Recent advances in understanding Type 1 Diabetes

A systematic review of the association of Type I diabetes with sensorineural hearing loss

OBJECTIVES

Type 1 diabetes (T1D) has been associated with several comorbidities such as ocular, renal, and cardiovascular complications. However, the effect of T1D on the auditory system and sensorineural hearing loss (SNHL) is still not clear. The aim of this study was to conduct a systematic review to evaluate whether T1D is associated with hearing impairment.

METHODS

The databases PubMed, Science Direct, Scopus, and EMBASE were searched in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) criteria. Three reviewers independently screened, selected, and extracted data. The Joanna Briggs Institute (JBI) Critical Appraisal Tools for Analytical cross-sectional and case-control studies were used to perform quality assessment and risk of bias analysis on eligible studies.

RESULTS

After screening a total of 463 studies, 11 eligible original articles were included in the review to analyze the effects of T1D on the auditory system. The included studies comprised cross-sectional and case-control investigations. A total of 5,792 patients were evaluated across the 11 articles included. The majority of the studies showed that T1D was associated with hearing impairment compared to controls, including differences in PTAs and OAEs, increased mean hearing thresholds, altered acoustic reflex thresholds, and problems with the medial olivocochlear (MOC) reflex inhibitory effect. Significant risk factors included older age, increased disease duration, and higher HbA1C levels.

CONCLUSIONS

This systematic review suggests that there is a correlation between T1D and impairment on the auditory system. A multidisciplinary collaboration between endocrinologists, otolaryngologists, and audiologists will lead to early detection of hearing impairment in people with T1D resulting in early intervention and better clinical outcomes in pursuit of improving the quality of life of affected individuals.

REGISTRATION

This systematic review is registered in PROSPERO (CRD42023438576).

PTPN2 Regulates the Interferon Signaling and Endoplasmic Reticulum Stress Response in Pancreatic β-Cells in Autoimmune Diabetes

Type 1 diabetes (T1D) results from autoimmune destruction of β-cells in the pancreas. Protein tyrosine phosphatases (PTPs) are candidate genes for T1D and play a key role in autoimmune disease development and β-cell dysfunction. Here, we assessed the global protein and individual PTP profiles in the pancreas from nonobese mice with early-onset diabetes (NOD) mice treated with an anti-CD3 monoclonal antibody and interleukin-1 receptor antagonist. The treatment reversed hyperglycemia, and we observed enhanced expression of PTPN2, a PTP family member and T1D candidate gene, and endoplasmic reticulum (ER) chaperones in the pancreatic islets. To address the functional role of PTPN2 in β-cells, we generated PTPN2-deficient human stem cell-derived β-like and EndoC-βH1 cells. Mechanistically, we demonstrated that PTPN2 inactivation in β-cells exacerbates type I and type II interferon signaling networks and the potential progression toward autoimmunity. Moreover, we established the capacity of PTPN2 to positively modulate the Ca2+-dependent unfolded protein response and ER stress outcome in β-cells. Adenovirus-induced overexpression of PTPN2 partially protected from ER stress-induced β-cell death. Our results postulate PTPN2 as a key protective factor in β-cells during inflammation and ER stress in autoimmune diabetes.

Neoepitopes in Type 1 Diabetes: Etiological Insights, Biomarkers and Therapeutic Targets

The mechanisms underlying type 1 diabetes (T1D) pathogenesis remain largely unknown. While autoantibodies to pancreatic beta-cell antigens are often the first biological response and thereby a useful biomarker for identifying individuals in early stages of T1D, their role in T1D pathogenesis is not well understood. Recognition of these antigenic targets by autoreactive T-cells plays a pathological role in T1D development. Recently, several beta-cell neoantigens have been described, indicating that both neoantigens and known T1D antigens escape central or peripheral tolerance. Several questions regarding the mechanisms by which tolerance is broken in T1D remain unanswered. Further delineating the timing and nature of antigenic responses could allow their use as biomarkers to improve staging, as targets for therapeutic intervention, and lead to a better understanding of the mechanisms leading to loss of tolerance. Multiple factors that contribute to cellular stress may result in the generation of beta-cell derived neoepitopes and contribute to autoimmunity. Understanding the cellular mechanisms that induce beta-cells to produce neoantigens has direct implications on development of therapies to intercept T1D disease progression. In this perspective, we will discuss evidence for the role of neoantigens in the pathogenesis of T1D, including antigenic responses and cellular mechanisms. We will additionally discuss the pathways leading to neoepitope formation and the cross talk between the immune system and the beta-cells in this regard. Ultimately, delineating the timing of neoepitope generation in T1D pathogenesis will determine their role as biomarkers as well as therapeutic targets.

IL-6 in inflammation, autoimmunity and cancer

IL-6 is involved both in immune responses and in inflammation, hematopoiesis, bone metabolism and embryonic development. IL-6 plays roles in chronic inflammation (closely related to chronic inflammatory diseases, autoimmune diseases and cancer) and even in the cytokine storm of corona virus disease 2019 (COVID-19). Acute inflammation during the immune response and wound healing is a well-controlled response, whereas chronic inflammation and the cytokine storm are uncontrolled inflammatory responses. Non-immune and immune cells, cytokines such as IL-1β, IL-6 and tumor necrosis factor alpha (TNFα) and transcription factors nuclear factor-kappa B (NF-κB) and signal transducer and activator of transcription 3 (STAT3) play central roles in inflammation. Synergistic interactions between NF-κB and STAT3 induce the hyper-activation of NF-κB followed by the production of various inflammatory cytokines. Because IL-6 is an NF-κB target, simultaneous activation of NF-κB and STAT3 in non-immune cells triggers a positive feedback loop of NF-κB activation by the IL-6-STAT3 axis. This positive feedback loop is called the IL-6 amplifier (IL-6 Amp) and is a key player in the local initiation model, which states that local initiators, such as senescence, obesity, stressors, infection, injury and smoking, trigger diseases by promoting interactions between non-immune cells and immune cells. This model counters dogma that holds that autoimmunity and oncogenesis are triggered by the breakdown of tissue-specific immune tolerance and oncogenic mutations, respectively. The IL-6 Amp is activated by a variety of local initiators, demonstrating that the IL-6-STAT3 axis is a critical target for treating diseases.

Protective Role of St. John's Wort and Its Components Hyperforin and Hypericin against Diabetes through Inhibition of Inflammatory Signaling: Evidence from In Vitro and In Vivo Studies

Diabetes mellitus is a very common chronic disease with progressively increasing prevalence. Besides the well-known autoimmune and inflammatory pathogenesis of type 1 diabetes, in many people, metabolic changes and inappropriate lifestyle favor a subtle chronic inflammatory state that contributes to development of insulin resistance and progressive loss of β-cell function and mass, eventually resulting in metabolic syndrome or overt type 2 diabetes. In this paper, we review the anti-inflammatory effects of the extract of Hypericum perforatum L. (St. John's wort, SJW) and its main active ingredients firstly in representative pathological situations on inflammatory basis and then in pancreatic β cells and in obese or diabetic animal models. The simultaneous and long-lasting inhibition of signal transducer and activator of transcription (STAT)-1, nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and mitogen-activated protein kinases (MAPKs)/c-jun N-terminal kinase (JNK) signaling pathways involved in pro-inflammatory cytokine-induced β-cell dysfunction/death and insulin resistance make SJW particularly suitable for both preventive and therapeutic use in metabolic diseases. Hindrance of inflammatory cytokine signaling is likely dependent on the hyperforin content of SJW extract, but recent data reveal that hypericin can also exert relevant protective effects, mediated by activation of the cyclic adenosine monophosphate (cAMP)/protein kinase cAMP-dependent (PKA)/adenosine monophosphate activated protein kinase (AMPK) pathway, against high-fat-diet-induced metabolic abnormalities. Actually, the mechanisms of action of the two main components of SJW appear complementary, strengthening the efficacy of the plant extract. Careful quantitative analysis of SJW components and suitable dosage, with monitoring of possible drug-drug interaction in a context of remarkable tolerability, are easily achievable pre-requisites for forthcoming clinical applications.

Extracellular Vesicles Derived Human-miRNAs Modulate the Immune System in Type 1 Diabetes

Extracellular vesicles with their molecular cargo can modulate target cell response and may affect the pathogenesis of diseases. The extracellular vesicles containing micro-RNAs (miRNAs), which are often studied as disease biomarkers, but rarely as mediators of the disease development. The role of extracellular vesicles derived miRNAs in type 1 diabetes is currently not well established. We observed a fraction of blood plasma extracellular vesicles positive for membrane proteins potentially associated with insulin-producing beta-cells and identified differentially expressed extracellular vesicles derived miRNAs in individuals with type 1 diabetes. These differentially expressed extracellular vesicles derived human miRNAs in participants with type 1 diabetes and participants with Langerhans islets beta-cells destruction showed the ability to activate TLR7/8 signaling cascade and increase activation as well as cytotoxicity of the effector blood immune cells with cytokine and chemokine release. Our results illustrate extracellular vesicles derived human miRNAs as modulators of the immune system in type 1 diabetes autoimmunity, providing potentially new insight into the pathogenesis of the disease, and novel molecular targets for intervention and type 1 diabetes prevention.

Interleukin-2 Therapy of Autoimmunity in Diabetes (ITAD): a phase 2, multicentre, double-blind, randomized, placebo-controlled trial

Type 1 diabetes is a common autoimmune disease due to destruction of pancreatic β cells, resulting in lifelong need for insulin. Evidence suggest that maintaining residual β-cell function can improve glucose control and reduce risk of hypoglycaemia and vascular complications. Non-clinical, preclinical and some preliminary clinical data suggest that low-dose interleukin-2 (IL-2) therapy could block pancreatic β cells destruction by increasing the number of functional regulatory T cells (Tregs) that inhibit islet-specific autoreactive effector T cells (Teffs). However, there is lack of data on the effect of low-dose IL-2 in newly diagnosed children and adolescents with T1D as well as lack of specific data on its potential effect on β-cell function. The ' Interleukin-2 Therapy of Autoimmunity in Diabetes (ITAD)' is a phase 2, multicentre, double-blind, randomised, placebo-controlled trial in children and adolescents (6-18 years; having detectable C-peptide) initiated within 6 weeks of T1D diagnosis. A total of 45 participants will be randomised in a 2:1 ratio to receive either ultra-low dose IL-2 (aldesleukin), at a dose of 0.2 x 10 6 IU/m 2 twice-weekly, given subcutaneously, or placebo, for 6 months. The primary objective is to assess the effects of ultra-low dose aldesleukin administration on endogenous β-cell function as measured by frequent home dried blood spot (DBS) fasting and post-prandial C-peptide in children and adolescents with newly diagnosed T1D. The secondary objectives are: 1) to assess the efficacy of regular dosing of aldesleukin in increasing Treg levels; 2) to confirm the clinical safety and tolerability of ultra-low dose aldesleukin; 3) to assess changes in the immune system indicating benefit or potential risk for future gains/loss in β-cell function and immune function; 4) to assess treatment effect on glycaemic control. Trial registration: EudraCT 2017-002126-20 (06/02/2019).

Human Leukocyte Antigen (HLA) and Islet Autoantibodies Are Tools to Characterize Type 1 Diabetes in Arab Countries: Emphasis on Kuwait

The incidence rate of type 1 diabetes in Kuwait had been increasing exponentially and has doubled in children ≤ 14 years old within almost two decades. Therefore, there is a dire need for a careful systematic familial cohort study. Several immunogenetic factors affect the pathogenesis of the disease. The human leukocyte antigen (HLA) accounts for the major genetic susceptibility to the disease. The triggering agents initiate disease onset by type 1 destruction of pancreatic β-cells. Both HLA and anti-islet antibodies can be used to characterize, predict susceptibility to the disease, innovate, or delay the β-cell destruction. Evidence from prospective longitudinal studies suggested that the underlying disease process represents a continuum that begins before the symptoms are clinically evident. Autoimmunity of the functional pancreatic β-cells results in symptomatic type 1 diabetes and lifelong insulin dependence. The autoantibodies against glutamic acid decarboxylase (GADA), insulinoma antigen-2 (IA-2A), insulin (IAA), and zinc transporter-8 (ZnT-8A) comprise the most reliable biomarkers for type 1 diabetes in both children and adults. Although Kuwait is the second among the top 10 countries with a high incidence rate of type 1 diabetes, there have been no proper diagnostic and prediction tools as per the World Health Organization. The Kuwaiti Type 1 Diabetes Study (KADS) was initiated to understand the disease pathogenesis as well as the HLA and anti-islet autoantibody profile of type 1 diabetes in Kuwait. Understanding the disease sequela in a homogenous gene pool and highly consanguineous population of Kuwaitis could help solve the challenges and pathogenesis, as well as hasten the prevention, of type 1 diabetes.

BET Proteins Are Required for Transcriptional Activation of the Senescent Islet Cell Secretome in Type 1 Diabetes

Type 1 diabetes (T1D) results from the progressive loss of pancreatic beta cells as a result of autoimmune destruction. We recently reported that during the natural history of T1D in humans and the female nonobese diabetic (NOD) mouse model, beta cells acquire a senescence-associated secretory phenotype (SASP) that is a major driver of disease onset and progression, but the mechanisms that activate SASP in beta cells were not explored. Here, we show that the SASP in islet cells is transcriptionally controlled by Bromodomain ExtraTerminal (BET) proteins, including Bromodomain containing protein 4 (BRD4). A chromatin analysis of key beta cell SASP genes in NOD islets revealed binding of BRD4 at active regulatory regions. BET protein inhibition in NOD islets diminished not only the transcriptional activation and secretion of SASP factors, but also the non-cell autonomous activity. BET protein inhibition also decreased the extent of SASP induction in human islets exposed to DNA damage. The BET protein inhibitor iBET-762 prevented diabetes in NOD mice and also attenuated SASP in islet cells in vivo. Taken together, our findings support a crucial role for BET proteins in the activation of the SASP transcriptional program in islet cells. These studies suggest avenues for preventing T1D by transcriptional inhibition of SASP.

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.

An ancestral retroviral protein identified as a therapeutic target in type-1 diabetes

Human endogenous retroviruses (HERVs), remnants of ancestral viral genomic insertions, are known to represent 8% of the human genome and are associated with several pathologies. In particular, the envelope protein of HERV-W family (HERV-W-Env) has been involved in multiple sclerosis pathogenesis. Investigations to detect HERV-W-Env in a few other autoimmune diseases were negative, except in type-1 diabetes (T1D). In patients suffering from T1D, HERV-W-Env protein was detected in 70% of sera, and its corresponding RNA was detected in 57% of peripheral blood mononuclear cells. While studies on human Langerhans islets evidenced the inhibition of insulin secretion by HERV-W-Env, this endogenous protein was found to be expressed by acinar cells in 75% of human T1D pancreata. An extensive immunohistological analysis further revealed a significant correlation between HERV-W-Env expression and macrophage infiltrates in the exocrine part of human pancreata. Such findings were corroborated by in vivo studies on transgenic mice expressing HERV-W-env gene, which displayed hyperglycemia and decreased levels of insulin, along with immune cell infiltrates in their pancreas. Altogether, these results strongly suggest an involvement of HERV-W-Env in T1D pathogenesis. They also provide potentially novel therapeutic perspectives, since unveiling a pathogenic target in T1D.

Childhood adiposity and risk of type 1 diabetes: A Mendelian randomization study

BACKGROUND

The incidence of type 1 diabetes (T1D) is increasing globally. One hypothesis is that increasing childhood obesity rates may explain part of this increase, but, as T1D is rare, intervention studies are challenging to perform. The aim of this study was to assess this hypothesis with a Mendelian randomization approach that uses genetic variants as instrumental variables to test for causal associations.

METHODS AND FINDINGS

We created a genetic instrument of 23 single nucleotide polymorphisms (SNPs) associated with childhood adiposity in children aged 2-10 years. Summary-level association results for these 23 SNPs with childhood-onset (<17 years) T1D were extracted from a meta-analysis of genome-wide association study with 5,913 T1D cases and 8,828 reference samples. Using inverse-variance weighted Mendelian randomization analysis, we found support for an effect of childhood adiposity on T1D risk (odds ratio 1.32, 95% CI 1.06-1.64 per standard deviation score in body mass index [SDS-BMI]). A sensitivity analysis provided evidence of horizontal pleiotropy bias (p = 0.04) diluting the estimates towards the null. We therefore applied Egger regression and multivariable Mendelian randomization methods to control for this type of bias and found evidence in support of a role of childhood adiposity in T1D (odds ratio in Egger regression, 2.76, 95% CI 1.40-5.44). Limitations of our study include that underlying genes and their mechanisms for most of the genetic variants included in the score are not known. Mendelian randomization requires large sample sizes, and power was limited to provide precise estimates. This research has been conducted using data from the Early Growth Genetics (EGG) Consortium, the Genetic Investigation of Anthropometric Traits (GIANT) Consortium, the Tobacco and Genetics (TAG) Consortium, and the Social Science Genetic Association Consortium (SSGAC), as well as meta-analysis results from a T1D genome-wide association study.

CONCLUSIONS

This study provides genetic support for a link between childhood adiposity and T1D risk. Together with evidence from observational studies, our findings further emphasize the importance of measures to reduce the global epidemic of childhood obesity and encourage mechanistic studies.

Type 1 Diabetes and Type 1 Interferonopathies: Localization of a Type 1 Common Thread of Virus Infection in the Pancreas

Type 1 diabetes (T1D) has been associated with both genetic and environmental factors. Increasing incidence of T1D worldwide is prompting researchers to adopt different approaches to explain the biology of T1D, beyond the presence and activity of autoreactive lymphocytes. In this review, we propose inflammatory pathways as triggers for T1D. Within the scope of those inflammatory pathways and in understanding the pathogenesis of disease, we suggest that viruses, in particular Coxsackieviruses, act by causing a type 1 interferonopathy within the pancreas and the microenvironment of the islet. As such, this connection and common thread represents an exciting platform for the development of new diagnostic, treatment and/or prevention options.

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.

Circulating microRNAs and diabetes mellitus: a novel tool for disease prediction, diagnosis, and staging?

Diabetes is a complex, multifactorial group of metabolic diseases characterized by chronic hyperglycaemia due to pancreatic beta-cell dysfunction and/or loss. It is characterized by an asymptomatic and highly variable prodromic phase, which renders diabetes mellitus difficult to be predicted with sufficient accuracy. Despite several efforts in the identification and standardization of newly trustable. Biomarkers able to predict and follow-up diabetes and to specifically subtype its different forms, few of them have proven of clinical utility. Recently, a new class of endogenous non-coding small RNAs, namely microRNAs, have been indicated as putative biomarkers, being released by cells and tissues and found in a cell-free circulating form in many biological fluids, including serum and/or plasma. MicroRNAs have been initially identified as promising biomarkers in cancer, and nowadays their application has been extended to other diseases, including diabetes. Although an increasing number of studies focused on the evaluation of circulating microRNAs in diabetes, few reproducibly identified microRNAs as biomarkers for disease prediction or follow-up. Technological problems as well as the need to obtain highly standardized operating procedures and methods are still an issue in such research field. In this review, we comprehensively resume the main and most recent findings on circulating microRNAs, and their possible use as biomarkers to predict and follow-up diabetes and its complications, as well as the methodological challenges to standardize accurate operating procedures for their analysis.