Feeding cycle-dependent circulating insulin fluctuation is not a dominant Zeitgeber for mouse peripheral clocks except in the liver: Differences between endogenous and exogenous insulin effects

Fluctuations in endogenous insulin during feeding cycles may not significantly synchronize peripheral clocks in most tissues except the liver.

• Mice fed during the daytime showed reversed insulin fluctuations compared to those fed at nighttime.
• Circadian phases of Per1 and Per2 gene expression were altered in the liver but not in heart, lung, white adipose, or skeletal muscle tissues.
• Injected exogenous insulin increased Akt activity and Per1 and Per2 gene expression across all examined tissues.
• Feeding cycle-dependent endogenous insulin rhythms may not serve as primary signals for synchronizing peripheral clocks outside the liver.

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