Overview of the effects of astaxanthin on the male reproductive system focusing on mechanism underling its action.

Male infertility is a serious public health concern, affecting nearly half of infertile couples. Oxidative stress (OS) is a biological condition noted as a key factor related to male infertility. This condition arises from an imbalance between reactive oxygen species (ROS) and antioxidative potential. Astaxanthin (AXT) is a lipid-soluble pigment with the high antioxidant activity compared to vitamin E and beta-carotene. It has been mentioned that AXT functions through antioxidative, anti-inflammatory, anti-apoptotic features. Several studies reported that AXT improves sperm parameters such as motility, viability, and morphology in in vivo and in vitro studies. This carotenoid reduces testosterone in prostate but increases it in testis and serum. In acute conditions such as testicular torsion, AXT has reduced oxidative damage, which is critical for preserving testicular function following torsion. Activating the nuclear factor erythroid 2-related factor 2 (Nrf2) pathway is a main factor involved in these three mechanisms. This review explores the therapeutic role of AXT in male reproductive health in normal and pathological situations, focusing on its molecular mechanisms. Overall, the evidence we have so far suggests that AXT can be used as a therapeutic option for male reproductive dysfunctions, highlighting the necessity for future clinical studies to confirm its efficacy and safety in humans.