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

Non-Classical Effects of FGF23: Molecular and Clinical Features

This article reviews the role of fibroblast growth factor 23 (FGF23) protein in phosphate metabolism, highlighting its regulation of vitamin D, parathyroid hormone, and bone metabolism. Although it was traditionally thought that phosphate-calcium homeostasis was controlled exclusively by parathyroid hormone (PTH) and calcitriol, pathophysiological studies revealed the influence of FGF23. This protein, expressed mainly in bone, inhibits the renal reabsorption of phosphate and calcitriol formation, mediated by the α-klotho co-receptor. In addition to its role in phosphate metabolism, FGF23 exhibits pleiotropic effects in non-renal systems such as the cardiovascular, immune, and metabolic systems, including the regulation of gene expression and cardiac fibrosis. Although it has been proposed as a biomarker and therapeutic target, the inhibition of FGF23 poses challenges due to its potential side effects. However, the approval of drugs such as burosumab represents a milestone in the treatment of FGF23-related diseases.

Circulating Monocyte Chemoattractant Protein-1 in Patients with Cardiogenic Shock Complicating Acute Myocardial Infarction Treated with Mild Hypothermia: A Biomarker Substudy of SHOCK-COOL Trial

Background: There is evidence that monocyte chemoattractant protein-1 (MCP-1) levels reflect the intensity of the inflammatory response in patients with cardiogenic shock (CS) complicating acute myocardial infarction (AMI) and have a predictive value for clinical outcomes. However, little is known about the effect of mild therapeutic hypothermia (MTH) on the inflammatory response in patients with CS complicating AMI. Therefore, we conducted a biomarker study to investigate the effect of MTH on MCP-1 levels in patients with CS complicating AMI. Methods: In the randomized mild hypothermia in cardiogenic shock (SHOCK-COOL) trial, 40 patients with CS complicating AMI were enrolled and assigned to MTH (33 °C) for 24 h or normothermia at a 1:1 ratio. Blood samples were collected at predefined time points at the day of admission/day 1, day 2 and day 3. Differences in MCP-1 levels between and within the MTH and normothermia groups were assessed. Additionally, the association of MCP-1 levels with the risk of all-cause mortality at 30 days was analyzed. Missing data were accounted for by multiple imputation as sensitivity analyses. Results: There were differences in MCP-1 levels over time between patients in MTH and normothermia groups (P for interaction = 0.013). MCP-1 levels on day 3 were higher than on day 1 in the MTH group (day 1 vs day 3: 21.2 [interquartile range, 0.25–79.9] vs. 125.7 [interquartile range, 87.3–165.4] pg/mL; p = 0.006) and higher than in the normothermia group at day 3 (MTH 125.7 [interquartile range, 87.3–165.4] vs. normothermia 12.3 [interquartile range, 0–63.9] pg/mL; p = 0.011). Irrespective of therapy, patients with higher levels of MCP-1 at hospitalization tended to have a decreased risk of all-cause mortality at 30 days (HR, 2.61; 95% CI 0.997–6.83; p = 0.051). Conclusions: The cooling phase of MTH had no significant effect on MCP-1 levels in patients with CS complicating AMI compared to normothermic control, whereas MCP-1 levels significantly increased after rewarming. Trial registration: NCT01890317.

Growth factors: avenues for the treatment of myocardial infarction and potential delivery strategies

Acute myocardial infarction (AMI) is one of the leading causes of death worldwide. Despite recent advances in clinical management, reoccurence of heart failure after AMI remains high, in part because of the limited capacity of cardiac tissue to repair after AMI-induced cell death. Growth factor-based therapy has emerged as an alternative AMI treatment strategy. Understanding the underlying mechanisms of growth factor cardioprotective and regenerative actions is important. This review focuses on the function of different growth factors at each stage of the cardiac repair process. Recent evidence for growth factor therapy in preclinical and clinical trials is included. Finally, different delivery strategies are reviewed with a view to providing workable strategies for clinical translation.

Laboratory Predictors of Prognosis in Cardiogenic Shock Complicating Acute Myocardial Infarction

Cardiogenic shock is a state of reduced cardiac output leading to hypotension, pulmonary congestion, and hypoperfusion of tissues and vital organs. Despite the advances in intensive care over the last years, the morbidity and mortality of patients remain high. The available studies of patients with cardiogenic shock suggest a connection between clinical variables, the level of biomarkers, the results of imaging investigations, strategies of management and the outcome of this group of patients. The management of patients with cardiogenic shock initially complicating acute myocardial infarction is challenging, and the number of studies in this area is growing fast. The purpose of this review is to summarize the currently available evidence on cardiogenic shock initially complicating acute myocardial infarction with particular attention to predictors of prognosis, focusing on laboratory variables (established and new), and to discuss the practical implementation. Currently available scoring systems developed during the past few decades predict the clinical outcome of this group of patients using some of the established biomarkers among other variables. With the new laboratory biomarkers that have shown their predictive value in cardiogenic shock outcomes, a new design of scoring systems would be of interest. Identifying high-risk patients offers the opportunity for early decision-making.

Comprehensive Expression Analysis of Cardiac Fibroblast Growth Factor 23 in Health and Pressure-induced Cardiac Hypertrophy

Enhanced fibroblast growth factor 23 (FGF23) is associated with left ventricular hypertrophy (LVH) in patients with chronic kidney and heart disease. Experimentally, FGF23 directly induces cardiac hypertrophy and vice versa cardiac hypertrophy stimulates FGF23. Besides the bone, FGF23 is expressed by cardiac myocytes, whereas its synthesis in other cardiac cell types and its paracrine role in the heart in health and disease is unknown. By co-immunofluorescence staining of heart tissue of wild-type mice, we show that Fgf23 is expressed by cardiac myocytes, fibroblasts and endothelial cells. Cardiac Fgf23 mRNA and protein level increases from neonatal to six months of age, whereas no age-related changes in bone Fgf23 mRNA expression were noted. Cardiac myocyte-specific disruption of Fgf23 using Cre-LoxP system (Fgf23fl/fl/cre+) caused enhanced mortality, but no differences in cardiac function or structure. Although pressure overload-induced cardiac hypertrophy induced by transverse aortic constriction (TAC) resulted in a slightly worse phenotype with a more severe reduced ejection fraction, higher end-systolic volume and more enlarged systolic LV diameter in Fgf23fl/fl/cre+ mice compared to controls, this was not translated to any worse cellular hypertrophy, fibrosis or chamber remodeling. TAC induced Fgf23 mRNA expression in whole cardiac tissue in both genotypes. Interestingly, co-immunofluorescence staining revealed enhanced Fgf23 synthesis in cardiac fibroblasts and endothelial cells but not in cardiac myocytes. RNA sequencing of isolated adult cardiac myocytes, cardiac fibroblasts and endothelial cells confirmed significantly higher Fgf23 transcription in cardiac fibroblasts and endothelial cells after TAC. Our data indicate that Fgf23 is physiologically expressed in various cardiac cell types and that cardiac fibroblasts and endothelial cells might be an important source of FGF23 in pathological conditions. In addition, investigations in Fgf23fl/fl/cre+ mice suggest that cardiac myocyte-derived FGF23 is needed to maintain cardiac function during pressure overload.

FGFR4 and Klotho Polymorphisms Are Not Associated with Cardiovascular Outcomes in Chronic Kidney Disease

INTRODUCTION

High plasma fibroblast growth factor 23 (FGF-23) predicts cardiovascular events in chronic kidney disease (CKD) patients. Experimental evidence suggests FGF receptor 4 (FGFR4) activation by FGF-23, and deficiency of the soluble form of its co-receptor Klotho promotes left-ventricular hypertrophy (LVH). To evaluate the clinical relevance of these findings, a Mendelian randomization study analyzed the association of genetic variants of FGFR4 and Klotho with echocardiographic parameters and cardiac events in CKD patients.

METHODS

The prospective Cardiovascular and Renal Outcome in CKD 2-4 Patients-The Fourth Homburg Evaluation study recruited CKD G2-G4 patients, of whom 519 consented to SNP genotyping (FGFR4: rs351855; Klotho: rs9536314). Echocardiographic examinations at baseline and 5 years later assessed prevalence of LVH by measurement of left-ventricular mass index (LVMI). Patients were followed for 5.1 ± 2.1 years for the primary endpoints of cardiac decompensation and atherosclerotic cardiovascular disease (ASCVD).

RESULTS

Carriers of the different alleles did neither differ in baseline LVMI (rs351855: p = 0.861; rs9536314: p = 0.379) nor in LVMI changes between baseline and follow-up (rs351855: p = 0.181; rs9536314: p = 0.995). Hundred and four patients suffered cardiac decompensation, and 144 patients had ASCVD. Time to cardiac decompensation (rs351855: p = 0.316; rs9536314: p = 0.765) and ASCVD (p = 0.508 and p = 0.800, respectively) did not differ between carriers of different alleles.

DISCUSSION/CONCLUSION

rs351855 and rs9536314 were not associated with LVMI or cardiac events. These findings do not provide evidence for a relevant clinical role of either FGFR4 stimulation or soluble form of Klotho deficiency in LVH development.

Association of Lymphocyte to Monocyte Ratio and Risk of in-Hospital Mortality in Patients with Cardiogenic Shock: A Propensity Score Matching Study

Background

Lymphocyte to monocyte ratio (LMR) has been long implicated in the prediction of many inflammatory-related diseases. However, the possible value as prognostic marker of LMR have not been evaluated in cardiogenic shock (CS) patients. The aim of the study was to assess the relationship between LMR on admission and in-hospital mortality in CS patients.

Methods

Data on patients diagnosed with CS were extracted from the Medical Information Mart for Intensive Care-IV (MIMIC-IV) database. We performed a single-institution, retrospective study of 1487 CS patients and determined the optimal cut-off for LMR by X-tile software. Propensity score matching (PSM) and inverse probabilities of treatment weighting (IPTW) were conducted to control confounders. Cox proportional hazards model was performed to evaluate the relationship between LMR and in-hospital mortality. Kaplan-Meier curves and receiver operating characteristics (ROC) analysis were applied to assess the prognostic value of LMR.

Results

The optimal cut-off value for LMR was 0.9. Cox proportional hazards model demonstrated that lower LMR (< 0.9) was independently associated with in-hospital mortality with hazard ratio (HR) of 1.40 (1.12-1.74, P = 0.003). The results were consistent with survival analyses (P < 0.001, Log rank test). Adding LMR< 0.9 to the sequential organ failure assessment (SOFA) score improved discrimination and risk stratification for in-hospital mortality.

Conclusion

Lower level of LMR is related to higher risk of in-hospital mortality of patients with CS. As an easily available biomarker, LMR can independently predict the in-hospital mortality in CS patients.

Intact fibroblast growth factor 23 levels and outcome prediction in patients with acute heart failure

Elevated fibroblast growth factor 23 (FGF23) levels are associated with adverse outcome in populations with cardiovascular disease and chronic kidney failure. It is unclear if FGF23 has significance in prognosis estimation in patients with acute heart failure (HF) when compared to traditional risk estimation tools. Serum levels of intact FGF23 were assessed in 139 patients admitted to the Intermediate Care Unit of a tertiary hospital for acute HF. Patients were followed-up for one year. After exclusion of patients who were lost to follow-up, data outliers, and patients with sampling errors, the final study cohort comprised 133 patients. The Seattle Heart Failure (SHF) Model was used to estimate one-year survival. FGF23 levels correlated with HF severity and were strongly associated with one-year mortality. Associations between one-year outcome and FGF23, assessed on day 1 after admission, were still evident after multivariable adjustment (OR 15.07; 95%CI 1.75-129.79; p = 0.014). FGF23 levels predicted the one-year outcome with similar accuracy as the SHF Model, both if assessed on day 1 and on day 2 after admission (FGF23d1: AUC 0.784; 95%CI 0.669-0.899; FGF23d2: AUC 0.766; 95%CI 0.631-0.901; SHF: AUC 0.771; 95%CI 0.651-0.891). The assessment of FGF23 in patients with acute HF might help identify high-risk patients that are more prone to complications, need a closer follow-up and more aggressive treatment.

Risk stratification in cardiogenic shock: a focus on the available evidence

Cardiogenic shock is a clinical syndrome which is defined as the presence of primary cardiac disorder that results in hypotension together with signs of organ hypoperfusion in the state of normovolaemia or hypervolaemia. It represents a complex life-threatening condition, characterized by a high mortality rate, that requires urgent diagnostic assessment as well as treatment; therefore, it is of paramount important to advocate for a thorough risk stratification. In fact, the early identification of patients that could benefit the most from more aggressive and invasive approaches could facilitate a more efficient resource allocation. This review attempts to critically analyse the current evidence on prognosis in cardiogenic shock, focusing in particular on clinical, laboratoristic and echocardiographic prognostic parameters. Furthermore, it focuses also on the available prognostic scores, highlighting the strengths and the possible pitfalls. Finally, it provides insights into future direction that could be followed in order to ameliorate risk stratification in this delicate subset of patients.

Predicting outcome in acute myocardial infarction: an analysis investigating 175 circulating biomarkers

AIMS 

There is a paucity of studies comprehensively comparing the prognostic value of larger arrays of biomarkers indicative of different pathobiological axes in acute myocardial infarction (MI).

METHODS AND RESULTS 

In this explorative investigation, we simultaneously analysed 175 circulating biomarkers reflecting different inflammatory traits, coagulation activity, endothelial dysfunction, atherogenesis, myocardial dysfunction and damage, apoptosis, kidney function, glucose-, and lipid metabolism. Measurements were performed in samples from 1099 MI patients (SWEDEHEART registry) applying two newer multimarker panels [Proximity Extension Assay (Olink Bioscience), Multiple Reaction Monitoring mass spectrometry]. The prognostic value of biomarkers regarding all-cause mortality, recurrent MI, and heart failure hospitalizations (median follow-up ≤6.6 years) was studied using Lasso analysis, a penalized logistic regression model that considers all biomarkers simultaneously while minimizing the risk for spurious findings. Tumour necrosis factor-related apoptosis-inducing ligand receptor 2 (TRAIL-R2), ovarian cancer-related tumour marker CA 125 (CA-125), and fibroblast growth factor 23 (FGF-23) consistently predicted all-cause mortality in crude and age/sex-adjusted analyses. Growth-differentiation factor 15 (GDF-15) was strongly predictive in the crude model. TRAIL-R2 and B-type natriuretic peptide (BNP) consistently predicted heart failure hospitalizations. No biomarker predicted recurrent MI. The prognostic value of all biomarkers was abrogated following additional adjustment for clinical variables owing to our rigorous statistical approach.

CONCLUSION 

Apart from biomarkers with established prognostic value (i.e. BNP and to some extent GDF-15), several 'novel' biomarkers (i.e. TRAIL-R2, CA-125, FGF-23) emerged as risk predictors in patients with MI. Our data warrant further investigation regarding the utility of these biomarkers for clinical decision-making in acute MI.

Sex-differences in circulating biomarkers during acute myocardial infarction: An analysis from the SWEDEHEART registry

BACKGROUND

Sex-differences in the pathobiology of myocardial infarction are well established but incompletely understood. Improved knowledge on this topic may help clinicians to improve management of men and women with myocardial infarction.

METHODS

In this registry-based cohort study (SWEDEHEART), we analyzed 175 circulating biomarkers reflecting various pathobiological axes in 856 men and 243 women admitted to Swedish coronary care units because of myocardial infarction. Two multimarker panels were applied (Proximity Extension Assay [Olink Bioscience], Multiple Reaction Monitoring mass spectrometry). Lasso analysis (penalized logistic regression), multiple testing-corrected Mann-Whitney tests and Cox regressions were used to assess sex-differences in the concentrations of these biomarkers and their implications on all-cause mortality and major adverse events (median follow-up up to 6.6 years).

RESULTS

Biomarkers provided a very high discrimination between both sexes, when considered simultaneously (c-statistics 0.972). Compared to women, men had higher concentrations of six biomarkers with the most pronounced differences seen for those reflecting atherogenesis, myocardial necrosis and metabolism. Women had higher concentrations of 14 biomarkers with the most pronounced differences seen for those reflecting activation of the renin-angiotensin-aldosterone axis, inflammation and for adipokines. There were no major variations between sexes in the associations of these biomarkers with outcome.

CONCLUSIONS

Severable sex-differences exist in the expression of biomarkers in patients with myocardial infarction. While these differences had no impact on outcome, our data suggest the presence of various sex-related pathways involved in the development of coronary atherosclerosis, the progression to plaque rupture and acute myocardial damage, with a greater heterogeneity in women.

The relationship between Fibroblast Growth Factor 23 (FGF23) and cardiac MRI findings following primary PCI in patients with acute first time STEMI

BACKGROUND

Fibroblast growth factor 23 (FGF23) is a regulator of mineral metabolism, that has been linked to myocardial remodeling including development of left ventricular (LV) hypertrophy and myocardial fibrosis. The aim of this study was to investigate the relationship between intact FGF23 (iFGF23), myocardial infarct size and LV remodeling following a first acute ST-elevation myocardial infarction (STEMI).

METHODS AND RESULTS

Forty-two consecutive patients with first-time STEMI, single vessel disease, successfully treated with primary percutaneous coronary intervention were included. Cardiac magnetic resonance (CMR) imaging was performed at day 2, 1 week, 2 months and 1 year post MI, and blood samples were drawn at admittance and at the same time points as the CMRs. The cohort was divided according to the presence or not of heart failure post MI. In the total cohort, iFGF23 (mean ± SD) was significantly lower at day 0 (33.7 ± 20.6 pg/ml) and day 2 (31.5 ± 23.4 pg/ml) compared with a reference interval based on 8 healthy adults (43.9 pg/ml ± 19.0 pg/ml). iFGF23 increased to normal levels (55.8 ± 23.4 pg/ml) seven days post MI. In the subset of patients with signs of acute heart failure, FGF23 was higher at all measured timepoints, reaching significantly higher FGF23 levels at 2 months and 1 year following revascularization.

CONCLUSION

There was a reduction in iFGF23 levels during the acute phase of MI, with a normalization at seven days following revascularization. During one-year follow-up, there was a gradual increase in iFGF23 levels in patients with heart failure.

Lactate and other biomarkers as treatment target in cardiogenic shock

PURPOSE OF REVIEW

Cardiogenic shock remains beside sudden cardiac death the most outcome relevant complication of acute myocardial infarction. Over the last two decades as confirmation of the benefit of early revascularization no further relevant improvement in outcome could be achieved. Biomarkers are important for diagnosis, monitoring, and management in cardiogenic shock patients.

RECENT FINDINGS

A bunch of different biomarkers have been associated with prognosis in patients with cardiogenic shock. In routine use standard parameters such as serum lactate or serum creatinine are still most important in monitoring these patients. These established markers outperformed novel markers in prognostic impact in recent trials.

SUMMARY

Biomarkers serve as important treatment targets and may help physicians in therapeutic decision-making. Furthermore, the complex pathophysiology of cardiogenic shock may be better understood by investigation of different biomarkers.

Molecular signature of cardiogenic shock

The incidence of cardiogenic shock (CS) has increased remarkably over the past decade and remains a challenging condition with mortality rates of ∼50%. Cardiogenic shock encompasses cardiac contractile dysfunction; however, it is also a multiorgan dysfunction syndrome, often complicated by a systemic inflammatory response with severe cellular and metabolic dysregulations. Here, we review the evidence on the biochemical manifestations of CS, elaborating on current gold standard biomarkers and novel candidates from molecular signatures of CS. Glucose and lactate, both identified over a century ago, remain the only clinically used biomarkers in current predictive risk scores. Novel genomic, transcriptomic, and proteomic data are discussed, and a recently reported molecular score derived from unbiased proteomic discovery, the CS4P, which includes liver fatty acid-binding protein, beta-2-microglobulin, fructose-bisphosphate aldolase B, and SerpinG1 is comprehensively described. Recent advances in -omics technologies provide new insight into a more holistic molecular signature of CS. Thus, we need to open new diagnostic and therapeutic avenues if we aim to improve outcomes.

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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.

Protein-based cardiogenic shock patient classifier

Aims

Cardiogenic shock (CS) is associated with high short-term mortality and a precise CS risk stratification could guide interventions to improve patient outcome. Here, we developed a circulating protein-based score to predict short-term mortality risk among patients with CS.

Methods and results

Mass spectrometry analysis of 2654 proteins was used for screening in the Barcelona discovery cohort (n = 48). Targeted quantitative proteomics analyses (n = 51 proteins) were used in the independent CardShock cohort (n = 97) to derive and cross-validate the protein classifier. The combination of four circulating proteins (Cardiogenic Shock 4 proteins—CS4P), discriminated patients with low and high 90-day risk of mortality. CS4P comprises the abundances of liver-type fatty acid-binding protein, beta-2-microglobulin, fructose-bisphosphate aldolase B, and SerpinG1. Within the CardShock cohort used for internal validation, the C-statistic was 0.78 for the CardShock risk score, 0.83 for the CS4P model, and 0.84 (P = 0.033 vs. CardShock risk score) for the combination of CardShock risk score with the CS4P model. The CardShock risk score with the CS4P model showed a marked benefit in patient reclassification, with a net reclassification improvement (NRI) of 0.49 (P = 0.020) compared with CardShock risk score. Similar reclassification metrics were observed in the IABP-SHOCK II risk score combined with CS4P (NRI =0.57; P = 0.032). The CS4P patient classification power was confirmed by enzyme-linked immunosorbent assay (ELISA).

Conclusion

A new protein-based CS patient classifier, the CS4P, was developed for short-term mortality risk stratification. CS4P improved predictive metrics in combination with contemporary risk scores, which may guide clinicians in selecting patients for advanced therapies.

SCAI clinical expert consensus statement on the classification of cardiogenic shock: This document was endorsed by the American College of Cardiology (ACC), the American Heart Association (AHA), the Society of Critical Care Medicine (SCCM), and the Society of Thoracic Surgeons (STS) in April 2019

BACKGROUND

The outcome of cardiogenic shock complicating myocardial infarction has not appreciably changed in the last 30 years despite the development of various percutaneous mechanical circulatory support options. It is clear that there are varying degrees of cardiogenic shock but there is no robust classification scheme to categorize this disease state.

METHODS

A multidisciplinary group of experts convened by the Society for Cardiovascular Angiography and Interventions was assembled to derive a proposed classification schema for cardiogenic shock. Representatives from cardiology (interventional, advanced heart failure, noninvasive), emergency medicine, critical care, and cardiac nursing all collaborated to develop the proposed schema.

RESULTS

A system describing stages of cardiogenic shock from A to E was developed. Stage A is "at risk" for cardiogenic shock, stage B is "beginning" shock, stage C is "classic" cardiogenic shock, stage D is "deteriorating", and E is "extremis". The difference between stages B and C is the presence of hypoperfusion which is present in stages C and higher. Stage D implies that the initial set of interventions chosen have not restored stability and adequate perfusion despite at least 30 minutes of observation and stage E is the patient in extremis, highly unstable, often with cardiovascular collapse.

CONCLUSION

This proposed classification system is simple, clinically applicable across the care spectrum from pre-hospital providers to intensive care staff but will require future validation studies to assess its utility and potential prognostic implications.

Predictors of Outcomes in Myocardial Infarction and Cardiogenic Shock

Myocardial infarction (MI) complicated by cardiogenic shock (MI-CS) is a major cause of cardiovascular morbidity and mortality. Predictors of outcomes in MI-CS include clinical, laboratory, radiologic variables, and management strategies. This article reviews the existing literature on short- and long-term predictors and risk stratification in MI complicated by CS.

Vitamin D treatment attenuates cardiac FGF23/FGFR4 signaling and hypertrophy in uremic rats

Background

Vitamin D deficiency and excess of circulating fibroblast growth factor 23 (FGF23) contribute to cardiovascular mortality in patients with chronic kidney disease (CKD). FGF23 activates FGF receptor 4 and (FGFR4) calcineurin/nuclear factor of activated T cells (NFAT) signaling in cardiac myocytes, thereby causing left ventricular hypertrophy (LVH). Here, we determined if 1,25-dihydroxyvitamin D (calcitriol) inhibits FGF23-induced cardiac signaling and LVH.

Methods

5/6 nephrectomized (5/6 Nx) rats were treated with different doses of calcitriol for 4 or 10 weeks and cardiac expression of FGF23/FGFR4 and activation of calcineurin/NFAT as well as LVH were analyzed. FGFR4 activation and hypertrophic cell growth were studied in cultured cardiac myocytes that were co-treated with FGF23 and calcitriol.

Results

In 5/6Nx rats with LVH, we detected elevated FGF23 expression in bone and myocardium, increased cardiac expression of FGFR4 and elevated cardiac activation of calcineurin/NFAT signaling. Cardiac expression levels of FGF23 and FGFR4 significantly correlated with the presence of LVH in uremic rats. Treatment with calcitriol reduced LVH as well as cardiac FGFR4 expression and calcineurin/NFAT activation. Bone and cardiac FGF23 expression were further stimulated by calcitriol in a dose-dependent manner, but levels of intact cardiac FGF23 protein were suppressed by high-dose calcitriol. In cultured cardiac myocytes, co-treatment with calcitriol blocked FGF23-induced activation of FGFR4 and hypertrophic cell growth.

Conclusions

Our data suggest that in CKD, cardioprotective effects of calcitriol stem from its inhibitory actions on the cardiac FGF23/FGFR4 system, and based on their counterbalancing effects on cardiac myocytes, high FGF23 and low calcitriol synergistically contribute to cardiac hypertrophy.

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.

FGF23 in Cardiovascular Disease: Innocent Bystander or Active Mediator?

Fibroblast growth factor-23 (FGF23) is a mainly osteocytic hormone which increases renal phosphate excretion and reduces calcitriol synthesis. These renal actions are mediated via alpha-klotho as the obligate co-receptor. Beyond these canonical "mineral metabolism" actions, FGF23 has been identified as an independent marker for cardiovascular risk in various patient populations. Previous research has linked elevated FGF23 predominantly to left-ventricular dysfunction and consecutive morbidity and mortality. Moreover, some experimental data suggest FGF23 as a direct and causal stimulator for cardiac hypertrophy via specific myocardial FGF23-receptor activation, independent from alpha-klotho. This hypothesis offers fascinating prospects in terms of therapeutic interventions, specifically in patients with chronic kidney disease (CKD) in whom the FGF23 system is strongly stimulated and in whom left-ventricular dysfunction is a major disease burden. However, novel data challenges the previous stand-alone hypothesis about a one-way road which guides unidirectionally skeletal FGF23 toward cardiotoxic effects. In fact, recent data point toward local myocardial production and release of FGF23 in cases where (acute) myocardial damage occurs. The effects of this local production and the physiological meaning are under current examination. Moreover, epidemiologic studies suggest that high FGF-23 may follow, rather than induce, myocardial disease in certain conditions. In summary, while FGF23 is an interesting link between mineral metabolism and cardiac function underlining the meaning of the bone-heart axis, more research is needed before therapeutic interventions may be considered.

C-terminal and intact FGF23 in critical illness and their associations with acute kidney injury and in-hospital mortality

BACKGROUND

FGF23 proved its value in prognostication of cardiovascular events and mortality among renal patients and general population. Limited data exist whether FGF23 may have any use in prediction of negative outcomes among critically ill patients admitted to intensive care unit (ICU).

METHODS

Single center cohort study performed among patients admitted to ICU. The primary exposure was FGF23 plasma concentration measured within 24 h of ICU admission. The primary outcome was incident Acute Kidney Injury (AKI) and in-hospital mortality during the ICU stay.

RESULTS

The study enrolled 79 patients admitted to ICU. C-terminal FGF23 (cFGF23) but not intact FGF23 (iFGF23) concentration was significantly elevated in patients, who acquired AKI and non-survivors (p < .001). ROC analysis of cFGF23 yielded an AUC of 0.81 and 0.85 for prediction of incident AKI and death during ICU stay, respectively. Multivariate analysis showed higher odds for AKI (OR 1.80; 95% CI 1.10-2.96) and in-hospital mortality (OR 2.85; 95% CI 1.60-5.06) for one unit increase of log transformed cFGF23.

CONCLUSIONS

cFGF23 measurement may serve as a novel biomarker for incident AKI and death among critically ill patients.

Changes in Serum Fibroblast Growth Factor 23 in Patients With Acute Myocardial Infarction

BACKGROUND

Fibroblast growth factor 23 (FGF23) induces cardiac remodeling. We investigated the changes in serum FGF23 levels in patients diagnosed with acute myocardial infarction (AMI).Methods and Results:A total of 44 patients diagnosed with AMI were included in the current study. All patients underwent emergency percutaneous coronary intervention (PCI). The median of peak creatine kinase (CK) and CKMB values was 1,816 U/L and 159 U/L, respectively. Serum levels of FGF23, calcium, and inorganic phosphate (iP) were measured before PCI, and on days 1, 3, 5, 7 after PCI. Serum FGF23 levels showed a slight, but significant decrease on days 1 and 3 after PCI, and a 1.5- and 2.0-fold increase on days 5 and 7, respectively, after PCI. As compared with propensity score-matched patients without AMI, serum FGF23 was significantly lower among the current cohort of AMI patients. In 22 subjects who underwent a follow-up echocardiographic examination at 6 months after the onset of AMI, the log-transformed relative increase in FGF23 on day 7 significantly and negatively correlated with changes between LVEF on admission and that at 6 months afterward.

CONCLUSIONS

After a slight decrease on days 1 and 3 after admission, serum FGF23 increased significantly on days 5 and 7. The underlying mechanism and potential clinical importance of these observations require further investigation.

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.

Fibroblast growth factor 23 as a predictor of cardiovascular and all-cause mortality in prospective studies

BACKGROUND AND AIMS

The prognostic value of fibroblast growth factor 23 (FGF23) for mortality remains controversial. We performed a meta-analysis of cohort studies to examine the controversial relationship between FGF23 and mortality.

METHODS

PubMed, EMBASE, the Cochrane Library databases and reference bibliographies were searched through September 2016 to identify prospective cohort studies with relative risks (RRs) and 95% confidence intervals (CIs) for FGF23 and mortality. A random effects model was used to pool the risk estimates. A dose-response analysis of the risk for all-cause mortality associated with FGF23 was conducted using the generalized least squares trend estimation method.

RESULTS

Nineteen prospective cohort studies were eligible for inclusion in this meta-analysis, of which 16 reported all-cause mortality and 9 reported cardiovascular mortality. During the follow-up periods ranging from 1 to 18.6 years, 5606 deaths occurred among 22,805 participants and 2458 cardiovascular deaths occurred among 28,845 participants. Elevated FGF23 was associated with an increased risk of all-cause mortality (RR 1.68; 95% CI 1.48-1.92) and cardiovascular mortality (RR 1.68; 95% CI 1.38-2.04) with moderate heterogeneity. These associations were not markedly modified by the geographic location, follow-up length, patient predisposition, FGF23 measurement or study quality. A sensitivity analysis yielded a similar effect on the pooled risk estimate. Evidence of a nonlinear relationship between FGF23 and all-cause mortality was observed in the dose-response analysis, with the risk gradually increasing as FGF23 increased.

CONCLUSIONS

This meta-analysis showed that individuals with increased plasma FGF23 levels might suffer a higher risk of all-cause mortality and cardiovascular mortality.

Fibroblast growth factor 23 as novel biomarker for early risk stratification after ST-elevation myocardial infarction

OBJECTIVE

Adverse left ventricular (LV) remodelling is the major determinant of heart failure and mortality in survivors of ST-elevation myocardial infarction (STEMI). The role of fibroblast growth factor 23 (FGF-23) for LV remodelling prediction after STEMI is unknown. We therefore aimed to investigate the relation between circulating FGF-23 and LV remodelling following revascularised STEMI.

METHODS

In this prospective observational study, we included 88 consecutive patients with STEMI treated by primary percutaneous coronary intervention. FGF-23 concentrations were measured 2 (IQR: 2-2) days after symptom onset. Cardiac magnetic resonance was performed 2 (IQR: 1-3) days as well as 4 (IQR: 4-5) months after infarction to evaluate LV remodelling, defined as ≥20% increase in LV end-diastolic volume.

RESULTS

Levels of FGF-23 were significantly higher in patients who developed LV remodelling (n=11, 13%) as compared with those without LV remodelling (152.6 (102.5-241.3) vs 75.8 (58.6-105.4) relative units per millilitre, p=0.002). The association between FGF-23 and LV remodelling remained significant (OR: 14.1, 95% CI 2.8 to 70.9; p=0.001) after adjustment for biomarkers reflecting myocardial necrosis (high-sensitivity cardiac troponin T (hs-cTnT)), myocardial stress (N-terminal pro B-type natriuretic peptide (NT-proBNP)) and inflammatory state (high-sensitivity C reactive protein (hs-CRP)). Moreover, a multimarker approach adding FGF-23 to the established LV remodelling-predictive biomarkers (hs-cTnT, NT-proBNP and hs-CRP) led to a net reclassification improvement of 0.92 (95% CI 0.44 to 1.41, p<0.001) and to an integrated discrimination improvement of 0.16 (95% CI 0.08 to 0.24, p<0.001).

CONCLUSIONS

Circulating FGF-23 is independently associated with LV remodelling after reperfused STEMI. A comprehensive multimarker strategy that includes FGF-23 provides incremental prognostic value for prediction of LV remodelling.

Response of fibroblast growth factor 23 to volume interventions in arterial hypertension and diabetic nephropathy

Fibroblast growth factor 23 (FGF-23) rises progressively in chronic kidney disease and is associated with adverse cardiovascular outcomes. FGF-23 putatively induces volume retention by upregulating the sodium-chloride cotransporter (NCC). We studied whether, conversely, interventions in volume status affect FGF-23 concentrations.We performed a post hoc analysis of 1) a prospective saline infusion study with 12 patients with arterial hypertension who received 2 L of isotonic saline over 4 hours, and 2) a randomized controlled trial with 45 diabetic nephropathy (DN) patients on background angiotensin-converting enzyme -inhibition (ACEi), who underwent 4 6-week treatment periods with add-on hydrochlorothiazide (HCT) or placebo, combined with regular sodium (RS) or low sodium (LS) diet in a cross-over design. Plasma C-terminal FGF-23 was measured by ELISA (Immutopics) after each treatment period in DN and before and after saline infusion in hypertensives.The patients with arterial hypertension were 45 ± 13 (mean ± SD) years old with an estimated glomerular filtration rate (eGFR) of 101 ± 18 mL/min/1.73 m. Isotonic saline infusion did not affect FGF-23 (before infusion: 68 median [first to third quartile: 58-97] relative unit (RU)/mL, after infusion: 67 [57-77] RU/mL, P = 0.37). DN patients were 65 ± 9 years old. During ACEi + RS treatment, eGFR was 65 ± 25 mL/min/1.73 m and albuminuria 649 mg/d (230-2008 mg/d). FGF23 level was 94 (73-141) RU/mL during ACEi therapy. FGF-23 did not change significantly by add-on HCT (99 [74-148] RU/mL), LS diet (99 [75-135] RU/mL), or their combination (111 [81-160] RU/mL, P = 0.15).Acute and chronic changes in volume status did not materially change FGF-23 in hypertensive patients and DN, respectively. Our data do not support a direct feedback loop between volume status and FGF-23 in hypertension or DN.

The association of admission blood glucose level with the clinical picture and prognosis in cardiogenic shock - Results from the CardShock Study

BACKGROUND

Critically ill patients often present with hyperglycemia, regardless of previous history of diabetes mellitus (DM). Hyperglycemia has been associated with adverse outcome in acute myocardial infarction and acute heart failure. We investigated the association of admission blood glucose level with the clinical picture and short-term mortality in cardiogenic shock (CS).

METHODS

Consecutively enrolled CS patients were divided into five categories according to plasma glucose level at the time of enrolment: hypoglycemia (glucose <4.0mmol/L), normoglycemia (4.0-7.9mmol/L), mild (8.0-11.9mmol/L), moderate (12.0-15.9mmol/L), and severe (≥16.0mmol/L) hyperglycemia. Clinical presentation, biochemistry, and short-term mortality were compared between the groups.

RESULTS

Plasma glucose level of 211 CS patients was recorded. Glucose levels were distributed equally between normoglycemia (26% of patients), mild (27%), moderate (19%) and severe (25%) hyperglycemia, while hypoglycemia (2%) was rare. Severe hyperglycemia was associated with higher blood leukocyte count (17.3 (5.8) E9/L), higher lactate level (4.4 (3.3-8.4) mmol/L) and lower arterial pH (7.23 (0.14)) compared with normoglycemia or mild to moderate hyperglycemia (p<0.001 for all). In-hospital mortality was highest among hypoglycemic (60%) and severely hyperglycemic (56%) patients, compared with 22% in normoglycemic group (p<0.01). Severe hyperglycemia was an independent predictor of in-hospital mortality (OR 3.7, 95% CI 1.19-11.7, p=0.02), when adjusted for age, gender, LVEF, lactate, and DM.

CONCLUSIONS

Admission blood glucose level has prognostic significance in CS. Mortality is highest among patients with severe hyperglycemia or hypoglycemia. Severe hyperglycemia is independently associated with high in-hospital mortality in CS. It is also associated with biomarkers of systemic hypoperfusion and stress response.

Mineral metabolism in heart disease

PURPOSE OF REVIEW

Strong experimental and clinical evidence points towards a substantial contribution of mineral metabolism disorders to the initiation and progression of cardiovascular disease. Vice versa, recent work suggests that cardiovascular disease may also cause mineral metabolism alterations.

RECENT FINDINGS

Experimental studies suggest that hyperphosphatemia, elevated plasma levels of phosphaturic hormones--parathyroid hormone and fibroblast growth factor-23 (FGF-23)--and hypovitaminosis D exert detrimental effects on vascular tissue and on the myocardium. Accordingly, in longitudinal clinical cohort studies, individuals with high plasma levels of phosphate, parathyroid hormone and FGF-23, and with low vitamin D levels, face worst cardiovascular prognosis.Notably, recent evidence suggests that cardiovascular disease may not only follow but also induce mineral metabolism disorders: severe derangements in mineral metabolism were observed in patients with acute heart failure, who face a tremendous increase in plasma FGF-23. Unfortunately, few prospective studies have been completed hitherto that specifically target components of the mineral metabolism for cardiovascular disease prevention or treatment.

SUMMARY

A bidirectional interaction exists between mineral metabolism disorders and cardiovascular disease. However, clinical evidence for a cardiovascular benefit of therapeutic interventions into mineral metabolism is outstanding.

Fibroblast growth factor 23 (FGF-23) is an early predictor of mortality in patients with cardiac arrest

BACKGROUND

Post-cardiac arrest management has seen significant advances with profound improvements in survival and neurologic outcome. However, early prognostication after return of spontaneous circulation remains most challenging. Biomarkers have evolved as helpful tools in identifying patients who are at increased risk of adverse outcome. While fibroblast growth factor 23 (FGF-23) has recently emerged as a promising predictor of mortality in patients with cardiogenic shock, its role in risk stratification in post-resuscitation management remains unresolved.

METHODS

This study included 90 patients who had been resuscitated and transferred to the ICU of the University Hospital Heidelberg. Survivors and non-survivors were retrospectively analyzed for known prognostic biomarkers as well as FGF-23 serum levels 24h and 72 h post cardiac arrest (CA).

RESULTS

FGF-23 levels were significantly elevated in non-survivors compared to survivors. ROC analysis of FGF-23 levels at 24h and 72 h post CA yielded an AUC of 0.759 and 0.726, respectively, for prediction of overall survival after 6 months. FGF-23 levels remained as significant prognosticators after adjusting for age, renal function, and initial cardiac rhythm. FGF-23 levels did not show significant differences in patient outcome after stratification for cardiac origin of CA or left ventricular dysfunction. Furthermore, FGF-23 levels were moderately predictive of poor neurologic outcome in ROC analysis on day 1 and day 3 post CA with an AUC of 0.738 and 0.687, respectively.

CONCLUSION

This study demonstrates elevated FGF-23 serum levels to be potentially helpful in prediction of mortality and poor neurological outcome as early as 24h post cardiac arrest.

Deregulated Renal Calcium and Phosphate Transport during Experimental Kidney Failure

Impaired mineral homeostasis and inflammation are hallmarks of chronic kidney disease (CKD), yet the underlying mechanisms of electrolyte regulation during CKD are still unclear. Here, we applied two different murine models, partial nephrectomy and adenine-enriched dietary intervention, to induce kidney failure and to investigate the subsequent impact on systemic and local renal factors involved in Ca(2+) and Pi regulation. Our results demonstrated that both experimental models induce features of CKD, as reflected by uremia, and elevated renal neutrophil gelatinase-associated lipocalin (NGAL) expression. In our model kidney failure was associated with polyuria, hypercalcemia and elevated urinary Ca(2+) excretion. In accordance, CKD augmented systemic PTH and affected the FGF23-αklotho-vitamin-D axis by elevating circulatory FGF23 levels and reducing renal αklotho expression. Interestingly, renal FGF23 expression was also induced by inflammatory stimuli directly. Renal expression of Cyp27b1, but not Cyp24a1, and blood levels of 1,25-dihydroxy vitamin D3 were significantly elevated in both models. Furthermore, kidney failure was characterized by enhanced renal expression of the transient receptor potential cation channel subfamily V member 5 (TRPV5), calbindin-D28k, and sodium-dependent Pi transporter type 2b (NaPi2b), whereas the renal expression of sodium-dependent Pi transporter type 2a (NaPi2a) and type 3 (PIT2) were reduced. Together, our data indicates two different models of experimental kidney failure comparably associate with disturbed FGF23-αklotho-vitamin-D signalling and a deregulated electrolyte homeostasis. Moreover, this study identifies local tubular, possibly inflammation- or PTH- and/or FGF23-associated, adaptive mechanisms, impacting on Ca(2+)/Pi homeostasis, hence enabling new opportunities to target electrolyte disturbances that emerge as a consequence of CKD development.

The impact of fibroblast growth factor-23 on the cardiovascular system in chronic kidney disease

Chronic kidney disease is associated with an accelerated risk of cardiovascular (CV) mortality. Seminal work over the last decade has identified abnormal bone metabolism as an important modulator of the increased CV burden in this cohort. In particular, FGF23, a phosphaturic hormone with serum levels found to be markedly elevated in chronic kidney disease, is independently associated with increased risks of all-cause mortality and CV events. This editorial will discuss the proposed mechanisms linking FGF23 to CV disease in chronic kidney disease, namely, direct cardiac myocyte toxicity, endothelial dysfunction and vascular calcification.

FGF23 in Acute and Chronic Illness

FGF23 is a bone-derived phosphaturic hormone that may become a useful biomarker for the identification of high-risk patients in chronic but also acute disease. It rises early in chronic kidney disease and is strongly and independently associated with excess morbidity and mortality. Emerging data suggest that FGF23 is also elevated in different scenarios of acute illness. In this review, we give an overview on the role of this interesting disease marker and potential and proven interventional strategies and discuss a blueprint for future research.