Angiotensin-converting enzyme gene polymorphism is correlated to diabetic retinopathy: a meta-analysis

Genetics of Diabetic Retinopathy, a Leading Cause of Irreversible Blindness in the Industrialized World

Diabetic retinopathy (DR) is a chronic complication of diabetes and a leading cause of blindness in the industrialized world. Traditional risk factors, such as glycemic control and duration of diabetes, are unable to explain why some individuals remain protected while others progress to a more severe form of the disease. Differences are also observed in DR heritability as well as the response to anti-vascular endothelial growth factor (VEGF) treatment. This review discusses various aspects of genetics in DR to shed light on DR pathogenesis and treatment. First, we discuss the global burden of DR followed by a discussion on disease pathogenesis as well as the role genetics plays in the prevalence and progression of DR. Subsequently, we provide a review of studies related to DR’s genetic contribution, such as candidate gene studies, linkage studies, and genome-wide association studies (GWAS) as well as other clinical and meta-analysis studies that have identified putative candidate genes. With the advent of newer cutting-edge technologies, identifying the genetic components in DR has played an important role in understanding DR incidence, progression, and response to treatment, thereby developing newer therapeutic targets and therapies.

Multilocus genetic risk score for diabetic retinopathy in the Han Chinese population of Taiwan

The aim of this study is to explore the effect of genetic variation on diabetic retinopathy (DR) risk in a Taiwanese population. The logistic regression model was used to evaluate the relationship between DR status and risk factors, including the conventional parameters and genetic risk score (GRS). Candidate single nucleotide polymorphisms (SNPs) in GRS were selected based on previous reports with a combined P < 10^-4 (genome-wide association) and P < 0.05 (meta-analysis). In total, 58 SNPs in 44 susceptibility loci were selected, and four were used to calculate GRS. After adjustment for age, systolic blood pressure, diabetes duration, and HbA1c, the DR risk was 4.95 times higher for patients in the top GRS third tile than for those in the bottom third tile (95% CI = 2.99-8.18; P < 0.001). The addition of genetic information improved DR prediction, increasing the area under the curve (AUC) from 0.72 to 0.77 (P = 0.0024) and improving the sensitivity of the model such that 40 more subjects were reclassified into DR status. The developed multivariate logistic regression model combining conventional risk factors and the multilocus GRS can predict DR, thus enabling timely treatment to reduce blindness in T2D patients.

The relationship between ACE/AGT gene polymorphisms and the risk of diabetic retinopathy in Chinese patients with type 2 diabetes

Aims:

This study aims to investigate the association between renin-angiotensin system gene polymorphism and diabetic retinopathy (DR) in Chinese patients with type 2 diabetes.

Methods:

We consecutively included 1491 patients for the assessment of ACE I/D and AGT M/T gene polymorphisms in 345 DR cases and 1146 patients without retinopathy (DNR). Albuminuria was defined by urine albumin creatinine ratio and albumin excretion rate.

Results:

Compared with the NDR patients, the DR cases displayed a higher proportion of diabetic nephropathy (32.68% vs. 6.52%, χ² = 150.713, p < 0.001). The DR cases and DNR individuals did not differ in the frequency of genotypes and alleles of ACE I/D and AGT M/T (all p > 0.05). Intriguingly, DR patients with obesity showed higher frequency of DD (χ² = 4.181, p = 0.041), but no significant difference exists in the other stratified BMI and hypertension analyses (all p > 0.05). Binary logistic regression displays that the association of the ACE and AGT gene polymorphisms in DR patients is not significant after adjusting for confounding covariates in all the comparisons.

Conclusions:

The ACE and AGT gene polymorphisms are not associated with the progress of diabetes developing into retinopathy in Chinese patients with type 2 diabetes. However, more investigations are needed to further prove the association.

Pharmacology of the retinal pigment epithelium, the interface between retina and body system

The retinal pigment epithelium (RPE) is a close, interactive partner to the photoreceptors as well as an interface with the endothelium of the choroid and thus with the body's circulatory system. To fulfill these roles, the RPE communicates with neighboring tissue by secretion of a large variety of factors and is able to react to secreted factors via a plethora of transmembrane receptors. Clinically relevant local pharmacological effects are caused by anti-VEGF-A treatment in choroidal neovascularization or by carboanhydrase inhibitors reducing fluid accumulation in the macula. Being exposed to the bloodstream, the RPE reacts to systemic disease, such as diabetes or hypertension, but also to systemic pharmacological intervention, for example to hypotensive drugs acting on the renin-angiotensin-system. Sustained pharmacological treatments, in particular, cause side effects at the RPE with consequences for both RPE function and photoreceptor survival. Among these are systemic inhibition of angiotensin-converting enzyme, insulin treatment in diabetes and anti-VEGF-A therapy. Given the special anatomical and functional relationships of the RPE, pharmacological intervention targeting either the eye or the body systemically should take potential alteration of RPE and subsequently photoreceptor function into account.

Plasminogen activator inhibitor-1 4G/5G polymorphism and retinopathy risk in type 2 diabetes: a meta-analysis

BACKGROUND

Mounting evidence has suggested that plasminogen activator inhibitor-1 (PAI-1) is a candidate for increased risk of diabetic retinopathy. Studies have reported that insertion/deletion polymorphism in the PAI-1 gene may influence the risk of this disease. To comprehensively address this issue, we performed a meta-analysis to evaluate the association of PAI-1 4G/5G polymorphism with diabetic retinopathy in type 2 diabetes.

METHODS

Data were retrieved in a systematic manner and analyzed using Review Manager and STATA Statistical Software. Crude odds ratios (ORs) with 95% confidence intervals (CIs) were used to assess the strength of associations.

RESULTS

Nine studies with 1, 217 cases and 1, 459 controls were included. Allelic and genotypic comparisons between cases and controls were evaluated. Overall analysis suggests a marginal association of the 4G/5G polymorphism with diabetic retinopathy (for 4G versus 5G: OR 1.13, 95%CI 1.01 to 1.26; for 4G/4G versus 5G/5G: OR 1.30, 95%CI 1.04 to 1.64; for 4G/4G versus 5G/5G + 4G/5G: OR 1.26, 95%CI 1.05 to 1.52). In subgroup analysis by ethnicity, we found an association among the Caucasian population (for 4G versus 5G: OR 1.14, 95% CI 1.00 to 1.30; for 4G/4G versus 5G/5G: OR 1.33, 95%CI 1.02 to 1.74; for 4G/4G versus 5G/5G + 4G/5G: OR 1.41, 95%CI 1.13 to 1.77). When stratified by the average duration of diabetes, patients with diabetes histories longer than 10 years have an elevated susceptibility to diabetic retinopathy than those with shorter histories (for 4G/4G versus 5G/5G: OR 1.47, 95%CI 1.08 to 2.00). We also detected a higher risk in hospital-based studies (for 4G/4G versus 5G/5G+4G/5G: OR 1.27, 95%CI 1.02 to 1.57).

CONCLUSIONS

The present meta-analysis suggested that 4G/5G polymorphism in the PAI-1 gene potentially increased the risk of diabetic retinopathy in type 2 diabetes and showed a discrepancy in different ethnicities. A higher susceptibility in patients with longer duration of diabetes (more than 10 years) indicated a gene-environment interaction in determining the risk of diabetic retinopathy.

Association of angiotensin-converting enzyme gene 2350 G/A polymorphism with diabetic retinopathy in Chinese Han population

The angiotensin-converting enzyme (ACE) gene is one of the most studied candidate genes related to diabetic retinopathy (DR). ACE 2350 G/A polymorphism (rs4343) is known among the polymorphisms of this gene to have the most significant effect on plasma ACE concentrations. The aim of the present study was to investigate the relationship between 2350 G/A polymorphism of ACE gene and the susceptibility of DR in Chinese Han population. A case-control study for 145 type 2 diabetes mellitus (DM) patients, including 63 type 2 DM without DR (NDR) and 82 type 2 DM with DR (DR), and 90 subjects of age, gender matched normal controls (NC group) was performed. ACE 2350 G/A genotypes were identified by polymerase chain reaction and restriction digestion in all study participants. The distribution of the ACE 2350 G/A genotypes (GG, GA, and AA) was 35.56, 45.55, and 18.89 % in the NC group, 28.57, 46.03, and 25.40 % in the NDR group, and 15.85, 46.34, and 37.81 % in the DR group, respectively. There were no significant differences in either genotype frequency distribution (P = 0.5266) or allele frequency distribution (P = 0.2425) between the NC group and NDR group. However, the distribution of genotype frequency (P = 0.0026) and allele frequency (P = 0.0003) in the DR group showed a significant difference when compared to that of NC group (P = 0.0075). Moreover, there was statistical difference in allele frequency distribution (P = 0.0328) between the DR group and the NDR group. No statistical differences were observed between ACE 2350 G/A polymorphism and the diabetes duration or types of DR. Results obtained in this study indicate that ACE 2350 G/A polymorphism is associated with DR in Han Chinese patients with type 2 DM.

Angiotensin-converting enzyme gene polymorphism is associated with proliferative diabetic retinopathy: a meta-analysis

The association of angiotensin-converting enzyme (ACE) gene polymorphism with diabetic retinopathy (DR) was investigated in many studies with conflicting results. To shed light on these inconclusive findings, a meta-analysis of all available studies relating I (insert)/D (delete) polymorphism to the risk of developing DR was conducted. This meta-analysis included genotype data on 2,342 cases with DR and 2,048 controls free of DR. Summary odds ratios were estimated. Potential sources of heterogeneity and bias were explored. Overall, in allelic genetic model, heterogeneity between studies was nonsignificant (P = 0.12). No publication bias was observed in the regression asymmetry test (τ = 0.84, P = 0.41). There was no significant association between this variant and DR. In additional analysis, the association of I/D variant with retinopathy was nonsignificant both in patients with type 1 diabetes (T1D) (1.01 [95% CI: 0.79-1.29]) and in patients with type 2 diabetes (T2D) (1.12 [95% CI: 0.93-1.35]). Significant association was not also observed between I/D variant and the background diabetic retinopathy (BDR). For the I/D polymorphism and its relationship to proliferative diabetic retinopathy (PDR), the dominant model showed nonsignificant heterogeneity among studies (P = 0.52; I (2) = 0%), and the fixed estimate pooled odd ratio (OR) JOP was significant, at 1.37 [95% CI: 1.02-1.84]. No association was observed between ACE I/D variant and DR, irrespective of the diabetic type. There was moderate evidence of its relationship to PDR, while its relationship to BDR was not found. Studies exploring the association between ACE I/D polymorphism and BDR or PDR may help us better understand the genetics of DR.

The relationship between ACE gene insertion/deletion polymorphism and diabetic retinopathy in Iranian patients with type 2 diabetes

BACKGROUND

The role of genetic factors in diabetic retinopathy (DR) is unclear. We investigated the relationship between DR and an insertion/deletion polymorphism in the angiotensin-converting enzyme (ACE) gene in Iranian patients with type 2 diabetes without overt nephropathy.

METHODS

A total of 178 consecutive type 2 diabetic patients with DR (Group A) and 206 type 2 diabetic patients without DR (Group B) were studied. The following variables were determined: age, sex, body mass index, diabetes duration, medications used, history of coronary artery disease and its complications, blood pressure (systolic and diastolic), fasting plasma glucose, hemoglobin A1c, total cholesterol, low- and high-density lipoproteins, triglycerides, plasma creatinine, and 24-h urine albumin excretion.

RESULTS

The groups were statistically similar in all variables except diabetes duration (P = 0.037), ACE activity (P < 0.001), and ACE genotype (P = 0.008). The DD genotype was significantly more common in Group A (32.6% versus 19.2% in Group B; P = 0.009). In multivariate regression analysis, the ID genotype (compared to the II genotype) was an independent predictor of DR (OR = 1.831, 95% CI = 1.074-3.124; P = 0.026).

CONCLUSIONS

The D allele of the ACE gene is independently associated with DR in Iranian type 2 diabetic patients.

A systematic meta-analysis of genetic association studies for diabetic retinopathy

OBJECTIVE

Diabetic retinopathy is a sight-threatening microvascular complication of diabetes with a complex multifactorial pathogenesis. A systematic meta-analysis was undertaken to collectively assess genetic studies and determine which previously investigated polymorphisms are associated with diabetic retinopathy.

RESEARCH DESIGN AND METHODS

All studies investigating the association of genetic variants with the development of diabetic retinopathy were identified in PubMed and ISI Web of Knowledge. Crude odds ratios (ORs) and 95% CIs were calculated for single nucleotide polymorphisms and microsatellite markers previously investigated in at least two published studies.

RESULTS

Twenty genes and 34 variants have previously been studied in multiple cohorts. The aldose reductase (AKR1B1) gene was found to have the largest number of polymorphisms significantly associated with diabetic retinopathy. The z-2 microsatellite was found to confer risk (OR 2.33 [95% CI 1.49-3.64], P = 2 x 10(-4)) in type 1 and type 2 diabetes and z+2 to confer protection (0.58 [0.36-0.93], P = 0.02) against diabetic retinopathy in type 2 diabetes regardless of ethnicity. The T allele of the AKR1B1 promoter rs759853 variant is also significantly protective against diabetic retinopathy in type 1 diabetes (0.5 [0.35-0.71], P = 1.00 x 10(-4)), regardless of ethnicity. These associations were also found in the white population alone (P < 0.05). Polymorphisms in NOS3, VEGF, ITGA2, and ICAM1 are also associated with diabetic retinopathy after meta-analysis.

CONCLUSIONS

Variations within the AKR1B1 gene are highly significantly associated with diabetic retinopathy development irrespective of ethnicity. Identification of genetic risk factors in diabetic retinopathy will assist in further understanding of this complex and debilitating diabetes complication.