Reversal of beta-cell suppression in vitro in pancreatic islets isolated from nonobese diabetic mice during the phase preceding insulin-dependent diabetes mellitus

Tracking Ca2+ Dynamics in NOD Mouse Islets During Spontaneous Diabetes Development

The mechanisms accounting for the functional changes of α- and β-cells over the course of type 1 diabetes (T1D) development are largely unknown. Permitted by our established technology of high spatiotemporal resolution imaging of cytosolic Ca2+ ([Ca2+]c) dynamics on fresh pancreas tissue slices, we tracked the [Ca2+]c dynamic changes, as the assessment of function, in islet α- and β-cells of female nonobese diabetic (NOD) mice during the development of spontaneous diabetes. We showed that, during the phases of islet inflammation, 8 mmol/L glucose-induced synchronized short [Ca2+]c events in β-cells were diminished, whereas long [Ca2+]c events were gradually more triggerable at substimulatory 4 and 6 mmol/L glucose. In the islet destruction phase, the synchronized short [Ca2+]c events in a subset of β-cells resumed at high glucose condition, while the long [Ca2+]c events were significantly elevated already at substimulatory glucose concentrations. In the α-cells, the glucose sensitivity of the [Ca2+]c events persisted throughout the course of T1D development. At the late islet destruction phase, the α-cell [Ca2+]c events exhibited patterns of synchronicity. Our work has uncovered windows of functional recovery in β-cells and potential α-cells functional synchronization in NOD mice over the course of T1D development.

ARTICLE HIGHLIGHTS

In NOD mice β-cells, 8 mmol/L glucose-induced synchronized short [Ca2+]c events diminish in the early phases of islet inflammation, and long Ca2+ events became more sensitive to substimulatory 4 and 6 mmol/L glucose. In the late islet destruction phase, the synchronized short [Ca2+]c events in a subset of β-cells resumed at 8 mmol/L glucose, while the long Ca2+ events were significantly elevated at substimulatory glucose concentrations. In the α-cells, the glucose sensitivity of the [Ca2+]c events persisted throughout the course of type 1 diabetes development. α-Cell [Ca2+]c events occasionally synchronize in the islets with severe β-cell destruction.

Pancreatic β-cells in type 1 and type 2 diabetes mellitus: different pathways to failure

Loss of functional β-cell mass is the key mechanism leading to the two main forms of diabetes mellitus - type 1 diabetes mellitus (T1DM) and type 2 diabetes mellitus (T2DM). Understanding the mechanisms behind β-cell failure is critical to prevent or revert disease. Basic pathogenic differences exist in the two forms of diabetes mellitus; T1DM is immune mediated and T2DM is mediated by metabolic mechanisms. These mechanisms differentially affect early β-cell dysfunction and eventual fate. Over the past decade, major advances have been made in the field, mostly delivered by studies on β-cells in human disease. These advances include studies of islet morphology and human β-cell gene expression in T1DM and T2DM, the identification and characterization of the role of T1DM and T2DM candidate genes at the β-cell level and the endoplasmic reticulum stress signalling that contributes to β-cell failure in T1DM (mostly IRE1 driven) and T2DM (mostly PERK-eIF2α dependent). Here, we review these new findings, focusing on studies performed on human β-cells or on samples obtained from patients with diabetes mellitus.

β-Cell-Derived Angiopoietin-1 Regulates Insulin Secretion and Glucose Homeostasis by Stabilizing the Islet Microenvironment

Islets are highly vascularized for prompt insulin secretion. Although angiopoietin-1 (Ang1) is a well-known angiogenic factor, its role in glucose homeostasis remains largely unknown. The objective of this study was to investigate whether and how Ang1 contributes to glucose homeostasis in response to metabolic challenge. We used inducible systemic Ang1 knockout (Ang1^sys-/-) and β-cell-specific Ang1 knockout (Ang1^β-cell-/-) mice fed a high-fat diet for 24 weeks. Although the degree of insulin sensitivity did not differ between Ang1^sys-/- and Ang1^sys+/+ mice, serum insulin levels were lower in Ang1^sys-/- mice, resulting in significant glucose intolerance. Similar results were observed in Ang1^β-cell-/- mice, suggesting a critical role of β-cell-derived Ang1 in glucose homeostasis. There were no differences in β-cell area or vasculature density, but glucose-stimulated insulin secretion was significantly decreased, and PDX-1 expression and GLUT2 localization were altered in Ang1^β-cell-/- compared with Ang1^β-cell+/+ mice. These effects were associated with less pericyte coverage, disorganized endothelial cell ultrastructure, and enhanced infiltration of inflammatory cells and upregulation of adhesion molecules in the islets of Ang1^β-cell-/- mice. In conclusion, β-cell-derived Ang1 regulates insulin secretion and glucose homeostasis by stabilizing the blood vessels in the islet and may be a novel therapeutic target for diabetes treatment in the future.

Early deficits in insulin secretion, beta cell mass and islet blood perfusion precede onset of autoimmune type 1 diabetes in BioBreeding rats

AIMS/HYPOTHESIS

Genetic studies show coupling of genes affecting beta cell function to type 1 diabetes, but hitherto no studies on whether beta cell dysfunction could precede insulitis and clinical onset of type 1 diabetes are available.

METHODS

We used 40-day-old BioBreeding (BB) DRLyp/Lyp rats (a model of spontaneous autoimmune type 1 diabetes) and diabetes-resistant DRLyp/+ and DR+/+ littermates (controls) to investigate beta cell function in vivo, and insulin and glucagon secretion in vitro. Beta cell mass was assessed by optical projection tomography (OPT) and morphometry. Additionally, measurements of intra-islet blood flow were performed using microsphere injections. We also assessed immune cell infiltration, cytokine expression in islets (by immunohistochemistry and qPCR), as well as islet Glut2 expression and ATP/ADP ratio to determine effects on glucose uptake and metabolism in beta cells.

RESULTS

DRLyp/Lyp rats were normoglycaemic and without traces of immune cell infiltrates. However, IVGTTs revealed a significant decrease in the acute insulin response to glucose compared with control rats (1685.3 ± 121.3 vs 633.3 ± 148.7; p < 0.0001). In agreement, insulin secretion was severely perturbed in isolated islets, and both first- and second-phase insulin release were lowered compared with control rats, while glucagon secretion was similar in both groups. Interestingly, after 5-7 days of culture of islets from DRLyp/Lyp rats in normal media, glucose-stimulated insulin secretion (GSIS) was improved; although, a significant decrease in GSIS was still evident compared with islets from control rats at this time (7393.9 ± 1593.7 vs 4416.8 ± 1230.5 pg islet^-1 h^-1; p < 0.0001). Compared with controls, OPT of whole pancreas from DRLyp/Lyp rats revealed significant reductions in medium (4.1 × 10⁹ ± 9.5 × 10⁷ vs 3.8 × 10⁹ ± 5.8 × 10⁷ μm³; p = 0.044) and small sized islets (1.6 × 10⁹ ± 5.1 × 10⁷ vs 1.4 × 10⁹ ± 4.5 × 10⁷ μm³; p = 0.035). Finally, we found lower intra-islet blood perfusion in vivo (113.1 ± 16.8 vs 76.9 ± 11.8 μl min^-1 [g pancreas]^-1; p = 0.023) and alterations in the beta cell ATP/ADP ratio in DRLyp/Lyp rats vs control rats.

CONCLUSIONS/INTERPRETATION

The present study identifies a deterioration of beta cell function and mass, and intra-islet blood flow that precedes insulitis and diabetes development in animals prone to autoimmune type 1 diabetes. These underlying changes in islet function may be previously unrecognised factors of importance in type 1 diabetes development.

AAV-mediated pancreatic overexpression of Igf1 counteracts progression to autoimmune diabetes in mice

Objective

Type 1 diabetes is characterized by autoimmune destruction of β-cells leading to severe insulin deficiency. Although many improvements have been made in recent years, exogenous insulin therapy is still imperfect; new therapeutic approaches, focusing on preserving/expanding β-cell mass and/or blocking the autoimmune process that destroys islets, should be developed. The main objective of this work was to test in non-obese diabetic (NOD) mice, which spontaneously develop autoimmune diabetes, the effects of local expression of Insulin-like growth factor 1 (IGF1), a potent mitogenic and pro-survival factor for β-cells with immunomodulatory properties.

Methods

Transgenic NOD mice overexpressing IGF1 specifically in β-cells (NOD-IGF1) were generated and phenotyped. In addition, miRT-containing, IGF1-encoding adeno-associated viruses (AAV) of serotype 8 (AAV8-IGF1-dmiRT) were produced and administered to 4- or 11-week-old non-transgenic NOD females through intraductal delivery. Several histological, immunological, and metabolic parameters were measured to monitor disease over a period of 28–30 weeks.

Results

In transgenic mice, local IGF1 expression led to long-term suppression of diabetes onset and robust protection of β-cell mass from the autoimmune insult. AAV-mediated pancreatic-specific overexpression of IGF1 in adult animals also dramatically reduced diabetes incidence, both when vectors were delivered before pathology onset or once insulitis was established. Transgenic NOD-IGF1 and AAV8-IGF1-dmiRT-treated NOD animals had much less islet infiltration than controls, preserved β-cell mass, and normal insulinemia. Transgenic and AAV-treated islets showed less expression of antigen-presenting molecules, inflammatory cytokines, and chemokines important for tissue-specific homing of effector T cells, suggesting IGF1 modulated islet autoimmunity in NOD mice.

Conclusions

Local expression of Igf1 by AAV-mediated gene transfer counteracts progression to diabetes in NOD mice. This study suggests a therapeutic strategy for autoimmune diabetes in humans.

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Local pancreatic IGF1 expression prevents spontaneous autoimmune diabetes.

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Protection achieved after one-time local administration of IGF1-encoding AAV vectors.

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Efficacious in animals treated early or once autoimmunity is already established.

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Protection through maintenance of β-cell mass and endogenous insulin secretion.

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Treatment leads to reduced infiltration and expression of immunity genes in islets.

Viral infections in type 1 diabetes mellitus--why the β cells?

Type 1 diabetes mellitus (T1DM) is caused by progressive autoimmune-mediated loss of pancreatic β-cell mass via apoptosis. The onset of T1DM depends on environmental factors that interact with predisposing genes to induce an autoimmune assault against β cells. Epidemiological, clinical and pathology studies in humans support viral infection--particularly by enteroviruses (for example, coxsackievirus)--as an environmental trigger for the development of T1DM. Many candidate genes for T1DM, such as MDA5, PTPN2 and TYK2, regulate antiviral responses in both β cells and the immune system. Cellular permissiveness to viral infection is modulated by innate antiviral responses that vary among different tissues or cell types. Some data indicate that pancreatic islet α cells trigger a more efficient antiviral response to infection with diabetogenic viruses than do β cells, and so are able to eradicate viral infections without undergoing apoptosis. This difference could account for the varying ability of islet-cell subtypes to clear viral infections and explain why chronically infected pancreatic β cells, but not α cells, are targeted by an autoimmune response and killed during the development of T1DM. These issues and attempts to target viral infection as a preventive therapy for T1DM are discussed in the present Review.

β cell death and dysfunction during type 1 diabetes development in at-risk individuals

Role of the funding source: Funding from the NIH was used for support of the participating clinical centers and the coordinating center. The funding source did not participate in the collection or the analysis of the data.

BACKGROUND

The β cell killing that characterizes type 1 diabetes (T1D) is thought to begin years before patients present clinically with metabolic decompensation; however, this primary pathologic process of the disease has not been measured.

METHODS

Here, we measured β cell death with an assay that detects β cell-derived unmethylated insulin (INS) DNA. Using this assay, we performed an observational study of 50 participants from 2 cohorts at risk for developing T1D from the TrialNet Pathway to Prevention study and of 4 subjects who received islet autotransplants.

RESULTS

In at-risk subjects, those who progressed to T1D had average levels of unmethylated INS DNA that were elevated modestly compared with those of healthy control subjects. In at-risk individuals that progressed to T1D, the observed increases in unmethylated INS DNA were associated with decreases in insulin secretion, indicating that the changes in unmethylated INS DNA are indicative of β cell killing. Subjects at high risk for T1D had levels of unmethylated INS DNA that were higher than those of healthy controls and higher than the levels of unmethylated INS DNA in the at-risk progressor and at-risk nonprogressor groups followed for 4 years. Evaluation of insulin secretory kinetics also distinguished high-risk subjects who progressed to overt disease from those who did not.

CONCLUSION

We conclude that a blood test that measures unmethylated INS DNA serves as a marker of active β cell killing as the result of T1D-associated autoimmunity. Together, the data support the concept that β cell killing occurs sporadically during the years prior to diagnosis of T1D and is more intense in the peridiagnosis period.

TRIAL REGISTRATION

Clinicaltrials.gov NCT00097292.

FUNDING

Funding was from the NIH, the Juvenile Diabetes Research Foundation, and the American Diabetes Association.

Beta cell imaging - a key tool in optimized diabetes prevention and treatment

The prevalence of diabetes is 382 million worldwide, and is expected to rise to 592 million in 2035 (http://www.idf.org/diabetesatlas); 2.5-15% of national annual healthcare budgets are related to diabetes care, potentially increasing to 40% in high-prevalence countries. Beta cell dysfunction and death are central events in diabetes pathogenesis, but the natural history of beta cell loss remains unknown. Clinical imaging of beta cells will play a pivotal role in developing strategies for optimized diabetes prevention and treatment.

Deoxyhypusine synthase promotes differentiation and proliferation of T helper type 1 (Th1) cells in autoimmune diabetes

In type 1 diabetes, cytokines arising from immune cells cause islet β cell dysfunction even before overt hyperglycemia. Deoxyhypusine synthase catalyzes the crucial hypusine modification of the factor eIF5A, which promotes the translation of a subset of mRNAs involved in cytokine responses. Here, we tested the hypothesis that deoxyhypusine synthase and, secondarily, hypusinated eIF5A contribute to the pathogenesis of type 1 diabetes using the non-obese diabetic (NOD) mouse model. Pre-diabetic NOD mice that received injections of the deoxyhypusine inhibitor N1-guanyl-1,7-diaminoheptane (GC7) demonstrated significantly improved glucose tolerance, more robust insulin secretion, and reduced insulitis compared with control animals. Analysis of tissues from treated mice revealed selective reductions in diabetogenic T helper type 1 (Th1) cells in the pancreatic lymph nodes, a primary site of antigen presentation. Isolated mouse CD90.2(+) splenocytes stimulated in vitro with anti-CD3/anti-CD28 and IL-2 to mimic autoimmune T cell activation exhibited proliferation and differentiation of CD4(+) T cell subsets (Th1, Th17, and Treg), but those treated with the deoxyhypusine synthase inhibitor GC7 showed a dose-dependent block in T cell proliferation with selective reduction in Th1 cells, similar to that observed in NOD mice. Inhibition of deoxyhypusine synthase blocked post-transcriptional expression of CD25, the high affinity IL-2 receptor α chain. Our results suggest a previously unrecognized role for deoxyhypusine synthase in promoting T cell proliferation and differentiation via regulation of CD25. Inhibition of deoxyhypusine synthase may provide a strategy for reducing diabetogenic Th1 cells and preserving β cell function in type 1 diabetes.

IL-2 immunotherapy reveals potential for innate beta cell regeneration in the non-obese diabetic mouse model of autoimmune diabetes

Type-1 diabetes (T1D) is an autoimmune disease targeting insulin-producing beta cells, resulting in dependence on exogenous insulin. To date, significant efforts have been invested to develop immune-modulatory therapies for T1D treatment. Previously, IL-2 immunotherapy was demonstrated to prevent and reverse T1D at onset in the non-obese diabetic (NOD) mouse model, revealing potential as a therapy in early disease stage in humans. In the NOD model, IL-2 deficiency contributes to a loss of regulatory T cell function. This deficiency can be augmented with IL-2 or antibody bound to IL-2 (Ab/IL-2) therapy, resulting in regulatory T cell expansion and potentiation. However, an understanding of the mechanism by which reconstituted regulatory T cell function allows for reversal of diabetes after onset is not clearly understood. Here, we describe that Ab/IL-2 immunotherapy treatment, given at the time of diabetes onset in NOD mice, not only correlated with reversal of diabetes and expansion of Treg cells, but also demonstrated the ability to significantly increase beta cell proliferation. Proliferation appeared specific to Ab/IL-2 immunotherapy, as anti-CD3 therapy did not have a similar effect. Furthermore, to assess the effect of Ab/IL-2 immunotherapy well after the development of diabetes, we tested the effect of delaying treatment for 4 weeks after diabetes onset, when beta cells were virtually absent. At this late stage after diabetes onset, Ab/IL-2 treatment was not sufficient to reverse hyperglycemia. However, it did promote survival in the absence of exogenous insulin. Proliferation of beta cells could not account for this improvement as few beta cells remained. Rather, abnormal insulin and glucagon dual-expressing cells were the only insulin-expressing cells observed in islets from mice with established disease. Thus, these data suggest that in diabetic NOD mice, beta cells have an innate capacity for regeneration both early and late in disease, which is revealed through IL-2 immunotherapy.

CD3 monoclonal antibodies: a first step towards operational immune tolerance in the clinic

Type 1 diabetes (T1D) is a prototypic organ-specific autoimmune disease resulting from the selective destruction of insulin-secreting β-cells within the pancreatic islets of Langerhans. It is caused by an immune-mediated inflammation, involving autoreactive CD4⁺ and CD8⁺ T lymphocytes that infiltrate the islets and initiate insulitis. The use of exogenous insulin is the current standard treatment. However, in spite of significant advances, this therapy is still associated with major constraints, including risk of hypoglycemia and severe degenerative complications. As T1D mainly affects children and young adults, any candidate immune therapy must be safe, and it must avoid a sustained depression of immune responses with all its attendant problems of recurrent infection and drug toxicity. In this context, inducing or restoring immune tolerance to target autoantigens would be the ideal approach. We refer to immune tolerance here as the selective damping of the damaging autoimmune response following a short treatment, while keeping intact the capacity of the host to respond normally to exogenous antigens. The therapeutic approach we discuss in this article originates from attempts to induce tolerance both to soluble antigens and tissue antigens (i.e. alloantigens and autoantigens) by using biological agents that selectively interfere with lymphocyte activation, namely polyclonal and monoclonal anti-T cell antibodies. The challenged dogma was that, in an adult-primed immune system, it was not possible to restore self-tolerance therapeutically without the use of exogenous autoantigen administration. The reality has been that, in diabetes, endogenous host autoantigen can fulfill this role because a significant amount of functioning β-cells remains, even at the time of established hyperglycemia. Experimental results obtained in the 1990s showed that a short-term CD3 antibody treatment in recently diagnosed diabetic non-obese diabetic (NOD) mice induced permanent remission of the disease by restoring self-tolerance. Based on these findings, phase I, II, and III trials were conducted using two distinct humanized Fc-mutated antibodies to human CD3, namely ChAglyCD3 (otelixizumab) and OKT3γ1 Ala-Ala (teplizumab). Overall, when dosing was adequate, the results demonstrated that CD3 antibodies preserved β-cell function very efficiently, maintaining significantly high levels of endogenous insulin secretion in treated patients for up to 24 months after treatment. These data provided the first proof of concept for a long-term therapeutic effect in T1D following a short course administration of a therapeutic agent. Our aim is to review these data and to discuss them in the context of the pitfalls linked to pharmaceutical development, especially in the context of pediatric patients, as in autoimmune diabetes.

Islet β-cell endoplasmic reticulum stress precedes the onset of type 1 diabetes in the nonobese diabetic mouse model

Type 1 diabetes is preceded by islet β-cell dysfunction, but the mechanisms leading to β-cell dysfunction have not been rigorously studied. Because immune cell infiltration occurs prior to overt diabetes, we hypothesized that activation of inflammatory cascades and appearance of endoplasmic reticulum (ER) stress in β-cells contributes to insulin secretory defects. Prediabetic nonobese diabetic (NOD) mice and control diabetes-resistant NOD-SCID and CD1 strains were studied for metabolic control and islet function and gene regulation. Prediabetic NOD mice were relatively glucose intolerant and had defective insulin secretion with elevated proinsulin:insulin ratios compared with control strains. Isolated islets from NOD mice displayed age-dependent increases in parameters of ER stress, morphologic alterations in ER structure by electron microscopy, and activation of nuclear factor-κB (NF-κB) target genes. Upon exposure to a mixture of proinflammatory cytokines that mimics the microenvironment of type 1 diabetes, MIN6 β-cells displayed evidence for polyribosomal runoff, a finding consistent with the translational initiation blockade characteristic of ER stress. We conclude that β-cells of prediabetic NOD mice display dysfunction and overt ER stress that may be driven by NF-κB signaling, and strategies that attenuate pathways leading to ER stress may preserve β-cell function in type 1 diabetes.

Contribution of different mechanisms to pancreatic beta-cell hyper-secretion in non-obese diabetic (NOD) mice during pre-diabetes

The development of insulin-dependent diabetes mellitus (IDDM) results from the selective destruction of pancreatic beta-cells. Both humans and spontaneous models of IDDM, such as NOD mice, have an extended pre-diabetic stage. Dynamic changes in beta-cell mass and function during pre-diabetes, such as insulin hyper-secretion, remain largely unknown. In this paper, we evaluated pre-diabetic female NOD mice at different ages (6, 10, and 14 weeks old) to illustrate alterations in beta-cell mass and function as disease progressed. We found an increase in beta-cell mass in 6-week-old NOD mice that may account for improved glucose tolerance in these mice. As NOD mice aged, beta-cell mass progressively reduced with increasing insulitis. In parallel, secretory ability of individual beta-cells was enhanced due to an increase in the size of slowly releasable pool (SRP) of vesicles. Moreover, expression of both SERCA2 and SERCA3 genes were progressively down-regulated, which facilitated depolarization-evoked secretion by prolonging Ca(2+) elevation upon glucose stimulation. In summary, we propose that different mechanisms contribute to the insulin hyper-secretion at different ages of pre-diabetic NOD mice, which may provide some new ideas concerning the progression and management of type I diabetes.

Current state of type 1 diabetes immunotherapy: incremental advances, huge leaps, or more of the same?

Thus far, none of the preclinically successful and promising immunomodulatory agents for type 1 diabetes mellitus (T1DM) has conferred stable, long-term insulin independence to diabetic patients. The majority of these immunomodulators are humanised antibodies that target immune cells or cytokines. These as well as fusion proteins and inhibitor proteins all share varying adverse event occurrence and severity. Other approaches have included intact putative autoantigens or autoantigen peptides. Considerable logistical outlays have been deployed to develop and to translate humanised antibodies targeting immune cells, cytokines, and cytokine receptors to the clinic. Very recent phase III trials with the leading agent, a humanised anti-CD3 antibody, call into question whether further development of these biologics represents a step forward or more of the same. Combination therapies of one or more of these humanised antibodies are also being considered, and they face identical, if not more serious, impediments and safety issues. This paper will highlight the preclinical successes and the excitement generated by phase II trials while offering alternative possibilities and new translational avenues that can be explored given the very recent disappointment in leading agents in more advanced clinical trials.

Evaluation of impaired beta-cell function in nonobese-diabetic (NOD) mouse model using bioluminescence imaging

Insulin-producing pancreatic β cells are functionally impaired or destroyed in diabetes mellitus. The onset of type 1 diabetes (T1D) represents the culmination of a prolonged prediabetic phase of immune-mediated β-cell destruction. To assess the in vivo metabolic status of these cells, we used the ATP-sensitive firefly luciferase bioluminescence imaging approach, as a noninvasive probe to monitor pathological alterations in β-cell function in the nonobese-diabetic (NOD) mouse model of T1D. Hence, we generated the ToIβ-NOD transgenic mice in which doxycycline-inducible luciferase gene is selectively expressed in β cells. A sharp reduction in bioluminescence emitted in vivo from β cells at the early stages, preceded by several weeks of a limited reduction in β-cell mass. Since this decline could be due to the ongoing inflammatory process occurring in vivo, we exposed control islets to inflammatory cytokines and observed a dramatic decrease in luciferase luminescence, which appears to be due in part to a decrease in protein levels and a drop in intracellular ATP levels. This is the first evidence that selective expression of the luciferase gene represents a sensitive method for noninvasive in vivo monitoring of early β-cell dysfunction, subtle metabolic changes, such as endogenous ATP levels, indicative of a pathological condition in a tissue at the cellular level.

Immune therapy for type 1 diabetes mellitus-what is unique about anti-CD3 antibodies?

Type 1 diabetes mellitus (T1DM) is a prototypic organ-specific autoimmune disease that results from selective destruction of insulin-secreting beta-cells by immune-mediated inflammation (insulitis), that is, the infiltration of pancreatic islets by autoreactive CD4(+) and CD8(+) T lymphocytes. Current treatment is substitutive-chronic use of exogenous insulin-which, in spite of considerable advances, is still associated with constraints and lack of effectiveness over the long-term in relation to the prevention of vascular and neurological complications. Finding a cure for T1DM is an important medical health challenge, as the disease's incidence is steadily increasing in industrialized countries and projections of future prevalence are alarming. Crucially, as T1DM mainly affects children and young adults, any candidate immune therapy must be safe and avoid chronic use of immunosuppressants that promote sustained depression of immune responses. The ideal approach would, therefore, involve induction or, in the case of established T1DM, restoration of immune tolerance to target autoantigens. This Review presents, in particular, two strategies that are still in clinical development but hold great promise. These strategies are focused on the use of candidate autoantigens and anti-CD3 monoclonal antibodies.

The role of inflammation in insulitis and beta-cell loss in type 1 diabetes

Type 1 diabetes mellitus (T1DM) is a chronic autoimmune disease with a strong inflammatory component. The latest studies indicate that innate immunity and inflammatory mediators have a much broader role in T1DM than initially assumed. Inflammation might contribute to early induction and amplification of the immune assault against pancreatic beta cells and, at later stages, to the stabilization and maintenance of insulitis. Inflammatory mediators probably contribute to the suppression of beta-cell function and subsequent apoptosis; they may also inhibit or stimulate beta-cell regeneration and might cause peripheral insulin resistance. The different effects of inflammation take place in different phases of the course of T1DM, and should be considered in the context of a 'dialog' between invading immune cells and the target beta cells. This dialog is mediated both by cytokines and chemokines that are released by beta cells and immune cells, and by putative, immunogenic signals that are delivered by dying beta cells. In this Review, we divided the role of inflammation in T1DM into three arbitrary stages: induction, amplification and maintenance or resolution of insulitis. These stages, and their progression or resolution, might depend on a patient's genetic background, which contributes to disease heterogeneity.

The role for endoplasmic reticulum stress in diabetes mellitus

Accumulating evidence suggests that endoplasmic reticulum (ER) stress plays a role in the pathogenesis of diabetes, contributing to pancreatic beta-cell loss and insulin resistance. Components of the unfolded protein response (UPR) play a dual role in beta-cells, acting as beneficial regulators under physiological conditions or as triggers of beta-cell dysfunction and apoptosis under situations of chronic stress. Novel findings suggest that "what makes a beta-cell a beta-cell", i.e., its enormous capacity to synthesize and secrete insulin, is also its Achilles heel, rendering it vulnerable to chronic high glucose and fatty acid exposure, agents that contribute to beta-cell failure in type 2 diabetes. In this review, we address the transition from physiology to pathology, namely how and why the physiological UPR evolves to a proapoptotic ER stress response and which defenses are triggered by beta-cells against these challenges. ER stress may also link obesity and insulin resistance in type 2 diabetes. High fat feeding and obesity induce ER stress in liver, which suppresses insulin signaling via c-Jun N-terminal kinase activation. In vitro data suggest that ER stress may also contribute to cytokine-induced beta-cell death. Thus, the cytokines IL-1beta and interferon-gamma, putative mediators of beta-cell loss in type 1 diabetes, induce severe ER stress through, respectively, NO-mediated depletion of ER calcium and inhibition of ER chaperones, thus hampering beta-cell defenses and amplifying the proapoptotic pathways. A better understanding of the pathways regulating ER stress in beta-cells may be instrumental for the design of novel therapies to prevent beta-cell loss in diabetes.

The use of CD3-specific antibodies in autoimmune diabetes: a step toward the induction of immune tolerance in the clinic

CD3-specific monoclonal antibodies were the first rodent monoclonals introduced in clinical practice in the mid 1980s as approved immunosuppressants to prevent and treat organ allograft rejection. Since then compelling evidence has been accumulated to suggest that in addition to their immunosuppressive properties, CD3-specific antibodies can also afford inducing immune tolerance especially in the context of ongoing immune responses. Thus, they are highly effective at restoring self-tolerance in overt autoimmunity, a capacity first demonstrated in the experimental setting, which was recently transferred to the clinic with success.

Drug Insight: new immunomodulatory therapies in type 1 diabetes

Animal models and human studies have provided strong evidence that the immune response that causes type 1A diabetes is initiated against a limited array of antigens but acquires breadth and depth until beta-cell mass has been critically compromised. Two recent trials confirmed the ability to identify relatives at risk for development of diabetes, but were unsuccessful in preventing disease. Treatment of at-risk individuals with oral insulin, which is postulated to be an antigen in the disease, did however show efficacy in a subgroup of these subjects, suggesting that antigen-specific prevention approaches might be successful in the right group of subjects at the right time. Earlier trials showed that the natural progression of disease can be altered with conventional immune suppression but these approaches have been supplanted by tolerance-induction strategies. Anti-CD3 monoclonal antibodies have shown efficacy in preventing the loss of insulin production over the first 2 years of disease without chronic immune suppression. The mechanisms are novel, and appear to involve induction of immune regulation by the monoclonal antibody. Ultimately, preservation and even improvement in beta-cell mass is the goal of therapy. The means needed to achieve this will depend on the timing and mechanisms of the immune intervention and might require combinations of agents.

The Cytokine Interleukin-1β Reduces the Docking and Fusion of Insulin Granules in Pancreatic β-Cells, Preferentially Decreasing the First Phase of Exocytosis

The prediabetic period in type I diabetes mellitus is characterized by the loss of first phase insulin release. This might be due to islet infiltration mediated by mononuclear cells and local release of cytokines, but the mechanisms involved are unknown. To determine the role of cytokines in insulin exocytosis, we have presently utilized total internal reflection fluorescence microscopy (TIRFM) to image and analyze the dynamic motion of single insulin secretory granules near the plasma membrane in live beta-cells exposed for 24 h to interleukin (IL)-1beta or interferon (IFN)-gamma. Immunohistochemistry observed via TIRFM showed that the number of docked insulin granules was decreased by 60% in beta-cells treated with IL-1beta, while it was not affected by exposure to IFN-gamma. This effect of IL-1beta was paralleled by a 50% reduction in the mRNA and the number of clusters of SNAP-25 in the plasma membrane. TIRF images of single insulin granule motion during a 15-min stimulation by 22 mm glucose in IL-1beta-treated beta-cells showed a marked reduction in the fusion events from previously docked granules during the first phase insulin release. Fusion from newcomers, however, was well preserved during the second phase of insulin release of IL-1beta-treated beta-cells. The present observations indicate that IL-1beta, but not IFN-gamma, has a preferential inhibitory effect on the first phase of glucose-induced insulin release, mostly via an action on previously docked granules. This suggests that beta-cell exposure to immune mediators during the course of insulitis might be responsible for the loss of first phase insulin release.

The use of monoclonal antibodies to restore self-tolerance in established autoimmunity

The author hopes to convince the reader that the data presented argue for a stage during the development of IDDM when beta-cell destruction can be counteracted and tolerance to beta cells restored, provided the immune aggression is arrested. This argument constitutes a solid rationale for immunointervention in established IDDM, especially by using potent agents such as CD3. The future for the application of monoclonal antibodies not only in autoimmunity but also in transplantation is exiting. With the development of humanized monoclonal antibodies, therapeutic uses for them are likely to expand. Enormous progress has been made in the last 15 years, and it is likely that before a similar time period has elapsed, monoclonal antibodies will have become standard tools that will dispense the need for long-term immunosuppression and its inherent dangers in various clinical arenas.

Long-term reversal of established autoimmunity upon transient blockade of the LFA-1/intercellular adhesion molecule-1 pathway

Transgenic models and administration of mAbs directed against the LFA-1/intercellular adhesion molecule 1 (ICAM-1) pathway have shown that these costimulatory molecules play a key role in generating effector cells mediating inflammatory responses. In this report, durable remission of recent diabetes in nonobese diabetic (NOD) mice was induced by transient expression of an immunoadhesin gene encoding the soluble form of ICAM-1 (sICAM-1/Ig). A single i.v. injection of an adenovirus vector encoding the immunoadhesin gene led to 70% diabetes remission as opposed to 0% in mice injected with a control adenovirus vector. Despite the rapid decline of sICAM-1/Ig serum levels, diabetes remission remained stable in 50% of NOD mice for >6 mo. sICAM-1/Ig expression also led to long-term protection against diabetes in prediabetic NOD mice. sICAM-1/Ig in vitro induced an agonistic effect of T cell activation in a TCR-transgenic model, increasing T cell proliferation and IL-2 secretion. Importantly, protected mice were not immunosuppressed because they rejected skin allografts normally and developed immunity against the adenovirus vector. Rather, sICAM-1/Ig induced active tolerance, as assessed by the persistence of diabetogenic T cells in protected mice and the reversal of protection by immunosuppression with cyclophosphamide.

Nonmitogenic CD3 antibody reverses virally induced (rat insulin promoter-lymphocytic choriomeningitis virus) autoimmune diabetes without impeding viral clearance

Treatment with nonmitogenic CD3 Ab reverses established autoimmune diabetes in nonobese diabetic mice by restoring self-tolerance, and is currently under clinical evaluation in patients presenting recent onset type I diabetes. Due to the immunosuppressive potential of this strategy, it was relevant to explore how this treatment would influence the outcome of concomitant viral infections. In this study, we used a transgenic model of virally induced autoimmune diabetes (rat insulin promoter-lymphocytic choriomeningitis virus) that allows for more precise tracking of the autoaggressive response and choice of the time point for initiation of autoimmunity. CD3 was most effective during a clearly defined prediabetic phase and prevented up to 100% of diabetes by drastically lowering activation of autoaggressive CD8 lymphocytes and their production of inflammatory cytokines. Interestingly, reversion of established disease could be achieved as well, when nonmitogenic CD3 was administered late during pathogenesis to overtly diabetic recipients. Most importantly, competence to clear viral infections was maintained. Thus, administration of nonmitogenic CD3 prevents diabetes by sufficient systemic reduction of (auto)aggressive lymphocytes, but without compromising antiviral immune competence.

Identification of novel cytokine-induced genes in pancreatic beta-cells by high-density oligonucleotide arrays

Type 1 diabetes is an autoimmune disease resulting from the selective destruction of insulin-producing beta-cells. Cytokines may contribute to pancreatic beta-cell death in type 1 diabetes. beta-cell exposure to interleukin (IL)-1beta induces functional impairment, whereas beta-cell culture for 6-9 days in the presence of IL-1beta and interferon (INF)-gamma leads to apoptosis. To clarify the mechanisms involved in these effects of cytokines, we studied the general pattern of cytokine-induced gene expression in beta-cells. Primary rat beta-cells were fluorescence-activated cell sorter-purified and exposed for 6 or 24 h to control condition, IL-1beta + INF-gamma, or IL-1beta alone (24 h only). Gene expression profile was analyzed in duplicate by oligonucleotide arrays. Nearly 3,000 transcripts were detected in controls and cytokine-treated beta-cells. Of these, 96 and 147 displayed changes in expression after 6 and 24 h, respectively, of exposure to IL-1beta + INF-gamma, whereas 105 transcripts were modified after a 24-h exposure to IL-1beta. The cytokine-responsive genes were clustered according to their biological functions. The major clusters observed were metabolism, signal transduction, transcription factors, protein synthesis/ processing, hormones, and related receptors. These modifications in gene expression may explain some of the cytokine effects in beta-cells, such as decreased protein biosynthesis and insulin release. In addition, there was induction of diverse cytokines and chemokines; this suggests that beta-cells may contribute to mononuclear cell homing during insulitis. Several of the cytokine-induced genes are potentially regulated by the transcription factor NF-kappaB. Clarification of the function of the identified cytokine-induced gene patterns may unveil some of the mechanisms involved in beta-cell damage and repair in type 1 diabetes.

Pathophysiology of impaired pulsatile insulin release

Plasma insulin displays 5-10 min oscillations. In Type 2 diabetes the regularity of the oscillations disappears, which may lead to insulin receptor down-regulation and glucose intolerance and explain why pulsatile delivery of the hormone has a greater hypoglycemic effect than continuous delivery. The rhythm is intrinsic to the islet. Variations in metabolism, cytoplasmic Ca(2+) concentration ([Ca(2+)](i)), other hormones, neuronal signaling and possibly beta-cell insulin receptor expression have been implicated in the regulation of plasma insulin oscillations. Most of these factors are important for amplitude-regulation of the insulin pulses. Although evidence exists supporting a role of both metabolism and [Ca(2+)](i) as pacemakers of the pulses, metabolic oscillations probably have a primary role and [Ca(2+)](i) oscillations a permissive role. Results from islets from animal models of diabetes suggest that altered plasma insulin pattern could be due to lowering of pulse amplitude of insulin oscillations rather than alterations in their frequency. Supporting a role of metabolism, altered plasma insulin oscillations were found in MODY2, MIDD and glycogenosis Type VII, which are linked to alterations in glucokinase, mitochondrial tRNALeu(UUR) and phosphofructokinase. Plasma insulin oscillations require coordination of islet secretory activities in the pancreas. The intrapancreatic ganglia have been suggested as coordinators. The diabetes-associated neuropathy may contribute to the deranged pattern as indicated by glucose intolerance in chagasic patients. Continued investigation of the role and regulation of pulsatile insulin release will lead to better understanding of the pathophysiology of impaired pulsatile insulin release, which could lead to new approaches to restore normal plasma insulin oscillations in diabetes and related diseases.

Beta-cell activity and destruction in type 1 diabetes

Type 1 diabetes is the result of a chronic inflammatory process that causes elimination of insulin-producing beta-cells, resulting in insulin deficiency and hyperglycemia. The destruction is thought to be mediated by an autoimmune process involving cytotoxic T cells recognizing beta-cell autoantigens in the context of MHC class I-peptide complexes. Autoantibodies against insulin, glutamic acid decarboxylase (GAD) and and ICA 512 protein tyrosine phosphatase are frequently found. At the clinical onset of diabetes, some beta-cells remain and after initiation of insulin treatment, most patients enter a period of remission, a phenomenon that may reflect diminished autoimmune activity in the islets. There is evidence to suggest that a further loss of beta-cells can be curtailed, and that patients, who maintain endogenous insulin production, have better glycemic control and less risk of complications. This is the basis for our current research. We are characterizing the remission phenomenon in epidemiological studies in order to identify determinants of beta-cell survival. In randomized, prospective multicenter trials, we are evaluating the benefit of beta-cell secretory rest for rescue of insulin production in patients at onset of clinical disease. In experimental studies, we are investigating expression and regulation of the key molecules of an autoimmune process in the islets. Further, selective beta-cell damage is induced in rat islets and measures to enhance beta-cell resistance and repair are being examined. We have recently identified a remarkable, beta-cell protective effect of K(ATP)-channel opening.

Novel experimental strategies to prevent the development of type 1 diabetes mellitus

Type 1 diabetes is an autoimmune disease leading to extensive destruction of the pancreatic beta-cells. Our research focusses on the role of beta-cells during the course of the disease, aiming at finding novel strategies to enhance beta-cell resistance against the cytotoxic damage inflicted by the immune system. Special attention has been paid to the possibility that cytokines released by the immune cells infiltrating the pancreatic islets can directly suppress and kill beta-cells. Certain cytokines (interleukin-1beta, tumor necrosis factor-alpha and interferon-gamma) either alone or in combination, are able to activate signal transduction pathways in beta-cells leading to transcription factor activation and de novo gene expression. In this context, it has been found that induction of inducible nitric oxide synthase mediates an elevated production of nitric oxide, which impairs mitochondrial function and causes DNA damage eventually leading to apoptosis and necrosis. However, other induced proteins SUCH AS heat shock protein 70 and superoxide dismutase may reflect a defense reaction elicited in the beta-cells by the cytokines. Our strategy is to further seek for proteins involved in both destruction and protection of beta-cells. Based on this knowledge, we plan to apply gene therapeutic approaches to increase expression of protective genes in beta-cells. If this is feasible we will then evaluate the function and survival of such modified beta-cells in animal models of type 1 diabetes such as the NOD mouse. The long-term goal for this research line is to find novel approaches to influence beta-cell resistance in humans at risk of developing type 1 diabetes.

Preserved pulsatile insulin release from prediabetic mouse islets

During the development of type I diabetes, the plasma insulin pattern changes. Because the islet secretory pattern has been implicated in this phenomenon, insulin release was measured from female nonobese diabetic (NOD) mouse islets isolated at different ages. Islets from 5-week-old mice were used as controls because they had no infiltrating mononuclear cells and insulin release rose almost 9-fold with maintained oscillatory frequency when the glucose concentration was raised from 3 to 11 mM. Islets isolated from 13- and 25-week-old mice were infiltrated with mononuclear cells. In these islets, increase in the glucose concentration from 3 to 11 mM only doubled insulin release. However, despite the cellular infiltration, insulin release was pulsatile. Islets from 13-week-old mice had reduced glucose oxidation rate. Culture of such islets for 7 days at 11.1 mM glucose causes a decrease in the number of mononuclear cells infiltrating the islets, which in the present study was accompanied by a normalization of both glucose oxidation and glucose-induced insulin release. In the presence of the mitochondrial substrate alpha-keto-isocaproate (5 mM) both control and infiltrated islets responded with pronounced insulin pulses with similar amplitudes. The results suggest that the deranged plasma insulin pattern observed during the development of type I diabetes may be related to decrease in the insulin pulse amplitude rather than loss of the pulsatile release from the islets.

Islet amyloid polypeptide (IAPP) secretion from pancreatic islets isolated from non-obese diabetic (NOD) mice

The secretion of islet amyloid polypeptide (IAPP) during the course of insulin-dependent diabetes mellitus (IDDM) is essentially unknown. In the present study we elucidated this issue by examining IAPP and insulin secretion from isolated pancreatic islets obtained from IDDM-prone female NOD mice aged 6-9 weeks and 12-15 weeks and from non-IDDM-prone male NMRI mice. Basal islet hormone secretion at 1.7 mM glucose and after stimulation with 17 mM glucose or with 17 mM glucose + 5 mM theophylline was studied acutely or after 1 week of tissue culture. The levels of glucose-stimulated insulin release from NOD mouse islets increased after tissue culture, whereas it remained unchanged in NMRI mouse islets. Overall changes in islet insulin secretion were accompanied by similar changes in IAPP secretion. Acute after isolation, islets from NMRI mice displayed a reduced IAPP/insulin secretion ratio in response to the stimulation, which could reflect a destabilized hormone release. When the NOD mouse islets at 6-9 weeks of age were exposed to secretory stimuli the molar ratio of IAPP/insulin secretion declined. At a later stage of advanced insulitis (12-15 weeks) also the basal IAPP/insulin secretory ratio at low glucose tended to decline. If extrapolated to the early prediabetic phase of human IDDM, this would mean that a relative hypersecretion of insulin in relation to IAPP might occur, due to an increased secretory demand for insulin or due to an intrinsic change in the biology of the secretory cells.

Comparison of mRNA contents of interleukin-1 beta and nitric oxide synthase in pancreatic islets isolated from female and male nonobese diabetic mice

Interleukin-1 beta (IL-1 beta) has been suggested to mediate beta-cell destruction in insulin-dependent diabetes mellitus (IDDM) by inducing nitric oxide production. In this study, we assessed the levels of IL-1 beta and the inducible form of nitric oxide synthase (iNOS), using a semi-quantitative polymerase chain reaction assay, and performed determinations of nitrite accumulation and IL-1 beta bioactivity, on pancreatic islets isolated from 5- and 16-week-old female and male nonobese diabetic (NOD) mice and from nondiabetes prone NMRI mice. NOD mouse islets contained notable amounts of IL-1 beta mRNA. At 5 weeks of age, but not at 16 weeks, the values were higher in islets isolated from NOD females compared to males. The IL-1 beta bioactivity showed differences roughly reflecting the mRNA levels in the NOD mouse islets. In the NMRI mouse islets the IL-1 beta bioactivity was very low. The expression of iNOS mRNA increased in both male and female islets between 5 and 16 weeks of age. Immunocytochemistry of pancreatic sections indicated the presence of macrophages especially in the peri-insular area of the NOD mice which suggests that IL-1 beta was produced by macrophages. The levels of IL-1 beta activity and mRNA in freshly isolated islets from NOD 5-weeks-old females did not correlate to the iNOS mRNA content or to the nitrite production. However, after incubation with IL-1 beta in vitro, both NOD and NMRI islets responded with a marked increase in nitric oxide production.(ABSTRACT TRUNCATED AT 250 WORDS)

Age-dependent sensitivity to streptozotocin of pancreatic islets isolated from female NOD mice

Streptozotocin (STZ), a selective beta-cell cytotoxin, given in multiple low doses to susceptible mouse strains causes insulin-dependent diabetes mellitus (IDDM) with an autoimmune pathology. Studies in the human suggest that environmental factors such as viruses and certain toxins may modulate the expression of the disease in genetically-prone individuals and the effect may also be age-dependent. Here we have examined the effects of graded, low doses of STZ on beta-cell function and insulin and DNA contents in vitro in cultured islets isolated from female IDDM-prone NOD mice at 4 weeks and at 8 weeks. Results were compared with islets from age and sex-matched non-diabetes prone C57BL/Ks mice. No changes in islet DNA or insulin contents were observed after an acute 30 min exposure to STZ (0, 1.1, 2.2 and 4.4 mM) in the two strains at each of the age groups. However, the DNA content in the NOD mouse islets tended to be lower at 8 weeks, being significant at 1.1 mM STZ. At 4 weeks, islets from NOD mice had a higher insulin content than the control mice but this declined at 8 weeks when it became comparable to the control strain. STZ caused a dose-dependent inhibition of islet glucose oxidation rates in all groups. However, at 4 weeks, exposure to 2.2 mM STZ resulted in a significantly greater inhibition in NOD mice than in age-matched control mice. This was reversed at 8 weeks when the islets from NOD mice showed a greater resistance to oxidative impairment than from C57BL/Ks mice. In the presence of 16.7 mM glucose, an inhibitory pattern, similar to the glucose oxidation rate, was also observed for insulin release. In the control mice the relative inhibition of insulin release and glucose oxidation rate was similar at 4 and 8 weeks. These results suggest that islets from the NOD mouse at 4 weeks and prior to insulitis are more sensitive to STZ-induced functional impairment. This enhanced sensitivity suggests that cumulative exposure of diabetes-prone islets to low doses of selective beta cell toxins may be a determinant for later development of IDDM.

Histological study of pancreatic beta-cell loss in relation to the insulitis process in the non-obese diabetic mouse

Non-obese diabetic (NOD) mice spontaneously develop an autoimmune diabetes with higher incidence in females than in males. In order to elucidate possible factors involved in the different incidence of diabetes between male and female mice, we studied the progression of pancreatic beta-cell loss in relation to mononuclear cell infiltration of the pancreas (insulitis). We examined the pancreas of 76 NOD mice (39 males and 37 females) of different ages. The beta-cell content was assessed by immunoperoxidase staining of sections with an anti-insulin serum and the severity of insulitis was determined by haematoxylin staining of the same sections. A semi-quantitative criterion was used to grade both parameters. The results showed that females have a faster loss of beta-cell mass, which progressively decreases with the increase of severity of insulitis. In males, a medium to severe degree of insulitis is required before initial loss of beta cells occurs. Under the age of 10 weeks there was a significantly lower content of beta cells in females than males (2.84 +/- 0.03 vs 2.67 +/- 0.07; P = 0.02). Since we never observed a significant difference in the degree of mononuclear cell infiltration in age-matched males and females, these data support the hypothesis of weaker beta-cell resistance to immunological attack in female mice. Thus beta-cell sensitivity, in addition to immunological activity, is an important factor in the pathogenesis of insulin dependent diabetes.

Human autoantibodies react with glutamic acid decarboxylase antigen in human and rat but not in mouse pancreatic islets

The presence of one of the major targets for autoantibodies in Type 1 (insulin-dependent) diabetes mellitus, the enzyme glutamic acid decarboxylase, was studied in human, rat and mouse pancreatic tissue using immunoprecipitation and immunohistochemical techniques. Immunoprecipitation of glutamic acid decarboxylase was attempted with lysates of [35S]-methionine-labelled rat or mouse pancreatic islets using two different glutamic acid decarboxylase antisera, one mouse monoclonal antibody raised against the 65 kDa isoform of the enzyme, sera from six patients with Type 1 diabetes, one patient with stiff-man syndrome and sera from 19 non-obese diabetic mice. The same sera were used for immunoperoxidase staining of cryosections of human, rat or mouse pancreas. Using patient sera glutamic acid decarboxylase was detected by immunoprecipitations from isolated rat islets but not from islets of five different mouse strains tested, including the non-obese diabetic mouse. When using the non-obese diabetic mouse sera, glutamic acid decarboxylase could not be detected in either rat or mouse tissue. Immunoperoxidase staining demonstrated high levels of glutamic acid decarboxylase in human and rat pancreatic islets but low levels in mouse islets. Direct measurements of enzyme activity showed glutamic acid decarboxylase to be present in mouse islets at a level of about 40% of that in rat islets, and subsequent Western blot analyses indicated that mouse islets express the 67 kDa isoform, whereas as in rat islets both the 67 and 65 kDa isoforms are present.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of infiltrating T cells for impaired glucose metabolism in pancreatic islets isolated from non-obese diabetic mice

Pancreatic islets isolated from non-obese diabetic (NOD) mice, all of which have insulitis, exhibit an impaired glucose metabolism. In order to investigate the role of infiltrating lymphocytes for this altered metabolism, we injected 12- to 13-week-old female NOD mice with monoclonal antibodies directed against either the alpha beta-T cell receptor, CD4+ or CD8+ T cells. Control NOD mice were injected with normal rat IgG or with the vehicle (phosphate buffered saline) alone. Injection of the three different monoclonal antibodies markedly reduced the mononuclear cell infiltration. An intravenous glucose tolerance test showed no differences between the groups. Islet insulin release in response to glucose was similar in all groups. In contrast, islets isolated from the control NOD mice with insulitis showed a high basal (1.7 mmol/l glucose) glucose oxidation rate and a small increase in the glucose oxidation rate in response to a high glucose concentration (16.7 mmol/l glucose). The monoclonal antibodies counteracted the elevated basal glucose oxidation rate of the islets. Parallel studies of stimulated mononuclear cells suggested that the contribution of glucose oxidized by islet-infiltrating lymphocytes could only partially explain the observed alterations in NOD mouse islet metabolism. Culture of islets obtained from NOD mice in the presence of the cytokine interleukin-1 beta induced a similar pattern of glucose metabolism as seen earlier in IgG or phosphate-buffered saline treated control NOD mice. In conclusion, alterations in the glucose oxidation rates seem to be an early sign of disturbance in islets isolated from NOD mice. These early alterations in glucose metabolism can be reversed in vivo by monoclonal antibodies directed against effector lymphocytes.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptive response in beta-cell function in pancreatic islets isolated from partially pancreatectomized rats

Before clinical onset of insulin-dependent diabetes mellitus a decreasing pancreatic beta-cell mass maintains glucose homeostasis. We currently aimed to study the function of pancreatic islets isolated 2 weeks after a 60% partial pancreatectomy (P) or after a sham operation (S) on adult rats. Experiments on the islets were subsequently performed acutely (day 0) and after 1 week (day 7) of tissue culture in medium RPMI 1640 (11.1 mM glucose) + 10% calf serum. There was no difference in the body weight 2 weeks after surgery. The pancreatic remnant weight of the P rats was 35% less than the pancreatic weight in the S rats. The islet DNA content was 25% higher in the islets of the P rats on day 0, indicating a stimulated islet growth. However, this difference did not remain after culture for 7 days. Islet proinsulin mRNA content and (pro)insulin biosynthesis rates were slightly increased in the islets of P rats on day 0, which could be due to the increased islet mass. The islet insulin content was not different on day 0, but was higher after culture in the islets of the P rats. The islet rates of glucose oxidation and insulin release were markedly higher in the P rats on day 0, suggesting a selective effect on these processes. A higher glucose oxidation rate was, however, not evident on day 7. The relative fraction of insulin-positive cells was slightly lowered in the islets of the P rats on day 0.(ABSTRACT TRUNCATED AT 250 WORDS)

First phase insulin release in the non-obese diabetic mouse: correlation with insulitis, beta cell number and autoantibodies

The ontogenic variation of beta cell function and its relationship with the degree of islet damage and levels of autoantibodies have been studied in the non-obese diabetic (NOD) mouse model. We conducted in vivo first phase insulin release (FPIR) in response to intravenous glucose and studied its correlation with the degree of insulitis, islet cell antibody (ICA) and insulin autoantibody (IAA) levels in female NOD mice cross-sectionally at days 40 (n = 19), 90 (n = 21), 150-160 (n = 21) and day 250 (n = 20). The mean +/- SEM FPIR values showed an age-related decline from day 40 (46.2 +/- 5.3 microU/ml) to day 150-160 (17.8 +/- 2.5 microU/ml) and then doubled at day 250 (34.5 +/- 5 microU/ml), while the mean +/- SEM insulitis scores increased progressively until day 150-160 (61.7 +/- 6.1%) and then declined slightly at day 250 to 50.2 +/- 6.2%. In female NOD mice with spontaneous diabetes (n = 4) and streptozotocin-induced diabetic Swiss mice (n = 5) FPIR was either absent or greatly attenuated. A statistically significant inverse correlation between FPIR and insulitis was found among NOD mice at days 90 (P = 0.02; r = -0.52) and 150-160 (P = 0.03; r = -0.48). However, no statistically significant correlation was observed at days 40 and 250. Morphometric techniques applied to day 150-160 pancreatic sections showed a statistically significant negative correlation between insulitis and beta cell number per unit area of islet tissue (P = 0.0001; r = - 0.75). At this age some islet beta cells showed different intensities of staining by immunofluorescence.(ABSTRACT TRUNCATED AT 250 WORDS)

Protection against hyperglycemia in female nonobese diabetic mice treated with 15-deoxyspergualin

The effects of 15-deoxyspergualin (15-DS), a newly described immunosuppressive agent, have been studied on the development of diabetes in female NOD mice. 15-DS treatment was started two weeks after weaning i.e. at five weeks of age. The mice received either one daily intraperitoneal injection of 15-DS (2.5 mg/kg body weight) or saline for two weeks. The mice were then injected every third day up to eight months of age for evaluation of the diabetes incidence. In another set of experiments the mice were treated up to three months of age, whereafter islet insulin release, islet insulin content and DNA content was measured together with an evaluation of spleen cell proliferation rates. Different spleen cell subsets were studied directly after the two weeks of daily injections. In the saline group 8 out of 9 mice developed diabetes, whereas only 4 out of 11 of the 15-DS treated mice became diabetic (p < 0.05). There was no difference between the groups in islet insulin release in response to glucose, however, the islet insulin release increased after one week in culture. The 15-DS treatment did not affect the insulin or DNA content of the isolated islets or the insulin concentration in the pancreas. No detectable changes in the relative number of CD4+ and CD8+ T-cell subsets in the spleen were seen and there were no obvious differences in splenocyte proliferation rates. The histological examinations of the pancreatic glands showed gradual increasing signs of islet inflammation with age and 15-DS could apparently not prevent this.(ABSTRACT TRUNCATED AT 250 WORDS)

Anti-alpha/beta T cell receptor monoclonal antibody provides an efficient therapy for autoimmune diabetes in nonobese diabetic (NOD) mice

The nonobese diabetic (NOD) mouse is a relevant model for studying human insulin-dependent diabetes mellitus (IDDM). The selective destruction of insulin-secreting cells in this model is subsequent to an autoimmune reaction directed towards the beta cells inside the islets of Langerhans of the pancreas. Given the key role played by T cells in the development of IDDM, we investigated a model of IDDM prevention in NOD mice by administration of a monoclonal antibody to the alpha/beta dimer of the T cell receptor for antigen. Our data provide evidence that aiming at the T cell receptor protects against both spontaneous and cyclophosphamide-induced diabetes in the NOD mouse. Interestingly, potential clinical application is suggested by the efficient and durable reversal of recent onset diabetes in mice treated with anti-alpha/beta monoclonal antibody within 1 week following the clinical discovery of IDDM.