Patients with renal dysfunction require a longer duration until blood pressure dips during the night

Hypertension as Cardiovascular Risk Factor in Chronic Kidney Disease

Hypertension is the leading modifiable cause of premature death and hence one of the global targets of World Health Organization for prevention. Hypertension also affects the great majority of patients with chronic kidney disease (CKD). Both hypertension and CKD are intrinsically related, as hypertension is a strong determinant of worse renal and cardiovascular outcomes and renal function decline aggravates hypertension. This bidirectional relationship is well documented by the high prevalence of hypertension across CKD stages and the dual benefits of effective antihypertensive treatments on renal and cardiovascular risk reduction. Achieving an optimal blood pressure (BP) target is mandatory and requires several pharmacological and lifestyle measures. However, it also requires a correct diagnosis based on reliable BP measurements (eg, 24-hour ambulatory BP monitoring, home BP), especially for populations like patients with CKD where reduced or reverse dipping patterns or masked and resistant hypertension are frequent and associated with a poor cardiovascular and renal prognosis. Even after achieving BP targets, which remain debated in CKD, the residual cardiovascular risk remains high. Current antihypertensive options have been enriched with novel agents that enable to lower the existing renal and cardiovascular risks, such as SGLT2 (sodium-glucose cotransporter-2) inhibitors and novel nonsteroidal mineralocorticoid receptor antagonists. Although their beneficial effects may be driven mostly from actions beyond BP control, recent evidence underline potential improvements on abnormal 24-hour BP phenotypes such as nondipping. Other promising novelties are still to come for the management of hypertension in CKD. In the present review, we shall discuss the existing evidence of hypertension as a cardiovascular risk factor in CKD, the importance of identifying hypertension phenotypes among patients with CKD, and the traditional and novel aspects of the management of hypertensives with CKD.

Association between urinary N-acetyl-β-glucosaminidase activity–urinary creatinine concentration ratio and risk of disability and all-cause mortality

Background

Recent studies have suggested that chronic kidney disease is associated with cardiovascular disease, dementia, and frailty, all of which cause disability and early death. We investigated whether increased activity of urinary N-acetyl-β-glucosaminidase (NAG), a marker of kidney injury, is associated with risk of disability or all-cause mortality in a general population.

Methods

Follow-up data from the Hidaka Cohort Study, a population-based cohort study of members of a Japanese rural community, were obtained via questionnaires completed by participants or their relatives. Multivariable analyses were used to investigate relations between urinary NAG activity–urinary creatinine concentration ratio and risk of disability or all-cause mortality.

Results

A total of 1182 participants were followed up for a median of 12.4 years. The endpoints were receipt of support under the public long-term care insurance program, and all-cause mortality. A total of 122 participants (10.3%) were reported to be receiving long-term care and 230 (19.5%) had died. After adjustment for cardiovascular risk factors along with physical activity, and using the quartile 1 results as a reference, the odds ratio (OR) for disability was 2.12 [95% confidence interval (95% confidence interval [CI]), 1.04–4.33; p = 0.038) and the hazard ratio (HR) for all-cause mortality was 1.65 (95% CI, 1.05–2.62; p = 0.031) in participants with urinary NAG/creatinine ratio in quartile 4. Similar results were obtained in participants without proteinuria: OR for disability, 2.46 (95% CI, 1.18–5.16; p = 0.017); and HR for all-cause mortality, 1.62 (95% CI, 1.00–2.63; p = 0.049).

Conclusions

Increased urinary NAG/creatinine ratio was associated with risk of disability or all-cause mortality in a general population.

Association Between Nocturnal Blood Pressure Dipping and Chronic Kidney Disease Among Patients With Controlled Office Blood Pressure

BACKGROUND

Although abnormal blood pressure (BP) patterns are associated with adverse cardiorenal outcomes, their associations are yet unquantified by nocturnal dipping status. We examined the association of nocturnal BP dipping pattern with albuminuria and kidney function among participants with controlled hypertension without prior advanced kidney disease.

METHODS

Ambulatory BP (ABP) measurements were collected from 995 middle-aged, cardiology clinic patients with controlled office BP (OBP) (<140/90 mm Hg). The magnitude of dipping was calculated as the difference between daytime and nighttime systolic BP (SBP) divided by daytime SBP. Accordingly, the participants were categorized as extreme-dipper (≥20%), dipper (10% to <20%), non-dipper (0% to <10%), or reverse-dipper (<0%). We analyzed the cross-sectional associations of dipping with albuminuria (urine albumin-to-creatinine ratio ≥30 mg/g) and decreased estimated glomerular filtration rate (<60 ml/min/1.73 m2), adjusting for OBP/ABP, antihypertensive class, body mass index, total cholesterol, fasting glucose, socioeconomic status, and health behavior.

RESULTS

The participants (mean age 60.2 years; 52.9% male) consisted of 13.5% extreme-dippers, 43.1% dippers, 34.7% non-dippers, and 8.7% reverse-dippers. In reference to dippers, odds ratios [95% confidence interval] for albuminuria were 1.73 [1.04-2.60] in reverse-dippers, 1.67 [1.20-2.32] in non-dippers, and 0.62 [0.38-1.04] in extreme-dippers. Likewise, abnormal dipping profile was associated with decreased kidney function: reverse-dipping, 2.02 [1.06-3.84]; non-dipping, 1.98 [1.07-3.08]; extreme-dipping, 0.69 [0.20-1.17]. The associations persisted among participants with more conservatively controlled OBP (<130/80 mm Hg).

CONCLUSIONS

Monitoring diurnal and nocturnal BP may identify chronic kidney disease otherwise overlooked based on OBP.

Baseline Urinary Angiotensinogen Excretion Predicts Deterioration of the Kidney Function in Patients with Chronic Kidney Disease

Objective The intrarenal renin-angiotensin system (RAS) is activated in patients with chronic kidney disease (CKD), and urinary angiotensinogen (AGT) levels, a surrogate marker of the intrarenal RAS activation, are associated with blood pressure (BP) and urinary albumin excretion. In addition, it has been shown that changes in urinary AGT levels correlate with annual changes in the estimated glomerular filtration rate (eGFR) in patients with type 2 diabetes and that elevated levels of urinary AGT in type 2 diabetic patients with albuminuria are a high-risk factor for worsening renal and cardiovascular complications. However, whether or not baseline urinary AGT levels predict deterioration of the kidney function in all patients with CKD is unclear. Methods We recruited 62 patients with CKD whose eGFR was >15 mL/min/1.73 m². We performed 24-hour ambulatory BP monitoring at 30-min intervals and daily urinary collection to examine the urinary AGT levels and albumin excretion and measured the levels of plasma angiotensin II (Ang II), a surrogate marker of circulating RAS. In addition, annual changes in the eGFR were followed up for 3.4±1.5 years. Results Annual changes in the eGFR were significantly and negatively associated with urinary AGT levels (r=-0.31, p=0.015) as well as the age, systolic BP, and urinary albumin levels. In contrast, annual changes in the eGFR were not correlated with plasma Ang II levels. Furthermore, when dividing patients into quartiles according to urinary AGT levels, patients with the highest urinary AGT levels showed a progressive decline in the eGFR. Conclusion These results suggest that elevated baseline urinary AGT levels can predict renal dysfunction in patients with CKD.

Prognostic Value of a Riser Pattern of Nighttime Blood Pressure in Very Elderly Adults of ≥80 Years: A General Practice-Based Prospective SEARCH Study

BACKGROUND

We examined our hypothesis that participants with higher mean nighttime blood pressure (BP) levels and/or those with a riser BP pattern, both measured by ambulatory blood pressure (BP) monitoring (ABPM), would show higher risk for cardiovascular disease (CVD) events compared to those with normal nighttime BP levels or a normal dipper BP pattern of circadian BP rhythm, even in very elderly participants in a general practice population.

METHODS

This prospective observational study enrolled 485 very elderly outpatients of ≥80 years (mean age: 83.2 ± 3.3 years; 44.7% male; 89.3% using antihypertensive medications). The prevalences of extreme dipper, dipper, nondipper, and riser status were 15.5%, 38.6%, 32.2%, and 13.8%, respectively.

RESULTS

During a mean follow-up of 3.9 years (1,734 person-years), 41 CVD events occurred. The participants with a riser pattern (higher nighttime systolic BP [SBP] than daytime SBP) showed a significantly higher risk for CVD events with adjustment for covariates: hazard ratio (HR), 2.61; 95% confidence interval (CI), 1.03-6.62. Even after adjusting for covariates and mean nighttime SBP level, the CVD risks in participants with a riser pattern remained significant: HR, 3.11; 95% CI, 1.10-8.88. On the other hand, all BP variables showed no significant risks for CVD events. In addition, when we divided study participants into quartiles by their ambulatory BP levels, none of the ambulatory BP variables showed a J- or U-shaped relationship with CVD event risk.

CONCLUSIONS

In very elderly general practice outpatients, a riser BP pattern was significantly associated with CVD events independently of mean nighttime BP.

The Urinary Angiotensinogen to Urinary Albumin Ratio Reflects Whether the Renin-angiotensin System in the Kidney Is Activated due to Filtration of Plasma Angiotensinogen through the Damaged Glomeruli or the Production of Angiotensinogen in the Proximal Tubules

Objective Urinary angiotensinogen (AGT) is a surrogate marker for intrarenal renin-angiotensin system (RAS) activity that plays an important role in the development of renal damage. Urinary AGT levels are determined by the filtration of plasma AGT through the damaged glomeruli and production of AGT in the proximal tubules. However, the relative merits of the filtration and production of urinary AGT levels in chronic kidney diseases (CKD) have not been clarified. Therefore, we investigated them in CKD patients. Methods We recruited 41 biopsy-proven patients diagnosed with IgA nephropathy (IgAN) in 31, membranous nephropathy (MN) in 5, and tubulointerstitial nephritis (TIN) in 5. The patients taking RAS blockers were excluded. Results The urinary albumin levels in MN patients were significantly higher and those in TIN patients significantly lower than in IgAN patients, and the urinary AGT levels in the MN and TIN patients were significantly higher than those in IgAN patients. Conversely, the urinary AGT-to-urinary albumin (urinary AGT/Alb) ratios were the same for IgAN and MN patients, and those of TIN patients were significantly higher than those of IgAN and MN patients. A multiple linear regression analysis revealed that the urinary AGT/Alb ratios had a significant positive association with IgAN and TIN after adjustments (β=0.75, and p<0.01). Conclusion These data suggest that the origins of urinary AGT may differ according to the etiology of renal damage [i.e. glomerular damage (such as IgAN and MN) or tubulointerstitial damage (such as TIN)], and a higher urinary AGT/Alb ratio, as in TIN, may reflect AGT production in the kidney.

Chronotherapy with a Renin-angiotensin System Inhibitor Ameliorates Renal Damage by Suppressing Intrarenal Renin-angiotensin System Activation

Objective The intrarenal renin-angiotensin system (RAS) is activated in chronic kidney disease (CKD) patients and is not suppressed at night in CKD patients showing nocturnal hypertension, contributing to renal damage. Furthermore, changes in RAS inhibitor administration from morning to evening, namely chronotherapy, ameliorates renal damage at night. We attempted to clarify whether or not chronotherapy ameliorates renal damage by suppressing the intrarenal RAS activity. Methods We recruited 34 CKD patients with RAS inhibitors in the morning. We conducted ambulatory blood pressure (BP) monitoring and urine collection and evaluated urinary albumin (Alb) and angiotensinogen (AGT), which are surrogate markers for intrarenal RAS activity during the day and at night, respectively. The same experiments were conducted after changing the administration time. The ratio of values associated with morning versus evening dosing was defined as the morning to evening (M/E) ratio. Results The M/E ratio of urinary Alb had a significant and positive relationship with that of urinary AGT during the day and at night in all CKD patients. However, no significant relationships were found between the M/E ratios of urinary Alb and AGT using multiple linear regression analyses. Conversely, there was a significant and positive relationship between the M/E ratios of urinary Alb and AGT at night but not during the day in CKD patients whose estimated glomerular filtration rate was <45 mL/min/1.73 m² and whose night-to-day ratio of systolic BP was >0.90, even after adjustment. Conclusion This study indicated that chronotherapy with RAS inhibitors improved the renal damage via intrarenal RAS suppression, especially in CKD patients with an impaired renal function and nocturnal hypertension.

Diurnal Regulation of Renal Electrolyte Excretion: The Role of Paracrine Factors

Many physiological processes, including most kidney-related functions, follow specific rhythms tied to a 24-h cycle. This is largely because circadian genes operate in virtually every cell type in the body. In addition, many noncanonical genes have intrinsic circadian rhythms, especially within the liver and kidney. This new level of complexity applies to the control of renal electrolyte excretion. Furthermore, there is growing evidence that paracrine and autocrine factors, especially the endothelin system, are regulated by clock genes. We have known for decades that excretion of electrolytes is dependent on time of day, which could play an important role in fluid volume balance and blood pressure control. Here, we review what is known about the interplay between paracrine and circadian control of electrolyte excretion. The hope is that recognition of paracrine and circadian factors can be considered more deeply in the future when integrating with well-established neuroendocrine control of excretion.

Circadian regulation of kidney function: finding a role for Bmal1

Mounting evidence suggests that there is an internal molecular "clock" within the kidney to help maintain normal renal function. Disturbance of the kidney circadian rhythm may pose a threat to water and electrolyte homeostasis and blood pressure regulation, among many other problems. The identification of circadian genes facilitated a more comprehensive appreciation of the importance of "keeping the body on time"; however, our knowledge is very limited with regard to how circadian genes regulate kidney function. In this brief review, we summarize recent progress in circadian control of renal physiology, with a particular focus on aryl hydrocarbon receptor nuclear translocator-like protein (Arntl1; also called Bmal1).

Sodium balance, circadian BP rhythm, heart rate variability, and intrarenal renin-angiotensin-aldosterone and dopaminergic systems in acute phase of ARB therapy

We have revealed that even in humans, activated intrarenal renin–angiotensin–aldosterone system (RAAS) enhances tubular sodium reabsorption to facilitate salt sensitivity and nondipper rhythm of blood pressure (BP), and that angiotensin receptor blocker (ARB) could increase daytime urinary sodium excretion rate (U_NaV) to produce lower sodium balance and restore nondipper rhythm. However, the sympathetic nervous system and intrarenal dopaminergic system can also contribute to renal sodium handling. A total of 20 patients with chronic kidney disease (61 ± 15 years) underwent 24‐h ambulatory BP monitoring before and during two‐day treatment with ARB, azilsartan. Urinary angiotensinogen excretion rate (U_AGTV, μg/gCre) was measured as intrarenal RAAS; urinary dopamine excretion rate (U_DAV, pg/gCre) as intrarenal dopaminergic system; heart rate variabilities (HRV, calculated from 24‐h Holter‐ECG) of non‐Gaussianity index λ_25s as sympathetic nerve activity; and power of high‐frequency (HF) component or deceleration capacity (DC) as parasympathetic nerve activity. At baseline, glomerular filtration rate correlated inversely with U_AGTV (r = −0.47, P = 0.04) and positively with U_DAV (r = 0.58, P = 0.009). HF was a determinant of night/day BP ratio (β = −0.50, F = 5.8), rather than DC or λ_25s. During the acute phase of ARB treatment, a lower steady sodium balance was not achieved. Increase in daytime U_NaV preceded restoration of BP rhythm, accompanied by decreased U_AGTV (r = −0.88, P = 0.05) and increased U_DAV (r = 0.87, P = 0.05), but with no changes in HRVs. Diminished sodium excretion can cause nondipper BP rhythm. This was attributable to intrarenal RAAS and dopaminergic system and impaired parasympathetic nerve activity. During the acute phase of ARB treatment, cooperative effects of ARB and intrarenal dopaminergic system exert natriuresis to restore circadian BP rhythm.

The association between circulating endostatin and a disturbed circadian blood pressure pattern in patients with type 2 diabetes

BACKGROUND

Endostatin, cleaved from collagen XVIII in the extracellular matrix, is a promising circulating biomarker for cardiovascular damage. It possesses anti-angiogenic and anti-fibrotic functions and has even been suggested to be involved in blood pressure regulation. Less is known if endostatin levels relate to circadian blood pressure patterns. In the present paper we studied the association between circulating levels of endostatin and nocturnal dipping in blood pressure.

METHODS

We used the CARDIPP-study, a cohort of middle aged, type 2 diabetics (n = 593, 32% women), with data on both 24-hour and office blood pressure, serum-endostatin, cardiovascular risk factors, and incident major cardiovascular events. Nocturnal dipping was defined as a >10% difference between day- and night-time blood pressures.

RESULTS

Two-hundred four participants (34%) were classified as non-dippers. The mean endostatin levels were significantly higher in non-dippers compared to dippers (mean ± standard deviation: 62.6 ± 1.8 µg/l vs. 58.7 ± 1.6 µg/l, respectively, p = .007). Higher serum levels of endostatin were associated with a diminished decline in nocturnal blood pressure adjusted for age, sex, HbA1c, mean systolic day blood pressure, hypertension treatment, glomerular filtration rate, and prevalent cardiovascular disease (regression coefficient per SD increase of endostatin -0.01, 95% CI, -0.02-(-0.001), p = .03). Structural equation modelling analyses suggest that endostatin mediates 7% of the association between non-dipping and major cardiovascular events.

CONCLUSION

We found an independent association between higher circulating levels of endostatin and a reduced difference between day- and night-time systolic blood pressure in patients with type 2 diabetes. Yet endostatin mediated only a small portion of the association between non-dipping and cardiovascular events arguing against a clinical utility of our findings.

Loss of nighttime blood pressure dipping as a risk factor for coronary artery calcification in nondialysis chronic kidney disease

Diurnal variations in blood pressure (BP) loss are closely associated with target organ damage and cardiovascular events. The quantity of coronary artery calcification (CAC) correlates with the atherosclerotic plaque burden, and an increased quantity indicates a substantially increased risk of cardiovascular events. This study investigated the nighttime diurnal variation in BP loss associated with CAC in patients with chronic kidney disease (CKD).Of the 1958 participants, we enrolled 722 participants with CKD without a history of acute coronary syndrome or symptomatic coronary artery disease. CAC was measured with computed tomography. BP was measured using 24-hour ambulatory BP monitoring. Central BP was measured using a SphygmoCor waveform analysis system.Participants with CAC had significantly higher 24-hour systolic, daytime systolic, and nighttime systolic ambulatory BP and central systolic BP. The percentage of participants with dipping loss was significantly higher among those with CAC. Multivariate logistic regression analysis indicated that dipping loss and dipping ratio were independently associated with CAC after adjusting for traditional and nontraditional cardiovascular risk factors and other BP parameters, including measurements of office-measured BP and central BP. The dipping status improved risk prediction for CAC after considering traditional risk factors and office-measured BP, using the net reclassification improvement and integrated discrimination improvement.Nighttime loss of diurnal variation in BP is an independent risk factor for CAC in CKD patients.

Relationship between diurnal blood pressure and renal histopathological changes in white coat hypertension

BACKGROUND

Multiple epidemiological studies have clearly demonstrated the macrovascular risks associated with white coat hypertension (WCH) or sustained hypertension (SH). In patients with WCH, there is no literature available on renal histopathological changes and that on blood pressure pattern and native kidney outcome is scant. We aimed to clarify the relationship between blood pressure variables and pathological features of kidney biopsies in living kidney donors with WCH.

METHODS

This cross-sectional study included living kidney donors with WCH (n = 10) and SH (n = 10), and 20 healthy kidney donors with similar demographic features (control group). Kidney allograft biopsy samples were obtained during transplantation and chronic glomerular, vascular and tubulointertitial changes were semiquantitatively scored according to the Banff classification.

RESULTS

The mean age of the 20 hypertensive subjects (Group 1) and controls (Group 2) was 59.3 ± 8.5 versus 59.6 ± 7.6 years and almost half were female. There was no difference in renal function parameters between the groups; however, kidney histopathology in Group 1 was worse than Group 2 with a chronicity index of 2.80 ± 1.67 versus 1.75 ± 1.16 (p = 0.02). There was no difference between histopathological scores of patients with WCH or SH (chronicity index: 2.60 ± 1.43 vs. 2.70 ± 1.70, p = 0.88). Night-to-day mean arterial pressure (MAP) ratio was significantly associated with chronicity index in patients with WCH. Moreover, WCH patients with non-dipper hypertensive pattern had a worse chronicity index.

CONCLUSIONS

Significant histopathological alterations in the kidney were observed in patients with WCH and SH, and were accentuated in WCH patients with non-dipper blood pressure pattern.

Addition of hydrochlorothiazide to angiotensin receptor blocker therapy can achieve a lower sodium balance with no acceleration of intrarenal renin angiotensin system in patients with chronic kidney disease

Objective:

Angiotensin receptor blockers (ARBs) produce a lower sodium (Na) balance, and the natriuretic effect is enhanced under Na deprivation, despite falls in blood pressure (BP) and glomerular filtration rate (GFR).

Methods:

The effect of additional hydrochlorothiazide (HCTZ; 12.5 mg/day) to ARB treatment (valsartan; 80 mg/day) on glomerulotubular Na balance was evaluated in 23 patients with chronic kidney disease.

Results:

Add-on HCTZ decreased GFR, tubular Na load, and tubular Na reabsorption (t_Na), although 24-hour urinary Na excretion (U_NaV) remained constant. Daily urinary angiotensinogen excretion (U_AGTV, 152±10→82±17 μg/g Cre) reduced (p=0.02). Changes in tubular Na load (r²=0.26) and t_Na (r²=0.25) correlated with baseline 24-hour U_AGTV. Changes in filtered Na load correlated with changes in nighttime systolic BP (r²=0.17), but not with changes in daytime systolic BP. The change in the t_Na to filtered Na load ratio was influenced by the change in daytime U_NaV (β=−0.67, F=16.8), rather than the change in nighttime U_NaV.

Conclusions:

Lower Na balance was produced by add-on HCTZ to ARB treatment without an increase of intra-renal renin-angiotensin system activity, leading to restoration of nocturnal hypertension. A further study is needed to demonstrate that the reduction of U_AGTV by additional diuretics to ARBs prevents the progression of nephropathy or cardiovascular events.

Use of Urine Biomarkers to Assess Sodium Intake: Challenges and Opportunities

This article summarizes current data and approaches to assess sodium intake in individuals and populations. A review of the literature on sodium excretion and intake estimation supports the continued use of 24-h urine collections for assessing population and individual sodium intake. Since 2000, 29 studies used urine biomarkers to estimate population sodium intake, primarily among adults. More than half used 24-h urine; the rest used a spot/casual, overnight, or 12-h specimen. Associations between individual sodium intake and health outcomes were investigated in 13 prospective cohort studies published since 2000. Only three included an indicator of long-term individual sodium intake, i.e., multiple 24-h urine specimens collected several days apart. Although not insurmountable, logistic challenges of 24-h urine collection remain a barrier for research on the relationship of sodium intake and chronic disease. Newer approaches, including modeling based on shorter collections, offer promise for estimating population sodium intake in some groups.

Age-Related Difference in the Sleep Pressure-Lowering Effect Between an Angiotensin II Receptor Blocker and a Calcium Channel Blocker in Asian Hypertensives

Sleep blood pressure (BP), which is partly determined by salt sensitivity and intake, is an important cardiovascular risk in hypertensives. However, there have been no studies on age-related differences in the sleep BP–lowering effect between angiotensin II receptor blockers and calcium channel blockers in Asians. Azilsartan Circadian and Sleep Pressure—the 1st Study was a multicenter, randomized, open-label, 2-parallel-group study conducted to compare the efficacy of 8-week oral treatment with an angiotensin II receptor blocker (azilsartan 20 mg) or a calcium channel blocker (amlodipine 5 mg) on sleep BP as evaluated by ambulatory BP monitoring. Among the overall population, amlodipine treatment achieved significantly greater reduction in sleep BP, awake BP, and 24-hour BP than azilsartan treatment. BP reduction by amlodipine was particularly pronounced in elderly hypertensive patients aged ≥60 years old. Among patients ≥60 years old, the amlodipine group had numerically, but not significantly, higher control rate of sleep BP compared with the azilsartan group. Similar results were found for awake BP and 24-hour BP. These results suggest a greater BP reduction/control by amlodipine compared with azilsartan and that reduction/control of BP by amlodipine was also more effective in the elderly population. As recommended in the American Society of Hypertension/The international Society of Hypertension and the National Institute for Health and Clinical Excellence guidelines for differentiating treatment according to age, amlodipine should be one of the options for starting treatment in the elderly population.

Clinical Trial URL—

http://clinicaltrials.gov/show/NCT01762501

Clinical Trial ID—

NCT01762501

Disparate assessment of clinic blood pressure and ambulatory blood pressure in differently aged patients with chronic kidney disease

BACKGROUND

Ambulatory blood pressure monitoring (ABPM) is recommended to assess hypertensive status in patients with chronic kidney disease (CKD). However, the difference in blood pressure (BP) based on clinic and ambulatory monitoring in CKD patients of different ages is not known.

METHODS

We recruited 1116 CKD patients admitted to our hospital division and referred with data in this cross-sectional study. Patients were divided into three groups: young, middle age and old. Inter-method agreement between clinic BP and ABPM in different age groups was assessed using the Kappa (κ) coefficient. Linear and logistic regression analyses were used to evaluate renal and cardiovascular parameters.

RESULTS

κ coefficient for inter-method agreement between clinic BP and ABP in patients from young, middle-age and old groups was 0.472 (p<0.001), 0.335 (p<0.001) and 0.102 (p=0.086), respectively. Age was the main factor determining the difference in clinic BP and ABP by multiple linear regression analyses. Prevalence of masked hypertension in older patients was higher than that in young and middle-age patients (p<0.001), and age was associated with the onset of masked hypertension. Age and ABP were independently correlated with estimated glomerular filtration rate (eGFR) and left ventricular mass index (LVMI), whereas age and clinic BP were associated with carotid intima media thickness (cIMT) by linear and logistic regression analyses.

CONCLUSIONS

We have provided evidence of disparate assessment of the diagnosis and correlation with TOD from clinic BP and ABP in untreated, different-aged, CKD patients. Good-quality, long-term, large longitudinal trials are needed to validate the role of ABPM for Chinese CKD patients.

Rationale, study design, and implementation of the ACS1 study: effect of azilsartan on circadian and sleep blood pressure as compared with amlodipine

Objective

The ACS1 (Azilsartan Circadian and Sleep Pressure – the first study) is a multicenter, randomized, open-label, two parallel-group study carried out to investigate the efficacy of an 8-week oral treatment with azilsartan 20 mg in comparison with amlodipine 5 mg.

Materials and methods

The patients with stage I or II primary hypertension will be randomly assigned to either an azilsartan group (n=350) or an amlodipine group (n=350). The primary endpoint is a change in nocturnal systolic blood pressure (BP) as measured by ambulatory BP monitoring at the end of follow-up relative to the baseline level during the run-in period. In addition, we will carry out the same analysis after dividing four different nocturnal BP dipping statuses (extreme-dippers, dippers, nondipper, and risers).

Conclusion

The findings of this study will help in establishing an appropriate antihypertensive treatment for hypertensive patients with a disrupted circadian BP rhythm.

Renal histopathological findings in relation to ambulatory blood pressure in chronic kidney disease patients

Recent studies have demonstrated that ambulatory blood pressure monitoring is useful for predicting the long-term renal prognosis and future cardiovascular events in chronic kidney disease patients. Currently, however, information is limited regarding the relationships between individual renal histopathological findings and abnormalities in ambulatory blood pressure. This retrospective cross-sectional study included a total of 138 patients, in whom both renal biopsies and ambulatory blood pressure monitoring were performed during the same admission period. Renal histopathological findings, including global glomerulosclerosis, interstitial fibrosis/tubular atrophy and the presence of arterial lesions and arteriole lesions, were scored and analyzed in relation to the ambulatory blood pressure values. Among these histopathological characteristics, only the severity of interstitial fibrosis/tubular atrophy exhibited a significant association with an increased mean value of daytime and nighttime blood pressure. However, the remaining histopathological features showed only trends or weak relationships with these values. In addition, a moderately advanced grade of interstitial fibrosis/tubular atrophy was found to be significantly associated with both daytime and nighttime hypertension, independent of the kidney function, overt proteinuria and the use of antihypertensive medications, according to multivariate analyses. Furthermore, the night-to-day ratio of the mean blood pressure displayed a significant increasing trend according to the grade of interstitial fibrosis/tubular atrophy. These results suggest that interstitial fibrosis/tubular atrophy is the most relevant renal histopathological parameter associated with abnormalities in ambulatory blood pressure, including nocturnal hypertension, in this population.

Assessment of the reductions in night-time blood pressure and dipping induced by antihypertensive medication using a home blood pressure monitor

BACKGROUND

Night-time blood pressure (BP) is strongly associated with hypertensive target organ damage; however, no previous studies have compared home BP monitor measurements of the reduction in night-time BP induced by antihypertensive medications with those obtained with ambulatory BP monitors.

METHODS

As part of the Japan Morning Surge-Target Organ Protection study, in which candesartan (thiazide diuretics were added, if needed) was administered to hypertensive patients in the morning or at bedtime, 50 hypertensive patients had their night-time home and ambulatory BP successfully measured at the baseline and 6 months. In addition, three night-time home BP readings were taken during sleeping hours (at 2, 3, and 4 o'clock) for 6 months.

RESULTS

The mean reduction in night-time BP did not differ significantly between home and ambulatory BP monitoring (10.4 ± 17.9/6.0 ± 12.0 vs. 13.3 ± 14.6/7.6 ± 8.9 mmHg, P = 0.219/0.344), but the differences varied among individual patients. The reduction in night-time BP according to home BP monitoring was significantly correlated with the value obtained with ambulatory BP monitoring (r = 0.51/0.38, P < 0.001/=0.006). The reduction in night-time SBP according to home BP monitoring was significantly correlated with the reductions in left ventricular mass index (r = 0.385, P = 0.013, N = 41) and Sokolow-Lyon voltage (r = 0.335, P = 0.035, N = 40).

CONCLUSION

Home BP monitoring produces estimates of mean night-time BP reductions comparable to those from ambulatory monitoring, while the differences varied among individual patients. The reduction in night-time home BP according to home BP monitoring is significantly correlated with the reduction in left ventricular hypertrophy.

Disturbed circadian rhythm of the intrarenal renin-angiotensin system: relevant to nocturnal hypertension and renal damage

BACKGROUND

The intrarenal renin-angiotensin system (RAS) plays an important role in the development of hypertension and renal damage. Disruption of diurnal blood pressure (BP) variation is an additional risk factor for renal damage. However, little is known regarding whether intrarenal RAS circadian rhythm exists or if it influences the disruption of diurnal BP and renal damage.

METHODS

We investigated the circadian rhythm of urinary angiotensinogen (U-AGT) that reflects intrarenal RAS activity in 14 individuals without chronic kidney disease (CKD) and 36 CKD patients classified according to circadian BP rhythms.

RESULTS

BP values were higher during the daytime than during the nighttime in both individuals without CKD and CKD patients. U-AGT levels were not different between the daytime and nighttime in individuals without CKD, but were significantly higher in the daytime in CKD patients (log U-AGT/creatinine: daytime, 2.39 ± 0.99; nighttime, 2.24 ± 1.06; p = 0.001). Furthermore, in CKD patients showing a riser pattern of circadian BP, U-AGT levels did not decrease during the nighttime compared with those in the daytime (log U-AGT/creatinine: daytime, 2.51 ± 0.65; nighttime, 2.52 ± 0.71; p = 0.78). Circadian fluctuation of albuminuria and proteinuria occurred parallel to that of the U-AGT levels. U-AGT levels were significantly and positively correlated with the levels of BP and circadian fluctuation of U-AGT was correlated with diurnal BP changes.

CONCLUSION

These data suggest that the circadian rhythm of intrarenal RAS activation may lead to renal damage and hypertension, which are associated with diurnal BP variation.

Angiotensin receptor blockers regulate the synchronization of circadian rhythms in heart rate and blood pressure

OBJECTIVE

The sympathetic nervous system plays an important role in blood pressure regulation even in the early stages of chronic kidney disease (CKD).

METHODS

To understand the role of the sympathetic system, we examined the relationship between day/night ratios of both heart rate (HR) and mean arterial pressure (MAP) as well as HR variability (HRV, SD) before and during an 8-week treatment with the angiotensin II receptor blocker (ARB), olmesartan, in 45 patients with CKD.

RESULTS

The day/night HR ratio strongly correlated with the day/night MAP ratio before and during ARB treatment. The ratio of [day/night HR ratio] over [day/night MAP ratio] was increased as renal function deteriorated at baseline (r = -0.31, P = 0.04), and it was attenuated (1.10 ± 0.10 to 1.06 ± 0.10; P = 0.04) and became independent of renal function during ARB treatment (r = -0.04, P = 0.8). ARB increased both the day/night HR ratio (1.17 ± 0.09 to 1.21 ± 0.13; P = 0.04) and HRV (10.6 ± 2.9 to 11.7 ± 4.2; P = 0.04), which were lower when baseline renal function deteriorated.

CONCLUSION

The present study indicates that there exists a close correlation in circadian rhythms between HR and MAP in CKD. Synchronization between the two rhythms was progressively lost as renal function deteriorated, and ARB partly restored the synchronization. These findings suggest that the sympathetic nervous system is activated as renal function deteriorates, and ARB may suppress its activation.

A pegylated leptin antagonist ameliorates CKD-associated cachexia in mice

Elevated serum leptin levels correlate with inflammation and predict changes in lean body mass in patients with CKD, and activation of the melanocortin system by leptin signaling mediates the pathophysiology of CKD-associated cachexia. We tested whether treatment with a pegylated leptin receptor antagonist (PLA) attenuates cachexia in mice with CKD. CKD and Sham mice received vehicle or PLA (2 or 7 mg/kg per day). At these doses, PLA did not influence serum leptin levels in mice. Treatment with 7 mg/kg per day PLA stimulated appetite and weight gain, improved lean mass and muscle function, reduced energy expenditure, and normalized the levels of hepatic TNF-α and IL-6 mRNA in mice with CKD. Furthermore, treatment with 7 mg/kg per day PLA attenuated the CKD-associated increase in the transcriptional and protein abundance of uncoupling proteins that mediates thermogenesis, and it normalized the molecular signatures of processes associated with muscle wasting in CKD, including proteolysis, myogenesis and muscle regeneration, and expression of proinflammatory muscle cytokines, such as IL-1α, -1β, and -6 and TNF-α. Our results suggest that leptin antagonism may represent a viable therapeutic strategy for cachexia in CKD.

Circadian rhythm of urinary potassium excretion during treatment with an angiotensin receptor blocker

INTRODUCTION

We have reported that the circadian rhythm of urinary potassium excretion (U(K)V) is determined by the rhythm of urinary sodium excretion (U(Na)V) in patients with chronic kidney disease (CKD). We also reported that treatment with an angiotensin receptor blocker (ARB) increased the U(Na)V during the daytime, and restored the non-dipper blood pressure (BP) rhythm into a dipper pattern. However, the circadian rhythm of U(K)V during ARB treatment has not been reported.

MATERIALS AND METHODS

Circadian rhythms of U(Na)V and U(K)V were examined in 44 patients with CKD undergoing treatment with ARB.

RESULTS

Whole-day U(Na)V was not altered by ARB whereas whole-day U(K)V decreased. Even during the ARB treatment, the significant relationship persisted between the night/day ratios of U(Na)V and U(K)V (r=0.56, p<0.0001). Whole-day U(K)V/U(Na)V ratio (p=0.0007) and trans-tubular potassium concentration gradient (p=0.002) were attenuated but their night/day ratios remained unchanged. The change in the night/day U(K)V ratio correlated directly with the change in night/day U(Na)V ratio (F=20.4) rather than with the changes in aldosterone, BP or creatinine clearance.

CONCLUSIONS

The circadian rhythm of U(K)V was determined by the rhythm of UNaV even during ARB treatment. Changes in the circadian U(K)V rhythm were not determined by aldosterone but by U(Na)V.

Reversed dipper blood-pressure pattern is closely related to severe renal and cardiovascular damage in patients with chronic kidney disease

BACKGROUND

A non-dipper blood pressure (BP) pattern is very common in chronic kidney disease (CKD) patients and affects the progression and development of cardiovascular disease. However, data on the reversed dipper BP pattern on target-organ damage in Chinese CKD patients are lacking.

METHODS

A total of 540 CKD patients were enrolled. Ambulatory blood pressure monitoring (ABPM), clinical BP, ultrasonographic assessment and other clinical data were collected. Univariate and multivariate analyses were used to ascertain the relationship between ABPM results and clinical parameters.

RESULTS

A total of 21.9% CKD patients had a reversed dipper BP pattern, 42% of patients had a non-dipper BP pattern and 36.1% of patients had a dipper BP pattern. Patients with reversed dipper BP pattern had the worst renal function and most severe cardiovascular damages among these CKD patients (p<0.05). The estimated glomerular filtration rate (eGFR) and left ventricular mass index (LVMI) correlated significantly with the rate of decline of nocturnal BP. A reversed dipper BP pattern was an independent factor affecting kidney damage and left ventricular hypertrophy. Age, lower hemoglobin level, higher 24-h systolic BP from ABPM, and higher serum phosphate levels were independent associated with a reversed dipper BP pattern after multivariate logistic regression analyses.

CONCLUSION

The reversed dipper BP pattern is closely related to severe renal damage and cardiovascular injuries in CKD patients, and special attention should be given to these CKD patients.

Plasma renin activity and the aldosterone-to-renin ratio are associated with the development of chronic kidney disease: the Ohasama Study

BACKGROUND

The aldosterone-to-renin ratio (ARR) is used to screen for primary aldosteronism and could be an index for salt sensitivity. The association between ARR and the development of chronic kidney disease (CKD) is completely unknown.

METHOD

A longitudinal observational study involving 689 participants from a general Japanese population (mean age 58.2 years; 68.5% women) who did not have CKD and were not receiving antihypertensive medication at baseline was conducted. The estimated glomerular filtration rate (eGFR) was calculated from serum creatinine levels, and CKD was defined as eGFR less than 60 ml/min per 1.73 m(2) and/or dipstick-positive proteinuria. The associations of baseline plasma renin activity (PRA), plasma aldosterone concentration, and ARR with the development of CKD were examined using Cox proportional hazard regression analysis adjusted for sex, age, BMI, smoking, drinking, history of hypercholesterolemia, diabetes mellitus, and cardiovascular disease, SBP, and baseline eGFR.

RESULTS

During a mean 9.1-year follow-up, 118 participants developed CKD. A 1 standard deviation increment in the natural log-transformed (ln) ARR was positively associated with the incidence of CKD (hazard ratio 1.29, P = 0.012). LnPRA showed an inverse association (hazard ratio 0.76, P = 0.007). Meanwhile, plasma aldosterone concentration was not associated with CKD. Individuals who developed CKD had significantly lower baseline PRA (0.97 vs. 1.14 ng/ml per h; P = 0.03) and higher baseline ARR levels [66.6 vs. 56.8 (pg/ml)/(ng/ml per h); P = 0.02] than those who did not.

CONCLUSIONS

Lower PRA and higher ARR were associated with the development of CKD in a general population, suggesting that they are independent predictors of CKD.

Duration until nighttime blood pressure fall indicates excess sodium retention

Impaired renal sodium excretion causes sodium retention, which prevents the nocturnal dip in blood pressure (BP); thus, high BP persists until excess sodium is excreted. The authors defined "dipping time" (DT) as the duration until the nocturnal BP falls below 90% of the daytime average. Diuretic (e.g., hydrochlorothiazide [HCTZ]) and angiotensin receptor blocker (ARB) are able to eliminate sodium retention and restore the non-dipper BP rhythm. Reanalysis of two previous studies demonstrate that HCTZ and ARB shortened the DT. Shortening DT correlated directly with the increase in daytime urinary sodium excretion (Study 2). DT can be used as a preliminary indicator of sodium retention.

Proximal tubular angiotensinogen in renal biopsy suggests nondipper BP rhythm accompanied by enhanced tubular sodium reabsorption

OBJECTIVES

The renal capacity for sodium excretion is impaired by a reduction in the glomerular ultrafiltration coefficient and by enhancement of the fractional tubular sodium reabsorption (FRNa), leading to a nondipper circadian blood pressure (BP) rhythm. Angiotensin II in the systemic circulation can be easily filtered across the glomerular capillary walls and stimulates renal proximal tubular angiotensinogen (PT-AGT) production, leading to the activation of intrarenal angiotensin II, which is known to augment the FRNa in animal models.

METHODS

We performed an immunohistochemical investigation to determine the contribution of PT-AGT to enhancement of FRNa and the nondipper circadian BP rhythm in 40 consecutive patients with primary IgA nephropathy (IgAN).

RESULTS

Immunostaining for PT-AGT was increased in the IgAN patients compared with control individuals (P = 0.04), and correlated directly with the FRNa (r = 0.39, P = 0.01) and the night/day ratio of BP (r = 0.38, P = 0.02), but not creatinine clearance (r = -0.008, P = 0.9). The night/day ratio of BP was determined by both creatinine clearance (r = -0.36, P = 0.03) and FRNa (r = 0.47, P = 0.006).

CONCLUSION

Tubular sodium reabsorption is stimulated by intrarenal angiotensin II, as indicated by PT-AGT, and contributes to the genesis of the nondipper BP rhythm. Further studies are needed to evaluate whether or not treatment to prevent sodium retention is useful for patients who exhibit increased PT-AGT in renal biopsies.

Nighttime Home Blood Pressure and the Risk of Hypertensive Target Organ Damage

In ambulatory blood pressure (BP) monitoring, nighttime BP has a superior ability to predict hypertensive target organ damage than awake BP. We evaluated whether nighttime BP, assessed by a home BP monitor, was associated with hypertensive target organ damage. We measured clinic BP, out-of-clinic BP including nighttime home BP, and the urinary albumin:creatinine ratio (UACR) in 854 patients who had cardiovascular risk factors. Nighttime home BP was measured at 2:00, 3:00, and 4:00 am, in addition to clinic, awake ambulatory, nighttime ambulatory, and awake home BP. Nighttime home systolic BP (SBP) was slightly higher than nighttime ambulatory SBP (difference, 2.6 mm Hg; P <0.001). Clinic ( r =0.186), awake ambulatory ( r =0.173), nighttime ambulatory ( r =0.194), awake home ( r =0.298), and nighttime home ( r =0.311) SBPs were all associated with log-transformed UACR (all P <0.001). The correlation coefficient for the relationship between nighttime home SBP and log-transformed UACR was significantly greater than that for the relationship between nighttime ambulatory SBP and log-transformed UACR ( P <0.001). The goodness of fit of the association between SBP and UACR was improved by adding nighttime home SBP to the other SBPs ( P <0.001). Nighttime home diastolic BP also improved the goodness-of-fit of the association between diastolic BP and UACR ( P =0.001). Similar findings were observed for the left ventricular mass index in the subgroup (N=594). In conclusion, nighttime home BP is slightly different from (but comparable to) nighttime ambulatory BP. The addition of nighttime home BP to other BP measures improves the association of BP with hypertensive target organ damage.

Day-night dip and early-morning surge in blood pressure in hypertension: prognostic implications

We investigated the relationship between the day-night blood pressure (BP) dip and the early morning BP surge in an cohort of 3012 initially untreated subjects with essential hypertension. The day-night reduction in systolic BP showed a direct association with the sleep trough (r = 0.564; P < 0.0001) and the preawakening (r = 0.554; P < 0.0001) systolic BP surge. Over a mean follow-up period of 8.44 years, 268 subjects developed a major cardiovascular event (composite of cardiovascular death, nonfatal myocardial infarction, nonfatal stroke, and heart failure requiring hospitalization) and 220 subjects died. In a Cox model, after adjustment for predictive covariates, including age, sex, diabetes mellitus, cigarette smoking, total cholesterol, left ventricular hypertrophy on ECG, estimated glomerular filtration rate, and average 24-hour systolic BP, a blunted sleep trough (≤ 19.5 mm Hg; quartile 1) and preawakening (≤ 9.5 mm Hg; quartile 1) BP surge was associated with an excess risk of events (hazard ratio, 1.66 [95% CI, 1.14-2.42]; P = 0.009; hazard ratio, 1.71 [95% CI, 1.12-2.71]; P = 0.013). After adjustment for the same covariates, neither the dipping pattern nor the measures of early morning BP surge were independent predictors of mortality. In conclusion, in initially untreated subjects with hypertension, a blunted day-night BP dip was associated with a blunted morning BP surge and vice versa. In these subjects, a blunted morning BP surge was an independent predictor of cardiovascular events, whereas an excessive BP surge did not portend an increased risk of events.

Predictors of proteinuria reduction by monotherapy with an angiotensin receptor blocker, olmesartan

INTRODUCTION

It is known that reduced glomerular filtration rate (GFR) is a crucial factor to limit the blood pressure lowering effect of antihypertensives. In the present study, we tested whether the effects of monotherapy with an angiotensin receptor blocker (ARB) to lower proteinuria could be restricted by reduced GFR.

MATERIALS AND METHODS

Thirty-five renal patients who had albuminuria more than 30 mg/day, but did not have diabetic nephropathy or nephrotic syndrome, were studied before and during eight weeks of monotherapy with ARB, olmesartan.

RESULTS

Blood pressure was lowered from 129 ± 18/79 ± 12 to 116 ± 18/72 ± 12 mmHg (p < 0.0001), while albuminuria was reduced from 614±630 to 343±472 mg/day (p < 0.0001). Albuminuria was inversely correlated with GFR both before and during treatment. Albuminuria reduction was enhanced as plasma renin activity (p = 0.047) and dose of olmesartan were increased (p = 0.04). Although the absolute reduction in proteinuria was not correlated with GFR (p = 0.56), the % reduction was significantly proportional with GFR (p = 0.027). Multiple regression analysis demonstrated that 64% of proteinuria reduction could be explained by baseline levels of albuminuria, GFR and renin activity.

CONCLUSIONS

The reduction in proteinuria by olmesartan may be roughly predicted using baseline GFR and other parameters. These findings clarify that the effect of ARB on proteinuria reduction is restricted by reduced GFR.

Angiotensin receptor blockers shift the circadian rhythm of blood pressure by suppressing tubular sodium reabsorption

Recently, we found that an angiotensin II receptor blocker (ARB) restored the circadian rhythm of the blood pressure (BP) from a nondipper to a dipper pattern, similar to that achieved with sodium intake restriction and diuretics (Fukuda M, Yamanaka T, Mizuno M, Motokawa M, Shirasawa Y, Miyagi S, Nishio T, Yoshida A, Kimura G. J Hypertens 26: 583-588, 2008). ARB enhanced natriuresis during the day, while BP was markedly lower during the night, resulting in the dipper pattern. In the present study, we examined whether the suppression of tubular sodium reabsorption, similar to the action of diuretics, was the mechanism by which ARB normalized the circadian BP rhythm. BP and glomerulotubular balance were compared in 41 patients with chronic kidney disease before and during ARB treatment with olmesartan once a day in the morning for 8 wk. ARB increased natriuresis (sodium excretion rate; U(Na)V) during the day (4.5 ± 2.2 to 5.5 ± 2.1 mmol/h, P = 0.002), while it had no effect during the night (4.3 ± 2.0 to 3.8 ± 1.6 mmol/h, P = 0.1). The night/day ratios of both BP and U(Na)V were decreased. The decrease in the night/day ratio of BP correlated with the increase in the daytime U(Na)V (r = 0.42, P = 0.006). Throughout the whole day, the glomerular filtration rate (P = 0.0006) and tubular sodium reabsorption (P = 0.0005) were both reduced significantly by ARB, although U(Na)V remained constant (107 ± 45 vs. 118 ± 36 mmol/day, P = 0.07). These findings indicate that the suppression of tubular sodium reabsorption, showing a resemblance to the action of diuretics, is the primary mechanism by which ARB can shift the circadian BP rhythm into a dipper pattern.

Chronic kidney disease, 24-h blood pressure and small vessel diseases are independently associated with cognitive impairment in lacunar infarct patients

Although the relationships between chronic kidney disease (CKD) and cognitive impairment (CI) have been highlighted, the etiology of CI in CKD remains uncertain. Subjects comprised 224 consecutive patients with symptomatic lacunar infarction who underwent magnetic resonance imaging and ambulatory blood pressure monitoring (ABPM). Diurnal blood pressure (BP) patterns were categorized into three groups: dippers, non-dippers and risers. Lacunar infarcts (LIs), including both symptomatic and silent and diffuse white matter lesions (WMLs), were graded into three grades according to their degree. The results of kidney function were evaluated using estimated glomerular filtration rate (eGFR), categorized into three groups: stage 1, >60; stage 2, 30-60; and stage 3, <30 ml min(-1) per 1.73 m(2). There were 44 patients with CI. Confluent WMLs, including WML 2 and WML 3, were found in 36 patients (81.8%), and multiple lacunae including LI 2 and LI 3 were found in 30 patients (68.1%) with CI. Age >75 years (odds ratio (OR), 5.5; P<0.05), male sex (OR, 2.8; P<0.05), non-dippers (OR, 6.3; P<0.05) and risers (OR, 5.6; P<0.05), eGFR 30-60 ml min(-1) per 1.73 m(2) (OR, 2.9; P<0.05) and eGFR <30 ml min(-1) per 1.73 m(2) (OR, 23.8; P<0.01), WML grade 2 (OR, 5.1; P<0.01) and WML grade 3 (OR, 45.2; P<0.001) and LI grade 2 (OR, 3.2; P<0.05) and LI grade 3 (OR, 6.4; P<0.05) were independently associated with CI. Age >75 years (OR, 4.1; P<0.05), eGFR 30-60 ml min(-1) per 1.73 m(2) (OR, 3.7; P<0.05) and eGFR <30 ml min(-1) per 1.73 m(2) (OR, 8.7; P<0.05) were independently associated with WML grade 3. Extensive small vessel diseases, CKD and non-dipping status were independently associated with CI. CKD appears to mainly contribute to vascular CI, whereas possibilities of overlapping with other mechanisms such as degenerative CI cannot be excluded. Strict night time BP control and renoprotective treatment may be warranted to prevent CI.

Renal dysfunction impairs circadian variation of endothelial function in patients with essential hypertension

Some cardiovascular disorders disturb circadian variation of endothelial function. We investigated whether deterioration of renal function alters circadian variation of endothelial function in patients with hypertension. Endothelial function was assessed by the peak forearm blood flow (FBF) response to reactive hyperemia, and 24-hour ambulatory blood pressure monitoring was performed in 25 patients with essential hypertension (61 ± 17 years). Relationships among renal function, 24-hour blood pressure, and endothelial function were analyzed. The ratio of nighttime to daytime mean arterial pressure was inversely correlated with estimated glomerular filtration rate (eGFR) (r = -0.43, P = .03). The FBF response to reactive hyperemia examined at 21:00, but not at 6:30 or 11:30, was significantly correlated with eGFR (r = 0.44, P = .03). Furthermore, the ratio of FBF response measured at 21:00 to that measured at 6:30 was independently correlated with eGFR (β = 0.47, P = .02). Renal dysfunction is associated with the derangement of circadian variation of both endothelial function and blood pressure. Nocturnal blood pressure is elevated, and evening endothelial function deteriorates in parallel with a decline in renal function in hypertensive patients.

Salt sensitivity and circadian rhythm of blood pressure: the keys to connect CKD with cardiovascular events

In healthy subjects, blood pressure (BP) drops by 10-20% during the night. Conversely, in patients with the salt-sensitive type of hypertension or chronic kidney disease, nighttime BP does not fall, resulting in an atypical pattern of circadian BP rhythm that does not dip. This pattern is referred to as the 'non-dipper' pattern. Loss of renal functional reserve, due to either reduced ultrafiltration capacity or enhanced tubular sodium reabsorption, induces the salt-sensitive type of hypertension. When salt intake is excessive in patients with salt-sensitive hypertension, the defect in sodium excretory capability becomes evident, resulting in elevated BP during the night. This nocturnal hypertension compensates for diminished natriuresis during the daytime and enhances pressure natriuresis during the night. Nocturnal hypertension and the non-dipper pattern of circadian BP rhythm cause cardiovascular events. When excess salt intake is loaded in patients who are in a salt-sensitive state, glomerular capillary pressure is also elevated, resulting in glomerular sclerosis and eventual renal failure. In this way, salt sensitivity and excess salt intake contribute to both cardiovascular and renal damage at the same time. We propose that salt sensitivity of BP and excess salt intake have important roles in the genesis of the cardiorenal connection. Salt sensitivity and circadian rhythm of BP are the keys to understanding the connections between cardiovascular and renal complications.