Genetic and immunological markers of insulin dependent diabetes in Black Americans

Association of HLA-DRB1 amino acid residues with giant cell arteritis: genetic association study, meta-analysis and geo-epidemiological investigation

INTRODUCTION

Giant cell arteritis (GCA) is an autoimmune disease commonest in Northern Europe and Scandinavia. Previous studies report various associations with HLA-DRB1*04 and HLA-DRB1*01; HLA-DRB1 alleles show a gradient in population prevalence within Europe. Our aims were (1) to determine which amino acid residues within HLA-DRB1 best explained HLA-DRB1 allele susceptibility and protective effects in GCA, seen in UK data combined in meta-analysis with previously published data, and (2) to determine whether the incidence of GCA in different countries is associated with the population prevalence of the HLA-DRB1 alleles that we identified in our meta-analysis.

METHODS

GCA patients from the UK GCA Consortium were genotyped by using single-strand oligonucleotide polymerization, allele-specific polymerase chain reaction, and direct sequencing. Meta-analysis was used to compare and combine our results with published data, and public databases were used to identify amino acid residues that may explain observed susceptibility/protective effects. Finally, we determined the relationship of HLA-DRB1*04 population carrier frequency and latitude to GCA incidence reported in different countries.

RESULTS

In our UK data (225 cases and 1378 controls), HLA-DRB1*04 carriage was associated with GCA susceptibility (odds ratio (OR) = 2.69, P = 1.5×10(-11)), but HLA-DRB1*01 was protective (adjusted OR = 0.55, P = 0.0046). In meta-analysis combined with 14 published studies (an additional 691 cases and 4038 controls), protective effects were seen from HLA-DR2, which comprises HLA-DRB1*15 and HLA-DRB1*16 (OR = 0.65, P = 8.2×10(-6)) and possibly from HLA-DRB1*01 (OR = 0.73, P = 0.037). GCA incidence (n = 17 countries) was associated with population HLA-DRB1*04 allele frequency (P = 0.008; adjusted R(2) = 0.51 on univariable analysis, adjusted R(2) = 0.62 after also including latitude); latitude also made an independent contribution.

CONCLUSIONS

We confirm that HLA-DRB1*04 is a GCA susceptibility allele. The susceptibility data are best explained by amino acid risk residues V, H, and H at positions 11, 13, and 33, contrary to previous suggestions of amino acids in the second hypervariable region. Worldwide, GCA incidence was independently associated both with population frequency of HLA-DRB1*04 and with latitude itself. We conclude that variation in population HLA-DRB1*04 frequency may partly explain variations in GCA incidence and that HLA-DRB1*04 may warrant investigation as a potential prognostic or predictive biomarker.

Incidence of insulin-requiring diabetes in the US military

AIMS/HYPOTHESIS

The aim of the study was to determine age- and race-related, and overall incidence rates of insulin-requiring diabetes in adults in the US military.

METHODS

Electronic records for admissions to US military and Tricare hospitals during 1990-2005 and visits to military clinics during 2000-2005 were identified using the Career History Archival Medical and Personnel System at the Naval Health Research Center, San Diego, CA, USA. Population data were obtained from the Defense Manpower Data Center and Defense Medical Epidemiology Database.

RESULTS

In men there were 2,918 new cases of insulin-requiring diabetes in 20,427,038 person-years at ages 18-44 years (median age 28 years) for a total age-adjusted incidence rate of 17.5 per 100,000 person-years (95% CI 16.4-18.6). Incidence rates were twice as high in black men as in white men (31.5 vs 14.5 per 100,000, p < 0.001). In women there were 414 new cases in 3,285,000 person-years at ages 18-44 years (median age 27 years), for a total age-adjusted incidence rate of 13.6 per 100,000 (95% CI 12.4-14.9). Incidence rates were twice as high in black women as in white women (21.8 vs 9.7 per 100,000, p < 0.001). In a regression model, incidence of insulin-requiring diabetes peaked annually in the winter-spring season (OR 1.46, p < 0.01). Race and seasonal differences persisted in the multivariate analysis.

CONCLUSIONS/INTERPRETATION

Differences in incidence rates by race and season suggest a need for further research into possible reasons, including the possibility of a contribution from vitamin D deficiency. Cohort studies using prediagnostic serum 25-hydroxyvitamin D should be conducted to further evaluate this relationship.

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.

Evaluation of leptin levels in subjects at risk for type 1 diabetes

Type 1 diabetes (T1DM) is increasing in incidence worldwide, particularly in young children. Studies have suggested that weight gain in early childhood may play a role in determining disease risk, with increased risk in children who have gained more weight. We hypothesized that leptin may be involved by promoting a Th1-type immune response in individuals at risk for the development of T1DM. Insulin, GAD65, and IA-2 autoantibodies and leptin levels were measured in relatives of T1DM patients and in control subjects. After adjusting for HLA risk and age, autoantibody-positive relatives were compared with sex- and BMI-matched autoantibody-negative control subjects. BMI-matched individuals had similar leptin levels, and the leptin levels increased with increasing BMI Z-score, as expected. However, we did not demonstrate higher leptin levels in autoantibody-positive relatives, compared with autoantibody-negative control subjects. Thus, elevations in leptin levels do not appear to be a major determinant of whether an individual develops autoimmunity. If elevated BMI and associated elevations in leptin levels are risk factors for the initiation and/or progression of autoimmunity, they may act more as permissive factors in this process, in the setting of a certain degree of genetic predisposition.

Autoimmunity and clinical course in children with type 1, type 2, and type 1.5 diabetes

AIMS

Both type 1 (T1D) and type 2 diabetes (T2D) are increasing in incidence in children; often an admixture of T1D and T2D features are present at diagnosis. We examined the relationship between diabetes autoantibodies (DAA), human leukocyte antigen (HLA), and clinical course in subjects grouped by clinical diabetes type.

METHODS

Subjects 8-18 years old with T1D, T2D, and mixed clinical features (T1.5D), were studied at diagnosis. DAA were measured in all subjects; a subset of subjects underwent HLA genotyping. Clinical course was followed in 84% of subjects for 47.9+8.7 months.

RESULTS

Eighty-nine percent of T1.5D subjects were positive for at least one DAA; 88% of HLA-typed subjects had risk HLA genotypes. Two subjects initially treated with oral agents were subsequently treated with insulin (50%); one had risk HLA, and the other was DAA positive. Thirty-three percent of T2D subjects were DAA positive and 93% were treated with oral agents at diagnosis. Three subjects were subsequently treated with insulin (21%); of these, two were DAA positive, and one had risk HLA. No subject who remained on diet therapy or oral agents had a combination of DAA-positivity and risk HLA genotype.

CONCLUSIONS

Children clinically classified with T1.5D or T2D have a high frequency of autoimmune markers and T1D-associated HLA alleles which appears to indicate a more aggressive diabetes disease process, as has been shown for DAA-positive adults with phenotypic T2D.

The relationship between immune-mediated Type 1 diabetes mellitus and ethnicity

OBJECTIVE

To determine the proportion of adults with newly diagnosed Type 1 diabetes that had immune-mediated disease (IMD).

SUBJECTS AND METHODS

Two hundred fifteen patients with hyperglycemia and symptoms of insulin deficiency were screened for antibodies [islet cell antibodies (ICA), insulin autoantibodies (IAA), and glutamatic acid decarboxylase antibodies (GADA(65))] and HLA DR/DQ markers of IMD.

RESULTS

The mean age was 34 years and the mean BMI was 30.0 kg/m(2); 21.8% were non-Hispanic white (NHW), 27% were Latin American (LA), 47.9% were African American (AA), and 3.3% of other (OT) ethnic origins. Sixty individuals (28%) had one or more autoantibodies [Ab(+)]: 62% of NHW, 19% of AA, and 19% of LA. BMI was significantly lower (P<.01) in Ab(+). At least one HLA-DQ allele for susceptibility for IMD was identified in 52% of Ab(+).

CONCLUSIONS

These results suggest that islet cell autoantibodies and HLA markers of susceptibility for IMD are frequent in individuals of varying ethnic backgrounds, older age at onset, and higher body weight. Since early insulin therapy could delay what may otherwise be rapid progression to complete insulinopenia in patients with IMD, screening of adult diabetic patients for IMD at diagnosis may be of benefit to long-term management.

Immune-mediated disease and secondary failure to oral therapy in type 2 diabetes mellitus

PURPOSE

To determine the proportion of adults with type 2 diabetes, who developed secondary failure to oral medications that had immune-mediated diabetes (IMD).

SUBJECTS AND METHODS

One hundred and eight subjects who failed to oral therapy were screened for autoantibodies (ICA, IAA, IA-2A, and GADA(65)) and HLA DR/DQ markers of IMD.

RESULTS

Mean age was 49 years and mean body mass index (BMI) was 31.5 kg/m(2); 21.3% were non-Hispanic White (NHW), 32.3% Latin American (LA), and 43.2% African American (AA). Fourteen percent had one or more autoantibodies [Ab(+)]: five NHW, three LA, and seven AA. Ab(+) patients were younger (P=.03) and had lower body weight (P=.05) than Ab(-) patients. HLA markers of susceptibility for IMD were identified in 64% Ab(+) and in 43% Ab(-) (chi(2), P=.46).

CONCLUSIONS

These results suggest that secondary failure to oral therapy can be due to continuing IMD in obese, type 2 diabetic individuals of varying ethnic backgrounds than those who have been traditionally associated with autoimmune type 1 diabetes. Screening for markers for IMD at diagnosis could be a useful way to predict those likely to develop secondary failure to oral therapy and may assist in the selection of medical therapy.

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.

High GAD65 autoantibody levels in nondiabetic adults are associated with HLA but not with CTLA-4 or INS VNTR

OBJECTIVES

To explore the relationship between genetic background and antibody levels in a nondiabetic population. We evaluated if high levels of autoantibodies against the 65 kDa isoform of glutamic acid decarboxylase (GAD65Ab), were associated with high-risk genes, i.e. HLA, CTLA-4 and INS VNTR genes.

DESIGN AND SUBJECTS

Seventy-five (M/F 39/36) subjects exceeding the 95th percentile of GAD65 autoantibody index and 75 age and sex matched subjects below the 95th percentile, randomly selected amongst participants in the Västerbotten Intervention Programme.

METHODS

The GAD65 Ab were measured in a radioligand-binding assay. HLA class II typing was performed by an oligoblot hybridization method. CTLA-4 repeat length was analysed and divided into short forms and long forms. Class I and class III alleles of INS VNTR were detected. Differences in distribution were tested by Pearson chi-square with Yates correction. Odds ratios (OR) were used to compare groups calculated with Cochran's and Mantel-Haenszel statistics.

RESULTS

The DQB1*0201-DQA1*0501-DRB1*03 haplotype was increased in subjects with high GAD65Ab levels (P = 0.04). This increase seemed to be explained by a difference in haplotype frequencies amongst men (P = 0.01). Calculating OR showed a significant association between the DQB1*0201-DQA1*0501-DRB1*03 haplotype and elevated levels of GAD65Ab in all subjects (OR 2.2, 95% CI 1.02-4.9) as well as in men (OR 4.6, 95% CI 1.3-15.9). There was no association between high levels of GAD65Ab and either INS VNTR or CTLA-4 polymorphisms.

CONCLUSION

Our study suggests that adult males with the DQB1*0201-DQA1*0501-DRB1*03 haplotype tend to develop high GAD65Ab titres. As none of these subjects have developed diabetes these data suggest that HLA may be important in GAD65Ab formation but that additional factors are required for the progression to overt type 1 diabetes.

Can MHC class II genes mediate resistance to type 1 diabetes?

Numerous studies have associated carriage of HLA-DRB1*1501, DQA1*0102 and DQB1*0602 (DR15, DQ6) with dominant resistance to type 1 diabetes and have concluded that one or more of the component HLA class II molecules mediate this effect. Mechanisms for MHC class II-mediated resistance to diabetes have been proposed from studies of transgenic mice, usually using the diabetes-prone non-obese diabetic (NOD) strain. However, these studies have not reached any consensus on a plausible mechanism. In this study we question why the role of central MHC genes in resistance to diabetes has not been addressed, as the central MHC carries markers of susceptibility to diabetes in linkage disequilibrium with several genes with known or putative immunoregulatory functions. To illustrate the type of studies required to address this issue, we selected diabetes patients and control subjects for carriage of HLA-DR15 and the C allele at position +738 in the inhibitor of kappa B-like gene (IKBL). These alleles mark the 7.1 haplotype (HLA-A3, B7, IKBL738*C, DR15, DQ6). HLA-DR15 was the most effective marker of resistance, but an effect may be evident with IKBL738*C in a larger study. Moreover, carriage of the entire haplotype was particularly rare in patients. The best explanation for this is that the critical gene lies between IKBL and HLA-DRB1, and is more closely linked to HLA-DRB1. Candidate genes at the centromeric end of the central MHC are reviewed, highlighting the need for further study.

The genetics of complex autoimmune diseases: non-MHC susceptibility genes

Susceptibility to complex autoimmune diseases (AIDs) is a multigenic phenotype affected by a variety of genetic and environmental or stochastic factors. After over a decade of linkage analyses, the identification of non-major histocompatibility complex (non-MHC) susceptibility alleles has proved to be difficult, predominantly because of extensive genetic heterogeneity and possible epistatic interactions among the multiple genes required for disease development. Despite these difficulties, progress has been made in elucidating the genetic mechanisms that influence the inheritance of susceptibility, and the pace of gene discovery is accelerating. An intriguing new finding has been the colocalization of several AID susceptibility genes in both rodent models and human linkage studies. This may indicate that several susceptibility alleles affect multiple AIDs, or alternatively that genomic organization has resulted in the clustering of many immune system genes. The completion of the human genome sequence, coupled with the imminent completion of the mouse genome, should yield key information that will dramatically enhance the rate of gene discovery in complex conditions such as AID susceptibility.

Early age of disease onset in African American type 1 diabetes patients is associated with DQB1*0201 allele

The goal of this study is to assess the association of HLA-DQ alleles with the age of onset of type 1 diabetes in African American patients. Using PCR oligonucleotide typing, HLA-DQA1 and DQB1 alleles were determined. DQA1*0301, DQB1*0201, and DQB1*0302 were significantly increased in African American patients. However, the DQB1*0602 allele was decreased in these patients. In addition, DQA1*0401 and DQB1*0402, were associated with protection in African Americans. When stratified by age of onset, prepubertal patients showed an absence of the protective allele DQB1*0602 and a significant increase in DQB1*0201 compared to postpubertal patients. The high frequency of the HLA-DQ susceptibility allele in pre-pubertal patients suggest that the biology of disease in this group may differ from type 1 diabetes with a later age of onset.

Donor-recipient sharing of HLA class II alleles predicts earlier recurrence and accelerated progression of hepatitis C following liver transplantation

Both direct viral cytopathic effects and host immune responses appear to be important in the pathogenesis of hepatitis C virus (HCV) infection. Liver transplantation provides a means to explore the role of the immune system in the development of HCV-related liver damage through comparing the natural history of HCV in patients with different degrees of donor-recipient human leukocyte antigen (HLA) matching. We evaluated 36 patients with recurrent hepatitis C viremia following liver transplantation to determine whether hepatocellular injury or progression to bridging fibrosis occur more rapidly when donor and recipients share HLA alleles. HLA typing for the HLA-A and HLA-B loci was performed by serological techniques and PCR-based oligotyping was used to type alleles of the DRB1, DRB3, DQA1, and DQB1 loci. A median of eight liver biopsies, obtained during a median follow-up of 36 months, were reviewed per patient. Donor-recipient sharing of alleles of HLA-DQB1 or DRB1 was associated with more rapid development of recurrent hepatitis by univariate analysis (chi2=5.7, P=0.02 and chi2=5.54, P=0.02 respectively). However, only sharing of HLA-DRB1 alleles was identified as an independent predictor of reduced time to recurrent histologic injury by multivariate analysis (chi2 =5.74, P=0.02). Furthermore, sharing of HLA-DRB3 and histologic evidence of rejection were associated with more rapid progression to bridging fibrosis both by univariate methods (chi2=4.12, P=0.04 and chi2=4.66, P=0.03 respectively), and by multivariate analysis (chi2=13.01, P=0.001). These findings suggest that HLA class II-restricted immune responses may contribute to the pathogenesis of HCV-related liver injury in liver transplant recipients.

HLA-DRB1 typing in rheumatoid arthritis: predicting response to specific treatments

OBJECTIVE

To determine the predictive value of shared epitope alleles for response to treatment in patients with rheumatoid arthritis.

METHODS

Patients from our previously published triple DMARD study were tested for the presence of shared epitope alleles (DRB1 *0401, 0404/0408, 0405, 0101, 1001, and 1402). Patients who were shared epitope positive were then compared with those who were negative to see if there was a differential effect on therapeutic response.

RESULTS

Shared epitope positive patients were much more likely to achieve a 50% response if treated with methotrexate-sulphasalazine-hydroxychloroquine compared with methotrexate alone (94% responders versus 32%, p < 0.0001). In contrast shared epitope negative patients did equally well regardless of treatment (88% responders for methotrexate-sulphasalazine-hydroxychloroquine versus 83% for methotrexate). Additionally, a trend toward an inverse relation of the gene dose was seen for response to methotrexate treatment (p = 0.05).

CONCLUSIONS

These data suggest that determining shared epitope status may provide clinical information useful in selecting among treatment options.