Cardiovascular disease, chronopharmacotherapy, and the molecular clock

Circadian Pattern of Acute Myocardial Infarction and Atrial Fibrillation in a Mediterranean Country: A study in Diabetic Patients

Background and objectives: The circadian pattern seems to play a crucial role in cardiovascular events and arrhythmias. Diabetes mellitus is a complex metabolic disorder associated with autonomic nervous system alterations and increased risk of microvascular and macrovascular disease. We sought to determine whether acute myocardial infarction (AMI) and atrial fibrillation (AF) follow a circadian pattern in diabetic patients in a Mediterranean country. Materials and Methods: This retrospective study included 178 diabetic patients (mean age: 67.7) with AMI or AF who were admitted to the coronary care unit. The circadian pattern of AMI and AF was identified in the 24-h period (divided in 3-h and 1-h intervals). Patients were also divided in 3 groups according to age; 40-65 years, 66-79 years and patients older than 80 years. A chi-square goodness-of-fit test was used for the statistical analysis. Results: AMI seems to occur more often in the midnight hours (21:00-23:59) (p < 0.001). Regarding age distribution, patients between 40 and 65 years were more likely to experience an AMI compared to other age groups (p < 0.001). Autonomic alterations, working habits, and social reasons might contribute to this phenomenon. AF in diabetic patients occurs more frequently at noon (12:00-14:59) (p = 0.019). Conclusions: Diabetic patients with AMI and AF seem to follow a specific circadian pattern in a Mediterranean country, with AMI occurring most often at midnight hours and AF mostly at noon. Autonomic dysfunction, glycemic fluctuations, intense anti-diabetic treatment before lunch, and patterns of insulin secretion and resistance may explain this pattern. More studies are needed to elucidate the circadian pattern of AMI and AF in diabetic patients to contribute to the development of new therapeutic approaches in this setting.

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.

Circadian clock and the onset of cardiovascular events

The onset of cardiovascular diseases often shows time-of-day variation. Acute myocardial infarction or ventricular arrhythmia such as ventricular tachycardia occurs mainly in the early morning. Multiple biochemical and physiological parameters show circadian rhythm, which may account for the diurnal variation of cardiovascular events. These include the variations in blood pressure, activity of the autonomic nervous system and renin-angiotensin axis, coagulation cascade, vascular tone and the intracellular metabolism of cardiomyocytes. Importantly, the molecular clock system seems to underlie the circadian variation of these parameters. The center of the biological clock, also known as the central clock, exists in the suprachiasmatic nucleus. In contrast, the molecular clock system is also activated in each cell of the peripheral organs and constitute the peripheral clock. The biological clock system is currently considered to have a beneficial role in maintaining the homeostasis of each organ. Discoordination, however, between the peripheral clock and external environment could potentially underlie the development of cardiovascular events. Therefore, understanding the molecular and cellular pathways by which cardiovascular events occur in a diurnal oscillatory pattern will help the establishment of a novel therapeutic approach to the management of cardiovascular disorders.

Clinical value of ambulatory blood pressure: Is it time to recommend for all patients with hypertension?

Hypertension is a very common disease, and office measurements of blood pressure are frequently inaccurate. Ambulatory Blood Pressure Monitoring (ABPM) offers a more accurate diagnosis, more detailed readings of average blood pressures, better blood pressure measurement during sleep, fewer false positives by detecting more white-coat hypertension, and fewer false negatives by detecting more masked hypertension. ABPM offers better management of clinical outcomes. For example, based on more accurate measurements of blood pressure variability, ABPM demonstrates that taking antihypertensive medication at night leads to better controlled nocturnal blood pressure, which translates into less end organ damage and fewer clinical complications of hypertension. For these reasons, albeit some shortcomings which were discussed, ABPM should be considered as a first-line tool for diagnosing and managing hypertension.

Circadian models of serum potassium, sodium, and calcium concentrations in healthy individuals and their application to cardiac electrophysiology simulations at individual level

In the article a brief description of the biological basis of the regulation of human biological clocks was presented in order to introduce the role of circadian rhythms in physiology and specifically in the pharmacological translational tools based on the computational physiology models to motivate the need to provide models of circadian fluctuation in plasma cations. The main aim of the study was to develop statistical models of the circadian rhythm of potassium, sodium, and calcium concentrations in plasma. The developed ion models were further tested by assessing their influence on QT duration (cardiac endpoint) as simulated by the biophysically detailed models of human left ventricular cardiomyocyte. The main results are model equations along with an electronic supplement to the article that contains a fully functional implementation of all models.

Circadian events in human diseases and in cytochrome P450-related drug metabolism and therapy

The biochemical basis of the mammalian circadian clock can be described by transcriptional-translational feedback loops with a period of about 24 h. Crucial endogenous factors are under circadian control (i.e., body temperature, blood pressure, hormone secretion and metabolite levels). Also, drug metabolism, including phases I-III and the drug-responsive nuclear receptors, is controlled by the clock. Disturbances in circadian rhythm in humans can lead to pathologies, which is exemplified by increased cancer risk in long-term shift workers. On the other hand, best tolerability of drugs with minimum side effects can be achieved if the timing of drug treatment is synchronized with the patients' individual clock. The aim of this review is to underline the importance of accepting the individuals' endogenous clock which can contribute to personalized, patient-friendly optimization of drug therapies.

Suprachiasmatic nucleus and autonomic nervous system influences on awakening from sleep

Awakening from sleep is a clear example of an event for which (biological) clocks are of great importance. We will review some major pathways the mammalian biological clock uses to ensure an efficient and coordinated wake-up process. First we show how this clock enforces daily rhythmicity onto the hypothalamo-pituitary-adrenal (HPA) axis, via projections to neuroendocrine neurons within the hypothalamus. Next we demonstrate how this brain clock controls plasma glucose concentrations, via projections to sympathetic and parasympathetic pre-autonomic neurons within the hypothalamus. Orexin neurons in the lateral hypothalamus appear to be an important hub in this awakening control network.