Unpredictable feeding schedules unmask a system for daily resetting of behavioural and metabolic food entrainment

Nov 16, 2007The European journal of neuroscience

Irregular meal times reveal a system that daily resets behavior and metabolism linked to food timing

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Abstract

Rats exposed to variable feeding schedules showed no robust adjustment in food anticipatory activity.

Both fixed and variable feeding schedules led to daily metabolic oscillations influenced by the last meal.
Rats on variable feeding schedules did not demonstrate anticipatory activity, unlike those on fixed schedules.
Increased expression of a neural activity marker was observed in specific hypothalamic regions 24 hours after the last meal in both groups.
Rats on fixed feeding schedules showed low expression of this marker in the suprachiasmatic nucleus, indicating a different response to feeding cues.
The study suggests that metabolic and behavioral rhythms can be reset daily, highlighting differences in responses between feeding schedules.

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Restricted feeding schedules (RFS) are a potent Zeitgeber that uncouples daily metabolic and clock gene oscillations in peripheral tissues from the suprachiasmatic nucleus (SCN), which remains entrained to the light-dark cycle. Under RFS, animals develop food anticipatory activity (FAA), characterized by arousal and increased locomotion. Food availability in nature is not precise, which suggests that animals need to adjust their food-associated activity on a daily basis. This study explored the capacity of rats to adjust to variable and unpredictable feeding schedules. Rats were exposed either to RFS with fixed daily meal (RF) or to a variable meal time (VAR) during the light phase. RF and VAR rats exhibited daily metabolic oscillations driven by the last meal event; however, VAR rats were not able to show a robust adjustment in the anticipating corticosterone peak. VAR rats were unable to exhibit FAA but exhibited a daily activation pattern in phase with the previous meal. In both groups the dorsomedial nucleus of the hypothalamus and arcuate nucleus, involved in energy balance, exhibited increased c-Fos expression 24 h after the last meal, while only RF rats exhibited low c-Fos expression in the SCN. Data show that metabolic and behavioural food-entrained rhythms can be reset on a daily basis; the two conditions elicit a similar hypothalamic response, while only the SCN is inhibited in rats exhibiting anticipatory activity. The variable feeding strategy uncovered a rapid (24-h basis) resetting mechanism for metabolism and general behaviour.

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Unpredictable feeding schedules unmask a system for daily resetting of behavioural and metabolic food entrainment

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