© 2001 American Heart Association, Inc.
Editorials |
Molecular Clock Mechanisms and Circadian Rhythms Intrinsic to the Heart
From the Division of Cardiology, Department of Pediatrics, University of Washington, and Children’s Hospital and Regional Medical Center, Seattle, Wash.
Correspondence to Michael A. Portman, MD, Department of Cardiology, Children’s Hospital and Regional Medical Center, 4800 Sand Point Way NE, PO Box 5371/CH-11, Seattle, WA 98105-0371. E-mail mportm@chmc.org
Key Words: function • gene expression • metabolism
Circadian rhythms are the external expression of an internal clock mechanism that measures daily time.1 Periodic environmental cues entrain or set the circadian clocks. The daily light-dark cycle represents the most dominant and potent entraining stimulus in mammals. An entrained clock coordinates physiological events to the 24-hour day. Normally, cardiovascular or hemodynamic parameters, such as heart rate and blood pressure, exhibit variations consistent with circadian rhythm. Additionally, several types of acute pathological cardiac events exhibit circadian or at least diurnal rhythm patterns. Specifically, the incidences of acute myocardial infarction, myocardial ischemia, out-of-hospital cardiac arrest, ventricular tachycardia, postmyocardial infarction, and sudden death in heart failure all vary according to the time of day.2–5 Also, diurnal rhythms can influence degree and form of cardiac hypertrophy and remodeling.6,7 For instance, the degree of nocturnal blood pressure elevation in patients with systemic hypertension correlates with the severity and concentricity of left ventricular hypertrophy.8,9 Investigators postulate that these circadian or diurnal variations depend on centrally mediated autonomic or neurohumoral activation. However, peak incidence for some acute events, such as sudden death, does not temporally correspond to the circadian sympathetic activation. Thus, alternative inputs or mechanisms for these rhythm patterns have been postulated. Regardless of the input, the intrinsic clock mechanism must respond and regulate some of the circadian rhythms within the heart itself.
The intrinsic response elements for the putative external circadian inputs had not until recently been identified or characterized in the heart.10,11 Circadian rhythms are controlled by a transcriptional feedback system fluctuating as
This article has been cited by other articles:
 |
|
 |
|
  S. Y. Boateng and P. H. Goldspink Assembly and maintenance of the sarcomere night and day Cardiovasc Res, March 1, 2008; 77(4): 667 - 675. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 N. Takeda, K. Maemura, S. Horie, K. Oishi, Y. Imai, T. Harada, T. Saito, T. Shiga, E. Amiya, I. Manabe, et al. Thrombomodulin Is a Clock-controlled Gene in Vascular Endothelial Cells J. Biol. Chem., November 9, 2007; 282(45): 32561 - 32567. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 P. Y. Woon, P. J. Kaisaki, J. Braganca, M.-T. Bihoreau, J. C. Levy, M. Farrall, and D. Gauguier Aryl hydrocarbon receptor nuclear translocator-like (BMAL1) is associated with susceptibility to hypertension and type 2 diabetes PNAS, September 4, 2007; 104(36): 14412 - 14417. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 T. Mohri, N. Emoto, H. Nonaka, H. Fukuya, K. Yagita, H. Okamura, and M. Yokoyama Alterations of Circadian Expressions of Clock Genes in Dahl Salt-Sensitive Rats Fed a High-Salt Diet Hypertension, August 1, 2003; 42(2): 189 - 194. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. Oserman, S. Watnick, T. F. Griffith, J. A. Coladonato, W. F. Owen, Jr, J. A. Vassalotti, R. Manfredini, B. Boari, O. la Cecilia, F. Portaluppi, et al. Does Time of Day of Hemodialysis Affect Survival? JAMA, March 13, 2002; 287(10): 1262 - 1264. [Full Text] [PDF]
|
|