Dendrobium Officinale Kimura et Migo Ameliorates Insulin Resistance in Rats with Diabetic Nephropathy.

BACKGROUND Emerging evidence suggests the potential of Dendrobium officinale Kimura et Migo (DO) in treating the complications of diabetes mellitus (DM). We evaluated the therapeutic potential of DO in treating diabetic nephropathy (DN) by preventing insulin resistance. MATERIAL AND METHODS A DN model was established. Mean glomerular volume of rats was estimated by the method of Weibel-Gomez. Reverse transcription quantitative polymerase chain reaction (RT-qPCR) was used to determine the expression of mRNAs and we used Western blot assay to determine the expression of proteins. The levels of fasting insulin (FINS) and glucagon (GLU) were measured and we assessed the levels of high-sensitivity C-reactive protein (hs-CRP), tumor necrosis factor-a (TNF-a), and interleukin-6 (IL-6) using the enzyme-linked immunosorbent assay (ELISA). RESULTS Compared with the Normal rats, the levels of urinary glucose, albuminuria, Scr, albuminuria/Scr and BUN, and the expression levels of CaN, TLR-2, TLR-4, MyD88, hs-CRP, TNF-a, and IL-6, the level of FINS, GLU, and HOMAIR were increased in DN, DO 1.0, DO 2.0, and DMBG groups. Compared with the DN rats, in DO 1.0, DO 2.0, and DMBG groups the glomerular volume was smaller, the levels of urinary glucose, albuminuria, Scr, albuminuria/Scr, and BUN, the expression levels of CaN, TLR-2, TLR-4, MyD88, hs-CRP, TNF-a, and IL-6, the level of FINS, GLU, and HOMA-IR were decreased. CONCLUSIONS We found that DO prevents insulin resistance in rats with DN. This may be associated with reduction of TLRs and inflammatory response, which should be further verified by loss of DO effects on DN after treatment of inhibitors of TLRs.

Neprilysin Deficiency Is Associated With Expansion of Islet ß-Cell Mass in High Fat-Fed Mice.

Neprilysin (NEP) is an endopeptidase known to modulate nervous, cardiovascular, and immune systems via inactivation of regulatory peptides. In addition, it may also contribute to impaired glucose homeostasis as observed in type 2 diabetes (T2D). Specifically, we and others have shown that NEP is upregulated under conditions associated with T2D, whereas NEP deficiency and/or inhibition improves glucose homeostasis via enhanced glucose tolerance, insulin sensitivity, and pancreatic ß-cell function. Whether increased ß-cell mass also occurs with lack of NEP activity is unknown. We sought to determine whether NEP deficiency confers beneficial effects on ß- and α-cell mass in a mouse model of impaired glucose homeostasis. Wild-type and NEP-/- mice were fed low- or high-fat diet for 16 weeks, after which pancreatic ß- and α-cell mass were assessed by immunostaining for insulin and glucagon, respectively. Following low-fat feeding, NEP-/- mice exhibited lower ß- and α-cell mass compared with wild-type controls. A high-fat diet had no effect on these parameters in wild-type mice, but in NEP-/- mice, it resulted in the expansion of ß-cell mass. Our findings support a role for NEP in modulating ß-cell mass, making it an attractive T2D drug target that acts via multiple mechanisms to affect glucose homeostasis.

Lineage conversion of mouse fibroblasts to pancreatic α-cells.

α-cells, which synthesize glucagon, also support ß-cell survival and have the capacity to transdifferentiate into ß-cells. However, the role of α-cells in pathological conditions and their putative clinical applications remain elusive due in large part to the lack of mature α-cells. Here, we present a new technique to generate functional α-like cells. α-like cells (iAlpha cells) were generated from mouse fibroblasts by transduction of transcription factors, including Hhex, Foxa3, Gata4, Pdx1 and Pax4, which induce α-cell-specific gene expression and glucagon secretion in response to KCl and Arg stimulation. The cell functions in vivo and in vitro were evaluated. Lineage-specific and functional-related gene expression was tested by realtime PCR, insulin tolerance test (ITT), glucose tolerance test (GTT), Ki67 and glucagon immunohistochemistry analysis were done in iAlpha cells transplanted nude mice. iAlpha cells possess α-cell function in vitro and alter blood glucose levels in vivo. Transplantation of iAlpha cells into nude mice resulted in insulin resistance and increased ß-cell proliferation. Taken together, we present a novel strategy to generate functional α-like cells for the purposes of disease modeling and regenerative medicine.

Comparison of pancreatic beta cells and alpha cells under hyperglycemia: Inverse coupling in pAkt-FoxO1.

Type 2 diabetes manifests beta cell deficiencies and alpha cell expansion which is consistent with relative insulin deficiency and glucagon oversecretion. The effects of hyperglycemia on alpha cells are not as understood in comparison to beta cells. Hyperglycemia increases oxidative stress, which induces Akt activation or FoxO activation, depending on cell type. Several studies independently reported that FoxO1 translocations in alpha cells and beta cells were opposite. We compared the responses of pancreatic alpha cells and beta cells against hyperglycemia. Alpha TC-1 cells and Beta TC-6 cells were incubated with control (5mM Glucose) or high glucose (33mM Glucose) with or without PI3K inhibitor or FoxO1 inhibitor. We assessed PI3K, pAkt and phosphorylated FoxO1 (pFoxO1) in both cell lines. Immunostaining of BrdU and FoxO1 was detected by green fluorescence microscopy and confocal microscopy. Hyperglycemia and H2O2 decreased PI3K and pAKT in beta cells, but increased them in alpha cells. FoxO1 localizations and pFoxO1 expressions between alpha cells and beta cells were opposite. Proliferation of beta cells was decreased, but alpha cell proliferation was increased under hyperglycemia. Antioxidant enzymes including superoxide dismutase (SOD) and catalase were increased in beta cells and they were reversed with FoxO1 inhibitor treatment. Increased proliferation in alpha cells under hyperglycemia was attenuated with PI3K inhibitor. In conclusion, hyperglycemia increased alpha cell proliferation and glucagon contents which are opposite to beta cells. These differences may be related to contrasting PI3K/pAkt changes in both cells and subsequent FoxO1 modulation.

Ellagic acid in Emblica officinalis exerts anti-diabetic activity through the action on ß-cells of pancreas.

PURPOSE: The present study was undertaken to explore the possible anti-diabetic mechanism(s) of Emblica officinalis (EO) and its active constituent, ellagic acid (EA), in vitro and in vivo. METHOD: Neonatal streptozotocin-induced non-obese type 2 diabetic rats were treated with a methanolic extract of EO (250 or 500 mg/kg) for 28 days, and blood glucose, serum insulin, and plasma antioxidant status were measured. Insulin and glucagon immunostaining and morphometry were performed in pancreatic section, and liver TBARS and GSH levels were measured. Additionally, EA was tested for glucose-stimulated insulin secretion and glucose tolerance test. RESULTS: Treatment with EO extract resulted in a significant decrease in the fasting blood glucose in a dose- and time-dependent manner in the diabetic rats. It significantly increased serum insulin in the diabetic rats in a dose-dependent manner. Insulin-to-glucose ratio was also increased by EO treatment. Immunostaining of pancreas showed that EO250 increased ß-cell size, but EO500 increased ß-cells number in diabetic rats. EO significantly increased plasma total antioxidants and liver GSH and decreased liver TBARS. EA stimulated glucose-stimulated insulin secretion from isolated islets and decreased glucose intolerance in diabetic rats. CONCLUSION: Ellagic acid in EO exerts anti-diabetic activity through the action on ß-cells of pancreas that stimulates insulin secretion and decreases glucose intolerance.

Distribution of islet hormones in human adult pancreatic ducts.

BACKGROUND/AIMS: The source of insulin-secreting cells from adult duct system is attractive, but its clinical practice remains poorly understood. Here, we aimed at identifying the distribution of secreted hormone reactive cells in adult ducts. METHODS: Consecutive pancreatic slices from nondiabetic subjects were subjected to immunohistochemistry and immunofluorescence to screen islet hormones (insulin; glucagon, Glu; somatostatin, Som; pancreatic polypeptide, PP) and exocrine biomarkers (cytokeratin 19, CK19; chromogranin A, CgA; amylase). All pancreatic sections were imaged using an optical or confocal microscope. RESULTS: Immunostaining results showed that insulin was expressed in adult ducts, in which the cell count was more than other islet hormone immunoactive cells. CK19-positive cells are mainly distributed in the ducts, whereas CgA-labeled cells are localized in endocrine cells. The duct branches visibly exhibited cell populations that co-expressed islet hormones in exocrine cell populations. CONCLUSIONS: In this report, our findings demonstrate that adult ductal cells that produce insulin may contribute to beta-cell proliferation.

Co-expression of the homologous proteases fibroblast activation protein and dipeptidyl peptidase-IV in the adult human Langerhans islets.

Fibroblast activation protein (FAP, seprase, EC 3.4.21.B28) and dipeptidyl peptidase-IV (DPP-IV, CD26, EC 3.4.14.5) are homologous serine proteases implicated in the modulation of the bioavailability and thus the function of a number of biologically active peptides. In spite of their generally nonoverlapping expression patterns, DPP-IV and FAP are co-expressed and probably co-regulated in certain cell types suggesting that for some biological processes their functional synergy is essential. By an in situ enzymatic activity assay, we show an abundant DPP-IV-like enzymatic activity sensitive to a highly specific DPP-IV inhibitor sitagliptin and corresponding DPP-IV immunoreactivity in the adult human islets of Langerhans. Moreover, the homologous protease FAP was present in the human endocrine pancreas and was co-expressed with DPP-IV. DPP-IV and FAP were found in the pancreatic alpha cells as determined by the co-localization with glucagon immunoreactivity. In summary, we show abundant enzymatic activity of the canonical DPP-IV (CD26) in Langerhans islets in the natural tissue context and demonstrate for the first time the co-expression of FAP and DPP-IV in pancreatic alpha cells in adult humans. Given their ability to proteolytically modify several biologically active peptides, both proteases have the potential to modulate the paracrine signaling in the human Langerhans islets.

Influence of melatonin receptor signalling on parameters involved in blood glucose regulation.

The pineal hormone melatonin is known to influence insulin secretion via the G-protein-coupled receptor isoforms MT1 and MT2. The present study was aimed to further elucide the impact of melatonin on blood glucose regulation. To this end, mouse lines were used, in which one of the two or both melatonin receptors were deleted. In comparison with wild-type mice of the same age (8-12 months old), increased plasma insulin and melatonin levels and decreased blood glucose levels and body weights were detected in the MT1- and double-knockout lines. The elimination of melatonin receptor signalling also altered blood glucose concentrations, body weight and melatonin and insulin levels when comparing wild-type and receptor knockout mice of different ages (6 wk and 8-12 months old); such changes, however, were dependent on the type of receptor deleted. Furthermore, reverse transcription polymerase chain reaction results provided evidence that melatonin receptor deficiency has an impact on transcript levels of pancreatic islet hormones as well as on pancreatic and hepatic glucose transporters (Glut1 and 2). Under stimulated insulin secretion in the presence of melatonin in the rat insulinoma ß-cells INS-1, the Glut1 transcript level was decreased. In conclusion, the present findings demonstrate that melatonin receptor knockout types affect blood glucose levels, body weight, plasma levels of melatonin and insulin, as well as pancreatic hormone and Glut1 expression in significantly different manners.

Label-free detection of insulin and glucagon within human islets of Langerhans using Raman spectroscopy.

Intrahepatic transplantation of donor islets of Langerhans is a promising therapy for patients with type 1 diabetes. It is of critical importance to accurately monitor islet quality before transplantation, which is currently done by standard histological methods that are performed off-line and require extensive sample preparation. As an alternative, we propose Raman spectroscopy which is a non-destructive and label-free technique that allows continuous real-time monitoring of the tissue to study biological changes as they occur. By performing Raman spectroscopic measurements on purified insulin and glucagon, we showed that the 520 cm(-1) band assigned to disulfide bridges in insulin, and the 1552 cm(-1) band assigned to tryptophan in glucagon are mutually exclusive and could therefore be used as indirect markers for the label-free distinction between both hormones. High-resolution hyperspectral Raman imaging for these bands showed the distribution of disulfide bridges and tryptophan at sub-micrometer scale, which correlated with the location of insulin and glucagon as revealed by conventional immunohistochemistry. As a measure for this correlation, quantitative analysis was performed comparing the Raman images with the fluorescence images, resulting in Dice coefficients (ranging between 0 and 1) of 0.36 for insulin and 0.19 for glucagon. Although the use of separate microscope systems with different spatial resolution and the use of indirect Raman markers cause some image mismatch, our findings indicate that Raman bands for disulfide bridges and tryptophan can be used as distinctive markers for the label-free detection of insulin and glucagon in human islets of Langerhans.

Large-molecule quantification: sensitivity and selectivity head-to-head comparison of triple quadrupole with Q-TOF.

BACKGROUND: Bioanalysts are continuously looking for innovative ideas or instruments to increase the sensitivity and selectivity of their assays. Research for better mass spectrometers is becoming crucial with the emerging trend of large-molecule quantification. This study lists the different advantages of high-resolution MS (HRMS) over standard triple quadrupole instruments and proposes basic guidelines on how to use HRMS for large-molecule quantification in a regulated environment. RESULTS: A direct comparison between HRMS and triple quadrupole instruments for the quantification of six different model peptides (desmopressin, calcitonin, enfuvirtide, exenatide, glucagon and somatostatin) was completed. The HRMS instrument, when used specifically for targeted quantification ('quant/quant'), showed equivalent or better sensitivity for all compounds tested. CONCLUSION: This paper demonstrates that the use of a HRMS instrument in a regulated environment is a viable technique for quantification of large molecules. The latter was able to allow flexibility and selectivity to adapt the specificity of each assay with sensitivity comparable to the triple quadrupole instrument.

Immunocytochemical staining for islet amyloid polypeptide in pancreatic endocrine tumors.

AIMS/HYPOTHESIS: Islet amyloid polypeptide is originally identified as the chief constituent of amyloid in insulinomas and type 2 diabetic islets. This study aimed to identify islet amyloid polypeptide by immunocytochemical staining in pancreatic endocrine tumors including 30 cases of insulinomas and non-ß-cell pancreatic endocrine tumors. RESULTS: In normal islets, 62% of islet cells and 52% of insulin cells were granularly positive for insulin and IAPP, respectively, with more insulin positive cells than IAPP positive cells and some densely positive staining for insulin and IAPP in irregularly shaped a nuclear, degenerating islet ß-cells. In pancreatic endocrine tumors, all 10 insulinomas were positive for islet amyloid polypeptide but 2 glucogonomas, 1 somatostatinoma, 6 of 7 pancreatic polypeptidomas, all 7 gastrinomas and all 3 non-functioning pancreatic endocrine tumors were negative for islet amyloid polypeptide whereas one pancreatic polypeptidoma was positive for islet amyloid polypeptide. METHODS: Using commercially available rabbit anti-islet amyloid polypeptide antibody, immunocytochemical staining was performed on 30 cases of pancreatic endocrine tumors, consisting of 10 insulinomas, 2 glucagonomas, 1 somatostatinoma, 7 pancreatic polypeptidomas, 7 gastrinomas and 3 non-functioning pancreatic endocrine tumors. Pancreatic tissues containing pancreatic endocrine tumors were systematically immunostained for insulin, glucagon, somatostatin, pancreatic polypeptide, gastrin and chromogranin A, in addition to islet amyloid polypeptide. When normal pancreatic tissues adjacent to pancreatic endocrine tumors were present, insulin, glucagon, somatostatin and islet amyloid polypeptide positive cells were counted for a total of 20 islets, which were divided into large islets and medium islets for each case. CONCLUSIONS/INTERPRETATIONS: All 10 insulinomas and 1 pancreatic polypeptidoma were granularly positive for islet amyloid polypeptide, suggesting all 10 insulinomas contained enough insulin granules for IAPP whereas only one non-ß-cell pancreatic endocrine tumor was co-localized with islet amyloid polypeptide in their secretary granules.

Simultaneous capillary electrophoresis competitive immunoassay for insulin, glucagon, and islet amyloid polypeptide secretion from mouse islets of Langerhans.

A capillary electrophoresis competitive immunoassay was developed for the simultaneous quantitation of insulin, glucagon, and islet amyloid polypeptide (IAPP) secretion from islets of Langerhans. Separation buffers and conditions were optimized for the resolution of fluorescein isothiocyanate (FITC)-labeled glucagon and IAPP immunoassay reagents, which were excited with the 488 nm line of an Ar(+) laser and detected at 520 nm with a photomultiplier tube (PMT). Cy5-labeled insulin immunoassay reagents were excited by a 635 nm laser diode module and detected at 700 nm with a separate PMT. Optimum resolution was achieved with a 20mM carbonate separation buffer at pH 9.0 using a 20 cm effective separation length with an electric field of 500 V/cm. Limits of detection for insulin, glucagon, and IAPP were 2, 3, and 3 nM, respectively. This method was used to monitor the simultaneous secretion of these peptides from as few as 14 islets after incubation in 4, 11, and 20 mM glucose for 6h. For insulin and IAPP, a statistically significant increase in secretion levels was observed, while glucagon levels were significantly reduced in the 4 and 11 mM glucose conditions. To further demonstrate the utility of the assay, the Ca(2+)-dependent secretion of these peptides was demonstrated which agreed with published reports. The ability to examine the secretion of multiple peptides may allow for the determination of regulation of secretory processes within islets of Langerhans.

Production of functional glucagon-secreting α-cells from human embryonic stem cells.

OBJECTIVE: Differentiation of human embryonic stem (hES) cells to fully developed cell types holds great therapeutic promise. Despite significant progress, the conversion of hES cells to stable, fully differentiated endocrine cells that exhibit physiologically regulated hormone secretion has not yet been achieved. Here we describe an efficient differentiation protocol for the in vitro conversion of hES cells to functional glucagon-producing α- cells. RESEARCH DESIGN AND METHODS: Using a combination of small molecule screening and empirical testing, we developed a six-stage differentiation protocol for creating functional α-cells. An extensive in vitro and in vivo characterization of the differentiated cells was performed. RESULTS: A high rate of synaptophysin expression (>75%) and robust expression of glucagon and the α-cell transcription factor ARX was achieved. After a transient polyhormonal state in which cells coexpress glucagon and insulin, maturation in vitro or in vivo resulted in depletion of insulin and other ß-cell markers with concomitant enrichment of α-cell markers. After transplantation, these cells secreted fully processed, biologically active glucagon in response to physiologic stimuli including prolonged fasting and amino acid challenge. Moreover, glucagon release from transplanted cells was sufficient to reduce demand for pancreatic glucagon, resulting in a significant decrease in pancreatic α-cell mass. CONCLUSIONS: These results indicate that fully differentiated pancreatic endocrine cells can be created via stepwise differentiation of hES cells. These cells may serve as a useful screening tool for the identification of compounds that modulate glucagon secretion as well as those that promote the transdifferentiation of α-cells to ß-cells.

The small intestine of the adult New Hampshire chicken: an immunohistochemical study.

The presence and distribution of glucose-dependent insulinotropic polypeptide or gastric inhibitory polypeptide (GIP), gastric-releasing peptide (GRP) and glucagon immunoreactivity were studied in the small intestine of the New Hampshire chicken using immunohistochemistry. This is the first report of the presence of GIP-immunoreactive (ir) cells in avian small intestine. GIP, GRP and glucagon immunoreactivity was localized in the epithelium of the villi and crypts of the duodenum, jejunum and ileum. In particular, both in the duodenum and in the jejunum immunoreactive endocrine cells to GIP, GRP and glucagon were observed. In the ileum, we noticed GIP-ir and glucagon-ir cells. GRP-ir was found in nerve fibres of all three segments of the small intestine. The distribution of these bioactive agents in the intestinal tract of the chicken suggests that GIP and glucagon may play a role in the enteropancreatic axis in which intestinal peptides modulate pancreas secretion.

Regional distribution and relative frequency of gastrointestinal endocrine cells in the ddN mice: an immunohistochemical study.

The distributions and frequencies of some endocrine cells in the eight portions of the gastrointestinal (GI) tract - fundus, pylorus, duodenum, jejunum, ileum, cecum, colon and rectum of the ddN mouse, were studied with immunohistochemical method using seven types of antisera against chromogranin (Cg) A serotonin, somatostatin, glucagon, gastrin, cholecystokinin (CCK)-8 and human pancreatic polypeptide (hPP). In the GI tract of ddN mice, CgA, serotonin, somatostatin, glucagon, gastrin, CCK-8 immunoreactive (IR) cells were identified with various frequencies, but hPP-IR cells were not observed in this study. Most of IR cells in the intestinal portion were generally spherical or spindle in shape (open type cell) whereas cells showing round in shape (close type cell) were found in the intestinal gland and stomach regions occasionally. They showed the highest frequency in the pylorus or colon. CgA-IR cells were observed from the pylorus to ileum. Serotonin-IR cells were detected throughout the whole GI tract except for the fundus. Somatostatin-IR cells were demonstrated throughout the whole GI tract except for the cecum and colon. Gastrin and CCK-8-IR cells were restricted to the pylorus and duodenum. In addition, a few glucagon-IR cells were restricted to the fundus and rectum. In conclusion, the general distribution patterns and relative frequency of GI endocrine cells of the ddN mouse was similar to that of other strains of mice. However, some strain and/or species-dependent unique distributions and frequencies of endocrine cells were also observed in the present study.

A case of recurrent type 1 diabetes mellitus with insulitis of transplanted pancreas in simultaneous pancreas-kidney transplantation from cardiac death donor.

AIMS/HYPOTHESIS: A 41-year-old woman undergoing simultaneous pancreas-kidney transplantation from an HLA-mismatched cardiac death donor abruptly developed overt hyperglycaemia under standard immunosuppressive therapy at 48 months after transplantation. Unexpectedly, we found insulitis in the transplanted pancreas and characterised the insulitis. METHODS: Pancreas graft biopsies were performed 3 years before and after the development of hyperglycaemia and the specimens were examined histologically. RESULTS: Insulitis was absent in the first biopsy, although oxidative DNA changes revealed by 8-hydroxy-2'-deoxyguanosine (8-OHdG) staining were diffusely present both in islet cells and exocrine cells. No Ki67-positive proliferating cells were seen in the islets. Anti-glutamic acid decarboxylase antibody was undetectable 6 months earlier but increased to 6.3 U/l at the development of hyperglycaemia. The level of anti-insulinoma-associated protein 2 antibody was 18.5 U/l. Insulin secretion was severely suppressed and insulin therapy was resumed. In the second biopsy, although acute allograft rejection was minimal, insulin-positive beta cells were markedly reduced, and glucagon-positive alpha cells predominated. CD3-positive T lymphocytes, CD8-positive cytotoxic T lymphocytes and CD68-positive macrophages infiltrated around and into islets. The infiltrating cells expressed Fas ligand as well as granzyme B. More than 80% of islets were affected by insulitis. 8-OHdG-positive cells were also present in islets and exocrine tissue. The percentage of Ki67-positive cells in total islet cells was 1.5%. There were no TUNEL-positive apoptotic cells in the islet cells. CONCLUSIONS/INTERPRETATION: The histological features of insulitis in transplanted pancreas were consistent with common type 1 diabetes mellitus, but the clinical course of the recurrence appeared to be more rapid.

Analysis of hydroxyl radical-induced oxidation process of glucagon by reversed-phase HPLC and ESI-MS/MS.

Structural modification of a polypeptide hormone, glucagon, by a hydroxyl radical in vitro was investigated by reversed-phase high-performance liquid chromatography (RP-HPLC), and the oxidized site of glucagon was detected by electrospray ionization tandem mass spectrometry (ESI-MS/MS). It was shown that (27)methionine (Met) was oxidized to (27)Met sulfoxide by hydroxyl radical, and the production rate of (27)Met sulfoxide was faster than that by hydrogen peroxide. In addition, production of (27)Met sulfoxide enantiomer was confirmed by RP-HPLC analysis. cAMP production in a HepG2 cell induced by (27)Met sulfoxide glucagon was reduced to approximately 75% as compared with that induced by the native form of glucagon.

Pancreatic endocrine microadenomatosis in patients with von Hippel-Lindau disease: characterization by VHL/HIF pathway proteins expression.

INTRODUCTION: Von Hippel-Lindau (VHL) disease is an inherited syndrome caused by germline mutation in the VHL tumor suppressor gene predisposing to pancreatic endocrine tumors (PET). Whether these tumors derive from preexisting endocrine microadenomatosis as in multiple endocrine neoplasia type 1 (MEN1) is yet unknown. pVHL regulates hypoxia-inducible factor (HIF) that causes transcription activity of target genes like carbonic anhydrase 9 (CA9), vascular endothelial growth factor (VEGF), and cyclin D1. Our aim was to look for overexpression of these molecules to identify precursor endocrine lesions in the pancreas of VHL patients. METHODS: Nontumoral pancreas of 18 VHL patients operated on for PET, was examined for microadenomatosis (70% of VHL patients operated on for PET. These results demonstrate that the pVHL/HIF pathway is involved very early in pancreatic endocrine tumorigenesis in this disease.

Serine protease inhibitor 8 is a novel immunohistochemical marker for neuroendocrine tumors of the pancreas.

OBJECTIVES/METHODS: The intracellular serine protease inhibitor 8 (SERPINB8) is expressed by squamous epithelium, monocytes, and a subset of neuroendocrine cells. Using immunohistochemistry, we now have further investigated the expression of SERPINB8 in normal neuroendocrine cells and its potential use as a marker to identify neuroendocrine tumors of the pancreas. RESULTS: In normal neuroendocrine tissues, strongest SERPINB8 expression was detected in islets of Langerhans of the pancreas. Moderate SERPINB8 expression was observed in neuroendocrine cells of the thyroid, adrenal cortex, colon, and pituitary gland. Fluorescent double staining revealed that in the pancreas, SERPINB8 is specifically expressed by insulin-producing beta cells. In a panel of 20 patients with pancreatic islet cell tumors, however, SERPINB8 was broadly expressed and not restricted to insulinomas. In islet cell tumors, SERPINB8 had a similar diagnostic sensitivity as compared with the widely used neuroendocrine markers chromogranin A and synaptophysin. When SERPINB8 was combined with these 2 markers, an even higher diagnostic sensitivity was reached. In contrast, exocrine adenocarcinomas of the pancreas showed no SERPINB8 expression. CONCLUSIONS: The SERPINB8 is expressed in normal neuroendocrine cells of several organs as well as in neuroendocrine tumors of the pancreas, where it can be used as an additional diagnostic immunohistochemical marker.