Dissociation of the diurnal variation of aldosterone and cortisol in anephric subjects

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.

The paradoxical effect of aldosterone on cardiovascular outcome in maintenance hemodialysis patients

Background

Patients with end-stage kidney disease face increased risk of cardiovascular events, and left ventricular diastolic dysfunction (LVDD) contributes to the high occurrence of cardiovascular mortality (CM). Although a high serum aldosterone (sALD) level is involved in the development of cardiovascular complications in the general population, this association is unclear in patients undergoing hemodialysis. We aimed to determine the impact of sALD on LVDD and CM among hemodialysis patients (HDPs).

Methods

We performed a prospective cohort study of maintenance HDPs without cardiovascular disease. The patients were divided into two groups according to the median level of sALD. All patients underwent baseline echocardiography to evaluate diastolic dysfunction (E/e´ ratio > 15). The LVDD and CM rates were compared between the high and low aldosterone groups.

Results

We enrolled a total of 60 adult patients (mean age, 57.9 ± 12.1 years; males, 30.0%). The low aldosterone group had an increased left ventricular diastolic dimension compared with the high aldosterone group (52.2 ± 8.4 mm vs. 50.3 ± 5.2 mm, respectively; p = 0.03). Low log-aldosterone (odds ratio [OR], 0.40; 95% confidence interval [CI], 0.19-0.86) and large left atrial dimension (OR, 1.31; 95% CI, 1.11-1.54) were independent risk factors for LVDD at baseline. In addition, Cox regression analysis demonstrated that low sALD was an independent predictor of CM in HDPs (hazard ratio, 0.46; 95% CI, 0.25-0.85; p = 0.01) during follow-up.

Conclusion

Low sALD was not only associated with LVDD but was also an independent predictor of CM among HDPs regardless of their interdialytic weight gain.

Physiological and drug-induced changes in blood levels of adrenal steroids and their precursors in cynomolgus monkeys: An application of steroid profiling by LC-MS/MS for evaluation of the adrenal toxicity

The adrenal gland is the most common toxicological target of drugs within the endocrine system, and inhibition of adrenal steroidogenesis can be fatal in humans. However, methods to evaluate the adrenal toxicity are limited. The aim of the present study was to verify the usefulness of simultaneous measurement of blood levels of multiple adrenal steroids, including precursors, as a method to evaluate drug effects on adrenal steroidogenesis in cynomolgus monkeys. With this aim, physiological and drug-induced changes in blood levels of adrenal steroids, including cortisol, aldosterone, androgen, and their precursors were examined. First, for physiological changes, intraday and interday changes in blood steroid levels were examined in male and female cynomolgus monkeys. The animals showed circadian changes in steroid levels that are similar to those in humans, while interday changes were relatively small in males. Next, using males, changes in blood steroid levels induced by ketoconazole and metyrapone were examined, which suppress adrenal steroidogenesis via inhibition of CYP enzymes. Consistent with rats and humans, both ketoconazole and metyrapone increased the deoxycorticosterone and deoxycortisol levels, probably via CYP11B1 inhibition, and the increase was observed earlier and with greater dynamic range than the changes in cortisol level. Changes in other steroid levels reflecting the drug mechanisms were also observed. In conclusion, this study showed that in cynomolgus monkeys, simultaneous measurement of blood levels of adrenal steroids, including precursors, can be a valuable method to sensitively evaluate drug effects on adrenal steroidogenesis and to investigate the underlying mechanisms.

The Circadian Clock in the Regulation of Renal Rhythms

Since the kidney is integral to maintenance of fluid and ion homeostasis, and therefore blood pressure regulation, its proper function is paramount. Circadian fluctuations in blood pressure, renal blood flow, glomerular filtration rate, and sodium and water excretion have been documented for decades, if not longer. Recent studies on the role of circadian clock proteins in the regulation of a variety of renal transport genes suggest that the molecular clock in the kidney controls circadian fluctuations in renal function. The circadian clock appears to be a critical regulator of renal function with important implications for the treatment of renal pathologies, which include chronic kidney disease and hypertension. The development, regulation, and mechanism of the kidney clock are reviewed here.

Circadian rhythm of salivary cortisol, plasma cortisol, and plasma ACTH in end-stage renal disease

OBJECTIVE

Patients with end-stage renal disease (ESRD) can display the features of endogenous hypercortisolism but are difficult to evaluate for Cushing's syndrome. We evaluated the circadian rhythm of plasma compared with salivary cortisol in subjects with ESRD.

DESIGN

Plasma and salivary cortisol and plasma ACTH samples were drawn frequently over 24 h in an inpatient research unit in stable ESRD subjects on daytime chronic hemodialysis (n=16) vs controls (n=8).

METHODS

Plasma cortisol was measured every 2 h from 0800 to 0600 h the following day. Salivary cortisol was measured every 2 h, except between 2400 and 0400 h (sleep time). Plasma ACTH measured in a subset of samples and C-reactive protein (CRP) was measured as a marker of a subclinical inflammatory state in all subjects.

RESULTS

ESRD subjects had a discernable circadian rhythm in plasma and salivary cortisol, but with a significantly higher nadir (1800-2400 h) compared with the controls (P=0.016-<0.001). After excluding four ESRD subjects without a normal circadian rhythm, the ESRD subjects still had higher nadir plasma and salivary cortisol and plasma ACTH compared with controls. There was no difference in the correlation of salivary and plasma cortisol in control vs ESRD subjects. ESRD subjects had higher CRP levels compared with controls.

CONCLUSIONS

ESRD subjects had increased late-night plasma and salivary cortisol and plasma ACTH levels. Late-night salivary cortisol is a reliable index of plasma cortisol in ESRD patients.

The midnight-to-morning urinary cortisol increment method is not reliable for the assessment of hypothalamic-pituitary-adrenal insufficiency in patients with end-stage kidney disease

A previous study reported that the midnight-to-morning urinary cortisol increment method could be used to reliably assess the insufficiency of the hypothalamic-pituitary-adrenal (HPA) axis. The principal aim of the present study is to verify whether the midnight-to-morning urinary cortisol increment is a reliable method for the assessment of the HPA axis in patients with various degrees of impaired kidney function. Fifty-six clinically stable patients with chronic kidney disease (CKD) and 14 healthy subjects were enrolled in the present study. Patients with CKD were divided on the basis of glomerular filtration rate (GFR) into the following arbitrary groups: mild (GFR: 60-89 ml/min/1.73 m2, no.=15), moderate (GFR: 30-59 ml/min/1.73 m2, no.=12) and severe kidney insufficiency (GFR: 15-29 ml/min/1.73 m2, no.=13), and hemodialysis patients. Plasma cortisol and ACTH levels were measured. The HPA axis was assessed by short Synacthen test and overnight dexamethasone suppression test. Double voided urine samples were collected at midnight and waking in the patients and the controls. Urinary free cortisol (UFC) and creatinine levels were measured and the UFC/creatinine ratio (Cort/Cr) was calculated. Then, the Cort/Cr increment was calculated as the morning Cort/Cr minus the midnight Cort/Cr. Baseline plasma cortisol levels were not significantly different between two groups. However, we found that CKD patients had significantly greater plasma ACTH levels than controls. The patients with CKD had also significantly lower morning UFC levels than controls and there was a progressive fall in morning UFC levels with decreasing GFR. The assessment of the HPA axis in patients with GFR lower than 29 ml/min was hampered by falsely abnormal responses to the midnight-to-morning urinary cortisol increment method. Plasma cortisol responded normally to exogenously administered ACTH, while plasma cortisol was suppressed by overnight dexamethasone administration in all patients with CKD. In conclusion, this method is not a reliable test for assessment of the HPA insufficiency in patients with GFR lower than 29 ml/min.

Hormonal responses to acute volume changes in anephric subjects

The response of plasma aldosterone and cortisol concentrations to acute volume depletion was studied in 18 chronically anephric subjects and four recently nephrectomized subjects. Volume-depleting hemodialysis and hemodialysis without volume depletion produced insignificant changes in plasma aldosterone concentrations in chronically anephric subjects. Failure of volume depletion to increase plasma aldosterone concentrations in these subjects could not be attributed to reductions in plasma potassium concentrations and was in marked contrast to the effect on plasma cortisol concentrations, which increased significantly during volume depletion. Changes in plasma cortisol concentrations exhibited a negative correlation with changes in diastolic blood pressure (r = -0.712, P less than 0.001) and were shown to correspond to similar changes in plasma ACTH concentrations. Comparable increases in plasma cortisol and ACTH concentrations were also demonstrated in the studies on recently nephrectomized subjects, who, in contrast to chronically anephric subjects, exhibited increases in plasma aldosterone concentrations which were concordant with the changes in plasma cortisol and ACTH concentrations. These findings suggest that plasma aldosterone concentrations are regulated by a volume-sensitive mechanism in recently nephrectomized subjects but not in chronically anephric subjects. We interpret these data as evidence of aldosterone responsiveness to ACTH that persists for a limited time only after removal of the stimulus provided by the renin-angiotensin system. Volume-related changes in plasma cortisol and ACTH concentrations occur in the absence of stimulation by a functioning renin-angiotensin system.

The effect of dialysate sodium concentration on body fluid compartment volume, plasma renin activity and plasma aldosterone concentration in chronic hemodialysis patients

Six stable chronic hemodialysis patients received six hemodialysis treatments: two each with the dialysate sodium concentration (DNa) 7% greater than serum sodium concentration, two with a DNa equal to serum sodium concentration and two with the DNa 7% less than the serum sodium concentration. During one treatment with each dialysate 2 kg of fluid was removed and during the other treatments the patient's weight was kept constant. Total body water (TBW), intracellular water (ICW), extracellular water (ECW), plasma volume (PV), plasma renin activity (PRA), aldosterone (ALDO), Na, BUN and osmolality were determined before and after each treatment. Fluid removal during dialysis had no effect on ICW with essentially all the fluid removed during dialysis coming from ECW. ICW increased with low DNa and decreased with high DNa. The effect of DNa on ECW and PV was the opposite of that on ICW. PRA increased and ALDO decreased during dialysis. Predialysis ALDO directly correlated with PRA (r = 0.68, p less than 0.001) but not with serum potassium concentration. Post dialysis ALDO was not significantly correlated with either PRA or potassium. Fluid removal and low DNa increased both PRA and ALDO. These studies indicate that water shifts from the extracellular space into intracellular space when DNa is lower than serum Na and the reverse is true when DNa exceeds serum Na. Plasma aldosterone decreases during dialysis despite an increase in PRA, possibly related to the decrease in serum potassium concentration. The effect of fluid removal and low DNa on PRA and ALDO may be related to a reduction in ECW and/or PV.