|Year : 2012 | Volume
| Issue : 2 | Page : 81-87
Association between 4G/4G plasminogen activator inhibitor-1 polymorphism, PAI-1 activity, and diabetic retinopathy
Hoiyda A. Abdel Rasol1, Fadia M Attia2, Somaia Ismail3, Amira A. Abdel Azeem4, Shahira R. Nowier4, Margeret A. Aziz5, Zeinab M. Osman5
1 Department of Clinical and Chemical Pathology, Fayoum University, Fayoum, Egypt
2 Department of Clinical and Chemical Pathology, Suez Canal University, Ismailia, Egypt
3 Department of Medical Molecular Genetics, Research Institute of Ophthalmology, Cairo, Egypt
4 National Research Centre, Ophthalmic Genetics, Research Institute of Ophthalmology, Cairo, Egypt
5 Department of Biochemistry and Ophthalmic, Research Institute of Ophthalmology, Cairo, Egypt
|Date of Submission||29-Nov-2011|
|Date of Acceptance||12-Jan-2012|
|Date of Web Publication||23-Jun-2014|
Hoiyda A. Abdel Rasol
Department of Clinical and Chemical Pathology, Fayoum University, Fayoum
Source of Support: None, Conflict of Interest: None
Plasminogen activator inhibitor-1 (PAI-1) is a key regulator of fibrinolysis; however, the relationship between PAI-1 and the most common diabetic microvascular complication, retinopathy, is unclear.
To examine the association between the 4G/4G polymorphism of the PAI-1 gene with diabetic retinopathy (DR) as well as with the plasma levels of the PAI-1 enzyme among Egyptian patients.
Participants and methods
Thirty-three patients who had type 2 diabetes for more than 10 years were compared with 63 patients with proliferative diabetic retinopathy (PDR). Both groups were compared with 48 control individuals. All groups were matched for age and sex. PAI-1 4G/5G genotyping was carried out by a PCR and the PAI-1 levels were measured by enzyme-linked immunosorbent assay testing.
Higher plasma PAI-1 activity was associated with a higher risk of DR. The overall frequency of the 4G allele was 54.54% among type 2 diabetes patients versus 78.79% among PDR patients (P<0.01). Using multivariate logistic regression analyses, patients with PDR had a higher representation of the genotype 4G/4G (P<0.05, odds ratio: 3.15, 95% confidence interval 0.13–0.89) and the 4G/4G patients studied had higher plasma levels of PAI-1 activity.
The PAI-1 gene polymorphism 4G/4G contributed to the genetic susceptibility to DR and a higher PAI-1 plasma level was independently associated with a higher risk of retinopathy among Egyptians.
Keywords: diabetic retinopathy, 4G/5G plasminogen activator inhibitor-1 polymorphism, PAI-1 activity
|How to cite this article:|
Abdel Rasol HA, Attia FM, Ismail S, Abdel Azeem AA, Nowier SR, Aziz MA, Osman ZM. Association between 4G/4G plasminogen activator inhibitor-1 polymorphism, PAI-1 activity, and diabetic retinopathy. Egypt J Haematol 2012;37:81-7
|How to cite this URL:|
Abdel Rasol HA, Attia FM, Ismail S, Abdel Azeem AA, Nowier SR, Aziz MA, Osman ZM. Association between 4G/4G plasminogen activator inhibitor-1 polymorphism, PAI-1 activity, and diabetic retinopathy. Egypt J Haematol [serial online] 2012 [cited 2021 Sep 18];37:81-7. Available from: http://www.ehj.eg.net/text.asp?2012/37/2/81/135059
| Introduction|| |
Type 2 diabetes (T2D) is a metabolic disorder associated with serious microvascular and macrovascular complications, including diabetic retinopathy (DR). DR is a major cause of blindness among diabetic adults, which is usually aggravated by poor glycemic control, hypertension, and longer disease duration. It is associated with a strong genetic predisposition, highlighted by the familial clustering of DR and the association of several gene polymorphisms. These include the aldose reductase, advanced glycation end-products receptor, adhesion molecules, and coagulation – and fibrinolytic – system gene polymorphisms, including the plasminogen activator system 1.
Plasminogen activator inhibitor-1 (PAI-1) is a single-chain glycoprotein, with a molecular weight of 50 000 Da, and is synthesized by endothelial cells and hepatocytes. PAI-1 regulates fibrinolysis by inhibiting tissue plasminogen activator (tPA) or urokinase. Its activity usually reflects excess of PAI-1 (fibrinolysis inhibitor), beyond that of tPA and the urokinase plasminogen activator (uPA) (fibrinolysis activators). Measurement of PAI-1 activity is then a good index for the assessment of excess fibrinolysis inhibition in blood. Studies have shown a relationship between increased PAI-1 concentrations and cardiovascular risk factors (obesity, hyperinsulinemia, hypertriglyceridemia, arteriothrombosis) 2.
In blood, fibrinolysis breaks down fibrin and maintains vessel patency, and in tissues, it breaks down the extracellular matrix and controls cell adhesion and migration and thus participates in tissue remodeling. Fibrinolysis is primarily regulated by PAI-1, which controls the extent of this potentially destructive protease system. Increased PAI-1 levels may predispose patients toward the formation of atherosclerosis plaque prone to rupture, with a high lipid-to-vascular smooth muscle cells ratio as a result of decreased cell migration 3. In patients with T2D, PAI-1 activity is elevated 4.
A sequence length polymorphism in the promoter region of the PAI-1 gene, a single guanosine insertion/deletion (I/D), commonly called 4G/5G, 675 bp upstream from the start of transcription has been identified to affect plasma PAI-1 activity levels. The 5G allele, but not the 4G allele, has been shown to contain an additional binding site for a DNA-binding protein that may play a pivotal role as a repressor during transcription. Increased concentrations of PAI-1 have been shown in individuals with the 4G/4G genotype, low levels of PAI-1 in individuals with the 5G/5G genotype, and intermediate levels in individuals with the 4G/5G genotype 5–7. If elevated levels of PAI-1 are associated with an increased risk of DR, genetic variation leading to lifelong exposure to elevated circulating PAI-1 levels may also predispose to the disease. Previous studies of the association between the 4G allele and DR have yielded conflicting results, ranging from strong links 8,9 to no association 4, 10, whereas others suggest that increased PAI-1 activity, independent of the 4G/4G genotype, may be implicated in the pathogenesis of DR 11,12.
The aim of this study is to investigate the association between the 4G/4G polymorphism of the PAI-1 gene with DR as well as with the plasma levels of the PAI-1 enzyme among Egyptian patients.
| Participants|| |
This case–control study was performed during 2009 and involved 96 unrelated Egyptian T2D patients recruited from the outpatient clinic of the Research Institute of Ophthalmology. The patients were compared with 48 age-matched and sex-matched control individuals. An informed consent was obtained from the patients and the control individuals. Patients were defined as having T2D according to the WHO criteria 13. The diagnosis of T2D was made on the basis of clinical features; none of the patients had ever had ketoacidosis and their initial T2D treatment included diet and/or oral antidiabetic drugs. Patients who required insulin had been treated with oral drugs for at least 2 years. All volunteers were asked about their smoking habits. Smokers were defined as persons smoking more than one cigarette a day; all others were classified as nonsmokers. Arterial blood pressure was measured after 5 min of rest using a standard sphygmomanometer. Hypertension was defined as a systolic blood pressure or a diastolic blood pressure 140 or 90 mmHg, respectively, or if the patient was on antihypertensive drugs. All patients were subjected to an ophthalmological examination, which included corrected visual acuity, fundus examination, slit-lamp biomicroscopic examination with and without a preset lens, and fundus photography. Proliferative diabetic retinopathy (PDR) was defined as neovascularization from the retinal surface into the vitreous space. Fundus examination shows new vessels on the disc (NVD) or new vessels elsewhere on the superficial retinal layers (NVE) or both; they may also show vitreous hemorrhage and retinal scarring. Fluorescein angiography was performed on some patients to confirm the fundus findings.
| Specimen collection|| |
A fasting venous blood sample of approximately 10 ml was withdrawn from the antecubital vein between 8:0 and 10:0 a.m. and was divided into three parts:
Four milliliters of blood was collected in a tube containing EDTA as an anticoagulant and then divided into two parts: one for the determination of glycosylated hemoglobin and the other for DNA extraction for the detection of the PAI-1 gene polymorphism.
- Four milliliters of blood was collected in a tube containing EDTA as an anticoagulant for the determination of PAI-1 activity. Plasma was aspirated from the middle layer to prevent contamination by platelet debris (platelet-poor plasma) and recentrifuged (10 min, 2500g) to obtain platelet-free plasma. The plasma was stored at −20°C for the determination of PAI-1 activity.
- Two milliliters of blood in a clean dry centrifuge tube was allowed to clot in a 37°C water bath, and centrifuged for 10 min at 3000g. Serum was divided into aliquots and stored at −20°C until assayed for total cholesterol, triglycerides, and high-density lipoprotein (HDL).
| Materials and methods|| |
PAI-1 activity was measured using the Zymutest PAI-1. The diluted plasma is introduced into a microwell coated with recombinant tPA. When present, PAI-1 binds to coated tPA. Only the active PAI-1 reacts with tPA and is fixed on the solid phase. Following a washing step, the immunoconjugate, which is a mouse monoclonal antibody specific for human PAI-1 coupled to horse radish peroxidase, is introduced, and binds to its specific epitope on immobilized PAI-1. Following another washing step, the peroxidase substrate, tetramethylbenzidine , in the presence of hydrogen peroxide, is introduced and a blue color develops. The color turns yellow when the reaction is stopped with sulfuric acid. The amount of color developed is directly proportional to the amount of human PAI-1 activity in the tested sample. The normal PAI-1 activity is usually low, as most of the PAI-1 is in the latent or in the inactive forms.
4G/5G polymorphism genotyping
Genomic DNA was extracted from peripheral venous blood using a salting-out protocol, as described by Miller et al. 14 PCR amplification of the promoter region containing the 4G/5G polymorphism was carried out to identify the PAI-1 genotypes. The PCR reaction used an upstream control primer (5º-AAG CTT TTA CCA TGG TAA CCC CTG GT-3º), an allele-specific primer 4G (5º-GTC TGG ACA CGT GGG GA-3º) or 5G (5º-GTC TGG ACA CGT GGG GG-3º), and a common downstream primer (5º-TGC AGC CAG CCA CGT GAT TGT CTA-3º). Two PCR reactions were run per sample (one for the 4G allele and one for the 5G allele), that is, each reaction contained a downstream primer, an upstream primer, and one primer for 4G or 5G. The 4G allele-specific PCR reaction mixture with a total volume of 25 µl contained 50–100 ng DNA, 1 U of Taq polymerase, 1× PCR buffer Taq, 0.8 mmol/l MgCl2, 50 µmol/l dNTPs, 200 nmol/l upstream primer, and 400 nmol/l allele-specific and downstream primers. The 5G allele-specific reaction was identical, except that MgCl2 was 1.1 mmol/l. The 4G allele thermal cycling conditions were as follows: 32 cycles of denaturation at 94°C for 35 s, annealing at 65°C for 35 s, and extension at 72°C for 70 s. The 5G allele thermal cycling conditions were the same, except that the final step involved 22 cycles and annealing was carried out at 58°C. The PCR product was electrophoresed on a 2.5% agarose gel stained with ethidium bromide. A 257 bp control band resulted from the upstream and the downstream primer. The 4G or 5G allele-specific primer and the downstream primer generated 139 bp fragments 15. Participants who showed amplification products with only 4G primers were 4G/4G heterozygote, those with only 5G primers were 5G/5G heterozygote, and those who had amplification products with both primers were 4G/5G heterozygote [Figure 1].
|Figure 1: PCR analysis of the 4G/5G insertion/deletion polymorphism of the human PAI-1 promoter. Genotyping was performed by PCR analysis using 1.5% agarose electrophoresis using a common downstream primer, a control primer (generating a 257 bp PCR product), and two allele-specific upstream primers, generating a 139 bp PCR product. For each individual, two PCR reactions (control primer, common downstream primer, and 4G-allele-specific primer or 5G-allele-specific primer, respectively) were performed. Some samples of the amplified DNA of 5G PCR using the ‘insertion’ primers for the PDR patients are shown. Patients in lanes 1, 2, 3, 5, 6, 9, 11, 14, 15, 18, 20, 21 had a 5G band at 139 bp and a control band at 257 bp. Lanes 4, 8, 10, 12, 13, 16, 17, 19 had a control band at 257 bp and no 5G band. Lane 7 shows no band for control or for amplified 5G (failure of DNA amplification). Fragment lengths are indicated by an arrow. M, ØX174 HaeIII molecular weight marker; PDR, proliferative diabetic retinopathy.|
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Glycosylated hemoglobin was measured using a cation exchange chromatography method to assess glycemic control. The procedure is a microchromatographic methodology for the quantification of glycosylated hemoglobin (nondiabetic reference range 5.5–7.7%) (GLYCO Hb Quick column procedure, Netherland) 16. Serum total cholesterol and triglyceride concentrations were determined enzymatically from blood. HDL-cholesterol was determined in the supernatant after the precipitation of the chylomicrons with phosphotungstic acid. Low-density lipoprotein (LDL)-cholesterol was calculated using the Friedewald formula 17. Patients who had serum triglyceride levels above 400 mg/dl were excluded.
Statistical analyses were carried out using the SPSS (statistical package for social science, Chicago, USA) version 17. Data were subjected to the Kolmogorov–Smirnov test to determine the distribution and method of analysis. Normally distributed quantitative variables are presented as mean±SD and the comparisons between groups were performed using Student’s t-test (age and duration of diabetes). Skewed data are expressed as median (range) and statistical significance was tested using the Mann–Whitney test as appropriate (total cholesterol, triglycerides, HDL, LDL, and PAI-1 activity). Categorical variables are given as percentages. The χ2-test was used to compare the demographic data, genotype, and allele distributions among the cases and the controls. Allele frequencies were determined using the gene-counting method. Odds ratios with 95% confidence intervals by logistic regression were used to analyze the occurrence of the frequency of genotypes after adjustment of age, sex, duration of diabetes, HbA1c, total cholesterol, triglycerides, and PAI-1 activity. The degree of association between variables was assessed using Pearson’s correlation coefficient (r). A P-value (two tailed) less than 0.05 was considered statistically significant.
| Results|| |
In this case–control study, 144 participants were enrolled. The participants’ demographic, clinical, and laboratory characteristics are shown in [Table 1]. The two groups of patients (first group with T2D, N=33, and second group with PDR, N=63) and the normal controls, N=48, were well matched in terms of sex and age (P>0.05). There were no statistically significant differences in the clinical data (duration of diabetes, hypertension, smoking, and parental consanguinity) between patients with T2D and those with PDR (P>0.05). There was a statistically increased percentage of a family history of DR in patients with DR compared with diabetic patients without retinopathy (P<0.001) and compared with the control participants (P<0.001). HbA1c, total cholesterol, triglycerides, LDL and HDL, and cholesterol levels were comparable between the PDR and the T2D patients; however, there was a statistically significant difference in PAI-1 activity concentrations (P<0.05). Also, there was a statistically significant difference between the control group and each of the studied groups (T2D and PDR) for HbA1c, total cholesterol, triglycerides, HDL, LDL, and PAI-1 activity.
|Table 1: Demographic, clinical, and laboratory characteristics of the participants studied|
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[Table 2] shows the logistic regression models of predictors of PDR: higher plasma PAI-1 activity was identified as an independent predictor of diabetic retinopathy, after adjusting for the major determinants of retinopathy (HbA1c, duration of diabetes, total cholesterol and triglycerides).
|Table 2: Logistic regression models of predictors of proliferative diabetic retinopathy|
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[Table 3] shows the correlation between PAI-1 activity and total cholesterol and triglycerides among the participants studied. PAI-1 activity plasma concentrations were positively correlated with total cholesterol (P<0.05) and triglycerides (P<0.05).
|Table 3: Correlation between plasminogen activator inhibitor-1 activity and total cholesterol, triglycerides among the participants studied|
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Determination of the PAI-1 genotypes was performed successfully in all the participants studied. Participants were classified into one of three PAI-1 genotypes: 4G/4G, 4G/5G, or 5G/5G. Genotype frequency in the control participants was (18.7% 4G/4G, 62.5% 4G/5G, and 18.7% 5G/5G). PDR genotypes were (66.7% 4G/4G, 22.2% 4G/5G, and 11.1% 5G/5G). For the T2D patients, the PAI-1 genotypes were (21.2% 4G/4G, 66.7% 4G/5G, and 12.1% 5G/5G). After adjustment for (sex, age, HbA1c, blood pressure, total cholesterol, triglycerides, and duration of T2D) in a logistic regression model, the PAI-1 4G/4G genotype was shown to represent an independent risk factor for PDR (P<0.05, odds ratio: 3.15, 95% confidence interval 0.13–0.89) [Table 4].
|Table 4: Distributions of plasminogen activator inhibitor-1 gene and allele frequencies among Egyptian type 2 diabetes patients with and without proliferative diabetic retinopathy|
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Among the T2D patients (those with and without PDR), the patients with the 4G/4G genotype had a higher frequency of PDR [Table 5] and those with the 4G/4G and 4G/5G genotypes had higher PAI-1 activity concentrations compared with those with the 5G/5G genotypes (2.5 vs. 0.9 ng/ml, P<0.01) and (1.9 vs. 0.9 ng/ml, P<0.001), respectively [Table 6].
|Table 5: Association between genotype and phenotype among Egyptian type 2 diabetes participants with and without proliferative diabetic retinopathy|
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|Table 6: Plasminogen activator inhibitor-1 activity in different genotypes|
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| Discussion|| |
The mechanism(s) by which PAI-1 influences DR pathogenesis remain to be elucidated. It is known that the retinal microvessels in T2D patients contain higher quantities of PAI-1 compared with age-matched nondiabetic controls, and that overexpression of PAI-1 in the retinal microvasculature of transgenic mice leads to retinal disease 1.
In this study, we aimed to examine the relationship between PAI-1 activity and a major complication of diabetes, retinopathy, among T2D patients. Also, we hypothesize that the PAI-1 polymorphism would influence the progression to DR. The two groups of patients (T2D patients with and without retinopathy) were matched with respect to the main demographic, clinical, and laboratory data to avoid bias caused by the influence of known risk factors and to rule out the possibility that patients were prone to DR because of longer exposure to hyperglycemia and poor glycemic control. Our T2D patients (with and without retinopathy) had a higher frequency of hypertension compared with the control participants, which is consistent with other findings that link hypertension and DR development, and also had elevated total cholesterol, triglycerides, and HbA1c, similar to the findings of the CURES Eye Study by Morange et al. 3 and Ezzidi et al. 1.
Our result, that is, higher plasma PAI-1 activity was independently associated with an increased risk of DR, after adjusting for retinopathy risk factors, agrees with the studies of Brazionis et al. 18 and Juhan-Vague et al. 19, who showed that PAI-1 activity, which is affected by the PAI-1 gene polymorphism and metabolic determinants, is elevated in patients with T2D. The relative excess of tPA may contribute to DR through impairment in cell–cell communication and neuronal degeneration and retinal toxicity. Moreover, a protective role for PAI-1 in preventing abnormal matrix remodeling has been proposed. Lipids may also modulate PAI-1 production, and links between lipids, DR, and nephropathy are known, with hypertriglyceridemia being associated with more severe DR. In addition, increased production of reactive oxygen species and inflammation may contribute to lower PAI-1 in DR. Brazionis et al. 18, Tarnow et al. 20, and Nagi et al. 21 showed that plasma PAI-1 levels were not elevated in patients with retinopathy.
There was a positive correlation between PA-1 activity and total cholesterol and triglycerides concentrations. These results are consistent with the study by Hunt et al. 22, which showed associations between the plasma levels of PAI-1 and parameters of insulin resistance, such as total cholesterol, triglycerides, HDL, LDL, and fasting glucose. PAI-1 is produced by the liver, vascular endothelium, and adipocytes. PAI-1 production is modulated by high glucose, insulin, and triglyceride-rich lipoproteins, such as very low-density lipoproteins . This is in agreement with the observed relationships between PAI-1 protein or activity levels and body habitus, insulin resistance and lipids, and the PAI-1-lowering effects of metformin, an insulin sensitizer, which also improves lipid levels. The observed link between lipid levels and PA1-1 may be related to common influencing factors of adiposity and insulin resistance. The effects of very low-density lipoproteins on hepatic and endothelial cell production or the activation of PAI-1 are also known. In a retinal microvascular cell culture system, we previously showed favorable effects on PAI-1 production by α-tocopherol enrichment of LDL 23.
The interaction between the PA/plasmin system and metabolic control is intriguing. Serum PAI-1 activity is found to be positively correlated with metabolic indices including fasting glucose, cholesterol, triglycerides, and BMI in T2D patients 24,25. This correlation effect was strongest among group of patients with the PAI-1 4G/4G genotype. Hence, patients with the PAI-1 4G/4G genotype may be more susceptible to the adverse effect of unsatisfactory metabolic control than others 26.
The frequencies of the PAI-1 (4G/5G) genotype and the 4G allele in Chinese diabetic patients (4G/4G : 4G/5G : 5G/5G=33 : 47 : 20%, 4G allele frequency=60%), were similar to those reported in Caucasian (4G/4G : 4G/5G : 5G/5G=35 : 51 : 14%, 4G allele frequency=60%) and Japanese T2D patients (4G/4G : 4G/5G : 5G/5G=31:56:13%, 4G allele frequency=60%) 26. The frequencies of the PAI-1 (4G/5G) genotype and the 4G allele of Egyptian diabetic patients was (4G/4G : 4G/5G : 5G/5G=51 : 37.5 : 11.5%, 4G allele frequency=69%).
In the present study, we described an apparent association between the 4G/4G PAI-1 genotype and DR, which seems to be an independent genetic risk factor for the prevalence of PDR in the Egyptian population. This result is in agreement with the studies of Ezzidi et al. 1, Funk et al. 9, Nagi et al. 21, and Erem et al. 8, who reported that in patients with T2D, the I/D PAI-1 gene polymorphism was shown to be associated with a higher risk of DR, with the effect of the I/D PAI-1 gene polymorphism on PAI-1 activity, but is inconsistent with other studies that failed to show any links between the 4G/5G polymorphism and DR 4, 10, 11, 12. It has also been suggested that PAI-1 4G/4G is associated with DR only in patients positive for the angiotensin-converting enzyme D/D genotype 12 or in those with elevated fibrinogen 11, thereby prompting speculation that the contribution of 4G/5G to DR might be dependent on the presence of additional risk factors. However, these conflicting findings may be reconciled by differences in ethnicity 4, 10, 11, 12, sample size 4, 10, and the failure to control for confounding factors (sex, HbA1c levels, obesity, and duration of diabetes) in some studies.
The functional I/D polymorphism, 4G/5G, is found 675 bp upstream of the transcriptional initiation site (PAI 4G, 5G) in the PAI-1 gene (7q21.3–q22). Although both alleles bind a transcriptional activator, the 5G allele reduces transcription by binding a repressor protein and is thereby associated with lower circulating PAI-1 concentrations 27. Unlike the 5G allele that binds a transcription repressor protein, resulting in low PAI-1 expression, the 4G allele does not bind a transcription repressor, thus conferring a ‘high PAI-1 expressor’ nature to the allele 1. The genetic variation in the PAI-1 gene is also associated with varying levels of PAI-1 activity in healthy individuals, in patients with coronary artery disease, and in patients with diabetes mellitus 26. Many different PAI-1 exposures have been assessed; some studies have evaluated the PAI-1 genotype, whereas others have evaluated PAI-1 activity or antigen levels in platelet-poor plasma or platelets. Our results of higher PAI-1 activity in patients with the 4G/4G genotype is consistent with the study by Tarnow et al. 22, who reported that the atherogenic allele was found more frequently in patients with DR, a condition characterized by elevated plasma PAI-1 in men, and also with the study by Kimura et al. 28, in which the PAI-1 4G/5G polymorphism was associated with plasma PAI-1 activity in patients with noninsulin-dependent diabetes mellitus with the highest level of PAI-1 activity. However, these results are inconsistent with the studies of Zietz et al. 11, Mansfield et al. 25, and Matsubara et al. 29, who found no significant association between the 4G/5G polymorphism and the plasma levels of PAI-1 in diabetic or nondiabetic patients.
This study has a number of strengths. Our findings were consistent with established associations, such as that between PAI-1 activity and PDR, indicating that the design and sample size were appropriate for the detection of these effects. Consistency in blood sample collection and handling reduced bias in the data set and circadian variation in PAI-1 activity. We used face-to-face interviews to reduce the likelihood of reporting errors in the collection of clinical, demographic, and lifestyle data.
In conclusion, we observed an association of the 4G/4G PAI-1 genotype polymorphism with DR among Egyptians. A higher PAI-1 plasma enzyme activity was independently associated with a higher risk of retinopathy, with a significant increase in the plasma levels of the participants who were homozygous for the 4G allele versus those who were homozygous for the 5G allele. If confirmed in independent studies, our findings might help explain at least some of the differences in diabetic microvascular risk profiles. These findings suggest that the examination of PAI-1 in patients with PDR may be useful for the prediction and prevention of macroangiopathy-related events.
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[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]