Vitamin D insufficiency, hemoglobin, and anemia in children with chronic kidney disease

Effect of histidine and carnosine on haemoglobin recovery in anaemia induced-kidney damage and iron-loading mouse models

Histidine and carnosine can form complexes with divalent metal ions such as Fe2+, potentially providing stability to intracellular labile iron. Anaemia is a common comorbidity in the late stages of kidney disease, and patients are treated with erythropoiesis-stimulating agents (ESAs) and iron supplementation. However, iron supplementation is also associated with worse long-term outcomes. The purpose of this study is to investigate how histidine and carnosine supplementation can reduce symptoms of anaemia of chronic kidney disease (CKD) and the effects associated with iron-overloaded conditions. Adenine-induced chronic kidney disease mice were treated with histidine and carnosine by oral gavage for 10 days. Additionally, a model involving iron overload in mice was established, and these mice received concurrent treatment with histidine and carnosine. Haemoglobin, non-haem iron, malondialdehyde (MDA) and iron parameters were measured. Carnosine increased erythropoietin (EPO) levels (35.62 µg/ml ± 11.43) and resulted in haemoglobin repletion (16.7 g/dL ± 3.4). When iron was supplemented alongside with histidine or carnosine, there were better effects on haemoglobin repletion (14.22 ± 1.7 and 13.82 ± 2.15 g/ dL respectively), ferritin (59.5 ± 16.4, 52 ± 29.5 µg/ml) and non-haem iron (0.8 ± 0.21, 0.7 ± 0.38 nmol/mg), than the group receiving iron alone (p < 0.05). Furthermore, histidine and carnosine reduced non-haem iron and MDA, in iron-loaded conditions (p < 0.05). These positive effects observed in histidine and carnosine could be associated with reactive oxygen species (ROS) scavenging. EPO restoring levels in CKD model and the increment in haemoglobin and ferritin in carnosine treatments suggested the potential formation of a ternary complex with iron-glutathione. In conclusion, our results indicate the beneficial effect of histidine and carnosine in the context of iron supplementation for the correction of haemoglobin and protection against iron-loaded conditions.

Effect of Vitamin D Supplementation on Serum Hepcidin Levels in Non-Diabetic Chronic Kidney Disease Patients

Introduction

Vitamin D deficiency and anemia frequently coexist. Moreover, vitamin D deficiency is found to play a role in chronic kidney disease (CKD)-associated anemia. We investigated the effect of cholecalciferol on serum hepcidin levels in vitamin D-deficient, non-diabetic individuals with CKD in a randomized, double-blind, placebo-controlled trial.

Methods

This study was performed on stored samples of our previously published randomized, double-blind, placebo-controlled trial of cholecalciferol supplementation in non-diabetic patients with stage III-IV CKD and vitamin D deficiency. Stable patients of either sex, aged 18-70 years, with non-diabetic stage III-IV CKD (estimated glomerular filtration rate between 15 and 60 ml/min/1.73 m2), and having serum 25-hydroxyvitamin D3 [25(OH) D] levels ≤20 ng/ml were included. Participants received either two directly observed oral doses of cholecalciferol (300,000 IU) or matching placebo at baseline and at eight weeks. Follow-up was done at 16 weeks. Serum hepcidin levels were analyzed at baseline and at 16 weeks.

Results

A total of 120 CKD patients were enrolled. Serum 25(OH) D levels were similar in the placebo and cholecalciferol groups at baseline (13.21 ± 4.78 ng/ml and 13.40 ± 4.42 ng/ml; P = 0.88). After 16 weeks, the serum 25(OH) D levels were found to be increased in the cholecalciferol group but not in the placebo group (between-group difference in mean change 23.40 ng/ml; 95% CI: 19.76 to 27.06; P < 0.001). Serum hepcidin levels were similar at baseline (median [IQR]: 33.6 [8.6-77.8] ng/ml vs. 24.6 [9.3-70.7] ng/ml, P = 0.903) and did not vary between groups at 16 weeks (median [IQR]: 41.5 [10.9-75.0] ng/ml vs. 34.8 [12.3-63.75] ng/ml, P = 0.703).

Conclusion

Our study provides preliminary data based on which a larger adequately powered clinical trial can be conducted to conclusively assess the impact of vitamin D supplementation on hepcidin levels and anemia in patients with CKD and vitamin D deficiency.

Development of an adaptive clinical web-based prediction tool for kidney replacement therapy in children with chronic kidney disease

Clinicians need improved prediction models to estimate time to kidney replacement therapy (KRT) for children with chronic kidney disease (CKD). Here, we aimed to develop and validate a prediction tool based on common clinical variables for time to KRT in children using statistical learning methods and design a corresponding online calculator for clinical use. Among 890 children with CKD in the Chronic Kidney Disease in Children (CKiD) study, 172 variables related to sociodemographics, kidney/cardiovascular health, and therapy use, including longitudinal changes over one year were evaluated as candidate predictors in a random survival forest for time to KRT. An elementary model was specified with diagnosis, estimated glomerular filtration rate and proteinuria as predictors and then random survival forest identified nine additional candidate predictors for further evaluation. Best subset selection using these nine additional candidate predictors yielded an enriched model additionally based on blood pressure, change in estimated glomerular filtration rate over one year, anemia, albumin, chloride and bicarbonate. Four additional partially enriched models were constructed for clinical situations with incomplete data. Models performed well in cross-validation, and the elementary model was then externally validated using data from a European pediatric CKD cohort. A corresponding user-friendly online tool was developed for clinicians. Thus, our clinical prediction tool for time to KRT in children was developed in a large, representative pediatric CKD cohort with an exhaustive evaluation of potential predictors and supervised statistical learning methods. While our models performed well internally and externally, further external validation of enriched models is needed.

Fibroblast growth-factor 23 and vitamin D are associated with iron deficiency and anemia in children with chronic kidney disease

BACKGROUND

This cross-sectional study investigates the association of fibroblast growth-factor 23 (FGF23) and other bone mineral parameters with iron status and anemia in pediatric chronic kidney disease (CKD).

METHODS

Serum calcium, phosphorus, 25-hydroxyvitamin D (25(OH)D), intact parathormone, c-terminal FGF23, a-Klotho, iron (Fe), ferritin, unsaturated iron-binding capacity, and hemoglobin (Hb) were measured in 53 patients from 5 to 19 years old with GFR < 60 mL/min/1.73 m2. Transferrin saturation (TSAT) was calculated.

RESULTS

Absolute (ferritin ≤ 100 ng/mL, TSAT ≤ 20%) and functional iron deficiency (ferritin > 100 ng/mL, TSAT ≤ 20%) were observed in 32% and 7.5% of patients, respectively. In CKD stages 3-4 (36 patients), lnFGF23 and 25(OH)D were correlated with Fe (rs =  - 0.418, p = 0.012 and rs = 0.467, p = 0.005) and TSAT (rs =  - 0.357, p = 0.035 and rs = 0.487, p = 0.003) but not to ferritin. In this patient group, lnFGF23 and 25(OH)D were correlated with Hb z-score (rs =  - 0.649, p < 0.001 and rs = 0.358, p = 0.035). No correlation was detected between lnKlotho and iron parameters. In CKD stages 3-4, in multivariate backward logistic regression analysis, including bone mineral parameters, CKD stage, patient age, and daily alphacalcidol dose as covariates, lnFGF23 and 25(OH)D were associated with low TSΑΤ (15 patients) (OR 6.348, 95% CI 1.106-36.419, and OR 0.619, 95% CI 0.429-0.894, respectively); lnFGF23 was associated with low Hb (10 patients) (OR 5.747, 95% CI 1.270-26.005); while the association between 25(OH)D and low Hb did not reach statistical significance (OR 0.818, 95% CI 0.637-1.050).

CONCLUSIONS

In pediatric CKD stages 3-4, iron deficiency and anemia are associated with increased FGF23, independently of Klotho. Vitamin D deficiency might contribute to iron deficiency in this population. A higher resolution version of the Graphical abstract is available as Supplementary information.

Changes in bone biomarkers in response to different dosing regimens of cholecalciferol supplementation in children with chronic kidney disease

BACKGROUND

The effect of different dosing regimens of cholecalciferol supplementation on bone biomarkers has not been studied in children with chronic kidney disease (CKD).

METHODS

This is a post hoc analysis of a multi-center randomized controlled trial which included children with CKD stages 2-4 with vitamin D deficiency (25-hydroxy vitamin D (25OHD) < 30 ng/ml) randomized 1:1:1 to receive an equivalent dose of oral cholecalciferol as daily, weekly or monthly treatment. Markers of bone formation (bone alkaline phosphatase (BAP), procollagen I N terminal peptide (PINP)), bone resorption (tartarate-resistant acid phosphatase 5b (TRAP), C terminal telopeptide (CTX)), and osteocyte markers (intact fibroblast growth factor 23 (iFGF23), sclerostin) and soluble klotho were measured at baseline and after 3 months of intensive replacement therapy. The change in biomarkers and ratio of markers of bone formation to resorption were compared between treatment arms. BAP and TRAP were expressed as age- and sex-specific z-scores.

RESULTS

25OHD levels increased with cholecalciferol supplementation, with 85% achieving normal levels. There was a significant increase in the BAP/TRAP ratio (p = 0.04), iFGF23 (p = 0.004), and klotho (p = 0.002) with cholecalciferol therapy, but this was comparable across all three therapy arms. The BAPz was significantly higher in the weekly arm (p = 0.01). The change in 25OHD (Δ25OHD) inversely correlated with ΔPTH (r =  - 0.4, p < 0.001).

CONCLUSIONS

Although cholecalciferol supplementation was associated with a significant increase in bone formation, the three dosing regimens of cholecalciferol supplementation have a comparable effect on the bone biomarker profile, suggesting that they can be used interchangeably to suit the patient's needs and optimize adherence to therapy. A higher resolution version of the Graphical abstract is available as Supplementary information.

The clinical relevance of native vitamin D in pediatric kidney disease

Hypovitaminosis D has been reported to be common in chronic kidney disease (CKD) as well as in proteinuric disorders. We reviewed available evidence to assess clinically relevant effects of low vitamin D status and native vitamin D (NVD) therapy, in pediatric renal diseases. Online medical databases were searched for articles related to vitamin D status, associations of hypovitaminosis D and effects of NVD therapy in kidney disease. Hypovitaminosis D was associated with worse skeletal, cardiovascular, inflammatory, and renal survival outcomes in CKD. Low serum 25 hydroxy-vitamin D (25[OH]D) levels correlated positively with glomerular filtration rate and negatively with serum parathyroid (PTH) levels. However, to date, evidence of benefit of NVD supplementation is restricted mainly to improvements in serum PTH, and biochemical 25[OH]D targets form the basis of clinical practice recommendations for NVD therapy. In nephrotic syndrome (NS) relapse, studies indicate loss of 25[OH]D along with vitamin D binding protein in urine, and serum total 25[OH]D levels are low. Preliminary evidence indicates that free 25[OH]D may be a better guide to the biologically active fraction. NVD therapy in NS does not show consistent results in improving skeletal outcomes and hypercalciuria has been reported when total 25[OH]D levels were considered as indication for therapy. NVD formulations should be regularised, and therapy monitored adequately to avoid adverse effects.

Urine alpha 1-microglobulin-to-creatinine ratio and beta 2-microglobulin-to-creatinine ratio for detecting CAKUT with kidney dysfunction in children

BACKGROUND

The leading cause of advanced chronic kidney disease (CKD) in children is congenital anomalies of the kidney and urinary tract (CAKUT). However, the most appropriate parameters of biochemical urine analysis for detecting CAKUT with kidney dysfunction are not known.

METHODS

The present observational study analyzed data on children with CAKUT (stage 2-4 CKD) and the general pediatric population obtained from school urine screenings. The sensitivity and specificity of urine alpha 1-microglobulin-, beta 2-microglobulin-, protein-, and the albumin-to-creatinine ratios (AMCR, BMCR, PCR, ACR, respectively) in detecting CAKUT with kidney dysfunction were compared with those of the conventional urine dipstick, and the most appropriate of these four parameters were evaluated.

RESULTS

In total, 77 children with CAKUT and 1712 subjects in the general pediatric population fulfilled the eligibility criteria. Conventional dipstick urinalysis was insufficient due to its low sensitivity; even when the threshold of proteinuria was +/-, its sensitivity was only 29.7% for stage 2 and 44.1% for stage 3 CKD. Among the four parameters assessed, the AMCR and BMCR were adequate for detecting CAKUT in children with stage 3-4 CKD (the respective sensitivity and specificity of the AMCR for detecting CAKUT in stage 3 CKD was 79.4% and 97.5% while that of BMCR was 82.4% and 97.5%). These data were validated using national cohort data.

CONCLUSION

AMCR and BMCR are superior to dipstick urinalysis, PCR, and ACR in detecting CAKUT with kidney dysfunction, particularly stage 3 CKD. However, for AMCR, external validation is required. A higher resolution version of the Graphical abstract is available as Supplementary information.

Prevalence and risk factors for functional iron deficiency in children with chronic kidney disease

INTRODUCTION

Anemia in chronic kidney disease (CKD) is multifactorial. The presence of functional iron deficiency (FID), whereby, there is a block in the transport of iron from macrophage to erythroid marrow is one possible etiology. In this study, we aim to assess the prevalence and risk factors of FID in pediatric CKD.

METHODS

A cross-sectional study was performed from March to December 2018, after obtaining Institute Ethical Clearance. Children aged ≤ 12 years with CKD, with or without iron supplementation who consented were enrolled. Patients on erythropoietin or on maintenance dialysis were excluded. Details of patients and diseases characteristics were recorded. Various laboratory parameters including complete blood count, red blood cell indices, hypochromic RBC, reticulocyte hemoglobin content, and serum ferritin were measured. Appropriate statistical tests were applied.

RESULTS

Out of 174 children, 127 (73%) had structural kidney disease as an etiology of CKD, and 110 (63%) had anemia. Prevalence of anemia was 44%, 43%, 74%, 64% and 92% in CKD stage 1, 2, 3, 4 and 5, respectively. Absolute iron deficiency was found in 66 (38%) even when some children were already on iron supplementation. FID was seen in 44 (25%) and on multivariate analysis, lower estimated glomerular filtration rate and mineral bone disease are associated risk factors.

CONCLUSION

FID is present in one-fourth of our CKD cohort. It should be considered when the response to adequate measures of improving hemoglobin level fails. More studies are required to know its impact on short-term and long-term patient-related outcomes such as quality of life and mortality.

Changes of Serum Ferritin, Hemoglobin, and Serum Iron (SI) and Treatment Effect of Iron Proteinsuccinylate Oral Solution Combined with Vitamin A and D Drops on Children with Nutritional Iron Deficiency Anemia

Objective

The purpose was to evaluate the treatment effect of iron proteinsuccinylate oral solution combined with vitamin A and D drops on children with nutritional iron deficiency anemia.

Methods

124 children treated in the outpatient department of our hospital from January 2017 to January 2020 were selected as the study subjects. They were randomly divided into control and observation two groups. The control group was treated with iron proteinsuccinylate oral solution (1.5 mL/kg) in the morning and evening, respectively. The observation group received adjuvant treatment with oral vitamin A and D drops based on the treatment of the control group. The treatment effect of proteinsuccinylate oral solution combined with vitamin A and D drops was evaluated by the serum iron (SI), serum ferritin (SF), and transferrin (TRF) levels, the values of CD3⁺, CD4⁺, and CD4⁺/CD8⁺, and other evaluation indicators.

Results

After treatment, the SI and SF levels of children in both groups significantly increased (P < 0.01) while the TRF level significantly decreased (P < 0.01), and the SI and SF levels in the observation group increased more significantly, and the TRF level decreased more significantly compared with those in the control group (P < 0.01). After treatment, the values of CD3⁺, CD4⁺, and CD4⁺/CD8⁺ of children in both groups significantly increased compared with those before treatment (P < 0.01), and the values of CD3⁺, CD4⁺, and CD4⁺/CD8⁺ increased more significantly in the observation group compared with those in the control group (P < 0.01). In addition, the evaluation results of treatment effect showed that the markedly effective rate in the observation group was significantly higher than that in the control group (P < 0.01).

Conclusion

Iron proteinsuccinylate oral solution combined with vitamin A and D drops can better improve the anemia symptoms in children, with high application value.

Population pharmacokinetics and dose optimisation of colecalciferol in paediatric patients with chronic kidney disease

Aims

The prevalence of vitamin D deficiency is high in children with chronic kidney disease (CKD). However, current dosing recommendations are based on limited pharmacokinetic (PK) data. This study aimed to develop a population PK model of colecalciferol that can be used to optimise colecalciferol dosing in this population.

Methods

Data from 83 children with CKD were used to develop a population PK model using a nonlinear mixed effects modelling approach. Serum creatinine and type of kidney disease (glomerular vs. nonglomerular disease) were investigated as covariates, and optimal dosing was determined based on achieving and maintaining 25‐hydroxyvitamin D (25(OH)D) concentration of 30–48 ng/mL.

Results

The time course of 25(OH)D concentrations was best described by a 1‐compartment model with the addition of a basal concentration parameter to reflect endogenous 25(OH)D production from diet and sun exposure. Colecalciferol showed wide between‐subject variability in its PK, with total body weight scaled allometrically the only covariate included in the model. Model‐based simulations showed that current dosing recommendations for colecalciferol can be optimised using a weight‐based dosing strategy.

Conclusion

This is the first study to describe the population PK of colecalciferol in children with CKD. PK model informed dosing is expected to improve the attainment of target 25(OH)D concentrations, while minimising the risk of overdosing.

The CKiD study: overview and summary of findings related to kidney disease progression

The Chronic Kidney Disease in Children (CKiD) cohort study is a North American (USA and Canada) multicenter, prospective study of children with chronic kidney disease (CKD). The original aims of the study were (1) to identify novel risk factors for CKD progression; (2) to measure the impact of kidney function decline on growth, cognition, and behavior; and (3) to characterize the evolution of cardiovascular disease risk factors. CKiD has developed into a national and international resource for the investigation of a variety of factors related to CKD in children. This review highlights notable findings in the area of CKD progression and outlines ongoing opportunities to enhance understanding of CKD progression in children. CKiD's contributions to the clinical care of children with CKD include updated and more accurate glomerular filtration rate estimating equations for children and young adults, and resources designed to help estimate the CKD progression timeline. In addition, results from CKiD have strengthened the evidence that treatment of hypertension and proteinuria should continue as a primary strategy for slowing the rate of disease progression in children.

Free 25-hydroxyvitamin-D concentrations are lower in children with renal transplant compared with chronic kidney disease

BACKGROUND

Total serum 25-hydroxyvitamin D [25(OH)D] is considered the best marker of vitamin D status and used routinely in clinical practice. However, 25(OH)D is predominantly bound to vitamin D-binding protein (VDBP), and it has been reported that the free-25(OH)D and 25(OH)D loosely bound to albumin fraction correlates better with clinical outcomes.

METHODS

We assessed total-25(OH)D, measured free-25(OH)D, and calculated free-25(OH)D and their relationship with VDBP and biomarkers of mineral metabolism in 61 children (22 CKD 2-3, 18 dialysis, and 21 post-transplant).

RESULTS

Total-25(OH)D concentrations were comparable across the three groups (p = 0.09), but free- and bioavailable-25(OH)D (free- and albumin-25(OH)D) were significantly lower in the transplant group (both: p = 0.01). Compared to CKD and dialysis patients, the transplant group had significantly higher VDBP concentrations (p = 0.03). In all three groups, total-25(OH)D concentrations were positively associated with measured free-, calculated free-, and bioavailable-25(OH)D. Multivariable regression analysis showed that total-25(OH)D was the only predictor of measured free-25(OH)D concentrations in the dialysis group (β = 0.9; R2 = 90%). In the transplant group, measured free-25(OH)D concentrations were predicted by both total-25(OH)D and VDBP concentrations (β = 0.6, - 0.6, respectively; R2 = 80%). Correlations between parathyroid hormone with total-25(OH)D and measured and calculated free-25(OH)D were only observed in the transplant group (all: p < 0.001).

CONCLUSIONS

In transplanted patients, VDBP concentrations were significantly higher compared to CKD and dialysis patients, and consequently, free-25(OH)D concentrations were lower, despite a comparable total-25(OH)D concentration. We suggest that free-25(OH)D measures may be required in children with CKD, dialysis, and transplant, with further research required to understand its association with markers of mineral metabolism.

Vitamin D Supplementation Modestly Reduces Serum Iron Indices of Healthy Arab Adolescents

Vitamin D deficiency has been shown to affect iron status via decreased calcitriol production, translating to decreased erythropoiesis. The present study aimed to determine for the first time whether vitamin D supplementation can affect iron levels among Arab adolescents. A total of 125 out of the initial 200 Saudi adolescents with vitamin D deficiency (serum 25(OH)D < 50 nmol/L) were selected from the Vitamin D-School Project of King Saud University in Riyadh, Saudi Arabia. Cluster randomization was done in schools, and students received either vitamin D tablets (1000 IU/day) (N = 53, mean age 14.1 ± 1.0 years) or vitamin D-fortified milk (40IU/200mL) (N = 72, mean age 14.8 ± 1.4 years). Both groups received nutritional counseling. Anthropometrics, glucose, lipids, iron indices, and 25(OH)D were measured at baseline and after six months. Within group analysis showed that post-intervention, serum 25(OH)D significantly increased by as much as 50%, and a parallel decrease of −42% (p-values <0.001 and 0.002, respectively) was observed in serum iron in the tablet group. These changes were not observed in the control group. Between-group analysis showed a clinically significant increase in serum 25(OH)D (p = 0.001) and decrease in iron (p < 0.001) in the tablet group. The present findings suggest a possible inhibitory role of vitamin D supplementation in the iron indices of healthy adolescents whose 25(OH)D levels are sub-optimal but not severely deficient, implying that the causal relationship between both micronutrients may be dependent on the severity of deficiency, type of iron disorder, and other vascular conditions that are known to affect hematologic indices. Well-designed, randomized trials are needed to confirm the present findings.