Interactive pediatric emergency checklists to the palm of your hand - How the Pedi Crisis App traveled around the world.

BACKGROUND: Cognitive aids help clinicians manage critical events and have been shown to improve outcomes by providing critical information at the point of care. Critical event guidelines, such as the Society of Pediatric Anesthesia's Critical Events Checklists described in this article, can be distributed globally via interactive smartphone apps. From October 1, 2013 to January 1, 2014, we performed an observational study to determine the global distribution and utilization patterns of the Pedi Crisis cognitive aid app that the Society for Pediatric Anesthesia developed. We analyzed distribution and utilization metrics of individuals using Pedi Crisis on iOS (Apple Inc., Cupertino, CA) devices worldwide. We used Google Analytics software (Google Inc., Mountain View, CA) to monitor users' app activity (eg, screen views, user sessions). METHODS: The primary outcome measurement was the number of user-sessions and geographic locations of Pedi Crisis user sessions. Each user was defined by the use of a unique Apple ID on an iOS device. RESULTS: Google Analytics correlates session activity with geographic location based on local Internet service provider logs. Pedi Crisis had 1 252 active users (both new and returning) and 4 140 sessions across 108 countries during the 3-month study period. Returning users used the app longer and viewed significantly more screens that new users (mean screen views: new users 1.3 [standard deviation +/-1.09, 95% confidence interval 1.22-1.55]; returning users 7.6 [standard deviation +/-4.19, 95% confidence interval 6.73-8.39]P<.01) CONCLUSIONS: Pedi Crisis was used worldwide within days of its release and sustained utilization beyond initial publication. The proliferation of handheld electronic devices provides a unique opportunity for professional societies to improve the worldwide dissemination of guidelines and evidence-based cognitive aids.

PDX-1 interaction and regulation of the Pancreatic Derived Factor (PANDER, FAM3B) promoter.

Pancreatic Derived Factor (PANDER) is a novel cytokine-like protein dominantly expressed within the endocrine pancreas. Our previous study demonstrated that the PANDER promoter was both tissue-specific and glucose-responsive. Surrounding the PANDER transcriptional start site are several putative A- and E-Box elements that may bind to the various pancreatic transcriptional factors of MafA, BETA2/NeuroD, and Pancreatic Duodenal Homeobox-1 (PDX-1). To characterize the transcriptional regulatory factors involved in PANDER gene expression, we performed co-transfection reporter gene analysis and demonstrated upregulation by all three transcription factors, with the greatest individual increase stemming from PDX-1. Potential binding of PDX-1 to A box (TAAT) regions of the PANDER promoter was demonstrated by chromatin immunoprecipitation (ChIP) and further corroborated by electrophoretic mobility shift assay (EMSA). Binding of PDX-1 to the A box regions was inhibited by mutagenized (TAGT) oligonucleotides. Site-directed mutagenesis of the three PDX-1 A box binding motifs revealed that A box sites 2 and 3 in combination were critical for maximal gene expression and deletion resulted in a 82% reduction in promoter activity. Furthermore, deletion of A box sites 2 and 3 completely diminished the glucose-responsiveness of the PANDER promoter. Our findings demonstrate that PANDER is a potential PDX-1 target gene and the A box sites within the promoter region are critical for basal and glucose-stimulated PANDER expression.

Leucine regulation of glucokinase and ATP synthase sensitizes glucose-induced insulin secretion in pancreatic beta-cells.

We have recently shown that leucine culture upregulates ATP synthase beta-subunit (ATPSbeta) and increases ATP level, cytosolic Ca(2+), and glucose-induced insulin secretion in rat islets. The aim is to test whether glucokinase expression is also affected in rat islets and its role in glucose sensitization during leucine culture. Leucine culture increased glucose-induced NAD(P)H level at 1 and 2 days but not at 1 week. The half-maximal effective concentration of the glucose response curve for NAD(P)H was left-shifted from 5-7 to 2-3 mmol/l. The effect was dose dependent and rapamycin insensitive. Leucine culture did not affect glyceraldehyde effects on NAD(P)H. Leucine pretreatment for 30 min had no effects on NAD(P)H levels. Leucine culture for 2 days also increased glucose-induced cytosolic Ca(2+) elevation, ATP level, and insulin secretion. Leucine increase of glucokinase mRNA levels occurred as early as day 1 and lasted through 1 week. That of ATPSbeta did not occur until day 2 and lasted through 1 week. Leucine effects on both mRNAs were dose dependent. The upregulation of both genes was confirmed by Western blotting. Leucine culture also increased glucose-induced insulin secretion, ATP level, glucokinase, and ATPSbeta levels of type 2 diabetic human islets. In conclusion, leucine culture upregulates glucokinase, which increases NAD(P)H level, and ATPSbeta, which increases oxidation of NADH and production of ATP. The combined upregulation of both genes increases glucose-induced cytosolic Ca(2+) and insulin secretion.

Tissue-specific and glucose-responsive expression of the pancreatic derived factor (PANDER) promoter.

Pancreatic derived factor (PANDER) is a recently identified cytokine-like protein that is dominantly expressed in the islets of Langerhans of the pancreas. To investigate the mechanism of tissue-specific regulation of PANDER, we identified and characterized the promoter region. The transcriptional start site was identified 520 bp upstream of the translational start codon by 5'-RLM-RACE. Computer algorithms identified several islet-associated and glucose-responsive binding motifs that included A and E boxes, hepatocyte nuclear factors 1 and 4, Oct-1, and signal transducer and activator of transcription 3, and 5. Reporter gene analysis revealed cell type-specific PANDER promoter expression in islet and liver-derived cell lines. Levels of PANDER mRNA were directly concordant to the observed cell type-specific PANDER promoter gene expression. The minimal element was mapped to the 5'-UTR and located between +200 and +491 relative to the transcriptional start site and imparted maximal gene expression. In addition, several putative glucose-responsive binding sites were further functionally characterized to reveal critical regulatory elements of PANDER. The PANDER promoter was demonstrated to be glucose-responsive in a dose-dependent manner in murine insulinoma beta-TC3 cells and primary murine islets, but unresponsive in glucagon-secreting alpha-TC3 cells. Our findings revealed that the 5'-UTR of PANDER contains the minimal element for gene expression and imparts both tissue-specificity and glucose-responsiveness. The regulation of PANDER gene expression mimics that of insulin and suggests a potential biological function of PANDER involved in metabolic homeostasis.

Mechanisms of glucose-induced secretion of pancreatic-derived factor (PANDER or FAM3B) in pancreatic beta-cells.

Pancreatic-derived factor (PANDER) is an islet-specific cytokine present in both pancreatic alpha- and beta-cells, which, in vitro, induces beta-cell apoptosis of primary islet and cell lines. In this study, we investigated whether PANDER is secreted by pancreatic alpha- and beta-cells and whether PANDER secretion is regulated by glucose and other insulin secretagogues. In mouse-derived insulin-secreting beta-TC3 cells, PANDER secretion in the presence of stimulatory concentrations of glucose was 2.8 +/- 0.4-fold higher (P < 0.05) than without glucose. Insulin secretion was similarly increased by glucose in the same cells. The total concentration of secreted PANDER in the medium was approximately 6-10 ng/ml (0.3-0.5 nmol/l) after a 24-h culture with glucose. L-Glucose failed to stimulate PANDER secretion in beta-TC3 cells. KCl stimulated PANDER secretion 2.1 +/- 0.1-fold compared with control without glucose. An L-type Ca2+ channel inhibitor, nifedipine, completely blocked both glucose- or KCl-induced insulin and PANDER secretion. In rat-derived INS-1 cells, glucose (20 mmol/l) stimulated PANDER secretion 4.4 +/- 0.9-fold, while leucine plus glutamine stimulated 4.4 +/- 0.7-fold compared with control without glucose. In mouse islets overexpressing PANDER, glucose (20 mmol/l) stimulated PANDER secretion 3.2 +/- 0.5-fold (P < 0.05) compared with basal (3 mmol/l glucose). PANDER was also secreted by alpha-TC3 cells but was not stimulated by glucose. Mutations of cysteine 229 or of cysteines 91 and 229 to serine, which may form one disulfide bond, and truncation of the COOH-terminus or NH2-terminus of PANDER all resulted in failure of PANDER secretion, even though these mutant or truncated PANDERs were highly expressed within the cells. In conclusion, we found that 1) PANDER is secreted from both pancreatic alpha- and beta-cells, 2) glucose stimulates PANDER secretion dose dependently in beta-cell lines and primary islets but not in alpha-cells, 3) PANDER is likely cosecreted with insulin via the same regulatory mechanisms, and 4) structure and conformation is vital for PANDER secretion.

PANDER-induced cell-death genetic networks in islets reveal central role for caspase-3 and cyclin-dependent kinase inhibitor 1A (p21).

PANcreatic DERived factor is an islet-specific cytokine that promotes apoptosis in primary islets and islet cell lines. To elucidate the genetic mechanisms of PANDER-induced cell death we performed expression profiling using the mouse PancChip version 5.0 in conjunction with Ingenuity Pathway Analysis. Murine islets were treated with PANDER and differentially expressed genes were identified at 48 and 72 h post-treatment. 64 genes were differentially expressed in response to PANDER treatment. 22 genes are associated with cell death. In addition, the genes with the highest fold change were linked with cell death or apoptosis. The most significantly affected gene at 48 h was the downregulated cyclin-dependent kinase inhibitor 1A (CDKN1A or p21). Approximately half of the genes impacted at 72 h were linked to cell death. Cell death differentially expressed genes were confirmed by quantitative RT-PCR. Further analysis identified cell death genetic networks at both time points with 21 of the 22 cell death genes related in various biological pathways. Caspase-3 (CASP3) was biologically linked to CDKN1A in several genetic networks and these two genes were further examined. Elevated cleaved CASP3 levels in PANDER-treated beta-TC3 insulinoma cells were found to abrogate CDKN1A expression. Levels of CDKN1A were not affected in the absence of cleaved CASP3. PANDER-induced downregulation of CDKN1A expression coupled with induced CASP3-activation may serve a central role in islet cell death and offers further insight into the mechanisms of cytokine-induced beta-cell apoptosis.

Glucose-dependent promotion of insulin release from mouse pancreatic islets by the insulin-mimetic compound L-783,281.

An insulin-mimetic compound (L-783,281) was used in an attempt to determine the role of the beta-cell insulin receptor (IR) on insulin release. Islets were isolated from C57Bl/6j mice and cultured for 1 to 4 days. Insulin release from individual islets perifused in the presence of 3 mmol/l glucose was 10.5 plus minus 1.4 pg/min. Addition of 10 micromol/l L-783,281 had no effect on the rate of insulin secretion. When L-783,281 was added to perifusion medium containing 11 mmol/l glucose, the insulin-mimetic compound significantly increased insulin release. Insulin release from the isolated islet is pulsatile. In the presence of 3 mmol/l glucose, addition of L-783,281 significantly decreased the frequency of the oscillations from 0.35 plus minus 0.03 to 0.22 plus minus 0.04 oscillations/min. Addition of L-783,281 to perifusion medium containing 11 mmol/l glucose had no effect on the frequency of the insulin pulses (0.30 plus minus 0.05 oscillations/min). These results indicate that activation of the beta-cell IR by L-783,281 augments insulin release in the presence of a stimulatory glucose concentration. At nonstimulatory glucose concentrations, activation of the beta-cell IR may affect mechanisms related to the frequency of the insulin pulses.

Insulin receptor signaling and sarco/endoplasmic reticulum calcium ATPase in beta-cells.

Glucose is the main physiological secretagogue for insulin secretion by pancreatic beta-cells, and the major biochemical mechanisms involved have been elucidated. In particular, an increase in intracellular calcium is important for insulin exocytosis. More recently, it has become apparent that the beta-cell also has many of the elements of the insulin receptor signal transduction pathway, including the insulin receptor and insulin receptor substrate (IRS) proteins 1 and 2. Studies with transgenic models have shown that the beta-cell-selective insulin receptor knockout and the IRS-1 knockout lead to reduced glucose-induced insulin secretion. Overexpression of the insulin receptor and IRS-1 in beta-cells results in increased insulin secretion and increased cytosolic Ca(2+). We have thus postulated the existence of a novel autocrine-positive feedback loop of insulin on its own secretion involving interaction with the insulin receptor signal transduction pathway and regulation of intracellular calcium homeostasis. Our current working hypothesis is that this glucose-dependent interaction occurs at the level of IRS-1 and the sarco(endo)plasmic reticulum calcium ATPase, the calcium pump of the endoplasmic reticulum.

Pancreatic-derived factor (FAM3B), a novel islet cytokine, induces apoptosis of insulin-secreting beta-cells.

PANDER (PANcreatic DERived factor, FAM3B), a newly discovered secreted cytokine, is specifically expressed at high levels in the islets of Langerhans of the endocrine pancreas. To evaluate the role of PANDER in beta-cell function, we investigated the effects of PANDER on rat, mouse, and human pancreatic islets; the beta-TC3 cell line; and the alpha-TC cell line. PANDER protein was present in alpha- and beta-cells of pancreatic islets, insulin-secreting beta-TC3 cells, and glucagon-secreting alpha-TC cells. PANDER induced islet cell death in rat and human islets. Culture of beta-TC3 cells with recombinant PANDER had a dose-dependent inhibitory effect on cell viability. This effect was also time-dependent. PANDER caused apoptosis of beta-cells as assessed by electron microscopy, annexin V fluorescent staining, and flow-cytometric terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling assay. PANDER did not affect cytosolic Ca(2+) levels or nitric oxide levels. However, PANDER activated caspase-3. Hence, PANDER may have a role in the process of pancreatic beta-cell apoptosis.

Rapamycin has a deleterious effect on MIN-6 cells and rat and human islets.

Rapamycin (sirolimus) is a macrolide fungicide with immunosuppressant properties that is used in human islet transplantation. Little is known about the effects of rapamycin on MIN-6 cells and islets. Rapamycin had a dose-dependent, time-dependent, and glucose-independent deleterious effect on MIN-6 cell viability. At day 1, using the MTT method, 0.01 nmol/l rapamycin reduced cell viability to 83 +/- 6% of control (P < 0.05). Using the calcein AM method, at day 2, 10 nmol/l rapamycin caused a reduction in cell viability to 73 +/- 5% of control (P < 0.001). Furthermore, 10 and 100 nmol/l rapamycin caused apoptosis in MIN-6 cells as assessed by the transferase-mediated dUTP nick-end labeling assay. Compared with control, there was a 3.1 +/- 0.6-fold increase (P < 0.01) in apoptosis in MIN-6 cells treated with 10 nmol/l rapamycin. A supra-therapeutic rapamycin concentration of 100 nmol/l significantly impaired glucose- and carbachol-stimulated insulin secretion in rat islets and had a deleterious effect on the viability of rat and human islets, causing apoptosis of both alpha- and beta-cells.

Interferon-gamma-induced regulation of the pancreatic derived cytokine FAM3B in islets and insulin-secreting betaTC3 cells.

The pancreatic-derived factor (PANDER, FAM3B) is a novel protein that is beta-cell specific and induces beta-cell death. PANDER is localized to insulin-containing granules-based on confocal microscopy and immunogold electron microscopy. PANDER protein was detected in the conditioned medium of betaTC3 cells. Using real-time reverse transcription-polymerase chain reaction, treatment of betaTC3 cells with IL-1beta + TNFalpha + IFNgamma induced a significant seven-fold increase in PANDER mRNA expression (n = 3; p < 0.01 at 24 h, p < 0.05 at 48 h), while IFNgamma alone caused a 3.2-fold increase (n = 3; p < 0.01 at 24 h) compared to unstimulated and time-matched vehicle controls. IL-1beta or TNFalpha alone had no effect. Under those conditions, a similar up-regulation was also observed in mouse islet cells, with increases in PANDER mRNA of 5.9-fold and 5.0-fold after treatment with IL-1beta + TNFalpha + IFNgamma or IFNgamma alone. Because PANDER mRNA expression is up-regulated by IFNgamma, a cytokine implicated in the pathogenesis of type 1 diabetes, PANDER may contribute to the pathogenesis of beta-cell death.

Distinguishing features of leucine and alpha-ketoisocaproate sensing in pancreatic beta-cells.

Culturing rat islets in high glucose (HG) increased 1-(14)C-alpha-ketoisocaproate (KIC) oxidation compared with culturing them in low glucose. Leucine caused insulin secretion (IS) in low glucose but not in HG rat islets, whereas KIC did so in both. Pretreatment with HG for 40 min abolished leucine stimulation of IS by mouse islets and prevented the cytosolic Ca(2+) rise without inhibiting IS and Ca(2+) increments caused by KIC. When islets were pretreated without glucose and glutamine, aminooxyacetic acid (AOA) markedly decreased KIC effects. When islets were pretreated without glucose and with glutamine, AOA potentiated leucine effects but attenuated KIC effects. AOA stimulated glutamine oxidation in the presence but not the absence of +/-2-amino-2-norbornane-carboxylic acid, a nonmetabolized leucine analog. Pretreatment with HG and glutamine partially reversed AOA inhibition of KIC effects. Glucose increased intracellular ATP and GTP, whereas it decreased ADP and GDP in beta HC9 cells. Glutamate dehydrogenase activity of beta HC9 cell extracts was increased by leucine and attenuated by GTP, but it was potentiated by ADP. In conclusion, leucine and KIC stimulated beta-cells via distinct mechanisms. Glutamate dehydrogenase is the sensor of leucine, whereas transamination plays an important role in KIC stimulation of pancreatic beta-cells.

Elevated portal vein drug levels of sirolimus and tacrolimus in islet transplant recipients: local immunosuppression or islet toxicity?

The recent success of islet transplantation using the Edmonton protocol involved the use of sirolimus, tacrolimus, and daclizumab for immunosuppression. Islets were infused into the portal circulation after transhepatic access. This protocol provided a unique opportunity to measure sirolimus and tacrolimus levels from the portal vein and compare them to systemic venous levels. A total of 11 portal venous samples with a corresponding peripheral venous sample were obtained from patients undergoing a first or second islet infusion and medication levels were obtained on both types of specimens. The portal-to-systemic drug level ratio ranged from 0.95 to 2.71 for sirolimus and 1.0 to 3.12 for tacrolimus. Given the potential toxicity of these agents to islets, the findings in this study may have implications for designing the next generation of immunosuppressive protocols for islet transplantation.

PEDSnet: a National Pediatric Learning Health System.

A learning health system (LHS) integrates research done in routine care settings, structured data capture during every encounter, and quality improvement processes to rapidly implement advances in new knowledge, all with active and meaningful patient participation. While disease-specific pediatric LHSs have shown tremendous impact on improved clinical outcomes, a national digital architecture to rapidly implement LHSs across multiple pediatric conditions does not exist. PEDSnet is a clinical data research network that provides the infrastructure to support a national pediatric LHS. A consortium consisting of PEDSnet, which includes eight academic medical centers, two existing disease-specific pediatric networks, and two national data partners form the initial partners in the National Pediatric Learning Health System (NPLHS). PEDSnet is implementing a flexible dual data architecture that incorporates two widely used data models and national terminology standards to support multi-institutional data integration, cohort discovery, and advanced analytics that enable rapid learning.

Demonstrated brain insulin resistance in Alzheimer's disease patients is associated with IGF-1 resistance, IRS-1 dysregulation, and cognitive decline.

While a potential causal factor in Alzheimer's disease (AD), brain insulin resistance has not been demonstrated directly in that disorder. We provide such a demonstration here by showing that the hippocampal formation (HF) and, to a lesser degree, the cerebellar cortex in AD cases without diabetes exhibit markedly reduced responses to insulin signaling in the IR→IRS-1→PI3K signaling pathway with greatly reduced responses to IGF-1 in the IGF-1R→IRS-2→PI3K signaling pathway. Reduced insulin responses were maximal at the level of IRS-1 and were consistently associated with basal elevations in IRS-1 phosphorylated at serine 616 (IRS-1 pS6¹6) and IRS-1 pS6³6/6³9. In the HF, these candidate biomarkers of brain insulin resistance increased commonly and progressively from normal cases to mild cognitively impaired cases to AD cases regardless of diabetes or APOE ε4 status. Levels of IRS-1 pS6¹6 and IRS-1 pS6³6/6³9 and their activated kinases correlated positively with those of oligomeric Aß plaques and were negatively associated with episodic and working memory, even after adjusting for Aß plaques, neurofibrillary tangles, and APOE ε4. Brain insulin resistance thus appears to be an early and common feature of AD, a phenomenon accompanied by IGF-1 resistance and closely associated with IRS-1 dysfunction potentially triggered by Aß oligomers and yet promoting cognitive decline independent of classic AD pathology.

Leucine metabolism in regulation of insulin secretion from pancreatic beta cells.

Leucine, a branched-chain amino acid that must be supplied in the daily diet, plays an important role in controlling protein synthesis and regulating cell metabolism in various cell types. In pancreatic beta cells, leucine acutely stimulates insulin secretion by serving as both metabolic fuel and allosteric activator of glutamate dehydrogenase to enhance glutaminolysis. Leucine has also been shown to regulate gene transcription and protein synthesis in pancreatic islet beta cells via both mTOR-dependent and -independent pathways at physiological concentrations. Long-term treatment with leucine has been shown to improve insulin secretory dysfunction of human diabetic islets via upregulation of certain key metabolic genes. In vivo, leucine administration improves glycemic control in humans and rodents with type 2 diabetes. This review summarizes and discusses the recent findings regarding the effects of leucine metabolism on pancreatic beta-cell function.

Liver-specific overexpression of pancreatic-derived factor (PANDER) induces fasting hyperglycemia in mice.

The pancreas-derived hormones, insulin and glucagon, are the two main regulators of glucose homeostasis. However, their actions can be modulated by the presence of other circulating factors including cytokines. Pancreatic-derived factor (PANDER) is a novel cytokine-like molecule secreted from the endocrine pancreas, but its biological function is currently unknown. To address this, we employed adenoviral gene delivery to develop a novel murine model of PANDER overexpression, which we used to study PANDER's effect on glucose homeostasis. Although serum metabolites in fed mice were unaffected by PANDER overexpression, fasting glucose, insulin, and corticosterone levels were significantly elevated. Additionally, PANDER-overexpressing mice displayed elevated glucose and insulin levels during a glucose tolerance test, indicating that glucose tolerance was impaired. However, there were no defects in glucose-stimulated insulin secretion or peripheral insulin sensitivity. Elevated transcription of hepatic gluconeogenic genes, PEPCK and G6Pase accompanied the fasting hyperglycemia observed in PANDER-overexpressing animals. Similarly, treatment of primary hepatocytes with PANDER-expressing adenovirus or PANDER-enriched conditioned medium elevated gluconeogenic gene expression and glucose output. PANDER treatment also resulted in higher levels of Ser133-phosphorylated cAMP-response element-binding protein in hepatocytes stimulated with 8-bromo-cAMP and dexamethasone and higher levels of intracellular cAMP upon stimulation with forskolin. In summary, we provide the first report that identifies PANDER as a regulator of hepatic glucose metabolism, where it serves as a novel factor that amplifies hepatic cAMP and cAMP-response element-binding protein signaling to induce gluconeogenic gene expression and glucose output.

Characterization of the expression, localization, and secretion of PANDER in alpha-cells.

The novel islet-specific protein PANcreatic DERived Factor (PANDER; FAM3B) has been extensively characterized with respect to the beta-cell, and these studies suggest a potential function for PANDER in the regulation of glucose homeostasis. Little is known regarding PANDER in pancreatic -cells, which are critically involved in maintaining euglycemia. Here we present the first report elucidating the expression and regulation of PANDER within the alpha-cell. Pander mRNA and protein are detected in alpha-cells, with primary localization to a glucagon-negative granular cytosolic compartment. PANDER secretion from alpha-cells is nutritionally and hormonally regulated by l-arginine and insulin, demonstrating similarities and differences with glucagon. Signaling via the insulin receptor (IR) through the PI3K and Akt/PKB node is required for insulin-stimulated PANDER release. The separate localization of PANDER and glucagon is consistent with their differential regulation, and the effect of insulin suggests a paracrine/endocrine effect on PANDER release. This provides further insight into the potential glucose-regulatory role of PANDER.

Targeted disruption of pancreatic-derived factor (PANDER, FAM3B) impairs pancreatic beta-cell function.

OBJECTIVE: Pancreatic-derived factor (PANDER, FAM3B) is a pancreatic islet-specific cytokine-like protein that is secreted from beta-cells upon glucose stimulation. The biological function of PANDER is unknown, and to address this we generated and characterized a PANDER knockout mouse. RESEARCH DESIGN AND METHODS: To generate the PANDER knockout mouse, the PANDER gene was disrupted and its expression was inhibited by homologous recombination via replacement of the first two exons, secretion signal peptide and transcriptional start site, with the neomycin gene. PANDER(-/-) mice were then phenotyped by a number of in vitro and in vivo tests to evaluate potential effects on glucose regulation, insulin sensitivity, and beta-cell morphology and function. RESULTS: Glucose tolerance tests demonstrated significantly higher blood glucose levels in PANDER(-/-) versus wild-type male mice. To identify the mechanism of the glucose intolerance, insulin sensitivity and pancreatic beta-cell function were examined. Hyperinsulinemic-euglycemic clamps and insulin tolerance testing showed similar insulin sensitivity for both the PANDER(-/-) and wild-type mice. The in vivo insulin response following intraperitoneal glucose injection surprisingly produced significantly higher insulin levels in the PANDER(-/-) mice, whereas insulin release was blunted with arginine administration. Islet perifusion and calcium imaging studies showed abnormal responses of the PANDER(-/-) islets to glucose stimulation. In contrast, neither islet architecture nor insulin content was impacted by the loss of PANDER. Interestingly, the elevated insulin levels identified in vivo were attributed to decreased hepatic insulin clearance in the PANDER(-/-) islets. Taken together, these results demonstrated decreased pancreatic beta-cell function in the PANDER(-/-) mouse. CONCLUSIONS: These results support a potential role of PANDER in the pancreatic beta-cell for regulation or facilitation of insulin secretion.

PANDER binds to the liver cell membrane and inhibits insulin signaling in HepG2 cells.

PANDER is a cytokine co-secreted with insulin from islet beta-cells. To date, the physiological function of PANDER remains largely unknown. Here we show that PANDER binds to the liver membrane by (125)I-PANDER saturation and competitive binding assays. In HepG2 cells, pre-treatment with PANDER ranging from 4 pM to 4 nM for 8h resulted in a maximal inhibition of insulin-stimulated activation of insulin receptor and insulin receptor substrate 1 by 52% and 63%, respectively. Moreover, PANDER treatment also reduced insulin-stimulated PI3K and pAkt levels by 55% and 48%, respectively. In summary, we have identified the liver as a novel target for PANDER, and PANDER may be involved in the progression of diabetes by regulating hepatic insulin signaling pathways.