Impact of melatonin supplementation in the rat spermatogenesis subjected to forced swimming exercise

Impact of melatonin administration on sperm quality, steroid hormone levels, and testicular blood flow parameters in small ruminants: A meta-analysis

Background and Aim

The impact of exogenous melatonin on the sperm quality of small ruminants is controversial. Therefore, this study aimed to synthesize previous findings on the influence of melatonin injection on sperm quality, steroid hormones, and testicular blood flow in small ruminants.

Materials and Methods

Thirty studies were analyzed by computing the raw mean difference (RMD) as the effect size between the control and melatonin treatment groups, using the inverse of the variance for the random-effect model of the method of moments by DerSimonian and Laird. We assessed heterogeneity among studies using Q test. I2 statistic was used to classify the observed heterogeneity. We used Egger's regression method to indicate publication bias.

Results

Melatonin injection (p < 0.05) affected sperm concentration (RMD = 0.42 × 109/mL), morphology (RMD = 2.82%), viability (RMD = 2.83%), acrosome integrity (RMD = 4.26%), and DNA integrity (RMD = 1.09%). Total motility (RMD = 5.62%), progressive motility (RMD = 7.90%), acrosome integrity (RMD = 8.68%), and DNA integrity (RMD = 2.01%) of post-thawed semen in the melatonin-treated group were also increased (p < 0.05). Similarly, treatment with melatonin (p < 0.05) enhanced total motility (RMD = 5.78%), progressive motility (RMD = 5.28%), curvilinear velocity (RMD = 4.09 μm/s), straight-line velocity (RMD = 5.61 μm/s), and average path velocity (RMD = 4.94 μm/s). Testosterone (RMD = 1.02 ng/mL) and estradiol 17-ß levels (RMD = 0.84 pg/mL) were elevated (p < 0.05) in the melatonin-injected group. Melatonin implantation ameliorated testicular blood flow, as indicated by a significant reduction (p < 0.05) in the resistive index (RMD = 0.11) and pulsatility index (RMD = -0.15).

Conclusion

Melatonin administration can increase the reproductive performance of small male ruminants.

Sea cucumber peptides positively regulate sexual hormones in male mice with acute exhaustive swimming: possibly through the Ca2+/PKA signaling pathway

Sea cucumber peptides (SCPs) have been proven to have many active functions; however, their impact on testosterone synthesis and the corresponding mechanism are not yet clear. This study attempts to explore the effects of SCPs on sex hormone regulation in acute exhaustive swimming (AES) male mice and the possible mechanisms. In the present study, SCP intervention significantly prolonged exhaustive swimming time and reduced exercise metabolite accumulation. The reproductive ability-related parameters including penile index, mating ability, testicular morphology, and sperm storage were dramatically improved by SCP intervention. Notably, SCPs markedly reversed the AES-induced decrease in serum testosterone (T), estradiol (E2), and follicle-stimulating hormone (FSH) levels. Moreover, treatment with a high dose of SCP (0.6 mg per g bw) significantly enhanced the expression of testosterone synthesis-related proteins in testis, meanwhile markedly increasing the gene expression of StAR, Hsd17b3, Hsd17b2, Ldlr, and Cyp19a1. Serum metabolomics results indicated that SCP intervention notably upregulated the expression of 1-stearoyl-2-arachidonoyl-sn-glycerol but downregulated the concentrations of succinate and DL-lactate. Furthermore, serum metabolomics combined with testicular transcriptome, western blot, and correlation analyses demonstrated that SCPs may regulate testosterone synthesis via the Ca2+/PKA signaling pathway. This study indicated that the SCP could be a potential dietary supplement to improve the symptoms of decreased sex hormones related to exercise fatigue.

Protective effects of melatonin against physical injuries to testicular tissue: A systematic review and meta-analysis of animal models

BACKGROUND

Modern societies face infertility as a global challenge. There are certain environmental conditions and disorders that damage testicular tissue and may cause male infertility. Melatonin, as a potential antioxidant, may protect testicular tissue. Therefore, we conducted this systematic review and meta-analysis to evaluate the effects of melatonin in animal models against physical, heat, and ischemic damage to the testicular tissue.

METHODS

PubMed, Scopus, and Web of Science were systematically searched to identify animal trials evaluating the protective effect of melatonin therapy on rodent testicular tissue when it is exposed to physical, thermal, ischemic, or hypobaric oxygen stress. Random-effect modeling was used to estimate the standardized mean difference and 95% confidence intervals based on the pooled data. Additionally, the Systematic Review Centre for Laboratory Animal Experimentation (SYRCLE) tool was used to assess the risk of bias. The study protocol was prospectively registered in PROSPERO (CRD42022354599).

RESULTS

A total of 41 studies were eligible for review out of 10039 records. Studies employed direct heat, cryptorchidism, varicocele, torsion-detorsion, testicular vascular occlusion, hypobaric hypoxia, ischemia-reperfusion, stress by excessive or restraint activity, spinal cord injury, and trauma to induce stress in the subjects. The histopathological characteristics of testicular tissue were generally improved in rodents by melatonin therapy. Based on the pooled data, sperm count, morphology, forward motility, viability, Johnsen's biopsy score, testicular tissue glutathione peroxidase, and superoxide dismutase levels were higher in the melatonin treatment rodent arms. In contrast, the malondialdehyde level in testicular tissue was lower in the treatment rodent arms. The included studies suffered from a high risk of bias in most of the SYRCLE domains.

CONCLUSION

This study concludes that melatonin therapy was associated with improved testicular histopathological characteristics, reproductive hormonal panel, and tissue markers of oxidative stress in male rodents with physical, ischemic, and thermal testicular injuries. In this regard, melatonin deserves scientific investigations as a potential protective drug against rodent male infertility.

SYSTEMATIC REVIEW REGISTRATION

https://www.crd.york.ac.uk/PROSPERO/, identifier CRD42022354599.

Circadian Rhythms and Melatonin Metabolism in Patients With Disorders of Gut-Brain Interactions

Circadian rhythms are cyclic patterns of physiological, behavioural and molecular events that occur over a 24-h period. They are controlled by the suprachiasmatic nucleus (SCN), the brain’s master pacemaker which governs peripheral clocks and melatonin release. While circadian systems are endogenous, there are external factors that synchronise the SCN to the ambient environment including light/dark cycles, fasting/fed state, temperature and physical activity. Circadian rhythms also provide internal temporal organisation which ensures that any internal changes that take place are centrally coordinated. Melatonin synchronises peripheral clocks to the external time and circadian rhythms are regulated by gene expression to control physiological function. Synchronisation of the circadian system with the external environment is vital for the health and survival of an organism and as circadian rhythms play a pivotal role in regulating GI physiology, disruption may lead to gastrointestinal (GI) dysfunction. Disorders of gut-brain interactions (DGBIs), also known as functional gastrointestinal disorders (FGIDs), are a group of diseases where patients experience reoccurring gastrointestinal symptoms which cannot be explained by obvious structural abnormalities and include functional dyspepsia (FD) and irritable bowel syndrome (IBS). Food timing impacts on the production of melatonin and given the correlation between food intake and symptom onset reported by patients with DGBIs, chronodisruption may be a feature of these conditions. Recent advances in immunology implicate circadian rhythms in the regulation of immune responses, and DGBI patients report fatigue and disordered sleep, suggesting circadian disruption. Further, melatonin treatment has been demonstrated to improve symptom burden in IBS patients, however, the mechanisms underlying this efficacy are unclear. Given the influence of circadian rhythms on gastrointestinal physiology and the immune system, modulation of these rhythms may be a potential therapeutic option for reducing symptom burden in these patients.

Dietary supplements in the management of varicocele-induced infertility: A review of potential mechanisms

Varicocele is a main cause of lower production of spermatozoon and infertility with multiple pathophysiological mechanisms. In the past decades, the use of dietary supplements has significantly increased due to both the modern lifestyle and the food shortages of the industrialised countries. The purpose of this review paper is to collect scientific evidences from basic and clinical studies which support the use of dietary supplements to define the clinical framework for patients with varicocele. In the present review, we used keywords such as dietary supplements, varicocele, male infertility, oxidative stress, DNA fragmentation, sperm parameters to find the proper articles. The standard search biomedical engines were used for seeking the papers. The use of dietary supplements such as minerals, vitamins and antioxidants has an essential role in the prevention and treatment of varicocele by increasing the levels of antioxidant enzymes (e.g. peroxidase, superoxide dismutase and catalase) and decreasing the levels of inflammatory markers (e.g. tumour necrosis factor-α, interleukin-6 and interleukin-1) in testis. According to the results, the dietary supplements may alleviate the spermatogenesis in varicocele patients through different mechanisms such as suppression of stress oxidative and inflammation in testicular tissue.

Melatonin protects prepuberal testis from deleterious effects of bisphenol A or diethylhexyl phthalate by preserving H3K9 methylation

A growing number of couples experience fertility issues with almost half being due to malefactors. The exposure to toxic environmental contaminants, such as endocrine disruptors (EDs), has been shown to negatively affect male fertility. EDs are present in the environment, and exposure to these toxins results in the failure of spermatogenesis. The deleterious effects of EDs on spermatogenesis have been well documented, whereas improvement of infertility associated with spermatogenesis defects remains a great challenge. Herein, we report that in vitro exposure of prepuberal mouse testes to two well-known endocrine disruptors (EDs), bisphenol A (BPA) or diethylhexyl phthalate (DEHP), impairs spermatogenesis with perturbing self-renewal, spermatogonia activity, and meiosis. Evidence indicates that such effects are likely due, at least in part, to decreased G9a-dependent H3K9 di-methylation. Of note, we found that melatonin (MLT) protected the testis from the negative ED impacts with preserving spermatogonia stem and meiotic cells, along with maintaining normal H3K9 di-methylation in these cells. Taken together, this work documents that BPA and EDHP adversely affect prepuberal spermatogenesis and perturb crucial epigenetic activities in male germ cells and highlight the protective ability of MLT.