Risk Factors and Outcomes Associated With Heart Failure With Preserved and Reduced Ejection Fraction in People With Chronic Kidney Disease

BACKGROUND

Heart failure (HF) is associated with poor outcomes in people with chronic kidney disease, yet it is unknown whether outcomes differ by HF subtype. This study aimed to examine associations of incident HF with preserved ejection fraction (HFpEF) versus HF with reduced ejection fraction (HFrEF) with progression to end-stage kidney disease (ESKD) and mortality.

METHODS

We studied individuals with chronic kidney disease in the CRIC study (Chronic Renal Insufficiency Cohort) who were free of HF at cohort entry. Incident HF hospitalizations were adjudicated and classified into HFpEF (ejection fraction, ≥50%) or HFrEF (ejection fraction, <50%) based on echocardiograms performed during the hospitalization or at a research study visit. ESKD was defined as need for chronic dialysis or kidney transplant. Cox proportional hazards were used to evaluate the association of time-updated HF subtype with risk of ESKD and mortality, adjusting for demographics, comorbidities, and medication use.

RESULTS

Among the 3557 study participants without HF at cohort entry, mean age was 57 years and mean estimated glomerular filtration rate was 45 mL/min per 1.73 m2. A total of 682 participants had incident HF. Incidence rates for HFpEF and HFrEF were 0.9 (95% CI, 0.8-1.0) and 0.7 (95% CI, 0.6-0.8) per 100 person-years, respectively (Pdifference=0.005). Associations of incident HF with progression to ESKD were not statistically different for HFpEF (hazard ratio, 2.06 [95% CI, 1.66-2.56]) and HFrEF (hazard ratio, 1.80 [95% CI, 1.36-2.38]; P=0.42). The associations with mortality were stronger for HFrEF (hazard ratio, 2.73 [95% CI, 2.24-3.33]) compared with HFpEF (hazard ratio, 1.99 [95% CI, 1.65-2.40]; P=0.0002).

CONCLUSIONS

In a chronic kidney disease population, the rates of HFpEF hospitalizations were greater than that of HFrEF. Risk of ESKD was high but not statically different across HF subtypes. There was a stronger association of HFrEF with mortality. Prevention and treatment of both HFpEF and HFrEF should be central priorities to improve outcomes in chronic kidney disease.

Acute Kidney Injury, Systemic Inflammation and Long-term Cognitive Function: ASSESS-AKI

BACKGROUND

Cognitive dysfunction is a well-known complication of chronic kidney disease, but it is less known whether cognitive decline occurs in survivors after acute kidney injury (AKI). We hypothesized that an episode of AKI is associated with poorer cognitive function, mediated, at least in part, by persistent systemic inflammation.

METHODS

ASSESS-AKI enrolled patients surviving three months after hospitalization with and without AKI matched based on demographics, comorbidities, and baseline kidney function. A subset underwent cognitive testing using the modified mini-mental status examination (3MS) at 3, 12, and 36 months. We examined the association of AKI with 3MS scores using mixed linear models and assessed the proportion of risk mediated by systemic inflammatory biomarkers.

RESULTS

Among 1538 participants in ASSESS-AKI, 1420 (92%) completed the 3MS assessment at 3 months and had a corresponding matched participant. Participants with AKI had lower 3MS scores at three years (difference -1.1 (95% CI: -2.0, -0.3) P=0.009) compared to participants without AKI. A higher proportion of AKI participants had a clinically meaningful (≥ 5 point) reduction in 3MS scores at three years compared to participants without AKI (14% vs. 10%, P=0.04). In mediation analyses, plasma soluble tumor necrosis factor receptor-1 (sTNFR-1) at three months after AKI mediated 35% (P=0.02) of the AKI related risk for 3MS scores at three years.

CONCLUSIONS

AKI was associated with lower 3MS scores and sTNFR-1 concentrations appeared to mediate a significant proportion of the risk of long-term cognitive impairment. Further work is needed to determine if AKI is causal or a marker for cognitive impairment.

Risk factors for hip and vertebral fractures in chronic kidney disease: the CRIC study

Fracture risk is high in chronic kidney disease (CKD) and underlying pathophysiology and risk factors may differ from the general population. In a cohort study of 3939 participants in the chronic renal insufficiency cohort (CRIC), we used Cox regression to test associations of putative risk factors with the composite of first hip or vertebral fracture assessed using hospital discharge codes. Mean age was 58 years, 45% were female, 42% were Black, and 13% were Hispanic. There were 82 hip and 24 vertebral fractures over a mean (SD) 11.1 (4.8) years (2.4 events per 1000 person-years [95% CI: 2.0, 2.9]). Measured at baseline, diabetes, lower body mass index (BMI), steroid use, proteinuria, and elevated parathyroid hormone (PTH) were each associated with fracture risk after adjusting for covariates. Lower time-updated estimated glomerular filtration rate (eGFR) was associated with fractures (HR 1.20 per 10 mL/min/1.73m2 lower eGFR; 95% CI: 1.04, 1.38) as were lower time-updated serum calcium and bicarbonate concentrations. Among time-updated categories of kidney function, hazard ratios (95% CI) for incident fracture were 4.53 (1.77, 11.60) for kidney failure treated with dialysis and 2.48 (0.86, 7.14) for post-kidney transplantation, compared with eGFR ≥60. Proton pump inhibitor use, dietary calcium intake, measures of vitamin D status, serum phosphate, urine calcium and phosphate, and plasma fibroblast growth factor-23 were not associated with fracture risk. In conclusion, lower eGFR in CKD is associated with higher fracture risk, which was highest in kidney failure. Diabetes, lower BMI, steroid use, proteinuria, higher serum concentrations of PTH, and lower calcium and bicarbonate concentrations were associated with fractures and may be modifiable risk factors.

Development and External Validation of Models to Predict Persistent Hypoxemic Respiratory Failure for Clinical Trial Enrichment

OBJECTIVES

Improving the efficiency of clinical trials in acute hypoxemic respiratory failure (HRF) depends on enrichment strategies that minimize enrollment of patients who quickly resolve with existing care and focus on patients at high risk for persistent HRF. We aimed to develop parsimonious models predicting risk of persistent HRF using routine data from ICU admission and select research immune biomarkers.

DESIGN

Prospective cohorts for derivation ( n = 630) and external validation ( n = 511).

SETTING

Medical and surgical ICUs at two U.S. medical centers.

PATIENTS

Adults with acute HRF defined as new invasive mechanical ventilation (IMV) and hypoxemia on the first calendar day after ICU admission.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

We evaluated discrimination, calibration, and practical utility of models predicting persistent HRF risk (defined as ongoing IMV and hypoxemia on the third calendar day after admission): 1) a clinical model with least absolute shrinkage and selection operator (LASSO) selecting Pa o2 /F io2 , vasopressors, mean arterial pressure, bicarbonate, and acute respiratory distress syndrome as predictors; 2) a model adding interleukin-6 (IL-6) to clinical predictors; and 3) a comparator model with Pa o2 /F io2 alone, representing an existing strategy for enrichment. Forty-nine percent and 69% of patients had persistent HRF in derivation and validation sets, respectively. In validation, both LASSO (area under the receiver operating characteristic curve, 0.68; 95% CI, 0.64-0.73) and LASSO + IL-6 (0.71; 95% CI, 0.66-0.76) models had better discrimination than Pa o2 /F io2 (0.64; 95% CI, 0.59-0.69). Both models underestimated risk in lower risk deciles, but exhibited better calibration at relevant risk thresholds. Evaluating practical utility, both LASSO and LASSO + IL-6 models exhibited greater net benefit in decision curve analysis, and greater sample size savings in enrichment analysis, compared with Pa o2 /F io2 . The added utility of LASSO + IL-6 model over LASSO was modest.

CONCLUSIONS

Parsimonious, interpretable models that predict persistent HRF may improve enrichment of trials testing HRF-targeted therapies and warrant future validation.

Identification of prognostic biomarkers for antibiotic associated nephrotoxicity in cystic fibrosis

BACKGROUND

Our objective was to discover novel urinary biomarkers of antibiotic-associated nephrotoxicity using an ex-vivo human microphysiological system (MPS) and to translate these findings to a prospectively enrolled cystic fibrosis (CF) population receiving aminoglycosides and/or polymyxin E (colistin) for a pulmonary exacerbation.

METHODS

We populated the MPS with primary human kidney proximal tubule epithelial cells (PTECs) from three donors and modeled nephrotoxin injury through exposure to 50 µg/mL polymyxin E for 72 h. We analyzed gene transcriptional responses by RNAseq and tested MPS effluents. We translated candidate biomarkers to a CF cohort via analysis of urine collected prior to, during and two weeks after antibiotics and patients were followed for a median of 3 years after antibiotic use.

RESULTS

Polymyxin E treatment resulted in a statistically significant increase in the pro-apoptotic Fas gene relative to control in RNAseq of MPS: fold-change = 1.63, FDR q-value = 7.29 × 10-5. Effluent analysis demonstrated an acute rise of soluble Fas (sFas) concentrations that correlated with cellular injury. In 16 patients with CF, urinary sFas concentrations were significantly elevated during antibiotic treatment, regardless of development of AKI. Over a median of three years of follow up, we identified seven cases of incident chronic kidney disease (CKD). Urinary sFas concentrations during antibiotic treatment were significantly associated with subsequent development of incident CKD (unadjusted relative risk = 2.02 per doubling of urinary sFas, 95 % CI = 1.40, 2.90, p < 0.001).

CONCLUSIONS

Using an ex-vivo MPS, we identified a novel biomarker of proximal tubule epithelial cell injury, sFas, and translated these findings to a clinical cohort of patients with CF.

Kidney Outcomes and Trajectories of Tubular Injury and Function in Critically Ill Persons with and without Coronavirus-2019

Background Coronavirus disease-2019 (COVID-19) may injure the kidney tubules via activation of inflammatory host responses and/or direct viral infiltration. Most studies of kidney injury in COVID-19 lacked contemporaneous controls or measured kidney biomarkers at a single time point. To better understand mechanisms of AKI in COVID-19, we compared kidney outcomes and trajectories of tubular injury, viability, and function in prospectively enrolled critically ill adults with and without COVID-19. Methods The COVID-19 Host Response and Outcomes (CHROME) study prospectively enrolled patients admitted to intensive care units in Washington state with symptoms of lower respiratory tract infection, determining COVID-19 status by nucleic acid amplification on arrival. We evaluated major adverse kidney events (MAKE) defined as a doubling of serum creatinine, kidney replacement therapy, or death, in 330 patients after inverse probability weighting. In the 181 patients with available biosamples, we determined trajectories of urine kidney injury molecule-1 (KIM-1) and epithelial growth factor (EGF), and urine:plasma ratios of endogenous markers of tubular secretory clearance. Results At ICU admission, mean age was 55\(\pm\)16 years; 45% required mechanical ventilation; and mean serum creatinine concentration was 1.1 mg/dL. COVID-19 was associated with a 70% greater incidence of MAKE (95% CI 1.05, 2.74) and a 741% greater incidence of KRT (95% CI 1.69, 32.41). The biomarker cohort had a median of three follow-up measurements. Urine EGF, secretory clearance ratios, and eGFR increased over time in the COVID-19 negative group but remained unchanged in the COVID-19 positive group. In contrast, urine KIM-1 concentrations did not significantly change over the course of the study in either group. Conclusions Among critically ill adults, COVID-19 is associated with a more protracted course of proximal tubular dysfunction.

Impaired incretin homeostasis in non-diabetic moderate-severe CKD

Background

Incretins are regulators of insulin secretion and glucose homeostasis that are metabolized by dipeptidyl peptidase-4 (DPP-4). Moderate-severe CKD may modify incretin release, metabolism, or response.

Methods

We performed 2-hour oral glucose tolerance testing (OGTT) in 59 people with non-diabetic CKD (eGFR<60 ml/min per 1.73 m2) and 39 matched controls. We measured total (tAUC) and incremental (iAUC) area under the curve of plasma total glucagon-like peptide-1 (GLP-1) and total glucose-dependent insulinotropic polypeptide (GIP). Fasting DPP-4 levels and activity were measured. Linear regression was used to adjust for demographic, body composition, and lifestyle factors.

Results

Mean eGFR was 38 ±13 and 89 ±17ml/min per 1.73 m2 in CKD and controls. GLP-1 iAUC and GIP iAUC were higher in CKD than controls with a mean of 1531 ±1452 versus 1364 ±1484 pMxmin, and 62370 ±33453 versus 42365 ±25061 pgxmin/ml, respectively. After adjustment, CKD was associated with 15271 pMxmin/ml greater GIP iAUC (95% CI 387, 30154) compared to controls. Adjustment for covariates attenuated associations of CKD with higher GLP-1 iAUC (adjusted difference, 122, 95% CI -619, 864). Plasma glucagon levels were higher at 30 minutes (mean difference, 1.6, 95% CI 0.3, 2.8 mg/dl) and 120 minutes (mean difference, 0.84, 95% CI 0.2, 1.5 mg/dl) in CKD compared to controls. There were no differences in insulin levels or plasma DPP-4 activity or levels between groups.

Conclusion

Incretin response to oral glucose is preserved or augmented in moderate-severe CKD, without apparent differences in circulating DPP-4 concentration or activity. However, neither insulin secretion nor glucagon suppression are enhanced.

Fibroblast Growth Factor 23 and Risk of Heart Failure Subtype: The CRIC (Chronic Renal Insufficiency Cohort) Study

Rationale & Objective

Heart failure (HF) is an important cause of morbidity and mortality among individuals with chronic kidney disease (CKD). A large body of evidence from preclinical and clinical studies implicates excess levels of fibroblast growth factor 23 (FGF23) in HF pathogenesis in CKD. It remains unclear whether the relationship between elevated FGF23 levels and HF risk among individuals with CKD varies by HF subtype.

Study Design

Prospective cohort study.

Settings & Participants

A total of 3,502 participants were selected in the Chronic Renal Insufficiency Cohort study.

Exposure

Baseline plasma FGF23.

Outcomes

Incident HF by subtype and total rate of HF hospitalization. HF was categorized as HF with preserved ejection fraction (HFpEF, ejection fraction [EF] ≥ 50%), HF with reduced EF (HFrEF, EF < 50%) and HF with unknown EF (HFuEF).

Analytical Approach

Multivariable-adjusted cause-specific Cox proportional hazards models were used to investigate associations between FGF23 and incident hospitalizations for HF by subtype. The Lunn-McNeil method was used to compare hazard ratios across HF subtypes. Poisson regression models were used to evaluate the total rate of HF.

Results

During a median follow-up time of 10.8 years, 295 HFpEF, 242 HFrEF, and 156 HFuEF hospitalizations occurred. In multivariable-adjusted cause-specific Cox proportional hazards models, FGF23 was significantly associated with the incidence of HFpEF (HR, 1.41; 95% CI, 1.21-1.64), HFrEF (HR, 1.27; 95% CI, 1.05-1.53), and HFuEF (HR, 1.40; 95% CI, 1.13-1.73) per 1 standard deviation (SD) increase in the natural log of FGF23. The Lunn-McNeil method determined that the risk association was consistent across all subtypes. The rate ratio of total HF events increased with FGF23 quartile. In multivariable-adjusted models, compared with quartile 1, FGF23 quartile 4 had a rate ratio of 1.81 (95% CI, 1.28-2.57) for total HF events.

Limitations

Self-report of HF hospitalizations and possible lack of an echocardiogram at time of hospitalization.

Conclusions

In this large multicenter prospective cohort study, elevated FGF23 levels were associated with increased risks for all HF subtypes.

Plain-Language Summary

Heart failure (HF) is a prominent cause of morbidity and mortality in individuals with chronic kidney disease (CKD). Identifying potential pathways in the development of HF is essential in developing therapies to prevent and treat HF. In a large cohort of individuals with CKD, the Chronic Renal Insufficiency Cohort (N = 3,502), baseline fibroblast growth factor-23 (FGF23), a hormone that regulates phosphorous, was evaluated in relation to the development of incident and recurrent HF with reduced, preserved, and unknown ejection fraction. In this large multicenter prospective cohort study, elevated FGF23 levels were associated with increased risk of all HF subtypes. These findings demonstrate the need for further research into FGF23 as a target in preventing the development of HF in individuals with CKD.

High-Density Lipoprotein Lipidomics and Mortality in CKD

Rationale & Objective

Patients with chronic kidney disease (CKD) have dysfunctional high-density lipoprotein (HDL) particles that lack cardioprotective properties; altered lipid composition may be associated with these changes. To investigate HDL lipids as potential cardiovascular risk factors in CKD, we tested the associations of HDL ceramides, sphingomyelins, and phosphatidylcholines with mortality.

Study Design

We leveraged data from a longitudinal prospective cohort of participants with CKD.

Setting & Participants

We included participants aged greater than 21 years with CKD, excluding those on maintenance dialysis or with prior kidney transplant.

Exposure

HDL particles were isolated using density gradient ultracentrifugation. We quantified the relative abundance of HDL ceramides, sphingomyelins, and phosphatidylcholines via liquid chromatography tandem mass spectrometry (LC-MS/MS).

Outcomes

Our primary outcome was all-cause mortality.

Analytical Approach

We tested associations using Cox regressions adjusted for demographics, comorbid conditions, laboratory values, medication use, and highly correlated lipids with opposed effects, controlling for multiple comparisons with false discovery rates (FDR).

Results

There were 168 deaths over a median follow-up of 6.12 years (interquartile range, 3.71-9.32). After adjustment, relative abundance of HDL ceramides (HR, 1.22 per standard deviation; 95% CI, 1.06-1.39), sphingomyelins with long fatty acids (HR, 1.44; 95% CI, 1.05-1.98), and saturated and monounsaturated phosphatidylcholines (HR, 1.22; 95% CI, 1.06-1.41) were significantly associated with increased risk of all-cause mortality (FDR < 5%).

Limitations

We were unable to test associations with cardiovascular disease given limited power. HDL lipidomics may not reflect plasma lipidomics. LC-MS/MS is unable to differentiate between glucosylceramides and galactosylceramides. The cohort was comprised of research volunteers in the Seattle area with CKD.

Conclusions

Greater relative HDL abundance of 3 classes of lipids was associated with higher risk of all-cause mortality in CKD; sphingomyelins with very long fatty acids were associated with a lower risk. Altered lipid composition of HDL particles may be a novel cardiovascular risk factor in CKD.

Plain-Language Summary

Patients with chronic kidney disease have abnormal high-density lipoprotein (HDL) particles that lack the beneficial properties associated with these particles in patients with normal kidney function. To investigate if small lipid molecules found on the surface of HDL might be associated with these changes, we tested the associations of lipid molecules found on HDL with death among patients with chronic kidney disease. We found that several lipid molecules found on the surface of HDL were associated with increased risk of death among these patients. These findings suggest that lipid molecules may be risk factors for death among patients with chronic kidney disease.

Metabolism and pharmacokinetics of vitamin D in patients with cystic fibrosis

Patients with cystic fibrosis (CF) commonly have lower circulating concentrations of 25-hydroxyvitamin D (25(OH)D) than healthy populations. We comprehensively compared measures of vitamin D metabolism among individuals with CF and healthy control subjects. In a cross-sectional study, serum from participants with CF (N = 83) and frequency-matched healthy control subjects by age and race (N = 82) were analyzed for: 25(OH)D2 and 25(OH)D3, 1α,25-dihydroxyvitamins D2 and D3 (1α,25(OH)2D2 and 1α,25(OH)2D3), 24,25-dihydroxyvitamin D3 (24,25(OH)2D3), 4β,25-dihydroxyvitamin D3 (4β,25(OH)2D3), 25-hydroxyvitamin D3-3-sulfate (25(OH)D3-S), and 25-hydroxyvitamin D3-3-glucuronide (25(OH)D3-G). In a 56-day prospective pharmacokinetic study, ∼25 μg deuterium-labeled 25(OH)D3 (d6-25(OH)D3) was administered intravenously to participants (N = 5 with CF, N = 5 control subjects). Serum was analyzed for d6-25(OH)D3 and d6-24,25(OH)2D3, and pharmacokinetic parameters were estimated. In the cross-sectional study, participants with CF had similar mean (SD) total 25(OH)D concentrations as control subjects (26.7 [12.3] vs. 27.7 [9.9] ng/mL) and had higher vitamin D supplement use (53% vs. 22%). However, participants with CF had lower total 1α,25(OH)2D (43.6 [12.7] vs. 50.7 [13.0] pg/mL), 4β,25(OH)2D3 (52.1 [38.9] vs. 79.9 [60.2] pg/mL), and 25(OH)D3-S (17.7 [11.6] vs. 30.1 [12.3] ng/mL) (p < 0.001 for all). The pharmacokinetics of d6-25(OH)D3 and d6-24,25(OH)D3 did not differ between groups. In summary, although 25(OH)D concentrations were comparable, participants with CF had lower 1α,25(OH)2D, 4β,25(OH)2D3, and 25(OH)D3-S concentrations than healthy controls. Neither 25(OH)D3 clearance, nor formation of 24,25(OH)2D3, appears to account for these differences and alternative mechanisms for low 25(OH)D in CF (i.e., decreased formation, altered enterohepatic recirculation) should be explored.

Evaluation of plasma sphingolipids as mediators of the relationship between kidney disease and cardiovascular events

BACKGROUND

Sphingolipids are a family of circulating lipids with regulatory and signaling roles that are strongly associated with both eGFR and cardiovascular disease. Patients with chronic kidney disease (CKD) are at high risk for cardiovascular events, and have different plasma concentrations of certain plasma sphingolipids compared to patients with normal kidney function. We hypothesize that circulating sphingolipids partially mediate the associations between eGFR and cardiovascular events.

METHODS

We measured the circulating concentrations of 8 sphingolipids, including 4 ceramides and 4 sphingomyelins with the fatty acids 16:0, 20:0, 22:0, and 24:0, in plasma from 3,463 participants in a population-based cohort (Cardiovascular Health Study) without prevalent cardiovascular disease. We tested the adjusted mediation effects by these sphingolipids of the associations between eGFR and incident cardiovascular disease via quasi-Bayesian Monte Carlo method with 2,000 simulations, using a Bonferroni correction for significance.

FINDINGS

The mean (±SD) eGFR was 70 (±16) mL/min/1.73 m2; 62% of participants were women. Lower eGFR was associated with higher plasma ceramide-16:0 and sphingomyelin-16:0, and lower ceramides and sphingomyelins-20:0 and -22:0. Lower eGFR was associated with risk of incident heart failure and ischemic stroke, but not myocardial infarction. Five of eight sphingolipids partially mediated the association between eGFR and heart failure. The sphingolipids associated with the greatest proportion mediated were ceramide-16:0 (proportion mediated 13%, 95% CI 8-22%) and sphingomyelin-16:0 (proportion mediated 10%, 95% CI 5-17%). No sphingolipids mediated the association between eGFR and ischemic stroke.

INTERPRETATION

Plasma sphingolipids partially mediated the association between lower eGFR and incident heart failure. Altered sphingolipids metabolism may be a novel mechanism for heart failure in patients with CKD.

FUNDING

This study was supported by T32 DK007467 and a KidneyCure Ben J. Lipps Research Fellowship (Dr. Lidgard). Sphingolipid measurements were supported by R01 HL128575 (Dr. Lemaitre) and R01 HL111375 (Dr. Hoofnagle) from the National Heart, Lung, and Blood Institute (NHLBI).

Vitamin D Metabolites and Risk of Cardiovascular Disease in Chronic Kidney Disease: The CRIC Study

Background The ratio of 24,25-dihydroxyvitamin D3/25-hydroxyvitamin D3 (vitamin D metabolite ratio [VDMR]) may reflect functional vitamin D activity. We examined associations of the VDMR, 25-hydroxyvitamin D (25[OH]D), and 1,25-dihydroxyvitamin D (1,25[OH]2D) with cardiovascular disease (CVD) in patients with chronic kidney disease. Methods and Results This study included longitudinal and cross-sectional analyses of 1786 participants from the CRIC (Chronic Renal Insufficiency Cohort) Study. Serum 24,25-dihydroxyvitamin D3, 25(OH)D, and 1,25(OH)2D were measured by liquid chromatography-tandem mass spectrometry 1 year after enrollment. The primary outcome was composite CVD (heart failure, myocardial infarction, stroke, and peripheral arterial disease). We used Cox regression with regression-calibrated weights to test associations of the VDMR, 25(OH)D, and 1,25(OH)2D with incident CVD. We examined cross-sectional associations of these metabolites with left ventricular mass index using linear regression. Analytic models adjusted for demographics, comorbidity, medications, estimated glomerular filtration rate, and proteinuria. The cohort was 42% non-Hispanic White race and ethnicity, 42% non-Hispanic Black race and ethnicity, and 12% Hispanic ethnicity. Mean age was 59 years, and 43% were women. Among 1066 participants without prevalent CVD, there were 298 composite first CVD events over a mean follow-up of 8.6 years. Lower VDMR and 1,25(OH)2D were associated with incident CVD before, but not after, adjustment for estimated glomerular filtration rate and proteinuria (hazard ratio, 1.11 per 1 SD lower VDMR [95% CI, 0.95-1.31]). Only 25(OH)D was associated with left ventricular mass index after full covariate adjustment (0.6 g/m2.7 per 10 ng/mL lower [95% CI, 0.0-1.3]). Conclusions Despite modest associations of 25(OH)D with left ventricular mass index, 25(OH)D, the VDMR, and 1,25(OH)2D were not associated with incident CVD in chronic kidney disease.

Incident Atrial Fibrillation and Risk of Dementia in a Diverse, Community-Based Population

Background Atrial fibrillation (AF) is the most common, clinically relevant arrhythmia in adults and associated with ischemic stroke and premature death. However, data are conflicting on whether AF is independently associated with risk of dementia, particularly in diverse populations. Methods and Results We identified all adults from 2 large integrated health care delivery systems between 2010 and 2017 and performed a 1:1 match of incident AF: no AF by age at index date, sex, estimated glomerular filtration rate category, and study site. Subsequent dementia was identified through previously validated diagnosis codes. Fine-Gray subdistribution hazard models were used to examine the association of incident AF (versus no AF) with risk of incident dementia, adjusting for sociodemographics and comorbidity and accounting for competing risk of death. Subgroup analyses by age, sex, race, ethnicity, and chronic kidney disease status were also performed. Among 196 968 matched adults, mean (SD) age was 73.6 (11.3) years, with 44.8% women, and 72.3% White. Incidence rates (per 100 person-years) for dementia over a median follow-up of 3.3 (interquartile range, 1.7-5.4) years were 2.79 (95% CI, 2.72-2.85) and 2.04 (95% CI, 1.99-2.08) per 100 person-years in persons with versus without incident AF, respectively. In adjusted models, incident AF was associated with a significantly greater risk of diagnosed dementia (subdistribution hazard ratio [sHR], 1.13 [95% CI, 1.09-1.16]). With additional adjustment for interim stroke events, the association of incident AF with dementia remained statistically significant (sHR, 1.10 [95% CI, 1.07-1.15]). Associations were stronger for age <65 (sHR, 1.65 [95% CI, 1.29-2.12]) versus ≥65 (sHR, 1.07 [95% CI, 1.03-1.10]) years (interaction P<0.001); and those without (sHR, 1.20 [95% CI, 1.14-1.26]) versus with chronic kidney disease (sHR, 1.06 [95% CI, 1.01-1.11]; interaction P<0.001). No meaningful differences were seen by sex, race, or ethnicity. Conclusions In a large, diverse community-based cohort, incident AF was associated with a modestly increased risk of dementia that was more prominent in younger patients and those without chronic kidney disease but did not substantially vary across sex, race, or ethnicity. Further studies should delineate mechanisms underpinning these findings, which may inform use of AF therapies.

Association of Kidney Function With Risk of Adverse Effects of Therapies for Atrial Fibrillation

Introduction

Atrial fibrillation (AF) is common in chronic kidney disease (CKD) and is treated with rate control medications, antiarrhythmic medications, as well as anticoagulation and procedures, each of which have associated risks. We aimed to evaluate the association of CKD status with the risks of adverse effects after initiation of AF therapies.

Methods

This was a cohort study of community-based adults who newly initiated rate control medications, antiarrhythmic medications, warfarin, direct oral anticoagulants (DOACs) or received AF procedures in the 1 year after diagnosis of AF. Baseline estimated glomerular filtration rate (eGFR) was calculated using outpatient serum creatinine measures. Adverse effects within 1 year related to each AF therapy or within 1 month of an AF procedure were ascertained from vital sign databases, electrocardiograms (ECGs), and administrative codes. Fine-Gray hazard models were used to study the association of eGFR categories with risk of adverse effects for each AF therapy.

Results

Among 115,564 patients with incident AF, lower eGFR (vs. eGFR ≥60 ml/min per 1.73 m²) was significantly associated with higher adjusted risk of adverse effects after initiation of rate control therapies (most commonly hypotension and bradycardia) as follows: eGFR 45-59 (hazard ratio [HR] 1.14, 95% confidence interval [CI] 1.07-1.22), 30-44 (HR 1.15, 95% CI 1.06-1.25), and 15-29 (HR 1.29, 95% CI: 1.12-1.47) ml/min per 1.73 m². Lower eGFR was associated with higher adjusted risk of adverse effects (most commonly prolonged QRS and QTc intervals) after initiation of an antiarrhythmic medication (vs. eGFR >60 ml/min per 1.73 m²) as follows: eGFR 45-59 (HR 1.12, 95% CI 1.01-1.23) and eGFR<15 (HR 1.43, 95% CI 1.01-2.01) ml/min per 1.73 m².

Conclusion

There was a graded association between lower eGFR and risk of major bleeding with warfarin use, with the greatest risk among those with eGFR <15 ml/min per 1.73 m² (HR of 2.93, 95% CI 1.99-4.30). There was no association of eGFR with major bleeding in patients receiving DOACs. Rates of adverse effects within 1 month of an AF procedure were low among patients with (n = 18) and without (n = 41) CKD and was underpowered for further analyses. In conclusion, lower eGFR was associated with significantly higher risks of adverse effects after initiation of commonly used therapies to treat AF. These data may help inform the complex therapeutic decisions in patients with CKD and AF.

High-Density Lipoprotein Lipidomics in Chronic Kidney Disease

BACKGROUND

Patients with chronic kidney disease (CKD) have dysfunctional high-density lipoprotein (HDL) particles as compared with the general population. Understanding the lipid composition of HDL may provide mechanistic insight. We tested associations of estimated glomerular filtration rate (eGFR) and albuminuria with relative HDL abundance of ceramides, sphingomyelins, and phosphatidylcholines in participants with CKD.

METHODS

We studied 490 participants with CKD from the Seattle Kidney Study. HDL was isolated from plasma; targeted lipidomics was used to quantify the relative abundance of ceramides, sphingomyelins, and phosphatidylcholines per 10 µg of total HDL protein. We evaluated the associations of eGFR and albuminuria with levels of individual lipids and lipid classes (including 7 ceramides, 6 sphingomyelins, and 24 phosphatidylcholines) using multivariable linear regression, controlling for multiple comparisons via the false discovery rate.

RESULTS

The mean (SD) eGFR was 45 (24) mL/min/1.73 m2; the median (IQR[interquartile range]) albuminuria was 108 (16, 686) mg/g (12.2 [1.8, 77.6] mg/mmol) urine creatinine. After adjusting for demographics, past medical history, laboratory values, and medication use, eGFR was not associated with higher relative abundance of any class of lipids or individual lipids. Greater albuminuria was significantly associated with a higher relative abundance of total ceramides and moderate-long R-chain sphingomyelins, ceramides 22:0 and 24:1, hexosylceramide 16:0, sphingomyelin 16:0, and phosphatidylcholines 29:0, 30:1, and 38:2; the strongest association was for hexosylceramide 16:0 (increase per doubling of urine albumin to creatinine ratio 0.022 (95% CI, 0.012-0.032).

CONCLUSIONS

Greater albuminuria was significantly associated with specific alterations in the lipid composition of HDL in participants with CKD.

Chronic Kidney Disease is Associated With Attenuated Plasma Metabolome Response to Oral Glucose Tolerance Testing

OBJECTIVE

Chronic kidney disease (CKD) is associated with decreased anabolic response to insulin contributing to protein-energy wasting. Targeted metabolic profiling of oral glucose tolerance testing (OGTT) may help identify metabolic pathways contributing to disruptions to insulin response in CKD.

METHODS

Using targeted metabolic profiling, we studied the plasma metabolome response in 41 moderate-to-severe nondiabetic CKD patients and 20 healthy controls at fasting and 2 hours after an oral glucose load. We used linear mixed modeling with random intercepts, adjusting for age, gender, race/ethnicity, body weight, and batch to assess heterogeneity in response to OGTT by CKD status.

RESULTS

Mean estimated glomerular filtration rate among CKD participants was 38.9 ± 12.7 mL/min per 1.73 m² compared to 87.2 ± 17.7 mL/min per 1.73 m² among controls. Glucose ingestion induced an anabolic response resulting in increased glycolysis products and a reduction in a wide range of metabolites including amino acids, tricarboxylic acid cycle intermediates, and purine nucleotides compared to fasting. Participants with CKD demonstrated a blunted anabolic response to OGTT evidenced by significant changes in 13 metabolites compared to controls. The attenuated metabolome response predominant involved mitochondrial energy metabolism, vitamin B family, and purine nucleotides. Compared to controls, CKD participants had elevated lactate:pyruvate (L:P) ratio and decreased guanosine diphosphate:guanosine triphosphate ratio during OGTT.

CONCLUSION

Metabolic profiling of OGTT response suggests a broad disruption of mitochondrial energy metabolism in CKD patients. These findings motivate further investigation into the impact of insulin sensitizers and mitochondrial targeted therapeutics on energy metabolism in patients with nondiabetic CKD.

The plasma free fraction of 25-hydroxyvitamin D3 is not strongly associated with 25-hydroxyvitamin D3 clearance in kidney disease patients and controls

Circulating 25-hydroxyvitamin D [25(OH)D] concentration is used to monitor vitamin D status. Plasma protein binding may influence the 25(OH)D dose-response to vitamin D treatment through a direct relationship between the plasma unbound ("free") fraction and clearance of 25(OH)D. We previously evaluated 25(OH)D3 clearance in relation to kidney function using intravenous administration of deuterium labeled 25(OH)D3. In this follow up study, we determined the free fraction of 25(OH)D3 in plasma (i.e., percent free 25(OH)D3) and the serum concentration and haplotype of vitamin D binding protein in these participants. We hypothesized that the percent free 25(OH)D3 would be positively associated with 25(OH)D3 clearance and would mediate associations between clearance and vitamin D binding protein (GC) haplotypes. Participants were mean (SD) age 64 (10) years and included 42 individuals with normal kidney function (controls), 24 individuals with chronic kidney disease, and 19 individuals with kidney failure on hemodialysis. Free plasma 25(OH)D2 and 25(OH)D3 concentrations were quantified with a new liquid chromatography-tandem mass spectrometry (LC-MS/MS) method. Because there is no reference measurement procedure for free 25(OH)D, we compared the new method with a widely-used predictive equation and a commercial immunoassay. The percent free 25(OH)D3 determined by predictive equation was weakly associated with 25(OH)D3 clearance (R = 0.27; P = 0.01). However, this association was absent when percent free 25(OH)D3 was determined using LC-MS/MS-measured free and total 25(OH)D3 concentrations. Method comparison uncovered a negative bias in immunoassay-measured free 25(OH)D concentrations among participants with kidney failure, so immunoassay results were not used to evaluate the association between percent free 25(OH)D3 and clearance. GC2 haplotype carriage was associated with 25(OH)D3 clearance. Among individuals with 2 relative to no GC2 alleles, clearance was 87 (95% CI: 15-158) mL/d greater. However, in contrast with the literature, GC2 carriage was not significantly related to DBP concentration or the percent free 25(OH)D3 (either predicted or measured). In conclusion, the free fraction of 25(OH)D3 is not strongly associated with 25(OH)D3 clearance but may explain small differences in clearance according to GC haplotype.

Effects of Vitamin D3 Supplementation on Cardiovascular and Cancer Outcomes by eGFR in VITAL

Background

Reduced 25-hydroxyvitamin D (25[OH]D) metabolism and secondary hyperparathyroidism are common with lower estimated glomerular filtration rate (eGFR) and may contribute to cardiovascular disease and cancer risk.

Methods

We assessed for heterogeneity by baseline eGFR of the effects of vitamin D3 on cardiovascular and cancer outcomes in the Vitamin D and Omega-3 Trial (VITAL). Participants were randomized to 2000 IU vitamin D3 and/or 1 g Ω-3 fatty acids daily using a placebo-controlled, two-by-two factorial design (5.3 years follow-up). Primary study end points were incident major cardiovascular events and invasive cancer. Changes in serum 25(OH)D and parathyroid hormone (PTH) were examined.

Results

Baseline eGFR was available for 15,917 participants. Participants' mean age was 68 years, and 51% were women. Vitamin D3 resulted in higher serum 25(OH)D compared with placebo (difference in change 12.5 ng/ml; 95% CI, 12 to 13.1 ng/ml), without heterogeneity by eGFR (P interaction, continuous eGFR=0.2). Difference in change in PTH between vitamin D3 and placebo was larger with lower eGFR (P interaction=0.05): -6.9 (95% CI, -10.5 to -3.4), -5.8 (95% CI, -8.3 to -3.4), -4 (95% CI, -5.9 to -2.2), and -3.8 (95% CI, -5.6 to -2) pg/ml for eGFR <60, 60-74, 75-89, and ≥90 ml/min per 1.73 m2, respectively. Effects of vitamin D3 supplementation on cardiovascular events (P interaction=0.61) and cancer (P interaction=0.89) did not differ by eGFR: HR=1.14 (95% CI, 0.73 to 1.79), HR=1.06 (95% CI, 0.75 to 1.5), HR=0.92 (95% CI, 0.67 to 1.25), and HR=0.92 (95% CI, 0.66 to 1.27) across eGFR categories for cardiovascular events and HR=1.63 (95% CI, 1.03 to 2.58), HR=0.85 (95% CI, 0.64 to 1.11), HR=0.84 (95% CI, 0.68 to 1.03), and 1.11 (95% CI, 0.92 to 1.35) for cancer, respectively.

Conclusions

We observed no significant heterogeneity by baseline eGFR in the effects of vitamin D3 supplementation versus placebo on cardiovascular or cancer outcomes, despite effects on 25(OH)D and PTH concentrations.

Biomarkers of Vitamin D Metabolism and Hip and Vertebral Fracture Risk: The Multi-Ethnic Study of Atherosclerosis

Studies on associations between biomarkers of vitamin D metabolism and fracture risk have focused predominantly on White or elderly populations and may not be generalizable to relatively healthy multiethnic populations. We tested associations of total 25-hydroxyvitamin D (25[OH]D), the ratio of 24,25-dihydroxyvitamin D3 to 25-hydroxyvitamin D3 (vitamin D metabolite ratio, VDMR), parathyroid hormone (PTH), and fibroblast growth factor-23 (FGF-23) concentrations measured in serum with risk of hip and vertebral fractures in the Multi-Ethnic Study of Atherosclerosis (MESA). Serum 25-hydroxyvitamin D2 and D3 and 24,25-dihydroxyvitamin D3 were measured by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The study cohort of 6466 participants was without clinically apparent cardiovascular disease and was 39% White, 27% Black, 22% Hispanic, and 12% Chinese. The mean age was 62 years, and 53% were female. There were 128 hip and vertebral fractures over a mean follow-up of 14.2 years. 25(OH)D, the VDMR, PTH, and FGF-23 were not significantly associated with fracture risk after adjustment for demographics, diabetes, smoking, systolic blood pressure, body mass index, medication use, albuminuria, and estimated glomerular filtration rate. Principal component analysis did not suggest differences in linear combinations of 25(OH)D, the VDMR, PTH, and FGF-23 between participants who experienced fractures and those who did not. We did not observe significant interaction between race and ethnicity and any biomarker of vitamin D metabolism on fracture risk. In conclusion, none of the four serum biomarkers of vitamin D metabolism investigated showed a significant association with fracture risk in relatively healthy multiethnic populations. © 2022 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Tubular Secretion and Estimated GFR Decline in the Jackson Heart Study

Introduction

Secretion of solutes by the proximal tubules represents an intrinsic kidney function not directly reflected by the glomerular filtration rate (GFR). The early loss of secretory clearance may reflect unrecognized kidney dysfunction, portending future disease progression.

Methods

We designed a nested case-control study within the Jackson Heart Study (JHS), a prospective study of African American adults in Mississippi, to associate baseline differences in proximal tubular secretion of 5 endogenously produced solutes with future estimated glomerular rate (eGFR) decline. We matched 127 pairs by creatinine-eGFR, age, diabetes, and sex among the patients who provided a 24-hour urine collection; cases had a ≥25% decline in eGFR compared to <10% in controls over 10 years of follow-up. We measured baseline plasma and urine concentrations of secretory solutes using liquid chromatography-mass spectrometry to determine the odds ratio of kidney disease progression.

Results

Mean age was 60 years; 76% were women; 30% had diabetes; mean baseline eGFR was 94±20 ml/min per 1.73 m². The eGFR decline over 10 years was 38±13% in cases and 0±10% in controls. After adjustment for the matching variables plus albuminuria, systolic blood pressure, body mass index, and smoking, each 50% lower kidney clearance of isovalerylglycine, kynurenic acid, and xanthosine were associated with 1.4 to 2.2 greater odds of eGFR decline. Kynurenic acid exhibited the strongest association; each 50% lower clearance of this secretory solute was associated with 2.20-fold higher odds of eGFR decline (95% confidence interval [CI] 1.32-3.67).

Conclusion

We found that in this community-based study of adults without significant kidney disease, lower proximal tubular secretory solute clearance is associated with future eGFR decline.

Association of Proximal Tubular Secretory Clearance with Long-Term Decline in Cognitive Function

BACKGROUND

People with chronic kidney disease (CKD) are at high risk for cognitive impairment and progressive cognitive decline. Retention of protein-bound organic solutes that are normally removed by tubular secretion is hypothesized to contribute to cognitive impairment in CKD.

METHODS

We followed 2362 participants who were initially free of cognitive impairment and stroke in the prospective Chronic Renal Insufficiency Cohort (CRIC) Study. We estimated tubular secretory clearance by the 24-hour kidney clearances of eight endogenous solutes that are primarily eliminated by tubular secretion. CRIC study investigators assessed participants' cognitive function annually using the Modified Mini-Mental State (3MS) Examination. Cognitive decline was defined as a sustained decrease of more than five points in the 3MS score from baseline. Using Cox regression models adjusted for potential confounders, we analyzed associations between secretory solute clearances, serum solute concentrations, and cognitive decline.

RESULTS

The median number of follow-up 3MS examinations was six per participant. There were 247 incident cognitive decline events over a median of 9.1 years of follow-up. Lower kidney clearances of five of the eight secretory solutes (cinnamoylglycine, isovalerylglycine, kynurenic acid, pyridoxic acid, and tiglylglycine) were associated with cognitive decline after adjustment for baseline eGFR, proteinuria, and other confounding variables. Effect sizes ranged from a 17% to a 34% higher risk of cognitive decline per 50% lower clearance. In contrast, serum concentrations of the solutes were not associated with cognitive decline.

CONCLUSIONS

Lower kidney clearances of secreted solutes are associated with incident global cognitive decline in a prospective study of CKD, independent of eGFR. Further work is needed to determine the domains of cognition most affected by decreased secretory clearance and the mechanisms of these associations.

Prevalence of SGLT2i and GLP1RA use among US adults with type 2 diabetes

AIMS

To determine national prevalence of sodium-glucose contransporter-2 inhibitor (SGLT2i) and glucagon-like peptide-1 receptor agonist (GLP1RA) use among adults with type 2 diabetes mellitus (T2DM).

METHODS

We studied adults with T2DM and eGFR ≥ 30 mL/min/1.73 m² who participated in the cross-sectional National Health and Nutrition Examination Survey (NHANES), focusing on the 2017-2020 examination cycle, a key time period prior to widespread dissemination of pivotal trial results and corresponding clinical practice guidelines. We tested prevalence of SGLT2i and GLP1RA use among subgroups based on demographic variables and relevant comorbidities, including chronic kidney disease (CKD), congestive heart failure (CHF), and atherosclerotic cardiovascular disease (ASCVD). We compared use of SGLT2i and GLP1RA to other glucose-lowering medications and assessed trends from prior NHANES cycles.

RESULTS

Among 1375 participants studied in 2017-2020, mean age was 60 years, 46% were women, 13% self-identified as non-Hispanic Black, 10% self-identified as Mexican American, 37% had CKD, 8.5% had CHF, and 23% had ASCVD. The prevalence of SGLT2i and GLP1RA use was 5.8% and 4.4%, respectively. Among adults with CKD, CHF, or ASCVD, SGLT2i were used by 7.7% and GLP1RA were used by 3.5%. Differences in SGLT2i or GLP1RA use were observed by age, race, ethnicity, health insurance status, body mass index, and by whether a single healthcare provider was identified as responsible for diabetes management. Biguanides, sulfonylureas, DPP-4 inhibitors, and insulin were used more frequently than SGLT2i or GLP1RA. Prevalence of SGLT2i but not GLP1RA use increased significantly from 2013-2014 to 2017-2020.

CONCLUSIONS

SGLT2i and GLP1RA use is low among adults with T2DM, including among those with strong indications. Enhanced implementation of these agents is crucial to improving kidney and cardiovascular outcomes and mitigating health disparities in T2DM.

Framingham and American College of Cardiology/American Heart Association Pooled Cohort Equations, High-Sensitivity Troponin T, and N-Terminal Pro-Brain-Type Natriuretic Peptide for Predicting Atherosclerotic Cardiovascular Events Across the Spectrum of Kidney Dysfunction

Background

Contemporary guidelines recommend using atherosclerotic cardiovascular disease screening tools to guide primary prevention. The performance of these scores is not well known in patients with moderate to advanced chronic kidney disease, particularly in combination with clinically available cardiac biomarkers including N‐terminal pro–brain‐type natriuretic peptide and high‐sensitivity troponin T (hsTnT).

Methods and Results

We studied 1027 participants from the Chronic Renal Insufficiency Cohort without self‐reported atherosclerotic cardiovascular disease who were not taking aspirin or statins at enrollment. Framingham Risk Score, Pooled Cohort Equation, N‐terminal pro–brain‐type natriuretic peptide, and hsTnT were measured at baseline. Outcomes included fatal and nonfatal myocardial infarction, stroke, and cardiac death. We calculated 10‐fold cross‐validated Harrell’s C‐indices for each risk score and cardiac biomarker alone and in combination. The C‐index (95% CI) for discrimination of atherosclerotic cardiovascular disease was 0.72 (0.67, 0.77) for the Framingham Risk Score, and 0.72 (0.67, 0.76) for the Pooled Cohort Equation. HsTnT had comparable discrimination to each risk score, and improved the discrimination of each (change in Framingham 0.029, 95% CI 0.003, 0.055; change in Pooled Cohort Equation 0.027, 95% CI 0.002, 0.052). N‐terminal pro–brain‐type natriuretic peptide had poorer discrimination than the risk scores and did not significantly improve their discrimination (change in Framingham 0.009, 95% CI −0.001, 0.018; change in Pooled Cohort Equation 0.011, 95% CI −0.001, 0.024).

Conclusions

The Framingham Risk Score and Pooled Cohort Equation demonstrated moderate discrimination for atherosclerotic cardiovascular disease in patients with chronic kidney disease. HsTnT, but not N‐terminal pro–brain‐type natriuretic peptide, improved their discrimination overall. Until chronic kidney disease–specific atherosclerotic cardiovascular disease risk scores can be developed, it may be worth considering how to incorporate hsTnT into existing clinical risk scores.

Patient-Reported Symptoms and Subsequent Risk of Myocardial Infarction in Chronic Kidney Disease

BACKGROUND AND OBJECTIVES

Although patient-reported symptoms often precede acute presentations of cardiovascular disease, patients with nondialysis-requiring CKD are less likely to have typical symptoms of atherosclerotic disease when presenting with acute myocardial infarction. However, the associations between typical atherosclerotic symptoms and subsequent risk of myocardial infarction are unknown in ambulatory patients with CKD.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

To determine whether typical atherosclerotic symptoms are associated with risk for subsequent myocardial infarction in people with CKD, we examined participants from the Chronic Renal Insufficiency Cohort Study. Chest pain, shortness of breath, and inability to climb stairs were evaluated annually using the Kidney Disease Quality of Life Instrument. Associations between categorical time-updated symptoms and physician-adjudicated incident myocardial infarction were assessed using Cox regression models.

RESULTS

Among 3910 participants (mean age of 58±11 years; mean eGFR =44±15 ml/min per 1.73 m2), there were 476 incident myocardial infarctions over a median follow-up period of 10.4 years (interquartile range, 5.36-12.6 years). Median time from symptom assessment to incident myocardial infarction was 213 days (interquartile range, 111-333 days). Compared with no symptoms, mild, and moderate or worse, symptoms of chest pain (hazard ratio, 1.30; 95% confidence interval, 1.01 to 1.67; and hazard ratio, 1.70; 95% confidence interval, 1.27 to 2.27, respectively) and shortness of breath (hazard ratio, 1.37; 95% confidence interval, 1.10 to 1.70; and hazard ratio, 1.33; 95% confidence interval, 1.05 to 1.69, respectively) were significantly associated with greater risks for subsequent myocardial infarction. Participants reporting mild and severe limitations in climbing stairs (versus no limitation) had significantly higher adjusted risk of myocardial infarction (hazard ratio, 1.44; 95% confidence interval, 1.10 to 1.89; and hazard ratio, 1.89; 95% confidence interval, 1.44 to 2.49, respectively).

CONCLUSIONS

In a large ambulatory cohort of adults with CKD, symptoms of atherosclerotic cardiovascular disease were strongly associated with a higher risk for subsequent myocardial infarction.

PODCAST

This article contains a podcast at https://www.asn-online.org/media/podcast/CJASN/2022_03_17_CJN12080921.mp3.

Prediction of Incident Heart Failure in CKD: The CRIC Study

Introduction

Heart failure (HF) is common in chronic kidney disease (CKD); identifying patients with CKD at high risk for HF may guide clinical care. We assessed the prognostic value of cardiac biomarkers and echocardiographic variables for 10-year HF prediction compared with a published clinical HF prediction equation in a cohort of participants with CKD.

Methods

We studied 2147 Chronic Renal Insufficiency Cohort (CRIC) participants without prior HF with complete clinical, cardiac biomarker (N-terminal brain natriuretic peptide [NT-proBNP] and high sensitivity troponin-T [hsTnT]), and echocardiographic data (left ventricular mass [LVM] and left ventricular ejection fraction [LVEF] data). We compared the discrimination of the 11-variable Atherosclerosis Risk in Communities (ARIC) HF prediction equation with LVM, LVEF, hsTnT, and NT-proBNP to predict 10-year risk of hospitalization for HF using a Fine and Gray modeling approach. We separately evaluated prediction of HF with preserved and reduced LVEF (LVEF ≥50% and <50%, respectively). We assessed discrimination with internally valid C-indices using 10-fold cross-validation.

Results

Participants' mean (SD) age was 59 (11) years, 53% were men, 43% were Black, and mean (SD) estimated glomerular filtration rate (eGFR) was 44 (16) ml/min per 1.73 m2. A total of 324 incident HF hospitalizations occurred during median (interquartile range) 10.0 (5.7-10.0) years of follow-up. The ARIC HF model with clinical variables had a C-index of 0.68. Echocardiographic variables predicted HF (C-index 0.70) comparably to the published ARIC HF model, while NT-proBNP and hsTnT together (C-index 0.73) had significantly better discrimination (P = 0.004). A model including cardiac biomarkers, echocardiographic variables, and clinical variables had a C-index of 0.77. Discrimination of HF with preserved LVEF was lower than for HF with reduced LVEF for most models.

Conclusion

The ARIC HF prediction model for 10-year HF risk had modest discrimination among adults with CKD. NT-proBNP and hsTnT discriminated better than the ARIC HF model and at least as well as a model with echocardiographic variables. HF clinical prediction models tailored to adults with CKD are needed. Until then, measurement of NT-proBNP and hsTnT may be a low-burden approach to predicting HF in this population, as they offer moderate discrimination.

Validation of the 24,25-dihydroxyvitamin D3 to 25-hydroxyvitamin D3 ratio as a biomarker of 25-hydroxyvitamin D3 clearance

The formation of 24,25-dihydroxyvitamin D (24,25(OH)₂D) from 25-hydroxyvitamin D (25(OH)D) is the primary mechanism for the metabolic clearance of 25(OH)D, and is regulated by tissue-level vitamin D activity. The ratio of 24,25(OH)₂D₃ to 25(OH)D₃ in blood (vitamin D metabolite ratio, VDMR) is postulated to be a marker of 25(OH)D₃ clearance, however this has never been tested. We measured baseline 24,25(OH)₂D₃ and 25(OH)D₃ concentrations in 87 participants by liquid chromatography-tandem mass spectrometry. Following an infusion of deuterated 25(OH)D₃, blood samples for each participant were collected over 56 days and analyzed for deuterated vitamin D metabolites. 25(OH)D₃ clearance and the deuterated metabolite-to-parent AUC ratio (ratio of the AUC of deuterated 24,25(OH)₂D₃ to that of deuterated 25(OH)D₃) were calculated. We compared the VDMR with these two measures using correlation coefficients and linear regression. Participants had a mean age of 64 ± 11years, 41 % were female, 30 % were self-described Black, 28 % had non-dialysis chronic kidney disease (CKD) and 23 % had kidney failure treated with hemodialysis. The VDMR was strongly correlated with 25(OH)D₃ clearance and the deuterated metabolite-to-parent AUC ratio (r = 0.51 and 0.76, respectively). Adjusting for 25(OH)D₃ clearance or the deuterated metabolite-to-parent AUC ratio in addition to clinical covariates, lower VDMR was observed in participants with CKD and kidney failure than in healthy controls; in Black than White participants; and in those with lower serum albumin. Our findings validate the VDMR as a measure of 25(OH)D₃ clearance. This relationship was biased by characteristics including race and kidney disease, which warrant consideration in studies assessing the VDMR.

Management of Adults with Newly Diagnosed Atrial Fibrillation with and without CKD

BACKGROUND

Atrial fibrillation (AF) is highly prevalent in CKD and is associated with worse cardiovascular and kidney outcomes. Limited data exist on use of AF pharmacotherapies and AF-related procedures by CKD status. We examined a large "real-world" contemporary population with incident AF to study the association of CKD with management of AF.

METHODS

We identified patients with newly diagnosed AF between 2010 and 2017 from two large, integrated health care delivery systems. eGFR (≥60, 45-59, 30-44, 15-29, <15 ml/min per 1.73 m²) was calculated from a minimum of two ambulatory serum creatinine measures separated by ≥90 days. AF medications and procedures were identified from electronic health records. We performed multivariable Fine-Gray subdistribution hazards regression to test the association of CKD severity with receipt of targeted AF therapies.

RESULTS

Among 115,564 patients with incident AF, 34% had baseline CKD. In multivariable models, compared with those with eGFR >60 ml/min per 1.73 m², patients with eGFR 30-44 (adjusted hazard ratio [aHR] 0.91; 95% CI, 0.99 to 0.93), 15-29 (aHR, 0.78; 95% CI, 0.75 to 0.82), and <15 ml/min per 1.73 m² (aHR, 0.64; 95% CI, 0.58-0.70) had lower use of any AF therapy. Patients with eGFR 15-29 ml/min per 1.73 m² had lower adjusted use of rate control agents (aHR, 0.61; 95% CI, 0.56 to 0.67), warfarin (aHR, 0.89; 95% CI, 0.84 to 0.94), and DOACs (aHR, 0.23; 95% CI, 0.19 to 0.27) compared with patients with eGFR >60 ml/min per 1.73 m². These associations were even stronger for eGFR <15 ml/min per 1.73 m². There was also a graded association between CKD severity and receipt of AF-related procedures (vs eGFR >60 ml/min per 1.73 m²): eGFR 30-44 ml/min per 1.73 (aHR, 0.78; 95% CI, 0.70 to 0.87), eGFR 15-29 ml/min per 1.73 m² (aHR, 0.73; 95% CI, 0.61 to 0.88), and eGFR <15 ml/min per 1.73 m² (aHR, 0.48; 95% CI, 0.31 to 0.74).

CONCLUSIONS

In adults with newly diagnosed AF, CKD severity was associated with lower receipt of rate control agents, anticoagulation, and AF procedures. Additional data on efficacy and safety of AF therapies in CKD populations are needed to inform management strategies.

Risk of Foot Ulcer and Lower-Extremity Amputation Among Participants in the Diabetes Control and Complications Trial/Epidemiology of Diabetes Interventions and Complications Study

OBJECTIVE

Intensive glycemic control reduces the risk of kidney, retinal, and neurologic complications in type 1 diabetes (T1D), but whether it reduces the risk of lower-extremity complications is unknown. We examined whether former intensive versus conventional glycemic control among Diabetes Control and Complications Trial (DCCT) participants with T1D reduced the long-term risk of diabetic foot ulcers (DFUs) and lower-extremity amputations (LEAs) in the subsequent Epidemiology of Diabetes Interventions and Complications (EDIC) study.

RESEARCH DESIGN AND METHODS

DCCT participants (n = 1,441) completed 6.5 years on average of intensive versus conventional diabetes treatment, after which 1,408 were enrolled in EDIC and followed annually over 23 years for DFU and LEA occurrences by physical examination. Multivariable Cox proportional hazard regression models estimated associations of DCCT treatment assignment and time-updated exposures with DFU or LEA.

RESULTS

Intensive versus conventional glycemic control was associated with a significant risk reduction for all DFUs (hazard ratio 0.77 [95% CI 0.60, 0.97]) and a similar magnitude but nonsignificant risk reduction for first-recorded DFUs (0.78 [0.59, 1.03]) and first LEAs (0.70 [0.36, 1.36]). In adjusted Cox models, clinical neuropathy, lower sural nerve conduction velocity, and cardiovascular autonomic neuropathy were associated with higher DFU risk; estimated glomerular filtration rate <60 mL/min/1.73 m2, albuminuria, and macular edema with higher LEA risk; and any retinopathy and greater time-weighted mean DCCT/EDIC HbA1c with higher risk of both outcomes (P < 0.05).

CONCLUSIONS

Early intensive glycemic control decreases long-term DFU risk, the most important antecedent in the causal pathway to LEA.

Serum Vitamin D: Correlates of Baseline Concentration and Response to Supplementation in VITAL-DKD

CONTEXT

The effect of daily vitamin D supplementation on the serum concentration of vitamin D (the parent compound) may offer insight into vitamin D disposition.

OBJECTIVE

To assess the total serum vitamin D response to vitamin D3 supplementation and whether it varies according to participant characteristics. To compare results with corresponding results for total serum 25-hydroxyvitamin D [25(OH)D], which is used clinically and measured in supplementation trials.

DESIGN

Exploratory study within a randomized trial.

INTERVENTION

2000 International Units of vitamin D3 per day (or matching placebo).

SETTING

Community-based.

PARTICIPANTS

161 adults (mean ± SD age 70 ± 6 years; 66% males) with type 2 diabetes.

MAIN OUTCOME MEASURES

Changes in total serum vitamin D and total serum 25(OH)D concentrations from baseline to year 2.

RESULTS

At baseline, there was a positive, nonlinear relation between total serum vitamin D and total serum 25(OH)D concentrations. Adjusted effects of supplementation were a 29.2 (95% CI: 24.3, 34.1) nmol/L increase in serum vitamin D and a 33.4 (95% CI: 27.7, 39.2) nmol/L increase in serum 25(OH)D. Among those with baseline 25(OH)D < 50 compared with ≥ 50 nmol/L, the serum vitamin D response to supplementation was attenuated (15.7 vs 31.2 nmol/L; interaction P-value = 0.02), whereas the serum 25(OH)D response was augmented (47.9 vs 30.7 nmol/L; interaction P-value = 0.05).

CONCLUSIONS

Vitamin D3 supplementation increases total serum vitamin D and 25(OH)D concentrations with variation according to baseline 25(OH)D, which suggests that 25-hydroxylation of vitamin D3 is more efficient when serum 25(OH)D concentration is low.

Prediction of Incident Atrial Fibrillation in Chronic Kidney Disease: The Chronic Renal Insufficiency Cohort Study

BACKGROUND AND OBJECTIVES

Atrial fibrillation (AF) is common in CKD and associated with poor kidney and cardiovascular outcomes. Prediction models developed using novel methods may be useful to identify patients with CKD at highest risk of incident AF. We compared a previously published prediction model with models developed using machine learning methods in a CKD population.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We studied 2766 participants in the Chronic Renal Insufficiency Cohort study without prior AF with complete cardiac biomarker (N-terminal pro-B-type natriuretic peptide and high-sensitivity troponin T) and clinical data. We evaluated the utility of machine learning methods as well as a previously validated clinical prediction model (Cohorts for Heart and Aging Research in Genomic Epidemiology [CHARGE]-AF, which included 11 predictors, using original and re-estimated coefficients) to predict incident AF. Discriminatory ability of each model was assessed using the ten-fold cross-validated C-index; calibration was evaluated graphically and with the Grønnesby and Borgan test.

RESULTS

Mean (SD) age of participants was 57 (11) years, 55% were men, 38% were Black, and mean (SD) eGFR was 45 (15) ml/min per 1.73 m2; 259 incident AF events occurred during a median of 8 years of follow-up. The CHARGE-AF prediction equation using original and re-estimated coefficients had C-indices of 0.67 (95% confidence interval, 0.64 to 0.71) and 0.67 (95% confidence interval, 0.64 to 0.70), respectively. A likelihood-based boosting model using clinical variables only had a C-index of 0.67 (95% confidence interval, 0.64 to 0.70); adding N-terminal pro-B-type natriuretic peptide, high-sensitivity troponin T, or both biomarkers improved the C-index by 0.04, 0.01, and 0.04, respectively. In addition to N-terminal pro-B-type natriuretic peptide and high-sensitivity troponin T, the final model included age, non-Hispanic Black race/ethnicity, Hispanic race/ethnicity, cardiovascular disease, chronic obstructive pulmonary disease, myocardial infarction, peripheral vascular disease, use of angiotensin-converting enzyme inhibitor/angiotensin receptor blockers, calcium channel blockers, diuretics, height, and weight.

CONCLUSIONS

Using machine learning algorithms, a model that included 12 standard clinical variables and cardiac-specific biomarkers N-terminal pro-B-type natriuretic peptide and high-sensitivity troponin T had moderate discrimination for incident AF in a CKD population.

Differences in proximal tubular solute clearance across common etiologies of chronic kidney disease

BACKGROUND

Laboratory measures of glomerular function such as the glomerular filtration rate (GFR) contribute toward clinical evaluation of chronic kidney disease (CKD). However, diverse CKD etiologies have distinct pathological mechanisms that may differentially impact the kidney tubules. Little is known regarding how tubular function changes with varying kidney disease types.

METHODS

We used targeted mass spectrometry to quantify paired serum and urine concentration of 11 solutes of proximal tubular secretion in 223 patients from an outpatient CKD cohort. We reviewed clinic notes to ascertain the primary CKD diagnosis and categorized these as vascular, diabetic, glomerular or tubulointerstitial. We used one-way analysis of variance to compare secretory solute clearance across diagnoses setting a false discovery threshold of ≤5% and used linear regression to compare differences after adjustments for estimated GFR, age, race, sex, body mass index and urine albumin excretion.

RESULTS

After full adjustment, glomerular disease was associated with higher clearances of three tubular secretory solutes compared with vascular disease: 48% higher isovalerylglycine clearance [95% confidence interval (CI) 18-87%], 28% higher kynurenic acid clearance (95% CI 3-59%) and 33% higher tiglylglycine clearance (95% CI 7-67%). Diabetic kidney disease (DKD) was associated with 39% higher isovalerylglycine clearance compared with vascular disease (95% CI 13-72%).

CONCLUSION

Glomerular disorders and DKD are associated with higher net clearances of several secretory solutes compared with vascular causes of kidney disease. These findings suggest that different underlying etiologies of CKD may differentially impact proximal tubular secretory pathways.

Body Composition Changes Following Dialysis Initiation and Cardiovascular and Mortality Outcomes in CRIC (Chronic Renal Insufficiency Cohort): A Bioimpedance Analysis Substudy

Rationale & Objective

Bioelectrical impedance analysis (BIA) provides a noninvasive assessment of body composition. BIA measures of nutritional (phase angle) and hydration (vector length) status are associated with survival among individuals with chronic kidney disease (CKD), including those receiving maintenance dialysis. However, little is known regarding changes in these parameters with CKD following the high-risk transition to maintenance dialysis.

Study Design

Observational study.

Settings & Participants

427 adults enrolled in the Chronic Renal Insufficiency Cohort (CRIC) Study, with BIA measurements performed within 1 year before and after initiation of maintenance dialysis.

Exposures

We calculated the changes in vector length and phase angle for patients with CKD transitioning to maintenance dialysis.

Outcomes

We examined the association of changes in vector length and phase angle during the transition to maintenance dialysis with risk for all-cause mortality or nonfatal myocardial infarction, stroke, or heart failure, adjusting for demographics, comorbid conditions, and nutritional parameters.

Results

Mean age was 58 ± 12 years and mean estimated glomerular filtration rate using the CKD Epidemiology Collaboration equation before dialysis initiation was 17.0 ± 8.7 mL/min/1.73 m². After covariate adjustment, mean changes in vector length and phase angle were 18 (95% CI, 7 to 30) Ω/m and -0.6  (95% CI, -1.3  to 0.1 ), respectively. Changes in both BIA parameters were not associated with risk for heart failure, stroke, myocardial infarction, or all-cause mortality: HR, 1.02 (95% CI, 0.91-1.14) per 1-SD increment in change for vector length and HR, 1.11 (95% CI, 0.88-1.41) per 1-SD increment in change for phase angle.

Limitations

Observational study, relatively small sample size.

Conclusions

In a multicenter cohort of patients with CKD who progressed to kidney failure, the transition to maintenance dialysis was associated with changes in body composition reflecting poorer cellular integrity and improved volume control. However, these longitudinal changes were not associated with adverse clinical events after dialysis initiation.

Effects of long-term vitamin D and n-3 fatty acid supplementation on inflammatory and cardiac biomarkers in patients with type 2 diabetes: secondary analyses from a randomised controlled trial

AIMS/HYPOTHESIS

Interventions that reduce inflammation may delay progression of microvascular and macrovascular complications in diabetes. We examined the effects of vitamin D₃ and/or n-3 fatty acid supplementation vs placebo on 5 year changes in serum inflammatory and cardiac biomarkers in adults with type 2 diabetes.

METHODS

This study reports pre-specified secondary outcomes of the Vitamin D and Omega-3 Trial to Prevent and Treat Diabetic Kidney Disease, in which 1312 US adults with type 2 diabetes and without known cardiovascular disease, malignancy, or end-stage kidney disease were randomised using computer-generated random numbers in blocks of eight to vitamin D₃ (2000 IU/day) vs placebo and n-3 fatty acids (eicosapentaenoic acid [EPA] and docosahexaenoic acid [DHA]; 1 g/day) vs placebo in a 2 × 2 factorial design. Participants, examiners, and researchers assessing outcomes were blinded to intervention assignment. We measured serum IL-6, high-sensitivity C-reactive protein (hsCRP) and N-terminal pro-B-type natriuretic peptide (NT-proBNP) at baseline and after 2 and 5 years.

RESULTS

A total of 333 participants were randomised to vitamin D₃ and placebo n-3 fatty acids, 289 to n-3 fatty acids and placebo vitamin D₃, 370 to vitamin D₃ and n-3 fatty acids, and 320 to 2 placebos; 989 (75%) and 934 (71%) participants returned blood samples at 2 and 5 years, respectively. Participants had a mean age of 67.6 years (46% women). Overall, baseline geometric means of IL-6, hsCRP and NT-proBNP were 1.2 pg/ml, 1.9 mg/l and 262 ng/l, respectively. After 5 years, mean IL-6 and hsCRP remained within 6% of their baseline values while mean NT-proBNP increased by 55% overall. Compared with placebo, participants assigned to vitamin D₃ had a 1.24-fold greater increase in NT-proBNP over 5 years (95% CI 1.09, 1.41; p = 0.003), while IL-6 and hsCRP did not have a significant difference in change. Comparing n-3 fatty acids with placebo, there was no significant difference in change in IL-6, hsCRP or NT-proBNP. No heterogeneity was observed in subgroup analyses accounting for baseline eGFR, urine albumin to creatinine ratio, initial biomarker concentration, 25-hydroxyvitamin D level or EPA+DHA index.

CONCLUSIONS/INTERPRETATION

Among adults with type 2 diabetes, supplementation with vitamin D₃ or n-3 fatty acids did not reduce IL-6, hsCRP or NT-proBNP over 5 years.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01684722 FUNDING: The study was funded by grant R01DK088762 from the National Institute of Diabetes and Digestive and Kidney Diseases. Graphical abstract.

Prediction of Kidney Drug Clearance: A Comparison of Tubular Secretory Clearance and Glomerular Filtration Rate

BACKGROUND

Although proximal tubular secretion is the primary mechanism of kidney drug elimination, current kidney drug dosing strategies are on the basis of eGFR.

METHODS

In a dedicated pharmacokinetic study to compare GFR with tubular secretory clearance for predicting kidney drug elimination, we evaluated stable outpatients with eGFRs ranging from 21 to 140 ml/min per 1.73 m². After administering single doses of furosemide and famciclovir (metabolized to penciclovir), we calculated their kidney clearances on the basis of sequential plasma and timed urine measurements. Concomitantly, we quantified eight endogenous secretory solutes in plasma and urine using liquid chromatography-tandem mass spectrometry and measured GFR by iohexol clearance (iGFR). We computed a summary secretion score as the scaled average of the secretory solute clearances.

RESULTS

Median iGFR of the 54 participants was 73 ml/min per 1.73 m². The kidney furosemide clearance correlated with iGFR (r=0.84) and the summary secretion score (r=0.86). The mean proportionate error (MPE) between iGFR-predicted and measured furosemide clearance was 30.0%. The lowest MPE was observed for the summary secretion score (24.1%); MPEs for individual secretory solutes ranged from 27.3% to 48.0%. These predictive errors were statistically indistinguishable. Penciclovir kidney clearance was correlated with iGFR (r=0.83) and with the summary secretion score (r=0.91), with similar predictive accuracy of iGFR and secretory clearances. Combining iGFR with the summary secretion score yielded only modest improvements in the prediction of the kidney clearance of furosemide and penciclovir.

CONCLUSIONS

Secretory solute clearance measurements can predict kidney drug clearances. However, tight linkage between GFR and proximal tubular secretory clearance in stable outpatients provides some reassurance that GFR, even when estimated, is a useful surrogate for predicting secretory drug clearances in such patients.

Association Between Kidney Clearance of Secretory Solutes and Cardiovascular Events: The Chronic Renal Insufficiency Cohort (CRIC) Study

RATIONALE & OBJECTIVE

The clearance of protein-bound solutes by the proximal tubules is an innate kidney mechanism for removing putative uremic toxins that could exert cardiovascular toxicity in humans. However, potential associations between impaired kidney clearances of secretory solutes and cardiovascular events among patients with chronic kidney disease (CKD) remains uncertain.

STUDY DESIGN

A multicenter, prospective, cohort study.

SETTING & PARTICIPANTS

We evaluated 3,407 participants from the Chronic Renal Insufficiency Cohort (CRIC) study.

EXPOSURES

Baseline kidney clearances of 8 secretory solutes. We measured concentrations of secretory solutes in plasma and paired 24-hour urine specimens using liquid chromatography-tandem mass spectrometry (LC-MS/MS).

OUTCOMES

Incident heart failure, myocardial infarction, and stroke events.

ANALYTICAL APPROACH

We used Cox regression to evaluate associations of baseline secretory solute clearances with incident study outcomes adjusting for estimated GFR (eGFR) and other confounders.

RESULTS

Participants had a mean age of 56 years; 45% were women; 41% were Black; and the median estimated glomerular filtration rate (eGFR) was 43 mL/min/1.73 m². Lower 24-hour kidney clearance of secretory solutes were associated with incident heart failure and myocardial infarction but not incident stroke over long-term follow-up after controlling for demographics and traditional risk factors. However, these associations were attenuated and not statistically significant after adjustment for eGFR.

LIMITATIONS

Exclusion of patients with severely reduced eGFR at baseline; measurement variability in secretory solutes clearances.

CONCLUSIONS

In a national cohort study of CKD, no clinically or statistically relevant associations were observed between the kidney clearances of endogenous secretory solutes and incident heart failure, myocardial infarction, or stroke after adjustment for eGFR. These findings suggest that tubular secretory clearance provides little additional information about the development of cardiovascular disease events beyond glomerular measures of GFR and albuminuria among patients with mild-to-moderate CKD.

Association of the Estimated Glomerular Filtration Rate With vs Without a Coefficient for Race With Time to Eligibility for Kidney Transplant

IMPORTANCE

Kidney transplant is associated with improved survival and quality of life among patients with kidney failure; however, significant racial disparities have been noted in transplant access. Common equations that estimate glomerular filtration rate (eGFR) include adjustment for Black race; however, how inclusion of the race coefficient in common eGFR equations corresponds with measured GFR and whether it is associated with delayed eligibility for kidney transplant listing are unknown.

OBJECTIVE

To compare eGFR with measured GFR and evaluate the association between eGFR calculated with vs without a coefficient for race and time to eligibility for kidney transplant.

DESIGN, SETTING, AND PARTICIPANTS

This prospective cohort study used data from the Chronic Renal Insufficiency Cohort, a multicenter cohort study of participants with chronic kidney disease (CKD). Self-identified Black participants from that study were enrolled between April 2003 and September 2008, with follow-up through December 2018. Statistical analyses were completed on November 11, 2020.

EXPOSURE

Estimated GFR, measured annually and estimated using the creatinine-based Chronic Kidney Disease-Epidemiology (CKD-EPI) equation with and without a race coefficient.

MAIN OUTCOMES AND MEASURES

Iothalamate GFR (iGFR) measured in a subset of participants (n = 311) and time to achievement of an eGFR less than 20 mL/min/1.73 m2, an established threshold for kidney transplant referral and listing.

RESULTS

Among 1658 self-identified Black participants, mean (SD) age was 58 (11) years, 848 (51%) were female, and mean (SD) eGFR was 44 (15) mL/min/1.73 m2. The CKD-EPI eGFR with the race coefficient overestimated iGFR by a mean of 3.1 mL/min/1.73 m2 (95% CI, 2.2-3.9 mL/min/1.73 m2; P < .001). The mean difference between CKD-EPI eGFR without the race coefficient and iGFR was of smaller magnitude (-1.7 mL/min/1.73 m2; 95% CI, -2.5 to -0.9 mL/min/1.73 m2). For participants with an iGFR of 20 to 25 mL/min/1.73 m2, the mean difference in eGFR with vs without the race coefficient and iGFR was 5.1 mL/min/1.73 m2 (95% CI, 3.3-6.9 mL/min/1.73 m2) vs 1.3 mL/min/1.73 m2 (95% CI, -0.3 to 2.9 mL/min/1.73 m2). Over a median follow-up time of 4 years (interquartile range, 1-10 years), use of eGFR calculated without vs with the race coefficient was associated with a 35% (95% CI, 29%-41%) higher risk of achieving an eGFR less than 20 mL/min/1.73 m2 and a shorter median time to this end point of 1.9 years.

CONCLUSIONS AND RELEVANCE

In this cohort study, inclusion of the race coefficient in the estimation of GFR was associated with greater bias in GFR estimation and with delayed achievement of a clinical threshold for kidney transplant referral and eligibility. These findings suggest that nephrologists and transplant programs should be cautious when using current estimating equations to determine kidney transplant eligibility.

Differences in 25-Hydroxyvitamin D Clearance by eGFR and Race: A Pharmacokinetic Study

BACKGROUND

Conversion of 25-hydroxyvitamin D (25[OH]D) to the active form of vitamin D occurs primarily in the kidney. Observational studies suggest 25(OH)D clearance from the circulation differs by kidney function and race. However, these potential variations have not been tested using gold-standard methods.

METHODS

We administered intravenous, deuterated 25(OH)D3 (d-25[OH]D3) in a pharmacokinetic study of 87 adults, including 43 with normal eGFR (≥60 ml/min per 1.73 m2), 24 with nondialysis CKD (eGFR <60 ml/min per 1.73 m2), and 20 with ESKD treated with hemodialysis. We measured concentrations of d-25(OH)D3 and deuterated 24,25-dihydroxyvitamin D3 at 5 minutes and 4 hours after administration, and at 1, 4, 7, 14, 21, 28, 42, and 56 days postadministration. We calculated 25(OH)D clearance using noncompartmental analysis of d-25(OH)D3 concentrations over time. We remeasured 25(OH)D clearance in a subset of 18 participants after extended oral vitamin-D3 supplementation.

RESULTS

The mean age of the study cohort was 64 years; 41% were female, and 30% were Black. Mean 25(OH)D clearances were 360 ml/d, 313 ml/d, and 263 ml/d in participants with normal eGFR, CKD, and kidney failure, respectively (P=0.02). After adjustment for age, sex, race, and estimated blood volume, lower eGFR was associated with reduced 25(OH)D clearance (β=-17 ml/d per 10 ml/min per 1.73 m2 lower eGFR; 95% CI, -21 to -12). Black race was associated with higher 25(OH)D clearance in participants with normal eGFR, but not in those with CKD or kidney failure (P for interaction=0.05). Clearance of 25(OH)D before versus after vitamin-D3 supplementation did not differ.

CONCLUSIONS

Using direct pharmacokinetic measurements, we show that 25(OH)D clearance is reduced in CKD and may differ by race.

CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER

Clearance of 25-hydroxyvitamin D in Chronic Kidney Disease (CLEAR), NCT02937350; Clearance of 25-hydroxyvitamin D3 During Vitamin D3 Supplementation (CLEAR-PLUS), NCT03576716.

Association of circulating cardiac biomarkers with electrocardiographic abnormalities in chronic kidney disease

BACKGROUND

Among patients with chronic kidney disease (CKD), the circulating cardiac biomarkers soluble ST2 (SST2), galectin-3, growth differentiation factor-15 (GDF-15), N-terminal pro-B-type natriuretic peptide (NT-proBNP) and high-sensitivity troponin-T (hsTnT) possibly reflect pathophysiologic processes and are associated with clinical cardiovascular disease. Whether these biomarkers are associated with electrocardiographic findings is not known. The aim of this study was to test the association between serum cardiac biomarkers and the presence of electrocardiographic changes potentially indicative of subclinical myocardial disease in patients with CKD.

METHODS

We performed a cross-sectional analysis using 3048 participants from the Chronic Renal Insufficiency Cohort (CRIC) without atrial fibrillation, atrioventricular block, bundle branch block or a pacemaker at the baseline visit. Using logistic regression, we tested the association of each of the five cardiac biomarkers with baseline electrocardiogram (ECG) findings: PR interval >200 ms, QRS interval >100 ms and a prolonged QTc interval. Models were adjusted for demographic variables, measures of kidney function, prevalent cardiovascular disease and cardiovascular risk factors.

RESULTS

In adjusted models, hsTnT levels associated with prolonged PR {odds ratio [OR] 1.23 [95% confidence interval (CI) 1.08-1.40]}, QRS [OR 1.28 (95% CI 1.16-1.42)] and QTc [OR 1.94 (95% CI 1.50-2.51)] intervals. NT-proBNP levels were associated with prolonged QRS [OR 1.11 (95% CI 1.06-1.16)] and QTc [OR 1.82 (95% CI 1.58-2.10)] intervals. SST2, galectin-3 and GDF-15 were not significantly associated with any of the ECG parameters.

CONCLUSIONS

hsTnT and NT-proBNP were associated with ECG measures indicative of subclinical myocardial dysfunction. These results may support future research investigating the significance of myocardial ischemia and volume overload in the pathogenesis of dysfunctional myocardial conduction in CKD.

Histopathologic and Clinical Features in Patients with Diabetes and Kidney Disease

BACKGROUND

The discovery of nondiabetic kidney disease (NDKD) in an individual patient with diabetes may have significant treatment implications. Extensive histopathologic data in this population are lacking, but they may provide insights into the complex pathogenesis of diabetic nephropathy (DN) and reveal specific phenotypes for the development of targeted therapies. This study seeks to elucidate the clinical and laboratory parameters associated with the spectrum of kidney histopathologic features in patients with diabetes.

METHODS

This study is a retrospective analysis of 399 kidney biopsies assessed from 2014 to 2016 at the University of Washington among patients with diabetes. More comprehensive clinical data were evaluated in a subset of 79 participants.

RESULTS

Of the 399 biopsies reviewed, 192 (48%) had a primary diagnosis of DN (including 26 with an additional diagnosis), and 207 (52%) had a primary diagnosis of NDKD (including 67 who also had DN). Retinopathy (sensitivity: 0.86; specificity: 0.81; OR, 27.1; 95% CI, 6.8 to 107.7) and higher levels of proteinuria (7.6 versus 4.1 g/d; P=0.004) were associated with DN, whereas a physician description of AKI was associated with a lower risk of DN (OR, 0.13; 95% CI, 0.04 to 0.38). The four most prevalent diagnoses in participants with NDKD were FSGS in 39, nephrosclerosis in 29, IgA nephropathy in 27, and acute tubular injury in 21.

CONCLUSIONS

Among patients with diabetes who undergo kidney biopsy in the Pacific Northwest, approximately half have DN, and half have NDKD. Retinopathy and more severe proteinuria were associated with DN, and AKI was a more common descriptor in NDKD.Podcast: This article contains a podcast at https://www.asnonline.org/media/podcast/K360/2020_11_25_KID0003962020.mp3.

Association of tubular solute clearances with the glomerular filtration rate and complications of chronic kidney disease: the Chronic Renal Insufficiency Cohort study

BACKGROUND

The secretion of organic solutes by the proximal tubules is an essential intrinsic kidney function. The degree to which secretory solute clearance corresponds with the glomerular filtration rate (GFR) and potential metabolic implications of net secretory clearance are largely unknown.

METHODS

We evaluated 1240 participants with chronic kidney disease (CKD) from the multicenter Chronic Renal Insufficiency Cohort (CRIC) Study. We used targeted mass-spectrometry to quantify candidate secretory solutes in paired 24-h urine and plasma samples. CRIC study personnel measured GFR using 125I-iothalamate clearance (iGFR). We used correlation and linear regression to determine cross-sectional associations of secretory clearances with iGFR and common metabolic complications of CKD.

RESULTS

Correlations between iGFR and secretory solute clearances ranged from ρ  = +0.30 for hippurate to ρ = +0.58 for kynurenic acid. Lower net clearances of most secretory solutes were associated with higher serum concentrations of parathyroid hormone (PTH), triglycerides and uric acid. Each 50% lower kynurenic acid clearance was associated with a 21% higher serum PTH concentration [95% confidence interval (CI) 15-26%] and a 10% higher serum triglyceride concentration (95% CI 5-16%) after adjustment for iGFR, albuminuria and other potential confounders. Secretory solute clearances were not associated with statistically or clinically meaningful differences in serum calcium, phosphate, hemoglobin or bicarbonate concentrations.

CONCLUSIONS

Tubular secretory clearances are modestly correlated with measured GFR among adult patients with CKD. Lower net secretory clearances are associated with selected metabolic complications independent of GFR and albuminuria, suggesting potential clinical and biological relevance.

Vitamin D in human serum and adipose tissue after supplementation

BACKGROUND

Serum 25-hydroxyvitamin D [25(OH)D] concentration is an indicator of vitamin D exposure, but it is also influenced by clinical characteristics that affect 25(OH)D production and clearance. Vitamin D is the precursor to 25(OH)D but is analytically challenging to measure in biological specimens.

OBJECTIVES

We aimed to develop and validate a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for quantification of vitamins D3 and D2 in serum and to explore the potential of circulating vitamin D as a biomarker of exposure in supplementation trials.

METHODS

The method was validated using guideline C62-A from the Clinical and Laboratory Standards Institute and was applied in 2 pilot clinical trials of oral vitamin D3 supplementation. Pilot study 1 included 22 adults randomly assigned to placebo or 2000 IU/d. Blood was collected at baseline, 1, 3, 6, and 12 mo. Pilot study 2 included 15 adults randomly assigned to 2000 or 4000 IU/d. Blood and subcutaneous (SUBQ) adipose tissue were collected at baseline and 3 mo.

RESULTS

In study 1, mean change (baseline to 3 mo) in serum vitamin D3 was -0.1 ng/mL in the placebo group and 6.8 ng/mL in the 2000 IU/d group (absolute difference: 6.9; 95% CI: 4.5, 9.3 ng/mL). In study 2, mean change (baseline to 3 mo) in serum vitamin D3 was 10.4 ng/mL in the 2000 IU/d group and 22.2 ng/mL in the 4000 IU/d group (fold difference: 2.15; 95% CI: 1.40, 3.37). Serum and adipose tissue vitamin D3 concentrations were correlated, and the dose-response of vitamin D3 in adipose mirrored that in serum.

CONCLUSIONS

We validated a sensitive, robust, and high-throughput LC-MS/MS method to quantify vitamins D3 and D2 in serum. Serum and SUBQ adipose tissue vitamin D3 concentrations increased proportionally to dose with 3 mo of daily supplementation.These trials were registered at clinicaltrials.gov as NCT00552409 (pilot study 1) and NCT01477034 (pilot study 2).