Department of Zoology, University of Delhi, Delhi, 110 007, India.
Department of Zoology, University of Delhi, Delhi, 110 007, India.
Environ Pollut. 2019 Nov;254(Pt A):112916. doi: 10.1016/j.envpol.2019.07.084. Epub 2019 Jul 26.
Light at night (LAN) negatively impacts the behaviour and physiology; however, very little is known about molecular correlates of LAN-induced effects in diurnal animals. Here, we assessed LAN-induced effects on behaviour and physiology, and examined molecular changes in the liver of diurnal zebra finches (Taeniopygia guttata). Birds were exposed to dim LAN (dLAN: 12L = 150 lux: 12D = 5 lux), with controls on 12L (150 lux): 12D (0 lux). dLAN altered daily activity-rest and eating patterns, induced nocturnal eating and caused body fattening and weight gain, and reduced nocturnal melatonin levels. Concomitant increased nighttime glucose levels, decreased daytime thyroxine and triglycerides levels, and hepatic lipid accumulation suggested the impairment of metabolism under dLAN. Transcriptional assays evidenced dLAN-induced negative effects on metabolism in the liver, the site of metabolic homeostasis. Particularly, increased g6pc and foxo1 mRNA expressions suggested an enhanced gluconeogenesis, while increased egr1 and star expressions suggested enhanced cholesterol biosynthesis and lipid metabolism, respectively. Similarly, overexpressed sirt1 indicated protection from the metabolic damage due to elevated gluconeogenesis and cholesterol biosynthesis under dLAN. However, no effect on genes involved in lipogenesis (fasn) and insulin signalling pathway (socs3 and insig1) might indicate for the post transcriptional/post translational modification effects or the involvement of other genetic pathways in LAN-induced effects. We also found daily rhythm in the hepatic expression of selected clock and clock-controlled genes (per2, bmal1 and reverb-beta), with an elevated mesor and amplitude of per2 oscillation, suggesting a role of per2 in the liver metabolism. These results demonstrate dLAN-induced negative effects on the behaviour and physiology, and provide molecular insights into metabolic risks of the exposure to illuminated nights to diurnal animals including humans in an urban setting.
夜间光（LAN）会对行为和生理产生负面影响；然而，对于光诱导效应在昼行动物中的分子相关性知之甚少。在这里，我们评估了 LAN 诱导对行为和生理的影响，并检查了昼行斑马雀（Taeniopygia guttata）肝脏中的分子变化。鸟类暴露于昏暗的 LAN（dLAN：12L=150 勒克斯：12D=5 勒克斯），对照组为 12L（150 勒克斯）：12D（0 勒克斯）。dLAN 改变了昼夜活动-休息和进食模式，诱导了夜间进食，并导致身体肥胖和体重增加，同时降低了夜间褪黑素水平。同时，夜间血糖水平升高，白天甲状腺素和甘油三酯水平降低，肝脏脂质积累表明 dLAN 下代谢受损。转录分析表明，dLAN 对肝脏代谢产生了负面影响，而肝脏是代谢稳态的部位。特别是，g6pc 和 foxo1 mRNA 表达增加表明糖异生增强，而 egr1 和 star 表达增加分别表明胆固醇生物合成和脂质代谢增强。同样，sirt1 的过度表达表明，由于 dLAN 下糖异生和胆固醇生物合成增加，对代谢损伤有保护作用。然而，参与脂肪生成（fasn）和胰岛素信号通路（socs3 和 insig1）的基因没有受到影响，这可能表明存在转录后/翻译后修饰作用，或者 LAN 诱导的效应涉及其他遗传途径。我们还发现，选定的时钟和时钟控制基因（per2、bmal1 和 reverb-beta）在肝脏中的表达存在昼夜节律，per2 振荡的中值和振幅升高，表明 per2 在肝脏代谢中起作用。这些结果表明 dLAN 对行为和生理产生了负面影响，并为夜间光照对包括人类在内的昼行动物的代谢风险提供了分子见解。
