Chapter 19 - The impact of the circadian timing system on cardiovascular and metabolic function
Introduction
Western societies are rife with cardiovascular disease, diabetes, and obesity. In the United States, it is estimated that 83 million adults have cardiovascular disease (Roger et al., 2011), 26 million have diabetes (Centers for Disease Control and Prevention, 2011), and 80 million are obese (Flegal et al., 2010). The influence of behaviors (e.g., poor diet and physical inactivity) as underlying causes for these diseases has been researched for decades. However, more recently, evidence has been accumulating for a contributing role of the endogenous circadian timing system and its disruption in cardiovascular and metabolic disorders. In this review, we discuss—with a focus on mammals and particularly humans—the impact of the circadian timing system, its interaction with behaviors (e.g., exercise), and its disturbance on cardiovascular and metabolic function.
Section snippets
The circadian timing system
Most life on earth—ranging from single cellular organisms, plants, flies, rats, to humans—contains an endogenous timing system that optimally synchronizes physiology and behavior (e.g., rest/activity and fasting/feedings cycles) with the solar day. The system is known as the circadian (“circa,” around; “dies,” day) timing system and has two core characteristics: (1) endogenous rhythmicity that cycles approximately every 24 h, even in the absence of cyclic changes in external factors such as
The internal clock and the timing of adverse cardiovascular events
Epidemiological data demonstrate a 24-h rhythm in the frequency of adverse cardiovascular events such as angina, myocardial infarction, stroke, arrhythmias, cardiac arrest, and sudden cardiac death (Fig. 1), with the highest incidence occurring between approximately 6 AM and noon (Cannon et al., 1997, Cohen et al., 1997, D'Avila et al., 1995, Elliott, 1998, Goldberg et al., 1990, Levine et al., 1992, Marler et al., 1989, Muller et al., 1985, Muller et al., 1987, Twidale et al., 1989, Willich et
Circadian disruption and cardiovascular function
In the previous section, we provided recent evidence for the impact of the circadian timing system on cardiovascular risk markers that—if confirmed in vulnerable populations—may contribute to the morning peak in adverse cardiovascular events. However, in healthy individuals, the circadian timing system has been proposed to optimally regulate many physiological processes to prepare for the varying demands across the sleep/wake cycle. If this would be the case, it would be expected that circadian
Circadian disruption and metabolic function
Human endogenous circadian rhythms have been observed in many factors related to metabolism. For example, glucose, insulin, cortisol, epinephrine, norepinephrine, and leptin display endogenous circadian variation (Morgan et al., 1998, Scheer et al., 2009, Scheer et al., 2010, Shea et al., 2005, Van Cauter et al., 1994, Wehr et al., 2001). Recent research demonstrates that amino acid plasma concentrations are under endogenous circadian control, through Krüppel-like factor 15-control of the
Summary
The circadian timing system orchestrates cyclic variations in numerous cardiovascular and metabolic functions independent of external influences such as darkness/light, sleep/wakefulness, rest/activity, and fasting/eating. At rest, the circadian timing system causes some factors to peak during the biological morning (e.g., cortisol, platelet expression of activated GPIIb-IIIa, P-selectin, and GP1b), which could potentiate the onset of adverse cardiovascular events at that time. This suggests
Acknowledgments
C. J. M. was supported by the National Space Biomedical Research Institute through NASA NCC 9-58. F. A. J. L. S. was supported by National Institute of Health Grants P30-HL101299 and R01 HL094806.
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2022, Eating BehaviorsCitation Excerpt :Observed shifts in meal timing and increased kcal intake later in the day are likely due to several biologically and behaviorally based factors. For example, there is increased recognition of the interconnectedness of circadian factors not only with sleep timing but also eating behaviors and metabolic outcomes (Jiang & Turek, 2017; McHill & Wright, 2017; Morris et al., 2012; Scheer et al., 2013). Of particular relevance to the present findings, an experimental study conducted with adults demonstrated the existence of endogenous circadian rhythms for hunger with peak hunger ratings in the evening (approximately 2000 h) (Scheer et al., 2013).