To the Editor:
In his paper entitled “Muscular Hypertension: Is Creatine Kinase Responsible for Hypertension in Blacks?”, Dr Pickering summarized our work on creatine kinase (CK) as a causal factor for hypertension. 1
CK is the central regulatory enzyme of energy metabolism, which rapidly provides adenosine triphosphate for energy‐demanding cellular responses, such as skeletal muscle and cardiovascular contractility, and for transmembranous ion transport including sodium retention in the kidney.
We had proposed that relatively high CK activity in these tissues enhances cellular energy reserve and the capacity to execute these energy‐demanding responses, leading to greater hypertension risk. 2 The focus of our work has been the enhanced cardiovascular contractility and renal sodium retention with high CK, 2 but skeletal muscle characteristics are indeed relevant in our hypothesis of CK affecting blood pressure. 3 In a recently published paper on hypertension risk in patients with idiopathic “hyperCKemia,” we detailed how the properties of skeletal muscle may affect blood pressure, as high skeletal muscle CK activity is associated with a predominance of type 2 fibers, lower oxidative capacity, and capillary rarefaction, which may contribute to the greater peripheral resistance and higher blood pressure levels seen in population subgroups with high CK. 3
Hypertension clearly is a multifactorial condition on environmental and physiologic levels. Our hypothesis on CK incorporates Dr Pickering's view on the involvement of skeletal muscle in hypertensive disease, as we propose that high tissue CK activity is a generalized condition, with widespread effects on organ systems including skeletal muscle, the cardiovascular system, and the kidney, facilitating the development of hypertension. 2 , 3
Energy metabolism is fundamental to cellular function. With our further studies, we hope to provide more data and raise more interest for the role of tissue CK and bioenergetics in the pathophysiology of hypertensive disease.—Lizzy M. Brewster, MD, PhD; Gert A. van Montfrans, MD, PhD, Department of Internal and Vascular Medicine, Academic Medical Center, University of Amsterdam, The Netherlands
References
- 1. Pickering TG. Muscular hypertension; is creatine kinase responsible for hypertension in blacks? J Clin Hypertens (Greenwich) 2008;10(1):73–76. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 2. Brewster LM, Mairuhu G, Bindraban NR, et al. Creatine kinase activity is associated with blood pressure. Circulation 2006;114:2034–2039. [DOI] [PubMed] [Google Scholar]
- 3. Brewster LM, van Bree S, Reijneveld JC, et al. Hypertension risk in idiopathic hyperCKemia. J Neurol 2008;255:11–15. [DOI] [PubMed] [Google Scholar]