Impact of fibroblast growth factor 23 on lipids and atherosclerosis in hemodialysis patients

Association between endothelial biomarkers and lipid and glycemic levels: a cross-sectional study with diabetic patients

Background: Biomarkers can help understand the impact of achieving therapeutic goals in developing vascular diseases in diabetics. Aim: To assess the association between lipid and glycemic profiles and endothelial biomarkers in diabetics. Methods: Cross-sectional study that evaluated lipid and glycemic levels and biomarkers (VCAM-1, Sdc-1, FGF-23 and KIM-1 in diabetics. Results: Higher VCAM-1 levels were associated with higher low-density lipoprotein cholesterol and non-high-density lipoprotein (HDL) cholesterol levels (in the group with inadequate glycohemoglobin A1c [HbA1c] levels), with higher glycemic levels (in the group with inadequate HDL cholesterol levels) and with lower HDL cholesterol levels (both groups). VCAM-1 was independently associated with not achieving adequate HbA1c levels. Conclusion: In uncontrolled diabetics, VCAM-1 was independently associated with having inadequate HbA1c levels, suggesting they may already have endothelial damage.

Fibroblast Growth Factor 23 and Muscle Wasting: A Metabolic Point of View

Protein energy wasting (PEW), mostly characterized by decreased body stores of protein and energy sources, particularly in the skeletal muscle compartment, is highly prevalent in patients with moderate to advanced chronic kidney disease (CKD). Fibroblast growth factor 23 (FGF23) is an endocrine hormone secreted from bone and has systemic actions on skeletal muscle. In CKD, FGF23 is elevated and its coreceptor α-klotho is suppressed. Multiple lines of evidence suggest that FGF23 is interconnected with various mechanisms of skeletal muscle wasting in CKD, including systemic and local inflammation, exaggerated oxidative stress, insulin resistance (IR), and abnormalities in adipocytokine metabolism. Investigation of metabolic actions of FGF23 on muscle tissue could provide new insights into metabolic and nutritional abnormalities observed in patients with CKD.

Association of erythropoietin resistance and fibroblast growth factor 23 in dialysis patients: Results from the Japanese Dialysis Outcomes and Practice Patterns Study

BACKGROUND

Fibroblast growth factor 23 (FGF23) plays an important role in chronic kidney disease (CKD)-related mineral and bone disorders. High FGF23 levels are associated with increased risk of anaemia in non-haemodialysis CKD patients. FGF23 also negatively regulates erythropoiesis in mice. We hypothesized that higher FGF23 levels are associated with increased erythropoietin hyporesponsiveness among haemodialysis patients.

METHODS

The study included 1044 patients from the Japanese Dialysis Outcomes and Practice Patterns Study (J-DOPPS) phase 5 (2012-2015). The outcome was erythropoiesis-stimulating agent hyporesponsiveness (ESA-hypo), defined as mean Hgb <10 g/dL and standardized mean ESA dose >6000 u/week over 4 months following FGF23 measurement. The association between ESA-hypo and FGF23 was estimated using multivariable-adjusted logistic generalized estimating equation regression models.

RESULTS

Patients with higher levels of FGF23 were younger and had higher levels of serum albumin, creatinine, albumin-corrected calcium, phosphorus, PTH, 25(OH)-vitamin D, and had higher percentages of intravenous (IV) iron, IV vitamin D and cinacalcet use. ESA-hypo was present in 144 patients (13.8%). Compared with the third quintile of FGF23 levels, the odds ratio (95% CI) of ESA-hypo was 2.14 (0.99, 4.62) and 1.74 (0.74, 4.11) for the first and fifth quintiles, respectively.

CONCLUSION

The lowest and highest levels of FGF23 were associated with higher odds of ESA-hypo in patients on maintenance haemodialysis, although the associations were not statistically significant. The relationship between FGF23 and anaemia, and particularly the increased risks of ESA-hypo at low FGF23 levels which might be the result of energy saving, must be confirmed in larger clinical studies.

Fibroblast growth factor-23 correlates with advanced disease conditions and predicts high risk of major adverse cardiac and cerebral events in end-stage renal disease patients undergoing continuous ambulatory peritoneal dialysis

BACKGROUND

This study aimed to investigate the correlation of serum fibroblast growth factor-23 (FGF-23) level with clinical indexes, in particular to explore the value of FGF-23 in predicting major adverse cardiac and cerebral event (MACCE) risk in end-stage renal disease (ESRD) patients undergoing continuous ambulatory peritoneal dialysis (CAPD).

METHODS

In 270 ESRD patients undergoing CAPD consecutively enrolled in this prospective cohort study, we collected serum samples and performed enzyme-linked immunosorbent assay to detect FGF-23 expression. MACCE-free survival was defined as the date from enrollment to the date of MACCE occurrence.

RESULTS

High levels of FGF-23 correlated with longer duration of dialysis (p = 0.002), elevated levels of calcium (p < 0.001), phosphorus (p = 0.037) and low density lipoprotein cholesterol (p = 0.027). MACCE occurrence rate was higher in the FGF-23 high-expression than low-expression group at 2 years (p = 0.028), 3 years (p = 0.001) and 4 years (p = 0.004). Kaplan-Meier curves revealed that MACCE-free survival was shorter in the FGF-23 high-expression than low-expression group (p = 0.004). Multivariate Cox's analysis showed that high FGF-23 expression (p = 0.011) as well as the duration of dialysis (p = 0.017), C-reactive protein (p = 0.011) and fasting blood glucose (p = 0.038) were independent predictive factors for reduced MACCE-free survival in ESRD patients undergoing CAPD.

CONCLUSION

High FGF-23 expression correlates with advanced disease conditions as well as increased MACCE risk, and is an independent factor predicting worse MACCE-free survival in ESRD patients undergoing CAPD.

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.

Association of High-Density Lipoprotein Subclasses with Chronic Kidney Disease Progression, Atherosclerosis, and Klotho

BACKGROUND

Atherosclerosis is often a complication of chronic kidney disease (CKD) because of dyslipidemia and CKD-mineral and bone disorder. High-density lipoproteins (HDLs) are grouped into various subclasses composed of multiple proteins and lipids, and their transformation is altered in CKD. We investigated the roles of lipoprotein subclasses in CKD progression, and atherosclerosis, and the relationships with Klotho and fibroblast growth factor (FGF) 23.

METHODS

Seventy-one CKD patients were enrolled in this prospective cohort study in Japan. The proportions of cholesterol level to total cholesterol level (cholesterol proportion) and lipoprotein particle numbers in 20 lipoprotein fractions were measured by a newly developed high-performance gel permeation chromatography.

RESULTS

Diabetic nephropathy was observed in 23.9% of the patients. The mean age was 75.0 years and estimated glomerular filtration rate (eGFR) was 17.2 ml/min./1.73m2. The lipoprotein particle numbers in small HDLs were higher in Stage 4 group than in Stage 5 group (p = 0.002). Multivariate regression analysis adjusted for baseline characteristics showed that the cholesterol proportions in very small HDLs were associated with eGFR change rate [F19 β = -17.63, p = 0.036] and ABI [F19 β = 0.047, p = 0.047] in Stage 4 group, and that serum soluble α-Klotho level was associated with the lipoprotein particle numbers in very small HDLs [F19 β = 0.00026, p = 0.012; F20 β = 0.00041, p = 0.036] in Stage 5 group.

CONCLUSIONS

This study showed that HDL subclasses are associated with CKD progression, ABI, and Klotho level in CKD-stage-specific manner.

The association of the Klotho polymorphism rs9536314 with parameters of calcium-phosphate metabolism in patients on long-term hemodialysis

BACKGROUND

Patients on long-term hemodialysis frequently suffer from complications, such as secondary hyperparathyroidism, bone fractures, and arteriosclerosis. The process of regulating Ca/P metabolism depends on factors, such as FGF23 and Klotho. This study aimed to answer the question of whether the Klotho polymorphism rs9536314 is associated with FGF23 plasma concentration.

METHODS

In 118 patients undergoing hemodialysis, blood was collected before and after hemodialysis. The following parameters were measured in plasma: FGF23, serum: Ca, P, PTH, HGB, and iron concentrations. The KL gene polymorphism rs9536314 was identified by PCR-RFLP.

RESULTS

The KL polymorphism rs9536314 was not associated with Ca, P, PTH, or FGF23. There was a negative correlation between FGF23 and blood HGB levels and positive correlation between FGF23 and ESA dose.

CONCLUSIONS

The results obtained may indicate that there is no association between the KL polymorphism and FGF23 concentration in patients undergoing long-term.

Prognostic importance of fibroblast growth factor-23 in dialysis patients

Introduction. In this study, we aimed to demonstrate the correlation of FGF-23 levels with bone-mineral metabolism, anemia, and the treatment in dialysis patients. Methods. Eighty-nine patients with similar age, gender, dialysis duration, and dialysis adequacy who were receiving hemodialysis replacement therapy for at least 6 months were included in the study. Serum iron, iron binding capacity, ferritin, hemoglobin (Hb), hematocrit (Htc), calcium (Ca), phosphorus (P), intact parathormone (iPTH), and FGF-23 levels were studied. In addition, active vitamin D and phosphate binders calcimimetic therapies that patients have received in the last 6 months were recorded. Results. It was determined that there was a positive correlation between serum FGF-23 values and PTH values (P < 0, 01) and Ca∗P values (P < 0, 01). A positive correlation was found between serum FGF-23 values and Ca values at a rate of 24,6% (P < 0, 05) and between P values at a rate of 59,1% (P < 0, 01). A positive correlation was determined between serum FGF-23 values and hemoglobin (Hb) values (P < 0, 05) and hematocrit (Htc) values (P < 0, 05). In multivariate analysis, no significant correlation was found between serum FGF-23 levels and Hb and Htc. Conclusion. The effects of high serum FGF-23 levels on different parameters may be correlated with the development of refractory secondary hyperparathyroidism.

The Association between Fibroblast Growth Factor-23 and Vascular Calcification Is Mitigated by Inflammation Markers

BACKGROUND

Fibroblast growth factor-23 (FGF-23) has been linked to vascular calcification, ventricular hypertrophy and mortality in chronic kidney disease (CKD), although these links may not be direct and independent. Similar grave outcomes are associated with inflammation and oxidative stress in CKD. Recently, accumulating evidence has linked components of phosphate homeostasis to inflammation and oxidative stress. The interaction between the triad of inflammation, FGF-23 and cardiovascular outcomes is underinvestigated.

METHODS

We studied 65 patients with stage 5 CKD on hemodialysis. Serum levels of FGF-23, high-sensitivity C-reactive protein (hsCRP), endogenous soluble receptor of advanced glycation end products (esRAGE), advanced oxidation protein products (AOPP), parathormone, lipids, calcium and phosphorous were measured. The aortic calcification index (ACI) was determined using non-contrast CT scans of the abdominal aorta.

RESULTS

FGF-23 was elevated (mean: 4,681 pg/ml, SD: 3,906) and correlated with hsCRP, esRAGE, AOPP, dialysis vintage and phosphorus in univariate analysis. In multiple regression analysis, hsCRP, AOPP and phosphorus but not esRAGE were all significantly correlated to FGF-23 (R² = 0.7, p < 0.001). In univariate analysis, ACI correlated with hsCRP, esRAGE, FGF-23, dialysis vintage, systolic blood pressure (BP) and serum cholesterol. In multiple regression analysis not including inflammation markers, ACI was associated with FGF-23. However, inclusion of inflammation markers in another multiple regression analyses showed that ACI correlated with hsCRP, BP, dialysis vintage and esRAGE but not with FGF-23 (R² = 0.65, p < 0.001).

CONCLUSION

FGF-23 is strongly correlated to various markers of inflammation and oxidative stress in hemodialysis patients. The association between FGF-23 and vascular calcification was mitigated when corrected for inflammation markers.

Determinants of fibroblast growth factor-23 and parathyroid hormone variability in dialysis patients

BACKGROUND/AIMS

Treatment strategies for abnormal mineral metabolism in chronic kidney disease are largely based on achieving target ranges of biomarkers that vary considerably over time, yet determinants of their variability are poorly defined.

METHODS

Observational study including 162 patients of three dialysis cohorts (peritoneal dialysis, n = 78; hemodialysis, n = 49; hemodiafiltration, n = 35). Clinical and biochemical determinants of parathyroid hormone (PTH) and fibroblast growth factor-23 (FGF23) variability were analyzed in the peritoneal dialysis cohort. All cohorts were used for comparison of PTH and FGF23 intra-subject variability (intra-class correlation), and their intra-subject variability in different modes of dialysis was explored.

RESULTS

High PTH variability was independently associated with lower 25-hydroxyvitamin D concentration and factors of lipid and glucose metabolism, whereas high FGF23 variability was mainly associated with lower baseline serum phosphorous. These results were consistent in multivariate and sensitivity analyses. The intra-subject variability of FGF23 was lower than for PTH irrespective of dialysis mode.

CONCLUSIONS

Baseline vitamin D status and serum phosphorous are independent determinants of the longitudinal variation in PTH and FGF23, respectively. The clinical utility of FGF23 measurement remains unknown, yet it appears favorable based on its greater temporal stability than PTH in dialysis patients.

Low body mass index and dyslipidemia in dialysis patients linked to elevated plasma fibroblast growth factor 23

BACKGROUND

Fibroblast growth factor 23 (FGF23) has been associated with death in dialysis patients. Since FGF23 shares structural features with FGF19 subfamily members that exert hormonal control of fat mass, we hypothesized that high circulating FGF23 concentrations would be associated with the development of a uremic lipid profile and lower body mass index (BMI).

METHODS

This study was conducted among 654 patients receiving chronic hemodialysis. C-terminal FGF23 concentrations were measured in stored plasma samples. Linear regression was used to examine the cross-sectional associations of plasma FGF23 concentrations with BMI, total cholesterol (TC), low-density lipoprotein-cholesterol (LDL-C), high-density lipoprotein-cholesterol (HDL-C) and triglycerides. Cox proportional hazard models were used to examine the association between FGF23 concentrations and all-cause mortality.

RESULTS

Participants had a mean age of 60 ± 11 years and a median (IQR) FGF23 concentration of 4,212 (1,411-13,816) RU/ml. An increase per SD in log10 FGF23 was associated with lower BMI (β = -1.11; p = 0.008), TC (β = -6.46; p = 0.02), LDL-C (β = -4.73; p = 0.04) and HDL-C (β = -2.14; p = 0.03); after adjusting for age, gender, race, cardiovascular risk factors, serum albumin, markers of mineral metabolism, and use of lipid-lowering drugs. The association of FGF23 with death was attenuated after adjustment for HDL-C (HR of highest quartile 1.53, 95% CI 1.06-2.20 compared to lowest quartile).

CONCLUSION

These results indicate that higher plasma FGF23 levels are associated with lower BMI and dyslipidemia in dialysis patients. The association between FGF23 and death may be mediated through unexplored metabolic risk factors unrelated to mineral metabolism.

The relationships between serum sTWEAK, FGF-23 levels, and carotid atherosclerosis in renal transplant patients

BACKGROUND

Cardiovascular disease is the main cause of mortality after renal transplantation. Soluble tumor necrosis factor-like weak inducer of apoptosis (sTWEAK) and fibroblast growth factor-23 (FGF-23) are two novel molecules that have been associated with atherosclerosis in different populations. In this cross-sectional study, we investigated the associations between sTWEAK, FGF-23, and carotid artery intima-media thickness (CA-IMT) in renal transplant patients.

METHODS

A total of 117 renal transplant patients were studied. CA-IMT was determined by B-mode Doppler ultrasonography. Serum sTWEAK and FGF-23 were measured by a commercially available enzyme-linked immunosorbent assay (ELISA).

RESULTS

Mean age was 39.6 ± 9.6 years and 51% of the patients were male. Mean sTWEAK level was 595 ± 225 pg/mL (158-1140), FGF-23 level was 92 ± 123 RU/mL (9.6-1006), and CA-IMT level was 0.62 ± 0.11 mm (0.40-0.98). sTWEAK level was positively correlated with CA-IMT. There was no association between sTWEAK and FGF-23 levels. FGF-23 was also associated with CA-IMT. In adjusted models using linear regression analysis, only age and serum TWEAK levels were predictors for CA-IMT.

CONCLUSION

There is a positive correlation between CA-IMT and sTWEAK, but not with FGF-23 levels in renal transplant patients.

FGF23 contributes to insulin sensitivity in obese adolescents - preliminary results

Fibroblast growth factor-23 (FGF23) is a hormonal regulator of circulating phosphate and vitamin D levels. Recent investigations revealed that besides a key role in the pathogenesis of calcium-phosphorus disorders, in some patients FGF23 may be an indicator of cardiovascular complications. As a 'hormone-like' factor, it may also be involved in some metabolic processes, especially in the metabolism of glucose and fat. Its potential contribution to metabolic syndrome (MS) development has not been confirmed yet.

OBJECTIVE

The study was to examine the possible correlations between FGF23 serum levels and body composition, blood pressure and selected parameters of glucose, insulin and fat metabolism in adolescents with simple obesity.

PATIENTS AND DESIGN

In 68 (35 female) adolescents (mean age 13·9 years) with simple obesity [mean BMI SDS 4·9 (95% CI 4·4-5·4)], the levels of FGF23, total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol and triglycerides were measured. Standard oral glucose tolerance tests were performed with the assessment of fasting and after 120' postload glucose and insulin levels; the insulin resistance index HOMA-IR was calculated.

RESULTS

Regardless of gender, there was a significant inverse correlation between FGF23 and fasting insulin level (r = -0·3), as well as HOMA-IR (r = -0·29). Multiple regression model showed the independent association between FGF23 and HOMA-IR.

CONCLUSION

FGF23 seems to be a novel factor contributing to insulin sensitivity. Further investigations are needed to define its role in the development of MS.

Fibroblast growth factor 23 and Inflammation in CKD

BACKGROUND AND OBJECTIVES

Levels of fibroblast growth factor 23 (FGF23) and inflammatory markers are commonly elevated in CKD, and each is associated with adverse clinical outcomes. This study tested the hypothesis that FGF23 is independently associated with inflammation in CKD.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

The association between levels of FGF23 and the inflammatory markers IL-6, C-reactive protein (CRP), TNF-α, and fibrinogen was assessed in a cross-sectional analysis of 3879 participants enrolled in the Chronic Renal Insufficiency Cohort (CRIC) study between June 2003 and September 2008.

RESULTS

FGF23 correlated directly with IL-6 (r=0.4), CRP (r=0.2), TNF-α (r=0.4), and fibrinogen (r=0.3; P<0.001 for each). In univariate and multivariable-adjusted linear regression analyses, natural log (ln) transformed FGF23 was significantly associated with lnIL-6, lnCRP, lnTNF-α, and fibrinogen (P<0.001 for each). Each unit higher lnFGF23 was associated with severe inflammation, defined as levels of all inflammatory markers in the highest 25th percentile, in univariate (odds ratio [OR], 2.4 [95% confidence interval (CI), 2.0-2.9]) and multivariable-adjusted (OR, 2.0 [95% CI, 1.6-2.5]) logistic regression analyses. Ascending FGF23 quartiles were independently associated with severe inflammation (OR, 5.6 for the highest versus lowest FGF23 quartile [95% CI, 2.3-13.9]; P for trend < 0.001).

CONCLUSIONS

Higher FGF23 levels are independently associated with higher levels of inflammatory markers in patients with CKD and with significantly greater odds of severe inflammation. Future studies should evaluate whether inflammation modifies the association between FGF23 and adverse outcomes in CKD.

Is fibroblast growth factor 23 a harbinger of mortality in CKD?

Fibroblast growth factor 23 (FGF23) is a novel hormone produced by bone with known functions to regulate urinary phosphate excretion, as well as vitamin D and PTH production. The discovery of this hormone roughly a decade ago has revolutionized the traditional theories regarding the mechanisms responsible for the mineral metabolism abnormalities that are commonly observed in patients with chronic kidney disease. Circulating FGF23 levels begin to rise in the early stages of kidney injury and become markedly elevated as kidney disease progresses. Recent reports have emerged which link these elevations in circulating FGF23 to multiple adverse outcomes. Most notably, a strong association between increments in FGF23 and cardiovascular pathology has been suggested in patients with both normal and abnormal renal function. Despite a growing body of evidence to suggest FGF23 as a contributor to morbidity and mortality in CKD, a cause-effect relationship for this association has not been established. This review highlights our current understanding of the regulation and function of FGF23 and examines the existing literature linking FGF23 with adverse outcomes.