Exploring the mechanism of trehalose: dual functions of PI3K/Akt and VPS34/mTOR pathways in porcine oocytes and cumulus cells

Autophagy, an intracellular recycling system, is essential for the meiotic maturation of porcine oocytes. Trehalose has been reported as a novel mammalian target of rapamycin (mTOR)-independent autophagy inducer in many cells. Furthermore, we previously have demonstrated that trehalose supplementation during in vitro maturation of porcine oocytes improves the developmental competence of parthenogenetic embryos, possibly via autophagic activation, whereas the underlying mechanisms remain unclear. Therefore, the aim of this study was to address this issue. We found that trehalose plays a role as an autophagy activator by autophagic flux assay and determined that it promotes phosphatidylinositol-3 kinase (PI3K)/protein kinase B (Akt) inhibition and vacuolar protein sorting 34 (VPS34)/mTOR activation by immunoblotting, both in cumulus cells (CCs) and oocytes. However, interestingly, the effects and the mechanisms regulated by trehalose were different in them, respectively. In CCs, the autophagy was activated through the improvement of lysosomal function/autophagic clearance viability by upregulation of coordinated lysosomal expression and regulation genes via PI3K/Akt inhibition. Whereas in oocytes, autophagy was activated via induction of VPS34, which directly influences autophagosome formation, and the precise meiotic process was ensured via Akt inhibition and mTOR activation. Taken together, this study furtherly elucidates the novel detailed mechanism of trehalose during porcine oocyte maturation, thus laying the biological foundations for pharmacological application.