Associations of Urine Biomarkers with Kidney Function Decline in HIV-Infected and Uninfected Men

BACKGROUND

HIV-infected (HIV+) persons are at increased risk of chronic kidney disease, but serum creatinine does not detect early losses in kidney function. We hypothesized that urine biomarkers of kidney damage would be associated with subsequent changes in kidney function in a contemporary cohort of HIV+ and HIV-uninfected (HIV-) men.

METHODS

In the Multicenter AIDS Cohort Study, we measured baseline urine concentrations of 5 biomarkers from 2009 to 2011 in 860 HIV+ and 337 HIV- men: albumin, alpha-1-microglobulin (α1m), interleukin-18 (IL-18), kidney injury molecule-1 (KIM-1), and procollagen type III N-terminal propeptide (PIIINP). We evaluated associations of urine biomarker concentrations with annual changes in estimated glomerular filtration rate (eGFR) using multivariable linear mixed models adjusted for demographics, traditional kidney disease risk factors, HIV-related risk factors, and baseline eGFR.

RESULTS

Over a median follow-up of 4.8 years, the average annual eGFR decline was 1.42 mL/min/1.73 m2/year in HIV+ men and 1.22 mL/min/1.73 m2/year in HIV- men. Among HIV+ men, the highest vs. lowest tertiles of albumin (-1.78 mL/min/1.73 m2/year, 95% CI -3.47 to -0.09) and α1m (-2.43 mL/min/1.73 m2/year, 95% CI -4.14 to -0.73) were each associated with faster annual eGFR declines after multivariable adjustment. Among HIV- men, the highest vs. lowest tertile of α1m (-2.49 mL/min/1.73 m2/year, 95% CI -4.48 to -0.50) was independently associated with faster annual eGFR decline. Urine IL-18, KIM-1, and PIIINP showed no independent associations with eGFR decline, regardless of HIV serostatus.

CONCLUSIONS

Among HIV+ men, higher urine albumin and α1m are associated with subsequent declines in kidney function, independent of eGFR.

Primary care physicians' perceptions of barriers and facilitators to management of chronic kidney disease: A mixed methods study

BACKGROUND

Given the high prevalence of chronic kidney disease (CKD), primary care physicians (PCPs) frequently manage early stage CKD. Nonetheless, there are challenges in providing optimal CKD care in the primary care setting. This study sought to understand PCPs' perceptions of barriers and facilitators to the optimal management of CKD.

STUDY DESIGN

Mixed methods study.

SETTINGS AND PARTICIPANTS

Community-based PCPs in four US cities: Baltimore, MD; St. Louis, MO; Raleigh, NC and San Francisco, CA.

METHODOLOGY

We used a self-administered questionnaire and conducted 4 focus groups of PCPs (n = 8 PCPs/focus group) in each city to identify key barriers and facilitators to management of patients with CKD in primary care.

ANALYTIC APPROACH

We conducted descriptive analyses of the survey data. Major themes were identified from audio-recorded interviews that were transcribed and coded by the research team.

RESULTS

Of 32 participating PCPs, 31 (97%) had been in practice for >10 years, and 29 (91%) practiced in a non-academic setting. PCPs identified multiple barriers to managing CKD in primary care including at the level of the patient (e.g., low awareness of CKD, poor adherence to treatment recommendations), the provider (e.g., staying current with CKD guidelines), and the health care system (e.g., inflexible electronic medical record, limited time and resources). PCPs desired electronic prompts and lab decision support, concise guidelines, and healthcare financing reform to improve CKD care.

CONCLUSIONS

PCPs face substantial but modifiable barriers in providing care to patients with CKD. Interventions that address these barriers and promote facilitative tools may improve PCPs' effectiveness and capacity to care for patients with CKD.

The SPRINT trial suggests that markers of tubule cell function in the urine associate with risk of subsequent acute kidney injury while injury markers elevate after the injury

Urine markers can quantify tubular function including reabsorption (α-1 microglobulin [α1m]) and β-2-microglobulin [β2m]) and protein synthesis (uromodulin). Individuals with tubular dysfunction may be less able to compensate to insults than those without, despite similar estimated glomerular filtration rate (eGFR) and albuminuria. Among Systolic Blood Pressure Intervention Trial (SPRINT) participants with an eGFR under 60 ml/min/1.73m2, we measured urine markers of tubular function and injury (neutrophil gelatinase-associated lipocalin [NGAL], kidney injury molecule-1 [KIM-1], interleukin-18 [IL-18], monocyte chemoattractant protein-1, and chitinase-3-like protein [YKL-40]) at baseline. Cox models evaluated associations with subsequent acute kidney injury (AKI) risk, adjusting for clinical risk factors, baseline eGFR and albuminuria, and the tubular function and injury markers. In a random subset, we remeasured biomarkers after four years, and compared changes in biomarkers in those with and without intervening AKI. Among 2351 participants, 184 experienced AKI during 3.8 years mean follow-up. Lower uromodulin (hazard ratio per two-fold higher (0.68, 95% confidence interval [0.56, 0.83]) and higher α1m (1.20; [1.01, 1.44]) were associated with subsequent AKI, independent of eGFR and albuminuria. None of the five injury markers were associated with eventual AKI. In the random subset of 947 patients with repeated measurements, the 59 patients with intervening AKI versus without had longitudinal increases in urine NGAL, IL-19, and YKL-40 and only 1 marker of tubule function (α1m). Thus, joint evaluation of tubule function and injury provided novel insights to factors predisposing to AKI, and responses to kidney injury.

Proteinuria Is Associated With Increased Risk of Fragility Fracture in Men With or at Risk of HIV Infection

BACKGROUND

Proteinuria has been associated with bone loss and fractures in general population, but data in HIV-infected population are lacking.

SETTING

Prospective, multicenter cohort study of men with or at risk of HIV infection.

METHODS

Between 2006 and 2015, urine protein measurements and bone fracture histories were ascertained semiannually in 947 HIV-infected (HIV+) and 969 HIV-uninfected (HIV-) men aged 40 years or older. Proteinuria was defined as protein-to-creatinine ratio ≥200 mg/g at ≥2 consecutive visits. Outcome measures (1) all fractures (excluding fractures of skull, face, and digits) and (2) fragility fractures (fractures of vertebral column, femur, wrist, and humerus). Multivariable Cox proportional hazards models assessed the association between proteinuria and fracture after adjusting for additional risk factors.

RESULTS

The overall period prevalence of proteinuria was higher among HIV+ than HIV- (29% vs 6%, P < 0.001). Men with proteinuria had a significantly higher risk of fragility fracture compared with men without proteinuria [adjusted hazard ratio (aHR) = 2.29 (1.12-4.66)] and did not differ by HIV serostatus (p-interaction = 0.83). The risk of all fractures was not statistically different between men with or without proteinuria [aHR = 1.31 (0.84-2.05)]. Among HIV+ men, the association between confirmed proteinuria and fragility fracture was attenuated [aHR = 2.12 (0.95-4.73)] after additional adjustment for CD4 T-cell count/mm, history of AIDS, the presence of detectable plasma HIV-1 RNA, and cumulative exposure to tenofovir disoproxil fumarate.

CONCLUSIONS

Proteinuria was more common in HIV+ than in HIV- men and was a strong independent risk factor for fragility fracture regardless of HIV serostatus. Proteinuria should prompt consideration of a thorough evaluation for bone disease among HIV+ persons.

Associations of serum and dialysate electrolytes with QT interval and prolongation in incident hemodialysis: the Predictors of Arrhythmic and Cardiovascular Risk in End-Stage Renal Disease (PACE) study

Background

Prolonged QT interval in hemodialysis patients may be associated with sudden cardiac death, however, few studies examined the longitudinal associations of modifiable factors such as serum and dialysate concentrations of calcium, potassium, and magnesium with corrected QT (QTc) prolongation in incident hemodialysis patients.

Methods

In 330 in-center hemodialysis participants from the PACE study who were followed up for one year, we examined the associations of predialysis serum electrolytes (total calcium [Ca], corrected Ca [cCa], ionized Ca [iCa], potassium [K], magnesium [Mg]), dialysate (dCa and dK), and serum-to-dialysate gradient measures with QTc interval and prolongation (≥460 ms in women and ≥ 450 ms in men).

Results

At the first study visit, 47% had QTc prolongation. Lower iCa and K were associated with longer QTc interval independent of potential confounders (QTc difference = 8.55[95% CI: 2.13, 14.97] ms for iCa; QTc difference = 9.89[1.58, 18.20] ms for K). Lower iCa was also associated with a higher risk of QTc prolongation. At 1 year of follow-up, 31% had persistent QTc prolongation. In longitudinal analyses, the associations of iCa and K with QTc interval remained significant, and lower K was associated with a higher risk of QTc prolongation while the association of iCa with QTc prolongation was borderline statistically significant. Serum Mg, dCa or dK, and respective gradients were not associated with QTc interval or prolongation.

Conclusion

Prolonged QTc is very common in incident hemodialysis participants and persists over follow-up. Ionized Ca and K are consistently inversely associated with QTc prolongation, which suggests closer monitoring for a low calcium or potassium level to mitigate risk.

Electronic supplementary material

The online version of this article (10.1186/s12882-019-1282-5) contains supplementary material, which is available to authorized users.

Correction: HIV Viremia and T-cell Activation Differentially Affect the Performance of Glomerular Filtration Rate Equations Based on Creatinine and Cystatin C

[This corrects the article DOI: 10.1371/journal.pone.0082028.].

Urinary Biomarkers of Tubular Damage Are Associated with Mortality but Not Cardiovascular Risk among Systolic Blood Pressure Intervention Trial Participants with Chronic Kidney Disease

BACKGROUND

Kidney tubulointerstitial fibrosis on biopsy is a strong predictor of chronic kidney disease (CKD) progression, and CKD is associated with elevated risk of cardiovascular disease (CVD). Tubular health is poorly quantified by traditional kidney function measures, including estimated glomerular filtration rate (eGFR) and albuminuria. We hypothesized that urinary biomarkers of tubular injury, inflammation, and repair would be associated with higher risk of CVD and mortality in persons with CKD.

METHODS

We measured urinary concentrations of interleukin-18 (IL-18), kidney injury molecule-1, neutrophil gelatinase-associated lipocalin, monocyte chemoattractant protein-1, and chitinase-3-like protein-1 (YKL-40) at baseline among 2,377 participants of the Systolic Blood Pressure Intervention Trial who had an eGFR < 60 mL/min/1.73 m2. We used Cox proportional hazards models to evaluate biomarker associations with CVD events and all-cause mortality.

RESULTS

At baseline, the mean age of participants was 72 ± 9 years, and eGFR was 48 ± 11 mL/min/1.73 m2. Over a median follow-up of 3.8 years, 305 CVD events (3.6% per year) and 233 all-cause deaths (2.6% per year) occurred. After multivariable adjustment including eGFR, albuminuria, and urinary creatinine, none of the biomarkers showed statistically significant associations with CVD risk. Urinary IL-18 (hazard ratio [HR] per 2-fold higher value, 1.14; 95% CI 1.01-1.29) and YKL-40 (HR per 2-fold higher value, 1.08; 95% CI 1.02-1.14) concentrations were each incrementally associated with higher mortality risk. Associations were similar when stratified by randomized blood pressure arm.

CONCLUSIONS

Among hypertensive trial participants with CKD, higher urinary IL-18 and YKL-40 were associated with higher risk of mortality, but not CVD.

Frailty, body composition and the risk of mortality in incident hemodialysis patients: the Predictors of Arrhythmic and Cardiovascular Risk in End Stage Renal Disease study

Background

Frail obese community-dwelling older adults are at increased mortality risk. Among hemodialysis (HD) patients, frailty is common and associated with increased mortality risk; however, in dialysis, obesity is associated with decreased mortality risk. Whether the frail-obese phenotype is associated with increased mortality risk among HD patients remains unclear.

Methods

This study included 370 incident HD patients enrolled in the Predictors of Arrhythmic and Cardiovascular Risk in End Stage Renal Disease (PACE) study. We measured frailty using the Fried phenotype, general obesity [body mass index (BMI) ≥30 kg/m2] and abdominal obesity [waist:hip ratio (WHR) ≥median WHR] and estimated their associations with mortality.

Results

The mean age was 55 years, with 42% female, 73% African American, 57% diabetic and 52% frail. Frail HD patients had higher mean BMI (frail = 30.3 kg/m2, non-frail = 28.3 kg/m2; P = 0.02) and similar WHR (P = 0.8). Twenty-two percent were frail with general obesity and 27% were frail with abdominal obesity. Frailty was associated with 1.66-fold increased mortality risk [95% confidence interval (CI) 1.03-2.67]. BMI was associated with a decreased mortality risk [25.0-29.9 kg/m2 hazard ratio (HR) 0.53 (95% CI 0.31-0.93); ≥30 kg/m2 HR 0.34 (95% CI 0.19-0.62)]. Frailty was associated with elevated mortality risk among HD patients with general [HR 3.77 (95% CI 1.10-12.92)] and abdominal obesity [HR 2.38 (95% CI 1.17-4.82)]. Frailty was not associated with mortality among HD patients without general or abdominal obesity.

Conclusions

In adults initiating HD, frailty was associated with elevated mortality risk, even among the obese. Frail-obese HD patients may be a high-risk, often-overlooked population, as obesity is assumed to be protective. Measurement of frailty and obesity may facilitate risk stratification.

Kidney disease risk factors associate with urine biomarkers concentrations in HIV-positive persons; a cross-sectional study

Background

HIV-positive persons bear an excess burden of chronic kidney disease (CKD); however, conventional methods to assess kidney health are insensitive and non-specific for detecting early kidney injury. Urinary biomarkers can detect early kidney injury, and may help mitigate the risk of overt CKD.

Methods

Cross-sectional study of HIV-positive persons in the Multicenter AIDS Cohort Study and the Women’s Interagency HIV Study. We measured levels of 14 biomarkers, capturing multiple dimensions of kidney injury. We then evaluated associations of known CKD risk factors with urine biomarkers using separate multivariable adjusted models for each biomarker.

Results

Of the 198 participants, one third were on HAART and virally suppressed. The vast majority (95%) had preserved kidney function as assessed by serum creatinine, with a median eGFR of 103 ml/min/1.73 m² (interquartile range (IQR): 88, 116). In our multivariable analyses, the associations of each CKD risk factor with urinary biomarker levels varied in magnitude. For example, HIV viral load was predominantly associated with elevations in interleukin(IL)-18, and albuminuria, while higher CD4 levels were associated with lower monocyte chemoattractant protein-1 (MCP-1) and β2-microglobulin. In contrast, older age was significantly associated with elevations in α1-microglobulin, kidney injury marker-1, clusterin, MCP-1, and chitinase-3-like protein-1 levels, as well as lower epidermal growth factor, and uromodulin levels.

Conclusions

Among HIV-positive persons, CKD risk factors are associated with unique and heterogeneous patterns of changes in urine biomarkers levels. Additional work is needed to develop parsimonious algorithms that integrate multiple biomarkers and clinical data to discern the risk of overt CKD and its progression.

Electronic supplementary material

The online version of this article (10.1186/s12882-018-1192-y) contains supplementary material, which is available to authorized users.

Association of Abdominal Adiposity with Cardiovascular Mortality in Incident Hemodialysis

BACKGROUND

The risk of cardiovascular mortality is high among adults with end-stage renal disease (ESRD) undergoing hemodialysis. Waist-to-hip ratio (WHR), a metric of abdominal adiposity, is a predictor of cardiovascular disease (CVD) and mortality in the general population; however, no studies have examined the association with CVD mortality, particularly sudden cardiac death (SCD), in incident hemodialysis.

METHODS

Among 379 participants incident (< 6 months) to hemodialysis enrolled in the Predictors of Arrhythmic and Cardiovascular Risk in ESRD study, we evaluated associations between WHR and risk of CVD mortality, SCD, and non-CVD mortality in Cox proportional hazards regression models.

RESULTS

At study enrollment, mean age was 55 years with 41% females, 73% African Americans, and 57% diabetics. Mean body mass index was 29.3 kg/m2, and mean WHR was 0.95. During a median follow-up time of 2.5 years, there were 35 CVD deaths, 15 SCDs, and 48 non-CVD deaths. Every 0.1 increase in WHR was associated with higher risk (hazard ratio [95% CI]) of CVD mortality (1.75 [1.06-2.86]) and SCD (2.45 [1.20-5.02]), but not non-CVD mortality (0.93 [0.59-1.45]), independently of demographics, body mass index, comorbidities, inflammation, and traditional CVD risk factors.

CONCLUSIONS

WHR is significantly associated with CVD mortality including SCD, independently of other CVD risk factors in incident hemodialysis. This simple, easily obtained bedside metric may be useful in dialysis patients for CVD risk stratification.

Association of Urinary Biomarkers of Kidney Injury with Estimated GFR Decline in HIV-Infected Individuals following Tenofovir Disoproxil Fumarate Initiation

BACKGROUND AND OBJECTIVES

Tenofovir disoproxil fumarate (tenofovir) is associated with elevated concentrations of biomarkers of kidney damage and dysfunction in individuals with HIV. The relationship of these kidney biomarkers with longitudinal kidney function decline is unknown.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We evaluated associations of 14 urinary biomarkers of kidney injury with changes in eGFR among 198 men and women with HIV who initiated tenofovir between 2009 and 2015 in the Multicenter AIDS Cohort Study and Women's Interagency HIV Study. Urinary biomarkers included albumin-to-creatinine ratio, α-1-microglobulin, β-2-microglobulin, cystatin C, kidney injury molecule-1 (KIM-1), IL-18, neutrophil gelatinase-associated lipocalin (NGAL), clusterin, osteopontin, uromodulin, monocyte chemoattractant protein-1, EGF, trefoil factor 3, and chitinase 3-like protein 1. We used multivariable linear mixed-effect models controlling for demographics, traditional kidney disease risk factors, and HIV-related risk factors to evaluate associations of baseline biomarkers with first-year changes in eGFR, and associations of year 1 and first-year change in biomarkers with changes in eGFR from year 1 to year 3. We used the least absolute shrinkage and selection operator method to identify a parsimonious set of biomarkers jointly associated with changes in eGFR.

RESULTS

Median eGFR before tenofovir initiation was 103 (interquartile range, 88-116) ml/min per 1.73 m2. During the first year of tenofovir use, eGFR decreased on average by 9.2 (95% confidence interval, 6.5 to 11.9) ml/min per 1.73 m2 and was stable afterward (decrease of 0.62; 95% confidence interval, -0.85 to 2.1 ml/min per 1.73 m2 per year). After multivariable adjustment, higher baseline β-2-microglobulin, KIM-1, and clusterin were associated with larger first-year eGFR declines, whereas higher baseline uromodulin was associated with a smaller eGFR decline. First-year increase in urinary cystatin C and higher year 1 IL-18 were associated with larger annual eGFR declines from year 1 to year 3. The parsimonious models identified higher pre-tenofovir clusterin and KIM-1, lower pre-tenofovir uromodulin, and higher year 1 IL-18 as jointly associated with larger eGFR declines.

CONCLUSIONS

Urinary biomarkers of kidney injury measured before and after tenofovir initiation are associated with subsequent changes in eGFR in individuals with HIV.

PODCAST

This article contains a podcast at https://www.asn-online.org/media/podcast/CJASN/2018_08_28_CJASNPodcast_18_9_S.mp3.

Obstructive Sleep Apnea Increases Sudden Cardiac Death in Incident Hemodialysis Patients

BACKGROUND

Mortality in end-stage renal disease (ESRD) occurs predominantly from cardiovascular disease (CVD) and sudden cardiac death (SCD). Obstructive sleep apnea (OSA) is characterized by periodic airflow limitation associated with sleep arousal and oxygen desaturation and is prevalent in patients with ESRD. Whether OSA increases the risk for SCD, cardiovascular and all-cause mortality among hemodialysis patients remains unknown.

METHODS

In a prospective cohort of 558 incident hemodialysis patients, we examined the association of OSA with all-cause mortality, cardiovascular mortality, and SCD using Cox proportional hazards models controlling for traditional CVD risk factors.

RESULTS

Sixty-six incident hemodialysis patients (12%) had OSA. Mean age (56 years) and percentage of males (56%) were identical in OSA and no-OSA groups. Fewer African Americans had OSA than non-African Americans (9 vs. 18%, respectively). Participants with OSA had higher body-mass index, Charlson comorbidity score, and left ventricular mass index and greater prevalence of diabetes and coronary artery disease. During 1,080 person-years of follow-up, 104 deaths occurred, 29% of which were cardiovascular. OSA was associated with a higher risk of all-cause mortality (HR 1.90 [95% CI 1.04-3.46]) and cardiovascular mortality (HR 3.62 [95% CI 1.36-9.66]) after adjusting for demographics and body-mass index. OSA was associated with a higher risk of SCD after adjusting for demographics (HR 3.28 [95% CI 1.12-9.57]) and multiple cardiovascular risk factors.

CONCLUSIONS

Incident hemodialysis patients with OSA are at increased risk of all-cause and cardiovascular mortality and SCD. Future studies should assess the impact of screening for OSA and OSA-targeted interventions on mortality in ESRD.

Plasma glucosylceramides and cardiovascular risk in incident hemodialysis patients

BACKGROUND

Recent population-based studies identified plasma sphingolipids as independent predictors of increased cardiovascular disease (CVD) morbidity and mortality. Understanding the impact of sphingolipids on CVD outcomes in patients on dialysis, who suffer from higher risk of these conditions, is important for risk assessment and treatment.

OBJECTIVE

To measure plasma sphingolipid levels and determine their associations with CVD in adults initiating maintenance hemodialysis.

METHODS

To evaluate associations of plasma sphingolipids with intermediate cardiovascular outcomes (hypertension, left ventricular hypertrophy, and decreased ejection fraction), cardiovascular mortality, and all-cause mortality in patients with end-stage renal disease, we measured plasma levels of ceramides, glucosylceramides, and lactosylceramides from the family of sphingolipids in 368 incident hemodialysis patients enrolled in the Predictors of Arrhythmic and Cardiovascular Risk in End-Stage Renal Disease study.

RESULTS

Glucosylceramide C16GC (per 1 log μM increase) was associated with higher odds of having uncontrolled hypertension (odds ratio [OR]: 1.34; 95% confidential interval [CI]: 1.01-1.76), left ventricular hypertrophy (OR: 1.53; 95% CI: 1.11-2.13), and reduced ejection fraction (OR: 1.05; 95% CI: 1.00-1.11) in fully adjusted models. During a median 2.5 years of follow-up, there were 78 deaths from all causes, of which 33 were from CVD. Mortality was higher among those in the highest tertile of C16GC for all causes (HR: 1.81; 95% CI: 1.02-3.22) and CVD (HR: 2.63, 95% CI: 1.08-6.55).

CONCLUSIONS

These results suggest that abnormal glycosphingolipid metabolism might contribute to increased CVD risk in end-stage renal disease.

The Expanding Role of APOL1 Risk in Chronic Kidney Disease and Cardiovascular Disease

Variants of the APOL1 gene, found primarily in individuals of African descent, are associated with various forms of kidney disease and kidney disease progression. Recent studies evaluating the association of APOL1 with cardiovascular disease have yielded conflicting results, and the potential role in cardiovascular disease remains unclear. In this review, we summarize the observational studies linking the APOL1 risk variants with chronic kidney and cardiovascular disease among persons of African descent.

Preventive nephrology in the era of "I" evidence: should we screen for chronic kidney disease?

In this issue, Ferguson and colleagues demonstrate that chronic kidney disease (CKD) screening in populations burdened with CKD may be cost effective. Whether we should screen for CKD, however, continues to be debated despite the availability of effective clinical strategies that mitigate the risks of CKD progression. This study highlights the need for pragmatic trials to test the effectiveness of early CKD detection combined with optimization of clinical management and calls for innovation to tackle CKD.

Association Between APOL1 Genotypes and Risk of Cardiovascular Disease in MESA (Multi-Ethnic Study of Atherosclerosis)

Background

APOL1 genetic variants confer an increased risk for kidney disease. Their associations with cardiovascular disease (CVD) are less certain. We aimed to compare the prevalence of subclinical CVD and incidence of atherosclerotic CVD and heart failure by APOL1 genotypes among self‐identified black participants of MESA (Multi‐Ethnic Study of Atherosclerosis).

Methods and Results

Cross‐sectional associations of APOL1 genotypes (high‐risk=2 alleles; low‐risk=0 or 1 allele) with coronary artery calcification, carotid‐intimal media thickness, and left ventricular mass were evaluated using logistic and linear regression. Longitudinal associations of APOL1 genotypes with incident myocardial infarction, stroke, coronary heart disease, and congestive heart failure were examined using Cox regression. We adjusted for African ancestry, age, and sex. We also evaluated whether hypertension or kidney function markers explained the observed associations. Among 1746 participants with APOL1 genotyping (mean age 62 years, 55% women, mean cystatin C–based estimated glomerular filtration rate 89 mL/min per 1.73 m², 12% with albuminuria), 12% had the high‐risk genotypes. We found no difference in prevalence or severity of coronary artery calcification, carotid‐intimal media thickness, or left ventricular mass by APOL1 genotypes. The APOL1 high‐risk group was 82% more likely to develop incident heart failure compared with the low‐risk group (95% confidence interval, 1.01–3.28). Adjusting for hypertension (hazard ratio, 1.80; 95% confidence interval, 1.00–3.24) but not markers of kidney function (hazard ratio, 1.86; 95% confidence interval, 1.03–3.35) slightly attenuated this association. The APOL1 high‐risk genotypes were not significantly associated with other clinical CVD outcomes.

Conclusions

Among blacks without baseline CVD, the APOL1 high‐risk variants may be associated with increased risk for incident heart failure but not subclinical CVD or incident clinical atherosclerotic CVD.

APOL1 Risk Variants, Incident Proteinuria, and Subsequent eGFR Decline in Blacks with Hypertension-Attributed CKD

BACKGROUND AND OBJECTIVES

The natural history of kidney disease among blacks who carry the APOL1 high-risk variants varies, with only a subgroup progressing to ESRD. We aimed to determine whether the APOL1 risk variants are associated with incident proteinuria in the context of hypertension-attributed CKD, and whether subsequent kidney function decline after the onset of proteinuria differs by APOL1 risk status.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Using Cox models, we studied the association between APOL1 risk status and incident proteinuria (defined as a doubling of urine protein-to-creatinine ratio to a level ≥0.22 g/g creatinine) among African-American Study of Kidney Disease and Hypertension (AASK) trial participants with APOL1 genotyping and without proteinuria at baseline.

RESULTS

Of the 480 participants in our study, 82 (17%) had the high-risk genotypes (2 alleles), and 254 (53%) developed proteinuria over a median follow-up of 6.8 years. At baseline, mean eGFR was lower in the APOL1 high-risk group compared with the low-risk group (0 or 1 allele; 49.6 versus 53.2 ml/min per 1.73 m2, respectively; P=0.02), but median proteinuria was similar (0.04 g/g creatinine for both groups; P=0.43). Individuals with the high-risk genotypes were 1.72-fold more likely to develop incident proteinuria compared with those with the low-risk genotypes (95% confidence interval, 1.27 to 2.32), independent of age, sex, ancestry, baseline eGFR, baseline systolic BP, and randomized treatment groups. Although eGFR declined faster after the onset of proteinuria, this rate did not differ significantly by APOL1 risk status.

CONCLUSIONS

Among blacks with established moderate CKD, the APOL1 high-risk variants are associated with greater risk of incident proteinuria. After proteinuria onset, kidney function declines more rapidly but does not differ by APOL1 risk status. This suggests that factors that lead to proteinuria, beyond APOL1, may additionally drive CKD progression.

Kidney Disease in HIV: Moving beyond HIV-Associated Nephropathy

In developed countries, remarkable advances in antiretroviral therapy have transformed HIV infection into a chronic condition. As a result, HIV-associated nephropathy, the classic HIV-driven kidney lesion among individuals of African descent, has largely disappeared in these regions. However, HIV-positive blacks continue to have much higher rates of ESRD than HIV-positive whites, which could be attributed to the APOL1 renal risk variants. Additionally, HIV-positive individuals face adverse consequences beyond HIV itself, including traditional risk factors for CKD and nephrotoxic effects of antiretroviral therapy. Concerns for nephrotoxicity also extend to HIV-negative individuals using tenofovir disoproxil fumarate-based pre-exposure prophylaxis for the prevention of HIV infection. Therefore, CKD remains an important comorbid condition in the HIV-positive population and an emerging concern among HIV-negative persons receiving pre-exposure prophylaxis. With the improved longevity of HIV-positive individuals, a kidney transplant has become a viable option for many who have progressed to ESRD. Herein, we review the growing knowledge regarding the APOL1 renal risk variants in the context of HIV infection, antiretroviral therapy-related nephrotoxicity, and developments in kidney transplantation among HIV-positive individuals.

Vitamin D Status and Kidney Function Decline in HIV-Infected Men: A Longitudinal Study in the Multicenter AIDS Cohort Study

Vitamin D may play an important role in a range of disease processes. In the general population, lower vitamin D levels have been associated with kidney dysfunction. HIV-infected populations have a higher risk of chronic kidney disease. Few studies have examined the link between lower vitamin D levels and kidney function decline among HIV-infected persons. We investigated the associations of serum 25-hydroxyvitamin D [25(OH)D] and 1,25-dihydroxyvitamin D [1,25(OH)2D] with kidney function decline in a cohort of HIV-infected white and black men under highly active antiretroviral therapy treatment in the vitamin D ancillary study of the Multicenter AIDS Cohort Study. The associations of 25(OH)D and 1,25(OH)2D with annual change in estimated glomerular filtration rate (eGFR) were evaluated using linear mixed effects models. This study included 187 whites and 86 blacks with vitamin D measures and eGFR ≥60 ml/min/1.73 m2 at baseline. Over a median follow-up of 8.0 years, lower 25(OH)D levels were significantly associated with faster eGFR decline in whites (adjusted annual change in eGFR, tertile 1: -2.06 ml/min/1.73 m2 vs. tertile 3: -1.23 ml/min/1.73 m2, p trend .03), while no significant association was detected in blacks. Lower 1,25(OH)2D was associated with faster kidney function decline in both whites and blacks, although the estimates were not statistically significant. In conclusion, lower 25(OH)D levels were significantly associated with faster eGFR decline in a cohort of HIV-infected white men, but not in those with black ancestry. Further research is warranted to investigate the association of 25(OH)D and 1,25(OH)2D with kidney function decline in larger and ethnically diverse populations.

APOL1 risk variants and death among African American hemodialysis patients: survival of the fittest?

Recent studies have focused on associations of the APOL1 risk variants with outcomes beyond kidney disease, including cardiovascular disease and mortality. Ma and colleagues now expand on this growing but contradicting body of work. Their analysis of a prevalent cohort of African American hemodialysis patients shows that the risk variants are associated with a survival benefit among nondiabetics. Whether this simply reflects a healthier status at hemodialysis initiation among those carrying 2 risk variants or whether these variants truly confer a survival advantage is unclear.

APOL1 genetic variants are not associated with longitudinal blood pressure in young black adults

Whether APOL1 polymorphisms contribute to the excess risk of hypertension among blacks is unknown. To assess this we evaluated whether self-reported race and, in blacks, APOL1 risk variants (high-risk [2 risk alleles] versus low-risk [0-1 risk allele]) were associated with longitudinal blood pressure. Blood pressure trajectories were determined using linear mixed-effects (slope) and latent class models (5 distinct groups) during 25 years of follow-up in the Coronary Artery Risk Development in Young Adults Study. Associations of race and APOL1 genotypes with blood pressure change, separately, using linear mixed-effects and multinomial logistic regression models, adjusting for demographic, socioeconomic, and traditional hypertension risk factors, anti-hypertensive medication use, and kidney function were evaluated. Among 1700 whites and 1330 blacks (13% APOL1 high-risk, mean age 25 years; 46% male) mean mid-, ([systolic + diastolic blood pressure]/2), systolic, and diastolic blood pressures were 89, 110, and 69 mm Hg, respectively. One percent of participants used anti-hypertensive medications at baseline. Compared to whites, blacks, regardless of APOL1 genotype, had significantly greater increases in mid-blood pressure and were more likely to experience significantly increasing mid-blood pressure trajectories with adjusted relative risk ratios of 5.21 and 7.27 for moderate-increasing and elevated-increasing versus low-stable blood pressure, respectively. Among blacks, longitudinal mid-blood pressure changes and mid-blood pressure trajectory classification were similar by APOL1 risk status. Modeling systolic and diastolic blood pressure as outcomes yielded similar findings. From young adulthood to mid-life, blacks have greater blood pressure increases versus whites that are not fully explained by traditional risk factors. Thus APOL1 variants are not associated with longitudinal blood pressure in blacks.

Predictors of Acute Renal Injury Study (PARIS) among HIV-positive individuals: design and methods

Background

Acute kidney injury (AKI), which is common among HIV-positive individuals, may contribute to the excess burden of chronic kidney disease (CKD) in this patient population; however, conventional clinical methods to detect AKI do not capture kidney injury sufficiently early to prevent irreversible damage. Further, large observational and interventional studies of AKI generally exclude HIV-positive persons in spite of their disproportionate risk.

Methods

The Predictors of Acute Renal Injury Study (PARIS) is a prospective observational cohort study among HIV-positive individuals established to determine the ability of candidate kidney injury biomarkers to predict future hospitalized clinical AKI, to characterize hospitalized subclinical AKI, and to discern the risk of progressive kidney disease following subclinical and clinical AKI. Among the candidate kidney injury markers, we will select the most promising to translate into a clinically viable, multiplex panel of urinary biomarkers which we will integrate with clinical factors to develop a model prognostic of risks for AKI and subsequent kidney function decline. This study has a targeted enrollment of 2000 participants. The overall follow-up of participants consists of two phases: 1) a 5-year active follow-up phase which involves serial evaluations at enrollment, annual clinic visits, and among participants who are hospitalized during this period, an evaluation at index hospitalization and 3 and 12 months post-hospitalization; and 2) a subsequent passive follow-up phase for the duration that the participant receives medical care at The Johns Hopkins Hospital.

Discussions

This study will serve as an important resource for future studies of AKI by establishing a repository with both ambulatory and inpatient biospecimens, a resource that is currently lacking in existing HIV clinical cohorts and studies of AKI. Upon completion of this study, the resulting prognostic model which will incorporate results from the multiplex HIV-AKI Risk Pane could serve as a pharmacodynamic endpoint for early phase therapeutic candidates for AKI.

Association of Arterial Stiffness and Central Pressure With Cognitive Function in Incident Hemodialysis Patients: The PACE Study

Introduction

Cognitive impairment commonly occurs in hemodialysis patients, with vascular disease potentially implicated in its pathogenesis. However, the relationship of detailed vascular assessment with cognitive function in patients new to hemodialysis has not been demonstrated.

Methods

In a prospective study of incident hemodialysis participants enrolled in the Predictors of Arrhythmic and Cardiovascular Risk in ESRD (PACE) study, we determined aortic stiffness by pulse-wave velocity (PWV), systemic arterial stiffness by the augmentation index (AIx) and central pulse pressure (cPP), and examined their associations with cognitive processing speed, executive function, and global cognitive impairment measured by the Trail making test A (TMTA), Trail making test B (TMTB), and the modified Mini-Mental State Exam (3MS).

Results

Mean baseline age was 55 ± 13 years, 58% were male, 72% were African American, 35% had coronary artery disease, 55% had diabetes, and 10% had cognitive impairment. At baseline, higher PWV and cPP were associated with a longer TMTA, and a higher PWV was associated with a longer TMTB, but the associations were attenuated after multivariable adjustment. At 1 year, PWV was not independently associated with TMTA, TMTB, or 3MS. However, unadjusted and adjusted analyses revealed every 10% increase in AIx and 10 mm Hg increase in cPP were associated with longer TMTB (time difference_AIx: 0.14; 95% confidence interval [CI]: 0.02−0.25 log-seconds; time difference_cPP: 0.11; 95% CI: 0.05−0.17 log-seconds) and global cognitive impairment (odds ratio [OR]_AIx: 10.23; 95% CI: 1.77−59.00; OR_cPP: 2.88; 95% CI: 1.48−5.59).

Discussion

Higher AIx and cPP, which are indicative of abnormal wave reflections in distal vessels, are associated with, and might contribute to, declining cognitive function in patients starting hemodialysis.

The Loss of GSTM1 Associates with Kidney Failure and Heart Failure

Glutathione S-transferase mu 1 (GSTM1) encodes an enzyme that catalyzes the conjugation of electrophilic compounds with glutathione to facilitate their degradation or excretion. The loss of one or both copies of GSTM1 is common in many populations and has been associated with CKD progression. With the hypothesis that the loss of GSTM1 is also associated with incident kidney failure and heart failure, we estimated GSTM1 copy number using exome sequencing reads in the Atherosclerosis Risk in Communities (ARIC) Study, a community-based prospective cohort of white and black participants. Overall, 51.2% and 39.8% of white participants and 25.6% and 48.5% of black participants had zero or one copy of GSTM1, respectively. Over a median follow-up of 24.6 years, 256 kidney failure events occurred in 5715 participants without prevalent kidney failure, and 1028 heart failure events occurred in 5368 participants without prevalent heart failure. In analysis adjusted for demographics, diabetes, and hypertension, having zero or one copy of GSTM1 associated with higher risk of kidney failure and heart failure (adjusted hazard ratio [95% confidence interval] for zero or one versus two copies of GSTM1: kidney failure, 1.66 [1.27 to 2.17]; heart failure, 1.16 [1.04 to 1.29]). Risk did not differ significantly between participants with zero and one copy of GSTM1 (P>0.10). In summary, the loss of GSTM1 was significantly associated with incident kidney and heart failure, independent of traditional risk factors. These results suggest GSTM1 function is a potential treatment target for the prevention of kidney and heart failure.