FIGURE 2.

Lipid signaling pathways during oocyte maturation. The flow chart representative diagram explaining the various signaling events occurs during mammalian oocyte maturation. Briefly, luteinizing hormone (LH) through its receptor luteinizing hormone receptor (LHR) stimulates the entry of arachidonic acid in theca cells (TCs) in the form of high density lipoprotein (HDL). Then HSL is activated through cAMP/PKA pathways, and initiates the release of cholesterol from lipid droplets. In the mitochondria, cholesterol molecules are converted into pregnenolone by action of steroidogenic acute regulatory protein (StAR). Furthermore, COX pathway is triggered inside the granulosa cells (GCs) via FSH stimulation which initiates the expression of aromatase and converts testosterone (T) into estradiol (E2). Estradiol further stimulates various pathways in the oocytes which safeguard the degradation of cAMP and concurrent inhibition of maturation-promoting factor (MPF). On the other hand, activation of progesterone (P4) signaling causes inhibition of cAMP production by blocking adenylate cyclase (AC) activity which results in MPF activation and GVBD.