Role of the circadian system in cardiovascular disease

Abstract

All species organize behaviors to optimally match daily changes in the environment, leading to pronounced activity/rest cycles that track the light/dark cycle. Endogenous, approximately 24-hour circadian rhythms in the brain, autonomic nervous system, heart, and vasculature prepare the cardiovascular system for optimal function during these anticipated behavioral cycles. Cardiovascular circadian rhythms, however, may be a double-edged sword. The normal amplified responses in the morning may aid the transition from sleep to activity, but such exaggerated responses are potentially perilous in individuals susceptible to adverse cardiovascular events. Indeed, the occurrence of stroke, myocardial infarction, and sudden cardiac death all have daily patterns, striking most frequently in the morning. Furthermore, chronic disruptions of the circadian clock, as with night-shift work, contribute to increased cardiovascular risk. Here we highlight the importance of the circadian system to normal cardiovascular function and to cardiovascular disease, and identify opportunities for optimizing timing of medications in cardiovascular disease.

The Circadian Syndrome: is the Metabolic Syndrome and much more!

“…Herein we discuss research findings relating to the proposed Circadian Syndrome risk components and comorbidities (Table 2). Hypertension Lack of nocturnal decline in blood pressure [30,62] High blood pressure [22] Lipids Disrupted lipid homeostasis [69,70] Obesity Disrupted diurnal rhythms in the white adipose tissue transcriptome [73] Obesity [22] Blood glucose levels Disrupted daily rhythms in blood glucose levels and glucose intolerance [17,21,75] Disrupted daily rhythms in blood glucose levels and glucose intolerance [22] Fatty liver Disrupted triglyceride accumulation, inflammation, oxidative stress and mitochondrial dysfunction [29] Depression Circadian disruption increases the incidences of depression [86,87] Circadian disruption increases the incidences of depression [22,83,84,[105][106][107][108][109][110] Sleep disturbances Circadian disturbances result in sleep loss and mistimed sleep [56,97] Proposing a Circadian Syndrome: Cardiovascular-related components Circadian oscillations have been reported for both physiological CVD regulation including heart rate and blood pressure [57], for cardiac disorders including arrythmias [58,59], and there is circadian variation in frequency of onset of myocardial infarction and sudden cardiac death [19,60].…”

“…Circadian oscillations have been reported for both physiological CVD regulation including heart rate and blood pressure , for cardiac disorders including arrythmias , and there is circadian variation in frequency of onset of myocardial infarction and sudden cardiac death .…”

Metabolic and cardiovascular consequences of shift work: The role of circadian disruption and sleep disturbances

“…Interestingly, recent evidence indicates that the composition of the human microbiome shows a 24‐hr variation that is affected by meal timing (Collado et al., ; Kaczmarek, Musaad, & Holscher, ). The function of the cardiovascular system is also subject to circadian regulation (Martino & Young, ; Thosar, Butler, & Shea, ). Circadian rhythms have been observed in blood pressure, heart rate, as well as in the parasympathetic and sympathetic modulation of the heart (Boudreau, Yeh, Dumont, & Boivin, ; Scheer et al., ).…”

“…These studies are typically conducted in healthy, non‐shift working participants under controlled laboratory conditions, because circadian misalignment is difficult to quantify in field conditions, as discussed above. Experimental protocols used to study the effects of circadian misalignment include forced desynchrony protocols, in which participants are exposed to non‐24‐hour sleep–wake and fasting–feeding cycles such that the endogenous circadian timing system becomes desynchronised from the behavioural cycles (Thosar et al., ). Circadian misalignment can also be experimentally induced by simulated night shift protocols, in which the sleep period is displaced to the daytime.…”

Chronotherapy for Hypertension

“…The daily patterns of behaviors including the sleep-wake, rest-activity and fasting-feeding cycles, influence the daily fluctuations of gastric pH, gastric emptying, gastrointestinal transit time, organ blood flow, liver enzyme activity, and renal function (1–4). The extent to which the internal circadian system also orchestrates these physiological variations is not well understood, although likely to be an important factor that interacts with these daily patterns of behaviors (5). The sum of these daily circadian (24-h) and behavioral physiological patterns can therefore affect a medication’s bioavailability and duration of action through absorption, distribution, metabolism and elimination.…”