Effects of short-term fasting on the rhythmic expression of core circadian clock and functional genes in skeletal muscle of goldfish (Carassius auratus).

Molecular oscillators exist in peripheral tissues like pacemaker cells. Food intake is a dominant zeitgeber for peripheral clocks in vertebrates. Fasting is a physiological stress that elicits well-known metabolic adaptations, however, little is known about the effects of the rhythmic expression of clock components in skeletal muscle following short-term fasting in goldfish. Here, we characterized the molecular clock components and their daily transcription in COSINOR, and assessed the effect of 7-day fasting on the circadian patterns of the candidate genes expression in goldfish skeletal muscle. For the core clock genes, clock, bmal1a, cry1, cry2, cry3, per1, per2 and per3 showed circadian rhythmicity in fed goldfish, but not for bmal1a, cry2 and per1 in the fasted state. Of the 8 candidate functional genes analyzed, igf1, igf2 and igfbp2 showed circadian rhythmicity in the fed state, but circadian pattern was only observed for mRNA of myog, igfbp2 and mstn in fasted goldfish. Additionally, Spelman's correlation analysis showed the circadian expression of the myog and mstn presented positive and negative correlation with the transcription pattern of clock and per2 genes in fasted goldfish, respectively. Our results demonstrated that the peripheral clocks might be reset to respond rapidly to withholding of food in teleost skeletal muscle.