Publications from Members of the BIIC

Glucose activates free fatty acid receptor 1 gene transcription via phosphatidylinositol-3-kinase-dependent O-GlcNAcylation of pancreas-duodenum homeobox-1.

All pubs - 1 hour 47 min ago

Glucose activates free fatty acid receptor 1 gene transcription via phosphatidylinositol-3-kinase-dependent O-GlcNAcylation of pancreas-duodenum homeobox-1.

Proc Natl Acad Sci U S A. 2012 Jan 30;

Authors: Kebede M, Ferdaoussi M, Mancini A, Alquier T, Kulkarni RN, Walker MD, Poitout V

Abstract
The G protein-coupled free fatty acid receptor-1 (FFA1/GPR40) plays a major role in the regulation of insulin secretion by fatty acids. GPR40 is considered a potential therapeutic target to enhance insulin secretion in type 2 diabetes; however, its mode of regulation is essentially unknown. The aims of this study were to test the hypothesis that glucose regulates GPR40 gene expression in pancreatic β-cells and to determine the mechanisms of this regulation. We observed that glucose stimulates GPR40 gene transcription in pancreatic β-cells via increased binding of pancreas-duodenum homeobox-1 (Pdx-1) to the A-box in the HR2 region of the GPR40 promoter. Mutation of the Pdx-1 binding site within the HR2 abolishes glucose activation of GPR40 promoter activity. The stimulation of GPR40 expression and Pdx-1 binding to the HR2 in response to glucose are mimicked by N-acetyl glucosamine, an intermediate of the hexosamine biosynthesis pathway, and involve PI3K-dependent O-GlcNAcylation of Pdx-1 in the nucleus. We demonstrate that O-GlcNAc transferase (OGT) interacts with the product of the PI3K reaction, phosphatidylinositol 3,4,5-trisphosphate (PIP(3)), in the nucleus. This interaction enables OGT to catalyze O-GlcNAcylation of nuclear proteins, including Pdx-1. We conclude that glucose stimulates GPR40 gene expression at the transcriptional level through Pdx-1 binding to the HR2 region and via a signaling cascade that involves an interaction between OGT and PIP(3) at the nuclear membrane. These observations reveal a unique mechanism by which glucose metabolism regulates the function of transcription factors in the nucleus to induce gene expression.

PMID: 22308370 [PubMed - as supplied by publisher]

Categories: Publications from Members of the BIIC

Exogenous insulin enhances glucose-stimulated insulin response in healthy humans independent of changes in free fatty acids.

All pubs - 1 hour 47 min ago

Exogenous insulin enhances glucose-stimulated insulin response in healthy humans independent of changes in free fatty acids.

J Clin Endocrinol Metab. 2011 Dec;96(12):3811-21

Authors: Lopez X, Cypess A, Manning R, O'Shea S, Kulkarni RN, Goldfine AB

Abstract
CONTEXT: Islet β-cells express both insulin receptors and insulin signaling proteins. Recent studies suggest insulin signaling is physiologically important for glucose sensing.
OBJECTIVE: Preexposure to insulin enhances glucose-stimulated insulin secretion (GSIS) in healthy humans. We evaluated whether the effect of insulin to potentiate GSIS is modulated through regulation of free fatty acids (FFA).
DESIGN AND SETTING: Subjects were studied on three occasions in this single-site study at an academic institution clinical research center.
PATIENTS: Subjects included nine healthy volunteers.
INTERVENTIONS: Glucose-induced insulin response was assessed on three occasions after 4 h saline (low insulin/sham) or isoglycemic-hyperinsulinemic (high insulin) clamps with or without intralipid and heparin infusion, using B28 Asp-insulin that could be distinguished from endogenous insulin immunologically. During the last 80 min of all three clamps, additional glucose was administered to stimulate insulin secretion (GSIS) with glucose concentrations maintained at similar concentrations during all studies.
MAIN OUTCOME MEASURE: β-Cell response to glucose stimulation was assessed.
RESULTS: Preexposure to exogenous insulin increased the endogenous insulin-secretory response to glucose by 32% compared with sham clamp (P = 0.001). This was accompanied by a drop in FFA during hyperinsulinemic clamp compared with the sham clamp (0.06 ± 0.02 vs. 0.60 ± 0.09 mEq/liter, respectively), which was prevented during the hyperinsulinemic clamp with intralipid/heparin infusion (1.27 ± 0.17 mEq/liter). After preexposure to insulin with intralipid/heparin infusion to maintain FFA concentration, GSIS was 21% higher compared with sham clamp (P < 0.04) and similar to preexposure to insulin without intralipid/heparin (P = 0.2).
CONCLUSIONS: Insulin potentiates glucose-stimulated insulin response independent of FFA concentrations in healthy humans.

PMID: 21956413 [PubMed - indexed for MEDLINE]

Categories: Publications from Members of the BIIC

Loss of glucagon-like peptide-2-induced proliferation following intestinal epithelial insulin-like growth factor-1-receptor deletion.

All pubs - 1 hour 47 min ago

Loss of glucagon-like peptide-2-induced proliferation following intestinal epithelial insulin-like growth factor-1-receptor deletion.

Gastroenterology. 2011 Dec;141(6):2166-2175.e7

Authors: Rowland KJ, Trivedi S, Lee D, Wan K, Kulkarni RN, Holzenberger M, Brubaker PL

Abstract
BACKGROUND & AIMS: Glucagon-like peptide-2 (GLP-2) is an intestinal hormone that promotes growth of the gastrointestinal tract. Although insulin-like growth factor (IGF)-1 and the IGF-1 receptor (IGF-1R) are required for GLP-2-induced proliferation of crypt cells, little is known about localization of the IGF-1R which mediates the intestinotropic actions of GLP-2.
METHODS: We examined intestinal growth and proliferative responses in mice with conditional deletion of IGF-1R from intestinal epithelial cells (IE-igf1rKO) after acute administration (30-90 min) of GLP-2, in response to 24-hour fasting and re-feeding (to induce GLP-2-dependent adaptation), and after chronic exposure (10 days) to GLP-2.
RESULTS: IE-igf1rKO mice had normal small intestinal weight, morphometric parameters, proliferative indices, and distribution of differentiated epithelial cell lineages. Acute administration of GLP-2 increased nuclear translocation of β-catenin in non-Paneth crypt cells and stimulated the crypt-cell proliferative marker c-Myc in control but not IE-igf1rKO mice. Small intestinal weight, crypt depth, villus height, and crypt-cell proliferation were decreased in control and IE-igf1rKO mice after 24-hour fasting. Although re-feeding control mice restored all of these parameters, re-fed IE-igf1rKO mice had reductions in adaptive regrowth of the villi and crypt-cell proliferation. Control mice that were given chronic GLP-2 had increases in small intestinal weight, mucosal cross-sectional area, crypt depth, villus height, and crypt-cell proliferation. However, the GLP-2-induced increase in crypt-cell proliferation was not observed in IE-igf1rKO mice, and growth of the crypt-villus axis was reduced.
CONCLUSIONS: The proliferative responses of the intestinal epithelium to exogenous GLP-2 administration and conditions of GLP-2-dependent adaptive re-growth require the intestinal epithelial IGF-1R.

PMID: 21925122 [PubMed - indexed for MEDLINE]

Categories: Publications from Members of the BIIC

Pancreatic beta cell mass PET imaging and quantification with [11C]DTBZ and [18F]FP-(+)-DTBZ in rodent models of diabetes.

All pubs - Fri, 02/10/2012 - 03:00

Pancreatic beta cell mass PET imaging and quantification with [11C]DTBZ and [18F]FP-(+)-DTBZ in rodent models of diabetes.

Mol Imaging Biol. 2011 Oct;13(5):973-84

Authors: Singhal T, Ding YS, Weinzimmer D, Normandin MD, Labaree D, Ropchan J, Nabulsi N, Lin SF, Skaddan MB, Soeller WC, Huang Y, Carson RE, Treadway JL, Cline GW

Abstract
PURPOSE: The aim of this study is to compare the utility of two positron emission tomography (PET) imaging ligands ((+)-[(11)C]dihydrotetrabenazine ([(11)C]DTBZ) and the fluoropropyl analog ([(18)F]FP-(+)-DTBZ)) that target islet β-cell vesicular monoamine transporter type II to measure pancreatic β-cell mass (BCM).
PROCEDURES: [(11)C]DTBZ or [(18)F]FP-(+)-DTBZ was injected, and serial PET images were acquired in rat models of diabetes (streptozotocin-treated and Zucker diabetic fatty) and β-cell compensation (Zucker fatty). Radiotracer standardized uptake values (SUV) were correlated to pancreas insulin content measured biochemically and histomorphometrically.
RESULTS: On a group level, a positive correlation of [(11)C]DTBZ pancreatic SUV with pancreas insulin content and BCM was observed. In the STZ diabetic model, both [(18)F]FP-(+)-DTBZ and [(11)C]DTBZ correlated positively with BCM, although only ∼25% of uptake could be attributed to β-cell uptake. [(18)F]FP-(+)-DTBZ displacement studies indicate that there is a substantial fraction of specific binding that is not to pancreatic islet β cells.
CONCLUSIONS: PET imaging with [(18)F]FP-(+)-DTBZ provides a noninvasive means to quantify insulin-positive BCM and may prove valuable as a diagnostic tool in assessing treatments to maintain or restore BCM.

PMID: 20824509 [PubMed - indexed for MEDLINE]

Categories: Publications from Members of the BIIC

Role of phospholipase Cε in physiological phosphoinositide signaling networks.

All pubs - Fri, 02/03/2012 - 03:00

Role of phospholipase Cε in physiological phosphoinositide signaling networks.

Cell Signal. 2012 Jan 20;

Authors: Smrcka AV, Brown JH, Holz GG

Abstract
Receptor-initiated phospholipase C activation and generation of IP(3) and DAG are important common triggers for a diversity of signal transduction processes in many cell types. Contributing to this diversity is the existence and differential cellular and subcellular distribution of distinct phospholipase C isoforms with distinct regulatory properties. The recently identified PLCε enzyme is an isoform that is uniquely regulated by multiple upstream signals including ras-family GTP binding proteins as well as heterotrimeric G-proteins. In this review we will consider the well documented biochemical regulation of this isoform in the context of cell and whole animal physiology and in the context of other G protein-regulated PLC isoforms. These studies together reveal a surprisingly wide range of unexpected functions for PLCε in cellular signaling, physiology and disease.

PMID: 22286105 [PubMed - as supplied by publisher]

Categories: Publications from Members of the BIIC

Insulin augmentation of glucose-stimulated insulin secretion is impaired in insulin-resistant humans.

All pubs - Tue, 01/31/2012 - 03:00

Insulin augmentation of glucose-stimulated insulin secretion is impaired in insulin-resistant humans.

Diabetes. 2012 Feb;61(2):301-9

Authors: Halperin F, Lopez X, Manning R, Kahn CR, Kulkarni RN, Goldfine AB

Abstract
Type 2 diabetes (T2D) is characterized by insulin resistance and pancreatic β-cell dysfunction, the latter possibly caused by a defect in insulin signaling in β-cells. We hypothesized that insulin's effect to potentiate glucose-stimulated insulin secretion (GSIS) would be diminished in insulin-resistant persons. To evaluate the effect of insulin to modulate GSIS in insulin-resistant compared with insulin-sensitive subjects, 10 participants with impaired glucose tolerance (IGT), 11 with T2D, and 8 healthy control subjects were studied on two occasions. The insulin secretory response was assessed by the administration of dextrose for 80 min following a 4-h clamp with either saline infusion (sham) or an isoglycemic-hyperinsulinemic clamp using B28-Asp-insulin (which can be distinguished immunologically from endogenous insulin) that raised insulin concentrations to high physiologic concentrations. Pre-exposure to insulin augmented GSIS in healthy persons. This effect was attenuated in insulin-resistant cohorts, both those with IGT and those with T2D. Insulin potentiates glucose-stimulated insulin secretion in insulin-resistant subjects to a lesser degree than in normal subjects. This is consistent with an effect of insulin to regulate β-cell function in humans in vivo with therapeutic implications.

PMID: 22275085 [PubMed - in process]

Categories: Publications from Members of the BIIC

Reactive oxygen species stimulate insulin secretion in rat pancreatic islets: studies using mono-oleoyl-glycerol.

All pubs - Thu, 01/26/2012 - 03:00

Reactive oxygen species stimulate insulin secretion in rat pancreatic islets: studies using mono-oleoyl-glycerol.

PLoS One. 2012;7(1):e30200

Authors: Saadeh M, Ferrante TC, Kane A, Shirihai O, Corkey BE, Deeney JT

Abstract
Chronic exposure (24-72 hrs) of pancreatic islets to elevated glucose and fatty acid leads to glucolipoxicity characterized by basal insulin hypersecretion and impaired glucose-stimulated insulin secretion (GSIS). Our aim was to determine the mechanism for basal hypersecretion of insulin. We used mono-oleoyl-glycerol (MOG) as a tool to rapidly increase lipids in isolated rat pancreatic ß-cells and in the clonal pancreatic ß-cell line INS-1 832/13. MOG (25-400 µM) stimulated basal insulin secretion from ß-cells in a concentration dependent manner without increasing intracellular Ca(2+) or O(2) consumption. Like GSIS, MOG increased NAD(P)H and reactive oxygen species (ROS). The mitochondrial reductant ß-hydroxybutyrate (ß-OHB) also increased the redox state and ROS production, while ROS scavengers abrogated secretion. Diazoxide (0.4 mM) did not prevent the stimulatory effect of MOG, confirming that the effect was independent of the K(ATP)-dependent pathway of secretion. MOG was metabolized to glycerol and long-chain acyl-CoA (LC-CoA), whereas, acute oleate did not similarly increase LC-CoA. Inhibition of diacylglycerol kinase (DGK) did not mimic the effect of MOG on insulin secretion, indicating that MOG did not act primarily by inhibiting DGK. Inhibition of acyl-CoA synthetase (ACS) reduced the stimulatory effect of MOG on basal insulin secretion by 30% indicating a role for LC-CoA. These data suggest that basal insulin secretion is stimulated by increased ROS production, due to an increase in the mitochondrial redox state independent of the established components of GSIS.

PMID: 22272304 [PubMed - in process]

Categories: Publications from Members of the BIIC

Epac2-dependent mobilization of intracellular Ca2+ by glucagon-like peptide-1 receptor agonist exendin-4 is disrupted in beta-cells of phospholipase C-epsilon knockout mice.

All pubs - Thu, 01/26/2012 - 03:00

Epac2-dependent mobilization of intracellular Ca2+ by glucagon-like peptide-1 receptor agonist exendin-4 is disrupted in beta-cells of phospholipase C-epsilon knockout mice.

J Physiol. 2012 Jan 23;

Authors: Dzhura I, Chepurny OG, Kelley GG, Leech CA, Roe MW, Dzhura E, Afshari P, Malik S, Rindler MJ, Xu X, Lu Y, Smrcka AV, Holz GG

Abstract
Not applicable.

PMID: 22271867 [PubMed - as supplied by publisher]

Categories: Publications from Members of the BIIC

Hyperglucagonemia precedes a decline in insulin secretion and causes hyperglycemia in chronically glucose-infused rats.

All pubs - Wed, 01/25/2012 - 03:00

Hyperglucagonemia precedes a decline in insulin secretion and causes hyperglycemia in chronically glucose-infused rats.

Am J Physiol Endocrinol Metab. 2011 Dec;301(6):E1174-83

Authors: Jamison RA, Stark R, Dong J, Yonemitsu S, Zhang D, Shulman GI, Kibbey RG

Abstract
Islet damage from glucose toxicity is implicated in the pathogenesis of type 2 diabetes, but the sequence of events leading to islet cell dysfunction and hyperglycemia remains unclear. To examine the early stages of islet pathology resulting from increased basal glucose loads, normal awake rats were infused with glucose continuously for 10 days. Plasma glucose and markers of islet and liver function were monitored throughout the infusion. After initial hyperglycemia, rats adapted to the infusion and maintained euglycemia for approximately 4 days. Continued infusion led to worsening hyperglycemia in just 5% of rats after 6 days, but 69% after 8 days and 89% after 10 days, despite unchanged basal and stimulated plasma insulin and C-peptide concentrations. In contrast, plasma glucagon concentrations increased fivefold. Endogenous glucose production (EGP) was appropriately suppressed after 4 days (2.8 ± 0.7 vs. 6.1 ± 0.4 mg·kg(-1)·min(-1) on day 0, P < 0.001) but tripled between days 4 and 8 (9.9 ± 1.7 mg·kg(-1)·min(-1), P < 0.01). Surprisingly, the increase in EGP was accompanied by increased mitochondrial phosphoenolpyruvate carboxykinase expression with appropriate suppression of the cytosolic isoform. Infusion of anti-glucagon antibodies normalized plasma glucose to levels identical to those on day 4 and ∼300 mg/dl lower than controls. This improved glycemia was associated with a 60% reduction in EGP. These data support the novel concept that glucose toxicity may first manifest as α-cell dysfunction prior to any measurable deficit in insulin secretion. Such hyperglucagonemia could lead to excessive glucose production overwhelming the capacity of the β-cell to maintain glucose homeostasis.

PMID: 21862723 [PubMed - indexed for MEDLINE]

Categories: Publications from Members of the BIIC

Cytoplasmic Polyadenylation Element Binding Protein Deficiency Stimulates PTEN and Stat3 mRNA Translation and Induces Hepatic Insulin Resistance.

All pubs - Tue, 01/24/2012 - 03:00

Cytoplasmic Polyadenylation Element Binding Protein Deficiency Stimulates PTEN and Stat3 mRNA Translation and Induces Hepatic Insulin Resistance.

PLoS Genet. 2012 Jan;8(1):e1002457

Authors: Alexandrov IM, Ivshina M, Jung DY, Friedline R, Ko HJ, Xu M, O'Sullivan-Murphy B, Bortell R, Huang YT, Urano F, Kim JK, Richter JD

Abstract
The cytoplasmic polyadenylation element binding protein CPEB1 (CPEB) regulates germ cell development, synaptic plasticity, and cellular senescence. A microarray analysis of mRNAs regulated by CPEB unexpectedly showed that several encoded proteins are involved in insulin signaling. An investigation of Cpeb1 knockout mice revealed that the expression of two particular negative regulators of insulin action, PTEN and Stat3, were aberrantly increased. Insulin signaling to Akt was attenuated in livers of CPEB-deficient mice, suggesting that they might be defective in regulating glucose homeostasis. Indeed, when the Cpeb1 knockout mice were fed a high-fat diet, their livers became insulin-resistant. Analysis of HepG2 cells, a human liver cell line, depleted of CPEB demonstrated that this protein directly regulates the translation of PTEN and Stat3 mRNAs. Our results show that CPEB regulated translation is a key process involved in insulin signaling.

PMID: 22253608 [PubMed - in process]

Categories: Publications from Members of the BIIC

Prevalence of hepatitis C virus genotype 1a in Japan and correlation of mutations in the NS5A region and single-nucleotide polymorphism of interleukin-28B with the response to combination therapy with pegylated-interferon-alpha 2b and ribavirin.

All pubs - Tue, 01/24/2012 - 03:00

Prevalence of hepatitis C virus genotype 1a in Japan and correlation of mutations in the NS5A region and single-nucleotide polymorphism of interleukin-28B with the response to combination therapy with pegylated-interferon-alpha 2b and ribavirin.

J Med Virol. 2012 Mar;84(3):438-44

Authors: Hayashi K, Katano Y, Kuzuya T, Tachi Y, Honda T, Ishigami M, Itoh A, Hirooka Y, Ishikawa T, Nakano I, Urano F, Yoshioka K, Toyoda H, Kumada T, Goto H

Abstract
Hepatitis C virus (HCV) genotype 1a is rare in Japanese patients and the clinical characteristics of this genotype remain unclear. The interferon (IFN) sensitivity-determining region (ISDR) and single-nucleotide polymorphisms (SNPs) of interleukin-28B (IL28B) among patients with HCV genotype 1b are associated with IFN response, but associations among patients with genotype 1a are largely unknown. This study investigated the clinical characteristics of genotype 1a and examined whether genomic heterogeneity of the ISDR and SNPs of IL28B among patients with HCV genotype 1a affects response to combination therapy with pegylated-IFN-α2b and ribavirin. Subjects comprised 977 patients infected with HCV genotype 1, including 574 men and 412 women (mean age, 55.2 ± 10.6 years). HCV was genotyped by direct sequencing of the 5'-untranslated region and/or core regions and confirmed by direct sequencing of the NS5A region. HCV genotypes 1a (n = 32) and 1b (n = 945) were detected. Twenty-three (71.9%) of the 32 patients with genotype 1a were patients with hemophilia who had received imported clotting factors. Prevalence of genotype 1a after excluding patients with hemophilia was thus 0.9%. Of the 23 patients with genotype 1a who completed IFN therapy, 11 (47.8%) were defined as achieving sustained virological response. Factors related to sustained virological response by univariate analysis were IL28B and ISDR. In conclusion, HCV genotype 1a is rare in Japan. The presence of IL28B genotype TT, and more than two mutations, in the ISDR are associated with a good response to IFN therapy in patients with HCV genotype 1a. J. Med. Virol. 84:438-444, 2012. © 2011 Wiley Periodicals, Inc.

PMID: 22246829 [PubMed - in process]

Categories: Publications from Members of the BIIC

Rates of insulin secretion in INS-1 cells are enhanced by coupling to anaplerosis and Kreb's cycle flux independent of ATP synthesis.

All pubs - Thu, 01/19/2012 - 03:00

Rates of insulin secretion in INS-1 cells are enhanced by coupling to anaplerosis and Kreb's cycle flux independent of ATP synthesis.

Biochem Biophys Res Commun. 2011 Nov 11;415(1):30-5

Authors: Cline GW, Pongratz RL, Zhao X, Papas KK

Abstract
Mechanistic models of glucose stimulated insulin secretion (GSIS) established in minimal media in vitro, may not accurately describe the complexity of coupling metabolism with insulin secretion that occurs in vivo. As a first approximation, we have evaluated metabolic pathways in a typical growth media, DMEM as a surrogate in vivo medium, for comparison to metabolic fluxes observed under the typical experimental conditions using the simple salt-buffer of KRB. Changes in metabolism in response to glucose and amino acids and coupling to insulin secretion were measured in INS-1 832/13 cells. Media effects on mitochondrial function and the coupling efficiency of oxidative phosphorylation were determined by fluorometrically measured oxygen consumption rates (OCRs) combined with (31)P NMR measured rates of ATP synthesis. Substrate preferences and pathways into the TCA cycle, and the synthesis of mitochondrial 2nd messengers by anaplerosis were determined by (13)C NMR isotopomer analysis of the fate of [U-(13)C] glucose metabolism. Despite similar incremental increases in insulin secretion, the changes of OCR in response to increasing glucose from 2.5 to 15mM were blunted in DMEM relative to KRB. Basal and stimulated rates of insulin secretion rates were consistently higher in DMEM, while ATP synthesis rates were identical in both DMEM and KRB, suggesting greater mitochondrial uncoupling in DMEM. The relative rates of anaplerosis, and hence synthesis and export of 2nd messengers from the mitochondria were found to be similar in DMEM to those in KRB. And, the correlation of total PC flux with insulin secretion rates in DMEM was found to be congruous with the correlation in KRB. Together, these results suggest that signaling mechanisms associated with both TCA cycle flux and with anaplerotic flux, but not ATP production, may be responsible for the enhanced rates of insulin secretion in more complex, and physiologically-relevant media.

PMID: 22008547 [PubMed - indexed for MEDLINE]

Categories: Publications from Members of the BIIC

CT-PET weighted image fusion for separately scanned whole body rat.

All pubs - Sat, 01/14/2012 - 03:00

CT-PET weighted image fusion for separately scanned whole body rat.

Med Phys. 2012 Jan;39(1):533

Authors: Suh JW, Kwon OK, Scheinost D, Sinusas AJ, Cline GW, Papademetris X

Abstract
Purpose: The limited resolution and lack of spatial information in positron emission tomography (PET) images require the complementary anatomic information from the computed tomography (CT) and/or magnetic resonance imaging (MRI). Therefore, multimodality image fusion techniques such as PET/CT are critical in mapping the functional images to structural images and thus facilitate the interpretation of PET studies. In our experimental situation, the CT and PET images are acquired in separate scanners at different times and the inherent differences in the imaging protocols produce significant nonrigid changes between the two acquisitions in addition to dissimilar image characteristics. The registration conditions are also poor because CT images have artifacts due to the limitation of current scanning settings, while PET images are very blurry (in transmission-PET) and have vague anatomical structure boundaries (in emission-PET).Methods: The authors present a new method for whole body small animal multimodal registration. In particular, the authors register whole body rat CT image and PET images using a weighted demons algorithm. The authors use both the transmission-PET and the emission-PET images in the registration process emphasizing particular regions of the moving transmission-PET image using the emission-PET image. After a rigid transformation and a histogram matching between the CT and the transmission-PET images, the authors deformably register the transmission-PET image to the CT image with weights based on the intensity-normalized emission-PET image. For the deformable registration process, the authors develop a weighted demons registration method that can give preferences to particular regions of the input image using a weight image.Results: The authors validate the results with nine rat image sets using the M-Hausdorff distance (M-HD) similarity measure with different outlier-suppression parameters (OSP). In comparison with standard methods such as the regular demons and the normalized mutual information (NMI)-based nonrigid free-form deformation (FFD) registration, the proposed weighted demons registration method shows average M-HD errors: 3.99 ± 1.37 (OSP = 10), 5.04 ± 1.59 (OSP = 20) and 5.92 ± 1.61 (OSP = ∞) with statistical significance (p < 0.0003) respectively, while NMI-based nonrigid FFD has average M-HD errors: 5.74 ± 1.73 (OSP = 10), 7.40 ± 7.84 (OSP = 20) and 9.83 ± 4.13 (OSP = ∞), and the regular demons has average M-HD errors: 6.79 ± 0.83 (OSP = 10), 9.19 ± 2.39 (OSP = 20) and 11.63 ± 3.99 (OSP = ∞), respectively. In addition to M-HD comparisons, the visual comparisons on the faint-edged region between the CT and the aligned PET images also show the encouraging improvements over the other methods.Conclusions: In the whole body multimodal registration between CT and PET images, the utilization of both the transmission-PET and the emission-PET images in the registration process by emphasizing particular regions of the transmission-PET image using an emission-PET image is effective. This method holds promise for other image fusion applications where multiple (more than two) input images should be registered into a single informative image.

PMID: 22225323 [PubMed - in process]

Categories: Publications from Members of the BIIC

Paramagnetic microparticles do not elicit islet cytotoxicity with co-culture or host immune reactivity after implantation.

All pubs - Tue, 01/10/2012 - 03:00

Paramagnetic microparticles do not elicit islet cytotoxicity with co-culture or host immune reactivity after implantation.

Xenotransplantation. 2011 Jul-Aug;18(4):239-44

Authors: Suszynski TM, Rizzari MD, Kidder LS, Mueller K, Chapman CS, Kitzmann JP, Pongratz RL, Cline GW, Todd PW, Kennedy DJ, O'Brien TD, Avgoustiniatos ES, Schuurman HJ, Papas KK

Abstract
BACKGROUND: Paramagnetic microparticles (MPs) may be useful in pancreatic islet purification, in particular purification of porcine islets as a potential xenotransplantation product. We assessed whether MPs affect islet function or induce an adverse effect following implantation.
METHODS: Porcine islets were co-cultured with 0, 500, and 1500 MPs per islet equivalent (IE) for 1 day and with 0 and 1500 MPs/IE for 7 days. Fractional viability was assessed using oxygen consumption rate normalized to DNA content (OCR/DNA) and after 7-day co-culture by perifusion glucose-stimulated insulin secretion (GSIS) and by transplantation under the renal capsule of diabetic nude mice. To assess an inflammatory response or immune reaction, MPs (∼10(7)) were implanted under the renal capsule of C57BL/6 mice.
RESULTS: No statistically significant differences were measured in OCR/DNA (mean ± SE) following 1-day co-culture with 0, 500, or 1500 MPs/IE (243.3 ± 4.5, 211.3 ± 8.1, or 230.6 ± 11.3 nmol/min·mgDNA, respectively) or following 7-day co-culture with 0 or 1500 MPs/IE (248.5 ± 1.4 or 252.9 ± 4.7 nmol/min·mgDNA, respectively). GSIS was not affected by the presence of MPs; first- and second-phase insulin area-under-the-curve (mean ± SE) reflected no statistically significant differences after 7-day co-culture between 0 and 1500 MPs/IE (8.36 ± 0.29 and 8.45 ± 0.70 pg/ml·min·ngDNA for first-phase; 69.73 ± 2.18 and 65.70 ± 4.34 pg/ml·min·ngDNA for second-phase, respectively). Islets co-cultured with MPs normalized hyperglycemia in diabetic nude mice, suggesting no adverse effects on in vivo islet function. Implantation of MPs did not elicit tissue injury, inflammatory change or immune reactivity.
CONCLUSION: MPs do not adversely affect islet viability or function during co-culture, and MPs are not immune reactive following implantation.

PMID: 21848541 [PubMed - indexed for MEDLINE]

Categories: Publications from Members of the BIIC

MT1-MMP modulates the mechanosensitivity of osteocytes.

All pubs - Fri, 01/06/2012 - 03:00

MT1-MMP modulates the mechanosensitivity of osteocytes.

Biochem Biophys Res Commun. 2011 Dec 19;

Authors: Kulkarni RN, Bakker AD, Gruber EV, Chae TD, Veldkamp JB, Klein-Nulend J, Everts V

Abstract
Membrane-type matrix metalloproteinase-1 (MT1-MMP) is expressed by mechanosensitive osteocytes and affects bone mass. The extracellular domain of MT1-MMP is connected to extracellular matrix, while its intracellular domain is a strong modulator of cell signaling. In theory MT1-MMP could thus transduce mechanical stimuli into a chemical response. We hypothesized that MT1-MMP plays a role in the osteocyte response to mechanical stimuli. MT1-MMP-positive and knockdown (siRNA) MLO-Y4 osteocytes were mechanically stimulated with a pulsating fluid flow (PFF). Focal adhesions were visualized by paxillin immunostaining. Osteocyte number, number of empty lacunae, and osteocyte morphology were measured in long bones of MT1-MMP(+/+) and MT1-MMP(-/-) mice. PFF decreased MT1-MMP mRNA and protein expression in MLO-Y4 osteocytes, suggesting that mechanical loading may affect pericellular matrix remodeling by osteocytes. MT1-MMP knockdown enhanced NO production and c-jun and c-fos mRNA expression in response to PFF, concomitantly with an increased number and size of focal adhesions, indicating that MT1-MMP knockdown osteocytes have an increased sensitivity to mechanical loading. Osteocytes in MT1-MMP(-/-) bone were more elongated and followed the principle loading direction, suggesting that they might sense mechanical loading. This was supported by a lower number of empty lacunae in MT1-MMP(-/-) bone, as osteocytes lacking mechanical stimuli tend to undergo apoptosis. In conclusion, mechanical stimulation decreased MT1-MMP expression by MLO-Y4 osteocytes, and MT1-MMP knockdown increased the osteocyte response to mechanical stimulation, demonstrating a novel and unexpected role for MT1-MMP in mechanosensing.

PMID: 22202174 [PubMed - as supplied by publisher]

Categories: Publications from Members of the BIIC

Accelerated Atherosclerosis in Apoe-/- Mice Heterozygous for the Insulin Receptor and the Insulin Receptor Substrate-1.

All pubs - Thu, 12/29/2011 - 03:00

Accelerated Atherosclerosis in Apoe-/- Mice Heterozygous for the Insulin Receptor and the Insulin Receptor Substrate-1.

Arterioscler Thromb Vasc Biol. 2011 Dec 22;

Authors: Galkina E, Butcher M, Keller SR, Goff M, Bruce A, Pei H, Sarembock IJ, Sanders JM, Nagelin MH, Srinivasan S, Kulkarni RN, Hedrick CC, Lattanzio FA, Dobrian AD, Nadler JL, Ley K

Abstract
OBJECTIVE: Prediabetic states are associated with accelerated atherosclerosis, but the availability of mouse models to study connections between these diseases has been limited. The aim of this study was to test the selective role of impaired insulin receptor/insulin receptor substrate-1 signaling on atherogenesis. METHODS AND RESULTS: To address the effects of impaired insulin signaling associated with hyperinsulinemia on atherosclerosis in the absence of obesity and hyperglycemia, we generated insulin receptor (Insr)/insulin receptor substrate-1 (Insr1) double heterozygous apolipoprotein (Apoe)-knockout mice (Insr(+/-)Irs1(+/-)Apoe(-/-)) mice. Insr(+/-)Irs1(+/-)Apoe(-/-) mice fed a Western diet for 15 weeks showed elevated levels of fasting insulin compared to Insr(+/+)Irs1(+/+)Apoe(-/-) mice. There were no significant differences in glucose, triglyceride, HDL, VLDL, cholesterol levels or free fatty acid in the plasma of Insr(+/-)Irs1(+/-)Apoe(-/-) and Insr(+/+)Irs1(+/+)Apoe(-/-) mice. Atherosclerotic lesions were increased in male (brachiocephalic artery) and female (aortic tree) Insr(+/-)Irs1(+/-)Apoe(-/-) compared to Insr(+/+)Irs1(+/+)Apoe(-/-) mice. Bone marrow transfer experiments demonstrated that nonhematopoietic cells have to be Insr(+/-)Irs1(+/-) to accelerate atherosclerosis. Impaired insulin signaling resulted in decreased levels of vascular phospho-eNOS, attenuated endothelium-dependent vasorelaxation and elevated VCAM-1 expression in aortas of Insr(+/-)Irs1(+/-)Apoe(-/-) mice. In addition, phospho-ERK and vascular smooth muscle cellproliferation were significantly elevated in aortas of Insr(+/-)Irs1(+/-)Apoe(-/-) mice. CONCLUSIONS: These results demonstrate that defective insulin signaling is involved in accelerated atherosclerosis in Insr(+/-)Irs1(+/-)Apoe(-/-) mice by promoting vascular dysfunction and inflammation.

PMID: 22199371 [PubMed - as supplied by publisher]

Categories: Publications from Members of the BIIC

Banting lecture 2011: hyperinsulinemia: cause or consequence?

All pubs - Tue, 12/27/2011 - 03:00

Banting lecture 2011: hyperinsulinemia: cause or consequence?

Diabetes. 2012 Jan;61(1):4-13

Authors: Corkey BE

Abstract
The Banting Medal for Scientific Achievement Award is the American Diabetes Association's highest scientific award and honors an individual who has made significant, long-term contributions to the understanding of diabetes, its treatment, and/or prevention. The award is named after Nobel Prize winner Sir Frederick Banting, who codiscovered insulin treatment for diabetes. Dr. Barbara E. Corkey received the American Diabetes Association's Banting Medal for Scientific Achievement at the Association's 71st Scientific Sessions, 24-28 June 2011, San Diego, California. She presented the Banting Lecture, "Hyperinsulinemia: Cause or Consequence?" on Sunday, 26 June 2011.

PMID: 22187369 [PubMed - in process]

Categories: Publications from Members of the BIIC

Erratum to: Palmitate induces a pro-inflammatory response in human pancreatic islets that mimics CCL2 expression by beta cells in type 2 diabetes.

All pubs - Thu, 12/22/2011 - 03:00

Erratum to: Palmitate induces a pro-inflammatory response in human pancreatic islets that mimics CCL2 expression by beta cells in type 2 diabetes.

Diabetologia. 2011 Dec 15;

Authors: Igoillo-Esteve M, Marselli L, Cunha DA, Ladrière L, Ortis F, Grieco FA, Dotta F, Weir GC, Marchetti P, Eizirik DL, Cnop M

PMID: 22170463 [PubMed - as supplied by publisher]

Categories: Publications from Members of the BIIC

IRE1-dependent activation of AMPK in response to nitric oxide.

All pubs - Thu, 12/22/2011 - 03:00

IRE1-dependent activation of AMPK in response to nitric oxide.

Mol Cell Biol. 2011 Nov;31(21):4286-97

Authors: Meares GP, Hughes KJ, Naatz A, Papa FR, Urano F, Hansen PA, Benveniste EN, Corbett JA

Abstract
While there can be detrimental consequences of nitric oxide production at pathological concentrations, eukaryotic cells have evolved protective mechanisms to defend themselves against this damage. The unfolded-protein response (UPR), activated by misfolded proteins and oxidative stress, is one adaptive mechanism that is employed to protect cells from stress. Nitric oxide is a potent activator of AMP-activated protein kinase (AMPK), and AMPK participates in the cellular defense against nitric oxide-mediated damage in pancreatic β-cells. In this study, the mechanism of AMPK activation by nitric oxide was explored. The known AMPK kinases LKB1, CaMKK, and TAK1 are not required for the activation of AMPK by nitric oxide. Instead, this activation is dependent on the endoplasmic reticulum (ER) stress-activated protein IRE1. Nitric oxide-induced AMPK phosphorylation and subsequent signaling to AMPK substrates, including Raptor, acetyl coenzyme A carboxylase, and PGC-1α, is attenuated in IRE1α-deficient cells. The endoribonuclease activity of IRE1 appears to be required for AMPK activation in response to nitric oxide. In addition to nitric oxide, stimulation of IRE1 endoribonuclease activity with the flavonol quercetin leads to IRE1-dependent AMPK activation. These findings indicate that the RNase activity of IRE1 participates in AMPK activation and subsequent signaling through multiple AMPK-dependent pathways in response to nitrosative stress.

PMID: 21896783 [PubMed - indexed for MEDLINE]

Categories: Publications from Members of the BIIC

Islet-selectivity of G-protein coupled receptor ligands evaluated for PET imaging of pancreatic β-cell mass.

All pubs - Thu, 12/22/2011 - 03:00

Islet-selectivity of G-protein coupled receptor ligands evaluated for PET imaging of pancreatic β-cell mass.

Biochem Biophys Res Commun. 2011 Sep 2;412(3):413-8

Authors: Cline GW, Zhao X, Jakowski AB, Soeller WC, Treadway JL

Abstract
A critical unmet need exists for methods to quantitatively measure endogenous pancreatic β-cell mass (BCM) for the clinical evaluation of therapies to prevent or reverse loss of BCM and diabetes progression. Our objective was to identify G-protein coupled receptors (GPCRs) that are expressed with a high degree of specificity to islet β-cells for receptor-targeted imaging of BCM. GPCRs enriched in pancreatic islets relative to pancreas acinar and hepatic tissue were identified using a database screen. Islet-specific expression was confirmed by human pancreas immunohistochemistry (IHC). In vitro selectivity assessment was determined from the binding and uptake of radiolabeled ligands to the rat insulinoma INS-1 832/13 cell line and isolated rat islets relative to the exocrine pancreas cell-type, PANC-1. Tail-vein injections of radioligands into rats were used to determine favorable image criteria of in vivo biodistribution to the pancreas relative to other internal organs (i.e., liver, spleen, stomach, and lungs). Database and IHC screening identified four candidate receptors for further in vitro and in vivo evaluation for PET imaging of BCM: prokineticin-1 receptor (PK-1R), metabotropic glutamate receptor type-5 (mGluR5), neuropeptide Y-2 receptor (NPY-2R), and glucagon-like peptide 1 receptor (GLP-1R). In vitro specificity ratios gave the following receptor rank order: PK-1R>GLP-1R>NPY-2R>mGluR5. The biodistribution rank order of selectivity to the pancreas was found to be PK-1R>VMAT2∼GLP-1R>mGluR5. Favorable islet selectivity and biodistribution characteristics suggest several GPCRs as potential targets for PET imaging of pancreatic BCM.

PMID: 21820405 [PubMed - indexed for MEDLINE]

Categories: Publications from Members of the BIIC