α-klotho and anemia in patients with chronic kidney disease patients: A new perspective

Ferric citrate for the treatment of hyperphosphatemia and iron deficiency anaemia in patients with NDD-CKD: a systematic review and meta-analysis

Background: The application of ferric citrate therapy has yielded unexpected benefits in recent years for Chronic kidney disease patients suffering from hyperphosphatemia and iron deficiency -anaemia. Despite this, earlier research on the impact of ferric citrate on NDD-CKD has been contentious. Objective: The goal of the meta-analysis is to evaluate the evidence regarding the advantages and dangers of ferric citrate for the treatment of hyperphosphatemia and iron deficiency anaemia in NDD-CKD patients. Methods: Between the start of the study and June 2022, we searched PubMed, Embase, Cochrane, EBSCO, Scopus, Web of Science, Wan Fang Data, CNKI, and VIP databases for randomised controlled trials of iron citrate for hyperphosphatemia and anaemia in patients with NDD-CKD. For binary categorical data, risk ratios (OR) were employed, and for continuous variables, weighted mean differences The effect sizes for both count and measurement data were expressed using 95% confidence intervals Results: The meta-analysis includes eight trials with a total of 1281 NDD-CKD patients. The phosphorus-lowering effect of ferric citrate was greater compared to the control group (WMD, -0.55, 95% CI, -0.81 to -0.28; I2 = 86%, p < 0.001). Calcium (WMD, 0.092; 95% CI, -0.051 to 0.234; p > 0.05; I2 = 61.9%), PTH (WMD, -0.10; 95% CI, -0.44 to 0.23; I2 = 75%, p > 0.05) and iFGF23 (WMD, -7.62; 95% CI, -21.18 to 5.94; I2 = 20%, p > 0.05) levels were not statistically different after ferric citrate treatment compared to control treatment. Furthermore, ferric citrate increased iron reserves and haemoglobin. The ferric citrate group had considerably greater levels than the controls. Ferric citrate, on the other hand, may raise the risk of constipation, diarrhoea, and nausea. Conclusion: This meta-analysis found that ferric citrate had a beneficial effect in the treatment of NDD-CKD, particularly in reducing blood phosphorus levels when compared to a control intervention. It also shown that ferric citrate has a favourable effect on iron intake and anaemia management. In terms of safety, ferric citrate may increase the likelihood of gastrointestinal side effects.

The association of soluble Klotho levels with anemia and hemoglobin variability in hemodialysis patients

INTRODUCTION

The anti-aging protein Klotho levels are decreased, and Klotho deficiency is associated with cardiovascular diseases in patients with chronic kidney disease. There are recent studies about the relation between soluble Klotho levels and anemia. We aimed to investigate the correlation of anemia and hemoglobin variability with soluble Klotho levels in hemodialysis patients.

METHODS

Ninety-one hemodialysis patients were included in this study. The mean hemoglobin value, hemoglobin variability, and coefficient of variation of hemoglobin for each patient were calculated. According to mean hemoglobin levels, two groups were defined as under 11 and ≥11 g/dl. Soluble Klotho levels of each patient were studied.

RESULTS

Mean hemoglobin levels, hemoglobin variability, and coefficient of variation of hemoglobin were not significantly correlated with soluble Klotho levels. According to mean hemoglobin levels under 11 and ≥ 11 g/dl, there was no statistically significant correlation between anemia and soluble Klotho levels.

CONCLUSION

Soluble Klotho levels were not associated with anemia and hemoglobin variability in hemodialysis patients. Further studies are needed to reveal the complicated relation between anemia and soluble Klotho levels.

Administration of α-Klotho Does Not Rescue Renal Anemia in Mice

Renal anemia is a common complication in chronic kidney disease (CKD), associated with decreased production of erythropoietin (EPO) due to loss of kidney function, and subsequent decreased red blood cell (RBC) production. However, many other factors play a critical role in the development of renal anemia, such as iron deficiency, inflammation, and elevated fibroblast growth factor 23 (FGF23) levels. We previously reported that inhibition of FGF23 signaling rescues anemia in mice with CKD. In the present study we sought to investigate whether α-Klotho deficiency present in CKD also contributes to the development of renal anemia. To address this, we administered α-Klotho to mice with CKD induced by an adenine-rich diet. Mice were sacrificed 24 h after α-Klotho injection, and blood and organs were collected immediately post-mortem. Our data show that α-Klotho administration had no beneficial effect in mice with CKD-associated anemia as it did not increase RBC numbers and hemoglobin levels, and it did not stimulate EPO secretion. Moreover, α-Klotho did not improve iron deficiency and inflammation in CKD as it had no effect on iron levels or inflammatory markers. Interestingly, Klotho supplementation significantly reduced the number of erythroid progenitors in the bone marrow and downregulated renal Epo and Hif2α mRNA in mice fed control diet resulting in reduced circulating EPO levels in these mice. In addition, Klotho significantly decreased intestinal absorption of iron in control mice leading to reduced serum iron and transferrin saturation levels. Our findings demonstrate that α-Klotho does not have a direct role in renal anemia and that FGF23 suppresses erythropoiesis in CKD via a Klotho-independent mechanism. However, in physiological conditions α-Klotho appears to have an inhibitory effect on erythropoiesis and iron regulation.

Association of fibroblast growth factor 23 and α-klotho in hemodialysis patients during administration of ferric citrate hydrate: post hoc analysis of ASTRIO study

Background

Fibroblast growth factor-23 (FGF23) and α-klotho are associated with anemia in patients with chronic kidney disease. In this post hoc analysis of the ASTRIO study (UMIN000019176), we investigated the relationship between FGF23 and α-klotho during treatment with an iron-based phosphate binder, ferric citrate hydrate (FC), compared with non-iron-based phosphate binders in hemodialysis (HD) patients. We examined the effect of iron absorption by FC on the relationship between FGF23 and α-klotho. There have been few clinical studies evaluating these biomarkers simultaneously in HD patients.

Methods

The ASTRIO study was a 24-week, randomized, open-label, multicenter trial. HD patients taking non-iron-based phosphate binder(s) were randomized at a 1:1 ratio to continue other binder(s) (control group) or switch to FC (FC group). Serum phosphate (P) and hemoglobin (Hb) were maintained within 3.5–6.0 mg/dL and 10–12 g/dL, respectively. Plasma levels of intact FGF23 (i-FGF23), C-terminal FGF23 (c-FGF23), and α-klotho were measured, as were iron-related parameters. Association analyses of FGF23 and α-klotho were conducted.

Results

Patients were randomized to FC (n = 48) and control (n = 45) groups. Serum ferritin significantly increased from baseline to end-of-treatment (EOT) in the FC group, compared with the control group (adjusted mean difference [95% confidence interval]: 79.5 [44.7, 114.4] ng/mL; p <  0.001). The mean change from baseline to EOT in c-FGF23 was significantly different between the FC and control groups (mean ± standard deviation (SD): − 0.2 ± 0.8 log_e pg/mL vs. 0.2 ± 0.8 log_e pg/mL, respectively; p = 0.04). The mean change from baseline to EOT in i-FGF23 and α-klotho were not significantly different between the FC and control groups (mean ± SD: − 0.1 ± 0.8 log_e pg/mL vs. 0.1 ± 0.9 log_e pg/mL; p = 0.33, and 2.0 ± 91.5 pg/mL vs. − 8.9 ± 145.3; p = 0.58, respectively). However, both forms of FGF23 and α-klotho were not significantly associated with each other in both groups.

Conclusions

Iron absorbed via FC administration in HD patients did not influence the correlation relationship between plasma levels of FGF23 and α-klotho under the condition of serum P and Hb were maintained.

Trial registration

ASTRIO study (UMIN000019176, registered at UMIN Clinical Trials Registry on October 1, 2015).

Impact of chronic kidney disease and anemia on health-related quality of life and work productivity: analysis of multinational real-world data

Background

Reductions in health-related quality of life (HRQoL) in patients with chronic kidney disease (CKD) are thought to be exacerbated by the low hemoglobin (Hb) levels that define anemia, a common complication of CKD. The current analysis evaluated the impact of anemia on HRQoL and work productivity in patients with non-dialysis dependent and dialysis-dependent CKD using real-world data.

Methods

Data were collected in France, Germany, Italy, Spain, the UK, the USA and China in 2012–2018 in the Adelphi Real World Disease Specific Programme™ for CKD, a large, cross-sectional, survey of physicians and their patients. Patients completed three patient-reported outcomes (PRO) instruments: the EuroQol 5-Dimension 3-level (EQ-5D-3 L), the Kidney Disease Quality of Life (KDQOL-36) instrument and the Work Productivity and Activity Impairment questionnaire. PROs were assessed by CKD stage and Hb levels, and regression analyses were performed with CKD stage and Hb level as independent variables and PROs as outcome variables, while adjusting for age, sex, CKD stage, comorbidities and cardiovascular risk.

Results

Overall, 5276 patients participated in the survey, including 28% stage 4 and 36% dialysis patients. Patients with lower Hb levels more often reported problems/issues on all EQ-5D-3 L domains (p < 0.0001). Regression analyses showed significant associations between lower Hb levels and the probability of low (< 0.8) EQ-5D-3 L utility scores (p < 0.0001) and low visual analog scale scores (p < 0.05), indicating poorer health status. Associations were seen even when adjusting for CKD stage and other potential confounding factors. Significant associations were observed between Hb level and the 12-Item Short-Form Health Survey (SF-12) Physical Component Summary, SF-12 Mental Component Summary and the three KDQOL-36 subscales (all p < 0.0001), and were confirmed using linear regression analyses adjusting for CKD stage and other potential confounders. Numerically greater work productivity losses and greater activity impairment were observed with lower Hb levels.

Conclusions

Lower Hb levels worsen the impact of CKD on HRQoL, and are associated with lower work productivity in patients with CKD. Assessment and treatment of anemia should be recognized as a key component of integral CKD management throughout all stages of the disease.

The EPO-FGF23 Signaling Pathway in Erythroid Progenitor Cells: Opening a New Area of Research

We provide an overview of the evidence for an erythropoietin-fibroblast growth factor 23 (FGF23) signaling pathway directly influencing erythroid cells in the bone marrow. We outline its importance for red blood cell production, which might add, among others, to the understanding of bone marrow responses to endogenous erythropoietin in rare hereditary anemias. FGF23 is a hormone that is mainly known as the core regulator of phosphate and vitamin D metabolism and it has been recognized as an important regulator of bone mineralization. Osseous tissue has been regarded as the major source of FGF23. Interestingly, erythroid progenitor cells highly express FGF23 protein and carry the FGF receptor. This implies that erythroid progenitor cells could be a prime target in FGF23 biology. FGF23 is formed as an intact, biologically active protein (iFGF23) and proteolytic cleavage results in the formation of the presumed inactive C-terminal tail of FGF23 (cFGF23). FGF23-knockout or injection of an iFGF23 blocking peptide in mice results in increased erythropoiesis, reduced erythroid cell apoptosis and elevated renal and bone marrow erythropoietin mRNA expression with increased levels of circulating erythropoietin. By competitive inhibition, a relative increase in cFGF23 compared to iFGF23 results in reduced FGF23 receptor signaling and mimics the positive effects of FGF23-knockout or iFGF23 blocking peptide. Injection of recombinant erythropoietin increases FGF23 mRNA expression in the bone marrow with a concomitant increase in circulating FGF23 protein. However, erythropoietin also augments iFGF23 cleavage, thereby decreasing the iFGF23 to cFGF23 ratio. Therefore, the net result of erythropoietin is a reduction of iFGF23 to cFGF23 ratio, which inhibits the effects of iFGF23 on erythropoiesis and erythropoietin production. Elucidation of the EPO-FGF23 signaling pathway and its downstream signaling in hereditary anemias with chronic hemolysis or ineffective erythropoiesis adds to the understanding of the pathophysiology of these diseases and its complications; in addition, it provides promising new targets for treatment downstream of erythropoietin in the signaling cascade.