Fibroblast Growth Factor (FGF) 23 Regulates the Plasma Levels of Parathyroid Hormone In Vivo Through the FGF Receptor in Normocalcemia, But Not in Hypocalcemia

Abstract Background Cardiac dysfunction and arrhythmia are common and onerous cardiovascular events in end-stage renal disease (ESRD) patients, especially those on dialysis. Fibroblast growth factor (FGF)-23 is a phosphate-regulating hormone whose levels dramatically increase as renal function declines. Beyond its role in phosphorus homeostasis, FGF-23 may elicit a direct effect on the heart. Whether FGF-23 modulates ventricular cardiac rhythm is unknown, prompting us to study its role on excitation–contraction (EC) coupling. Methods We examined FGF-23 in vitro actions on EC coupling in adult rat native ventricular cardiomyocytes using patch clamp and confocal microscopy and in vivo actions on cardiac rhythm using electrocardiogram. Results Compared with vehicle treatment, FGF-23 induced a significant decrease in rat cardiomyocyte contraction, L-type Ca2+ current, systolic Ca2+ transients and sarcoplasmic reticulum (SR) load and SR Ca2+-adenosine triphosphatase 2a pump activity. FGF-23 induced pro-arrhythmogenic activity in vitro and in vivo as automatic cardiomyocyte extracontractions and premature ventricular contractions. Diastolic spontaneous Ca2+ leak (sparks and waves) was significantly increased by FGF-23 via the calmodulin kinase type II (CaMKII)-dependent pathway related to hyperphosphorylation of ryanodine receptors at the CaMKII site Ser2814. Both contraction dysfunction and spontaneous pro-arrhythmic Ca2+ events induced by FGF-23 were blocked by soluble Klotho (sKlotho). Conclusions Our results show that FGF-23 reduces contractility and enhances arrhythmogenicity through intracellular Ca2+ mishandling. Blocking its actions on the heart by improving sKlotho bioavailability may enhance cardiac function and reduce arrhythmic events frequently observed in ESRD.

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Fibroblast Growth Factor 23 Stimulates Cardiac Fibroblast Activity through Phospholipase C-Mediated Calcium Signaling

International Journal of Molecular Sciences ◽

10.3390/ijms23010166 ◽

2021 ◽

Vol 23 (1) ◽

pp. 166

Author(s):

Ting-Wei Lee ◽

Cheng-Chih Chung ◽

Ting-I Lee ◽

Yung-Kuo Lin ◽

Yu-Hsun Kao ◽

...

Keyword(s):

Growth Factor ◽

Phospholipase C ◽

Fibroblast Growth Factor ◽

Collagen Type ◽

Cardiac Fibroblast ◽

Enzyme Linked Immunosorbent Assay ◽

Fibroblast Growth ◽

Fgf Receptor ◽

Expression Levels ◽

Fgf 23

Fibroblast growth factor (FGF)-23 induces hypertrophy and calcium (Ca2+) dysregulation in cardiomyocytes, leading to cardiac arrhythmia and heart failure. However, knowledge regarding the effects of FGF-23 on cardiac fibrogenesis remains limited. This study investigated whether FGF-23 modulates cardiac fibroblast activity and explored its underlying mechanisms. We performed MTS analysis, 5-ethynyl-2’-deoxyuridine assay, and wound-healing assay in cultured human atrial fibroblasts without and with FGF-23 (1, 5 and 25 ng/mL for 48 h) to analyze cell proliferation and migration. We found that FGF-23 (25 ng/mL, but not 1 or 5 ng/mL) increased proliferative and migratory abilities of human atrial fibroblasts. Compared to control cells, FGF-23 (25 ng/mL)-treated fibroblasts had a significantly higher Ca2+ entry and intracellular inositol 1,4,5-trisphosphate (IP3) level (assessed by fura-2 ratiometric Ca2+ imaging and enzyme-linked immunosorbent assay). Western blot analysis showed that FGF-23 (25 ng/mL)-treated cardiac fibroblasts had higher expression levels of calcium release-activated calcium channel protein 1 (Orai1) and transient receptor potential canonical (TRPC) 1 channel, but similar expression levels of α-smooth muscle actin, collagen type IA1, collagen type Ⅲ, stromal interaction molecule 1, TRPC 3, TRPC6 and phosphorylated-calcium/calmodulin-dependent protein kinase II when compared with control fibroblasts. In the presence of ethylene glycol tetra-acetic acid (a free Ca2+ chelator, 1 mM) or U73122 (an inhibitor of phospholipase C, 1 μM), control and FGF-23-treated fibroblasts exhibited similar proliferative and migratory abilities. Moreover, polymerase chain reaction analysis revealed that atrial fibroblasts abundantly expressed FGF receptor 1 but lacked expressions of FGF receptors 2-4. FGF-23 significantly increased the phosphorylation of FGF receptor 1. Treatment with PD166866 (an antagonist of FGF receptor 1, 1 μM) attenuated the effects of FGF-23 on cardiac fibroblast activity. In conclusion, FGF-23 may activate FGF receptor 1 and subsequently phospholipase C/IP3 signaling pathway, leading to an upregulation of Orai1 and/or TRPC1-mediated Ca2+ entry and thus enhancing human atrial fibroblast activity.

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Fibroblast Growth Factor 23 (FGF23) Induces Ventricular Arrhythmias and Prolongs QTc Interval in Mice in an FGF Receptor 4-Dependent Manner

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.00798.2020 ◽

2021 ◽

Author(s):

Jonah M. Graves ◽

Julian A. Vallejo ◽

Chelsea S. Hamill ◽

Derek Wang ◽

Rohan Ahuja ◽

...

Keyword(s):

Growth Factor ◽

Fibroblast Growth Factor ◽

Ventricular Arrhythmias ◽

Ex Vivo ◽

Fibroblast Growth Factor 23 ◽

Left Ventricular ◽

Qtc Interval ◽

Fibroblast Growth ◽

Fgf Receptor

Fibroblast growth factor 23 (FGF23) is a phosphate regulating protein hormone released by osteocytes. FGF23 becomes markedly elevated in chronic kidney disease (CKD), for which the leading cause of death is cardiovascular disease, particularly sudden cardiac death. Previously, we found that FGF23 increases intracellular Ca2+ in cardiomyocytes and alters contractility in mouse ventricles ex vivo via FGF-receptor 4 (FGFR4). In the present study, we demonstrate that FGF23 induces cardiac arrhythmias and prolongs QTc interval in mice, and we tested whether these effects are mediated through FGFR4. In isolated Langendorff perfused hearts, FGF23 perfusion increased mechanical arrhythmias in the form of premature ventricular beats (PVBs), and induced runs of ventricular tachycardia in six of 11 animals, which were attenuated with pretreatment of an anti-FGFR4 blocking antibody. Ex vivo ECG analysis of isolated intact hearts showed increased ventricular arrhythmias and QTc prolongation after FGF23 infusion compared to vehicle. In vivo, injection of FGF23 into the jugular vein led to the emergence of premature ventricular contractions (PVCs) in 5 out of 11 experiments. FGF23 also produced a significant lengthening effect upon QTc interval in vivo. In vivo FGFR4 blockade ameliorated the arrhythmogenic and QTc prolonging effects of FGF23. Finally, FGF23 increased cardiomyocyte Ca2+ levels in intact left ventricular muscle which was inhibited by FGR4 blockade. We conclude that FGF23/FGFR4 signaling in the heart may contribute to ventricular arrhythmogenesis and repolarization disturbances commonly observed in patients with CKD via Ca2+ overload and may be an important therapeutic target to reduce cardiac mortality in CKD.

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Parathyroid hormone receptor signaling in osteocytes increases the expression of fibroblast growth factor-23 in vitro and in vivo

Bone ◽

10.1016/j.bone.2011.06.025 ◽

2011 ◽

Vol 49 (4) ◽

pp. 636-643 ◽

Cited By ~ 166

Author(s):

Yumie Rhee ◽

Nicoletta Bivi ◽

Emily Farrow ◽

Virginia Lezcano ◽

Lilian I. Plotkin ◽

...

Keyword(s):

Parathyroid Hormone ◽

Growth Factor ◽

Fibroblast Growth Factor ◽

Hormone Receptor ◽

Fibroblast Growth Factor 23 ◽

Fibroblast Growth ◽

Receptor Signaling ◽

Parathyroid Hormone Receptor

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Tumor-induced osteomalacia

Journal of Onco-Nephrology ◽

10.1177/2399369318810623 ◽

2018 ◽

Vol 2 (2-3) ◽

pp. 92-101

Author(s):

Robert F Reilly

Keyword(s):

Vitamin D ◽

Alkaline Phosphatase ◽

Parathyroid Hormone ◽

Growth Factor ◽

Fusion Protein ◽

Fibroblast Growth Factor ◽

Definitive Treatment ◽

Phosphorus Concentration ◽

Fibroblast Growth ◽

Fgf 23

Tumor-induced osteomalacia is a rare paraneoplastic syndrome with approximately 500 cases reported. It presents with a variety of nonspecific symptoms including weakness, muscle and bone pain, and fracture. Characteristic laboratory findings are hypophosphatemia, an elevated alkaline phosphatase, normal parathyroid hormone, normal serum calcium concentration, and an inappropriately low 1,25(OH)2-vitamin D3 concentration. Initially, tumor-induced osteomalacia is misdiagnosed in over 95% of cases. Hypophosphatemia results from renal phosphate wasting occurring as a consequence of FGF-23 production by the tumor. FGF-23 reduces expression and stimulates endocytosis of two sodium-phosphate cotransporters found in the luminal membrane of the proximal tubule resulting in renal phosphate wasting. FGF-23 also inhibits the formation and stimulates the degradation of 1,25(OH)2 vitamin D3. The most common tumor causing tumor-induced osteomalacia is a mixed connective tissue tumor known as a “phosphaturic mesenchymal tumor.” Due to its rarity, it is often misdiagnosed. Molecular studies have shed light on the mechanisms of tumorigenesis with the identification of a fibronectin and fibroblast growth factor receptor 1 fusion protein expressed in about half of cases and a fibronectin and fibroblast growth factor 1 fusion protein in a small subset of tumors. Often small and slow growing, the tumors may be found in unusual locations, such as the extremities and nasal sinuses and are difficult to localize. Definitive treatment involves identification and removal of the tumor. Absent tumor removal, therapeutic goals include improvement of symptoms, raising the serum phosphorus concentration to the lower limit of normal, and maintenance or achievement of normal parathyroid hormone and alkaline phosphatase concentration. Two recent drugs that target pathways involved in the molecular pathogenesis of tumor-induced osteomalacia have recently been developed and are in early-phase clinical trials: the humanized anti-FGF-23 monoclonal antibody burosumab (KRN23) and the FGFR-1,2,3 inhibitor NVP-BGJ398.

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Fibroblast growth factor receptor levels decrease during chick embryogenesis.

The Journal of Cell Biology ◽

10.1083/jcb.110.2.503 ◽

1990 ◽

Vol 110 (2) ◽

pp. 503-509 ◽

Cited By ~ 61

Author(s):

B B Olwin ◽

S D Hauschka

Keyword(s):

Growth Factor ◽

Fibroblast Growth Factor ◽

Binding Sites ◽

Specific Binding ◽

Growth Factor Receptor ◽

Receptor Protein ◽

Chick Embryos ◽

Fibroblast Growth ◽

Fgf Receptor

Two putative receptors for fibroblast growth factor (FGF) of approximately 150 and 200 kD were identified in membrane preparations from chick embryos. Specific binding (femtomoles/milligram) of 125I-aFGF to whole chick embryonic membranes was relatively constant from day 2 to 7, then decreased fivefold between days 7 and 13. Day-19 chick embryos retained 125I-aFGF binding at low levels to brain, eye, and liver tissues but not to skeletal muscle or cardiac tissues. The 200-kD FGF receptor began to decline between day 4.5 and 7 and was barely detectable by day 9, whereas the 150-kD FGF receptor began to decline by day 7 but was still detectable in day-9 embryonic membranes. It is not known whether the two FGF-binding proteins represent altered forms of one polypeptide, but it is clear that their levels undergo differential changes during development. Because endogenous chick FGF may remain bound to FGF receptor in membrane preparations, membranes were treated with acidic (pH 4.0) buffers to release bound FGF; such treatment did not affect 125I-aFGF binding and moderately increased the number of binding sites in day-7 and -19 embryos. Consequently, the observed loss of high affinity 125I-aFGF binding sites and FGF-binding polypeptides most likely represents a loss of FGF receptor protein. These experiments provide in vivo evidence to support the hypothesis that regulation of FGF receptor levels may function as a mechanism for controlling FGF-dependent processes during embryonic development.

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Effects of different 1-34 parathyroid hormone dosages on fibroblast growth factor-23 secretion in human bone marrow cells following osteogenic differentiation

Orthopedic Reviews ◽

10.4081/or.2014.5314 ◽

2014 ◽

Vol 6 (2) ◽

Author(s):

Frank-Peter Tillmann ◽

Daniela Hofen ◽

Monika Herten ◽

Rüdiger Krauspe ◽

Marcus Jäger

Keyword(s):

Bone Marrow ◽

Vitamin D ◽

Parathyroid Hormone ◽

Growth Factor ◽

Osteogenic Differentiation ◽

Fibroblast Growth Factor ◽

Bone Marrow Cells ◽

Fibroblast Growth ◽

Trap 5B ◽

Fgf 23

The importance of fibroblast growth factor (FGF)-23 as part of a hormonal bone-kidney-axis has been well established. Lately, FGF-23 has been suggested as an independent risk factor of death in patients on chronic hemodialysis. Hyperparathyroidism is a common feature of advanced kidney failure or end-stage renal disease. The independent effect of elevated parathyroid hormone (PTH) levels on FGF-23 secretion is still a matter of debate and has not yet been studied in an <em>in</em> <em>vitro</em> model of human bone marrow cells (BMC) during osteogenic differentiation. BMC from three different donors were cultivated for 4 weeks in cell cultures devoid of vitamin D either without 1-34 PTH or with PTH concentrations of 10 or 100 pmol/L, respectively. After 28 days, protein expression of the cells was determined by immunocytochemical staining, whereas real time-polymerase chain reaction served to analyze gene expression of several osteoblastic (osteocalcin, RANKL, Runx-2 and ostase) and osteoclastic markers (RANK, TRAP-5b). The concentrations of FGF-23, ostase and TRAP-5b were determined by ELISA at weeks 2, 3 and 4. We found a basal expression of FGF-23 with no increase in FGF-23 secretion after stimulation with 10 pmol/L 1-34 PTH. Stimulation with 100 pmol/L PTH resulted in an increase in FGF-23 expression (14.1±3.6 pg/mL with no PTH, 13.7±4.0 pg/mL with 10 pmol/L, P=0.84 and 17.6±3.4 pg/mL with 100 pmol/L, P=0.047). These results suggest a vitamin D and PTH-independent FGF-23 expression in human BMC after osteogenic stimulation. As only higher PTH levels stimulated FGF-23 expression, a threshold level might be hypothesized.

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GFR-Specific versus GFR-Agnostic Cutoffs for Parathyroid Hormone and Fibroblast Growth Factor-23 in Advanced Chronic Kidney Disease

American Journal of Nephrology ◽

10.1159/000501189 ◽

2019 ◽

Vol 50 (2) ◽

pp. 105-114

Author(s):

Mark Canney ◽

Ognjenka Djurdjev ◽

Mila Tang ◽

Claudia Zierold ◽

Frank Blocki ◽

...

Keyword(s):

Chronic Kidney Disease ◽

Parathyroid Hormone ◽

Growth Factor ◽

Kidney Disease ◽

Fibroblast Growth Factor ◽

Fibroblast Growth Factor 23 ◽

Reference Ranges ◽

Fibroblast Growth ◽

Advanced Chronic Kidney Disease ◽

Fgf 23

Background: In the majority of patients with advanced chronic kidney disease (CKD), values of parathyroid hormone (PTH1–84) and fibroblast growth factor 23 (FGF-23) exceed the normal reference range, potentially as an appropriate adaptation to reduced glomerular filtration rate (GFR). We tested whether GFR-specific cutoffs for PTH1–84 and FGF-23 could better identify patients with inappropriately high PTH1–84 and FGF-23 for their degree of CKD and thereby improve prognostication of clinical outcomes compared to a uniform threshold. Methods: Prospective pan-Canadian cohort of 1,812 patients with mean estimated GFR (eGFR) 28.9 mL/min/1.73 m2 followed for a median of 52 months. Repeated log-rank tests were used to identify optimal cutoffs for PTH1–84 and FGF-23 within eGFR strata (<20, 20–29 and ≥30 mL/min/1.73 m2) that maximally differentiated high- and low-risk populations for (1) cardiovascular (CV) events (fatal or nonfatal myocardial infarction, coronary revascularization, stroke, heart failure) and (2) renal events (initiation of chronic renal replacement therapy). In multivariable models, we examined the association between GFR-specific cutoffs and outcomes and compared their added prognostic value to existing uniform thresholds. Results: Risk-based cutoffs for PTH1–84 and FGF-23 increased in a graded fashion with decreasing eGFR. Among patients with eGFR <20 mL/min/1.73 m2, CV risk-based cutoffs for PTH1–84 and FGF-23 were 3.4 and 5.5 times the upper limit of normal, respectively, and reclassified 31.9 and 35.1% of patients when added to a multivariable base model for CV events. In contrast, the addition of PTH1–84 and FGF-23 to the base model using uniform cutoffs failed to reclassify such patients. Similar findings were demonstrated for renal outcomes. Conclusion: GFR-specific risk-based cutoffs for PTH1–84 and FGF-23 may facilitate more meaningful risk stratification in advanced CKD than current GFR-agnostic reference ranges derived from healthy adults. This may be most applicable in those with severely reduced GFR.

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Fibroblast growth factor-23 is associated with parathyroid hormone and renal function in a population-based cohort of elderly men

Acta Endocrinologica ◽

10.1530/eje-07-0534 ◽

2008 ◽

Vol 158 (1) ◽

pp. 125-129 ◽

Cited By ~ 41

Author(s):

Richard Marsell ◽

Elin Grundberg ◽

Tijana Krajisnik ◽

Hans Mallmin ◽

Magnus Karlsson ◽

...

Keyword(s):

Renal Function ◽

Parathyroid Hormone ◽

Growth Factor ◽

Fibroblast Growth Factor ◽

Association Studies ◽

Fibroblast Growth Factor 23 ◽

Population Based ◽

Fibroblast Growth

ObjectiveFibroblast growth factor-23 (FGF23) is a circulating factor involved in phosphate (Pi) and vitamin D metabolism. Serum FGF23 is increased at later stages of chronic kidney disease due to chronic hyperphosphatemia and decreased renal clearance. Recent studies also indicate that FGF23 may directly regulate the expression of parathyroid hormone (PTH) in vitro. Therefore, the objective of the current study was to determine the relationship between FGF23, PTH, and other biochemistries in vivo in subjects with no history of renal disease.DesignSerum biochemistries were measured in a subsample of the population-based Swedish part of the MrOS study. In total, 1000 Caucasian men aged 70–80 years were randomly selected from the population.MethodsIntact FGF23, Pi, calcium, albumin, estimated glomerular filtration rate (eGFR, calculated from cystatin C), PTH, and 25(OH)D3 were measured. Association studies were performed using linear univariate and multivariate regression analyses.ResultsThe median FGF23 level was 36.6 pg/ml, ranging from 0.63 to 957 pg/ml. There was a significant correlation between log FGF23 and eGFR (r=−0.21; P<0.00001) and log PTH (r=0.13; P<0.001). These variables remained as independent predictors of FGF23 in multivariate analysis. In addition, log PTH (β=0.082; P<0.05) and eGFR (β=−0.090; P<0.05) were associated with log FGF23 in subjects with eGFR>60 ml/min. Only eGFR (β=−0.35; P<0.0001) remained as a predictor of log FGF23 in subjects with eGFR<60 ml/min.ConclusionsSerum FGF23 and PTH are associated in vivo, supporting recent findings that FGF23 directly regulates PTH expression in vitro. Additionally, eGFR is associated with FGF23 in subjects with normal or mildly impaired renal function, indicating that GFR may modulate FGF23 levels independent of serum Pi.

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