Associations of CKD risk factors and longitudinal changes in urine biomarkers of kidney tubules among women living with HIV

BACKGROUND

Novel urine biomarkers have enabled the characterization of kidney tubular dysfunction and injury among persons living with HIV, a population at an increased risk of kidney disease. Even though several urine biomarkers predict progressive kidney function decline, antiretroviral toxicity, and mortality in the setting of HIV infection, the relationships among the risk factors for chronic kidney disease (CKD) and urine biomarkers are unclear.

METHODS

We assessed traditional and infection-related CKD risk factors and measured 14 urine biomarkers at baseline and at follow-up among women living with HIV in the Women's Interagency Health Study (WIHS). We then used simultaneously adjusted multivariable linear regression models to evaluate the associations of CKD risk factors with longitudinal changes in biomarker levels.

RESULTS

Of the 647 women living with HIV in this analysis, the majority (67%) were Black, the median age was 45 years and median follow-up time was 2.5 years. Each traditional and infection-related CKD risk factor was associated with a unique set of changes in urine biomarkers. For example, baseline hemoglobin a1c was associated with worse tubular injury (higher interleukin [IL]-18), proximal tubular reabsorptive dysfunction (higher α1-microglobulin), tubular reserve (lower uromodulin) and immune response to injury (higher chitinase-3-like protein-1 [YKL-40]). Furthermore, increasing hemoglobin a1c at follow-up was associated with further worsening of tubular injury (higher kidney injury molecule-1 [KIM-1] and IL-18), as well as higher YKL-40. HCV co-infection was associated with worsening proximal tubular reabsorptive dysfunction (higher β2-microglobulin [β2m]), and higher YKL-40, whereas HIV viremia was associated with worsening markers of tubular and glomerular injury (higher KIM-1 and albuminuria, respectively).

CONCLUSIONS

CKD risk factors are associated with unique patterns of biomarker changes among women living with HIV, suggesting that serial measurements of multiple biomarkers may help in detecting and monitoring kidney disease in this setting.

Kidney tubule health scores and their associations with incident CKD in women living with HIV

OBJECTIVES

Individual kidney tubule biomarkers are associated with chronic kidney disease (CKD) risk in people living with HIV (PLWH). Whether a combination of kidney biomarkers can be integrated into informative summary scores for PLWH is unknown.

METHODS

We measured eight urine biomarkers of kidney tubule health at two visits over a 3-year period in 647 women living with HIV in the Women's Interagency Health Study. We integrated biomarkers into factor scores using exploratory factor analysis. We evaluated associations between CKD risk factors and factor scores, and used generalized estimating equations to determine associations between factor scores and risk of incident CKD.

RESULTS

Factor analysis identified two unique factor scores: a tubule reabsorption score comprising alpha-1-microglobulin, beta-2-microglobulin and trefoil factor-3; and a tubule injury score comprising interleukin-18 and kidney injury molecule-1. We modelled the two factor scores in combination with urine epidermal growth factor (EGF) and urine albumin. Predominantly HIV-related CKD risk factors were independently associated with worsening tubule reabsorption scores and tubule injury scores. During a median follow-up of 7 years, 9.7% (63/647) developed CKD. In multivariable time-updated models that adjusted for other factor scores and biomarkers simultaneously, higher tubule reabsorption scores [risk ratio (RR) = 1.27, 95% confidence interval (CI): 1.01-1.59 per 1 SD higher time-updated score], higher tubule injury scores (RR = 1.36, 95% CI: 1.05-1.76), lower urine EGF (RR = 0.75, 95% CI: 0.64-0.87), and higher urine albumin (RR = 1.20, 95% CI: 1.02-1.40) were jointly associated with risk of incident CKD.

CONCLUSIONS

We identified two novel and distinct dimensions of kidney tubule health that appear to quantify informative metrics of CKD risk in PLWH.

Frailty, Age, and Postdialysis Recovery Time in a Population New to Hemodialysis

Background

Frailty, a phenotype characterized by decreased physiologic reserve and the inability to recover following confrontation with a stressor like hemodialysis, may help identify which patients on incident hemodialysis will experience longer postdialysis recovery times. Recovery time is associated with downstream outcomes, including quality of life and mortality. We characterized postdialysis recovery times among patients new to hemodialysis and quantified the association between frailty and hemodialysis recovery time.

Methods

Among 285 patients on hemodialysis enrolled in the Predictors of Arrhythmic and Cardiovascular Risk in End Stage Renal Disease (PACE) study, frailty was measured using the Fried phenotype. Self-reported recovery time was obtained by telephone interview. We estimated the association of frailty (intermediately frail and frail versus nonfrail) and postdialysis recovery time using adjusted negative binomial regression.

Results

Median time between dialysis initiation and study enrollment was 3.4 months (IQR, 2.7-4.9), and that between initiation and recovery time assessment was 11 months (IQR, 9.3-15). Mean age was 55 years, 24% were >65 years, and 73% were Black; 72% of individuals recovered in ≤1 hour, 20% recovered in 1-6 hours, 5% required 6-12 hours to recover, and <5% required >12 hours to recover. Those with intermediate frailty, frailty, and age ≤65 years had 2.56-fold (95% CI, 1.45 to 4.52), 1.72-fold (95% CI, 1.03 to 2.89), and 2.35-fold (95% CI, 1.44 to 3.85) risks, respectively, of longer recovery time independent of demographic characteristics, comorbidity, and dialysis-related factors.

Conclusions

In adults new to hemodialysis, frailty was independently associated with prolonged postdialysis recovery. Future studies should assess the effect of frailty-targeted interventions on recovery time to improve clinical outcomes.

Patient Awareness of CKD: A Systematic Review and Meta-analysis of Patient-Oriented Questions and Study Setting

RATIONALE & OBJECTIVE

Patient awareness of disease is the first step toward effective management and disease control. Awareness of chronic kidney disease (CKD) has consistently been shown to be low, but studies estimating patient awareness of CKD have used different methods. We sought to determine whether the estimated prevalence of CKD awareness differed by the wording used to ascertain awareness or by setting characteristics.

STUDY DESIGN

Systematic review and meta-analysis.

SETTING & STUDY POPULATIONS

Adults with CKD not receiving dialysis.

SELECTION CRITERIA FOR STUDIES

We included studies that estimated CKD awareness, determined CKD status by laboratory criteria, and provided the exact question wording used to ascertain awareness.

DATA EXTRACTION

2 reviewers independently extracted data for each study; discordance was resolved by a third independent reviewer.

ANALYTICAL APPROACH

Mixed-effects models were used to calculate pooled CKD awareness estimates and 95% CIs.

RESULTS

32 studies were included. Publication year ranged from 2004 to 2017, with study populations ranging from 107 to 28,923 individuals. CKD awareness in individual studies ranged from 0.9% to 94.0%. Pooled CKD awareness was 19.2% (95% CI, 10.0%-33.6%) overall and was 26.5% (95% CI, 11.9%-48.9%) among individuals with an estimated glomerular filtration rate < 60 mL/min/1.73 m2. "Kidney problem" was the most sensitive question for CKD awareness (58.7%; 95% CI, 32.4%-80.8%); "weak or failing kidneys" was the least sensitive (12.3%; 95% CI, 4.5%-29.4%). CKD awareness was highest among patients from nephrology practices (86.2%; 95% CI, 74.9%-93.0%) and lowest in the general population (7.3%; 95% CI, 5.0%-10.5%).

LIMITATIONS

Significant heterogeneity across studies overall and among examined subgroups of wording and study setting.

CONCLUSIONS

Differently worded questions may lead to widely different estimates of CKD awareness. Consistent terminology is likely needed to most effectively surveil and leverage CKD awareness to improve management and disease control.

Urinary Biomarkers and Kidney Outcomes: Impact of Indexing Versus Adjusting for Urinary Creatinine

RATIONALE & OBJECTIVE

Urinary biomarker concentrations are frequently indexed to urinary creatinine (Ucr) concentration in spot samples to account for urine dilution; however, this may introduce biases. We evaluated whether indexing versus adjusting urinary biomarker concentrations for Ucr concentration altered their associations with outcomes.

STUDY DESIGN

Observational cohort.

SETTING & PARTICIPANTS

We analyzed data from 2,360 Systolic Blood Pressure Intervention Trial (SPRINT) participants with estimated glomerular filtration rates < 60 mL/min/1.73 m2 and urinary albumin (UAlb) and 8 urinary kidney tubule biomarkers measured at baseline.

OUTCOMES

The primary outcome was a composite of cardiovascular disease events; secondary outcomes were all-cause mortality and a composite of kidney outcomes (50% estimated glomerular filtration rate decline, end-stage kidney disease, or transplantation).

ANALYTICAL APPROACH

We used Cox proportional hazards regression to examine the associations of 1/Ucr with outcomes and compared the associations of UAlb and 8 individual urinary tubule biomarkers with outcomes, analyzed by indexing to Ucr, adjusting for 1/Ucr or the biomarker alone (without Ucr concentration).

RESULTS

During a median follow-up of 3.3 years, 307 composite cardiovascular events, 166 deaths, and 34 composite kidney outcomes occurred. After multivariable adjustment, 1/Ucr was significantly associated with cardiovascular events (HR, 1.27 per 2-fold higher; 95% CI, 1.11-1.45), not associated with either mortality (HR, 1.06; 95% CI, 0.87-1.28) or kidney events (HR, 1.49; 95% CI, 0.95-2.35). For UAlb and urinary tubule biomarker concentrations, most risk estimates were not significantly different when indexed to Ucr concentration versus adjusted for 1/Ucr.

LIMITATIONS

Cohort excluded patients with diabetes and overall had low levels of albuminuria.

CONCLUSIONS

1/Ucr is independently associated with cardiovascular events in trial participants with chronic kidney disease. Indexing versus adjusting for 1/Ucr does not significantly change the associations of most urinary biomarkers with clinical outcomes.

Biomarkers of Kidney Tubule Health, CKD Progression, and Acute Kidney Injury in SPRINT (Systolic Blood Pressure Intervention Trial) Participants

RATIONALE & OBJECTIVE

The Systolic Blood Pressure Intervention Trial (SPRINT) compared the effect of intensive versus standard systolic blood pressure targets on cardiovascular morbidity and mortality. In this ancillary study, we evaluated the use of exploratory factor analysis (EFA) to combine biomarkers of kidney tubule health in urine and plasma and then study their role in longitudinal estimated glomerular filtration rate (eGFR) change and risk of acute kidney injury (AKI).

STUDY DESIGN

Observational cohort nested in a clinical trial.

SETTING & PARTICIPANTS

2,351 SPRINT participants with eGFR < 60 mL/min/1.73 m² at baseline.

EXPOSURE

Levels of neutrophil gelatinase-associated lipocalin (NGAL), interleukin 18 (IL-18), chitinase-3-like protein (YKL-40), kidney injury molecule 1 (KIM-1), monocyte chemoattractant protein 1 (MCP-1), α₁-microglobulin (A1M) and β₂-microglobulin (B2M), uromodulin (UMOD), fibroblast growth factor 23 (FGF-23), and intact parathyroid hormone (PTH).

OUTCOME

Longitudinal changes in eGFR and risk of AKI.

ANALYTICAL APPROACH

We performed EFA to capture different tubule pathophysiologic processes. We used linear mixed effects models to evaluate the association of each factor with longitudinal changes in eGFR. We evaluated the association of the tubular factors scores with AKI using Cox proportional hazards regression.

RESULTS

From 10 biomarkers, EFA generated 4 factors reflecting tubule injury/repair (NGAL, IL-18, and YKL-40), tubule injury/fibrosis (KIM-1 and MCP-1), tubule reabsorption (A1M and B2M), and tubule reserve/mineral metabolism (UMOD, FGF-23, and PTH). Each 1-SD higher tubule reserve/mineral metabolism factor score was associated with a 0.58% (95% CI, 0.39%-0.67%) faster eGFR decline independent of baseline eGFR and albuminuria. Both the tubule injury/repair and tubule injury/fibrosis factors were independently associated with future risk of AKI (per 1 SD higher, HRs of 1.18 [95% CI, 1.10-1.37] and 1.23 [95% CI, 1.02-1.48], respectively).

LIMITATIONS

The factors require validation in other settings.

CONCLUSIONS

EFA allows parsimonious subgrouping of biomarkers into factors that are differentially associated with progressive eGFR decline and AKI. These subgroups may provide insights into the pathological processes driving adverse kidney outcomes.

Urine Biomarkers of Kidney Tubule Health and Incident CKD Stage 3 in Women Living With HIV: A Repeated Measures Study

Rationale & Objective

Single measurements of urinary biomarkers reflecting kidney tubule health are associated with chronic kidney disease (CKD) risk in HIV infection, but the prognostic value of repeat measurements over time is unknown.

Study Design

Cohort study.

Setting & Participants

647 women living with HIV infection enrolled in the Women’s Interagency Health Study.

Exposures

14 urinary biomarkers of kidney tubule health measured at 2 visits over a 3-year period.

Outcome

Incident CKD, defined as estimated glomerular filtration rate (eGFR) < 60 mL/min/1.73 m² at two 6-month visits and an average eGFR decline ≥ 3% per year.

Analytical Approach

We used multivariable generalized estimating equations adjusting for CKD risk factors to evaluate baseline, time-updated, and change-over-time biomarker associations with incident CKD. We compared CKD discrimination between models with and without a parsimoniously selected set of biomarkers.

Results

During a median 7 years of follow-up, 9.7% (63/647) developed CKD. In multivariable-adjusted analyses, 3 of 14 baseline biomarkers associated with incident CKD. In contrast, 10 of 14 time-updated biomarkers and 9 of 14 biomarkers modeled as change over time associated with incident CKD. Urinary epidermal growth factor (EGF), α₁-microglobulin (A1M), and albumin were selected using penalized regression methods. In the time-updated model, lower urinary EGF (risk ratio [RR] per 2-fold higher time-updated biomarker levels, 0.69; 95% CI, 0.58-0.81), higher urinary A1M (RR, 1.47; 95% CI, 1.25-1.73), and higher urinary albumin excretion (RR, 1.21; 95% CI, 1.03-1.42) were jointly associated with increased risk for CKD. Compared with a base model (C statistic, 0.75), CKD discrimination improved after adding urinary EGF, A1M, and albumin values across baseline (C = 0.81), time-updated (C = 0.83), and change-over-time (C = 0.83) models (P < 0.01 for all).

Limitations

Observational design, incident CKD definition limited to eGFR.

Conclusions

Repeat urinary biomarker measurements for kidney tubule health have stronger associations with incident CKD compared with baseline measurements and moderately improve CKD discrimination in women living with HIV infection.

Functional outcomes of sleep predict cardiovascular intermediary outcomes and all-cause mortality in incident hemodialysis patients

STUDY OBJECTIVES

Patients with end-stage kidney disease (ESKD) commonly experience sleep disturbances. Sleep disturbance has been inconsistently associated with mortality risk in hemodialysis patients, but the burden of symptoms from sleep disturbances has emerged as a marker that may shed light on these discrepancies and guide treatment decisions. This study examines whether functional outcomes of sleep are associated with increased risk of intermediary CV outcomes or mortality among adults initiating hemodialysis.

METHODS

In 228 participants enrolled in the Predictors of Arrhythmic and Cardiovascular risk in ESRD (PACE) study, the Functional Outcomes of Sleep Questionnaire-10 (FOSQ-10), which assesses functional outcomes of daytime sleepiness, was administered within 6 months of enrollment. Intermediary CV outcomes included QTc [ms], heart rate variance [ms²], left ventricular mass index [g/m², LVMI], and left ventricular hypertrophy [LVH]. The association of FOSQ-10 score with all-cause mortality was examined using proportional hazards regression. Results: Mean age was 55 years, median BMI was 28 kg/m² (IQR 24,33), with 70% African Americans. Median FOSQ-10 score was 19.7 (IQR: 17.1,20.0). A 10% lower FOSQ-10 score was associated with increased mortality risk (HR 1.09, 95%CI 1.01-1.18). Lower FOSQ-10 scores were associated with longer QTc duration and lower heart rate variance, but not LVMI or LVH.

CONCLUSIONS

In adults initiating dialysis, sleep-related functional impairment is common and is associated with intermediary cardiovascular disease measures and increased mortality risk. Future studies should assess the impact of screening for sleep disturbances in ESKD patients to identify individuals at increased risk for cardiovascular complications and death.

Chronic kidney disease detection, staging and treatment in cardiovascular disease prevention

Globally, nearly 10% of the population has chronic kidney disease (CKD), defined as a glomerular filtration rate less than 60 mL/min/1.73 m² and/or a urinary albumin to creatinine ratio greater than 30 mg/g (3 mg/mmol). Persons with CKD have a substantially high risk of cardiovascular disease. Indeed, most persons with CKD are far more likely to develop a cardiovascular event than to progress to end-stage kidney disease. Although early detection and staging of CKD could help prevent its cardiovascular consequences, current rates of testing for CKD are very low, even among high-risk populations such as persons with diabetes, hypertension and cardiovascular disease. In this review, we first describe the need to test for both estimated glomerular filtration rate and albuminuria among persons at high risk of CKD in order to properly stage CKD and enhance cardiovascular risk stratification. We then discuss how detection and staging for CKD could help prioritise patients at high risk of atherosclerotic cardiovascular disease and heart failure who could derive the largest benefit from cardiovascular preventive interventions. In addition, we discuss the central role of CKD detection and staging in the initiation of cardiorenal preventive therapies, such as the sodium-glucose cotransporter 2 inhibitors, which have shown overwhelming evidence of cardiorenal protection. We conclude by discussing strategies to overcome historical barriers to CKD detection and treatment.

Biomarkers of Immune Activation and Incident Kidney Failure With Replacement Therapy: Findings From the African American Study of Kidney Disease and Hypertension

RATIONALE & OBJECTIVE

Immune activation is fundamental to the pathogenesis of many kidney diseases. Innate immune molecules such as soluble urokinase-type plasminogen activator receptor (suPAR) have been linked to the incidence and progression of chronic kidney disease (CKD). Whether other biomarkers of immune activation are associated with incident kidney failure with replacement therapy (KFRT) in African Americans with nondiabetic kidney disease is unclear.

STUDY DESIGN

Prospective cohort.

SETTING & PARTICIPANTS

African American Study of Kidney Disease and Hypertension (AASK) participants with available baseline serum samples for biomarker measurement.

PREDICTORS

Baseline serum levels of soluble tumor necrosis factor receptor 1 (sTNFR1), sTNFR2, tumor necrosis factor α (TNF-α), and interferon γ (IFN-γ).

OUTCOMES

Incident KFRT, all-cause mortality.

ANALYTICAL APPROACH

Cox proportional hazards models.

RESULTS

Among 500 participants with available samples, mean glomerular filtration rate was 44.7mL/min/1.73m², and median urinary protein-creatinine ratio was 0.09g/g at baseline. Over a median follow up of 9.6 years, there were 161 (32%) KFRT and 113 (23%) death events. In models adjusted for demographic and clinical factors and baseline kidney function, each 2-fold higher baseline level of sTNFR1, sTNFR2, and TNF-α was associated with 3.66-fold (95% CI, 2.31-5.80), 2.29-fold (95% CI, 1.60-3.29), and 1.35-fold (95% CI, 1.07-1.71) greater risks of KFRT, respectively; in comparison, each doubling of baseline suPAR concentration was associated with 1.39-fold (95% CI, 1.04-1.86) greater risk of KFRT. sTNFR1, sTNFR2, and TNF-α were also significantly associated with death (up to 2.2-fold higher risks per 2-fold higher baseline levels; P≤0.01). IFN-γ was not associated with either outcome. None of the biomarkers modified the association of APOL1 high-risk status (genetic risk factors for kidney disease among individuals of African ancestry) with KFRT (P>0.05 for interaction).

LIMITATIONS

Limited generalizability to other ethnic groups or causes of CKD.

CONCLUSIONS

Among African Americans with CKD attributed to hypertension, baseline levels of sTNFR1, sTNFR2, and TNF-α but not IFN-γ were associated with KFRT and mortality.

Association of Non-Steroidal Anti-Inflammatory Drugs with Kidney Health in Ambulatory Older Adults

BACKGROUND/OBJECTIVES

Non-steroidal anti-inflammatory drugs (NSAIDs) can cause kidney injury, especially in older adults. However, previously reported associations between NSAID use and kidney health outcomes are inconsistent and limited by reliance on serum creatinine-based GFR estimates. This analysis investigated the association of NSAID use with kidney damage in older adults using multiple kidney health measures.

DESIGN

Cross-sectional and longitudinal analyses.

SETTING

Multicenter, community-based cohort.

PARTICIPANTS

Two thousand nine hundred and ninty nine older adults in the Health ABC Study. A subcohort (n = 500) was randomly selected for additional biomarker measurements.

EXPOSURE

Prescription and over-the-counter NSAID use ascertained by self-report.

MEASUREMENTS

Baseline estimated glomerular filtration rate (eGFR) by cystatin C (cysC), urine albumin-to-creatinine ratio (ACR), kidney injury molecule-1 (KIM-1), and interleukin-18 (IL-18) were measured in 2,999 participants; alpha-1 microglobulin (α1m), neutrophil gelatinase-associated lipocalin (NGAL), propeptide type III procollagen (PIIINP), and uromodulin (UMOD) were measured in 500 participants. GFR was estimated three times over 10 years and expressed as percent change per year.

RESULTS

Participants had a mean age of 74 years, 51% were female, and 41% African-American. No eGFR differences were detected between NSAID users (n = 655) and non-users (n = 2,344) at baseline (72 ml/min/1.73 m² in both groups). Compared to non-users, NSAID users had lower adjusted odds of having ACR greater than 30 mg/g (0.67; 95% confidence interval (CI) = 0.51-0.89) and lower mean urine IL-18 concentration at baseline (-11%; 95% CI = -4% to -18%), but similar mean KIM-1 (5%; 95% CI = -5% to 14%). No significant differences in baseline concentrations of the remaining urine biomarkers were detected. NSAID users and non-users did not differ significantly in the rate of eGFR decline (-2.2% vs -2.3% per year).

CONCLUSION

Self-reported NSAID use was not associated with kidney dysfunction or injury based on multiple measures, raising the possibility of NSAID use without kidney harm in ambulatory older adults. More research is needed to define safe patterns of NSAID consumption.

Identification of Novel Biomarkers and Pathways for Coronary Artery Calcification in Nondiabetic Patients on Hemodialysis Using Metabolomic Profiling

BACKGROUND

A better understanding of the pathophysiology involving coronary artery calcification (CAC) in patients on hemodialysis (HD) will help to develop new therapies. We sought to identify the differences in metabolomics profiles between patients on HD with and without CAC.

METHODS

In this case-control study, nested within a cohort of 568 incident patients on HD, the cases were patients without diabetes with a CAC score >100 (n=51), and controls were patients without diabetes with a CAC score of zero (n=48). We measured 452 serum metabolites in each participant. Metabolites and pathway scores were compared using Mann-Whitney U tests, partial least squares-discriminant analyses, and pathway enrichment analyses.

RESULTS

Compared with controls, cases were older (64±13 versus 42±12 years) and were less likely to be Black (51% versus 94%). We identified three metabolites in bile-acid synthesis (chenodeoxycholic, deoxycholic, and glycolithocholic acids) and one pathway (arginine/proline metabolism). After adjusting for demographics, higher levels of chenodeoxycholic, deoxycholic, and glycolithocholic acids were associated with higher odds of having CAC; comparing the third with the first tertile of each bile acid, the OR was 6.34 (95% CI, 1.12 to 36.06), 6.73 (95% CI, 1.20 to 37.82), and 8.53 (95% CI, 1.50 to 48.49), respectively. These associations were no longer significant after further adjustment for coronary artery disease and medication use. Per 1 unit higher in the first principal component score, arginine/proline metabolism was associated with CAC after adjusting for demographics (OR, 1.83; 95% CI, 1.06 to 3.15), and the association remained significant with additional adjustments for statin use (OR, 1.84; 95% CI, 1.04 to 3.27).

CONCLUSIONS

Among patients on HD without diabetes mellitus, chenodeoxycholic, deoxycholic, and glycolithocholic acids may be potential biomarkers for CAC, and arginine/proline metabolism is a plausible mechanism to study for CAC. These findings need to be confirmed in future studies.

APOL1 Risk Variants and Subclinical Cardiovascular Disease in Incident Hemodialysis Patients

Introduction

To better understand the impact of APOL1 risk variants in end-stage renal disease (ESRD) we evaluated associations of APOL1 risk variants with subclinical cardiovascular disease (CVD) and mortality among African Americans initiating hemodialysis and enrolled in the Predictors of Arrhythmic and Cardiovascular Risk in ESRD cohort study.

Methods

We modeled associations of APOL1 risk status (high = 2; low = 0/1 risk alleles) with baseline subclinical CVD (left ventricular [LV] hypertrophy; LV mass; ejection fraction; coronary artery calcification [CAC]; pulse wave velocity [PWV]) using logistic and linear regression and all-cause or cardiovascular mortality using Cox models, adjusting for age, sex, and ancestry. In sensitivity analyses, we further adjusted for systolic blood pressure and Charlson Comorbidity Index.

Results

Of 267 African American participants successfully genotyped for APOL1, 27% were high-risk carriers, 41% were women, and mean age was 53 years. At baseline, APOL1 high- versus low-risk status was independently associated with 50% and 53% lower odds of LV hypertrophy and CAC, respectively, and 10.7% lower LV mass. These associations were robust to further adjustment for comorbidities but not systolic blood pressure. APOL1 risk status was not associated with all-cause or cardiovascular mortality (mean follow-up 2.5 years).

Conclusion

Among African American patients with incident hemodialysis, APOL1 high-risk status was associated with better subclinical measures of CVD but not mortality.

Association of APOL1 Genotypes With Measures of Microvascular and Endothelial Function, and Blood Pressure in MESA

Background

APOL1 high‐risk genotypes are associated with increased risk for hypertension‐attributed kidney disease among Black adults in the United States. Biopsy studies show differences in kidney vasculature by APOL1 status; less is known about the variants' associations with systemic vascular and endothelial function. Whether APOL1 risk variants are associated with blood pressure (BP) is also uncertain.

Methods and Results

Using linear regression, we examined cross‐sectional associations of APOL1 risk genotypes (high=2 risk alleles, low=0 or 1 risk allele) with subclinical measures of vascular function (small arterial elasticity, n=1586; large arterial elasticity, n=1586; ascending aortic distensibility, n=985) and endothelial function (flow‐mediated dilation, n=777). Using linear mixed‐effects models, we studied longitudinal associations of APOL1 risk genotypes with BP (n=1619), adjusting for age, sex, and African ancestry. Among 1619 (12% APOL1 high‐risk) Black participants in MESA (Multi‐Ethnic Study of Atherosclerosis), mean age was 62 years old, 58% had hypertension, and mean systolic BP was 131 mm Hg at baseline. At examination 1 (2000–2002), there was no significant difference in small arterial elasticity, large arterial elasticity, ascending aortic distensibility, or flow‐mediated dilation in participants with APOL1 high‐ versus low‐risk genotypes (P>0.05 for all). Over a mean follow‐up of 7.8 years, relative annual changes in systolic and diastolic BP and pulse pressure did not differ significantly by APOL1 risk status (between‐group differences of −0.20, −0.14, and −0.25, respectively; P>0.05 for all).

Conclusions

Among Black participants in MESA, APOL1 high‐risk genotypes were not associated with subclinical vascular and endothelial function or BP trajectories. The relationship of APOL1 with kidney disease may be intrinsic to the kidney rather than through peripheral effects on systemic vasculature or BP.

Associations of Serum Calciprotein Particle Size and Transformation Time With Arterial Calcification, Arterial Stiffness, and Mortality in Incident Hemodialysis Patients

RATIONALE & OBJECTIVE

Characteristics of the transformation of primary to secondary calciprotein particles (CPPs) in serum, including the size of secondary CPP (CPP2) aggregates and the time of transformation (T₅₀), may be markers for arterial calcification in patients undergoing hemodialysis (HD). We examined the associations of CPP2 aggregate size and T₅₀ with arterial calcification in incident HD patients.

STUDY DESIGN

Prospective cohort study.

SETTING & PARTICIPANTS

Incident HD patients (n=402with available CPP2 measures and n=388with available T₅₀ measures) from the Predictors of Arrhythmic and Cardiovascular Risk in End-Stage Renal Disease (PACE) Study PREDICTORS: Serum CPP2 size and T₅₀ at baseline.

OUTCOMES

Primary outcomes were baseline coronary artery and thoracic aorta calcifications. Exploratory outcomes included baseline arterial stiffness, measured by pulse wave velocity (PWV) and ankle brachial index, and longitudinally, repeat measures of PWV and all-cause mortality.

ANALYTICAL APPROACH

Tobit regression, multiple linear regression, Poisson regression, linear mixed-effects regression, and Cox proportional hazards regression.

RESULTS

Mean age was 55±13 years, 41% were women, 71% were Black, and 57% had diabetes mellitus. Baseline CPP2 size and T₅₀ were correlated with baseline fetuin A level (r=-0.59 for CPP2 and 0.44 for T₅₀; P<0.001 for both), but neither was associated with baseline measures of arterial calcification or arterial stiffness. Baseline CPP2 size and T₅₀ were not associated with repeat measures of PWV. During a median follow-up of 3.5 (IQR, 1.7-6.2) years, larger CPP2 was associated with higher risk for mortality (HR, 1.17 [95% CI, 1.05-1.31] per 100nm larger CPP2 size) after adjusting for demographics and comorbid conditions, but there was no association between baseline T₅₀ and risk for mortality.

LIMITATIONS

Possible imprecision in assays, small sample size, limited generalizability to incident HD populations with different racial composition, and residual confounding.

CONCLUSIONS

In incident HD patients, neither CPP2 size nor T₅₀ was associated with prevalent arterial calcification and stiffness. Larger CPP2 was associated with risk for mortality, but this finding needs to be confirmed in future studies.

Calcification Biomarkers, Subclinical Vascular Disease, and Mortality Among Multiethnic Dialysis Patients

Introduction

Vascular calcification and stiffness are associated with higher mortality and cardiovascular disease in hemodialysis patients, but the underlying mechanism is not well elucidated and previous studies have been contradictory. We sought to determine the association of circulating calcification biomarkers with calcification, stiffness, and mortality in a multiethnic incident dialysis population.

Methods

Among 391 incident hemodialysis participants enrolled in the Predictors of Arrhythmic and Cardiovascular Risk in End Stage Renal Disease (PACE) study, we examined the cross-sectional associations of baseline fibroblast growth factor 23 (FGF23), desphospho-uncarboxylated matrix Gla protein (dp-ucMGP), fetuin-A, and osteoprotegerin (OPG) according to total coronary artery calcium score (CAC, using the Agatston calcification criteria) at baseline, vascular stiffness (pulse wave velocity [PWV]) over 4 study visits, and all-cause mortality.

Results

Patients' mean age was 55 years; 40% were female, 72% were African American, and 58% had diabetes. Higher OPG and FGF23 were associated with a 1.09-fold (per 5-pmol/l increase in OPG; 95% confidence interval [CI]: 1.01-1.17) and 1.12-fold (per increase of 100 log RU/ml in FGF23; 95% CI: 1.02‒1.34) higher prevalence of CAC, independent of demographics, comorbidities, dialysis factors, and serum klotho levels. Higher OPG was associated with higher baseline PWV. Higher FGF23 was associated with lower PWV over follow-up. dp-ucMGP and fetuin-A were not associated with either CAC or vascular stiffness. After adjustment, circulating biomarkers were not associated with mortality risk.

Conclusion

Several circulating calcification biomarkers were only modestly associated with subclinical cardiovascular disease in an incident multiethnic hemodialysis population; none were associated with mortality. Understanding whether these associations persist in larger, diverse hemodialysis populations is warranted before planning trials.

Frailty Prevalence in Younger End-Stage Kidney Disease Patients Undergoing Dialysis and Transplantation

BACKGROUND

Frailty, originally characterized in community-dwelling older adults, is increasingly being studied and implemented for adult patients with end-stage kidney disease (ESKD) of all ages (>18 years). Frailty prevalence and manifestation are unclear in younger adults (18-64 years) with ESKD; differences likely exist based on whether the patients are treated with hemodialysis (HD) or kidney transplantation (KT).

METHODS

We leveraged 3 cohorts: 378 adults initiating HD (2008-2012), 4,304 adult KT candidates (2009-2019), and 1,396 KT recipients (2008-2019). The frailty phenotype was measured within 6 months of dialysis initiation, at KT evaluation, and KT admission. Prevalence of frailty and its components was estimated by age (≥65 vs. <65 years). A Wald test for interactions was used to test whether risk factors for frailty differed by age.

RESULTS

In all 3 cohorts, frailty prevalence was higher among older than younger adults (HD: 71.4 vs. 47.3%; candidates: 25.4 vs. 18.8%; recipients: 20.8 vs. 14.3%). In all cohorts, older patients were more likely to have slowness and weakness but less likely to report exhaustion. Among candidates, older age (odds ratio [OR] = 1.79, 95% CI: 1.47-2.17), non-Hispanic black race (OR = 1.30, 95% CI: 1.08-1.57), and dialysis type (HD vs. no dialysis: OR = 2.06, 95% CI: 1.61-2.64; peritoneal dialysis vs. no dialysis: OR = 1.78, 95% CI: 1.28-2.48) were associated with frailty prevalence, but sex and Hispanic ethnicity were not. These associations did not differ by age (pinteractions > 0.1). Similar results were observed for recipients and HD patients.

CONCLUSIONS

Although frailty prevalence increases with age, younger patients have a high burden. Clinicians caring for this vulnerable population should recognize that younger patients may experience frailty and screen all age groups.

Chronic Kidney Disease Awareness and Longitudinal Health Outcomes: Results from the REasons for Geographic And Racial Differences in Stroke Study

BACKGROUND

The majority of people with chronic kidney disease (CKD) are unaware of their kidney disease. Assessing the clinical significance of increasing CKD awareness has critical public health and healthcare delivery implications. Whether CKD awareness among persons with CKD is associated with longitudinal health behaviors, disease management, and health outcomes is unknown.

METHODS

We analyzed data from participants with CKD in the REasons for Geographic And Racial Differences in Stroke study, a national, longitudinal, population-based cohort. Our predictor was participant CKD awareness. Outcomes were (1) health behaviors (smoking avoidance, exercise, and nonsteroidal anti-inflammatory drug use); (2) CKD management indicators (angiotensin-converting enzyme inhibitor or angiotensin receptor blocker use, statin use, systolic blood pressure, fasting blood glucose, and body mass index); (3) change in estimated glomerular filtration rate (eGFR) and urine albumin-to-creatinine ratio (UACR); and (4) health outcomes (incident end-stage kidney disease [ESKD], coronary heart disease [CHD], stroke, and death). Logistic and linear regressions were used to examine the association of baseline CKD awareness with outcomes of interest, adjusted for CKD stage and participant demographic and clinical factors.

RESULTS

Of 6,529 participants with baseline CKD, 285 (4.4%) were aware of their CKD. Among the 3,586 participants who survived until follow-up (median 9.5 years), baseline awareness was not associated with subsequent odds of health behaviors, CKD management indicators, or changes in eGFR and UACR in adjusted analyses. Baseline CKD awareness was associated with increased risk of ESKD (adjusted hazard ratio [aHR] 1.44; 95% CI 1.08-1.92) and death (aHR 1.18; 95% CI 1.00-1.39), but not with subsequent CHD or stroke, in adjusted models.

CONCLUSIONS

Individuals aware of their CKD were more likely to experience ESKD and death, suggesting that CKD awareness reflects disease severity. Most persons with CKD, including those that are high-risk, remain unaware of their CKD. There was no evidence of associations between baseline CKD awareness and longitudinal health behaviors, CKD management indicators, or eGFR decline and albuminuria.

HIV preexposure prophylaxis with tenofovir disoproxil fumarate/emtricitabine and changes in kidney function and tubular health

OBJECTIVE

To evaluate the effects of HIV preexposure prophylaxis (PrEP) with tenofovir disoproxial fumurate (TDF)/emtricitabine (FTC) on kidney function and kidney tubular health.

DESIGN

The Iniciativa Profilaxis Pre-Exposicion open-label extension (iPrEx-OLE) study enrolled former PrEP trial participants to receive open-label TDF/FTC. This study included 123 iPrEx-OLE participants who demonstrated PrEP adherence.

METHODS

We compared estimated glomerular filtration rate calculated using serum creatinine (eGFRcr), serum cystatin C (eGFRcys), and in combination (eGFRcr-cys), and a panel of 14 urine biomarkers reflecting kidney tubular health before and 6 months after PrEP initiation.

RESULTS

At baseline, mean eGFRcr, eGFRcys, and eGFRcr-cys were 108.3, 107.0, and 111.1 ml/min per 1.73 m, respectively. Six months after PrEP initiation, eGFRcr declined by -4% (95% CI: -5.7 to -2.4%), eGFRcys declined by -3.3% (95% CI: -8.3 to 1.9%), and eGFRcr-cys declined by -4.1% (95% CI: -7.5 to -0.7%). From the urine biomarker panel, α1-microglobulin and β2-microglobulin increased by 22.7% (95% CI: 11.8--34.7%) and 14.1% (95% CI: -6.1 to 38.6%), whereas chitinase-3-like 1 protein and monocyte chemoattractant protein-1 decreased by -37.7% (95% CI: -53.0 to -17.3%) and -15.6% (95% CI: -31.6 to 4.2%), respectively. Ten of the 14 urine biomarkers, including albumin, had estimated changes of less than 12% with wide confidence intervals.

CONCLUSION

Six months of PrEP with TDF/FTC was associated with decreases in eGFRcr and eGFRcys. We also observed for the first time changes in flour of 14 urine biomarkers reflecting kidney tubular health. These findings demonstrate that PrEP has direct effects on eGFR and the proximal tubule.

The epidemiology of chronic kidney disease (CKD) in rural East Africa: A population-based study

Background

Chronic kidney disease (CKD) may be common among individuals living in sub-Saharan Africa due to the confluence of CKD risk factors and genetic predisposition.

Methods

We ascertained the prevalence of CKD and its risk factors among a sample of 3,686 participants of a population-based HIV trial in rural Uganda and Kenya. Prevalent CKD was defined as a serum creatinine-based estimated glomerular filtration rate <60 mL/min/1.73m² or proteinuria (urine dipstick ≥1+). We used inverse-weighting to estimate the population prevalence of CKD, and multivariable log-link Poisson models to assess the associations of potential risk factors with CKD.

Results

The estimated CKD prevalence was 6.8% (95% CI 5.7–8.1%) overall and varied by region, being 12.5% (10.1–15.4%) in eastern Uganda, 3.9% (2.2–6.8%) in southwestern Uganda and 3.7% (2.7–5.1%) in western Kenya. Risk factors associated with greater CKD prevalence included age ≥60 years (adjusted prevalence ratio [aPR] 3.5 [95% CI 1.9–6.5] compared with age 18–29 years), HIV infection (aPR 1.6 [1.1–2.2]), and residence in eastern Uganda (aPR 3.9 [2.6–5.9]). However, two-thirds of individuals with CKD did not have HIV, diabetes, or hypertension as risk factors. Furthermore, we noted many individuals who did not have proteinuria had dipstick positive leukocyturia or hematuria.

Conclusion

The prevalence of CKD is appreciable in rural East Africa and there are considerable regional differences. Conventional risk factors appear to only explain a minority of cases, and leukocyturia and hematuria were common, highlighting the need for further research into understanding the nature of CKD in sub-Saharan Africa.

APOL1 Nephropathy Risk Alleles and Mortality in African American Adults: A Cohort Study

RATIONALE & OBJECTIVE

APOL1 nephropathy risk alleles are associated with the development of chronic kidney disease (CKD) in African Americans. Although CKD is an established risk factor for mortality, associations of APOL1 risk alleles with mortality are uncertain.

STUDY DESIGN

Prospective cohort.

SETTINGS & PARTICIPANTS

10,380 African American and 17,485 white American participants in the Reasons for Geographic and Racial Differences in Stroke (REGARDS) Study.

EXPOSURES

APOL1 nephropathy risk alleles.

OUTCOMES

All-cause and cause-specific mortality.

ANALYTICAL APPROACH

Cox proportional hazards models were used to examine the association of APOL1 high-risk genotypes (2 risk alleles) versus APOL1 low-risk genotypes (0/1 risk allele) with all-cause and cause-specific mortality in African Americans and examine the risk for all-cause mortality in African Americans with high-risk genotypes versus African Americans with low-risk genotypes and white Americans.

RESULTS

APOL1 high-risk participants were younger and had a higher prevalence of albuminuria than low-risk participants. There was no statistically significant association of APOL1 high- versus low-risk genotypes with all-cause mortality in models adjusted for sociodemographic variables, comorbid conditions, and kidney function (HR, 0.88; 95% CI, 0.77-1.01). After further adjustment for genetic ancestry in a subset with available data, a statistically significant association emerged (HR, 0.81; 95% CI, 0.69-0.96). Associations differed by CKD status (Pinteraction=0.04), with African Americans with high-risk genotypes having lower risk for mortality than those with low-risk genotypes in fully adjusted models (HR, 0.78; 95% CI, 0.62-0.99) among those with CKD, but not those without CKD (HR, 0.84; 95% CI, 0.66-1.05). Compared with white Americans, African Americans with high-risk genotypes had a similar rate of mortality, whereas African Americans with low-risk genotypes had a higher rate of mortality (HR, 1.07; 95% CI, 1.00-1.14) in fully adjusted models.

LIMITATIONS

Lack of follow-up measures of kidney function.

CONCLUSIONS

African Americans with high-risk APOL1 genotypes had lower mortality than those with low-risk genotypes in multivariable-adjusted models including genetic ancestry.

Association of Statin Use With Kidney Damage and Function Among HIV-Infected Men

BACKGROUND

Chronic kidney disease (CKD) occurs commonly among HIV-infected persons. Statins may delay CKD onset and progression through their cholesterol-lowering and pleiotropic effects.

METHODS

Among 850 HIV-infected men from the Multicenter AIDS Cohort Study with stored urine samples (2009-2011), we evaluated cross-sectional associations of statin use with urine biomarkers of kidney damage [albumin-to-creatinine ratio (ACR), alpha-1-microglobulin, interleukin-18, kidney injury molecule-1, and procollagen type III N-terminal propeptide] using multivariable linear regression. We evaluated the longitudinal associations of statin use with annual change in estimated glomerular filtration rate by creatinine (eGFR) using linear mixed models, and with incident proteinuria and incident CKD (eGFR <60 mL/min/1.73 m) using Cox proportional hazards regression. We used inverse probability weighting to address potential confounding related to statin use.

RESULTS

Statin users comprised 30% of participants. In adjusted analyses, each year of cumulative statin use was associated with 4.0% higher baseline ACR levels (P = 0.05), but there was no association with baseline levels of other urine biomarkers. Statin use had no overall association with annual eGFR decline. Among participants with baseline proteinuria, statin use was modestly associated with slower annual eGFR decline compared to non-use (adjusted difference: 1.33 mL/min/1.73 m per year; 95% confidence interval: -0.07 to 2.70). Statin use was not associated with risk of incident proteinuria or incident CKD.

CONCLUSIONS

Statin use was associated with higher baseline ACR, but not with biomarkers of tubulointerstitial injury. Statin use was associated with modestly slower eGFR decline only among participants with baseline proteinuria. Although these findings may be susceptible to confounding by indication, they suggest a limited effect of statins on CKD risk among HIV-infected men.

Hemodialysis Procedure-Associated Autonomic Imbalance and Cardiac Arrhythmias: Insights From Continuous 14-Day ECG Monitoring

Background

In patients with end‐stage kidney disease, sudden cardiac death is more frequent after a long interdialytic interval, within 6 hours after the end of a hemodialysis session. We hypothesized that the occurrence of paroxysmal arrhythmias is associated with changes in heart rate and heart rate variability in different phases of hemodialysis.

Methods and Results

We conducted a prospective ancillary study of the Predictors of Arrhythmic and Cardiovascular Risk in End Stage Renal Disease cohort. Continuous ECG monitoring was performed using an ECG patch, and short‐term heart rate variability was measured for 3 minutes every hour (by root mean square of the successive normal‐to‐normal intervals, spectral analysis, Poincaré plot, and entropy), up to 300 hours. Out of enrolled participants (n=28; age 54±13 years; 57% men; 96% black; 33% with a history of cardiovascular disease; left ventricular ejection fraction 70±9%), arrhythmias were detected in 13 (46%). Nonsustained ventricular tachycardia occurred more frequently during/posthemodialysis than pre‐/between hemodialysis (63% versus 37%, P=0.015). In adjusted for cardiovascular disease time‐series analysis, nonsustained ventricular tachycardia was preceded by a sudden heart rate increase (by 11.2 [95% CI 10.1–12.3] beats per minute; P<0.0001). During every‐other‐day dialysis, root mean square of the successive normal‐to‐normal intervals had a significant circadian pattern (Mesor 10.6 [ 95% CI 0.9–11.2] ms; amplitude 1.5 [95% CI 1.0–3.1] ms; peak at 02:01 [95% CI 20:22–03:16] am; P<0.0001), which was replaced by a steady worsening on the second day without dialysis (root mean square of the successive normal‐to‐normal intervals −1.41 [95% CI −1.67 to −1.15] ms/24 h; P<0.0001).

Conclusions

Sudden increase in heart rate during/posthemodialysis is associated with nonsustained ventricular tachycardia. Every‐other‐day hemodialysis preserves circadian rhythm, but a second day without dialysis is characterized by parasympathetic withdrawal.