| 1. |
- Friederich, Malou, 1983-, et al.
(author)
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Identification and distribution of uncoupling protein isoforms in the normal and diabetic rat kidney
- 2009
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In: Advances in Experimental Medicine and Biology. - New York : Springer. - 0065-2598 .- 2214-8019. - 9780387859972 ; 645, s. 205-212
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Journal article (peer-reviewed)abstract
- Uncoupling protein (UCP)-2 and -3 are ubiquitously expressed throughout the body but there is currently no information regarding the expression and distribution of the different UCP isoforms in the kidney. Due to the known cross-reactivity of the antibodies presently available for detection of UCP-2 and -3 proteins, we measured the mRNA expression of UCP-1, -2 and -3 in the rat kidney in order to detect the kidney-specific UCP isoforms. Thereafter, we determined the intrarenal distribution of the detected UCP isoforms using immunohistochemistry. Thereafter, we compared the protein levels in control and streptozotocin-induced diabetic rats using Western blot. Expressions of the UCP isoforms were also performed in brown adipose tissue and heart as positive controls for UCP-1 and 3, respectively. UCP-2 mRNA was the only isoform detected in the kidney. UCP-2 protein expression in the kidney cortex was localized to proximal tubular cells, but not glomerulus or distal nephron. In the medulla, UCP-2 was localized to cells of the medullary thick ascending loop of Henle, but not to the vasculature or parts of the nephron located in the inner medulla. Western blot showed that diabetic kidneys have about 2.5-fold higher UCP-2 levels compared to controls. In conclusion, UCP-2 is the only isoform detectable in the kidney and UCP-2 protein can be detected in proximal tubular cells and cells of the medullary thick ascending loop of Henle. Furthermore, diabetic rats have increased UCP-2 levels compared to controls, but the mechanisms underlying this increase and its consequences warrants further studies.
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| 2. |
- Friederich, Malou, et al.
(author)
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Uncoupling protein-2 in diabetic kidneys : increased protein expression correlates to increased non-transport related oxygen consumption
- 2008
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In: Advances in Experimental Medicine and Biology. - Boston, MA : Springer Berlin/Heidelberg. - 0065-2598 .- 2214-8019. ; 614, s. 37-43, s. 37-43
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Journal article (peer-reviewed)abstract
- Diabetic patients have an elevated risk to develop renal dysfunction and it has been postulated that altered energy metabolism is involved. We have previously shown that diabetic rats have markedly decreased oxygen availability in the kidney, resulting from increased oxygen consumption. A substantial part of the increased oxygen consumption is unrelated to tubular transport, suggesting decreased mitochondrial efficiency. In this study, we investigated the protein expression of mitochondrial uncoupling protein (UCP)-2 in kidney tissue from control and streptozotocin (STZ)-induced diabetic rats. Protein levels of UCP-2 were measured in adult male control and STZ-diabetic Wistar Furth as well as Sprague Dawley rats in both the kidney cortex and medulla by Western blot technique. Two weeks of hyperglycemia resulted in increased protein levels of UCP-2 in kidneys from both Wistar Furth and Sprague Dawley rats. Both cortical and medullary UCP-2 levels were elevated 2-3 fold above control levels. We conclude that sustained STZ-induced hyperglycemia increases the kidney levels of mitochondrial UCP-2, which could explain the previously reported increase in non-transport related oxygen consumption in diabetic kidneys. The elevated UCP-2 levels may represent an effort to reduce the increased production of superoxide radicals which is evident during diabetes.
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| 3. |
- Johansson, Magnus, 1976-, et al.
(author)
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Prolactin treatment improves engraftment and function of transplanted pancreatic islets
- 2009
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In: Endocrinology. - : The Endocrine Society. - 0013-7227 .- 1945-7170. ; 150:4, s. 1646-1653
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Journal article (peer-reviewed)abstract
- Transplantation of pancreatic islets is clinically used to treat type 1 diabetes, but requires multiple donors. Previous experimental studies have demonstrated that transplanted islets have a low blood vessel density, which leads to a hypoxic microenvironment. The present study tested the hypothesis that experimental prolactin pretreatment, a substance which seems to stimulate angiogenesis in endogenous islets, would increase graft blood vessel density, thereby improving transplantation outcome. Pancreatic islets from C57BL/6 mice were incubated with prolactin (500 ng/ml) or vehicle during the last 24 h of culture before syngeneic transplantation beneath the renal capsule, or recipients were injected with prolactin or vehicle for the first 7 days after transplantation. One month post-transplantation, graft vascular density, blood flow, oxygen tension, endocrine volume and function was evaluated. Also human islets were incubated with prolactin or vehicle before experimental transplantation and investigated for vascular engraftment. Vascular engraftment of syngeneically transplanted mouse islets was improved by both in vivo and in vitro prolactin pretreatment. Moreover, prolactin pretreatment in vitro of islets used for transplantation improved recovery from diabetes in a minimal islet mass model. Interestingly, also human islets subjected to prolactin treatment before experimental transplantation demonstrated improved revascularization, blood perfusion and oxygen tension when evaluated one month post-transplantation. We conclude that prolactin may improve engraftment of transplanted pancreatic islets. The protocol with pretreatment of islets ex vivo could minimize the risk of side effects when used in the clinical setting.
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| 4. |
- Johansson, Åsa, 1981-, et al.
(author)
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Angiostatic factors normally restrict islet endothelial cell proliferation and migration : implications for islet transplantation
- 2009
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In: Transplant International. - : Frontiers Media SA. - 0934-0874 .- 1432-2277. ; 22:12, s. 1182-1188
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Journal article (peer-reviewed)abstract
- New blood vessel formation in transplanted islets occurs within 7-14 days posttransplantation through both the expansion of donor islet endothelium and ingrowth of blood vessels from the implantation organ. However, several studies indicate that although the islets attract recipient blood vessels, the formed intra-islet vascular network is insufficient, which affects islet posttransplant function. This study aimed to develop an in vitro model to investigate the migration and proliferation properties of isolated liver and islet endothelium. Rat islet or liver endothelium was purified using Bandeiraea simplicifolia (BS-1)-coated Dynabeads. The liver endothelium displayed an increased migration towards islet-conditioned medium, and this chemo-attractant effect was fully prevented by adding a neutralizing vascular endothelial growth factor (VEGF)-antibody. In contrast, islet-produced VEGF failed to induce islet endothelial cell migration and only had marginal effects on islet endothelial cell proliferation. These properties could, however, be activated through blocking the effects of either endostatin, thrombospondin-1 or α1-antitrypsin. In conclusion, VEGF may attract recipient blood vessels towards intrahepatically transplanted islets, but intra-islet vascular expansion is hampered by angiostatic factors present within the islets and the islet endothelium. Inhibition of these early after transplantation may provide a strategy to restore the islet vascular network and improve islet graft function.
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| 5. |
- Mokhtari, Dariush, et al.
(author)
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Increased Hsp70 expression attenuates cytokine-induced cell death in islets of Langerhans from Shb knockout mice
- 2009
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In: Biochemical and Biophysical Research Communications - BBRC. - : Elsevier BV. - 0006-291X .- 1090-2104. ; 387:3, s. 553-557
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Journal article (peer-reviewed)abstract
- Type 1 diabetes may depend on cytokine-induced beta-cell death and therefore the current investigation was performed in order to elucidate this response in Shb-deficient islets. A combination of interleukin-1beta and interferon-gamma caused a diminished beta-cell death response in Shb null islets. Furthermore, the induction of an unfolded protein response (UPR) by adding cyclopiazonic acid did not increase cell death in Shb-deficient islets, despite simultaneous expression of UPR markers. The heat-shock protein Hsp70 was more efficiently induced in Shb knockout islets, providing an explanation for the decreased susceptibility of Shb-deficient islets to cytokines. It is concluded that islets deficient in the Shb protein are less susceptible to cytotoxic conditions, and that this partly depends on their increased ability to induce Hsp70 under such circumstances. Interference with Shb signaling may provide means to improve beta-cell viability under conditions of beta-cell stress.
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| 6. |
- Olerud, Johan, et al.
(author)
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Improved vascular engraftment and graft function after inhibition of the angiostatic factor thrombospondin-1 in mouse pancreatic islets
- 2008
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In: Diabetes. - : American Diabetes Association. - 0012-1797 .- 1939-327X. ; 57:7, s. 1870-1877
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Journal article (peer-reviewed)abstract
- OBJECTIVE: Insufficient development of a new intra-islet capillary network after transplantation may be one contributing factor to the failure of islet grafts in clinical transplantation. The present study tested the hypothesis that the angiostatic factor thrombospondin-1 (TSP-1), which is normally present in islets, restricts intra-islet vascular expansion posttransplantation. RESEARCH DESIGN AND METHODS: Pancreatic islets of TSP-1-deficient (TSP-1(-/-)) mice or wild-type islets transfected with siRNA for TSP-1 were transplanted beneath the renal capsule of syngeneic or immunocompromised recipient mice. RESULTS: Both genetically TSP-1(-/-) islets and TSP-1 siRNA-transfected islet cells demonstrated an increased vascular density when compared with control islets 1 month after transplantation. This was also reflected in a markedly increased blood perfusion and oxygenation of the grafts. The functional importance of the improved vascular engraftment was analyzed by comparing glucose-stimulated insulin release from islet cells transfected with either TSP-1 siRNA or scramble siRNA before implantation. These experiments showed that the increased revascularization of grafts composed of TSP-1 siRNA-transfected islet cells correlated to increments in both their first and second phase of glucose-stimulated insulin secretion. CONCLUSIONS: Our findings demonstrate that inhibition of TSP-1 in islets intended for transplantation may be a feasible strategy to improve islet graft revascularization and function.
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| 7. |
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| 8. |
- Olerud, Johan, et al.
(author)
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Neural crest stem cells increase beta cell proliferation and improve islet function in co-transplanted murine pancreatic islets
- 2009
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In: Diabetologia. - : Springer Science and Business Media LLC. - 0012-186X .- 1432-0428. ; 52:12, s. 2594-2601
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Journal article (peer-reviewed)abstract
- AIMS/HYPOTHESIS: Long-term graft survival after islet transplantation to patientswith type 1 diabetes is insufficient, necessitating the development of newstrategies to enhance transplant viability. Here we investigated whetherco-transplantation of neural crest stem cells (NCSCs) with islets improves islet survival and function in normoglycaemic and diabetic mice. METHODS: Islets alone or together with NCSCs were transplanted under the kidney capsule tonormoglycaemic or alloxan-induced diabetic mice. Grafts were analysed for size,proliferation, apoptosis and insulin release. In diabetic recipients bloodglucose levels were examined before and after graft removal. RESULTS: In mixedtransplants NCSCs actively migrated and extensively associated withco-transplanted pancreatic islets. Proliferation of beta cells was markedlyincreased and transplants displayed improved insulin release in normoglycaemicmice compared with those receiving islet-alone transplants. Mixed grafts survivedsuccessfully and partially restored normoglycaemia in alloxan-induced diabeticmice. CONCLUSIONS/INTERPRETATION: Co-grafting of NCSCs with pancreatic isletsimproved insulin release in mixed transplants and enhanced beta cellproliferation, resulting in increased beta cell mass. This co-transplantationmodel offers an opportunity to restore neural-islet interactions and improveislet functions after transplantation.
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| 9. |
- Olerud, Johan, 1977-
(author)
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Role of Thrombospondin-1 in Endogenous and Transplanted Pancreatic Islets
- 2009
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Doctoral thesis (other academic/artistic)abstract
- Type 1 diabetes mellitus is a severe life-long disease with a pronounced risk of developing secondary complications. One way to avoid the latter is to restore the fine tuning of blood glucose homeostasis by transplantation of pancreatic islets. However, isolated islets need to be properly engrafted and to re-establish a vascular network in order to regain function. Earlier studies have shown that pancreatic islets experimentally transplanted to e.g. the liver or the kidney become poorly revascularized. In the present thesis, mice deficient of the angiostatic factor thrombospondin-1 (TSP-1) were found to have an impaired beta-cell function. Development of this beta-cell dysfunction was prevented by treatment of TSP-1 deficient mice from birth with the TGFbeta-1 activating sequence of TSP-1. TSP-1 in islets was predominantly expressed in the endothelial cells. Isolated islet endothelial cells was observed to have a low proliferatory and migratory capacity towards angiogenic stimuli, but this could be reversed by neutralizing antibodies to the angiostatic factors alpha1-antitrypsin, endostatin or TSP-1. Transient downregulation of TSP-1 expression in mouse islet cells prior to transplantation improved graft revascularization, blood perfusion, oxygenation and function when evaluated one-month post-transplantation. The same result was achieved when islets or recipients of islets were pre-treated with the hormone prolactin one-month post-transplantation. The present study illustrates the importance of the angiostatic factor TSP-1 for islet beta-cell function and engraftment of islets following transplantation. Interference with TSP-1 can possibly be used to improve the results of clinical islet transplantation.
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| 10. |
- Olerud, Johan, et al.
(author)
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Vascular niche of pancreatic islets
- 2009
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In: Expert Review of Endocrinology & Metabolism. - : Informa UK Limited. - 1744-6651 .- 1744-8417. ; 4:5, s. 481-491
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Journal article (peer-reviewed)abstract
- Pancreatic islets are highly vascularized micro-organs. Approximately 10% of an islet consists of blood vessels. The induction and maintenance of the islet vascular system depend on VEGF secreted from β-cells. VEGF is also critical for the phenotype of the islet vasculature by induction of a vast number of fenestrae. The islet vasculature serves the role of supplying the endocrine cells with oxygen and nutrients, but may also be important for proper glucose sensing of the cells, for paracrine support of endocrine function and growth, and for drainage of metabolites and secreted islet hormones into the systemic circulation. Emerging evidence suggests an important role of islet endothelial cells to maintain β-cell function and growth by secretion of molecules such as hepatocyte growth factor, thrombospondin-1 and laminins, thereby forming a vascular niche for the endocrine cells.
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