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

Cardiovascular Calcifications Are Correlated with Inflammation in Hemodialysis Patients

Background and Objectives: The main cause of morbidity and mortality in hemodialysis patients is cardiovascular disease, which is quite common. The main objective of our study was to investigate the relationship between oxidative stress, inflammation, and vascular and valvular calcifications in hemodialysis patients. Materials and Methods: This observational study had 54 hemodialysis patients, with an average age of 60.46 ± 13.18 years. Cardiovascular ultrasound was used to detect and/or measure aortic and mitral valve calcifications, carotid and femoral atheroma plaques, and common carotid intima-media thickness. The aortic calcification score was determined using a lateral abdomen plain radiograph. The inflammatory, oxidative, metabolic, and dietary statuses, as well as demographic characteristics, were identified. Results: There were significant correlations between the levels of IL-6 and carotid plaque number (p = 0.003), fibrinogen level and aortic valve calcifications (p = 0.05), intima-media thickness (p = 0.0007), carotid plaque number (p = 0.035), femoral plaque number (p = 0.00014), and aortic calcifications score (p = 0.0079). Aortic annulus calcifications (p = 0.03) and intima-media thickness (p = 0.038) were adversely linked with TNF-α. Nutrition parameters were negatively correlated with atherosclerosis markers: number of carotid plaques with albumin (p = 0.013), body mass index (p = 0.039), and triglycerides (p = 0.021); number of femoral plaques with phosphorus (0.013), aortic calcifications score with albumin (p = 0.051), intima-media thickness with LDL-cholesterol (p = 0.042). Age and the quantity of carotid plaques, femoral plaques, and aortic calcifications were linked with each other (p = 0.0022, 0.00011, and 0.036, respectively). Aortic annulus calcifications (p = 0.011), aortic valve calcifications (p = 0.023), and mitral valve calcifications (p = 0.018) were all associated with an increased risk of death. Conclusions: Imaging measures of atherosclerosis are adversely connected with dietary status and positively correlated with markers of inflammation and risk of mortality.

Altered serum metabolome associated with vascular calcification developed from CKD and the critical pathways

Introduction

Vascular calcification (VC) is more likely to be detected in the chronic kidney disease (CKD) population. The mechanism of VC development from CKD is different from that for simple VC and has always been a major research area. The aim of this study was to detect alterations in the metabolome during development of VC in CKD and to identify the critical metabolic pathways and metabolites involved in its pathogenesis.

Methods

Rats in the model group were given an adenine gavage combined with a high-phosphorus diet to imitate VC in CKD. The aorta calcium content was measured and used to divide the model group into a VC group and non-vascular calcification group (non-VC group). The control group was fed a normal rat diet and given a saline gavage. Ultra-high-performance liquid chromatography-mass spectrometry (UHPLC-MS) was used to determine the altered serum metabolome in the control, VC, and non-VC groups. The identified metabolites were mapped into the Kyoto Encyclopedia of Genes and Genomes (KEGG) database (https://www.genome.jp/kegg/) for pathway and network analyses.

Result

There were 14 metabolites that changed significantly in the VC group, with three metabolic pathways playing critical roles in the pathogenesis of VC in CKD: steroid hormone biosynthesis; valine, leucine and isoleucine biosynthesis; and pantothenate and CoA biosynthesis.

Conclusion

Our results indicated changes in the expression of steroid sulfatase and estrogen sulfotransferase, and down-regulation of the in situ synthesis of estrogens in the VC group. In conclusion, the serum metabolome alters significantly during the pathogenesis of VC in CKD. The key pathways, metabolites, and enzymes we identified are worth further study and may become a promising therapeutic target for the treatment of VC in CKD.

Significance of serum FGF-23 for risk assessment of contrast-associated acute kidney injury and clinical outcomes in patients undergoing coronary angiography

Background

Fibroblast growth factor (FGF)-23 levels rise as kidney function declines. Whether elevated FGF-23 levels are associated with an increased risk for contrast-associated acute kidney injury (CA-AKI) and major adverse cardiovascular events (MACE) in patients undergoing coronary angiography remain uncertain.

Methods

In total, 492 patients receiving coronary angiography were enrolled. Their serum FGF-23 levels were measured before administration of contrast media. The occurrence of CA-AKI was defined as a rise in serum creatinine of 0.5 mg/dL or a 25% increase from the baseline value within 48 h after the procedure. All patients were followed up for at least 1 year or until the occurrence of MACE including death, nonfatal myocardial infarction (MI), and ischemic stroke.

Results

Overall, CA-AKI occurred in 41 (8.3%) patients. During a median follow-up of 2.6 years, there were 24 deaths, 3 nonfatal MIs, and 7 ischemic strokes. Compared with those in the lowest FGF-23 tertile, individuals in the highest FGF-23 tertile had a significantly higher incidence of CA-AKI (P < 0.001) and lower incidence of MACE-free survival (P = 0.001). In multivariate regression analysis, higher FGF-23 level was found to be independently associated with a graded risk for CA-AKI (OR per doubling, 1.90; 95% CI 1.48–2.44) and MACE (HR per doubling, 1.25; 95% CI 1.02–1.52).

Conclusions

Elevated FGF-23 levels were associated with an increased risk for CA-AKI and future MACE among patients undergoing coronary angiography. FGF-23 may play a role in early diagnosis of CA-AKI and predicting clinical outcomes after coronary angiography.

Decreased concentration of klotho and increased concentration of FGF23 in the cerebrospinal fluid of patients with narcolepsy

OBJECTIVE

to explore the status of concentration of klotho and fibroblast growth factor 23 (FGF23) in cerebrospinal fluid (CSF) of patients with narcolepsy.

PATIENTS/METHODS

59 patients with narcolepsy and 17 control individuals were enrolled. We used radioimmunoassay, human klotho enzyme-linked immunosorbent assay (ELISA), human intact FGF23 ELISA and spectrophotometry to measure hypocretin-1, klotho, FGF-23 and phosphorus, respectively. T-Student Test was used to compare klotho and phosphate concentrations, Mann-Whitney U Test were used to compare FGF-23 levels between groups. ANOVA Test was used to compare klotho and phosphate CSF concentrations among narcolepsy patients with CSF hypocretin-1 <110 pg/ml (HCRT-) and narcolepsy patients with CSF hypocretin-1 >110 pg/ml (HCRT+) versus control subjects.

RESULTS

Klotho and phosphorus CSF levels were lower in narcoleptic patients than in control (908.18 ± 405.51 versus 1265.78 ± 523.26 pg/ml; p = 0.004 and 1.34 ± 0.25 versus 1.58 ± 0.23 mg/dl; p = 0.001, respectively). We found higher FGF-23 levels in narcoleptic patients (5.51 versus 4.00 pg/mL; p = 0.001). Klotho and phosphorus CSF levels were lower in both HCRT- and HCRT+ than controls. Moreover, there were higher FGF-23 levels in both HCRT-/HCRT+ groups versus controls. However, we did not find differences comparing HCRT- and HCRT+ groups, analyzing CSF klotho, FGF-23 or phosphorus levels.

CONCLUSIONS

Patients with narcolepsy have decreased CSF concentration of klotho and increased CSF levels of FGF-23. These findings may play a role in understanding the pathogenesis of narcolepsy.

[Low serum Klotho level as a predictor of calcification of the heart and blood vessels in patients with CKD stages 2-5D]

Cardiovascular calcification (CVC) makes a significant contribution to the manifestation of cardiovascular complications in patients with chronic kidney disease. Early CVC markers are currently being actively studied to optimize cardio-renoprotective strategies. We performed a prospective comparative analysis of the following factors: FGF-23, a-Klotho, sclecrostin, phosphate, parathyroid hormone, the estimated glomerular filtration rate (eGFR), central systolic pressure as an independent determinant of CVC.

MATERIALS AND METHODS

The study included 131 patients with chronic kidney disease 25D st. Serum levels of FGF-23, Klotho, and sclerostin were evaluated using the ELISA method. Vascular augmentation (stiffness) indices, central arterial pressure (using the SphygmoCor device), calcification of heart valves and the degree of aortic calcification (aortic radiography) were also investigated. The observation period was 2 years.

RESULTS

According to the Spearman correlation analysis, the percent of calcification increase and the change in Klotho level are most related. According to ROC analysis, a decrease in serum levels of Klotho by 50 units or more is a significant predictor of an increase in aortic calcification of 50% or more with a sensitivity of 86% and a specificity of 77%. Using logistic regression analysis, it was found that a serum Klotho level 632 pg/L predicts an eGFR below a median level of 48 ml/min/1.73 m2 with a sensitivity of 85.5% and a specificity of 78.5%. Wherein OR 17.477 (CI 95% 8.04637.962; p0.001).

CONCLUSION

The factor most associated with CVC is Klotho. Decreased serum level of Klotho is a predictor of aortic calcification. In addition, the initial serum level of Klotho is a predictor of eGFR after 2 years.

Altered Mineral Metabolism and Disequilibrium Between Calcification Promoters and Inhibitors in Chronic Hemodialysis Patients

Patients undergoing long-term hemodialysis (HD) are known to have abnormal blood concentrations of antioxidant minerals; concurrent oxidative stress can contribute to increased vascular calcification. This study aims to evaluate the associations between circulating antioxidant minerals and clinical biomarkers of vascular calcification in HD patients. Blood biochemical parameters, antioxidant minerals (selenium (Se), zinc (Zn), copper (Cu), and magnesium (Mg)), and several promoters and inhibitors of calcification (matrix Gla protein (MGP), fibroblast growth factor-23 (FGF-23), matrix metalloproteinases (MMP-2 and -9), and tissue inhibitors of metalloproteinase (TIMP-1 and -2)) were determined in HD patients (n = 62) and age- and sex-matched healthy individuals (n = 30). Compared with healthy subjects, HD patients had significantly lower plasma concentrations of Se and Zn, increased Cu and Mg, and higher levels of oxidative stress and inflammatory markers (Cu/Zn ratios, malondialdehyde (MDA), advanced glycation end products (AGEs), and C-reactive protein (CRP)). We observed that HD patients had significantly lower concentrations of MGP and higher levels of FGF-23, MMP-2 and -9, TIMP-1 and -2, and MMP-2/TIMP-2 and MMP-9/TIMP-1 ratios. We also observed significant relationships between the concentrations of these minerals and calcification biomarkers in HD patients. These results suggest that changes in the homeostasis of antioxidant minerals (Se, Zn, Cu, and Mg) may contribute to the effects of oxidative stress and inflammatory status, thereby participating in the mechanism for accelerated vascular calcification in patients undergoing long-term HD.

Micro RNA-192 Is Negatively Associated With Cardiovascular Events Among Wait-Listed Potential Kidney Transplant Recipients on Hemodialysis Over a 5-year Follow-up Period

BACKGROUND

Patients with chronic renal disease are susceptible to accelerated vascular calcification and cardiovascular morbidity and mortality. Micro RNAs (miRNAs) have been linked to the pathogenesis of cardiovascular diseases in the general population.

AIM

This study was carried out to evaluate the link between miRNA 192 and vascular calcification, pre-existing as well as newly occurring major adverse cardiovascular events, and mortality among hemodialysis patients who are also considered to be potential kidney transplant recipients.

METHODS

We screened 64 potential transplant recipients on hemodialysis at our university hospital. Pre-existing overt cardiovascular disease was recorded; new adverse cardiovascular events and all causes of death over an observational period of 5 years were prospectively followed. Vascular calcification was measured in the aorta using computerized tomography scans, and micro RNA 192 was measured.

RESULTS

The final study population included 55 patients followed for 63 months. Micro RNA 192 was significantly lower in patients who had preexisting cardiovascular disease (P = .015) as well and in all patients who had experienced any event by the end of the observational period (P = .012). A multiregression analysis model including micro RNA, age, dialysis vintage, intradialytic hypotension, vascular calcification, diabetes, systolic blood pressure, and smoking found the only independently correlating factor to cardiovascular events in this model to be micro RNA (β = -0.286, P = .05).

CONCLUSIONS

MiRNA 192 levels are significantly lower among patients experiencing cardiovascular events while on hemodialysis awaiting kidney transplantation.

Regulation of fibroblast growth factor 23 (FGF23) in health and disease

Fibroblast growth factor 23 (FGF23) is mainly produced in the bone and, upon secretion, forms a complex with a FGF receptor and coreceptor αKlotho. FGF23 can exert several endocrine functions, such as inhibiting renal phosphate reabsorption and 1,25-dihydroxyvitamin D3 production. Moreover, it has paracrine activities on several cell types, including neutrophils and hepatocytes. Klotho and Fgf23 deficiencies result in pathologies otherwise encountered in age-associated diseases, mainly as a result of hyperphosphataemia-dependent calcification. FGF23 levels are also perturbed in the plasma of patients with several disorders, including kidney or cardiovascular diseases. Here, we review mechanisms controlling FGF23 production and discuss how FGF23 regulation is perturbed in disease.

Low protein diet with essential amino acids ketoanalogues combination can affect serum FGF-23 and Klotho levels in chronic kidney disease 3b-4 stages patients: randomized pilot study

Protein restriction diet (PRD) with ketoanalagues of essential amino acids (KA) combination can improve of chronic kidney disease (CKD) course while, the precise mechanisms of PRD + KAA action in CKD are not known yet. We have conducted a prospective, randomized, controlled study of PRD and KAA patient’s group in compare with PRD without KAA group in regarding to serum Klotho and FGF-23 levels in patients with CKD. Materials and methods. The study included 79 CKD 3b-4 stages patients, non - diabetic etiology, used PRD (0.6 g/kg/day). The patients were randomized in two groups: 42 patients, received PRD + KAA (Group 1) and 37 patients continued the PRD without KAA (Group 2). Serum FGF-23 (Human FGF-23 ELISA kit with antibodies to native FGF-23 molecule, Merk Millipore MILLENZFGF-23-32K), Klotho (Human soluble Klotho with antiKlotho monoclonal antibodies, IBL-Takara 27998-96Well) levels, as well as instrumental examination: bioimpedance analysis [assess of muscle body mass (MBM), fat body mass (FBM), body mass index (BMI) and others]; sphygmography [assess of augmentation (stiffness) indices (AI), central (aortal) blood pressure (CBP) by «Sphygmacor» device]; as well as echocardiography [assess of cardiac (valvular) calcification score (CCS) and left ventricular myocardium mass index (LVMMI)], were studded in addition to conventional examination. Results and discussion. To the end of 14th month of the study the PRD group reached a body mass index (BMI) decrease (p=0.046), including MBM in men (p=0.027) and woman (p=0.044). In addition, higher FGF-23 (p=0.029), and lower Klotho (p=0.037) serum levels were revealed in the PRD group compared to the PRD+KAA group as well as the increase in AI (p=0.034), CCS (p=0.048), and LVMMI (p=0.023). Conclusion. Use of PRD + KAA provides adequate nutrition status and more efficient correction of FGF-23 and Klotho imbalance in CKD progression that may contribute to alleviation of both cardiovascular calcification and cardiac remodeling in CKD. Importantly, a prolonged PRD use without supplementation of KAA may lead to malnutrition signs.

Chronic Kidney Disease and Pulse Wave Velocity: A Narrative Review

Chronic kidney disease (CKD) is associated with excess cardiovascular mortality, resulting from both traditional and nontraditional, CKD-specific, cardiovascular risk factors. Nontraditional risk factors include the entity Chronic Kidney Disease-Mineral and Bone Disorder (CKD-MBD) which is characterised by disorders of bone and mineral metabolism, including biochemical abnormalities of hyperphosphatemia and hyperparathyroidism, renal osteodystrophy, and vascular calcification. Increased arterial stiffness in the CKD population can be attributed amongst other influences to progression of vascular calcification, with significant resultant contribution to the cardiovascular disease burden. Pulse wave velocity (PWV) measured over the carotid-femoral arterial segments is the noninvasive gold-standard technique for measurement of aortic stiffness and has been suggested as a surrogate cardiovascular end-point. A PWV value of 10 m/s or greater has been recommended as a suitable cut-off for an increased risk of cardiovascular mortality. CKD is a risk factor for an excessive rate of increase in aortic stiffness, reflected by increases in PWV, and increased aortic PWV in CKD shows faster progression than for individuals with normal kidney function. Patients with varying stages of CKD, as well as those on dialysis or with a kidney transplant, have different biological milieu which influence aortic stiffness and associated changes in PWV. This review discusses the pathophysiology of arterial stiffness with CKD and outlines the literature on PWV across the spectrum of CKD, highlighting that determination of arterial stiffness using aortic PWV can be a useful diagnostic and prognostic tool for assessing cardiovascular disease in the CKD population.

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.

Fibroblast growth factor 23 does not directly influence skeletal muscle cell proliferation and differentiation or ex vivo muscle contractility

Skeletal muscle dysfunction accompanies the clinical disorders of chronic kidney disease (CKD) and hereditary hypophosphatemic rickets. In both disorders, fibroblast growth factor 23 (FGF23), a bone-derived hormone regulating phosphate and vitamin D metabolism, becomes chronically elevated. FGF23 has been shown to play a direct role in cardiac muscle dysfunction; however, it is unknown whether FGF23 signaling can also directly induce skeletal muscle dysfunction. We found expression of potential FGF23 receptors ( Fgfr1-4) and α-Klotho in muscles of two animal models (CD-1 and Cy/+ rat, a naturally occurring rat model of chronic kidney disease-mineral bone disorder) as well as C2C12 myoblasts and myotubes. C2C12 proliferation, myogenic gene expression, oxidative stress marker 8-OHdG, intracellular Ca2+ ([Ca2+]i), and ex vivo contractility of extensor digitorum longus (EDL) or soleus muscles were assessed after treatment with various amounts of FGF23. FGF23 (2-100 ng/ml) did not alter C2C12 proliferation, expression of myogenic genes, or oxidative stress after 24- to 72-h treatment. Acute or prolonged FGF23 treatment up to 6 days did not alter C2C12 [Ca2+]i handling, nor did acute treatment with FGF23 (9-100 ng/ml) affect EDL and soleus muscle contractility. In conclusion, although skeletal muscles express the receptors involved in FGF23-mediated signaling, in vitro FGF23 treatments failed to directly alter skeletal muscle development or function under the conditions tested. We hypothesize that other endogenous substances may be required to act in concert with FGF23 or apart from FGF23 to promote muscle dysfunction in hereditary hypophosphatemic rickets and CKD.

Fibroblast growth factor 23 and renal function among young and healthy individuals

BACKGROUND

Fibroblast growth factor 23 (FGF-23), an osteocyte hormone involved in the regulation of phosphate metabolism, is associated with incident and progressive chronic kidney disease. We aimed to assess the association of FGF-23 with renal parameters, vascular function and phosphate metabolism in a large cohort of young and healthy individuals.

METHODS

Healthy individuals aged 25-41 years were included in a prospective population-based study. Fasting venous blood and morning urinary samples were used to measure plasma creatinine, cystatin C, endothelin-1, phosphate and plasma FGF-23 as well as urinary creatinine and phosphate. Multivariable regression models were constructed to assess the relationship of FGF-23 with parameters of renal function, endothelin-1 and fractional phosphate excretion.

RESULTS

The median age of 2077 participants was 37 years, 46% were males. The mean estimated glomerular filtration rate (eGFR - CKD-EPI creatinine-cystatin C equation) and fractional phosphate excretion were 110 mL/min/1.73 m2 and 8.7%, respectively. After multivariable adjustment, there was a significant inverse relationship of FGF-23 with eGFR (β per 1 log-unit increase -3.81; 95% CI [-5.42; -2.20]; p<0.0001). Furthermore, we found a linear association between FGF-23 and endothelin-1 (β per 1 log-unit increase 0.06; [0.01, 0.11]; p=0.01). In addition, we established a significant relationship of FGF-23 with fractional phosphate excretion (β per 1 log-unit increase 0.62; [0.08, 1.16]; p=0.03).

CONCLUSIONS

Increasing plasma FGF-23 levels are strongly associated with decreasing eGFR and increasing urinary phosphate excretion, suggesting an important role of FGF-23 in the regulation of kidney function in young and healthy adults.

Effect of essential amino acid кetoanalogues and protein restriction diet on morphogenetic proteins (FGF-23 and Кlotho) in 3b-4 stages chronic кidney disease patients: a randomized pilot study

BACKGROUND

A low protein diet (LPD) with essential amino acid ketoanalogue supplementation (KA) may contribute in improving of chronic kidney disease (CKD), while the exact mechanisms of KA's effect are not established yet. We have conducted a prospective, randomized, controlled comparative study of LPD + KA and LPD alone in relation to serum Klotho, FGF-23 levels in CKD patients.

METHODS

79 non-diabetic CKD 3b-4 stage patients, compliant with LPD diet (0.6 g/kg of body weight/day), had been selected. The patients were randomized into two groups. The first group (42 patients) received LPD + КA. The second group (37 patients) continued the LРD alone. In addition to routine tests, serum Klotho, FGF-23 levels, as well as bioimpedance analysis, sphygmography (stiffness (augmentation) indices (AI), central (aortal) blood pressure) with a «SphygmaCor» device; echocardiography (valvular calcification score (VCS) and LVMMI), were performed.

RESULTS

There were body mass indices' decrease (p = 0.046), including muscle body mass in men (p = 0.027) and woman (p = 0.044) in the LPD group to the end of study (14th month). In addition, lower FGF-23 (p = 0.029), and higher sKlotho (p = 0.037) were detected in the LPD + KA group compared to the LPD one. The increase in AI (p = 0.034), VCS (p = 0.048), and LVMMI (p = 0.023) was detected more often in the LPD group at the end of study.

CONCLUSION

LPD + KA provides support for nutrition status and contributes to more efficient correction of FGF-23 and Klotho abnormalities that may result in cardiovascular calcification and cardiac remodeling decreasing in CKD. At the same time, a prolonged LPD alone may lead to malnutrition.

Is fibroblast growth factor 23 a new cardiovascular risk marker in gestational diabetes?

OBJECTIVE

This study was designed to compare the serum levels of fibroblast growth factor 23 (FGF23) among patients with gestational diabetes mellitus (GDM) and healthy pregnant women, and to evaluate the association between hormonal and metabolic parameters.

SUBJECTS AND METHODS

A total of 82 pregnant women were consecutively enrolled in the study. Of these, 46 were diagnosed as having GDM; the remaining 36 healthy pregnant women served as controls in a cross-sectional study design. The womens' ages ranged from 22 to 38 years and gestational ages, from 24 to 28 weeks. Serum samples were analyzed for FGF23 levels using an enzyme-linked immunosorbent assay.

RESULTS

Serum FGF23 levels were increased in patients with GDM compared with controls (median, 65.3 for patients with GDM vs. 36.6 ng/mL for healthy controls; p = 0.019). Mean fasting glucose (105.6 ± 7.4 vs. 70.2 ± 7.2 mg/dL, p < 0.001), HbA1c (5.6 ± 0.5 vs. 4.9 ± 0.5%, p < 0.001), insulin (median, 11.1 vs. 8.7 µIU/mL, p = 0.006) and HOMA-IR (3.0 (1.8) vs 1.4 (0.6), p < 0.001) levels were significantly higher in patients with GDM than in controls. Serum FGF23 level was positively correlated with body mass index (r2 = 0.346, p < 0.05), FPG (r2 = 0.264, p < 0.05), insulin (r2 = 0.388, p < 0.05), HOMA-IR (r2 = 0.384, p < 0.05).

CONCLUSION

Serum FGF23 levels were higher in women with GDM compared with controls. The present findings suggest that FGF23 could be a useful marker of cardiovascular disease in GDM.

Effect of Omega-3 Fatty Acid Supplementation on Plasma Fibroblast Growth Factor 23 Levels in Post-Myocardial Infarction Patients with Chronic Kidney Disease: The Alpha Omega Trial

Fibroblast growth factor 23 (FGF23) is an independent risk factor for cardiovascular mortality in chronic kidney disease. Omega-3 (n-3) fatty acid consumption has been inversely associated with FGF23 levels and with cardiovascular risk. We examined the effect of marine n-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) and plant-derived alpha-linolenic acid (ALA) on plasma FGF23 levels in post-myocardial infarction patients with chronic kidney disease. In the randomized double-blind Alpha Omega Trial, 4837 patients with a history of myocardial infarction aged 60-80 years (81% men) were randomized to one of four trial margarines supplemented with a targeted additional intake of 400 mg/day EPA and DHA, 2 g/day ALA, EPA-DHA plus ALA, or placebo for 41 months. In a subcohort of 336 patients with an eGFR < 60 mL/min/1.73 m² (creatinine-cystatin C-based CKD-EPI formula), plasma C-terminal FGF23 was measured by ELISA at baseline and end of follow-up. We used analysis of covariance to examine treatment effects on FGF23 levels adjusted for baseline FGF23. Patients consumed 19.8 g margarine/day on average, providing an additional amount of 236 mg/day EPA with 158 mg/day DHA, 1.99 g/day ALA or both, in the active intervention groups. Over 79% of patients were treated with antihypertensive and antithrombotic medication and statins. At baseline, plasma FGF23 was 150 (128 to 172) RU/mL (mean (95% CI)). After 41 months, overall FGF23 levels had increased significantly (p < 0.0001) to 212 (183 to 241) RU/mL. Relative to the placebo, the treatment effect of EPA-DHA was indifferent, with a mean change in FGF23 (95% CI) of -17 (-97, 62) RU/mL (p = 0.7). Results were similar for ALA (36 (-42, 115) RU/mL) and combined EPA-DHA and ALA (34 (-44, 113) RU/mL). Multivariable adjustment, pooled analyses, and subgroup analyses yielded similar non-significant results. Long-term supplementation with modest quantities of EPA-DHA or ALA does not reduce plasma FGF23 levels when added to cardiovascular medication in post-myocardial patients with chronic kidney disease.

Extrarenal effects of FGF23

Chronic kidney disease (CKD) is associated with an increased risk of cardiovascular mortality, infections, and impaired cognitive function. It is characterized by excessively increased levels of the phosphaturic hormone fibroblast growth factor 23 (FGF23) and a deficiency of its co-receptor Klotho. Despite the important physiological effect of FGF23 in maintaining phosphate homeostasis, there is increasing evidence that higher FGF23 levels are a risk factor for mortality and cardiovascular disease. FGF23 directly induces left ventricular hypertrophy via activation of the FGF receptor 4/calcineurin/nuclear factor of activated T cells signaling pathway. By contrast, the impact of FGF23 on endothelial function and the development of atherosclerosis are poorly understood. The results of recent experimental studies indicate that FGF23 directly impacts on hippocampal neurons and may thereby impair learning and memory function in CKD patients. Finally, it has been shown that FGF23 interferes with the immune system by directly acting on polymorphonuclear leukocytes and macrophages. In this review, we discuss recent data from clinical and experimental studies on the extrarenal effects of FGF23 with respect to the cardiovascular, central nervous, and immune systems.

Advanced glycation end products stimulate gene expression of fibroblast growth factor 23

SCOPE

Osteoblasts produce fibroblast growth factor 23 (FGF23), a hormone inhibiting renal phosphate reabsorption and the formation of biologically active vitamin D, calcitriol. FGF23-deficient mice age rapidly and develop age-associated diseases at least in part due to massive calcification. Elevated FGF23 serum levels are detected in patients suffering from acute and chronic renal, cardiovascular, inflammatory, and metabolic diseases. Advanced glycation end products (AGEs) are sugar-modified proteins, nucleic acid, and lipids which contribute to these disorders. Here, we studied the significance of AGEs for the generation of FGF23.

METHODS AND RESULTS

As AGE sources, bread crust extract (BCE) and ribose-modified bovine serum albumin (r-BSA) were used. UMR106 osteoblast-like cells were exposed to BCE and r-BSA, and Fgf23 transcripts were determined by qRT-PCR. UMR106 cells express the receptor for AGEs, RAGE. BCE and r-BSA were powerful stimulators of Fgf23 transcription. NFκB inhibitor wogonin and store-operated calcium entry (SOCE) antagonist 2-APB attenuated the r-BSA and BCE effects on FGF23 synthesis.

CONCLUSION

Sources of AGEs induce the transcription of Fgf23 in UMR cells. At least in part, the effect is mediated through up-regulation of NFκB and subsequent SOCE. AGE-induced FGF23 production may contribute to increased FGF23 serum levels observed in chronic disease.

Is Fibroblast growth factor 23 the leading cause of increased mortality among chronic kidney disease patients? A narrative review

The death rate among chronic kidney disease patients is the highest compared to other chronic diseases. 60% of these fatalities are cardiovascular. Cardiovascular calcifications and chronic inflammation affect almost all chronic kidney disease patients and are associated with cardiovascular mortality. Fibroblast growth factor 23 is associated with vascular calcification. Systemic inflammation in chronic kidney disease patients is multifactorial. The role of systemic inflammation in the pathogenesis of vascular calcification was recently reappraised. Fibroblast growth factor 23 was accused as a direct stimulus of left ventricular hypertrophy, uremic inflammation, and impaired neutrophil function. This review will discuss the underlying mechanisms that underlie the link between Fibroblast growth factor 23 and increased mortality encountered among chronic kidney disease patients.

FGF23 and inflammation

Systemic inflammation is a recognized feature in chronic kidney disease (CKD). The role of systemic inflammation in the pathogenesis of vascular calcification was recently settled. FGF23 was recently accused as a direct stimulus of systemic inflammation. This finding explains the strong association of FGF23 to vascular calcification and increased mortality among CKD.

Vascular calcification: When should we interfere in chronic kidney disease patients and how?

Chronic kidney disease (CKD) patients are endangered with the highest mortality rate compared to other chronic diseases. Cardiovascular events account for up to 60% of the fatalities. Cardiovascular calcifications affect most of the CKD patients. Most of this calcification is related to disturbed renal phosphate handling. Fibroblast growth factor 23 and klotho deficiency were incriminated in the pathogenesis of vascular calcification through different mechanisms including their effects on endothelium and arterial wall smooth muscle cells. In addition, deficient klotho gene expression, a constant feature of CKD, promotes vascular pathology and shares in progression of the CKD. The role of gut in the etio-pathogenesis of systemic inflammation and vascular calcification is a newly discovered mechanism. This review will cover the medical history, prevalence, pathogenesis, clinical relevance, different tools used to diagnose, the ideal timing to prevent or to withhold the progression of vascular calcification and the different medications and medical procedures that can help to prolong the survival of CKD patients.

Fibroblast growth factor 23 directly targets hepatocytes to promote inflammation in chronic kidney disease

Patients with chronic kidney disease (CKD) develop increased levels of the phosphate-regulating hormone, fibroblast growth factor (FGF) 23, that are associated with a higher risk of mortality. Increases in inflammatory markers are another common feature that predicts poor clinical outcomes. Elevated FGF23 is associated with higher circulating levels of inflammatory cytokines in CKD, which can stimulate osteocyte production of FGF23. Here, we studied whether FGF23 can directly stimulate hepatic production of inflammatory cytokines in the absence of α-klotho, an FGF23 coreceptor in the kidney that is not expressed by hepatocytes. By activating FGF receptor isoform 4 (FGFR4), FGF23 stimulated calcineurin signaling in cultured hepatocytes, which increased the expression and secretion of inflammatory cytokines, including C-reactive protein. Elevating serum FGF23 levels increased hepatic and circulating levels of C-reactive protein in wild-type mice, but not in FGFR4 knockout mice. Administration of an isoform-specific FGFR4 blocking antibody reduced hepatic and circulating levels of C-reactive protein in the 5/6 nephrectomy rat model of CKD. Thus, FGF23 can directly stimulate hepatic secretion of inflammatory cytokines. Our findings indicate a novel mechanism of chronic inflammation in patients with CKD and suggest that FGFR4 blockade might have therapeutic anti-inflammatory effects in CKD.

Comparing different calcification scores to detect outcomes in chronic kidney disease patients with vascular calcification

BACKGROUND

There is no consensus on the most appropriate technique to diagnose vascular calcification in chronic kidney disease. This is primarily because of the absence of direct comparisons of predictive values of the various calcification scores, especially outside the coronary vascular beds, to detect clinical outcomes.

METHODS

We included 93 haemodialysis patients and performed 6 vascular calcification scores: two scores utilised simple X-rays of abdominal aorta and peripheral vessels. CT scans of the thoracic, upper abdominal and lower abdominal aorta were performed to calculate the aortic calcification index and CT of the pelvis for calcification of iliac vessels. Patients were followed for 63months (mean 46.8months) for first major cardiovascular events and mortality.

RESULTS

Nineteen cardiovascular events and 28 deaths occurred. Calcification was detected more sensitively in central and peripheral beds using CT scans compared to X-rays (p<0.001). CT scans detected calcification more frequently in distal than proximal vascular beds (p<0.001). Calcification of the pelvic vessels and lower abdominal aorta were most predictive of events including pre-existing cardiovascular disease O.R. 6.5 (95% C.I. 2-22; p=0.001) and O.R. 3 (95% C.I. 1.1-9; p=0.035); new major cardiovascular events H.R. 4.2 (95% C.I. 1.5-11; p=0.006) and H.R. 2 (95% C.I. 0.8-5.3; p=0.1) as well as mortality H.R. 2.8 (95% C.I. 1.3-6; p=0.01) and H.R. 2.2 (95% C.I. 1.04-5; p=0.04) respectively.

CONCLUSIONS

CT based techniques are more sensitive than plain X-rays at detecting peripheral and aortic vascular calcifications. Distal CT scans of the aorta and pelvic vessels have the highest predictive value for cardiovascular events and mortality.

MICS, an easily ignored contributor to arterial calcification in CKD patients

In chronic kidney disease (CKD), simultaneous mineral and skeleton changes are prevalent, known as CKD-mineral bone disorder (CKD-MBD). Arterial calcification (AC) is a clinically important complication of CKD-MBD. It can increase arterial stiffness, which leads to severe cardiovascular events. However, current treatments have little effect on regression of AC, as its mechanisms are still unclear. There are multiple risk factors of AC, among which Malnutrition-Inflammation Complex Syndrome (MICS) is a new and crucial one. MICS, a combined syndrome of malnutrition and inflammation, generally begins at the early stage of CKD and becomes obvious in end-stage renal disease (ESRD). It was linked to reverse epidemiology and associated with increased cardiovascular mortality in ESRD patients. Recent data suggest that MICS can trigger CKD-MBD and accelerate the course of AC. In this present review, we summarize the recent understanding about the aggravating effects of MICS on AC and discuss the possible underlying mechanisms. A series of findings indicate that targeting MICS will provide a potential strategy for treating AC in CKD.

Stop chronic kidney disease progression: Time is approaching

Progression of chronic kidney disease (CKD) is inevitable. However, the last decade has witnessed tremendous achievements in this field. Today we are optimistic; the dream of withholding this progression is about to be realistic. The recent discoveries in the field of CKD management involved most of the individual diseases leading the patients to end-stage renal disease. Most of these advances involved patients suffering diabetic kidney disease, chronic glomerulonephritis, polycystic kidney disease, renal amyloidosis and chronic tubulointerstitial disease. The chronic systemic inflammatory status and increased oxidative stress were also investigated. This inflammatory status influences the anti-senescence Klotho gene expression. The role of Klotho in CKD progression together with its therapeutic value are explored. The role of gut as a major source of inflammation, the pathogenesis of intestinal mucosal barrier damage, the role of intestinal alkaline phosphatase and the dietary and therapeutic implications add a novel therapeutic tool to delay CKD progression.

Bone mineral disorder in chronic kidney disease: Klotho and FGF23; cardiovascular implications

Cardiovascular factors are one of the main causes of morbidity and mortality in patients with chronic kidney disease. Bone mineral metabolism disorders and inflammation are pathological conditions that involve increased cardiovascular risk in chronic kidney disease. The cardiovascular risk involvement of bone mineral metabolism classical biochemical parameters such as phosphorus, calcium, vitamin D and PTH is well known. The newest markers, FGF23 and klotho, could also be implicated in cardiovascular disease.

FGF23 from bench to bedside

There is a strong association between elevated circulating fibroblast growth factor-23 (FGF23) levels and adverse outcomes in patients with chronic kidney disease (CKD) of all stages. Initially discovered as a regulator of phosphate and vitamin D homeostasis, FGF23 has now been implicated in several pathophysiological mechanisms that may negatively impact the cardiovascular and renal systems. FGF23 is purported to have direct (off-target) effects in the myocardium, as well as canonical effects on FGF receptor/α-klotho receptor complexes in the kidney to activate the renin-angiotensin-aldosterone system, modulate soluble α-klotho levels, and increase sodium retention, to cause left ventricular hypertrophy (LVH). Conversely, FGF23 could be an innocent bystander produced in response to chronic inflammation or other processes associated with CKD that cause LVH and adverse cardiovascular outcomes. Further exploration of these complex mechanisms is needed before modulation of FGF23 can become a legitimate clinical target in CKD.

Inflammation but not obesity or insulin resistance is associated with increased plasma fibroblast growth factor 23 concentration in the elderly

BACKGROUND

Fibroblast growth factor 23 (FGF23) is a hormone involved in calcium-phosphate homoeostasis. The data of recently published studies suggest that FGF-23 may also play a role in some metabolic processes beyond mineral metabolism, such as insulin resistance or energy homoeostasis. The aim of the study was to attempt the relationships between plasma cFGF-23 (C-terminal) and iFGF-23 (intact) concentrations and the occurrence of obesity, insulin resistance and inflammation in elderly population.

MATERIALS AND METHODS

The analysis included 3115 elderly subjects (1485 women). During three visits, a questionnaire survey, comprehensive geriatric assessment and anthropometric measurements were performed as well as blood and urine samples were collected by trained nurses. Serum phosphorus, calcium, intact parathormone (iPTH), 25(OH)D3 , iFGF-23 and cFGF-23, insulin, glucose, albumin (also in urine), creatinine, hs-CRP, interleukin-6 and NT-proBNP concentrations were assessed. HOMA-IR was calculated according to the standard formula.

RESULTS

Both forms of FGF23, iPTH and 25-OH-D3 levels were not related to the occurrence of obesity and insulin resistance. Increase in phosphorus, iPTH and NT-proBNP concentrations is associated with rise in plasma iFGF23 and cFGF23 levels. Additionally, increase in hs-CRP explained the elevated plasma iFGF23 levels. In multiple regression models, circulating iFGF23 and cFGF23 level's variability in elderly population were explained by changes in serum phosphorus, iPTH, eGFR, hs-CRP and NT-proBNP levels but not by BMI and HOMA-IR values.

CONCLUSION

In conclusion, our study shows that increased levels of both circulating Fibroblast growth factor 23 forms in elderly subjects are associated with inflammation but not obesity or insulin resistance per se.

FGF-23 levels in patients with critical carotid artery stenosis

The aim of this study was to evaluate fibroblast growth factor (FGF)-23 serum levels and its tissue expression in patients with critical carotid artery stenosis (CAS). We selected 35 patients with critical CAS undergoing carotid thromboendoarterectomy. In each patient, FGF-23 serum levels were evaluated just prior to the surgery (t0) and 30 min (t1) thereafter. Moreover, macrophage cytokines were measured at baselines. Carotid artery specimens were used for immune histochemistry. On the basis of the histology, the patients were divided into 2 groups: A with complicated plaque and B with uncomplicated plaque. Twenty complicated plaques (57.14%, group A,) and 15 uncomplicated (42.86%, group B) were evaluated: calcifications were present in 16/20 (80%) complicated plaques and in 6/15 (40%) uncomplicated plaques. An inflammatory infiltrate was observed in 26/35 carotid samples: 18/26 (69.23%) complicated and 8/26 (30.76%) uncomplicated. FGF-23(+) cells were present in 17/20 complicated (85%) and in 8 uncomplicated (53%) plaques. The double-staining immunofluorescence confirmed that macrophage cells (CD68(+)) were also positive for FGF-23 staining. Serum levels of FGF-23 were significantly higher in group A versus group B at t0 (p < 0.05) and t1 (p 0.0047). Moreover, in group A patients a significant increase of FGF-23 serum levels was observed at t1 in comparison with t0 (p 0.0011). Our results suggest that FGF-23 acts in the late phases of atherosclerotic disease and may potentially represent a marker of complications in critical CAS.

[FGF23 and the heart]

The prevalence of chronic kidney disease (CKD) has now reached epidemic proportions and it is very likely that it will continue to rise with the increasing prevalence of juvenile diabetes mellitus, hypertension and aging population. CKD is a risk factor for cardiovascular disease (CVD) and cardiovascular disease can lead to CKD. It is also well known that patients with CKD have a higher risk of death from CVD than of progressing to end-stage renal disease that requires renal replacement therapy. In patients with CKD, there is a higher mortality from sudden cardiac death and congestive heart failure than coronary artery disease, which is not the case in the general population. The high prevalence of congestive heart failure in CKD is due to cardiac remodeling which progresses from concentric remodeling to concentric and eccentric hypertrophy, leading to left ventricular hypertrophy with both systolic and diastolic dysfunction. Recent studies have suggested that, in patients with chronic kidney disease, common traditional risk factors for cardiovascular disease such as hypertension, hyperlipidemia and obesity may not be the main determinants of cardiovascular disease. Among the various non-traditional cardiovascular risk factors present in patients with chronic kidney disease, abnormalities of CKD related mineral and bone disorder, which includes elevated fibroblast growth factor 23 (FGF23) have been one of the most extensively studied. However, after many years of research, the debate over the exact pathways by which FGF23 may lead to increased CVD still continues. FGF23 may have both direct and indirect effects on the cardiovascular system. Better understanding of the most relevant pathophysiologic pathways for FGF23 may lead to therapeutic interventions against cardiovascular disease in patients with CKD.