The Clinical And Basic Study Of Seminal Plasma Vitamin D With The Indicators Of Male Reproductive Function

BACKGROUND:Vitamin D refers to a group of fat-soluble steroids that play a pronounced role in regulating the homeostasis of calcium and phosphorus in the body.In humans,the most important compounds in this group of steroids are vitamin D3(cholecalciferol)and vitamin D2(ergocalciferol).Both vitamin D2 and vitamin D3 undergo their first hydroxylation in the liver to yield 25 hydroxyvitamin D(25(OH)D),which is the major form of vitamin D in circulation and is the best indicator for assessing vitamin D level.25(OH)D is transported to the kidney where,through another hydroxylation process,it becomes the biologically active form 1?,25-dihydroxycholecalciferol(1,25(OH)2D).Vitamin D deficiency is regarded as a widespread health problem.In recent decades,researches on vitamin D have extended the spectrum to the male reproductive system.Previous studies on the relationship between the overall level of vitamin D and semen quality have presented conflicting results.OBJECTIVE:In this study,we aimed to evaluate the associations of male reproductive function with both serum and seminal plasma vitamin D levels and study the mechanisms underlying these by incubating spermatozoa with 1,25(OH)2D in vitro.METHODS:Clinical trial:Based on the enrollment and exclusion criteria,men for andrological evaluation owing to male infertility or normal physical examination were included in our study.25(OH)D was detected using an electrochemiluminescence method.Then the relationships between serum and seminal plasma 25(OH)D with semen quality,sperm kinetic parameters,Anti-Mullerian Hormone(AMH),Inhibin B(INHB)and seminal plasma biochemical markers were evaluated.In vitro:Spermatozoa were isolated by density gradient centrifugation method and were incubated in the medium without or with different concentrations of 1,25(OH)2D.Then the kinectic parameters,upward migration and relative makers of spermatozoa were detected.RESULTS:Positive relationships of serum 25(OH)D with semen volume,seminal plasma fructose and zinc were identified.Seminal plasma 25(OH)D level showed no relationship with serum 25(OH)D level,while it had positive associations with semen volume and the 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.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(H89)reversed the increase of ATP production.The concentrations of cytoplasmic calcium ions and nicotinamide adenine dinucleotde(NADH)were both enhanced,PLC(Phospholipase C)inhibitor U-73122 reversed the increase of cytoplasmic calcium ions and NADH,while mitochondrial calcium uniporter(MCU)inhibitor,Ruthenium 360(Ru360)did not reverse the increase of NADH and ATP production.CONCLUSIONS:1.Seminal plasma vitamin D may be involved in regulating sperm motility.2.1,25(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.