receptor.

Early low-dose ghrelin intervention via miniosmotic pumps could protect against the progressive dopaminergic neuron loss in Parkinson's disease mice.

Ghrelin has been identified as a multifunctional peptide that has a potential application for treating Parkinson's disease (PD). The objective of this study was to assess the effects of subcutaneous administration of low-dose ghrelin via miniosmotic pumps on PD progression. The decreased levels of total and active ghrelin in plasma were rescued by ghrelin administration in PD mice. Interestingly, ghrelin did not affect weight gain in wild-type mice but improved weight loss in PD mice. We observed the attenuation of dopaminergic neuron loss in substantia nigra and a low level of dopamine content in the striatum in PD mice with ghrelin treatment. Ghrelin administration could improve the microenvironment of dopaminergic neurons by inhibiting microglial proliferation and proinflammatory cytokine expression and could enhance cell survival by upregulating Bcl-2/Bax ratio and superoxide dismutase1 protein level in the substantia nigra of PD mice. Subcutaneous administration of low-dose ghrelin could prevent the onset of the progression of PD and also provide a possible method for ghrelin application to cure PD.

Neuroendocrine Response to Exogenous Ghrelin Administration, Combined With Alcohol, in Heavy-Drinking Individuals: Findings From a Randomized, Double-Blind, Placebo-Controlled Human Laboratory Study.

BACKGROUND: Accumulating evidence has established a role for the orexigenic hormone ghrelin in alcohol-seeking behaviors. Accordingly, the ghrelin system may represent a potential pharmacotherapeutic target for alcohol use disorder. Ghrelin modulates several neuroendocrine pathways, such as appetitive, metabolic, and stress-related hormones, which are particularly relevant in the context of alcohol use. The goal of the present study was to provide a comprehensive assessment of neuroendocrine response to exogenous ghrelin administration, combined with alcohol, in heavy-drinking individuals. METHODS: This was a randomized, crossover, double-blind, placebo-controlled human laboratory study, which included 2 experimental alcohol administration paradigms: i.v. alcohol self-administration and i.v. alcohol clamp. Each paradigm consisted of 2 counterbalanced sessions of i.v. ghrelin or placebo administration. Repeated blood samples were collected during each session, and peripheral concentrations of the following hormones were measured: leptin, glucagon-like peptide-1, pancreatic polypeptide, gastric inhibitory peptide, insulin, insulin-like growth factor-1, cortisol, prolactin, and aldosterone. RESULTS: Despite some statistical differences, findings were consistent across the 2 alcohol administration paradigms: i.v. ghrelin, compared to placebo, increased blood concentrations of glucagon-like peptide-1, pancreatic polypeptide, cortisol, and prolactin, both acutely and during the whole session. Lower levels of leptin and higher levels of aldosterone were also found during the ghrelin vs placebo session. CONCLUSION: These findings, gathered from a clinically relevant sample of heavy-drinking individuals with alcohol use disorder, provide a deeper insight into the complex interplay between ghrelin and appetitive, metabolic, and stress-related neuroendocrine pathways in the context of alcohol use.

Continuous ghrelin infusion attenuates the postoperative inflammatory response in patients with esophageal cancer.

PURPOSE: The aim of this study was to clarify whether ghrelin infusion is useful for suppressing inflammatory responses after esophagectomy. METHODS: A phase I study of ghrelin administration after esophagectomy was performed in 20 patients with esophageal cancer. The anti-inflammatory effect of ghrelin was compared with 20 consecutive patients who did not receive ghrelin infusion. Additionally, 10 patients with intermittent infusion for 10 days were compared with 10 patients with continuous infusion for 5 days. The primary endpoint was the duration of systemic inflammatory response syndrome (SIRS). Secondary endpoints included postoperative complications, serum C-reactive protein (CRP), interleukin-6 (IL-6), and growth hormone (GH) levels. RESULTS: No adverse events of ghrelin administration occurred. Patients with ghrelin infusion had higher plasma ghrelin levels on postoperative day (POD) 3 (p = 0.003) and shorter SIRS duration (p = 0.007) than patients without ghrelin infusion. Although SIRS duration was similar (p = 0.19), patients with continuous ghrelin infusion had significantly higher plasma ghrelin (p < 0.001) and GH levels (p = 0.002) on POD 3 than patients with intermittent ghrelin infusion. Serum CRP and IL-6 levels on POD 3 tended to be lower in the continuous infusion versus intermittent infusion group. CONCLUSIONS: Ghrelin was safely administered after esophagectomy and may reduce excess postoperative inflammatory responses. Continuous infusion is better for this purpose than intermittent infusion.