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Rationale and Approaches to Phosphate and Fibroblast Growth Factor 23 Reduction in CKD.

ABSTRACT: Patients with CKD often progress to ESRD and develop cardiovascular disease (CVD), yet available therapies only modestly improve clinical outcomes. Observational studies report independent associations between elevated serum phosphate and fibroblast growth factor 23 (FGF23) levels and risks of ESRD, CVD, and death. Phosphate excess induces arterial calcification, and although elevated FGF23 helps maintain serum phosphate levels in the normal range in CKD, it may contribute mechanistically to left ventricular hypertrophy (LVH). Consistent epidemiologic and experimental findings suggest the need to test therapeutic approaches that lower phosphate and FGF23 in CKD. Dietary phosphate absorption is one modifiable determinant of serum phosphate and FGF23 levels. Limited data from pilot studies in patients with CKD stages 3-4 suggest that phosphate binders, low phosphate diets, or vitamin B3 derivatives, such as niacin or nicotinamide, may reduce dietary phosphate absorption and serum phosphate and FGF23 levels. This review summarizes current knowledge regarding the deleterious systemic effects of phosphate and FGF23 excess, identifies questions that must be addressed before advancing to a full-scale clinical outcomes trial, and presents a novel therapeutic approach to lower serum phosphate and FGF23 levels that will be tested in the COMBINE Study: The CKD Optimal Management With BInders and NicotinamidE study.

SUBMITTER: Isakova T

PROVIDER: S-EPMC4587706 | biostudies-other | 2015 Oct

REPOSITORIES: biostudies-other

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Rationale and Approaches to Phosphate and Fibroblast Growth Factor 23 Reduction in CKD.

Isakova Tamara T Ix Joachim H JH Sprague Stuart M SM Raphael Kalani L KL Fried Linda L Gassman Jennifer J JJ Raj Dominic D Cheung Alfred K AK Kusek John W JW Flessner Michael F MF Wolf Myles M Block Geoffrey A GA

Journal of the American Society of Nephrology : JASN 20150512 10

Patients with CKD often progress to ESRD and develop cardiovascular disease (CVD), yet available therapies only modestly improve clinical outcomes. Observational studies report independent associations between elevated serum phosphate and fibroblast growth factor 23 (FGF23) levels and risks of ESRD, CVD, and death. Phosphate excess induces arterial calcification, and although elevated FGF23 helps maintain serum phosphate levels in the normal range in CKD, it may contribute mechanistically to lef ...[more]

PMID: 25967123

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Project description:BACKGROUND AND OBJECTIVES:Epidemiologic studies suggest that higher serum phosphaturic hormone fibroblast growth factor 23 levels are associated with increase morbidity and mortality. The aim of the FGF23 Reduction Efficacy of a New Phosphate Binder in CKD Trial was to evaluate the effect of sevelamer carbonate on serum C-terminal fibroblast growth factor 23 levels in normophosphatemic patients with CKD stage 3b/4. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS:Patients with CKD, eGFR between 45 and 15 ml/min per 1.73 m2, fasting serum phosphate concentration >3.1 mg/dl, and serum C-terminal fibroblast growth factor 23 >80 relative units/ml were included in our double-blind, placebo-controlled, randomized multicenter study. All patients received 100,000 IU cholecalciferol at time of randomization. Participants received either placebo or sevelamer carbonate 4.8 g daily during a 12-week period. Biologic parameters, including serum C-terminal fibroblast growth factor 23, intact fibroblast growth factor 23, and ?-klotho, were evaluated at baseline and 12 weeks after inclusion. RESULTS:Of 96 screened patients, 78 (mean±SD age: 63±13 years old; 70% men; mean eGFR: 27±9 ml/min per 1.73 m2) met the inclusion criteria. At baseline, mean eGFR was 27±9 ml/min per 1.73 m2, mean serum phosphate level was 3.8±0.5 mg/dl, and median (interquartile range) serum C-terminal fibroblast growth factor 23 level was 157 (120-241) relative units/ml. After 12 weeks of treatment, urinary phosphate-to-creatinine ratio fell significantly in the sevelamer group. The sevelamer and placebo groups did not differ significantly in terms of median change in serum C-terminal fibroblast growth factor 23 levels: the median (interquartile range) change was 38 (-13-114) relative units/ml in the placebo group and 37 (-1-101) relative units/ml in the sevelamer group (P=0.77). There was no significant difference in serum intact fibroblast growth factor 23, ?-klotho, or phosphate levels changes between the two groups. Serum total and LDL cholesterol levels fell significantly in the sevelamer group. CONCLUSIONS:In our double-blind, placebo-controlled, randomized study performed in normophosphatemic patients with CKD, a 12-week course of sevelamer carbonate significantly reduced phosphaturia without changing serum phosphorus but did not significantly modify serum C-terminal fibroblast growth factor 23 and intact fibroblast growth factor 23 or ?-klotho levels.

Project description:Rationale & objectiveAn elevated fibroblast growth factor 23 (FGF-23) level is independently associated with adverse outcomes in populations with chronic kidney disease, but it is unknown whether FGF-23 testing can improve clinical risk prediction in individuals.Study designProspective cohort study.Setting & participantsParticipants in the Chronic Renal Insufficiency Cohort (CRIC) Study (n = 3,789).ExposureBaseline carboxy-terminal FGF-23 (cFGF-23) level.OutcomesAll-cause and cardiovascular (CV) mortality, incident end-stage renal disease (ESRD), heart failure (HF) admission, and atherosclerotic events at 3, 5, and 8 years.Analytical approachWe assessed changes in model performance by change in area under the receiver operating characteristic curve (ΔAUC), integrated discrimination improvement (IDI), relative IDI, and net reclassification index (NRI) above standard clinical factors. We performed sensitivity analyses, including an additional model comparing the addition of phosphate rather than cFGF-23 level and repeating our analyses using an internal cross-validation cohort.ResultsAddition of a single baseline value of cFGF-23 to a base prediction model improved prediction of all-cause mortality (ΔAUC, 0.017 [95% CI, 0.001-0.033]; IDI, 0.021 [95% CI, 0.006-0.036]; relative IDI, 32.7% [95% CI, 8.5%-56.9%]), and HF admission (ΔAUC, 0.008 [95% CI, 0.0004-0.016]; IDI, 0.019 [95% CI, 0.004-0.034]; relative IDI, 10.0% [95% CI, 1.8%-18.3%]), but not CV mortality, ESRD, or atherosclerotic events at 3 years of follow-up. The NRI did not reach statistical significance for any of the 3-year outcomes. The incremental predictive utility of cFGF-23 level diminished in analyses of the 5- and 8-year outcomes. The cFGF-23 models outperformed the phosphate model for each outcome.LimitationsPower to detect increased CV mortality likely limited by low event rate. The NRI is not generalizable without accepted prespecified risk thresholds.ConclusionsAmong individuals with CKD, single measurements of cFGF-23 improve prediction of risks for all-cause mortality and HF admission but not CV mortality, ESRD, or atherosclerotic events. Future studies should evaluate the predictive utility of repeated cFGF-23 testing.

Dataset Information

Rationale and Approaches to Phosphate and Fibroblast Growth Factor 23 Reduction in CKD.

Publications

Rationale and Approaches to Phosphate and Fibroblast Growth Factor 23 Reduction in CKD.

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