The Lipidomic Profiling of Ovine Sperm Reveals Metabolic Alterations and Key Biomarkers After Cryopreservation

BACKGROUND: Lipids plays a vital role in sperm capacity acquisition, and yet the effect of cryopreservation on lipid profile has received little attention so far. OBJECTIVE: To evaluate the change in lipids of ovine sperm upon cryopreservation. MATERIALS AND METHODS: Ovine semen was aliquoted into two parts: one being the fresh control and the other used for cryopreservation. The targeted lipidomic analysis was performed between fresh and cryopreserved sperm samples. RESULTS: Cryopreservation resulted in 53 up-regulated and 163 down-regulated lipids. Downregulation prevails. Most differentiated lipids were glycerophospholipid, fatty acyl, glycerolipid, sphingolipid, prenol lipid and sterol, and they were highly correlated with one another (correlation coefficient r > 0.8). Major pathway enrichments were glycerophospholipid metabolism, glycosylphosphatidylinositol-anchor biosynthesis, glycine, serine and threonine metabolism, biosynthesis of unsaturated fatty acids, actin cytoskeleton regulation, pathogenic infection and autophagy. In glycerophospholipid metabolism, the phosphatidyl-ethanolamine Class II series and phosphatidyl-L-serine Class II series had the largest numbers of differentially-expressed lipids, some significantly down-regulated and others up-regulated. In contrast, all lipids of the 1,2-diacyl-snglycerol-3P Class II series were significantly down-regulated. CONCLUSION: Cryopreservation altered the sperm lipid profile, and the changes in 1,2-diacyl-sn-glycerol-3P, phosphatidylethanolamine and phosphatidyl-L-serine can be good biomarkers for sperm quality change.