Serum level of the phosphaturic factor FGF23 is associated with abdominal aortic calcification in men: the STRAMBO study

Role of klotho and fibroblast growth factor 23 in arterial calcification, thickness, and stiffness: a meta-analysis of observational studies

This meta-analysis was conducted to clarify the role of klotho and fibroblast growth factor 23 (FGF-23) in human arterial remodeling across recent studies, in terms of arterial calcification, thickness, and stiffness. A systematic literature search was conducted on five databases for articles up to December 2023. Arterial calcification, thickness, and stiffness were determined using the calcification score and artery affected, carotid intima-media thickness (CIMT), and pulse wave velocity (PWV), respectively. Sixty-two studies with a total of 27,459 individuals were included in this meta-analysis. Most studies involved chronic kidney disease patients. Study designs were mostly cross-sectional with only one case-control and nine cohorts. FGF-23 was positively correlated with arterial calcification (r = 0.446 [0.254-0.611], p < 0.0001 and aOR = 1.36 [1.09-1.69], p = 0.006), CIMT (r = 0.188 [0.02-0.354], p = 0.03), and PWV (r = 0.235 [0.159-0.310], p < 0.00001). By contrast, Klotho was inversely correlated with arterial calcification (r = - 0.388 [- 0.578 to - 0.159], p = 0.001) and CIMT (r = - 0.38 [- 0.53 to - 0.207], p < 0.00001). In conclusion, FGF-23 and Klotho were associated with arterial calcification, thickness, and stiffness, clarifying their role in arterial remodeling processes.

Future treatment of vascular calcification in chronic kidney disease

INTRODUCTION

Cardiovascular disease (CVD) is one of the global leading causes of morbidity and mortality in chronic kidney disease (CKD) patients. Vascular calcification (VC) is a major cause of CVD in this population and is the consequence of complex interactions between inhibitor and promoter factors leading to pathological deposition of calcium and phosphate in soft tissues. Different pathological landscapes are associated with the development of VC, such as endothelial dysfunction, oxidative stress, chronic inflammation, loss of mineralization inhibitors, release of calcifying extracellular vesicles (cEVs) and circulating calcifying cells.

AREAS COVERED

In this review, we examined the literature and summarized the pathophysiology, biomarkers and focused on the treatments of VC.

EXPERT OPINION

Even though there is no consensus regarding specific treatment options, we provide the currently available treatment strategies that focus on phosphate balance, correction of vitamin D and vitamin K deficiencies, avoidance of both extremes of bone turnover, normalizing calcium levels and reduction of inflammatory response and the potential and promising therapeutic approaches liketargeting cellular mechanisms of calcification (e.g. SNF472, TNAP inhibitors).Creating novel scores to detect in advance VC and implementing targeted therapies is crucial to treat them and improve the future management of these patients.

Urinary phosphate is associated with cardiovascular disease incidence

INTRODUCTION

Elevated phosphate (P) in urine may reflect a high intake of inorganic P salts from food additives. Elevated P in plasma is linked to vascular dysfunction and calcification.

OBJECTIVE

To explore associations between P in urine as well as in plasma and questionnaire-estimated P intake, and incidence of cardiovascular disease (CVD).

METHODS

We used the Swedish Mammography Cohort-Clinical, a population-based cohort study. At baseline (2004-2009), P was measured in urine and plasma in 1625 women. Dietary P was estimated via a food-frequency questionnaire. Incident CVD was ascertained via register-linkage. Associations were assessed using Cox proportional hazards regression.

RESULTS

After a median follow-up of 9.4 years, 164 composite CVD cases occurred (63 myocardial infarctions [MIs] and 101 strokes). Median P (percentiles 5-95) in urine and plasma were 2.4 (1.40-3.79) mmol/mmol creatinine and 1.13 (0.92-1.36) mmol/L, respectively, whereas dietary P intake was 1510 (1148-1918) mg/day. No correlations were observed between urinary and plasma P (r = -0.07) or dietary P (r = 0.10). Urinary P was associated with composite CVD and MI. The hazard ratio of CVD comparing extreme tertiles was 1.57 (95% confidence interval 1.05, 2.35; P trend 0.037)-independently of sodium excretion, the estimated glomerular filtration rate, both P and calcium in plasma, and diuretic use. Association with CVD for plasma P was 1.41 (0.96, 2.07; P trend 0.077).

CONCLUSION

Higher level of urinary P, likely reflecting a high consumption of highly processed foods, was linked to CVD. Further investigation is needed to evaluate the potential cardiovascular toxicity associated with excessive intake of P beyond nutritional requirements.

SIRT6-PAI-1 axis is a promising therapeutic target in aging-related bone metabolic disruption

The mechanistic regulation of bone mass in aged animals is poorly understood. In this study, we examined the role of SIRT6, a longevity-associated factor, in osteocytes, using mice lacking Sirt6 in Dmp-1-expressing cells (cKO mice) and the MLO-Y4 osteocyte-like cell line. cKO mice exhibited increased osteocytic expression of Sost, Fgf23 and senescence inducing gene Pai-1 and the senescence markers p16 and Il-6, decreased serum phosphate levels, and low-turnover osteopenia. The cKO phenotype was reversed in mice that were a cross of PAI-1-null mice with cKO mice. Furthermore, senescence induction in MLO-Y4 cells increased the Fgf23 and Sost mRNA expression. Sirt6 knockout and senescence induction increased HIF-1α binding to the Fgf23 enhancer sequence. Bone mass and serum phosphate levels were higher in PAI-1-null aged mice than in wild-type mice. Therefore, SIRT6 agonists or PAI-1 inhibitors may be promising therapeutic options for aging-related bone metabolism disruptions.

Fasudil Ameliorates Osteoporosis Following Myocardial Infarction by Regulating Cardiac Calcitonin Secretion

We hypothesis that Rho kinase inhibitor fasudil ameliorates osteoporosis following myocardial infarction (MI) by regulating cardiac calcitonin secretion. A mice model of MI and cultured neonatal cardiomyocytes exposed to hypoxia and serum deprivation (H/SD), and fibroblasts exposed to TGF-β were used, respectively. Cardiac function in vivo was assessed with echocardiography. Osteoporosis in vivo was assessed with X-ray and micro-CT. In vivo and in vitro studies used histological and immunohistochemical techniques, along with western blots. In mice post-MI, fasudil ameliorates the microstructure and bone metabolism of the lumbar, improved cardiac function, and attenuated myocardial fibrosis. In vitro, fasudil or αCGRP could effectively inhibit the proliferation of primary fibroblasts treated with TGF-β. Moreover, fasudil ameliorates the cardiac calcitonin secretion induced by MI in vivo or by H/SD in vitro. Our findings suggest that fasudil improved MI-induced osteoporosis by promoting cardiac secreting calcitonin.

Effect of pioglitazone on serum FGF23 levels among patients with diabetic kidney disease: a randomized controlled trial

AIM

Elevated fibroblast growth factor-23 (FGF23) is an established marker of cardiovascular disease among patients with type 2 diabetes (T2DM) and chronic kidney disease (CKD). Recently, circulating FGF23 positively correlated with insulin resistance level among patients with CKD. Pioglitazone improves insulin sensitivity and it may have potential for treating CKD-related FGF23 overactivity.

METHODS

A randomized, open-label, controlled trial was performed among patients with T2DM and CKD. Eligible participants were randomly assigned to either oral 15 mg/day of pioglitazone (N = 22) or control group (N = 24) for 16 weeks. Serum FGF23 and homeostatic Model Assessment of Insulin Resistance (HOMA-IR) were measured.

RESULTS

Forty-six patients completed the trial. After 16 weeks of treatment, significant decreases in serum intact FGF23 level (median change - 49.01 (IQR, - 103.51 to - 24.53) vs. 1.07 (IQR, - 22.4-39.53) pg/mL, P = 0.01) and HOMA-IR (mean change - 1.41 (95% CI, - 2.24 to - 0.57) vs. - 0.05 (95% CI, - 1.00-0.89), P = 0.031) were observed in the pioglitazone group compared with the control group. HemoglobinA1C also significantly decreased in the pioglitazone group compared with the control group. No difference was found in the changes of serum phosphorus, calcium and serum intact parathyroid hormone between the two groups. Changes of FGF23 were positively associated with changes of HOMA-IR (R = 0.47) and insulin levels (R = 0.47). No serious adverse event was reported during the study.

CONCLUSION

This study confirmed that pioglitazone effectively reduced serum FGF23 levels and related to improved insulin sensitivity among patients with T2DM and CKD.

CLINICAL TRIAL REGISTRATION

TCTR20210316009.

Changes in Serum Intact Fibroblast Growth Factor 23 Concentrations From Midlife to Late Life and Their Predictors in the Community: The ARIC Study

Objective

To investigate longitudinal changes in the blood concentration of fibroblast growth factor 23 (FGF23) from midlife to late life and their major predictors in the general population.

Patients and Methods

In 14,444 participants of the Atherosclerosis Risk in Communities Study, we analyzed the association of 31,095 measurements of serum intact FGF23 with age using data from 3 visits (visit 2 [N=13,460; mean age, 57 years]; visit 3 [N=12,323; mean age, 60 years]; and visit 5 [N=6122; mean age, 76 years]) and a linear mixed-effects model. Among 5804 participants who had FGF23 measurements at both visits 3 and 5, we explored predictors of FGF23 change from midlife to late life using linear regression models. Prespecified risk factors were estimated glomerular filtration rate, body mass index, ever smoking, ever drinker, diabetes, hypertension, history of cardiovascular disease, total cholesterol, and high-density lipoprotein cholesterol.

Results

Median FGF23 concentrations were 41.9 pg/mL (interquartile interval [IQI], 33.9 to 51.8 pg/mL) at visit 2, 38.3 pg/mL (IQI, 30.6 to 48.3 pg/mL) at visit 3, and 55.0 pg/mL (IQI, 44.4 to 70.3 pg/mL) at visit 5. A linear mixed-effects model showed that the association of FGF23 with age was nonlinear, with a slight decline or no change in age 45-60 years and a monotonic increase in age greater than or equal to 65 years (FGF23, +10 to 15 pg/mL per 10 years of age). In a multivariable linear regression model, significantly greater increases in FGF23 were noted, with midlife estimated glomerular filtration rate less than 60 mL/min per 1.73 m2 vs more than or equal to 60 mL/min per 1.73 m2 (ΔFGF23, +4.4 pg/mL [95% CI, 0.9 to 8.0]), diabetes vs no diabetes (ΔFGF23, +6.2 pg/mL [95% CI, 4.1 to 8.3]), and hypertension vs no hypertension (ΔFGF23, +4.1 pg/mL [95% CI, 2.7 to 5.4]).

Conclusion

FGF23 did not show any major changes in midlife but increased linearly in late life. Reduced kidney function, diabetes, and hypertension were robustly associated with a greater increase in FGF23. Further investigations are needed to understand the potential mechanisms linking these conditions to an increase in FGF23 concentrations.

18-year change in serum intact fibroblast growth factor 23 from midlife to late life and risk of mortality: the ARIC Study

Objective

Fibroblast growth factor 23 (FGF23) concentration increases in response to declining kidney function to preserve normal phosphate concentrations. However, the etiological association of change in FGF23 concentration with mortality has not been examined in the general population.

Design and methods

We analyzed 5458 participants of the Atherosclerosis Risk in Communities Study who had intact FGF23 and estimated glomerular filtration rate (eGFR) assessed during midlife (visit 3, 1993-1995, mean age: 58 years) and late life (visit 5, 2011-2013, 76 years) to examine the association of FGF23 change over 18 years from mid-life to late life with the subsequent risk of mortality in late life using Cox regression models.

Results

The median 18-year change in intact FGF23 was +17.3 pg/mL. During a median follow-up of 7.2 years following visit 5, 1176 participants died. In multivariable Cox models, elevated mortality was seen in the highest quartile of FGF23 change (ΔFGF23: ≥31.3 pg/mL) (adjusted hazard ratio (aHR): 1.61 (95%CI: 1.36-1.90), or 1.37 (1.15-1.64) after additionally adjusting for eGFR change, compared with the lowest quartile (≤6.4 pg/mL)). When both FGF23 change and FGF23 in late life were simultaneously entered into the Cox model, FGF23 in late life, but not FGF23 change, was an independent predictor of mortality; however, we observed a high correlation between FGF23 change from midlife to late life and FGF23 in late life (r = 0.77).

Conclusions

Serum intact FGF23 change from midlife to late life was associated with subsequent risk of mortality independent of decline in kidney function. Our findings further support the implications of FGF23 beyond its association with kidney function.

BRCA 1, 2 mutation and earlier menopause. Could BRCA 1, 2 be used as predictor of menopause?

Many studies have shown that BRCA mutation is not only related to cancer but also to ovarian aging. Studies in both human and mice oocytes have shown that Double-strand breaks (DSBs) accumulate with age. Genome-wide association studies (GWAS) have found 44 genetic loci that are related to variations when a female is about to have menopause. BRCA1 is involved in these 44 loci that are associated with the age of menopause. This review has gathered all results of literature search about the association between BRCA genes and early menopause. The majority of the articles found that women with BRCA mutation have earlier menopause compared to non-carriers. In conclusion, in the near future BRCA1,2 genes could be used as predictive biomarkers of menopause.

Pathophysiological Implications of Imbalances in Fibroblast Growth Factor 23 in the Development of Diabetes

Observational studies have associated the increase in fibroblast growth factor (FGF) 23 levels, the main regulator of phosphate levels, with the onset of diabetes. These studies open the debate on the plausible existence of undescribed diabetogenic mechanisms derived from chronic supraphysiological levels of FGF23, a prevalent condition in chronic kidney disease (CKD) and end-stage renal disease (ESRD) patients. These maladaptive and diabetogenic responses to FGF23 may occur at different levels, including a direct effect on the pancreatic ß cells, and an indirect effect derived from the stimulation of the synthesis of pro-inflammatory factors. Both mechanisms could be mediated by the binding of FGF23 to noncanonical receptor complexes with the subsequent overactivation of signaling pathways that leads to harmful effects. The canonical binding of FGF23 to the receptor complex formed by the receptor FGFR1c and the coreceptor αKlotho activates Ras/MAPK/ERK signaling. However, supraphysiological concentrations of FGF23 favor non-αKlotho-dependent binding of this molecule to other FGFRs, which could generate an undesired overactivation of the PLCγ/CN/NFAT pathway, as observed in cardiomyocytes and hepatocytes. Moreover, the decrease in αKlotho expression may constitute a contributing factor to the appearance of these effects by promoting the nonspecific activation of the PLCγ/CN/NFAT to the detriment of the αKlotho-dependent Ras/MAPK/ERK pathway. The description of these mechanisms would allow the development of new therapeutic targets susceptible to be modified by dietary changes or by pharmacological intervention.

High Cardiovascular Risk in Older Men With Severe Peripheral Artery Calcification on High-Resolution Peripheral QCT Scans: The STRAMBO Study

[Figure: see text].

High Cardiovascular Risk in Older Men with Poor Bone Microarchitecture-The Prospective STRAMBO Study

Data on the association between bone microarchitecture and cardiovascular disease (CVD) in men are scarce. We studied the link of bone microarchitecture and areal bone mineral density (aBMD) with the risk of major adverse coronary event (MACE) in a cohort of men aged 60 to 87 years followed prospectively for 8 years. At baseline, aBMD was measured using a Hologic Discovery-A device. Bone microarchitecture was assessed at distal radius and tibia by high-resolution peripheral quantitative computed tomography (XtremeCT Scanco device). During the study, 53 men had incident MACE. The analyses were adjusted for confounders related to bone and CVD. In 813 men (53 MACEs), higher aBMD at the lumbar spine, hip, whole body, and radius was associated with lower risk of MACE (hazard ratio [HR] = 0.44-0.71/SD, p < .025 to < .001). In 745 men having valid distal radius scan (47 MACEs), higher cortical density (Ct.BMD) and higher cortical thickness (Ct.Th^d ) were associated with lower risk of MACE. This risk was higher in men in the lowest quintile of cortical measures versus the four upper quintiles combined (Ct.BMD: HR = 2.12, 95% confidence interval [CI] 1.08-4.17, p < .025). Findings were similar in 779 men having valid distal tibia scan (48 MACEs). At both sites, higher estimated stiffness and higher failure load were associated with a lower risk of MACE. The risk of MACE was higher in men in the lowest quintile of the measures of bone strength versus four upper quintiles jointly (distal radius stiffness: HR = 2.46, 95% CI 1.27-4.74, p < .01). Similar results were obtained in 638 men without prior fragility fracture and in 689 men without ischemic heart disease at baseline. Thus, in older men followed prospectively for 8 years, higher aBMD, preserved cortical bone status, and higher estimated bone strength were associated with lower risk of MACE after adjustment for relevant confounders. © 2021 American Society for Bone and Mineral Research (ASBMR).

Effects of dietary phosphates from organic and inorganic sources on parameters of phosphorus homeostasis in healthy adult dogs

BACKGROUND

The impact of dietary phosphorus (P) excess, especially on renal and cardiovascular health, has been investigated in several species, but little is known in dogs.

OBJECTIVE

The aim of this study was to examine effects of different P sources on concentration and postprandial kinetics of selected parameters of P homeostasis in dogs.

METHODS

Eight beagles received one control diet (P 0.5% dry matter [DM]) and three high P diets (poultry meal, NaH2PO4, and KH2PO4; P 1.7% DM) for 18d. Urine samples were collected pre- and postprandially while faeces were collected quantitatively for 5d and analysed for minerals. On day 18, blood was sampled 1h pre- and 0.5, 1, 1.5, 2, 3, 5 and 7h postprandially.

RESULTS

Pi (KH2PO4, NaH2PO4) but not organic P caused an increased apparent P digestibility and significantly influenced kinetics of serum FGF23, parathyroid hormone, P, CrossLaps and bonespecific alkaline phosphatase, demonstrating a disrupted calcium (Ca) and P homeostasis with potential harm for renal, cardiovascular and skeletal health.

CONCLUSIONS

Results of feeding Pi to dogs indicate distinct disturbances of Ca and P metabolism, in contrast to organic sources. The use of Pi in food can therefore not be considered as safe. Further research, especially on dose and long-term effects, is warranted.

Association between shift work and biological factors including FGF-23, klotho, and serum 25-(OH) vitamin D3 among Korean firefighters: a cross-sectional study

STUDY OBJECTIVES

Shift work is known to be detrimental to an individual's health as it disrupts the circadian rhythm and is a risk factor for cancer. It has been reported that elevated fibroblast growth factor (FGF)-23, increased serum soluble α-klotho, and decreased vitamin D3 are associated with cancer progression. We studied the relationship between shift work and the levels of FGF-23, α-klotho, and vitamin D3 amongst firefighters, as they work in long shifts outside the traditional daytime schedule.

METHODS

The study consisted of 450 participants who were firefighters. We measured FGF-23, α-klotho, and vitamin D3 levels in their blood and a set of questionnaires were given to the participants to evaluate their health habits. After determining and adjusting for potential confounding factors, we compared the levels of FGF-23, α-klotho, and serum vitamin D3 by job and shift types.

RESULTS

FGF-23 and α-klotho levels were significantly higher in shift workers than traditional day workers, and in 3-day cycle shift workers than workers with another shift schedule. When the levels of these substances were compared based on different types of jobs, firefighters had a lower level of vitamin D3. We conclude that shift work is positively correlated with the levels of FGF-23 and α-klotho.

CONCLUSIONS

Levels of FGF-23 and α-klotho were linked to shift work and job types. Although vitamin levels did not differ by shift types, vitamin D3 levels were lower in firefighters. These findings suggest that high levels of FGF-23 and α-klotho are potential risk factors for cancer among firefighters.

Plasma Fibroblast Growth Factor 23 Concentration Is Associated with Intracranial Cerebral Atherosclerosis in Acute Ischemic Stroke Patients

BACKGROUND AND PURPOSE

Fibroblast growth factor 23 (FGF23) is associated with atherosclerosis via nitric-oxide-associated endothelial dysfunction and calcium-phosphate-related bone mineralization. This study aimed to determine the association of the plasma FGF23 concentration with intracranial cerebral atherosclerosis (ICAS) and extracranial cerebral atherosclerosis (ECAS).

METHODS

We prospectively enrolled 262 first-ever ischemic stroke patients in whom brain magnetic resonance was performed and a blood sample acquired within 24 h after admission. Plasma FGF23 concentrations were measured using an enzyme-linked immunosorbent assay. The presence of ICAS or ECAS was defined as a ≥50% decrease in arterial diameter in magnetic resonance angiography. The burden of cerebral atherosclerosis was calculated by adding the total number of vessels defined as ICAS or ECAS.

RESULTS

Our study population included 152 (58.0%) males. The mean age was 64.7 years, and the plasma FGF23 concentration was 347.5±549.6 pg/mL (mean±SD). ICAS only, ECAS only, and both ICAS and ECAS were present in 31.2% (n=82), 4.9% (n=13), and 6.8% (n=18) of the subjects, respectively. In multivariate binary and ordinal logistic analyses, after adjusting for sex, age, and variables for which p<0.1 in the univariate analysis, the plasma FGF23 concentration (per 100 pg/mL) was positively correlated with the presence of ICAS [odds ratio (OR)=1.07, 95% CI=1.00-1.15, p=0.039], burden of ICAS (OR=1.09, 95% CI=1.04-1.15, p=0.001), and burden of ECAS (OR=1.06, 95% CI=1.00-1.12, p=0.038), but it was not significantly related to the presence of ECAS (OR=1.05, 95% CI=0.99-1.12, p=0.073).

CONCLUSIONS

The plasma FGF23 may be a potential biomarker for cerebral atherosclerosis, particularly the presence and burden of ICAS in stroke patients.

Developmental Changes in Phosphate Homeostasis

Phosphate is a multivalent ion critical for a variety of physiological functions including bone formation, which occurs rapidly in the developing infant. In order to ensure maximal bone mineralization, young animals must maintain a positive phosphate balance. To accomplish this, intestinal absorption and renal phosphate reabsorption are greater in suckling and young animals relative to adults. This review discusses the known intestinal and renal adaptations that occur in young animals in order to achieve a positive phosphate balance. Additionally, we discuss the ontogenic changes in phosphotropic endocrine signalling as it pertains to intestinal and renal phosphate handling, including several endocrine factors not always considered in the traditional dogma of phosphotropic endocrine signalling, such as growth hormone, triiodothyronine, and glucocorticoids. Finally, a proposed model of how these factors may contribute to achieving a positive phosphate balance during development is proposed.

Fibroblast growth factor 23 expression in human calcified vascular tissues

Vascular calcification is a major risk for cardiovascular disease and implies the transformation of smooth muscle cells to an osteoblastic phenotype as a consequence of dysregulation of calcium and phosphate metabolism. Fibroblast growth factor (FGF) 23 is the most potent phosphate regulator. Observational studies suggest that high levels of FGF23 are related to cardiovascular morbidity and mortality. In this work, we determined the levels of both the intact and the carboxi-terminal fragments of circulating FGF23 in 133 patients with established cardiovascular disease, the expression of FGF23, its receptors 1 and 3, and its co-receptor Klotho in vascular fragments of aorta, carotid and femoral in 43 out of this group of patients, and in a control group of 20 organ donors. Patients with atherosclerosis and vascular calcification presented increased levels of FGF23 respect to the control group. Vascular immunoreactivity for FGF23 was also significantly increased in patients with vascular calcification as compared to patients without calcification and to controls. Finally, gene expression of FGF23 and RUNX2 were also higher and directly related in vascular samples with calcification. Conversely, expression of Klotho was reduced in patients with cardiovascular disease when comparing to controls. In conclusion, our findings link the calcification of the vascular tissue with the expression of FGF23 in the vessels and with the elevation of circulating levels this hormone.

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

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

Label-free quantitative proteomics identifies Smarca4 is involved in vascular calcification

Vascular calcification (VC) is a pathological process characterized by abnormal deposition of calcium phosphate, hydroxyapatite and other mineral substances in the vascular wall. Hyperphosphorus is an important risk factor associated with VC in the general population and patients with chronic kidney disease (CKD). However, there is still a lack of early biomarkers for hyperphosphorus induced VC. We established a calcific rat aorta vascular smooth muscle cells (RASMCs) model by stimulating with β-glycerophosphate. Then we performed label-free quantitative proteomics combined with liquid chromatograph–mass spectrometer/mass spectrometer (LC-2D-MS/MS）analysis and bioinformatics analysis to find the potential biomarkers for VC. In the current study, we identified 113 significantly proteins. Fifty six of these proteins were significantly up-regulated and the other 57 proteins were significantly decreased in calcific RASMCs, compared to that of normal control cells (fold-change (fc)>1.2, p < .05). Bioinformatics analysis indicated that these significant proteins mainly involved in the placenta blood vessel development and liver regeneration. Their molecule function was cell adhesion molecule binding. Among them, Smarca4 is significantly up-regulated in calcific RASMCs with fc = 2.72 and p = .01. In addition, we also established VC rat model. Real-time quantitative PCR analysis confirmed that the expression of Smarca4 was significantly increased in the aorta of calcified rat. Consistent with the up-regulation of Smarca4, the expression of VC associated microRNA such as miR-133b and miR-155 was also increased. Consequently, our study demonstrates that Smarca4 is involved in hyperphosphorus-induced VC. This finding may contribute to the early diagnosis and prevention of VC.

FGF23: Clinical usefulness and analytical evolution

Fibroblast Growth Factor 23 (FGF23) is a key hormone for the regulation of phosphate homeostasis. Over the past decades, FGF23 was the subject of intense research in the fields of nephrology and the cardiology. It presents a remarkable correlation with well-established biomarkers of cardiovascular disorders in both chronic kidney disease (CKD) and heart failure (HF) patients. The interest of FGF23 lies in its early-onset in the primary course of CKD as well as in the incremental prognosis information it conveys in both CKD and HF. Different types of assays of FGF-23 testing exist, those targeting the intact form (iFGF23), the other one detecting terminal fragments (cFGF23). The issue is still pending which assay suits best for clinical use. Recently, the implementation of this biomarker on multianalyzer platforms, on which other markers of phospho-calcic balance are set up, allows a rapid turn-around-time and a potential financial gain. However, despite the good analytical performances of the automated methods, there is a poor harmonization between assays. The introduction of an international certified reference material should standardize the measurement and improve the harmonization of results from different laboratories. A deeper understanding of physio-pathological mechanisms and processing of FGF-23 should reinforce its clinical indications and might also identify new therapeutic targets for the treatment of CKD and HF.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Premature ovarian aging in BRCA carriers: a prototype of systemic precocious aging?

Purpose

Though former evidence implies a correlation of breast cancer susceptibility gene (BRCA) mutation with reduced ovarian reserve, the data is yet inconsistent. Our aim was to investigate biomarkers of ovarian aging in a cohort of young healthy carriers of the BRCA mutation. We hypothesized that the role played by BRCA genes in aging pathways is not exclusive to the ovary.

Experimental Design

Healthy female BRCA carriers, 40 years or younger and healthy male BRCA carriers, 50 years or younger, were enrolled in the study. Serum anti-mullerian Hormone (AMH), fibroblast growth factor-23 (FGF-23), Klotho and IL-1 were measured by enzyme-linked immunosorbent assay (ELISA). Ovarian AMH and protein kinase B (AKT) mRNA from BRCA carriers who underwent prophylactic oophorectomy and from age-matched, healthy, non-carriers who underwent partial oophorectomy due to benign conditions were analyzed by qPCR.

Results

Thirty-three female (median age 35y) and 20 male (44y) BRCA carriers were enrolled into the study and matched to control non-carriers (34y and 43y, respectively). Serum AMH level was significantly lower in BRCA female carriers than in both non-carrier controls and age-matched nomograms. The levels of ovarian AMH and AKT mRNA were significantly lower in carriers than in controls. The systemic aging cytokines FGF-23, klotho and IL-1 displayed a differential expression in carriers of both genders. FGF-23 level was higher in carriers (P=0.06).

Conclusions

Our results suggest a link between BRCA mutation, accelerated ovarian aging and systemic aging-related pathophysiology.

Fibroblast growth factor-23 in patients with homozygous familial hypercholesterolemia

BACKGROUND

Patients with homozygous familial hypercholesterolemia (HoFH) develop significant vascular calcification early in life, the cause of which is not yet fully understood. Patients with chronic kidney disease have similar vascular calcification, with fibroblast growth factor-23 (FGF23) implicated in these patients.

OBJECTIVE

To determine whether there was a difference in FGF23 between patients with HoFH and age- and gender-matched controls and whether there is a correlation between FGF23 and serum low-density lipoprotein, total cholesterol, and carotid intima-media thickness in patients with HoFH.

METHODS

The study was a cross-sectional review involving 30 patients with HoFH attending the Charlotte Maxeke Johannesburg Academic Hospital Lipid Clinic in Parktown, South Africa, as well as 30 age- and gender-matched healthy controls. FGF23, fasting lipid profiles, calcium, and phosphate were measured. B-mode ultrasonography of the carotid arteries was done to assess the extent and severity of arterial calcification.

RESULTS

There was no difference in mean FGF23 between the patient and control groups (62.07 ± 26.42 pg/mL vs 63.69 ± 19.84 pg/mL; P = .4621) nor was there any correlation between FGF23 and low-density lipoprotein cholesterol (P = .9483 and .8474) or total cholesterol (P = .9261 and .859). In the HoFH patients, FGF23 did not correlate significantly with any cardiovascular disease.

CONCLUSIONS

Serum FGF23 is not elevated in patients with HoFH when compared to non-familial hypercholesterolemia age- and gender-matched controls, and there is no correlation between serum FGF23 and cardiovascular disease in patients with HoFH. FGF23 does not appear to be a major factor for arterial calcification in HoFH.

Multiple faces of fibroblast growth factor-23

PURPOSE OF REVIEW

This review examines the role of fibroblast growth factor-23 (FGF-23) in mineral metabolism, innate immunity and adverse cardiovascular outcomes.

RECENT FINDINGS

FGF-23, produced by osteocytes in bone, activates FGFR/α-Klotho (α-Kl) complexes in the kidney. The resulting bone-kidney axis coordinates renal phosphate reabsorption with bone mineralization, and creates a counter-regulatory feedback loop to prevent vitamin D toxicity. FGF-23 acts to counter-regulate the effects of vitamin D on innate immunity and cardiovascular responses. FGF-23 is ectopically expressed along with α-Kl in activated macrophages, creating a proinflammatory paracrine signaling pathway that counters the antiinflammatory actions of vitamin D. FGF-23 also inhibits angiotensin-converting enzyme 2 expression and increases sodium reabsorption in the kidney, leading to hypertension and left ventricular hypertrophy. Finally, FGF-23 is purported to cause adverse cardiac and impair neutrophil responses through activation of FGFRs in the absence of α-Kl. Although secreted forms of α-Kl have FGF-23 independent effects, the possibility of α-Kl independent effects of FGF-23 is controversial and requires additional experimental validation.

SUMMARY

FGF-23 participates in a bone-kidney axis regulating mineral homeostasis, proinflammatory paracrine macrophage signaling pathways, and in a bone-cardio-renal axis regulating hemodynamics that counteract the effects of vitamin D.

Predictive Value of Aortic Valve Calcification for Periprocedural Myocardial Injury in Patients Undergoing Percutaneous Coronary Intervention

AIMS

Previous studies have shown that aortic valve calcification (AVC) was associated with cardiovascular events and mortality. On the other hand, periprocedural myocardial injury (PMI) in percutaneous coronary intervention (PCI) is a well-known predictor of subsequent mortality and poor clinical outcomes. The purpose of the study was to assess the hypothesis that the presence of AVC could predict PMI in PCI.

METHODS

This study included 370 patients treated with PCI for stable angina pectoris. AVC was defined as bright echoes ＞1 mm on one or more cusps of the aortic valve on ultrasound cardiography (UCG). PMI was defined as an increase in high-sensitivity troponin T level of ＞5 times the upper normal limit (＞0.070 ng/ml) at 24 hours after PCI.

RESULTS

AVC was detected in 45.9% of the patients (n=170). The incidence of PMI was significantly higher in the patients with AVC than in those without AVC (43.5% vs 21.0%, p＜0.001). The presence of AVC independently predicted PMI after adjusting for other significant variables (odds ratio 2.26, 95% confidence interval 1.37-3.74, p=0.002). Other predictors were male sex, age, estimated glomerular filtration rate, and total stent length. Furthermore to predict PMI, adding AVC to the established risk factors significantly improved the area under the receiver operating characteristic curves, from 0.68 to 0.72, of the PMI prediction model (p=0.025).

CONCLUSION

The presence of AVC detected in UCG could predict the incidence of PMI.

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

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

FGF23 and inflammation

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

Aortic Artery and Cardiac Valve Calcification are Associated with Mortality in Chinese Hemodialysis Patients: A 3.5 Years Follow-up

BACKGROUND

This study was to investigate the relationship among aortic artery calcification (AAC), cardiac valve calcification (CVC), and mortality in maintenance hemodialysis (MHD) patients.

METHODS

All MHD patients in Shanghai Ruijin Hospital in July 2011 were included. To follow up for 42 months, clinical data, predialysis blood tests, echocardiography, and lateral lumbar X-ray plain radiography results were collected. Plasma FGF23 level was measured using a C-terminal assay.

RESULTS

Totally, 110 MHD patients were involved in this study. Of which, 64 (58.2%) patients were male, the mean age was 55.2 ± 1.4 years old, and the median dialysis duration was 29.85 (3.0-225.5) months. About 25.5% of the 110 MHD patients had CVC from echocardiography while 61.8% of the patients had visible calcification of aorta from lateral lumbar X-ray plain radiography. After 42 months follow-up, 25 (22.7%) patients died. Kaplan-Meier analysis showed that patients with AAC or CVC had a significant greater number of all-cause and cardiovascular deaths than those without. In multivariate analyses, the presence of AAC was a significant factor associated with all-cause mortality (hazard ratio [HR]: 3.149, P = 0.025) in addition to lower albumin level and lower 25-hydroxy Vitamin D (25(OH)D) level. The presence of CVC was a significant factor associated with cardiovascular mortality (HR: 3.800, P = 0.029) in addition to lower albumin level and lower 25(OH)D level.

CONCLUSION

Lateral lumbar X-ray plain radiography and echocardiography are simple methods to detect AAC and CVC in dialysis patients. The presence of AAC and CVC was independently associated with mortality in MHD patients. Regular follow-up by X-ray and echocardiography could be a useful method to stratify mortality risk in MHD patients.

Elevation in fibroblast growth factor 23 and its value for identifying subclinical atherosclerosis in first-degree relatives of patients with diabetes

Accumulating evidence supported an association between diabetes and fibroblast growth factor 23 (FGF23). The goal of the present study was to explore alteration in serum FGF23 levels and to assess its value for identifying subclinical atherosclerosis in normoglycemic individuals with a first-degree family history of diabetes (FHD). The study enrolled 312 subjects with a first-degree FHD and 1407 subjects without an FHD. Serum FGF23 levels were detected by a sandwich enzyme-linked immunosorbent assay. Serum FGF23 levels were much higher in subjects with a first-degree FHD than in those without an FHD (P = 0.006). A first-degree FHD was positively associated with serum FGF23 levels, independent of C-IMT and cardiovascular factors (both P < 0.05). In subjects with a first-degree FHD, only those with serum FGF23 levels in the upper quartile were more likely to have an increased C-IMT (odds ratio = 2.263, P < 0.05). As conclusions, a first-degree FHD contributes to the increased serum FGF23 levels independently. Subjects with a first-degree FHD need higher serum FGF23 levels to indicate subclinical atherosclerosis. The influence of a first-degree FHD on serum FGF23 levels should be considered to avoid overestimating the risk of cardiovascular disease in normoglycemic individuals with a first-degree FHD.

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

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

Predictors of abdominal aortic calcification progression in patients with chronic kidney disease without hemodialysis

BACKGROUND AND AIMS

Abdominal aortic calcification (AAC) is an important predictor of cardiovascular mortality in patients with chronic kidney disease (CKD). However, little is known regarding AAC progression in these patients. This study aimed to identify risk factors associated with AAC progression in patients with CKD without hemodialysis.

METHODS

We recruited 141 asymptomatic patients with CKD without hemodialysis [median estimated glomerular filtration rate (eGFR), 40.3 mL/min/1.73 m²] and evaluated the progression of the abdominal aortic calcification index (ACI) over 3 years. To identify risk factors contributing to the rate of ACI progression, the associations between baseline clinical characteristics and annual change in ACI for each CKD category were analyzed. The annual change of ACI (ΔACI/year) was calculated as follows: (second ACI - first ACI)/duration between the two evaluations.

RESULTS

Median ΔACI/year values significantly increased in advanced CKD stages (0.73%, 0.87%, and 2.24%/year for CKD stages G1-2, G3, and G4-5, respectively; p for trend = 0.041). The only independent risk factor for AAC progression in mild to moderate CKD (G1-3, eGFR ≥ 30 mL/min/1.73 m²) was pulse pressure level (β = 0.258, p = 0.012). In contrast, parathyroid hormone (PTH) level was significantly correlated with ΔACI/year (β = 0.426, p = 0.007) among patients with advanced CKD (G4-5, eGFR < 30 mL/min/1.73 m²).

CONCLUSIONS

This study suggests that the AAC progression rate was significantly accelerated in patients with advanced CKD. In addition, measuring PTH is useful to evaluate both bone turnover and AAC progression in patients with advanced CKD.

Abdominal aortic calcification in patients with CKD

Background

Abdominal aortic calcification (AAC) is independently associated with cardiovascular events in dialysis patients and in the general population. However, data in non-dialysis chronic kidney disease (CKD) patients are limited. We analyzed determinants and prognostic value of AAC in non-dialysis CKD patients.

Methods

We included patients with CKD not receiving renal replacement therapy from the MASTERPLAN study, a randomized controlled trial that started in 2004. In the period 2008–2009, an X-ray to evaluate AAC was performed in a subgroup of patients. We studied AAC using a semi-quantitative scoring system by lateral lumbar X-ray. We used baseline and 2-year data to find determinants of AAC. We used a composite cardiovascular endpoint and propensity score matching to evaluate the prognostic value of AAC.

Results

In 280 patients an X-ray was performed. In 79 patients (28 %) the X-ray showed no calcification, in 62 patients (22 %) calcification was minor (<4), while 139 patients (50 %) had moderate or heavy calcification (≥4). Older age, prior cardiovascular disease, higher triglyceride levels, and higher phosphate levels were independent determinants of a calcification score ≥4. AAC score ≥4 was independently associated with cardiovascular events, with a hazard ratio of 5.5 (95 % confidence interval 1.2–24.8).

Conclusions

Assessment of AAC can identify CKD patients at higher cardiovascular risk, and may provide important information for personalized treatment. Whether this approach will ultimately translate into better outcomes remains to be answered.

Electronic supplementary material

The online version of this article (doi:10.1007/s40620-015-0260-7) contains supplementary material, which is available to authorized users.

Plasma FGF23 and Calcified Atherosclerotic Plaque in African Americans with Type 2 Diabetes Mellitus

BACKGROUND

Fibroblast growth factor 23 (FGF23) is a phosphaturic hormone implicated in disorders of serum phosphorus concentration and vitamin D. The role of FGF23 in vascular calcification remains controversial.

METHODS

Relationships between FGF23 and coronary artery calcified atherosclerotic plaque (CAC), aortoiliac calcified plaque (CP), carotid artery CP, volumetric bone mineral density (vBMD), albuminuria, and estimated glomerular filtration rate (eGFR) were determined in 545 African Americans with type 2 diabetes (T2D) and preserved kidney function in African American-Diabetes Heart Study participants. Generalized linear models were fitted to test associations between FGF23 and cardiovascular, bone, and renal phenotypes, and change in measurements over time, adjusting for age, gender, African ancestry proportion, body mass index, diabetes duration, hemoglobin A1c, blood pressure, renin-angiotensin-system inhibitors, statins, calcium supplements, serum calcium, and serum phosphate.

RESULTS

The sample was 56.7% female with a mean (SD) age of 55.6 (9.6) years, diabetes duration of 10.3 (8.2) years, eGFR 90.9 (22.1) ml/min/1.73 m2, urine albumin:creatinine ratio (UACR) 151 (588) (median 13) mg/g, plasma FGF23 161 (157) RU/ml, and CAC 637 (1,179) mg. In fully adjusted models, FGF23 was negatively associated with eGFR (p < 0.0001) and positively associated with UACR (p < 0.0001) and CAC (p = 0.0006), but not with carotid CP or aortic CP. Baseline FGF23 concentration did not associate with changes in vBMD or CAC after a mean of 5.1 years follow-up.

CONCLUSIONS

Plasma FGF23 concentrations were independently associated with subclinical coronary artery disease, albuminuria, and kidney function in the understudied African American population with T2D. Findings support relationships between FGF23 and vascular calcification, but not between FGF23 and bone mineral density, in African Americans lacking advanced nephropathy.

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.

Association of bone-derived biomarkers with vascular calcification in chronic hemodialysis patients

BACKGROUND

Abdominal aortic calcification (AAC) is commonly observed in chronic dialysis patients and is associated with cardiovascular and all-cause mortality. We investigated the factors associated with AAC and analyze the relationship between bone-derived biomarkers and AAC.

METHODS

We enrolled 227 stable hemodialysis patients. Vascular calcifications were assessed using lateral lumbar radiography of the abdominal aorta. Demographic data were collected and serum levels of biochemical and bone-derived biomarkers, including sclerostin, Dickkopf-1 (DKK-1), and fibroblast growth factor 23 (FGF23), were measured.

RESULTS

One hundred sixty-one patients (71.0%) had AAC. Patients with AAC score≧13 were older, with higher body mass index (BMI), serum calcium, calcium phosphate product, high-sensitivity C-reactive protein (hsCRP), and FGF23 levels. Sclerostin and DKK-1 levels were inversely associated with AAC severity, and FGF23 was directly related to vascular calcification. Hypertension, vascular disease, hsCRP, FGF23, and sclerostin were independent AAC determinants.

CONCLUSIONS

Chronic hemodialysis patients have a high prevalence of vascular calcifications. Levels of circulating sclerostin, DKK-1, and FGF23 were related to AAC severity. Sclerostin and FGF23 were independently associated with AAC.

Serum fetuin-A levels and abdominal aortic calcification in healthy men - The STRAMBO study

Vascular calcification results from an imbalance between increased extracellular levels of calcium and phosphate, reduced solubility, and low levels of calcification inhibitors in blood or the vascular wall. Fetuin-A is a major circulating calcification inhibitor. Rodent models of fetuin-A deficit indicate its calcification inhibiting potential. Clinical studies suggest its role as a biomarker in vascular disease. This cross-sectional study was performed in a cohort of 974 men aged ≥ 40 years (average 68 years) consisting of men holding health insurance cover with Mutuelle des Travailleurs de la Région Lyonnaise. Abdominal aortic calcification (AAC) was assessed semi-quantitatively on lateral dual energy X-ray absorptiometry (DXA) spine scans. Serum fetuin-A was measured by an immunoassay. After adjustment for confounders (age, lifestyle, body composition, health status, treatment, glomerular filtration rate [GFR], hormones, and cytokines), prevalence of severe AAC (AAC score>4) decreased with increasing fetuin-A levels (OR=0.68 per SD increase, 95% CI: 0.54-0.84, p<0.001). After adjustment for confounders, low fetuin-A and hypertension were each associated with higher odds of AAC>4. Coexistence of low serum fetuin-A levels and heavy smoking, elevated fibroblast growth factor 23 levels or low serum dickkopf-1 levels were associated with higher odds of AAC>4. Similar results were obtained for 789 men with GFR>60 mL/min/1.73 m(2). Similar results were obtained when severe AAC was defined as AAC score >3 or AAC>5. Thus, lower serum fetuin-A levels are associated with severe AAC, suggesting that poor calcification inhibitory potential contributes to vascular calcification, independently of renal impairment.

Fibroblast Growth Factor 23 Is Associated With Carotid Plaque Presence and Area: The Northern Manhattan Study

OBJECTIVE

Elevated fibroblast growth factor 23 (FGF23), a hormone that regulates phosphate homeostasis, has been associated with mortality, cardiovascular events, and stroke, and to arterial calcification in chronic kidney disease, but its role in atherosclerosis is unclear and population-based studies are lacking. We hypothesized that elevated FGF23 would associate with carotid plaque presence, area, and echogenicity in the race/ethnically diverse community-based Northern Manhattan Study (NOMAS) sample.

APPROACH AND RESULTS

There were 1512 stroke-free NOMAS participants with FGF23 and 2-dimensional carotid ultrasound data (mean age, 68±9 years; 61% women; 62% Hispanic, 18% black, and 18% white). We used multivariable linear and logistic regression to evaluate FGF23, continuously and by quintiles, as a correlate of carotid plaque, plaque area (cubic root transformed), and echogenicity adjusting for sociodemographic and vascular risk factors. Participants with FGF23 levels in the top quintile were more likely to have carotid plaque (odds ratio, 1.49; 95% confidence interval, 1.02-2.19; P=0.04) and larger plaque area (β=0.32 mm(2), 95% confidence interval, 0.10-0.53 mm(2); P=0.004) than those in the lowest quintile, adjusting for estimated glomerular filtration rate, demographics, and vascular risk factors. Linear regression models also showed that log transformed FGF23 (LnFGF23) associated with greater odds of plaque presence (odds ratio, 1.26 per LnFGF23; 95% confidence interval, 1.01-1.58; P=0.04), and plaque area (β=0.19 mm(2) per LnFGF23; 95% confidence interval, 0.07-0.31 mm(2); P=0.002).

CONCLUSIONS

Higher FGF23 associated with greater likelihood and burden of carotid atherosclerosis independent of CKD. Atherosclerosis may be a mechanism through which FGF23 increases cardiovascular events and stroke.

High Parathyroid Hormone Level and Osteoporosis Predict Progression of Coronary Artery Calcification in Patients on Dialysis

Coronary artery calcifications (CACs) are observed in most patients with CKD on dialysis (CKD-5D). CACs frequently progress and are associated with increased risk for cardiovascular events, the major cause of death in these patients. A link between bone and vascular calcification has been shown. This prospective study was designed to identify noninvasive tests for predicting CAC progression, including measurements of bone mineral density (BMD) and novel bone markers in adult patients with CKD-5D. At baseline and after 1 year, patients underwent routine blood tests and measurement of CAC, BMD, and novel serum bone markers. A total of 213 patients received baseline measurements, of whom about 80% had measurable CAC and almost 50% had CAC Agatston scores>400, conferring high risk for cardiovascular events. Independent positive predictors of baseline CAC included coronary artery disease, diabetes, dialysis vintage, fibroblast growth factor-23 concentration, and age, whereas BMD of the spine measured by quantitative computed tomography was an inverse predictor. Hypertension, HDL level, and smoking were not baseline predictors in these patients. Three quarters of 122 patients completing the study had CAC increases at 1 year. Independent risk factors for CAC progression were age, baseline total or whole parathyroid hormone level greater than nine times the normal value, and osteoporosis by t scores. Our results confirm a role for bone in CKD-associated CAC prevalence and progression.

Vascular calcification: from pathophysiology to biomarkers

The link between vascular calcification (VC) and increased mortality is now well established. Over time, as clinical importance of this phenomenon has begun to be fully considered, scientists have highlighted more and more physiopathological mechanisms and signaling pathways that underlie VC. Several conditions such as diabetes, dyslipidemia and renal diseases are undoubtedly identified as predisposing factors. But even if the process is better understood, many questions still remain unanswered. This review briefly develops the various theories that attempt to explain mineralization genesis. Nonetheless, the main purpose of the article is to provide a profile of the various existing biomarkers of VC. Indeed, in the past years, a lot of inhibitors and promoters, which form a dense and interconnected network, were identified. Given importance to assess and control mineralization process, a focusing on accumulated knowledge of each marker seemed to be necessary. Therefore, we tried to define their respective role in the physiopathology and how they can contribute to calcification risk assessment. Among these, Klotho/fibroblast growth factor-23, fetuin-A, Matrix Gla protein, Bone morphogenetic protein-2, osteoprotegerin, osteopontin, osteonectin, osteocalcin, pyrophosphate and sclerostin are specifically discussed.

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.

FGF23 directly impairs endothelium-dependent vasorelaxation by increasing superoxide levels and reducing nitric oxide bioavailability

Fibroblast growth factor 23 (FGF23) is secreted primarily by osteocytes and regulates phosphate and vitamin D metabolism. Elevated levels of FGF23 are clinically associated with endothelial dysfunction and arterial stiffness in chronic kidney disease (CKD) patients; however, the direct effects of FGF23 on endothelial function are unknown. We hypothesized that FGF23 directly impairs endothelial vasorelaxation by hindering nitric oxide (NO) bioavailability. We detected expression of all four subtypes of FGF receptors (Fgfr1-4) in male mouse aortas. Exogenous FGF23 (90-9,000 pg/ml) did not induce contraction of aortic rings and did not relax rings precontracted with PGF2α. However, preincubation with FGF23 (9,000 pg/ml) caused a ∼36% inhibition of endothelium-dependent relaxation elicited by acetylcholine (ACh) in precontracted aortic rings, which was prevented by the FGFR antagonist PD166866 (50 nM). Furthermore, in FGF23-pretreated (9,000 pg/ml) aortic rings, we found reductions in NO levels. We also investigated an animal model of CKD (Col4a3(-/-) mice) that displays highly elevated serum FGF23 levels and found they had impaired endothelium-dependent vascular relaxation and reduced nitrate production compared with age-matched wild types. To elucidate a mechanism for the FGF23-induced impairment, we measured superoxide levels in endothelial cells and aortic rings and found that they were increased following FGF23 treatment. Crucially, treatment with the superoxide scavenger tiron reduced superoxide levels and also restored aortic relaxation to ACh. Therefore, our data suggest that FGF23 increases superoxide, inhibits NO bioavailability, and causes endothelial dysfunction in mouse aorta. Together, these data provide evidence that high levels of FGF23 contribute to cardiovascular dysfunction.

A current understanding of vascular calcification in CKD

Patients with chronic kidney disease (CKD) and end-stage renal disease (ESRD) have significant cardiovascular morbidity and mortality that is in part due to the development of vascular calcification. Vascular calcification is an active, highly regulated process that shares many similarities with normal bone formation. New discoveries related to extracellular vesicles, microRNAs, and calciprotein particles continue to reveal the mechanisms that are involved in the initiation and progression of vascular calcification in CKD. Further innovations in these fields are critical for the development of biomarkers and therapeutic options for patients with CKD and ESRD.

Bone: a new endocrine organ at the heart of chronic kidney disease and mineral and bone disorders

Recent reports of several bone-derived substances, some of which have hormonal properties, have shed new light on the bone-cardiovascular axis. Deranged concentrations of humoral factors are not only epidemiologically connected to cardiovascular morbidity and mortality, but can also be causally implicated, especially in chronic kidney disease. FGF23 rises exponentially with advancing chronic kidney disease, seems to reach maladaptive concentrations, and then induces left ventricular hypertrophy, and is possibly implicated in the process of vessel calcification. Sclerostin and DKK1, both secreted mainly by osteocytes, are important Wnt inhibitors and as such can interfere with systems for biological signalling that operate in the vessel wall. Osteocalcin, produced by osteoblasts or released from mineralised bone, interferes with insulin concentrations and sensitivity, and its metabolism is disturbed in kidney disease. These bone-derived humoral factors might place the bone at the centre of cardiovascular disease associated with chronic kidney disease. Most importantly, factors that dictate the regulation of these substances in bone and subsequent secretion into the circulation have not been researched, and could provide entirely new avenues for therapeutic intervention.

Quantitative analysis of abdominal aortic calcification in CKD patients without dialysis therapy by use of the Agatston score

BACKGROUND/AIM

The aim of the present study was to quantitatively examine factors associated with aortic calcification in non-dialysis CKD patients.

METHODS

We quantitatively investigated aortic calcification from the renal artery to the bifurcation in 149 non-dialysis CKD patients (58±16 years; 96 males and 53 females, 48 diabetics; eGFR 40.3 ± 29.3 ml/min), and measured Agatston scores using multi-slice computed tomography.

RESULT

Of 149 patients, aortic calcification was present in 117. In patients with aortic calcification, age (p<0.001), C-reactive protein (p<0.001), and intact-PTH (p < 0.001) were significantly higher, estimated glomerular filtration rate (eGFR) was significantly lower (p<0.001), and diabetes was observed more often (p<0.05). In regards to the degree of aortic calcification, the Agatston scores correlated significantly and positively with age (ρ=0.438, p<0.001) and serum phosphate (ρ=0.208, p=0.024), and correlated significantly but negatively with e-GFR (ρ=-0.353, p<0.001). In multiple regression analysis, eGFR was associated significantly and independently with the log [Agatston score] (β=-0.346, p<0.01), after adjustment for several confounders including serum phosphate and the presence of diabetes.

CONCLUSIONS

Hyperphospatemia, chronic inflammation, diabetes, and decreased GFR are associated significantly with the presence of aortic calcification in non-dialysis CKD patients. Decreased eGFR was associated significantly and independently with the quantitative degree of aortic calcification.