A type 1 diabetes subgroup with a female bias is characterised by failure in tolerance to thyroid peroxidase at an early age and a strong association with the cytotoxic T-lymphocyte-associated antigen-4 gene

Cluster of differentiation molecules in the metabolic syndrome

Metabolic syndrome (MetS) represents a significant public health concern due to its association with an increased risk of cardiovascular disease, type 2 diabetes, and other serious health conditions. Despite extensive research, the underlying molecular mechanisms contributing to MetS pathogenesis remain elusive. This review aims to provide a comprehensive overview of the molecular mechanisms linking MetS and cluster of differentiation (CD) markers, which play critical roles in immune regulation and cellular signaling. Through an extensive literature review with a systematic approach, we examine the involvement of various CD markers in MetS development and progression, including their roles in adipose tissue inflammation, insulin resistance, dyslipidemia, and hypertension. Additionally, we discuss potential therapeutic strategies targeting CD markers for the management of MetS. By synthesizing current evidence, this review contributes to a deeper understanding of the complex interplay between immune dysregulation and metabolic dysfunction in MetS, paving the way for the development of novel therapeutic interventions.

Genetic variants and risk of endocrine autoimmunity in relatives of patients with Addison's disease

Since individuals with Addison's disease (AD) present considerable co-occurrence of additional autoimmune conditions, clustering of autoimmunity was also predicted among their relatives. The study was aimed to assess circulating autoantibodies in first-degree relatives of patients with AD and to correlate them with the established genetic risk factors (PTPN22 rs2476601, CTLA4 rs231775, and BACH2 rs3757247). Antibodies were evaluated using validated commercial assays, and genotyping was performed using TaqMan chemistry. The studied cohort comprised 112 female and 75 male relatives. Circulating autoantibodies were found in 69 relatives (36.9%). Thyroid autoantibodies, that is antibodies to thyroid peroxidase (aTPO) and thyroglobulin (aTg), were detectable in 25.1 and 17.1% relatives, respectively. Antibodies to 21-hydroxylase (a21OH) were found in 5.8% individuals, and beta cell-specific antibodies to ZnT8, GAD, and IA2 were found in 7.5, 8.0, and 2.7%, respectively. The prevalence of a21OH (P = 0.0075; odds ratio (OR) 7.68; 95% CI 1.903-36.0), aTPO (P < 0.0001; OR 3.85; 95% CI 1.873-7.495), and aTg (P < 0.0001; OR 7.73; 95% CI 3.112-19.65), as well as aGAD (P = 0.0303; OR 3.38; 95% CI 1.180-9.123) and aZnT8 (P = 0.032; OR 6.40; 95% CI 1.846-21.91), was significantly increased in carriers of rs2476601 T allele. Moreover, T allele appeared to be a risk factor for multiple circulating autoantibody specificities (P = 0.0009; OR 5.79; 95% CI 1.962-15.81). None of the studied autoantibodies demonstrated significant association with rs231775 in CTLA4 (P > 0.05), and only weak association was detected between BACH2 rs3757247 and circulating aTPO (P = 0.0336; OR 2.12; 95%CI 1.019-4.228). In conclusion, first-degree relatives of patients with AD, carriers of the PTPN22 rs2476601 T allele, are at particular risk of developing autoantibodies to endocrine antigens.

CTLA4, SH2B3, and CLEC16A diversely affect the progression of early islet autoimmunity in relatives of Type 1 diabetes patients

The HLA region is the major genetic risk determinant of Type 1 diabetes. How non-HLA loci contribute to the genetic risk is incompletely understood, but there are indications that at least some impact progression of asymptomatic autoimmunity. We examined whether SNPs in 7 susceptibility loci (INS, SH2B3, PTPN2, PTPN22, CTLA4, CLEC16A, and IL2RA) could improve prediction of the progression from single to multiple autoantibody positivity, and from there on to diagnosis. SNPs were genotyped in persistently autoantibody positive relatives by allelic discrimination qPCR and disease progression was studied by multivariate Cox regression analysis. In our cohort, only the CTLA4 GA genotype (rs3087243, P = 0.002) and the CLEC16A AA genotype (rs12708716, P = 0.021) were associated with accelerated progression from single to multiple autoantibody positivity, but their effects were restricted to presence of HLA-DQ2/DQ8, and IAA as first autoantibody, respectively. The interaction of CTLA4 and HLA-DQ2/DQ8 overruled the effect of DQ2/DQ8 alone. The HLA-DQ2/DQ8-mediated risk of progression to multiple autoantibodies nearly entirely depended on heterozygosity for CTLA4. The SH2B3 TT genotype (rs3184504) was protective for HLA-DQ8 positive subjects (P = 0.003). At the stage of multiple autoantibodies, only the CTLA4 GA genotype was a minor independent risk factor for progression towards clinical diabetes (P = 0.034). Our study shows that non-HLA polymorphisms impact progression of islet autoimmunity in a subgroup-, stage- and SNP-specific way, suggesting distinct mechanisms. If confirmed, these findings may help refine risk assessment, follow-up, and prevention trials in risk groups.

Correlations between Biochemical Markers in Thyroid Pathology with those in Carbohydrates Metabolism

Thyroid dysfunction is increasingly found in patients with diabetes. Diabetes can affect thyroid function to a variable extent and unrecognized thyroid dysfunction, not only worsens metabolic control, but also prevents the management of diabetes. The aim of this study was to screen the incidence of thyroid disease in Constanta County, Romania in patients diagnosed with type II diabetes, in order to assess the tendency to associate thyroid hormone dysfunction with the diabetic process by correlating glycemic parameters and thyroid profile in serum. The study included a number of 153 patients who presented within 3 months for blood tests, in compliance with GDPR rules. The following parameters were processed from these patients: FT3 - free triiodothyronine, FT4 - free thyroxine, TSH - thyroid stimulating hormone, Anti-TPO - thyroid peroxidase antibodies (anti-thyroid peroxidase), Serum glucose, Glycosylated haemoglobin - HbA1C. In patients of both sexes studied, the mean TSH was 3.15 IU / ml, males’ TSH mean being 2.82 IU / ml and higher, but not above the maximum limit. Blood glucose ranged from an average of 92.11 mg / dl in the 153 patients, 92.41 mg / dl in male patients and 93.82 mg / dl in female patients. Glycated haemoglobin (%) ranged from 6.79% in female patients to 6.21% in male patients, with a mean of 6.5%.

Pathology derived from disorders of carbohydrate metabolism may be present in patients with thyroid changes.

Multiple inducers and novel roles of autoantibodies against the obligatory NMDAR subunit NR1: a translational study from chronic life stress to brain injury

Circulating autoantibodies (AB) of different immunoglobulin classes (IgM, IgA, and IgG), directed against the obligatory N-methyl-D-aspartate-receptor subunit NR1 (NMDAR1-AB), belong to the mammalian autoimmune repertoire, and appear with age-dependently high seroprevalence across health and disease. Upon access to the brain, they can exert NMDAR-antagonistic/ketamine-like actions. Still unanswered key questions, addressed here, are conditions of NMDAR1-AB formation/boosting, intraindividual persistence/course in serum over time, and (patho)physiological significance of NMDAR1-AB in modulating neuropsychiatric phenotypes. We demonstrate in a translational fashion from mouse to human that (1) serum NMDAR1-AB fluctuate upon long-term observation, independent of blood-brain barrier (BBB) perturbation; (2) a standardized small brain lesion in juvenile mice leads to increased NMDAR1-AB seroprevalence (IgM + IgG), together with enhanced Ig-class diversity; (3) CTLA4 (immune-checkpoint) genotypes, previously found associated with autoimmune disease, predispose to serum NMDAR1-AB in humans; (4) finally, pursuing our prior findings of an early increase in NMDAR1-AB seroprevalence in human migrants, which implicated chronic life stress as inducer, we independently replicate these results with prospectively recruited refugee minors. Most importantly, we here provide the first experimental evidence in mice of chronic life stress promoting serum NMDAR1-AB (IgA). Strikingly, stress-induced depressive-like behavior in mice and depression/anxiety in humans are reduced in NMDAR1-AB carriers with compromised BBB where NMDAR1-AB can readily reach the brain. To conclude, NMDAR1-AB may have a role as endogenous NMDAR antagonists, formed or boosted under various circumstances, ranging from genetic predisposition to, e.g., tumors, infection, brain injury, and stress, altogether increasing over lifetime, and exerting a spectrum of possible effects, also including beneficial functions.

Autoimmune thyroid disease and type 1 diabetes mellitus: same pathogenesis; new perspective?

Autoimmune thyroid disease (AITD) and type 1 diabetes mellitus (T1DM) are two common autoimmune diseases that can occur concomitantly. In general, patients with diabetes have a high risk of AITD. It has been proposed that a complex genetic basis together with multiple nongenetic factors make a variable contribution to the pathogenesis of T1DM and AITD. In this paper, we summarize current knowledge in the field regarding potential pathogenic factors of T1DM and AITD, including human leukocyte antigen, autoimmune regulator, lymphoid protein tyrosine phosphatase, forkhead box protein P3, cytotoxic T lymphocyte-associated antigen, infection, vitamin D deficiency, and chemokine (C-X-C motif) ligand. These findings offer an insight into future immunotherapy for autoimmune diseases.

Tipping the balance: inhibitory checkpoints in intestinal homeostasis

The small intestinal and colonic lamina propria are populated with forkhead box P3 (FOXP3)⁺CD4⁺ regulatory T cells (Tregs) and interleukin-10-producing T cells that orchestrate intestinal tolerance to harmless microbial and food antigens. Expression of co-inhibitory receptors such as CTLA-4 and PD-1 serve as checkpoints to these cells controlling their T-cell receptor (TCR)-mediated and CD28-mediated activation and modulating the phenotype of neighboring antigen presenting cells. Recent discoveries on the diversity of co-inhibitory receptors and their selective cellular expression has shed new light on their tissue-dependent function. In this review, we provide an overview of the co-inhibitory pathways and checkpoints of Treg and effector T cells and their mechanisms of action in intestinal homeostasis. Better understanding of these inhibitory checkpoints is desired as their blockade harbors clinical potential for the treatment of cancer and their stimulation may offer new opportunities to treat chronic intestinal inflammation such as inflammatory bowel disease.

Identifying genetic risk loci for diabetic complications and showing evidence for heterogeneity of type 1 diabetes based on complications risk

There is a growing body of evidence suggesting that type 1 diabetes (T1D) is a genetically heterogeneous disease. However, the extent of this heterogeneity, and what observations may distinguish different forms, is unclear. One indicator may be T1D-related microvascular complications (MVCs), which are familial, but occur in some families, and not others. We tested the hypothesis that T1D plus MVC is genetically distinct from T1D without MCV. We studied 415 families (2,462 individuals, 896 with T1D) using genome-wide linkage analysis, comparing families with and without MVC. We also tested for interaction between identified loci and alleles at the HLA-DRB1 locus. We found significant linkage scores at 1p36.12, 1q32.1, 8q21.3, 12p11.21 and 22q11.21. In all regions except 1p36.12, linkage scores differed between MVC-based phenotype groups, suggesting that families with MVCs express different genetic influences than those without. Our linkage results also suggested gene-gene interaction between the above putative loci and the HLA region; HLA-based strata produced significantly increased linkage scores in some strata, but not others within a phenotype group. We conclude that families with type 1 diabetes plus MVCs are genetically different from those with diabetes alone.

Genetic Polymorphisms of Cytotoxic T-Lymphocyte Antigen 4 in Primary Biliary Cholangitis: A Meta-Analysis

Background and Aim

The connection between gene polymorphisms of cytotoxic T-lymphocyte-associated protein 4 (CTLA4) and primary biliary cholangitis (PBC) is still vague and blurred. The purpose of this study is to precisely estimate the association of the polymorphisms of CTLA4 with the risk of PBC by using a meta-analysis.

Methods

PubMed and the Chinese National Knowledge Infrastructure (CNKI) database were used to search correlative literatures, and the documents which were about the relationships between the polymorphisms of CTLA4 (rs231775, rs231725, rs3087243, and rs5742909) and PBC were collected as of June 2016. The strength of correlation based on odds ratios (ORs) and its 95% confidence intervals (95%CIs) was computed by STATA.

Results

Generally, in rs231775, a significant risk was found in G allele, the value of OR was 1.32, and its 95%CI was 1.19 to 1.47. The same situation was found in A allele of rs231725, the value of OR was 1.33, and its 95%CI was 1.22 to 1.45. As genotypic level, different genotypic models were also found to have obvious relevance with PBC in rs231775 and rs231725. No obvious connections were found in other SNPs.

Conclusion

This study indicated that the polymorphisms of rs231775 and rs231725 would be the risk factors of PBC.

Immune checkpoint therapy and type 1 diabetes

Type 1 diabetes is caused by destruction of insulin-producing beta cells of the pancreas. The etiology of type 1 diabetes is immune-mediated by either an organ-specific autoimmune mechanism in autoimmune type 1 diabetes or a still unknown but probably immune-mediated mechanism in fulminant type 1 diabetes. Immunomodulation is therefore expected to accelerate or inhibit type 1 diabetes. Recent progress in anti-cancer therapy by immune-checkpoint blockade, such as anti-PD-1 and anti-CTLA4 monoclonal antibodies, has markedly improved the prognosis of patients with advanced cancers. These drugs activate anti-tumor immunity by blocking inhibitory signals of T lymphocytes. Activation of immunological pathways, however, is expected to accelerate immune-mediated diseases. In fact, the development of autoimmune-thyroid diseases and type 1 diabetes, including fulminant type 1 diabetes, has been reported in patients treated with immune checkpoint blockers. The development of fulminant type 1 diabetes is a major concern because of its abrupt onset and very rapid progression, leading to death unless proper treatment is initiated immediately after diagnosis. In this review, the development of type 1 diabetes with immune-checkpoint therapy and its etiological background are discussed.

High frequency of vitamin D receptor gene polymorphism FokI in Brazilian Type 1 diabetes mellitus patients with clinical autoimmune thyroid disease

BACKGROUND

Polymorphisms of vitamin D receptor (VDR) gene have been studied as genetic markers of type 1 diabetes mellitus (T1DM) and some studies have reported associations with autoimmune thyroid disease. The aim of this study was to evaluate the relationship between VDR FokI polymorphism (rs10735810), thyroid autoimmunity and thyroid dysfunction (TD) in Brazilian T1DM.

METHODS

One-hundred-eighty T1DM patients were evaluated for age, duration of diabetes (DDM), positivity to TPO Antibody (TPOA), GAD Antibody (GADA), IA2 Antibody (IA2A) and fasting serum C-peptide (FCP) according to diagnosis of TD. PCR-RFLP analyses were carried out for VDR polymorphism FokI.

RESULTS

TPOA positivity (80.0 vs. 25.0 %, p < 0.001) and GADA positivity (56.0 vs. 30.3 %, p = 0.01) were higher in T1DM patients with TD with the same age and DDM than the group without TD, with no difference of FCP and IA2A positivity. We observed higher prevalence of VDR FokI in T1DM with TD (ff and Ff 73.9 % with TD vs. 52.7 % without TD, p = 0.05). Positivity to TPOA and presence of FokI polymorphism were significantly associated with the concurrence of TD in T1DM patients (OR 18.1; CI 3.7-87.0; p < 0.001).

CONCLUSIONS

The VDR FokI polymorphism (rs10735810) was associated to persistence of GADA, TPOA positivity and TD in Brazilian T1DM. Positivity to TPOA and VDR polymorphism FokI were strongly associated with concurrence of T1D and TD. These data collaborate to understanding the joint susceptibility genes for TD in T1DM.

Genome wide identification of new genes and pathways in patients with both autoimmune thyroiditis and type 1 diabetes

Autoimmune thyroid diseases (AITD) and Type 1 diabetes (T1D) frequently occur in the same individual pointing to a strong shared genetic susceptibility. Indeed, the co-occurrence of T1D and AITD in the same individual is classified as a variant of the autoimmune polyglandular syndrome type 3 (designated APS3v). Our aim was to identify new genes and mechanisms causing the co-occurrence of T1D + AITD (APS3v) in the same individual using a genome-wide approach. For our discovery set we analyzed 346 Caucasian APS3v patients and 727 gender and ethnicity matched healthy controls. Genotyping was performed using the Illumina Human660W-Quad.v1. The replication set included 185 APS3v patients and 340 controls. Association analyses were performed using the PLINK program, and pathway analyses were performed using the MAGENTA software. We identified multiple signals within the HLA region and conditioning studies suggested that a few of them contributed independently to the strong association of the HLA locus with APS3v. Outside the HLA region, variants in GPR103, a gene not suggested by previous studies of APS3v, T1D, or AITD, showed genome-wide significance (p < 5 × 10(-8)). In addition, a locus on 1p13 containing the PTPN22 gene showed genome-wide significant associations. Pathway analysis demonstrated that cell cycle, B-cell development, CD40, and CTLA-4 signaling were the major pathways contributing to the pathogenesis of APS3v. These findings suggest that complex mechanisms involving T-cell and B-cell pathways are involved in the strong genetic association between AITD and T1D.

The association of cytotoxic T-lymphocyte antigen-4 + 49A/G and CT60 polymorphisms with type 1 diabetes and latent autoimmune diabetes in Chinese adults

OBJECTIVE

The aim of this study was to investigate the association of cytotoxic T-lymphocyte antigen-4 (CTLA-4) + 49A/G and CT60 polymorphisms with latent autoimmune diabetes in adults (LADA) and the genetic differences between LADA, type 1 diabetes (T1DM), and type 2 diabetes (T2DM) in a Chinese population.

SUBJECTS

A total of 231 LADA, 402 T1DM, and 330 T2DM patients as well as 482 nondiabetic controls were recruited in the study.

METHODS

CTLA-4 + 49A/G and CT60 polymorphisms were analyzed by polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP). The level of glutamic acid decarboxylase antibodies (GADAs) was detected by a radioligand binding assay.

RESULTS

The CTLA-4 + 49A/G risk genotype GG was most frequent in T1DM patients (45.3%), followed by LADA patients (44.2%) and T2DM patients (38.8%). Significantly higher frequencies of the risk genotype GG were observed in the T1DM (OR = 1.532, 95% CI 1.168-2.010, P = 0.002) and LADA patients (OR = 1.464, 95% CI 1.063-2.017, P = 0.019). The frequencies of the CTLA-4 CT60 risk genotype GG were 65.2, 61.9, 58.5, and 56.4% in the T1DM, LADA, T2DM, and control groups, respectively. The CTLA-4 CT60 GG risk genotypes were only associated with T1DM (OR = 1.445, 95% CI 1.1-1.898, P = 0.008). Compared with controls, patients having a high titer of GADA (GADA ≥ 180 IU/ml) had higher frequencies of the GG risk genotype of CTLA-4 + 49 A/G (49.4% vs. 35.1% OR = 1.807, 95% CI 1.125-2.903, P = 0.014), but there was no difference between patients having a low titer of GADA and controls.

CONCLUSION

The CTLA-4 + 49 A/G polymorphism confers genetic susceptibility to LADA and T1DM, while the CTLA-4 CT60 polymorphism is only associated with T1DM in Chinese population. The CTLA-4 + 49 A/G genotype distribution in LADA is associated with the GADA level.

Allelic variant in CTLA4 is associated with thyroid failure and faster β-cell exhaustion in latent autoimmune diabetes in adults

BACKGROUND

The aim of the study was to investigate the role of the cytotoxic T-lymphocyte-associated protein 4 (CTLA4) G6230A variant on the susceptibility of latent autoimmune diabetes in adults (LADA) as a whole and in the subset of patients who share autoimmune thyroid disease (AITD).

METHODS

The study included 202 LADA, 1373 patients with early onset type 1 diabetes (T1D), 130 patients with late-onset T1D, 188 patients with non-autoimmune diabetes and 1904 healthy controls. Thyrotropin (thyrotropin-stimulating hormone; TSH) and antibodies against thyroid peroxidase were analyzed in all patients. The CTLA4 G6230A variant was assessed in LADA, early and late-onset T1D patients as well as in the controls.

RESULTS

The frequency of CTLA4 G alleles and genotypes in LADA patients did not differ significantly from that in the other groups, regardless of its association with AITD. We found an increased frequency of G allele-containing genotypes within LADA patients who had higher TSH compared with those with normal TSH (P = 0.002). Moreover, LADA patients carrying G allele-containing genotypes were more likely to require insulin therapy within 4 years of diagnosis (P = 0.002).

CONCLUSIONS

The G6230A CTLA4 variant does not confer susceptibility to LADA in Sardinian patients even when associated with AITD. However, it helps identify a particular subset of LADA patients with more clinically severe disease, both for thyroid dysfunction and diabetes.

Dissecting the role of the FOXP3 gene in the joint genetic susceptibility to autoimmune thyroiditis and diabetes: a genetic and functional analysis

We have previously shown that a (TC)n microsatellite in intron 5 of the Forkhead Box Protein 3 (FOXP3) gene was associated with a variant of the autoimmune polyglandular syndrome type 3 (APS3v), that is defined as the co-occurrence of type 1 diabetes (T1D) and autoimmune thyroiditis (AITD). Allele 10, containing 25 repeats of the microsatellite (long repeats), is preferentially transmitted to offspring with APS3v, while allele 2, containing 14 repeats of the microsatellite (short repeats), is protective. We hypothesized that the long repeats of the intron 5 microsatellite decrease FOXP3 splicing and function, thereby reducing regulatory T cell activity and promoting the development of APS3v. We cloned genomic DNA from two males hemizygous for the long and short repeats of the microsatellite on their X-chromosomes and transfected them into human embryonic kidney 293 (HEK 293) cells to perform direct splicing analysis. We identified a novel splice variant of FOXP3 lacking exon 6, and showed that it is expressed in human thymus and lymph node. However, the length of the repeats in the microsatellite did not significantly influence the expression of this FOXP3 splice variant in vitro. Interestingly, this splice variant was expressed in human regulatory T cells, suggesting that it may play a role in their function. In conclusion, we identified a novel splice variant FOXP3Δ6. The role of its expression in regulatory T cells in the development of autoimmunity remains to be determined.

Common variants on cytotoxic T lymphocyte antigen-4 polymorphisms contributes to type 1 diabetes susceptibility: evidence based on 58 studies

In the past decade, a number of case–control studies have been carried out to investigate the relationship between the CTLA4 gene polymorphisms and type 1 diabetes (T1D). However, these studies have yielded contradictory results. To investigate this inconsistency, we performed a meta-analysis of all available studies dealing with the relationship between the CTLA4 polymorphism and T1D. In total, 58 association studies on two CTLA4 polymorphisms (G49A and C60T) and risk of T1D, including a total of 30,723 T1D cases and 45,254 controls were included. In a combined analysis, the summary per-allele odds ratio (OR) for T1D of the G49A and C60T polymorphism was 1.42 [95% confidence interval (CI): 1.31–1.53, P<10⁻⁵] and 1.23 (95% CI: 1.18–1.29, P<10⁻⁵), respectively. Significant results were also observed using dominant or recessive genetic model. In the subgroup analysis by ethnicity and sample size, significantly increased risks were also found for these polymorphisms. This meta-analysis demonstrated that the G49A and C60T polymorphism of CTLA4 is a risk factor associated with increased T1D susceptibility, but these associations vary in different ethnic populations.

Genetic interactions among Idd3, Idd5.1, Idd5.2, and Idd5.3 protective loci in the nonobese diabetic mouse model of type 1 diabetes

In the NOD mouse model of type 1 diabetes, insulin-dependent diabetes (Idd) loci control the development of insulitis and diabetes. Independently, protective alleles of Idd3/Il2 or Idd5 are able to partially protect congenic NOD mice from insulitis and diabetes, and to partially tolerize islet-specific CD8(+) T cells. However, when the two regions are combined, mice are almost completely protected, strongly suggesting the existence of genetic interactions between the two loci. Idd5 contains at least three protective subregions/causative gene candidates, Idd5.1/Ctla4, Idd5.2/Slc11a1, and Idd5.3/Acadl, yet it is unknown which of them interacts with Idd3/Il2. Through the use of a series of novel congenic strains containing the Idd3/Il2 region and different combinations of Idd5 subregion(s), we defined these genetic interactions. The combination of Idd3/Il2 and Idd5.3/Acadl was able to provide nearly complete protection from type 1 diabetes, but all three Idd5 subregions were required to protect from insulitis and fully restore self-tolerance. By backcrossing a Slc11a1 knockout allele onto the NOD genetic background, we have demonstrated that Slc11a1 is responsible for the diabetes protection resulting from Idd5.2. We also used Slc11a1 knockout-SCID and Idd5.2-SCID mice to show that both loss-of-function alleles provide protection from insulitis when expressed on the SCID host alone. These results lend further support to the hypothesis that Slc11a1 is Idd5.2.

The B7-independent isoform of CTLA-4 functions to regulate autoimmune diabetes

The critical role of CTLA-4 in inhibiting Ag-driven T cell responses upon engagement with its ligands, B7-1 and B7-2 and its importance for peripheral T cell tolerance and T cell homeostasis has been studied intensively. The CTLA-4 splice variant ligand-independent (li)-CTLA-4 is expressed in naive and activated T cells and can actively alter T cell signaling despite its lack of a B7 binding domain. To study the effect of li-CTLA-4 in regulating T cell responses in the context of autoimmunity, we engineered a B6.CTLA-4 (floxed-Exon2)-BAC-transgene, resulting in selective expression of li-CTLA-4 upon Cre-mediated deletion of Exon 2. Introducing the B6.BAC into the NOD background, which is genetically deficient for li-CTLA-4, restores mRNA levels of li-CTLA-4 to those observed in C57BL/6 mice. Furthermore, re-expressing this ligand nonbinding isoform in NOD mice reduced IFN-γ production in T effector cells accompanied by a significant decrease in insulitis and type 1 diabetes frequency. However, selective expression of li-CTLA-4 could not fully rescue the CTLA-4 knockout disease phenotype when bred onto NOD.BDC2.5.CTLA-4 knockout background because of the requirement of the full-length, B7-binding CTLA-4 molecule on T effector cells. Thus, the li-CTLA-4 form, when expressed at physiologic levels in the CTLA-4-sufficient NOD background can suppress autoimmunity; however, the functionality of the li-CTLA-4 isoform depends on the presence of the full-length molecule to alter effector T cell signaling.

Association of cytotoxic T-lymphocyte associated antigen 4 gene polymorphism with type 1 diabetes mellitus: a meta-analysis

To evaluate the association between costimulatory molecule cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4) gene polymorphism and type 1 diabetes mellitus(T1DM), sixty-three published studies before December, 2011 were included. Meta-analysis was performed for each genotype in a random/fixed effect model. The combined odds ratio (OR) with 95% confidence interval (95%CI) was calculated to estimate the strength of the association. Overall, significant correlation was noted between CTLA-4 gene polymorphism (i.e. +49A/G, CT60A/G in a per-allele model) and the risk of T1DM (for +49A/G: OR=1.47, 95%CI=1.36-1.60, P<0.001; for CT60A/G: OR=1.31, 95%CI=1.18-1.45, P<0.001). However, no significant association was noted between C(-318)T polymorphism and T1DM. In the subgroup analysis, for +49A/G and CT60A/G, the statistically significant associations were also demonstrated in diverse racial descents (Caucasian and Asian) and age of onset (<20 years and >20 years). In conclusion, our results suggest that CTLA-4 polymorphism contributes to the susceptibility of T1DM.

Evidence for the role of STAT4 as a general autoimmunity locus in the Korean population

BACKGROUND

Recently, the association of a common STAT4 haplotype with type 1 diabetes (T1D) as well as rheumatoid arthritis has been documented in Caucasians and Koreans. STAT4 is involved in the signalling of interleukin-12 and γIFN, as well as interleukin-23. To discover genes affecting the susceptibility of common autoimmune diseases, we studied the association of polymorphisms in STAT4 with autoimmune thyroid disease (AITD) as well as T1D in the Korean population.

SUBJECTS AND METHODS

Four single-nucleotide polymorphisms on the chromosome 2q (rs11889341, rs7574865, rs8179673, and rs10181656), which were found to associate with rheumatoid arthritis were examined for association in a Korean sample of 428 AITD, 418 T1D patients, and 1060 controls.

RESULTS

The minor alleles of all four single-nucleotide polymorphisms and the reconstructed STAT4 haplotypes conferred significant degree of risk for AITD (p=10(-2) to 10(-4)). Although we found a weak association of rs11889341 with T1D (p<0.05), the same haplotypes were not associated with T1D susceptibility. When we stratified T1D patients according to the age of onset, the minor alleles of all four single-nucleotide polymorphisms and the same haplotypes showed significant association with the susceptibility of T1D in the early-onset subgroup (p<0.01), not in the late-onset subgroup.

CONCLUSION

STAT4 alleles and the same haplotypes might influence cytokine signalling, and therefore the development of AITD as well as T1D. These results reinforce the influence of STAT4 gene as a general autoimmune gene.

The past, present, and future of genetic associations in type 1 diabetes

Type 1 diabetes mellitus (T1DM) is an autoimmune disease affecting approximately one in 300 individuals in the United States. The majority of genetic research to date has focused on the heritability that predisposes to islet autoimmunity and T1DM. The evidence so far points to T1DM being a polygenic, common, complex disease with major susceptibility lying in the major histocompatibility complex (MHC) on chromosome 6 with other smaller effects seen in loci outside of the MHC. With recent advances in technology, novel means of exploring the human genome have given way to new information in the development of T1DM. The newest technologies, namely high-throughput polymorphism typing and sequencing, have led to a paradigm shift in studying common diseases such as T1DM. In this review we highlight the advances in genetic associations in T1DM in the last several decades and how they have led to a better understanding of T1DM pathogenesis.

Genetic analysis of adult-onset autoimmune diabetes

OBJECTIVE

In contrast with childhood-onset type 1 diabetes, the genetics of autoimmune diabetes in adults are not well understood. We have therefore investigated the genetics of diabetes diagnosed in adults positive for autoantibodies.

RESEARCH DESIGN AND METHODS

GAD autoantibodies (GADAs), insulinoma-associated antigen-2 antibodies (IA-2As), and islet cell autoantibodies were measured at time of diagnosis. Autoantibody-positive diabetic subjects (n = 1,384) and population-based control subjects (n = 2,235) were genotyped at 20 childhood-onset type 1 diabetes loci and FCRL3, GAD2, TCF7L2, and FTO.

RESULTS

PTPN22 (1p13.2), STAT4 (2q32.2), CTLA4 (2q33.2), HLA (6p21), IL2RA (10p15.1), INS (11p15.5), ERBB3 (12q13.2), SH2B3 (12q24.12), and CLEC16A (16p13.13) were convincingly associated with autoimmune diabetes in adults (P ≤ 0.002), with consistent directions of effect as reported for pediatric type 1 diabetes. No evidence of an HLA-DRB1*03/HLA-DRB1*04 (DR3/4) genotype effect was obtained (P = 0.55), but it remained highly predisposing (odds ratio 26.22). DR3/4 was associated with a lower age at diagnosis of disease, as was DR4 (P = 4.67 × 10(-6)) but not DR3. DR3 was associated with GADA positivity (P = 6.03 × 10(-6)) but absence of IA-2A (P = 3.22 × 10(-7)). DR4 was associated with IA-2A positivity (P = 5.45 × 10(-6)).

CONCLUSIONS

Our results are consistent with the hypothesis that the genetics of autoimmune diabetes in adults and children are differentiated by only relatively few age-dependent genetic effects. The slower progression toward autoimmune insulin deficiency in adults is probably due to a lower genetic load overall combined with subtle variation in the HLA class II gene associations and autoreactivity.

The genetics of pemphigus

Pemphigus vulgaris (PV) is an autoimmune blistering disorder with a complex etiology involving an interplay of genetic as well as environmental factors, most of which remain unknown. Despite the identification of several human leukocyte antigen (HLA) alleles as risk factors for disease, no other non-HLA genes have clearly been implicated in disease susceptibility. Newer candidate gene and whole-genome approaches are needed to illuminate the full palate of genetic risk elements in PV. Based on this information, genetic-based tools can be expected to provide a scientific rationale for future clinical decision-making by physicians and facilitate an era of personalized medicine.

PTPN22 1858T is not a risk factor for North American pemphigus vulgaris

Alterations in the protein tyrosine phosphatase N22 (PTPN22) gene affect the threshold for lymphocyte activation. The PTPN22 1858T polymorphism leads to uninhibited T-cell receptor cascade propagation. An elevated PTPN22 1858C/T genotype frequency has been correlated with several autoimmune disorders which have T-cell and humoral components. However, a recent Tunisian report demonstrated no association between PTPN22 1858T and patients with Pemphigus vulgaris (PV), an autoantibody-associated blistering disorder. Because PTPN22 1858T allele frequency is known to vary across ethnic populations, we conducted a case-control study investigating the relationship between PTPN22 1858T and PV in North American patients of either Ashkenazi Jewish or Caucasian (non-Ashkenazi) decent. Participant genotype was determined in 102 PV patients and 102 healthy controls by restriction fragment length polymorphism-polymerase chain reaction genotyping. Relationships were calculated using Fisher's exact tests and chi-squared tests. We report that the PTPN22 1858C/T genotype is not significantly associated with PV in either Caucasians (P = 0.83) or Ashkenazi Jews (P = 0.60). Further stratification of the patient population by gender, age of disease onset, HLA-type, family history of autoimmune disease, history of anti-desmoglein (anti-Dsg) 3 or anti-Dsg1 antibody response, history of lesion morphology, and disease duration did not uncover significant associations between the PTPN22 1858T allele and PV subgroups. Our data indicate that the PTPN22 1858T mutation is not associated with PV in the North American population. We do observe an elevation of PTPN22 1858C/T genotype frequency in male PV patients. Further investigation will be required to determine if this trend reaches significance in larger studies.

Genome-wide association analysis of autoantibody positivity in type 1 diabetes cases

The genetic basis of autoantibody production is largely unknown outside of associations located in the major histocompatibility complex (MHC) human leukocyte antigen (HLA) region. The aim of this study is the discovery of new genetic associations with autoantibody positivity using genome-wide association scan single nucleotide polymorphism (SNP) data in type 1 diabetes (T1D) patients with autoantibody measurements. We measured two anti-islet autoantibodies, glutamate decarboxylase (GADA, n = 2,506), insulinoma-associated antigen 2 (IA-2A, n = 2,498), antibodies to the autoimmune thyroid (Graves') disease (AITD) autoantigen thyroid peroxidase (TPOA, n = 8,300), and antibodies against gastric parietal cells (PCA, n = 4,328) that are associated with autoimmune gastritis. Two loci passed a stringent genome-wide significance level (p<10⁻¹⁰): 1q23/FCRL3 with IA-2A and 9q34/ABO with PCA. Eleven of 52 non-MHC T1D loci showed evidence of association with at least one autoantibody at a false discovery rate of 16%: 16p11/IL27-IA-2A, 2q24/IFIH1-IA-2A and PCA, 2q32/STAT4-TPOA, 10p15/IL2RA-GADA, 6q15/BACH2-TPOA, 21q22/UBASH3A-TPOA, 1p13/PTPN22-TPOA, 2q33/CTLA4-TPOA, 4q27/IL2/TPOA, 15q14/RASGRP1/TPOA, and 12q24/SH2B3-GADA and TPOA. Analysis of the TPOA-associated loci in 2,477 cases with Graves' disease identified two new AITD loci (BACH2 and UBASH3A).

Autoantibodies are important markers for autoimmune diseases such as type 1 diabetes and Graves' disease. However, little is known about the genetic factors that control their production. To improve our understanding of this genetic basis, we measured four autoantibodies in a collection of up to 8,300 type 1 diabetes cases plasma samples. We combined these measurements with genome-wide genotype data to conduct four independent genome-wide association studies. Two loci showed unequivocal evidence of autoantibody association: the FCRL3 locus and the ABO blood group locus. Variants in the FCRL3 gene have been previously associated with autoimmune diseases, but such associations have not been reported for ABO blood group genotypes. In addition, we found extensive overlap between type 1 diabetes and autoantibody loci, and these findings provide new information about the role of these risk variants. Lastly, we hypothesized that loci associated with thyroid autoantibodies are strong candidates for association with thyroid autoimmune disorders. We confirmed this hypothesis by genotyping these variants in an independent cohort of Graves' disease cases, and we found evidence for two new Graves' disease loci.

The interface between thyroid and diabetes mellitus

Thyroid disease and type 1 but also type 2 diabetes mellitus (DM) are strongly associated, and this has important clinical implications for insulin sensitivity and treatment requirements. The pathophysiological basis of this association has only recently been better elucidated. It rests on a complex interaction of common signalling pathways and, in the case of type 1 diabetes and autoimmune thyroid disease, on a linked genetic susceptibility. The pathophysiological mechanisms underlying this linked regulation are increasingly being unravelled. They are exemplified in the regulation of 5' adenosine monophosphate-activated protein kinase (AMPK), a central target not only for the modulation of insulin sensitivity but also for the feedback of thyroid hormones on appetite and energy expenditure. The present review will discuss these concepts and their consequences for the clinical care of patients with DM and thyroid disorders. Moreover, it makes reference to the added effect of metformin in suppressing TSH.

High titre of antiglutamic acid decarboxylase autoantibody is a strong predictor of the development of thyroid autoimmunity in patients with type 1 diabetes and latent autoimmune diabetes in adults

OBJECTIVE

Type 1 diabetes mellitus (T1DM) is frequently associated with autoimmune thyroid diseases (AITD), but little is known about the risk of AITD in latent autoimmune diabetes in adults (LADA). We evaluated the genetic and immunological factors involved in the development of thyroid autoimmunity in patients with LADA and T1DM.

PATIENTS AND MEASUREMENTS

One hundred and ninety T1DM and 135 LADA patients were recruited in the study. Thyroid peroxidase antibody (TPOAb), thyroglobulin antibody (TGAb), glutamic acid decarboxylase antibody (GADA) and thyroid function were measured. The cytotoxic-lymphocyte-associated antigen-4 (CTLA-4) +49A/G and CT60 polymorphisms and the human leucocyte antigen (HLA)-DQA1-DQB1 genotype were determined.

RESULTS

The prevalence of thyroid antibodies (TGAb and/or TPOAb) and thyroid dysfunction was 27·4% and 9·5% in patients with T1DM, and 21·5% and 11·1% in patients with LADA. Thyroid-antibody-positive T1DM patients had higher frequencies of GADA and HLA-DQA1*03-DQB1*0401 haplotypes than thyroid-antibody negatives (P < 0·05). Thyroid-antibody-positive LADA patients had higher GADA titre, lower C-peptide levels and higher frequencies of HLA-DQA1*03-DQB1*0401 haplotypes (P < 0·05). The CTLA-4 +49A/G and CT60 polymorphism was associated with T1DM complicated with thyroid autoimmunity (OR = 2·33 and 2·54). Logistic regression revealed that only high-titre GADA was associated with development of thyroid autoimmunity in patients with T1DM and LADA (OR = 3·50 and 3·10, respectively), and the presence of thyroid antibody predicted high risk for thyroid dysfunction in patients with T1DM and LADA (OR = 9·25 and 10·70, respectively).

CONCLUSION

Regular screening of thyroid antibody and function are recommended, especially in patients with T1DM and LADA with high GADA titre.

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 reference human genome demonstrates high risk of type 1 diabetes and other disorders

Personal genome resequencing has provided promising lead to personalized medicine. However, due to the limited samples and the lack of case/control design, current interpretation of personal genome sequences has been mainly focused on the identification and functional annotation of the DNA variants that are different from the reference genome. The reference genome was deduced from a collection of DNAs from anonymous individuals, some of whom might be carriers of disease risk alleles. We queried the reference genome against a large high-quality disease-SNP association database and found 3,556 disease-susceptible variants, including 15 rare variants. We assessed the likelihood ratio for risk for the reference genome on 104 diseases and found high risk for type 1 diabetes (T1D) and hypertension. We further demonstrated that the risk of T1D was significantly higher in the reference genome than those in a healthy patient with a whole human genome sequence. We found that the high T1D risk was mainly driven by a R260W mutation in PTPN22 in the reference genome. Therefore, we recommend that the disease-susceptible variants in the reference genome should be taken into consideration and future genome sequences should be interpreted with curated and predicted disease-susceptible loci to assess personal disease risk.

Type 1 diabetes associated with Hashimoto's thyroiditis and juvenile rheumatoid arthritis: a case report with clinical and genetic investigations

Autoimmune diseases are initiated by interaction between genetic and environmental factors and caused by the loss of immunologic tolerance to self-antigens. They cluster within families and individuals, but the aggregation in a triad is quite rare. We report a case of a young girl affected by three organ-specific autoimmune disorders, from which type 1 diabetes developed first, then Hashimoto's thyroiditis and juvenile rheumatoid arthritis were diagnosed. Hitherto unreported detailed genetic studies included genotyping of HLA class II, CTLA4, and PTPN22 gene regions. These genes have been associated with autoimmunity in general and some of their variants confer increased risk to all three diseases. Our results - with the limitation of reporting only on a single patient - contribute to the complex genetic background of these clustering organ-specific autoimmune diseases and the analysis of further similar cases might help to reveal how the major and minor genetic factors determine the individual clinical phenotype.

CTLA4 CT60 single-nucleotide polymorphism is associated with Slovenian inflammatory bowel disease patients and regulates expression of CTLA4 isoforms

We have evaluated functional polymorphism (rs3087243; in literature known also as CTLA4 CT60) in the cytotoxic T lymphocyte antigen 4 (CTLA4) gene, previously associated with several autoimmune diseases, for potential association with inflammatory bowel diseases (IBD). In addition, we investigated correlations between CTLA4 CT60 polymorphism and CTLA4 gene expression in peripheral blood lymphocytes and colon biopsies from IBD patients. We genotyped CTLA4 CT60 polymorphism in 266 healthy control subjects and 481 IBD patients and found statistically lower frequency of CTLA4 CT60 AA genotype in IBD patients (13.72%) compared to control subjects (23.31%; p&#x2009;=&#x2009;0.001, odds ratio [OR]&#x2009;=&#x2009;0.504) as well as lower allele frequency of minor A allele in IBD patients (0.346) compared to control subjects (0.461, p&#x2009;&lt;&#x2009;0.001, OR&#x2009;=&#x2009;0.623). The association was confirmed with both major forms of IBD, Crohn's disease, and ulcerative colitis (UC), but was slightly stronger in UC patients, particularly when we compared allele frequency of A allele in UC patients (0.299) and control subjects (0.461, p&#x2009;&lt;&#x2009;0.001, OR&#x2009;=&#x2009;0.500). We found lower expression of the CTLA4 gene in blood lymphocytes from IBD patients compared to control subjects (p&#x2009;&lt;&#x2009;0.001) and higher CTLA4 expression in biopsies taken from inflamed part of the colon compared to noninflamed part of the colon (p&#x2009;=&#x2009;0.021). We found lower expression of soluble CTLA4 isoform than membrane-bound full-length isoform in peripheral blood lymphocytes from IBD patients compared to control subjects (p&#x2009;=&#x2009;0.010) and in lymphocytes from IBD patients with CTLA4 CT60 GG genotype compared to IBD patients with AA genotype (p&#x2009;=&#x2009;0.034). Our genotype and gene expression data suggest that CTLA4 plays a role in IBD pathogenesis. Polymorphism CTLA4 CT60 contributes to genetic susceptibility to IBD in Slovenian population and regulates expression of CTLA4 isoforms.

Shared molecular amino acid signature in the HLA-DR peptide binding pocket predisposes to both autoimmune diabetes and thyroiditis

There is strong genetic association between type 1A diabetes (T1D) and autoimmune thyroid disease (AITD). T1D and AITD frequently occur together in the same individual, a condition classified as a variant of the autoimmune polyglandular syndrome type 3 (APS3). Because T1D and AITD are individually strongly associated with different HLA class II sequences, we asked which HLA class II pocket sequence and structure confer joint susceptibility to both T1D and AITD in the same individual (APS3v). We sequenced the HLA-DR gene in 105 APS3v patients and 153 controls, and identified a pocket amino acid signature, DRβ-Tyr-26, DRβ-Leu-67, DRβ-Lys-71, and DRβ-Arg-74, that was strongly associated with APS3v (P = 5.4 × 10(-14), odds ratio = 8.38). Logistic regression analysis demonstrated that DRβ-Leu-67 (P = 9.4 × 10(-13)) and DRβ-Arg-74 (P = 1.21 × 10(-13)) gave strong independent effects on disease susceptibility. Structural modeling studies demonstrated that pocket 4 was critical for the development of T1D+AITD; all disease-associated amino acids were linked to areas of the pocket that interact directly with the peptide and, therefore, influence peptide binding. The disease-susceptible HLA-DR pocket was more positively charged (Lys-71, Arg-74) compared with the protective pocket (Ala-71, Gln-74). We conclude that a specific pocket amino acid signature confers joint susceptibility to T1D+AITD in the same individual by causing significant structural changes in the MHC II peptide binding pocket and influencing peptide binding and presentation. Moreover, Arg-74 is a major amino acid position for the development of several autoimmune diseases. These findings suggest that blocking the critical Arg-74 pocket might offer a method for treating certain autoimmune conditions.

Genetics of the autoimmune polyglandular syndrome type 3 variant

BACKGROUND

Autoimmune thyroid diseases (AITD) and type 1 diabetes (T1D) are the most common autoimmune endocrine disorders. They occur frequently together in the same individual. This disease combination is denominated as autoimmune polyglandular syndrome type 3 variant (APS3v). This review aims to describe the genetic and pathological background of the syndrome. The joint susceptibility genes for AITD and T1D as well as the underlying pathogenetic mechanisms contributing to the development of autoimmunity are summarized.

SUMMARY

Family and population studies showed that the APS3v syndrome has a strong genetic background. Whole genome and candidate gene approaches identified several gene variations that are present in both AITD and T1D. Most important common disease susceptibility genes are human leucocyte antigen (chromosome 6), cytotoxic T-lymphocyte-associated antigen 4 (chromosome 2), protein tyrosine phosphatase nonreceptor type 22 (chromosome 1), forkhead box P3 (X chromosome), and the interleukin-2 receptor alpha/CD25 gene region (chromosome 10), all of which contributing to the susceptibility to APS3v. With respect to the underlying pathogenetic mechanisms, these genes are altogether involved in the immune regulation, in particular in the immunological synapse and T-cell activation. In addition to these common genes, there are further candidate genes with joint risk for AITD and T1D, in particular the v-erb-b2 erythroblastic leukemia viral oncogene homolog 3 gene (chromosome 12) and C-type lectin domain family 16 member A gene (chromosome 16). The latter one might be involved in pathogen recognition.

CONCLUSIONS

AITD and T1D share common susceptibility gene variants that possibly act pleiotropically as risk factors for the development of autoimmunity in APS3v. The functional consequences of the genetic variants as well as their interactions should be explored in greater detail. In particular, the functional consequences of the variants of forkhead box P3 predisposing to APS3v need to be elucidated. Finally, further large-scale genome-wide associations studies of single-nucleotide polymorphism variations capturing many thousand individual genetic profiles are warranted to identify further genes that are linked to the etiology of APS3v.

Autoimmune polyendocrine syndromes: clues to type 1 diabetes pathogenesis

Autoimmune diseases such as type 1 diabetes are complex in their pathogenesis. One approach to improving our understanding of type 1 diabetes is the study of diseases that represent more extreme examples of autoimmunity. Autoimmune polyendocrine syndromes (APS) are relatively rare diseases that often include type 1 diabetes as part of the disease phenotype. Recently, there has been tremendous progress in unraveling some of the underlying mechanisms of APS. Here, we highlight the APS disorders with the perspective of the clues they can offer to the pathogenesis and treatment of type 1 diabetes.

Analysis of 19 genes for association with type I diabetes in the Type I Diabetes Genetics Consortium families

In recent years the pace of discovery of genetic associations with type I diabetes (T1D) has accelerated, with the total number of confirmed loci, including the major histocompatibility complex (MHC) region, reaching 43. However, much of the deciphering of the associations at these, and the established T1D loci, has yet to be performed in sufficient numbers of samples or with sufficient markers. Here, 257 single-nucleotide polymorphisms (SNPs) have been genotyped in 19 candidate genes (INS, PTPN22, IL2RA, CTLA4, IFIH1, SUMO4, VDR, PAX4, OAS1, IRS1, IL4, IL4R, IL13, IL12B, CEACAM21, CAPSL, Q7Z4c4(5Q), FOXP3, EFHB) in 2300 affected sib-pair families and tested for association with T1D as part of the Type I Diabetes Genetics Consortium's candidate gene study. The study had approximately 80% power at alpha=0.002 and a minor allele frequency of 0.2 to detect an effect with a relative risk (RR) of 1.20, which drops to just 40% power for a RR of 1.15. At the INS gene, rs689 (-23 HphI) was the most associated SNP (P=3.8 x 10(-31)), with the estimated RR=0.57 (95% confidence interval, 0.52-0.63). In addition, rs689 was associated with age-at-diagnosis of T1D (P=0.001), with homozygosity for the T1D protective T allele, delaying the onset of T1D by approximately 2 years in these families. At PTPN22, rs2476601 (R620W), in agreement with previous reports, was the most significantly associated SNP (P=6.9 x 10(-17)), with RR=1.55 (1.40-1.72). Evidence for association with T1D was observed for the IFIH1 SNP, rs1990760 (P=7.0 x 10(-4)), with RR=0.88 (0.82-0.95) and the CTLA4 SNP rs1427676 (P=0.0005), with RR=1.14 (1.06-1.23). In contrast, no convincing evidence of association was obtained for SUMO4, VDR, PAX4, OAS1, IRS1, IL4, IL4R, IL13, IL12B, CEACAM21 or CAPSL gene regions (http://www.T1DBase.org).

No association of multiple type 2 diabetes loci with type 1 diabetes

AIMS/HYPOTHESIS

We used recently confirmed type 2 diabetes gene regions to investigate the genetic relationship between type 1 and type 2 diabetes, in an average of 7,606 type 1 diabetic individuals and 8,218 controls, providing >80% power to detect effects as small as an OR of 1.11 at a false-positive rate of 0.003.

METHODS

The single nucleotide polymorphisms (SNPs) with the most convincing evidence of association in 12 type 2 diabetes-associated gene regions, PPARG, CDKAL1, HNF1B, WFS1, SLC30A8, CDKN2A-CDKN2B, IGF2BP2, KCNJ11, TCF7L2, FTO, HHEX-IDE and THADA, were analysed in type 1 diabetes cases and controls. PPARG and HHEX-IDE were additionally tested for association in 3,851 type 1 diabetes families. Tests for interaction with HLA class II genotypes, autoantibody status, sex, and age-at-diagnosis of type 1 diabetes were performed with all 12 gene regions.

RESULTS

Only PPARG and HHEX-IDE showed any evidence of association with type 1 diabetes cases and controls (p = 0.004 and p = 0.003, respectively; p > 0.05 for other SNPs). The potential association of PPARG was supported by family analyses (p = 0.003; p (combined) = 1.0 x 10(-4)). No SNPs showed evidence of interaction with any covariate (p > 0.05).

CONCLUSIONS/INTERPRETATION

We found no convincing genetic link between type 1 and type 2 diabetes. An association of PPARG (rs1801282/Pro12Ala) could be consistent with its known function in inflammation. Hence, our results reinforce evidence suggesting that type 1 diabetes is a disease of the immune system, rather than being due to inherited defects in beta cell function or regeneration or insulin resistance.

Autoimmunity risk alleles in costimulation pathways

SUMMARY

The basis for susceptibility to common autoimmune diseases is a complex interplay between multiple genetic and environmental risk factors. We have now entered a new generation of genetic study designs which has not only furthered our understanding of the individual mechanisms involved in the common human autoimmune diseases but also has pointed towards common pathways. In this review we focus on costimulatory mechanisms with the most convincing association results in large collections of patients and control subjects. These include the genes encoding cytotoxic T-lymphocyte antigen-4, CD58, CD40, inducible T-cell costimulator ligand, CD244, CD226, tumor necrosis factor (TNF) (ligand) superfamily member 4, TNF superfamily member 15, and programmed cell death 1. The unbiased genome-wide association scans suggest that indeed immune related genes underlie the pathogenesis of human autoimmune disease with common involvement of costimulatory pathways. The identification of allelic variants associated with disease risk followed by understanding their functional outcomes and affected pathways provides a rationale approach for drug design.

Association studies of the SAS-ZFAT, IL-23R, IFIH1 and FOXP3 genes in autoimmune thyroid disease

Autoimmune thyroid diseases (AITDs) are complex diseases caused by an interaction between susceptibility genes and environmental triggers. Genetic susceptibility in combination with external factors, such as dietary iodine, is believed to initiate the autoimmune response against thyroid antigens. Abundant epidemiological data, including family and twin studies, point to a strong genetic influence in the development of AITDs. Various techniques have been employed to identify genes contributing to the etiology of AITDs, including candidate gene analysis and whole-genome screening. These studies have enabled the identification of several loci (genetic regions) that are linked to AITDs and, in some of these loci, putative AITD-susceptibility genes have been identified. Some of these genes/loci are unique to Graves' disease (GD) and Hashimoto's thyroiditis (HT), and some are common to both diseases, indicating that there is a shared genetic susceptibility to GD and HT. The putative GD and HT susceptibility genes include both immune-modifying genes (e.g., HLA, CTLA-4 and PTPN22) and thyroid-specific genes (e.g., TSHR and Tg). In this special report, we focus on the newest genes identified and not on those previously identified, such as HLA and CTLA-4, for which there are many reviews.

Autoimmune thyroiditis and diabetes: dissecting the joint genetic susceptibility in a large cohort of multiplex families

CONTEXT

Epidemiological data support a shared genetic susceptibility to autoimmune thyroid disease (AITD) and type 1 diabetes (T1D). Both diseases frequently occur within the same family and in the same individual. Patients developing both T1D and AITD are considered to have an autoimmune polyglandular syndrome type 3 variant (APS3v).

OBJECTIVE

The goals of this study were to identify the joint susceptibility loci/genes for T1D and AITD.

SETTINGS

The study was conducted at an academic medical center.

PARTICIPANTS AND MAIN OUTCOME MEASURES

We used whole genome and candidate gene approaches in a data set of 88 families multiplex for T1D and AITD (448 individuals).

RESULTS

We identified three loci, on chromosomes 2p, 6p, and Xp, showing linkage when individuals with either T1D or AITD were classified as affected. The 6p locus contained the human leukocyte antigen class II genes, and the Xp locus contained the FOXP3 gene. Three loci, on 2q, 6p (human leukocyte antigen class II), and Xp, showed evidence for linkage when only APS3v individuals (T1D+AITD) were classified as affected. Analysis of positional candidate genes strongly supported CTLA-4 as the gene on 2q associated with APS3v and FOXP3 as the gene on Xp associated with T1D or AITD and APS3v. In addition, the PTPN22 and insulin variable number tandem repeat genes showed significant associations with T1D or AITD in our families.

CONCLUSIONS

Our results demonstrate a strong shared genetic susceptibility to T1D and AITD, with most shared genes involved in immune regulation, suggesting that immune dysregulation plays an important role in the joint susceptibility to T1D and AITD.

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.

Gene-gene interactions in the NOD mouse model of type 1 diabetes

Human genome wide association studies (GWAS) have recently identified at least four new, non-MHC-linked candidate genes or gene regions causing type one diabetes (T1D), highlighting the need for functional models to investigate how susceptibility alleles at multiple common genes interact to mediate disease. Progress in localizing genes in congenic strains of the nonobese diabetic (NOD) mouse has allowed the reproducible testing of gene functions and gene-gene interactions that can be reflected biologically as intrapathway interactions, for example, IL-2 and its receptor CD25, pathway-pathway interactions such as two signaling pathways within a cell, or cell-cell interactions. Recent studies have identified likely causal genes in two congenic intervals associated with T1D, Idd3, and Idd5, and have documented the occurrence of gene-gene interactions, including "genetic masking", involving the genes encoding the critical immune molecules IL-2 and CTLA-4. The demonstration of gene-gene interactions in congenic mouse models of T1D has major implications for the understanding of human T1D since such biological interactions are highly likely to exist for human T1D genes. Although it is difficult to detect most gene-gene interactions in a population in which susceptibility and protective alleles at many loci are randomly segregating, their existence as revealed in congenic mice reinforces the hypothesis that T1D alleles can have strong biological effects and that such genes highlight pathways to consider as targets for immune intervention.

Joint genetic susceptibility to type 1 diabetes and autoimmune thyroiditis: from epidemiology to mechanisms

Type 1 diabetes (T1D) and autoimmune thyroid diseases (AITD) frequently occur together within families and in the same individual. The co-occurrence of T1D and AITD in the same patient is one of the variants of the autoimmune polyglandular syndrome type 3 [APS3 variant (APS3v)]. Epidemiological data point to a strong genetic influence on the shared susceptibility to T1D and AITD. Recently, significant progress has been made in our understanding of the genetic association between T1D and AITD. At least three genes have been confirmed as major joint susceptibility genes for T1D and AITD: human leukocyte antigen class II, cytotoxic T-lymphocyte antigen 4 (CTLA-4), and protein tyrosine phosphatase non-receptor type 22. Moreover, the first whole genome linkage study has been recently completed, and additional genes will soon be identified. Not unexpectedly, all the joint genes for T1D and AITD identified so far are involved in immune regulation, specifically in the presentation of antigenic peptides to T cells. One of the lessons learned from the analysis of the joint susceptibility genes for T1D and AITD is that subset analysis is a key to dissecting the etiology of complex diseases. One of the best demonstrations of the power of subset analysis is the CTLA-4 gene in T1D. Although CTLA-4 showed very weak association with T1D, when analyzed in the subset of patients with both T1D and AITD, the genetic effect of CTLA-4 was significantly stronger. Gene-gene and genetic-epigenetic interactions most likely play a role in the shared genetic susceptibility to T1D and AITD. Dissecting these mechanisms will lead to a better understanding of the etiology of T1D and AITD, as well as autoimmunity in general.

Genetic Basis of Type 1 Diabetes: Similarities and Differences between East and West

Type 1 diabetes is a multifactorial disease caused by a complex interaction of genetic and environmental factors. The genetic factors involved consist of multiple susceptibility genes, at least five of which, HLA, INS, CTLA4, PTPN22 and IL2RA/CD25, have been shown to be associated with type 1 diabetes in Caucasian (Western) populations, as has recently been confirmed by genome-wide association studies. It has been proposed, however, that the contribution of these genes to type 1 diabetes susceptibility may be different in Asian (Eastern) populations. HLA and INS genes are consistently associated with type 1 diabetes in both Caucasian and Asian populations, but apparent differences in disease-associated alleles and haplotypes are observed between Japanese and Caucasian subjects. The association of CTLA4 with type 1 diabetes is concentrated in a subset of patients with autoimmune thyroid disease (AITD) in both Japanese and Caucasian populations, while the association of PTPN22 with type 1 diabetes in Japanese and most Asian populations is not as clear as in Caucasians. IL2RA/CD25 genes seem to be similarly distributed in type 1 diabetes patients in the two populations, whereas genetic heterogeneity may exist regarding SUMO4, with an association of the M55V variant with type 1 diabetes observed in Asians, but not in Caucasians. Genome-wide association studies (GWA) are largely outstanding for Asian populations but they are now underway in Japan. This review reports on the discovered similarities and differences in susceptibility genes for type 1 diabetes between East and West and discusses the most recent observations made by the involved investigators.

Extreme genetic risk for type 1A diabetes in the post-genome era

A series of genes and loci influencing the genetic risk of type 1A (immune-mediated) diabetes are now well characterized. These include genes of the major histocompatibility complex (MHC), polymorphisms 5' of the insulin gene, and PTPN22, as well as more recently defined loci from genome-wide association studies. By far the major determinants of risk for type 1A diabetes are genes within or linked to the MHC and in particular alleles of class II genes (HLA-DR, DQ, and DP). There is evidence that MHC class I alleles contribute and there are additional MHC-linked influences such that for a major subset of relatives of patients there is a risk as high as 80% for siblings, and for the general population a risk as high as 20% can be defined at birth just by analyzing the MHC. We believe the search for additional MHC loci will require analysis of the remarkable long-range identity (up to 9 million base pairs) of extended MHC haplotypes. Current prediction algorithms will likely be greatly improved for the general population when the additional contributing loci of the MHC are defined.

Interactions between Idd5.1/Ctla4 and other type 1 diabetes genes

Two loci, Idd5.1 and Idd5.2, that determine susceptibility to type 1 diabetes (T1D) in the NOD mouse are on chromosome 1. Idd5.1 is likely accounted for by a synonymous single nucleotide polymorphism in exon 2 of Ctla4: the B10-derived T1D-resistant allele increases the expression of the ligand-independent isoform of CTLA-4 (liCTLA-4), a molecule that mediates negative signaling in T cells. Idd5.2 is probably Nramp1 (Slc11a1), which encodes a phagosomal membrane protein that is a metal efflux pump and is important for host defense and Ag presentation. In this study, two additional loci, Idd5.3 and Idd5.4, have been defined to 3.553 and 78 Mb regions, respectively, on linked regions of chromosome 1. The most striking findings, however, concern the evidence we have obtained for strong interactions between these four disease loci that help explain the association of human CTLA4 with T1D. In the presence of a susceptibility allele at Idd5.4, the CTLA-4 resistance allele causes an 80% reduction in T1D, whereas in the presence of a protective allele at Idd5.4, the effects of the resistance allele at Ctla4 are modest or, as in the case in which resistance alleles at Idd5.2 and Idd5.3 are present, completely masked. This masking of CTLA-4 alleles by different genetic backgrounds provides an explanation for our observation that the human CTLA-4 gene is only associated with T1D in the subgroup of human T1D patients with anti-thyroid autoimmunity.