Effects of Exercise on the Expression of miRNA in Myocardium of C57BL/6 Mice and the Regulation of miRNA in Cardiac Hypertrophy

Objective: To discuss the effects of different exercise on the cardiac structure and miRNA,determine the novel mechanism of cardiac hypertrophy involving post-transcriptional regulation by miRNA in mice.Methods: Male C57BL/6 mice(n=8/group) were randomized into three groups: sedentary control group(C),a bout of exhaustive exercise group(E),8 weeks(wks) training group(T).Mice in T undertook a swimming protocol for 8 wks,5 days/wk,from the 1st to 5th wk,they were trained one time a day in the evening,from the 6th to 8th wk,trained twice a day with a 6h interval.Swimming 30min in the 1st wk,and exercise duration was increased 10min per wk to 90min and maintained in the 8th and 9th wk.In the last wk,mice were measured by echocardiography,miRNA-1,133a,208a,499 was performed by real-time PCR in the sample obtained from sacrificed mice.Result: Swimming training increased the left ventricular wall thickness and ventricular end-diastolic dimension indicating cardiac hypertrophy had been induced.Compared to C,miRNA-1,133a,208a and 499 of E were up-regulated significantly(P<0.01).In T,miRNA-208a was also up-regulated(P<0.05),but the increased extent was lower than that in E,miRNA-1,133a were down regulated significantly(P<0.01),and miRNA-499 did not increase apparently.Conclusion: 8 wks swimming training could induce cardiac hypertrophy in C57BL/6 mice,a bout of exhaustive exercise increased the expression of miRNA,endurance training decreased the expression of miRNA-1,133a and elevated the miRNA-208a,499 regulatory pathway,miRNA were involved in cardiac remodeling and benefited the formation of cardiac hypertrophy.