Adropin: A New Regulator of Testicular Function—What Do We Know So Far?

Adropin, a peptide hormone first identified by microarray analysis of gene expression in mice's liver, is expressed in multiple organs, including the brain, liver, and heart. It is a key regulator of carbohydrates and lipid metabolism. Moreover, it has anti-inflammatory and antioxidative effects. It enhances blood vessel dilation and is essential for the normal development and function of the cerebellum. It acts through binding to multiple receptors, primarily the orphan G protein-coupled receptor, which is expressed in various tissues, including the central nervous system, liver, heart, kidneys, and testis, suggesting a direct role of adropin in modulating the function of multiple organs. This review discusses recently identified testicular functions regulated by adropin. Some studies have demonstrated that adropin can stimulate testosterone synthesis in testicular Leydig cells by enhancing the expression of steroidogenic enzymes. Moreover, it increases germ cell proliferation and sperm formation by inhibiting apoptosis and oxidative stress. Current evidence remains limited, and further studies are required to clarify the underlying mechanisms of adropin in reproductive physiology. Moreover, its potential role in conditions associated with altered testosterone levels or impaired spermatogenesis remains speculative and requires validation in well-designed clinical studies.