The role of endothelial dysfunction in the pathophysiology of erectile dysfunction in diabetes and in determining response to treatment

The management of erectile dysfunction in men with diabetes mellitus unresponsive to phosphodiesterase type 5 inhibitors

INTRODUCTION

Erectile dysfunction is associated with diabetes mellitus with an estimated prevalence of 52.5% in the diabetic population. The first-line therapy for erectile dysfunction is phosphodiesterase type 5 inhibitors, but data suggest that diabetic men may be less responsive than non-diabetic men. Thus, other treatments, including intracavernosal injections, intraurethral prostaglandin, vacuum erection devices and penile prosthetic surgery, should be considered in management of diabetic men with erectile dysfunction refractory to phosphodiesterase type 5 inhibitors. Furthermore, combination therapy of phosphodiesterase type 5 inhibitors and other oral treatments such as arginine or l-carnitine may have synergistic effects resulting in better outcomes. In addition, there are novel therapies such as low-intensity shockwave therapy and stem-cell therapy, which may also be effective in targeted treatment modalities. Furthermore, studies suggest that erectile dysfunction can be improved by targeting concurrent comorbidities or metabolic diseases such as depression, hypertension, hypogonadism, and dyslipidaemia. We present an evidence-based narrative review focusing on the management of erectile dysfunction in diabetic men who have not responded to phosphodiesterase type 5 inhibitors.

CONCLUSIONS

Both clinicians and patients should be aware of the different management options in diabetic patients who have not responded to phosphodiesterase type 5 inhibitors.

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 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.

Urogenital Autonomic Dysfunction in Diabetes

This review details the epidemiology, possible mechanisms, and risk factors associated with urogenital autonomic dysfunction in diabetes. Autonomic neuropathy in diabetes is associated with various urological complications including bladder and sexual dysfunction. Several studies have reported the high prevalence of bladder and sexual dysfunction in both men and women. The DCCT/EDIC UroEDIC study examined the association between cardiovascular autonomic neuropathy and bladder and sexual dysfunction in a large cohort of participants with type 1 diabetes and was the first to report significant associations. Future studies are needed to further evaluate the association of urogenital complications and autonomic dysfunction in diabetes.

Surgical outcomes and complications of Tube® (Promedon) malleable penile prostheses in diabetic versus non-diabetic patients with erectile dysfunction

OBJECTIVE

To evaluate surgical outcome, complications, and patients satisfaction with the Tube® (Promedon, Cordoba, Argentina) malleable penile prosthesis in diabetic and non-diabetic patients with refractory erectile dysfunction (ED).

PATIENTS AND METHODS

The records of 128 eligible patients who received Tube malleable penile prostheses at our institute between September 2008 and October 2015 were reviewed.

RESULTS

Of the 128 patients, who received Tube penile prostheses at our institute, 53 were diabetics and 75 were non-diabetics. Both groups of patients were comparable for mean age, education level, marital status, hospital stay, time to commencing sexual intercourse, and median follow-up. Complications included: inter-corporeal septal perforation (2.3%), glanular urethral injury (1.5%), acute urinary retention (3.9%), superficial wound infection (7%), penile discomfort (9.4%), and penile prostheses infection (5.5%). Moreover, 3.9% developed atrophy of the cavernosal tissue, 5.5% experienced bad cosmesis, 6.3% experienced ejaculatory disorders, and 2.3% developed bladder calculi. In all, 13 prostheses (9.4%) were removed, seven of them due to infection, three on the patients' demand and three due to mechanical failure. The satisfaction rates with the prostheses were 77.3% and 79.4% in the diabetic and non-diabetic patients, respectively; with an overall satisfaction rate of 78.5%. There was no significant difference in the complication rate or prostheses infection between diabetic and non-diabetic patients.

CONCLUSION

Tube malleable penile prostheses are associated with low complication and high satisfaction rates. There was no significant difference in the complication rate or prostheses infection between diabetic and non-diabetic patients. A prospective comparative study with a large number of patients is recommended.

Erectile dysfunction and its management in patients with diabetes mellitus

Diabetes can be described as a syndrome of multiple closely related conditions induced by a chronic state of hyperglycaemia resulting from defective insulin secretion, insulin action or both. Chronic complications associated with diabetes (including neuropathy, vascular disease, nephropathy and retinopathy) are common, and of these, erectile dysfunction (ED) deserves special attention. ED and its correlation with cardiovascular disease require careful evaluation and appropriate treatment. PDE5 inhibitors (PDE5is) are an important tool for the treatment of ED, with new drugs coming onto the market since the late 90s. This review offers an overview of PDE5is and their use in treating ED in diabetes. We underline the differences between different types of PDE5i, focusing on available doses, duration of action, T ½, side effects and selectivity profiles in relation to patients with diabetes. We also discuss the link between diabetes and ED in presence of various associated cofactors (obesity, hypertension and its pharmacological treatments, atherosclerosis, hyperhomocysteinaemia, neuropathy, nephropathy, hypogonadism and depression). Finally a number of past and ongoing clinical trials on the use of PDE5is in patients with diabetes are presented to offer an overview of the appropriate treatment of ED in this condition.

Sexual dysfunction in diabetes

We aimed to summarize the etiology, clinical characteristics, diagnosis, and possible treatment options of sexual dysfunction in diabetic patients of both sexes. Details of dysfunction in diabetic women are less conclusive than in men due to the lack of standardized evaluation of sexual function in women. Male sexual dysfunction is a common complication of diabetes, including abnormalities of orgasmic/ejaculatory function and desire/libido in addition to penile erection. The prevalence of erectile dysfunction (ED) among diabetic men varies from 35% to 75%. Diabetes-induced ED has a multifactorial etiology including metabolic, neurologic, vascular, hormonal, and psychological components. ED should be regarded as the first sign of cardiovascular disease because it can be present before development of symptomatic coronary artery disease, as larger coronary vessels better tolerate the same amount of plaque compared to smaller penile arteries. The diagnosis of ED is based on validated questionnaires and determination of functional and organic abnormalities. First-, second- and third-line therapy may be applied. Phosphodiesterase-5 (PDE-5) inhibitor treatment from the first-line options leads to smooth muscle relaxation in the corpus cavernosum and enhancement in blood flow, resulting in erection during sexual stimulus. The use of PDE-5 inhibitors in the presence of oral nitrates is strictly contraindicated in diabetic men, as in nondiabetic subjects. All PDE-5 inhibitors have been evaluated for ED in diabetic patients with convincing efficacy data. Second-line therapy includes intracavernosal, trans- or intraurethral administration of vasoactive drugs or application of a vacuum device. Third-line therapies are the implantation of penile prosthesis and penile revascularization.

Serum High-Sensitivity C-Reactive Protein Levels and Response to 5 mg Tadalafil Once Daily in Patients With Erectile Dysfunction and Diabetes

Purpose

We studied the relative importance of high-sensitivity C-reactive protein (hs-CRP) concentrations in patients with erectile dysfunction (ED) and diabetes and determined whether the hs-CRP level predicts the response to treatment with 5 mg tadalafil once daily.

Materials and Methods

We enrolled 102 men (aged 40-60 years) with diabetes and ED. All patients completed the International Index of Erectile Function (IIEF) questionnaire and were given 5 mg tadalafil daily. The IIEF and serum hs-CRP levels in patients and healthy controls and in patient responders and nonresponders to 5 mg tadalafil once daily were compared.

Results

Median age was 53.2 years (range, 45 to 62 years) in patients and 55.6 years (range, 47 to 64 years) in healthy controls (p=0.158). The median duration of diabetes was 54.3 months (range, 34 to 70 months). The median IIEF and hs-CRP level were 12.1 (range, 5 to 20) and 0.21 mg/dL (range, 0.05 to 0.6 mg/dL) in patients and 28.2 (range, 13 to 31) and 0.09 mg/dL (range, 0.04 to 0.2 mg/dL) in the controls, respectively (pIIEF=0.000, pCRP=0.031). After tadalafil treatment, 71 patients (69.6%) achieved an erection sufficient for sexual intercourse, whereas 31 (30.4%) did not. The median age of the tadalafil nonresponders was 56.2 years (range, 45 to 64 years) and that of the responders was 51.3 years (range, 42 to 62 years; p=0.065). Median hs-CRP levels were 0.31 mg/dL (range, 0.18 to 0.62 mg/dL) in nonresponders and 0.14 mg/dL (range, 0.09 to 0.4 mg/dL) in responders, respectively (p=0.028).

Conclusions

Serum hs-CRP was significantly higher in patients with ED and diabetes mellitus than in patients without ED. A significant correlation was observed between serum hs-CRP levels, the degree of ED, and responsiveness to tadalafil.

Arterial erectile dysfunction: different severities of endothelial apoptosis between diabetic patients "responders" and "non responders" to sildenafil

BACKGROUND

The low pharmacological response to phosphodiesterase type 5 inhibitors represents an expression of higher endothelial damage in certain categories of patients with erectile dysfunction and high cardiovascular risk. The present study evaluated this objective in type 2 diabetic patients with erectile dysfunction, classified as "non responders" to Sildenafil.

METHODS

Eighteen "responder" and twelve "non responder" type 2 diabetic patients were evaluated, relatively to different levels of endothelial damage, through the diagnostic use of a new immunophenotype of circulating endothelial progenitor cells (CD45neg/CD34pos/CD144pos) and endothelial microparticles (CD45neg/CD144pos/Annexin Vpos), recently developed and published by our group.

RESULTS

"Non responder" patients showed a significant higher severity [8.0±3.0 (International Index of Erectile Function-abbreviated version with 5 questions) vs 14.0±3.0] and duration (10.0±2.0 vs 7.0±2.0 years) of erectile dysfunction, higher level of penile arterial insufficiency (peak systolic velocity=13.0±16.0 vs 28.0±26.0cm/s; acceleration time=153±148 vs 125±128 mm/s) and finally a significant higher level of endothelial apoptosis [0.15±0.13 vs 0.05±.0.03% (serum concentrations of endothelial microparticles)] associated with higher serum concentrations of circulating late immunophenotype of endothelial progenitor cells (0.40±0.35 vs 0.12±.0.10%).

CONCLUSIONS

The results of this study corroborate the clinical value of the low clinical response to phosphodiesterase type 5 inhibitors in the treatment of erectile dysfunction in the patients with high cardiovascular risk profile, such as diabetics. In addition, the markers used in this study confirm their potential application in clinical practice as useful indicators of endothelial alteration. However, in the future we will have to assess a larger number of patients and for a longer period of observation in order to better understand the causal and temporal relations.

Improvement of erectile function by Korean red ginseng (Panax ginseng) in a male rat model of metabolic syndrome

The seriousness of metabolic syndrome is not due to the disease itself but its promotion of other diseases, such as erectile dysfunction and cardiovascular and cerebrovascular diseases. We investigated the effects of Korean red ginseng (KRG, Panax ginseng) extract on erectile function in a rat model of metabolic syndrome. We divided the rats into three groups: control, metabolic syndrome+normal saline (N/S) and metabolic syndrome+KRG. To determine the occurrence of metabolic syndrome in all groups, body weight and various biochemical parameters (e.g., blood glucose, insulin, cholesterol) were measured, and the intra-abdominal glucose tolerance test was performed. To investigate penile erection, the peak intracavernosal pressure (ICP), mean arterial pressure (MAP) and Masson's trichrome stain were evaluated. Erectile function was also investigated by measuring the cyclic guanosine monophosphate (cGMP) levels of the corpus cavernosum. We found that the various biochemical parameters and body weight were similar in the metabolic syndrome+KRG group and the control group, although the values were slightly higher. The peak ICP/MAP ratio of the metabolic syndrome+N/S group was markedly decreased compared to the other groups. The cGMP level of the corpus cavernosum in the metabolic syndrome+N/S group was significantly lower than that of the other groups. As demonstrated in this model of metabolic syndrome with erectile dysfunction, KRG may improve erectile function.

Time-dependent changes of erectile function in diabetic rats: role of systemic endothelial dysfunction

PURPOSE

To understand the potential contribution of systemic endothelial dysfunction to diabetic erectile dysfunction, and the time course of erectile dysfunction in a streptozotocin (STZ)-induced diabetic rat model.

MATERIALS AND METHODS

Among 84, 12-week-old Sprague-Dawley rats, 48 rats received intraperitoneal STZ and were classified into six groups of diabetes by the period of observation (n=8). The remaining 36 rats were also grouped, similar to the diabetic groups, and served as normal controls. After 4, 6, 8, 10, 12, and 14 weeks of diabetes (serum glucose >250 mg%), all rats underwent cavernous nerve electrostimulation (3 V, 0.2 ms, 30 sec) with varying frequency (2.5~20 Hz). At the end of the study, 8 ml of blood was taken to measure the plasma markers of endothelial function and glycosylated hemoglobin.

RESULTS

Compared to the control, significant reduction of erectile response was not observed until eight weeks after diabetes induction. The diabetic rats had elevation of all plasma markers except for l-selectin. However, the correlation analysis revealed that no systemic marker of endothelial dysfunction was associated with change in erectile function. Only the level of hemoglobin A1c (HbA1c) showed a modest but significant correlation with the peak intracavernosal pressure, corrected by mean arterial pressure (ρ=-0.183), and the area under the curve of the cavernosometry (ρ=-0.207).

CONCLUSIONS

Significant reduction of erectile function was not observed until eight weeks after the induction of diabetes. Except for HbA1c, there was no systemic marker associated with endothelial activation and erectile function in the diabetic rats.

Testosterone and phosphodiesterase type-5 inhibitors: new strategy for preventing endothelial damage in internal and sexual medicine?

Normal vascular endothelium is essential for the synthesis and release of substances affecting vascular tone (e.g. nitric oxide; NO), cell adhesion (e.g. endothelins, interleukins), and the homeostasis of clotting and fibrinolysis (e.g. plasminogen inhibitors, von Willebrand factor). The degeneration of endothelial integrity promotes adverse events (AEs) leading to increased atherogenesis and to the development of vascular systemic and penile end-organ disease. Testosterone (T) is an important player in the regulation of vascular tone through non-genomic actions exerted via blockade of extracellular-calcium entry or activation of potassium channels; also, adequate T concentrations are paramount for the regulation of phosphodiesterase type-5 (PDE5) expression and finally, for the actions exerted by hydrogen sulphide, a gas involved in the alternative pathway controlling vasodilator responses in penile tissue. It is known that an age-related decline of serum T is reported in approximately 20 to 30% of men whereas T deficiency is reported in up to 50% of men with metabolic syndrome or diabetes. A number of laboratory and human studies have shown the combination of T and other treatments for erectile dysfunction (ED), such as PDE5 inhibitors, to be more beneficial in patients with ED and hypogonadism, who fail monotherapy for sexual disturbances.The aim of this review is to show evidence on the role of T and PDE5 inhibitors, alone or in combination, as potential boosters of endothelial function in internal medicine diseases associated with reduced T or NO bioavailability, i.e. metabolic syndrome, obesity, diabetes, coronary artery disease, hyperhomocysteinemia, that share common risk factors with ED. Furthermore, the possibility of such a strategy to prevent endothelial dysfunction in men at increased cardiovascular risk is discussed.

Erectile dysfunction and diabetes: a review of the current evidence-based medicine and a synthesis of the main available therapies

AIM

This review aimed to provide an update of the epidemiology, pathophysiology and management of erectile dysfunction (ED) in diabetes patients.

METHODS

Data on the management of ED in diabetes patients in the literature were analyzed using Medline, and by matching the following keywords: diabetes; erectile dysfunction; endothelial dysfunction; cardiovascular disease; phosphodiesterase inhibitors; intracavernous injection; and penile prosthesis.

RESULTS

ED has a higher incidence in diabetic patients. The pathophysiology is multifactorial, involving endothelial dysfunction, specific complications of diabetes and psychological factors. Recent studies have shown that ED is able to predict future cardiovascular events not only in non-diabetics, but also in patients with diabetes. ED could also be a potential marker to screen for silent coronary artery disease. The management of ED has been revolutionized by the discovery of phosphodiesterase type-5 (PDE5) inhibitors, the first-line therapeutic options for diabetic men with ED that are efficient and safe. As a second line, intracavernous injections remain a gold-standard treatment, although a vacuum device can be used as well. In cases of failure, penile prosthesis may be considered. Hypogonadism, commonly found in diabetics, may require identification and treatment. Optimalized glycaemic control, management of associated co-morbidities and lifestyle modifications are essential in all patients. As ED and diabetes negatively impact male self-esteem, and generate depression and anxiety, the psychological treatment of patients is also likely to be beneficial.

CONCLUSION

The aetiology of diabetic ED is multifactorial. Endothelial dysfunction is the link between diabetes-induced ED and coronary artery disease. A global approach is needed for the successful management of diabetic ED.

Population-based estimates of medical comorbidities in erectile dysfunction in a Taiwanese population

INTRODUCTION

Erectile dysfunction (ED) is usually associated with systemic disorders. This population-based study supports and expands on previous research. It also presents data in a Taiwanese male population where existing data on this topic remain sparse.

AIM

The aim of this study is to analyze the prevalence and risk of 36 medical comorbidities in patients with ED compared with the general population.

METHODS

A total of 2,213 patients with ED and 11,065 matching controls were selected from the Taiwan National Health Insurance Research Dataset. We chose 22 comorbidities from the Elixhauser comorbidity index, 10 highly prevalent medical conditions in an Asian population, and four male gender-specific comorbidities for analysis.

MAIN OUTCOME MEASUREMENT

Conditional logistic regression analyses conditioned on age group and monthly income were performed to investigate the risk of various comorbidities for patients with and without ED, after adjusting for the geographic region and level of urbanization of the patient's community.

RESULTS

Patients with ED were at an increased risk for multiple systemic comorbidities. Conditional regression analyses showed that patients with ED were at a higher risk for hypertrophy of the prostate (odds ratio [OR] = 12.87), chronic prostatitis (OR = 9.36), alcohol abuse (OR = 3.60), drug abuse (OR = 2.62), urinary incontinence (OR = 2.58), ankylosing spondylitis (OR = 2.19), peripheral vascular disorder (OR = 1.98), ischemic heart disease (OR = 1.94), psychoses (OR = 1.97), depression (OR = 1.88), uncomplicated diabetes (OR = 1.91), complicated diabetes (OR = 1.84), hepatitis B or C (OR = 1.71), hyperlipidemia (OR = 1.69), and chronic pulmonary disease (OR = 1.55) than patients without ED.

CONCLUSION

The results show that patients with ED have a higher prevalence of multiple noncardiovascular comorbidities than the general population in Taiwan.

Evaluation of erectile dysfunction and associated cardiovascular risk using structured questionnaires in Chinese type 2 diabetic men

Erectile dysfunction (ED) is not uncommon, but frequently underdiagnosed in type 2 diabetic men. In this study, we aimed to explore the frequency and severity of ED in Chinese type 2 diabetic men using a structured questionnaire. We furthermore sought to investigate the associations of ED with diabetes-related complications and metabolic indices. A consecutive cohort of 313 Chinese type 2 diabetic men aged between 25 and 76 years attending a diabetic centre were recruited between October 2006 and June 2007. Of the study population, the frequency of ED was 39.3% according to the National Institutes of Health (NIH) Consensus Conference criteria, compared with 84.3% (41.7% of them having moderate to severe ED) as diagnosed by International Index of Erectile Function (IIEF-5) questionnaire. After adjusting for potential confounding factors by multivariable logistic regression, ED defined by NIH criterion was associated with advanced age [OR = 1.05 (95% CI 1.01-1.09), p = 0.012], the presence of diabetic retinopathy [OR = 2.43 (95% CI 1.27-4.66), p = 0.008] and coronary heart disease [OR = 2.63 (95% CI 1.21-5.70), p = 0.015]. ED defined by IIEF-5 was associated with advanced age [OR = 1.12 (95% CI 1.06-1.17), p < 0.0001], use of insulin therapy [OR = 2.94 (95% CI 1.12-7.73), p = 0.029] and urinary albumin-creatinine ratio [OR = 2.29 (95% CI 1.05-5.01), p = 0.037]. In conclusion, ED was highly prevalent in Chinese type 2 diabetic men and was associated with multiple cardiovascular risk factors and complications. Advanced age, use of insulin therapy, the existence of microvascular complications such as retinopathy, albuminuria and coronary heart disease were associated with ED. NIH criteria diagnosed a much lower rate of ED compared with IIEF-5. Overall, structured questionnaires are useful and objective tools to detect ED, which should prompt a comprehensive risk assessment in these subjects.

The effect of intracavernous injection of adipose tissue-derived stem cells on hyperlipidemia-associated erectile dysfunction in a rat model

INTRODUCTION

Hyperlipidemia has been associated with erectile dysfunction (ED) via damage to the cavernous endothelium and nerves. Adipose tissue-derived stem cells (ADSC) have been shown to differentiate into endothelial cells and secrete vasculotrophic and neurotrophic factors.

AIM

To assess whether ADSC have therapeutic effects on hyperlipidemia-associated ED.

METHODS

Twenty-eight male rats were induced to develop hyperlipidemia with a high-fat diet (hyperlipidemic rats, HR). Ten additional male rats were fed a normal diet to serve as controls (normal rats, NR). Five months later, all rats were subjected to ADSC isolation from paragonadal fat. The cells were cultured for 1 week, labeled with 5-ethynyl-2'-deoxyuridine (EdU), and then injected autologously into the corpus cavernosum of 18 HR. The remaining 10 HR rats were injected with phosphate buffered saline (PBS). At 2 and 14 days post-transplantation, four rats in the HR + ADSC group were sacrificed for tracking of the transplanted cells. At 28 days post-transplantation, all remaining rats were analyzed for serum biochemistry, erectile function, and penile histology.

MAIN OUTCOME MEASURES

Erectile function was assessed by intracavernous pressure (ICP) measurement during electrostimulation of the cavernous nerve. Cavernous nerves, endothelium, and smooth muscle were assessed by immunohistochemistry.

RESULTS

Serum total cholesterol and low-density lipoprotein levels were significantly higher in HR than in NR. High-density lipoprotein level was significantly lower in HR than in NR. Mean ICP/mean arterial pressure ratio was significantly lower in HR + PBS than in NR + PBS or HR + ADSC. Neuronal nitric oxide synthase (nNOS)-positive nerve fibers and endothelial cells were fewer in HR + PBS than in HR + ADSC. Smooth muscle content was significantly higher in both HR groups than in NR.

CONCLUSIONS

Hyperlipidemia is associated with abnormalities in both the nerves and endothelium. Treatment with ADSC ameliorates these adverse effects and holds promise as a potential new therapy for ED.

Diabetes exacerbates the functional deficiency of NO/cGMP pathway associated with erectile dysfunction in human corpus cavernosum and penile arteries

INTRODUCTION

Diabetic men with erectile dysfunction (ED) are less responsive to therapy with type 5 phosphodiesterase (PDE5) inhibitors. Although an impairment of the nitric oxide (NO)/cyclic guanosin-monophosphate (cGMP) pathway has been shown in diabetic ED vs. non-diabetic ED, the functionality of NO/cGMP pathway in non-diabetic and diabetic ED patients with respect to non-ED patients has not been established.

AIM

The aim of this study is to evaluate the function of NO/cGMP signalling in human erectile tissues from ED patients exploring the added impact of diabetes.

METHODS

Corpus cavernosum strips (human corpus cavernosum [HCC]) and penile resistance arteries (HPRA) were collected from penile specimens from organ donors (OD) and from diabetic and non-diabetic men with ED undergoing penile prosthesis implantation.

MAIN OUTCOME MEASURES

Relaxations to acetylcholine, electrical field stimulation, sodium nitroprusside, and sildenafil were evaluated in phenylephrine-contracted HCC and norepinephrine-contracted HPRA. cGMP content in HCC was also determined.

RESULTS

The impairment of endothelium-dependent relaxation in HCC and HPRA from ED patients was exacerbated by diabetes (E(max) 76.1, 62.9, and 49.3% in HCC and 73.1, 59.8, and 46.0% in HPRA from OD, non-diabetic and diabetic ED, respectively). Hypertension, hypercholesterolemia, or aging did not exert a further impairment of endothelial relaxation among ED patients. Diabetes also causes a further impairment of neurogenic relaxation in HCC and HPRA. The basal and stimulated content of cGMP in HCC was significantly decreased in patients with ED, but specially reduced in diabetic patients. Diabetes clearly impaired PDE5 inhibitor-induced vasodilation of HPRA from ED patients.

CONCLUSIONS

ED is related to impaired vasodilation, reduced relaxant capacity, and diminished cGMP content in penile tissue. These alterations are more severe in diabetes and accompany reduced relaxant efficacy of PDE5 inhibition. Thus, an exacerbated reduction of nitric oxide/cGMP signaling could be responsible for ED in diabetic men and would explain their reduced response to treatment.

Management of erectile dysfunction in diabetes: an update for 2008

Tumescence occurs as a result of nitric oxide (NO)-mediated smooth muscle relaxation of the erectile tissue leading to engorgement of the corpus cavernosum. The process is initiated by neuronal NO release and maintained by NO released by the local vascular endothelium. Erectile dysfunction (ED) affects 30% to 40% of diabetic men and occurs as a result of endothelial dysfunction and autonomic neuropathy. The close association with endothelial dysfunction means ED is an early marker of cardiovascular risk. Managing ED is easy and must be part of a diabetes care service. Phosphodiesterase type 5 inhibitors are the treatment of choice, but are effective in only 50% to 60% of diabetic men. The reasons for nonresponsiveness remain uncertain and research is needed in this area. There has been much recent interest in the potential relationship between late-onset hypogonadism and diabetes, but there is no evidence of a causal relationship and the evidence in favor of treating borderline hypogonadism in diabetes is limited.

Efficacy of tadalafil once daily in men with diabetes mellitus and erectile dysfunction

AIMS

Erectile dysfunction (ED) is a common comorbidity in men with diabetes mellitus. Tadalafil 10 or 20 mg taken on demand is efficacious and safe for men with diabetes and ED. Recently, continuous treatment with tadalafil has been proposed, addressing ED management as any other chronic condition. This study examined whether once-daily tadalafil 2.5 and 5 mg is efficacious for men with diabetes and ED.

METHODS

This randomized, double-blind, placebo-controlled, multicentre, 12-week study enrolled 298 men with diabetes and ED to once-daily treatment with placebo, tadalafil 2.5 mg or tadalafil 5 mg. Primary efficacy measures were International Index of Erectile Function Erectile Function (IIEF EF) Domain score, and patient success rates for vaginal penetration and completion of intercourse. Patient satisfaction, endothelial function biomarkers, and safety were also assessed.

RESULTS

Patients receiving either dose of tadalafil had clinically and statistically significant improvements in IIEF EF and statistically significant improvements in mean success rates for vaginal penetration, completion of intercourse, and overall treatment satisfaction (P < or = 0.005 tadalafil vs. placebo, all measures). Endothelial dysfunction biomarkers were unchanged. The most common adverse events were headache, back pain and dyspepsia.

CONCLUSIONS

In this first study of men with diabetes and ED, once-daily tadalafil 2.5 and 5 mg was efficacious and well tolerated, suggesting this may be an alternative to on-demand treatment for some men, eliminating the need to plan sex within a limited timeframe.

Chronic treatment with a type 5 phosphodiesterase inhibitor suppresses apoptosis of corporal smooth muscle by potentiating Akt signalling in a rat model of diabetic erectile dysfunction

OBJECTIVES

To examine whether chronic treatment with a type 5 phosphodiesterase inhibitor (PDE5I) could suppress corporal apoptosis via potentiation of Akt signalling in diabetic erectile dysfunction.

METHODS

Sprague-Dawley rats (12 wk old) were divided into three groups (n=12 in each): normal control, diabetes (DM), and diabetes treated with PDE5I (DM+PDE5I). The rats in the diabetic groups received a single injection of streptozotocin (50mg/kg), and from 8 wk after establishment of diabetes, DM and DM+PDE5I were treated with vehicle and PDE5I (SK-3530, 10mg/kg), respectively, for 4 wk. After 12 wk of streptozotocin injections, six rats in each group underwent cavernosometry with cavernous nerve electrostimulation (2V, 0.2 ms, 50s, 2.5-20 Hz). The penile tissues from the remaining six rats were used for immunohistochemical evaluation of apoptosis, immunoblotting for the phosphorylation of Akt and its downstream molecule Bad, and a colorimetric assay of caspase activity.

RESULTS

Rats in the DM group showed markedly lower erectile parameters than those in the control group, whereas rats in the DM+PDE5I group showed normalized results. Despite persistent hyperglycaemia, PDE5I treatment significantly reduced the mean apoptotic index (39.6+/-4.6 vs. 21.3+/-1.7, p<0.05). Densitometry revealed significantly higher levels of Akt and Bad phosphorylation, implying inhibition of pro-apoptotic stimuli. PDE5I treatment also significantly inhibited the activities of cavernosal caspase 3 and caspase 9, the main effectors of apoptosis.

CONCLUSIONS

Chronic treatment with PDE5I activated Akt signalling, which suppressed pro-apoptotic stimuli and maintained erectile function in rat model of diabetic erectile dysfunction.

Improvement of vascular function by acute and chronic treatment with the PDE-5 inhibitor sildenafil in experimental diabetes mellitus

BACKGROUND AND PURPOSE

Diabetes-associated vascular dysfunction contributes to increased cardiovascular risk. We investigated whether the phosphodiesterase-5 inhibitor sildenafil would improve vascular function in diabetic rats.

EXPERIMENTAL APPROACH

Male Wistar rats were injected with streptozotocin (50 mg kg(-1), i.v.) to induce insulin-deficient diabetes. Direct effects of sildenafil as well as modification of endothelium-dependent and -independent vasorelaxation were investigated in vitro. The effects of acute and chronic (2 week) treatment in vivo of sildenafil on vascular function were also characterized in isolated aortic segments in organ bath chambers 4 weeks after diabetes induction.

KEY RESULTS

Sildenafil induced a concentration-dependent vasorelaxation, which was attenuated by the nitric oxide (NO) synthase inhibitor, N(G)-nitro-L-arginine. Acetylcholine-induced endothelium-dependent as well as endothelium-independent relaxation induced by the NO donor, DEA-NONOate, was significantly reduced in aortae from diabetic rats. Incubation with sildenafil in vitro normalized both endothelium-dependent and -independent relaxation in aortae from diabetic rats. Acute as well as chronic in vivo treatment with sildenafil resulted in enhanced endothelium-dependent and -independent vasorelaxation. Superoxide formation was increased in diabetes, associated with enhanced membrane expression of the NAD(P)H oxidase subunit gp91(phox) and Rac, which were both reduced by chronic treatment with sildenafil.

CONCLUSIONS AND IMPLICATIONS

We demonstrate that sildenafil treatment rapidly and chronically improves vascular relaxation in diabetic rats. Treatment with sildenafil might provide a similarly beneficial effect in diabetic patients.

Chronic sildenafil in men with diabetes and erectile dysfunction

Erectile dysfunction frequently represents a neurovascular complication of diabetes mellitus, and it has been calculated that almost 50% of diabetic men will have erectile dysfunction within 6 years after diagnosis. Penile endothelial and smooth muscle cell dysfunction are due to molecular pathway abnormalities (i.e., activation of PKC, increased oxidative stress and overproduction of advanced-glycosylation end products). The response rate to oral drug therapies, such as sildenafil, is lower than in most other groups. Because therapeutic alternatives (i.e., intracavernous injections with vasoactive agents) are not curative, clinical trials aimed to demonstrate rehabilitative effects with daily phosphodiesterase type-5 inhibitors are ongoing. If this approach proves successful, it will determine many advantages over the intracavernosal treatment and potentially induce sexual rehabilitation.

Overexpression of arginase in the aged mouse penis impairs erectile function and decreases eNOS activity: influence of in vivo gene therapy of anti-arginase

Since both increased nitric oxide (NO) synthase (NOS) abundance and diminished NO signaling have been reported in the aging penis, the role of NO in the adaptations of aging remains controversial. Here we tested the hypothesis that arginase, an enzyme that competes with NOS for the substrate l-arginine, contributes to erectile dysfunction with advanced age in the B6/129 mouse strain. Arginase protein abundance, mRNA expression, and enzyme activity were elevated in aged compared with young penile endothelial cells. In addition, endothelial NOS (NOS3) protein abundance was greater in aged versus young penile endothelial cells, whereas NOS activity and cGMP levels were reduced. Calcium-dependent l-arginine-to-l-citrulline conversion and cGMP formation increased significantly in aged mouse penes in the presence of the arginase inhibitor 2(S)-amino-6-boronohexanoic acid (ABH). However, there was no effect on l-arginine-to-l-citrulline conversion or cGMP accumulation in the endothelium from young mouse penes. To assess the functional role of arginase in the inhibition of NOS pathway responsiveness in the penis, we evaluated the effects of ABH and an adeno-associated virus encoding an antisense sequence to arginase I (AAVanti-arginase) on erectile function in vivo. ABH and AAVanti-arginase enhanced endothelium-dependent erectile responses in the aged mice without altering endothelium-independent responses. Paralleling our in vitro observations, ABH or AAVanti-arginase did not affect vascular responses in the young mice. Inhibition of the arginase pathway improves endothelial function in the aging penile circulation, suggesting that the arginase pathway may be exploited to improve erectile dysfunction associated with aging.