Effects of 12 weeks' treatment with a proton pump inhibitor on insulin secretion, glucose metabolism and markers of cardiovascular risk in patients with type 2 diabetes: a randomised double-blind prospective placebo-controlled study.

AIMS/HYPOTHESIS: Recent studies suggest that proton pump inhibitor treatment may increase insulin secretion and improve glucose metabolism in type 2 diabetes. In a randomised double-blind prospective placebo-controlled 2 × 2 factorial study, we examined the effect of esomeprazole on insulin secretion, HbA(1c) and cardiovascular risk factors in type 2 diabetes. METHODS: Forty-one patients with type 2 diabetes using dietary control or oral glucose-lowering treatment were randomised to receive add-on esomeprazole 40 mg (n = 20) or placebo (n = 21) for 12 weeks. Randomisation was carried out prior to inclusion on the basis of a computer-generated random-number list. The allocation sequence was concealed in sealed envelopes from the researcher enrolling and assessing participants. The study was undertaken at Steno Diabetes Center, Gentofte, Denmark. The primary outcome was change in AUC for insulin levels during a meal test. Secondary outcomes were the levels of HbA(1c) and biochemical markers of cardiovascular risk, including lipids, coagulation factors, inflammation markers, markers of endothelial function and 24 h ambulatory BP measurements. RESULTS: Forty-one participants were analysed. In the esomeprazole-treated group the AUC for insulin did not change (before vs after treatment: 28,049 ± 17,659 vs 27,270 ± 32,004 pmol/l × min (p = 0.838). In the placebo group AUC for insulin decreased from 27,392 ± 14,348 pmol/l × min to 22,938 ± 11,936 pmol/l × min (p = 0.002). Esomeprazole treatment (n = 20) caused a ninefold increase in the AUC for gastrin. HbA(1c) increased from 7.0 ± 0.6% (53 ± 5 mmol/mol) to 7.3 ± 0.8% (56 ± 6 mmol/mol) in the esomeprazole-treated group and from 7.0 ± 0.6% (53 ± 5 mmol/mol) to 7.4 ± 0.8% (57 ± 6 mmol/mol) in the placebo group (n = 21) (p for difference in change >0.05). Except for BP, there were no differences between the groups in the markers of cardiovascular risk (p > 0.05). Monitoring of 24 h ambulatory BP showed a significant decrease in daytime systolic BP, daytime diastolic BP and 24 h diastolic BP in the placebo group (p < 0.05). No change in BP was seen in the patients treated with esomeprazole. CONCLUSIONS/INTERPRETATION: Treatment with esomeprazole over 12 weeks did not improve insulin secretion, glycaemic control or cardiovascular disease biomarkers in patients with type 2 diabetes.

Upregulation of alpha cell glucagon-like peptide 1 (GLP-1) in Psammomys obesus--an adaptive response to hyperglycaemia?

AIMS/HYPOTHESIS: The hormone glucagon-like peptide 1 (GLP-1) is released in response to a meal from the intestinal L-cells, where it is processed from proglucagon by the proconvertase (PC)1/3. In contrast, in the adult islets proglucagon is processed to glucagon by the PC2 enzyme. The aim of the study was to evaluate if, during the development of diabetes, alpha cells produce GLP-1 that, in turn, might trigger beta cell growth. METHODS: Beta cell mass, GLP-1 and insulin levels were measured in the gerbil Psammomys obesus (P. obesus), a rodent model of nutritionally induced diabetes. Furthermore, the presence of biologically active forms of GLP-1 and PC1/3 in alpha cells was demonstrated by immunofluorescence, and the release of GLP-1 from isolated P. obesus, mouse and human islets was investigated. RESULTS: During the development of diabetes in P. obesus, a significant increase in GLP-1 was detected in the portal vein (9.8 ± 1.5 vs 4.3 ± 0.7 pmol/l, p < 0.05), and in pancreas extracts (11.4 ± 2.2 vs 5.1 ± 1.3 pmol/g tissue, p < 0.05). Freshly isolated islets from hyperglycaemic animals released more GLP-1 following 24 h culture than islets from control animals (28.2 ± 4.4 pmol/l vs 5.8 ± 2.4, p < 0.01). GLP-1 release was increased from healthy P. obesus islets following culture in high glucose for 6 days (91 ± 9.1 pmol/l vs 28.8 ± 6.6, p < 0.01). High levels of GLP-1 were also found to be released from human islets. PC1/3 colocalised weakly with alpha cells. CONCLUSIONS/INTERPRETATION: GLP-1 release from alpha cells is upregulated in P. obesus during the development of diabetes. A similar response is seen in islets exposed to high glucose, which supports the hypothesis that GLP-1 released from alpha cells promotes an increase in beta cell mass and function during metabolic challenge such as diabetes.

ß-cell specific overexpression of suppressor of cytokine signalling-3 does not protect against multiple low dose streptozotocin induced type 1 diabetes in mice.

We investigated the impact of ß-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-1ß (25U/ml) or a combination of human IL-1ß (25U/ml) and murine IFN-γ (1000U/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 IL-1ß or IL-1ß+IFN-γ 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 ß-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.

Treatment with a proton pump inhibitor improves glycaemic control in Psammomys obesus, a model of type 2 diabetes.

AIMS/HYPOTHESIS: Gastrin has been implicated in islet growth/neogenesis, and proton pump inhibitors (PPIs) have been shown to increase endogenous gastrin levels in animals and humans. Therefore, we investigated the effect of PPIs in a model of type 2 diabetes, Psammomys obesus. METHODS: P. obesus (morning blood glucose [mBG] 16.9 +/- 0.6 mmol/l) were treated with vehicle or different doses (1-15 mg/kg) of lansoprazole for 17 days. RESULTS: Treatment with lansoprazole resulted in up to ninefold dose-dependent increases in endogenous gastrin levels (p < 0.05 for 10 mg/kg lansoprazole vs vehicle). There was a significant reduction in mBG levels in all animals in the high-dose lansoprazole groups during the 17 day treatment period, whereas there was no significant improvement in mBG in animals in the vehicle groups. The mBG at end of study was 18.2 +/- 2.1, 8.7 +/- 2.2 (p < 0.01), and 6.1 +/- 2.3 (p < 0.001) mmol/l for vehicle and lansoprazole 10 and 15 mg/kg, respectively. The animals treated with 15 mg/kg lansoprazole, compared with vehicle, had a 2.3-fold increase in the intensity of insulin staining in beta cells (p=0.0002) and 50% higher beta cell mass (p=0.04). CONCLUSIONS/INTERPRETATIONS: The PPI lansoprazole had significant glucose-lowering effects in an animal model of type 2 diabetes, an effect that is most likely mediated through an increase in endogenous gastrin levels.

Functional SOCS1 polymorphisms are associated with variation in obesity in whites.

AIMS/HYPOTHESIS: The suppressor of cytokine signalling 1 (SOCS1) is a natural inhibitor of cytokine and insulin signalling pathways and may also play a role in obesity. In addition, SOCS1 is considered a candidate gene in the pathogenesis of both type 1 diabetes (T1D) and type 2 diabetes (T2D). The objective was to perform mutation analysis of SOCS1 and to test the identified variations for association to T2D-related quantitative traits, T2D or T1D. METHODS: Mutation scanning was performed by direct sequencing in 27 white Danish subjects. Genotyping was carried out by TaqMan allelic discrimination. A total of more than 8100 individuals were genotyped. RESULTS: Eight variations were identified in the 5' untranslated region (UTR) region. Two of these had allele frequencies below 1% and were not further examined. The six other variants were analysed in groups of T1D families (n = 1461 subjects) and T2D patients (n = 1430), glucose tolerant first-degree relatives of T2D patients (n = 212) and normal glucose tolerant (NGT) subjects. The rs33977706 polymorphism (-820G > T) was associated with a lower body mass index (BMI) (p = 0.004). In a second study (n = 4625 NGT subjects), significant associations of both the rs33977706 and the rs243330 (-1656G > A) variants to obesity were found (p = 0.047 and p = 0.015) respectively. The rs33977706 affected both binding of a nuclear protein to and the transcriptional activity of the SOCS1 promoter, indicating a relationship between this polymorphism and gene regulation. CONCLUSIONS/INTERPRETATION: This study demonstrates that functional variations in the SOCS1 promoter may associate with alterations in BMI in the general white population.

Suppressor of cytokine signalling-3 expression inhibits cytokine-mediated destruction of primary mouse and rat pancreatic islets and delays allograft rejection.

AIMS/HYPOTHESIS: The pro-inflammatory cytokines IL-1 and IFNgamma are critical molecules in immune-mediated beta cell destruction leading to type 1 diabetes mellitus. Suppressor of cytokine signalling (SOCS)-3 inhibits the cytokine-mediated destruction of insulinoma-1 cells. Here we investigate the effect of SOCS3 in primary rodent beta cells and diabetic animal models. METHODS: Using mice with beta cell-specific Socs3 expression and a Socs3-encoding adenovirus construct, we characterised the protective effect of SOCS3 in mouse and rat islets subjected to cytokine stimulation. In transplantation studies of NOD mice and alloxan-treated mice the survival of Socs3 transgenic islets was investigated. RESULTS: Socs3 transgenic islets showed significant resistance to cytokine-induced apoptosis and impaired insulin release. Neither glucose-stimulated insulin release, insulin content or glucose oxidation were affected by SOCS3. Rat islet cultures transduced with Socs3-adenovirus displayed reduced cytokine-induced nitric oxide and apoptosis associated with inhibition of the IL-1-induced nuclear factor-kappaB and mitogen-activated protein kinase (MAPK) pathways. Transplanted Socs3 transgenic islets were not protected in diabetic NOD mice, but showed a prolonged graft survival when transplanted into diabetic allogenic BALB/c mice. CONCLUSIONS/INTERPRETATION: SOCS3 inhibits IL-1-induced signalling through the nuclear factor-kappaB and MAPK pathways and apoptosis induced by cytokines in primary beta cells. Moreover, Socs3 transgenic islets are protected in an allogenic transplantation model. SOCS3 may represent a target for pharmacological or genetic engineering in islet transplantation for treatment of type 1 diabetes mellitus.

Transcriptional profiling of type 1 diabetes genes on chromosome 21 in a rat beta-cell line and human pancreatic islets.

We recently finemapped a type 1 diabetes (T1D)-linked region on chromosome 21, indicating that one or more T1D-linked genes exist in this region with 33 annotated genes. In the current study, we have taken a novel approach using transcriptional profiling in predicting and prioritizing the most likely candidate genes influencing beta-cell function in this region. Two array-based approaches were used, a rat insulinoma cell line (INS-1alphabeta) overexpressing pancreatic duodenum homeobox 1 (pdx-1) and treated with interleukin 1beta (IL-1beta) as well as human pancreatic islets stimulated with a mixture of cytokines. Several candidate genes with likely functional significance in T1D were identified. Genes showing differential expression in the two approaches were highly similar, supporting the role of these specific gene products in cytokine-induced beta-cell damage. These were genes involved in cytokine signaling, oxidative phosphorylation, defense responses and apoptosis. The analyses, furthermore, revealed several transcription factor binding sites shared by the differentially expressed genes and by genes demonstrating highly similar expression profiles with these genes. Comparable findings in the rat beta-cell line and human islets support the validity of the methods used and support this as a valuable approach for gene mapping and identification of genes with potential functional significance in T1D, within a region of linkage.

Identification and characterization of secretagogin promoter activity.

Secretagogin is a newly identified calcium-binding protein selectively expressed in neuroendocrine tissue and pancreatic beta-cells. The function of secretagogin is unknown, but it has been suggested in beta-cells to influence calcium-influx, insulin secretion and proliferation, and has been observed downregulated in diabetes-prone BB rat islets exposed to cytokines. In the present study, we identified and characterized promoter activity of a human 1498 bp sequence upstream the transcription start site. The promoter sequence showed subtle but significant regulation by glucose within the normo-physiological range. Glucose also led to changes in expression of secretagogin protein in INS-1e cells, but not in primary cells from non-diabetes-prone Wistar Furth rats. No effects of cytokines neither on promoter activity nor protein expression were observed. The promoter region was furthermore screened by direct sequencing, and 11 polymorphisms were identified. Genotyping in a large homogenous Type 1 diabetes (T1D) family collection did not reveal association with T1D.

Anaesthesia-induced hyperglycaemia early in life is not predictive for development of diabetes in diabetes-prone BB rats.

Type 1 diabetes (T1D) is an autoimmune disease in genetically predisposed individuals characterised by selective destruction of the beta-cells. Development of diabetes is in the asymptomatic pre-diabetic period characterised by impaired first-phase insulin response and the first clinical symptom is elevated blood glucose (BG). It is still uncertain whether stress or incidental hyperglycaemia can be regarded as predictors for development of T1D or not, even when immunologic and genetic markers for T1D are considered. The aim of this study was to investigate if there was any relationship between elevated BG in 30-day-old anaesthetised pre-diabetic diabetes-prone Bio Breeding (BB-DP) rats and later development of diabetes. Rats anaesthetised by intraperitoneal (ip) injection for islet transplantation displayed significantly higher BG values (Delta1.27 mmol/l, p=8.27x10(-12)) compared to non-anaesthetised non-transplanted rats, indicating that ip injection and/or anaesthesia induce a higher BG level. Linear regression analysis of BG and time of onset of diabetes in transplanted and non-transplanted BB-DP rats revealed no correlation (R(2) at 0.0075 and 0.0324 and p-values at 0.56 and 0.23 respectively). We were not able to identify any association or correlation between the induced temporary hyperglycaemia in 30-day-old BB-DP rats and later development of diabetes.

Gene expression profiles during beta cell maturation and after IL-1beta exposure reveal important roles of Pdx-1 and Nkx6.1 for IL-1beta sensitivity.

AIM/HYPOTHESIS: Maturation of the beta cells in the islets of Langerhans is dependent upon sequential activation of different transcription factors such as Pdx-1 and Nkx6.1. This maturation is associated with an acquired sensitivity to cytokines and may eventually lead to type 1 diabetes. The aims of this study were to characterise changes in mRNA expression during beta cell maturation as well as after interleukin-1beta (IL-1beta) exposure. METHODS: Transcriptome analyses were performed on two phenotypes characterised as a glucagon-producing pre-beta-cell phenotype (NHI-glu), which matures to an IL-1beta-sensitive insulin-producing beta cell phenotype (NHI-ins). Beta cell lines over-expressing Pdx-1 or Nkx6.1, respectively, were used for functional characterisation of acquired IL-1beta sensitivity. RESULTS: During beta cell maturation 98 fully annotated mRNAs changed expression levels. Of these, 50 were also changed after 24 h of IL-1beta exposure. In addition, 522 and 197 fully annotated mRNAs, not affected by maturation, also changed expression levels following IL-1beta exposure of the beta cell and the pre-beta-cell phenotype, respectively. Beta cell maturation was associated with an increased expression of Nkx6.1, whereas both Pdx-1 and Nkx6.1 expression were decreased following IL-1beta exposure. Over-expression of Nkx6.1 or Pdx-1 in cell lines resulted in a significantly increased sensitivity to IL-1beta. CONCLUSIONS/INTERPRETATION: These results suggest that the final beta cell maturation accompanied by increased IL-1beta sensitivity is, in part, dependent upon the expression of genes regulated by Pdx-1 and Nkx6.1. Future classification of the genes regulated by these transcription factors and changed during beta cell maturation should elucidate their role in the acquired sensitivity to IL-1beta and may be helpful in identifying new targets for intervention/prevention strategies.

Suppressor of cytokine signalling (SOCS)-3 protects beta cells against IL-1beta-mediated toxicity through inhibition of multiple nuclear factor-kappaB-regulated proapoptotic pathways.

AIMS/HYPOTHESIS: The proinflammatory cytokine IL-1beta induces apoptosis in pancreatic beta cells via pathways dependent on nuclear factor-kappaB (NF-kappaB), mitogen-activated protein kinase, and protein kinase C. We recently showed suppressor of cytokine signalling (SOCS)-3 to be a natural negative feedback regulator of IL-1beta- and IFN-gamma-mediated signalling in rat islets and beta cell lines, preventing their deleterious effects. However, the mechanisms underlying SOCS-3 inhibition of IL-1beta signalling and prevention against apoptosis remain unknown. METHODS: The effect of SOCS-3 expression on the global gene-expression profile following IL-1beta exposure was microarray-analysed using a rat beta cell line (INS-1) with inducible SOCS-3 expression. Subsequently, functional analyses were performed. RESULTS: Eighty-two known genes and several expressed sequence tags (ESTs) changed expression level 2.5-fold or more in response to IL-1beta alone. Following 6 h of IL-1beta exposure, 23 transcripts were up-regulated. Of these, several, including all eight transcripts relating to immune/inflammatory response pathways, were suppressed by SOCS-3. Following 24 h of IL-1beta exposure, secondary response genes were detected, affecting metabolism, energy generation, protein synthesis and degradation, growth arrest, and apoptosis. The majority of these changes were prevented by SOCS-3 expression. Multiple IL-1beta-induced NF-kappaB-dependent proapoptotic early response genes were inhibited by SOCS-3 expression, suggesting that SOCS-3 inhibits NF-kappaB-mediated signalling. These observations were experimentally confirmed in functional analyses. CONCLUSIONS/INTERPRETATION: This study suggests that there is an unexpected cross-talk between the SOCS/IFN and the IL-1beta pathways of signalling in pancreatic beta cells, which could lead to a novel perspective of blocking two important proapoptotic pathways in pancreatic beta cells by influencing a single signalling molecule, namely SOCS-3.

Mutation analysis of suppressor of cytokine signalling 3, a candidate gene in Type 1 diabetes and insulin sensitivity.

AIMS/HYPOTHESIS: Beta cell loss in Type 1 and Type 2 diabetes mellitus may result from apoptosis and necrosis induced by inflammatory mediators. The suppressor of cytokine signalling (SOCS)-3 is a natural inhibitor of cytokine signalling and also influences insulin signalling. SOCS3 could therefore be a candidate gene in the development of Type 1 and Type 2 diabetes mellitus. METHODS: Mutation analysis of the SOCS3 gene was performed in 21 patients with Type 1 diabetes mellitus and in seven healthy subjects. An identified promoter variant was examined in (i) 250 families with Type 1 diabetic family members (1097 individuals); (ii) 212 glucose-tolerant first-degree relatives of Type 2 diabetic patients; and (iii) 370 population-based young, healthy subjects who were unrelated. RESULTS: Three mutations were identified in the promoter region, but none in the coding region or the 3'UTR. Two of the three mutations had allele frequencies below 1% whereas the C -920-->A substitution had a minor allele frequency of 8%. In the group of young healthy subjects the insulin sensitivity index was higher among homozygous carriers of the A-allele than among heterozygous and wild-type subjects ( p=0.027, uncorrected). The same trend was found in the group of first-degree relatives of Type 2 diabetic patients. No association or linkage was found to Type 1 diabetes mellitus. CONCLUSIONS/INTERPRETATION: Homozygosity for the A-allele of the C -920-->A promoter polymorphism of the SOCS3 gene may be associated with increased whole-body insulin sensitivity, but deserves further investigation.

Identification of a type 1 diabetes-associated CD4 promoter haplotype with high constitutive activity.

CD4 is a candidate gene in autoimmune diseases, including Type 1 diabetes mellitus (T1DM), because the CD4 receptor is crucial for appropriate antigen responses of CD4(+) T cells. We previously found linkage between a CD4-1188(TTTTC)(5-14) promoter polymorphism and T1DM. In the present study, we screened the human CD4 promoter for mutations and identified three frequent single nucleotide polymorphisms (SNPs): CD4-181C/G, CD4-521C/G and CD4-1050T/C. The SNPs are in strong linkage disequilibrium (LD) and association with the CD4-1188(TTTTC)(5-14) alleles, and we observed nine CD4 promoter haplotypes, of which four are frequent. We genotyped the SNPs in 253 Danish T1DM families (1129 individuals) and found evidence for linkage and association of a CD4 (A4(-1188)T(-1050)G(-521)C(-181)) haplotype to T1DM. In reporter studies, we show that (1) the T1DM-associated CD4 haplotype encodes high constitutive promoter activity and (2) the CD4-181G variant encodes higher stimulated promoter activity than the CD4-181C variant. This difference is in part neutralized in the frequently occurring CD4 promoter haplotypes by the more upstream genetic variants. Thus, we report functional impact of a novel CD4-181C/G SNP on stimulated CD4 promoter activity and the identification of a novel CD4 haplotype with high constitutive promoter activity that is linked and associated with T1DM.

Changes in expression of IL-1 beta influenced proteins in transplanted islets during development of diabetes in diabetes-prone BB rats.

AIMS/HYPOTHESIS: Type 1 diabetes mellitus is a multifactorial autoimmune disease characterised by selective destruction of beta cells in the islets of Langerhans. We have previously shown that IL-1 beta modulates beta cell function, causes beta cell death and induces expression changes in 82 out of 1815 protein spots detected by two-dimensional gel electrophoresis (2-DGE) in diabetes-prone bio-breeding (BB-DP) rat islets in vitro. The aim of this study was to describe the relevance of these proteins in the development of diabetes in vivo. METHODS: Syngeneic neonatal islets ( n=200) were transplanted under the kidney capsule of 30-day-old BB-DP and control rats, removed to different time points after transplantation or at the onset of diabetes, and metabolically labelled with S(35)-methionine for 2-DGE. The 82 proteins were re-localised and followed. In addition, transplants were examined for expression of IL-1 beta mRNA by in situ hybridisation. RESULTS: All 82 proteins could be re-localised in all syngeneic transplants from BB-DP and control rats. A total of 60 of the 82 proteins were changed during development of diabetes. Of the 82 proteins, 32 were changed in expression at the onset of diabetes compared to non-diabetic BB-DP rats, and 25 of these were changed as by IL-1 beta in vitro. Highest expression of IL-1 beta mRNA was found at the onset of diabetes. CONCLUSIONS/INTERPRETATION: IL-1 beta-induced protein expression changes in islets in vitro also occur in vivo and change in a complex pattern during the development of diabetes in the BB-DP rat. No single protein seems to be responsible for the development of diabetes, but rather the cumulative numbers of changes seem to interfere with the intracellular stability of the beta cell.

Protein expression changes in a cell system of beta-cell maturation reflect an acquired sensitivity to IL-1beta.

AIM/HYPOTHESIS: Type 1 diabetes mellitus (T1DM) is caused by specific destruction of the pancreatic beta cells in the islets of Langerhans. Increased sensitivity to cytokines, in particular to interleukin-1beta (IL-1beta) seems to be an acquired trait during beta-cell maturation. In response to cytokines both protective and deleterious mechanisms are induced in beta cells, and when the deleterious prevail, T1DM develops. The aims of this study were to identify perturbation in protein patterns (PiPP) associated with beta-cell maturation, and compare these changes to previous analyses of IL-1beta exposed rat islets. For this purpose, proteome analyses were carried out using a cell-line, which matures from a glucagon-producing pre-beta-cell phenotype (NHI-glu) to an insulin-producing beta-cell phenotype (NHI-ins). We have previously shown that this maturation is accompanied by acquired sensitivity to the toxic effects of IL-1beta. METHODS: 2D-gel electrophoresis was used to separate the proteins and MALDI-MS and database searches were performed to identify the proteins. RESULTS: During beta-cell maturation 135 protein spots out of 2239 detectable changed expression levels. Of these, 74 were down-regulated, 44 up-regulated, 16 were suppressed and 1 was expressed de novo. Using MALDI-MS, positive identification was obtained for 93 out of the 135 protein-spots revealing 97 different proteins. Of these, 22 proteins were in common with changes identified in previous proteome analysis of perturbation in protein pattern in IL-1beta exposed rat islets. Several of the proteins were present in more than one spot suggesting post-translational modification. CONCLUSION/INTERPRETATION: Several proteins and protein modifications were identified that could be critically involved in beta-cell maturation, insulin-gene expression and the acquired IL-1beta sensitivity.

The JNK binding domain of islet-brain 1 inhibits IL-1 induced JNK activity and apoptosis but not the transcription of key proapoptotic or protective genes in insulin-secreting cell lines.

The stress-activated protein kinase c-Jun NH2-terminal kinase (JNK) is a central signal for interleukin-1beta (IL-1beta)-induced apoptosis in insulin-producing beta-cells. The cell-permeable peptide inhibitor of JNK (JNKI1), that introduces the JNK binding domain (JBD) of the scaffold protein islet-brain 1 (IB1) inside cells, effectively prevents beta-cell death caused by this cytokine. To define the molecular targets of JNK involved in cytokine-induced beta-cell apoptosis we investigated whether JNKI1 or stable expression of JBD affected the expression of selected pro- and anti-apoptotic genes induced in rat (RIN-5AH-T2B) and mouse (betaTC3) insulinoma cells exposed to IL-1beta. Inhibition of JNK significantly reduced phosphorylation of the specific JNK substrate c-Jun (p<0.05), IL-1beta-induced apoptosis (p<0.001), and IL-1beta-mediated c-fos gene expression. However, neither JNKI1 nor JBD did influence IL-1beta-induced NO synthesis or iNOS expression or the transcription of the genes encoding mitochondrial manganese superoxide dismutase (MnSOD), catalase (CAT), glutathione peroxidase (GPx), glutathione-S-transferase rho (GSTrho), heat shock protein (HSP) 70, IL-1beta-converting enzyme (ICE), caspase-3, apoptosis-inducing factor (AIF), Bcl-2 or Bcl-xL. We suggest that the anti-apoptotic effect of JNK inhibition by JBD is independent of the transcription of major pro- and anti-apoptotic genes, but may be exerted at the translational or posttranslational level.

IL-1beta induced protein changes in diabetes prone BB rat islets of Langerhans identified by proteome analysis.

AIMS/HYPOTHESIS: Type I (insulin-dependent) diabetes mellitus is characterized by selective destruction of the insulin producing beta cells. Interleukin-1beta (IL-1beta) modulates the beta-cell function, protein synthesis, energy production and causes apoptosis. We have previously shown changes in the expression of 82 out of 1 815 protein spots detected by two dimensional gel electrophoresis in IL-1beta exposed diabetes prone Bio Breeding (BB-DP) rat islets of Langerhans in vitro. The aim of this study was to identify the proteins in these 82 spots by mass spectrometry and compare these changes with those seen in IL-1beta exposed Wistar Furth (WF) rat islets. METHODS: The 82 protein spots, that changed expression after IL-1beta exposure, were all re-identified on preparative gels of 200 000 neonatal WF rat islets, cut out and subjected to mass spectrometry for identification. RESULTS: Forty-five different proteins were identified from 51 spots and grouped according to function: (i) energy transduction and redox potentials; (ii) glycolytic and Krebs cycle enzymes; (iii) protein, DNA and RNA synthesis, chaperoning and protein folding; (iv) signal transduction, regulation, differentiation and apoptosis; (v) cellular defence; and (vi) other functions. Comparison of IL-1beta exposed BB-DP and WF islets showed common changes in 14 proteins and several proteins influencing similar pathways, suggesting that similar routes in the two strains lead to beta-cell destruction. CONCLUSION/INTERPRETATION: We demonstrate that proteome analysis is a powerful tool to identify proteins and pathways in BB-DP rat islets exposed to IL-1beta.

No evidence of a functionally significant polymorphism of the BCL2 gene in Danish, Finnish and Basque type 1 diabetes families.

Accumulating evidence has suggested a role for the anti-apoptotic protein BCL2 in the development of autoimmune diseases, including type 1 diabetes mellitus (T1DM). Recently, the first BCL2 polymorphism (Ala43Thr) with association to T1DM in a Japanese population was reported. The polymorphism was found significantly more frequent in control individuals (14.5%) than in T1DM patients (6.8%), and was furthermore found to be functionally relevant, promoting a increased sensitivity to apoptosis when overexpressed in an IL-7 dependent mouse pre-B cell line. To investigate the relevance of the polymorphism in Caucasians, we have genotyped nearly 1400 individuals comprising Danish, Finnish and Basque T1DM family materials, using a PCR-based RFLP assay. In contrast to what was observed in Japanese diabetic/control individuals, we find no evidence for association of the BCL2 Ala43Thr polymorphism to T1DM in Danish, Finnish and Basque Type 1 diabetes families.

Suppressor of cytokine signaling 3 (SOCS-3) protects beta -cells against interleukin-1beta - and interferon-gamma -mediated toxicity.

Suppressor of cytokine signaling 3 (SOCS-3) is a negative feedback regulator of IFN-gamma signaling, shown up-regulated in mouse bone marrow cells by the proinflammatory cytokines interleukin-1beta (IL-1beta), tumor necrosis factor-alpha (TNF-alpha), and IFN-gamma. IL-1beta and IFN-gamma alone, or potentiated by TNF-alpha, are cytotoxic to the insulin producing pancreatic beta-cells and beta-cell lines in vitro and suggested to contribute to the specific beta-cell destruction in Type-1 diabetes mellitus (T1DM). Using a doxycycline-inducible SOCS-3 expression system in the rat beta-cell line INS-1, we demonstrate that the toxic effect of both IL-1beta or IFN-gamma at concentrations that reduced the viability by 50% over 3 days, was fully preventable when SOCS-3 expression was turned on in the cells. At cytokine concentrations or combinations more toxic to the cells, SOCS-3 overexpression yielded a partial protection. Whereas SOCS-3-mediated inhibition of IFN-gamma signaling is described in other cell systems, SOCS-3 mediated inhibition of IL-1beta signaling has not previously been described. In addition we show that SOCS-3 prevention of IL-1beta-induced toxicity is accompanied by inhibited transcription of the inducible nitric oxide synthase (iNOS) by 80%, resulting in 60% decreased formation of the toxic nitric oxide (NO). Analysis of isolated native rat islets exposed to IL-1beta revealed a naturally occurring but delayed up-regulated SOCS-3 transcription. Influencing SOCS-3 expression thus represents an approach for affecting cytokine-induced signal transduction at a proximal step in the signal cascade, potentially useful in future therapies aimed at reducing the destructive potential of beta-cell cytotoxic cytokines in T1DM, as well as other cytokine-dependent diseases.

Strain-dependent difference in inducible nitric oxide synthesis (iNOS) expression in rat pancreatic islets correlates with interferon regulating factor 1 (IRF-1) and heat shock protein 70 (HSP70) expression.

UNLABELLED: Nitric oxide (NO) may be a necessary but not sufficient mediator of cytokine-mediated, selective beta-cell destruction. Previously, we have described a difference in NO-dependent IL-1beta sensitivity in vivo and in vitro of pancreatic islets from two rat strains, Brown Norway (BN) and Wistar Kyoto (WK), the latter being the more sensitive strain. Here we investigated whether strain-dependent, differential islet iNOS expression was associated with differences in islet expression of the IL-1 receptor type 1(IL-1RI) or interferon regulating factor 1 (IRF-1), and/or caused differences in HSP70 expression, a marker of cell defence against oxidative stress. METHODS: isolated islets from both rat strains were exposed to increasing concentrations of IL-1beta (0-150 pg/ml) for 24 hours or for varying culture periods (4-48 hours) to 15 pg/ml of IL-1beta. MEASUREMENTS: accumulated insulin and nitrite release into incubation medium, and islet mRNA and protein expression of iNOS, IL-1RI, IRF-1 and HSP70 by semi-quantitative RT-PCR and Western blotting. RESULTS: Higher insulin and lower nitrite release into the incubation medium were seen for BN compared to WK rats islets in both dose- and time-response experiments. IRF-1 expression preceded iNOS expression and was more pronounced in WK than in BN islets. No strain differences were observed for islet expression of IL-1RI. A strain-dependent HSP70 expression in response to IL-1beta with the highest levels in WK rat islets following iNOS expression was seen. CONCLUSION: There was a strain-dependent difference in iNOS expression which was associated with IRF-1 and HSP70 expression.