Altered Circadian Timing System-Mediated Non-Dipping Pattern of Blood Pressure and Associated Cardiovascular Disorders in Metabolic and Kidney Diseases

Mineralocorticoid receptor blockade protects the kidneys but does not affect inverted blood pressure rhythm in hypertensive transgenic (mRen-2)27 rats

Aldosterone regulates blood pressure (BP) through water and sodium balance. In our study, we studied if continuous treatment with a mineralocorticoid receptor antagonist, spironolactone (30 mg/kg/day) for 20 days can: 1) attenuate hypertension development and restore inverted 24-h BP rhythm in hypertensive transgenic (mRen-2)27 rats (TGR) measured by telemetry; 2) improve function of the kidneys and heart; 3) be protective against high salt load (1% in water) by mitigating oxidative injury and improving kidney function. Spironolactone decreased albuminuria and 8-isoprostane in normal and salt load conditions in BP-independent effects. Salt load increased BP, impaired autonomic balance, suppressed plasma aldosterone level and increased natriuresis, albuminuria and oxidative injury in TGR. Spironolactone did not restore the inverted 24-h rhythm of BP in TGR, therefore, mineralocorticoids are not crucial in regulation of BP daily profile. Spironolactone improved kidney function, decreased oxidative stress and was protective against high salt load in the BP-independent manner.

Pathophysiology of the Nondipping Blood Pressure Pattern

The nondipping blood pressure (BP) pattern corresponds to a disruption in the circadian BP rhythm with an insufficient decrease in BP levels during nighttime sleep as observed using 24-hour ambulatory BP monitoring. Patients with nondipping BP pattern have poorer renal and cardiovascular outcomes, independent of their average 24-hour BP levels. The pathophysiology of nondipping BP is complex and involves numerous mechanisms: perturbations of (1) the circadian rhythm, (2) the autonomic nervous system, and (3) water and sodium regulation. This review provides an outline of the pathways potentially involved in the nondipping BP profile in different conditions. A recent hypothesis is also discussed involving the role of gut microbiota in the dipping/nondipping patterns, via the fecal diet-derived short chain fatty acids.

Non-dipping blood pressure pattern is associated with higher risk of new-onset diabetes in hypertensive patients with obstructive sleep apnea: UROSAH data

OBJECTIVE

Impairment of circadian blood pressure (BP) patterns has been associated with cardiovascular risks and events in individuals with hypertension and in general populations, which are more likely to be found in obstructive sleep apnea (OSA). The aim of this study was to investigate the association of non-dipping BP pattern with new-onset diabetes in hypertensive patients with OSA, based on Urumqi Research on Sleep Apnea and Hypertension (UROSAH) data.

MATERIALS AND METHODS

This retrospective cohort study included 1841 hypertensive patients at least 18 years of age, who were diagnosed with OSA without baseline diabetes and had adequate ambulatory blood pressure monitoring (ABPM) data at enrollment. The exposure of interest for the present study was the circadian BP patterns, including non-dipping and dipping BP pattern, and the study outcome was defined as the time from baseline to new-onset diabetes. The associations between circadian BP patterns and new-onset diabetes were assessed using Cox proportional hazard models.

RESULTS

Among 1841 participants (mean age: 48.8 ± 10.5 years, 69.1% male), during the total follow-up of 12172 person-years with a median follow-up of 6.9 (inter quartile range: 6.0-8.0) years, 217 participants developed new-onset diabetes with an incidence rate of 17.8 per 1000 person-years. The proportion of non-dippers and dippers at enrollment in this cohort was 58.8% and 41.2%, respectively. Non-dippers were associated with higher risk of new-onset diabetes compared with dippers (full adjusted hazard ratio [HR]=1.53, 95% confidence interval [CI]: 1.14-2.06, P=0.005). Multiple subgroup and sensitivity analyses yielded similar results. We further explored the association of systolic and diastolic BP patterns with new-onset diabetes separately, and found that diastolic BP non-dippers were associated with higher risk of new-onset diabetes (full adjusted HR=1.54, 95% CI: 1.12-2.10, P=0.008), whereas for systolic BP non-dippers, the association was nonsignificant after adjusted the confounding covariates (full adjusted HR=1.35, 95% CI: 0.98-1.86, P=0.070).

CONCLUSIONS

Non-dipping BP pattern is associated with an approximately 1.5-fold higher risk of new-onset diabetes in hypertensive patients with OSA, suggesting that non-dipping BP pattern may be an important clinical implication for the early prevention of diabetes in hypertensive patients with OSA.

The faecal abundance of short chain fatty acids is increased in men with a non-dipping blood pressure profile

BACKGROUND AND AIMS

Gut microbiota (GM) has been involved in the pathophysiology of hypertension (HT), notably via short chain fatty acids (SCFAs). Among the clinical manifestations of HT, the absence of a significant drop in night-time blood pressure (BP) (also known as the non-dipping BP profile) has been associated with poor renal and cardiovascular outcomes. The putative link between GM-derived metabolites and BP dipping status is still unknown.

METHODS

Male volunteers (n = 44) were prospectively subjected to 24-hour ambulatory blood pressure monitoring, stool sample collection and a medical questionnaire. Metabolomics analyses of stool samples were conducted using Nuclear Magnetic Resonance (NMR).

RESULTS

Higher amounts of acetate, butyrate and propionate were found in the stools of non-dippers (n = 12) versus dippers (n = 26) (p = 0.0252, p = 0.0468, and p = 0.0496, respectively; n = 38 in toto). NMR spectral data were not interpretable in 5 dippers and 1 non-dipper. A similar significant association was found when including only patients without anti-HT medications (p = 0.0414, p = 0.0108, and p = 0.0602, respectively; n = 21 in toto). A not significant trend was observed when focussing only on HT patients without anti-HT medications (p = 0.0556; n = 14 in toto).

CONCLUSION

Our pilot study highlights a putative link between GM-derived SCFAs and the BP dipping status, independently of the BP status itself or the anti-hypertensive medications.

Valsartan-mediated chronotherapy in spontaneously hypertensive rats via targeting clock gene expression in vascular smooth muscle cells

OBJECTIVE

This study was to investigate the underlying mechanisms of valsartan chronotherapy in regulating blood pressure variability.

METHODS

RT-PCR was used to assay clock genes expression rhythm in the hypothalamus, aortic vessels, and target organs after valsartan chronotherapy. WB was used to measure Period 1 (Per1), Period 2 (Per2) protein expression in aortic vessels, as well as to measure phosphorylation of 20-kDa regulatory myosin light chain (MLC₂₀) in VSMCs.

RESULTS

Specific clock genes in the hypothalamus, and Per1 and Per2 in aorta abdominalis, exhibited disordered circadian expression in vivo. Valsartan asleep time administration (VSA) restored circadian clock gene expression in a tissue- and gene-specific manner. In vitro, VSA was more efficient in blocking angiotensin II relative to VWA, which led to differential circadian rhythms of Per1 and Per2, ultimately corrected MLC₂₀ phosphorylation.

CONCLUSION

VSA may be efficacious in regulating circadian clock genes rhythm, then concomitantly correct circadian blood pressure rhythms.

Association of morning hypertension with chronic kidney disease progression and cardiovascular events in patients with chronic kidney disease and hypertension

BACKGROUND AND AIM

Associations of morning hypertension with chronic kidney disease are rarely investigated in prospective studies. We aim to investigate the predictive value of uncontrolled morning hypertension (UMH) to chronic kidney disease (CKD) progression and cardiovascular (CV) events in patients with CKD and hypertension.

METHODS AND RESULTS

In this prospective two-center observational study, 304 hypertensive patients with CKD were enrolled. Time to total mortality, CKD progression and CV events was recorded; Kaplan-Meier survival function estimates and Multivariable Cox proportional hazard model were used to investigate associations between UMH and outcomes. The study protocol was approved by the Institutional Review Board (http://www.thaiclinicaltrials.org; TCTR20180313004). After a follow-up for median 30 months, 23 (7.6%) patients died, 34 (11.2%) had CKD progression, and 95 (31.3%) occurred new-onset CV events, respectively. UMH was shown to be a strong predictor of CKD progression [hazard ratio (HR) 2.46, 95% confidence interval (CI) 1.22-4.94] and CV events (HR 1.69, 95% CI 1.12-2.53). When morning hypertension was analyzed as a continuous variable, morning systolic blood pressure (per 10 mmHg) was also shown to be predictive to CKD progression (HR 1.28, 95% CI 1.07-1.53, P < 0.01) and CV events (HR 1.15, 95% CI 1.03-1.28, P < 0.01).

CONCLUSIONS

UMH is strongly associated with CKD progression and CV events in patients with CKD and hypertension. UMH in CKD patients deserves further attentions.

Nocturnal heart rate rising is a risk factor for poor renal outcomes in patients with chronic kidney disease and hypertension

The association of heart rate (HR) dipping pattern with renal outcomes in chronic kidney disease (CKD) patients with hypertension has never been investigated. In order to demonstrate if HR dipping pattern is a risk factor for renal outcomes, cardiovascular (CV) diseases, and mortality in hypertensive patients with CKD, we conducted the prospective longitudinal observational study. Patients were divided into three groups according to their nocturnal HR: HR dippers (night-day HR ratio ≤ 0.9), HR non-dippers (0.9 < night-day HR ratio ≤ 1.0), and HR risers (night-day HR ratio > 1.0). The primary outcome was renal endpoint, a composite outcome of progression to end-stage renal disease (ESRD) or estimated glomerular filtration rate (eGFR) decline ≥ 50%; the secondary outcomes included poor renal outcomes, CV events, and death. A total of 34 (11.3%) patients reached renal endpoint after a follow-up of 34 ± 17 months. Both HR non-dippers and HR risers were predictive to renal endpoint (hazard ratio 2.58, 95% confidence interval (CI) 1.04- 6.4, P = .04; hazard ratio 3.95, 95% CI 1.33- 11.79, P = .01, respectively), while only HR risers was shown to be correlated with a decline in eGFR≥ 50% (hazard ratio 5.28, 95% CI 1.45-19.16, P < .05), and decline in eGFR (β -0.17, 95% CI -0.33- -0.01, P = .04). No predictive value was found for HR dipping pattern to mortality and CV events. In conclusion, our study provided the first evidence that HR non-dippers, especially risers were a risk factor for poor renal outcomes in hypertensive patients with CKD.

The Vascular Circadian Clock in Chronic Kidney Disease

Chronic kidney disease is associated with extremely high cardiovascular mortality. The circadian rhythms (CR) have an impact on vascular function. The disruption of CR causes serious health problems and contributes to the development of cardiovascular diseases. Uremia may affect the master pacemaker of CR in the hypothalamus. A molecular circadian clock is also expressed in peripheral tissues, including the vasculature, where it regulates the different aspects of both vascular physiology and pathophysiology. Here, we address the impact of CKD on the intrinsic circadian clock in the vasculature. The expression of the core circadian clock genes in the aorta is disrupted in CKD. We propose a novel concept of the disruption of the circadian clock system in the vasculature of importance for the pathology of the uremic vasculopathy.

Circadian Blood Pressure Rhythm in Cardiovascular and Renal Health and Disease

Blood pressure (BP) follows a circadian rhythm, it increases on waking in the morning and decreases during sleeping at night. Disruption of the circadian BP rhythm has been reported to be associated with worsened cardiovascular and renal outcomes, however the underlying molecular mechanisms are still not clear. In this review, we briefly summarized the current understanding of the circadian BP regulation and provided therapeutic overview of the relationship between circadian BP rhythm and cardiovascular and renal health and disease.

Possible benefits of exogenous melatonin for individuals on dialysis: a narrative review on potential mechanisms and clinical implications

Prevention of oxidative stress and inflammation in chronic kidney disease patients (CKD) on dialysis may reduce dialysis-associated complications. Administration of powerful antioxidants may improve the consequences of peritoneal dialysis (PD) and hemodialysis (HD). This narrative review aimed to show the potential therapeutic effects of melatonin (MLT) on the consequences of CKD patients receiving HD or PD. The results of preclinical and clinical studies have proven that CKD and dialysis are accompanied by reduced endogenous MLT levels and related complications such as sleep disorders. Enhanced oxidative stress, inflammation, cellular damages, and renal fibrosis, along with dysregulation of the renin-angiotensin system (RAS), have been observed in CKD and patients on dialysis. Results of studies have revealed that the restoration of MLT via the exogenous source may regulate oxidative stress, inflammation, and RAS functions, inhibit fibrosis, and improve complications in patients with long-term dialysis patients. In summary, treatment of patients with CKD and dialysis with exogenous MLT is suggested as a practical approach in reducing the outcomes and improving the quality of life in patients via antioxidant, anti-inflammatory, and anti-fibrotic signaling pathways. Therefore, this hormone can be considered in clinical practice to manage dialysis-related complications.

Human Stool Metabolome Differs upon 24 h Blood Pressure Levels and Blood Pressure Dipping Status: A Prospective Longitudinal Study

Dysbiosis of gut microbiota (GM) has been involved in the pathophysiology of arterial hypertension (HT), via a putative role of short chain fatty acids (SCFAs). Its role in the circadian regulation of blood pressure (BP), also called “the dipping profile”, has been poorly investigated. Sixteen male volunteers and 10 female partners were subjected to 24 h ambulatory BP monitoring and were categorized in normotensive (NT) versus HT, as well as in dippers versus non-dippers. Nuclear magnetic resonance (NMR)-based metabolomics was performed on stool samples. A 5-year comparative follow-up of BP profiles and stool metabolomes was done in men. Significant correlations between stool metabolome and 24 h mean BP levels were found in both male and female cohorts and in the entire cohort (R² = 0.72, R² = 0.79, and R² = 0.45, respectively). Multivariate analysis discriminated dippers versus non-dippers in both male and female cohorts and in the entire cohort (Q² = 0.87, Q² = 0.98, and Q² = 0.68, respectively). Fecal amounts of acetate, propionate, and butyrate were higher in HT versus NT patients (p = 0.027; p = 0.015 and p = 0.015, respectively), as well as in non-dippers versus dippers (p = 0.027, p = 0.038, and p = 0.036, respectively) in the entire cohort. SCFA levels were significantly different in patients changing of dipping status over the 5-year follow-up. In conclusion, stool metabolome changes upon global and circadian BP profiles in both genders.

Circadian rhythms of mineral metabolism in chronic kidney disease-mineral bone disorder

PURPOSE OF REVIEW

The circadian rhythms have a systemic impact on all aspects of physiology. Kidney diseases are associated with extremely high-cardiovascular mortality, related to chronic kidney disease-mineral bone disorder (CKD-MBD), involving bone, parathyroids and vascular calcification. Disruption of circadian rhythms may cause serious health problems, contributing to development of cardiovascular diseases, metabolic syndrome, cancer, organ fibrosis, osteopenia and aging. Evidence of disturbed circadian rhythms in CKD-MBD parameters and organs involved is emerging and will be discussed in this review.

RECENT FINDINGS

Kidney injury induces unstable behavioral circadian rhythm. Potentially, uremic toxins may affect the master-pacemaker of circadian rhythm in hypothalamus. In CKD disturbances in the circadian rhythms of CKD-MBD plasma-parameters, activin A, fibroblast growth factor 23, parathyroid hormone, phosphate have been demonstrated. A molecular circadian clock is also expressed in peripheral tissues, involved in CKD-MBD; vasculature, parathyroids and bone. Expression of the core circadian clock genes in the different tissues is disrupted in CKD-MBD.

SUMMARY

Disturbed circadian rhythms is a novel feature of CKD-MBD. There is a need to establish which specific input determines the phase of the local molecular clock and to characterize its regulation and deregulation in tissues involved in CKD-MBD. Finally, it is important to establish what are the implications for treatment including the potential applications for chronotherapy.

Extreme dipping: is the cardiovascular risk increased? An unsolved issue

: Extreme dipping (i.e. a marked blood pressure fall during night-time period) is an alteration of circadian blood pressure (BP) rhythm frequently observed in the setting of systemic hypertension as well as in the general population. Some reports have suggested that cardiovascular prognosis in extreme dippers (ED) is similar as in dippers, whereas other studies have documented either a better or worse prognosis in ED. Available information on clinical and prognostic implications of ED is scanty and data provided by studies are controversial. Furthermore, a comprehensive report summarizing the key features of this BP pattern is lacking. The present review focuses on a number of issues concerning ED pattern such as the prevalence and clinical correlates, mechanisms underlying this BP phenotype association with hypertension mediated organ damage (HMOD) and prognostic value in predicting cardiovascular events and all-cause mortality. The reported prevalence of this BP rhythm alteration ranges from 5% to 30%, depending on diagnostic criteria, clinical and demographic characteristics of subjects. Most studies targeting the association of this condition with HMOD failed to find consistent findings in support of an adverse impact of ED on vascular, renal of cardiac structure and function. Available data on ED as compared to low risk reference group (i.e. dippers) do not allow to conclude that high BP variability resulting from a marked BP fall at night adversely affects cardiovascular prognosis at the community level and in the general hypertensive population. Thus, further studies aimed to assess the prognostic significance of ED as well as the impact of therapeutic interventions aimed to normalize this circadian BP pattern, are highly needed.

Blood Pressure Non-Dipping and Obstructive Sleep Apnea Syndrome: A Meta-Analysis

Aim: We examined the reduced blood pressure (BP) nocturnal fall in patients with obstructive sleep apnea (OSA) by a meta-analysis including studies that provided data on prevalence rates of non-dipping (ND) pattern during 24-h ambulatory blood pressure monitoring (ABPM). Design: The PubMed, OVID-MEDLINE, and Cochrane CENTRAL literature databases were searched for appropriate articles without temporal restriction up to April 2019 through focused and sensitive search methods. Studies were identified by crossing the search terms as follows: “obstructive sleep apnea”, “sleep quality”, “non dipping”, “reduced nocturnal BP fall”, “circadian BP variation”, “night-time BP”, and “ambulatory blood pressure monitoring”. Results: Meta-analysis included 1562 patients with OSA from different clinical settings and 957 non-OSA controls from 14 studies. ND pattern prevalence in patients with OSA widely varied among studies (36.0–90.0%). This was also the case for non-OSA controls (33.0% to 69.0%). Overall, the ND pattern, assessed as an event rate in the pooled OSA population, was 59.1% (confidence interval (CI): 52.0–65.0%). Meta-analysis of the seven studies comparing the prevalence of ND pattern in participants with OSA and controls showed that OSA entails a significantly increased risk of ND (Odds ratio (OR) = 1.47, CI: 1.07–1.89, p < 0.01). After the exclusion of patients with mild OSA, OR increased to 1.67 (CI: 1.21–2.28, p < 0.001). Conclusions: The present meta-analysis, extending previous information on the relationship between OSA and impaired BP dipping, based on single studies, suggests that this condition increases by approximately 1.5 times the likelihood of ND, which is a pattern associated with a greater cardiovascular risk than normal BP dipping.

Non-dipping blood pressure pattern and new-onset diabetes in a 21-year follow-up

Purpose: Non-dipping blood pressure (BP) pattern has been associated with metabolic changes and cardiovascular events. With regard of diabetes, studies are scarce. Our aim was to investigate if there is an association between changes in dipping patterns and incidence of diabetes. Materials and methods: A 24-h ambulatory BP measurement was recorded in addition to other laboratory measurements, and a questionnaire and physical examination were carried out in the baseline study and after 21-year follow-up among a study population (n = 449) consisting of randomly selected middle-aged Finnish females and males without diabetes. Results: 128 (28.5%) developed diabetes during the follow-up. The incidence of new-onset diabetes was the highest, 41.0%, among those subjects who were non-dippers (their systolic BP declined <10% from daytime to nighttime) in the baseline and also in the follow-up study, while the incidence of diabetes was 19.6% in the dipper - dipper (a nighttime decline of systolic BP 10% or more) group (p = 0.003). The difference remained statistically significant after adjustment with age, sex, body mass index, fasting glucose, triglycerides, and insulin levels, smoking status, 24-h mean systolic BP, high-sensitivity C-reactive protein, estimated glomerular filtration and diuretics use. In logistic regression analysis, the non-dipper - non-dippers were at higher risk of diabetes compared with dipper - dipper group (OR = 2.27, 95% CI: 1.13-4.56, p = 0.022). Conclusions: Our prospective study shows that there is an independent association between non-dipping BP pattern and the incidence of diabetes in a 21-year follow-up.

The circadian protein CLOCK regulates cell metabolism via the mitochondrial carrier SLC25A10

Physiological function and metabolic regulation are the most important outputs of circadian clock controls in mammals. Mitochondrial respiration and ROS production show rhythmic activity. Mitochondrial carriers, which are responsible for mitochondrial substance transfer, are vital for mitochondrial metabolism. Clock (Circadian Locomotor Output Cycles Kaput) is the first core circadian gene identified in mammalian animals. However, whether CLOCK protein can regulate mitochondrial functions via mitochondrial carriers is unclear. Here, we showed that CLOCK can bind to the mitochondrial carrier SLC25A10. For further analysis, we established a Slc25a10^-/--Hepa1-6 cell line using CRISPR/Cas9 gene-editing technology. Slc25a10^-/--Hepa1-6 cells showed disordered glucose homeostasis, increased oxidative stress levels, and damaged electron transport chains. Next, using an immunoprecipitation assay, we found that amino acids 43-84 and 169-210 in SLC25A10 are key sites that respond to CLOCK binding. Finally, forced expression of wild-type SLC25A10 in Slc25a10^-/--Hepa1-6 cells could compensate for the loss of SLC25A10; the decreased glucose metabolism, severe oxidative stress and damaged electron transport chain were recovered. In addition, a mutant Slc25a10 with changes in two key sites did not show a rescue effect. In conclusion, we identified a new protein-protein interaction mechanism in which CLOCK can directly regulate cell metabolism via the mitochondrial membrane transporter SLC25A10. Our study might provide some new insights into the relationship between circadian clock and mitochondrial metabolism.

Association of Papillary Thyroid Carcinoma with Primary Aldosteronism

Objective The association of primary aldosteronism (PA) with thyroid disease has already been suggested. The aim of this study was to examine the presence of PA in patients with papillary thyroid carcinoma (PC) and to characterize such PC patients with PA. Methods We examined the presence of PA in 81 consecutive patients with PC, whose random sitting blood pressure (BP) was ≥140/90 mmHg in the office (n= 68), who had an incidental adrenal tumor or adrenal enlargement (n=9), or who showed hypokalemia (n=4). Thirty-one of these 81 patients had been treated with anti-hypertensive drugs. The plasma aldosterone concentration (PAC) and plasma renin activity (PRA) were first measured before operation in 16 patients and after operation in 65 patients. PA was diagnosed according to the guidelines of the Japan Endocrine Society. Results Forty patients with PC with a random PAC/PRA ratio of over 200 were subjected to a further study (12 of these patients had been treated with anti-hypertensive drugs). Ultimately, 15 patients with PC were diagnosed with PA. Adrenal venous sampling was done in 9 out of 15 patients with PC associated with PA. No patients were diagnosed as having unilateral lesions. Among the 15 patients, white-coat hypertension was observed in 5 patients, and normotension was observed in 1 patient. Conclusion These findings suggest that the prevalence of PA may be high among patients with PC. An active examination is needed to detect PA, as its signs and symptoms may be mild in patients with PC associated with hypertension.

A time to fight: Circadian control of aggression and associated autonomic support

The central circadian clock, located in the suprachiasmatic nucleus of the mammalian hypothalamus (SCN), regulates daily behavioral rhythms including the temporal propensity for aggressive behavior. Such aggression propensity rhythms are regulated by a functional circuit from the SCN to neurons that drive attack behavior in the ventromedial hypothalamus (VMH), via a relay in the subparaventricular zone (SPZ). In addition to this pathway, the SCN also regulates sleep-wake and locomotor activity rhythms, via the SPZ, in a circuit to the dorsomedial hypothalamus (DMH), a structure that is also known to play a key role in autonomic function and the sympathetic "fight-or-flight" response (which prepares the body for action in stressful situations such as an agonistic encounter). While the autonomic nervous system is known to be under pronounced circadian control, it is less apparent how such autonomic rhythms and their underlying circuitry may support the temporal propensity for aggressive behavior. Additionally, it is unclear how circadian and autonomic dysfunction may contribute to aberrant social and emotional behavior, such as agitation and aggression. Here we review the literature concerning interactions between the circadian and autonomic systems and aggression, and we discuss the implications of these relationships for human neural and behavioral pathologies.