Plasma Proteins associated with Chronic Histopathologic Lesions on Kidney Biopsy

BACKGROUND

The severity of chronic histopathologic lesions on kidney biopsy is independently associated with higher risk of progressive chronic kidney disease (CKD). Because kidney biopsies are invasive, identification of blood markers that report on underlying kidney histopathology has the potential to enhance CKD care.

METHODS

We examined the association between 6592 plasma protein levels measured by aptamers and the severity of interstitial fibrosis and tubular atrophy (IFTA), glomerulosclerosis, arteriolar sclerosis, and arterial sclerosis among 434 participants of the Boston Kidney Biopsy Cohort. For proteins significantly associated with at least one histologic lesion, we assessed renal arteriovenous protein gradients among 21 individuals who had undergone invasive catheterization and assessed the expression of the cognate gene among 47 individuals with single cell RNA sequencing data in the Kidney Precision Medicine Project.

RESULTS

In models adjusted for estimated glomerular filtration rate (eGFR), proteinuria, and demographic factors, we identified 35 proteins associated with one or more chronic histologic lesions, including 20 specific for IFTA, 8 specific for glomerulosclerosis, and 1 specific for arteriolar sclerosis. In general, higher levels of these proteins were associated with more severe histologic score and lower eGFR. Exceptions included testican-2 and NELL1, which were associated with less glomerulosclerosis and IFTA, respectively, and higher eGFR; notably, both of these proteins demonstrated significantly higher levels from artery to renal vein, demonstrating net kidney release. In the Kidney Precision Medicine Project, 13 of the 35 protein hits had cognate gene expression enriched in one or more cell types in the kidney, including podocyte expression of select glomerulosclerosis markers (including testican-2) and tubular expression of several IFTA markers (including NELL1).

CONCLUSIONS

Proteomic analysis identified circulating proteins associated with chronic histopathologic lesions, some of which have concordant site-specific expression within the kidney.

Integrated Proteomic and Metabolomic Modules associated with Risk of Kidney Disease Progression

BACKGROUND

Proteins and metabolites play crucial roles in various biological functions and are frequently interconnected through enzymatic or transport processes.

METHODS

We present an integrated analysis of 4,091 proteins and 630 metabolites in the Chronic Renal Insufficiency Cohort Study (N=1,708; average follow-up for kidney failure [KF], 9.5 years, with 537 events). Proteins and metabolites were integrated using an unsupervised clustering method and we assessed associations between clusters and CKD progression and kidney failure using Cox proportional hazards models. Analyses were adjusted for demographics and risk factors including the estimated glomerular filtration rate (eGFR) and urine protein-creatinine ratio. Associations were identified in a discovery sample (random two-thirds, N=1139) and then evaluated in a replication sample (one-third, N=569).

RESULTS

We identified 139 modules of correlated proteins and metabolites, which were represented by their principal components (PC). Modules and PC loadings were projected onto the replication sample which demonstrated a consistent network structure. Two modules, representing a total of 236 proteins and 82 metabolites, were robustly associated with both CKD progression and kidney failure in both discovery and validation samples. Using gene set enrichment, several transmembrane related terms were identified as over-represented in these modules. Transmembrane-ephrin receptor activity displayed the largest odds (OR = 13.2, P-value = 5.5×10 -5 ). A module containing CRIM1 and NPNT expressed in podocytes demonstrated particularly strong associations with kidney failure (P-value = 2.6×10 -5 ).

CONCLUSIONS

This study demonstrates that integration of the proteome and metabolome can identify functions of pathophysiologic importance in kidney disease.

Dihydropyridine Calcium Channel Blockers and Kidney Outcomes

BACKGROUND

Early trials of dihydropyridine calcium channel blockers (DCCBs) suggest a detrimental effect on intraglomerular pressure and an association with albuminuria.

OBJECTIVE

We sought to evaluate the associations of DCCB initiation with albuminuria and kidney failure with replacement therapy (KFRT) and to determine whether renin-angiotensin system (RAS) blockade modified these associations.

DESIGN

We conducted a target trial emulation study using a new user, active comparator design and electronic health record data from Geisinger Health.

PARTICIPANTS

We included patients without severe albuminuria or KFRT who were initiated on a DCCB or thiazide (active comparator) between January 1, 2004, and December 31, 2019.

MAIN MEASURES

Using inverse probability of treatment weighting, we performed doubly robust Cox proportional hazards regression to estimate the association of DCCB initiation with incident severe albuminuria (urine albumin to creatinine ratio > 300 mg/g) and KFRT, overall and stratified by RAS blocker use.

KEY RESULTS

There were 11,747 and 26,758 eligible patients initiating a DCCB and thiazide, respectively, with a weighted baseline mean age of 60 years, systolic blood pressure of 143 mm Hg, and eGFR of 86 mL/min/1.73 m2, and with a mean follow-up of 8 years. Compared with thiazides, DCCBs were significantly associated with the development of severe albuminuria (hazard ratio [HR], 1.29; 95% confidence interval [CI], 1.16-1.43), with attenuation of risk in the presence of RAS blockade (P for interaction < 0.001). The risk of KFRT was increased among patients without RAS blockade (HR, 1.66; 95% CI, 1.19-2.31), but not with RAS blockade (P for interaction = 0.005).

CONCLUSIONS

DCCBs were associated with increased risk of albuminuria and, in the absence of RAS blockade, KFRT. These findings suggest coupling DCCB therapy with RAS blockade may mitigate adverse kidney outcomes.

Serum Metabolomic Markers of Protein-Rich Foods and Incident CKD: Results From the Atherosclerosis Risk in Communities Study

Rationale & Objective

While urine excretion of nitrogen estimates the total protein intake, biomarkers of specific dietary protein sources have been sparsely studied. Using untargeted metabolomics, this study aimed to identify serum metabolomic markers of 6 protein-rich foods and to examine whether dietary protein-related metabolites are associated with incident chronic kidney disease (CKD).

Study Design

Prospective cohort study.

Setting & Participants

A total of 3,726 participants from the Atherosclerosis Risk in Communities study without CKD at baseline.

Exposures

Dietary intake of 6 protein-rich foods (fish, nuts, legumes, red and processed meat, eggs, and poultry), serum metabolites.

Outcomes

Incident CKD (estimated glomerular filtration rate < 60 mL/min/1.73 m2 with ≥25% estimated glomerular filtration rate decline relative to visit 1, hospitalization or death related to CKD, or end-stage kidney disease).

Analytical Approach

Multivariable linear regression models estimated cross-sectional associations between protein-rich foods and serum metabolites. C statistics assessed the ability of the metabolites to improve the discrimination of highest versus lower 3 quartiles of intake of protein-rich foods beyond covariates (demographics, clinical factors, health behaviors, and the intake of nonprotein food groups). Cox regression models identified prospective associations between protein-related metabolites and incident CKD.

Results

Thirty significant associations were identified between protein-rich foods and serum metabolites (fish, n = 8; nuts, n = 5; legumes, n = 0; red and processed meat, n = 5; eggs, n = 3; and poultry, n = 9). Metabolites collectively and significantly improved the discrimination of high intake of protein-rich foods compared with covariates alone (difference in C statistics = 0.033, 0.051, 0.003, 0.024, and 0.025 for fish, nuts, red and processed meat, eggs, and poultry-related metabolites, respectively; P < 1.00 × 10-16 for all). Dietary intake of fish was positively associated with 1-docosahexaenoylglycerophosphocholine (22:6n3), which was inversely associated with incident CKD (HR, 0.82; 95% CI, 0.75-0.89; P = 7.81 × 10-6).

Limitations

Residual confounding and sample-storage duration.

Conclusions

We identified candidate biomarkers of fish, nuts, red and processed meat, eggs, and poultry. A fish-related metabolite, 1-docosahexaenoylglycerophosphocholine (22:6n3), was associated with a lower risk of CKD.

Association of Sevelamer Initiation with Gastrointestinal Bleeding Hospitalization in Individuals Requiring Hemodialysis

Introduction Case reports have suggested a causative role between sevelamer use and subsequent gastrointestinal bleeding (GIB), but no large observational studies have evaluated this association. Methods Using the United States Renal Data System database from 2015 to 2019, we examined the association between initiation of sevelamer (versus non-sevelamer containing phosphate binders) and GIB hospitalization as well as all-cause mortality among individuals on hemodialysis. We emulated a target trial using Cox regression models and inverse probability of treatment weights to estimate the adjusted hazard ratios (HR) across outcomes and subgroups. Results Among 21,354 new users of phosphate binders (11,276 sevelamer and 10,078 non-sevelamer) with baseline lab data (calcium, phosphorus, hemoglobin, and albumin), there were 2,811 GIB hospitalizations and 5,920 deaths after a median follow-up of 1.3 years. Compared with the initiation of non-sevelamer binders, sevelamer was not associated with an increased risk of GIB hospitalization (89 vs. 90 events per 1000 person-years; IPTW-HR 0.98, 95% CI 0.91 - 1.06) or all-cause mortality (220 vs. 224 events per 1000 person-years; IPTW-HR 0.98 95% CI 0.93 - 1.03). Subgroup analyses (such as diabetes and anti-coagulation use) were generally consistent, and there was no association between sevelamer dose and GIB hospitalization. Conclusion Among patients requiring hemodialysis, sevelamer (vs non-sevelamer) containing phosphate binders was not associated with increased risk of GIB hospitalization.

Accuracy of GFR estimating equations based on creatinine, cystatin C or both in routine care

BACKGROUND

New equations to estimate glomerular filtration rate based on creatinine (eGFRcr), cystatin C (eGFRcys) or both (eGFRcr-cys) have been developed by the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) and the European Kidney Function Consortium (EKFC). There is a need to evaluate the performance of these equations in diverse European settings to inform implementation decisions, especially among people with key comorbid conditions.

METHODS

We performed a cross-sectional study including 6174 adults referred for single-point plasma clearance of iohexol in Stockholm, Sweden, with 9579 concurrent measurements of creatinine and cystatin C. We assessed the performance of the CKD-EPI 2009/2012/2021, EKFC 2021/2023, revised Lund-Malmö (RLM) 2011 and Caucasian, Asian, Pediatric and Adult (CAPA) 2014 equations against measured GFR (mGFR).

RESULTS

Mean age was 56 years, median mGFR was 62 mL/min/1.73 m2 and 40% were female. Comorbid conditions were common: cardiovascular disease (30%), liver disease (28%), diabetes (26%) and cancer (26%). All eGFRcr-cys equations had small bias and P30 (the percentage of estimated values within 30% of mGFR) close to 90%, and performed better than eGFRcr or eGFRcys equations. Among eGFRcr equations, CKD-EPI 2009 and CKD-EPI 2021 showed larger bias and lower P30 than EKFC 2021 and RLM. There were no meaningful differences in performance across eGFRcys equations. Findings were consistent across comorbid conditions, and eGFRcr-cys equations showed good performance in patients with liver disease, cancer and heart failure.

CONCLUSIONS

In conclusion, eGFRcr-cys equations performed best, with minimal variation among equations in this Swedish cohort. The lower performance of CKD-EPI eGFRcr equations compared with EKFC and RLM may reflect differences in population characteristics and mGFR methods. Implementing eGFRcr equations will require a trade-off between accuracy and uniformity across regions.

Association of Low Glomerular Filtration Rate With Adverse Outcomes at Older Age in a Large Population With Routinely Measured Cystatin C

BACKGROUND

The commonly accepted threshold of glomerular filtration rate (GFR) to define chronic kidney disease (CKD) is less than 60 mL/min/1.73 m2. This threshold is based partly on associations between estimated GFR (eGFR) and the frequency of adverse outcomes. The association is weaker in older adults, which has created disagreement about the appropriateness of the threshold for these persons. In addition, the studies measuring these associations included relatively few outcomes and estimated GFR on the basis of creatinine level (eGFRcr), which may be less accurate in older adults.

OBJECTIVE

To evaluate associations in older adults between eGFRcr versus eGFR based on creatinine and cystatin C levels (eGFRcr-cys) and 8 outcomes.

DESIGN

Population-based cohort study.

SETTING

Stockholm, Sweden, 2010 to 2019.

PARTICIPANTS

82 154 participants aged 65 years or older with outpatient creatinine and cystatin C testing.

MEASUREMENTS

Hazard ratios for all-cause mortality, cardiovascular mortality, and kidney failure with replacement therapy (KFRT); incidence rate ratios for recurrent hospitalizations, infection, myocardial infarction or stroke, heart failure, and acute kidney injury.

RESULTS

The associations between eGFRcr-cys and outcomes were monotonic, but most associations for eGFRcr were U-shaped. In addition, eGFRcr-cys was more strongly associated with outcomes than eGFRcr. For example, the adjusted hazard ratios for 60 versus 80 mL/min/1.73 m2 for all-cause mortality were 1.2 (95% CI, 1.1 to 1.3) for eGFRcr-cys and 1.0 (CI, 0.9 to 1.0) for eGFRcr, and for KFRT they were 2.6 (CI, 1.2 to 5.8) and 1.4 (CI, 0.7 to 2.8), respectively. Similar findings were observed in subgroups, including those with a urinary albumin-creatinine ratio below 30 mg/g.

LIMITATION

No GFR measurements.

CONCLUSION

Compared with low eGFRcr in older patients, low eGFRcr-cys was more strongly associated with adverse outcomes and the associations were more uniform.

PRIMARY FUNDING SOURCE

Swedish Research Council, National Institutes of Health, and Dutch Kidney Foundation.

Association of eGFR and Albuminuria with Venous Thromboembolism

BACKGROUND

CKD has been implicated as a risk factor of venous thromboembolism, but the evidence is limited to relatively healthy populations. The objective of this study was to discern whether parameters of kidney function and damage are associated with the occurrence of venous thromboembolism after hospitalization.

METHODS

We conducted a retrospective study including 23,899 and 11,552 adult individuals hospitalized within Geisinger Health System and New York University (NYU) Langone Health from 2004 to 2019 and 2012 to 2022, respectively. A Poisson model was used to evaluate adjusted incidence rates of venous thromboembolism according to eGFR and albuminuria categories in each cohort. Cox proportional hazards models were used to analyze associations of eGFR and urinary albumin-to-creatinine ratio (UACR) with venous thromboembolism, and hazard ratios (HRs) were meta-analyzed across cohorts.

RESULTS

Both lower eGFR and higher UACR were associated with higher risks of venous thromboembolism. In the Geisinger cohort, the incidence of venous thromboembolism after hospital discharge ranged from 10.7 (95% confidence interval [CI], 9.2 to 12.6) events per 1000 person-years in individuals in G1A1 (eGFR >90 ml/min per 1.73 m 2 and UACR <30 mg/g) to 27.7 (95% CI, 20.6 to 37.2) events per 1000 person-years in individuals with G4-5A3 (eGFR <30 ml/min per 1.73 m 2 and UACR >300 mg/g). A similar pattern was observed in the NYU cohort. Meta-analyses of the two cohorts showed that every 10 ml/min per 1.73 m 2 reduction in eGFR below 60 ml/min per 1.73 m 2 was associated with a 6% higher risk of venous thromboembolism (HR 1.06 [95% CI, 1.02 to 1.11], P = 0.01), and each two-fold higher UACR was associated with a 5% higher risk of venous thromboembolism (HR 1.05 [95% CI, 1.03 to 1.07], P < 0.001).

CONCLUSIONS

Both eGFR and UACR were independently associated with higher risk of venous thromboembolism after hospitalization. The incidence rate was higher with greater severity of CKD.

PODCAST

This article contains a podcast at https://dts.podtrac.com/redirect.mp3/www.asn-online.org/media/podcast/CJASN/2023_12_14_CJN0000000000000352.mp3.

Development and Validation of the American Heart Association's PREVENT Equations

BACKGROUND

Multivariable equations are recommended by primary prevention guidelines to assess absolute risk of cardiovascular disease (CVD). However, current equations have several limitations. Therefore, we developed and validated the American Heart Association Predicting Risk of CVD EVENTs (PREVENT) equations among US adults 30 to 79 years of age without known CVD.

METHODS

The derivation sample included individual-level participant data from 25 data sets (N=3 281 919) between 1992 and 2017. The primary outcome was CVD (atherosclerotic CVD and heart failure). Predictors included traditional risk factors (smoking status, systolic blood pressure, cholesterol, antihypertensive or statin use, and diabetes) and estimated glomerular filtration rate. Models were sex-specific, race-free, developed on the age scale, and adjusted for competing risk of non-CVD death. Analyses were conducted in each data set and meta-analyzed. Discrimination was assessed using the Harrell C-statistic. Calibration was calculated as the slope of the observed versus predicted risk by decile. Additional equations to predict each CVD subtype (atherosclerotic CVD and heart failure) and include optional predictors (urine albumin-to-creatinine ratio and hemoglobin A1c), and social deprivation index were also developed. External validation was performed in 3 330 085 participants from 21 additional data sets.

RESULTS

Among 6 612 004 adults included, mean±SD age was 53±12 years, and 56% were women. Over a mean±SD follow-up of 4.8±3.1 years, there were 211 515 incident total CVD events. The median C-statistics in external validation for CVD were 0.794 (interquartile interval, 0.763-0.809) in female and 0.757 (0.727-0.778) in male participants. The calibration slopes were 1.03 (interquartile interval, 0.81-1.16) and 0.94 (0.81-1.13) among female and male participants, respectively. Similar estimates for discrimination and calibration were observed for atherosclerotic CVD- and heart failure-specific models. The improvement in discrimination was small but statistically significant when urine albumin-to-creatinine ratio, hemoglobin A1c, and social deprivation index were added together to the base model to total CVD (ΔC-statistic [interquartile interval] 0.004 [0.004-0.005] and 0.005 [0.004-0.007] among female and male participants, respectively). Calibration improved significantly when the urine albumin-to-creatinine ratio was added to the base model among those with marked albuminuria (>300 mg/g; 1.05 [0.84-1.20] versus 1.39 [1.14-1.65]; P=0.01).

CONCLUSIONS

PREVENT equations accurately and precisely predicted risk for incident CVD and CVD subtypes in a large, diverse, and contemporary sample of US adults by using routinely available clinical variables.

Glucagon-like peptide-1 receptor agonists and the risk of atrial fibrillation in adults with diabetes: a real-world study

BACKGROUND

Glucagon-like peptide-1 receptor agonists (GLP-1RA) have cardiovascular benefits in type 2 diabetes, but none of the cardiovascular trials studied atrial fibrillation/atrial flutter (AF) as a primary endpoint. Data from post-marketing surveillance studies remains sparse.

OBJECTIVE

To examine the real-world risk of AF comparing GLP-1RA with other non-insulin glucose-lowering agents.

DESIGN

Cohort study using de-identified electronic health record data from the Optum Labs Data Warehouse.

PARTICIPANTS

Adult patients with diabetes who were newly prescribed add-on non-insulin glucose-lowering agents and were on metformin between 2005-2020.

EXPOSURES

New users of GLP-1RA were separately compared with new users of dipeptidyl peptidase-4 inhibitors (DPP4i) and sodium-glucose cotransporter 2 inhibitors (SGLT2i), using 1:1 propensity score matching to adjust for differences in patient characteristics.

MAIN MEASURES

The primary outcome was incident AF, defined and captured by diagnosis code for AF. Incidence rate difference (IRD) and hazard ratio (HR) were estimated in the matched cohorts.

KEY RESULTS

In the matched cohort of 14,566 pairs of GLP-1RA and DPP4i followed for a median of 3.8 years, GLP-1RA use was associated with a lower risk of AF (IRD, -1.0; 95% CI, -1.8 to -0.2 per 1000 person-years; HR, 0.82; 95% CI, 0.70 to 0.96). In the matched cohort of 9,424 pairs of patients on GLP-1RA and SGLT2i with a median follow-up of 2.9 years, there was no difference in the risk for AF (IRD, 0.4; 95% CI -0.7 to 1.5 per 1000 person-years; HR, 1.12; 95% CI, 0.89 to 1.42).

CONCLUSIONS

In this real-word study, GLP-1RA was associated with a lower risk of AF compared with DPP4i, but no difference compared with SGLT2i, suggesting that cardiovascular benefits of GLP-1RA use may extend to prevention for AF in patients with diabetes. Our findings call for future randomized controlled trials to focus on the effects of GLP-1RA on AF prevention.

Associations of Baseline and Longitudinal Serum Uromodulin With Kidney Failure and Mortality: Results From the African American Study of Kidney Disease and Hypertension (AASK) Trial

RATIONALE & OBJECTIVE

Uromodulin (UMOD) is the most abundant protein found in urine and has emerged as a promising biomarker of tubule health. Circulating UMOD is also detectable, but at lower levels. We evaluated whether serum UMOD levels were associated with the risks of incident kidney failure with replacement therapy (KFRT) and mortality.

STUDY DESIGN

Prospective cohort.

SETTING & PARTICIPANTS

Participants in AASK (the African American Study of Kidney Disease and Hypertension) with available stored serum samples from the 0-, 12-, and 24-month visits for biomarker measurement.

PREDICTORS

Baseline log-transformed UMOD and change in UMOD over 2 years.

OUTCOMES

KFRT and mortality.

ANALYTICAL APPROACH

Cox proportional hazards and mixed-effects models.

RESULTS

Among 500 participants with baseline serum UMOD levels (mean age, 54y; 37% female), 161 KFRT events occurred during a median of 8.5 years. After adjusting for baseline demographic factors, clinical factors, glomerular filtration rate, log-transformed urine protein-creatinine ratio, and randomized treatment groups, a 50% lower baseline UMOD level was independently associated with a 35% higher risk of KFRT (adjusted HR, 1.35; 95% CI, 1.07-1.70). For annual UMOD change, each 1-standard deviation lower change was associated with a 67% higher risk of KFRT (adjusted HR, 1.67; 95% CI, 1.41-1.99). Baseline UMOD and UMOD change were not associated with mortality. UMOD levels declined more steeply for metoprolol versus ramipril (P<0.001) as well as for intensive versus standard blood pressure goals (P = 0.002).

LIMITATIONS

Small sample size and limited generalizability.

CONCLUSIONS

Lower UMOD levels at baseline and steeper declines in UMOD over time were associated with a higher risk of subsequent KFRT in a cohort of African American adults with chronic kidney disease and hypertension.

PLAIN-LANGUAGE SUMMARY

Prior studies of uromodulin (UMOD), the most abundant protein in urine, and kidney disease have focused primarily on urinary UMOD levels. The present study evaluated associations of serum UMOD levels with the risks of kidney failure with replacement therapy (KFRT) and mortality in a cohort of African American adults with hypertension and chronic kidney disease. It found that participants with lower levels of UMOD at baseline were more likely to experience KFRT even after accounting for baseline kidney measures. Similarly, participants who experienced steeper annual declines in UMOD also had a heightened risk of kidney failure. Neither baseline nor annual change in UMOD was associated with mortality. Serum UMOD is a promising biomarker of kidney health.

Eicosanoids and Related Metabolites Associated with ESKD in a Community-Based Cohort

Key Points

High-throughput eicosanoid profiling can identify metabolites that may play a protective role in the development of kidney disease. In contrast to many other nonlipid metabolites, eicosanoid levels are minimally related with kidney filtration cross-sectionally.

Background

Eicosanoids are derivatives of polyunsaturated fatty acids and participate in the inflammatory response and the maintenance of endothelial function. Specific eicosanoids have been linked to various diseases, including hypertension and asthma, and may also reduce renal blood flow. A systematic investigation of eicosanoid-related metabolites and adverse kidney outcomes could identify key mediators of kidney disease and inform ongoing work in drug development.

Methods

Profiling of eicosanoid-related metabolites was performed in 9650 participants in the Atherosclerosis Risk in Communities Study (visit 2; mean age, 57 years). The associations between metabolite levels and the development of ESKD was investigated using Cox proportional hazards regression (n =256 events; median follow-up, 25.5 years). Metabolites with statistically significant associations with ESKD were evaluated for a potential causal role using bidirectional Mendelian randomization techniques, linking genetic instruments for eicosanoid levels to genomewide association study summary statistics of eGFR.

Results

The 223 eicosanoid-related metabolites that were profiled and passed quality control (QC) were generally uncorrelated with eGFR in cross-sectional analyses (median Spearman correlation, −0.03; IQR, −0.05 to 0.002). In models adjusted for multiple covariates, including baseline eGFR, three metabolites had statistically significant associations with ESKD (P value < 0.05/223). These included a hydroxyoctadecenoic acid, a dihydroxydocosapentaenoic acid, and arachidonic acid, with higher levels of the former two protective against ESKD and higher levels of arachidonic acid having a positive association with risk of ESKD. Mendelian randomization analyses suggested a causal role for the hydroxyoctadecenoic and arachidonic acid in determining eGFR. Spectral analysis identified the former metabolite as either 11-hydroxy-9-octadecenoic acid or 10-hydroxy-11-octadecenoic acid.

Conclusions

High-throughput eicosanoid profiling can identify metabolites that may play a protective role in the development of kidney disease.

Baclofen and the risk of fall and fracture in older adults: A real-world cohort study

BACKGROUND

The growth of oral muscle relaxant prescriptions among older adults in the United States is concerning due to the drugs' adverse sedative effects. Baclofen is a gamma-aminobutyric acid agonist muscle relaxant that is associated with encephalopathy. We characterized the risk of fall and fracture associated with oral baclofen against other muscle relaxants (tizanidine or cyclobenzaprine) in older adults.

METHODS

We designed a new-user, active-comparator study using tertiary health system data from Geisinger Health, Pennsylvania (January 2005 through December 2018). Older adults (aged ≥65 years) newly treated with baclofen, tizanidine, or cyclobenzaprine were included. Propensity score-based inverse probability of treatment weighting (IPTW) was used to balance the treatment groups on 58 baseline characteristics. Fine-Gray competing risk regression was used to estimate the risk of fall and fracture.

RESULTS

The study cohort comprised of 2205 new baclofen users, 1103 new tizanidine users, and 9708 new cyclobenzaprine users. During a median follow-up of 100 days, baclofen was associated with a higher risk of fall compared to tizanidine (IPTW incidence rate, 108.4 vs. 61.9 per 1000 person-years; subdistribution hazard ratio [SHR], 1.68 [95% CI, 1.20-2.36]). The risk of fall associated with baclofen was comparable to cyclobenzaprine (SHR, 1.17 [95% CI, 0.93-1.47]) with a median follow-up of 106 days. The risk of fracture was similar among patients treated with baclofen versus tizanidine (SHR, 0.85 [95% CI, 0.63-1.14]) or cyclobenzaprine (SHR, 0.85 [95% CI, 0.67-1.07]).

CONCLUSIONS

The risk of fall associated with baclofen was greater than tizanidine, but not compared to cyclobenzaprine in older adults. The risk of fracture was comparable among the older users of baclofen, tizanidine, and cyclobenzaprine. Our findings may inform risk-benefit considerations in the increasingly common clinical encounters where oral muscle relaxants are prescribed.

Cigarette Smoking and Risk of Hospitalization With Acute Kidney Injury: The Atherosclerosis Risk in Communities (ARIC) Study

RATIONALE & OBJECTIVE

Smoking is a modifiable risk factor for various adverse events. However, little is known about the association of smoking with the incidence of acute kidney injury (AKI) in the general population. This study investigated the association of cigarette smoking with the risk of AKI.

STUDY DESIGN

Prospective observational study.

SETTING & PARTICIPANTS

14,571 participants (mean age 55±6 years, 55% women, and 25% Black participants) from the ARIC study visit 1 (1987-1989) followed through December 31, 2019.

EXPOSURE

Smoking parameters (status, duration, pack-years, intensity, and years since cessation).

OUTCOME

Incident hospitalization with AKI, defined by a hospital discharge with a diagnostic code relevant to AKI.

ANALYTICAL APPROACH

Multivariable Cox regression models.

RESULTS

Over a median follow-up period of 26.3 years, 2,984 participants had an incident hospitalization with AKI. Current and former smokers had a significantly higher risk of AKI compared to never smokers after adjusting for potential confounders (HR, 2.22 [95% CI, 2.02-2.45] and 1.12 [1.02-1.23], respectively). A dose-response association was consistently seen for each of smoking duration, pack-years, and intensity with AKI (eg, HR, 1.19 [95% CI, 1.16-1.22] per 10 years of smoking). When years since cessation were considered as a time-varying exposure, the risk of AKI associated with smoking compared with current smokers began to decrease after 10 years, and became similar to never smokers at 30 years (HR for≥30 years, 1.07 [95% CI, 0.97-1.20] vs never smokers).

LIMITATIONS

Self-reported smoking measurements and missing outpatient AKI cases.

CONCLUSIONS

In a community-based cohort, all smoking parameters were robustly associated with the risk of AKI. Smoking cessation was associated with decreased risk of AKI, although the excess risk lasted up to 30 years. Our study supports the importance of preventing smoking initiation and promoting smoking cessation for the risk of AKI.

PLAIN-LANGUAGE SUMMARY

Smoking is a behavior that is associated with many negative health effects. It is not well understood how smoking relates to the occurrence of acute kidney injury (AKI) in the community. In this study, we looked at data from a group of 14,571 adults who were followed for 26 years to see how different aspects of smoking (such as whether someone smoked, how long they smoked for, how many cigarettes they smoked per day, and whether they quit smoking) were related to AKI. We found that smoking was strongly linked to an increased risk of AKI. This risk decreased after 5-10 years of quitting smoking, but the excess risk lasted up to 30 years. This study shows the importance of preventing people from starting smoking and to encourage smokers to quit to reduce their risk of AKI.

Advances in the management of chronic kidney disease

Chronic kidney disease (CKD) represents a global public health crisis, but awareness by patients and providers is poor. Defined as persistent abnormalities in kidney structure or function for more than three months, manifested as either low glomerular filtration rate or presence of a marker of kidney damage such as albuminuria, CKD can be identified through readily available blood and urine tests. Early recognition of CKD is crucial for harnessing major advances in staging, prognosis, and treatment. This review discusses the evidence behind the general principles of CKD management, such as blood pressure and glucose control, renin-angiotensin-aldosterone system blockade, statin therapy, and dietary management. It additionally describes individualized approaches to treatment based on risk of kidney failure and cause of CKD. Finally, it reviews novel classes of kidney protective agents including sodium-glucose cotransporter-2 inhibitors, glucagon-like peptide-1 receptor agonists, non-steroidal selective mineralocorticoid receptor antagonists, and endothelin receptor antagonists. Appropriate, widespread implementation of these highly effective therapies should improve the lives of people with CKD and decrease the worldwide incidence of kidney failure.

Preeclampsia and Long-term Kidney Outcomes: An Observational Cohort Study

RATIONALE & OBJECTIVE

Preeclampsia is a pregnancy-related complication characterized by acute hypertension and end-organ dysfunction. We evaluated the long-term association between preeclampsia and the risk of developing chronic hypertension and kidney disease.

STUDY DESIGN

Observational cohort study.

SETTING & PARTICIPANTS

27,800 adults with deliveries in the Geisinger Health System between 1996 and 2019.

EXPOSURE

Preeclampsia.

OUTCOME

Hypertension, reduced estimated glomerular filtration rate (eGFR)<60mL/min/1.73m2), and albuminuria>300mg/g.

ANALYTICAL APPROACH

Propensity-score matching and Cox proportional hazards models to evaluate the association between preeclampsia and incident hypertension, reduced eGFR, and albuminuria.

RESULTS

Of 27,800 adults with pregnancies during the study period (mean age, 28 years; 3% Black race), 2,977 (10.7%) had at least 1 pregnancy complicated by preeclampsia. After matching for multiple characteristics, individuals with preeclampsia had a higher risk of developing chronic hypertension (HR, 1.77 [95% CI, 1.45-2.16]), eGFR<60mL/min/1.73m2 (HR, 3.23 [95% CI, 1.64-6.36]), albuminuria (HR, 3.60 [95% CI, 2.38-5.44]), and a subsequent episode of preeclampsia (HR, 24.76 [95% CI, 12.47-48.36]), compared with matched controls without preeclampsia. Overall, postpartum follow-up testing was low. In the first 6 months after delivery, 31% versus 14% of individuals with and without preeclampsia had serum creatinine tests, respectively, and testing for urine protein was the same in both groups, with only 26% having follow-up testing.

LIMITATIONS

Primarily White study population, observational study, reliance on ICD codes for medical diagnosis.

CONCLUSIONS

Individuals with a pregnancy complicated by preeclampsia had a higher risk of hypertension, reduced eGFR, and albuminuria compared with individuals without preeclampsia.

PLAIN-LANGUAGE SUMMARY

Preeclampsia is a significant contributor to perinatal and maternal morbidity and is marked by new-onset hypertension and end-organ damage, including acute kidney injury or proteinuria. To gain insight into the long-term kidney effects of the disease, we compared adults with deliveries complicated by preeclampsia with those without preeclampsia in the Geisinger Health System, while also assessing postpartum testing rates. Our results demonstrate that pregnant individuals with preeclampsia are at a heightened risk for future hypertension, reduced eGFR, and albuminuria, with overall low rates of postpartum testing among both individuals with and without preeclampsia. These findings underscore the need to consider preeclampsia as an important risk factor for the development of chronic kidney disease. Further studies are required to determine optimal postpreeclampsia monitoring strategies.

Implementation of the Kidney Failure Risk Equation in a United States Nephrology Clinic

Introduction

The kidney failure risk equation (KFRE) estimates a person's risk of kidney failure and has great potential utility in clinical care.

Methods

We used mixed methods to explore implementation of the KFRE in nephrology clinics.

Results

KFRE scores were integrated into the electronic health record at Johns Hopkins Medicine and were displayed to nephrology providers. Documentation of KFRE scores increased over time, reaching 25% of eligible outpatient nephrology clinic notes at month 11. Three providers documented KFRE scores in >75% of notes, whereas 25 documented scores in <10% of notes. Surveys and focus groups of nephrology providers were conducted to probe provider views on the KFRE. Survey respondents (n = 25) reported variability in use of KFRE for decisions such as maintaining nephrology care, referring for transplant evaluation, or providing dialysis modality education. Provider perspectives on the use of KFRE, assessed in 2 focus groups of 4 providers each, included 3 common themes as follows: (i) KFRE scores may be most impactful in the care of specific subsets of people with chronic kidney disease (CKD); (ii) there is uncertainty about KFRE risk-based thresholds to guide clinical care; and (iii) education of patients, nephrology providers, and non-nephrology providers on appropriate interpretations of KFRE scores may help maximize their utility.

Conclusion

Implementation of the KFRE was limited by non-uniform provider adoption of its use, and limited knowledge about utilization of the KFRE in clinical decisions.

Associations of Apixaban Dose With Safety and Effectiveness Outcomes in Patients With Atrial Fibrillation and Severe Chronic Kidney Disease

BACKGROUND

Recommendations for apixaban dosing on the basis of kidney function are inconsistent between the US Food and Drug Administration and European Medicines Agency for patients with atrial fibrillation. Optimal apixaban dosing in chronic kidney disease remains unknown.

METHODS

With the use of deidentified electronic health record data from the Optum Labs Data Warehouse, patients with atrial fibrillation and chronic kidney disease stage 4/5 initiating apixaban between 2013 and 2021 were identified. Risks of bleeding and stroke/systemic embolism were compared by apixaban dose (5 versus 2.5 mg), adjusted for baseline characteristics by the inverse probability of treatment weighting. The Fine-Gray subdistribution hazard model was used to account for the competing risk of death. Cox regression was used to examine risk of death by apixaban dose.

RESULTS

Among 4313 apixaban new users, 1705 (40%) received 5 mg and 2608 (60%) received 2.5 mg. Patients treated with 5 mg apixaban were younger (mean age, 72 versus 80 years), with greater weight (95 versus 80 kg) and higher serum creatinine (2.7 versus 2.5 mg/dL). Mean estimated glomerular filtration rate was not different between the groups (24 versus 24 mL·min-1·1.73 m-2). In inverse probability of treatment weighting analysis, apixaban 5 mg was associated with a higher risk of bleeding (incidence rate 4.9 versus 2.9 events per 100 person-years; incidence rate difference, 2.0 [95% CI, 0.6-3.4] events per 100 person-years; subdistribution hazard ratio, 1.63 [95% CI, 1.04-2.54]). There was no difference between apixaban 5 mg and 2.5 mg groups in the risk of stroke/systemic embolism (3.3 versus 3.0 events per 100 person-years; incidence rate difference, 0.2 [95% CI, -1.0 to 1.4] events per 100 person-years; subdistribution hazard ratio, 1.01 [95% CI, 0.59-1.73]), or death (9.9 versus 9.4 events per 100 person-years; incidence rate difference, 0.5 [95% CI, -1.6 to 2.6] events per 100 person-years; hazard ratio, 1.03 [95% CI, 0.77-1.38]).

CONCLUSIONS

Compared with 2.5 mg, use of 5 mg apixaban was associated with a higher risk of bleeding in patients with atrial fibrillation and severe chronic kidney disease, with no difference in the risk of stroke/systemic embolism or death, supporting the apixaban dosing recommendations on the basis of kidney function by the European Medicines Agency, which differ from those issued by the US Food and Drug Administration.

Plasma Biomarkers and Incident CKD Among Individuals Without Diabetes

Rationale & Objective

Biomarkers of kidney disease progression have been identified in individuals with diabetes and underlying chronic kidney disease (CKD). Whether or not these markers are associated with the development of CKD in a general population without diabetes or CKD is not well established.

Study Design

Prospective observational cohort.

Setting & Participants

In the Atherosclerosis Risk in Communities) study, 948 participants were studied.

Exposures

The baseline plasma biomarkers of kidney injury molecule-1 (KIM-1), monocyte chemoattractant protein-1 (MCP-1), soluble urokinase plasminogen activator receptor (suPAR), tumor necrosis factor receptor 1 (TNFR-1), tumor necrosis factor receptor 2 (TNFR-2), and human cartilage glycoprotein-39 (YKL-40) measured in 1996-1998.

Outcome

Incident CKD after 15 years of follow-up defined as ≥40% estimated glomerular filtration rate decline to <60 mL/min/1.73 m2 or dialysis dependence through United States Renal Data System linkage.

Analytical Approach

Logistic regression and C statistics.

Results

There were 523 cases of incident CKD. Compared with a random sample of 425 controls, there were greater odds of incident CKD per 2-fold higher concentration of KIM-1 (OR, 1.49; 95% CI, 1.25-1.78), suPAR (OR, 2.57; 95% CI, 1.74-3.84), TNFR-1 (OR, 2.20; 95% CI, 1.58-3.09), TNFR-2 (OR, 2.03; 95% CI, 1.37-3.04). After adjustment for all biomarkers, KIM-1 (OR, 1.42; 95% CI, 1.19-1.71), and suPAR (OR, 1.86; 95% CI, 1.18-2.92) remained associated with incident CKD. Compared with traditional risk factors, the addition of all 6 biomarkers improved the C statistic from 0.695-0.731 (P < 0.01) and using the observed risk of 12% for incident CKD, the predicted risk gradient changed from 5%-40% (for the 1st-5th quintile) to 4%-44%.

Limitations

Biomarkers and creatinine were measured at one time point.

Conclusions

Higher levels of KIM-1, suPAR, TNFR-1, and TNFR-2 were associated with higher odds of incident CKD among individuals without diabetes.

Plain-Language Summary

For people with diabetes or kidney disease, several biomarkers have been shown to be associated with worsening kidney disease. Whether these biomarkers have prognostic significance in people without diabetes or kidney disease is less studied. Using the Atherosclerosis Risk in Communities study, we followed individuals without diabetes or kidney disease for an average of 15 years after biomarker measurement to see if these biomarkers were associated with the development of kidney disease. We found that elevated levels of KIM-1, suPAR, TNFR-1, and TNFR-2 were associated with the development of kidney disease. These biomarkers may help identify individuals who would benefit from interventions to prevent the development of kidney disease.

Discordances Between Creatinine- and Cystatin C-Based Estimated GFR and Adverse Clinical Outcomes in Routine Clinical Practice

RATIONALE & OBJECTIVE

Cystatin C is recommended for measuring estimated glomerular filtration rate (eGFR) when estimates based on creatinine (eGFRcr) are not thought to be accurate enough for clinical decision making. While global adoption is slow, routine cystatin C testing in Sweden has been available for over a decade, providing real-world evidence about the magnitude of differences between eGFRcys and eGFRcr and their association with clinical outcomes.

STUDY DESIGN

Observational study.

SETTING & PARTICIPANTS

158,601 adults (48% women; mean age 62 years, eGFRcr 80, and eGFRcys 73mL/min/1.73/m2) undergoing testing for creatinine and cystatin C on the same day in connection with a health care encounter during 2010-2018 in Stockholm, Sweden.

EXPOSURE

Percentage difference of eGFRcys minus eGFRcr (eGFRdiff).

OUTCOME

Kidney failure with replacement therapy (KFRT), acute kidney injury (AKI), atherosclerotic cardiovascular disease (ASCVD), heart failure, and death.

ANALYTICAL APPROACH

Multivariable Cox proportional hazards regression.

RESULTS

Discordances between eGFRcr and eGFRcys were common, with eGFRcys being lower than eGFRcr (negative eGFRdiff) in most cases (65%). Patients with larger negative eGFRdiff were older, more often female, with higher eGFRcr and albuminuria, and more comorbid conditions. Compared with patients with similar eGFRcys and eGFRcr, the lowest quartile (eGFRcys > 27% lower than eGFRcr) had the higher HR of all study outcomes: AKI, 2.6 (95% CI, 2.4-2.9); KFRT, 1.4 (95% CI, 1.2-1.6); ASCVD, 1.4 (95% CI, 1.3-1.5); heart failure, 2.0 (95% CI, 1.9-2.2); and all-cause death, 2.6 (95% CI, 2.5-2.7). Conversely, patients in the highest quartile (positive eGFRdiff) were at lower risk.

LIMITATIONS

Observational study, lack of information on indications for cystatin C testing.

CONCLUSIONS

Cystatin C testing in routine care shows that many patients have a lower eGFRcys than eGFRcr, and these patients have a higher risk of multiple adverse outcomes.

PLAIN-LANGUAGE SUMMARY

Clinicians require guidance when there are discrepancies between the estimated glomerular filtration rate based on creatinine (eGFRcr) and based on cystatin C (eGFRcys) in the same individual. Routine cystatin C testing in Sweden for over a decade permits exploration of how common and large these discrepancies are, and their associations with adverse clinical outcomes. In this observational study, we found that discordances between eGFRcys and eGFRcr are common, and 1 in 4 patients tested had an eGFRcys > 28% lower than their eGFRcr. We also show that an eGFRcys that is lower than the eGFRcr consistently identifies patients at higher risk of adverse outcomes, including cardiovascular events, kidney replacement therapy, acute kidney injury, and death.

Differences in the Circulating Proteome in Individuals with versus without Sickle Cell Trait

BACKGROUND

Sickle cell trait affects approximately 8% of Black individuals in the United States, along with many other individuals with ancestry from malaria-endemic regions worldwide. While traditionally considered a benign condition, recent evidence suggests that sickle cell trait is associated with lower eGFR and higher risk of kidney diseases, including kidney failure. The mechanisms underlying these associations remain poorly understood. We used proteomic profiling to gain insight into the pathobiology of sickle cell trait.

METHODS

We measured proteomics ( N =1285 proteins assayed by Olink Explore) using baseline plasma samples from 592 Black participants with sickle cell trait and 1:1 age-matched Black participants without sickle cell trait from the prospective Women's Health Initiative cohort. Age-adjusted linear regression was used to assess the association between protein levels and sickle cell trait.

RESULTS

In age-adjusted models, 35 proteins were significantly associated with sickle cell trait after correction for multiple testing. Several of the sickle cell trait-protein associations were replicated in Black participants from two independent cohorts (Atherosclerosis Risk in Communities study and Jackson Heart Study) assayed using an orthogonal aptamer-based proteomic platform (SomaScan). Many of the validated sickle cell trait-associated proteins are known biomarkers of kidney function or injury ( e.g. , hepatitis A virus cellular receptor 1 [HAVCR1]/kidney injury molecule-1 [KIM-1], uromodulin [UMOD], ephrins), related to red cell physiology or hemolysis (erythropoietin [EPO], heme oxygenase 1 [HMOX1], and α -hemoglobin stabilizing protein) and/or inflammation (fractalkine, C-C motif chemokine ligand 2/monocyte chemoattractant protein-1 [MCP-1], and urokinase plasminogen activator surface receptor [PLAUR]). A protein risk score constructed from the top sickle cell trait-associated biomarkers was associated with incident kidney failure among those with sickle cell trait during Women's Health Initiative follow-up (odds ratio, 1.32; 95% confidence interval, 1.10 to 1.58).

CONCLUSIONS

We identified and replicated the association of sickle cell trait with a number of plasma proteins related to hemolysis, kidney injury, and inflammation.

Proteomics of CKD progression in the chronic renal insufficiency cohort

Progression of chronic kidney disease (CKD) portends myriad complications, including kidney failure. In this study, we analyze associations of 4638 plasma proteins among 3235 participants of the Chronic Renal Insufficiency Cohort Study with the primary outcome of 50% decline in estimated glomerular filtration rate or kidney failure over 10 years. We validate key findings in the Atherosclerosis Risk in the Communities study. We identify 100 circulating proteins that are associated with the primary outcome after multivariable adjustment, using a Bonferroni statistical threshold of significance. Individual protein associations and biological pathway analyses highlight the roles of bone morphogenetic proteins, ephrin signaling, and prothrombin activation. A 65-protein risk model for the primary outcome has excellent discrimination (C-statistic[95%CI] 0.862 [0.835, 0.889]), and 14/65 proteins are druggable targets. Potentially causal associations for five proteins, to our knowledge not previously reported, are supported by Mendelian randomization: EGFL9, LRP-11, MXRA7, IL-1 sRII and ILT-2. Modifiable protein risk markers can guide therapeutic drug development aimed at slowing CKD progression.

Estimated Glomerular Filtration Rate, Albuminuria, and Adverse Outcomes: An Individual-Participant Data Meta-Analysis

Importance

Chronic kidney disease (low estimated glomerular filtration rate [eGFR] or albuminuria) affects approximately 14% of adults in the US.

Objective

To evaluate associations of lower eGFR based on creatinine alone, lower eGFR based on creatinine combined with cystatin C, and more severe albuminuria with adverse kidney outcomes, cardiovascular outcomes, and other health outcomes.

Design, Setting, and Participants

Individual-participant data meta-analysis of 27 503 140 individuals from 114 global cohorts (eGFR based on creatinine alone) and 720 736 individuals from 20 cohorts (eGFR based on creatinine and cystatin C) and 9 067 753 individuals from 114 cohorts (albuminuria) from 1980 to 2021.

Exposures

The Chronic Kidney Disease Epidemiology Collaboration 2021 equations for eGFR based on creatinine alone and eGFR based on creatinine and cystatin C; and albuminuria estimated as urine albumin to creatinine ratio (UACR).

Main Outcomes and Measures

The risk of kidney failure requiring replacement therapy, all-cause mortality, cardiovascular mortality, acute kidney injury, any hospitalization, coronary heart disease, stroke, heart failure, atrial fibrillation, and peripheral artery disease. The analyses were performed within each cohort and summarized with random-effects meta-analyses.

Results

Within the population using eGFR based on creatinine alone (mean age, 54 years [SD, 17 years]; 51% were women; mean follow-up time, 4.8 years [SD, 3.3 years]), the mean eGFR was 90 mL/min/1.73 m2 (SD, 22 mL/min/1.73 m2) and the median UACR was 11 mg/g (IQR, 8-16 mg/g). Within the population using eGFR based on creatinine and cystatin C (mean age, 59 years [SD, 12 years]; 53% were women; mean follow-up time, 10.8 years [SD, 4.1 years]), the mean eGFR was 88 mL/min/1.73 m2 (SD, 22 mL/min/1.73 m2) and the median UACR was 9 mg/g (IQR, 6-18 mg/g). Lower eGFR (whether based on creatinine alone or based on creatinine and cystatin C) and higher UACR were each significantly associated with higher risk for each of the 10 adverse outcomes, including those in the mildest categories of chronic kidney disease. For example, among people with a UACR less than 10 mg/g, an eGFR of 45 to 59 mL/min/1.73 m2 based on creatinine alone was associated with significantly higher hospitalization rates compared with an eGFR of 90 to 104 mL/min/1.73 m2 (adjusted hazard ratio, 1.3 [95% CI, 1.2-1.3]; 161 vs 79 events per 1000 person-years; excess absolute risk, 22 events per 1000 person-years [95% CI, 19-25 events per 1000 person-years]).

Conclusions and Relevance

In this retrospective analysis of 114 cohorts, lower eGFR based on creatinine alone, lower eGFR based on creatinine and cystatin C, and more severe UACR were each associated with increased rates of 10 adverse outcomes, including adverse kidney outcomes, cardiovascular diseases, and hospitalizations.

Circulating Proteins and Mortality in CKD: A Proteomics Study of the AASK and ARIC Cohorts

Rationale & Objective

Proteomics could provide pathophysiologic insight into the increased risk of mortality in patients with chronic kidney disease (CKD). This study aimed to investigate associations between the circulating proteome and all-cause mortality among patients with CKD.

Study Design

Observational cohort study.

Setting & Participants

Primary analysis in 703 participants in the African American Study of Kidney Disease and Hypertension (AASK) and validation in 1,628 participants with CKD in the Atherosclerosis Risk in Communities (ARIC) study who attended visit 5.

Exposure

Circulating proteins.

Outcome

All-cause mortality.

Analytical Approach

Among AASK participants, we evaluated the associations of 6,790 circulating proteins with all-cause mortality using multivariable Cox proportional hazards models. Proteins with significant associations were further studied in ARIC Visit 5 participants with CKD.

Results

In the AASK cohort, the mean age was 54.5 years, 271 (38.5%) were women, and the mean measured glomerular filtration rate (GFR) was 46 mL/min/1.73 m2. The median follow-up was 9.6 years, and 7 distinct proteins were associated with all-cause mortality at the Bonferroni-level threshold (P < 0.05 of the 6,790) after adjustment for demographics and clinical factors, including baseline measured estimated GFR and proteinuria. In the ARIC visit 5 cohort, the mean age was 77.2 years, 903 (55.5%) were women, the mean estimated GFR was 54 mL/min/1.73 m2 and median follow-up was 6.9 years. Of the 7 proteins found in AASK, 3 (β2-microglobulin, spondin-1, and N-terminal pro-brain natriuretic peptide) were available in the ARIC data, with all 3 significantly associated with death in ARIC.

Limitations

Possibility of unmeasured confounding. Cause of death was not known.

Conclusions

Using large-scale proteomic analysis, proteins were reproducibly associated with mortality in 2 cohorts of participants with CKD.

Plain-Language Summary

Patients with chronic kidney disease (CKD) have a high risk of premature death, with various pathophysiological processes contributing to this increased risk of mortality. This observational cohort study aimed to investigate the associations between circulating proteins and all-cause mortality in patients with CKD using large-scale proteomic analysis. The study analyzed data from the African American Study of Kidney Disease and Hypertension (AASK) study and validated the findings in the Atherosclerosis Risk in Communities (ARIC) Study. A total of 6,790 circulating proteins were evaluated in AASK, and 7 proteins were significantly associated with all-cause mortality. Three of these proteins (β2-microglobulin, spondin-1, and N-terminal pro-brain natriuretic peptide (BNP)) were also measured in ARIC and were significantly associated with death. Additional studies assessing biomarkers associated with mortality among patients with CKD are needed to evaluate their use in clinical practice.

Associations of N-terminal pro-B-type natriuretic peptide, estimated glomerular filtration rate, and mortality in US adults

BACKGROUND

NT-proBNP is an important predictor of mortality but is inversely related to estimated glomerular filtration rate (eGFR). Whether the prognostic value of NT-proBNP is similar at different levels of kidney function is unknown.

AIMS

We evaluated the association of NT-proBNP with eGFR and its implications for all-cause and cardiovascular mortality risk in the general population.

METHODS

We included adults without prior cardiovascular disease from the National Health and Nutrition Examination Survey (NHANES) 1999 to 2004. We used linear regression to characterize the cross-sectional associations of NT-proBNP with eGFR. We used Cox regression to assess the prospective associations of NT-proBNP with mortality across categories of eGFR.

RESULTS

Among 11,456 participants (mean age 43 years, 48% female, 71% White, 11% Black), there was an inverse association between NT-proBNP and eGFR, which was stronger in those with more impaired kidney function. Per 15-unit decrease in eGFR, NT-proBNP was 4.3-fold higher for eGFR<30; 1.7-fold higher for eGFR 30 to 60, 1.4-fold higher for eGFR 61 to 90, 1.1-fold higher for eGFR 91 to 120 mL/min/1.73 m2. Over a median 17.6 years of follow-up, 2,275 deaths (622 cardiovascular) occurred. Higher NT-proBNP was associated with higher all-cause (HR per doubling of NT-proBNP: 1.20, 95% CI: 1.16-1.25) and cardiovascular mortality (HR: 1.34, 95% CI 1.25-1.44). Associations were similar across eGFR categories (P-interaction >.10). Adults with NT-proBNP≥450 pg/mL and eGFR<60 mL/min/1.73m2 had 3.4-fold higher all-cause mortality and 5.5-fold higher cardiovascular mortality risk, compared to those with NT-proBNP<125 pg/mL and eGFR>90 mL/min/1.73m2.

CONCLUSION

Despite its strong inverse association with eGFR, NT-proBNP has robust associations with mortality across the full range of kidney function in the general US adult population.

Long-term Visit-to-Visit Variability in Hemoglobin A1c and Kidney-Related Outcomes in Persons With Diabetes

RATIONALE & OBJECTIVE

To characterize associations between long-term visit-to-visit variability of hemoglobin A1c (HbA1c) and risk of adverse kidney outcomes in patients with diabetes.

STUDY DESIGN

Observational study.

SETTING & PARTICIPANTS

93,598 adults with diabetes undergoing routine care in Stockholm, Sweden.

EXPOSURES AND PREDICTORS

Categories of baseline and time-varying HbA1c variability score (HVS, the percentage of total HbA1c measures that vary by>0.5% [5.5mmol/mol] during a 3-year window): 0-20%, 21%-40%, 41%-60%, 61%-80%, and 81%-100%, with 0-20% as the reference group.

OUTCOME

Chronic kidney disease (CKD) progression (composite of>50% estimated glomerular filtration rate [eGFR] decline and kidney failure), acute kidney disease (AKI by clinical diagnosis or transient creatinine elevations according to KDIGO criteria), and worsening of albuminuria.

ANALYTICAL APPROACH

Multivariable Cox proportional hazards regression.

RESULTS

Compared with persons showing low HbA1c variability (HVS 0-20%), any increase in variability was associated with a higher risk of adverse kidney outcomes beyond mean HbA1c. For example, for patients with a baseline HbA1c variability of 81%-100%, the adjusted HR was 1.6 (95% CI, 1.47-1.74) for CKD progression, 1.23 [1.16-1.3] for AKI, and 1.28 [1.21-1.36] for worsening of albuminuria. The results were consistent across subgroups (diabetes subtypes, baseline eGFR, or albuminuria categories), in time-varying analyses and in sensitivity analyses including time-weighted average HbA1c or alternative metrics of variability.

LIMITATIONS

Observational study, limitations of claims data, lack of information on diet, body mass index, medication changes, and diabetes duration.

CONCLUSIONS

Higher long-term visit-to-visit HbA1c variability is consistently associated with the risks of CKD progression, AKI, and worsening of albuminuria.

PLAIN-LANGUAGE SUMMARY

The evidence for current guideline recommendations derives from clinical trials that focus on a single HbA1c as the definitive measure of efficacy of an intervention. However, long-term visit-to-visit fluctuations of HbA1c may provide additional value in the prediction of future kidney complications. We evaluated the long-term fluctuations in glycemic control in almost 100,000 persons with diabetes undergoing routine care in Stockholm, Sweden. We observed that higher long-term HbA1c fluctuation is consistently associated with the risks of chronic kidney disease progression, worsening of albuminuria and acute kidney injury. This finding supports a role for long-term glycemic variability in the development of kidney complications and illustrates the potential usefulness of this metric for risk stratification at the bedside beyond a single HbA1c test.

Discrepancies between Cystatin C-Based and Creatinine-Based eGFR

BACKGROUND

Recent guidance suggests clinicians increase use of cystatin C for the estimation of GFR. Discrepant levels of creatinine- versus cystatin C-based eGFR (eGFRcr versus eGFRcys) can occur and might signify inaccurate estimation of GFR using creatinine alone. This study sought to enhance the knowledge of the risk factors and clinical implications of having a large eGFR discrepancy.

METHODS

Participants in the Atherosclerosis Risk in Communities Study, a prospective cohort study of US adults, were followed over 25 years. eGFR discrepancy was measured at five clinical visits and defined as eGFRcys either 30% lower or higher than eGFRcr, the current clinical standard of care. The associations between eGFR discrepancies and kidney-related laboratory parameters were assessed using linear and logistic regression and long-term adverse outcomes, including kidney failure, AKI, heart failure, and death, using Cox proportional hazards models.

RESULTS

Among 13,197 individuals (mean age 57 [SD 6] years, 56% women, 25% Black race), 7% had eGFRcys 30% lower than eGFRcr at visit 2 (1990-1992), and this proportion increased over time to 23% by visit 6 (2016-2017). By contrast, the percent with eGFRcys 30% higher than eGFRcr was relatively stable (3%-1%). Independent risk factors for having eGFRcys 30% lower than eGFRcr included older age, female sex, non-Black race, higher eGFRcr, higher body mass index, weight loss, and current smoking. Those with eGFRcys 30% lower than eGFRcr had more anemia and higher uric acid, fibroblast growth factor 23, and phosphate levels as well as higher risk of subsequent mortality, kidney failure, AKI, and heart failure compared with those with similar eGFRcr and eGFRcys values.

CONCLUSIONS

Having eGFRcys lower than eGFRcr was associated with worse kidney-related laboratory derangements and a higher risk of adverse health outcomes.

PODCAST

This article contains a podcast at https://dts.podtrac.com/redirect.mp3/www.asn-online.org/media/podcast/CJASN/2023_09_08_CJN0000000000000217.mp3.

A genome-wide association study identifies 41 loci associated with eicosanoid levels

Eicosanoids are biologically active derivatives of polyunsaturated fatty acids with broad relevance to health and disease. We report a genome-wide association study in 8406 participants of the Atherosclerosis Risk in Communities Study, identifying 41 loci associated with 92 eicosanoids and related metabolites. These findings highlight loci required for eicosanoid biosynthesis, including FADS1-3, ELOVL2, and numerous CYP450 loci. In addition, significant associations implicate a range of non-oxidative lipid metabolic processes in eicosanoid regulation, including at PKD2L1/SCD and several loci involved in fatty acyl-CoA metabolism. Further, our findings highlight select clearance mechanisms, for example, through the hepatic transporter encoded by SLCO1B1. Finally, we identify eicosanoids associated with aspirin and non-steroidal anti-inflammatory drug use and demonstrate the substantial impact of genetic variants even for medication-associated eicosanoids. These findings shed light on both known and unknown aspects of eicosanoid metabolism and motivate interest in several gene-eicosanoid associations as potential functional participants in human disease.

Proteomics analysis of plasma from middle-aged adults identifies protein markers of dementia risk in later life

A diverse set of biological processes have been implicated in the pathophysiology of Alzheimer's disease (AD) and related dementias. However, there is limited understanding of the peripheral biological mechanisms relevant in the earliest phases of the disease. Here, we used a large-scale proteomics platform to examine the association of 4877 plasma proteins with 25-year dementia risk in 10,981 middle-aged adults. We found 32 dementia-associated plasma proteins that were involved in proteostasis, immunity, synaptic function, and extracellular matrix organization. We then replicated the association between 15 of these proteins and clinically relevant neurocognitive outcomes in two independent cohorts. We demonstrated that 12 of these 32 dementia-associated proteins were associated with cerebrospinal fluid (CSF) biomarkers of AD, neurodegeneration, or neuroinflammation. We found that eight of these candidate protein markers were abnormally expressed in human postmortem brain tissue from patients with AD, although some of the proteins that were most strongly associated with dementia risk, such as GDF15, were not detected in these brain tissue samples. Using network analyses, we found a protein signature for dementia risk that was characterized by dysregulation of specific immune and proteostasis/autophagy pathways in adults in midlife ~20 years before dementia onset, as well as abnormal coagulation and complement signaling ~10 years before dementia onset. Bidirectional two-sample Mendelian randomization genetically validated nine of our candidate proteins as markers of AD in midlife and inferred causality of SERPINA3 in AD pathogenesis. Last, we prioritized a set of candidate markers for AD and dementia risk prediction in midlife.

Accuracy of GFR Estimating Equations in Patients with Discordances between Creatinine and Cystatin C-Based Estimations

SIGNIFICANCE STATEMENT

Large discordances between eGFR on the basis of creatinine (eGFR cr ) or cystatin C (eGFR cys ) are common in clinical practice. However, which GFR estimating equation (eGFR cr , eGFR cys , or eGFR cr-cys ) is most accurate in these settings is not known. In this real-world study of 9404 concurrent measurements of creatinine, cystatin C, and iohexol clearance, all three equations performed similarly when eGFR cr and eGFR cys were similar (45% of cases). However, with large discordances (55% of cases), eGFR cr-cys was much more accurate than either alone. These findings were consistent among individuals with cardiovascular disease, heart failure, diabetes mellitus, liver disease, and cancer who have been underrepresented in research cohorts. Thus, when eGFR cr and eGFR cys are largely discordant in clinical practice, eGFR cr-cys is more accurate than eGFR cr or eGFR cys .

BACKGROUND

Cystatin C is recommended as a confirmatory test to eGFR when more precise estimates are needed for clinical decision making. Although eGFR on the basis of both creatinine and cystatin (eGFR cr-cys ) is the most accurate estimate in research studies, it is uncertain whether this is true in real-world settings, particularly when there are large discordances between eGFR based on creatinine (eGFR cr ) and that based on cystatin C (eGFR cys ).

METHODS

We included 6185 adults referred for measured GFR (mGFR) using plasma clearance of iohexol in Stockholm, Sweden, who had 9404 concurrent measurements of creatinine, cystatin C, and iohexol clearance. The performance of eGFR cr , eGFR cys , and eGFR cr-cys was assessed against mGFR with median bias, P30 , and correct classification of GFR categories. We stratified analyses within three categories: eGFR cys at least 20% lower than eGFR cr (eGFR cys eGFR cr ).

RESULTS

eGFR cr and eGFR cys were similar in 4226 (45%) samples, and among these samples all three estimating equations performed similarly. By contrast, eGFR cr-cys was much more accurate in cases of discordance. For example, when eGFR cys eGFR cr (8% of samples), the median biases were -4.5, 8.4, and 1.4 ml/min per 1.73m 2 . The findings were consistent among individuals with cardiovascular disease, heart failure, diabetes mellitus, liver disease, and cancer.

CONCLUSIONS

When eGFR cr and eGFR cys are highly discordant in clinical practice, eGFR cr-cys is more accurate than either eGFR cr or eGFR cys .

Unbiased Human Kidney Tissue Proteomics Identifies Matrix Metalloproteinase 7 as a Kidney Disease Biomarker

SIGNIFICANCE STATEMENT

Although gene expression changes have been characterized in human diabetic kidney disease (DKD), unbiased tissue proteomics information for this condition is lacking. The authors conducted an unbiased aptamer-based proteomic analysis of samples from patients with DKD and healthy controls, identifying proteins with levels that associate with kidney function (eGFR) or fibrosis, after adjusting for key covariates. Overall, tissue gene expression only modestly correlated with tissue protein levels. Kidney protein and RNA levels of matrix metalloproteinase 7 (MMP7) strongly correlated with fibrosis and with eGFR. Single-cell RNA sequencing indicated that kidney tubule cells are an important source of MMP7. Furthermore, plasma MMP7 levels predicted future kidney function decline. These findings identify kidney tissue MMP7 as a biomarker of fibrosis and blood MMP7 as a biomarker for future kidney function decline.

BACKGROUND

Diabetic kidney disease (DKD) is responsible for close to half of all ESKD cases. Although unbiased gene expression changes have been extensively characterized in human kidney tissue samples, unbiased protein-level information is not available.

METHODS

We collected human kidney samples from 23 individuals with DKD and ten healthy controls, gathered associated clinical and demographics information, and implemented histologic analysis. We performed unbiased proteomics using the SomaScan platform and quantified the level of 1305 proteins and analyzed gene expression levels by bulk RNA and single-cell RNA sequencing (scRNA-seq). We validated protein levels in a separate cohort of kidney tissue samples as well as in 11,030 blood samples.

RESULTS

Globally, human kidney transcript and protein levels showed only modest correlation. Our analysis identified 14 proteins with kidney tissue levels that correlated with eGFR and found that the levels of 152 proteins correlated with interstitial fibrosis. Of the identified proteins, matrix metalloprotease 7 (MMP7) showed the strongest association with both fibrosis and eGFR. The correlation between tissue MMP7 protein expression and kidney function was validated in external datasets. The levels of MMP7 RNA correlated with fibrosis in the primary and validation datasets. Findings from scRNA-seq pointed to proximal tubules, connecting tubules, and principal cells as likely cellular sources of increased tissue MMP7 expression. Furthermore, plasma MMP7 levels correlated not only with kidney function but also associated with prospective kidney function decline.

CONCLUSIONS

Our findings, which underscore the value of human kidney tissue proteomics analysis, identify kidney tissue MMP7 as a diagnostic marker of kidney fibrosis and blood MMP7 as a biomarker for future kidney function decline.

Transcriptome- and proteome-wide association studies nominate determinants of kidney function and damage

BACKGROUND

The pathophysiological causes of kidney disease are not fully understood. Here we show that the integration of genome-wide genetic, transcriptomic, and proteomic association studies can nominate causal determinants of kidney function and damage.

RESULTS

Through transcriptome-wide association studies (TWAS) in kidney cortex, kidney tubule, liver, and whole blood and proteome-wide association studies (PWAS) in plasma, we assess for effects of 12,893 genes and 1342 proteins on kidney filtration (glomerular filtration rate (GFR) estimated by creatinine; GFR estimated by cystatin C; and blood urea nitrogen) and kidney damage (albuminuria). We find 1561 associations distributed among 260 genomic regions that are supported as putatively causal. We then prioritize 153 of these genomic regions using additional colocalization analyses. Our genome-wide findings are supported by existing knowledge (animal models for MANBA, DACH1, SH3YL1, INHBB), exceed the underlying GWAS signals (28 region-trait combinations without significant GWAS hit), identify independent gene/protein-trait associations within the same genomic region (INHBC, SPRYD4), nominate tissues underlying the associations (tubule expression of NRBP1), and distinguish markers of kidney filtration from those with a role in creatinine and cystatin C metabolism. Furthermore, we follow up on members of the TGF-beta superfamily of proteins and find a prognostic value of INHBC for kidney disease progression even after adjustment for measured glomerular filtration rate (GFR).

CONCLUSION

In summary, this study combines multimodal, genome-wide association studies to generate a catalog of putatively causal target genes and proteins relevant to kidney function and damage which can guide follow-up studies in physiology, basic science, and clinical medicine.

Genetic studies of paired metabolomes reveal enzymatic and transport processes at the interface of plasma and urine

The kidneys operate at the interface of plasma and urine by clearing molecular waste products while retaining valuable solutes. Genetic studies of paired plasma and urine metabolomes may identify underlying processes. We conducted genome-wide studies of 1,916 plasma and urine metabolites and detected 1,299 significant associations. Associations with 40% of implicated metabolites would have been missed by studying plasma alone. We detected urine-specific findings that provide information about metabolite reabsorption in the kidney, such as aquaporin (AQP)-7-mediated glycerol transport, and different metabolomic footprints of kidney-expressed proteins in plasma and urine that are consistent with their localization and function, including the transporters NaDC3 (SLC13A3) and ASBT (SLC10A2). Shared genetic determinants of 7,073 metabolite-disease combinations represent a resource to better understand metabolic diseases and revealed connections of dipeptidase 1 with circulating digestive enzymes and with hypertension. Extending genetic studies of the metabolome beyond plasma yields unique insights into processes at the interface of body compartments.

Proteomics: Progress and Promise of High-Throughput Proteomics in Chronic Kidney Disease

Current proteomic tools permit the high-throughput analysis of the blood proteome in large cohorts, including those enriched for chronic kidney disease (CKD) or its risk factors. To date, these studies have identified numerous proteins associated with cross-sectional measures of kidney function, as well as with the longitudinal risk of CKD progression. Representative signals that have emerged from the literature include an association between levels of testican-2 and favorable kidney prognosis and an association between levels of TNFRSF1A and TNFRSF1B and worse kidney prognosis. For these and other associations, however, understanding whether the proteins play a causal role in kidney disease pathogenesis remains a fundamental challenge, especially given the strong impact that kidney function can have on blood protein levels. Prior to investing in dedicated animal models or randomized trials, methods that leverage the availability of genotyping in epidemiologic cohorts-including Mendelian randomization, colocalization analyses, and proteome-wide association studies-can add evidence for causal inference in CKD proteomics research. In addition, integration of large-scale blood proteome analyses with urine and tissue proteomics, as well as improved assessment of posttranslational protein modifications (e.g., carbamylation), represent important future directions. Taken together, these approaches seek to translate progress in large-scale proteomic profiling into the promise of improved diagnostic tools and therapeutic target identification in kidney disease.

Alterations in the Circulating Proteome Associated with Albuminuria

SIGNIFICANCE STATEMENT

We describe circulating proteins associated with albuminuria in a population of African American Study of Kidney Disease and Hypertension with CKD (AASK) using the largest proteomic platform to date: nearly 7000 circulating proteins, representing approximately 2000 new targets. Findings were replicated in a subset of a general population cohort with kidney disease (ARIC) and a population with CKD Chronic Renal Insufficiency Cohort (CRIC). In cross-sectional analysis, 104 proteins were significantly associated with albuminuria in the Black group, of which 67 of 77 available proteins were replicated in ARIC and 68 of 71 available proteins in CRIC. LMAN2, TNFSFR1B, and members of the ephrin superfamily had the strongest associations. Pathway analysis also demonstrated enrichment of ephrin family proteins.

BACKGROUND

Proteomic techniques have facilitated understanding of pathways that mediate decline in GFR. Albuminuria is a key component of CKD diagnosis, staging, and prognosis but has been less studied than GFR. We sought to investigate circulating proteins associated with higher albuminuria.

METHODS

We evaluated the cross-sectional associations of the blood proteome with albuminuria and longitudinally with doubling of albuminuria in the African American Study of Kidney Disease and Hypertension (AASK; 38% female; mean GFR 46; median urine protein-to-creatinine ratio 81 mg/g; n =703) and replicated in two external cohorts: a subset of the Atherosclerosis Risk in Communities (ARIC) study with CKD and the Chronic Renal Insufficiency Cohort (CRIC).

RESULTS

In cross-sectional analysis, 104 proteins were significantly associated with albuminuria in AASK, of which 67 of 77 available proteins were replicated in ARIC and 68 of 71 available proteins in CRIC. Proteins with the strongest associations included LMAN2, TNFSFR1B, and members of the ephrin superfamily. Pathway analysis also demonstrated enrichment of ephrin family proteins. Five proteins were significantly associated with worsening albuminuria in AASK, including LMAN2 and EFNA4, which were replicated in ARIC and CRIC.

CONCLUSIONS

Among individuals with CKD, large-scale proteomic analysis identified known and novel proteins associated with albuminuria and suggested a role for ephrin signaling in albuminuria progression.

Baclofen and the Risk of Encephalopathy: A Real-World, Active-Comparator Cohort Study

OBJECTIVE

To quantify the risk of encephalopathy associated with oral baclofen compared with other muscle relaxants-tizanidine or cyclobenzaprine.

PATIENTS AND METHODS

We conducted a new-user, active-comparator study of 2 pairwise cohorts using tertiary health system data from Geisinger Health in Pennsylvania (January 1, 2005, through December 31, 2018). Adults (aged ≥18 years) newly treated with baclofen or tizanidine were included in cohort 1. Adults newly treated with baclofen or cyclobenzaprine were included in cohort 2. Propensity score-based inverse probability of treatment weighting (IPTW) was used to balance the respective cohorts on 45 patient characteristics. Fine-Gray competing risk regression was used to estimate the risk of encephalopathy.

RESULTS

Cohort 1 included 16,192 new baclofen users and 9782 new tizanidine users. The 30-day risk of encephalopathy was higher in patients treated with baclofen vs tizanidine (IPTW incidence rate, 64.7 vs 28.3 per 1000 person-years) with an IPTW subdistribution hazard ratio (SHR) of 2.29 (95% CI, 1.43 to 3.67). This risk persisted through 1 year (SHR, 1.32 [95% CI, 1.07 to 1.64]). Similarly in cohort 2, baclofen vs cyclobenzaprine was associated with a greater risk of encephalopathy at 30 days (SHR, 2.35 [95% CI, 1.59 to 3.48]) that persisted through the first year of treatment (SHR, 1.94 [95% CI, 1.56 to 2.40]).

CONCLUSION

The risk of encephalopathy was greater with baclofen vs tizanidine or cyclobenzaprine use. The elevated risk was apparent as early as 30 days and persisted through the first year of treatment. Our findings from routine care settings may inform shared treatment decisions between patients and prescribers.

Major cardiovascular events and subsequent risk of kidney failure with replacement therapy: a CKD Prognosis Consortium study

AIMS

Chronic kidney disease (CKD) increases risk of cardiovascular disease (CVD). Less is known about how CVD associates with future risk of kidney failure with replacement therapy (KFRT).

METHODS AND RESULTS

The study included 25 903 761 individuals from the CKD Prognosis Consortium with known baseline estimated glomerular filtration rate (eGFR) and evaluated the impact of prevalent and incident coronary heart disease (CHD), stroke, heart failure (HF), and atrial fibrillation (AF) events as time-varying exposures on KFRT outcomes. Mean age was 53 (standard deviation 17) years and mean eGFR was 89 mL/min/1.73 m2, 15% had diabetes and 8.4% had urinary albumin-to-creatinine ratio (ACR) available (median 13 mg/g); 9.5% had prevalent CHD, 3.2% prior stroke, 3.3% HF, and 4.4% prior AF. During follow-up, there were 269 142 CHD, 311 021 stroke, 712 556 HF, and 605 596 AF incident events and 101 044 (0.4%) patients experienced KFRT. Both prevalent and incident CVD were associated with subsequent KFRT with adjusted hazard ratios (HRs) of 3.1 [95% confidence interval (CI): 2.9-3.3], 2.0 (1.9-2.1), 4.5 (4.2-4.9), 2.8 (2.7-3.1) after incident CHD, stroke, HF and AF, respectively. HRs were highest in first 3 months post-CVD incidence declining to baseline after 3 years. Incident HF hospitalizations showed the strongest association with KFRT [HR 46 (95% CI: 43-50) within 3 months] after adjustment for other CVD subtype incidence.

CONCLUSION

Incident CVD events strongly and independently associate with future KFRT risk, most notably after HF, then CHD, stroke, and AF. Optimal strategies for addressing the dramatic risk of KFRT following CVD events are needed.

The association between socioeconomic status and use of potentially inappropriate medications in older adults

BACKGROUND

Potentially inappropriate medication (PIM) use is an important public health problem, particularly among older adults who may need multiple pharmacologic therapies for various chronic conditions. As socioeconomic status (SES) affects the quality of healthcare that individuals receive, SES may be associated with the use of PIM in older adults. This study aimed to determine whether low SES is associated with increased use of PIM.

METHODS

We studied 4927 participants (aged 66-90 years) who were on at least one medication at visit five (2011-2013) of the Atherosclerosis Risk in Communities Study. We created a cumulative SES score categorized as high (7-9), middle (3-6), and low (0-2) based on education, income, and area deprivation index. We use multivariable logistic regression to examine the associations between SES and use of two or more PIM for older adults, defined by the 2019 Beers Criteria.

RESULTS

A total of 31.0% and 6.9% of the participants used one or more PIM and two or more PIM, respectively. After adjusting for demographic characteristics and insurance type, low cumulative SES score was associated with significantly greater use of two or more PIM (odds ratio [OR] = 1.83 [95% confidence interval (CI) 1.18-2.86]), as was middle cumulative SES score (OR = 1.40 [95% CI 1.06-1.83]), compared to high cumulative SES score. The results remained significant after further adjusting for comorbidities and medication burden for low cumulative SES score (OR = 1.66 [95%CI 1.02-2.71]).

CONCLUSIONS

We found that lower SES was associated with greater use of PIM among older adults independent of their medication burden and comorbidities, suggesting socioeconomic disparities in quality of medication management. Focused efforts targeting older adults with low SES to reduce PIM use may be needed to prevent adverse drug events.

Proteomic Predictors of Incident Diabetes: Results From the Atherosclerosis Risk in Communities (ARIC) Study

OBJECTIVE

The plasma proteome preceding diabetes can improve our understanding of diabetes pathogenesis.

RESEARCH DESIGN AND METHODS

In 8,923 Atherosclerosis Risk in Communities (ARIC) Study participants (aged 47-70 years, 57% women, 19% Black), we conducted discovery and internal validation for associations of 4,955 plasma proteins with incident diabetes. We externally validated results in the Singapore Multi-Ethnic Cohort (MEC) nested case-control (624 case subjects, 1,214 control subjects). We used Cox regression to discover and validate protein associations and risk-prediction models (elastic net regression with cardiometabolic risk factors and proteins) for incident diabetes. We conducted a pathway analysis and examined causality using genetic instruments.

RESULTS

There were 2,147 new diabetes cases over a median of 19 years. In the discovery sample (n = 6,010), 140 proteins were associated with incident diabetes after adjustment for 11 risk factors (P < 10-5). Internal validation (n = 2,913) showed 64 of the 140 proteins remained significant (P < 0.05/140). Of the 63 available proteins, 47 (75%) were validated in MEC. Novel associations with diabetes were found for 22 the 47 proteins. Prediction models (27 proteins selected by elastic net) developed in discovery had a C statistic of 0.731 in internal validation, with ΔC statistic of 0.011 (P = 0.04) beyond 13 risk factors, including fasting glucose and HbA1c. Inflammation and lipid metabolism pathways were overrepresented among the diabetes-associated proteins. Genetic instrument analyses suggested plasma SHBG, ATP1B2, and GSTA1 play causal roles in diabetes risk.

CONCLUSIONS

We identified 47 plasma proteins predictive of incident diabetes, established causal effects for 3 proteins, and identified diabetes-associated inflammation and lipid pathways with potential implications for diagnosis and therapy.

A Novel Creatinine Muscle Index Based on Creatinine Filtration: Associations with Frailty and Mortality

SIGNIFICANCE STATEMENT

Low muscle mass is related to frailty and increased mortality in older adults. However, muscle mass is not easily assessed in routine clinical practice. This paper describes a novel creatinine muscle index (CMI) on the basis of serum creatinine and cystatin C. CMI was moderately associated with frailty among older adults. A significantly higher proportion of individuals with weak grip strength were in the lowest tertile of CMI. The index was also associated with mortality. These results are consistent with the hypothesis that creatinine filtration may be an index of muscle mass, which may have utility in clinical practice.

BACKGROUND

Low muscle mass is related to frailty and increased mortality in older adults. However, muscle mass is not easily assessed in routine clinical practice.

METHODS

This study describes a novel creatinine muscle index (CMI) on the basis of serum creatinine and cystatin C in a community-based sample of older adults from the Atherosclerosis Risk in Communities Study. Analyses included 4639 participants who attended visit 5 (2011-2013) and 12,786 participants who attended visit 2 (1990-1992). CMI was defined as creatinine filtration (the product of serum creatinine times eGFR on the basis of cystatin C) and was analyzed in sex-specific tertiles. Cross-sectional associations of CMI with a frailty trichotomy, defined by the number (robust [0]/prefrail [1-2]/frail [3-5]) of five frailty components (weight loss, slowness, exhaustion, weakness, and low physical activity), were studied using polychotomous logistic regression and binary logistic regression with each frailty component. Cox regression was used to estimate associations of CMI at visit 5 and visit 2 with mortality. Models were adjusted for demographics, clinical variables, and comorbid conditions.

RESULTS

CMI (tertile 1 versus 3) was moderately associated with frailty (visit 5: adjusted odds ratio 4.23 [95% confidence interval (CI), 2.02 to 8.87] in men and 2.34 [95% CI, 1.41 to 3.89] in women) and with mortality (visit 5: adjusted hazard ratio 1.45 [95% CI, 1.08 to 1.94] in men and 1.55 [95% CI, 1.13 to 2.12] in women; similar results were seen at visit 2).

CONCLUSION

Lower CMI was associated with frailty and increased mortality, two clinical outcomes known to be associated with decreased muscle mass. Creatinine filtration may be an index of muscle mass and have utility in clinical practice, particularly at low levels.

The Kidney Failure Risk Equation: Evaluation of Novel Input Variables including eGFR Estimated Using the CKD-EPI 2021 Equation in 59 Cohorts

SIGNIFICANCE STATEMENT

The kidney failure risk equation (KFRE) uses age, sex, GFR, and urine albumin-to-creatinine ratio (ACR) to predict 2- and 5-year risk of kidney failure in populations with eGFR <60 ml/min per 1.73 m 2 . However, the CKD-EPI 2021 creatinine equation for eGFR is now recommended for use but has not been fully tested in the context of KFRE. In 59 cohorts comprising 312,424 patients with CKD, the authors assessed the predictive performance and calibration associated with the use of the CKD-EPI 2021 equation and whether additional variables and accounting for the competing risk of death improves the KFRE's performance. The KFRE generally performed well using the CKD-EPI 2021 eGFR in populations with eGFR <45 ml/min per 1.73 m 2 and was not improved by adding the 2-year prior eGFR slope and cardiovascular comorbidities.

BACKGROUND

The kidney failure risk equation (KFRE) uses age, sex, GFR, and urine albumin-to-creatinine ratio (ACR) to predict kidney failure risk in people with GFR <60 ml/min per 1.73 m 2 .

METHODS

Using 59 cohorts with 312,424 patients with CKD, we tested several modifications to the KFRE for their potential to improve the KFRE: using the CKD-EPI 2021 creatinine equation for eGFR, substituting 1-year average ACR for single-measure ACR and 1-year average eGFR in participants with high eGFR variability, and adding 2-year prior eGFR slope and cardiovascular comorbidities. We also assessed calibration of the KFRE in subgroups of eGFR and age before and after accounting for the competing risk of death.

RESULTS

The KFRE remained accurate and well calibrated overall using the CKD-EPI 2021 eGFR equation. The other modifications did not improve KFRE performance. In subgroups of eGFR 45-59 ml/min per 1.73 m 2 and in older adults using the 5-year time horizon, the KFRE demonstrated systematic underprediction and overprediction, respectively. We developed and tested a new model with a spline term in eGFR and incorporating the competing risk of mortality, resulting in more accurate calibration in those specific subgroups but not overall.

CONCLUSIONS

The original KFRE is generally accurate for eGFR <45 ml/min per 1.73 m 2 when using the CKD-EPI 2021 equation. Incorporating competing risk methodology and splines for eGFR may improve calibration in low-risk settings with longer time horizons. Including historical averages, eGFR slopes, or a competing risk design did not meaningfully alter KFRE performance in most circumstances.

Association of Kidney Function Measures With Signs of Neurodegeneration and Small Vessel Disease on Brain Magnetic Resonance Imaging: The Atherosclerosis Risk in Communities (ARIC) Study

RATIONALE & OBJECTIVE

Chronic kidney disease (CKD) is a risk factor for cognitive decline, but evidence is limited on its etiology and morphological manifestation in the brain. We evaluated the association of estimated glomerular filtration rate (eGFR) and urinary albumin-creatinine ratio (UACR) with structural brain abnormalities visible on magnetic resonance imaging (MRI). We also assessed whether this association was altered when different filtration markers were used to estimate GFR.

STUDY DESIGN

Cross-sectional study nested in a cohort study.

SETTING & PARTICIPANTS

1,527 participants in the Atherosclerosis Risk in Communities (ARIC) Study.

PREDICTORS

Log(UACR) and eGFR based on cystatin C, creatinine, cystatin C and creatinine in combination, or β2-microglobulin (B2M).

OUTCOMES

Brain volume reduction, infarcts, microhemorrhages, white matter lesions.

ANALYTICAL APPROACH

Multivariable linear and logistic regression models fit separately for each predictor based on a 1-IQR difference in the predictor value.

RESULTS

Each 1-IQR lower eGFR was associated with reduced cortex volume (regression coefficient: -0.07 [95% CI, -0.12 to-0.02]), greater white matter hyperintensity volume (logarithmically transformed; regression coefficient: 0.07 [95% CI, 0.01-0.15]), and lower white matter fractional anisotropy (regression coefficient: -0.08 [95% CI, -0.17 to-0.01]). The results were similar when eGFR was estimated with different equations based on cystatin C, creatinine, a combination of cystatin C and creatinine, or B2M. Higher log(UACR) was similarly associated with these outcomes as well as brain infarcts and microhemorrhages (odds ratios per 1-IQR-fold greater UACR of 1.31 [95% CI, 1.13-1.52] and 1.30 [95% CI, 1.12-1.51], respectively). The degree to which brain volume was lower in regions usually susceptible to Alzheimer disease and LATE (limbic-predominant age-related TDP-43 [Tar DNA binding protein 43] encephalopathy) was similar to that seen in the rest of the cortex.

LIMITATIONS

No inference about longitudinal effects due to cross-sectional design.

CONCLUSIONS

We found eGFR and UACR are associated with structural brain damage across different domains of etiology, and eGFR- and UACR-related brain atrophy is not selective for regions typically affected by Alzheimer disease and LATE. Hence, Alzheimer disease or LATE may not be leading contributors to neurodegeneration associated with CKD.

Anemia Prevalence, Type, and Associated Risks in a Cohort of 5.0 Million Insured Patients in the United States by Level of Kidney Function

RATIONALE & OBJECTIVE

Anemia is common in chronic kidney disease (CKD); although anemia is associated with adverse outcomes, the available treatments are not ideal. We characterized the burden, risk factors for, and risks associated with anemia by estimated glomerular filtration rate (eGFR) and hemoglobin level.

STUDY DESIGN

Cross-sectional and prospective cohort study.

SETTING & PARTICIPANTS

Outpatient data from 5,004,957 individuals across 57 health care centers in the United States from 2016 to 2019, extracted from the Optum Labs Data Warehouse.

EXPOSURE

Severity of anemia, presence of low iron test results, eGFR.

OUTCOME

Incident kidney failure with replacement therapy, cardiovascular disease, coronary heart disease, stroke, heart failure, death.

ANALYTICAL APPROACH

The prevalences of anemia, low iron test results, vitamin B12 deficiency, and erythropoiesis-stimulating agent (ESA) use, stratified by sex and eGFR, were characterized. Polychotomous logistic regression was used to estimate the adjusted odds ratios of different hemoglobin levels across eGFR. Cox proportional hazards regression was used to calculate adjusted hazard ratios for adverse outcomes across hemoglobin level.

RESULTS

The mean age was 54 years, and 42% were male. Lower eGFR was very strongly associated with increased prevalence of anemia, even after adjustment. Although iron studies were checked infrequently in patients with anemia, low iron test results were highly prevalent in those tested: 60.4% and 81.3% of men and women, respectively. ESA use was uncommon, with a prevalence of use of<4%. Lower hemoglobin was independently associated with increased risk of incident kidney failure with replacement therapy, cardiovascular disease, coronary heart disease, stroke, heart failure, and death.

LIMITATIONS

Reliance on ICD codes for medical diagnoses, death information obtained from claims data, observational study.

CONCLUSIONS

Severe anemia was common and strongly associated with lower eGFR and multiple adverse outcomes. Low-iron test results were highly prevalent in those tested despite iron studies being checked infrequently. ESA use in nondialysis CKD patients was uncommon.