| 1. |
- Knip, Mikael, et al.
(författare)
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Environmental triggers and determinants of type 1 diabetes
- 2005
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Ingår i: Diabetes. - 0012-1797 .- 1939-327X. ; 54:SUPPL. 2
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Tidskriftsartikel (refereegranskat)abstract
- Type 1 diabetes is perceived as a chronic immune-mediated disease with a subclinical prodromal period characterized by selective loss of insulin-producing β-cells in the pancreatic islets in genetically susceptible subjects. A series of evidence supports a critical role of exogenous factors in the development of type 1 diabetes, such as 1) the fact that <10% of individuals with HLA-conferred diabetes susceptibility do progress to clinical disease, 2) a pairwise concordance of type 1 diabetes of <40% among monozygotic twins, 3) a more than 10-fold difference in the disease incidence among Caucasians living in Europe, 4) a several-fold increase in the incidence over the last 50 years, and 5) migration studies indicating that the disease incidence has increased in population groups who have moved from a low-incidence to a high-incidence region. This article discusses the trigger-booster hypothesis claiming that the diabetic disease process is triggered by an exogenous factor with definite seasonal variation and driven by one or several other environmental determinants. In addition, there are a series of modifying factors affecting the fate and pace of the process. Accordingly, progression to clinical type 1 diabetes typically requires the unfortunate combination of genetic disease susceptibility, a diabetogenic trigger, and a high exposure to a driving antigen. © 2005 by the American Diabetes Association.
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| 2. |
- Kolak, Maria, et al.
(författare)
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Adipose tissue inflammation and increased ceramide content characterize subjects with high liver fat content independent of obesity
- 2007
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Ingår i: Diabetes. - : American Diabetes Association. - 0012-1797 .- 1939-327X. ; 56:8, s. 1960-1968
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: We sought to determine whether adipose tissue is inflamed in individuals with increased liver fat (LFAT) independently of obesity.RESEARCH DESIGN AND METHODS: A total of 20 nondiabetic, healthy, obese women were divided into normal and high LFAT groups based on their median LFAT level (2.3 +/- 0.3 vs. 14.4 +/- 2.9%). Surgical subcutaneous adipose tissue biopsies were studied using quantitative PCR, immunohistochemistry, and a lipidomics approach to search for putative mediators of insulin resistance and inflammation. The groups were matched for age and BMI. The high LFAT group had increased insulin (P = 0.0025) and lower HDL cholesterol (P = 0.02) concentrations.RESULTS: Expression levels of the macrophage marker CD68, the chemokines monocyte chemoattractant protein-1 and macrophage inflammatory protein-1alpha, and plasminogen activator inhibitor-1 were significantly increased, and those of peroxisome proliferator-activated receptor-gamma and adiponectin decreased in the high LFAT group. CD68 expression correlated with the number of macrophages and crown-like structures (multiple macrophages fused around dead adipocytes). Concentrations of 154 lipid species in adipose tissue revealed several differences between the groups, with the most striking being increased concentrations of triacylglycerols, particularly long chain, and ceramides, specifically Cer(d18:1/24:1) (P = 0.01), in the high LFAT group. Expression of sphingomyelinases SMPD1 and SMPD3 were also significantly increased in the high compared with normal LFAT group.CONCLUSIONS: Adipose tissue is infiltrated with macrophages, and its content of long-chain triacylglycerols and ceramides is increased in subjects with increased LFAT compared with equally obese subjects with normal LFAT content. Ceramides or their metabolites could contribute to adverse effects of long-chain fatty acids on insulin resistance and inflammation.
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| 3. |
- Kos, K., et al.
(författare)
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Regulation of the fibrosis and angiogenesis promoter SPARC/osteonectin in human adipose tissue by weight change, leptin, insulin, and glucose : Regulation of SPARC in human adipose tissue
- 2009
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Ingår i: Diabetes. - : American Diabetes Association. - 1939-327X .- 0012-1797. ; 58:8, s. 1780-8
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: Matricellular Secreted Protein, Acidic and Rich in Cysteine (SPARC), originally discovered in bone as osteonectin, is a mediator of collagen deposition and promotes fibrosis. Adipose tissue collagen has recently been found to be linked with metabolic dysregulation. Therefore, we tested the hypothesis that SPARC in human adipose tissue is influenced by glucose metabolism and adipokines. RESEARCH DESIGN AND METHODS: Serum and adipose tissue biopsies were obtained from morbidly obese nondiabetic subjects undergoing bariatric surgery and lean control subjects for analysis of metabolic markers, SPARC, and various cytokines (RT-PCR). Additionally, 24 obese subjects underwent a very-low-calorie diet of 1,883 kJ (450 kcal)/day for 16 weeks and serial subcutaneous-abdominal-adipose tissue (SCAT) biopsies (weight loss: 28 +/- 3.7 kg). Another six lean subjects underwent fast-food-based hyperalimentation for 4 weeks (weight gain: 7.2 +/- 1.6 kg). Finally, visceral adipose tissue explants were cultured with recombinant leptin, insulin, and glucose, and SPARC mRNA and protein expression determined by Western blot analyses. RESULTS: SPARC expression in human adipose tissue correlated with fat mass and was higher in SCAT. Weight loss induced by very-low-calorie diet lowered SPARC expression by 33% and increased by 30% in adipose tissue of subjects gaining weight after a fast-food diet. SPARC expression was correlated with leptin independent of fat mass and correlated with homeostasis model assessment-insulin resistance. In vitro experiments showed that leptin and insulin potently increased SPARC production dose dependently in visceral adipose tissue explants, while glucose decreased SPARC protein. CONCLUSIONS: Our data suggest that SPARC expression is predominant in subcutaneous fat and its expression and secretion in adipose tissue are influenced by fat mass, leptin, insulin, and glucose. The profibrotic effects of SPARC may contribute to metabolic dysregulation in obesity.
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| 4. |
- Onozato, Maristela L, et al.
(författare)
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Expression of NG,NG-dimethylarginine dimethylaminohydrolase and protein arginine N-methyltransferase isoforms in diabetic rat kidney: effects of angiotensin II receptor blockers
- 2008
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Ingår i: Diabetes. - : American Diabetes Association. - 0012-1797 .- 1939-327X. ; 57:1, s. 172-180
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Tidskriftsartikel (refereegranskat)abstract
- Objective: The nitric oxide (NO) synthase inhibitor, asymmetric dimethylarginine (ADMA) is generated by protein arginine N-methyltransferase (PRMT)-1 and is metabolized by NG, NG-dimethylarginine dimethylaminohydrolase (DDAH). We tested the hypothesis that increased serum ADMA (SADMA) in the streptozotocin (STZ)-induced rat model of diabetes mellitus (DM) is mediated by an angiotensin receptor blocker– sensitive change in DDAH or PRMT expression.Research design and Methods: Data were compared from 4 groups of rats: sham injected controls; untreated STZ- DM at 4 weeks; STZ-DM rats administered the angiotensin II receptor blocker telmisartan for 2 weeks; control rats administered telmisartan for 2 weeks.Results: Immunostaining and Western blotting of microdissected nephron segments localized DDAH I in the proximal tubules and DDAH II in the glomeruli, afferent arterioles, macula densa and distal nephron. Renal angiotensin II and SADMA increased with DM but were normalized by 2 weeks of telmisartan. DDAH I expression was decreased in DM kidneys while DDAH II expression was increased. These changes were reversed by telmisartan which also reduced expression of PRMT-1 and -5. Telmisartan increased expressions of DDAH I but decreased DDAH II in Ang II-stimulated kidney slices ex-vivo.Conclusion: Renal angiotensin II and SADMA are increased in insulinopenic DM. They are normalized by an angiotensin II receptor blocker which increases the renal expression of DDAH I, decreases PRMT-1 and increases renal NO metabolites.
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| 5. |
- Palm, Fredrik, et al.
(författare)
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Reduced nitric oxide concentration in the renal cortex of streptozotocin-induced diabetic rats : effects on renal oxygenation and microcirculation
- 2005
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Ingår i: Diabetes. - 0012-1797 .- 1939-327X. ; 54:11, s. 3282-7
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Tidskriftsartikel (refereegranskat)abstract
- Nitric oxide (NO) regulates vascular tone and mitochondrial respiration. We investigated the hypothesis that there is reduced NO concentration in the renal cortex of diabetic rats that mediates reduced renal cortical blood perfusion and oxygen tension (P O2). Streptozotocin-induced diabetic and control rats were injected with l-arginine followed by Nomega-nitro-L-arginine-metyl-ester (L-NAME). NO and P O2 were measured using microsensors, and local blood flow was recorded by laser-Doppler flowmetry. Plasma arginine and asymmetric dimethylarginine (ADMA) were analyzed by high-performance liquid chromatography. L-Arginine increased cortical NO concentrations more in diabetic animals, whereas changes in blood flow were similar. Cortical P O2 was unaffected by L-arginine in both groups. L-NAME decreased NO in control animals by 87 +/- 15 nmol/l compared with 45 +/- 7 nmol/l in diabetic animals. L-NAME decreased blood perfusion more in diabetic animals, but it only affected P O2 in control animals. Plasma arginine was significantly lower in diabetic animals (79.7 +/- 6.7 vs. 127.9 +/- 3.9 mmol/l), whereas ADMA was unchanged. A larger increase in renal cortical NO concentration after l-arginine injection, a smaller decrease in NO after L-NAME, and reduced plasma arginine suggest substrate limitation for NO formation in the renal cortex of diabetic animals. This demonstrates a new mechanism for diabetes-induced alteration in renal oxygen metabolism and local blood flow regulation.
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| 6. |
- Paulsson, Johan, 1976-, et al.
(författare)
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Aberrant processing of human proislet amyloid polypeptide results in increased amyloid formation
- 2005
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Ingår i: Diabetes. - : American Diabetes Association. - 0012-1797 .- 1939-327X. ; 54:7, s. 2117-2125
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Tidskriftsartikel (refereegranskat)abstract
- The amyloid present in the islets of Langerhans in type 2 diabetes is polymerized islet amyloid polypeptide (IAPP). The precursor protein proIAPP is posttranslationally modified, a process involving the removal of NH2- and COOH-terminal flanking peptides. This step is performed by the prohormone convertases PC2 and PC1/3. PC2 processes proIAPP preferably at the NH 2-terminal processing site, and PC1/3 processes proIAPP exclusively at the COOH-terminal site. Little is known regarding the exact circumstances leading to islet amyloid formation. In this study, we have examined the possible significance of aberrant processing of proIAPP on amyloid formation in several in vitro cellular systems. In our studies, human (h)-proIAPP was transfected into β-TC-6 cells expressing both prohormone convertases and in which proIAPP is processed into IAPP. Additionally, h-proIAPP was transfected into three different pituitary-derived cell lines with different prohormone convertase profiles: AtT-20 cells (deficient in PC2), GH3 cells (deficient in PC1/3), and GH4C1 cells (deficient in both convertases). We followed the processing of h-proIAPP with antibodies specific for the respective cleavage sites and stained the cells with Congo red to verify the accumulation of amyloid. Incomplete processing of h-proIAPP that occurs in AtT-20 and GH4C1 cells resulted in the formation of intracellular amyloid. No amyloid developed in β-TC-6 and GH3 cells lines with full processing of proIAPP. An intracellular increase in proIAPP and/or its metabolic products may thus promote intracellular amyloid formation, thereby causing cell death. When extracellularly exposed, this amyloid might act as template for continuing amyloid formation from processed IAPP released from the surrounding β-cells. © 2005 by the American Diabetes Association.
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| 7. |
- Skarsvik, Susanne, 1978-, et al.
(författare)
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Decreased in vitro type 1 immune response against coxsackie virus B4 in children with type 1 diabetes
- 2006
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Ingår i: Diabetes. - : American Diabetes Association. - 0012-1797 .- 1939-327X. ; 55:4, s. 996-1003
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Tidskriftsartikel (refereegranskat)abstract
- Enteroviruses, particularly Coxsackie virus B4 (CVB4), are considered to be involved in the pathogenesis of type 1 diabetes. We wanted to compare the characteristics of T-cell immune response to CVB4 in children with type 1 diabetes and healthy children with and without HLA risk-associated haplotypes (HLA-DR3-DQ2 or HLA-DR4-DQ8) for type 1 diabetes. Peripheral blood mononuclear cells (PBMCs) were isolated and cultured with CVB4 and analyzed for cytokine and chemokine receptors by flow cytometry and for expression of transcription factors Tbet and GATA-3 by RT-PCR and Western blot. Culture supernatants were analyzed for secretion of γ-interferon (IFN-γ). In children with type 1 diabetes, a decreased percentage of T-cells expressed CCR2, CXCR6, interleukin (IL)-18R, and IL-12Rβ2-chain after in vitro stimulation with CVB4 in comparison with healthy children with or without HLA risk genotype. Moreover, we found that children with type 1 diabetes had decreased IFN-γ secretion and expression of Tbet, both on mRNA and protein level, in CVB4-stimulated PBMCs. Accordingly, children with type 1 diabetes show an impaired type 1 immune response against CVB4 compared with healthy children. This may lead to a delayed clearance of the virus and, at least partly, explain why children with type 1 diabetes may be more prone to CVB4 infections and related complications, such as β-cell damage.
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| 8. |
- Vaarala, Outi, 1962-, et al.
(författare)
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Insulin treatment in patients with type 1 diabetes induces upregulation of regulatory T-cell markers in peripheral blood mononuclear cells stimulated with insulin in vitro
- 2006
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Ingår i: Diabetes. - : American Diabetes Association. - 0012-1797 .- 1939-327X. ; 55:12, s. 3446-3454
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Tidskriftsartikel (refereegranskat)abstract
- Patients with type 1 diabetes are treated with daily injections of human insulin, an autoantigen expressed in thymus. Natural CD4+CD25high regulatory T-cells are derived from thymus, and accordingly human insulin-specific regulatory T-cells should exist. We had a chance to study peripheral blood mononuclear cells (PBMCs) from children with type 1 diabetes both before and after starting insulin treatment, and thus we could analyze the effects of insulin treatment on regulatory T-cells in children with type 1 diabetes. PBMCs were stimulated for 72 h with bovine/human insulin. The mRNA expression of regulatory T-cell markers (transforming growth factor-β, Foxp3, cytotoxic T-lymphocyte antigen-4 [CTLA-4], and inducible co-stimulator [ICOS]) or cytokines (γ-interferon [IFN-γ], interleukin [IL]-5, IL-4) was measured by quantitative RT-PCR. The secretion of IFN-γ, IL-2, IL-4, IL-5, and IL-10 was also studied. The expression of Foxp3, CTLA-4, and ICOS mRNAs in PBMCs stimulated with bovine or human insulin was higher in patients on insulin treatment than in patients studied before starting insulin treatment. The insulin-induced Foxp3 protein expression in CD4+CD25 high cells was detectable in flow cytometry. No differences were seen in cytokine activation between the patient groups. Insulin stimulation in vitro induced increased expression of regulatory T-cell markers, Foxp3, CTLA-4, and ICOS only in patients treated with insulin, suggesting that treatment with human insulin activates insulin-specific regulatory T-cells in children with newly diagnosed type 1 diabetes. This effect of the exogenous autoantigen could explain the difficulties to detect in vitro T-cell proliferation responses to insulin in newly diagnosed patients. Furthermore, autoantigen treatment-induced activation of regulatory T-cells may contribute to the clinical remission of the disease. © 2006 by the American Diabetes Association.
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| 9. |
- Vaarala, Outi, et al.
(författare)
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The "perfect storm" for type 1 diabetes - the complex interplay between intestinal microbiota, gut permeability, and mucosal immunity
- 2008
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Ingår i: Diabetes. - : American Diabetes Association. - 0012-1797 .- 1939-327X. ; 57:10, s. 2555-2562
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Tidskriftsartikel (refereegranskat)abstract
- It is often stated that type 1 diabetes results from a complex interplay between varying degrees of genetic susceptibility and environmental factors. While agreeing with this principal, our desire is that this Perspectives article will highlight another complex interplay potentially associated with this disease involving facets related to the gut, one where individual factors that, upon their interaction with each another, form a "perfect storm" critical to the development of type 1 diabetes. This trio of factors includes an aberrant intestinal microbiota, a "leaky" intestinal mucosal barrier, and altered intestinal immune responsiveness. Studies examining the microecology of the gastrointestinal tract have identified specific microorganisms whose presence appears related (either quantitatively or qualitatively) to disease, in type 1 diabetes, a role for microflora in the pathogenesis of disease has recently been suggested. Increased intestinal permeability has also been observed in animal models of type 1 diabetes as well as in humans with or at increased-risk for the disease. Finally, an altered mucosal immune system has been associated with the disease and is likely a major contributor to the failure to form tolerance, resulting in the autoimmunity that underlies type 1 diabetes. Herein, we discuss the complex interplay between these factors and raise testable hypotheses that form a fertile area for future investigations as to the role of the gut in the pathogenesis and prevention of type 1 diabetes.
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