Effects of Burosumab Treatment on Mineral Metabolism in Children and Adolescents With X-linked Hypophosphatemia

CONTEXT

Burosumab has been approved for the treatment of children and adults with X-linked hypophosphatemia (XLH). Real-world data and evidence for its efficacy in adolescents are lacking.

OBJECTIVE

To assess the effects of 12 months of burosumab treatment on mineral metabolism in children (aged <12 years) and adolescents (aged 12-18 years) with XLH.

DESIGN

Prospective national registry.

SETTING

Hospital clinics.

PATIENTS

A total of 93 patients with XLH (65 children, 28 adolescents).

MAIN OUTCOME MEASURES

Z scores for serum phosphate, alkaline phosphatase (ALP), and renal tubular reabsorption of phosphate per glomerular filtration rate (TmP/GFR) at 12 months.

RESULTS

At baseline, patients showed hypophosphatemia (-4.4 SD), reduced TmP/GFR (-6.5 SD), and elevated ALP (2.7 SD, each P < .001 vs healthy children) irrespective of age, suggesting active rickets despite prior therapy with oral phosphate and active vitamin D in 88% of patients. Burosumab treatment resulted in comparable increases in serum phosphate and TmP/GFR in children and adolescents with XLH and a steady decline in serum ALP (each P < .001 vs baseline). At 12 months, serum phosphate, TmP/GFR, and ALP levels were within the age-related normal range in approximately 42%, 27%, and 80% of patients in both groups, respectively, with a lower, weight-based final burosumab dose in adolescents compared with children (0.72 vs 1.06 mg/kg, P < .01).

CONCLUSIONS

In this real-world setting, 12 months of burosumab treatment was equally effective in normalizing serum ALP in adolescents and children, despite persistent mild hypophosphatemia in one-half of patients, suggesting that complete normalization of serum phosphate is not mandatory for substantial improvement of rickets in these patients. Adolescents appear to require lower weight-based burosumab dosage than children.

TAPT1-at the crossroads of extracellular matrix and signaling in Osteogenesis imperfecta

Osteogenesis imperfecta (OI) is a hereditary skeletal disorder primarily affecting collagen type I structure and function, causing bone fragility and occasionally versatile extraskeletal symptoms. This study expands the spectrum of OI-causing TAPT1 mutations and links extracellular matrix changes to signaling regulation.

Lifetime impact of achondroplasia study in Europe (LIAISE): findings from a multinational observational study

BACKGROUND

Achondroplasia, caused by a pathogenic variant in the fibroblast growth factor receptor 3 gene, is the most common skeletal dysplasia. The Lifetime Impact of Achondroplasia Study in Europe (LIAISE; NCT03449368) aimed to quantify the burden of achondroplasia among individuals across a broad range of ages, including adults.

METHODS

Demographic, clinical and healthcare resource use data were collected from medical records of achondroplasia patients enrolled in 13 sites across six European countries in this retrospective, observational study. Descriptive statistics or event rates per 100 person-years were calculated and compared across age groups as well as by history of limb lengthening. Patient-reported outcomes (quality of life [QoL], pain, functional independence, work productivity and activity impairments) were evaluated using questionnaires at the time of enrolment. An exploratory analysis investigated correlations between height (z-score or centimetres) and patient-reported outcomes.

RESULTS

Overall, 186 study patients were included, with a mean age of 21.7 ± 17.3 years (range 5.0-84.4). At least one complication or surgery was reported for 94.6% and 72.0% of patients, respectively, at a rate of 66.6 and 21.5 events per 100 person-years. Diverse medical and surgical complications were reported for all ages in a bimodal distribution, occurring more frequently in the youngest and oldest age groups. A total of 40 patients had previously undergone limb lengthening (capped at 20% per the study protocol). The most frequent surgery types varied by age, in line with complication profiles. Healthcare resource use was high across all age groups, especially among the youngest and oldest individuals, and did not differ substantially according to history of limb lengthening. Compared to general population values, patients reported impaired QoL particularly for physical functioning domains. In addition, patients reported difficulty carrying out daily activities independently and pain starting in childhood. Patient height correlated with multiple patient-reported outcomes.

CONCLUSIONS

The findings of this study suggest that, across an individual's lifetime, achondroplasia is associated with multisystem complications, reduced QoL and functionality, and increased pain. These results highlight the large amount of healthcare resources that individuals with achondroplasia require throughout their lifespans and provide novel insights into current achondroplasia management practices across Europe. Trial registration ClinicalTrials.gov, NCT03449368, Submitted 14 December 2017 - prospectively registered, https://clinicaltrials.gov/ct2/show/record/NCT03449368.

Cataract in children and adolescents with type 1 diabetes. Insights from the German/Austrian DPV registry

OBJECTIVE

To study diabetic cataract in type 1 diabetes in a large pediatric cohort.

METHODS

The 92,633 patients aged 0.5-21 years from German/Austrian multicenter diabetes registry (DPV) were analyzed. The 235 patients (0.25%) with diabetic cataract were found, 200 could be categorized: 67 with early cataract (3 months before diabetes onset - 12 months afterwards), 133 with late cataract (>12 months after diabetes onset). Regression models adjusted for age and gender were used to compare clinical parameters at diabetes onset. Regression models for patients with late cataract were implemented for the total documentation period and additionally adjusted for diabetes duration.

RESULTS

Rate of cataract development shows a peak at diabetes onset and declines with longer diabetes duration. Patients with cataract showed strong female preponderance. Patients developing early cataract were older at diabetes onset (12.8 years [11.8/13.9] vs. 8.9 [8.9/9.0]; p < 0.001) and showed higher HbA1c than patients without cataract (9.0% [8.55/9.38] vs. 7.6% [7.60/7.61]; p < 0.001). They had lower height-SDS, (-0.22 [-0.48/0.04] vs. 0.25 [0.24/0.26]; p < 0.001), lower weight-SDS (-0.31 [-0.55/-0.08] vs. 0.21 [0.20/0.21]; p < 0.001) and lower BMI-SDS (-0.25 [-0.49/-0.02] vs. 0.12 [0.12/0.13); p = 0.002). Patients with late cataract showed higher HbA1c at diabetes onset (8.35% [8.08/8.62] vs. 8.04% [8.03/8.05]; p = 0.023) and higher mean HbA1c during total documentation period (8.00% [7.62/8.34] vs. 7.62% [7.61/7.63]; p = 0.048).

CONCLUSIONS

Our data confirm known demographic and clinical characteristics of patients developing early cataract. Hyperglycemia-induced osmotic damage to lens fibers at diabetes onset might be the main pathomechanism. Long term glycemic control is associated with cataract development.

Pediatric Reference Centiles of Bone Mineral Density and Body Composition of Lower Limbs

Localized neurological diseases such as spina bifida are often accompanied by normal upper limb and spinal bone mineral density (BMD), whereas regional BMD of the lower limbs may be decreased. Therefore, regional BMD measurements may be more accurate to quantify regional bone health. Until now, no pediatric reference centiles of bone mineral density and body composition of the lower extremities are available for Hologic DXA systems. The objective was to generate age-and sex specific reference centiles of DXA scans of lower limbs for Hologic DXA systems. Data from the National Health and Nutrition Examination Survey of the period 1999-2004 (age 8 - 20 years) were used to generate age-specific and sex-specific reference centiles for the non-Hispanic Black, non-Hispanic White and Mexican-American NHANES study population. The LMS method was used to calculate the reference centiles. Data of DXA scans of 2233 non-Hispanic black children (880 females), 1869 non-Hispanic white children (803 females) and 2350 Mexican American children (925 females) were used to create age-specific and sex-specific reference curves. We presented age-and sex-specific reference centiles for regional bone mineral density, bone mineral content, lean body mass and fat mass at the lower limbs for children and adolescents which were ethnicity specific and directly applicable to Hologic QDR-4500A fan-beam densitometer.

Association of muscle mass and fat mass on low-density-lipoprotein cholesterol and triglyceride plasma concentration in children and adolescents

OBJECTIVES

Obesity has often been associated with high low-density-lipoprotein cholesterol (LDL-C) and triglyceride plasma concentrations, known risk factors for diabetes mellitus and cardiovascular disease. Study objective was to evaluate the association of LDL-C and triglyceride plasma concentration with muscle and fat mass in children and adolescents.

METHODS

We analyzed data of the National Health and Nutrition Examination Survey (1999-2004) to estimate lean muscle and fat mass assessed by dual-energy X-ray absorptiometry (DXA) of participants whose lipid profiles had been examined. Fat mass was operationalized by DXA-determined fat mass index (FMI). Muscle mass was assessed by appendicular lean mass index (aLMI). High LDL-C and triglyceride concentration was defined as above 130 mg/dL.

RESULTS

For the evaluation of the association of LDL-C and triglyceride plasma concentration with LMI and FMI Z-scores, the data of 2,487 children and adolescents (age 8-19 years) (984 females) were eligible. High aLMI showed no association with LDL-C or triglyceride concentration, but high FMI showed significant association with LDL-C and triglyceride plasma concentration in the bivariate regression analysis.

CONCLUSIONS

Isolated muscle mass increase may not be protective against high LDL-C and triglycerides plasma levels in children and adolescents. Thus, exercise may lead to risk factor reduction mainly through fat mass reduction.

Reference Centiles to Monitor the 6-minute-walk Test in Ambulant Children with Cerebral Palsy and Identification of Effects after Rehabilitation Utilizing Whole-body Vibration

Background: Children with cerebral palsy present age-driven development in gross motor skills and walking capacity. Aims: To precisely monitor the 6-minute walk test (6MWT) in children with CP, GMFCS levels 1 and 2 over 6 months and to assess the effect of a 6-month rehabilitation program including whole-body vibration. Methods: Retrospective analysis of data of 157 children with CP who received standardized rehabilitation (DRKS00011331). 6MWT was assessed at the start (M0) and end of the training (M6), as well as at a 6-month follow-up (M12). Centiles were created using the lambda-mu-sigma (LMS) method. Results: We created 6MWT percentiles using data of all 157 children (M0 data). A medium treatment effect size (Cohen's d = 0.69) was found (M6 and M12 data). Conclusions: The generated centiles may help monitor 6MWT changes over 6 months. Combining WBV and conventional physiotherapy can significantly improve 6MWT in children with CP. Abbreviations: 6MWT: 6-Minute Walk Test; CP: Cerebral palsy; ES: effect size; GMFCS: Gross Motor Function Classification System; GMFM-66: Gross Motor Function Measure 66; LOESS: locally weighted scatterplot smoothing; LMS: lambda-mu-sigma; MCID: minimal clinical important difference; SD: standard deviation; SRM: standardized response mean; WBV: whole-body vibration.

Interaction between KDELR2 and HSP47 as a Key Determinant in Osteogenesis Imperfecta Caused by Bi-allelic Variants in KDELR2

Osteogenesis imperfecta (OI) is characterized primarily by susceptibility to fractures with or without bone deformation. OI is genetically heterogeneous: over 20 genetic causes are recognized. We identified bi-allelic pathogenic KDELR2 variants as a cause of OI in four families. KDELR2 encodes KDEL endoplasmic reticulum protein retention receptor 2, which recycles ER-resident proteins with a KDEL-like peptide from the cis-Golgi to the ER through COPI retrograde transport. Analysis of patient primary fibroblasts showed intracellular decrease of HSP47 and FKBP65 along with reduced procollagen type I in culture media. Electron microscopy identified an abnormal quality of secreted collagen fibrils with increased amount of HSP47 bound to monomeric and multimeric collagen molecules. Mapping the identified KDELR2 variants onto the crystal structure of G. gallus KDELR2 indicated that these lead to an inactive receptor resulting in impaired KDELR2-mediated Golgi-ER transport. Therefore, in KDELR2-deficient individuals, OI most likely occurs because of the inability of HSP47 to bind KDELR2 and dissociate from collagen type I. Instead, HSP47 remains bound to collagen molecules extracellularly, disrupting fiber formation. This highlights the importance of intracellular recycling of ER-resident molecular chaperones for collagen type I and bone metabolism and a crucial role of HSP47 in the KDELR2-associated pathogenic mechanism leading to OI.

Signaling pathways affected by mutations causing osteogenesis imperfecta

Osteogenesis imperfecta (OI) is a clinically and genetically heterogeneous connective tissue disorder characterized by bone fragility and skeletal deformity. To maintain skeletal strength and integrity, bone undergoes constant remodeling of its extracellular matrix (ECM) tightly controlled by osteoclast-mediated bone resorption and osteoblast-mediated bone formation. There are at least 20 recognized OI-forms caused by mutations in the two collagen type I-encoding genes or genes implicated in collagen folding, posttranslational modifications or secretion of collagen, osteoblast differentiation and function, or bone mineralization. The underlying disease mechanisms of non-classical forms of OI that are not caused by collagen type I mutations are not yet completely understood, but an altered ECM structure as well as disturbed intracellular homeostasis seem to be the main defects. The ECM orchestrates local cell behavior in part by regulating bioavailability of signaling molecules through sequestration, release and activation during the constant bone remodeling process. Here, we provide an overview of signaling pathways that are associated with known OI-causing genes and discuss the impact of these genes on signal transduction. These pathways include WNT-, RANK/RANKL-, TGFβ-, MAPK- and integrin-mediated signaling as well as the unfolded protein response.

Bone Microarchitecture Assessed by Trabecular Bone Score Is Independent of Mobility Level or Height in Pediatric Patients with Cerebral Palsy

Bone strength and fracture risk do not only depend on bone density, but also on bone structure. The trabecular bone score (TBS) evaluates homogeneity of bone microarchitecture indirectly by measuring gray-level variations of two-dimensional (2D) DXA images. Although TBS is well-established for adults, there have been only few publications in pediatrics. In this monocentric retrospective analysis, we investigated TBS in children and adolescents with cerebral palsy (CP), a patient group vulnerable to low bone mineral mass due to impaired mobility. The influence of different parameters on TBS and areal BMD (aBMD) were evaluated, as well as the relationship between TBS and aBMD. We compared TBS values of our study population to a reference population. A total of 472 lumbar spine-dual-energy X-ray absorptiometry (LS-DXA) scans of children and adolescents with CP (205 female), aged between 4 and 18 years, were analyzed. The DXA-scans were part of the routine examination. The children had no records of fractures or specific bone diseases. Our study population with CP had similar TBS as the reference population. TBS did not increase with age until an inflection point at 10 years in females, and 12 years in males. Girls had significantly higher TBS than boys (p = .049) and pubertal girls aged 8 to 13 years had significantly higher TBS than prepubertal girls (p = .009). TBS standard deviation score for age (SDS-TBS) and aBMD Z-scores correlated weakly (p < .001; R = 0.276 [males], R = 0.284 [females]). Other than for aBMD Z-scores, SDS-TBS was not influenced by age-adjusted height Z-scores and there was no significant difference in SDS-TBS when grouped by mobility levels, using the Gross Motor Function Classification System (GMFCS). Our results indicate that children with CP have a similar homogeneous distribution of trabecular microarchitecture as controls. Puberty initiation appears to be essential for increase of TBS with age and for sex differences. TBS seems less influenced by body composition, height, and mobility than aBMD. © 2020 The Authors. Journal of Bone and Mineral Research published by American Society for Bone and Mineral Research.

Osteogenesis imperfecta-pathophysiology and therapeutic options

Osteogenesis imperfecta (OI) is a rare congenital disease with a wide spectrum of severity characterized by skeletal deformity and increased bone fragility as well as additional, variable extraskeletal symptoms. Here, we present an overview of the genetic heterogeneity and pathophysiological background of OI as well as OI-related bone fragility disorders and highlight current therapeutic options.

The most common form of OI is caused by mutations in the two collagen type I genes. Stop mutations usually lead to reduced collagen amount resulting in a mild phenotype, while missense mutations mainly provoke structural alterations in the collagen protein and entail a more severe phenotype. Numerous other causal genes have been identified during the last decade that are involved in collagen biosynthesis, modification and secretion, the differentiation and function of osteoblasts, and the maintenance of bone homeostasis.

Management of patients with OI involves medical treatment by bisphosphonates as the most promising therapy to inhibit bone resorption and thereby facilitate bone formation. Surgical treatment ensures pain reduction and healing without an increase of deformities. Timely remobilization and regular strengthening of the muscles by physiotherapy are crucial to improve mobility, prevent muscle wasting and avoid bone resorption caused by immobilization. Identification of the pathomechanism for SERPINF1 mutations led to the development of a tailored mechanism-based therapy using denosumab, and unraveling further pathomechanisms will likely open new avenues for innovative treatment approaches.

Effect of an interval rehabilitation program with home-based, vibration-assisted training on the development of muscle and bone in children with cerebral palsy - an observational study

Objectives In children with cerebral palsy (CP), the most common cause of physical impairment in childhood, less muscle and bone growth has been reported, when compared with typically developing children. The aim of this study was to evaluate the effect of an intensive rehabilitation program including physiotherapy in combination with 6 months of home-based, vibration-assisted training on muscle and bone growth in children with CP. Methods We included children with CP, who participated in a rehabilitation program utilizing whole-body vibration (WBV). Muscle mass was quantified by appendicular lean mass index (App-LMI) and bone mass by total-body-less-head bone mineral content (TBLH-BMC) assessed by Dual-energy X-ray absorptiometry (DXA) at the beginning of rehabilitation and one year later. To assess the functional muscle-bone unit, the relation of TBLH-BMC to TBLH lean body mass (TBLH-LBM) was used. Results The study population included 128 children (52 females, mean age 11.9 ± 2.7). App-LMI assessed in kg/m2 increased significantly after rehabilitation. The age-adjusted Z-score for App-LMI showed no significant change. TBLH-BMC assessed in gram increased significantly. The Z-scores for TBLH-BMC decreased lesser than expected by the evaluation of the cross-sectional data at the beginning of rehabilitation. The parameter T B L H - B M C T B L H - L B M $\frac{TBLH-BMC}{TBLH-LBM}$ did not change relevantly after 12 months. Conclusions Muscle growth and to a lesser extent bone growth could be increased in children with CP. The intensive rehabilitation program including WBV seemed to have no direct effect on the bone, but the observed anabolic effect on the bone, may only been mediated through the muscle.

Reference Centiles for the Evaluation of Nutritional Status in Children using Body Fat Percentage, Fat Mass and Lean Body Mass Index

BACKGROUND

Body fat percentage (BF%), fat mass index (FMI), and lean body mass index (LBMI) are often used to evaluate the nutritional status of children. Until now, no pediatric FMI reference centiles are applicable for GE Healthcare Lunar DXA systems. The aim of the study was to generate age-specific BF%, FMI, and LBMI references centiles for GE Healthcare Lunar DXA systems.

METHODOLOGY

Published values from the National Health and Nutrition Examination Survey 1999-2004 (age 8-20 years) were used to generate the reference centiles for the non-Hispanic black, non-Hispanic white, and Mexican American NHANES population. The LMS and LMSP methods were used to generate the reference centiles.

RESULTS

Data of 2433 non-Hispanic black children (972 females), 2026 non-Hispanic white children (873 females), and 2547 Mexican American children (1010 females) were eligible.

CONCLUSIONS

We presented age-specific reference centiles for BF%, FMI, and LBMI for children and adolescents which were ethnicity specific (non-Hispanic black, non-Hispanic white, and Mexican American) and directly applicable to Prodigy and iDXA GE Healthcare Lunar systems with software version 14.0. We proposed the use of BF%, FMI, and LBMI together to evaluate nutritional status in children.

One-Minute Walk Test in Children with Cerebral Palsy GMFCS Level 1 and 2: Reference Values to Identify Therapeutic Effects after Rehabilitation

Background: Children with cerebral palsy (CP) show age-driven development and individual fluctuations in walking capacity.Aim: 1. To precisely quantify 1MWT changes in children with CP, GMFCS level 1 and 2, generating 1MWT percentiles, depicting expected development over 6 months; 2. to assess the effect of a 6-month rehabilitation using whole-body vibration (WBV).Methods: Retrospective data analysis in 210 children with CP, GMFCS 1 and 2 who received standardized rehabilitation (DRKS00011331). 1MWT was assessed before (M0) and after treatment (M6), and at a 6-month follow-up (M12). Centiles were created using the lambda-mu-sigma method. Cohen's d was used to assess effect size.Results: We created 1MWT percentiles using data of all 210 children (M0 data). A small treatment effect size (d = 0.46) was found (M6 and M12 data).Conclusions: Using the generated centiles clinicians may monitor 1MWT changes over 6 months. Combining WBV and conventional physiotherapy may improve 1MWT in children with CP.Abbreviations: 1MWT: One-Minute Walk Test; 6MWT: Six-Minute Walk Test; CP: Cerebral palsy; ES: effect size; GMFCS: Gross Motor Function Classification System; GMFM-66: Gross Motor Function Measure 66; LOESS: Locally Estimated Scatterplot Smoothing; LMS: lambda-mu-sigma; SD: standard deviation; WBV: whole-body-vibration.

Osteogenesis imperfecta – Pathophysiologie und aktuelle Behandlungsstrategien

Die Osteogenesis imperfecta (OI) ist eine angeborene Erkrankung des Knochens und Bindegewebes. Sie geht mit einer erhöhten Frakturneigung, Deformierung der Extremität, aber auch mit extraskelettalen Symptomen einher. Nach einer kurzen Darstellung von Klinik, Diagnostik und aktueller Therapie folgt ein umfassender Überblick über die genetischen und pathophysiologischen Grundlagen der Erkrankung und die daraus abgeleiteten zukünftigen therapeutischen Möglichkeiten.

Ungefähr 80 % der Patienten haben eine Mutation in den Kollagen-Genen COL1A1 und COL1A2. Bei diesen Patienten ist für das Kollektiv keine klare Genotyp-Phänotyp-Korrelation beschrieben. Stoppmutationen führen in der Regel zu einem quantitativen Kollagendefekt, wodurch weniger normales Kollagen gebildet wird und ein eher leichter Phänotyp entsteht. Missense-Mutationen führen zu strukturell verändertem Kollagen (qualitativer Defekt) und zu einem schwereren Phänotyp. Trotzdem gibt es Unterschiede und Vorhersagen über den individuellen Verlauf sind nur sehr eingeschränkt möglich. Neben Veränderungen in den Kollagen-Genen gibt es Mutationen, welche die Kollagenmodifikation und die Kollagensekretion betreffen. Eine eigene Gruppe bilden Gene, welche an der Osteoblastendifferenzierung beteiligt sind. Wie auch bei den weiteren, nicht näher zugeordneten Genen sind dies häufig übergeordnete Gene, deren Funktion in der Osteogenese nicht völlig verstanden ist.

Abgeleitet aus den pathophysiologischen Grundlagen, können vorhandene Medikamente zukünftig womöglich zielgerichtet eingesetzt werden. So ist der „Receptor-Activator-of-Nuclear-Factor-Kappa B-Ligand“ (RANKL)-Antikörper Denosumab spezifischer als Bisphosphonate und wird schon heute bei OI-Typ VI (SERPINF1) verwendet. Weitere Medikamente wie Anti-Sklerostin oder Stammzelltherapien werden unter Berücksichtigung der Pathophysiologie aktuell entwickelt.

The Appendicular Lean Mass Index Is a Suitable Surrogate for Muscle Mass in Children with Cerebral Palsy

BACKGROUND

Densitometrically measured lean body mass (LBM) is often used to quantify skeletal muscle mass in children with cerebral palsy (CP). Since LBM depends on the individual's height, the evaluation of $\frac{{{\rm{LBM}}}}{{heigh{t^2}}}\ $ (lean BMI) is often recommended. However, LBM includes not only skeletal muscle mass but also the mass of skin, internal organs, tendons, and other components. This limitation applies to a far lesser extent to the appendicular lean mass index (LMIapp).

OBJECTIVES

The aim of the study was to evaluate skeletal muscle mass in children with CP using total lean BMI (LMItot) and LMIapp.

METHODS

The present study was a monocentric retrospective analysis of prospectively collected data among children and adolescents with CP participating in a rehabilitation program. In total, 329 children with CP [148 females; Gross Motor Function Classification Scale (GMFCS) I, 32 children; GMFCS II, 73 children; GMFCS III, 133 children; GMFCS IV, 78 children; and GMFCS V, 13 children] were eligible for analysis. The mean age was 12.3 ± 2.75 y. Pediatric reference centiles for age-adjusted LMIapp were generated using data from NHANES 1999-2004. Low skeletal muscle mass was defined as a z score for DXA determined LMItot and LMIapp less than or equal to -2.0.

RESULTS

The z scores for LMIapp were significantly lower than LMItot in children with CP, GMFCS levels II-V (P < 0.001), with the exception of GMFCS level I (P = 0.121), where no significant difference was found. The prevalence of low LMItot (16.1%; 95% CI: 16.1, 20.1%) was significantly lower (P < 0.001) than the prevalence of LMIapp (42.2%; 95% CI: 36.9, 47.9%) in the study population.

CONCLUSIONS

The prevalence of low skeletal muscle mass in children with CP might be underestimated by LMItot. LMIapp is more suitable for the evaluation of skeletal muscle mass in children with CP.

Anthropometric measurements to identify undernutrition in children with cerebral palsy

AIM

To evaluate the diagnostic performance of anthropometric indicators to identify undernutrition in children with cerebral palsy (CP).

METHOD

The present study was a monocentric retrospective analysis of prospectively collected data among children and adolescents with CP participating in a rehabilitation program. Undernutrition was defined as a z-score for dual-energy X-ray absorptiometry (DXA) determined body fat percentage less or equal to -2.0. The cut-off values for body mass index (BMI) of the World Health Organization (WHO) and the Centers for Disease Control and Prevention (CDC), and the cut-off values for BMI and height for age of the Robert Koch Institut (RKI) were evaluated.

RESULTS

In total, 329 children with CP (181 males, 148 females, Gross Motor Function Classification System levels I-V) were eligible for analysis. The mean age was 12 years 4 months (SD 2y 9mo). The BMI cut-off values showed the following sensitivities and specificities: WHO, sensitivity of 0.474 (95% confidence interval [CI] 0.244-0.711), specificity of 0.897 (95% CI: 0.857-0.928); CDC, sensitivity of 0.632 (95% CI: 0.384-0.837), specificity of 0.819 (95% CI: 0.772-0.861); RKI, sensitivity of 0.789 (95% CI: 0.544-0.939), specificity of 0.732 (95% CI: 0.679-0.781); and for height for age, sensitivity of 0.263 (95% CI: 0.091-0.512), specificity of 0.668 (95% CI: 0.612-0.720).

INTERPRETATION

BMI had a high specificity but very low sensitivity in identifying undernutrition in children with CP. Z-scores for height for age had even lower specificity and sensitivity and seemed not to be appropriate for predicting undernutrition in children with CP.

WHAT THIS PAPER ADDS

Body mass index (BMI) z-scores had a high specificity but very low sensitivity in identifying undernutrition in children with cerebral palsy (CP). Height z-scores were not appropriate for predicting undernutrition in children with CP. Undernutrition assessed by BMI was overestimated in children with CP versus when assessed by dual-energy X-ray absorptiometry (DXA).

Inverse Association of High-Density Lipoprotein Cholesterol Concentration with Muscle Mass in Children

Background: Obesity was often associated with low high-density lipoprotein (HDL) cholesterol concentration, which is an established cardiovascular risk factor. Objectives: To evaluate the association of HDL-cholesterol concentration with fat and muscle mass in children and adolescents. Methods: Data of the National Health and Nutrition Examination Survey (1999-2004) were used to estimate fat and muscle mass by dual-energy X-ray absorptiometry (DXA) of the participants who had also an examination of their lipid profiles. Fat mass was assessed by DXA-determined fat mass index (FMI). Muscle mass was operationalized by appendicular lean mass index (LMI). Low HDL-cholesterol concentration was defined as <40 mg/dL. Results: For the evaluation of the association of HDL-cholesterol concentration with FMI and LMI Z-scores, the data of 6288 children and adolescents (age 8-19 years) (2535 females) were eligible. In the study population, the prevalence of low HDL-cholesterol concentration increased with rising FMI and appendicular LMI Z-scores. Conclusions: The study results suggested that there is a counterintuitive, inverse association of muscle mass and HDL-cholesterol concentration.

Individualized treatment with denosumab in children with osteogenesis imperfecta - follow up of a trial cohort

Background

Osteogenesis imperfecta (OI) is a rare disease leading to hereditary bone fragility. Nearly 90% of cases are caused by mutations in the collagen genes COL1A1/A2 (classical OI) leading to multiple fractures, scoliosis, short stature and nonskeletal findings as blue sclera, hypermobility of joints, bone pain and delayed motor function development. Bisphosphonates are used in most moderate and severely affected patients assuming that an increase of bone mineral density might reduce fractures and bone pain in patients with OI. Denosumab as a RANK ligand antibody inhibiting osteoclast maturation has been approved for osteoporosis treatment in adults. First data from small clinical trials promised a high efficacy of Denosumab in children with OI. Aim of this analysis was a retrospective evaluation of an individualized biomarker-associated treatment regime with Denosumab in 10 children with classical OI which were followed for 1 year after their participation in a pilot trial with Denosumab. Therefore urinary deoxypyridinoline levels were evaluated frequently as an osteoclastic activity marker and depending on that levels Denosumab injections were scheduled individually.

Methods

Ten patients (age range: 6.16–12.13 years; all participated in the former OI-AK phase 2 trial (NCT01799798)) were included in the follow-up period. Denosumab was administered subcutaneously depending on the individual urinary excretion course of deoxypyridinoline (DPD/Crea) as osteoclastic activity marker with 1 mg/kg body weight. DPD/Crea levels were evaluated before denosumab administration and afterwards. If patients present after an initial decrease after injection with a re-increase up to the DPD/crea level before Denosumab injection next dosage was planned. Changes of areal bone mineral density (aBMD) using dual energy x-ray absorptiometry of the lumbar spine after 12 month was evaluated. Safety was assessed by bone metabolism markers and side effect reporting.

Results

During follow-up mean relative change of lumbar aBMD was − 6.4%. Lumbar spine aBMD z-Scores decreased from − 1.01 ± 2.61 (mean ± SD) to − 1.91 ± 2.12 (p = 0.015). Mobility changed not significantly (GMFM-88 -6.49 ± 8.85% (p = 0.08). No severe side effects occurred. Dose intervals could be extended in the mean from 12 weeks previously to 20.3 weeks.

Conclusions

On average, it was possible to prolong the intervals between drug administrations and to reduce the total dose about by 25% without a decrease of mobility or change of vertebral shape despite a reduction of lumbar aBMD during 1 year of biomarker-directed Denosumab treatment. Further trials are necessary to balance side effects and highest efficacy in children.

Interaction of body fat percentage and height with appendicular functional muscle-bone unit

The interaction of body fat percentage and height with appendicular BMC for LBM was analyzed. Only body fat had significant negative correlation with the appendicular BMC for LBM.

PURPOSE/INTRODUCTION

For the clinical evaluation of the functional muscle-bone unit, it was proposed to evaluate the adaptation of the bone to the acting forces. A frequently used parameter for this is the total body less head bone mineral content (TBLH-BMC) determined by dual-energy X-ray absorptiometry (DXA) in relation to the total body lean body mass (LBM). Body fat percentage seemed to correlate negatively and height positively with TBLH-BMC for LBM. It was supposed that appendicular BMC for LBM is a more accurate surrogate for the functional muscle-bone unit since appendicular LBM does not incorporate the mass of internal organs. The aim of this study was to analyze the interaction of body fat percentage and height with appendicular BMC for LBM.

METHODS

As part of the National Health and Nutrition Examination Survey (NHANES) study, between the years 1999 and 2004, whole-body DXA scans on randomly selected Americans from 8 years of age were carried out. From all eligible DXA scans, three major US ethnic groups were evaluated (non-Hispanic Whites, non-Hispanic Blacks, and Mexican Americans) for further statistical analysis.

RESULTS

For the statistical analysis, the DXA scans of 8190 non-Hispanic White children and adults (3903 female), of 4931 non-Hispanic Black children and adults (2250 female), and 5421 of Mexican American children and adults (2424 female) were eligible. Only body fat had a significant negative correlation with the appendicular BMC for LBM.

CONCLUSIONS

Only body fat had significant negative correlation with appendicular BMC for LBM, and thus, should be addressed when evaluating functional muscle-bone unit.

Current and Emerging Therapeutic Options for the Management of Rare Skeletal Diseases

Increasing knowledge in the field of rare diseases has led to new therapeutic approaches in the last decade. Treatment strategies have been developed after elucidation of the underlying genetic alterations and pathophysiology of certain diseases (e.g., in osteogenesis imperfecta, achondroplasia, hypophosphatemic rickets, hypophosphatasia and fibrodysplasia ossificans progressiva). Most of the drugs developed are specifically designed agents interacting with the disease-specific cascade of enzymes and proteins involved. While some are approved (asfotase alfa, burosumab), others are currently being investigated in phase III trials (denosumab, vosoritide, palovarotene). To offer a multi-disciplinary therapeutic approach, it is recommended that patients with rare skeletal disorders are treated and monitored in highly specialized centers. This guarantees the greatest safety for the individual patient and offers the possibility of collecting data to further improve treatment strategies for these rare conditions. Additionally, new therapeutic options could be achieved through increased awareness, not only in the field of pediatrics but also in prenatal and obstetric specialties. Presenting new therapeutic options might influence families in their decision of whether or not to terminate a pregnancy with a child with a skeletal disease.

TBS as a Tool to Differentiate the Impact of Antiresorptives onCortical and Trabecular Bone in Children With OsteogenesisImperfecta

INTRODUCTION/BACKGROUND

Osteogenesis imperfecta is a hereditary connective tissue disorder, resulting in low bone mass and high bone fragility. Dual-energy X-ray absorptiometry (DXA) and in adulthood also the trabecular bone score (TBS) are well established to assess bone health and fracture risk. The purpose of this investigation was to assess the usefulness of TBS in respect to different treatment regimes in children with osteogenesis imperfecta. Changes of areal bone mineral density (aBMD) and TBS using DXA scans of children treated with antiresorptive therapies were evaluated.

METHODOLOGY

DXA scans (aBMD, TBS) of 8 children with OI were evaluated. The scans were taken during a 1 yr period of treatment with bisphosphonates and during 1 yr pilot trial using denosumab. Changes of aBMD and TBS during both treatment regimens were compared.

RESULTS

During bisphosphonate treatment aBMD increased about 6.2%, while TBS increased about 2.1%. The difference between aBMD and TBS before and after bisphosphonate treatment was not significant (p = 0.25). During denosumab treatment aBMD increased around 25.1%, while TBS increased 6.7%. The change of aBMD was significant (p = 0.007), as was the difference between aBMD and TBS (p < 0.001).

CONCLUSIONS

Denosumab had a significant effect on both aBMD and TBS but was significantly more pronounced in aBMD. These results suggest a stronger effect of denosumab on cortical bone and the growth plate in comparison to bisphosphonates. Beside the lack of paediatric reference data and the small sample size, the results suggest TBS to be a useful tool for monitoring skeletal changes during development, growth, and antiresorptive therapy in children with OI.

Diagnostic performance of an artificial neural network to predict excess body fat in children

BACKGROUND

Waist circumference (WC) and z scores of body mass index (BMI) are commonly used to predict childhood obesity, although BMI and WC have a limited sensitivity.

OBJECTIVES

To generate an artificial neural network (ANN), using the input parameters age, height, weight, and WC, to predict excess body fat in children.

METHODS

As part of the National Health and Nutrition Examination Survey (NHANES) study, in the years 1999 to 2004, the body fat percentage of randomly selected Americans from 8 to 19 years were measured using whole-body dual energy X-ray absorptiometry (DXA) scans. Excess body fat was defined as a body fat percentage ≥ 85th centile.

RESULTS

The data of 1999 children (856 female) were eligible. In females, the sensitivity of the BMI, WC, and ANN approaches to predict excess body fat were 0.751 (95% CI, 0.730-0.771), 0.523 (0.487-0.559), and 0.782 (0.754-0.810), respectively. In males, the sensitivity of the BMI, WC, and ANN approaches to predict excess body fat were 0.721 (95% CI, 0.699-0.743), 0.572 (0.549-0.594), and 0.795 (0.768-0.821).

CONCLUSIONS

Only in boys, the diagnostic performance in identifying excess body fat was better by using an ANN than by applying BMI and WC z scores. In girls, the ANN and BMI z scores performed comparable and significantly better than WC z scores.

Individualized evaluation of lumbar bone mineral density and bone mineral apparent density in children and adolescents

Lumbar spine bone mineral density (LS-BMD) assessed by dual-energy X-ray absorptiometry (DXA) is used in children to evaluate bone health. LS-BMD results in children are influenced significantly by height and BMI. An adjustment for these parameters may improve the clinical use of the method.

PURPOSE/INTRODUCTION

DXA evaluation is considered useful in children to assess bone health. For this purpose, lumbar spine bone mineral density (LS-BMD) and bone mineral apparent density (LS-BMAD) are often used. The aim of the study was to estimate the effect of height and BMI on LS-BMD and LS-BMAD in children and adolescents and to develop a method to adjust individual results for these factors.

METHODS

As part of the National Health and Nutrition Examination Survey (NHANES) study, between the years 2005 and 2010 lumbar DXA scans on randomly selected Americans from 8 to 20 years of age were carried out. From all eligible DXA scans, three major US ethnic groups were evaluated (Non-Hispanic Whites, Non-Hispanic Blacks, and Mexican Americans) for further statistical analysis. The relationship between height as well as BMI for age Z-scores and age-adjusted LS-BMD and LS-BMAD Z-scores was analyzed.

RESULTS

For the statistical analysis, the DXA scans of 1799 non-Hispanic White children (823 females), of 1696 non-Hispanic Black children (817 females), and of 1839 Mexican American children (884 females) were eligible. The statistical analysis showed that taller and heavier children had significantly (p < 0.001) higher age-adjusted LS-BMD Z-scores than shorter and lighter children. But on LS-BMAD, only BMI and not height had a significant influence.

CONCLUSIONS

LS-BMD results in children were influenced significantly by their height and BMI, the LS-BMAD results were only influenced by their BMI. For the first time, the proposed method adjusts LS-BMD and LS-BMAD to BMI. An adjustment of the LS-BMD and LS-BMAD results to these factors might improve the clinical significance of an individual result.

Quantum dots modulate leukocyte adhesion and transmigration depending on their surface modification

Although different nanosized materials, including quantum dots (QDs), are intended to be used for biomedical applications, their interactions with microvessels and their inflammatory potential are largely unknown. In this in vivo study we report that leukocyte recruitment is modulated in the presence of quantum dots. We found that the surface chemistry of QDs strongly affects their localization in postcapillary venules, their uptake by perivascular macrophages, and their potential to modify steps of leukocyte recruitment.

HCN1 channels constrain DHPG-induced LTD at hippocampal Schaffer collateral-CA1 synapses

HCN channels play a fundamental role in determining resting membrane potential and regulating synaptic function. Here, we investigated the involvement of HCN channels in basal synaptic transmission and long-term depression (LTD) at the Schaffer collateral-CA1 synapse. Bath application of the HCN channel blocker ZD7288 (10 microM) caused a significant increase in synaptic transmission that was due to an enhancement in AMPA receptor-mediated excitatory postsynaptic potentials. This enhancement was accompanied by a significant decrease in the paired-pulse ratio (PPR), suggesting a presynaptic mechanism. Experiments with the irreversible use-dependent NMDA receptor blocker MK-801 showed that ZD7288 led to an increase in glutamate release probability. LTD induced by brief application of (RS)-3,5-dihydroxyphenylglycine (DHPG, 100 microM, 10 min) was significantly enhanced when HCN channels were blocked by ZD7288 (10 microM) prior to DHPG application. Moreover, the concomitant increase in PPR after DHPG-induced LTD was significantly larger than without ZD7288 bath application. Conversely, ZD7288 application after DHPG washout did not alter DHPG-LTD. A significant enhancement of DHPG-LTD was also observed in HCN1-deficient mice as compared with wild types. However, LTD induced by low-frequency stimulation (LFS) remained unaltered in HCN1-deficient mice, suggesting a differential effect of HCN1 channels on synaptic plasticity constraining DHPG-LTD, but not LFS-LTD.

Dopamine induces contraction in the proximal, but relaxation in the distal rat isolated small intestine

In the gut, dopamine is released by enteric neurons and modulates motility of small intestine smooth muscle cells. Here, we systematically analyzed the dopamine-induced effects on the longitudinal smooth muscle of different sections of the rat isolated small intestine. We found that exogenous dopamine had biphasic effects and could lead to both an early contraction and a late relaxation, depending on the region of small intestine. Thus, dopamine-induced early contractions were commonly observed in the duodenum, but less frequently in the jejunum, and rarely in the ileum. The amplitudes of these early contractions showed a striking regional dependence (duodenum>jejunum>ileum) and were significantly blocked by SCH23390 and raclopride. Conversely, dopamine-induced late relaxations were regularly obtained in the ileum and in the jejunum, but less frequently in the duodenum. Interestingly, the amplitudes of these relaxations showed an inverse regional dependence (ileum>jejunum>duodenum), and were insensitive to dopamine receptor antagonists. Rather, they were significantly inhibited by propranolol and prazosin. We conclude that dopamine exerts differential effects on smooth muscle motility in different regions within the rat small intestine. In proximal parts, dopamine predominantly causes D(1) and D(2) dopamine receptor-dependent contraction, whereas it leads to alpha and beta adrenoceptor-dependent relaxation in more distal parts.

High K+-induced contraction requires depolarization-induced Ca2+ release from internal stores in rat gut smooth muscle

AIM

Depolarization-induced contraction of smooth muscle is thought to be mediated by Ca2+ influx through voltage-gated L-type Ca2+channels. We describe a novel contraction mechanism that is independent of Ca2+ entry.

METHODS

Pharmacological experiments were carried out on isolated rat gut longitudinal smooth muscle preparations, measuring isometric contraction strength upon high K+-induced depolarization.

RESULTS

Treatment with verapamil, which presumably leads to a conformational change in the channel, completely abolished K+-induced contraction, while residual contraction still occurred when Ca2+ entry was blocked with Cd2+. These results were further confirmed by measuring intracellular Ca2+ transients using Fura-2. Co-application of Cd2+ and the ryanodine receptor blocker DHBP further reduced contraction, albeit incompletely. Additional blockage of either phospholipase C (U 73122) or inositol 1,4,5-trisphophate (IP3)receptors (2-APB) abolished most contractions, while sole application of these blockers and Cd2+ (without parallel ryanodine receptor manipulation) also resulted in incomplete contraction block.

CONCLUSION

We conclude that there are parallel mechanisms of depolarization-induced smooth muscle contraction via (a) Ca2+ entry and (b) Ca2+ entry-independent, depolarization-induced Ca2+-release through ryanodine receptors and IP3, with the latter being dependent on phospholipase C activation.

Centrosomal microtubule plus end tracking proteins and their role in Dictyostelium cell dynamics

Microtubules interact with huge protein complexes not only with their minus ends but also with their peripheral plus ends. The centrosome at their minus ends nucleates and organizes the microtubule cytoskeleton. The microtubule plus end complex seems to be required for the capture of microtubule tips at cortical sites by mediating interactions of microtubule tips with cortical actin as well as with membrane proteins. This process plays a major role in nuclear migration, spindle orientation and directional cell movement. Five potential members of the microtubule plus end complex have already been identified in Dictyostelium, DdCP224, DdEB1, DdLIS1, the dynein heavy chain and dynein intermediate chain. DdCP224 and DdEB1 are the Dictyostelium representatives of the XMAP215- and EB1-family, respectively. Both are not only concentrated at microtubule tips, they are also centrosomal components. The centrosomal binding domain of DdCP224 resides within the C-terminal fifth of the protein. DdCP224 is involved in the centrosome duplication cycle and cytokinesis. DdEB1 is the first member of the EB1 protein family that is also a genuine centrosomal component. A DdEB1 null mutant revealed that DdEB1 is required for mitotic spindle formation. DdEB1 coprecipitates and colocalizes with DdCP224 suggesting that these proteins act together in their functions. One of these functions could be dynein/dynactin-dependent interaction of microtubule tips with the cell cortex that is thought to determine the positioning of the microtubule-organizing center (MTOC) and the direction of migration.