Association of serum intact fibroblast growth factor 23 with left ventricular mass and different echocardiographic findings in patients on hemodialysis

The anti-aging factor Klotho protects against acquired long QT syndrome induced by uremia and promoted by fibroblast growth factor 23

BACKGROUND

Chronic kidney disease (CKD) is associated with increased propensity for arrhythmias. In this context, ventricular repolarization alterations have been shown to predispose to fatal arrhythmias and sudden cardiac death. Between mineral bone disturbances in CKD patients, increased fibroblast growth factor (FGF) 23 and decreased Klotho are emerging as important effectors of cardiovascular disease. However, the relationship between imbalanced FGF23-Klotho axis and the development of cardiac arrhythmias in CKD remains unknown.

METHODS

We carried out a translational approach to study the relationship between the FGF23-Klotho signaling axis and acquired long QT syndrome in CKD-associated uremia. FGF23 levels and cardiac repolarization dynamics were analyzed in patients with dialysis-dependent CKD and in uremic mouse models of 5/6 nephrectomy (Nfx) and Klotho deficiency (hypomorphism), which show very high systemic FGF23 levels.

RESULTS

Patients in the top quartile of FGF23 levels had a higher occurrence of very long QT intervals (> 490 ms) than peers in the lowest quartile. Experimentally, FGF23 induced QT prolongation in healthy mice. Similarly, alterations in cardiac repolarization and QT prolongation were observed in Nfx mice and in Klotho hypomorphic mice. QT prolongation in Nfx mice was explained by a significant decrease in the fast transient outward potassium (K⁺) current (I_tof), caused by the downregulation of K⁺ channel 4.2 subunit (Kv4.2) expression. Kv4.2 expression was also significantly reduced in ventricular cardiomyocytes exposed to FGF23. Enhancing Klotho availability prevented both long QT prolongation and reduced I_tof current. Likewise, administration of recombinant Klotho blocked the downregulation of Kv4.2 expression in Nfx mice and in FGF23-exposed cardiomyocytes.

CONCLUSION

The FGF23-Klotho axis emerges as a new therapeutic target to prevent acquired long QT syndrome in uremia by minimizing the predisposition to potentially fatal ventricular arrhythmias and sudden cardiac death in patients with CKD.

Renal and extrarenal effects of fibroblast growth factor 23

Fibroblast growth factor 23 (FGF23) is a hormone with a central role in the regulation of phosphate homeostasis. This regulation is accomplished by the coordinated modulation of renal phosphate handling, vitamin D metabolism and parathyroid hormone secretion. Patients with kidney disease have increased circulating levels of FGF23 and in other patient populations and in healthy individuals, FGF23 levels also rise following an increase in dietary phosphate intake. Maladaptive increases in FGF23 have a detrimental effect on several organs and tissues and, importantly, these pathological changes most likely contribute to increased morbidity and mortality. For example, in the context of heart disease, FGF23 is involved in the development of pathological hypertrophy that can lead to congestive heart failure. Increased FGF23 concentrations can also lead to microcirculatory changes, in particular reduced vasodilatory capacity, and collectively these cardiovascular changes can compromise tissue perfusion. In addition, FGF23 is associated with inflammation and an increased risk of infection; other potentially detrimental effects of FGF23 are likely to emerge in the future. Most importantly, recent insights demonstrate that FGF23 can be therapeutically targeted, which holds promise for the treatment of many patients in a variety of clinical settings.

Meta-Analysis of the Association between Fibroblast Growth Factor 23 and Mortality and Cardiovascular Events in Hemodialysis Patients

INTRODUCTION

This study was conducted to ensure the correlation between fibroblast growth factor 23 (FGF23) and death and cardiovascular events in hemodialysis patients.

METHODS

We conducted a literature search of PubMed database to April 2018 for relevant articles that reported the association between FGF23 and risk of all-cause mortality and cardiovascular disease (CVD) events. The meta-analysis was performed using the Revman 5.3 software.

RESULTS

A total of 7 articles were included, and all reported mortality in hemodialysis patients, and 3 reported cardiovascular events in hemodialysis patients. Since the current reagent can detect C-terminal FGF23 (cFGF23) and intact-FGF23 (iFGF23), we discuss the association between cFGF23 and iFGF23 and death and cardiovascular events in hemodialysis patients. The correlation between serum iFGF23 levels and death in hemodialysis patients: high levels of iFGF23 vs. low levels of iFGF23: RR 1.14, 95% CI (1.01-1.30), p = 0.04 (I2 = 0%, p = 0.38). The correlation between serum C-terminal levels and death in hemodialysis patients: high levels of cFGF23 versus low levels of cFGF23: RR 1.39, 95% CI (1.21-1.59), p < 0.001 (I2 = 2%, p = 0.38). The correlation of serum iFGF23 levels with cardiovascular events: high levels of iFGF23 versus low levels of iFGF23: RR 1.21, 95% CI (1.13-1.30), p < 0.001 (I2 = 0%, p = 0.49). A paper has reported the association between cFGF23 and CVD events, so we did not conduct meta-analysis.

CONCLUSIONS

Elevated serum FGF23 levels are positively associated with all-cause mortality and cardiovascular events in hemodialysis patients, with a 14 or 39% increase in all-cause mortality and a 21% increased risk of cardiovascular events.