Circadian Influences on Myocardial Ischemia-Reperfusion Injury and Heart Failure.

The impact of circadian rhythms on cardiovascular function and disease development is well established, with numerous studies in genetically modified animals emphasizing the circadian molecular clock's significance in the pathogenesis and pathophysiology of myocardial ischemia and heart failure progression. However, translational preclinical studies targeting the heart's circadian biology are just now emerging and are leading to the development of a novel field of medicine termed circadian medicine. In this review, we explore circadian molecular mechanisms and novel therapies, including (1) intense light, (2) small molecules modulating the circadian mechanism, and (3) chronotherapies such as cardiovascular drugs and meal timings. These promise significant clinical translation in circadian medicine for cardiovascular disease. (4) Additionally, we address the differential functioning of the circadian mechanism in males versus females, emphasizing the consideration of biological sex, gender, and aging in circadian therapies for cardiovascular disease.

Pioneering new frontiers in circadian medicine chronotherapies for cardiovascular health.

Cardiovascular disease (CVD) is a global health concern. Circadian medicine improves cardiovascular care by aligning treatments with our body's daily rhythms and their underlying cellular circadian mechanisms. Time-based therapies, or chronotherapies, show special promise in clinical cardiology. They optimize treatment schedules for better outcomes with fewer side effects by recognizing the profound influence of rhythmic body cycles. In this review, we focus on three chronotherapy areas (medication, light, and meal timing) with potential to enhance cardiovascular care. We also highlight pioneering research in the new field of rest, the gut microbiome, novel chronotherapies for hypertension, pain management, and small molecules that targeting the circadian mechanism.

Toward Precision Medicine: Circadian Rhythm of Blood Pressure and Chronotherapy for Hypertension - 2021 NHLBI Workshop Report.

Healthy individuals exhibit blood pressure variation over a 24-hour period with higher blood pressure during wakefulness and lower blood pressure during sleep. Loss or disruption of the blood pressure circadian rhythm has been linked to adverse health outcomes, for example, cardiovascular disease, dementia, and chronic kidney disease. However, the current diagnostic and therapeutic approaches lack sufficient attention to the circadian rhythmicity of blood pressure. Sleep patterns, hormone release, eating habits, digestion, body temperature, renal and cardiovascular function, and other important host functions as well as gut microbiota exhibit circadian rhythms, and influence circadian rhythms of blood pressure. Potential benefits of nonpharmacologic interventions such as meal timing, and pharmacologic chronotherapeutic interventions, such as the bedtime administration of antihypertensive medications, have recently been suggested in some studies. However, the mechanisms underlying circadian rhythm-mediated blood pressure regulation and the efficacy of chronotherapy in hypertension remain unclear. This review summarizes the results of the National Heart, Lung, and Blood Institute workshop convened on October 27 to 29, 2021 to assess knowledge gaps and research opportunities in the study of circadian rhythm of blood pressure and chronotherapy for hypertension.

Circadian-Regulated Cell Death in Cardiovascular Diseases.

BACKGROUND: Over the past several years, a variety of human and animal studies have shown that circadian clocks regulate biological cardiovascular rhythms in both health and disease. For example, heart rate and blood pressure fluctuate over 24-hour daily periods, such that levels are higher in the morning and progressively decline in the evening. METHODS AND RESULTS: It is interesting to note that the timing of the administration of various cardiac treatments can also benefit some cardiovascular outcomes. Circadian rhythms have been implicated in the pathogenesis of a number of cardiovascular diseases, including myocardial infarction, ischemia-reperfusion injury after myocardial infarction, and heart failure. Cell death is a major component of ischemia-reperfusion injury and posited as the central underlying cause of ventricular remodeling and cardiac dysfunction following myocardial infarction. It is notable that the time of day profoundly influences cardiac tolerance and sensitivity to cardiac injury. CONCLUSIONS: Herein, we highlight the novel relationship between circadian rhythms and homeostatic processes that governs cell fate by apoptosis, necrosis, and autophagy. Understanding how these intricate processes interconnect at the cellular level is of paramount clinical importance for optimizing treatment strategies to achieve maximum cardiovascular outcome.

Consequences of Circadian and Sleep Disturbances for the Cardiovascular System.

Circadian rhythms play a crucial role in our cardiovascular system. Importantly, there has been a recent flurry of clinical and experimental studies revealing the profound adverse consequences of disturbing these rhythms on the cardiovascular system. For example, circadian disturbance worsens outcome after myocardial infarction with implications for patients in acute care settings. Moreover, disturbing rhythms exacerbates cardiac remodelling in heart disease models. Also, circadian dyssynchrony is a causal factor in the pathogenesis of heart disease. These discoveries have profound implications for the cardiovascular health of shift workers, individuals with circadian and sleep disorders, or anyone subjected to the 24/7 demands of society. Moreover, these studies give rise to 2 new frontiers for translational research: (1) circadian rhythms and the cardiac sarcomere, which sheds new light on our understanding of myofilament structure, signalling, and electrophysiology; and (2) knowledge translation, which includes biomarker discovery (chronobiomarkers), timing of therapies (chronotherapy), and other new promising approaches to improve the management and treatment of cardiovascular disease. Reconsidering circadian rhythms in the clinical setting benefits repair mechanisms, and offers new promise for patients.

Therapeutic applications of circadian rhythms for the cardiovascular system.

The cardiovascular system exhibits dramatic time-of-day dependent rhythms, for example the diurnal variation of heart rate, blood pressure, and timing of onset of adverse cardiovascular events such as heart attack and sudden cardiac death. Over the past decade, the circadian clock mechanism has emerged as a crucial factor regulating these daily fluctuations. Most recently, these studies have led to a growing clinical appreciation that targeting circadian biology offers a novel therapeutic approach toward cardiovascular (and other) diseases. Here we describe leading-edge therapeutic applications of circadian biology including (1) timing of therapy to maximize efficacy in treating heart disease (chronotherapy); (2) novel biomarkers discovered by testing for genomic, proteomic, metabolomic, or other factors at different times of day and night (chronobiomarkers); and (3) novel pharmacologic compounds that target the circadian mechanism with potential clinical applications (new chronobiology drugs). Cardiovascular disease remains a leading cause of death worldwide and new approaches in the management and treatment of heart disease are clearly warranted and can benefit patients clinically.

The primary benefits of angiotensin-converting enzyme inhibition on cardiac remodeling occur during sleep time in murine pressure overload hypertrophy.

OBJECTIVES: Our objective was to test the hypothesis that there is a significant diurnal variation for the therapeutic benefit of angiotensin-converting enzyme (ACE) inhibitors on pressure-overload cardiovascular hypertrophy. BACKGROUND: Physiological and molecular processes exhibit diurnal rhythms that may affect efficacy of disease treatment (chronotherapy). Evidence suggests that the heart primarily remodels during sleep. Although a growing body of clinical and epidemiological evidence suggests that the timing of therapy, such as ACE inhibition, alters diurnal blood pressure patterns in patients with hypertension, the benefits of chronotherapy on myocardial and vascular remodeling have not been studied. METHODS: We examined the effects of the short-acting ACE inhibitor, captopril, on the structure and function of cardiovascular tissue subjected to pressure overload by transverse aortic constriction (TAC) in mice. Captopril (15 mg/kg intraperitoneally) or placebo was administered at either murine sleep time or wake time for 8 weeks starting 1 week after surgery. RESULTS: TAC mice given captopril at sleep time had improved cardiac function and significantly decreased heart: body weight ratios, myocyte cross-sectional areas, intramyocardial vascular medial wall thickness, and perivascular collagen versus TAC mice given captopril or placebo during wake time. Captopril induced similar drops in blood pressure at sleep or wake time, suggesting that time-of-day differences were not attributable to blood pressure changes. These beneficial effects of captopril were correlated with diurnal changes in ACE mRNA expression in the heart. CONCLUSIONS: The ACE inhibitor captopril benefited cardiovascular remodeling only when administered during sleep; wake-time captopril ACE inhibition was identical to that of placebo. These studies support the hypothesis that the heart (and vessels) remodel during sleep time and also illustrate the importance of diurnal timing for some cardiovascular therapies.

Diurnal physiology: core principles with application to the pathogenesis, diagnosis, prevention, and treatment of myocardial hypertrophy and failure.

The circadian system has been shown to be fundamentally important in human health and disease. Recently, there have been major advances in our understanding of daily rhythmicity, and its relevance to human physiology, and to the pathogenesis and treatment of cardiac hypertrophy and heart failure. Cardiovascular tissues, such as heart and blood vessels, show remarkable daily variation in gene expression, metabolism, growth, and remodeling. Moreover, synchrony of daily molecular and physiological rhythms is integral to healthy organ growth and renewal. Disruption of these rhythms adversely affects normal growth, also the remodeling mechanisms in disease, leading to gross abnormalities in heart and vessels. These observations provide new insights into the pathogenesis, diagnosis, treatment, and prevention of heart disease. In this review, we focus on the recent advances in circadian biology and cardiovascular function, with particular emphasis on how this applies to human myocardial hypertrophy and heart failure, and the implications and importance for translational medicine.