Circadian expression of clock genes is maintained in the liver of Vitamin A-deficient mice

In mammals, circadian oscillators exist not only in the central clock of the suprachiasmatic nucleus (SCN) but also in peripheral tissues such as the liver, heart and kidneys. Peripheral clocks are entrained to the SCN clock by both neural and humoral signals. Vitamin A might be one candidate that synchronizes peripheral clocks by activating its ligand-dependent nuclear receptors in mammals. The present study examines the effect of a Vitamin A deficiency on the circadian expression of clock genes in the mouse liver. Serum Vitamin A levels remained constant throughout the day in control mice, and were significantly reduced in Vitamin A-deficient mice. Northern blots showed that circadian expression of the clock genes mPer1, mPer2, Clock, and BMAL1, and of the clock-controlled output gene D-site binding protein (DBP), was maintained in Vitamin A-deficient mice. Our results suggest that dietary Vitamin A is not essential for generating circadian rhythms of peripheral clocks in mammals.