The relationship between angiotensin-converting enzyme insertion/deletion polymorphism and proliferative retinopathy in type 2 diabetes

The Role of Genetic Polymorphisms in Diabetic Retinopathy: Narrative Review

Diabetic retinopathy (DR) is renowned as a leading cause of visual loss in working-age populations with its etiopathology influenced by the disturbance of biochemical metabolic pathways and genetic factors, including gene polymorphism. Metabolic pathways considered to have an impact on the development of the disease, as well as genes and polymorphisms that can affect the gene expression, modify the quantity and quality of the encoded product (protein), and significantly alter the metabolic pathway and its control, and thus cause changes in the functioning of metabolic pathways. In this article, the screening of chromosomes and the most important genes involved in the etiology of diabetic retinopathy is presented. The common databases with manuscripts published from January 2000 to June 2023 have been taken into consideration and chosen. This article indicates the role of specific genes in the development of diabetic retinopathy, as well as polymorphic changes within the indicated genes that may have an impact on exacerbating the symptoms of the disease. The collected data will allow for a broader look at the disease and help to select candidate genes that can become markers of the disease.

No Association of Angiotensin-Converting Enzyme Insertion/Deletion (ACE I/D) Gene Polymorphism in the Susceptibility to Diabetic Retinopathy in Type 2 Diabetes Mellitus Patients: An Updated Meta-Analysis

Diabetic retinopathy (DR) is a complex and multifactorial pathology encompassing environmental, metabolic, and polygenic influences. Among the genes possibly involved in the development and progression of DR, the Angiotensin I-converting enzyme (ACE) gene stands out, which presents an insertion (I) or deletion (D) polymorphism of a 287 bp Alu repetitive sequence in intron 16. Thus, this study aimed to perform a systematic review with meta-analysis to elucidate the relationship between the ACE gene (I/D) polymorphism (rs1799752) and the development and progression of DR in type 2 diabetic patients. PubMed/MEDLINE, Embase, Web of Science, and Scopus databases were systematically searched to retrieve articles that investigated the association between ACE gene (I/D) polymorphism in DR patients. Sixteen articles were included in the systematic review. The results describe no significant association between the polymorphism and DR risk (OR = 1.12; CI = 0.96-1.31; and p = 0.1359) for genotypic analysis by the dominant model (II vs. ID+DD). Moreover, we also observed no significant association between the D allele on the allele frequency analysis (I vs. D) and the DR risk (OR = 1.10; CI = 0.98-1.23; and p = 0.1182). Forest plot analysis revealed that the discrepancy between previous studies most likely arose from variations in their sample sizes. In conclusion, I/D polymorphism appears to be not involved in the susceptibility to and progression of the DR in type 2 diabetic 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.

Genetics in diabetic retinopathy: current concepts and new insights

There is emerging evidence which indicates the essential role of genetic factors in the development of diabetic retinopathy (DR). In this regard it should be highlighted that genetic factors account for 25-50% of the risk of developing DR. Therefore, the use of genetic analysis to identify those diabetic patients most prone to developing DR might be useful in designing a more individualized treatment. In this regard, there are three main research strategies: candidate gene studies, linkage studies and Genome-Wide Association Studies (GWAS). In the candidate gene approach, several genes encoding proteins closely related to DR development have been analyzed. The linkage studies analyze shared alleles among family members with DR under the assumption that these predispose to a more aggressive development of DR. Finally, Genome-Wide Association Studies (GWAS) are a new tool involving a massive evaluation of single nucleotide polymorphisms (SNP) in large samples. In this review the available information using these three methodologies is critically analyzed. A genetic approach in order to identify new candidates in the pathogenesis of DR would permit us to design more targeted therapeutic strategies in order to decrease this devastating complication of diabetes. Basic researchers, ophthalmologists, diabetologists and geneticists should work together in order to gain new insights into this issue.

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.

Relationship of vascular endothelial growth factor (VEGF) +405 G/C polymorphism and proliferative retinopathy in patients with type 2 diabetes

The role of the vascular endothelial growth factor (VEGF) gene polymorphism in proliferative diabetic retinopathy (PDR) is controversial. VEGF seems to play a central role in mediating microvascular pathology in proliferative diabetic retinopathy (PDR). Recently, a +405 G/C VEGF polymorphism was shown to be associated with PDR. The aim of the current study was to evaluate whether the VEGF gene polymorphism is an independent risk factor for severity of diabetic retinopathy in an Iranian adult population. A total of 119 consecutive patients with PDR (group A) and 279 patients with nonproliferative diabetic retinopathy NPDR (group B) were studied. Patients were recruited from the eye clinic of Ahvaz Jondi Shapour University of Medical Sciences between January 2007 and April 2009. After extraction of genomic DNA, genotyping of the +405 G/C polymorphism of the VEGF gene was performed by polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) analysis. Demographic, anthropometric, and plasma biochemistry data were recorded. In univariate analysis, the groups were statistically similar in all variables except for hemoglobin A1c (HbA1c) and +405 G/C polymorphism. The distribution of the GC genotype was significantly different in patients with PDR compared with NPDR. In a multivariate logistic regression analysis (using sex and body mass index as clinically significant variables and HbA1c and genotype as statistically significant variables) was then used to determine independent associations and adjusted odds ratios (ORs), the GG genotype (compared with the CC genotype) was an independent predictor of PDR [OR = 1.87, 95% confidence interval (CI) = 1.034-3.383 P = 0.039]. The HbA1c was more common in the PDR group (P = 0.004); in a multivariate regression, the association remained significant (OR = 1.194, 95% CI = 1.056-1.350, P = 0.005). These findings suggest that the VEGF +405 GG polymorphism might be associated with the risk of proliferative diabetic retinopathy in an Iranian population.

The relationship between angiotensin converting enzyme insertion/deletion polymorphism and age-related macular degeneration

BACKGROUND

To assess the role of serum angiotensin converting enzyme (ACE) levels and ACE insertion /deletion (I/D) genetic polymorphism in Turkish age-related macular degeneration (AMD) patients and control subjects.

METHODS

This prospective study consisted of 78 patients with AMD and 68 control subjects. The I/D polymorphism of the ACE was carried out by polymerase chain reaction. Serum ACE levels were determined by using the ELISA method.

RESULTS

There was no significant difference in the mean serum values of ACE between the control and patient groups (p = 0.107). The genotypic frequencies of ACE polymorphism in the control and patient groups were not significantly different either (p = 0.218).

CONCLUSION

We could not show a significant role of serum ACE levels and ACE I/D genetic polymorphism in the etiopathogenesis of AMD in the Turkish population, and our findings did not support the idea that serum ACE levels and ACE DD genotype were risk factors for AMD.

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.

The insertion/deletion polymorphism of the angiotensin-converting enzyme gene is associated with progression, but not development, of albuminuria in Iranian patients with type 2 diabetes

INTRODUCTION

The insertion/deletion (I/D) polymorphism of the angiotensin-converting enzyme (ACE) gene has been shown to be associated with a number of complications of type 2 diabetes.

RESULTS

on the development and progression of albuminuria, however, have remained controversial, with ethnic differences being a potential reason.The present study is the first report to examine Iranian patients.

METHODS

Patients (322; 162 males) with type 2 diabetes were categorised in this cross-sectional study into the following groups: normoalbuminuria (n=145), microalbuminuria (n=129) and macroalbuminuria (n=48).ACE gen I/D polymorphism genotypes were determined using the polymerase chain reaction method.

RESULT

s. The distribution of ACE genotypes was significantly different among the groups (p<0.001), with the II genotype decreasing and the DD genotype increasing in frequency with increasing severity of albuminuria. Multivariate regression analysis showed that the ACE genotype did not change the odds of having microalbuminuria versus normoalbuminuria, while the D allele independently increased the odds of having macroalbuminuria versus microalbuminuria approximately threefold (p<0.01).

CONCLUSIONS

In Iranian patients with type 2 diabetes, the D allele is associated with progression, but not development, of albuminuria.