Androgen-dependent nitric oxide release in rat penis correlates with levels of constitutive nitric oxide synthase isoenzymes

Systemic testosterone for the treatment of female sexual interest and arousal disorder (FSIAD) in the postmenopause

INTRODUCTION

Female sexual interest and arousal disorder (FSIAD) is the most prevalent female sexual dysfunction in the postmenopause.

OBJECTIVE

The aim of this review is to provide a summary of the currently available evidence on the use of testosterone in the treatment of FSIAD in postmenopausal women.

METHODS

A narrative review on the topic was performed. Only randomized controlled trials (RCTs) and systematic reviews and meta-analysis were considered. 123 articles were screened, 105 of them assessed for eligibility, and finally 9 were included in qualitative synthesis following the PRISMA declaration.

RESULTS

Current evidence recommends, with moderate therapeutic benefit, the use of systemic transdermal testosterone within the premenopausal physiological range in postmenopausal women with Hypoactive Sexual Desire Disorder (HSDD), the previous entity for low desire dysfunction, not primarily related to modifiable factors or comorbidities such as relationship or mental health problems. The available evidence is based on studies with heterogeneity on their design (different testosterone doses, routes of administration, testosterone use in combination and alone, sexual instruments of measurement). There is no data indicating severe short-term adverse effects, although long-term safety data is lacking.

CONCLUSIONS

Despite having testosterone as a valuable tool, therapeutic strategies are lacking in the pharmacological field of HSDD/FSIAD. Neuroimaging studies could provide valuable information regarding the sexual desire substrate and suggest the potential application of already approved drugs for women with a good safety profile. The use of validated instruments for HSDD in postmenopausal women, considering the level of distress, is necessary to be able to draw robust conclusions on the evaluated treatments.

S-Nitroso-N-acetylpenicillamine impregnated latex: A new class of barrier contraception for the prevention of intercourse-associated UTIs

Urinary tract infections (UTIs) are some of the most common infections seen in humans, affecting over half of the female population. Though easily and quickly treatable, if gone untreated for too long, UTIs can lead to narrowing of the urethra as well as bladder and kidney infections. Due to the disease potential, it is crucial to mitigate the development of UTIs throughout healthcare. Unfortunately, sexual activity and the use of condoms have been identified as common risk factors for the development of sexually acquired UTIs. Therefore, this study outlines a potential alteration to existing condom technology to decrease the risk of developing sexually acquired UTIs using S-nitroso-N-acetylpenicillamine (SNAP), a nitric oxide (NO) donor. Herein, varying concentrations of SNAP are integrated into commercialized condoms through a facile solvent swelling method. Physical characterization studies showed that 72%-100% of the ultimate tensile strength was maintained with lower SNAP concentrations, validating the modified condom's mechanical integrity. Additionally, the evaluation of room-temperature storage stability via NO release analysis outlined a lack of special storage conditions needed compared to commercial products. Moreover, these samples exhibited >90% relative cell viability and >96% bacterial killing, proving biocompatibility and antimicrobial properties. SNAP-Latex maintains the desired condom durability while demonstrating excellent potential as an effective new contraceptive technology to mitigate the occurrence of sexually acquired UTIs.

Effects of transplantation of umbilical cord blood mononuclear cells into the scrotum on sexual function in elderly mice

Aim: This study investigated the effect of allografting umbilical cord blood mononuclear cells (UCBMCs) into the scrotum on sexual function in male elderly mice. Methods: UCBMCs were injected once into the scrotal sheath cavity of elderly mice. Results: The transplanted UCBMCs survived in the scrotal sheath cavity for 1 month. The mice had significantly increased blood testosterone concentrations, cyclic guanosine monophosphate (cGMP) levels and total nitric oxide synthase (T-NOS) activity in the corpus cavernosum and an increase in the number of mouse matings within 30 min (all p = 0.000). Conclusion: Scrotum-implanted UCBMCs improve the sexual function of male elderly mice through testosterone production and the NOS/cGMP pathway, which may provide an innovative transplantation approach for the treatment of erectile dysfunction.

Combined levothyroxine and testosterone treatment for restoring erectile dysfunction in propylthiouracil-induced hypothyroid rats

BACKGROUND

Sexual dysfunction may indicate severe endocrine diseases. Recent research has suggested a link between hypothyroidism, low testosterone (T) levels, and erectile dysfunction (ED); however, the exact cause is unknown.

AIM

We sought to investigate possible beneficial effects of levothyroxine and T alone or in combination on ED in propylthiouracil (PTU)-induced hypothyroid rats.

METHODS

Adult Wistar rats (n = 35) were divided into 5 groups: control, PTU-induced hypothyroidism, PTU + levothyroxine, PTU + Sustanon (a mixture of 4 types of T: propionate, phenylpropionate, isocaproate, and decanoate) and PTU + levothyroxine + Sustanon. PTU was given in drinking water for 6 weeks. Four weeks after PTU administration, levothyroxine (20 μg microgram kg/day, oral) and Sustanon (10 mg/kg/week, intramuscular) were given for 2 weeks. Serum levels of total T, triiodothyronine (T3), and thyroxine (T4) were determined. In vivo erectile response and in vitro relaxant responses were measured. Localization of neuronal nitric oxide synthase (nNOS), endothelial NOS (eNOS), and phosphodiesterase type 5 (PDE5) were determined using immunohistochemical analysis. The relative area of smooth muscle to collagen was measured using Masson trichrome staining.

OUTCOMES

Outcome variables included in vivo erectile function, in vitro relaxant and contractile responses of corpus cavernosum (CC) strips; protein localization of eNOS, nNOS, and PDE5; and smooth muscle content in penile tissue.

RESULTS

The rat model of hypothyroidism showed a significant decline in serum levels of total T, T3, and T4. Levothyroxine increased T3 and T4 levels, whereas Sustanon normalized only total T levels. Combined treatment enhanced all hormone levels. Rats with hypothyroidism displayed the lowest erectile response (P < 0.001 vs controls). Combined treatment returned reduced responses, while partial amelioration was observed after levothyroxine and Sustanon treatment alone. Acetylcholine (P < 0.01 vs controls), electrical field stimulation (P < 0.001 vs controls), and sildenafil-induced relaxant responses (P < 0.05 vs controls) were decreased in the CC strips from hypothyroid rats. The combined treatment increased the reduction in relaxation responses. Levothyroxine and Sustanon restored decreases in eNOS and nNOS expression in the hypothyroid group. There was no significant difference in PDE5 expression among groups. Monotreatment partially enhanced reduced smooth muscle mass, while combined therapy completely recovered.

CLINICAL IMPLICATIONS

The combination of thyroid hormones and T is likely to be a therapeutic approach for treatment of hypothyroidism-induced ED in men.

STRENGTHS AND LIMITATIONS

Beneficial effects of levothyroxine and Sustanon treatment were shown in vitro and in vivo in PTU-induced hypothyroid rats. The main limitation of the study was the lack of measurement of androgen-sensitive organ weights and luteinizing hormone, follicle-stimulating hormone, and prolactin levels.

CONCLUSION

These findings demonstrate that neurogenic and endothelium-dependent relaxation responses are reduced by hypothyroidism, which is detrimental to T levels and erectile responses. Levothyroxine and Sustanon combination medication was able to counteract this effect.

Testosterone replacement therapy and erectile dysfunction

Testosterone (T) deficiency and erectile dysfunction (ED) are independently functionally and socially impairing, and their concurrence in men can be challenging to treat. Successful management requires an understanding of the mechanisms through which T underlies normal erectile function. While the literature elucidating some of these mechanisms is vast (e.g., androgen regulation of the activity of nitric oxygen synthase and phosphodiesterase type 5) for others it is scarce (e.g., catalysts of castration-induced corporal fibrosis). The randomized controlled trial data for the efficacy of T replacement as mono- or combination therapy to treat ED has been conflicting. Positive results were frequently not clinically meaningful. Meta-analyses have been helpful in illuminating trends that seem to be promising. Consensus is still lacking in several areas, such as the threshold of low T severity for which replacement therapy is most beneficial; the timing for initiating combination therapy; and the duration of treatment.

Testosterone attenuates hypoxia-induced hypertension by affecting NRF1-mediated transcriptional regulation of ET-1 and ACE

Hypertension induced by hypoxia at high altitude is one of the typical symptoms of high-altitude reactions (HARs). Emerging evidence indicates that endothelial abnormalities, including increases in angiotensin-2 (Ang-2) and endothelin-1 (ET-1), are closely associated with hypertension. Thus, low blood oxygen-induced endothelial dysfunction through acceleration of Ang-2 and ET-1 synthesis may alleviate HARs. In this study, we investigated the effects of hypoxia on rat blood pressure (BP) and endothelial injury. We found that BP increased by 10 mmHg after treatment with 10% O₂ (~5500 m above sea level) for 24 h. Consistently, serum Ang-2 and ET-1 levels were increased along with decreases in NO levels. In endothelial cells, angiotensin-1-converting enzyme (ACE) and ET-1 expression levels were upregulated. Interestingly, nuclear respiratory factor 1 (NRF1) levels were also upregulated, consistent with the changes in ACE and ET-1 levels. We further demonstrated that NRF1 transcriptionally activated ACE and ET-1 by directly binding to their promoter regions, suggesting that the endothelial cell dysfunction induced by hypoxia was due to NRF1-dependent upregulation of ACE and ET-1. Surprisingly, testosterone supplementation showed significant protective effects on BP, while castration induced even higher BPs in rats exposed to hypoxia. We further showed that physiological testosterone repressed NRF1 expression in vivo and in vitro and thereby reduced Ang-2 and ET-1 levels, which was dependent on hypoxia. In summary, we have identified that physiological testosterone protects against hypoxia-induced hypertension through inhibition of NRF1, which transcriptionally regulates ACE and ET-1 expression.

The serum levels of testosterone in coronary artery disease patients; relation to NO, eNOS, endothelin-1, and disease severity

OBJECTIVES

The changes in testosterone level and its correlation with the endothelial nitric oxide systems balance in patients with coronary artery disease (CAD) remains uncertain. Therefore, in our study, we aimed to evaluate the levels of testosterone, endothelin-1 (ET-1), nitric oxide (NO), and endothelial NOS (eNOS) in CAD patients, and control group to find the relationship between these parameters and disease severity.

METHODS

Forty-four patients as CAD group with significant (≥50%) stenosis confirmed by angiography was included in the study, and 40 healthy men were included as the control group. According to the number of vessels obstruction, CAD severity was determined. The serum indicated parameters were assessed to discriminate between patients and controls.

RESULTS

It was found that testosterone levels in the CDA group were significantly lower than those of the control group (p<0.05). In addition, the level of ET-1 in the CAD group was higher than that in the control group, but levels of NO and eNOS in observation were significantly lower than those in the control group (p<0.05). The correlation analysis revealed that testosterone was passivity correlated with serum NO levels (r=0.550, p=0.001).

CONCLUSIONS

The current study reports that serum levels of testosterone are closely related to endothelial NO levels and might be of relevance to the pathogenesis of endothelial dysfunction and disease severity in CAD patients.

Erectile Dysfunction in Men on the Rise: Is There a Link with Endocrine Disrupting Chemicals?

Erectile dysfunction (ED) is one of the most prevalent chronic conditions affecting men. ED can arise from disruptions during development, affecting the patterning of erectile tissues in the penis and/or disruptions in adulthood that impact sexual stimuli, neural pathways, molecular changes, and endocrine signalling that are required to drive erection. Sexual stimulation activates the parasympathetic system which causes nerve terminals in the penis to release nitric oxide (NO). As a result, the penile blood vessels dilate, allowing the penis to engorge with blood. This expansion subsequently compresses the veins surrounding the erectile tissue, restricting venous outflow. As a result, the blood pressure localised in the penis increases dramatically to produce a rigid erection, a process known as tumescence. The sympathetic pathway releases noradrenaline (NA) which causes detumescence: the reversion of the penis to the flaccid state. Androgen signalling is critical for erectile function through its role in penis development and in regulating the physiological processes driving erection in the adult. Interestingly, estrogen signalling is also implicated in penis development and potentially in processes which regulate erectile function during adulthood. Given that endocrine signalling has a prominent role in erectile function, it is likely that exposure to endocrine disrupting chemicals (EDCs) is a risk factor for ED, although this is an under-researched field. Thus, our review provides a detailed description of the underlying biology of erectile function with a focus on the role of endocrine signalling, exploring the potential link between EDCs and ED based on animal and human studies.

Heterogeneity and Dynamics of Vasculature in the Endocrine System During Aging and Disease

The endocrine system consists of several highly vascularized glands that produce and secrete hormones to maintain body homeostasis and regulate a range of bodily functions and processes, including growth, metabolism and development. The dense and highly vascularized capillary network functions as the main transport system for hormones and regulatory factors to enable efficient endocrine function. The specialized capillary types provide the microenvironments to support stem and progenitor cells, by regulating their survival, maintenance and differentiation. Moreover, the vasculature interacts with endocrine cells supporting their endocrine function. However, the structure and niche function of vasculature in endocrine tissues remain poorly understood. Aging and endocrine disorders are associated with vascular perturbations. Understanding the cellular and molecular cues driving the disease, and age-related vascular perturbations hold potential to manage or even treat endocrine disorders and comorbidities associated with aging. This review aims to describe the structure and niche functions of the vasculature in various endocrine glands and define the vascular changes in aging and endocrine disorders.

Testosterone Therapy After Prostate Cancer Treatment: A Review of Literature

INTRODUCTION

Although testosterone therapy (TTh) is the standard practice in otherwise healthy hypogonadal men, this therapy has historically been contraindicated in men with a history of prostate cancer. Recent evidence suggests that there is minimal or no prostate cancer growth in the setting of TTh administration in men definitively treated for non-metastatic prostate cancer.

OBJECTIVE

To review the evidence supporting the safety and efficacy of TTh in patients previously treated for localized prostate cancer.

METHODS

A literature review of the PubMed database was performed to identify studies evaluating the safety and efficacy of TTh in patients with a history of prostate cancer. Search terms included Testosterone Therapy, Testosterone Replacement Therapy and Radical Prostatectomy, Radiotherapy, External Beam Radiation Therapy, EBRT, Brachytherapy; Prostate Cancer and Hypogonadism, Low Testosterone; Bipolar Androgen Therapy.

RESULTS

Available literature provides evidence for the safe application of TTh in patients previously treated for prostate cancer with either radical prostatectomy or radiotherapy. Furthermore, there exists evidence that severely hypogonadal levels of testosterone may lead to worse oncological outcomes. More recent research has begun to elucidate the effectiveness of bipolar androgen deprivation therapy in the treatment of prostate cancer. This mechanism of action increases the level of evidence indicating that the traditional management of maintaining testosterone levels at low levels may no longer be standard of care. TTh likely has a role in improved erectile function and other quality-of-life concerns in patients developing testosterone deficiency after being treated for prostate cancer.

CONCLUSIONS

TTh should be offered to select hypogonadal patients who have a history of definitively treated prostate cancer. Adequately designed randomized controlled trials are necessary to confirm the safety and efficacy of TTh in this population. Natale C, Carlos C, Hong J, et al. Testosterone Replacement Therapy After Prostate Cancer Treatment: A Review of Literature. Sex Med Rev 2021;9:393-405.

Constitutive LH receptor activity impairs NO-mediated penile smooth muscle relaxation

Timely activation of the luteinizing hormone receptor (LHCGR) is critical for fertility. Activating mutations in LHCGR cause familial male-limited precocious puberty (FMPP) due to premature synthesis of testosterone. A mouse model of FMPP (KiLHRD582G), expressing a constitutively activating mutation in LHCGR, was previously developed in our laboratory. KiLHRD582G mice became progressively infertile due to sexual dysfunction and exhibited smooth muscle loss and chondrocyte accumulation in the penis. In this study, we tested the hypothesis that KiLHRD582G mice had erectile dysfunction due to impaired smooth muscle function. Apomorphine-induced erection studies determined that KiLHRD582G mice had erectile dysfunction. Penile smooth muscle and endothelial function were assessed using penile cavernosal strips. Penile endothelial cell content was not changed in KiLHRD582G mice. The maximal relaxation response to acetylcholine and the nitric oxide donor, sodium nitroprusside, was significantly reduced in KiLHRD582G mice indicating an impairment in the nitric oxide (NO)-mediated signaling. Cyclic GMP (cGMP) levels were significantly reduced in KiLHRD582G mice in response to acetylcholine, sodium nitroprusside and the soluble guanylate cyclase stimulator, BAY 41-2272. Expression of NOS1, NOS3 and PKRG1 were unchanged. The Rho-kinase signaling pathway for smooth muscle contraction was not altered. Together, these data indicate that KiLHRD582G mice have erectile dysfunction due to impaired NO-mediated activation of soluble guanylate cyclase resulting in decreased levels of cGMP and penile smooth muscle relaxation. These studies in the KiLHRD582G mice demonstrate that activating mutations in the mouse LHCGR cause erectile dysfunction due to impairment of the NO-mediated signaling pathway in the penile smooth muscle.

Low androgen status inhibits erectile function by inducing eNOS uncoupling in rat corpus cavernosum

BACKGROUND

The number of erectile dysfunction (ED) patients is increasing annually. How to improve the effectiveness of ED treatment is an important issue for the field of andrology.

OBJECTIVES

To investigate whether low androgen status impairs the erectile function of rats by regulated endothelial nitric oxide synthase (eNOS) uncoupling.

MATERIALS AND METHODS

Thirty-six 8-week-old male Sprague Dawley (SD) rats were randomly divided into six groups as follows: 4-week sham-operated group (4w-sham), 4-week castration group (4w-cast), 4-week castration + testosterone (T) group (4w-cast + T), 8-week sham-operated group (8w-sham), 8-week castration group (8w-cast), and 8-week castration + T group (8w-cast + T). Three mg/kg of T was subcutaneously injected every other day in castration + T groups. The ratio of the maximum intracavernous pressure/the mean arterial pressure (ICPmax/MAP), the level of serum T, dihydrobiopterin(BH2 ), tetrahydrobiopterin (BH4 ), nitric oxygen(NO), 3-nitrotyrosine(3NT), dihydrofolate reductase (DHFR), guanosine triphosphate cyclohydrolase 1 (GTPCH1), nicotinamide adenine dinucleotide phosphate oxidase 2 (NOX2), and eNOS monomers/dimers in the corpus cavernosum were detected.

RESULTS

The ratio of ICPmax/MAP and BH4 /BH2 , the level of serum T, NO, and GTPCH1 decreased significantly in castration groups compared with sham-operated groups and castration + T groups (P < .05) and decreased significantly in 8w-cast group compared with 4w-cast group (P < .05). The expression of 3NT and NOX2 and the ratio of eNOS monomers/dimers increased significantly in castration groups compared with sham-operated groups and castration + T groups (P < .01) and increased significantly in 8w-cast group compared with 4w-cast group (P < .01). The expression of DHFR in 4w-cast group was significantly higher than that in 4w-sham group and 4w-cast + T group (P < .01) and in 8w-cast group was significantly lower than that in 8w-sham group and 8w-cast + T group (P < .01).

DISCUSSION AND CONCLUSION

Low androgen status induces eNOS uncoupling by reducing BH4 /BH2 and increasing 3NT. Due to the decreased NO production, the erectile function of the rats was impaired.

The Role of Testosterone in Amplifying the Effect of a Phosphodiesterase Type 5 Inhibitor After Pelvic Irradiation

BACKGROUND

After radiotherapy, the risk of hypogonadism increases, and the incidence of erectile dysfunction increases with time.

AIM

We investigated the effect of testosterone and a phosphodiesterase type 5 inhibitor (PDE5I) on erectile tissue after radiotherapy.

METHODS

12 male Wistar rats were assigned to each of 5 groups (group C: control; group R: radiation; group RPT: radiation, testosterone, and a PDE5I; group RP: radiation and a PDE5I; and group RT: radiation and testosterone). A 12.5 Gy/fraction dose was administered to the rectum in groups R, RPT, RP, and RT. Udenafil (20 mg/kg) was administered daily via nasogastric tubes in group RPT and group RP for 4 weeks starting 1 day after radiotherapy. Testosterone enanthate (25 mg/kg, IM) was administered immediately after radiotherapy in group RT and group RPT. 6 rats from each group were used to evaluate endothelial nitric oxide synthase (eNOS), neuronal nitric oxide synthase (nNOS), and NOX2, and cavernosal pressure was evaluated in the other 6 rats in each group.

OUTCOME

Testosterone enhanced the effect of PDE5I on penile tissue after radiotherapy by amplifying the nitric oxide synthase activity.

RESULTS

eNOS mRNA expression increased in response to either testosterone replacement or PDE5I administration after radiotherapy. nNOS mRNA expression did not significantly increase in response to testosterone replacement, but testosterone significantly enhanced the effect of PDE5I on nNOS mRNA expression. Testosterone significantly amplified the effect of PDE5I on both eNOS and nNOS protein expression. Both testosterone and PDE5I reduced NOX2 protein expression. The intracavernosal pressure during electrical stimulation showed that testosterone alone did not significantly enhance erectile function.

CLINICAL TRANSLATION

Clinicians should consider both hypoxic tissue damage and hypogonadism during and after radiation, and the combination of testosterone and PDE5I could be more beneficial for preserving erectile tissue than either individual treatment.

STRENGTHS & LIMITATIONS

This study describes the role of testosterone in amplifying the effect of a PDE5I on pelvic radiotherapy-induced hypogonadism. However, we did not show the time-dependent effects of testosterone and PDE5I.

CONCLUSIONS

Despite the fact that the intracavernosal pressure during electrical stimulation did not significantly increase with testosterone replacement after radiotherapy, important changes in nitric oxide synthase activity and superoxide regulation might have amplifying effects on erectile tissue. Therefore, we recommend that physicians monitor testosterone levels and should not hesitate to combine testosterone and PDE5I in cases of radiation-induced hypogonadism if testosterone replacement is not contraindicated. Lee DS, Sohn DW. The Role of Testosterone in Amplifying the Effect of a Phosphodiesterase Type 5 Inhibitor After Pelvic Irradiation. J Sex Med 2020;17:1268-1279.

Hormone-dependent medial preoptic/lumbar spinal cord/autonomic coordination supporting male sexual behaviors

Testosterone (T) can act directly through neural androgen receptors (AR) to facilitate male sexual behavior; however, T's metabolites also can play complicated and interesting roles in the control of mating. One metabolite, dihydrotestosterone (DHT) binds to AR with significantly greater affinity than that of T. Is that important behaviorally? Another metabolite, estradiol (E), offers a potential alternative route of facilitating male mating behavior by acting through estradiol receptors (ER). In this review we explore the roles and relative importance of T as well as E and DHT at various levels of the neuroaxis for the activation of male sex behavior in common laboratory animals and, when relevant research findings are available, in man.

Testosterone replacement in transgenic sickle cell mice controls priapic activity and upregulates PDE5 expression and eNOS activity in the penis

Sickle cell disease (SCD)-associated priapism is characterized by decreased nitric oxide (NO) signaling and downregulated phosphodiesterase (PDE)5 protein expression and activity in the penis. Priapism is also associated with testosterone deficiency, but molecular mechanisms underlying testosterone effects in the penis in SCD are not known. Given the critical role of androgens in erection physiology and NO synthase (NOS)/PDE5 expression, we hypothesized that testosterone replacement to eugonadal testosterone levels reduces priapism by reversing impaired endothelial (e)NOS activity and molecular abnormalities involving PDE5. Adult male transgenic Berkeley sickle cell (Sickle) and wild-type (WT) mice were implanted with testosterone pellets, which release 1.2 μg testosterone/day for 21 days, or vehicle. After 21 days, animals underwent erectile function assessment followed by collection of blood for serum testosterone measurements, penes for molecular analysis, and seminal vesicles as testosterone-responsive tissue. Serum testosterone levels were measured by radioimmunoassay; protein expressions of PDE5, α-smooth muscle actin, eNOS and nNOS, and phosphorylation of PDE5 at Ser-92, eNOS at Ser-1177, neuronal (n) NOS at Ser-1412, and Akt at Ser-473 were measured by Western blot in penile tissue. Testosterone treatment reversed downregulated serum testosterone levels and increased (p < 0.05) the weight of seminal vesicles in Sickle mice to levels comparable to that of WT mice, indicating restored testosterone levels in Sickle mice. Testosterone treatment reduced (p < 0.05) prolonged detumescence in Sickle mice and normalized downregulated P-PDE5 (Ser-92), PDE5, P-eNOS (Ser-1177), and P-Akt (Ser-473) protein expressions in the Sickle mouse penis. Testosterone treatment did not affect P-nNOS (Ser-1412), eNOS, nNOS, or α-smooth muscle actin protein expressions in the Sickle mouse penis. In conclusion, in the mouse model of human SCD, increasing testosterone to eugonadal levels reduced priapic activity and reversed impaired Akt/eNOS activity and PDE5 protein expression in the penis.

Translational Perspective on the Role of Testosterone in Sexual Function and Dysfunction

INTRODUCTION

The biological importance of testosterone is generally accepted by the medical community; however, controversy focuses on its relevance to sexual function and the sexual response, and our understanding of the extent of its role in this area is evolving.

AIM

To provide scientific evidence examining the role of testosterone at the cellular and molecular levels as it pertains to normal erectile physiology and the development of erectile dysfunction and to assist in guiding successful therapeutic interventions for androgen-dependent sexual dysfunction.

METHODS

In this White Paper, the Basic Science Committee of the Sexual Medicine Society of North America assessed the current basic science literature examining the role of testosterone in sexual function and dysfunction.

RESULTS

Testosterone plays an important role in sexual function through multiple processes: physiologic (stimulates activity of nitric oxide synthase), developmental (establishes and maintains the structural and functional integrity of the penis), neural (development, maintenance, function, and plasticity of the cavernous nerve and pelvic ganglia), therapeutically for dysfunctional regulation (beneficial effect on aging, diabetes, and prostatectomy), and phosphodiesterase type 5 inhibition (testosterone supplement to counteract phosphodiesterase type 5 inhibitor resistance).

CONCLUSION

Despite controversies concerning testosterone with regard to sexual function, basic science studies provide incontrovertible evidence for a significant role of testosterone in sexual function and suggest that properly administered testosterone therapy is potentially advantageous for treating male sexual dysfunction.

Comparison of the Effects of Elaeagnus angustifolia Flower Capsule and Sildenafil Citrate Tablet on Anxiety Resulting From Sexual Dysfunction in Women Referring to the Selected Clinics of Shiraz University of Medical Sciences

Dissatisfaction from sexual relationships can result in deprivation as well as problems, such as depression, anxiety, and destruction of family’s mental health. One hundred twenty-five women (18 to 40 years) who suffered from hypoactive sexual desire disorder were divided into Elaeagnus angustifolia flower (4.5 g g daily for 35 days), sildenafil citrate tablet (50 mg for 4 weeks), and control groups. The study data were collected using the Female Sexual Function Index and Spielberger’s questionnaire and measurement of thyroid-stimulating hormone and prolactin hormone. In the Elaeagnus angustifolia group, the mean score of state and trait anxiety decreased after the intervention. In the sildenafil citrate group also, the mean score of state anxiety decreased from 22.15 ± 4.98 to 20.1 ± 5.15 ( P = .001) and that of trait anxiety decreased from 23.07 ± 4.44 to 21.55 ± 4.82 ( P = .002) after the intervention. Consumption of sildenafil citrate tablet was effective in reduction of the mean score of anxiety resulting from sexual dysfunction.

Role of androgens in modulating male and female sexual function

Advancement in basic and clinical research has provided considerable evidence suggesting a key role of androgens in the physiology and pathophysiology of sexual function. Evidence from clinical studies in men and women with androgen deficiency support a role of androgens in maintaining sexual function in men and women and are integral in maintaining sexual health. Preclinical studies utilizing male animal models demonstrated a role of androgens in maintenance of: (i) penile tissue structural integrity, (ii) penile trabecular smooth muscle growth and function, (iii) integrity of penile nerve fiber network, (iv) signaling pathways in the corpora cavernosa, (v) myogenic and adipogenic differentiation in the corpora cavernosa, (vi) physiological penile response to stimuli, and (vii) facilitating corporeal hemodynamics. These findings strongly suggest a role for androgen in the physiology of penile erection. In addition, clinical studies in hypogonadal men with erectile dysfunction treated with testosterone provided invaluable information on restoring erectile function and improving ejaculatory function. Similarly, clinical studies in surgically or naturally postmenopausal women with androgen deficiency suggested that androgens are important for maintaining sexual desire and testosterone treatment was shown to improve sexual desire, arousal and orgasm. Furthermore, studies in female animal models demonstrated that androgens maintain the integrity of vaginal nerve fiber network, muscularis volume, and enhance genital blood flow and mucification. Based on the biochemical, physiological and clinical findings from human and animal studies, we suggest that androgens are integral for maintaining sexual function and play a critical role in maintaining sexual health in men and women.

Erectogenic and Aphrodisiac Effects of Butea frondosa Koenig ex Roxb. in Rats: Involvement of Enzyme Inhibition

Butea frondosa Koenig ex Roxb. (BF) is traditionally used to manage male sexual disorders including erectile dysfunction (ED). Methanol extract of BF (bark) inhibited Rho-kinase 2 (ROCK-II) enzyme activity in vitro with an IC₅₀ of 20.29 ± 1.83 μg/mL. The relaxant effect of methanol extract of BF (MEBF) was studied on phenylephrine precontracted corpus cavernosum smooth muscle (CCSM) isolated from young rats. The effect of MEBF treatment on sexual behaviour of both young (5 month) and aged (24 month) rats was also studied in addition to the influence on smooth muscle, collagen (collagen-I and -III) level in penis, and sperm characteristics of young and aged rats. MEBF relaxed CCSM up to 21.77 ± 2.57% and increased sexual behavior of young and aged rats. This increase in sexual function could be attributed to ROCK-II inhibition and increase in ratio of smooth muscle to collagen level in rat penile tissue. Increased sperm production and decreased defective sperms in young and aged rats corroborate the usefulness of Butea frondosa in male infertility in addition to ED.

Androgen depletion in humans leads to cavernous tissue reorganization and upregulation of Sirt1-eNOS axis

Aging and physiological androgen decay leads to structural changes in corpus cavernosum (CC) that associate with erectile function impairment. There is evidence that such changes relate to nitric oxide (NO) bioavailability, an endothelial compound produced by the action of endothelial NO synthase (eNOS), and is regulated by sirtuin-1 (Sirt1), a NAD(+)-dependent protein deacetylase. Taking into account the reduced NO synthesis observed in aging and erectile dysfunction, we aimed to characterize human CC of androgen-deprived, young, and aged individuals postulating that androgen deprivation induces modifications similar to those observed in aging. Human penile fragments were collected from young individuals submitted to male-to-female sex reassignment procedure, who undergone an androgen deprivation chemical regimen, from young organ donors and from aged patients submitted to penile deviation surgery. They were processed for histomorphometric analysis of smooth muscle (SM) and connective tissues (CT), and dual-immunofluorescence of alpha-actin/vWf or Sirt1, and endothelin-1/eNOS. Estrogen receptors were analyzed by immunohistochemistry and semiquantification of Sirt1, eNOS, and phospho-Akt was assayed by Western blotting. Androgen withdrawal, similarly to aging, leads to a noteworthy reduction of SM-to-CT ratio in CC. However, in contrast to young and aged, a significant increase in penile Sirt1 expression accompanied by an increase in total eNOS expression was observed in androgen-depleted individuals. No changes were evidenced in phospho-Akt system and estrogen receptors were undetectable. These findings indicate that Sirt1 regulates the expression of eNOS in human CC employing mechanisms influenced by androgen depletion.

Atorvastatin improves erectile dysfunction in patients initially irresponsive to Sildenafil by the activation of endothelial nitric oxide synthase

This study aimed at comparing the effects of atorvastatin and vitamin E on erectile dysfunction in patients initially irresponsive to sildenafil, with investigation into the underlying possible mechanisms. Sixty patients were randomly divided into three groups: the atorvastatin group received 80 mg daily, the vitamin E group received 400 IU daily and the control group received placebo capsules. Patients were examined both before and after 6 weeks of treatment for biochemical tests; Superoxide dismutase (SOD), glutathione peroxidase (GPO), C-reactive protein (CRP), interleukin-6 (IL-6), nitric oxide (NO) and endothelial nitric oxide synthase (eNOS) and for erectile function tests; International index of erectile function (IIEF-5) scores and Rigiscan. Both atorvastatin and vitamin E showed a statistically significant GPO increase (P<0.05) and a statistically significant IL-6 decrease (P<0.05). Only atorvastatin showed a statistically significant increase in NO (15.19%, P<0.05), eNOS (20.58%, P<0.01), IIEF-5 score (53.1%, P<0.001) and Rigiscan rigidity parameters (P<0.01), in addition to a statistically significant decrease in CRP (57.9%, P<0.01). However, SOD showed a statistically significant increase only after vitamin E intake (23.1%, P<0.05). Both atorvatstain and vitamin E had antioxidant and anti-inflammatory activities. Although activating eNOS by atorvastatin was the real difference, and expected to be the main mechanism for NO increase and for improving erectile dysfunction. Atorvastatin, but not vitamin E, is a promising drug for sildenafil nonresponders.

Impact of androgen deprivation therapy on sexual function

Many patients with prostate cancer for whom androgen deprivation therapy (ADT) is indicated are young and desire to remain sexually active. In such patients, the side effects of androgen therapy on sexual function can be a source of serious reduction in overall quality of life. Providing the appropriate treatment options in this patient population is therefore essential. Nevertheless, treating such patients is challenging and an understanding of the underlying mechanisms of sexual physiology and pathophysiology is crucial to optimal patient care. In this paper, we reviewed what was known regarding the effects of ADT on sexual function in animal models and we also provided a detailed review on the effects of ADT on sexual health in humans and its treatment.

Connecting the Lines between Hypogonadism and Atherosclerosis

Epidemiological studies show that atherosclerotic cardiovascular disease is a leading cause of morbidity and mortality worldwide and point to gender differences with ageing males being at highest risk. Atherosclerosis is a complex process that has several risk factors and mediators. Hypogonadism is a commonly undiagnosed disease that has been associated with many of the events, and risk factors leading to atherosclerosis. The mechanistic relations between testosterone levels, atherosclerotic events, and risk factors are poorly understood in many instances, but the links are clear. In this paper, we summarize the research journey that explains the link between hypogonadism, each of the atherosclerotic events, and risk factors. We look into the different areas from which lessons could be learned, including epidemiological studies, animal and laboratory experiments, studies on androgen deprivation therapy patients, and studies on testosterone-treated patients. We finish by providing recommendations for the clinician and needs for future research.

Emerging concepts in erectile preservation following radical prostatectomy: a guide for clinicians

Radical prostatectomy (RP) is a commonly performed procedure for the management of prostate cancer. While documented oncologic outcome for early stage disease is excellent, functional impairments such as incontinence and erectile dysfunction (ED) are common after the procedure. Recent evidence has implicated cavernous nerve damage and subsequent corporal oxygen deprivation, as well as corporal inflammation, in the pathogenesis of post-RP ED. Targeted therapies such as oral phosphodiesterase-5 inhibitors, mechanical vacuum erection devices, local alprostadil delivery and testosterone replacement (for hypogonal patients) have demonstrated some efficacy in the management of post-RP ED. This review aggregates much of the recent data in support of these therapies and critically reviews them. The article then presents tools to assess patients and partner sexual function to aid in identifying and monitoring post-RP ED. Finally, the article describes a protocol in use at Baylor College of Medicine as a guide toward the development of a protocol for erectile preservation (EP). The purpose of this work is to educate clinicians on emerging concepts in EP and provide an implementable protocol for use in practice.

Hypoactive Sexual Desire Disorder and Current Pharmacotherapeutic Options in Women

Hypoactive Sexual Desire Disorder (HSDD) is the most common female sexual dysfunction. The diagnosis of HSDD requires the existence of personal distress or interpersonal difficulties associated with low sexual desire, that cannot be explained by any other psychiatric affection and that is not exclusively due to a disease or substance. HSDD can have a serious effect on emotional wellbeing and interpersonal relationships, and it occurs in premenopausal and postmenopausal women. The Decreased Sexual Desire Screener is a shortened diagnostic method designed to help doctors who are not specialized in female sexual dysfunction to diagnose acquired HSDD in women. There is evidence that treatment with androgens or with estrogens is effective in HSDD; however, important unanswered questions still exist. Presently, new therapeutic strategies to combat HSDD are being researched, including novel methods of testosterone provision and drugs that act upon the CNS.

The impact of irritative lower urinary tract symptoms on erectile dysfunction in aging Taiwanese males

OBJECTIVE

This study assessed the possible associations between lower urinary tract symptoms (LUTS) and erectile dysfunction (ED) in aging Taiwanese males and investigated the impact of various aspects of LUTS on ED.

METHODS

A free health screening for aging males (> or =40 years old) was conducted in Kaohsiung Medical University Hospital. All the subjects had completed clinical data and answered questionnaires. ED and LUTS were assessed by validated symptom scales: the International Index of Erectile Function-5 (IIEF-5) and the International Prostate Symptom Score (IPSS).

RESULTS

A total of 339 eligible patients enrolled in this study with a mean age of 60.1 years old. In multiple logistic regression analysis, age and IPSS (p < 0.001 and p = 0.013, respectively) were significantly associated with ED after controlling other comorbidities. In a further age-adjusted multiple regression analysis, our results showed that irritative symptoms (p = 0.042) have a more significant association with ED than the obstructive symptoms (p = 0.101).

CONCLUSIONS

Our results indicate that age and LUTS are the two most independent risk factors for ED. Aging Taiwanese males with LUTS are at increasing risk for ED, especially for those with significant irritative symptoms.

Female sexual dysfunction

Sexual dysfunctions diminish the quality of life for many women, frequently causing enough distress to warrant the diagnosis of a sexual disorder. Problems with sexual function can occur in any stage of the sexual response cycle. Dysfunction is further influenced by a variety of factors: medical, psychiatric, cultural, and stage of life. A variety of treatment modalities exist, though current research has not yet provided Food and Drug Administration-approved therapies for sexual disorders in women.

Molecular Yin and Yang of erectile function and dysfunction

In regard to erectile function, Yin is flaccidity and Yang erection. In the past decade, research has mostly focused on the Yang aspect of erectile function. However, in recent years, the Yin side is attracting increasingly greater attention. This is due to the realization that penile flaccidity is no less important than penile erection and is actively maintained by mechanisms that play critical roles in certain types of erectile dysfunction (ED); for example, in diabetic patients. In addition, there is evidence that the Yin and Yang signaling pathways interact with each other during the transition from flaccidity to erection, and vice versa. As such, it is important that we view erectile function from not only the Yang but also the Yin side. The purpose of this article is to review recent advances in the understanding of the molecular mechanisms that regulate the Yin and Yang of the penis. Emphasis is given to the Rho kinase signaling pathway that regulates the Yin, and to the cyclic nucleotide signaling pathway that regulates the Yang. Discussion is organized in such a way so as to follow the signaling cascade, that is, beginning with the extracellular signaling molecules (e.g., norepinephrin and nitric oxide) and their receptors, converging onto the intracellular effectors (e.g., Rho kinase and protein kinase G), branching into secondary effectors, and finishing with contractile molecules and phosphodiesterases. Interactions between the Yin and Yang signaling pathways are discussed as well.

Risk of erectile dysfunction induced by arsenic exposure through well water consumption in Taiwan

BACKGROUND

Erectile dysfunction (ED) has a profound impact on the quality of life of many men. Many risk factors are associated with ED, such as aging, sex hormone levels, hypertension, cardiovascular diseases, and diabetes mellitus. Arsenic exposure could damage peripheral vessels and increase the risk of cardiovascular disease. However, the relationship between arsenic exposure and ED has seldom been evaluated.

OBJECTIVES

In this study we aimed to investigate whether exposure to arsenic enhances the risk of ED.

METHODS

We recruited 177 males >or= 50 years of age through health examinations conducted in three hospitals in Taiwan. We used a questionnaire (International Index of Erectile Function-5) to measure the level of erectile function. Sex hormones, including total testosterone and sex hormone-binding globulin, were determined by radioimmunoassay. We used another standardized questionnaire to collect background and behavioral information (e.g., cigarette smoking; alcohol, tea, or coffee drinking; and physical activity).

RESULTS

The prevalence of ED was greater in the arsenic-endemic area (83.3%) than in the non-arsenic-endemic area (66.7%). Subjects with arsenic exposure > 50 ppb had a significantly higher risk of developing ED than those with exposure <or= 50 ppb, after adjusting for age, cigarette smoking, diabetes mellitus, hypertension, and cardiovascular disease [odds ratio (OR) = 3.4]. Results also showed that the risk of developing severe ED was drastically enhanced by arsenic exposure (OR = 7.5), after adjusting for free testosterone and traditional risk factors of ED.

CONCLUSIONS

Results suggested that chronic arsenic exposure has a negative impact on erectile function.

The associations among eNOS G894T gene polymorphism, erectile dysfunction and related risk factors

OBJECTIVE

To investigate the possible correlations among eNOS G894T polymorphism, erectile dysfunction (ED) and related risk factors in a Taiwanese population.

MATERIALS AND METHODS

In all, 151 patients with ED and 77 healthy controls were enrolled. All the men had a complete clinical history taken and laboratory data was collected. To assess erectile conditions the five-item version of the International Index of Erectile Function (IIEF-5) was used. The eNOS G894T polymorphisms were determined using the polymerase chain reaction-restriction fragment length polymorphism method.

RESULTS

In all, 228 men were enrolled with a mean (sd) age of 58.6 (9.7) years. In a univariate analysis, age, serum testosterone level, and the prevalence of diabetes mellitus (DM) and hypertension were significantly different between patients with ED and the healthy controls (P < 0.01). In the multiple logistic regression analysis, DM, age and hypogonadism were three independent risk factors for ED (P = 0.018, P = 0.046 and P = 0.016, respectively). The prevalence of ED in T allele carriers (GT/TT) was significantly greater than in G allele carriers (GG; 80.0% vs 63.3%, P = 0.04). Also the eNOS 894T allele carriers had significantly lower IIEF-5 scores than the eNOS 894G allele carriers, at 13.2 (5.3) vs 15.7 (6.1) (P = 0.01) and it was associated with increment of T allele number (11.0 (5.6) vs 13.6 (5.2) vs 15.7 (6.1); P = 0.03).

CONCLUSION

Our results indicate that DM, age and hypoganadism are three significant independent risk factors for ED. Also, in the Taiwanese population, the eNOS 894T allele carriers are at greater risk of ED, both in prevalence and severity, and this might be a factor of genetic susceptibility.

Transforming growth factor-beta1 null mutation causes infertility in male mice associated with testosterone deficiency and sexual dysfunction

TGFbeta1 is a multifunctional cytokine implicated in gonad and secondary sex organ development, steroidogenesis, and spermatogenesis. To determine the physiological requirement for TGFbeta1 in male reproduction, Tgfb1 null mutant mice on a Prkdc(scid) immunodeficient background were studied. TGFbeta1-deficient males did not deposit sperm or induce pseudopregnancy in females, despite an intact reproductive tract with morphologically normal penis, seminal vesicles, and testes. Serum and intratesticular testosterone and serum androstenedione were severely diminished in TGFbeta1-deficient males. Testosterone deficiency was secondary to disrupted pituitary gonadotropin secretion because serum LH and to a lesser extent serum FSH were reduced, and exogenous LH replacement with human chorionic gonadotropin (hCG) induced serum testosterone to control levels. In the majority of TGFbeta1-deficient males, spermatogenesis was normal and sperm were developmentally competent as assessed by in vitro fertilization. Analysis of sexual behavior revealed that although TGFbeta1 null males showed avid interest in females and engaged in mounting activity, intromission was infrequent and brief, and ejaculation was not attained. Administration of testosterone to adult males, even after neonatal androgenization, was ineffective in restoring sexual function; however, erectile reflexes and ejaculation could be induced by electrical stimulation. These studies demonstrate the profound effect of genetic deficiency in TGFbeta1 on male fertility, implicating this cytokine in essential roles in the hypothalamic-pituitary-gonadal axis and in testosterone-independent regulation of mating competence.

Androgen Deficiency and Abnormal Penile Duplex Parameters in Obese Men with Erectile Dysfunction

INTRODUCTION

The clinical identification of metabolic syndrome is based on measures of abdominal obesity, atherogenic dyslipidemia, elevated blood pressure, and glucose intolerance. However, the impact of hypogonadism associated with obesity on penile hemodynamics is not well investigated.

AIM

In this retrospective study, we sought to evaluate the effect of obesity on serum total testosterone (TT) level and penile duplex parameters in men with erectile dysfunction (ED).

METHODS

Our participants (N = 158) were evaluated for erectile function using an abridged, five-item version of the International Index of Erectile Function-5. Determination of body mass index (BMI) was performed. Measurements of TT, fasting lipid profile, and blood sugar were conducted. Penile hemodynamics was assessed using intracavernosal injection and penile duplex study.

MAIN OUTCOME MEASURES

Bivariate associations among BMI and serum testosterone, blood pressure, and lipid profile, as well as penile duplex parameters. We compared all clinical, laboratory, and penile duplex parameters between lean men (BMI < 25) and overweight and obese men (BMI >or= 25).

RESULTS

The participants' age ranged between 20 and 56 years. A significant negative correlation between BMI and TT was detected (r = -0.431, P = 0.0001). Hypogonadism was identified in 54/158 (34.2%) of men with ED. The incidence of hypogonadism varied from as low as 1/18 (5.6%) in lean men to as high as 18/36 (50%) to 21/35 (60%) in morbid and severe obesity, respectively. Vasculogenic ED was detected in 32/54 (59.3%) men with BMI >or= 25, compared with 5/18 (27.8%) in lean men (P = 0.029). In order to study the effect of obesity on erectile function, cases with other risk factors were excluded. Of 67 men suffering from ED with no other risk factor(s) apart from obesity, vasculogenic ED was detected in 32/54 (59.3%) men with BMI >or= 25, compared with 3/13 (23.1%) in lean men (P = 0.029).

CONCLUSION

Obesity is associated with lower TT and disturbances of penile hemodynamics. It is an independent clinical factor for vasculogenic ED.