Genetic markers in early diabetic retinopathy of adolescents with type I diabetes

Exploring the Connection Between HLA Class I and Class II Genotypes and Diabetic Retinopathy: A Comprehensive Review of Experimental Evidence

Diabetic retinopathy (DR) is a microvascular complication associated with diabetes mellitus (DM). During the course of the disease, high blood glucose levels induce damage to the vasculature of the retina and promote neovascularization. Although numerous environmental risk factors have been associated with the emergence of DR, the role of genetics should not be underestimated. The human leukocyte antigen (HLA) plays a significant role in the regulation of the immune system. DR exhibits significant heterogeneity among patients, with differences in how the disease presents and progresses over time. The HLA gene, characterized by its extensive genetic variation, largely contributes to this diverse spectrum. Differences in HLA allele frequencies among healthy people, diabetic patients without retinopathy, and diabetic patients with different stages of retinopathy highlight the need for proper management of the disease. This comprehensive review outlines the current understanding of the relationship between HLA class I and class II variants and DR, shedding light on their potential significance as early onset indicators, prognostic indicators, and important risk factors for the development of this retinal condition.

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.

Unraveling the role of genetics in the pathogenesis of diabetic retinopathy

Diabetic retinopathy (DR) is a microvascular disease of the retina and the leading cause of visual disability in diabetic patients. Genetic factors have shown to play a pivotal role in DR onset, and several candidate genes have been associated with its progression. A literature search was performed to identify the genes known to be associated with DR through linkage analysis, candidate gene association, and genome-wide association studies (GWAS). A further literature search was performed to discover their potential connection with various biological pathways. A total of 65 genes were found and several of these genes belong to major signaling pathways known to play a significant role in DR, including systemic inflammation, angiogenesis, and neurogenesis. A comprehensive analysis presented in this review will be helpful in unraveling the role of genetics in the pathogenesis of DR.

Current trends in the monitoring and treatment of diabetic retinopathy in young adults

The diagnosis and treatment of diabetic retinopathy (DR) in young adults have significantly improved in recent years. Research methods have widened significantly, for example, by introducing spectral optical tomography of the eye. Invasive diagnostics, for example, fluorescein angiography, are done less frequently. The early introduction of an insulin pump to improve the administration of insulin is likely to delay the development of diabetic retinopathy, which is particularly important for young patients with type 1 diabetes mellitus (T1DM). The first years of diabetes occurring during childhood and youth are the most appropriate to introduce proper therapeutic intervention before any irreversible changes in the eyes appear. The treatment of DR includes increased metabolic control, laserotherapy, pharmacological treatment (antiangiogenic and anti-inflammatory treatment, enzymatic vitreolysis, and intravitreal injections), and surgery. This paper summarizes the up-to-date developments in the diagnostics and treatment of DR. In the literature search, authors used online databases, PubMed, and clinitrials.gov and browsed through individual ophthalmology journals, books, and leading pharmaceutical company websites.

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.

Heritability of the severity of diabetic retinopathy: the FIND-Eye study

PURPOSE

Diabetic retinopathy (DR) and diabetic nephropathy (DN) are serious microvascular complications of diabetes mellitus. Correlations between severity of DR and DN and computed heritability estimates for DR were determined in a large, multiethnic sample of diabetic families. The hypothesis was that (1) the severity of DR correlates with the presence and severity of nephropathy in individuals with diabetes mellitus, and (2) the severity of DR is under significant familial influence in members of multiplex diabetic families.

METHODS

The Family Investigation of Nephropathy and Diabetes (FIND) was designed to evaluate the genetic basis of DN in American Indians, European Americans, African Americans, and Mexican Americans. FIND enrolled probands with advanced DN, along with their diabetic siblings who were concordant and discordant for nephropathy. These diabetic family members were invited to participate in the FIND-Eye study to determine whether inherited factors underlie susceptibility to DR and its severity. FIND-Eye participants underwent eye examinations and had fundus photographs taken. The severity of DR was graded by using the Early Treatment Diabetic Retinopathy Study Classification (ETDRS). Sib-sib correlations were calculated with the SAGE 5.0 program FCOR, to estimate heritability of retinopathy severity.

RESULTS

This report summarizes the results for the first 2368 diabetic subjects from 767 families enrolled in FIND-Eye; nearly 50% were Mexican American, the largest single ethnicity within FIND. The overall prevalence of DR was high; 33.4% had proliferative DR; 7.5%, 22.8%, and 9.5% had severe, moderate, and mild nonproliferative DR, respectively; 26.6% had no DR. The severity of DR was significantly associated with severity of DN, both by phenotypic category and by increasing serum creatinine concentration (chi(2) = 658.14, df = 20; P < 0.0001). The sib-sib correlation for DR severity was 0.1358 in the total sample and 0.1224 when limited to the Mexican-American sample. Broad sense heritabilities for DR were 27% overall and 24% in Mexican-American families. The polygenic heritability of liability for proliferative DR approximated 25% in this FIND-Eye sample.

CONCLUSIONS

These data confirm that the severity of DR parallels the presence and severity of nephropathy in individuals with diabetes mellitus. The severity of DR in members of multiplex diabetic families appears to have a significant familial connection.

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.

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.

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.

Familial clustering of diabetic retinopathy in South Indian Type 2 diabetic patients

AIM

The aim of the study was to determine whether there is familial clustering of diabetic retinopathy among South Indian Type 2 diabetic subjects.

METHODS

During the period September 1991 to September 1997, 322 families with at least two diabetic siblings who were registered at our centre and had undergone a retinal examination were selected for the study. The sibling with the longest duration of diabetes was defined as the proband. The prevalence of retinopathy was compared between the siblings of probands with and without retinopathy.

RESULTS

Diabetic retinopathy was diagnosed in 11.2% of the siblings of the probands without diabetic retinopathy and in 35.3% of the siblings of the probands with diabetic retinopathy (P < 0.0001). The increased prevalence of retinopathy among siblings of probands with retinopathy represented all grades of retinopathy, namely non-proliferative diabetic retinopathy with and without maculopathy and proliferative diabetic retinopathy, although the latter did not reach statistical significance due to the small numbers. Hypertension, metabolic control and the duration of diabetes among the probands did not affect the clustering of retinopathy. The odds ratio for retinopathy in the siblings of probands with retinopathy after adjusting for age, glycosylated haemoglobin, duration of diabetes, proteinuria and other confounding variables was 3.37(95% confidence interval 1.56-7.29, P = 0.002).

CONCLUSIONS

Familial clustering of diabetic retinopathy was three times higher in siblings of Type 2 diabetic subjects with diabetic retinopathy.

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.

Retinopathy in juvenile diabetes: a 10-year (1990-2000) review

Diabetic retinopathy (DR) is the most frequent complication of diabetes and a leading cause of impaired vision in the Western world. There is general agreement that early diagnosis and treatment of DR can slow its progression and help to prevent blindness. However, as a result of its asymptomatic nature and its etiopathogenesis, which is still unclear due to its multifactorial complexity, DR-related blindness has a growing social impact in industrialized countries. Therefore, in order to gain a better understanding of this serious disease, the author performed an updated 10-year review of risk factors and management of DR in type 1 diabetes.