| 1. |
- Amisten, Stefan, et al.
(författare)
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A comparative analysis of human and mouse islet G-protein coupled receptor expression
- 2017
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- G-protein coupled receptors (GPCRs) are essential for islet function, but most studies use rodent islets due to limited human islet availability. We have systematically compared the GPCR mRNA expression in human and mouse islets to determine to what extent mouse islets can be used as surrogates for human islets to study islet GPCR function, and we have identified species-specific expression of several GPCRs. The A 3 receptor (ADORA3) was expressed only in mouse islets and the A 3 agonist MRS 5698 inhibited glucose-induced insulin secretion from mouse islets, with no effect on human islets. Similarly, mRNAs encoding the galanin receptors GAL 1 (GALR1), GAL 2 (GALR2) and GAL 3 GALR3) were abundantly expressed in mouse islets but present only at low levels in human islets, so that it reads (GALR3) and galanin inhibited insulin secretion only from mouse islets. Conversely, the sst1 receptor (SSTR1) was abundant only in human islets and its selective activation by CH 275 inhibited insulin secretion from human islets, with no effect on mouse islets. Our comprehensive human and mouse islet GPCR atlas has demonstrated that species differences do exist in islet GPCR expression and function, which are likely to impact on the translatability of mouse studies to the human context.
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| 2. |
- Amisten, Stefan, et al.
(författare)
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Activation of imidazoline receptor I-2, and improved pancreatic beta-cell function in human islets
- 2018
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Ingår i: Journal of Diabetes and Its Complications. - : Elsevier BV. - 1056-8727. ; 32:9, s. 813-818
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Tidskriftsartikel (refereegranskat)abstract
- Aim: The impact of BL11282, an imidazoline receptor (NISCH) agonist, on potentiation of glucose-stimulated insulin secretion (GSIS) from isolated human non-diabetic (ND) and type 2 diabetic (T2D) islets was investigated. Methods: Analysis of mRNA was performed by RNA-sequencing and qPCR Insulin and cAMP by RIA and EUSA respectively. Results: RNA-sequencing data revealed that NISCH is highly expressed in fat tissues, islets, liver and muscles, with eight detectable splice variants of transcripts in islets. NISCH had a positive correlation with GLP-1 (GLP1R) and GIP (GIPR) receptor transcripts. The expression of NISCH was confirmed by qPCR in human islets. NISCH and GLP1R were comparably higher expressed in mouse islets compared to human islets. GSIS was dose-dependently potentiated by BL11282 from incubated islets of ND and T2D human islet donors. The insulinotropic action of BL11282 was associated with increased cAMP. While the harmful effect of high glucose on reductive capacity of islet cells was enhanced by glibenclamide during long-term culture, it was counteracted by BL11282 or Bt2-cAMP. BL11282 also increased proliferation of INS-1 cells during long-time culture. Conclusion: Our data suggest that BL11282 potentiates GSIS by an action involving cAMP/PKA system and BL11282 could be an attractive insulinotropic and beta-cell protective agent. (C) 2018 Elsevier Inc. All rights reserved.
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| 3. |
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| 4. |
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| 5. |
- Amisten, Stefan, et al.
(författare)
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ADP mediates inhibition of insulin secretion by activation of P2Y13 receptors in mice.
- 2010
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Ingår i: Diabetologia. - : Springer Science and Business Media LLC. - 1432-0428 .- 0012-186X. ; Jul 1, s. 1927-1934
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Tidskriftsartikel (refereegranskat)abstract
- AIMS/HYPOTHESES: To investigate the effects of extracellular purines on insulin secretion from mouse pancreatic islets. METHODS: Mouse islets and beta cells were isolated and examined with mRNA real-time quantification, cAMP quantification and insulin and glucagon secretion. ATP release was measured in MIN6c4 cells. Insulin and glucagon secretion were measured in vivo after glucose injection. RESULTS: Enzymatic removal of extracellular ATP at low glucose levels increased the secretion of both insulin and glucagon, while at high glucose levels insulin secretion was reduced and glucagon secretion was stimulated, indicating an autocrine effect of purines. In MIN6c4 cells it was shown that glucose does induce release of ATP into the extracellular space. Quantitative real-time PCR demonstrated the expression of the ADP receptors P2Y(1) and P2Y(13) in both intact mouse pancreatic islets and isolated beta cells. The stable ADP analogue 2-MeSADP had no effect on insulin secretion. However, co-incubation with the P2Y(1) antagonist MRS2179 inhibited insulin secretion, while co-incubation with the P2Y(13) antagonist MRS2211 stimulated insulin secretion, indicating that ADP acting via P2Y(1) stimulates insulin secretion, while signalling via P2Y(13) inhibits the secretion of insulin. P2Y(13) antagonism through MRS2211 per se increased the secretion of both insulin and glucagon at intermediate (8.3 mmol/l) and high (20 mmol/l) glucose levels, confirming an autocrine role for ADP. Administration of MRS2211 during glucose injection in vivo resulted in both increased secretion of insulin and reduced glucose levels. CONCLUSIONS/INTERPRETATION: In conclusion, ADP acting on the P2Y(13) receptors inhibits insulin release. An antagonist to P2Y(13) increases insulin release and could be evaluated for the treatment of diabetes.
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| 6. |
- Amisten, Stefan, et al.
(författare)
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An atlas and functional analysis of G-protein coupled receptors in human islets of Langerhans
- 2013
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Ingår i: Pharmacology and Therapeutics. - : Elsevier BV. - 0163-7258. ; 139:3, s. 359-391
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Forskningsöversikt (refereegranskat)abstract
- G-protein coupled receptors (GPCRs) regulate hormone secretion from islets of Langerhans, and recently developed therapies for type-2 diabetes target islet GLP-1 receptors. However, the total number of GPCRs expressed by human islets, as well as their function and interactions with drugs, is poorly understood. In this review we have constructed an atlas of all GPCRs expressed by human islets: the 'islet GPCRome'. We have used this atlas to describe how islet GPCRs interact with their endogenous ligands, regulate islet hormone secretion, and interact with drugs known to target GPCRs, with a focus on drug/receptor interactions that may affect insulin secretion. The islet GPCRome consists of 293 GPCRs, a majority of which have unknown effects on insulin, glucagon and somatostatin secretion. The islet GPCRs are activated by 271 different endogenous ligands, at least 131 of which are present in islet cells. A large signalling redundancy was also found, with 119 ligands activating more than one islet receptor. Islet GPCRs are also the targets of a large number of clinically used drugs, and based on their coupling characteristics and effects on receptor signalling we identified 107 drugs predicted to stimulate and 184 drugs predicted to inhibit insulin secretion. The islet GPCRome highlights knowledge gaps in the current understanding of islet GPCR function, and identifies GPCR/ligand/drug interactions that might affect insulin secretion, which are important for understanding the metabolic side effects of drugs. This approach may aid in the design of new safer therapeutic agents with fewer detrimental effects on islet hormone secretion. (C) 2013 Elsevier Inc. All rights reserved.
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| 7. |
- Amisten, Stefan, et al.
(författare)
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An atlas of G-protein coupled receptor expression and function in human subcutaneous adipose tissue.
- 2015
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Ingår i: Pharmacology and Therapeutics. - : Elsevier BV. - 0163-7258. ; 146:Sep 19, s. 61-93
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Forskningsöversikt (refereegranskat)abstract
- G-protein coupled receptors (GPCRs) are involved in the regulation of adipose tissue function, but the total number of GPCRs expressed by human subcutaneous adipose tissue, as well as their function and interactions with drugs, is poorly understood. We have constructed an atlas of all GPCRs expressed by human subcutaneous adipose tissue: the 'adipose tissue GPCRome', to support the exploration of novel control nodes in metabolic and endocrine functions. This atlas describes how adipose tissue GPCRs regulate lipolysis, insulin resistance and adiponectin and leptin secretion. We also discuss how adipose tissue GPCRs interact with their endogenous ligands and with GPCR-targeting drugs, with a focus on how drug/receptor interactions may affect lipolysis, and present a model predicting how GPCRs with unknown effects on lipolysis might modulate cAMP-regulated lipolysis. Subcutaneous adipose tissue expresses 163 GPCRs, a majority of which have unknown effects on lipolysis, insulin resistance and adiponectin and leptin secretion. These GPCRs are activated by 180 different endogenous ligands, and are the targets of a large number of clinically used drugs. We identified 119 drugs, acting on 23 GPCRs, that are predicted to stimulate lipolysis and 173 drugs, acting on 25 GPCRs, that are predicted to inhibit lipolysis. This atlas highlights knowledge gaps in the current understanding of adipose tissue GPCR function, and identifies GPCR/ligand/drug interactions that might affect lipolysis, which is important for understanding and predicting metabolic side effects of drugs. This approach may aid in the design of new, safer therapeutic agents, with fewer undesired effects on lipid homeostasis.
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| 8. |
- Amisten, Stefan, et al.
(författare)
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Anti-diabetic action of all- trans retinoic acid and the orphan G protein coupled receptor GPRC5C in pancreatic beta-cells
- 2017
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Ingår i: Endocrine Journal. - 0918-8959. ; 64:3, s. 325-338
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Tidskriftsartikel (refereegranskat)abstract
- Pancreatic islets express high levels of the orphan G-protein coupled receptor C5C (GPRC5C), the function of which remains to be established. Here we have examined the role of GPRC5C in the regulation of insulin secretion and beta-cell survival and proliferation using human and mouse pancreatic islets. The expression of GPRC5C was analysed by RNA-sequencing, qPCR, western blotting and confocal microscopy. Insulin secretion and cell viability were determined by RIA and MTS assays, respectively. GPRC5C mRNA expression and protein level were reduced in the islets from type-2 diabetic donors. RNA sequencing in human islets revealed GPRC5C expression correlated with the expression of genes controlling apoptosis, cell survival and proliferation. A reduction in Gprc5c mRNA and protein expression was observed in islets isolated from old mice (>46 weeks of age) compared to that in islets from newborn (<3 weeks) mice. Down-regulation of Gprc5c led to both moderately reduced glucose-stimulated insulin release and also reduced cAMP content in mouse islets. Potentiation of glucose-stimulated insulin secretion concomitant with enhanced islet cAMP level by all-trans retinoic acid (ATRA) was attenuated upon Gprc5c-KD. ATRA also increased [Ca+2](i) in Huh7-cells. Gprc5c over expression in Huh7 cells was associated with increased ERK1/2 activity. Gprc5c-KD in clonal MIN6c4 cells reduced cell proliferation and in murine islets increased apoptosis and the sensitivity of primary islet cells to a cocktail of pro-apoptotic cytokines. Our results demonstrate that agents activating GPRC5C represent a novel modality for the treatment and/or prevention of diabetes by restoring and/or maintaining functional beta-cell mass.
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| 9. |
- Amisten, Stefan, et al.
(författare)
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Gene expression profiling for the identification of G-protein coupled receptors in human platelets
- 2008
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Ingår i: Thrombosis Research. - : Elsevier BV. - 1879-2472 .- 0049-3848. ; 122:1, s. 47-57
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Tidskriftsartikel (refereegranskat)abstract
- INTRODUCTION AND MATERIALS AND METHODS: G-protein coupled receptors (GPCRs) play an important role in platelet aggregation. To identify new platelet GPCRs, a platelet gene expression profile was generated and validated using quantitative real-time PCR. RESULTS: In total, mRNA of 28 GPCR genes was detected in human platelets. The 12 most abundant platelet GPCR transcripts were: thrombin receptor PAR1 (1865+/-178%), ADP receptor P2Y(12) (459+/-88%), succinate receptor 1 (257+/-48%), ADP receptor P2Y(1) (100%), orphan P2RY(10) (68.2+/-3.3%), lysophosphatidic acid receptors GPR23 (48.2+/-11%) and GPR92 (26.1+/-3.3%), adrenergic receptor alpha(2A) (18.4+/-4.4%), orphan EBI2 (6.31+/-0.42), adenosine receptors A(2A) (2.94+/-0.24%) and A(2B) (2.88+/-0.16%) and lysophosphatidic acid receptor LPA(1) (2.59+/-0.39%) (% relative to the chosen calibrator P2Y(1)). A surprising G-protein coupled receptor redundancy was found: two ADP receptors (P2Y(1) and P2Y(12)), three adenosine receptors (A(2A), A(2B), and A(1)), four lysophosphatidic acid receptors (LPA(1), LPA(3), GPR23 and GPR92), two l-glutamate receptors (mGlu(3) and mGlu(4)) and two serotonin receptors (5-HT(1F) and 5-HT(4)). The adenosine receptor A(2B) gene expression was validated with protein expression and functional studies. Western blot confirmed A(2B) receptor protein expression and platelet flow cytometry demonstrated inhibition of the effect of NECA by the adenosine A(2B)-antagonist MRS1754. CONCLUSIONS: We have detected several GPCRs not previously known to be expressed in platelets, including a functional adenosine A(2B) receptor. The findings could improve our understanding of platelet aggregation and provide new targets for drug development.
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| 10. |
- Amisten, Stefan
(författare)
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Genetic studies on cardiovascular disease - identification of novel drug targets
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The aim of this thesis was to identify novel potential drug targets of cardiovascular disease with a focus on G-protein coupled receptors. We identified a common genetic variant of the ATP receptor P2Y11, where an alanine is substituted with a threonine at position 87 of the P2Y11 receptor that increases the risk of developing acute myocardial infarction. Also, the Thr-87 variant of P2Y11 is associated with elevated serum concentrations of C-reactive protein. In CHO cells, ATP?S stimulated recombinant P2Y11 Thr-87 displayed a reduced cAMP response compared to the P2Y11 Ala-87 variant. We hypothesize that a loss of a protective mechanism mediated by P2Y11 cAMP signaling is involved in the increased risk of myocardial infarction seen in the AMI case-control study. Polymorphisms forming a H2 haplotype of the ADP receptor P2Y12 have been linked to an increased platelet response to ADP and increased risks of atherosclerosis and peripheral arterial disease. We show that a polymorphism of the P2Y13 gene, causing a methionine to threonine substitution at position 158 of the P2Y13 receptor, is in complete linkage disequilibrium with the P2Y12 H2 haplotype. However, in three separate populations, we found no association between the P2Y12 H2 haplotype/P2Y13 Thr-158 polymorphisms and myocardial infarction, type 2 diabetes or any examined cardiovascular risk factor. G-protein coupled receptors are important regulators of platelet activation. Using microarray, we identified several G-protein coupled receptors in platelets whose expression in platelets has not previously been known. To illustrate our findings, we demonstrate for the first time adenosine A2B receptor mediated inhibition of platelet activation. Finally, using a unique in vitro model, we examined the molecular response to the implantation of bare metal and drug-eluting cardiovascular stents into human arteries. We found several differentially expressed genes involved in the regulation of inflammation, endothelial cell function, platelet activation and cellular proliferation. We hope that our model will increase the understanding of the processes involved in restenosis and late stent thrombosis associated with bare metal and drug-eluting stents and that our model may be useful in the development of next generation drug eluting stents.
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| 11. |
- Amisten, Stefan, et al.
(författare)
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Increased risk of acute myocardial infarction and elevated levels of C-reactive protein in carriersof the Thr-87 variant of the ATP receptor P2Y11.
- 2007
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Ingår i: European Heart Journal. - : Oxford University Press (OUP). - 1522-9645 .- 0195-668X. ; 28:1, s. 13-18
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Tidskriftsartikel (refereegranskat)abstract
- Aims Extracellular ATP acting on the P2Y(11) receptor regulates inflammatory cells. We hypothesized that polymorphisms in the receptor could influence the risk of acute myocardial infarction (AMI). Methods and results In the Malmo diet and cancer AMI case-control study (n = 3732) the P2Y(11) gene Thr-87 polymorphism was present in 19.8% of the controls and 22.9% in AMI patients (OR 1.21; P = 0.03). Stronger associations were found in patients with family history (FH) of AMI, 1.32; early-onset (EO) AMI, 1.43; or EO AMI combined with FH, 1.50; supporting a genetic mechanism. The Thr-87 homozygotes had an even greater risk of AMI, 1.94 (P = 0.04); and 2.48 in the EO AMI subgroup, suggesting a genetic dosage effect. In the cardiovascular risk factor group (n = 6055), 21.3% carried the Thr-87 allele. C-reactive protein was elevated in Thr-87 carriers: 1.6 mg/L vs. 1.3 mg/L (P = 0.001). No difference was seen for blood pressure, lipids, body mass index, smoking, or diabetes mellitus. Conclusion The common Ala-87-Thr polymorphism of the P2Y(11) receptor is associated with AMI and increased levels of C-reactive protein. We hypothesize that an inflammatory mechanism might be involved. The P2Y(11) receptor is a promising new drug target in the prevention of AMI.
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| 12. |
- Amisten, Stefan, et al.
(författare)
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The P2Y(13) Met-158-Thr Polymorphism, Which Is in Linkage Disequilibrium with the P2Y(12) Locus, Is Not Associated with Acute Myocardial Infarction.
- 2008
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 3:1
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND AND AIMS: The aims of this study were to investigate (1) if P2Y(12) polymorphisms defining the P2Y(12) H2 allele are associated with any other SNPs that may explain the previously reported association with increased ADP induced platelet activation and association with peripheral arterial disease and coronary artery disease and (2) if such variants are associated with acute myocardial infarction (AMI) or classical risk factors for AMI. METHODS AND RESULTS: The P2Y(13) Met-158-Thr polymorphism was found to be in linkage disequilibrium (LD) with the P2Y(12) H2 haplotype (all examined SNPs: D' = 1.0, r(2) = 0.936-1.0), defining a novel P2Y(12) H2/P2Y(13) Thr-158 haplotype. Genotyping of an AMI case control population (n = 1244 cases, 2488 controls) revealed no association of the P2Y(13) Thr-158 allele with AMI (OR = 0.96, 95% C.I. 0.82-1.12, P = 0.63). Also, no differences between the genotype frequencies of P2Y(13) Met-158-Met and Met-158-Thr/Thr-158-Thr were seen in AMI case-control subpopulations (early onset AMI OR = 1.06, 95% C.I. 0.85-1.31, P = 0.62); family history of AMI (OR = 0.98, 95% C.I. 0.78-1.22, P = 0.83) nor in early onset AMIs with family history of AMI (OR = 1.0, 95% C.I. 0.74-1.36, P = 1.0). Genotyping of the P2Y(13) Met-158-Thr polymorphism in a population based sample (n = 6055) revealed no association with cardiovascular risk factors. In addition, the P2Y(13) Met-158-Thr polymorphism was genotyped in a diabetes case-control population, and associations were found neither with DM nor with any examined DM risk factors. CONCLUSION GENOTYPING: The P2Y(13) Met-158-Thr polymorphism is in tight LD with the P2Y(12) locus but is not associated with AMI or classical cardiovascular risk factors.
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| 13. |
- Atanes, Patricio, et al.
(författare)
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Defining G protein-coupled receptor peptide ligand expressomes and signalomes in human and mouse islets
- 2018
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Ingår i: Cellular and Molecular Life Sciences. - : Springer Science and Business Media LLC. - 1420-682X .- 1420-9071. ; 75:16, s. 3039-3050
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Tidskriftsartikel (refereegranskat)abstract
- Introduction: Islets synthesise and secrete numerous peptides, some of which are known to be important regulators of islet function and glucose homeostasis. In this study, we quantified mRNAs encoding all peptide ligands of islet G protein-coupled receptors (GPCRs) in isolated human and mouse islets and carried out in vitro islet hormone secretion studies to provide functional confirmation for the species-specific role of peptide YY (PYY) in mouse islets. Materials and methods: GPCR peptide ligand mRNAs in human and mouse islets were quantified by quantitative real-time PCR relative to the reference genes ACTB, GAPDH, PPIA, TBP and TFRC. The pathways connecting GPCR peptide ligands with their receptors were identified by manual searches in the PubMed, IUPHAR and Ingenuity databases. Distribution of PYY protein in mouse and human islets was determined by immunohistochemistry. Insulin, glucagon and somatostatin secretion from islets was measured by radioimmunoassay. Results: We have quantified GPCR peptide ligand mRNA expression in human and mouse islets and created specific signalomes mapping the pathways by which islet peptide ligands regulate human and mouse GPCR signalling. We also identified species-specific islet expression of several GPCR ligands. In particular, PYY mRNA levels were ~ 40,000-fold higher in mouse than human islets, suggesting a more important role of locally secreted Pyy in mouse islets. This was confirmed by IHC and functional experiments measuring insulin, glucagon and somatostatin secretion. Discussion: The detailed human and mouse islet GPCR peptide ligand atlases will allow accurate translation of mouse islet functional studies for the identification of GPCR/peptide signalling pathways relevant for human physiology, which may lead to novel treatment modalities of diabetes and metabolic disease.
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| 14. |
- Balhuizen, Alexander, et al.
(författare)
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Activation of G protein-coupled receptor 30 modulates hormone secretion and counteracts cytokine-induced apoptosis in pancreatic islets of female mice.
- 2010
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Ingår i: Molecular and Cellular Endocrinology. - : Elsevier BV. - 1872-8057 .- 0303-7207. ; 320, s. 16-24
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Tidskriftsartikel (refereegranskat)abstract
- The role of the newly discovered estrogen receptor GPR30 in islet physiology and pathophysiology is unclear. We examined GPR30 expression in relation to hormone secretion and possible anti-apoptotic effects in isolated mouse islets using the synthetic GPR30 ligand G-1. The mRNA and protein expression of GPR30 was analyzed by qPCR, Western blot and confocal microscopy. Hormone secretion and cAMP content were determined with RIA and apoptosis in islet cells with the Annexin-V method. GPR30 mRNA and protein expression was markedly higher in islets from females compared to male. This gender difference was not found for the genomic estrogen receptors ERalpha and ERbeta, the ERalpha expression being 10-fold higher than ERbeta in both genders. Confocal microscopy revealed abounden GPR30 expression in insulin, glucagon and somatostatin cells. Dose-response studies of G-1 vs 17beta-estradiol in isolated islets at 1 or 12mM glucose showed an almost identical pattern in that both compounds increased insulin and inhibited glucagon and somatostatin secretion. ICI-182,780 and EM-652, potent antagonists of the 17beta-estradiol receptors (ERalpha and ERbeta) did not influence the amplifying effect of G-1 or 17beta-estradiol on cAMP content or insulin secretion from isolated islets. Cytokine-induced (IL-1beta+TNFalpha+INFgamma) apoptosis in islets, cultured for 24h at 5mM glucose, was almost abolished by G-1 or 17beta-estradiol treatment. Addition of ICI-182,780 or EM-652 did not affect this beneficial effect of G-1 or 17beta-estradiol. Taken together, our findings show that GPR30 is expressed in most islet endocrine cells. The synthetic GPR30 ligand G-1 mimics the non-genomic effects of 17beta-estradiol on islet hormone secretion, cAMP content in islets and its anti-apoptotic effects. G-1 or analogs thereof might be new potential candidates in the therapeutic strategy for type 2 diabetes in women.
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| 15. |
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| 16. |
- Braun, Oscar, et al.
(författare)
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Residual platelet ADP reactivity after clopidogrel treatment is dependent on activation of both the unblocked P2Y(1) and the P2Y (12) receptor and is correlated with protein expression of P2Y (12).
- 2007
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Ingår i: Purinergic Signalling. - : Springer Science and Business Media LLC. - 1573-9546 .- 1573-9538. ; 3:3, s. 195-201
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Tidskriftsartikel (refereegranskat)abstract
- Two ADP receptors have been identified on human platelets: P2Y(1) and P2Y(12). The P2Y(12) receptor blocker clopidogrel is widely used to reduce the risks in acute coronary syndromes, but, currently, there is no P2Y(1) blocker in clinical use. Evidence for variable responses to clopidogrel has been described in several reports. The mechanistic explanation for this phenomenon is not fully understood. The aim of this study was to examine mechanisms responsible for variability of 2MeS-ADP, a stable ADP analogue, induced platelet reactivity in clopidogrel-treated patients. Platelet reactivity was assessed by flow cytometry measurements of P-selectin (CD62P) and activated GpIIb/IIIa complex (PAC-1). Residual 2MeS-ADP activation via the P2Y(12) and P2Y(1) receptors was determined by co-incubation with the selective antagonists AR-C69931 and MRS2179 in vitro. P2Y(1) and P2Y(12) receptor expression on both RNA and protein level were determined, as well as the P2Y(12) H1 or H2 haplotypes. Our data suggest that the residual platelet activation of 2MeS-ADP after clopidogrel treatment is partly due to an inadequate antagonistic effect of clopidogrel on the P2Y(12) receptor and partly due to activation of the P2Y(1) receptor, which is unaffected by clopidogrel. Moreover, a correlation between increased P2Y(12) protein expression on platelets and decreased response to clopidogrel was noticed, r(2)=0.43 (P<0.05). No correlation was found between P2Y(12) mRNA levels and clopidogrel resistance, indicating post-transcriptional mechanisms. To achieve additional ADP inhibition in platelets, antagonists directed at the P2Y(1) receptor could be more promising than the development of more potent P2Y(12) receptor antagonists.
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| 17. |
- De Marinis, Yang, et al.
(författare)
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Enhancement of glucagon secretion in mouse and human pancreatic alpha cells by protein kinase C (PKC) involves intracellular trafficking of PKCalpha and PKCdelta.
- 2010
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Ingår i: Diabetologia. - : Springer Science and Business Media LLC. - 1432-0428 .- 0012-186X. ; 53:4, s. 717-729
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Tidskriftsartikel (refereegranskat)abstract
- AIMS/HYPOTHESIS: Protein kinase C (PKC) regulates exocytosis in various secretory cells. Here we studied intracellular translocation of the PKC isoenzymes PKCalpha and PKCdelta, and investigated how activation of PKC influences glucagon secretion in mouse and human pancreatic alpha cells. METHODS: Glucagon release from intact islets was measured in static incubations, and the amounts released were determined by RIA. Exocytosis was monitored as increases in membrane capacitance using the patch-clamp technique. The expression of genes encoding PKC isoforms was analysed by real-time PCR. Intracellular PKC distribution was assessed by confocal microscopy. RESULTS: The PKC activator phorbol 12-myristate 13-acetate (PMA) stimulated glucagon secretion from mouse and human islets about fivefold (p < 0.01). This stimulation was abolished by the PKC inhibitor bisindolylmaleimide (BIM). Whereas PMA potentiated exocytosis more than threefold (p < 0.001), BIM inhibited alpha cell exocytosis by 60% (p < 0.05). In mouse islets, the PKC isoenzymes, PKCalpha and PKCbeta1, were highly abundant, while in human islets PKCeta, PKCepsilon and PKCzeta were the dominant variants. PMA stimulation of human alpha cells correlated with the translocation of PKCalpha and PKCdelta from the cytosol to the cell periphery. In the mouse alpha cells, PKCdelta was similarly affected by PMA, whereas PKCalpha was already present at the cell membrane in the absence of PMA. This association of PKCalpha in alpha cells was principally dependent on Ca(2+) influx through the L-type Ca(2+) channel. CONCLUSIONS/INTERPRETATION: PKC activation augments glucagon secretion in mouse and human alpha cells. This effect involves translocation of PKCalpha and PKCdelta to the plasma membrane, culminating in increased Ca(2+)-dependent exocytosis. In addition, we demonstrated that PKCalpha translocation and exocytosis exhibit differential Ca(2+) channel dependence.
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| 18. |
- De Marinis, Yang, et al.
(författare)
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GLP-1 inhibits and adrenaline stimulates glucagon release by differential modulation of N- and L-type Ca2+ channel-dependent exocytosis.
- 2010
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Ingår i: Cell Metabolism. - : Elsevier BV. - 1550-4131. ; 11:6, s. 543-553
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Tidskriftsartikel (refereegranskat)abstract
- Glucagon secretion is inhibited by glucagon-like peptide-1 (GLP-1) and stimulated by adrenaline. These opposing effects on glucagon secretion are mimicked by low (1-10 nM) and high (10 muM) concentrations of forskolin, respectively. The expression of GLP-1 receptors in alpha cells is <0.2% of that in beta cells. The GLP-1-induced suppression of glucagon secretion is PKA dependent, is glucose independent, and does not involve paracrine effects mediated by insulin or somatostatin. GLP-1 is without much effect on alpha cell electrical activity but selectively inhibits N-type Ca(2+) channels and exocytosis. Adrenaline stimulates alpha cell electrical activity, increases [Ca(2+)](i), enhances L-type Ca(2+) channel activity, and accelerates exocytosis. The stimulatory effect is partially PKA independent and reduced in Epac2-deficient islets. We propose that GLP-1 inhibits glucagon secretion by PKA-dependent inhibition of the N-type Ca(2+) channels via a small increase in intracellular cAMP ([cAMP](i)). Adrenaline stimulates L-type Ca(2+) channel-dependent exocytosis by activation of the low-affinity cAMP sensor Epac2 via a large increase in [cAMP](i).
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| 19. |
- Dunér, Pontus, et al.
(författare)
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Adhesion G Protein-Coupled Receptor G1 (ADGRG1/GPR56) and Pancreatic beta-Cell Function
- 2016
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Ingår i: Journal of Clinical Endocrinology & Metabolism. - : The Endocrine Society. - 0021-972X .- 1945-7197. ; 101:12, s. 4637-4645
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Tidskriftsartikel (refereegranskat)abstract
- Context: Adhesion G protein-coupled receptor (GPCR)-G1 (ADGRG1) is the most abundant GPCR in human pancreatic islets, but its role in islet function is unclear. Objective: Investigate how ADGRG1 expression and activation by its ligand, collagen III, impacts beta-cell function in normal and type 2 diabetic (T2D) islets. Design: Genes associated with the ADGRG1 in human islets was probed by RNA-sequencing of human pancreatic islet isolated from cadaveric donors, followed by functional studies on beta-cell proliferation, apoptosis, and insulin secretion in human and mouse islets and in INS-1 cells. Main Outcome Measures: Changes in beta-cell gene expression, proliferation, apoptosis, and insulin secretion were quantified by RNA-sequencing, qPCR, Thymidine incorporation, Western blotting, and RIA, respectively. Results: ADGRG1 is the most abundant GPCR mRNA in both human and mouse islets, and its expression in human islets strongly correlates with genes important for beta-cell function and T2D risk. The expression of ADGRG1 was reduced in islets of T2D donors, in db/db mouse islets, and in isolated human islets exposed to chronic hyperglycemia. Beneficial effects of collagen type III on beta-cell function via activation of the cAMP/protein kinase A pathway, suppression of RhoA and caspase-3 activity, increased beta-cell viability, and proliferation were abolished when ADGRG1 was down-regulated in beta-cells. Conclusions: We demonstrate a mechanistic link between ADGRG1 expression and beta-cell function. Pharmacological agents that promote expression or activation of the ADGRG1 receptor may represent a novel approach for the treatment of T2D.
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| 20. |
- Jönsson, Daniel, et al.
(författare)
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LPS induces GROalpha chemokine production via NF-kappaB in oral fibroblasts.
- 2009
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Ingår i: Inflammation Research. - : Springer Science and Business Media LLC. - 1420-908X .- 1023-3830. ; 58:11, s. 791-796
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Tidskriftsartikel (refereegranskat)abstract
- Objective and design Chemotaxis of neutrophils from blood to the inflammation process plays an important role in development of periodontal inflammation. The novel chemokine GRO alpha, also named CXCL1, is a strong chemoattractant for neutrophils. Data on production and regulation of GRO alpha by oral fibroblasts have not previously been presented. Materials and methods GRO alpha mRNA and protein levels were determined in human periodontal ligament cells and mouse gingival fibroblasts by quantitative real-time PCR and ELISA. Results We disclose that both human periodontal ligament cells and mouse gingival fibroblasts produce GRO alpha in response to LPS stimulation. Stimulation with LPS for 24 h increased both mRNA for GRO alpha and GRO alpha protein. The steroid hormone estrogen had no effect on LPS-induced GRO alpha mRNA expression. Treatment with the glucocorticoid dexamethasone attenuated LPS-induced GRO alpha production, and the NF-kappa B blocker MG 132 fully prevented LPS-induced GRO alpha. Conclusions Oral fibroblasts respond to LPS stimulation by increasing GRO alpha production via the transcription factor NF-kappa B, suggesting that this mechanism may be involved in development of periodontal inflammation.
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| 21. |
- Jönsson, Daniel, et al.
(författare)
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LPS induces GROα chemokine production via NFκB in oral fibroblasts
- 2009
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Ingår i: Inflammation Research. - : Springer. - 1023-3830 .- 1420-908X. ; 11:58, s. 791-796
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE AND DESIGN: Chemotaxis of neutrophils from blood to the inflammation process plays an important role in development of periodontal inflammation. The novel chemokine GROalpha, also named CXCL1, is a strong chemoattractant for neutrophils. Data on production and regulation of GROalpha by oral fibroblasts have not previously been presented. MATERIALS AND METHODS: GROalpha mRNA and protein levels were determined in human periodontal ligament cells and mouse gingival fibroblasts by quantitative real-time PCR and ELISA. RESULTS: We disclose that both human periodontal ligament cells and mouse gingival fibroblasts produce GROalpha in response to LPS stimulation. Stimulation with LPS for 24 h increased both mRNA for GROalpha and GROalpha protein. The steroid hormone estrogen had no effect on LPS-induced GROalpha mRNA expression. Treatment with the glucocorticoid dexamethasone attenuated LPS-induced GROalpha production, and the NF-kappaB blocker MG 132 fully prevented LPS-induced GROalpha. CONCLUSIONS: Oral fibroblasts respond to LPS stimulation by increasing GROalpha production via the transcription factor NF-kappaB, suggesting that this mechanism may be involved in development of periodontal inflammation.
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| 22. |
- Kumar, Rajesh, et al.
(författare)
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Insulinotropic and Antidiabetic Effects of 17{beta}-Estradiol and the GPR30 Agonist G-1 on Human Pancreatic Islets.
- 2011
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Ingår i: Endocrinology. - : The Endocrine Society. - 0013-7227 .- 1945-7170. ; 152:7, s. 2568-2579
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Tidskriftsartikel (refereegranskat)abstract
- We have recently shown that 17β-estradiol (E2) and the synthetic G protein-coupled receptor 30 (GPR30) ligand G-1 have antiapoptotic actions in mouse pancreatic islets, raising the prospect that they might exert beneficial effects also in human islets. The objective of the present study was to identify the expression of GPR30 in human islets and clarify the role of GPR30 in islet hormone secretion and β-cell survival. GPR30 expression was analyzed by confocal microscopy, Western blot, and quantitative PCR in islets from female and male donors. Hormone secretion, phosphatidylinositol hydrolysis, cAMP content, and caspase-3 activity in female islets were determined with conventional methods and apoptosis with the annexin-V method. Confocal microscopy revealed GPR30 expression in islet insulin, glucagon, and somatostatin cells. GPR30 mRNA and protein expression was markedly higher in female vs. male islets. An amplifying effect of G-1 or E2 on cAMP content and insulin secretion from isolated female islets was not influenced by the E2 genomic receptor (ERα and ERβ) antagonists ICI 182,780 and EM-652. Cytokine-induced (IL-1β plus TNFα plus interferon-γ) apoptosis in islets cultured for 24 h at 5 mmol/liter glucose was almost abolished by G-1 or E2 treatment and was not affected by the nuclear estrogen receptor antagonists. Concentration-response studies on female islets from healthy controls and type 2 diabetic subjects showed that both E2 and G-1 displayed important antidiabetic actions by improving glucose-stimulated insulin release while suppressing glucagon and somatostatin secretion. In view of these findings, we propose that small molecules activating GPR30 could be promising in the therapy of diabetes mellitus.
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| 23. |
- Lood, Christian, et al.
(författare)
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Platelet transcriptional profile and protein expression in patients with systemic lupus erythematosus: up-regulation of the type I interferon system is strongly associated with vascular disease.
- 2010
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Ingår i: Blood. - : American Society of Hematology. - 1528-0020 .- 0006-4971. ; Jul 1, s. 1951-1957
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Tidskriftsartikel (refereegranskat)abstract
- Patients with systemic lupus erythematosus (SLE) have a markedly increased risk to develop cardiovascular disease, and traditional cardiovascular risk factors fail to account for this increased risk. We used microarray to probe the platelet transcriptome in individuals with SLE and healthy controls, and the gene and protein expression of a subset of differentially expressed genes was further investigated and correlated to platelet activation status. Real-time PCR was used to confirm a type I interferon (IFN) gene signature in patients with SLE, and the IFN-regulated proteins PRKRA, IFITM1 and CD69 (p<0.0001) were found to be up-regulated in platelets from SLE patients as compared to healthy volunteers. Notably, patients with a history of vascular disease had increased expression of type I IFN-regulated proteins as well as more activated platelets as compared with patients without vascular disease. We suggest that interferogenic immune complexes stimulate production of IFNalpha which up-regulates the megakaryocytic type I IFN-regulated genes and proteins. This could affect platelet activation and contribute to development of vascular disease in SLE. In addition, platelets with type I IFN signature could be a novel marker for vascular disease in SLE.
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| 24. |
- McCloskey, Conor, et al.
(författare)
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Kv1.3 is the exclusive voltage-gated K plus channel of platelets and megakaryocytes: roles in membrane potential, Ca2+signalling and platelet count
- 2010
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Ingår i: Journal of Physiology. - : Wiley. - 1469-7793 .- 0022-3751. ; 588:9, s. 1399-1406
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Tidskriftsartikel (refereegranskat)abstract
- A delayed rectifier voltage-gated K+ channel (Kv) represents the largest ionic conductance of platelets and megakaryocytes, but is undefined at the molecular level. Quantitative RT-PCR of all known Kv alpha and ancillary subunits showed that only Kv1.3 (KCNA3) is substantially expressed in human platelets. Furthermore, megakaryocytes from Kv1.3-/- mice or from wild-type mice exposed to the Kv1.3 blocker margatoxin completely lacked Kv currents and displayed substantially depolarised resting membrane potentials. In human platelets, margatoxin reduced the P2X(1)- and thromboxaneA(2) receptor-evoked [Ca2+](i) increases and delayed the onset of store-operated Ca2+ influx. Megakaryocyte development was normal in Kv1.3-/- mice, but the platelet count was increased, consistent with a role of Kv1.3 in apoptosis or decreased platelet activation. We conclude that Kv1.3 forms the Kv channel of the platelet and megakaryocyte, which sets the resting membrane potential, regulates agonist-evoked Ca2+ increases and influences circulating platelet numbers.
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| 25. |
- Meidute, Sandra, et al.
(författare)
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GPR40 protein levels are crucial to the regulation of stimulated hormone secretion in pancreatic islets. Lessons from spontaneous obesity-prone and non-obese type 2 diabetes in rats.
- 2013
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Ingår i: Molecular and Cellular Endocrinology. - : Elsevier BV. - 1872-8057 .- 0303-7207. ; 381:1-2, s. 150-159
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Tidskriftsartikel (refereegranskat)abstract
- The role of islet GPR40 protein in the pathogenesis of diabetes is unclear. We explored the influence of GPR40 protein levels on hormone secretion in islets from two rat models of spontaneous type 2 diabetes displaying either hyperlipidaemia or hyperglycaemia. GPR40 expression was analysed by confocal microscopy, Western blot and qPCR in islets from preobese Zucker (fa/fa) rats, diabetic Goto-Kakizaki (GK) rats, and controls. Confocal microscopy of control islets showed expression of GPR40 protein in insulin, glucagon and somatostatin cells. GPR40 expression was strongly increased in islets of hyperlipidaemic fa/fa rats and coincided with a concentration-related increase in palmitate-induced release of insulin and glucagon and its inhibition of somatostatin release. Conversely, hyperglycaemic GK islets displayed an extremely faint expression of GPR40 as did high-glucose-cultured control islets. This was reflected in abolished palmitate-induced hormone response in GK islets and high-glucose-cultured control islets. The palmitate antagonist rosiglitazone promoted reappearance of GPR40 in high-glucose-cultured islets and served as partial agonist in glucose-stimulated insulin release. GPR40 protein is abundantly expressed in pancreatic islets and modulates stimulated hormone secretion. Mild hyperlipidaemia in obesity-prone diabetes creates increased GPR40 expression and increased risk for an exaggerated palmitate-induced insulin response and lipotoxicity, a metabolic situation suitable for GPR40 antagonist treatment. Chronic hyperglycaemia creates abrogated GPR40 expression and downregulated insulin release, a metabolic situation suitable for GPR40 agonist treatment to avoid glucotoxicity. GPR40 protein is interactively modulated by both free fatty acids and glucose and is a promising target for pharmacotherapy in different variants of type 2 diabetes.
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| 26. |
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| 27. |
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| 28. |
- Parandeh, Fariborz, et al.
(författare)
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Inhibitory effect of UDP-glucose on cAMP generation and insulin secretion
- 2020
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Ingår i: The Journal of biological chemistry. - 1083-351X. ; 295:45, s. 15245-15252
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Tidskriftsartikel (refereegranskat)abstract
- Type-2 diabetes (T2D) is a global disease caused by the inability of pancreatic β-cells to secrete adequate insulin. However, the molecular mechanisms underlying the failure of β-cells to respond to glucose in T2D remains unknown. Here, we investigated the relative contribution of UDP-glucose (UDP-G), a P2Y14-specific agonist, in the regulation of insulin release using human isolated pancreatic islets and INS-1 cells. P2Y14 was expressed in both human and rodent pancreatic β-cells. Dose-dependent activation of P2Y14 by UDP-G suppressed glucose-stimulated insulin secretion (GSIS) and knockdown of P2Y14 abolished the UDP-G effect. 12-h pretreatment of human islets with pertussis-toxin (PTX) improved GSIS and prevented the inhibitory effect of UDP-G on GSIS. UDP-G on GSIS suppression was associated with suppression of cAMP in INS-1 cells. UDP-G decreased the reductive capacity of nondiabetic human islets cultured at 5 mm glucose for 72 h and exacerbated the negative effect of 20 mm glucose on the cell viability during culture period. T2D donor islets displayed a lower reductive capacity when cultured at 5 mm glucose for 72 h that was further decreased in the presence of 20 mm glucose and UDP-G. Presence of a nonmetabolizable cAMP analog during culture period counteracted the effect of glucose and UDP-G. Islet cultures at 20 mm glucose increased apoptosis, which was further amplified when UDP-G was present. UDP-G modulated glucose-induced proliferation of INS-1 cells. The data provide intriguing evidence for P2Y14 and UDP-G's role in the regulation of pancreatic β-cell function.
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| 29. |
- Parandeh, Fariborz, et al.
(författare)
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Uridine diphosphate (UDP) stimulates insulin secretion by activation of P2Y(6) receptors.
- 2008
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Ingår i: Biochemical and Biophysical Research Communications. - : Elsevier BV. - 1090-2104 .- 0006-291X. ; 6;370:3, s. 499-503
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Tidskriftsartikel (refereegranskat)abstract
- We examined the transcriptional expression and functional effects of receptors for the extracellular pyrimidines uridine triphosphate (UTP) and uridine diphosphate (UDP), on insulin and glucagon secretion in isolated mouse pancreatic islets and purified beta-cells. Using real-time PCR, the UDP receptor P2Y(6) was found to be highly expressed in both whole islets and beta-cells purified by repeated counter-flow elutriation, whereas no mRNA expression for UTP receptors P2Y(4) and P2Y(2) could be detected. Functional in vitro experiments revealed that the P2Y(6) agonist UDPbetaS dose-dependently enhanced insulin and glucagon release during short-term incubation (1h), while P2Y(6) activation during a longer period (24h), selectively increased insulin release, especially at high glucose levels. The corresponding EC(50) value for UDPbetaS ranged from 3.2x10(-8)M to 1.6x10(-8)M for both glucose concentrations. The P2Y(6) antagonist MRS2578 inhibited the effects of UDPbetaS, supporting a P2Y(6) specific effect. In addition to negative RT-PCR results, the lack of response to UTPgammaS a selective P2Y(2/4) agonist further rule out the involvement of P2Y(2/4) receptors in the islet hormone release. Our results suggest a modulatory role for UDP via a functional active P2Y(6) receptor in the regulation of islet hormone release.
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| 30. |
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| 31. |
- Samuelsson, Martin, et al.
(författare)
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The IgD C(H)1 region contains the binding site for the human respiratory pathogen Moraxella catarrhalis IgD-binding protein MID.
- 2006
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Ingår i: European Journal of Immunology. - : Wiley. - 1521-4141 .- 0014-2980. ; 9:Sep;36, s. 2525-2534
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Tidskriftsartikel (refereegranskat)abstract
- The Moraxella catarrhalis IgD-binding protein (MID) has a unique specificity for human IgD, and the sequence with maximal IgD binding is located within the amino acids MID962-1200. In the present paper, we examined the MID binding site on IgD using a series of recombinant Ig. Full-length IgD, IgD F(ab')(2), and an IgD F(ab') C290R mutant lacking the inter-heavy-chain cysteine 290 were manufactured. Furthermore, a series of IgD/IgG chimeras were constructed. ELISA, dot blot and flow cytometry were used to study the binding of purified Ig to native MID, recombinant MID912-1200 or to Moraxella with or without MID. MID962-1200 bound both the IgD F(ab')(2) and F(ab') C290R, indicating that the binding occurred independently of antibody structure. When amino acids 157-224 of the IgD C(H)1 region were substituted with IgG sequences, binding by M. catarrhalis or recombinant MID962-1200 was abolished. Subsequent smaller substitutions of IgD C(H)1 157-224 with IgG sequences led us to conclude that IgD C(H)1 amino acids 198-206 were crucial for the interaction between MID and IgD.
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| 32. |
- Soni, Arvind, et al.
(författare)
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GPRC5B a putative glutamate-receptor candidate is negative modulator of insulin secretion
- 2013
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Ingår i: Biochemical and Biophysical Research Communications. - : Elsevier BV. - 1090-2104 .- 0006-291X. ; 441:3, s. 643-648
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Tidskriftsartikel (refereegranskat)abstract
- GPRC5B is an orphan receptor belonging to the group C family of G protein-coupled receptors (GPCRs). GPRC5B is abundantly expressed in both human and mouse pancreatic islets, and both GPRC5B mRNA and protein are up-regulated 2.5-fold in islets from organ donors with type 2 diabetes. Expression of Gprc5b is 50% lower in islets isolated from newborn (<3 weeks) than in adult (>36 weeks) mice. Lentiviral shRNA-mediated down-regulation of Gprc5b in intact islets from 12 to 16 week-old mice strongly (2.5-fold) increased basal (I mmol/l) and moderately (40%) potentiated glucose (20 mmol/l) stimulated insulin secretion and also enhanced the potentiating effect of glutamate on insulin secretion. Downregulation of Gprc5b protected murine insulin-secreting clonal MIN6 cells against cytokine-induced apoptosis. We propose that increased expression of GPRC5B contributes to the reduced insulin secretion and beta-cell viability observed in type-2 diabetes. Thus, pharmacological targeting of GPRC5B might provide a novel means therapy for the treatment and prevention of type-2 diabetes. (C) 2013 Elsevier Inc. All rights reserved.
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| 33. |
- Tolhurst, Gwen, et al.
(författare)
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Expression profiling and electrophysiological studies suggest a major role for Orai1 in the store-operated Ca2+ influx pathway of platelets and megakaryocytes
- 2008
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Ingår i: Platelets. - : Informa UK Limited. - 1369-1635 .- 0953-7104. ; 19:4, s. 308-313
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Tidskriftsartikel (refereegranskat)abstract
- Store-operated Ca2+ influx represents a major route by which cytosolic Ca2+ can be elevated during platelet activation, yet its molecular identity in this cell type remains highly controversial. Using quantitative RT-PCR analysis of candidate receptor-operated cation entry pathways in human platelets, we show a 30-fold higher expression of message for the recently discovered Orai1 store-operated Ca2+ channel, and also the store Ca2+ sensor STIM1, when compared to the non-selective cation channels TRPC1, TRPC6 and TRPM2. Orai1 and STIM1 gene transcripts were also detected at higher levels than TRPC1, TRPC6 and TRPM2 in primary murine megakaryocytes and human megakaryocytic cell lines. In direct electrophysiological recordings from murine megakaryocytes, Ca2+ ionophore-induced store depletion stimulated CRAC currents, which are known to require Orai1, and these overlapped with TRPC6-like currents following P2Y receptor activation. Together with recent transgenic studies, these data provide evidence for STIM1:Orai1 as a primary pathway for agonist-evoked Ca2+ influx in the platelet and megakaryocyte.
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