RT-PCR and immunocytochemistry studies support the presence of somatostatin, cortistatin and somatostatin receptor subtypes in rat Kupffer cells

Serum Cortistatin Level in Type 2 Diabetes Mellitus and Its Relationship with Nonalcoholic Fatty Liver Disease

Purpose

To evaluate serum cortistatin (CST) levels in type 2 diabetes mellitus (T2DM) patients with or without non-alcoholic fatty liver disease (NAFLD) and to examine the relationship between CST and NAFLD.

Methods

A total of 90 T2DM patients, which included 56 NAFLD patients (referred to as DM+NAFLD group) and 34 patients without NAFLD (DM-only group), and 83 non-diabetes individuals that included 39 NAFLD patients (NAFLD-only group) and 44 without NAFLD that acted as the normal-control group (NC group). The differences in the serum CST levels between the groups were compared, and the correlations between CST and other variables were calculated by applying both correlational analysis and multiple linear regression analysis.

Results

The mean serum CST levels were significantly lower in the DM+NAFLD and DM groups than in the NC group (P < 0.05). In addition, the CST levels were lower in the DM group relative to that in the NAFLD group (P < 0.05). However, no statistical difference was noted in the serum CST between diabetic patients with and without NAFLD (P > 0.05). Similarly, in the non-diabetic group, the serum CST level was not significantly different between individuals with and without NAFLD (P > 0.05). Furthermore, the serum CST levels were negatively associated with the levels of total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), fasting plasma glucose (FPG), homeostasis model assessment-insulin resistance (HOMA-IR), and insulin cell function index (HOMA-β). Conversely, the serum CST levels were positively associated with high-density lipoprotein cholesterol (HDL-C). The data obtained through multiple linear regression implied that LDL-C and HOMA-β, but not HOMA-IR, were closely related to serum CST levels.

Conclusion

T2DM was related to decreased serum CST. However, serum CST was correlated with HOMA-β in T2DM patients, while HOMA-IR was not. There was no correlation between CST and NAFLD.

CORTISTATIN REGULATES FIBROSIS AND MYOFIBROBLAST ACTIVATION IN EXPERIMENTAL HEPATOTOXIC- AND CHOLESTATIC-INDUCED LIVER INJURY

BACKGROUND AND PURPOSE

Liver fibrosis induced by chronic hepatic injury remains as a major cause of morbidity and mortality worldwide. Identification of susceptibility/prognosis factors and new therapeutic tools for treating hepatic fibrotic disorders are urgent medical needs. Cortistatin is a neuropeptide with potent anti-inflammatory and anti-fibrotic activities in lung that binds to receptors that are expressed in liver fibroblasts and hepatic stellate cells. We evaluated the capacity of cortistatin to regulate liver fibrosis.

EXPERIMENTAL APPROACH

We experimentally induced liver fibrosis in mice by chronic CCl₄ exposition and bile duct ligation and evaluated the histopathological signs and fibrotic markers.

KEY RESULTS

Hepatic expression of cortistatin inversely correlated with liver fibrosis grade in mice and humans with hepatic disorders. Cortistatin-deficient mice showed exacerbated signs of liver damage and fibrosis and increased mortality rates when challenged to hepatotoxic and cholestatic injury. Compared to wild-type mice, non-parenchymal liver cells isolated from cortistatin-deficient mice showed increased presence of cells with activated myofibroblast phenotypes and a differential genetic signature that is indicative of activated hepatic stellate cells and periportal fibroblasts and of myofibroblasts with active contractile apparatus. Cortistatin treatment reversed in vivo and in vitro these exaggerated fibrogenic phenotypes and protected from progression to severe liver fibrosis in response to hepatic injury.

CONCLUSION AND IMPLICATIONS

We identify cortistatin as an endogenous molecular break of liver fibrosis and its deficiency as a potential poor-prognosis marker for chronic hepatic disorders that course with fibrosis. Cortistatin-based therapies emerge as attractive strategies for ameliorating severe hepatic fibrosis of various etiologies.

Local treatment of liver metastases by administration of 177Lu-octreotate via isolated hepatic perfusion - A preclinical simulation of a novel treatment strategy

INTRODUCTION

Systemic ¹⁷⁷Lu-octreotate treatment for metastatic neuroendocrine tumours is restricted by organs at risk. By administering ¹⁷⁷Lu-octreotate during isolated hepatic perfusion (IHP), the uptake in organs at risk might be strongly reduced. The aim of this study was to investigate the feasibility to use the combination of IHP and radionuclide therapy.

METHODS

To simulate IHP, the liver of a pig was prepared for ex vivo perfusion. Blood containing 490 MBq ¹⁷⁷Lu-octreotate was circulated through the liver for 60 min, after which the liver was rinsed. After IHP, the liver was examined by SPECT/CT. Lastly, an intraoperative gamma detector (IGD) was used to determine ¹⁷⁷Lu activity concentration in the liver and results were compared with the activity concentration in corresponding liver biopsies.

RESULTS

Detector measurements over the liver during the IHP showed a fast increase with a maximum after approximately 10-15 min. After IHP, about 75% of the ¹⁷⁷Lu in the liver could be washed out. The SPECT/CT images revealed a relatively inhomogeneous distribution. Nevertheless, the IGD values of ¹⁷⁷Lu activity concentration showed acceptable agreement with the biopsy values.

CONCLUSIONS

Our results in pig show that it could be feasible to treat patients with liver metastases from NETs with ¹⁷⁷Lu-octreotate via IHP ¹⁷⁷. However, an inhomogeneous distribution of ¹⁷⁷Lu-octreotate in normal liver tissue is expected, and in order to determine the activity concentration with satisfactory accuracy using an IGD, measurements need to be performed at several positions over the liver.

Circulating levels of cortistatin are correlated with metabolic parameters in patients with newly diagnosed type 2 diabetes mellitus

Cortistatin (CST) is a recently discovered cyclic neuropeptide with multiple bioactive effects. The aim of this study was to investigate the relationship between plasma CST and various metabolic markers in patients with newly diagnosed type 2 diabetes mellitus (T2DM). For this study, 60 patients with newly diagnosed T2DM and 38 age- and gender-matched healthy controls were recruited. Fasting plasma glucose (FPG), serum insulin and hemoglobin A_1c (HbA_1c) levels and a blood lipid profile were obtained with commercially available diagnostic reagents. CST plasma levels were determined using an enzyme immunoassay kit. The results showed that the plasma levels of CST were substantially lower in patients with newly diagnosed T2DM compared with the healthy controls. Plasma CST levels were positively correlated with high-density lipoprotein and negatively related to FPG, serum insulin, the homeostasis model assessment of insulin resistance (HOMA-IR) and HbA_1c in all subjects. Further analysis showed that CST levels were positively correlated with systolic blood pressure and negatively correlated with FPG, serum insulin, HOMA-IR and HbA_1c in patients with newly diagnosed T2DM. Moreover, logistic regression analyses indicated that plasma CST was correlated with newly diagnosed T2DM. In conclusion, patients with newly diagnosed T2DM had significantly lower plasma levels of CST than healthy controls, and plasma CST was associated with glucose metabolism and insulin resistance, indicating a potential role of CST in the development of T2DM.

Pituitary protein 7B2 plasma levels in patients with liver disease: Comparisons with other hormones and neuropeptides

7B2, a protein initially isolated from the porcine pituitary gland, has been identified in numerous animal and human tissues, with the highest concentrations in the pituitary and hypothalamus. The 7B2 molecule is highly evolutionarily conserved and is considered to be indispensable in the function and regulation of proprotein convertase 2 (PC2). In the present study, the plasma 7B2 immunoreactivity (7B2-IR) of 18 patients with liver disease was studied. Of these patients, seven (three male and four female), aged 37–67 [54.6±13.5 (SD)] years, suffered from liver cirrhosis of cryptogenic (n=2) or alcoholic (n=5) aetiology. The remaining 11 patients (four male and seven female), aged 22–76 [56.1±17.6 (SD)] years, suffered from miscellaneous liver abnormalities. The clinical diagnosis was confirmed in the majority of patients by the histological examination of a percutaneous liver biopsy or by appropriate radiological investigations. Plasma bilirubin, alkaline phosphatase, aspartate aminotransferase, albumin, prothrombin time, electrolytes, urea and creatinine were measured. The plasma 7B2-IR levels were estimated using a sensitive radioimmunoassay (RIA), and the elution position of 7B2-IR was verified by gel chromatography. The mean plasma 7B2-IR concentration in patients with liver disease was 99.44±15.9 pmol/l. In the patients with hepatocellular damage due to metastatic tumours [Ca bronchus, carcinoid (n=6)], the 7B2-IR concentrations were significantly higher [185±36.9 pmol/l, (P<0.05)] compared with the overall subjects with liver damage. The results of the present study demonstrate that 7B2-IR is increased in liver disease, with the highest levels detected in patients with tumourous liver conditions.

Activation of somatostatin 2 receptors in the brain and the periphery induces opposite changes in circulating ghrelin levels: functional implications

Somatostatin is an important modulator of neurotransmission in the central nervous system and acts as a potent inhibitor of hormone and exocrine secretion and regulator of cell proliferation in the periphery. These pleiotropic actions occur through interaction with five G protein-coupled somatostatin receptor subtypes (sst(1) (-) (5)) that are widely expressed in the brain and peripheral organs. The characterization of somatostatin's effects can be investigated by pharmacological or genetic approaches using newly developed selective sst agonists and antagonists and mice lacking specific sst subtypes. Recent evidence points toward a divergent action of somatostatin in the brain and in the periphery to regulate circulating levels of ghrelin, an orexigenic hormone produced by the endocrine X/A-like cells in the rat gastric mucosa. Somatostatin interacts with the sst(2) in the brain to induce an increase in basal ghrelin plasma levels and counteracts the visceral stress-related decrease in circulating ghrelin. By contrast, stimulation of peripheral somatostatin-sst(2) signaling results in the inhibition of basal ghrelin release and mediates the postoperative decrease in circulating ghrelin. The peripheral sst(2)-mediated reduction of plasma ghrelin is likely to involve a paracrine action of D cell-derived somatostatin acting on sst(2) bearing X/A-like ghrelin cells in the gastric mucosa. The other member of the somatostatin family, named cortistatin, in addition to binding to sst(1) (-) (5) also directly interacts with the ghrelin receptor and therefore may simultaneously modulate ghrelin release and actions at target sites bearing ghrelin receptors representing a link between the ghrelin and somatostatin systems.

Somatostatin receptor activation (sst(1) -sst(5) ) differentially influences human retinal pigment epithelium cell viability

PURPOSE

To investigate the differential effects of somatostatin and its receptors (sst(1-5) ) on the viability of cultured human retinal pigment epithelium (hRPE) cells.

METHODS

MTT [3 (4, 5-dimethylthiazol-2yl)-2, 5 diphenyltetrazolium bromide], APO Percentage(TM) and trypan blue assays were performed to assess the mechanisms via which somatostatin (10(-10) -10(-4) m) and selective receptor (sst(1-5) ) ligands (10(-12) -10(-4) m) affect cell viability. The effect of orthovanadate (phosphatase inhibitor, 10(-7) -10(-5) m) on somatostatin's (10(-5) m) actions was examined, and western blot analysis was employed to determine the presence of ssts and phosphotyrosine phosphatase SHP-1 in human RPE cells.

RESULTS

Somatostatin and selective ligands for the five somatostatin receptor subtypes (sst(1-5) ) decreased cell viability in a concentration-dependent manner. The observed decrease in cell number was partly because of apoptosis via the activation of sst(1) and sst(5) receptors. Activation of sst(2) , sst(3) and sst(4) receptors led to inhibition of cell growth that did not involve apoptosis, but rather antiproliferative actions. SHP-1 was found in the human RPE cells and sodium orthovanadate reversed somatostatin's actions.

CONCLUSIONS

This study provides new information regarding the involvement of ssts in human RPE cell viability and suggests that a pathway involving the phosphotyrosine phosphatase may mediate somatostatin's actions.

Isolation of rat Kupffer cells by ex vivo perfusion and their primary culture

AIM: To explore a convenient and effective method for isolation and primary culture of rat Kupffer cells (KCs) in vitro.

METHODS: Ex vivo rat liver tissue was perfused with collagenase IV and diced into small pieces. The diced tissue was digested for 30 min at 37℃and centrifuged to remove hepatocytes. KCs were then separated by means of Percoll density gradient centrifugation and selective adherence. Phagocytosis assay and immunocytochemistry for ED2 were used to identify cells isolated.

RESULTS: The average cell yield per gram of liver before plastic adherence was (2.1 ± 0.3) × 10⁶, and (1.5 ± 0.1) × 10⁶following plastic adherence. The viability of KCs isolated was higher than 92% as determined by trypan blue exclusion. The purity of KCs, identified by immunocytochemistry for ED2, was higher than 90%. Cultured KCs were functionally intact and exhibited irregular shape.

CONCLUSION: The method for isolation and culture of Kupffer cells by ex vivo perfusion is convenient, efficient and stable. Cultured Kupffer cells retain naive biological characteristics and can be used in future studies.

A neurotransmitter system that regulates macrophage pro-inflammatory functions

Neurotransmitters released through peripheral and autonomic nerves play an important role in the signaling from the cells of the nervous system to lymphocytes, macrophages and other cells of the immune system. Macrophages are related to numerous physiological and pathological inflammatory processes since their cytokines play an important role in the defensive responses against invasive microorganisms, atherosclerosis progress, insulin resistance, behavior deviation, hematopoiesis feedback, degenerative chronic diseases and the stimulation of the hypothalamus-hypophysis-adrenal axis. Production of pro-inflammatory cytokines by macrophages is the main target for the modulatory activity of diverse neurotransmitters. In this brief review, we show how some neurotransmitters released by the central or the autonomic nervous systems down-regulate peripheral macrophages' inflammatory functions to balance immune protective mechanisms, although they can also promote the collateral progress of diverse diseases. The possible therapeutic uses of some neurotransmitters and the agonists or antagonist of their respective receptors are included as well.

Endocrine actions of cortistatin: in vivo studies

Cortistatin (CST) shares high structural homology with somatostatin (SST) and binds all SST-receptors (SST-R) subtypes with similar affinity. However, CST actions, tissue expression patterns and regulation do not fully overlap with those of SST, and, moreover, CST, but not SST, also binds and activates proadrenomedullin N-terminal peptide receptor (MrgX2) and shows binding affinity to ghrelin receptor (GHS-R1a). Several studies performed to clarify the endocrine actions of CST, compared with SST, showed that, in humans, CST and SST share the same endocrine actions, i.e. inhibition of GH and insulin secretion in physiological conditions and in acromegaly. A similar inhibitory effect on PRL and ACTH secretion was shown in acromegaly, prolactinoma or in Cushing's disease. This identity of endocrine actions by CST and SST suggests that SST-R activation by CST overrides any other independent action of this peptide mediated by other receptors. Thus, in terms of endocrine actions, CST can well be considered a natural alternative to SST.

Brain-gut communication: cortistatin, somatostatin and ghrelin

Although cortistatin (CST) shares great structural homology with somatostatin (SST) and binds to all SST receptor subtypes with similar affinity, these neurohormones have divergent biological roles, as evidenced by their different patterns of tissue expression and biological actions. Moreover, CST, but not SST, can bind to the proadrenomedullin N-terminal peptide (PAMP) receptor MrgX2 and type 1a growth hormone secretagogue (GHS) receptor (GHSR-1a), also known as the 'ghrelin' receptor. These findings suggest that CST-specific actions could be mediated by the GHSR-1a and CST might represent a link between the ghrelin and the SST systems. Here, we review the data leading to this working hypothesis and discuss the in vitro, in vivo and clinical implications of potential SST-receptor-independent, GHSR-1a-mediated neuroendocrine and metabolic effects of CST.