Obesity during childhood and adolescence augments bone mass and bone dimensions

Patterns of linear growth and skeletal maturation from birth to 18 years of age in overweight young adults

OBJECTIVE

To estimate differences in skeletal maturity and stature from birth to age 18 years between individuals who are overweight vs normal weight in young adulthood.

PATIENTS AND METHODS

Weight, length and height, and relative skeletal age (skeletal-chronological age) were assessed annually from birth to age 18 years in 521 subjects (255 women) in the Fels Longitudinal Study who were overweight or obese (body mass index (BMI) >25 kg m(-2), n=131) or normal weight (n=390) in young adulthood (18-30 years). Generalized estimating equations were used to test for skeletal maturity and stature differences by young adult BMI status.

RESULTS

Differences in height increased during puberty, being significant for girls at ages 10 to 12 years, and for boys at ages 11 to 13 years (P-values<0.001), with overweight or obese adults being ∼3 cm taller at those ages than normal weight adults. These differences then diminished so that by age 18 years, overweight or obese adults were not significantly different in stature to their normal weight peers. Differences in skeletal maturity were similar, but more pervasive; overweight or obese adults were more skeletally advanced throughout childhood. Skeletal maturity differences peaked at chronological age 12 in boys and 14 in girls (P-values<0.001), with overweight or obese adults being ∼1 year more advanced than normal weight adults.

CONCLUSIONS

This descriptive study is the first to track advanced skeletal maturity and linear growth acceleration throughout infancy, childhood and adolescence in individuals who become overweight, showing that differences occur primarily around the time of the pubertal growth spurt. Increased BMI in children on a path to becoming overweight adults precedes an advancement in skeletal development and subsequently tall stature during puberty. Further work is required to assess the predictive value of accelerated pubertal height growth for assessing obesity risk in a variety of populations.

Hip bone strength indices in overweight and control adolescent boys

The influence of being overweight on bone strength in adolescents remains controversial. The aim of this study was to compare hip bone strength indices in overweight and control adolescent boys using hip structure analysis (HSA). This study included 25 overweight adolescent boys [body mass index (BMI) >25 kg/m(2)] and 31 maturation-matched controls (BMI <25 kg/m(2)). Body composition and bone mineral density were assessed by dual-energy X-ray absorptiometry (DXA). To evaluate hip bone strength, DXA scans were analyzed at femoral neck, intertrochanteric, and femoral shaft by the HSA program. Cross-sectional area (CSA), an index of axial compression strength, section modulus (Z), an index of bending strength, cross-sectional moment of inertia (CSMI), cortical thickness (CT), and buckling ratio (BR) were measured from bone mass profiles. Body weight, lean mass, fat mass, and BMI were higher in overweight boys compared to controls (P < 0.001). CSA, CSMI, and Z of the three sites (femoral neck, intertrochanteric, and femoral shaft) were higher in overweight boys compared to controls (P < 0.01). BR was not significantly different between the two groups at the three sites. After adjustment for either body weight, BMI, or fat mass, using a one-way analysis of covariance, there were no differences between the two groups regarding the HSA variables (CSA, Z, CSMI, CT, and BR). After adjusting for lean mass, overweight boys displayed higher values of femoral shaft CSA, CSMI, and Z in comparison to controls (P < 0.05). In conclusion, this study suggests that overweight adolescent boys have greater indices of bone axial and bending strength in comparison to controls at the femoral neck, the intertrochanteric, and the femoral shaft.

Skeletal muscle fat content is inversely associated with bone strength in young girls

Childhood obesity is an established risk factor for metabolic disease. The influence of obesity on bone development, however, remains controversial and may depend on the pattern of regional fat deposition. Therefore, we examined the associations of regional fat compartments of the calf and thigh with weight-bearing bone parameters in girls. Data from 444 girls aged 9 to 12 years from the Jump-In: Building Better Bones study were analyzed. Peripheral quantitative computed tomography (pQCT) was used to assess bone parameters at metaphyseal and diaphyseal sites of the femur and tibia along with subcutaneous adipose tissue (SAT, mm(2) ) and muscle density (mg/cm(3) ), an index of skeletal muscle fat content. As expected, SAT was positively correlated with total-body fat mass (r = 0.87-0.89, p < .001), and muscle density was inversely correlated with total-body fat mass (r = -0.24 to -0.28, p < .001). Multiple linear regression analyses with SAT, muscle density, muscle cross-sectional area, bone length, maturity, and ethnicity as independent variables showed significant associations between muscle density and indices of bone strength at metaphyseal (β = 0.13-0.19, p < .001) and diaphyseal (β = 0.06-0.09, p < .01) regions of the femur and tibia. Associations between SAT and indices of bone strength were nonsignificant at all skeletal sites (β = 0.03-0.05, p > .05), except the distal tibia (β = 0.09, p = .03). In conclusion, skeletal muscle fat content of the calf and thigh is inversely associated with weight-bearing bone strength in young girls.

Correlation of insulin sensitivity with bone mineral status in obese adolescents with nonalcoholic fatty liver disease

AIM

The aim of this study was to investigate the relationships between bone mineral density (BMD) vs insulin resistance and metabolic risk factors in obese adolescents with nonalcoholic fatty liver disease (NAFLD).

PATIENTS AND METHODS

Eighty-two obese adolescents [45 girls and 37 boys, mean age: 12·3 ± 1·7 years, mean body mass index-standard deviation score (BMI-SDS): 1·9 ± 0·2] and 30 control subjects (15 girls and 15 boys, mean age: 12·3 ± 1·45 years, mean BMI-SDS: 0·5 ± 0·7) were enrolled the study. The obese subjects were divided into two groups based on the presence or absence of liver steatosis with high transaminases (NAFLD group and non-NAFLD group). Insulin resistance was evaluated by homeostasis model assessment (HOMA-IR) from fasting samples. BMD was determined by dual-energy X-ray absorptiometry.

RESULTS

Fasting insulin levels in the NAFLD group were significantly higher than in the non-NAFLD obese (32·3 ± 24·0 vs 11·02 ± 2·95 mU/l, P < 0·001) and control groups (8·4 ± 2·4 mU/l, P< 0·001). The NAFLD group had higher values of HOMA-IR than the non-NAFLD obese (7·3 ± 0·1 vs 2·3 ± 0·7, P < 0·001) and control groups (1·8 ± 0·5, P < 0·001). BMD-SDS measurements were lower in the NAFLD group than in the non-NAFLD (0·56 ± 0·3 vs 1·02 ± 0·9, P < 0·001) and control groups (0·56 ± 0·3 vs 1·37 ± 1·04, P < 0·001). BMD-SDS was positively correlated with BMI-SDS (r = 0·530, P = 0·004) and negatively correlated with HOMA-IR (r = -0·628, P = 0·017) in the NAFLD obese group.

CONCLUSION

This study reports the association between BMD-SDS and insulin resistance in obese adolescents both with and without NAFLD, although the NAFLD group had a lower BMD-SDS than the non-NAFLD group. We suggest that NAFLD has a detrimental effect on bone health in adolescents, and it is correlated with increased insulin resistance.

Longitudinal changes in calcaneal quantitative ultrasound measures during childhood

This longitudinal study examined how calcaneal quantitative ultrasound (QUS) measures change during childhood while taking into account skeletal maturation, body mass index (BMI), and physical activity. The study reported sex differences in QUS growth curves and an inverse relationship between BMI and speed of sound (SOS) measures.

INTRODUCTION

The aim of this study was to examine how calcaneal QUS parameters change over time during childhood and to determine what factors influence these changes.

METHODS

The study sample consisted of a total of 192 Caucasian children participating in the Fels Longitudinal Study. A total of 548 calcaneal broadband ultrasound attenuation (BUA) and SOS observations were obtained between the ages of 7.6 and 18 years. The best fitting growth curves were determined using statistical methods for linear mixed effect models.

RESULTS

There are significant sex differences in the pattern of change in QUS parameters (p < 0.05). The relationship between QUS measures and skeletal age is best described by a cubic growth curve in boys and a linear pattern among girls. Boys experience their most rapid growth in BUA and SOS in early and late adolescence, while girls experience constant growth throughout childhood. Adiposity levels were significantly associated with the changes in SOS among boys (p < 0.001) and girls (p < 0.01), indicating that children with higher BMI are likely to have lower SOS over time compared to children with lower BMI. For girls, physical activity levels showed positive associations with changes in QUS measures (p < 0.05).

CONCLUSION

This study documents significant sex differences in the pattern of change in QUS measures over childhood and adolescence. Our study also shows significant influences of adiposity and physical activity on the pattern of change in QUS measures during childhood.

Association between upper extremity fractures and weight status in children

OBJECTIVES

Our objective was to determine the odds of having an increased weight status among children with upper extremity fracture (UEF) compared with 3 control groups without fractures.

METHODS

This is a secondary analysis of data from the Pediatric Risk of Admission (PRISA and PRISA II) data sets. Patients without chronic illness between the ages of 5 to 14 years were included in the following groups: (1) UEF study group, (2) upper extremity nonfracture injured control group, (3) minor-head-injured control group, and (4) noninjured probability control group. Weight for age/sex percentiles was used to evaluate weight status. The proportions of patients with weight for age/sex greater than the 50th, 85th, and 95th percentiles were determined. Logistic regression was used to generate odds ratios comparing the UEF group with each control group stratified by age.

RESULTS

This analysis included 308 patients in the 5- to 9-year age group and 207 patients in the 10- to 14-year age group. The odds of having a weight greater than the 50th percentile for age/sex were significantly increased among children with UEF aged 5 to 9 years compared with all control groups. There were no significant differences in the corresponding odds ratios for children with UEF aged 10 to 14 years compared with controls.

CONCLUSIONS

These findings may be related to differential injury mechanisms, mobility patterns, or underlying patient vulnerability to fracture based on weight status and bone qualities in prepubescent versus pubescent populations. Further investigation should explore fracture epidemiology and fracture risk in children stratified by age.

Changes in cortical bone response to high-fat diet from adolescence to adulthood in mice

Diabetic obesity is associated with increased fracture risk in adults and adolescents. We find in both adolescent and adult mice dramatically inferior mechanical properties and structural quality of cortical bone, in agreement with the human fracture data, although some aspects of the response to obesity appear to differ by age.

INTRODUCTION

The association of obesity with bone is complex and varies with age. Diabetic obese adolescents and adult humans have increased fracture risk. Prior studies have shown reduced mechanical properties as a result of high-fat diet (HFD) but do not fully address size-independent mechanical properties or structural quality, which are important to understand material behavior.

METHODS

Cortical bone from femurs and tibiae from two age groups of C57BL/6 mice fed either HFD or low-fat diet (LFD) were evaluated for structural and bone turnover changes (SEM and histomorphometry) and tested for bending strength, bending stiffness, and fracture toughness. Leptin, IGF-I, and non-enzymatic glycation measurements were also collected.

RESULTS

In both young and adult mice fed on HFD, femoral strength, stiffness, and toughness are all dramatically lower than controls. Inferior lamellar and osteocyte alignment also point to reduced structural quality in both age groups. Bone size was largely unaffected by HFD, although there was a shift from increasing bone size in obese adolescents to decreasing in adults. IGF-I levels were lower in young obese mice only.

CONCLUSIONS

While the response to obesity of murine cortical bone mass, bone formation, and hormonal changes appear to differ by age, the bone mechanical properties for young and adult groups are similar. In agreement with human fracture trends, adult mice may be similarly susceptible to bone fracture to the young group, although cortical bone in the two age groups responds to diabetic obesity differently.

Influence of age and morphological characteristics on whole body, lumbar spine, femoral neck and 1/3 radius bone mineral apparent density in a group of Lebanese adolescent boys

The purpose of this study was to analyse the relationships between age, morphological characteristics (weight, height, body mass index (BMI), fat and lean mass), daily calcium intake (DCI), physical activity and bone mineral apparent density (BMAD) of the whole body (WB), lumbar spine (L2-L4), femoral neck (FN) and 1/3 radius in a group of Lebanese adolescent boys. This study included 60 Lebanese adolescent (16.8 ± 2.1 years old) boys. Body composition and bone mineral density (BMD) were assessed by dual-energy X-ray absorptiometry (DXA). BMAD values of the WB, L2-L4, FN and 1/3 radius were calculated. Physical activity and DCI were assessed using questionnaires. Age was positively related to WB, L2-L4 and 1/3 radius BMD and BMAD. Weight, lean mass and BMI were positively related to WB, L2-L4, FN and 1/3 radius BMD. Moreover, weight, lean mass and BMI were positively associated with L2-L4 and FN BMAD but not with BMAD of the WB and the 1/3 radius, while fat mass percentage was negatively associated with WB BMAD. In conclusion, this study shows that weight, lean mass and BMI are positively associated with BMAD of the weight-bearing bones (L2-L4 and FN) but not with BMAD of the WB and the 1/3 radius in adolescent boys.

BMD-associated variation at the Osterix locus is correlated with childhood obesity in females

Recent genome wide association studies (GWAS) have revealed a number of genetic variants robustly associated with bone mineral density (BMD) and/or osteoporosis. Evidence from epidemiological and clinical studies has shown an association between BMD and BMI, presumably as a consequence of bone loading. We investigated the 23 previously published BMD GWAS-derived loci in the context of childhood obesity by leveraging our existing genome-wide genotyped European American cohort of 1106 obese children (BMI ≥ 95th percentile) and 5997 controls (BMI < 95th percentile). Evidence of association was only observed at one locus, namely Osterix (SP7), with the G allele of rs2016266 being significantly over-represented among childhood obesity cases (P = 2.85 × 10(-3)). When restricting these analyses to each gender, we observed strong association between rs2016266 and childhood obesity in females (477 cases and 2867 controls; P = 3.56 × 10(-4)), which survived adjustment for all tests applied. However, no evidence of association was observed among males. Interestingly, Osterix is the only GWAS locus uncovered to date that has also been previously implicated in the determination of BMD in childhood. In conclusion, these findings indicate that a well established variant at the Osterix locus associated with increased BMD is also associated with childhood obesity primarily in females.

Low vitamin D status among obese adolescents: prevalence and response to treatment

PURPOSE

To explore the prevalence of low vitamin D status among obese adolescents and to examine the effect of current management of low vitamin D status in these patients.

METHODS

A retrospective chart review of obese adolescents who had been screened for vitamin D status by serum total 25-hydroxyvitamin D (25(OH)D) level. Vitamin D deficiency was defined as 25(OH)D level of <20 ng/mL, vitamin D insufficiency as 25(OH)D level of 20-30 ng/mL, and vitamin D sufficiency as 25(OH)D level of >30 ng/mL. Adolescents with vitamin D deficiency were treated with 50,000 IU of vitamin D once a week for 6-8 weeks, whereas adolescents with vitamin D insufficiency were treated with 800 IU of vitamin D daily for 3 months. Repeat 25(OH)D was obtained after treatment.

RESULTS

The prevalence rate of low vitamin D status among 68 obese adolescents (53% females, 47% males, age: 17 ± 1 years, body mass index: 38 ± 1 kg/m(2), Hispanic: 45%, African American: 40%, Caucasian: 15%) was 100% in females and 91% in males. Mean (±SE) 25(OH)D level was significantly higher in summer (20 ± 8 ng/mL) than in spring (14 ± 4 ng/mL, p < .02), and significantly lower in winter (15 ± 7 ng/mL) than in fall (25 ± 15 ng/mL, p < .05). Although there was a significant (p < .00001) increase in mean 25(OH)D after the initial course of treatment with vitamin D, 25(OH)D levels normalized in only 28% of the participants. Repeat courses with the same dosage in the other 72% did not significantly change their low vitamin D status.

CONCLUSIONS

Increased surveillance and possibly higher vitamin D doses are warranted for obese adolescents whose total 25(OH)D levels do not normalize after the initial course of treatment.

Adolescent obesity, bone mass, and cardiometabolic risk factors

OBJECTIVE

To compare bone mass between overweight adolescents with and without cardiometabolic risk factors (CMR). Associations of bone mass with CMR and adiposity were also determined.

STUDY DESIGN

Adolescents (aged 14 to 18 years) who were overweight were classified as healthy (n = 55), having one CMR (1CMR; n = 46), or having two or more CMR (≥2CMR; n = 42). CMRs were measured with standard methods and defined according to pediatric definitions of metabolic syndrome. Total body bone mass, fat mass, and fat-free soft tissue mass were measured with dual-energy X-ray absorptiometry. Visceral adipose tissue and subcutaneous abdominal adipose tissue were assessed with magnetic resonance imaging.

RESULTS

After controlling for age, sex, race, height, and fat-free soft tissue mass, the healthy group had 5.4% and 6.3% greater bone mass than the 1CMR and ≥2CMR groups, respectively (both P values <.04). With multiple linear regression, adjusting for the same co-variates, visceral adipose tissue (β = -0.22), waist circumference (β = -0.23), homeostasis model assessment of insulin resistance (β = -0.23), and high-density lipoprotein cholesterol level (β = 0.22) were revealed to be associated with bone mass (all P values <.04). There was a trend toward a significant inverse association between bone mass and fasting glucose level (P = .056). No relations were found between bone mass and fat mass, subcutaneous abdominal adipose tissue, blood pressure, or triglyceride level.

CONCLUSION

Being overweight with metabolic abnormalities, particularly insulin resistance, low high-density lipoprotein cholesterol level, and visceral adiposity, may adversely influence adolescent bone mass.

Bone mineral content and density in overweight and control adolescent boys

The aim of this study was to compare bone mineral content (BMC) and areal bone mineral density (aBMD) in overweight and control adolescent boys. This study included 27 overweight (body mass index [BMI] > 25 kg/m²) adolescent (17.1 ± 2.1 yr old) boys and 29 maturation-matched (16.7 ± 2.0 yr old) controls (BMI< 25 kg/m²). Bone mineral area (BMA), BMC, and aBMD were assessed by dual-energy X-ray absorptiometry (DXA) at the whole body (WB), lumbar spine (L2-L4), total hip (TH), femoral neck (FN), and left forearm (ultra distal [UD], mid Radius, 1/3 Radius, and total Radius). Body composition (lean mass, fat mass, and fat mass percentage) was assessed also by DXA. The expressions WB BMC/height, WB aBMD/height, and WB BMAD were used to adjust for WB bone size. WB BMC, WB BMC/height, WB BMA, L2-L4 aBMD, TH aBMD, FN aBMD, and UD aBMD were higher in overweight boys compared with controls (p < 0.05). However, WB BMAD was lower in overweight boys compared with controls (p < 0.05). After adjustment for weight, lean mass, or BMI, using a one-way analysis of covariance, there were no differences between the 2 groups (overweight and controls) regarding bone characteristics (BMC, BMA, aBMD, BMC/height, aBMD/height, and BMAD of the WB and aBMD of the lumbar spine; the TH; the FN; and the forearm). In conclusion, this study shows that after adjusting for weight, lean mass, or BMI, there are no differences between overweight and control adolescent boys regarding aBMD values.

Gender differences in bone mineral density in obese children during pubertal development

OBJECTIVE

To investigate whether body mass index (BMI) and body composition can affect peak bone mass in a population of obese (OB) (BMI SDS>2.0) and normal weight (NORM) (BMI-SD score <2.0) pubertal subjects (Tanner stage T3 to T5).

PATIENTS AND METHODS

151 subjects (81 OB, age 14.5±2.4 yr) were analyzed using dual-X-ray absorbiometry technique to study Lumbar and whole body bone mineral density (BMD) (areal, normalized for height) and Z-score, lean mass (LM) and lean/fat ratio.

RESULTS

As a whole group, OB males did not show any significant difference in bone parameters vs NORM, while OB females showed higher bone density parameters (p<0.05). When grouped according to T, while OB males showed higher bone density at T3-4 stage (p<0.01), and lower at T5 (p<0.01) compared to NORM, OB females showed a tendency through increased BMD at T3-4 and T5 although statistically different only at T5. BMD was independently correlated to LM, lean/fat ratio, and testosterone in NORM males and, at lower level, in OB males, while to LM in NORM females and only to age in OB females.

CONCLUSION

Our data seem to confirm the possible negative influence of obesity on bone density in boys, a possible explanation could be an unfavorable body composition during sexual maturation that seems not to affect bone development in adolescents girls.

The accrual of bone mass during childhood and puberty

PURPOSE OF REVIEW

To assess factors that influence the tempo of bone mass accrual with emphasis on obesity, exercise, and nutritional factors.

RECENT FINDINGS

The prevalence of childhood obesity has increased dramatically throughout the world. Recent studies suggest that adiposity may be detrimental to development of bone strength parameters, and bone mass accrual during growth. Weight-bearing exercise during prepubertal and peripubertal period appears to enhance bone strength parameters. Maternal ultraviolet B radiation exposure and vitamin D status has been shown to have a positive effect on neonatal bone status, which appears to track up to the prepubertal period. Administration of vitamin D with or without calcium, but not calcium alone, during the prepubertal period might be an important 'window' for improving skeletal mineralization.

SUMMARY

Obesity in children appears to be detrimental to development of bone strength parameters and bone mass accrual. Weight-bearing exercise during prepubertal and peripubertal period and vitamin D supplementation during pregnancy, infancy, and peripubertal period might be important for bone mass accrual. However, adequately powered randomized controlled trials with follow-up into adulthood are needed to determine if these interventions improve the tempo of bone mass accrual.

Relationship between weight and bone mineral density in adolescents on hormonal contraception

STUDY OBJECTIVE

Since bone loss has been observed among adolescents on depot medroxyprogesterone acetate (DMPA), a clinical population that commonly experiences weight gain, we were interested in examining the direct relationship between body weight and bone mineral density (BMD) in adolescents on DMPA as compared to those on oral contraceptive pills (OC) or on no hormonal contraception (control).

DESIGN

Prospective, Longitudinal study.

SETTING

Four urban adolescent health clinics in a large metropolitan area.

PARTICIPANTS

Postmenarcheal girls, age 12-18 years, selecting DMPA, OC or no hormonal contraception.

INTERVENTIONS

At baseline, 6, 12, 18, and 24 months, all study participants underwent measurement of weight and BMD of the hip and spine.

MAIN OUTCOME MEASURES

The correlation between weight and BMD, and the correlation between change in weight and change in BMD were assessed at each time point.

RESULTS

Body weight was significantly (P < 0.05) positively correlated with femoral neck BMD and spine BMD at each time point regardless of contraceptive method. Change in body weight at 12 and 24 months was highly correlated with change in femoral neck BMD (P < 0.0001) for all treatment groups. No statistically significant correlation between change in weight and change in spine BMD was seen in the DMPA, OC, or control subjects at 12 or 24 months.

CONCLUSION

Weight gain on DMPA may mitigate loss of BMD among adolescent users.

Bone and fat relationships in postadolescent black females: a pQCT study

Despite adolescent black females experiencing the highest rates of obesity, the effect of excess fat mass on bone structure and strength in this population is unknown. Our findings in postadolescent black females suggest that excess weight in the form of fat mass may adversely influence cortical bone structure and strength.

INTRODUCTION

Although adolescent obesity has been associated with reduced bone structure and strength in white females, this relationship has not been studied in adolescent black females, a population experiencing the highest rates of obesity. Our objective was to compare bone structure and strength between postadolescent black females with normal and high levels of adiposity.

METHODS

Black females with ≤ 32% body fat were classified as normal body fat (NF; n = 33, aged 19.3 ± 1.3 years); females exceeding this cutoff were classified as high body fat (HF; n = 15, aged 19.0 ± 1.1 years). Using peripheral quantitative computed tomography, tibial and radial bones were scanned at the 4% (trabecular) and 20% (cortical) sites from the distal metaphyses. Fat-free soft-tissue mass (FFST) and %body fat were assessed by dual-energy X-ray absorptiometry.

RESULTS

After controlling for either FFST or body weight, the HF vs. NF group had lower total cross-sectional area (CSA; 9-17%), cortical CSA (6-15%), and strength-strain index (SSI; 13-24%) at the cortical site of the tibia (all p < 0.05). At the cortical site of the radius, the HF vs. NF group had lower total CSA (14%, p = 0.03), cortical CSA (9%, p = 0.04), and SSI (15%, p = 0.07) after control for body weight. There were no group differences in either the FFST-adjusted cortical bone values at the radius or in the trabecular bone parameters (body weight- or FFST-adjusted) at the tibia and radius.

CONCLUSIONS

Consistent with our adiposity and bone data in late-adolescent white females, our findings in black females entering adulthood also suggest that obesity may adversely influence cortical bone strength.

Effects of diet-induced obesity and voluntary wheel running on the microstructure of the murine distal femur

Background

Obesity and osteoporosis, two possibly related conditions, are rapidly expanding health concerns in modern society. Both of them are associated with sedentary life style and nutrition. To investigate the effects of diet-induced obesity and voluntary physical activity we used high resolution micro-computed tomography (μCT) together with peripheral quantitative computed tomography (pQCT) to examine the microstructure of the distal femoral metaphysis in mice.

Methods

Forty 7-week-old male C57BL/6J mice were assigned to 4 groups: control (C), control + running (CR), high-fat diet (HF), and high-fat diet + running (HFR). After a 21-week intervention, all the mice were sacrificed and the left femur dissected for pQCT and μCT measurements.

Results

The mice fed the high-fat diet showed a significant weight gain (over 70% for HF and 60% for HFR), with increased epididymal fat pad mass and impaired insulin sensitivity. These obese mice had significantly higher trabecular connectivity density, volume, number, thickness, area and mass, and smaller trabecular separation. At the whole bone level, they had larger bone circumference and cross-sectional area and higher density-weighted maximal, minimal, and polar moments of inertia. Voluntary wheel running decreased all the cortical bone parameters, but increased the trabecular mineral density, and decreased the pattern factor and structure model index towards a more plate-like structure.

Conclusions

The results suggest that in mice the femur adapts to obesity by improving bone strength both at the whole bone and micro-structural level. Adaptation to running exercise manifests itself in increased trabecular density and improved 3D structure, but in a limited overall bone growth

Obesity in pediatric orthopaedics

Obesity is a rapidly expanding health problem in children and adolescents and is the most prevalent nutritional problem for children in the United States. Some believe that obesity has become a major epidemic in American children, with the prevalence having more than doubled since 1980. This epidemic has led to a near-doubling in hospitalizations with a diagnosis of obesity between 1999 and 2005 and an increase in costs from $125.9 million to $237.6 million between 2001 and 2005. This article describes some of the orthopaedic conditions commonly encountered in overweight/obese children and adolescents, classically infantile and adolescent tibia vara and slipped capital femoral epiphysis. Also discussed are genu valgum, which has been associated with obesity, and other difficulties encountered in providing orthopaedic care to obese children.

Bone mineral content and density in obese, overweight, and normal-weighted sedentary adolescent girls

PURPOSE

The aim of this study was to compare the whole body (WB) bone mineral content (BMC) and bone mineral density (BMD) in obese, overweight, and normal-weighted adolescent sedentary girls.

METHODS

This study included 17 obese, 27 overweight, and 21 normal-weighted adolescent (aged, 12-20) sedentary (practicing less than 2 hours of physical activity/week) girls. The three groups (obese, overweight, and normal) were matched for age and maturation index (years since menarche). BMC, bone mineral area (BMA), BMD, and body composition were assessed by dual-energy X-ray asborptiometry. Bone mineral apparent density (BMAD) was calculated for the WB.

RESULTS

Obese girls had higher BMC values than overweight and normal-weighted girls (p < .05 and p < .001, respectively). Overweight girls had higher BMC values than normal-weighted girls (p < .05). BMD values were not different among the three groups. However, obese and overweight girls had lower BMAD and higher BMC/height values in comparison with normal-weighted girls (p < .05). Finally, after adjustment for lean mass, BMC, BMA, BMD, and BMAD were not different among the three groups.

CONCLUSION

In this population, overweight and obesity are associated with higher BMC, BMC/height, and lower BMAD of the WB. This study suggests that BMD, BMC, BMA, and BMAD of the WB are not significantly different among the three groups (obese, overweight, and normal) after adjustment for lean mass. Therefore, our results suggest that the skeleton of the overweight and the obese girls adapts to the increased lean mass.

Forearm fractures in children and bone health

PURPOSE OF REVIEW

Summary highlighting the evidence that bone health may affect forearm fracture risk in children.

RECENT FINDINGS

Although the incidence of other fractures and injuries are decreasing, the incidence of forearm fractures is increasing in otherwise healthy children. There is a growing volume of research that forearm fracture risk in children may be related to deficiencies in parameters of bone health. Available evidence of this relationship was summarized and included direct links to bone health (measurement of bone properties), indirect links to bone health (diet, vitamin D status, BMI), and genetic analyses.

SUMMARY

There is consistent and convincing evidence of an association between bone mineral density and forearm fracture risk in children. Studies of calcium intake and supplementation are less extensive in scope but suggest that effects of calcium deficiency on the radius may contribute to childhood forearm fracture risk. Forearm fracture risk in obese children is likely to reflect a combination of suboptimal bone health status and behavioral characteristics. Published data on the role of vitamin D status and genetic factors are limited but merit further consideration. Further investigation is needed to better understand the factors contributing to forearm fracture risk in children and translate this knowledge into effective clinical prevention and practice.

Lower bone mass in prepubertal overweight children with prediabetes

Childhood studies of the fat-bone relationship are conflicting, possibly reflecting the influence of metabolic abnormalities in some but not all obese children. Bone mass was compared between prepubertal overweight children with (n = 41) and without (n = 99) prediabetes. Associations of bone mass with measures of total and central adiposity, glucose intolerance, insulin sensitivity, lipid profile, systemic inflammation, and osteocalcin also were determined. In 140 overweight children aged 7 to 11 years, an oral glucose tolerance test was used to identify those with prediabetes and for determination of glucose, 2-hour glucose, glucose area under the curve (AUC), insulin, 2-hour insulin, and insulin AUC. Blood samples also were assessed for lipids, C-reactive protein, and osteocalcin. Total-body bone mineral content (BMC), fat-free soft tissue mass (FFST), and fat mass (FM) were measured by dual-energy X-ray absorptiometry (DXA). Visceral adipose tissue (VAT) and subcutaneous abdominal adipose tissue (SAAT) were assessed using MRI. Total-body BMC was 4% lower in overweight children with prediabetes than in those without prediabetes after controlling for sex, race, height, and weight (p = .03). In the total sample, FM was positively related with BMC (β = 0.16, p = .01) after adjusting for sex, race, height, and FFST. However, VAT (β = -0.13, p = .03) and SAAT (β = -0.34, p = .02) were inversely associated with BMC after controlling for sex, race, height, FFST, FM, and SAAT or VAT. No significant associations were found between BMC and the biochemical measurements. Prepubertal overweight children with prediabetes may be at risk for poor skeletal development. In addition, it appears that greater levels of central rather than total adiposity may be deleterious for developing bone.

Obesity reduces bone density associated with activation of PPARγ and suppression of Wnt/β-catenin in rapidly growing male rats

BACKGROUND

It is well established that excessive consumption of a high fat diet (HFD) results in obesity; however, the consequences of obesity on postnatal skeletal development have not been well studied.

METHODOLOGY AND PRINCIPAL FINDINGS

Total enteral nutrition (TEN) was used to feed postnatal day 27 male rats intragastrically with a high 45% fat diet (HFD) for four weeks to induce obesity. Fat mass was increased compared to rats fed TEN diets containing 25% fat (medium fat diet, MFD) or a chow diet (low fat diet, LFD) fed ad libitum with matched body weight gains. Serum leptin and total non-esterified fatty acids (NEFA) were elevated in HFD rats, which also had reduced bone mass compared to LFD-fed animals. This was accompanied by decreases in bone formation, but increases in the bone resorption. Bone marrow adiposity and expression of adipogenic genes, PPARγ and aP2 were increased, whereas osteoblastogenic markers osteocalcin and Runx2 were decreased, in bone in HFD rats compared to LFD controls. The diversion of stromal cell differentiation in response to HFD stemmed from down-regulation of the key canonical Wnt signaling molecule β-catenin protein and reciprocal up-regulation of nuclear PPARγ expression in bone. In a set of in vitro studies using pluripotent ST2 bone marrow mesenchymal stromal cells treated with serum from rats on the different diets or using the free fatty acid composition of NEFA quantified in rat serum from HFD-fed animals by GC-MS, we were able to recapitulate our in vivo findings.

CONCLUSIONS/SIGNIFICANCE

These observations strongly suggest that increased NEFA in serum from rats made obese by HFD-feeding impaired bone formation due to stimulation of bone marrow adipogenesis. These effects of obesity on bone in early life may result in impaired attainment of peak bone mass and therefore increase the prevalence of osteoporosis later on in life.

Biologic therapy and its effect on skeletal development in children with chronic inflammation

Chronic inflammatory conditions in children such as juvenile idiopathic arthritis, inflammatory bowel disease, cystic fibrosis and systemic lupus erythematosus can cause reduced linear growth, final height and bone mass. There are many mechanisms leading to these skeletal alterations but inflammation itself is considered to play an important role. Biologic therapy is being used increasingly for the treatment of chronic inflammatory conditions and may also be effective in improving growth and skeletal development. The main aim of this article is to summarize the effects of inflammation on growth and skeletal development and evaluate the effects of biologic therapy on growth and skeletal development in children with chronic inflammatory conditions.

Femoral neck geometry in overweight and normal weight adolescent girls

Being overweight is associated with increased bone mineral content, bone mineral density (BMD), and bone strength in adults. However, the effect of being overweight on bone strength during adolescence is poorly understood. The aim of this study was to compare femoral neck geometry in overweight and normal weight adolescent girls. This study included 22 overweight (BMI > 25 kg/m(2)) adolescent girls (15.4 +/- 2.4 years old) and 20 maturation-matched (15.2 +/- 1.9 years old) controls (BMI < 25 kg/m(2)). Body composition and BMD were assessed by dual-energy X-ray absorptiometry (DXA). To evaluate bone geometry, DXA scans were analyzed at the femoral neck by the hip structure analysis (HSA) program. Cross-sectional area (CSA), an index of axial compression strength, section modulus (Z), an index of bending strength, cross-sectional moment of inertia (CSMI), cortical thickness (CT), and buckling ratio (BR) were measured from bone mass profiles. Lean mass, body weight, fat mass, and BMI were higher in overweight girls compared to controls (P < 0.001). CSA, Z, and CSMI were higher in overweight girls compared to controls (P < 0.05; P < 0.01 and P < 0.01, respectively). CT and BR were not significantly different between the two groups. After adjustment for body weight, lean mass, or fat mass, using a one-way analysis of covariance (ANCOVA), there were no differences between the two groups (overweight and controls) regarding the HSA variables (CSA, Z, CSMI, CT, and BR). In conclusion, this study suggests that overweight adolescent girls have greater indices of bone axial and bending strength in comparison to controls at the femoral neck.

Dietary patterns associated with fat and bone mass in young children

BACKGROUND

Obesity and osteoporosis have origins in childhood, and both are affected by dietary intake and physical activity. However, there is little information on what constitutes a diet that simultaneously promotes low fat mass and high bone mass accrual early in life.

OBJECTIVE

Our objective was to identify dietary patterns related to fat and bone mass in children during the age period of 3.8-7.8 y.

DESIGN

A total of 325 children contributed data from 13 visits over 4 separate study years (age ranges: 3.8-4.8, >4.8-5.8, >5.8-6.8, and >6.8-7.8 y). We performed reduced-rank regression to identify dietary patterns related to fat mass and bone mass measured by dual-energy X-ray absorptiometry for each study year. Covariables included race, sex, height, weight, energy intake, calcium intake, physical activity measured by accelerometry, and time spent viewing television and playing outdoors.

RESULTS

A dietary pattern characterized by a high intake of dark-green and deep-yellow vegetables was related to low fat mass and high bone mass; high processed-meat intake was related to high bone mass; and high fried-food intake was related to high fat mass. Dietary pattern scores remained related to fat mass and bone mass after all covariables were controlled for (P < 0.001-0.03).

CONCLUSION

Beginning at preschool age, diets rich in dark-green and deep-yellow vegetables and low in fried foods may lead to healthy fat and bone mass accrual in young children.

Percent fat mass is inversely associated with bone mass and hip geometry in rural Chinese adolescents

This study was an attempt to examine the phenotypic, genetic, and environmental correlations between percent fat mass (PFM) and bone parameters, especially hip geometry, among 786 males and 618 females aged 13 to 21 years from a Chinese twin cohort. PFM, bone area (BA), bone mineral content (BMC), cross-sectional area (CSA), and section modulus (SM) were obtained by dual-energy X-ray absorptiometry. Multiple linear regression models were used to assess the PFM-bone relationships. A structural equation model for twin design was used to estimate genetic/environmental influences on individual phenotype and phenotypic correlations. After controlling for body weight and other pertinent covariates, we observed inverse associations between PFM and bone parameters: Compared with the lowest age- and gender-specific tertile of PFM, males in the highest tertile of PFM had lower measures of whole-body-less-head BA (WB-BA), lumbar spine BA (L(2)-L(4)-BA), total-hip BA (TH-BA), total-hip BMC, CSA, and SM (p < .005 for all, adjusted p < .05). Similar inverse associations were observed in females for all the preceding parameters except WB-BA and L2-L(4)-BA. These associations did not vary significantly by Tanner stages. In both genders, the estimated heritabilities were 80% to 86% for BMC, 67% to 80% for BA, 74% to 77% for CSA, and 64% for SM. Both shared genetics and environmental factors contributed to the inverse PFM-bone correlations. We conclude that in this sample of relatively lean Chinese adolescents, at a given body weight, PFM is inversely associated with BA, BMC, and hip geometry in both genders, and such associations are attributed to both shared genetic and environmental factors.

The effects of L-thyroxin replacement therapy on bone minerals and body composition in hypothyroid children

INTRODUCTION

Prolonged treatment with levothyroxine 4 (L-T4) is a well known risk factor for osteoporosis. Patients on L-T4 replacement occasionally have a subnormal TSH, which carries a risk of development of bone loss. Thyroid hormones directly affect bone cells, stimulating osteoclastic and osteoblastic activity with a predominance of bone resorption and decrease of bone mineral density (BMD).

MATERIAL AND METHODS

The study included 35 hypothyroid patients with mean age 11.57 ±5.06, while 26 age- and sex-matched children served as controls. Dual energy X-ray absorptiometry (DXA) was done to detect the bone mineral density (BMD), bone mineral content (BMC) and Z score in lumbar and femur neck regions. Body composition was also studied by DXA. Calcium, phosphorus, osteocalcin as a bone formation marker, osteoprotegerin as an indicator of osteoclast activity and urinary deoxypyridinoline as a bone collagen breakdown marker were assessed.

RESULTS

No significant differences were detected in lumbar Z score (-0.12 ±0.66) and femur Z score (-0.17 ±0.58) compared to controls (-0.33 ±0.74 and -0.21 ±0.53 respectively). Bone mineral density and BMC were not significantly different from controls. No significant difference was detected between cases and controls in body composition. A positive correlation was detected between BMD and age (r=0.857, p<0.01), and with the period of treatment (r=0.766, p<0.01). A positive correlation was found between BMD and total body fat (r=0.693, p<0.01), and with abdominal fat (r=0.667, p<0.01).

CONCLUSIONS

Levothyroxine 4 treatment in hypothyroid children does not alter bone metabolism and body composition.

Is childhood obesity associated with bone density and strength in adulthood?

Associations between childhood obesity and adult bone traits were assessed among 62 obese premenopausal women, of which 12 had been obese since childhood (ObC), and 50 had gained excess weight in adulthood (ObA). Body composition and bone mineral content (BMC) of the total body, spine, and proximal femur were assessed with DXA. Total cross-sectional area and cortical (diaphyseal CoD) and trabecular (epiphyseal TrD) bone density of the radius and tibia were measured with pQCT. Compared to ObA-group, ObC-group was 5.2 cm taller having 2.5 and 3.5 kg more lean and fat mass, respectively. Depending on the statistical adjustment, ObC-group had 5-10% greater TrD both in tibia and in radius. The remaining bone traits did not significantly differ between the groups. Current preliminary observations bring up an interesting question whether childhood obesity can result in denser trabecular bone in adulthood. However, prudence must be exercised in the statistical adjustment.

Biopsychosocial variables associated with substantial bone mineral density loss during the use of depot medroxyprogesterone acetate in adolescents: adolescents who lost 5% or more from baseline vs. those who lost less than 5%

BACKGROUND

It is unclear why some adolescents experience substantial bone mineral density (BMD) loss, while others experience a minimal decrease during depot medroxyprogesterone acetate (DMPA) use. We examined biopsychosocial factors in adolescents who experienced ≥5% BMD loss from baseline compared with adolescents who experienced <5% BMD loss during DMPA use.

STUDY DESIGN

A multicenter, prospective, nonrandomized study of 181 female adolescents who initiated DMPA for contraception was conducted. BMD (by dual-energy X-ray absorptiometry) and serum estradiol were measured at initiation and every 6 months for 240 weeks of DMPA use.

RESULTS

Half of participants experienced BMD loss of ≥5% from baseline at the hip, and a quarter experienced BMD loss of ≥5% at the lumbar spine (BMD substantial losers, SL). Hip and lumbar spine BMD-SL received a significantly greater number of DMPA injections than non-SL (p<.001). Decreased estradiol levels did not statistically differ between BMD loss subgroups. Hip BMD-SL had significantly lower baseline body mass index (BMI) than non-SL (p=.002), and there was an inverse relationship between weight gain and degree of BMD loss. Mean calcium intake was significantly lower (p<.05) in hip BMD-SL, and reported alcohol use was significantly higher (p<.05) in lumbar spine BMD-SL compared with non-SL.

CONCLUSIONS

BMD loss of ≥5% was more common at the hip than at the lumbar spine among adolescents using DMPA. Decreased serum estradiol levels did not correlate with magnitude of BMD loss. Lower BMI and calcium intake and greater alcohol use were associated with greater BMD loss in adolescents using DMPA.

Comparisons of obesity assessments in over-weight elementary students using anthropometry, BIA, CT and DEXA

Obesity was characterized in Korean elementary students using different obesity assessment tests on 103 overweight elementary students from three schools of Jeonbuk Province. The body mass index (BMI) and obesity index (OI) were compared, and the data using DEXA and CT were compared with the data using BIA and a tape measure. The results of this study are as follows: first, 27 students who were classified as obese by OI were classified as overweight by BMI, and 3 students who were classified as standard weight by BMI were classified as overweight by OI. Secondly, by DEXA and BIA measurements, there was 1.51% difference in body fat percentage (boys 1.66%, girls 1.17%) and the difference in body fat mass between boys and girls was 0.77 kg (boys 0.85 kg, girls 0.59 kg), but those differences in body fat percentage and mass were not statistically significant. Thirdly, the average total abdominal fat (TAF) measured by CT scans of obese children was more significantly related with subcutaneous fat (r = 0.983, P < 0.01) than visceral fat (r = 0.640, P < 0.01). Also, TAF were highest significant with waist circumference by a tape measure (r = 0.744, P < 0.01). In summary, as there are some differences of assessment results between two obesity test methods (BMI, OI), we need more definite standards to determine the degree of obesity. The BIA seems to be the most simple and effective way to measure body fat mass, whereas waist/hip ratio (WHR) using a tape measurer is considered to be the most effective method for assessing abdominal fat in elementary students.

Bone mineral density after bone marrow transplantation in childhood: measurement and associations

This study examined the bone mineral density (BMD) of 46 (median age 16.3, 8-29) survivors of autologous and allogeneic bone marrow transplantation (BMT). Areal (g/m2) BMD was acquired with dual energy x-ray absorptiometry and volumetric (g/cm3) BMD values were calculated. Abnormal BMD was identified in 24% (11/46) of survivors with areal measures and 22% (10/46) with volumetric measures. Comparison of areal and volumetric BMD revealed the measures were highly correlated (r = 0.73, p<0.001) but clinical diagnosis of osteopenia/osteoporosis were not consistent. Volumetric z-scores were higher for 7/8 of the survivors who were < 3rd percentile for height. Associations of BMD and body composition and disease and treatment factors were assessed with multiple linear regression. When controlling for other significant associations and cumulative steroid dose, the body composition measure of fat mass index (FMI) was associated with higher volumetric BMD z-scores (CI: 0.006, 0.193; p = 0.037). CNS irradiation (CI: -1.710,-0.200; p = 0.015), age at time of testing (CI: -0.116, -0.024; p = 0.004) and female sex (CI: -1.375, -0.155; p = 0.015) were associated with lower volumetric BMD z-scores.

CONCLUSIONS

Childhood BMT survivors are at risk for diminished BMD. Areal and volumetric DEXA derived measures of BMD are highly correlated and volumetric measures may correct for underestimation of BMD in BMT survivors who are small for age. Survivors who received CNS irradiation, are older and female may be at greater risk for diminished BMD while fat mass is associated with higher BMD in childhood BMT survivors.

Factors associated with bone mineral density and content in 7-year-old children

OBJECTIVE

To evaluate the bone status of 7-year-old school children in Reykjavik, Iceland, and to see if gender, height, lean body mass and fat mass is associated with bone mineral density (BMD) and bone mineral content (BMC) in the lumbar vertebrae and hip.

STUDY DESIGN

A cross-sectional study of a sample of 7-year-old school children.

SETTING

Six elementary schools in Reykjavik, Iceland.

SUBJECTS

All children attending second grade in these six schools were invited to participate. Three hundred twenty-six children were invited and 211 (65%) participated in the study.

MAIN OUTCOME MEASURES

Lean body mass, bone mineral density, bone mineral content and total fat mass.

RESULTS

Both BMD and BMC were positively correlated with sex, height and lean body mass. Fat mass was positively correlated to BMC but not BMD in the total body and lumbar vertebrae. When analyzed with multiple linear regression, the bone area and lean body mass (LBM) were positively associated with BMC in the hip and total body, but total fat mass (TFM) was negatively associated with BMC, the model explaining about 88% of the variance (R2) in the total body bone mineral content (TBMC) and 74% of the variance (R2) in the BMC of the hip. LBM was positively associated with total body bone mineral density (TBMD) but TFM negatively associated. Neither height nor gender contributed to total BMC and BMD in our multiple linear regression models.

CONCLUSION

The study emphasizes that fat mass may play different roles in children and adults and that both LBM and TFM should be taken into consideration when interpreting BMC and BMD for children.

Relationship of total body fat mass to weight-bearing bone volumetric density, geometry, and strength in young girls

Understanding the influence of total body fat mass (TBFM) on bone during the peri-pubertal years is critical for the development of future interventions aimed at improving bone strength and reducing fracture risk. Thus, we evaluated the relationship of TBFM to volumetric bone mineral density (vBMD), geometry, and strength at metaphyseal and diaphyseal sites of the femur and tibia of young girls. Data from 396 girls aged 8-13 years from the "Jump-In: Building Better Bones" study were analyzed. Bone parameters were assessed using peripheral quantitative computed tomography (pQCT) at the 4% and 20% distal femur and 4% and 66% distal tibia of the non-dominant leg. Bone parameters at the 4% sites included trabecular vBMD, periosteal circumference, and bone strength index (BSI), while at the 20% femur and 66% tibia, parameters included cortical vBMD, periosteal circumference, and strength-strain index (SSI). Multiple linear regression analyses were used to assess associations between bone parameters and TBFM, controlling for muscle cross-sectional area (MCSA). Regression analyses were then repeated with maturity, bone length, physical activity, and ethnicity as additional covariates. Analysis of covariance (ANCOVA) was used to compare bone parameters among tertiles of TBFM. In regression models with TBFM and MCSA, associations between TBFM and bone parameters at all sites were not significant. TBFM explained very little variance in all bone parameters (0.2-2.3%). In contrast, MCSA was strongly related (p<0.001) to all bone parameters, except cortical vBMD. The addition of maturity, bone length, physical activity, and ethnicity did not alter the relationship between TBFM and bone parameters. With bone parameters expressed relative to total body mass, ANCOVA showed that all outcomes were significantly (p<0.001) greater in the lowest compared to the middle and highest tertiles of TBFM. Although TBFM is correlated with femur and tibia vBMD, periosteal circumference, and strength in young girls, this relationship is significantly attenuated after adjustment for MCSA. Nevertheless, girls with higher TBFM relative to body mass have markedly diminished vBMD, geometry, and bone strength at metaphyseal and diaphyseal sites of the femur and tibia.

Influence of the weight status on bone mineral content and bone mineral density in a group of Lebanese adolescent girls

AIM

The aim of this study was to determine the influence of being overweight on whole-body (WB) bone mineral content (BMC) and bone mineral density (BMD) in a group of Lebanese adolescent girls.

METHODS

This study included 32 overweight (BMI>25 kg/m2) adolescent girls (15.3+/-2.3 years old) and 24 maturation-matched (15.7+/-1.7 years old) controls (BMI<25 kg/m2). Bone mineral area (BMA), BMC, BMD at the WB and body composition (lean mass and fat mass) were assessed by dual-energy X-ray absorptiometry (DXA). Calculation of the ratio BMC/height and bone mineral apparent density (BMAD) were completed for the WB.

RESULTS

Expressed as crude values, BMA, BMC and the ratio BMC/height were higher in overweight adolescent girls compared to controls. After adjusting for body weight, there were no differences in BMC or in the ratio BMC/height between the two groups. However, BMA was lower in overweight girls compared to controls. After adjusting for either lean mass or fat mass, there were no significant differences between the two groups regarding these variables: BMC, BMA, BMD, BMC/height and BMAD.

CONCLUSION

This study suggests that the positive effect of overweight on BMC is due to body weight. In fact, the difference in BMC between the overweight and the control girls disappears after adjusting for body weight. In contrast, overweight girls have lower BMA compared to controls when values are adjusted to body weight.

Bone accretion in adolescents using the combined estrogen and progestin transdermal contraceptive method Ortho Evra: a pilot study

OBJECTIVE

To date, there are no data regarding the effect of the transdermal combined estrogen and progestin contraceptive Ortho Evra on bone mineral content (BMC) and bone mineral density (BMD). We examined the effects of transdermally delivered ethinyl estradiol and norelgestromin on whole body (WB) BMC and BMD of the hip and lumbar spine (LS) of adolescent girls.

METHODS

In a matched case-control study, girls (n = 5) who applied Ortho Evra for days 1-21 followed by days 22-28 free of medication for 13 cycles (about 12 months) were compared with 5 age- and ethnicity-matched control girls. Evaluations of calcium intake; bone-protective physical activity; bone densitometry (DXA, QDR 4500A, Hologic); bone formation markers serum osteocalcin (OC) and bone-specific alkaline phosphatase (BAP); bone resorption marker urinary N-telopeptide (uNTX); insulin growth factor-1 (IGF-1); and sex hormone binding globulin (SHBG) were carried out at initiation, 6 months, and 12 months. Changes from baseline were compared using mixed models, adjusting for follow-up comparisons using the Holm Test (sequential Bonferroni).

RESULTS

There were no significant differences (SD) between groups at baseline in age, gynecologic age, WBBMC, hip BMD, and LSBMD. Girls on Ortho Evra did not change significantly in WBBMC (12-month mean increase 0.2% +/- 0.8%), whereas controls did (3.9% +/- 1.8%, P < or = .001, adjusted P = .002), with SD between the 2 groups (P = .007, adjusted P = .036). Adolescents on Ortho Evra did not change significantly in hip BMD (12-month mean increase 0.5% +/- 0.6%), whereas controls did (2.7% +/- 0.6%, P < or = .001, adjusted P = .004), with SD between the 2 groups (P = .024) prior to adjustment for multiple comparisons, but no SD after adjustment (P = .096). Similarly, although the increase in LSBMD within the control group after 12 months (mean increase 2.8% +/- 1.0%) was statistically significant (P = .009, adjusted P = .044), the change within the treatment group (12-month mean increase 0.8% +/- 0.8%) was not. However, percent LSBMD changes after 12 months did not significantly differ between the 2 groups before or after adjustment for multiple comparisons. Calcium intake and bone-protective physical activity did not significantly predict BMC and BMD changes of study participants. There was a significantly greater increase in SHBG levels in the treatment group after 6 months (P = .003, adjusted P = .013) and 12 months (P < or = .001, adjusted P < or = .001) than in controls. Changes in levels of OC, BAP, uNTX, and IGF-1 were not significantly different between the 2 groups.

CONCLUSIONS

Ortho Evra use attenuates bone mass acquisition in young women who are still undergoing skeletal maturation. This attenuation may be attributed in part to increased SHBG levels, which reduce the concentrations of free estradiol and free testosterone that are available to interact with receptors on the bone. Clinical implications remain to be determined in studies with a larger number of adolescents.

Overweight children have a greater proportion of fat mass relative to muscle mass in the upper limbs than in the lower limbs: implications for bone strength at the distal forearm

BACKGROUND

The influence of adiposity on upper-limb bone strength has rarely been studied in children, despite the high incidence of forearm fractures in this population.

OBJECTIVE

The objective was to compare the influence of muscle and fat tissues on bone strength between the upper and lower limbs in prepubertal children.

DESIGN

Bone mineral content, total bone cross-sectional area, cortical bone area (CoA), cortical thickness (CoTh) at the radius and tibia (4% and 66%, respectively), trabecular density (TrD), bone strength index (4% sites), cortical density (CoD), stress-strain index, and muscle and fat areas (66% sites) were measured by using peripheral quantitative computed tomography in 427 children (206 boys) aged 7-10 y.

RESULTS

Overweight children (n = 93) had greater values for bone variables (0.3-1.3 SD; P < 0.0001) than did their normal-weight peers, except for CoD 66% and CoTh 4%. The between-group differences were 21-87% greater at the tibia than at the radius. After adjustment for muscle cross-sectional area, TrD 4%, bone mineral content, CoA, and CoTh 66% at the tibia remained greater in overweight children, whereas at the distal radius total bone cross-sectional area and CoTh were smaller in overweight children (P < 0.05). Overweight children had a greater fat-muscle ratio than did normal-weight children, particularly in the forearm (92 +/- 28% compared with 57 +/- 17%). Fat-muscle ratio correlated negatively with all bone variables, except for TrD and CoD, after adjustment for body weight (r = -0.17 to -0.54; P < 0.0001).

CONCLUSIONS

Overweight children had stronger bones than did their normal-weight peers, largely because of greater muscle size. However, the overweight children had a high proportion of fat relative to muscle in the forearm, which is associated with reduced bone strength.

Relation of body fat indexes to vitamin D status and deficiency among obese adolescents

BACKGROUND

Data on the relation between vitamin D status and body fat indexes in adolescence are lacking.

OBJECTIVE

The objective was to identify factors associated with vitamin D status and deficiency in obese adolescents to further evaluate the relation of body fat indexes to vitamin D status and deficiency.

DESIGN

Data from 58 obese adolescents were obtained. Visceral adipose tissue (VAT) was measured by computed tomography. Dual-energy X-ray absorptiometry was used to measure total bone mineral content, bone mineral density, body fat mass (FM), and lean mass. Relative measures of body fat were calculated. Blood tests included measurements of 25-hydroxyvitamin D [25(OH)D], parathyroid hormone (PTH), osteocalcin, type I collagen C-telopeptide, hormones, and metabolic factors. Vitamin D deficiency was defined as 25(OH)D < 20 ng/mL. PTH elevation was defined as PTH > 65 ng/mL.

RESULTS

The mean (+/-SD) age of the adolescents was 14.9 +/- 1.4 y; 38 (66%) were female, and 8 (14%) were black. The mean (+/-SD) body mass index (in kg/m(2)) was 36 +/- 5, FM was 40.0 +/- 5.5%, and VAT was 12.4 +/- 4.3%. Seventeen of the adolescents were vitamin D deficient, but none had elevated PTH concentrations. Bone mineral content and bone mineral density were within 2 SDs of national standards. In a multivariate analysis, 25(OH)D decreased by 0.46 +/- 0.22 ng/mL per 1% increment in FM (beta +/- SE, P = 0.05), whereas PTH decreased by 0.78 +/- 0.29 pg/mL per 1% increment in VAT (P = 0.01).

CONCLUSIONS

To the best of our knowledge, our results show for the first time that obese adolescents with 25(OH)D deficiency, but without elevated PTH concentrations, have a bone mass within the range of national standards (+/-2 SD). The findings provide initial evidence that the distribution of fat may be associated with vitamin D status, but this relation may be dependent on metabolic factors. This study was registered at www.clinicaltrials.gov as NCT00209482, NCT00120146.

[Association among weight loss, bone mass, body composition and dietary intake of post-pubertal obese adolescents]

OBJECTIVE

To verify the effects of weight loss on bone mass of obese adolescents submitted to a nutritional intervention based on a hypocaloric diet and nutritional advice over a nine-month-period.

METHODS

Anthropometry, body composition, BMD and dietary intake were evaluated.

RESULTS

Fifty-five adolescents, 78.2% females, within an average age of 16.6 (1.4) years old participated in the study. Sixteen participants who completed the study did not lose weight. The group that adhered to the nutritional intervention had a mean weight loss of 6.2 (4.6)% baseline. There was a significant increase in total BMD and bone mineral content (BMC) in those adolescents who did not lose weight, while increased BMC and bone area were verified in participants who lost weight, mainly when associated with body composition alterations while changing weight.

CONCLUSION

The increment in bone mineral density, even throughout weight loss, has showed no negative effect on bone mass and has also emphasized the importance of nutritional improvement in total bone mass during adolescence.

Relationships of acylated and des-acyl ghrelin levels to bone mineralization in obese children and adolescents

AIMS

Bodyweight is a significant predictor of bone mass. Hormonal factors are thought to play a role in the mechanisms controlling the association of body weight and fat mass with bone mass. Very recently, the orexigenic hormone ghrelin has also been implicated in bone metabolism. In this study we examined the associations of circulating acylated and des-acyl ghrelin concentrations with measures of bone in a group of obese children and adolescents as well as in a group of healthy control children. We also determined whether the associations were independent of body composition, chronological age, gender, Tanner stage, and leptin, glucose, insulin and insulin-like growth factor (IGF)-1 levels.

METHODS

We performed a prospective cross-sectional study of 100 obese children [age, 8.9 (8.3 to 9.4); BMI-Standard Deviation Score (SDS), 2.2 (2.0 to 2.3)], and 100 age-matched lean healthy subjects. Fasting insulin, leptin, IGF-1, acylated and total ghrelin were measured by radioimmunoassay. Des-acyl ghrelin values were calculated as total ghrelin minus acylated ghrelin. Whole body (WB) and lumbar spine (LS) BMD, and BMC as well as body composition were assessed by DXA (Hologic QDR-4500W). LS volumetric BMD (BMAD) was estimated using the formula of Katzman (BMC/area(1.5)), while WB BMC data were expressed as BMC/height.

RESULTS

Backward linear regression analysis was performed for individual groups, with age, gender, Tanner stage, weight, height, body composition (lean and fat mass), acylated ghrelin, des-acyl ghrelin, leptin, glucose, insulin, and IGF-1, entered into the model. In healthy children, acylated ghrelin was a significant and independent negative predictor of WB BMD, and WB BMC/height, while lean mass was positively associated significantly with these bone measures. In contrast, in obese children, a positive significant association was observed between des-acyl ghrelin and WB BMD as well as WB BMC/height, along with lean mass, and to a lesser degree, with fat mass. Acylated as well as des-acyl ghrelin were not significant predictors of LS BMD and LS BMAD in obese as well as control children.

CONCLUSIONS

The results of this investigation indicate that the influence of the two distinct isoforms of ghrelin on BMD is mediated by specific body composition parameters in obese and control healthy children.

Disordered-eating attitudes in relation to bone mineral density and markers of bone turnover in overweight adolescents

PURPOSE

To examine the relationships between cognitive eating restraint and both bone mineral density (BMD) and markers of bone turnover in overweight adolescents.

METHODS

One hundred thirty-seven overweight (BMI 39.1 +/- 6.8 kg/m(2)) African American and Caucasian adolescent (age = 14.4 +/- 1.4 years) girls (66.4%) and boys were administered the Eating Disorder Examination (EDE) interview and Eating Inventory (EI) questionnaire and underwent dual energy X-ray absorptiometry (DXA) to measure total lumbar spine BMD. Markers of bone formation (serum bone specific alkaline phosphatase and osteocalcin), bone resorption (24-hour urine N-telopeptides), and stress (urine free cortisol) were measured.

RESULTS

After accounting for the contribution of demographics, height, weight, serum 25-hydroxyvitamin D, and depressive symptoms, adolescents' weight concern, as assessed by interview, was a significant contributor to the model of urine free cortisol (beta = .30, p < .05). Shape concern, as also assessed by interview, was significantly associated with lumbar spine bone mineral density (beta = -.15, p < .05). Dietary restraint was not a significant predictor in any of these models.

CONCLUSIONS

These findings suggest that among severely overweight adolescents, dissatisfaction with shape and weight may be salient stressors. Future research is required to illuminate the relationship between bone health and disordered-eating attitudes in overweight adolescents.

Bone mineral density and body composition in male children with hypogonadism

Estrogen deficiency in females and androgen deficiency in males may harm periosteal and endosteal apposition, reduce bone size and both cortical and trabecular thickness, modifying in this way the bone structure later in life. To date, few systematic studies on bone mineral density (BMD) and hypogonadism in adolescents are available. Therefore we aimed to determine if sexual hormone deficiency during pubertal age might have an impact on peak bone mass and body composition. We compared areal BMD (L-aBMD), volumetric lumbar spine BMD (L-vBMD), lumbar spine Z-score (L-Z-score), lumbar spine bone mineral content (L-BMC), whole body (wbBMD), normalized whole body (n-wbBMD) BMD, and whole body BMC (wb-BMC) of 25 male children with hypogonadism (HYPO) with 37 sex-, age-, and body mass index-matched healthy subjects (CNT) using dual-energy X-ray absorptiometry. Furthermore we analyzed whether a difference in lean (lean%) and fat (fat%) mass as percentage of body weight and as a lean/fat ratio is present in the two groups of children. HYPO demonstrated a statistically lower L-aBMD, LvBMD, L-BMC, Z score, wbBMD, n-wbBMD, and wb-BMC compared to CNT. CNT showed a higher lean% and lower fat% and a higher lean/fat ratio when compared with HYPO group. Lean mass correlated positively with L-aBMD, L-BMC, and wb-BMC. Our study seems to confirm previous observations that sex hormone deficiency during puberty reduces bone mass accrual. Body composition alterations may play a role in bone parameters during development in healthy as such as in hypogonadal children during developmental age.

Divergent effects of glucocorticoids on cortical and trabecular compartment BMD in childhood nephrotic syndrome

Glucocorticoid (GC) effects on skeletal development have not been established. The objective of this pQCT study was to assess volumetric BMD (vBMD) and cortical dimensions in childhood steroid-sensitive nephrotic syndrome (SSNS), a disorder with minimal independent deleterious skeletal effects. Tibia pQCT was used to assess trabecular and cortical vBMD, cortical dimensions, and muscle area in 55 SSNS (age, 5-19 yr) and >650 control participants. Race-, sex-, and age-, or tibia length-specific Z-scores were generated for pQCT outcomes. Bone biomarkers included bone-specific alkaline phosphatase and urinary deoxypyridinoline. SSNS participants had lower height Z-scores (p < 0.0001) compared with controls. In SSNS, Z-scores for cortical area were greater (+0.37; 95% CI = 0.09, 0.66; p = 0.01), for cortical vBMD were greater (+1.17; 95% CI = 0.89, 1.45; p < 0.0001), and for trabecular vBMD were lower (-0.60; 95% CI, = -0.89, -0.31; p < 0.0001) compared with controls. Muscle area (+0.34; 95% CI = 0.08, 0.61; p = 0.01) and fat area (+0.56; 95% CI = 0.27, 0.84; p < 0.001) Z-scores were greater in SSNS, and adjustment for muscle area eliminated the greater cortical area in SSNS. Bone formation and resorption biomarkers were significantly and inversely associated with cortical vBMD in SSNS and controls and were significantly lower in the 34 SSNS participants taking GCs at the time of the study compared with controls. In conclusion, GCs in SSNS were associated with significantly greater cortical vBMD and cortical area and lower trabecular vBMD, with evidence of low bone turnover. Lower bone biomarkers were associated with greater cortical vBMD. Studies are needed to determine the fracture implications of these varied effects.

Musculoskeletal effects of obesity

PURPOSE OF REVIEW

The problem of obesity has become a global concern, with increased prevalence reported in the literature. Numerous comorbid conditions are known to be associated with obesity; its relationship with the development and function of the musculoskeletal system in the growing child is poorly understood. This article reviews the current literature on the various musculoskeletal effects associated with obesity in children and adolescents.

RECENT FINDINGS

The association between obesity and various musculoskeletal disorders such as slipped capital femoral epiphysis and Blount disease is well reported. Its effects on the structure and function of the musculoskeletal system have not been well documented. Recent studies suggest an increased association between obesity and musculoskeletal pain and increased fracture risk. The limitations imposed by increasing body mass appear to be directly reflected in the child's level of activity and overall functional capacity.

SUMMARY

Obesity continues to pose a serious health concern. Its impact on the development of the child's musculoskeletal system is still poorly understood. Recent data suggests that obesity affects the child's locomotor system both functionally and structurally. As the obesity epidemic grows, newer studies will be needed to help us fully understand the true impact of obesity on the musculoskeletal system of the growing child.