Fibroblast growth factor 23, iron and inflammation - are they related in early stages of chronic kidney disease?

Research Progress of Fibroblast Growth Factor 21 in Fibrotic Diseases

Fibrosis is a common pathological outcome of chronic injuries, characterized by excessive deposition of extracellular matrix components in organs, as seen in most chronic inflammatory diseases. At present, there is an increasing tendency of the morbidity and mortality of diseases caused by fibrosis, but the treatment measures for fibrosis are still limited. Fibroblast growth factor 21 (FGF21) belongs to the FGF19 subfamily, which also has the name endocrine FGFs because of their endocrine manner. In recent years, it has been found that plasma FGF21 level is significantly correlated with fibrosis progression. Furthermore, there is evidence that FGF21 has a pronounced antifibrotic effect in a variety of fibrotic diseases. This review summarizes the biological effects of FGF21 and discusses what is currently known about this factor and fibrosis disease, highlighting emerging insights that warrant further research.

Novel Iron Parameters in Patients with Type 2 Diabetes Mellitus in Relation to Kidney Function

BACKGROUND/AIMS

Anemia of chronic disease is a common feature in diabetes and chronic kidney disease. Hepcidin is the key element involved in iron metabolism; however, studies on new indices of iron status are still ongoing. The aim of the study was to assess novel iron parameters in patients with type 2 diabetes mellitus in relation to kidney function.

METHODS

The study included 80 type 2 diabetic patients and 23 healthy volunteers. Standard laboratory measurements were used to measure the iron status, complete blood count, creatinine, the estimated glomerular filtration rate (eGFR), serum lipids, and brain natriuretic peptides (BNPs). Commercially available kits were used to measure hepcidin-25, the soluble transferrin receptor (sTfR), growth differentiation factor-15 (GDF-15), and hypoxia-inducible factor-1 alpha.

RESULTS

Anemia was present in 65% of the studied patients. The control group was found to have significantly higher hepcidin, sTfR, and GDF-15, and lower hemoglobin and iron. When compared with patients with eGFR values ≥60 mL/min/1.73 m² and <60 mL/min/1.73 m², we found that patients with higher eGFR had higher hemoglobin, ferritin, and HIF-1 alpha, lower BNP, and were younger. We found that levels of HIF-1 alpha are negligible in the studied population and were related to age only in patients with eGFR values ≥60 mL/min/1.73 m².

CONCLUSION

A comprehensive assessment of iron status is rarely performed. Novel biomarkers of iron metabolism are not generally related to kidney function. Whether the assessment of HIF-1 alpha would be a marker of efficient anemia therapy with HIF-prolyl hydroxylase inhibitors is still a matter for further study.

The Assessment of the Usefulness of Selected Markers in the Diagnosis of Chronic Kidney Disease in Children

INTRODUCTION

The kidney deterioration, which starts in childhood often leads to end-stage renal failure in the future. Therefore, searching for an early, sensitive, and specific biomarkers became a paramount for chronic kidney disease diagnosis. The aim of this study was the assessment of markers: KIM-1, FGF-23, NAG, NGAL, and uromodulin for diagnosis of preclinical phase of the disease in children.

PATIENTS AND METHODS

59 children (15 boys, 44 girls from 6 months to 17 years old) with kidney disorders, which had clinical indications for renoscintigraphy, were included in the study. All patients were divided depending on the result of renoscintigraphy (renal scarring vs normal kidney picture) and depending on the level of estimated glomerular filtration rate (glomerular hyperfiltration vs normal filtration rate). The concentration of uromoduline, KIM-1, FGF-23, NAG, and NGAL in serum and of NGAL and uromoduline in urine were measured in all studied groups.

RESULTS

The children with glomerular hyperfiltration had a statistically significantly higher serum values of FGF-23 and NGAL than the children with normal filtration rate (P < .05). There were no statistically significant differences in serum concentrations of tested markers in children with renal scars in comparison to children with normal renal image. There was no statistically significant difference in the concentration of tested markers in urine.

CONCLUSIONS

The study confirmed the possible usefulness of FGF-23 and NGAL in detecting the preclinical-stage of renal disease associated with glomerular hyperfiltration in children. The study do not allow to indicate markers, which could be useful in the early diagnosis of kidney damage visible in the scintigraphic examination.

Pregnancy-associated plasma protein A as a predictor of all-cause mortality and cardiovascular events in patients with chronic kidney disease: a meta-analysis of prospective studies

INTRODUCTION

The aim of the study was to assess the association of elevated serum pregnancy associated plasma protein A (PAPP-A) and the risk of all-cause mortality, cardiovascular events and mortality due to infection in patients with chronic kidney disease (CKD).

MATERIAL AND METHODS

We systematically searched the Medline database up to March 2017. A random effects model was used to pool the relative risks (RRs) and their 95% confidence intervals (CIs). Sensitivity analysis and subgroup analysis were performed to explore the potential sources of heterogeneity.

RESULTS

Six studies involving 2034 subjects were included. The pooled RRs for the risk of all-cause mortality and cardiovascular events were 1.50 (95% CI: 1.17-1.92), 1.26 (95% CI: 0.95-1.69), respectively. Sensitivity analysis by excluding each individual study showed no influence on the main results. Subgroup analysis showed that age, male proportion, follow-up term, and assay methods were not modifiable factors.

CONCLUSIONS

Our study suggests that elevated serum PAPP-A is associated with the risk of all-cause mortality in patients with CKD.

Iron Infusion and Induced Hypophosphatemia: The Role of Fibroblast Growth Factor-23

The mechanism of action of fibroblast growth factor-23 (FGF23) is becoming increasingly clearer as a result of studies that have defined its structure and pleiotropic effects. Furthermore, data are emerging on the effects exerted on this hormone by iron administration. Ten main iron formulations are recognized (with clear differences in composition and possible reactions of intolerance and anaphylaxis), which are indicated for iron deficiency anemia, including nephropathic subjects, as suggested by medical guidelines. With some types of iron formulation (especially iron carboxymaltose) a particular side effect has been observed: hypophosphatemia, mediated by FGF23. This review aims to draw attention to this correlation and the contradiction represented by the presence of both positive and negative modulation by FGF23, with the effects induced by its increase even after long-term treatment with iron formulation. However, more evidence is needed to understand the reasons for this differential stimulation.

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.

A Wearable Iron-Based Implant as an Intramedullary Nail in Tibial Shaft Fracture of Sheep

A stable repaired fracture is the key factor responsible for the recovery of a damaged bone. The iron-based implant is one of the biodegradable metals that have been proven safe as a fracture fixation device. The objective of our experimental approach was to examine the potential of the iron-based implant as a biodegradable metal in tibia shaft fracture in sheep chronically. The samples used for this experiment were iron-based and stainless steel implants. Each had a diameter of 5 mm. These samples were analyzed through 3 phases which are material characterization, in vitro and in vivo examination. The samples were examined using a scanning electron microscope with energy dispersive spectrometer and X-ray diffraction. Based on the analysis carried out, the samples contained 90,02% and 60,81% Fe for iron-based implant and stainless implant, respectively. Both implants maintained high viability when being in contact with calf pulmonary artery endothelial cells, indicating that both implants had a minimum response to the cell in a hemocytometer and methyl tetrazolium (MTT) assay. The systemic effect of the implants was observed using hematology and blood chemistry examination. Data collection also shows that both implants also had a minimum response to the erythrocytes, leucocytes, blood chemistry, and blood mineral during the period of observation. Therefore, it could be concluded that the iron-based implant is tolerable for a period of 9 months. It also has the potential to be used as a biodegradable orthopedic implant.

Interleukin-6 Contributes to the Development of Anemia in Juvenile CKD

Introduction

Anemia is a common complication of chronic kidney disease (CKD) in children; however, the role of inflammation in its pathogenesis remains incompletely understood.

Methods

To elucidate the role of interleukin (IL)-6 in renal anemia, we induced CKD by adenine diet in juvenile wild-type (WT) and IL-6 deficient (Il6KO) mice, and examined serum IL-6 and relevant parameters in children with CKD.

Results

WT-CKD mice developed anemia despite increases in serum erythropoietin and displayed low serum iron and elevated serum IL-6. IL-6 deficiency resulted in a significant improvement of red blood cell count and hemoglobin in CKD mice. This effect was associated with improvement of hypoferremia by Il6 deletion, likely mediated by hepcidin. However, correction of hypoferremia by oral iron supplementation in WT-CKD mice did not fully replicate the protective effects of Il6 deletion, suggesting an additional iron-independent role for IL-6 in CKD-anemia. Indeed, Il6 deletion mitigated the severity of renal fibrosis and alleviated relative erythropoietin insufficiency in CKD mice. Cytokine profiling in a pediatric CKD cohort demonstrated that of 10 cytokines (IL-1β, IL-2, IL-4, IL-6, IL-8, IL-10, IL-12, IL-13, tumor necrosis factor (TNF)-α, and interferon-γ), only IL-6 was significantly (inversely) associated with hemoglobin when adjusted for glomerular filtration rate (GFR). The association between IL-6 and hemoglobin in children with CKD remained significant after adjustment for CKD stage, iron therapy, and hepcidin.

Discussion

IL-6 contributes to development of anemia in juvenile CKD, through mechanisms that include induction of hypoferremia, aggravation of renal fibrosis, and alteration of the erythropoietin axis. IL-6 appears to be a promising therapeutic target in the management of CKD-anemia.