Predominance of DR3 in Somali children with type 1 diabetes in the twin cities, Minnesota.

BACKGROUND: Minnesota is home to the largest Somali population in USA, and pediatric diabetes teams are seeing increasing numbers of Somali children with diabetes. OBJECTIVE: To assess the immune basis of diabetes in Somali children in the Twin Cities, Minnesota. METHODS: A total of 31 Somali children ≤19 yr were treated for type 1 diabetes (T1D) at the University of Minnesota Masonic Children's Hospital and Children's Hospitals and Clinics of Minnesota underwent analysis of human leukocyte antigen (HLA) alleles (n = 30) and diabetes autoantibodies [glutamic acid decarboxylase (GAD65), islet antigen 2 (IA-2), zinc transporter 8 (ZnT8); n = 31]. HLA alleles were analyzed in 49 Somalis without diabetes (controls). Anti-transglutaminase autoantibodies (TGA) for celiac disease were also measured. RESULTS: In Somali children with T1D aged 13.5 ± 5 yr (35% female, disease duration 6.5 ± 3.6 yr), the most common HLA allele was DRB1*03:01 (93%, compared with 45% of Somali controls), followed by DRB1*13:02 (27%). There was a relatively low frequency of DR4 (13%). Controls showed a similar pattern. All 31 participants were positive for at least one diabetes autoantibody. Insulin antibodies were positive in 84% (all were on insulin). Excluding insulin antibodies, 23 (74%) subjects tested positive for at least one other diabetes autoantibody; 32% had 1 autoantibody, 32% had 2 autoantibodies, and 10% had 3 autoantibodies. GAD65 autoantibodies were found in 56% of subjects, IA-2 in 29%, and ZnT8 in 26%. Four (13%) were TGA positive. CONCLUSION: The autoantibody and HLA profiles of Somali children with diabetes are consistent with autoimmune diabetes. Their HLA profile is unique with an exceptionally high prevalence of DRB1*03:01 allele and relative paucity of DR4 alleles compared with African Americans with T1D.

Single nucleotide transcription factor 7-like 2 (TCF7L2) gene polymorphisms in antiislet autoantibody-negative patients at onset of diabetes.

CONTEXT: There is controversy as to whether type 2 diabetes genetic susceptibility contributes to type 1 diabetes, and it is not known what proportion of islet autoantibody-negative new onset subjects have type 2 diabetes risk alleles. OBJECTIVES: We designed this study to evaluate whether two type 2 diabetes-associated single nucleotide polymorphisms (SNPs) of transcription factor 7-like 2 (TCF7L2) gene are associated with the development of islet autoantibody-negative diabetes vs. islet autoantibody-positive diabetes in young patients and whether these SNPs are associated with specific clinical phenotypes. DESIGN: Autoantibody against glutamic acid decarboxylase 65, islet cell antibody 512bdc (form of IA-2), insulin, ZnT8 transporter, and cytoplasmic islet cell antibody were assayed in patients with new onset diabetes seen at the Barbara Davis Center using sera obtained within 2 wk of diagnosis. We genotyped two noncoding variants in the TCF7L2 gene, rs12255372 and rs7903146, in diabetic subjects and normal controls. RESULTS: A total of 140 patients (15.7%) were negative for all islet autoantibodies among 893 subjects less than age 25 at the onset of diabetes. The allele and genotype frequencies of two SNPs showed that these are associated (odds ratio up to 4) with the development of diabetes in the autoantibody-negative diabetic cohort, but not in the autoantibody-positive diabetic cohort. CONCLUSION: TCF7L2 type 2 diabetes susceptibility alleles are associated with islet autoantibody-negative but not autoantibody-positive new onset diabetes in young patients.

Type 1 diabetes: chronic progressive autoimmune disease.

A wealth of data in animal models indicates that type 1A diabetes results from T cell-mediated specific destruction of islet beta cells. There is evidence for the NOD mouse model that insulin is the primary autoantigen and a specific insulin peptide B:9-23 is central to pathogenesis. It is also now possible to predict the development of type 1A (immune mediated) diabetes for the great majority of individuals with a combination of genetic, immunological and metabolic parameters. Such prediction is possible because of the chronic nature of the autoimmunity and loss of beta cell function that precedes the disease. Given the ability to predict type 1A diabetes trials at all stages of the disorder to prevent beta cell destruction are now possible.

Prevalence of autoantibody-negative diabetes is not rare at all ages and increases with older age and obesity.

OBJECTIVE: A significant percentage of nonautoimmune forms of diabetes presents among children in all age groups, with a remarkable increase with age. DESIGN: From October 1992 to October 2004, a total of 859 children less than 18 yr of age were newly diagnosed with diabetes at the Barbara Davis Center for Childhood Diabetes and had blood samples obtained within 2 wk of disease onset for analysis of antiislet autoantibodies to glutamic acid decarboxylase-65, insulinoma-associated antigen-2, insulin, and islet cell autoantibodies. The relationship of autoantibody positivity with human leukocyte antigen (HLA) class II, body mass index (BMI), glycosylated hemoglobin, age, and ethnicity was analyzed. RESULTS: Overall 19% (159 of 859) of these children with newly diagnosed diabetes were negative for all autoantibodies, and autoantibody negativity was significantly increased with age (P < 0.01). The Hispanic and Black subjects had significantly increased autoantibody negativity among older children with higher BMI than White subjects. The patients with the highest risk HLA genotype, DR3-DQ2/DR4-DQ8, were significantly less autoantibody negative (P = 0.001), whereas the HLA-protective allele, DQB1*0602, was significantly increased among the autoantibody-negative patients (P < 0.0001). Insulin autoantibodies were dramatically age dependent and were inversely correlated with age in both prevalence (P < 0.0001) and levels (P < 0.0001). Autoantibody positivity was inversely correlated with both BMI and age using multivariate analysis (P < 0.0001 and P = 0.0078, respectively). CONCLUSIONS: A significant percentage of children newly diagnosed with diabetes are negative for all antiislet autoantibodies with a marked increase in obesity-associated autoantibody-negative diabetes after age 10, suggesting diabetes heterogeneity at all ages.

Multi-SNP analysis of MHC region: remarkable conservation of HLA-A1-B8-DR3 haplotype.

Technology has become available to cost-effectively analyze thousands of single nucleotide polymorphisms (SNPs). We recently confirmed by genotyping a small series of class I alleles and microsatellite markers that the extended haplotype HLA-A1-B8-DR3 (8.1 AH) at the major histocompatibility complex (MHC) is a common and conserved haplotype. To further evaluate the region of conservation of the DR3 haplotypes, we genotyped 31 8.1 AHs and 29 other DR3 haplotypes with a panel of 656 SNPs spanning 4.8 Mb in the MHC region. This multi-SNP evaluation revealed a 2.9-Mb region that was essentially invariable for all 31 8.1 AHs. The 31 8.1 AHs were >99.9% identical for 384 consecutive SNPs of the 656 SNPs analyzed. Future association studies of MHC-linked susceptibility to type 1 diabetes will need to account for the extensive conservation of the 8.1 AH, since individuals who carry this haplotype provide no information about the differential effects of the alleles that are present on this haplotype.

Specific human leukocyte antigen DQ influence on expression of antiislet autoantibodies and progression to type 1 diabetes.

CONTEXT: Human leukocyte antigen (HLA) DQ haplotypes have the strongest genetic association with type 1 diabetes (T1DM) risk. OBJECTIVE: The objective of the study was to analyze whether HLA DQ alleles influence the development of antiislet autoantibodies, the progression to T1DM among autoantibody-positive relatives, or both. DESIGN: The Diabetes Prevention Trial-1 screened more than 90,000 nondiabetic relatives of patients for cytoplasmic islet-cell autoantibody (ICA) expression between 1994 and 2002. SETTING: The study was conducted in the general community. PARTICIPANTS: The Diabetes Prevention Trial-1 found 2817 ICA-positive relatives who were tested for biochemical autoantibodies (GAD65, ICA512, and insulin) and HLA-DQ haplotypes, and 2796 of them were followed up for progression to diabetes for up to 8 yr (median, 3.6 yr). MAIN OUTCOME MEASURE: Progression to T1DM was measured. RESULTS: High-risk DQ haplotypes and genotypes were associated with a higher percentage of relatives expressing multiple biochemical autoantibodies and higher T1DM risk (e.g., respectively, 59 and 36% at 5 yr for carriers of the DQA1*0301-DQB1*0302/DQA1*0501-DQB1*0201 genotype). The number of autoantibodies expressed significantly increased T1DM risk and across different DQ genotypes, autoantibody positivity directly correlated with diabetes risk. However, multivariate analyses indicated that the influence of most genotypes on T1DM risk was not independent from autoantibody expression, with the possible exception of DQA1*0102-DQB1*0602. Specific genotypic combinations conferred 5-yr diabetes risks significantly lower (e.g. 7%-DQA1*0201-DQB1*0201/DQA1*0501-DQB1*0201 and 14%-DQA1*0301-DQB1*0301/DQA1*0501-DQB1*0201) than when those haplotypes were found in other combinations. CONCLUSION: HLA DQ alleles determine autoantibody expression, which is correlated with diabetes progression. Among autoantibody-positive relatives, most HLA DQ genotypes did not further influence T1DM risk.

"Extended" A1, B8, DR3 haplotype shows remarkable linkage disequilibrium but is similar to nonextended haplotypes in terms of diabetes risk.

To evaluate potential differential diabetes risk of DR3 haplotypes we have evaluated class I alleles as well as two microsatellites previously associated with differential risk associated with DR3 haplotypes. We found that over one-third of patient DR3 chromosomes consisted of an extended DR3 haplotype, from DQ2 to D6S2223 (DQ2, DR3, D6S273-143, MIC-A5.1, HLA-B8, HLA-Cw7, HLA-A1, and D6S2223-177) with an identical extended haplotype in controls. The extended haplotype was present more frequently (35.1% of autoimmune-associated DR3 haplotypes, 39.4% of control DR3 haplotypes) than other haplotypes (no other haplotype >5% of DR3 haplotypes) and remarkably conserved, but it was not transmitted from parents to affected children more frequently than nonconserved DR3-bearing haplotypes. This suggests that if all alleles are truly identical for the major A1, B8, DR3 haplotype (between A1 and DR3), with different alleles on nonconserved haplotypes without differential diabetes risk, then in this region of the genome DR3-DQ2 may be the primary polymorphisms of common haplotypes contributing to diabetes risk.

Association of non-HLA genes with type 1 diabetes autoimmunity.

Approximately 50% of the genetic risk for type 1 diabetes is attributable to the HLA region. We evaluated associations between candidate genes outside the HLA region-INS, cytotoxic T-lymphocyte-associated antigen (CTLA)-4, interleukin (IL)-4, IL-4R, and IL-13 and islet autoimmunity among children participating in the Diabetes Autoimmunity Study in the Young (DAISY). Children with persistent islet autoantibody positivity (n = 102, 38 of whom have already developed diabetes) and control subjects (n = 198) were genotyped for single nucleotide polymorphisms (SNPs) in the candidate genes. The INS-23Hph1 polymorphism was significantly associated with both type 1 diabetes (OR = 0.30; 95% CI 0.13-0.69) and persistent islet autoimmunity but in the latter, only in children with the HLA-DR3/4 genotype (0.40; 0.18-0.89). CTLA-4 promoter SNP was significantly associated with type 1 diabetes (3.52; 1.22-10.17) but not with persistent islet autoimmunity. Several SNPs in the IL-4 regulatory pathway appeared to have a predisposing effect for type 1 diabetes. Associations were found between both IL-4R haplotypes and IL-4-IL-13 haplotypes and persistent islet autoimmunity and type 1 diabetes. This study confirms the association between the INS and CTLA-4 loci and type 1 diabetes. Genes involved in the IL-4 regulatory pathway (IL-4, IL-4R, IL-13) may confer susceptibility or protection to type 1 diabetes depending on individual SNPs or specific haplotypes.

Celiac disease and HLA in a Bedouin kindred.

We report the prevalence of celiac disease (CD) and its relationship with other autoimmune diseases and HLA haplotypes in a Bedouin kindred. Of 175 individuals sampled and typed for autoantibodies and HLA class II genotypes, six (3.4%) members had CD, and an additional 10 (5.7%) members tested positive for autoantibodies to transglutaminase (TgAA+). Several CD/TgAA+ relatives also had islet cell antigen or adrenal autoimmunity. Affected relatives are more closely related than expected from the pedigree relationships of all family members and were more often the offspring of consanguineous marriages. Individuals with CD or TgAA+ were enriched for DRB1*0301-DQA1*0501-DQB1*0201, a haplotype previously reported as high risk for CD. There was also an increased frequency of DQB1*0201/DQB1*0201 homozygotes among affected relatives. We found no evidence that DRB1*0701-DQA1*0201-DQB1*0201/DRB1*11-DQA1*0501-DQB1*0301 is a high-risk genotype, consistent with other studies of Arab communities. In addition, a nonparametric linkage analysis of 376 autosomal markers revealed suggestive evidence for linkage on chromosome 12p13 at marker D12S364 (NPL = 2.009, p = 0.0098). There were no other significant results, including the HLA region or any other previously reported regions. This could reflect the reduced power of family-based linkage and association analyses in isolated inbred populations.

HLA-DRB1*15:01-DQA1*01:02-DQB1*06:02 Haplotype Protects Autoantibody-Positive Relatives From Type 1 Diabetes Throughout the Stages of Disease Progression.

The HLA-DRB1*15:01-DQA1*01:02-DQB1*06:02 haplotype is linked to protection from the development of type 1 diabetes (T1D). However, it is not known at which stages in the natural history of T1D development this haplotype affords protection. We examined a cohort of 3,358 autoantibody-positive relatives of T1D patients in the Pathway to Prevention (PTP) Study of the Type 1 Diabetes TrialNet. The PTP study examines risk factors for T1D and disease progression in relatives. HLA typing revealed that 155 relatives carried this protective haplotype. A comparison with 60 autoantibody-negative relatives suggested protection from autoantibody development. Moreover, the relatives with DRB1*15:01-DQA1*01:02-DQB1*06:02 less frequently expressed autoantibodies associated with higher T1D risk, were less likely to have multiple autoantibodies at baseline, and rarely converted from single to multiple autoantibody positivity on follow-up. These relatives also had lower frequencies of metabolic abnormalities at baseline and exhibited no overall metabolic worsening on follow-up. Ultimately, they had a very low 5-year cumulative incidence of T1D. In conclusion, the protective influence of DRB1*15:01-DQA1*01:02-DQB1*06:02 spans from autoantibody development through all stages of progression, and relatives with this allele only rarely develop T1D.

Insulin autoimmunity: prediction/precipitation/prevention type 1A diabetes.

Type 1 diabetes of both the NOD mouse and man is associated with autoimmunity directed against insulin which is the only beta cell specific autoantigen identified to date. One can use autoantibodies to insulin to predict diabetes, use insulin peptides to create insulin autoantibodies, insulitis and diabetes, and use insulin or its peptides in animal models to prevent diabetes. An expanding set of resources are now available for the development and testing in man of therapies to prevent type 1 diabetes, and a number of trials utilizing insulin peptides are now underway.

MICA gene polymorphism in HBDI multiplex families.

T1DM is a disease that affects pancreatic beta cells and results in severe insulin depletion. T1DM is a multigenic disease, and the strongest genetic association with this disease is shown by the genes in MHC class II, namely, DQA1 and DQB1. The other gene that has been implicated in susceptibility to T1DM is the MICA gene that lies within the MHC class I region. This gene has been investigated in many autoimmune diseases, including T1DM, in case-control as well as in family studies. The aim of our study was to test the transmission of MICA microsatellite alleles from unaffected parents to T1DM- affected offspring in HBDI multiplex nuclear families. We also looked at the transmission of MICA alleles together with high-risk DQA1-DQB1 haplotypes to determine the independent transmission of MICA alleles. We observed that MICA6 and MICA9 are transmitted to affected offspring less frequently than expected, and MICA5.1 was more frequently transmitted. DQA1 and DQB1 high-risk haplotypes were transmitted more frequently than expected and DQ6, which is a protective haplotype, was less frequently transmitted to affected offspring. Analysis of MICA-DQA1-DQB1 transmission showed that certain MICA alleles are preferably transmitted as a part of high-risk haplotypes, which might indicate that MICA together with high-risk HLA is associated with T1DM in this family material. However, this latter analysis should be repeated on a larger family sample.

Ethnic differences in the associations between the HLA-DRB1*04 subtypes and type 1 diabetes.

The HLA genotype DRB1*03,DQB1*0201/DRB1*04,DQB1*0302 confers a 25-fold increase in the risk of type 1 diabetes. In persons with this genotype, DRB1*0405, *0402, and *0401 subtypes have been reported to further increase risk, whereas the *0403 and *0406 alleles confer a relative protection. We compared the frequencies of the DRB1*04 alleles in 193 type 1 diabetic patients with the HLA-DRB1*03,DQB1*0201/DRB1*04,DQB1*0302 genotype (140 non-Hispanic white [NHW] and 53 Hispanic) and 205 nondiabetic controls (142 NHW and 63 Hispanic). In addition, 87 NHW first-degree relatives of type 1 diabetes patients were studied: 33 positive and 54 negative for autoantibodies to insulin, GAD65, or IA-2. The HLA-DRB1 was typed using standard PCR SSOP methods. DRB1*0401 (OR, 2.19; 95% CI, 1.36-3.54) in NHW and *0405 (OR, 3.78; 95% CI, 1.43-10.0) in Hispanics were significantly associated with T1DM, whereas DRB1*0403 was protective (OR, 0.19; 95% CI, 0.04-0.89 in NHWs; OR, 0.10; 95% CI, 0.01-0.83 in Hispanics). Associations between the DRB1*04 alleles and prediabetic islet autoimmunity were generally in the same direction as those with diabetes. Among diabetic patients, the mean age of diagnosis appeared to be higher among those with the *0403 and *0407 allele compared with the others. In summary, on the DRB1*03,DQB1*0201/DRB1*04,DQB1*0302 genotypes, the *0403 allele confers relative protection from type 1 diabetes and development of islet autoantibodies in both Hispanics and NHWs and is associated with older age at diabetes diagnosis. Although the associations between diabetes and *0401 and *0405 appear to differ somewhat between Hispanics and NHWs, overall there is no significant difference between these two ethnic groups.

Caspase 7 is a positional candidate gene for IDDM 17 in a Bedouin Arab family.

The IDDM 17 locus was mapped to an 8-cM interval at chromosome 10q25.1 based on linkage in a large Bedouin Arab family with 19 affected relatives. Caspase 7 (CASP7), an apoptosis-related cysteine protease, is one of the few known genes in this region. CASP7 is involved in the activation cascade of caspases responsible for apoptosis execution. Only 1 of the 18 SNPs in CASP7 (SNP144692) differed significantly in frequency in the haplotypes found in affected individuals compared to control Bedouin haplotypes. This same SNP showed evidence of association with diabetes in a subset of patients (DR3/DR4*0302) from HBDI families.

Single nucleotide polymorphism study of IDDM 17 in a Bedouin Arab family.

Type 1 diabetes is an autoimmune disease caused by a combination of genetic and environmental factors. On the basis of a genomic search for linkage in a Bedouin Arab family with 19 members with type 1 diabetes, we previously mapped the IDDM 17 locus to the chromosome 10q25.1 region. The result from a recent genome scan showed suggestive evidence of linkage of IDDM 17 in a subset of Caucasian families in which all affected individuals have DR3, indicating that the IDDM 17 locus might have a measurable effect in Caucasian populations from the United Kingdom and the United States. High-resolution SNP typing provides strong evidence of linkage disequilibrium to the IDDM 17 locus.

Establishing insulin 1 and insulin 2 knockout congenic strains on NOD genetic background.

As insulin is a major autoantigen in autoimmune diabetes and because the insulin gene region locus in humans has been linked to diabetes risk, we have bred insulin gene knockouts onto the NOD mouse. Mice differ from humans in terms that they express two nonallelic genes of insulin. Insulin 2 is the murine homologue of the human insulin gene and is located on mouse chromosome 7. Insulin 1 is thought to have evolved by a gene duplication event, lacks the second intron of the insulin 2 gene, and is located on mouse chromosome 19. The differential thymic expression of the insulin gene may be important for central tolerance induction. Here, we present the initial establishment of congenic knockouts and characterization of the congenic intervals corresponding to insulin 1 and insulin 2 knockout genes on mouse chromosome 19 and 7, respectively.

IDDM17: polymorphisms in the AMACO gene are associated with dominant protection against type 1A diabetes in a Bedouin Arab family.

Haplotype blocks characterized from 78 single-nucleotide polymorphisms (SNPs) in a 1- to 2-centiMorgan region in the human diabetes susceptibility gene IDDM17 were tested for association with type 1 diabetes mellitus (T1DM). Two haplotypes in two adjacent blocks in AMACO, a von Willebrand factor homologue, appear to be associated with the absence of T1DM; transmission tests support this hypothesis. Interestingly, in both haplotype blocks, a single SNP distinguishes the protective haplotype from the other haplotypes. One SNP is noncoding, whereas the other SNP causes a change from glutamic acid to glycine. Future work in identifying the protective allele includes association tests of block haplotypes in other populations.

A second-generation genome screen for linkage to type 1 diabetes in a Bedouin Arab family.

IDDM17 on chromosome 10 was identified in an initial genome screen of 13 members (10 affected) of a large Bedouin Arab family that had 19 relatives affected with type 1 diabetes. Two more children have now been diagnosed with the disease. A second genome screen with 45 members (17 affected members, spouses, and offspring; 382 markers) was performed. A parallel version of Genehunter was used for parametric and nonparametric linkage analyses. The nonparametric linkage analysis (NPL) confirmed the IDDM17 locus (NPL = 3.79; P = 0.001) with a prominent LOD (logarithm of the odds = 2.38) peak. These results demonstrate the strong potential of genetically homogenous, extended families for mapping genes that contribute to a complex disease.

Establishment of native insulin-negative NOD mice and the methodology to distinguish specific insulin knockout genotypes and a B:16 alanine preproinsulin transgene.

We hypothesize that NOD mice without native insulin, but with an altered insulin B:9-23 sequence, will be completely protected from diabetes/insulitis if insulin B:9-23 is an essential T cell epitope. To investigate this hypothesis, we have established initial insulin 1- and 2-negative NOD mice with a transgene directing production of preproinsulin with alanine at position B:16 rather than the native tyrosine of both insulin 1 and insulin 2. Sets of primers for PCR-based assays have been created and validated. They are able to distinguish the presence or absence of the insulin gene knockouts and of both native insulin 1 and insulin 2 (and thus distinguish heterozygous versus homozygous knockouts), as well as the presence of the altered insulin transgene, B:16 alanine preproinsulin. Four B:16 alanine transgenic founders were produced directly in NOD mice and, by intercrossing, initial live native insulin-negative B:16 alanine transgenic mice have been generated.