Association of coronary artery disease, erectile dysfunction, and endothelial nitric oxide synthase polymorphisms

Relationship between vitamin D receptors gene polymorphism and arteriogenic erectile dysfunction

BACKGROUND

Over the past few decades, a number of studies have linked vitamin-D deficiency with ED (Erectile dysfunction) risk factors. There is a clear correlation between VD (vitamin-D) levels and ED, according to observational and interventional researches that have been reported in the literature. This crucial information encouraged scientists to investigate the impact of VD on erectile function in greater detail. The fact that vitamin D is a component of a healthy penis that begins in early life has just come to light, however there haven't been many research looking at the connection between vitamin D receptor gene polymorphism and erectile dysfunction.

OBJECTIVE

To evaluate the relationship between arteriogenic erectile dysfunction and the vitamin D receptor gene polymorphism.

SUBJECTS AND METHODS

Between October 2022 and October 2023, at Al-Azhar University Hospitals, 40 patients with arteriogenic ED and 40 healthy controls underwent informed consent, a detailed history, a physical examination, a penile duplex ultrasound and the extraction of peripheral blood to determine the type of polymorphism for each of the vitamin D receptors: FokI, BsmI, ApaI and TaqI by polymerase chain reaction (PCR).

RESULTS

There is no statistically significant association between arteriogenic erectile dysfunction and the vitamin D receptors (VDR) gene polymorphisms FokI, BsmI, ApaI and TaqI.

CONCLUSION

Since there is no statistically significant association between the polymorphism of the vitamin D receptor (VDR) gene and arteriogenic erectile dysfunction, it is advised to investigate other VDR gene polymorphisms as well as alternative clinical subtypes of erectile dysfunction.

Associations between body mass index, waist circumference and erectile dysfunction: a systematic review and META-analysis

Growing evidence reports that obesity might play a role in erectile dysfunction (ED), but limited knowledge is available. We conducted a meta-analysis to estimate the prevalence of ED in overweight men and men with obesity. We performed a systematic review up to 01/04/2019 to investigate the associations between obesity and ED. Applying a random-effect model, we calculated the prevalence of ED, the odds ratio (OR) for the presence of ED by Body Mass Index (BMI) categories and the mean differences between ED and controls in BMI and Waist Circumference (WC). Among 3409 studies, we included 45 articles with 42,489 men (mean age = 55 years). Taking normal weight men as reference, the prevalence of ED was significantly higher in overweight (OR = 1.31; 95%CI: 1.13-1.51; I² = 72%) and in men with obesity (OR = 1.60; 95%CI: 1.29-1.98; I² = 79%). Adjusting our analyses for potential confounders, the results were confirmed in men with obesity (OR = 1.46; 95%CI: 1.24-1.72; I² = 72%). ED was associated with significant higher values of BMI (MD = 0.769; 95%CI: 0.565-0.973 Kg/m²; I² = 78%) and WC (MD = 5.251 cm; 95%CI: 1.295-9.208; I² = 96%). Considering the high prevalence of ED among men with obesity, clinicians should screen for this clinical condition in this population. Findings from the present study suggest that reducing adiposity is a crucial approach in patients with ED who are affected by obesity.

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.

Vitamin D and Male Erectile Function: An Updated Review

Literature support that vitamin-D is important for different systems of the human body including, but not limited to endocrine and immune systems, vasculature and endothelial function of the body. Male erectile function depends on many factors and can be perceived as a health indicator of the body. Epidemiological data have shown that vitamin-D deficiency is also associated with erectile dysfunction. In this review, our aim is to interpret the mechanisms by which vitamin-D might regulate anatomy and physiology of penis. Evidence showed that vitamin-D is needed for an adequate erectile function. Briefly, vitamin-D is crucial for a better healthy body and sexual activity.

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.

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.

The role of vitamin D supplementation on erectile function

In the last few years growing evidence highlighted vitamin D (VD) deficiency is one of the several dynamics that associates with increased atherosclerotic cardiovascular (ASCV) diseases. ASCV diseases and erectile dysfunction (ED) share common risk factors such as diabetes mellitus, hypertension, smoking, hyperlipidemia, and a sedentary lifestyle. The aim of this review was to summarize current progress in VD research by focusing effect of low VD level on different body systems and erectile function. Here we examine research linking VD deficiency and ED and discuss how VD influences ED and its classic risk factors that also associate to increased ED risk. We also summarize research indicating that VD associates with reduced risk of several nonvascular contributing factors for ED. Available literature demonstrates relatively high rates of low VD serum levels in ED patients. Based on the preclinical and clinical data available in the literature, to date, we infer that VD play a critical role in maintaining erectile function in humans. Nevertheless, this should also be tested through randomized controlled studies on the effect of VD supplementation with larger population.

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.

[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.

Association of endothelial nitric oxide synthase gene polymorphisms with coronary artery disease: an updated meta-analysis and systematic review

Several association studies of endothelial nitric oxide synthase (NOS3) gene polymorphisms with respect to coronary artery disease (CAD) have been published in the past two decades. However, their association with the disease, especially among different ethnic subgroups, still remains controversial. This prompted us to conduct a systematic review and an updated structured meta-analysis, which is the largest so far (89 articles, 132 separate studies, and a sample size of 69,235), examining association of three polymorphic forms of the NOS3 gene (i.e. Glu298Asp, T786-C and 27bp VNTR b/a) with CAD. In a subgroup analysis, we tested their association separately among published studies originating predominantly from European, Middle Eastern, Asian, Asian-Indian and African ancestries. The pooled analysis confirmed the association of all the three selected SNP with CAD in three different genetic models transcending all ancestries worldwide. The Glu298Asp polymorphism showed strongest association (OR range = 1.28–1.52, and P<0.00001 for all comparisons), followed by T786-C (OR range = 1.34–1.42, and P<0.00001 for all comparisons) and 4b/a, (OR range = 1.19–1.41, and P≤0.002 for all comparisons) in our pooled analysis. Subgroup analysis revealed that Glu298Asp (OR range = 1.54–1.87, and P<0.004 for all comparisons) and 4b/a (OR range = 1.71–3.02, and P<0.00001 for all comparisons) have highest degree of association amongst the Middle Easterners. On the other hand, T786-C and its minor allele seem to carry a highest risk for CAD among subjects of Asian ancestry (OR range = 1.61–1.90, and P≤0.01 for all comparisons).

Endothelial nitric oxide synthase (eNOS) 4b/a gene polymorphisms and coronary artery disease: evidence from a meta-analysis

A variety of studies have suggested that the 4b/a polymorphism in the endothelial nitric oxide synthase (eNOS) was associated with coronary artery disease (CAD) risk. However, the data remain conflicting. The aim of the present meta-analysis was to estimate the overall association between risk of CAD and eNOS 4b/a polymorphism. Case-control, cohort or cross-sectional studies evaluating the association between eNOS 4b/a polymorphism and CAD susceptibility were systematically identified in PubMed up to 31 October 2013. Pooled odds ratios (OR) and corresponding 95% confidence intervals (CIs) were calculated to assess the association in overall and subgroup analyses. A total of 10,617 cases and 8302 controls from 37 studies were included in the study. The results of overall analysis revealed significant positive associations between CAD risk and eNOS 4b/a polymorphism in homozygote comparisons (OR = 1.47, 95% CI = 1.16–1.87), heterozygote comparisons (OR = 1.14, 95% CI = 1.02–1.27) and dominant models (OR = 1.18, 95% CI = 1.06–1.33). In subgroup analyses, similar associations were identified in African individuals, as determined using population-based source subgroups and noted in small-and-moderate sample size subgroups (case sample size or control sample size <500). The current meta-analysis revealed that eNOS 4b/a polymorphisms could be a risk factor for developing CAD, particularly in African populations and population-based subgroups.

Nitric oxide-mediated coronary flow regulation in patients with coronary artery disease: recent advances

Nitric oxide (NO) formed via endothelial NO synthase (eNOS) plays crucial roles in the regulation of coronary blood flow through vasodilatation and decreased vascular resistance, and in inhibition of platelet aggregation and adhesion, leading to the prevention of coronary circulatory failure, thrombosis, and atherosclerosis. Endothelial function is impaired by several pathogenic factors including smoking, chronic alcohol intake, hypercholesterolemia, obesity, hyperglycemia, and hypertension. The mechanisms underlying endothelial dysfunction include reduced NO synthase (NOS) expression and activity, decreased NO bioavailability, and increased production of oxygen radicals and endogenous NOS inhibitors. Atrial fibrillation appears to be a risk factor for endothelial dysfunction. Endothelial dysfunction is an important predictor of coronary artery disease (CAD) in humans. Penile erectile dysfunction, associated with impaired bioavailability of NO produced by eNOS and neuronal NOS, is also considered to be highly predictive of ischemic heart disease. There is evidence suggesting an important role of nitrergic innervation in coronary blood flow regulation. Prophylactic and therapeutic measures to eliminate pathogenic factors inducing endothelial and nitrergic nerve dysfunction would be quite important in preventing the genesis and development of CAD.

Milk casein-derived tripeptides, VPP and IPP induced NO production in cultured endothelial cells and endothelium-dependent relaxation of isolated aortic rings

Milk casein-derived tripeptides, valyl prolyl proline (VPP), and isoleucyl prolyl proline (IPP) inhibit angiotensin-converting enzyme (ACE) and both fermented milk and proteolytic hydrolysates of milk casein containing these peptides exert blood pressure-lowering effects in animals and humans. On the top of these results, we have recently reported that the hydrolysate of milk casein containing both VPP and IPP improved the vascular endothelial function of subjects with stage I hypertension, enforcing us to elucidate the mechanism of the improvement of endothelial dysfunction by these peptides. For this purpose, we examined the effect of VPP and IPP on induction of nitric oxide (NO) production using cultured vascular endothelial cells and isolated arterial vessels. When both VPP and IPP were added to the medium of cultured endothelial cells at final concentrations of more than 100 nmol/l, the NO(x) (NO(2) and NO(3)) concentration in the medium was significantly higher than that of the control. Moreover, both VPP and IPP induced endothelium-dependent relaxation of isolated aortic rings, and these effects were inhibited by NO synthase inhibitors, K channel inhibitors, and bradykinin B2 receptor antagonists. These lines of results suggested that both VPP and IPP induced production of vasodilative substances including NO.

Cell membrane stretch activates intermediate-conductance Ca2+-activated K+ channels in arterial smooth muscle cells

The aim of this study is to determine the signal transduction of membrane stretch on intermediate-conductance Ca(2+)-activated K(+) (IKca) channels in rat aorta smooth muscle cells using the patch-clamp technique. To stretch the cell membrane, both suction to the rear end of patch pipette and hypotonic shock were used. In cell-attached and inside-out patch configurations, the open probability of IKca channels increased when 20- to 45-mmHg suction was applied. Hyposmotic swelling efficiently increased IKca channel current. When the Ca(2+)-free solution was superfused, the activation of IKca current by the hyposmotic swelling was reduced. Furthermore, gadolinium (Gd(3+)) attenuated the activation of IKca channels induced by hyposmotic swelling, whereas nicardipine did not. In the experiments with Ca(2+)-free bath solution, pretreatment with GF109203X, a protein kinase C (PKC) inhibitor, completely abolished the stretch-induced activation of IKca currents. The stretch-induced activation of IKca channels was strongly inhibited by cytochalasin D, indicating a role for the F-actin in modulation of IKca channels by changes in cell stretching. These data suggest that cell membrane stretch activates IKca channels. In addition, the activation is associated with extracellular Ca(2+) influx through stretch-activated nonselective cation channels, and is also modulated by the F-actin cytoskeleton and the activation of PKC.

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.

Erectile dysfunction and risk of clinical cardiovascular events: a meta-analysis of seven cohort studies

INTRODUCTION

For many years, erectile dysfunction (ED) has been considered as a complication of cardiovascular disease (CVD) or regarded as a late consequence of generalized arterial disease. However, a growing body of evidence suggests that ED is an early manifestation of atherosclerosis and a precursor to systemic vascular disease.

AIM

We conducted a meta-analysis to evaluate the association between ED and the risk of CVD events.

METHODS

Relevant studies published between January 1966 and September 2009 were identified by searching Medline, Embase, and The Cochrane Library. Studies were selected using a prior defined criteria. The strength of the relationship between ED and CVD events was assessed by adjusted relative risks (RRs).

MAIN OUTCOME MEASURES

The adjusted RRs of CVD events.

RESULTS

A total of 45,558 participants from seven cohort studies (eight full-text articles) were identified in this meta-analysis. The studies provided adjusted RRs estimates for ED subjects comparing with health subjects, leading to a pooled adjusted RR of 1.47 (95% confidence interval [CI], 1.29-1.66, P < 0.001; P for heterogeneity = 0.152; I(2)  = 36.2%) for CVD events. The risks of CVD, all-cause mortality and myocardial infarction were 1.41 (95% CI, 1.22-1.64 P < 0.001), 1.23 (95% CI, 1.02-1.48; P = 0.034), and 1.43 (95% CI, 1.10-1.85 P = 0.007), respectively. The overall adjusted RR decreased significant from 1.63 (<7 years) to 1.37 (≥ 7 years) along with the elongation of follow-up.

CONCLUSIONS

There is evidence of an increased risk of CVD events for patients with ED. Patients who are discovered to have ED are supposed to be thoroughly assessed for cardiovascular risk and occult systemic vascular disease.