Effects Of High-intensity Interval Training On Mitochondrial Quality Control System-related Proteins And Glucose Metabolism-related Enzymes In Mice Myocardium

Objective: Mitochondria can produce ATP to supply energy for cells through oxidative phosphorylation(OXPHOS)in the respiratory chain.Mitochondrial quality control system is the basis of maintaining healthy mitochondrial network.Its dynamic balance is very important to the stability of mitochondrial function.Glucose metabolism includes anaerobic glycolysis and aerobic oxidation of glucose.It can release a lot of energy in the process of catabolism to maintain the energy supply of the body.Previous studies have found that knockout of OPA1,a key gene in the mitochondrial quality control system,impairs OXPHOS function in the mitochondria of mice T cells and leads to increased cellular glycolysis.Therefore,the changes of mitochondrial quality control system can also affect the level of glucose metabolism.The rhythmic contraction of the myocardium can provide energy for the moving body,and long-term regular exercise can also improve cardiac function.High intensity interval training(HIIT),as a new type of exercise that combines two energy supply modes of both glycolysis and aerobic oxidation,has the characteristics of short time,high intensity and high energy consumption.It not only has high requirements for cardiac function,but also can effectively promote cardiac health.However,it is unclear whether the mechanism of HIIT improving cardiac function is related to the improvement of the expression of myocardial mitochondrial quality control system-related proteins and glucose metabolism-related enzymes.Therefore,this study aims to observe the effects of HIIT on the expression of myocardial mitochondrial quality control system-related proteins and glucose metabolism-related enzymes,so as to provide a theoretical basis for HIIT to promote cardiac health.Methods: Seven-week-old male C57BL/6J mice were randomly divided into sedentary control group(CON group,n=22)and high-intensity interval training group(HIIT group,n=22).The mice in the CON group did not exercise,while the mice in the HIIT group received HIIT treadmill training for 6 weeks,5 days a week.Blood lactate levels were measured immediately after the last exercise at weeks 2,4 and 6.24h after the last exercise,the heart tissue was taken,and the left ventricular muscle of the heart tissue was cut for Western blot and RT-PCR experiments.The expression of myocardial mitochondrial quality control system-related proteins and glycolysis and aerobic oxidation-related enzymes were detected by Western blot;the gene expression of OXPHOS complex I～V in myocardial mitochondria was detected by RT-PCR.Results:(1)Effect of HIIT on blood lactate level in mice: the blood lactate level in HIIT group was significantly increased immediately after the last exercise in the second,fourth and sixth weeks(p < 0.01),and had an increasing trend.(2)Effects of HIIT on myocardial mitochondrial quality control system-related proteins: 6 weeks of HIIT increased the expression of mitochondrial biogenesis proteins PGC-1α,NRF1 and TFAM(p<0.01,p<0.05,p<0.05);Reduced the expression of mitochondrial fusion protein MFN2(p < 0.05);The expression of mitochondrial fusion protein OPA1 was increased(p < 0.05);Reduced the expression of mitochondrial fission proteins DRP1 and FIS1(p<0.05,p<0.01);Reduced the expression of mitophagy protein PARKIN(p<0.01).(3)Effects of HIIT on the genes expression of OXPHOS complex in myocardial mitochondria of mice: 6 weeks of HIIT significantly up-regulated the expression of NDUFS8,SDHb,COX5 b,ATP5a1 genes(p<0.01,p<0.05,p<0.001,p<0.05).(4)Effects of HIIT on myocardial glucose metabolism related enzymes: 6 weeks of HIIT significantly increased the expression of HK,the key protein of myocardial glycolysis,and CS,the key protein of aerobic oxidation(p<0.01,p<0.05).Conclusion: 6 weeks of HIIT can improve the expression of myocardial mitochondrial quality control system-related proteins,enhance the gene level of mitochondrial oxidative phosphorylation complex,and increase the protein expression of glucose metabolism-related enzymes.The improvement in the levels of these proteins and genes may be one of the mechanisms by which HIIT enhances cardiac function.