Reference intervals in Danish children and adolescents for bone turnover markers carboxy-terminal cross-linked telopeptide of type I collagen (ß-CTX), pro-collagen type I N-terminal propeptide (PINP), osteocalcin (OC) and bone-specific alkaline phosphatase (bone ALP).

PURPOSE: Bone turnover markers (BTM) are gaining ground in clinical practice but to fully use their potential there is a need for establishing valid reference intervals (RI). Consequently, the purpose of the study was to establish general RI as well as suggested clinical RI for carboxy-terminal cross-linked telopeptide of type I collagen (ß-CTX), pro-collagen type I N-terminal propeptide (PINP), osteocalcin (OC) and bone-specific alkaline phosphatase (bone ALP) in children and adolescents. METHOD: BTM were measured on Danish children and adolescents participating in the CHAMPS-study DK. A total of 762 participants were included (8-18 years, 50.4% girls) contributing a total of 1410 study visits. The RI was calculated based on 2-years age spans. Participants with biochemical signs of metabolic bone disease were excluded. RESULTS: The differences in RI between age groups clearly reflect changes in growth with an initial increase in BTM, greatest in boys, and a subsequent decrease most pronounced in girls. ß-CTX and PINP are markers most affected by these changes, compared to OC and bone ALP. The suggested clinical 95% RI included participants with vitamin D insufficiency but no biochemical signs of metabolic bone disease which did not markedly alter the RI. CONCLUSION: RI for ß-CTX, PINP, OC and bone ALP varies with age and sex. ß-CTX and PINP which reflect bone resorption and formation processes are mostly affected by these changes. We suggest a set of clinically applicable 95% RI for the four BTM to heighten the usefulness and generalizability of the RI.

Glycemic control and bone mineral density in children and adolescents with type 1 diabetes.

BACKGROUND/OBJECTIVE: Fracture risk is increased in patients with type 1 diabetes. We aimed to evaluate bone mineral density (BMD) and to identify risk factors associated to lower BMD in Danish children and adolescents with type 1 diabetes. METHODS: In this cross-sectional study BMD Z-score were determined by dual-energy X-ray absorptiometry (DXA) from a cohort of otherwise healthy children and adolescents with type 1 diabetes. Puberty Tanner stage, hemoglobin A1c (HbA1c), disease duration, and age at diabetes onset were investigated for associations to DXA results. RESULTS: We included 85 patients, 39 girls, 46 boys, with a median (range) age of 13.2 (6-17) years; disease duration 4.2 (0.4-15.9) years; HbA1c of the last year 61.8 (41-106) mmol/mol. Our patients were taller and heavier than the background population. When adjusted for increased height SD and body mass index SD, no overall difference in BMD Z-score was found. When stratified by sex, boys had significantly increased adjusted mean BMD Z-score, 0.38 (95% confidence interval [CI]: 0.13;0.62), girls; -0.27 (95% CI: -0.53;0.00). For the whole cohort, a negative correlation between mean latest year HbA1c and BMD Z-score was found, adjusted ß -0.019 (95%CI: -0.034;-0.004, P = 0.01). Poor glycemic control (HbA1c > 58 mmol/mol [7.5%]) within the latest year was likewise negatively correlated with BMD Z-score, adjusted ß -0.35 (95%CI: -0.69;-0.014, P = 0.04). CONCLUSIONS: Our study suggests that elevated blood glucose has a negative effect on the bones already before adulthood in patients with type 1 diabetes, although no signs of osteoporosis were identified by DXA.

Bone mass development is sensitive to insulin resistance in adolescent boys.

PURPOSE: Insulin resistance may exert a negative influence on bone mass in childhood and adolescence. The objective was to assess the association between insulin resistance and total body less head (TBLH) bone mineral content (BMC) and to investigate whether body composition, physical activity or osteocalcin levels may influence this association. METHODS: A longitudinal study with follow-up over more than 6 years was performed and included 562 apparently healthy participants with a mean age of 9.6 years at baseline. Participants underwent DXA scanning at baseline. At the two follow-ups, participants had performed another DXA scanning, had blood samples taken for fasting insulin, glucose and osteocalcin and had physical activity measured with an accelerometer. HOMA-IR was calculated as an index of insulin resistance. RESULTS: HOMA-IR was negatively associated with TBLH BMC in boys at follow-ups (ß = -31.4, p < 0.001) after adjustment for maturity, height, bone area, and baseline level of TBLH BMC. The negative association remained almost unchanged after further adjustments for body composition and physical activity. No association between HOMA-IR and TBLH BMC was found in girls. CONCLUSION: Insulin resistance may be detrimental for bone development through puberty in boys independent of body composition and the level of physical activity.

Bone Mass Development in Childhood and Its Association with Physical Activity and Vitamin D Levels. The CHAMPS-Study DK.

This longitudinal study examined associations of bone mass with physical activity and vitamin D level over more than 6 years through puberty. A total of 663 participants (320 boys) with mean age 9.6 years at baseline (10-17 years at follow-up), underwent dual energy X-ray absorptiometry, anthropometry and blood samples for vitamin D at least twice during the study period (with three possible time-points). Physical activity was assessed using accelerometers at follow-up. A positive association was found between percent time spent at vigorous physical activity and total-body less head bone mineral content (ß = 5.8, p = 0.002). The magnitude of this association increased with maturational development; thus physical activity may have a greater influence on bone mass in the more mature participants. The vitamin D levels were also positively associated with bone mass. A high degree of tracking was observed with changes in anthropometric Z scores predictive of deviation from tracking. No environmental factor predicted deviation from tracking.

A calcium-sensing receptor mutation causing hypocalcemia disrupts a transmembrane salt bridge to activate ß-arrestin-biased signaling.

The calcium-sensing receptor (CaSR) is a G protein-coupled receptor (GPCR) that signals through Gq/11 and Gi/o to stimulate cytosolic calcium (Ca2+i) and mitogen-activated protein kinase (MAPK) signaling to control extracellular calcium homeostasis. Studies of loss- and gain-of-function CASR mutations, which cause familial hypocalciuric hypercalcemia type 1 (FHH1) and autosomal dominant hypocalcemia type 1 (ADH1), respectively, have revealed that the CaSR signals in a biased manner. Thus, some mutations associated with FHH1 lead to signaling predominantly through the MAPK pathway, whereas mutations associated with ADH1 preferentially enhance Ca2+i responses. We report a previously unidentified ADH1-associated R680G CaSR mutation, which led to the identification of a CaSR structural motif that mediates biased signaling. Expressing CaSRR680G in HEK 293 cells showed that this mutation increased MAPK signaling without altering Ca2+i responses. Moreover, this gain of function in MAPK activity occurred independently of Gq/11 and Gi/o and was mediated instead by a noncanonical pathway involving ß-arrestin proteins. Homology modeling and mutagenesis studies showed that the R680G CaSR mutation selectively enhanced ß-arrestin signaling by disrupting a salt bridge formed between Arg680 and Glu767, which are located in CaSR transmembrane domain 3 and extracellular loop 2, respectively. Thus, our results demonstrate CaSR signaling through ß-arrestin and the importance of the Arg680-Glu767 salt bridge in mediating signaling bias.

The influence of anthropometry and body composition on children's bone health: the childhood health, activity and motor performance school (the CHAMPS) study, Denmark.

Overweight, physical inactivity and sedentary behaviour have become increasing problems during the past decade. Increased sedentary behaviour may change the body composition (BC) by increasing the fat mass relative to the lean mass (LM). These changes may influence bone health to describe how anthropometry and BC predict the development of the bone accruement. The longitudinal study is a part of The CHAMPS study-DK. Children were DXA scanned at baseline and at 2-year follow-up. BC (LM, BF %) and BMC, BMD and BA were measured. The relationship between bone traits, anthropometry and BC was analysed by multilevel regression analyses. Of the invited children, 742/800 (93%) accepted to participate. Of these, 682/742 (92%) participated at follow-up. Mean (range) of age at baseline was 9.5 years (7.7-12.1). Height, BMI, LM and BF % predicted bone mineral accrual and bone size positively and independently. Height and BMI are both positive predictors of bone accruement. LM is a more precise predictor of bone traits than BF % in both genders. The effects of height and BMI and LM on bone accruement are nearly identical in the two genders, while changes in BF % have different but positive effects on bone accretion in both boys and girls.

The impact on children's bone health of a school-based physical education program and participation in leisure time sports: the Childhood Health, Activity and Motor Performance School (the CHAMPS) study, Denmark.

OBJECTIVE: To evaluate the effect of a school based physical education (PE) program and the amount of leisure time sport (LTS) on children's bone health and to examine if LTS influences the impact of school type on children's bone health. METHODS: Children attending "sports" schools (6 × 45 min PE lessons per week) were compared to children at "traditional" schools (2 × 45 min of PE lessons per week) in Svendborg, Denmark. Whole-body DXA scans were performed at baseline (2008) and at a two-year follow-up (2010). Bone mineral content (BMC), bone mineral density (BMD), and bone area (BA) were measured. Multilevel regression analyses examined the impact of school type and LTS participation on bone. RESULTS: 742/800 (93%) invited children accepted to participate. 682/742 (92%) participated at two-year follow-up. Mean (SD) age was 9.5 years (0.9) at baseline. A positive association between LTS and BMC, BMD (p<0.001) and for BA (p<0.05) (total body less head (TBLH) and lower limb (LL)) was found. All effects regarding school type were insignificant. CONCLUSION: A positive impact of attending LTS on bone traits was found. There was no effect on BMC, BMD and BA (TBLH, and LL) for children attending sports schools compared to traditional schools.

The intensity of physical activity influences bone mineral accrual in childhood: the childhood health, activity and motor performance school (the CHAMPS) study, Denmark.

BACKGROUND: Studies indicate genetic and lifestyle factors can contribute to optimal bone development. In particular, the intensity level of physical activity may have an impact on bone health. This study aims to assess the relationship between physical activity at different intensities and Bone Mineral Content (BMC), Bone Mineral Density (BMD) and Bone Area (BA) accretion. METHODS: This longitudinal study is a part of The CHAMPS study-DK. Whole-body DXA scans were performed at baseline and after two years follows up. BMC, BMD, and BA were measured. The total body less head (TBLH) values were used. Physical activity (PA) was recorded by accelerometers (ActiGraph, model GT3X). Percentages of different PA intensity levels were calculated and log odds of two intensity levels of activity relative to the third level were calculated. Multilevel regression analyses were used to assess the relationship between the categories of physical activity and bone traits. RESULTS: Of 800 invited children, 742 (93%) accepted to participate. Of these, 682/742 (92%) participated at follow up. Complete datasets were obtained in 602/742 (81%) children. Mean (range) of age was 11.5 years (9.7-13.9). PA at different intensity levels was for boys and girls respectively, sedentary 62% and 64%, low 29% for both genders and moderate to high 9% and 7% of the total time. Mean (range) BMC, BMD, and BA was 1179 g (563-2326), 0.84 g/cm2 (0.64-1.15) and 1393 cm2 (851-2164), respectively. Valid accelerometer data were obtained for a mean of 6.1 days, 13 hours per day. CONCLUSIONS: There 7was a positive relationship between the log odds of moderate to high-level PA versus low level activity and BMC, BMD and BA. Children with an increased proportion of time in moderate to high-level activity as opposed to sedentary and low-level activity achieved positive effects on BMC, BMD and BA.

Prednisolone reduces the ability of serum to activate the IGF1 receptor in vitro without affecting circulating total or free IGF1.

OBJECTIVE: End-point bioassays based on thymidine or sulfate incorporation have demonstrated that glucocorticoid (GC) treatment inhibits serum IGF1 action, but the mechanism is unknown as serum IGF1 concentrations have been reported to either increase or remain unchanged. AIM: To investigate whether GC treatment affects the ability of serum to activate the IGF1 receptor (IGF1R) in vitro (i.e. bioactive IGF1), using a specific cell-based IGF1 kinase receptor activation assay. SUBJECTS AND METHODS: Twenty children with stable asthma (age 7.7-13.8 years) treated for 1 week with 5 mg prednisolone in a randomized, double-blind, placebo-controlled crossover study. Non-fasting serum samples were collected in the afternoon after each 7-day period and assayed for bioactive IGF1, free IGF1, total IGFs, IGF-binding proteins (IGFBPs), and insulin. RESULTS: Prednisolone treatment reduced IGF1 bioactivity by 12.6% from 2.22±0.18 to 1.94±0.15 µg/l (P=0.01) compared with placebo. In contrast, no changes were observed for (µg/l; placebo vs prednisolone) total IGF1 (215±27 vs 212±24), free IGF1 (1.50±0.16 vs 1.43±0.17), total IGF2 (815±26 vs 800±31), IGFBP3 (3140±101 vs 3107±95), IGFBP2 (238±21 vs 220±19), IGFBP1 (32±6 vs 42±10), or IGFBP1-bound IGF1 (24±5 vs 26±7). Insulin remained unchanged as did IGFBP levels as estimated by western ligand blotting. Prednisolone had no direct effects on IGF1R phosphorylation. CONCLUSIONS: Our study gives evidence that GC treatment induces a circulating substance that is able to inhibit IGF1R activation in vitro without affecting circulating free or total IGF1. This may be one of the mechanisms by which GC inhibits IGF1 action in vivo. However, the nature of this circulating substance remains to be identified.

[Delayed psychomotor development caused by malignant infantile osteopetrosis]. / Psykomotorisk retardering på baggrund af malign infantil osteopetrose.

Malignant infantile osteopetrosis (MIOP) is a hereditary bone disorder caused by osteoclastic dysfunction. Within the first year of life affected children present with recurrent infections, vision impairment, failure to thrive, bone marrow failure, and at later stages neurological deficits and ultimately death. Bone marrow transplant (BMT) is the only curative treatment. We present a patient with MIOP, who showed the first symptoms at three weeks of age, and the disease was diagnosed at 11 months of age. The boy had a successful BMT after which the delayed psychomotor development improved.

Short-term growth after withdrawal of exogenous glucocorticoids.

BACKGROUND: The growth-suppressive effect of systemic glucocorticoids in children is well established, however, recovery of growth after withdrawal of short-term treatment in school-age children has not been evaluated. OBJECTIVE: To assess short-term growth after withdrawal of systemic glucocorticoids. METHODS: A post-hoc analysis of data from a double-blind lower leg growth trial which compared 5 mg prednisolone once daily in the evening with placebo was performed. The study consisted of run-in, treatment, wash-out and run-out periods of 1 week duration. In 10 children with asthma (mean age 11 years) lower leg growth measured with the knemometer could be studied up to 3 weeks after withdrawal of prednisolone. RESULTS: Mean (SEM) lower leg growth rates during run-in, prednisolone treatment and the first, second and third weeks after withdrawal of prednisolone were 0.48 (0.15), -0.27 (0.20), 0.53 (0.19), 0.72 (0.16) and 0.66 (0.14) mm/week, p < 0.001. Mean growth rates during run-in and the first, second and third weeks after withdrawal of prednisolone did not vary, p = 0.68. CONCLUSION: Recovery of suppressed lower leg growth rates occurs within a week after withdrawal of exogenous glucocorticoids.

Does vitamin D administered to children with asthma treated with inhaled glucocorticoids affect short-term growth or bone turnover?

Our objective was to assess whether administration of 25-OH-vitamin D to children with asthma treated with inhaled dry-powder budesonide 400 microg daily affects short-term growth or markers of bone turnover. We utilized a randomized, double-blind, two-period crossover trial with run-in and washout periods of 2 weeks and treatment periods of 4 weeks duration. The setting was an Outpatient clinic in a secondary referral center. Subjects included 14 boys and 3 girls with a mean age of 11.7 (range, 6.1-14.4) years. Interventions included 15 microg (600 IU) 25-OH-vitamin D (cholecalciferol) in one tablet ABCDin(R) once daily in the morning. Primary outcome measures were: lower leg growth rate, serum osteocalcin, and serum markers of type I collagen turnover, i.e., the amino terminal propeptide of type I procollagen (PINP), the carboxy terminal propeptide of type I procollagen (PICP) (formation markers), and the carboxy terminal pyridinoline cross-linked telopeptide of type I collagen (ICTP) (degradation markers). Secondary outcome measures were parameters of asthma control and serum 25-OH-vitamin D. Lower leg growth rate was 0.22 mm/week during vitamin D and 0.25 mm/week during placebo treatment (NS). Osteocalcin was 59.9 and 57.8 microg/l during vitamin D and placebo treatment, respectively, PINP 574 and 565 microg/l, PICP 381 and 382 microg/l, and ICTP 11.5 and 11.1 microg/l, respectively (NS). Serum 25-OH-vitamin D was 76.3 nmol/l and 48.2 nmol/l, respectively (P < 0.001). There were no statistically significant differences in measures of pulmonary function. In conclusion, administration of 25-OH-vitamin D does not affect short-term growth or markers of bone turnover in children with asthma treated with inhaled dry-powder budesonide 400 microg daily.

Differential effects of short-term prednisolone treatment on peripheral and abdominal subcutaneous thickness in children assessed by ultrasound.

Long-term glucocorticoid excess decreases peripheral and increases abdominal subcutaneous thickness. Short-term prednisolone treatment is used in the treatment of many acute and chronic conditions in children. The aim of the present study was to elucidate if changes in thickness of cutis, subcutis, or dermal water content may be induced by short-term prednisolone treatment in children. Twenty children with asthma aged 7.7-13.8 years were included in a double-blind, randomized, placebo-controlled crossover trial. Active treatment was 5mg prednisolone daily. Treatment, run-in, and wash-out periods were 1 week. On days 1 and 7 of each treatment period, 20 MHz ultrasound scanning of the skin was performed on the thigh, forearm, and abdomen. Prednisolone treatment was associated with decreases in the total thickness of the cutis and subcutis in the thigh (0.28 mm) and forearm (0.15 mm), and an increase in the abdomen (0.23 mm). During placebo treatment the thickness was increased in the thigh (0.07 mm) and abdomen (0.05 mm), and reduced in the forearm (0.03 mm). The differences between prednisolone and placebo treatment were statistically significant in the thigh (P=0.04). The increase in thickness in the abdomen during prednisolone treatment was statistically significantly different from the reductions in the thigh (P=0.03) and forearm (P=0.05). There were no statistically significant differences in the dermal thickness or water content during prednisolone treatment compared to placebo.Short-term treatment with 5mg prednisolone daily may cause differential effects in peripheral and abdominal subcutaneous thickness in children.