Type 1 diabetes in offspring of parents with type 1 diabetes: the tip of an autoimmune iceberg?

The immunology of type 1 diabetes

Following the seminal discovery of insulin a century ago, treatment of individuals with type 1 diabetes (T1D) has been largely restricted to efforts to monitor and treat metabolic glucose dysregulation. The recent regulatory approval of the first immunotherapy that targets T cells as a means to delay the autoimmune destruction of pancreatic β-cells highlights the critical role of the immune system in disease pathogenesis and tends to pave the way for other immune-targeted interventions for T1D. Improving the efficacy of such interventions across the natural history of the disease will probably require a more detailed understanding of the immunobiology of T1D, as well as technologies to monitor residual β-cell mass and function. Here we provide an overview of the immune mechanisms that underpin the pathogenesis of T1D, with a particular emphasis on T cells.

Type 1 Diabetes Screening and Diagnosis

Those with concerning signs or symptoms should be evaluated for type 1 diabetes (T1D). Those with first-degree relatives with T1D or based on the presence of high-risk genes are at increased risk and benefit from screening. Universal screening should be considered in light of new potential therapies to delay disease progression. Although oral glucose tolerance test is the gold standard for T1D staging, there are multiple tools available when oral glucose tolerance test is not feasible. Risk score calculations increase the ability to predict disease progression. Testing should be repeated when symptoms of overt diabetes mellitus are not present.

Immune-related adverse events after immune check point inhibitors: Understanding the intersection with autoimmunity

Immune checkpoint inhibitor therapies act through blockade of inhibitory molecules involved in the regulation of T cells, thus releasing tumor specific T cells to destroy their tumor targets. However, immune checkpoint inhibitors (ICI) can also lead to a breach in self-tolerance resulting in immune-related adverse events (irAEs) that include tissue-specific autoimmunity. This review addresses the question of whether the mechanisms that drive ICI-induced irAEs are shared or distinct with those driving spontaneous autoimmunity, focusing on ICI-induced diabetes, ICI-induced arthritis, and ICI-induced thyroiditis due to the wealth of knowledge about the development of autoimmunity in type 1 diabetes, rheumatoid arthritis, and Hashimoto's thyroiditis. It reviews current knowledge about role of genetics and autoantibodies in the development of ICI-induced irAEs and presents new studies utilizing single-cell omics approaches to identify T-cell signatures associated with ICI-induced irAEs. Collectively, these studies indicate that there are similarities and differences between ICI-induced irAEs and autoimmune disease and that studying them in parallel will provide important insight into the mechanisms critical for maintaining immune tolerance.

Clinical and experimental treatment of type 1 diabetes

Type 1 diabetes (T1D) is an autoimmune disease resulting in the destruction of the insulin-producing pancreatic beta cells. Disease progression occurs along a trajectory from genetic risk, the development of islet autoantibodies, and autoreactive T cells ultimately progressing to clinical disease. Natural history studies and mechanistic studies linked to clinical trials have provided insight into the role of the immune system in disease pathogenesis. Here, we review our current understanding of the underlying etiology of T1D, focusing on the immune cell types that have been implicated in progression from pre-symptomatic T1D to clinical diagnosis and established disease. This knowledge has been foundational for the development of immunotherapies aimed at the prevention and treatment of T1D.

Diabetes: discovery of insulin, genetic, epigenetic and viral infection mediated regulation

Diabetes mellitus, commonly referred to as diabetes, is a combination of many metabolic diseases. Insulin deficiency in our body is the main cause of diabetes. Insulin is one of the most well studied proteins, yet the genesis of its discovery was not getting much attention so far. Nevertheless, the history of the discovery of insulin is an exemplary of solving observational and scientific riddles, drudgery, patience and even professional turmoil. It is an inspiration for all medical personnel and scientists who are practising in the field of molecular medicine. Additionally, the genetic and epigenetic regulation of different types of diabetes needs to be addressed because of the widespread nature of the disease. Diabetes not only involves genetic predisposition but environmental factors, lifestyle etc. can be the major contributor for its inception. Nonetheless, viral infections at an early age are also found to trigger the onset of type I diabetes. In this review article, the history of the discovery of insulin is detailed along with the justification for the genetic and epigenetic regulatory mechanisms of diabetes and explained how viral infections can also trigger the onset of diabetes.

Genetic aspects of type 1 diabetes

Type 1 diabetes mellitus (T1DM) is characterized by autoimmune destruction of pancreatic beta-cells in genetically predisposed individuals, eventually resulting in severe insulin deficiency. It is the most common form of diabetes in children and adolescents. Genetic susceptibility plays a crucial role in development of T1DM. The human leukocyte antigen complex plays a key role in the pathogenesis of T1DM. Furthermore, genome-wide association studies and linkage analysis have recently made a significant contribution to current knowledge relative to the impact of genetics on T1DM development and progression. This review focuses on current knowledge of genetics as a pathogenesis for T1DM. It also discusses mechanisms by which genes influence the risk of developing T1DM as well as the clinical and research applications of genetic risk scores in T1DM.

Mitochondrial haplogroups are not associated with diabetic retinopathy in a large Australian and British Caucasian sample

Mitochondrial haplogroups H1, H2 and UK have previously been reported to be associated with proliferative diabetic retinopathy (PDR) in Caucasian patients with diabetes. We aimed to replicate this finding with a larger sample and expand the analysis to include different severities of DR, and diabetic macular edema (DME). Caucasian participants (n = 2935) with either type 1 or type 2 diabetes from the Australian Registry of Advanced Diabetic Retinopathy were enrolled in this study. Twenty-two mitochondrial single nucleotide polymorphisms were genotyped by MassArray and haplogroups reconstructed using Haplogrep. Chi square tests and logistic regressions were used to test associations between haplogroup and DR phenotypes including any DR, non-proliferative DR (NPDR), proliferative DR (PDR) and DME. After stratifying the samples in type 1 and type 2 diabetes groups, and adjusting for sex, age, diabetes duration, concurrent HbA1c and hypertension, neither haplogroups H1, H2, UK, K or JT were associated with any DR, NPDR, PDR or DME.

Clinical and biochemical characteristics of familial type 1 diabetes mellitus (FT1DM) compared to non-familial type 1 DM (NFT1DM)

INTRODUCTION

Familial type 1 diabetes mellitus (FT1DM) comprises parent-offspring and sib-pair subgroups. The clinical and genetic characteristics of FT1DM cases with and without affected family members have been previously studied with varying results. Some investigators found similarity of presenting features whereas others reported significant differences between the two groups.

OBJECTIVE

To describe the clinical and biochemical characteristics of children with FT1DM in comparison with those with non-familial type 1 diabetes mellitus (NFT1DM).

PATIENTS AND METHODS

We performed a cross-sectional retrospective study in a cohort of children and adolescents with T1DM (n=424) aged between 6 months - 16 years attending to Hamad General Hospital Pediatric Diabetes Center, Doha (Qatar) from 2012-2016. They were divided into 2 groups. Group 1 consisted of 62 children and adolescent with FT1DM (parent-offspring or sib-pair). The other group (Group 2) consisted of 431 children and adolescents with NFT1DM. The clinical presentation and prevalence of β-cell autoimmunity (anti-glutamic acid decarboxylase (GAD) antibodies , anti-islet cell and anti-insulin antibodies), thyroid function (Free thyroxine: FT4 and thyroid-stimulating hormone: TSH), anti-thyroid peroxidase antibody (TPO) and anti-tissue transglutaminase (ATT) at their first presentation were recorded, described and analyzed.

RESULTS

FT1 DM was more prevalent in boys versus girls (1.4:1, respectively) whereas the prevalence of NFT1DM did not differ between genders (1:1.1, respectively). F1DM occurred relatively early in childhood (40.7% before the age of 4 years and 72% before 9 years of age) versus NFT1DM which occurred relatively later in life (80% after the age of 4 years and 40% after the age of 9 years). 35.2% of FT1DM presented with diabetic ketoacidosis (DKA) versus 32.5% of T1DM patients. Anti-islet antibodies (Ab) were detected more frequently in FT1DM versus NFT1DM. The prevalence of positive anti-insulin and anti- GAD antibodies did not differ between the two groups. Anti TPO were detected in 27.2% of NFT1DM and 35.5% of FT1DM. A primary hypothyroidism, with positive ATPO, was more prevalent in FT1DM versus NFT1DM. ATT IgA was high in 5% of NFT1DM and 19.8% of FT1DM whereas ATT IgG was high in 4.4 % of NFT1DM and 15.4% of FT1DM.

CONCLUSIONS

FT1DM is more prevalent in boys versus girls and occurs earlier in childhood compared to NFT1DM. Primary hypothyroidism was more prevalent in NFT1DM versus FT1DM. Anti-islet Ab and ATT antibodies were more prevalent in the FT1DM versus NFT1DM. The genetic background may explain some differences between FT1DM and NFT1DM including the age of onset, gender affection, as well as associated autoimmune disorders.

Genetics of type 1 diabetes

Type 1 diabetes (T1D) results from immune-mediated loss of pancreatic beta cells leading to insulin deficiency. It is the most common form of diabetes in children, and its incidence is on the rise. This article reviews the current knowledge on the genetics of T1D. In particular, we discuss the influence of HLA and non-HLA genes on T1D risk and disease progression through the preclinical stages of the disease, and the development of genetic scores that can be applied to disease prediction. Racial/ethnic differences, challenges and future directions in the genetics of T1D are also discussed.

Clinical and research uses of genetic risk scores in type 1 diabetes

Type 1 diabetes (T1D) is a chronic disease of high blood glucose caused by autoimmune destruction of pancreatic beta cells eventually resulting in severe insulin deficiency. T1D has a significant heritable risk. Genetic associations found are particularly strong in the HLA class II region but T1D is a polygenic disease associated with over 60 loci across the genome. Polygenic risk scores are one method of summing these genetic risk elements as a single continuous variable. This review discusses the clinical and research utility of genetic risk scores in T1D particularly in disease prediction and progression. We also explore creative uses of genetic risk scores in big data and the limitations of using a genetic risk score. The increase in publically available genetic data and rapid fall in costs of genotyping mean that a T1D genetic risk score (T1D GRS) is likely to prove useful for disease prediction, discrimination, investigation of unusual cohorts, and investigation of biology in large datasets where genetic data are available.

Genetic Risk Scores for Type 1 Diabetes Prediction and Diagnosis

PURPOSE OF REVIEW

About 50% of the heritability of type 1 diabetes (T1D) is attributed to human leukocyte antigen (HLA) alleles and the remainder to several (close to 50) non-HLA loci. A current challenge in the field of the genetics of T1D is to apply the knowledge accumulated in the last 40 years towards differential diagnosis and risk assessment.

RECENT FINDINGS

T1D genetic risk scores seek to combine the information from HLA and non-HLA alleles to improve the accuracy of diagnosis, prediction, and prognosis. Here, we describe genetic risk scores that have been developed and validated in various settings and populations. Several genetic scores have been proposed that merge disease risk information from multiple genetic factors to optimize the use of genetic information and ultimately improve prediction and diagnosis of T1D.

Coexistent autoimmunity in familial type 1 diabetes: increased susceptibility in sib-pairs?

BACKGROUND

Type 1 diabetes (T1D) patients are at risk for additional autoimmune diseases (AID).

OBJECTIVE

To compare the characteristics of associated autoimmunity among familial (parent-offspring and sib-pair) subgroups and sporadic T1D patients.

PATIENTS AND METHODS

Data regarding AID in T1D patients and their nuclear family members were extracted from medical files of 121 multiplex T1D families (58 parent-offspring, 63 sib-pairs) and 226 sporadic controls followed between 1979 and 2008.

RESULTS

The prevalence of associated autoimmunity was similar in familial and sporadic cases (33.6 vs. 32.7%). The frequency of additional AID and percentage of patients with two or more coexistent AID were significantly higher among sib-pairs than parent-offspring (p = 0.05 and p = 0.04, respectively). The median time elapsed between diagnosis of T1D and occurrence of additional autoimmunity tended to be shorter in the sib-pairs. Only in familial cases did a positive autoimmune family background predict the development of coexistent autoimmunity (OR = 2.11, CI [1.0, 4.49] p = 0.05).

CONCLUSIONS

Among sib-pairs with T1D, the higher prevalence of additional AID, the increased number of diseases per person, and the relatively earlier appearance of associated AID suggest an increased susceptibility for coexistent autoimmunity in this subgroup. Positive family history for autoimmunity in multiplex T1D families increased their risk for co-occurrence of AID.

Familial association between type 1 diabetes and other autoimmune and related diseases

AIMS/HYPOTHESIS

In the era of genome-wide association studies, familial risks are used to estimate disease heritability and success in gene identification. We wanted to estimate associations between type 1 diabetes mellitus and 33 autoimmune and related diseases in parents, offspring, singleton siblings and twins.

METHODS

The availability of a Multigeneration Register in Sweden provides reliable access to families throughout the last century. The diseases in individual family members were obtained through linkage to the Hospital Discharge Register. Standardised incidence ratios (SIRs) were calculated as relative risks of contracting type 1 diabetes in family members of affected patients compared with those lacking affected family members.

RESULTS

Among a total of 450,899 patients, 21,168 were diagnosed with type 1 diabetes. Familial cases amounted to 10.3% of all type 1 diabetes patients. SIR for type 1 diabetes was 8.23 in offspring of affected parents, 11.92 in singleton siblings, 39.22 in multiplex families and 21.88 in twins; the calculated risk for monozygotic twins was 32.33. Type 1 diabetes in offspring was associated with 13 diseases in parents, including Addison's disease (SIR 2.41), asthma (1.38), coeliac disease (2.73), Graves' disease/hyperthyroidism (1.86), Hashimoto disease/hypothyroidism (2.35), pernicious anaemia (3.09), primary biliary cirrhosis (3.63), rheumatoid arthritis (2.12), sarcoidosis (1.62), systemic lupus erythematosus (2.04), ulcerative colitis (1.23) and Wegener's granulomatosis (2.12).

CONCLUSIONS/INTERPRETATION

The concordant familial risks for type 1 diabetes were high and the calculated risk for multiplex families and monozygotic twins may be explained by epistatic gene x gene or gene x environment interactions. Familial associations with several autoimmune and related diseases suggest genetic sharing and challenge to gene identification.

Targeting of pancreatic glia in type 1 diabetes

OBJECTIVE

Type 1 diabetes reflects autoimmune destruction of beta-cells and peri-islet Schwann cells (pSCs), but the mechanisms of pSC death and the T-cell epitopes involved remain unclear.

RESEARCH DESIGN AND METHODS

Primary pSC cultures were generated and used as targets in cytotoxic T-lymphocyte (CTL) assays in NOD mice. Cognate interaction between pSC and CD8(+) T-cells was assessed by transgenic restoration of beta2-microglobulin (beta2m) to pSC in NOD.beta2m(-/-) congenics. I-A(g7) and K(d) epitopes in the pSC antigen glial fibrillary acidic protein (GFAP) were identified by peptide mapping or algorithms, respectively, and the latter tested by immunotherapy.

RESULTS

pSC cultures did not express major histocompatibility complex (MHC) class II and were lysed by ex vivo CTLs from diabetic NOD mice. In vivo, restoration of MHC class I in GFAP-beta2m transgenics significantly accelerated adoptively transferred diabetes. Target epitopes in the pSC autoantigen GFAP were mapped to residues 79-87 and 253-261 for K(d) and 96-110, 116-130, and 216-230 for I-A(g7). These peptides were recognized spontaneously in NOD spleens as early as 2.5 weeks of age, with proliferative responses peaking around weaning and detectable lifelong. Several were also recognized by T-cells from new-onset type 1 diabetic patients. NOD mouse immunotherapy at 8 weeks with the CD8(+) T-cell epitope, GFAP 79-87 but not 253-261, significantly inhibited type 1 diabetes and was associated with reduced gamma-interferon production to whole protein GFAP.

CONCLUSIONS

Collectively, these findings elucidate a role for pSC-specific CD8(+) T-cells in islet inflammation and type 1 diabetes pathogenesis, further supporting neuronal involvement in beta-cell demise.