FGF-23: the rise of a novel cardiovascular risk marker in CKD

FGF23 as a Potential Pathophysiological Factor in Peripheral Arterial Disease Associated with Chronic Kidney Disease

Fibroblast growth factor 23 (FGF23) levels are often elevated in chronic kidney disease (CKD). FGF23 and inflammation are common characteristics in CKD, and both are associated with worse disease progression and the occurrence of complications. The existence of an interaction between FGF23 and inflammation has been suggested, each of which influences the expression and activity of the other, leading to a vicious feedback loop with adverse outcomes, including cardiovascular disease and mortality. In this work, we determined circulating FGF23 levels in a group of patients with CKD stages 3 and 4 subjected to elective femoral endarterectomy due to established peripheral artery disease (PAD), a condition resulting from an athero-inflammatory process, and we studied its associations with different inflammatory markers and mediators. We evaluated its association with serum tumor necrosis factor (TNF)α, interleukin (IL) 6, and IL10, as well as with the gene expression levels of these parameters and A disintegrin and metalloproteinase domain-containing protein (ADAM) 17 in femoral vascular tissue and peripheral blood circulating cells (PBCCs). We also analyzed its association with serum concentrations of C-reactive protein (CRP), the systemic immune inflammation index (SII), and the neutrophil-to-lymphocyte ratio (NLR). Finally, we determined the vascular immunoreactivity of protein TNFα in a subgroup of patients. FGF23 concentrations were independently associated with circulating and PBCC mRNA levels of TNFα. Worst kidney function and diabetes were also found to be contributing to FGF23 levels. Patients with higher levels of FGF23 also had greater vascular immunoreactivity for TNFα.

Cardiovascular Consequences of Uremic Metabolites: an Overview of the Involved Signaling Pathways

The crosstalk of the heart with distant organs such as the lung, liver, gut, and kidney has been intensively approached lately. The kidney is involved in (1) the production of systemic relevant products, such as renin, as part of the most essential vasoregulatory system of the human body, and (2) in the clearance of metabolites with systemic and organ effects. Metabolic residue accumulation during kidney dysfunction is known to determine cardiovascular pathologies such as endothelial activation/dysfunction, atherosclerosis, cardiomyocyte apoptosis, cardiac fibrosis, and vascular and valvular calcification, leading to hypertension, arrhythmias, myocardial infarction, and cardiomyopathies. However, this review offers an overview of the uremic metabolites and details their signaling pathways involved in cardiorenal syndrome and the development of heart failure. A holistic view of the metabolites, but more importantly, an exhaustive crosstalk of their known signaling pathways, is important for depicting new therapeutic strategies in the cardiovascular field.

Progression of Vascular Calcification and Clinical Outcomes in Patients Receiving Maintenance Dialysis

Importance

Baseline findings from the China Dialysis Calcification Study (CDCS) revealed a high prevalence of vascular calcification (VC) among patients with end-stage kidney disease; however, data on VC progression were limited.

Objectives

To understand the progression of VC at different anatomical sites, identify risk factors for VC progression, and assess the association of VC progression with the risk of cardiovascular events and death among patients receiving maintenance dialysis.

Design, Setting, and Participants

This cohort study was a 4-year follow-up assessment of participants in the CDCS, a nationwide multicenter prospective cohort study involving patients aged 18 to 74 years who were undergoing hemodialysis or peritoneal dialysis. Participants were recruited from 24 centers across China between May 1, 2014, and April 30, 2015, and followed up for 4 years. A total of 1489 patients receiving maintenance dialysis were included in the current analysis. Data were analyzed from September 1 to December 31, 2021.

Exposures

Patient demographic characteristics and medical history; high-sensitivity C-reactive protein laboratory values; serum calcium, phosphorus, and intact parathyroid hormone (iPTH) values; and previous or concomitant use of medications.

Main Outcomes and Measures

The primary outcome was progression of VC at 3 different anatomical sites (coronary artery, abdominal aorta, and cardiac valves) and identification of risk factors for VC progression. Participants received assessments of coronary artery calcification (CAC), abdominal aortic calcification (AAC), and cardiac valve calcification (CVC) at baseline, 24 months, 36 months, and 48 months. Secondary outcomes included (1) the association between VC progression and the risk of all-cause death, cardiovascular (CV)-related death, and a composite of all-cause death and nonfatal CV events and (2) the association between achievement of serum calcium, phosphorus, and iPTH target levels and the risk of VC progression.

Results

Among 1489 patients, the median (IQR) age was 51.0 (41.0-60.0) years; 59.5% of patients were male. By the end of 4-year follow-up, progression of total VC was observed in 86.5% of patients; 69.6% of patients had CAC progression, 72.4% had AAC progression, and 33.4% had CVC progression. Common risk factors for VC progression at the 3 different anatomical sites were older age and higher fibroblast growth factor 23 levels. Progression of CAC was associated with a higher risk of all-cause death (model 1 [adjusted for age, sex, and body mass index]: hazard ratio [HR], 1.97 [95% CI, 1.16-3.33]; model 2 [adjusted for all factors in model 1 plus smoking status, history of diabetes, and mean arterial pressure]: HR, 1.89 [95% CI, 1.11-3.21]; model 3 [adjusted for all factors in model 2 plus calcium, phosphorus, intact parathyroid hormone, and fibroblast growth factor 23 levels and calcium-based phosphate binder use]: HR, 1.92 [95% CI, 1.11-3.31]) and the composite of all-cause death and nonfatal CV events (model 1: HR, 1.98 [95% CI, 1.19-3.31]; model 2: HR, 1.91 [95% CI, 1.14-3.21]; model 3: HR, 1.95 [95% CI, 1.14-3.33]) after adjusting for all confounding factors except the presence of baseline calcification. Among the 3 targets of calcium, phosphorus, and iPTH, patients who achieved no target levels (model 1: odds ratio [OR], 4.75 [95% CI, 2.65-8.52]; model 2: OR, 4.81 [95% CI, 2.67-8.66]; model 3 [for this analysis, adjusted for all factors in model 2 plus fibroblast growth factor 23 level and calcium-based phosphate binder use]: OR, 2.76 [95% CI, 1.48-5.16]), 1 target level (model 1: OR, 3.71 [95% CI, 2.35-5.88]; model 2: OR, 3.62 [95% CI, 2.26-5.78]; model 3: OR, 2.19 [95% CI, 1.33-3.61]), or 2 target levels (model 1: OR, 2.73 [95% CI, 1.74-4.26]; model 2: OR, 2.69 [95% CI, 1.71-4.25]; model 3: OR, 1.72 [95% CI, 1.06-2.79]) had higher odds of CAC progression compared with patients who achieved all 3 target levels.

Conclusions and Relevance

In this study, VC progressed rapidly in patients undergoing dialysis, with different VC types associated with different rates of prevalence and progression. Consistent achievement of serum calcium, phosphorus, and iPTH target levels was associated with a lower risk of CAC progression. These results may be useful for increasing patient awareness and developing appropriate strategies to improve the management of chronic kidney disease-mineral and bone disorder among patients undergoing dialysis.

Evaluation of the association of serum glypican-4 with prevalent and future kidney function

Serum glypican-4 (GPC4) has been identified as an insulin-sensitizing adipokine serving as a marker for body mass index and insulin resistance in humans. The association of circulating GPC4 with kidney function is to date largely unexplored. Therefore, we aimed to evaluate the association between serum GPC4 and prevalent as well future kidney function in a prospective cohort study. The study included 456 Caucasian coronary angiography patients. After a median follow up period of 3.4 years, data on kidney function was reassessed in all patients. Chronic kidney disease (CKD) was defined by decreased estimated glomerular filtration rate (eGFR) < 60 mL/min/1.73 m² or albuminuria. At baseline, serum GPC4 was significantly associated with decreased eGFR (adjusted odds ratio (OR) per standard deviation = 4.75 [2.66–8.48]; P <  0.001), albuminuria (OR = 1.49 [1.15–1.92]; P = 0.002), and, accordingly, with CKD (OR = 1.75 [1.35–2.26]; P < 0.001). GPC4 levels also significantly and independently predicted the incidence of newly diagnosed decreased eGFR (OR = 2.74 [1.82–4.14]; P < 0.001, albuminuria (OR = 1.58 [1.01–2.46]; P = 0.043, and CKD (OR = 2.16 [1.45–3.23]; P < 0.001). ROC analysis indicated an additional predictive value of GPC4 to a basic prediction model for newly diagnosed CKD and eGFR < 60 mL/min/1.73 m². Our study, therefore, indicates that high serum GPC4 is associated with decreased prevalent and future kidney function.

The Correlation of Fibroblast Growth Factor 23 with Cardiac Remodeling in Essential Hypertension with Normal Renal Function

Background Fibroblast growth factor 23 (FGF23), a glycoprotein regulating calcium phosphorus homeostasis, has been linked to cardiovascular diseases. We aimed to evaluate the correlation of FGF23 levels and cardiac remodeling (left atrial [LA] enlargement and left ventricular hypertrophy [LVH]) in essential hypertension (EH) with normal renal function, and explore the diagnostic values of FGF23 and B-type natriuretic peptide (BNP) in cardiac remodeling. Methods and Results We enrolled 40 healthy control subjects (Group I) and 146 EH patients (Group II). Plasma FGF23 concentration was measured in all subjects. In this study, FGF23 level was significantly higher in Group II (660.77[446.26, 1001.72]) pg/mL compared with the controls (73.23[52.92, 103.69]) pg/mL (P<0.001). Logistic regression analysis revealed that FGF23 was independently correlated to LVH and LA enlargement. Receiver operating characteristic (ROC) curve indicated FGF23 had an optimal cutoff of 834.63 pg/mL for LVH (area under ROC curve [AUC], 0.913; 95%CI, 0.863-0.963), and 497.06 pg/mL for LA enlargement (AUC, 0.694; 95%CI, 0.612-0.768). The DeLong test was performed to compare AUCs of FGF23 and BNP, and the AUC of FGF23 (0.913) was statistically higher compared to AUC of BNP (0.661) (DeLong test: P < 0.001) in the diagnosis of LVH. Conclusion Plasma FGF23 level elevated in EH, increased with the progress of cardiac remodeling, and was independently related to LVH and LA enlargement. The diagnostic value of FGF23 in cardiac remodeling, especially for LVH, was superior to BNP.

Tubular Cell Glucose Metabolism Shift During Acute and Chronic Injuries

Acute and chronic kidney disease are responsible for large healthcare costs worldwide. During injury, kidney metabolism undergoes profound modifications in order to adapt to oxygen and nutrient shortage. Several studies highlighted recently the importance of these metabolic adaptations in acute as well as in chronic phases of renal disease, with a potential deleterious effect on fibrosis progression. Until recently, glucose metabolism in the kidney has been poorly studied, even though the kidney has the capacity to use and produce glucose, depending on the segment of the nephron. During physiology, renal proximal tubular cells use the beta-oxidation of fatty acid to generate large amounts of energy, and can also produce glucose through gluconeogenesis. In acute kidney injury, proximal tubular cells metabolism undergo a metabolic shift, shifting away from beta-oxidation of fatty acids and gluconeogenesis toward glycolysis. In chronic kidney disease, the loss of fatty acid oxidation is also well-described, and data about glucose metabolism are emerging. We here review the modifications of proximal tubular cells glucose metabolism during acute and chronic kidney disease and their potential consequences, as well as the potential therapeutic implications.

Fibroblast growth factor 23 is induced by an activated renin-angiotensin-aldosterone system in cardiac myocytes and promotes the pro-fibrotic crosstalk between cardiac myocytes and fibroblasts

Background

Fibroblast growth factor 23 (FGF23) is discussed as a new biomarker of cardiac hypertrophy and mortality in patients with and without chronic kidney disease (CKD). We previously demonstrated that FGF23 is expressed by cardiac myocytes, enhanced in CKD and induces cardiac hypertrophy via activation of FGF receptor 4 independent of its co-receptor klotho. The impact of FGF23 on cardiac fibrosis is largely unknown.

Methods

By conducting a retrospective case-control study including myocardial autopsy samples from 24 patients with end-stage CKD and in vitro studies in cardiac fibroblasts and myocytes, we investigated the pro-fibrotic properties of FGF23.

Results

The accumulation of fibrillar collagens I and III was increased in myocardial tissue of CKD patients and correlated with dialysis vintage, klotho deficiency and enhanced cardiac angiotensinogen (AGT) expression. Using human fibrosis RT2 Profiler PCR array analysis, transforming growth factor (TGF)-β and its related TGF-β receptor/Smad complexes, extracellular matrix remodeling enzymes and pro-fibrotic growth factors were upregulated in myocardial tissue of CKD patients. FGF23 stimulated cell proliferation, migration, pro-fibrotic TGF-β receptor/Smad complexes and collagen synthesis in cultured cardiac fibroblasts. In isolated cardiac myocytes, FGF23 enhanced collagen remodeling, expression of pro-inflammatory genes and pro-survival pathways and induced pro-hypertrophic genes. FGF23 stimulated AGT expression in cardiac myocytes and angiotensin II and aldosterone, as components of the renin-angiotensin-aldosterone system (RAAS), induced FGF23 in cardiac myocytes.

Conclusions

Our data demonstrate that activated RAAS induces FGF23 expression in cardiac myocytes and thereby stimulates a pro-fibrotic crosstalk between cardiac myocytes and fibroblasts, which may contribute to myocardial fibrosis in CKD.

Ageing characteristics of bone indicated by transcriptomic and exosomal proteomic analysis of cortical bone cells

BACKGROUND

Degenerative changes in the skeleton play an important role in ageing. As the foremost sensors and orchestrators of bone remodelling, osteocytes contribute significantly to the health of the skeleton. Embedded in a mineralized bone matrix, the osteocyte network and the surrounding lacunar canaliculae work together as a functional syncytium-the osteocytic lacunar-canalicular system (OLCS). However, changes in the OLCS during ageing and related mechanisms cannot be fully understood by using traditional histological analysis.

METHODS

To link the phenotypes of aged osteocytes and their functional changes during ageing, we analysed the changes in the gene expression profiles of bone cells and the proteomic profiles of OLCS exosomes derived from aged and young cortical bone.

RESULTS

Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis of differentially expressed genes (DEGs) suggested that a decline in cell energy metabolism and an increased level of the proinflammatory state are major characteristics of bone ageing. Moreover, some DEGs were key regulators of bone mechanical sensation and bone remodelling, which are indicative of reduced bone-specific function with age. Further, the identified proteins in OLCS exosomes showed potential changes in the secretory function bone. Compared with young controls, the decreased functional proteins in aged OLCS exosomes were enriched mainly in GO terms that included regulating bone development and remodelling, cell-matrix adhesion, and cell clearance and homeostasis. Notably, several functions of exosomal proteins of the aged group revealed potential new roles, such as regulating innate and adaptive immunity, wound healing, and angiogenesis and eliminating oxidative stress.

CONCLUSION

The information obtained from bone cells and OLCS exosomes will help us discover new features of bone ageing.

Markers of vitamin D metabolism and incidence of clinically diagnosed abdominal aortic aneurysm: The Atherosclerosis Risk in Communities Study

Little is known about whether markers of vitamin D metabolism are associated with the development of abdominal aortic aneurysm (AAA), though these markers have been linked to other cardiovascular diseases. We tested the hypotheses that risk of AAA is higher among individuals with low serum concentrations of 25-hydroxy vitamin D [25(OH)D], and among those with elevated concentrations of calcium, fibroblast growth factor 23 (FGF23), phosphorus, and parathyroid hormone (PTH) using data from a cohort of black and white individuals with long-term follow-up. Markers of vitamin D metabolism were measured using serum collected in 1990-1992 from ARIC study participants (mean ± SD age 56.9 ± 5.7 years, 43.2% male, 23.9% black). A total of 12,770 participants were followed until 2011 for incident AAA. Multivariable-adjusted Cox regression models were used. A total of 449 incident AAA events occurred over a median follow-up of 19.7 years. For the association between serum calcium and risk of incident AAA there was evidence of interaction by sex ( p-interaction 0.02). Among women, in the fully adjusted model, the hazard ratio (95% confidence interval) comparing the highest to lowest quartile was 2.43 (1.25-4.73), whereas in men it was 1.01 (0.72-1.43). Not associated with risk of incident AAA were 25(OH)D, FGF23, phosphorus, and PTH. In this large prospective cohort, there was little evidence that markers of vitamin D metabolism are associated with risk of incident AAA. The positive association of calcium with AAA among women may warrant further investigation and replication in other populations.

Blood pressure targets for hemodialysis patients

The association between blood pressure (BP) and mortality is unique in hemodialysis patients compared with that in the general population. This is because of an altered benefit-risk balance associated with BP reduction in these patients. An adequately designed study comparing BP targets in hemodialysis patients remains to be conducted. The current evidence available to guide dialysis providers regarding treatment strategies for managing hypertension in this population is limited to large observational studies and small randomized controlled trials. In this opinion article, we review these data and discuss the key points regarding BP management for hemodialysis patients. Our aim is to provide a practical opinion regarding BP targets that nephrologists can incorporate into clinical practice, with a focus on moving away from dialysis unit BPs and focusing on out-of-dialysis unit BPs.

Fibroblast growth factor 23 dysregulates late sodium current and calcium homeostasis with enhanced arrhythmogenesis in pulmonary vein cardiomyocytes

Fibroblast growth factor 23 (FGF23), elevated in chronic renal failure, increases atrial arrhythmogenesis and dysregulates calcium homeostasis. Late sodium currents (I_Na-Late) critically induces ectopic activity of pulmoanry vein (the most important atrial fibrillation trigger). This study was to investigate whether FGF23 activates the I_Na-Late leading to calcium dysregulation and increases PV arrhythmogenesis. Patch clamp, western blot, and confocal microscopy were used to evaluate the electrical activities, calcium homeostasis, and mitochondrial reactive oxygen species (ROS) in PV cardiomyocytes with or without FGF23 (0.1 or 1 ng/mL) incubation for 4~6 h. Compared to the control, FGF23 (1 ng/mL, but not 0.1 ng/mL)-treated PV cardiomyocytes had a faster beating rate. FGF23 (1 ng/mL)-treated PV cardiomyocytes had larger I_Na-Late, calcium transients, and mitochondrial ROS than controls. However, ranolazine (an inhibitor of I_Na-Late) attenuated FGF23 (1 ng/mL)-increased beating rates, calcium transients and mitochondrial ROS. FGF23 (1 ng/mL)-treated PV cardiomyocytes exhibited larger phosphorylation of calcium/calmodulin-dependent protein kinase II (CaMKII). Chelerythrine chloride (an inhibitor of protein kinase C) decreased I_Na-Late in FGF23 (1 ng/mL)-treated PV cardiomyocytes. However, KN93 (a selective CaMKII blocker) decreased I_Na-Late in control and FGF23 (1 ng/mL)-treated PV cardiomyocytes to a similar extent. In conclusion, FGF23 increased PV arrhythmogenesis through sodium and calcium dysregulation by acting protein kinase C signaling.

Impact of Altered Mineral Metabolism on Pathological Cardiac Remodeling in Elevated Fibroblast Growth Factor 23

Clinical and experimental studies indicate a possible link between high serum levels of fibroblast growth factor 23 (FGF23), phosphate, and parathyroid hormone (PTH), deficiency of active vitamin D (1,25D) and klotho with the development of pathological cardiac remodeling, i.e., left ventricular hypertrophy and myocardial fibrosis, but a causal link has not been established so far. Here, we investigated the cardiac phenotype in klotho hypomorphic (kl/kl) mice and Hyp mice, two mouse models of elevated FGF23 levels and klotho deficiency, but differing in parameters of mineral metabolism, by using histology, quantitative real-time PCR, immunoblot analysis, and serum and urine biochemistry. Additionally, the specific impact of calcium, phosphate, PTH, and 1,25D on hypertrophic growth of isolated neonatal rat cardiac myocytes was investigated in vitro. Kl/kl mice displayed high serum Fgf23 levels, increased relative heart weight, enhanced cross-sectional area of individual cardiac myocytes, activated cardiac Fgf23/Fgf receptor (Fgfr) 4/calcineurin/nuclear factor of activated T cell (NFAT) signaling, and induction of pro-hypertrophic NFAT target genes including Rcan1, bMHC, brain natriuretic peptide (BNP), and atrial natriuretic peptide (ANP) as compared to corresponding wild-type (WT) mice. Investigation of fibrosis-related molecules characteristic for pathological cardiac remodeling processes demonstrated ERK1/2 activation and enhanced expression of Tgf-β1, collagen I, and Mmp2 in kl/kl mice than in WT mice. In contrast, despite significantly elevation of serum and cardiac Fgf23, and reduced renal klotho expression, Hyp mice showed no signs of pathological cardiac remodeling. Kl/kl mice showed enhanced serum calcium and phosphate levels, while Hyp mice showed unchanged serum calcium levels, lower serum phosphate, and elevated serum iPTH concentrations compared to corresponding WT mice. In cultured cardiac myocytes, treatment with both calcium or phosphate significantly upregulated endogenous Fgf23 mRNA expression and stimulated hypertrophic cell growth and expression of pro-hypertrophic genes. The treatment with PTH induced hypertrophic cell growth only, and stimulation with 1,25D had no significant effects. In conclusion, our data indicate that Hyp mice, in contrast to kl/kl mice appear to be protected from pathological cardiac remodeling during conditions of high FGF23 levels and klotho deficiency, which may be due, at least in part, to differences in mineral metabolism alterations, i.e., hypophosphatemia and lack of hypercalcemia.

Paracrine Effects of FGF23 on the Heart

Fibroblast growth factor (FGF) 23 is a phosphaturic hormone primarily secreted by osteocytes to maintain phosphate and mineral homeostasis. In patients with and without chronic kidney disease, enhanced circulating FGF23 levels associate with pathologic cardiac remodeling, i.e., left ventricular hypertrophy (LVH) and myocardial fibrosis and increased cardiovascular mortality. Experimental studies demonstrate that FGF23 promotes hypertrophic growth of cardiac myocytes via FGF receptor 4-dependent activation of phospholipase Cγ/calcineurin/nuclear factor of activated T cell signaling independent of its co-receptor klotho. Recent studies indicate that FGF23 is also expressed in the heart, and markedly enhanced in various clinical and experimental settings of cardiac remodeling and heart failure independent of preserved or reduced renal function. On a cellular level, FGF23 is expressed in cardiac myocytes and in other non-cardiac myocytes, including cardiac fibroblasts, vascular smooth muscle and endothelial cells in coronary arteries, and in inflammatory macrophages. Current data suggest that secreted by cardiac myocytes, FGF23 can stimulate pro-fibrotic factors in myocytes to induce fibrosis-related pathways in fibroblasts and consequently cardiac fibrosis in a paracrine manner. While acting on cardiac myocytes, FGF23 directly induces pro-hypertrophic genes and promotes the progression of LVH in an autocrine and paracrine fashion. Thus, enhanced FGF23 may promote cardiac injury in various clinical settings not only by endocrine but also via paracrine/autocrine mechanisms. In this review, we discuss recent clinical and experimental data regarding molecular mechanisms of FGF23's paracrine action on the heart with respect to pathological cardiac remodeling.

Racial Variations in the Markers of Mineral Bone Disorders in CKD Patients in South Africa

Introduction

Several studies showed that serum intact parathyroid hormone (PTH), phosphate, and vitamin D levels differ across races. These comparative studies were largely carried out between Caucasians and black Americans. However, little is known of the existence of these associations in an African population with chronic kidney disease (CKD).

Methods

This cross-sectional multicenter study involved 293 CKD patients from 3 renal units in Johannesburg, South Africa.

Results

The 293 CKD patients (208 blacks, 85 whites) had an overall mean age of 51.1 ± 13.6 years, and black patients were significantly younger than the white patients (48.4 ± 13.6 years vs. 57.1 ± 15.5 years; P < 0.001). Compared with whites, blacks had higher median intact PTH (498 [range: 37–1084] pg/ml vs. 274 [range: 131–595] pg/ml; P = 0.03), alkaline phosphatase (122 [range: 89–192] U/L vs. 103 [range: 74–144] U/L; p = 0.03), and mean 25 OH vitamin D₃ (26.8 ± 12.7 ng/ml vs. 22.7 ± 12.2 ng/ml, P = 0.01) levels, whereas their median fibroblast growth factor (FGF) level was 23 (100 [range: 34–639] pg/ml vs. 233 [range: 80–1370] pg/ml; P = 0.002), and their mean serum phosphate (1.3 ± 0.5 vs. 1.5 ± 0.5; P = 0.001) levels were significantly lower. In multivariable analyses, black race was independently associated with increased log PTH (β = 0.488, P = 0.01) and decreased log FGF-23 (β = −0.636, P = 0.02). Similarly, blacks had a 3.08 times higher likelihood (95% confidence interval: 1.51–6.30; P = 0.002) of developing severe hyperparathyroidism than whites.

Conclusion

This study highlighted the existence of racial differences in the circulating markers of mineral bone disorders in an African CKD population.

FGF23 Level and Intima-Media Thickness Are Elevated From Early Stages of Chronic Kidney Disease

Considering high cardiovascular (CV) risk in chronic kidney disease (CKD), the aim of this cross-sectional study was to assess the association between carotid intima-media thickness (IMT) and fibroblast growth factor (FGF) 23 as important players in CV pathophysiology. Eighty-seven patients with mean estimated glomerular filtration rate 40.1 mL/min per 1.73 m² were involved. FGF23 and IMT were elevated from early stages of CKD. Mean IMT value was 1.10 ± 0.20 mm, being significantly elevated starting from early CKD, showing no correlation with FGF23 (r = -0.01, P = -0.91). Unlike the FGF23 level that followed worsening of kidney function, IMT was increasing only in the initial CKD stages, with no further increase from CKD stage 3 on. Although we found no direct association between current use of vitamin D and statin therapy, this may be associated with the sustained reference values of lipid and vitamin D status under treatment that further preclude worsening of IMT in patients with advanced CKD.

Serum fibroblast growth factor-23 and incident hypertension: the Atherosclerosis Risk in Communities (ARIC) Study

OBJECTIVE

Elevated serum fibroblast growth factor-23 (FGF23), an endogenous hormone, is associated with disturbed mineral homeostasis, cardiovascular disease, and chronic kidney disease. It is unclear whether FGF23 impacts the development of incident hypertension. We examined the association between elevated FGF23 and incident hypertension in a community-based cohort.

METHOD

We investigated the association of serum FGF23, measured at baseline (1990-1992), with incident hypertension at two follow-up visits (1993-1995 and 1996-1998) in 7948 middle-aged men and women without hypertension at baseline participating in the Atherosclerosis Risk in Communities Study. Incident hypertension was determined by measured blood pressure (DBP ≥ 90 mmHg or SBP ≥ 140 mmHg) and/or self-reported hypertension medication use at follow-up exams. Complementary log-log models that accounted for interval censoring were used to model the association between FGF23 and incident hypertension.

RESULTS

During a median follow-up of 5.9 years, 27% (2152/7948) participants developed hypertension. A nonlinear association between serum FGF23 and incident hypertension was observed; only persons in the highest decile of serum FGF23 had an increased risk of incident hypertension. After adjustment for demographics, behaviors, and adiposity, the hazard ratio for incident hypertension was 1.24 (95% confidence interval: 1.11, 1.39) for the highest decile of FGF23 compared with the lowest quintile. The association was further attenuated in the final model after adjusting for renal function (hazard ratio: 1.21, 95% confidence interval: 1.08, 1.35).

CONCLUSION

High levels (≥60.6 pg/ml) of FGF23 are associated with a modestly increased risk of incident hypertension in the general population, independent of kidney function.

Occurrence and severity of non-occlusive mesenteric ischemia (NOMI) after cardiovascular surgery correlate with preoperatively assessed FGF-23 levels

Purpose

To evaluate the value of preoperatively assessed fibroblast growth factor 23 (FGF-23) levels and to correlate FGF-23 with angiographic findings in non-occlusive mesenteric (NOMI) ischemia using a standardized scoring system.

Materials and methods

Between 2/2011 and 3/2012 a total of 865 patients (median age: 67 years) underwent cardiovascular surgery during this ethics committee approved, prospective study. 65 of these patients had clinical suspicion of NOMI and consequently underwent catheter angiography of the superior mesenteric artery. Images were assessed using a standardized reporting system (Homburg-NOMI-Score). These data were correlated to following preoperative parameters of kidney function: cystatin C, creatinine, FGF-23 and estimated glomerular filtration rate (eGFR), and outcome data (death, acute renal failure) using linear and logistic regressions, as well as nonparametric tests.

Results

Significant correlations were found between FGF-23 and the angiographic appearance of NOMI (p = 0.03). Linear regression analysis showed no significant correlation to the severity of NOMI with creatinine (p = 0.273), cystatin C (p = 0.484), cystatin C eGFR (p = 0.914) and creatinine eGFR (p = 0.380). Logistic regression revealed a significant correlation between death and the Homburg-NOMI-Score (p<0.001), but not between development of NOMI and acute renal failure (p = 0.122). The ROC Analysis yielded an area under the curve of 0.695 (95% CI: 0.627–0.763) with a sensitivity of 0.672 and specificity of 0.658.

Conclusions

FGF-23 significantly correlates with the severity of NOMI, which is in contrast to other renal function parameters. The applied scoring system allows to predict mortality in NOMI patients.

Interorgan handling of fibroblast growth factor-23 in humans

Fibroblast growth factor-23 (FGF-23) accumulates in blood of patients with chronic kidney disease (CKD) and is associated both with cardiovascular complications and disease progression. However, our knowledge of the sites and mechanisms that regulate plasma FGF-23 is still incomplete. We measured plasma intact FGF-23 across the kidney, splanchnic organs, and lung in 11 patients [estimated glomerular filtration rate (eGFR) 60 ± 6 ml/min] during elective diagnostic cardiac catheterizations. In these patients FGF-23 was removed by the kidney, with a fractional extraction (FE) of ∼22%. The FE of FGF-23 across the kidney was similar to that of creatinine (∼17%, P = NS). In addition, the FGF-23 FE by the kidney was significantly directly related to eGFR (r = 0.709 P = 0.018) and to kidney creatinine FE (r = 0.736 P = 0.013) but only as a trend to plasma phosphate levels (r = 0.55, P = 0.18). There was no difference in FGF-23 levels in blood perfusing splanchnic organs and cardiopulmonary bed. However, the arterial-venous difference of FGF-23 across the lung was directly related to FGF-23 pulmonary artery levels, suggesting that the lung, and possibly the heart, participate in the homeostasis of plasma FGF-23 when its systemic levels are increased. Our data show that the human kidney is the only site for FGF-23 removal from blood and suggest that FGF-23 is predominantly removed by glomerular filtration. The kidney ability to remove FGF-23 from the circulation likely accounts for the early increase in blood of FGF-23 in patients with CKD.

The role of mineral and bone disorders in the development and progression of cardiac and renal pathology in patients with type 1 diabetes mellitus of long duration

AIMS

The objective of our study was to evaluate the role of mineral and bone metabolism disorders associated with chronic kidney disease (MBD-CKD) in the development and progression of cardiac and renal pathology in patients with type 1 diabetes mellitus (T1DM) of long duration.

METHODS

We investigated 96 patients with T1DM of long duration, with CKD at different stages (0-5), including patients on hemodialysis (HD) and with kidney transplantation (KT). Along with overall clinical examination, we assessed markers of MBD (calcium, phosphorus, parathormone, vitamin D, fibroblast growth factor (FGF) 23) and levels of cardiac injury marker (atrial natriuretic peptide, NT-proBNP). Multispiral computer tomography with Agatston index calculation was also included.

RESULTS

Decreased kidney function was associated with increased of levels phosphorus, parathormone, FGF 23, and vitamin D deficiency, with the highest deviation from the reference ranges seen in patients on HD with a very high risk of cardiovascular events. In KT patients with satisfactory graft function, these parameters were at the same levels as in patients with CKD stages 0-4. Progression of cardiovascular pathology was accompanied by elevation of NT-proBNP levels as CKD duration increased, decreased glomerular filtration rate, and were correlated with the main parameters of mineral homeostasis. The severity of coronary arteries calcification was associated with patient age and duration of T1DM and arterial hypertension.

CONCLUSIONS

Development and progression of kidney dysfunction is accompanied by MBD, a significant factor in progression of cardiac pathology, which remains a major cause of mortality in this patient population.

Serum phosphate is an independent predictor of the total aortic calcification volume in non-hemodialysis patients undergoing cardiovascular surgery

BACKGROUND

A high serum phosphate level is a well-known risk factor for vascular calcification (VC) in patients on hemodialysis (HD). However, the association between the serum phosphate level and VC in non-HD patients is unclear. Our aim was to assess the impact of serum phosphate level on aortic calcification (AC) volume in non-HD patients undergoing cardiovascular surgery.

METHODS

A total of 117 patients who underwent thoracoabdominal computed tomography as a preoperative general evaluation before cardiovascular surgery were enrolled. The total AC volume was quantified using the volume-rendering method by extracting the area ≥130HU within the entire aorta. The total AC volume index (AC-VI) was estimated as the total AC volume divided by the body surface area.

RESULTS

In the 117 patients (64.7±13.1 years, 39% women), the median total AC-VI was 1.23mL/m(2). The mean estimated glomerular filtration rate (eGFR), adjusted serum calcium levels, and serum phosphate levels were 63.8±19.9mL/min/1.73m(2), 9.1±0.4mg/dL, and 3.6±0.6mg/dL, respectively. When the patients were classified into four quartiles based on their total AC-VI value, the serum phosphate level showed a positive correlation with a probability of being in the highest AC-VI quartile (R(2)=0.0146, p=0.0383) whereas the adjusted serum calcium level did not show a significant correlation (R(2)=0.0040, p=0.2615). A similar relationship between the serum phosphate level, adjusted serum calcium level, and AC-VI was confirmed when the total AC-VI was divided into the thoracic AC-VI and abdominal AC-VI. Multivariate analysis indicated that the serum phosphate level was an independent positive predictor of higher total AC-VI quartiles (β=0.8013, p=0.0160).

CONCLUSIONS

An increase in serum phosphate level was associated with an increased AC burden in non-HD patients undergoing cardiovascular surgery.

High-Flux Hemodialysis Benefits Hemodialysis Patients by Reducing Serum FGF-23 Levels and Reducing Vascular Calcification

Background

High- and low-flux hemodialysis (HFHD and LFHD, respectively) are dialysis procedures designed to eliminate blood toxins that accumulate in end-stage renal disease. HFHD may reduce vascular calcification by removing serum fibroblast growth factor 23 (FGF-23). However, whether HFHD is better than LFHD is still under debate. We therefore compared the efficacy of HFHD and LFHD in controlling FGF-23 and vascular calcification.

Material/Methods

Fifty hemodialysis patients were recruited and randomly treated with either HFHD or LFHD. Fasting venous blood was collected at baseline, six months, and twelve months after the treatment. We then measured levels of FGF-23, calcium, phosphorus, parathyroid hormone, and alkaline phosphatase. Further, abdominal lateral radiographs were taken to calculate aorta abdominalis calcification scores (AACs).

Results

Compared to the LFHD group, FGF-23 and AACs in the HFHD group significantly decreased after 12 months treatment (p=0.049 and p=0.002, respectively). AACs were positively correlated with FGF-23 in all patients (p=0.004), the HFHD group alone (p=0.040), and the LFHD group alone (p=0.037). We also found that older patients, patients with higher blood phosphorus levels, and higher FGF-23 levels had an increased risk of aorta abdominalis calcification (p=0.048, p=0.003, p=0.001, respectively). HFHD was more able to reduce the risk of aorta abdominalis calcification than LFHD (p=0.003).

Conclusions

FGF-23 is an independent risk factor for the development of vascular calcification. HFHD may benefit hemodialysis patients by reducing serum FGF-23 levels and controlling vascular calcification.

Increased FGF23 serum level is associated with unstable carotid plaque in type 2 diabetic subjects with internal carotid stenosis

Background

The object of this study was to investigate the potential role of FGF23 on plaque stability in type 2 diabetic patients with internal carotid artery stenosis.

Methods

In this retrospective observational study, we analyzed FGF23 serum level in 361 type 2 diabetic patients with internal carotid artery stenosis undergoing carotid endarterectomy and in 598 diabetic controls without carotid atherosclerosis.

Results

We found that FGF23 median serum levels was significantly higher in patients than in diabetic controls [67.7 (59.5–77.8) pg/mL and 43.89 (37.5–50.4), P < 0.001] and was significantly and independently associated with unstable plaque in patients with internal carotid artery stenosis [OR, 5,71 (95 % CI, 2.09–15.29].

Conclusions

We have found, for the first time, that FGF23 could be associated with unstable plaque in type 2 diabetic patients with internal carotid artery stenosis.

Prevalence and correlates of mitral annular calcification in adults with chronic kidney disease: Results from CRIC study

BACKGROUND

Risk factors for mitral annular calcification (MAC) and cardiovascular disease (CVD) demonstrate significant overlap in the general population. The aim of this paper is to determine whether there are independent relationships between MAC and demographics, traditional and novel CVD risk factors using cardiac CT in the Chronic Renal Insufficiency Cohort (CRIC) in a cross-sectional study.

METHODS

A sample of 2070 subjects underwent coronary calcium scanning during the CRIC study. Data were obtained for each participant at time of scan.

SUBJECTS

were dichotomized into the presence and absence of MAC. Differences in baseline demographic and transitional risk factor data were evaluated across groups. Covariates used in multivariable adjustment were age, gender, BMI, HDL, LDL, lipid lowering medications, smoking status, family history of heart attack, hypertension, diabetes mellitus, phosphate, PTH, albuminuria, and calcium.

RESULTS

Our study consisted of 2070 subjects, of which 331 had MAC (prevalence of 16.0%). The mean MAC score was 511.98 (SD 1368.76). Age and white race remained independently associated with presence of MAC. Decreased GFR was also a risk factor. African American and Hispanic race, as well as former smoking status were protective against MAC. In multivariable adjusted analyses, the remaining covariates were not significantly associated with MAC. Among renal covariates, elevated phosphate was significant.

CONCLUSION

In the CRIC population, presence of MAC was independently associated with age, Caucasian race, decreased GFR, and elevated phosphate. These results are suggested by mechanisms of dysregulation of inflammation, hormones, and electrolytes in subjects with renal disease.

Fibroblast growth factor 23: associations with antiretroviral therapy in patients co-infected with HIV and hepatitis C

OBJECTIVES

Fibroblast growth factor 23 (FGF23) has been associated with cardiovascular mortality. We estimate associations between the level of plasma FGF23 and exposure to abacavir (ABC) and to other components of antiretroviral therapy in patients co-infected with HIV and hepatitis C.

METHODS

Both intact and c-terminal FGF23 were measured in plasma using commercial assays for a sub-cohort of 295 patients selected at random from the 1150 patients enrolled in the Canadian Co-infection Cohort. The multiplicative effects of antiretroviral drug exposures and covariates on median FGF23 were then estimated using a hierarchical Bayesian model.

RESULTS

The median level of intact FGF23 was independent of either past or recent exposure to abacavir, with multiplicative ratios of 1.00 and 1.07, 95% credible intervals 0.90-1.12 and 0.94-1.23, respectively. Median intact FGF23 tended to increase with past use of both nonnucleoside reverse-transcriptase inhibitors and protease inhibitors, but tended to decrease with recent use of either tenofovir, efavirenz or lopinavir. There were no obvious associations between the median level of c-terminal FGF23 and individual drugs or drug classes. Age, female gender, smoking and the aspartate aminotransferase to platelet ratio index were all associated with a higher median c-terminal FGF23 but not with a higher median intact FGF23.

CONCLUSIONS

The level of FGF23 in plasma was independent of exposure to ABC. Lower levels of intact FGF23 with recent use of tenofovir, efavirenz or lopinavir may reflect their adverse effects on bone and vitamin D metabolism relative to other drugs in their respective drug classes.

Novel iron-containing phosphate binders for treatment of hyperphosphatemia

INTRODUCTION

Hyperphosphatemia is a frequent complication of chronic kidney disease and is associated with increased mortality. Despite side effects, risk of accumulation and high costs, phosphate binders (PBs) have become the crucial cornerstone of therapy. The iron-containing PB sucroferric oxyhydroxide (SO) and ferric citrate hydrate (FCH) have entered the market and other candidates are prior market entry.

AREAS COVERED

A literature search was performed using MEDLINE and EMBASE databases to identify references on iron-containing PB with particular regard to efficacy, safety and potential benefits. Additional hand searches were conducted along with a full-text review of any citation that appeared relevant.

EXPERT OPINION

On the highly competitive market, where the 'ideal' PB is still unknown, novel substances that offer clear benefits over available drugs are desired. Although SO and FCH showed similar efficacy and safety compared to sevelamer, head-to-head studies with lanthanum carbonate are absent. Clinical 1-year data in a limited patient cohort suggested improved adherence for SO and a large randomized controlled trial showed significant reduction in hospitalizations and costs for FCH. Additional large randomized controlled trials have now to prove these possible advantages. Cost-effectiveness in comparison to other PB and the exclusion of significant harms under long-term treatment will determine the future use of both drugs.

A single preoperative FGF23 measurement is a strong predictor of outcome in patients undergoing elective cardiac surgery: a prospective observational study

Introduction

Several scoring systems have been developed to predict postoperative mortality and complications in patients undergoing cardiac surgery. However, these computer-based calculations are time- and cost-intensive. A simple but highly predictive test for postoperative risk would be of clinical benefit with respect to increasingly scarce hospital resources. We therefore assessed the predictive power of fibroblast growth factor 23 (FGF23) measurement compared with an established scoring system.

Methods

We conducted a prospective interdisciplinary observational study at the Saarland University Medical Centre that included 859 patients undergoing elective cardiac surgery between January 2010 and March 2011 with a median follow-up after discharge of 822 days. We compared a single preoperative measurement of FGF23 as a prognostic tool with the 18 parameters comprising EuroSCORE II with respect to postoperative mortality, acute kidney injury, non-occlusive mesenteric ischemia, clinical course and long-term outcome.

Results

Preoperative FGF23 levels were highly predictive of postoperative outcome and complications. The predictive value of FGF23 for mortality in the receiver operating characteristic curve was greater than the EuroSCORE II (area under the curve: 0.800 versus 0.725). Moreover, preoperative FGF23 independently predicted postoperative acute kidney injury and non-occlusive mesenteric ischemia comparably to the EuroSCORE II. Finally, FGF23 was found to be an independent predictor of clinical course parameters, including duration of surgery, ventilation time and length of stay.

Conclusions

In patients undergoing elective cardiac surgery, a simple preoperative FGF23 measurement is a powerful indicator of surgical mortality, postoperative complications and long-term outcome. Its utility compares to the widely used EuroSCORE II.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-015-0925-6) contains supplementary material, which is available to authorized users.

Plasma fibroblast growth factor 23 and risk of cardiovascular disease: results from the EPIC-Germany case-cohort study

Increased fibroblast growth factor 23 (FGF23) concentrations have emerged as a novel risk factor for heart failure and stroke but not for myocardial infarction (MI). Yet, most studies on MI were conducted in coronary artery disease (CAD) patients and the elderly. Evidence is unclear in subjects without CAD and for stroke subtypes. We investigated the relationships between FGF23 and overall major cardiovascular endpoints, incident MI, ischemic (IS) and haemorrhagic stroke (HS) in middle-aged adults without pre-existing cardiovascular disease. We used a case-cohort study nested within the European Prospective Investigation into Cancer and Nutrition-Germany, including a randomly drawn subcohort (n = 1,978), incident MI (n = 463) and stroke cases (n = 359 IS; n = 88 HS) identified during a mean follow-up of 8.2 years. Compared with participants with FGF23 levels in the lowest quartile, those in the highest quartile had a 36% increased risk for cardiovascular events [hazard ratio: 1.36, 95% confidence interval (CI): 1.02-1.82] after adjustment for established cardiovascular risk factors, patahyroid hormone and 25-hydroxyvitamin D3 levels, dietary calcium and phosphorus intake, and kidney function. However, sub-analyses revealed significant relationships with risk of MI and HS, but not IS. Compared with the lowest quartile, individuals in the top two FGF23 quartiles had a 1.62 (95% CI 1.07-2.45) fold increased risk for MI and a 2.61 (95% CI 1.23-5.52) fold increase for HS. Increased FGF23 emerged as a risk factor for both MI and HS. Further studies are warranted to confirm these results and to identify underlying mechanisms.

Fibroblast growth factor 23 in acute myocardial infarction complicated by cardiogenic shock: a biomarker substudy of the Intraaortic Balloon Pump in Cardiogenic Shock II (IABP-SHOCK II) trial

Introduction

Cardiogenic shock (CS) is the leading cause of death in patients hospitalized with acute myocardial infarction (AMI). Biomarkers might help in risk stratification and understanding of pathophysiology. Preliminary data suggests that patients with CS face a profound increase in the osteocyte-derived hormone fibroblast growth factor 23 (FGF-23), which acts as a negative regulator of serum phosphate levels. The present study aimed to assess the predictive role of FGF-23 for clinical outcome in a large cohort of CS patients with and without renal dysfunction.

Methods

In the randomized Intraaortic Balloon Pump in Cardiogenic Shock II (IABP-SHOCK II) trial, 600 patients with CS complicating AMI were assigned to therapy with or without IABP. Our predefined biomarker substudy included 182 patients. Blood sampling was performed in a standardized procedure at three different time points (day 1 (day of admission), day 2 and day 3). Differences in outcome of patients with FGF-23 levels < and > median were compared by log-rank testing. Stepwise logistic regression modeling was performed to identify predictors of death at 30 days and Cox regression analysis for time to death during the first year.

Results

At all three time points, nonsurvivors had significantly higher FGF-23 levels compared to survivors (P <0.001 for all). Patients with FGF-23 levels above the median (395 RU/mL [interquartile range 102;2,395]) were characterized by an increased 30-day mortality and 1-year mortality. In multivariable analysis FGF-23 levels remained independent predictors for 30-day (odds ratio per 10log 1.80, 95% confidence interval (CI) 1.11 to 2.92; P = 0.02) and 1-year mortality (hazard ratio 1.50, 95% CI 1.11 to 2.04, P = 0.009). After stratifying the patients according to their baseline serum creatinine levels, the negative prognostic association of increased FGF-23 was only significant in those with serum creatinine greater than median.

Conclusions

In CS, high levels of FGF-23 are independently related to a poor clinical outcome. However, this prognostic association appears only to apply in patients with impaired renal function.

Trial registration

ClinicalTrials.gov NCT00491036. Registered 22 June 2007.

Circulating fibroblast growth factor-23 and the incidence of atrial fibrillation: the Atherosclerosis Risk in Communities study

Background

Increased concentrations of circulating fibroblast growth factor 23 (FGF‐23) have been associated with higher risk of cardiovascular disease. The association between FGF‐23 and the risk of atrial fibrillation (AF), a common arrhythmia, is less defined. Thus, we explored whether FGF‐23 concentration was associated with AF incidence in a large community‐based cohort.

Methods and Results

We studied 12 349 men and women enrolled in the Atherosclerosis Risk in Communities (ARIC) study, without prevalent AF at baseline in 1990–1992. Serum intact FGF‐23 concentration was measured with the Kainos 2‐site ELISA. Incident AF through 2010 was ascertained from study ECGs and hospital discharge codes. Cox proportional hazards models adjusted for potential confounding factors, including kidney function, were used to estimate the association between FGF‐23 and AF risk. We identified 1572 AF events during a mean follow‐up of 17 years. In multivariable analysis, a difference of 1 SD (16 pg/mL) in baseline FGF‐23 was not associated with the risk of AF (hazard ratio [HR], 1.04; 95% confidence interval [CI], 0.99, 1.09). Results were similar when FGF‐23 was modeled in quartiles (HR, 1.09; 95% CI, 0.94, 1.26, comparing extreme quartiles). Reduced kidney function was associated with increased AF risk across quartiles of FGF‐23 levels.

Conclusion

In this large community‐based cohort, baseline FGF‐23 levels were not associated with AF risk independently of kidney function. Our results do not support a major role for FGF‐23 as a risk factor for AF or as a mediator of the association between chronic kidney disease and AF.

FGF-23 is associated with increased disease severity and early mortality in cardiogenic shock

BACKGROUND

Despite the increased use of percutaneous interventions, infarction-related cardiogenic shock (CS) is still associated with high mortality. Biomarkers might be helpful to identify patients at risk, and point towards novel therapeutic strategies in CS. The phosphaturic hormone fibroblast growth factor 23 (FGF-23) has recently been introduced as a predictor for mortality in patients with chronic systolic heart failure. However, its predictive role in CS has not been investigated so far.

METHODS AND RESULTS

FGF-23 was measured in 51 patients with CS. Eighteen patients with uncomplicated acute myocardial infarction (AMI) and 940 patients with stable coronary artery disease (CAD) undergoing elective coronary angiography included in a previous study served as control groups. Compared with patients with stable CAD, FGF-23 was profoundly elevated in patients with CS, but not in patients with uncomplicated AMI (CAD: 131.1 ± 9.5; AMI: 175.3 ± 57.2; CS: 1684.4 ± 591.7 rU/ml, p<0.0001 CS vs. CAD). In patients with CS, FGF-23 correlated significantly with the SAPS II score (r=0.461, p=0.0003) and NT-pro BNP levels (r=0.489, p=0.001). Patients were stratified as "survivors" and "non-survivors" according to their 28-day mortality. The overall 28-day-mortality-rate was 37%. Non-survivors of CS showed significantly higher FGF-23 levels compared with survivors (3260.1 ± 1514.7 vs. 847.9 ± 182.4 rU/ml, p=0.028). In the ROC curve analysis, FGF-23 levels predicted 28-day mortality (area under the curve (AUC) 0.686, p=0.028), and FGF-23 level of 1180 rU/ml was identified as optimal cut-off value. In a multivariate Cox proportional hazard model adjusted for gender, blood pressure, ejection fraction and levels of creatine kinase, FGF-23 levels above 1180 rU/ml significantly predicted 28-day mortality (hazard ratio (HR) 2.74, 95% CI 1.01-7.04, p=0.037).

CONCLUSION

In CS, a tremendous increase in FGF-23 occurs, and high levels of FGF-23 are associated with poor outcome.

Fibroblast growth factor-23 and incident coronary heart disease, heart failure, and cardiovascular mortality: the Atherosclerosis Risk in Communities study

BACKGROUND

Fibroblast growth factor-23 (FGF-23) is a hormone involved in phosphorous regulation and vitamin D metabolism that may be associated with cardiovascular risk, and it is a potential target for intervention. We tested whether elevated FGF-23 is associated with incident coronary heart disease, heart failure, and cardiovascular mortality, even at normal kidney function.

METHODS AND RESULTS

A total of 11 638 Atherosclerosis Risk In Communities study participants, median age 57 at baseline (1990-1992), were followed through 2010. Cox regression was used to evaluate the independent association of baseline serum active FGF-23 with incident outcomes. Models were adjusted for traditional cardiovascular risk factors and estimated glomerular filtration rate. During a median follow-up of 18.6 years, 1125 participants developed coronary heart disease, 1515 developed heart failure, and 802 died of cardiovascular causes. For all 3 outcomes, there was a threshold, whereby FGF-23 was not associated with risk at <40 pg/mL but was positively associated with risk at >40 pg/mL. Compared with those with FGF-23 <40 pg/mL, those in the highest FGF-23 category (≥ 58.8 pg/mL) had a higher risk of incident coronary heart disease (adjusted hazard ratio, 95% CIs: 1.65, 1.40 to 1.94), heart failure (1.75, 1.52 to 2.01), and cardiovascular mortality (1.65, 1.36 to 2.01). Associations were modestly attenuated but remained statistically significant after further adjustment for estimated glomerular filtration rate. In stratified analyses, similar results were observed in African Americans and among persons with normal kidney function.

CONCLUSIONS

High levels of serum FGF-23 were associated with increased risk of coronary heart disease, heart failure, and cardiovascular mortality in this large, biracial, population-based cohort. This association was independent of traditional cardiovascular risk factors and kidney function.

Associations of FGF-23 and sKlotho with cardiovascular outcomes among patients with CKD stages 2-4

BACKGROUND AND OBJECTIVES

CKD-mineral and bone disorders (CKD-MBD) measures contribute to cardiovascular morbidity in patients with CKD. Among these, fibroblast growth factor (FGF)-23 and its coreceptor Klotho may exert direct effects on vascular and myocardial tissues. Klotho exists in a membrane-bound and a soluble form (sKlotho). Recent experimental evidence suggests sKlotho has vasculoprotective functions.

DESIGN, SETTINGS, PARTICIPANTS, & MEASUREMENTS

Traditional and novel CKD-MBD variables were measured among 444 patients with CKD stages 2-4 recruited between September 2008 and November 2012 into the ongoing CARE FOR HOMe study. Across tertiles of baseline sKlotho and FGF-23, the incidence of two distinct combined end points was analyzed: (1) the first occurrence of an atherosclerotic event or death from any cause and (2) the time until hospital admission for decompensated heart failure or death from any cause.

RESULTS

Patients were followed for 2.6 (interquartile range, 1.4-3.6) years. sKlotho tertiles predicted neither atherosclerotic events/death (fully adjusted Cox regression analysis: hazard ratio [HR] for third versus first sKlotho tertile, 0.75 [95% confidence interval (95% CI), 0.43-1.30]; P=0.30) nor the occurrence of decompensated heart failure/death (HR for third versus first sKlotho tertile, 0.81 [95% CI, 0.39-1.66]; P=0.56). In contrast, patients in the highest FGF-23 tertile had higher risk for both end points in univariate analysis. Adjustment for kidney function attenuated the association between FGF-23 and atherosclerotic events/death (HR for third versus first FGF-23 tertile, 1.23 [95% CI, 0.58-2.61]; P=0.59), whereas the association between FGF-23 and decompensated heart failure/death remained significant after adjustment for confounders (HR for third versus first FGF-23 tertile, 4.51 [95% CI, 1.33-15.21]; P=0.02).

CONCLUSIONS

In this prospective observational study of limited sample size, sKlotho was not significantly related to cardiovascular outcomes. FGF-23 was significantly associated with future decompensated heart failure but not incident atherosclerotic events.

Coronary artery calcification in chronic kidney disease: An update

Arterial calcification is a well-recognized complication of advanced atherosclerosis. Chronic kidney disease (CKD) is characterized by significantly more pronounced, disseminated and fast-progressing calcification of the vascular system, including the coronary arteries. New computed tomography-based imaging techniques allow for the noninvasive assessment and monitoring of calcification in different vascular sites. Coronary artery calcification (CAC) develops early in the course of CKD and is tightly associated with mineral and bone disorders, which include but are not limited to secondary hyperparathyroidism. In this review, recent data on the pathogenesis of CAC development and progression are discussed, with a special emphasis on fibroblast growth factor 23 and its co-receptor, klotho. The prevalence, progression and prognostic significance of CAC are reviewed separately for patients with end-stage renal disease treated with dialysis, kidney transplant recipients and patients with earlier stages of CKD. In the last section, therapeutic considerations are discussed, with special attention paid to the importance of treatment that addresses mineral and bone disorders of CKD.

Treatment of phosphate retention: The earlier the better?

Over the last 15 years, our knowledge and understanding of the underlying mechanisms involved in the regulation of calcium and phosphate homeostasis in chronic kidney disease have advanced dramatically. Contrary to general opinion in the 20(th) century that moderate hypercalcemia and hyperphosphatemia were acceptable in treating secondary hyperparathyroidism, the calcium and phosphate load is increasingly perceived to be a major trigger of vascular and soft tissue calcification. The current treatment options are discussed in view of historical developments and the expectations of the foreseeable future, focusing on the early treatment of hyperphosphatemia. At present, we lack indisputable evidence that active intervention using currently available drugs is of benefit to patients in chronic kidney disease stages 3 and 4.

Cytokine networking of innate immunity cells: a potential target of therapy

Innate immune cells, particularly macrophages and epithelial cells, play a key role in multiple layers of immune responses. Alarmins and pro-inflammatory cytokines from the IL (interleukin)-1 and TNF (tumour necrosis factor) families initiate the cascade of events by inducing chemokine release from bystander cells and by the up-regulation of adhesion molecules required for transendothelial trafficking of immune cells. Furthermore, innate cytokines produced by dendritic cells, macrophages, epithelial cells and innate lymphoid cells seem to play a critical role in polarization of helper T-cell cytokine profiles into specific subsets of Th1/Th2/Th17 effector cells or regulatory T-cells. Lastly, the innate immune system down-regulates effector mechanisms and restores homoeostasis in injured tissue via cytokines from the IL-10 and TGF (transforming growth factor) families mainly released from macrophages, preferentially the M2 subset, which have a capacity to induce regulatory T-cells, inhibit the production of pro-inflammatory cytokines and induce healing of the tissue by regulating extracellular matrix protein deposition and angiogenesis. Cytokines produced by innate immune cells represent an attractive target for therapeutic intervention, and multiple molecules are currently being tested clinically in patients with inflammatory bowel disease, rheumatoid arthritis, systemic diseases, autoinflammatory syndromes, fibrosing processes or malignancies. In addition to the already widely used blockers of TNFα and the tested inhibitors of IL-1 and IL-6, multiple therapeutic molecules are currently in clinical trials targeting TNF-related molecules [APRIL (a proliferation-inducing ligand) and BAFF (B-cell-activating factor belonging to the TNF family)], chemokine receptors, IL-17, TGFβ and other cytokines.

Association between circulating fibroblast growth factor 23, α-Klotho, and the left ventricular ejection fraction and left ventricular mass in cardiology inpatients

Background

Fibroblast growth factor 23 (FGF23), with its co-receptor Klotho, plays a crucial role in phosphate metabolism. Several recent studies suggested that circulating FGF23 and α-Klotho concentrations might be related to cardiovascular abnormalities in patients with advanced renal failure.

Purpose

Using data from 100 cardiology inpatients who were not undergoing chronic hemodialysis, the association of circulating levels of FGF23, α-Klotho, and other calcium-phosphate metabolism-related parameters with the left ventricular ejection fraction (LVEF) and left ventricular mass (LVM) was analyzed.

Methods and Results

LVEF was measured using the modified Simpson method for apical 4-chamber LV images and the LVM index (LVMI) was calculated by dividing the LVM by body surface area. Univariate analysis showed that log transformed FGF23, but not that of α-Klotho, was significantly associated with LVEF and LVMI with a standardized beta of −0.35 (P<0.001) and 0.26 (P<0.05), respectively. After adjusting for age, sex, estimated glomerular filtration rate, and serum concentrations of intact parathyroid hormone, and 25-hydroxyvitamin D as covariates into the statistical model, log-transformed FGF23 was found to be a statistically positive predictor for decreased left ventricular function and left ventricular hypertrophy.

Conclusions

In cardiology department inpatients, circulating FGF23 concentrations were found to be associated with the left ventricular mass and LVEF independent of renal function and other calcium-phosphate metabolism-related parameters. Whether modulation of circulating FGF23 levels would improve cardiac outcome in such a high risk population awaits further investigation.

Single FGF-23 measurement and time-averaged plasma phosphate levels in hemodialysis patients

BACKGROUND AND OBJECTIVES

Plasma phosphate levels display considerable intraindividual variability. The phosphatonin fibroblast growth factor 23 is a central regulator of plasma phosphate levels, and it has been postulated to be a more stable marker than conventional CKD-mineral and bone disorder parameters. Thus, fibroblast growth factor 23 has been hypothesized to reflect time-averaged plasma phosphate levels in CKD patients.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Among 40 patients from the outpatient dialysis center, serial measurements of plasma calcium and phosphate (before every dialysis session) as well as C-terminal fibroblast growth factor 23, parathyroid hormone, and alkaline phosphatase (one time weekly) were performed over a study period of 4 weeks in November and December of 2011. Intraindividual variability of repeated plasma fibroblast growth factor 23 measurements compared with other CKD-mineral and bone disorder markers was tested, and the association of a single plasma fibroblast growth factor 23 measurement with time-averaged plasma phosphate levels was analyzed.

RESULTS

Against expectations, intraindividual variability of fibroblast growth factor 23 (median coefficient of variation=27%; interquartile range=20-35) was not lower than variability of plasma phosphate (median coefficient of variation=15%; interquartile range=10-20), parathyroid hormone (median coefficient of variation=24%; interquartile range=15-39), plasma calcium (median coefficient of variation=3%; interquartile range=2-4), or alkaline phosphatase (median coefficient of variation=5%; interquartile range=3-10). Moreover, the correlation between the last fibroblast growth factor 23 measurement after 4 weeks and time-averaged plasma phosphate did not surpass the correlation between the last fibroblast growth factor 23 measurement and a single plasma phosphate value (r=0.67, P<0.001; r=0.76, P<0.001, respectively).

CONCLUSIONS

Surprisingly, fibroblast growth factor 23 was not more closely associated to time-averaged plasma phosphate levels than a single plasma phosphate value, and it did not show a lower intraindividual variability than other tested markers of CKD-mineral and bone disorder. Thus, fibroblast growth factor 23 should not be used in clinical practice as a reflector of time-averaged plasma phosphate levels.

Immune dysfunction in uremia

Kidney dysfunction leads to disturbed renal metabolic activities and to impaired glomerular filtration, resulting in the retention of toxic solutes affecting all organs of the body. Cardiovascular disease (CVD) and infections are the main causes for the increased occurrence of morbidity and mortality among patients with chronic kidney disease (CKD). Both complications are directly or indirectly linked to a compromised immune defense. The specific coordinated roles of polymorphonuclear leukocytes (PMNLs), monocytes/macrophages, lymphocytes and antigen-presenting cells (APCs) in maintaining an efficient immune response are affected. Their normal response can be impaired, giving rise to infectious diseases or pre-activated/primed, leading to inflammation and consequently to CVD. Whereas the coordinated removal via apoptosis of activated immune cells is crucial for the resolution of inflammation, inappropriately high apoptotic rates lead to a diminished immune response. In uremia, the balance between pro- and anti-inflammatory and between pro- and anti-apoptotic factors is disturbed. This review summarizes the interrelated parameters interfering with the immune response in uremia, with a special focus on the non-specific immune response and the role of uremic toxins.