HLA-DQB1*0201/0302 is associated with severe retinopathy in patients with IDDM

Importance of Autoimmune Responses in Progression of Retinal Degeneration Initiated by Gene Mutations

Inherited retinal diseases (IRDs) are clinically and genetically heterogeneous rare disorders associated with retinal dysfunction and death of retinal photoreceptor cells, leading to blindness. Among the most frequent and severe forms of those retinopathies is retinitis pigmentosa (RP) that affects 1:4,000 individuals worldwide. The genes that have been implicated in RP are associated with the proteins present in photoreceptor cells or retinal pigment epithelium (RPE). Asymmetric presentation or sudden progression in retinal disease suggests that a gene mutation alone might not be responsible for retinal degeneration. Immune responses could directly target the retina or be site effect of immunity as a bystander deterioration. Autoantibodies against retinal autoantigens have been found in RP, which led to a hypothesis that autoimmunity could be responsible for the progression of photoreceptor cell death initiated by a genetic mutation. The other contributory factor to retinal degeneration is inflammation that activates the innate immune mechanisms, such as complement. If autoimmune responses contribute to the progression of retinopathy, this could have an implication on treatment, such as gene replacement therapy. In this review, we provide a perspective on the current role of autoimmunity/immunity in RP pathophysiology.

Human Leukocyte Antigens class II (HLA II) gene profile from an admixed population of patients with type 1 diabetes with severe diabetic retinopathy: a nested case-control study in Brazil

BACKGROUND

Although the well-established role of the HLA genes on the predisposition of type 1 diabetes (T1D), its contribution to the development and progression of diabetic retinopathy is still unclear, especially in admixed populations. We aimed to study the relationship between HLA alleles and severe diabetic retinopathy in a highly admixed population of T1D patients.

METHODS

This was a nested case-control study based on a cross-sectional, nationwide survey conducted in Brazil. We included 117 patients with severe diabetic retinopathy and 117 random controls composed of T1D patients without retinopathy, matched for diabetes duration. HLA-class II genes (HLA-DRB1, -DQA1, and -DQB1) were genotyped using the SSO and NGS methods.

RESULTS

Haplotypes HLA-DRB1*04:05 ~ DQA1*03:01 g ~ DQB1*03:02 (OR 1.75, CI 0.97-3.16, p value 0.058) and HLA-DRB1*13:02 ~ DQA1*01:02 ~ DQB1*06:04 (OR 5.18, CI 1.12-23.09, p value 0.019) were more prevalent on the severe DR group but they did not present statistically difference after Bonferroni correction. The most frequent haplotype on both groups was HLA-DRB1*03:01 ~ DQA1*05:01 g ~ DQB1*02:01 (29.6% on severe DR and 33.33% on the control group).

CONCLUSIONS

Our study showed no influence of HLA genes on the development of DR. Further longitudinal data is needed to better understand the role of genetic factors on this multifactorial significant microvascular complication.

Birth Weight and Diabetic Retinopathy: Results From the Population-Based Gutenberg Health Study (GHS)

PURPOSE

This study investigates the relationship between diabetic retinopathy (DR) and birth weight (BW) in diabetic subjects sampled from the general population.

METHODS

The Gutenberg Health Study (GHS) is a population-based, observational cohort study in participants aged from 35 to 74 years. Criteria for diabetes diagnosis were HbA1c ≥6.5% at study entry, a doctor-diagnosis of diabetes, or diabetes medication. The presence of DR was determined by evaluating fundus photographs. BW was assessed by self-reports. GHS participants were divided into three different BW groups (low: <2500 g; normal: 2500-4000 g; high:>4000 g). Logistic regression analysis was conducted as uni- and multivariable analysis with adjustment for age and sex. Effect mediators were separately investigated.

RESULTS

A total of 1,124 GHS participants (7.5% of the cohort) had diabetes at study entry. Of these, 402 subjects (35.8%) had gradable fundus photographs, reported BW data and were included into this study. Overall, 91/402 subjects (23%) had DR. With regard to BW groups, DR was descriptively more frequent in subjects with low (28.1% [95%-CI: 14.4-47.0%; n = 32]) and high BW (30.8% [95%-CI: 19.1-45.3%; n = 52]) compared to normal BW (20.8% [95%-CI: 16.5-25.7%; n = 318]). Both high and low BW were associated with DR in multivariable analysis (high: OR = 1.68, p = .037; low: OR = 1.81, p = .05). The BW effect was mediated by duration of diabetes in both BW groups and by arterial hypertension in the low BW group.

CONCLUSION

Low and high BW in persons with diabetes is related to higher risk of diabetic retinopathy. Longer duration of diabetes and higher prevalence of arterial hypertension are factors in these subjects explaining the elevated risk.

HLA-DQB1 Subtypes Predict Diabetic Retinopathy in Patients with Type I Diabetes Mellitus

Purpose

To investigate if diabetic patients without diabetic retinopathy despite long disease duration have different human leukocyte antigen (HLA) status vs those with an early onset of retinopathy.

Methods

Retrospective, nonrandomized, masked comparative study. Type 1 diabetic patients with a disease onset before age 30 were recruited to the study. The study population consisted of two groups of diabetic patients: those with normal retinopathy course (retinopathy developed during the first 20 years of diabetes onset) (23 patients) and those with postponed retinopathy (no obvious retinopathy in spite of passing 20 years of diabetes) (19 patients). These groups were matched with regard to level of glycemic control, blood pressure, and lipid profile. A group of 23 healthy patients served as controls. HLA-DQB1 typing of blood samples was done using a polymerase chain reaction with sequence-specific primer (PCR-SSP) method.

Results

HLA-DQB1*0201/HLA-DQB1*0501 and HLA-DQB1*0201/HLA-DQB1*0504 haplotypes were more common among type 1 diabetic patients with normal retinopathy course than those with postponed retinopathy (26.1% vs 0.0%; p=0.019). HLA-DQB1*0301 and HLA-DQB1*0304 were less common among those diabetic patients with normal retinopathy course than those with a postponed retinopathy (63.2% vs 34.8%; p=0.067).

Conclusions

Some haplotypes seem to predispose diabetic patients to diabetic retinopathy. HLA typing may be beneficial for predicting the prognosis of diabetic retinopathy in younger diabetic patients.

Linkage Analysis of Genomic Regions Contributing to the Expression of Type 1 Diabetes Microvascular Complications and Interaction with HLA

We conducted linkage analysis to follow up earlier work on microvascular complications of type 1 diabetes (T1D). We analyzed 415 families (2,008 individuals) previously genotyped for 402 SNP markers spanning chromosome 6. We did linkage analysis for the phenotypes of retinopathy and nephropathy. For retinopathy, two linkage peaks were mapped: one located at the HLA region and another novel locus telomeric to HLA. For nephropathy, a linkage peak centromeric to HLA was mapped, but the linkage peak telomeric to HLA seen in retinopathy was absent. Because of the strong association of T1D with DRB1*03:01 and DRB1*04:01, we stratified our analyses based on families whose probands were positive for DRB1*03:01 or DRB1*04:01. When analyzing the DRB1*03:01-positive retinopathy families, in addition to the novel telomeric locus, one centromeric to HLA was identified at the same location as the nephropathy peak. When we stratified on DRB1*04:01-positive families, the HLA telomeric peak strengthened but the centromeric peak disappeared. Our findings showed that HLA and non-HLA loci on chromosome 6 are involved in T1D complications' expression. While the HLA region is a major contributor to the expression of T1D, our results suggest an interaction between specific HLA alleles and other loci that influence complications' expression.

Association between TNF-α -308G/A polymorphism and diabetic nephropathy risk: a meta-analysis

Background

Several candidate genes on the short arm of chromosome 6 including the HLA locus, TNF, LTA and AGER could be associated with late diabetic complications. The aim of our study was therefore to explore whether polymorphisms (TNF -308 G→A, LTA T60N C→A and AGER -374 T→A) in these genes alone or together (as haplotypes) increased the risk for diabetic complications.

Methodology/Principal Findings

The studied polymorphisms were genotyped in 742 type 1 and 2957 type 2 diabetic patients as well as in 206 non-diabetic control subjects. The Haploview program was used to analyze putative linkage disequilibrium between studied polymorphisms. The TNF, LTA and AGER polymorphisms were associated with the HLA-DQB1 risk genotypes. The AGER -374 A allele was more common in type 1 diabetic patients with than without diabetic nephropathy (31.2 vs. 28.4%, p = 0.007). In a logistic regression analysis, the LTA but not the AGER polymorphism was associated with diabetic nephropathy (OR 2.55[1.11–5.86], p = 0.03). The AGER -374 A allele was associated with increased risk of sight threatening retinopathy in type 2 diabetic patients (1.65[1.11–2.45], p = 0.01) and also with increased risk for macrovascular disease in type 1 diabetic patients (OR 2.05[1.19–3.54], p = 0.01), but with decreased risk for macrovascular disease in type 2 diabetic patients (OR 0.66[0.49–0.90], p = 0.009). The TNF A allele was associated with increased risk for macrovascular complications in type 2 (OR 1.53 [1.04–2.25], p = 0.03, but not in type 1 diabetic patients.

Conclusions/Significance

The association between diabetic complications and LTA, TNF and AGER polymorphisms is complex, with partly different alleles conferring susceptibility in type 1 and type 2 diabetic patients. We can not exclude the possibility that the genes are part of a large haplotype block that also includes HLA-DQB1 risk genotypes.

[Human leukocyte antigen (HLA) system in ophthalmology]

Various inflammatory and non-inflammatory eye diseases are associated with specific HLA isotypes. Therefore, HLA isotyping can be a useful diagnostic tool for these diseases and has already been shown to reduce the rejection rate of corneal allografts. Unfortunately, the volume of published data and the varying quality of these publications complicate obtaining good overview in this field. This review briefly summarizes the genetic structure of the HLA system and elucidates differences between HLA classes I and II in the context of antigen presentation. Possible mechanisms of HLA associations in the field of ophthalmology are discussed, and finally different tools (e.g. genome wide association studies) for assessing associations of HLA isotypes with different ocular diseases are examined.

HLA class I and II alleles are associated with microvascular complications of type 1 diabetes

Although HLA alleles are associated with type 1 diabetes, association with microvascular complications remains controversial. We tested HLA association with complications in multiplex type 1 diabetes families. Probands from 425 type 1 diabetes families from the Human Biological Data Interchange (HBDI) collection were analyzed. The frequencies of specific HLA alleles in patients with complications were compared with the frequencies in complications-free patients. The complications we examined were: retinopathy, neuropathy, and nephropathy. We used logistic regression models with covariates to estimate odds ratios. We found that the DRB1*03:01 allele is a protective factor for complications (OR=0.58; p=0.03), as is the DQA1*05:01-DQB1*02:01 haplotype found in linkage disequilibrium with DRB1*03:01 (OR=0.59; p=0.031). The DRB1*04:01 allele showed no evidence of association (OR=1.13; p=0.624), although DRB1*04:01 showed suggestive evidence when the carriers of the protective DRB1*03:01 were removed from the analysis. The class II DQA1*03:01-DQB1*03:02 haplotype was not associated with complications, but the class I allele B*39:06 (OR=3.27; p=0.008) suggested a strong positive association with complications. Our results show that in type 1 diabetes patients, specific HLA alleles may be involved in susceptibility to, or protection from, microvascular complications.

[Susceptibility genes, HLA and diabetic retinopathy in the Algerian population]

BACKGROUND

Diabetic retinopathy (DR) is the most frequent microvascular complication of type I diabetes (T1D). Some well-controlled type I diabetics may develop DR, while other poorly-controlled diabetics do not develop DR. This might be explained by certain susceptibility genes or protective genes. The purpose of our study is to search for any association between the HLA class I and II markers and DR in the Algerian population.

PATIENTS AND METHODS

This study was carried out in 52 T1D subjects with and without DR compared to 140 healthy controls. HLA typing was performed using the "microlymphocytotoxicity" technique.

RESULTS

The frequency of HLA-A29 and HLA-DR9 antigens is higher in T1D with DR compared to T1D without DR and to controls with frequencies of HLA-A29 (59.26% vs. 0%, OR=∞, pc=4.6×10(-7)), (59.26% vs. 5.66%, OR=24.24, pc=7.6×10-10) and HLA-DR9 (29.63% vs. 0%, OR=∞, pc=1.310(-3)), (29.63% vs. 4.29%, OR=9.40, pc=7.010(-5)) respectively. However, the frequency of HLA-B49 antigen is significantly lower in T1D with DR than in T1D without DR (3.7% vs. 28%, OR=0.10, pc=8.8×10(-3)) and compared to controls (3.7% vs. 22.64%, OR=0.13, pc=0.011).

CONCLUSION

HLA-A29 and HLA-DR9 antigens are probably markers of susceptibility for DR while HLA-B49 antigen is probably associated with a protective effect in the Algerian population.

HLA genes, islet autoantibodies and residual C-peptide at the clinical onset of type 1 diabetes mellitus and the risk of retinopathy 15 years later

Aims/Hypothesis

HLA genes, islet autoantibodies and residual C-peptide were studied to determine the independent association of each exposure with diabetic retinopathy (DR), 15 years after the clinical onset of type 1 diabetes in 15–34 year old individuals.

Methods

The cohort was identified in 1992 and 1993 by the Diabetes Incidence Study in Sweden (DISS), which investigates incident cases of diabetes for patients between 15 and 34 years of age. Blood samples at diagnosis were analyzed to determine HLA genotype, islet autoantibodies and serum C-peptide. In 2009, fundus photographs were obtained from patient records. Study measures were supplemented with data from the Swedish National Diabetes Registry.

Results

The prevalence of DR was 60.2% (148/246). Autoantibodies against the 65 kD isoform of glutamate decarboxylase (GADA) at the onset of clinical diabetes increased the risk of DR 15 years later, relative risk 1.12 for each 100 WHO units/ml, [95% CI 1.02 to 1.23]. This equates to risk estimates of 1.27, [95% CI 1.04 to 1.62] and 1.43, [95% CI 1.06 to 1.94] for participants in the highest 25^th (GADA>233 WHO units/ml) and 5^th percentile (GADA>319 WHO units/ml) of GADA, respectively. These were adjusted for duration of diabetes, HbA_1c, treated hypertension, sex, age at diagnosis, HLA and C-peptide. Islet cell autoantibodies, insulinoma-antigen 2 autoantibodies, residual C-peptide and the type 1 diabetes associated haplotypes DQ2, DQ8 and DQ6 were not associated with DR.

Conclusions

Increased levels of GADA at the onset of type 1 diabetes were associated with DR 15 years later. These results, if confirmed, could provide additional insights into the pathogenesis of the most common microvascular complication of diabetes and lead to better risk stratification for both patient screenings and DR treatment trials.

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.

Could diabetic retinopathy be an autoimmune disease?

Diabetic retinopathy is a common and progressive complication of diabetes mellitus. It is characterized by the loss of pericytes, hypertrophy of basement membrane, microaneurysms formation, increased vascular permeability, capillary occlusions, neovascularisation and fibrovascular proliferation. The pathogenesis of diabetic retinopathy is still insufficiently understood, although some reports have implicated the role of the immune system. We hypothesize that, according to some current data diabetic retinopathy could also be considered as an autoimmune disease. The finding of antipericyte and antiendothelial cell autoantibodies in the circulation of diabetic patients strongly suggests that some autoimmune activity has been involved in the early pathophysiology of diabetic retinopathy. There is even more evidence that implicates the presence of autoimmune mechanisms in the proliferative stage of this disease: elevated levels of tumor necrosis factor-alpha, interleukin-8 and soluble interleukin-2 receptor in the serum of diabetic patients, increased vitreous concentration of the interleukin-6 and interleukin-8 in patients with proliferative retinopathy. Furthermore, preretinal membranes in diabetic patients contain deposits of immunoglobulins, activated complement components, monocytes, T and B lymphocytes, fibroblastes and lymphokynes. In diabetic patients human leukocyte antigen DR and DQ expression on the retinal vascular endothelial cells as well as on pigment and nonpigment epithelial cells was found. These antigens are normally restricted to immunocompetent cells and play an important regulatory role in the immune response. Their aberrant expression has been found on nonlymphoid cells in various autoimmune diseases whilst abnormal expression of DR and DQ antigens at sites where they do not normally exist would result in autoimmunity by converting the target cell into a functional antigen-presenting cell. In conclusion, although the pathogenesis of diabetic retinopathy is not completely understood it is known that the immune system is certainly involved in its development. However, there is increasing evidence of the presence of some autoimmune processes in the early stages of diabetic retinopathy and particularly in its proliferative phases. Consequently, diabetic retinopathy could also be considered as an autoimmune disease.

HLA and eye disease: a synopsis

Human leukocyte antigen (HLA) gene products have been implicated in the pathogenesis of an increasing number of eye diseases, mainly inflammatory in nature. This perspective reviews the current hypotheses for why HLA polymorphisms are associated with specific eye diseases. Statistical problems in studies involving HLA associations are discussed, and possible solutions outlined. The relevance of HLA testing in routine ophthalmic practice, its practical and cost implications is also assessed.

Glutamic Acid Decarboxylase Autoantibody Prevalence and Association with HLA Genotype in Patients with Younger-Onset Type 1 Diabetes and Proliferative Diabetic Retinopathy

OBJECTIVE

To investigate the relationship of HLA status and autoantibodies to glutamic acid decarboxylase (GAD) in proliferative diabetic retinopathy (PDR) to assess the role of autoimmunity and genetic markers in retinopathy.

DESIGN

Retrospective, nonrandomized, comparative study.

PARTICIPANTS

Patients who had suffered from type 1 diabetes for >10 years and who had been first diagnosed as diabetic under 30 years of age were studied. They were classified into 3 groups: 20 patients with diabetes and PDR (PDR group), 22 patients who had diabetes and severe nonproliferative diabetic retinopathy (SNPDR group), and 25 patients who had diabetes with no diabetic retinopathy (non-DR group).

METHODS

Blood was collected, and the relationship between HLA status and GAD autoantibody positivity in diabetic retinopathy was investigated in a cross-sectional study.

MAIN OUTCOME MEASURES

Human leukocyte antigen status and GAD autoantibody positivity.

RESULTS

The highest positive rate of GAD autoantibody was 56.0% in the non-DR group, followed by the SNPDR group (40.1%) and the PDR group (15.0%). The frequencies of the HLA-DQ4 and -DR4/-DQ4 haplotypes were significantly higher in the PDR group (75.0% and 65%, respectively) than in the SNPDR group (40.9% and 31.8%) or the non-DR group (40.0% and 28.0%) (P = 0.035 and P = 0.026, respectively). The prevalence of GAD antibodies was lower in patients with the HLA-DR4 and HLA-DQ4 alleles and -DR4/-DQ4 haplotype frequencies in the PDR group (P = 0.018, P = 0.0088, and P = 0.0031, respectively).

CONCLUSIONS

We found that the existence of GAD antibodies is inversely related and HLA status is directly related to the stage or severity of retinopathy.

HLA-DRB1, -DQA1, and -DQB1 subtypes or ACE gene polymorphisms do not seem to be risk markers for severe retinopathy in younger Type 1 diabetic patients

The aim of this study was to test the hypothesis that HLA-DRB1, -DQA1, and -DQB1 subgroups or angiotensin-converting enzyme (ACE) gene polymorphisms are associated with severe retinopathy in younger Type 1 diabetic patients. Twenty-four Type 1 diabetic patients who had received panretinal photocoagulation for severe nonproliferative or proliferative diabetic retinopathy were compared with 24 Type 1 diabetic patients (participating in a photographic screening program with regular fundus examinations) with no or minimal retinopathy, matched for age at onset and duration of diabetes. The HLA-DRB1-DQA1-B1 haplotype 04-03-0302 represented 22/48 (46%) in the severe and 21/48 (44%) in the no/minimal retinopathy group, respectively (n.s.). The most common genotype, 03-0501-0201/04-03-0302, occurred in 8/24 (33%) with severe and 10/24 (42%) with no/minimal retinopathy, respectively (n.s.). There were no statistical differences between patients with severe and no/minimal retinopathy whether DRB1, DQA1, or DQB1 alleles, haplotypes, or genotypes were analysed. The ACE gene polymorphism was almost identical between patients with severe and no/minimal retinopathy, and serum ACE levels did not differ. Thus, in the present study on a small group with carefully characterised diabetic retinopathy phenotypes, there was no indication that HLA-DRB1, -DQA1, and -DQB1 subtypes or ACE gene polymorphisms were associated with severe retinopathy in younger Type 1 diabetic 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.

Genetic polymorphism of HLA DR in a Scottish population of patients with pars planitis

PURPOSE

Human leucocyte antigen (HLA) class II influences the immunological susceptibility for a variety of diseases including many types of non-infectious intraocular inflammation. Previous studies on North American patients with pars planitis, a subtype of intermediate uveitis, reported an increased prevalence of HLA DR15 in this population. In contrast, two European studies could not find an association between HLA DR2 or its allelic subtype DR15 and various forms of intermediate uveitis. We therefore investigated the genotype frequency of HLA DR alleles in a Scottish population of patients with typical pars planitis.

METHODS

Twenty patients with pars planitis were identified from the uveitis database of Grampian University Hospitals. Only patients with bilateral vitritis and snowbanks in at least one eye in the absence of systemic disease were included in the study. Fifteen patients and 34 healthy controls underwent HLA DR genotyping for all DRB genes using PCR sequence specific primers.

RESULTS

HLA DR15 was found in 13% of patients with pars planitis and in 24% of controls. There was no statistically significant difference between these two groups. Furthermore, the frequencies of HLA DR 1, 3-14, and 16 did not differ significantly between patients and controls.

CONCLUSIONS

There appears to be no association between the occurrence of pars planitis and the HLA DR15 or other known HLA DR genotypes in Scottish patients. However, the small sample size limits the power of this study.

Relationship between human leukocyte antigen status and proliferative diabetic retinopathy in patients with younger-onset type 1 diabetes mellitus

PURPOSE

To investigate the relationship between human leukocyte antigen (HLA) status and proliferative diabetic retinopathy (PDR) to assess the genetic basis of PDR in younger type 1 diabetic patients.

DESIGN

Retrospective, nonrandomized, comparative trial.

METHOD

Patients who were diagnosed with type 1 diabetes under 30 years of age (range, 13-28) and had a disease duration of more than 10 years were studied. The patients were divided into two groups: 30 patients who had undergone vitreous surgery younger than 40 years old (the PDR group) and 50 patients without retinopathy (the non-DR group). The duration of diabetes and the level of glycemic control were matched between the two groups. The control group consisted of 50 healthy patients. HLA-A, -B, -C, -DR, and -DQ typing of blood samples was done using the standard microcytotoxicity method.

RESULTS

The frequency of HLA-B62, Cw4, and DQ4 was significantly higher in the PDR group than in the non-DR group (P =.0020, P =.048, and P =.0026, respectively). The Cw4-DR4-DQ4 haplotype frequency was significantly higher in the PDR group than in the control group and the non-DR group (P =.0059).

CONCLUSIONS

Our results suggests that HLA-B62, Cw4, and DQ4 may be useful for predicting the prognosis of retinopathy in patients with younger-onset type 1 diabetes.

Molecular genetics of microvascular disease in diabetic retinopathy

Diabetic retinopathy is a sight-threatening complication of the retinal microvasculature. While important environmental factors have been clearly identified as influencing its development, increasing evidence suggests that diabetic retinopathy has a genetic component. A variety of studies have explored associations between candidate genes and frequency and severity of retinopathy. Overall, this review has found that the majority of candidate genes studied exhibit weak or no association with retinopathy status, and where associations have been detected these results have not been replicated in multiple populations. This may reflect inaccurate case definition, small subject numbers and possibly inadequate markers for genetic studies.

HLA-DPB1*0401 is associated with dominant protection against type 1 diabetes in the general Saudi population and in subjects with a high-risk DR/DQ haplotype

The human leukocyte antigen (HLA) class II DQB1*0201/0202-DRB1*04 genotype has been identified as predisposing to type 1 diabetes [insulin-dependent diabetes mellitus (IDDM)] in the Saudi Arabian population (P = 0.0002; odds ratio = 0.67; 95% confidence interval = 0.009-0.381). In this study, we searched for a factor at the DPB1 locus by analysing DPB1 polymorphism using sequence-based typing in 86 Saudi IDDM patients and control subjects, all carrying the HLA-DRB1*04/DQB1*02 haplotype or the known susceptibility allele DQB1*0201/0202. Significant protection was conferred by DPB1*0401, which was observed in 17 of 50 control subjects (55%) and 2 of 36 IDDM patients (5%) with the DQB1*0201/0202 allele (P = 0.0012; odds ratio = 8.75; confidence interval = 1.72-59.70). Our data showing a high frequency of the DPB1*0401 allele even in the presence of the predisposing DQB1*02 allele in healthy subjects may indicate a protective effect of this combination of HLA alleles against type 1 diabetes. This finding supports the hypothesis that protective HLA class II genes can override the risk conferred by HLA-DQ susceptibility alleles. Further studies using larger cohorts of control subjects and patients should be undertaken to confirm this observation.

A common polymorphism in the 5'-untranslated region of the VEGF gene is associated with diabetic retinopathy in type 2 diabetes

Vascular endothelial growth factor (VEGF), a major mediator of vascular permeability and angiogenesis, may play a pivotal role in mediating the development and progression of diabetic retinopathy. In the present study, we examined the genetic variations of the VEGF gene to assess its possible relation to diabetic retinopathy in type 2 diabetic patients. Among seven common polymorphisms in the promoter region, 5'-untranslated region (UTR) and 3'UTR of the VEGF gene, genotype distribution of the C(-634)G polymorphism differed significantly (P = 0.011) between patients with (n = 150) and without (n = 118) retinopathy, and the C allele was significantly increased in patients with retinopathy compared with those without retinopathy (P = 0.0037). The odds ratio (OR) for the CC genotype of C(-634)G to the GG genotype was 3.20 (95% CI 1.45-7.05, P = 0.0046). The -634C allele was significantly increased in patients with nonproliferative diabetic retinopathy (non-PDR) (P = 0.0026) and was insignificantly increased in patients with proliferative diabetic retinopathy (PDR) (P = 0.081) compared with patients without retinopathy, although frequencies of the allele did not differ significantly between the non-PDR and PDR groups. Logistic regression analysis revealed that the C(-634)G polymorphism was strongly associated with an increased risk of retinopathy (P = 0.0018). Furthermore, VEGF serum levels were significantly higher in healthy subjects with the CC genotype of the C(-634)G polymorphism than in those with the other genotypes. These data suggest that the C(-634)G polymorphism in the 5'UTR of the VEGF gene is a novel genetic risk factor for diabetic retinopathy.

Human lymphocyte antigen DR7 protects against proliferative retinopathy with type II diabetes mellitus

BACKGROUND

This study was undertaken in order to analyze the genetic incidence of human lymphocyte antigen diabetic retinopathy (HLA-DR) and its influence in proliferative diabetic retinopathy (PDR).

METHODS

We designed a case-control study in which 127 mestizo Mexican patients with DM II and diabetic retinopathy were studied. DNA was extracted and HLA-DR regions were amplified using PCR. Alleles were determined by DNA hybridization. Diagnosis was assessed clinically and by fluorescein angiography. Incidence of HLA-DR alleles in patients was compared with an ethnically matched control group of healthy subjects (n = 98). Statistical significance was established with non-parametric tests.

RESULTS

Patients with diabetic retinopathy showed less frequency of HLA-D11 compared with the control group (p = 0.043). NPDR patients with 10 or more years of DM II showed an increase of HLA-DR7 (p = 0.01).

CONCLUSIONS

Our results suggest that the presence of HLA-DR7 protects against the development of proliferative disease in the diabetic Mexican population.

Diabetic retinopathy and HLA antigens in type 2 diabetes mellitus

PURPOSE

Diabetic retinopathy is the most common complication of diabetes mellitus. No single predisposing factor has been identified, and genetic factors may play a role in the development of severe retinopathy. In this study, we investigated the association between diabetic retinopathy and HLA antigens in type 2 diabetes mellitus.

METHODS

This study was conducted at the retina unit of the Department of Ophthalmology of Ondokuz Mayis University between October 1999 and March 2000, and included 46 diabetics with non-proliferative retinopathy and 30 with proliferative retinopathy, with 30 nondiabetic controls. HLA class I (A, B, C) antigens were studied by Terasaki's microlymphocytotoxicity test and HLA class II (DR, DQ) typing was carried out using a polymerase chain reaction-sequence specific primer.

RESULTS

HLA-DR4 and DQ8 frequencies were higherin patients with non-proliferative retinopathy than those with proliferative retinopathy, and HLA-DR7 frequency was higher in patients with proliferative retinopathy than non-proliferative cases (p<0.05). No significant differences in HLA antigens were found between patient groups and controls.

CONCLUSIONS

The differences in HLA antigen frequencies between patients with and without proliferative retinopathy suggest a genetic contribution to diabetic retinopathy.

HLA-DR3 and DR4 and their relation to the incidence and progression of diabetic retinopathy

PURPOSE

Cross-sectional data from the Wisconsin Epidemiologic Study of Diabetic Retinopathy indicated that patients with HLA-DR4, but not DR3, were more likely to have prevalent proliferative retinopathy than those without both antigens. We describe the relation of HLA-DR3 and DR4 antigens to the 14-year incidence and progression of diabetic retinopathy and macular edema in this cohort.

DESIGN

A population-based cohort study.

PARTICIPANTS

A probability sample of male and female patients receiving primary care for diabetes in 11 counties of southern Wisconsin.

METHODS

Participants were invited for a baseline examination in 1980 to 1982, with follow-up examinations at 4, 10, and 14 years later. At the 4-year examination, a random sample of participants (n = 428) diagnosed with diabetes before the age of 30 and taking insulin were selected for HLA-DR typing.

MAIN OUTCOME MEASURES

Fourteen-year incidence and progression of diabetic retinopathy and macular edema based on masked stereoscopic fundus photographic grading.

RESULTS

There was no relation between HLA-DR3 and DR4 status with the 14-year incidence and progression of diabetic retinopathy, progression to proliferative retinopathy, and incidence of macular edema. Patients with either HLA-DR3 or DR4 were less likely to progress to proliferative retinopathy compared with those who were negative for both, although these relations were not statistically significant. The associations did not vary after adjusting for hypertension status, baseline retinopathy, and glycosylated hemoglobin levels, or after stratifying by duration of diabetes (less than 10 years vs. 10 years or more) and age at diagnosis of diabetes (less than 15 years vs. 15 years or more). Furthermore, 10-year mortality and 14-year nephropathy rates did not differ by HLA-DR3 or DR4 status, suggesting that selective mortality did not explain the pattern of associations seen.

CONCLUSIONS

In contrast to the initial cross-sectional findings, these data suggest that HLA-DR3 or DR4 status is unrelated to 14-year incidence and progression of diabetic retinopathy. The discrepancy may be related to increasing homogeneity of retinopathy and diminishing power to detect small differences, but it may also reflect the uncertain and inconsistent effects of HLA-DR3 or DR4 on the development and progression of diabetic retinopathy.

Fetal growth is not associated with early onset of severe retinopathy in type 1 diabetes mellitus

Reduced fetal growth has been suggested as a possible risk factor for diabetic nephropathy. The aim of the present study was to examine whether there could be an association also with rapidly progressing severe retinopathy in younger type 1 diabetic patients. Maternal pregnancy, as well as birth parameters of 27 type 1 diabetic patients with severe retinopathy diagnosis at a median age of 25 years, were studied retrospectively. The control group consisted of 22 type 1 diabetic patients with mild background retinopathy and with similar age, age at onset, and duration of diabetes. Mothers of the subjects with severe retinopathy had a higher body mass index (P = 0.03) but similar age, blood pressure levels, and weight gain during pregnancy as those of the control group. All but four babies, two in each group, were born after 37 completed gestational weeks. There were no differences regarding birth weight or of relative birth weight corrected for gestational length. Head circumference, birth length, and placenta weight were similar. The results indicate that fetal growth is not a factor of major importance for the development of severe retinopathy in younger type 1 diabetic patients.

The human leukocyte antigen complex and chronic ocular inflammatory disorders

PURPOSE

To review the role of gene products from the human leukocyte antigen (HLA) complex in the normal functioning of the immune system, ocular inflammation, and models of autoimmunity.

METHOD

A review of recently published reports.

RESULTS

Many chronic ocular inflammatory diseases are associated with specific alleles of the HLA complex. Understanding how HLA gene products function normally provides clues to the mechanism of disease associations. In the thymus, these molecules control the shape of the developing T-cell repertoire, leading to self-tolerance. In the periphery, HLA molecules bind and present peptide fragments to T cells, leading to a variety of effector functions. Although effector functions are for the most part beneficial, models are reviewed in which peptide-HLA interactions lead to T-cell responses with pathologic consequences. Herpes stromal keratitis is an informative animal model highlighting the role of self-tolerance, infection, and molecular mimicry in the development of autoimmunity.

CONCLUSIONS

Human leukocyte antigen gene products may be associated with chronic inflammatory disorders through the unique presentation of "disease-inducing" peptides or the development of a T-cell repertoire prone to autoreactivity and molecular mimicry.

Genotyping and functional analysis of a polymorphic (CCTTT)(n) repeat of NOS2A in diabetic retinopathy

Accumulating evidence shows that the severity and rapidity of onset of diabetic retinopathy are influenced by genetic factors. Expression of the nitric oxide synthases is altered in the retinal vasculature in the early stages of diabetic retinopathy. We analyzed the allele distribution of a polymorphic pentanucleotide repeat within the 5' upstream promoter region of the NOS2A gene in samples of diabetic patients. In diabetic patients from Northern Ireland, the 14-repeat allele of the NOS2A marker was significantly associated with the absence of diabetic retinopathy. Carriers of this repeat had 0.21-fold the relative risk of developing diabetic retinopathy than noncarriers of this allele. They also had significantly fewer renal and cardiovascular complications. The ability of differing numbers of (CCTTT)(n) pentanucleotide repeats to induce transcription of the NOS2A gene was analyzed using a luciferase reporter gene assay in transfected colonic carcinoma cells. Interleukin 1beta (IL-1beta) induction was most effective in constructs carrying the 14-repeat allele. When cells were incubated in 25 mM glucose to mimic the diabetic state, IL-1beta induction was inhibited in all cases, but to a significantly lesser extent with the 14-repeat allele. These unique properties of the 14-repeat allele may confer selective advantages in diabetic individuals, which may delay or prevent microvascular complications of diabetes.

Human RAGE GLY82SER dimorphism and HLA class II DRB1-DQA1-DQB1 haplotypes in type 1 diabetes

Advanced glycation end products (AGEs) are believed to play an important role in the development of diabetic complications. AGEs increase in diabetes and modulate cellular functions through binding to a specific cell surface receptor (RAGE). The RAGE gene maps to chromosome 6p in the HLA class III area and is telomeric to the class II region at 250 kb from DRA. A recent report described the characterization of a major RAGE gene variant as a biallelic single base polymorphism (G/A 557) in the exon 3 sequence leading to a change of a glycine to a serine at position 82. Using DGGE and PCR-RFLP, we have investigated the distribution of this dimorphism in conjunction with HLA class II genes in large populations of type 1 diabetic patients and healthy subjects. Although no association of this RAGE gene polymorphism with disease susceptibility was found, we report a strong linkage disequilibrium between the variant carrying the serine amino acid at position 82 and two HLA-DR2 and HLA-DR4 specificities. In particular, we describe two major extensive HLA class II haplotypes associated with this serine variant and identified as DRB1*0401-DQA1*0301-DQB1*0301 in the diabetic group and DRB1*1501-DQA1*0102-DQB1*0602 in control individuals. These data were partially confirmed by family transmission analysis.

Type 1 Diabetes

Type 1 (insulin-dependent) diabetes occurs worldwide and can appear at any age. The genetic susceptibility is strongly associated with HLA-DQ and DR on chromosome 6, but genetic factors on other chromosomes such as the insulin gene on chromosome 11 and the cytotoxic T-lymphocyte antigen gene on chromosome 2 may modulate disease risk. Numerous studies further support the view that environmental factors are important. Gestational infections may contribute to initiation, whereas later infections may accelerate islet β-cell autoimmunity. The pathogenesis is strongly related to autoimmunity against the islet β cells. Markers of autoimmunity include autoantibodies against glutamic acid decarboxylase, insulin, and islet cell antigen-2, a tyrosine phosphatase-like protein. Molecular techniques are used to establish reproducible and precise autoantibody assays, which have been subject to worldwide standardization. The diagnostic sensitivity (40–80%) and specificity (99%) of all three autoantibodies for type 1 diabetes are high, and double or triple positivity among first-degree relatives predicts disease. Combined genetic and antibody testing improved prediction in the general population despite the transient nature of these autoantibodies. Classification of diabetes has also been improved by autoantibody testing and may be used in type 2 diabetes to predict secondary failure and insulin requirement. Islet autoantibodies do not seem to be related to late complications but rather to metabolic control, perhaps because the presence of islet cell autoantibodies marks different residual β-cell function. Combined genetic and autoantibody screening permit rational approaches to identify subjects for secondary and tertiary intervention trials.

Inverse relationship between GAD65 antibody levels and severe retinopathy in younger type 1 diabetic patients

Several risk factors for severe non-proliferative and proliferative retinopathy in type 1 diabetes mellitus have been proposed without explaining the rapid progression of retinopathy in some patients. Since GAD65 autoantibodies (GAD65Abs) are detected against glutamic acid decarboxylase (GAD), which is mainly expressed in islets and nervous tissue in type 1 diabetic patients, the aim of the present investigation was to test the hypothesis whether GAD65Abs are associated with rapidly progressing severe retinopathy. Patients with severe non-proliferative or proliferative retinopathy (n = 27) were compared with another group, which in spite of long diabetes duration had no or only mild signs of retinopathy (n = 28). GAD65Abs were analysed in a radioimmunoassay using in vitro translated human GAD65, and the levels were expressed as an index in relation to positive and negative reference samples. Using a cut-off level representing the 99th percentile of normals, 6/27 (22%) with and 9/28 (32%) without severe retinopathy were considered GAD65Ab positive. Although there was no difference in the number of GAD65Ab positive patients, the GAD65Ab levels were lower in patients with (0.30; 0.11-0.64) than without (0.68; 0.34-1.12) severe retinopathy (P = 0.03). The patients were also subjected to HLA-DR and DQ typing by PCR and hybridization with oligospecific probes. DQ2/8 was more common in patients with (56%) than without (29%) severe retinopathy (P = 0.05), but DQ2/8 could not account for the lower GAD65Ab levels in patients with severe retinopathy. It is concluded that GAD65Ab levels are inversely correlated with severe retinopathy in young type 1 diabetic patients.

Genetic Approach for Insulin-Independent Diabetes Mellitus in Clinical Practice

Insulin-independent diabetes mellitus (IDDM) is a polygenic disease with an environmental component. Technological advances and large collection families allowed genetic factors understanding. On clinical practice, two questions could be asked. First, will the genetic markers be of interest in disease prediction either in family studies or in the main population? Secondly, will the genetic approach explain the physiopathological process of the disease? Initially, the gene candidate approach led to the identification of two important loci: Linkage with the human leukocyte antigen (HLA) locus showed the importance of the autoimmune part. Linkage of insulin-independent diabetes mellitus with insulin locus gave a mechanistic answer for disease susceptibility. These two loci can be used as prediction markers, but only in family studies. Since 1993, a whole genome approach has been performed and has led to the identification of other susceptibility loci. These initial results are in progress and should have important implications for public health strategies.