The circadian rhythm regulates branched-chain amino acids metabolism in fast muscle of Chinese perch () during short-term fasting by Clock-KLF15-Bcat2 pathway.

As an internal time-keeping mechanism, circadian rhythm plays crucial role in maintaining homoeostasis when in response to nutrition change; meanwhile, branched-chain amino acids (BCAA) in skeletal muscle play an important role in preserving energy homoeostasis during fasting. Previous results from our laboratory suggested that fasting can influence peripheral circadian rhythm and BCAA metabolism in fish, but the relationship between circadian rhythm and BCAA metabolism, and whether circadian rhythm regulates BCAA metabolism to maintain physiological homoeostasis during fasting remains unclear. This study shows that the expression of fifteen core clock genes as well as and is highly responsive to short-term fasting in fast muscle of , and the correlation coefficient between and expression is enhanced after fasting treatment. Furthermore, we demonstrate that the transcriptional expression of is regulated by Clock, and the transcriptional expression of is regulated by KLF15 by using dual-luciferase reporter gene assay and -morpholinos-mediated gene knockdown technique. Therefore, fasting imposes a dynamic coordination of transcription between the circadian rhythm and BCAA metabolic pathways. The findings highlight the interaction between circadian rhythm and BCAA metabolism and suggest that fasting induces a switch in expression through affecting the rhythmic expression of , and then KLF15 promotes the transcription of to enhance the metabolism of BCAA, thus maintaining energy homoeostasis and providing energy for skeletal muscle as well as other tissues.