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

Urine Biomarkers of Kidney Tubule Health and Risk of Incident CKD in Persons Without Diabetes: The ARIC, MESA, and REGARDS Studies

Rationale & Objective

Tubulointerstitial damage is a feature of early chronic kidney disease (CKD), but current clinical tests capture it poorly. Urine biomarkers of tubulointerstitial health may identify risk of CKD.

Study Design

Prospective cohort (Atherosclerosis Risk in Communities [ARIC]) and case-cohort (Multi-Ethnic Study of Atherosclerosis [MESA] and Reasons for Geographic and Racial Differences in Stroke [REGARDS]).

Setting & Participants

Adults with estimated glomerular filtration rate (eGFR) ≥60 mL/min/1.73 m2 and without diabetes in the ARIC, REGARDS, and MESA studies.

Exposures

Baseline urine monocyte chemoattractant protein-1 (MCP-1), alpha-1-microglobulin (α1m), kidney injury molecule-1, epidermal growth factor, and chitinase-3-like protein 1.

Outcome

Incident CKD or end-stage kidney disease.

Analytical Approach

Multivariable Cox proportional hazards regression for each cohort; meta-analysis of results from all 3 cohorts.

Results

872 ARIC participants (444 cases of incident CKD), 636 MESA participants (158 cases), and 924 REGARDS participants (488 cases) were sampled. Across cohorts, mean age ranged from 60 ± 10 to 63 ± 8 years, and baseline eGFR ranged from 88 ± 13 to 91 ± 14 mL/min/1.73 m2. In ARIC, higher concentrations of urine MCP-1, α1m, and kidney injury molecule-1 were associated with incident CKD. In MESA, higher concentration of urine MCP-1 and lower concentration of epidermal growth factor were each associated with incident CKD. In REGARDS, none of the biomarkers were associated with incident CKD. In meta-analysis of all 3 cohorts, each 2-fold increase α1m concentration was associated with incident CKD (HR, 1.19; 95% CI, 1.08-1.31).

Limitations

Observational design susceptible to confounding; competing risks during long follow-up period; meta-analysis limited to 3 cohorts.

Conclusions

In 3 combined cohorts of adults without prevalent CKD or diabetes, higher urine α1m concentration was independently associated with incident CKD. 4 biomarkers were associated with incident CKD in at least 1 of the cohorts when analyzed individually. Kidney tubule health markers might inform CKD risk independent of eGFR and albuminuria.

Mediation analysis of chronic kidney disease risk factors using kidney biomarkers in women living with HIV

OBJECTIVE

Novel urinary biomarkers reflecting kidney tubule health are associated with chronic kidney disease (CKD) risk in persons living with HIV. However, it is unknown whether these biomarkers provide mechanistic insight into the associations between clinical risk factors for CKD and subsequent CKD risk.

METHODS

Among 636 women living with HIV in the Women's Interagency HIV Study with estimated glomerular filtration rate (eGFR) >60 ml/min/1.73 m 2 , we used a counterfactual approach to causal mediation analysis to evaluate the extent to which systolic blood pressure (SBP), diastolic blood pressure (DBP), hemoglobin a1c (Hba1c) and serum albumin associations with incident CKD were mediated by eight urine proteins. These biomarkers reflect proximal tubular reabsorptive dysfunction (α1-microglobulin [a1m], β2-microglobulin, trefoil factor 3); tubular injury (interleukin 18 [IL-18], kidney injury molecule 1 [KIM-1]); kidney repair (epidermal growth factor); tubular reserve (uromodulin); and glomerular injury (urinary albumin). Incident CKD was defined as eGFR <60 ml/min/1.73 m 2 measured at two consecutive 6-month visits with an average annual eGFR decline ≥3% per year.

RESULTS

During a median follow-up of 7 years, 11% developed CKD. Urinary albumin and KIM-1 mediated 32% (95% CI: 13.4%, 76.6%) and 23% (6.9%, 60.7%) of the association between SBP and incident CKD, respectively; and 19% (5.1%, 42.3%) and 22% (8.1%, 45.7%) of the association between DBP and incident CKD, respectively. Urinary albumin, α1m, and IL-18 were significant mediators of the association between Hba1c and incident CKD. None of the eight biomarkers mediated the association between serum albumin and incident CKD.

CONCLUSIONS

Among women living with HIV, several urinary biomarkers reflecting distinct dimensions of kidney health may partially explain the associations between SBP, DBP, and Hba1c and subsequent CKD risk.

Association of urine biomarkers of kidney health with subclinical cardiovascular disease among men with and without HIV

OBJECTIVE

The aim of this study was to determine whether urine biomarkers of kidney health are associated with subclinical cardiovascular disease among men with and without HIV.

DESIGN

A cross-sectional study within the Multicenter AIDS Cohort Study (MACS) among 504 men with and without HIV infection who underwent cardiac computed tomography scans and had urine biomarkers measured within the preceding 2 years.

METHODS

Our primary predictors were four urine biomarkers of endothelial (albuminuria), proximal tubule dysfunction (alpha-1-microglobulin [A1 M] and injury (kidney injury molecule-1 [KIM-1]) and tubulointerstitial fibrosis (pro-collagen-III N-terminal peptide [PIIINP]). These were evaluated for association with coronary artery calcium (CAC) prevalence, CAC extent, total plaque score, and total segment stenosis using multivariable regression.

RESULTS

Of the 504 participants, 384 were men with HIV (MWH) and 120 were men without HIV. In models adjusted for sociodemographic factors, cardiovascular disease risk factors, eGFR, and HIV-related factors, each two-fold higher concentration of albuminuria was associated with a greater extent of CAC (1.35-fold higher, 95% confidence interval 1.11-1.65), and segment stenosis (1.08-fold greater, 95% confidence interval 1.01-1.16). Associations were similar between MWH and men without HIV in stratified analyses. The third quartile of A1 M showed an association with greater CAC extent, total plaque score, and total segment stenosis, compared with the lowest quartile.

CONCLUSION

Worse endothelial and proximal tubule dysfunction, as reflected by higher urine albumin and A1 M, were associated with greater CAC extent and coronary artery stenosis.

Ambulatory urine biomarkers associations with acute kidney injury and hospitalization in people with HIV

BACKGROUND

People with HIV (PWH) generally have worse ambulatory levels of kidney injury biomarkers and excess risk of acute kidney injury (AKI) compared to persons without HIV. We evaluated whether ambulatory measures of subclinical kidney injury among PWH are associated with subsequent AKI.

METHODS

In the Predictors of Acute Renal Injury Study (PARIS), which enrolled 468 PWH from April 2016 to August 2019, we measured 10 urine biomarkers of kidney health (albumin, a1m, b2M, NGAL, IL18, KIM-1, EGF, UMOD, MCP-1, YKL40) at baseline and annually during follow-up. Using multivariable Cox regression models, we evaluated baseline and time-updated biomarker associations with the primary outcome of AKI (≥0.3 mg/dl or ≥1.5-times increase in serum creatinine from baseline) and secondary outcome of all-cause hospitalization.

RESULTS

At baseline, the mean age was 53 years old, and 45% self-identified as female. In time-updated models adjusting for sociodemographic factors, comorbidities, albuminuria, estimated glomerular filtration rate, and HIV-associated factors, higher KIM-1 [hazard ratio (HR) = 1.30 per twofold higher; 95% confidence interval (CI) 1.03-1.63] and NGAL concentrations (HR = 1.24, 95% CI 1.06-1.44) were associated with higher risk of hospitalized AKI. Additionally, in multivariable, time-updated models, higher levels of KIM-1 (HR = 1.19, 95% CI 1.00, 1.41), NGAL (HR = 1.13, 95% CI 1.01-1.26), and MCP-1 (HR = 1.20, 95% CI 1.00, 1.45) were associated with higher risk of hospitalization.

CONCLUSIONS

Urine biomarkers of kidney tubular injury, such as KIM-1 and NGAL, are strongly associated with AKI among PWH, and may hold potential for risk stratification of future AKI.

Urine Alpha-1-Microglobulin Levels and Acute Kidney Injury, Mortality, and Cardiovascular Events following Cardiac Surgery

INTRODUCTION

Urine alpha-1-microglobulin (Uα1m) elevations signal proximal tubule dysfunction. In ambulatory settings, higher Uα1m is associated with acute kidney injury (AKI), progressive chronic kidney disease (CKD), cardiovascular (CV) events, and mortality. We investigated the associations of pre- and postoperative Uα1m concentrations with adverse outcomes after cardiac surgery.

METHODS

In 1,464 adults undergoing cardiac surgery in the prospective multicenter Translational Research Investigating Biomarker Endpoints for Acute Kidney Injury (TRIBE-AKI) cohort, we measured the pre-and postoperative Uα1m concentrations and calculated the changes from pre- to postoperative concentrations. Outcomes were postoperative AKI during index hospitalization and longitudinal risks for CKD incidence and progression, CV events, and all-cause mortality after discharge. We analyzed Uα1m continuously and categorically by tertiles using multivariable logistic regression and Cox proportional hazards regression adjusted for demographics, surgery characteristics, comorbidities, baseline estimated glomerular filtration rate, urine albumin, and urine creatinine.

RESULTS

There were 230 AKI events during cardiac surgery hospitalization; during median 6.7 years of follow-up, there were 212 cases of incident CKD, 54 cases of CKD progression, 269 CV events, and 459 deaths. Each 2-fold higher concentration of preoperative Uα1m was independently associated with AKI (adjusted odds ratio [aOR] = 1.36, 95% confidence interval 1.14-1.62), CKD progression (adjusted hazard ratio [aHR] = 1.46, 1.04-2.05), and all-cause mortality (aHR = 1.19, 1.06-1.33) but not with incident CKD (aHR = 1.21, 0.96-1.51) or CV events (aHR = 1.01, 0.86-1.19). Postoperative Uα1m was not associated with AKI (aOR per 2-fold higher = 1.07, 0.93-1.22), CKD incidence (aHR = 0.90, 0.79-1.03) or progression (aHR = 0.79, 0.56-1.11), CV events (aHR = 1.06, 0.94-1.19), and mortality (aHR = 1.01, 0.92-1.11).

CONCLUSION

Preoperative Uα1m concentrations may identify patients at high risk of AKI and other adverse events after cardiac surgery, but postoperative Uα1m concentrations do not appear to be informative.

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.

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.

The utility of kidney injury molecule-1 as an early biomarker of kidney injury in people living with HIV

There are increasing reports of antiretroviral therapy (ART) drug-related kidney dysfunction. Traditional markers of kidney dysfunction such as urine protein/creatinine ratio and estimated glomerular filtration rate (eGFR) have thus far proven ineffective at detecting some sub-clinical forms of ART-related kidney injury. This is a cross-sectional examination of 114 people living with HIV (PLWH), either naïve (N =104) or treatment experienced (N =10). Urinary kidney injury molecule-1 (KIM-1 ng/mg) thresholds were estimated using electrochemiluminescent assays from stored urine samples and normalised for urinary creatinine excretion (KIM-1/Cr). Correlation coefficients and predictors of kidney tubular injury were compared and derived for both adjusted and unadjusted urinary KIM-1/CR (ng/mg). In PLWH (both ART-naïve and treatment experienced) had a higher baseline unadjusted and adjusted median (≥3.7 ng/mg) and upper tertile (≥6.25 ng/mg) urinary KIM-1/Cr levels compared to either non-normal volunteers (0.39 ng/mg) or those with acute kidney injury in the general population (0.57 ng/mg). When upper tertile KIM-1/Cr (≥6.25 ng/mg) was utilised as a marker of kidney injury, eGFR (ml/min/1.73 m²), white Caucasian ethnicity, and protease inhibitor exposure were significantly associated with increased risk of kidney injury in multivariate analyses (odds ratio 0.91, confidence interval [CI] 0.68–0.98, P = 0.02; odds ratio 8.9, CI 1.6–48.6, p = 0.01; and odds ratio 0.05, CI 0.03–0.9, p =0.04, respectively). We found a significant degree of sub-clinical kidney injury (high unadjusted and adjusted KIM-1/Cr) in PLWH with normal kidney function (eGFR ≥60 ml/min/1.73 m²). We also found a higher baseline KIM-1/Cr (ng/mg) in our study cohort than reported both in normal volunteers and patients with kidney injury in the general population.

Cystatin C and Urine Albumin to Creatinine Ratio Predict 5-Year Mortality and Cardiovascular Events in People Living With HIV

BACKGROUND

Identifying people with HIV (PWH) at risk for chronic kidney disease, cardiovascular events, and death is crucial. We evaluated biomarkers to predict all-cause mortality and cardiovascular events, and measured glomerular filtration rate (mGFR) slope.

METHODS

Biomarkers were measured at enrollment. Baseline and 5-year mGFR were measured by plasma iohexol clearance. Outcomes were a composite criterion of all-cause mortality and/or cardiovascular events, and mGFR slope.

RESULTS

Of 168 subjects, 146 (87.4%) had undetectable HIV load. Median follow-up was 59.1 months (interquartile range, 56.2-62.1). At baseline, mean age was 49.5 years (± 9.8) and mean mGFR 98.9 mL/min/1.73m2 (± 20.6). Seventeen deaths and 10 cardiovascular events occurred during 5-year follow-up. Baseline mGFR was not associated with mortality/cardiovascular events. In multivariable analysis, cystatin C (hazard ratio [HR], 5.978; 95% confidence interval [CI], 2.774-12.88; P < .0001) and urine albumin to creatinine ratio (uACR) at inclusion (HR, 1.002; 95% CI, 1.001-1.004; P < .001) were associated with mortality/cardiovascular events. Area under receiver operating curve of cystatin C was 0.67 (95% CI, .55-.79) for mortality/cardiovascular event prediction. Biomarkers were not associated with GFR slope.

CONCLUSIONS

uACR and cystatin C predict all-cause mortality and/or cardiovascular events in PWH independently of mGFR.

Elevated cardiac risk score by Atherosclerotic Cardiovascular Disease calculation is associated with albuminuria in older people living with HIV

: Globally, the proportion of older people living with HIV (PLWH) is growing and the burden of noncommunicable diseases, including cardiac and renal disease, is increasing. There are few studies of renal disease and cardiac risk in older PLWH. This study investigates the relationship between albuminuria and cardiac risk as estimated by the Atherosclerotic Cardiovascular Disease 10-year risk calculator. We report that albuminuria is associated with a higher Atherosclerotic Cardiovascular Disease risk score in both diabetic and nondiabetic older PLWH.

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.

Management of Presumed Acute Kidney Injury during Hypertensive Therapy: Stay Calm and Carry on?

BACKGROUND

Recent studies have demonstrated that intensive blood pressure control is associated with improved cardiovascular outcomes. Acute kidney injury (AKI), however, was more common in the intensive treatment group prompting concern in the nephrology community.

SUMMARY

Clinical trials on hypertension control have traditionally defined AKI by changes in serum creatinine. However, serum creatinine has several inherent limitations as a marker of kidney injury, with various factors influencing its production, secretion, and elimination. Urinary biomarkers of kidney injury and repair have the potential to provide insight on the presence and phenotype of kidney injury. In both the Systolic Blood Pressure Intervention Trial and the Action to Control Cardiovascular Risk in Diabetes study, urinary biomarkers have suggested that the increased risk of AKI associated with intensive treatment was due to hemodynamic changes rather than structural kidney injury. As such, clinicians who encounter rises in serum creatinine during intensification of hypertension therapy should "stay calm and carry on." Alternative explanations for serum creatinine elevation should be considered and addressed if appropriate. When the rise in serum creatinine is limited, particularly if albuminuria is stable or improving, intensive blood pressure control should be continued for its potential long-term benefits. Key Messages: Increases in serum creatinine during intensification of blood pressure control may not necessarily reflect kidney injury. Clinicians should evaluate for other contributing factors before stopping therapy. Urinary biomarkers may address limitations of serum creatinine as a marker of kidney injury.