Increased fat mass is associated with increased bone size but reduced volumetric density in pre pubertal children

Inverted U-Shaped Relationship between Obesity Parameters and Bone Mineral Density in Korean Adolescents

As the association between obesity and bone health remains controversial in children and adolescents, we investigate the effects of obesity parameters on bone mineral density (BMD) in 2060 Korean adolescents who participated in the 2008-2011 Korea National Health and Nutrition Examination Survey (KNHANES). Multiple regression analysis and analysis of covariance (ANCOVA) were conducted to examine both the linear and non-linear associations between total-body-less-head (TBLH) BMD and four obesity parameters: body mass index, waist circumference, waist-to-height ratio, and total-body fat mass (FM). In a multiple linear regression analysis adjusted for age, menarcheal status (in females only), and total-body lean mass, there was no significant linear association between obesity parameters and TBLH BMD, except for total-body FM in males. However, upon adding a second-order polynomial term for each obesity parameter, a significant quadratic relationship between all obesity parameters and TBLH BMD was observed, with the corresponding quadratic term being negative. The results of ANCOVA also revealed an inverted U-shaped relationship between each obesity parameter and TBLH BMD. Our findings suggest the existence of an optimal range of obesity parameters for developing or maintaining optimal bone health in Korean Adolescents. Deviation from this range, in either direction (being underweight or having obesity), may compromise bone health.

Impaired Bone Architecture in Peripubertal Children With HIV, Despite Treatment With Antiretroviral Therapy: A Cross-Sectional Study From Zimbabwe

HIV infection has multi-system adverse effects in children, including on the growing skeleton. We aimed to determine the association between chronic HIV infection and bone architecture (density, size, strength) in peripubertal children. We conducted a cross-sectional study of children aged 8 to 16 years with HIV (CWH) on antiretroviral therapy (ART) and children without HIV (CWOH) recruited from schools and frequency-matched for age strata and sex. Outcomes, measured by tibial peripheral quantitative computed tomography (pQCT), included 4% trabecular and 38% cortical volumetric bone mineral density (vBMD), 4% and 38% cross-sectional area (CSA), and 38% stress-strain index (SSI). Multivariable linear regression tested associations between HIV status and outcomes, stratified by sex and puberty (Tanner 1-2 versus 3-5), adjusting for age, height, fat mass, physical activity, and socioeconomic and orphanhood statuses. We recruited 303 CWH and 306 CWOH; 50% were female. Although CWH were similar in age to CWOH (overall mean ± SD 12.4 ± 2.5 years), more were prepubertal (ie, Tanner 1; 41% versus 23%). Median age at ART initiation was 4 (IQR 2-7) years, whereas median ART duration was 8 (IQR 6-10) years. CWH were more often stunted (height-for-age Z-score <-2) than those without HIV (33% versus 7%). Both male and female CWH in later puberty had lower trabecular vBMD, CSA (4% and 38%), and SSI than those without HIV, whereas cortical density was similar. Adjustment explained some of these differences; however, deficits in bone size persisted in CWH in later puberty (HIV*puberty interaction p = 0.035 [males; 4% CSA] and p = 0.029 [females; 38% CSA]). Similarly, puberty further worsened the inverse association between HIV and bone strength (SSI) in both males (interaction p = 0.008) and females (interaction p = 0.004). Despite long-term ART, we identified deficits in predicted bone strength in those living with HIV, which were more overt in the later stages of puberty. This is concerning, as this may translate to higher fracture risk later in life. © 2022 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Pediatric obesity-Long-term consequences and effect of weight loss

Childhood obesity is, according to the WHO, one of the most serious challenges of the 21st century. More than 100 million children have obesity today. Already during childhood, almost all organs are at risk of being affected by obesity. In this review, we present the current knowledge about diseases associated with childhood obesity and how they are affected by weight loss. One major causative factor is obesity-induced low-grade chronic inflammation, which can be observed already in preschool children. This inflammation-together with endocrine, paracrine, and metabolic effects of obesity-increases the long-term risk for several severe diseases. Type 2 diabetes is increasingly prevalent in adolescents and young adults who have had obesity during childhood. When it is diagnosed in young individuals, the morbidity and mortality rate is higher than when it occurs later in life, and more dangerous than type 1 diabetes. Childhood obesity also increases the risk for several autoimmune diseases such as multiple sclerosis, Crohn's disease, arthritis, and type 1 diabetes and it is well established that childhood obesity also increases the risk for cardiovascular disease. Consequently, childhood obesity increases the risk for premature mortality, and the mortality rate is three times higher already before 30 years of age compared with the normal population. The risks associated with childhood obesity are modified by weight loss. However, the risk reduction is affected by the age at which weight loss occurs. In general, early weight loss-that is, before puberty-is more beneficial, but there are marked disease-specific differences.

Association between body mass index, bone bending strength, and BMD in young sedentary women

The rationale was to determine whether body mass index (BMI) is a predictor of bone bending strength and bone mineral density (BMD) in young sedentary women. Results show that BMI is not a predictor of bone bending strength and that young women with low BMI also have low BMD.

INTRODUCTION

The purpose of this study was to determine whether body mass index (BMI) is a predictor of tibial or ulnar bending strength and bone mineral density (BMD) in sedentary women.

METHODS

Sedentary women (n = 34), age 19-27 years, with low BMI (LBMI < 18.5 kg/m², n = 16), and normal or high BMI (NHBMI between 18.5 and 29.9 kg/m², n = 18) participated as study subjects. Study outcomes included tibial and ulnar bending strength (EI in Nm²) using a non-invasive mechanical response tissue analyzer (MRTA); BMD and bone mineral content (BMC) of the whole body (WB), femoral neck (FN), total hip (TH), lumbar spine 1-4 (LS1-4), and ulna; and bone turnover biomarkers.

RESULTS

The LBMI group have lower (p < 0.01) body weight [group difference (Δ) = 32.0%], lean mass (LM) (Δ = 23.1%), fat mass (FM) (Δ = 77.2%), and tibial bending strength (Δ = 22.0%), compared to the NHBMI. The LBMI group also have lower (all p < 0.025) BMC in WB (Δ = 19.9%), FN (Δ = 20.1%) and TH (Δ = 19.0%), compared to the NHMBI, not in BMD results. Multivariate regression analysis shows that significant predictors of tibial bending strength are tibia length (adjusted R² = .341), age (adjusted R² = .489), ulna BMD (adjusted R² = .536), and LM (adjusted R² = .580). BMI was positively correlated with tibial EI (p < 0.05), height, weight, FM, LM, body fat% (all p < 0.01), and BMD of WB, FN, TH, and LS 1-4 (p < 0.05 or < 0.01).

CONCLUSIONS

Our results show that BMI is not a significant predictor of tibial or ulnar bending strength in young sedentary women.

Association between Body Composition and Bone Mineral Density in Children and Adolescents: A Systematic Review and Meta-Analysis

Background: Bone mass acquisition during growth is a major determinant of the risk of developing osteoporosis later in life. Body composition is an anthropometric determinant of bone mineral density (BMD) and significantly influences its development during childhood and adolescence. Objective: This study aimed to systematically examine the association between body composition and bone mineral density in children and adolescents. Methods: Observational studies addressing this association were identified from PubMed (MEDLINE), Embase, Scopus and the Cochrane Library (up to January 2021). The study populations consisted of healthy children and adolescents. The DerSimonian and Laird method was used to compute pooled estimates of effect size and the respective 95% confidence intervals for upper limbs, femoral neck (FN), lumbar spine (LS) and total body, respectively. Subgroup analyses were further performed based on age, sex and ethnicity. Results: Thirty-one published studies were eligible for inclusion in this systematic review and meta-analysis, including three longitudinal studies. The combined population from all the studies amounted to 21,393 (11,205 males and 10,188 females). The pooled estimates of the correlation coefficients for lean mass (LM) and BMD ranged from 0.53 to 0.74 (p < 0.050), and the pooled regression coefficients ranged from 0.23 to 0.79 for FN, LS and total body (p < 0.050). For fat mass (FM), the pooled correlation coefficients ranged from 0.10 to 0.50 (p < 0.050) and the pooled regression coefficient was only significant for FN BMD with a weak strength (pooled β = 0.07, p < 0.050). The pooled regression coefficients for body fat percentage (BF%) were between −0.54 and −0.04 (p < 0.050). The subgroup analysis revealed a stronger association in Asians than in Caucasians for LM and in males compared to females for BF% (p < 0.050). Conclusions: This systematic review and meta-analysis supports a positive association between LM and BMD. BF% appears to have a deleterious effect on bone acquisition in children and adolescents.

Association between Body Fat and Elevated Blood Pressure among Children and Adolescents Aged 7-17 Years: Using Dual-Energy X-ray Absorptiometry (DEXA) and Bioelectrical Impedance Analysis (BIA) from a Cross-Sectional Study in China

To investigate the associations between body fat percentage (BF%) with childhood blood pressure (BP) levels and elevated BP (EBP) risks, and further examine the validity of bioelectrical impedance analysis (BIA), we conducted a cross-sectional study of 1426 children and adolescents aged 7–17 years in Beijing, 2020. EBP, including elevated systolic BP (ESBP) and elevated diastolic BP (EDBP), was defined based on the age- and sex-specific 90th BP reference values of children and adolescents in China. BF% was measured by dual-energy X-ray absorptiometry (DEXA) and BIA devices, and was divided into four quartiles. Log-binomial models were applied to calculate odds ratios (ORs) and 95% confidence intervals (95%CI). Girls tended to have higher BF% levels than boys (p < 0.05). There was 41.0% of girls who developed EBP. High BF% was associated with increased BP levels with ORs of 0.364 (95%CI = 0.283–0.444) for SBP, 0.112 (95%CI = 0.059–0.165) for DBP, and 1.043 (95%CI = 1.027–1.059) for EBP, while the effects were more pronounced in girls and older-aged children. BIA devices agreed well with BF% assessment obtained by DEXA. High BF% might have negative effects on childhood BP. Convenient measurements of body fat might help to assess childhood obesity and potential risks of hypertension.

Non-linear association of body composition and its components with bone density in Iranian children and adolescents

Peak bone mass is established during childhood. This study aimed to evaluate the associations of the components of overall body mass with areal bone mineral density Z-score in children. The findings of this study showed that children with greater overall body mass had higher aBMD Z-score.

PURPOSE

Peak bone mass is established during childhood and adolescence. One of the important factors influencing predicted bone mass tracking in childhood and adolescence is alteration in the body composition during this growth period. This study aimed to evaluate the associations of the components of overall body mass with areal bone mineral density Z-score in children and adolescents.

METHODS

In this cross-sectional study, 478 healthy Iranian children and adolescents (237 girls and 241 boys) who had DXA measures participated. We evaluated the linearity of associations using generalized additive models.

RESULTS

Children's mean age was14 years with a range of 9-18 years, and 49.6% were girls. We found an increase in aBMD Z-score with increasing overall body mass (r = 0.25, p < 0.001). We observed this association with fat-free mass and total fat mass up to the 60th (~30 Kg) and 75th percentile (~12.5 Kg) [0.051 (95% CI, 0.027-0.075) increase in aBMD Z-score per 1 Kg increase in fat-free mass and 0.079 (95% CI, 0.044-0.114) increase in aBMD Z-score per 1 Kg increase in the total fat mass]. The correlation between Z-score of overall body mass and its components with aBMD Z-score was strongly positive. (P value < 0.001 for all) CONCLUSION: The findings of this study showed that children with greater overall body mass had higher aBMD Z-score. In addition, this study adds to a growing literature, suggesting that the relationship between body composition and BMD may be influenced by the pattern of fat and fat-free mass distribution in population.

Association Between Physical Fitness and Bone Strength and Structure in 3- to 5-Year-Old Children

BACKGROUND

The positive association between physical fitness and bone structure has been widely investigated in children and adolescents, yet no studies have evaluated this influence in young children (ie, preschoolers).

HYPOTHESIS

Fit children will present improved bone variables when compared with unfit children, and no sex-based differences will emerge in the sample.

STUDY DESIGN

Cross-sectional study.

LEVEL OF EVIDENCE

Level 3.

METHODS

Handgrip strength, standing long jump (SLJ), speed/agility, balance, and cardiorespiratory fitness (CRF) were assessed using the Assessing FITness levels in PREschoolers (PREFIT) test battery in 92 children (50 boys; age range, 3-5 years). A peripheral quantitative computed tomography scan was performed at 38% of the length of the nondominant tibia. Cluster analysis from handgrip strength, SLJ, speed/agility, and CRF was developed to identify fitness groups. Bone variables were compared between sexes and between cluster groups. The association between individual physical fitness components and different bone variables was also tested.

RESULTS

Three cluster groups emerged: fit (high values on all included physical fitness variables), strong (high strength values and low speed/agility and CRF), and unfit (low strength, speed/agility, and CRF). The fit group presented higher values than the strong and unfit groups for total and cortical bone mineral content, cortical area, and polar strength strain index (all P < 0.05). The fit group also presented a higher cortical thickness when compared with the unfit group (P < 0.05). Handgrip, SLJ, and speed/agility predicted all bone variables except for total and cortical volumetric bone mineral density. No differences were found for bone variables between sexes.

CONCLUSION

The results suggest that global fitness in preschoolers is a key determinant for bone structure and strength but not volumetric bone mineral density.

CLINICAL RELEVANCE

Physical fitness is a determinant for tibial bone mineral content, structure, and strength in very young children. Performing physical fitness tests could provide useful information related to bone health in preschoolers.

Arachidonic acid exacerbates diet-induced obesity and reduces bone mineral content without impacting bone strength in growing male rats

Long-chain polyunsaturated fatty acids modulate bone mass and adipocyte metabolism. Arachidonic acid (AA, C20:4 n-6) is elevated in obesity and postulated to stimulate bone resorption. This study aimed to determine the effect of AA on bone mass, quality, and adiposity in diet-induced obesity during growth. Male Sprague-Dawley rats (n=42, 4-week) were randomized into groups fed a control diet (CTRL, AIN-93G), high-fat diet (HFD, 35% kcal fat) or HFD + AA (1% w/w diet) for 6 weeks. Body composition, bone mineral density and microarchitecture were measured using dual-energy X-ray absorptiometry and micro-computed tomography. Red blood cell fatty acid profile was measured with gas chromatography. Group differences were evaluated using repeated measures two-way analysis of variance with Tukey-Kramer post hoc testing. Total energy intake did not differ among diet groups. At week 6, HFD + AA had significantly greater body fat % (12%), body weight (6%) and serum leptin concentrations (125%) than CTRL, whereas visceral fat (mass and %, assessed with micro-computed tomography) was increased in both HFD and HFD + AA groups. HFD + AA showed reduced whole body bone mineral content and femur mid-diaphyseal cortical bone cross-sectional area than HFD and CTRL, without impairment in bone strength. Contrarily, HFD + AA had greater femur metaphyseal trabecular vBMD (35%) and bone volume fraction (5%) compared to controls. Inclusion of AA elevated leptin concentrations in male rats. The early manifestations of diet-induced obesity on bone mass were accelerated with AA. Studies of longer duration are needed to clarify the effect of AA on peak bone mass following growth cessation.

Dietary inflammatory index® and cortical bone outcomes in healthy adolescent children

Diet is thought to modulate inflammation. This study shows no relationships between the dietary inflammatory index (DII) and biomarkers of inflammation or bone after adjusting for covariates. Monocyte chemoattractant protein-1 was inversely associated with peripheral tibia cortical thickness and prospective childhood studies should be conducted to better understand this relationship and to determine if there are long-term consequences in adulthood.

INTRODUCTION

Examine the relationships between the DII-scores and bone and biomarkers of inflammation in 290 adolescents, ages 9-13 years.

METHODS

DII-scores were calculated from 3-day diet records and categorized into tertiles, low (< - 1.34), medium (- 1.34 to 1.41), and high (> 1.41) inflammation. Radius and tibia bone were assessed via peripheral quantitative computed tomography (Stratec XCT 2000) at the 66% site relative to the distal growth plate. Fasting serum was measured for tumor necrosis factor alpha (TNF-α), interleukin-6 (IL-6), vascular endothelial growth factor (VEGF), and monocyte chemoattractant protein-1 (MCP-1). The relationships between DII-scores and bone and biomarkers of inflammation were assessed using bivariate and partial correlations adjusting for sexual maturation, sex, race, muscle cross-sectional area, and height. ANOVA/ANCOVA models were used to compare DII-tertiles with dependent variables.

RESULTS

DII-scores were negatively associated with tibia trabecular area (TtAr; r = - .141, P = .019), periosteal perimeter (PsPM; r = - .145, P = .016), endosteal perimeter (r = - .145, P = .016), strength strain index (SSI; r = - .129, P = .032), and radius TtAr (r = - .140, P = .020), PsPM (r = -.138, P = .027) and SSI (r = -.131, P = .036) but nullified when adjusting for covariates. Tibia PsPM was higher in the low DII group compared to the medium (P = .050) and high (P = .046) groups but nullified after controlling for covariates. DII-scores were not associated with TNF-α, VEGF, or IL-6, but were associated with MCP-1 only in the unadjusted model (r = .125, P = .042). In the adjusted model, MCP-1 was inversely associated with tibia cortical thickness (r = -.150 P = .030).

CONCLUSION

The DII-scores were not related to biomarkers of inflammation or bone; however, the biomarker of inflammation, MCP-1 was negatively associated with tibia CtTh. Future prospective pediatric studies should be conducted to better understand this relationship and determine if there are long-term implications in adulthood.

Bone Health, Body Composition, and Vitamin D Status of Black Preadolescent Children in South Africa

Optimal bone health is important in children to reduce the risk of osteoporosis later in life. Both body composition and vitamin D play an important role in bone health. This study aimed to describe bone health, body composition, and vitamin D status, and the relationship between these among a group of conveniently sampled black preadolescent South African children (n = 84) using a cross-sectional study. Body composition, bone mineral density (BMD), and bone mineral content (BMC) were assessed using dual x-ray absorptiometry. Levels of 25-hydroxyvitamin D (25(OH)D) (n = 59) were assessed using dried blood spots. A quarter (25%) of children presented with low bone mass density for their chronological age (BMD Z-score < -2) and 7% with low BMC-for-age (BMC Z-score < -2), while only 34% of the children had sufficient vitamin D status (25(OH)D ≥ 30 ng/mL). Lean mass was the greatest body compositional determinant for variances observed in bone health measures. Body composition and bone health parameters were not significantly different across vitamin D status groups (p > 0.05), except for lumbar spine bone mineral apparent density (LS-BMAD) (p < 0.01). No association was found between bone parameters at all sites and levels of 25(OH)D (p > 0.05). Further research, using larger representative samples of South African children including all race groups is needed before any conclusions and subsequent recommendation among this population group can be made.

Body composition and bone mineral density in childhood

BACKGROUND

Body mass compartments may have different directions of influence on bone accrual. Studies of children are limited by relatively small sample sizes and typically make strong assumptions of linear regression.

OBJECTIVE

To evaluate associations of overall body mass, components of overall body mass (fat-free and total fat), and components of total fat mass (truncal and non-truncal fat), measured via dual-energy X-ray absorptiometry (DXA) and anthropometry, with total body less head areal bone mineral density (aBMD) Z-score in mid-childhood.

METHODS

We performed a cross-sectional study among 876 Boston-area children who had DXA measures. We evaluated linearity of associations using generalized additive models.

RESULTS

Children were median 7.7 (range 6-10) years of age, and 61% were white. After adjustment for sociodemographics and other compartments of body mass, overall body mass, particularly the fat-free mass component, appeared to have a positive relationship with aBMD Z-score [e.g., 0.25 (95% CI: 0.23, 0.28) per 1-kg fat-free mass]. The relationship between truncal fat and aBMD Z-score appeared non-linear, with a negative association only in children with levels of fat mass in the upper 15th percentile [-0.17 (95% CI: -0.26, -0.07) aBMD Z-score per 1-kg truncal fat mass], while non-truncal fat mass was not associated with aBMD Z-score.

CONCLUSIONS

Our analyses suggest that central adiposity is associated with lower aBMD Z-score only in children with the highest levels of abdominal fat. This finding raises the possibility of a threshold above which central adipose tissue becomes more metabolically active and thereby adversely impacts bone.

Relative contributions of lean and fat mass to bone strength in young Hispanic and non-Hispanic girls

BACKGROUND

With the high prevalence of childhood obesity, especially among Hispanic children, understanding how body weight and its components of lean and fat mass affect bone development is important, given that the amount of bone mineral accrued during childhood can determine osteoporosis risk later in life. The aim of this study was to assess the independent contributions of lean and fat mass on volumetric bone mineral density (vBMD), geometry, and strength in both weight-bearing and non-weight-bearing bones of Hispanic and non-Hispanic girls.

METHODS

Bone vBMD, geometry, and strength were assessed at the 20% distal femur, the 4% and 66% distal tibia, and the 66% distal radius of the non-dominant limb of 326, 9- to 12-year-old girls using peripheral quantitative computed tomography (pQCT). Total body lean and fat mass were measured by dual-energy x-ray absorptiometry (DXA). Multiple linear regression was used to assess the independent relationships of fat and lean mass with pQCT bone measures while adjusting for relevant confounders. Potential interactions between ethnicity and both fat and lean mass were also tested.

RESULTS

Lean mass was a significant positive contributor to all bone outcomes (p < 0.05) with the exception of vBMD at diaphyseal sites. Fat mass was a significant contributor to bone strength at weight bearing sites, but did not significantly contribute to bone strength at the non-weight bearing radius and was negatively associated with radius cortical content and thickness. Bone measures did not significantly differ between Hispanic and non-Hispanic girls, although there was a significant interaction between ethnicity and fat mass with total bone area at the femur (p = 0.02) and 66% tibia (p = 0.005) as well as bone strength at the femur (p = 0.03).

CONCLUSION

Lean mass is the main determinant of bone strength for appendicular skeletal sites. Fat mass contributes to bone strength in the weight-bearing skeleton but does not add to bone strength in non-weight-bearing locations and may potentially be detrimental. Bone vBMD, geometry, and strength did not differ between Hispanic and non-Hispanic girls; fat mass may be a stronger contributor to bone strength in weight-bearing bones of Hispanic girls compared to non-Hispanic.

Obesity in Pediatric Trauma

Obese children with high-energy injuries present with more severe injuries, more extremity injuries, and higher Injury Severity Scores. They are at increased risk for complications, prolonged ventilation, and ICU stay and have increased mortality. Obesity is associated with altered bone mass accrual and higher fracture rates. Obese patients have a higher risk of loss of reduction of forearm fractures, more severe supracondylar fractures, and a higher likelihood of lateral condyle fractures. Obese patients are more likely to have complications with femur fractures and have higher rates of foot and ankle fracture.

Relationships between markers of inflammation and bone density: findings from the Hertfordshire Cohort Study

Among 365 Hertfordshire Cohort Study participants (aged 59-71 years at baseline), higher adiponectin and adiponectin to leptin ratios were associated with lower baseline lumbar spine and femoral neck bone mineral density (BMD). Lower IL-10 was associated with accelerated decline in lumbar spine BMD. This suggests that bone health can be influenced by changes in immune phenotype and alterations in adipokine homeostasis.

INTRODUCTION

The aim of this study was to examine the association between indices of inflammation and BMD in a population-based cohort of older adults in the UK.

METHODS

Analyses were based on a sample of 194 men and 171 women of the Hertfordshire Cohort Study (community-living, older adults). Dual energy X-ray absorptiometry (DXA) was performed at the lumbar spine and proximal femur at baseline and repeated at a median of 4.5 years (inter-quartile range 3.6 to 5.2). Inflammatory markers (CRP, TNF, IL-1β, IL-6, IL-8, IL-10, adiponectin and leptin) were ascertained at baseline using enzyme-linked immunosorbent assay (ELISA) techniques and Bio-Plex Pro Assays. Gender-adjusted linear regression was used to examine the associations between markers of inflammation and outcomes with and without adjustment for anthropometric and lifestyle factors.

RESULTS

The mean (SD) ages at baseline were 64.4 (2.5) and 66.5 (2.7) years for men and women respectively. Higher levels of adiponectin and adiponectin to leptin ratios were each associated with lower baseline lumbar spine and femoral neck BMD in gender-adjusted (p < 0.01) and fully adjusted (p < 0.05) analyses. Lower levels of IL-10 and TNF were each associated with accelerated decline in lumbar spine BMD in both gender-adjusted (p ≤ 0.05) and fully adjusted (p < 0.05) analyses.

CONCLUSIONS

In a cohort of older adults, high levels of adiponectin and adiponectin to leptin ratios were both associated with lower BMD at the lumbar spine and femoral neck at baseline, and lower IL-10 was associated with accelerated decline in BMD at the lumbar spine. This adds weight to the theory that bone health can be influenced by changes in immune phenotype and alterations in adipokine homeostasis.

Physical Fitness, Adiposity, and Diets as Surrogate Measures of Bone Health in Schoolchildren: A Biochemical and Cross-Sectional Survey Analysis

This study aimed to investigate the associations between adiposity, muscular fitness (MF), diet, sun exposure, and physical activity profiles as surrogate measures with bone health status in a sample of schoolchildren aged 8-18 yr old. A total of 250 Egyptian schoolchildren aged 8-18 yr were randomly invited to participate in these cross-sectional survey analyses. Calcaneal broadband ultrasound attenuation (c-BUA), bone mineral density (BMD), and bone formation markers (total calcium, serum bone alkaline phosphatase, and osteocalcin) were measured as markers of bone health. Adiposity profile, MF, physical activity (PA), sun exposure, Ca, and vitamin D dietary intake as related cofactors of bone health were measured by using prevalidated questionnaires and standard analytical techniques. A total of 85% (n = 213) of the study population showed normal bone health and 14.8% (n = 37) had abnormal bone health; most of them are girls (67.6%) classified according to BMD and c-BUA Z-scores into osteopenia (9.6%) and osteoporosis (5.2%). Compared with boys, higher correlations between c-BUA, bone mineral content, and BMD measures in the femoral neck, lumbar spine, whole body, and bone markers were reported in girls with lower bone mass. There was a positive significant correlation between body mass index, adiposity, sun exposure, MF, PA status, Ca and vitamin D intake, and c-BUA and BMD score analyses. These parameters were shown to be associated with about ~57.3%-88.4% of bone health characteristics of children and adolescents with osteopenia and osteoporosis. In children and adolescents, sun exposure, Ca and vitamin D diets, adiposity, PA, and changes in the levels of Ca, osteocalcin, and serum bone alkaline phosphatase were shown to be associated with bone health. Also, a significant correlation was reported between c-BUA score, dual-energy X-ray absorptiometry-BMD measures, and bone markers at clinically important bone sites of girls and boys. However, further clinical trials should be studied to consider c-BUA and bone markers as the benchmark estimates of bone mass for diagnostic purposes in young ages.

Estimating body mass and composition from proximal femur dimensions using dual energy x-ray absorptiometry

Body mass prediction from the skeleton most commonly employs femoral head diameter (FHD). However, theoretical predictions and empirical data suggest the relationship between mass and FHD is strongest in young adults, that bone dimensions reflect lean mass better than body or fat mass and that other femoral measurements may be superior. Here, we generate prediction equations for body mass and its components using femoral head, neck and proximal shaft diameters and body composition data derived from dual-energy x-ray absorptiometry (DXA) scans of young adults (n = 155, 77 females and 78 males, mean age 22.7 ± 1.3 years) from the Andhra Pradesh Children and Parents Study, Hyderabad, India. Sex-specific regression of log-transformed data on femoral measurements predicted lean mass with smaller standard errors of estimate (SEEs) than body mass (12-14% and 16-17% respectively), while none of the femoral measurements were significant predictors of fat mass. Subtrochanteric mediolateral shaft diameter gave lower SEEs for lean mass in both sexes and for body mass in males than FHD, while FHD was a better predictor of body mass in women. Our results provide further evidence that lean mass is more closely related to proximal femur dimensions than body or fat mass and that proximal shaft diameter is a better predictor than FHD of lean but not always body mass. The mechanisms underlying these relationships have implications for selecting the most appropriate measurement and reference sample for estimating body or lean mass, which also depend on the question under investigation.

Relationship between body mass, lean mass, fat mass, and limb bone cross-sectional geometry: Implications for estimating body mass and physique from the skeleton

OBJECTIVES

Estimating body mass from skeletal dimensions is widely practiced, but methods for estimating its components (lean and fat mass) are poorly developed. The ability to estimate these characteristics would offer new insights into the evolution of body composition and its variation relative to past and present health. This study investigates the potential of long bone cross-sectional properties as predictors of body, lean, and fat mass.

MATERIALS AND METHODS

Humerus, femur and tibia midshaft cross-sectional properties were measured by peripheral quantitative computed tomography in sample of young adult women (n = 105) characterized by a range of activity levels. Body composition was estimated from bioimpedance analysis.

RESULTS

Lean mass correlated most strongly with both upper and lower limb bone properties (r values up to 0.74), while fat mass showed weak correlations (r ≤ 0.29). Estimation equations generated from tibial midshaft properties indicated that lean mass could be estimated relatively reliably, with some improvement using logged data and including bone length in the models (minimum standard error of estimate = 8.9%). Body mass prediction was less reliable and fat mass only poorly predicted (standard errors of estimate ≥11.9% and >33%, respectively).

DISCUSSION

Lean mass can be predicted more reliably than body mass from limb bone cross-sectional properties. The results highlight the potential for studying evolutionary trends in lean mass from skeletal remains, and have implications for understanding the relationship between bone morphology and body mass or composition.

Body fat mass, lean body mass and associated biomarkers as determinants of bone mineral density in children 6-8years of age - The Physical Activity and Nutrition in Children (PANIC) study

Lean body mass (LM) has been positively associated with bone mineral density (BMD) in children and adolescents, but the relationship between body fat mass (FM) and BMD remains controversial. Several biomarkers secreted by adipose tissue, skeletal muscle, or bone may affect bone metabolism and BMD. We investigated the associations of LM, FM, and such biomarkers with BMD in children. We studied a population sample of 472 prepubertal Finnish children (227 girls, 245 boys) aged 6-8years. We assessed BMD, LM, and FM using whole-body dual-energy x-ray absorptiometry and analysed several biomarkers from fasting blood samples. We studied the associations of LM, FM, and the biomarkers with BMD of the whole body excluding the head using linear regression analysis. LM (standardized regression coefficient β=0.708, p<0.001), FM (β=0.358, p<0.001), and irisin (β=0.079, p=0.048) were positive correlates for BMD adjusted for age, sex, and height in all children. These associations remained statistically significant after further adjustment for LM or FM. The positive associations of dehydroepiandrosterone sulphate (DHEAS), insulin, homeostatic model assessment for insulin resistance (HOMA-IR), leptin, free leptin index, and high-sensitivity C-reactive protein and the negative association of leptin receptor with BMD were explained by FM. The positive associations of DHEAS and HOMA-IR with BMD were also explained by LM. Serum 25-hydroxyvitamin D was a positive correlate for BMD adjusted for age, sex, and height and after further adjustment for FM but not for LM. LM and FM were positive correlates for BMD also in girls and boys separately. In girls, insulin, HOMA-IR, leptin, and free leptin index were positively and leptin receptor was negatively associated with BMD adjusted for age, height, and LM. After adjustment for age, height, and FM, none of the biomarkers was associated with BMD. In boys, leptin and free leptin index were positively and leptin receptor was negatively associated with BMD adjusted for age, height, and LM. After adjustment for age, height and FM, 25(OH)D was positively and IGF-1 and leptin were negatively associated with BMD. FM strongly modified the association between leptin and BMD. LM but also FM were strong, independent positive correlates for BMD in all children, girls, and boys. Irisin was positively and independently associated with BMD in all children. The associations of other biomarkers with BMD were explained by LM or FM.

Obesity is associated with vitamin D deficiency in Danish children and adolescents

BACKGROUND

Sufficient serum concentrations of vitamin D are required to maintain bone health during growth. The aims of this study were to determine whether vitamin D deficiency is more prevalent among children and adolescents with obesity compared to their normal weight peers and to identify clinical and biochemical variables associated with vitamin D deficiency.

METHODS

One thousand four hundred and eighty-four children and adolescents with overweight/obesity and 2143 population-based controls were recruited from the Danish Childhood Obesity Biobank. Anthropometric variables and fasting concentrations of serum 25-hydroxy vitamin D (25-OH-D), plasma parathyroid hormone (PTH), calcium and phosphate were assessed at baseline. Vitamin D deficiency was defined as serum 25-OH-D concentrations <30 nmol/L. Linear and logistic regressions were used to identify variables associated with vitamin D deficiency.

RESULTS

A total of 16.5% of the children and adolescents with obesity (body mass index [BMI] standard deviation score [SDS]>2.33) exhibited vitamin D deficiency, with an odds ratio (OR) 3.41 (confidence interval [CI]: 2.27-5.71; p<0.0001) for being vitamin D deficient compared to their normal weight peers. BMI-SDS was independently and inversely associated with serum 25-OH-D concentrations. Other independent risk factors for vitamin D deficiency were being older than 14 years (OR: 2.39; CI: 1.28-4.48; p=0.006), more than 4 daily hours of screen time (OR: 4.56; CI: 2.59-8.05; p<0.0001) and blood sample assessment during winter-spring (OR: 6.44; CI: 4.47-9.26; p<0.0001).

CONCLUSIONS

Vitamin D deficiency was common among Danish children and adolescents with obesity. The degree of obesity was independently associated with lower serum 25-OH-D concentrations.

The Association of Fat and Lean Tissue With Whole Body and Spine Bone Mineral Density Is Modified by HIV Status and Sex in Children and Youth

BACKGROUND

HIV-infected (HIV-pos) male children/youth showed lower bone mineral density at sexual maturity than HIV-uninfected (HIV-neg) females. It is not known whether complications of HIV disease, including abnormal body fat distribution, contribute to lower bone accrual in male HIV-pos adolescents.

METHODS

In a cross-sectional study, we evaluated the relationship between body composition (fat and lean mass) and bone mass in HIV-pos and HIV-neg children/youth and determined if it is modified by HIV status and sex. We used generalized estimating equations to simultaneously model the effect of fat/lean mass on multiple bone outcomes, including total body bone mineral density and bone mineral content and spine bone mineral density. We evaluated effect modification by HIV and sex.

RESULTS

The analysis cohort consisted of 143 HIV-neg and 236 HIV-pos, of whom 55% were black non-Hispanic and 53% were male. Ages ranged from 7 to < 25 years. Half of the children/youth were at Tanner stage 1 and 20% at Tanner 5. Fat mass was more strongly positively correlated with bone mass in HIV-neg than HIV-pos children/youth and these relationships were more evident for total body bone than spine outcomes. Within HIV strata, fat mass and bone were more correlated in female than male children/youth. The relationship between lean mass and bone varied by sex, but not by HIV status.

CONCLUSIONS

HIV disease diminishes the positive relationship of greater fat mass on bone mass in children/youth. Disruptions in body fat distribution, which are common in HIV disease, may have an impact on bone accretion during pubertal development.

Bone Health is Maintained, While Fat Mass is Reduced in Pre-pubertal Children with Obesity Participating in a 1-Year Family-Centered Lifestyle Intervention

Diet and physical activity (PA) influence bone health in children. This study tested whether increasing milk and milk products and weight-bearing types of PA favorably changed bone outcomes assessed by dual-energy X-ray absorptiometry (DXA) and bone biomarkers in children with obesity participating in a 1-year family-centered lifestyle intervention. Children were randomized to one of three groups: Control (Ctrl; no intervention), Standard treatment (StnTx: two servings milk and milk products/day; meet PA guidelines plus weight-bearing PA three times/week), or Modified treatment (ModTx: four servings milk and milk products/day; meet PA guidelines plus daily weight-bearing PA). Baseline and 12-month measurements included DXA scans for whole body (WB), lumbar spine (LS), lumbar lateral spine (LLS), and ultra-distal (UD) ulna + radius for bone mineral content (BMC), areal bone mineral density (aBMD) and BMD z-scores. Fat mass index (FMI), fat-free mass index (FFMI), and biomarkers of bone metabolism were assessed. Seventy-eight children 6-8 years old were recruited (mean body mass index for-age z-score: 3.3 ± 1.2). Compared to baseline, all groups increased BMC of WB, LS, and LLS (p < 0.001), whereas only StnTx increased UD ulna + radius BMC at 12 months (p < 0.05). At 12 months, WB-BMD z-scores were significantly lower in Ctrl (p < 0.05), whereas WB and LLS aBMD increased in StnTx and ModTx (p < 0.001) but not in Ctrl. All groups increased FFMI (p < 0.001), while only Ctrl increased FMI (p < 0.001). Bone biomarkers did not change over time. Participating in a family-centered lifestyle intervention based on Canadian diet and PA guidelines maintained bone health in obese children.

The Relationship Between Body Composition and Bone Quality Measured with HR-pQCT in Peritoneal Dialysis Patients

BACKGROUND

Bone is known to be impaired in chronic kidney disease and dialysis patients. Recent studies have shown that body composition (fat mass and lean mass) may impact bone health. Some of these effects may be related to mediators that are secreted by adipose tissue.

METHODS

The aim of this study was to evaluate the association between body composition (dual x-ray absorptiometry [DEXA]) and adipokines (leptin, adiponectin), with bone density and microarchitecture assessed with high-resolution peripheral quantitative computed tomography (HR-pQCT) in chronic peritoneal dialysis (PD) patients in a single-center prospective study.

RESULTS

Twenty-three patients with a median age of 61 years and body mass index (BMI) of 27 kg/m² were recruited. On univariate analysis, age was negatively associated with total volumetric bone mineral density (vBMD) (r = -0.75, p < 0.01), cortical vBMD (r = -0.85, p < 0.01), and cortical thickness (r = -0.71, p < 0.01). There was a negative association between leptin and cortical thickness (r = -0.48, p = 0.021). Fat mass (FM) was negatively correlated with cortical thickness (r = -0.52, p = 0.012). No association was found between bone parameters and dialysis duration, serum insulin, intact parathyroid hormone, osteocalcin, and adiponectin. The short dialysis vintage could in part explain the lack of correlation with bone parameters. In multivariate analysis, FM was significantly and negatively correlated with total vBMD, cortical and trabecular thickness.

CONCLUSIONS

These data suggest that FM is negatively associated with bone quality in PD patients, supporting a relation between body composition and bone that is independent from other dialysis-associated complications. The relative contribution of the different fat deposits (visceral versus subcutaneous) needs to be assessed in future studies.

Bone-Fat Interaction

Marrow adipose tissue (MAT) is a recently identified endocrine organ capable of modulating a host of responses. Given its intimate proximity to the bone microenvironment, the impact marrow adipocytes exert on bone has attracted much interest and scientific inquiry. Although many questions and controversies remain about marrow adipocytes, multiple conditions/disease states in which alterations occur have provided clues about their function. The consensus is that MAT is associated inversely with bone density and quality. While further investigation is warranted, MAT has clearly been demonstrated as an active dynamic depot that contributes to bone turnover and overall metabolic homeostasis.

Body Composition, Nutritional Profile and Muscular Fitness Affect Bone Health in a Sample of Schoolchildren from Colombia: The Fuprecol Study

The objective of the present study is to investigate the relationships between body composition, nutritional profile, muscular fitness (MF) and bone health in a sample of children and adolescents from Colombia. Participants included 1118 children and adolescents (54.6% girls). Calcaneal broadband ultrasound attenuation (c-BUA) was obtained as a marker of bone health. Body composition (fat mass and lean mass) was assessed using bioelectrical impedance analysis. Furthermore height, weight, waist circumference and Tanner stage were measured and body mass index (BMI) was calculated. Standing long-jump (SLJ) and isometric handgrip dynamometry were used respectively as indicators of lower and upper body muscular fitness. A muscular index score was also computed by summing up the standardised values of both SLJ and handgrip strength. Dietary intake and degree of adherence to the Mediterranean diet were assessed by a 7-day recall questionnaire for food frequency and the Kidmed questionnaire. Poor bone health was considered using a z-score cut off of ≤-1.5 standard deviation. Once the results were adjusted for age and Tanner stage, the predisposing factors of having a c-BUA z-score ≤-1.5 standard deviation included being underweight or obese, having an unhealthy lean mass, having an unhealthy fat mass, SLJ performance, handgrip performance, and unhealthy muscular index score. In conclusion, body composition (fat mass and lean body mass) and MF both influenced bone health in a sample of children and adolescents from Colombia. Thus promoting strength adaptation and preservation in Colombian youth will help to improve bone health, an important protective factor against osteoporosis in later life.

Associations Between Body Composition and Bone Health in Children and Adolescents: A Systematic Review

More clarification on the associations between children's and adolescents' lean and fat mass (LM and FM) on the one hand and their bone health on the other hand is needed, given the rising prevalence of overweight and obesity in this population. This systematic literature review aimed to describe the current evidence on these associations. Data sources were Medline/PubMed, EMBASE, CINAHL and The Cochrane Library (up to November 2014). Search items included LM, FM, children and adolescents (0-18 years), bone health measured with dual-energy X-ray absorptiometry and peripheral quantitative computed tomography (pQCT) and search items concerning study design: observational and longitudinal studies. The study populations were healthy children and adolescents including obese children. Children with other diseases and clinical series of study subjects were excluded. Based on the studies included in this review (n = 19), there is a consensus that the contribution of LM to the variance of the different bone parameters is larger than the contribution of FM and that an increase in LM is associated with an increase in bone parameters. Most of the studies indicated that the increase in bone parameters seen in overweight and obese children and adolescents is due to an increase in LM and not to greater FM. The results on the association between body fat and bone parameters were contradictory and depended on children's age and sex. Still more data from studies with a longitudinal study design using (high resolution) pQCT and a representative sample are needed to get further insight in the associations between body fat and bone parameters in children, specifically concerning differences in sex, skeletal site and fat depots.

Methodological considerations when studying the skeletal response to glucose intolerance using the diet-induced obesity model

The prevalence of obesity and type 2 diabetes mellitus (T2DM) continues to rise, and as a result, research aimed at understanding the molecular basis for the co-morbidities has become an area of much scientific interest. Among the more recently recognized chronic complications of T2DM is the increased risk of fracture, especially hip fracture, that has been reported independent of bone mineral density (BMD). A widely used animal model to study how the development and progression of impaired glucose tolerance affect the skeleton has been the diet-induce obesity (DIO) model. As the name implies, this model employs the use of a version of high-fat diets to induce obesity and the subsequent metabolic perturbations that occur with T2DM. Although the model offers a number of advantages, the literature reveals some inconsistent results. Upon further review, discrepancies in the choice of the experimental high-fat diets and the control diets have become a point of major concern. The variability between diets and study design has made it difficult to compare data and results across studies. Therefore, this review aims to provide guidelines that should be employed when designing studies using DIO models of T2DM.

Vitamin D deficiency is associated with prediabetes in obese Swedish children

AIM

Low vitamin D levels have been associated with obesity and living in areas that lack sunshine, such as northern Europe. The aim of this study was to investigate the vitamin D status of a group of obese children in Sweden and to investigate the associations between vitamin D status and markers of glucose metabolism and metabolic risk markers.

METHODS

This was a prospective cross-sectional study of 202 obese children between 4.5 and 17.9 years of age who had been referred to the National Childhood Obesity Centre at Karolinska University Hospital, Stockholm. We examined age, gender, 25-hydroxyvitamin D (25(OH)D), f-glucose, f-insulin and metabolic risk markers. Vitamin D deficiency was defined as less than 30 25(OH)D nmol/L. Children with and without a vitamin D deficiency were compared.

RESULTS

Just over a third (33.2%) of our study population had vitamin D levels <30 nmol/L 25(OH)D. A significant interaction effect was found between age and 25(OH)D. An association was also found between low 25(OH)D levels and impaired fasting glycaemia (IFG) independent of age and season.

CONCLUSION

Low vitamin D levels were common among obese adolescents living in Sweden and were strongly associated with age and associated with a higher risk of IFG.

Peripheral quantitative computed tomography (pQCT) for the assessment of bone strength in most of bone affecting conditions in developmental age: a review

Peripheral quantitative computed tomography provides an automatical scan analysis of trabecular and cortical bone compartments, calculating not only their bone mineral density (BMD), but also bone geometrical parameters, such as marrow and cortical Cross-Sectional Area (CSA), Cortical Thickness (CoTh), both periosteal and endosteal circumference, as well as biomechanical parameters like Cross-Sectional Moment of Inertia (CSMI), a measure of bending, polar moment of inertia, indicating bone strength in torsion, and Strength Strain Index (SSI). Also CSA of muscle and fat can be extracted. Muscles, which are thought to stimulate bones to adapt their geometry and mineral content, are determinant to preserve or increase bone strength; thus, pQCT provides an evaluation of the functional 'muscle-bone unit', defined as BMC/muscle CSA ratio. This functional approach to bone densitometry can establish if bone strength is normally adapted to the muscle force, and if muscle force is adequate for body size, providing more detailed insights to targeted strategies for the prevention and treatment of bone fragility. The present paper offers an extensive review of technical features of pQCT and its possible clinical application in the diagnostic of bone status as well as in the monitoring of the skeleton's health follow-up.

Influence of body weight on bone mass, architecture and turnover

Weight-dependent loading of the skeleton plays an important role in establishing and maintaining bone mass and strength. This review focuses on mechanical signaling induced by body weight as an essential mechanism for maintaining bone health. In addition, the skeletal effects of deviation from normal weight are discussed. The magnitude of mechanical strain experienced by bone during normal activities is remarkably similar among vertebrates, regardless of size, supporting the existence of a conserved regulatory mechanism, or mechanostat, that senses mechanical strain. The mechanostat functions as an adaptive mechanism to optimize bone mass and architecture based on prevailing mechanical strain. Changes in weight, due to altered mass, weightlessness (spaceflight), and hypergravity (modeled by centrifugation), induce an adaptive skeletal response. However, the precise mechanisms governing the skeletal response are incompletely understood. Furthermore, establishing whether the adaptive response maintains the mechanical competence of the skeleton has proven difficult, necessitating the development of surrogate measures of bone quality. The mechanostat is influenced by regulatory inputs to facilitate non-mechanical functions of the skeleton, such as mineral homeostasis, as well as hormones and energy/nutrient availability that support bone metabolism. Although the skeleton is very capable of adapting to changes in weight, the mechanostat has limits. At the limits, extreme deviations from normal weight and body composition are associated with impaired optimization of bone strength to prevailing body size.

Longitudinal associations between bone and adipose tissue biochemical markers with bone mineralization in boys during puberty

Background

We investigated longitudinal relationships between the biochemical markers of bone and adipose tissue with bone mineral content (BMC), bone mineral density (BMD), moderate-to-vigorous physical activity (MVPA) and sedentary time (SED) in pubertal boys.

Methods

Ninety-six boys (11.9 ± 0.6 years old) were measured at baseline, after 12 and 24 months. Body composition (fat mass [FM], lean body mass [LBM]), and whole body (WB), lumbar spine (LS) and femoral neck (FN) BMD and BMC were assessed. Additionally, serum leptin, adiponectin, osteocalcin (OC) and C-terminal telopeptide of type I collagen (CTX) were measured.

Results

OC had a strong longitudinal inverse effect on changes in WB_BMD (p < 0.001) and LS_BMD (p = 0.021), while CTX had an inverse effect only on changes in FN_BMD (p = 0.011). Leptin had an inverse effect on changes in WB_BMC/WB_BMD (p = 0.001), FN_BMD (p = 0.002) and LS_BMD (p = 0.001). MVPA showed a longitudinal inverse effect on changes in leptin (p = 0.030), however no longitudinal effect of SED to biochemical markers of bone and adipose tissue was found.

Conclusions

Bone metabolism markers have negative effect on bone mineral accrual during puberty. Increases in MVPA affect leptin, suggesting a positive link of MVPA through leptin metabolism on increases in bone mineralization during puberty.

Associations between adiposity, hormones, and gains in height, whole-body height-adjusted bone size, and size-adjusted bone mineral content in 8- to 11-year-old children

We examined fat-independent associations of hormones with height and whole-body bone size and mineral content in 633 school children. IGF-1 and osteocalcin predict growth in height, while fat, osteocalcin, and in girls also, IGF-1 predict growth in bone size. Leptin and ghrelin are inversely associated with bone size in girls.

INTRODUCTION

Obesity causes larger bone size and bone mass, but the role of hormones in this up-regulation of bone in obesity is not well elucidated. We examined longitudinal associations between baseline body fat mass (FM), and fat-independent fasting levels of ghrelin, adiponectin, leptin, insulin, insulin-like growth factor-I (IGF-1), osteocalcin, and intact parathyroid hormone, and subsequent changes in height and in whole-body height-adjusted bone area "BAheight" and size-adjusted bone mineral content "BMCsize" in 8- to 11-year-olds.

METHODS

Analyses were carried out separately for boys (n = 325) and girls (n = 308) including data from baseline, 3 and 6 months from OPUS School Meal Study.

RESULTS

In both sexes: gain in BAheight was positively associated with baseline FM (≥2.05 cm(2)/kg, both p ≤ 0.003). Furthermore, gain in height was positively associated with baseline IGF-1 (≥0.02 cm/ng/ml, p = 0.001) and osteocalcin (≥0.13 cm/ng/ml, p ≤ 0.009); and gain in BAheight was positively associated with baseline osteocalcin (≥0.35 cm(2)/ng/ml, p ≤ 0.019). In girls only, gain in BAheight was also positively associated with baseline IGF-1 (0.06 cm(2)/ng/ml, p = 0.017) and inversely associated with both baseline ghrelin (-0.01 cm(2)/pg/ml, p = 0.001) and leptin (-1.21 cm(2)/μg/ml, p = 0.005). In boys, gain in BMCsize was positively associated with osteocalcin (0.18 g/ng/ml, p = 0.030).

CONCLUSIONS

This large longitudinal study suggests that in 8- to 11-year-old children, IGF-1 and osteocalcin predict growth in height, while FM, osteocalcin, and in girls also, IGF-1 predict growth in BAheight. Fat-independent inverse associations of leptin and ghrelin with BAheight in girls' are contrary to proposed growth-stimulating effects of leptin. Osteocalcin in boys predicts gain in BMCsize.

Skeletal muscle and pediatric bone development

PURPOSE OF REVIEW

The purpose of this review is to summarize the recent clinical findings surrounding the muscle-bone relationships in children, while considering muscle adiposity, endocrine factors, and lifestyle influences (i.e., diet and exercise) involved in pediatric musculoskeletal development.

RECENT FINDINGS

Positive relationships between cortical bone geometry and muscle mass, size and function have been reported. Prospective studies in particular have helped clarify some of the inconsistent relationships between muscle and cortical bone volumetric density. Muscle fat is associated with impaired glucose handling and muscular functionality, which may in turn have a downstream effect on cortical bone growth during adolescence. Lifestyle factors such as healthful diets and higher impact physical activities can promote optimal skeletal development by improving the muscular phenotype and endocrine profile.

SUMMARY

Muscle and bone are two intricately-related tissue types; however, factors such as sex, maturation, study design, and outcome measures studied can modify this relationship. Further research is warranted to understand the impact of muscle adiposity on cardiometabolic health, muscle function and, subsequently, pediatric musculoskeletal development and fracture risk. Following age-specific diet and physical activity recommendations should be a major focus in obtaining optimal muscle and bone development throughout maturation.

Longitudinal changes in lean mass predict pQCT measures of tibial geometry and mineralisation at 6-7 years

BACKGROUND

Studies in childhood suggest that both body composition and early postnatal growth are associated with bone mineral density (BMD). However, little is known of the relationships between longitudinal changes in fat (FM) and lean mass (LM) and bone development in pre-pubertal children. We therefore investigated these associations in a population-based mother-offspring cohort, the Southampton Women's Survey.

METHODS

Total FM and LM were assessed at birth and 6-7 years of age by dual-energy x-ray absorptiometry (DXA). At 6-7 years, total cross-sectional area (CSA) and trabecular volumetric BMD (vBMD) at the 4% site (metaphysis) of the tibia was assessed using peripheral quantitative computed tomography [pQCT (Stratec XCT-2000)]. Total CSA, cortical CSA, cortical vBMD and strength-strain index (SSI) were measured at the 38% site (diaphysis). FM, LM and bone parameters were adjusted for age and sex and standardised to create within-cohort z-scores. Change in LM (ΔLM) or FM (ΔFM) was represented by change in z-score from birth to 7 years old and conditioned on the birth measurement. Linear regression was used to explore the associations between ΔLM or ΔFM and standardised pQCT outcomes, before and after mutual adjustment and for linear growth. The β-coefficient represents SD change in outcome per unit SD change in predictor.

RESULTS

DXA at birth, in addition to both DXA and pQCT scans at 6-7 years, were available for 200 children (48.5% male). ΔLM adjusted for ΔFM was positively associated with tibial total CSA at both the 4% (β=0.57SD/SD, p<0.001) and 38% sites (β=0.53SD/SD, p<0.001), cortical CSA (β=0.48SD/SD, p<0.001) and trabecular vBMD (β=0.30SD/SD, p<0.001), but not with cortical vBMD. These relationships persisted after adjustment for linear growth. In contrast, ΔFM adjusted for ΔLM was only associated with 38% total and cortical CSA, which became non-significant after adjustment for linear growth.

CONCLUSION

In this study, gain in childhood LM was positively associated with bone size and trabecular vBMD at 6-7 years of age. In contrast, no relationships between change in FM and bone were observed, suggesting that muscle growth, rather than accrual of fat mass, may be a more important determinant of childhood bone development.

Physical activity and bone health in schoolchildren: the mediating role of fitness and body fat

BACKGROUND

The relationship between physical activity (PA) and bone health is well known, although the role of percent body fat (%BF) and fitness as confounders or mediators in this relationship remains uncertain.

OBJECTIVE

To examine whether the association between PA and bone mineral content (BMC) is mediated by %BF and cardiorespiratory fitness (CRF).

METHODS

In this cross sectional study, BMC, total %BF (by DXA), vigorous PA (VPA), CRF, age and height were measured in 132 schoolchildren (62 boys, aged 8-11 years). ANCOVA was used to test differences in BMC by %BF, CRF and VPA, controlling for different sets of confounders. Simple mediation analyses and serial multiple mediation analyses were fitted to examine whether the relationship between PA and BMC is mediated by %BF and fitness.

RESULTS

Children with high %BF had higher total body BMC than their peers after controlling for all sets of confounders. Children with good CRF or VPA had significantly less total body BMC after controlling for age and sex but in children with good CRF this inverse relation disappeared after adjusting by %BF. %BF and CRF both act as a full mediator in the association between VPA and BMC, after inclusion of the potential confounders in the models.

CONCLUSION

Fitness and %BF seem to have a mediator role on the relationship between physical activity and bone mass.

Leptin may play a role in bone microstructural alterations in obese children

CONTEXT

Bone mass is low and fracture risk is higher in obese children. Hormonal changes in relation to skeletal microstructure and biomechanics have not been studied in obese children.

OBJECTIVE

The objective of the study was to ascertain the relationships of obesity-related changes in hormones with skeletal microstructure and biomechanics.

DESIGN

High resolution peripheral quantitative computed tomography (HR-pQCT) was used to compare three-dimensional cortical and trabecular microstructure and biomechanics at load-bearing and nonload bearing sites in obese and lean children. The relationship between leptin, adiponectin, testosterone, estrogen, osteocalcin and sclerostin and skeletal microstructure was also determined.

SETTING

The study was conducted at a tertiary pediatric endocrine unit in the United Kingdom.

PARTICIPANTS

Obese and lean children were matched by gender and pubertal stage.

RESULTS

Radial cortical porosity (mean difference -0.01 [95% CI: -0.02, -0.004], P = .003) and cortical pore diameter (mean difference -0.005 mm [95% CI: -0.009, -0.001], P = .011) were lower in obese children. Tibial trabecular thickness was lower (mean difference -0.009 mm [95% CI: -0.014, -0.004], P = .003), and trabecular number was higher (mean difference 0.23 mm(-1) [95% CI: 0.08, 0.38], P = .004) in obese children. At the radius, fat mass percentage negatively correlated with cortical porosity (r = -0.57, P < .001) and pore diameter (r = -0.38, P = .02) and negatively correlated with trabecular thickness (r = -0.62, P < .001) and trabecular von Mises stress (r = -0.39, P = .019) at the tibia. No difference was observed in the other biomechanical parameters of the radius and tibia. Leptin was higher in obese children (805.3 ± 440.6 pg/ml vs 98.1 ± 75.4 pg/ml, P < .001) and was inversely related to radial cortical porosity (r = 0.60, 95% CI: [-0.80, -0.30], P < .001), radial cortical pore diameter (r = 0.51, 95% CI [-0.75, -0.16], P = .002), tibial trabecular thickness (r = 0.55, 95% CI: [-0.78, -0.21], P = .001) and tibial trabecular von Mises stress (r = -0.39, 95% CI: -0.65, 0.04, P = .02).

CONCLUSION

Childhood obesity alters radial and tibial microstructure. Leptin may direct these changes. Despite this, the biomechanical properties of the radius and tibia do not adapt sufficiently in obese children to withstand the increased loading potential from a fall. This may explain the higher incidence of fracture in obese children.

Altered lower extremity fracture characteristics in obese pediatric trauma patients

OBJECTIVE

To determine whether there are differences in fracture patterns and femur fracture treatment choices in obese versus nonobese pediatric trauma patients.

DESIGN

Prognostic study, retrospective chart review.

SETTING

Two level I pediatric trauma centers.

PATIENTS

The trauma registries of 2 pediatric hospitals were queried for patients with lower extremity long-bone fractures resulting from blunt trauma. 2858 alerts were examined, and 397 patients had lower extremity fractures. Three hundred thirty-one patients with a total of 394 femur or tibia fractures met the inclusion criteria, and 70 patients (21%) were obese.

MAIN OUTCOME MEASUREMENTS

Weight for age >95th percentile was defined as obese. Radiographs were reviewed, and fractures were classified according the OTA/AO pediatric fracture classification system. Fracture patterns (OTA subsegment), severity, and choice of intervention for femur fractures were the primary outcomes.

RESULTS

Overall, obese patients were twice as likely [risk ratio (RR), 2.20; 95% confidence interval (CI), 1.25-3.89] to have fractures involving the physis. Physeal fracture risk was greater for femur fractures (RR, 3.25; 95% CI, 1.35-7.78) than tibia fractures (RR, 1.58; 95% CI, 0.76-3.26). Severity did not differ between groups. Obese patients with femur fractures were more likely to be treated with locked nails.

CONCLUSIONS

Obese pediatric trauma patients are more likely to sustain fractures involving the physis than nonobese patients. This could be related to intrinsic changes to the physis related to obesity or altered biomechanical forces. This is consistent with the observed relationships between obesity and other conditions affecting the physis including Blount disease and slipped capital femoral epiphysis.

LEVEL OF EVIDENCE

Prognostic Level II. See Instructions for Authors for a complete description of levels of evidence.

Body composition during childhood and adolescence: relations to bone strength and microstructure

CONTEXT

Numerous studies have examined the association of body composition with bone development in children and adolescents, but none have used micro-finite element (μFE) analysis of high-resolution peripheral quantitative computed tomography images to assess bone strength.

OBJECTIVE

This study sought to examine the relations of appendicular lean mass (ALM) and total body fat mass (TBFM) to bone strength (failure load) at the distal radius and tibia.

DESIGN, PARTICIPANTS, AND SETTING

This was a cross-sectional study of 198 healthy 8- to <15-year-old boys (n = 109) and girls (n = 89) performed in a Clinical Research Unit.

RESULTS

After adjusting for bone age, height, fracture history, ALM, and TBFM, multiple linear regression analyses in boys and girls, separately, showed robust positive associations between ALM and failure loads at both the distal radius (boys: β = 0.92, P < .001; girls: β = 0.66, P = .001) and tibia (boys: β = 0.96, P < .001; girls: β = 0.66, P < .001). By contrast, in both boys and girls the relationship between TBFM and failure load at the distal radius was virtually nonexistent (boys: β = -0.07; P = .284; girls: β = -0.03; P = .729). At the distal tibia, positive, albeit weak, associations were observed between TBFM and failure load in both boys (β = 0.09, P = .075) and girls (β = 0.17, P = .033).

CONCLUSIONS

Our data highlight the importance of lean mass for optimizing bone strength during growth, and suggest that fat mass may have differential relations to bone strength at weight-bearing vs non-weight-bearing sites in children and adolescents. These observations suggest that the strength of the distal radius does not commensurately increase with excess gains in adiposity during growth, which may result in a mismatch between bone strength and the load experienced by the distal forearm during a fall. These findings may explain, in part, why obese children are over-represented among distal forearm fracture cases.

Metabolic, cardiovascular and anthropometric differences between prepubertal girls and boys

OBJECTIVE

We aimed to assess possible differences in insulin sensitivity and other metabolic, anthropometric and cardiovascular parameters between boys and girls prior to puberty.

METHODS

We studied 85 healthy prepubertal children (33 girls and 52 boys) aged 8.7 ± 1.9 years (range 4.0-11.9 years), born 38-40 weeks gestation, and of birth weight appropriate-for-gestational-age. Insulin sensitivity was measured using frequently sampled intravenous glucose tests and Bergman's minimal model. Other clinical assessments included anthropometric measures, fasting lipid and hormonal profiles, body composition from whole-body dual-energy X-ray absorptiometry and 24-h ambulatory blood pressure monitoring.

RESULTS

Prepubertal girls and boys were of similar parent-adjusted height SDS (P = 0.26), but girls had considerably more body fat (P < 0.0001), less fat-free mass (P = 0.0002) and greater abdominal adiposity (P < 0.0001). These differences in body composition were independent of adrenal androgens. Insulin sensitivity was 18% lower in girls (11.0 vs 13.4 × 10(-4) /min (mU/l); P = 0.028), but this difference disappeared with adjustment for adiposity and DHEAS concentrations. There were, however, some apparent sex differences in cardiovascular parameters, with girls displaying increased heart rate and reduced blood pressure dipping. Girls also had higher triglyceride concentrations (+23%; P = 0.036).

CONCLUSION

There are a number of anthropometric, metabolic and cardiovascular differences between sexes prior to the appearance of external signs of puberty. Although differences in insulin sensitivity were eliminated when adiposity and DHEAS concentrations were accounted for, there were independent differences in body composition and cardiovascular parameters. Thus, gender, adrenarche and adiposity should be accounted for in studies examining metabolic and cardiovascular outcomes prior to puberty.

Quantitative computer tomography in children and adolescents: the 2013 ISCD Pediatric Official Positions

In 2007, International Society of Clinical Densitometry Pediatric Positions Task Forces reviewed the evidence for the clinical application of peripheral quantitative computed tomography (pQCT) in children and adolescents. At that time, numerous limitations regarding the clinical application of pQCT were identified, although its use as a research modality for investigation of bone strength was highlighted. The present report provides an updated review of evidence for the clinical application of pQCT, as well as additional reviews of whole body QCT scans of the central and peripheral skeletons, and high-resolution pQCT in children. Although these techniques remain in the domain of research, this report summarizes the recent literature and evidence of the clinical applicability and offers general recommendations regarding the use of these modalities in pediatric bone health assessment.

Growth from birth to adulthood and bone phenotype in early old age: a British birth cohort study

There is growing evidence that early growth influences bone mass in later life but most studies are limited to birth weight and/or early infant growth and dual-energy X-ray absorptiometry (DXA) measurements. In a British birth cohort study with prospective measures of lifetime height and weight, we investigated the growth trajectory in relation to bone in males (M) and females (F) at 60 to 64 years old. Outcomes were DXA measures of hip and spine areal bone density (aBMD) (n = 1658) and pQCT measures of distal and diaphyseal radius cross-sectional area (CSA), strength, and volumetric bone density (vBMD) (n = 1350 of the 1658). Regression models examined percentage change in bone parameters with standardized measures of birth weight, height, and weight. A series of conditional growth models were fitted for height and weight gain (using intervals: birth-2, 2-4, 4-7, 7-15, 15-20, 20-36, and 36-64 years) and height gain (using intervals: 2-4, 4-7, 7-15, and 15-36 years). Birth weight was positively related to bone CSA (M: 1.4%; 95% confidence interval [CI], 0.3%-2.5%; F: 1.3%; 95% CI, 0.3%-2.4% per 1 SD increase in birth weight for diaphyseal CSA) and strength (M: 1.8%; 95% CI, 0.3-3.4; F: 2.0%; 95% CI, 0.5-3.5). No positive associations were found with trabecular, total, or cortical vBMD. One SD change in prepubertal and postpubertal height and weight velocities were associated with between 2% and 5% greater bone CSA and strength. Height gain in later years was negatively associated with trabecular vBMD. Weight gain velocity during the adult years was positively associated with up to 4% greater trabecular and total BMD, and 4% greater aBMD at hip and spine. In a cohort born in the early post-war period, higher birth weight, gaining weight and height faster than others, particularly through the prepubertal and postpubertal periods, was positively related to bone strength, mostly through greater bone CSA, at 60 to 64 years.

Immature mice are more susceptible to the detrimental effects of high fat diet on cancellous bone in the distal femur

With the increasing prevalence of obesity among children and adolescents, it is imperative to understand the implications of early diet-induced obesity on bone health. We hypothesized that cancellous bone of skeletally immature mice is more susceptible to the detrimental effects of a high fat diet (HFD) than mature mice, and that removing excess dietary fat will reverse these adverse effects. Skeletally immature (5weeks old) and mature (20weeks old) male C57BL/6J mice were fed either a HFD (60% kcal fat) or low fat diet (LFD; 10% kcal fat) for 12weeks, at which point, the trabecular bone structure in the distal femoral metaphysis and third lumbar vertebrae were evaluated by micro-computed tomography. The compressive strength of the vertebrae was also measured. In general, the HFD led to deteriorations in cancellous bone structure and compressive biomechanical properties in both age groups. The HFD-fed immature mice had a greater decrease in trabecular bone volume fraction (BVF) in the femoral metaphysis, compared to mature mice (p=0.017 by 2-way ANOVA). In the vertebrae, however, the HFD led to similar reductions in BVF and compressive strength in the two age groups. When mice on the HFD were switched to a LFD (HFD:LFD) for an additional 12weeks, the femoral metaphyseal BVF in immature mice showed no improvements, whereas the mature mice recovered their femoral metaphyseal BVF to that of age-matched lean controls. The vertebral BVF and compressive strength of HFD:LFD mouse bones, following diet correction, were equivalent to those of LFD:LFD mice in both age groups. These data suggest that femoral cancellous metaphyseal bone is more susceptible to the detrimental effects of HFD before skeletal maturity and is less able to recover after correcting the diet. Negative effects of HFD on vertebrae are less severe and can renormalize with LFD:LFD mice after diet correction, in both skeletally immature and mature animals.

Fetal and infant growth predict hip geometry at 6 y old: findings from the Southampton Women's Survey

BACKGROUND

We investigated relationships between early growth and proximal femoral geometry at age 6 y in a prospective population-based cohort, the Southampton Women's Survey.

METHODS

In 493 mother-offspring pairs, we assessed linear size using high-resolution ultrasound at 11, 19, and 34 wk gestation (femur length) and at birth and 1, 2, 3, 4, and 6 y (crown-heel length/height). SD scores were created and conditional regression modeling generated mutually independent growth variables. Children underwent hip dual-energy X-ray absorptiometry (DXA) at 6 y; hip structure analysis software yielded measures of geometry and strength.

RESULTS

There were strong associations between early linear growth and femoral neck section modulus (Z) at 6 y, with the strongest relationships observed for femur growth from 19 to 34 wk gestation (β = 0.26 cm(3)/SD, P < 0.0001), and for height growth from birth to 1 y (β = 0.25 cm(3)/SD, P < 0.0001) and 1 to 2 y (β = 0.33 cm(3)/SD, P < 0.0001), with progressively weaker relationships over years 3 (β = 0.23 cm(3)/SD, P = 0.0002) and 4 (β = 0.10 cm(3)/SD, P = 0.18).

CONCLUSION

These results demonstrate that growth before age 3 y predicts proximal femoral geometry at 6 y old. These data suggest critical periods in which there is capacity for long-term influence on the later skeletal growth trajectory.

Assessing early growth and adiposity: report from an EarlyNutrition Academy workshop

This report provides a summary of a workshop organised by the European Commission-funded EarlyNutrition Project and the EarlyNutrition Academy. Accurate and reliable methods to assess body composition are needed in research on prenatal and early post-natal influences of nutrition on later health because common surrogate measures of maternal and offspring adiposity (body fat content), such as body mass index (BMI), have relatively poor predictive power for the risk of later disease. The key goals of the workshop were to discuss approaches to assess growth and body composition from pregnancy to adolescence, to summarise conclusions and to prepare a framework for research in the EarlyNutrition Project. The participants concluded that there is a pressing need to harmonise the methodologies for assessing body composition, recognising that each has advantages and limitations. Essential core measurements across studies assessing early growth and body composition were identified, including weight, length, BMI, waist and mid-upper arm circumference, subscapular and triceps skinfold thicknesses, and bioelectrical impedance analysis. In research settings with access to more sophisticated technologies, additional methods could include dual-energy X-ray absorptiometry, peripheral quantitative computed tomography, ultrasound assessment of regional body fat, magnetic resonance imaging (MRI), air displacement plethysmography (ADP), and deuterium dilution. These provide richer data to answer research questions in greater depth but also increase costs. Where overall whole-body composition is the primary outcome measure, ADP or tracer dilution should be used whenever possible. Where regional distribution of body fat is of greater interest, an imaging technique such as MRI is preferred.

Fat mass increase in 7-year-old children: more bone area but lower bone mineral density

The main aims of this study were, to evaluate what effect a change in fat mass (FM) and lean body mass (LBM) has on bone parameters over 2 years' time, in 7-year-old school children and to see what effect fitness had on bone parameters in these children. A repeated-measures design study was conducted where children born in 1999 from six elementary schools in Reykjavik, Iceland were measured twice. All children attending second grade in these six schools were invited to participate. Three hundred twenty-one children were invited, 211 underwent dual-energy X-ray absorptiometry (DXA) scans at the age of seven, and 164 (78 %) of the 211 had DXA scans again 2 years later. Increase in both FM and LBM was associated with increased total body bone mineral content (BMC) and bone area (BA). An increase in FM was more strongly positively associated with BA while an increase in LBM was more strongly associated with an increase in BMC. An increase in FM was negatively associated with change in bone mineral density (BMD), but an increase in LBM was positively associated with change in BMD. Fitness was positively associated with bone parameters when weight, height and sex were accounted for. The present results suggest that an increase in fat mass over 2 years is associated with an increase in BA and BMC, but a decrease in BMD in the whole body. An increase in LBM accrual, on the other hand, is positively associated with all bone parameters in the body. Fitness is associated with both BMC and BMD but not BA.