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Background Hypoxia-inducible factor prolyl hydroxylase inhibitors such as vadadustat may provide an oral alternative to injectable erythropoiesis-stimulating agents for treating anemia in patients receiving peritoneal dialysis. In two randomized (1:1), global, phase 3, open-label, sponsor-blind, parallel-group, active-controlled noninferiority trials in patients with dialysis-dependent chronic kidney disease (INNO2VATE), vadadustat was noninferior to darbepoetin alfa with respect to cardiovascular safety and hematological efficacy. Vadadustat's effects in patients receiving only peritoneal dialysis is unclear. Methods We conducted a post hoc analysis of patients in the INNO2VATE trials receiving peritoneal dialysis at baseline. The prespecified primary safety endpoint was time to first major cardiovascular event (MACE; defined as all-cause mortality or nonfatal myocardial infarction or stroke). The primary efficacy endpoint was mean change in hemoglobin from baseline to the primary efficacy period (weeks 24–36). Results Of the 3923 patients randomized in the two INNO2VATE trials, 309 were receiving peritoneal dialysis (vadadustat, n = 152; darbepoetin alfa, n = 157) at baseline. Time to first MACE was similar in the vadadustat and darbepoetin alfa groups (hazard ratio 1.10; 95% CI 0.62, 1.93). In patients receiving peritoneal dialysis, the difference in mean change in hemoglobin concentrations was −0.10 g/dL (95% CI −0.33, 0.12) in the primary efficacy period. The incidence of treatment-emergent adverse events (TEAEs) was 88.2% versus 95.5%, and serious TEAEs was 52.6% versus 73.2% in the vadadustat and darbepoetin alfa groups, respectively. Conclusions In the subgroup of patients receiving peritoneal dialysis in the phase 3 INNO2VATE trials, safety and efficacy of vadadustat were similar to darbepoetin alfa.

Background Soluble Klotho has multiple systemic salutary effects. In animals, both acute and chronic kidney disease models display systemic Klotho deficiency. As such, there is considerable interest in investigating soluble Klotho as a biomarker in patients with different types and severity of kidney diseases. Unfortunately, there remains uncertainty regarding the best method to measure soluble Klotho in human serum samples. Methods Using human serum samples obtained from several clinical cohorts with a wide range of kidney function, we measured soluble Klotho using a commercial enzyme-linked immunosorbent assay (ELISA) as well as with an immunoprecipitation–immunoblot (IP–IB) assay utilizing a synthetic antibody with high affinity and specificity for Klotho. Recovery of spiking with a known amount of exogenous Klotho was tested. A subset of samples was analyzed with and without the addition of a protease inhibitor cocktail at the time of collection or after the first freeze–thaw cycle to determine if these maneuvers influenced performance. Results The IP–IB assay was superior to the ELISA at recovery of exogenous Klotho (81–115% versus 60–81%) across the spectrum of kidney function. Klotho measurements by IP–IB were highly correlated with estimated glomerular filtration rate (eGFR) (R = 0.80, P Conclusions The IP–IB assay is preferable to the commercial ELISA to measure soluble Klotho concentrations in never-thawed serum samples of humans with varying severity of kidney disease. However, due to the labor-intensive nature of the IP–IB assay, further research is needed to secure an assay suitable for high-throughput work.

Aims Biomarkers of kidney tubule injury, inflammation and fibrosis have been studied extensively and established as risk markers of adverse kidney and cardiovascular disease (CVD) outcomes. However, associations of markers of kidney tubular function with adverse clinical events have not been well studied, especially in persons with chronic kidney disease (CKD). Methods and results Using a sample of 2377 persons with CKD at the baseline Systolic Blood Pressure Intervention Trial (SPRINT) visit, we evaluated the association of three urine tubular function markers, alpha-1 microglobulin (α1m), beta-2 microglobulin (β2m), and uromodulin, with a composite CVD endpoint (myocardial infarction, acute coronary syndrome, stroke, acute decompensated heart failure, or death from cardiovascular causes) and mortality using Cox proportional hazards regression, adjusted for baseline estimated glomerular filtration rate (eGFR), albuminuria, and CVD risk factors. In unadjusted analysis, over a median follow-up of 3.8 years, α1m and β2m had positive associations with composite CVD events and mortality, whereas uromodulin had an inverse association with risk for both outcomes. In multivariable analysis including eGFR and albuminuria, a two-fold higher baseline concentration of α1m was associated with higher risk of CVD [hazard ratio (HR) 1.25; 95% confidence interval (CI): 1.10–1.45] and mortality (HR 1.25; 95% CI: 1.10–1.46), whereas β2m had no association with either outcome. A two-fold higher uromodulin concentration was associated with lower CVD risk (HR 0.79; 95% CI: 0.68–0.90) but not mortality (HR 0.86; 95% CI: 0.73–1.01) after adjusting for similar confounders. Conclusion Among non-diabetic persons with CKD, biomarkers of tubular function are associated with CVD events and mortality independent of glomerular function and albuminuria.

Background Chronic kidney disease (CKD) is frequently accompanied by thyroid hormone dysfunction. It is currently unclear whether these alterations are the cause or consequence of CKD. This study aimed at studying the effect of thyroid hormone alterations on renal function in cross-sectional and longitudinal analyses in individuals from all adult age groups. Methods Individual participant data (IPD) from 16 independent cohorts having measured thyroid stimulating hormone, free thyroxine levels and creatinine levels were included. Thyroid hormone status was defined using clinical cut-off values. Estimated glomerular filtration rates (eGFR) were calculated by means of the four-variable Modification of Diet in Renal Disease (MDRD) formula. For this IPD meta-analysis, eGFR at baseline and eGFR change during follow-up were computed by fitting linear regression models and linear mixed models in each cohort separately. Effect estimates were pooled using random effects models. Results A total of 72 856 individuals from 16 different cohorts were included. At baseline, individuals with overt hypothyroidism (n = 704) and subclinical hypothyroidism (n = 3356) had a average (95% confidence interval) −4.07 (−6.37 to −1.78) and −2.40 (−3.78 to −1.02) mL/min/1.73 m2 lower eGFR as compared with euthyroid subjects (n = 66 542). In (subclinical) hyperthyroid subjects (n = 2254), average eGFR was 3.01 (1.50–4.52) mL/min/1.73 m2 higher. During 329 713 patient years of follow-up, eGFR did not decline more rapidly in individuals with low thyroid function compared with individuals with normal thyroid function. Conclusions Low thyroid function is not associated with a deterioration of renal function. The cross-sectional association may be explained by renal dysfunction causing thyroid hormone alterations.

Uric acid is associated with increased risk of cardiovascular disease and arterial stiffness in patients with hypertension or stroke. It remains unknown if uric acid is associated with arterial stiffness in the general population.We analyzed the association between serum uric acid levels and measures of arterial stiffness such as carotid-femoral pulse wave velocity (CF PWV), carotid-radial pulse wave velocity (CR PWV) and augmentation index (AI) in 4,140 participants from the Generation 3 Framingham cohort using linear regression.Mean (SD) age was 40.0 (8.8) years and mean (SD) serum uric acid levels were 5.3 (1.5) mg/dl. Mean (SD) CF PWV was 7.0 (1.4) m/s. Individuals in the highest quartile of uric acid were more likely to be male, have a higher prevalence of hypertension, higher BMI, fasting glucose and insulin, and lower estimated glomerular filtration rate (eGFR). Multivariate adjusted means of CF PWV were 6.90, 6.94, 7.06, and 7.15 m/s for uric acid quartile 1, 2, 3, and 4 respectively. In unadjusted analysis each 1mg/dl increase in uric acid was associated with higher CF-PWV (β = 0.27; 95% CI = 0.25, 0.29; P0.0001). This was attenuated but remained significant after adjusting for age, sex, smoking, hypertension, BMI, fasting glucose, insulin, animal protein intake, and eGFR (β= 0.06; 95% CI = 0.02, 0.09; P0.0007). There was no association between serum uric acid levels and AI upon adjustment for cardiovascular risk factors.Serum uric acid levels are significantly associated with CF PWV and CR PWV in a younger Caucasian population.

BACKGROUND: Animal studies suggest that acidosis protects against arterial calcification, which contributes to arterial stiffness. The goal of this study was to investigate the associations of serum bicarbonate and pH with arterial stiffness in community-living older adults. METHODS: We performed cross-sectional analyses among 1698 well-functioning participants 70–79 years of age. Bicarbonate and pH were measured by arterialized venous blood gas at the point of care. Bicarbonate was categorized into low (7.40–7.42 and >7.42. Arterial stiffness was evaluated by pulse wave velocity (PWV) and high ankle-brachial index (ABI; >1.3/incompressible). We used linear and logistic regression to evaluate the association of bicarbonate and AVpH with PWV and high ABI, respectively. RESULTS: The mean age was 76 years and 15% had an estimated glomerular filtration rate (eGFR)

Background. An elevated triglyceride level is associated with cardiovascular and all-cause mortality in the general population. The associations between serum triglyceride and all-cause mortality among patients with chronic kidney disease (CKD) are unclear. Methods. Patients with Stage 3 and Stage 4 CKD (estimated glomerular filtration rate 15–59 mL/min/1.73 m 2 ) who had serum triglycerides measured prior to being classified as CKD were included. We examined the associations of serum triglyceride levels with all-cause mortality among 25 641 Stage 3 and Stage 4 CKD patients using Cox proportional hazard models and Kaplan–Meier survival curves. Results. In the Cox model, after adjusting for relevant covariates including other lipid parameters, serum triglyceride level 150–199 mg/dL was not associated with death [hazard ratio (HR) 1.00, 95% confidence interval (95% CI) 0.92–1.10] relative to serum triglyceride

Background Associations of inflammation with age-related pathologies are documented; however, it is not understood how changes in inflammation over time impact healthy aging. Methods We examined associations of long-term change in C-reactive protein (CRP) and interleukin-6 (IL-6) with concurrent onset of physical and cognitive impairment, subsequent cardiovascular disease (CVD), and mortality in 1,051 participants in the Cardiovascular Health Study All Stars Study. Biomarkers were measured in 1996-1997 and 2005-2006. Results In 2005-2006, median age was 84.9 years, 63% were women and 17% non-white; 21% had at least a doubling in CRP over time and 23% had at least a doubling in IL-6. Adjusting for demographics, CVD risk factors, and 1996-1997 CRP level, each doubling in CRP change over 9 years was associated with higher risk of physical or cognitive impairment (odds ratio 1.29; 95% confidence interval 1.15, 1.45). Results were similar for IL-6 (1.45; 1.20, 1.76). A doubling in IL-6 change over time, but not CRP, was associated with incident CVD events; hazard ratio (95% confidence interval) 1.34 (1.03, 1.75). Doubling in change in each biomarker was individually associated with mortality (CRP: 1.12 [1.03, 1.22]; IL-6 1.39 [1.16, 1.65]). In models containing both change and 2005-2006 level, only level was associated with CVD events and mortality. Conclusions Although increases in inflammation markers over 9 years were associated with higher concurrent risk of functional impairment and subsequent CVD events and mortality, final levels of each biomarker appeared to be more important in determining risk of subsequent events than change over time.

Disorders of mineral metabolism are associated with a greater risk for cardiovascular (CVD) events in patients with kidney failure.1–3 Recent studies demonstrate that this link may exist in the general population as well,4–6 even in individuals with ostensibly normal kidney function. Specifically, higher serum intact parathyroid hormone (iPTH) and phosphorus levels and lower 25-hydroxyvitamin D levels are associated with incidence4–7 and recurrence8 of CVD events, CVD mortality,5,6,9 and peripheral arterial disease10 in community-living populations, independent of kidney function and traditional CVD risk factors. Although the mechanisms responsible are unknown, it is possible that disordered mineral metabolism may contribute to arterial calcium deposition and associated arterial stiffening. Therefore arterial stiffening may be in the causal pathway between altered mineral metabolism and CVD events. Several studies have shown that abnormalities in mineral metabolism are associated with arterial calcification in community-living populations,7,10–12 but the relationship with arterial stiffening remains largely untested. There are no studies to our knowledge that evaluate the relationships between serum mineral metabolism markers and arterial pulse wave velocity (aPWV) in community-living populations. Increasingly, aPWV has been used as a clinical gold-standard measure of large-artery stiffness. This measure is associated with CVD risk factors and independently associated with incidence rates of CVD events and CVD mortality in community-living elderly persons.13 In order to investigate the potential mechanisms linking abnormalities in mineral metabolism with CVD events, we evaluated the associations between mineral metabolism markers (serum 25-hydroxyvitamin D, iPTH, phosphorus, and calcium) and aPWV in a community-living population of well-functioning elderly persons who were part of the Health Aging and Body Composition (Health ABC) study. We hypothesized that higher serum phosphorus and iPTH and lower 25-hydroxyvitamin D would be associated with greater aPWV, independent of kidney function and traditional CVD risk factors.

Cardiovascular disease is the leading cause of premature mortality in autosomal dominant polycystic kidney disease (ADPKD). We examined peripheral augmentation index (AIx) as a measure of systemic vascular function and circulating markers of vascular inflammation in patients with ADPKD.Fifty-two ADPKD patients with hypertension and estimated glomerular filtration rate (eGFR)60 mL/min/1.73 m(2), 50 ADPKD patients with hypertension and eGFR ≥ 60 mL/min/1.73 m(2), 42 normotensive ADPKD patients with eGFR ≥ 60 mL/min/1.73 m(2) and 51 normotensive healthy controls were enrolled in this study. AIx was measured from peripheral artery tone recordings using finger plethysmography. Serum levels of soluble intercellular adhesion molecule (ICAM)-1, vascular cell adhesion molecule-1, P-selectin, E-selectin, soluble Fas (sFas) and Fas ligand (FasL) were measured as markers of vascular inflammation.AIx was higher in all three patient groups with ADPKD compared to healthy controls (P0.05). AIx was similar between the normotensive ADPKD patients with eGFR ≥ 60 mL/min/1.73 m(2) and hypertensive ADPKD patients with eGFR60 mL/min/1.73 m(2) (P0.05). ICAM, P-selectin, E-selectin and sFas were higher and FasL lower in all ADPKD groups compared to controls (P0.05). ICAM, P-selectin and E-selectin were similar between the normotensive ADPKD patients with eGFR ≥ 60 mL/min/1.73 m(2) and hypertensive ADPKD patients with eGFR60 mL/min/1.73 m(2) (P0.05). According to multiple regression analysis, predictors of AIx in ADPKD included age, height, heart rate and mean arterial pressure (P0.05). Vascular inflammatory markers were not predictors of AIx in ADPKD.Systemic vascular dysfunction, manifesting as an increase in AIx and vascular inflammation is evident in young normotensive ADPKD patients with preserved renal function. Vascular inflammation is not associated with elevated AIx in ADPKD.

Background. Kidney disease is a risk factor for mortality and cardiovascular disease in older adults, but the separate and combined effects of albuminuria and cystatin C, a novel marker of glomerular filtration, are not known. Methods. We examined associations of these markers with mortality and cardiovascular outcomes during a median follow-up of 8.3 years in 3291 older adults in the Cardiovascular Health Study. Kidney disease was assessed using urinary albumin/creatinine ratio (ACR), cystatin C and Modification of Diet in Renal Disease estimated glomerular filtration rate (eGFR). We defined subgroups based on presence of microalbuminuria (MA, ACR > 30 mg/g) and categories of normal kidney function (cystatin C 60 mL/min/1.73 m2); preclinical kidney disease (cystatin C level > 1.0 mg/l but eGFR > 60 mL/min/1.73 m2); and chronic kidney disease (CKD) (eGFR < 60 mL/min/1.73 m2). Cox proportional hazards models were used to examine associations between these six subgroups and all-cause or cardiovascular mortality, myocardial infarction and heart failure. Results. One thousand one hundred fifty (34.9%) had normal kidney function (12.2% with MA), 1518 (46.1%) had preclinical kidney disease (17.9% with MA) and 622 (18.9%) had CKD (47% with MA). After adjustment, the presence of either preclinical kidney disease or MA was associated with an over 50% increase in mortality risk; the presence of both was associated with a 2.4-fold mortality risk. Those with CKD and MA were at highest risk, with a nearly 4-fold mortality risk. Conclusion. Elevated cystatin C and albuminuria are common, identify different subsets of the older population, and are independent, graded risk factors for cardiovascular disease and mortality.

Background. Kidney function declines with age, but a substantial portion of this decline has been attributed to the higher prevalence of risk factors for kidney disease at older ages. The effect of age on kidney function has not been well described in a healthy population across a wide age spectrum. Methods. The authors pooled individual-level cross-sectional data from 18 253 persons aged 28–100 years in four studies: the Cardiovascular Health Study; the Health, Aging and Body Composition Study; the Multi-Ethnic Study of Atherosclerosis and the Prevention of Renal and Vascular End-Stage Disease cohort. Kidney function was measured by cystatin C. Clinical risk factors for kidney disease included diabetes, hypertension, obesity, smoking, coronary heart disease, cerebrovascular disease, peripheral arterial disease and heart failure. Results. Across the age range, there was a strong, non-linear association of age with cystatin C concentration. This association was substantial, even among participants free of clinical risk factors for kidney disease; mean cystatin C levels were 46% higher in participants 80 and older compared with those

Vascular remodeling may be a mechanism linking chronic kidney disease to cardiovascular disease. Whether early kidney dysfunction is associated with small and large arterial remodeling is not well understood. Using multivariable linear regression, back-transforming beta-coefficients to relative difference, the authors studied the association of cystatin C, creatinine-based estimated glomerular filtration rate (GFR), and albuminuria with small (SAE) and large (LAE) arterial elasticity and aortic distensibility among 6,282 participants in the Multiethnic Study of Atherosclerosis at baseline (2000-2002). Compared with the lowest quintile, higher quintiles of cystatin C were incrementally associated with lower SAE: third quintile relative difference = -5% (95% confidence interval (CI): -8, -2); fourth quintile relative difference = -10% (95% CI: -13, -8); and highest quintile relative difference = -16% (95% CI: -20, -12). By use of creatinine, the association was observed only among those with chronic kidney disease (estimated GFR