Effects of n-6 and n-3 polyunsaturated acid-rich soybean phosphatidylcholine on membrane lipid profile and cryotolerance of human sperm.

ABSTRACT

OBJECTIVE: To study the effects of n-6 and n-3 polyunsaturated acid-rich soybean phosphatidylcholine (soy-PC) on sperm cryotolerance with regard to sperm membrane lipid profile, membrane surface integrity, and routine semen parameters. DESIGN: Experimental study. SETTING: University-affiliated tertiary hospital. PATIENT(S) A total of 20 normospermic fertile men. INTERVENTION(S) Semen samples examined for differences in semen parameters, sperm membrane lipid profile, and plasma membrane surface both before and after cryopreservation using basic freezing medium with N-tris(hydroxymethyl)-methyl-2-aminoethane sulfonic acid (TES) and tris-(hydroxymethyl)-aminomethane (TRIS) supplemented with purified soy-PC (TEST-PC) or egg yolk (TEST-Y), both alone or in association (TEST-Y-PC). MAIN OUTCOME MEASURE(S) Conventional semen parameters and membrane lipid profile by matrix-assisted laser/desorption ionization mass spectrometry (MALDI-MS). RESULT(S) Postthaw sperm cell motility, vitality, and morphology parameters were similar for soy-PC (TEST-PC) and egg yolk (TEST-Y) cryoprotectants. However, sperm exposed to TEST-Y-PC presented better kinetic parameters, which were similar to the original quality of the fresh semen. Human sperm MALDI-MS lipid profiles revealed that the relative abundance of glycerophospholipids of m/z 760.44 [PC (341)+H]+, 781.55 [SM (200) +Na]+, 784.55 [PC (363) +H]+, 806.64 [PC (386) +H]+, 807.64 [SM (221) +Na]+, and 809.64 [SM (220) +Na]+ increased in soy-PC samples (TEST-PC). Nonetheless, only one lipid (m/z 781.55, [SM (200) +Na]+) statistically significantly changed when sperm was cryopreserved in TEST-Y-PC. CONCLUSION(S) Sphingomyelin was defined as a prospective biomarker of soy-PC treatment, and it could be related to the positive cryoprotective effects of soy-PC in human sperm, opening new perspectives to design of a more efficient synthetic cryoprotectant medium containing purified egg yolk biomolecules combined with soy-PC.