Molecular time: an often overlooked dimension to 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.

One Health: Circadian Medicine Benefits Both Non-human Animals and Humans Alike

Circadian biology's impact on human physical health and its role in disease development and progression is widely recognized. The forefront of circadian rhythm research now focuses on translational applications to clinical medicine, aiming to enhance disease diagnosis, prognosis, and treatment responses. However, the field of circadian medicine has predominantly concentrated on human healthcare, neglecting its potential for transformative applications in veterinary medicine, thereby overlooking opportunities to improve non-human animal health and welfare. This review consists of three main sections. The first section focuses on the translational potential of circadian medicine into current industry practices of agricultural animals, with a particular emphasis on horses, broiler chickens, and laying hens. The second section delves into the potential applications of circadian medicine in small animal veterinary care, primarily focusing on our companion animals, namely dogs and cats. The final section explores emerging frontiers in circadian medicine, encompassing aquaculture, veterinary hospital care, and non-human animal welfare and concludes with the integration of One Health principles. In summary, circadian medicine represents a highly promising field of medicine that holds the potential to significantly enhance the clinical care and overall health of all animals, extending its impact beyond human healthcare.

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.

Circadian disruption during fetal development promotes pathological cardiac remodeling in male mice

Disruption of circadian rhythms during fetal development may predispose mice to developing heart disease later in life. Here, we report that male, but not female, mice that had experienced chronic circadian disturbance (CCD) in utero were more susceptible to pathological cardiac remodeling compared with mice that had developed under normal intrauterine conditions. CCD-treated males showed ventricular chamber dilatation, enhanced myocardial fibrosis, decreased contractility, higher rates of induced tachyarrhythmia, and elevated expression of biomarkers for heart failure and myocardial remodeling. In utero CCD exposure also triggered sex-dependent changes in cardiac gene expression, including upregulation of the secretoglobin gene, Scgb1a1, in males. Importantly, cardiac overexpression of Scgb1a1 was sufficient to induce myocardial hypertrophy in otherwise naive male mice. Our findings reveal that in utero CCD exposure predisposes male mice to pathological remodeling of the heart later in life, likely as a consequence of SCGB1A1 upregulation.

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.

Dependence of clinical outcomes on time of hospital admission in patients with ST-segment elevation myocardial infarction

BACKGROUND

There are conflicting results in studies investigating the effects of percutaneous coronary intervention (PCI) on the prognosis of patients with ST-segment elevation myocardial infarction (STEMI) during or outside of usual hospital working hours. While some researchers have reported higher mortality rates in STEMI patients admitted outside of working hours, others did not find a statistically significant difference.

OBJECTIVES

Investigate the short-term endpoints and long-term outcomes of STEMI patients by time of admission.

DESIGN

Retrospective SETTING: Tertiary percutaneous coronary intervention center.

PATIENTS AND METHODS

Patients were grouped by admission, which consisted of four intervals: 06:00 to <12:00, 12:00 to <18:00, 18:00 to <24:00, and 24:00 to <06:00. We analyzed demographic, clinical and mortality by admission time interval and mortality by multivariate analyses, including the time intervals.

MAIN OUTCOME MEASURES

Clinical data and mortality SAMPLE SIZE: 735 patients; median (IQR) age 62 (22) years; 215 (29.3%) women.

RESULTS

Patients admitted at night were 1.37 times more likely to experience pulmonary edema than patients whose symptoms started in the daytime (P=.012); 32.9% of the patients whose symptoms started at night presented with Killip class II-IV, while during the daytime, 21.4% presented with Killip class II-IV (P=.001). Among the patients, the most common was inferior STEMI (38.6%). However, no-reflow was significantly higher during the daytime compared to the nighttime (P=.12). The risk of the cardiac arrest on admission was 1.2 times higher in patients admitted at night (P=.034). Neither time interval of admission nor several other variables had an effect on clinical outcome or mortality.

CONCLUSIONS

While patients admitted at night presented with pulmonary edema and cardiogenic shock more frequently, no reflow was observed during the day after the procedure. Although patients admitted at night with STEMI presented with worse clinical conditions, similar results were observed between the groups in clinical outcomes.

LIMITATIONS

More "real world" results might have been obtained if the study had replicated more typical referral conditions for PCI.

CONFLICT OF INTEREST

None.

A brief morning rest period benefits cardiac repair in pressure overload hypertrophy and postmyocardial infarction

Rest has long been considered beneficial to patient healing; however, remarkably, there are no evidence-based experimental models determining how it benefits disease outcomes. Here, we created an experimental rest model in mice that briefly extends the morning rest period. We found in 2 major cardiovascular disease conditions (cardiac hypertrophy, myocardial infarction) that imposing a short, extended period of morning rest each day limited cardiac remodeling compared with controls. Mechanistically, rest mitigates autonomic-mediated hemodynamic stress on the cardiovascular system, relaxes myofilament contractility, and attenuates cardiac remodeling genes, consistent with the benefits on cardiac structure and function. These same rest-responsive gene pathways underlie the pathophysiology of many major human cardiovascular conditions, as demonstrated by interrogating open-source transcriptomic data; thus, patients with other conditions may also benefit from a morning rest period in a similar manner. Our findings implicate rest as a key driver of physiology, creating a potentially new field - as broad and important as diet, sleep, or exercise - and provide a strong rationale for investigation of rest-based therapy for major clinical diseases.

Influence of Intermittent Fasting During Ramadan on Circadian Variation of Symptom-Onset and Prehospital Time Delay in Acute ST-Segment Elevation Myocardial Infarction

Ramadan interferes with circadian rhythms mainly by disturbing the routine patterns of feeding and smoking. The objective of this study was to investigate the circadian pattern of ST elevation acute myocardial infarction (STEMI) during the month of Ramadan. We studied consecutive STEMI patients 1 month before and after Ramadan (non-Ramadan group-NRG) and during Ramadan (Ramadan group-RG). The RG group was also divided into two groups, based on whether they chose to fast: fasting (FG) and non-fasting group (NFG). The time of STEMI onset was compared. A total of 742 consecutive STEMI patients were classified into 4 groups by 6 h intervals according to time-of-day at symptom onset. No consistent circadian variation in the onset of STEMI was observed both between the RG (P = .938) and NRG (P = .766) or between the FG (P = .232) and NFG (P = .523). When analyzed for subgroups of the study sample, neither smoking nor diabetes showed circadian rhythm. There was a trend towards a delay from symptom onset to hospital presentation, particularly at evening hours in the RG compared with the control group. In conclusion, there was no significant difference in STEMI onset time, but the time from symptom onset to hospital admission was significantly delayed during Ramadan.

Obesity Induces Disruption of Microvascular Endothelial Circadian Rhythm

Obese individuals are at significantly elevated risk of developing cardiovascular disease (CVD). Additionally, obesity has been associated with disrupted circadian rhythm, manifesting in abnormal sleeping and feeding patterns. To date, the mechanisms linking obesity, circadian disruption, and CVD are incompletely understood, and insight into novel mechanistic pathways is desperately needed to improve therapeutic potential and decrease morbidity and mortality. The objective of this study was to investigate the roles of metabolic and circadian disruptions in obesity and assess their contributions in promoting vascular disease. Lean (db/+) and obese (db/db) mice were subjected to 12 weeks of constant darkness to differentiate diurnal and circadian rhythms, and were assessed for changes in metabolism, gene expression, and vascular function. Expression of endothelial nitric oxide synthase (eNOS), an essential enzyme for vascular health, was blunted in obesity and correlated with the oscillatory loss of the novel regulator cezanne (OTUD7B). Lean mice subjected to constant darkness displayed marked reduction in vasodilatory capacity, while endothelial dysfunction of obese mice was not further compounded by diurnal insult. Endothelial gene expression of essential circadian clock components was altered in obesity, but imperfectly phenocopied in lean mice housed in constant darkness, suggesting overlapping but separate mechanisms driving endothelial dysfunction in obesity and circadian disruption. Taken together, these data provide insight into the nature of endothelial circadian rhythm in obesity and suggest a distinct mechanism by which obesity causes a unique circadian defect in the vasculature.

The role of the cardiomyocyte circadian clocks in ion channel regulation and cardiac electrophysiology

Daily variations in cardiac electrophysiology and the incidence for different types of arrhythmias reflect ≈24 h changes in the environment, behaviour and internal circadian rhythms. This article focuses on studies that use animal models to separate the impact that circadian rhythms, as well as changes in the environment and behaviour, have on 24 h rhythms in heart rate and ventricular repolarization. Circadian rhythms are initiated at the cellular level by circadian clocks, transcription-translation feedback loops that cycle with a periodicity of 24 h. Several studies now show that the circadian clock in cardiomyocytes regulates the expression of cardiac ion channels by multiple mechanisms; underlies time-of-day changes in sinoatrial node excitability/intrinsic heart rate; and limits the duration of the ventricular action potential waveform. However, the 24 h rhythms in heart rate and ventricular repolarization are primarily driven by autonomic signalling. A functional role for the cardiomyocyte circadian clock appears to buffer the heart against perturbations. For example, the cardiomyocyte circadian clock limits QT-interval prolongation (especially at slower heart rates), and it may facilitate the realignment of the 24 h rhythm in heart rate to abrupt changes in the light cycle. Additional studies show that modifying rhythmic behaviours (including feeding behaviour) can dramatically impact the 24 h rhythms in heart rate and ventricular repolarization. If these mechanisms are conserved, these studies suggest that targeting endogenous circadian mechanisms in the heart, as well as modifying the timing of certain rhythmic behaviours, could emerge as therapeutic strategies to support heart function against perturbations and regulate 24 h rhythms in cardiac electrophysiology.

Contemporary impact of circadian symptom-onset patterns of acute ST-Segment elevation myocardial infarction on long-term outcomes after primary percutaneous coronary intervention

BACKGROUND

Daytime variation with regard to onset time of ST-elevation myocardial infarction (STEMI) symptoms has been observed. Nevertheless, with the advanced medical therapy, it is not uncertainty if a similar circadian pattern of STEMI symptom onset occurs, as well as its possible impact on clinical outcomes. Few long-term data are available. We assess the impact of circadian symptom-onset patterns of STEMI on major adverse cardiovascular events (MACE) in more contemporary patients treated with primary percutaneous coronary intervention (PPCI).

METHODS AND RESULTS

A total of 1099 consecutive STEMI patients undergoing PPCI ≤12h from symptom onset during 2013 to 2019 were classified into 4 groups by 6-h intervals according to time-of-day at symptom onset: night (0:00-5:59), morning (6:00-11:59), afternoon (12:00-17:59), and evening (18:00-23:59). Incidence of MACE including cardiovascular death and nonfatal MI during a median follow-up of 48 months was compared among the 4 groups. A morning peak of symptom onset of STEMI was detected during the period 06:00-11:59 (p < .001). Compared with other three 6-h intervals, the incidence of long-term MACE during night onset-time (18.8%, 10.1%, 10.7% and 12.4%, p = .020) was significant higher that was driven by more mortality (13.1%, 6.5%, 7.1%and 7.7%, p = .044). Night symptom-onset STEMI was independently associated with subsequent MACE (hazard ratio = 1.57, 95%CI: 1.09-2.27, p = .017) even after multivariable adjustment.

CONCLUSIONS

Circadian variation of STEMI symptom-onset with morning predominance still exists in contemporary practice. Night symptom-onset STEMI was independently associated with increased risk of MACE in Chinese patients treated with PPCI.

Sleep Neurobiology and the Critical Care Environment

TOPIC

Sleep in the intensive care unit can be poorly consolidated and highly fragmented. This review examines the neurobiology of normal and abnormal sleep, with a focus on the changes that occur in the intensive care unit environment.

CLINICAL RELEVANCE

Patients in the intensive care unit demonstrate a lack of rapid-eye-movement sleep and an inability to effectively transition from light to deep stages of sleep. These abnormalities can adversely affect hemodynamic parameters and physiological and psychological outcomes.

PURPOSE

To describe the brain mechanisms and electroencephalographic characteristics of wakefulness and the different stages of sleep. This review also describes how sleep can be altered by hospitalization in the intensive care unit and how nurses can design interventions that improve sleep and outcomes.

CONTENT COVERED

The review examines sleep mechanisms, including brain electrical activity, regulatory centers in the brain, and circadian and diurnal patterns of sleep and hemodynamic function. Nursing interventions for specific patient risk factors in the intensive care unit are proposed.

Epigenetic role of N6-methyladenosine (m6A) RNA methylation in the cardiovascular system

As the most prevalent and abundant transcriptional modification in the eukaryotic genome, the continuous and dynamic regulation of N6-methyladenosine (m6A) has been shown to play a vital role in physiological and pathological processes of cardiovascular diseases (CVDs), such as ischemic heart failure (HF), myocardial hypertrophy, myocardial infarction (MI), and cardiomyogenesis. Regulation is achieved by modulating the expression of m6A enzymes and their downstream cardiac genes. In addition, this process has a major impact on different aspects of internal biological metabolism and several other external environmental effects associated with the development of CVDs. However, the exact molecular mechanism of m6A epigenetic regulation has not been fully elucidated. In this review, we outline recent advances and discuss potential therapeutic strategies for managing m6A in relation to several common CVD-related metabolic disorders and external environmental factors. Note that an appropriate understanding of the biological function of m6A in the cardiovascular system will pave the way towards exploring the mechanisms responsible for the development of other CVDs and their associated symptoms. Finally, it can provide new insights for the development of novel therapeutic agents for use in clinical practice.

Circadian variation of the QT interval and heart rate variability and their interrelationship

BACKGROUND

Whether the QT interval displays circadian rhythm after heart rate correction is unresolved and the relationship of QT interval to heart rate variability (HRV) is uncertain.

OBJECTIVES

To test the hypothesis that there is a circadian rhythm to QT interval and HRV and determine the relationship between QTc and HRV.

METHODS

The hourly average ECG data from 24-h ECGs were examined in individuals (50 without medications and 9 on beta blockers only) with no evidence of coronary artery disease or structural heart disease. The QT duration of normal QRS complexes from a series of 30-s windows was measured. The presence of circadian rhythm was tested by the data analytic approach of goodness of fit to a cosine function.

RESULTS

QT interval with and without heart rate correction showed a circadian rhythm for five heart rate adjustment formulae except for the Bazett formula. HRV also showed circadian rhythm but with different acrophages and nadirs depending on the HRV component. There were significant (p < 0.05) positive correlations of QTc with pNN50 rms-SD and SDNN and significant (p < 0.05) negative correlations with SDANN and Tri. The beta blocker group did not generally show circadian rhythm for QT interval or HRV.

CONCLUSION

QT, after heart rate adjustment, and HRV have circadian rhythmicity. There are significant correlations between QT interval and HRV indices. Circadian rhythm was blunted with beta blockers. The data are consistent with the concept of a predominance of parasympathetic activity to increase QTc and sympathetic activity to shorten QTc, even after 'correction' of the QT interval for heart rate.

Oxidative Stress in Ischemic Heart Disease

One of the novel interesting topics in the study of cardiovascular disease is the role of the oxidation system, since inflammation and oxidative stress are known to lead to cardiovascular diseases, their progression and complications. During decades of research, many complex interactions between agents of oxidative stress, oxidation, and antioxidant systems have been elucidated, and numerous important pathophysiological links to na number of disorders and diseases have been established. This review article will present the most relevant knowledge linking oxidative stress to vascular dysfunction and disease. The review will focus on the role of oxidative stress in endotheleial dysfunction, atherosclerosis, and other pathogenetic processes and mechanisms that contribute to the development of ischemic heart disease.

Circadian influence on inflammatory response during cardiovascular disease

Circadian rhythms follow a 24 h day and night cycle, regulate vital physiological processes, and are especially relevant to cardiovascular growth, renewal, repair, and remodeling. A recent flurry of clinical and experimental studies reveals a profound circadian influence on immune responses in cardiovascular disease. The first section of this review summarizes the importance of circadian rhythms for cardiovascular health and disease. The second section introduces the circadian nature of inflammatory responses. The third section combines these to elucidate a new role for the circadian system, influencing inflammation in heart disease, especially myocardial infarction. Particular focus is on circadian regulation of the NACHT, LRR, and PYD domains-containing protein 3 inflammasome, neutrophils, monocytes/macrophages, and T cells involved in cardiac repair. A role for biological sex is noted. The final section explores circadian influences on inflammation in other major cardiovascular conditions. Circadian regulation of inflammation has profound implications for benefitting the diagnosis, treatment, and prognosis of patients with cardiovascular disease.

Circadian influence on the microbiome improves heart failure outcomes

Myocardial infarction (MI) leading to heart failure (HF) is a major cause of death worldwide. Previous studies revealed that the circadian system markedly impacts cardiac repair post-MI, and that light is an important environmental factor modulating the circadian influence over healing. Recent studies suggest that gut physiology also affects the circadian system, but how it contributes to cardiac repair post-MI and in HF is not well understood. To address this question, we first used a murine coronary artery ligation MI model to reveal that an intact gut microbiome is important for cardiac repair. Specifically, gut microbiome disruption impairs normal inflammatory responses in infarcted myocardium, elevates adverse cardiac gene biomarkers, and leads to worse HF outcomes. Conversely, reconstituting the microbiome post-MI in mice with prior gut microbiome disruption improves healing, consistent with the notion that normal gut physiology contributes to cardiac repair. To investigate a role for the circadian system, we initially utilized circadian mutant Clock∆19/∆19 mice, revealing that a functional circadian mechanism is necessary for gut microbiome benefits on post-MI cardiac repair and HF. Finally, we demonstrate that circadian-mediated gut responses that benefit cardiac repair can be conferred by time-restricted feeding, as wake time feeding of MI mice improves HF outcomes, but these benefits are not observed in MI mice fed during their sleep time. In summary, gut physiology is important for cardiac repair, and the circadian system influences the beneficial gut responses to improve post-MI and HF outcomes.

Circadian mutant mice with obesity and metabolic syndrome are resilient to cardiovascular disease

Obesity and metabolic syndrome commonly underlie cardiovascular disease. Clock^Δ19/Δ19 mice fed a normal diet develop obesity and metabolic syndrome; however, it is not known whether they develop or are resilient to cardiovascular disease. We found that Clock^Δ19/Δ19 mice do not develop cardiac dysfunction, despite their underlying conditions. Moreover, in contrast to wild-type controls fed a high-fat diet (HFD), Clock^Δ19/Δ19 HFD mice still do not develop cardiovascular disease. Indeed, Clock^Δ19/Δ19 HFD mice have preserved heart weight despite their obesity, no cardiomyocyte hypertrophy, and preserved heart structure and function, even after 24 wk of a HFD. To determine why Clock^Δ19/Δ19 mice are resilient to cardiac dysfunction despite their underlying obesity and metabolic conditions, we examined global cardiac gene expression profiles by microarray and bioinformatics analyses, revealing that oxidative stress pathways were involved. We examined the pathways in further detail and found that 1) SIRT-dependent oxidative stress pathways were not directly involved in resilience; 2) 4-hydroxynonenal (4-HNE) increased in wild-type HFD but not Clock^Δ19/Δ19 mice, suggesting less reactive oxygen species in Clock^Δ19/Δ19 mice; 3) cardiac catalase (CAT) and glutathione peroxidase (GPx) increased, suggesting strong antioxidant defenses in the hearts of Clock^Δ19/Δ19 mice; and 4) Pparγ was upregulated in the hearts of Clock^Δ19/Δ19 mice; this circadian-regulated gene drives transcription of CAT and GPx, providing a molecular basis for resilience in the Clock^Δ19/Δ19 mice. These findings shed new light on the circadian regulation of oxidative stress and demonstrate an important role for the circadian mechanism in resilience to cardiovascular disease.NEW & NOTEWORTHY We examined whether obesity and metabolic syndrome underlie the development of cardiac dysfunction in circadian mutant Clock^Δ19/Δ19 mice. Surprisingly, we demonstrate that although Clock^Δ19/Δ19 mice develop metabolic dysfunction, they are protected from cardiac hypertrophy, left ventricular remodeling, and diastolic dysfunction, in contrast to wild-type controls, even when challenged with a chronic high-fat diet. These findings shed new light on the circadian regulation of oxidative stress pathways, which can mediate resilience to cardiovascular disease.

Regulator of Calcineurin (RCAN): Beyond Down Syndrome Critical Region

The regulator of calcineurin (RCAN) was first reported as a novel gene called DSCR1, encoded in a region termed the Down syndrome critical region (DSCR) of human chromosome 21. Genome sequence comparisons across species using bioinformatics revealed three members of the RCAN gene family, RCAN1, RCAN2, and RCAN3, present in most jawed vertebrates, with one member observed in most invertebrates and fungi. RCAN is most highly expressed in brain and striated muscles, but expression has been reported in many other tissues, as well, including the heart and kidneys. Expression levels of RCAN homologs are responsive to external stressors such as reactive oxygen species, Ca2+, amyloid β, and hormonal changes and upregulated in pathological conditions, including Alzheimer's disease, cardiac hypertrophy, diabetes, and degenerative neuropathy. RCAN binding to calcineurin, a Ca2+/calmodulin-dependent phosphatase, inhibits calcineurin activity, thereby regulating different physiological events via dephosphorylation of important substrates. Novel functions of RCANs have recently emerged, indicating involvement in mitochondria homeostasis, RNA binding, circadian rhythms, obesity, and thermogenesis, some of which are calcineurin-independent. These developments suggest that besides significant contributions to DS pathologies and calcineurin regulation, RCAN is an important participant across physiological systems, suggesting it as a favorable therapeutic target.

Complexities in cardiovascular rhythmicity: perspectives on circadian normality, ageing and disease

Biological rhythms exist in organisms at all levels of complexity, in most organs and at myriad time scales. Our own biological rhythms are driven by energy emitted by the sun, interacting via our retinas with brain stem centres, which then send out complex messages designed to synchronize the behaviour of peripheral non-light sensing organs, to ensure optimal physiological responsiveness and performance of the organism based on the time of day. Peripheral organs themselves have autonomous rhythmic behaviours that can act independently from central nervous system control but is entrainable. Dysregulation of biological rhythms either through environment or disease has far-reaching consequences on health that we are only now beginning to appreciate. In this review, we focus on cardiovascular rhythms in health, with ageing and under disease conditions.

Combined treatment of melatonin and sodium tanshinone IIA sulfonate reduced the neurological and cardiovascular toxicity induced by deltamethrin in zebrafish

The pyrethroid insecticide deltamethrin has been reported to have an effect on vertebrate development and cardiovascular disease. Sodium tanshinone IIA sulfonate (STS) is considered to have cardioprotective effects and melatonin is known to regulate sleep-waking cycles. In this experiment, we used transgenic zebrafish Tg (kdrl:mCherry) and Tg (myl7:GFP) to investigate whether STS and melatonin could reverse the cardiovascular toxicity and neurotoxicity induced by deltamethrin. Zebrafish embryos were exposed to 25 μg/L deltamethrin at 10 hpf and treated with 100 mmol/L STS and 1 μmol/L melatonin showed that deltamethrin treatment affected normal cardiovascular development. In situ hybridization and qRT-PCR results showed that deltamethrin could interfere with the normal expression of cardiovascular development-related genes vegfr2, shh, gata4, nkx2.5, causing functional defects in the cardiovascular system. In addition, deltamethrin could affect the sleep-waking behavior of larvae, increasing the activity of larvae, decreasing the rest behavior and the expression of hcrt, hcrtr, aanat2 were down-regulated. The addition of melatonin and STS can significantly alleviate cardiovascular toxicity and sleep-waking induced by deltamethrin, while restoring the expression of related genes to normal levels. Our study demonstrates the role of STS and melatonin in protecting cardiovascular and sleep-waking behavior caused by deltamethrin.

Cerebral Small Vessel Diseases and Sleep Related Strokes

BACKGROUND AND PURPOSE

Sleep related Stroke (SRS) is common and has been associated with cerebral small vessel diseases (SVD) in ischemic strokes (ISs). We tested the hypothesis that SRS is associated with SVD in both ischemic and hemorrhagic stroke.

METHODS

Prospectively collected data from patients consecutively enrolled after intracerebral hemorrhage (ICH) related to SVD or after IS were analyzed. Symptom onset was recorded as SRS versus awake. Each ICH was grouped according to lobar and deep locations. The IS cohort was etiologically characterized based on the Causative Classification of Stroke system. Frequencies of SRS within and between ICH and IS cohorts as well as its associations (etiology, risk factors) were analyzed.

RESULTS

We analyzed 1812 IS (mean age 67.9 years ± 15.9 years, 46.4% female) and 1038 ICH patients (mean age 72.5 years ± 13.0 years, 45.4% female). SRS was significantly more common among SVD-related ICH patients (n = 276, 26.6%) when compared to all IS (n = 363, 20.0%, P < .001) and in both, small artery occlusion (SAO) related IS and lobar ICH within the respective IS and ICH cohorts (16.3% SRS versus 9.1% awake for SAO within all IS, P < .001; and 57.1% SRS versus 47.7% awake for lobar bleeds within all ICH, P = .008). These associations remained significant after controlling for age, sex and risk factors.

CONCLUSIONS

SRS was associated with SVD. The SAO etiology and cerebral amyloid angiopathy related lobar ICH suggest that the presence of SVD can interact with sleep or arousal related hemodynamic changes to cause ischemic and hemorrhagic stroke.

Sleep Apnea and Cardiovascular Disease: An Enigmatic Risk Factor

Synchronization of molecular, metabolic, and cardiovascular circadian oscillations is fundamental to human health. Sleep-disordered breathing, which disrupts such temporal congruence, elicits hemodynamic, autonomic, chemical, and inflammatory disturbances with acute and long-term consequences for heart, brain, and circulatory and metabolic function. Sleep apnea afflicts a substantial proportion of adult men and women but is more prevalent in those with established cardiovascular diseases and especially fluid-retaining states. Despite the experimental, epidemiological, observational, and interventional evidence assembled in support of these concepts, this substantial body of work has had relatively modest pragmatic impact, thus far, on the discipline of cardiology. Contemporary estimates of cardiovascular risk still are derived typically from data acquired during wakefulness. The impact of sleep-related breathing disorders rarely is entered into such calculations or integrated into diagnostic disease-specific algorithms or therapeutic recommendations. Reasons for this include absence of apnea-related symptoms in most with cardiovascular disease, impediments to efficient diagnosis at the population level, debate as to target, suboptimal therapies, difficulties mounting large randomized trials of sleep-specific interventions, and the challenging results of those few prospective cardiovascular outcome trials that have been completed and reported. The objectives of this review are to delineate the bidirectional interrelationship between sleep-disordered breathing and cardiovascular disease, consider the findings and implications of observational and randomized trials of treatment, frame the current state of clinical equipoise, identify principal current controversies and potential paths to their resolution, and anticipate future directions.

Circadian clock genes and myocardial infarction in patients with type 2 diabetes mellitus

Disruption of circadian clock may trigger the onset of diabetes mellitus and myocardial infarction. Type 2 diabetes mellitus (T2DM) is well-known risk factors for cardiovascular diseases and myocardial infarction. We performed a case-control study, where we explored the possible association between single nucleotide polymorphisms in three circadian rhythm genes (ARNTL, CLOCK, and PER2) and myocardial infarction in 657 patients with T2DM. The study group consisted of 231 patients with myocardial infarction and T2DM and a control group of 426 T2DM patients. We hypothesized that variations in the circadian rhythm genes in patients with T2DM could be an additional risk factor for myocardial infarction. The statistically significant difference was found in allelic (p = 1.1 × 10-5) and genotype distribution (p = 1.42 × 10-4) between two groups of the rs12363415 at the ARNTL gene locus. We provide evidence that genetic variability in the ARNTL gene might be associated with myocardial infarction in patients with T2DM.

Time-of-day at symptom onset was not associated with infarct size and long-term prognosis in patients with ST-segment elevation myocardial infarction

Background

ST-segment elevation myocardial infarction (STEMI) displays circadian variability with the highest incidence in the morning hours. Data on whether the time-of-day at symptom onset affects infarct size or patients’ long-term prognosis are conflicting. We sought to investigate the association of time-of-day at symptom onset with infarct size or long-term mortality in patients with STEMI undergoing primary percutaneous coronary intervention (PPCI).

Methods

This study included 1206 STEMI patients undergoing PPCI. All patients underwent single photon emission computed tomography (SPECT) imaging with 99mTc-sestamibi before and 7–14 days after PPCI. The co-primary endpoints were final infarct size on day 10 after STEMI and all-cause mortality at 5-year follow-up. Time-of-day at symptom onset of STEMI was categorized in 6-h intervals.

Results

In patients presenting from 0 to 6 h, 6 to 12 h, 12 to 18 h, and 18 to 24 h, the infarct sizes (median [25th–75th percentiles]) were 10.0 [3.0–24.7], 10.0 [3.0–24.0], 10.0 [3.0–22.0], and 9.0 [3.0–21.0] of the left ventricle, respectively (p = 0.87); the Kaplan–Meier estimates of 5-year all-cause mortality were 13.6%, 8.7%, 13.7% and 9.3%, respectively (log-rank test p = 0.30). After adjustment, time-of-day was not associated with infarct size (p ≥ 0.76 for comparisons with infarct size from reference [6–12 h] time interval) or 5-year all-cause mortality (p ≥ 0.25 for comparisons with mortality from reference [6–12 h] time interval). Time-of-day at symptom onset of STEMI was not associated with differences in the recovery of left ventricular ejection fraction 6 months after STEMI.

Conclusions

In patients with STEMI undergoing PPCI, time-of-day at symptom onset was neither associated with scintigraphic infarct size, left ventricular ejection fraction recovery at 6 months nor with 5-year mortality.

Electronic supplementary material

The online version of this article (10.1186/s12967-019-1934-z) contains supplementary material, which is available to authorized users.

The Clock Mechanism Influences Neurobiology and Adaptations to Heart Failure in Clock∆19/∆19 Mice With Implications for Circadian Medicine

In this study we investigated the role of the circadian mechanism on cognition-relevant brain regions and neurobiological impairments associated with heart failure (HF), using murine models. We found that the circadian mechanism is an important regulator of healthy cognitive system neurobiology. Normal Clock∆19/∆19 mice had neurons with smaller apical dendrite trees in the medial prefrontal cortex (mPFC), and hippocampus, showed impaired visual-spatial memory, and exhibited lower cerebrovascular myogenic tone, versus wild types (WT). We then used the left anterior descending coronary artery ligation model to investigate adaptations in response to HF. Intriguingly, adaptations to neuron morphology, memory, and cerebrovascular tone occurred in differing magnitude and direction between Clock∆19/∆19 and WT mice, ultimately converging in HF. To investigate this dichotomous response, we performed microarrays and found genes crucial for growth and stress pathways that were altered in Clock∆19/∆19 mPFC and hippocampus. Thus these data demonstrate for the first time that (i) the circadian mechanism plays a role in neuron morphology and function; (ii) there are changes in neuron morphology and function in HF; (iii) CLOCK influences neurobiological gene adaptations to HF at a cellular level. These findings have clinical relevance as patients with HF often present with concurrent neurocognitive impairments. There is no cure for HF, and new understanding is needed to reduce morbidity and improve the quality of life for HF patients.

Vasculature on the clock: Circadian rhythm and vascular dysfunction

The master mammalian circadian clock (i.e. central clock), located in the suprachiasmatic nucleus of the hypothalamus, orchestrates the synchronization of the daily behavioural and physiological rhythms to better adapt the organism to the external environment in an anticipatory manner. This central clock is entrained by a variety of signals, the best established being light and food. However, circadian cycles are not simply the consequences of these two cues but are generated by endogenous circadian clocks. Indeed, clock machinery is found in mainly all tissues and cell types, including cells of the vascular system such as endothelial cells, fibroblasts, smooth muscle cells and stem cells. This machinery physiologically contributes to modulate the daily vascular function, and its disturbance therefore plays a major role in the pathophysiology of vascular dysfunction. Therapies targeting the circadian rhythm may therefore be of benefit against vascular disease.

Genetic variations in circadian rhythm genes and susceptibility for myocardial infarction

Disruption of endogenous circadian rhythms has been shown to increase the risk of developing myocardial infarction (MI), suggesting that circadian genes might play a role in determining disease susceptibility. We conducted a case-control study on 200 patients hospitalized due to MI and 200 healthy controls, investigating the association between MI and single nucleotide polymorphisms (SNPs) in four circadian genes (ARNTL, CLOCK, CRY2, and PER2). The variants of all four genes were chosen based on their previously reported association with cardiovascular risk factors, which have a major influence on the occurrence of myocardial infarction. Statistically significant differences, assessed through Chi-square analysis, were found in genotype distribution between cases and controls of the PER2 gene rs35333999 (p=0.024) and the CRY2 gene rs2292912 (p=0.028); the corresponding unadjusted odds ratios, also significant, were respectively OR=0.49 (95% CI 0.26-0.91) and OR=0.32 (95% CI 0.11-0.89). Our data suggest that genetic variability in the CRY2 and PER2 genes might be associated with myocardial infarction.

Implications of disturbances in circadian rhythms for cardiovascular health: A new frontier in free radical biology

Cell autonomous circadian "clock" mechanisms are present in virtually every organ, and generate daily rhythms that are important for normal physiology. This is especially relevant to the cardiovascular system, for example the circadian mechanism orchestrates rhythms in heart rate, blood pressure, cardiac contractility, metabolism, gene and protein abundance over the 24-h day and night cycles. Conversely, disturbing circadian rhythms (e.g. via shift work, sleep disorders) increases cardiovascular disease risk, and exacerbates cardiac remodelling and worsens outcome. Notably, reactive oxygen species (ROS) are important contributors to heart disease, especially the pathophysiologic damage that occurs after myocardial infarction (MI, heart attack). However, little is known about how the circadian mechanism, or rhythm desynchrony, is involved in these key pathologic stress responses. This review summarizes the current knowledge on circadian rhythms in the cardiovascular system, and the implications of rhythm disturbances for cardiovascular health. Furthermore, we highlight how free radical biology coincides with the pathogenesis of myocardial repair and remodelling after MI, and indicate a role for the circadian system in the oxidative stress pathways in the heart and brain after MI. This fusion of circadian biology with cardiac oxidative stress pathways is novel, and offers enormous potential for improving our understanding and treatment of heart disease.

High dietary sodium causes dyssynchrony of the renal molecular clock in rats

Speed JS, Hyndman KA, Roth K, Heimlich JB, Kasztan M, Fox BM, Johnston JG, Becker BK, Jin C, Gamble KL, Young ME, Pollock JS, Pollock DM. High dietary sodium causes dyssynchrony of the renal molecular clock in rats. Am J Physiol Renal Physiol 314: F89-F98, 2018. First published September 27, 2017; doi:10.1152/ajprenal.00028.2017.-Dyssynchrony of circadian rhythms is associated with various disorders, including cardiovascular and metabolic diseases. The cell autonomous molecular clock maintains circadian control; however, environmental factors that may cause circadian dyssynchrony either within or between organ systems are poorly understood. Our laboratory recently reported that the endothelin (ET-1) B (ETB) receptor functions to facilitate Na+ excretion in a time of day-dependent manner. Therefore, the present study was designed to determine whether high salt (HS) intake leads to circadian dyssynchrony within the kidney and whether the renal endothelin system contributes to control of the renal molecular clock. We observed that HS feeding led to region-specific alterations in circadian clock components within the kidney. For instance, HS caused a significant 5.5-h phase delay in the peak expression of Bmal1 and suppressed Cry1 and Per2 expression in the renal inner medulla, but not the renal cortex, of control rats. The phase delay in Bmal1 expression appears to be mediated by ET-1 because this phenomenon was not observed in the ETB-deficient rat. In cultured inner medullary collecting duct cells, ET-1 suppressed Bmal1 mRNA expression. Furthermore, Bmal1 knockdown in these cells reduced epithelial Na+ channel expression. These data reveal that HS feeding leads to intrarenal circadian dyssynchrony mediated, in part, through activation of ETB receptors within the renal inner medulla.

Diurnal changes and levels of fibrin generation are not altered by continuous positive airway pressure (CPAP) in obstructive sleep apnoea (OSA)

Obstructive sleep apnoea (OSA) is associated with increased cardiovascular disease (CVD) risk. In the general population, CVD events peak at 9:00–10:00 AM, associated with diurnal changes in thrombotic potential. However in OSA, these CVD events occur frequently at night. Measuring thrombotic potential across the sleep-wake cycle may provide insight into the temporal association of OSA with CVD. This study aimed to determine diurnal changes in fibrin generation in OSA and whether treatment of OSA with continuous positive airway pressure (CPAP) alters fibrin generation across the sleep-wake cycle. In a randomised placebo-controlled crossover trial, patients with OSA were assigned to two months each of therapeutic CPAP and placebo. After each treatment period, fibrin generation was determined by overall haemostatic potential assay at seven time points over 24 hours (h). Twenty-eight patients (25 men, 3 women) with severe OSA (Apnoea Hypopnoea Index = 37.9 ± 23.9/h, Oxygen Desaturation Index 31.3 ± 22.4/h) completed the study. All parameters, except lag time to fibrin generation, showed significant diurnal changes, both on CPAP and placebo. Compared to 9:00 AM, fibrin generation parameters were significantly lower at midnight and 3:00 AM for overall coagulation potential (OCP), overall haemostasis potential (OHP), maximum optical density, and maximum slope (all p≤0.001). CPAP produced no change in fibrin generation parameters compared to placebo. In severe OSA patients, fibrin generation peaked at 6:00 AM and 9:00 AM rather than during the sleep period (midnight and 3:00 AM). These findings suggest a prothrombotic shift in the morning similar to individuals without OSA. There was no difference between CPAP and placebo on fibrin generation.

Circadian Variation of Ventricular Arrhythmias in Catecholaminergic Polymorphic Ventricular Tachycardia

OBJECTIVES

The aim of this paper was to investigate whether ventricular arrhythmias in children with catecholaminergic polymorphic ventricular tachycardia (CPVT) show circadian patterns.

BACKGROUND

Circadian arrhythmic patterns have been established in long QT, Brugada, and early repolarization, but have not been investigated in CPVT.

METHODS

This is a multicenter, retrospective review of pediatric CPVT patients, age <21 years at diagnosis. Timing of ventricular tachycardia (VT ≥3 beats) was assessed during 24-h continuous monitoring (Holter, implantable loop recorder, implantable cardioverter defibrillator) and by eliminating sleep hours, in addition to sporadic exercise stress tests. Morning was defined as 6:00 am to 11:59 am, afternoon 12:00 pm to 5:59 pm, and evening 6:00 pm to 11:59 pm. Distribution of VT events was compared by time of day, day of week, age, and sex.

RESULTS

Eighty patients (53% male), 61% with an ICD, experienced 423 VT events during a median follow-up time of 6 years (interquartile range: 2 to 10 years). When compared to morning hours, VT was more likely to occur in the afternoon (odds ratio [OR]: 2.54; 95% confidence interval [CI]: 1.69 to 3.83) or evening hours (OR: 2.91; 95% CI: 1.82 to 4.67). The predominance of afternoon/evening events persisted regardless of age, gender, or day of the week. Among 50 patients who underwent exercise stress tests, VT was significantly more likely to occur in the afternoon (OR: 3.00; 95% CI: 1.39 to 6.48).

CONCLUSIONS

In pediatric CPVT patients, ventricular arrhythmias are more likely to occur in the afternoon and evening hours. Because children's activity levels peak in both the morning and afternoon, the lack of arrhythmias in the morning hours raises questions whether factors other than adrenergic stimulation influence arrhythmia induction in pediatric patients with CPVT.

Environmental Determinants of Cardiovascular Disease

Many features of the environment have been found to exert an important influence on cardiovascular disease (CVD) risk, progression, and severity. Changes in the environment because of migration to different geographic locations, modifications in lifestyle choices, and shifts in social policies and cultural practices alter CVD risk, even in the absence of genetic changes. Nevertheless, the cumulative impact of the environment on CVD risk has been difficult to assess and the mechanisms by which some environment factors influence CVD remain obscure. Human environments are complex, and their natural, social, and personal domains are highly variable because of diversity in human ecosystems, evolutionary histories, social structures, and individual choices. Accumulating evidence supports the notion that ecological features such as the diurnal cycles of light and day, sunlight exposure, seasons, and geographic characteristics of the natural environment such as altitude, latitude, and greenspaces are important determinants of cardiovascular health and CVD risk. In highly developed societies, the influence of the natural environment is moderated by the physical characteristics of the social environments such as the built environment and pollution, as well as by socioeconomic status and social networks. These attributes of the social environment shape lifestyle choices that significantly modify CVD risk. An understanding of how different domains of the environment, individually and collectively, affect CVD risk could lead to a better appraisal of CVD and aid in the development of new preventive and therapeutic strategies to limit the increasingly high global burden of heart disease and stroke.

Protein phosphatases 1 and 2A and their naturally occurring inhibitors: current topics in smooth muscle physiology and chemical biology

Protein phosphatases 1 and 2A (PP1 and PP2A) are the most ubiquitous and abundant serine/threonine phosphatases in eukaryotic cells. They play fundamental roles in the regulation of various cellular functions. This review focuses on recent advances in the functional studies of these enzymes in the field of smooth muscle physiology. Many naturally occurring protein phosphatase inhibitors with different relative PP1/PP2A affinities have been discovered and are widely used as powerful research tools. Current topics in the chemical biology of PP1/PP2A inhibitors are introduced and discussed, highlighting the identification of the gene cluster responsible for the biosynthesis of calyculin A in a symbiont microorganism of a marine sponge.

mRNA levels of circadian clock components Bmal1 and Per2 alter independently from dosing time-dependent efficacy of combination treatment with valsartan and amlodipine in spontaneously hypertensive rats

Chronopharmacological effects of antihypertensives play a role in the outcome of hypertension therapy. However, studies produce contradictory findings when combination of valsartan plus amlodipine (VA) is applied. Here, we hypothesized different efficacy of morning versus evening dosing of VA in spontaneously hypertensive rats (SHR) and the involvement of circadian clock genes Bmal1 and Per2. We tested the therapy outcome in short-term and also long-term settings. SHRs aged between 8 and 10 weeks were treated with 10 mg/kg of valsartan and 4 mg/kg of amlodipine, either in the morning or in the evening with treatment duration 1 or 6 weeks and compared with parallel placebo groups. After short-term treatment, only morning dosing resulted in significant blood pressure (BP) control (measured by tail-cuff method) when compared to placebo, while after long-term treatment, both dosing groups gained similar superior results in BP control against placebo. However, mRNA levels of Bmal1 and Per2 (measured by RT-PCR) exhibited an independent pattern, with similar alterations in left and right ventricle, kidney as well as in aorta predominantly in groups with evening dosing in both, short-term and also long-term settings. This was accompanied by increased cardiac mRNA expression of plasminogen activator inhibitor-1. In summary, morning dosing proved to be advantageous due to earlier onset of antihypertensive action; however, long-term treatment was demonstrated to be effective regardless of administration time. Our findings also suggest that combination of VA may serve as an independent modulator of circadian clock and might influence disease progression beyond the primary BP lowering effect.

Chronobiology of Acute Aortic Dissection in the Marfan Syndrome (from the National Registry of Genetically Triggered Thoracic Aortic Aneurysms and Cardiovascular Conditions and the International Registry of Acute Aortic Dissection)

Marfan syndrome (MFS) is an autosomal dominant connective tissue disease associated with acute aortic dissection (AAD). We used 2 large registries that include patients with MFS to investigate possible trends in the chronobiology of AAD in MFS. We queried the International Registry of Acute Aortic Dissection (IRAD) and the Genetically Triggered Thoracic Aortic Aneurysms and Cardiovascular Conditions (GenTAC) registry to extract data on all patients with MFS who had suffered an AAD. The group included 257 patients with MFS who suffered an AAD from 1980 to 2012. The chi-square tests were used for statistical testing. Mean subject age at time of AAD was 38 years, and 61% of subjects were men. AAD was more likely in the winter/spring season (November to April) than the other half of the year (57% vs 43%, p = 0.05). Dissections were significantly more likely to occur during the daytime hours, with 65% of dissections occurring from 6 a.m. to 6 p.m. (p = 0.001). Men were more likely to dissect during the daytime hours (6 a.m. to 6 p.m.) than women (74% vs 51%, p = 0.01). These insights offer a glimpse of the times of greatest vulnerability for patients with MFS who suffer from this catastrophic event. In conclusion, the chronobiology of AAD in MFS reflects that of AAD in the general population.

Disrupting the key circadian regulator CLOCK leads to age-dependent cardiovascular disease

The circadian mechanism underlies daily rhythms in cardiovascular physiology and rhythm disruption is a major risk factor for heart disease and worse outcomes. However, the role of circadian rhythms is generally clinically unappreciated. Clock is a core component of the circadian mechanism and here we examine the role of Clock as a vital determinant of cardiac physiology and pathophysiology in aging. Clock^Δ19/Δ19 mice develop age-dependent increases in heart weight, hypertrophy, dilation, impaired contractility, and reduced myogenic responsiveness. Young Clock^Δ19/Δ19 hearts express dysregulated mRNAs and miRNAs in the PTEN-AKT signal pathways important for cardiac hypertrophy. We found a rhythm in the Pten gene and PTEN protein in WT hearts; rhythmic oscillations are lost in Clock^Δ19/Δ19 hearts. Changes in PTEN are associated with reduced AKT activation and changes in downstream mediators GSK-3β, PRAS40, and S6K1. Cardiomyocyte cultures confirm that Clock regulates the AKT signalling pathways crucial for cardiac hypertrophy. In old Clock^Δ19/Δ19 mice cardiac AKT, GSK3β, S6K1 phosphorylation are increased, consistent with the development of age-dependent cardiac hypertrophy. Lastly, we show that pharmacological modulation of the circadian mechanism with the REV-ERB agonist SR9009 reduces AKT activation and heart weight in old WT mice. Furthermore, SR9009 attenuates cardiac hypertrophy in mice subjected to transverse aortic constriction (TAC), supporting that the circadian mechanism plays an important role in regulating cardiac growth. These findings demonstrate a crucial role for Clock in growth and renewal; disrupting Clock leads to age-dependent cardiomyopathy. Pharmacological targeting of the circadian mechanism provides a new opportunity for treating heart disease.

Diurnal Rhythm of Cardiac Troponin: Consequences for the Diagnosis of Acute Myocardial Infarction

BACKGROUND

Interpretation of serial high-sensitivity cardiac troponin (hs-cTn) measurements for the diagnosis of acute myocardial infarction (AMI) assumes random fluctuation of hs-cTn around an individual's homeostatic set point. The aim of this study was to challenge this diagnostic concept.

METHODS

Study 1 examined the presence of a diurnal hs-cTn rhythm by hourly blood sampling, day and night, in 24 individuals without a recent history of AMI. Study 2 assessed morning vs evening diagnostic accuracy of hs-cTnT and hs-cTnI in a prospective multicenter diagnostic study of 2782 unselected patients, presenting to the emergency department with acute chest pain.

RESULTS

In study 1, hs-cTnT, but not hs-cTnI, exhibited a diurnal rhythm, characterized by gradually decreasing concentrations throughout daytime, rising concentrations during nighttime, to peak concentrations in the morning (mean 16.2 ng/L at 8:30 AM and 12.1 ng/L at 7:30 PM). In study 2, the hs-cTnT rhythm was confirmed by higher hs-cTnT concentrations in early-morning presenters compared to evening presenters with an adjudicated diagnosis of noncardiac disease. The diagnostic accuracy [area under the receiver-operation characteristics curve (AUC)] of hs-cTnT at presentation, 1 h, and for the combination of absolute changes with presenting concentration, were very high and comparable among patients presenting early morning as compared to evening (all AUC &gt;0.93). hs-cTnI exhibited no diurnal rhythm with no differences in AUC among early-morning and evening presenters.

CONCLUSIONS

Rhythmic diurnal variation of hs-cTnT is a general phenomenon that is not seen with hs-cTnI. While the diurnal hs-cTnT rhythm does not seem to affect the diagnostic accuracy of hs-cTnT for AMI, it should be considered when using hs-cTnT for screening purposes.

Clinical Trial Registration

1. Circadian Variation of Cardiac Troponin, NCT02091427, www.clinicaltrials.gov/ct2/show/NCT02091427. 2. Advantageous Predictors of Acute Coronary Syndrome Evaluation (APACE) Study, NCT00470587, www.clinicaltrials.gov/ct2/show/NCT00470587.

Day-night dependence of gene expression and inflammatory responses in the remodeling murine heart post-myocardial infarction

Diurnal or circadian rhythms are fundamentally important for healthy cardiovascular physiology and play a role in timing of onset and tolerance to myocardial infarction (MI) in patients. Whether time of day of MI triggers different molecular and cellular responses that can influence myocardial remodeling is not known. This study was designed to test whether time of day of MI triggers different gene expression, humoral, and innate inflammatory responses that contribute to cardiac repair after MI. Mice were infarcted by left anterior descending coronary artery ligation (MI model) within a 2-h time window either shortly after lights on or lights off, and the early remodeling responses at 8 h postinfarction were examined. We found that sleep-MI preferentially triggers early expression of genes associated with inflammatory responses, whereas wake-MI triggers more genes associated with metabolic pathways and transcription/translation, by microarray analyses. Homozygous clock mutant mice exhibit altered diurnal gene expression profiles, consistent with their cycling before onset of MI. In the first 8 h, crucial for innate immune responses to MI, there are also significant differences in sleep-MI and wake-MI serum cytokine responses and in neutrophil infiltration to infarcted myocardium. By 1-wk post-MI, there are differences in survivorship between the sleep and wake MI mice that could be explained by the different molecular and cellular responses. Our whole body physiology, tissues, and cells exhibit endogenous daily rhythms, and understanding their role in triggering effective responses after MI could lead to new strategies to benefit patients with cardiovascular disease.

Commentary on: "Levofloxacin-Induced QTc Prolongation Depends on the Time of Drug Administration"

Circadian variations in the corrected QT (QTc) interval have been documented in clinical trials. Animal models show circadian variations in expression of the cardiac ion channels that are necessary to maintain the heart's electrophysiological properties. Can these diurnal rhythms in QTc affect the ability of a drug to delay cardiac repolarization?

Circadian exosomal expression of renal thiazide-sensitive NaCl cotransporter (NCC) and prostasin in healthy individuals

PURPOSE

A circadian timing system is involved in the maintenance of fluid and electrolyte balance and blood pressure control. Aldosterone and vasopressin modulate ion transporters and channels crucial in sodium (Na) and water reabsorption such as the epithelium Na channel and the renal thiazide-sensitive NaCl cotransporter (NCC). We analyzed in urinary exosomes the intraday variations of NCC and prostasin expression and the association with electrolytes and water balance parameters.

EXPERIMENTAL DESIGN

Blood and urine samples were collected at five time points during the day from five healthy subjects. Blood renin, aldosterone, cortisol, ACTH, and plasmatic and urinary Na, potassium, creatinine, adiuretin (ADH), NCC, and prostasin were evaluated.

RESULTS

ACTH and cortisol showed a circadian pattern, similarly to aldosterone, while exosomal NCC and prostasin pattern were similar to urinary ADH, decreased in the morning and subsequently increased in the afternoon and evening.

CONCLUSIONS AND CLINICAL RELEVANCE

In urinary exosomes, NCC and prostasin had a diurnal pattern parallel to ADH and aquaporin 2, confirming that, in healthy subjects, both prostasin and NCC relate to water balance. These results provide suggestions for a possible chronotherapeutic approach in patients treated with thiazides, diuretic drugs acting as specific inhibitors of NCC-mediated Na reabsorption.

The role of variability in night-time mean heart rate on the prediction of ventricular arrhythmias and all-cause mortality in implantable cardioverter defibrillator patients

AIMS

This study was to use implantable cardioverter defibrillator (ICD) home monitoring (HM) feature to evaluate the role of mean night-time heart rate (MNHR) in the occurrence of ventricular arrhythmias (VAs) and mortality.

METHODS AND RESULTS

This study retrospectively analysed clinical and ICD device data in 318 ICD patients. Data of the first 30-day MNHR (recorded 02:00-06:00 am) by HM were collected. The average and standard deviation of 30-day MNHR (AVHR and SDHR, respectively) were then determined in each patient. The primary endpoint was appropriate ICD treatment of VAs. The secondary endpoint was all-cause mortality. During a mean follow-up period of 32 ± 10 months, 179 of the 318 patients (56.3%) experienced VAs, 123 patients (38.7%) were treated by ICD shocks, and 37 patients (11.6%) died. The overall SDHR in this study cohort was 4.5 ± 3.0 bpm. Based on the receiver operating characteristic curve, the cut-off value of SDHR = 3.685 bpm was identified to predict VAs. In the Kaplan-Meier survival, SDHR ≥ 3.685 bpm was associated with increased VAs [hazard ratio (HR) = 1.885; 95% confidence interval (CI) = 1.362-2.609; P < 0.001], shock events (HR = 1.637; 95% CI = 1.11-2.414; P = 0.013), all-cause mortality (HR = 2.42; 95% CI = 1.266-4.627; P = 0.008), and the combined endpoints (HR = 1.872; 95% CI = 1.365-2.567; P < 0.001). In univariate and multivariate Cox models (adjusting for clinical factors), SDHR ≥ 3.685 bpm was still an independent predictor for all endpoints.

CONCLUSION

In ICD population, SDHR ≥ 3.685 bpm was an independent predictor for VAs and all-cause mortality.

Altered myocardial metabolic adaptation to increased fatty acid availability in cardiomyocyte-specific CLOCK mutant mice

A mismatch between fatty acid availability and utilization leads to cellular/organ dysfunction during cardiometabolic disease states (e.g., obesity, diabetes mellitus). This can precipitate cardiac dysfunction. The heart adapts to increased fatty acid availability at transcriptional, translational, post-translational and metabolic levels, thereby attenuating cardiomyopathy development. We have previously reported that the cardiomyocyte circadian clock regulates transcriptional responsiveness of the heart to acute increases in fatty acid availability (e.g., short-term fasting). The purpose of the present study was to investigate whether the cardiomyocyte circadian clock plays a role in adaptation of the heart to chronic elevations in fatty acid availability. Fatty acid availability was increased in cardiomyocyte-specific CLOCK mutant (CCM) and wild-type (WT) littermate mice for 9weeks in time-of-day-independent (streptozotocin (STZ) induced diabetes) and dependent (high fat diet meal feeding) manners. Indices of myocardial metabolic adaptation (e.g., substrate reliance perturbations) to STZ-induced diabetes and high fat meal feeding were found to be dependent on genotype. Various transcriptional and post-translational mechanisms were investigated, revealing that Cte1 mRNA induction in the heart during STZ-induced diabetes is attenuated in CCM hearts. At the functional level, time-of-day-dependent high fat meal feeding tended to influence cardiac function to a greater extent in WT versus CCM mice. Collectively, these data suggest that CLOCK (a circadian clock component) is important for metabolic adaption of the heart to prolonged elevations in fatty acid availability. This article is part of a Special Issue entitled: Heart Lipid Metabolism edited by G.D. Lopaschuk.

Mining the Dynamic Genome: A Method for Identifying Multiple Disease Signatures Using Quantitative RNA Expression Analysis of a Single Blood Sample

Background: Blood has advantages over tissue samples as a diagnostic tool, and blood mRNA transcriptomics is an exciting research field. To realize the full potential of blood transcriptomic investigations requires improved methods for gene expression measurement and data interpretation able to detect biological signatures within the “noisy” variability of whole blood. Methods: We demonstrate collection tube bias compensation during the process of identifying a liver cancer-specific gene signature. The candidate probe set list of liver cancer was filtered, based on previous repeatability performance obtained from technical replicates. We built a prediction model using differential pairs to reduce the impact of confounding factors. We compared prediction performance on an independent test set against prediction on an alternative model derived by Weka. The method was applied to an independent set of 157 blood samples collected in PAXgene tubes. Results: The model discriminated liver cancer equally well in both EDTA and PAXgene collected samples, whereas the Weka-derived model (using default settings) was not able to compensate for collection tube bias. Cross-validation results show our procedure predicted membership of each sample within the disease groups and healthy controls. Conclusion: Our versatile method for blood transcriptomic investigation overcomes several limitations hampering research in blood-based gene tests.