Plasminogen activator inhibitor-1 and apolipoprotein E gene polymorphisms and diabetic angiopathy

Serpin Family E Member 1 Tag Single-Nucleotide Polymorphisms in Patients with Diabetic Nephropathy: An Association Study and Meta-Analysis Using a Genetic Model-Free Approach

BACKGROUND

Many lines of evidence highlight the genetic contribution on the development of diabetic nephropathy (DN). One of the studied genes is SERPINE1 whose the role in the risk of developing DN remains questionable. In order to elucidate the contribution of SERPINE1 in DN progression in the context of type 2 diabetes mellitus (T2DM), we conducted an association study and meta-analysis of SERPINE1 genetic variants.

MATERIALS AND METHODS

A total of 190 patients with DN, 150 T2DM (type 2 diabetes mellitus) patients without DN and 238 healthy controls were recruited. We selected five tag single-nucleotide polymorphisms (SNPs) from the HapMap. The generalized odds ratio (ORG) was calculated to estimate the risk on DN development. Subgroup analyses based on ethnicity and type of diabetes were also performed.

RESULTS

Both the present association study regarding SERPINE1 SNPs (rs2227667, rs2070682, rs1050813, rs2227690, rs2227692) did not found any significant association between SERPINE1 variants and DN and the meta-analysis of variant 4G>5G (rs1799889) did not also reveal a significant association between 4G>5G variant and DN in main and subgroup analyses.

DISCUSSION

In conclusion, the present association study and meta-analysis provides strong evidence that SERPINE1 genetic variant 4G>5G is not implicated in the risk or development of DN in Caucasians. Further studies in other populations remain to further investigate the role of this variant in the course of DN.

The susceptibility of SERPINE1 rs1799889 SNP in diabetic vascular complications: a meta-analysis of fifty-one case-control studies

BACKGROUND

The serine protease inhibitor-1 (SERPINE1) rs1799889 single nucleotide polymorphism (SNP) has been constantly associated with diabetes mellitus (DM) and its vascular complications. The aim of this meta-analysis was to evaluate this association with combined evidences.

METHODS

The systematic search was performed for studies published up to March 2021 which assess the associations between SERPINE1 rs1799889 SNP and the risks of DM, diabetic retinopathy (DR), diabetic cardiovascular disease (CVD) and diabetic nephropathy (DN). Only case-control studies were identified, and the linkage between SERPINE1 rs1799889 polymorphism and diabetic vascular risks were evaluated using genetic models.

RESULTS

51 comparisons were enrolled. The results revealed a significant association with diabetes risk in overall population (allelic: OR = 1.34, 95 % CI = 1.14-1.57, homozygous: OR = 1.66, 95 % CI = 1.23-2.14, heterozygous: OR = 1.35, 95 % CI = 1.08-1.69, dominant: OR = 1.49, 95 % CI = 1.18-1.88, recessive: OR = 1.30, 95 % CI = 1.06-1.59) as well as in Asian descents (allelic: OR = 1.45, 95 % CI = 1.16-1.82, homozygous: OR = 1.88, 95 % CI = 1.29-2.75, heterozygous: OR = 1.47, 95 % CI = 1.08-2.00, dominant: OR = 1.64, 95 % CI = 1.21-2.24, recessive: OR = 1.46, 95 % CI = 1.09-1.96). A significant association was observed with DR risk (homozygous: OR = 1.25, 95 % CI = 1.01-1.56, recessive: OR = 1.20, 95 % CI = 1.01-1.43) for overall population, as for the European subgroup (homozygous: OR = 1.32, 95 % CI = 1.02-1.72, recessive: OR = 1.38, 95 % CI = 1.11-1.71). A significant association were shown with DN risk for overall population (allelic: OR = 1.48, 95 % CI = 1.15-1.90, homozygous: OR = 1.92, 95 % CI = 1.26-2.95, dominant: OR = 1.41, 95 % CI = 1.01-1.97, recessive: OR = 1.78, 95 % CI = 1.27-2.51) and for Asian subgroup (allelic: OR = 1.70, 95 % CI = 1.17-2.47, homozygous: OR = 2.46, 95 % CI = 1.30-4.66, recessive: OR = 2.24, 95 % CI = 1.40-3.59) after ethnicity stratification. No obvious association was implied with overall diabetic CVD risk in any genetic models, or after ethnicity stratification.

CONCLUSIONS

SERPINE1 rs1799889 4G polymorphism may outstand for serving as a genetic synergistic factor in overall DM and DN populations, positively for individuals with Asian descent. The association of SERPINE1 rs1799889 SNP and DR or diabetic CVD risks was not revealed.

Association of plasminogen activator inhibitor-1 4G5G Polymorphism with risk of diabetic nephropathy and retinopathy: a systematic review and meta-analysis

Background

The 4G5G polymorphism of Plasminogen activator inhibitor-1 (PAI-1) gene is reported to be associated with diabetes nephropathy and retinopathy (DNR) risk. However, the findings are conflicting. Herein, we conducted a case-control and meta-analysis study to explore the association of PAI-1 4G5G polymorphism with risk of DNR.

Methods

We retrieved PubMed, EMBASE, Web of Knowledge, and CNKI databases and screened eligible studies up to August 15, 2020. The strength of associations was assessed by odd ratio (OR) and the corresponding 95% confidence interval (95% CI).

Results

A total of 27 case-control studies including 16 studies with 1,825 cases case and 1,731 controls on DN and eleven studies with 1,397 cases and 1,545 controls on DR were selected. Pooled data showed that the PAI-1 4G5G polymorphism was significantly associated with DN (allele model: OR = 0.674, 95% CI 0.524-0.865, p = 0.002; homozygote model: OR = 0.536, 95% CI 0.351-0.817, p = 0.004; heterozygote model: OR = 0.621, 95% CI 0.427-0.903, p = 0.013; dominant model: OR = 0.575, 95% CI 0.399-0.831, p = 0.003; and recessive model: OR = 0.711, 95% CI 0.515-0.981, p = 0.038) and DR (homozygote model: OR = 0.770, 95% CI 0.621-0.955, p = 0.0.017) risk. Stratified analyses by ethnicity indicated that PAI-1 4G5G polymorphism was associated with DN and DR risk in Asians and Caucasians, respectively.

Conclusions

The present meta-analysis revealed that the PAI-1 4G5G polymorphism was associated with increased risk of DN and DR risk. However, well-designed large-scale clinical studies are required to further validate our results.

Apolipoprotein E-related glomerular disorders

Of the glomerular disorders that occur due to apolipoprotein E (apoE) mutations, apoE2 homozygote glomerulopathy and lipoprotein glomerulopathy (LPG) have been characterized. ApoE2 homozygote glomerulopathy has been found in individuals expressing homozygous apoE2/2. This was characterized histologically by glomerulosclerosis with marked infiltration of foam cells derived from macrophages, and occasionally with non-lamellated lipoprotein thrombi. Recently, several cases of apoE Toyonaka (Ser197Cys) combined with homozygous apoE2/2 have been reported, in which non-immune membranous nephropathy-like features were observed in glomeruli. Interestingly, in these cases, apoE accumulation was identified by tandem mass spectrometry. Therefore, it is speculated that these findings may arise from apoE molecules without lipids, which result from hinge damage by apoE Toyonaka and may cross the glomerular basement membrane as small molecules. LPG is primarily associated with heterozygous apoE mutations surrounding the low-density lipoprotein-receptor binding site, and it is histologically characterized by lamellated lipoprotein thrombi that lack foam cells. Recent studies have suggested that LPG can be induced by thermodynamic destabilization, hydrophobic surface exposure, and the aggregation of apoE resulting from the incompatibility of apoE mutated residues within helical regions. Additionally, apoE5 may play a supporting role in the development of LPG and in lipid-induced kidney diseases via hyperlipoproteinemia. Thus, it is interesting that many apoE mutations contribute to characteristic glomerular disorders through various mechanisms. In particular, macrophages may uptake lipoproteins into the cytoplasm and contribute to the development of apoE2 homozygote glomerulopathy as foam cells, and their dysfunction may contribute to the accumulation of lipoproteins in the glomerulus, causing lipoprotein thrombi in LPG.

Association between Apolipoprotein E Polymorphism and Chronic Kidney Disease in the Korean General Population: Dong-gu Study

Background

Few studies have investigated the association between Apolipoprotein E (APOE) polymorphisms and chronic kidney disease (CKD) in the general population, and their results are inconsistent.

Methods

The current study population was composed of 9,033 subjects aged ≥ 50 years who participated in the baseline survey of the Dong-gu Study, which was conducted in Korea between 2007 and 2010. APOE polymorphisms were identified by polymerase chain reaction, and the estimated glomerular filtration rate (eGFR) was calculated using the Modification of Diet in Renal Disease equation.

Results

Individuals with the APOE E2 allele had significantly lower total and low density lipoprotein cholesterol levels, those with the APOE E4 allele had lower high density lipoprotein (HDL) cholesterol levels, and those with the APOE E3 allele had lower log-triglyceride levels. Adjusting for covariates (sex, age, body mass index, smoking, systolic blood pressure, hypertension, diabetes, total cholesterol, HDL cholesterol, log-transformed triglycerides, and log-transformed albumin to creatinine ratio), mean eGFR was not significantly different among APOE alleles (E2, 69.4 mL/min/1.73 m²; E3, 69.5 mL/min/1.73 m²; E4, 69.4 ml/min/1.73 m²; P = 0.873). Additionally, the odds ratios (ORs) indicated that APOE polymorphisms were not independent risk factors for CKD (OR, 1.07; 95% confidence interval [CI], 0.91 to 1.26 for the E2 vs. E3 allele; OR, 1.01; 95% CI, 0.88 to 1.16 for the E4 vs. E3 allele).

Conclusion

APOE polymorphisms were not associated with either eGFR or CKD in the general Korean population.

Apolipoprotein polymorphism is associated with pro-thrombotic profile in non-demented dyslipidemic subjects

Apolipoprotein gene polymorphism has an important role in lipid metabolism and in the development of cerebro- and cardio-vascular disease (CCVD), including dementia. Dyslipidemia and hemostatic abnormalities are key risk factors associated with athero-sclerotic events preceding CCVD. The aim of this study was to evaluate the possible relationships of various apolipoprotein-species with hemostatic parameters and cognitive function. Lipid profile, gene polymorphism, coagulation markers, and mini-mental state examination (MMSE) scores were assessed in 109 dys-lipidemic subjects and in 107 healthy control volunteers. Thrombin-activatable fibrinolysis inhibitor (TAFI) plasma levels were significantly higher in apolipoprotein-E2 (apoE2) patients when compared to other apoE forms. The apoA5 -1131T>C polymorphism was associated with elevated D-dimer concentration in dyslipidemic TT homozygous individuals. MMSE did not correlate with lipid or coagulation profile. These data suggest that apoE and apoA5 variants have an effect on hemostatic parameters, but they neither influence nor predict cognitive performance in non-demented individuals.

PAI-1 -675 4G/5G polymorphism in association with diabetes and diabetic complications susceptibility: a meta-analysis study

A meta-analysis was performed to assess the association between the PAI-1 -675 4G/5G polymorphism and susceptibility to diabetes mellitus (DM), diabetic nephropathy (DN), diabetic retinopathy (DR) and diabetic coronary artery disease (CAD). A literature-based search was conducted to identify all relevant studies. The fixed or random effect pooled measure was calculated mainly at the allele level to determine heterogeneity bias among studies. Further stratified analyses and sensitivity analyses were also performed. Publication bias was examined by the modified Begg’s and Egger’s test. Twenty published articles with twenty-seven outcomes were included in the meta-analysis: 6 studies with a total of 1,333 cases and 3,011 controls were analyzed for the PAI-1 -675 4G/5G polymorphism with diabetes risk, 7 studies with 1,060 cases and 1,139 controls for DN risk, 10 studies with 1,327 cases and 1,557 controls for DR and 4 studies with 610 cases and 1,042 controls for diabetic CAD risk respectively. Using allelic comparison (4G vs. 5G), the PAI-1 -675 4G/5G polymorphism was observed to have no significant association with diabetes (REM OR 1.07, 95% CI 0.96, 1.20), DN (REM OR 1.10, 95% CI 0.98, 1.25), DR (REM OR 1.09, 95% CI 0.97, 1.22) or diabetic CAD risk (REM OR 1.07, 95% CI 0.81, 1.42), and similar results were obtained in the dominant, recessive and co-dominant models. Our meta-analyses suggest that the PAI-1 -675 4G/5G polymorphism might not be a risk factor for DM, DN, DR or diabetic CAD risk in the populations investigated. This conclusion warrants confirmation by further studies.

Plasma plasminogen activator inhibitor-1 is associated with end-stage proliferative diabetic retinopathy in the Northern Chinese Han population

Objective. To identify predictors of end-stage proliferative diabetic retinopathy (PDR) in a cohort of individuals with type 2 diabetes mellitus (T2DM) from the Northern Chinese Han population. Methods. We investigated characteristics of 153 consecutive diabetic patients with end-stage PDR (62 males, 91 females), 123 consecutive PDR patients without end-stage PDR (48 males, 75 females), and 151 normal subjects (63 males, 88 females). Only one eye of each patient or healthy subject was included in this study. Univariate logistic regression models and multivariate logistic regression models were constructed to evaluate the predictors of end-stage PDR. Results. In univariate analysis, systolic blood pressure, diastolic blood pressure, duration of diabetes, family history of T2DM, and plasminogen activator inhibitor-1 (PAI-1) were significently associated with end-stage PDR. After multivariate analysis, family history of T2DM, plasma PAI-1 levels, smoking, and duration of diabetes were four positive predictors associated with end-stage PDR. Conclusions. Higher plasma levels of PAI-1 were associated with end-stage PDR in the Northern Chinese Han population with T2DM.

Low but sustained coagulation activation ameliorates glucose-induced podocyte apoptosis: protective effect of factor V Leiden in diabetic nephropathy

Whereas it is generally perceived to be harmful, enhanced coagulation activation can also convey salutary effects. The high prevalence of the prothrombotic factor V Leiden (FVL) mutation in whites has been attributed to a positive selection pressure (eg, resulting from reduced blood loss or improved survival in sepsis). The consequences of enhanced coagulation activation, as observed in FVL carriers, on microvascular diabetic complications remain unknown. We therefore investigated the role of FVL in diabetic nephropathy. In heterozygous or homozygous diabetic FVL mice, albuminuria and indices of diabetic nephropathy were reduced compared with diabetic wild-type mice. This was associated with reduced glomerular apoptosis and preservation of podocytes in diabetic FVL-positive mice. In vitro, low-dose thrombin (50pM) prevented, whereas high-dose thrombin (20nM) aggravated, glucose-induced apoptosis in podocytes. In diabetic patients, the FVL mutation, but not the plasminogen activator inhibitor-1 4G/5G polymorphism, is associated with reduced albuminuria, which is consistent with a nephroprotective role of low but sustained thrombin generation. Consistently, anticoagulation of diabetic FVL-positive mice with hirudin abolished the nephroprotective effect. These results identify a nephroprotective function of low but sustained thrombin levels in FVL carriers, supporting a dual, context-dependent function of thrombin in chronic diseases.

Association analysis of ADPRT1, AKR1B1, RAGE, GFPT2 and PAI-1 gene polymorphisms with chronic renal insufficiency among Asian Indians with type-2 diabetes

BACKGROUND

To determine association of nine single nucleotide polymorphisms (SNPs) in ADP ribosyltransferase-1 (ADPRT1), aldo-keto reductase family 1 member B1 (AKR1B1), receptor for advanced glycation end-products (RAGE), glutamine:fructose-6-phosphate amidotransferase-2 (GFPT2), and plasminogen activator inhibitor-1 (PAI-1) genes with chronic renal insufficiency (CRI) among Asian Indians with type 2 diabetes; and to identify epistatic interactionss between genes from the present study and those from renin-angiotensin-aldosterone system (RAAS), and chemokine-cytokine, dopaminergic and oxidative stress pathways (previously investigated using the same sample set).

METHODS

Type 2 diabetes subjects with CRI (serum creatinine > or =3.0 mg/dl) constituted the cases (n = 196), and ethnicity and age matched individuals with diabetes for a duration of > or = 10 years, normal renal functions and normoalbuminuria recruited as controls (n = 225). Allelic and genotypic constitution of 10 polymorphisms (SNPs) from five genes namely--ADPRT1, AKR1B1, RAGE, GFPT2 and PAI-1 with diabetic CRI was investigated. The genetic associations were evaluated by computation of odds ratio and 95% confidence interval. Multiple logistic regression analysis was carried out to correlate various clinical parameters with genotypes, and to study epistatic interactions between SNPs in different genes.

RESULTS

Single nucleotide polymorphisms -429 T>C in RAGE and rs7725 C>T SNP in 3' UTR in GFPT2 gene showed a trend towards association with diabetic CRI. Investigation using miRBase statistical tool revealed that rs7725 in GFPT2 was a perfect target for predicted miRNA (hsa miR-378) suggesting the presence of the variant 'T' allele may result in an upregulation of GFPT2 contributing to diabetic renal complication. Epistatic interaction between SNPs in transforming growth factor TGF-beta1 (investigated using the same sample set and reported elsewhere) and GFPT2 genotype was observed.

CONCLUSIONS

Association of SNPs in RAGE and GFPT2 suggest that the genes involved in modulation of oxidative pathway could be major contributor to diabetic chronic renal insufficiency. In addition, GFPT2 mediated overproduction of TGF-beta1 leading to endothelial expansion and thereby CRI seems likely, suggested by our observation of a significant interaction between GFPT2 with TGF-beta1 genes. Further, identification of predicted miRNA targets spanning the associated SNP in GFPT2 implicates the rs7725 SNP in transcriptional regulation of the gene, and suggests GFPT2 could be a relevant target for pharmacological intervention. Larger replication studies are needed to confirm these observations.

Genetic diversity of the apolipoprotein E gene and diabetic nephropathy: a meta-analysis

In the past decade, a number of case-control studies have been carried out to investigate the relationship between the ApoE polymorphism and diabetic nephropathy. However, the results have been inconclusive. To investigate this inconsistency, we performed a meta-analysis of all available studies dealing with the relationship between the ApoE polymorphism and DN. The 23 studies in the meta- analysis included 6,012 diabetic patients with (n = 2,979) and without (n = 3,033) DN. The ApoE ε2 allele was significantly associated with DN (OR = 1.64, 95% CI: 1.26-2.13; P(Z) = 0.00027), whereas the ε4 allele was non-significantly associated with DN (OR = 0.93, 95% CI: 0.78-1.11; P(Z) = 0.418). However, significant heterogeneity was detected. In further subgroup analyses, genotyping methods, outcome of cases and duration of diabetes in controls were found to explain some of the heterogeneity. Genotypic analysis also found a strong association between the ε2 carriers and DN (OR = 1.61, 95% CI: 1.22-2.13; P(Z) = 0.001) and indicated that ε4 tended to have a marginally significant protective effect for DN (OR = 0.82, 95% CI: 0.65-1.03; P(Z) = 0.085). The results of our meta-analysis support a genetic association between the ApoE polymorphism and DN. ε2 increases the risk of DN in diabetes patients, while ε4 trends to be protective. These findings may have implications for therapeutic intervention in diabetic nephropathy.

Associations between apolipoprotein E gene polymorphism and plasminogen activator inhibitor-1 and atherogenic lipid profile in dialysis patients

BACKGROUND

Apolipoprotein-E (ApoE) gene polymorphism has an important role in lipoprotein metabolism and could participate in the development of cardiovascular diseases (CVD). Plasminogen activator inhibitor-1 (PAI-1) is also regarded as a risk factor for CVD. The aim of the present study is to further investigate the possible link(s) between ApoE gene polymorphism and plasma PAI-1 antigen and serum lipid profile in peritoneal dialysis (PD) and hemodialysis (HD) patients.

MATERIAL AND METHODS

We studied 72 PD patients (38 female, mean age 49.9 +/- 16.1 years), 72 HD patients (22 female, mean age 57.4 +/- 14.6 years), and 42 healthy subjects (21 female, mean age 50.1 +/- 18.6 years). Serum lipid parameters, plasma PAI-1 levels, and ApoE genotypes were determined in all subjects.

RESULTS

The distribution of ApoE genotypes and alleles frequencies was similar in dialysis patients and healthy controls. In PD patients, total cholesterol (TC), low-density lipoprotein (LDL)-C, and ApoB levels were significantly higher than that of HD patients. HD patients with E3/4 genotype had elevated TC, LDL-C and ApoB levels compared with E3/3 genotype. TC and triglyceride levels were also higher in E3/4 genotype than that of E2/3 genotype. PD and HD patients showed a significantly increased PAI-1 levels compared with controls, whereas PAI-1 levels were highest in HD patients. There was no significant relation between ApoE genotypes and PAI-1 levels.

CONCLUSIONS

The present study suggests that ApoE polymorphism significantly affects serum lipid profile in HD patients and epsilon4 allele carriers are more susceptible to have atherogenic lipid profile.

Plasminogen activator inhibitor-1 production is pathogenetic in experimental murine diabetic renal disease

AIMS/HYPOTHESIS

Plasminogen activator inhibitor-1 (PAI-1, also known as serpin peptidase inhibitor, clade E [nexin, plasminogen activator inhibitor type 1], member 1 [SERPINE1]) plays a pathogenetic role in renal fibrosis. It is upregulated in experimental and human diabetic nephropathy. These studies assessed the effect of PAI-1 deficiency and overproduction on renal disease in experimental diabetes.

MATERIALS AND METHODS

Diabetes was induced by injection of streptozotocin in 6-week-old PAI-1-deficient mice, transgenic mice overexpressing Pai-1 and control mice. Animals were killed after 24 weeks of diabetes or after observation alone.

RESULTS

Pai-1 mRNA was upregulated in kidneys from genetically normal mice with diabetes and in non-diabetic Pai-1 transgenic mice. PAI-1 was not further increased in kidneys from Pai-1 transgenic mice with diabetes. Diabetes-associated albuminuria and glomerular injury, as well as renal alpha-smooth muscle actin production, were ameliorated in diabetic PAI-1-deficient mice, an amelioration associated with attenuated increases in renal matrix metallopeptidase-2 expression and activity. Diabetic Pai-1 transgenic mice did not develop increased albuminuria or glomerular injury, but the tubulointerstitial area was modestly enhanced. In addition to the findings in diabetic mice, abnormalities also developed in 30-week-old PAI-1-deficient and Pai-1 transgenic mice without diabetes. PAI-1 deficiency resulted in increased tubulointerstitial area, TGFB1 protein and alpha-smooth muscle actin. Non-diabetic 30-week-old Pai-1 transgenic mice developed similar renal abnormalities and increased matrix metallopeptidase-2 activity, together with a modest increase in serum glucose and HbA(1c).

CONCLUSIONS/INTERPRETATION

These results demonstrate that endogenous PAI-1 deficiency protects mice from glomerular injury in longer term diabetes and that endogenous PAI-1 maintains normal renal interstitial structure in ageing not associated with diabetes.

Association of lipoprotein lipase S447X, apolipoprotein E exon 4, and apoC3 -455T>C polymorphisms on the susceptibility to diabetic nephropathy

Diabetic nephropathy (DN) is the leading cause of end-stage renal disease. In DN patients, triglyceride (TG) level is elevated and lipoprotein lipase (LPL) activity, which hydrolyzes TG, is decreased. The LPL S447X and apolipoprotein E (APOE) exon 4 polymorphisms affect TG levels, and the APOC3 -455T>C polymorphism affects LPL activity. Our aim was to examine the association of these polymorphisms with nephropathy in type 2 diabetes. We examined these polymorphisms in a case-control study of type 2 diabetic patients including 374 with DN and 392 without DN. LPL 447X-containing genotypes (447X+) were significantly decreased in DN patients [18.6 vs 25.6%, odds ratio (OR) = 0.66, p = 0.02], as were APOE epsilon3/epsilon3 genotypes (64.8 vs 73.1%, OR = 0.68, p = 0.01). In addition, combinations of genotypes [APOE epsilon3/epsilon3 and LPL 447X+ (OR = 0.56), APOC3 CC and LPL 447X+ (OR = 0.31), APOE epsilon3/epsilon3 and APOC3 CC (OR = 0.61] were protective for DN compared with the most common combination of the respective polymorphisms. Our findings suggest the importance of interactions among lipid genes in modulating the risk of DN.

Effect of polymorphisms of the MTHFR and APOE genes on susceptibility to diabetes and severity of diabetic retinopathy in Brazilian patients

Diabetes mellitus (DM) is a highly prevalent complex genetic disorder. There has been a worldwide effort in the identification of susceptibility genes for DM and its complications, and the 5-10-methylenetetrahydrofolate reductase (MTHFR) and apolipoprotein-E (APOE) genes have been considered good candidate susceptibility genes to this condition. The objectives of the present study were to determine if the 677T MTHFR and epsilon2/epsilon3/epsilon4 APOE alleles are risk factors for DM and for severity of diabetic retinopathy (DR). A total of 248 individuals were studied: 107 healthy individuals and 141 diabetic patients (46 with type 1 diabetes and 95 with type 2 diabetes), who also had DR (81 with non-proliferative DR and 60 with proliferative DR). The polymorphisms were analyzed by PCR followed by digestion with restriction enzyme or the single-nucleotide primer extension method. No evidence of association between the 677TT genotype of MTHFR gene and DM [cases: TT = 10/95 (10.6%); controls: TT = 14/107 (13%)] or with severity of DR was observed [cases: TT = 5/60 (8.5%); controls: TT = 9/81 (11.1%); P > 0.05]. We also did not find evidence of an association between APOE alleles and proliferative DR (epsilon2, epsilon3 and epsilon4 in cases: 9, 76, and 15%, and in controls: 5, 88, and 12%, respectively) but the carriers of epsilon2 allele were more frequent among patients with type 2 DM and DR than in controls [cases: 15/95 (15.8%); controls: 7/107 (6.5%); P < 0.05]. Therefore, our results suggest that the epsilon2 allele/APOE might be a risk factor for diabetes in the Brazilian population.

Apolipoprotein E gene polymorphisms are not associated with diabetic retinopathy: the atherosclerosis risk in communities study

PURPOSE

Polymorphism of the apolipoprotein E (APOE) gene has been associated with dyslipidemia and cardiovascular disease. This study examines the association of APOE polymorphisms and diabetic retinopathy.

DESIGN

Population-based cross-sectional study.

METHODS

We studied 1,398 people aged 49 to 73 years with diabetes selected from four United States communities. We performed retinal photography on one randomly selected eye and graded for the presence and severity of diabetic retinopathy using a modification of the Early Treatment Diabetic Retinopathy Study scale. We performed genotyping of common polymorphic APOE alleles using polymerase chain reaction on genomic DNA from venous blood leukocytes.

RESULTS

The prevalence of diabetic retinopathy and hard exudates was 15.0% and 5.3% in Caucasians (n = 935), and 24.6% and 9.7% in African-Americans (n = 463), with type 2 diabetes. APOE gene polymorphisms were not associated with diabetic retinopathy in either Caucasians or African-Americans. In African-Americans, the 2/4 genotype (n = 6) was associated with increased prevalence of hard exudates (odds ratio [OR] 4.10, 95% confidence interval [CI] 1.30 to 12.90), as was the 2/3 genotype (n = 9, OR 2.64, 95% CI 1.01 to 6.95). No association between APOE genotypes and hard exudates was found in Caucasians.

CONCLUSIONS

These data suggest that APOE gene polymorphisms are not associated with diabetic retinopathy in either Caucasians or African-Americans with type 2 diabetes.

Impact of Lipoprotein Glomerulopathy on the Relationship Between Lipids and Renal Diseases

Lipoprotein glomerulopathy (LPG) is a unique entity of renal lipidosis characterized by peculiar histopathologic characteristics of lipoprotein thrombi and an abnormal plasma lipoprotein profile resembling type III hyperlipoproteinemia, with a marked increase in serum apolipoprotein E (apoE) concentrations. At present, 65 cases have been reported worldwide, although most patients are found in Japan and east Asian countries. Recently, we identified 4 types of novel apoE mutations associated with LPG. In particular, a mutation designated apoE Sendai, in which arginine 145 is substituted with proline, occurs in the majority of Japanese patients. The virus-mediated transduction of apoE Sendai resulting in the development of LPG in apoE-deficient mice confirms the etiologic role of apoE mutation in LPG. Conversely, experimental graft-versus-host disease induced in Fc receptor gamma-chain-deficient mice showed LPG-like lesions in glomeruli without apoE mutations. Considered together, we believe that intrinsic factors in the kidney also contribute to the induction of LPG. Today, apoE and related lipid abnormalities are reported to have an important role in the development of various renal diseases, eg, diabetic nephropathy and immunoglobulin A nephropathy. In this article, we review clinical and histopathologic features of LPG, describe the etiologic role of apoE variants and intrinsic renal factors, and discuss the impact of LPG on mechanisms of other renal diseases.

Assessment of 115 candidate genes for diabetic nephropathy by transmission/disequilibrium test

Several lines of evidence, including familial aggregation, suggest that allelic variation contributes to risk of diabetic nephropathy. To assess the evidence for specific susceptibility genes, we used the transmission/disequilibrium test (TDT) to analyze 115 candidate genes for linkage and association with diabetic nephropathy. A comprehensive survey of this sort has not been undertaken before. Single nucleotide polymorphisms and simple tandem repeat polymorphisms located within 10 kb of the candidate genes were genotyped in a total of 72 type 1 diabetic families of European descent. All families had at least one offspring with diabetes and end-stage renal disease or proteinuria. As a consequence of the large number of statistical tests and modest P values, findings for some genes may be false-positives. Furthermore, the small sample size resulted in limited power, so the effects of some tested genes may not be detectable, even if they contribute to susceptibility. Nevertheless, nominally significant TDT results (P < 0.05) were obtained with polymorphisms in 20 genes, including 12 that have not been studied previously: aquaporin 1; B-cell leukemia/lymphoma 2 (bcl-2) proto-oncogene; catalase; glutathione peroxidase 1; IGF1; laminin alpha 4; laminin, gamma 1; SMAD, mothers against DPP homolog 3; transforming growth factor, beta receptor II; transforming growth factor, beta receptor III; tissue inhibitor of metalloproteinase 3; and upstream transcription factor 1. In addition, our results provide modest support for a number of candidate genes previously studied by others.

Influence of apolipoprotein E genotype on progression of diabetic nephropathy

AIMS

Diabetic nephropathy progresses at a variable rate part of which may be explained by genetic polymorphisms. ApoE polymorphisms are associated with progression of atherosclerosis and because of the similarities between atherosclerosis and glomerulosclerosis, we chose to examine apoE and its role in progression of diabetic nephropathy.

METHODS

The apoE genotypes of 90 patients with type 2 diabetes and nephropathy who were recruited into a 2-year prospective randomised controlled study comparing intensive medical management with routine clinical care were analysed. The primary endpoint was the rate of progression of renal disease in the second year.

RESULTS

The apoE genotype frequencies were 49 with E3/3, 20 with E2/3, 17 with E3/4 and 4 with of E2/4. There were no significant differences in age, degree of renal failure, BP, albuminuria or glycaemic control between any genotype. The rate of progression of renal failure of patients with the E3/4 genotype was 0.80 ml/min/month compared to 0.30 ml/min/month for E2/3 and 0.18 ml/min/month for those with E3/3. Patients with E3/4 genotype had significantly faster rates of progression in the second year when compared with the other 3 genotypes (0.80 vs. 0.25 ml/min/month, p = 0.012). There was no difference in mortality according to apoE genotype.

CONCLUSION

Patients who possess the apoE3/4 genotype had significantly faster rates of progression of renal failure.

Evidence for different susceptibility genes for proteinuria and ESRD in type 2 diabetes

Proteinuria and impaired kidney function are 2 major traits of diabetic nephropathy that aggregate (are heritable) in families of diabetic individuals. Although both traits are heritable, they are not genetically correlated. These findings not only support the hypothesis that the development of diabetic nephropathy consists of 2 distinct disease processes (ie, increasing proteinuria and declining kidney function) but also strongly justify searches for the putative genes that separately determine variation in these processes. These searches have used both genome-wide scans and candidate-gene approaches. By use of genome-scan approaches, several research groups have identified genetic regions on chromosomes 7q, 18q, and 22q that harbor genes that determine either variation in urinary albumin excretion or susceptibility to proteinuria in families who have type 2 diabetes. The evidence for linkage in these 3 genetic regions was suggestive or strong, but, except for 7q, the regions did not overlap across studies. Two genome scans performed in families who have type 2 diabetes identified genetic regions on chromosome 3q, 6q, 7p, and 18q that harbor susceptibility genes that determine variation in glomerular filtration rate or susceptibility to the development of end-stage renal disease (ESRD). The region on 7p overlapped in both studies. Optimism is growing that a positional cloning approach applied to these putative genetic regions will lead to the isolation of the susceptibility genes for proteinuria and ESRD. Meanwhile, significant efforts that make use of the candidate-gene approach have been directed to the search for susceptibility genes for diabetic nephropathy. Unfortunately, positive findings have not been consistent.

Diabetic nephropathy: of mice and men

Accumulating evidence supports intrinsic genetic susceptibility as an important variable in the progression of diabetic nephropathy in people. Mice provide an experimental platform of unparalleled power for dissecting the genetics of mammalian diseases; however, phenotypic analysis of diabetic mice lags behind that already established for humans. Standardized benchmarks of hyperglycemia, albuminuria, and measurements of renal failure remain to be developed for different inbred strains of mice. The most glaring deficiency has been the lack of a diabetic mouse model that develops progressively worsening renal insufficiency, the sine qua non of diabetic nephropathy in humans. Differences in susceptibility of these inbred strains to complications of diabetes mellitus provide a possible avenue to dissect the genetic basis of diabetic nephropathy; however, the identification of those strains and/or mutants most susceptible to renal injury from diabetes mellitus is lacking. Identification of a mouse model that faithfully mirrors the pathogenesis of DN in humans will undoubtedly facilitate the development of new diagnostic and therapeutic interventions.

Mouse models of diabetic nephropathy

Mice provide an experimental model of unparalleled flexibility for studying mammalian diseases. Inbred strains of mice exhibit substantial differences in their susceptibility to the renal complications of diabetes. Much remains to be established regarding the course of diabetic nephropathy (DN) in mice as well as defining those strains and/or mutants that are most susceptible to renal injury from diabetes. Through the use of the unique genetic reagents available in mice (including knockouts and transgenics), the validation of a mouse model reproducing human DN should significantly facilitate the understanding of the underlying genetic mechanisms that contribute to the development of DN. Establishment of an authentic mouse model of DN will undoubtedly facilitate testing of translational diagnostic and therapeutic interventions in mice before testing in humans.

Apolipoprotein E and renal disease

Apolipoprotein E (ApoE) is a major constituent of plasma lipoproteins with many biological actions of great significance. Beyond the known influence of ApoE polymorphisms on serum lipid profile, the pathogenesis of atherosclerosis, and the development of neurodegenerative disorders, ApoE also has a major role in the pathogenesis and progression of a variety of renal diseases, as well as in the atherosclerotic complications associated with them. Briefly, the polymorphisms of ApoE are major determinants of plasma lipid levels in uremic patients. They may affect the risk for cardiovascular disease in this population, predispose to the development of diabetic nephropathy, influence the severity of certain glomerulopathies, and regulate mesangial and glomerular functions locally in the kidney microenvironment. Finally, certain mutations of the ApoE gene are associated with a recently described nephropathy, termed lipoprotein glomerulopathy.

APOE polymorphism and the progression of diabetic nephropathy in Japanese subjects with type 2 diabetes: results of a prospective observational follow-up study

OBJECTIVE

The aim of this study is to clarify the conflicting results of the epsilon2/epsilon3/epsilon4 APOE polymorphism as a risk factor on diabetic nephropathy by a cohort study.

RESEARCH DESIGN AND METHODS

A total of 429 Japanese subjects with type 2 diabetes and with normoalbuminuria (n = 299) or with microalbuminuria (n = 130) were enrolled in a prospective observational follow-up study during 1995-1998 and followed until 2001 (for at least 3 years). The endpoint was the occurrence of a renal event defined as the progression to a higher stage of diabetic nephropathy.

RESULTS

During the study (the mean follow-up period: 4.4 +/- 1.0 years), 31 of 429 subjects progressed: 21 from normoalbuminuria to microalbuminuria and 10 from microalbuminuria to overt proteinuria. The allele frequency of the APOE polymorphism was significantly different between the progressors and the nonprogressors. Eight of 42 epsilon2 carriers (19%) progressed, whereas 23 of 387 noncarriers (6%) progressed with a relative risk of 3.2 (95% CI 1.5-6.7). When subjects were stratified by renal status at baseline, each relative risk for the progression in the epsilon2 carriers was 2.7 (0.99-7.4) in those with normoalbuminuria and 4.2 (1.3-13.3) in those with microalbuminuria. Furthermore, when analyzed only in subjects with normoalbuminuria and short duration of diabetes (<15 years) at baseline, the risk in the epsilon2 carriers became higher to 3.2 (1.2-8.8).

CONCLUSIONS

Our follow-up study indicates that the epsilon2 allele of the APOE polymorphism is a prognostic risk factor for both the onset and the progression of diabetic nephropathy in Japanese type 2 diabetes.

Molecular genetics of microvascular disease in diabetic retinopathy

Diabetic retinopathy is a sight-threatening complication of the retinal microvasculature. While important environmental factors have been clearly identified as influencing its development, increasing evidence suggests that diabetic retinopathy has a genetic component. A variety of studies have explored associations between candidate genes and frequency and severity of retinopathy. Overall, this review has found that the majority of candidate genes studied exhibit weak or no association with retinopathy status, and where associations have been detected these results have not been replicated in multiple populations. This may reflect inaccurate case definition, small subject numbers and possibly inadequate markers for genetic studies.

Kidney disease, genotype and the pathogenesis of vasculopathy

PURPOSE OF REVIEW

The two leading causes of end-stage renal disease in the United States are diabetes mellitus and hypertensive nephrosclerosis, accounting for over two-thirds of all cases. In many patients both diseases are associated with small- and large-vessel disease, commonly attributed to hypertension or accelerated atherosclerosis. Recent investigations, however, have suggested that renal large-vessel and microvascular disease may be independent contributors to progressive kidney failure.

RECENT FINDINGS

Although genes have not been definitely linked to renal vascular disease, population- and family-based epidemiology of kidney disease, segregation analysis of Pima and Caucasian families in which diabetic nephropathy is clustered, and the positional cloning of genes responsible for rare, familial glomerulosclerosis syndromes support the hypothesis that genes regulate the pathogenesis of renal disease. This review highlights developments in our current understanding of vasculopathy and its role in renal disease, and it summarizes evidence suggesting that genetic determinants for the vascular phenotype are associated with common causes of chronic renal failure.

SUMMARY

With the application of genomics and proteomics methodologies to drug discovery, the identification of renal susceptibility genes should identify new mechanisms of progressive renal disease pathogenesis and generate novel target molecules for the treatment of kidney disease.

Chronic graft dysfunction in renal transplant patients: potential role of plasminogen activator inhibitor type 1

BACKGROUND

Chronic allograft nephropathy is the main cause of long-term kidney graft loss. The plasminogen activator inhibitor type 1 (PAI-1) is a potential fibrogenic molecule whose secretion is regulated by several metabolic, inflammatory, and genetic factors. We aimed to determine whether PAI-1 secretion in renal transplant patients is correlated with the decline in renal function after transplantation.

METHODS

Renal transplant patients (145 male/71 female) were included in the study 1-27 years after transplantation (median of follow-up: 7.35 years). At inclusion, routine clinical and biological data were collected, the 4G/5G polymorphism of the recipient PAI-1 gene was determined, and the PAI-1 plasma level was measured.

RESULTS

The mean rate of decline in renal function was -4.26+/-0.30 ml/min/year. By multiple linear regression analysis, the rate of decline in renal function was significantly correlated with proteinuria (P=0.0176), occurrence of late acute rejection episodes (P=0.0001), and PAI-1 plasma level (P=0.0051). In addition, PAI-1 plasma level was also significantly correlated with body mass index (P=0.038), insulin (P<0.0001), platelet count (P<0.0001), and fibrinogen (P=0.024). The PAI-1 gene polymorphism tested did not influence the rate of decline in renal function after transplantation nor the plasma level of PAI-1 antigen.

CONCLUSION

We conclude that PAI-1, whose secretion is determined in large part by metabolic and inflammatory factors, may be implicated in the rate of decline in renal function after transplantation.

Progression of diabetic nephropathy: role of plasma homocysteine and plasminogen activator inhibitor-1

Among patients with diabetic nephropathy, the decline in glomerular filtration rate (GFR) varies substantially, ranging from 2 to 20 mL/min per year. Identification of predictors of progression in diabetic nephropathy is important. Plasma total homocysteine (tHcy) rises with urinary albumin excretion rate in diabetes, and plasminogen activator inhibitor-1 (PAI-1) has been correlated with increased matrix accumulation in various glomerulopathies. In this prospective observational cohort study, we evaluated the importance of baseline tHcy and PAI-1 as predictors of the rate of decline in GFR. Baseline tHcy and PAI-1 were measured in 157 type 1 diabetic patients with diabetic nephropathy (92 men; mean age, 41 +/- 10 years; mean diabetes duration, 27 +/- 8 years; median GFR, 80 mL/min/1.73 m(2) [range, 23 to 143 mL/min/1.73 m(2)]). Hereafter, GFR was measured yearly with a plasma clearance technique for at least 3 years (median, 7 years [range, 3.0 to 8.3 years]). The mean rate of decline in GFR was 3.7 +/- 0.3 mL/min per year. A linear regression analysis revealed a borderline significant relationship between rate of decline in GFR and tHcy (P = 0.069) and PAI-1 (P = 0.087). Analysis of the rate of decline in GFR and tertiles of tHcy and PAI-1 revealed that increasing levels of tHcy were correlated with a significantly faster decline in GFR (P = 0.025), whereas increasing levels of PAI-1 were not. After adjustment for other well-established risk factors for progression of nephropathy in a multiple linear regression analysis, however, neither tHcy levels nor PAI-1 levels were independent predictors of rate of decline in GFR.

Genetic susceptibility to macrovascular complications of type 2 diabetes mellitus

Patients with type 2 diabetes mellitus have a threefold increased risk of developing macrovascular disease such that 75% of such patients will die of cardiovascular complications. This increased risk is, however, not completely explained by traditional risk factors such as smoking, hypercholesterolaemia, hypertension and glycaemic control. Moreover, the fact that not all patients with type 2 diabetes develop these complications, together with evidence of family clustering (a heritability of 50%), suggests that a proportion of the susceptibility to ischaemic heart disease in type 2 diabetes may be genetic. Unravelling the polygenic susceptibility factors for the complications of a disease that itself has multifactorial inheritance has proved difficult and has focused largely on the candidate gene approach. A review of some of the studies testing candidate genes specifically in patients with both type 2 diabetes and ischaemic heart disease is presented. These studies focus largely on four main areas: lipoprotein metabolism, glycation and oxidation pathways, haemostatic cascade, and other candidate genes.

Apolipoprotein E gene polymorphism is not a strong risk factor for diabetic nephropathy and retinopathy in Type I diabetes: case-control study

BACKGROUND

The gene encoding apolipoprotein E (APOE) has been proposed as a candidate gene for vascular complications in Type I diabetes. This study aimed to investigate the influence of three-allelic variations in the APOE gene for the development of diabetic retinopathy and nephropathy.

RESULTS

Neither APOE alleles frequencies or APOE genotypes frequencies differed between Type I diabetic groups either with or without nephropathy. Similar results were found for patients with and without diabetic retinopathy.

CONCLUSIONS

APOE gene polymorphism does not determine genetic susceptibility for the development of diabetic retinopathy in Type I diabetes patients. Association between APOE gene polymorphism and diabetic nephropathy may be weak or moderate, but not strong.