Dimly illuminated nights alter behavior and negatively affect fat metabolism in adult male zebra finches.

This experiment investigated the effects of an ecologically relevant level of dim light at night (dLAN) on behavior, physiology and fat metabolism associated gene expressions in central and peripheral tissues of adult male zebra finches that were hatched and raised in 12:12 h LD cycle (Ev, day = 150 ± 5 lx; Ev, night = 0 lx) at 22 ± 2 °C temperature. Half of the birds (n = 8) were maintained on LD cycle and temperature, as before (control), to the other half of birds the 12 h dark period was dimly illuminated at ~ 5 lx (dim light at night, dLAN; Ev, day = 150 ± 5 lx; Ev, night =  ~ 5 lx) for 6 weeks. The exposure to dLAN altered the 24 h activity and feeding patterns with enhanced activity and feeding at night. Birds under dLAN fattened and gained weight, and had higher night glucose levels. Concurrently, a negative effect of dLAN was found on mRNA expression of ppar-alpha and cd36 genes involved in the fat metabolism in the hypothalamus, intestine, liver and muscle. These results suggest a more global effect of dLAN exposure on obesity and perhaps long-term health risks due to obesity-related complications to diurnal animals including humans inhabiting an urbanized environment.