Appropriate exercise training (ExT) has been shown to decrease high blood pressure. Accumulating data have indicated the beneficial effects of ExT on prehypertension. This study tested whether prehypertension ExT protects against hypertension and cardiac remodeling in spontaneously hypertensive rats (SHR) and explored the underlying mechanisms by examining the cardiac angiotensin-converting enzyme (ACE) and ACE2 signaling axes. Low-intensity ExT was started in male SHR and control Wistar-Kyoto rats prior to the onset of hypertension and maintained for 8 or 16 weeks. Blood pressure (BP) was measured biweekly by the tail-cuff method. Cardiac function and remodeling were assessed, and changes in the ACE and ACE2 axes were examined after the final ExT session. The results showed that prehypertension ExT slowed the onset and progression of hypertension in SHR. In parallel, hypertrophy in the hearts of hypertensive rats was attenuated, myocardial fibrosis was reduced, and impairment of left ventricular diastolic function was reduced. In the SHR myocardium, the levels of components involved in the ACE-Ang II-AT1 axis were homogeneously and progressively increased, whereas those involved in the ACE2-Ang(1-7)-MAS axis were heterogeneously decreased. Different temporal responses were observed for the key effectors Ang II and Ang(1-7). Myocardial Ang II levels were progressively increased in SHR and were consistently reduced by ExT. By contrast, Ang(1-7) decreased only after 16 weeks of sedentariness, and this decrease was abolished by ExT. In addition, 16 weeks of ExT increased the levels of Ang(1-7) in normotensive control rats. In summary, prehypertension ExT attenuates hypertension and cardiac remodeling. Downregulation of Ang II seems to serve as a protective mechanism during ExT, while upregulation of Ang(1-7) is induced after a relatively long period of ExT.
Keywords: Cardiac remodeling; Exercise training; Hypertension; Prehypertension; Renin–angiotensin system.