Association analysis of CA repeat polymorphism of the endothelial nitric oxide synthase gene with essential hypertension in Japanese

Gene polymorphisms in calcium-calmodulin pathway: Focus on cardiovascular disease

Cardiovascular disease is the leading cause of death in industrialized countries and affects an increasing number of people. Several risk factors play an important role in the etiology of this disease, such as an unhealthy lifestyle. It is increasingly clear that genetic factors influencing the molecular basis of excitation-contraction mechanisms in the heart could contribute to modify the individual's risk. Thanks to the progress that has been made in understanding calcium signaling in the heart, it is assumed that calmodulin can play a crucial role in the excitation-contraction coupling. In fact, calmodulin (CaM) binds calcium and consequently regulates calcium channels. Several works show how some polymorphic variants can be considered predisposing factors to complex pathologies. Therefore, we hypothesize that the identification of polymorphic variants of proteins involved in the CaM pathway could be important for understanding how genetic traits can influence predisposition to myocardial infarction. This review considers each pathway of the three different isoforms of calmodulin (CaM1; CaM2; CaM3) and focuses on some common proteins involved in the three pathways, with the aim of analyzing the polymorphisms studied in the literature and understanding if they are associated with cardiovascular disease.

Glu298Asp Endothelial Nitric Oxide Synthase Polymorphism Is a Risk Factor for Erectile Dysfunction in the Mexican Mestizo Population

Penile erection depends on the balanced action between antagonist vasoactive molecules such as nitric oxide (NO) and angiotensin. Endothelial nitric oxide synthase (eNOS) and angiotensin-converting enzyme (ACE) polymorphisms have been associated with endothelial dysfunction, which is described as a cause of erectile dysfunction (ED). Endothelial NOS and ACE are both regulators of vascular and corporal smooth muscle tone, which are connected by interaction between the NO-cyclic guanosine monophosphate pathway and the renin-angiotensin system. We analyzed the frequencies of 894 G/T (Glu298Asp) eNOS and ACE I/D polymorphisms in Mexican patients with ED (n=53) and in an age-matched control group (n=62). The populations analyzed were in Hardy Weinberg equilibrium. We found significant differences in allelic (chi2=4.42; P=.03) and genotypic frequencies (chi2=3.96; P=.04) between patients and controls for the 894 G/T eNOS polymorphism. Presence of the 894T allele in carriers increased the risk of ED (odds ratio [TT + GT versus GG] = 2.37; 95% confidence interval, 1.08 to 5.21; P=.02). Multiple logistic regression analysis showed that the Glu298Asp polymorphism was an independent factor for ED, as was diabetes mellitus, hypertension, cardiac disease, and cigarette smoking. No association was found between ACE I/D polymorphism and ED in the population studied. Therefore, our results suggest that Glu298Asp eNOS polymorphism plays a role as a genetic susceptibility factor for ED.

Sexual dysfunction in male schizophrenia: influence of antipsychotic drugs, prolactin and polymorphisms of the dopamine D2 receptor genes

Aim: Sexual dysfunction induced by antipsychotic drug treatment is under investigated and under reported. This study aimed to determine the influence of genetic polymorphisms in the D2 dopamine receptor (DRD2) and endothelial nitric oxide synthase (eNOS) genes, and the possible role of blood prolactin concentrations on sexual function in schizophrenic patients. Materials & methods: Male remitted schizophrenic patients (n = 100), who were living with a sexual partner and receiving antipsychotic drug monotherapy for at least 6 months, were assessed for sexual and erectile dysfunction using the Arizona Sexual Experience Scale and the five-item version of the International Index of Erectile Function. Blood samples were taken for plasma prolactin determination and genotyped for four polymorphisms: DRD2 (-141C Ins/Del and Taq1A) and eNOS gene (G894T and T-786C). Results: The -141C Ins/Del, but not Taq1A, polymorphism of the DRD2 gene was significantly associated with sexual dysfunction with the del allele being less frequent in sexual dysfunction subjects. Neither of the eNOS polymorphisms, G894T or T-786C, was significantly associated with sexual or erectile dysfunction. Prolactin concentrations were significantly higher in patients with erectile dysfunction but did not reach significance in those with sexual dysfunction. Prolactin was also reduced in -141C Del allele carriers. The frequency and severity of sexual dysfunction in the patients receiving typical antipsychotics was significantly greater than those receiving risperidone or clozapine, while prolactin concentrations were significantly higher in subjects receiving risperidone compared with those receiving clozapine or typical antipsychotics. Conclusion: This is the first evidence indicating that antipsychotic drug treatment in men is associated with a variant in the DRD2 gene in which the -141C Del allele might be a protective factor. While this may, in part, be mediated by effects on prolactin, other factors are likely to contribute to the greater sexual dysfunction in patients receiving typical antipsychotics.

Original submitted 25 January 2011; Revision submitted 21 March 2011

Genetics of athletic performance

Performance enhancing polymorphisms (PEPs) are examples of natural genetic variation that affect the outcome of athletic challenges. Elite athletes, and what separates them from the average competitor, have been the subjects of discussion and debate for decades. While training, diet, and mental fitness are all clearly important contributors to achieving athletic success, the fact that individuals reaching the pinnacle of their chosen sports often share both physical and physiological attributes suggests a role for genetics. That multiple members of a family often participate in highly competitive events, such as the Olympics, further supports this argument. In this review, we discuss what is known regarding the genes and gene families, including the mitochondrial genome, that are believed to play a role in human athletic performance. Where possible, we describe the physiological impact of the critical gene variants and consider predictions about other potentially important genes. Finally, we discuss the implications of these findings on the future for competitive athletics.

Haplotype-based case-control study of receptor (calcitonin) activity-modifying protein-1 gene in cerebral infarction

Calcitonin gene-related peptide (CGRP) receptor is a complex molecule that consists of calcitonin receptor-like receptor and receptor activity-modifying protein-1 (RAMP1). It was recently reported that RAMP1-deficient mice (RAMP1(-/-)) showed inflammatory responses with a transiently significant increase in serum CGRP levels and proinflammatory cytokines when compared with RAMP1(+/+) mice. The aim of this study was to investigate the relationship between the human RAMP1 gene and cerebral infarction (CI) using single-nucleotide polymorphisms (SNPs) in a Japanese population. We selected six SNPs in the human RAMP1 gene (rs3754701, rs3769048, rs7557078, rs1584243, rs10199956 and rs7590387) and performed a case-control study using each SNP and haplotype in 171 CI patients and 234 controls. There were no significant differences in overall distribution of genotype and allele frequencies of the SNPs between the CI and control groups. However, there was a significant difference in overall distribution between the CI and control groups (P<0.001) in the haplotype-based case-control study with the combinations of rs3754701-rs3769048-rs7590387. The T-A-C susceptibility haplotype for CI was significantly more frequent than in the control group (P=0.0024). The results suggest that the T-A-C haplotype is a genetic marker for CI, and that RAMP1 or neighbouring genes are associated with increased susceptibility to CI.

Association of a 27-bp repeat polymorphism in intron 4 of endothelial constitutive nitric oxide synthase gene with myocardial infarction in Tunisian patients

BACKGROUND

Nitric oxide (NO) produced by endothelial nitric oxide synthase (eNOS) mediates endothelium-dependent vasodilatation and antithrombotic action. Controversial results regarding the association of eNOS gene (NOS3) polymorphisms with myocardial infarction (MI) have been reported. In the present study, we examined a possible association between a 27-base pair (bp) repeat polymorphism in intron 4 of the NOS3 gene and MI in a subgroup of the Tunisian population.

METHODS

A total of 310 Tunisian patients with MI and 250 healthy controls were included in the study. The NOS3 gene intron 4a4b variable number of tandem repeats polymorphism was analyzed by PCR.

RESULTS

A significant difference in genotype distribution and allele frequency was observed between patients and controls. Patients with MI had a frequency of 4.8% for the 4a4a genotype, 33.9% for the 4a4b genotype and 61.3% for the 4b4b genotype. Controls had a frequency of only 1.6% for the 4a4a genotype, 24.4% for the 4a4b genotype and 74.0% for the 4b4b genotype (chi2=11.81, p=0.003). The MI patient group showed a significant higher frequency of the 4a allele compared to controls (0.218 vs. 0.139; chi2=5.81, p=0.01).

CONCLUSIONS

In the present study, a significant association between the NOS34a/4b gene polymorphism (presence of 4a allele) and MI in the Tunisian population was found.

Endothelial nitric oxide synthase gene polymorphism and elite endurance athlete status: the Genathlete study

In the Genathlete study, we examined the contribution of three polymorphisms in the endothelial nitric oxide synthase (NOS3) gene to discriminate elite endurance athletes (EEA) from sedentary controls (SC). The EEA group included a total of 316 Caucasian males with a VO2max >75 mL/kg. The SC group comprised 299 unrelated sedentary Caucasian males who had VO2max values below 50 mL/kg. The polymerase chain reaction technique was used to amplify a microsatellite (CA)(n) repeat in intron 13, a 27 bp repeat in intron 4 and a third fragment in exon 7 containing the Glu298Asp SNP. No difference was found between the EEA and SC groups for the 27 bp repeat and the Glu298Asp polymorphism. Chi-square analysis of the overall allelic distribution of the (CA)(n) repeat revealed no significant difference between the two groups (P=0.135). However, comparing carriers and non-carriers for the most common (CA)(n) repeat alleles, we found significant differences between SC and EEA, with more EEA subjects carrying the 164 bp allele (P=0.007). In summary, we found suggestive evidence that the 164 bp allele of the (CA)(n) repeat in intron 13 is associated with EEA status and may account for some of the differences between EEA and SC.

Endothelial nitric oxide synthase G894T gene polymorphism in Chilean subjects with coronary artery disease and controls

BACKGROUND

Nitric oxide (NO) from the endothelium, produced by oxidation of l-arginine to L-citruline for the action at the endothelial nitric oxide synthase (eNOS), is considered an important atheroprotective factor. The Glu298Asp (G894T) polymorphic variant of the eNOS gene has been implicated in the development of coronary artery disease (CAD). We investigated the association between occurrence of CAD documented by angiography and the G894T polymorphism of the NOS3 gene in Chilean individuals.

METHODS

A total of 112 unrelated patients with diagnosis of CAD and 72 controls were included in this study. G894T gene polymorphism was analyzed by polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP).

RESULTS

The frequency of TT homozygous genotype for G894T polymorphism was 7% in CAD patients and 1% in the control group. However, the genotype distribution and allele frequencies were not significantly different between CAD and control subjects (P>0.05). Moreover, the odds ratio for CAD associated with the T variant failed to reach statistical significance (OR=1.5; 95% CI: 0.87-2.59, P>0.05).

CONCLUSION

These findings suggest that the G894T polymorphism of the eNOS gene was not associated with CAD in Chilean individuals.

Nitric oxide and the vascular endothelium

The vascular endothelium synthesises the vasodilator and anti-aggregatory mediator nitric oxide (NO) from L-arginine. This action is catalysed by the action of NO synthases, of which two forms are present in the endothelium. Endothelial (e)NOS is highly regulated, constitutively active and generates NO in response to shear stress and other physiological stimuli. Inducible (i)NOS is expressed in response to immunological stimuli, is transcriptionally regulated and, once activated, generates large amounts of NO that contribute to pathological conditions. The physiological actions of NO include the regulation of vascular tone and blood pressure, prevention of platelet aggregation and inhibition of vascular smooth muscle proliferation. Many of these actions are a result of the activation by NO of the soluble guanylate cyclase and consequent generation of cyclic guanosine monophosphate (cGMP). An additional target of NO is the cytochrome c oxidase, the terminal enzyme in the electron transport chain, which is inhibited by NO in a manner that is reversible and competitive with oxygen. The consequent reduction of cytochrome c oxidase leads to the release of superoxide anion. This may be an NO-regulated cell signalling system which, under certain circumstances, may lead to the formation of the powerful oxidant species, peroxynitrite, that is associated with a variety of vascular diseases.

Genetic determinants of blood pressure regulation

Hypertension is a multifactorial disorder that probably results from the inheritance of a number of susceptibility genes and involves multiple environmental determinants. Existing evidence suggests that the genetic contribution to blood pressure variation is about 30-50%. Although a number of candidate genes have been studied in different ethnic populations, results from genetic analysis are still inconsistent and specific causes of hypertension remain unclear. Furthermore, the abundance of data in the literature makes it difficult to piece together the puzzle of hypertension and to define candidate genes involved in the dynamic of blood pressure regulation. In this review, we attempt to highlight the genetic basis of hypertension pathogenesis, focusing on the most important existing genetic variations of candidate genes and their potential role in the development of this disease. Our objective is to review current knowledge and discuss limitations to clinical applications of genotypic information in the diagnosis, evaluation and treatment of hypertension. Finally, some principles of pharmacogenomics are presented here along with future perspectives of hypertension.

Variable number of tandem repeat of the 5'-flanking region of type-C human natriuretic peptide receptor gene influences blood pressure levels in obesity-associated hypertension

The gene for natriuretic peptides receptor C (NPRC), which is a candidate susceptibility gene for essential hypertension (EH) or obese hypertension, plays a key role in the regulation of plasma levels and biological effects of natriuretic peptides. The aims of the present study were to find new genetic markers in the 5'-flanking region of the NPRC gene and to assess relationships between variants and phenotypes of EH, including EH in obese patients. Using polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) analysis, we discovered a novel six-nucleotide repeat polymorphism located 4 base pairs (bp) upstream of the major transcriptional initiation site. We performed association analysis of this variable number of tandem repeat (VNTR) in 242 EH patients and 212 normotensive controls (NT). Although no significant difference in overall frequency of VNTR was found between NT and EH groups, the blood pressure level of EH patients with the 5/6 genotype was significantly higher in obese subjects. This suggests that the VNTR of the 5'-flanking region of the NPRC gene influences blood pressure levels in obesity-associated hypertension.

Genetic variations related to hypertension: a review

Hypertension is a complex multifactorial disorder with genetic, environmental and demographic factors contributing to its prevalence. The genetic element contribution to blood pressure variation ranges from 30 to 50%. Therefore, identifying hypertension susceptibility genes will help understanding the pathophysiology of the disease. In addition to the potential impact of genomic information in selecting antihypertensive drug therapy, it may also help in recognizing those at risk of developing the disease, which may lead to new preventive approaches. Several strategies and methods have been used to identify hypertension susceptibility genes. Currently, genetic analysis of such data produced complex results, which makes it difficult to draw final conclusion on the use of genomic data in management of hypertension. This review attempts to summarize present known genetic variations that may be implicated in the pathogenesis of hypertension and to discuss various research strategies used to identify them. It also highlights some of the opportunities and challenges, which may be encountered in interpreting the value of these genetic variations to improve management of hypertension.

Diabetic nephropathy: of mice and men

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

Haplotype-Based Case-Control Study Revealing an Association between the Adrenomedullin Gene and Proteinuria in Subjects with Essential Hypertension

Adrenomedullin (AM) has various physiological actions on the cardiovascular system, including vasodilatation, diuresis, natriuresis, inhibition of aldosterone secretion, and increases of the cardiac output, all of which cause hypotension. Since AM plays a role in the pathophysiology of vascular diseases, genes controlling AM might be involved in the development and etiology of essential hypertension (EH). However, there have been few studies examining the relationship between the AM gene and hypertension. The aims of this study were to genotype some of the genetic markers for the human AM gene in Japanese subjects, and via a haplotype-based case-control study, assess the association between and the AM gene and EH or its risk factors, such as hyperlipidemia, renal damage, and proteinuria. We genotyped 205 EH patients and 210 age-matched normotensive (NT) individuals for two single nucleotide polymorphisms of rs4399321, rs7944706 and a microsatellite polymorphism located approximately 5,400 base pairs downstream of the 3' end of the human AM gene. The overall distribution in each variant and haplotype did not significantly differ between the two groups. However, after dividing the groups into those subjects with and without proteinuria, the haplotype analysis revealed a positive association. In conclusion, a possible mutation linked to the haplotype may indicate a genetic predisposition for proteinuria in EH.

Multilocus analysis of hypertension: a hierarchical approach

While hypertension is a complex disease with a well-documented genetic component, genetic studies often fail to replicate findings. One possibility for such inconsistency is that the underlying genetics of hypertension is not based on single genes of major effect, but on interactions among genes. To test this hypothesis, we studied both single locus and multilocus effects, using a case-control design of subjects from Ghana. Thirteen polymorphisms in eight candidate genes were studied. Each candidate gene has been shown to play a physiological role in blood pressure regulation and affects one of four pathways that modulate blood pressure: vasoconstriction (angiotensinogen, angiotensin converting enzyme - ACE, angiotensin II receptor), nitric oxide (NO) dependent and NO independent vasodilation pathways and sodium balance (G protein-coupled receptor kinase, GRK4). We evaluated single site allelic and genotypic associations, multilocus genotype equilibrium and multilocus genotype associations, using multifactor dimensionality reduction (MDR). For MDR, we performed systematic reanalysis of the data to address the role of various physiological pathways. We found no significant single site associations, but the hypertensive class deviated significantly from genotype equilibrium in more than 25% of all multilocus comparisons (2,162 of 8,178), whereas the normotensive class rarely did (11 of 8,178). The MDR analysis identified a two-locus model including ACE and GRK4 that successfully predicted blood pressure phenotype 70.5% of the time. Thus, our data indicate epistatic interactions play a major role in hypertension susceptibility. Our data also support a model where multiple pathways need to be affected in order to predispose to hypertension.

The microsatellite alleles on chromosome 1 associated with essential hypertension and blood pressure levels

Essential hypertension (EH) is thought to be a polygenic disease. Several candidate genes of this disease have been investigated in studies using polymorphic genetic markers, but some studies have failed to show any association of EH with these genes. In this experiment, we used microsatellite markers on chromosome 1, and performed an association study between EH and control subjects. Genomic DNA was amplified with fluorescently labelled primers from the Applied Biosystems PRISM linkage mapping set HD-5 comprising 63 highly polymorphic microsatellite markers with an average spacing of 4.5 cM. We isolated three loci showing significant differences: D1S507, D1S2713 and D1S2842. The P-values of the allele with the greatest post hoc contributions in D1S507, D1S2713 and D1S2842 were 0.0008, 0.0062 and 0.0084, respectively. All these values were significant after Bonferroni correction. Furthermore, we found that the three microsatellite alleles were associated with the levels of systolic blood pressure. These data suggest that there are at least the three susceptibility loci for EH on chromosome 1, and that a case-control study using microsatellite markers on genomewide basis is a useful method for isolating the susceptibility loci of multifactorial disorders.

The T-786C and Glu298Asp polymorphisms of the endothelial nitric oxide gene affect the forearm blood flow responses of Caucasian hypertensive patients

OBJECTIVES

We sought to investigate whether two polymorphisms located in the promoter (T(-786)C) and exon 7 (Glu298Asp) of the endothelial nitric oxide (NO) synthase (eNOS) gene affected agonists-mediated NO release.

BACKGROUND

Endothelial dysfunction can be genetically determined. Therefore, we investigated whether two polymorphisms located in the eNOS gene affected agonists-mediated NO release.

METHODS

We compared endothelial-dependent and -independent vasodilation of the different eNOS genotypes in a cross-sectional study on 187 subjects, of whom 137 were uncomplicated essential hypertensive patients (PH) (49 +/- 9 years, 151 +/- 11/99 +/- 5 mm Hg) and 50 healthy normotensive subjects (NT) (43 +/- 16 years, 123 +/- 10/78 +/- 7 mm Hg). Endothelial-dependent and -independent vasodilation was assessed as the forearm blood flow response to incrementally increasing doses of acetylcholine (0.15, 0.45, 1.5, 4.5, 15 microg/100 ml/min) and sodium nitroprusside (1, 2, 4 microg/100 ml/min), respectively. Genotyping was performed with melting curve analysis (Lightcycler) of polymerase chain reaction products from acceptor (5' end-labeled with LCRed 640) and donor probes (3' end-labeled with fluorescein) specific for each polymorphism. The genotype distribution of T(-786)C (CC = 21.9%, CT = 48.7%, TT = 29.4%) and Glu298Asp (GG = 39.0%, GT =51.9%, TT = 9.1%) was similar in PH and NT. A repeated measure analysis of variance showed a blunting of endothelium-dependent vasodilation in PH compared with NT (p < 0.001). A significant effect of the T(-786)C (p = 0.002) but not of the Glu298Asp (p = NS) eNOS polymorphism on endothelial-dependent vasodilation was found. However, we also detected a significant interaction between the T(-786)C and Glu298Asp polymorphism (p < 0.001). No effect on either polymorphism on endothelial-independent vasodilation was seen.

CONCLUSIONS

The T(-786)C promoter polymorphism and its interaction with exon 7 Glu298Asp affect endothelium-dependent vasodilation in mild-to-moderate PH patients and NT Caucasian subjects.

The T-786C endothelial nitric oxide synthase genotype is a novel risk factor for coronary artery disease in Caucasian patients of the GENICA study

OBJECTIVES

We investigated the association of polymorphisms in the promoter region and exon 7 endothelial nitric oxide synthase (eNOS) gene with coronary artery disease (CAD).

BACKGROUND

Endothelial dysfunction foretells cardiovascular events and can be genetically determined.

METHODS

We genotyped for the promoter (T(-786)C) and exon 7 (Glu298Asp, G(894)T) polymorphisms in 1,225 subjects; 1,106 were consecutive patients undergoing coronary angiography and 119 control subjects without any cardiovascular risk factors. Genotyping was performed with melting curve analysis of polymerase chain reaction products from allele-specific acceptor and donor probes that were 5'- and 3'-end labeled with LCRed640 and fluorescein, respectively; CAD was assessed by quantitative coronary angiography. We performed multiple logistic regression analysis for the effect of the T(-786)C, the missense Glu298Asp variant, and other coronary risk factors on two- and three-vessel CAD.

RESULTS

The overall genotype distribution of T(-786)C (CC = 17.7%, CT = 40.4%, and TT = 41.9%) and Glu298Asp (GG = 43.3%, GT = 37.0%, and TT = 19.7%) was consistent with the Hardy-Weinberg equilibrium. The regression analysis showed that the T(-786)C, but not the missense Glu298Asp variant, significantly predicted CAD, independent of other risk factors. Compared with TT homozygous, subjects carrying the C allele had a significant (p = 0.002) increase in the odds ratio of harboring two- or three-vessel CAD of 1.672 (95% confidence interval, 1.062 to 2.527). A subgroup analysis confirmed this effect of the T(-786)C polymorphism in men (p = 0.007), cigarette smokers (p = 0.001), subjects older than 60 years of age (p = 0.007), with hypercholesterolemia (p = 0.011), low high-density lipoprotein cholesterol (p = 0.006), and overweight or with obesity (p = 0.041).

CONCLUSIONS

The C allele at the T(-786)C endothelial nitric oxide synthase polymorphism is associated with a higher risk of multivessel CAD in Caucasians.

A method to detect the G894T polymorphism of the NOS3 gene. Clinical validation in familial hypercholesterolemia

An endothelial nitric oxide synthase gene (NOS3) polymorphism in exon 7 (G894T), resulting in Glu298Asp substitution at protein level, has been associated with myocardial infarction, hypertension and coronary atherosclerosis in some populations. This polymorphism is usually identified by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). However, the procedures described to date do not eliminate the possibility of misclassification and either require confirmation by DNA sequencing or are time-consuming. In this study, a PCR-RFLP procedure to detect the G894T polymorphism at the NOS3 was optimized by the introduction of a constitutive cleavage site in the amplification product. This cleavage site provides an internal control for enzymatic activity to avoid mistyping. The method was validated by the study of 35 white unrelated individuals with familial hypercholesterolemia and 70 controls. The frequency of the variant allele (T) was similar between both groups (27% vs. 22%, NS), and comparable to the frequency found in other white populations. However, future studies are necessary to confirm these data. In summary, the optimized procedure for detection of the G894T NOS3 polymorphism is rapid, simple, and does not require confirmatory tests. Using this method, we found no association between this polymorphism and familial hypercholesterolemia.

Association of a CD18 gene polymorphism with a reduced risk of restenosis after coronary stenting

Inflammatory mechanisms play an important role in the process of restenosis after percutaneous coronary interventions, with cell adhesion molecules, including Mac-1 (CD11b/CD18), as key mediators. A single nucleotide polymorphism, 1323C/T, located in exon 11 of the CD18 gene has been previously described, but its functional and clinical significances have not yet been studied. We assessed whether an association exists between this polymorphism and restenosis after coronary stenting. Clinical and angiographic measures of restenosis were evaluated over 1 year after coronary stent placement in 1,207 consecutive patients. Angiographic restenosis was defined as a > or =50% diameter stenosis at follow-up angiography. Determination of the CD18 1323C/T genotype was based on the polymerase chain reaction technique. The frequency of the T allele was 0.34 and its presence reduced the 1-year risk of a major adverse cardiac event (death, myocardial infarction, target vessel revascularization) by 29% (p = 0.011). Carriers of the T allele had a significantly lower risk of angiographic restenosis compared with noncarriers (odds ratio 0.71, 95% confidence interval 0.55 to 0.92). The incidence of restenosis decreased as a function of the number of T alleles: 38.1% in patients with genotype CC, 31.7% in patients with genotype CT, and 26.0% in patients with genotype TT (p = 0.004). Thus, the 1323T allele of the CD18 gene is associated, in a gene dose-dependent manner, with a lower incidence of angiographic restenosis after coronary stenting. This finding suggests that Mac-1 is involved in the development of restenosis after coronary stent placement.

Association analyses between genetic polymorphisms of endothelial nitric oxide synthase gene and hypertension in Japanese: The Suita Study

OBJECTIVES

Endothelium-derived nitric oxide plays a key role in the regulation of vascular tone. Recently, endothelial nitric oxide synthase (eNOS) gene polymorphisms were reported to be associated with hypertension or coronary spasm. We investigated the association between the eNOS gene polymorphisms and hypertension in a large population-based sample of 4055 Japanese.

DESIGN AND METHODS

We investigated two polymorphisms of the eNOS gene, Glu298Asp polymorphism of exon 7 and T(-786)C polymorphism of the promoter region. The genotype distribution in hypertensive subjects was compared to that in the other subjects. The influence of the genotype on blood pressure values was analyzed in the subjects not taking hypertensive medication. The promoter activities of the eNOS gene with the (-786)T or (-786)C allele were measured by a luciferase reporter gene assay.

RESULTS

There was significant linkage disequilibrium between the two polymorphisms (P < 0.0001). The genotype distribution of the Glu298Asp or T(-786)C polymorphism did not differ between the hypertensive and the other subjects. No significant differences in the blood pressure of subjects not taking hypertensive medication were observed among the three genotypes of Glu298Asp or T(-786)C polymorphisms. No significant differences in the promoter activity were observed between bovine endothelial cells transfected with the (-786)T and (-786)C alleles.

CONCLUSIONS

Our data suggested that these polymorphisms of the eNOS gene are unlikely to be major factors in the susceptibility to hypertension in the Japanese population studied.

Therapeutic implications of human endothelial nitric oxide synthase gene polymorphism

Vascular endothelial dysfunction is now recognized as a common phenomenon in an array of cardiovascular disorders. Production of nitric oxide via the endothelial isoform of nitric oxide synthase [eNOS (previously termed NOS3 or ecNOS)] is vital for a healthy endothelium; several polymorphic variations of the gene encoding eNOS (NOS3) are now known and have been investigated with respect to disease risk. Surprisingly, only approximately half of these studies have demonstrated significant associations between NOS3 polymorphisms and cardiovascular disease, and many reports are contradictory. Central issues include adequate statistical power, appropriateness of control cohorts, multigene interactions and plausible biological consequences. So far, the inconsistencies are not unique to the NOS3 polymorphisms, but probably represent the broad challenges in defining genetic aspects of complex disease processes.

Relationship between the G894T polymorphism (Glu298Asp variant) in endothelial nitric oxide synthase and nitric oxide-mediated endothelial function in human atherosclerosis

Nitric oxide (NO), produced by endothelial nitric oxide synthase (eNOS), plays important roles in normal vascular homeostasis, and reduced endothelial NO bioactivity is an important feature of vascular disease states. The Glu298Asp (G894T) polymorphic variant of eNOS has been associated with vascular disease, but functional data are lacking. Accordingly, we examined the relationships between NO-mediated endothelial function, the presence of the eNOS Glu298Asp variant, and clinical risk factors for atherosclerosis. Endothelium-dependent vasorelaxations to different agonists were determined in human saphenous veins obtained from patients with coronary artery disease and identified risk factors (n = 104). Patients were genotyped for the eNOS G894T polymorphism. Nitric oxide-mediated endothelial vasorelaxations were highly variable between patients. Reduced vasorelaxations were associated with increased number of clinical risk factors for atherosclerosis (r = - 0.54, P < 0.001), whereas the Glu298Asp variant was not associated with any differences in contractions to phenylephrine, NO-mediated vasorelaxations to acetylcholine, bradykinin or calcium ionophore, or relaxations to the NO donor sodium nitroprusside. Increased atherosclerotic risk factors, but not the presence of the eNOS Glu298Asp variant, are associated with impaired nitric oxide-mediated endothelial vasomotor function, suggesting that this polymorphism does not have a major direct functional effect on vascular eNOS activity in human atherosclerosis.

Genetic analysis of nitric oxide and endothelin in end-stage renal disease

BACKGROUND

Genetic factors have been implicated in the development of the common aetiologies of end-stage renal disease (ESRD), including renal failure attributed to hypertension, diabetes mellitus, systemic lupus erythematosus and human immunodeficiency virus infection. Nitric oxide (NO) and endothelin are powerful vasoactive mediators involved in inflammation and regulation of vascular tone and blood pressure. We evaluated the role of the neuronal constitutive (NOS1) and endothelial constitutive (NOS3) nitric oxide synthase genes and the endothelin-1 (EDN-1) gene in predisposition to chronic renal failure in African-Americans.

METHODS

The study population for the linkage and association analyses in ESRD consisted of 361 individuals from 168 multiplex African-American families. These individuals comprised 207 unweighted sibling pairs concordant for all-cause ESRD. Microsatellite markers NOS1B (NOS1), D7S636 (NOS3) and CPHD1-1/2 (EDN-1) were genotyped in the sample. In addition, a mutation, Glu298Asp, in exon 7 of NOS3 and a 27 bp variable number tandem repeat (VNTR) marker in intron 4 of NOS3 were evaluated in the sibling pairs and in an additional 92 unrelated African-Americans with type 2 diabetes mellitus-associated ESRD (singletons). Association analyses utilized the relative predispositional effect method. Model independent linkage analyses were performed using GeneHunter-plus and MapMaker/SIBS (exclusion analysis) software.

RESULTS

Significant evidence for association with ESRD was detected for alleles 7 and 9 of the NOS1 gene (11.9 and 34.2%, respectively, in unrelated probands of ESRD families versus 6.5 and 27.5%, respectively, in race-matched controls, both P:<0.01). These associations were maintained when the unrelated first sibling from each family was used in a case-control comparison and was most pronounced in the non-diabetic ESRD cases. The NOS3 and EDN-1 markers failed to provide consistent evidence for association in the sibling pairs and the diabetic ESRD singletons, although we identified two novel endothelial constitutive NOS4 (ecNOS4) VNTR alleles in African-Americans. Significant evidence for linkage was not detected between the NOS genes or the EDN-1 gene in either all-cause ESRD or when the ESRD sibling pairs were stratified by aetiology (type 2 diabetic ESRD or non-diabetic aetiologies).

CONCLUSION

Based upon the consistent allelic associations, we believe that further evaluation of the NOS1 gene in ESRD susceptibility in African-Americans is warranted.

Association analyses of endothelial nitric oxide synthase gene polymorphisms in essential hypertension

Endothelial nitric oxide synthase (eNOS), encoded by NOS3, is a potent regulator of vasomotor tone and peripheral resistance. Congenic experiments indicate that a chromosomal segment containing the rat eNOS gene contributes to rat spontaneous hypertension (HT). A role for NOS3 in onset of essential hypertension (HT) is, however, controversial. We therefore decided to test NOS3 polymorphisms in a set of patients who have an accentuated ability to show an existing genetic association. The 112 HT subjects had two HT parents and the normotensive (NT) subjects had two NT parents. All were Anglo-Celtic whites. The two most promising polymorphisms, viz, a biallelic variable number of tandem repeats (VNTR) in intron 4 and an exon 7 variant that leads to an amino acid change (Glu298Asp), were genotyped by PCR (and BanII digestion in the case of the latter). Frequency of the minor allele of the VNTR was 0.11 in the NT and 0.10 in the HT subjects (P = .9). For the exon 7 variant, Asp298 frequency was 0.30 and 0.32 in each respective group (P = .6). Tracking was seen for the Asp298 allele with elevation in body mass index (P = .034), and the minor allele of the VNTR with elevation in LDL (P = .007) and reduction in HDL (P = .048). In conclusion, we saw no association of NOS3 markers with HT in the population studied. However, possible genotypic effects on plasma lipids and body mass index might warrant further studies, especially in view of possible associations with heart disease.

Endothelial nitric oxide synthase gene sequence variations and vascular disease

Genes contribute significantly to interpopulation differences in vascular disease. Endothelial nitric oxide synthase (eNOS)-a key regulator of vascular nitric oxide production-has been investigated extensively to determine the relevance of DNA variants in the eNOS gene and vascular diseases. Variants in the promoter region, introns, and exons have been explored in a large number of populations but findings have been inconsistent. This paper reviews the current status of functional significance for reported sequence variations in the eNOS gene and the relevance of these variants to different forms of vascular diseases.

The molecular basis of hypertension

More than 50 million Americans display blood pressures outside the safe physiological range. Unfortunately for most individuals, the molecular basis of hypertension is unknown, in part because pathological elevations of blood pressure are the result of abnormal expression of multiple genes. This review identifies a number of important blood pressure regulatory genes including their loci in the human, mouse, and rat genome. Phenotypes of gene deletions and overexpression in mice are summarized. More detailed discussion of selected gene products follows, beginning with proteins involved in ion transport, specifically the epithelial sodium channel and sodium proton exchangers. Next, proteins involved in vasodilation/natriuresis are discussed with emphasis on natriuretic peptides, guanylin/uroguanylin, and nitric oxide. The renin angiotensin aldosterone system has an important role antagonizing the vasodilatory cyclic GMP system.

Risk of advanced diabetic nephropathy in type 1 diabetes is associated with endothelial nitric oxide synthase gene polymorphism

Risk of advanced diabetic nephropathy in type 1 diabetes is associated with endothelial nitric oxide synthase gene polymorphism.

BACKGROUND

Polymorphisms in the endothelial nitric oxide synthase gene (eNOS) may be implicated in the development of nephropathy in patients with type 1 or insulin-dependent diabetes mellitus (IDDM).

METHODS

Three groups of IDDM patients were selected to study this hypothesis: cases with advanced diabetic nephropathy (N = 78), cases with overt proteinuria but normal serum creatinine (N = 74), and controls with normoalbuminuria despite 15 years of diabetes (N = 195). Parents of 132 cases and 53 controls were also examined and were used for the transmission disequilibrium test, a family-based study design to test association.

RESULTS

We examined four eNOS polymorphisms, and two were associated with diabetic nephropathy in the case-control comparisons: a T to C substitution in the promoter at position -786 and the a-deletion/b-insertion in intron 4. For the former, the risk of developing advanced nephropathy was higher for C allele homozygotes than for the other two genotypes (odds ratio 2.8, 95% CI, 1.4 to 5.6). For the latter polymorphism, it was the a-deletion carriers that had the higher risk (odds ratio 2.3, 95% CI, 1.3 to 4.0) in comparison with noncarriers. Both polymorphisms were analyzed together as haplotypes in a family-based study using the transmission disequilibrium test. The C/a-deletion haplotype was transmitted from heterozygous parents to cases with advanced diabetic nephropathy with a significantly higher frequency than expected (P = 0.004).

CONCLUSION

The findings of the case-control and family-based studies demonstrate clearly that DNA sequence differences in eNOS influence the risk of advanced nephropathy in type 1 diabetes.

Linkage analysis of endothelial nitric oxide synthase gene with human blood pressure

OBJECTIVE

Endothelial nitric oxide exerts important effects on the regulation of vascular tone and structure. Variants of the endothelial nitric oxide synthase gene (eNOS) have been associated with hypertension and myocardial infarction, although some reports have shown negative linkage with hypertension. To examine whether the region encoding the eNOS gene is linked with physiological blood pressure variation, we undertook a linkage analysis of this region in the general population.

DESIGN

In healthy volunteer families, we used two independent quantitative linkage analyses to examine the relationship between genotypes and phenotypes, with both parametric and non-parametric and single-locus and multi-point methods.

METHODS

We selected 260 families comprising mother and father (aged 40-70 years) and two natural offspring (aged 18-30 years) from the Victorian Family Heart Study. After standardized measurement of clinical data and extraction of DNA, all family members were genotyped at five microsatellite loci including the CA repeat in the eNOS gene by a PCR method. The quantitative linkage analyses were conducted according to two different analysis programs, the Genetic Analysis System (GAS) and the MAPMAKER/SIBS.

RESULTS

With both linkage analyses, we found no linkage between any of the loci on chromosome 7q35-36 and the phenotypes systolic and diastolic blood pressure, mean arterial pressure, pulse pressure, pulse rate, weight, height and body mass index.

CONCLUSION

Based on these results, we conclude that in this population the eNOS gene is not linked to the physiological variation of blood pressure and other related phenotypes.

Association between a sequence variant in the IL-4 gene promoter and FEV(1) in asthma

Recent family-based studies have revealed evidence for linkage of human chromosome 5q31 to the diagnosis of asthma, elevated serum IgE levels, and bronchial hyperresponsiveness. Among the candidate genes in this region is the gene encoding for human interleukin-4 (IL-4). We reasoned that this gene could also serve as a candidate gene with respect to asthma severity as indicated by the FEV(1) measured when bronchodilator treatment was withheld. To test this hypothesis, we examined a large population of patients with asthma (ascertained without respect to genetic characteristics), for associations between a genetic variant in the IL-4 promoter region (C-589T) and asthma severity, as indicated by FEV(1). We used amplification by the polymerase chain reaction followed by BsmF1 restriction digestion to assign genotypes at the IL-4 promoter C-589T locus. We compared genotypes at this locus in 772 Caucasian and African American patients with asthma of varying severity, and we used multiple regression analysis to relate genotypic findings to FEV(1). Among white individuals, the homozygous presence of the C-589T IL-4 promoter genotype (TT) was associated with a FEV(1) below 50% of predicted (p = 0.013; OR, 1.44; 95% CI: 1.09 to 1.90). Subjects with the TT genotype had mean FEV(1) (% predicted) values 4.5% lower than those of subjects with the wild-type (CC) genotype at this locus. FEV(1) values of white patients with a CC or CT genotype were broadly distributed, whereas the TT genotype was associated with a narrow distribution of low FEV(1) values. The frequency of the T allele was significantly greater (p = 1 x 10(-)(23)) among African American asthmatics (0.544) than among white asthmatics (0.183). These data provide the first evidence associating FEV(1) in patients with asthma and genetic determinants at any locus. Our data are consistent with the idea that the FEV(1) in asthma is the result of multiple factors; one of these factors is the genotype at the IL-4 C-589T locus. This locus is associated with a small but significant decrement in pulmonary function among white asthmatic subjects.

Nitric oxide, nitric oxide synthase, and hypertensive vascular disease

In normotension the endothelium produces mainly nitric oxide (NO) and prostacyclin, and the vasodilator and growth inhibitory influence predominates. Hypertension, however, is associated with a shift towards enhanced constriction and vascular hypertrophy. These effects are associated with an apparent decrease in the production of bioactive NO and concomitant increase in the generation of oxygen-derived free radicals, such as superoxide anions (O(2)-). While the enzymatic source of endothelial O(2)- has been debated intensely over the past few years, it may well turn out that the endothelial NO synthase is itself an important producer of O(2)-. Because the redox state of endothelial cells and, for example, the activation of redox-sensitive transcription factors is regulated by the balance between NO and O(2)- production, endothelial NO synthase may well be the most crucial enzyme determining the anti- or prohypertensive and eventually proatherogenic state of the vascular wall.

Cardiac genes and gene databases for cardiovascular disease genetics

Genes play a very important role in the etiology of hypertension. This paper reviews the current pool of candidate genes for human hypertension. Some of the genes studied in rat models of hypertension are also discussed. The methods for studying the genetics of hypertension are reviewed. A discussion of the role of cardiac gene libraries and gene databases in the characterization of cardiovascular disease is also included. This review is concluded by a discussion on the future role of genomics and cardiovascular gene databases in medical research.

Nitric oxide synthase gene polymorphism and its influence on cardiovascular disease

Several lines of evidence indicate a significant association between variations of the endothelial constitutive nitric oxide synthase gene and the incidence of cardiovascular disease, and discrepant findings may be attributable to racial differences. The detection of functional allelic polymorphisms may be needed to confirm this association, because direct evidence to support a causative role for the endothelial constitutive nitric oxide synthase gene is not yet available. There are no available data to confirm that neural and inducible nitric oxide synthases are associated with cardiovascular diseases.