Chronic kidney disease: mineral and bone disorder in children

A Cross-sectional Study on Fibroblast Growth Factor 23 and Other Markers of Mineral Metabolism in Healthy Children in India

Fibroblast growth factor 23 (FGF23) plays a significant role in phosphate homeostasis but data on children are limited. We aimed to detect FGF23 levels in 107 healthy children aged 6-16 years and evaluate its correlation with markers of phosphate and calcium metabolism, and the dietary intake of calcium, phosphate, and proteins. Height, weight, and Tanner stages were measured, and dietary intake was calculated. Biochemical analyses of hemoglobin, serum calcium, phosphate, creatinine, Vitamin D, and plasma parathyroid hormone (PTH) and FGF23 levels were performed, alongside their associations with FGF23. Of the children, 65.4% were males. Their mean body mass index was 15.79 ± 2.96 for males and 16.5 ± SD 2.72 for females. The mean Vitamin D and PTH levels were 29.7 ± 1.1 ng/mL and 29.2 ± 1.2 pg/mL, respectively. The mean FGF23 levels were 159 ± 15.2 reference units (RU)/mL. The mean FGF23 levels were significantly higher in females (209.3 ± 31 RU/mL) than in males (132.3 ± 15.1 RU/mL). All biochemical parameters were within the normal range. FGF23 correlated with age, weight, and height, but not Vitamin D, PTH, or dietary calcium and phosphate. FGF23 showed a negative correlation with hemoglobin levels (r = -0.23). Since most children had a nonvegetarian diet, the FGF23 levels were not assessed in vegetarians. These observations were attributed to the rural lifestyle favoring adequate exposure to sunlight and physical activity. The increased FGF23 levels in females, the trends in urban settings, and the levels in strictly vegetarian diets need further study.

Pediatric CKD-MBD: existing and emerging treatment approaches

The effects of bone and mineral metabolism on skeletal formation, as well as vascular and soft tissue calcifications, define chronic kidney disease-metabolic bone disease (CKD-MBD). Treatment recommendations center on establishing adequate vitamin D status, phosphate control through diet restriction and phosphate binders, and the use of vitamin D analogs for specific indications. Several emerging bone-promoting therapies have now been studied in adults with CKD, including bisphosphonates and denosumab. These approaches are associated with improved bone mass and, in some cases, decreased fracture rates in adults with CKD-MBD and are of potential interest for some children with CKD-MBD. In children with CKD and immobilization and/or muscle weakness, bisphosphonates appear to be an effective treatment to increase bone mass; baseline assessment and careful monitoring of bone density and/or bone biopsy findings are important in consideration of any new bone therapies for children with CKD-MBD.

Calcitriol levels and the stage of chronic kidney disease in children

Background Kidney damage in chronic kidney disease (CKD) disrupts the 1?-hydroxylase enzyme, preventing the conversion of vitamin D into the active form of calcitriol. To our knowledge, no previous studies have assessed calcitriol levels in children with CKD. Decreased vitamin D levels may occur at an early stage of the disease, so it is important to evaluate calcitriol levels in children with early stage CKD. Objective To assess calcitriol levels in children with CKD according to disease stage and other characteristics. Methods This cross-sectional study was conducted on 43 pediatric CKD patients at Dr. M Djamil Hospital, Padang, Indonesia. We recorded patient characteristics and performed laboratory tests, including routine hematology, blood urea nitrogen (BUN), creatinine, uric acid, electrolytes, calcium, and calcitriol levels. Based on estimated glomerular filtration rate (GFR), patients were grouped into either early-stage (stages I and II), or advanced-stage (stages III to V) CKD. Univariate and multivariate analyses were conducted to determine the association between calcitriol levels with disease stage and other characteristics. Results The overall mean calcitriol level of our subjects was 108.77 (SD 10.79) pmol/L. Mean levels at each CKD stage from I to V were 164.28 (SD 160.90), 94.14 (SD 50.63), 72.16 (SD 13.18), 62.92 (SD 4.87), and 67.51 (SD 4.87) pmol/L, respectively. Calcitriol levels did not differ significantly by CKD stage (P=0.114) when each stage from I to V was considered separately. There was no significant difference in calcitriol levels by growth characteristics (P=0.944), etiology (P=0.311), or anemic status (P=0.104). However, low calcitriol levels were found in all subjects with advanced stage CKD, compared to 63.6% subjects with early stage CKD  (P=0.004). Mean calcitriol levels were significantly lower in CKD stage IV (P=0.049) and stage V (P=0.027) compared to stage I. Conclusions The decrease in calcitriol level occurs at an early stage in CKD. Calcitriol levels are significantly lower in advanced stage than in early stage CKD.

Bone Quality in CKD Patients: Current Concepts and Future Directions - Part I

BACKGROUND

There is ample evidence that patients with CKD have an increased risk of osteoporotic fractures. Bone fragility is not only influenced by low bone volume and mass but also by poor microarchitecture and tissue quality. More emphasis has been given to the quantitative rather than qualitative assessment of bone health, both in general population and CKD patients. Although bone mineral density (BMD) is a very useful clinical tool in assessing bone strength, it may underestimate the fracture risk in CKD patients. Serum and urinary bone biomarkers have been found to be reflective of bone activities and predictive of fractures independently of BMD in CKD patients. Bone quality and fracture risk in CKD patients can be better assessed by utilizing new technologies such as trabecular bone score and high-resolution imaging studies. Additionally, invasive assessments such as bone histology and micro-indentation are useful counterparts in the evaluation of bone quality.

SUMMARY

A precise diagnosis of the underlying skeletal abnormalities in CKD patients is crucial to prevent further bone loss and fractures. We must consider bone quantity and quality abnormalities for management of CKD patients. Here in this part I, we are focusing on advances in bone quality diagnostics that are expected to help in proper understanding of the bone health in CKD patients.

KEY MESSAGES

Assessment of bone quality and quantity in CKD patients is essential. Both noninvasive and invasive techniques for the assessment of bone quality are available.

Tumor necrosis factor-alpha is associated with mineral bone disorder and growth impairment in children with chronic kidney disease

BACKGROUND

Mineral and bone disorder (MBD) and growth impairment are common complications of pediatric chronic kidney disease (CKD). Chronic inflammation detrimentally affects bone health and statural growth in non-CKD settings, but the impact of inflammation on CKD-MBD and growth in pediatric CKD remains poorly understood. This study assessed associations between inflammatory cytokines with biomarkers of CKD-MBD and statural growth in pediatric CKD.

METHODS

This is a cross-sectional study of children with predialysis CKD stages II-V. Cytokines (IL-1b, IL-4, IL-6, IL-8, IL-10, IL-12, IL-13, TNF-α, interferon-γ), bone alkaline phosphatase (BAP), and procollagen type 1 N-terminal propeptide (P1NP) were measured at the same time as standard CKD-MBD biomarkers. Associations between cytokines, CKD-MBD biomarkers, and height z-score were assessed using linear regression analysis.

RESULTS

Among 63 children, 52.4% had stage 3 CKD, 76.2% non-glomerular CKD etiology, and 21% short stature. TNF-α was the only cytokine associated with parathyroid hormone (PTH) independent of glomerular filtration rate. After stratification by low, medium, and high TNF-α tertiles, significant differences in PTH, serum phosphorus, alkaline phosphatase, BAP, P1NP, and height z-score were found. In a multivariate analysis, TNF-α positively associated with phosphorus, PTH, and alkaline phosphatase and inversely associated with height z-score, independent of kidney function, age, sex, and active vitamin D analogue use.

CONCLUSIONS

TNF-α is positively associated with biomarkers of CKD-MBD and inversely associated with height z-score, indicating that inflammation likely contributes to the development of CKD-MBD and growth impairment in pediatric CKD. Prospective studies to definitively assess causative effects of inflammation on bone health and growth in children with CKD are warranted.

Use of a Phosphorus Points Education Program to Maintain Normal Serum Phosphorus in Pediatric Chronic Kidney Disease: A Case Report

A 14-year-old male, with chronic kidney disease stage 4 (glomerular filtration rate 20 mL/min/1.73 m²) secondary to reflux nephropathy required dietary modification with evidence of renal osteodystrophy, presented with elevated serum phosphorus and parathyroid hormone. He was educated using a novel phosphorus point system where 1 point is equivalent to ∼50 mg of phosphorus. Dietary counseling was provided by a pediatric renal dietitian on phosphorus content of foods the patient typically consumed and converted to point system for daily tracking. The family reported limiting daily phosphorus points to less than 20 points daily for 15 months. The family completed a 3-day food record and provided points assigned to each food item. A Spearman's correlation of 0.7 (P < .001) was found between the family's and the dietitian's assignment of phosphorus points. The patient's recorded phosphorus intake remained below 1000 mg each day and met estimated calorie and protein needs. The patient also continued with age-appropriate weight gain and linear growth. Laboratory values showed phosphorus and intact parathyroid hormone remained within desired range. A phosphorus point system tool can be used to maintain normal serum phosphorus levels and subsequently prevent secondary hyperparathyroidism in patients with pediatric chronic kidney disease.

High calcium, phosphate and calcitriol supplementation leads to an osteocyte-like phenotype in calcified vessels and bone mineralisation defect in uremic rats

A link between vascular calcification and bone anomalies has been suggested in chronic kidney disease (CKD) patients with low bone turnover disease. We investigated the vascular expression of osteocyte markers in relation to bone microarchitecture and mineralization defects in a model of low bone turnover CKD rats with vascular calcification. CKD with vascular calcification was induced by 5/6 nephrectomy followed by high calcium and phosphate diet, and vitamin D supplementation (Ca/P/VitD). CKD + Ca/P/VitD group (n = 12) was compared to CKD + normal diet (n = 12), control + normal diet (n = 8) and control + Ca/P/VitD supplementation (n = 8). At week 6, tibia, femurs and the thoracic aorta were analysed by Micro-Ct, histomorphometry and for expression of osteocyte markers. High Ca/P/VitD treatment induced vascular calcification only in CKD rats, suppressed serum parathyroid hormone levels and led to higher sclerostin, DKK1 and FGF23 serum levels. Expression of sclerostin, DKK1 and DMP1 but not FGF23 were increased in calcified vessels from CKD + Ca/P/VitD rats. Despite low parathyroid hormone levels, tibia bone cortical thickness was significantly lower in CKD + Ca/P/VitD rats as compared to control rats fed a normal diet, which is likely the result of radial growth impairment. Finally, Ca/P/VitD treatment in CKD rats induced a bone mineralization defect, which is likely explained by the high calcitriol dose. In conclusion, Ca/P/VitD supplementation in CKD rats induces expression of osteocyte markers in vessels and bone mineralisation anomalies. Further studies should evaluate the mechanisms of high dose calcitriol-induced bone mineralisation defects in CKD.

Bridging adults and paediatrics with secondary hyperparathyroidism receiving haemodialysis: a pharmacokinetic-pharmacodynamic analysis of cinacalcet

Aims

The aims of this study were to develop a pharmacokinetic (PK) and PK‐pharmacodynamic (PK/PD) model of cinacalcet in adults and paediatrics with secondary hyperparathyroidism (SHPT) on dialysis, to test covariates of interest, and to perform simulations to inform dosing in paediatrics with SHPT.

Methods

Cinacalcet PK, intact parathyroid hormone (iPTH) and corrected calcium (cCa) time courses following multiple daily oral doses (1–300 mg) were modelled using a nonlinear mixed effects modelling approach using data from eight clinical studies. Model‐based trial simulations, using adult or paediatric titration schemas, predicted efficacy (iPTH change from baseline and proportion achieving iPTH decrease ≥30%) and safety (cCa change from baseline and proportion achieving cCa ≤8.4 mg/dL) endpoints at 24 weeks.

Results

Cinacalcet PK parameters were described by a two‐compartment linear model with delayed first‐order absorption‐elimination (apparent clearance = 287.74 L h⁻¹). Simulations suggested that paediatric starting doses (1, 2.5, 5, 10 and 15 mg) would provide PK exposures less than or similar to a 30 mg adult dose. The titrated dose simulations suggested that the mean (prediction interval) proportion of paediatric and adult subjects achieving ≥30% reduction in iPTH from baseline at Week 24 was 49% (36%, 62%), and 70.1% (62.5%, 77%), respectively. Additionally, the mean (confidence interval) proportion of paediatric and adult subjects achieving cCa ≤8.4 mg dL⁻¹ at Week 24 was 8% (2%, 18%) and 23.6% (17.5%, 30.5%), respectively.

Conclusions

Model‐based simulations showed that the paediatric cinacalcet starting dose (0.2 mg kg⁻¹), titrated to effect, would provide the desired PD efficacy (PTH suppression <30%) while minimizing safety concerns (hypocalcaemia).

An open-label, single-dose study to evaluate the safety, tolerability, pharmacokinetics, and pharmacodynamics of cinacalcet in pediatric subjects aged 28 days to < 6 years with chronic kidney disease receiving dialysis

BACKGROUND

Calcimimetics, shown to control biochemical parameters of secondary hyperparathyroidism (SHPT), have well-established safety and pharmacokinetic profiles in adult end-stage renal disease subjects treated with dialysis; however, such studies are limited in pediatric subjects.

METHODS

In this study, the safety, tolerability, pharmacokinetics (PK), and pharmacodynamics (PD) of cinacalcet were evaluated in children with chronic kidney disease (CKD) and SHPT receiving dialysis. Twelve subjects received a single dose of cinacalcet (0.25 mg/kg) orally or by nasogastric or gastric tube. Subjects were randomized to one of two parathyroid hormone (PTH) and serum calcium sampling sequences: [(1) 2, 8, 48 h; or (2) 2, 12, 48 h] and assessed for 72 h after dosing.

RESULTS

Median plasma cinacalcet t_max was 1 h (range 0.5-4.0 h); mean (SD) C_max and AUC_last were 2.83 (1.98) ng/mL and 11.8 (8.74) h*ng/mL, respectively; mean (SD) half-life (t_1/2) was 3.70 (2.57) h. Dose adjustments, based upon body weight (mg/kg), minimized the effects of age, body weight, body surface area, and body mass index on cinacalcet PK. Reductions in serum PTH levels from baseline were observed at 2 to 8 h post-dose (median 10.8 and 29.6%, respectively), returned towards baseline by 12-72 h and were inversely related to changes in the plasma cinacalcet PK profile. Single-dose cinacalcet was well-tolerated with no unexpected safety findings and a PK/PD, safety profile similar to adults.

CONCLUSIONS

In conclusion, a single 0.25 mg/kg dose of cinacalcet was evaluated to be a safe starting dose in these children aged < 6 years.

The impact of vitamin D supplementation on musculoskeletal health outcomes in children, adolescents, and young adults living with HIV: A systematic review

OBJECTIVE

HIV-positive children, adolescents, and young adults are at increased risk poor musculoskeletal outcomes. Increased incidence of vitamin D deficiency in youth living with HIV may further adversely affect musculoskeletal health. We investigated the impact of vitamin D supplementation on a range of musculoskeletal outcomes among individuals aged 0-25 years living with HIV.

METHODS

A systematic review was conducted using databases: PubMed/Medline, CINAHL, Web of Knowledge, and EMBASE. Interventional randomised control trials, quasi-experimental trials, and previous systematic reviews/meta-analyses were included. Outcomes included: BMD, BMC, fracture incidence, muscle strength, linear growth (height-for-age Z-score [HAZ]), and biochemical/endocrine biomarkers including bone turnover markers.

RESULTS

Of 497 records, 20 studies met inclusion criteria. Thirteen studies were conducted in North America, one in Asia, two in Europe, and four in Sub-Saharan Africa. High-dose vitamin D supplementation regimens (1,000-7,000 IU/day) were successful in achieving serum 25-hydroxyvitamin-D (25OHD) concentrations above study-defined thresholds. No improvements were observed in BMD, BMC, or in muscle power, force and strength; however, improvements in neuromuscular motor skills were demonstrated. HAZ was unaffected by low-dose (200-400 IU/day) supplementation. A single study found positive effects on HAZ with high-dose supplementation (7,000 vs 4,000IU/day).

CONCLUSIONS

Measured bone outcomes were unaffected by high-dose vitamin D supplementation, even when target 25OHD measurements were achieved. This may be due to: insufficient sample size, follow-up, intermittent dosing, non-standardised definitions of vitamin D deficiency, or heterogeneity of enrolment criteria pertaining to baseline vitamin D concentration. High-dose vitamin D may improve HAZ and neuromuscular motor skills. Adequately powered trials are needed in settings where HIV burden is greatest. PROSPERO Number: CRD42016042938.

A Cross-Sectional Study of Growth and Metabolic Bone Disease in a Pediatric Global Cohort Undergoing Chronic Hemodialysis

OBJECTIVE

We sought to assess worldwide differences among pediatric patients undergoing hemodialysis. Because practices differ widely regarding nutritional resources, treatment practice, and access to renal replacement therapy, investigators from the Pediatric Investigation and Close Collaboration to examine Ongoing Life Outcomes, the pediatric subset of the MONitoring Dialysis Outcomes Cohort (PICCOLO MONDO) performed this cross-sectional study. We hypothesized that growth would be better in developed countries, possibly at the expense of bone mineral disease.

STUDY DESIGN

In this cross-sectional study, we analyzed growth by height z score and recommended age-specific bone mineral metabolism markers from 225 patients <18 years of age maintained on hemodialysis, between the years of 2000 to 2012 from 21 countries in different regions.

RESULTS

The patients' median age was 16 (IQR 14-17) years, and 45% were females. A height z score less than the third percentile was noted in 34% of the cohort, whereas >66% of patients reported normal heights, with patients from North America having the greatest proportion (>80%). More than 70% of the entire cohort had greater than the age-recommended levels of phosphorus, particularly in the Asia-Pacific and North America, where we also observed the greatest body mass index z score (0.99 ± 1.6) and parathyroid hormone levels (557.1 [268.4-740.5]). Below-recommended parathyroid hormone levels were noted in 26% and elevated levels in 61% of the entire sample, particularly in the Asia Pacific region. Lower-than-recommended calcium levels were noted in 36% of the entire cohort, particularly in Latin America.

CONCLUSIONS

We found regional differences in growth- and age-adjusted bone mineral metabolism markers. Children from North America had the best growth, received the most dialysis, but also had the worst phosphate control and body mass index z scores.

Assessment of Quality of Life among Children with End-Stage Renal Disease: A Cross-Sectional Study

Background

Measuring health-related quality of life is considered an important outcome indicator in evaluating health-care interventions and treatments and in understanding the burden of diseases.

Objectives

This study aimed at assessing quality of life among children with end-stage renal disease, either undergoing hemodialysis or had renal transplantation therapy and comparing it with healthy controls.

Methods

A cross-sectional study was conducted between December 2016 and May 2017 in Abo El-Reesh Pediatric Hospital using parent/child reports of generic module for QoL assessment: PedsQL^TM Inventory version 4 for both cases and controls. Disease-specific module: PedsQL^TM ESRD version 3 was used for ESRD cases. 55 ESRD cases and 86 controls were enrolled in the study.

Results

Statistically significant difference between ESRD cases and controls regarding all aspects of QoL was found; total QoL mean score was 58.4 ± 15.3 and 86.8 ± 10 among cases and controls, respectively. All individual QoL domains were significantly worse in ESRD cases. Transplantation group had better Spearman's correlation between child and parents' scores which showed significant positive moderate correlation.

Conclusions

ESRD and its treatment modalities are affecting negatively all aspects of quality of life; incorporating QoL assessment and management is highly recommended.

The interplay between bone and vessels in pediatric CKD: lessons from a single-center study

OBJECTIVE

Mineral and bone disorders associated to chronic kidney disease (CKD-MBD) are a daily challenge for pediatric nephrologists, with a significant risk of long-term bone and vascular comorbidities.

METHODS

This single-center study is a prospective transversal evaluation of pediatric CKD patients of our center, part of the European 4C study. In addition to clinical and biochemical data, vascular and bone evaluation was performed: 24-h blood pressure assessment, carotid intima-media thickness (cIMT), pulse wave velocity (PWV), and high-resolution peripheral quantitative computed tomography (HR-pQCT) at the ultra-distal tibia. Results are presented as median (range).

RESULTS

At a median age of 12.9 years (10.2-17.9), SDS height of - 1.0 (- 3.3-1.2) and estimated glomerular filtration rate (eGFR) of 33 mL/min/1.73m² (11-72), 32 patients (8 girls) were evaluated. Median calcium, phosphate, parathyroid hormone (PTH), and 25 OHD3 levels were 2.44 mmol/L (2.24-2.78), 1.43 mmol/L (1.0-2.7), 80 pg/mL (9-359), and 70 nmol/L (32-116), respectively. Bivariate Spearman and backward multivariable analyses showed that calcium and bone trabecular thickness (Tb.Th), were positively associated with diastolic and mean arterial blood pressure (both for the 24 h, day and night assessment), whereas PTH and vitamin D did not predict blood pressure.

CONCLUSIONS

We show that the greater the serum levels of calcium, the greater the (diastolic and mean) blood pressure; moreover, the greater the Tb. Th, the greater the (diastolic and mean) blood pressure. The role of calcium supplements to explain such findings in early pediatric CKD can be discussed.

The Body-wide Transcriptome Landscape of Disease Models

Virtually all diseases affect multiple organs. However, our knowledge of the body-wide effects remains limited. Here, we report the body-wide transcriptome landscape across 13–23 organs of mouse models of myocardial infarction, diabetes, kidney diseases, cancer, and pre-mature aging. Using such datasets, we find (1) differential gene expression in diverse organs across all models; (2) skin as a disease-sensor organ represented by disease-specific activities of putative gene-expression network; (3) a bone-skin cross talk mediated by a bone-derived hormone, FGF23, in response to dysregulated phosphate homeostasis, a known risk-factor for kidney diseases; (4) candidates for the signature activities of many more putative inter-organ cross talk for diseases; and (5) a cross-species map illustrating organ-to-organ and model-to-disease relationships between human and mouse. These findings demonstrate the usefulness and the potential of such body-wide datasets encompassing mouse models of diverse disease types as a resource in biological and medical sciences. Furthermore, the findings described herein could be exploited for designing disease diagnosis and treatment.

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Body-wide multi-organ transcriptome datasets encompassing diverse disease models

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Skin is a disease-sensor organ, and FGF23 mediates a bone-skin cross talk in diseases

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Diverse putative inter-organ cross talk selectively associates with diseases

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A cross-species map illustrating the mouse-human relationships

A Method for Assessing the Retention of Trace Elements in Human Body Using Neural Network Technology

Models that describe the trace element status formation in the human organism are essential for a correction of micromineral (trace elements) deficiency. A direct trace element retention assessment in the body is difficult due to the many internal mechanisms. The trace element retention is determined by the amount and the ratio of incoming and excreted substance. So, the concentration of trace elements in drinking water characterizes the intake, whereas the element concentration in urine characterizes the excretion. This system can be interpreted as three interrelated elements that are in equilibrium. Since many relationships in the system are not known, the use of standard mathematical models is difficult. The artificial neural network use is suitable for constructing a model in the best way because it can take into account all dependencies in the system implicitly and process inaccurate and incomplete data. We created several neural network models to describe the retentions of trace elements in the human body. On the model basis, we can calculate the microelement levels in the body, knowing the trace element levels in drinking water and urine. These results can be used in health care to provide the population with safe drinking water.

The chronic kidney disease - Mineral bone disorder (CKD-MBD): Advances in pathophysiology

The causes of excess cardiovascular mortality associated with chronic kidney disease (CKD) have been attributed in part to the CKD-mineral bone disorder syndrome (CKD-MBD), wherein, novel cardiovascular risk factors have been identified. New advances in the causes of the CKD-MBD are discussed in this review. They demonstrate that repair and disease processes in the kidneys release factors to the circulation that cause the systemic complications of CKD. The discovery of WNT inhibitors, especially Dickkopf 1 (Dkk1), produced during renal repair as participating in the pathogenesis of the vascular and skeletal components of the CKD-MBD implied that additional pathogenic factors are critical. This lead to the discovery that activin A is a second renal repair factor circulating in increased levels during CKD. Activin A derives from peritubular myofibroblasts of diseased kidneys, wherein it stimulates fibrosis, and decreases tubular klotho expression. Activin A binds to the type 2 activin A receptor, ActRIIA, which is variably affected by CKD in the vasculature. In diabetic/atherosclerotic aortas, specifically in vascular smooth muscle cells (VSMC), ActRIIA signaling is inhibited and contributes to CKD induced VSMC dedifferentiation, osteogenic transition and neointimal atherosclerotic calcification. In nondiabetic/nonatherosclerotic aortas, CKD increases VSMC ActRIIA signaling, and vascular fibroblast signaling causing the latter to undergo osteogenic transition and stimulate vascular calcification. In both vascular situations, a ligand trap for ActRIIA prevented vascular calcification. In the skeleton, activin A is responsible for CKD stimulation of osteoclastogenesis and bone remodeling increasing bone turnover. These studies demonstrate that circulating renal repair and injury factors are causal of the CKD-MBD and CKD associated cardiovascular disease.

Clinical practice recommendations for treatment with active vitamin D analogues in children with chronic kidney disease Stages 2-5 and on dialysis

In patients with chronic kidney disease (CKD), renal synthesis of active vitamin D [1,25-dihydroxyvitamin D (1,25(OH)2D)] declines and is associated with hypocalcaemia, secondary hyperparathyroidism and the spectrum of CKD-mineral and bone disorder (MBD). In advanced CKD, active vitamin D analogues, including alfacalcidol, calcitriol and paricalcitol, are routinely administered. There are few studies on the use of vitamin D analogues in children with CKD and on dialysis. It is difficult to define bone-specific outcomes that can guide treatment with active vitamin D analogues in children with CKD-MBD. A core working group (WG) of the European Society for Paediatric Nephrology (ESPN) CKD-MBD and Dialysis WGs has developed recommendations for the use of active vitamin D therapy in children with CKD and on dialysis. A second document in parallel with this one covers treatment recommendations for native vitamin D therapy. The WGs have performed an extensive literature review to include systematic reviews and randomized controlled trials in adults and children with CKD and prospective observational studies in children with CKD. The Grading of Recommendation, Assessment, Development and Evaluation (GRADE) system was used to develop and grade the recommendations. In the absence of applicable study data, the opinion of experts from the ESPN CKD-MBD and Dialysis WGs is provided, but clearly GRADE-ed as such and must be carefully considered by the treating physician and adapted to individual patient needs as appropriate.

The Kidney-Vascular-Bone Axis in the Chronic Kidney Disease-Mineral Bone Disorder

The last 25 years have been characterized by dramatic improvements in short-term patient and allograft survival after kidney transplantation. Long-term patient and allograft survival remains limited by cardiovascular disease and chronic allograft injury, among other factors. Cardiovascular disease remains a significant contributor to mortality in native chronic kidney disease as well as cardiovascular mortality in chronic kidney disease more than doubles that of the general population. The chronic kidney disease (CKD)-mineral bone disorder (MBD) is a syndrome recently coined to embody the biochemical, skeletal, and cardiovascular pathophysiology that results from disrupting the complex systems biology between the kidney, skeleton, and cardiovascular system in native and transplant kidney disease. The CKD-MBD is a unique kidney disease-specific syndrome containing novel cardiovascular risk factors, with an impact reaching far beyond traditional notions of renal osteodystrophy and hyperparathyroidism. This overview reviews current knowledge of the pathophysiology of the CKD-MBD, including emerging concepts surrounding the importance of circulating pathogenic factors released from the injured kidney that directly cause cardiovascular disease in native and transplant chronic kidney disease, with potential application to mechanisms of chronic allograft injury and vasculopathy.

Chronic kidney disease in children

Chronic kidney disease (CKD) is a major health problem worldwide. Although relatively uncommon in children, it can be a devastating illness with many long-term consequences. CKD presents unique features in childhood and may be considered, at least in part, as a stand-alone nosologic entity. Moreover, some typical features of paediatric CKD, such as the disease aetiology or cardiovascular complications, will not only influence the child's health, but also have long-term impact on the life of the adult that they will become. In this review we will focus on the unique issues of paediatric CKD, in terms of aetiology, clinical features and treatment. In addition, we will discuss factors related to CKD that start during childhood and require appropriate treatments in order to optimize health outcomes and transition to nephrologist management in adult life.

Peritonitis in children with automated peritoneal dialysis: a single-center study of a 10-year experience

Peritoneal dialysis (PD) constitutes the preferred dialysis modality for children requiring renal replacement therapy with peritonitis being one of the most common complications of PD. This study was performed to evaluate the epidemiology, microbiology, and outcomes of PD-associated peritonitis in Greek children for a 10-year period. A total of 27 patients (16 males) with a mean age 121.8 ± 57.2 months were retrospective analyzed. Patients were on PD therapy for a mean duration of 45.2 ± 26.1 months. We found 23 episodes of PD-associated peritonitis occurred in 9 out of 27 patients (0.23 episodes/patient-year), with four patients experienced two or more peritonitis episodes. Gram-positive bacteria were responsible for 15 (65.2%) peritonitis episodes, with Staphylococcus aureus being the predominant specie isolated in 30.4% of cases. A total of seven episodes of exit-site infections (ESIs) were identified in five patients (0.069 episodes/patient-year) with the most common bacteria isolated being S. aureus (57.4%). Initial antibiotic treatment included intraperitoneal vancomycin plus ceftazidime in the majority of cases (82.6%). At the end of study, 12 (44.4%) patients remained on PD, 11 (41.8%) underwent renal transplantation, 2 (7.4%) shifted to hemodialysis and unfortunately, two patients (7.4%) died. Conclusively, our study revealed a noticeable low peritonitis and ESIs rate as compared to international data and represents the first evaluation of the characteristics and outcomes of peritonitis in the Greek pediatric PD population.

Prevalence of Hyperparathyroidism, Mineral and Bone Disorders in Children with Advanced Chronic Kidney Disease

OBJECTIVE

To identify the prevalence and risk factors for secondary hyperparathyroidism in children with advanced stages of chronic kidney disease (CKD).

METHODS

A retrospective cross-sectional observational study of clinical and laboratory data of pediatric patients with CKD stage 3, 4 was conducted from 2005 through 2013 at a single center in the Kingdom of Saudi Arabia.

RESULTS

One hundred nineteen children (60.5 % boys) with mean age of 10.1 ± 5.1 y were included in the study. The mean eGFR (estimated Glomerular Filtration Rate) was 18.3 ± 15.4 ml/min/1.73m(2) and the mean intact parathyroid hormone (iPTH) level was 62.2 ± 89.4 pmol/L. Patients with a high iPTH had lower eGFR than those who were euparathyroid (16 ± 13.4 vs. 29.7 ± 19 ml/min/1.73m(2), respectively; p = 0.006), had lower calcium levels (2.2 ± 0.3 vs. 2.4 ± 0.3 mmol/L; p = 0.03) and a lower bicarbonate level (21.2 ± 4.2 vs. 23.3 ± 3.2 mmol/L; p = 0.04). Three children with hyperparthyrodism (4.9 %) had fractures, 16 (26.2 %) had bone deformities compared to 5 in the euoparathyroid group (p = 0.012). Parathyroid hormone negatively correlated with the patient's eGFR (r = -0.55), serum calcium (r = -0.43), and positively correlated with serum phosphate (r = 0.38).

CONCLUSIONS

The single most important predictor of hyperparathyroidism in children in the present sample was eGFR.

Practical Nutrition Management of Children with Chronic Kidney Disease

Chronic kidney disease (CKD) introduces a unique set of nutritional challenges for the growing and developing child. This article addresses initial evaluation and ongoing assessment of a child with CKD. It aims to provide an overview of nutritional challenges unique to a pediatric patient with CKD and practical management guidelines. Caloric assessment in children with CKD is critical as many factors contribute to poor caloric intake. Tube feeding is a practical option to provide the required calories and fluid in children who have difficulty with adequate oral intake. Protein intake should not be limited and should be further adjusted for protein loss with dialysis. Supplementation or restriction of sodium is patient specific. Urine output, fluid status, and modality of dialysis are factors that influence sodium balance. Hyperkalemia poses a significant cardiac risk, and potassium is closely monitored. In addition to a low potassium diet, potassium binders may be prescribed to reduce potassium load from oral intake. Phosphorus and calcium play a significant role in cardiovascular and bone health. Phosphorus binders have helped children and families manage phosphorus levels in conjunction with a phosphorus-restricted diet. Nutritional management of children with CKD is a challenge that requires continuous reassessment and readjustment as the child ages, CKD progresses, and urine output decreases.

[Vitamin D deficiency in childhood: an opportunity for prevention]

The prevalence of vitamin D deficiency in the pediatric population has increased in recent years and continues to be underdiagnosed and undertreated. According to data from the "ENSANUT 2006" (National Health and Nutrition Survey), the prevalence of vitamin D deficiency in Mexico was 16% in children aged 2-12 years. Vitamin D plays a critical role in the formation and bone homeostasis and consequently on growth. Its deficiency is clearly associated with diseases such as rickets and osteomalacia, and it has been linked to other diseases such as obesity, metabolic syndrome, diabetes, cancer, respiratory infections and immune system disease. Specific risk groups have been described in the medical literature for vitamin D deficiency in which supplementation may offer a benefit. Currently, there is still controversy in defining the serum levels of proficiency and dose supplementation. In Mexico, the daily suggested intake of vitamin D is 5.6μg (224 IU), which is significantly lower than the recommendations in the U.S. and Europe (i.e., between 400 and 1000 IU/day). An increase in vitamin D deficiency has been reported in recent years. There is no consensus regarding the sufficiency levels of vitamin D. Cut-off values vary from 20 to 30ng/ml. Therefore, the objective of this review was to provide an overview of the problem in the pediatric population and to describe the groups at risk, as well as to analyze the current recommendations for vitamin D supplementation. Vitamin D deficiency was considered rare in Mexico according to the National Institute of Medical Science and Nutrition Salvador Zubirán. Lack of evidence did not help to establish the international recommended daily intake. Currently, vitamin D deficiency must be recognized as a health problem, worthy of attention and action. We suggest that prospective studies are carried out in our country where the relationship between serum vitamin D deficiency and poor bone mineralization will be established.

Pathophysiology of the chronic kidney disease-mineral bone disorder

PURPOSE OF REVIEW

The causes of excess cardiovascular mortality associated with chronic kidney disease (CKD) have been attributed in part to the CKD-mineral bone disorder syndrome (CKD-MBD), wherein, novel cardiovascular risk factors have been identified. The causes of the CKD-MBD are not well known and they will be discussed in this review

RECENT FINDINGS

The discovery of WNT (portmanteau of wingless and int) inhibitors, especially Dickkopf 1, produced during renal repair and participating in the pathogenesis of the vascular and skeletal components of the CKD-MBD implied that additional pathogenic factors are critical, leading to the finding that activin A is a second renal repair factor circulating in increased levels during CKD. Activin A derives from peritubular myofibroblasts of diseased kidneys, where it stimulates fibrosis, and decreases tubular klotho expression. The type 2 activin A receptor, ActRIIA, is decreased by CKD in atherosclerotic aortas, specifically in vascular smooth muscle cells (VSMC). Inhibition of activin signaling by a ligand trap inhibited CKD induced VSMC dedifferentiation, osteogenic transition and atherosclerotic calcification. Inhibition of activin signaling in the kidney decreased renal fibrosis and proteinuria.

SUMMARY

These studies demonstrate that circulating renal repair factors are causal for the CKD-MBD and CKD associated cardiovascular disease, and identify ActRIIA signaling as a therapeutic target in CKD that links progression of renal disease and vascular disease.

Automated Greulich-Pyle bone age determination in children with chronic kidney disease

BACKGROUND

Growth restriction and retarded bone age are common findings in children with chronic kidney disease (CKD). We compared the automated BoneXpert™ method with the manual assessment of an X-ray of the non-dominant hand.

METHODS

In this retrospective multicenter study, 359 patients with CKD stages 2-5, aged 2-14.5 (girls) or 2.5-17 years (boys) were included. Bone age was determined manually by three experts (according to Greulich and Pyle). Automated determination of bone age was performed using the image analysis software BoneXpert™.

RESULTS

There was a strong correlation between the automatic and the manual method (r = 0.983, p < 0.001). The automatic method tended to generate higher bone age values (0.64 ± 0.73 years) in the younger patients (4-5 years) and to underestimate retardation or acceleration of bone age. The so-called "bone health index" (BHI) was reduced in comparison to the reference population. Bone health index standard deviation score (BHI-SDS) was not related to the stage of CKD, but weakly negatively correlated with plasma PTH concentrations (r = 0.12, p = 0.019).

CONCLUSIONS

BoneXpert™ allows an objective, time-saving, and in general valid bone age assessment in children with CKD. Possible underestimation of retarded or accelerated bone age should be taken into account. Validation of the BHI needs further study.

Feeding soy protein isolate and oils rich in omega-3 polyunsaturated fatty acids affected mineral balance, but not bone in a rat model of autosomal recessive polycystic kidney disease

Background

Polycystic kidney disease (PKD), a genetic disorder characterized by multiple cysts and renal failure at an early age. In children, kidney disease is often accompanied by disordered mineral metabolism, failure to achieve peak bone mass, and reduced adult height. Optimizing bone health during the growth stage may preserve against bone loss associated with early renal dysfunction in PKD. Dietary soy protein and omega-3 polyunsaturated fatty acid (n-3 PUFA) have been reported to ameliorate PKD and to promote bone health. The study objective was to determine the bone effects of feeding soy protein and/or n-3 PUFAs in a rat model of PKD.

Methods

Weanling female PCK rats (n = 12/group) were randomly assigned to casein + corn oil (Casein + CO), casein + soybean oil (Casein + SO), soy protein isolate + soybean oil (SPI + SO) or soy protein isolate + 1:1 soybean oil:salmon oil blend (SPI + SB) for 12 weeks.

Results

Rats fed SPI + SO diet had shorter (P = 0.001) femur length than casein-fed rats. Rats fed SPI + SO and SPI + SB diet had higher (P = 0.04) calcium (Ca) and phosphorus (P) retention. However, there were no significant differences in femur and tibial Ca, P or bone mass between diet groups. There were also no significant difference in bone microarchitecture measured by micro-computed tomography or bone strength determined by three-point bending test between diet groups.

Conclusions

Early diet management of PKD using SPI and/or n-3 PUFAs influenced bone longitudinal growth and mineral balance, but neither worsened nor enhanced bone mineralization, microarchitecture or strength.

Markers of bone metabolism are affected by renal function and growth hormone therapy in children with chronic kidney disease

Objectives

The extent and relevance of altered bone metabolism for statural growth in children with chronic kidney disease is controversial. We analyzed the impact of renal dysfunction and recombinant growth hormone therapy on a panel of serum markers of bone metabolism in a large pediatric chronic kidney disease cohort.

Methods

Bone alkaline phosphatase (BAP), tartrate-resistant acid phosphatase 5b (TRAP5b), sclerostin and C-terminal FGF-23 (cFGF23) normalized for age and sex were analyzed in 556 children aged 6–18 years with an estimated glomerular filtration rate (eGFR) of 10–60 ml/min/1.73m². 41 children receiving recombinant growth hormone therapy were compared to an untreated matched control group.

Results

Standardized levels of BAP, TRAP5b and cFGF-23 were increased whereas sclerostin was reduced. BAP was correlated positively and cFGF-23 inversely with eGFR. Intact serum parathormone was an independent positive predictor of BAP and TRAP5b and negatively associated with sclerostin. BAP and TRAP5B were negatively affected by increased C-reactive protein levels. In children receiving recombinant growth hormone, BAP was higher and TRAP5b lower than in untreated controls. Sclerostin levels were in the normal range and higher than in untreated controls. Serum sclerostin and cFGF-23 independently predicted height standard deviation score, and BAP and TRAP5b the prospective change in height standard deviation score.

Conclusion

Markers of bone metabolism indicate a high-bone turnover state in children with chronic kidney disease. Growth hormone induces an osteoanabolic pattern and normalizes osteocyte activity. The osteocyte markers cFGF23 and sclerostin are associated with standardized height, and the markers of bone turnover predict height velocity.