Pathogenic mechanisms in type 1 diabetes: the islet is both target and driver of disease

Pathological mechanisms of type 1 diabetes in children: investigation of the exosomal protein expression profile

Introduction

Type 1 diabetes (T1D) is a serious autoimmune disease with high morbidity and mortality. Early diagnosis and treatment remain unsatisfactory. While the potential for development of T1D biomarkers in circulating exosomes has attracted interest, progress has been limited. This study endeavors to explore the molecular dynamics of plasma exosome proteins in pediatric T1D patients and potential mechanisms correlated with T1D progression.

Methods

Liquid chromatography-tandem mass spectrometry with tandem mass tag (TMT)6 labeling was used to quantify exosomal protein expression profiles in 12 healthy controls and 24 T1D patients stratified by age (≤ 6 years old and > 6 years old) and glycated hemoglobin (HbA1c) levels (> 7% or > 7%). Integrated bioinformatics analysis was employed to decipher the functions of differentially expressed proteins, and Western blotting was used for validation of selected proteins' expression levels.

Results

We identified 1035 differentially expressed proteins (fold change > 1.3) between the T1D patients and healthy controls: 558 in those ≤ 6-year-old and 588 in those > 6-year-old. In those who reached an HbA1c level < 7% following 3 or more months of insulin therapy, the expression levels of most altered proteins in both T1D age groups returned to levels comparable to those in the healthy control group. Bioinformatics analysis revealed that differentially expressed exosome proteins are primarily related to immune function, hemostasis, cellular stress responses, and matrix organization. Western blotting confirmed the alterations in RAB40A, SEMA6D, COL6A5, and TTR proteins.

Discussion

This study delivers valuable insights into the fundamental molecular mechanisms contributing to T1D pathology. Moreover, it proposes potential therapeutic targets for improved T1D management.

Particle-Based therapies for antigen specific treatment of type 1 diabetes

Type 1 diabetes mellitus (T1D) is the leading metabolic disorder in children worldwide. Over time, incidence rates have continued to rise with 20 million individuals affected globally by the autoimmune disease. The current standard of care is costly and time-consuming requiring daily injections of exogenous insulin. T1D is mediated by autoimmune effector responses targeting autoantigens expressed on pancreatic islet β-cells. One approach to treat T1D is to skew the immune system away from an effector response by taking an antigen-specific approach to heighten a regulatory response through a therapeutic vaccine. An antigen-specific approach has been shown with soluble agents, but the effects have been limited. Micro or nanoparticles have been used to deliver a variety of therapeutic agents including peptides and immunomodulatory therapies to immune cells. Particle-based systems can be used to deliver cargo into the cell and microparticles can passively target phagocytic cells. Further, surface modification and controlled release of encapsulated cargo can enhance delivery over soluble agents. The induction of antigen-specific immune tolerance is imperative for the treatment of autoimmune diseases such as T1D. This review highlights studies that utilize particle-based platforms for the treatment of T1D.

The future treatment for type 1 diabetes: Pig islet- or stem cell-derived β cells?

Replacement of β cells is only a curative approach for type 1 diabetes (T1D) patients to avoid the threat of iatrogenic hypoglycemia. In this pursuit, islet allotransplantation under Edmonton's protocol emerged as a medical miracle to attain hypoglycemia-free insulin independence in T1D. Shortage of allo-islet donors and post-transplantation (post-tx) islet loss are still unmet hurdles for the widespread application of this therapeutic regimen. The long-term survival and effective insulin independence in preclinical studies have strongly suggested pig islets to cure overt hyperglycemia. Importantly, CRISPR-Cas9 technology is pursuing to develop "humanized" pig islets that could overcome the lifelong immunosuppression drug regimen. Lately, induced pluripotent stem cell (iPSC)-derived β cell approaches are also gaining momentum and may hold promise to yield a significant supply of insulin-producing cells. Theoretically, personalized β cells derived from a patient's iPSCs is one exciting approach, but β cell-specific immunity in T1D recipients would still be a challenge. In this context, encapsulation studies on both pig islet as well as iPSC-β cells were found promising and rendered long-term survival in mice. Oxygen tension and blood vessel growth within the capsules are a few of the hurdles that need to be addressed. In conclusion, challenges associated with both procedures, xenotransplantation (of pig-derived islets) and stem cell transplantation, are required to be cautiously resolved before their clinical application.

Liraglutide protects β-cells in novel human islet spheroid models of type 1 diabetes

To enable accurate, high-throughput and longer-term studies of the immunopathogenesis of type 1 diabetes (T1D), we established three in-vitro islet-immune injury models by culturing spheroids derived from primary human islets with proinflammatory cytokines, activated peripheral blood mononuclear cells or HLA-A2-restricted preproinsulin-specific cytotoxic T lymphocytes. In all models, β-cell function declined as manifested by increased basal and decreased glucose-stimulated insulin release (GSIS), and decreased intracellular insulin content. Additional hallmarks of T1D progression such as loss of the first-phase insulin response (FFIR), increased proinsulin-to-insulin ratios, HLA-class I expression, and inflammatory cytokine release were also observed. Using these models, we show that liraglutide, a glucagon-like peptide 1 receptor agonist, prevented loss of GSIS under T1D-relevant stress, by preserving the FFIR and decreasing immune cell infiltration and cytokine secretion. Our results corroborate that liraglutide mediates an anti-inflammatory effect that aids in protecting β-cells from the immune-mediated attack that leads to T1D.

Investigating the efficacy of baricitinib in new onset type 1 diabetes mellitus (BANDIT)—study protocol for a phase 2, randomized, placebo controlled trial

Background

Type 1 diabetes (T1D) places an extraordinary burden on individuals and their families, as well as on the healthcare system. Despite recent advances in glucose sensors and insulin pump technology, only a minority of patients meet their glucose targets and face the risk of both acute and long-term complications, some of which are life-threatening.

The JAK-STAT pathway is critical for the immune-mediated pancreatic beta cell destruction in T1D. Our pre-clinical data show that inhibitors of JAK1/JAK2 prevent diabetes and reverse newly diagnosed diabetes in the T1D non-obese diabetic mouse model. The goal of this study is to determine if the JAK1/JAK2 inhibitor baricitinib impairs type 1 diabetes autoimmunity and preserves beta cell function.

Methods

This will be as a multicentre, two-arm, double-blind, placebo-controlled randomized trial in individuals aged 10–30 years with recent-onset T1D. Eighty-three participants will be randomized in a 2:1 ratio within 100 days of diagnosis to receive either baricitinib 4mg/day or placebo for 48 weeks and then monitored for a further 48 weeks after stopping study drug. The primary outcome is the plasma C-peptide 2h area under the curve following ingestion of a mixed meal. Secondary outcomes include HbA1c, insulin dose, continuous glucose profile and adverse events. Mechanistic assessments will characterize general and diabetes-specific immune responses.

Discussion

This study will determine if baricitinib slows the progressive, immune-mediated loss of beta cell function that occurs after clinical presentation of T1D. Preservation of beta cell function would be expected to improve glucose control and prevent diabetes complications, and justify additional trials of baricitinib combined with other therapies and of its use in at-risk populations to prevent T1D.

Trial registration

ANZCTR ACTRN12620000239965. Registered on 26 February 2020. ClinicalTrials.gov NCT04774224. Registered on 01 March 2021

Endosomal Sequestration of TLR4 Antibody Induces Myeloid-Derived Suppressor Cells and Reverses Acute Type 1 Diabetes

We previously showed that treating NOD mice with an agonistic monoclonal anti-TLR4/MD2 antibody (TLR4-Ab) reversed acute type 1 diabetes (T1D). Here, we show that TLR4-Ab reverses T1D by induction of myeloid-derived suppressor cells (MDSCs). Unbiased gene expression analysis after TLR4-Ab treatment demonstrated upregulation of genes associated with CD11b+Ly6G+ myeloid cells and downregulation of T-cell genes. Further RNA sequencing of purified, TLR4-Ab-treated CD11b+ cells showed significant upregulation of genes associated with bone marrow-derived CD11b+ cells and innate immune system genes. TLR4-Ab significantly increased percentages and numbers of CD11b+ cells. TLR4-Ab-induced CD11b+ cells, derived ex vivo from TLR4-Ab-treated mice, suppress T cells, and TLR4-Ab-conditioned bone marrow cells suppress acute T1D when transferred into acutely diabetic mice. Thus, the TLR4-Ab-induced CD11b+ cells, by the currently accepted definition, are MDSCs able to reverse T1D. To understand the TLR4-Ab mechanism, we compared TLR4-Ab with TLR4 agonist lipopolysaccharide (LPS), which cannot reverse T1D. TLR4-Ab remains sequestered at least 48 times longer than LPS within early endosomes, alters TLR4 signaling, and downregulates inflammatory genes and proteins, including nuclear factor-κB. TLR4-Ab in the endosome, therefore, induces a sustained, attenuated inflammatory response, providing an ideal "second signal" for the activation/maturation of MDSCs that can reverse acute T1D.

Mistaken Identity: The Role of Autoantibodies in Endocrine Disease

BACKGROUND

Autoimmune endocrine diseases can be thought of as a case of mistaken identity. The immune system mistakenly attacks one's own cells, as if they were foreign, which typically results in endocrine gland hypofunction and inadequate hormone production. Type 1 diabetes mellitus and autoimmune thyroid disorders (Hashimoto and Graves diseases) are the most common autoimmune endocrine disorders, while conditions such as Addison disease are encountered less frequently. Autoantibody production can precede clinical presentation, and their measurement may aid verification of an autoimmune process and guide appropriate treatment modalities.

CONTENT

In this review, we discuss type 1 diabetes mellitus, autoimmune thyroid disorders, and Addison disease, emphasizing their associated autoantibodies and methods for clinical detection. We will also discuss efforts to standardize measurement of autoantibodies.

CONCLUSIONS

Autoimmune endocrine disease progression may take months to years and detection of associated autoantibodies may precede clinical onset of disease. Although detection of autoantibodies is not necessary for diagnosis, they may be useful to verify an autoimmune process.

Hybrid computational modeling demonstrates the utility of simulating complex cellular networks in type 1 diabetes

Persistent destruction of pancreatic β-cells in type 1 diabetes (T1D) results from multifaceted pancreatic cellular interactions in various phase progressions. Owing to the inherent heterogeneity of coupled nonlinear systems, computational modeling based on T1D etiology help achieve a systematic understanding of biological processes and T1D health outcomes. The main challenge is to design such a reliable framework to analyze the highly orchestrated biology of T1D based on the knowledge of cellular networks and biological parameters. We constructed a novel hybrid in-silico computational model to unravel T1D onset, progression, and prevention in a non-obese-diabetic mouse model. The computational approach that integrates mathematical modeling, agent-based modeling, and advanced statistical methods allows for modeling key biological parameters and time-dependent spatial networks of cell behaviors. By integrating interactions between multiple cell types, model results captured the individual-specific dynamics of T1D progression and were validated against experimental data for the number of infiltrating CD8+T-cells. Our simulation results uncovered the correlation between five auto-destructive mechanisms identifying a combination of potential therapeutic strategies: the average lifespan of cytotoxic CD8+T-cells in islets; the initial number of apoptotic β-cells; recruitment rate of dendritic-cells (DCs); binding sites on DCs for naïve CD8+T-cells; and time required for DCs movement. Results from therapy-directed simulations further suggest the efficacy of proposed therapeutic strategies depends upon the type and time of administering therapy interventions and the administered amount of therapeutic dose. Our findings show modeling immunogenicity that underlies autoimmune T1D and identifying autoantigens that serve as potential biomarkers are two pressing parameters to predict disease onset and progression.

Vitamin D pathway gene polymorphisms, vitamin D level, and cytokines in children with type 1 diabetes

AIMS

The study aimed to examine genetic polymorphism of vitamin D-related genes and association between those genes and vitamin D and cytokines levels in children with type 1 diabetes (T1D).

MATERIALS AND METHODS

This study was conducted among 100 T1D children and 100 controls at Division of Endocrinology and Metabolism, Department of Pediatrics, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand, during 2016 to 2018. Vitamin D metabolite levels were measured by liquid chromatography-tandem mass spectrometry method, serum cytokine levels of IFN- ɣ, IL-10, IL-13, IL-17α, IL-2, IL-4, IL-6, and TNF-α by immunoassay, and genetic variations at VDR, CYP2R1, CYP27B1, GC, DHCR7, and CYP24A1 by polymerase chain reaction-restriction fragment length polymorphism method.

RESULTS

A relationship between studied single nucleotide polymorphisms and T1D was found in CYP2R1 (rs10741657) (GA, OR: 1.83, 95% CI: 1.01-3.31; p = 0.04). VDR haplotypes were also remarkably different between T1D patients and controls. Controls had higher frequency of haplotype TACT than T1D patients (p = 0.02). Vitamin D and all cytokine levels, except for IL-17α, were significantly increased in T1D compared to controls. The polymorphism of DHCR7 (rs12785878) was positively associated with 25OHD₃ and 3epi25OHD₃ levels and was negatively associated with 25OHD₂ level. On the other hand, polymorphism of CYP27B1 (rs4646536) was negatively associated with 3epi25OHD₃ level. Polymorphisms of CYP27B1 (rs4646536) and GC (rs2282679) were positively associated with TNF-α levels. VDR variation of rs1544410, rs731236, and rs7975232 also showed negative association with IL-10 levels. In contrast, the level of IL-10 was positively associated with DHCR7 (rs12785878).

CONCLUSION

Relationships between T1D and CYP2R1 polymorphism and VDR haplotype were found. Vitamin D gene-related variations were associated with vitamin D and circulating cytokine levels in children with T1D.

Thymic atrophy creates holes in Treg-mediated immuno-regulation via impairment of an antigen-specific clone

Age-related thymic atrophy results in reduced output of naïve conventional T (Tcon) cells. However, its impact on regulatory T (Treg) cells is insufficiently understood. Given evidence that thymic Treg (tTreg) cell generation is enhanced in the aged, atrophy thymus and that the aged periphery accumulates peripheral Treg (pTreg) cells, we asked why these Treg cells are unable to effectively attenuate increased autoreactivity-induced chronic inflammation in the elderly. We designed a mock-self-antigen chimera mouse model, in which membrane-bound ovalbumin (mOVA) transgenic mice, bearing a FoxN1-floxed gene for induction of conditional thymic atrophy, received OVA-specific (OT-II) T-cell receptor (TCR) transgenic progenitor cells. The chimeric mice with thymic atrophy exhibited a significant decrease in OVA-specific tTreg and pTreg cells but not polyclonal (pan)-Treg cells. These OVA-specific pTreg cells were significantly less able to suppress OVA-specific stimulation-induced proliferation in vitro and exhibited lower FoxP3 expression. Additionally, we conducted preliminary TCR repertoire diversity sequencing for Treg cells among recent thymic emigrants (RTEs) from Rag^GFP -FoxP3^RFP dual-reporter mice and observed a trend for decreased diversity in mice with thymic atrophy compared to littermates with normal thymus. These data indicate that although the effects of age-related thymic atrophy do not affect pan-Treg generation, certain tissue-specific Treg clones may experience abnormal agonist selection. This, combined with enhanced pan-pTreg cells, may greatly contribute to age-related chronic inflammation, even in the absence of acute autoimmune disease in the elderly.

Modeling Type 1 Diabetes Using Pluripotent Stem Cell Technology

Induced pluripotent stem cell (iPSC) technology is increasingly being used to create in vitro models of monogenic human disorders. This is possible because, by and large, the phenotypic consequences of such genetic variants are often confined to a specific and known cell type, and the genetic variants themselves can be clearly identified and controlled for using a standardized genetic background. In contrast, complex conditions such as autoimmune Type 1 diabetes (T1D) have a polygenic inheritance and are subject to diverse environmental influences. Moreover, the potential cell types thought to contribute to disease progression are many and varied. Furthermore, as HLA matching is critical for cell-cell interactions in disease pathogenesis, any model that seeks to test the involvement of particular cell types must take this restriction into account. As such, creation of an in vitro model of T1D will require a system that is cognizant of genetic background and enables the interaction of cells representing multiple lineages to be examined in the context of the relevant environmental disease triggers. In addition, as many of the lineages critical to the development of T1D cannot be easily generated from iPSCs, such models will likely require combinations of cell types derived from in vitro and in vivo sources. In this review we imagine what an ideal in vitro model of T1D might look like and discuss how the required elements could be feasibly assembled using existing technologies. We also examine recent advances towards this goal and discuss potential uses of this technology in contributing to our understanding of the mechanisms underlying this autoimmune condition.

Harnessing CD8+ T-cell exhaustion to treat type 1 diabetes

Although immune interventions have shown great promise in type 1 diabetes mellitus (T1D) clinical trials, none are yet in routine clinical use or able to achieve insulin independence in patients. In addition to this, the principles of T1D treatment remain essentially unchanged since the isolation of insulin, almost a century ago. T1D is characterized by insulin deficiency as a result of destruction of insulin-producing beta cells mediated by autoreactive T cells. Therapies that target beta-cell antigen-specific T cells are needed to prevent T1D. CD8⁺ T-cell exhaustion is an emerging area of research in chronic infection, cancer immunotherapy, and more recently, autoimmunity. Recent data suggest that exhausted T-cell populations are associated with improved markers of T1D. T-cell exhaustion is both characterized and mediated by inhibitory receptors. This review aims to identify which inhibitory receptors may prove useful to induce T-cell exhaustion to treat T1D and identify limitations and gaps in the current literature.

Beta Cell Therapies for Preventing Type 1 Diabetes: From Bench to Bedside

Type 1 diabetes (T1D) is a chronic metabolic disease characterized by insulin deficiency, generally resulting from progressive autoimmune-mediated destruction of pancreatic beta cells. While the phenomenon of beta cell autoimmunity continues to be an active area of investigation, recent evidence suggests that beta cell stress responses are also important contributors to disease onset. Here we review the pathways driving different kinds of beta cell dysfunction and their respective therapeutic targets in the prevention of T1D. We discuss opportunities and important open questions around the effectiveness of beta cell therapies and challenges for clinical utility. We further evaluate ways in which beta cell drug therapy could be combined with immunotherapy for preventing T1D in light of our growing appreciation of disease heterogeneity and patient endotypes. Ultimately, the emergence of pharmacologic beta cell therapies for T1D have armed us with new tools and closing the knowledge gaps in T1D etiology will be essential for maximizing the potential of these approaches.

IL-17F induces inflammation, dysfunction and cell death in mouse islets

Type 17 immune responses, typified by the production of the cytokines IL-17A and IL-17F, have been implicated in the development of type 1 diabetes in animal models and human patients, however the underlying pathogenic mechanisms have not been clearly elucidated. While previous studies show that IL-17A enhances inflammatory gene expression and cell death in mouse β-cells and human islets, the function of IL-17F in pancreatic β-cells is completely untested to date. Here we show that IL-17F exhibits potent pathogenic effects in mouse β-cell lines and islets. IL-17F signals via the IL-17RA and -RC subunits in β-cells and in combination with other inflammatory cytokines induces expression of chemokine transcripts, suppresses the expression of β-cell identity genes and impairs glucose stimulated insulin secretion. Further IL-17F induces cell death in primary mouse islets. This occurs via Jnk, p38 and NF-κB dependent induction of Nos2 and is completely ablated in the presence of an inducible nitric oxide synthase (iNOS) inhibitor. Together these data indicate that IL-17F possesses similar pathogenic activities to IL-17A in mouse β-cell lines and islets and is likely to be a type 17 associated pathogenic factor in type 1 diabetes.

Antidiabetic Potential of Prosopis farcta Roots: In Vitro Pancreatic Beta Cell Protection, Enhancement of Glucose Consumption, and Bioassay-Guided Fractionation

By using the streptozotocin- (STZ-) induced cytotoxicity in β-TC3 cells as an assay model, a bioassay-guided fractionation study was employed to isolate and characterize the potential antidiabetic principles of roots of Prosopis farcta. A combination of open column chromatography on reverse-phase silica gel using a water-ethanol gradient (10 : 90 to 100 : 0) followed by HPLC-based fractionation led to an active compound that appears to be composed of carbohydrate/sugar. When cell viability under STZ was reduced to 49.8 ± 4% (mean ± SD), treatment with the active compound at the concentration of 0.5 mg/mL either as a coadministration or a pretreatment improved the viability to 93 ± 1.9% and 91.5 ± 7%, respectively. The reduction in the mitochondrial membrane potential by STZ (47.34 ± 8.9% of control) was similarly recovered to 84.5 ± 4.3 (coadministration) and 88 ± 5.5% (pretreatment) by the active fraction. The bioassay-guided fractionation, β-cell protective effect, and increased glucose consumption (up to 1.49-fold increase) in hepatocytes by the extracts and active fraction are also discussed.

Aging and stress induced β cell senescence and its implication in diabetes development

Cellular senescence is a well-established defensive mechanism for tumor suppression, and is also proposed to play a crucial role in embryonic development, wound repair, aging and age-related diseases. Senescent cell is characterized by the marked morphological changes and active metabolism along with a distinctive senescence associated secretion phenotype (SASP). Cellular senescence is triggered by multiple endogenous and exogenous stressors, which collectively induce three types of senescence. It is believed that senescence represents a programmed phenomenon to facilitate β cell functional maturation and, therefore, senescence has been suggested to be involved in β cell regeneration, insulin secretion and diabetes development. Nevertheless, despite past extensive studies, the exact impact of senescence on β cell viability, regeneration and functionality, and its relevance to the development of diabetes are yet to be fully addressed. In this review, we will summarize the recent progress in β cell senescence, through which we intend to spark more instructive discussion and perspective with regard to the mechanisms underlying β cell senescence and their links to the pathogenesis of diabetes and the development of therapeutic strategies.

IL-21 regulates SOCS1 expression in autoreactive CD8+ T cells but is not required for acquisition of CTL activity in the islets of non-obese diabetic mice

In type 1 diabetes, maturation of activated autoreactive CD8⁺ T cells to fully armed effector cytotoxic T lymphocytes (CTL) occurs within the islet. At present the signals required for the maturation process are poorly defined. Cytokines could potentially provide the necessary "third signal" required to generate fully mature CTL capable of killing insulin-producing β-cells. To determine whether autoreactive CTL within islets respond to cytokines we generated non-obese diabetic (NOD) mice with a reporter for cytokine signalling. These mice express a reporter gene, hCD4, under the control of the endogenous regulatory elements for suppressor of cytokine signalling (SOCS)1, which is itself regulated by pro-inflammatory cytokines. In NOD mice, the hCD4 reporter was expressed in infiltrated islets and the expression level was positively correlated with the frequency of infiltrating CD45⁺ cells. SOCS1 reporter expression was induced in transferred β-cell-specific CD8⁺ 8.3T cells upon migration from pancreatic draining lymph nodes into islets. To determine which cytokines induced SOCS1 promoter activity in islets, we examined hCD4 reporter expression and CTL maturation in the absence of the cytokine receptors IFNAR1 or IL-21R. We show that IFNAR1 deficiency does not confer protection from diabetes in 8.3 TCR transgenic mice, nor is IFNAR1 signalling required for SOCS1 reporter upregulation or CTL maturation in islets. In contrast, IL-21R-deficient 8.3 mice have reduced diabetes incidence and reduced SOCS1 reporter activity in islet CTLs. However IL-21R deficiency did not affect islet CD8⁺ T cell proliferation or expression of granzyme B or IFNγ. Together these data indicate that autoreactive CD8⁺ T cells respond to IL-21 and not type I IFNs in the islets of NOD mice, but neither IFNAR1 nor IL-21R are required for islet intrinsic CTL maturation.

Children with type 1 diabetes of early age at onset - immune and metabolic phenotypes

Objectives We aimed to evaluate children with type 1 diabetes (T1D) with early age at onset (EAO) for clinical, immune and metabolic features in order to identify age-related disease phenotypes. Methods Comparative study of two groups of T1D children: EAO (≤5 years) and later age at onset (LAO; >5 years), regarding the presence of other autoimmune (AI) diseases, diabetes ketoacidosis and immunologic profile at onset and metabolic data 1 year after diagnosis. Statistical analysis was performed with significance set for p < 0.05. Results The study included 137 children (EAO = 52, mean age 3.6 ± 1.5 [mean ± standard deviation (SD)] and LAO = 85, mean age 10.4 ± 2.9). EAO was more associated with concomitant AI diseases (p = 0.032). Despite no differences in disease onset, EAO presented with lower C-peptide levels (p = 0.01) and higher absolute lymphocyte number (p < 0.0001), with an inverse correlation between these two variables (p = 0.028). Additionally, the EAO group had a higher frequency of serum detection of three antibodies (Abs) (p = 0.0008), specifically insulin Abs (p = 0.0001). One year after diagnosis, EAO had higher total daily insulin (TDI) dose (p = 0.008), despite similar hemoglobin A1c (HbA1c). Conclusions Our data show an association of EAO T1D with more AI diseases, higher number of Abs, lower initial insulin reservoir and higher insulin requirements 1 year after diagnosis. In this group, immune imbalance seems more evident and disease progression faster, probably reflecting distinct "immune environment" with different ages at disease onset. Further studies in the field of immunogenetics and immune tolerance are required, to improve patient stratification and find novel targets for therapeutic intervention.

Soluble FAS ligand is not required for pancreatic islet inflammation or beta-cell destruction in non-obese diabetic mice

CD8⁺ T cells play a central role in beta-cell destruction in type 1 diabetes. CD8⁺ T cells use two main effector pathways to kill target cells, perforin plus granzymes and FAS ligand (FASL). We and others have established that in non-obese diabetic (NOD) mice, perforin is the dominant effector molecule by which autoreactive CD8⁺ T cells kill beta cells. However, blocking FASL pharmacologically was shown to protect NOD mice from diabetes, indicating that FASL may have some role. FASL can engage with its receptor FAS on target cells either as membrane bound or soluble FASL. It has been shown that membrane-bound FASL is required to stimulate FAS-induced apoptosis in target cells, whereas excessive soluble FASL can induce NF-κB-dependent gene expression and inflammation. Because islet inflammation is a feature of autoimmune diabetes, we tested whether soluble FASL could be important in disease pathogenesis independent of its cell death function. We generated NOD mice deficient in soluble FASL, while maintaining expression of membrane-bound FASL due to a mutation in the FASL sequence required for cleavage by metalloproteinase. NOD mice lacking soluble FASL had normal numbers of lymphocytes in their spleen and thymus. Soluble FASL deficient NOD mice had similar islet inflammation as wild-type NOD mice and were not protected from diabetes. Our data indicate that soluble FASL is not required in development of autoimmune diabetes.

Long noncoding RNA: an emerging player in diabetes and diabetic kidney disease

Diabetic kidney disease (DKD) is among the most common complications of diabetes mellitus (DM), and remains the leading cause of end-stage renal diseases (ESRDs) in developed countries, with no definitive therapy yet available. It is imperative to decipher the exact mechanisms underlying DKD and identify novel therapeutic targets. Burgeoning evidence indicates that long non-coding RNAs (lncRNAs) are essential for diverse biological processes. However, their roles and the mechanisms of action remain to be defined in disease conditions like diabetes and DKD. The pathogenesis of DKD is twofold, so is the principle of treatments. As the underlying disease, diabetes per se is the root cause of DKD and thus a primary focus of therapy. Meanwhile, aberrant molecular signaling in kidney parenchymal cells and inflammatory cells may directly contribute to DKD. Evidence suggests that a number of lncRNAs are centrally involved in development and progression of DKD either via direct pathogenic roles or as indirect mediators of some nephropathic pathways, like TGF-β1, NF-κB, STAT3 and GSK-3β signaling. Some lncRNAs are thus likely to serve as biomarkers for early diagnosis or prognosis of DKD or as therapeutic targets for slowing progression or even inducing regression of established DKD. Here, we elaborated the latest evidence in support of lncRNAs as a key player in DKD. In an attempt to strengthen our understanding of the pathogenesis of DKD, and to envisage novel therapeutic strategies based on targeting lncRNAs, we also delineated the potential mechanisms of action as well as the efficacy of targeting lncRNA in preclinical models of DKD.

Targeted Elimination of Senescent Beta Cells Prevents Type 1 Diabetes

Type 1 diabetes (T1D) is an organ-specific autoimmune disease characterized by hyperglycemia due to progressive loss of pancreatic beta cells. Immune-mediated beta cell destruction drives the disease, but whether beta cells actively participate in the pathogenesis remains unclear. Here, we show that during the natural history of T1D in humans and the non-obese diabetic (NOD) mouse model, a subset of beta cells acquires a senescence-associated secretory phenotype (SASP). Senescent beta cells upregulated pro-survival mediator Bcl-2, and treatment of NOD mice with Bcl-2 inhibitors selectively eliminated these cells without altering the abundance of the immune cell types involved in the disease. Significantly, elimination of senescent beta cells halted immune-mediated beta cell destruction and was sufficient to prevent diabetes. Our findings demonstrate that beta cell senescence is a significant component of the pathogenesis of T1D and indicate that clearance of senescent beta cells could be a new therapeutic approach for T1D.

LPS enhances CTB-INSULIN induction of IDO1 and IL-10 synthesis in human dendritic cells

Autoantigen-specific immunotherapy promises effective treatment for devastating tissue specific autoimmune diseases like multiple sclerosis (MS) and type 1 diabetes (T1D). Because activated dendritic cells (DCs) stimulate the differentiation of autoreactive T cells involved in the initiation of autoimmunity, blocking the activation of DCs may be an effective strategy for inhibiting tissue specific autoimmunity. Following this approach, immature DCs were shown to remain inactive after treatment with chimeric fusion proteins composed of the cholera toxin B subunit adjuvant linked to autoantigens like proinsulin (CTB-INS). Mass spectrometer analysis of human DCs treated with CTB-INS suggest that upregulation of the tryptophan catabolic enzyme indoleamine 2, 3-dioxygenase (IDO1) is responsible for inhibiting DC activation thereby resulting in a state of immunological tolerance within the DC. Here we show that the fusion protein CTB-INS inhibits human monocyte derived DC (moDC) activation through stimulation of IDO1 biosynthesis and that the resultant state of DC tolerance can be further enhanced by the presence of residual E. coli lipopolysaccharide (LPS) present in partially purified CTB-INS preparations. Additional experiments showed that LPS enhancement of DC tolerance was dependent upon stimulation of IDO1 biosynthesis. LPS stimulation of increased levels of IDO1 in the DC resulted in increased secretion of kynurenines, tryptophan degradation products known to suppress DC mediated pro-inflammatory T cell differentiation and to stimulate the proliferation of regulatory T cells (Tregs). Further, the presence of LPS in CTB-INS treated DCs stimulated the biosynthesis of costimulatory factors CD80 and CD86 but failed to upregulate maturation factor CD83, suggesting CTB-INS treated DCs may be maintained in a state of semi-activation. While treatment of moDCs with increasing amounts of LPS free CTB-INS was shown to increase DC secretion of the anti-inflammatory cytokine IL-10, the presence of residual LPS in partially purified CTB-INS preparations dramatically increased IL-10 secretion, suggesting that CTB-INS may enhance DC mediated immunological tolerance by stimulating the proliferation of anti-inflammatory T cells. While the extraction of LPS from bacterial generated CTB-INS may remove additional unknown factors that may contribute to the regulation of IDO1 levels, together, our experimental data suggest that LPS stimulates the ability of CTB-INS to induce IDO1 and IL-10 important factors required for establishment of a state of functional immunological tolerance in human DCs. Regulation of the ratio of LPS to CTB-INS may prove to be an effective method for optimization of readily available "off the shelf" CTB-INS mediated immune-therapy for tissue specific autoimmune diseases including type 1 diabetes.

eIF5A inhibition influences T cell dynamics in the pancreatic microenvironment of the humanized mouse model of Type 1 Diabetes

We have developed a transgenic mouse model of Type 1 Diabetes (T1D) in which human GAD65 is expressed in pancreatic β-cells, and human MHC-II is expressed on antigen presenting cells. Induced GAD65 antigen presentation activates T-cells, which initiates the downstream events leading to diabetes. In our humanized mice, we have shown downregulation of eukaryotic translation initiation factor 5 A (elF5A), expressed only in actively dividing mammalian cells. In-vivo inhibition of elF5A hypusination by deoxyhypusine synthase (DHS) inhibitor "GC7" was studied; DHS inhibitor alters the pathophysiology in our mouse model by catalyzing the crucial hypusination and the rate-limiting step of elF5A activation. In our mouse model, we have shown that inhibition of eIF5A resets the pro-inflammatory bias in the pancreatic microenvironment. There was: (a) reduction of Th1/Th17 response, (b) an increase in Treg numbers, (c) debase in IL17 and IL21 cytokines levels in serum, (d) lowering of anti-GAD65 antibodies, and (e) ablation of the ER stress that improved functionality of the β-cells, but minimal effect on the cytotoxic CD8 T-cell (CTL) mediated response. Conclusively, immune modulation, in the case of T1D, may help to manipulate inflammatory responses, decreasing disease severity, and may help manage T1D in early stages of disease. Our study also demonstrates that without manipulating the CTLs mediated response extensively, it is difficult to treat T1D.

Insulin: a review of analytical methods

Insulin is an important polypeptide hormone that regulates carbohydrate metabolism.

Oral LPS Dosing Induces Local Immunological Changes in the Pancreatic Lymph Nodes in Mice

Lacking the initial contact between the immune system and microbial-associated molecular patterns (MAMPs), such as lipopolysaccharides (LPS), early in life, may be regarded as one of the causal factors of the increasing global increase in the incidence of autoimmune diseases, such as type 1 diabetes (T1D). Previously, a reduced incidence of T1D accompanied by dramatically increased abundances of both the mucin-metabolising bacterium Akkermansia muciniphila, and LPS-carrying Proteobacteria was observed, when vancomycin was given to pups of nonobese diabetic (NOD) mice. While the T1D incidence reducing effect of A. muciniphila has been shown in further studies, little is known as to whether the increased abundance of LPS-carrying bacteria also has a protective effect. Therefore, we fed NOD pups with Eschericia coli LPS orally from birth to weaning, which decreased the gene expressions of TNFα, IL-10, IL-6, IFNγ, IL-1β, IL-2, IL-4, and FoxP3 in the pancreatic lymph nodes, while the same gene expression profile in the spleen was unaffected. However, no significant difference in the incidence of T1D, gut microbiota composition, or ileum expression of the genetic markers of gut permeability, Claudin8, Occludin, Zonulin-1 (Tjp1), Claudin15, Muc1, and Muc2 were observed in relation to LPS ingestion. It is, therefore, concluded that early life oral E. coli LPS has an impact on the local immune response, which, however, did not influence T1D incidence in NOD mice later in life.

Antigen recognition in autoimmune diabetes: a novel pathway underlying disease initiation

Development of human autoimmune disorders results from complex interplay among genetic, environmental, and immunological risk factors. Despite much heterogeneity in environmental triggers, the leading genes that give the propensity for tissue-specific autoimmune diseases, such as type 1 diabetes, are those associated with particular class II major histocompatibility complex alleles. Such genetic predisposition precipitates presentation of tissue antigens to MHC-II-restricted CD4 T cells. When properly activated, these self-reactive CD4 T cells migrate to the target tissue and trigger the initial immune attack. Using the non-obese diabetic mouse model of spontaneous autoimmune diabetes, much insight has been gained in understanding how presentation of physiological levels of self-antigens translates into pathological outcomes. In this review, we summarize recent advances illustrating the features of the antigen presenting cells, the sites of the antigen recognition, and the nature of the consequent T cell responses. We emphasize emerging evidence that highlights the importance of systemic presentation of catabolized tissue antigens in mobilization of pathogenic T cells. The implication of these studies in therapeutic perspectives is also discussed.

Approaches and advances in the genetic causes of autoimmune disease and their implications

Genome-wide association studies are transformative in revealing the polygenetic basis of common diseases, with autoimmune diseases leading the charge. Although the field is just over 10 years old, advances in understanding the underlying mechanistic pathways of these conditions, which result from a dense multifactorial blend of genetic, developmental and environmental factors, have already been informative, including insights into therapeutic possibilities. Nevertheless, the challenge of identifying the actual causal genes and pathways and their biological effects on altering disease risk remains for many identified susceptibility regions. It is this fundamental knowledge that will underpin the revolution in patient stratification, the discovery of therapeutic targets and clinical trial design in the next 20 years. Here we outline recent advances in analytical and phenotyping approaches and the emergence of large cohorts with standardized gene-expression data and other phenotypic data that are fueling a bounty of discovery and improved understanding of human physiology.

Revealing the specificity of regulatory T cells in murine autoimmune diabetes

Regulatory T cells (Tregs) control organ-specific autoimmunity in a tissue antigen-specific manner, yet little is known about their specificity in a natural repertoire. In this study, we used the nonobese diabetic (NOD) mouse model of autoimmune diabetes to investigate the antigen specificity of Tregs present in the inflamed tissue, the islets of Langerhans. Compared with Tregs present in spleen and lymph node, Tregs in the islets showed evidence of antigen stimulation that correlated with higher proliferation and expression of activation markers CD103, ICOS, and TIGIT. T cell receptor (TCR) repertoire profiling demonstrated that islet Treg clonotypes are expanded in the islets, suggesting localized antigen-driven expansion in inflamed islets. To determine their specificity, we captured TCRαβ pairs from islet Tregs using single-cell TCR sequencing and found direct evidence that some of these TCRs were specific for islet-derived antigens including insulin B:9-23 and proinsulin. Consistently, insulin B:9-23 tetramers readily detected insulin-specific Tregs in the islets of NOD mice. Lastly, islet Tregs from prediabetic NOD mice were effective at preventing diabetes in Treg-deficient NOD.CD28^-/- recipients. These results provide a glimpse into the specificities of Tregs in a natural repertoire that are crucial for opposing the progression of autoimmune diabetes.

Alteration in CD8+ T cell subsets in enterovirus-infected patients: An alarming factor for type 1 diabetes mellitus

Type 1 diabetes is a multi-factorial disease that can develop due to the combination of genetic and environmental factors. Viruses, particularly enteroviruses, are major environmental candidates in the pathogenesis of type 1 diabetes, even though the mechanisms of pathogenicity of these viruses and their effects on the immune system have not been understood very well yet. Previous studies show that any imbalance in the population of different lymphocyte subsets could develop autoimmune diseases. Our theory is that enteroviral infection causes an impairment in the distribution of lymphocyte subtypes and consequently results in the diabetes onset in some individuals. Therefore, in this project, we evaluated the distribution of T CD8+ lymphocytes and their subsets in type 1 diabetes patients. This study was conducted to investigate the relationship between enteroviral infection and type 1 diabetes mellitus in an Iranian population, and suggestion a predicting approach for susceptible subjects.

NF-κB is weakly activated in the NOD mouse model of type 1 diabetes

Type 1 diabetes is an autoimmune disease characterised by selective destruction of pancreatic beta cells by the immune system. The transcription factor nuclear factor-kappa B (NF-κB) regulates innate and adaptive immune responses. Using gene targeting and in vitro analysis of pancreatic islets and immune cells, NF-κB activation has been implicated in type 1 diabetes development. Here we use a non-obese diabetic (NOD) mouse model that expresses a luciferase reporter of transcriptionally active NF-κB to determine its activation in vivo during development of diabetes. Increased luciferase activity was readily detected upon treatment with Toll-like receptor ligands in vitro and in vivo, indicating activation of NF-κB. However, activated NF-κB was detectable at low levels above background in unmanipulated NOD mice, but did not vary with age, despite the progression of inflammatory infiltration in islets over time. NF-κB was highly activated in an accelerated model of type 1 diabetes that requires CD4⁺ T cells and inflammatory macrophages. These data shed light on the nature of the inflammatory response in the development of type 1 diabetes.

GRP94 Is an Essential Regulator of Pancreatic β-Cell Development, Mass, and Function in Male Mice

Deficiencies in pancreatic β-cell mass contribute to both type 1 and type 2 diabetes. We investigated the role of the glucose-regulated protein (GRP) 94, an endoplasmic reticulum protein abundantly expressed in the pancreatic acini and islets, in β-cell development, survival, and function. We used a conditional knockout (KO) mouse in which the GRP94 gene, Hsp90b1, was specifically deleted in pancreatic and duodenal homeobox 1 (Pdx1)-expressing cells. These Hsp90b1 flox/flox;Pdx1Cre KO mice exhibited pancreatic hypoplasia at embryonic day (E) 16.5 to E18.5 and had significantly reduced β-cell mass at 4 weeks after birth. Further mechanistic studies showed that deletion of GRP94 reduced β-cell proliferation with increased cell apoptosis in both Pdx1+ endocrine progenitor cells and differentiated β cells. Although Hsp90b1 flox/flox;Pdx1Cre KO mice remained euglycemic at 8 weeks of age, they exhibited impaired glucose tolerance. In aggregate, these findings indicate that GRP94 is an essential regulator of pancreatic β-cell development, mass, and function.

Agent-based modeling of the interaction between CD8+ T cells and Beta cells in type 1 diabetes

We propose an agent-based model for the simulation of the autoimmune response in T1D. The model incorporates cell behavior from various rules derived from the current literature and is implemented on a high-performance computing system, which enables the simulation of a significant portion of the islets in the mouse pancreas. Simulation results indicate that the model is able to capture the trends that emerge during the progression of the autoimmunity. The multi-scale nature of the model enables definition of rules or equations that govern cellular or sub-cellular level phenomena and observation of the outcomes at the tissue scale. It is expected that such a model would facilitate in vivo clinical studies through rapid testing of hypotheses and planning of future experiments by providing insight into disease progression at different scales, some of which may not be obtained easily in clinical studies. Furthermore, the modular structure of the model simplifies tasks such as the addition of new cell types, and the definition or modification of different behaviors of the environment and the cells with ease.

Bringing the human pancreas into focus: new paradigms for the understanding of Type 1 diabetes

Type 1 diabetes affects increasingly large numbers of people globally (including at least half a million children under the age of 14 years) and it remains an illness with life-long and often devastating consequences. It is surprising, therefore, that the underlying aetiology of Type 1 diabetes remains poorly understood. This is largely because the cellular and molecular processes leading to the loss of β cells in the pancreas have rarely been studied at, or soon after, the onset of disease. Where such studies have been undertaken, a number of surprises have emerged which serve to challenge conventional wisdom. In particular, it is increasingly understood that the process of islet inflammation (insulitis) is much less florid in humans than in certain animal models. Moreover, the profile of immune cells involved in the inflammatory attack on β cells is variable and this variation occurs at the level of individual patients. As a result, two distinct profiles of insulitis have now been defined that are differentially aggressive and that might, therefore, require specifically tailored therapeutic approaches to slow the progression of disease. In addition, the outcomes are also different in that the more aggressive form (termed 'CD20Hi') is associated with extensive β-cell loss and an early age of disease onset (<7 years), while the less aggressive profile (known as 'CD20Lo') is associated with later onset (>13 years) and the retention of a higher proportion of residual β cells. In the present review, these new findings are explained and their implications evaluated in terms of future therapies.

Repurposed JAK1/JAK2 Inhibitor Reverses Established Autoimmune Insulitis in NOD Mice

Recent advances in immunotherapeutics have not yet changed the routine management of autoimmune type 1 diabetes. There is an opportunity to repurpose therapeutics used to treat other diseases to treat type 1 diabetes, especially when there is evidence for overlapping mechanisms. Janus kinase (JAK) 1/JAK2 inhibitors are in development or clinical use for indications including rheumatoid arthritis. There is good evidence for activation of the JAK1/JAK2 and signal transducer and activator of transcription (STAT) 1 pathway in human type 1 diabetes and in mouse models, especially in β-cells. We tested the hypothesis that using these drugs to block the JAK-STAT pathway would prevent autoimmune diabetes. The JAK1/JAK2 inhibitor AZD1480 blocked the effect of cytokines on mouse and human β-cells by inhibiting MHC class I upregulation. This prevented the direct interaction between CD8⁺ T cells and β-cells, and reduced immune cell infiltration into islets. NOD mice treated with AZD1480 were protected from autoimmune diabetes, and diabetes was reversed in newly diagnosed NOD mice. This provides mechanistic groundwork for repurposing clinically approved JAK1/JAK2 inhibitors for type 1 diabetes.

Development of the Nonobese Diabetic Mouse and Contribution of Animal Models for Understanding Type 1 Diabetes

In 1974, the discovery of a mouse and a rat that spontaneously developed hyperglycemia led to the development of 2 autoimmune diabetes models: nonobese diabetic (NOD) mouse and Bio-Breeding rat. These models have contributed to our understanding of autoimmune diabetes, provided tools to dissect autoimmune islet damage, and facilitated development of early detection, prevention, and treatment of type 1 diabetes. The genetic characterization, monoclonal antibodies, and congenic strains have made NOD mice especially useful.Although the establishment of the inbred NOD mouse strain was documented by Makino et al (Jikken Dobutsu. 1980;29:1-13), this review will focus on the not-as-well-known history leading to the discovery of a glycosuric female mouse by Yoshihiro Tochino. This discovery was spearheaded by years of effort by Japanese scientists from different disciplines and dedicated animal care personnel and by the support of the Shionogi Pharmaceutical Company, Osaka, Japan. The history is based on the early literature, mostly written in Japanese, and personal communications especially with Dr Tochino, who was involved in diabetes animal model development and who contributed to the release of NOD mice to the international scientific community. This article also reviews the scientific contributions made by the Bio-Breeding rat to autoimmune diabetes.

Type I Interferon Is a Catastrophic Feature of the Diabetic Islet Microenvironment

A detailed understanding of the molecular pathways and cellular interactions that result in islet beta cell (β cell) destruction is essential for the development and implementation of effective therapies for prevention or reversal of type 1 diabetes (T1D). However, events that define the pathogenesis of human T1D have remained elusive. This gap in our knowledge results from the complex interaction between genetics, the immune system, and environmental factors that precipitate T1D in humans. A link between genetics, the immune system, and environmental factors are type 1 interferons (T1-IFNs). These cytokines are well known for inducing antiviral factors that limit infection by regulating innate and adaptive immune responses. Further, several T1D genetic risk loci are within genes that link innate and adaptive immune cell responses to T1-IFN. An additional clue that links T1-IFN to T1D is that these cytokines are a known constituent of the autoinflammatory milieu within the pancreas of patients with T1D. The presence of IFNα/β is correlated with characteristic MHC class I (MHC-I) hyperexpression found in the islets of patients with T1D, suggesting that T1-IFNs modulate the cross-talk between autoreactive cytotoxic CD8⁺ T lymphocytes and insulin-producing pancreatic β cells. Here, we review the evidence supporting the diabetogenic potential of T1-IFN in the islet microenvironment.

Human islet cells are killed by BID-independent mechanisms in response to FAS ligand

Cell death via FAS/CD95 can occur either by activation of caspases alone (extrinsic) or by activation of mitochondrial death signalling (intrinsic) depending on the cell type. The BH3-only protein BID is activated in the BCL-2-regulated or mitochondrial apoptosis pathway and acts as a switch between the extrinsic and intrinsic cell death pathways. We have previously demonstrated that islets from BID-deficient mice are protected from FAS ligand-mediated apoptosis in vitro. However, it is not yet known if BID plays a similar role in human beta cell death. We therefore aimed to test the role of BID in human islet cell apoptosis immediately after isolation from human cadaver donors, as well as after de-differentiation in vitro. Freshly isolated human islets or 10-12 day cultured human islet cells exhibited BID transcript knockdown after BID siRNA transfection, however they were not protected from FAS ligand-mediated cell death in vitro as determined by DNA fragmentation analysis using flow cytometry. On the other hand, the same cells transfected with siRNA for FAS-associated via death domain (FADD), a molecule in the extrinsic cell death pathway upstream of BID, showed significant reduction in cell death. De-differentiated islets (human islet-derived progenitor cells) also demonstrated similar results with no difference in cell death after BID knockdown as compared to scramble siRNA transfections. Our results indicate that BID-independent pathways are responsible for FAS-dependent human islet cell death. These results are different from those observed in mouse islets and therefore demonstrate potentially alternate pathways of FAS ligand-induced cell death in human and mouse islet cells.

Association between telomere length and diabetes mellitus: A meta-analysis

Objective We investigated the relationship between diabetes and telomere length by meta-analysis. Methods We searched five popular databases for articles published between 1990 and 2015 using "diabetes" and "telomere" as search terms. Data were processed with RevMan5, and random- or fixed-effects meta-analysis was applied. The effects of geographical region, diabetes type, body mass index (BMI), age and sex were examined. Funnel plots were applied to evaluate publication bias. Results Seventeen articles were obtained from 571 references. We identified a significant association between telomere length and diabetes mellitus (standardized mean difference [SMD]: -3.41; 95% confidence interval [CI]: -4.01, -2.80; heterogeneity, I2 = 99%) by comparing 5575 patients with diabetes and 6349 healthy individuals. The pooled SMD by geographic region indicated a significant association between shortened telomere length and diabetes mellitus (SMD: -3.41; 95% CI: -4.01, -2.80; heterogeneity, I2 = 99%). In addition, telomere length was significantly associated with age (SMD: -3.41; 95% CI: -4.01, -2.80), diabetes type (SMD: -3.41; 95% CI: -4.01, -2.80), BMI (SMD: -1.61; 95% CI: -1.98, -1.23) and sex (SMD: -4.94; 95% CI: -9.47, -0.40). Conclusions The study demonstrated a close relationship between diabetes mellitus and telomere length, which was influenced by region, age, diabetes type, BMI and sex.

Therapeutic potential of umbilical cord blood cells for type 1 diabetes mellitus

Type 1 diabetes mellitus (T1DM) is a chronic disorder that results from autoimmune-mediated destruction of pancreatic islet β-cells. However, to date, no conventional intervention has successfully treated the disease. The optimal therapeutic method for T1DM should effectively control the autoimmunity, restore immune homeostasis, preserve residual β-cells, reverse β-cell destruction, and protect the regenerated insulin-producing cells against re-attack. Umbilical cord blood is rich in regulatory T (T(reg)) cells and multiple types of stem cells that exhibit immunomodulating potential and hold promise in their ability to restore peripheral tolerance towards pancreatic islet β-cells through remodeling of immune responses and suppression of autoreactive T cells. Recently, reinfusion of autologous umbilical cord blood or immune cells from cord blood has been proposed as a novel therapy for T1DM, with the advantages of no risk to the donors, minimal ethical concerns, a low incidence of graft-versus-host disease and easy accessibility. In this review, we revisit the role of autologous umbilical cord blood or immune cells from cord blood-based applications for the treatment of T1DM.

Perforin facilitates beta cell killing and regulates autoreactive CD8+ T-cell responses to antigen in mouse models of type 1 diabetes

In type 1 diabetes, cytotoxic CD8(+) T lymphocytes (CTLs) directly interact with pancreatic beta cells through major histocompatibility complex class I. An immune synapse facilitates delivery of cytotoxic granules, comprised mainly of granzymes and perforin. Perforin deficiency protects the majority of non-obese diabetic (NOD) mice from autoimmune diabetes. Intriguingly perforin deficiency does not prevent diabetes in CD8(+) T-cell receptor transgenic NOD8.3 mice. We therefore investigated the importance of perforin-dependent killing via CTL-beta cell contact in autoimmune diabetes. Perforin-deficient CTL from NOD mice or from NOD8.3 mice were significantly less efficient at adoptive transfer of autoimmune diabetes into NODRag1(-/-) mice, confirming that perforin is essential to facilitate beta cell destruction. However, increasing the number of transferred in vitro-activated perforin-deficient 8.3 T cells reversed the phenotype and resulted in diabetes. Perforin-deficient NOD8.3 T cells were present in increased proportion in islets, and proliferated more in response to antigen in vivo indicating that perforin may regulate the activation of CTLs, possibly by controlling cytokine production. This was confirmed when we examined the requirement for direct interaction between beta cells and CD8(+) T cells in NOD8.3 mice, in which beta cells specifically lack major histocompatibility complex (MHC) class I through conditional deletion of β2-microglobulin. Although diabetes was significantly reduced, 40% of these mice developed diabetes, indicating that NOD8.3 T cells can kill beta cells in the absence of direct interaction. Our data indicate that although perforin delivery is the main mechanism that CTL use to destroy beta cells, they can employ alternative mechanisms to induce diabetes in a perforin-independent manner.

Beta-cell destruction and preservation in childhood and adult onset type 1 diabetes

Previous studies describing the symptomatic onset of type 1 diabetes (T1D) and rate of beta-cell loss (C-peptide) support the notion that childhood onset T1D exhibits more severe beta-cell depletion compared to adult onset T1D. To test this notion, we performed whole pancreas analyses in two T1D cases, one of childhood onset (7-year old, onset at 1.5-year) along with an adult onset case (43-year old with onset at 27-year). Both cases were matched for age and gender with control subjects. Striking regional differences in beta-cell loss were observed in both T1D cases, with severity of loss in the order of tail > body > head regions. In contrast, pancreatic alpha- and delta-cell mass was similar in controls and T1D patients. In the childhood onset T1D case, no intra-islet beta-cells were detected while in the adult onset case, beta-cell containing islets were found, exclusively in the head region. In the latter case, considerable numbers of small cellular clusters negative for three major endocrine hormones were observed, in islets with or without beta-cells. Ultrastructural analysis suggests these cells correspond to degenerating beta-cells, with empty granular membranes and abnormal morphology of nuclei with intranuclear pseudo-inclusions, adjacent to healthy alpha- and delta-cells. These results support a hypothesis that during T1D development in childhood, beta-cells are more susceptible to autoimmune destruction or immune attack is more severe, while beta-cell death in the adult onset T1D may be more protracted and incomplete. In addition, T1D may be associated with the formation of "empty" beta-cells, an interesting population of cells that may represent a key facet to the disorder's pathogenesis.

Mouse pancreatic beta cells express MHC class II and stimulate CD4(+) T cells to proliferate

Type 1 diabetes results from destruction of pancreatic beta cells by autoreactive T cells. Both CD4(+) and CD8(+) T cells have been shown to mediate beta-cell killing. While CD8(+) T cells can directly recognize MHC class I on beta cells, the interaction between CD4(+) T cells and beta cells remains unclear. Genetic association studies have strongly implicated HLA-DQ alleles in human type 1 diabetes. Here we studied MHC class II expression on beta cells in nonobese diabetic mice that were induced to develop diabetes by diabetogenic CD4(+) T cells with T-cell receptors that recognize beta-cell antigens. Acute infiltration of CD4(+) T cells in islets occurred with rapid onset of diabetes. Beta cells from islets with immune infiltration expressed MHC class II mRNA and protein. Exposure of beta cells to IFN-γ increased MHC class II gene expression, and blocking IFN-γ signaling in beta cells inhibited MHC class II upregulation. IFN-γ also increased HLA-DR expression in human islets. MHC class II(+) beta cells stimulated the proliferation of beta-cell-specific CD4(+) T cells. Our study indicates that MHC class II molecules may play an important role in beta-cell interaction with CD4(+) T cells in the development of type 1 diabetes.

Autoreactive T cells induce necrosis and not BCL-2-regulated or death receptor-mediated apoptosis or RIPK3-dependent necroptosis of transplanted islets in a mouse model of type 1 diabetes

AIMS/HYPOTHESIS

Type 1 diabetes results from T cell-mediated destruction of pancreatic beta cells. The mechanisms of beta cell destruction in vivo, however, remain unclear. We aimed to test the relative roles of the main cell death pathways: apoptosis, necrosis and necroptosis, in beta cell death in the development of CD4(+) T cell-mediated autoimmune diabetes.

METHODS

We altered expression levels of critical cell death proteins in mouse islets and tested their ability to survive CD4(+) T cell-mediated attack using an in vivo graft model.

RESULTS

Loss of the B cell leukaemia/lymphoma 2 (BCL-2) homology domain 3-only proteins BIM, PUMA or BID did not protect beta cells from this death. Overexpression of the anti-apoptotic protein BCL-2 or combined deficiency of the pro-apoptotic multi-BCL2 homology domain proteins BAX and BAK also failed to prevent beta cell destruction. Furthermore, loss of function of the death receptor Fas or its essential downstream signalling molecule Fas-associated death domain (FADD) in islets was also not protective. Using electron microscopy we observed that dying beta cells showed features of necrosis. However, islets deficient in receptor-interacting serine/threonine protein kinase 3 (RIPK3), a critical initiator of necroptosis, were still normally susceptible to CD4(+) T cell-mediated destruction. Remarkably, simultaneous inhibition of apoptosis and necroptosis by combining loss of RIPK3 and overexpression of BCL-2 in islets did not protect them against immune attack either.

CONCLUSIONS/INTERPRETATION

Collectively, our data indicate that beta cells die by necrosis in autoimmune diabetes and that the programmed cell death pathways apoptosis and necroptosis are both dispensable for this process.

Proinsulin-specific, HLA-DQ8, and HLA-DQ8-transdimer-restricted CD4+ T cells infiltrate islets in type 1 diabetes

Type 1 diabetes (T1D) develops when insulin-secreting β-cells, found in the pancreatic islets of Langerhans, are destroyed by infiltrating T cells. How human T cells recognize β-cell-derived antigens remains unclear. Genetic studies have shown that HLA and insulin alleles are the most strongly associated with risk of T1D. These long-standing observations implicate CD4(+) T-cell responses against (pro)insulin in the pathogenesis of T1D. To dissect the autoimmune T-cell response against human β-cells, we isolated and characterized 53 CD4(+) T-cell clones from within the residual pancreatic islets of a deceased organ donor who had T1D. These 53 clones expressed 47 unique clonotypes, 8 of which encoded proinsulin-specific T-cell receptors. On an individual clone basis, 14 of 53 CD4(+) T-cell clones (26%) recognized 6 distinct but overlapping epitopes in the C-peptide of proinsulin. These clones recognized C-peptide epitopes presented by HLA-DQ8 and, notably, HLA-DQ8 transdimers that form in HLA-DQ2/-DQ8 heterozygous individuals. Responses to these epitopes were detected in the peripheral blood mononuclear cells of some people with recent-onset T1D but not in HLA-matched control subjects. Hence, proinsulin-specific, HLA-DQ8, and HLA-DQ8-transdimer-restricted CD4(+) T cells are strongly implicated in the autoimmune pathogenesis of human T1D.

Islet inflammation in human type 1 diabetes mellitus

Type 1 diabetes mellitus (T1DM) is caused by the selective deletion of pancreatic β-cells in response to an assault mounted within the pancreas by infiltrating immune cells. However, this apparently clear and focussed annunciation conceals a stark reality in which the cellular and molecular events leading to β-cell loss remain poorly understood in humans. This reflects the difficulty of studying these processes in living individuals and the fact that, using pathological specimens, islet inflammation has been analysed in fewer than 200 recent-onset cases of T1DM worldwide, over the past century. Nevertheless, insights have been gained and the composition of the islet infiltrate is being disclosed. This is shown to be primarily lymphocytic in nature, with populations of both CD8+ and CD4+ T cells displaying an autoreactivity against specific islet antigenic peptides. The T cells are often accompanied by influent CD20+ B cells, although new data imply that the proportions of these individual cell types vary and that patients fall into at least two distinct categories having either a hyper-immune (CD20Hi) or a pauci-immune (CD20Lo) phenotype. The overall rate of β-cell decline appears to correlate with these two phenotypes such that hyper-immune patients lose β-cells more quickly and tend to develop disease at an earlier age than those with the pauci-immune profile. In this article, we review the evidence which underpins our current understanding of the aetiology of T1DM and highlight both the established features as well as areas of on-going ambiguity and debate.