Evidence for Presence and Functional Effects of Kv1.1 Channels in β-Cells: General Survey and Results from mceph/mceph Mice

BACKGROUND:Voltage-dependent K(+) channels (Kv) mediate repolarisation of β-cell action potentials, and thereby abrogate insulin secretion. The role of the Kv1.1 K(+) channel in this process is however unclear. We tested for presence of Kv1.1 in different species and tested for a functional role of Kv1.1 by assessing pancreatic islet function in BALB/cByJ (wild-type) and megencephaly (mceph/mceph) mice, the latter having a deletion in the Kv1.1 gene. METHODOLOGY/PRINCIPAL FINDINGS:Kv1.1 expression was detected in islets from wild-type mice, SD rats and humans, and expression of truncated Kv1.1 was detected in mceph/mceph islets. Full-length Kv1.1 protein was present in islets from wild-type mice, but, as expected, not in those from mceph/mceph mice. Kv1.1 expression was localized to the β-cell population and also to α- and δ-cells, with evidence of over-expression of truncated Kv1.1 in mceph/mceph islets. Blood glucose, insulin content, and islet morphology were normal in mceph/mceph mice, but glucose-induced insulin release from batch-incubated islets was (moderately) higher than that from wild-type islets. Reciprocal blocking of Kv1.1 by dendrotoxin-K increased insulin secretion from wild-type but not mceph/mceph islets. Glucose-induced action potential duration, as well as firing frequency, was increased in mceph/mceph mouse β-cells. This duration effect on action potential in β-cells from mceph/mceph mice was mimicked by dendrotoxin-K in β-cells from wild-type mice. Observations concerning the effects of both the mceph mutation, and of dendrotoxin-K, on glucose-induced insulin release were confirmed in pancreatic islets from Kv1.1 null mice. CONCLUSION/SIGNIFICANCE:Kv1.1 channels are expressed in the β-cells of several species, and these channels can influence glucose-stimulated insulin release

Expression of Cocaine- and Amphetamine-Regulated Transcript Is Associated with Worse Survival in Small Bowel Carcinoid Tumors

Purpose: Cocaine-and amphetamine-regulated transcript (CART) peptide exerts several regulatory functions acting both as neurotransmitter and hormone. We recently showed that CART is expressed in various neuroendocrine tumors, including small bowel carcinoids. The main objective of the present study was to examine whether CART expression is associated with survival in patients with small bowel carcinoid. Secondary aims were to assess whether CART expression is associated with other tumor characteristics or clinical symptoms. Experimental Design: Specimens from 97 patients with small bowel carcinoids were examined for CART expression using immunohistochemistry. A CART score was introduced on the basis of the proportion of CART immunoreactive cells. On inclusion, specimens were examined by routine histopathologic methods and detailed clinical patient data were retrieved. The effect of CART on cell viability was assessed in vitro using two intestinal tumor cell lines. Results: Expression of CART (P = 0.011) and increasing CART score (P = 0.033) were associated with worse disease-specific survival. Adjusting for age, disease stage, and tumor grade in multivariable analysis, CART expression was still associated with worse survival [Low CART HR, 5.47; 95% confidence interval (CI), 0.71-42.46; and High CART HR, 9.44; 95% CI, 1.14-78.14]. CART expression was not associated with patient age, disease stage, tumor grade, or any presenting symptom. Supporting our clinical data, we found that CART promoted tumor cell viability in vitro in two different tumor cell lines. Conclusion: Expression of CART in small bowel carcinoid tumors is associated with worse survival. Clin Cancer Res; 18(13); 3668-76. (C)2012 AACR

Malignant presacral ghrelinoma with long-standing hyperghrelinaemia

Background. A 57-year old man with low-back pain was found to have a 3 x 3 x 3 cm presacral neuroendocrine tumour (NET) with widespread metastases, mainly to the skeleton. His neoplastic disease responded well to peptide receptor radionuclide therapy (PRRT) with the radiotagged somatostatin agonist Lu-177-DOTATATE. During almost 10 years he was fit for a normal life. He succumbed to an intraspinal dissemination. Procedures. A resection of the rectum, with a non-radical excision of the adjacent NET, was made. In addition to computerized tomography (CT), receptor positron emission tomography (PET) with Ga-68-labelled somatostatin analogues was used. Observations. The NET showed the growth pattern and immunoprofile of a G2 carcinoid. A majority cell population displayed immunoreactivity to ghrelin, exceptionally with co-immunoreactivity to motilin. Somatostatin receptor scintigraphy and Ga-68-DOTATATE PET-CT demonstrated uptake in the metastatic lesions. High serum concentrations of total (desacyl-)ghrelin were found with fluctuations reflecting the severity of the symptoms. In contrast, the concentrations of active (acyl-)ghrelin were consistently low, as were those of chromogranin A (CgA).Conclusions. Neoplastically transformed ghrelin cells can release large amounts of desacyl-ghrelin, evoking an array of non-specific clinical symptoms. Despite an early dissemination to the skeleton, a ghrelinoma can be compatible with longevity after adequate radiotherapy

Histidine decarboxylase and urinary methylimidazoleacetic acid in gastric neuroendocrine cells and tumours

AIM: To study histidine decarboxylase (HDC) expression in normal and neoplastic gastric neuroendocrine cells in relationship to the main histamine metabolite. METHODS: Control tissues from fundus (n = 3) and corpus (n = 3) mucosa of six patients undergoing operations for gastric adenocarcinoma, biopsy and/or gastric surgical specimens from 64 patients with primary gastric neuroendocrine tumours (GNETs), as well as metastases from 22 of these patients, were investigated using conventional immunohistochemistry and double immunofluorescence with commercial antibodies vs vesicular monoamine transporter 2 (VMAT-2), HDC and ghrelin. The urinary excretion of the main histamine metabolite methylimidazoleacetic acid (U-MeImAA) was determined using high-performance liquid chromatography in 27 of the 64 patients. RESULTS: In the gastric mucosa of the control tissues, co-localization studies identified neuroendocrine cells that showed immunoreactivity only to VMAT-2 and others with reactivity only to HDC. A third cell population co-expressed both antigens. There was no co-expression of HDC and ghrelin. Similar results were obtained in the foci of neuroendocrine cell hyperplasia associated with chronic atrophic gastritis type A and also in the tumours. The relative incidence of the three aforementioned markers varied in the tumours that were examined using conventional immunohistochemistry. All of these GNETs revealed both VMAT-2 and HDC immunoreactivity, and their metastases showed an immunohistochemical pattern and frequency similar to that of their primary tumours. In four patients, increased U-MeImAA excretion was detected, but only two of the patients exhibited related endocrine symptoms. CONCLUSION: Human enterochromaffin-like cells appear to partially co-express VMAT-2 and HDC. Co-expression of VMAT-2 and HDC might be required for increased histamine production in patients with GNETs.Funding Agencies|Selander Foundation; Foundation for Clinical Cancer Research in Jonkoping</p

Histidine decarboxylase and urinary methylimidazoleacetic acid in gastric neuroendocrine cells and tumours

AIM: To study histidine decarboxylase (HDC) expression in normal and neoplastic gastric neuroendocrine cells in relationship to the main histamine metabolite. METHODS: Control tissues from fundus (n = 3) and corpus (n = 3) mucosa of six patients undergoing operations for gastric adenocarcinoma, biopsy and/or gastric surgical specimens from 64 patients with primary gastric neuroendocrine tumours (GNETs), as well as metastases from 22 of these patients, were investigated using conventional immunohistochemistry and double immunofluorescence with commercial antibodies vs vesicular monoamine transporter 2 (VMAT-2), HDC and ghrelin. The urinary excretion of the main histamine metabolite methylimidazoleacetic acid (U-MeImAA) was determined using high-performance liquid chromatography in 27 of the 64 patients. RESULTS: In the gastric mucosa of the control tissues, co-localization studies identified neuroendocrine cells that showed immunoreactivity only to VMAT-2 and others with reactivity only to HDC. A third cell population co-expressed both antigens. There was no co-expression of HDC and ghrelin. Similar results were obtained in the foci of neuroendocrine cell hyperplasia associated with chronic atrophic gastritis type A and also in the tumours. The relative incidence of the three aforementioned markers varied in the tumours that were examined using conventional immunohistochemistry. All of these GNETs revealed both VMAT-2 and HDC immunoreactivity, and their metastases showed an immunohistochemical pattern and frequency similar to that of their primary tumours. In four patients, increased U-MeImAA excretion was detected, but only two of the patients exhibited related endocrine symptoms. CONCLUSION: Human enterochromaffin-like cells appear to partially co-express VMAT-2 and HDC. Co-expression of VMAT-2 and HDC might be required for increased histamine production in patients with GNETs.Funding Agencies|Selander Foundation; Foundation for Clinical Cancer Research in Jonkoping</p