Erectile Dysfunction

Diabetic neuropathy

PURPOSE OF REVIEW

Diabetes is the most common cause of peripheral neuropathy in the world. More than half of patients with diabetes have neuropathy, and half of patients with neuropathy have diabetes. Diabetic neuropathy is a major cause of disability and health care expense. This article reviews the various forms of diabetic neuropathy with a focus on diagnosis and treatment.

RECENT FINDINGS

Diabetes causes a wide variety of peripheral nerve problems. These can be divided into chronic neuropathies, of which distal symmetric polyneuropathy is the most common, and acute neuropathies, such as diabetic amyotrophy. There is growing evidence suggesting that prediabetic levels of hyperglycemia and other consequences of obesity and dyslipidemia contribute to neuropathy risk. Evolving literature suggests that many of the acute diabetic neuropathies are related to inflammatory mechanisms. An important exception is treatment-related neuropathy, previously known as "insulin neuritis".

SUMMARY

While disease-altering therapy continues to prove elusive, our understanding of basic disease mechanisms is improving, and new diagnostic and research tools will hopefully lead to novel therapies for distal symmetric diabetic polyneuropathy.

Erectile dysfunction: a new plague

Erectile dysfunction has the potential to affect all men, of all ages and of all ethnicities, it does not discriminate. It has the power to emasculate men, impacting on their daily lives.

Role of hydrogen sulfide in the physiology of penile erection

Hydrogen sulfide (H(2)S), which is a well-known toxic gas, has recently been recognized as a biological messenger that plays an important role in physiological and pathophysiological conditions. Relatively high levels of H(2)S have been discovered in mammalian tissues. It is mainly synthesized by 2 enzymes, including cystathionine β-synthase and cystathionine γ-lysase, which utilize L-cysteine as substrate to produce H(2)S. H(2)S has been demonstrated to exhibit potent vasodilator activity both in vitro and in vivo by relaxing vascular smooth muscle. Recently, H(2)S has been discovered in penile tissue with smooth muscle relaxant effects. Furthermore, other effects of H(2)S could play a role in the physiology of erection. Understanding H(2)S in the physiology of erection might provide alternative erectile dysfunction strategies for those patients with poor or no response to type 5 phosphodiesterase inhibitors. This review intends to present the H(2)S pathway in penile tissue and the potential role of H(2)S in the physiology of erections.

New insights into hypertension-associated erectile dysfunction

PURPOSE OF REVIEW

Erectile dysfunction is recognized as a quality-of-life disorder that needs to be treated. Currently, it is estimated to affect as many as 30 million American men. Thirty percent of hypertensive patients complain of erectile dysfunction. The understanding of common mechanisms involved in the cause of erectile dysfunction associated with hypertension, and the investigation of antihypertensive drugs that impact erectile dysfunction, will provide important tools toward identifying new therapeutic targets that will improve the quality of life for patients in these conditions.

RECENT FINDINGS

Hypertension and erectile dysfunction are closely intertwined diseases, which have endothelial dysfunction as a common base. During hypertension and/or erectile dysfunction, disturbance of endothelium-derived factors can lead to an increase in vascular smooth muscle (VSM) contraction. Hypertension can lead to erectile dysfunction as a consequence of high blood pressure (BP) or due to antihypertensive treatment. However, growing evidence suggests erectile dysfunction is an early sign for hypertension. Also, some phosphodiesterase-5 inhibitors used to treat erectile dysfunction can improve BP, but the link between these conditions has not been totally understood.

SUMMARY

This review will discuss the interplay between hypertension and erectile dysfunction, exploring newest insights regarding hypertension-associated erectile dysfunction, as well as the effect of antihypertensive drugs in erectile dysfunction patients.

Effect of felodipine with irbesartan or metoprolol on sexual function and oxidative stress in women with essential hypertension

OBJECTIVE

To evaluate the impact of felodipine with irbesartan on sexual function compared with felodipine with metoprolol in hypertensive women.

METHODS

This was a prospective, randomized, parallel, active-controlled, open-label study (ClinicalTrials.org: NCT01238705) in 160 women (18-60 years) with mild or moderate hypertension, randomized to a once-daily treatment with felodipine combined with irbesartan or metoprolol for 48 weeks. Patients' sexual function was evaluated using a female sexual function index (FSFI) questionnaire at baseline and after 24 and 48 weeks of therapy. Levels of serum estradiol, testosterone, 8-hydroxy-2'-deoxyguanosine (8-OHdG), 4-hydroxynonenal (4-HNE) and malondialdehyde (MDA) were measured.

RESULTS

The two combination regimens were similarly effective in lowering blood pressure. After 48 weeks, in felodipine-irbesartan group, total scores of FSFI improved (P < 0.001). Items showing improvement in scores corresponded to desire, arousal and orgasm (P < 0.001; P = 0.002; P = 0.049, respectively). Levels of estradiol increased under treatment with felodipine-irbesartan (P = 0.003) and decreased under felodipine-metoprolol treatment (P < 0.001). The concentration of testosterone declined after felodipine-irbesartan therapy (P < 0.001) and increased under felodipine-metoprolol treatment (P < 0.001). In the felodipine-irbesartan group, decreases of 8-OHdG, 4-HNE (P < 0.001) and MDA (P < 0.001) were observed. The felodipine-irbesartan combination resulted in less oxidative stress. The differences in changes in 8-OHdG, 4-HNE and MDA between the two groups were significant (P < 0.05).

CONCLUSION

These results suggested that the felodipine-irbesartan combination regimen improved sexual function in hypertensive women, whereas felodipine-metoprolol regiment did not. The reason for the different influence of these two combination therapy on female sexual function might be their different impacts on oxidative stress and hormone levels.

Erectile dysfunction in obstructive sleep apnea syndrome--prevalence and determinants

INTRODUCTION

OSAS (Obstructive Sleep apnea syndrome) is defined by recurrent episodes of upper airway obstruction during sleep, causing multiple clinical consequences. Literature review suggests that OSAS induces a spectrum of abnormalities in neural, hormonal and vascular regulation that contribute to the development of ED (erectile dysfunction). The aims of this study were to estimate the prevalence of ED in OSAS patients and evaluate its determinants.

METHODS

62 patients from Hospital S. João Sleep Laboratory with newly diagnosed OSAS were included in the study and answered the IIEF-5 (international index erectile function 5 item version) questionnaire.

RESULTS

The prevalence of ED in OSAS patients was 64.4%. Age and Diabetes constituted themselves as independent risk factors for more severe degrees of ED: OR=1.226 (95%CI: 1.062-1.415) and OR=31.205 (95%CI: 1.222-796.557), respectively. Compared with nonsmokers, ex-smokers group revealed a positive association with ED: OR=4.32 (95%CI: 1.09-17.11). Hypertension and ACEI (angiotensin converting enzyme inhibitors) or ARB (angiotensin II receptor blockers) therapy were also correlated to ED symptoms: OR=3.25 (95%CI: 1.09-9.65) and 7.39 (95%CI: 1.52-35.99), respectively. No association was found relating BMI (p=0.254), alcoholic habits (p=0.357), acute myocardial infarction (p=0.315), dyslipidemia (p=0.239),metabolic syndrome (p=0.215) and ED. OSAS severity was not associated with ED in our sample.

CONCLUSIONS

The prevalence of ED in OSAS patients is high. ED determinants in our sample were age and diabetes. Past smoking habits, hypertension and ACEI/ARB therapy also revealed a statistically significant association with ED.

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.

Characterization of the vasculature supplying the genital tissues in female rats

INTRODUCTION

The internal pudendal arteries are the key resistance vessels controlling the peripheral circulatory component of sexual responses in both male and females. Previous studies in the male rat demonstrated that this vessel has markedly heightened susceptibility to vascular damage compared with other vessels in the body. Evidence suggests that the female may also be susceptible to vascular pathologies contributing to sexual dysfunction.

AIM

The aim of this study is to characterize the anatomical, morphological, and functional properties of the pudendal artery in female rats.

METHODS

The pelvic arteries in young Sprague-Dawley female rats were dissected to generate a composite representation of the vascular gross anatomy. Morphometry was performed on perfusion-fixed pudendal arteries whereas others were mounted in a wire myograph to assess responses to vasoactive drugs. These measures were contrasted with a previous study examining male rats.

MAIN OUTCOME MEASURES

Outcome measures used are gross anatomy, lumen diameter, wall thickness, cross-sectional area, and contractile responses in the internal pudendal artery.

RESULTS

The gross anatomy of the pudendal artery in female rats appears to parallel that found in male rats, acting as the primary feeder vessel of the clitoral, labial, and vaginal tissue. Compared with the male rat, the female pudendal artery has a smaller lumen diameter (169 ± 5.7 vs. 303 ± 13.8 µm), wall thickness (14 ± 0.7 vs. 47 ± 2.2 µm), and cross-sectional area (8 ± 0.4 vs. 52 ± 3.4 × 103 µm(2) ). These structural differences also translate into a decreased contractile capacity of the pudendal arteries from female rats vs. male rats (8.1 ± 2.7 vs. 20 ± 1.4 mN).

CONCLUSIONS

Although the gross anatomical features of the vasculature tree supplying the genital tissue in male and female rats appear to have similarities, the tissue-specific properties of the vessel itself have a very different structure-function balance. We hypothesize that this discordance likely reflects the very different sex-specific roles of this vessel in regulating blood flow during arousal.

Mechanisms of penile erection and basis for pharmacological treatment of erectile dysfunction

Erection is basically a spinal reflex that can be initiated by recruitment of penile afferents, both autonomic and somatic, and supraspinal influences from visual, olfactory, and imaginary stimuli. Several central transmitters are involved in the erectile control. Dopamine, acetylcholine, nitric oxide (NO), and peptides, such as oxytocin and adrenocorticotropin/α-melanocyte-stimulating hormone, have a facilitatory role, whereas serotonin may be either facilitatory or inhibitory, and enkephalins are inhibitory. The balance between contractant and relaxant factors controls the degree of contraction of the smooth muscle of the corpora cavernosa (CC) and determines the functional state of the penis. Noradrenaline contracts both CC and penile vessels via stimulation of α₁-adrenoceptors. Neurogenic NO is considered the most important factor for relaxation of penile vessels and CC. The role of other mediators, released from nerves or endothelium, has not been definitely established. Erectile dysfunction (ED), defined as the "inability to achieve or maintain an erection adequate for sexual satisfaction," may have multiple causes and can be classified as psychogenic, vasculogenic or organic, neurologic, and endocrinologic. Many patients with ED respond well to the pharmacological treatments that are currently available, but there are still groups of patients in whom the response is unsatisfactory. The drugs used are able to substitute, partially or completely, the malfunctioning endogenous mechanisms that control penile erection. Most drugs have a direct action on penile tissue facilitating penile smooth muscle relaxation, including oral phosphodiesterase inhibitors and intracavernosal injections of prostaglandin E₁. Irrespective of the underlying cause, these drugs are effective in the majority of cases. Drugs with a central site of action have so far not been very successful. There is a need for therapeutic alternatives. This requires identification of new therapeutic targets and design of new approaches. Research in the field is expanding, and several promising new targets for future drugs have been identified.

[Vessel aging. The role of oxidative stress and protein glycation]

The slow procession of the primary mechanisms of aging leads, at first, to unnoticed changes in the vascular system. Endothelial dysfunction is one of the earliest markers in aging vessels, caused by oxidative stress via the reduction of the availability of NO, on the one hand, and the nitrosylation of proteins, on the other hand. At the same time, glycation of the proteins of the extracellular matrix leads to stiffening of the vessel wall. Together with the loss of elastic fibers, e.g., elastin, this leads to the age-related changes of the vessels. Knowledge of these primary mechanisms of aging may lead to the development of new drugs.