Endothelial Nitric Oxide Synthase Gene Intron 4 (VNTR) Polymorphism and Vascular Access Graft Thrombosis

[Effect of genetic polymorphisms on functioning of a permanent vascular access in patients on dialysis]

Thromboses and stenoses of permanent vascular access appear to be a serious hazard for patients with end-stage kidney disease on programmed haemodialysis. Relapses of these pathological conditions are the cause of repeated hospitalization, secondary surgical interventions and may eventually lead to impossibility of carrying out procedures of haemodialysis. Often, vascular access dysfunction occurs for no apparent reason, thus underlying the importance of studies aimed at revealing additional factors of intravascular thrombogenesis and neointimal formation in a vascular access, including the works dedicated to studying genetic predictors of the development of the above-mentioned complications. The authors examined herein the role of polymorphisms of the genes of endothelin-1 (END-1), nitric oxide synthase-3 (NOS-3), angiotensinogen-2 (AGT-2), angiotensinogen-1 (AGT-1), angiotensinogen 2 receptor type 1 (AGTR1), mitochondrial superoxide dismutase-2 (SOD-2), catalase (CAT) superoxide dismutase-1 (SOD-1) and angiotensin converting enzyme (ACE) in the functional state of permanent vascular access in patients on dialysis. The obtained results demonstrated direct cause-and-effect relationships between polymorphisms lys-198 asn in the END-1 gene, C60T, T58C in the SOD-2 gene and the function of vascular access. The presence of END-1 gene lys-198 asn polymorphism in a homozygous state (allele 1) was associated with a high risk of an unsatisfactory condition of permanent vascular access (p=0.019).

Endothelial nitric oxide synthase intron 4a/b polymorphism in coronary artery disease in Thrace region of Turkey

Coronary artery disease (CAD) is one of the frequent cardiovascular mortality causes in the world. Common risk factors explain only about half the risk of CAD. The healthy familial predisposition to CAD, combined with advances in genetic analysis, has led to a number of studies in recent years making an effort to identify the genetic factors that influence the risk. The approach taken by most studies was to examine the association of naturally occurring genetic polymorphisms in candidate genes with risk of or severity of CAD. Endothelial nitric oxide synthase (eNOS) is important for vascular and tissue protection and is found in endothelial cells that encompass the entire vasculature, including the vessels in the heart. Nitric oxide (NO) is produced in a catabolic reaction in the endothelial cells, neurons, glia and macrophages by nitric oxide synthase (NOS) isoenzymes. eNOS is a subgroup of this family of enzymes that catalyses the production of nitric oxide (NO) from L-arginine and oxygen, which leads to vascular relaxation by activating the guanylate cyclase. This finally induces smooth muscle relaxation. The aim of this study was to investigate the allelic frequency and the genotypic distribution of the variable number of tandem repeat 27 (27 VNTR) gene polymorphism in intron 4 of the eNOS (eNOS 4a/b) gene in Thrace region, to compare CAD patients with appropriate healthy controls and to correlate the genetic findings with CAD subtypes. The study group included 281 (153 subjects with CAD and 128 controls) patients. The eNOS polymorphism was identified with a polymerase chain reaction. Genotypes were defined as aa, ab and bb according to the presence of a and b alleles. In this case–control study, we found that there was sensible correlation between eNOS gene intron 4a/b VNTR polymorphism and the risk of CAD in Thrace region of Turkey. However, there was no major difference for the genotype distribution and the allelic frequency among the CAD subtypes. Further studies on the interaction of such genes are needed to clarify the association between eNOS 4a/b polymorphism and CAD patients.

Genetic causation of neointimal hyperplasia in hemodialysis vascular access dysfunction

The major cause of hemodialysis vascular access failure is venous stenosis resulting from neointimal hyperplasia. Genetic factors have been shown to be associated with cardiovascular disease and peripheral vascular disease (PVD) in the general population. Genetic factors may also play an important role in vascular access stenosis and development of neointimal hyperplasia by affecting pathways that lead to inflammation, endothelial function, oxidative stress, and vascular smooth muscle proliferation. This review will discuss the role of genetics in understanding neointimal hyperplasia development in hemodialysis vascular access dysfunction and other disease processes with similar neointimal hyperplasia development such as coronary artery disease and PVD.

The association between eNOS intron 4 VNTR polymorphism and delayed graft function of kidney allografts

Nitric oxide (NO) is a multifunctional agent which serves as a key signaling molecule in physiological processes such as host defense, neuronal communication, and the regulation of vascular tone. Different polymorphic variations have been identified in the human NOS3 (eNOS) gene.The aim of the present study was to examine the association between polymorphisms of the NOS3 gene (G894T substitution within exon 7 and intron 4 VNTR polymorphism) and the development of delayed graft function as well as acute and chronic rejection.One hundred eighty-seven recipients of first renal transplants were included in the study. There were no significant associations between these polymorphisms and acute and chronic kidney allograft rejection. The intron 4 polymorphism was associated with delayed graft function after transplantation. The results of this study suggest that patients with the a allele of the eNOS intron 4 VNTR polymorphism may be predisposed to delayed graft function.

Endothelial function and endothelial nitric oxide synthase intron 4a/b polymorphism in primary hyperparathyroidism

BACKGROUND AND AIM

Patients with symptomatic primary hyperparathyroidism (pHT) have increased cardiovascular morbidity and mortality. Endothelial nitric oxide synthase (eNOS) intron 4a/b polymorphism is associated with coronary artery disease and hypertension in various populations. Our aim is to evaluate endothelial function in patients with pHT during pre-operative hypercalcemic and post-operative normocalcemic periods and to determine whether intron 4a/b polymorphism of eNOS gene influences endothelial function.

SUBJECTS AND METHODS

Forty patients with pHT (age 48.48+/-11.64 yr) were examined pre-operatively and reexamined 5.8+/-1.9 months after parathyroidectomy. Forty-three healthy subjects (age 47.13+/-8.14 yr) were served as control group. Endothelial function was determined by flow-mediated dilation of brachial artery (FMD). eNOS4a/b polymorphism was detected by polymerase chain reaction.

RESULTS

FMD was significantly lower in patients pre-operatively compared with controls (8.48+/-1.78% vs 19.49+/-2.34%, p<0.001). FMD improved significantly after parathyroidectomy (16.19+/-2.16%, p<0.001 compared with pre-operative measurements), but was still significantly lower than controls (p<0.001). The distribution of eNOS4a/b genotype frequencies was not significantly different between patients and controls. Logistic regression analysis showed that increased serum calcium (>2.47 mmol/l) and PTH concentrations (>7.75 pmol/l) were significant independent predictors of lower FMD (<16.7%). ENOS4a/b polymorphism did not enter in this model.

CONCLUSION

Impaired endothelial function in patients with pHT improves after successful parathyroid surgery. No compelling data are evident to suggest that eNOS4a/b polymorphism modifies the endothelial function in patients with pHT.