Melatonin Improves Erectile Function in Rats With Chronic Lower Body Ischemia

A review of experimental techniques for erectile function researches and development of medical technology using animal erectile dysfunction models in sexual and reproductive medicine

Background

Erectile dysfunction (ED) is one of the causes of male infertility and is a disease that requires treatment. The first‐line drugs for ED are phosphodiesterase 5 (PDE‐5) inhibitors, and further treatment options are currently limited. Medical technologies, such as genetic control and regenerative medicine, are developing rapidly. Research on erectile function is progressing rapidly, coupled with technological innovations in other areas.

Methods

A PubMed search using the keywords “animal (rat, mouse, rabbit, dog, and monkey)” and “erectile” was conducted, and all relevant peer‐reviewed English results were evaluated.

Main findings

The methods for evaluating erectile function include intracavernous pressure (ICP) measurements, isometric tension studies, and dynamic infusion cavernosometry. Papers also reported various disease model animals for the study of diabetes mellitus, cavernous nerve injury, and drug‐induced ED.

Conclusion

Basic research on ED treatment has progressed rapidly over the past 20 years. In particular, research on the mechanism of ED has been accelerated by the publication of a study on the evaluation of erectile function using ICP measurements in rats. In addition, molecular biological experimental methods such as polymerase chain reaction (PCR) and western blotting have become relatively easy to perform due to technological progress, thus advancing research development.

Curcumin slow-release membrane promotes erectile function and penile rehabilitation in a rat model of cavernous nerve injury

Male erectile dysfunction (ED) caused by cavernous nerve injury is a common complication of pelvic surgery, radiotherapy, transurethral surgery or other operations. However, clinical treatment for iatrogenic or traumatic male ED is difficult and not satisfactory. Many studies have shown that curcumin can promote the repair and regeneration of peripheral nerves; however, whether curcumin can rescue cavernous nerve injury is unknown, and the poor bioavailability of curcumin limits its application in vivo. Hence, the study was conducted. A curved slow-release membrane was produced, and the properties were examined. In addition, the effects of the curcumin slow-release membrane on cavernous nerve-injured SD rats were studied. We found that polylactic acid-glycolic acid-polyethylene glycol (PLGA-PEG) can be used as a good carrier material for curcumin, and curcumin-loaded PLGA-PEG membranes can effectively rescue the cavernous nerve in SD rats, restore the continuity of the cavernous nerve, and increase the expression of nNOS mRNA and proteins in penile tissue, which can improve the penile erectile function of injured SD rats, reduce the degree of penile tissue fibrosis, and effectively promote penis rehabilitation. The curcumin slow-release membrane is proposed to be a new therapeutic approach for penile rehabilitation of cavernous nerve injury.

Melatonin receptor 1A gene polymorphism rs13140012 and serum melatonin in atherosclerotic versus non-atherosclerotic Egyptian ESRD patients: pilot study

Aim

To study the relationship between melatonin levels and Melatonin membrane receptor 1A (MTNR1A) SNP (rs13140012) in end-stage renal disease patients (ESRD) in Alexandria, Egypt on maintenance hemodialysis with or without atherosclerosis.

Materials and methods

40 end-stage renal disease patients on regular hemodialysis were divided into 2 subgroups, one with (n = 20) and one without atherosclerosis (n = 20) and normal subjects (n = 40). Serum melatonin, carotid intimal medial thickness (CIMT) were measured. Melatonin membrane receptor 1A (MTNR1A) SNP (rs13140012) genotyping was done using 5'nuclease Allelic discrimination.

Results

Serum melatonin was significantly lower in ESRD patients [1.6 to 11.30 (pg/mL) with a median of 2.5] than the control group [20.50 to 56.40 (pg/mL) with a median of 35.20]. Serum melatonin was significantly lower in atherosclerotic patients subgroup [1.6–2.50 (pg/mL) with a median value of 2.30] than non-atherosclerotic patients subgroup [2.0–11.30 (pg/mL) with a median of 4.9]. No significant association was found between serum melatonin and (MTNR1A) SNP (rs13140012) (p = 0.633).

Conclusion

These results lead us to suggest that melatonin production is impaired in ESRD patients (included in this pilot study), and this impairment is more evident in atherosclerotic ESRD patients.

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.

Low serum melatonin levels are associated with erectile dysfunction

OBJECTIVE

Melatonin is a hormone secreted from the pineal gland and has anti-oxidative and anti-inflammatory effects. Oxidative stress is considered as an important factor in the etiology of erectile dysfunction (ED), and in many experimental models, positive results have been obtained with melatonin treatment. This study aimed to measure serum melatonin levels in ED patients and to investigate the possible relationship between ED and melatonin levels.

MATERIALS AND METHODS

Sixty-two patients diagnosed with mild, moderate or severe ED according to the five-item International Erectile Function Index (IIEF-5) and 22 healthy individuals were included in the study. The serum melatonin levels, anthropometric data, and other biochemical and hormonal parameters of all the subjects were recorded. Detailed anamnesis was also obtained in terms of diabetes, hypertension, cardiovascular diseases, smoking status, and alcohol use.

RESULTS

The serum melatonin level was found 34.2±13.3 ng/dL in the mild ED group, 33.3±14.7 ng/dL in the moderate ED group, 34.8±17.2 ng/dL in the severe ED group, and 44.6±16.5 ng/dL in the control group. The serum melatonin levels were significantly lower in all ED groups compared to the control group (p=0.019). There was no significant difference in the serum melatonin levels between the three ED groups. Diabetes, hypertension, cardiovascular diseases, smoking and alcohol use were not significantly different between the ED groups (p>0.05).

CONCLUSION

We consider that if our findings are supported by further studies with larger populations, the measurement of the serum melatonin level may have a future role in the diagnosis and treatment of ED.