Exercise training reverses myocardial dysfunction induced by CaMKIIδC overexpression by restoring Ca2+-homeostasis

Høydal, M. A. et al. (2016) Exercise training reverses myocardial dysfunction induced by CaMKIIδC overexpression by restoring Ca2+-homeostasis. Journal of Applied Physiology, 121(1), pp. 212-220. (doi: 10.1152/japplphysiol.00188.2016) (PMID:27231311)

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Several conditions of heart disease, including heart failure and diabetic cardiomyopathy, are associated with upregulation of cytosolic Ca2+/calmodulin-dependent protein kinase II (CaMKIIδC) activity. In the heart, CaMKIIδC isoform targets several proteins involved in intracellular Ca2+ homeostasis. We hypothesized that high-intensity endurance training activates mechanisms that enable a rescue of dysfunctional cardiomyocyte Ca2+ handling and thereby ameliorate cardiac dysfunction despite continuous and chronic elevated levels of CaMKIIδC. CaMKIIδC transgenic (TG) and wild-type (WT) mice performed aerobic interval exercise training over 6 wk. Cardiac function was measured by echocardiography in vivo, and cardiomyocyte shortening and intracellular Ca2+ handling were measured in vitro. TG mice had reduced global cardiac function, cardiomyocyte shortening (47% reduced compared with WT, P < 0.01), and impaired Ca2+ homeostasis. Despite no change in the chronic elevated levels of CaMKIIδC, exercise improved global cardiac function, restored cardiomyocyte shortening, and reestablished Ca2+ homeostasis to values not different from WT. The key features to explain restored Ca2+ homeostasis after exercise training were increased L-type Ca2+ current density and flux by 79 and 85%, respectively (P < 0.01), increased sarcoplasmic reticulum (SR) Ca2+-ATPase (SERCA2a) function by 50% (P < 0.01), and reduced diastolic SR Ca2+ leak by 73% (P < 0.01), compared with sedentary TG mice. In conclusion, exercise training improves global cardiac function as well as cardiomyocyte function in the presence of a maintained high CaMKII activity. The main mechanisms of exercise-induced improvements in TG CaMKIIδC mice are mediated via increased L-type Ca2+ channel currents and improved SR Ca2+ handling by restoration of SERCA2a function in addition to reduced diastolic SR Ca2+ leak.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Smith, Professor Godfrey and Kemi, Dr Ole and Kettlewell, Dr Sarah
Authors: Høydal, M. A., Stølen, T. O., Kettlewell, S., Maier, L. S., Brown, J. H., Sowa, T., Catalucc, D., Condorelli, G., Kemi, O. J., Smith, G. L., and Wisløff, U.
College/School:College of Medical Veterinary and Life Sciences > School of Cardiovascular & Metabolic Health
Journal Name:Journal of Applied Physiology
Publisher:American Physiological Society
ISSN (Online):1522-1601
Published Online:11 July 2016
Copyright Holders:Copyright © 2016 the American Physiological Society
First Published:First published in Journal of Applied Physiology 121(1):212-220
Publisher Policy:Reproduced in accordance with the copyright policy of the publisher
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