The effect of high fat diet on daily rhythm of the core clock genes and muscle functional genes in the skeletal muscle of Chinese soft-shelled turtle (Trionyx sinensis)

In the present study, we sought to investigate the influence of high fat diet on the core clock genes and the muscle functional genes daily expression in the skeletal muscle of Chinese soft-shelled turtle. The turtles were fed by two diets including a control fat diet (the CON treatment, 7.98% lipid) and a high fat diet (the HFD treatment, 13.86% lipid) for six weeks and administrated by the photophase regimen of 24 h light/dark (12L:12D) cycle. After the feeding trial experiment, we measured the daily expression levels of 17 core clock genes (Clock, Bmal1/2, NPAS2, Tim, Cry1/2, Per1/2, DBP, AANAT, NIFL3, BHLHE40, NR1D2, RORA, RORB, RORC) and 12 muscle functional genes (FBXO32, MBNL1, MSTN, Myf5, Myf6, MyoD, MyoG, MyoM1, PPARa, PDK4, Trim63, UCP3) in the skeletal muscle of the two treatments. The results showed that except for Bmal1, NPAS2, Per2 and RORB, the expression of the other 13 core clock genes exhibited circadian oscillation in the CON treatment. Among the 12 muscle functional genes, MBNL1, PDK4 and MyoM1 did not exhibit circadian oscillation in the CON treatment. In the HFD treatment, the circadian rhythms expressional patterns of the 8 core clock genes (Clock, Bmal2, Cry2, Per1, DBP, NFIL3, BHLHE40 and RORA) and 6 muscle functional genes (MSTN, Myf5, MyoD, MyoG, PPARa and Trim63) were disrupted. In addition, compared with the CON treatment, the circadian expression of the 5 core clock genes (Tim, Cry1, AANAT, NR1D2, RORC) and the 3 muscle functional genes (FBXO32, Myf6, UCP3) showed the advanced or delayed expression peaks in the HFD treatment. In CON treatment, the circadian expression of the MyoG, MyoD, Myf6, FBXO32 and PPARa showed positive or negative correlation with the transcription pattern of Clock, Bmal2, Cry1/2, Per1/2. However, only the FBXO32 and Myf6 presented positive or negative correlation with the circadian expression of Cry1, RORB, AANAT and Tim in HFD treatment. In summary, these results demonstrate that the disruption of the circadian rhythm of the core clock genes and muscle functional genes in the skeletal muscle is closely associated with feeding high fat diet to Chinese soft-shelled turtle.