Insulin gene VNTR, CTLA-4 +49A/G and HLA-DQB1 alleles distinguish latent autoimmune diabetes in adults from type 1 diabetes and from type 2 diabetes group

Recent research has underlined the need to explore pathogenic, genetic and clinical spectrum of adult onset autoimmune diabetes, also known as latent autoimmune diabetes in adults (LADA). We aimed to investigate whether genetic factors that are associated with type 1 diabetes (T1D) susceptibility, namely HLA-DQB1 alleles, cytotoxic T-lymphocyte antigen 4 gene (CTLA-4) and insulin gene (INS) polymorphisms, are also associated with an atypical subset of patients diagnosed with type 2 diabetes (T2D). The case-control study included 70 T1D, 305 T2D and 252 nondiabetic controls. The T2D group was divided into atypical T2D (LADA, n = 61) or typical T2D (n = 244) subgroups based on the presence of at least one pancreas-specific antibody. Our data suggested that HLA-DQB1 alleles of all three risk classes, INS variable number of tandem repeat (VNTR) I/I and CTLA-4 +49 GG or AG genotypes, were independent risk factors for developing LADA and could be used as a diagnostic tool to discriminate between LADA and T2D. Additionally, there was an increased association between LADA and CTLA-4 diabetes-susceptibility genotypes and decreased association with INS VNTR and high-risk HLA-DQB1 alleles, compared with T1D. Our study suggested the need for further investigation into the genetic background and functional genomics of LADA in comparison with T1D and T2D.     

Type 1 diabetes linked PTPN22 gene polymorphism is associated with the frequency of circulating regulatory T cells

Dysfunction of FOXP3-positive regulatory T cells (Tregs) likely plays a major role in the pathogenesis of multiple autoimmune diseases including type 1 diabetes (T1D). Whether genetic polymorphisms associated with the risk of autoimmune diseases affect Treg frequency or function is currently unclear. Here, we analysed the effect of T1D-associated major HLA class II haplotypes and seven single nucleotide polymorphisms in six non-HLA genes [INS (rs689), PTPN22 (rs2476601), IL2RA (rs12722495 and rs2104286), PTPN2 (rs45450798), CTLA4 (rs3087243), and ERBB3 (rs2292239)] on peripheral blood Treg frequencies. These were determined by flow cytometry in 65 subjects who had progressed to T1D, 86 islet autoantibody-positive at-risk subjects, and 215 islet autoantibody-negative healthy controls. The PTPN22 rs2476601 risk allele A was associated with an increase in total (p = 6 × 10⁻⁶) and naïve (p = 4 × 10⁻⁵) CD4+CD25+CD127lowFOXP3+ Treg frequencies. These findings were validated in a separate cohort comprising ten trios of healthy islet autoantibody-negative children carrying each of the three PTPN22 rs2476601 genotypes AA, AG, and GG (p = 0.005 for total and p = 0.03 for naïve Tregs, respectively). In conclusion, our analysis implicates the autoimmune PTPN22 rs2476601 risk allele A in controlling the frequency of Tregs in human peripheral blood.     

PTPN22 Single-Nucleotide Polymorphisms in Iranian Patients with Type 1 Diabetes Mellitus

Background: PTPN22 plays a crucial role in regulating the function of various cells of the immune system, particularly T cells. Polymorphisms of the PTPN22 gene have been associated with many autoimmune diseases, including type 1 diabetes (T1D) which is a T-cell-mediated disease.

Objective: The present study was aimed at genotyping of an Iranian population for five polymorphisms of the PTPN22 gene.

Methods: The study population consisted of 99 T1D patients and 100 healthy controls. We genotyped five single-nucleotide polymorphisms (SNPs) (rs12760457, rs1310182, rs1217414, rs33996649, and rs2476601) of the PTPN22 gene.

Results: Regarding the variant rs2476601, genotypes AG and GG were increased and decreased in T1D patients compared with controls, respectively. Further, alleles G and A of this SNP were found to be decreased and increased in T1D patients, respectively (p value = 0.001). However, T1D and control groups did not differ on genotype distribution or allele frequency for other investigated SNPs.

Conclusions: The PTPN22 rs2476601 minor allele (A) was associated with T1D in Iran, accounting for its pathophysiology in autoimmune diseases.     

人白细胞抗原DQB1基因与1型糖尿病相关性研究

目的　研究四川地区汉族人群人类白细胞抗原 (humanleucocyteantigen ,HLA)DQB1基因与 1型糖尿病 (type 1diabetesmellitus ,T1DM )发病年龄及糖尿病自身抗体的相关性。 方法　应用聚合酶链反应 序列特异性引物方法对 46例T1DM患者和 5 2名正常人进行HLA DQB1基因分型 ,并对T1DM患者以酶联免疫吸附法定性检测谷氨酸脱羧酶抗体 (glutamicaciddecarboxylaseantibody ,GADA)及抗胰岛细胞抗体 (isletcellantibody ,ICA)。结果　DQB1 0 2 0 1基因阳性率T1DM组高于对照组 (OR =18,P <0 .0 0 5 ) ;而DQB1 0 60 1、 0 60 2基因阳性率对照组高于T1DM组 (OR分别为 0 .0 7、0 3 1,P <0 .0 5 )。DQB1 0 60 2基因阳性率在发病年龄≥ 2 0岁T1DM组高于 <2 0岁组 (P <0 .0 5 )。携带DQB1 0 2 0 1基因的患者中 ,GADA阳性率明显高于此基因阴性的患者 (P <0 .0 2 5 )。结论　四川地区汉族人群中DQB1 0 2 0 1可能是 1型糖尿病的易感基因 ,而DQB1 0 60 2、 0 60 1是保护性基因 ,且DQB1 0 60 2基因的存在有可能推迟 1型糖尿病的发病 ;DQB1 0 2 0 1的阳性率与GADA阳性率正相关。     

The 1858T PTPN22 gene variant contributes to a genetic risk of type 1 diabetes in a Ukrainian population

The 1858T variant of the protein tyrosine phosphatase gene, PTPN22, is associated with an increased risk of several autoimmune diseases. The aim of this study has been to investigate the possible association of 1858C-->T PTPN22 polymorphism and type 1 diabetes (T1D) in Caucasians from Ukraine. Overall, the distribution of 1858 PTPN22 genotypes differed significantly between the T1D patient group (n = 296) and the control group (n = 242) (P = 0.0036). When both groups were classified according to sex, the TT genotype and T allele showed a statistically significant higher frequency in T1D female patients (5.9 and 22.8%, respectively) in comparison with the female controls (0 and 11.9%) (P = 0.008 for both analyses). The patients with the TT genotype were significantly younger at the onset of T1D compared with those with genotypes TC and CC (P = 0.035 and 0.019, respectively). In our Ukrainian Caucasian cohort, we confirmed the association between T1D and the PTPN22,1858T allele.     

The association between rs1893217, rs478582 in PTPN2 and T1D risk with different diagnosed age,and related clinical characteristics in Chinese Han population

Objective: To investigate the association between polymorphisms in PTPN2 (rs1893217 and rs478582) and type 1 diabetes (T1D) risk with different diagnosed age, as well as related clinical characteristics in Chinese Han population.

Methods: A total of 2270 Chinese Han individuals (1023 T1D patients and 1247 healthy controls) were genotyped for rs1893217 and rs478582. And 306 newly diagnosed T1D patients were measured for C-peptide levels based on a standard mixed-meal tolerance test. In addition, 40 healthy controls were analyzed for different T cell subsets by multi-color flow cytometry.

Results: Neither rs1893217 nor rs478582 showed any association with T1D risk under an additive model. Stratified analysis for T1D diagnosed age revealed that rs1893217, but not rs478582, was significantly associated with T1D patients diagnosed age ≤18 (OR =0.80, 95% CI: 0.67–0.97, p?=?0.02). For those diagnosed age >18, neither of them showed any association. We also found that rs1893217 had a higher positive rate of ZnT8A (CC vs. TT carrier, OR = 2.07, 95% CI: 1.07–4.03, p?=?0.026) and IA-2A (CT vs. TT carrier, OR = 1.36, 95% CI: 1.02–1.80, p?=?0.038). Furthermore, for rs478582, compared with TT, healthy individuals carrying CC/CT carriers had significantly lower frequency and Helios expression of naive Treg subsets (p?=?0.049 and 0.048 respectively), but not secreting or activating Treg subsets. In addition, we did not find any association between these two polymorphisms and residual β-cell function in newly diagnosed T1D patients.

Conclusions: Our results suggest that rs1893217 may increase the risk of early-onset T1D and affect humoral immunity, while rs478582 may affect Treg subsets.     

Association between PTPN22 C1858T and type 1 diabetes: a replication in continental Italy

The missense PTPN22 C1858T polymorphism recently emerged as an important population-independent risk factor for type 1 diabetes (T1D) and other autoimmune diseases. The PTPN22 gene encodes the lymphoid tyrosine phosphatase (LYP), a negative regulator of signal transduction through the T-cell receptor. Although the frequency of the polymorphism is variable among different ethnic groups, the association between PTPN22 *T1858 and T1D has been replicated in several populations. Here, we contribute the first replication of the association between PTPN22 and T1D in populations from continental Italy, carried out in two independent samples of T1D patients ( N  = 216 and 82) and controls ( N  = 271 and 89). Our data also suggest that T1D carriers of the *T1858 allele could be at increased risk for other comorbid autoimmune disorders.     

Gliadin,endomysial and thyroid antibodies in patients with latent autoimmune diabetes of adults (LADA)

Latent autoimmune diabetes of adults (LADA) manifested after the age of 35 is characterized by the presence of disease-specific autoantibodies (anti-glutamate decarboxylase GADAb, anti-IA2Ab). However, autoimmunity in Type 1 diabetes mellitus is not targeted only to pancreatic beta-cells. No data have so far been published concerning the antibodies associated with other autoimmune disease in LADA patients. The presence of anti-thyroglobulin (TGAb), anti-thyroid peroxidase (TPOAb), anti-gliadin IgA (AGAAb) and IgG (AGGAb) and endomysial antibodies (EMAb) in sera of 68 diabetics typed as LADA was compared with the antibody presence in sera of 85 patients with Type 2 diabetes. We found a significantly higher occurrence of gliadin antibodies in LADA patients: the rate of AGGAb was 19.1% in comparison with 3.5% in the T2DM group (P = 0.0026), the rate of AGAAb was 13.2% in comparison with 3.5% (P = 0.035). The prevalence of EMAb was very low in both groups (1.5% and 0). The two groups differed significantly in the TPOAb rate: 22.1% in LADA compared to 9.4% in T2DM (P = 0.04), whereas no significant difference was found in the presence of TGAb (8.8% and 3.5%, P = 0.187). In comparison with T2DM patients, LADA patients were found to express higher antibody activity against gluten-related antigens and against TPO.     

Latent autoimmune diabetes in adults in a population-based cohort of Polish patients with newly diagnosed diabetes mellitus

Introduction

Latent autoimmune diabetes in adults (LADA) is a slowly developing form of autoimmune diabetes characterized by the presence of type 1 diabetes-associated autoantibody. The aim of this study was to determine the incidence and characteristics of LADA in a population-based cohort of Polish patients with newly-diagnosed diabetes.

Material and methods

The study cohort was taken from the resident population of the city Białystok, Poland, during the period 1 January to 31 December 2003, aged 20-64 years. During this period we identified 231 cases of diabetes. We measured glutamic acid decarboxylase (GADA) and insulin antibody (IAA), insulin, C peptide and glycated hemoglobin (HbA_1c). Diagnosis of LADA was made according to Immunology Diabetes Society and Action LADA criteria.

Results

The incidence of LADA was 10 per year per 100 000 people. The proportion of patients with LADA was 8.9% among newly diagnosed cases with diabetes. Patients with LADA were younger at diagnosis (48.5 ±9.4 years vs. 54.8 ±10.6 years, p < 0.01), had lower body mass index (26.9 ±9.3 kg/m² vs. 29.5 ±5.2 kg/m², p < 0.05), C peptide (126 ±127 pmol/l vs. 446 ±592 pmol/l, p < 0.001), and were less insulin resistant (HOMA IR 0.94 ±0.85 vs. 3.6±4.4, p < 0.001) compared to patients with type 2 diabetes. Glycated hemoglobin and fasting glucose were similar in patients with LADA and type 2 diabetes.

Conclusions

In addition to GAD, anti-insulin antibodies are useful for diagnosing autoimmune diabetes in adults. Patients with LADA have similar glucose control parameters (HbA_1c) compared to patients with type 2 diabetes, although they are usually younger and have a lower body mass index. Patients with LADA make up a significant proportion of newly diagnosed people with diabetes mellitus in a Polish population.     

Analysis of PTPN22, ZFAT and MYO9B polymorphisms in Turner Syndrome and risk of autoimmune disease

Turner syndrome (TS) is one of the most common sexual chromosome abnormalities and is clearly associated with an increased risk of autoimmune diseases, particularly thyroid disease and coeliac disease (CD). Single‐nucleotide polymorphism analyses have been shown to provide correlative evidence that specific genes are associated with autoimmune disease. Our aim was to study the functional polymorphic variants of PTPN22 and ZFAT in relation to thyroid disease and those of MYO9B in relation to CD. A cross‐sectional comparative analysis was performed on Mexican mestizo patients with TS and age‐matched healthy females. Our data showed that PTPN22 C1858T (considered a risk variant) is not associated with TS (X² = 3.50, p = .61, and OR = 0.33 [95% CI = 0.10–1.10]). Also, ZFAT was not associated with TS (X² = 1.2, p = .28, and OR = 1.22 [95% CI = 0.84–1.79]). However, for the first time, rs2305767 MYO9B was revealed to have a strong association with TS (X² = 58.6, p = .0001, and OR = 10.44 [95% C = 5.51–19.80]), supporting a high level of predisposition to CD among TS patients. This report addresses additional data regarding the polymorphic variants associated with autoimmune disease, one of the most common complications in TS.     

The association of PTPN22 (rs2476601) and IL2RA (rs11594656) polymorphisms with T1D in Egyptian children

BackgroundType 1 diabetes mellitus (T1D) is a T cell-mediated autoimmune disease characterized by the destruction of pancreatic β cells. PTPN22 and IL2RA polymorphisms have been found to be associated with several autoimmune diseases including T1D.AimsWe aimed to elucidate the role of PTPN22 and IL2RA polymorphisms in predisposition of T1D in Egyptian children.MethodsWe studied 150 children and adolescents with T1D and 165 healthy controls. The PTPN22 (rs2476601) and IL2RA (rs11594656) polymorphisms were genotyped using polymerase chain reaction.ResultsWe found that carriers of the T allele of PTPN22 were significantly more likely to develop T1D (OR = 2.2, 95% CI = 1.2–4, P = 0.01). Also, the carrier of TT genotype and T allele of IL2RA more likely to develop T1D (OR = 2.8, 1.4, respectively, P = 0.03). There was a statistically significant association between T allele of PTPN22 gene and females ⩽10 years old at the onset of diabetes (OR = 4, 95% CI = 1.2–13.4, P = 0.019).ConclusionThis study suggests a possible association between the T allele of PTPN22 gene and TT genotype of IL2RA with T1D in studied Egyptian children, especially, females with early onset diabetes who carried the 1858T allele.     

Interplay between PTPN22 C1858T polymorphism and cow's milk formula exposure in type 1 diabetes

Genetic heterogeneity may affect the analysis of risk factors associated with type 1 diabetes (T1D). We studied the effect of the INS −23A/T, PTPN22 1858C/T, and CTLA-4 +49A/G polymorphisms on the emergence of T1D-associated autoimmunity in children exposed to cow's milk (CM) based formula during early or late infancy. The study comprised of 156 children from the Finnish DIPP cohort who had developed ≥ 2 types of autoantibodies (ICA, IAA, GADA or IA-2A) or clinical T1D and 563 control children. The PTPN22 1858T allele was associated with the appearance of the autoantibodies and clinical T1D among children exposed to CM formula before the age of 6 months (PTPN22: for all P ≤ 0.001, Log Rank test), but not among children exposed later on. Cox regression analysis showed an interaction between early CM exposure and 1858T allele and enhanced appearance of ICA, IAA and IA-2A (for all P ≤ 0.04). Our results imply that the PTPN22 polymorphism affects the development of T1D-associated autoimmunity only if children are exposed to CM formula during early infancy suggesting an interplay between genetic and environmental factors. This may provide an explanation for the contradictory findings on the significance of CM formula exposure in T1D.     

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.     

The case for an autoimmune aetiology of type 1 diabetes

Type 1 diabetes (T1D) develops when there are insufficient insulin‐producing beta cells to maintain glucose homeostasis. The prevailing view has been that T1D is caused by immune‐mediated destruction of the pancreatic beta cells. However, several recent papers have challenged the long‐standing paradigm describing T1D as a tissue‐specific autoimmune disease. These authors have highlighted the gaps in our knowledge and understanding of the aetiology of T1D in humans. Here we review the evidence and argue the case for the autoimmune basis of human T1D. In particular, recent analysis of human islet‐infiltrating T cells brings important new evidence to this question. Further data in support of the autoimmune basis of T1D from many fields, including genetics, experimental therapies and immunology, is discussed. Finally, we highlight some of the persistent questions relating to the pathogenesis of human type 1 diabetes that remain to be answered.     

Association of HLA-DRB1 and -DQB1 alleles with type 1 (autoimmune) diabetes in African Arabs: systematic review and meta-analysis

Several studies confirmed the association of HLA-DRB1 and -DQB1 alleles with altered risk of type 1 diabetes (T1D). However, data from individual studies based on small sample sizes yielded often conflicting findings in African Arabs. This is a systematic review and meta-analysis aimed at comprehensively evaluating this association with T1D, using molecular HLA data. Relevant studies were identified through systemic search of Medline/PubMed, Cochrane, Science Direct, ResearchGate, and EMBASE databases. Statistical analysis was carried out using RevMan, and Comprehensive Meta-analysis programs. Given the heterogeneity of African Arabs, we also performed subgroup analysis according to ethnicity. Analysis of sensitivity, heterogeneity, and publication bias were performed to validate the outcome of the findings. This meta-analysis included 862 T1DM cases, along with 1,390 normoglycemic control, and comprised ten comparisons. Our study indicates that DRB1*03 (OR = 2.86), DRB1*04 (OR = 2.78), and DQB1*02 (OR = 2.29), are positively associated with increased risk of T1DM, while DRB1*07 (OR = 0.48), DRB1*11 (OR = 0.20), DRB1*13 (OR = 0.47), DRB1*15 (OR = 0.30), DQB1*05 (OR = 0.39), and DQB1*06 (OR = 0.27) were negatively associated with T1D, suggesting a protective role against T1D. This meta-analysis was characterized by low heterogeneity, sensitivity, and publication bias, indicating the robustness and reliability of the results.

Background: Several studies confirmed the association of HLA-DRB1 and –DQB1 alleles with altered risk of type 1 diabetes (T1D). However, data from individual studies based on small sample sizes yielded often conflicting findings in African Arabs. This is a systematic review and meta-analysis aimed at comprehensively evaluating this association with T1D, using molecular HLA data.

Methods: Relevant studies were identified through systemic search of Medline/PubMed, Cochrane, Science Direct, ResearchGate, and EMBASE databases. Statistical analysis was carried out using Revman, and Comprehensive Meta-analysis programs. Given the heterogeneity of African Arabs, we also performed subgroup analysis according to ethnicity. Analysis of sensitivity, heterogeneity, and pub¬lication bias were performed to validate the outcome of the findings. This meta-analysis included 862 T1DM cases, along with 1,390 normoglycemic control, and comprised ten comparisons.

Results: Our study indicates that DRB1*03 (OR = 2.86), DRB1*04 (OR = 2.78), and DQB1*02 (OR = 2.29), are positively associated with increased risk of T1DM, while DRB1*07 (OR = 0.48), DRB1*11 (OR = 0.20), DRB1*13 (OR = 0.47), DRB1*15 (OR = 0.30), DQB1*05 (OR = 0.39), and DQB1*06 (OR = 0.27) were negatively associated with T1D, suggesting a protective role against T1D. Conclusion: This meta-analysis was characterized by low heterogeneity, sensitivity, and publication bias, indicating the robustness and reliability of the results.     

我国北方地区Ⅰ型糖尿病患者与HLA-DR,DQ的关联研究

目的 研究我国北方胰岛素依赖型糖尿病人与ＨＬＡ－ＤＲ,ＤＱ的关联。方法 对华北地区５３名胰岛素依赖型糖尿病（ＩＤＤＭ）儿童进行了ＨＬＡ－ＤＲＢ１、ＤＱＡ１、ＤＱＢ１、分型,同１８５名进行了同样分型的华北正常对照人群进行关联分析。结果 发现ＤＲＢ１＊０３０１／ＤＲＢ１＊０４杂合子个体具有最高的风险（ＲＲ＝５１．１３）。进上不分析ＤＱ分子,将ＤＱα链第５２位为精氨酸和ＤＱβ链第５７位为非天冬氨酸分别命     

The PTPN22 1858T allele but not variants in the proximal promoter region of IL‐21 gene is associated with the susceptibility to type 1 diabetes and the presence of autoantibodies in a Brazilian cohort

Interleukin (IL)-21 and protein tyrosine phosphatase non-receptor 22 (PTPN22) regulate lymphocyte function and have been implicated in the pathogenesis of autoimmune diabetes. We sequenced the proximal promoter of the IL-21 gene for the first time and analysed the PTPN22 1858T polymorphism in type 1A diabetes (T1AD) patients and healthy controls (HC). We correlated the frequencies of islet and extra-pancreatic autoantibodies with genotypes from both loci. The case series comprised 612 T1AD patients and 792 HC. Genotyping of PTPN22 C1858T was performed on 434 T1AD patients and 689 HC. The −448 to +83 base pairs (bp) region of the IL-21 gene was sequenced in 309 Brazilian T1AD and 189 HC subjects. We also evaluated human leucocyte antigen (HLA) DR3/DR4 alleles. The frequencies of glutamic acid decarboxylase (GAD65), tyrosine phosphatase-like protein (IA)-2, anti-nuclear antibody (ANA), thyroid peroxidase (TPO), thyroglobulin (TG), thyrotrophin receptor autoantibody (TRAb), anti-smooth muscle (ASM) and 21-hydroxylase (21-OH) autoantibodies were higher in T1AD patients than in HC. The PTPN22 1858T allele was associated with an increased risk for developing T1AD [odds ratio (OR) = 1·94; P < 0·001], particularly in patients of European ancestry, and with a higher frequency of GAD65 and TG autoantibodies. HLA-DR3/DR4 alleles predominated in T1AD patients. A heterozygous allelic IL-21 gene variant (g.-241 T > A) was found in only one patient. In conclusion, only PTPN22 C1858T polymorphism and HLA-DR3 and/or DR4 alleles, but not allelic variants in the 5′-proximal region of the IL-21 gene were associated with T1AD risk. Patients with T1AD had increased frequencies of anti-islet-cell, anti-thyroid, anti-nuclear, anti-smooth muscle and anti-21-OH autoantibodies. The C1858T PTPN22 polymorphism was also associated with a higher frequency of GAD65 and TG autoantibodies.     

The association of specific HLA class I and II alleles with type 1 diabetes among Filipinos

The genetic predisposition to type 1 diabetes among Filipinos was examined by PCR/SSOP HLA class I and II typing of 90 patients and 94 general population controls. The HLA-DRB1, DQB1, and the A, B, and C loci were typed using the reverse SSO probe line-blot method while the DPB1 and DPA1 loci were typed using the SSO probe dot blot method. The Filipino population has a distinctive frequency distribution of HLA class II alleles as well as linkage disequilibrium patterns: a DR-DQ haplotype, unique to Filipinos, contains a DRB1 allele (*0405) positively associated with type 1 diabetes in other populations and DQA1 and DQB1 alleles (*0101-*0503) that are negatively associated in other populations. Specific DR-DQ haplotypes or alleles could be identified as susceptible, neutral or protective based on the distribution among Filipino patients and controls. The DR9 and DR3 haplotypes showed the most dramatic increase among patients (0.156 vs 0.063) and (0.172 vs 0.042), respectively. Among Filipinos, the DR3/9 genotype confers approximately the same risk as the well-known high-risk DR3/4 genotype, similar to that for DR3/3 and DR9/9. The common DR2 haplotype in the Philippines (DRB1*1502-DQB1*0502) was only slightly decreased in type 1 diabetic patients (0.200 in patients vs 0.270 in controls). Another DR2 haplotype, DRB1*1502-DQB1*0501, was significantly decreased among patients. In addition, haplotypes containing DQB1*06 alleles, such as the DRB1*0803-DQB1*0601 (OR = 0.1), are strongly protective. The DR4 allele group was also increased in Filipino patients compared to controls. In this population there is, as in other populations, a hierarchy of type 1 diabetes associations among the many different DR4 haplotypes (n = 15). The high-risk haplotypes in this population are the very rare DRB1*0405-DQB1*0302 and DQB1*0405-DQB1*0201, followed by the more common DRB1*0405-DQB1*0401 and DRB1*0405-DQB1*0402. The DRB1*0403-DQB1*0302 is protective. The DRB1*0405-DQB1*05031 haplotype, which is unique to Filipinos, appears to be "neutral". HLA-DPB1*0202 was significantly increased among patients (0.056 vs 0.011; with OR = 5.3); this increase does not appear to simply reflect linkage disequilibrium with high risk DR-DQ haplotypes. The observed distribution of HLA class II alleles among Filipino patients and controls strongly supports the notion that specific combinations of alleles at the DRB1, DQB1, DQA1, and DPB1 loci are critical in determining the risk for type 1 diabetes. Specific HLA class I alleles also show significant associations with type 1 diabetes in this population. HLA-A*2402 and *2403 were increased among patients; however, 2407 was decreased. Inaddition, A *1101 was significantly decreased among patients (OR = 0.51). Moreover, these HLA-A associations do not appear attributable to linkage disequilibrium with the DR-DQ region. The allele B*5801 was increased in patients while B*1301 was decreased; both of these associations, however, reflected linkage disequilibrium with high-risk and with protective DR-DQ haplotypes, respectively. The HLA-C*0102 and *0302 alleles were increased (0.089 vs 0.037 and 0.122 vs 0.064) while C*1502 and *0702 (0.028 vs 0.080 and 0.217 vs 0.330) were decreased. The observed associations of C*0102 and C*1502 do not simply reflect linkage disequilibrium with high-risk DR-DQ haplotypes. Thus, specific HLA class I-A and C alleles were associated with type 1 diabetes in the Filipinos and may, in combination with high risk DR-DQ haplotypes, significantly modify disease risk.     

Insulin-like growth factor 1 promoter polymorphism influences insulin gene variable number of tandem repeat-associated risk for juvenile onset type 1 diabetes

Insulin-like growth factor 1 (IGF1) plays an important role in the development and function of pancreatic beta-cells and contributes to infant growth, which we recently reported to be associated with type 1 diabetes (T1D). Here, we studied an IGF1 microsatellite in 206 families with T1D and its interaction with the polymorphism near the insulin (INS) gene variable number of tandem repeats. The IGF1 microsatellite was associated with T1D (P = 0.045), which was mainly caused by a protective effect of the 194 bp allele (36% transmission to affected offspring). Interestingly, co-segregation of this IGF1 194 bp allele affected the risk of INS alleles. These results provide the first evidence for an association of IGF1 with T1D and imply that co-inheritance of these functional genetic variants of IGF1 and insulin predispose to T1D.     

The glutamic acid decarboxylase 65 immunoglobulin G subclass profile differs between adult-onset type 1 diabetes and latent autoimmune diabetes in adults (LADA) up to 3 years after clinical onset

Autoantibodies against glutamic acid decarboxylase 65 (GADA) are found frequently in patients with autoimmune diabetes. Immunoglobulin (Ig)G₁ is the most frequent subclass among the GADA IgG subclasses. IgG₄ is a more common subclass in latent autoimmune diabetes in adults (LADA) at clinical onset compared to type 1 diabetes. The aim of this work was to study the different GADA-IgG subclass profiles during a 3-year follow-up in these groups of autoimmune diabetes. Adult-onset subjects, classified as either type 1 (n = 40) or LADA (n = 43), were included in the study. New samples were collected every year from these patients. In addition to conventional GADA analyses, GADA-IgG subclasses were also analysed with a radioimmunoprecipitation assay using biotin-conjugated antibodies (directed against human IgG subclasses and IgM) and streptavidin Sepharose. During 3 years'' follow-up, all the IgG subclass levels decreased in type 1 diabetes – IgG₁: P < 0·001; IgG₂: P < 0·001; IgG₃: P < 0·001; IgG₄: P < 0·05 (Friedman''s’ test) – while levels remained stable for all four subclasses in LADA. GADA IgM, however, decreased in both groups (P < 0·001). Patients with LADA have higher GADA IgG₃ and IgG₄ at clinical onset and seem to maintain the levels and profile of their IgG subclasses up to 3 years after clinical onset, while all the GADA IgG subclass levels decrease in type 1 diabetic patients. This indicates a persistent different immune response in LADA compared to type 1 diabetes and further indicates the difference in pathogenesis.