Moderate Continuous Aerobic Exercise Training Improves Cardiomyocyte Contractility in Β1 Adrenergic Receptor Knockout Mice

Abstract

BackgroundThe lack of cardiac β1-adrenergic receptors (β1-AR) negatively affects the regulation of both cardiac inotropy and lusitropy, leading, in the long term, to heart failure (HF). Moderate-intensity aerobic exercise (MCAE) is recommended as an adjunctive therapy for patients with HF.ObjectiveWe tested the effects of MCAE on the contractile properties of left ventricular (LV) myocytes from β1 adrenergic receptor knockout (β1ARKO) mice.MethodsFour- to five-month-old male wild type (WT) and β1ARKO mice were divided into groups: WT control (WTc) and trained (WTt); and β1ARKO control (β1ARKOc) and trained (β1ARKOt). Animals from trained groups were submitted to a MCAE regimen (60 min/day; 60% of maximal speed, 5 days/week) on a treadmill, for 8 weeks. P ≤ 0.05 was considered significant in all comparisons.ResultsThe β1ARKO and exercised mice exhibited a higher (p < 0.05) running capacity than WT and sedentary ones, respectively. The β1ARKO mice showed higher body (BW), heart (HW) and left ventricle (LVW) weights, as well as the HW/BW and LVW/BW than WT mice. However, the MCAE did not affect these parameters. Left ventricular myocytes from β1ARKO mice showed increased (p < 0.05) amplitude and velocities of contraction and relaxation than those from WT. In addition, MCAE increased (p < 0.05) amplitude and velocities of contraction and relaxation in β1ARKO mice.ConclusionMCAE improves myocyte contractility in the left ventricle of β1ARKO mice. This is evidence to support the therapeutic value of this type of exercise training in the treatment of heart diseases involving β1-AR desensitization or reduction.

A systematic comparison of exercise training protocols on animal models of cardiovascular capacity

“…Long-term exercise models are the most common procedure to carry out animal exercise training from weeks to months at 45 min-1 h/day and 5 days/week [59–61]. The animal treadmill or voluntary wheels are normally used as the modality to perform dynamic exercise and static & resistive exercise respectively.…”

Non-Pharmacological Treatment of Cardiovascular Disease | Importance of Physical Exercise

“…In articles recently published in this journal, the role of exercise and its molecular mechanisms of action have been evaluated in different heart disease experimental models. 3,5,11-13 The beneficial effects on cardiac remodeling have been frequently observed, such as attenuation of myocardial hypertrophy and left ventricular dysfunction. 7,14 However, unexpected results have drawn attention to the need for better clarification of the subject.…”

“…7,14 However, unexpected results have drawn attention to the need for better clarification of the subject. For instance, Rodrigues et al 13 submitted beta-adrenergic receptor knockout mice, which may develop heart failure, to treadmill training for eight weeks. Surprisingly, the trained knockout animals showed a higher increase in functional capacity and myocardial contractility than the trained control animals.…”

Endothelial Function and Physical Exercise

“…Physical exercises have been advocated for the promotion of health and the non-pharmacological treatment of cardiovascular diseases. Regular practice of exercises results in numerous health benefits, such as improvement in body composition, physical capacity, insulin resistance, endothelial function, arterial hypertension, antioxidant status, quality of life, 4 - 12 and an important effect on the endothelial system. During its practice, increased blood flow and shear stress improve vascular homeostasis by reducing the production of reactive oxygen species, and increasing the availability of nitric oxide in the endothelium.…”