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 hundred and twenty-two men were included in our study. Vitamin D was detected using an electrochemiluminescence 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 increased after incubation with 1,25(OH)2D, especially upon incubation for 30 min with it at a concentration of 0.1 nmol l-1. Under these incubation conditions, the upward migration of spermatozoa increased remarkably with increasing adenosine triphosphate (ATP) concentration. The concentration of cyclic adenosine monophosphate (cAMP) and the activity of protein kinase A (PKA) were both elevated, and the PKA inhibitor, N-[2-(p-Bromocinnamylamino)ethyl]-5-isoquinolinesulfonamide dihydrochloride (H89) reversed the increase of ATP production. The concentrations of cytoplasmic calcium ions and nicotinamide 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 involved 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 increase in intracellular calcium ions.

Objective Male infertility accounts for 40 to 50% of the total number of infertility in the world. Among many factors that cause male infertility, vitamin D is considered to be directly related to male fertility. The purpose of this study was to explore the relationship between serum and seminal plasma vitamin D and male reproductive function, and provide a more comprehensive research direction for studying the specific mechanism of vitamin D on male reproduction. Methods A total of 198 infertile males, receiving andrological examination from June 2017 to January 2018 in the Center for Reproductive Medicine, Jinling Hospital (Nanjing, China) was included in our study. Serum and seminal plasma vitamin D levels were measured by electrochemiluminescence immunoassay (ECLIA) kits. The associations between vitamin D and biomarkers of male reproduction were analyzed. Results Serum 25(OH) vitamin D level [26.17(19.61-31.99)ng/mL] was in positive relation with semen volume[3.8(3.1-4.8)ng/mL] (r=0.229,P=0.003). Seminal plasma 25(OH) vitamin D level was not related to serum 25(OH) vitamin D level, but in negative relation with sperm concentration(r=0.174,P=0.016) and positive relation with semen volume(r=0.271,P=0.0001). Serum 25(OH) vitamin D level was in positive relation with seminal plasma fructose concentration(r=0.256,P=0.002), total fructose content (r=0.310,P=0.0002) and total zinc content(r=0.26,P=0.002). The level of serum and seminal plasma vitamin D leve was not related to serum anti-Mullerian hormone(AMH), seminal plasma AMH, serum inhibin (INH B) and seminal plasma INH B(P>0.05). Conclusion Vitamin D is associated with affiliated gland function. The seminal vesicles and prostate produced by semen may be the main source of vitamin D in the male reproductive system.

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 hundred and twenty-two men were included in our study. Vitamin D was detected using an electrochemiluminescence 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 increased after incubation with 1,25(OH)₂D, especially upon incubation for 30 min with it at a concentration of 0.1 nmol l^-1. Under these incubation conditions, the upward migration of spermatozoa increased remarkably with increasing adenosine triphosphate (ATP) concentration. The concentration of cyclic adenosine monophosphate (cAMP) and the activity of protein kinase A (PKA) were both elevated, and the PKA inhibitor, N-[2-(p-Bromocinnamylamino)ethyl]-5-isoquinolinesulfonamide dihydrochloride (H89) reversed the increase of ATP production. The concentrations of cytoplasmic calcium ions and nicotinamide 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 involved 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 increase in intracellular calcium ions.
Adenosine Triphosphate/metabolism* ; Adult ; Calcium/metabolism* ; Cyclic AMP/metabolism* ; Cyclic AMP-Dependent Protein Kinases/metabolism* ; Humans ; Male ; Semen/metabolism* ; Semen Analysis ; Signal Transduction/physiology* ; Sperm Motility/physiology* ; Spermatozoa/metabolism* ; Vitamin D/pharmacology* ; Vitamin D Deficiency/blood* ; Wit and Humor as Topic ; Young Adult