The effect of vitamin D on sperm motility and the underlying mechanism

Vitamin D deficiency is a common health issue around the world. We therefore evaluated the associations of semen quality with both serum and seminal plasma vitamin D levels and studied the mechanisms underlying these by incubating spermatozoa with 1,25(OH)2D in vitro. Two hun dred and twenty-two men were in eluded in our study. Vitamin D was detected using an electrochemilumi nesce nee method. Spermatozoa used for in vitro experiments were isolated by density gradient centrifugation. Positive relationships of serum 25(OH)D with semen volume and seminal plasma fructose were identified. Seminal plasma 25(OH)D level showed no relationship with serum 25(OH)D level, while it was inversely associated with sperm concentration and positively correlated with semen volume and sperm kinetic values. In vitro, sperm kinetic parameters in creased after in cubation with 1,25(OH)2D, especially upon in cubation for 30 min with it at a concen tration of 0.1 nmol l-1. Under these in cubation conditions, the upward migratio n of spermatozoa in creased remarkably with increasing ade nosine triphosphate (ATP) con centratio n. The concentrati on of cyclic ade nosine mono phosphate (cAMP) and the activity of protei n kinase A (PKA) were both elevated, and the PKA inhibitor, N-[2-(p-Bromocinnamylamino)ethyl]-5-isoquinolinesulfonamide dihydrochloride (H89) reversed the in crease of ATP producti on. The conce ntrations of cytoplasmic calcium ions and n icotinamide adenine dinucleotide (NADH) were both enhanced, while mitochondrial calcium uniporter (MCU) inhibitor, Ruthenium 360 (Ru360) did not reverse the increase of ATP production. Therefore, seminal plasma vitamin D may be invoIved in regulating sperm motility, and 1,25(OH)2D may enhance sperm motility by promoting the synthesis of ATP both through the cAMP/PKA pathway and the in crease in in tracellular calcium ions.