Hyperhomocysteinaemia in rats is associated with erectile dysfunction by impairing endothelial nitric oxide synthase activity

Repeated platelet-rich plasma injections improve erectile dysfunction in a rat model of hyperhomocysteinemia

ABSTRACT

Platelet-rich plasma (PRP) shows promise as a regenerative modality for mild-to-moderate erectile dysfunction (ED). However, its efficacy in treating severe ED remains unknown. Blood samples from 8-week-old male rats were used to prepare PRP through a two-step centrifugation procedure, followed by chitosan activation and freeze thaw cycle. A hyperhomocysteinemia (HHcy)-related ED model was established using a methionine-enriched diet, and an apomorphine (APO) test was conducted during the 4 th week. APO-negative rats were divided into two groups and were injected with PRP or saline every 2 weeks. Erectile function and histological analyses of the corpus cavernosum were performed during the 16 th week. The results revealed that erectile function was significantly impaired in rats with HHcy-related ED compared to that in age-matched rats but was improved by repeated PRP injections. Immunofluorescence staining revealed a reduction in reactive oxygen species and additional benefits on the recovery of structures within the corpus cavernosum in rats that received PRP treatment compared to those in the saline-injected control group. Therefore, PRP could enhance functional and structural recovery in a severe HHcy-related ED model. A notable strength of the present study lies in the use of a repeated intracavernous injection method, mirroring protocols used in human studies, which offers more reliable results for translating the findings to humans.

Methylenetetrahydrofolate reductase (MTHFR) polymorphisms in andrology-a narrative review

Background and Objective

Methylenetetrahydrofolate reductase (MTHFR) is a key enzyme involved in folate metabolism and one-carbon metabolism. MTHFR gene polymorphism affects enzyme activity. MTHFR gene polymorphism is closely related to many human diseases, such as cardiocerebrovascular diseases, diabetes, neural tube defects (NTDs), tumors, and so on. In the field of Andrology, MTHFR gene polymorphism may be associated with male infertility and erectile dysfunction (ED), and there is a possibility of treating male infertility and ED by supplementing with folic acid. However, its exact pathophysiologic mechanism is not fully understood. We sought to obtain a robust understanding of the interactions between MTHFR gene polymorphism, oxidative stress, DNA methylation, hyperhomocysteinemia (HHcy), male infertility, and ED.

Methods

We performed a non-systematic literature review using the PubMed database to identify articles specifically related to MTHFR, male infertility and ED.

Key Content and Findings

Our literature review on MTHFR gene polymorphism in male infertility patients indicates a significant association between C677T gene polymorphism and male infertility. There is limited literature on the correlation between ED and MTHFR gene polymorphism, and there are two different conclusions, related and unrelated. More clinical data are needed to clarify the conclusion. There is a possibility of using folic acid supplementation to treat male infertility and ED, especially for patients with thymine-thymine (TT) genotype. Future research is necessary to further understand the relationship between MTHFR gene polymorphism and male infertility and ED.

Conclusions

Our literature review on MTHFR gene polymorphism in male infertility patients indicates a significant association between C677T gene polymorphism and male infertility. Folic acid supplementation can improve sperm quality. The correlation between MTHFR gene polymorphisms and ED is questionable and needs to be confirmed by more clinical data. MTHFR gene polymorphisms are associated with homocysteine (Hcy) levels, which affects vascular endothelial function and may be related to the development of vascular ED (VED). Folic acid supplementation improves International Index for Erectile Function (IIEF) questionnaire scores in ED patients in whom phosphodiesterase 5 inhibitor (PDE5i) alone is ineffective.

Dietary intakes of vitamin B6, folate, vitamin B12 and erectile dysfunction: a national population-based study

Background

While deficiencies in vitamin B6, folate, and vitamin B12 are linked to various human diseases, including anemia, depression, peripheral neuropathy, and cardiovascular disease (CVD), literature regarding the association between vitamin B6, folate, and vitamin B12 and erectile dysfunction (ED) is scarce. We aimed to determine the dietary intake of vitamin B6, folate, and vitamin B12 and ED in the United States population.

Methods

We extracted data from the 2001-2004 cycles of the National Health and Nutrition Examination Survey (NHANES). Dietary intakes of B vitamins were collected based on one 24-hour dietary recall. The association between dietary intake of vitamin B6, folate, vitamin B12 and ED was examined using multivariate logistic regression models.

Results

A total of 3,875 participants were included for analysis, with 1,201 reporting ED and 2,894 not experiencing ED. The multivariable odds ratios (ORs) for the highest vs. lowest quartiles of vitamin B6 was 0.77 [95% confidence interval (CI): 0.60-0.99; P for trend =0.03] for the prevalence of ED. Subgroup analyses demonstrated a significant inverse association between dietary intake of vitamin B6, folate, vitamin B12 and the prevalence of ED among men aged ≤60 years, individuals of Mexican American and non-Hispanic White ethnicity, and those without a history of CVD, diabetes, hypertension, and high cholesterol.

Conclusions

The consumption of dietary vitamin B6, folate, and vitamin B12 was significantly linked to decreased risks of ED among younger healthier men, suggesting a potential protective role of these nutrients against ED in United States adults.

Homocysteine levels correlate with velocimetric parameters in patients with erectile dysfunction undergoing penile duplex ultrasound

INTRODUCTION

Hyperhomocysteinemia may contribute to the development of endothelial dysfunction and, consequently, atherosclerosis, a systemic disease involving the vessels that may affect the cavernous arteries leading to vasculogenic erectile dysfunction. Our study aims therefore to explore the relationship between homocysteine levels and velocimetric parameters detected by basal penile duplex ultrasound such as peak systolic velocity and flaccid penile acceleration in patients with erectile dysfunction.

METHODS

A cross-sectional study was conducted collecting clinical, metabolic, hormonal, and instrumental (basal penile duplex ultrasound) data in patients affected by vasculogenic erectile dysfunction.

RESULTS

Data of 126 subjects affected by erectile dysfunction were collected. Mean age was 52.1 ± 12.6 years, whereas mean body mass index was 25.6 ± 4.0 kg/m² . Basal penile duplex ultrasound showed peak systolic velocity values of 13.1 ± 2.9 cm/s and mean flaccid penile acceleration of 2.28 ± 0.70 m/s² , with a strong correlation among these two parameters (r = 0.690; p < 0.001). Frankly pathological values of peak systolic velocity and flaccid penile acceleration were detected in 39.7% and 4.8% of the subjects examined, respectively. Mean homocysteine levels were 14.9 ± 9.5 μmol/l. Homocysteine values >15 μmol/l were found in 26% of the subjects with erectile dysfunction. Peak systolic velocity values and homocysteine levels showed an inverse correlation (r = -0.213; p = 0.03). Similarly, flaccid penile acceleration values were inversely correlated to homocysteine levels (r = -0.199; p = 0.05). In addition, an inverse correlation was found between both peak systolic velocity and flaccid penile acceleration and body mass index, atherogenic lipid pattern, and age. Homocysteine and metabolic parameters showed no significant correlations.

CONCLUSION

Hyperhomocysteinemia is highly prevalent in erectile dysfunction patients. The results of our study show that homocysteine levels correlate with velocimetric parameters assessed by basal penile duplex ultrasound, confirming the role of hyperhomocysteinemia in the genesis of erectile dysfunction of arterial origin.

Effect of Antioxidants Supplementation on Erectile Dysfunction: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

INTRODUCTION

In Erectile dysfunction (ED) patients, phosphodiesterase type 5 (PDE5) inhibitors are considered as the first-line therapy. However, 30-50% of ED patients fail to follow this therapeutic option because of adverse events, lack of efficacy, or drug costs. Antioxidant supplementation is widely applied in clinical practice and viewed as a potential therapeutic option for ED. Therefore, it is attractive to assess the effect of antioxidants supplementation on ED patients.

OBJECTIVES

To evaluate the effects of antioxidants supplementation on ED.

METHODS

Published randomized controlled trials of antioxidants in ED were searched in the PubMed, Embase, and Cochrane Library databases from inception to October 3, 2021. Meta-analyses were carried out using a random-effects model. The results were presented as standard mean differences (SMDs) with their 95% confidence intervals (CIs).

RESULTS

Eighteen studies with 1,331 ED patients were included in the study. Compared with placebo, antioxidants alone treatment showed a statistical increase in International Index of Erectile Function (IIEF) score (SMD = 1.93; 95% CI: 0.15, 3.72; P = .034). Compared with placebo, antioxidants compound treatment elicited a significant increase in IIEF score (SMD = 2.74; 95% CI: 1.67, 3.81; P < .001) as well as sexual satisfaction score (SMD = 1.61; 95% CI: 0.63, 2.59; P = .001). Compared with the PDE5 inhibitors alone, combination of PDE5 inhibitors and antioxidants showed a significant increase in IIEF score (SMD = 1.1; 95% CI: 0.51, 1.68; P < .001) and sexual satisfaction score (SMD = 1.28; 95% CI: 0.06, 2.51; P = .04).

CONCLUSION

This study found that the effect of antioxidant alone treatment on ED may be limited. However, antioxidant compound treatment, as well as combination of PDE5 inhibitors and antioxidants, were associated with improved ED, and can be considered as an accessary therapeutic option for ED. Su L, Yang Z, Qu H, et al. Effect of Antioxidants Supplementation on Erectile Dysfunction: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Sex Med Rev 2021;XX:XXX-XXX.

Tetrathiomolybdate Partially Alleviates Erectile Dysfunction of Type 1 Diabetic Rats Through Affecting Ceruloplasmin/eNOS and Inhibiting Corporal Fibrosis and Systemic Inflammation

INTRODUCTION

Patients with erectile dysfunction induced by diabetes mellitus (DMED) show a poor effect rate for oral phosphodiesterase type 5 inhibitors (PDE5is). Therefore, the new therapeutic strategy is necessary in patients with DMED.

AIM

To investigate whether Tetrathiomolybdate (TM) supplementation could ameliorate DMED by activation of eNOS.

METHODS

Twenty-four diabetic rats were induced by intraperitoneal injection of streptozotocin (STZ) and the other 6 normal rats constituted the control group. Eight weeks later, the erectile function of rats was assessed with an apomorphine test. Only some rats with DMED were treated with TM orally every day for 4 weeks; the other rats remained in the same condition for 4 weeks. After 1 week washout, the erectile function of rats in each group was evaluated. Then, the serum concentration of IL-6 and histologic changes of corpus cavernosum were measured.

MAIN OUTCOME MEASURE

Erectile function was measured after DMED rats treated with TM. The cavernosum level of Ceruloplasmin (Cp), eNOS, endothelial cell content, corporal fibrosis, apoptosis rate and the serum level of IL-6 were also assayed.

RESULTS

Erectile function in the DMED group was significantly impaired compared with the control group and was partly, but significantly, improved in the DMED+TM group. The DMED group showed upregulation of Cp and inhibition of eNOS, but the inhibition was partly reversed in the DMED+TM group. The DMED group showed serious corporal fibrosis. However, TM supplementation partly increased the ratio of smooth muscle to collagen, decreased the ratio of apoptosis. What's more, gavage administration of TM profoundly decreased the serum level of IL-6 in DMED rats.

CONCLUSION

TM supplementation inhibits endothelial dysfunction, corporal fibrosis, and systemic inflammation, ultimately leading to partial improvement of DMED in rats. Yin Y, Peng J, Zhou J, et al., Tetrathiomolybdate Partially Alleviates Erectile Dysfunction of Type 1 Diabetic Rats Through Affecting Ceruloplasmin/eNOS and Inhibiting Corporal Fibrosis and Systemic Inflammation. Sex Med 2021;XX:XXXXXX.

Hyperhomocysteinemia: Focus on Endothelial Damage as a Cause of Erectile Dysfunction

Erectile Dysfunction (ED) is defined as the inability to maintain and/or achieve a satisfactory erection. This condition can be influenced by the presence of atherosclerosis, a systemic pathology of the vessels that also affects the cavernous arteries and which can cause an alteration of blood flow at penile level. Among the cardiovascular risk factors affecting the genesis of atherosclerosis, hyperhomocysteinemia (HHcys) plays a central role, which is associated with oxidative stress and endothelial dysfunction. This review focuses on the biological processes that lead to homocysteine-induced endothelial damage and discusses the consequences of HHcys on male sexual function

Ameliorative effect of ozagrel, a thromboxane A2 synthase inhibitor, in hyperhomocysteinemia-induced experimental vascular cognitive impairment and dementia

The present study investigates the effect of ozagrel, a selective thromboxane A2 (TXA2) inhibitor, in rat model of hyperhomocysteinemia (HHcy)-induced vascular cognitive impairment and dementia (VCID). Wistar rats were administered L-methionine (1.7 g/kg/day; p.o. × 8 weeks) to induce VCID. Morris water maze (MWM) test was employed to assess learning and memory. Endothelial dysfunction was assessed in the isolated aorta by observing endothelial-dependent vasorelaxation and levels of serum nitrite. Various biochemical and histopathological estimations were also performed. L-methionine produced significant impairment in endothelium-dependent vasorelaxation and decreases serum nitrite levels indicating endothelial dysfunction. Further, these animals performed poorly on MWM, depicting impairment of learning and memory. Further, a significant rise in brain oxidative stress level (indicated by increase in brain thiobarbituric acid-reactive species and decrease in reduced glutathione levels), brain acetylcholinesterase activity, brain myeloperoxidase activity, brain TNF-α and IL-6 levels, and brain leukocyte (neutrophil) infiltration was also observed. Treatment of ozagrel (10 and 20 mg/kg, p. o.)/donepezil (0.5 mg/kg, i.p., serving as standard) ameliorated L-methionine-induced endothelial dysfunction, memory deficits, and biochemical and histopathological changes. It may be concluded that ozagrel markedly improved endothelial dysfunction, learning and memory, and biochemical and histopathological alteration associated with L-methionine-induced VCID and that TXA2 can be considered as an important therapeutic target for the management of VCID.

Human tissue kallikrein-1 protects against the development of erectile dysfunction in a rat model of hyperhomocysteinemia

The aim of this study was to investigate the mechanism by which a diet inducing high hyperhomocysteinemia (HHcy) leads to the deterioration of erectile function in rats and whether this is inhibited by expression of the human tissue kallikrein-1 (hKLK1) gene. We established a rat model of HHcy by feeding methionine (Met)-rich diets to male Sprague-Dawley (SD) rats. Male wild-type SD rats (WTRs) and transgenic rats harboring the hKLK1 gene (TGRs) were fed a normal diet until 10 weeks of age. Then, 30 WTRs were randomly divided into three groups as follows: the control (n = 10) group, the low-dose (4% Met, n = 10) group, and the high-dose (7% Met, n = 10) group. Another 10 age-matched TGRs were fed the high-dose diet and designated as the TGR+7% Met group. After 30 days, in all four groups, erectile function was measured and penile tissues were harvested to determine oxidative stress, endothelial cell content, and penis fibrosis. Compared with the 7% Met group, the TGR+7% Met group showed diminished HHcy-induced erectile dysfunction (ED), indicating the improvement caused by hKLK1. Regarding corpus cavernosum endothelial cells, hKLK1 preserved endothelial cell-cell junctions and endothelial cell content, and activated protein kinase B/endothelial nitric oxide synthase (Akt/eNOS) signaling. Fibrosis assessment indicated that hKLK1 preserved normal penis structure by inhibiting apoptosis in the corpus cavernosum smooth muscle cells. Taken together, these findings showed that oxidative stress, impaired corpus cavernosum endothelial cells, and severe penis fibrosis were involved in the induction of ED by HHcy in rats, whereas hKLK1 preserved erectile function by inhibiting these pathophysiological changes.

Calpain inhibition improves erectile function in diabetic mice via upregulating endothelial nitric oxide synthase expression and reducing apoptosis

Calpain activation contributes to hyperglycemia-induced endothelial dysfunction and apoptosis. This study was designed to investigate the role of calpain inhibition in improving diabetic erectile dysfunction (ED) in mice. Thirty-eight-week-old male C57BL/6J mice were divided into three groups: (1) nondiabetic control group, (2) diabetic mice + vehicle group, and (3) diabetic mice + MDL28170 (an inhibitor of calpain) group. Type 1 diabetes was induced by intraperitoneal injection of streptozotocin at 60 mg kg⁻¹ body weight for 5 consecutive days. Thirteen weeks later, diabetic mice were treated with MDL28170 or vehicle for 4 weeks. The erectile function was assessed by electrical stimulation of the cavernous nerve. Penile tissues were collected for measurement of calpain activity and the endothelial nitric oxide synthase (eNOS)-nitric oxide (NO)-cyclic guanosine monophosphate (cGMP) pathway. Terminal deoxynucleotidyl transferase 2'-deoxyuridine 5'-triphosphate nick end labeling (TUNEL) staining was used to evaluate apoptosis. Caspase-3 expression and activity were also measured to determine apoptosis. Our results showed that erectile function was enhanced by MDL28170 treatment in diabetic mice compared with the vehicle diabetic group. No differences in calpain-1 and calpain-2 expressions were observed among the three groups. However, calpain activity was increased in the diabetic group and reduced by MDL28170. The eNOS-NO-cGMP pathway was upregulated by MDL28170 treatment in diabetic mice. Additionally, MDL28170 could attenuate apoptosis and increase the endothelium and smooth muscle levels in corpus cavernosum. Inhibition of calpain could improve erectile function, probably by upregulating the eNOS-NO-cGMP pathway and reducing apoptosis.

Melatonin Treatment Ameliorates Hyperhomocysteinemia-Induced Impairment of Erectile Function in a Rat Model

BACKGROUND

Hyperhomocysteinemia (HHcy) has been reported to be strongly correlated with the occurrence of erectile dysfunction (ED), but the mechanisms are not fully understood. Moreover, whether melatonin could be a potential treatment of HHcy-induced ED needs to be elucidated.

AIM

The aim of this study was to investigate the effects of melatonin on HHcy-induced ED and the potential mechanisms via modulating oxidative stress and apoptosis.

METHODS

The Sprague-Dawley (SD) rat model of HHcy was induced by 7% methionine (Met)-rich diets. 36 male SD rats were randomly distributed into 3 groups (n = 12 per group): control group, 7% Met group, and 7% Met + melatonin (Mel; 10 mg/kg, intraperitoneal injection) treatment group. After 4 weeks, the erectile function of all rats was evaluated by electrical stimulation of the cavernous nerve. Histologic and molecular alterations of the corpus cavernosum were also analyzed by immunofluorescence, immunohistochemistry, enzyme-linked immunosorbent assay, Western blotting, and polymerase chain reaction.

OUTCOMES

HHcy-induced ED rat models were successfully established, and Mel could preserve erectile function mainly through inhibiting oxidative stress via the Erk1/2/Nrf2/HO-1 signaling pathway and suppression of apoptosis.

RESULTS

Erectile function was significantly reduced in the rats with HHcy compared with that in the control group and was ameliorated in the HHcy rats treated with Mel. Compared with the control group, the rats in the HHcy group showed the following: (1) higher levels of total plasma homocysteine; (2) fewer neuronal nitric oxide synthase-positive cells in the corpus cavernous; (3) higher levels of reactive oxygen species and malondialdehyde, higher expression levels of nicotinamide adenine dinucleotide phosphate oxidase, and lower activities of superoxide dismutase, indicating an overactivated oxidative stress; (4) lower expression levels of Erk1/2/Nrf2/HO-1 signaling pathway components; and (5) higher levels of apoptosis, as determined by the expression levels of Bax, Bcl-2, and caspase 3. Mel treatment improved the erectile response, as well as histologic and molecular alterations.

CLINICAL TRANSLATION

Our study on a rodent model of HHcy provided evidence that Mel could be a potential therapeutic method for HHcy-related ED.

CONCLUSIONS

Mel treatment improves erectile function in rats with HHcy probably by potential antioxidative stress activity. This finding provides evidence for a potential new therapy for HHcy-induced ED. Tang Z, Song J, Yu, Z, et al. Melatonin Treatment Ameliorates Hyperhomocysteinemia-Induced Impairment of Erectile Function in a Rat Model. J Sex Med 2019;16:1506-1517.