长期高强度间歇训练加重自发性高血压大鼠心肌纤维化

Long-Term High-Intensity Interval Training Exacerbates Myocardial Fibrosis in Spontaneously Hypertensive Rats

目的:探讨中等强度持续训练(MICT)和高强度间歇训练(HIIT)对自发性高血压大鼠(SHR)心肌胶原代谢的影响及机制。方法:45只雄性SHR随机分为安静对照组(SHR-UT)、中等强度持续运动组(SHR-MT)和HIIT组(SHR-HT),同时将15只Wistar-Kyoto大鼠作为正常血压组(WKY)。WKY和SHRUT组大鼠保持安静状态,SHR-MT和SHR-HT组分别进行18周MICT或HIIT。末次实验后48 h利用超声心动图检测心脏结构与功能,Masson和HE染色进行组织病理学观察并分别获取心脏胶原容积分数(CVF)和心肌细胞横截面积(CSA),比色法测定心肌Ⅰ型胶原(ColⅠ)含量,RT-PCR法检测心肌胚胎基因[心钠素(ANP)和β-肌球蛋白重链(β-MHC)]mRNA表达量,Western blot法检测心肌基质金属蛋白酶-2(MMP-2)(包括64 kDa MMP-2和72 kDa MMP-2)、组织金属蛋白酶抑制物-2(TIMP-2)、转化生长因子-β1(TGF-β1)、结缔组织生长因子(CTGF)和α-平滑肌肌动蛋白(α-SMA)蛋白表达量。结果:与WKY组比较,SHR-UT组大鼠发生病理性心脏肥大(向心性),心肌细胞CSA、CVF和ColⅠ含量增加(P<0.05),心功能下降(P<0.05),ANP和β-MHC mRNA以及TGF-β1、CTGF和α-SMA蛋白表达量上调(P<0.05),64 kDa MMP-2/TIMP-2比值下降(P<0.05)。与SHR-UT组比较,SHR-MT组出现生理性心脏肥大(离心性),心肌细胞CSA无显著性变化(P>0.05),CVF和Col-Ⅰ含量下降(P<0.05),心功能升高(P<0.05),ANP和β-MHC mRNA以及TGF-β1、CTGF和α-SMA蛋白表达下调(P<0.05),64 kDa MMP-2/TIMP-2比值增加(P<0.05);SHR-HT组发生病理性心脏肥大(离心性),心肌细胞CSA无显著性变化,CVF和Col-Ⅰ含量升高,心功能下降,ANP和β-MHC mRNA表达量上调(P<0.05),TGF-β1、CTGF和α-SMA蛋白表达量则无显著性变化(P>0.05),64 kDa MMP-2/TIMP-2比值下降(P<0.05)。72 kDa MMP-2蛋白表达量在各组间均无显著性差异(P>0.05)。结论:18周MICT通过降低胶原合成并促进其降解以及抑制成纤维细胞向成肌纤维细胞分化而改善心肌胶原过度沉积,进而延缓心脏重塑和心衰进程;HIIT则通过抑制胶原降解(但对胶原合成无显著影响)加重心肌纤维化(反应性心肌纤维化),继而加速SHR心脏重塑和心衰进程。长期运动训练对高血压的心脏健康效应具有训练强度依赖性。

Objective To compare the effect and mechanism of the moderate intensity continuous training(MICT)and high intensity interval training(HIIT)on the myocardial collagen metabolism of spontaneously hypertensive rats(SHRs).Methods Forty-five male SHRs were randomly divided into a SHR-untraining(SHR-UT),a SHR-MICT(SHR-MT)and a SHR-HIIT(SHR-HT)group,each of 15,and another 15 Wistar-Kyoto(WKY)rats were chosen into a normotensive group.Rats of WKY and SHR-UT groups were kept at rest while those of SHR-MT and SHR-HT groups underwent MICT or HIIT for 18 weeks respectively.Forty-eight hours after the last experiment,the cardiac structure and function were detected using the echocardiography,and the myocardial collagen volume fraction(CVF)and cross sectional area(CSA)were observed histopathologically using Masson and Hematoxylin staining.The colorimetric method was used to determine the content of myocardial type Ⅰ collagen(Col Ⅰ).Western blotting was employed to measure the protein expression of matrix metalloproteinase-2(MMP-2)(including 64 kDa MMP-2 and 72 kDa MMP-2),tissue inhibitors of metalloproteinase-2(TIMP-2),transforming growth factor-β1(TGF-β1),connective tissue growth factor(CTGF)andα-smooth muscle actin(α-SMA).The mRNA expression of fetal genes including atrial natriuretic peptide(ANP)and β-myosin heavy chain(β-MHC)was detected using the reverse transcription-polymerase chain reaction.Results Compared with WKY group,rats in SHR-UT group showed pathological cardiac hypertrophy(centrality),with significantly increased content of the myocardial CSA,CVF and Col-Ⅰ,as well as ANP and β-MHC mRNA,and TGF-β1,CTGF andα-SMA protein(P<0.05 for all),together with reduced cardiac function and 64 kDa MMP-2/TIMP-2 ratio(P<0.05).Compared with SHR-UT group,SHR-MT group showed physiological cardiac hypertrophy(eccentric),with increased cardiac function and 64 kDa MMP-2/TIMP-2 ratio,decreased CVF and Col Ⅰ content,down-regulated ANP and β-MHC mRNA,and TGF-β1,CTGF andα-SMA protein(P<0.05 for all)but no no significant differences in the myocardial(CSA)(P>0.05).Compared with SHR-UT group,SHR-HT group developed physiological cardiac hypertrophy(eccentric),with cardiac function decreased significantly(P<0.05),ANP andβ-MHC mRNA upregulated(P<0.05),and CVF and Col Ⅰ content increased(P<0.05)significantly,but without significant differences in the TGF-β1,CTGF andα-SMA protein(P>0.05).There was no significant difference in the average 72 kDa MMP-2 expression among all groups(P>0.05).Conclusion MICT of 18 weeks improves myocardial collagen overdeposition through reducing collagen synthesis,promoting its degradation and inhibiting differentiation of fibroblasts into myofibroblasts,thus delaying the process of cardiac remodeling and heart failure.However,HIIT aggravates cardiac fibrosis(reactive cardiac fibrosis)through suppression of the collagen degradation without significant effect on the collagen synthesis,and then accelerates cardiac remodeling and heart failure process in SHR.Therefore,long-term exercise training has an intensity-dependent effect on the cardiac health of hypertension rats.