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Introduction: Proinflammatory cytokines are implicated in pancreatic ß cell failure in type 1 and type 2 diabetes and are known to stimulate alternative RNA splicing and the expression of nonsense-mediated RNA decay (NMD) components. Here, we investigate whether cytokines regulate NMD activity and identify transcript isoforms targeted in ß cells. Methods: A luciferase-based NMD reporter transiently expressed in rat INS1(832/13), human-derived EndoC-ßH3, or dispersed human islet cells is used to examine the effect of proinflammatory cytokines (Cyt) on NMD activity. The gain- or loss-of-function of two key NMD components, UPF3B and UPF2, is used to reveal the effect of cytokines on cell viability and function. RNA-sequencing and siRNA-mediated silencing are deployed using standard techniques. Results: Cyt attenuate NMD activity in insulin-producing cell lines and primary human ß cells. These effects are found to involve ER stress and are associated with the downregulation of UPF3B. Increases or decreases in NMD activity achieved by UPF3B overexpression (OE) or UPF2 silencing raise or lower Cyt-induced cell death, respectively, in EndoC-ßH3 cells and are associated with decreased or increased insulin content, respectively. No effects of these manipulations are observed on glucose-stimulated insulin secretion. Transcriptomic analysis reveals that Cyt increases alternative splicing (AS)-induced exon skipping in the transcript isoforms, and this is potentiated by UPF2 silencing. Gene enrichment analysis identifies transcripts regulated by UPF2 silencing whose proteins are localized and/or functional in the extracellular matrix (ECM), including the serine protease inhibitor SERPINA1/α-1-antitrypsin, whose silencing sensitizes ß-cells to Cyt cytotoxicity. Cytokines suppress NMD activity via UPR signaling, potentially serving as a protective response against Cyt-induced NMD component expression. Conclusion: Our findings highlight the central importance of RNA turnover in ß cell responses to inflammatory stress. [ABSTRACT FROM AUTHOR]

Chronic low grade inflammation is closely linked to obesity-associated insulin resistance. To examine how administration of the anti-inflammatory compound indomethacin, a general cyclooxygenase inhibitor, affected obesity development and insulin sensitivity, we fed obesity-prone male C57BL/6J mice a high fat/high sucrose (HF/HS) diet or a regular diet supplemented or not with indomethacin (±INDO) for 7 weeks. Development of obesity, insulin resistance, and glucose intolerance was monitored, and the effect of indomethacin on glucose-stimulated insulin secretion (GSIS) was measured in vivo and in vitro using MIN6 β-cells. We found that supplementation with indomethacin prevented HF/HS-induced obesity and diet-induced changes in systemic insulin sensitivity. Thus, HF/HS+INDO-fed mice remained insulin-sensitive. However, mice fed HF/HS+INDO exhibited pronounced glucose intolerance. Hepatic glucose output was significantly increased. Indomethacin had no effect on adipose tissue mass, glucose tolerance, or GSIS when included in a regular diet. Indomethacin administration to obese mice did not reduce adipose tissue mass, and the compensatory increase in GSIS observed in obese mice was not affected by treatment with indomethacin. We demonstrate that indomethacin did not inhibit GSIS per se, but activation of GPR40 in the presence of indomethacin inhibited glucose-dependent insulin secretion in MIN6 cells. We conclude that constitutive high hepatic glucose output combined with impaired GSIS in response to activation of GPR40-dependent signaling in the HF/HS+INDO-fed mice contributed to the impaired glucose clearance during a glucose challenge and that the resulting lower levels of plasma insulin prevented the obesogenic action of the HF/HS diet.

BackgroundInnate immunity contributes to the pathogenesis of autoimmune diseases, such as type 1 diabetes, but until now no randomised, controlled trials of blockade of the key innate immune mediator interleukin-1 have been done. We aimed to assess whether canakinumab, a human monoclonal anti-interleukin-1 antibody, or anakinra, a human interleukin-1 receptor antagonist, improved β-cell function in recent-onset type 1 diabetes.MethodsWe did two randomised, placebo-controlled trials in two groups of patients with recent-onset type 1 diabetes and mixed-meal-tolerance-test-stimulated C peptide of at least 0·2 nM. Patients in the canakinumab trial were aged 6-45 years and those in the anakinra trial were aged 18-35 years. Patients in the canakinumab trial were enrolled at 12 sites in the USA and Canada and those in the anakinra trial were enrolled at 14 sites across Europe. Participants were randomly assigned by computer-generated blocked randomisation to subcutaneous injection of either 2 mg/kg (maximum 300 mg) canakinumab or placebo monthly for 12 months or 100 mg anakinra or placebo daily for 9 months. Participants and carers were masked to treatment assignment. The primary endpoint was baseline-adjusted 2-h area under curve C-peptide response to the mixed meal tolerance test at 12 months (canakinumab trial) and 9 months (anakinra trial). Analyses were by intention to treat. These studies are registered with ClinicalTrials.gov, numbers NCT00947427 and NCT00711503, and EudraCT number 2007-007146-34.FindingsPatients were enrolled in the canakinumab trial between Nov 12, 2010, and April 11, 2011, and in the anakinra trial between Jan 26, 2009, and May 25, 2011. 69 patients were randomly assigned to canakinumab (n=47) or placebo (n=22) monthly for 12 months and 69 were randomly assigned to anakinra (n=35) or placebo (n=34) daily for 9 months. No interim analyses were done. 45 canakinumab-treated and 21 placebo-treated patients in the canakinumab trial and 25 anakinra-treated and 26 placebo-treated patients in the anakinra trial were included in the primary analyses. The difference in C peptide area under curve between the canakinumab and placebo groups at 12 months was 0·01 nmol/L (95% CI -0·11 to 0·14; p=0·86), and between the anakinra and the placebo groups at 9 months was 0·02 nmol/L (-0·09 to 0·15; p=0·71). The number and severity of adverse events did not differ between groups in the canakinumab trial. In the anakinra trial, patients in the anakinra group had significantly higher grades of adverse events than the placebo group (p=0·018), which was mainly because of a higher number of injection site reactions in the anakinra group.InterpretationCanakinumab and anakinra were safe but were not effective as single immunomodulatory drugs in recent-onset type 1 diabetes. Interleukin-1 blockade might be more effective in combination with treatments that target adaptive immunity in organ-specific autoimmune disorders.FundingNational Institutes of Health and Juvenile Diabetes Research Foundation.

OBJECTIVE: To examine whether iron intake and genetically determined iron overload interact in predisposing to the development of childhood islet autoimmunity (IA) and type 1 diabetes (T1D). RESEARCH DESIGN AND METHODS: In The Environmental Determinants of Diabetes in the Young (TEDDY) study, 7,770 genetically high-risk children were followed from birth until the development of IA and progression to T1D. Exposures included energy-adjusted iron intake in the first 3 years of life and a genetic risk score (GRS) for increased circulating iron. RESULTS: We found a U-shaped association between iron intake and risk of GAD antibody as the first autoantibody. In children with GRS ≥2 iron risk alleles, high iron intake was associated with an increased risk of IA, with insulin as first autoantibody (adjusted hazard ratio 1.71 [95% CI 1.14; 2.58]) compared with moderate iron intake. CONCLUSIONS: Iron intake may alter the risk of IA in children with high-risk HLA haplogenotypes. [ABSTRACT FROM AUTHOR]

Pancreatic [beta] cell mass and function increase in conditions of enhanced insulin demand such as obesity. Failure to adapt leads to diabetes. The molecular mechanisms controlling this adaptive process are unclear. Fas is a death receptor involved in [beta] cell apoptosis or proliferation, depending on the activity of the caspase-8 inhibitor FLIP. Here we show that the Fas pathway also regulates [beta] cell secretory function. We observed impaired glucose tolerance in Fas-deficient mice due to a delayed and decreased insulin secretory pattern. Expression of PDX-1, a [beta] cell-specific transcription factor regulating insulin gene expression and mitochondrial metabolism, was decreased in Fasdeficient [beta] cells. As a consequence, insulin and ATP production were severely reduced and only partly compensated for by increased [beta] cell mass. Up-regulation of FLIP enhanced NF-[kappa]B activity via NF-[kappa]B-inducing kinase and RelB. This led to increased PDX-1 and insulin production independent of changes in cell turnover. The results support a previously undescribed role for the Fas pathway in regulating insulin production and release. diabetes | IL-1 | insulin