动物造模 Z-bio 2022-12-19 279

　　Objective The level of skeletal muscle glucose metabolism is an important factor affecting aerobic exercise ability, and the level of skeletal muscle glucose metabolism is regulated by the biological clock. Chrono is a clock gene newly discovered in recent years. It can feedback inhibit the transcription of the core clock transcription factor BMAL1 to its downstream clock target gene, and is considered to be a transcription inhibitor of BMAL1. Studies have shown that BMAL1 is involved in the regulation of skeletal muscle glucose metabolism, while CHRONO, as a transcription inhibitor of BMAL1, has no known effect on exercise ability and glucose tolerance through CHRONO-BMAL1 pathway. Therefore, this study intends to explore the effects of CHRONO-BMAL1 pathway on glucose tolerance and exercise ability through skeletal muscle specific Chrono overexpression mice and wild type mice, and provide theoretical basis for clarifying the new mechanism of regulating glucose tolerance and affecting skeletal muscle health.

　　Methods There were 20 healthy 8-week old C57BL/6N wild mice (WT) and 20 skeletal muscle specific Chrono overexpression mice (TG), half male and half female. The body weight and food intake of mice were recorded, body composition tests were conducted, and the mice were tested for autonomous activity, incremental load exercise ability, glucose tolerance and grip strength. The skeletal muscles of mice were weighed, and real-time fluorescent quantitative PCR was performed to detect the mRNA expression of Chrono, MyhcI, MyhcIIa, MyhcIIb, MyhcIIx, and Pdha1, and the kit was used to detect the muscle glycogen content.

　　Results (1) Compared with WT rats, TG rats had significantly lower autonomic activity and incremental load exercise ability (P<0.05 or P<0.01); (2) Compared with WT rats, the weight of gastrocnemius, quadriceps femoris, soleus, extensor digitorum longus and tibialis anterior muscle in TG rats were significantly increased (P<0.01), while the weight of gastrocnemius and quadriceps femoris in female TG rats was significantly lower than that in male TG rats (P<0.01); (3) Compared with WT rats, the grasping force of the forelimbs of male TG rats was significantly decreased (P<0.05), and the expression of Myhc type II mRNA in skeletal muscle was also significantly decreased or showed a downward trend. The grasping force of female TG rats and the expression of type II mRNA in muscle fibers were significantly higher than those of male TG rats (P<0.05 or P<0.01); (4) Compared with WT rats, the blood glucose value and area under the curve of TG rats at each point during glucose tolerance test were significantly increased (P<0.01), while the female TG rats were significantly lower than the male TG rats (P<0.01); (5) Compared with WT mice, the muscle glycogen content of TG mice was significantly increased (P<0.05), and the expression of Pdha1 mRNA was significantly reduced or showed a decreasing trend. The muscle glycogen content and the expression of Pdha1 mRNA in female TG mice were significantly higher than those in male TG mice (P<0.05 or P<0.01).

　　Conclusion The overexpression of Chrono in skeletal muscle can reduce the spontaneous activity of mice, lead to the decrease of glucose tolerance, and affect the aerobic exercise ability.