Effects Of Endurance Exercise On Mitochondrial Biogenesis Of ICR Mice's Heart Muscle

Studies found that after regular exercise, a greater degree of adaptive change of the function and morphogenesis of cardiac muscle have been observed. From the microscopic point of view, the most significant change is from the mitochondria, the growing number of mitochondria, the improvements of related enzymes' activity, enhanced the overall number and function of the mitochondrial, and that mitochondrial biogenesis. Mitochondrial biogenesis occurs complex, needs the coordination control of the nuclear DNA and mitochondrial DNA. At present, a large number of studies have shown that, NRFs and ERRs, mediate gene expression of nuclear respiratory genes and mitochondrial respiration related genes, mitochondrial transcription factor Tfam/TFBMs regulate transcription and replication of mitochondrial DNA, and transcription coactivators such as PGC-1 family integrate and regulate the two thanscription factors.PGC-1 family played a key role in the body's adaptive changes to long-term movement. PGC-1αcan coactivate nuclear respiratory factor NRFs, regulating the gene expression of a variety of nuclear-encoded mitochondrial metabolism-related genes and Tfam, TFBMs genes. Mitochondrial transcription factor such as Tfam, TFB1M and TFB2M regulates a variety of mtDNA-coded mitochondrial energy metabolism-related gene expression and mtDNA replication, and promote mitochondrial biogenesis.Based on PGC-1 family playing a key rule in important physiological functions, and mitochondrial biogenesis with Tfam, TFBMs, this study attempts to study the effects of endurance exercise on mtDNA content and the gene expression of PGC-1α/β, Tfam, TFBMs in different months of mice's myocardial mitochondria, and then discusses the effects of endurance exercise on mitochondrial biogenesis so as to provide a theoretical basis on endurance exercise improving the function of the body.Objective:To compare the effects of endurance exercise on mtDNA content and the gene expression of PGC-lα/β, Tfam, TFBMs in different months of mice's myocardial mitochondria, and then discuss the impact of endurance exercise on myocardial mitochondrial biogenesis, in the perspective of the level of gene transcription and mitochondrial DNA content.Methods:After a week's adaptive training,32 male ICR mice were randomly divided into YC,YE,OC andOE group, n=8. Mice of different months with incremental exercise test, YE, OE groups of mice treadmill trained at the 65% to 75% maximum load for 4-weeks,6 days a week, once a day, remaining 1h.24h after the last training, all mice were killed, myocardium was extracted, extraction of total myocardial DNA, detect copy volume of ATPase6, mt1000 and cytB; extraction of total myocardial RNA, detect the mRNA expression of PGC-1α, PGC-1β,Tfam, TFB1/2M gene; extraction of myocardial mitochondria, in which ROS levels was detected.Results:(1) There was no significant difference in mice's body weight between the YE and YC group, as well as the OE and OC group.(2) Compared with the YC group, myocardial mitochondrial ROS level in the YE group increased; Compared with the OC group, myocardial mitochondrial ROS level in the OE group decreased.(3) There was no significant difference in mice's myocardial mtDNA content between the YE and YC group, as well as OE and OC group; Compared with the OC group, mice's myocardial mtDNA content of OE group was significantly increased.(4) There was no significant difference in mice's myocardial mRNA expression of PGC-1αand PGC-1βbetween the YC and YE group; Compared with the OC group, mRNA expression of PGC-1βin the OE group was significantly increased, while mRNA expression of PGC-1αin the OE group was significantly decreased.(5) There was no significant difference in mice's myocardial mRNA expression of Tfam, TFB1M and TFB2M between the YC and YE group; Compared with the OC group, mice's myocardial mRNA expression of Tfam, TFB1M and TFB2M in the OE group increased.Conclusion:(1) Endurance training can promote ten months old ICR mice mitochondrial biogenesis, mitochondrial biogenesis of mice's cardiac muscle may also be affected by age. (2) Endurance training-induced mitochondria biogenesis of ICR mice's cardiac muscle may be related to PGC-1α, PGC-1β, Tfam, TFB1M,TFB2M genes and so on. In which, PGC-1αmay plays a role to maintain the normal steady state of myocardial mitochondrial function, and PGC-1βis more involved in the cardiac adaptation to chronic long-term endurance training. Tfam, TFB1M and TFB2M mediated transcription and replication of mtDNA,which plays an important role in adaptation of cardiac mitochondrial biogenesis to sports.