T-786C Polymorphism in Promoter of eNOS Gene as Genetic Risk Factor in Patients With Erectile Dysfunction in Turkish Population

Erectile dysfunction in cardiovascular patients: A prospective study of the eNOS gene T-786C, G894T, and INTRON variable number of the tandem repeat functional interaction

BACKGROUND

Cardiovascular disease induces erectile dysfunction modulated by endothelial nitric oxide synthase enzyme and an impaired ejection fraction that restricts penis vascular congestion. However, the mechanisms regulating endothelial dysfunction are not understood.

OBJECTIVES

Exploring the functional impact of endothelial nitric oxide synthase genetic polymorphisms on erectile dysfunction and drug therapy optimization in high-risk cardiovascular disease patients.

MATERIALS AND METHODS

Patients with erectile dysfunction symptoms and candidates for andrology therapy were included (n = 112). Clinical data and endothelial nitric oxide synthase rs1799983 (G894T) and rs2070744 (T-786C), genotyped by fluorescence polarization assays, were registered. The 27-bp variable number of the tandem repeat polymorphism in intron 4 (intron4b/a) was analyzed by polymerase chain reaction-restriction fragment length polymorphism. Association analyses were run with the R-3.2.0 software.

RESULTS

A significant association between endothelial nitric oxide synthase 786-TT (p = 0.005) and the aa/ac of intron 4 variable number of the tandem repeat (p = 0.02) with higher erectile dysfunction susceptibility was observed in cardiovascular disease patients (60 ± 9 years, 66% severe erectile dysfunction, 56% ejection fraction). After 3-months of phosphodiesterase type 5 inhibitors, erectile dysfunction (International Index of Erectile Function, 50 ± 16 scores, the International Index of Erectile Function-Erectile Function 21 ± 10 scores, p < 0.001) and sexual quality of life (modified Sexual Life Quality Questionnaire 55 ± 23 scores, p < 0.001) had significantly improved. The cardiovascular ejection fraction was influenced positively with better sexual quality of life (0.1941), and also in the endothelial nitric oxide synthase G894-T allele (p = 0.076) carriers, which could merit future analyses. Erectile dysfunction was present as the primary clinical manifestation in 62% of cases, with cardiovascular disease occurring concurrently. Only former smokers and obese subjects debuted prior to cardiovascular disease than to erectile dysfunction.

CONCLUSIONS

Our study provides comprehensive insights into the functional interaction linking endothelial nitric oxide synthase gene polymorphisms, erectile function, and ejection fraction in high-risk cardiovascular disease patients. Future therapeutic strategies could target endothelial nitric oxide synthase activity by including lifestyle changes and epigenetic modulations.

Genes Predisposing to Erectile Dysfunction and Management: A Review

Background: The burden of erectile dysfunction (ED) is rising worldwide due to unresponsiveness of some affected individuals to existing drugs and treatment strategies. Fortunately, improvement in biological techniques has led to the understanding that some cases of the disorder may have a genetic etiology, which, when fully understood, may lead to improved treatment.

Objective: This review articulated established ED candidate genes and pathophysiology to assist researchers and medical practitioners to formulate effective drugs and treatment procedures.

Methods: The Google search engine was used to retrieve relevant information on the topic from reputable academic databases, including PubMed, Medline, Google Scholar, Scopus, and SpringerLink.

Results: The search discovered 10 ED candidate genes, which are SIM1, SLC6A4, 5-HTTLPR, TGFB1, DAT1, MC4R, NOS3, GNB3, AR, and MTHFR. Polymorphisms or mutations in these genes may disrupt erectile activities of the hypothalamus, neurotransmitters such as dopamine, serotonin, and nitric oxide as well as relaxation of penile tissues. Clinical presentations of ED include loss of erection, weak vaginal penetration, premature ejaculation, and anejaculation. Each gene has a distinct mechanism, which, if targeted in the affected may reverse the disorder or reduce the effects.

Conclusion: Some cases of ED are genetic, which, when fully understood, may give an insight into new treatment procedures or improve on the current ones. Medical practitioners are advised to formulate treatment procedures that target the affected gene (s) in individuals.

Priapism in sickle cell disease: Associations between NOS3 and EDN1 genetic polymorphisms and laboratory biomarkers

Priapism is a urologic emergency characterized by an uncontrolled, persistent and painful erection in the absence of sexual stimulation, which can lead to penile fibrosis and impotence. It is highly frequent in sickle cell disease (SCD) associated with hemolytic episodes. Our aim was to investigate molecules that may participate in the regulation of vascular tone. Eighty eight individuals with SCD were included, of whom thirty-seven reported a history of priapism. Priapism was found to be associated with alterations in laboratory biomarkers, as well as lower levels of HbF. Patients with sickle cell anemia using hydroxyurea and those who received blood products seemed to be less affected by priapism. Multivariate analysis suggested that low HbF and NOm were independently associated with priapism. The frequency of polymorphisms in genes NOS3 and EDN1 was not statistically significant between the studied groups, and the presence of the variant allele was not associated with alterations in NOm and ET-1 levels in patients with SCD. The presence of the variant allele in the polymorphisms investigated did not reveal any influence on the occurrence priapism. Future studies involving larger samples, as well as investigations including patients in priapism crisis, could contribute to an enhanced understanding of the development of priapism in SCD.

Genetics and erectile dysfunction: leveraging early foundations for new discoveries

There is considerable interest in understanding the genetics of erectile dysfunction (ED). Since early twin studies that suggested a genetic component to ED, multiple candidate gene studies have identified genetic variants that may be associated with ED. Genome-wide association studies (GWAS) have overcome some of the criticism of the candidate gene approach. Two recent GWAS studies have identified loci near SIM1 that may be associated with ED and have renewed interest in the leptin melanocortin signaling pathway. We review the current literature on the genetic basis of ED by highlighting several candidate genes and genetic variants associated with ED.

Gene Polymorphisms Affecting Erectile Dysfunction

INTRODUCTION

Erectile dysfunction (ED) is usually developed from psychological, neurological, hormonal, and vascular pathologies or a combination of these factors. However, the possible genetic polymorphisms that might underlie this disorder were not thoroughly investigated.

OBJECTIVES

This review article aimed to assess the possible involvement of gene polymorphisms in men with ED.

METHODS

A systematic review was conducted until January 2020 based on a search of all relevant articles in many electronic sites such as PubMed, Medline Medical Subject Headings, Science Direct, Scopus, Cochrane Library, EMBASE, CINAHL, and Egyptian Knowledge Bank databases with no language restriction. Keywords used to assess the outcome and estimates for relevant associations were sexual health, genes, erectile dysfunction, polymorphisms, and cavernous tissues.

RESULTS

Many genetic studies were carried out to inspect the contribution of different encoded genotypes and ED. Overall, 50 studies were reviewed and were classified as per the type of gene polymorphisms. These studies have investigated 10,174 men with ED compared with 6,891 healthy men as controls. 35 studies were case-controlled, 13 cross-sectional cohort studies, one retrospective study, and one genome-wide association study. So far, the most relevant gene polymorphisms linked with men with ED included endothelial nitric oxide synthase (eNOS), angiotensin-converting enzyme (ACE), androgen receptor (AR) CAG repeat, G-protein β3 (GNB3) subunit, methylenetetrahydrofolate reductase (MTHFR), vascular endothelial growth factor (VEGF), TGFB1, proprotein convertase subtilisin/kexin type 9 (PCSK9), ARG1, DRD2, DRD4, DDAH, and HNF4A genes. Both PROGINS and IGFBP-3 polymorphisms were investigated in only one study each but with irrelevant significance.

CONCLUSIONS

Although several genetic studies exposed the association between different genotypes and men with ED with varied outcomes, such a relationship should not be overlooked. Therefore, more studies should be encouraged to elucidate the exact role, if any, for such association. Mostafa T, Taymour M. Gene Polymorphisms Affecting Erectile Dysfunction. Sex Med 2020;8:561-572.

The association of Intron 4 VNTR and Glu298Asp polymorphisms of the nitric oxide synthetase 3 gene and vasculogenic erectile dysfunction in Turkish men

Several studies have focused on the impaired role of endothelial nitric oxide synthase (NOS3) gene polymorphism and its association to erectile dysfunction (ED). However, currently controversial results have been reported due to their significant heterogeneity. The present study aimed to assess the genotypic distribution and the allelic frequency of Intron 4 VNTR and Glu298Asp gene polymorphisms in vasculogenic ED patients compared to healthy controls of a specific region of Turkey. A total of 75 patients with ED (median age: 56, IQR:10.5) and 75 healthy controls (median age: 56, IQR:10.5) were prospectively analyzed. All subjects were equally evaluated by the same physician with detailed history-taking, physical examination, International Index of Erectile Function (IIEF) questionnaire, and blood tests (incl. glucose, testosterone, triglyceride and total cholesterol level). Those with an IIEF score under 26 were considered to have ED, by classifying them according to their scores as mild (22-25), moderate (11-21) and severe (1-10) ED. Color doppler ultrasonography was carried out in patients with an IIEF score <22. Hypertension, diabetes mellitus, coronary artery disease, and smoking status were significantly associated with the ED group compared to control subjects with p values of <0.001, <0.001, 0.002 and <0.001, respectively. Overall genotype frequencies was 47 (31%) a/a, 22 (15%) a/b, 82 (55%) b/b for Intron 4 VNTR and 56 (37%) GG, 78 (52%) GT, 16 (11%) TT for the Glu298Asp polymorphism. The frequencies of Intron 4 VNTR a/a allele and Glu298Asp GT allele were associated with severe ED, while a/b and TT were associated with moderate or mild, and b/b and GG were associated with no ED. In contrast to Glu298Asp, statistically significant differences in genotypic frequencies of Intron 4 VNTR gene polymorphism between ED and control subjects was established. Abbreviations: NO: nitric oxide, NOS: nitric oxide synthase, NOS3: endothelial nitric oxide synthase, NOS2: inducible nitric oxide synthase, NOS1: neuronal nitric oxide synthase, HT: hypertension, DM: diabetes mellitus, CAD: coronary artery disease, ED: erectile dysfunction, IIEF: international index of erectile function, VNTR: variable number of tandem repeats, CDU: color doppler ultrasonography, PCR: polymerase chain reaction.

Back to Stir It Up: Erectile Dysfunction in an Evolutionary, Developmental, and Clinical Perspective

In this review, we analyze erectile dysfunction (ED) in the context of sexual selection. We highlight that ED is a specific human male characteristic linked to the loss of the baculum or penile bone and results from a range of physical and psychological factors. We discuss evolutionary interpretations that consider dysfunctional penile erection as an honest signal of a low-quality male. We further emphasize the importance of considering psychosocial context and early attachment dynamics for understanding the etiology of some types of ED. Finally, we suggest that the integration of developmental factors for understanding the emergence of this sexual disorder is instrumental for the calibration of more effective therapies.

Endothelial nitric oxide synthase gene polymorphisms and erectile dysfunction in chronic pain

OBJECTIVES

To investigate whether endothelial nitric oxide synthase (eNOS) T786C, 4VNTR and G894 T gene polymorphisms could mediate in andrological treatment response in Spaniards.

SUBJECT PATIENTS/METHODS

The study participants were Spaniard males with erectile dysfunction (ED) and chronic pain (n = 105) recruited at the Pain Unit. eNOS polymorphisms were genotyped by quantitative polymerase chain reaction using Taqman specific probes. Statistical analyses were carried out using R-3.2.4 software.

RESULTS

A total of 69 patients required andrological treatment and 76% of them improved ED upon iPED5 (20%), testosterone (35%) or iPDE5/testosterone treatment (45%); being significantly better in T786C-CC patients. Multivariate regression analysis indicated that age, opioid daily dose and carriage of T786C-C allele influenced the risk and ED severity in Spaniard chronic pain patients.

CONCLUSION

T786C polymorphism at eNOS locus appeared to be a major contributor in the variable erectile function iPDE5/testosterone response in Spaniards.

Association between eNOS Gene Polymorphism (T786C and VNTR) and Sickle Cell Disease Patients in Ghana

Endothelial nitric oxide synthase (eNOS) variants have been found to be associated with several vascular disorders as well as the pathogenesis of sickle cell disease (SCD) complications such as vaso-occlusive crises (VOC). Studies on eNOS gene variants among SCD patients are rare in Ghana and several other African countries. The current study aimed to determine a possible association between variants of the eNOS gene (variable number of tandem repeats in intron 4 and T786C) in SCD complications among Ghanaian patients. This was a cross-sectional study involving 89 HbSS patients with complications and 46 HbSS patients without complications. Genomic DNA was extracted from leukocytes in the buffy coat and separated from collected whole blood samples of the study participants. PCR amplification, followed by restriction fragment length polymorphism (RFLP) was used to genotype T786C (rs2070744) variants. Variable number of tandem repeats (VNTR) in intron 4 was genotyped by PCR and direct electrophoresis. There was a significant difference in the genotype frequency of the T786C variant between HbSS patients with complications and those without complications (p = 0.0165). However, there was no significant difference in the VNTR intron 4 variant of the eNOS gene between patients with complications and those without complications (p > 0.05). The study shows an association between the eNOS gene variant (T786C) and complications in SCD.

Association of endothelial nitric oxide synthase polymorphisms with an increased risk of erectile dysfunction

The purpose of our meta-analysis is to examine the associations between three single nucleotide polymorphisms of endothelial nitric oxide synthase (eNOS) gene, G894T, intron 4 and T-786C, and the risk of erectile dysfunction. An electronic database search was performed to identify case-control studies reporting the association between single nucleotide polymorphisms of eNOS gene and erectile dysfunction. Stringent inclusion and exclusion criteria were employed to select high-quality studies for this meta-analysis. Comprehensive Meta-analysis 2.0 software (Biostat Inc., Englewood, New Jersey, USA) was used for statistical analysis of the data extracted from the selected studies. From the initial 203 articles retrieved from database search, this meta-analysis finally selected 12 high-quality case-control studies that conformed to our inclusion criteria. The 12 studies contained a total of 1962 patients with erectile dysfunction and 1752 healthy controls. The results of our meta-analysis showed that G894T correlated with an increased risk erectile dysfunction under both the allele and dominant models (allele: OR = 1.556, 95% CI = 1.064–2.275, P = 0.023; dominant: OR = 1.613, 95% CI = 1.050–2.476, P = 0.029). A similar association was found between T-786C and erectile dysfunction under the allele model (OR = 1.679, 95% CI = 1.341–2.102, P < 0.001), but not under the dominant model (all P > 0.05). Our meta-analysis showed that the two single nucleotide polymorphisms in eNOS gene, G894T and T-786C, are strongly associated with the risk of erectile dysfunction.

Hypertension might be a risk factor for erectile dysfunction: a meta-analysis

The study aimed to evaluate whether hypertension was a risk factor for erectile dysfunction (ED). Databases including PubMed and Embase were retrieved to identify studies related to hypertension in ED patients. Odds ratio (OR) and 95% confidence interval (CI) were used as the effect size. Subgroup analyses stratified by total number of enrolled subjects and research regions were performed. Sensitivity analysis was performed by removing a single study at one time. Egger's test was used to evaluate the publication bias. Totally, 40 studies including 121,641 subjects were included in the meta-analysis. As a result, hypertension was closely related to ED (OR = 1.74, 95% CI, 0.63-0.80, p < .01). Subgroup analysis indicated hypertension was the risk factor for ED whatever the participants numbers. When stratified by different regions, hypertension was a risk factor for ED in Africa (OR = 3.35, 95% CI, 1.45-7.77, p < .01), Americas (OR = 1.97, 95% CI, 1.68-2.31, p < 0.01), Asia (OR = 1.46, 95% CI, 1.16-1.84, p < .01) and Europe (OR = 1.83, 95% CI, 1.34-2.49, p < .01), but not in Australia. Hypertension may be a potential risk factor for ED.

Pharmacogenetics of erectile dysfunction: navigating into uncharted waters

Sildenafil and other PDE-5 inhibitors have revolutionized erectile dysfunction (ED) treatment. However, a significant number of patients do not respond or present adverse reactions to these drugs. While genetic polymorphisms may underlie this phenomenon, very little research has been undertaken in this research field. Most of the current knowledge is based on sildenafil, thus almost completely ignoring other important pharmacological therapies. Currently, the most promising genes with pharmacogenetic implications in ED are related to the nitric oxide and cGMP pathway, although other genes are likely to affect the responsiveness to treatment of ED. Nevertheless, the small number of studies available opens the possibility of further exploring other genes and phenotypes related to ED. This article provides a comprehensive overview of the genes being tested for their pharmacogenetic relevance in the therapy of ED.

Endothelial nitric oxide synthase: From biochemistry and gene structure to clinical implications of NOS3 polymorphisms

Nitric oxide (NO) is an important vasodilator with a well-established role in cardiovascular homeostasis. While mediator is synthesized from L-arginine by neuronal, endothelial, and inducible nitric oxide synthases (NOS1,NOS3 and NOS2 respectively), NOS3 is the most important isoform for NO formation in the cardiovascular system. NOS3 is a dimeric enzyme whose expression and activity are regulated at transcriptional, posttranscriptional,and posttranslational levels. The NOS3 gene, which encodes NOS3, exhibits a number of polymorphic sites including single nucleotide polymorphisms (SNPs), variable number of tandem repeats (VNTRs), microsatellites, and insertions/deletions. Some NOS3 polymorphisms show functional effects on NOS3 expression or activity, thereby affecting NO formation. Interestingly, many studies have evaluated the effects of functional NOS3 polymorphisms on disease susceptibility and drug responses. Moreover, some studies have investigated how NOS3 haplotypes may impact endogenous NO formation and disease susceptibility. In this article,we carried out a comprehensive review to provide a basic understanding of biochemical mechanisms involved in NOS3 regulation and how genetic variations in NOS3 may translate into relevant clinical and pharmacogenetic implications.

Genetics of resistant hypertension: a novel pharmacogenomics phenotype

Resistant hypertension (RHTN), defined as an uncontrolled blood pressure despite the use of multiple antihypertensive medications, is an increasing clinical problem associated with increased cardiovascular (CV) risk, including stroke and target organ damage. Genetic variability in blood pressure (BP)-regulating genes and pathways may, in part, account for the variability in BP response to antihypertensive agents, when taken alone or in combination, and may contribute to the RHTN phenotype. Pharmacogenomics focuses on the identification of genetic factors responsible for inter-individual variability in drug response. Expanding pharmacogenomics research to include patients with RHTN taking multiple BP-lowering medications may identify genetic markers associated with RHTN. To date, the available evidence surrounding pharmacogenomics in RHTN is limited and primarily focused on candidate genes. In this review, we summarize the most current data in RHTN pharmacogenomics and offer some recommendations on how to advance the field.

[Genetic aspects of erectile dysfunction]

BACKGROUND

Erectile dysfunction (ED) is a common disorder in man that influences the quality of life of the patient and his partner. Known risk factors for ED comprise diabetes, coronary artery disease, hypertension but also lifestyle modifications such as smoking, diminished physical activity as well as obesity. In this manuscript the current scientific literature about genetics and erectile dysfunction is reviewed.

MATERIALS AND METHODS

A literature search using the databank PubMed covering the topics genetics and erectile dysfunction was performed and relevant papers selected for presentation.

RESULTS

Several aspects of genetics and ED are described in the current literature. Association studies of candidate polymorphisms and ED risk in comparison to healthy controls is a major area of research. Another topic is the genome-wide search for candidate polymorphisms with erectile dysfunction. The paper closes with the presentation of the pharmacogenomic analysis of treatment response to phosphodiesterase-5 inhibitors.

DISCUSSION

The heterogeneous results of genetic association studies are possibly due to small sample sizes of the study population and/or due to ethnic differences of the analyzed populations. This underlines the need for validation of this data in larger prospective multinational multicenter studies.

T-786C, G894T, and intron 4 VNTR (4a/b) polymorphisms of the endothelial nitric oxide synthase gene in bladder cancer cases

The aim of the present study was to determine whether endothelial nitric oxide synthase (eNOS) gene polymorphisms play a role in development of bladder cancer in the Turkish population. The study was performed on 75 patients (64 men, 11 women) with bladder cancer and 143 healthy individuals (107 men, 36 women) with any kind of cancer history. Three eNOS gene polymorphisms (T-786C promoter region, G894T and intron 4 VNTR 4a/b) were determined with polymerase chain reaction and restriction fragment lenght polymorphism methods. In our study, GT and TT genotypes for eNOS G894T polymorphism were found to significantly vary among patients with bladder cancer and control group (OR: 0.185, CI: 0.078-0.439, p=0.0001 and OR: 0.324, CI: 0.106-0.990, p=0.026). Also, the frequency of the 894T allele was significantly higher in patients with bladder cancer (51%). No association was identified for eNOS T-786C and intron 4 VNTR 4a/b polymorphisms between patients with bladder cancer and control groups in our Turkish population.

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.

RETRACTED: G-protein β3 subunit gene 825C/T polymorphism and its association with the presence, severity, and duration of vasculogenic erectile dysfunction

This article has been retracted: please see Elsevier Policy on Article Withdrawal ( https://www.elsevier.com/about/policies/article-withdrawal ). This article has been retracted at the request of the ASRM Publications Committee and the Editor in Chief. The Committee reviewed concerns related to the validity of data reported in this article. After finding numerous errors in the data in Tables 1 and 2, it asked the corresponding author for original data and other evidence pertaining to the underlying study, but no evidence was provided. The author's former institution also declined to investigate. The Committee and the Editor in Chief concluded that they could not vouch for the validity of the data and have determined to retract the article.

Association of the T-786C, G894T and 4a/4b polymorphisms of the endothelial nitric oxide synthase gene with vasculogenic erectile dysfunction in Iranian subjects

OBJECTIVE

• To investigate the association of the T-786C, G894T and variable number of tandem repeats (VNTRs) in intron 4 (a/b) polymorphisms of the eNOS gene in Iranian subjects with vasculogenic erectile dysfunction (ED).

PATIENTS AND METHODS

• A total of 322 consecutive patients with vasculogenic ED were recruited. Patients with concomitant risk factors for ED were excluded. • Patients with ED were identified based on history-taking, detailed physical examination, serum biochemistry, sex hormone measurements, application of the International Index of Erectile Function (IIEF) questionnaire, and penile duplex Doppler ultrasonography after intracavernosal injection of 20 µg prostaglandin E(1) . The control group comprised 318 age-matched healthy male volunteers. • Genotyping was performed by polymerase chain reaction-restriction fragment length polymorphism and the T-786C, G894T and VNTR intron 4 polymorphisms of the eNOS gene were determined.

RESULTS

• After multivariate regression analysis, significant differences were seen in the frequencies of genotypes and alleles of the two T-786C and G894T polymorphisms when patients with ED and normal controls were compared. • In a multiple logistic regression analysis, the odds ratio (OR) of increased ED was strongly associated with the -786C allele [adjusted OR = 3.12, 95% confidence interval (CI) = 2.28-4.25; P= 0.001] and the 894T allele (adjusted OR = 3.87, 95% CI = 2.53-4.87; P= 0.001). • The data showed a higher prevalence of the T-786C CC genotype (adjusted OR = 2.72, 95% CI = 1.88-3.65; P= 0.006), and the G894T GT (adjusted OR = 1.72, 95% CI 1.24-2.83; P= 0.037) and G894T TT genotypes (adjusted OR = 3.42, 95% CI 2.42-4.26; P= 0.001) in patients with ED than in the controls.

CONCLUSIONS

• The findings of the present study suggest that the eNOS T-786C and G894T polymorphisms are strong predictors of the predisposition to ED in addition to traditional risk factors, signifying a genetic influence for this multifactorial disease. • Further studies in different ethnic populations are needed to better elucidate the role of eNOS gene polymorphism in the pathogenesis of ED.

Role of methylenetetrahydrofolate reductase gene polymorphisms (C677T, A1298C, and G1793A) in the development of early onset vasculogenic erectile dysfunction

BACKGROUND AND AIMS

The methylenetetrahydrofolate reductase (MTHFR) gene plays a key role in the metabolism of folate and homocysteine (Hcy) and its mutations have been associated with high serum Hcy level. Elevated serum Hcy has been linked to impaired endothelial function and occlusive vascular disease. We studied the association among the different genotypes of all three MTHFR polymorphisms (C677T, A1298C, and G1793A) and the risk of early-onset vasculogenic erectile dysfunction (VED).

METHODS

We performed a case-control study of 114 men with early-onset VED and 228 age-matched controls. Genotyping of MTHFR gene polymorphisms was performed using polymerase chain reaction restriction fragment length polymorphism (PCR-RLFP) technique. We also measured plasma lipids, Hcy, folate, and vitamin B12 levels.

RESULTS

Patients with early-onset VED had higher serum Hcy levels (12.29 ± 2.32 vs. 9.82 ± 2.35 μmol/L, p = 0.001) and higher prevalence of 677TT homozygocity compared to controls (15.8% vs. 11.4%, p = 0.01). Serum Hcy concentration was significantly higher in individuals with 677TT, 1298CC, and 1793GG genotypes. Subgroup analysis according to severity of ED (mild, moderate, and severe) showed that patients with severe VED had higher serum Hcy levels compared to patients with mild VED (13.48 ± 2.51 vs. 11.21 ± 2.32 μmol/L, p = 0.001).

CONCLUSIONS

Odds ratio seems to demonstrate that individuals with the MTHFR 677TT genotype and the 677TT + 1298AC combined genotype had a 3.16- and 3.89-fold increased risk for developing VED, suggesting a possible association of MTHFR polymorphisms with the risk of early-onset VED.

Endothelial nitric oxide synthase polymorphisms and erectile dysfunction: a meta-analysis

INTRODUCTION

Erectile dysfunction (ED) is a common disorder noted for affecting quality of life. Several studies have reported the influence of endothelial nitric oxide synthase (eNOS) polymorphisms on ED susceptibility. However, results of association studies with individually low statistical power are conflicting.

AIM

Our study aimed to carry out a meta-analysis estimating the association between eNOS variants and the risk of ED.

METHODS

Studies regarding the association between eNOS polymorphisms and ED were searched in Medline and Embase databases. The relevant studies that met the inclusion criteria were eligible for the analysis.

MAIN OUTCOME MEASURES

Five genetic models and a generalized odds ratio (OR(G) ) were used to estimate the association between eNOS G894T and variable number of 27-bp tandem repeats in intron 4 (4 VNTR) and the risk of ED.

RESULTS

Nine articles were included in our meta-analysis. Overall, significant association between the 894T variant and an increased risk of ED was derived for all genetic contrasts except for the recessive model (allele contrast: OR = 1.64, 95% confidence interval [CI]: 1.03-2.60). The meta-analysis based on the OR(G) also produced significant results: OR(G) = 1.64, 95% CI: 1.03-2.61. Significant heterogeneity and publication bias were detected. The cumulative meta-analysis showed the OR increased from 2003 to 2009 and then declined in 2010. Instability in the relative change of OR was observed. Regarding 4 VNTR and its association with ED, the overall analysis showed a lack of significant association (OR = 0.96, 95% CI: 0.72-1.28). No evidence for heterogeneity among studies was observed. Subgroup analysis by ethnicity and recruitment strategy also yielded nonsignificant results.

CONCLUSION

The result supports that G894T variant is associated with an increase in the risk of ED. No evidence for a significant association between 4VNTR and ED is observed. The results of the present meta-analysis should be interpreted with caution. Further confirmation in large and well-designed studies is needed.