Pancreatic endocrine function in cystic fibrosis

To characterize pancreatic endocrine secretion and to examine interrelationships among alterations in alpha, beta, and pancreatic polypeptide cell function in patients with cystic fibrosis (CF), we studied 19 patients with exocrine insufficiency (EXO), including 9 receiving insulin therapy (EXO-IT); 10 patients with no exocrine insufficiency (NEXO); and 10 normal control subjects. First-phase C-peptide response to intravenously administered glucose was significantly impaired in CF patients with exocrine insufficiency (EXO-IT = 0.02 +/- 0.01; EXO = 0.11 +/- 0.02; NEXO = 0.25 +/- 0.05; control subjects = 0.30 +/- 0.04 nmol/L). Lowering fasting glucose levels with exogenous insulin administration in EXO-IT did not improve beta cell responsivity to glucose. The C-peptide response to arginine was less impaired (EXO-IT = 0.12 +/- 0.02; EXO = 0.15 +/- 0.02; NEXO = 0.23 +/- 0.06; control subjects = 0.28 +/- 0.04 nmol/L). Alpha cell function, measured as peak glucagon secretion in response to hypoglycemia, was diminished in EXO but not NEXO (EXO-IT = 21 +/- 10; EXO = 62 +/- 19; NEXO = 123 +/- 29; control subjects = 109 +/- 12 ng/L). Despite diminished glucagon response, EXO patients recovered normally from hypoglycemia. Peak pancreatic polypeptide response to hypoglycemia distinguished CF patients with exocrine insufficiency from those without exocrine insufficiency (EXO-IT = 3 +/- 2; EXO = 3 +/- 1; NEXO = 226 +/- 68; control subjects = 273 +/- 100 pmol/L). Thus CF patients with exocrine disease have less alpha, beta, and pancreatic polypeptide cell function than CF patients without exocrine disease. These data suggest either that exocrine disease causes endocrine dysfunction in CF or that a common pathogenic process simultaneously and independently impairs exocrine and endocrine function.

Glucagon, catecholamine and pancreatic polypeptide secretion in type I diabetic recipients of pancreas allografts

Successful pancreas transplantation in type I diabetic patients restores normal fasting glucose levels and biphasic insulin responses to glucose. However, virtually no data from pancreas recipients are available relative to other islet hormonal responses or hormonal counterregulation of hypoglycemia. Consequently, glucose, glucagon, catecholamine, and pancreatic polypeptide responses to insulin-induced hypoglycemia and to stimulation with arginine and secretin were examined in 38 diabetic pancreas recipients, 54 type I diabetic nonrecipients, and 26 nondiabetic normal control subjects. Glucose recovery after insulin-induced hypoglycemia in pancreas recipients was significantly improved. Basal glucagon levels were significantly higher in recipients compared with nonrecipients and normal subjects. Glucagon responses to insulin-induced hypoglycemia were significantly greater in the pancreas recipients compared with nonrecipients and similar to that observed in control subjects. Glucagon responses to intravenous arginine were significantly greater in pancreas recipients than that observed in both the nonrecipients and normal subjects. No differences were observed in epinephrine responses during insulin-induced hypoglycemia. No differences in pancreatic polypeptide responses to hypoglycemia were observed when comparing the recipient and nonrecipient groups, both of which were less than that observed in the control subjects. Our data demonstrate significant improvement in glucose recovery after hypoglycemia which was associated with improved glucagon secretion in type I diabetic recipients of pancreas transplantation.

Roux-en-Y drainage of the pancreatic stump decreases pancreatic fistula after distal pancreatic resection

Clinically relevant fistula after distal pancreatic resection occurs in 5-30% of patients, prolonging recovery and considerably increasing in-hospital stay and costs. We tested whether routine drainage of the pancreatic stump into a Roux-en-Y limb after distal pancreatic resection decreased the incidence of fistula. From October 2001, data of all patients undergoing pancreatic distal resection were entered in a prospective database. From June 2003 after resection, the main pancreatic duct and the pancreatic stump were oversewn, and in addition, anastomosed into a jejunal Roux-en-Y limb by a single-layer suture (n = 23). A drain was placed near the anastomosis, and all patients received octreotide for 5-7 days postoperatively. The volume of the drained fluid was registered daily, and concentration of amylase was measured and recorded every other day. Patient demographics, hospital stay, pancreatic fistula incidence (> or =30 ml amylase-rich fluid/day on/after postoperative day 10), perioperative morbidity, and follow-up after discharge were compared with our initial series of patients (treated October 2001-May 2003) who underwent oversewing only (n = 20). Indications, patient demographics, blood loss, and tolerance of an oral diet were similar. There were four (20%) pancreatic fistulas in the "oversewn" group and none in the anastomosis group (p < 0.05). Nonsurgical morbidity, in-hospital stay, and follow-up were comparable in both groups.

Proapoptotic BH3-only protein Bid is essential for death receptor-induced apoptosis of pancreatic beta-cells

OBJECTIVE: Apoptosis of pancreatic beta-cells is critical in both diabetes development and failure of islet transplantation. The role in these processes of pro- and antiapoptotic Bcl-2 family proteins, which regulate apoptosis by controlling mitochondrial integrity, remains poorly understood. We investigated the role of the BH3-only protein Bid and the multi-BH domain proapoptotic Bax and Bak, as well as prosurvival Bcl-2, in beta-cell apoptosis. RESEARCH DESIGN AND METHODS: We isolated islets from mice lacking Bid, Bax, or Bak and those overexpressing Bcl-2 and exposed them to Fas ligand, tumor necrosis factor (TNF)-alpha, and proinflammatory cytokines or cytotoxic stimuli that activate the mitochondrial apoptotic pathway (staurosporine, etoposide, gamma-radiation, tunicamycin, and thapsigargin). Nuclear fragmentation was measured by flow cytometry. RESULTS: Development and function of islets were not affected by loss of Bid, and Bid-deficient islets were as susceptible as wild-type islets to cytotoxic stimuli that cause apoptosis via the mitochondrial pathway. In contrast, Bid-deficient islets and those overexpressing antiapoptotic Bcl-2 were protected from Fas ligand-induced apoptosis. Bid-deficient islets were also resistant to apoptosis induced by TNF-alpha plus cycloheximide and were partially resistant to proinflammatory cytokine-induced death. Loss of the multi-BH domain proapoptotic Bax or Bak protected islets partially from death receptor-induced apoptosis. CONCLUSIONS: These results demonstrate that Bid is essential for death receptor-induced apoptosis of islets, similar to its demonstrated role in hepatocytes. This indicates that blocking Bid activity may be useful for protection of islets from immune-mediated attack and possibly also in other pathological states in which beta-cells are destroyed.

Expression and hypoxic regulation of the endothelin system in endocrine cells of human and rat pancreatic islets

CONTEXT: The success of pancreatic islet transplantation depends largely on the capacity of the islet graft to survive the initial phase immediately after transplantation until revascularization is completed. Endothelin-1 (ET-1) is a strong vasoconstrictor which has been involved in solid organ graft failure but is also known to be a potent mitogenic/anti-apoptotic factor which could also potentially enhance the survival of the transplanted islets. OBJECTIVE: Characterization of the endothelin system with regard to a potential endothelin agonist/antagonist treatment. DESIGN: Regulated expression of the endothelin system in human and rat pancreatic islets and beta-cell lines was assessed by means of immunohistochemistry, competition binding studies, western blot, RT-PCR, real-time PCR and transplant studies. RESULTS: ET-1, ETA- and ETB-receptor immunoreactivity was identified in the endocrine cells of human and rat pancreatic islets. The corresponding mRNA was detectable in rat beta-cell lines and isolated rat and human pancreatic islets. Competition binding studies on rat islets revealed binding sites for both receptor types. ET-1 stimulated the phosphorylation of mitogen-activated protein kinase, which was prevented by ETA- and ETB-receptor antagonists. After exposure to hypoxia equal to post-transplant environment oxygen tension, mRNA levels of ET-1 and ETB-receptor of human islets were robustly induced whereas ETA-receptor mRNA did not show significant changes. Immunostaining signals for ET-1 and ETA-receptor of transplanted rat islets were markedly decreased when compared to native pancreatic sections. CONCLUSIONS: In pancreatic islets, ET-1 and its receptors are differentially expressed by hypoxia and after transplantation. Our results provide the biological basis for the study of the potential use of endothelin agonists/antagonists to improve islet transplantation outcome.

Tmem27: a cleaved and shed plasma membrane protein that stimulates pancreatic beta cell proliferation

The signals and molecular mechanisms that regulate the replication of terminally differentiated beta cells are unknown. Here, we report the identification and characterization of transmembrane protein 27 (Tmem27, collectrin) in pancreatic beta cells. Expression of Tmem27 is reduced in Tcf1(-/-) mice and is increased in islets of mouse models with hypertrophy of the endocrine pancreas. Tmem27 forms dimers and its extracellular domain is glycosylated, cleaved and shed from the plasma membrane of beta cells. This cleavage process is beta cell specific and does not occur in other cell types. Overexpression of full-length Tmem27, but not the truncated or soluble protein, leads to increased thymidine incorporation, whereas silencing of Tmem27 using RNAi results in a reduction of cell replication. Furthermore, transgenic mice with increased expression of Tmem27 in pancreatic beta cells exhibit increased beta cell mass. Our results identify a pancreatic beta cell transmembrane protein that regulates cell growth of pancreatic islets.

A pancreatic islet-specific microRNA regulates insulin secretion

MicroRNAs (miRNAs) constitute a growing class of non-coding RNAs that are thought to regulate gene expression by translational repression. Several miRNAs in animals exhibit tissue-specific or developmental-stage-specific expression, indicating that they could play important roles in many biological processes. To study the role of miRNAs in pancreatic endocrine cells we cloned and identified a novel, evolutionarily conserved and islet-specific miRNA (miR-375). Here we show that overexpression of miR-375 suppressed glucose-induced insulin secretion, and conversely, inhibition of endogenous miR-375 function enhanced insulin secretion. The mechanism by which secretion is modified by miR-375 is independent of changes in glucose metabolism or intracellular Ca2+-signalling but correlated with a direct effect on insulin exocytosis. Myotrophin (Mtpn) was predicted to be and validated as a target of miR-375. Inhibition of Mtpn by small interfering (si)RNA mimicked the effects of miR-375 on glucose-stimulated insulin secretion and exocytosis. Thus, miR-375 is a regulator of insulin secretion and may thereby constitute a novel pharmacological target for the treatment of diabetes.

Pancreatic stone protein is highly increased during posttraumatic sepsis and activates neutrophil granulocytes

OBJECTIVES: The level of pancreatic stone protein/regenerating protein (PSP/reg), a secretory protein produced in the pancreas, increases dramatically during pancreatic disease. However, after stress (e.g., anesthesia), PSP/reg levels are increased transiently in animals without pancreatic injury. Therefore, we aimed to determine whether PSP/reg is an acute-phase protein after nonpancreatic trauma. PATIENTS: Eighty-three polytraumatic patients without pancreatic damage. MEASUREMENTS AND MAIN RESULTS: We compared serum PSP/reg levels from polytraumatic patients without pancreatic damage with those in healthy controls (n = 38). C-reactive protein, interleukin-6, procalcitonin, and leukocyte numbers were also compared. The expression of CD62L and CD11b on neutrophils after exposure to PSP/reg was analyzed by flow cytometry. Thirty-three patients (39%) developed sepsis, 32 (38%) had local infections, and 18 (21%) had no infections. At admission, PSP/reg serum levels (10.2 [6.2-14.5] ng/mL; median [interquartile range]) were comparable with those in healthy controls (10.4 [7.5-12.3] ng/mL). During hospital stay, PSP/reg levels were elevated significantly in patients with sepsis (146.4 ng/mL) and in patients with infections (111.4 ng/mL) compared with patients without infections (22.8 ng/mL). Furthermore, binding of fluorescein isothiocyanate-labeled recombinant PSP/reg to human neutrophils was demonstrated. Recombinant PSP/reg elicited a dose-dependent shedding of L-selectin (CD62L) and upregulation of beta2-integrin (CD11b) in neutrophils, which indicates that PSP/reg activates neutrophils. CONCLUSIONS: We conclude that PSP/reg is up-regulated in blood after trauma, and the PSP/reg level is related to the severity of inflammation. Furthermore, PSP/reg binds to and activates neutrophils. Therefore, PSP/reg might be an acute-phase protein that could serve as a marker for posttraumatic complications.

VHL inactivation is an important pathway for the development of malignant sporadic pancreatic endocrine tumors

A small subset of familial pancreatic endocrine tumors (PET) arises in patients with von Hippel-Lindau syndrome and these tumors may have an adverse outcome compared to other familial PET. Sporadic PET rarely harbors somatic VHL mutations, but the chromosomal location of the VHL gene is frequently deleted in sporadic PET. A subset of sporadic PET shows active hypoxia signals on mRNA and protein level. To identify the frequency of functionally relevant VHL inactivation in sporadic PET and to examine a possible prognostic significance we correlated epigenetic and genetic VHL alterations with hypoxia signals. VHL mutations were absent in all 37 PETs examined. In 2 out of 35 informative PET (6%) methylation of the VHL promoter region was detected and VHL deletion by fluorescence in situ hybridization was found in 14 out of 79 PET (18%). Hypoxia inducible factor 1alpha (HIF1-alpha), carbonic anhydrase 9 (CA-9), and glucose transporter 1 (GLUT-1) protein was expressed in 19, 27, and 30% of the 152 PETs examined. Protein expression of the HIF1-alpha downstream target CA-9 correlated significantly with the expression of CA-9 RNA (P<0.001), VHL RNA (P<0.05), and VHL deletion (P<0.001) as well as with HIF1-alpha (P<0.005) and GLUT-1 immunohistochemistry (P<0.001). These PET with VHL alterations and signs of hypoxia signalling were characterized by a significantly shortened disease-free survival. We conclude that VHL gene impairment by promoter methylation and VHL deletion in nearly 25% of PET leads to the activation of the HIF-pathway. Our data suggest that VHL inactivation and consecutive hypoxia signals may be a mechanism for the development of sporadic PET with an adverse outcome.

Clinical benefit and quality of life in patients with advanced pancreatic cancer receiving gemcitabine plus capecitabine versus gemcitabine alone: a randomized multicenter phase III clinical trial--SAKK 44/00-CECOG/PAN.1.3.001

To compare clinical benefit response (CBR) and quality of life (QOL) in patients receiving gemcitabine (Gem) plus capecitabine (Cap) versus single-agent Gem for advanced/metastatic pancreatic cancer.

ISL1 expression is not restricted to pancreatic well-differentiated neuroendocrine neoplasms, but is also commonly found in well and poorly differentiated neuroendocrine neoplasms of extrapancreatic origin

The human insulin gene enhancer-binding protein islet-1 (ISL1) is a transcription factor involved in the differentiation of the neuroendocrine pancreatic cells. Recent studies identified ISL1 as a marker for pancreatic well-differentiated neuroendocrine neoplasms. However, little is known about ISL1 expression in pancreatic poorly differentiated and in extrapancreatic well and poorly differentiated neuroendocrine neoplasms. We studied the immunohistochemical expression of ISL1 in 124 neuroendocrine neoplasms. Among pancreatic neuroendocrine neoplasms, 12/13 with poor differentiation were negative, whereas 5/7 with good differentiation but a Ki67 >20% were positive. In extrapancreatic neuroendocrine neoplasms, strong positivity was found in Merkel cell carcinomas (25/25), pulmonary small cell neuroendocrine carcinomas (21/23), medullary thyroid carcinomas (9/9), paragangliomas/pheochromocytomas (6/6), adrenal neuroblastomas (8/8) and head and neck neuroendocrine carcinomas (4/5), whereas no or only weak staining was recorded in pulmonary carcinoids (3/15), olfactory neuroblastomas (1/4) and basaloid head and neck squamous cell carcinomas (0/15). ISL1 stained the neuroendocrine carcinoma component of 5/8 composite carcinomas and also normal neuroendocrine cells in the thyroid, adrenal medulla, stomach and colorectum. Poorly differentiated neuroendocrine neoplasms, regardless of their ISL1 expression, were usually TP53 positive. Our results show the almost ubiquitous expression of ISL1 in extrapancreatic poorly differentiated neuroendocrine neoplasms and neuroblastic malignancies and its common loss in pancreatic poorly differentiated neuroendocrine neoplasms. These findings modify the role of ISL1 as a marker for pancreatic neuroendocrine neoplasms and suggest that ISL1 has a broader involvement in differentiation and growth of neuroendocrine neoplasms than has so far been assumed.