title: Endurance exercise modifies the circadian clock in zebrafish (Danio rerio) temperature independently.
abstract: OBJECTIVE
  Several rodent and human studies revealed that physical exercise acts as a non-photic zeitgeber for the circadian clock. The intrinsic entraining mechanism is still unknown, although it was assumed that the exercise-mediated increase in core temperature could be the underlying zeitgeber. As the homoeostatic control of mammalian core temperature interferes strongly with the investigation of this hypothesis, the present study used the poikilotherm zebrafish to answer this question.
  
  
  METHODS
  Gene transcription levels of the two circadian core clock genes period1 and clock1 were quantified using real-time qPCR of whole animal zebrafish larvae.
  
  
  RESULTS
  Long-term endurance exercise of zebrafish larvae aged 9-15 days post-fertilization (dpf) or 21-32 dpf at a constant water temperature of 25 °C caused significantly altered transcription levels of the circadian genes period1 and clock1. Cosinor analysis of diurnal transcription profiles obtained after 3 days of swim training revealed significant differences regarding acrophase, mesor and amplitude of period1, resulting in a phase delay of the gene oscillation. After termination of the exercise bout, at 15 dpf, oscillation amplitudes of both circadian genes were significantly reduced.
  
  
  CONCLUSIONS
  The results showed that physical exercise is able to affect the transcription of circadian genes in developing zebrafish larvae. Considering the poikilothermy of zebrafish, an exercise-mediated change in body core temperature could be excluded as the underlying intrinsic zeitgeber. However, the day-active zebrafish arises as a useful model to address the synchronizing effect of exercise on the circadian clock.
authors: Institut für Zoologie, Universität Innsbruck, Technikerstr, Austria. margit.egg@uibk.ac.at
authors: M
authors: M
authors: Egg
authors: A
authors: A
authors: Tischler
authors: T
authors: T
authors: Schwerte
authors: A
authors: A
authors: Sandbichler
authors: C
authors: C
authors: Folterbauer
authors: B
authors: B
authors: Pelster
mesh_terms: D000818:Animals; D001831:Body Temperature / Q000502:physiology*; D057906:Circadian Clocks / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D056950:Period Circadian Proteins / Q000235:genetics / Q000378:metabolism; D010805:Physical Conditioning, Animal / Q000502:physiology*; D010807:Physical Endurance / Q000502:physiology*; D015027:Zebrafish / Q000502:physiology*; D029961:Zebrafish Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D004268:DNA-Binding Proteins; D056950:Period Circadian Proteins; D029961:Zebrafish Proteins; C541354:clocka protein, zebrafish; C539026:per1a protein, zebrafish