MALDI-TOF Mass Spectrometry Reveals the Effect of Acetyl-L-Carnitine on the Lipid Profile of Buffalo Oocytes and Cumulus Cells During In Vitro Maturation

Lipids in cumulus-oocyte complexes are important actors in molecular signalling pathways and are influenced by maturation conditions. Acetyl-L-carnitine (ALC) is a carrier involved in fatty acid transport and is a promoter of β-oxidation. Although the embryonic development potential of oocytes can be improved when ALC is added to the maturation medium, the effects of ALC on the lipid content and composition of oocytes and cumulus cells remain unknown. In this study, the effect of ALC supplementation on the lipid profiles of buffalo oocytes and cumulus cells after in vitro maturation was evaluated using positive-ion matrix-assisted laser desorption ionisation time-of-flight mass spectrometry (MALDI-TOF MS). Orthogonal projections to latent structures discriminant analysis was used to analyse the data. The lipid profiles of oocytes and cumulus cells differed following ALC treatment. Four lipids were significantly different in oocytes and eight in granulosa cells. ALC treatment significantly reduced the cellular content of these lipids, with the exception of phosphatidylcholine [PC(36:3) + H] + in oocytes and triacylglycerol [TAG(58:8) + NH4] + in granulosa cells. Further staining experiments confirmed that ALC treatment reduced the total lipid content in oocytes. Therefore, ALC treatment alters lipid metabolism in oocytes and cumulus cells during their maturation and accelerates lipid metabolism in oocytes. The findings of this study demonstrate that ALC enhances the rate of oocyte maturation by altering lipid metabolism in oocytes, providing both a clear direction for further research into regulatory mechanisms as well as a foundation for further improving oocyte maturation rates.