Bone-derived C-terminal FGF23 cleaved peptides increase iron availability in acute inflammation.

Inflammation leads to functional iron deficiency by increasing the expression of the hepatic iron regulatory peptide hepcidin. Inflammation also stimulates fibroblast growth factor 23 (FGF23) production by increasing both Fgf23 transcription and FGF23 cleavage, which paradoxically leads to excess in C-terminal FGF23 peptides (Cter-FGF23), rather than intact FGF23 (iFGF23) hormone. We determined that the major source of Cter-FGF23 is osteocytes and investigated whether Cter-FGF23 peptides play a direct role in the regulation of hepcidin and iron metabolism in response to acute inflammation. Mice harboring an osteocyte-specific deletion of Fgf23 showed a ∼90% reduction in Cter-FGF23 levels during acute inflammation. Reduction in Cter-FGF23 led to a further decrease in circulating iron in inflamed mice owing to excessive hepcidin production. We observed similar results in mice showing impaired FGF23 cleavage owing to osteocyte-specific deletion of Furin. We next showed that Cter-FGF23 peptides bind members of the bone morphogenetic protein (BMP) family, BMP2 and BMP9, which are established inducers of hepcidin. Coadministration of Cter-FGF23 and BMP2 or BMP9 prevented the increase in Hamp messenger RNA and circulating hepcidin levels induced by BMP2/9, resulting in normal serum iron levels. Finally, injection of Cter-FGF23 in inflamed Fgf23KO mice and genetic overexpression of Cter-Fgf23 in wild type mice also resulted in lower hepcidin and higher circulating iron levels. In conclusion, during inflammation, bone is the major source of Cter-FGF23 secretion, and independently of iFGF23, Cter-FGF23 reduces BMP-induced hepcidin secretion in the liver.

Oral Sodium Bicarbonate and Bone Turnover in CKD: A Secondary Analysis of the BASE Pilot Trial.

SIGNIFICANCE STATEMENT: In CKD, metabolic acidosis is commonly treated with alkali in the hope that it will improve bone health. In a post hoc analysis of the Bicarbonate Administration to Stabilize eGFR Pilot Trial, we investigated whether sodium bicarbonate affects serum levels of bone turnover markers and other hormones related to bone health in individuals with CKD who have normal to slightly reduced total CO2 (20-28 mEq/L). Sodium bicarbonate increased serum levels of α-klotho but had no significant effect on other bone health markers, including intact fibroblast growth factor-23 (iFGF-23), intact parathyroid hormone (iPTH), and bone-specific alkaline phosphatase (B-SAP). Further study is needed to determine the effect of bicarbonate administration on clinical aspects of bone health. BACKGROUND: Treatment with alkali has been hypothesized to improve bone health in CKD by mitigating adverse effects of acid on bone mineral. We investigated the effect of treatment with sodium bicarbonate on bone turnover markers and other factors related to bone metabolism in CKD. METHODS: This is a post hoc analysis of the Bicarbonate Administration to Stabilize eGFR Pilot Trial in which 194 individuals with CKD and serum total CO2 20-28 mEq/L were randomly assigned to placebo or one of two doses of sodium bicarbonate (0.5 or 0.8 mEq/kg lean body weight per day) for 28 weeks. The following serum measurements were performed at baseline, week 12, and week 28: B-SAP, c-telopeptide, procollagen type I intact N-terminal propeptide, iPTH, iFGF-23, soluble klotho, 25-hydroxyvitamin D, 1,25-dihydroxyvitamin D, and tartrate-resistant acid phosphatase 5b. The difference (sodium bicarbonate versus placebo) in mean change of each bone biomarker from baseline was determined using linear mixed models. RESULTS: One hundred sixty-eight participants submitted samples for post hoc investigations. Mean eGFR was 37±10 ml/min per 1.73 m2 and mean total CO2 was 24±3 mEq/L at baseline. Sodium bicarbonate induced a dose-dependent increase in soluble klotho levels compared with placebo. There was no significant effect of treatment with either dose of sodium bicarbonate on any of the other bone biomarkers, including iFGF-23, iPTH, and B-SAP. Effects on bone biomarkers were similar in those with baseline serum total CO2 <24 mEq/L compared with those with total CO2 ≥24 mEq/L. CONCLUSIONS: In this pilot trial of individuals with CKD and total CO2 20-28 mEq/L, sodium bicarbonate treatment increased serum klotho levels but did not affect other bone health markers over 28 weeks. CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER: ClinicalTrials.gov, NCT02521181.

Klotho and Clinical Outcomes in CKD: Findings From the Chronic Renal Insufficiency Cohort (CRIC) Study.

RATIONALE & OBJECTIVE: Klotho deficiency may affect clinical outcomes in chronic kidney disease (CKD) through fibroblast growth factor-23 (FGF23)-dependent and -independent pathways. However, the association between circulating Klotho and clinical outcomes in CKD remains unresolved and was the focus of this study. STUDY DESIGN: Prospective observational study. SETTING & PARTICIPANTS: 1,088 participants in the Chronic Renal Insufficiency Cohort (CRIC) Study with an estimated glomerular filtration rate (eGFR) of 20-70mL/min/1.73m2. EXPOSURE: Plasma Klotho level at the year-1 study visit. OUTCOMES: 5-year risks of all-cause mortality, heart failure hospitalization, atherosclerotic cardiovascular events, and a composite kidney end point that comprised a sustained 50% decrease in eGFR, dialysis, kidney transplant, or eGFR<15mL/min/1.73m2. ANALYTICAL APPROACH: We divided Klotho into 6 groups to account for its nonnormal distribution. We used Cox proportional hazards regression and subdistribution hazards models to compare survival and clinical outcomes, respectively, between Klotho groups. We sequentially adjusted for demographic characteristics, kidney function, cardiovascular risk factors, sample age, and FGF23. RESULTS: Mean eGFR was 42mL/min/1.73m2, and median Klotho concentration was 0.31ng/mL (IQR, 0.10-3.27ng/mL). When compared with the lowest Klotho group, survival (HR, 0.77; 95% CI, 0.32-1.89), heart failure hospitalization (HR, 1.10; 95% CI, 0.38-3.17), atherosclerotic cardiovascular events (HR, 1.19; 95% CI, 0.57-2.52), and CKD progression (HR, 1.05; 95% CI, 0.58-1.91) did not differ in the high Klotho group. In contrast, FGF23 was significantly associated with mortality and heart failure hospitalization independent of Klotho levels. LIMITATIONS: Despite adjustments, we cannot exclude the potential influence of residual confounding or sample storage on the results. A single measurement of plasma Klotho concentration may not capture Klotho patterns over time. CONCLUSIONS: In a large, diverse, well-characterized CKD cohort, Klotho was not associated with clinical outcomes, and Klotho deficiency did not confound the association of FGF23 with mortality or heart failure hospitalization. PLAIN-LANGUAGE SUMMARY: Klotho is a protein that is vital to mineral metabolism and aging and may protect against cardiovascular disease. Klotho levels decrease in chronic kidney disease (CKD), but the association between Klotho and clinical outcomes in CKD remains uncertain. In a prospective cohort study of more than 1,000 people with CKD, circulating Klotho levels were not associated with kidney disease progression, cardiovascular outcomes, or mortality. These results suggest that the decrease in circulating Klotho levels in CKD does not play a prominent role in the development of poor clinical outcomes.

Effectiveness of an Intervention to Improve Decision Making for Older Patients With Advanced Chronic Kidney Disease : A Randomized Controlled Trial.

BACKGROUND: Older patients with advanced chronic kidney disease (CKD) face difficult decisions about managing kidney failure, frequently experiencing decisional conflict, regret, and treatment misaligned with preferences. OBJECTIVE: To assess whether a decision aid about kidney replacement therapy improved decisional quality compared with usual care. DESIGN: Multicenter, randomized, controlled trial. (ClinicalTrials.gov: NCT03522740). SETTING: 8 outpatient nephrology clinics associated with 4 U.S. centers. PARTICIPANTS: English-fluent patients, 70 years and older with nondialysis CKD stages 4 to 5 recruited from 2018 to 2020. INTERVENTION: DART (Decision-Aid for Renal Therapy) is an interactive, web-based decision aid for older adults with CKD. Both groups received written education about treatments. MEASUREMENTS: Change in the decisional conflict scale (DCS) score from baseline to 3, 6, 12, and 18 months. Secondary outcomes included change in prognostic and treatment knowledge and change in uncertainty. RESULTS: Among 400 participants, 363 were randomly assigned: 180 to usual care, 183 to DART. Decisional quality improved with DART with mean DCS declining compared with control (mean difference, -8.5 [95% CI, -12.0 to -5.0]; P < 0.001), with similar findings at 6 months, attenuating thereafter. At 3 months, knowledge improved with DART versus usual care (mean difference, 7.2 [CI, 3.7 to 10.7]; P < 0.001); similar findings at 6 months were modestly attenuated at 18 months (mean difference, 5.9 [CI, 1.4 to 10.3]; P = 0.010). Treatment preferences changed from 58% "unsure" at baseline to 28%, 20%, 23%, and 14% at 3, 6, 12, and 18 months, respectively, with DART, versus 51% to 38%, 35%, 32%, and 18% with usual care. LIMITATION: Latinx patients were underrepresented. CONCLUSION: DART improved decision quality and clarified treatment preferences among older adults with advanced CKD for 6 months after the DART intervention. PRIMARY FUNDING SOURCE: Patient-Centered Outcomes Research Institute (PCORI).

Development and Validation of the Rating of CKD Knowledge Among Older Adults (Know-CKD) With Kidney Failure.

RATIONALE & OBJECTIVE: Few older adults with kidney failure engage in shared decision making (SDM) for kidney replacement therapy. The lack of instruments to assess SDM-relevant knowledge domains may contribute to this. We assessed the reliability and validity of a new instrument, the Rating of CKD Knowledge Older Adults (Know-CKD). STUDY DESIGN: Multistage process, including a stakeholder-engaged development phase, pilot testing, and validation of a knowledge instrument using a cross-sectional survey of older adults with CKD. SETTING & PARTICIPANTS: 363 patients aged 70+years with nondialysis advanced chronic kidney disease (CKD) (estimated glomerular filtration rate [eGFR]<30mL/min/1.73m2) in Boston, Chicago, Portland, ME, and San Diego from June 2018 and January 2020. EXPOSURE: Educational level, higher literacy (Single Item Literacy Screener [SILS]) and numeracy (Subjective Numeracy Scale [SNS]), having participated in clinic-sponsored dialysis education, and self-reported "feeling informed" about options for treatment. OUTCOME: Validity and reliability of the Know-CKD instrument. ANALYTICAL APPROACH: Reliability was assessed with the Kuder-Richardson-20 coefficient. Construct validity was demonstrated by testing a priori hypotheses using t test, analysis of variance (ANOVA) tests, and linear regression analyses. RESULTS: The mean (± SD) participant age was 77.6±5.9 years, and mean eGFR was 22.7±7.2mL/min/1.73m2; 281 participants (78%) self-reported as White. The 12-item Know-CKD assessment had good reliability (Kuder-Richardson-20 reliability coefficient=0.75), and a mean score of 58.2% ± 22.3 SD. The subscales did not attain acceptable reliability. The proportion answering correctly on each item ranged from 20.1% to 91.7%. In examining construct validity, the hypothesized associations held; Know-CKD significantly associated with higher education (ß=6.98 [95% CI, 1.34-12.61], P=0.02), health literacy (ß = -12.67 [95% CI, -19.49 to-5.86], P≤0.001), numeracy per 10% higher (ß=1.85 [95% CI, 1.02-2.69], P≤0.001), and attendance at dialysis class (ß=18.28 [95% CI, 13.30-23.27], P≤0.001). These associations were also observed for the subscales except for prognosis (not associated with literacy or numeracy). LIMITATIONS: Know-CKD is only available in English and has been used only in research settings. CONCLUSIONS: For older adults facing dialysis initiation decisions, Know-CKD is a valid, reliable, and easy to administer measure of knowledge. Further research should examine the relationship of kidney disease knowledge and SDM, patient satisfaction, and clinical outcomes. PLAIN-LANGUAGE SUMMARY: The Rating of CKD Knowledge Among Older Adults (Know-CKD) study measures knowledge of chronic kidney disease (CKD) and is designed for older adults. Most existing knowledge measures for CKD focus on people of all ages and all CKD stages. This measure is useful because it will allow researchers to assess how well patient education efforts are working. Patient education is a way to help patients make decisions about their care. We describe how the measure was developed by a team of doctors, researchers, and patients, and how the measure performed among persons with advanced CKD aged 70 years and older. Know-CKD can inform efforts to improve shared decision-making research and practice for older patients with kidney disease.

Systematic integrated analysis of genetic and epigenetic variation in diabetic kidney disease.

Poor metabolic control and host genetic predisposition are critical for diabetic kidney disease (DKD) development. The epigenome integrates information from sequence variations and metabolic alterations. Here, we performed a genome-wide methylome association analysis in 500 subjects with DKD from the Chronic Renal Insufficiency Cohort for DKD phenotypes, including glycemic control, albuminuria, kidney function, and kidney function decline. We show distinct methylation patterns associated with each phenotype. We define methylation variations that are associated with underlying nucleotide variations (methylation quantitative trait loci) and show that underlying genetic variations are important drivers of methylation changes. We implemented Bayesian multitrait colocalization analysis (moloc) and summary data-based Mendelian randomization to systematically annotate genomic regions that show association with kidney function, methylation, and gene expression. We prioritized 40 loci, where methylation and gene-expression changes likely mediate the genotype effect on kidney disease development. Functional annotation suggested the role of inflammation, specifically, apoptotic cell clearance and complement activation in kidney disease development. Our study defines methylation changes associated with DKD phenotypes, the key role of underlying genetic variations driving methylation variations, and prioritizes methylome and gene-expression changes that likely mediate the genotype effect on kidney disease pathogenesis.

Fibroblast growth factor-23 and subclinical markers of cardiac dysfunction: The coronary artery risk development in young adults (CARDIA) study.

BACKGROUND: Elevated Fibroblast Growth Factor-23 (FGF23) levels have been associated with greater left ventricular mass (LVM) and heart failure. Whether higher FGF23 is associated with higher LVH prevalence and longitudinal changes in LVM and myocardial strain in middle-aged adults without cardiovascular disease (CVD) or chronic kidney disease (CKD) is unknown. METHODS: We studied 3,113 adults without CVD at baseline participating in the Year 25 (2010-2011) follow-up exam of the Coronary Artery Risk Development in Young Adults (CARDIA) study. We studied the association of Year 25 c-terminal FGF23 concentrations with indexed LVM (LVMI=LVM/height2.7), LVH and myocardial strain as assessed by speckle tracking strain echocardiography. Among the 2,758 (88.6%) participants who returned for the Year 30 examination, we also investigated the association of Year 25 FGF23 with 5 Year change in LVMI, strain parameters and incident LVH. RESULTS: The mean age was 50.0 (±3.6) years, 56.8% were female, 45.7% were Black and 6.4% had CKD. There was 6.0% LVH prevalence at Year 25. Mean 5 Year change in LVMI was 5.3 (±7.7) grams/meter. In multivariable models, FGF23 in the highest quartile was associated with greater odds of LVH at Year 25 compared to lower quartiles. [Odds Ratio 95% CI: 1.81 (1.28, 2.58)] with similar findings after exclusion of participants with CKD. There was no interaction between FGF23 and race (P = .18) or sex (P = .80). There was no association between FGF23 and global longitudinal strain. There was no association between FGF23 and 5 Year change in LVMI. There was no association between higher FGF23 and 5 year incident LVH. CONCLUSIONS: In a middle-aged adult population without known CVD or CKD, higher FGF23 was associated with greater odds of LVH, but not with greater increases in LVM over time. Further study is needed to elucidate whether FGF23 is a risk marker for underlying LVH or a mechanism for increased LVM over time in younger and middle-aged adult populations without CKD.

Variation in Definitions of Kidney Abnormality in Patients with Spina Bifida: A Systematic Scoping Review.

PURPOSE: We systematically reviewed the variability in definitions of kidney abnormality (KA) outcomes in individuals with spina bifida (SB). MATERIALS AND METHODS: A systematic scoping review was conducted using MEDLINE, Embase™, Cochrane Library, CINAHL, PsycInfo®, Web of Science™ and ClinicalTrials.gov for articles from time of database inception to September 2020. No language or patient age restrictions were applied. Primary research articles involving individuals with SB where KA was assessed as an outcome were included. Means of assessing KA and defining KA severity were abstracted. RESULTS: Of 2,034 articles found, 274 were included in the review. Most articles were published after 1990 (63.5%) and included pediatric-only populations (0-18 years; 60.5%). KA outcomes were identified by imaging-based anatomical outcomes (84.7%), serum-based outcomes (44.9%), imaging-based functional outcomes (5.5%), urine-based outcomes (3.3%) and diagnoses of end-stage kidney disease (2.6%) or chronic kidney disease otherwise unspecified (1.8%). Hydronephrosis was the most commonly used specific outcome (64.6%, 177/274) with 19.8% (35/177) of articles defining hydronephrosis severity. Hydronephrosis was used more frequently in articles with pediatric-only populations. Creatinine and cystatin-C were used in 82.1% (101/123) and 17.9% (22/123) of articles reporting serum-based outcomes, respectively, with 32.7% and 50.0% of articles defining estimated glomerular filtration rate (GFR) severity. Serum-based outcomes were more common in articles including adults >18 years. Measured GFR was assessed in 9.9% (27/274) of articles, with 44.4% (12/27) of articles defining GFR severity. CONCLUSIONS: Significant variability exists in how authors define KA with few specifically defining KA severity. Consensus and consistency in defining KA outcomes are needed.

The Association of Health Literacy with Health-Related Quality of Life in Youth and Young Adults with Spina Bifida: A Cross-Sectional Study.

OBJECTIVE: The objective of the study was to determine if health literacy is associated with health-related quality of life (HRQOL) in adolescents and young adults (AYAs) with spina bifida. STUDY DESIGN: Between June 2019 and March 2020, the Patient-Reported Outcome Measurement Information System Pediatric Global Health-7 (PGH-7), a measure of HRQOL, and the Brief Health Literacy Screening Tool (BRIEF) were administered to patients ≥12 years old with a diagnosis of spina bifida seen in our multidisciplinary spina bifida center. Questionnaires were completed at scheduled clinic visits. The primary outcome was the PGH-7 normalized T-score. The primary exposure was the BRIEF score. Demographic and clinical characteristics were obtained from the medical record. Nested, multivariable linear regression models assessed the association between health literacy and the PGH-7 score. RESULTS: Of 232 eligible patients who presented to clinic, 226 (97.4%) met inclusion criteria for this study. The median age was 17.0 years (range: 12-31). Most individuals were female (54.0%) and had myelomeningocele (61.5%). Inadequate, marginal, and adequate health literacy levels were reported by 35.0%, 28.3%, and 36.7% of individuals. In univariable analysis, higher health literacy levels were associated with higher PGH-7 scores. In nested, sequentially adjusted multivariable linear regression models, a higher health literacy level was associated with a stepwise increase in the PGH-7 score. In the fully adjusted model, adequate health literacy and marginal health literacy, compared with inadequate health literacy, were associated with increases in a PGH-7 score of 3.3 (95% CI: 0.2-6.3) and 1.1 (95% CI: -2.0 to 4.2), respectively. CONCLUSIONS: Health literacy was associated with HRQOL after adjusting for demographic and clinical factors. Strategies incorporating health literacy are needed to improve HRQOL in AYAs with spina bifida.

Shared Decision Making Among Older Adults With Advanced CKD.

RATIONALE & OBJECTIVE: Older adults with advanced chronic kidney disease (CKD) face difficult decisions about dialysis initiation. Although shared decision making (SDM) can help align patient preferences and values with treatment options, the extent to which older patients with CKD experience SDM remains unknown. STUDY DESIGN: A cross-sectional analysis of patient surveys examining decisional readiness, treatment options education, care partner support, and SDM. SETTING & PARTICIPANTS: Adults aged 70 years or older from Boston, Chicago, San Diego, or Portland (Maine) with nondialysis advanced CKD. PREDICTORS: Decisional readiness factors, treatment options education, and care partner support. OUTCOMES: Primary: SDM measured by the 9-item Shared Decision Making Questionnaire (SDM-Q-9) instrument, with higher scores reflecting greater SDM. Exploratory: Factors associated with SDM. ANALYTICAL APPROACH: We used multivariable linear regression models to examine the associations between SDM and predictors, controlling for demographic and health factors. RESULTS: Among 350 participants, mean age was 78 ± 6 years, 58% were male, 13% identified as Black, and 48% had diabetes. Mean SDM-Q-9 score was 52 ± 28. SDM item agreement ranged from 41% of participants agreeing that "my doctor and I selected a treatment option together" to 73% agreeing that "my doctor told me that there are different options for treating my medical condition." In multivariable analysis adjusted for demographic characteristics, lower estimated glomerular filtration rate, and diabetes, being "well informed" and "very well informed" about kidney treatment options, having higher decisional certainty, and attendance at a kidney treatment options class were independently associated with higher SDM-Q-9 scores. LIMITATIONS: The cross-sectional study design limits the ability to make temporal associations between SDM and the predictors. CONCLUSIONS: Many older patients with CKD do not experience SDM when making dialysis decisions, emphasizing the need for greater access to and delivery of education for individuals with advanced CKD.

Ten-Year Risk-Prediction Equations for Incident Heart Failure Hospitalizations in Chronic Kidney Disease: Findings from the Chronic Renal Insufficiency Cohort Study and the Multi-Ethnic Study of Atherosclerosis.

BACKGROUND: Heart failure (HF) is a leading contributor to cardiovascular morbidity and mortality in the population with chronic kidney disease (CKD). HF risk prediction tools that use readily available clinical parameters to risk-stratify individuals with CKD are needed. METHODS: We included Black and White participants aged 30-79 years with CKD stages 2-4 who were enrolled in the Chronic Renal Insufficiency Cohort (CRIC) study and were without self-reported cardiovascular disease. We assessed model performance of the Pooled Cohort Equations to Prevent Heart Failure (PCP-HF) to predict incident hospitalizations due to HF and refit the PCP-HF in the population with CKD by using CRIC data-derived coefficients and survival from CRIC study participants in the CKD population (PCP-HFCKD). We investigated the improvement in HF prediction with inclusion of estimated glomerular filtration rate (eGFR) and urine albumin-to-creatinine ratio (UACR) into the PCP-HFCKD equations by change in C-statistic, net reclassification improvement (NRI), and integrated discrimination improvement index (IDI). We validated the PCP-HFCKD with and without eGFR and UACR in Multi-Ethnic Study of Atherosclerosis (MESA) participants with CKD. RESULTS: Among 2328 CRIC Study participants, 340 incident HF hospitalizations occurred over a mean follow-up of 9.5 years. The PCP-HF equations did not perform well in most participants with CKD and had inadequate discrimination and insufficient calibration (C-statistic 0.64-0.71, Greenwood-Nam-D'Agostino (GND) chi-square statistic P value < 0.05), with modest improvement and good calibration after being refit (PCP-HFCKD: C-statistic 0.61-0.78), GND chi-square statistic P value > 0.05). Addition of UACR, but not eGFR, to the refit PCP-HFCKD improved model performance in all race-sex groups (C-statistic [0.73-0.81], GND chi-square statistic P value > 0.05, delta C-statistic ranging from 0.03-0.11 and NRI and IDI P values < 0.01). External validation of the PCP-HFCKD in MESA demonstrated good discrimination and calibration. CONCLUSIONS: Routinely available clinical data that include UACR in patients with CKD can reliably identify individuals at risk of HF hospitalizations.

A review of ferric citrate clinical studies, and the rationale and design of the Ferric Citrate and Chronic Kidney Disease in Children (FIT4KiD) trial.

Pediatric chronic kidney disease (CKD) is characterized by many co-morbidities, including impaired growth and development, CKD-mineral and bone disorder, anemia, dysregulated iron metabolism, and cardiovascular disease. In pediatric CKD cohorts, higher circulating concentrations of fibroblast growth factor 23 (FGF23) are associated with some of these adverse clinical outcomes, including CKD progression and left ventricular hypertrophy. It is hypothesized that lowering FGF23 levels will reduce the risk of these events and improve clinical outcomes. Reducing FGF23 levels in CKD may be accomplished by targeting two key stimuli of FGF23 production-dietary phosphate absorption and iron deficiency. Ferric citrate is approved for use as an enteral phosphate binder and iron replacement product in adults with CKD. Clinical trials in adult CKD cohorts have also demonstrated that ferric citrate decreases circulating FGF23 concentrations. This review outlines the possible deleterious effects of excess FGF23 in CKD, summarizes data from the adult CKD clinical trials of ferric citrate, and presents the Ferric Citrate and Chronic Kidney Disease in Children (FIT4KiD) study, a randomized, placebo-controlled trial to evaluate the effects of ferric citrate on FGF23 in pediatric patients with CKD stages 3-4 (ClinicalTrials.gov Identifier NCT04741646).

Advance Care Planning in Older Adults with CKD: Patient, Care Partner, and Clinician Perspectives.

BACKGROUND: Older patients with advanced CKD are at high risk for serious complications and death, yet few discuss advance care planning (ACP) with their kidney clinicians. Examining barriers and facilitators to ACP among such patients might help identify patient-centered opportunities for improvement. METHODS: In semistructured interviews in March through August 2019 with purposively sampled patients (aged ≥70 years, CKD stages 4-5, nondialysis), care partners, and clinicians at clinics in across the United States, participants described discussions, factors contributing to ACP completion or avoidance, and perceived value of ACP. We used thematic analysis to analyze data. RESULTS: We conducted 68 semistructured interviews with 23 patients, 19 care partners, and 26 clinicians. Only seven of 26 (27%) clinicians routinely discussed ACP. About half of the patients had documented ACP, mostly outside the health care system. We found divergent ACP definitions and perspectives; kidney clinicians largely defined ACP as completion of formal documentation, whereas patients viewed it more holistically, wanting discussions about goals, prognosis, and disease trajectory. Clinicians avoided ACP with patients from minority groups, perceiving cultural or religious barriers. Four themes and subthemes informing variation in decisions to discuss ACP and approaches emerged: (1) role ambiguity and responsibility for ACP, (2) questioning the value of ACP, (3) confronting institutional barriers (time, training, reimbursement, and the electronic medical record, EMR), and (4) consequences of avoiding ACP (disparities in ACP access and overconfidence that patients' wishes are known). CONCLUSIONS: Patients, care partners, and clinicians hold discordant views about the responsibility for discussing ACP and the scope for it. This presents critical barriers to the process, leaving ACP insufficiently discussed with older adults with advanced CKD.

Subtyping CKD Patients by Consensus Clustering: The Chronic Renal Insufficiency Cohort (CRIC) Study.

BACKGROUND: CKD is a heterogeneous condition with multiple underlying causes, risk factors, and outcomes. Subtyping CKD with multidimensional patient data holds the key to precision medicine. Consensus clustering may reveal CKD subgroups with different risk profiles of adverse outcomes. METHODS: We used unsupervised consensus clustering on 72 baseline characteristics among 2696 participants in the prospective Chronic Renal Insufficiency Cohort (CRIC) study to identify novel CKD subgroups that best represent the data pattern. Calculation of the standardized difference of each parameter used the cutoff of ±0.3 to show subgroup features. CKD subgroup associations were examined with the clinical end points of kidney failure, the composite outcome of cardiovascular diseases, and death. RESULTS: The algorithm revealed three unique CKD subgroups that best represented patients' baseline characteristics. Patients with relatively favorable levels of bone density and cardiac and kidney function markers, with lower prevalence of diabetes and obesity, and who used fewer medications formed cluster 1 (n=1203). Patients with higher prevalence of diabetes and obesity and who used more medications formed cluster 2 (n=1098). Patients with less favorable levels of bone mineral density, poor cardiac and kidney function markers, and inflammation delineated cluster 3 (n=395). These three subgroups, when linked with future clinical end points, were associated with different risks of CKD progression, cardiovascular disease, and death. Furthermore, patient heterogeneity among predefined subgroups with similar baseline kidney function emerged. CONCLUSIONS: Consensus clustering synthesized the patterns of baseline clinical and laboratory measures and revealed distinct CKD subgroups, which were associated with markedly different risks of important clinical outcomes. Further examination of patient subgroups and associated biomarkers may provide next steps toward precision medicine.

Iron status, fibroblast growth factor 23 and cardiovascular and kidney outcomes in chronic kidney disease.

Disordered iron and mineral homeostasis are interrelated complications of chronic kidney disease that may influence cardiovascular and kidney outcomes. In a prospective analysis of 3747 participants in the Chronic Renal Insufficiency Cohort Study, we investigated risks of mortality, heart failure, end-stage kidney disease (ESKD), and atherosclerotic cardiovascular disease according to iron status, and tested for mediation by C-terminal fibroblast growth factor 23 (FGF23), hemoglobin and parathyroid hormone. Study participants were agnostically categorized based on quartiles of transferrin saturation and ferritin as "Iron Replete" (27.1% of participants; referent group for all outcomes analyses), "Iron Deficiency" (11.1%), "Functional Iron Deficiency" (7.6%), "Mixed Iron Deficiency" (iron indices between the Iron Deficiency and Functional Iron Deficiency groups; 6.3%), "High Iron" (9.2%), or "Non-Classified" (the remaining 38.8% of participants). In multivariable-adjusted Cox models, Iron Deficiency independently associated with mortality (hazard ratio 1.28, 95% confidence interval 1.04-1.58) and heart failure (1.34, 1.05- 1.72). Mixed Iron Deficiency associated with mortality (1.61, 1.27-2.04) and ESKD (1.33, 1.02-1.73). High Iron associated with mortality (1.54, 1.24-1.91), heart failure (1.58, 1.21-2.05), and ESKD (1.41, 1.13-1.77). Functional Iron Deficiency did not significantly associate with any outcome, and no iron group significantly associated with atherosclerotic cardiovascular disease. Among the candidate mediators, FGF23 most significantly mediated the risks of mortality and heart failure conferred by Iron Deficiency. Thus, alterations in iron homeostasis associated with adverse cardiovascular and kidney outcomes in patients with chronic kidney disease.

Mineral bone disease in autosomal dominant polycystic kidney disease.

Mice with disruption of Pkd1 in osteoblasts demonstrate reduced bone mineral density, trabecular bone volume and cortical thickness. To date, the bone phenotype in adult patients with autosomal dominant polycystic kidney disease (ADPKD) with stage I and II chronic kidney disease has not been investigated. To examine this, we characterized biochemical markers of mineral metabolism, examined bone turnover and biology, and estimated risk of fracture in patients with ADPKD. Markers of mineral metabolism were measured in 944 patients with ADPKD and other causes of kidney disease. Histomorphometry and immunohistochemistry were compared on bone biopsies from 20 patients with ADPKD with a mean eGFR of 97 ml/min/1.73m2 and 17 healthy individuals. Furthermore, adults with end stage kidney disease (ESKD) initiating hemodialysis between 2002-2013 and estimated the risk of bone fracture associated with ADPKD as compared to other etiologies of kidney disease were examined. Intact fibroblast growth factor 23 was higher and total alkaline phosphatase lower in patients with compared to patients without ADPKD with chronic kidney disease. Compared to healthy individuals, patients with ADPKD demonstrated significantly lower osteoid volume/bone volume (0.61 vs. 1.21%) and bone formation rate/bone surface (0.012 vs. 0.026 µm3/µm2/day). ESKD due to ADPKD was not associated with a higher risk of fracture as compared to ESKD due to diabetes (age adjusted incidence rate ratio: 0.53 (95% confidence interval 0.31, 0.74) or compared to other etiologies of kidney disease. Thus, individuals with ADPKD have lower alkaline phosphatase, higher circulating intact fibroblast growth factor 23 and decreased bone formation rate. However, ADPKD is not associated with higher rates of bone fracture in ESKD.

Diagnostic Test Characteristics of Ultrasound Based Hydronephrosis in Identifying Low Kidney Function in Young Patients with Spina Bifida: A Retrospective Cohort Study.

PURPOSE: Kidney dysfunction in spina bifida is usually detected by low estimated glomerular filtration rate or ultrasound based hydronephrosis. We assessed the diagnostic test characteristics of hydronephrosis for detecting low estimated glomerular filtration rate, hypothesizing that hydronephrosis has low sensitivity compared to cystatin C based estimated glomerular filtration rate. MATERIALS AND METHODS: We conducted a single center, retrospective cohort study, including patients with spina bifida from 2012-2017 with 2 kidneys and complete data needed to calculate estimated glomerular filtration rate via multiple pediatric (age 1-17.9 years) or adult (age ≥18 years) estimating equations. We evaluated the association of hydronephrosis status (high grade, low grade or none) with estimated glomerular filtration rate, adjusting for small kidney size and scarring, and calculated diagnostic test characteristics of hydronephrosis for low estimated glomerular filtration rate. RESULTS: We analyzed 247 patients (176 children and 71 adults). Mean±SD age was 13.7±6.6 years, and 81% of patients had myelomeningocele. Hydronephrosis (77% low grade) was found in 35/176 children and 18/71 adults. Hydronephrosis was associated with low estimated glomerular filtration rate in stepwise fashion, independent of kidney size and scarring. However, across cystatin C based pediatric equations, any hydronephrosis (compared to none) had 23%-48% sensitivity, and high grade hydronephrosis (compared to none or low grade) had 4%-15% sensitivity for estimated glomerular filtration rate <90 ml/min/1.73 m2, which remained unchanged after excluding small kidneys and scarring. Across cystatin C based adult equations, any and high grade hydronephrosis had 55%-75% and 40%-100% sensitivity, respectively, for estimated glomerular filtration rate <90 ml/min/1.73 m2, although with wide confidence intervals. Specificity was higher with high grade vs any hydronephrosis. Sensitivities were higher for estimated glomerular filtration rate <60 ml/min/1.73 m2. CONCLUSIONS: Hydronephrosis was associated with low estimated glomerular filtration rate but had poor sensitivity for cystatin C based estimated glomerular filtration rate <90 ml/min/1.73 m2, especially among children with spina bifida.

Design and Rationale of HiLo: A Pragmatic, Randomized Trial of Phosphate Management for Patients Receiving Maintenance Hemodialysis.

RATIONALE & OBJECTIVE: Hyperphosphatemia is a risk factor for poor clinical outcomes in patients with kidney failure receiving maintenance dialysis. Opinion-based clinical practice guidelines recommend the use of phosphate binders and dietary phosphate restriction to lower serum phosphate levels toward the normal range in patients receiving maintenance dialysis, but the benefits of these approaches and the optimal serum phosphate target have not been tested in randomized trials. It is also unknown if aggressive treatment that achieves unnecessarily low serum phosphate levels worsens outcomes. STUDY DESIGN: Multicenter, pragmatic, cluster-randomized clinical trial. SETTING & PARTICIPANTS: HiLo will randomize 80-120 dialysis facilities operated by DaVita Inc and the University of Utah to enroll 4,400 patients undergoing 3-times-weekly, in-center hemodialysis. INTERVENTION: Phosphate binder prescriptions and dietary recommendations to achieve the "Hi" serum phosphate target (≥6.5 mg/dL) or the "Lo" serum phosphate target (<5.5 mg/dL). OUTCOMES: Primary outcome: Hierarchical composite outcome of all-cause mortality and all-cause hospitalization. Main secondary outcomes: Individual components of the primary outcome. RESULTS: The trial is currently enrolling. LIMITATIONS: HiLo will not adjudicate causes of hospitalizations or mortality and does not protocolize use of specific phosphate binder classes. CONCLUSIONS: HiLo aims to address an important clinical question while more generally advancing methods for pragmatic clinical trials in nephrology by introducing multiple innovative features including stakeholder engagement in the study design, liberal eligibility criteria, use of electronic informed consent, engagement of dietitians to implement the interventions in real-world practice, leveraging electronic health records to eliminate dedicated study visits, remote monitoring of serum phosphate separation between trial arms, and use of a novel hierarchical composite outcome. TRIAL REGISTRATION: Registered at ClinicalTrials.gov with study number NCT04095039.

Patient Education for Kidney Failure Treatment: A Mixed-Methods Study.

RATIONALE & OBJECTIVE: Education programs are needed for people with advanced chronic kidney disease to understand kidney failure treatment options and participate in shared decision-making (SDM). Little is known about the content and accessibility of current education programs or whether they support SDM. STUDY DESIGN: Stakeholder-engaged, mixed-methods design incorporating qualitative observations and interviews, and a quantitative content analysis of slide presentations. SETTING & PARTICIPANTS: Four sites located in Boston, Chicago, Portland (Maine), and San Diego. ANALYTICAL APPROACH: Thematic analysis based on the Ottawa Framework (observations and interviews) and descriptive statistical analysis (slide presentations). RESULTS: Data were collected from observations of 9 education sessions, 5 semistructured interviews with educators, and 133 educational slide presentations. Sites offered group classes or one-on-one sessions. Development, quality, and accuracy of educational materials varied widely. Educators emphasized dialysis (often in-center hemodialysis), with little mention of conservative management. Educators reported patients were often referred too late to education sessions and that some patients become overwhelmed if they learn of the implications of kidney failure in a group setting. Commonly, sessions were general and did not provide opportunities for tailored information most supportive of SDM. Few nephrologists were involved in education sessions or aware of the educational content. Content gaps included prognosis, decision support, mental health and cognition, advance care planning, cost, and diet. Slide presentations used did not consistently reflect best practices related to health literacy. LIMITATIONS: Findings may not be broadly generalizable. CONCLUSIONS: Education sessions focused on kidney failure treatment options do not consistently follow best practices related to health literacy or for supporting SDM. To facilitate SDM, the establishment of expectations for kidney failure treatment options should be clearly defined and integrated into the clinical workflow. Addressing content gaps, health literacy, and communication with nephrologists is necessary to improve patient education in the setting of advanced chronic kidney disease.

Fibroblast Growth Factor 23 and Exercise Capacity in Heart Failure with Preserved Ejection Fraction.

BACKGROUND: Heart failure with preserved ejection fraction (HFpEF) is characterized by left ventricular hypertrophy and decreased exercise capacity. Fibroblast growth factor 23 (FGF23), a hormone involved in phosphate, vitamin D, and iron homeostasis, is linked to left ventricular hypertrophy and HF. We measured c-terminal FGF23 (cFGF23) and intact FGF23 (iFGF23) levels and examined their associations with exercise capacity in patients with HFpEF. METHODS AND RESULTS: Using multivariable linear regression and linear mixed models, we studied the associations of cFGF23 and iFGF23 with baseline and mean weekly change over 24 weeks in peak oxygen consumption and 6-minute walk distance in individuals enrolled in the Phosphodiesterase-5 Inhibition to Improve Clinical Status and Exercise Capacity in HFpEF trial. Our study population included 172 individuals with available plasma for cFGF23 and iFGF23 measurements. Median (25th-75th percentile) baseline cFGF23 and iFGF23 levels were 208.7 RU/mL (132.1-379.5 RU/mL) and 90.3 pg/mL (68.6-128.5 pg/mL), respectively. After adjustment for cardiovascular disease and hematologic and kidney parameters, higher cFGF23 was independently associated with a lower peak oxygen consumption at baseline. Higher iFGF23 was independently associated with shorter 6-minute walk distance at baseline. No significant associations were appreciated with the longitudinal outcomes. CONCLUSIONS: In patients with HFpEF, higher FGF23 levels are independently associated with decreased exercise capacity at baseline.