| 1. |
- Wendt, Anna, et al.
(author)
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Synapsins I and II Are Not Required for Insulin Secretion from Mouse Pancreatic beta-cells
- 2012
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In: Endocrinology. - : The Endocrine Society. - 0013-7227 .- 1945-7170. ; 153:5, s. 2112-2119
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Journal article (peer-reviewed)abstract
- Synapsins are a family of phosphoproteins that modulate the release of neurotransmitters from synaptic vesicles. The release of insulin from pancreatic beta-cells has also been suggested to be regulated by synapsins. In this study, we have utilized a knock out mouse model with general disruptions of the synapsin I and II genes [synapsin double knockout (DKO)]. Stimulation with 20 mM glucose increased insulin secretion 9-fold in both wild-type (WT) and synapsin DKO islets, whereas secretion in the presence of 70 mM K+ and 1mM glucose was significantly enhanced in the synapsin DKO mice compared to WT. Exocytosis in single beta-cells was investigated using patch clamp. The exocytotic response, measured by capacitance measurements and elicited by a depolarization protocol designed to visualize exocytosis of vesicles from the readily releasable pool and from the reserve pool, was of the same size in synapsin DKO and WT beta-cells. The increase in membrane capacitance corresponding to readily releasable pool was approximately 50fF in both genotypes. We next investigated the voltage-dependent Ca2+ influx. In both WT and synapsin DKO beta-cells the Ca2+ current peaked at 0 mV and measured peak current (I-p) and net charge (Q) were of similar magnitude. Finally, ultrastructural data showed no variation in total number of granules (N-v) or number of docked granules (N-s) between the beta-cells from synapsin DKO mice and WT control. We conclude that neither synapsin I nor synapsin II are directly involved in the regulation of glucose-stimulated insulin secretion and Ca-2-dependent exocytosis in mouse pancreatic beta-cells. (Endocrinology 153: 2112-2119, 2012)
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| 2. |
- Andersson, Sofia A, et al.
(author)
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Reduced insulin secretion correlates with decreased expression of exocytotic genes in pancreatic islets from patients with type 2 diabetes.
- 2012
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In: Molecular and Cellular Endocrinology. - : Elsevier BV. - 1872-8057 .- 0303-7207. ; 364:1-2, s. 36-45
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Journal article (peer-reviewed)abstract
- Reduced insulin release has been linked to defect exocytosis in β-cells. However, whether expression of genes suggested to be involved in the exocytotic process (exocytotic genes) is altered in pancreatic islets from patients with type 2 diabetes (T2D), and correlate to insulin secretion, needs to be further investigated. Analysing expression levels of 23 exocytotic genes using microarray revealed reduced expression of five genes in human T2D islets (χ(2)=13.25; p<0.001). Gene expression of STX1A, SYT4, SYT7, SYT11, SYT13, SNAP25 and STXBP1 correlated negatively to in vivo measurements of HbA1c levels and positively to glucose stimulated insulin secretion (GSIS) in vitro in human islets. STX1A, SYT4 and SYT11 protein levels correspondingly decreased in human T2D islets. Moreover, silencing of SYT4 and SYT13 reduced GSIS in INS1-832/13 cells. Our data support that reduced expression of exocytotic genes contributes to impaired insulin secretion, and suggest decreased expression of these genes as part of T2D pathogenesis.
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| 3. |
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| 4. |
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| 5. |
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| 6. |
- Ahmed Khandker, Meftun, et al.
(author)
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Mitochondrial proteome analysis reveals altered expression of voltage dependent anion channels in pancreatic beta-cells exposed to high glucose
- 2010
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In: Islets. - : Informa UK Limited. - 1938-2022 .- 1938-2014. ; 2:5, s. 283-292
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Journal article (peer-reviewed)abstract
- Chronic hyperglycemia leads to deterioration of insulin release from pancreatic beta-cells as well as insulin action on peripheral tissues. However, the mechanism underlying beta-cell dysfunction resulting from glucose toxicity has not been fully elucidated. The aim of the present study was to define a set of alterations in mitochondrial protein profiles of pancreatic beta-cell line in response to glucotoxic condition using 2-DE and tandem mass spectrometry. INS1E cells were incubated in the presence of 5.5 and 20 mM glucose for 72 hrs and mitochondria were isolated. Approximately 75 protein spots displayed significant changes (p < 0.05) in relative abundance in the presence of 20 mM glucose compared to controls. Mitochondrial proteins downregulated under glucotoxic conditions includes ATP synthase a chain and delta chain, malate dehydrogenase, aconitase, trifunctional enzyme beta subunit, NADH-cytochrome b5 reductase and voltage-dependent anion-selective channel protein (VDAC) 2. VDAC 1, 75 kDa glucose-regulated protein, heat shock protein (HSP) 60 and HSP10 were found to be upregulated. The orchestrated changes in expression of VDACs and multiple other proteins involved in nutrient metabolism, ATP synthesis, cellular defense, glycoprotein folding and mitochondrial DNA stability may explain cellular dysfunction in glucotoxicity resulting in altered insulin secretion.
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| 7. |
- Alonso-Magdalena, Paloma, et al.
(author)
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Antidiabetic Actions of an Estrogen Receptor beta Selective Agonist
- 2013
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In: Diabetes. - : American Diabetes Association. - 1939-327X .- 0012-1797. ; 62:6, s. 2015-2025
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Journal article (peer-reviewed)abstract
- The estrogen receptor beta (ER beta) is emerging as an important player in the physiology of the endocrine pancreas. We evaluated the role and antidiabetic actions of the ER beta selective agonist WAY200070 as an insulinotropic molecule. We demonstrate that WAY200070 enhances glucose-stimulated insulin secretion both in mouse and human islets. In vivo experiments showed that a single administration of WAY200070 leads to an increase in plasma insulin levels with a concomitant improved response to a glucose load. Two-week treatment administration increased glucose-induced insulin release and pancreatic beta-cell mass and improved glucose and insulin sensitivity. In addition, streptozotocin-nicotinamide-induced diabetic mice treated with WAY200070 exhibited a significant improvement in plasma insulin levels and glucose tolerance as well as a regeneration of pancreatic beta-cell mass. Studies performed in db/db mice demonstrated that this compound restored first-phase insulin secretion and enhanced pancreatic beta-cell mass. We conclude that ER beta agonists should be considered as new targets for the treatment of diabetes.
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| 8. |
- Alonso-Magdalena, P, et al.
(author)
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Antidiabetic actions of an estrogen receptor β selective agonist
- 2013
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In: Diabetes. - : American Diabetes Association. - 1939-327X .- 0012-1797. ; 62:6, s. 2015-2025
-
Journal article (peer-reviewed)abstract
- The estrogen receptor β (ERβ) is emerging as an important player in the physiology of the endocrine pancreas. We evaluated the role and antidiabetic actions of the ERβ selective agonist WAY200070 as an insulinotropic molecule. We demonstrate that WAY200070 enhances glucose-stimulated insulin secretion both in mouse and human islets. In vivo experiments showed that a single administration of WAY200070 leads to an increase in plasma insulin levels with a concomitant improved response to a glucose load. Two-week treatment administration increased glucose-induced insulin release and pancreatic β-cell mass and improved glucose and insulin sensitivity. In addition, streptozotocin-nicotinamide–induced diabetic mice treated with WAY200070 exhibited a significant improvement in plasma insulin levels and glucose tolerance as well as a regeneration of pancreatic β-cell mass. Studies performed in db/db mice demonstrated that this compound restored first-phase insulin secretion and enhanced pancreatic β-cell mass. We conclude that ERβ agonists should be considered as new targets for the treatment of diabetes.
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| 9. |
- Amanizadeh, Farhad, et al.
(author)
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Starve fed emulsion copolymerization of vinyl acetate and 1-hexene at ambient pressure
- 2014
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In: Polymer international. - : Wiley. - 0959-8103 .- 1097-0126. ; 63:10, s. 1850-1855
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Journal article (peer-reviewed)abstract
- A novel emulsion copolymer of vinyl acetate (VAc) and 1-hexene was synthesized at ambient pressure. The feeding technique, initiation system and reaction time of the copolymerization were optimized based on molecular characteristics such as the weight contribution of 1-hexene in the copolymer chains and glass transition temperature (T-g) as well as on bulk properties like minimum film-formation temperature (MFFT) and solid content. According to nuclear magnetic resonance spectroscopy and differential scanning calorimetry results, the combination of starve feeding and redox initiation, within a reaction time of 4h, effectively led to the copolymerization at ambient pressure between highly reactive polar VAc monomers and non-polar 1-hexene monomers of low reactivity. The copolymer showed a lower T-g and MFFT, and a reasonable solid content compared to the poly(vinyl acetate) (PVAc) homopolymer. The consumption rate, hydrolysis of acetate groups and chain transfer reactions during the polymerization were followed using infrared spectroscopy. Based on the results, the undesirable reactions between the VAc blocks were hindered by the neighbouring 1-hexene molecules. Tensile testing revealed an improvement in the toughness and elongation at break of VAc-1-hexene films compared to PVAc films.
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| 10. |
- Amisten, Stefan, et al.
(author)
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ADP mediates inhibition of insulin secretion by activation of P2Y13 receptors in mice.
- 2010
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In: Diabetologia. - : Springer Science and Business Media LLC. - 1432-0428 .- 0012-186X. ; Jul 1, s. 1927-1934
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Journal article (peer-reviewed)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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| 11. |
- Amisten, Stefan, et al.
(author)
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An atlas and functional analysis of G-protein coupled receptors in human islets of Langerhans
- 2013
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In: Pharmacology and Therapeutics. - : Elsevier BV. - 0163-7258. ; 139:3, s. 359-391
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Research review (peer-reviewed)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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| 12. |
- Balhuizen, Alexander, et al.
(author)
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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
-
In: Molecular and Cellular Endocrinology. - : Elsevier BV. - 1872-8057 .- 0303-7207. ; 320, s. 16-24
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Journal article (peer-reviewed)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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| 13. |
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| 14. |
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| 15. |
- Berglund, Lisa, et al.
(author)
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Nuclear Factor of Activated T Cells Regulates Osteopontin Expression in Arterial Smooth Muscle in Response to Diabetes-Induced Hyperglycemia
- 2010
-
In: ARTERIOSCLEROSIS THROMBOSIS AND VASCULAR BIOLOGY. - Baltimore : Lippincott Williams & Wilkins. - 1079-5642. ; 30, s. 154-218
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Journal article (peer-reviewed)abstract
- Objective-Hyperglycemia is a recognized risk factor for cardiovascular disease in diabetes. Recently, we reported that high glucose activates the Ca2+/calcineurin-dependent transcription factor nuclear factor of activated T cells (NFAT) in arteries ex vivo. Here, we sought to determine whether hyperglycemia activates NFAT in vivo and whether this leads to vascular complications. Methods and Results-An intraperitoneal glucose-tolerance test in mice increased NFATc3 nuclear accumulation in vascular smooth muscle. Streptozotocin-induced diabetes resulted in increased NFATc3 transcriptional activity in arteries of NFAT-luciferase transgenic mice. Two NFAT-responsive sequences in the osteopontin (OPN) promoter were identified. This proinflammatory cytokine has been shown to exacerbate atherosclerosis and restenosis. Activation of NFAT resulted in increased OPN mRNA and protein in native arteries. Glucose-induced OPN expression was prevented by the ectonucleotidase apyrase, suggesting a mechanism involving the release of extracellular nucleotides. The calcineurin inhibitor cyclosporin A or the novel NFAT blocker A-285222 prevented glucose-induced OPN expression. Furthermore, diabetes resulted in higher OPN expression, which was significantly decreased by in vivo treatment with A-285222 for 4 weeks or prevented in arteries from NFATc3(-/-) mice. Conclusions-These results identify a glucose-sensitive transcription pathway in vivo, revealing a novel molecular mechanism that may underlie vascular complications of diabetes.
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| 16. |
- Bolmeson, Caroline, et al.
(author)
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Differences in islet-enriched miRNAs in healthy and glucose intolerant human subjects.
- 2011
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In: Biochemical and Biophysical Research Communications. - : Elsevier BV. - 1090-2104 .- 0006-291X. ; Dec, s. 16-22
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Journal article (peer-reviewed)abstract
- Many microRNAs (miRNAs) are known to be cell-type specific and are implicated in development of diseases. We investigated the global expression pattern of miRNAs in human pancreatic islets compared to liver and skeletal muscle, using bead-based technology and quantitative RT-PCR. In addition to the known islet-specific miR-375, we also found enrichment of miR-127-3p, miR-184, miR-195 and miR-493∗ in the pancreatic islets. The expression of miR-375, miR-127-3p, miR-184 and the liver-enriched miR-122 were positively correlated to insulin biosynthesis, while the expression of miR-127-3p and miR-184 were negatively correlated to glucose-stimulated insulin secretion (GSIS). These correlations were absent in islets of glucose intolerant donors (HbA1c⩾6.1). We suggest the presence of an islet-specific miRNA network, which consists of at least miR-375, miR-127-3p and miR-184, potentially involved in insulin secretion. Our results provide new insight into miRNA-mediated regulation of insulin secretion in healthy and glucose intolerant subjects.
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| 17. |
- De Marinis, Yang, et al.
(author)
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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
-
In: Cell Metabolism. - : Elsevier BV. - 1550-4131. ; 11:6, s. 543-553
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Journal article (peer-reviewed)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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| 18. |
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| 19. |
- Hellman, Bo, et al.
(author)
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Isolated mouse islets respond to glucose with an initial peak of glucagon release followed by pulses of insulin and somatostatin in antisynchrony with glucagon
- 2012
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In: Biochemical and Biophysical Research Communications - BBRC. - : Elsevier BV. - 0006-291X .- 1090-2104. ; 417:4, s. 1219-1223
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Journal article (peer-reviewed)abstract
- Recent studies of isolated human islets have shown that glucose induces hormone release with repetitive pulses of insulin and somatostatin in antisynchrony with those of glucagon. Since the mouse is the most important animal model we studied the temporal relation between hormones released from mouse islets. Batches of 5-10 islets were perifused and the hormones measured with radioimmunoassay in 30 s fractions. At 3 mM glucose, hormone secretion was stable with no detectable pulses of glucagon, insulin or somatostatin. Increase of glucose to 20 mM resulted in an early secretory phase with a glucagon peak followed by peaks of insulin and somatostatin. Subsequent hormone secretion was pulsatile with a periodicity of 5 min. Cross-correlation analyses showed that the glucagon pulses were antisynchronous to those of insulin and somatostatin. In contrast to the marked stimulation of insulin and somatostatin secretion, the pulsatility resulted in inhibition of overall glucagon release. The cytoarchitecture of mouse islets differs from that of human islets, which may affect the interactions between the hormone-producing cells. Although indicating that paracrine regulation is important for the characteristic patterns of pulsatile hormone secretion, the mouse data mimic those of human islets with more than 20-fold variations of the insulin/glucagon ratio. The data indicate that the mouse serves as an appropriate animal model for studying the temporal relation between the islet hormones controlling glucose production in the liver.
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| 20. |
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| 21. |
- Jabar Muhammed, Sarheed, et al.
(author)
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Pancreatic β-cell dysfunction, expression of iNOS and the effect of phosphodiesterase inhibitors in human pancreatic islets of type 2 diabetes.
- 2012
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In: Diabetes, Obesity and Metabolism. - : Wiley. - 1462-8902. ; 14:11, s. 1010-1019
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Journal article (peer-reviewed)abstract
- AIMS: Induction of iNOS in pancreatic islets leads to exaggerated NO production associated with dysfunctional β-cells. We examined insulin secretion, iNOS expression and its relation to the cAMP system in islets from human type 2 diabetes. METHODS: Insulin, glucagon and cAMP were analyzed by RIA; iNOS or PDE expression by qPCR, Western blot and confocal microscopy; cell viability by MTS. RESULTS: Diabetic islets displayed impaired insulin and glucagon responses to glucose, disturbed cAMP generation, and high iNOS mRNA and protein expression. Confocal microscopy showed iNOS protein expression in diabetic islets being confined to insulin, glucagon and somatostatin cells. Culture of diabetic islets at 5.5 mmol/l glucose with dibutyryl-cAMP (Bt(2) -cAMP) for 24 h was accompanied by marked suppression of iNOS mRNA, reduced nitrite production and increased insulin secretion. Diabetic islets displayed marked increase in PDE3A and PDE3B mRNA expression. Short-time incubation of diabetic islets showed, among the PDE inhibitors tested, cilostazol being most favourable to increase insulin secretion. Diabetic islets were most susceptible to long-term (72 h) culture at high glucose (20 mmol/l) reacting with increased apoptosis. Bt(2) -cAMP and the PDE inhibitors cilostazol, milrinone and IBMX efficiently increased cell viability at high glucose during culture. Defective glucose-stimulated insulin release upon induction of iNOS was restored by iNOS inhibitor aminoguanidine. CONCLUSION: Our results suggest that in islets from type 2 diabetes, stimulatory effects in certain cAMP-compartments induced by PDE inhibitors might play a central role in the suppression of iNOS, resulting in increased β-cell viability and improved secretory response to glucose.
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| 22. |
- Jimenez, Javier, et al.
(author)
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Abnormally decreased NO and augmented CO production in islets of the leptin-deficient ob/ob mouse might contribute to explain hyperinsulinemia and islet survival in leptin-resistant type 2 obese diabetes.
- 2011
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In: Regulatory Peptides. - : Elsevier BV. - 1873-1686 .- 0167-0115. ; 170, s. 43-51
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Journal article (peer-reviewed)abstract
- The role of the gaseous messengers NO and CO for β-cell function and survival is controversial. We examined this issue in the hyperglycemic-hyperinsulinemic ob/ob mouse, an animal model of type 2 obese diabetes, by studying islets from obese vs lean mice regarding glucose-stimulated insulin release in relation to islet NO and CO production and the influence of modulating peptide hormones. Glucose-stimulated increase in ncNOS-activity in incubated lean islets was converted to a decrease in ob/ob islets associated with markedly increased insulin release. Both types of islet displayed iNOS activity appearing after ~60min in high-glucose. In ob/ob islets the insulinotropic peptides glucagon, GLP-1 and GIP suppressed NOS activities and amplified glucose-stimulated insulin release. The insulinostatic peptide leptin induced the opposite effects. Suppression of islet CO production inhibited, while stimulation amplified glucose-stimulated insulin release. Nonincubated isolated islets from young and adult obese mice displayed very low ncNOS and negligible iNOS activity. In contrast, production of CO, a NOS inhibitor, was impressively raised. Glucose injections induced strong activities of islet NOS isoforms in lean but not in obese mice and confocal microscopy revealed iNOS expression only in lean islets. Islets from ob/ob mice existing in a hyperglycemic in vivo milieu maintain elevated insulin secretion and protection from glucotoxicity through a general suppression of islet NOS activities achieved by leptin deficiency, high CO production and insulinotropic cyclic-AMP-generating hormones. Such a beneficial effect on islet function and survival might have its clinical counterpart in human leptin-resistant type 2 obese diabetes with hyperinsulinemia.
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| 23. |
- Kalis, Martins, et al.
(author)
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α 1-antitrypsin enhances insulin secretion and prevents cytokine-mediated apoptosis in pancreatic β-cells.
- 2010
-
In: Islets. - : Informa UK Limited. - 1938-2022 .- 1938-2014. ; 2:3, s. 185-189
-
Journal article (peer-reviewed)abstract
- α1-antitrypsin (AAT) is a serine protease inhibitor, which recently has been shown to prevent type 1 diabetes (T1D) development, to prolong islet allograft survival and to inhibit β-cell apoptosis in vivo. It has also been reported that T1D patients have significantly lower plasma concentrations of AAT suggesting the potential role of AAT in the pathogenesis of T1D. We have investigated whether plasma-purified AAT can affect β-cell function in vitro. INS-1E cells or primary rat pancreatic islets were used to study the effect of AAT on insulin secretion after glucose, glucagon-like peptide-1 (GLP-1) and forskolin stimulation and on cytokine-mediated apoptosis. The secreted insulin and total cyclic AMP (cAMP) were determined using radioimmunoassay and apoptosis was evaluated by propidium iodide staining followed by FACS analysis. We found that AAT increases insulin secretion in a glucose-dependent manner, potentiates the effect of GLP-1 and forskolin and neutralizes the inhibitory effect of clonidine on insulin secretion. The effect of AAT on insulin secretion was accompanied by an increase in cAMP levels. In addition, AAT protected INS-1E cells from cytokine-induced apoptosis. Our findings show that AAT stimulates insulin secretion and protects β-cells against cytokine-induced apoptosis, and these effects of AAT seem to be mediated through the cAMP pathway. In view of these novel findings we suggest that AAT may represent a novel anti-inflammatory compound to protect β-cells under the immunological attack in T1D but also therapeutic strategy to potentiate insulin secretion in type 2 diabetes (T2D).
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| 24. |
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| 25. |
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| 26. |
- Kumar, Rajesh, et al.
(author)
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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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In: Endocrinology. - : The Endocrine Society. - 0013-7227 .- 1945-7170. ; 152:7, s. 2568-2579
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Journal article (peer-reviewed)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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| 27. |
- Kumar, Rajesh, et al.
(author)
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Proghrelin peptides: Desacyl ghrelin is a powerful inhibitor of acylated ghrelin, likely to impair physiological effects of acyl ghrelin but not of obestatin A study of pancreatic polypeptide secretion from mouse islets.
- 2010
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In: Regulatory Peptides. - : Elsevier BV. - 1873-1686 .- 0167-0115. ; 164, s. 65-70
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Journal article (peer-reviewed)abstract
- BACKGROUND: Proghrelin, produced by the ghrelin (A-like) cells of the gastric mucosa, gives rise to cleavage products, including desacyl ghrelin, acyl ghrelin and obestatin. The products are thought to be secreted concomitantly. In an earlier study we found acyl ghrelin and obestatin, but not desacyl ghrelin, to suppress the release of hormones from isolated islets of mouse and rat pancreas. RESULTS: Using isolated mouse pancreatic islets to study the suppression of the spontaneous secretion of pancreatic polypeptide (PP) by acyl ghrelin and obestatin, we determined the EC(50) values for the two peptides. For acyl ghrelin it was 2x10(-13)M (ranging from 1.7 to 2.8x10(-13)M), for obestatin it was 10(-13)M (ranging from 0.3 to 1.1x10(-13)M). The Hill coefficient (i.e. the midpoint slope) for the acyl ghrelin dose-response curve was 0.30 (ranging from 0.21 to 0.35); the corresponding value for obestatin was 0.35 (ranging from 0.21 to 0.35). The PP-releasing effect of acyl ghrelin, but not that of obestatin, was counteracted by desacyl ghrelin. The acyl ghrelin dose-response curve was shifted to the right in a parallel manner by increasing concentrations of desacyl ghrelin. A Schild plot was constructed with a slope of 0.78, giving an apparent pA(2) value of 14. CONCLUSIONS: The results favour the view that acyl ghrelin and obestatin suppress spontaneous PP secretion at physiologically relevant concentrations and that they act on separate receptors. However, we conclude also that desacyl ghrelin acts as a competitive, surmountable (and quite potent) inhibitor of acyl ghrelin. In view of the allegedly high circulating concentrations of desacyl ghrelin it is to be expected that the effect of acyl ghrelin - but not that of obestatin - will be impaired, in fact probably severely blunted by desacyl ghrelin, thereby compromising the functional significance of circulating acyl ghrelin. In addition, we suggest that isolated pancreatic islets are well suited for studies of receptors to acyl ghrelin and obestatin, and that suppression of PP secretion represents a convenient way to measure the effect of both these peptides.
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| 28. |
- Lyssenko, Valeriya, et al.
(author)
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Pleiotropic Effects of GIP on Islet Function Involve Osteopontin
- 2011
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In: Diabetes. - : American Diabetes Association. - 1939-327X .- 0012-1797. ; 60:9, s. 2424-2433
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Journal article (peer-reviewed)abstract
- OBJECTIVE-The incretin hormone GIP (glucose-dependent insulinotropic polypeptide) promotes pancreatic beta-cell function by potentiating insulin secretion and beta-cell proliferation. Recently, a combined analysis of several genome-wide association studies (Meta-analysis of Glucose and Insulin-Related Traits Consortium [MAGIC]) showed association to postprandial insulin at the GIP receptor (GIPR) locus. Here we explored mechanisms that could explain the protective effects of GIP on islet function. RESEARCH DESIGN AND METHODS-Associations of GIPR rs10423928 with metabolic and anthropometric phenotypes in both nondiabetic (N = 53,730) and type 2 diabetic individuals (N = 2,731) were explored by combining data from 11 studies.Insulin secretion was measured both in vivo in nondiabetic subjects and in vitro in islets from cadaver donors. Insulin secretion was also measured in response to exogenous GIP. The in vitro measurements included protein and gene expression as well as measurements of beta-cell viability and proliferation. RESULTS-The A allele of GIPR rs10423928 was associated with impaired glucose- and GIP-stimulated insulin secretion and a decrease in BMI, lean body mass, and waist circumference. The decrease in BMI almost completely neutralized the effect of impaired insulin secretion on risk of type 2 diabetes. Expression of GIPR mRNA was decreased in human islets from carriers of the A allele or patients with type 2 diabetes. GIP stimulated osteopontin (OPN) mRNA and protein expression. OPN expression was lower in carriers of the A allele. Both GIP and OPN prevented cytokine-induced reduction in cell viability (apoptosis). In addition, OPN stimulated cell proliferation in insulin-secreting cells. CONCLUSIONS-These findings support beta-cell proliferative and antiapoptotic roles for GIP in addition to its action as an incretin hormone. Identification of a link between GIP and OPN may shed new light on the role of GIP in preservation of functional beta-cell mass in humans. Diabetes 60:2424-2433, 2011
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| 29. |
- Mahdi, Taman, et al.
(author)
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Secreted frizzled-related protein 4 reduces insulin secretion and is overexpressed in type 2 diabetes.
- 2012
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In: Cell Metabolism. - : Elsevier BV. - 1550-4131. ; 16:5, s. 625-633
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Journal article (peer-reviewed)abstract
- A plethora of candidate genes have been identified for complex polygenic disorders, but the underlying disease mechanisms remain largely unknown. We explored the pathophysiology of type 2 diabetes (T2D) by analyzing global gene expression in human pancreatic islets. A group of coexpressed genes (module), enriched for interleukin-1-related genes, was associated with T2D and reduced insulin secretion. One of the module genes that was highly overexpressed in islets from T2D patients is SFRP4, which encodes secreted frizzled-related protein 4. SFRP4 expression correlated with inflammatory markers, and its release from islets was stimulated by interleukin-1β. Elevated systemic SFRP4 caused reduced glucose tolerance through decreased islet expression of Ca(2+) channels and suppressed insulin exocytosis. SFRP4 thus provides a link between islet inflammation and impaired insulin secretion. Moreover, the protein was increased in serum from T2D patients several years before the diagnosis, suggesting that SFRP4 could be a potential biomarker for islet dysfunction in T2D.
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| 30. |
- Meidute, Sandra, et al.
(author)
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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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In: Molecular and Cellular Endocrinology. - : Elsevier BV. - 1872-8057 .- 0303-7207. ; 381:1-2, s. 150-159
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Journal article (peer-reviewed)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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| 31. |
- Obermüller, Stefanie, et al.
(author)
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Defective secretion of islet hormones in chromogranin-B deficient mice
- 2010
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In: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 5:1, s. e8936-
-
Journal article (peer-reviewed)abstract
- Granins are major constituents of dense-core secretory granules in neuroendocrine cells, but their function is still a matter of debate. Work in cell lines has suggested that the most abundant and ubiquitously expressed granins, chromogranin A and B (CgA and CgB), are involved in granulogenesis and protein sorting. Here we report the generation and characterization of mice lacking chromogranin B (CgB-ko), which were viable and fertile. Unlike neuroendocrine tissues, pancreatic islets of these animals lacked compensatory changes in other granins and were therefore analyzed in detail. Stimulated secretion of insulin, glucagon and somatostatin was reduced in CgB-ko islets, in parallel with somewhat impaired glucose clearance and reduced insulin release, but normal insulin sensitivity in vivo. CgB-ko islets lacked specifically the rapid initial phase of stimulated secretion, had elevated basal insulin release, and stored and released twice as much proinsulin as wildtype (wt) islets. Stimulated release of glucagon and somatostatin was reduced as well. Surprisingly, biogenesis, morphology and function of insulin granules were normal, and no differences were found with regard to beta-cell stimulus-secretion coupling. We conclude that CgB is not required for normal insulin granule biogenesis or maintenance in vivo, but is essential for adequate secretion of islet hormones. Consequentially CgB-ko animals display some, but not all, hallmarks of human type-2 diabetes. However, the molecular mechanisms underlying this defect remain to be determined.
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| 32. |
- Olsson, Anders H, et al.
(author)
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Decreased expression of genes involved in oxidative phosphorylation in human pancreatic islets from patients with type 2 diabetes.
- 2011
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In: European Journal of Endocrinology. - 1479-683X. ; 165, s. 589-595
-
Journal article (peer-reviewed)abstract
- OBJECTIVE: Gene expression alterations, especially in target tissues of insulin, have been associated with type 2 diabetes (T2D). Here, we examined if genes involved in oxidative phosphorylation (OXPHOS) show differential gene expression and DNA methylation in pancreatic islets from patients with T2D compared with non-diabetic donors. DESIGN AND METHODS: Gene expression was analyzed in human pancreatic islets from 55 non-diabetic donors and 9 T2D donors using microarray. RESULTS: While the expected number of OXPHOS genes with reduced gene expression is 7.21 we identified 21 down-regulated OXPHOS genes in pancreatic islets from patients with T2D using microarray analysis. This gives a ratio of observed over expected OXPHOS genes of 26.37 using a Χ(2)-test with p = 1.52•10-7. The microarray data was validated by qRT-PCR for four selected OXPHOS genes; NDUFA5, NDUFA10, COX11 and ATP6V1H. All four OXPHOS genes were significantly down-regulated in islets from patients with T2D compared with non-diabetic donors using qRT-PCR (p≤0.01). Furthermore, HbA1c levels correlated negatively with gene expression of NDUFA5, COX11 and ATP6V1H (p less than 0.05). Gene expression of NDUFA5, NDUFA10, COX11 and ATP6V1H correlated positively with glucose-stimulated insulin secretion (p less than 0.03). Finally, DNA methylation was analyzed upstream of the transcription start for NDUFA5, COX11 and ATP6V1H. However, none of the analyzed CpG sites in the three genes showed differences in DNA methylation in islets from donors with T2D compared with non-diabetic donors. CONCLUSION: Pancreatic islets from patients with T2D show decreased expression of a set of OXPHOS genes, which may lead to impaired insulin secretion.
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| 33. |
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| 34. |
- Poornejad, Nafiseh, et al.
(author)
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Improvement of Ethanol Production from Spruce by Solvent Pretreatment
- 2010
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Conference paper (other academic/artistic)abstract
- Lignocelluloses are abundant and inexpensive resources that can be used for production of bioethanol. However, these materials, especially softwoods, are resistant to enzymatic hydrolysis and a pretreatment process is necessary for efficient conversion to ethanol. The pretreatment is intended to render the cellulose amenable to enzymatic hydrolysis and subsequent fermentation to bioethanol. Several methods has been suggested for the pretreatment of lignocelluloses. The pretreatment with cellulose solvents are among the promising methods since they can perform in mild processing conditions. N-Methylmorpholine-N-oxide (NMMO) is among the industrial solvents which can dissolve cellulose by breaking intermolecular interactions. NMMO is nowadays used in the industrial Lyocell process, which is one of the modern and environmentally friendly industrial fiber-making technologies. It does not produce any toxic waste pollutants, and can be recovered over 98%. The pretreatment of lignocellulose by NMMO can modify the crystal structure of cellulose. In the current work a commercial grade 50% (W/W) NMMO solution was used for pretreatment of spruce. The NMMO solution was concentrated by vacuum evaporation to 85% NMMO. The pretreatment performed at 120ºC for 3 h. The pretreated wood species were then regenerated by addition of boiling distilled water, followed by vacuum filtration and washing. The pretreated and untreated spruce species were enzymatically hydrolyzed by commercial cellulase (celluclast 1.5L, Novozyme, Denmark) and Β-glucosidase (Novozyme 188, Novozyme, Denmark) at 45ºC for 96h. A thermotolerant strain of Saccharomyces cerevisiae was used for fermentation. Inoculum was aerobically cultivated at 30 °C and 120 rpm for 24 h. The enzymatic hydrolyzate was supplemented with necessary nutrient and fermented by the yeast for 24h at 30 °C and 120 rpm. The liquid samples were analyzed by HPLC. The results showed that the yield of ethanol increased from 7.2 g/g to 77 g/g, when the wood treated with the solvent. Formation of glycerol and other metabolites were also detected and discussed. It can be concluded that the method can be a promising alternative for pretreatment of softwoods for bioethanol production.
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| 35. |
- Prokopenko, Inga, et al.
(author)
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A Central Role for GRB10 in Regulation of Islet Function in Man.
- 2014
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In: PLoS Genetics. - : Public Library of Science (PLoS). - 1553-7404 .- 1553-7390. ; 10:4
-
Journal article (peer-reviewed)abstract
- Variants in the growth factor receptor-bound protein 10 (GRB10) gene were in a GWAS meta-analysis associated with reduced glucose-stimulated insulin secretion and increased risk of type 2 diabetes (T2D) if inherited from the father, but inexplicably reduced fasting glucose when inherited from the mother. GRB10 is a negative regulator of insulin signaling and imprinted in a parent-of-origin fashion in different tissues. GRB10 knock-down in human pancreatic islets showed reduced insulin and glucagon secretion, which together with changes in insulin sensitivity may explain the paradoxical reduction of glucose despite a decrease in insulin secretion. Together, these findings suggest that tissue-specific methylation and possibly imprinting of GRB10 can influence glucose metabolism and contribute to T2D pathogenesis. The data also emphasize the need in genetic studies to consider whether risk alleles are inherited from the mother or the father.
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| 36. |
- Rosengren, Anders, et al.
(author)
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Reduced Insulin Exocytosis in Human Pancreatic β-cells With Gene Variants Linked to Type 2 Diabetes.
- 2012
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In: Diabetes. - : American Diabetes Association. - 1939-327X .- 0012-1797. ; 61:7, s. 1726-1733
-
Journal article (peer-reviewed)abstract
- The majority of genetic risk variants for type 2 diabetes (T2D) affect insulin secretion, but the mechanisms through which they influence pancreatic islet function remain largely unknown. We functionally characterized human islets to determine secretory, biophysical, and ultrastructural features in relation to genetic risk profiles in diabetic and nondiabetic donors. Islets from donors with T2D exhibited impaired insulin secretion, which was more pronounced in lean than obese diabetic donors. We assessed the impact of 14 disease susceptibility variants on measures of glucose sensing, exocytosis, and structure. Variants near TCF7L2 and ADRA2A were associated with reduced glucose-induced insulin secretion, whereas susceptibility variants near ADRA2A, KCNJ11, KCNQ1, and TCF7L2 were associated with reduced depolarization-evoked insulin exocytosis. KCNQ1, ADRA2A, KCNJ11, HHEX/IDE, and SLC2A2 variants affected granule docking. We combined our results to create a novel genetic risk score for β-cell dysfunction that includes aberrant granule docking, decreased Ca(2+) sensitivity of exocytosis, and reduced insulin release. Individuals with a high risk score displayed an impaired response to intravenous glucose and deteriorating insulin secretion over time. Our results underscore the importance of defects in β-cell exocytosis in T2D and demonstrate the potential of cellular phenotypic characterization in the elucidation of complex genetic disorders.
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| 37. |
- Salehi, S Albert, et al.
(author)
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The insulinogenic effect of whey protein is partially mediated by a direct effect of amino acids and GIP on beta-cells
- 2012
-
In: Nutrition & Metabolism. - : Springer Science and Business Media LLC. - 1743-7075. ; 9
-
Journal article (peer-reviewed)abstract
- Background: Whey protein increases postprandial serum insulin levels. This has been associated with increased serum levels of leucine, isoleucine, valine, lysine, threonine and the incretin hormone glucose-dependent insulinotropic polypeptide (GIP). We have examined the effects of these putative mediators of whey's action on insulin secretion from isolated mouse Langerhans islets. Methods: Mouse pancreatic islets were incubated with serum drawn from healthy individuals after ingestion of carbohydrate equivalent meals of whey protein (whey serum), or white wheat bread (control serum). In addition the effect of individual amino acid combinations on insulin secretion was also tested. Furthermore, the stimulatory effects of whey serum on insulin secretion was tested in vitro in the absence and presence of a GIP receptor antagonist ((Pro(3)) GIP[mPEG]). Results: Postprandial amino acids, glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide 1 (GLP-1) responses were higher after whey compared to white wheat bread. A stimulatory effect on insulin release from isolated islets was observed with serum after whey obtained at 15 min (+87%, P < 0.05) and 30 min (+139%, P < 0.05) postprandially, compared with control serum. The combination of isoleucine, leucine, valine, lysine and threonine exerted strong stimulatory effect on insulin secretion (+270%, P < 0.05), which was further augmented by GIP (+558% compared to that produced by glucose, P < 0.05). The stimulatory action of whey on insulin secretion was reduced by the GIP-receptor antagonist (Pro(3)) GIP[mPEG]) at both 15 and 30 min (-56% and -59%, P < 0.05). Conclusions: Compared with white wheat bread meal, whey causes an increase of postprandial insulin, plasma amino acids, GIP and GLP-1 responses. The in vitro data suggest that whey protein exerts its insulinogenic effect by preferential elevation of the plasma concentrations of certain amino acids, GIP and GLP-1.
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| 38. |
- Soni, Arvind, et al.
(author)
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GPRC5B a putative glutamate-receptor candidate is negative modulator of insulin secretion
- 2013
-
In: Biochemical and Biophysical Research Communications. - : Elsevier BV. - 1090-2104 .- 0006-291X. ; 441:3, s. 643-648
-
Journal article (peer-reviewed)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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| 39. |
- Soriano, Sergi, et al.
(author)
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Rapid Insulinotropic Action of Low Doses of Bisphenol-A on Mouse and Human Islets of Langerhans: Role of Estrogen Receptor beta
- 2012
-
In: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 7:2
-
Journal article (peer-reviewed)abstract
- Bisphenol-A (BPA) is a widespread endocrine-disrupting chemical (EDC) used as the base compound in the manufacture of polycarbonate plastics. It alters pancreatic beta-cell function and can be considered a risk factor for type 2 diabetes in rodents. Here we used ER beta(-/-) mice to study whether ER beta is involved in the rapid regulation of K-ATP channel activity, calcium signals and insulin release elicited by environmentally relevant doses of BPA (1 nM). We also investigated these effects of BPA in beta-cells and whole islets of Langerhans from humans. 1 nM BPA rapidly decreased K-ATP channel activity, increased glucose-induced [Ca2+](i) signals and insulin release in beta-cells from WT mice but not in cells from ER beta(-/-) mice. The rapid reduction in the K-ATP channel activity and the insulinotropic effect was seen in human cells and islets. BPA actions were stronger in human islets compared to mouse islets when the same BPA concentration was used. Our findings suggest that BPA behaves as a strong estrogen via nuclear ER beta and indicate that results obtained with BPA in mouse beta-cells may be extrapolated to humans. This supports that BPA should be considered as a risk factor for metabolic disorders in humans.
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| 40. |
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| 41. |
- Tan, Chanyuan, et al.
(author)
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ADP receptor P2Y(13) induce apoptosis in pancreatic beta-cells.
- 2010
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In: Cellular and Molecular Life Sciences. - : Springer Science and Business Media LLC. - 1420-9071 .- 1420-682X. ; 67, s. 445-453
-
Journal article (peer-reviewed)abstract
- Pancreatic beta-cell loss represents a key factor in the pathogenesis of diabetes. Since the influence of purinergic signaling in beta-cell apoptosis has not been much investigated, we examined the role of the ADP receptor P2Y(13) using the pancreatic insulinoma-cell line MIN6c4 as a model system. Real time-PCR revealed high expression of the ADP receptors P2Y(1) and P2Y(13). Adding the ADP analogue, 2MeSADP, to MIN6c4 cells induced calcium influx/mobilization and inhibition of cAMP production by activation of P2Y(1) and P2Y(13), respectively. 2MeSADP reduced cell proliferation and increased Caspase-3 activity; both these effects could be fully reversed by the P2Y(13) receptor antagonist MRS2211. We further discovered that blocking the P2Y(13) receptor results in enhanced ERK1/2, Akt/PKB and CREB phosphorylation mechanisms involved in beta-cell survival. These results indicate that P2Y(13) is a proapoptotic receptor in beta-cells as the P2Y(13) receptor antagonist MRS2211 is able to protect the cells from ADP induced apoptosis.
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| 42. |
- Taneera, Jalal, et al.
(author)
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A Systems Genetics Approach Identifies Genes and Pathways for Type 2 Diabetes in Human Islets
- 2012
-
In: Cell Metabolism. - : Elsevier BV. - 1550-4131 .- 1932-7420. ; 16:1, s. 122-134
-
Journal article (peer-reviewed)abstract
- Close to 50 genetic loci have been associated with type 2 diabetes (T2D), but they explain only 15% of the heritability. In an attempt to identify additional T2D genes, we analyzed global gene expression in human islets from 63 donors. Using 48 genes located near T2D risk variants, we identified gene coexpression and protein-protein interaction networks that were strongly associated with islet insulin secretion and HbA(1c). We integrated our data to form a rank list of putative T2D genes, of which CHL1, LRFN2, RASGRP1, and PPM1K were validated in INS-1 cells to influence insulin secretion, whereas GPR120 affected apoptosis in islets. Expression variation of the top 20 genes explained 24% of the variance in HbA(1c) with no claim of the direction. The data present a global map of genes associated with islet dysfunction and demonstrate the value of systems genetics for the identification of genes potentially involved in T2D.
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| 43. |
- Taneera, Jalal, et al.
(author)
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gamma-Aminobutyric acid (GABA) signalling in human pancreatic islets is altered in type 2 diabetes
- 2012
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In: Diabetologia. - : Springer Science and Business Media LLC. - 0012-186X .- 1432-0428. ; 55:7, s. 1985-1994
-
Journal article (peer-reviewed)abstract
- gamma-Aminobutyric acid (GABA) is a signalling molecule in the interstitial space in pancreatic islets. We examined the expression and function of the GABA signalling system components in human pancreatic islets from normoglycaemic and type 2 diabetic individuals. Expression of GABA signalling system components was studied by microarray, quantitative PCR analysis, immunohistochemistry and patch-clamp experiments on cells in intact islets. Hormone release was measured from intact islets. The GABA signalling system was compromised in islets from type 2 diabetic individuals, where the expression of the genes encoding the alpha 1, alpha 2, beta 2 and beta 3 GABA(A) channel subunits was downregulated. GABA originating within the islets evoked tonic currents in the cells. The currents were enhanced by pentobarbital and inhibited by the GABA(A) receptor antagonist, SR95531. The effects of SR95531 on hormone release revealed that activation of GABA(A) channels (GABA(A) receptors) decreased both insulin and glucagon secretion. The GABA(B) receptor antagonist, CPG55845, increased insulin release in islets (16.7 mmol/l glucose) from normoglycaemic and type 2 diabetic individuals. Interstitial GABA activates GABA(A) channels and GABA(B) receptors and effectively modulates hormone release in islets from type 2 diabetic and normoglycaemic individuals.
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