IDDM2/insulin VNTR modifies risk conferred by IDDM1/HLA for development of Type 1 diabetes and associated autoimmunity

The countdown to type 1 diabetes: when, how and why does the clock start?

'The clock to type 1 diabetes has started when islet antibodies are first detected', commented George Eisenbarth with regard to the pathogenesis of type 1 diabetes. This review focuses on 'starting the clock', i.e. the initiation of pre-symptomatic islet autoimmunity/the first appearance of islet autoantibodies. In particular, this review addresses why susceptibility to developing islet autoimmunity is greatest in the first 2 years of life and why beta cells are a frequent target of the immune system during this fertile period. A concept for the development of beta cell autoimmunity in childhood is discussed and three factors are highlighted that contribute to this early predisposition: (1) high beta cell activity and potential vulnerability to stress; (2) high rates of and first exposures to infection; and (3) a heightened immune response, with a propensity for T helper type 1 (Th1) immunity. Arguments are presented that beta cell injury, accompanied by activation of an inflammatory immune response, precedes the initiation of autoimmunity. Finally, the implications for strategies aimed at primary prevention for a world without type 1 diabetes are discussed.

A classification and regression tree analysis identifies subgroups of childhood type 1 diabetes

Background

Diabetes in childhood and adolescence includes autoimmune and non-autoimmune forms with heterogeneity in clinical and biochemical presentations. An unresolved question is whether there are subtypes, endotypes, or theratypes within these forms of diabetes.

Methods

The multivariable classification and regression tree (CART) analysis method was used to identify subgroups of diabetes with differing residual C-peptide levels in patients with newly diagnosed diabetes before 20 years of age (n=1192). The robustness of the model was assessed in a confirmation and prognosis cohort (n=2722).

Findings

The analysis selected age, haemoglobin A1c (HbA1c), and body mass index (BMI) as split parameters that classified patients into seven islet autoantibody-positive and three autoantibody-negative groups. There were substantial differences in genetics, inflammatory markers, diabetes family history, lipids, 25-OH-Vitamin D3, insulin treatment, insulin sensitivity and insulin autoimmunity among the groups, and the method stratified patients with potentially different pathogeneses and prognoses. Interferon-ɣ and/or tumour necrosis factor inflammatory signatures were enriched in the youngest islet autoantibody-positive groups and in patients with the lowest C-peptide values, while higher BMI and type 2 diabetes characteristics were found in older patients. The prognostic relevance was demonstrated by persistent differences in HbA1c at 7 years median follow-up.

Interpretation

This multivariable analysis revealed subgroups of young patients with diabetes that have potential pathogenetic and therapeutic relevance.

Funding

The work was supported by funds from the German Federal Ministry of Education and Research (01KX1818; FKZ 01GI0805; DZD e.V.), the Innovative Medicine Initiative 2 Joint Undertaking INNODIA (grant agreement No. 115797), the German Robert Koch Institute, and the German Diabetes Association.

Genetic associations at regulatory phenotypes improve fine-mapping of causal variants for 12 immune-mediated diseases

The resolution of causal genetic variants informs understanding of disease biology. We used regulatory quantitative trait loci (QTLs) from the BLUEPRINT, GTEx and eQTLGen projects to fine-map putative causal variants for 12 immune-mediated diseases. We identify 340 unique loci that colocalize with high posterior probability (≥98%) with regulatory QTLs and apply Bayesian frameworks to fine-map associations at each locus. We show that fine-mapping credible sets derived from regulatory QTLs are smaller compared to disease summary statistics. Further, they are enriched for more functionally interpretable candidate causal variants and for putatively causal insertion/deletion (INDEL) polymorphisms. Finally, we use massively parallel reporter assays to evaluate candidate causal variants at the ITGA4 locus associated with inflammatory bowel disease. Overall, our findings suggest that fine-mapping applied to disease-colocalizing regulatory QTLs can enhance the discovery of putative causal disease variants and enhance insights into the underlying causal genes and molecular mechanisms.

100 Years of Insulin: Lifesaver, immune target, and potential remedy for prevention

In this review, we bring our personal experiences to showcase insulin from its breakthrough discovery as a life-saving drug 100 years ago to its uncovering as the autoantigen and potential cause of type 1 diabetes and eventually as an opportunity to prevent autoimmune diabetes. The work covers the birth of insulin to treat patients, which is now 100 years ago, the development of human insulin, insulin analogues, devices, and the way into automated insulin delivery, the realization that insulin is the primary autoimmune target of type 1 diabetes in children, novel approaches of immunotherapy using insulin for immune tolerance induction, the possible limitations of insulin immunotherapy, and an outlook how modern vaccines could remove the need for another 100 years of insulin therapy.

Oral insulin immunotherapy in children at risk for type 1 diabetes in a randomised controlled trial

AIMS/HYPOTHESIS

Oral administration of antigen can induce immunological tolerance. Insulin is a key autoantigen in childhood type 1 diabetes. Here, oral insulin was given as antigen-specific immunotherapy before the onset of autoimmunity in children from age 6 months to assess its safety and immune response actions on immunity and the gut microbiome.

METHODS

A phase I/II randomised controlled trial was performed in a single clinical study centre in Germany. Participants were 44 islet autoantibody-negative children aged 6 months to 2.99 years who had a first-degree relative with type 1 diabetes and a susceptible HLA DR4-DQ8-containing genotype. Children were randomised 1:1 to daily oral insulin (7.5 mg with dose escalation to 67.5 mg) or placebo for 12 months using a web-based computer system. The primary outcome was immune efficacy pre-specified as induction of antibody or T cell responses to insulin and measured in a central treatment-blinded laboratory.

RESULTS

Randomisation was performed in 44 children. One child in the placebo group was withdrawn after the first study visit and data from 22 insulin-treated and 21 placebo-treated children were analysed. Oral insulin was well tolerated with no changes in metabolic variables. Immune responses to insulin were observed in children who received both insulin (54.5%) and placebo (66.7%), and the trial did not demonstrate an effect on its primary outcome (p = 0.54). In exploratory analyses, there was preliminary evidence that the immune response and gut microbiome were modified by the INS genotype Among children with the type 1 diabetes-susceptible INS genotype (n = 22), antibody responses to insulin were more frequent in insulin-treated (72.7%) as compared with placebo-treated children (18.2%; p = 0.03). T cell responses to insulin were modified by treatment-independent inflammatory episodes.

CONCLUSIONS/INTERPRETATION

The study demonstrated that oral insulin immunotherapy in young genetically at-risk children was safe, but was not associated with an immune response as predefined in the trial primary outcome. Exploratory analyses suggested that antibody responses to oral insulin may occur in children with a susceptible INS genotype, and that inflammatory episodes may promote the activation of insulin-responsive T cells.

TRIAL REGISTRATION

Clinicaltrials.gov NCT02547519 FUNDING: The main funding source was the German Center for Diabetes Research (DZD e.V.).

Maternal Type 1 Diabetes Reduces Autoantigen-Responsive CD4+ T Cells in Offspring

Autoimmunity against pancreatic β-cell autoantigens is a characteristic of childhood type 1 diabetes (T1D). Autoimmunity usually appears in genetically susceptible children with the development of autoantibodies against (pro)insulin in early childhood. The offspring of mothers with T1D are protected from this process. The aim of this study was to determine whether the protection conferred by maternal T1D is associated with improved neonatal tolerance against (pro)insulin. Consistent with improved neonatal tolerance, the offspring of mothers with T1D had reduced cord blood CD4⁺ T-cell responses to proinsulin and insulin, a reduction in the inflammatory profile of their proinsulin-responsive CD4⁺ T cells, and improved regulation of CD4⁺ T cell responses to proinsulin at 9 months of age, as compared with offspring with a father or sibling with T1D. Maternal T1D was also associated with a modest reduction in CpG methylation of the INS gene in cord blood mononuclear cells from offspring with a susceptible INS genotype. Our findings support the concept that a maternal T1D environment improves neonatal immune tolerance against the autoantigen (pro)insulin.

Variants in the BACH2 and CLEC16A gene might be associated with susceptibility to insulin-triggered type 1 diabetes

AIM/INTRODUCTION

Insulin administration was found to trigger type 1 diabetes in six Japanese type 2 diabetes patients with type 1 diabetes high-risk human leukocyte antigen class II and the class I allele of the insulin gene variable number tandem repeat genotype. The objective of the present study was to assess the contribution of non-human leukocyte antigen single-nucleotide polymorphisms (SNPs) to the risk of developing insulin-triggered type 1 diabetes.

MATERIALS AND METHODS

We genotyped 13 type 1 diabetes susceptible SNPs in six patients and compared them with those in Japanese controls (Hap Map3-JPT). The SNPs that showed statistically significant results were further analyzed using non-diabetic control participants and participants with type 2 diabetes at the Ehime University Hospital.

RESULTS

The risk allele frequency of BACH2 rs3757247 in the six patients was significantly more frequent than that in 86 Japanese controls (P = 0.038). No significant difference in the allele frequency was observed in the other SNPs. This result was confirmed by the findings that the risk allele frequency of BACH2 in the six patients was significantly higher than that in the non-diabetic control participants (n = 179) and type 2 diabetes with or without insulin treatment (n = 154 or n = 152; P = 0.035, 0.034 or 0.037, respectively). Despite being statistically not significant, the six patients were all homozygous for the CLEC16A rs12708716 risk allele and five were homozygous for the CLEC16A rs2903692 risk allele.

CONCLUSIONS

In addition to type 1 diabetes high-risk human leukocyte antigen class II and the class I allele of the insulin gene variable number tandem repeat genotype, the possibility that the risk variants of BACH2 and CLEC16A could contribute to the development of insulin-triggered type 1 diabetes cannot be excluded.

Oral insulin therapy for primary prevention of type 1 diabetes in infants with high genetic risk: the GPPAD-POInT (global platform for the prevention of autoimmune diabetes primary oral insulin trial) study protocol

INTRODUCTION

The POInT study, an investigator initiated, randomised, placebo-controlled, double-blind, multicentre primary prevention trial is conducted to determine whether daily administration of oral insulin, from age 4.0 months to 7.0 months until age 36.0 months to children with elevated genetic risk for type 1 diabetes, reduces the incidence of beta-cell autoantibodies and diabetes.

METHODS AND ANALYSIS

Infants aged 4.0 to 7.0 months from Germany, Poland, Belgium, UK and Sweden are eligible if they have a >10.0% expected risk for developing multiple beta-cell autoantibodies as determined by genetic risk score or family history and human leucocyte antigen genotype. Infants are randomised 1:1 to daily oral insulin (7.5 mg for 2 months, 22.5 mg for 2 months, 67.5 mg until age 36.0 months) or placebo, and followed for a maximum of 7 years. Treatment and follow-up is stopped if a child develops diabetes. The primary outcome is the development of persistent confirmed multiple beta-cell autoantibodies or diabetes. Other outcomes are: (1) Any persistent confirmed beta-cell autoantibody (glutamic acid decarboxylase (GADA), IA-2A, autoantibodies to insulin (IAA) and zinc transporter 8 or tetraspanin 7), or diabetes, (2) Persistent confirmed IAA, (3) Persistent confirmed GADA and (4) Abnormal glucose tolerance or diabetes.

ETHICS AND DISSEMINATION

The study is approved by the ethical committees of all participating clinical sites. The results will be disseminated through peer-reviewed journals and conference presentations and will be openly shared after completion of the trial.

TRIAL REGISTRATION NUMBER

NCT03364868.

Characteristics of slow progression to diabetes in multiple islet autoantibody-positive individuals from five longitudinal cohorts: the SNAIL study

AIMS/HYPOTHESIS

Multiple islet autoimmunity increases risk of diabetes, but not all individuals positive for two or more islet autoantibodies progress to disease within a decade. Major islet autoantibodies recognise insulin (IAA), GAD (GADA), islet antigen-2 (IA-2A) and zinc transporter 8 (ZnT8A). Here we describe the baseline characteristics of a unique cohort of 'slow progressors' (n = 132) who were positive for multiple islet autoantibodies (IAA, GADA, IA-2A or ZnT8A) but did not progress to diabetes within 10 years.

METHODS

Individuals were identified from five studies (BABYDIAB, Germany; Diabetes Autoimmunity Study in the Young [DAISY], USA; All Babies in Southeast Sweden [ABIS], Sweden; Bart's Oxford Family Study [BOX], UK and the Pittsburgh Family Study, USA). Multiple islet autoantibody characteristics were determined using harmonised assays where possible. HLA class II risk was compared between slow progressors and rapid progressors (n = 348 diagnosed <5 years old from BOX) using the χ² test.

RESULTS

In the first available samples with detectable multiple antibodies, the most frequent autoantibodies were GADA (92%), followed by ZnT8A (62%), IAA (59%) and IA-2A (41%). High risk HLA class II genotypes were less frequent in slow (28%) than rapid progressors (42%, p = 0.011), but only two slow progressors carried the protective HLA DQ6 allele.

CONCLUSION

No distinguishing characteristics of slow progressors at first detection of multiple antibodies have yet been identified. Continued investigation of these individuals may provide insights into slow progression that will inform future efforts to slow or prevent progression to clinical diabetes.

A novel approach for the analysis of longitudinal profiles reveals delayed progression to type 1 diabetes in a subgroup of multiple-islet-autoantibody-positive children

AIMS/HYPOTHESIS

Progression to type 1 diabetes in children and adolescents is not uniform. Based on individual genetic background and environment, islet autoimmunity may develop at variable age, exhibit different autoantibody profiles and progress to clinical diabetes at variable rates. Here, we aimed to quantify the qualitative dynamics of sequential islet autoantibody profiles in order to identify longitudinal patterns that stratify progression rates to type 1 diabetes in multiple-autoantibody-positive children.

METHODS

Qualitative changes in antibody status on follow-up and progression rate to diabetes were analysed in 88 children followed from birth in the prospective BABYDIAB study who developed multiple autoantibodies against insulin (IAA), GAD (GADA), insulinoma-associated antigen-2 (IA-2A) and/or zinc transporter 8 (ZnT8A). An algorithm was developed to define similarities in sequential autoantibody profiles and hierarchical clustering was performed to group children with similar profiles.

RESULTS

We defined nine clusters that distinguished children with respect to their sequential profiles of IAA, GADA, IA-2A and ZnT8A. Progression from first autoantibody appearance to clinical diabetes between clusters ranged from 6% (95% CI [0, 16.4]) to 73% (28.4, 89.6) within 5 years. Delayed progression was observed in children who were positive for only two autoantibodies, and for a cluster of 12 children who developed three or four autoantibodies but were IAA-negative in their last samples, nine of whom lost IAA positivity during follow-up. Among all children who first seroconverted to IAA positivity and developed at least two other autoantibodies (n = 57), the 10 year risk of diabetes was 23% (0, 42.9) in those who became IAA-negative during follow-up compared with 76% (58.7, 85.6) in those who remained IAA-positive (p = 0.004).

CONCLUSIONS/INTERPRETATION

The novel clustering approach provides a tool for stratification of islet autoantibody-positive individuals that has prognostic relevance, and new opportunities in elucidating disease mechanisms. Our data suggest that losing IAA reactivity is associated with delayed progression to type 1 diabetes in multiple-islet-autoantibody-positive children.

Primary prevention of beta-cell autoimmunity and type 1 diabetes - The Global Platform for the Prevention of Autoimmune Diabetes (GPPAD) perspectives

OBJECTIVE

Type 1 diabetes can be identified by the presence of beta-cell autoantibodies that often arise in the first few years of life. The purpose of this perspective is to present the case for primary prevention of beta-cell autoimmunity and to provide a study design for its implementation in Europe.

METHODS

We examined and summarized recruitment strategies, enrollment rates, and outcomes in published TRIGR, FINDIA and BABYDIET primary prevention trials, and the TEDDY intensive observational study. A proposal for a recruitment and implementation strategy to perform a phase II/III primary prevention randomized controlled trial in infants with genetic risk for developing beta-cell autoimmunity is outlined.

RESULTS

Infants with a family history of type 1 diabetes (TRIGR, BABYDIET, TEDDY) and infants younger than age 3 months from the general population (FINDIA, TEDDY) were enrolled into these studies. All studies used HLA genotyping as part of their eligibility criteria. Predicted beta-cell autoimmunity risk in the eligible infants ranged from 3% (FINDIA, TEDDY general population) up to 12% (TRIGR, BABYDIET). Amongst eligible infants, participation was between 38% (TEDDY general population) and 97% (FINDIA). Outcomes, defined as multiple beta-cell autoantibodies, were consistent with predicted risks. We subsequently modeled recruitment into a randomized controlled trial (RCT) that could assess the efficacy of oral insulin treatment as adapted from the Pre-POINT pilot trial. The RCT would recruit infants with and without a first-degree family history of type 1 diabetes and be based on general population genetic risk testing. HLA genotyping and, for the general population, genotyping at additional type 1 diabetes susceptibility SNPs would be used to identify children with around 10% risk of beta-cell autoimmunity. The proposed RCT would have 80% power to detect a 50% reduction in multiple beta-cell autoantibodies by age 4 years at a two-tailed alpha of 0.05, and would randomize around 1160 infants to oral insulin or placebo arms in order to fulfill this. It is estimated that recruitment would require testing of between 400,000 and 500,000 newborns or infants.

CONCLUSION

It is timely and feasible to establish a platform for primary prevention trials for type 1 diabetes in Europe. This multi-site European infrastructure would perform RCTs, supply data coordination and biorepository, provide cohorts for mechanistic and observational studies, and increase awareness for autoimmune diabetes.

Staging presymptomatic type 1 diabetes: a scientific statement of JDRF, the Endocrine Society, and the American Diabetes Association

Insights from prospective, longitudinal studies of individuals at risk for developing type 1 diabetes have demonstrated that the disease is a continuum that progresses sequentially at variable but predictable rates through distinct identifiable stages prior to the onset of symptoms. Stage 1 is defined as the presence of β-cell autoimmunity as evidenced by the presence of two or more islet autoantibodies with normoglycemia and is presymptomatic, stage 2 as the presence of β-cell autoimmunity with dysglycemia and is presymptomatic, and stage 3 as onset of symptomatic disease. Adoption of this staging classification provides a standardized taxonomy for type 1 diabetes and will aid the development of therapies and the design of clinical trials to prevent symptomatic disease, promote precision medicine, and provide a framework for an optimized benefit/risk ratio that will impact regulatory approval, reimbursement, and adoption of interventions in the early stages of type 1 diabetes to prevent symptomatic disease.

Non-HLA gene effects on the disease process of type 1 diabetes: From HLA susceptibility to overt disease

In addition to the HLA region numerous other gene loci have shown association with type 1 diabetes. How these polymorphisms exert their function has not been comprehensively described, however. We assessed the effect of 39 single nucleotide polymorphisms (SNP) on the development of autoantibody positivity, on progression from autoantibody positivity to clinical disease and on the specificity of the antibody initiating the autoimmune process in 521 autoantibody-positive and 989 control children from a follow-up study starting from birth. Interestingly, PTPN2 rs45450798 gene polymorphism was observed to strongly affect the progression rate of beta-cell destruction after the appearance of humoral beta-cell autoimmunity. Moreover, primary autoantigen dependent associations were also observed as effect of the IKZF4-ERBB3 region on the progression rate of β-cell destruction was restricted to children with GAD antibodies as their first autoantibody whereas the effect of the INS rs 689 polymorphism was observed among subjects with insulin as the primary autoantigen. In the whole study cohort, INS rs689, PTPN22 rs2476601 and IFIH1 rs1990760 polymorphisms were associated with the appearance of beta-cell autoantibodies. These findings provide new insights into the role of genetic factors implicated in the pathogenesis of type 1 diabetes. The effect of some of the gene variants is restricted to control the initiation of β-cell autoimmunity whereas others modify the destruction rate of the β-cells. Furthermore, signs of primary autoantigen-related pathways were detected.

Predictors of Progression From the Appearance of Islet Autoantibodies to Early Childhood Diabetes: The Environmental Determinants of Diabetes in the Young (TEDDY)

OBJECTIVE

While it is known that there is progression to diabetes in <10 years in 70% of children with two or more islet autoantibodies, predictors of the progression to diabetes are only partially defined.

RESEARCH DESIGN AND METHODS

The Environmental Determinants of Diabetes in the Young (TEDDY) study has observed 8,503 children who were at increased genetic risk for autoimmune diabetes. Insulin autoantibodies (IAAs), GAD65 autoantibodies (GADAs), and insulinoma-associated protein 2 autoantibodies (IA-2As) were measured every 3 months until 4 years of age and every 6 months thereafter; if results were positive, the autoantibodies were measured every 3 months.

RESULTS

Life table analysis revealed that the cumulative incidence of diabetes by 5 years since the appearance of the first autoantibody differed significantly by the number of positive autoantibodies (47%, 36%, and 11%, respectively, in those with three autoantibodies, two autoantibodies, and one autoantibody, P < 0.001). In time-varying survival models adjusted for first-degree relative status, number of autoantibodies, age at first persistent confirmed autoantibodies, and HLA genotypes, higher mean IAA and IA-2A levels were associated with an increased risk of type 1 diabetes in children who were persistently autoantibody positive (IAAs: hazard ratio [HR] 8.1 [95% CI 4.6-14.2]; IA-2A: HR 7.4 [95% CI 4.3-12.6]; P < 0.0001]). The mean GADA level did not significantly affect the risk of diabetes.

CONCLUSIONS

In the TEDDY study, children who have progressed to diabetes usually expressed two or more autoantibodies. Higher IAA and IA-2A levels, but not GADA levels, increased the risk of diabetes in those children who were persistently autoantibody positive.

Role of Type 1 Diabetes-Associated SNPs on Risk of Autoantibody Positivity in the TEDDY Study

The Environmental Determinants of Diabetes in the Young (TEDDY) study prospectively follows 8,677 children enrolled from birth who carry HLA-susceptibility genotypes for development of islet autoantibodies (IA) and type 1 diabetes (T1D). During the median follow-up time of 57 months, 350 children developed at least one persistent IA (GAD antibody, IA-2A, or micro insulin autoantibodies) and 84 of them progressed to T1D. We genotyped 5,164 Caucasian children for 41 non-HLA single nucleotide polymorphisms (SNPs) that achieved genome-wide significance for association with T1D in the genome-wide association scan meta-analysis conducted by the Type 1 Diabetes Genetics Consortium. In TEDDY participants carrying high-risk HLA genotypes, eight SNPs achieved significant association to development of IA using time-to-event analysis (P < 0.05), whereof four were significant after adjustment for multiple testing (P < 0.0012): rs2476601 in PTPN22 (hazard ratio [HR] 1.54 [95% CI 1.27-1.88]), rs2292239 in ERBB3 (HR 1.33 [95% CI 1.14-1.55]), rs3184504 in SH2B3 (HR 1.38 [95% CI 1.19-1.61]), and rs1004446 in INS (HR 0.77 [0.66-0.90]). These SNPs were also significantly associated with T1D in particular: rs2476601 (HR 2.42 [95% CI 1.70-3.44]). Although genes in the HLA region remain the most important genetic risk factors for T1D, other non-HLA genetic factors contribute to IA, a first step in the pathogenesis of T1D, and the progression of the disease.

Risk genes and autoantibodies in Egyptian children with type 1 diabetes - low frequency of autoantibodies in carriers of the HLA-DRB1*04:05-DQA1*03-DQB1*02 risk haplotype

BACKGROUND

The study aimed to define the frequencies of type 1 diabetes-associated gene polymorphisms and their associations with various diabetes-associated autoantibodies in Egyptian children.

METHODS

One hundred and one children with type 1 diabetes and 160 healthy controls from the same region were studied for HLA-DQB1, HLA-DQA1, and HLA-DRB1 (DR4 subtypes) alleles; for INS and protein tyrosine phosphatase, non-receptor type 22 gene polymorphisms (rs689 and rs2476601); and for diabetes-associated autoantibodies.

RESULTS

Most children with diabetes (77.2%) were positive for the HLA-(DR3)-DQA1*05-DQB1*02 (DR3-DQ2) haplotype compared with 26.2% of the controls (OR = 9.5; p < 0.001). HLA-DRB1*04:02-DQA1*03-DQB1*03:02 (DR4-DQ8) (26.7%, OR = 3.3; p < 0.001), DRB1*04:05-DQA1*03-DQB1*02 (DR4-DQ2) (23.8%, OR 5.2; p < 0.001), and DRB1*04:05-DQA1*03-DQB1*03:02 (DR4-DQ8) (8.9%, OR = 7.7; p = 0.007) were also significantly increased. HLA-(DR15)-DQB1*06:01, (DR13)-DQB1*06:03, and DRB1*04:03-DQA1*03-DQB1*03:02 were the most protective haplotypes with OR values from 0.04 to 0.06. Patients positive for DR3-DQ2 but negative for DR4 haplotypes had a high frequency of glutamic acid decarboxylase antibodies (78%; p < 0.001 versus other genotypes), but only 26.6% of those with DR3-DQ2/DR4-DQ2 tested positive for glutamic acid decarboxylase antibodies (p = 0.006 versus other genotypes). Subjects with the DR4-DQ8 haplotype without DR3-DQ2 or DR4-DQ2 were more often positive for islet antigen-2 and zinc transporter 8 antibodies (55.5%, p = 0.007 and 55.5%, p = 0.01 respectively). The AA genotype of the INS gene was more common in patients than in controls (75.2 versus 59.5%, OR = 2.07; p = 0.018).

CONCLUSIONS

Besides a strong HLA-DR3-DQ2 association, a relatively high frequency of the DR4-DQ2 haplotype characterized the diabetic population. The low frequency of autoantibodies in children with HLA-DR4-DQ2 may indicate specific pathogenetic pathways associated with this haplotype.

Feature ranking of type 1 diabetes susceptibility genes improves prediction of type 1 diabetes

AIMS/HYPOTHESIS

More than 40 regions of the human genome confer susceptibility for type 1 diabetes and could be used to establish population screening strategies. The aim of our study was to identify weighted sets of SNP combinations for type 1 diabetes prediction.

METHODS

We applied multivariable logistic regression and Bayesian feature selection to the Type 1 Diabetes Genetics Consortium (T1DGC) dataset with genotyping of HLA plus 40 SNPs within other type 1 diabetes-associated gene regions in 4,574 cases and 1,207 controls. We tested the weighted models in an independent validation set (765 cases, 423 controls), and assessed their performance in 1,772 prospectively followed children.

RESULTS

The inclusion of 40 non-HLA gene SNPs significantly improved the prediction of type 1 diabetes over that provided by HLA alone (p = 3.1 × 10(-25)), with a receiver operating characteristic AUC of 0.87 in the T1DGC set, and 0.84 in the validation set. Feature selection identified HLA plus nine SNPs from the PTPN22, INS, IL2RA, ERBB3, ORMDL3, BACH2, IL27, GLIS3 and RNLS genes that could achieve similar prediction accuracy as the total SNP set. Application of this ten SNP model to prospectively followed children was able to improve risk stratification over that achieved by HLA genotype alone.

CONCLUSIONS

We provided a weighted risk model with selected SNPs that could be considered for recruitment of infants into studies of early type 1 diabetes natural history or appropriately safe prevention.

Insulin administration may trigger type 1 diabetes in Japanese type 2 diabetes patients with type 1 diabetes high-risk HLA class II and the insulin gene VNTR genotype

CONTEXT

Insulin administration causes various types of immune responses to insulin. We previously reported three cases of type 1 diabetes mellitus (T1DM) triggered by insulin administration in Japanese type 2 diabetes mellitus patients.

OBJECTIVE

The objective of this study was to collect information and characterize insulin-triggered T1DM immunologically and genetically.

METHODS

Data for six patients (four men and two women) with insulin-triggered T1DM aged 59.5 ± 12.8 years were collected. Serum or urinary C-peptides, islet-related autoantibodies, insulin antibody, human leukocyte antigen, or the insulin gene variable number of tandem repeat genotype were analyzed. Th1- or Th2-associated responses were evaluated using an Enzyme-Linked ImmunoSpot assay.

RESULTS

None of the subjects had received insulin therapy or had an autoantibody to the 65-kDa isoform of glutamic acid decarboxylase before insulin administration. After insulin administration blood glucose control deteriorated acutely without any apparent cause, whereas C-peptide levels rapidly decreased to insulin-deficient levels. The mean duration of insulin administration to the development of T1DM was 7.7 ± 6.1 months. Islet-related autoantibodies became positive, whereas insulin allergy or a high titer of insulin antibody was observed in several cases. All had T1DM high-risk human leukocyte antigen class II (IDDM1) and the insulin gene variable number of tandem repeats genotype (IDDM2). GAD-reactive and insulin peptide-reactive Th1 cells, but not Th2 cells, were identified in two of four cases.

CONCLUSIONS

The findings suggest that insulin administration may have triggered TIDM in patients with type 2 diabetes mellitus. IDDM1 and IDDM 2 as well as autoreactive T cells may contribute to the development of T1DM. Developing insulin-triggered T1DM if a patient's blood glucose control acutely deteriorates after insulin administration should be carefully considered.

Improving prediction of type 1 diabetes by testing non-HLA genetic variants in addition to HLA markers

OBJECTIVE

The purpose of this study was to explore whether non-human leukocyte antigen (non-HLA) genetic markers can improve type 1 diabetes(T1D) prediction in a prospective cohort with high-risk HLA-DR,DQ genotypes.

METHODS

The Diabetes Autoimmunity Study in the Young (DAISY) follows prospectively for the development of T1D and islet autoimmunity (IA)children at increased genetic risk. A total of 1709 non-Hispanic White DAISY participants have been genotyped for 27 non-HLA single nucleotide polymorphisms (SNPs) and one microsatellite.

RESULTS

In multivariate analyses adjusting for family history and HLA-DR3/4 genotype, PTPN22 (rs2476601) and two UBASH3A (rs11203203 and rs9976767) SNPs were associated with development of IA [hazard ratio(HR)=1.87, 1.55, and 1.54, respectively, all p ≤ 0.003], while GLIS3 and IL2RA showed borderline association with development of IA. INS,UBASH3A, and IFIH1 were significantly associated with progression from IA to diabetes (HR=1.65, 1.44, and 1.47, respectively, all p ≤ 0.04), while PTPN22 and IL27 showed borderline association with progression from IA to diabetes. In survival analysis, 45% of general population DAISY children with PTPN22 rs2476601 TT or HLA-DR3/4 and UBASH3A rs11203203 AA developed diabetes by age 15, compared with 3% of children with all other genotypes (p<0.0001). Addition of non-HLA markers to HLA-DR3/4,DQ8 did not improve diabetes prediction in first-degree relatives.

CONCLUSION

Addition of PTPN22 and UBASH3A SNPs to HLA-DR,DQ genotyping can improve T1D risk prediction.

Assessment of type 1 diabetes risk conferred by HLA-DRB1, INS-VNTR and PTPN22 genes using the Bayesian network approach

BACKGROUND

Determining genetic risk is a fundamental prerequisite for the implementation of primary prevention trials for type 1 diabetes (T1D). The aim of this study was to assess the risk conferred by HLA-DRB1, INS-VNTR and PTPN22 single genes on the onset of T1D and the joint risk conferred by all these three susceptibility loci using the Bayesian Network (BN) approach in both population-based case-control and family clustering data sets.

METHODOLOGY/PRINCIPAL FINDINGS

A case-control French cohort, consisting of 868 T1D patients and 73 French control subjects, a French family data set consisting of 1694 T1D patients and 2340 controls were analysed. We studied both samples separately applying the BN probabilistic approach, that is a graphical model that encodes probabilistic relationships among variables of interest. As expected HLA-DRB1 is the most relevant susceptibility gene. We proved that INS and PTPN22 genes marginally influence T1D risk in all risk HLA-DRB1 genotype categories. The absolute risk conferred by carrying simultaneously high, moderate or low risk HLA-DRB1 genotypes together with at risk INS and PTPN22 genotypes, was 11.5%, 1.7% and 0.1% in the case-control sample and 19.8%, 6.6% and 2.2% in the family cohort, respectively.

CONCLUSIONS/SIGNIFICANCE

This work represents, to the best of our knowledge, the first study based on both case-control and family data sets, showing the joint effect of HLA, INS and PTPN22 in a T1D Caucasian population with a wide range of age at T1D onset, adding new insights to previous findings regarding data sets consisting of patients and controls <15 years at onset.

Associations of polymorphisms in non-HLA loci with autoantibodies at the diagnosis of type 1 diabetes: INS and IKZF4 associate with insulin autoantibodies

OBJECTIVE

More than 50 loci outside the human leukocyte antigen (HLA) region have been confirmed to affect type 1 diabetes (T1D) risk but their effect on β-cell autoimmunity is poorly defined. We analyzed the association of 35 single nucleotide polymorphism (SNP) markers previously associated with T1D with the presence of disease-predictive autoantibodies at the time of T1D diagnosis.

SUBJECTS AND METHODS

The study cohort comprised 1554 children diagnosed with T1D before the age of 15 yr. The associations between various genotypes and positivity for antibodies against islet cells [islet cell antibodies (ICA)], insulin [insulin autoantibodies (IAA)], glutamic acid decarboxylase (GADA), islet antigen 2 (IA2A), and zinc transporter 8 (ZnT8A) were analyzed.

RESULTS

INS gene polymorphism rs689 and IKZF4 polymorphism (rs1701704) were strongly associated with IAA positivity at the time of T1D diagnosis (p = 0.000004 and 0.00044, respectively). The presence of the T1D-risk conferring INS AA genotype was associated with IAA. In contrast, the presence of the susceptible C allele of the IKZF4 marker was inversely associated with IAA. The INS and IKZF4 polymorphisms were not significantly associated with ICA, GADA, IA2A, or ZnT8A positivity.

CONCLUSIONS

Both INS and IKZF4 polymorphisms modified the probability of IAA positivity at time of T1D onset but the inverse association of IKZF4 risk allele with IAA suggests that the IKZF4 polymorphism is involved in a pathway of β-cell autoimmunity alternate to the route characterized by IAA and development of T1D in early childhood. The IKZF4 gene encodes Eos, which is implicated to play an important role in Treg programming where this gene might exert its influence on T1D risk.

Patterns of β-cell autoantibody appearance and genetic associations during the first years of life

We analyzed demographic and genetic differences between children with various diabetes-associated autoantibodies reflecting the autoimmune process. In a prospective birth cohort comprising children with HLA-conferred susceptibility to type 1 diabetes (T1D), the pattern of autoantibody appearance was analyzed in 520 children with advanced β-cell autoimmunity associated with high risk for disease. In 315 cases, a single biochemical autoantibody could be identified in the first positive sample as insulin (insulin autoantibody [IAA]) in 180, as GAD (GAD antibody [GADA]) in 107, and as IA-2 antigen (IA-2 antibody [IA-2A]) in 28. The age at seroconversion differed significantly between the three groups (P = 0.003). IAA as the first autoantibody showed a peak time of appearance during the second year of life, whereas GADA as the first autoantibody peaked later, between 3 and 5 years of age. The risk-associated insulin gene rs689 A/A genotypes were more frequent in children with IAA as the first autoantibody compared with the other children (P = 0.002). The primary autoantigen in the development of β-cell autoimmunity and T1D seems to strongly correlate with age and genetic factors, indicating heterogeneity in the initiation of the disease process.

Characteristics of rapid vs slow progression to type 1 diabetes in multiple islet autoantibody-positive children

AIMS/HYPOTHESIS

Islet autoantibody-positive children progress to type 1 diabetes at variable rates. In our study, we asked whether characteristic autoantibody and/or gene profiles could be defined for phenotypes showing extreme progression.

METHODS

Autoantibodies to insulin (IAA), GAD (GADA), insulinoma-associated antigen-2 (IA-2A) and zinc transporter 8 (ZnT8A) were measured in follow-up sera, and genotyping for type 1 diabetes susceptibility genes (HLA-DR/HLA-DQ, INS variable number of tandem repeats [VNTR] and single nucleotide polymorphisms at PTPN22, PTPN2, ERBB3, IL2, SH2B3, CTLA4, IFIH1, KIAA0350 [also known as CLEC16A], CD25, IL18RAP, IL10, COBL) was performed on the DNA samples of children born to a parent with type 1 diabetes and prospectively followed from birth for up to 22 years.

RESULTS

Of the 1,650 children followed, 23 developed multiple autoantibodies and progressed to diabetes within 3 years (rapid progressors), while 24 children developed multiple autoantibodies and remained non-diabetic for more than 10 years from seroconversion (slow progressors). Rapid and slow progressors were similar with respect to HLA-DR/HLA-DQ genotypes, development of IAA, GADA and ZnT8A, and progression to multiple autoantibodies. In contrast, IA-2A development was considerably delayed in the slow progressors. Furthermore, both groups were effectively distinguished by the combined presence or absence of type 1 diabetes susceptibility alleles of non-HLA genes, most notably IL2, CD25, INS VNTR, IL18RAP, IL10, IFIH1 and PTPN22, and discrimination was improved among children carrying high-risk HLA-DR/HLA-DQ genotypes.

CONCLUSIONS/INTERPRETATION

Our data suggest that genotypes of non-HLA type 1 diabetes susceptibility genes influence the likelihood or rate of diabetes progression among children with multiple islet autoantibodies.

Activation of islet autoreactive naïve T cells in infants is influenced by homeostatic mechanisms and antigen-presenting capacity

Islet autoimmunity precedes type 1 diabetes onset. We previously found that islet autoimmunity rarely starts before 6 months of age but reaches its highest incidence already at ∼1 year of age. We now examine whether homeostatic expansion and immune competence changes seen in a maturating immune system may account for this marked variation in islet autoimmunity risk in the first year of life. We found naïve proinsulin- and GAD65-responsive T cells in cord blood (CB) of healthy newborns, with highest responses observed in children with type 1 diabetes-susceptible HLA-DRB1/DQB1 genotypes. Homeostatic expansion characteristics with increased IL-7 concentrations and enhanced T-cell responsiveness to IL-7 were observed throughout the first year of life. However, the ability of antigen-presenting cells to activate naïve T cells was compromised at birth, and CB monocytes had low surface expression of CD40 and HLA class II. In contrast, antigen presentation and expression of these molecules had reached competent adult levels by the high incidence age of 8 months. We propose that temporal changes in islet autoimmunity seroconversion in infants are a consequence of the changing balance between homeostatic drive and antigen presentation competence. These findings are relevant for early prevention of type 1 diabetes.

IA-2 autoantibody affinity in children at risk for type 1 diabetes

Autoantibodies to insulinoma-associated protein 2 (IA-2A) are associated with increased risk for type 1 diabetes. Here we examined IA-2A affinity and epitope specificity to assess heterogeneity in response intensity in relation to pathogenesis and diabetes risk in 50 children who were prospectively followed from birth. At first IA-2A appearance, affinity ranged from 10(7) to 10(11)L/mol and was high (>1.0×10(9)L/mol) in 41 (82%) children. IA-2A affinity was not associated with epitope specificity or HLA class II haplotype. On follow-up, affinity increased or remained high, and IA-2A were commonly against epitopes within the protein tyrosine phosphatase-like IA-2 domain and the homologue protein IA-2β. IA-2A were preceded or accompanied by other islet autoantibodies in 49 (98%) children, of which 34 progressed to diabetes. IA-2A affinity did not stratify diabetes risk. In conclusion, the IA-2A response in children is intense with rapid maturation against immunogenic epitopes and a strong association with diabetes development.

Influence of type 1 diabetes genes on disease progression: similarities and differences between countries

Type 1 diabetes (T1D) is an autoimmune disease causing the destruction of pancreatic beta cells. The onset of clinical T1D is preceded by a time period called pre-diabetes, the duration of which varies widely. However, not all subjects developing beta-cell autoimmunity progress to clinical T1D. The inherited risk for T1D is determined by the human leukocyte antigen (HLA) class II genes, HLA class I genes, and several loci outside the HLA area. Although the role of the genetic risk variants in disease pathogenesis is not completely understood, some of the variants affecting disease risk are thought to influence the initiation of beta-cell autoimmunity whereas others seem to play a role during the later stages of the autoimmune process. In this review we describe the current knowledge on the genetic factors mediating the fate of already-established beta-cell autoimmunity and the rate of beta-cell destruction.

A strategy for combining minor genetic susceptibility genes to improve prediction of disease in type 1 diabetes

Genome-wide association studies have identified gene regions associated with type 1 diabetes. The aim of this study was to determine how the combined allele frequency of multiple susceptibility genes can stratify islet autoimmunity and/or type 1 diabetes risk. Children of parents with type 1 diabetes and prospectively followed from birth for the development of islet autoantibodies and diabetes were genotyped for single-nucleotide polymorphisms at 12 type 1 diabetes susceptibility genes (ERBB3, PTPN2, IFIH1, PTPN22, KIAA0350, CD25, CTLA4, SH2B3, IL2, IL18RAP, IL10 and COBL). Non-human leukocyte antigen (HLA) risk score was defined by the total number of risk alleles at these genes. Receiver operator curve analysis showed that the non-HLA gene combinations were highly effective in discriminating diabetes and most effective in children with a high-risk HLA genotype. The greatest diabetes discrimination was obtained by the sum of risk alleles for eight genes (IFIH1, CTLA4, PTPN22, IL18RAP, SH2B3, KIAA0350, COBL and ERBB3) in the HLA-risk children. Non-HLA-risk allele scores stratified risk for developing islet autoantibodies and diabetes, and progression from islet autoimmunity to diabetes. Genotyping at multiple susceptibility loci in children from affected families can identify neonates with sufficient genetic risk of type 1 diabetes to be considered for early intervention.

A functional framework for interpretation of genetic associations in T1D

Susceptibility to type 1 diabetes is attributable to genes that link disease progression to distinct steps in immune activation, expansion, and regulation. Recent studies illustrate examples of disease-associated variants that function in multiple cell types and independent pathways, some that impact different steps of a single mechanistic pathway, and some that are functionally interactive for deterministic events in setting thresholds for immune response.

Effects of non-HLA gene polymorphisms on development of islet autoimmunity and type 1 diabetes in a population with high-risk HLA-DR,DQ genotypes

We assessed the effects of non-HLA gene polymorphisms on the risk of islet autoimmunity (IA) and progression to type 1 diabetes in the Diabetes Autoimmunity Study in the Young. A total of 1,743 non-Hispanic, white children were included: 861 first-degree relatives and 882 general population children identified as having high-risk HLA-DR/DQ genotypes for type 1 diabetes. Of those, 109 developed IA and 61 progressed to diabetes. Study participants were genotyped for 20 non-HLA polymorphisms, previously confirmed as type 1 diabetes susceptibility loci. PTPN22 and UBASH3A predicted both IA and diabetes in regression models controlling for family history of type 1 diabetes and presence of HLA-DR3/4-DQB1*0302 genotype. In addition, PTPN2 predicted IA whereas INS predicted type 1 diabetes. The final multivariate regression models for both IA and type 1 diabetes included PTPN22, UBASH3A, and INS, in addition to family history of type 1 diabetes and HLA-DR3/4. In general population children, the most frequent combinations including these five significant predictors conferred hazard ratio of up to 13 for IA and >40 for type 1 diabetes. Non-HLA susceptibility alleles may help estimate risk for development of type 1 diabetes in the general population. These findings require replication in different populations.

Etiopathogenesis of insulin autoimmunity

Autoimmunity against pancreatic islet beta cells is strongly associated with proinsulin, insulin, or both. The insulin autoreactivity is particularly pronounced in children with young age at onset of type 1 diabetes. Possible mechanisms for (pro)insulin autoimmunity may involve beta-cell destruction resulting in proinsulin peptide presentation on HLA-DR-DQ Class II molecules in pancreatic draining lymphnodes. Recent data on proinsulin peptide binding to type 1 diabetes-associated HLA-DQ2 and -DQ8 is reviewed and illustrated by molecular modeling. The importance of the cellular immune reaction involving cytotoxic CD8-positive T cells to kill beta cells through Class I MHC is discussed along with speculations of the possible role of B lymphocytes in presenting the proinsulin autoantigen over and over again through insulin-carrying insulin autoantibodies. In contrast to autoantibodies against other islet autoantigens such as GAD65, IA-2, and ZnT8 transporters, it has not been possible yet to standardize the insulin autoantibody test. As islet autoantibodies predict type 1 diabetes, it is imperative to clarify the mechanisms of insulin autoimmunity.

Beyond the hormone: insulin as an autoimmune target in type 1 diabetes

Insulin is not only the hormone produced by pancreatic β-cells but also a key target antigen of the autoimmune islet destruction leading to type 1 diabetes. Despite cultural biases between the fields of endocrinology and immunology, these two facets should not be regarded separately, but rather harmonized in a unifying picture of diabetes pathogenesis. There is increasing evidence suggesting that metabolic factors (β-cell dysfunction, insulin resistance) and immunological components (inflammation and β-cell-directed adaptive immune responses) may synergize toward islet destruction, with insulin standing at the crossroad of these pathways. This concept further calls for a revision of the classical dichotomy between type 1 and type 2 diabetes because metabolic and immune mechanisms may both contribute to different extents to the development of different forms of diabetes. After providing a background on the mechanisms of β-cell autoimmunity, we will explain the role of insulin and its precursors as target antigens expressed not only by β-cells but also in the thymus. Available knowledge on the autoimmune antibody and T-cell responses against insulin will be summarized. A unifying scheme will be proposed to show how different aspects of insulin biology may lead to β-cell destruction and may be therapeutically exploited. We will argue about possible reasons why insulin remains the mainstay of metabolic control in type 1 diabetes but has so far failed to prevent or halt β-cell autoimmunity as an immune modulatory reagent.

Immune intervention with T regulatory cells: past lessons and future perspectives for type 1 diabetes

In type 1 diabetes (T1D), insulin-producing pancreatic β-cells are attacked and destroyed by the immune system. Although man-made insulin is life-saving, it is not a cure and it cannot prevent long-term complications. In addition, most T1D patients would do almost anything to achieve release from the burden of daily glucose monitoring and insulin injection. Despite the formation of very large and promising clinical trials, a means to prevent/cure T1D in humans remains elusive. This has led to an increasing interest in the possibility of using T cells with regulatory properties (Treg cells) as a biological therapy to preserve and restore tolerance to self-antigens. In the present review we will attempt to consolidate learning from the past and to describe what we now believe could in the future become a successful Treg-cell based immune intervention in T1D.

Age of islet autoantibody appearance and mean levels of insulin, but not GAD or IA-2 autoantibodies, predict age of diagnosis of type 1 diabetes: diabetes autoimmunity study in the young

OBJECTIVE

We evaluated predictors of progression to diabetes in children with high-risk HLA genotypes and persistent islet autoantibodies.

RESEARCH DESIGN AND METHODS

The Diabetes Autoimmunity Study in the Young (DAISY) followed 2,542 children with autoantibodies measured to GAD, IA-2, and insulin.

RESULTS

Persistent islet autoantibodies developed in 169 subjects, and 55 of those progressed to diabetes. Children expressing three autoantibodies showed a linear progression to diabetes with 74% cumulative incidence by the 10-year follow-up compared with 70% with two antibodies and 15% with one antibody (P < 0.0001). Both age of appearance of first autoantibody and insulin autoantibody (IAA) levels, but not GAD or IA-2 autoantibodies, were major determinants of the age of diabetes diagnosis (r = 0.79, P < 0.0001).

CONCLUSIONS

In the DAISY cohort, 89% of children who progressed to diabetes expressed two or more autoantibodies. Age of diagnosis of diabetes is strongly correlated with age of appearance of first autoantibody and IAA levels.

Primary dietary intervention study to reduce the risk of islet autoimmunity in children at increased risk for type 1 diabetes: the BABYDIET study

OBJECTIVE

To determine whether delaying the introduction of gluten in infants with a genetic risk of islet autoimmunity is feasible, safe, and may reduce the risk of type 1 diabetes-associated islet autoimmunity.

RESEARCH DESIGN AND METHODS

A total of 150 infants with a first-degree family history of type 1 diabetes and a risk HLA genotype were randomly assigned to a first gluten exposure at age 6 months (control group) or 12 months (late-exposure group) and were followed 3 monthly until the age of 3 years and yearly thereafter for safety (for growth and autoantibodies to transglutaminase C [TGCAs]), islet autoantibodies to insulin, GAD, insulinoma-associated protein 2, and type 1 diabetes.

RESULTS

Adherence to the dietary-intervention protocol was reported from 70% of families. During the first 3 years, weight and height were similar in children in the control and late-exposure groups, as was the probability of developing TGCAs (14 vs. 4%; P = 0.1). Eleven children in the control group and 13 children in the late-exposure group developed islet autoantibodies (3-year risk: 12 vs. 13%; P = 0.6). Seven children developed diabetes, including four in the late-exposure group. No significant differences were observed when children were analyzed as per protocol on the basis of the reported first gluten exposure of the children.

CONCLUSIONS

Delaying gluten exposure until the age of 12 months is safe but does not substantially reduce the risk for islet autoimmunity in genetically at-risk children.

Genetics of type 1 diabetes

BACKGROUND

Type 1 diabetes, a multifactorial disease with a strong genetic component, is caused by the autoimmune destruction of pancreatic β cells. The major susceptibility locus maps to the HLA class II genes at 6p21, although more than 40 non-HLA susceptibility gene markers have been confirmed.

CONTENT

Although HLA class II alleles account for up to 30%-50% of genetic type 1 diabetes risk, multiple non-MHC loci contribute to disease risk with smaller effects. These include the insulin, PTPN22, CTLA4, IL2RA, IFIH1, and other recently discovered loci. Genomewide association studies performed with high-density single-nucleotide-polymorphism genotyping platforms have provided evidence for a number of novel loci, although fine mapping and characterization of these new regions remain to be performed. Children born with the high-risk genotype HLADR3/4-DQ8 comprise almost 50% of children who develop antiislet autoimmunity by the age of 5 years. Genetic risk for type 1 diabetes can be further stratified by selection of children with susceptible genotypes at other diabetes genes, by selection of children with a multiple family history of diabetes, and/or by selection of relatives that are HLA identical to the proband.

SUMMARY

Children with the HLA-risk genotypes DR3/4-DQ8 or DR4/DR4 who have a family history of type 1 diabetes have more than a 1 in 5 risk for developing islet autoantibodies during childhood, and children with the same HLA-risk genotype but no family history have approximately a 1 in 20 risk. Determining extreme genetic risk is a prerequisite for the implementation of primary prevention trials, which are now underway for relatives of individuals with type 1 diabetes.

The association of variable number of tandem repeats of the insulin gene with susceptibility to type 1 diabetes among Korean subjects

BACKGROUND

There is ethnic variation in the variable number of tandem repeats of the insulin gene (INS VNTR), one of the susceptibility loci for developing type 1 diabetes (T1D). We evaluated the influence of the genotypes and subdivisions of INS VNTR on the development of T1D in Korean subjects.

METHODS

The study included 352 Korean patients, under the age of 18 years who were diagnosed as having T1D, and 356 control subjects. The insulin - 23HphI A/T single nucleotide polymorphism was used as a marker of class I and III alleles. Surrounding polymorphisms at nucleotide positions + 1127, + 1140, + 2331 and + 2336 were determined as subdivisions of INS VNTR.

RESULTS

Classes I/I, I/III and III/III were observed at frequencies of 95.8, 4.2 and 0% among all subjects, respectively. Class I/III genotype was significantly less frequent in patients with T1D than in controls (2.56 versus 5.90%; odds ratio 0.419; P = 0.039). In a subdivision analysis, the ID/ID genotype was decreased among patients (P = 0.017, adjusted P = 0.085) and the IC allele tended to increase. The frequency of the class I/III genotype was significantly lower among patients who were diagnosed when younger than 7 years of age than in controls (odds ratio 0.115; P = 0.011).

CONCLUSIONS

INS VNTR has predominance of class I over class III alleles and is associated with susceptibility to T1D in Koreans. In addition, INS VNTR shows distinctive susceptibility according to the age at the onset of T1D.

Advances in the prediction and natural history of type 1 diabetes

Type 1 diabetes (T1D) has the hallmark characteristics of autoimmunity superimposed on genetic susceptibility. Both genes (HLA) and immune markers (autoantibodies) have been validated as predictive markers of the subsequent development of the disease in higher-risk relatives and the lower-risk general population. Over the last three decades, using a combination of genes, immune, and metabolic markers, clinicians are now able to quantify an individual's disease risk from 1 in 100,000 to more than 1 in 2. This article reviews these biomarkers and T1D prediction strategies, and discusses potential implications of prediction and natural history for the pathogenesis of T1D.

Insulin gene VNTR genotype associates with frequency and phenotype of the autoimmune response to proinsulin

Immune responses to autoantigens are in part controlled by deletion of autoreactive cells through genetically regulated selection mechanisms. We have directly analyzed peripheral CD4+ proinsulin (PI) 76–90 (SLQPLALEGSLQKRG)-specific T cells using soluble fluorescent major histocompatibility complex class II tetramers. Subjects with type I diabetes and healthy controls with high levels of peripheral proinsulin-specific T cells were characterized by the presence of a disease-susceptible polymorphism in the insulin variable number of tandem repeats (INS-VNTR) gene. Conversely, subjects with a ‘protective' polymorphism in the INS-VNTR gene had nearly undetectable levels of proinsulin tetramer-positive T cells. These results strongly imply a direct relationship between genetic control of autoantigen expression and peripheral autoreactivity, in which proinsulin genotype restricts the quantity and quality of the potential T-cell response. Using a modified tetramer to isolate low-avidity proinsulin-specific T cells from subjects with the susceptible genotype, transcript arrays identified several induced pro-apoptotic genes in the control, but not diabetic subjects, likely representing a second peripheral mechanism for maintenance of tolerance to self antigens.

Thymus-specific deletion of insulin induces autoimmune diabetes

Insulin expression in the thymus has been implicated in regulating the negative selection of autoreactive T cells and in mediating the central immune tolerance towards pancreatic beta-cells. To further explore the function of this ectopic insulin expression, we knocked out the mouse Ins2 gene specifically in the Aire-expressing medullary thymic epithelial cells (mTECs), without affecting its expression in the beta-cells. When further crossed to the Ins1 knockout background, both male and female pups (designated as ID-TEC mice for insulin-deleted mTEC) developed diabetes spontaneously around 3 weeks after birth. beta-cell-specific autoimmune destruction was observed, as well as islet-specific T cell infiltration. The presence of insulin-specific effector T cells was shown using ELISPOT assays and adoptive T cell transfer experiments. Results from thymus transplantation experiments proved further that depletion of Ins2 expression in mTECs was sufficient to break central tolerance and induce anti-insulin autoimmunity. Our observations may explain the rare cases of type 1 diabetes onset in very young children carrying diabetes-resistant HLA class II alleles. ID-TEC mice could serve as a new model for studying this pathology.

Do non-HLA genes influence development of persistent islet autoimmunity and type 1 diabetes in children with high-risk HLA-DR,DQ genotypes?

OBJECTIVE

Specific alleles of non-HLA genes INS, CTLA-4, and PTPN22 have been associated with type 1 diabetes. We examined whether some of these alleles influence development of islet autoimmunity or progression from persistent islet autoimmunity to type 1 diabetes in children with high-risk HLA-DR,DQ genotypes.

RESEARCH DESIGN AND METHODS

Since 1993, the Diabetes Autoimmunity Study in the Young (DAISY) has followed 2,449 young children carrying HLA-DR,DQ genotypes associated with type 1 diabetes. Of those, 112 have developed islet autoimmunity (persistent autoantibodies to insulin, GAD65, and/or IA-2), and 47 of these have progressed to type 1 diabetes. The influence of polymorphisms of INS(-23Hph1), CTLA-4(T17A), and PTPN22(R620W) on development of persistent islet autoimmunity and progression to type 1 diabetes was evaluated by parametric models and by survival analyses.

RESULTS

PTPN22(R620W) allele T was associated with development of persistent islet autoimmunity (hazard ratio 1.83 [95% CI 1.27-2.63]) controlling for ethnicity, presence of HLA-DR3/4,DQB1*0302, and having a first-degree relative with type 1 diabetes. Survival analyses showed a significantly (P = 0.002) higher risk of persistent islet autoimmunity by age 10 years for the TT genotype (27.3%) than for the CT or CC genotype (7.9 and 5.3%, respectively). Cumulative risk of persistent islet autoimmunity was slightly higher (P = 0.02) for the INS(-23Hph1) AA genotype (7.8%) than for the AT or TT genotype (4.2 and 6.4% risk by age 10 years, respectively).

CONCLUSIONS

Whereas the HLA-DR3/4,DQB1*0302 genotype had a dramatic influence on both development of islet autoimmunity and progression to type 1 diabetes, the PTPN22(R620W) T allele significantly influences progression to persistent islet autoimmunity in the DAISY cohort.

Maternal type 1 diabetes reduces the risk of islet autoantibodies: relationships with birthweight and maternal HbA(1c)

AIMS/HYPOTHESIS

The risk of type 1 diabetes is reduced in the children of mothers with type 1 diabetes compared with children of fathers with type 1 diabetes. We asked whether children of mothers with type 1 diabetes also have a decreased risk of developing islet autoantibodies, and which factors associated with maternal diabetes contribute to a reduced islet autoantibody risk in offspring.

METHODS

Singleton offspring of a mother (n = 1,008) or father with type 1 diabetes (n = 578) from the BABYDIAB study were included. Children were followed from birth for the development of islet autoantibodies defined as two or more autoantibodies to insulin, glutamic acid decarboxylase or insulinoma antigen 2 in two or more blood samples.

RESULTS

Islet autoantibody risk was lower in children of mothers with type 1 diabetes (5 year risk, 3.2% vs 5.7% in children of fathers with type 1 diabetes; p = 0.04). Among factors that differed between pregnancies from mothers with and without type 1 diabetes, birthweight was associated with islet autoantibody risk. Risk was reduced in children with birthweights in the lower (adjusted HR 0.33; 95% CI 0.14-0.75; p = 0.009) and upper (HR 0.45; 95% CI 0.21-0.97; p = 0.04) tertiles compared with the middle tertile. A sub-analysis of maternal HbA(1c) suggested that moderately elevated third trimester maternal HbA(1c) was also associated with a reduced islet autoantibody risk in children of mothers with type 1 diabetes (5.7-7%; HR 0.38; 95% CI 0.15-0.96; p = 0.04 vs children of mothers with HbA(1c) < 5.7%).

CONCLUSIONS/INTERPRETATION

The risk of islet autoimmunity is modified by maternally influenced events such as birthweight.

Modulating the natural history of type 1 diabetes in children at high genetic risk by mucosal insulin immunization

Mucosal administration of insulin represents an attractive antigen-specific therapeutic approach to preventing type 1 diabetes. It can prevent autoimmune diabetes in animal models, but although it has been shown to be safe, it has not yet been proven effective in human studies. Efficacy may depend on the dose and route at which insulin is administered, the stage in type 1 diabetes pathogenesis at which treatment is initiated, and the study cohort that is treated. We have proposed Pre-POINT (Primary Oral/intranasal INsulin Trial), a dose-finding safety and immune efficacy pilot study for primary mucosal insulin therapy in islet autoantibody-negative children at high genetic risk for type 1 diabetes who naturally first develop autoimmunity to insulin. Pre-POINT aims to identify an optimal insulin dose and route of application (orally or intranasally) that is well tolerated and can induce an immune response to insulin for additional use in a phase II/III primary prevention trial in children at risk.

Reduced CD4+T cell activation in children with type 1 diabetes carrying the PTPN22/Lyp 620Trp variant

The 620Trp variant of the LYP protein, encoded by the lymphoid tyrosine phosphatase 22 gene (PTPN22), is associated with autoimmunity. In this study we aimed at characterising the role of this variant on lymphocyte activation. We analysed cytokine secretion and proliferation of peripheral blood mononuclear cells (PBMCs) and CD4(+)T cells in a cohort of clinically non-diabetic, multiple autoantibody-positive children, healthy controls and in children with type 1 diabetes (T1D). We found a decreased proliferation and IL-2 production of CD4(+)T cells after anti-CD3/anti-CD28 stimulation (p=0.04 for IL-2) among T1D patients. In addition, a profoundly decreased intracellular calcium flux in CD4(+)T cells after PHA stimulus was detected among 620Trp carriers. In contrast, no effect of this polymorphism on tuberculin and tetanus toxoid induced PBMC proliferation and cytokine secretion was observed in autoantibody positive children, healthy controls and children with newly-diagnosed T1D. In conclusion, the LYP 620Trp variant is associated with reduced activation, proliferation and IL-2 production in CD4(+)T cells among T1D patients. In accordance with our previous findings on the key role of this variant on disease progression, this mechanism is likely to contribute to the development of beta-cell specific autoimmunity.

Insulin VNTR I/III genotype is associated with autoantibodies against glutamic acid decarboxylase in newly diagnosed type 1 diabetes

BACKGROUND

In type 1 diabetes (T1D), the influence of age at diagnosis and of the IDDM1 and IDDM2 genetic susceptibility loci on the profile of beta-cell autoantibodies has been demonstrated. We studied these associations in a group of 92 patients (children, adolescents and adults, aged 2-62 years) with newly diagnosed T1D.

METHODS

The prevalence of the HLA-DQB1*02 and *0302 alleles and of the classes of variable number of tandem repeats (VNTR) of the insulin gene (INS), and of beta-cell autoantibodies (GADA, IA-2A, ICA and IAA) was determined. Statistical analysis was performed using linear and logistic regression models.

RESULTS

The presence of IAA, IA-2A and ICA, but not of GADA, was negatively associated with age at diagnosis. Younger patients were more likely to have multiple autoantibodies. There was a tendency of a higher prevalence of IAA in patients with the HLA-DQB1*02/0302 genotype or with the DQB1*0302 allele compared to patients lacking these markers. As a novel observation, the INS VNTR I/III genotype was significantly associated with the presence of GADA (OR = 4.79; p = 0.018).

CONCLUSION

The association between the INS VNTR I/III genotype and GADA may suggest that in patients with T1D lacking the INS VNTR I/I genotype, the effect of other susceptibility factors prevails, which promotes the development of autoimmunity to beta-cell antigens other than insulin.

GAD autoantibody affinity and epitope specificity identify distinct immunization profiles in children at risk for type 1 diabetes

OBJECTIVE

Autoantibodies to insulin and GAD are features of preclinical type 1 diabetes in children. For insulin autoantibodies, the antibody affinity and epitope specificity predict which children progress to diabetes. We asked whether autoantibodies to GAD (GADAs) are heterogeneous in affinity and epitope recognition and whether diabetes-related GADA are restricted to high-affinity responses.

RESEARCH DESIGN AND METHODS

GADA affinity was measured by competitive binding experiments with [(125)I]-labeled and -unlabeled recombinant human GAD65 in the first GADA-positive sample from 95 children with a type 1 diabetes family history who were prospectively followed from birth and in follow-up samples from 65 of these children.

RESULTS

At first GADA appearance, affinity ranged from 10(7) to 10(10) l/mol. Affinity was higher in multiple islet autoantibody-positive children (P < 0.0001) and in HLA DR3-positive children (P = 0.006). GADA affinities were >10(9) l/mol in 52 of 53 multiple autoantibody-positive children. In contrast, children who were single GADA positive often had lower affinity GADA and/or GADA with specificities that were restricted to minor NH(2)-terminal GAD65 epitopes. At follow-up, affinity increased from low to high in 3 of 65 children. All 24 children who developed diabetes had high-affinity GADAs before diabetes onset.

CONCLUSIONS

Children develop discrete, heterogeneous antibody responses to GAD that could arise from distinct immunization events, only some of which are diabetes relevant. Subtyping the GADA responses using affinity measurement will improve type 1 diabetes risk assessment.

Fetal growth is increased by maternal type 1 diabetes and HLA DR4-related gene interactions

AIMS/HYPOTHESIS

Intrauterine growth in non-diabetic pregnancies is reported to be influenced by type 1 diabetes susceptibility genes. In particular, the high-risk HLA DR4_DQB1*0302 haplotype is associated with increased birthweight. The aim of this study was to determine whether HLA DR4 was associated with increased birthweight in a maternal diabetes environment and whether effects persisted during early childhood.

SUBJECTS AND METHODS

Birthweight and gestational age were obtained in singleton births from mothers with type 1 diabetes (n = 1161) or whose fathers or siblings have type 1 diabetes (n = 872). Weight and height at ages 2 and 5 years were obtained from paediatric records. Data were adjusted for (gestational) age and sex and expressed as percentiles of German reference data. HLA DR typing was obtained for all children and 1090 children also had insulin gene (INS) variable number of tandem repeats (VNTR) typing.

RESULTS

Maternal type 1 diabetes was associated with increased birthweight, gestational age and birthweight percentiles (all p < 0.0001). In children of mothers with type 1 diabetes, birthweight percentile was further related to maternal HbA(1c) during pregnancy (r = 0.26; p < 0.0001) and was independently increased if children had HLA DR4 alleles (76th vs 64th percentile; p < 0.0001). HLA DR4 was not associated with birthweight in children of non-diabetic mothers. Birthweight was not associated with INS VNTR genotypes. High birthweight, but not HLA DR4 was associated with increased weight and BMI at ages 2 and 5 years (p < 0.0001).

CONCLUSIONS/INTERPRETATION

Our findings are consistent with the hypothesis that a diabetic intrauterine environment interacts with gene(s) marked by the type 1 diabetes susceptibility HLA DR4 alleles to increase fetal growth.

Insulin protects islets from apoptosis via Pdx1 and specific changes in the human islet proteome

Insulin is both a hormone regulating energy metabolism and a growth factor. We and others have shown that physiological doses of insulin initiate complex signals in primary human and mouse beta-cells, but the functional significance of insulin's effects on this cell type remains unclear. In the present study, the role of insulin in beta-cell apoptosis was examined. Exogenous insulin completely prevented apoptosis induced by serum withdrawal when given at picomolar or low nanomolar concentrations but not at higher concentrations, indicating that physiological concentrations of insulin are antiapoptotic and that insulin signaling is self-limiting in islets. Insulin treatment was associated with the nuclear localization of Pdx1 and the prosurvival effects of insulin were largely absent in islets 50% deficient in Pdx1, providing direct evidence that Pdx1 is a signaling target of insulin. Physiological levels of insulin did not increase Akt phosphorylation, and the protective effects of insulin were only partially altered in islets lacking 80% of normal Akt activity, suggesting the presence of additional insulin-regulated antiapoptotic pathways. Proteomic analysis of insulin-treated human islets revealed significant changes in multiple proteins. Bridge-1, a Pdx1-binding partner and regulator of beta-cell survival, was increased significantly at low insulin doses. Together, these data suggest that insulin can act as a master regulator of islet survival by regulating Pdx1.