Gómez-Boronat Miguel, Sáiz Nuria, Delgado María J, de Pedro Nuria, Isorna Esther
Departamento de Genética, Fisiología y Microbiología, Unidad Docente de Fisiología Animal, Facultad de Ciencias Biológicas, Universidad Complutense de Madrid, Madrid, Spain.
Front Physiol. 2018 Dec 5;9:1749. doi: 10.3389/fphys.2018.01749. eCollection 2018.
The circadian system controls temporal homeostasis in all vertebrates. The light-dark (LD) cycle is the most important ("time giver") of circadian system, but feeding time also acts as a potent synchronizer in the functional organization of the teleost circadian system. In mammals is well known that food intake during the rest phase promotes circadian desynchrony which has been associated with metabolic diseases. However, the impact of a misalignment of LD and feeding cycles in the entrainment of fish circadian oscillators is largely unknown. The objective of this work was to investigate how a time-lag feeding alters temporal homeostasis and if this could be considered a stressor. To this aim, goldfish maintained under a 12 h light-12 h darkness were fed at mid-photophase (SF6) or mid-scotophase (SF18). Daily rhythms of locomotor activity, clock genes expression in hypothalamus, liver, and head kidney, and circulating cortisol were studied. Results showed that SF6 fish showed daily rhythms of and in all studied tissues, being in antiphase with rhythms of genes, as expected for proper functioning clocks. The 12 h shift in scheduled feeding induced a short phase advance (4-5-h) of the clock genes daily rhythms in the hypothalamus, while in the liver the shift for clock genes expression rhythms was the same that the feeding time shift (∼12 h). In head kidney, acrophases of genes underwent a 12-h shift in SF18 animals, but only 6 h shift for . Plasma cortisol levels showed a significant daily rhythm in animals fed at SF6, but not in SF18 fish fed, which displayed higher cortisol values throughout the 24-h. Altogether, results indicate that hypothalamus, liver, and head kidney oscillate in phase in SF6 fish, but these clocks are desynchronized in SF18 fish, which could explain cortisol alterations. These data reinforce the hypothesis that the misalignment of external cues (daily photocycle and feeding time) alters fish temporal homeostasis and it might be considered a stressor for the animals.
昼夜节律系统控制着所有脊椎动物的时间稳态。明暗（LD）循环是昼夜节律系统最重要的“时间给予者”，但进食时间在硬骨鱼昼夜节律系统的功能组织中也起着强大的同步作用。在哺乳动物中，众所周知，休息阶段的食物摄入会促进昼夜节律失调，这与代谢疾病有关。然而，LD和进食周期失调对鱼类昼夜节律振荡器的夹带影响在很大程度上尚不清楚。这项工作的目的是研究时间滞后喂养如何改变时间稳态，以及这是否可被视为一种应激源。为此，将饲养在12小时光照-12小时黑暗条件下的金鱼在光照中期（SF6）或黑暗中期（SF18）喂食。研究了运动活动、下丘脑、肝脏和头肾中时钟基因表达以及循环皮质醇的每日节律。结果表明，SF6组金鱼在所有研究组织中均表现出 和 的每日节律，与时钟基因的节律呈反相，这是正常运行时钟所预期的。预定进食时间提前12小时导致下丘脑时钟基因每日节律出现短暂的相位提前（4-5小时），而在肝脏中，时钟基因表达节律的变化与进食时间的变化相同（约12小时）。在头肾中，SF18组动物中 基因的峰值相位发生了12小时的变化，但 仅发生了6小时的变化。血浆皮质醇水平在SF6组喂食的动物中表现出显著的每日节律，但在SF18组喂食的金鱼中没有，后者在24小时内皮质醇值更高。总之，结果表明，SF6组金鱼的下丘脑、肝脏和头肾相位振荡，但这些时钟在SF18组金鱼中不同步，这可以解释皮质醇的变化。这些数据强化了这样一种假设，即外部线索（每日光周期和进食时间）的失调会改变鱼类的时间稳态，并且可能被认为是动物的一种应激源。
