Advanced glycation end products in human penis: elevation in diabetic tissue, site of deposition, and possible effect through iNOS or eNOS

Sexual Dysfunction in Diabetic Patients: Τhe Role of Advanced Glycation End Products

Sexual dysfunction is a common but underestimated disorder of diabetic patients of both genders, entailing specific and complex pathogenesis and severely affecting reproductive health and quality of life. Hyperglycemia, dyslipidemia, hypertension, obesity, aging, and psychological factors underlie its pathogenesis. A large body of evidence indicates that advanced glycation end products and oxidative stress have a distinct impact on the pathogenesis of diabetes and its complications, including hypogonadism, which is closely related to sexual dysfunction. Advanced glycation end products seem to affect sexual function either directly by accumulation in various regions of the reproductive system and/or correlation or indirectly through oxidative stress induction via several mechanisms. They are also involved in the pathogenesis of diabetic complications, which are related to sexual dysfunction. Herein, we review the issue of sexual dysfunction in diabetic males and females, with special emphasis on the impact of advanced glycation end products in the pathogenesis of sexual dysfunction, the relationship of advanced glycation end products with low testosterone levels in diabetic subjects, which account for the proportion of disorder and the available therapeutic interventions.

The effect of a-Lipoic acid (ALA) on oxidative stress, inflammation, and apoptosis in high glucose-induced human corneal epithelial cells

PURPOSE

Oxidative stress and inflammation had been proved to play important role in the progression of diabetic keratopathy (DK). The excessive accumulation of AGEs and their bond to AGE receptor (RAGE) in corneas that cause the formation of oxygen radicals and the release of inflammatory cytokines, induce cell apoptosis. Our current study was aimed to evaluate the effect of ALA on AGEs accumulation as well as to study the molecular mechanism of ALA against AGE-RAGE axis mediated oxidative stress, apoptosis, and inflammation in HG-induced HCECs, so as to provide cytological basis for the treatment of DK.

METHODS

HCECs were cultured in a variety concentration of glucose medium (5.5, 10, 25, 30, 40, and 50 mM) for 48 h. The cell proliferation was evaluated by CCK-8 assay. Apoptosis was investigated with the Annexin V- fluorescein isothiocyanate (V-FITC)/PI kit, while, the apoptotic cells were determined by flow cytometer and TUNEL cells apoptosis Kit. According to the results of cell proliferation and cell apoptosis, 25 mM glucose medium was used in the following HG experiment. The effect of ALA on HG-induced HCECs was evaluated. The HCECs were treated with 5.5 mM glucose (normal glucose group, NG group), 5.5 mM glucose + 22.5 mM mannitol (osmotic pressure control group, OP group), 25 mM glucose (high glucose group, HG group) and 25 mM glucose + ALA (HG + ALA group) for 24 and 48 h. The accumulation of intracellular AGEs was detected by ELISA kit. The RAGE, catalase (CAT), superoxide dismutase 2 (SOD2), cleaved cysteine-aspartic acid protease-3 (Cleaved caspase-3), Toll-like receptors 4 (TLR4), Nod-like receptor protein 3 (NLRP3) inflammasome, interleukin 1 beta (IL-1 ß), and interleukin 18 (IL-18) were quantified by RT-PCR, Western blotting, and Immunofluorescence, respectively. Reactive oxygen species (ROS) production was evaluated by fluorescence microscope and fluorescence microplate reader.

RESULTS

When the glucose medium was higher than 25 mM, cell proliferation was significantly inhibited and apoptosis ratio was increased (P < 0.001). In HG environment, ALA treatment alleviated the inhibition of HCECs in a dose-dependent manner, 25 μM ALA was the minimum effective dose. ALA could significantly reduce the intracellular accumulation of AGEs (P < 0.001), activate protein and genes expression of CAT and SOD2 (P < 0.001), and therefore inhibited ROS-induced oxidative stress and cells apoptosis. Besides, ALA could effectively down-regulate the protein and gene level of RAGE, TLR4, NLRP3, IL-1B, IL-18 (P < 0.05), and therefore alleviated AGEs-RAGE-TLR4-NLRP3 pathway-induced inflammation in HG-induced HCECs.

CONCLUSION

Our study indicated that ALA could be a desired treatment for DK due to its potential capacity of reducing accumulation of advanced glycation end products (AGEs) and down-regulating AGE-RAGE axis-mediated oxidative stress, cell apoptosis, and inflammation in high glucose (HG)-induced human corneal epithelial cells (HCECs), which may provide cytological basis for therapeutic targets that are ultimately of clinical benefit.

Association between Advanced Glycation End-Products, Carotenoids, and Severe Erectile Dysfunction

PURPOSE

To investigate the association between skin advanced glycation end-products (AGEs) levels, blood antioxidative vitamin and carotenoid concentrations, and severe erectile dysfunction (ED) in community-dwelling men.

MATERIALS AND METHODS

This cross-sectional study used the 5-Item International Index of Erectile Function to identify 335 community-dwelling men with ED. The accumulation of skin AGEs was assessed noninvasively by measuring skin autofluorescence. Background-adjusted multivariable logistic regression analyses using the inverse probability of treatment weighting method were performed to evaluate the effects of AGEs, vitamins, and carotenoids on severe ED. Moreover, multiple linear regression analyses were performed to assess the association between skin AGEs levels and serum carotenoid concentrations.

RESULTS

The median age of study participants was 57 years. Of the 335 men, 289 (86.3%) and 46 (13.7%) were classified into the mild/moderate and severe ED groups, respectively. Multivariable analyses revealed that skin AGEs levels, blood vitamins C and E, lutein, zeaxanthin, β-cryptoxanthin, α-carotene, β-carotene, total lycopene, and cis-lycopenes concentrations were significantly associated with severe ED, whereas all-trans lycopene concentrations were not. In the multiple linear regression analyses, serum zeaxanthin concentrations were negatively and significantly correlated with skin AGEs levels.

CONCLUSIONS

Higher skin AGEs levels and lower blood antioxidative vitamin and carotenoid concentrations were significantly associated with severe ED. Serum zeaxanthin levels were negatively and significantly correlated with skin AGEs levels, suggesting the possible effects of zeaxanthin on ED by decreasing tissue AGEs levels.

The therapeutic effect of ALT-711 on erectile function in rats treated with high-level AGEs (advanced glycation end products) containing diet

To investigate, if advanced glycation end products (AGEs) are involved in erectile dysfunction (ED) and also ALT-711, a cross-link breaker of AGEs, has the therapeutic potential against the development of ED in rats treated with high concentrated AGEs including food. For this purpose, 30 male Harlan Spraque-Dawley rats randomly were divided into three groups; (1) control rats treated with regular diet, (2) rats treated with high-level of AGE specific diet for 6 months, and (3) rats having AGE-diet treated with ALT-711 for the final 3 months of 6 months of AGE-diet period. Erectile response to cavernosal nerve stimulation (CNS), protein expression of neuronal nitric oxide synthase (nNOS) and levels of AGEs, Malondialdehyde (MDA), cyclic guanosine monophosphate (cGMP) were determined in penile tissues. Erectile responses to CNS and penile nNOS and cGMP content were significantly reduced, while AGEs and MDA were elevated in penises of Group-2. Treatment with ALT-711 reversed ED and depletion of both nNOS and cGMP. Additionally, ALT-711 treatment reduced penile tissue AGEs and MDA expression. In present study: rats without any co-morbidity such as diabetes mellitus (DM) and chronic renal failure (CRF) were treated with high-level AGEs containing food. Our results suggest that ALT-711 may be an interesting and promising approach in the treatment of AGEs-related ED.

Erectile Dysfunction in Individuals with Type 1 Diabetes is Associated with Long-term Metabolic Control and Diabetic Complications: A Cross-Sectional Study

Background  Erectile dysfunction (ED) affects approximately 38% of individuals with type 1 diabetes (T1DM). Skin autofluorescence (AF) reflects skin advanced glycation end product (AGE) deposits and is a marker of long-term glycemia control. Objective  The study investigates the relationship between ED and diabetes control in patients with T1DM. Methods  Adult patients with T1DM visiting the Diabetology Department were cross-sectionally investigated. Medical history, anthropometric features, and laboratory findings were collected. All individuals filled the International Index of Erectile Function (IIEF-5). IIEF-5 total score < 22 represented the presence of ED. AF was measured on the volar aspect of the forearm using AGE Reader. Insulin resistance (IR) was assessed by the estimated glucose disposal rate. Descriptive statistics and multivariate logistic regression analyses were performed. The adjusted covariates were general risk factors of ED. Results  Of a total of n  = 70 patients, n  = 30 (42.9%) suffered from ED. The presence of ED was associated with higher glycated hemoglobin level (OR, 95% CI; 1.62, 1.02-2.60; p  = 0.043), presence of at least one diabetic complication (3.49, 1.10-11.03; p  = 0.03), and skin AF (9.20, 1.60-52.94; p  = 0.01), but not with IR (0.78, 0.57-2.60; p  = 0.12). Skin AF values ≥ 2.2 indicates presence of ED with a sensitivity of 70.0% and a specificity of 77.5%. Area under the curve was equal to 0.72 (95% CI: 0.60-0.85). Conclusions  The presence of ED in individuals with T1DM is associated with HbA1c, the presence of at least one diabetic complication, and skin AF.

Potential Effect of the Circadian Clock on Erectile Dysfunction

The circadian rhythm is an internal timing system, which is generated by circadian clock genes. Because the circadian rhythm regulates numerous cellular, behavioral, and physiological processes, organisms have evolved with intrinsic biological rhythms to adapt the daily environmental changes. A variety of pathological events occur at specific times, while disturbed rhythms can lead to metabolic syndrome, vascular dysfunction, inflammatory disorders, and cancer. Therefore, the circadian clock is considered closely related to various diseases. Recently, accumulated data have shown that the penis is regulated by the circadian clock, while erectile function is impaired by an altered sleep-wake cycle. The circadian rhythm appears to be a novel therapeutic target for preventing and managing erectile dysfunction (ED), although research is still progressing. In this review, we briefly summarize the superficial interactions between the circadian clock and erectile function, while focusing on how disturbed rhythms contribute to risk factors of ED. These risk factors include NO/cGMP pathway, atherosclerosis, diabetes mellitus, lipid abnormalities, testosterone deficiency, as well as dysfunction of endothelial and smooth muscle cells. On the basis of recent findings, we discuss the potential role of the circadian clock for future therapeutic strategies on ED, although further relevant research needs to be performed.

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.

Role of Glucose-Lowering Medications in Erectile Dysfunction

Erectile dysfunction (ED) is a long-term complication of type 2 diabetes (T2D) widely known to affect the quality of life. Several aspects of altered metabolism in individuals with T2D may help to compromise the penile vasculature structure and functions, thus exacerbating the imbalance between smooth muscle contractility and relaxation. Among these, advanced glycation end-products and reactive oxygen species derived from a hyperglycaemic state are known to accelerate endothelial dysfunction by lowering nitric oxide bioavailability, the essential stimulus of relaxation. Although several studies have explained the pathogenetic mechanisms involved in the generation of erectile failure, few studies to date have described the efficacy of glucose-lowering medications in the restoration of normal sexual activity. Herein, we will present current knowledge about the main starters of the pathophysiology of diabetic ED and explore the role of different anti-diabetes therapies in the potential remission of ED, highlighting specific pathways whose activation or inhibition could be fundamental for sexual care in a diabetes setting.

Assessment of the efficacy of α-lipoic acid in treatment of diabetes mellitus patients with erectile dysfunction: A protocol for systematic review and meta-analysis

BACKGROUND

Diabetes mellitus with erectile dysfunction (DMED) is one of the most common causes of disability in diabetic population, and its pathogenesis is related to a variety of factors. Because its pathogenesis is complex and the existing treatment methods have limitations, DMED is difficult to treat in clinical. Recently, some studies have shown that α-lipoic acid (ALA) is associated with DMED, but there is no systematic review and meta-analysis on the relationship between ALA and DMED.

METHODS

We will search each database from the built-in until July 2020. The English literature mainly searches Cochrane Library, PubMed, EMBASE, and Web of Science, while the Chinese literature comes from CNKI, CBM, VIP, and Wangfang database. Simultaneously we will retrieve clinical registration tests and grey literatures. This study only screen the clinical randomized controlled trials (RCTs) about ALA for DMED to assess its efficacy. The 2 researchers worked independently on literature selection, data extraction, and quality assessment. The dichotomous data is represented by relative risk (RR), and the continuous is expressed by mean difference (MD) or standard mean difference (SMD), eventually the data is synthesized using a fixed effect model (FEM) or a random effect model (REM) depending on whether or not heterogeneity exists. Erectile dysfunction (ED) will be diagnosed by the International Index of Erectile Function 5 (IIEF-5) score. Finally, meta-analysis was conducted by RevMan software version 5.3.

RESULTS

This study will synthesize and provide high quality to evaluate the effectiveness of ALA supplementation for the treatment of DMED.

CONCLUSION

This systematic review aims to provide new options for ALA supplementation treatment of DMED in terms of its efficacy and safety.

PROSPERO REGISTRATION NUMBER

INPLASY202070130.

Sexual dysfunction in men with type II diabetes

Background:

Diabetes mellitus (DM) is a chronic disease inducing short-term and long-term complications including sexual dysfunction (SD) which can consequently reduce patients’ quality of life. Given the limited literature on frequency of SD in men experiencing diabetes in northern Iran, the present study was conducted in the city of Sari in Mazandaran Province, with the aim of investigating SD in men with type II diabetes.

Methods:

Using a descriptive cross-sectional research design, a total number of 350 male patients suffering from type II diabetes referring to endocrinology clinics in the city of Sari in. The patients were requested to fill out the demographic questionnaire, depression, anxiety and stress scale-21 items (DASS-21) and the 15-question International Index of Erectile Function (IIEF). The data were analyzed using the IBM SPSS statistics software

Results:

The average period of time in which the patients were facing diabetes was 3.65±5.75 years. The IIEF mean score was equal to 16.98±43.79. Erectile dysfunction (ED) was also evident in 152 patients (62.2%). Moreover, increase in age had significantly decreased the IIEF scores (p<0.001). The chance of being affected with ED among diabetic patients above 50 was 11.21 times as much as those below 50 years of age (odds ratio (OR): 11.21, 95% confidence interval (CI): 6.40-19.62).

Conclusion:

Concerning the high prevalence rate of ED in men suffering from type II diabetes, doctors are required to directly ask them about sexual disorders in follow-up visits. Furthermore, using screening questionnaires can be helpful in identifying this problem.

Association of advanced glycation end-product accumulation with overactive bladder in community-dwelling elderly: A cross-sectional Sukagawa study

Objective

This study aimed to evaluate the influence of advanced glycation end-product (AGE) accumulation on the prevalence and severity of overactive bladder (OAB) in community-dwelling elderly adults.

Methods

We conducted a cross-sectional study involving 269 Japanese community dwellers aged ≥75 years in 2015. AGE accumulation was non-invasively measured via skin autofluorescence (SAF) values using AGE Reader. The primary and secondary outcomes were the presence and severity of OAB evaluated using the Overactive Bladder Symptom Score (OABSS). Individuals with an urgency score of ≥2 and sum score of ≥3 were considered to have OAB. The associations of SAF with the prevalence and severity of OAB were assessed using logistic and linear regression models, respectively, adjusted for clinically important confounders.

Results

The median age of participants was 78 years. Of 269 participants, 110 (40.9%) were men and 75 (27.9%) had OAB. The median SAF was 2.2 arbitrary units (AUs). Increasing median SAF was observed with increasing age. Multivariable analysis revealed that SAF was not associated with either the likelihood of having OAB (odds ratio per AU=0.77, 95% confidence interval: 0.37–1.62) or the natural log-transformed OABSS (β per AU=−0.07, 95% confidence interval: −0.26–0.12).

Conclusions

In this study, AGE accumulation, as assessed by SAF, was not associated with the prevalence and severity of OAB in Japanese community-dwelling elderly people aged ≥75 years.

Supplementary Nitric Oxide Donors and Exercise as Potential Means to Improve Vascular Health in People with Type 1 Diabetes: Yes to NO?

Type 1 diabetes (T1D) is associated with a greater occurrence of cardiovascular pathologies. Vascular dysfunction has been shown at the level of the endothelial layers and failure to maintain a continuous pool of circulating nitric oxide (NO) has been implicated in the progression of poor vascular health. Biochemically, NO can be produced via two distinct yet inter-related pathways that involve an upregulation in the enzymatic activity of nitric oxide synthase (NOS). These pathways can be split into an endogenous oxygen-dependent pathway i.e., the catabolism of the amino acid L-arginine to L-citrulline concurrently yielding NO in the process, and an exogenous oxygen-independent one i.e., the conversion of exogenous inorganic nitrate to nitrite and subsequently NO in a stepwise fashion. Although a body of research has explored the vascular responses to exercise and/or compounds known to stimulate NOS and subsequently NO production, there is little research applying these findings to individuals with T1D, for whom preventative strategies that alleviate or at least temper vascular pathologies are critical foci for long-term risk mitigation. This review addresses the proposed mechanisms responsible for vascular dysfunction, before exploring the potential mechanisms by which exercise, and two supplementary NO donors may provide vascular benefits in T1D.

Decreased expression of pigment epithelium-derived factor within the penile tissues contributes to erectile dysfunction in diabetic rats

Increased production of reactive oxygen species (ROS) and inflammation are major contributors to the development and progression of diabetes-associated erectile dysfunction (DMED). As an endogenous antioxidant and anti-inflammatory factor, the potential implication of pigment epithelium-derived factor (PEDF) in DMED has not been revealed. To assess the potential antioxidant and anti-inflammatory functions of PEDF in DMED, we first demonstrated that PEDF was significantly decreased at the levels of the mRNA and protein in the penis of diabetic rats compared with normal controls. To test the hypothesis that decreased the penile levels of PEDF are associated with oxidative stress and inflammation in DMED, an adenovirus expressing PEDF (Ad-PEDF) or the same titer of control virus (Ad-GFP) was intracavernously administered at 2 weeks after diabetic onset. After 6 weeks of treatment, we found that administration of Ad-PEDF could significantly increase erectile response to cavernosal nerve stimulation in the diabetic rats by restoring the endothelial NO synthase (eNOS), P-eNOS, and neuronal NO synthase (nNOS) protein levels to the standard levels represented in normal rats and by suppressing the levels of tumor necrosis factor-α (TNF-α) and oxidative stress. In conclusion, the present data indicated that the antioxidant and anti-inflammatory potential of PEDF plays important role in restoring erectile function by the inhibition of oxidative stress and TNF-α production.

A meta-analysis on efficacy and tolerability of sildenafil for erectile dysfunction in patients with diabetes mellitus

Erectile dysfunction (ED) is a common complication in patients with diabetes mellitus (DM). Sildenafil, a phosphodiesterase-5 inhibitor, is commonly used in patients with ED. This meta-analysis was planned to determine the strength of evidence to assess the efficacy and tolerability of sildenafil in patients with DM-associated ED. Electronic searches were carried out to identify randomized controlled trials (RCTs) which reported clinical efficacy of sildenafil in patients with DM-associated ED. Data were extracted and methodological quality was assessed. Relative Risk (RR) with 95% confidence intervals (CIs) was estimated for the dichotomous outcomes, and the mean difference with 95% CI was estimated for continuous data. Eight randomized controlled trials (RCTs) involving 1172 patients met with our inclusion criteria. In comparison to placebo, sildenafil significantly improved the overall sexual performance in patients of ED associated with DM with relative risk (RR) of answering “yes” to global efficiency question being 3.99 (95% CI: 2.58–6.18) compared to placebo. The rate of discontinuation due to treatment-related adverse reactions was 2.4% in sildenafil arm with RR of 2.67 (95% CI: 0.74–9.62). Sildenafil is an effective and safe medication for the treatment of ED associated with DM.

Erection-stimulating, anti-diabetic and antioxidant properties of Hunteria umbellata and Cylicodiscus gabunensis water extractable phytochemicals

Background Herbs have been used as an aphrodisiac since ages. This study was designed to investigate the effects of Hunteria umbellata (HU) seeds and Cylicodiscus gabunensis (CG) stem barks aqueous extracts on key enzymes relevant to erectile dysfunction (phosphodiesterase-5 and arginase) and type-2 diabetes (α-amylase and α-glucosidase). Methods In ascertaining the erectogenic and antidiabetic properties of the extracts, the effects of the extracts on activities of some enzymes relevant to erectile dysfunction (arginase and phosphodiesterase-5) and type-2 diabetes (α-amylase and α-glucosidase) were determined. Antioxidant properties of the extracts were assessed through several antioxidant assays (DPPH˙, OH˙). Furthermore, their phenolic constituents were estimated and quantified using HPLC. Results The results revealed that both extracts inhibited α-amylase and α-glucosidase in a concentration-dependent manner. HU showed higher α-amylase (IC50=221.30 µg/mL) and α-glucosidase (IC50=184.35 µg/mL) inhibition than CG. Also, both extracts inhibited phosphodiesterase-5 and arginase in a dose-dependent manner in vitro; nevertheless, HU showed higher inhibition [phosphodiesterase-5 (IC50=539.72 µg/mL); arginase (41.53 µg/mL)] than CG [phosphodiesterase-5 (IC50=611.35 µg/mL); arginase (47.95 µg/mL)]. In addition, the extracts possess antioxidant properties through radical (DPPH and OH) scavenging and metal (Fe2+) chelating abilities. HPLC analysis of phenolic constituents revealed the abundance of gallic acid, chlorogenic acid, caffeic acid, ellagic acid and quercetin. Conclusions The ability of samples' extract to inhibit some of key enzymes relevant to erectile dysfunction and type-2 diabetes could render them cheap, natural and alternative therapy with erectogenic and antidiabetic potentials.

Advanced Glycation End Products and Risks for Chronic Diseases: Intervening Through Lifestyle Modification

Advanced glycation end products (AGEs) are a family of compounds of diverse chemical nature that are the products of nonenzymatic reactions between reducing sugars and proteins, lipids, or nucleic acids. AGEs bind to one or more of their multiple receptors (RAGE) found on a variety of cell types and elicit an array of biologic responses. In this review, we have summarized the data on the nature of AGEs and issues associated with their measurements, their receptors, and changes in their expression under different physiologic and disease states. Last, we have used this information to prescribe lifestyle choices to modulate AGE-RAGE cycle for better health.

Skin autofluorescence (a marker for advanced glycation end products) and erectile dysfunction in diabetes

AIM

Although diabetes-related erectile dysfunction (ED) has many etiological factors, little is known about the putative pathophysiological role of advanced glycation end products (AGEs). Skin autofluorescence is a noninvasive marker of AGEs. Recent studies have evidenced a relationship between skin autofluorescence and several complications of diabetes. We hypothesized that AGEs (assessed by skin autofluorescence) are associated with ED in diabetes patients.

METHODS

Between March 2014 and April 2015, 42 patients with type 1 diabetes (T1D) and 44 patients with type 2 diabetes (T2D) were consecutively enrolled in a descriptive, cross-sectional study and compared to 54 healthy controls. ED was evaluated via the 5-item version of the International Index of Erectile Function (IIEF-5). Skin autofluorescence was measured on the volar aspect of the arm with an AGE-Reader.

RESULTS

Patients with diabetes had a mean±standard deviation age of 50±15 and a mean duration of diabetes of 16±12years. Skin autofluorescence was strongly and significantly correlated with the IIEF-5 score in the T1D subgroup (r=-0.52; P=0.004), the T2D subgroup (r=-0.32; P<0.03) and in the whole group of diabetic patients (r=-0.49; P<0.0001). In multivariate analyses that controlled for potentially confounding clinical and biochemical factors, only skin autofluorescence was still significantly correlated with the IIEF-5 score (P<0.0001). A receiver operating characteristic analysis revealed that a skin autofluorescence value ≥3.2AU determined severe ED with a sensitivity of 60% and a specificity of 87% in diabetic patients.

CONCLUSION

Skin autofluorescence is significantly associated with ED in diabetes, independently of classical confounding factors.

eNOS Function and Dysfunction in the Penis

Endothelial nitric oxide (NO) synthase (eNOS) has an indispensable role in the erectile response. In the penis, eNOS activity and endothelial NO bioavailability are regulated by multiple post-translatlonal molecular mechanisms, such as eNOS phosphorylation, eNOS interaction with regulatory proteins and contractile pathways, and actions of reactive oxygen species (ROS). These mechanisms regulate eNOS-mediated responses under physiologic circumstances and provide various mechanisms whereby endothelial NO availability may be altered in states of vasculogenlc erectile dysfunction (ED), in view of the recent advances in the field of eNOS function in the penis and its role in penile erection, the emphasis in this review is placed on the mechanisms regulating eNOS activity and its interaction with the RhoA/Rho-kinase pathway in the physiology of penile erection and the pathophysiology of ED.

A2B Adenosine Receptor Agonist Improves Erectile Function in Diabetic Rats

Diabetes is an important risk factor for erectile dysfunction (ED). Recent studies have indicated that A2B adenosine receptor (ADORA2B) signaling is essential for penile erection. Thus, we hypothesize that diabetic ED may be attributed to impaired A2B adenosine signaling. To test this hypothesis, we generated diabetic rats by injecting streptozocin as animal model. After 12 weeks, immunohistochemistry staining was used to localize the expression of ADORA2B. Western Blot and quantitative PCR were employed to determine ADORA2B expression level. Intracavernosal pressure (ICP) measurement was used to evaluate erectile function. Diabetic rats received a single intravenous injection of BAY 60-6583, an ADORA2B agonist, or vehicle solution, at 60 min before the ICP measurement. The results showed that ADORA2B expressed in the nerve bundle, smooth muscle, and endothelium in penile tissue of control mice. Western Blot and quantitative PCR results indicated that the expression levels of ADORA2B protein and mRNA were significantly reduced in penile tissues of diabetic rats. Functional studies showed that the erectile response induced by electrical stimulation was remarkably decreased in diabetic rats, compared with age-matched control rats. However, at 60 min after BAY 60-6583 treatment, the erectile function was improved in diabetic rats, suggesting that enhancement of ADORA2B signaling may improve erectile function in diabetic ED. This preclinical study has revealed a previously unrecognized therapeutic possibility of BAY 60-6583 as an effective and mechanism-based drug to treat diabetic ED. In conclusion, we propose that impaired A2B adenosine signaling is one of the pathological mechanisms of diabetic ED.

Chronic administration of sildenafil improves erectile function in a rat model of chronic renal failure

The relationship between erectile dysfunction (ED) and chronic renal failure (CRF) has been reported in several studies. This study aimed to investigate whether the chronic use of sildenafil could enhance the erectile capacity in CRF-induced rats. In addition, we assessed the effect of that treatment on certain molecules, which have been suggested to play crucial roles in erectile physiology and CRF-related ED as well. Three groups of animals were utilized: (1) age-matched control rats, (2) CRF-induced rats, (3) CRF-induced rats treated with chronic administration of sildenafil (5 mg kg⁻¹ p.o. for 6 weeks [treatment started after 6 weeks of CRF induction]). At 3 months, all animals underwent cavernosal nerve stimulation (CNS) to assess erectile function. Penile tissue advanced glycation end products (AGE's)/5-hydroxymethyl-2-furaldehyde, malondialdehyde (MDA), cGMP (ELISA), inducible nitric oxide synthase (iNOS) and neuronal NOS (nNOS) (Western blot) analyses were performed in all rat groups. CRF-induced rats had a significant decrease in erectile function when compared to control rats (P < 0.05). The increase in both intracavernosal pressure (ICP) and area under the curve of CRF-induced rats treated with sildenafil (Group 3) was greater than CRF-induced rats (Group 2). Additionally, sildenafil treatment decreased AGE, MDA and iNOS levels, while it preserved nNOS and cGMP contents in CRF-induced penile tissue. Decreased AGE, MDA, iNOS and increased nNOS, cGMP levels at the sildenafil-treated group increased both ICP and Total ICP to CNS, which led to improve erectile function in CRF-induced rats. The results of the present study revealed the therapeutic effect of chronic sildenafil administration on erectile function in CRF-induced rats.

Effects of prolonged ingestion of epigallocatechin gallate on diabetes type 1-induced vascular modifications in the erectile tissue of rats

Diabetes Mellitus type 1 is a metabolic disease that predisposes to erectile dysfunction, partly owing to structural and molecular changes in the corpus cavernosum (CC) vessels. The aim of this study was to determine the effects of early treatment with the antioxidant epigallocatechin gallate (EGCG) in cavernous diabetes-induced vascular modifications. Diabetes was induced in two groups of young Wistar rats; one group was treated with EGCG for 10 weeks. A reduction in smooth muscle content was observed in the CC of diabetic rats, which was significantly attenuated with EGCG consumption. No differences were observed among groups, neither in the expression of VEGF assayed by western blotting nor in the immunofluorescent labeling of vascular endothelial growth factor (VEGF) and its receptors (VEGFR1 and VEGFR2). VEGFR2 was restricted to the endothelium, whereas VEGF and VEGFR1 co-localized in the smooth muscle layer. With regard to the Angiopoietin/Tie-2 system, no quantitative differences in Angiopoietin 1 were observed among the experimental groups. Ang1 localization was restricted to the smooth muscle layer, and receptor Tie2 and Angiopoietin 2 were both expressed in the endothelium. In brief, our results suggest that EGCG consumption prevented diabetes-induced loss of cavernous smooth muscle but does not affect vascular growth factor expression in young rats.

Differences Between Tg2576 and Wild Type Mice in the NMDA Receptor-Nitric Oxide Pathway After Prolonged Application of a Diet High in Advanced Glycation End Products

It has been suggested that advanced glycation end (AGE) products, via cognate receptor activation, are implicated in several diseases, including Alzheimer's disease. The NMDA receptor-nitric oxide pathway appears to be influenced by AGE products and involved in the pathogenesis of this type of dementia. In this study, C57BL/6J (WT) and transgenic (Tg2576) mice expressing human mutant amyloid precursor protein were kept on prolonged (8 months) diets containing regular or high amounts of AGE products. After the decapitation of 11-months old mice, brain tissue analyses were performed [expressions of the NR1, NR2A and NR2B subunits of NMDA receptors, activities of neuronal, endothelial and inducible nitric oxide synthase (nNOS, eNOS and iNOS)]. Moreover, levels of malondialdehyde and of human amyloid β 1-42 were estimated. We found increased activity of nNOS in WT mice maintained on a high compared to regular AGE diet; however, no similar differences were found in Tg2576 mice. In addition, we observed an increase in NR1 expression in Tg2576 compared to WT mice, both kept on a diet high in AGE products. Correlation analyses performed on mice kept on the regular AGE diet supported close links between particular subunits (NR2A-NR2B, in WT as well as in Tg2576 mice), between subunits and synthase (NR2A/NR2B-nNOS, only in WT mice) or between particular synthases (nNOS-iNOS, only in WT). Correlation analysis also revealed differences between WT mice kept on both diets (changed correlations between NR2A/NR2B-nNOS, between nNOS-eNOS and between eNOS-iNOS). Malondialdehyde levels were increased in both Tg2576 groups when compared to the corresponding WT mice, but no effects of the diets were observed. Analogously, no significant effects of diets were found in the levels of soluble or insoluble amyloid β 1-42 in Tg2576 mice. Our results demonstrate that prolonged ingestion of AGE products can influence the NMDA receptor-nitric oxide pathway in the brain and that only WT mice, not Tg2576 mice, are able to maintain homeostasis among subunits and synthases or among particular synthases. The prolonged application of AGE products enhanced differences between 11-months old Tg2576 and WT mice regarding this pathway. Observed differences in the pathway between WT mice kept on regular or high AGE diets suggest that the prolonged application of a diet low in AGE products could have beneficial effects in older or diabetic people and perhaps also in people with Alzheimer's disease.

A comprehensive review of urologic complications in patients with diabetes

Diabetes Mellitus (DM) is a chronic disease characterized by hyperglycemia, as a result of abnormal insulin production, insulin function, or both. DM is associated with systemic complications, such as infections, neuropathy and angiopathy, which involve the genitourinary tract. The three most significant urologic complications include: bladder cystopathy, sexual dysfunction and urinary tract infections. Almost half of the patients with DM have bladder dysfunction or cystopathy, which can be manifested in women as hypersensitivity (in 39-61% of the diabetic women) or neurogenic bladder. In males it can be experienced as lower urinary tract symptoms (in 25% of diabetic males with a nearly twofold increased risk when seen by age groups). Additionally, an increased prostate volume affects their micturition as well as their urinary tract. Involving sexual dysfunction in women, it includes reduced libido, decreased arousal, clitoral erectile dysfunction and painful or non-sensitive intercourse; and in diabetic males it varies from low libido, ejaculatory abnormalities and erectile dysfunction. Globally, sexual disorders have a prevalence of 18-42%. Erectile dysfunction is ranked as the third most important complication of DM. Urinary tract infections are observed frequently in diabetic patients, and vary from emphysematous infections, Fournier gangrene, staghorn infected lithiasis to repetitive bacterial cystitis. The most frequent finding in diabetic women has been lower urinary tract infections. Because of the high incidence of obesity worldwide and its association with diabetes, it is very important to keep in mind the urologic complication associated with DM in patients, in order to better diagnose and treat this population.

How to treat erectile dysfunction in men with diabetes: from pathophysiology to treatment

Erectile dysfunction (ED) is highly prevalent affecting at least 50 % of men with diabetes mellitus (DM). DM may cause ED through a number of pathophysiological pathways. These include neuropathy, endothelial dysfunction, cavernosal smooth muscle structural/functional changes, and hormonal changes. Lifestyle changes, diabetes control, and treatment of hypogonadism are important as the first step in ED management since there is no curative treatment for ED. Phosphodiesterase type 5 inhibitors (PDE5i) are the first-line treatment option. Intracavernous administration of vasoactive drugs is commonly used as a second-line medical treatment when PDE5i have failed. Alprostadil is the most widely used drug in this second-line setting. The combination of papaverine, phentolamine, and alprostadil represents the most efficacious intracavernous pharmacologic treatment option that may save non-responders to alprostadil. Penile prosthesis implantation can be considered in treatment refractory cases, with excellent functional and safety results in the properly informed patients.

Advanced glycation end-products: a common pathway in diabetes and age-related erectile dysfunction

Reactive derivatives of non-enzymatic glucose-protein condensation reactions integrate a heterogeneous group of irreversible adducts called advanced glycation end-products (AGEs). Numerous studies have investigated the role of the AGEs in cardiovascular system; however, its contribution to erectile dysfunction (ED) that is an early manifestation of cardiovascular disease has been less intensively investigated. This review summarizes the most recent advances concerning AGEs effects in the cavernous tissue of the penis and in ED onset, particularly on diabetes and aging, conditions that not only favor AGEs formation, but also increase risk of developing ED. The specific contribution of AGE on intra- and extracellular deposition of insoluble complexes, interference in activity of endothelial nitric oxide (NO) synthase, NO bioavailability, endothelial-dependent vasodilatation, as well as molecular pathways activated by receptor of AGEs are presented. Finally, the interventional actions that prevent AGEs formation, accumulation or activity in the cavernous tissue and that include nutritional pattern modulation, nutraceuticals, exercise, therapeutic strategies (statins, anti-diabetics, inhibitors of phosphodiesterase-5, anti-hypertensive drugs) and inhibitors of AGEs formation and crosslink breakers, are discussed. From this review, we conclude that despite the experiments conducted in animal models pointing to the AGE/RAGE axis as a potential interventional target with respect to ED associated with diabetes and aging, the clinical data have been very disappointing and, until now, did not provide evidence of benefits of treatments directed to AGE inactivation.

Acute macrovascular dysfunction in patients with type 2 diabetes induced by ingestion of advanced glycated β-lactoglobulins

OBJECTIVE

Recent evidence indicates that heat-enhanced food advanced glycation end products (AGEs) adversely affect vascular function. The aim of this study was to examine the acute effects of an oral load of heat-treated, AGE-modified β-lactoglobulins (AGE-BLG) compared with heat-treated, nonglycated BLG (C-BLG) on vascular function in patients with type 2 diabetes mellitus (T2DM).

RESEARCH DESIGN AND METHODS

In a double-blind, controlled, randomized, crossover study, 19 patients with T2DM received, on two different occasions, beverages containing either AGE-BLG or C-BLG. We measured macrovascular [brachial ultrasound of flow-mediated dilatation (FMD)] and microvascular (laser-Doppler measurements of reactive hyperemia in the hand) functions at baseline (T0), 90 (T90), and 180 (T180) min.

RESULTS

Following the AGE-BLG, FMD decreased at T90 by 80% from baseline and remained decreased by 42% at T180 (P < 0.05 vs. baseline, P < 0.05 vs. C-BLG at T90). By comparison, following C-BLG, FMD decreased by 27% at T90 and 51% at T180 (P < 0.05 vs. baseline at T180). A significant decrease in nitrite (T180) and nitrate (T90 and T180), as well as a significant increase in N(ε)-carboxymethyllisine, accompanied intake of AGE-BLG. There was no change in microvascular function caused by either beverage.

CONCLUSIONS

In patients with T2DM, acute oral administration of a single AGE-modified protein class significantly though transiently impaired macrovascular function in concert with decreased nitric oxide bioavailability. These AGE-related changes were independent of heat treatment.

Panax notoginseng saponins improve the erectile dysfunction in diabetic rats by protecting the endothelial function of the penile corpus cavernosum

Diabetes mellitus (DM)-associated ED is predominantly due to neurovascular dysfunction mediated by nitric oxide (NO) suppression. Panax notoginseng saponins (PNS) are widely used for treating cardiovascular disease in China. The aim of this study was to evaluate the effects of PNS on penile erection and corpus cavernosum tissues in rats with diabetes-associated ED. Four weeks after PNS treatment, erectile function was assessed by intracavernous pressure (ICP) and mean arterial pressure (MAP) measurements. The level of NO, cyclic guanosine monophosphate (cGMP) and advanced glycation end products (AGEs) in cavernous tissue were assessed. Immunohistochemical staining and TUNEL (terminal deoxynucleotidyl transferase dUTP nick end labeling) were performed for detecting endothelial NO synthase (eNOS) and apoptosis, respectively. The results show that ICP/MAP ratio was significantly increased in high-dose (150 mg kg(-1) per day) PNS-treated group compared with the diabetic ED untreated group (DM group). Compared with the untreated group, the expression of eNOS and the levels of NO and cGMP were increased in the PNS-treated groups. Moreover, apoptosis was markedly decreased in the group that received 150 mg kg(-1) per day of PNS. These results suggest that PNS may be used for improving the ED in diabetic rats via the NO/cGMP pathway and restores the function of endothelium in corpus cavernosum.

Effect of Chronic Ischemia on Constitutive and Inducible Nitric Oxide Synthase Expression in Erectile Tissue

Arterial occlusive disease is one of the leading causes of organic erectile dysfunction (ED). Recent studies have shown that the incidence of cardiovascular disease closely correlates with the prevalence of ED. Also, ED is thought to be an early signal of impending cardiovascular problems. We previously found that the atherosclerosis of iliohypogastric arteries in the rabbit causes ED, down-regulates cavernosal neuronal nitric oxide synthase (nNOS) gene expression, and impairs NO synthesis. The goal of this study was to determine the effect of atherosclerosis-induced ischemia on cavernosal nNOS, endothelial NOS (eNOS), and inducible NOS (iNOS) expression and NO-mediated smooth muscle relaxation in the rabbit. Our study showed that iliac artery blood flow, intracavernosal blood flow, and intracavernosal oxygen tension were unchanged 4 weeks after the induction of arterial atherosclerosis, whereas they were significantly diminished at weeks 8 and 16. Erectile responses to nerve stimulation and cavernosal smooth muscle relaxation were unchanged at week 4 and were significantly diminished at weeks 8 and 16 after the induction of atherosclerosis. Western blotting showed that cavernosal nNOS and eNOS protein levels were unaffected at week 4 but were significantly decreased at weeks 8 and 16 after the induction of atherosclerosis. iNOS protein, however, markedly increased during the course of the induced arterial disease. Immunohistochemical staining showed no change in cavernosal eNOS or nNOS expression at week 4. A dramatic decrease in both was evident at 8 and 16 weeks. iNOS expression progressively increased between 4 and 16 weeks of atherosclerosis. Down-regulation of nNOS and eNOS, along with up-regulation of iNOS, may explain ischemic cavernosal smooth muscle relaxation impairment in the rabbit. Ischemically altered NOS expression may be of great pathophysiologic importance in atherosclerosis-induced ED. These data may provide further insight into the mechanism of arteriogenic ED.

Efficacy and safety of once-daily tadalafil in men with erectile dysfunction who reported no successful intercourse attempts at baseline

INTRODUCTION

Tadalafil is efficacious and well tolerated for erectile dysfunction (ED), but effects in men with "complete ED" are unclear.

AIM

To investigate effects of once-daily tadalafil in men with no successful intercourse attempts at baseline.

METHODS

Through a post hoc, pooled-data analysis of four randomized, double-blind trials on the effects of tadalafil 2.5 or 5 mg (vs. placebo) in men with ED, we evaluated efficacy and safety in subjects with 0 "yes" responses to Sexual Encounter Profile question 3 (SEP3) during an initial 4-week treatment-free run-in period.

MAIN OUTCOME MEASURES

Changes from baseline in the SEP diary and the International Index of Erectile Function-erectile function (IIEF-EF) domain were subjected to analysis of covariance models.

RESULTS

Five hundred ninety-five subjects with no successful attempts at baseline were included in the analysis. The mean (± standard deviation) age was 58.2 ± 10.7 years; and most subjects had ED for ≥ 1 year (95.0%). ED was severe in 61.5% and moderate in 26.4%. Approximately 45% had diabetes mellitus or hypertension. After 12 weeks, the mean per-patient SEP3 percentage increased from 0% to 32.4% with tadalafil 2.5 mg and to 46.4% with tadalafil 5 mg (each P < 0.001 vs. placebo). Corresponding data for successful penetration (SEP2) were increases from 21.1% to 48.2% with tadalafil 2.5 mg and from 24.4% to 66.2% with 5 mg (each P < 0.001 vs. placebo). Mean IIEF-EF increased from 9.7 to 15.7 with tadalafil 2.5 mg and from 10.7 to 19.2 with 5 mg (each P < 0.001 vs. placebo). Tadalafil also significantly improved the intercourse-satisfaction and overall-satisfaction domains (vs. placebo). Both doses of tadalafil were generally well tolerated, with adverse event rates similar to placebo.

CONCLUSIONS

The posttreatment intercourse success rate was 32% and 46% for tadalafil 2.5 mg and 5 mg, respectively, in men with no successful intercourse attempts at baseline.

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.

Pathophysiology of diabetic erectile dysfunction: potential contribution of vasa nervorum and advanced glycation endproducts

Erectile dysfunction (ED) due to diabetes mellitus remains difficult to treat medically despite advances in pharmacotherapeutic approaches in the field. This unmet need has resulted in a recent re-focus on the pathophysiology, in order to understand the cellular and molecular mechanisms leading to ED in diabetes. Diabetes-induced ED is often resistant to PDE5 inhibitor treatment, thus there is a need to discover targets that may lead to novel approaches for a successful treatment. The aim of this brief review is to update the reader in some of the latest development on that front, with a particular focus on the role of impaired neuronal blood flow and the formation of advanced glycation endproducts.

Effect of icarisid II on diabetic rats with erectile dysfunction and its potential mechanism via assessment of AGEs, autophagy, mTOR and the NO-cGMP pathway

Erectile dysfunction (ED) is a major complication of diabetes mellitus. Icariin has been shown to enhance erectile function through its bioactive form, icarisid II. This study investigates the effects of icarisid II on diabetic rats with ED and its potential mechanism via the assessment of advanced glycosylation end products (AGEs), autophagy, mTOR and the NO-cGMP pathway. Icarisid II was extracted from icariin by an enzymatic method. In the control and diabetic ED groups, rats were administered normal saline; in the icarisid II group, rats were administered icarisid II intragastrically. Erectile function was evaluated by measuring intracavernosal pressure/mean arterial pressure (ICP/MAP). AGE concentrations, nitric oxide synthase (NOS) activity and cGMP concentration were assessed by enzyme immunoassay. Cell proliferation was analysed using methyl thiazolyl tetrazolium assay and flow cytometry. Autophagosomes were observed by transmission electron microscopy, monodansylcadaverine staining and GFP-LC3 localisation. The expression of NOS isoforms and key proteins in autophagy were examined by western blot. Our results have shown that Icarisid II increased ICP/MAP values, the smooth muscle cell (SMC) growth curve, S phase and SMC/collagen fibril (SMC/CF) proportions and decreased Beclin 1 (P<0.05). Icarisid II significantly increased the proliferative index and p-p70S6K(Thr389) levels and decreased the numbers of autophagosomes and the levels of LC3-II (P<0.01). Icarisid II decreased AGE concentrations and increased cGMP concentration, NOS activity (P<0.05) and cNOS levels (P<0.01) in the diabetic ED group. Therefore, Icarisid II constitutes a promising compound for diabetic ED and might be involved in the upregulation of SMC proliferation and the NO-cGMP pathway and the downregulation of AGEs, autophagy and the mTOR pathway.

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.

Markers of erectile dysfunction

With the development and marketing of oral pharmacotherapy that is both noninvasive and successful in treating erectile dysfunction (ED), the quest to identify markers of organic ED lost ground. Indeed, the multi-factorial nature of ED may have led many researchers to conclude that searching for a universal marker of ED was futile. However, the realization that ED is strongly correlated with the overall health of men, and may act as a predictor for the development of cardiovascular disease (CVD) and diabetes, has stimulated interest in identifying genes that can distinguish organic ED. In addition, the potential ability to suggest to the patient that ED is reversible (i.e., psychogenic) with a simple test would be of significance to both the physician and patient, as well as for reimbursement issues for therapy by insurance companies. Such a marker may also act as a non-subjective measure of the degree of ED and the efficacy of treatment. This review discusses the importance of identifying such markers and recent work identifying potential markers in human patients.

Cannabinoid/agonist WIN 55,212-2 reduces cardiac ischaemia–reperfusion injury in Zucker diabetic fatty rats: role of CB2 receptors and iNOS/eNOS

BACKGROUND

Diabetes increases cardiac damage after myocardial ischaemia. Cannabinoids can protect against myocardial ischaemia/reperfusion injury. The aim of this study was to examine the cardioprotective effect of the cannabinoid agonist WIN 55,212-2 (WIN) against ischaemia/reperfusion injury in an experimental model of type 2 diabetes. We performed these experiments in the Zucker diabetic fatty rat, and focused on the role of cannabinoid receptors in modulation of cardiac inducible nitric oxide synthase (iNOS)/endothelial-type nitric oxide synthase (eNOS) expression.

METHODS

Male 20-week-old Zucker diabetic fatty rats were treated with vehicle, WIN, the selective CB1 or CB2 receptor antagonists AM251 and AM630, respectively, AM251 + WIN or AM630 + WIN. Hearts were isolated from these rats, and the cardiac functional response to ischaemia/reperfusion injury was evaluated. In addition, cardiac iNOS and eNOS expression were determined by western blot.

RESULTS

WIN significantly improved cardiac recovery after ischaemia/ reperfusion in the hearts from Zucker diabetic fatty rats by restoring coronary perfusion pressure and heart rate to preischaemic levels. Additionally, WIN decreased cardiac iNOS expression and increased eNOS expression after ischaemia/reperfusion in diabetic hearts. WIN-induced cardiac functional recovery was completely blocked by the CB2 antagonist AM630. However, changes in NOS isoenzyme expression were not affected by the CB antagonists.

CONCLUSIONS

This study shows a cardioprotective effect of a cannabinoid agonist on ischaemia/reperfusion injury in an experimental model of a metabolic disorder. The activation mainly of CB2 receptors and the restoration of iNOS/eNOS cardiac equilibrium are mechanisms involved in this protective effect. These initial studies have provided the basis for future research in this field.

Effect of intensive glycemic therapy on erectile function in men with type 1 diabetes

PURPOSE

We determined whether intensive glycemic therapy reduces the risk of erectile dysfunction in men with type 1 diabetes enrolled in the Diabetes Control and Complications Trial.

MATERIALS AND METHODS

The Diabetes Control and Complications Trial randomized 761 men with type 1 diabetes to intensive or conventional glycemic therapy at 28 sites between 1983 and 1989, of whom 366 had diabetes for 1 to 5 years and no microvascular complications (primary prevention cohort), and 395 had diabetes for 1 to 15 years with nonproliferative retinopathy or microalbuminuria (secondary intervention cohort). Subjects were treated until 1993, and followed in the Epidemiology of Diabetes Interventions and Complications study. In 2003 we conducted an ancillary study using a validated assessment of erectile dysfunction in 571 men (80% participation rate), 291 in the primary cohort and 280 in the secondary cohort.

RESULTS

Of the participants 23% reported erectile dysfunction. The prevalence was significantly lower in the intensive vs conventional treatment group in the secondary cohort (12.8% vs 30.8%, p = 0.001) but not in the primary cohort (17% vs 20.3%, p = 0.49). The risk of erectile dysfunction in primary and secondary cohorts was directly associated with mean HbA1c during the Diabetes Control and Complications Trial, and Epidemiology of Diabetes Interventions and Complications combined. Age, peripheral neuropathy and lower urinary tract symptoms were other risk factors.

CONCLUSIONS

A period of intensive therapy significantly reduced the prevalence of erectile dysfunction 10 years later among those men in the secondary intervention cohort but not in the primary prevention cohort. Higher HbA1c was significantly associated with risk in both cohorts. These findings provide further support for early implementation of intensive insulin therapy in young men with type 1 diabetes.

Arginase II deletion increases corpora cavernosa relaxation in diabetic mice

INTRODUCTION

Diabetes-induced erectile dysfunction involves elevated arginase (Arg) activity and expression. Because nitric oxide (NO) synthase and Arg share and compete for their substrate L-arginine, NO production is likely linked to regulation of Arg. Arg is highly expressed and implicated in erectile dysfunction.

AIM

It was hypothesized that Arg-II isoform deletion enhances relaxation function of corpora cavernosal (CC) smooth muscle in a streptozotocin (STZ) diabetic model.

METHODS

Eight weeks after STZ-induced diabetes, vascular functional studies, Arg activity assay, and protein expression levels of Arg and constitutive NOS (using Western blots) were assessed in CC tissues from nondiabetic wild type (WT), diabetic (D) WT (WT + D), Arg-II knockout (KO), and Arg-II KO+D mice (N = 8-10 per group).

MAIN OUTCOME MEASURES

Inhibition or lack of arginase results in facilitation of CC relaxation in diabetic CC.

RESULTS

Strips of CC from Arg-II KO mice exhibited an enhanced maximum endothelium-dependent relaxation (from 70 + 3% to 84 + 4%) and increased nitrergic relaxation (by 55%, 71%, 42%, 42%, and 24% for 1, 2, 4, 8 and 16 Hz, respectively) compared with WT mice. WT + D mice showed a significant reduction of endothelium-dependent maximum relaxation (44 + 8%), but this impairment of relaxation was significantly prevented in Arg-II KO+D mice (69 + 4%). Sympathetic-mediated and alpha-adrenergic agent-induced contractile responses also were increased in CC strips from D compared with non-D controls. Contractile responses were significantly lower in Arg-II KO control and D versus the WT groups. WT + D mice increased Arg activity (1.5-fold) and Arg-II protein expression and decreased total and phospho-eNOS at Ser-1177, and nNOS levels. These alterations were not seen in Arg-II KO mice. Additionally, the Arg inhibitor BEC (50 µM) enhanced nitrergic and endothelium-dependent relaxation in CC of WT + D mice.

CONCLUSION

These studies show for the first time that Arg-II deletion improves CC relaxation in type 1 diabetes.

Molecular targets for diabetes mellitus-associated erectile dysfunction

Protein expression profiles in rat corporal smooth muscle tissue were compared between animal models of streptozotocin-induced diabetes mellitus (STZ-DM) and age-matched controls (AMCs) at 1 week and 2 months after induction of hyperglycemia with STZ treatment. At each time point, protein samples from four STZ-DM and four AMC rat corpora tissues were prepared independently and analyzed together across multiple quantitative two-dimensional gels using a pooled internal standard sample to quantify expression changes with statistical confidence. A total of 170 spots were differential expressed among the four experimental groups. A subsequent mass spectrometry analysis of the 170 spots identified a total of 57 unique proteins. Network analysis of these proteins using MetaCore suggested altered activity of transcriptional factors that are of too low abundance to be detected by the two-dimensional gel method. The proteins that were down-regulated with diabetes include isoforms of collagen that are precursors to fibril-forming collagen type 1; Hsp47, which assists and mediates the proper folding of procollagen; and several proteins whose abundance is controlled by sex hormones (e.g. CRP1 and A2U). On the other hand, proteins seen or predicted to be up-regulated include proteins involved in cell apoptosis (e.g. p53, 14-3-3-gamma, Serpinf1, Cct4, Cct5, and Sepina3n), proteins that neutralize the biological activity of nerve growth factor (e.g. anti-NGF 30), and proteins involved in lipid metabolism (e.g. apoA-I and apoA-IV). Subsequent Western blot validation analysis of p53, 14-3-3-gamma, and Hsp47 confirmed increased p53 and 14-3-3-gamma and decreased Hsp47 levels in separate samples. According to the results from the Western blot analysis, Hsp47 protein showed a approximately 3-fold decrease at 1 week and was virtually undetectable at 2 months in diabetic versus control. Taken together, our results identify novel candidate proteins playing a role in erectile dysfunction in diabetes resulting from STZ treatment.

Effects of diabetes and elevated glucose on nitrergic relaxations in the isolated duodenum of the rat

Nitrergic relaxations of the isolated duodenum, induced by streptozotocin, were investigated in the experimental 8-week diabetes rat model. The effects of elevated glucose were also examined in the incubated duodenal muscles (in Krebs-Henseleit solution containing 44 mM glucose for 6 h) taken from nondiabetic rats. The relaxations induced by electrical field stimulation (EFS) and nicotine were significantly reduced in diabetic rats compared with control rats. Incubating of duodenal tissues in medium containing elevated glucose revealed significantly impaired relaxations to EFS and nicotine compared to responses obtained after normal glucose incubation. However, the relaxant responses to sodium nitroprusside and papaverine were similar in all groups. Incubating in hyperosmolar solutions containing sucrose, the relaxant responses were not affected. In conclusion, impairment of NO-mediated relaxations in diabetes may be related to hyperglycemia. The alterations caused by elevated glucose are not due to a hyperosmotic effect because the same concentration of sucrose had no effect on the relaxations.

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.