Polymorphism of the manganese superoxide dismutase gene but not of vascular endothelial growth factor gene is a risk factor for diabetic retinopathy

Associations between Vascular Endothelial Growth Factor Gene Polymorphisms and Different Types of Diabetic Retinopathy Susceptibility: A Systematic Review and Meta-Analysis

BACKGROUND

Vascular endothelial growth factor (VEGF) gene polymorphisms have been shown to be associated with the risk of diabetic retinopathy (DR), but the results were inconsistent. The aim of this study was to systematically assess the associations between VEGF gene polymorphisms and different types of DR (nonproliferative DR and proliferative DR).

METHODS

Electronic databases PubMed, Embase, Web of Science, CNKI, and WANFANG DATA were searched for articles on the associations between VEGF gene polymorphisms and different types of DR up to November 6, 2019. Pooled odds ratios (ORs) and 95% confidence intervals (CIs) were calculated, and subgroup analyses were conducted by ethnicity. Sensitivity analysis was conducted to assess the stability of the results. Publication bias was assessed by using the Egger regression asymmetry test and visualization of funnel plots. A systematic review was conducted for polymorphisms with a high degree of heterogeneity (I ² > 75%) or studied in only one study.

RESULTS

A total of 13 and 18 studies analyzed the associations between VEGF SNPs and nonproliferative DR (NPDR) as well as proliferative DR (PDR), respectively. There were significant associations between rs2010963 and NPDR in Asian (dominant model: OR = 1.29, 95%CI = 1.04 - 1.60); and rs2010963 is associated with PDR in total population (dominant model: OR = 1.20, 95%CI = 1.03 - 1.41), either Asian (recessive model: OR = 1.57, 95%CI = 1.04 - 2.35) or Caucasian (recessive model: OR = 1.83, 95%CI = 1.28 - 2.63). Rs833061 is associated with PDR in Asian (recessive model: OR = 1.58, 95%CI = 1.11 - 2.26). Rs699947 is associated with NPDR in the total population (dominant model: OR = 2.04, 95%CI = 1.30 - 3.21) and associated with PDR in Asian (dominant model: OR = 1.72, 95%CI = 1.05 - 2.84).

CONCLUSIONS

Rs2010963, rs833061, and rs699947 are associated with NPDR or PDR, which may be involved in the occurrence and development of DR.

Riding the tiger - physiological and pathological effects of superoxide and hydrogen peroxide generated in the mitochondrial matrix

Elevated mitochondrial matrix superoxide and/or hydrogen peroxide concentrations drive a wide range of physiological responses and pathologies. Concentrations of superoxide and hydrogen peroxide in the mitochondrial matrix are set mainly by rates of production, the activities of superoxide dismutase-2 (SOD2) and peroxiredoxin-3 (PRDX3), and by diffusion of hydrogen peroxide to the cytosol. These considerations can be used to generate criteria for assessing whether changes in matrix superoxide or hydrogen peroxide are both necessary and sufficient to drive redox signaling and pathology: is a phenotype affected by suppressing superoxide and hydrogen peroxide production; by manipulating the levels of SOD2, PRDX3 or mitochondria-targeted catalase; and by adding mitochondria-targeted SOD/catalase mimetics or mitochondria-targeted antioxidants? Is the pathology associated with variants in SOD2 and PRDX3 genes? Filtering the large literature on mitochondrial redox signaling using these criteria highlights considerable evidence that mitochondrial superoxide and hydrogen peroxide drive physiological responses involved in cellular stress management, including apoptosis, autophagy, propagation of endoplasmic reticulum stress, cellular senescence, HIF1α signaling, and immune responses. They also affect cell proliferation, migration, differentiation, and the cell cycle. Filtering the huge literature on pathologies highlights strong experimental evidence that 30-40 pathologies may be driven by mitochondrial matrix superoxide or hydrogen peroxide. These can be grouped into overlapping and interacting categories: metabolic, cardiovascular, inflammatory, and neurological diseases; cancer; ischemia/reperfusion injury; aging and its diseases; external insults, and genetic diseases. Understanding the involvement of mitochondrial matrix superoxide and hydrogen peroxide concentrations in these diseases can facilitate the rational development of appropriate therapies.

Association of SOD2 A16V and PON2 S311C polymorphisms with polycystic ovary syndrome in Chinese women

PURPOSE

To investigate the relationship between superoxide dismutase 2 (SOD2) A16V and paraoxonase 2 (PON2) S311C gene variants and the risk of polycystic ovary syndrome (PCOS) and evaluate the effects of the genotypes on clinical, hormonal, metabolic and oxidative stress indexes in Chinese women.

METHODS

This is a cross-sectional study of 932 patients with PCOS and 745 control women. For the clinical and metabolic association study of genotypes, 631 patients and 492 controls were included after excluding the subjects with interferential factors. Genotypes were determined by polymerase chain reaction (PCR) and restriction fragment length polymorphism analysis. Serum total oxidant status, total antioxidant capacity (T-AOC), oxidative stress index and malondialdehyde (MDA) levels, and clinical and metabolic parameters were also analyzed.

RESULTS

The prevalence of the A allele of SOD2 A16V polymorphism was significantly greater in patients with PCOS than in control subjects. Genotype (AA + AV) remained a significant predictor for PCOS in prognostic models including age, body mass index, insulin resistance index, high-density lipoprotein (HDL), low-density lipoprotein (LDL), and triglycerides (TGs) as covariates. Patients carrying the A allele had significantly higher serum luteinizing hormone (LH) levels, and the ratio of LH to follicle-stimulating hormone compared with patients with the VV genotype. We also showed that patients carrying the C allele of the PON2 S311C polymorphism had lower T-AOC compared with patients carrying the SS genotype. However, no significant differences were observed in the frequencies of the S311C genotypes and alleles of the PON2 gene between PCOS and control groups.

CONCLUSION

The SOD2 A16V, but not PON2 S311C, polymorphism may be one of the genetic determinants for PCOS in Chinese women.

Oxidative Stress as the Main Target in Diabetic Retinopathy Pathophysiology

Diabetic retinopathy (DR) is one of the most common complications of diabetes mellitus (DM) causing vision impairment even at young ages. There are numerous mechanisms involved in its development such as inflammation and cellular degeneration leading to endothelial and neural damage. These mechanisms are interlinked thus worsening the diabetic retinopathy outcome. In this review, we propose oxidative stress as the focus point of this complication onset.

Diabetic macular oedema: under-represented in the genetic analysis of diabetic retinopathy

Diabetic retinopathy, a complication of both type 1 and type 2 diabetes, is a complex disease and is one of the leading causes of blindness in adults worldwide. It can be divided into distinct subclasses, one of which is diabetic macular oedema. Diabetic macular oedema can occur at any time in diabetic retinopathy and is the most common cause of vision loss in patients with type 2 diabetes. The purpose of this review is to summarize the large number of genetic association studies that have been performed in cohorts of patients with type 2 diabetes and published in English-language journals up to February 2017. Many of these studies have produced positive associations with gene polymorphisms and diabetic retinopathy. However, this review highlights that within this large body of work, studies specifically addressing a genetic association with diabetic macular oedema, although present, are vastly under-represented. We also highlight that many of the studies have small patient numbers and that meta-analyses often inappropriately combine patient data sets. We conclude that there will continue to be conflicting results and no meaningful findings will be achieved if the historical approach of combining all diabetic retinopathy disease states within patient cohorts continues in future studies. This review also identifies several genes that would be interesting to analyse in large, well-defined cohorts of patients with diabetic macular oedema in future candidate gene association studies.

Polymorphisms of Antioxidant Genes as a Target for Diabetes Management

Diabetes mellitus (DM) is one of the most important health problems with increasing prevalence worldwide. Oxidative stress, a result of imbalance between reactive oxygen species (ROS) generation and antioxidant defense mechanisms has been demonstrated as the main pathology in DM. Hyperglycemia-induced ROS productions can induce oxidative stress through four major molecular mechanisms including the polyol pathway, advanced glycation end- products formation, activation of protein kinase C isoforms, and the hexosamine pathways. In the development of type 2 DM (T2DM) and its complications, genetic and environmental factors play important roles. Therefore, the aim of this review was to focus on the assessment of single-nucleotide polymorphisms within antioxidant enzymes including superoxide dismutase, catalase, glutathione peroxidase, glutathione-S-transferase, nitric oxide synthase, and NAD(P)H oxidase and their association with T2DM. The results would be helpful in understanding the mechanisms involved in pathogenesis of disease besides discovering new treatment approaches in management of DM.

Association between the vascular endothelial growth factor single nucleotide polymorphisms and diabetic retinopathy risk: A meta-analysis

BACKGROUND

The aim of the present study was to reveal the relationship between vascular endothelial growth factor (VEGF) single nucleotide polymorphisms (SNPs) and susceptibility to diabetic retinopathy (DR).

METHODS

A literature review was conducted (PubMed, Web of Science, Embase) to identify papers about VEGF SNPs and DR published up to 23 September 2015. The VEGF gene SNPs analyzed with regard to DR susceptibility were rs2010963 (G > C), rs833061 (T > C), rs699947 (C > A), rs3025039 (C > T) and rs1570360 (G > A). Pooled odds ratios (OR) and 95% confidence intervals (CI) were calculated, and meta-analyses were performed using fixed or random effects models.

RESULTS

Sixteen studies were included in the meta-analysis. Significant associations between the rs3025039 (C > T) polymorphism and increased DR risk were found in the allele model (T/C; pooled OR 1.60, 95% CI 1.07-2.41, P = 0.02), homozygote model (TT/CC; pooled OR 2.08, 95% CI 1.29-3.35, P = 0.003), heterozygote model (TC/CC; pooled OR 1.68, 95% CI 1.04-2.72, P = 0.04), dominant model (TT+TC/CC; pooled OR 1.72, 95% CI 1.06-2.80, P = 0.03), and recessive model (TT/TC+CC; pooled OR 1.80, 95% CI 1.12-2.90, P = 0.02). For rs833061, a significant association between VEGF SNPs and DR was found only in the allele model (C/T; pooled OR 6.34, 95% CI 2.10-19.14, P = 0.001).

CONCLUSIONS

The rs3025039 and rs833061 SNPs are most likely associated with an increased risk of DR. The T allele in rs3025039 and the C allele in rs833061 are associated with increased DR susceptibility.

MnSOD Val16Ala polymorphism associated with retinopathy risk in diabetes: a PRISMA-compliant Meta-analysis of case-control studies

AIM

To investigate the association of Manganese superoxide dismutase (MnSOD) Val16Ala polymorphism with diabetic retinopathy (DR).

METHODS

PubMed, Embase, China National Knowledge Infrastructure, and Wanfang databases were searched. The pooled odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to evaluate the strength of the association. Subgroup, sensitivity, and cumulative analyses were performed. Publication bias was also analyzed.

RESULTS

Eight studies were included in the pooled analysis. The MnSOD Val16Ala polymorphism was associated with the risk of DR under the dominant model (OR=0.66, 95%CI=0.48-0.91, P<0.0001), this result was demonstrated to be relatively stable in cumulative analysis. No significant publication bias was found. This polymorphism was also associated with the risk of DR in Caucasians under the dominant model (OR=0.64, 95%CI=0.42-0.97, P=0.04,) and in Asians under the recessive model (OR=0.31, 95%CI=0.11-0.88, P=0.03).

CONCLUSION

These findings suggest that the MnSOD Val16Ala polymorphism is a risk factor for DR, and that more attention should be paid to carriers of these susceptibility genes.

Oxidative stress gene polymorphisms may have an impact in the development of ischemic stroke

BACKGROUND

Antioxidants are responsible for detoxification of harmful effects of reactive oxygen species. Genetic factors may influence antioxidant activity as a result of polymorphisms on antioxidant enzymes. These polymorphisms can be risk in ischemic stroke (IS) risk. IS is a disorder with genetic and environmental factors contributing to overall risk. Although a few studies have been conducted, there have been no reports on catalase (CAT C262T), manganese superoxide dismutase (MnSOD Ala16Val) and glutathione peroxidase 1 (GPX1 Pro198Leu) gene polymorphisms and IS risk.

METHODS

We aimed to perform a case-control study to increase the awareness of the impact of oxidative stress (OS) gene polymorphism in the development of IS. A restriction fragment length polymorphism-polymerase chain reaction was used to determine genotypes. The interactions between genes and smoking and possible risk factors were evaluated.

RESULTS

An approximately four-fold higher IS risk was found in patients with the Val allele compared to the Ala allele. Smoking was a risk factor in the development of IS for CAT TT and MnSOD Ala/Val genotypes; we found a 3.5- to 5.5-fold higher IS risk in CAT TT and MnSOD Ala/Val genotypes. Different logistic regression models were performed for possible risk factors (smoking, body mass index, low-density lipoprotein and diabetes mellitus). The IS risk increases statistically significant only with age by multiple logistic regression analysis. CAT gene polymorphisms in IS patients were not different from controls.

CONCLUSIONS

It is unlikely that CAT and GPX1 single nucleotide polymorphisms are risk factors for IS. The results of the present study show that smoking may be a risk factor for IS risk in patients with MnSOD mutant genotypes.

Candidate gene studies of diabetic retinopathy in human

Diabetic retinopathy (DR) is a multifactorial disease with complex pathophysiology. It is the main cause of blindness among the people in productive age. The purpose of this literature review is to highlight recent achievements in the genetics of diabetic retinopathy with particular focus on candidate gene studies. We summarized most of the available published data about candidate genes for diabetic retinopathy with the goal to identify main genetic aspects. We conclude that genetic studies reported contradictory findings and no genetic variants meet criteria of a diagnostic marker, or significantly elucidate the root of DR development. Based on these findings it is important to continue with the research in the field of DR genetics, mainly due to the fact that currently new possibilities and approaches associated with utilization of next-generation sequencing are available.

The effects of rosuvastatin on lipid-lowering, inflammatory, antioxidant and fibrinolytics blood biomarkers are influenced by Val16Ala superoxide dismutase manganese-dependent gene polymorphism

Rosuvastatin is a cholesterol-lowering drug that also attenuates the inflammatory process and oxidative stress via the reduction of superoxide anion production. Superoxide anions are metabolized by manganese-dependent superoxide dismutase (MnSOD or SOD2) in the mitochondria. In humans, there is a gene polymorphism where a change of alanine (Ala) to valine (Val) occurs at the 16th amino acid (Ala16Val-SOD2). The VV genotype has been associated with the risk of developing several metabolic diseases, such as hypercholesterolemia. Thus, to further explore this phenomenon, this study investigated the influence of the Val16Ala-SOD2 polymorphism on the lipid profile and inflammatory and fibrinolytic biomarkers of 122 hypercholesterolemic patients undergoing the first pharmacological cholesterol-lowering therapy who were treated with 20 mg rosuvastatin for 120 days. The findings indicate that the VV patients who present a low-efficiency SOD2 enzyme exhibit an attenuated response to rosuvastatin compared with the A-allele patients. The effect of rosuvastatin on inflammatory and fibrinolytic biomarkers was also less intense in the VV patients. These results suggest some pharmacogenetic effects of Val16Ala-SOD2 in hypercholesterolemia treatment.

Interplay between Superoxide Dismutase, Glutathione Peroxidase, and Peroxisome Proliferator Activated Receptor Gamma Polymorphisms on the Risk of End-Stage Renal Disease among Han Chinese Patients

Background. Single nucleotide polymorphisms (SNPs) of antioxidants, including superoxide dismutase 2 (SOD2) and glutathione peroxidase 1 (GPX1), play an important role in the risk for cancer and metabolic disorders. However, little is known regarding the effect of antioxidant SNPs on renal events. Methods. We prospectively enrolled multicenter patients with end-stage renal disease (ESRD) and those without chronic kidney disease (CKD) of Han Chinese origin, with SOD2 (Val16Ala), GPX1 (Pro197Leu), and PPAR-γ (Pro12Ala, C161T) genotyped. Multiple regression analyses were conducted to evaluate the significant risk determinants for ESRD. Results. Compared to ESRD patients, non-CKD subjects were more likely to have T allele at SOD2 Val16Ala (p = 0.036) and CC genotype at PPAR-γ Pro12Ala (p = 0.028). Regression analysis showed that TT genotype of SOD2 Val16Ala conferred significantly lower ESRD risk among patients without diabetes (odds ratio 0.699; p = 0.018). GPX1 SNP alone did not alter the risk. We detected significant interactions between SNPs including PPAR-γ Pro12Ala, C161T, and GPX1 regarding the risk of ESRD. Conclusion. This is the first and largest study on the association between adverse renal outcomes and antioxidant SNPs among Han Chinese population. Determination of SOD2 and PPAR-γ SNPs status might assist in ESRD risk estimation.

Elevated Levels of Plasma IgA Autoantibodies against Oxidized LDL Found in Proliferative Diabetic Retinopathy but Not in Nonproliferative Retinopathy

Aims. This study investigated the association of autoantibodies binding to oxidized low-density lipoproteins (oxLDL) in diabetic retinopathy (DR). Methods. Plasma from 229 types 1 and 2 patients with DR including diabetic macular edema (DME) and proliferative diabetic retinopathy (PDR) was analysed with ELISA-based assay to determine IgA, IgG, and IgM autoantibody levels binding to oxLDL. The controls were 106 diabetic patients without retinopathy (NoDR) and 139 nondiabetic controls (C). Results. PDR group had significantly higher IgA autoantibody levels than DME or NoDR: mean 94.9 (SD 54.7) for PDR, 75.5 (41.8) for DME (p = 0.001), and 76.1 (48.2) for NoDR (p = 0.008). There were no differences in IgG, IgM, or IgA that would be specific for DR or for DME. Type 2 diabetic patients had higher levels of IgA autoantibodies than type 1 diabetic patients (86.0 and 65.5, resp., p = 0.004) and the highest levels in IgA were found in type 2 diabetic patients with PDR (119.1, p > 0.001). Conclusions. IgA autoantibodies were increased in PDR, especially in type 2 diabetes. The high levels of IgA in PDR, and especially in type 2 PDR patients, reflect the inflammatory process and enlighten the role of oxLDL and its autoantibodies in PDR.

Association between a vascular endothelial growth factor gene polymorphism (rs2146323) and diabetic retinopathy: a meta-analysis

Background

Vascular endothelial growth factor (VEGF) is thought to play an important role in the pathogenesis of diabetic retinopathy (DR). Previous studies have associated the VEGF rs2146323 polymorphism with the risk of DR. However, the results of these studies are inconsistent. A meta-analysis was performed to evaluate the association between the VEGF rs2146323 polymorphism and the risk of DR.

Methods

The PubMed, EMBASE, Web of Science and Google Scholar literature databases until March 2015 were searched. The differences in the studies were expressed in the form of an odds ratio (OR) and the corresponding 95 % confidence interval (CI). Heterogeneity among the studies was tested using the I² statistic based on the Q test.

Results

A total of four studies (598 cases and 709 controls) were included in the meta-analysis. A significant association was found involving the rs2146323 polymorphism in the dominant model (CA + AA VS. CC) (OR = 1.38, CI = 1.10–1.72, P = 0.005) and the co-dominant model (CA VS. CC) (OR = 1.37, CI = 1.08–1.74, P = 0.008).

Conclusions

Our meta-analysis confirmed the association between the VEGF rs2146323 polymorphism and the risk of DR.

Association study of C936T polymorphism of the VEGF gene and the C242T polymorphism of the p22phox gene with diabetes mellitus type 2 and distal diabetic polyneuropathy

Even with long‑term glycemic control, diabetes mellitus type 2 (DM2) remains the predominant cause of diabetic neuropathy. Single nucleotide polymorphism (SNP) C936T of the vascular endothelial growth factor (VEGF) gene and the SNP C242T of the p22phox (CYBA) gene have been investigated in relation to DM2 and its complications. The aim of the present study was to investigate the association between these two SNPs and DM2, and also between the SNPs and the signs and symptoms of diabetic distal polyneuropathy. The DM2 group consisted of 98 individuals and the control group consisted of 104 individuals. The results demonstrated that there was no association between the different genotypes or alleles and increased risk of the disease (P>0.05). With SNP C242T, a significant association with body mass index between the CTxTT genotypes (P=0.043) was identified; and the greatest body mass indexes were among individuals with the TT genotype. An association between the degree of neuropathic symptoms and genotypic/allelic distribution of these polymorphisms was not observed. In conclusion, the investigated polymorphisms are not correlated with the risk of developing DM2.

Polymorphism of VEGF gene in susceptibility to chronic immune-mediated inflammatory diseases: a meta-analysis

Background Vascular endothelial growth factor (VEGF) is an important angiogenic factor and may be connected with chronic immune-mediated inflammatory diseases (IMIDs) to some extent. However, previous researches about the relationship between the +405G>C (dbSNP: rs2010963) polymorphism in VEGF gene and the risk of IMIDs are controversial and inconsistent. So we conducted this meta-analysis to assess whether the relationship between the +405G>C polymorphism in the 5'-UTR region of VEGF gene and IMID susceptibility exists. Methods Our literature search was conducted on the PubMed, Embase, Web of science, Chinese National Knowledge Infrastructure, and Chinese Biomedical databases to retrieve for eligible studies. Odds ratios as well as their 95 % confidence intervals were utilized to deduce the possible relationship. Results A total number of 5175 patients with IMIDs and 7069 healthy controls from 27 case-control studies were included. For the overall eligible data collected in our meta-analysis, there was no marked relationship between +405G>C polymorphism and the risk of IMIDs. However, subgroup analysis by ethnicity suggested that +405C allele could be a protective factor for IMIDs in Asians, whereas an opposite conclusion was drawn in Caucasians. Conclusion Thus, we may come to the conclusion that the VEGF +405G>C polymorphism could be associated with IMIDs, and the correlation might vary with ethnic groups.

Manganese superoxide dismutase and oxidative stress modulation

Oxidative stress is characterized by imbalanced reactive oxygen species (ROS) production and antioxidant defenses. Two main antioxidant systems exist. The nonenzymatic system relies on molecules to directly quench ROS and the enzymatic system is composed of specific enzymes that detoxify ROS. Among the latter, the superoxide dismutase (SOD) family is important in oxidative stress modulation. Of these, manganese-dependent SOD (MnSOD) plays a major role due to its mitochondrial location, i.e., the main site of superoxide (O(2)(·-)) production. As such, extensive research has focused on its capacity to modulate oxidative stress. Early data demonstrated the relevance of MnSOD as an O(2)(·-) scavenger. More recent research has, however, identified a prominent role for MnSOD in carcinogenesis. In addition, SOD downregulation appears associated with health risk in heart and brain. A single nucleotide polymorphism which alters the mitochondria signaling sequence for the cytosolic MnSOD form has been identified. Transport into the mitochondria was differentially affected by allelic presence and a new chapter in MnSOD research thus begun. As a result, an ever-increasing number of diseases appear associated with this allelic variation including metabolic and cardiovascular disease. Although diet and exercise upregulate MnSOD, the relationship between environmental and genetic factors remains unclear.

Association of Superoxide dismutases (SOD1 and SOD2) and Glutathione peroxidase 1 (GPx1) gene polymorphisms with type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) is a metabolic disorder resulting from oxidative stress (OS), the root cause of insulin resistance, β-cell dysfunction, and impaired glucose tolerance. Antioxidant enzymes play key roles in cellular defense and can be used as important biomarkers for T2DM. The present study was undertaken to evaluate three genetic polymorphisms viz. SOD1 + 35A/C, SOD2 + 47C/T, and GPx + 599C/T in 207 T2DM cases and 210 healthy controls from North India. DNA was extracted from blood samples and genotyping was done by PCR-RFLP. Genotypic/allelic frequencies and haplotype/gene-gene interaction analysis were performed using SPSS (version 15.0) and SHEsis (v. online). Except age, all other biochemical parameters showed highly significant association in T2DM cases (P < 0.001). In North Indian population, SOD1 + 35A/C variant was monomorphic. Genotype/allele frequencies of SOD2 + 47C/T polymorphism and carriage rate of 'C' allele showed significant association (p < 0.05, < 0.001; OR 2.434). Genotype/allele frequencies of GPx1 + 599C/T and carriage rate showed no association although the odds ratio of GPx1 'C' allele indicated a 1.362 times higher risk of T2DM. SOD2 'CT' and GPx1 'CC' genotypes showed maximum association with biochemical parameters. Haplotype/gene-gene interaction analysis in controls and cases showed that SOD2 + 47C/T and GPx1 + 599C/T were in linkage disequilibrium (D: 0.168; r(2): 0.10) and individuals with this combination had a 1.273 times higher risk [OR; CI (95%)] of developing T2DM. Thus, we conclude that it is essential to assess the combinatorial association of gene variants with T2DM in order to identify risk haplotypes in a population.

The MnSOD Ala16Val SNP: relevance to human diseases and interaction with environmental factors

The relevance of reactive oxygen species (ROS) production relies on the dual role shown by these molecules in aerobes. ROS are known to modulate several physiological phenomena, such as immune response and cell growth and differentiation; on the other hand, uncontrolled ROS production may cause important tissue and cell damage, such as deoxyribonucleic acid oxidation, lipid peroxidation, and protein carbonylation. The manganese superoxide dismutase (MnSOD) antioxidant enzyme affords the major defense against ROS within the mitochondria, which is considered the main ROS production locus in aerobes. Structural and/or functional single nucleotide polymorphisms (SNP) within the MnSOD encoding gene may be relevant for ROS detoxification. Specifically, the MnSOD Ala16Val SNP has been shown to alter the enzyme localization and mitochondrial transportation, affecting the redox status balance. Oxidative stress may contribute to the development of type 2 diabetes, cardiovascular diseases, various inflammatory conditions, or cancer. The Ala16Val MnSOD SNP has been associated with these and other chronic diseases; however, inconsistent findings between studies have made difficult drawing definitive conclusions. Environmental factors, such as dietary antioxidant intake and exercise have been shown to affect ROS metabolism through antioxidant enzyme regulation and may contribute to explain inconsistencies in the literature. Nevertheless, whether environmental factors may be associated to the Ala16Val genotypes in human diseases still needs to be clarified.

Manganese superoxide dismutase (SOD2) polymorphisms, plasma advanced oxidation protein products (AOPP) concentration and risk of kidney complications in subjects with type 1 diabetes

Aims

Oxidative stress is involved in the pathophysiology of diabetic nephropathy. Manganese superoxide dismutase (SOD2) catalyses the dismutation of superoxide, regulates the metabolism of reactive oxygen species in the mitochondria and is highly expressed in the kidney. Plasma concentration of advanced oxidation protein products (AOPP), a marker of oxidative stress, was found to be increased in patients with kidney disease. We investigated associations of SOD2 allelic variations, plasma SOD activity and AOPP concentration with diabetic nephropathy in type 1 diabetic subjects.

Methods

Eight SNPs in the SOD2 region were analysed in 1285 Caucasian subjects with type 1 diabetes from the SURGENE prospective study (n = 340; 10-year follow-up), GENESIS (n = 501) and GENEDIAB (n = 444) cross-sectional studies. Baseline plasma concentration of AOPP and SOD activity were measured in GENEDIAB participants. Hazard ratio (HR) and odds ratio (OR) were determined for incidence and prevalence of nephropathy. Analyses were adjusted or stratified by retinopathy stages.

Results

In the SURGENE cohort, the T-allele of rs4880 (V16A) was associated with the incidence of renal events (new cases, or the progression to a more severe stage of nephropathy; HR 1.99, 95% CI 1.24–3.12, p = 0.004) and with the decline in estimated glomerular filtration rate (eGFR) during follow-up. Similar associations were observed for rs2758329 and rs8031. Associations were replicated in GENESIS/GENEDIAB cohorts, in the subset of participants without proliferative retinopathy, and were confirmed by haplotype analyses. Risk allele and haplotype were also associated with higher plasma AOPP concentration and lower SOD activity.

Conclusions

SOD2 allelic variations were associated with the incidence and the progression of diabetic nephropathy, with a faster decline in eGFR and with plasma AOPP concentration and SOD activity in subjects with type 1 diabetes. These results are consistent with a role for SOD2 in the protection against oxidative stress and kidney disease in type 1 diabetes.

Meta-analysis of association between the -2578C/A polymorphism of the vascular endothelial growth factor and retinopathy in type 2 diabetes in Asians and Caucasians

BACKGROUND AND OBJECTIVES

Vascular endothelial growth factor (VEGF) has been shown to play an important role in the development and progress of diabetic retinopathy (DR). A number of case-control studies focused on the association between VEGF -2578C/A and risk for DR. But the results were not always consistent, so we performed a meta-analysis to evaluate the precise association between this variant and risk for DR.

METHODS

All publications on the association between VEGF -2578C/A polymorphism and DR were searched in the following electronic databases: PubMed, Embase, the Cochrane Library and Chinese Biomedical Literature Database, with the last report up to January 2013. This meta-analysis was assessed by Review Manager 5.1.

RESULTS

A total of 6 studies were involved in this meta-analysis, including 835 cases and 867 controls. Overall, we found a significant association between this polymorphism and DR (A vs. C: OR=1.49, 95% CI=1.26-1.77, p<0.00001; AA vs. CA+CC: OR=1.26, 95% CI=0.94-1.68, p=0.12; AA+CA vs. CC: OR=1.56, 95% CI=1.27-1.91, p<0.00001; AA vs. CC: OR=1.67, 95% CI=1.20-2.32, p=0.003; CA vs. CC: OR=1.51, 95% CI=1.21-1.87, p=0.0002), but we did not find any significant association in Caucasians in subgroup analysis. The results were not materially altered after the studies which did not fulfill the Hardy-Weinberg equilibrium were excluded.

CONCLUSION

Our meta-analysis supports the association between the VEGF -2578C/A polymorphism and DR, but not in the Caucasian population.

Association of rs6265 and rs2030324 polymorphisms in brain-derived neurotrophic factor gene with Alzheimer's disease: a meta-analysis

Background

The association between polymorphisms rs6265 and rs2030324 in brain-derived neurotrophic factor (BDNF) and Alzheimer’s disease (AD) has been widely reported, but the results remain controversial.

Methods

A comprehensive search of Pubmed, Web of Science, China National Knowledge Infrastructure (CNKI), Wanfang Med Online and China Biology Medical literature database (CBM) was performed. Pooled odds ratios (ORs) with 95% confidence intervals (CIs) were calculated using fixed or random-effects models. We excluded the studies with OR>3.0 or OR<0.3 for sensitive analysis. Subgroup analysis by ethnicity, form of AD and gender was carried out. Meta-regression was conducted to explore the potential sources of between-study heterogeneity.

Results

29 articles with 7548 cases and 7334 controls concerning rs6265 and 22 articles with 5796 cases and 5706 controls concerning rs2030324 were included in this meta-analysis. The combined evidence suggested rs6265 contributing significantly to the increased risk of AD in females (codominant: fixed-effects model (FEM): OR = 1.13, 95% CI = 1.04–1.23; dominant: FEM: OR = 1.17, 95% CI = 1.05–1.31), especially for Caucasian females (codominant: FEM: OR = 1.18, 95% CI = 1.03–1.34; dominant: FEM: OR = 1.18, 95% CI = 1.01–1.37) and female late-onset Alzheimer’s disease (LOAD) patients (codominant: FEM: OR = 1.22, 95% CI = 1.05–1.41; dominant: FEM: OR = 1.23, 95% CI = 1.03–1.46). No evidence indicated an association between rs2030324 with AD in codominant (random-effects model (REM): OR = 1.06, 95% CI = 0.89–1.26) and dominant (REM: OR = 1.05, 95% CI = 0.86–1.27) models.

Conclusion

This meta-analysis suggested A allele of rs6265 might increase the risk of AD in Caucasian females and female LOAD patients. In addition, no evidence indicated an association between rs2030324 with AD. Further studies are needed to confirm these results.

Association of RAGE (p.Gly82Ser) and MnSOD (p.Val16Ala) polymorphisms with diabetic retinopathy in T2DM patients from north India

AIMS

The present study aimed to examine the association of RAGE (p.Gly82Ser) and MnSOD (p.Val16Ala) polymorphisms with diabetic retinopathy (DR) in north Indian T2DM patients.

METHODS

In this case-control association study, 758 T2DM patients were recruited. 446 with retinal neovascularization, microneurysms and hemorrhages were considered as cases (DR) and 312 patients with T2DM and no clinical signs of retinopathy (DNR), were recruited as controls. Genotypes for RAGE (p.Gly82Ser) and MnSOD (p.Val16Ala) polymorphisms were generated by direct sequencing of amplified products.

RESULTS

Genotype distribution of p.Gly82Ser (RAGE) and p.Val16Ala (MnSOD) polymorphisms were significantly different between DR and DNR (p<0.05) whereas distribution of allele frequency did not differ significantly (p>0.05). A significantly higher frequency of homozygous Ser82 genotype in DR patients was detected compared with DNR (2.4% vs 0.64%) for p.Gly82Ser (RAGE) polymorphism whereas there was a higher frequency of homozygous Ala16 genotype for p.Val16Ala (MnSOD) polymorphism in DR patients compared with DNR (22.6% vs 19.3%). Binary logistic analyses showed an association of homozygous recessive genotype Ser82 with DR (OR: 2.63%, 95% CI: 0.16-15.88, p<0.033) for p.Gly82Ser (RAGE) polymorphism. However, we did not find a significant association of p.Val16Ala polymorphism in MnSOD with retinopathy.

CONCLUSIONS

The findings indicate a statistically significant association of p.Gly82Ser polymorphism in RAGE with DR in T2DM patients.

Challenges in elucidating the genetics of diabetic retinopathy

IMPORTANCE

In the past decade, significant progress in genomic medicine and technologic developments has revolutionized our approach to common complex disorders in many areas of medicine, including ophthalmology. A disorder that still needs major genetic progress is diabetic retinopathy (DR), one of the leading causes of blindness in adults.

OBJECTIVE

To perform a literature review, present the current findings, and highlight some key challenges in DR genetics.

DESIGN, SETTING, AND PARTICIPANTS

We performed a thorough literature review of the genetic factors for DR, including heritability scores, twin studies, family studies, candidate gene studies, linkage studies, and genome-wide association studies (GWASs).

MAIN OUTCOME MEASURES

Environmental and genetic factors for DR.

RESULTS

Although there is clear demonstration of a genetic contribution in the development and progression of DR, the identification of susceptibility loci through candidate gene approaches, linkage studies, and GWASs is still in its infancy. The greatest obstacles remain a lack of power because of small sample size of available studies and a lack of phenotype standardization.

CONCLUSIONS AND RELEVANCE

The field of DR genetics is still in its infancy and is a challenge because of the complexity of the disease. This review outlines some strategies and lessons for future investigation to improve our understanding of this complex genetic disorder.

The associations between VEGF gene polymorphisms and diabetic retinopathy susceptibility: a meta-analysis of 11 case-control studies

AIMS. Published data on the associations of VEGF polymorphisms with diabetic retinopathy (DR) susceptibility are inconclusive. A systematic meta-analysis was undertaken to clarify this topic. METHODS. Data were collected from the following electronic databases: PubMed, Embase, OVID, Web of Science, Elsevier Science Direct, Excerpta Medica Database (EMBASE), and Cochrane Library with the last report up to January 10, 2014. ORs and 95% CIs were calculated for VEGF-2578C/A (rs699947), -1154G/A (rs1570360), -460T/C (rs833061), -634G>C (rs2010963), and +936C/T (rs3025039) in at least two published studies. Meta-analysis was performed in a fixed/random effect model by using the software STATA 12.0. RESULTS. A total of 11 studies fulfilling the inclusion criteria were included in this meta-analysis. A significant relationship between VEGF+936C/T (rs3025039) polymorphism and DR was found in a recessive model (OR = 3.19, 95% CI = 1.20-8.41, and P(z) = 0.01) in Asian and overall populations, while a significant association was also found between -460T/C (rs833061) polymorphism and DR risk under a recessive model (OR = 2.12, 95% CI = 1.12-4.01, and P(z) = 0.02). CONCLUSIONS. Our meta-analysis demonstrates that +936C/T (rs3025039) is likely to be associated with susceptibility to DR in Asian populations, and the recessive model of -460T/C (rs833061) is associated with elevated DR susceptibility.

Association of VEGF gene polymorphisms with diabetic retinopathy: a meta-analysis

Background

Studies on the association of vascular endothelial growth factor (VEGF) gene -460T/C and -2578C/A polymorphisms with diabetic retinopathy (DR) have reported conflicting results. The aim of the present study was to assess the association by using meta-analysis.

Methods

A systematic search of electronic databases (PubMed, EMBASE, Elsevier Science Direct, ISI Web of Science, CBM, CNKI and VIP) was carried out until Sept 18, 2013. The pooled odds ratios (ORs) and their corresponding 95% confidence intervals (CIs) were used to assess the strength of the association.

Results

Eleven studies (-460T/C: 6 studies including 932 cases and 722 controls; -2578C/A: 6 studies including 1,071 cases and 1,137 controls) were involved in this meta-analysis. Significant association was found for -460T/C polymorphism (C versus T: OR=1.48, 95%CI=1.07–2.05, P=0.02; TC+CC versus TT: OR=1.78, 95%CI=1.02–3.12, P=0.04; CC versus TT+TC: OR=1.76, 95%CI=1.10–2.81, P=0.02), but not for -2578C/A polymorphism (P>0.05). Similar results were found in the subgroup analysis.

Conclusions

This meta-analysis demonstrates that DR is associated with VEGF gene -460T/C polymorphism, but not -2578C/A polymorphism. Further case-control studies based on larger sample size are still needed, especially for -2578C/A polymorphism.

Two polymorphisms (rs699947, rs2010963) in the VEGFA gene and diabetic retinopathy: an updated meta-analysis

Background

The vascular endothelial growth factor (VEGFA) gene has been suggested to play an important role in the pathogenesis of diabetic retinopathy (DR). However, the results have been inconsistent. In this study, we performed a meta-analysis to clarify the associations between VEGFA polymorphisms and DR risk.

Methods

Published literature from PubMed, EMBASE, Web of Science and Google Scholar were retrieved. Pooled odds ratios (ORs) with 95% confidence intervals (CIs) were calculated using fixed- or random-effects model.

Results

A total of eight studies (1204 cases and 1198 controls) for rs699947 polymorphism and ten studies (1666 cases and 1782 controls) for rs2010963 polymorphism were included in the meta-analysis. The results suggested that rs699947 polymorphism was marginally associated with DR under a homogeneous co-dominant model (AA vs. CC: OR = 1.69, 95% CI = 1.03-2.77, p = 0.040) and a dominant model (AA + AC vs. CC: OR = 1.38, 95% CI = 1.01-1.90, p = 0.040), whereas the association between rs2010963 polymorphism and DR was not significant under all genetic models (all p > 0.05). In the subgroup analysis, the effect size for rs699947 polymorphism was only marginally significant among European populations under a dominant model (OR = 1.47, 95% CI = 1.07–2.02, p = 0.018), but not among East Asians. After exclusion of outliers which were the source of between-study heterogeneity, there was significant association between rs699947 polymorphism and DR under a homogeneous co-dominant model (OR = 1.64, 95% CI = 1.18-2.28, p = 0.003), even after multiple comparison correction.

Conclusions

Our meta-analysis confirmed the significant association between rs699947 polymorphism and DR after exclusion of outliers, and rs2010963 polymorphism might be not associated with DR.

Manganese supplementation protects against diet-induced diabetes in wild type mice by enhancing insulin secretion

Mitochondrial dysfunction is both a contributing mechanism and complication of diabetes, and oxidative stress contributes to that dysfunction. Mitochondrial manganese-superoxide dismutase (MnSOD) is a metalloenzyme that provides antioxidant protection. We have previously shown in a mouse model of hereditary iron overload that cytosolic iron levels affected mitochondrial manganese availability, MnSOD activity, and insulin secretion. We therefore sought to determine the metallation status of MnSOD in wild-type mice and whether altering that status affected β-cell function. 129/SvEVTac mice given supplemental manganese exhibited a 73% increase in hepatic MnSOD activity and increased metallation of MnSOD. To determine whether manganese supplementation offered glucose homeostasis under a situation of β-cell stress, we challenged C57BL/6J mice, which are more susceptible to diet-induced diabetes, with a high-fat diet for 12 weeks. Manganese was supplemented or not for the final 8 weeks on that diet, after which we examined glucose tolerance and the function of isolated islets. Liver mitochondria from manganese-injected C57BL/6J mice had similar increases in MnSOD activity (81%) and metallation as were seen in 129/SvEVTac mice. The manganese-treated group fed high fat had improved glucose tolerance (24% decrease in fasting glucose and 41% decrease in area under the glucose curve), comparable with mice on normal chow and increased serum insulin levels. Isolated islets from the manganese-treated group exhibited improved insulin secretion, decreased lipid peroxidation, and improved mitochondrial function. In conclusion, MnSOD metallation and activity can be augmented with manganese supplementation in normal mice on normal chow, and manganese treatment can increase insulin secretion to improve glucose tolerance under conditions of dietary stress.

VEGF -634G>C polymorphism and diabetic retinopathy risk: a meta-analysis

BACKGROUND

Vascular endothelial growth factor (VEGF), a multifunctional cytokine that promotes angiogenesis and is a potent mediator of microvascular permeability, which is critical for the development of diabetic retinopathy (DR). It has demonstrated that VEGF -634G>C (rs2010963) polymorphism alters the transcriptional activity of the gene. However, studies on the association between VEGF -634G>C polymorphism and DR in type 2 diabetes have reported conflicting results. Thus, the aim of the present study was to investigate whether VEGF -634G>C polymorphism is associated with the risk of DR in type 2 diabetes.

METHODS

A systematic search of electronic databases (PubMed, Embase and Web of Science) and reference lists of relevant articles was carried out until September 15, 2012. The pooled odds ratios (ORs) and their corresponding 95% confidence interval (CI) were calculated by a fixed effect model.

RESULTS

A total of 1525 DR cases and 1422 diabetic without retinopathy (DWR) controls in 9 independent studies were included in the meta-analysis. A significant relationship between VEGF -634G>C polymorphism and DR was found in an allelic genetic model (OR: 1.13, 95% CI: 1.01 to 1.25, P=0.03) and a recessive genetic model (OR: 1.26, 95% CI: 1.02 to 1.55, P=0.03).

CONCLUSION

Our research confirmed the association between the VEGF -634G>C polymorphism and DR in subjects with type 2 diabetes. Well-designed studies with larger sample size and more ethnic groups are required to further validate the results.

Association of manganese superoxide dismutase and glutathione S-transferases genotypes with myocardial infarction in patients with type 2 diabetes mellitus

AIM

In the present study we investigated the association between genetic polymorphisms with functional effects on redox regulation: Val16Ala of manganese superoxide dismutase (MnSOD), polymorphic deletions of glutathione S-transferases M1 (GSTM1) and T1 (GSTT1) and Ile105Val of glutathione S-transferase P1 (GSTP1) and myocardial infarction (MI) in a group of patients with type 2 diabetes mellitus.

METHODS

The study population consisted of 463 Caucasian subjects with type 2 diabetes mellitus of more than 10 years' duration: 206 patients with MI and 257 patients with no history of coronary artery disease (CAD). Genotypes were determined by polymerase chain reaction (PCR) with restriction fragment length polymorphism (RFLP) and with multiplex PCR.

RESULTS

The genotype distributions of tested single nucleotide polymorphisms did not show significant difference between cases and controls. After adjustment for age, gender, smoking, BMI, duration of diabetes and lipid parameters carriers of GSTM1/GSTT1-null haplotype showed an increased risk for MI (OR=3.22, 95% CI 1.37-5.04, p=0.03).

CONCLUSIONS

The GSTM1/GSTT1 haplotype might be a genetic risk factor for MI in patients with type 2 diabetes mellitus.

Inflammatory cytokines in vitro production are associated with Ala16Val superoxide dismutase gene polymorphism of peripheral blood mononuclear cells

Obesity is considered a chronic low-grade inflammatory state associated with a chronic oxidative stress caused by superoxide production (O(2)(-)). The superoxide dismutase manganese dependent (SOD2) catalyzes O(2)(-) in H(2)O(2) into mitochondria and is encoded by a single gene that presents a common polymorphism that results in the replacement of alanine (A) with a valine (V) in the 16 codon. This polymorphism has been implicated in a decreased efficiency of SOD2 transport into targeted mitochondria in V allele carriers. Previous studies described an association between VV genotype and metabolic diseases, including obesity and diabetes. However, the causal mechanisms to explain this association need to be more elucidated. We postulated that the polymorphism could influence the inflammatory response. To test our hypothesis, we evaluated the in vitro cytokines production by human peripheral blood mononuclear cells (PBMCs) carrier's different Ala16Val-SOD2 genotypes (IL-1, IL-6, IL-10, TNF-α, IFN-γ). Additionally, we evaluated if the culture medium glucose, enriched insulin, could influence the cytokine production. Higher levels of proinflammatory cytokines were observed in VV-PBMCs when compared to AA-PBMCs. However, the culture medium glucose and enriched insulin did not affect cytokine production. The results suggest that Ala16Val-SOD2 gene polymorphism could trigger the PBMCs proinflammatory cytokines level. However, discerning if a similar mechanism occurs in fat cells is an open question.

Relationships between single nucleotide polymorphisms of antioxidant enzymes and disease

The presence and progression of numerous diseases have been linked to deficiencies in antioxidant systems. The relationships between single nucleotide polymorphisms (SNPs) arising from specific antioxidant enzymes and diseases associated with elevated oxidative stress have been studied with the rationale that they may be useful in screening for diseases. The purpose of this narrative review is to analyse evidence from these studies. The antioxidant enzyme SNPs selected for analysis are based on those most frequently investigated in relation to diseases in humans: superoxide dismutase (SOD2) Ala16Val (80 studies), glutathione peroxidise (GPx1) Pro197Leu (24 studies) and catalase C-262T (22 studies). Although the majority of evidence supports associations between the SOD2 Ala16Val SNP and diseases such as breast, prostate and lung cancers, diabetes and cardiovascular disease, the presence of the SOD2 Ala16Val SNP confers only a small, clinically insignificant reduction (if any) in the risk of these diseases. Other diseases such as bladder cancer, liver disease, nervous system pathologies and asthma have not been consistently related to this SOD SNP genotype. The GPx1 Pro197Leu and catalase C-262T SNP genotypes have been associated with breast cancer, but only in a small number of studies. Thus, currently available evidence suggests antioxidant enzyme SNP genotypes are not useful for screening for diseases in humans.

Association of the C47T polymorphism in SOD2 with diabetes mellitus and diabetic microvascular complications: a meta-analysis

AIMS/HYPOTHESIS

A meta-analysis was performed to assess the association of C47T (rs4880) (also called Val16Ala) polymorphism in SOD2 gene with reduced risk of diabetes mellitus, including type 1 and type 2 diabetes, and diabetic microvascular complications (DMI) including diabetic nephropathy, diabetic retinopathy and diabetic polyneuropathy.

METHODS

A comprehensive search was conducted to identify all case-control or cohort design studies of the above-mentioned associations. The fixed or random effect pooled measure was selected on the basis of homogeneity test among studies. Heterogeneity among studies was evaluated using the I (2). Meta-regression and the 'leave one out' sensitive analysis of Patsopoulos et al. were used to explore potential sources of between-study heterogeneity. Publication bias was estimated using modified Egger's linear regression test as proposed by Harbord et al.

RESULTS

Seventeen articles were included. After excluding articles that deviated from Hardy-Weinberg equilibrium in cases and/or in controls, and were also the key contributors to between-study heterogeneity, the meta-analysis showed a significant association of the C allele with reduced risk of DMI in dominant (OR 0.788, 95% CI 0.680-0.914), recessive (OR 0.808, 95% CI 0.685-0.953) and codominant (OR 0.828, 95% CI 0.751-0.913) models. It also showed a significant association with reduced risk of diabetic nephropathy in the dominant model (OR 0.801, 95% CI 0.664-0.967), and reduced risk of diabetic retinopathy in the dominant (OR 0.601, 95% CI 0.423-0.855), recessive (OR 0.548, 95% CI 0.369-0.814) and codominant (OR 0.651, 95% CI 0.517-0.820) models.

CONCLUSIONS/INTERPRETATION

The meta-analysis suggested that C allele of C47T polymorphism in SOD2 gene has protective effects on risk of DMI, diabetic nephropathy and diabetic retinopathy. This risk needs to be confirmed by further studies.

Papel do fator de crescimento vascular endotelial na angiogênese e na retinopatia diabética

A retinopatia diabética (RD) é uma complicação microvascular do diabetes melito, sendo importante causa de cegueira adquirida. Fatores angiogênicos, como o vascular endothelial growth factor (VEGF), estão envolvidos na patogênese da RD. O VEGF-A é uma citocina potente e multifuncional que atua por meio dos receptores VEGFR-1 e VEGFR-2 expressos no endotélio vascular causando aumento da permeabilidade vascular e estímulo à neovascularização em processos fisiológicos e patológicos. O VEGFR-2 é o principal mediador mitogênico, angiogênico e do aumento da permeabilidade vascular. Alguns polimorfismos do VEGF têm sido estudados na suscetibilidade e risco de progressão da RD. Importante associação entre o polimorfismo 634C/G e a presença de RD é relatada principalmente em relação ao alelo C. A homozigose CC estaria relacionada à RD proliferativa (RDP) e a níveis sérico e vítreo aumentados de VEGF, sugerindo que a presença do alelo C seja um fator de risco independente para RD. Os conhecimentos sobre o VEGF levaram ao desenvolvimento de agentes antiVEGF com o objetivo de inibir a neovascularização patológica e são uma realidade na prática médica do tratamento da RD.

Genome-wide association study of diabetic retinopathy in a Taiwanese population

PURPOSE

Diabetic retinopathy (DR) is a microvascular complication of diabetes with a complex multifactorial pathogenesis. The aim of this study was to identify the susceptibility genes that increase the risk of DR in type 2 diabetes (T2D) and to further elucidate the underlying mechanism of DR pathogenesis.

DESIGN

A case-control study.

PARTICIPANTS

We included 749 unrelated individuals with T2D (174 with DR and 575 without DR) and 100 nondiabetic controls.

METHODS

We conducted a genome-wide association study using Illumina HumanHap550-Duo BeadChips.

MAIN OUTCOME MEASURES

Compared with the genotypic distribution of single nucleotide polymorphisms (SNPs) between subjects with DR and without DR.

RESULTS

Using statistical models, we selected a total of 12 SNPs with P-values <1 × 10(-6) that were associated with DR. After controlling for diabetes duration and hemoglobin A(1C), 9 of the 12 SNPs located on 5 chromosomal regions were found to be associated with DR. Five loci not previously associated with DR susceptibility were identified in and around the following genes: MYSM1 (Myb-like, SWIRM, and MPN domains 1) located on chromosome 1p (odds ratio [OR], 1.50; 95% confidence interval [CI], 1.03-2.20); PLXDC2 (plexin domain-containing 2) located on the chromosome 10p (OR, 1.67; 95% CI, 1.06-2.65); ARHGAP22 (Rho GTPase-activating protein 22) located on chromosome 10q (OR, 1.65; 95% CI, 1.05-2.60); and HS6ST3 (heparan sulfate 6-O-sulfotransferase 3) located on chromosome 13q (OR, 2.33; 95% CI, 1.13-4.77). The SNPs rs13163610 and rs17376456 located in the unknown gene on chromosome 5q were also associated with DR (OR, 3.63; 95% CI, 1.38-9.58).

CONCLUSIONS

We identified a genetic association for susceptibility to DR in 5 novel chromosomal regions and PLXDC2 and ARHGAP22, the latter 2 of which are genes implicated in endothelial cell angiogenesis and increased capillary permeability. These findings suggest unsuspected pathways in the pathogenesis of DR.

Association between the -634C/G polymorphisms of the vascular endothelial growth factor and retinopathy in type 2 diabetes: a meta-analysis

AIMS

To investigate the association of vascular endothelial growth factor (VEGF) -634C/G polymorphism with retinopathy in type 2 diabetes.

METHODS

8 studies with 1183 cases and 1057 controls were included. Allelic and genotypic comparisons between cases and controls were evaluated.

RESULTS

Our meta-analysis did not suggest a significant association of the -634C/G polymorphism with diabetic retinopathy (DR) and proliferative diabetic retinopathy (PDR) (P>0.05). The pooled odds ratios (ORs) for allelic frequency comparison, recessive model comparison, dominant model comparison, and additive model showed that the -634C/G polymorphism is significantly associated with nonproliferative diabetic retinopathy (NPDR): OR=1.61 [95% confidence interval (CI, 1.23, 2.10)], P=0.0005, P(heterogeneity)=0.38, OR=2.24 [95% CI (1.15, 4.39)], P=0.02, P(heterogeneity)=0.24, OR=1.87 [95% CI (1.01, 3.48)], P=0.05, P(heterogeneity)=0.16, and OR=2.91 [95% CI (1.33, 6.39)], P=0.008, P(heterogeneity)=0.26, respectively. However, in sensitivity analyses, we only detected a marginally significant association of the C allele with NPDR: OR=1.54 [95% CI (1.00, 2.39)], P=0.05, P(heterogeneity)=0.17.

CONCLUSIONS

Our meta-analysis does not support the association of the VEGF -634C/G polymorphism with DR and PDR. Significant association between this polymorphism and NPDR was detected in this meta-analysis. However, this association is not robust and could be due to chance.