Circadian characteristics of urinary epinephrine and norepinephrine from healthy young women in Japan and U.S.A

Nighttime administration of antihypertensive medication: a review of chronotherapy in hypertension

Hypertension remains a global health concern because of suboptimal blood pressure control despite advancements in antihypertensive treatments. Chronotherapy, defined as evening or bedtime administration of medication based on biological rhythms, is emerging as a potential strategy to improve blood pressure control and treatment outcomes. Clinical trials have investigated the potential effects of nighttime administration of antihypertensive medication in the improvement of 24 hours blood pressure control and reduction of cardiovascular risk. Implementing chronotherapy in clinical practice could have significant implications in enhancing blood pressure control and improving clinical outcomes in patients with hypertension, particularly those with resistant hypertension. However, recent trials have reported contradictory results, causing confusion in real-world practice. Herein we review, analyze, and critique the current evidence and propose suggestions regarding the clinical application and future directions of chronotherapy.

Chrono-nutrition for hypertension

Despite the advancement in blood pressure (BP) lowering medications, uncontrolled hypertension persists, underscoring a stagnation of effective clinical strategies. Novel and effective lifestyle therapies are needed to prevent and manage hypertension to mitigate future progression to cardiovascular and chronic kidney diseases. Chrono-nutrition, aligning the timing of eating with environmental cues and internal biological clocks, has emerged as a potential strategy to improve BP in high-risk populations. The aim of this review is to provide an overview of the circadian physiology of BP with an emphasis on renal and vascular circadian biology. The potential of Chrono-nutrition as a lifestyle intervention for hypertension is discussed and current evidence for the efficacy of time-restricted eating is presented.

Guidelines for the design and conduct of human clinical trials on ingestion-time differences - chronopharmacology and chronotherapy - of hypertension medications

Current hypertension guidelines fail to provide a recommendation on when-to-treat, thus disregarding relevant circadian rhythms that regulate blood pressure (BP) level and 24 h patterning and medication pharmacokinetics and pharmacodynamics. The ideal purpose of ingestion-time (chronopharmacology, i.e. biological rhythm-dependent effects on the kinetics and dynamics of medications, and chronotherapy, i.e. the timing of pharmaceutical and other treatments to optimize efficacy and safety) trials should be to explore the potential impact of endogenous circadian rhythms on the effects of medications. Such investigations and outcome trials mandate adherence to the basic standards of human chronobiology research. In-depth review of the more than 150 human hypertension pharmacology and therapeutic trials published since 1974 that address the differential impact of upon-waking/morning versus at-bedtime/evening schedule of treatment reveals diverse protocols of sometimes suboptimal or defective design and conduct. Many have been "time-of-day," i.e. morning versus evening, rather than circadian-time-based, and some relied on wake-time office BP rather than around-the-clock ambulatory BP measurements (ABPM). Additionally, most past studies have been of too small sample size and thus statistically underpowered. As of yet, there has been no consensual agreement on the proper design, methods and conduct of such trials. This Position Statement recommends ingestion-time hypertension trials to follow minimum guidelines: (i) Recruitment of participants should be restricted to hypertensive individuals diagnosed according to ABPM diagnostic thresholds and of a comparable activity/sleep routine. (ii) Tested treatment-times should be selected according to internal biological time, expressed by the awakening and bed times of the sleep/wake cycle. (iii) ABPM should be the primary or sole method of BP assessment. (iv) The minimum-required features for analysis of the ABPM-determined 24 h BP pattern ought to be the asleep (not "nighttime") BP mean and sleep-time relative BP decline, calculated in reference to the activity/rest cycle per individual. (v) ABPM-obtained BP means should be derived by the so-called adjusted calculation procedure, not by inaccurate arithmetic averages. (vi) ABPM should be performed with validated and calibrated devices at least hourly throughout two or more consecutive 24 h periods (48 h in total) to achieve the highest reproducibility of mean wake-time, sleep-time and 48 h BP values plus the reliable classification of dipping status. (vii) Calculation of minimum required sample size in adherence with proper statistical methods must be provided. (viii) Hypertension chronopharmacology and chronotherapy trials should preferably be randomized double-blind, randomized open-label with blinded-endpoint, or crossover in design, the latter with sufficient washout period between tested treatment-time regimens.

New perspectives on the definition, diagnosis, and treatment of true arterial hypertension

INTRODUCTION

Office blood pressure measurements (OBPM), still used today for diagnosis and management of hypertension, fail to reveal clinically important features of the mostly predictable blood pressure (BP) 24 h pattern, and lead to >45% of individuals being misclassified. Current hypertension guidelines do not provide recommendation on when-to-treat, despite multiple prospective clinical trials documenting improved normalization of 24 h BP pattern and significant reduction in cardiovascular disease (CVD) events when hypertension medications are ingested at bedtime rather than upon waking.

AREAS COVERED

In this review, the authors discuss current evidence on the: (i) most relevant attributes of the 24 h BP pattern deterministic of CVD risk; (ii) asleep systolic BP (SBP) mean as the most significant therapeutic target for CVD risk reduction; (iii) ingestion-time differences in pharmacodynamics of BP-lowering medications as reported with high consistency in multiple clinical trials; and (iv) enhanced prevention of CVD events achieved by bedtime hypertension chronotherapy.

EXPERT OPINION

Several prospective trials consistently document asleep SBP mean and sleep-time relative SBP decline (dipping) constitute highly significant CVD risk factors, independent of OBPM. Bedtime, compared to customary upon-waking, hypertension chronotherapy reduces risk of major CVD events. Collectively, these findings call for new definition of true hypertension and, accordingly, its proper diagnosis and management.

Bedtime Chronotherapy with Conventional Hypertension Medications to Target Increased Asleep Blood Pressure Results in Markedly Better Chronoprevention of Cardiovascular and Other Risks than Customary On-awakening Therapy

The bases for bedtime hypertension chronotherapy (BHCT) as superior chronoprevention against cardiovascular disease (CVD) are: (1) correlation between blood pressure (BP) and various risks is greater for ambulatory BP monitoring (ABPM) than office BP measurements (OBPM); (2) asleep BP mean is a better predictor of CVD risk than ABPM awake and 24-hour means and OBPM; and (3) targeting of asleep BP by BHCT with one or more conventional medications versus usual on-awakening therapy better reduces major and total CVD events. BHCT offers the most cost-effective chronoprevention against adverse CVD outcomes in regular and vulnerable renal, diabetic, and resistant hypertensive patients.

Chronotherapy with conventional blood pressure medications improves management of hypertension and reduces cardiovascular and stroke risks

Correlation between blood pressure (BP) and target organ damage, vascular risk and long-term patient prognosis is greater for measurements derived from around-the-clock ambulatory BP monitoring than in-clinic daytime ones. Numerous studies consistently substantiate the asleep BP mean is both an independent and a much better predictor of cardiovascular disease (CVD) risk than either the awake or 24 h means. Sleep-time hypertension is much more prevalent than suspected, not only in patients with sleep disorders, but also among those who are elderly or have type 2 diabetes, chronic kidney disease or resistant hypertension. Hence, cost-effective adequate control of sleep-time BP is of marked clinical relevance. Ingestion time, according to circadian rhythms, of hypertension medications of six different classes and their combinations significantly affects BP control, particularly sleep-time BP, and adverse effects. For example, because the high-amplitude circadian rhythm of the renin-angiotensin-aldosterone system activates during nighttime sleep, bedtime vs. morning ingestion of angiotensin-converting enzyme inhibitors and angiotensin receptor blockers better reduces the asleep BP mean, with additional benefit, independent of medication terminal half-life, of converting the 24 h BP profile into more normal dipper patterning. The MAPEC (Monitorización Ambulatoria para Predicción de Eventos Cardiovasculares) study, first prospective randomized treatment-time investigation designed to test the worthiness of bedtime chronotherapy with ⩾1 conventional hypertension medications so as to specifically target attenuation of asleep BP, demonstrated, relative to conventional morning therapy, 61% reduction of total CVD events and 67% decrease of major CVD events, that is, CVD death, myocardial infarction, and ischemic and hemorrhagic stroke. The MAPEC study, along with other earlier conducted less refined trials, documents the asleep BP mean is the most significant prognostic marker of CVD morbidity and mortality; moreover, it substantiates attenuation of the asleep BP mean by a bedtime hypertension treatment strategy entailing the entire daily dose of ⩾1 hypertension medications significantly reduces CVD risk in both general and more vulnerable hypertensive patients, that is, those diagnosed with chronic kidney disease, diabetes and resistant hypertension.

Contribution of the external urethral sphincter to urinary void size in unanesthetized unrestrained rats

AIMS

In anesthetized rats, voiding is typically associated with phasic activation (bursting) of the external urethral sphincter (EUS). During spontaneous voiding in unanesthetized, unrestrained rats, EUS bursting is the most common form of EUS activity exhibited, but it is not necessary for productive voiding to occur. The aim of the present study was to determine which aspects of EUS activity contributed to void size during bursting and non-bursting voiding in conscious, freely moving rats.

METHODS

Female rats were implanted with electrodes adjacent to the EUS for recording electromyographic activity (EMG). EUS EMG recordings were performed during 24-hr sessions in a metabolic cage while voided urine was continuously collected and weighed.

RESULTS

Void size was positively correlated with the duration of the intra-burst silent and active periods and variables reflecting the overall intensity and duration of bursting, particularly at lower frequencies within the 3-10 Hz range of EUS bursting. In addition, void size was inversely related to the frequency of bursting and to the average EMG amplitude during voiding, both in voids with and without bursting.

CONCLUSIONS

EUS bursting contributes to productive voiding when bursting is present. Lower bursting frequencies elicit more productive voiding than do higher frequencies. In the absence of bursting, the association of increased void size with smaller average EUS EMG amplitude suggests that conscious rats can perform synergic voiding (i.e., bladder contraction with EUS relaxation) that is comparable to that seen in humans and other typically non-bursting species. Neurourol. Urodynam. 35:696-702, 2016. © 2015 Wiley Periodicals, Inc.

Chronotherapy improves blood pressure control and reduces vascular risk in CKD

In patients with chronic kidney disease (CKD), the prevalence of increased blood pressure during sleep and blunted sleep-time-relative blood pressure decline (a nondipper pattern) is very high and increases substantially with disease severity. Elevated blood pressure during sleep is the major criterion for the diagnoses of hypertension and inadequate therapeutic ambulatory blood pressure control in these patients. Substantial, clinically meaningful ingestion-time-dependent differences in the safety, efficacy, duration of action and/or effects on the 24 h blood pressure pattern of six different classes of hypertension medications and their combinations have been substantiated. For example, bedtime ingestion of angiotensin-converting-enzyme inhibitors and angiotensin-receptor blockers is more effective than morning ingestion in reducing blood pressure during sleep and converting the 24 h blood pressure profile into a dipper pattern. We have identified a progressive reduction in blood pressure during sleep--a novel therapeutic target best achieved by ingestion of one or more hypertension medications at bedtime--as the most significant predictor of decreased cardiovascular risk in patients with and without CKD. Recent findings suggest that in patients with CKD, ambulatory blood pressure monitoring should be used for the diagnosis of hypertension and assessment of cardiovascular disease risk, and that therapeutic strategies given at bedtime rather than on awakening are preferable for the management of hypertension.

Administration-time differences in effects of hypertension medications on ambulatory blood pressure regulation

Specific features of the 24-h blood pressure (BP) pattern are linked to progressive injury of target tissues and risk of cardiovascular disease (CVD) events. Several studies have consistently shown an association between blunted asleep BP decline and risk of fatal and nonfatal CVD events. Thus, there is growing focus on ways to properly control BP during nighttime sleep as well as during daytime activity. One strategy, termed chronotherapy, entails the timing of hypertension medications to endogenous circadian rhythm determinants of the 24-h BP pattern. Significant and clinically meaningful treatment-time differences in the beneficial and/or adverse effects of at least six different classes of hypertension medications, and their combinations, are now known. Generally, calcium channel blockers (CCBs) are more effective with bedtime than morning dosing, and for dihydropyridine derivatives bedtime dosing significantly reduces risk of peripheral edema. The renin-angiotensin-aldosterone system is highly circadian rhythmic and activates during nighttime sleep. Accordingly, evening/bedtime ingestion of the angiotensin-converting enzyme inhibitors (ACEIs) benazepril, captopril, enalapril, lisinopril, perindopril, quinapril, ramipril, spirapril, trandolapril, and zofenopril exerts more marked effect on the asleep than awake systolic (SBP) and diastolic (DBP) BP means. Likewise, the bedtime, in comparison with morning, ingestion schedule of the angiotensin-II receptor blockers (ARBs irbesartan, olmesartan, telmisartan, and valsartan exerts greater therapeutic effect on asleep BP, plus significant increase in the sleep-time relative BP decline, with the additional benefit, independent of drug terminal half-life, of converting the 24-h BP profile into a more normal dipping pattern. This is the case also for the bedtime versus upon-awakening regimen of combination ARB-CCB, ACEI-CCB, and ARB-diuretic medications. The chronotherapy of conventional hypertension medications constitutes a new and cost-effective strategy for enhancing the control of daytime and nighttime SBP and DBP levels, normalizing the dipping status of their 24-h patterning, and potentially reducing the risk of CVD events and end-organ injury, for example, of the blood vessels and tissues of the heart, brain, kidney, and retina.

Circadian rhythms in urinary functions: possible roles of circadian clocks?

Circadian clocks are the endogenous oscillators that harmonize a variety of physiological processes within the body. Although many urinary functions exhibit clear daily or circadian variation in diurnal humans and nocturnal rodents, the precise mechanisms of these variations are as yet unclear. In this review, we briefly introduce circadian clocks and their organization in mammals. We then summarize known daily or circadian variations in urinary function. Importantly, recent findings by others as well as results obtained by us suggest an active role of circadian clock genes in various urinary functions. Finally, we discuss possible research avenues for the circadian control of urinary function.

Circadian rhythms in blood pressure regulation and optimization of hypertension treatment with ACE inhibitor and ARB medications

Specific features of the 24 h-blood pressure (BP) pattern are linked to the progressive injury of target tissues and risk of cardiac and cerebrovascular events. Studies have consistently shown an association between blunted asleep BP decline and increased incidence of fatal and nonfatal cardiovascular events. Thus, there is growing interest in how to achieve better BP control during nighttime sleep in addition to during daytime activity, according to the particular requirements of each hypertension patient. One approach takes into consideration the endogenous circadian rhythm-determinants of the 24-h BP pattern, especially, the prominent day-night variation of the renin-angiotensin-aldosterone system, which activates during nighttime sleep. A series of clinical studies have demonstrated a different effect of the angiotensin-converting enzyme (ACE) inhibitors benazepril, captopril, enalapril, lisinopril, perindopril, quinapril, ramipril, spirapril, and trandolapril when routinely ingested in the morning vs. the evening. In most cases, the evening schedule exerts a more marked effect on the asleep than awake BP means. Similarly, a once-daily evening, in comparison to morning, ingestion schedule of the angiotensin receptor blockers (ARBs) irbesartan, olmesartan, telmisartan, and valsartan exerts greater therapeutic effect on asleep BP, plus significant increase in the sleep-time relative BP decline, with normalization of the circadian BP profile toward a more dipping pattern, independent of drug terminal half-life. Chronotherapy, the timing of treatment to body rhythms, is a cost-effective means of both individualizing and optimizing the treatment of hypertension through normalization of the 24-h BP level and profile, and it may constitute an effective option to reduce cardiovascular risk.

Circadian variation of blood pressure: the basis for the chronotherapy of hypertension

Ambulatory blood pressure (BP) measurements present a close correlation with target organ damage and cardiovascular events, including myocardial infarction, stroke and cardiovascular mortality. With the use of this measurement technique, a significant circadian variation has been shown to characterize BP. This circadian BP variation, although affected by a variety of external factors, represents the influence of internal factors such as ethnicity, gender, autonomic nervous system tone, vasoactive hormones, and hematologic and renal variables. In most individuals, BP presents a morning increase, a small post-prandial valley, and a deeper descent during nocturnal rest. However, under certain pathophysiological conditions, the nocturnal BP decline may be reduced or even reversed. This cannot be determined by traditional clinical or home BP assessments. Subjects with a diminished nocturnal BP decline (non-dipper pattern) have a significantly worse prognosis than the ones with a normal dipper pattern. In particular, the non-dipper circadian BP pattern represents a risk factor for left ventricular hypertrophy, microalbuminuria, cerebrovascular disease, congestive heart failure, vascular dementia and myocardial infarction. The normalization of the circadian BP pattern to a dipper profile is a novel therapeutic goal, and accumulating medical evidence suggests this can delay the progression towards the renal and cardiovascular pathology known to be a consequence of the non-dipper BP pattern. The features of the circadian BP profile have direct implications for improving the drug-delivery of antihypertensive therapies as well as the qualification of patients for medication trials and assessment.

Role of sleep-wake cycle on blood pressure circadian rhythms and hypertension

Stages of different depth characterize the temporal organization of sleep. Each stage exerts an effect on blood pressure (BP) regulation and contributes to its 24-h variation. The main determinant of the circadian influences of sleep and wakefulness on BP is the daytime sympathetic and nighttime parasympathetic prevalence, but many other physiologic mechanisms known either to induce sleep or determine arousal may play an important role in the mediation of sleep influences on BP. Alteration of one or more of such mechanisms may be reflected in altered circadian BP rhythms. Sleep- and arousal-related mechanisms and phenomena that affect circadian BP rhythms include neurohumoral sleep factors (arginine vasopressin, vasoactive intestinal peptide, somatotropin, insulin, steroid hormones and metabolites, and serotonin among others) and waking factors (corticotropin-releasing factor, adrenocorticotropin, thyrotropin-releasing hormone, endogenous opioids, and prostaglandin (E(2))). Pathologic respiratory variations (sleep-disordered breathing) and insomnia are major causes of the sleep-related alteration of the circadian BP profile, including loss of the expected normal decline in BP by 10-20% from the daytime level. A great number of medical disorders can cause insomnia, but objective sleep studies have been performed only in a minority of them. Overall, the sleep-related pathophysiological mechanisms actually involved in causing altered circadian BP rhythms in different normotensive and hypertensive conditions are not completely understood. In any case, changes in the circadian BP rhythm are known to be strongly related to one's risk of cardiovascular morbidity and mortality, thus representing strong prognostic indicators worthy of further investigation.

Hormonal responses to exercise after partial sleep deprivation and after a hypnotic drug-induced sleep

The aim of this study was to determine the hormonal responses, which are dependent on the sleep wake cycle, to strenuous physical exercise. Exercise was performed after different nocturnal regimens: (i) a baseline night preceded by a habituation night; (ii) two nights of partial sleep deprivation caused by a delayed bedtime or by an early awakening; and (iii) two nights of sleep after administration of either a hypnotic compound (10 mg zolpidem) or a placebo. Eight well-trained male endurance athletes with a maximal oxygen uptake of 63.5 +/- 3.8 ml x kg(-1) x min(-1) (mean value +/- s(x)) were selected on the basis of their sleeping habits and their physical training. Polygraphic recordings of EEG showed that both nights with partial sleep loss led to a decrease (P< 0.01) in stage 2 and rapid eye movement sleep. A delayed bedtime also led to a decrease (P < 0.05) in stage 1 sleep. Zolpidem had no effect on the different stages of sleep. During the afternoon after an experimental night, exercise was performed on a cycle ergometer. After a 10-min warm-up, the participants performed 30 min steady-state cycling at 75% VO(2-max) followed by a progressively increased workload until exhaustion. The recovery period lasted 30 min. Plasma growth hormone, prolactin, cortisol, catecholamine and lactate concentrations were measured at rest, during exercise and after recovery. The concentration of plasma growth hormone and catecholamine were not affected by partial sleep deprivation, whereas that of plasma prolactin was higher (P < 0.05) during the trial after an early awakening. Plasma cortisol was lower (P < 0.05) during recovery after both sleep deprivation conditions. Blood lactate was higher (P < 0.05) during submaximal exercise performed after both a delayed bedtime and an early awakening. Zolpidem-induced sleep did not affect the hormonal and metabolic responses to subsequent exercise. Our results demonstrate only minor alterations in the hormonal responses to exercise after partial sleep deprivation.

Endocrine mechanisms of blood pressure rhythms

The temporal organization of blood pressure is mainly controlled by neuroendocrine mechanisms. The monoaminergic systems appear to integrate the major driving factors of temporal variability, but evidence also indicates a role of the hypothalamic-pituitary-adrenal, hypothalamic-pituitary-thyroid, opioid, renin-angiotensin-aldosterone, and endothelial systems as well as other vasoactive peptides. Although their hormonal secretions are typically episodic, the probability of secretory episodes is "gated" by mechanisms that are coupled either to sleep or to an endogenous pacemaker which usually is predominantly (though not only) circadian. Many hormones with established actions on the cardiovascular system (arginine vasopressin, vasoactive intestinal peptide, melatonin, somatotropin, insulin, steroids, serotonin, CRF, ACTH, TRH, endogenous opioids, and prostaglandin E2) are also involved in sleep induction or arousal. Hence, physical, mental, and pathologic stimuli, which may drive activation or inhibition of these neuroendocrine effectors of biologic rhythmicity, may also interfere with the temporal blood pressure structure. On the other hand, the immediate adaptation of the exogenous components of blood pressure rhythms to the demands of the environment are modulated by the circadian-time-dependent responsiveness of the biologic oscillators and their neuroendocrine effectors. These notions may contribute to a better understanding of the pathophysiology and therapeutics of changes in blood pressure.

The acute effects of experimental short-term evening and night shifts on human circadian rhythm: the oral temperature, heart rate, serum cortisol and urinary catecholamines levels

This study was designed to examine the temporal changes in circadian rhythm of oral temperature, heart rate, serum cortisol and urinary catecholamines levels due to experimental short-term shifts. The six subjects were assigned to consecutive day (work 0800-1600 hours; sleep 0000-0800 hours), evening (1600-2400 hours; 0400-1200 hours), and night (0000-0800 hours; 1200-2000 hours) shifts of 2 days each scheduled as hospital shiftwork by nurses, in random order, during which data were collected every 4 h throughout the experimental periods. According to acrophases of a fitted cosine curve and visual inspection on chronograms, the phases of circadian rhythms were delayed to different degrees in the evening shifts with a minimum of about 1 h for oral temperature and a maximum of about 4 h for urinary free noradrenaline. The corresponding phase delays were larger in the night shift for oral temperature (about 3 h), resting heart rate (about 5 h) and urinary free noradrenaline (about 13 h); the diurnal variations of serum cortisol and urinary free adrenaline were greatly modified, and their circadian rhythmicities disappeared, indicating that the normal circadian phase relations of these variables were disrupted more by the night shift. The comparison of chronograms and correlation analyses revealed that the 4-h mean heart rate and urinary free noradrenaline were largely affected by rest-activity level in connection with shifts, while the resting heart rate and urinary free adrenaline were less affected. On the other hand, the sleep factor (time of onset and/or period) seemed to be more potent in modifying the circadian rhythm of serum cortisol, especially with the night shifts.

Masking in humans: the problem and some attempts to solve it

Different types of masking are discussed together with an account of the masking effect that the sleep-wake cycle exerts upon the circadian rhythms of body temperature and urinary excretion. The relative importance to masking of the several components of differences between sleeping and wakefulness are then assessed. Means to deal with the problem of masking fall into two major categories. These attempt to minimise masking effects by protocols such as constant routines or control days, and mathematical models which separate results obtained in the presence of masking influences into endogenous and exogenous components. (The problem of the extent to which masking influences can render the endogenous component of a rhythm an impure reflection of the internal oscillator is considered also.) These different techniques are compared with respect to their usefulness and assumptions. Finally, a brief speculation is given of the usefulness of masking.