The aim is to describe a simple and feasible model for the diagnosis of insulinoma. This retrospective study enrolled 37 patients with insulinoma and 44 patients with hypoglycemia not due to insulinoma at the First Affiliated Hospital of Guangxi Medical University. General demographic and clinical characteristics; hemoglobin A1c (HbA1c), insulin and C-peptide concentrations; and the results of 2-h oral glucose tolerance tests (OGTT) were recorded, and a logistic regression model predictive of insulinoma was determined. Body mass index (BMI), HbA1c concentration, 0-h C-peptide concentration, and 0-h and 1-h plasma glucose concentrations (P < 0.05 each) were independently associated with insulinoma. A regression prediction model was established through multivariate logistics regression analysis: Logit p = 7.399+(0.310 × BMI) - (1.851 × HbA1c) - (1.467 × 0-h plasma glucose) + (1.963 × 0-h C-peptide) - (0.612 × 1-h plasma glucose). Using this index to draw a receiver operating characteristic (ROC) curve, the area under the curve (AUC) was found to be 0.957. The optimal cut-off value was - 0.17, which had a sensitivity of 89.2% and a specificity of 86.4%. Logit P ≥ - 0.17 can be used as a diagnostic marker for predicting insulinoma in patients with hypoglycemia.

Insulinomas, neuroendocrine tumors arising from pancreatic beta cells, often show overexpression of the glucagon-like peptide-1 receptor. Therefore, imaging with glucagon-like peptide analog exendin-4 can be used for diagnosis and preoperative localization. This review presents an overview of the development and clinical implementation of exendin-based tracers for nuclear imaging, and the potential use of exendin-4 based tracers for optical imaging and therapeutic applications such as peptide receptor radionuclide therapy or targeted photodynamic therapy.

The islets of Langerhans of the pancreas are the primary endocrine organ responsible for regulating whole body glucose homeostasis. The use of isolated primary islets for research development and training requires organ resection, careful digestion, and isolation of the islets from nonendocrine tissue. This process is time consuming, expensive, and requires substantial expertise. For these reasons, we sought to develop a more rapidly obtainable and consistent model system with characteristic islet morphology and function that could be employed to train personnel and better inform experiments prior to using isolated rodent and human islets. Immortalized β cell lines reflect several aspects of primary β cells, but cell propagation in monolayer cell culture limits their usefulness in several areas of research, which depend on islet morphology and/or functional assessment. In this manuscript, we describe the propagation and characterization of insulinoma pseudo-islets (IPIs) from a rat insulinoma cell line INS832/3. IPIs were generated with an average diameter of 200 μm, consistent with general islet morphology. The rates of oxygen consumption and mitochondrial oxidation-reduction changes in response to glucose and metabolic modulators were similar to isolated rat islets. In addition, the dynamic insulin secretory patterns of IPIs were similar to primary rat islets. Thus, INS832/3-derived IPIs provide a valuable and convenient model for accelerating islet and diabetes research.

A case is reported of a patient who presented with symptomatic hypoglycaemia and who had three pancreatic tumours resected over the ensuing eight years. Immunocytochemistry demonstrated two of these to be insulinomas and the third to be a glucagonoma. In addition metastatic spread of cells positive for glucagon had occurred to a lymph node and multiple nodules staining positively for glucagon were present in the remainder of the pancreas.

Islet cell tumors associated with exocrine elements are rare. An insulinoma was removed from the head of the pancreas of a 33-year-old woman. Ultrastructural and immunohistochemical studies demonstrated that, in addition to the endocrine cells, the tumor had a small population of cells with an acinar cell morphology. Rare cells exhibiting both endocrine and exocrine features (amphicrine cells) were also identified. Another unusual finding in this case was the presence of a large number of intracytoplasmic filamentous inclusions that, even though they have been observed in other neoplasms, have not previously been reported in endocrine tumors of the pancreas. The demonstration of cells with mixed endocrine features supports the concept that both the endocrine and exocrine portions of the components of the pancreas have a common embryologic origin.

Human insulinomas are rare, benign, slowly proliferating, insulin-producing beta cell tumors that provide a molecular "recipe" or "roadmap" for pathways that control human beta cell regeneration. An earlier study revealed abnormal methylation in the imprinted p15.5-p15.4 region of chromosome 11, known to be abnormally methylated in another disorder of expanded beta cell mass and function: the focal variant of congenital hyperinsulinism. Here, we compare deep DNA methylome sequencing on 19 human insulinomas, and five sets of normal beta cells. We find a remarkably consistent, abnormal methylation pattern in insulinomas. The findings suggest that abnormal insulin (INS) promoter methylation and altered transcription factor expression create alternative drivers of INS expression, replacing canonical PDX1-driven beta cell specification with a pathological, looping, distal enhancer-based form of transcriptional regulation. Finally, NFaT transcription factors, rather than the canonical PDX1 enhancer complex, are predicted to drive INS transactivation.

The authors report a case of a woman affected by pancreatic insulinoma who had been suffering from recurrent and misdiagnosed hypoglycemic attacks since 3 years. The total loss of warning neurogenic symptoms replaced by sudden onset of neuroglycopenic symptoms had delayed the proper and early diagnosis because of repeated and useless cardiovascular and neurological investigations. Moreover, it is stressed how difficult is to reveal such neoplasia that, despite the severe symptoms, are usually small in size and often undetectable even with TC scan. Therefore, when clinical pattern is strongly suggestive for insulinoma the use of invasive angiography or other techniques is mandatory and often conclusive. Actually clinical data have the priority in whole diagnostic pathway.

Leptin acts not only on hypothalamic centers to control food intake but has additional functions in peripheral tissues, e.g. inhibition of insulin secretion from pancreatic islets. The leptin receptor (LEPRb) is a class I cytokine receptor that mediates activation of STAT transcription factors. In this study, we characterise the regulation of inflammation-related genes by leptin in insulinoma cells and compare the effect of transcriptional regulation by leptin with that of other cytokines.

Hypoglycemia is increasingly recognized as a complication of bariatric surgery. Typically, hypoglycemia does not appear immediately postoperatively, but rather more than 1 year later, and usually occurs 1-3 h after meals. While rare, insulinoma has been reported after bariatric surgery. Clinical factors which should raise suspicion for insulinoma and the need for comprehensive clinical and biochemical evaluation include hypoglycemia occurring in the fasting state, predating bariatric surgery, and/or worsening immediately postoperatively, and lack of response to conservative therapy. Localization and successful resection of insulinoma can be achieved using novel endoscopic ultrasound and surgical approaches. In summary, hypoglycemia presenting shortly after gastric bypass or with a dominant fasting pattern should be fully evaluated to exclude insulinoma. Additionally, evaluation prior to gastric bypass should include screening for history of hypoglycemia symptoms.

Insulinomas are pancreatic neuroendocrine tumors (pNET), usually benign. Akt/p27kip1 is an intracellular pathway overexpressed in many pNET. There are no data regarding its expression in human insulinomas. We aimed to investigate the expression of Akt and p27kip1 in 24 human insulinomas and to compare them to their expression in normal surrounding islets. Staining was performed on embedded paraffin tissue using polyclonal antibodies against total Akt, p-Akt, p27kip1, and pp27kip1. p-Akt was the predominant form in insulinomas; they presented lower Akt and p-Akt expression than normal islets in 83.3% and 87.5% of tumors, respectively. p27kip1 and pp27kip1 were mainly cytoplasmic in both insulinomas and normal tissue. Cytoplasmic pp27kip1 staining was higher in insulinomas and surprisingly nearly half of the insulinomas also presented nuclear p27kip1 (p = 0.029). No differences were observed in the subcellular localization of p27kip1 and activation of Akt between benign and malignant insulinomas. The low expression of Akt seen in insulinomas might explain the usual benign behavior of this type of pNET. Cytoplasmic p27kip1 in both insulinomas and normal islet cells could reflect the low rate of replication of beta cells, while nuclear p27kip1 would seem to indicate stabilization and nuclear anchoring of the cyclin D-Cdk4 complex. Our data seem to suggest that the Akt pathway is not involved in human insulinoma tumorigenesis.

Glucose stimulation induces expression of the transcription factors Egr-1 and c-Jun as well as phosphorylation of CREB and c-Jun in insulinoma cells. The activator protein-1 (AP-1) binding sites within the c-Jun promoter, the serum response elements (SREs) within the Egr-1 promoter, and cyclic AMP response elements (CREs) function as glucose responsive element. Glucose-induced transcriptional regulation was attenuated by inhibition of L-type Ca(2+) channels, or chelating cytoplasmic Ca(2+). It has been proposed that a rise in nuclear Ca(2+) is required for CREB-mediated transcription of CRE-regulated genes, while elevated cytoplasmic Ca(2+) levels trigger an upregulation of SRE-containing genes. Here, we show that a rise in cytoplasmic Ca(2+) is required for AP-1, CRE, and SRE mediated transcription in glucose-stimulated insulinoma cells. Buffering Ca(2+) in the nucleus or the endoplasmic reticulum had no inhibitory effect upon transcription. However, overexpression of the mitochondrial protein Fis-1 or inhibition of the GTPase Drp-1 impaired glucose-stimulated gene transcription in insulinoma cells, suggesting that the mitochondria play an important role in regulating Ca(2+) mediated gene transcription. The extracellular signal-regulated protein kinase functions as an essential link connecting glucose stimulation, the rise in cytoplasmic Ca(2+), and enhanced transcription in insulinoma cells.

Pancreatic neuroendocrine tumors are rare with an incident rate of 5 cases per million individuals. Tuberous sclerosis complex is an autosomal dominant disease. This disease involves multisystem and occurs in one out of every 6,000-10,000 individuals. In this study, we describe a 47-year-old male known tuberous sclerosis patient with an insulinoma. The tumor was incidentally detected in follow-up imaging for a previous ampulla of Vater tubular adenoma. However, the patient reported symptoms of hypoglycemia. The insulinoma was enucleated successfully. Histopathology revealed a well-differentiated, grade one neuroendocrine tumor measuring around 2 cm in diameter. Seven cases were reported in the literature of tuberous sclerosis-associated insulinoma. The 7 reported cases had different hypoglycemia related symptoms. The reported tumors varied in size and location on the pancreas. This paper details the eighth case worldwide where an insulinoma occurred in a tuberous sclerosis patient.

Kinesin family member 4A (KIF4A), located in the human chromosome band Xq13.1, is aberrantly overexpressed in various cancers. Our study intended to assess the expression of KIF4A in insulinoma and to gain new insights into the molecular mechanisms of this rare disease. First, KIF4A was significantly recruited in pancreatic endocrine cells relative to other cell types. A significant correlation existed between the overexpression of KIF4A and the poor survival of pancreatic adenocarcinoma patients. As revealed by CCK-8, TUNEL assay, flow cytometry, wound healing, Matrigel-transwell, senescence-associated β-galactosidase staining, ELISA, and subcutaneous tumor formation analysis in nude mice, knocking down KIF4A significantly inhibited the growth and metastasis of insulinoma cells in vivo and in vitro. Mechanistically, we observed that KIF4A promoter sequences had reduced H3K27me3 modifications, and decline in enhancer of zeste homolog-2 (EZH2) expression promoted KIF4A expression by reducing the modification, thus leading to insulinoma. Moreover, EZH2 knockdown-induced insulinoma cell proliferation was dependent on KIF4A overexpression since KIF4A knockdown eradicated shEZH2-induced proliferation of insulinoma cells. In summary, KIF4A was identified as a possible therapeutic target for insulinoma.

Specifying the exact localization of insulinoma remains challenging due to the lack of insulinoma-specific imaging methods. Recently, glucagon-like peptide-1 receptor (GLP-1R)-targeted imaging, especially positron emission tomography (PET), has emerged. Although various radiolabeled GLP-1R agonist exendin-4-based probes with chemical modifications for PET imaging have been investigated, an optimal candidate probe and its scanning protocol remain a necessity. Thus, we investigated the utility of a novel exendin-4-based probe conjugated with polyethylene glycol (PEG) for [18F]FB(ePEG12)12-exendin-4 PET imaging for insulinoma detection. We utilized [18F]FB(ePEG12)12-exendin-4 PET/CT to visualize mouse tumor models, which were generated using rat insulinoma cell xenografts. The probe demonstrated high uptake value on the tumor as 37.1 ± 0.4%ID/g, with rapid kidney clearance. Additionally, we used Pdx1-Cre;Trp53R172H;Rbf/f mice, which developed endogenous insulinoma and glucagonoma, since they enabled differential imaging evaluation of our probe in functional pancreatic neuroendocrine neoplasms. In this model, our [18F]FB(ePEG12)12-exendin-4 PET/CT yielded favorable sensitivity and specificity for insulinoma detection. Sensitivity: 30-min post-injection 66.7%, 60-min post-injection 83.3%, combined 100% and specificity: 30-min post-injection 100%, 60-min post-injection 100%, combined 100%, which was corroborated by the results of in vitro time-based analysis of internalized probe accumulation. Accordingly, [18F]FB(ePEG12)12-exendin-4 is a promising PET imaging probe for visualizing insulinoma.

Insulinoma is a rare type tumor and its genetic features remain largely unknown. This study aimed to search for potential key genes and relevant enriched pathways of insulinoma.The gene expression data from GSE73338 were downloaded from Gene Expression Omnibus database. Differentially expressed genes (DEGs) were identified between insulinoma tissues and normal pancreas tissues, followed by pathway enrichment analysis, protein-protein interaction (PPI) network construction, and module analysis. The expressions of candidate key genes were validated by quantitative real-time polymerase chain reaction (RT-PCR) in insulinoma tissues.A total of 1632 DEGs were obtained, including 1117 upregulated genes and 514 downregulated genes. Pathway enrichment results showed that upregulated DEGs were significantly implicated in insulin secretion, and downregulated DEGs were mainly enriched in pancreatic secretion. PPI network analysis revealed 7 hub genes with degrees more than 10, including GCG (glucagon), GCGR (glucagon receptor), PLCB1 (phospholipase C, beta 1), CASR (calcium sensing receptor), F2R (coagulation factor II thrombin receptor), GRM1 (glutamate metabotropic receptor 1), and GRM5 (glutamate metabotropic receptor 5). DEGs involved in the significant modules were enriched in calcium signaling pathway, protein ubiquitination, and platelet degranulation. Quantitative RT-PCR data confirmed that the expression trends of these hub genes were similar to the results of bioinformatic analysis.The present study demonstrated that candidate DEGs and enriched pathways were the potential critical molecule events involved in the development of insulinoma, and these findings were useful for better understanding of insulinoma genesis.

The objective of this study is to evaluate the insulin secretion of mixed aggregates of insulinoma cells (INS-1) and gelatin hydrogel microspheres after their subcutaneous transplantation.

Insulinomas are rare functional pancreatic neuroendocrine tumours. As previous data on the long-term prognosis of insulinoma patients are scarce, we studied the morbidity and mortality in the Finnish insulinoma cohort.

Little information is available regarding triple-phase computed tomography (CT) of canine pancreatic insulinoma. A few case reports with small numbers of cases have indicated that hyper-attenuation in the arterial phase was a common finding on multi-phasic CT in dogs with insulinoma. Our purpose was to clarify the characteristic findings of dogs with insulinoma on triple-phase CT. Nine dogs with insulinoma that underwent triple-phase CT were included in the present study. Attenuation patterns in the arterial phase indicated hypo-attenuation in 4 cases and hyper-attenuation in 2 cases. In the remaining 3 cases, 1 case showed hypo-attenuation and 1 case showed hyper-attenuation in the pancreatic phase, and 1 case presented hyper-attenuation in the later phase. Altogether, 5 cases showed hypo and 4 cases showed hyper-attenuation in at least one phase. The enhancement pattern was homogenous in 7 cases and heterogeneous in 2 cases. Tumor margins were well-defined in 5 cases and ill-defined in 4 cases. Capsule formation was present in 5 cases and absent in 4 cases. In conclusion, it is important to note that hypo-attenuation was as common as hyper-attenuation in dogs with insulinoma in triple-phase CT in at least one phase. Additionally, mass lesions were most conspicuous not only in the arterial phase but in the pancreatic and later phases in some cases. Therefore, it is important to perform triple-phase CT and notice about variable findings for the detection of canine pancreatic insulinoma.

Rat insulinoma INS-1 cells are widely used to study insulin secretory mechanisms. Studies have shown that a population of INS-1 cells are bi-hormonal, co-expressing insulin, and proglucagon proteins. They coined this population as immature cells since they co-secrete proglucagon-derived peptides from the same secretory vesicles similar to that of insulin. Since proglucagon encodes multiple peptides including glucagon, glucagon-like-peptide-1 (GLP-1), GLP-2, oxyntomodulin, and glicentin, their specific expression and secretion are technically challenging. In this study, we aimed to focus on glucagon expression which shares the same amino acid sequence with glicentin and proglucagon. Validation of the anti-glucagon antibody (Abcam) by Western blotting techniques revealed that the antibody detects proglucagon (≈ 20 kDa), glicentin (≈ 9 kDa), and glucagon (≈ 3 kDa) in INS-1 cells and primary islets, all of which were absent in the kidney cell line (HEK293). Using the validated anti-glucagon antibody, we showed by immunofluorescence imaging that a population of INS-1 cells co-express insulin and proglucagon-derived proteins. Furthermore, we found that chronic treatment of INS-1 cells with high-glucose decreases insulin and glucagon content, and also reduces the percentage of bi-hormonal cells. In line with insulin secretion, we found glucagon and glicentin secretion to be induced in a glucose-dependent manner. We conclude that INS-1 cells are a useful model to study glucose-stimulated insulin secretion, but not that of glucagon or glicentin. Our study suggests Western blotting technique as an important tool for researchers to study proglucagon-derived peptides expression and regulation in primary islets in response to various metabolic stimuli.

Uncoupling protein 2 (UCP2) regulates glucose-stimulated insulin secretion in pancreatic beta-cells. UCP2 content, measured by calibrated immunoblot in INS-1E insulinoma cells (a pancreatic beta-cell model) grown in RPMI medium, and INS-1E mitochondria, was 2.0 ng/million cells (7.9 ng/mg mitochondrial protein). UCP2 content was lower in cells incubated without glutamine and higher in cells incubated with 20 mM glucose, and varied from 1.0-4.4 ng/million cells (2.7-14.5 ng/mg mitochondrial protein). This dynamic response to nutrients was achieved by varied expression rates against a background of a very short UCP2 protein half-life of about 1 h.