Paredes J F, López-Olmeda J F, Martínez F J, Sánchez-Vázquez F J
a Department of Physiology , Faculty of Biology, Regional Campus of International Excellence "Campus Mare Nostrum", University of Murcia , Murcia , Spain.
Chronobiol Int. 2015;32(10):1438-48. doi: 10.3109/07420528.2015.1104327. Epub 2015 Nov 23.
Despite numerous studies about fish nutrition and lipid metabolism, very little is known about the daily rhythm expression of lipogenesis and lipolysis genes. This research aimed to investigate the existence of daily rhythm expressions of the genes involved in lipid metabolism and their synchronization to different light/dark (LD) and feeding cycles in zebra fish liver. For this purpose, three groups of zebra fish were submitted to a 12:12 h LD cycle. A single daily meal was provided to each group at various times: in the middle of the light phase (ML); in the middle of the dark phase (MD); at random times. After 20 days of acclimation to these experimental conditions, liver samples were collected every 4 h in one 24-h cycle. The results revealed that most genes displayed a significant daily rhythm with an acrophase of expression in the dark phase. The acrophase of lipolytic genes (lipoprotein lipase - lpl, peroxisome proliferator-activated receptor - pparα and hydroxyacil CoA dehydrogenase - hadh) was displayed between ZT 02:17 h and ZT 18:31 h. That of lipogenic genes (leptin-a - lepa, peroxisome proliferator-activated receptor - pparγ, liver X receptor - lxr, insulin-like growth factor - igf1, sterol regulatory element-binding protein - srebp and fatty acid synthase - fas) was displayed between ZT 15:25 h and 20:06 h (dark phase). Feeding time barely influenced daily expression rhythms, except for lxr in the MD group, whose acrophase shifted by about 14 h compared with the ML group (ZT 04:31 h versus ZT 18:29 h, respectively). These results evidence a strong synchronization to the LD cycle, but not to feeding time, and most genes showed a nocturnal acrophase. These findings highlight the importance of considering light and feeding time to optimize lipid metabolism and feeding protocols in fish farming.
尽管有大量关于鱼类营养和脂质代谢的研究，但对于脂肪生成和脂肪分解基因的昼夜节律表达却知之甚少。本研究旨在调查斑马鱼肝脏中参与脂质代谢的基因是否存在昼夜节律表达，以及它们与不同光/暗（LD）和喂食周期的同步情况。为此，将三组斑马鱼置于12:12小时的LD周期中。每天在不同时间给每组提供一顿饭：在光照阶段的中间（ML）；在黑暗阶段的中间（MD）；在随机时间。在适应这些实验条件20天后，在一个24小时周期内每4小时收集一次肝脏样本。结果显示，大多数基因呈现出显著的昼夜节律，表达高峰期出现在黑暗阶段。脂肪分解基因（脂蛋白脂肪酶 - lpl、过氧化物酶体增殖物激活受体 - pparα和羟酰基辅酶A脱氢酶 - hadh）的表达高峰期出现在ZT 02:17小时至ZT 18:31小时之间。脂肪生成基因（瘦素-a - lepa、过氧化物酶体增殖物激活受体 - pparγ、肝脏X受体 - lxr、胰岛素样生长因子 - igf1、固醇调节元件结合蛋白 - srebp和脂肪酸合酶 - fas）的表达高峰期出现在ZT 15:25小时至20:06小时之间（黑暗阶段）。喂食时间对昼夜表达节律的影响很小，除了MD组中的lxr，其表达高峰期与ML组相比偏移了约14小时（分别为ZT 04:31小时和ZT 18:29小时）。这些结果表明与LD周期有很强的同步性，但与喂食时间无关，并且大多数基因呈现夜间表达高峰期。这些发现突出了在养鱼业中考虑光照和喂食时间以优化脂质代谢和喂食方案的重要性。
