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Scand Cardiovasc J. 2019 Sep 10:1-8. doi: 10.1080/14017431.2019.1658893. [Epub ahead of print]

Effect of exercise training on cardiac metabolism in rats with heart failure.

Author information

1
Department of Circulation and Medical Imaging, NTNU, Norwegian University of Science and Technology , Trondheim , Norway.
2
Clinic of Cardiology, St Olavs Hospital , Trondheim , Norway.
3
Clinic of Cardiothoracic Surgery, St Olavs Hospital , Trondheim , Norway.
4
Department of Diagnostic Imaging, Akershus University Hospital , Lørenskog , Norway.

Abstract

Objectives. Heart failure (HF) impairs resting myocardial energetics, myocardial mitochondrial performance, and maximal oxygen uptake (VO2max). Exercise training is included in most rehabilitation programs and benefits HF patients. However, the effect of exercise intensity on cardiac mitochondrial respiration and concentrations of the key bioenergetic metabolites phosphocreatine (PCr), adenosine triphosphate (ATP), and inorganic phosphate (Pi) is unclear. This study aimed to investigate the effects of exercise training at different intensities in rats with HF. Methods. Rats underwent myocardial infarction or sham operations and were divided into three subgroups: sedentary, moderate intensity, or high intensity. The impact of HF and 6 weeks of exercise training on energy metabolism was evaluated by 31P magnetic resonance spectroscopy and mitochondrial respirometry. The concentrations of PCr, ATP, and Pi were quantified by magnetic resonance spectroscopy. VO2max was measured by treadmill respirometry. Results. Exercise training increased VO2max in sham and HF. PCr/ATP ratio was reduced in HF (p < .01) and remained unchanged by exercise training. PCr concentration was significantly lower in HF compared to sham (p < .01). Moderate and high-intensity exercise training increased ATP in HF and sham. HF impaired complex I (CI) and complex II (p = .034) respiration. High-intensity exercise training recovered CI respiration in HF rats compared to HF sedentary (p = .014). Conclusions. Exercise training improved cardiac performance, as indicated by increased VO2max and higher exercise capacity, without changing the myocardial PCr/ATP ratio. These observations suggest that the PCr/ATP biomarker is not suited to evaluate the beneficial effects of exercise training in the heart. The exact mechanisms require further investigations, as exercise training did increase ATP levels and CI respiration.

KEYWORDS:

31P MRS; ATP; Myocardial infarction; exercise; high-energy phosphate; magnetic resonance spectroscopy; mitochondrial respirometry; phosphocreatine

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