Association of polymorphisms in the erythropoietin gene with diabetic retinopathy: a case–control study and systematic review with meta-analysis

Background

Diabetic retinopathy (DR) is characterized by ischemia, hypoxia, and angiogenesis. Erythropoietin (EPO), an angiogenic hormone, is upregulated in DR, and the association of EPO genetic variants with DR is still uncertain, as conflicting results have been reported. Therefore, we performed a case–control study followed by a meta-analysis to investigate whether the rs1617640, rs507392, and rs551238 polymorphisms in EPO gene are associated with DR.

Methods

The case–control study included 1042 Southern Brazilians with type 2 diabetes (488 without DR and 554 with DR). Eligible studies for the meta-analysis were searched from electronic databases up to June 1, 2021. Pooled odds ratios (ORs) and 95% confidence intervals (CIs) were estimated for five genetic inheritance models.

Results

The minor alleles of the EPO polymorphisms had nearly the same frequency in all groups of patients (35%), and no association was detected with DR in the case–control study. The meta-analysis included 14 independent sets of cases and controls with 9117 subjects for the rs1617640 polymorphism and nine independent sets with more than 5000 subjects for the rs507392 and rs551238 polymorphisms. The G allele of the rs1617640 polymorphism was suggestively associated with DR under the dominant (OR = 0.82, 95% CI: 0.68–0.98), heterozygous additive (OR = 0.82, 95% CI: 0.69–0.97), and overdominant (OR = 0.88, 95% CI: 0.79–0.97) models. In the subgroup analyses, the G allele was also suggestively associated with proliferative DR (PDR), non-proliferative DR (NPDR), and DR (PDR + NPDR) among patients with type 1 diabetes (T1DM) or non-Asian ancestry. After considering the Bonferroni correction for multiple comparisons, the G allele remained associated with NPDR and DR in T1DM. Regarding the rs507392 and rs551238 polymorphisms, no association was found between these variants and DR.

Conclusion

Our findings provide additional support to EPO as a susceptibility gene for DR, with the rs1617640 polymorphism deserving further investigation.

Serum levels and polymorphisms of matrix metalloproteinases (MMPs) in carotid artery atherosclerosis: higher MMP-9 levels are associated with plaque vulnerability

CONTEXT

Matrix metalloproteinases are involved in atherosclerosis and plaque vulnerability.

OBJECTIVE

To investigate serum levels and genetic polymorphisms of matrix metalloproteinases (MMPs) -1, -3 and -9 in patients submitted to carotid endarterectomy.

METHODS

Genetic polymorphisms were evaluated using polymerase chain reaction (PCR-RFLP); serum levels were measured using ELISA; histological sections were stained with Picrosirius Red to analyze the fibrous cap thickness, lipid core and collagen content and with hematoxylin--eosin to detect the presence of intraplaque hemorrhage.

RESULTS

MMP-9 serum levels were significantly higher in patients with a thinner fibrous cap (p = 0.033) or acute or recent intraplaque hemorrhage (p = 0.008) on histology, as well as in patients with previous stroke (p = 0.009) or peripheral vascular disease (p = 0.049). No consistent associations were observed between different MMP genotypes and fibrous cap thickness, lipid core, collagen content or intraplaque hemorrhage.

CONCLUSIONS

MMP-9 serum levels were consistently associated with markers of carotid atherosclerosis and lesion vulnerability, whereas specific MMP genotypes were not.

Association study of sorbitol dehydrogenase -888G>C polymorphism with type 2 diabetic retinopathy in Caucasian-Brazilians

Diabetic retinopathy (DR) is a common chronic complication of diabetes and remains the leading cause of blindness in working-aged people. Hyperglycemia increases glucose flux through the polyol pathway, in which aldose reductase converts glucose into intracellular sorbitol, which is subsequently converted to fructose by sorbitol dehydrogenase (SDH). The accelerated polyol pathway triggers a cascade of events leading to retinal vascular endothelial dysfunction and the eventual development of DR. Polymorphisms in the gene encoding aldose reductase have been consistently associated with DR. However, only two studies have analyzed the relationship between polymorphisms in the gene encoding SDH (SORD) and DR. In this case-control study, we investigated whether the -888G > C polymorphism (rs3759890) in the SORD gene is associated with the presence or severity of DR in 446 Caucasian-Brazilians with type 2 diabetes (241 subjects with and 205 subjects without DR). The -888G > C polymorphism was also examined in 105 healthy Caucasian blood donors, and the genotyping of this polymorphism was carried out by real-time PCR. The genotype and allele frequencies of the -888G > C polymorphism in patients with type 2 diabetes were similar to those of blood donors (G allele frequency = 0.16 in both groups of subjects). Similarly, the genotype and allele frequencies in patients with DR or the proliferative form of DR were similar to those of patients without this complication (P > 0.05 for all comparisons). Thus, our findings suggest that the -888G > C polymorphism in the SORD gene is not involved in the pathogenesis of DR in type 2 diabetes.

Risk factors for hypertensive disorders of pregnancy in southern Brazil

OBJECTIVE

The aim of the study was to identify the frequency of risk factors for hypertensive disorders in pregnancy in Southern Brazil.

METHODS

The study included 161 patients with hypertensive disorders and 169 control subjects matched by age and ethnicity. The frequency of the risk factors was compared by Fisher's exact test, chi-square and Student's t test. A multivariate logistic regression analysis assessed the independent role of clinical, social and demographic factors which were associated with occurrence of the hypertensive disease in pregnancy in the univariate analysis.

RESULTS

Patients enrolled in the study were predominantly Caucasian (73%) and the mean age was 29. In the multivariate analysis, the variables associated were: family history of preeclampsia (p = 0.001; OR = 3.88; 95% CI = 1.77-8.46), diabetes (p = 0.021; OR = 3.87; 95% CI = 1.22-12.27) and chronic hypertension (p = 0.002; OR = 7.05; 95% CI = 1.99-24.93).

CONCLUSION

The risk factors associated with hypertensive disorders in pregnancy appear to be similar to those reported in other countries. The knowledge of the risk factors could be helpful in a prenatal care.

The catalase -262C/T promoter polymorphism and diabetic complications in Caucasians with type 2 diabetes

Catalase is a central antioxidant enzyme constituting the primary defense against oxidative stress. In this study, we investigated whether the functional -262C/T polymorphism in the promoter of catalase gene is associated with the presence of diabetic retinopathy (DR), diabetic nephropathy (DN) and ischemic heart disease (IHD) in 520 Caucasian-Brazilians with type 2 diabetes. The -262C/T polymorphism was also examined in 100 Caucasian blood donors. Patients underwent a clinical and laboratory evaluation consisting of a questionnaire, physical examination, assessment of diabetic complications and laboratory tests. Genotype analysis was performed using the polymerase chain reaction followed by digestion with restriction enzyme. The genotype and allele frequencies of the -262C/T polymorphism in patients with type 2 diabetes were very similar to those of blood donors (T allele frequency=0.20 and 0.18, respectively). Likewise, there were no differences in either genotype or allele frequencies between type 2 diabetic patients with or without DR, DN or IHD. Thus, our results do not support the hypothesis that the -262C/T polymorphism is related to the development of DR, DN or IHD in patients with type 2 diabetes. Further studies are necessary to elucidate the role of catalase gene polymorphisms in the pathogenesis of diabetic complications.

The -106CC genotype of the aldose reductase gene is associated with an increased risk of proliferative diabetic retinopathy in Caucasian-Brazilians with type 2 diabetes

Diabetic retinopathy is a sight-threatening chronic complication of diabetes mellitus and is the leading cause of acquired blindness in adults. The -106C>T polymorphism in the promoter region of the aldose reductase (AR) gene has been shown to be associated with the susceptibility to diabetic nephropathy in type 2 diabetes, but the findings regarding the occurrence of diabetic retinopathy are conflicting. In this case-control study, we investigated whether the -106C>T polymorphism in the AR gene is involved in the development and progression of diabetic retinopathy in 579 Brazilians with type 2 diabetes (424 Caucasian- and 155 African-Brazilians). Patients underwent a clinical and laboratory evaluation consisting of a questionnaire, physical examination, assessment of diabetic complications and laboratory tests. Genotype analysis was performed using the polymerase chain reaction followed by digestion with restriction enzyme. Logistic regression analysis was used to control for independent risk factors associated with diabetic retinopathy. There were no differences in either genotype or allele frequencies for the -106C>T polymorphism between type 2 diabetic patients with or without diabetic retinopathy, in both ethnic groups. However, the CC genotype was associated with an increased risk of having proliferative diabetic retinopathy in Caucasian-Brazilians with type 2 diabetes (odds ratio (OR)=2.04; 95% confidence interval (CI)=1.21-3.45; P=0.007), independently of other risk factors associated with this complication. Thus, our results show that the -106CC genotype (-106C>T polymorphism) in the AR gene is related to the progression of diabetic retinopathy in Caucasian-Brazilians with type 2 diabetes.

The -374A allele of the receptor for advanced glycation end products gene is associated with a decreased risk of ischemic heart disease in African-Brazilians with type 2 diabetes

Three functional polymorphisms described in the promoter of receptor for advanced glycation end products (RAGE) gene were shown to have a marked effect on transcriptional activity. The few studies which analyzed the relationship between these three polymorphisms and the diabetic complications have shown conflicting results. In this case-control study, we evaluated the association between the -429T>C, the -374T>A and the 63bp insertion/deletion (I/D) polymorphisms in the RAGE gene, and the presence of diabetic retinopathy, diabetic nephropathy and ischemic heart disease, in 703 Brazilians with type 2 diabetes (520 Caucasian- and 183 African-Brazilians). Patients underwent a clinical and laboratory evaluation consisting of a questionnaire, physical examination, assessment of diabetic complications and blood collection. Genotype analysis was performed using the polymerase chain reaction and allele-specific restriction. Logistic regression analyses were used to examine associations between the clinical and genetic variables and the presence of diabetic complications. No association between the -429C, the -374A and the 63bp D alleles and diabetic retinopathy, diabetic nephropathy or ischemic heart disease was observed in Caucasian-Brazilians with type 2 diabetes. However, the -374A allele was associated with a decreased risk of having ischemic heart disease in African-Brazilian type 2 diabetic patients [odds ratio (OR)=0.35; 95% confidence interval (CI)=0.15-0.81; P=0.014], independently of other risk factors associated with this complication. Thus, our results show that the -374A allele (-374T>A polymorphism) in the RAGE gene is related to the susceptibility of developing ischemic heart disease in African-Brazilians with type 2 diabetes.

Prevalência de complicações micro e macrovasculares e de seus fatores de risco em pacientes com diabetes melito do tipo 2 em atendimento ambulatorial

BACKGROUND

Type 2 diabetes (DM2) has been related to the development of macroangiopatic [coronary heart disease (CHD), peripheral vascular disease (PVD) and stroke] and microangiopatic [retinopathy, nephropathy, and distal sensory neuropathy (DSN)] complications. The aims of this study were to analyze prevalence of complications in DM2 patients and to estimate their associated risk factors.

METHODS

Cross-sectional study, including 927 out patients with DM2 from three medical centers in Rio Grande do Sul: Hospital de Clinicas de Porto Alegre (n = 475), Grupo Hospitalar Conceicao (n = 229) and Hospital Sao Vicente de Paula (n = 223). Of the patients 42% were male, mean age was 59 +/- 10 years and the median known duration of DM2 was 11 (5-43) years. Retinopathy was identified by direct fundoscopy; CHD by WHO questionnaire and/or abnormal ECG and/or perfusion abnormalities on myocardial scintigraphy; DSN by compatible symptoms and absent sensation on 10 g monofilament and/or tune fork; PVD by the presence of claudication and absent foot pulses; stroke by presence of sequels and history; and nephropathy by the urinary albumin excretion rate (>20 microg/min). Hypertension was defined by blood pressure (>140/90 mmHg) and/or use of antihypertensive drugs. Body mass index (BMI, kg/m2) and waist-to-hip ratio (WHR) were calculated.

RESULTS

CHD was present in 36% and PVD in 33% of the patients. Among the microvascular, 37% had nephropathy (12% with macroalbuminuria); 48% retinopathy (15% proliferative retinopathy). DSN was present in 36%. Seventy three percent of the patients presented arterial hypertension. Cholesterol levels were >200 mg/dl in 64% and BMI > 30 kg/m2 in 36%. Twenty two percent of patients were smokers and 21% ex-smokers.

CONCLUSION

Diabetic complications are frequent among out patients referring to general hospitals. Almost all patients presented at least one risk factor for cardiovascular disease, justifying the efforts for identification and adequate control.