Mitochondrial genetic variation and risk of chronic kidney disease and acute kidney injury in UK Biobank participants.

Experimental models suggest an important role for mitochondrial dysfunction in the pathogenesis of chronic kidney disease (CKD) and acute kidney injury (AKI), but little is known regarding the impact of common mitochondrial genetic variation on kidney health. We sought to evaluate associations of inherited mitochondrial DNA (mtDNA) variation with risk of CKD and AKI in a large population-based cohort. We categorized UK Biobank participants who self-identified as white into eight distinct mtDNA haplotypes, which were previously identified based on their associations with phenotypes associated with mitochondrial DNA copy number, a measure of mitochondrial function. We used linear and logistic regression models to evaluate associations of these mtDNA haplotypes with estimated glomerular filtration rate by serum creatinine and cystatin C (eGFRCr-CysC, N = 362,802), prevalent (N = 416 cases) and incident (N = 405 cases) end-stage kidney disease (ESKD), AKI defined by diagnostic codes (N = 14,170 cases), and urine albumin/creatinine ratio (ACR, N = 114,662). The mean age was 57 ± 8 years and the mean eGFR was 90 ± 14 ml/min/1.73 m2. MtDNA haplotype was significantly associated with eGFR (p = 2.8E-12), but not with prevalent ESKD (p = 5.9E-2), incident ESKD (p = 0.93), AKI (p = 0.26), or urine ACR (p = 0.54). The association of mtDNA haplotype with eGFR remained significant after adjustment for diabetes mellitus and hypertension (p = 1.2E-10). When compared to the reference haplotype, mtDNA haplotypes I (ß = 0.402, standard error (SE) = 0.111; p = 2.7E-4), IV (ß = 0.430, SE = 0.073; p = 4.2E-9), and V (ß = 0.233, SE = 0.050; p = 2.7E-6) were each associated with higher eGFR. Among self-identified white UK Biobank participants, mtDNA haplotype was associated with eGFR, but not with ESKD, AKI or albuminuria.

Kidney Transplant Outcomes From Deceased Donors Who Received Dialysis.

Importance: Recipient outcomes after kidney transplant from deceased donors who received dialysis prior to kidney donation are not well described. Objective: To compare outcomes of transplant recipients who received kidneys from deceased donors who underwent dialysis prior to kidney donation vs recipients of kidneys from deceased donors who did not undergo dialysis. Design, Setting, and Participants: A retrospective cohort study was conducted including data from 58 US organ procurement organizations on deceased kidney donors and kidney transplant recipients. From 2010 to 2018, 805 donors who underwent dialysis prior to kidney donation were identified. The donors who underwent dialysis prior to kidney donation were matched 1:1 with donors who did not undergo dialysis using a rank-based distance matrix algorithm; 1944 kidney transplant recipients were evaluated. Exposure: Kidney transplants from deceased donors who underwent dialysis prior to kidney donation compared with kidney transplants from deceased donors who did not undergo dialysis. Main Outcomes and Measures: The 4 study outcomes were delayed graft function (defined as receipt of dialysis by the kidney recipient ≤1 week after transplant), all-cause graft failure, death-censored graft failure, and death. Results: From 2010 to 2018, 1.4% of deceased kidney donors (805 of 58 155) underwent dialysis prior to kidney donation. Of these 805 individuals, 523 (65%) donated at least 1 kidney. A total of 969 kidneys (60%) were transplanted and 641 kidneys (40%) were discarded. Among the donors with kidneys transplanted, 514 (mean age, 33 years [SD, 10.8 years]; 98 had hypertension [19.1%] and 36 had diabetes [7%]) underwent dialysis prior to donation and were matched with 514 (mean age, 33 years [SD, 10.9 years]; 98 had hypertension [19.1%] and 36 had diabetes [7%]) who did not undergo dialysis. Kidney transplants from donors who received dialysis prior to donation (n = 954 kidney recipients) were associated with a higher risk of delayed graft function compared with kidney transplants from donors who did not receive dialysis (n = 990 kidney recipients) (59.2% vs 24.6%, respectively; adjusted odds ratio, 4.17 [95% CI, 3.28-5.29]). The incidence rates did not significantly differ at a median follow-up of 34.1 months for all-cause graft failure (43.1 kidney transplants per 1000 person-years from donors who received dialysis prior to donation vs 46.9 kidney transplants per 1000 person-years from donors who did not receive dialysis; adjusted hazard ratio [HR], 0.90 [95% CI, 0.70-1.15]), for death-censored graft failure (22.5 vs 20.6 per 1000 person-years, respectively; adjusted HR, 1.18 [95% CI, 0.83-1.69]), or for death (24.6 vs 30.8 per 1000 person-years; adjusted HR, 0.76 [95% CI, 0.55-1.04]). Conclusions and Relevance: Compared with receiving a kidney from a deceased donor who did not undergo dialysis, receiving a kidney from a deceased donor who underwent dialysis prior to kidney donation was associated with a significantly higher incidence of delayed graft function, but no significant difference in graft failure or death at follow-up.

Untargeted metabolomics of perfusate and their association with hypothermic machine perfusion and allograft failure.

Although hypothermic machine perfusion (HMP) is associated with improved kidney graft viability and function, the underlying biological mechanisms are unknown. Untargeted metabolomic profiling may identify potential metabolites and pathways that can help assess allograft viability and contribute to organ preservation. Therefore, in this multicenter study, we measured all detectable metabolites in perfusate collected at the beginning and end of deceased-donor kidney perfusion and evaluated their associations with graft failure. In our cohort of 190 kidney transplants, 33 (17%) had death-censored graft failure over a median follow-up of 5.0 years (IQR 3.0-6.1 years). We identified 553 known metabolites in perfusate and characterized their experimental and biological consistency through duplicate samples and unsupervised clustering. After perfusion-time adjustment and false discovery correction, six metabolites in post-HMP perfusate were significantly associated with death-censored graft failure, including alpha-ketoglutarate, 3-carboxy-4-methyl-5-propyl-2-furanpropanoate, 1-carboxyethylphenylalanine, and three glycerol-phosphatidylcholines. All six metabolites were associated with an increased risk of graft failure (Hazard Ratio per median absolute deviation range 1.04-1.45). Four of six metabolites also demonstrated significant interaction with donation after cardiac death with notably greater risk in the donation after cardiac death group (Hazard Ratios up to 1.69). Discarded kidneys did not have significantly different levels of any death-censored graft failure-associated metabolites. On interrogation of pathway analysis, production of reactive oxygen species and increased metabolism of fatty acids were upregulated in kidneys that subsequently developed death-censored graft failure. Thus, further understanding the role of these metabolites may inform the HMP process and help improve the objective evaluation of allograft offers, thereby reducing the discard of potentially viable organs.

The ASSESS-AKI Study found urinary epidermal growth factor is associated with reduced risk of major adverse kidney events.

Biomarkers of tubular function such as epidermal growth factor (EGF) may improve prognostication of participants at highest risk for chronic kidney disease (CKD) after hospitalization. To examine this, we measured urinary EGF (uEGF) from samples collected in the Assessment, Serial Evaluation, and Subsequent Sequelae of Acute Kidney Injury (ASSESS-AKI) Study, a multi-center, prospective, observational cohort of hospitalized participants with and without AKI. Cox proportional hazards regression was used to investigate the association of uEGF/Cr at hospitalization, three months post-discharge, and the change between these time points with major adverse kidney events (MAKE): CKD incidence, progression, or development of kidney failure. Clinical findings were paired with mechanistic studies comparing relative Egf expression in mouse models of kidney atrophy or repair after ischemia-reperfusion injury. MAKE was observed in 20% of 1,509 participants over 4.3 years of follow-up. Each 2-fold higher level of uEGF/Cr at three months was associated with decreased risk of MAKE (adjusted hazards ratio 0.46, 95% confidence interval: 0.39-0.55). Participants with the highest increase in uEGF/Cr from hospitalization to three-month follow-up had a lower risk of MAKE (adjusted hazards ratio 0.52; 95% confidence interval: 0.36-0.74) compared to those with the least change in uEGF/Cr. A model using uEGF/Cr at three months combined with clinical variables yielded moderate discrimination for MAKE (area under the curve 0.73; 95% confidence interval: 0.69-0.77) and strong discrimination for kidney failure at four years (area under the curve 0.96; 95% confidence interval: 0.92-1.00). Accelerated restoration of Egf expression in mice was seen in the model of adaptive repair after injury, compared to a model of progressive atrophy. Thus, urinary EGF/Cr may be a biomarker of distal tubular health, with higher concentrations and increased uEGF/Cr post-discharge independently associated with reduced risk of MAKE in hospitalized patients.

Deceased-Donor Acute Kidney Injury and Acute Rejection in Kidney Transplant Recipients: A Multicenter Cohort.

RATIONALE & OBJECTIVE: Donor acute kidney injury (AKI) activates innate immunity, enhances HLA expression in the kidney allograft, and provokes recipient alloimmune responses. We hypothesized that injury and inflammation that manifested in deceased-donor urine biomarkers would be associated with higher rates of biopsy-proven acute rejection (BPAR) and allograft failure after transplantation. STUDY DESIGN: Prospective cohort. SETTING & PARTICIPANTS: 862 deceased donors for 1,137 kidney recipients at 13 centers. EXPOSURES: We measured concentrations of interleukin 18 (IL-18), kidney injury molecule 1 (KIM-1), and neutrophil gelatinase-associated lipocalin (NGAL) in deceased donor urine. We also used the Acute Kidney Injury Network (AKIN) criteria to assess donor clinical AKI. OUTCOMES: The primary outcome was a composite of BPAR and graft failure (not from death). A secondary outcome was the composite of BPAR, graft failure, and/or de novo donor-specific antibody (DSA). Outcomes were ascertained in the first posttransplant year. ANALYTICAL APPROACH: Multivariable Fine-Gray models with death as a competing risk. RESULTS: Mean recipient age was 54 ± 13 (SD) years, and 82% received antithymocyte globulin. We found no significant associations between donor urinary IL-18, KIM-1, and NGAL and the primary outcome (subdistribution hazard ratio [HR] for highest vs lowest tertile of 0.76 [95% CI, 0.45-1.28], 1.20 [95% CI, 0.69-2.07], and 1.14 [95% CI, 0.71-1.84], respectively). In secondary analyses, we detected no significant associations between clinically defined AKI and the primary outcome or between donor biomarkers and the composite outcome of BPAR, graft failure, and/or de novo DSA. LIMITATIONS: BPAR was ascertained through for-cause biopsies, not surveillance biopsies. CONCLUSIONS: In a large cohort of kidney recipients who almost all received induction with thymoglobulin, donor injury biomarkers were associated with neither graft failure and rejection nor a secondary outcome that included de novo DSA. These findings provide some reassurance that centers can successfully manage immunological complications using deceased-donor kidneys with AKI.

Evaluation of Plasma Biomarkers to Predict Major Adverse Kidney Events in Hospitalized Patients With COVID-19.

RATIONALE & OBJECTIVE: Patients hospitalized with COVID-19 are at increased risk for major adverse kidney events (MAKE). We sought to identify plasma biomarkers predictive of MAKE in patients hospitalized with COVID-19. STUDY DESIGN: Prospective cohort study. SETTING & PARTICIPANTS: A total of 576 patients hospitalized with COVID-19 between March 2020 and January 2021 across 3 academic medical centers. EXPOSURE: Twenty-six plasma biomarkers of injury, inflammation, and repair from first available blood samples collected during hospitalization. OUTCOME: MAKE, defined as KDIGO stage 3 acute kidney injury (AKI), dialysis-requiring AKI, or mortality up to 60 days. ANALYTICAL APPROACH: Cox proportional hazards regression to associate biomarker level with MAKE. We additionally applied the least absolute shrinkage and selection operator (LASSO) and random forest regression for prediction modeling and estimated model discrimination with time-varying C index. RESULTS: The median length of stay for COVID-19 hospitalization was 9 (IQR, 5-16) days. In total, 95 patients (16%) experienced MAKE. Each 1 SD increase in soluble tumor necrosis factor receptor 1 (sTNFR1) and sTNFR2 was significantly associated with an increased risk of MAKE (adjusted HR [AHR], 2.30 [95% CI, 1.86-2.85], and AHR, 2.26 [95% CI, 1.73-2.95], respectively). The C index of sTNFR1 alone was 0.80 (95% CI, 0.78-0.84), and the C index of sTNFR2 was 0.81 (95% CI, 0.77-0.84). LASSO and random forest regression modeling using all biomarkers yielded C indexes of 0.86 (95% CI, 0.83-0.89) and 0.84 (95% CI, 0.78-0.91), respectively. LIMITATIONS: No control group of hospitalized patients without COVID-19. CONCLUSIONS: We found that sTNFR1 and sTNFR2 are independently associated with MAKE in patients hospitalized with COVID-19 and can both also serve as predictors for adverse kidney outcomes. PLAIN-LANGUAGE SUMMARY: Patients hospitalized with COVID-19 are at increased risk for long-term adverse health outcomes, but not all patients suffer long-term kidney dysfunction. Identification of patients with COVID-19 who are at high risk for adverse kidney events may have important implications in terms of nephrology follow-up and patient counseling. In this study, we found that the plasma biomarkers soluble tumor necrosis factor receptor 1 (sTNFR1) and sTNFR2 measured in hospitalized patients with COVID-19 were associated with a greater risk of adverse kidney outcomes. Along with clinical variables previously shown to predict adverse kidney events in patients with COVID-19, both sTNFR1 and sTNFR2 are also strong predictors of adverse kidney outcomes.

Plasma Soluble Tumor Necrosis Factor Receptor Concentrations and Clinical Events After Hospitalization: Findings From the ASSESS-AKI and ARID Studies.

RATIONALE & OBJECTIVE: The role of plasma soluble tumor necrosis factor receptor 1 (sTNFR1) and sTNFR2 in the prognosis of clinical events after hospitalization with or without acute kidney injury (AKI) is unknown. STUDY DESIGN: Prospective cohort. SETTING & PARTICIPANTS: Hospital survivors from the ASSESS-AKI (Assessment, Serial Evaluation, and Subsequent Sequelae of Acute Kidney Injury) and ARID (AKI Risk in Derby) studies with and without AKI during the index hospitalization who had baseline serum samples for biomarker measurements. PREDICTORS: We measured sTNFR1 and sTNFR2 from plasma samples obtained 3 months after discharge. OUTCOMES: The associations of biomarkers with longitudinal kidney disease incidence and progression, heart failure, and death were evaluated. ANALYTICAL APPROACH: Cox proportional hazard models. RESULTS: Among 1,474 participants with plasma biomarker measurements, 19% had kidney disease progression, 14% had later heart failure, and 21% died during a median follow-up of 4.4 years. For the kidney outcome, the adjusted HRs (AHRs) per doubling in concentration were 2.9 (95% CI, 2.2-3.9) for sTNFR1 and 1.9 (95% CI, 1.5-2.5) for sTNFR2. AKI during the index hospitalization did not modify the association between biomarkers and kidney events. For heart failure, the AHRs per doubling in concentration were 1.9 (95% CI, 1.4-2.5) for sTNFR1 and 1.5 (95% CI, 1.2-2.0) for sTNFR2. For mortality, the AHRs were 3.3 (95% CI, 2.5-4.3) for sTNFR1 and 2.5 (95% CI, 2.0-3.1) for sTNFR2. The findings in ARID were qualitatively similar in terms of the magnitude of association between biomarkers and outcomes. LIMITATIONS: Different biomarker platforms and AKI definitions; limited generalizability to other ethnic groups. CONCLUSIONS: Plasma sTNFR1 and sTNFR2 measured 3 months after hospital discharge were independently associated with clinical events regardless of AKI status during the index admission. sTNFR1 and sTNFR2 may assist with the risk stratification of patients during follow-up.

Biomarkers of eGFR decline after cardiac surgery in children: findings from the ASSESS-AKI study.

BACKGROUND: Children who require surgery for congenital heart disease have increased risk for long-term chronic kidney disease (CKD). Clinical factors as well as urine biomarkers of tubular health and injury may help improve the prognostication of estimated glomerular filtration rate (eGFR) decline. METHODS: We enrolled children from 1 month to 18 years old undergoing cardiac surgery in the ASSESS-AKI cohort. We used mixed-effect models to assess the association between urinary biomarkers (log2-transformed uromodulin, NGAL, KIM-1, IL-18, L-FABP) measured 3 months after cardiac surgery and cyanotic heart disease with the rate of eGFR decline at annual in-person visits over 4 years. RESULTS: Of the 117 children enrolled, 30 (24%) had cyanotic heart disease. During 48 months of follow-up, the median eGFR in the subgroup of children with cyanotic heart disease was lower at all study visits as compared with children with acyanotic heart disease (p = 0.01). In the overall cohort, lower levels of both urine uromodulin and IL-18 after discharge were associated with eGFR decline. After adjustment for age, RACHS-1 surgical complexity score, proteinuria, and eGFR at the 3-month study visit, lower concentrations of urine uromodulin and IL-18 were associated with a monthly decline in eGFR (uromodulin ß = 0.04 (95% CI: 0.00-0.09; p = 0.07) IL-18 ß = 0.07 (95% CI: 0.01-0.13; p = 0.04), ml/min/1.73 m2 per month). CONCLUSIONS: At 3 months after cardiac surgery, children with lower urine uromodulin and IL-18 concentrations experienced a significantly faster decline in eGFR. Children with cyanotic heart disease had a lower median eGFR at all time points but did not experience faster eGFR decline. A higher-resolution version of the Graphical abstract is available as Supplementary information.

Longitudinal TNFR1 and TNFR2 and Kidney Outcomes: Results from AASK and VA NEPHRON-D.

BACKGROUND: Higher baseline levels of soluble TNF receptors (TNFR1 and TNFR2) have been associated with progressive CKD. Whether longitudinal changes in these biomarkers of inflammation are also associated with worse kidney outcomes has been less studied. METHODS: We evaluated associations of longitudinal changes in TNFR1 and TNFR2 with ESKD in the African American Study of Kidney Disease and Hypertension (AASK; 38% female; 0% diabetes) and kidney function decline (first occurrence of ≥30 ml/min per 1.73 m2 or ≥50% eGFR decline if randomization eGFR ≥60 or <60 ml/min per 1.73 m2, respectively; ESKD) in the Veterans Affairs Nephropathy in Diabetes trial (VA NEPHRON-D; 99% male; 100% diabetes) using Cox models. Biomarkers were measured from samples collected at 0-, 12-, and 24-month visits for AASK (serum) and 0- and 12-month visits for VA NEPHRON-D (plasma). Biomarker slopes (AASK) were estimated using linear mixed-effects models. Covariates included sociodemographic/clinical factors, baseline biomarker level, and kidney function. RESULTS: There were 129 ESKD events over a median of 7.0 years in AASK (n=418) and 118 kidney function decline events over a median of 1.5 years in VA NEPHRON-D (n=754). In AASK, each 1 SD increase in TNFR1 and TNFR2 slope was associated with 2.98- and 1.87-fold higher risks of ESKD, respectively. In VA NEPHRON-D, each 1 SD increase in TNFR1 and TNFR2 was associated with 3.20- and 1.43-fold higher risks of kidney function decline, respectively. CONCLUSIONS: Among individuals with and without diabetes, longitudinal increases in TNFR1 and TNFR2 were each associated with progressive CKD, independent of initial biomarker level and kidney function.

Angiopoietins as Prognostic Markers for Future Kidney Disease and Heart Failure Events after Acute Kidney Injury.

BACKGROUND: The mechanisms underlying long-term sequelae after AKI remain unclear. Vessel instability, an early response to endothelial injury, may reflect a shared mechanism and early trigger for CKD and heart failure. METHODS: To investigate whether plasma angiopoietins, markers of vessel homeostasis, are associated with CKD progression and heart failure admissions after hospitalization in patients with and without AKI, we conducted a prospective cohort study to analyze the balance between angiopoietin-1 (Angpt-1), which maintains vessel stability, and angiopoietin-2 (Angpt-2), which increases vessel destabilization. Three months after discharge, we evaluated the associations between angiopoietins and development of the primary outcomes of CKD progression and heart failure and the secondary outcome of all-cause mortality 3 months after discharge or later. RESULTS: Median age for the 1503 participants was 65.8 years; 746 (50%) had AKI. Compared with the lowest quartile, the highest quartile of the Angpt-1:Angpt-2 ratio was associated with 72% lower risk of CKD progression (adjusted hazard ratio [aHR], 0.28; 95% confidence interval [CI], 0.15 to 0.51), 94% lower risk of heart failure (aHR, 0.06; 95% CI, 0.02 to 0.15), and 82% lower risk of mortality (aHR, 0.18; 95% CI, 0.09 to 0.35) for those with AKI. Among those without AKI, the highest quartile of Angpt-1:Angpt-2 ratio was associated with 71% lower risk of heart failure (aHR, 0.29; 95% CI, 0.12 to 0.69) and 68% less mortality (aHR, 0.32; 95% CI, 0.15 to 0.68). There were no associations with CKD progression. CONCLUSIONS: A higher Angpt-1:Angpt-2 ratio was strongly associated with less CKD progression, heart failure, and mortality in the setting of AKI.

Trends in the procurement and discard of kidneys from deceased donors with acute kidney injury.

Kidney allocation trends from deceased donors with acute kidney injury (AKI) have not been characterized since initial Kidney Donor Profile Index reporting in 2012 and its use under the revised Kidney Allocation System (KAS) in 2014. We conducted a retrospective analysis of US registry data to characterize kidney procurement and discard trends in deceased donors with AKI, defined by ≥50% or ≥0.3 mg/dl (≥4.0 mg/dl or ≥200% for stage 3) increase in terminal serum creatinine from admission. From 2010 to 2020, 172 410 kidneys were procured from 93 341 deceased donors 16 years or older; 34 984 kidneys were discarded (17 559 from AKI donors). The proportion of stage 3 AKI donors doubled from 6% (412/6841) in 2010 to 12% (1365/11493) in 2020. Procurement of stage 3 AKI kidneys increased from 51% (423/824) to 80% (2183/2730). While discard of stage 3 AKI kidneys increased from 41% (175/423) in 2010 to 44% (960/2183) in 2020, this increase was not statistically significant in interrupted time-series analysis following KAS implementation (slope difference -0.41 [-3.22, 2.4], and level change 3.09 [-6.4, 12.6]). In conclusion, the absolute number of stage 3 AKI kidneys transplanted has increased. Ongoing high discard rates of these kidneys suggest opportunities for improved utilization.

Prognostic Significance of Urinary Biomarkers in Patients Hospitalized With COVID-19.

RATIONALE & OBJECTIVE: Acute kidney injury (AKI) is common in patients with coronavirus disease 2019 (COVID-19) and associated with poor outcomes. Urinary biomarkers have been associated with adverse kidney outcomes in other settings and may provide additional prognostic information in patients with COVID-19. We investigated the association between urinary biomarkers and adverse kidney outcomes among patients hospitalized with COVID-19. STUDY DESIGN: Prospective cohort study. SETTING & PARTICIPANTS: Patients hospitalized with COVID-19 (n=153) at 2 academic medical centers between April and June 2020. EXPOSURE: 19 urinary biomarkers of injury, inflammation, and repair. OUTCOME: Composite of KDIGO (Kidney Disease: Improving Global Outcomes) stage 3 AKI, requirement for dialysis, or death within 60 days of hospital admission. We also compared various kidney biomarker levels in the setting of COVID-19 versus other common AKI settings. ANALYTICAL APPROACH: Time-varying Cox proportional hazards regression to associate biomarker level with composite outcome. RESULTS: Out of 153 patients, 24 (15.7%) experienced the primary outcome. Twofold higher levels of neutrophil gelatinase-associated lipocalin (NGAL) (HR, 1.34 [95% CI, 1.14-1.57]), monocyte chemoattractant protein (MCP-1) (HR, 1.42 [95% CI, 1.09-1.84]), and kidney injury molecule 1 (KIM-1) (HR, 2.03 [95% CI, 1.38-2.99]) were associated with highest risk of sustaining primary composite outcome. Higher epidermal growth factor (EGF) levels were associated with a lower risk of the primary outcome (HR, 0.61 [95% CI, 0.47-0.79]). Individual biomarkers provided moderate discrimination and biomarker combinations improved discrimination for the primary outcome. The degree of kidney injury by biomarker level in COVID-19 was comparable to other settings of clinical AKI. There was evidence of subclinical AKI in COVID-19 patients based on elevated injury biomarker level in patients without clinical AKI defined by serum creatinine. LIMITATIONS: Small sample size with low number of composite outcome events. CONCLUSIONS: Urinary biomarkers are associated with adverse kidney outcomes in patients hospitalized with COVID-19 and may provide valuable information to monitor kidney disease progression and recovery.

Urinary Biomarkers of Tubular Health and Risk for Kidney Function Decline or Mortality in Diabetes.

INTRODUCTION: Diabetes is a leading cause of end-stage kidney disease (ESKD). Biomarkers of tubular health may prognosticate chronic kidney disease (CKD) progression beyond estimated glomerular filtration rate (eGFR) and urine albumin-to-creatinine ratio (UACR). METHODS: We examined associations of five urinary biomarkers of tubular injury and repair (NGAL, KIM-1, IL-18, MCP-1, YKL-40) with kidney function decline (first occurrence of a decrease in eGFR ≥30 mL/min/1.73 m2 if randomization eGFR ≥60 or ≥50% if randomization eGFR <60; ESKD) and all-cause mortality among 1,135 VA NEPHRON-D trial participants with baseline UACR ≥300 mg/g and available urine samples. Covariates included age, sex, race, BMI, systolic BP, HbA1c, treatment arm, eGFR, and UACR. In a subset of participants with 12-month samples (n = 712), we evaluated associations of KIM-1, MCP-1, and YKL-40 change (from baseline to 12 months) with eGFR decline (from 12 months onward). RESULTS: At baseline, mean age was 65 years, mean eGFR was 56 mL/min/1.73 m2, and median UACR was 840 mg/g. Over a median of 2.2 years, 13% experienced kidney function decline and 9% died. In fully adjusted models, the highest versus lowest quartiles of MCP-1 and YKL-40 were associated with 2.18- and 1.76-fold higher risks of kidney function decline, respectively. One-year changes in KIM-1, MCP-1, and YKL-40 were not associated with subsequent eGFR decline. Higher baseline levels of NGAL, IL-18, MCP-1, and YKL-40 levels (per 2-fold higher) were independently associated with 10-40% higher risk of mortality. CONCLUSION: Among Veterans with diabetes and CKD, urinary biomarkers of tubular health were associated with kidney function decline and mortality.

Results from the TRIBE-AKI Study found associations between post-operative blood biomarkers and risk of chronic kidney disease after cardiac surgery.

Patients undergoing cardiac surgery are placed under intense physiologic stress. Blood and urine biomarkers measured peri-operatively may help identify patients at higher risk for adverse long-term kidney outcomes.We sought to determine independent associations of various biomarkers with development or progression of chronic kidney disease (CKD) following cardiac surgery. In this sub-study of the prospective cohort -TRIBE-AKI Study, we evaluated 613 adult patients undergoing cardiac surgery in Canada in our primary analysis and tested the association of 40 blood and urinary biomarkers with the primary composite outcome of CKD incidence or progression. In those with baseline estimated glomerular filtration rate (eGFR) over 60 mL/min/1.73m2, we defined CKD incidence as a 25% reduction in eGFR and an eGFR under 60. In those with baseline eGFR under 60 mL/min/1.73m2, we defined CKD progression as a 50% reduction in eGFR or eGFR under 15. Results were evaluated in a replication cohort of 310 patients from one study site in the United States. Over a median follow-up of 5.6 years, 172 patients developed the primary outcome. Each log increase in basic fibroblast growth factor (adjusted hazard ratio 1.52 [95% confidence interval 1.19, 1.93]), Kidney Injury Molecule-1 (1.51 [0.98, 2.32]), N-terminal pro-B-type natriuretic peptide (1.19 [1.01, 1.41]), and tumor necrosis factor receptor 1 (1.75 [1.18, 2.59]) were associated with outcome after adjustment for demographic factors, serum creatinine, and albuminuria. Similar results were noted in the replication cohort. Although there was no interaction by acute kidney injury in continuous analysis, mortality was higher in the no acute kidney injury group by biomarker tertile. Thus, elevated post-operative levels of blood biomarkers following cardiac surgery were independently associated with the development of CKD. These biomarkers can provide additional value in evaluating CKD incidence and progression after cardiac surgery.

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.

24-hour ambulatory blood pressure monitoring 9 years after pediatric cardiac surgery: a pilot and feasibility study.

BACKGROUND: Children undergoing cardiac surgery are at risk of high blood pressure (BP), a risk factor for cardiovascular and kidney disease. Twenty-four-hour ambulatory BP monitoring (ABPM) is a reference standard hypertension (HTN) test. Little data exist on ABPM abnormalities in children several years post cardiac surgery. This study aimed to (a) determine ABPM feasibility; (b) describe and compare ABPM measures and abnormalities (percent load, masked HTN [MH]; non-dipping, mean systolic/diastolic BP > 95th percentile; pre-HTN (ABPM); white-coat HTN [WCH]) to casual BP; and (c) compare BP in patients with and without acute kidney injury (AKI). METHODS: Prospective, follow-up pilot study of children (0-18 years) who underwent cardiac surgery from 2007 to 2009 at Montreal Children's Hospital. We recorded if participants had post-operative AKI and assessed the following outcomes at 9-year follow-up: casual BP classified by three single-visit measures (normal; elevated BP [eBPSingleVisit]; HTNSingleVisit); ABPM. Bivariable analyses were used to compare characteristics between groups. RESULTS: Twenty-three patients (median [interquartile range], 8.6 [8.0, 9.0] years post cardiac surgery) were included; 16 (70%) male. Six participants (26%) had eBPSingleVisit or higher. On ABPM, 11 (48%) had ≥ 1 abnormality: 9 (39%) had non-dipping; 3 (13%) had pre-HTN; 3 (13%) had WCH; none had HTN or MH. There were no differences in ABPM according to AKI status. CONCLUSION: Our pilot study determined that ABPM was feasible in children years after cardiac surgery and frequently identified ABPM abnormalities. Future research in larger populations is needed to define specific risk factors for HTN in children after cardiac surgery.

Contemporary incidence and risk factors of post transplant Erythrocytosis in deceased donor kidney transplantation.

BACKGROUND: Post-Transplant erythrocytosis (PTE) has not been studied in large recent cohorts. In this study, we evaluated the incidence, risk factors, and outcome of PTE with current transplant practices using the present World Health Organization criteria to define erythrocytosis. We also tested the hypothesis that the risk of PTE is greater with higher-quality kidneys. METHODS: We utilized the Deceased Donor Study which is an ongoing, multicenter, observational study of deceased donors and their kidney recipients that were transplanted between 2010 and 2013 across 13 centers. Eryrthocytosis is defined by hemoglobin> 16.5 g/dL in men and> 16 g/dL in women. Kidney quality is measured by Kidney Donor Profile Index (KDPI). RESULTS: Of the 1123 recipients qualified to be in this study, PTE was observed at a median of 18 months in 75 (6.6%) recipients. Compared to recipients without PTE, those with PTE were younger [mean 48±11 vs 54±13 years, p < 0.001], more likely to have polycystic kidney disease [17% vs 6%, p < 0.001], have received kidneys from younger donors [36 ±13 vs 41±15 years], and be on RAAS inhibitors [35% vs 22%, p < 0.001]. Recipients with PTE were less likely to have received kidneys from donors with hypertension [16% vs 32%, p = 0.004], diabetes [1% vs 11%, p = 0.008], and cerebrovascular event (24% vs 36%, p = 0.036). Higher KDPI was associated with decreased PTE risk [HR 0.98 (95% CI: 0.97-0.99)]. Over 60 months of follow-up, only 17 (36%) recipients had sustained PTE. There was no association between PTE and graft failure or mortality, CONCLUSIONS: The incidence of PTE was low in our study and PTE resolved in majority of patients. Lower KDPI increases risk of PTE. The underutilization of RAAS inhibitors in PTE patients raises the possibility of under-recognition of this phenomenon and should be explored in future studies.

Improving the prediction of long-term readmission and mortality using a novel biomarker panel.

OBJECTIVE: Several short-term readmission and mortality prediction models have been developed using clinical risk factors or biomarkers among patients undergoing coronary artery bypass graft (CABG) surgery. The use of biomarkers for long-term prediction of readmission and mortality is less well understood. Given the established association of cardiac biomarkers with short-term adverse outcomes, we hypothesized that 5-year prediction of readmission or mortality may be significantly improved using cardiac biomarkers. MATERIALS AND METHODS: Plasma biomarkers from 1149 patients discharged alive after isolated CABG surgery from eight medical centers were measured in a cohort from the Northern New England Cardiovascular Disease Study Group between 2004 and 2007. We assessed the added predictive value of a biomarker panel with a clinical model against the clinical model alone and compared the model discrimination using the area under the receiver operating characteristic (AUROC) curves. RESULTS: In our cohort, 461 (40%) patients were readmitted or died within 5 years. Long-term outcomes were predicted by applying the STS ASCERT clinical model with an AUROC of 0.69. The biomarker panel with the clinical model resulted in a significantly improved AUROC of 0.74 (p value <.0001). Across 5 years, the hazard ratio for patients in the second to fifth quintile predicted probabilities from the biomarker augmented STS ASCERT model ranged from 2.2 to 7.9 (p values <.001). CONCLUSIONS: We report that a panel of biomarkers significantly improved prediction of long-term readmission or mortality risk following CABG surgery. Our findings suggest biomarkers help clinical care teams better assess the long-term risk of readmission or mortality.

Association of plasma-soluble ST2 and galectin-3 with cardiovascular events and mortality following cardiac surgery.

BACKGROUND: Cardiac surgery induces hemodynamic stress on the myocardium, and this process can be associated with significant post-operative morbidity and mortality. Soluble suppression of tumorigenicity 2 (sST2) and galectin-3 (gal-3) are biomarkers of myocardial remodeling and fibrosis; however, their potential association with post-operative changes is unknown. METHODS: We measured peri-operative plasma sST2 and gal-3 levels in two prospective cohorts (TRIBE-AKI and NNE) of over 1800 patients who underwent cardiac surgery. sST2 and gal-3 levels were evaluated for association with a composite primary outcome of cardiovascular event or mortality over median follow-up periods of 3.4 and 6.0 years, respectively, for the two cohorts. Meta-analysis of hazard ratio estimates from the cohorts was performed using random effects models. RESULTS: Cohorts demonstrated event rates of 70.2 and 66.8 per 1000 person-years for the primary composite outcome. After adjustment for clinical covariates, higher post-operative sST2 and gal-3 levels were significantly associated with cardiovascular event or mortality [pooled estimate HRs: sST2 1.29 (95% CI 1.16, 1.44); gal-3 1.26 (95% CI 1.09, 1.46)]. These associations were not significantly modified by pre-operative congestive heart failure or AKI. CONCLUSIONS: Higher post-operative sST2 and gal-3 values were associated with increased incidence of cardiovascular event or mortality. These two biomarkers should be further studied for potential clinical utility for patients undergoing cardiac surgery.

Kidney Biomarkers of Injury and Repair as Predictors of Contrast-Associated AKI: A Substudy of the PRESERVE Trial.

RATIONALE & OBJECTIVE: The PRESERVE trial used a 2 × 2 factorial design to compare intravenous saline solution with intravenous sodium bicarbonate solution and oral N-acetylcysteine with placebo for the prevention of 90-day major adverse kidney events and death (MAKE-D) and contrast-associated acute kidney injury (CA-AKI) among patients with chronic kidney disease undergoing angiography. In this ancillary study, we evaluated the predictive capacities of preangiography injury and repair proteins in urine and plasma for MAKE-D, CA-AKI, and their impact on trial design. STUDY DESIGN: Longitudinal analysis. SETTING & PARTICIPANTS: A subset of participants from the PRESERVE trial. EXPOSURES: Injury (KIM-1, NGAL, and IL-18) and repair (MCP-1, UMOD, and YKL-40) proteins in urine and plasma 1 to 2 hours preangiography. OUTCOMES: MAKE-D and CA-AKI. ANALYTICAL APPROACH: We analyzed the associations of preangiography biomarkers with MAKE-D and with CA-AKI. We evaluated whether the biomarker levels could enrich the MAKE-D event rate and improve future clinical trial efficiency through an online biomarker prognostic enrichment tool available at prognosticenrichment.com. RESULTS: We measured plasma biomarkers in 916 participants and urine biomarkers in 797 participants. After adjusting for urinary albumin-creatinine ratio and baseline estimated glomerular filtration rate, preangiography levels of 4 plasma (KIM-1, NGAL, UMOD, and YKL-40) and 3 urine (NGAL, IL-18, and YKL-40) biomarkers were associated with MAKE-D. Only plasma KIM-1 level was significantly associated with CA-AKI after adjustment. Biomarker levels provided modest discriminatory capacity for MAKE-D. Screening patients using the 50th percentile of preangiography plasma KIM-1 or YKL-40 levels would have reduced the required sample size by 30% (∼2,000 participants). LIMITATIONS: Evaluation of prognostic enrichment does not account for changing trial costs, time needed to screen patients, or loss to follow-up. Most participants were male, limiting the generalizability of our findings. CONCLUSIONS: Preangiography levels of injury and repair biomarkers modestly predict the development of MAKE-D and can be used to improve the efficiency of future CA-AKI trials.