Obestatin: a new metabolic player in the pancreas and white adipose tissue

Protective role of melatonin against adipose-hepatic metabolic comorbidities in experimentally induced obese rat model

Background

Adipose and hepatic metabolic dysfunctions are critical comorbidities that also aggravate insulin resistance in obese individuals. Melatonin is a low-cost agent and previous studies suggest that its use may promote metabolic health. However, its effects on some comorbidities associated with obesity are unknown. Herein, we investigated the hypothesis that melatonin supplementation would attenuate adipose-hepatic metabolic dysfunction in high fat diet (HFD)-induced obesity in male Wistar rats.

Materials and methods

Twenty-four adult male Wistar rats (n = 6/group) were used: Control group received vehicle (normal saline), obese group received 40% high fat diet, melatonin-treated group received 4 mg/kg of melatonin, and obese plus melatonin group received 40% HFD and melatonin. The treatment lasted for 12 weeks.

Results

HFD caused increased food intake, body weight, insulin level, insulin resistance and plasma and liver lipid but decreased adipose lipid. In addition, HFD also increased plasma, adipose and liver malondialdehyde, IL-6, uric acid and decreased Glucose-6-phosphate dehydrogenase, glutathione, nitric oxide and circulating obestatin concentration. However, these deleterious effects except food intake were attenuated when supplemented with melatonin.

Conclusion

Taken together, the present results indicate that HFD exposure causes adipose-hepatic metabolic disturbance in obese animals, which are accompanied by oxidative stress and inflammation. In addition, the present results suggest that melatonin supplementation attenuates adipose-hepatic metabolic dysfunction, accompanying obesity by suppression of oxidative stress/inflammation-dependent mechanism and increasing circulating obestatin.

The investigation effect of weight loss on serum vaspin, apelin-13, and obestatin levels in obese individual

Objectives

It was aimed to investigate if there were any significant corresponding changes on adipokine levels in obese subjects who achieved a 10% reduction in body weight.

Methods

Thirty obese and 25 healthy adults were enrolled in present study, and serum levels of vaspin, apelin-13, obestatin, and insulin were determined with the ELISA method.

Results

The serum obestatin and apelin-13 values of the obese group obtained as basal and after weight loss was significantly lower than in controls (p<0.05, p<0.01, p<0.01, p<0.05, respectively); however, weight loss did not cause significant changes on these parameters in obese groups (p>0.05). The vaspin level did not differ between the groups (p>0.05). The obese group had characterized increased serum insulin and insulin resistance assessment by the homeostatic assay (HOMA-IR) levels compared to controls (p<0.01, p<0.05, respectively); also, weight loss caused a significant decrease in these parameters compared to basal levels (p<0.01). No significant correlation was detected among the vaspin, apelin-13 and obestatin levels in the obese group (p>0.05).

Conclusions

Obese individuals exhibited decreased levels of apelin-13 and obestatin. Moreover, 10% weight loss caused a significant reduction of insulin resistance, but no significant change was detected on apelin-13, obestatin, and vaspin levels.

β-cell replenishment: Possible curative approaches for diabetes mellitus

AIMS

Diabetes mellitus (DM) is a disorder of heterogeneous etiology marked by persistent hyperglycemia. Exogenous insulin is the only treatment for type 1 diabetes (T1D). Islet transplantation is a potential long cure for T1D but is disapproved due to the possibility of immune rejection in the later stage. The approaches used for treating type 2 diabetes (T2D) include diet restrictions, weight management and pharmacological interventions. These procedures have not been able to boost the quality of life for diabetic patients owing to the complexity of the disorder.

DATA SYNTHESIS

Hence, research has embarked on permanent ways of managing, or even curing the disease. One of the possible approaches to restore the pancreas with new glucose-responsive β-cells is by their regeneration. Regeneration of β-cells include islet neogenesis, dedifferentiation, and trans-differentiation of the already differentiated cells.

CONCLUSIONS

This review briefly describes the islet development, functions of β-cells, mechanism and factors involved in β-cell death. It further elaborates on the potential of the existing and possible therapeutic modalities involved in the in-vivo replenishment of β-cells with a focus on exercise, diet, hormones, small molecules, and phytochemicals.

Efficacy of two adjuvant systems to promote humoral immunity to the pre-proghrelin peptide obestatin in pigs: consequences for the growth of piglets to weaning

The poor antigenicity of peptide antigens demands the selection of effective adjuvants to induce humoral immunity. The peptides obestatin and ghrelin from the pro-hormone pre-proghrelin were initially identified as antagonistic in regulating feeding behaviour, with obestatin being suppressive. The efficacy of two adjuvant systems, DEAE with the oil polysorbate emulsion of BP85:Span80 and the surfactant-oil system Montanide (ISA 50v) were therefore assessed with an obestatin-ovalbumin conjugate injected into late pregnant sows. This enabled the supply of antibodies directed against obestatin to newborn piglets through colostrum with the objective of promoting ghrelin secretion and therefore increasing feeding behaviour. Pregnant Landrace × Large White sows (n = 28) were immunised with 0.5 mg obestatin-ovalbumin in 2 mL DEAE:BP85:Span80 (DEAE; n = 14) or with 2 mL Montanide (ISA 50v: n = 14) as adjuvants at days 91 and 105 of gestation. After farrowing, piglets remained with their mothers during the lactation period and were weighed after weaning at Day 28. Antibody titres (unitless) in colostrum were assessed by ELISA as 5543 ± 2388 and 3139 ± 1151 for the DEAE and Montanide adjuvants respectively. These were associated with total IgG of 67.7 ± 3 and 82.3 ± 4.8 mg/mL respectively (P = 0.018). Piglet plasma titres were 5100 ± 1576 and 5762 ± 1688 for DEAE and Montanide respectively at Day 5 postpartum. These titres were still detectable through to Day 28 (titres of 1213 ± 389 and 665 ± 203 respectively (P = 0.176). However, sow colostral antibody titres were not related to piglet antibody concentrations on D5 (r = –0.225, P = 0.341). Sow plasma antibody titres were not related to titres at Day 28 in piglets across treatments (r = 0.198, P = 0.402). The concentration of ghrelin in colostrum was 672 ± 78 and 666 ± 39 pg/mL for the DEAE and Montanide groups, respectively, leading to piglet plasma concentrations on Day 5 of 1105 ± 164 and 530 ± 84 pg/mL (P = 0.002). Animals grew from birthweights of 1.7 ± 0.1 and 1.8 ± 0.1 (P = 0.993) to 7.7 ± 1.2 and 7.8 ± 1.0 kg (P = 0.295) at weaning, representing growth rates of 200.5 ± 52.9 and 225.5 ± 53.4 g/day (P = 0.181). There was a significant negative correlation between piglet D28 antibody titre and growth rate to weaning with the Montanide adjuvant (r = 0.116, P = 0.035) but not for the DEAE (r = –0.118, P = 0.411). Although both adjuvants were capable of generating high antibody titres, the DEAE dextran was likely to be the most effective adjuvant to induce a humoral immune response to develop further with a commercial vaccine.

Ghrelin forms in the modulation of energy balance and metabolism

Ghrelin is a gastric hormone circulating in acylated (AG) and unacylated (UnAG) forms. This narrative review aims at presenting current emerging knowledge on the impact of ghrelin forms on energy balance and metabolism. AG represents ~ 10% of total plasma ghrelin, has an appetite-stimulating effect and is the only form for which a receptor has been identified. Moreover, other metabolic AG-induced effects have been reported, including the modulation of glucose homeostasis with stimulation of liver gluconeogenesis, the increase of fat mass and the improvement of skeletal muscle mitochondrial function. On the other hand, UnAG has no orexigenic effects, however recent reports have shown that it is directly involved in the modulation of skeletal muscle energy metabolism by improving a cluster of interlinked functions including mitochondrial redox activities, tissue inflammation and insulin signalling and action. These findings are in agreement with human studies which show that UnAG circulating levels are positively associated with insulin sensitivity both in metabolic syndrome patients and in a large cohort from the general population. Moreover, ghrelin acylation is regulated by a nutrient sensor mechanism, specifically set on fatty acids availability. These recent findings consistently point towards a novel independent role of UnAG as a regulator of muscle metabolic pathways maintaining energy status and tissue anabolism. While a specific receptor for UnAG still needs to be identified, recent evidence strongly supports the hypothesis that the modulation of ghrelin-related molecular pathways, including those involved in its acylation, may be a potential novel target in the treatment of metabolic derangements in disease states characterized by metabolic and nutritional complications.Level of evidence Level V, narrative review.

The expressions of some metabolic hormones (leptin, ghrelin and obestatin) in the tissues of sheep tongue

In this study, we aimed to observe the localization and expression of peptide hormones-leptin, ghrelin and obestatin-in the sheep tongue by immunohistochemistry. For that purpose, tongues of ten adult sheep were used. Leptin expression of moderate intensity was observed in the basal and parabasal epithelial cells of the luminal epithelium, and leptin was strongly expressed in the taste buds of the circumvallate and fungiform papillae and in von Ebner's glands. Ghrelin was primarily expressed in some of the skeletal muscle cells and the smooth muscle cells of the middle layer of blood vessels. A strong expression was observed in the epithelial cells lining the base of the groove surrounding the circumvallate papillae. Obestatin expression was particularly strong in the epithelial cells of the salivary ducts. It was also stronger in the von Ebner's glands than in the seromucous glands. Leptin, ghrelin and obestatin were shown to be produced at varying levels in different cell types, including epithelial, stromal and skeletal muscle cells, as well as in ganglion neurons, neural plexuses and blood vessels in the sheep tongue. Cellular localization and expression of these peptide hormones have not been investigated in many species including sheep.

Development and Characteristics of Pancreatic Epsilon Cells

Pancreatic endocrine cells expressing the ghrelin gene and producing the ghrelin hormone were first identified in 2002. These cells, named ε cells, were recognized as the fifth type of endocrine cells. Differentiation of ε cells is induced by various transcription factors, including Nk2 homeobox 2, paired box proteins Pax-4 and Pax6, and the aristaless-related homeobox. Ghrelin is generally considered to be a "hunger hormone" that stimulates the appetite and is produced mainly by the stomach. Although the population of ε cells is small in adults, they play important roles in regulating other endocrine cells, especially β cells, by releasing ghrelin. However, the roles of ghrelin in β cells are complex. Ghrelin contributes to increased blood glucose levels by suppressing insulin release from β cells and is also involved in the growth and proliferation of β cells and the prevention of β cell apoptosis. Despite increasing evidence and clarification of the mechanisms of ε cells over the last 20 years, many questions remain to be answered. In this review, we present the current evidence for the participation of ε cells in differentiation and clarify their characteristics by focusing on the roles of ghrelin.

Exogenous obestatin decreases beta-cell apoptosis and alfa-cell proliferation in high fat diet and streptozotocin induced type 2 diabetic rats

Type 2 diabetes is a chronic metabolic disease characterized by progressive decrease of islet cell function. Delaying the process of islet failure remains a challenging goal in diabetes care. Previous studies have confirmed the role of obestatin, a gut peptide that belongs to ghrelin family, in the mediation of glucose metabolism. This study aimed to observe the long term effects of exogenous obestatin on glucose metabolism in type 2 diabetes rat model. Type 2 diabetic rat model was set up by high-fat diet (60%) followed by a low dose of streptozotocin intra-peritoneal injection. Exogenous obestatin was administered at a dose of 20 nmol/kg for 12 weeks by intraperitoneal injection. Compared to placebo group (saline intraperitoneal injection), obestatin treatment decreased the glucagon levels and increased the c-peptide levels. Furthermore, obestatin treatment led to a significant restoration of islet morphology, increasing insulin and reducing glucagon expressions. Apoptosis assay showed a reduction in the number of TUNEL positive-cells. The up-regulation of Akt and GSK3β in pancreas was confirmed by Real-Time PCR. These results demonstrated that obestatin might have a potential therapeutic relevance in improving islet cell function, including increasing insulin secretion through inhibiting beta cell apoptosis and decreasing glucagon secretion by inhibiting alfa cell proliferation in type 2 diabetes. In spite of its role in these phenomena, it is necessary to further discuss, especially regarding the role of obestatin on glucagon.

Serum ghrelin and obestatin levels in HIV-infected patients: Effect of 36 weeks of antiretroviral treatment

INTRODUCTION

Patients with HIV+ often present lipid disturbances. The role of ghrelin and obestatin in these lipid disturbances is not clear. The effect of antiretroviral (ART) drugs on those molecules is also unknown. This study measured ghrelin and obestatin levels, as well as metabolic markers, in patients with HIV+ before and after 36 weeks of ART.

MATERIAL AND METHODS

Twenty HIV-positive, ART-naïve patients who started a scheme consisting of tenofovir/emtricitabine+lopinavir/ritonavir were enrolled. Plasma samples were collected before and after 36 weeks of treatment. Serum ghrelin and obestatin levels were quantitated by ELISA; glucose, cholesterol, and triglyceride levels were measured by colorimetric and enzymatic methods, and cardiovascular risk was calculated by the atherogenic index of plasma (AIP).

RESULTS

All patients completed 36 weeks of ART. Total cholesterol (p<0.001), LDL-C (p=0.019), HDL-C (p=0.003), VLDL-C (p=0.002), and triglyceride levels (p=0.021) significantly increased after treatment. AIP revealed increased cardiovascular risk at baseline, which remained high after treatment. There was a statistically significant increase in obestatin level in the unpaired and paired analyses, while ghrelin levels only showed a trend to increase. Changes in ghrelin and obestatin levels positively correlated, but no correlation was seen with any metabolic parameter.

CONCLUSION

After 36 weeks of ART, patients showed an altered lipid profile, but there were no significant changes in cardiovascular risk. Ghrelin and obestatin levels increased after 36 weeks of ART, but the increase was only significant for obestatin. Changes in ghrelin and obestatin positively correlate.

Serum obestatin and omentin levels in patients with diabetic nephropathy

INTRODUCTION

Diabetic nephropathy is the leading cause of chronic kidney disease and accounts for almost 45% of all new patients requiring renal replacement therapy. Omentin and obestatin, two novel proteins were suggested to be associated with insulin resistance, type 2 diabetes and cardiovascular risk factors. Thus, we postulated that they may also have an association with diabetic nephropathy which is known to be an independent cardiovascular risk factor. In order to investigate such an association we compared serum omentin and obestatin levels in type 2 diabetic patients with normoalbuminuria (NA) and macroalbuminuria (MA).

MATERIALS AND METHODS

A total of 81 type 2 diabetic patients were separated into two groups according to their proteinuria status; patients with NA (n = 39) and patients with MA (n = 42). Two groups were compared in terms of serum omentin and obestatin levels.

RESULTS

While s erum omentin levels did not differ among two groups (P = 0.407), serum obestatin levels were significantly higher in MA group (P = 0.001).

CONCLUSION

The results of this study showed that higher serum levels of obestatin were associated with macro albuminuria suggesting that obestatin may have a role in underlying pathogenic mechanisms that leads to diabetic nephropathy.

Combination of Obestatin and Bone Marrow Mesenchymal Stem Cells Prevents Aggravation of Endocrine Pancreatic Damage in Type II Diabetic Rats

One of the new promising therapies in treatment of diabetes mellitus is mesenchymal stem cells (MSCs) which have an interesting therapeutic potentiality based on their paracrine effect and transdifferentiation potentiality. Also obestatin improves the generation of functional β cells/islet-like cell clusters in vitro, suggesting implications for cell-based replacement therapy in diabetes. So the aim of this study was to evaluate the effect of combination of both MSCs and obestatin on an experimental model of type II diabetes mellitus (T2DM). Sixty male rats were divided into; group I (control group), group II (T2DM group) induced by administration of high fat diet (HFD) and injection of streptozotocin (STZ) in low dose, group III (T2DM treated with MSCs), group IV (T2DM treated with obestatin), group V (T2DM treated with MSCs and obestatin). Fasting blood glucose, C-peptide, insulin and lipid profile were measured. HOMA-IR and HOMA-β were calculated. Pancreatic expression of insulin, glucagon like peptide -1 (GLP-1) and pancreatic duodenal homeobox 1 (Pdx1) mRNA levels were measured. In addition pancreatic histological changes, insulin and Bax were analyzed by immunohistochemical examination of islets of Langerhans. Diabetic rats showed significant increase in HOMA-IR, serum glucose and lipid profile levels with significant decrease in insulin, HOMA-β, GLP-1 and Pdx1 levels. MSCs and obestatin caused significant improvement in all parameters with more significant improvement in combined therapy. The protective effects afforded by MSCs and obestatin may derive from improvement of the metabolic profile, antiapoptosis and by increase in pancreatic GLP-1and Pdx1 gene expression.

Long-term obestatin treatment of mice type 2 diabetes increases insulin sensitivity and improves liver function

PURPOSE

Obestatin and ghrelin are peptides encoded by the preproghrelin gene. Obestatin inhibits food intake, in addition to regulation of glucose and lipid metabolism. Here, we test the ability of obestatin at improving metabolic control and liver function in type 2 diabetic animals (type 2 diabetes mellitus).

METHODS

The effects of chronic obestatin treatment of mice with experimentally induced type 2 diabetes mellitus on serum levels of glucose and lipids, and insulin sensitivity are characterized. In addition, alterations of hepatic lipid and glycogen contents are evaluated.

RESULTS

Obestatin reduced body weight and decreased serum glucose, fructosamine, and β-hydroxybutyrate levels, as well as total and low-density lipoprotein fractions of cholesterol. In addition, obestatin increased high-density lipoproteins cholesterol levels and enhanced insulin sensitivity in mice with type 2 diabetes mellitus. Moreover, obestatin diminished liver mass, hepatic triglycerides and cholesterol contents, while glycogen content was higher in livers of healthy and mice with type 2 diabetes mellitus treated with obestatin. These changes were accompanied by reduction of increased alanine aminotransferase, aspartate aminotransferase, and gamma glutamyl transpeptidase in T2DM mice with type 2 diabetes mellitus. Obestatin increased adiponectin levels and reduced leptin concentration. Obestatin influenced the expression of genes involved in lipid and carbohydrate metabolism by increasing Fabp5 and decreasing G6pc, Pepck, Fgf21 mRNA in the liver. Obestatin increased both, AKT and AMPK phosphorylation, and sirtuin 1 (SIRT1) protein levels as well as mRNA expression in the liver.

CONCLUSION

Obestatin improves metabolic abnormalities in type 2 diabetes mellitus, restores hepatic lipid contents and decreases hepatic enzymes. Therefore, obestatin could potentially have a therapeutic relevance in treating of insulin resistance and metabolic dysfunctions in type 2 diabetes mellitus.

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;Ghsr^f/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 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.

Treatment of lean and diet-induced obesity (DIO) mice with a novel stable obestatin analogue alters plasma metabolite levels as detected by untargeted LC-MS metabolomics

INTRODUCTION

Obestatin is a controversial gastrointestinal peptide purported to have metabolic actions.

OBJECTIVES

This study investigated whether treatment with a stable obestatin analogue (PEG-OB(Cys¹⁰, Cys¹³)) changed plasma metabolite levels firstly in lean and subsequently in diet-induced obesity (DIO) C57BL6/J mice.

METHODS

Untargeted LC-HRMS metabolomics experiments were carried out in ESI + mode with plasma extracts from both groups of animals. Data were normalised, multivariate and univariate statistical analysis performed and metabolites of interest putatively identified.

RESULTS

In lean mice, 39 metabolites were significantly changed by obestatin treatment and the majority of these were increased, including various C16 and C18 moieties of phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine and monoacylglycerol, along with vitamin A, vitamin D3, tyrosine, acetylcarnitine and 2α-(hydroxymethyl)-5α-androstane-3β,17β-diol. Decreased concentrations of glycolithocholic acid, 3-dehydroteasterone and various phospholipids were observed. In DIO mice, 25 metabolites were significantly affected and strikingly, the magnitudes of changes here were generally much greater in DIO mice than in lean mice, and in contrast, the majority of metabolite changes were decreases. Four metabolites affected in both groups included glycolithocholic acid, and three different long-chain (C18) phospholipid molecules (phosphatidylethanolamine, platelet activating factor (PAF), and monoacylglycerol). Metabolites exclusively affected in DIO mice included various phosphatidylcholines, lysophosphatidylcholines and fatty acyls, as well as creatine and oxidised glutathione.

CONCLUSION

This investigation demonstrates that obestatin treatment affects phospholipid turnover and influences lipid homeostasis, whilst providing convincing evidence that obestatin may be acting to ameliorate diet-induced impairments in lipid metabolism, and it may influence steroid, bile acid, PAF and glutathione metabolism.

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

Objective

Several 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.

Aim

The 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.

Methods

Acute 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.

Results

Treatment 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.

Conclusion

Treatment 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.

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 16 nmol/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.

Ghrelin-Derived Peptides: A Link between Appetite/Reward, GH Axis, and Psychiatric Disorders?

Psychiatric disorders are often associated with metabolic and hormonal alterations, including obesity, diabetes, metabolic syndrome as well as modifications in several biological rhythms including appetite, stress, sleep-wake cycles, and secretion of their corresponding endocrine regulators. Among the gastrointestinal hormones that regulate appetite and adapt the metabolism in response to nutritional, hedonic, and emotional dysfunctions, at the interface between endocrine, metabolic, and psychiatric disorders, ghrelin plays a unique role as the only one increasing appetite. The secretion of ghrelin is altered in several psychiatric disorders (anorexia, schizophrenia) as well as in metabolic disorders (obesity) and in animal models in response to emotional triggers (psychological stress …) but the relationship between these modifications and the physiopathology of psychiatric disorders remains unclear. Recently, a large literature showed that this key metabolic/endocrine regulator is involved in stress and reward-oriented behaviors and regulates anxiety and mood. In addition, preproghrelin is a complex prohormone but the roles of the other ghrelin-derived peptides, thought to act as functional ghrelin antagonists, are largely unknown. Altered ghrelin secretion and/or signaling in psychiatric diseases are thought to participate in altered appetite, hedonic response and reward. Whether this can contribute to the mechanism responsible for the development of the disease or can help to minimize some symptoms associated with these psychiatric disorders is discussed in the present review. We will thus describe (1) the biological actions of ghrelin and ghrelin-derived peptides on food and drugs reward, anxiety and depression, and the physiological consequences of ghrelin invalidation on these parameters, (2) how ghrelin and ghrelin-derived peptides are regulated in animal models of psychiatric diseases and in human psychiatric disorders in relation with the GH axis.