Illuminated night alters behaviour and negatively affects physiology and metabolism in diurnal zebra finches

Aug 4, 2019Environmental pollution (Barking, Essex : 1987)

Nighttime light changes behavior and harms body function and metabolism in daytime-active zebra finches

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Abstract

Dim light at night (dLAN) exposure resulted in significant behavioral and physiological changes in zebra finches.

dLAN altered daily activity-rest and eating patterns, leading to nocturnal eating and weight gain.
Reduced nocturnal melatonin levels and increased nighttime glucose levels were observed under dLAN conditions.
Decreased daytime thyroxine and triglyceride levels, along with hepatic lipid accumulation, suggested metabolic impairment.
Increased expressions of certain genes indicated enhanced gluconeogenesis and cholesterol biosynthesis in the liver.
No changes were found in genes related to fat production and insulin signaling, suggesting alternative regulatory mechanisms.
Daily rhythms in the expression of clock genes were noted, indicating a potential role in liver metabolism.

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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.

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Illuminated night alters behaviour and negatively affects physiology and metabolism in diurnal zebra finches

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