Effects Of Obestatin Research Articles

Obestatin prevents H2O2-induced damage through activation of TrkB in RGC-5 cells

BackgroudIn the early stage of diabetic retinopathy, the damage of retinal ganglion cells already exists, promoting the development of the disease. The aim of this study was to investigate the protective role and the mechanisms of obestatin against H2O2-induced damage in RGC-5 cells. MethodsRGC-5 cells were incubated with various concentrations of obestatin for 24h before H2O2 added. The survival rates of RGC-5 were measured by MTT assay. The expression of apoptosis-related proteins and TrkB pathway-related proteins were detected by Western blot analysis. ResultsOur data showed that H2O2 evidently decreased the survival rate of RGC-5 cells. However, obestatin pretreatment reversed the decreased activity. Moreover, obestatin effectively increased the expression of Bcl-2 and decreased the expression of Bax. In addition, obestatin potentially plays a role in protecting RGC-5 by activating of TrkB. Obestatin notablely increased the phosphorylation of TrkB, AKT and ERK1/2. All these effects of obestatin can be inhibited by GLP-1R antagonist exendin (9-39). ConclusionsObestatin prevents H2O2-induced damage in RGC-5 cells by activating TrkB pathway. Moreover, GLP-1R is closely related to the function of obestatin in RGC-5 cells.

Obestatin stimulates the somatotrophic axis activity in sheep

The effects of obestatin (an anorexigenic peripheral peptide) on somatotrophic axis activity in ruminants have not yet been determined. The aim of this study was to investigate the consequence of intracerebroventricular infusions of obestatin on the activity of the somatotrophic axis in peripubertal female sheep. Animals were randomly divided into two groups: control group received intracerebroventricular infusions of the vehicle, and the obestatin group was infused with obestatin (25 µg/120 µL h−1). The series of four hourly infusions on three consecutive days were performed. The blood samples were collected on day 0 and on day 3. Immediately after the end of experiment sheep were slaughtered. Parts of the brains were fixed in situ for further immunohistochemical analysis, while the remaining brains were frozen for Real Time RT-qPCR analysis.Substantial changes in the activity of the somatotrophic axis were observed in obestatin-infused sheep. In those animals obestatin evoked an increase in growth hormone-releasing hormone (GHRH) mRNA expression and a decrease in somatostatin mRNA expression in the anterior hypothalamic area. Moreover, a decrease in somatostatin immunoreactivity in the periventricular nucleus and an increase in somatostatin immunopositive fibers in the median eminence were noted. Changes in the GHRH and somatostatin activity are associated with an increase in growth hormone (GH) gene expression and in the amount of GH immunoreactive material stored in the somatotrophic pituitary cells. Consequently, an increase in GH concentration in the peripheral blood, due to an increase in the number of pulses was observed.It was revealed that obestatin affects the somatostatin/GHRH/GH system at the level of protein synthesis, accumulation and release. It is suggested that obestatin participates in the mechanism modulating somatotrophic axis activity at the central level by stimulating GH release through suppression of somatostatin output. Thereby, it can be concluded that obestatin may be involved in the modulation of growth processes in sheep.

P.1.l.023 - Obestatin effect on pain sensitivity, caused by chemical and thermal stimulus in BALB/c white mice

P.1.l.023 - Obestatin effect on pain sensitivity, caused by chemical and thermal stimulus in BALB/c white mice

Obestatin Plays Beneficial Role in Cardiomyocyte Injury Induced by Ischemia-Reperfusion In Vivo and In Vitro.

BackgroundObestatin, primarily recognized as a peptide within the gastrointestinal system, has been shown to benefit the cardiovascular system. We designed this experiment to study the protective role and underlying mechanism of obestatin against ischemia-reperfusion(I/R) injury in myocardial cells.Material/MethodsIn an In vivo experiment, LAD was ligated for 0.5 h and then opened for reperfusion with obestatin for 24 h. Then, the infarction area was shown with TTC staining, and inflammation factors in serum were analyzed by qRT-PCR. In primary cultured cardiomyocytes, we measured the level of LDH, MDA, GSH, and SOD. Finally, we assessed cells apoptosis using flow cytometry and detected the concentrations of caspase-3, Bax, and Bcl-2 using Western blot analysis.ResultsTTC staining showed that in the 3 obestatin groups, the infarct area became smaller with the increase of obestatin concentration. Obestatin also inhibited LDH expression in rat serum and decreased mRNA levels of TNF-α, IL-6, ICAM-1, and iNOS in rat cardiomyocytes after reperfusion. In primary cultured cardiomyocytes, obestatin decreased LDH content and increased GSH level after I/R injury. Obestatin was also found to antagonize the apoptosis of cardiomyocytes in a dose-dependent manner. Western blot analysis showed that obestatin downregulated the expression of caspase-3 and Bax and upregulated the expression of Bcl-2.ConclusionsObestatin can protect cardiomyocyte from I/R-induced injury in vitro and in vivo. This beneficial effect is closely related with its properties of anti-inflammation, anti-cytotoxicity, and anti-apoptosis. The protective effect of obestatin might be associated with activation of Bcl-2 and inhibition of caspase-3 and Bax.

Obestatin stimulates glucose-induced insulin secretion through ghrelin receptor GHS-R

Orexigenic hormone ghrelin and anorexic hormone obestatin are encoded by the same preproghrelin gene. While it is known that ghrelin inhibits glucose-stimulated insulin secretion (GSIS), the effect of obestatin on GSIS is unclear. Ghrelin’s effect is mediated by its receptor Growth Hormone Secretagogue Receptor (GHS-R), but the physiologically relevant receptor of obestatin remains debatable. Here we have investigated the effect of obestatin on GSIS in vitro, in vivo and ex vivo, and tested whether obestatin regulates insulin secretion through GHS-R. We found that under hyperglycemic condition, obestatin augments GSIS in rat insulinoma cells (INS-1) and in pancreatic islets from ghrelin−/− mice. Surprisingly, obestatin-induced GSIS was absent in β-cells in which GHS-R was suppressed. Obestatin-induced insulin secretion was abolished in the circulation of Ghsr−/− mice, and in pancreatic islets isolated from Ghsr−/− mice. We also found that obestatin-induced GSIS was attenuated in islets isolated from β-cell-specific Ghsr knockout MIP-Cre/ERT;Ghsrf/f mice. Our data collectively demonstrate that obestatin is a potent insulin secretagogue under hyperglycemic condition, and obestatin’s effect on insulin secretion is mediated by GHS-R in pancreatic β-cells. Our findings reveal an intriguing insight that obestatin and ghrelin have opposing effects on insulin secretion, and both are mediated through ghrelin receptor GHS-R.

Obestatin improves oxidative brain damage and memory dysfunction in rats induced with an epileptic seizure

Obestatin was shown to alleviate renal, gastrointestinal and haemorrhage-induced brain injury in rats. In order to investigate the neuroprotective effects of obestatin on seizure-induced oxidative brain injury, an epileptic seizure was induced with a single intraperitoneal (i.p.) dose of pentylenetetrazole (PTZ, 45mg/kg) in male Wistar rats. Thirty minutes before the PTZ injection, rats were treated with either saline or obestatin (1μg/kg, i.p.). Seizure was video-taped and then evaluated by using Racine’s scoring (0–5). For the assessment of memory function, passive-avoidance test was performed before seizure induction, which was repeated on the 3rd day of seizure. The rats were decapitated at the 24th or 72nd hour of seizures and brain tissues were obtained for histopathological examination and for measuring levels of malondialdehyde (MDA), glutathione (GSH), reactive oxygen radicals and myeloperoxidase (MPO) activity. Obestatin treatment reduced the average seizure score, decreased the occurrence and duration of generalized tonic-clonic seizures, presenting with a shorter latency to their onset. Increased lipid peroxidation and enhanced generation of oxygen-derived radicals detected at the post-seizure 72nd h were suppressed by the consecutive treatments of obestatin, but no changes were observed by the single obestatin treatment in the 24-h seizure group. Neuronal damage and increased GFAP immunoreactivity, observed in the hippocampal areas and cortex of PTZ-induced rats were alleviated in 3-day obestatin-treated PTZ group. PTZ-induced memory dysfunction was significantly improved in obestatin-treated PTZ group as compared to saline-treated rats. The present data indicate that obestatin ameliorated the severity of PTZ-induced seizures, improved memory dysfunction and reduced neuronal damage by limiting oxidative damage.

Vascular Effects of Obestatin in Lean and Obese Subjects.

Obese patients have impaired vasodilator reactivity and increased endothelin 1 (ET-1)-mediated vasoconstriction, two abnormalities contributing to vascular dysfunction. Obestatin, a product of the ghrelin gene, in addition to favorable effects on glucose and lipid metabolism, has shown nitric oxide (NO)-dependent vasodilator properties in experimental models. Given these premises, we compared the effects of exogenous obestatin on forearm flow in lean and obese subjects and assessed its influence on ET-1-dependent vasoconstrictor tone in obesity. In both lean and obese participants, infusion of escalating doses of obestatin resulted in a progressive increase in blood flow from baseline (both P < 0.001). This vasodilation was predominantly mediated by enhanced NO activity, because NG-monomethyl-l-arginine markedly blunted the flow response to obestatin in both groups (both P < 0.05 vs. saline). In obese subjects, antagonism of ETA receptors by BQ-123 increased forearm flow during saline (P < 0.001) but did not induce additional vasodilation (P > 0.05) during obestatin. Circulating obestatin levels were not different between lean and obese participants (P = 0.41). Our findings indicate that obestatin causes NO-dependent vasodilation in the human circulation. This effect is preserved in obesity, where it is accompanied by reduced ET-1-mediated vasoconstriction. These latter observations make obestatin a promising target for vascular prevention in obesity and diabetes.

Obestatin improves hepatic injury induced by ischemia/reperfusion in rats: Role of nitric oxide.

Hepatic ischemia/reperfusion (I/R) injury is a common clinical problem. The present study was conducted to evaluate the protective effect of obestatin against I/R-induced liver injury. Rats were divided into three groups (n = 10): control sham-operated group, I/R group and obestatin treatment group. Rats of I/R group and obestatin treatment group underwent partial hepatic ischemia for 60 min followed by 90 min reperfusion. At the beginning of the 90-min reperfusion period, rats of obestatin treatment group were injected with obestatin (100 μg/kg) intravenously. At the end of the experiment the animals were sacrificed and blood and liver tissue samples were obtained. Liver function enzymes, alanine aminotransferase (ALT) and aspartate aminotransferase (AST), as well as inflammatory biomarkers, tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6), were determined in the serum. Also, total oxidative status (TOS), total antioxidant status (TAS) and oxidative stress index (OSI) were measured in hepatic tissue. Liver tissue damage was examined by histopathology. In addition, the expression levels of nitric oxide synthase (NOS) subtypes, endothelial (eNOS) and inducible (iNOS) in liver samples were assessed by Western blotting. Obestatin significantly counteracted I/R-induced liver damage mainly through reducing oxidative stress, inhibiting the release of pro-inflammatory cytokines and modulation of nitric oxide levels.

EFFECT OF OBESTATIN ON CARDIOVASCULAR SYSTEM IN TYPE II DIABETIC RAT MODEL

Background: Obestatin (OB) is a novel anorexiogenic peptide produced in the stomach. It has been shown to regulate glucose and lipid metabolism. However, its potential role in cardiovascular control is still not clear and controversial. Aim of the work: To evaluate the in vivo and in vitro effects of Obestatin on cardiovascular system in both normal and diabetic rats. Also, to identify the possible mechanism of its action. Material and methods: 40 healthy male albino rats weighing 180-200 gm. were used and divided into two main groups: In vivo experiments subdivided into normal (n= 10 ) and Type II Diabetes induced groups (n=10) In which heart rate and blood pressure were recorded before and after OB (100 Mg/kg body weight) injection , In vitro experiments subdivided into normal (n= 10) and Type II Diabetes induced group ( n= 10) in which the effect of OB (1 nmol/l) alone and its effect in presence of β –blocker propranolol (30Mmol/l) and α blocker prazosin (3Mmol/l) on amplitude and frequency of cardiac contractility were studied ,also effects of OB alone (100 pmol/l) and in presence of LNAME(0.3Mmol/l) on contraction induced by phenylephrine (10 Mmol/L) of isolated thoracic aorta. Type II Diabetes induced by feeding rats for two weeks a high-fat diet (58% fat, 25% protein, 17% carbohydrates as percentage of total calories). On day 13, rats were given a single intraperitoneal injection of streptozotocin (25 mg/kg body). Results: Obestatin injection showed no significant difference on blood pressure and heart rate in both normal and diabetic rats, However in vitro studies showed that OB has both positive inotropic and chronotropic effects on isolated heart of both normal and diabetic rats which were blocked by propranolol but not by prazocin. Moreover, OB produced significant vascular relaxation of isolated rat thoracic aorta of the normal group which was attenuated by L-NAME in normal rats. However, the relaxation effect of OB was much weaker in diabetic rats and was blocked by L-NAME. Conclusion: Obestatin improves cardiac function and exerts vasodilator effects via nitric oxide (NO) release, so it may be decrease systemic vascular resistance in type II diabetes. Key words: Obestatin, type II diabetic rats, propranolol, prazocin, isolated thoracic aorta.

Therapeutic Effect of Obestatin in the Course of Cerulein-Induced Acute Pancreatitis.

The aim of this study was to determine the impact of obestatin therapy on the course of cerulein-induced pancreatitis. Acute pancreatitis was induced by cerulein given intraperitoneally 5 times with 1 hour intervals at the dose of 50 μg/kg per dose. Obestatin was administered twice a day at the dose of 8 nmol/kg per dose, starting the first dose 24 hours after the last injection of cerulein. Severity of acute pancreatitis (AP) was examined at 0 hour or 1, 2, 3, 5, 7, and 10 days after the last injection of cerulein. Administration of cerulein led to development of acute edematous pancreatitis in all rats, and maximal severity of this disease was observed 24 hours after induction of pancreatitis. Treatment with obestatin reduced morphological signs of pancreatic damage (pancreatic edema, leukocyte infiltration, vacuolization of acinar cells) and led to earlier regeneration of the pancreas. Biochemical indexes of severity of pancreatitis such as serum activity of pancreatic digestive enzymes were significantly reduced in animals treated with obestatin. These effects were accompanied by increase in pancreatic DNA synthesis and decrease in serum level of proinflammatory interleukin 1β. In addition, administration of obestatin improved pancreatic blood flow in rats with AP. Treatment with exogenous obestatin reduces severity of AP and accelerates pancreatic recovery.

Obestatin attenuated doxorubicin-induced cardiomyopathy via enhancing long noncoding Mhrt RNA expression.

The emergence of side-effect of doxorubicin in cardiomyopathy and heart failure has led to the search for diverse strategies to prevent its cytotoxic effects. This study was to determine the role of obestatin on doxorubicin-induced cardiomyocytes apoptosis and possible underlying mechanism. Sprague Dawley rats were divided into 3 groups and received treatment for a total of 6 weeks: group1, untreated normal rats; group2, Doxorubicin-induced heart cardiomyopathy (DC) rats; and group3, obestatin treated HC rats. Doxorubicin (2.5mg/kg) or obestatin (100μg/kg/d) were discontinuously administered via intraperitoneal injection. Primary cardiomyocytes and H9C2 cell line were used for in vitro experiments. Mhrt and Nrf2 (nuclear factor erythroid 2 -related factor 2) mRNA expressions were determined using qRT-PCR. Expression of Nrf2 protein was determined using western blotting. TUNEL assay was performed to evaluate cell apoptosis. Administration of obestatin significantly improved doxorubicin-induced dysfunction of left ventricular contractility function, moreover, resulted in upregulation of Mhrt and Nrf2 in failing myocardial tissue. Co-incubation of obestatin and doxorubicin in primary cardiomyocytes also enhanced Mhrt and Nrf2 expression as well as prevented cell apoptosis in comparison with doxorubicin only. Manipulation of cellular Mhrt by pcDNA-Mhrt or si-Mhrt transfection positively regulated Nrf2 expression in doxorubicin-incubated cardiomyocytes. Silencing Mhrt reversed cardioprotective effects of obestatin both in vivo and in vitro. Administration of obestatin attenuates doxorubicin-induced cardiac dysfunction via preservation of cardiomyocytes apoptosis in a Mhrt-Nrf2 dependent pathway.

Obestatin and Ghrelin May Have a Complementary Function During Acute and Chronic Period in Mice.

Obestatin is described as an anorexigenic peptide, and has adverse effects of ghrelin. It has no inhibitory effects on acute/chronic food intake, and it has been reported by several researchers. The role of obestatin in metabolism is still not clear. In the present study, the purpose is to determine the effects of chronically administrated obestatin. For this purpose, (1 µmol/kg; i.p.) or ghrelin (1 µmol/kg; i.p.) and food restriction (24h fast:24h fed) on plasma obestatin, ghrelin, leptin, insulin, cholecystokinin (CCK) and glucose levels, and body weight gain were investigated for 14 days in mice. Additionally, mice were treated with acute ip (100 nmol/kg) injections of obestatin or ghrelin to investigate the food consumptions, plasma obestatin and ghrelin levels to determine unknown acute effects of obestatin. Plasma ghrelin levels increased significantly in obestatin administered mice when compared with the control group for chronic treatment. This increase is consistent with immunohistochemical findings which claim that the number of ghrelin and obestatin immunopositive cells in fundus tissue of stomach are considerably high in obestatin treated animals. Plasma obestatin and ghrelin levels has shown an increase endogenously in food restricted mice, but plasma leptin and insulin levels have been found to be lower compared to the control group. Acute administration of obestatin caused a decrease in plasma obestatin level at 60 min after injection and had no effect on the reduction of food intake in each treatment time. These results imply that obestatin may not itself be involved in the metabolism regulation; however, obestatin accompanied by ghrelin may play a role in the long-term regulation of metabolism.

Effect of obestatin on normal, diabetic, and obese male albino rats

Aim This work was performed to study the effect of obestatin on normal, diabetic, and obese male albino rats. Materials and methods A total of 60 male albino rats were divided into six groups: group 1 was the normal control group; group 2, the obestatin-treated group, was injected with 100 μg/kg of obestatin subcutaneously twice daily for 1 week; group 3 was the diabetic control group; group 4, the obestatin-treated diabetic group, was injected with obestatin as in group 2; group 5 was the obese control group; and group 6, the obestatin-treated obese group, was injected with obestatin as in group 2. At the end of the experimental period, serum samples were collected after decapitation for estimation of fasting glucose, insulin, triglyceride (TG), and total cholesterol. BMI was also measured. Results After 1 week of obestatin treatment, the obestatin-treated control group showed insignificant changes in serum fasting glucose, insulin, TG, and total cholesterol levels with the exception of BMI, which showed a significant decrease as compared with the normal control group. However, the obestatin-treated diabetic group showed a significant decrease in serum fasting glucose, TG, and total cholesterol levels, with a significant increase in insulin level, but an insignificant change in BMI as compared with the diabetic control group. In contrast, the obestatin-treated obese group showed insignificant changes in serum fasting glucose and insulin, but significant decrease in serum TG, total cholesterol levels, and BMI as compared with the obese control group. Conclusion From these results, we conclude that there is a significant role for obestatin in the regulation of carbohydrate and lipid metabolism, shown from its effect on glucose, insulin, and serum lipids. Thus, obestatin administration develops new and more efficient therapeutic approaches to treat diabetes and obesity.

Anti-inflammatory role of obestatin in autoimmune myocarditis.

Obestatin is a popular endogeneous peptide, known to have an autoimmune regulatory effect on energy metabolism and the gastrointestinal system. Studies regarding the anti-inflammatory effects of obestatin are scarce. The aim of this study was to show the anti-inflammatory effect of obestatin in an experimental model of autoimmune myocarditis in rats. Experimental autoimmune myocarditis was induced in Lewis rats by immunization with subcutaneous administration of porcine cardiac myosin, twice at 7-day intervals. Intraperitoneal pretreatment with obestatin (50μg/kg) was started before the induction of myocarditis and continued for 3weeks. The severity of myocarditis was evidenced by clinical, echocardiographic and histological findings. In addition, by-products of neutrophil activation, lipid peroxidation, inflammatory and anti-inflammatory cytokines were measured in serum. Obestatin significantly ameliorated the clinical and histopathological severity of autoimmune myocarditis. Therapeutic effects of obestatin in myocarditis were associated with reduced lipid peroxidation, suppression of polymorphonuclear leukocyte infiltration and enhancement of glutathione synthesis, inhibition of serum inflammatory and activation of anti-inflammatory cytokines. Histopathologically, the left ventricle was significantly dilated, and its wall thickened, along with widespread lymphocytic and histocytic infiltration. The myocardium was severely infiltrated with relatively large mononuclear cells. These histopathological changes were observed in lesser degrees in obestatin-treated rats. This study demonstrated a novel anti-inflammatory effect of obestatin in an experimental model of autoimmune myocarditis. Consequently, obestatin administration may represent a promising therapeutic approach for myocarditis and dilated cardiomyopathy in the future.

Obestatin promotes proliferation and survival of adult hippocampal progenitors and reduces amyloid-β-induced toxicity

The ghrelin gene-derived peptide obestatin promotes survival in different cell types through a yet undefined receptor; however, its potential neuroprotective activities are still unknown. Here, obestatin effects were investigated on proliferation and survival of adult rat hippocampal progenitor cells (AHPs). Obestatin immunoreactivity was found in AHPs; moreover, obestatin binding to AHPs was displaced by the GLP-1R agonist Ex-4 and antagonist Ex-9. Furthermore, obestatin increased cell proliferation and survival in growth factor deprived medium and inhibited apoptosis; these effects were blocked by Ex-9. The underlying mechanisms involved Gαs/cAMP/PKA/CREB signaling, phosphorylation of ERK1/2 and PI3K/Akt, and the PI3K targets GSK-3β/β-catenin and mTOR. Obestatin also counteracted Aβ1-42-induced detrimental effects through inhibition of GSK-3β activity and Tau hyperphosphorylation, main hallmarks of neuronal death in Alzheimer's disease. These findings indicate a novel protective role for obestatin in AHPs and candidate this peptide as potential therapeutic target for increasing neurogenesis and for approaching neurodegenerative disorders.

Obestatin Accelerates the Recovery in the Course of Ischemia/Reperfusion-Induced Acute Pancreatitis in Rats.

ObjectiveSeveral previous studies have shown that obestatin exhibits protective and regenerative effects in some organs including the stomach, kidney, and the brain. In the pancreas, pretreatment with obestatin inhibits the development of cerulein-induced acute pancreatitis, and promotes survival of pancreatic beta cells and human islets. However, no studies investigated the effect of obestatin administration following the onset of experimental acute pancreatitis.AimThe aim of this study was to evaluate the impact of obestatin therapy in the course of ischemia/reperfusion-induced pancreatitis. Moreover, we tested the influence of ischemia/reperfusion-induced acute pancreatitis and administration of obestatin on daily food intake and pancreatic exocrine secretion.MethodsAcute pancreatitis was induced by pancreatic ischemia followed by reperfusion of the pancreas. Obestatin (8nmol/kg/dose) was administered intraperitoneally twice a day, starting 24 hours after the beginning of reperfusion. The effect of obestatin in the course of necrotizing pancreatitis was assessed between 2 and 14 days, and included histological, functional, and biochemical analyses. Secretory studies were performed on the third day after sham-operation or induction of acute pancreatitis in conscious rats equipped with chronic pancreatic fistula.ResultsTreatment with obestatin ameliorated morphological signs of pancreatic damage including edema, vacuolization of acinar cells, hemorrhages, acinar necrosis, and leukocyte infiltration of the gland, and led to earlier pancreatic regeneration. Structural changes were accompanied by biochemical and functional improvements manifested by accelerated normalization of interleukin-1β level and activity of myeloperoxidase and lipase, attenuation of the decrease in pancreatic DNA synthesis, and by an improvement of pancreatic blood flow. Induction of acute pancreatitis by pancreatic ischemia followed by reperfusion significantly decreased daily food intake and pancreatic exocrine secretion. Administration of obestatin at doses used was without significant effect with regard to daily food intake or pancreatic exocrine secretion in sham-operated rats, as well as in rats with acute pancreatitis. On the other hand, obestatin abolished a statistical significance of difference in food intake between animals with AP and control animals without pancreatic fistula and induction of AP.ConclusionTreatment with the exogenous obestatin reduces severity of ischemia/reperfusion-induced acute pancreatitis and accelerates recovery in this disease. The involved mechanisms are likely to be multifactorial, and are mediated, at least in part, by anti-inflammatory properties of obestatin.

The effect of obestatin on anxiety-like behaviour in mice

Obestatin is a 23 amino acid-peptide, derived from the same preproghrelin-gene as ghrelin. Obestatin was originally reported as a ghrelin antagonist with anorexigenic activity, but later it was proven to be involved in multiple processes including sleep, memory retention, anxiety, morphine-induced analgesia and withdrawal. In the present study, in male CFLP mice, by using computerised open field (OF) and elevated plus maze (EPM) tests we have investigated the behavioural effects of the acute intracerebroventricular (icv) administration of obestatin alone, and following ghrelin receptor blockage with [d-Lys3]-Growth Hormone Releasing Peptide-6 ([d-Lys3]- GHRP6) or corticotropin-releasing hormone (CRH) receptor 1 antagonism with antalarmin. Plasma corticosterone levels were measured for each treatment group by using chemofluorescent assay. Our results in the EPM test showed that obestatin reduced the percent of time spent in the open arms. The basal locomotor activity (ambulation distance and time, rearing and jumping) was not influenced significantly neither in the obestatin-treated groups, nor in those receiving pre-treatment with antalarmin or [d-Lys3]-GHRP6. The percentage of central ambulation distance however was decreased by obestatin, while the percentage of time spent in the central zone showed a decreasing tendency. The administration of antalarmin or [d-Lys3]-GHRP6 have both reversed the effect of obestatin on central ambulation. Plasma corticosterone levels were elevated by obestatin, which effect was antagonised by the injection of antalarmin. These are the first results to indicate that obestatin exerts anxiogenic-like effect in mice, which might be mediated through ghrelin receptor and CRH activation.

Pretreatment with obestatin reduces the severity of ischemia/reperfusion-induced acute pancreatitis in rats

Obestatin, as ghrelin, has been originally extracted from the stomach, which remains its major source. Previous studies have shown that administration of obestatin exhibits protective and healing-promoting effects in several organs, including the stomach and kidney. In pancreas, pretreatment with obestatin inhibits the development of cerulein-induced acute pancreatitis and promotes survival of pancreatic beta cells and human islets. The aim of the present study was to check the universality of protective effect of obestatin in the pancreas. For this reason we investigated the influence of obestatin administration on the development of ischemia/reperfusion-induced pancreatitis. Acute pancreatitis was induced by pancreatic ischemia followed by reperfusion of the gland. Obestatin (4, 8 or 16nmol/kg/dose) was administered intraperitoneally twice: 0.5h before exposure to ischemia, and 3h after the first injection. The effect of obestatin on the course of necrotizing pancreatitis was assessed after 6-h reperfusion, and included histological, functional, and biochemical analyses. Treatment with obestatin reduced morphological signs of pancreatic damage including edema, vacuolization of acinar cells, hemorrhages, acinar necrosis, and leukocyte infiltration of the gland. These effects were accompanied by an improvement of pancreatic DNA synthesis and superoxide dismutase activity, and a decrease in serum level of lipase and pro-inflammatory interleukin-1β. Moreover pretreatment with obestatin reduced myeloperoxidase activity and malondialdehyde concentration in pancreatic tissue of rats with acute pancreatitis. Conclusions: Administration of obestatin inhibits the development of ischemia/reperfusion-induced acute pancreatitis. This observation, taken together with previous findings that obestatin protects the pancreas against cerulein-induced pancreatitis, indicates that protective effect of obestatin in the pancreas is universal and independent of the primary cause of acute pancreatitis.

Obestatin partially suppresses ghrelin stimulation of appetite in “high-responders” grass carp, Ctenopharyngodon idellus

Ghrelin and obestatin are two gastrointestinal peptides obtained by post-translational processing of a common precursor, preproghrelin. The effect of obestatin on food intake is still controversial. The aim of the present study was to investigate the effects of ghrelin and obestatin on food intake in grass carp, Ctenopharyngodon idellus. Fish received intraperitoneal (IP) injection of saline, ghrelin (100ngg−1BW), obestatin-like (25ngg−1BW) and ghrelin in combination with obestatin-like. Ghrelin stimulation of food intake varied considerably among individual fish with 70.8% eliciting a robust response. In these high-responders, food intake was significantly increased by IP ghrelin within 2h. Co-administration of ghrelin and obestatin-like resulted in a decrease in food intake, indicating that obestatin was able to antagonize the effect of ghrelin. However, IP obestatin-like alone could not regulate food intake in grass carp. RT-PCR analysis demonstrated that IP ghrelin peptide led to a significant increase in mRNA abundance of NPY, Y8a and Y8b genes compared to saline injected fish, while in combination with obestatin-like peptide decreased ghrelin-induced gene expressions of these three genes. IP sole obestatin-like peptide did not modify the expression levels of NPY, Y8a, Y8b, CART and POMC compared to the control group. Therefore, IP administration of obestatin-like peptide, partially blocking the ghrelin-induced appetite, investigated the possible involvement of obestatin as a mediator of the ghrelin stimulatory action on food intake, at least in “high-responders” grass carp.

Abstract 11694: The Gut Hormone Obestatin Induces Nitric Oxide-Dependent Vasodilation and Inhibits Endothelin-1 Activity in Obese Patients

Obese patients have vascular dysfunction related to impaired nitric oxide (NO)-dependent vasodilation and increased endothelin (ET)-1 activity. Obestatin is a gastrointestinal peptide with favorable metabolic actions linked to obesity and diabetes; it has also been shown to exert cardiovascular benefits in experimental models by producing vascular relaxation via specific activation of endothelium-dependent NO signaling. Here we tested the hypothesis that obestatin might have advantageous impacts on the NO pathway and the ET-1 system in patients with central obesity. To this purpose, forearm blood flow responses to intra-arterial infusion of graded doses of exogenous obestatin (0.2; 0.4; 0.8; 1,6; 3.2 nmol/min, each dose given for 5 min) were assessed in lean subjects (n=5) and in patients with central obesity (n=14), during the concurrent infusion of saline and after NO inhibition by L-NMMA (4 μmol/min for 15 min). In another group of obese patients (n=10), vascular responses to selective blockade of ET A receptors (BQ-123, 10 nmol/min for 60 min) were measured in the absence and the presence of obestatin (0.8 nmol/min). In lean subjects, before NO synthase inhibition obestatin resulted in a progressive increase in forearm flow (60% at the highest dose; P&lt;0.001 vs. baseline); obestatin-induced vasodilation, however, was completely abolished by L-NMMA (P&lt;0.001 vs. saline). Similarly, in obese patients obestatin induced a significant vasodilation (45%; P&lt;0.001 vs. baseline), which was blunted by L-NMMA (16%; P&lt;0.01 vs. saline). Before obestatin, in obese patients ET A receptor blockade resulted in a marked vasodilation (39% flow increase at 60 min; P&lt;0.001 vs. baseline), which was totally abrogated in the presence of obestatin (P&lt;0.001 vs. absence). In conclusion, obestatin produces vasorelaxation in healthy humans via specific activation of endothelium-dependent NO signaling. This beneficial effect of obestatin is preserved in obese arteries, where it is associated with inhibition of ET-1 signaling. These actions of obestatin, therefore, may be important in the normal regulation of vascular function and are clearly relevant to obesity, a condition characterized by increased prevalence of hypertension and cardiovascular complications.