Search

In fish breeding practices, gamete maturity of females is vital to reproductive success. For some species, it is possible to estimate the female maturation status based on abdomen observation, but quite difficult for some species which mature at big size. To screen out the potential biomarker in fish blood relating to female maturation, we employed the approach integrating the UPLC-MS/MS and RNA-seq techniques to investigate the metabolites and genes reflecting the sexual maturation and spawning of female blunt snout bream Megalobrama amblycephala. The study included four groups, 1-year-old immature female individuals, 2-year-old immature female individuals, 2-year-old sexually mature female individuals, and 2-year-old sexually mature female individuals after 24 h of successful spawning. The upregulated metabolites in mature females were involved in "steroid hormone biosynthesis," "metabolic pathways," "glycerophospholipid metabolism," etc. compared with those of immature individuals. As the key intermediate of steroid hormone biosynthesis, 17α-hydroxypregnenolone exhibited the highest level in 2-year-old mature females than in the immature females. Meanwhile, the metabolites (i.e., dodecanoic acid and myristic acid) participating in fatty acid synthesis exhibited much lower levels in the females after spawning than those before spawning. In addition to the metabolites, the genes involved in ovarian steroidogenesis were significantly upregulated in the 2-year-old immature females compared to the 1-year-old immature females, indicating that the ovarian steroidogenesis plays important roles in ovarian development of M. amblycephala at the early stages. The significant upregulation of genes (i.e., itpr1, camk2, and mekk2) involved in the "GnRH signaling pathway" was observed in the mature females compared with the immature females, which indicated that the estrogen levels increased after female maturation in M. amblycephala. Moreover, many genes (e.g., gck, creb1, tf2-9, ryr2, asgr1, and creb1) regulating insulin secretion and thyroid hormone synthesis were significantly downregulated after female spawning. The dynamics of gene expression and metabolites observed in this study provide novel cues for guiding fish practical artificial reproduction. [ABSTRACT FROM AUTHOR]

Introduction: In some fish species, it is difficult to distinguish mature females from immature females or females that have already spawned via appearance or other convenient methods. Few studies have investigated plasma metabolite profiling for the prediction of fish maturation. Objectives: We investigated the comprehensive metabolic profiles of plasma among immature females and mature females ready to spawn, as well as already spawned breeders of blunt snout bream ( Megalobrama amblycephala). The purpose of this study was to screen out potential biomarkers for sexually mature female M. amblycephala compared to immature female individuals and already spawned breeders. Methods: Three groups were set up in this study, which included 1-year-old immature females, 2-year-old sexually mature females ready to spawn and successfully spawned females of M. amblycephala. Plasma samples were collected to investigate comprehensive metabolic profiles through UPLC-MS/MS based on a metabolomics analysis method. Results: According to multivariate and univariate statistical analysis, plasma metabolite profiles of the three groups were clearly separated. The differential plasma metabolites from three hormone related pathways including the GnRH signaling pathway, steroid hormone biosynthesis and steroid biosynthesis, were analyzed. A total of 29 metabolites were identified as differential biomarkers associated with the female maturation status. Conclusion: The identified potential biomarkers could be useful in separating mature M. amblycephala from immature individuals or ovulation-induced female individuals, which would allow for more effective artificial breeding. The results may contribute to a better understanding of the maturation mechanisms of fish in the aspect of metabolomics. [ABSTRACT FROM AUTHOR]