An observational study on disturbed peripheral circadian rhythms in hemodialysis patients

The association between circadian syndrome and chronic kidney disease in an aging population: a 4-year follow-up study

Introduction

Circadian syndrome (CircS) is proposed as a novel risk cluster based on reduced sleep duration, abdominal obesity, depression, hypertension, dyslipidemia and hyperglycemia. However, the association between CircS and chronic kidney disease (CKD) remains unclear. To investigate the cross-sectional and longitudinal association between CircS and CKD, this study was performed.

Methods

A national prospective cohort (China Health and Retirement Longitudinal Study, CHARLS) was used in this study. To define CKD, the estimated glomerular filtration rate (eGFR) was calculated based on the 2012 CKD-EPI creatinine-cystatin C equation. Participants with eGFR <60 mL.min-1/1.73/m2 were diagnosed with CKD. Multivariate binary logistic regression was used to assess the cross-sectional association between CircS and CKD. Subgroup and interactive analyses were performed to determine the interactive effects of covariates. In the sensitivity analysis, the obese population was excluded and another method for calculating the eGFR was used to verify the robustness of previous findings. In addition, participants without CKD at baseline were followed up for four years to investigate the longitudinal relationship between CircS and CKD.

Results

A total of 6355 participants were included in this study. In the full model, CircS was positively associated with CKD (OR = 1.28, 95% CI = 1.04-1.59, P < 0.05). As per one increase of CircS components, there was a 1.11-fold (95% CI = 1.04-1.18, P < 0.05) risk of prevalent CKD in the full model. A significant interactive effect of hyperuricemia in the CircS-CKD association (P for interaction < 0.01) was observed. Sensitivity analyses excluding the obese population and using the 2009 CKD-EPI creatinine equation to diagnose CKD supported the positive correlation between CircS and CKD. In the 2011-2015 follow-up cohort, the CircS group had a 2.18-fold risk of incident CKD (95% CI = 1.33-3.58, P < 0.01) in the full model. The OR was 1.29 (95% CI = 1.10-1.51, P < 0.001) with per one increase of CircS components.

Conclusion

CircS is a risk factor for CKD and may serve as a predictor of CKD for early identification and intervention.

Arrhythmia and Time of Day in Maintenance Hemodialysis: Secondary Analysis of the Monitoring in Dialysis Study

Rationale & Objective

The incidence of arrhythmia varies by time of day. How this affects individuals on maintenance dialysis is uncertain. Our objective was to quantify the relationship of arrhythmia with the time of day and timing of dialysis.

Study Design

Secondary analysis of the Monitoring in Dialysis study, a multicenter prospective cohort study.

Settings & Participants

Loop recorders were implanted for continuous cardiac monitoring in 66 participants on maintenance dialysis with a follow up of 6 months.

Exposure

Time of day based on 6-hour intervals.

Outcomes

Event rates of clinically significant arrhythmia.

Analytical Approach

Negative binomial mixed effects regression models for repeated measures were used to evaluate data from the Monitoring in Dialysis study for differences in diurnal patterns of clinically significant arrhythmia among those with end-stage kidney disease with heart failure and end-stage kidney disease alone. We additionally analyzed rates according to presence of heart failure, time of dialysis shift, and dialysis versus nondialysis day.

Results

Rates of clinically significant arrhythmia peaked between 12:00 AM and 5:59 AM and were more than 1.5-fold as frequent during this interval than the rest of the day. In contrast, variations in atrial fibrillation peaked between 6:00 AM and 11:59 AM, but variations across the day were qualitatively small. Clinically significant arrhythmia occurred at numerically higher rate in individuals with end-stage kidney disease and heart failure (5.9 events/mo; 95% CI, 1.3-26.8) than those without heart failure (4.0 events/mo; 95% CI, 0.9-17.9). Although differences in overall rate were not significant, their periodicity was significantly different (P < 0.001), with a peak between 12:00 AM and 6:00 AM with kidney failure alone and between 6:00 AM and 11:59 AM in those with heart failure. Although the overall clinically significant arrhythmia rate was similar in morning compared with evening dialysis shifts (P = 0.43), their periodicity differed with a peak between 12:00 AM and 5:59 AM in those with AM dialysis and a later peak between 6:00 AM and 11:59 AM in those with PM shifts.

Limitations

Post hoc analysis, unable to account for unmeasured confounders.

Conclusion

Clinically significant arrhythmias showed strong diurnal patterns with a maximal peak between 12:00 AM and 5:59 AM and noon. Although overall arrhythmia rates were similar, the peak rate occurred overnight in individuals without heart failure and during the morning in individuals with heart failure. Further exploration of the influence of circadian rhythm on arrhythmia in the setting of hemodialysis is needed.

Reciprocal regulation between the molecular clock and kidney injury

Tubulointerstitial fibrosis is the common pathological substrate for many etiologies leading to chronic kidney disease. Although perturbations in the circadian rhythm have been associated with renal disease, the role of the molecular clock in the pathogenesis of fibrosis remains incompletely understood. We investigated the relationship between the molecular clock and renal damage in experimental models of injury and fibrosis (unilateral ureteral obstruction, folic acid, and adenine nephrotoxicity), using genetically modified mice with selective deficiencies of the clock components Bmal1, Clock, and Cry We found that the molecular clock pathway was enriched in damaged tubular epithelial cells with marked metabolic alterations. In human tubular epithelial cells, TGFβ significantly altered the expression of clock components. Although Clock played a role in the macrophage-mediated inflammatory response, the combined absence of Cry1 and Cry2 was critical for the recruitment of neutrophils, correlating with a worsening of fibrosis and with a major shift in the expression of metabolism-related genes. These results support that renal damage disrupts the kidney peripheral molecular clock, which in turn promotes metabolic derangement linked to inflammatory and fibrotic responses.

The circadian clock remains intact, but with dampened hormonal output in heart failure

BACKGROUND

Circadian (24-h) rhythms are important regulators in physiology and disease, but systemic disease may disrupt circadian rhythmicity. Heart failure (HF) is a systemic disease affecting hormonal regulation. We investigate whether HF affects the rhythmic expression of melatonin and cortisol, main endocrine products of the central clock, and cardiac-specific troponin in patients. We corroborate the functionality of the peripheral clock directly in the organs of translational models, inaccessible in human participants.

METHODS

We included 46 HF patients (71.7% male, median age of 60 years, NYHA class II (32.6%) or III (67.4%), ischemic cardiomyopathy (43.5%), comorbidities: diabetes 21.7%, atrial fibrillation 30.4%), and 24 matched controls. Blood was collected at seven time-points during a 24-h period (totalling 320 HF and 167 control samples) for melatonin, cortisol, and cardiac troponin T (cTnT) measurements after which circadian rhythms were assessed through cosinor analyses, both on the individual and the group level. Next, we analysed peripheral circadian clock functionality using cosinor analysis in male animal HF models: nocturnal mice and diurnal zebrafish, based on expression of core clock genes in heart, kidneys, and liver, every 4 h during a 24-h period in a light/darkness synchronised environment.

FINDINGS

Melatonin and cortisol concentrations followed a physiological 24-h pattern in both patients and controls. For melatonin, acrophase occurred during the night for both groups, with significantly decreased amplitude (median 5.2 vs 8.8, P = 0.0001) and circadian variation ([maximum]/[minimum]) in heart failure patients. For cortisol, mesor showed a significant increase for HF patients (mean 331.9 vs 275.1, P = 0.017) with a difference of 56.8 (95% CI 10.3-103.3) again resulting in a relatively lower variation: median 3.9 vs 6.3 (P = 0.0058). A nocturnal blood pressure dip was absent in 77.8% of HF patients. Clock gene expression profiles (Bmal, Clock, Per, Cry) were similar and with expected phase relations in animal HF models and controls, demonstrating preserved peripheral clock functionality in HF. Furthermore, oscillations in diurnal zebrafish were expectedly in opposite phases to those of nocturnal mice. Concordantly, cTnT concentrations in HF patients revealed significant circadian oscillations.

INTERPRETATION

Central clock output is dampened in HF patients while the molecular peripheral clock, as confirmed in animal models, remains intact. This emphasises the importance of taking timing into account in research and therapy for HF, setting the stage for another dimension of diagnostic, prognostic and therapeutic approaches.

FUNDING

Hartstichting.

Melatonin Treatment in Kidney Diseases

Melatonin is a neurohormone that is mainly secreted by the pineal gland. It coordinates the work of the superior biological clock and consequently affects many processes in the human body. Disorders of the waking and sleeping period result in nervous system imbalance and generate metabolic and endocrine derangements. The purpose of this review is to provide information regarding the potential benefits of melatonin use, particularly in kidney diseases. The impact on the cardiovascular system, diabetes, and homeostasis causes melatonin to be indirectly connected to kidney function and quality of life in people with chronic kidney disease. Moreover, there are numerous reports showing that melatonin plays a role as an antioxidant, free radical scavenger, and cytoprotective agent. This means that the supplementation of melatonin can be helpful in almost every type of kidney injury because inflammation, apoptosis, and oxidative stress occur, regardless of the mechanism. The administration of melatonin has a renoprotective effect and inhibits the progression of complications connected to renal failure. It is very important that exogenous melatonin supplementation is well tolerated and that the number of side effects caused by this type of treatment is low.

Circadian rhythms and renal pathophysiology

The reality of life in modern times is that our internal circadian rhythms are often out of alignment with the light/dark cycle of the external environment. This is known as circadian disruption, and a wealth of epidemiological evidence shows that it is associated with an increased risk for cardiovascular disease. Cardiovascular disease remains the top cause of death in the United States, and kidney disease in particular is a tremendous public health burden that contributes to cardiovascular deaths. There is an urgent need for new treatments for kidney disease; circadian rhythm-based therapies may be of potential benefit. The goal of this Review is to summarize the existing data that demonstrate a connection between circadian rhythm disruption and renal impairment in humans. Specifically, we will focus on chronic kidney disease, lupus nephritis, hypertension, and aging. Importantly, the relationship between circadian dysfunction and pathophysiology is thought to be bidirectional. Here we discuss the gaps in our knowledge of the mechanisms underlying circadian dysfunction in diseases of the kidney. Finally, we provide a brief overview of potential circadian rhythm-based interventions that could provide benefit in renal disease.

Cortisol excess in chronic kidney disease - A review of changes and impact on mortality

Chronic kidney disease (CKD) describes the long-term condition of impaired kidney function from any cause. CKD is common and associated with a wide array of complications including higher mortality, cardiovascular disease, hypertension, insulin resistance, dyslipidemia, sarcopenia, osteoporosis, aberrant immune function, cognitive impairment, mood disturbances and poor sleep quality. Glucocorticoids are endogenous pleiotropic steroid hormones and their excess produces a pattern of morbidity that possesses considerable overlap with CKD. Circulating levels of cortisol, the major active glucocorticoid in humans, are determined by a complex interplay between several processes. The hypothalamic-pituitary-adrenal axis (HPA) regulates cortisol synthesis and release, 11β-hydroxysteroid dehydrogenase enzymes mediate metabolic interconversion between active and inactive forms, and clearance from the circulation depends on irreversible metabolic inactivation in the liver followed by urinary excretion. Chronic stress, inflammatory states and other aspects of CKD can disturb these processes, enhancing cortisol secretion via the HPA axis and inducing tissue-resident amplification of glucocorticoid signals. Progressive renal impairment can further impact on cortisol metabolism and urinary clearance of cortisol metabolites. Consequently, significant interest exists to precisely understand the dysregulation of cortisol in CKD and its significance for adverse clinical outcomes. In this review, we summarize the latest literature on alterations in endogenous glucocorticoid regulation in adults with CKD and evaluate the available evidence on cortisol as a mechanistic driver of excess mortality and morbidity. The emerging picture is one of subclinical hypercortisolism with blunted diurnal decline of cortisol levels, impaired negative feedback regulation and reduced cortisol clearance. An association between cortisol and adjusted all-cause mortality has been reported in observational studies for patients with end-stage renal failure, but further research is required to assess links between cortisol and clinical outcomes in CKD. We propose recommendations for future research, including therapeutic strategies that aim to reduce complications of CKD by correcting or reversing dysregulation of cortisol.

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.

Prolactin and Other Pituitary Disorders in Kidney Disease

Prolactin levels are increased in chronic kidney disease (CKD) as a result of reduced clearance and increased secretion. Hyperprolactinemia manifests as galactorrhea and hypogonadism. Treatment of hyperprolactinemia should focus on improving bothersome galactorrhea or hypogonadism by using dopamine agonists and/or replacement of sex hormone(s). Changes in the hypothalamic-pituitary-adrenal axis in CKD are characterized by increases in adrenocorticotropic hormone (ACTH) and cortisol levels, largely preserved circadian rhythms of ACTH and cortisol, and a normal response of cortisol to ACTH, metyrapone, and insulin-induced hypoglycemia. However, the hypothalamic-pituitary-adrenal axis is less inhibited by 1 mg dexamethasone but retains normal suppression by higher-dose dexamethasone. Diagnosis of adrenal insufficiency in CKD patients, as in normal subjects, usually is made by finding a subnormal cortisol response to ACTH. The mainstay of treatment of adrenal insufficiency is to replace glucocorticoid hormone. Cushing's disease in CKD is difficult to diagnose and relies on the dexamethasone suppression test and the midnight salivary cortisol test because the 24-hour urine free cortisol test is not useful because it is increased already in CKD. Treatment of Cushing's disease involves surgery, complemented by radiation and/or medical therapy if necessary. Growth hormone levels are increased and insulin-like growth factor 1 levels are normal in patients with CKD. In a normal patient with CKD, as in one with acromegaly, there can be a paradoxic increase in growth hormone after an oral glucose load. Therefore, diagnosis of acromegaly in renal insufficiency is challenging. The treatment of choice for acromegaly is surgery, although data for medical treatment for acromegaly in CKD are rare. In patients with renal impairment, arginine vasopressin levels are increased as a result of decreased clearance, and there also is impairment of arginine vasopressin signaling in renal tubules. Diabetes insipidus can be masked in advanced kidney disease until kidney transplantation. Diagnosis of the syndrome of inappropriate antidiuretic hormone is similar in mild or moderate kidney disease as in normal subjects, but is challenging in patients with advanced kidney disease owing to the impairment in urine dilution.

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.

Circadian rhythms and the kidney

Numerous physiological functions exhibit substantial circadian oscillations. In the kidneys, renal plasma flow, the glomerular filtration rate and tubular reabsorption and/or secretion processes have been shown to peak during the active phase and decline during the inactive phase. These functional rhythms are driven, at least in part, by a self-sustaining cellular mechanism termed the circadian clock. The circadian clock controls different cellular functions, including transcription, translation and protein post-translational modifications (such as phosphorylation, acetylation and ubiquitylation) and degradation. Disruption of the circadian clock in animal models results in the loss of blood pressure control and substantial changes in the circadian pattern of water and electrolyte excretion in the urine. Kidney-specific suppression of the circadian clock in animals implicates both the intrinsic renal and the extrarenal circadian clocks in these pathologies. Alterations in the circadian rhythm of renal functions are associated with the development of hypertension, chronic kidney disease, renal fibrosis and kidney stones. Furthermore, renal circadian clocks might interfere with the pharmacokinetics and/or pharmacodynamics of various drugs and are therefore an important consideration in the treatment of some renal diseases or disorders.

Circadian regulation of renal function

The kidneys regulate many vital functions that require precise control throughout the day. These functions, such as maintaining sodium balance or regulating arterial pressure, rely on an intrinsic clock mechanism that was commonly believed to be controlled by the central nervous system. Mounting evidence in recent years has unveiled previously underappreciated depth of influence by circadian rhythms and clock genes on renal function, at the molecular and physiological level, independent of other external factors. The impact of circadian rhythms in the kidney also affects individuals from a clinical standpoint, as the loss of rhythmic activity or clock gene expression have been documented in various cardiovascular diseases. Fortunately, the prognostic value of examining circadian rhythms may prove useful in determining the progression of a kidney-related disease, and chronotherapy is a clinical intervention that requires consideration of circadian and diurnal rhythms in the kidney. In this review, we discuss evidence of circadian regulation in the kidney from basic and clinical research in order to provide a foundation on which a great deal of future research is needed to expand our understanding of circadian relevant biology.

Pilot Study of Metabolomics and Psychoneurological Symptoms in Women With Early Stage Breast Cancer

Many women with breast cancer experience symptoms of pain, fatigue, and depression, collectively known as psychoneurologic (PN) symptoms, during and after chemotherapy treatment. Evidence that inflammatory dysfunction related to cancer and its treatments contributes to the development and persistence of PN symptoms through several interrelated pathways is accumulating. However, a major limiting factor in more precisely identifying the biological mechanisms underlying these symptoms is the lack of biological measures that represent a holistic spectrum of biological responses. Metabolomics allows for examination of multiple, co-occurring metabolic pathways and provides a systems-level perspective on biological mechanisms that may contribute to PN symptoms.

METHODS

In this pilot study, we performed serum metabolome analysis using liquid chromatography high-resolution mass spectrometry of global and targeted metabolomics from the tryptophan pathway from archived samples from 19 women with early-stage breast cancer. We used paired t tests to compare metabolite concentrations and Pearson's correlation coefficients to examine concomitant changes in metabolite concentrations and PN symptoms before and after chemotherapy.

RESULTS

Levels of pain, fatigue, and depression increased after chemotherapy. Compared with pre-chemotherapy, global metabolites post-chemotherapy were characterized by higher concentrations of acetyl-l-alanine and indoxyl sulfate and lower levels of 5-oxo-l-proline. Targeted analysis indicated significantly higher kynurenine levels and kynurenine/tryptophan ratios post-chemotherapy. Symptoms of pain and fatigue had strong associations with multiple global and several targeted metabolites.

CONCLUSION

Results demonstrated that metabolomics may be useful for elucidating biological mechanisms associated with the development and severity of PN symptoms, specifically pain and fatigue, in women with early-stage breast cancer.

Effect of extended hours dialysis on sleep quality in a randomized trial

AIM

Poor sleep quality is common in haemodialysis patients and associated with worse outcomes. In this pre-specified analysis, we examined the impact of extended hours haemodialysis on sleep quality.

METHODS

The ACTIVE Dialysis trial randomized 200 participants to extended (≥24 h/week) or standard (target 12-15 h) hours haemodialysis over 12 months. Sleep quality was measured in the Kidney Disease Quality of Life Short Form 1.3 (KDQOL-SF) by overall sleep quality score (0-10, 10 = 'very good') and the sleep subscale (0-100, 100 = 'best possible sleep') every 3 months via blinded telephone interview. The average intervention effect was calculated by mixed linear regression adjusted by time point and baseline score. Factors predicting sleep quality were assessed by multivariate regression analysis.

RESULTS

Overall sleep quality score and sleep subscale at baseline were similar in both groups (5.9 [95%CI 5.4-6.4] vs. 6.3 [5.9-6.8]; 65.0 [60.9-69.1] vs. 63.2 [59.1-67.3]; extended and standard hours, respectively). Extended hours haemodialysis led to a non-significant improvement in overall sleep quality score (average intervention effect 0.44 (-0.01 to 0.89), P = 0.053) and sleep subscale (average intervention effect 3.58 (-0.02 to 7.18), P = 0.051). Poor sleep quality was associated with being female and with current smoking. Sleep quality was positively associated with EuroQol-5D (EQ5D) and the SF-36 Physical Component and Mental Component Summary Scores but not with hospitalizations.

CONCLUSION

Sleep quality was not significantly improved by extended hours dialysis in this study. Sleep quality is positively correlated with quality of life in haemodialysis patients and is poorer in women and current smokers.

Circadian disruption: New clinical perspective of disease pathology and basis for chronotherapeutic intervention

Biological processes are organized in time as innate rhythms defined by the period (τ), phase (peak [Φ] and trough time), amplitude (A, peak-trough difference) and mean level. The human time structure in its entirety is comprised of ultradian (τ < 20 h), circadian (20 h > τ < 28 h) and infradian (τ > 28 h) bioperiodicities. The circadian time structure (CTS) of human beings, which is more complicated than in lower animals, is orchestrated and staged by a brain central multioscillator system that includes a prominent pacemaker - the suprachiasmatic nuclei of the hypothalamus. Additional pacemaker activities are provided by the pineal hormone melatonin, which circulates during the nighttime, and the left and right cerebral cortices. Under ordinary circumstances this system coordinates the τ and Φ of rhythms driven by subservient peripheral cell, tissue and organ clock networks. Cyclic environmental, feeding and social time cues synchronize the endogenous 24 h clocks and rhythms. Accordingly, processes and functions of the internal environment are integrated in time for maximum biological efficiency, and they are also organized and synchronized in time to the external environment to ensure optimal performance and response to challenge. Artificial light at night (ALAN) exposure can alter the CTS as can night work, which, like rapid transmeridian displacement by air travel, necessitates realignment of the Φ of the multitude of 24 h rhythms. In 2001, Stevens and Rea coined the phrase "circadian disruption" (CD) to label the CTS misalignment induced by ALAN and shift work (SW) as a potential pathologic mechanism of the increased risk for cancer and other medical conditions. Current concerns relating to the effects of ALAN exposure on the CTS motivated us to renew our long-standing interest in the possible role of CD in the etiopathology of common human diseases and patient care. A surprisingly large number of medical conditions involve CD: adrenal insufficiency; nocturia; sleep-time non-dipping and rising blood pressure 24 h patterns (nocturnal hypertension); delayed sleep phase syndrome, non-24 h sleep/wake disorder; recurrent hypersomnia; SW intolerance; delirium; peptic ulcer disease; kidney failure; depression; mania; bipolar disorder; Parkinson's disease; Smith-Magenis syndrome; fatal familial insomnia syndrome; autism spectrum disorder; asthma; byssinosis; cancers; hand, foot and mouth disease; post-operative state; and ICU outcome. Poorly conceived medical interventions, for example nighttime dosing of synthetic corticosteroids and certain β-antagonists and cyclic nocturnal enteral or parenteral nutrition, plus lifestyle habits, including atypical eating times and chronic alcohol consumption, also can be causal of CD. Just as surprisingly are the many proven chronotherapeutic strategies available today to manage the CD of several of these medical conditions. In clinical medicine, CD seems to be a common, yet mostly unrecognized, pathologic mechanism of human disease as are the many effective chronotherapeutic interventions to remedy it.