Polymorphisms of eNOS gene are associated with diabetic nephropathy: a meta-analysis

The Effect of Selected Nitric Oxide Synthase Polymorphisms on the Risk of Developing Diabetic Nephropathy

BACKGROUND

Nitric oxide synthase (NOS) is an enzyme that catalyzes the formation of nitric oxide (NO), the altered production of which is characteristic of diabetic nephropathy. NOS exists in three isoforms: NOS1, NOS2, and NOS3. Moreover, there are reports about the potential role of NOS3 polymorphisms in the development of diabetes complications. The aim of this study was to assess the role of selected NOS polymorphisms-rs3782218 (NOS1), rs1137933 (NOS2), rs1799983, rs2070744, and rs61722009 (NOS3)-in the risk of developing diabetic nephropathy and in the likelihood of renal replacement therapy.

METHODS

The studied polymorphisms were analyzed in a group of 232 patients divided into three groups. Four polymorphisms (rs3782218, rs1137933, rs1799983, rs2070744) were genotyped using the PCR-RFLP, while the rs61722009 polymorphism was genotyped using the PCR.

RESULTS

The C/C genotype and the C allele of the rs3782218 polymorphism (NOS1) were associated with an increased risk of developing diabetic nephropathy and an increased likelihood of renal replacement therapy. In turn, the G allele of the rs1137933 polymorphism (NOS2) reduces the likelihood of renal replacement therapy.

CONCLUSIONS

The specific genotypes or alleles of the rs3782218 (NOS1) and rs1137933 (NOS2) polymorphisms seem to be potential risk factors for diabetic nephropathy and renal replacement therapy.

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.

Pink pressure: beetroot (Beta vulgaris rubra) as a possible novel medical therapy for chronic kidney disease

Chronic kidney disease (CKD) manifests with systemic inflammation, oxidative stress, and gut dysbiosis, resulting in metabolic disorders and elevated rates of cardiovascular disease-associated death. These all correlate with a high economic cost to healthcare systems. Growing evidence indicates that diet is an indispensable ally in the prevention and management of CKD and its complications. In this context, the root vegetable beetroot (Beta vulgaris rubra) deserves special attention because it is a source of several bioactive compounds, such as nitrate, betaine, and betalain, and has shown beneficial effects in CKD, including reduction of blood pressure, anti-inflammatory effects, and antioxidant actions by scavenging radical oxidative species, as observed in preclinical studies. Beetroot consumption as a possible therapeutic strategy to improve the clinical treatment of patients with CKD and future directions for clinical studies are addressed in this narrative review.

Association of polymorphisms in serotonin and nitric oxide genes with clinical outcome of dengue in Brazilian northeast population

Serotonin and nitric oxide seem to be involved in Dengue virus infection. The aim of this study was to investigate if SNPs in serotonin and nitric oxide are associated with dengue severity. A retrospective case-control study was conducted, with groups of dengue fever (DF; n = 78) and dengue hemorrhagic fever patients (DHF; n = 49). Genotyping was performed using qPCR and PCR. The power of the sample size was calculated by G*power software. The heterozygous SL for 5-HTTLPR SNP was significantly correlated with protection against progression to DHF in the codominant SS/SL/LL (OR = 0.22, 95% CI = 0.06-0.81, p = 0.011) and overdominant models SL vs SS + LL (OR = 0.19, 95% CI = 0.06-0.65, p = 0.003). For the ENOS (rs1799983) SNP, the genotype GT was positively associated with protection for development of the clinical form in DHF compared to dengue fever (OR = 0.39, 95% CI = (0.13-1.14), p = 0.0058) in codominant GG/GT/TT and overdominant model GT vs GG + TT (OR = 0.35, 95% CI = (0.12-1.02), p = 0.04). To our knowledge, this is the first study to identify the association of the serotonin and nitric oxide SNPs with dengue severity.

The roles of endothelial nitric oxide synthase gene polymorphisms in diabetes mellitus and its associated vascular complications: a systematic review and meta-analysis

PURPOSE

The roles of endothelial nitric oxide synthase (eNOS) gene polymorphisms in diabetes mellitus (DM) were intensively analyzed, but the results of these studies were inconsistent. Therefore, we performed this study to better assess the relationship between eNOS genetic variations and DM.

METHODS

Eligible studies were searched in PubMed, Medline, Embase, and Web of Science. Odds ratios (ORs) with 95% confidence intervals (CIs) were used to assess correlations between eNOS polymorphisms and DM.

RESULTS

A total of 91 studies were finally included in our analyses. Significant associations with the susceptibility to DM were detected for the rs891512, rs1799983, rs2070744, and rs869109213 polymorphisms. As for vascular complications in DM, significant associations with the susceptibility to diabetic nephropathy were detected for the rs1799983 and rs2070744 polymorphisms. In addition, we also found that the rs1799983 polymorphism was significantly associated with the susceptibility to peripheral artery disease, whereas the rs2070744 polymorphism was significantly associated with the susceptibility to coronary artery disease in DM patients. Further subgroup analyses on the basis of type of disease and ethnicity of participants showed similar positive results.

CONCLUSIONS

In conclusion, our findings indicate that rs891512, rs1799983, rs2070744, and rs869109213 polymorphisms may serve as genetic biomarkers of DM, while rs1799983, rs2070744, and rs869109213 polymorphisms may contribute to the development of vascular complications in DM.

NOS3 Polymorphisms and Chronic Kidney Disease

Chronic kidney disease (CKD) is a multifactorial pathophysiologic irreversible process that often leads to a terminal state in which the patient requires renal replacement therapy. Most cases of CKD are due to chronic-degenerative diseases and endothelial dysfunction is one of the factors that contribute to its pathophysiology. One of the most important mechanisms for proper functioning of the endothelium is the regulation of the synthesis of nitric oxide. This compound is synthesized by the enzyme nitric oxide synthase, which has 3 isoforms. Polymorphisms in the NOS3 gene have been implicated as factors that alter the homeostasis of this mechanism. The Glu298Asp polymorphisms 4 b/a and -786T>C of the NOS3 gene have been associated with a more rapid deterioration of kidney function in patients with CKD. These polymorphisms have been evaluated in patients with CKD of determined and undetermined etiology and related to a more rapid deterioration of kidney function.

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.

Polymorphisms of Antioxidant Genes as a Target for Diabetes Management

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

Polymorphisms in oxidative stress pathway genes and risk of diabetic nephropathy in South Indian type 2 diabetic patients

AIM

Diabetic nephropathy (DN), a common microvascular complication of type 2 diabetes mellitus (T2DM) is polygenic, with a vast array of genes contributing to disease susceptibility. Accordingly, we explored the association between DN and six polymorphisms in oxidative stress related genes, namely eNOS, p22phox subunit of NAD(P)H oxidase, PARP-1 and XRCC1 in South Indian T2DM subjects.

METHODS

The study included 155 T2DM subjects with DN and 162 T2DM patients with no evidence of DN. The selected polymorphisms were genotyped by polymerase chain reaction and Taqman allele discrimination assay.

RESULTS

No significant difference was observed in the genotype and allele distribution of eNOS -786T > C, intron 4a4b, p22phox 242C > T and XRCC1 Arg399Gln polymorphisms between T2DM groups with and without DN. Contrastingly, there appeared to be a significant association of eNOS 894G > T and PARP-1 Val762Ala polymorphisms with DN wherein, the presence of 894T allele was associated with an enhanced risk for DN [P = 0.005; OR = 1.78 (1.17-2.7)], while the 762Ala allele seemed to confer significant protection against DN [P = 0.02; OR = 0.59 (0.37-0.92)]. Multiple logistic regression analysis revealed a significant and independent association of eNOS 894G > T, PARP-1 Val762Ala polymorphisms and hypertension with DN in T2DM individuals.

CONCLUSIONS

eNOS 894G > T and PARP-1 Val762Ala polymorphisms appeared to associate significantly with DN, with the former contributing to an enhanced risk and the latter to a reduced susceptibility to DN in South Indian T2DM individuals.

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.

Association between genetic polymorphisms of ACE & eNOS and diabetic nephropathy

Diabetic nephropathy (DN) is the leading cause of end-stage renal disease, with multiple genetic and environmental factors involving in its etiology. ACE and eNOS gene were considered to have important roles in the development and progression of DN. In this study, a case-control study was carried out to investigate the effects of 7 SNPs in ACE gene and 2 SNPs in eNOS gene in the development of DN in Northern China.7 SNPs including A240T, A2350G, A5466C, A2215G, T3892C, C1237T and C3409T of ACE gene and 2 SNPs (G894T and T786C) of eNOS gene were genotyped by polymerase chain reaction restriction fragment length polymorphism method. 431 type 2 diabetic patients with nephropathy (cases) were compared to 420 type 2 diabetic patients without nephropathy (controls) in the study. Data were analyzed by SPSS 17.0 and HaploView software. The frequency distribution of A2350G, 4 haplotyps in ACE gene and G894T in eNOS gene were demonstrated to be different between case and control groups significantly. Whereas other SNPs and haplotypes had no differences in two cohorts. The results revealed that variations of ACE and eNOS gene had association with DN, which indicated ACE and eNOS gene may play an important role in pathogenesis of DN in Northern Chinese Han population.

NOS3 894G>T polymorphism is associated with progression of kidney disease and cardiovascular morbidity in type 2 diabetic patients: NOS3 as a modifier gene for diabetic nephropathy?

BACKGROUND/AIMS

We have previously associated SNP 894G>T in the NOS3 gene with diabetic nephropathy (DN) using multi-locus analysis. Variant 894G>T has been widely studied as a DN susceptibility factor with contradictory results. In the present study we genotyped 894G>T in the cohort of prospectively followed type 2 diabetics with the aim to investigate its possible role in the progression of DN and development of morbidity and mortality associated with diabetes.

METHODS

311 subjects with defined stage of DN were enrolled in the study and followed up for a median of 38 months. We considered three end-points: progression of DN, major cardiovascular event and all-cause mortality.

RESULTS

Considering baseline GFR, age at enrolment and diabetes duration as confounders, Cox regression analysis identified 894GT genotype as a risk factor for DN progression (HR = 1.843 [95% CI 1.088 - 3.119], P = 0.023) and 894TT genotype as a risk factor for major cardiovascular event (HR = 2.515 [95% CI 1.060 - 5.965], P = 0.036).

CONCLUSION

We ascertained the significant effect of the NOS3 894G>T variant on DN progression and occurrence of major cardiovascular event in T2DM subjects. Based on these results NOS3 can be considered a modifier gene for DN.

Endothelial nitric oxide synthase gene polymorphisms and prostate cancer risk in Serbian population

Genome-wide association studies (GWAS) have identified over 46 SNPs associated with human prostate cancer (PCa). Some studies have shown correlation of the nitric oxide synthase (NOS) NOS3 gene polymorphisms with the risk and/or progression of PCa. This study aimed to evaluate the association of NOS3 gene polymorphisms (-786T>C, -764A>G, -714G>T, -690C>T, -649G>A and 894G>T) with PCa risk and progression. 150 patients with PCa, 150 patients with BPH and 100 age-matched healthy controls were recruited in this study. Genotyping of promoter polymorphisms was performed by bi-directional DNA sequencing, and for 894G>T by RFLP analysis. There was no significant association between the alleles and genotypes of these genetic variants and PCa risk. For -786T>C polymorphism, we found that C allele is associated with absence of metastases, assuming dominant genetic model (P = 0.049; OR, 0.50; 95% CI, 0.25-1.00). It was found that, compared with NOS3 -690C>T variant CC genotype, CT and TT genotypes confer decreased risk of developing metastases (dominant model, P = 0.015, OR, 0.24; 95% CI, 0.07-0.88) and show association with low clinical tumour stage, compared with stages T3 and T4 (dominant model, P = 0.046, OR, 0.20; 95% CI, 0.04-1.02). Genetic variants -764A>G, -714G>T, -649G>A were not detected in our study group. There is evidence of an inverse correlation of the NOS3 894G>T minor allele with high serum PSA (>20 ng/ml) (dominant model, P = 0.013, OR, 0.37; 95% CI, 0.17-0.82). Our results suggest that NOS3 gene polymorphisms are genetic susceptibility factors for the progression of PCa and patient outcome.

Genetic variants of eNOS gene may modify the susceptibility to idiopathic male infertility

In testis, eNOS is responsible for synthesis of nitric oxide (NO) which is an essential gas message regulator in spermatogenesis, suggesting that eNOS gene plays a role in normal spermatogenesis and the genetic variants of eNOS gene may be potential genetic risk factors of spermatogenesis impairment. In this study, the polymorphic distributions of three common polymorphism loci including T-786C, 4A4B and G894T in eNOS gene were investigated in 355 Chinese infertile patients with azoospermia or oligozoospermia and 246 healthy fertile men and a meta-analysis was carried in order to explore the possible relationship between the three loci of eNOS gene and male infertility with spermatogenesis impairment. As a result, allele -786C of T-786C (11.4% versus 6.5%, p = 0.004) and 4A of 4A4B (11.0% versus 6.3%, p = 0.005) as well as genotype TC of T-786C (22.8% versus 13.0%, p = 0.002) and AB of 4A4B (18% versus 11%, p = 0.015) were significantly associated with idiopathic male infertility. The haplotypes T-4A-G (7.4% versus 4.1%, p = 0.015) and C-4B-G (7.6% versus 4.4%, p = 0.028) could increase the susceptibility to male infertility, whereas haplotype T-4B-G (67.0% versus 75.2%, p = 0.002) might be a protective factor for male infertility. The results of meta-analysis revealed that the polymorphism of T-786C was associated with male infertility. These findings suggested that the variants of eNOS gene may modify the susceptibility to male infertility with impaired spermatogenesis.

Association of eNOS gene intron 4 a/b VNTR polymorphisms in children with nephrotic syndrome

To investigate the association of endothelial nitric oxide synthase gene intron 4 (eNOS4) polymorphisms with nephrotic syndrome, the eNOS4 genotypes were assessed in 161 children with nephrotic syndrome in comparison with 78 healthy subjects. We classified the children with nephritic syndrome into 2 groups: as steroid-sensitive nephrotic syndrome (SSNS) (n=125) and steroid-resistant nephrotic syndrome (SRNS) (n=36). The eNOS4 polymorphisms were analyzed by polymerase chain reaction. The frequencies of eNOS4 aa, ab and bb genotypes were 3%, 31%, and 66% in all the nephrotic syndrome groups, and 1%, 23%, and 76% in the control group (x(2)=2.87, p>0.05). In addition, the frequencies of eNOS4 aa, ab and bb genotypes were 2%, 33%, and 65% in SSNS group, and 5%, 28%, and 67% in the SRNS group (x(2)=1.13, p=0.567). The present study is the first to investigate eNOS4 gene polymorphisms in children with SSNS and SRNS. Our data show that the eNOS4 gene polymorphisms were not associated with the development, frequent relapse and response to steroid in nephritic syndrome.

[Advances of genetics in diabetic nephropathy]

Diabetic nephropathy (DN) is one of the most serious chronic complications of diabetes mellitus. The observed incidence patterns in different ethnics and familial clustering have suggested that the genetic factor plays an important role in the development and progression of DN. This paper reviews the recent advances on genetics of DN, including candidate genes association studies, linkage studies and genome-wide association studies (GWASs). Candidate genes association studies and meta-analysis showed that a few candidate genes have been reproducibly associated with DN, such as ACE, AGT and PPARG genes. Linkage studies and genome-wide linkage studies have also identified susceptibility chromosomal loci. With the development of high-throughput sequencing and chip techniques, GWAS has become an important strategy to identify variants responsible for DN. The genetic factor has been the significant contribution to the pathobiology of DN. However, it is not the only cause of the pathobiology of DN, because the environment factor also influences the pathobiology of DN. Nonetheless, genetic studies may provide valuable information for the pathobiology of nephropathy and potential targets of its treatment.

eNOS deficiency predisposes podocytes to injury in diabetes

Endothelial nitric oxide synthase (eNOS) deficiency may contribute to the pathogenesis of diabetic nephropathy in both experimental models and humans, but the underlying mechanism is not fully understood. Here, we studied two common sequelae of endothelial dysfunction in diabetes: glomerular capillary growth and effects on neighboring podocytes. Streptozotocin-induced diabetes increased glomerular capillary volume in both C57BL/6 and eNOS(-/-) mice. Inhibiting the vascular endothelial growth factor receptor attenuated albuminuria in diabetic C57BL/6 mice but not in diabetic eNOS(-/-) mice, even though it inhibited glomerular capillary enlargement in both. In eNOS(-/-) mice, an acute podocytopathy and heavy albuminuria occurred as early as 2 weeks after inducing diabetes, but treatment with either captopril or losartan prevented these effects. In vitro, serum derived from diabetic eNOS(-/-) mice augmented actin filament rearrangement in cultured podocytes. Furthermore, conditioned medium derived from eNOS(-/-) glomerular endothelial cells exposed to both high glucose and angiotensin II activated podocyte RhoA. Taken together, these results suggest that the combined effects of eNOS deficiency and hyperglycemia contribute to podocyte injury, highlighting the importance of communication between endothelial cells and podocytes in diabetes. Identifying mediators of this communication may lead to the future development of therapies targeting endothelial dysfunction in albuminuric individuals with diabetes.

Relationship between five GLUT1 gene single nucleotide polymorphisms and diabetic nephropathy: a systematic review and meta-analysis

So far, case-control studies on the association between glucose transporter 1 (GLUT1) gene single nucleotide polymorphisms (SNPs) and diabetic nephropathy (DN) have generated considerable controversy. To clarify the linkage of GLUT1 SNPs on the risk of DN, a systematic review and meta-analysis was performed. A comprehensive literature search of electronic databases was conducted to obtain relative studies. Nine case-control studies were included. Significant differences were found between XbaI SNP (rs841853) and increased risk of DN in all genetic models. Subgroup analyses for Caucasians population and DN from both type 1 and type 2 diabetes also revealed positive results. For Enh2-1 SNP (rs841847), Enh2-2 SNP (rs841848) and HaeIII SNP (rs1385129), obvious linkages were demonstrated in recessive model. However, analysis for the association between HpyCH4V SNP (rs710218) and the susceptibility of DN showed no significance. Likewise, negative outcome was also found in the assessment for the influence of XbaI or Enh2-2 SNP on the pathogenesis progress of DN. The evidence currently available shows that XbaI, Enh2 and HaeIII SNPs, but not HpyCH4V SNP, in GLUT1 gene may be genetic susceptibility to DN. However, data does not support the association between either XbaI or Enh2-2 SNP and the severity of DN.

The role of nitric oxide in the dysregulation of the urine concentration mechanism in diabetes mellitus

Uncontrolled diabetes mellitus results in osmotic diuresis. Diabetic patients have lowered nitric oxide (NO) which may exacerbate polyuria. We examined how lack of NO affects the transporters involved in urine concentration in diabetic animals. Diabetes was induced in rats by streptozotocin. Control and diabetic rats were given L-NAME for 3 weeks. Urine osmolality, urine output, and expression of urea and water transporters and the Na-K-2Cl cotransporter were examined. Predictably, diabetic rats presented with polyuria (increased urine volume and decreased urine osmolality). Although metabolic parameters of control rats were unaffected by L-NAME, treated diabetic rats produced 30% less urine and osmolality was restored. UT-A1 and UT-A3 were significantly increased in diabetic rat inner medulla. While L-NAME treatment alone did not alter UT-A1 or UT-A3 abundance, absence of NO prevented the upregulation of both transporters in diabetic rats. Similarly, AQP2 and NKCC2 abundance was increased in diabetic animals however, expression of these transporters were unchanged by L-NAME treatment of diabetes. Increased expression of the concentrating transporters observed in diabetic rats provides a compensatory mechanism to decrease solute loss despite persistent glycosuria. Our studies found that although diabetic-induced glycosylation remained increased, total protein expression was decreased to control levels in diabetic rats treated with L-NAME. While the role of NO in urine concentration remains unclear, lowered NO associated with diabetes may be deleterious to the transporters’ response to the subsequent osmotic diuresis.

Nitric oxide synthase derangements and hypertension in kidney disease

PURPOSE OF REVIEW

Nitric oxide deficiency occurs by multiple mechanisms and contributes to the pathogenesis of progression of chronic kidney disease (CKD) and its cardiovascular complications. This article concentrates on recent developments on the regulation of the endogenous nitric oxide synthase (NOS) inhibitor asymmetric dimethylarginine (ADMA) in CKD and on the importance of the nitric oxide synthases in kidney disease progression, particularly in diabetic nephropathy.

RECENT FINDINGS

The increased plasma ADMA seen in renal disease is generally predictive of severity of CKD progression and cardiovascular risk. However, some assumptions about the control of ADMA have been challenged: the primacy of the kidney as a metabolic organ for plasma ADMA regulation has come under scrutiny and the relative importance of the two isoforms of the ADMA-metabolizing enzymes dimethylarginine dimethylaminohydrolases (DDAHs) is being re-evaluated. Alterations in NOS also contribute to CKD progression with the endothelial isoform playing a major role in diabetic nephropathy.

SUMMARY

Improving our understanding of ADMA regulation is important since pharmacologic targeting of DDAH is underway. The major role of endothelial NOS-derived nitric oxide in diabetic nephropathy should lead to novel therapies. The beneficial actions of dietary nitrate supplementation on blood pressure and kidney disease are of considerable clinical relevance.

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.