Effects of exercise training on cardiac function and myocardial remodeling in post myocardial infarction rats

Abstract

Objective-To test the hypothesis that early exercise training after myocardial infarction (MI) could preserve cardiac function, alleviate left ventricular (LV) remodeling and induce a protective effect on morphology.Methods-Male Sprague-Dawley rats underwent coronary ligation or sham operation, and were assigned to 3 groups: Sham, sedentary MI (SedMI), and exercise MI (ExMI). We measured the changes in collagen volume fraction, matrix metalloproteinase (MMP) 1, tissue inhibitor matrix metalloproteinase 1 (TIMP-1), angiotensin II receptor type 1 (AT1), and angiotensin converting enzyme (ACE) at gene and protein levels after 8 weeks of exercise training. Cardiac functions were determined by echocardiographic and hemodynamic measurements.Results-Early exercise training after MI had no effect on LV wall thinning. Cardiac function was significantly preserved in the ExMI group in comparison to the SedMI group. The collagen volume fraction in the ExMI group was significantly lower than in the SedMI group. Compared to the SedMI group, the ExMI group showed a markedly decrease at both the gene and protein levels in TIMP-1 (P<0.05). No significant differences were found in MMP-1 among the three groups. MMP-1/TIMP-1 ratio in the ExMI group was significantly higher than in the SedMI group. In addition, the expression of AT1 protein in the ExMI group was significantly lower than in the SedMI group. Furthermore, both ACE mRNA expression and ACE binding in the ExMI group are significantly decreased compared to the SedMI group.Conclusions-Our results suggest that early exercise training after MI reduces TIMP-1 expression, improves the balance between MMPs and TIMPs, and mitigates the expressions of ACE and AT1 receptor. These improvements, in turn, attenuate myocardial fibrosis and preserve post-MI cardiac function.

Expression of MicroRNA-29 and Collagen in Cardiac Muscle after Swimming Training in Myocardial-Infarcted Rats

“…However, this reduction did not influence the expression of collagens. We speculate that the gene expression of collagens might be attenuated by some conditions in the infarction zone, such as increased cell death [3,7]. Furthermore impaired microvasculature must have been responsible for the non significant effect of exercise in this region [3,33].…”

“…After MI, complex molecular and structural modifications occur in both the infarcted and non-infarcted myocardium [3,4]. The myocardial tissue is composed of different cell types such as myocytes, fibroblasts and vascular cells which play critical roles during the remodeling process [5,6,7]. Cardiac fibrosis is characterized by an increase in cardiac collagen content and is a dynamic process that plays a essential role in the progression of heart failure after MI.…”

Cardiovascular Effects of Exercise Training

“…In a rat model of ischemic CHF, the beneficial training effects on local neurohumoral balance were analyzed in the noninfarcted LV myocardium. Xu and colleagues 77 found a significant reduction of myocardial angiotensin-converting enzyme mRNA expression and AT 1 -receptor expression after 8 weeks of treadmill training. This finding is of special importance given the fact that Ͼ90% of angiotensin II is produced locally in the myocardium and implies that local angiotensin II levels are significantly reduced by training.…”

“…This reduction also translates into reduced fibrogenesis, as indicated by reduced tissue inhibitor of metalloproteinase-1 expression with unchanged matrix metalloproteinase (MMP)-1 expression and reduced collagen volume fraction in the exercised animals. 77 Diastolic Heart Failure Heart failure with normal ejection fraction is a comparatively new disease category that includes patients who display the typical clinical, physiological, and neurohormonal heart failure phenotype in the absence of reduced LV ejection fraction. 78 Thus far, no specific pharmaceutical therapy for heart failure with normal ejection fraction has been found.…”

Associação de betabloqueadores e treinamento físico na insuficiência cardíaca de camundongos

“…Other effects of physical training on minimizing the process of myocardial failure have recently been shown and may be associated with a reduction in proteins associated with fibrosis and cardiac remodeling, among other factors 39,40 .…”