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Martino FK, di Vico V, Basso A, Gobbi L, Stefanelli LF, Cacciapuoti M, Bettin E, Del Prete D, Scaparrotta G, Nalesso F, Calò LA. The Role of Daily Dialysate Calcium Exposure in Phosphaturic Hormones in Dialysis Patients. Life (Basel) 2024; 14:964. [PMID: 39202706 PMCID: PMC11355329 DOI: 10.3390/life14080964] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2024] [Revised: 07/21/2024] [Accepted: 07/26/2024] [Indexed: 09/03/2024] Open
Abstract
Managing mineral bone disease (MBD) could reduce cardiovascular risk and improve the survival of dialysis patients. Our study focuses on the impact of calcium bath exposure in dialysis patients by comparing peritoneal dialysis patients (PD, intervention group) and hemodialysis patients (HD, control group). We assessed various factors, including calcium, phosphorus, magnesium, PTH, vitamin D 25-OH, C-terminal telopeptide (CTX), and FGF-23 levels, as well as the calcium bath six hours before the blood sample and the length of daily calcium exposure. We enrolled 40 PD and 31 HD patients with a mean age of 68.7 ± 13.6 years. Our cohort had median PTH and FGF-23 levels of 194 ng/L (Interquartile range [IQR] 130-316) and 1296 pg/mL (IQR 396-2698), respectively. We identified the length of exposure to a 1.25 mmol/L calcium bath, phosphate levels, and CTX as independent predictors of PTH (OR 0.279, p = 0.011; OR 0.277, p = 0.012; OR 0.11, p = 0.01, respectively). In contrast, independent predictors of FGF-23 were phosphate levels (OR 0.48, p < 0.001) and serum calcium levels (OR 0.25, p = 0.015), which were affected by the calcium bath. These findings suggest that managing dialysate calcium baths impacts phosphaturic hormones and could be a critical factor in optimizing CKD-MBD treatment in PD patients, sparking a new avenue of research and potential interventions.
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Affiliation(s)
- Francesca K. Martino
- Nephrology, Dialysis and Transplantation Unit, Department of Medicine (DIMED), University of Padova, 35128 Padua, Italy; (V.d.V.); (A.B.); (L.G.); (L.F.S.); (M.C.); (E.B.); (D.D.P.); (G.S.); (L.A.C.)
| | | | | | | | | | | | | | | | | | - Federico Nalesso
- Nephrology, Dialysis and Transplantation Unit, Department of Medicine (DIMED), University of Padova, 35128 Padua, Italy; (V.d.V.); (A.B.); (L.G.); (L.F.S.); (M.C.); (E.B.); (D.D.P.); (G.S.); (L.A.C.)
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FGF23: A Review of Its Role in Mineral Metabolism and Renal and Cardiovascular Disease. DISEASE MARKERS 2021; 2021:8821292. [PMID: 34055103 PMCID: PMC8149241 DOI: 10.1155/2021/8821292] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/18/2020] [Revised: 11/01/2020] [Accepted: 05/04/2021] [Indexed: 01/03/2023]
Abstract
FGF23 is a hormone secreted mainly by osteocytes and osteoblasts in bone. Its pivotal role concerns the maintenance of mineral ion homeostasis. It has been confirmed that phosphate and vitamin D metabolisms are related to the effect of FGF23 and its excess or deficiency leads to various hereditary diseases. Multiple studies have shown that FGF23 level increases in the very early stages of chronic kidney disease (CKD), and its concentration may also be highly associated with cardiac complications. The present review is limited to some of the most important aspects of calcium and phosphate metabolism. It discusses the role of FGF23, which is considered an early and sensitive marker for CKD-related bone disease but also as a novel and potent cardiovascular risk factor. Furthermore, this review gives particular attention to the reliability of FGF23 measurement and various confounding factors that may impact on the clinical utility of FGF23. Finally, this review elaborates on the clinical usefulness of FGF23 and evaluates whether FGF23 may be considered a therapeutic target.
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Bouma-de Krijger A, Vervloet MG. Fibroblast growth factor 23: are we ready to use it in clinical practice? J Nephrol 2020; 33:509-527. [PMID: 32130720 PMCID: PMC7220896 DOI: 10.1007/s40620-020-00715-2] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2020] [Accepted: 02/15/2020] [Indexed: 12/15/2022]
Abstract
Patients with chronic kidney disease (CKD) have a greatly enhanced risk of cardiovascular morbidity and mortality. Over the past decade it has come clear that a disturbed calcium-phosphate metabolism, with Fibroblast Growth Factor-23 as a key hormone, is partly accountable for this enhanced risk. Numerous studies have been performed unravelling FGF23s actions and its association with clinical conditions. As FGF23 is strongly associated with adverse outcome it may be a promising biomarker for risk prediction or, even more important, targeting FGF23 may be a strategy to improve patient outcome. This review elaborates on the clinical usefulness of FGF23 measurement. Firstly it discusses the reliability of the FGF23 measurement. Secondly, it evaluates whether FGF23 measurement may lead to improved patient risk classification. Finally, and possibly most importantly, this review evaluates if lowering of FGF23 should be a target for therapy. For this, the review discusses the current evidence indicating that FGF23 may be in the causal pathway to cardiovascular pathology, provides an overview of strategies to lower FGF23 levels and discusses the current evidence concerning the benefit of lowering FGF23.
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Affiliation(s)
- Annet Bouma-de Krijger
- Department of Nephrology, Amsterdam Cardiovascular Science, Amsterdam University Medical Center, De Boelelaan 1117, 1081 HV Amsterdam, The Netherlands
| | - Marc G. Vervloet
- Department of Nephrology, Amsterdam Cardiovascular Science, Amsterdam University Medical Center, De Boelelaan 1117, 1081 HV Amsterdam, The Netherlands
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Variability in measures of mineral metabolism in children on hemodialysis: impact on clinical decision-making. Pediatr Nephrol 2017; 32:2311-2318. [PMID: 28667458 DOI: 10.1007/s00467-017-3730-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/05/2017] [Revised: 06/13/2017] [Accepted: 06/15/2017] [Indexed: 01/30/2023]
Abstract
BACKGROUND Variability in measures of mineral metabolism has not been studied in pediatric end stage kidney disease. We sought to determine the intra-individual variability in measures of mineral metabolism in children on hemodialysis (HD) and its impact on clinical decision-making. METHODS We conducted a prospective single-center study of children (3.6-17.3 years old) on chronic HD. Serial twice weekly measures of serum calcium, phosphate and intact parathyroid hormone (PTH), as well as weekly measures of fibroblast growth factor 23 (FGF23) and vitamin D metabolites, were obtained over a 12-week period in 10 children. Samples (n = 226) were assayed in a single batch at the end of the study. RESULTS The median intra-individual coefficient of variation (CV) calculated by 4-week blocks was 5.1-6.5% for calcium, 9.5-14.9% for phosphate and 32.7-33.4% for PTH. The median overall CV for FGF23 was 44.4%. Using the first value of each block as a reference, subsequent values would dictate a discrepant management decision 33-56%, 19-28%, and 30-33% of the time for calcium, phosphate, and PTH, respectively. Adjusting for sex and age, most of the variability in phosphate and PTH was attributable to within-participant variability. For calcium, 49% of the variability was attributable to day of blood collection (Monday vs. Friday). The median (range) of an individual participant's values within clinical target ranges was 55% (26-86%) for calcium, 58% (0-96%) for phosphate, and 21% (0-64%) for PTH. CONCLUSIONS There is considerable intra-individual variability in measures of mineral metabolism that serve as surrogate markers for bone health in children on HD. Within a 4-week period, at least 20-30% of measures would dictate a discrepant decision from the referent measure of that month. These findings have important implications for clinical decision-making and underscore the need to base therapeutic decisions on trends rather than single measurements.
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Chang WX, Xu N, Kumagai T, Shiraishi T, Kikuyama T, Omizo H, Sakai K, Arai S, Tamura Y, Ota T, Shibata S, Fujigaki Y, Shen ZY, Uchida S. The Impact of Normal Range of Serum Phosphorus on the Incidence of End-Stage Renal Disease by A Propensity Score Analysis. PLoS One 2016; 11:e0154469. [PMID: 27123981 PMCID: PMC4849666 DOI: 10.1371/journal.pone.0154469] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2016] [Accepted: 04/14/2016] [Indexed: 12/16/2022] Open
Abstract
Background Although hyperphosphatemia is deemed a risk factor of the progression of chronic kidney disease (CKD), it remains unclear whether the normal range of serum phosphorus likewise deteriorates CKD. A propensity score analysis was applied to examine the causal effect of the normal range of serum phosphorus on the incidence of end-stage renal disease (ESRD). Methods A retrospective CKD cohort of 803 participants in a single institution was analyzed. Propensity score was estimated using 22 baseline covariates by multivariate binary logistic regression for the different thresholds of time-averaged phosphorus (TA-P) in the normal range of serum phosphorus incremented by 0.1 mg/dL from 3.3 to 4.5 mg/dL. Results The incidence rate of ESRD was 33.9 per 1,000 person-years over median follow-up of 4.3 years. Total patients showed the mean baseline phosphorus of 3.37 mg/dL and were divided to quartile. The higher quartile was associated with the parameters consistent with the advancement of CKD. A stratified Cox regression showed the highest hazard ratio (HR) at TA-P 3.4 mg/dL (HR 17.60, 95% CI 3.92–78.98) adjusted for baseline covariates such as sex, age, diabetic nephropathy, estimated GFR, serum albumin, Na-Cl, phosphorus, LDL-C and proteinuria. Adjusted HRs remained high up to TA-P 4.2 mg/dL (HR 2.22, 95% CI 1.33–3.71). After propensity score matching conducted at the thresholds of TA-P 3.4, 3.6, 3.8 and 4.0 mg/dL, the higher levels of TA-P showed the higher HRs by Kaplan-Meier analysis (p < 0.05 by stratified log-rank test). The numbers needed to treat were calculated as 3.9 to 5.3 over 5 years. Conclusions The propensity score analysis shows that even the normal range of serum phosphorus clearly accelerates CKD progression to ESRD. Our results encourage clinicians to target serum phosphorus to inhibit CKD progression in the manner of ‘the lower the better.’
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Affiliation(s)
- Wen Xiu Chang
- Department of Nephrology, Tianjin First Central Hospital, Tianjin, China
| | - Ning Xu
- Department of Nephrology, Tianjin First Central Hospital, Tianjin, China
| | - Takanori Kumagai
- Support for Community Medicine Endowed Chair, Teikyo University School of Medicine, Tokyo, Japan
- Department of Internal Medicine, Teikyo University School of Medicine, Tokyo, Japan
| | - Takeshi Shiraishi
- Support for Community Medicine Endowed Chair, Teikyo University School of Medicine, Tokyo, Japan
- Department of Internal Medicine, Teikyo University School of Medicine, Tokyo, Japan
| | - Takahiro Kikuyama
- Department of Internal Medicine, Teikyo University School of Medicine, Tokyo, Japan
| | - Hiroki Omizo
- Department of Internal Medicine, Teikyo University School of Medicine, Tokyo, Japan
| | - Kazuhiro Sakai
- Department of Internal Medicine, Teikyo University School of Medicine, Tokyo, Japan
| | - Shigeyuki Arai
- Department of Internal Medicine, Teikyo University School of Medicine, Tokyo, Japan
| | - Yoshifuru Tamura
- Department of Internal Medicine, Teikyo University School of Medicine, Tokyo, Japan
| | - Tatsuru Ota
- Department of Internal Medicine, Teikyo University School of Medicine, Tokyo, Japan
| | - Shigeru Shibata
- Department of Internal Medicine, Teikyo University School of Medicine, Tokyo, Japan
| | - Yoshihide Fujigaki
- Department of Internal Medicine, Teikyo University School of Medicine, Tokyo, Japan
| | - Zhong Yang Shen
- Department of Organ Transplantation, Tianjin First Central Hospital, Tianjin, China
| | - Shunya Uchida
- Department of Internal Medicine, Teikyo University School of Medicine, Tokyo, Japan
- * E-mail:
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Chang WX, Asakawa S, Toyoki D, Nemoto Y, Morimoto C, Tamura Y, Ota T, Shibata S, Fujigaki Y, Shen ZY, Uchida S. Predictors and the Subsequent Risk of End-Stage Renal Disease - Usefulness of 30% Decline in Estimated GFR over 2 Years. PLoS One 2015; 10:e0132927. [PMID: 26177463 PMCID: PMC4503403 DOI: 10.1371/journal.pone.0132927] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2014] [Accepted: 06/21/2015] [Indexed: 12/31/2022] Open
Abstract
Background A goal of searching risk factors for chronic kidney disease (CKD) is to halt progressing to end-stage renal disease (ESRD) by potential intervention. To predict the future ESRD, 30% decline in estimated GFR over 2 years was examined in comparison with other time-dependent predictors. Methods CKD patients who had measurement of serum creatinine at baseline and 2 years were enrolled (n = 701) and followed up to 6 years. Time-dependent parameters were calculated as time-averaged values over 2 years by a trapezoidal rule. Risk factors affecting the incidence of ESRD were investigated by the extended Cox proportional hazard model with baseline dataset and 2-year time-averaged dataset. Predictive significance of 30% decline in estimated GFR over 2 years for ESRD was analyzed. Results For predicting ESRD, baseline estimated GFR and proteinuria were the most influential risk factors either with the baseline dataset or the 2-year time-averaged dataset. Using the 2-year time-averaged dataset, 30% decline in estimated GFR over 2 years by itself showed the highest HR of 31.6 for ESRD whereas addition of baseline estimated GFR, proteinuria, serum albumin and hemoglobin yielded a better model by a multivariate Cox regression model. This novel surrogate was mostly associated with time-averaged proteinuria over 2 years with the cut-off of ~1 g/g creatinine. Conclusion These results suggest that decline in estimated GFR and proteinuria are the risk factors while serum albumin and hemoglobin are the protective factors by the time-to-event analysis. Future incidence of ESRD is best predicted by 30% decline in eGFR over 2 years that can be modified by intervention to proteinuria, hemoglobin, uric acid, phosphorus, blood pressure and use of renin-angiotensin system inhibitors in the follow-up of 2 years.
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Affiliation(s)
- Wen Xiu Chang
- Department of Internal Medicine, Teikyo University School of Medicine, Tokyo, Japan
- Department of Nephrology, Tianjin First Central Hospital, Tianjin, China
| | - Shinichiro Asakawa
- Department of Internal Medicine, Teikyo University School of Medicine, Tokyo, Japan
| | - Daigo Toyoki
- Department of Internal Medicine, Teikyo University School of Medicine, Tokyo, Japan
| | - Yoshikazu Nemoto
- Department of Internal Medicine, Teikyo University School of Medicine, Tokyo, Japan
| | - Chikayuki Morimoto
- Department of Internal Medicine, Teikyo University School of Medicine, Tokyo, Japan
| | - Yoshifuru Tamura
- Department of Internal Medicine, Teikyo University School of Medicine, Tokyo, Japan
| | - Tatsuru Ota
- Department of Internal Medicine, Teikyo University School of Medicine, Tokyo, Japan
| | - Shigeru Shibata
- Department of Internal Medicine, Teikyo University School of Medicine, Tokyo, Japan
| | - Yoshihide Fujigaki
- Department of Internal Medicine, Teikyo University School of Medicine, Tokyo, Japan
| | - Zhong Yang Shen
- Department of Organ Transplantation, Tianjin First Central Hospital, Tianjin, China
| | - Shunya Uchida
- Department of Internal Medicine, Teikyo University School of Medicine, Tokyo, Japan
- * E-mail:
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Lin JCF, Liang WM. Mortality and complications after hip fracture among elderly patients undergoing hemodialysis. BMC Nephrol 2015; 16:100. [PMID: 26149489 PMCID: PMC4492013 DOI: 10.1186/s12882-015-0099-0] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2014] [Accepted: 06/28/2015] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Osteoporotic hip fractures cause high mortality and morbidity in elderly adults. Compared to the general population, subjects with end-stage renal disease and hemodialysis often develop mineral bone disorders and have a higher risk for hip fractures. METHODS We conducted a matched cohort study design and used competing risk analysis to estimate the cumulative incidence of the complication rate. Subjects aged greater than 60 years with hip fracture were selected from Taiwan's National Health Insurance Research Database covering a period from 1997 to 2007, and these subjects were followed up until 2009. We used the Kaplan-Meier method to estimate the overall survival and used the log-rank test and multiple Cox proportional hazards model to explore the risk factors for survival. The cumulative incidence of the first complication was estimated using competing risk analysis. RESULTS Among hemodialysis subjects, the three-month, one-year, two-year and five-year mortality rates were 17.3 %, 37.2 %, 51.5 %, and 80.5 %, respectively; the one-year and five-year cumulative incidences of the first surgical complication were 14.2 % and 20.6 %, respectively; and the three-month cumulative incidence of the first medical complication was 24.1 %. Hemodialysis subjects presented a 2.32 times (95 % CI: 2.16-2.49) higher hazard ratio of overall death, 1.15 times (95 % CI: 1.01-1.30) higher sub-hazard ratio (sub-HR) of surgical complications, and 1.35 times (95 % CI: 1.21-1.52) higher sub-HR of the first medical complication than non-hemodialysis controls. CONCLUSIONS The overall mortality and complication rates of hemodialysis subjects after surgery for hip fracture were significantly higher than those of non-hemodialysis subjects. Further prospective studies which include important risk factors are necessary to more precisely quantify the adjusted effect of hemodialysis.
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Affiliation(s)
- Jeff Chien-Fu Lin
- Department of Statistics, National Taipei University, Taipei, Taiwan. .,Department of Orthopedic Surgery, Wan Fang Hospital, Taipei Medical University, Taipei, Taiwan.
| | - Wen-Miin Liang
- Graduate Institute of Biostatistics, Biostatistics Center, Department of Public Health, China Medical University, Taichung, Taiwan.
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Saab G, Lam M, Navaneethan SD, Slatopolsky E. Should Monitoring of Fibroblast Growth Factor-23 Levels in Dialysis Patients Be a Part of Routine Clinical Practice? Semin Dial 2014; 27:565-8. [DOI: 10.1111/sdi.12274] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Affiliation(s)
- Georges Saab
- MetroHealth Medical Center and Case Western Reserve University; Cleveland Ohio
| | - Mildred Lam
- MetroHealth Medical Center and Case Western Reserve University; Cleveland Ohio
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Trivedi H, Szabo A, Zhao S, Cantor T, Raff H. Circadian variation of mineral and bone parameters in end-stage renal disease. J Nephrol 2014; 28:351-9. [PMID: 25138650 DOI: 10.1007/s40620-014-0124-6] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2014] [Accepted: 07/12/2014] [Indexed: 11/25/2022]
Abstract
BACKGROUND Mineral and bone parameters are actively managed in end-stage renal disease (ESRD). However, whether these undergo circadian variation is not known. We investigated the circadian variation of mineral and bone parameters in patients on long-term hemodialysis. METHODS Seventeen ESRD patients on long-term hemodialysis and eight volunteers without kidney disease were enrolled. Subjects had all medications that affect calcium-phosphate-parathyroid hormone balance (phosphate binders, vitamin D analogues, and calcimimetics) discontinued. Thereafter, for a period of 5 days, subjects consumed a diet controlled in calcium (1,200 mg per day) and phosphorus (1,000 mg per day) content. On the sixth day (a non-dialysis day for the ESRD patients), enrollees underwent twelve 2-h blood draws for phosphate, ionized calcium, parathyroid hormone (PTH), total 25-hydroxy vitamin D (25OHD), and fibroblast growth factor-23 (FGF-23). RESULTS In the ESRD patients plasma phosphate demonstrated significant circadian variation (P < 0.00001). The peak occurred around 3:30 am and nadir occurred around 11:00 am. Ionized calcium (P = 0.0036), PTH (P = 0.0004) and 25OHD (P = 0.009) also varied significantly during the circadian period; for ionized calcium peak and nadir occurred around 12:15 pm and 8:00 pm, parathyroid hormone 5:45 pm and 10:15 am, and 25OHD 9:45 am and 4:00 pm respectively. FGF-23 did not show a significant circadian variation. Only phosphate (P < 0.0001) and PTH (P = 0.00008) demonstrated circadian variation in the control group. CONCLUSIONS Blood concentrations of phosphate, calcium, PTH and 25-hydroxy vitamin D, exhibit a circadian variation in patients with ESRD. Knowledge of these phenomena is pertinent for the interpretation of clinical testing.
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Affiliation(s)
- Hariprasad Trivedi
- Divisions of Nephrology, Department of Medicine, Medical College of Wisconsin, 9200 W. Wisconsin Ave., CLCC 5220, Milwaukee, WI, 53226, USA,
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Abstract
The emergence of fibroblast growth factor 23 as a potentially modifiable risk factor in CKD has led to growing interest in its measurement as a tool to assess patient risk and target therapy. This review discusses the analytical and clinical challenges faced in translating fibroblast growth factor 23 testing into routine practice. As for other bone mineral markers, agreement between commercial fibroblast growth factor 23 assays is poor, mainly because of differences in calibration, but also, these differences reflect the variable detection of hormone fragments. Direct comparison of readout from different assays is consequently limited and likely hampers setting uniform fibroblast growth factor 23-directed targets. Efforts are needed to standardize assay output to enhance clinical use. Fibroblast growth factor 23 is robustly associated with cardiovascular and renal outcomes in patients with CKD and adds value to risk assessments based on conventional risk factors. Compared with most other mineral markers, fibroblast growth factor 23 shows better intraindividual temporal stability, with minimal diurnal and week-to-week variability, but substantial interindividual variation, maximizing discriminative power for risk stratification. Conventional therapeutic interventions for the CKD-mineral bone disorder, such as dietary phosphate restriction and use of oral phosphate binders or calcimimetics, are associated with variable efficacy at modulating circulating fibroblast growth factor 23 concentrations, like they are for other mineral metabolites. Dual therapy with dietary phosphate restriction and noncalcium-based binder use achieves the most consistent fibroblast growth factor 23-lowering effect and seems best monitored using an intact assay. Additional studies are needed to evaluate whether strategies aimed at reducing levels or antagonizing its action have beneficial effects on clinical outcomes in CKD patients. Moreover, a better understanding of the mechanisms driving fibroblast growth factor 23 elevations in CKD is needed to inform the use of therapeutic interventions targeting fibroblast growth factor 23 excess. This evidence must be forthcoming to support the use of fibroblast growth factor 23 measurement and fibroblast growth factor 23-directed therapy in the clinic.
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Affiliation(s)
- Edward R Smith
- Department of Nephrology, The Royal Melbourne Hospital, Melbourne, Victoria, Australia
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Abstract
There is growing interest in the role of fibroblast growth factor 23 (FGF23) in various diseases of disordered mineral metabolism. In chronic kidney disease (CKD), where biochemical evidence of mineral disturbances is especially common, FGF23 measurement has been advocated as an early and sensitive marker for CKD-related bone disease. In this setting, FGF23 analysis may also improve the discrimination of risk of adverse renal and cardiovascular outcomes and aid targeting of those patients that are likely to benefit from interventions. Nonetheless, while the physiological relevance of FGF23 in the control of mineral metabolism is now firmly established, relatively little attention has been paid to important preanalytical and analytical aspects of FGF23 measurement that may impact on its clinical utility. Here we review these issues and discuss the suitability of FGF23 testing strategies for routine clinical practice. The current ‘state-of-the-art’ enzyme-linked immunosorbent assay methods for FGF23 measurement show poor agreement due to differences in FGF23 fragment detection, antibody specificity and calibration. Such analytical variability does not permit direct comparison of FGF23 measurements made with different assays and is likely to at least in part account for some of the inconsistencies noted between observational studies. From a clinical perspective, the lack of concordance has implications for the development of standardized reference intervals and clinical decision limits. Finally, the inherent assay-dependent biological variability of plasma FGF23 concentration can further complicate the interpretation of results and the design of FGF23-based testing protocols. Currently, it would be premature to consider incorporating FGF23 measurements into standard testing repertoires.
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Affiliation(s)
- Edward R Smith
- Department of Renal Medicine, Eastern Health Clinical School, Faculty of Medicine Nursing and Health Sciences, Monash University, Box Hill, Victoria, Australia
| | - Lawrence P McMahon
- Department of Renal Medicine, Eastern Health Clinical School, Faculty of Medicine Nursing and Health Sciences, Monash University, Box Hill, Victoria, Australia
| | - Stephen G Holt
- Department of Renal Medicine, Eastern Health Clinical School, Faculty of Medicine Nursing and Health Sciences, Monash University, Box Hill, Victoria, Australia
- Department of Nephrology, The Royal Melbourne Hospital, Parkville, Victoria, Australia
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Adema AY, de Borst MH, Ter Wee PM, Vervloet MG. Dietary and pharmacological modification of fibroblast growth factor-23 in chronic kidney disease. J Ren Nutr 2013; 24:143-50. [PMID: 24216259 DOI: 10.1053/j.jrn.2013.09.001] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2013] [Revised: 08/15/2013] [Accepted: 09/02/2013] [Indexed: 12/16/2022] Open
Abstract
Increased levels of phosphorus and fibroblast growth factor-23 (FGF-23) are strong predictors of cardiovascular morbidity and mortality. From a physiological perspective and supported by some data, phosphorus is the main driver for FGF-23 secretion. Therefore, it is conceivable that interventions aiming at restriction of phosphorus uptake from the gastrointestinal tract may lower serum FGF-23 levels and improve cardiovascular risk and subsequently survival. It is not currently known to what extend phosphorus and FGF-23 are independent risk factors, and therefore both need to be targeted. However, their respective metabolisms are tightly connected. Control of phosphorus levels in chronic kidney disease (CKD) patients is attempted mainly by restriction of dietary intake and the use of phosphorus binders. In this review, it is outlined that not just the amount of dietary phosphorus intake is important but also its type (organic vs. inorganic), its source (animal vs. plant derived), and the protein-to-phosphorus ratio in the bioavailability of phosphorus from food. This qualitative aspect of diet is likely a neglected aspect of dietary counseling in CKD. However, in more advanced stages of CKD, dietary restriction of phosphorus alone is usually not sufficient to control hyperphosphatemia, and phosphorus binders are indicated. The inexpensive, calcium-containing dietary phosphorus binders are used commonly worldwide. However, they are not suitable for every patient because of the association with elevated serum calcium, increase in vascular and valvular calcification scores, and cardiovascular and all-cause mortality. The calcium content itself in these binders has recently been implicated to upregulate FGF-23. For that reason, the noncalcium, aluminum-free agents such as sevelamer and lanthanum are being advocated. However, these drugs do not have a clearly defined effect on circulating levels of FGF-23. Although it is conceivable that targeting FGF-23 may lead to improved clinical outcomes, this remains speculative. Therefore, more studies are needed to answer the question if this can be achieved with any of the phosphorus binders, or by another (additional) pharmacological intervention.
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Affiliation(s)
- Aaltje Y Adema
- Department of Nephrology, VU University Medical Centre, Amsterdam, The Netherlands.
| | - Martin H de Borst
- Division of Nephrology, Department of Internal Medicine, University Medical Centre, Groningen and University of Groningen, Groningen, The Netherlands
| | - Piet M Ter Wee
- Department of Nephrology, VU University Medical Centre, Amsterdam, The Netherlands
| | - Marc G Vervloet
- Department of Nephrology, VU University Medical Centre, Amsterdam, The Netherlands
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