The Effect And Mechanism Of Aerobic Exercise On Fast And Slow Muscle Fibers In Zebrafish At Different Months

Objective:This experiment uses the anatomical characteristics of the fast and slow muscle fiber separation of the model organism zebrafish to perform aerobic exercise intervention on wild-type female zebrafish at the age of 4 months,12 months,and 18 months,and explore the effect of aerobic exercise on the muscle fiber morphology and aerobic exercise of wild-type female zebrafish of different months of age.Ability and the influence of fast and slow muscles,and further explore the role of CaN/PGC-1α/Mef2 signaling pathway in the induction of zebrafish skeletal muscle fiber transformation during aerobic exercise.This will enable us to further understand the impact of aerobic exercise on the fast and slow muscle fibers of skeletal muscle and the key regulatory factors involved.Methods:Wild-type female zebrafish of the same month old with similar health,body size and athletic ability were randomly divided into a quiet control group(n=15)and an exercise group(n=15): the 4-month-old quiet control group(4 Con,n=15),4 Month-old exercise group(4Exe,n=15),12-month-old quiet control group(12 Con,n=15),12-month-old exercise group(12 Exe,n=15),18-month-old quiet control group(18 Con,n=15),18-month-old exercise group(18 Exe,n=15).A constant-temperature swimming training device was used for 4 weeks of aerobic exercise intervention in the exercise group,with a swimming speed of 13.5 cm/s,training for 5 days a week,and continuous exercise training for 6 hours a day.After four weeks of exercise intervention,Loligo Systems was used to measure the extreme swimming speed of each group of zebrafish.The muscle tissue of the tail was taken 24 hours after the last exercise was used for the detection of experimental indicators.HE staining to observe the morphological changes of the cross-section of zebrafish tail muscle;immunofluorescence staining to identify slow muscle fibers in the cross-section of zebrafish tail muscle;RT-qPCR technology to detect fast muscle marker genes: tnnc2,mylpfa(mylz2/mlc2f),myhc4,The expression levels of slow muscle marker genes smyhc1,smyhc2,tnnc1 b,tnnt1 andnfatc1、ppargc1α、mef2、myod and foxo1 related to the signal pathway;CaN activity was detected by colorimetry.Results :(1)The length and weight of zebrafish in the exercise group did not change significantly compared with the quiet control group(P>0.05).(2)The results of HE staining showed that the morphology of muscle fibers was normal.Compared with the quiet control group of the same month,the muscle fibers of the exercise group were significantly enlarged(P<0.01,P<0.001).(3)The results of immunofluorescence staining showed that the area of slow muscle fibers in the exercise group increased compared with the quiet control group at the same month age(P<0.05).(4)Evaluation of aerobic exercise capacity: Compared with the quiet control group at the same age,the aerobic exercise capacity of the exercise group was improved(P<0.05,P<0.01).(5)RT-qPCR results showed that compared with the quiet control group of the same month,the expression of fast muscle marker mRNA in the exercise group decreased(P < 0.05,P < 0.01);the expression of slow muscle marker mRNA increased(P < 0.05,P < 0.01);4 Exe group nfatc1,ppargc1α,mef2,myod mRNA expression increased(P < 0.05,P < 0.01);12 Exe group ppargc1α,myod mRNA expression increased(P<0.05,P<0.01),foxo1 mRNA expression Decrease(P<0.05);the expression levels of ppargc1α and mef2 mRNA in the 18 Exe group increased(P<0.01);(6)The colorimetric test results showed that compared with the quiet control group of the same month,the 4 Exe group and the 18 Exe group The activity of CaN was higher than that of the quiet control group(P<0.05).Conclusion:(1)Aerobic exercise training with a peripheral swimming speed of 13.5 cm/s can promote the hypertrophy of the tail muscle fibers of wild-type female zebrafish,increase the proportion of slow muscle area and aerobic exercise capacity,and promote the increase in the expression of slow muscle marker genes and fast muscle markers Decreased gene expression.(2)The up-regulation of CaN/PGC-1α/Mef2 signaling pathway expression may induce the transition from fast muscle to slow muscle in wild-type female zebrafish at 4 months,12 months,and18 months.