ICA+ relatives with DQA1*0102/DQB1*0602 have expected 0602 sequence and DR types

Differential HLA Association of GAD65 and IA2 Autoantibodies in North Indian Type 1 Diabetes Patients

The human leucocyte antigen (HLA) association with type 1 diabetes (T1D) is well known but there are limited studies investigating the association between β-cell autoantibodies and HLA genes. We evaluated the prevalence of GAD65 and IA-2 autoantibodies (GADA and IA2A) in 252 T1D patients from North India and investigated the genetic association of GADA and IA2A with HLA class I and class II genes/haplotypes. GADA and IA2A were detected in 50.79% and 15.87% of T1D patients, respectively, while only 8.73% had both GADA and IA2A. HLA-DRB1^∗03 was observed to be significantly higher in GADA+ T1D patients as compared to GADA- (91.41% vs. 66.13%, Bonferroni-corrected P (P _c) = 1.11 × 10^-5; OR = 5.45; 95% CI: 2.67-11.08). Similarly, HLA-DQB1^∗02 was found to be significantly increased in GADA+ patients (94.53%, P _c = 2.19 × 10^-5; OR = 6.27; 95% CI: 2.7-14.49) as compared to GADA- (73.39%). The frequencies of HLA-DRB1^∗04 and DQB1^∗03 were increased in IA2A+ patients (45.0% and 52.5%, respectively) as compared to that in IA2A- (25.94% and 33.96%, respectively). Further, the frequency of DRB1^∗03-DQB1^∗02 haplotype was found to be significantly increased in GADA+ T1D patients as compared to GADA- (60.55% vs. 41.94%, P = 3.94 × 10^-5; OR = 2.13; 95%CI = 1.49-3.03). Similarly, HLA-DRB1^∗04-DQB1^∗03 haplotype was found to be significantly increased in IA2A+ T1D patients compared to IA2A- patients (22.5% vs. 12.97%; P = 0.041; OR = 1.95; 95%CI = 1.08-3.52). None of the HLA class I genes (HLA-A, B, and Cw) was found to be associated with GADA or IA2A in people with T1D. Our findings suggest that HLA-DRB1^∗03/DQB1^∗02 and HLA-DRB1^∗04/DQB1^∗03 might play an important role in the development of GADA and IA2A, respectively.

Interaction between Treg apoptosis pathways, Treg function and HLA risk evolves during type 1 diabetes pathogenesis

We have previously reported increased apoptosis of regulatory T cells (Tregs) in recent-onset Type 1 Diabetes subjects (RO T1D) in the honeymoon phase and in multiple autoantibody-positive (Ab+) subjects, some of which are developing T1D. We have also reported that increased Treg apoptosis was associated with High HLA risk and that it subsided with cessation of honeymoon period. In this report, we present results generated using genetics, genomics, functional cell-based assays and flow cytometry to assess cellular changes at the T-cell level during T1D pathogenesis. We measured ex vivo Treg apoptosis and Treg function, surface markers expression, expression of HLA class II genes, the influence of HLA risk on Treg apoptosis and function, and evaluated contribution of genes reported to be involved in the apoptosis process. This integrated comprehensive approach uncovered important information that can serve as a basis for future studies aimed to modulate Treg cell responsiveness to apoptotic signals in autoimmunity. For example, T1D will progress in those subjects where increased Treg apoptosis is accompanied with decreased Treg function. Furthermore, Tregs from High HLA risk healthy controls had increased Treg apoptosis levels and overexpressed FADD but not Fas/FasL. Tregs from RO T1D subjects in the honeymoon phase were primarily dying through withdrawal of growth hormones with contribution of oxidative stress, mitochondrial apoptotic pathways, and employment of TNF-receptor family members. Ab+ subjects, however, expressed high inflammation level, which probably contributed to Treg apoptosis, although other apoptotic pathways were also activated: withdrawal of growth hormones, oxidative stress, mitochondrial apoptosis and Fas/FasL apoptotic pathways. The value of these results lie in potentially different preventive treatment subjects would receive depending on disease progression stage when treated.

HLA class II alleles specify phenotypes of ketosis-prone diabetes

OBJECTIVE

Ketosis-prone diabetes (KPD) comprises four subgroups based on the presence or absence of beta-cell autoantibodies (A+ or A-) and beta-cell functional reserve (beta+ or beta-). Genetic factors could contribute to their distinctive phenotypes. Our aim was to specify the role of HLA class II alleles associated with susceptibility or resistance to autoimmune type 1 diabetes in determining KPD phenotypes.

RESEARCH DESIGN AND METHODS

A total of 185 adults presenting with diabetic ketoacidosis were followed longitudinally for a mean of 5.5 years, with measurements of autoantibodies, beta-cell functional reserve, insulin sensitivity, and insulin requirement. Frequencies of susceptibility and resistance alleles at HLA DQA1, DQB1, and DRB1 loci were correlated with clinical and phenotypic features of KPD subgroups and compared with those of ethnic-specific population control subjects.

RESULTS

Susceptibility alleles were more frequent (P < 0.0001) in the two A+ than the two A- KPD subgroups; in the latter, the frequency was no greater than in population control subjects (except for DQB1*0302). Susceptibility alleles differentiated the two clinically similar beta- subgroups (more frequent in A+beta- than A-beta- KPD; P < 0.01). Resistance alleles were more frequent in the two beta+ than the two beta- KPD subgroups (P < 0.01). The frequencies of certain susceptibility (e.g., DQB1*02) and resistance (DQB1*0602) alleles were higher in African-American A-beta+ KPD patients than in African-American control subjects. DQB1*0302 was more frequent in all KPD subgroups compared with control subjects.

CONCLUSIONS

HLA class II alleles associated with susceptibility or resistance to autoimmune type 1 diabetes help specify the four subgroups of KPD. Inheritance of these alleles may influence long-term beta-cell functional reserve.

Differential effects of DRB1*0301 and DQA1*0501-DQB1*0201 on the activation and progression of islet cell autoimmunity

Autoimmune diabetes shows extreme variation in age of onset and clinical presentation, although most studies have been done in children with the most severe subtype. Disease risk is strongly associated with HLA-DRB1*0301-DQA1*0501-DQB1*0201 (DR3-DQ2), but it has not been possible to separate the effects of the DR and DQ alleles. We have identified a large Bedouin kindred in which a high prevalence of islet autoimmunity is associated with two different DR3 haplotypes, one carrying the usual DQ2 and the other carrying DQA1*0102-DQB1*0502 (DQ5). Results of prospective follow-up studies indicate that DR3 is associated with the initial activation of islet autoimmunity whereas DQ2 is associated with early-onset and severe clinical disease. The association signals map to a 350-kb interval, thus implicating primary effects for DR3 and DQ2. Overall, our results emphasize the importance of prospective genetic studies that examine the full range of variation in the initiation, progression and expression of autoimmune disease.

High frequency of abnormal glucose tolerance in DQA1*0102/DQB1*0602 relatives identified as part of the Diabetes Prevention Trial--Type 1 Diabetes

AIMS/HYPOTHESIS

Immunological and genetic markers can be used to assess risk of developing type 1 diabetes prior to the onset of clinical symptoms. Autoantibody-positive relatives of patients with type 1 diabetes are at increased risk for disease, while the presence of HLA DQA1*0102/DQB1*0602 is thought to confer protection. Using the unique population identified by the Diabetes Prevention Trial--Type Diabetes (DPT-1), our aim was to determine if these individuals were protected from type 1 diabetes.

METHODS

We described metabolic and immunological characteristics of islet cell cytoplasmic autoantibodies-positive relatives with DQB1*0602 identified as part of DPT-1.

RESULTS

We found that 32% of DQB1*0602-positive relatives identified through the DPT-1 had abnormalities of glucose tolerance despite the fact that only 19% had multiple type 1 diabetes-associated autoantibodies and only 13% had abnormal insulin secretion, markers typically associated with the disease. In addition, these markers were not associated with abnormal glucose tolerance. In contrast, the DQB1*0602-positive relatives had elevated fasting insulin (117+/-10 pmol/l) and homeostasis model assessment of insulin resistance (HOMA-R) (4.90+/-0.5) values, which are more commonly associated with type 2 diabetes. The later marker of insulin resistance was associated with glucose tolerance status.

CONCLUSIONS/INTERPRETATION

Our data indicate that DQA1*0102/DQB1*0602 relatives identified through DPT-1 have a high frequency of abnormal glucose tolerance and a disease phenotype with characteristics of type 1 and type 2 diabetes. Thus, multiple pathways to abnormal glucose tolerance are present within families of these type 1 patients.

Ketosis-prone diabetes: dissection of a heterogeneous syndrome using an immunogenetic and beta-cell functional classification, prospective analysis, and clinical outcomes

Ketosis-prone diabetes is heterogeneous. Its causes could include novel beta-cell functional defects. To characterize such defects, 103 patients with diabetic ketoacidosis were evaluated for beta-cell autoimmunity and human leukocyte antigen (HLA) class II alleles, with longitudinal measurements of beta-cell function and biochemical and clinical parameters. They were classified into four A beta groups, based on the presence of glutamic acid decarboxylase (GAD)65, GAD67, or IA-2 autoantibodies (A+ or A-) and beta-cell functional reserve (beta+ or beta-). The group distribution was: 18 A+beta-, 23 A-beta-, 11 A+beta+, and 51 A-beta+. Collectively, the two beta- groups differed from the two beta+ groups in earlier onset and longer duration of diabetes, lower body mass index, less glycemic improvement, and persistent insulin requirement. HLA class II genotyping showed that the A-beta- group differed from the A+beta- group in having lower frequencies of two alleles strongly associated with autoimmune type 1 diabetes susceptibility: DQA*03 and DQB1*02. Similarly, the A-beta+ group differed from the A+beta+ group in having a lower frequency of DQB1*02. Ketosis-prone diabetes comprises at least four etiologically distinct syndromes separable by autoantibody status, HLA genotype, and beta-cell functional reserve. Novel, nonautoimmune causes of beta-cell dysfunction are likely to underlie the A-beta+ and A-beta- syndromes.