Association of endothelial nitric oxide synthase Glu298Asp, 4b/a, and -786T>C gene variants with diabetic nephropathy

Association between nitric oxide synthase (NOS3) gene polymorphisms and diabetic nephropathy: An updated meta-analysis

Polymorphisms located within NOS3 gene have been investigated as susceptibility variants for diabetic nephropathy (DN) in type 2 diabetes mellitus (T2DM) in a large number of studies. However, these previous articles yielded inconsistent results and we aimed at elucidating the impact of NOS3 variants on DN risk in T2DM by conducting an updated systematic data synthesis. A total of 36 studies (12,807 participants) were selected for qualitative data synthesis, while 33 records with 11,649 subjects were included in the meta-analysis. The pooled analysis demonstrated the association of minor alleles of rs2070744 and rs1799983 with an increased susceptibility to DN (P < 0.001 and P = 0.015 for allelic model, respectively). For both of these variants, a significant effect of subgrouping according to ethnicity was found. Rs869109213 displayed an association with DN susceptibility, with pooled effect measures indicating a predisposing effect of the minor allele a (Prec = 0.002, ORrec = 1.960, 95%CI 1.288-2.983; Paavs. bb = 0.001, ORaavs. bb = 2.014, 95%CI 1.316-3.083). These findings support the effects of NOS3 variants on the risk of developing DN in T2DM.

Risk association of the nitric oxide synthase VNTR intron 4 a/b variant with diabetic nephropathy - a pilot study

Diabetic nephropathy (DN) is known to be a leading complication of type 2 diabetes mellitus (T2D). This study evaluated whether the VNTR intron 4 a/b and rs1799983 polymorphisms of endothelial-derived nitric oxide synthase (eNOS) gene modulated the risk of developing DN in Asian Indian patients. The eNOS variants were genotyped in 200 patients, 100 with DN and 100 without DN. A significant risk association was observed for the VNTR intron 4 a/b (p < 0.05). Haplotype analysis revealed that the allele combination of rs1799983894 G/Intron 4b and rs1799983894 T/Intron 4b had a statistically significant inverse association with DN.

Transcriptomic analysis of diabetic kidney disease and neuropathy in mouse models of type 1 and type 2 diabetes

Diabetic kidney disease (DKD) and diabetic peripheral neuropathy (DPN) are common complications of type 1 (T1D) and type 2 (T2D) diabetes. However, the mechanisms underlying pathogenesis of these complications are unclear. In this study, we optimized a streptozotocin-induced db/+ murine model of T1D and compared it to our established db/db T2D mouse model of the same C57BLKS/J background. Glomeruli and sciatic nerve transcriptomic data from T1D and T2D mice were analyzed by self-organizing map and differential gene expression analysis. Consistent with prior literature, pathways related to immune function and inflammation were dysregulated in both complications in T1D and T2D mice. Gene-level analysis identified a high degree of concordance in shared differentially expressed genes (DEGs) in both complications and across diabetes type when using mice from the same cohort and genetic background. As we have previously shown a low concordance of shared DEGs in DPN when using mice from different cohorts and genetic backgrounds, this suggests that genetic background may influence diabetic complications. Collectively, these findings support the role of inflammation and indicate that genetic background is important in complications of both T1D and T2D.

Association between the Polymorphisms rs2070744, 4b/a and rs1799983 of the NOS3 Gene with Chronic Kidney Disease of Uncertain or Non-Traditional Etiology in Mexican Patients

Background and Objectives: Chronic Kidney Disease of uncertain or non-traditional etiology (CKDnT) is a form of chronic kidney disease of undetermined etiology (CKDu) and is not associated with traditional risk factors. The aim of this study was to investigate the association of polymorphisms rs2070744, 4b/a and rs1799983 of the NOS3 gene with CKDnT in Mexican patients. Materials and Methods: We included 105 patients with CKDnT and 90 controls. Genotyping was performed by PCR-RFLP's, genotypic and allelic frequencies were determined and compared between the two groups using χ2 analysis, and differences were expressed as odd ratios with 95% confidence intervals (CI). Values of p < 0.05 were considered statistically significant. Results: Overall, 80% of patients were male. The rs1799983 polymorphism in NOS3 was found to be associated with CKDnT in the Mexican population (p = 0.006) (OR = 0.397; 95% CI, 0.192-0.817) under a dominant model. The genotype frequency was significantly different between the CKDnT and control groups (χ2 = 8.298, p = 0.016). Conclusions: The results of this study indicate that there is an association between the rs2070744 polymorphism and CKDnT in the Mexican population. This polymorphism can play an important role in the pathophysiology of CKDnT whenever there is previous endothelial dysfunction.

Epithelial nitric oxide synthases (eNOS) 894 G < T polymorphism and diabetic nephropathy susceptibility: A meta-analysis

Objective

To investigate the epithelial nitric oxide synthases (eNOS) 894 G < T polymorphism and diabetic nephropathy (DN) susceptibility by pooling the open published data.

Methods

Studies relevant to eNOS 894 G < T polymorphism and DN susceptibility published in PubMed, EMBASE, Medline, CNKI, and Wanfang databases were systematically screened by using the text words of endothelial nitric oxide synthase, eNOS, NOS-3, G894T, rs179983, polymorphism, diabetic nephropathy, and DN. The correlation between eNOS 894 G < T polymorphism and DN susceptibility was demonstrated by odds ratio (OR) and corresponding 95% confidence interval (95% CI). The data were combined through fixed or random effect model according to statistical heterogeneity. The publication bias was assessed by Begg’s funnel plot and Egger’s line regression test.

Results

Twenty-six case-control studies relevant to eNOS 894 G < T polymorphism and DN susceptibility were identified by electronic searching of the related databases. Type 2 diabetes mellitus (T2MD) patients with T allele had increased susceptibility to DN compared with G allele under homologous gene model (TT vs GG) (OR = 1.40, 95% CI: 1.16–1.69, p = 0.001), dominant gene model (TT + GT) vs GG (OR = 1.61, 95% CI: 1.30–2.00, p = 0.000) and recessive gene model TT vs (GT + GG) (OR = 1.39, 95% CI: 1.16–1.66, p = 0.000). Publication bias was not statistically significant for homologous and recessive gene model.

Conclusion

Based on the present evidence, DN risk was increased in T2MD cases with T allele compared to G allele.

Evaluation of Association Studies and Meta-Analyses of eNOS Polymorphisms in Type 2 Diabetes Mellitus Risk

Background: Numerous studies reported the associations between endothelial nitric oxide synthase (eNOS) polymorphisms (4b/a VNTR (rs869109213), G894T (rs1799983) and T786C (rs2070744)) and type 2 diabetes mellitus (T2DM) risk. However, the conclusions were incongruent. Moreover, since no published meta-analyses were performed, a key issue regarding false-positive results needs to be addressed. Furthermore, four new articles have been published on these issues. Therefore, an updated meta-analysis was conducted to further explore these associations.

Objectives: To investigate the association between eNOS 4b/a, G894T and T786C polymorphisms and T2DM risk.

Methods: Studies were searched by using the PubMed, China National Knowledge Infrastructure (CNKI), Medline, Embase, International Statistical Institute (ISI) and the China Wanfang databases. Odds ratios (ORs) with 95% confidence intervals (CIs) were used to evaluate the associations using five genetic models. Furthermore, the false-positive report probability (FPRP), Bayesian false discovery probability (BFDP), and the Venice criteria were employed to assess the credibility of statistically significant associations.

Results: Overall, the eNOS 4b/a polymorphism was associated with a significantly decreased T2DM risk in Asians (bb vs. aa: OR = 0.44, 95% CI = 0.23–0.84; ab + bb vs. aa: OR = 0.45, 95% CI = 0.24–0.86; bb vs. aa + ab: OR = 0.73, 95% CI = 0.59–0.91; b vs. a: OR = 0.71, 95% CI = 0.57–0.88); the eNOS G894T polymorphism was associated with a significantly increased T2DM risk in Asians (GT vs. GG: OR = 1.52, 95% CI = 1.15–2.01; GT + TT vs. GG: OR = 1.52, 95% CI = 1.15–2.01; T vs. G: OR = 1.39, 95% CI = 1.09–1.76); the eNOS T786C polymorphism was associated with a significantly increased T2DM risk in Indian (TC vs. TT: OR = 1.93, 95% CI = 1.27–2.94; TC + CC vs. TT: OR = 2.06, 95%CI = 1.26–3.36; C vs. T: OR = 1.90, 95%CI = 1.17–3.08). However, when a sensitivity analysis was performed after excluding low quality and Hardy–Weinberg Disequilibrium (HWD) studies, no significant association was found for the eNOS G894T polymorphism. After credibility assessment, we identified “less-credible positive results” for the statistically significant associations in the current meta-analysis.

Conclusion: In conclusion, this article suggests that all substantial relationships between eNOS 4b/a, G894T, and T786C polymorphisms and T2DM risk are most likely due to false positive results rather than real connections or biological variables.

Association between nitric oxide synthase T-786C genetic polymorphism and chronic kidney disease: Meta-analysis incorporating trial sequential analysis

BACKGROUND

Several meta-analyses of the relationship between endothelial nitric oxide synthase (eNOS) T-786C gene polymorphism and chronic kidney disease (CKD) have been published. However, the results of these studies were inconsistent, and it is undetermined whether sample sizes are sufficient to reach a definite conclusion.

OBJECTIVE

To elucidate the relationship between T-786C and CKD by combining previous studies with our case-control sample and incorporate trial sequential analysis (TSA) to verify whether the sample size is adequate to draw a definite conclusion.

METHODS

PubMed and Embase databases were searched for relevant articles on eNOS T-786C and CKD before February 28, 2021. TSA was also incorporated to ascertain a conclusion. A total of 558 hemodialysis cases in the case-control study was recruited from nine dialysis centers in the northern area of Taiwan in 2020. Additionally, 640 healthy subjects of the control group, with estimated glomerular filtration rate (eGFR) ≥ 60 mL/min/1.73 m2, were selected from participants of the annual elderly health examination program at the Tri-Service General Hospital. The functional analysis was based on eQTL data from GTExPortal.

RESULTS

After screening with eligibility criteria, 15 papers were included and eventually combined in a meta-analysis. The result of the TSA showed that the sample size for Caucasians was adequate to ascertain the correlation between eNOS T-786C and CKD but was insufficient for Asians. Therefore, we added our case-control samples (n = 1198), though not associated with CKD (odds ratio [OR] = 1.01, 95% confidence interval [CI] = 0.69-1.46), into a meta-analysis, which supported that eNOS T-786C was significantly associated with CKD in Asians (OR = 1.39, 95% CI = 1.04-1.85) by using an adequate cumulative sample size (n = 4572) analyzed by TSA. Data of eQTL from GTEx showed that T-786C with the C minor allele exhibited relatively lower eNOS mRNA expression in whole blood, indicating the hazardous role of eNOS T-786C in CKD.

CONCLUSIONS

eNOS T-786C genetic polymorphism was of conclusive significance in the association with CKD among Asians in our meta-analysis. Our case-control samples play a decisive role in changing conclusions from indefinite to definite.

Association of eNOS and MCP-1 Genetic Variants with Type 2 Diabetes and Diabetic Nephropathy Susceptibility: A Case-Control and Meta-Analysis Study

Type 2 diabetes (T2D) and its secondary complications result from the complex interplay of genetic and environmental factors. To understand the role of these factors on disease susceptibility, the present study was conducted to assess the association of eNOS and MCP-1 variants with T2D and diabetic nephropathy (DN) in two ethnically and geographically different cohorts from North India. A total of 1313 subjects from two cohorts were genotyped for eNOS (rs2070744, rs869109213 and rs1799983) and MCP-1 (rs1024611 and rs3917887) variants. Cohort-I (Punjab) comprised 461 T2D cases (204 T2D with DN and 257 T2D without DN) and 315 healthy controls. Cohort-II (Jammu and Kashmir) included 337 T2D (150 T2D with DN and 187 T2D without DN) and 200 controls. Allele, genotype and haplotype frequencies were compared among the studied participants, and phenotype-genotype interactions were determined. Meta-analysis was performed to investigate the association between the selected variants and disease susceptibility. All three eNOS variants were associated with 1.5-4.0-fold risk of DN in both cohorts. MCP-1 rs1024611 conferred twofold risk towards DN progression in cohort-II, while rs3917887 provided twofold risk for both T2D and DN in both cohorts. eNOS and MCP-1 haplotypes conferred risk for T2D and DN susceptibility. Phenotype-genotype interactions showed significant associations between the studied variants and anthropometric and biochemical parameters. In meta-analysis, all eNOS variants conferred risk towards DN progression, whereas no significant association was observed for MCP-1 rs1024611. We show evidences for an association of eNOS and MCP-1 variants with T2D and DN susceptibility.

Genetic and Epigenomic Modifiers of Diabetic Neuropathy

Diabetic neuropathy (DN), the most common chronic and progressive complication of diabetes mellitus (DM), strongly affects patients’ quality of life. DN could be present as peripheral, autonomous or, clinically also relevant, uremic neuropathy. The etiopathogenesis of DN is multifactorial, and genetic components play a role both in its occurrence and clinical course. A number of gene polymorphisms in candidate genes have been assessed as susceptibility factors for DN, and most of them are linked to mechanisms such as reactive oxygen species production, neurovascular impairments and modified protein glycosylation, as well as immunomodulation and inflammation. Different epigenomic mechanisms such as DNA methylation, histone modifications and non-coding RNA action have been studied in DN, which also underline the importance of “metabolic memory” in DN appearance and progression. In this review, we summarize most of the relevant data in the field of genetics and epigenomics of DN, hoping they will become significant for diagnosis, therapy and prevention of DN.

Endothelial nitric oxide synthase c.-813C>T predicts for proteinuria in metastatic breast cancer patients treated with bevacizumab-based chemotherapy

PURPOSE

To investigate the association between single nucleotide polymorphisms (SNPs) in endothelial nitric oxide synthase (eNOS) and interleukin-8 (IL-8) genes and risk of developing bevacizumab-related adverse events in metastatic breast cancer (mBC) patients.

PATIENTS AND METHODS

mBC patients candidate to receive bevacizumab-based chemotherapy were enrolled in this pharmacogenetic study. eNOS c.-813C>T and c.894G>T, and IL-8 c.-251A>T were analyzed by real time PCR on genomic DNA extracted from peripheral blood. Univariate analysis was performed to test the association between each SNP and treatment-related toxicities.

RESULTS

Seventy-six mBC patients were enrolled in the present study. Patients carrying the homozygous variant eNOS c.-813TT genotype showed a statistically significant occurrence of any grade proteinuria when compared to CT or CC genotypes (p = 0.004). No significant association of proteinuria with IL-8 SNP or hypertension with selected eNOS and IL-8 SNPs was found.

CONCLUSIONS

These findings suggest an association between the eNOS c.-813C>T polymorphism and the development of proteinuria in mBC patients receiving a bevacizumab-based chemotherapy.

Nitric Oxide Gene Polymorphism is a Risk Factor for Diabetic Nephropathy and Atherosclerosis in Type 1 Diabetic Patients

AIM:

To assess the risk factor for diabetic atherosclerosis nephropathy and diabetic nephropathy in type 1 diabetic patients.

PATIENTS AND METHODS:

Thirty healthy volunteers age and sex-matched and Sixty-five type 1 diabetic patient were in rolled in the study. The mean age of patients was 17.99 ± 2.59 years, mean age of onset of diabetes was 7.00 ± 3.28 years, mean duration of diabetes was 10.91 ± 3.54 years. Glycosylated sex-matched (HbA1c) was assessed in blood samples, serum lipid profile was determined, and serum level of oxidised low-density lipoprotein (OxLDL), and nitric oxide was evaluated by enzyme-linked immunosorbent assay (ELISA) technique. Nitric oxide 894G > T genotype was analysed by (PCR-RFLP) method and confirmed by Sequencing. Assessment of the albumin / creatinine ratio was done in urine samples. Renal Doppler and Carotid intima-media thickness (cIMT) via ultrasound was also performed.

RESULTS:

OxLDL, lipid profile, albumin/creatinine ratio, cIMT and resistivity index were significantly higher in diabetic patients while nitric oxide was significantly lower. Nitric oxide genotype shows no significant difference between diabetic’s patients and controls. Diabetic patients with homozygous NO had a significantly lower serum level of Nitric oxide, a significantly higher OxLDL, albumin / creatinine ratio and lipid profile.

CONCLUSION:

diabetic patients are liable for the occurrence of early diabetic nephropathy and atherosclerosis as a result of the presence of low level of nitric oxide. Nitric oxide gene polymorphism 894G > T in diabetic patients is a risk factor for diabetic nephropathy and atherosclerosis.

CNDP1, NOS3, and MnSOD Polymorphisms as Risk Factors for Diabetic Nephropathy among Type 2 Diabetic Patients in Malaysia

Type 2 diabetes mellitus (T2DM) is associated with a high incidence of nephropathy. The aim of this study was to investigate the association of a genetic polymorphism of carnosinase (CNDP1-D18S880 and -rs2346061), endothelial nitric oxide synthase (NOS3-rs1799983), and manganese superoxide dismutase (MnSOD-rs4880) genes with the development of diabetic nephropathy among Malaysian type 2 diabetic patients. A case-control association study was performed using 652 T2DM patients comprising 227 Malays (without nephropathy = 96 and nephropathy = 131), 203 Chinese (without nephropathy = 95 and nephropathy = 108), and 222 Indians (without nephropathy = 136 and nephropathy = 86). DNA sequencing was performed for the D18S880 of CNDP1, while the rest were tested using DNA Sequenom MassARRAY to identify the polymorphisms. DNA was extracted from the secondary blood samples taken from the T2DM patients. The alleles and genotypes were tested using four genetic models, and the best mode of inheritance was chosen based on the least p value. The rs2346061 of CNDP1 was significantly associated with diabetic nephropathy among the Indians only with OR = 1.94 and 95% CI = (1.76–3.20) and fitted best the multiplicative model, while D18S880 was associated among all the three major races with the Malays having the strongest association with OR = 2.46 and 95% CI = (1.48–4.10), Chinese with OR = 2.26 and 95% CI = (1.34–3.83), and Indians with OR = 1.77 and 95% CI = (1.18–2.65) in the genotypic multiplicative model. The best mode of inheritance for both MnSOD and NOS3 was the additive model. For MnSOD-rs4880, the Chinese had OR = 2.8 and 95% CI = (0.53–14.94), Indians had OR = 2.4 and 95% CI = (0.69–2.84), and Malays had OR = 2.16 and 95% CI = (0.54–8.65), while for NOS3-rs1799983, the Indians had the highest risk with OR = 3.16 and 95% CI = (0.52–17.56), followed by the Chinese with OR = 3.55 and 95% CI = (0.36–35.03) and the Malays with OR = 2.89 and 95% CI = (0.29–28.32). The four oxidative stress-related polymorphisms have significant effects on the development of nephropathy in type 2 diabetes patients. The genes may, therefore, be considered as risk factors for Malaysian subjects who are predisposed to T2DM nephropathy.

Association of eNOS and ACE gene polymorphisms as a genetic risk factor in gestational diabetes in Iranian women

Background

Gestational diabetes mellitus (GDM) is the most popular metabolic disease during pregnancy. The aim of the present study was to investigate any possible association between eNOS Glu298Asp and ACE I/D gene polymorphisms and the risk of GDM in a group of Iranian pregnant women.

Methods

In this case-control study 204 pregnant women were recruited (94 cases and 110 controls). Genomic DNA was isolated from whole blood and genotyping was performed by the Polymerase Chain Reaction-Restriction Fragment Length Polymorphism (PCR- RFLP) and only PCR for eNOS and ACE polymorphisms respectively.

Results

Frequencies of GT and TT genotype of eNOS polymorphism among women with and without GDM were 67.90% vs. 74.47 and 7.41% vs. 8.51% respectively (P = 0.4). Corresponding figures for DD genotype of ACE polymorphism among GDM patients was more than that in healthy women (51.65% vs. 63.81% respectively). Conversely, ACE heterozygote genotype was more common in diabetic women (35.16% vs. 26.67% respectively). Although these differences were not statistically significant (P = 0.2).

Conclusions

Our study showed that there is no association between the presence of eNOS and ACE gene polymorphisms and developing gestational diabetes mellitus among pregnant women in our population. Further longitudinal and multicenter studies should be carried out to assess the exact metabolic effects of these polymorphisms.

Acute Kidney Injury and Progression of Diabetic Kidney Disease

Diabetic kidney disease, commonly termed diabetic nephropathy (DN), is the most common cause of end-stage kidney disease (ESKD) worldwide. The characteristic histopathology of DN includes glomerular basement membrane thickening, mesangial expansion, nodular glomerular sclerosis, and tubulointerstitial fibrosis. Diabetes is associated with a number of metabolic derangements, such as reactive oxygen species overproduction, hypoxic state, mitochondrial dysfunction, and inflammation. In the past few decades, our knowledge of DN has advanced considerably although much needs to be learned. The traditional paradigm of glomerulus-centered pathophysiology has expanded to the tubule-interstitium, the immune response and inflammation. Biomarkers of proximal tubule injury have been shown to correlate with DN progression, independent of traditional glomerular injury biomarkers such as albuminuria. In this review, we summarize mechanisms of increased susceptibility to acute kidney injury in diabetes mellitus and the roles played by many kidney cell types to facilitate maladaptive responses leading to chronic and end-stage kidney disease.

Endothelial nitric oxide synthase gene (T786C and G894T) polymorphisms in Egyptian patients with type 2 diabetes

BACKGROUND

Genetic factors play important role in the development of type 2 diabetes and diabetic nephropathy. Endothelial nitric oxide synthase (eNOS) gene is responsible for the bioavailability of nitric oxide and endothelial function.

AIM

To assess the association of the endothelial nitric oxide synthase (eNOS) (T786C and G894T) single nucleotide polymorphisms with Egyptian type 2 diabetes mellitus and diabetic nephropathy.

PATIENTS AND METHODS

A total of 200 type 2 diabetic patients and 100 apparently healthy volunteers as controls were included in the study. They were subjected to clinical examination and laboratory tests: fasting blood glucose, HBA1C, lipid profile, serum creatinine, blood urea and albumin creatinine ratio (ACR). Assessment of the T786C and G894T polymorphisms in the eNOS gene was done using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP).

RESULTS

There was no significant difference in distribution of eNOS T-786C polymorphism between patients and controls; TT genotype of eNOS G894T was more frequent in diabetic patients with and without albuminuria compared to controls. Patients were divided into 3 groups according to ACR. Normoalbuminuria: 37 patients with ACR ≤ 30 mg/g, microalbuminuria: 96 patients with ACR > 30 mg/g and ≤ 300 mg/g, and macroalbuminuria: 67 patients with ACR > 300 mg/g. There was no significant difference in genotype distribution of eNOS T-786C between the 3 groups of diabetic patients. The prevalence of TT genotype of eNOS G894T was higher in microalbuminuria patients compared to other groups.

CONCLUSION

eNOS G894T variant may increase risk of type 2 diabetes with lack of association between eNOS T786C, eNOS G894T and DN in Egyptians.

Association of NOS2 and NOS3 gene polymorphisms with susceptibility to type 2 diabetes mellitus and diabetic nephropathy in the Chinese Han population

Inducible nitric oxide synthase (NOS2) and endothelial nitric oxide synthase (NOS3) gene play important roles in the susceptibility to type 2 diabetes mellitus (T2DM). The present study aims to detect the potential association of NOS2 and NOS3 gene polymorphisms with the susceptibility toT2DM and diabetic nephropathy (DN) in the Chinese Han population. Four hundred and ninety T2DM patients and 485 healthy controls were enrolled in this case-control study. The genotypes of NOS2 and NOS3 gene polymorphisms were analyzed by the polymerase chain reaction (PCR)-ligase detection reaction (LDR) method. Our data demonstrated that the NOS2 rs2779248 and NOS2 rs1137933 genetic polymorphisms were significantly associated with the increased susceptibility to T2DM in the heterozygote comparison, dominant model, and allele contrast; and NOS3 rs3918188 genetic polymorphism was significantly associated with the increased susceptibility to T2DM in the homozygote comparison and recessive model. The allele-C and genotype-TC of NOS2 rs2779248, allele-A and genotype-GA of NOS2 rs1137933 and genotype-AA of NOS3 rs3918188 genetic polymorphisms might be the risk factors for increasing the susceptibility to T2DM. And a significant haplotype effect of NOS2 rs10459953/C- rs1137933/G- rs2779248/T was found between T2DM cases and controls. Moreover, NOS3 rs1800783 polymorphism was significantly associated with the increased susceptibility to DN in the heterozygote comparison, recessive model and allele contrast. At last, a positive correlation of family history of diabetes with NOS3 rs11771443 polymorphism was found in DN. These preliminary findings indicate that the NOS2 rs2779248, NOS2 rs1137933, and NOS3 rs3918188 genetic polymorphisms are potentially related to the susceptibility to T2DM, and the rs1800783 polymorphism might be considered as genetic risk factors for diabetic nephropathy, and family history of diabetes was closely associated with rs11771443 polymorphism in DN, and the genetic variants might be used as molecular markers for evaluating the risk of T2DM and diabetic nephropathy. © 2016 IUBMB Life, 68(7):516-525, 2016.

Genotypic and phenotypic predictors of inflammation in patients with chronic kidney disease

BACKGROUND

In complex diseases such as chronic kidney disease (CKD), the risk of clinical complications is determined by interactions between phenotypic and genotypic factors. However, clinical epidemiological studies rarely attempt to analyse the combined effect of large numbers of phenotype and genotype features. We have recently shown that the relaxed linear separability (RLS) model of feature selection can address such complex issues. Here, it is applied to identify risk factors for inflammation in CKD.

METHODS

The RLS model was applied in 225 CKD stage 5 patients sampled in conjunction with dialysis initiation. Fifty-seven anthropometric or biochemical measurements and 79 genetic polymorphisms were entered into the model. The model was asked to identify phenotypes and genotypes that, when combined, could separate inflamed from non-inflamed patients. Inflammation was defined as a high-sensitivity C-reactive protein concentration above the median (5 mg/L).

RESULTS

Among the 60 genotypic and phenotypic features predicting inflammation, 31 were genetic. Among the 10 strongest predictors of inflammation, 8 were single nucleotide polymorphisms located in the NAMPT, CIITA, BMP2 and PIK3CB genes, whereas fibrinogen and bone mineral density were the only phenotypic biomarkers.

CONCLUSION

These results indicate a larger involvement of hereditary factors in inflammation than might have been expected and suggest that inclusion of genotype features in risk assessment studies is critical. The RLS model demonstrates that inflammation in CKD is determined by an extensive panel of factors and may prove to be a suitable tool that could enable a much-needed multifactorial approach as opposed to the commonly utilized single-factor analysis.

Genetic risk of type 2 diabetes in populations of the African continent: A systematic review and meta-analyses

BACKGROUND

Type 2 diabetes (T2D) is growing faster in Africa than anywhere else, driven by the dual effects of genetic and environmental factors. We conducted a systematic review and meta-analyses of published studies on genetic markers of T2D in populations within Africa.

METHODS

Multiple databases were searched for studies of genetic variants associated with T2D in populations living in Africa. Studies reporting on the association of a genetic marker with T2D or indicators of glycaemia were included. Data were extracted on study design and characteristics, genetic determinants, effect estimates of associations with T2D.

FINDINGS

Overall, 100 polymorphisms in 57 genes have been investigated in relation with T2D in populations within Africa, in 60 studies. Almost all studies used the candidate gene approach, with >88% published during 2006-2014 and 70% (42/60) originating from Tunisia and Egypt. Polymorphisms in ACE, AGRP, eNOS, GSTP1, HSP70-2, MC4R, MTHFR, PHLPP, POL1, TCF7L2, and TNF-α gene were found to be associated with T2D, with overlapping effect on various cardiometabolic traits. The polymorphisms investigated in multiple studies mostly had consistent effects across studies, with only modest or no statistical heterogeneity. Effect sizes were modestly significant [e.g., odd ratio 1.49 (95%CI 1.33-1.66) for TCF7L2 (rs7903146)]. Underpowered genome-wide studies revealed no diabetes risk loci specific to African populations.

INTERPRETATION

Current evidence on the genetic markers of T2D in African populations mostly originate from North African countries, is overall scanty and largely insufficient to reliably inform the genetic architecture of T2D across Africa.

Correlation of Endothelial Nitric Oxide Synthase Gene Polymorphism (GG, TT and GT Genotype) with Proteinuria and Retinopathy in Type 2 Diabetic Patients

BACKGROUND

Nephropathy is the most important leading cause of end stage renal failure in type 2 diabetic patients, so numerous studies were done to diagnose and evaluate risk factors of diabetic nephropathy (DN). Some gene polymorphisms may be associated with progression or regression of DN, so the aim of this study was to compare prevalence of eNOS gene polymorphism in diabetic patients with controls and its association with diabetic nephropathy.

MATERIALS AND METHODS

In a cross-sectional study, 94 type 2 diabetic patients and 94 normal participants were enrolled. Patients without retinopathy were excluded from this study. For all of the patients, fasting blood sugar (FBS), 2 hours post-prandial (BS), Blood Urea Nitrogen (BUN), Creatinine (Cr), 24 hours urine protein were measured in the case group. Endothelial nitric oxide synthetase gene polymorphism was evaluated in the case and control groups.

RESULTS

There was no significant difference based on age and sex between patients in case and control groups. GG genotype of eNOS was less common in the patient group compared to control group. There was no difference between prevalence of TT, GT or GG genotype based on age and sex. There was no correlation between diabetic retinopathy or proteinuria and genotypes of eNOs.

CONCLUSION

The study showed that in type 2 diabetic patients, NOS gene polymorphism was more common compared to normal population; however, there is no correlation between this gene polymorphism and proteinuria or retinopathy in these patients.

Association of common eNOS/NOS3 polymorphisms with preeclampsia in Tunisian Arabs

We investigated the association of endothelial nitric oxide synthase (NOS3) polymorphisms -786T>C, 27-bp repeat 4b/4a, and Glu298Asp with preeclampsia (PE). This was a case-control study involving 345 unrelated Tunisian women with PE and 289 unrelated age- and ethnically matched control women. The -786C allele was significantly increased in PA patients when compared to healthy controls (P=0.015). In contrast, MAF of Glu298Asp (P=0.103) and 4b/4a (P=0.168) were not significantly different between the study groups. Higher frequencies of heterozygous Glu298/298Asp and homozygous -786T/-786T genotypes were seen in PE cases compared to healthy subjects. The combination of genotypes 221 (-786T>C, Glu298Asp, 4a/4a) was more in PE cases compared with control women (17.68% vs. 8.36%; P=0.029). Multivariate regression analysis confirmed this association. Genetic variation at the NOS3 locus represents a genetic risk factor for increased susceptibility to PE.

Identifying Common Genetic Risk Factors of Diabetic Neuropathies

Type 2 diabetes mellitus (T2DM) is a global public health problem of epidemic proportions, with 60-70% of affected individuals suffering from associated neurovascular complications that act on multiple organ systems. The most common and clinically significant neuropathies of T2DM include uremic neuropathy, peripheral neuropathy, and cardiac autonomic neuropathy. These conditions seriously impact an individual's quality of life and significantly increase the risk of morbidity and mortality. Although advances in gene sequencing technologies have identified several genetic variants that may regulate the development and progression of T2DM, little is known about whether or not the variants are involved in disease progression and how these genetic variants are associated with diabetic neuropathy specifically. Significant missing heritability data and complex disease etiologies remain to be explained. This article is the first to provide a review of the genetic risk variants implicated in the diabetic neuropathies and to highlight potential commonalities. We thereby aim to contribute to the creation of a genetic-metabolic model that will help to elucidate the cause of diabetic neuropathies, evaluate a patient's risk profile, and ultimately facilitate preventative and targeted treatment for the individual.

Semaphorin3a promotes advanced diabetic nephropathy

The onset of diabetic nephropathy (DN) is highlighted by glomerular filtration barrier abnormalities. Identifying pathogenic factors and targetable pathways driving DN is crucial to developing novel therapies and improving the disease outcome. Semaphorin3a (sema3a) is a guidance protein secreted by podocytes. Excess sema3a disrupts the glomerular filtration barrier. Here, using immunohistochemistry, we show increased podocyte SEMA3A in renal biopsies from patients with advanced DN. Using inducible, podocyte-specific Sema3a gain-of-function (Sema3a(+)) mice made diabetic with streptozotocin, we demonstrate that sema3a is pathogenic in DN. Diabetic Sema3a(+) mice develop massive proteinuria, renal insufficiency, and extensive nodular glomerulosclerosis, mimicking advanced DN in humans. In diabetic mice, Sema3a(+) exacerbates laminin and collagen IV accumulation in Kimmelstiel-Wilson-like glomerular nodules and causes diffuse podocyte foot process effacement and F-actin collapse via nephrin, αvβ3 integrin, and MICAL1 interactions with plexinA1. MICAL1 knockdown and sema3a inhibition render podocytes not susceptible to sema3a-induced shape changes, indicating that MICAL1 mediates sema3a-induced podocyte F-actin collapse. Moreover, sema3a binding inhibition or podocyte-specific plexinA1 deletion markedly ameliorates albuminuria and abrogates renal insufficiency and the diabetic nodular glomerulosclerosis phenotype of diabetic Sema3a(+) mice. Collectively, these findings indicate that excess sema3a promotes severe diabetic nephropathy and identifies novel potential therapeutic targets for DN.

Contribution of eNOS variants to the genetic susceptibility of coronary artery disease in a Tunisian population

Nitric oxide (NO), produced by the enzyme endothelial nitric oxide synthase (eNOS), has critical roles in the regulation of vascular homeostasis and prevention of atherogenesis by inhibiting leukocytes, platelet activation, and smooth muscle cell proliferation. There is strong experimental and clinical evidence that abnormalities in eNOS availability play an important role in the pathophysiology of coronary artery disease (CAD). Controversial results regarding the association of eNOS gene polymorphisms with CAD have been reported. The aim of this study is to investigate the relationship of the 894G>T (rs1799983) and 4a/4b (rs61722009) polymorphisms of the eNOS gene with the presence of CAD in the Tunisian population. A total of 332 patients with CAD and 368 controls were included in this study. The 894G>T (rs1799983) single-nucleotide polymorphisms were analyzed by polymerase chain reaction-restriction fragment length polymorphism, and 4a/4b (rs61722009) polymorphism just by polymerase chain reaction (PCR). eNOS rs1799983 was significantly associated with CAD under the additive, dominant, but not recessive, models (additive model OR: 2.81; 95% CI [2.05-3.85]; p<0.001, dominant model OR: 2.84; 95% CI [2.09-3.86]; p<0.001, and recessive models p=0.09). This remained significant after adjustment for age, gender, diabetes, smoking, and hypertension. In contrast to eNOS rs1799983, eNOS rs61722009 was not associated with CAD under any of the genetic models tested. These findings suggest that the G894T (rs1799983) polymorphism of the eNOS gene was associated with CAD in Tunisian patients.

Cyclic nucleotide signalling in kidney fibrosis

Kidney fibrosis is an important factor for the progression of kidney diseases, e.g., diabetes mellitus induced kidney failure, glomerulosclerosis and nephritis resulting in chronic kidney disease or end-stage renal disease. Cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) were implicated to suppress several of the above mentioned renal diseases. In this review article, identified effects and mechanisms of cGMP and cAMP regarding renal fibrosis are summarized. These mechanisms include several signalling pathways of nitric oxide/ANP/guanylyl cyclases/cGMP-dependent protein kinase and cAMP/Epac/adenylyl cyclases/cAMP-dependent protein kinase. Furthermore, diverse possible drugs activating these pathways are discussed. From these diverse mechanisms it is expected that new pharmacological treatments will evolve for the therapy or even prevention of kidney failure.

Association of genetic variants with diabetic nephropathy

Diabetic nephropathy accounts for the most serious microvascular complication of diabetes mellitus. It is suggested that the prevalence of diabetic nephropathy will continue to increase in future posing a major challenge to the healthcare system resulting in increased morbidity and mortality. It occurs as a result of interaction between both genetic and environmental factors in individuals with both type 1 and type 2 diabetes. Genetic susceptibility has been proposed as an important factor for the development and progression of diabetic nephropathy, and various research efforts are being executed worldwide to identify the susceptibility gene for diabetic nephropathy. Numerous single nucleotide polymorphisms have been found in various genes giving rise to various gene variants which have been found to play a major role in genetic susceptibility to diabetic nephropathy. The risk of developing diabetic nephropathy is increased several times by inheriting risk alleles at susceptibility loci of various genes like ACE, IL, TNF-α, COL4A1, eNOS, SOD2, APOE, GLUT, etc. The identification of these genetic variants at a biomarker level could thus, allow the detection of those individuals at high risk for diabetic nephropathy which could thus help in the treatment, diagnosis and early prevention of the disease. The present review discusses about the various gene variants found till date to be associated with diabetic nephropathy.

Association of the endothelial nitric oxide synthase gene G894T polymorphism with the risk of diabetic nephropathy in Qassim region, Saudi Arabia-A pilot study

BACKGROUND

Diabetic nephropathy (DN) is a chronic microangiopathic complication of type 2 diabetes mellitus (DM).Vascular endothelial dysfunction resulting from impaired nitric oxide synthase (NOS) activity in the vascular endothelial cells has been suggested as playing an important role in the pathogenesis of diabetic nephropathy (DN). Endothelial nitric oxide synthase (E-NOS) gene G894T polymorphism has been reported to be associated with endothelial dysfunction leading to DN. Our objective was to evaluate the association of G894T polymorphism of eNOS gene with the risk of DN among type 2 diabetic Saudi patients.

METHODS

One hundred and twenty subjects were included in this study. They were divided into three groups. Group I, 40 controls. Group II, 40 type 2 diabetic patients without nephropathy. Group III, 40 type2 diabetic patients with nephropathy. Endothelial nitric oxide synthase (eNOS) G894Tpolymorphism was detected by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Plasma nitric oxide (NO) levels were estimated.

RESULTS

E-NOS genotype frequency showed non-significant differences among the all studied groups (p > 0.05). Both diabetic groups had significantly higher plasma nitrate levels than in controls with a significant increase in group III than in group II patients (all p < 0.0001). E NOS 894TT genotype was associated with higher plasma nitrate levels in all groups.

CONCLUSION

E-NOS gene SNP is not considered as genetic risk factor for DN among type 2 diabetic Saudi patients. The higher plasma levels of nitrates as a marker of oxidative stress in diabetic patients with nephropathy suggest the possible role of oxidative stress but not e-NOS gene SNP in pathogenesis of the DN.

Endothelial nitric oxide synthase (eNOS) 4b/a polymorphism and the risk of diabetic nephropathy in type 2 diabetes mellitus: A meta-analysis

Many studies have accessed the association between eNOS-4b/a polymorphism and the risk of diabetic nephropathy (DN) among type 2 diabetic subjects. However, the results are conflicting and inconclusive. The aim of current meta-analysis was to more precisely estimate the relationship. Pubmed, Embase, the China National Knowledge Infrastructure and the Wanfang Database were searched for articles published up to May 26th, 2013 that addressed eNOS-4b/a polymorphism and the risk of DN among type 2 diabetic subjects. 18 studies were included in this meta-analysis. eNOS-4b/a polymorphisms were associated with an overall significantly increased risk of DN (allele model: OR = 1.44, 95% CI = 1.14-1.82; additive model: OR = 2.03, 95% CI = 1.14-3.62; dominant model: OR = 1.34, 95% CI = 1.07-1.68; recessive model: OR = 2.01, 95% CI = 1.12-3.61). Subgroup analysis revealed a significant association between the eNOS-4b/a polymorphism and DN in Asian population, especially in Chinese population, but not in non Asian populations. Our meta-analysis supported an association between the 4b/a polymorphism of eNOS gene and increased risk of DN in type 2 diabetes among Asians, especially in Chinese population.

Association between a 27-bp variable number of tandem repeat polymorphism in intron 4 of the eNOS gene and risk for diabetic retinopathy Type 2 diabetes mellitus: a meta-analysis

PURPOSE

Imbalance in the production of endothelial nitric oxide synthase (eNOS), which plays an essential role in retinal vascular function, can lead to the development of diabetic retinopathy (DR). To thoroughly address this issue, we performed an updated meta-analysis to evaluate the association between the eNOS 27VNTR (4b/4a) polymorphism and DR in type 2 diabetes mellitus (T2DM).

METHODS

A search was conducted of PubMed and Chinese language (WanFang) databases through 3 March 2013. Data were retrieved in a systematic manner and analyzed using Stata Statistical Software. Crude odds ratios (ORs) with 95% confidence intervals (CIs) were used to assess the strength of associations.

RESULTS

Based on the search criteria for DR susceptibility related to the 27VNTR (4b/4a) polymorphism of the eNOS gene, 16 case-control studies (15 articles), comprising 3227 T2DM patients with DR and 3437 T2DM patients without DR, were retrieved. Although no significant associations were uncovered in either the overall analysis or DR subtype groups, a decreased association was detected between the African- (allelic contrast: OR = 0.75, 95% CI = 0.65-0.88) or population-based (PB) studies (dominant genetic model: OR = 0.91, 95% CI = 0.83-0.98) and the eNOS 27VNTR (4b/4a) polymorphism. Stratification according to average duration of DM revealed that T2DM patients with histories of >10 years had an elevated susceptibility to DR compared with those with histories of shorter durations (homozygote comparison: OR = 1.67, 95% CI = 1.09-2.58).

CONCLUSIONS

The present meta-analysis suggests that the eNOS 27VNTR (4b/4a) polymorphism potentially decreases the risk of developing DR in T2DM African individuals. The higher degree of susceptibility in patients with longer (>10 years) durations of DM is indicative of the involvement of a gene-environment interaction in determining the risk for DR. Further studies, based on larger sample sizes and additional gene-environment interactions, should be conducted to elucidate the role of eNOS gene polymorphisms, especially 27VNTR (4b/4a), in the risk for DR.

Nitric oxide system and diabetic nephropathy

About 30% of patients with type 2 diabetes mellitus develop clinically overt nephropathy. Hyperglycemia is necessary, but not sufficient, to cause the renal damage that leads to kidney failure. Diabetic nephropathy (DN) is a multifactorial disorder that results from interaction between environmental and genetic factors. In the present article we will review the role of the nitric oxide synthase (NOS) in the pathogenesis of DN.Nitric oxide (NO) is a short-lived gaseous lipophilic molecule produced in almost all tissues, and it has three distinct genes that encode three NOS isoforms: neuronal (nNOS), inducible (iNOS) and endothelial (eNOS).The correct function of the endothelium depends on NO, participating in hemostasis control, vascular tone regulation, proliferation of vascular smooth muscle cells and blood pressure homeostasis, among other features. In the kidney, NO plays many different roles, including control of renal and glomerular hemodynamics. The net effect of NO in the kidney is to promote natriuresis and diuresis, along with renal adaptation to dietary salt intake.The eNOS gene has been considered a potential candidate gene for DN susceptibility. Three polymorphisms have been extensively researched: G894T missense mutation (rs1799983), a 27-bp repeat in intron 4, and the T786C single nucleotide polymorphism (SNP) in the promoter (rs2070744). However, the potential link between eNOS gene variants and the induction and progression of DN yielded contradictory results in the literature.In conclusion, NOS seems to be involve in the development and progression of DN. Despite the discrepant results of many studies, the eNOS gene is also a good candidate gene for DN.

Endothelial nitric oxide synthase gene polymorphisms and risk of diabetic nephropathy: a systematic review and meta-analysis

Background

Nitric oxide (NO) has numerous functions in the kidney, including control of renal and glomerular hemodynamics, by interfering at multiple pathological and physiologically critical steps of nephron function. Endothelial NOS (eNOS) gene has been considered a potential candidate gene to diabetic nephropathy (DN) susceptibility. Endothelial nitric oxide synthase gene (eNOS-3) polymorphisms have been associated with DN, however some studies do not confirm this association. The analyzed polymorphisms were 4b/4a, T-786C, and G986T.

Methods

The Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) statement was used in this report. Case–control studies that had diabetic patients with DN as cases and diabetic patients without nephropathy as controls, as well as that evaluated at least one of the three polymorphisms of interest were considered eligible. All studies published up until December 31^st, 2012 were identified by searching electronic databases. Hardy-Weinberg equilibrium assessment was performed. Gene-disease association was measured using odds ratio estimation based on the following genetic contrast/models: (1) allele contrast; (2) additive model; (3) recessive model; (4) dominant model and (4) co-dominant model.

Results

Twenty-two studies were eligible for meta-analysis (4b/a: 15 studies, T-786C: 5 studies, and G984T: 12 studies). Considering 4b/a polymorphism, an association with DN was observed for all genetic models: allele contrast (OR = 1.14, CI: 1.04-1.25); additive (OR = 1.77, CI: 1.37-2.28); recessive (OR = 1.77, CI: 1.38-2,27); dominant (OR = 1.12, CI: 1.01-1.24), with the exception for co-dominance model. As well, T-786C polymorphism showed association with all models, with exception for co-dominance model: allele contrast (OR = 1.22, CI: 1.07-1.39), additive (OR = 1.52, CI: 1.18-1.97), recessive (OR = 1.50, CI: 1.16-1.93), and dominant (OR = 1.11, CI: 1.01-1.23). For the G894T polymorphism, an association with DN was observed in allelic contrast (OR = 1.12, CI: 1.03-1.25) and co-dominance models (OR = 1.13, CI: 1.04-1.37).

Conclusions

In the present study, there was association of DN with eNOS 4b/a and T-786C polymorphism, which held in all genetic models tested, except for co-dominance model. G894T polymorphism was associated with DN only in allele contrast and in co-dominance model. This data suggested that the eNOS gene could play a role in the development of DN.

VEGF and podocytes in diabetic nephropathy

Vascular endothelial growth factor-A (VEGF-A) is a protein secreted by podocytes that is necessary for survival of endothelial cells, podocytes, and mesangial cells. VEGF-A regulates slit-diaphragm signaling and podocyte shape via VEGF-receptor 2-nephrin-nck-actin interactions. Chronic hyperglycemia-induced excess podocyte VEGF-A and low endothelial nitric oxide drive the development and the progression of diabetic nephropathy. The abnormal cross-talk between VEGF-A and nitric oxide pathways is fueled by the diabetic milieu, resulting in increased oxidative stress. Recent findings on these pathogenic molecular mechanisms provide new potential targets for therapy for diabetic renal disease.

The renal endothelium in diabetic nephropathy

Diabetic nephropathy is the leading cause of end-stage renal disease. Diabetes mellitus is characterized by generalized endothelial dysfunction. However, recent data also emphasizes the role of local renal endothelium dysfunction in the pathogenesis of diabetic nephropathy. Hyperglycemia triggers a complex network of signal-transduction molecules, transcription factors, and mediators that culminate in endothelial dysfunction. In the glomerulus, vascular endothelial growth factor-A (VEGF)-induced neoangiogenesis may contribute to the initial hyperfiltration and microalbuminuria due to increased filtration area and immaturity of the neovessels, respectively. However, subsequent decrease in podocytes number decreases VEGF production resulting in capillary rarefaction and decreased glomerular filtration rate (GFR). Decreased nitric oxide availability also plays a significant role in the development of advanced lesions of diabetic nephropathy through disruption of glomerular autoregulation, uncontrolled VEGF action, release of prothrombotic substances by endothelial cells and angiotensin-II-independent aldosterone production. In addition, disturbances in endothelial glycocalyx contribute to decreased permselectivity and microalbuminuria; whereas there are recent evidences that reduced glomerular fenestral endothelium leads to decreased GFR levels. Endothelial repair mechanisms are also impaired in diabetes, since circulating endothelial progenitor cells number is decreased in diabetic patients with microalbuminuria. Finally, in the context of elevated profibrotic cytokine transforming growth factor-β levels, endothelial cells also confer to the deteriorating process of fibrosis in advanced diabetic nephropathy through endothelial to mesenchymal transition.

The endothelium in diabetic nephropathy

The long-term complications of diabetes are characterized by pathologic changes in both the microvasculature and conduit vessels. Although the fenestrated glomerular endothelium classically has been viewed as providing little in the way of an impediment to macromolecular flow, increasing evidence illustrates that this is not the case. Rather, hyperglycemia-mediated endothelial injury may predispose to albuminuria in diabetes both through direct effects and through bidirectional communication with neighboring podocytes. Although neo-angiogenesis of the glomerular capillaries may be a feature of early diabetes, particularly in the experimental setting, loss of capillaries in the glomerulus and in the interstitium are key events that each correlate closely with declining glomerular filtration rate in patients with diabetic nephropathy. The hypoxic milieu that follows the microvascular rarefaction provides a potent stimulus for fibrogenesis, leading to the glomerulosclerosis and tubulointerstitial fibrosis that characterize advanced diabetic kidney disease. Given the pivotal role the endothelium plays in both the development and the progression of diabetic nephropathy we need effective strategies that prevent its loss or accelerate its regeneration. Such advances likely will lead not only to improved tissue oxygenation and reduced fibrosis, but also to improved long-term renal function.

Effects of stimulation of soluble guanylate cyclase on diabetic nephropathy in diabetic eNOS knockout mice on top of angiotensin II receptor blockade

The prevalence of diabetes mellitus and its complications, such as diabetic nephropathy (DN), is rising worldwide and prevention and treatment are therefore becoming increasingly important. Therapy of DN is particularly important for patients who do not adequately respond to angiotensin receptor blocker (ARB) treatment. Novel approaches include the stimulation of soluble guanylate cyclase (sGC) as it is reported to have beneficial effects on cardiac and renal damage. We aimed to investigate the effects of the sGC stimulator riociguat and ARB telmisartan on kidney function and structure in a hypertensive model of diabetic nephropathy. Seventy-six diabetic male eNOS knockout C57BL/6J mice were randomly divided after having received streptozotocin: telmisartan (1 mg/kg/d), riociguat (3 mg/kg/d), riociguat+telmisartan (3+1 mg/kg/d), and vehicle. Fourteen mice were used as non-diabetic controls. Treatment duration was 11 weeks. Glucose concentrations were increased and similar in all diabetic groups. Telmisartan insignificantly reduced blood pressure by 5.9 mmHg compared with diabetic controls (111.2±2.3 mmHg vs. 117.1±2.2 mmHg; p = 0.071). Treatment with riociguat both alone and in combination with telmisartan led to a significant reduction of blood pressure towards diabetic vehicle (105.2±2.5 mmHg and 105.0±3.2 mmHg, respectively, vs. 117.1±2.2 mmHg). Combined treatment also significantly decreased albuminuria compared with diabetic controls (47.3±9.6 µg/24 h vs. 170.8±34.2 µg/24 h; p = 0.002) reaching levels similar to those of non-diabetic controls (34.4±10.6 µg/24 h), whereas the reduction by single treatment with either telmisartan (97.8±26.4 µg/24 h) or riociguat (97.1±15.7 µg/24 h) was not statistically significant. The combination treatment led to a significant (p<0.01) decrease of tissue immunoreactivity of malondialdehyde, as consequence of reduced oxidative stress. In conclusion, stimulation of sGC significantly reduced urinary albumin excretion in diabetic eNOS knockout mice treated already with ARB. Thus, this new drug class on top of standard ARBs administration may offer a new therapeutic approach for patients resistant to ARB treatment.

A novel multiplex PCR-RFLP method for simultaneous detection of the MTHFR 677 C > T, eNOS +894 G > T and - eNOS -786 T > C variants among Malaysian Malays

BACKGROUND

Hyperhomocysteinemia as a consequence of the MTHFR 677 C > T variant is associated with cardiovascular disease and stroke. Another factor that can potentially contribute to these disorders is a depleted nitric oxide level, which can be due to the presence of eNOS +894 G > T and eNOS -786 T > C variants that make an individual more susceptible to endothelial dysfunction. A number of genotyping methods have been developed to investigate these variants. However, simultaneous detection methods using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis are still lacking. In this study, a novel multiplex PCR-RFLP method for the simultaneous detection of MTHFR 677 C > T and eNOS +894 G > T and eNOS -786 T > C variants was developed. A total of 114 healthy Malay subjects were recruited. The MTHFR 677 C > T and eNOS +894 G > T and eNOS -786 T > C variants were genotyped using the novel multiplex PCR-RFLP and confirmed by DNA sequencing as well as snpBLAST. Allele frequencies of MTHFR 677 C > T and eNOS +894 G > T and eNOS -786 T > C were calculated using the Hardy Weinberg equation.

METHODS

The 114 healthy volunteers were recruited for this study, and their DNA was extracted. Primer pair was designed using Primer 3 Software version 0.4.0 and validated against the BLAST database. The primer specificity, functionality and annealing temperature were tested using uniplex PCR methods that were later combined into a single multiplex PCR. Restriction Fragment Length Polymorphism (RFLP) was performed in three separate tubes followed by agarose gel electrophoresis. PCR product residual was purified and sent for DNA sequencing.

RESULTS

The allele frequencies for MTHFR 677 C > T were 0.89 (C allele) and 0.11 (T allele); for eNOS +894 G > T, the allele frequencies were 0.58 (G allele) and 0.43 (T allele); and for eNOS -786 T > C, the allele frequencies were 0.87 (T allele) and 0.13 (C allele).

CONCLUSIONS

Our PCR-RFLP method is a simple, cost-effective and time-saving method. It can be used to successfully genotype subjects for the MTHFR 677 C > T and eNOS +894 G > T and eNOS -786 T > C variants simultaneously with 100% concordance from DNA sequencing data. This method can be routinely used for rapid investigation of the MTHFR 677 C > T and eNOS +894 G > T and eNOS -786 T > C variants.

Concomitant presence of endothelial nitric oxide 894T and angiotensin II-converting enzyme D alleles are associated with diabetic nephropathy in a Kurdish population from Western Iran

AIM

The present study investigated the influence of insertion (I)/deletion (D) polymorphism of the angiotensin II-converting enzyme (ACE) gene in combination with endothelial nitric oxide (eNOS) G894T polymorphism on the predisposition to diabetic nephropathy (DN).

METHODS

Using polymerase chain reaction (PCR) and PCR-restriction fragment length polymorphism (PCR-RFLP) method, the ACE and eNOS polymorphisms were genotyped in 72 microalbuminuric, 68 macroalbuminuric and 72 normoalbuinuric type 2 diabetes mellitus (T2DM) patients from Western Iran.

RESULTS

The presence of eNOS T or ACE D allele was not associated with increased risk of macroalbuminuria (odds ratio (OR) = 1.36, P = 0.27 and OR = 1.6, P = 0.062, respectively). However, in the presence of both alleles there was a trend towards increased risk of macroalbuminuria (fivefold, P = 0.05).

CONCLUSION

Our study indicates that the concomitant presence of both ACE D and eNOS T alleles tends to be associated with an elevation risk of macroalbuminuria compared with the presence of each polymorphism alone. This risk could be attributed to the increasing activity of ACE and angiotensin II level in the presence of D allele and decreasing NO production in the presence of T allele accelerating diabetic nephropathy.

Endothelial nitric oxide synthase gene polymorphisms and the risk of diabetic nephropathy in type 2 diabetes mellitus

Endothelial dysfunction plays an important role in the pathogenesis of diabetic vascular disease, including diabetic nephropathy (DN). Endothelial nitric oxide synthase (eNOS) gene polymorphisms that affect eNOS activity are associated with endothelial dysfunction. The aim of this study was to evaluate the association of three polymorphisms of the eNOS gene (894G>T, -786T>C, and 27-bp-VNTR) with the risk of DN among type 2 diabetic patients. A total of 400 type 2 diabetic patients were enrolled in this study. The DN group comprised 200 patients; the group of diabetics without nephropathy comprised another 200 patients. Genetic analysis for eNOS gene polymorphisms was done in all subjects. Measurement of nitric oxide levels was estimated. The C allele for -786T>C and the T allele for 894G>T were significantly more frequent in diabetics with nephropathy than in diabetics without nephropathy (p<0.001; odds ratio [OR] and 95% confidence interval [CI] for the C allele=1.64 [1.24-2.17] and p<0.001; OR and 95% CI=1.7 [1.27-2.26] for the T allele). The haplotypes CTa (with all the mutant alleles) and CTb were significantly more common in patients with DN (p=0.01 and 0.003, respectively). These results suggested that the eNOS polymorphisms might represent genetic determinants for developing DN in type 2 diabetic Egyptians.

Assessment of diabetic nephropathy in the Akita mouse

Akita mice have type 1 diabetes mellitus caused by a spontaneous point mutation in the Ins2 gene which leads to misfolding of insulin, resulting in pancreatic β-cell failure. Akita mice develop pronounced and sustained hyperglycemia, high levels of albuminuria, and consistent histopathological changes, suggesting that these mice may be suitable as an experimental platform for modeling diabetic nephropathy. One key feature of diabetic kidney disease in Akita mice is that the severity of renal injury is significantly influenced by genetic background. In this chapter, we describe the Akita model and present some of the experimental studies utilizing Akita mice as a model of type 1 diabetes. For example, deficiency in bradykinin receptors, endothelial nitric oxide synthase, or angiotensin-converting enzyme 2 leads to development of functionally and structurally more advanced diabetic nephropathy in these mice, while ketogenic diet has been shown to reverse kidney injury associated with diabetes. This chapter also describes the application of 24-h urine collections from mice for careful measurement of urinary albumin excretion.

Role of blood pressure and the renin-angiotensin system in development of diabetic nephropathy (DN) in eNOS-/- db/db mice

Randomized clinical trials have clearly shown that inhibition of the renin-angiotensin system (RAS) will slow the rate of progression of diabetic nephropathy, but controversy remains about whether the observed beneficial effects result from more than control of blood pressure. Deletion of eNOS in a model of type II diabetes, db/db mice (eNOS(-/-) db/db), induces an accelerated nephropathy and provides an excellent model of human diabetic nephropathy. As is frequently seen in type II diabetes, blood pressure is moderately elevated in eNOS(-/-) db/db mice. To determine the role of elevated blood pressure per se vs. additional deleterious effects of the RAS in mediation of disease progression, 8-wk-old eNOS(-/-) db/db mice were randomly divided into three groups: vehicle, treatment with the angiotensin-converting enzyme inhibitor (ACEI) captopril, or treatment with "triple therapy" (hydralazine, resperine, hydrocholorothiazide), and the animals were euthanized after treatment for 12 wk. Blood pressure was reduced to comparable levels with ACE inhibition or triple therapy. Although both treatment regimens decreased development of diabetic nephropathy, ACE inhibition led to more profound reductions in albuminuria, glomerulosclerosis, markers of tubulointerstitial injury, macrophage infiltration, and markers of inflammation. Therefore, this animal model suggests that while there is an important role for blood pressure control, RAS blockade provides additional benefits in slowing the progression of diabetic nephropathy.

Relationship of endothelial nitric oxide synthase (eNOS) gene polymorphisms with diabetic retinopathy in Caucasians with type 2 diabetes

BACKGROUND

Nitric oxide synthesized by endothelial nitric oxide synthase (eNOS) plays a key role in the regulation of endothelial function, and controversial results regarding the association of eNOS gene polymorphisms with diabetic complications have been reported.

MATERIALS AND METHODS

In this case-control study, the relationship of the -786T/C, the VNTR intron 4 a/b and the 894G/T (Glu298Asp) polymorphisms in the eNOS gene with the presence or severity of diabetic retinopathy was analyzed in 630 Caucasian-Brazilians with type 2 diabetes (434 with and 196 without diabetic retinopathy). Genotyping of eNOS polymorphisms was carried out using the PCR or PCR-RFLP method, and haplotype frequencies were estimated using a Bayesian method.

RESULTS

Genotype and allele frequencies in patients with any degree of diabetic retinopathy or proliferative diabetic retinopathy were not significantly different from those of patients without this complication for all eNOS polymorphisms. Likewise, there were no differences in haplotype frequencies among diabetic patients with or without diabetic retinopathy (p values > 0.05 for all comparisons).

CONCLUSION

Our findings do not support the hypothesis that the -786T/C, the VNTR intron 4 a/b and the 894G/T (Glu298Asp) polymorphisms in the eNOS gene play a role in the pathogenesis of diabetic retinopathy in type 2 diabetes.

Impact of nitric oxide synthase Glu298Asp polymorphism on the development of end-stage renal disease in type 2 diabetic Egyptian patients

BACKGROUND

Nitric oxide is an important regulator of renal hemodynamics. This study aimed to investigate the role of endothelial nitric oxide synthase (eNOS) gene polymorphism in type 2 diabetic patients with end-stage renal disease (ESRD) and to elucidate any alteration of nitric oxide synthase (NOS) activity caused by this polymorphism.

METHODS

The study included 80 patients with type 2 diabetes of >10 years duration (40 with diabetes-derived ESRD, 40 without nephropathy) and 20 healthy controls. Plasma nitrate/nitrite level, and serum NOS activity were measured and eNOS Glu298Asp genotypes were determined.

RESULTS

The frequency of Glu/Glu (GG) genotype in diabetics with ESRD was lower than controls. However, the frequency of Asp/Asp (TT) genotype was increased in diabetics with ESRD as compared to those without nephropathy and controls. Diabetics with ESRD had significantly lower nitrate/nitrite level and NOS activity than those without nephropathy. Diabetic patients with TT genotype are at a significant risk for ESRD. Moreover, subjects carrying TT genotype had lower nitrate/nitrite level and NOS activity than those carrying GG genotype. In diabetics with ESRD, creatinine clearance was positively correlated with both nitrate/nitrite level and NOS activity.

CONCLUSIONS

These results imply that TT genotype of eNOS may be associated with an increased risk of ESRD in Egyptian type 2 diabetics. It could represent a useful genetic marker to identify diabetics at high risk for the development of ESRD. However, larger future prospective studies are required to confirm the role of eNOS gene polymorphism in the progression of diabetic nephropathy to ESRD.

Interaction of eNOS polymorphism with MTHFR variants increase the risk of diabetic nephropathy and its progression in type 2 diabetes mellitus patients

The present study has investigated the role of endothelial nitric oxide (eNOS) G894T polymorphism and its interaction with methylenetetrahydrofolate reductase (MTHFR) C677T and A1298C variants on the predisposition to diabetic nephropathy and its progression. Using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method the eNOS G894T and MTHFR polymorphisms were detected in 72 microalbuminuric, 68 macroalbuminuric, and 72 normoalbuinuric type 2 diabetes mellitus (T2DM) patients from Western Iran. The presence of GT and GT + TT genotypes of eNOS were associated with insignificantly 1.86- and 1.68-fold increased risk of macroalbuminuria, respectively and 1.21- and 1.13-fold increased risk of microalbuminuria, respectively. However, the concomitant presence of eNOST and MTHFR 1298C alleles were significantly increased the risk of macroalbuminuria (6.6-fold, P < 0.001) and progression from micro- to macro-albuminuria (3.85 times, P = 0.011). Also, the presence of both alleles of eNOST and MTHFR 677T were significantly associated with increased risk of macroalbuminuria (4.8-fold, P = 0.005). The presence of GT + TT genotypes of eNOS was significantly associated with increased risk of coronary artery disease in micro- and macro-albuminuric patients compared to normoalbuminuric patients. The concomitant presence of three mutant alleles significantly increased the risk of macroalbuminuria and progression from micro- to macro-albuminuria 38.5- and 10.5-fold, respectively. Our study indicated that eNOS T allele interacts with MTHFR variants, especially MTHFR A1298C to increase the risk of macroalbuminuria and progression from micro-to macro-albuminuria. Also, Interaction between three alleles of eNOST, MTHFR 677T, and 1298C highly increased the risk of macroalbuminuria and progression of diabetic nephropathy in T2DM patients.