Repositioning the Early Pathology of Type 1 Diabetes to the Extraislet Vasculature

Type 1 diabetes (T1D) is a prototypic T cell-mediated autoimmune disease. Because the islets of Langerhans are insulated from blood vessels by a double basement membrane and lack detectable lymphatic drainage, interactions between endocrine and circulating T cells are not permitted. Thus, we hypothesized that initiation and progression of anti-islet immunity required islet neolymphangiogenesis to allow T cell access to the islet. Combining microscopy and single cell approaches, the timing of this phenomenon in mice was situated between 5 and 8 wk of age when activated anti-insulin CD4 T cells became detectable in peripheral blood while peri-islet pathology developed. This "peri-insulitis," dominated by CD4 T cells, respected the islet basement membrane and was limited on the outside by lymphatic endothelial cells that gave it the attributes of a tertiary lymphoid structure. As in most tissues, lymphangiogenesis seemed to be secondary to local segmental endothelial inflammation at the collecting postcapillary venule. In addition to classic markers of inflammation such as CD29, V-CAM, and NOS, MHC class II molecules were expressed by nonhematopoietic cells in the same location both in mouse and human islets. This CD45- MHC class II+ cell population was capable of spontaneously presenting islet Ags to CD4 T cells. Altogether, these observations favor an alternative model for the initiation of T1D, outside of the islet, in which a vascular-associated cell appears to be an important MHC class II-expressing and -presenting cell.

Deletion of the clock gene Bmal2 leads to alterations in hypothalamic clocks, circadian regulation of feeding and energy balance

BMAL2 (ARNTL2) is a paralog of BMAL1 that can form heterodimers with the other circadian factors CLOCK and NPAS2 to activate transcription of clock and clock-controlled genes. To assess a possible role of Bmal2 in the circadian regulation of metabolism, we investigated daily variations of energy metabolism, feeding behavior, and locomotor behavior, as well as ability to anticipate restricted food access in male mice knock-out for Bmal2 (B2KO). While their amount of food intake and locomotor activity were normal compared to wild-type mice, B2KO mice displayed increased adiposity (1.5-fold higher) and fasted hyperinsulinemia (4-fold higher) and tended to have lower energy expenditure at night. Impairment of the master clock in the suprachiasmatic nuclei was evidenced by the shorter free-running period (-14 min/cycle) of B2KO mice compared to wild-type controls, and by a loss of daily rhythmicity in expression of intracellular metabolic regulators (e.g., Lipoprotein lipase and Uncoupling protein 2). The circadian window of eating was longer in B2KO mice. The circadian patterns of food intake and meal numbers were bimodal in control mice, but not in B2KO mice. In response to restricted feeding, food-anticipatory activity was almost prevented in B2KO mice, suggesting altered food clock that controls anticipation of food availability. In the mediobasal hypothalamus of B2KO mice, expression of genes coding orexigenic neuropetides (including Neuropeptide y and Agouti-Related Peptide) was down-regulated, while Lipoprotein lipase expression lost its rhythmicity. Together, these data highlight that BMAL2 has major impacts on brain regulation of metabolic rhythms, sleep-wake cycle and food anticipation.Significance statement Circadian misalignment is now recognized as a condition triggering metabolic disorders. Using a combination of behavioral, physiological and molecular approaches in the hypothalamus, we report here that ablation of Bmal2 impairs function of hypothalamic clocks, modifies temporal distribution of food intake and energy expenditure, and leads to increased adiposity. These findings highlighting that close interactions between circadian rhythmicity and metabolic pathways are dysfunctional in the absence of Bmal2, and reveal that the transcription factor BMAL2 plays a role in the brain regulation of circadian clocks and energy metabolism. Accordingly, this work provides new evidence that altered circadian rhythmicity can be involved in the etiology of metabolic diseases.

First-in-human, double-blind, randomized phase 1b study of peptide immunotherapy IMCY-0098 in new-onset type 1 diabetes

BACKGROUND

Type 1 diabetes (T1D) is a CD4⁺ T cell-driven autoimmune disease characterized by the destruction of insulin-producing pancreatic β-cells by CD8⁺ T cells. Achieving glycemic targets in T1D remains challenging in clinical practice; new treatments aim to halt autoimmunity and prolong β-cell survival. IMCY-0098 is a peptide derived from human proinsulin that contains a thiol-disulfide oxidoreductase motif at the N-terminus and was developed to halt disease progression by promoting the specific elimination of pathogenic T cells.

METHODS

This first-in-human, 24-week, double-blind phase 1b study evaluated the safety of three dosages of IMCY-0098 in adults diagnosed with T1D < 6 months before study start. Forty-one participants were randomized to receive four bi-weekly injections of placebo or increasing doses of IMCY-0098 (dose groups A/B/C received 50/150/450 μg for priming followed by three further administrations of 25/75/225 μg, respectively). Multiple T1D-related clinical parameters were also assessed to monitor disease progression and inform future development. Long-term follow-up to 48 weeks was also conducted in a subset of patients.

RESULTS

Treatment with IMCY-0098 was well tolerated with no systemic reactions; a total of 315 adverse events (AEs) were reported in 40 patients (97.6%) and were related to study treatment in 29 patients (68.3%). AEs were generally mild; no AE led to discontinuation of the study or death. No significant decline in C-peptide was noted from baseline to Week 24 for dose A, B, C, or placebo (mean change - 0.108, - 0.041, - 0.040, and - 0.012, respectively), suggesting no disease progression.

CONCLUSIONS

Promising safety profile and preliminary clinical response data support the design of a phase 2 study of IMCY-0098 in patients with recent-onset T1D.

TRIAL REGISTRATION

IMCY-T1D-001: ClinicalTrials.gov NCT03272269; EudraCT: 2016-003514-27; and IMCY-T1D-002: ClinicalTrials.gov NCT04190693; EudraCT: 2018-003728-35.

High Prevalence of NASH and Advanced Fibrosis in Type 2 Diabetes: A Prospective Study of 330 Outpatients Undergoing Liver Biopsies for Elevated ALT, Using a Low Threshold

OBJECTIVE

Most people with type 2 diabetes (T2DM) and nonalcoholic steatohepatitis (NASH) or advanced fibrosis (AF) remain undiagnosed, resulting in missed opportunities for early intervention. This multicenter, prospective study assessed the yield of using routinely available data to identify these patients.

RESEARCH DESIGN AND METHODS

A total of 713 outpatients with T2DM, screened in four diabetology clinics for nonalcoholic fatty liver disease according to American Diabetes Association criteria, were referred to hepatologists for further work-up (Fibrosis-4 and vibration-controlled transient elastography [VCTE]). A liver biopsy was proposed when ALT levels were persistently >20 IU/L in female patients or >30 IU/L in male patients, in the absence of other liver disease.

RESULTS

Liver biopsies were performed in 360 patients and considered adequate for reading after central review for 330 specimens (median patient age, 59 years; male patients, 63%; median BMI and HbA1C values, 32 and 7.5%, respectively). Prevalence of NASH, AF, and cirrhosis were 58%, 38%, and 10%, respectively. Liver lesions were independently associated with the components of metabolic syndrome but not with the micro- and macrovascular complications of T2DM. Models based on routinely available data with or without VCTE had good accuracy to predict AF (respectively: area under the receiver operating characteristic curve [AUROC], 0.84 and 0.77; and correctly classified 59% and 45%) and NASH (respectively: AUROC, 0.82 and 0.81; 44% and 42%).

CONCLUSIONS

Despite the use of a low ALT threshold, prevalence of NASH (58%) or AF (38%) was high. Routinely available data had a high yield in identifying patients with T2DM with AF and/or NASH requiring further liver assessment.

Icos gene disruption in non-obese diabetic mice elicits myositis associated with anti-troponin T3 autoantibodies

AIMS

Idiopathic inflammatory myopathies (IIM) are autoimmune inflammatory disorders leading to skeletal muscle weakness and disability. The pathophysiology of IIM is poorly understood due to the scarcity of animal disease models. Genetic deletion of Icos or Icosl (inducible T cell co-stimulator/ligand) in non-obese diabetic (NOD) mice leads to muscle disease. Our aim was to characterise Icos^-/- NOD myopathy and to search for novel autoantibodies (aAbs) in this model.

METHODS

Diabetes, weight, myopathy incidence/clinical score and grip strength were assessed over time. Locomotor activity was analysed with the Catwalk XT gait analysis system. Muscle histology was evaluated in haematoxylin/eosin and Sirius red-stained sections, and immune infiltrates were characterised by immunofluorescence and flow cytometry. 2D gel electrophoresis of muscle protein extracts and mass spectrometry were used to identify novel aAbs. NOD mice were immunised with troponin T3 (TNNT3) in incomplete Freund's adjuvant (IFA) and R848. An addressable laser bead immunoassay (ALBIA) was developed to measure aAb IgG serum levels.

RESULTS

Icos^-/- NOD mice did not exhibit diabetes but developed spontaneous progressive myositis with decreased muscle strength and altered locomotor activity. Muscle from these mice exhibited myofibre necrosis, myophagocytosis, central nuclei, fibrosis and perimysial and endomysial cell infiltrates with macrophages and T cells. We identified anti-TNNT3 aAbs in diseased mice. Immunisation of NOD mice with murine TNNT3 protein led to myositis development, supporting its pathophysiological role.

CONCLUSIONS

These data show that Icos^-/- NOD mice represent a spontaneous model of myositis and the discovery of anti-TNNT3 aAb suggests a new autoantigen in this model.

Insulin allergy: a diagnostic and therapeutic strategy based on a retrospective cohort and a case-control study

AIMS/HYPOTHESIS

Insulin allergy is a rare but significant clinical challenge. We aimed to develop a management workflow by (1) validating clinical criteria to guide diagnosis, based on a retrospective cohort, and (2) assessing the diagnostic performance of confirmatory tests, based on a case-control study.

METHODS

In the retrospective cohort, patients with suspected insulin allergy were classified into three likelihood categories according to the presence of all (likely insulin allergy; 26/52, 50%), some (possible insulin allergy; 9/52, 17%) or none (unlikely insulin allergy; 17/52, 33%) of four clinical criteria: (1) recurrent local or systemic immediate or delayed hypersensitivity reactions; (2) reactions elicited by each injection; (3) reactions centred on the injection sites; and (4) reactions observed by the investigator (i.e. in response to an insulin challenge test). All underwent intradermal reaction (IDR) tests. A subsequent case-control study assessed the diagnostic performance of IDR, skin prick and serum anti-insulin IgE tests in ten clinically diagnosed insulin allergy patients, 24 insulin-treated non-allergic patients and 21 insulin-naive patients.

RESULTS

In the retrospective cohort, an IDR test validated the clinical diagnosis in 24/26 (92%), 3/9 (33%) and 0/14 (0%) likely, possible and unlikely insulin allergy patients, respectively. In the case-control study, an IDR test was 80% sensitive and 100% specific and identified the index insulin(s). The skin prick and IgE tests had a marginal diagnostic value. Patients with IDR-confirmed insulin allergy were treated using a stepwise strategy.

CONCLUSIONS/INTERPRETATION

Subject to validation, clinical likelihood criteria can effectively guide diabetologists towards an insulin allergy diagnosis before undertaking allergology tests. An IDR test shows the best diagnostic performance. A progressive management strategy can subsequently be implemented. Continuous subcutaneous insulin infusion is ultimately required in most patients.

CLINICALTRIALS

gov: NCT01407640.

Preclinical Models to Evaluate the Human Response to Autoantigen and Antigen-Specific Immunotherapy in Human Type 1 Diabetes

Type 1 Diabetes (T1D) is an autoimmune disease that results from the destruction of pancreatic islet β-cells by auto-reactive T cells. The clinical management of T1D faces the lack of fully predictive biomarkers in its preclinical stage and of antigen-specific therapies to induce or re-induce immune tolerance to β-cell autoantigens and prevent its development. From a therapeutic standpoint, preclinical models of T1D have fallen short of directly translating into humans. To circumvent this limitation, preclinical models are being optimized to allow defining autoantigen epitopes that are presented to T cells and directly apply to the human. In this review, we propose to make a point on the latest available models such as humanized immunodeficient NOD mice models and HLA and autoantigen transgenic mice and their application in the context of T1D.

Environmental Triggering of Type 1 Diabetes Autoimmunity

Type 1 diabetes (T1D) is a chronic autoimmune disease in which pancreatic islet β cells are destroyed by immune cells, ultimately leading to overt diabetes. The progressive increase in T1D incidence over the years points to the role of environmental factors in triggering or accelerating the disease process which develops on a highly multigenic susceptibility background. Evidence that environmental factors induce T1D has mostly been obtained in animal models. In the human, associations between viruses, dietary habits or changes in the microbiota and the development of islet cell autoantibodies or overt diabetes have been reported. So far, prediction of T1D development is mostly based on autoantibody detection. Future work should focus on identifying a causality between the different environmental risk factors and T1D development to improve prediction scores. This should allow developing preventive strategies to limit the T1D burden in the future.

Immunoregulated insulitis and slow-progressing type 1 diabetes after duodenopancreatectomy

AIMS/HYPOTHESIS

We report the case of a woman who underwent a partial pancreatectomy for a serous cystadenoma when aged 56 years. She had been diagnosed with diabetes 6 years before and had Hashimoto's thyroiditis. Despite positive anti-GAD autoantibodies (GADA) and previous surgery, she was transiently weaned off long-acting insulin. Blood glucose levels remained well controlled with low-dose long-acting insulin. Insulin needs eventually increased 8 years after surgery, in conjunction with anti-zinc transporter 8 (ZnT8) seroconversion and decreasing residual C-peptide. We hypothesised that the surgical pancreas specimens and blood autoimmune T cell responses may provide correlates of this indolent clinical course.

METHODS

Beta and alpha cell area and insulitis were quantified on pancreas head tissue sections obtained at surgery. Blood T cell responses against beta cell antigens were analysed by enzyme-linked immunospot.

RESULTS

Pancreas sections displayed reduced beta cell and normal alpha cell area (0.27% and 0.85% of section area, respectively). High-grade insulitis was observed, mostly in insulin-containing islets, with a peri-insulitis pattern enriched in T cells positive for regulatory forkhead box protein 3 (FOXP3). In vitro challenge with beta cell antigens of circulating T cells collected 4 and 9 years after surgery revealed dominant and persistent IL-10 responses; IFN-γ responses increasing at 9 years, after anti-ZnT8 seroconversion, was observed.

CONCLUSIONS/INTERPRETATION

Despite persistent GADA and the histopathological finding of insulitis and decreased beta cell area 6 years after diabetes diagnosis, glycaemic control was maintained with low-dose insulin up to 8 years after surgery. Regulated T cell responses towards beta cell antigens and FOXP3-positive peri-insulitis suggest spontaneous long-term regulation of islet autoimmunity after substantial beta cell loss, and eventual autoimmune progression upon anti-ZnT8 seroconversion.

A Humanized Mouse Strain That Develops Spontaneously Immune-Mediated Diabetes

To circumvent the limitations of available preclinical models for the study of type 1 diabetes (T1D), we developed a new humanized model, the YES-RIP-hB7.1 mouse. This mouse is deficient of murine major histocompatibility complex class I and class II, the murine insulin genes, and expresses as transgenes the HLA-A*02:01 allele, the diabetes high-susceptibility HLA-DQ8A and B alleles, the human insulin gene, and the human co-stimulatory molecule B7.1 in insulin-secreting cells. It develops spontaneous T1D along with CD4⁺ and CD8⁺ T-cell responses to human preproinsulin epitopes. Most of the responses identified in these mice were validated in T1D patients. This model is amenable to characterization of hPPI-specific epitopes involved in T1D and to the identification of factors that may trigger autoimmune response to insulin-secreting cells in human T1D. It will allow evaluating peptide-based immunotherapy that may directly apply to T1D in human and complete preclinical model availability to address the issue of clinical heterogeneity of human disease.

MAIT cell alterations in adults with recent-onset and long-term type 1 diabetes

AIMS/HYPOTHESIS

Mucosal-associated invariant T (MAIT) cells are innate-like T lymphocytes expressing an αβ T cell antigen receptor that recognises the MHC-related 1 molecule. MAIT cells are altered in children at risk for and with type 1 diabetes, and mouse model studies have shown MAIT cell involvement in type 1 diabetes development. Since several studies support heterogeneity in type 1 diabetes physiopathology according to the age of individuals, we investigated whether MAIT cells were altered in adults with type 1 diabetes.

METHODS

MAIT cell frequency, phenotype and function were analysed by flow cytometry, using fresh peripheral blood from 21 adults with recent-onset type 1 diabetes (2-14 days after disease onset) and 47 adults with long-term disease (>2 years after diagnosis) compared with 55 healthy blood donors. We also separately analysed 17 women with long-term type 1 diabetes and an associated autoimmune disease, compared with 30 healthy women and 27 women with long-term type 1 diabetes.

RESULTS

MAIT cells from adults with recent-onset type 1 diabetes, compared with healthy adult donors, harboured a strongly activated phenotype indicated by an elevated CD25⁺ MAIT cell frequency. In adults with long-term type 1 diabetes, MAIT cells displayed an activated and exhausted phenotype characterised by high CD25 and programmed cell death 1 (PD1) expression and a decreased production of proinflammatory cytokines, IL-2, IFN-γ and TNF-α. Even though MAIT cells from these patients showed upregulated IL-17 and IL-4 production, the polyfunctionality of MAIT cells was decreased (median 4.8 vs 13.14% of MAIT cells, p < 0.001) and the frequency of MAIT cells producing none of the effector molecules analysed increased (median 34.40 vs 19.30% of MAIT cells, p < 0.01). Several MAIT cell variables correlated with HbA_1c level and more particularly in patients with recent-onset type 1 diabetes. In women with long-term type 1 diabetes, MAIT cell alterations were more pronounced in those with an associated autoimmune disease than in those without another autoimmune disease. In women with long-term type 1 diabetes and an associated autoimmune disease, there was an increase in CD69 expression and a decrease in the survival B-cell lymphoma 2 (BCL-2) (p < 0.05) and CD127 (IL-7R) (p < 0.01) marker expression compared with women without a concomitant autoimmune disorder. Concerning effector molecules, TNF-α and granzyme B production by MAIT cells was decreased.

CONCLUSIONS/INTERPRETATION

Alterations in MAIT cell frequency, phenotype and function were more pronounced in adults with long-term type 1 diabetes compared with adults with recent-onset type 1 diabetes. There were several correlations between MAIT cell variables and clinical characteristics. Moreover, the presence of another autoimmune disease in women with long-term type 1 diabetes further exacerbated MAIT cell alterations. Our results suggest that MAIT cell alterations in adults with type 1 diabetes could be associated with two aspects of the disease: impaired glucose homeostasis; and autoimmunity.

Prospective external validation of a new non-invasive test for the diagnosis of non-alcoholic steatohepatitis in patients with type 2 diabetes

BACKGROUND

One of the unmet needs in patients with type 2 diabetes mellitus (T2DM) is the prediction of non-alcoholic liver disease by non-invasive blood tests, for each of the three main histological features, fibrosis, non-alcoholic steatohepatitis (NASH) and steatosis.

AIMS

To validate externally the performances of a recent panel, Nash-FibroTest, for the assessment of the severity of fibrosis stages, NASH grades and steatosis grades.

METHODS

We prospectively analysed 272 patients with T2DM. Standard definitions of stages and grades were used, and analyses were centralised and blinded. The performances of the FibroTest, NashTest-2 and SteatoTest-2 were assessed using the Obuchowski measure (OM), the main outcome recommended as a summary measure of accuracy includeing all pairwise stages and grades comparisons, which is not provided par the extensively used binary area under the ROC curve.

RESULTS

The diagnostic performance of each component of the panel was significant. OM (SE; significance) of the FibroTest, the NashTest-2 and the SteatoTest-2 was 0.862 (0.012; P < 0.001), 0.827 (0.015; P < 0.001) and 0.794 (0.020; P < 0.01), respectively. For ballooning and lobular inflammation, OM was 0.794 (0.021; P < 0.001) and 0.821 (0.017; P < 0.001), respectively. In a post hoc analysis the FibroTest outperformed VCTE by 4.1% (2.5-6.5; P < 0.001) for reliability, with a non-significant difference for OM for fibrosis staging, 0.859 (0.012) for FibroTest vs 0.870 (0.009) for VCTE.

CONCLUSIONS

From a single blood sample, the panel provides non-invasive diagnosis of the stages of fibrosis, and the grades of NASH and steatosis in patients with T2DM.

TRIAL REGISTRATION NUMBER

NCT03634098.

Impact of personalized text messages from pharmacists on medication adherence in type 2 diabetes in France: A real-world, randomized, comparative study

OBJECTIVE

A real-world, randomized study assessing the impact of a new, personalized, pharmacist-led text messaging service for managing type 2 diabetes (T2D).

METHODS

Messages were tailored to patient's needs based on their disease management habits, propensity for reactance, and physical activity levels at baseline. Treatment adherence (assed using the Morisky Medication Adherence Scale, MMAS-8, questionnaire), clinical factors (body mass index and physical activity) and biological markers for T2D were compared between patients who received a text message daily for 3 months in addition to standard care (SMS group) and those who received standard care alone (control group).

RESULTS

114 pharmacies recruited 499 patients. Greater increases in global MMAS-8 scores were observed after 3 months for the SMS group than for the control group, however, this improvement was not sustained after the text messages stopped. Body mass index was found to improve with the text messaging service.

CONCLUSION

This study indicated that personalized text messages provided by community pharmacists can have an impact on adherence levels among T2D patients.

PRACTICE IMPLICATIONS

Pharmacy-led innovations, such as text messaging services, could be used to accompany patients in their treatment and to improve patient understanding of their illness between healthcare appointments.

[Reforming Biosciences and Health Research: Part I, Funding]

The COVID-19 pandemic occurred in the context of a dramatic decline in support for biological and health research in France. An analysis of resources allocated to this sector shows that the credits in 2020 correspond to only 17.2 % of the total credits allocated to research, the lowest ratio inat least 15 years. Another weakness in the system of support for hospital research is the way funds from the health insurance system are allocated. To bring it into line with international best practices, the task of allocating these funds should be entrusted to a "Hospital Research Orientation Council", which should also be involved in the implementation of national research programming. Another article deals with the organization of research. Recommendations are also made to improve the functioning of the research system at the local level, particularly in university hospitals, and at the national level.

Outcome of SARS-CoV-2 infection is linked to MAIT cell activation and cytotoxicity

Immune system dysfunction is paramount in coronavirus disease 2019 (COVID-19) severity and fatality rate. Mucosal-associated invariant T (MAIT) cells are innate-like T cells involved in mucosal immunity and protection against viral infections. Here, we studied the immune cell landscape, with emphasis on MAIT cells, in cohorts totaling 208 patients with various stages of disease. MAIT cell frequency is strongly reduced in blood. They display a strong activated and cytotoxic phenotype that is more pronounced in lungs. Blood MAIT cell alterations positively correlate with the activation of other innate cells, proinflammatory cytokines, notably interleukin (IL)-18, and with the severity and mortality of severe acute respiratory syndrome coronavirus 2 infection. We also identified a monocyte/macrophage interferon (IFN)-α-IL-18 cytokine shift and the ability of infected macrophages to induce the cytotoxicity of MAIT cells in an MR1-dependent manner. Together, our results suggest that altered MAIT cell functions due to IFN-α-IL-18 imbalance contribute to disease severity, and their therapeutic manipulation may prevent deleterious inflammation in COVID-19 aggravation.

Targeting the NADPH Oxidase-4 and Liver X Receptor Pathway Preserves Schwann Cell Integrity in Diabetic Mice

Diabetes triggers peripheral nerve alterations at a structural and functional level, collectively referred to as diabetic peripheral neuropathy (DPN). This work highlights the role of the liver X receptor (LXR) signaling pathway and the cross talk with the reactive oxygen species (ROS)-producing enzyme NADPH oxidase-4 (Nox4) in the pathogenesis of DPN. Using type 1 diabetic (T1DM) mouse models together with cultured Schwann cells (SCs) and skin biopsies from patients with type 2 diabetes (T2DM), we revealed the implication of LXR and Nox4 in the pathophysiology of DPN. T1DM animals exhibit neurophysiological defects and sensorimotor abnormalities paralleled by defective peripheral myelin gene expression. These alterations were concomitant with a significant reduction in LXR expression and increase in Nox4 expression and activity in SCs and peripheral nerves, which were further verified in skin biopsies of patients with T2DM. Moreover, targeted activation of LXR or specific inhibition of Nox4 in vivo and in vitro to attenuate diabetes-induced ROS production in SCs and peripheral nerves reverses functional alteration of the peripheral nerves and restores the homeostatic profiles of MPZ and PMP22. Taken together, our findings are the first to identify novel, key mediators in the pathogenesis of DPN and suggest that targeting LXR/Nox4 axis is a promising therapeutic approach.

Structure and function of the exocrine pancreas in patients with type 1 diabetes

In the last 10 years, several studies have shown that the pancreas of patients with type 1 diabetes (T1D), and even of subjects at risk for T1D, was smaller than the pancreas from healthy subjects. This arose the question of the relationships between the endocrine and exocrine parts of the pancreas in T1D pathogenesis. Our review underlines that histological anomalies of the exocrine pancreas are common in patients with T1D: intralobular and interacinar fibrosis, acinar atrophy, fatty infiltration, leucocytic infiltration, and pancreatic arteriosclerosis are all frequent observations. Moreover, 25% to 75% of adult patients with T1D present with pancreatic exocrine dysfunction. Our review summarizes the putative causal factors for these structural and functional anomalies, including: 1/ alterations of insulin, glucagon, somatostatin and pancreatic polypeptide secretion, 2/ global pancreatic inflammation 3/ autoimmunity targeting the exocrine pancreas, 4/ vascular and neural abnormalities, and 5/ the putative involvement of pancreatic stellate cells. These observations have also given rise to new theories on T1D: the primary event of T1D pathogenesis could be non-specific, e.g bacterial or viral or chemical, resulting in global pancreatic inflammation, which in turn could cause beta-cell predominant destruction by the immune system. Finally, this review emphasizes that it is advisable to evaluate pancreatic exocrine function in patients with T1D presenting with gastro-intestinal complaints, as a clinical trial has shown that pancreatic enzymes replacement therapy can reduce the frequency of hypoglycemia and thus might improve quality of life in subjects with T1D and exocrine failure.

Lymphocyte-Derived Exosomal MicroRNAs Promote Pancreatic β Cell Death and May Contribute to Type 1 Diabetes Development

Type 1 diabetes is an autoimmune disease initiated by the invasion of pancreatic islets by immune cells that selectively kill the β cells. We found that rodent and human T lymphocytes release exosomes containing the microRNAs (miRNAs) miR-142-3p, miR-142-5p, and miR-155, which can be transferred in active form to β cells favoring apoptosis. Inactivation of these miRNAs in recipient β cells prevents exosome-mediated apoptosis and protects non-obese diabetic (NOD) mice from diabetes development. Islets from protected NOD mice display higher insulin levels, lower insulitis scores, and reduced inflammation. Looking at the mechanisms underlying exosome action, we found that T lymphocyte exosomes trigger apoptosis and the expression of genes involved in chemokine signaling, including Ccl2, Ccl7, and Cxcl10, exclusively in β cells. The induction of these genes may promote the recruitment of immune cells and exacerbate β cell death during the autoimmune attack. Our data point to exosomal-miRNA transfer as a communication mode between immune and insulin-secreting cells.

Humanized Mouse Model to Study Type 1 Diabetes

Key requirements in type 1 diabetes (T1D) are in setting up new assays as diagnostic biomarkers that will apply to prediabetes, likely T-cell assays, and in designing antigen-specific therapies to prevent T1D development. New preclinical models of T1D will be required to help with advancing both aims. By crossing mouse strains that lack either murine MHC class I and class II genes and insulin genes, we developed YES mice that instead express human HLA-A*02:01, HLA-DQ8, and insulin genes as transgenes. The metabolic and immune phenotype of YES mice is basically identical to that of the parental strains. YES mice remain insulitis and diabetes free up to 1 year of follow-up, maintain normoglycemia to an intraperitoneal glucose challenge in the long-term range, have a normal β-cell mass, and show normal immune responses to conventional antigens. This new model has been designed to evaluate adaptive immune responses to human insulin on a genetic background that recapitulates a human high-susceptibility HLA-DQ8 genetic background. Although insulitis free, YES mice develop T1D when challenged with polyinosinic-polycytidylic acid. They allow the characterization of preproinsulin epitopes recognized by CD8⁺ and CD4⁺ T cells upon immunization against human preproinsulin or during diabetes development.

The Spontaneous Autoimmune Neuromyopathy in ICOSL-/- NOD Mice Is CD4+ T-Cell and Interferon-γ Dependent

Abrogation of ICOS/ICOS ligand (ICOSL) costimulation prevents the onset of diabetes in the non-obese diabetic (NOD) mouse but, remarkably, yields to the development of a spontaneous autoimmune neuromyopathy. At the pathological level, ICOSL^−/− NOD mice show stronger protection from insulitis than their ICOS^−/− counterparts. Also, the ICOSL^−/− NOD model carries a limited C57BL/6 region containing the Icosl nul mutation, but, in contrast to ICOS^−/− NOD mice, no gene variant previously reported as associated to NOD diabetes. Therefore, we aimed at providing a detailed characterization of the ICOSL^−/− NOD model. The phenotype observed in ICOSL^−/− NOD mice is globally similar to that observed in ICOS^−/− and ICOS^−/−ICOSL^−/− double-knockout NOD mice, manifested by a progressive locomotor disability first affecting the front paws as observed by catwalk analysis and a decrease in grip test performance. The pathology remains limited to peripheral nerve and striated muscle. The muscle disease is characterized by myofiber necrosis/regeneration and an inflammatory infiltrate composed of CD4⁺ T-cells, CD8⁺ T-cells, and myeloid cells, resembling human myositis. Autoimmune neuromyopathy can be transferred to NOD.scid recipients by CD4⁺ but not by CD8⁺ T-cells isolated from 40-week-old female ICOSL^−/− NOD mice. The predominant role of CD4⁺ T-cells is further demonstrated by the observation that neuromyopathy does not develop in CIITA^−/−ICOSL^−/− NOD in contrast to β2microglobulin^−/−ICOSL^−/− NOD mice. Also, the cytokine profile of CD4⁺ T-cells infiltrating muscle and nerve of ICOSL^−/− NOD mice is biased toward a Th1 pattern. Finally, adoptive transfer experiments show that diabetes development requires expression of ICOSL, in contrast to neuromyopathy. Altogether, the deviation of autoimmunity from the pancreas to skeletal muscles in the absence of ICOS/ICOSL signaling in NOD mice is strictly dependent on CD4⁺ T-cells, leads to myofiber necrosis and regeneration. It provides the first mouse model of spontaneous autoimmune myopathy akin to human myositis.

β-cell Mass in Nondiabetic Autoantibody-Positive Subjects: An Analysis Based on the Network for Pancreatic Organ Donors Database

CONTEXT

Little information is available about β-cell mass in antibody-positive (Ab+) nondiabetic subjects.

OBJECTIVE

We have investigated whether the publicly available virtual slides of the Network for Pancreatic Organ Donors with Diabetes (nPOD) project can be used to assess β-cell mass and distribution in nondiabetic antibody-negative (Ab−) and antibody-positive (Ab+) subjects and in patients with recent-onset type 1 diabetes (T1D).

SUBJECTS AND METHODS

We developed a semi-automated quantification method and applied it to 415 insulin-stained slides from 69 Ab− subjects, 101 slides from 18 Ab+ subjects, and 46 slides from eight recent-onset (<3 y) T1D subjects. Among these subjects, 48, 17, and seven had an available pancreatic mass, respectively, and were used for the quantification of β-cell mass.

RESULTS

In Ab− subjects, the β-cell and endocrine mass were 0.66 ± 0.42 and 1.0 ± 0.65 g, respectively. Nonexocrine tissue represented 29% of pancreatic area, a proportion that increased with age. Proportional β-cell area relative to total pancreatic area was higher in the tail compared with head (0.83 vs 0.71%; P < .001). In Ab+ subjects, β-cell mass and β-cell area were similar to those of Ab− individuals, whereas these parameters were dramatically decreased in recent-onset T1D patients.

CONCLUSION

The virtual slides of the nPOD project can be used for quantification projects. In Ab+ nondiabetic subjects, the β-cell mass was not decreased. However, as this cohort is largely composed of donors from the general population, with a single autoantibody, future studies with a larger number of donors with multiple autoantibodies and predisposing human leucocyte antigen genes are required to better define the dynamics of β-cell destruction in the preclinical phases of T1D.

Circadian rhythm-related genes: implication in autoimmunity and type 1 diabetes

Recent gene association and functional studies have proven the implication of several circadian rhythm-related genes in diabetes. Diabetes has been related to variation in central circadian regulation and peripheral oscillation. Different transcriptional regulators have been identified. Circadian genes are clearly implicated in metabolic pathways, pancreatic function and in type 2 diabetes. Much less evidence has been shown for the link between circadian regulation and type 1 diabetes. The hypothesis that circadian genes are involved in type 1 diabetes is reinforced by findings that the immune system undergoes circadian variation and that several autoimmune diseases are associated with circadian genes. Recent findings in the non-obese diabetic mouse model pinpoint to specific mechanisms controlling type 1 diabetes by the clock-related gene Arntl2 in the immune system.

Mucosal-associated invariant T cell alterations in obese and type 2 diabetic patients

Obesity and type 2 diabetes (T2D) are associated with low-grade inflammation, activation of immune cells, and alterations of the gut microbiota. Mucosal-associated invariant T (MAIT) cells, which are innate-like T cells that recognize bacterial ligands, are present in blood and enriched in mucosal and inflamed tissues. Here, we analyzed MAIT cells in the blood and adipose tissues of patients with T2D and/or severe obesity. We determined that circulating MAIT cell frequency was dramatically decreased in both patient groups, and this population was even undetectable in some obese patients. Moreover, in both patient groups, circulating MAIT cells displayed an activated phenotype that was associated with elevated Th1 and Th17 cytokine production. In obese patients, MAIT cells were more abundant in adipose tissue than in the blood and exhibited a striking IL-17 profile. Bariatric surgery in obese patients not only improved their metabolic parameters but also increased circulating MAIT cell frequency at 3 months after surgery. Similarly, cytokine production by blood MAIT cells was strongly decreased after surgery. This study reveals profound MAIT cell abnormalities in patients harboring metabolic disorders, suggesting their potential role in these pathologies.

Potential role of IL-17-producing iNKT cells in type 1 diabetes

We explored in this study the status and potential role of IL-17-producing iNKT cells (iNKT17) in type 1 diabetes (T1D) by analyzing these cells in patients with T1D, and in NOD mice, a mouse model for T1D. Our analysis in mice showed an increase of iNKT17 cells in NOD vs control C57BL/6 mice, partly due to a better survival of these cells in the periphery. We also found a higher frequency of these cells in autoimmune-targeted organs with the occurrence of diabetes, suggesting their implication in the disease development. In humans, though absent in fresh PMBCs, iNKT17 cells are detected in vitro with a higher frequency in T1D patients compared to control subjects in the presence of the proinflammatory cytokine IL-1β, known to contribute to diabetes occurrence. These IL-1β-stimulated iNKT cells from T1D patients keep their potential to produce IFN-γ, a cytokine that drives islet β-cell destruction, but not IL-4, with a reverse picture observed in healthy volunteers. On the whole, our results argue in favour of a potential role of IL-17-producing iNKT cells in T1D and suggest that inflammation in T1D patients could induce a Th1/Th17 cytokine secretion profile in iNKT cells promoting disease development.

Plasmacytoid dendritic cells license regulatory T cells, upon iNKT-cell stimulation, to prevent autoimmune diabetes

Invariant NKT (iNKT)-cell stimulation with exogenous specific ligands prevents the development of type 1 diabetes (T1D) in NOD mice. Studies based on anti-islet T-cell transfer showed that iNKT cells prevent the differentiation of these T cells into effector T cells in the pancreatic lymph nodes (PLNs). We hypothesize that this defective priming could be explained by the ability of iNKT cells to induce tolerogenic dendritic cells (DCs) in the PLNs. We evaluated the effect of iNKT-cell stimulation on T1D development by transferring naïve diabetogenic BDC2.5 T cells into proinsulin 2(-/-) NOD mice treated with a long-lasting α-galactosylceramide regimen. In this context, iNKT cells induce the conversion of BDC2.5 T cells into Foxp3(+) Treg cells in the PLNs accumulating in the pancreatic islets. Furthermore, tolerogenic plasmacytoid DCs (pDCs) characterized by low MHC class II molecule expression and TGF-β production are critical in the PLNs for the recruitment of Treg cells into the pancreatic islets by inducing CXCR3 expression. Accordingly, pDC depletion in α-galactosylceramide-treated proinsulin 2(-/-) NOD mice abrogates the protection against T1D. These findings reveal that upon repetitive iNKT-cell stimulation, pDCs are critical for the recruitment of Treg cells in the pancreatic islets and the prevention of T1D development.

The targeting of β-cells by T lymphocytes in human type 1 diabetes: clinical perspectives

This review focuses on genes that control β-cell targeting in autoimmune, type 1-dependent, diabetes (T1D) and on insulin as the major autoantigen recognized by T lymphocytes throughout the disease process. T1D associates with multiple gene variants. Beyond genes that predispose to general failure of immune tolerance to self, loci identified by the analysis of crosses between non-obese diabetic (NOD) and conventional mouse strains harbour genes that control β-cell targeting or the deviation of autoimmunity towards other tissues. We report here the role of genes encoding co-activation molecules involved in the activation of T lymphocytes, ICOS and ICOS ligand (B7RP1). NOD mice which are deficient in either of these two molecules are protected from diabetes, but instead develop a neuromuscular autoimmune disease. We also report the characterization in humans of T lymphocytes that are specific for major β-cell autoantigens, especially insulin. This opens the way towards new bioassays in the diagnosis of autoimmunity and towards autoantigen-specific immunotherapy in T1D. In order to develop a new preclinical model of T1D that would allow testing insulin epitopes to induce immune tolerance in vivo, we developed a mouse that is deficient in endogenous major histocompatibility complex class I and class II genes and deficient for the two murine insulin genes and that express human class I, class II and insulin genes.

Diagnosing diabetic foot osteomyelitis in patients without signs of soft tissue infection by coupling hybrid 67Ga SPECT/CT with bedside percutaneous bone puncture

OBJECTIVE

Successful treatment of osteomyelitis is more likely with accurate diagnosis and identification of the causative pathogens. This typically requires obtaining a specimen of bone, usually by image-guided biopsy. We sought to develop a simpler bedside method for definitively diagnosing osteomyelitis.

RESEARCH DESIGN AND METHODS

Over 2 years, we enrolled consecutive patients presenting to our diabetic foot clinic with a foot ulcer and clinically suspected osteomyelitis but without soft tissue infection. Each underwent hybrid (67)Ga single-photon emission computed tomography and X-ray computed tomography (SPECT/CT) imaging; those with a positive scan underwent bedside percutaneous bone puncture. Patients with a positive bone culture received culture-guided antibiotic therapy. Patients with negative (67)Ga SPECT/CT imaging or with positive imaging but negative bone culture were not treated with antibiotics. All patients were followed up for ≥ 1 year.

RESULTS

Among 55 patients who underwent (67)Ga SPECT/CT imaging, 13 had negative results and all of their foot ulcers resolved without antibiotic therapy. Among 42 with positive imaging, 2 were excluded (for recent antibiotic therapy) and 40 had bone punctures (3 punctured twice): 19 had negative results, 3 of which were likely false negatives, and 24 had positive results (all gram-positive cocci). At follow-up, 3 patients had died, 3 had undergone amputation, and 47 had no evidence of foot infection. The sensitivity and specificity of this combined method were 88.0 and 93.6%, respectively, and the positive and negative predictive values were 91.7 and 90.7%, respectively.

CONCLUSIONS

Coupling of (67)Ga SPECT/CT imaging and bedside percutaneous bone puncture appears to be accurate and safe for diagnosing diabetic foot osteomyelitis in patients without signs of soft tissue infection, obviating the need for antibiotic treatment in 55% of suspected cases.

A simple and fast non-radioactive bridging immunoassay for insulin autoantibodies

Type 1 diabetes (T1D) is an autoimmune disease which results from the destruction of pancreatic beta cells. Autoantibodies directed against islet antigens are valuable diagnostic tools. Insulin autoantibodies (IAAs) are usually the first to appear and also the most difficult to detect amongst the four major islet autoantibodies. A non-radioactive IAA bridging ELISA was developed to this end. In this assay, one site of the IAAs from serum samples is bound to a hapten-labeled insulin (GC300-insulin), which is subsequently captured on anti-GC300 antibody-coated 96-well plates. The other site of the IAAs is bound to biotinylated insulin, allowing the complex to be detected by an enzyme-streptavidin conjugate. In the present study, 50 serum samples from patients with newly diagnosed T1D and 100 control sera from non-diabetic individuals were analyzed with our new assay and the results were correlated with an IAA radioimmunoassay (RIA). Using IAA bridging ELISA, IAAs were detected in 32 out of 50 T1D children, whereas with IAA RIA, 41 out of 50 children with newly diagnosed T1D were scored as positive. In conclusion, the IAA bridging ELISA could serve as an attractive approach for rapid and automated detection of IAAs in T1D patients for diagnostic purposes.

Effect of dietary protein on post-prandial glucose in patients with type 1 diabetes

BACKGROUND

In flexible insulin therapy, determination of the prandial insulin dose only takes into account the carbohydrate content of the evening meal, and not the protein content. Protein can, however, contribute to gluconeogenesis. We compared the glycaemic effect of a standard evening meal with that of a test evening meal enriched in protein.

METHODS

The present study was conducted in 28 C-peptide negative patients with type 1 diabetes. Two evening meals that were similar in content, except that one was enriched by the addition of 300 g of 0%-fat fromage frais, were taken on two consecutive days. Insulin doses were maintained exactly the same before both evening meals. Patients were monitored with a continuous glucose-monitoring device.

RESULTS

Patients ate similar quantities at both evening meals, except for protein (21.5 g more at the test evening meal). The preprandial insulin dose was 0.96 (0.4) U per 10 g carbohydrates. After correction for differences of interstitial glucose at the start of the evening meals, both interstitial and capillary glucose levels were similar after both evening meals, except for the late-post-prandial interstitial glucose level.

CONCLUSIONS

We found no effect of dietary protein on post-prandial-, overnight- or late-night glucose levels in patients with type 1 diabetes. This confirms that dietary proteins need not be included in the calculation of prandial insulin dose.

Factors associated with the presence of glutamic acid decarboxylase and islet antigen-2 autoantibodies in patients with long-standing type 1 diabetes

AIM

Glutamic acid decarboxylase (GAD) and/or islet antigen-2 (IA-2) autoantibodies (ab) are present in 90% of patients at the onset of type 1 diabetes (T1D). Few studies have shown that they may persist in the long-term. We analysed the frequency of GADab and IA-2ab and the factors associated with their persistency in patients with long-lasting T1D.

METHODS

This cross-sectional study included 430 adult patients with T1D of at least 10-year duration, consecutively seen over one year. GADab and IA-2ab were determined by radio-binding assays. Autoantibodies to thyroperoxydase, gastric parietal cells and transglutaminase were assessed in 418 patients, and HLA DRB1 genotyping in 359. Parameters associated with the persistency of antibodies were studied by multivariate analysis.

RESULTS

Median age at diagnosis of T1D was 12 years, and median diabetes duration was 19 years. Extrapancreatic autoimmunity was present in 38% of the patients, and associated autoimmune diseases in 21%. GADab and/or IA-2ab were found in 56% of the patients, and in 32% in those with more than 25-year diabetes duration. GADab were more frequent than IA-2ab. Female sex, an older age at diagnosis, and a shorter duration of diabetes were independently associated with the presence of ab. The same factors and the DR3 allele were associated with GADab, while only diabetes duration and the DR4 allele were associated with IA-2ab.

CONCLUSION

In a large proportion of the patients with T1D, the long-term persistency of diabetes-associated antibodies allows aetiological diagnosis, even far from the onset of hyperglycaemia.

Pancreatic islet autoimmunity

Type 1 diabetes (T1D) represents 10 to 15% of all forms of diabetes. Its incidence shows a consistent rise in all countries under survey. Evidence for autoimmunity in human T1D relies on the detection of insulitis, of islet cell antibodies, of activated β-cell-specific T lymphocytes and on the association of T1D with a restricted set of class II major histocompatibility complex (MHC) alleles. However, mechanisms that initiate the failure of immune tolerance to β-cell autoantigens remain elusive in common forms of T1D. T1D commonly develop as a multifactorial disease in which environmental factors concur with a highly multigenic background. The disease is driven by the activation of T-lymphocytes against pancreatic β-cells. Several years elapse between initial triggering of the autoimmune response to β cells, as evidenced by the appearance or islet cell autoantibodies, and the onset of clinical diabetes, defining a prediabetes stage. Active mechanisms hold back autoreactive effector T-cells in prediabetes, in particular a subset of CD4+ T-cells (T(reg)) and other regulatory T-cells, such as invariant NKT cells. There is evidence in experimental models that systemic or local infections can trigger autoimmune reactions to β-cells. However, epidemiological observations that have accumulated over years have failed to identify undisputable environmental factors that trigger T1D. Moreover, multiple environmental factors may intervene in the disease evolution and protective as weel as triggering environmental factors may be involved. Available models also indicate that local signals within the islets are required for full-blown diabetes to develop. Many autoantigens that are expressed by β-cells but also by the other endocrine islet cells and by neurons are recognized by lymphocytes along the development of T1D. The immune image of β-cells is that of native components of the β-cell membrane, as seen by B-lymphocytes, and of fragments of intracellular β-cell proteins in the form of peptides loaded onto class I MHC molecules on the β-cell surface and class I and class II molecules onto professional antigen presenting cells. Given the key role of T lymphocytes in T1D, the cartography of autoantigen-derived peptides that are presented to class I-restricted CD8(+) T-cells and class II-restricted CD4(+) T-cells is of outmost importance and is a necessary step in the development of diagnostic T-cell assays and of immunotherapy of T1D.

HLA-B7-restricted islet epitopes are differentially recognized in type 1 diabetic children and adults and form weak peptide-HLA complexes

The cartography of β-cell epitopes targeted by CD8(+) T cells in type 1 diabetic (T1D) patients remains largely confined to the common HLA-A2 restriction. We aimed to identify β-cell epitopes restricted by the HLA-B7 (B*07:02) molecule, which is associated with mild T1D protection. Using DNA immunization on HLA-B7-transgenic mice and prediction algorithms, we identified GAD and preproinsulin candidate epitopes. Interferon-γ (IFN-γ) enzyme-linked immunospot assays on peripheral blood mononuclear cells showed that most candidates were recognized by new-onset T1D patients, but not by type 2 diabetic and healthy subjects. Some epitopes were highly immunodominant and specific to either T1D children (GAD(530-538); 44% T cell-positive patients) or adults (GAD(311-320); 38%). All epitopes displayed weak binding affinity and stability for HLA-B7 compared with HLA-A2-restricted ones, a general feature of HLA-B7. Single-cell PCR analysis on β-cell-specific (HLA-B7 tetramer-positive) T cells revealed uniform IFN-γ and transforming growth factor-β (TGF-β) mRNA expression, different from HLA-A2-restricted T cells. We conclude that HLA-B7-restricted islet epitopes display weak HLA-binding profiles, are different in T1D children and adults, and are recognized by IFN-γ(+)TGF-β(+)CD8(+) T cells. These features may explain the T1D-protective effect of HLA-B7. The novel epitopes identified should find valuable applications for immune staging of HLA-B7(+) individuals.

Pancreatic exocrine function in patients with diabetes

BACKGROUND

Decreased function of the exocrine pancreas is frequent in patients with diabetes. Our aim was to investigate clinical correlates of pancreatic exocrine failure in patients with diabetes.

PATIENTS AND METHODS

We investigated exocrine function by assaying both elastase-1 concentration and chymotrypsin activity in 667 patients. We conducted separate analysis on patients with Type 1 diabetes and patients with Type 2 diabetes. Patients were separated into three groups according to whether both elastase-1 concentration and chymotrypsin activity were normal, or one or both were altered.

RESULTS

A total of 667 consecutive patients were analysed, including 195 with Type 1 and 472 with Type 2 diabetes. Elastase-1 concentration was <200 μg/g in 23% of the patients. Chymotrypsin activity was <6 U/g in 26% of the patients. In 66% of the patients elastase-1 concentration was >200 ug/g and chymotrypsin activity >6 U/g. One test was below threshold in 19%, both in 15%. In patients with Type 1 diabetes, the three groups defined by results of elastase-1 concentration and chymotrypsin activity differed with regard to duration of diabetes and prevalence of glutamic acid decarboxylase antibodies, but not BMI or HbA(1c) , or prevalence of retinopathy, neuropathy, nephropathy or vascular disease. In patients with Type 2 diabetes, the three groups differed with regard to BMI, use of insulin and vascular disease, but not known duration.

CONCLUSION

Factors associated with pancreatic exocrine failure differ in patients with Type 1 diabetes compared with patients with type 2 diabetes. In patients with Type 2 diabetes, association of decreased pancreatic exocrine function with BMI and vascular disease suggests a role of pancreatic arteriopathy.

Zinc transporter (ZnT)8(186-194) is an immunodominant CD8+ T cell epitope in HLA-A2+ type 1 diabetic patients

AIMS/HYPOTHESIS

Anti-zinc transporter (ZnT)8 autoantibodies are commonly detected in type 1 diabetic patients. We hypothesised that ZnT8 is also recognised by CD8(+) T cells and aimed to identify HLA-A2 (A*02:01)-restricted epitope targets.

METHODS

Candidate epitopes were selected by ZnT8 plasmid DNA immunisation of HLA-A2/DQ8 transgenic mice and tested for T cell recognition in peripheral blood mononuclear cells of type 1 diabetic, type 2 diabetic and healthy participants by IFN-γ enzyme-linked immunospot.

RESULTS

White HLA-A2(+) adults (83%) and children (60%) with type 1 diabetes displayed ZnT8-reactive CD8(+) T cells that recognised a single ZnT8(186-194) (VAANIVLTV) epitope. This ZnT8(186-194)-reactive fraction accounted for 50% to 53% of total ZnT8-specific CD8(+) T cells. Another sequence, ZnT8(153-161) (VVTGVLVYL), was recognised in 20% and 25% of type 1 diabetic adults and children, respectively. Both epitopes were type 1 diabetes-specific, being marginally recognised by type 2 diabetic and healthy participants (7-12% for ZnT8(186-194), 0% for ZnT8(153-161)).

CONCLUSIONS/INTERPRETATION

ZnT8-reactive CD8(+) T cells are predominantly directed against the ZnT8(186-194) epitope and are detected in a majority of type 1 diabetic patients. The exceptional immunodominance of ZnT8(186-194) may point to common environmental triggers precipitating beta cell autoimmunity.

Changes in microRNA expression contribute to pancreatic β-cell dysfunction in prediabetic NOD mice

During the initial phases of type 1 diabetes, pancreatic islets are invaded by immune cells, exposing β-cells to proinflammatory cytokines. This unfavorable environment results in gene expression modifications leading to loss of β-cell functions. To study the contribution of microRNAs (miRNAs) in this process, we used microarray analysis to search for changes in miRNA expression in prediabetic NOD mice islets. We found that the levels of miR-29a/b/c increased in islets of NOD mice during the phases preceding diabetes manifestation and in isolated mouse and human islets exposed to proinflammatory cytokines. Overexpression of miR-29a/b/c in MIN6 and dissociated islet cells led to impairment in glucose-induced insulin secretion. Defective insulin release was associated with diminished expression of the transcription factor Onecut2, and a consequent rise of granuphilin, an inhibitor of β-cell exocytosis. Overexpression of miR-29a/b/c also promoted apoptosis by decreasing the level of the antiapoptotic protein Mcl1. Indeed, a decoy molecule selectively masking the miR-29 binding site on Mcl1 mRNA protected insulin-secreting cells from apoptosis triggered by miR-29 or cytokines. Taken together, our findings suggest that changes in the level of miR-29 family members contribute to cytokine-mediated β-cell dysfunction occurring during the initial phases of type 1 diabetes.