Relation of bone mineral density with clinical and laboratory parameters in pre-pubertal children with cystic fibrosis

Cystic fibrosis related bone disease in children: Can it be predicted?

BACKGROUND&AIMS

Cystic fibrosis (CF) -related bone disease (CFBD) is an important complication of CF, and low BMD in childhood is a precursor of CFBD. Here, we aimed to investigate bone turnover biomarkers, including osteocalcin (OC), receptor activator of nuclear factor kappa B ligand (RANKL) and osteoprotegerin (OPG) in relation to low BMD in children with CF (cwCF). We also evaluated factors which could affect bone turnover with particular emphasis on fat-free mass (FFM), forced expiratory volume in 1 s (FEV1), hand grip strength (HGS), and functional capacity and physical activity.

METHODS

Sixteen cwCF aged 8-18 years with moderate low BMD (group1) and 64 cwCF with normal BMD (group2) were enrolled. Serum RANKL, OC, and OPG were determined by immunoenzymatic assays. Multiple parameters including pancreatic status, lung functions, body mass index (BMI), FFM measured by bioelectric impedance analysis (BIA), 6-minute walk test, vitamin D, nutritional intake, HGS, functional capacity and physical activity, serum and urine biomarkers were compared between the two groups.

RESULTS

We found similar serum levels of RANKL (p = 0.501), OC (p = 0.445), OPG (p = 0.380), and RANKL/OPG ratio (p = 0.449) between group1 and group2 in cwCF. BMI z-score (p < 0.001), FFMI z-score (p < 0.001), FEV1 z-score (p = 0.007), and right-HGS (%pred) (p = 0.009) significantly differed between the two groups. Multivariate linear regression revealed that the only factors that predicted BMD were FFMI z-score and HGS %pred.

CONCLUSION

Serum OC, OPG, RANKL and RANKL/OPG ratio did not predict BMD in cwCF. FFMI z-score and HGS %pred measured by non-invasive and practical methods were the best predictors of BMD.

The Effects of Ivacaftor on Bone Density and Microarchitecture in Children and Adults with Cystic Fibrosis

CONTEXT

Cystic fibrosis (CF) transmembrane conductance (CFTR) dysfunction may play a role in CF-related bone disease (CFBD). Ivacaftor is a CFTR potentiator effective in improving pulmonary and nutritional outcomes in patients with the G551D-CFTR mutation. The effects of ivacaftor on bone health are unknown.

OBJECTIVE

To determine the impact of ivacaftor on bone density and microarchitecture in children and adults with CF.

DESIGN

Prospective observational multiple cohort study.

SETTING

Outpatient clinical research center within a tertiary academic medical center.

PATIENTS OR OTHER PARTICIPANTS

Three cohorts of age-, race-, and gender-matched subjects were enrolled: 26 subjects (15 adults and 11 children) with CF and the G551D-CFTR mutation who were planning to start or had started treatment with ivacaftor within 3 months (Ivacaftor cohort), 26 subjects with CF were not treated with ivacaftor (CF Control cohort), and 26 healthy volunteers.

INTERVENTIONS

All treatments, including Ivacaftor, were managed by the subjects' pulmonologists.

MAIN OUTCOME MEASURES

Bone microarchitecture by high-resolution peripheral quantitative computed tomography (HR-pQCT), areal bone mineral density (aBMD) by dual-energy X-ray absorptiometry (DXA) and bone turnover markers at baseline, 1, and 2 years.

RESULTS

Cortical volume, area, and porosity at the radius and tibia increased significantly in adults in the Ivacaftor cohort. No significant differences were observed in changes in aBMD, trabecular microarchitecture, or estimated bone strength in adults or in any outcome measures in children.

CONCLUSIONS

Treatment with ivacaftor was associated with increases in cortical microarchitecture in adults with CF. Further studies are needed to understand the implications of these findings.

Circulating biomarkers of antioxidant status and oxidative stress in people with cystic fibrosis: A systematic review and meta-analysis

Introduction

Oxidative stress may play an important role in the pathophysiology of cystic fibrosis (CF). This review aimed to quantify CF-related redox imbalances.

Methods

Systematic searches of the Medline, CINAHL, CENTRAL and PsycINFO databases were conducted. Mean content of blood biomarkers from people with clinically-stable CF and non-CF controls were used to calculate the standardized mean difference (SMD) and 95% confidence intervals (95% CI).

Results

Forty-nine studies were eligible for this review including a total of 1792 people with CF and 1675 controls. Meta-analysis revealed that protein carbonyls (SMD: 1.13, 95% CI: 0.48 to 1.77), total F₂-isoprostane 8-iso-prostaglandin F_2α (SMD: 0.64, 95% CI: 0.23 to 1.05) and malondialdehyde (SMD: 1.34, 95% CI: 0.30 to 2.39) were significantly higher, and vitamins A (SMD: −0.66, 95% CI -1.14 to −0.17) and E (SMD: −0.74, 95% CI: −1.28 to −0.20), β-carotene (SMD: −1.80, 95% CI: −2.92 to −0.67), lutein (SMD: −1.52, 95% CI: −1.83 to −1.20) and albumin (SMD: −0.98, 95% CI: −1.68 to −0.27) were significantly lower in the plasma or serum of people with CF versus controls.

Conclusions

This systematic review and meta-analysis found good evidence for reduced antioxidant capacity and elevated oxidative stress in people with clinically-stable CF.

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Blood biomarkers of oxidative stress were elevated in stable CF vs non-CF controls.

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Lipid peroxidation was positively correlated with age and immune cell count in CF.

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Antioxidants vitamins A & E, β-carotene, lutein and albumin were lower in stable CF.

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Antioxidants were positively correlated with body mass index and lung function in CF.

Peripheral quantitative computed tomography detects differences at the radius in prepubertal children with cystic fibrosis compared to healthy controls

Introduction

In 2015, 11.9% of people with cystic fibrosis (CF) in the United States had osteopenia, 5.1% osteoporosis, and 0.3% experienced a fracture. Screening for CF-related bone disease starts in childhood, and dual energy x-ray absorptiometry (DXA) is the recommended method. It is unknown whether peripheral quantitative computed tomography (pQCT) can detect deficits earlier than DXA. This study compared pQCT and DXA scans in a group of pre-pubertal children with CF and healthy controls.

Methods

This was a cross-sectional study of children at Tanner stage 1. A pQCT scan of the radius at proximal and distal sites was performed plus a total body DXA scan. Serum C-reactive protein, interleukin-6 and tumor necrosis factor-alpha were also measured.

Results

A total of 34 subjects completed the study; 14 with CF and 20 controls. At the distal radius, pQCT showed a lower total bone mineral density (BMD) Z-score for the CF group (P = 0.01 and P = 0.03 for 2 different reference databases) compared to controls. At the proximal site, the polar strength-strain index was lower in the CF group (P = 0.017). Finally, the total body BMD Z-score by DXA was lower in the CF group, although it did not meet the definition of reduced bone density (P = 0.004). Biomarkers of inflammation were not different.

Conclusions

In this group of pre-pubertal children with CF, measures of bone strength and density by both pQCT and DXA were reduced compared to healthy controls.

Young adults with cystic fibrosis have altered trabecular microstructure by ITS-based morphological analysis

Young adults with cystic fibrosis have compromised plate-like trabecular microstructure, altered axial alignment of trabeculae, and reduced connectivity between trabeculae that may contribute to the reduced bone strength and increased fracture risk observed in this patient population.

INTRODUCTION

The risk of fracture is increased in patients with cystic fibrosis (CF). Individual trabecular segmentation (ITS)-based morphological analysis of high-resolution peripheral quantitative computed tomography (HR-pQCT) images segments trabecular bone into individual plates and rods of different alignment and connectivity, which are important determinants of trabecular bone strength. We sought to determine whether alterations in ITS variables are present in patients with CF and may help explain their increased fracture risk.

METHODS

Thirty patients with CF ages 18-40 years underwent DXA scans of the hip and spine and HR-pQCT scans of the radius and tibia with further assessment of trabecular microstructure by ITS. These CF patients were compared with 60 healthy controls matched for age (±2 years), race, and gender.

RESULTS

Plate volume fraction, thickness, and density as well as plate-plate and plate-rod connectivity were reduced, and axial alignment of trabeculae was lower in subjects with CF at both the radius and the tibia (p < 0.05 for all). At the radius, adjustment for BMI eliminated most of these differences. At the tibia, however, reductions in plate volume fraction and number, axially aligned trabeculae, and plate-plate connectivity remained significant after adjustment for BMI alone and for BMI and aBMD (p < 0.05 for all).

CONCLUSIONS

Young adults with CF have compromised plate-like and axially aligned trabecular morphology and reduced connectivity between trabeculae. ITS analysis provides unique information about bone integrity, and these trabecular deficits may help explain the increased fracture risk in adults with CF not accounted for by BMD and/or traditional bone microarchitecture measurements.

Evaluation of factors related to bone disease in Polish children and adolescents with cystic fibrosis

PURPOSE

The aim of the study was to evaluate factors related to bone formation and resorption in Polish children and adolescents with cystic fibrosis and to examine the effect of nutritional status, biochemical parameters and clinical status on bone mineral density.

MATERIALS AND METHODS

The study group consisted of 100 children and adolescents with cystic fibrosis with a mean age 13.4 years old. Anthropometric measurements, included body height, body mass and body mass index (BMI); bone mineral densitometry and biochemical testing were performed. Bone mineral density was measured using a dual-energy X-ray absorption densitometer. Biochemical tests included serum calcium, phosphorus, parathyroid hormone and vitamin D concentrations, as well as 24-h urine calcium and phosphorus excretion. Pulmonary function was evaluated using FEV1%, and clinical status was estimated using the Shwachman-Kulczycki score.

RESULTS

Standardized body height, body mass and BMI were significantly lower than in the reference population. Mean serum vitamin D concentration was decreased. Pulmonary disease was generally mild, with a mean FEV1% of 81%. Multivariate linear regression revealed that the only factors that had a significant effect on bone marrow density were BMI and FEV1%. There were no significant correlations between bone mineral density and the results of any of the biochemical tests performed.

CONCLUSIONS

Nutritional status and bone mineral density were significantly decreased in children and adolescents with cystic fibrosis. In spite of abnormalities in biochemical testing, the factors that were found to have the strongest effect on bone mineral density were standardized BMI and clinical status.

Bone health in children and adolescents with chronic diseases that may affect the skeleton: the 2013 ISCD Pediatric Official Positions

The aim of this Task Force was to review the use of dual-energy X-ray absorptiometry (DXA) in children and adolescents with underlying chronic diseases that pose risk factors for compromised bone health, such as inflammation, glucocorticoid therapy, or decreased mobility. The Task Force systematically analyzed more than 270 studies, with an emphasis on those published in the interval since the original 2007 Position Statements. Important developments over this period included prospective cohort studies demonstrating that DXA measures of areal bone mineral density (aBMD) predicted incident fractures and the development of robust reference data and strategies to adjust for bone size in children with growth impairment. In this report, we summarize the current literature on the relationship between DXA-based aBMD and both fracture (vertebral and non-vertebral) outcomes and non-fracture risk factors (e.g., disease characteristics, ambulatory status, and glucocorticoid exposure) in children with chronic illnesses. Most publications described the aBMD profile of children with underlying diseases, as well as the cross-sectional or longitudinal relationship between aBMD and clinically relevant non-fracture outcomes. Studies that addressed the relationship between aBMD and prevalent or incident fractures in children with chronic illnesses are now emerging. In view of these updated data, this report provides guidelines for the use of DXA-based aBMD in this setting. The initial recommendation that DXA is part of a comprehensive skeletal healthy assessment in patients with increased risk of fracture is unchanged. Although the prior guidelines recommended DXA assessment in children with chronic diseases at the time of clinical presentation with ongoing monitoring, this revised Position Statement focuses on the performance of DXA when the patient may benefit from interventions to decrease their elevated risk of a clinically significant fracture and when the DXA results will influence that management.

Increased whole body hydroxyproline production as assessed by a new stable isotope technique is associated with hip and spine bone mineral loss in cystic fibrosis

BACKGROUND & AIMS

Bone mineral loss, reduced lung function and impaired nutritional status are frequently present in children with Cystic Fibrosis (CF). Blood concentrations and urinary excretion of hydroxyproline (OH-PRO) have been used as markers of bone mineral status and lung function in CF.

OBJECTIVE

To examine whether whole body hydroxyproline production, as assessed by a new stable isotope methodology, is increased in pediatric patients with CF and associated with bone mineral loss, lung function decline and impaired nutritional status.

DESIGN

In a cross-sectional study in 15 pediatric patients with CF and 17 healthy young control subjects, whole body hydroxyproline production (Wb OH-PRO) was assessed in the postabsorptive state by primed-constant and continuous infusion of the stable isotope 2-D-OH-PRO for 3 h. Bone mineral density (BMD) of whole body, hip and spin, and body composition (fat mass and fat-free mass) were determined by dual-energy X-ray Absorptiometry (DXA). Plasma isotopic enrichments and OH-PRO concentrations were measured by LC/MS/MS.

RESULTS

Higher values for WbOH-PRO production and plasma OH-PRO concentrations were found in pediatric CF patients than in the healthy young subjects (p < 0.001). WbOH-PRO production was significantly correlated with plasma OH-PRO concentrations in the CF (r: 0.70, p = 0.007) but not in the healthy group. WbOH-PRO production in CF was associated with low BMD values in hip (r = -0.61, p = 0.02) and spine (r = -0.59, p = 0.02) but not with whole body BMD, lung function or body composition.

CONCLUSION

A new stable isotope approach revealed enhanced levels of whole body hydroxyproline production rate in pediatric patients with CF, indicative of enhanced whole body collagen breakdown. Increased levels for whole body hydroxyproline production in CF were associated with severe bone mineral loss in hip and spine but not with lung function decline or impaired nutritional status. Registration ClinicalTrials.gov = NCT01172301.

Bone turnover markers, osteoprotegerin and RANKL cytokines in children with cystic fibrosis

PURPOSE

Some scientific studies show decreased bone mineral density and increased fracture frequency in adult patients with cystic fibrosis (CF). The mechanism for early bone loss in CF patients are multifactorial: chronic pulmonary inflammation, malnutrition, reduced physical activity, delayed pubertal maturation. The aim of this study was to assess bone metabolism markers with special attention paid to osteoprotegerin (OPG) and receptor activator of nuclear factor κB ligand (RANKL) balance in CF children.

MATERIAL AND METHODS

The study included 35 children with diagnosed CF and 35 healthy controls aged 5-9 years (median 7.0 years). Serum levels of fat soluble vitamins were measured by chemiluminescence (vitamin D) and HPLC (vitamins A, E) methods. Concentrations of bone metabolism markers were determined by immunoenzymatic assay.

RESULTS

Mean levels of fat soluble vitamins (A, D, E) were lower in patients with CF compared to controls. In CF children we observed a significant (p<0.01) decrease in concentration of bone formation marker (osteocalcin) and similar bone resorption markers (CTX, TRACP5b) in comparison with healthy children. The serum level of OPG was significantly lower (p<0.05) and RANKL nearly 2-fold higher in patients with CF than in the healthy ones. The ratio of OPG to RANKL was about 2-fold lower in children with CF compared to healthy peers (p<0.01).

CONCLUSION

In CF children, an imbalance between bone formation and resorption processes occurs. An increase serum RANKL concentration coexisting with lower levels of OPG may be associated with intensification of bone resorption.

The impact of dysglycaemia on bone mineral accrual in young people with cystic fibrosis

OBJECTIVE

The effect of dysglycaemia on bone mineral density (BMD) has not been studied in young people with CF. We examined factors associated with BMD in a tertiary paediatric CF clinic.

DESIGN

Retrospective, clinic-based study at The Children's Hospital at Westmead, Sydney.

PATIENTS

Young people with CF aged ≤ 18 years.

MEASUREMENTS

Bone mineral density was measured by dual-energy X-ray absorptiometry; main outcome measures were total body (TB), lumbar spine (LS) and femoral neck (FN) BMD and bone mineral content (BMC), and LS volumetric BMD (vBMD), reported as z scores for height. Dysglycaemia, based on oral glucose tolerance test, was defined as CF-related diabetes (CFRD) or impaired glucose tolerance (IGT).

RESULTS

Overall, 14 of 81 (17%) had CFRD, 6 (7%) IGT and 61 (76%) normal glucose tolerance (NGT). Mean age was 14.9 ± 2.4 years and mean height z score -0.68 ± 1.39. Osteopenic (z score ≤-2) TB, LS or FN BMD was present in 30 of 81 (37%), BMC in 42 (52%) and vBMD in 10 (5%). Across the three groups, there were differences in LS vBMD (CFRD, -0.67 ± 0.76; IGT, -0.52 ± 0.76; NGT, -0.05 ± 1.39; P = 0.04), LS BMD (P < 0.01), LS BMC (P = 0.01) and TB BMD (P = 0.01). In multivariate linear regression, LS BMC was associated with dysglycaemia (β = 0.56; 95% CI, 0.00-1.13; P = 0.05) and approached significance for FEV(1) (β = 0.01; 95% CI, 0.00-0.02; P = 0.06).

CONCLUSIONS

Dysglycaemia is associated with reduced bone mass accrual in youth with CF, in addition to recognized factors such as abnormal lung function, poor nutritional status and disease severity. Bone health assessment is essential in youth with CF.