Sarah Seiler

FGF-23 and future cardiovascular events in patients with chronic kidney disease before initiation of dialysis treatment

BACKGROUND High levels of the phosphaturic hormone fibroblast growth factor 23 (FGF-23) predict mortality in haemodialysis patients. The prognostic relevance of increased plasma FGF-23 levels in patients with less advanced chronic kidney disease (CKD) who are not on dialysis therapy is presently unknown. METHODS We measured plasma c-terminal FGF-23 levels in 149 CKD patients not undergoing dialysis treatment. Patients were stratified by their baseline FGF-23 levels (>104 vs ≤ 104 rU/mL) and followed for a period of 4.8  ±  0.9 years. During the follow-up, the pre-specified combined clinical endpoint was the first occurrence of a cardiovascular event, e.g. myocardial infarction, coronary artery angioplasty/stenting/bypass surgery, stroke, carotid endarterectomy/stenting, non-traumatic lower extremity amputation, lower limb artery surgery/angioplasty/stenting or death. RESULTS At baseline, elevated FGF-23 levels >104 rU/mL were associated with more advanced CKD. Traditional cardiovascular risk factors and prevalent cardiovascular disease did not differ between CKD patients with high vs low FGF-23 levels. Fifty patients experienced a cardiovascular event during follow-up. Compared with CKD patients with FGF-23 ≤104 rU/mL, CKD patients with FGF-23 levels above the cut-off had worse event-free survival at univariate (log-rank test P  =  0.012) and multivariate analysis [hazard ratio 2.49 (95% CI 1.40-4.39); P = 0.002]. CONCLUSIONS Elevated FGF-23 plasma levels predict cardiovascular events in CKD patients not on dialysis therapy. This finding complements two recent cohort studies in which incident and prevalent haemodialysis patients with highest FGF-23 levels had worst survival. Lowering FGF-23 levels (e.g. by oral phosphate binder medication) could emerge as a promising new therapeutic option to reduce cardiovascular morbidity in CKD patients.

Plasma Klotho is not related to kidney function and does not predict adverse outcome in patients with chronic kidney disease

A decreased expression of the fibroblast growth factor (FGF)-23 coreceptor Klotho was postulated as an early alteration in chronic kidney disease mineral and bone disorder, resulting in a compensatory increase in plasma FGF-23 levels. Klotho exists in both membrane-bound and secreted (sKlotho) forms, the latter of which may exert vasculoprotective effects. Here we analyzed plasma sKlotho levels in a large cohort of 312 patients with stage 2-4 chronic kidney disease, and assessed plasma levels of FGF-23, sKlotho, parathyroid hormone, and urinary fractional phosphate excretion. Patients were prospectively followed for an average of 2.2 years for the occurrence of death or initiation of renal replacement therapy. The levels of sKlotho were significantly associated with age, but not with the glomerular filtration rate or other parameters of calcium-phosphate metabolism. Moreover, while patients with high FGF-23 levels faced worst outcome even after adjustment for confounders, we found no prognostic impact of sKlotho. Thus, plasma levels of sKlotho were not related to kidney function and did not predict adverse outcome in patients with chronic kidney disease. Future studies are needed to understand how tissue expression, urinary excretion, and plasma levels of Klotho diverge in progressive chronic kidney disease.

Clinical relevance of FGF-23 in chronic kidney disease

Fibroblast growth factor (FGF)-23 is a recently discovered regulator of calcium-phosphate metabolism. Whereas other known FGFs mainly act in a paracrine manner, FGF-23 has significant systemic effects. Together with its cofactor Klotho, FGF-23 enhances renal phosphate excretion in order to maintain serum phosphate levels within the normal range. In patients with chronic kidney disease (CKD), FGF-23 levels rise in parallel with declining renal function long before a significant increase in serum phosphate concentration can be detected. However, in cross-sectional studies increased FGF-23 levels in patients with CKD were found to be associated not only with therapy-resistant secondary hyperparathyroidism but were also independently related to myocardial hypertrophy and endothelial dysfunction after adjustment for traditional markers of calcium-phosphate metabolism. Finally, in prospective studies high serum FGF-23 concentrations predicted faster disease progression in CKD patients not on dialysis, and increased mortality in patients receiving maintenance hemodialysis. FGF-23 may therefore prove to be an important therapeutic target in the management of CKD.

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.

Carbamylated low-density lipoprotein induces endothelial dysfunction

AIMS Cardiovascular events remain the leading cause of death in Western world. Atherosclerosis is the most common underlying complication driven by low-density lipoproteins (LDL) disturbing vascular integrity. Carbamylation of lysine residues, occurring primarily in the presence of chronic kidney disease (CKD), may affect functional properties of lipoproteins; however, its effect on endothelial function is unknown. METHODS AND RESULTS Low-density lipoprotein from healthy donors was isolated and carbamylated. Vascular reactivity after treatment with native LDL (nLDL) or carbamylated LDL (cLDL) was examined in organ chambers for isometric tension recording using aortic rings of wild-type or lectin-like-oxidized LDL receptor-1 (LOX-1) transgenic mice. Reactive oxygen species (ROS) and nitric oxide (NO) production were determined using electron spin resonance spectroscopy. The effect of LDL-carbamyl-lysine levels on cardiovascular outcomes was determined in patients with CKD during a median follow-up of 4.7 years. Carbamylated LDL impaired endothelium-dependent relaxation to acetylcholine or calcium-ionophore A23187, but not endothelium-independent relaxation to sodium nitroprusside. In contrast, nLDL had no effect. Carbamylated LDL enhanced aortic ROS production by activating NADPH-oxidase. Carbamylated LDL stimulated endothelial NO synthase (eNOS) uncoupling at least partially by promoting S-glutathionylation of eNOS. Carbamylated LDL-induced endothelial dysfunction was enhanced in LOX-1 transgenic mice. In patients with CKD, LDL-carbamyl-lysine levels were significant predictors for cardiovascular events and all-cause mortality. CONCLUSIONS Carbamylation of LDL induces endothelial dysfunction via LOX-1 activation and increased ROS production leading to eNOS uncoupling. This indicates a novel mechanism in the pathogenesis of atherosclerotic disease which may be pathogenic and prognostic in patients with CKD and high plasma levels of cLDL.

Lower Apo A-I and Lower HDL-C Levels Are Associated With Higher Intermediate CD14++CD16+ Monocyte Counts That Predict Cardiovascular Events in Chronic Kidney Disease

Objective— Patients with chronic kidney disease (CKD) display impaired cholesterol efflux capacity and elevated CD14++CD16+ monocyte counts. In mice, dysfunctional cholesterol efflux causes monocytosis. It is unknown whether cholesterol efflux capacity and monocyte subsets are associated in CKD. Approach and Results— In 438 patients with CKD, mediators of cholesterol efflux capacity (high-density lipoprotein cholesterol/apolipoprotein A-I) and monocyte subsets were analyzed as predictors of cardiovascular events. Monocyte subset-specific intracellular lipid content, CD36, CD68, and ABCA1 were measured in a subgroup. Experimentally, we analyzed subset-specific cholesterol efflux capacity and response to oxidized low-density lipoprotein cholesterol stimulation in CKD. Epidemiologically, both low Apo-I and low high-density lipoprotein cholesterol were associated with high CD14++CD16+ monocyte counts in linear regression analyses (apolipoprotein A-I: &bgr;=−0.171; P<0.001; high-density lipoprotein cholesterol: &bgr;=−0.138; P=0.005), but not with counts of other monocyte subsets. In contrast to apolipoprotein A-I or high-density lipoprotein cholesterol, higher CD14++CD16+ monocyte counts independently predicted cardiovascular events (hazard ratio per increase of 1 cell/&mgr;L: 1.011 [1.003–1.020]; P=0.007). Experimentally, CD14++CD16+ monocytes demonstrated preferential lipid accumulation, high CD36, CD68, and low ABCA1 expression and, consequently, displayed low cholesterol efflux capacity, avid oxidized low-density lipoprotein cholesterol uptake, and potent intracellular interleukin-6, interleukin-1&bgr;, and tumor necrosis factor-&agr; production. Conclusions— Taken together, mediators of cholesterol efflux are associated with CD14++CD16+ monocyte counts, which independently predict adverse outcome in CKD.

HDL Cholesterol Is Not Associated with Lower Mortality in Patients with Kidney Dysfunction

In the general population, HDL cholesterol (HDL-C) is associated with reduced cardiovascular events. However, recent experimental data suggest that the vascular effects of HDL can be heterogeneous. We examined the association of HDL-C with all-cause and cardiovascular mortality in the Ludwigshafen Risk and Cardiovascular Health study comprising 3307 patients undergoing coronary angiography. Patients were followed for a median of 9.9 years. Estimated GFR (eGFR) was calculated using the Chronic Kidney Disease Epidemiology Collaboration eGFR creatinine-cystatin C (eGFRcreat-cys) equation. The effect of increasing HDL-C serum levels was assessed using Cox proportional hazard models. In participants with normal kidney function (eGFR>90 ml/min per 1.73 m(2)), higher HDL-C was associated with reduced risk of all-cause and cardiovascular mortality and coronary artery disease severity (hazard ratio [HR], 0.51, 95% confidence interval [95% CI], 0.26-0.92 [P=0.03]; HR, 0.30, 95% CI, 0.13-0.73 [P=0.01]). Conversely, in patients with mild (eGFR=60-89 ml/min per 1.73 m(2)) and more advanced reduced kidney function (eGFR<60 ml/min per 1.73 m(2)), higher HDL-C did not associate with lower risk for mortality (eGFR=60-89 ml/min per 1.73 m(2): HR, 0.68, 95% CI, 0.45-1.04 [P=0.07]; HR, 0.84, 95% CI, 0.50-1.40 [P=0.50]; eGFR<60 ml/min per 1.73 m(2): HR, 1.18, 95% CI, 0.60-1.81 [P=0.88]; HR, 0.82, 95% CI, 0.40-1.69 [P=0.60]). Moreover, Cox regression analyses revealed interaction between HDL-C and eGFR in predicting all-cause and cardiovascular mortality (P=0.04 and P=0.02, respectively). We confirmed a lack of association between higher HDL-C and lower mortality in an independent cohort of patients with definite CKD (P=0.63). In summary, higher HDL-C levels did not associate with reduced mortality risk and coronary artery disease severity in patients with reduced kidney function. Indeed, abnormal HDL function might confound the outcome of HDL-targeted therapies in these patients.

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

Elevated plasma levels of the phosphaturic hormone fibroblast growth factor 23 (FGF-23) are a hallmark of chronic kidney disease (CKD)-mineral and bone disorder. FGF-23 allows serum phosphate levels within physiological limits to be maintained in progressive CKD until end-stage renal disease is reached. Despite its seemingly beneficial role in phosphate homeostasis, several prospective studies in dialysis patients and in patients with less advanced CKD associated elevated FGF-23 with poor cardiovascular and renal outcome. Moreover, very recent evidence suggests an adverse prognostic impact of elevated FGF-23 even in subjects without manifest CKD. These epidemiological data are supplemented by laboratory findings that reveal a pathophysiological role of FGF-23 in the pathogenesis of myocardial injury. In aggregate, these clinical and experimental data identify FGF-23 as a promising target of novel therapeutic interventions in CKD and beyond, which should be tested in future clinical trials.

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.

Haemodialysis-induced transient CD16+ monocytopenia and cardiovascular outcome

BACKGROUND Haemodialysis with bioincompatible membranes led to transient leukocyte activation and intra-dialytic leukopenia due to endothelial adherence. After the introduction of biocompatible membranes, only CD16(+) (i.e. CD14(++)CD16(+) and CD14((+))CD16(+)) monocytes showed an impressive transient intra-dialytic decrease. Presently, it is unclear whether this CD16(+) monocyte drop is detrimental. We investigated whether a prominent intra-dialytic decrease of CD16(+) monocytes predicts future cardiovascular (CV) events. METHODS We measured leukocyte and monocyte subpopulations in 70 patients before and 10 min after haemodialysis initiation. Patients were stratified by their intra-dialytic CD14(++)CD16(+) monocyte drop (pre-defined major drop: decline of cell counts at 10 min to <50% of pre-dialytic values; pre-defined minor drop: decline to values >50% of pre-dialytic counts). Patients were followed up for 42 +/- 2 months; endpoints were CV events and death. RESULTS Patients with a minor CD14(++)CD16(+) monocyte drop had more CV events than patients with a major drop. In multivariate analysis, a minor CD14(++)CD16(+) monocyte drop was the strongest independent predictor of future CV events [hazard ratio 2.405 (95% CI 1.192-4.854)]. CONCLUSIONS These data refute the assumption that a prominent intra-dialytic decrease of CD14(++)CD16(+) monocytes is detrimental. Instead, a minor cell drop could mirror CD14(++)CD16(+) monocyte dysfunction, with inadequate migratory reaction towards an immunologic stimulus posed by membrane and tubing contact.