肾去交感神经对肥胖相关性房颤大鼠心房神经和结构重构的影响及其机制

Effect of renal denervation on atrial neural and structural remodeling in rats with obesity-related atrial fibrillation and its mechanism

目的:探讨肾去交感神经(renal denervation, RDN)在治疗肥胖相关性大鼠心房颤动(atrial fibrillation, AF)中的作用。方法:构建高脂饮食喂养的大鼠AF易感模型,对照组以标准饮食喂养,RDN组通过外科加化学消融方法实现RDN。通过Western blot检测肾脏酪氨酸羟化酶的表达水平;在体电生理仪检测大鼠心脏电生理指标,包括心房有效不应期(atrial effective refractory period, AERP)、AF诱发率和AF持续时间;超声心动图评估大鼠心脏结构和功能的改变;PowerLab生物信息采集系统分析大鼠心脏自主神经系统张力的改变;通过透射电镜观察大鼠心房肌线粒体结构变化;Western blot检测哺乳动物雷帕霉素靶蛋白(mammalian target of rapamycin, mTOR)和磷酸化mTOR(phosphorylated mTOR, p-mTOR)蛋白水平;Masson和HE染色观察左心房组织结构变化。结果:(1)与标准饮食组相比,高脂饮食喂养大鼠AF诱发率显著升高,AF持续时间显著延长,AERP显著降低;RDN可降低高脂饮食喂养大鼠AF诱发率,缩短AF持续时间,并恢复AERP。(2)高脂饮食大鼠心脏自主神经低频显著增加,自主神经高频显著降低,RDN后自主神经高频显著恢复,表明RDN可以逆转高脂饮食诱导的心脏自主神经系统紊乱。(3)超声结果发现,与标准饮食组相比,高脂饮食组大鼠左心房内径和左心室收缩末期内径(left ventricular endsystolic diameter, LVESD)增大,左心室射血分数(left ventricular ejection fraction, LVEF)和左心室短轴缩短率(left ventricular fractional shortening, LVFS)降低;RDN后,高脂饮食大鼠LVEF和LVFS升高,LVESD减小,表明RDN可减轻高脂饮食诱导的心脏功能和结构损伤。(4)Masson和HE染色结果显示,相较于标准饮食组,高脂饮食大鼠心房纤维化及心房肌细胞肥大增加;在RDN后心房纤维化得到明显缓解。(5)透射电镜下观察到高脂饮食喂养大鼠心房线粒体功能结构受损、排列紊乱、空泡增加等,Western blot结果显示高脂饮食喂养大鼠左心房mTOR和p-mTOR蛋白水平升高;RDN后线粒体自噬及结构损伤减轻。结论:RDN可通过缓解自主神经系统紊乱及心脏结构和功能重构,减弱高脂饮食诱导的AF易感性增加。

AIM:To investigate the role of renal denervation(RDN)in treatment of obesity-related atrial fibrillation(AF)in rats.METHODS:A high-fat diet AF-susceptible rat model was constructed.The rats in control group was fed with a standard diet,while those in RDN group was subjected to RDN via surgical and chemical ablation.The renal tyrosine hydroxylase expression level was detected by Western blot.An in vivo electrophysiological instrument was used to detect the cardiac electrophysiological parameters of rats,including atrial effective refractory period(AERP),AF induction rate,and AF duration.Alterations in cardiac structure and function of the rats were assessed using echocar‑diography. PowerLab bioinformatics acquisition system was used to analyze alterations in the tension of the rat cardiac au-tonomic nervous system. Transmission electron microscopy was used to further observe structural changes in the rat atrial mitochondria. The protein levels of mammalian target of rapamycin (mTOR) and phosphorylated mTOR (p-mTOR) were detected by Western blot. Masson staining and HE staining were used to detect the extent of structural changes in the left atrium. RESULTS: (1) Compared with standard diet group, the AF induction rate and duration of the rats fed with a high-fat diet were significantly increased;however, the AERP significantly decreased. RDN reduced the increases in AF induction rate and duration in the rats fed with a high-fat diet, and even restored the AERP. (2) Cardiac low frequency significantly increased whereas cardiac high frequency decreased in heart autonomic nerves of the rats fed with a high-fat diet. After RDN, low frequency was significantly restored, suggesting that RDN could reverse the cardiac autonomic ner-vous system disorder induced by a high-fat diet. (3) Ultrasound results showed that compared with standard diet group, the left atrial diameter and left ventricular end-systolic diameter (LVESD) of the rats fed with high-fat diet were increased, whereas the left ventricular ejection fraction (LVEF) and left ventricular fractional shortening (LVFS) were decreased. Af-ter RDN, the LVEF and LVFS of high-fat diet-fed rats increased, whereas the LVESD decreased. Ultrasound results showed that RDN could attenuate the cardiac functional and structural damage induced by a high-fat diet. Masson and HE staining results showed that compared with standard diet group, atrial fibrosis and atrial cardiomyocyte hypertrophy in-creased in high-fat diet-fed rats, while atrial fibrosis was significantly attenuated after RDN. (4) Transmission electron mi-croscopy showed that the functional structure of atrial mitochondria in high-fat diet-fed rats was damaged, with disordered arrangement and increased number of vacuoles. Western blot results showed that mTOR and p-mTOR protein levels in-creased in the left atrium of high-fat diet-fed rats. Mitochondrial autophagy and structural damage were attenuated after RDN. CONCLUSION: Renal denervation may reduce high-fat diet-induced AF susceptibility via alleviating autonomic nervous system disorders and cardiac structural and functional remodeling.