| 1. |
- Blixt, Martin, et al.
(författare)
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Pancreatic islets of bank vole show signs of dysfunction after prolonged exposure to high glucose concentrations in vitro
- 2010
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Ingår i: Journal of Endocrinology. - 0022-0795 .- 1479-6805. ; 206:1, s. 47-54
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Tidskriftsartikel (refereegranskat)abstract
- Bank voles develop glucose intolerance/diabetes mellitus when kept in captivity. We have characterized beta-cell function of glucose intolerant/diabetic animals, and found that this animal model has features of both human type 1 and type 2 diabetes. The aim of this study was to study the functional alterations of islets isolated from glucose tolerant bank voles after a prolonged exposure to various glucose concentrations in vitro. For this purpose, pancreatic islets from normal (glucose tolerant) male and female bank voles were cultured at different glucose concentrations (5.6, 11.1 (control), or 28 mM) whereupon islet functions were examined. Overall, islet insulin output was lowered at 5.6 mM glucose, and similar to control, or enhanced after culture in 28 mM glucose. High glucose culture led to decreased insulin contents, but there was no change in islet DNA content and in morphological assessments of cell death, with the latter findings suggesting that the so-called glucotoxicity had not evolved. A slight gender difference was observed in that islets isolated from females exhibited a glucose-regulated (pro) insulin biosynthesis rate and insulin gene expression. In conclusion, we have found that islets isolated from female and male bank voles are affected by glucose concentrations in vitro in that some signs of dysfunction were observed upon high glucose exposure. A minor gender difference was observed suggesting that the islets of the females may more readily adapt to the elevated glucose concentration than islets of the male bank voles. It could be that these in vitro gender differences observed may represent a mechanism underlying the gender difference in diabetes development observed among bank voles. Journal of Endocrinology (2010) 206, 47-54
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| 2. |
- Blixt, Martin, 1977-
(författare)
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The bank vole (Myodes glareolus) – a novel animal model for the study of diabetes mellitus
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The bank vole (Microtus arvalis) develops glucose intolerance both when kept in captivity and in the wild state. Glucose intolerant bank voles kept in captivity exhibited polydipsia, polyuria, hyperglycemia, hyperinsulinemia, islet autoantibodies and a markedly changed islet structure resembling so–called hydropic degeneration. Islets showing hydropic degeneration have reduced β–cell mass. However, the relative islet size to total pancreas area was not changed. Pancreatic islet isolated from glucose intolerant bank voles had an altered islet function showing signs of being exposed to an increased functional demand on their β–cells. Also, islets from male bank voles seem more affected than the islets from females. Islets isolated from glucose tolerant male bank voles cultured for 5 days at 28 mM glucose did not reveal any change in insulin gene expression or insulin biosynthesis rate. However, islets from female bank voles displayed a glucose concentration dependent response. This suggests that there is gender difference in that, islets of female more easily than islets of males adapt to elevated glucose concentration. Furthermore, islets isolated from glucose tolerant males had reduced insulin gene expression after exposure to proinflammatory cytokines for 48 hrs. This effect seemed to be NO-independent since only a minor elevation of nitrite accumulation in the medium was seen, and the use of iNOS inhibitor could not counteract the cytokine effect. The observed response seen in bank vole islets upon exposure to various glucose concentrations or proinflammatory cytokines is similar to those seen in studies of human islets. The bank vole may therefore represent a novel animal model for the study of diabetes. An unresolved issue is the role of the Ljungan virus which is found in the bank vole colony. Bank voles developing glucose intolerance display features of both human type 1 and type 2 diabetes, where environmental factors seems to play an important role as determinant. Our findings suggest that bank voles bred in the laboratory may develop more of a type 2 diabetes. However, bank voles caught in nature instead may rather develop a type 1 form of the disease.
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| 3. |
- Börjesson, Andreas, et al.
(författare)
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beta-cell specific overexpression of suppressor of cytokine signalling-3 does not protect against multiple low dose streptozotocin induced type 1 diabetes in mice
- 2011
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Ingår i: Immunology Letters. - : Elsevier BV. - 0165-2478 .- 1879-0542. ; 136:1, s. 74-79
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Tidskriftsartikel (refereegranskat)abstract
- We investigated the impact of beta-cell specific overexpression of suppressor of cytokine signalling-3 (SOCS-3) on the development of multiple low dose streptozotocin (MLDSTZ) induced Type 1 diabetes and the possible mechanisms involved. MLDSTZ treatment was administered to RIP-SOCS-3 transgenic and wild-type (wt) mice and progression of hyperglycemia monitored. Isolated islets from both strains were exposed to human IL-1 beta (25 U/ml) or a combination of human IL-1 beta (25 U/ml) and murine IFN-gamma (1000 U/ml) for 24h or 48h and we investigated the expression of IL-1 receptor antagonist (IL-1Ra) mRNA in islet cells and secretion of IL-1Ra into culture medium. MLDSTZ treatment caused gradual hyperglycemia both in the wt mice and in the transgenic mice with the latter tending to be more sensitive. In vitro experiments on wt and transgenic islets did not reveal any differences in sensitivity to damaging effects of STZ. Exposure of wt islets to 1L-1 beta or IL-1 beta + IFN-gamma seemed to lead to a failing IL-1Ra response from SOCS-3 transgenic islets. It could be that an increased expression of a possible protective molecule against beta-cell destruction may lead to a dampered response of another putative protective molecule. This may have counteracted a protective effect against MLDSTZ in SOCS-3 transgenic mice.
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| 4. |
- Carlsson, Annika, et al.
(författare)
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Concomitant Enzyme-Linked Immunosorbent Assay Measurements of Rat Insulin, Rat C-Peptide, and Rat Proinsulin from Rat Pancreatic Islets : Effects of Prolonged Exposure to Different Glucose Concentrations
- 2010
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Ingår i: Endocrinology. - : The Endocrine Society. - 0013-7227 .- 1945-7170. ; 151:10, s. 5048-5052
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Tidskriftsartikel (refereegranskat)abstract
- Until now, there have been few assays to measure C-peptide and proinsulin in the rat. We used a well-established rat insulin ELISA and validated two novel ELISAs for rat C-peptide and rat/mouse proinsulin to examine secretion and content of insulin, proinsulin, and C-peptide from rat islets cultured for 72 h at different glucose concentrations in culture medium. To examine long-term effects in vitro rather than short-term effects of exposure to low, normal, and high glucose, the exposure time to the different glucose concentrations was set to 72 h. The measurement uncertainty of the values obtainable from the ELISAs was determined by calculation of the variation pattern from the intraassay variation generated by unknown samples, and repeatability was determined by analysis of controls. The precision study and the analysis of controls confirm that the validated ELISAs for rat C-peptide and proinsulin would be useful for further studies on the effects of preculture in different glucose concentrations. The higher the glucose concentration used during the 72-h culture period of rat islets, the higher insulin, C-peptide and proinsulin values were obtained in a subsequent short-term glucose-challenge experiment. The proportion of proinsulin to insulin secreted increased, as did islet content, with increasing glucose concentration during preculture. We also observed a nonequimolar, glucose-dependent secretion and content of rat insulin over rat C-peptide after culture at 11.1 and 28 mM glucose.
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| 5. |
- Chowdhury, Azazul Islam, et al.
(författare)
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Functional differences between aggregated and dispersed insulin-producing cells
- 2013
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Ingår i: Diabetologia. - : Springer Science and Business Media LLC. - 0012-186X .- 1432-0428. ; 56:7, s. 1557-1568
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Tidskriftsartikel (refereegranskat)abstract
- Beta cells situated in the islet of Langerhans respond more vigorously to glucose than do dissociated beta cells. Mechanisms for this discrepancy were studied by comparing insulin-producing MIN6 cells aggregated into pseudoislets with MIN6 monolayer cells and mouse and human islets. MIN6 monolayers, pseudoislets and mouse and human islets were exposed to glucose, alpha-ketoisocaproic acid (KIC), pyruvate, KIC plus glutamine and the phosphatidylinositol 3-kinase (PI3K) inhibitors LY294002 or wortmannin. Insulin secretion (ELISA), cytoplasmic Ca2+ concentration ([Ca2+](c); microfluorometry), glucose oxidation (radiolabelling), the expression of genes involved in mitochondrial metabolism (PCR) and the phosphorylation of insulin receptor signalling proteins (western blotting) were measured. Insulin secretory responses to glucose, pyruvate, KIC and glutamine were higher in pseudoislets than monolayers and comparable to those of human islets. Glucose oxidation and genes for mitochondrial metabolism were upregulated in pseudoislets compared with single cells and monolayers, respectively. Phosphorylation at the inhibitory S636/639 site of IRS-1 was significantly higher in monolayers and dispersed human and mouse cells than pseudoislets and intact human and mouse islets. PI3K inhibition only slightly attenuated glucose-stimulated insulin secretion from monolayers, but substantially reduced that from pseudoislets and human and mouse islets without suppressing the glucose-induced [Ca2+](c) response. We propose that islet architecture is critical for proper beta cell mitochondrial metabolism and IRS-1 signalling, and that PI3K regulates insulin secretion at a step distal to the elevation of [Ca2+](c).
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| 6. |
- Lindgren, Stefan, et al.
(författare)
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Medical education in Sweden
- 2011
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Ingår i: Medical teacher. - London : Update. - 0142-159X .- 1466-187X. ; 33:10, s. 798-803
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Tidskriftsartikel (refereegranskat)abstract
- Undergraduate medical education in Sweden has moved from nationally regulated, subject-based courses to programmes integrated either around organ systems or physiological and patho-physiological processes, or organised around basic medical science in conjunction with clinical specialities, with individual profiles at the seven medical schools. The national regulations are restricted to overall academic and professional outcomes. The 51/2 year long university undergraduate curriculum is followed by a mandatory 18 months internship, delivered by the County Councils. While quality control and accreditation for the university curriculum is provided by the Swedish National Agency for Higher Education, no such formal control exists for the internship; undergraduate medical education is therefore in conflict with EU directives from 2005. The Government is expected to move towards 6 years long university undergraduate programmes, leading to licence, which will facilitate international mobility of both Swedish and foreign medical students and doctors. Ongoing academic development of undergraduate education is strengthened by the Bologna process. It includes outcome (competence)-based curricula, university Masters level complying with international standards, progression of competence throughout the curriculum, student directed learning, active participation and roles in practical clinical education and a national assessment model to assure professional competence. In the near future, the dimensioning of Swedish undergraduate education is likely to be decided more by international demands and aspects of quality than by national demands for doctors.
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| 7. |
- Ludvigsen, Eva, et al.
(författare)
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Altered Expression of Somatostatin Receptors in Pancreatic Islets from NOD Mice Cultured at Different Glucose Concentrations In Vitro and in Islets Transplanted to Diabetic NOD Mice In Vivo
- 2011
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Ingår i: Experimental Diabetes Research. - : Hindawi Limited. - 1687-5214 .- 1687-5303. ; 2011, s. 623472-
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Tidskriftsartikel (refereegranskat)abstract
- Somatostatin acts via five receptors (sst1-5). We investigated if the changes in pancreatic islet sst expression in diabetic NOD mice compared to normoglycemic mice are a consequence of hyperglycemia or the ongoing immune reaction in the pancreas. Pancreatic islets were isolated from NOD mice precultured for 5 days and further cultured for 3 days at high or low glucose before examined. Islets were also isolated from NOD mice and transplanted to normal or diabetic mice in a number not sufficient to cure hyperglycemia. After three days, the transplants were removed and stained for sst1-5 and islet hormones. Overall, changes in sst islet cell expression were more common in islets cultured in high glucose concentration in vitro as compared to the islet transplantation in vivo to diabetic mice. The beta and PP cells exhibited more frequent changes in sst expression, while the alpha and delta cells were relatively unaffected by the high glucose condition. Our findings suggest that the glucose level may alter sst expressed in islets cells; however, immune mechanisms may counteract such changes in islet sst expression.
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| 8. |
- Rydgren, Tobias, et al.
(författare)
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Administration of IL-1 Trap prolongs survival of transplanted pancreatic islets to type 1 diabetic NOD mice
- 2013
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Ingår i: Cytokine. - : Elsevier BV. - 1043-4666 .- 1096-0023. ; 63:2, s. 123-129
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Tidskriftsartikel (refereegranskat)abstract
- We previously reported that IL-1 Trap (a hybrid molecule consisting of the extracellular domain of IL-1 receptor accessory protein and IL-1 receptor type 1 arranged inline and fused to the Fc-portion of IgG1) can protect rat pancreatic islets in vitro against noxious effects induced by IL-1 beta. In this study we tested the effect of administration of a murine IL-1 Trap on the recurrence of disease (ROD) model in non-obese diabetic (NOD) mice. Spontaneously diabetic female NOD mice received implantation of a curative number (600) of syngeneic pancreatic islets beneath their left kidney capsule from young healthy NOD mouse donors. Once a day, the mice were injected subcutaneously with IL-1 Trap (30 mg/kg bodyweight), or an equimolar dose Fc-control protein (8.4 mg/kg bodyweight) or saline. The treatments were maintained until ROD (i.e. a blood glucose value >= 11.1 mM for 2 consecutive days) or until 5 days after transplantation. 3 out of 11 mice treated with IL-1 Trap showed a significantly increased graft survival compared to all other mice, and analysis of relative cytokine mRNA levels in isolated spleen cells showed elevated IL-4 mRNA levels, but no differences in FoxP3 or iNOS staining of grafts, from mice treated with IL-1 Trap, at both endpoints, compared to both control groups. Administration of IL-1 Trap counteracts islet cell destruction in the NOD mouse model of type 1 diabetes. In part this could be due to a shift towards Th2 cytokine production seen in IL-1 Trap treated animals.
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| 9. |
- Rydgren, Tobias, et al.
(författare)
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Elevated glucagon-like peptide-1 plasma levels, as a possible adaptive response, in diabetic NOD mice
- 2012
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Ingår i: Biochemical and Biophysical Research Communications - BBRC. - : Elsevier BV. - 0006-291X .- 1090-2104. ; 423:3, s. 583-587
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Tidskriftsartikel (refereegranskat)abstract
- The incretin glucagon-like peptide-1 (GLP-1) and other GLP-1 receptor agonists have been shown to cause both antiapoptotic as well as regenerative effects on beta-cells in different animal models for diabetes. Our aim of this study was to test the hypothesis that spontaneously diabetic non obese diabetic (NOD) mice show an altered expression of GLP-1 compared to normoglycemic age-matched controls as a consequence of a diabetic state. To do this we used an ELISA prototype for mouse GLP-1 to measure plasma total GLP-1 from recently diabetic NOD mice as well as from age-matched normoglycemic NOD mice (controls). We also stained sections of pancreatic glands for GLP-1 from diabetic NOD mice and controls. We found increased levels of plasma total GLP-1 in diabetic NOD mice, when compared to control mice, both from non-fasted mice and from mice fasted for 2 h. Furthermore, diabetic NOD mice displayed a higher GLP-1 response to an oral glucose tolerance test, compared to control mice. We also found that sections of pancreatic glands from diabetic NOD mice had an increased GLP-1 positive islet area in regard to relative islet area (i.e. total islet area / total pancreas area of the sections) compared to control mice. To our knowledge, this study is the first to show increased levels of GLP-1 in plasma in spontaneously diabetic NOD mice. We suggest that these results might represent a compensatory mechanism of the diabetic NOD mice to counteract beta-cell loss and hyperglycemia.
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| 10. |
- Saksida, Tamara, et al.
(författare)
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Macrophage migration inhibitory factor deficiency protects pancreatic islets from palmitic acid-induced apoptosis
- 2012
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Ingår i: Immunology and Cell Biology. - : Wiley. - 0818-9641 .- 1440-1711. ; 90:7, s. 688-698
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Tidskriftsartikel (refereegranskat)abstract
- As a result of chronic exposure to high levels of free fatty acids, glucose and inflammatory mediators beta-cell apoptosis occurs at the end stage of obesity-associated type 2 diabetes (T2D). One potentially deleterious molecule for beta-cell function associated with T2D and obesity in humans is macrophage migration inhibitory factor (MIF). Therefore, the aim of this study was to explore MIF expression in vivo during development of obesity and insulin resistance in high-fat diet (HFD)-fed C57BL/6 mice and whether MIF inhibition could affect beta-cell apoptosis and dysfunction induced by palmitic acid (PA) in vitro. Indeed, increase in systemic and locally produced MIF correlated well with the weight gain, triglyceride upregulation, glucose intolerance and insulin resistance, which developed in HFD-fed mice. In in vitro settings PA dose-dependently induced MIF secretion before apoptosis development in islets. Further, mif gene deletion, mRNA silencing or protein inhibition rescued beta-cells from PA-induced apoptosis as measured by MTT assay and histone-DNA enzyme linked immuno sorbent assay. Protection from induced apoptosis was mediated by altered activation of caspase pathway and correlated with changes in the level of Bcl-2 family members. Further, MIF inhibition conveyed a significant resistance to PA-induced downregulation of insulin and PDX-1 expression and ATP content. However, beta-cell function was not entirely preserved in the absence of MIF judging by low glucose oxidation and depolarized mitochondria! membrane. In conclusion, the observed considerable preservation of beta-cells from nutrient-induced apoptosis might implicate MIF as a potential therapeutic target in the later stage of obesity-associated T2D.
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| 11. |
- Schreiber, Olof, et al.
(författare)
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iNOS-Dependent Increase in Colonic Mucus Thickness in DSS-Colitic Rats
- 2013
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 8:8, s. e71843-
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Tidskriftsartikel (refereegranskat)abstract
- Aim: To investigate colonic mucus thickness in vivo in health and during experimental inflammatory bowel disease. Methods: Colitis was induced with 5% DSS in drinking water for 8 days prior to experiment, when the descending colonic mucosa of anesthetized rats was studied using intravital microscopy. Mucus thickness was measured with micropipettes attached to a micromanipulator. To assess the contributions of NOS and prostaglandins in the regulation of colonic mucus thickness, the non-selective NOS-inhibitor L-NNA (10 mg/kg bolus followed by 3 mg/kg/h), the selective iNOS-inhibitor L-NIL (10 mg/kg bolus followed by 3 mg/kg/h) and the non-selective COX-inhibitor diclofenac (5 mg/kg) were administered intravenously prior to experiment. To further investigate the role of iNOS in the regulation of colonic mucus thickness, iNOS -/- mice were used. Results: Colitic rats had a thicker firmly adherent mucus layer following 8 days of DSS treatment than untreated rats (88 +/- 2 mu m vs 76 +/- 1 mu m). During induction of colitis, the thickness of the colonic mucus layer initially decreased but was from day 3 significantly thicker than in untreated rats. Diclofenac reduced the mucus thickness similarly in colitic and untreated rats (-16 +/- 5 mu m vs -14 +/- 2 mu m). While L-NNA had no effect on colonic mucus thickness in DSS or untreated controls (+3 +/- 2 mm vs +3 +/- 1 mu m), L-NIL reduced the mucus thickness significantly more in colitic rats than in controls (-33 +/- 4 mu m vs -10 +/- 3 mu m). The importance of iNOS in regulating the colonic mucus thickness was confirmed in iNOS-/- mice, which had thinner colonic mucus than wild-type mice (35 +/- 3 mu m vs 50 +/- 2 mu m, respectively). Furthermore, immunohistochemistry revealed increased levels of iNOS in the colonic surface epithelium following DSS treatment. Conclusion: Both prostaglandins and nitric oxide regulate basal colonic mucus thickness. During onset of colitis, the thickness of the mucus layer is initially reduced followed by an iNOS mediated increase.
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| 12. |
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| 13. |
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| 14. |
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| 15. |
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| 16. |
- Stojanovic, Ivana, et al.
(författare)
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Macrophage migration inhibitory factor (MIF) enhances palmitic acid- and glucose-induced murine beta cell dysfunction and destruction in vitro.
- 2012
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Ingår i: Growth Factors. - : Informa UK Limited. - 0897-7194 .- 1029-2292. ; 30:6, s. 385-393
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Tidskriftsartikel (refereegranskat)abstract
- Although several reports suggest a potentially deleterious role of macrophage migration inhibitory factor (MIF) in type 2 diabetes (T2D) pathology, it is still unclear how this pro-inflammatory cytokine acts on pancreatic beta cells. The aim of the present study was to evaluate MIF effects on murine beta cells in the in vitro settings mimicking T2D-associated conditions. Results indicate that recombinant MIF further increased apoptosis of pancreatic islets or MIN6 cells upon exposure to palmitic acid or glucose. This was accompanied by upregulation of several pro-apoptotic molecules. Furthermore, MIF potentiated nutrient-induced islet cell dysfunction, as revealed by lower glucose oxidation rate, ATP content, and depolarized mitochondrial membrane. The final outcome was potentiation of mitochondrial apoptotic pathway. The observed upregulation of nutrient-induced islet cell dysfunction and apoptosis by MIF implicates that silencing MIF may be beneficial for maintaining integrity of endocrine pancreas in obesity-associated T2D.
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| 17. |
- Sällström, Johan, et al.
(författare)
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High-protein-induced glomerular hyperfiltration is independent of the tubuloglomerular feedback mechanism and nitric oxide synthases
- 2010
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Ingår i: American Journal of Physiology. Regulatory Integrative and Comparative Physiology. - : American Physiological Society. - 0363-6119 .- 1522-1490. ; 299:5, s. R1263-R1268
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Tidskriftsartikel (refereegranskat)abstract
- A high protein intake is associated with increased glomerular filtration rate (GFR), which has been suggested to be mediated by reduced signaling of the tubuloglomerular feedback (TGF) mechanism. Nitric oxide (NO) has been shown to contribute to high protein-induced glomerular hyperfiltration, but the specific NO synthase (NOS) isoform responsible is not clear. In this study, a model for high-proteininduced hyperfiltration in conscious mice was developed. Using this model, we investigated the role of TGF using adenosine A(1)-receptor knockout mice lacking the TGF mechanism. Furthermore, the role of the different NOS isoforms was studied using neuronal-, inducible-, and endothelial-NOS knockout mice, and furthermore, wild-type mice acutely administered with the unspecific NOS inhibitor N-omega-nitro-L-arginine methyl ester (100 mg/kg). GFR was measured consecutively in mice given a low-protein diet (8% casein) for 10 days, followed by a high-protein diet (50% casein) for 10 days. All mice developed high protein-induced hyperfiltration to a similar degree. These results demonstrate that high protein-induced glomerular hyperfiltration is independent of the TGF mechanism and NOS isoforms.
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| 18. |
- Tian, Geng, et al.
(författare)
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Glucose- and Hormone-Induced cAMP Oscillations in α- and β-Cells Within Intact Pancreatic Islets
- 2011
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Ingår i: Diabetes. - : American Diabetes Association. - 0012-1797 .- 1939-327X. ; 60:5, s. 1535-1543
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVEcAMP is a critical messenger for insulin and glucagon secretion from pancreatic beta- and alpha-cells, respectively. Dispersed beta-cells show cAMP oscillations, but the signaling kinetics in cells within intact islets of Langerhans is unknown.RESEARCH DESIGN AND METHODSThe subplasma-membrane cAMP concentration ([cAMP](pm)) was recorded in alpha-and beta-cells in the mantle of intact mouse pancreatic islets using total internal reflection microscopy and a fluorescent translocation biosensor. Cell identification was based on the opposite effects of adrenaline on cAMP in alpha- and beta-cells.RESULTSIn islets exposed to 3 mmol/L glucose, [cAMP](pm) was low and stable. Glucagon and glucagon-like peptide-1(7-36)-amide (GLP-1) induced dose-dependent elevation of [cAMP](pm), often with oscillations synchronized among beta-cells. Whereas glucagon also induced [cAMP](pm) oscillations in most alpha-cells, < 20% of the alpha-cells responded to GLP-1. Elevation of the glucose concentration to 11-30 mmol/L in the absence of hormones induced slow [cAMP](pm) oscillations in both alpha- and beta-cells. These cAMP oscillations were coordinated with those of the cytoplasmic Ca2+ concentration ([Ca2+](i)) in the beta-cells but not caused by the changes in [Ca2+](i) . The transmembrane adenylyl cyclase (AC) inhibitor 2'5'-dideoxyadenosine suppressed the glucose- and hormone-induced [cAMP](pm) elevations, whereas the preferential inhibitors of soluble AC, KH7, and 1,3,5(10)-estratrien-2,3,17-beta-triol perturbed cell metabolism and lacked effect, respectively.CONCLUSIONSOscillatory [cAMP](pm) signaling in secretagogue-stimulated beta-cells is maintained within intact islets and depends on transmembrane AC activity. The discovery of glucose- and glucagon-induced [cAMP](pm) oscillations in alpha-cells indicates the involvement of cAMP in the regulation of pulsatile glucagon secretion.
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