Rat Ghrelin Research Articles

Does ghrelin regulate intestinal motility in rabbits? An in vitro study using isolated duodenal strips

Rabbit duodenum has been used for examining the ability of motilin to cause muscle contraction in vitro. A motilin-related peptide, ghrelin, is known to be involved in the regulation of gastrointestinal (GI) motility in various animals, but its ability to cause rabbit GI contraction have not been well examined. The aim of this study is to clarify the action of rat ghrelin and its interaction with motilin in the rabbit duodenum. The mRNA expression of ghrelin and motilin receptors was also examined using RT-PCR. Rat ghrelin (10−9–10−6 M) did not change the contractile activity of the duodenum measured by the mean muscle tonus and area under the curve of contraction waves. In agreement with this result, the distribution of ghrelin receptor mRNA in the rabbit GI tract varied depending on the GI region from which the samples were taken; the expression level in the duodenum was negligible, but that in the esophagus or stomach was significant. On the other hand, motilin (10−10–10−6 M) caused a concentration-dependent contraction by means of increased mean muscle tonus, and consistently, motilin receptor mRNA was expressed heterogeneously depending on the GI region (esophagus = stomach = colon = rectum < duodenum = jejunum = ileum < cecum). Expression level of motilin receptor was comparable to that of ghrelin receptor in the esophagus and stomach. Pretreatment with ghrelin (10−6 M) prior to motilin did not affect the contractile activity of motilin in the duodenum. In conclusion, ghrelin does not affect muscle contractility or motilin-induced contraction in the rabbit duodenum, which is due to the lack of ghrelin receptors. The present in vitro results suggest that ghrelin might not be a regulator of intestinal motility in rabbits.

Appetite–regulating hormones in rats with fructose-induced metabolic changes

Objectives: The aim of this research is to examine the effects of fructose-drinking on the plasma levels of appetite-regulating hormones insulin, leptin and ghrelin in male and female rats. Methods: Mature Wistar rats were divided as follows: two control groups - male (CM) and female (CF); two fructose-drinking groups - male (FDM) and female (FDF), received 15% fructose solution. The experiment lasted 11 weeks. At the end, insulin, leptin and ghrelin levels as well as lipid and glucose profile were assessed. Results: Plasma concentrations of the examined hormones were elevated in fructose-drinking groups. However, in the FDM group only the leptin levels were significantly increased compared to the control. In the FDF group, all three appetite-regulating hormones showed the highest concentrations in comparison to the other groups. Conclusion: Sex hormones may affect the appetite-regulation signals and could be a factor contributing to degree of metabolic changes caused by long-term fructose overconsumption.

Thermally oxidized sunflower oil diet alters leptin/ghrelin balance and lipid profile in rats: Possible role of reactive aldehydes in dyslipidemia.

Sunflower oil is a common edible oil in the world, which is highly prone to oxidative degradation during the frying process. The present study aimed to investigate the effects of products obtained from the thermal oxidation process of sunflower oil on metabolic indices, and the secretion status of leptin and ghrelin in rats. In vivo studies were designed after determining the rate of formation of active aldehydes and peroxide value in sunflower oil following 300°C in a period of 30-240 min. To this end, 36 rats in 6 separate groups were fed with 2ml of normal saline, fresh sunflower oil, and heated oils at 30, 60, 120, and 240 min for 45 days. Finally, lipid profile changes and leptin/ghrelin secretion were examined, along with histological changes in the liver tissue. The results indicated a significant increase in serum LDL, VLDL and triglycerides, and a decrease in HDL, in the groups treated with heated oils. These changes were associated with a higher accumulation of triglycerides, active aldehydes, and histological changes in the hepatic tissue. Although the serum ghrelin level in the groups receiving heated oil did not change significantly compared to the fresh oil, the serum leptin level increased significantly in the groups receiving heated oil. According to our findings, increasing the time of sunflower oil heating enhanced the formation of active aldehydes, so that daily consumption of such oxidized oils might be associated with the occurrence of dyslipidemia, fatty liver and the development of leptin resistance. PRACTICAL APPLICATIONS: Sunflower oil is highly prone to oxidative degradation during the frying process. Increasing time of sunflower oil heating enhanced the formation of active aldehydes. Daily consumption of oxidized oils might be associated with the occurrence of dyslipidemia, fatty liver and the development of leptin resistance.

Effects of electroacupuncture on the expression of hypothalamic neuropeptide Y and ghrelin in pubertal rats with polycystic ovary syndrome.

BackgroundPolycystic ovary syndrome often starts in puberty, and its pathogenesis is not clear. This study aimed to explore the pathogenesis of pubertal polycystic ovary syndrome (PCOS) and assess the therapeutic effect of electroacupuncture on pubertal PCOS.MethodsDihydrotestosterone (DHT) was used to induce rat models of pubertal PCOS. pubertal rats with PCOS were randomly divided into a model group (M), an electroacupuncture group (EA), and a sham acupuncture group (SA). Age-matched normal rats were regarded as normal controls (N). Rats were treated with EA or SA five times a week for 25 minutes during their 6th–7th week. At the end of the experiment, we observed any changes in ovarian morphology; detected levels of metabolic indices in serum, the hypothalamus and pancreas.ResultsEA significantly improved estrous cycle disorders and the ovarian polycystic morphology in pubertal rats with PCOS, but SA only improved disorders of the estrous cycle. The serum levels of insulin, neuropeptide Y(NPY) and fasting blood glucose(FBG) increased significantly (both p < 0.01), while the serum levels of ghrelin(GHRL) decreased in the model group (p < 0.01). After treatment with EA, the levels of NPY (p < 0.01) and FBG (p < 0.05) went into decrease, whereas the levels of GHRL (p < 0.05) and insulin (p < 0.01) increased. There was few differences in the hypothalamic expression of galanin (GAL), galanin-like peptide (GALP) and ghrelin receptor(GHSR) between the four groups. The upregulation of NPY mRNA and neuropeptide Y2 receptor(NPY2R) mRNA and the downregulation of GHRL protein and mRNA in the hypothalamus, and the increased expression of NPY and NPY2R as well as the decreased expression of GHRL in the arcuate nucleus (ARC) can be rescued by EA. But, surprisingly, SA seem to make no difference to the levels of FBG and insulin, and the protein expression of ghrelin in the hypothalamus and ARC. Co-expression of kisspeptin and GHSR, and co-expression of gonadotrophin releasing hormone(GnRH) and NPY2R were observed in ARC. No differences were found between groups in protein of GAL, GALP and GHRL expression in the pancreas. Neither EA nor SA can attenuate the upregulated kisspeptin protein expression in the pancreas of PCOS model rats.ConclusionsEA and SA improved the symptoms of pubertal PCOS rats, and the mechanism might be associated with regulating hypothalamic NPY and ghrelin levels.

The Effect of Low Doses of Radon on Ghrelin and Glucose Levels in Rats with Multiple Low-Dose Streptozotoccin-induced Type 2 Diabetes Mellitus

AIM: The aim of our research was to identify the ghrelin concentration in experimental animals with type 2 diabetes mellitus (T2DM) and to study the effect of radon hormesis balneotherapy using natural thermal waters of Tskaltubo spring, practically, its effect on ghrelin and glucose metabolism. MATERIALS AND METHODS: To study the effect of radon in balneotherapy, group of experimental animals (multiple low doses streptozotocin-induced T2DM Wistar rats were used) went through the procedure of inhalation of radon by the Tskaltubo mineral water pool, once daily, during 10 days. In animals of the control groups, inhalation with radon was not used. The experimental group and the control group were brought from Tskaltubo to Tbilisi to the Ivane Beritashvili experimental biomedicine center, where the blood of the rats was analyzed. RESULTS: After radon inhalation therapy with Tskaltubo mineral water, a normalization of the ghrelin levels was observed in the experimental group and despite the different body weight, the levels were approximately the same and close to those of the control group. In the experimental group, ghrelin level normalization was accompanied by glycemia normalization. CONCLUSION: This research showed that Tskaltubo mineral water radon inhalation caused hormesis, which consequently decreased ghrelin levels in rodents with T2DM and obesity and the result was stable during 3 months. Ghrelin level stabilization positively influenced on glucose levels. The result of our experiment gives us a stimulus to continue future research to find more specific neurochemical mechanisms participating in radon hormesis processes and positively influencing on glucose levels and T2DM outcome.

Changes of plasma concentration and gene expression of ghrelin and leptin in rats receiving kisspeptin and morphine.

Kisspeptin is a hypothalamic peptide which stimulates hypothalamus- pituitary- gonadal (HPG) axis. Morphine is an alkaloid which suppresses reproduction. Ghrelin and leptin are metabolic peptides which play role in relaying information to the HPG axis. In the present study, the interaction effects of kisspeptin and morphine were investigated on plasma and gene expression levels of leptin and ghrelin. Twenty adult male Wistar rats randomized in four groups were received injection of saline, kisspeptin (1.00 nmol), morphine (5.00 mg kg-1) or Kisspeptin + morphine. Rats were received kisspeptin and morphine via third cerebral ventricular and subcutaneous injection, respectively. Ten male rats in two groups were received intravenous injection of saline or kisspeptin (7.50 nmol). Blood samples, hypothalamic and adipose tissue samples were collected. Plasma and gene expression levels of ghrelin and leptin were measured using the methods of enzyme-linked immunosorbent assay and real time-PCR, respectively. Morphine significantly increased plasma concentration and hypothalamic mRNA levels of ghrelin compared to saline while kisspeptin significantly decreased them compared to saline. Morphine significantly decreased plasma and mRNA levels of leptin in adipose tissue compared to saline, however, kisspeptin did not increase plasma and mRNA levels of leptin in adipose tissue compared to saline. Kisspeptin significantly decreased the effects of morphine on plasma concentration and hypothalamic gene expression levels of ghrelin compared to morphine alone, however, it did not affect morphine influence on plasma and leptin gene expression levels compared to morphine alone. Kisspeptin and morphine might partly be involved in the regulation of reproductive activity via regulation the metabolic hormones synthesis.

Assessment of Ulva lactuca Extract on Inflammatory Markers in Fructose Fed Experimental Rats

Adipose tissue controls energy homeostasis. Adipocytes secrete hormones and inflammation-related adipokines in addition to storing fat. Green seaweeds are a typical dietary element in Eastern Asian nations like India. They are rich in proteins, vitamins, minerals, fibre, polyunsaturated fatty acids, and bioactive compounds. This study examined Ulva lactuca extract's influence on hormones and anti-inflammatory markers in fructose-fed rats. High fructose-fed rats had elevated blood leptin, IL-6, TNF-, and decreased adiponectin and ghrelin. Ulva lactuca extract improved leptin, IL-6, TNF-, adiponectin, and ghrelin in obese rats. Ulva lactuca may restore adipose tissue function owing to saponin, steroids, alkaloids, polyphenol, and glycoside

Effect of Allium sativum extract in combination -with orlistat on insulin resistance and disrupted metabolic hormones in high fat diet induced obese rats

Obesity has increased in epidemic proportions globally and the current antiobesity drugs have treatment limitations which further reduce treatment benefits. The aim of this study was to evaluate the effect of Allium sativum and Orlistat on insulin resistance, fatty acid content and metabolic hormones; leptin, ghrelin and adiponectin in high-fat diet-induced obese rat model. The sprague-dawley rats used in this study were fed with standard chow as control diet, Fat emulsion as high-fat diet (HFD), HFD+ Orlistat, HFD+ A. sativum extract and HFD+ Orlistat+ A. sativum extract. Free fatty acid, serum glucose, insulin, leptin, ghrelin, adiponectin, and Homeostasis model assessment for insulin resistance (HOMA-IR) index were determined using standard methods. HFD significantly increased (P < .001) body weight, serum glucose, free fatty acid content, serum insulin, HOMA-IR and serum leptin. Furthermore, HFD reduced the serum levels of ghrelin and adiponectin when compared to control rats. The combined administration of A. sativum and orlistat resulted in a decrease in the body weight and HOMA-IR and also improved serum levels of glucose, insulin, leptin, ghrelin and adiponectin in obese rats fed with HFD. This suggests A. sativum in combination with orlistat, has the potential to ameliorate insulin resistance and metabolic hormones disrupted by obesity

Liver-Expressed Antimicrobial Peptide 2 antagonizes the insulinostatic effect of ghrelin in rat isolated pancreatic islets.

The hormone ghrelin is the endogenous agonist of the G protein-coupled receptor (GPCR) termed growth hormone secretagogue receptor (GHSR). Ghrelin inhibits glucose-stimulated insulin secretion by activating pancreatic GHSR. Recently, Liver-Expressed Antimicrobial Peptide 2 (LEAP2) was recognized as an endogenous GHSR ligand that blocks ghrelin-induced actions. Nonetheless, the effect of LEAP2 on glucose-stimulated insulin secretion from pancreatic islets is unknown. We aimed at exploring the activity of LEAP2 on glucose-stimulated insulin secretion. Islets of Langerhans isolated from rat pancreas were exposed to glucose in the presence or in the absence of LEAP2 and ghrelin and then insulin secretion was assayed. LEAP2 did not modulate glucose-stimulated insulin secretion. However, LEAP2 blocked the insulinostatic action of ghrelin. Our data show that LEAP2 behaves as an antagonist of pancreatic GHSR.

A closer look at alcohol-induced changes in the ghrelin system: novel insights from preclinical and clinical data.

Ghrelin is a gastric-derived peptide hormone with demonstrated impact on alcohol intake and craving, but the reverse side of this bidirectional link, that is, the effects of alcohol on the ghrelin system, remains to be fully established. To further characterize this relationship, we examined (1) ghrelin levels via secondary analysis of human laboratory alcohol administration experiments with heavy-drinking participants; (2) expression of ghrelin, ghrelin receptor, and ghrelin-O-acyltransferase (GOAT) genes (GHRL, GHSR, and MBOAT4, respectively) in post-mortem brain tissue from individuals with alcohol use disorder (AUD) versus controls; (3) ghrelin levels in Ghsr knockout and wild-type rats following intraperitoneal (i.p.) alcohol administration; (4) effect of alcohol on ghrelin secretion from gastric mucosa cells ex vivo and GOAT enzymatic activity in vitro; and (5) ghrelin levels in rats following i.p. alcohol administration versus a calorically equivalent non-alcoholic sucrose solution. Acyl- and total-ghrelin levels decreased following acute alcohol administration in humans, but AUD was not associated with changes in central expression of ghrelin system genes in post-mortem tissue. In rats, alcohol decreased acyl-ghrelin, but not des-acyl-ghrelin, in both Ghsr knockout and wild-type rats. No dose-dependent effects of alcohol were observed on acyl-ghrelin secretion from gastric mucosa cells or on GOAT acylation activity. Lastly, alcohol and sucrose produced distinct effects on ghrelin in rats despite equivalent caloric value. Our findings suggest that alcohol acutely decreases peripheral ghrelin concentrations in vivo, but not in proportion to alcohol's caloric value or through direct interaction with ghrelin-secreting gastric mucosal cells, the ghrelin receptor, or the GOAT enzyme.

Chronic Standard Scheduled-Diet Improves Memory Performance and Is Associated with Positive Correlation between Plasma Ghrelin and Hippocampal Dopamine Level in Rats

Chronic Standard Scheduled-Diet Improves Memory Performance and Is Associated with Positive Correlation between Plasma Ghrelin and Hippocampal Dopamine Level in Rats

Plasma ghrelin, adiponectin and leptin levels in obese rats with type 2 diabetes mellitus after sleeve gastrectomy and gastric plication.

The prevalence of obesity has increased in recent decades and has become a public health problem. In obesity patients the metabolism of almost all adipokines is markedly dysregulated. Studies regarding levels of ghrelin, leptin, and adiponectin after bariatric surgery reveal contradictory results. The purpose of the present study was to analyze modification of body weight and plasma levels of fasting glucose, ghrelin, adiponectin and leptin, in obese rats with T2DM after sleeve gastrectomy (SG), gastric plication (GP) and sham-operated (SO). Eighteen specimens where randomized to three weight-matched groups: Group SG underwent sleeve gastrectomy (n=6), group GP underwent gastric plication (n=6) and the control group SO underwent sham surgery (n=6). Upon surgery a normal rat chow diet (Bio-Serv® product no. F4031) was fed to the rats until the end of the experiment. Additional blood samples were harvested after 4 weeks. The results revealed that body mass decreased in the SG (783.17±101.39 vs. 658.33±86.57 g; P<0.0001) and the GP (781.33±103.12 vs. 702.33±84.06 g; P=0.004) rats after surgery. There were significant lower fasting glucose levels at 4 weeks postoperative in the SG group compared to the SO group (83.1±12.81 vs. 104.5±9.81 mg/dl; P=0.016). The same trend was observed in the GP group vs. the SO group (86.7±11.43 vs. 104.5±9.81 mg/dl; P=0.026). There was no difference regarding mean glucose levels between the SG group compared to the GP group (P>0.05). Plasma acylated ghrelin and leptin levels decreased four weeks after surgery compared to preoperative levels, while adiponectin levels increased four weeks after surgery in the SG and GP groups, respectively. The present study revealed that plasma glucose levels, ghrelin and leptin levels decreased after SG and GP, while adiponectin levels improved. This suggests that there may be hormonal contribution in weight loss.

Pathogenetic mechanisms for the development of hematological disorders in induced fatty liver disease in Wistar rats and assessment of the regulatory effects of carnosine and α-lipoic acid

The study of the relationship between hematopoiesis and metabolism is now particularly relevant in view of the high incidence of alimentary dependent diseases, including non-alcoholic fatty liver disease. In this regard, pathogenetic factors of this disease development are studied actively in order to choose adequate drug therapy and usage of bioactive substances with antioxidant properties. The aim of the study was to study the pathogenetic relationship of hematological disorders and imbalance of growth factors, leptin and ghrelin in male Wistar rats in the model of the initial stage of non-alcoholic fatty liver disease development and to assess the regulatory effect of minor bioactive substances - carnosine and α-lipoic acid. Material and methods. The studies were performed on male Wistar rats with initial body weight 150±10 g within 8 weeks. Animals were divided into 5 groups (n=8 in each). Rats of the control group received a complete modified diet AIN93M, in which soybean oil was replaced with sunflower oil and lard (1:1). Rats of the experimental groups consumed high-calorie choline-deficient diet (HCCDD), in which fat content was 45%, fructose content - 20% of the energy value of the diet. Rats of the 2nd group were fed HCCDD without any supplements, the 3rd group - with the addition of carnosine (75 mg/kg body weight), the 4th group - with the addition of α-lipoic acid (75 mg/kg body weight), the 5th group - with the combined addition of carnosine and α-lipoic acid in a total dose of 150 mg/kg body weight. Hematological values were determined on a hematological analyzer. The content of ghrelin and leptin, as well as growth factors GM-CSF and M-CSF in blood plasma and adipose tissue lysates, was determined by multiplex immunoassay using xMAP technology. Results. Rat intake of HCCDD resulted in decreased hemoglobin levels and red blood cell scores compared to controls. Diet enrichment with carnosine and α-lipoic acid did not have a reliable effect on these indicators. Carnosine intake had a protective effect on erythrocyte volume, a decrease of which was recorded in other experimental groups. HCCDD stimulated the growth of the absolute number of leukocytes in peripheral blood due to granulocytes and mononuclears. The enrichment of HCCDD with carnosine and α-lipoic acid led to a further increase in leukocytosis, the maximum level of which was observed in the group of rats fed HCCDD, simultaneously enriched with carnosine and α-lipoic acid (14.86±1.48×109/l compared to 8.67±1.23×109/l in control). All diets used in the research had no effect on the number of erythrocytes and platelets in the peripheral blood of rats. The use of both HCCDD alone and in combination with carnosine or α-lipoic acid intake had a negative effect on the level of growth factors GM-CSF and M-CSF in blood plasma and adipose tissue. The consumption of HCCDD caused an increase in leptin blood level (8.54±0.69 compared to 2.58±0.37 pg/ml in control, р<0.05), which was normalized by enriching the diet with carnosine and α-lipoic acid. Ghrelin blood level significantly decreased in all experimental groups compared to the control: by 30% in rats fed and by almost 50% when carnosine and α-lipoic acid were added to HCCDD. The intake of α-lipoic acid led to hormone level changes in adipose tissue lysates, leptin content decreased (2.31±0.11 vs 2.77±0.15 pg/ml), while ghrelin level significantly increased (0.35±0.14 vs 0.20±0.06 pg/ml), compared with the control group (р<0.05). Conclusion. The revealed interrelation of parameters of the cellular composition of peripheral blood and hemoglobin content with the changes in the content of GM-CSF, M-CSF, leptin and ghrelin in blood plasma and adipose tissue indicates the mutual influence of the studied CSF, leptin, ghrelin and added antioxidants (carnosine and α-lipoic acid) on the regulatory mechanisms of hematopoiesis in rats fed HCCDD.

Salmon acyl-ghrelin increases food intake and reduces doxorubicin-induced myocardial apoptosis in rats, likely by anti-oxidative activity

We had reported that orally administered ghrelin-containing salmon stomach extract prevents doxorubicin (DOX)-induced cardiotoxicity. In this study, we investigated the binding affinity of salmon ghrelin to rat ghrelin receptor and the cardioprotective effects of subcutaneous (sc) injected synthetic salmon ghrelin in rats with DOX-induced acute heart failure in order to clarify the potential efficacy of salmon ghrelin. Intracellular calcium mobilization assay was performed on rat GHS-R1a-expressing CHO cells to reveal ghrelin activity. Rats were divided into five groups; the normal control (I), and toxic control (II) groups were given saline (sc, twice daily), and the salmon acyl-ghrelin (sAG) (III), salmon unacylated-ghrelin (sUAG) (IV), and rat acyl-ghrelin (rAG) (V) groups were given corresponding synthetic ghrelins (sc, twice daily), respectively. After seven days of treatment, DOX (20 mg/kg BW) or saline was administered to the corresponding groups by intraperitoneal injection. The toxic control group was the negative control group for the DOX-induced cardiotoxicity groups. While sAG displayed similar affinity to rAG upon application to GHS-R1a-expressing cells, and also decreased DOX-induced apoptosis and increased food intake, sUAG did not. Both sAG and rAG improved DOX-induced deterioration, showing anti-oxidative activity. The anti-oxidative activity of sAG might contribute to the protective effects on cardiomyocytes. The results also suggest that, similar to rAG, sAG is a potent protectant against DOX-induced cardiotoxicity and a potential functional component in orally administered ghrelin-containing salmon stomach extract, which prevented DOX-induced cardiotoxicity in our previous study.

Effects of Progressive Aerobic Training on Serum and Gastric Acylated Ghrelin, IGF-1 and Body Weight in Female Rats

Background: It is generally believed that physical activity can lead to increased food intake, whereas some studies state that exercise can have inhibitory effects on appetite and calorie intake. Objectives: The purpose of this study was to examine the changes in the level of gastric and serum ghrelin, body weight, and serum IGF-1 after a period of progressive aerobic training (PAT) in female rats. Methods: After one week of familiarization with treadmill running, 16 adult female rats were randomly assigned to two groups: control (n = 8) and aerobic exercise (n = 8). The exercise protocol consisted of progressive aerobic running on the treadmill for three months (5 days a week). Forty-eight hours after the last exercise session, the animals were sacrificed. Serum levels of ghrelin, IGF-1, and ghrelin content in the gastric tissue were measured using the ELISA method. An Independent t-test was used for comparison of data between the two groups. Results: The results indicated that three months of PAT had no significant effect on gastric (P = 0.51) and serum acylated ghrelin (P = 0.15), weight changes (P = 0.42), and serum IGF-1 (P = 0.56) compared to the control group. Conclusions: Three months of PAT in female animals had no effects on ghrelin level, food intake and weight loss, and serum IGF-1 level. It seems that there are sex-specific hormonal and appetite responses to progressive aerobic training.

Motilin- and ghrelin-induced contractions in isolated gastrointestinal strips from three species of frogs

Ghrelin (GHRL) and motilin (MLN), gut peptides isolated from the mucosa of the stomach and duodenum, respectively, stimulate gastrointestinal (GI) motility in mammals and birds. However, the functions of MLN and GHRL in amphibian GI tracts have not been examined in detail. To clarify the regulation of GI motility by the two peptides, the effects of human MLN and rat GHRL on contractility of isolated GI strips from three species of frogs, the black-spotted pond frog (pond frog; Pelophylax nigromaculata), bullfrog (Lithobates catesbeiana) and Western clawed frog (Xenopus; Xenopus tropicalis), were examined in in vitro experiments. The GI tract of each frog was divided into the stomach, upper intestine, middle intestine and lower intestine. Human MLN caused contractions of the stomach in the pond frog and upper intestine in the bullfrog and Xenopus, but other GI regions were insensitive to human MLN. Erythromycin did not cause contraction of the upper intestine of the bullfrog and Xenopus. Rat GHRL did not cause contraction of the stomach and small intestines in the pond frog and bullfrog, but it caused a concentration-dependent contraction in the stomach and upper intestine of Xenopus, while des-acyl rat GHRL did not cause any contraction of them. In conclusion, human MLN caused the contraction of the stomach or upper intestine in the three species of frogs, but GHRL was effective only in the stomach and upper intestine of Xenopus. On the basis of these data, MLN but not GHRL causes the GI region-dependent contractions in the frogs.

Vitamin C protects against chronic social isolation stress-induced weight gain and depressive-like behavior in adult male rats.

Objective. Considering the importance of ghrelin in stress-induced hyperphagia and a role of antioxidants in decreasing body weight, in the present study, the effect of vitamin C (VitC) on ghrelin secretion and food intake following chronic social isolation (CIS) was evaluated in rats.Methods. Thirty two male Wistar rats (200-220g) were randomly divided into: control, VitC, CIS, and CIS + VitC groups. Animals received VitC (500 mg/kg/day)/saline by gavage for 3 weeks. For 24 h cumulative and post 18-20 h fasting food intake, fasting plasma ghrelin level, and body weight were measured. Gastric histopathology was also evaluated.Results. Results showed a marked increase in fasting plasma ghrelin and food intake in stressed rats compared to controls. VitC prevented the increases in stressed rats. Histological assessment indicated a positive effect of VitC on gastric glandular cells compared to control, an effect that might partially be a reason of significant increase of plasma ghrelin levels in VitC rats. Elevated plasma ghrelin in VitC group was even higher than that one in stressed group, whereas there were no significant changes in the food intake. Assessment of the percentage of changes in body weight during 21 days showed a significant increase in stressed rats compared to controls. Vitamin C treatment prevented this increase. Stressed rats also displayed depression-like behavior as indicated by sucrose test, whereas VitC ameliorated it.Conclusions. The data of the present study indicate that VitC may overcome ghrelin-induced hyperphagia and improve the abnormal feeding and depressive behavior in CIS rats.

Correction of immunosuppression in aged septic rats by human ghrelin and growth hormone through the vagus nerve-dependent inhibition of TGF-\u03b2 production

BackgroundCo-administration of human ghrelin and growth hormone (GH) reverse immunosuppression in septic aged animals, but the mechanism remains elusive. Here, we hypothesize that ghrelin and GH co-treatment restores the immune response in aged septic rats by inhibiting the production of transforming growth factor-β (TGF-β), an immunoregulatory cytokine, through the vagus nerve.MethodsMale aged Fischer rats (22–23-month-old) were made septic by cecal ligation and puncture (CLP) with or without dissecting the vagus nerve (vagotomy). Human ghrelin and GH or vehicle (PBS) were administrated subcutaneously at 5 h post CLP. After 20 h of CLP, serum and spleens were harvested.ResultsSerum TGF-β levels were increased in septic aged rats, while ghrelin and GH treatment significantly reduced its levels. Expression of TGF-β in the spleen was upregulated after sepsis, while ghrelin and GH treatment significantly inhibited its expression. TNF-α and IL-6 levels were significantly reduced after ex vivo LPS stimulation of splenocytes from rats that underwent CLP compared to sham rats; while these levels were significantly higher in splenocytes from ghrelin and GH-treated CLP rats compared to vehicle-treated CLP rats. Ghrelin and GH treatment reduced program death receptor-1 (PD-1) expression, increased human leukocyte antigen-DR (HLA-DR) expression, attenuated lymphopenia, and cleaved caspase-3 levels in the spleen of septic aged rats. Vagotomy diminished the beneficial effects of ghrelin and GH treatment in septic rats. In vitro, the addition of ghrelin, GH, or ghrelin and GH together had no effect on restoring immune response in splenocytes from CLP rats following LPS stimulation, indicating the requirement of the vagus nerve for ghrelin and GH’s effect.ConclusionsGhrelin and GH attenuate immunosuppression in aged septic rats through the vagus nerve-dependent inhibition of TGF-β production.

Electroacupuncture Upregulated Ghrelin in Rats with Functional Dyspepsia via AMPK/TSC2/Rheb-Mediated mTOR Inhibition

BackgroundGastrointestinal motility disorder is an important pathological basis for functional dyspepsia (FD). Epigastric ache and discomfort are the main symptoms of FD, and ghrelin deficiency is closely related to the occurrence and development of FD. While electroacupuncture (EA) alleviated the symptoms of FD patients and improved their quality of life, there is a lack of sufficient mechanistic evidence to support these beneficial effects.MethodsAn in vivo FD model was established in wild-type and mammalian target of rapamycin (mTOR) knockout (−/−) rats. FD rats were subjected to EA with or without mTOR agonists or inhibitors. Gastric emptying and intestinal propulsion were assessed, and pathological changes in the hypothalamus, gastric antrum, and small intestine were examined histologically. In addition, ghrelin expression and AMPK/TSC2/Rheb/mTOR activation were detected by quantitative reverse transcription polymerase chain reaction and western blot.ResultsEA alone or in combination with mTOR inhibitors improved gastrointestinal function in FD rats by increasing the rates of intestinal propulsion and gastric emptying, and pathological changes in the hypothalamus, gastric antrum, and small intestine were alleviated. This may be related to the significant upregulation of ghrelin expression and the effective activation of the AMPK/TSC2/Rheb/mTOR signaling pathway. Interestingly, EA also improved gastrointestinal function and ghrelin expression in mTOR (−/−) KO FD rats.ConclusionAltering the level of ghrelin by regulating AMPK/TSC2/Rheb-mediated mTOR inhibition is an important way through which EA treats FD. The complex EA-mediated regulatory mechanisms of the brain–gut axis still require further exploration.

Neuroprotective effect of ghrelin in methamphetamine-treated male rats

This study aimed to investigate the effects of ghrelin, as a neuroprotective agent, on cognitive impairment and apoptosis pathway in methamphetamine-treated male rats. Sixty adult male Wistar rats were randomly divided into six groups (n = 10): Saline/Saline (SS), Saline/Ghrelin (SG), Methamphetamine/Simultaneous Saline (MSS), Methamphetamine/Simultaneous Ghrelin (MSG), Methamphetamine/Delayed Saline (MDS), and Methamphetamine/Delayed ghrelin (MDG). Methamphetamine (5 mg/kg) and ghrelin (5 nM/kg) were injected intraperitoneally. Spatial and passive avoidance memories were evaluated by Morris water maze (MWM) and Shuttle box, respectively. Hippocampal expression levels of Cytochrome-C, Caspase 3, and Bax/Bcl-2 ratio were evaluated by Western blotting. TUNEL assay was performed to detect hippocampal neuronal apoptosis. Our results showed that time spent in the target quadrant in MSS group was less than the control group. However, simultaneous ghrelin treatment could increase it. Ghrelin treatment reversed methamphetamine effects on hippocampal protein expression of Caspase 3 and Cytochrome-C, and BAX/Bcl-2 ratio. TUNEL assay showed an increase in the number of apoptotic cells in methamphetamine-treated animals, while ghrelin treatment decreased apoptosis. These results indicate that ghrelin treatment could improve spatial memory and reduce neuronal apoptosis in the hippocampus of methamphetamine-treated animals.