Escobar Sebastián, Felip Alicia, Zanuy Silvia, Carrillo Manuel
Instituto de Acuicultura Torre de la Sal (IATS), Consejo Superior de Investigaciones Científicas (CSIC), 12595 Ribera de Cabanes S/N, Castellón, Spain.
Instituto de Acuicultura Torre de la Sal (IATS), Consejo Superior de Investigaciones Científicas (CSIC), 12595 Ribera de Cabanes S/N, Castellón, Spain.
Comp Biochem Physiol A Mol Integr Physiol. 2016 Sep;199:38-46. doi: 10.1016/j.cbpa.2016.05.005. Epub 2016 May 7.
Previous works on European sea bass have determined that long-term exposure to restrictive feeding diets alters the rhythms of some reproductive/metabolic hormones, delaying maturation and increasing apoptosis during gametogenesis. However, exactly how these diets affect key genes and hormones on the brain-pituitary-gonad (BPG) axis to trigger puberty is still largely unknown. We may hypothesize that all these signals could be integrated, at least in part, by the kisspeptin system. In order to capture a glimpse of these regulatory mechanisms, kiss1 and kiss2 mRNA expression levels and those of their kiss receptors (kiss1r, kiss2r) were analyzed in different areas of the brain and in the pituitary of pubertal male sea bass during gametogenesis. Furthermore, other reproductive hormones and factors as well as the percentage of males showing full spermiation were also analyzed. Treated fish fed maintenance diets provided evidence of overexpression of the kisspeptin system in the main hypophysiotropic regions of the brain throughout the entire sexual cycle. Conversely, Gnrh1 and gonadotropin pituitary content and plasma sexual steroid levels were downregulated, except for Fsh levels, which were shown to increase during spermiation. Treated fish exhibited lower rates of spermiation as compared to control group and a delay in its accomplishment. These results demonstrate how the kisspeptin system and plasma Fsh levels are differentially affected by maintenance diets, causing a retardation, but not a full blockage of the reproductive process in the teleost fish European sea bass. This suggests that a hormonal adaptive strategy may be operating in order to preserve reproductive function in this species.
先前针对欧洲海鲈的研究已确定，长期摄食限制型日粮会改变某些生殖/代谢激素的节律，延迟性腺成熟并增加配子发生过程中的细胞凋亡。然而，这些日粮究竟如何影响脑-垂体-性腺（BPG）轴上的关键基因和激素以触发青春期，目前仍 largely unknown。我们可以推测，所有这些信号可能至少部分地由 kisspeptin 系统整合。为了初步了解这些调节机制，在配子发生过程中，对青春期雄性欧洲海鲈的大脑不同区域和垂体中的 kiss1 和 kiss2 mRNA 表达水平及其 kiss 受体（kiss1r、kiss2r）的表达水平进行了分析。此外，还分析了其他生殖激素和因子以及完全排精的雄性比例。喂食维持日粮的处理组鱼显示，在整个性周期中，大脑主要促垂体区域的 kisspeptin 系统过表达。相反，Gnrh1、垂体促性腺激素含量和血浆性类固醇水平下调，但 Fsh 水平除外，Fsh 水平在排精期间升高。与对照组相比，处理组鱼的排精率较低，且排精延迟。这些结果表明，维持日粮如何差异性地影响 kisspeptin 系统和血浆 Fsh 水平，导致欧洲海鲈这一硬骨鱼的生殖过程延迟，但并非完全阻断。这表明可能存在一种激素适应性策略，以维持该物种的生殖功能。
