Abstract
Although several studies have been conducted to study leptin function, information is very scarce on the molecular mechanism of leptin in fatty acid β-oxidation and oocytes maturation in fish. In this study, we investigated the potential role of fatty acid β-oxidation in leptin-mediated oocytes maturation in Pelteobagrus fulvidraco. Exp. 1 investigated the transcriptomic profiles of ovary and the differential expression of genes involved in β-oxidation and oocytes maturation following rt-hLEP injection; rt-hLEP injection was associated with significant changes in the expression of genes, including twenty-five up-regulated genes (CPT1, Acsl, Acadl, Acadm, Hadhb, Echsl, Hsd17b4, Acca, PPARα, CYP8B1, ACOX1, ACBP, MAPK, RINGO, Cdc2, MEK1, IGF-1R, APC/C, Cdk2, GnRHR, STAG3, SMC1, FSHβ and C-Myc) and ten down-regulated gene (PPARγ, FATCD36, UBC, PDK1, Acads, Raf, Fizzy, C3H-4, Raf and PKC), involved in fatty acid β-oxidation and oocytes maturation. In Exp. 2, rt-hLEP and specific inhibitors AG490 (JAK-STAT inhibitor) were used to explore whether leptin induced oocytes maturation, and found that leptin incubation increased the diameters of oocytes and percentage of germinal vesicle breakdown (GVBD)-MII oocytes, up-regulated mRNA levels of genes involved in oocytes maturation and that leptin-induced oocyte maturation was related to activation of JAK-STAT pathway. In Exp. 3, primary oocytes of P. fulvidraco were treated with (R)-(+)-etomoxir (an inhibitor of β-oxidation) or l-carnitine (an enhancer of β-oxidation) for 48 h under rt-hLEP incubation. Exp. 3 indicated that the inhibition of fatty acid β-oxidation resulted in the down-regulation of gene expression involved in oocytes maturation, and repressed the leptin-induced up-regulation of these gene expression. Activation of fatty acid β-oxidation improved the maturation rate and mean diameter of oocytes, and up-regulated gene expression involved in oocytes maturation. Leptin is one of the main factors that links fatty acid β-oxidation with oocyte maturation; β-oxidation is essential for leptin-mediated oocyte maturation in fish.
Highlights
In fish, the oocyte undergoes meiotic resumption after completion of vitellogenic process
In this study, the ovarian transcriptome information of P. fulvidraco by RNA-seq technology was determined, and the differential expression of genes involved in fatty acid β-oxidation and oocytes maturation following recombinant human leptin (rt-hLEP) administration were investigated
We investigated the differentially expressed genes involved in fatty acid β-oxidation and oocytes maturation in ovary of P. fulvidraco following rt-hLEP injection by RNA-seq technology
Summary
The oocyte undergoes meiotic resumption after completion of vitellogenic process. Studies using pharmacological inhibitors have determined the essential role of fatty acid β-oxidation in both oocyte nuclear maturation and developmental competence [5,6]. Up-regulation of fatty acid β-oxidation in COCs has been used to demonstrate the crucial role of this metabolic pathway for developmental competence in vitro [7,8]. All of these studies only involved the changes of very limited genes’ mRNA levels related to the fatty acid β-oxidation during oocyte maturation [7,9]. There are significant differences in ovary development and oocyte maturations between mammals and fish. It remains cautious when extrapolating the results in mammals to fish
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