| 1. |
- Andersson, Annika K., 1974-
(författare)
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Role of Inducible Nitric Oxide Synthase and Melatonin in Regulation of β-cell Sensitivity to Cytokines
- 2003
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The mechanisms of β-cell destruction leading to type 1 diabetes are complex and not yet fully understood, but infiltration of the islets of Langerhans by autoreactive immune cells is believed to be important. Activated macrophages and T-cells may then secrete cytokines and free radicals, which could selectively damage the β-cells. Among the cytokines, IL-1β, IFN-γ and TNF-α can induce expression of inducible nitric synthase (iNOS) and cyclooxygenase-2. Subsequent nitric oxide (NO) and prostaglandin E2 (PGE2) formation may impair islet function.In the present study, the ability of melatonin (an antioxidative and immunoregulatory hormone) to protect against β-cell damage induced by streptozotocin (STZ; a diabetogenic and free radical generating substance) or IL-1β exposure was examined. In vitro, melatonin counteracted STZ- but not IL-1β-induced islet suppression, indicating that the protective effect of melatonin is related to interference with free radical generation and DNA damage, rather than NO synthesis. In vivo, non-immune mediated diabetes induced by a single dose of STZ was prevented by melatonin.Furthermore, the effects of proinflammatory cytokines were examined in islets obtained from mice with a targeted deletion of the iNOS gene (iNOS -/- mice) and wild-type controls. The in vitro data obtained show that exposure to IL-1β or (IL-1β + IFN-γ) induce disturbances in the insulin secretory pathway, which were independent of NO or PGE2 production and cell death. Initially after addition, in particular IL-1β seems to be stimulatory for the insulin secretory machinery of iNOS –/- islets, whereas IL-1β acts inhibitory after a prolonged period. Separate experiments suggest that the stimulatory effect of IL-1β involves an increased gene expression of phospholipase D1a/b. In addition, the formation of new insulin molecules appears to be affected, since IL-1β and (IL-1β + IFN-γ) suppressed mRNA expression of both insulin convertase enzymes and insulin itself.
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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. |
- Bohman, Sara, 1981-
(författare)
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Microencapsulation of Pancreatic Islets : A Non-Vascularised Transplantation Model
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Transplantation of pancreatic islets is a potential treatment of type 1 diabetes that aims to restore normal blood glucose control. By encapsulating the islets in alginate, they can be protected from rejection. The aim of this thesis was to study the biology of encapsulated islets and to use the technique of microencapsulation to study the effect of transplantation in a system that is separated from direct contact with the vascular system and the host tissue at the transplantation site.Encapsulated islets can effectively reverse hyperglycaemia after transplantation into the peritoneal cavity of diabetic mice. A period of culture before encapsulation and transplantation did not affect their insulin release or curative capability. Pre-culture with exendin-4 improved insulin secretion, but not to the extent that the long term outcome in our transplantation model was improved. Despite being able to reach and retain normoglycaemia, microencapsulated islets transplanted intraperitoneally decreased in size. More specifically the number of beta cells in each individual islet was decreased. However, in contrast to previous studies using non-encapsulated islets, the alpha cell number was maintained, and thus the capsule seems to protect these peripherally located and otherwise exposed cells. As the capsule also prevents revascularisation of the islets, the model was used to study the importance of vascular supply for islet amyloid formation. Islet amyloid is a possible reason for the long-term failure of transplanted islets. It is likely that their low vascular density causes a disturbed local clearance of IAPP and insulin that starts the aggregation of IAPP. Indeed, encapsulated islets had an accelerated amyloid formation compared to normal islets, and might serve as a model for further studies of this process.In conclusion, although revascularisation is not a prerequisite for islet graft function, it plays an important role for islet transplantation outcome.
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| 4. |
- Börjesson, Andreas, 1976-
(författare)
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Investigations of Strategies to Counteract Proinflammatory Cytokines in Experimental Type 1 Diabetes
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Type 1 diabetes (T1D) is a chronic autoimmune disease targeted against the pancreatic β-cells. Proinflammatory cytokines are considered to play a major role in the destruction of the insulin-producing β-cells. This thesis studied strategies to counteract proinflammatory cytokines in experimental T1D. Both animal models for T1D as well as β-cell preparations exposed in vitro to putative noxious conditions were examined.In the first study we observed that cytokine treatment of mouse pancreatic islets lacking inducible nitric oxide synthase (iNOS) induced a prolongation of the early stimulatory phase of glucose stimulated insulin secretion. Various experiments led to the conclusion that this prolonged stimulatory effect may involve the DAG/PLD/PKC pathway.Next, we transplanted mouse islets deficient in iNOS to spontaneously diabetic NOD mice. We observed a normalization of hyperglycemia but not a delayed allograft rejection compared to transplanted wild type islets. Thus, absence of iNOS in the graft was not sufficient to prolong allograft survival.In paper III we found that sustained glucose stimulation of rat pancreatic islets was coupled to a decreased conversion of proinsulin to insulin. Islet treatment with IL-1β was also coupled to a decreased proinsulin conversion. Islet proconvertase activity may be a target in islet damage.In paper IV prolactin (PRL) was administered to mice in the multiple low dose streptozotocin model and we observed that PRL enhanced a Th2 response. This may contribute to the protective action by PRL in this model of autoimmune T1D.Finally, by examining β-cells overexpressing Suppressor of cytokine signalling 3 (SOCS-3) it was found that this could inhibit IL-1β induced signalling through the NF-κB and MAPK pathways. SOCS-3 overexpression also inhibited apoptosis induced by cytokines in primary β-cells. Lastly, we demonstrated that SOCS-3 transgenic islets were protected in an allogeneic transplantation model.
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| 5. |
- Karlsson, Maria G. E.
(författare)
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The Importance of Cell-Mediated Immunity for the Development of Type 1 Diabetes
- 2000
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background Type I (insulin-dependent) diabetes mellitus is an autoimmune disease characterised by infiltration of T-lymphocytes in the islets of Langerhans. In particular, activated Th1-like lymphocytes secreting IFN-γ are suggested to contribute to the inflammatory process and the destruction of ß-cells, whereas Th2-like cells producing IL-4 might even be protective. Environmental factors (diet, viruses, stress etc.) and autoantigens, e.g. Glutamic Acid Decarboxylase (GAD65) and insulin, are suggested to initiate the autoimmune process resulting in type I diabetes.Aim To estimate the immunological balance of Th1/Th2-like lymphocytes, spontaneously and after stimulation with antigens, in high-risk first degree relatives of type 1 diabetic children and in children with newly diagnosed type 1 diabetes.Materials and methods Peripheral blood mononuclear cells (PBMC) from healthy high-risk first-degree relatives (ICA ≥ 20) and newly diagnosed type 1 diabetic children were examined and compared with the response seen in PBMC from healthy controls matched for age and HLA-type (DR3 and/or DR4).Expression of IFN-γ and IL-4 mRNA was determined by RT-PCR or real-time RTPCR and IFN-γ and IL-4 by ELISPOT or ELISA, spontaneously and after stimulation with GAD65 , insulin, bovine serum albumin (BSA), the ABBOS-peptide and ß-lactoglobulin (ßLG). Cytokine expression and secretion was compared to the production of diabetes-associated autoantibodies and to the secretion of endogenous insulin.Results The epitope of GAD65, that mimics the Coxsackie B virus, caused increased IFN-γ mRNA expression in activated Th1-like lymphocytes from newly diagnosed diabetic children. This suggests that GAD65 might be involved in the development of type I diabetes. On the contrary, cow's milk proteins caused increased IFN-γ and IL- 4 mRNA expression in activated Th1- and Th2-like lymphocytes from both diabetic and healthy children. This does not support the hypothesis that cow's milk antigens are important for the development of type 1 diabetes.Overwhelming secretion of IFN-γ was observed in high-risk first-degree relatives of type 1 diabetic children. High-risk individuals still have the ability to change a Th1-like immune deviation into a more protective Th2-like response in the presence of GAD65 and insulin.Conclusions GAD65, but not cow's milk proteins, causes a Th1-like deviation in type 1 diabetic children. High-risk individuals are capable to deviate a Th1-like immune system into a more protective Th2-like response in the presence of autoantigens. These results can be useful in future therapeutic approaches.
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| 6. |
- Ludvigsen, Eva, 1974-
(författare)
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Somatostatin Receptor Expression and Biological Functions in Endocrine Pancreatic Cells
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Type 1 diabetes is resulting from the selective destruction of insulin-producing beta-cells within the pancreatic islets. Somatostatin acts as an inhibitor of hormone secretion through specific receptors (sst1-5).All ssts were expressed in normal rat and mouse pancreatic islets, although the expression intensity and the co-expression pattern varied between ssts as well as between species. This may reflect a difference in response to somatostatin in islet cells of the two species.The Non-Obese Diabetic (NOD) mouse model is an experimental model of type 1 diabetes, with insulitis accompanied by spontaneous hyperglycaemia. Pancreatic specimens from NOD mice at different age and stage of disease were stained for ssts. The islet cells of diabetic NOD mice showed increased islet expression of sst2-5 compared to normoglycemic NOD mice. The increase in sst2-5 expression in the islets cells may suggest either a contributing factor in the process leading to diabetes, or a defense response against ongoing beta-cell destruction.Somatostatin analogues were tested on a human endocrine pancreatic tumour cell line and cultured pancreatic islets. Somatostatin analogues had an effect on cAMP accumulation, chromogranin A secretion and MAP kinase activity in the cell line. Treatment of rat pancreatic islets with somatostatin analogues with selective receptor affinity was not sufficient to induce an inhibition of insulin and glucagon secretion. However, a combination of selective analogues or non-selective analogues via co-stimulation of receptors can cause inhibition of hormone production. For insulin and glucagon, combinations of sst2 + sst5 and sst1 + sst2, respectively, showed a biological effect.In summary, knowledge of islet cell ssts expression and the effect of somatostatin analogues with high affinity to ssts may be valuable in the future attempts to influence beta-cell function in type 1 diabetes mellitus, since down-regulation of beta-cell function may promote survival of these cells during the autoimmune attack.
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| 7. |
- Luo, Zhengkang, 1994-
(författare)
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Immunological strategies for counteracting type 1 diabetes focusing on IL-35 producing regulatory immune cells
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Type 1 diabetes (T1D) is an autoimmune disease where pancreatic β-cells are attacked by immune cells. Regulatory T (Treg) cells play critical roles in suppressing immune responses and their involvement have been intensively studied in T1D. Low dose IL-2 has been proposed to selectively boost Treg cells in T1D, with only limited success. We thus further decreased the IL-2 dosage and treated multiple low dose streptozotocin (MLDSTZ) mice with an ultra-low dose IL-2, but it did not protect STZ mice from hyperglycemia. Similarly, low dose IL-2 only partially prevented diabetes. Treg cells’ phenotype was not protected by either dose. These data suggest that alternative IL-2 therapies might be considered. Regulatory B (Breg) cells suppress pro-inflammatory immune responses by producing anti-inflammatory cytokines IL-10 and IL-35. Decreased IL-35+ and increased IFN-γ+ Breg cell proportions were found in T1D patients, and in diabetic mice. IL-35 treatment prevented increased IFN-γ+ Breg cell proportions in STZ mice. These data illustrate Breg cells’ involvement in T1D, and IL-35 treatment prevents hyperglycemia by maintaining Breg cells’ phenotype.Treg cells’ involvement in diabetic nephropathy (DN) has not been studied. Lower plasma IL-35 was found in DN patients than in T1D patients without DN and healthy controls, and was strongly correlated with kidney function. Decreased IL-35+ and increased IL-17+ Treg cells were found in DN patients. Moreover, Foxp3+ cell infiltration was found in the kidneys of diabetic mice, but it failed to counteract mononuclear cell infiltration. IL-35 treatment prevented DN and Treg cells’ phenotypic shift in STZ mice by maintaining the transcription factor Eos. These results demonstrate that IL-35 may be used to prevent DN. Given the instability of IL-35, we explored the effect of IL-6 signaling blockade. Anti-IL-6R completely protected STZ mice from diabetes. Proteomics indicated enhanced metabolism and down-regulated pro-inflammatory pathways. It maintained Treg cells’ phenotype by increasing IL-35 and decreasing IFN-γ production. It also reduced the number of macrophages and conventional dendritic cells type 2 and their CD80 expression. STZ mice remained normoglycemic despite the discontinuation of anti-IL-6R treatment. Therefore, our results illustrate the outcomes of several potential T1D immunotherapies and highlight the involvement of IL-35 producing immune cells in controlling the disease.
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| 8. |
- Rydgren, Tobias, 1973-
(författare)
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Experimental Studies Aiming to Prevent Type 1 Diabetes Mellitus
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Type 1 diabetes mellitus (T1DM) is an autoimmune disease in which T-cells and macrophages invade the islets of Langerhans and selectively destroy the insulin producing β-cells, either directly or through the secretion of e.g. cytokines and nitric oxide (NO). This thesis has studied possible strategies to prevent T1DM. In β-cells and macrophages, NO is produced by inducible nitric oxide synthase (iNOS). In the first study, we found that 1400W, a highly selective inhibitor of iNOS could prevent interleukin (IL)-1β induced suppression of rat islet function in vitro, but not diabetes induced by multiple low dose streptozotocin (MLDS), a well established animal model for autoimmune diabetes, in vivo. Next, we wanted to test a new type of high affinity blocker of IL-1 action, called IL-1 trap, in vitro. Here we found that an IL-1 trap could prevent the suppressive effects by IL-1β on rat pancreatic islet function. Also, it was sufficient to block the action of IL-1β to prevent islet cell death induced by a combination of IL-1β, tumor necrosis factor-α and interferon-γ.In study III, a murine IL-1 trap was found to prolong islet graft survival in the recurrence of disease (ROD) model, a T1DM model that involves syngeneic transplantation of healthy pancreatic islets to diabetic nonobese diabetic mice. Mice treated with IL-1 trap displayed an increased mRNA level of the cytokine IL-4 in isolated spleen cells. This suggests a shift towards Th2-cytokine production, which in part could explain the results. Finally, simvastatin an anti-hypercholesterolemic drug that possesses anti-inflammatory properties e.g. by interfering with transendothelial migration of leukocytes to sites of inflammation was studied. We found that the administration of simvastatin could delay, and in some mice prevent, the onset of MLDS-diabetes, and prolong islet graft survival in the ROD model.
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| 9. |
- Sandberg, Monica, 1964-
(författare)
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Intracellular Degradation of Insulin in Pancreatic Islets
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- There is a substantial intracellular degradation of insulin in pancreatic islets. This may be a physiological process, which, in correspondence with biosynthesis and secretion of insulin, would optimize the secretory granule content of the pancreatic β-cell. Insulin degradation may be effected by crinophagy, a process where secretory granules fuse with lysosomes. The general aim of this thesis was to investigate possible control mechanisms for intracellular degradation of insulin and crinophagy in isolated pancreatic islets. In islets incubated at low glucose concentrations there was an insulin degradation and this correlated well with the ultrastructural findings, where a lot of secondary lysosomes containing secretory granules were found. In islets incubated at a high glucose concentration there was no insulin degradation and the ultrastructure revealed only a few insulin granules and mostly primary lysosomes, indicating that there was no crinophagic activity. With interleukin-1β the islet insulin degradation, nitric oxide production and prostaglandin E2 production were increased. The effects were abolished either by inhibition of inducible nitric oxide synthetase by aminoguanidine, or by the specific cyclooxygenase-2 inhibitor rofecoxib. These findings indicate that there is a connection between the intracellular degradation of insulin, production of nitric oxide and cyclooxygenase-2 activation. The nitric oxide donor DETA/NO enhanced the intracellular degradation of insulin and cyclooxygenase-2 activation with subsequent production of prostaglandin E2, suggesting that the link between nitric oxide and insulin degradation may be a cyclooxygenase-2 activation and subsequent prostaglandin E2 production. With corticosterone added to islet incubations the insulin degradation decreased, which paralleled with a diminished crinophagy and formation of prostaglandin E2. With progesterone there was instead an increase in insulin degradation and crinophagy and an increased formation of prostaglandin E2. These effects were abolished by mifepristone, an inhibitor of intracellular corticosterone and progesterone receptors. This suggests that the effects from these steroids are exerted via a change in islet gene expression and cyclooxygenase-2 activation. It was also concluded that phospholipase A2 is involved in insulin degradation and that the isoform secretory phospholipase A2 may be involved in triggering this process. This suggests that cyclooxygenase-2 activation with a subsequent production of prostaglandin E2 may provide a control mechanism for intracellular degradation of insulin and crinophagy in pancreatic islets.
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| 10. |
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