Maturation of buffalo oocytes in vitro with acetyl-l-carnitine improves cryotolerance due to changes in mitochondrial function and the membrane lipid profile

The effects of acetyl-l-carnitine (ALC) supplementation during IVM on subsequently vitrified buffalo oocytes were evaluated, followed by determination of the mitochondrial DNA copy number, measurement of mitochondrial membrane potential (MMP) and identification of the lipid profile of oocyte membranes as markers of oocyte quality after vitrification. Supplementation with ALC during IVM significantly improved the rates of oocyte cleavage and morula and blastocyst formation, and increased MMP after vitrification compared with unsupplemented vitrified oocytes (P < 0.05). Using a bidirectional orthogonal projection to latent structures discriminant analysis based on positive ion matrix-assisted laser desorption ionisation time-of-flight mass spectrometry data, five phospholipid ions (m/z 728.7 (phosphatidylcholine (PC) 32:3), 746.9 (PC 32:5), 760.6 (PC 34:1), 768.8 (PC P-36:3) and 782.6 (PC 36:4); P < 0.05) were identified as significantly more abundant in fresh oocytes than in unsupplemented vitrified oocytes. Meanwhile, three phospholipid ions (m/z 734.6 (PC 32:0), 760.6 (PC 34:1), and 782.6 (PC 36:4); P < 0.05) were more abundant in ALC-supplemented vitrified oocytes than in unsupplemented vitrified oocytes. Therefore, supplementation with ALC during IVM may improve buffalo oocyte quality after vitrification by enhancing mitochondrial function and altering the phospholipid composition of vitrified oocyte membranes.