Understanding the aging mechanism of the male reproductive system and developing anti-aging interventions are essential for preventing age-related male infertility. The pineal hormone melatonin has been effectively used as an antioxidant and anti-apoptotic molecule in various cells and tissues. However, the effects of melatonin on d-galactose (D-gal)-induced aging have not been studied with regards to testicular function. Thus, we investigated whether melatonin suppresses the dysfunction of male reproductive function induced by D-gal treatment. The mice were divided into the following four groups receiving treatments for six weeks: phosphate-buffered saline (PBS) group, d-galactose (200 mg/kg) group, melatonin (20 mg/kg) group, and d-galactose (200 mg/kg)+ melatonin (20 mg/kg) group. At six weeks of treatments, sperm parameters, body and testes weight, gene and protein expression of germ cell and spermatozoa marker were analyzed. Our results showed that melatonin suppressed the decrease in body weight, sperm vitality, motility, and gene expression levels of spermatozoa markers such as Protamine 1, PGK2, Camk4, TP1, and Crem in the testis of D-gal-induced aging models. However, the gene expression levels of the pre-meiotic and meiotic markers in the testes did not change in the D-gal-injected model. The injection of D-gal impaired the decreased expression of steroidogenic enzyme genes, such as HSD3b1, Cyp17a1, and Cyp11a1, but melatonin inhibited the decrease in the expression of these genes. In addition, protein levels of spermatozoa and germ cell markers were evaluated by immunostaining and immunoblotting. Consistent with the qPCR results, PGK2 protein levels were decreased by d-galactose treatment. A decrease in PGK2 protein levels by D-gal was inhibited by melatonin treatment. In conclusion, melatonin administration improves testicular function with age.
Keywords: Aging; Germ cell; Melatonin; Spermatozoa; Steroidogenesis; d-galactose.
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