Fibroblast Growth Factor-23 Quartile Research Articles

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

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. Prospective cohort study. A total of 3,502 participants were selected in the Chronic Renal Insufficiency Cohort study. Baseline plasma FGF23. 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). 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. 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. Self-report of HF hospitalizations and possible lack of an echocardiogram at time of hospitalization. In this large multicenter prospective cohort study, elevated FGF23 levels were associated with increased risks for all HF subtypes. 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.

Relationship of Fibroblast Growth Factor 23 With Hospitalization for Heart Failure and Cardiovascular Outcomes in Patients Undergoing Cardiac Surgery.

Background Fibroblast growth factor 23 (FGF-23) is crucial in regulating phosphate and vitamin D metabolism and is moreover associated with an increased cardiovascular risk. The specific objective of this study was to investigate the influence of FGF-23 on cardiovascular outcomes, including hospitalization for heart failure (HHF), postoperative atrial fibrillation, and cardiovascular death, in an unselected patient population after cardiac surgery. Methods and Results Patients undergoing elective coronary artery bypass graft and/or cardiac valve surgery were prospectively enrolled. FGF-23 blood plasma concentrations were assessed before surgery. A composite of cardiovascular death/HHF was chosen as primary end point. A total of 451 patients (median age 70 years; 28.8% female) were included in the present analysis and followed over a median of 3.9 years. Individuals with higher FGF-23 quartiles showed elevated incidence rates of the composite of cardiovascular death/HHF (quartile 1, 7.1%; quartile 2, 8.6%; quartile 3, 15.1%; and quartile 4, 34.3%). After multivariable adjustment, FGF-23 modeled as a continuous variable (adjusted hazard ratio for a 1-unit increase in standardized log-transformed biomarker, 1.82 [95% CI, 1.34-2.46]) as well as using predefined risk groups and quartiles remained independently associated with the risk of cardiovascular death/HHF and the secondary outcomes, including postoperative atrial fibrillation. Reclassification analysis indicated that the addition of FGF-23 to N-terminal pro-B-type natriuretic peptide provides a significant improvement in risk discrimination (net reclassification improvement at the event rate, 0.58 [95% CI, 0.34-0.81]; P<0.001; integrated discrimination increment, 0.03 [95% CI, 0.01-0.05]; P<0.001). Conclusions FGF-23 is an independent predictor of cardiovascular death/HHF and postoperative atrial fibrillation in individuals undergoing cardiac surgery. Considering an individualized risk assessment, routine preoperative FGF-23 evaluation may improve detection of high-risk patients.

FGF23 and Cardiovascular Structure and Function in Advanced Chronic Kidney Disease.

Fibroblast growth factor 23 (FGF23) is a bone-derived phosphatonin that is elevated in chronic kidney disease (CKD) and has been implicated in the development of cardiovascular disease. It is unknown whether elevated FGF23 in CKD is associated with impaired cardiovascular functional capacity, as assessed by maximum exercise oxygen consumption (VO2Max). We sought to determine whether FGF23 is associated with cardiovascular functional capacity in patients with advanced CKD and after improvement of VO2Max by kidney transplantation. We performed secondary analysis of 235 patients from the Cardiopulmonary Exercise Testing in Renal Failure and After Kidney Transplantation (CAPER) cohort, which recruited patients with stage 5 CKD who underwent kidney transplantation or were waitlisted and hypertensive controls. All patients underwent cardiopulmonary exercise testing (CPET) and echocardiography and were followed longitudinally for 1 year after study enrollment. Patients across FGF23 quartiles differed in BMI (P=0.004) and mean arterial pressure (P<0.001) but did not significantly differ in sex (P=0.5) or age (P=0.08) compared with patients with lower levels of FGF23. Patients with higher FGF23 levels had impaired VO2Max (Q1: 24.2±4.8 ml/min per kilogram; Q4: 18.6±5.2 ml/min per kilogram; P<0.001), greater left ventricular mass index (LVMI; P<0.001), reduced HR at peak exercise (P<0.001), and maximal workload (P<0.001). Kidney transplantation conferred a significant decline in FGF23 at 2 months (P<0.001) before improvement in VO2Max at 1 year (P=0.008). Multivariable regression modeling revealed that changes in FGF23 was significantly associated with VO2Max in advanced CKD (P<0.001) and after improvement after kidney transplantation (P=0.006). FGF23 was associated with LVMI before kidney transplantation (P=0.003), however this association was lost after adjustment for dialysis status (P=0.4). FGF23 was not associated with LVMI after kidney transplantation in all models. FGF23 levels are associated with alterations in cardiovascular functional capacity in advanced CKD and after kidney transplantation. FGF23 is only associated with structural cardiac adaptations in advanced CKD but this was modified by dialysis status, and was not associated after kidney transplantation.

Prognostic Value of Fibroblast Growth Factor 23 in Autosomal Dominant Polycystic Kidney Disease

IntroductionAutosomal dominant polycystic kidney disease (ADPKD) is characterized by progressive cyst growth and a loss of functioning renal mass, but a decline in glomerular filtration rate (GFR) and onset of end-stage renal disease (ESRD) occur late in the disease course. There is therefore a great need for early prognostic biomarkers in this disorder.MethodsWe measured baseline serum fibroblast growth factor 23 (FGF23) levels in 192 patients with ADPKD from the Consortium for Radiologic Imaging Studies of PKD (CRISP) cohort that were followed for a median of 13 years and tested the association between FGF23 levels and change over time in height-adjusted total kidney volume (htTKV), GFR, and time to the composite endpoints of ESRD, death, and doubling of serum creatinine.ResultsPatients in the highest quartile for baseline FGF23 level had a higher rate of increase in htTKV (0.95% per year, P = 0.0016), and faster rate of decline in GFR (difference of −1.03 ml/min/1.73 m2 per year, P = 0.005) compared with the lowest quartile, after adjusting for other covariates, including htTKV and genotype. The highest quartile of FGF23 was also associated with a substantial increase in risk for the composite endpoint of ESRD, death, or doubling of serum creatinine (hazard ratio [HR] of 2.45 in the fully adjusted model, P = 0.03).ConclusionFGF23 is a prognostic biomarker for disease progression and clinically important outcomes in ADPKD, and has additive value to established imaging and genetic biomarkers.

Change in FGF23 concentration over time and its association with all-cause mortality in patients treated with haemodialysis or haemodiafiltration.

BackgroundPrevious studies in patients on haemodialysis (HD) have shown an association of fibroblast growth factor 23 (FGF23) with all-cause mortality. As of yet, the result of FGF23 lowering on mortality is unknown in this population.MethodsFGF23 was measured in a subset of 404 patients from the Dutch CONvective TRansport STudy (CONTRAST study) [a randomized trial in prevalent dialysis patients comparing HD and haemodiafiltration (HDF) with clinical outcome] at baseline and Months 6 and 12. A substantial decline of FGF23 change over time was anticipated in patients randomized to HDF since HDF induces higher dialytic clearance of FGF23. The associations of both baseline FGF23 and 6-months change in FGF23 with all-cause mortality were analysed. In addition, the difference in FGF23 change between HD and HDF was explored. Furthermore, the role of dialysis modality in the association between FGF23 change and outcome was analysed.ResultsNo association was observed between quartiles of baseline FGF23 and all-cause mortality. Over 6 months, FGF23 declined in patients on HDF, whereas FGF23 remained stable in patients on HD. A decrease in FGF23 was not associated with improved survival compared with a stable FGF23 concentration. However, increasing FGF23 was associated with a significantly higher mortality risk, both in crude and fully adjusted models [hazard ratio 2.01 (95% confidence interval 1.30–3.09)].ConclusionWhereas no association between a single value of FGF23 and all-cause mortality was found, increasing FGF23 concentrations did identify patients at risk for mortality. Since lowering FGF23 did not improve outcome, this study found no argument for therapeutically lowering FGF23.

Racial Differences in the Associations Between Food Insecurity and Fibroblast Growth Factor 23 in the Coronary Artery Risk Development in Young Adults Study

Food insecurity is associated with consumption of phosphate additive-laden processed food and beverage products, which could result in higher levels of fibroblast growth factor 23 (FGF23) to compensate for the increased dietary phosphate load. We sought to determine whether food insecurity is associated with higher levels of FGF23. We stratified analyses by race since differences may occur between food insecurity and diet quality across races. The longitudinal community-based Coronary Artery Risk Development in Young Adults Study recruited from 4 US centers: Birmingham, AL; Chicago, IL; Minneapolis, MN; and Oakland, CA, during the cohort inception in 1985/1986. This analysis included 3,421 black and white participants from Coronary Artery Risk Development in Young Adults follow-up years 20, 25, and 30 who were enrolled in the study between the ages of 18 and 30 years. Econometric fixed effects models stratified by race that adjust by design for all time-invariant covariates were used to model the longitudinal association of food insecurity, defined as the self-reported ability to afford desired quantity and quality of food. The main outcome of interest was changing to the highest quartile of plasma FGF-23 concentrations. During follow-up, 29% of blacks and 14% of whites experienced change in food security. Developing food insecurity was associated with a 1.48 greater odds of increasing to the highest quartile of FGF23 (95% confidence interval 1.02-2.15) among blacks; however, there was no significant longitudinal association among whites (odds ratio=1.14, 95% confidence interval 0.67-1.95). Among blacks, food insecurity was associated with an increase in levels of FGF23. Although phosphate consumption was presumed to mediate the association between food insecurity and FGF23 levels, we were unable to directly test this pathway.

FGF23 (Fibroblast Growth Factor-23) and Incident Hypertension in Young and Middle-Aged Adults: The CARDIA Study.

Blacks have the highest prevalence of hypertension in the United States. Higher levels of FGF23 (fibroblast growth factor-23) have been associated with worse cardiovascular outcomes. Whether FGF23 is associated with rising blood pressure (BP) and racial differences in incident hypertension is unclear. We studied 1758 adults (45.0±3.7 years; 57.8% female; 36.9% black) without hypertension or cardiovascular disease who participated in the year 20 (2005-2006) follow-up examination of the CARDIA study (Coronary Artery Risk Development in Young Adults). We investigated the associations of baseline (year 20) cFGF23 (C-terminal FGF23) levels with longitudinal BP patterns and incident hypertension (defined as being on antihypertensive medication, systolic BP ≥130 or diastolic BP ≥80 mm Hg) during 2 follow-up visits (years 25 and 30). During follow-up, 35.2% of participants developed hypertension. In multivariable linear mixed models, there were greater increases in systolic BP from year 20 to 25 and year 25 to 30 in the highest FGF23 quartile relative to the lowest quartile (+2.1 mm Hg, P=0.0057 and +2.2 mm Hg, P=0.0108, respectively for each time period), whereas there were greater increases in diastolic BP from year 20 to 25 in the highest quartile relative to the lowest (+1.6 mm Hg; P=0.0024). In multivariable modified Poisson regression analyses, the highest FGF23 quartile was associated with a 45% greater risk of developing hypertension during follow-up compared with the lowest quartile (relative risk, 1.45 [1.18-1.77]). Results did not vary by race (Pinteraction=0.1523). Higher FGF23 levels are independently associated with rising BP over time and an increased risk of incident hypertension but not racial differences in hypertension.

Circulating Fibroblast Growth Factor-23 Levels are Associated with an Increased Risk of Anemia Development in Patients with Nondialysis Chronic Kidney Disease

Fibroblast growth factor-23 (FGF23) is an established biomarker of adverse outcomes in patients with chronic kidney disease (CKD). Several cross-sectional studies have suggested a possible association between FGF23 and anemia in these patients. In this large-scale prospective cohort study, we investigated this relationship and examined whether high FGF23 levels increase the risk of incident anemia. This prospective longitudinal study included 2,089 patients from the KoreaN cohort study for Outcome in patients With CKD. Anemia was defined as hemoglobin level <13.0 g/dl (men) and <12.0 g/dl (women). Log-transformed FGF23 significantly correlated with hepcidin but inversely correlated with iron profiles and hemoglobin. Multivariate logistic regression showed that log-transformed FGF23 was independently associated with anemia (odds ratio [OR], 1.14; 95% confidence interval [CI], 1.04–1.24, P = 0.01). Among 1,164 patients without anemia at baseline, 295 (25.3%) developed anemia during a median follow-up of 21 months. In fully adjusted multivariable Cox models, the risk of anemia development was significantly higher in the third (hazard ratio [HR], 1.66; 95% CI, 1.11–2.47; P = 0.01) and fourth (HR, 1.84; 95% CI, 1.23–2.76; P = 0.001) than in the first FGF23 quartile. In conclusion, high serum FGF23 levels were associated with an increased risk for anemia in patients with nondialysis CKD.

Fibroblast Growth Factor 23: A Biomarker of Kidney Function Decline

Background: Fibroblast growth factor 23 (FGF-23) is a hormone that regulates phosphorus levels and vitamin D metabolism. Previous studies have shown FGF-23 to be a risk factor for incident end-stage renal disease; however, there are less data on the association of FGF-23 with earlier kidney-related outcomes. Methods: Serum FGF-23 was assayed using an intact ELISA assay in 2,496 participants of the Healthy Aging and Body Composition Study, a cohort of well-functioning older adults. Kidney function was estimated by assaying cystatin C at baseline and years 3 and 10. The associations between FGF-23 and decline in kidney function (defined by estimated glomerular filtration rate (eGFR) decline ≥30% or ≥3 mL/min/year) and incident chronic kidney disease (CKD; incident eGFR <60 mL/min/1.73 m² and ≥1 mL/min/year decline) were evaluated. Models were adjusted for demographics, baseline eGFR, urine albumin/creatinine ratio, comorbidity, and serum calcium, phosphorus, 25(OH) vitamin D and parathyroid hormone. Results: The mean (SD) age was 75 (3) years, with 52% female and 38% black. There were 405 persons with 30% decline, 702 with >3 mL/min/year decline, and 536 with incident CKD. In fully adjusted continuous models, doubling of FGF-23 concentrations was not associated with kidney function decline (OR [95% CI] = 0.98 [0.82–1.19] for ≥30% decline and OR 1.17 [95% CI 1.00–1.37] for ≥3 mL/min/year decline), or incident CKD (incident rate ratio [IRR] 1.05 [95% CI 0.91–1.22]). In adjusted quartile analysis, the highest quartile of FGF-23 was significantly associated with incident CKD (IRR 1.27 [95% CI 1.02–1.58] for highest vs. lowest quartile). Conclusion: Higher FGF-23 concentrations were not consistently associated with decline in kidney function or incident CKD in community-dwelling older adults.

Abstract P303: Racial Differences in the Associations Between Food Insecurity and Fibroblast Growth Factor 23 (FGF23) in The Coronary Artery Risk Development in Young Adults (CARDIA) Study

Introduction: Elevated Fibroblast Growth Factor 23 (FGF23) - an endocrine hormone linked to cardiovascular and kidney disease outcomes - is a compensatory response to high dietary phosphate load or chronic kidney disease. Large quantities of inorganic phosphates additives are found in processed foods, and food insecurity is associated with higher consumption of processed foods. Hypothesis: We hypothesized that developing food insecurity is associated with an increase in FGF23. Methods: We included CARDIA study participants with a stored plasma sample available from at least two consecutive exams at years 20, 25, and 30 (N=3,421). Food insecurity was assessed through a single question about ability to afford quantity and quality of food. FGF23 levels were assessed using a commercial c-terminal ELISA. Due to a strong right skew in FGF23 levels, we divided FGF23 in quartiles and compared the highest quartile to the combined lower three quartiles using logistic regression. Econometric fixed effects models that adjust by design for all time-invariant covariates were used to model the longitudinal association between simultaneous within-person change in food insecurity and FGF23. Due to an interaction between food insecurity and race ( p =0.002), we stratified by race. Results: About 29% of blacks and 14% of whites experienced change in food insecurity during follow-up. Developing food insecurity was associated with a 1.46 greater odds of increasing to the highest quartile of FGF23 (95% CI: 1.02,2.10) among blacks; however, there was no significant longitudinal association among whites (OR=1.05; 95% CI: 0.62,1.77). Conclusions: Using models that tightly control for all time-invariant confounding, we found that developing food insecurity was associated with increases in FGF23 among blacks. The differential increases in blacks as compared to whites may be due to differences in dietary changes in response to developing food insecurity. Previous research has shown racial differences in dietary quality by food insecurity.

Fibroblast Growth Factor 23 Associates with Death in Critically Ill Patients.

Dysregulated mineral metabolism is a common and potentially maladaptive feature of critical illness, especially in patients with AKI, but its association with death has not been comprehensively investigated. We sought to determine whether elevated plasma levels of the osteocyte-derived, vitamin D-regulating hormone, fibroblast growth factor 23 (FGF23), are prospectively associated with death in critically ill patients with AKI requiring RRT, and in a general cohort of critically ill patients with and without AKI. We measured plasma FGF23 and other mineral metabolite levels in two cohorts of critically ill patients (n=1527). We included 817 patients with AKI requiring RRT who enrolled in the ARF Trial Network (ATN) study, and 710 patients with and without AKI who enrolled in the Validating Acute Lung Injury biomarkers for Diagnosis (VALID) study. We hypothesized that higher FGF23 levels at enrollment are independently associated with higher 60-day mortality. In the ATN study, patients in the highest compared with lowest quartiles of C-terminal (cFGF23) and intact FGF23 (iFGF23) had 3.84 (95% confidence interval, 2.31 to 6.41) and 2.08 (95% confidence interval, 1.03 to 4.21) fold higher odds of death, respectively, after adjustment for demographics, comorbidities, and severity of illness. In contrast, plasma/serum levels of parathyroid hormone, vitamin D metabolites, calcium, and phosphate were not associated with 60-day mortality. In the VALID study, patients in the highest compared with lowest quartiles of cFGF23 and iFGF23 had 3.52 (95% confidence interval, 1.96 to 6.33) and 1.93 (95% confidence interval, 1.12 to 3.33) fold higher adjusted odds of death. Higher FGF23 levels are independently associated with greater mortality in critically ill patients.

Association of Fibroblast Growth Factor 23 With Risk of Incident Coronary Heart Disease in Community-Living Adults

Higher circulating fibroblast growth factor 23 (FGF23) concentrations are associated with cardiovascular disease events linked to heart failure, but associations of FGF23 with coronary heart disease (CHD) have been less consistent. To determine the association of plasma FGF23 concentrations with incident CHD and whether this association differs by race, sex, or chronic kidney disease status. We examined the association of FGF23 concentrations with incident CHD risk within the Reasons for Geographic and Racial Differences in Stroke study, a prospective cohort of black and white adults 45 years and older enrolled between January 2003 and October 2007 with follow-up through December 31, 2011. Using a case-cohort design, we measured FGF23 concentrations in 829 participants who developed incident CHD and in 812 participants randomly selected from the Reasons for Geographic and Racial Differences in Stroke study cohort (cohort random sample). To account for the stratified sampling design, the cohort random sample was weighted back to the original cohort overall (n = 22 127). Cox proportional hazards models were used to examine the association of FGF23 concentration with incident CHD, adjusting for CHD risk factors and kidney function. In prespecified analyses, we examined whether race, sex, or chronic kidney disease modified the association of FGF23 concentration with incident CHD. Plasma C-terminal FGF23 concentrations. Investigator-adjudicated incident CHD events. Of the 22 127 participants in the weighted cohort random sample, 13 059 (58.9%) were female and 9435 (42.6%) were black, and the mean age was 64.3 (95% CI, 63.7-64.9) years. Greater age, lower estimated glomerular filtration rate, higher urine albumin to creatinine ratio, and female sex were associated with higher FGF23 concentration at baseline. In multivariable models adjusted for established CHD risk factors and kidney function, higher FGF23 concentrations were associated with greater risk of CHD (hazard ratio [HR] comparing fourth with first quartile, 2.15; 95% CI, 1.35-3.42). The magnitude and strength of these associations differed by sex. However, these differences were no longer observed when adjusting for hormone therapy in women (men: HR comparing fourth with first quartile, 2.40; 95% CI, 1.30-4.42; women: HR comparing fourth with first quartile, 2.34; 95% CI, 1.04-5.27) or when using sex-specific FGF23 quartiles (men: HR comparing fourth with first quartile, 2.65; 95% CI, 1.43-4.90; women: HR comparing fourth with first quartile, 2.26; 95% CI, 1.02-5.03). Higher FGF23 concentrations were associated with greater risk of CHD. Heterogeneity in the association by sex may be caused by differences in the distribution of plasma FGF23 concentrations or the use of hormone therapy in men vs women.

Fibroblast Growth Factor 23 Levels Associate with AKI and Death in Critical Illness.

Elevated plasma levels of the osteocyte-derived hormone fibroblast growth factor 23 (FGF23) have emerged as a powerful biomarker of cardiovascular disease and death in patients with CKD. Whether elevated urinary or plasma FGF23 levels are prospectively associated with AKI and death in critically ill patients is unknown. We therefore conducted a prospective cohort study of 350 critically ill patients admitted to intensive care units at an academic medical center to investigate whether higher urinary FGF23 levels associate with the composite end point of AKI or in-hospital mortality (AKI/death). We measured urinary FGF23 levels within 24 hours of admission to the intensive care unit. In a subcohort (n=131) we also measured plasma levels of FGF23, calcium, phosphate, parathyroid hormone, and vitamin D metabolites. Urinary and plasma FGF23 levels, but not other mineral metabolites, significantly associated with AKI/death. In multivariate analyses, patients in the highest compared with the lowest quartile of urinary FGF23 had a 3.9 greater odds (95% confidence interval, 1.6 to 9.5) of AKI/death. Higher urinary FGF23 levels also independently associated with greater hospital, 90-day, and 1-year mortality; longer length of stay; and several other important adverse outcomes. In conclusion, elevated FGF23 levels measured in the urine or plasma may be a promising novel biomarker of AKI, death, and other adverse outcomes in critically ill patients.

Inflammation and elevated levels of fibroblast growth factor 23 are independent risk factors for death in chronic kidney disease

Inflammation is a consequence of chronic kidney disease (CKD) and is associated with adverse outcomes in many clinical settings. Inflammation stimulates production of fibroblast growth factor 23 (FGF23), high levels of which are independently associated with mortality in CKD. Few large-scale prospective studies have examined inflammation and mortality in patients with CKD, and none tested the interrelationships among inflammation, FGF23, and risk of death. Therefore, we conducted a prospective investigation of 3875 participants in the Chronic Renal Insufficiency Cohort (CRIC) study with CKD stages 2 to 4 to test the associations of baseline plasma interleukin-6, high-sensitivity C-reactive protein, and FGF23 levels with all-cause mortality, censoring at the onset of end-stage renal disease. During a median follow-up of 6.9 years, 550 participants died (20.5/1000 person-years) prior to end-stage renal disease. In separate multivariable-adjusted analyses, higher levels of interleukin-6 (hazard ratio per one standard deviation increase of natural log-transformed levels) 1.35 (95% confidence interval, 1.25-1.46), C-reactive protein 1.28 (1.16-1.40), and FGF23 1.45 (1.32-1.60) were each independently associated with increased risk of death. With further adjustment for FGF23, the risks of death associated with interleukin-6 and C-reactive protein were minimally attenuated. Compared to participants in the lowest quartiles of inflammation and FGF23, the multivariable-adjusted hazard ratio of death among those in the highest quartiles of both biomarkers was 4.38 (2.65-7.23) for interleukin-6 and FGF23, and 5.54 (3.04-10.09) for C-reactive protein and FGF23. Thus, elevated levels of interleukin-6, C-reactive protein, and FGF23 are independent risk factors for mortality in CKD.

Dietary factors and fibroblast growth factor-23 levels in young adults with African ancestry.

Fibroblast growth factor-23 (FGF23), a phosphaturic hormone secreted mainly by osteocytes, maintains serum phosphate levels within a tight range by promoting phosphaturia. Previous studies have mainly focused on the link between FGF23 levels and dietary intake of phosphate, but other dietary factors may also influence FGF23 levels. This cross-sectional study pooled three populations of young adults with African ancestry (452 in Chicago, IL, USA; 477 in Victoria, Seychelles; and 482 in Kumasi, Ghana) with estimated glomerular filtration rate >80ml/min/1.73m2 to examine the association of dietary factors based on two 24-h recalls with FGF23 levels measured using a C-terminal assay. Linear regression was used to examine the association between log-transformed FGF23 levels and quartiles of calorie-adjusted dietary factors with adjustment for covariates. In the pooled sample of 1411 study participants, the mean age was 35.2 (6.2) years and 45.3% were male. Median plasma C-terminal FGF23 values in relative units (RU)/ml were 59.5 [interquartile range (IQR) 44.1, 85.3] in the USA, 43.2 (IQR 33.1, 57.9) in Seychelles, and 34.0 (IQR 25.2, 50.4) in Ghana. With adjustment for covariates, increasing quartiles of calcium and animal protein and decreasing quartiles of vegetable protein, fiber, and magnesium intake were associated with significantly higher FGF23 levels compared to the lowest quartile. After further adjustment for dietary factors, significant trends in FGF23 levels were noted only for quartiles of calcium, fiber, and magnesium intake (P<0.001). Dietary factors other than phosphate are associated with FGF23 levels in young adults.

Association of Fibroblast Growth Factor 23 With Atrial Fibrillation in Chronic Kidney Disease, From the Chronic Renal Insufficiency Cohort Study.

Levels of fibroblast growth factor 23 (FGF23) are elevated in chronic kidney disease (CKD) and strongly associated with left ventricular hypertrophy, heart failure, and death. Whether FGF23 is an independent risk factor for atrial fibrillation in CKD is unknown. To investigate the association of FGF23 with atrial fibrillation in CKD. Prospective cohort study of 3876 individuals with mild to severe CKD who enrolled in the Chronic Renal Insufficiency Cohort Study between June 19, 2003, and September 3, 2008, and were followed up through March 31, 2013. Baseline plasma FGF23 levels. Prevalent and incident atrial fibrillation. The study cohort comprised 3876 participants. Their mean (SD) age was 57.7 (11.0) years, and 44.8% (1736 of 3876) were female. Elevated FGF23 levels were independently associated with increased odds of prevalent atrial fibrillation (n = 660) after adjustment for cardiovascular and CKD-specific factors (odds ratio of highest vs lowest FGF23 quartile, 2.30; 95% CI, 1.69-3.13; P < .001 for linear trend across quartiles). During a median follow-up of 7.6 years (interquartile range, 6.3-8.6 years), 247 of the 3216 participants who were at risk developed incident atrial fibrillation (11.9 events per 1000 person-years). In fully adjusted models, elevated FGF23 was independently associated with increased risk of incident atrial fibrillation after adjustment for demographic, cardiovascular, and CKD-specific factors, and other markers of mineral metabolism (hazard ratio of highest vs lowest FGF23 quartile, 1.59; 95% CI, 1.00-2.53; P = .02 for linear trend across quartiles). The results were unchanged when further adjusted for ejection fraction, but individual adjustments for left ventricular mass index, left atrial area, and interim heart failure events partially attenuated the association of elevated FGF23 with incident atrial fibrillation. Elevated FGF23 is independently associated with prevalent and incident atrial fibrillation in patients with mild to severe CKD. The effect may be partially mediated through a diastolic dysfunction pathway that includes left ventricular hypertrophy, atrial enlargement, and heart failure events.

Fibroblast Growth Factor 23 and Incidence of Subarachnoid Hemorrhage: Nested Case-Control Study.

Fibroblast growth factor 23 (FGF23) is a hormone with regulatory effects on mineral metabolism and arterial calcification. We aimed to study the association between FGF23 and risk of incident subarachnoid hemorrhage (SAH) in a nested case-control study. FGF23 was analyzed in stored blood samples from incident SAH cases (n=79) and control subjects (n=232), participating in the prospective, population-based Malmö Diet and Cancer Study. The association between FGF23 and SAH was studied using conditional logistic regression. High FGF23 was associated with incident SAH. In the highest compared with the lowest quartile of FGF23, the odds ratio for SAH was 3.28 (95% confidence interval, 1.34-8.00), P for trend=0.006, after adjustment for SAH risk factors. High FGF23 was associated with increased risk of incident SAH in subjects from the general population. Further studies should elucidate whether FGF23 is a causal risk factor for SAH, or could be used in risk prediction.

Low Vitamin D and High Fibroblast Growth Factor 23 Serum Levels Associate with Infectious and Cardiac Deaths in the HEMO Study.

Longitudinal studies testing the relationship between repeated measures of vitamin D or fibroblast growth factor 23 (FGF23) and infectious and cardiac hospitalizations and death in hemodialysis patients have not been reported. We examined the association between yearly 25-hydroxyvitamin D (25(OH)D), 1,25-dihydroxyvitamin D (1,25(OH)2D), and FGF23 serum levels and various clinical outcomes using time-dependent Cox regression models with repeated yearly measures and fixed-covariate Cox models with only baseline values after controlling for important clinical covariates in the HEMO study. During a median follow-up of 3 years, 582 of the 1340 participants died, and 499 and 514 participants had a hospitalization or death attributed to infectious and cardiac causes, respectively. Patients in the highest 25(OH)D quartile had the lowest risk of infectious events (hazard ratio [HR] 0.66 versus the lowest quartile; 95% confidence interval [95% CI], 0.49-0.89), cardiac events (HR, 0.71; 95% CI, 0.53-0.96), and all-cause mortality (HR, 0.46; 95% CI, 0.34-0.62) in time-dependent analyses. No significant associations of 1,25(OH)2D with clinical outcomes were observed in time-dependent or fixed-covariate Cox models. In contrast, the highest FGF23 quartile was associated with a higher risk of infectious events (HR, 1.57 versus the lowest quartile; 95% CI, 1.13-2.18), cardiac events (HR, 1.49; 95% CI, 1.06-2.08), and all-cause mortality (HR, 1.50; 95% CI, 1.07-2.12) in fixed-covariate Cox models. The addition of inflammation markers into the statistical models did not attenuate these associations. Thus, disordered mineral metabolism may affect outcomes in chronic hemodialysis patients.

Associations of fibroblast growth factor-23 with markers of inflammation, insulin resistance and obesity in adults.

IntroductionElevated fibroblast growth factor-23 (FGF23) is an established marker of cardiovascular disease. The underlying reason(s) for the rise accompanying cardiovascular health decline are unclear. Prior studies have shown that FGF23 concentrations are associated with markers of inflammation and insulin resistance but they have been limited by a focus on persons with chronic kidney disease (CKD) and lack of race and sex diversity. The objective of this study was to examine the associations of FGF23 and markers of inflammation, insulin resistance, and anthropometrics in a large cohort of community-dwelling adults.MethodsAssociations of FGF23 with markers of inflammation [interleukin-6 (IL-6), IL-10, high sensitivity-CRP (hsCRP)], insulin utilization [resistin, adiponectin, homeostatic model assessment of insulin resistance (HOMA-IR)] and anthropometrics [BMI and waist circumference (WC)] were examined cross-sectionally in a 1,040 participants randomly selected from the Reason for Geographic and Racial Differences in Stroke (REGARDS) Study, a national study of black and white adults ≥45 years. Effect modification by race and CKD status was tested, and stratified models were analyzed accordingly.ResultsMedian FGF23 concentration was 69.6 RU/ml (IQR: 53.2, 102.7). Higher quartiles of FGF23 were associated with higher mean concentrations of IL-6, IL-10, hsCRP and resistin (P trend<0.001 for all). There were no significant differences in HOMA-IR, adiponectin concentrations, BMI, or WC across FGF23 quartiles in the crude analyses. CKD significantly modified the relationships between FGF23 and inflammatory markers, HOMA-IR, BMI and WC (P ≤ 0.01 for all). In linear regression models adjusted for sociodemographic and clinical variables, FGF23 was positively associated with IL-6, hsCRP, IL-10, HOMA-IR, BMI and WC in individuals without CKD, but not among individuals with CKD. Additionally, FGF23 was positively associated with resistin irrespective of CKD status.ConclusionsElevated FGF23 concentrations may be considered a biomarker for decline in metabolic function among individuals with normal kidney function.

Abstract W P148: Elevated Fibroblast Growth Factor 23 Associates with Greater White Matter Lesion Load and MRI-Defined Infarction: The Northern Manhattan Study (NOMAS)

INTRODUCTION: Elevated fibroblast growth factor 23 (FGF23) regulates phosphate homeostasis and has been linked with mortality, cardiovascular events, and stroke. However, the role of FGF23 as a risk factor for subclinical cerebrovascular damage (SCVD) is not known. METHODS: We used multivariable linear and logistic regression to evaluate associations between FGF23, continuously and by quartiles, with white matter hyperintensity volume (WMHV), expressed as percent intracranial volume (%ICV), and subclinical brain infarction (SBI) in a race/ethnically diverse communitybased sample. RESULTS: There were 1,170 strokefree NOMAS participants with FGF23 levels and quantitative MRI data on WMHV and SBI. Participants with FGF23 levels in the top quartile (range=84.98 to1424.59 RU/mL) had greater WMHV (β=0.19 %ICV, 95% CI=0.04 to 0.33 %ICV, p=0.01) compared to those in the lowest quartile (range=15.41 to 48.96 RU/mL), adjusted for demographics, vascularrisk factors, and estimated glomerular filtration rate (eGFR). These findings remained significant in those without evidence of chronic kidney disease (CKD). The highest quartile of FGF23 also associated with greater odds of SBI, but this effect was not significant after adjusting for demographic factors and eGFR. However, sex was an effect modifier ofFGF23 in relation to odds of SBI (p for interaction=0.03). Stratified by sex, FGF23 was associated with greater odds of SBI in men (OR=1.7, 95% CI=1.0 to 2.6, p=0.03) after adjusting for demographics, vascular risk factors, and eGFR, but not among women. CONCLUSIONS: These crosssectional communitybased data from a diverse urban sample suggest elevated FGF23 may be a risk factor for small vessel disease, as well as MRIdefined brain infarction in men, independent of CKD. Prospective data on elevated FGF23 and SCVD are needed.