Antioxidant icariside II combined with insulin restores erectile function in streptozotocin-induced type 1 diabetic rats

Therapeutic Challenges of Diabetes Mellitus-Related Erectile Dysfunction and The Potential Therapeutic Role of Medicinal Plants: A Narrative Review

Erectile dysfunction (ED) is a common male sexual dysfunction and can be induced by diabetes mellitus (DM). Diabetes mellitus-induced erectile dysfunction (DMED) affects various aspects of the patient's quality of life, mental well-being, and relationship dynamics. Given the increasing incidence of DM worldwide, the incidence of DMED is expected to increase accordingly. There are more challenges to treat DMED compared to non-DMED. The efficacy of oral phosphodiesterase-5 inhibitors is often ineffective in DMED and there is a need to search for effective drugs. Medicinal plants such as Eucommia ulmoides Oliv. Leaf, Cordycep militaris have been used in treating DMED in some experiments. And some ingredients from the medicinal plants such as Icariside II, Panax notoginseng Saponins have also shown to be beneficial in improving erectile function in animal models of DMED. These medicinal plants and ingredients may act by regulating hormone levels, ameliorating oxidative damage, and promoting NO/cGMP. We summarize the challenges in treating DMED due to related complicated pathogenesis and limited therapeutic options, while particularly highlight the role of the medicinal plants and their ingredients in DMED.

Effects of Anti-Diabetic Drugs on Erectile Dysfunction: A Systematic Review and Meta-Analysis

Background

Erectile dysfunction (ED) is considered one of the complications of diabetes mellitus (DM), affecting about 35-75% of diabetic patients. Studies suggest that anti-diabetic drugs could potentially alleviate ED in diabetics, yet the effects of different drug classes remain unknown.

Objective

Our study aims to investigate the influence of various anti-diabetic drugs on ED.

Materials and Methods

Adhering to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, a systematic review and meta-analysis were carried out, focusing on clinical research linking anti-diabetic drugs and ED. Relevant studies were sought from PubMed, Embase, and Cochrane Library databases. Review Manager 5.4.1 facilitated meta-analysis and subgroup analysis, while Stata 15.1 was employed for sensitivity analysis to ensure result robustness.

Results

An initial search yielded 3,906 articles across databases. After screening the titles and abstracts of 3,906 articles and performing a full-text review of 30 selected articles, we selected three studies for analysis ultimately. Our most significant finding is that glucagon-like peptide-1 receptor agonists (GLP-1RAs) show an advantage over metformin in improving erectile dysfunction in diabetic patients (Z = 2.41, P = 0.02), with a particularly notable effect observed in patients with higher BMI or obesity (Z = 2.26, P = 0.02). This suggests that GLP-1RAs may offer a promising therapeutic option for this patient population. Additionally, thiazolidinediones may enhance sexual function, although their safety and efficacy require further confirmation. Acarbose, insulin, and sodium-glucose cotransporter-2 inhibitors (SGLT-2i) also show potential for positively impacting ED, but more research is needed to establish their efficacy. Finally, the impact of metformin and sulfonylureas on ED remains uncertain, with mixed evidence from existing studies.

Conclusion

In conclusion, GLP-1RAs demonstrate an advantage over metformin in improving erectile dysfunction in diabetic patients. Other antidiabetic drugs also show potential for enhancing erectile function in this population, but further extensive clinical trials are needed to address knowledge gaps and safety concerns.

Icariin inhibits hyperglycemia-induced cell death in penile cavernous tissue and improves erectile function in type 1 diabetic rats

Background

Hyperglycemia can cause endothelial cell (EC) and smooth muscle cell (SMC) death in the penile cavernous tissue of rats and lead to erectile dysfunction (ED).

Objectives

To investigate the proportions of apoptotic, pyroptotic, and ferroptotic cells among ECs and SMCs in the penile cavernous tissue of type 1 diabetic (T1DM) rats and the mechanism by which icariin (ICA) improves the erectile function of T1DM rats.

Methods

A total of 24 9-week-old Sprague-Dawley (SD) rats were randomly divided into 4 groups (n = 6): control group, control + ICA group, diabetic mellitus (DM) group, and DM + ICA group. T1DM rats were generated via the intraperitoneal injection of STZ (45 mg/kg). After 8 weeks, the rats in the control + ICA group and the DM + ICA group were administered ICA (10 mg/kg/d) by gavage for 4 weeks. ROS, MDA, SOD, GSH, SM/C, and NO levels, and GPX4, ACSL4, caspase-1, GSDMD, caspase-3, CD31, α-SMA, and p-eNOS/eNOS expression in penile cavernous tissue and the ICPmax/MAP of 21-week-old rats were detected.

Results

The percentage of pyroptotic SMCs in penile cavernosum was no statistically significant difference among these groups. Vs control group, the percentages of apoptotic (20.70% ± 1.60%), pyroptotic (21.02% ± 1.97%), and ferroptotic (9.01% ± 2.00%) ECs and the percentages of apoptotic (15.47% ± 1.36%) and ferroptotic (26.33% ± 3.11%) SMCs in the penile cavernous tissue of the DM group were significantly greater. Vs DM group, the percentages of apoptotic (9.13% ± 1.28%), pyroptotic (13.22 ± 1.26%), and ferroptotic (4.01% ± 0.86%) ECs and the percentages of apoptotic (11.60% ± 1.91%) and ferroptotic (12.71% ± 2.92%) SMCs of the DM + ICA group were significantly lower. Vs the DM group, the levels of caspase-1, GSDMD, ACSL4, and ROS were significantly lower in the penile cavernous tissue of the DM + ICA group. Meanwhile, the levels of GPX4 and maximum intracavernous pressure/mean arterial pressure (ICPmax/MAP) were significantly higher.

Clinical Implications

The combined inhibition of apoptosis, pyroptosis, and ferroptosis in penile cavernous tissue by ICA provides a theoretical basis for the clinical development of multi-target drugs for the treatment of type 1 diabetes-induced ED.

Strengths and Limitations

Further experiments are required to clarify whether other types of cell death are involved in the loss of ECs and SMCs in the penile cavernous tissue of T1DM rats.

Conclusion

Inhibiting oxidative stress and thereby inhibiting apoptosis, pyroptosis, and ferroptosis in ECs and SMCs of penile cavernous tissue constitute one of the mechanisms through which ICA improves erectile function in T1DM rats.

Pharmacological and Therapeutic Potential of a Natural Flavonoid Icariside II in Human Complication

Emerging challenges to human health necessitate a coordinated effort to find both preventative and therapeutic techniques, with natural products at the forefront of attempts to gain novel medicines and minimize disease transmission and related death. The medicinal potential of chemicals contained in plants has been known for centuries, leading to its use in homes and clinics for the treatment of numerous disorders. Despite global advancements, plant-based medicines continue to be utilized to treat various pathological illnesses or as alternatives to contemporary pharmaceuticals. The safety and low toxicity of natural products have led to their increasing acceptability for the prevention or treatment of many ailments. Flavonoids are biologically active compounds that are classified as polyphenols, which are a type of secondary metabolite found in all plants. Icariside II (ICA-II) is one of the secondary metabolites that belong to the flavonoid category of phytochemicals and is present in Epimedium brevicornum Maxim. In recent years, ICA-II has been discovered to show anti-inflammatory, antioxidant, anticancer, renal protecting, and cardiac protective effects, as well as several other biological characteristics. This review is focused on the exploration of the pharmacological activities of ICA-II. ICA-II is considered a prospective candidate for future clinical investigations due to a number of therapeutic properties.

Causal association between antidiabetic drugs and erectile dysfunction: evidence from Mendelian randomization

Background

Antidiabetic drugs are widely used in clinical practice as essential drugs for the treatment of diabetes. The effect of hypoglycemic drugs on erectile dysfunction has not been fully proven due to the presence of multiple confounding factors.

Methods

Two-sample Mendelian randomization (TSMR) was used to examine the causal effect of antidiabetic drugs (including metformin, insulin and gliclazide) on erectile dysfunction. We used five robust analytic methods, of which the inverse variance weighting (IVW) method was the primary method, and also assessed factors such as sensitivity, pleiotropy, and heterogeneity. Effect statistics for exposures and outcomes were downloaded from publicly available data sets, including open Genome-Wide Association Studies (GWAS) and the UK Biobank (UKB).

Results

In some of the hypoglycemic drug use, there was a significant causal relationship between metformin use and erectile dysfunction [Beta: 4.9386; OR:1.396E+02 (95% CI:9.13-2135); p-value: 0.0004), suggesting that metformin increased the risk of erectile dysfunction development. Also, we saw that gliclazide use also increased the risk of erectile dysfunction [Beta: 11.7187; OR:0.0125 (95% CI:12.44-1.21E+09); P value: 0.0125). There was no significant causal relationship between insulin use and erectile dysfunction [Beta: 3.0730; OR:21.6071 (95% CI:0.24-1942.38); p-value: 0.1806).Leave-one-out, MR-Egger, and MR-PRESSO analyses produced consistent results.

Conclusion

The use of metformin and gliclazide have the potential to increase the risk of erectile dysfunction. There is no causal relationship between the use of insulin and erectile dysfunction.

Mechanisms of Flavonoids and Their Derivatives in Endothelial Dysfunction Induced by Oxidative Stress in Diabetes

Diabetic complications pose a significant threat to life and have a negative impact on quality of life in individuals with diabetes. Among the various factors contributing to the development of these complications, endothelial dysfunction plays a key role. The main mechanism underlying endothelial dysfunction in diabetes is oxidative stress, which adversely affects the production and availability of nitric oxide (NO). Flavonoids, a group of phenolic compounds found in vegetables, fruits, and fungi, exhibit strong antioxidant and anti-inflammatory properties. Several studies have provided evidence to suggest that flavonoids have a protective effect on diabetic complications. This review focuses on the imbalance between reactive oxygen species and the antioxidant system, as well as the changes in endothelial factors in diabetes. Furthermore, we summarize the protective mechanisms of flavonoids and their derivatives on endothelial dysfunction in diabetes by alleviating oxidative stress and modulating other signaling pathways. Although several studies underline the positive influence of flavonoids and their derivatives on endothelial dysfunction induced by oxidative stress in diabetes, numerous aspects still require clarification, such as optimal consumption levels, bioavailability, and side effects. Consequently, further investigations are necessary to enhance our understanding of the therapeutic potential of flavonoids and their derivatives in the treatment of diabetic complications.

N-acetylcysteine ameliorates erectile dysfunction in rats with hyperlipidemia by inhibiting oxidative stress and corpus cavernosum smooth muscle cells phenotypic modulation

Hyperlipidemia is a major risk factor for erectile dysfunction (ED). Oxidative stress and phenotypic modulation of corpus cavernosum smooth muscle cells (CCSMCs) are the key pathological factors of ED. N-acetylcysteine (NAC) can inhibit oxidative stress; however, whether NAC can alleviate pathological variations in the corpus cavernosum and promote erectile function recovery in hyperlipidemic rats remains unclear. A hyperlipidemia model was established using 27 eight-week-old male Sprague-Dawley (SD) rats fed a high-fat and high-cholesterol diet (hyperlipidemic rats, HR). In addition, 9 male SD rats were fed a normal diet to serve as controls (NC). HR rats were divided into three groups: HR, HR+normal saline (NS), and HR+NAC (n = 9 for each group; NS or NAC intraperitoneal injections were administered daily for 16 weeks). Subsequently, the lipid profiles, erectile function, oxidative stress, phenotypic modulation markers of CCSMCs, and tissue histology were analyzed. The experimental results revealed that erectile function was significantly impaired in the HR and HR + NS groups, but enhanced in the HR + NAC group. Abnormal lipid levels, over-activated oxidative stress, and multi-organ lesions observed in the HR and HR + NS groups were improved in the HR + NAC group. Moreover, the HR group showed significant phenotypic modulation of CCSMCs, which was also inhibited by NAC treatment. This report focuses on the therapeutic effect of NAC in restoring erectile function using a hyperlipidemic rat model by preventing CCSMC phenotypic modulation and attenuating oxidative stress.

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.

Extracellular Matrix and Protein Phosphorylation Dysregulation Related to Diabetes-Induced Erectile Dysfunction

Diabetes can cause erectile dysfunction (ED) in more than half of male patients. However, the mechanisms underlying diabetes-induced erectile dysfunction (DED) remain unknown. This study is aimed at systematically analyzing the cellular and molecular mechanisms leading to DED using bioinformatic analysis and providing molecular targets for predicting and treating DED. In total, we identified 800 DEGs in the DED samples compared with those in the control group. The 407 upregulated DEGs were mainly enriched in glucose and lipid metabolism-related pathways, and the 393 downregulated DEGs were primarily enriched in tissue development and structure. Dysregulated extracellular matrix genes (especially collagen and elastin) may be closely related to damage to the erectile function of the corpus cavernosum. Sixteen hub genes and 24 modules were detected with hub genes and MCODE analysis. The consensus sequence AAA (G/C) AAA was observed at the promoter sites of most genes that were enriched in the “posttranslational protein phosphorylation” pathway. These genes had abundant phosphorylation sites. Furthermore, 20 TFs targeting DEGs were identified using ChEA3 tool. In conclusion, our research comprehensively and systematically describes the molecular characteristics of DED and suggests that dysregulated extracellular matrix genes and protein phosphorylation may play critical roles in DED. Therefore, they may be potential markers for diagnosing and treating DED.

Paeonol ameliorates diabetic erectile dysfunction by inhibiting HMGB1/RAGE/NF-kB pathway

BACKGROUND

The management of diabetes mellitus-induced erectile dysfunction (DMED) is progressively becoming tricky due to the surge in the number of patients and the poor efficiency of phosphodiesterase type 5 inhibitors in DMED. Paeonol (Pae), as a traditional Chinese medicine, has been more and more widely used in the treatment of diabetic complications. However, whether Pae could be a potential therapeutic drug of DMED needs to be further evaluated.

OBJECTIVES

To investigate the pharmacological effect and possible mechanism of Pae in the treatment of DMED.

METHODS

Intraperitoneal streptozotocin injection and an apomorphine test were used to construct the model of DMED. Seventeen DMED rats were divided into two groups: DMED group (n = 8) and DMED+Pae group (Pae; 100 mg/kg/d; oral administration; n = 9). In addition, there were still 10 normal age-matched male rats as control group. Four weeks later, the cavernous nerve electric stimulation was carried out to measure the erectile response. Moreover, the corpus cavernosum smooth muscle cells (CCSMCs) were primarily isolated and exposed to high glucose (HG) stimulation, Pae treatment and glycyrrhizin (GL; the selective inhibitor of HMGB1). After an incubation for 1 week, the CCSMCs were harvested for detection.

RESULTS

The impairment of erectile function was observed in DMED rats compared with control samples, accompanied by the upregulation of HMGB1/RAGE/NF-κB Pathway. The lower nitric oxide and cGMP level and the higher level of inflammation, fibrosis, and apoptosis were also observed in DMED rats. It showed contrast that Pae treatment could improve the erectile function, as well as histologic alteration and related molecular changes. In addition, Pae could downregulate the HMGB1/RAGE/NF-κB pathway to regulate the apoptosis and inflammation levels of CCSMCs in high-glucose conditions, which is similar to the results of GL treatment.

CONCLUSION

Pae alleviated ED in DMED rats, likely by inhibiting HMGB1/RAGE/NF-κB Pathway, inflammatory, apoptosis, and fibrotic activity, and moderating endothelial dysfunction. Our study provide evidence for a potential new therapy for DMED.

Effects of diet and antihyperglycemic drugs on erectile dysfunction: A systematic review

BACKGROUND

Erectile dysfunction is recognized as one of the complications of diabetes mellitus. To date, a wide gap of knowledge is present on the efficacy of pharmacological treatments of diabetes mellitus on erectile function, acting not only through metabolic control. Similarly, the effects of different diet regimens on erectile dysfunction are still debated.

OBJECTIVES

We aimed to explore the effects of diet and antihyperglycemic drugs, considering both old and novel therapeutic approaches, on erectile function.

MATERIALS/METHODS

We performed a systematic review, following the PRISMA guidelines. The research was conducted on studies reporting erectile dysfunction assessment in subjects with diabetes and the relationship with diet and antihyperglycemic drugs.

RESULTS

The Mediterranean diet was effective in most studies for the protection of erectile function. Furthermore, antihyperglycemic drugs seem to show an overall protective role on erectile function.

DISCUSSION/CONCLUSION

Although encouraging results are present for all classes of antihyperglycemic drugs, several studies are needed in humans, mainly on acarbose, pioglitazone, dipeptidyl-peptidase-4 inhibitors, and sodium-glucose cotransporter-2 inhibitors.

Therapeutic effects of icariin and icariside II on diabetes mellitus and its complications

Diabetes mellitus (DM) is a global health issue in the twenty-first century, and there are numerous challenges in preventing and alleviating its chronic complications. The herb Epimedium has beneficial therapeutic effects on various human diseases, including DM. Its major flavonoid component, icariin, has significant anti-DM activity and may help improve pancreatic β-cell dysfunction and insulin resistance. Furthermore, preclinical evidence has shown that icariin and its in vivo bioactive form, icariside II, have preventive and therapeutic effects on several diabetic complications, including diabetic cardiomyopathy, diabetic vascular endothelial disorder, diabetic nephropathy, and diabetic erectile dysfunction. In this review, we present the general and toxicological information concerning icariin and icariside II and review the anti-DM effects of icariin from a molecular perspective. Additionally, we discuss the potential benefits of icariin and icariside II on the important pathological mechanisms of various diabetic complications. Despite positive preclinical evidence, additional investigations are needed before relevant clinical studies can be conducted. Therefore, we conclude with suggestions for future research. Hopefully, this review will provide a comprehensive molecular perspective for future research and product development related to icariin and icariside II in treating DM and diabetic complications.

[Effects of 4'-O-methylochnaflavone on endothelial dysfunction induced by palmitic acid in rat cavernous endothelial cells]

OBJECTIVE

To investigate the effect of biflavonoid 4'-O-methylochnaflavone (MF) on palmitic acid-induced endothelial dysfunction in rat cavernous endothelial cells (RCECs).

METHODS

The isolated RCECs were commercially available and randomly divided into four groups: normal+BSA group (NC group), palmitic acid (PA) group, MF group, and icariside Ⅱ (ICA Ⅱ) group. The protein expression levels of protein kinase B (PKB/AKT) and endothelial nitric oxide synthase (eNOS) in each group were evaluated via Western blotting. The differences in the intracellular nitric oxide of RCECs treated by MF or ICA Ⅱ were detected by DAF-FM DA that served as a nitric oxide fluorescent probe. Effects of MF and ICA Ⅱ on cell proliferation of PA-stimulated RCECs were determined via CCK-8 assay.

RESULTS

The content of nitric oxide in RCECs was significantly increased after the treatment of MF and ICA Ⅱ in comparison with the NC group (P < 0.05). Moreover, compared with ICA Ⅱ group, MF demonstrated a more obvious effect in promoting nitric oxide production (P < 0.05). Compared with the NC group, the expression levels of eNOS and AKT in the PA group were significantly decreased, indicating that a model for simulating the high-fat environment in vitro was successfully constructed (P < 0.05). Meanwhile, the intervention of MF and ICA Ⅱ could effectively increase the expression of eNOS and AKT, suggesting that MF and ICA Ⅱ could promote the recovery of endothelial dysfunction caused by high levels of free fatty acids (P < 0.05). The results of CCK-8 assays showed that PA could significantly reduce the proli-feration ability of RCECs (P < 0.05). Furthermore, the decreased cell viability induced by PA was significantly elevated by treatment with ICA Ⅱ and MF (P < 0.05).

CONCLUSION

In RCECs, MF and ICA Ⅱ could effectively increase the content of nitric oxide. The down-regulation of the expression of proteins associated with the AKT/eNOS pathway after PA treatment revealed that this pathway was involved in the development of endothelial dysfunction, which could be effectively reversed by MF and ICA Ⅱ. In addition, the cell proliferation ability was significantly decreased following PA treatment, but MF and ICA Ⅱ could restore the above changes. Overall, biflavonoid MF has an obvious repairing effect on PA-stimulated endothelial dysfunction.

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.

The near-infrared dye IR-61 restores erectile function in a streptozotocin-induced diabetes model via mitochondrial protection

This study aimed to evaluate the therapeutic effect of IR-61, a novel mitochondrial heptamethine cyanine dye with antioxidant effects, on diabetes mellitus-induced erectile dysfunction (DMED). Eight-week-old male Sprague-Dawley rats were intraperitoneally injected with streptozotocin (STZ) to induce type 1 diabetes. Eight weeks after STZ injection, all rats were divided into three groups: the control group, DM group, and DM + IR-61 group. In the DM + IR-61 group, the rats were administered IR-61 (1.6 mg kg^-1) twice a week by intravenous injection. At week 13, erectile function was evaluated by determining the ratio of the maximal intracavernous pressure to mean arterial pressure, and the penises were then harvested for fluorescent imaging, transmission electron microscopy, histological examinations, and Western blot analysis. Whole-body imaging suggested that IR-61 was highly accumulated in the penis after intravenous injection. IR-61 treatment significantly improved the maximal ICP of diabetic rats. Additionally, IR-61 ameliorated diabetes-induced inflammation, apoptosis, and phenotypic transition of corpus cavernosum smooth muscle cells (CCSMCs) in penile tissue. IR-61 also attenuated mitochondrial damage, reduced reactive oxygen species production in the corpus cavernosum and upregulated sirtuin1 (SIRT1), sirtuin3 (SIRT3), nuclear factor (erythroid-derived 2)-like 2 (Nrf2), and heme oxygenase expression in penile tissue. In conclusion, IR-61 represents a potential therapeutic option for DMED by protecting the mitochondria of CCSMCs, which may be mediated by activation of the SIRT1, SIRT3, and Nrf2 pathways.

Harnessing Stem Cell Potential for the Treatment of Erectile Function in Men with Diabetes Mellitus: From Preclinical/Clinical Perspectives to Penile Tissue Engineering

Background::

According to the World Health Organization, more than 150 million people are diabetic, and this number will increase twofold by the year 2025. Diabetes-related complications affect all body organ systems, including the penis. Diabetes-induced Erectile Dysfunction (ED) is caused by neuropathy of the penile nerves and vasculopathy involving the smooth muscle and endothelium of the corpus cavernosum.

Objective::

This study aims to present an overview of Stem Cell (SC) research in diabetic animal models of ED, focusing on the function, signaling, and niches that have a prominent role in the regeneration of cavernosal cells and penile tissues. We highlight common erectile pathologies caused by diabetes and review relevant preclinical trials. We also discuss paracrine mechanisms of various SC therapies involved in the repair of endothelial cells and cavernous nerves in these diabetic models.

Method::

A PubMed search was performed, with dates ranging from inception until Mar 31, 2019.

Results::

This review provides a comprehensive evaluation of the various strategies that have been investigated for improving SC delivery methods, through preclinical literature and published clinical trials regarding ED in men with diabetes. Various cell-type applications have benefited erectile function in diabetic models of ED.

Conclusion::

This review examines the progress and remaining challenges in diabetes-related SC research regarding ED. Moving forward, it is only with a combined effort of basic biology and translational work that the potential of SC-based therapies in diabetes in ED can be realized.

Icariside II, a PDE5 Inhibitor, Suppresses Oxygen-Glucose Deprivation/Reperfusion-Induced Primary Hippocampal Neuronal Death Through Activating the PKG/CREB/BDNF/TrkB Signaling Pathway

Background

Ischemic stroke remains the leading cause of death and adult disability. Cerebral ischemic/reperfusion (I/R) injury is caused by ischemic stroke thereafter aggravates overwhelming neuronal apoptosis and even the death of neurons. Of note, hippocampus is more susceptive to cerebral I/R injury than the other brain region. This study was designed to explore the effects and mechanism of icariside II (ICS II), a pharmacologically active compound exists in herbal Epimedii with previous study-proved as a phosphodiesterase 5 (PDE5) inhibitor, on the oxygen glucose deprivation/reoxygenation (OGD/R)-induced primary hippocampal neurons injury.

Methods

Effects of ICS II on primary hippocampal neuronal impairment and apoptosis induced by OGD/R were examined by MTT, lactate dehydrogenase (LDH) release, TUNEL staining, and flow cytometry, respectively. Activation of memory-related signaling pathways was measured using Western blot analysis. The direct interaction between ICS II and PDE5 was further evaluated by molecular docking.

Results

ICS II (12.5, 25, 50 μM) markedly abrogated OGD/R-induced hippocampal neuronal death as suggested by the increase in neurons viability and the decrease in cellular LDH release. Furthermore, ICS II not only effectively decreased the protein expression and activity of PDE5, restored the 3′5′-cyclic guanosine monophosphate (cGMP) level and its downstream target protein kinase G (PKG) activity but also increased the phosphorylation of cAMP response element binding protein (CREB) level, expressions of brain derived neurotrophic factor (BDNF), and tyrosine protein kinase B (TrkB). Mechanistically, the inhibitory effects of ICS II were abrogated by Rp-8-Br-cGMP (a PKG inhibitor) or ANA-12 (a TrkB inhibitor), which further confirmed that the favorable effects of ICS II were attributed to its activation of the PKG/CREB/BDNF signaling pathways. Intriguingly, ICS II might effectively bind and inhibited PDE5 activity as demonstrated by relatively high binding scores (−6.52 kcal/mol).

Conclusions

ICS II significantly rescues OGD/R-induced hippocampal neuronal injury. The mechanism is, at least partly, due to inhibition of PDE5 and activation of PKG/CREB/BDNF/TrkB signaling pathway. Hence it is thought that ICS II might be a potential naturally PDE5 inhibitor to combat cerebral I/R injury.

Icariside II, a phosphodiesterase 5 inhibitor, attenuates cerebral ischaemia/reperfusion injury by inhibiting glycogen synthase kinase-3β-mediated activation of autophagy

Background and Purpose

Cerebral ischaemia/reperfusion causes exacerbated neuronal damage involving excessive autophagy and neuronal loss. The present study was designed to investigate the effect of icariside II, one of main active ingredients of Herba Epimedii on this loss and whether this is related to its PDE 5 inhibitory action.

Experimental Approach

Focal cerebral ischaemia was induced in the rat by transient middle cerebral artery occlusion over 2 hr, followed by reperfusion with icariside II, 3‐methylamphetamine or rapamycin. The effect of icariside II was determined measuring behaviour changes and the size of the infarction. The expressions of PDE 5, autophagy‐related proteins and the level of phosphorylation of glycogen synthase kinase‐3β (GSK‐3β) were determined. Cultured primary cortical neurons were subjected to oxygen and glucose deprivation followed by reoxygenation in the presence and absence of icariside II. A surface plasmon resonance assay and molecular docking were used to explore the interactions of icariside II with PDE 5 or GSK‐3β.

Key Results

Icariside II not only protected against induced ischaemic reperfusion injury in rats but also attenuated such injury in primary cortical neurons. The neuroprotective effects of icariside II on such injury were attributed to interfering with the PKG/GSK‐3β/autophagy axis by directly bounding to PDE 5 and GSK‐3β.

Conclusions and Implications

These findings indicate that icariside II attenuates cerebral I/R‐induced injury via interfering with PKG/GSK‐3β/autophagy axis. This study raises the possibility that icariside II and other PDE 5 inhibitors maybe effective in the treatment ischaemia stroke.

Effects of icariside II on brain tissue oxidative stress and Nrf2/HO-1 expression in rats with cerebral ischemia-reperfusion injury1

PURPOSE

To investigate the effects of icariside II on brain tissue oxidative stress and Nrf2/HO-1 expression in rats with cerebral ischemia-reperfusion injury (CIRI).

METHODS

One hundred SD rats were randomly divided into sham-operated, model, and 5, 10 and 20 mg/kg icariside II groups, 20 rats in each group. The middle cerebral artery occlusion model (ischemia for 2 h followed by reperfusion for 24 h) was established in the later 4 groups. In later 3 groups, at reperfusion beginning, the rats were intragastrically administrated with 5, 10 and 20 mg/kg icariside II, respectively. After 24 h of reperfusion, the neurological severity score, cerebral water content and cerebral infarction volume, brain tissue oxidative stress indexes and Nrf2 and HO-1 protein expressions were determined.

RESULTS

Compared with model group, in 20 mg/kg icariside II group the neurological severity score, cerebral water content and cerebral infarction volume, brain tissue ROS content and MDA level were significantly decreased (P<0.05), and the brain tissue SOD, GSH-Px and catalase levels and Nrf2 and HO-1 protein levels were significantly increased (P<0.05).

CONCLUSION

Icariside II can alleviate the CIRI in rats through reducing brain tissue oxidative stress and improving Nrf2/HO-1 expression.

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.

Neuroprotective effects of melatonin on erectile dysfunction in streptozotocin-induced diabetic rats

PURPOSE

To explore the neuroprotective effects and its possible mechanisms of melatonin (MT) on erectile dysfunction in streptozotocin-induced diabetic rats.

METHODS

Twenty-eight Sprague-Dawley rats received intraperitoneal injection of streptozotocin and 8 weeks later, the determined diabetic rats randomly got intraperitoneal injection of phosphate buffer solution (PBS) or MT. Another 12 normal rats received PBS treatment. Four weeks later, intracavernous pressure, mean arterial pressure, pathological changes in penis, and major pelvic ganglion (MPG) were measured. Malondialdehyde, superoxide dismutase, p38 and p-p38 levels in penis were detected.

RESULTS

Diabetic rats showed significant decreases of erectile function accompanied with serious neuropathy in dorsal penile nerve (DPN) and MPG, meanwhile collagen deposition, oxidative stress, and p-p38 levels in penis were elevated. Melatonin treatment partially but significantly improved the erectile function, ameliorated neuropathy in DPN and MPG, and decreased collagen deposition, oxidative stress, and p-p38 levels in diabetic rats.

CONCLUSIONS

Melatonin treatment helps improve erectile function and ameliorate neuropathy and fibrosis in diabetic rats. These may be associated with reductions in oxidative stress, p38MAPK signaling pathway, and neuropathy.

Pharmacotherapy for erectile dysfunction in diabetic males

INTRODUCTION

Numerous studies have highlighted the intimate association between erectile dysfunction (ED) and diabetes mellitus (DM). However, the true pathogenesis of ED among diabetic men has not yet been fully discovered. The treatment of ED in diabetic patients remains an interesting area of research. The last two decades have witnessed phenomenal advances in the management of ED with the efficacy of pharmacotherapy for ED in diabetic patients encouraging, especially with introduction of innovative conservative tools for treatment.

AREAS COVERED

The aim of this review is to discuss the currently available information on ED pharmacotherapy in diabetic males and provide an expert perspective on the current treatment strategies.

EXPERT OPINION

Conservative treatment remains the initial step for the treatment of ED in diabetic patients. This kind of therapy consists of different modalities including: oral treatments, intracavernosal pharmacotherapy, and evolving modalities such as soluble guanylate cyclase activators, stem cells (SCs), and alternative treatments such as herbal treatment and transdermal/topical pharmacotherapy. However, it should be noted that the currently available pharmacotherapy is still far from ideal. One hopes to witness new drugs and technologies that may revolutionize ED treatment in the future, especially in such complex cases as DM.

In Situ Activation and Preservation of Penile Progenitor Cells Using Icariside II in an Obesity-Associated Erectile Dysfunction Rat Model

Obesity-associated erectile dysfunction (ED) involves pathologic change that may be related to deficit of the penile endogenous stem/progenitor cells. Therefore, an in-depth study of the penile stem/progenitor cells in the pathogenesis of ED is warranted. For this study, eight Zucker Lean (ZUC-Lepr^fa 186; ZL group) and 16 Zucker Fatty (ZUC-Lepr^fa 185; ZF) male rats received an intraperitoneal injection of 5-ethynyl-2-deoxyuridine (EdU) to track endogenous stem cells. Twelve weeks later, the ZF rats were randomized to gavage feeding with 1.5 mg/kg/day of icariside II (ZF + ICA II group) or the solvent (ZF group). Treatment lasted 4 weeks and was followed by a 1-week washout period. ZF rats had impaired erectile function with related pathologic changes compared with ZL rats. ICA II treatment restored erectile function and prevented smooth muscle atrophy, endothelial dysfunction, and lipid accumulation compared with no treatment. EdU label-retaining cell levels were higher in the ZF + ICA II group compared with the ZF group. Histone 3 phosphorylation at Ser 10, a specific mitotic cell marker, was additionally used to identify dividing cells. ICA II activated more penile stem cells to proliferate in ZF rats compared with ZL rats. These results suggest that ZF rats can be used as a model for obesity-associated ED and that ICA II improves erectile function and pathologic changes through endogenous progenitor cell preservation and proliferation.

IcarisideII improves left ventricular remodeling in spontaneously hypertensive rats by inhibiting the ASK1-JNK/p38 signaling pathway

Inhibition or removal of excess reactive oxygen species can effectively protect cellular function or reduce cell death because oxidative stress is the main cause of cellular damage in many diseases. The flavonoid compound IcarisideII having a slight inhibitory effect on PDE5, is the main active components of epimedium in vivo and has a wide range of pharmacological effects on oxidation and apoptosis. However, whether IcarisideII has the same protective effect on ventricular remodeling in spontaneously hypertensive rats (SHR) is unknown. We found that compared with WKY rats, SHRs exhibited noticeable arterial hypertension. Additionally, echocardiography showed that the diameter of the left ventricle was enlarged, wall thickness was increased, and ejection fraction and short axis shortening rate were reduced. H&E staining demonstrated that SHR cells were disordered and noticeably hypertrophic. Masson trichrome staining revealed significant myocardial fibrosis in the myocardium. Tunel staining indicated that 4.39 times the percent of apoptotic cells were present in SHRs compared to WKY rats. In our study, intra-gastric administration of IcarisideII decreased blood pressure, promoted heart function recovery and improved ventricular remodeling in SHRs. Additionally, it reduced myocardial fibrosis, inhibited myocardial apoptosis, decreased the generation of reactive oxygen species and improved SOD activity. IcarisideII down-regulated the activation of the oxidative stress associated proteins ASK1, p38 and JNK; inhibited the expression of p53, Bax and cleaved-caspase3 in the mitochondrial apoptosis pathway; and up-regulated the expression of Bcl-2. In conclusion, this study indicates that IcarisideII can inhibit myocardial apoptosis and improve left ventricular remodeling in SHRs. It can be inferred that this mechanism may be related to the inhibition of the ASK1-JNK/p38 signaling pathway.

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.

Molecular mechanisms associated with diabetic endothelial-erectile dysfunction

Erectile dysfunction (ED) is a common complication of diabetes, affecting up to 75% of all diabetic men. Although the aetiology of diabetic ED is multifactorial, endothelial dysfunction is recognized as a mainstay in the pathophysiology of the disease. Endothelial dysfunction is induced by the detrimental actions of high glucose levels and increased oxidative stress on endothelial cells that make up the vascular lining. Besides directly injuring the endothelium, diabetes might also hamper vascular repair mechanisms of angiogenesis and vasculogenesis. These states exacerbate and maintain endothelial dysfunction, impairing vasorelaxation events and cavernosal blood perfusion, which are crucial for normal erectile function.