规律运动对心肌Nmnat基因敲减果蝇心脏收缩功能和节律的影响

Effects of Regular Exercise on Cardiac Systolic Function and Rhythm of Drosophila with Myocardial Nmnat Gene Expression Knockdown

目的:研究生命早期和中老龄期实施运动干预对心脏烟酰胺单核苷酸腺苷转移酶(Nmnat)基因敲减条件下果蝇心脏收缩功能、心脏节律、运动能力和生命周期的影响,探讨Nmnat在运动抗心脏衰老中的功能。方法:基因型y[1]v[1];P{y[+t7.7]v[+t1.8]=TRi P.JF03337}att P2处女蝇分别与W1118、hand-Gal4雄蝇杂交,收集F1代Nmnat RNAi/+(Nmnat基因正常表达品系)、hand>Nmnat RNAi(心肌Nmnat基因敲减品系)雌蝇各1600只,两品系均随机分为4组:1周龄平台对照组、1周龄平台运动组、5周龄平台对照组、5周龄平台运动组,每组400只,1、5周龄平台运动组分别于2天龄、30天龄时实施连续5 d,2.5 h/d运动方案,采用q RTPCR技术检测心脏Nmnat基因表达;应用M-mode心动图检测运动结束后次日果蝇心功能;采用攀爬指数(CI)评定运动能力;统计存活情况。结果:1周龄敲减平台对照组心肌Nmnat的相对表达量较1周龄正常表达平台对照组约下降50%(P<0.001);与正常表达平台对照组相比,同龄敲减平台对照组舒张直径(DD)、收缩直径(SD)增加(P<0.001),缩短分数(FS)下降(P<0.001),收缩间期不齐指数(SIAI)升高(P<0.01,P<0.001);与1周龄敲减平台对照组相比,1周龄敲减平台运动组FS增加(P<0.001),SIAI下降(P<0.05);1周龄敲减平台运动组CI大于同龄敲减平台对照组;与1周龄平台对照组相比,相同遗传背景1周龄平台运动组存活曲线右移、上移,与5周龄敲减平台对照组相比,5周龄敲减平台运动组中位生存期缩短(P<0.05)。结论:Nmnat在维持心脏正常收缩功能和节律方面发挥重要作用。较早年龄段运动能有效改善果蝇因Nmnat基因敲减引起的心脏收缩功能下降和收缩间期节律紊乱,延缓增龄引起的运动能力下降,延长果蝇寿命。其机制可能与运动上调Nmnat表达,提高NAD+水平有关,而随年龄增加,NAD+水平降低、能量代谢下降将导致运动干预效果减弱。

Objective To study the effects of regular exercise on the cardiac systolic function,cardiac rhythm,climbing ability and lifespan of fruit flies with cardiac nicotinamide mononucleotide adenylyltransferase （Nmnat）gene expression knockdown at young and middle-old age,and explore the anti- aging function of Nmnat. Methods The virgin flies with y [1]v [1];P {y [＋t7.7] v [＋tl.8]=TRiP.JF03337}attP2 genotype were cross-fertilized with Wms flies and hand-Gal4 flies respectively,then the female F1 progeny with Nmnat RNAi/＋ and hand〉Nmnat RNAi （cardiac Nmnat gene knockdown）were collected and respectively divided into their 1-week old and 5-week old control groups and exercise groups. The flies in the exercise groups at 2 days old and 30 days old performed platform exercise 2.5 hours per day for 5 days. The Nmnat mRNA expression in cardiac muscle was measured by Real time qPCR and heart function was recorded by M-mode echocardiography. The exercise capacity was assessed using climbing index and survival rate. Results The expression of Nmnat in 1-week old hand〉Nmnat RNAi control group was approximately decreased by 50 percent compared to 1-week old Nmnat RNAi/＋ control group （P〈0.001）. The diastolic diameter and systolic diameter increased significantly （P〈0.001） ,fractional shortening （FS）decreased obviously （P〈0.001） ,systolic interval arrhythmia index （SIA!） increased markedly （P〈0.01, P〈0.001 ）in hand〉Nmnat RNAi control groups as compared with age-matched Nmnat RNAi/＋ control groups. By contrast with 1-week old hand〉Nmnat RNAi control group,FS significantly increased（P〈0.001 ）,SIAI decreased（P〈0.05）in 1-week old hand〉Nmnat RNAi control group, and the CI in 1-week old hand〉Nmnat exercise group was higher than 1-week old hand〉Nmnat RNAi control group. Conclusion Nicotinamide mononucleotide adenylyhransferase plays an important role in maintaining cardiac systolic function and rhythm in the drosophila heart. Exercise in early age can improve the cardiac systolic function and rhythm caused by knockdown of myocardial nicotinamide mononucleotide adenylyhransferase.