FEEDING ENTRAINMENT OF FOOD-ANTICIPATORY ACTIVITY ANDper1EXPRESSION IN THE BRAIN AND LIVER OF ZEBRAFISH UNDER DIFFERENT LIGHTING AND FEEDING CONDITIONS

Abstract

Food provided on a periodic basis can act as a potent synchronizer, being a stronger zeitgeber than light for peripheral oscillators in mammals. In fish, however, little is known about the influence of feeding time on the circadian pacemaker and the relationship between central and peripheral oscillators. The aim of this research was to investigate the influence of mealtime on the activity rhythms, and on central (brain) and peripheral (liver) oscillators in zebrafish. The authors tested different feeding times under a light-dark (LD) cycle and the endogenous origin of food-anticipatory activity (FAA) by feeding zebrafish at a fixed time under constant bright-light conditions (LL). The authors then measured locomotor activity and the expression of the clock gene per1 in animals under a LD cycle and fed at random times during the light phase, with restricted feeding at the mid-light phase (ML) or with restricted feeding during the mid-dark phase (MD). Finally, the authors measured locomotor activity and per1 expression in fish maintained under LL under either random feeding or scheduled feeding. Zebrafish displayed FAA in all the groups fed at a fixed time but not when feeding was randomly scheduled. Under LL, fish entrainment persisted, and when released under fasting conditions FAA free-ran with a circa-24-h period. The expression of per1 in the brain of fish under LD showed a daily rhythm with the acrophase (peak time) at the end of the dark phase regardless of feeding schedule. This brain rhythm disappeared in LL fish under both random feeding and scheduled feeding. Feeding at MD advanced the phase of per1 in the liver by 7 h compared with the ML-fed group phase (23:54 versus 07:23 h, respectively). In addition, under LL scheduled feeding entrained the rhythms of per1 expression in the liver. This study reveals for the first time that scheduled feeding entrains peripheral oscillators in a fish species, zebrafish, which is a powerful model widely used for molecular genetics and for the study of basic clock mechanisms of the vertebrate circadian system.

Cloning, tissue expression pattern and daily rhythms of Period1, Period2, and Clock transcripts in the flatfish Senegalese sole, Solea senegalensis

“…Moreover, in zebraWsh (Danio rerio), peripheral tissues and cells lines have been shown to be light responsive (Tamai et al 2005;Whitmore et al 2000), which allows direct entrainment of peripheral circadian clocks independently from the central oscillator. Interestingly, in most recent works, entrainment of central (brain) and peripheral (liver) tissues by both light and feeding cycles has also been demonstrated in Wsh (Cavallari et al 2011;Feliciano et al 2011;Lopez-Olmeda et al 2010).…”

“…The liver was also selected ( Fig. 7; Table 2), because it exhibited an important expression of clock genes in the RT-PCR study and feeding-entrained liver oscillators have been reported in Wsh (Cavallari et al 2011;Feliciano et al 2011;Lopez-Olmeda et al 2010). In all tissues examined, Per2 expression was signiWcantly lower than those of Per1 and Clock (compare the scales of y axis in Figs.…”

β-Adrenergic Signaling Regulates Evolutionarily Derived Sleep Loss in the Mexican Cavefish

“…The fish are capable of generating free-running 47-hour rhythms in response to feeding [Cavallari et al, 2011]. Feeding entrainment has been observed in Danio, suggesting that this process is conserved in terranean and subterranean fish populations [Lopez-Olmeda et al, 2010]. It will be of great interest to determine whether A. mexicanus, like P. andruzzi, can generate food-entrained circadian rhythms.…”

Interplay between the endocrine and circadian systems in fishes

“…However, when the LD cycle is present, the rhythms exhibit greater amplitudes, suggesting that both environmental signals work together in sustaining the molecular clockwork, at least in the liver , Sánchez-Bretaño et al 2015b. When both zeitgebers (LD and feeding-fasting cycles) are present, the brain oscillators appear to be driven by the LD cycle, whereas the clock gene oscillations in the liver are more dependent on feeding schedule (zebrafish: López-Olmeda et al 2010;sea bream: Vera et al 2013). In goldfish, a unique meal may shift the clock gene rhythms in the liver (Feliciano et al 2011), which matches the findings in mammals, where a high dependence of clock liver entrainment on feeding cues has been reported (Stokkan et al 2001, Kornmann et al 2007, Patton & Mistlberger 2013.…”