Effects of a long-acting secretin peptide analog alone and in combination with a GLP-1R agonist in a diet-induced obesity mouse model.

OBJECTIVE: Obesity is a major global health problem which can be targeted with new mechanistic diverse pharmacological interventions. Here we evaluate a new long-acting secretin receptor agonist as a potential treatment for obesity. METHODS: BI-3434 was designed as a secretin analog with stabilized peptide backbone and attached fatty acid-based half-life extension group. The peptide was evaluated in vitro for its ability to stimulate cAMP accumulation in a cell line stably expressing recombinant secretin receptor. On the functional level, stimulation of lipolysis in primary adipocytes after treatment with BI-3434 was determined. The ability of BI-3434 to activate secretin receptor in vivo was assessed in a cAMP reporter CRE-Luc mouse model. Furthermore, a diet-induced obesity mouse model was used to test the effects of BI-3434 on body weight and food intake following repeated daily subcutaneous administration alone and in combination with a GLP-1R agonist. RESULTS: BI-3434 potently activated human secretin receptor. However, lipolysis was only weakly induced in primary murine adipocytes. BI-3434 had an extended half-life compared to endogenous secretin and activated target tissues like pancreas, adipose tissue, and stomach in vivo. BI-3434 did not lower food intake in lean or diet-induced obese mice, but it increased energy expenditure after daily administration. This led to a loss of fat mass, which did not translate in a significant effect on body weight. However, treatment in combination with a GLP-1R agonist led to a synergistic effect on body weight loss. CONCLUSIONS: BI-3434 is a highly potent and selective agonist of secretin receptor with an extended pharmacokinetic (PK) profile. Increased energy expenditure after daily treatment with BI-3434 suggests that secretin receptor is involved in metabolic regulation and energy homeostasis. Targeting secretin receptor alone may not be an efficient anti-obesity treatment, but could be combined with anorectic principles like GLP-1R agonists.

Prolonged administration of a secretin receptor antagonist inhibits biliary senescence and liver fibrosis in Mdr2 -/- mice.

BACKGROUND AND AIMS: Secretin (SCT) and secretin receptor (SR, only expressed on cholangiocytes within the liver) play key roles in modulating liver phenotypes. Forkhead box A2 (FoxA2) is required for normal bile duct homeostasis by preventing the excess of cholangiocyte proliferation. Short-term administration of the SR antagonist (SCT 5-27) decreased ductular reaction and liver fibrosis in bile duct ligated and Mdr2 -/- [primary sclerosing cholangitis (PSC), model] mice. We aimed to evaluate the effectiveness and risks of long-term SCT 5-27 treatment in Mdr2 -/- mice. APPROACH AND RESULTS: In vivo studies were performed in male wild-type and Mdr2 -/- mice treated with saline or SCT 5-27 for 3 months and human samples from late-stage PSC patients and healthy controls. Compared with controls, biliary SCT/SR expression and SCT serum levels increased in Mdr2 -/- mice and late-stage PSC patients. There was a significant increase in ductular reaction, biliary senescence, liver inflammation, angiogenesis, fibrosis, biliary expression of TGF-ß1/VEGF-A axis, and biliary phosphorylation of protein kinase A and ERK1/2 in Mdr2 -/- mice. The biliary expression of miR-125b and FoxA2 decreased in Mdr2 -/- compared with wild-type mice, which was reversed by long-term SCT 5-27 treatment. In vitro , SCT 5-27 treatment of a human biliary PSC cell line decreased proliferation and senescence and SR/TGF-ß1/VEGF-A axis but increased the expression of miR-125b and FoxA2. Downregulation of FoxA2 prevented SCT 5-27-induced reduction in biliary damage, whereas overexpression of FoxA2 reduced proliferation and senescence in the human PSC cell line. CONCLUSIONS: Modulating the SCT/SR axis may be critical for managing PSC.

Secretin as a Satiation Whisperer With the Potential to Turn into an Obesity-curbing Knight.

The obesity pandemic requires effective preventative and therapeutic intervention strategies. Successful and sustained obesity treatment is currently limited to bariatric surgery. Modulating the release of gut hormones is considered promising to mimic bariatric surgery with its beneficial effects on food intake, body weight, and blood glucose levels. The gut peptide secretin was the first molecule to be termed a hormone; nevertheless, only recently has it been established as a legitimate anorexigenic peptide. In contrast to gut hormones that crosstalk with the brain either directly or by afferent neuronal projections, secretin mediates meal-associated brown fat thermogenesis to induce meal termination, thereby qualifying this physiological mechanism as an attractive, peripheral target for the treatment of obesity. In this perspective, it is of pivotal interest to deepen our as yet superficial knowledge on the physiological roles of secretin as well as meal-associated thermogenesis in energy balance and body weight regulation. Of note, the emerging differences between meal-associated thermogenesis and cold-induced thermogenesis must be taken into account. In fact, there is no correlation between these 2 entities. In addition, the investigation of potential effects of secretin in hedonic-driven food intake, bariatric surgery and chronic treatment using suitable application strategies to overcome pharmacokinetic limitations will provide further insight into its potential to influence energy balance. The aim of this article is to review the facts on secretin's metabolic effects, address prevailing gaps in our knowledge, and provide an overview on the opportunities and challenges of the therapeutic potential of secretin in body weight control.

Secretin-Enhanced MRCP: How and Why-AJR Expert Panel Narrative Review.

Secretin-enhanced MRCP (S-MRCP) has advantages over standard MRCP for imaging of the pancreaticobiliary tree. Through the use of secretin to induce fluid production from the pancreas and leveraging of fluid-sensitive MRCP sequences, S-MRCP facilitates visualization of ductal anatomy, and the findings provide insight into pancreatic function, allowing radiologists to provide additional insight into a range of pancreatic conditions. This narrative review provides detailed information on the practical implementation of S-MRCP, including patient preparation, logistics of secretin administration, and dynamic secretin-enhanced MRCP acquisition. Also discussed are radiologists' interpretation and reporting of S-MRCP examinations, including assessments of dynamic compliance of the main pancreatic duct and of duodenal fluid volume. Established indications for S-MRCP include pancreas divisum, anomalous pancreaticobiliary junction, Santorinicele, Wirsungocele, chronic pancreatitis, main pancreatic duct stenosis, and assessment of complex postoperative anatomy. Equivocal or controversial indications are also described along with an approach to such indications. These indications include acute and recurrent acute pancreatitis, pancreatic exocrine function, sphincter of Oddi dysfunction, and pancreatic neoplasms.

Impaired Renal HCO3- Excretion in Cystic Fibrosis.

BACKGROUND: Patients with cystic fibrosis (CF) do not respond with increased urinary HCO3- excretion after stimulation with secretin and often present with metabolic alkalosis. METHODS: By combining RT-PCR, immunohistochemistry, isolated tubule perfusion, in vitro cell studies, and in vivo studies in different mouse models, we elucidated the mechanism of secretin-induced urinary HCO3- excretion. For CF patients and CF mice, we developed a HCO3- drinking test to assess the role of the cystic fibrosis transmembrane conductance regulator (CFTR) in urinary HCO3-excretion and applied it in the patients before and after treatment with the novel CFTR modulator drug, lumacaftor-ivacaftor. RESULTS: ß-Intercalated cells express basolateral secretin receptors and apical CFTR and pendrin. In vivo application of secretin induced a marked urinary alkalization, an effect absent in mice lacking pendrin or CFTR. In perfused cortical collecting ducts, secretin stimulated pendrin-dependent Cl-/HCO3- exchange. In collecting ducts in CFTR knockout mice, baseline pendrin activity was significantly lower and not responsive to secretin. Notably, patients with CF (F508del/F508del) and CF mice showed a greatly attenuated or absent urinary HCO3--excreting ability. In patients, treatment with the CFTR modulator drug lumacaftor-ivacaftor increased the renal ability to excrete HCO3-. CONCLUSIONS: These results define the mechanism of secretin-induced urinary HCO3- excretion, explain metabolic alkalosis in patients with CF, and suggest feasibility of an in vivo human CF urine test to validate drug efficacy.

MRI assessed pancreatic morphology and exocrine function are associated with disease burden in chronic pancreatitis.

BACKGROUND AND AIM: The aim of this study was to explore the association between morphological and functional secretin-stimulated MRI parameters with hospitalization, quality of life (QOL), and pain in patients with chronic pancreatitis (CP). PATIENTS AND METHODS: This prospective cohort study included 82 patients with CP. Data were obtained from clinical information, QOL, and pain as assessed by questionnaires (The European Organization for Research and Treatment of Cancer Quality of Life Questionnaire and modified Brief Pain Inventory short form). Secretin-stimulated MRI morphological parameters included pancreatic gland volume, main pancreatic duct diameter, the modified Cambridge Classification of Duct Abnormality, apparent diffusion coefficient, fat signal fraction, and the pancreatic secretion volume as a functional parameter. The primary outcomes were time to first hospitalization related to the CP, as well as annual hospitalization frequency and duration. The secondary outcomes were pain severity, QOL, and pain interference scores. RESULTS: A main pancreatic duct diameter below 5 mm was associated with reduced time to first hospitalization (hazard ratio=2.06; 95% confidence interval: 1.02-4.17; P=0.043). Pancreatic secretion volume was correlated with QOL (r=0.31; P=0.0072) and pain interference score (r=-0.27; P=0.032), and fecal elastase was also correlated with QOL (r=0.28; P=0.017). However, functional and morphological findings were not related to pain intensity. CONCLUSION: Advanced pancreatic imaging techniques may be a highly sensitive tool for prognostication and monitoring of disease activity and its consequences.

Reconstruction of the mouse extrahepatic biliary tree using primary human extrahepatic cholangiocyte organoids.

The treatment of common bile duct (CBD) disorders, such as biliary atresia or ischemic strictures, is restricted by the lack of biliary tissue from healthy donors suitable for surgical reconstruction. Here we report a new method for the isolation and propagation of human cholangiocytes from the extrahepatic biliary tree in the form of extrahepatic cholangiocyte organoids (ECOs) for regenerative medicine applications. The resulting ECOs closely resemble primary cholangiocytes in terms of their transcriptomic profile and functional properties. We explore the regenerative potential of these organoids in vivo and demonstrate that ECOs self-organize into bile duct-like tubes expressing biliary markers following transplantation under the kidney capsule of immunocompromised mice. In addition, when seeded on biodegradable scaffolds, ECOs form tissue-like structures retaining biliary characteristics. The resulting bioengineered tissue can reconstruct the gallbladder wall and repair the biliary epithelium following transplantation into a mouse model of injury. Furthermore, bioengineered artificial ducts can replace the native CBD, with no evidence of cholestasis or occlusion of the lumen. In conclusion, ECOs can successfully reconstruct the biliary tree, providing proof of principle for organ regeneration using human primary cholangiocytes expanded in vitro.

Secretin-stimulated MRI assessment of exocrine pancreatic function in patients with cystic fibrosis and healthy controls.

PURPOSE: Secretin-stimulated magnetic resonance imaging (s-MRI) and pancreatic diffusion weighted imaging (DWI) are novel non-invasive imaging techniques for assessment of exocrine pancreatic insufficiency (EPI). The aim was to validate s-MRI assessed pancreatic secreted volume using novel semi-automatic quantification software, and to assess the ability of s-MRI with DWI to diagnose EPI in patients with cystic fibrosis (CF). METHODS: s-MRI and DWI was performed in 19 patients with CF (median age 21 years; range 16-56; eight men) and in 10 healthy controls (HC) (median age 46 years; range 20-65; four men). Sequential coronal T2-weighted images covering the duodenum and small bowel and axial DWI were acquired before and 1, 5, 9, and 13 min after secretin stimulation. A short endoscopic secretin test was used as reference method for EPI. RESULTS: CF patients with EPI had lower apparent diffusion coefficient before secretin in the pancreatic head (P < 0.001) and lower secreted bowel fluid volumes (P = 0.035) compared to HC and CF patients without EPI. ROC curve analyses identified that secreted fluid volume after 13 min yielded the highest diagnostic accuracy for diagnosing EPI (AUC 0.93; 95% CI [0.80-1.00]). CONCLUSION: Pancreatic s-MRI is useful for the assessment of exocrine pancreatic function with high diagnostic accuracy for the diagnosis of EPI in CF.

Structure-Activity Relationship Studies of N- and C-Terminally Modified Secretin Analogs for the Human Secretin Receptor.

The pleiotropic role of human secretin (hSCT) validates its potential use as a therapeutic agent. Nevertheless, the structure of secretin in complex with its receptor is necessary to develop a suitable therapeutic agent. Therefore, in an effort to design a three-dimensional virtual homology model and identify a peptide agonist and/or antagonist for the human secretin receptor (hSR), the significance of the primary sequence of secretin peptides in allosteric binding and activation was elucidated using virtual docking, FRET competitive binding and assessment of the cAMP response. Secretin analogs containing various N- or C-terminal modifications were prepared based on previous findings of the role of these domains in receptor binding and activation. These analogs exhibited very low or no binding affinity in a virtual model, and were found to neither exhibit in vitro binding nor agonistic or antagonistic properties. A parallel analysis of the analogs in the virtual model and in vitro studies revealed instability of these peptide analogs to bind and activate the receptor.

[Latest advances in chronic pancreatitis]. / Últimos avances en pancreatitis crónica.

This article summarizes some of the recent and clinically relevant advances in chronic pancreatitis. These advances mainly concern the early diagnosis of the disease, the treatment of symptoms and complications, mainly pain and pancreatic exocrine insufficiency, and the diagnosis and therapy of autoimmune pancreatitis. The multimodal dynamic endoscopic ultrasound-guided secretin-stimulated evaluation of the pancreas provides relevant morphological and functional information for the diagnosis of chronic pancreatitis at early stages. Extracorporeal shock wave lithotripsy in patients with calcifying pancreatitis and endoscopic pancreatic stent placement are effective alternatives for pain therapy in patients with chronic pancreatitis. Presence of pancreatic exocrine insufficiency in patients with chronic pancreatitis is associated with a significantly increase of mortality rate. Despite that, pancreatic enzyme replacement therapy is not prescribed in the majority of patients with pancreatic exocrine insufficiency, or it is prescribed at a low dose. The newly developed and commercialized needles for endoscopic ultrasound-guided pancreatic biopsy are effective in retrieving appropriate tissue samples for the histological diagnosis of autoimmune pancreatitis. Maintenance therapy with azathioprine is effective and safe to prevent relapses in patients with autoimmune pancreatitis.

Ischemia reperfusion of the hepatic artery induces the functional damage of large bile ducts by changes in the expression of angiogenic factors.

Liver transplantation and cholangiocarcinoma induce biliary dysfunction following ischemia reperfusion (IR). The function of the intrahepatic biliary tree is regulated by both autocrine and paracrine factors. The aim of the study was to demonstrate that IR-induced damage of cholangiocytes is associated with altered expression of biliary angiogenic factors. Normal and bile duct ligation rats underwent 24-h sham or hepatic reperfusion after 30 min of transient occlusion of the hepatic artery (HAIR) or portal vein (PVIR) before collecting liver blocks and cholangiocyte RNA or protein. We evaluated liver histology, biliary apoptosis, proliferation and expression of VEGF-A/C, VEGFR-2/3, Ang-1/2, and Tie-1/2 in liver sections and isolated small and large cholangiocytes. Normal rat intrahepatic cholangiocyte cultures (NRICC) were maintained under standard conditions in normoxic or under a hypoxic atmosphere for 4 h and then transferred to normal conditions for selected times. Subsequently, we measured changes in biliary proliferation and apoptosis and the expression of VEGF-A/C and VEGFR-2/3. In vivo, HAIR (but not PVIR) induced damage of large bile ducts and decreased proliferation and secretin-stimulated cAMP levels. HAIR-induced damage of large bile ducts was associated with increased expression of VEGF-A/C, VEGFR-2/3, Ang-1/2, and Tie-1/2. In vitro, under hypoxic conditions, there was increased apoptosis and reduced proliferation of NRICC concomitant with enhanced expression of VEGF-A/C and VEGFR-2/3. The functional damage of large bile ducts by HAIR and hypoxia is associated with increased expression of angiogenic factors in small cholangiocytes, presumably due to a compensatory mechanism in response to biliary damage.

Development and functional characterization of extrahepatic cholangiocyte lines from normal rats.

BACKGROUND: Since limited in vitro tools exist for evaluating the pathophysiology of extrahepatic bile ducts, we aim to develop an extrahepatic cholangiocyte culture system from normal rats. METHODS: Extrahepatic ducts were dissected from rats, cut in half length-wise and cultured on collagen-I coated plates. Transepithelial electrical resistance was measured. At ∼85% confluence, in extrahepatic cholangiocytes we measured: (i) cell size and distribution, and expression for cytokeratin-19, secretin, secretin receptor and somatostatin receptor type II (SSTR2), cystic fibrosis transmembrane conductance regulator (CFTR), chloride bicarbonate anion exchanger 2 (AE2), vascular endothelial growth factor-A (VEGF-A) and nerve growth factor (NGF); and (ii) the effect of secretin and/or somatostatin on 3'-5'-cyclic adenosine monophosphate (cAMP) levels and proliferation. RESULTS: Cytokeratin-positive extrahepatic cholangiocytes were cultured for 6 passages to form a cell monolayer. Cholangiocytes proliferated to confluence over a 2-week period. The size of extrahepatic cholangiocytes averaged ∼16 µm. Extrahepatic ducts and cholangiocytes were positive for secretin, secretin receptor and SSTR2, CFTR, AE2, VEGF-A and NGF. In extrahepatic cholangiocyte cultures, secretin increased cAMP (prevented by somatostatin), chloride efflux and proliferation. CONCLUSIONS: Extrahepatic cholangiocyte cultures may be important for studying diseases targeting extrahepatic cholangiocytes such as biliary atresia.

Secretin: historical perspective and current status.

This review describes the history of secretin discovery, identification, purification, and structural determination; cloning of secretin and its receptor; synthetic secretin; and highly specific and sensitive radioimmunoassay to define the characteristic physiological role on postprandial pancreatic fluid and bicarbonate secretion, which requires robust potentiation by cholecystokinin. Secretin plays a key role in the negative and positive regulatory mechanisms of exocrine pancreatic secretion. Secretin-releasing peptides were discovered in duodenal acid perfusates of both rat and dog and in canine pancreatic juice. The release and action of secretin and secretin-releasing peptides are in part mediated via vagovagal reflex mechanism involving afferent sensory neurons in proximal intestine and efferent cholinergic neurons in the pancreas. Besides acetylcholine, many neurotransmitters or neuromodulators influence release and action of secretin. The action of secretin in the pancreas depends on insulin, which also suppresses local release of somatostatin and pancreatic polypeptide. Thus, release and action of secretin are mediated via neurohormonal interaction. Clinical conditions with hypersecretinemia and hyposecretinemia are discussed. Synthetic human secretin is used for studies of exocrine pancreatic secretion, secretin-enhanced magnetic resonance cholangiopancreatography combined with exocrine pancreatic function test and diagnosis of gastrinoma syndrome. Therapeutic use of secretin is considered for the relief of severe pain in chronic pancreatitis.

Ion transport in human pancreatic duct epithelium, Capan-1 cells, is regulated by secretin, VIP, acetylcholine, and purinergic receptors.

OBJECTIVES: The objective of the study was to establish a solid model of polarized epithelium for human pancreatic ducts, where electrical parameters could be measured as indicators of ion transport. Further, we aimed to determine functional expression of several receptors, in particular, purinergic receptors, and determine their effects on ion transport. METHODS: Human adenocarcinoma cell line Capan-1 cells were grown on permeable supports and set in Ussing chambers for electrophysiological recordings. Transepithelial voltage (Vte), resistance, and short-circuit currents (Isc) were measured in response to agonists. RESULTS: Secretin, vasoactive intestinal peptide (VIP), acetylcholine, forskolin, ionomycin, adenosine 5'-triphosphate (ATP), uridine 5'-triphosphate (UTP), 3'-O-(4-benzoyl)benzoyl ATP, and adenosine induced lumen negative Vte and Isc. These changes were consistent with anion secretion, as verified in forskolin-stimulated preparations. Extracellular nucleotides, ATP, and UTP, applied from luminal and basolateral sides, caused largest responses: Vte increased up to -5 mV, Isc increased to 20 to 30 µA/cm, and resistance decreased by up to 200 Ω·cm. CONCLUSIONS: Transepithelial transport in human pancreatic duct epithelium, Capan-1 cells, is regulated by secretin, VIP, acetylcholine, adenosine, and purinergic P2 receptors; and this human model has a good potential for studies of physiology and pathophysiology of pancreatic duct ion transport.

Tumor necrosis factor-α promotes bile ductular transdifferentiation of mature rat hepatocytes in vitro.

We previously showed that mature hepatocytes could transdifferentiate into bile ductular cells when placed in a collagen-rich microenvironment. To explore the mechanism of transdifferentiation, we examined whether inflammatory cytokines affected the phenotype of hepatocytes in a three-dimensional culture system. Spheroidal aggregates of rat hepatocytes were embedded within a type I collagen gel matrix and cultured in the presence of various cytokines. In the control, hepatocytes gradually lost expression of albumin, tyrosine aminotransferase, and hepatocyte nuclear factor (HNF)-4α, while aberrantly expressed bile ductular markers, including cytokeratin 19 (CK 19) and spermatogenic immunoglobulin superfamily (SgIGSF). Among the cytokines examined, tumor necrosis factor (TNF)-α inhibited expression of albumin and HNF-4α, both at mRNA and protein levels. After culturing for 2 weeks with TNF-α, hepatocytic spheroids were transformed into extensively branching tubular structures composed of CK 19- and SgIGSF-positive small cuboidal cells. These cells responded to secretin with an increase in secretion and expressed functional bile duct markers. TNF-α also induced the phosphorylation of Jun N-terminal kinase (JNK) and c-Jun, and the morphogenesis was inhibited by SP600125, a specific JNK inhibitor. Furthermore, in chronic rat liver injury induced by CCl(4) , ductular reaction in the centrilobular area demonstrated strong nuclear staining of phosphorylated c-Jun. Our results demonstrate that TNF-α promotes the ductular transdifferentiation of hepatocytes and suggest a role of TNF-α in the pathogenesis of ductular reaction.

Insignificant effect of secretin in rodent models of polycystic kidney and liver disease.

Polycystic kidney (PKD) and liver (PLD) diseases cause significant morbidity and mortality. A large body of evidence indicates that cyclic AMP plays an important role in their pathogenesis. Clinical trials of drugs that reduce cyclic AMP levels in target tissues are now in progress. Secretin may contribute to adenylyl cyclase-dependent urinary concentration and is a major agonist of adenylyl cyclase in cholangiocytes. To investigate the role of secretin in PKD and PLD, we have studied the expression of secretin and the secretin receptor in rodent models orthologous to autosomal recessive (PCK rat) and dominant (Pkd2(-/WS25) mouse) PKD; the effects of exogenous secretin administration to PCK rats, PCK rats lacking circulating vasopressin (PCK(di/di)), and Pkd2(-/WS25) mice; and the impact of a nonfunctional secretin receptor on disease development in Pkd2(-/WS25):SCTR(-/-) double mutants. Renal and hepatic secretin and secretin receptor mRNA and plasma secretin were increased in both models, and secretin receptor protein was increased in the kidneys and liver of Pkd2(-/WS25) mice. However, exogenous secretin administered subcutaneously via osmotic pumps had minimal or negligible effects and the absence of a functional secretin receptor had no influence on the severity of PKD or PLD. Therefore, it is unlikely that by itself secretin plays a significant role in the pathogenesis of PKD and/or PLD.

Secretin receptor promotes the proliferation of endocrine tumor cells via the PI3K/AKT pathway.

The secretin receptor (SR), a G protein-coupled receptor, mediates the effects of the gastrointestinal hormone secretin on digestion and water homeostasis. Recently, high SR expression has been observed in pancreatic ductal adenocarcinomas, cholangiocellular carcinomas, gastrinomas, and bronchopulmonary carcinoid tumors. Receptor overexpression associates with enhanced secretin-mediated signaling, but whether this molecule plays an independent role in tumorigenesis is currently unknown. We recently discovered that pheochromocytomas developing in rats affected by the MENX (multiple endocrine neoplasia-like) syndrome express at very high-level Sctr, encoding SR. We here report that SR are also highly abundant on the membranes of rat adrenal and extraadrenal pheochromocytoma, starting from early stages of tumor development, and are functional. PC12 cells, the best characterized in vitro pheochromocytoma model, also express Sctr at high level. Thus, we used them as model to study the role of SR in neoplastic transformation. Small interfering RNA-mediated knockdown of Sctr decreases PC12 cells proliferation and increases p27 levels. The proproliferative effect of SR in PC12 cells is mediated, in part, by the phosphatidylinositol 3 kinase (PI3K)/serine-threonine protein kinase (AKT) pathway. Transfection of Sctr in Y1 adrenocortical carcinoma cells, expressing low endogenous levels of Sctr, stimulates cell proliferation also, in part, via the PI3K/AKT signaling cascade. Because of the link between SR and PI3K/AKT signaling, tumor cells expressing high levels of the receptor (MENX-associated primary pheochromocytoma and NCI-H727 human bronchopulmonary carcinoid cells) respond well and in a SR-dependent manner to PI3K inhibitors, such as NVP-BEZ235. The association between SR levels and response to PI3K inhibition might open new avenues for the treatment of tumors overexpressing this receptor.

Glucose-mediated control of ghrelin release from primary cultures of gastric mucosal cells.

The peptide hormone ghrelin is released from a distinct group of gastrointestinal cells in response to caloric restriction, whereas its levels fall after eating. The mechanisms by which ghrelin secretion is regulated remain largely unknown. Here, we have used primary cultures of mouse gastric mucosal cells to investigate ghrelin secretion, with an emphasis on the role of glucose. Ghrelin secretion from these cells upon exposure to different d-glucose concentrations, the glucose antimetabolite 2-deoxy-d-glucose, and other potential secretagogues was assessed. The expression profile of proteins involved in glucose transport, metabolism, and utilization within highly enriched pools of mouse ghrelin cells and within cultured ghrelinoma cells was also determined. Ghrelin release negatively correlated with d-glucose concentration. Insulin blocked ghrelin release, but only in a low d-glucose environment. 2-Deoxy-d-glucose prevented the inhibitory effect of high d-glucose exposure on ghrelin release. mRNAs encoding several facilitative glucose transporters, hexokinases, the ATP-sensitive potassium channel subunit Kir6.2, and sulfonylurea type 1 receptor were expressed highly within ghrelin cells, although neither tolbutamide nor diazoxide exerted direct effects on ghrelin secretion. These findings suggest that direct exposure of ghrelin cells to low ambient d-glucose stimulates ghrelin release, whereas high d-glucose and glucose metabolism within ghrelin cells block ghrelin release. Also, low d-glucose sensitizes ghrelin cells to insulin. Various glucose transporters, channels, and enzymes that mediate glucose responsiveness in other cell types may contribute to the ghrelin cell machinery involved in regulating ghrelin secretion under these different glucose environments, although their exact roles in ghrelin release remain uncertain.

Indomethacin antagonizes EP(2) prostanoid receptor activation in LS174T human colon cancer cells.

Increases in the level of cyclooxygenase (COX)-2 and prostanoids such as prostaglandin E(2) (PGE(2)) are considered biomarkers of colorectal cancer. Therefore, non-steroidal anti-inflammatory drugs (NSAID) have been used to reduce the risk of cancer development by reducing prostanoid biosynthesis as COX inhibitors. Along with their activity as COX inhibitors, NSAID have been reported to have other effects. One major NSAID, indomethacin, has been shown to have several effects independent of COX inhibition. To further examine the COX-inhibition-independent effects of indomethacin on colorectal cancer, we used human colon cancer LS174T cells, known to have express little COX-2 and have no detectable PGE(2) production. Here we show that indomethacin has a potential antagonizing effect on human EP(2) receptors. We believe this study raises the reasons to use indomethacin as a lead-compound for setting up another EP(2) receptor-specific antagonist as a relatively cost-efficient strategy for anti-cancer medication in the future.