Fat and bone in children: differential effects of obesity on bone size and mass according to fracture history

Explainable predictive models of short stature and exploration of related environmental growth factors: a case-control study

BACKGROUND

Short stature is a prevalent pediatric endocrine disorder for which early detection and prediction are pivotal for improving treatment outcomes. However, existing diagnostic criteria often lack the necessary sensitivity and specificity because of the complex etiology of the disorder. Hence, this study aims to employ machine learning techniques to develop an interpretable predictive model for normal-variant short stature and to explore how growth environments influence its development.

METHODS

We conducted a case‒control study including 100 patients with normal-variant short stature who were age-matched with 200 normal controls from the Endocrinology Department of Nanjing Children's Hospital from April to September 2021. Parental surveys were conducted to gather information on the children involved. We assessed 33 readily accessible medical characteristics and utilized conditional logistic regression to explore how growth environments influence the onset of normal-variant short stature. Additionally, we evaluated the performance of the nine machine learning algorithms to determine the optimal model. The Shapley additive explanation (SHAP) method was subsequently employed to prioritize factor importance and refine the final model.

RESULTS

In the multivariate logistic regression analysis, children's weight (OR = 0.92, 95% CI: 0.86, 0.99), maternal height (OR = 0.79, 95% CI: 0.72, 0.87), paternal height (OR = 0.83, 95% CI: 0.75, 0.91), sufficient nighttime sleep duration (OR = 0.48, 95% CI: 0.26, 0.89), and outdoor activity time exceeding three hours (OR = 0.02, 95% CI: 0.00, 0.66) were identified as protective factors for normal-variant short stature. This study revealed that parental height, caregiver education, and children's weight significantly influenced the prediction of normal-variant short stature risk, and both the random forest model and gradient boosting machine model exhibited the best discriminatory ability among the 9 machine learning models.

CONCLUSIONS

This study revealed a close correlation between environmental growth factors and the occurrence of normal-variant short stature, particularly anthropometric characteristics. The random forest model and gradient boosting machine model performed exceptionally well, demonstrating their potential for clinical applications. These findings provide theoretical support for clinical identification and preventive measures for short stature.

Body shape from birth to adulthood is associated with skeletal development: A Mendelian randomization study

BACKGROUND

Observational studies have shown that childhood obesity is associated with adult bone health but yield inconsistent results. We aimed to explore the potential causal association between body shape and skeletal development.

METHODS

We used two-sample Mendelian randomization (MR) to estimate causal relationships between body shape from birth to adulthood and skeletal phenotypes, with exposures including placental weight, birth weight, childhood obesity, BMI, lean mass, fat mass, waist circumference, and hip circumference. Independent genetic instruments associated with the exposures at the genome-wide significance level (P < 5 × 10-8) were selected from corresponding large-scale genome-wide association studies. The inverse-variance weighted analysis was chosen as the primary method, and complementary MR analyses included the weighted median, MR-Egger, weighted mode, and simple mode.

RESULTS

The MR analysis shows strong evidence that childhood (β = -1.29 × 10-3, P = 8.61 × 10-5) and adulthood BMI (β = -1.28 × 10-3, P = 1.45 × 10-10) were associated with humerus length. Tibiofemoral angle was negatively associated with childhood BMI (β = -3.60 × 10-1, P = 3.00 × 10-5) and adolescent BMI (β = -3.62 × 10-1, P = 2.68 × 10-3). In addition, genetically predicted levels of appendicular lean mass (β = 1.16 × 10-3, P = 1.49 × 10-13), whole body fat mass (β = 1.66 × 10-3, P = 1.35 × 10-9), waist circumference (β = 1.72 × 10-3, P = 6.93 × 10-8) and hip circumference (β =1.28 × 10-3, P = 4.34 × 10-6) were all associated with tibia length. However, we found no causal association between placental weight, birth weight and bone length/width.

CONCLUSIONS

This large-scale MR analysis explores changes in growth patterns in the length/width of major bone sites, highlighting the important role of childhood body shape in bone development and providing insights into factors that may drive bone maturation.

Abnormal Bone Turnover Observed in Obese Children based on Puberty Stage-Specific Bone Turnover Marker Reference

CONTEXT

Childhood and adolescence are critical periods for lifelong bone health. The impact of obesity on these phases is controversial, which may be due to the lack of standards for age-, sex-, and puberty-specific bone turnover markers (BTMs) that could sensitively reflect bone metabolism.

OBJECTIVE

To generate age-, sex, and puberty stage-specific BTM reference curves in children and adolescents and to explore the effect of obesity on bone metabolism in the Chinese population.

METHODS

Our study was part of the Evaluation and Monitoring on School-based Nutrition and Growth in Shenzhen study. A total of 800 participants aged 6∼18 years with normal body mass index (BMI) were selected to establish BTM reference curves for boys and girls at different ages under different pubertal development stages. Additionally, 200 participants with obesity (BMI > 95th percentile) were matched with healthy children from the original cohort at a 1:1 ratio. All participants underwent bone mineral density assessment, and serum levels of procollagen type 1 N-propeptide (P1NP) and β-C-telopeptide of type I collagen (CTX) were measured.

RESULTS

The BTM values presented significant age, sex, and puberty stage differences. Analysis of serum BTMs based on the established reference revealed a higher percentage of low-level P1NP in boys with obesity (P = .005); no significant difference was observed in girls. However, the obese group showed a significantly higher proportion of high β-CTX levels for girls, not boys (P = .022).

CONCLUSION

We provide age-, sex-, and puberty stage-specific P1NP and β-CTX reference curves. According to these, obesity appeared to be a negative factor for bone formation in boys and for bone resorption in girls.

Short-term effects of Mediterranean diet on nutritional status in adults affected by Osteogenesis Imperfecta: a pilot study

BACKGROUND

Osteogenesis Imperfecta (OI) is a heterogeneous group of connective tissue disorders, characterized by varying degrees of skeletal fragility. Patients experience a range of comorbidities, such as obesity, cardiovascular, and gastrointestinal complications, especially in adulthood. All aspects that could benefit from dietary intervention. The aim of this study was to evaluate the effects of a 6-months restricted Mediterranean Diet (rMD) on nutritional status in adult patients affected by OI. We carried out a 6-months longitudinal pilot study. 14 adults (median age: 35 years; 7 women; 7 OI type III) where recruited in 2019 among the members of As.It.O.I., the Italian Association of Osteogenesis Imperfecta. As.It.O.I. All the evaluations were performed at the University of Milan, Italy. The rMD provided a reduction of 30% from daily total energy expenditure. 45% of calories derived from carbohydrates, 35% from fat and 0.7-1.0 g/kg of body weight from proteins. Comparisons of continuous variables after 6 months of intervention were performed by the paired t-test. All P-values were two-tailed, and p < 0.05 was considered significant.

RESULTS

Patients showed significant improvement in anthropometric measurements (BMI = 30.5 vs 28.1 kg/cm2, p < 0.001; Body Fat % = 32.9 vs 29.9, p = 0.006; Waist circumferences = 83.6 vs 79.6 cm; p < 0.001; Arm Fat Area = 29.8 vs 23.07 cm2; p < 0.011) and energy expenditure (REE/kg = 27.2 vs 29.2 kcal/kg, p < 0.001). Glucose and lipid profiles improved (Δglycemia = - 8.6 ± 7.3 mg/dL, p = 0.003; ΔTC = - 14.6 ± 20.1 mg/dL, p = 0.036; ΔLDL = - 12.0 ± 12.1 mg/dL, p = 0.009). Adherence to the MD significantly increased, moving from a moderate to a strong adherence and reporting an increased consumption of white meat, legumes, fish, nuts, fruits and vegetables.

CONCLUSION

A rMD was effective in improving nutritional status and dietary quality in adults with OI. These results underscores the need to raise awareness of nutrition as part of the multidisciplinary treatment of this disease.

Assessment of Biochemical Bone Turnover Markers in Polish Healthy Children and Adolescents

BACKGROUND

Assessing bone turnover in paediatric populations is crucial for understanding the physiological changes occurring during skeletal development and identifying potential abnormalities. The objective of this study was to assess osteocalcin (OC), bone alkaline phosphatase (BALP), and C-terminal telopeptide of type I collagen (CTX-I) levels reflecting bone formation and resorption for age and sex in Polish healthy children and adolescents.

MATERIALS AND METHODS

A total of 355 healthy normal-weight children and adolescents (46.5% girls) aged 1-18 years old were recruited. Total body less head (TBLH) and spine L1-L4 were used in children to assess bone mineral density (BMD) by dual-energy X-ray absorptiometry (DXA). Bone marker concentrations were determined by immunoenzymatic methods.

RESULTS

Bone marker levels in girls and boys started with higher values in the first year of life and subsequently decreased until reaching a nadir during the prepubertal period. The pubertal peak values of bone markers were reached at 11-13 years old in boys and at 9-11 years old in girls. After puberty, the adolescents showed a gradual decline in bone marker concentrations to the values observed in adults. We found positive correlations between OC level and TBLH-BMD (r = 0.329, p = 0.002), TBLH-BMD Z-score (r = 0.245, p = 0.023), and L1-L4 BMD (r = 0.280, p = 0.009) in the prepubertal group.

CONCLUSIONS

We showed serum levels of bone turnover markers-BALP, OC, and CTX-I-in relation to age and sex in healthy Polish children and adolescents. The age intervals of these markers for girls and boys aged 1-18 years old may be clinically useful in the assessment of bone metabolism in individuals with skeletal disorders.

Bone mass accrual in children

PURPOSE OF REVIEW

Bone accrual during childhood and adolescence is critical for the attainment of peak bone mass and is a major contributing factor towards osteoporosis in later life. Bone mass accrual is influenced by nonmodifiable factors, such as genetics, sex, race, ethnicity, and puberty, as well as modifiable factors, such as physical activity and diet. Recent progress in bone imaging has allowed clinicians and researchers to better measure the morphology, density, and strength of the growing skeleton, thereby encompassing key characteristics of peak bone strength. In this review, the patterning of bone accrual and contributors to these changes will be described, as well as new techniques assessing bone mass and strength in pediatric research and clinical settings.

RECENT FINDINGS

This review discusses factors influencing peak bone mass attainment and techniques used to assess the human skeleton.

SUMMARY

The rate of bone accrual and the magnitude of peak bone mass attainment occurs in specific patterns varying by sex, race, ethnicity, longitudinal growth, and body composition. Physical activity, diet, and nutritional status impact these processes. There is a need for longitudinal studies utilizing novel imaging modalities to unveil factors involved in the attainment and maintenance of peak bone strength.

Added value of waist circumference to body mass index for predicting fracture risk in obesity: a prospective study from the CARTaGENE cohort

Larger waist circumference is significantly associated with an increased risk of distal lower limb fractures in individuals aged 40-70 years with a body mass index within the normal or overweight category. Therefore, waist circumference provides additive information to body mass index for the identification of individuals at risk of obesity-related fractures.

INTRODUCTION

Waist circumference (WC) is a stronger risk factor of metabolic disorders than body mass index (BMI), but whether it holds true for fracture risk prediction remains unclear. We aimed to evaluate relationships between WC and fracture incidence within BMI categories and evaluate whether BMI modifies these relationships.

METHODS

Men and women aged 40-70 years from the CARTaGENE cohort were divided by BMI category at baseline: normal weight, overweight, and obesity. Incident fractures were identified over 7 years via linkage with healthcare administrative databases. Cox proportional hazard models estimated the relationships between WC and incident fractures at any site and by skeletal site within each BMI category. Results are reported as adjusted hazard ratios (95% confidence intervals) per 10 cm increase in WC. Effect modification was evaluated qualitatively by comparing relationships between BMI categories.

RESULTS

Of the 18 236 individuals included, 754 sustained a fracture. Significant relationships were found between WC and distal lower limb fractures in the normal (1.25 [1.08, 1.45]) and overweight (1.28 [1.07, 1.52]) BMI categories, but not in the obesity category. In the overweight category, we found an increased risk of distal upper limb fractures with increasing WC (1.49 [1.04, 2.15]). No significant relationship was observed regarding WC and fracture risk at any site or major osteoporotic fractures. An effect modification of BMI on the relationships between WC and distal lower limb fractures was observed.

CONCLUSION

WC provides both independent and additive information to BMI for the identification of individuals at risk of obesity-related fractures.

Differences in bone accrual over one year in young girls with obesity compared to Normal weight controls

Despite higher bone mineral density (BMD), women with obesity are at an increased risk of fracture compared to normal-weight women. Optimal adolescent bone accrual is critical for normal peak bone mass acquisition and future bone health. Whereas several studies have examined the impact of low body weight on bone accrual in youth, data are lacking regarding the impact of obesity on bone accrual. We examined bone accrual over one year in young women with moderate to severe obesity (OB) (n = 21) versus normal-weight controls (NWC) (n = 50). Participants were 13-25 years old. We used dual-energy X-ray absorptiometry to assess areal BMD (aBMD) and high resolution peripheral quantitative computed tomography (distal radius and tibia) to assess volumetric BMD (vBMD), bone geometry, and microarchitecture. Analyses were controlled for age and race. The mean age was 18.7 ± 2.7 years. OB and NWC were similar for age, race, height, and physical activity. OB had a higher BMI (p < 0.0001) and younger menarchal age (p = 0.022) than NWC. Over one year, OB did not demonstrate the increase in total hip BMD observed in NWC (p = 0.03). Increases in percent cortical area and cortical thickness, and cortical and total vBMD at the radius were lower in OB than in NWC (p ≤ 0.037). Groups did not differ for tibial bone accrual. We demonstrate that longitudinal bone accrual is impaired at the total hip and radial cortex in young women with obesity, raising concerns regarding their future bone health.

Vitamin D and Bone fragility in Individuals with Osteogenesis Imperfecta: A Scoping Review

Vitamin D affects several body functions, and thus general health, due to its pleiotropic activity. It plays a key role in bone metabolism, and its deficiency impacts bone development, leading to bone fragility. In osteogenesis imperfecta (OI), a group of hereditary connective tissue disorders characterized by bone fragility, additional factors, such as vitamin D deficiency, can affect the expression of the phenotype and aggravate the disorder. The aim of this scoping review was to assess the incidence of vitamin D deficit in OI patients and the association between vitamin D status and supplementation in individuals affected by OI. We searched the PubMed Central and Embase databases and included studies published between January/2000 and October/2022 evaluating vitamin D measurement and status (normal, insufficiency, deficiency) and supplementation for OI. A total of 263 articles were identified, of which 45 were screened by title and abstract, and 10 were included after a full-text review. The review showed that low levels of vitamin D was a frequent finding in OI patients. Vitamin D supplementation was mainly indicated along with drug therapy and calcium intake. Even if widely used in clinical practice, vitamin D supplementation for OI individuals still needs a better characterization and harmonized frame for its use in the clinical setting, as well as further studies focusing on its effect on bone fragility.

Decreased bone mass in adolescents with bone fragility fracture but not in young children: a case-control study

Background

The incidence of distal forearm fracture due to minimal/moderate trauma shows a bimodal distribution for age at event, with one peak occurring during early adolescence, in both boys and girls and the other one in postmenopausal females. The aim of this study was, therefore, to document whether the relationship between bone mineral density and fracture is different in young children compared with adolescents.

Methods

A matched-pair, case-control study has been conducted to evaluate bone mineral density in 469 young children and 387 adolescents of both sexes, with/without fracture due to minimal/moderate trauma with assurance that the compared groups were equally susceptible to the outcome event. All fractures were radiographically confirmed. The study utilized bone mineral areal density of the total body, spine, hips, and forearm; volumetric bone mineral density of the forearm; and metacarpal radiogrammetry measurements. The study controlled for skeletal development, bone geometry, body composition, hand grip strength, calcium intake, and vitamin D status.

Results

Adolescents with distal forearm fracture have reduced bone mineral density at multiple skeletal regions of interest. This was documented by the bone mineral areal density measurements at multiple skeletal sites (p < 0.001), volumetric bone mineral density measurements of the forearm (p < 0.0001), and metacarpal radiogrammetry (p < 0.001). Adolescent females with fracture had reduced cross-sectional areas of the radius and metacarpals. The bone status of young female and male children with fracture was no different to its controls. Increased body fatness was more prevalent among fracture cases than in controls. Around 72% of young female and male children with fracture had serum 25-hydroxyvitamin D levels below the threshold of 31 ng/ml, compared with only 42% of female controls and to 51% of male controls.

Conclusions

Adolescents with bone fragility fracture had reduced bone mineral density at multiple skeletal regions of interest, whereas this was not the case with younger children. The results of the study may have implications for the prevention of bone fragility in this segment of the pediatric population.

Muscle-to-Bone and Soft Tissue-to-Bone Ratio in Children and Adolescents with Obesity

OBJECTIVES

To explore the total and regional muscle-to-bone ratio in children and adolescents with obesity and compare the muscle-to-bone ratio (MBR) and soft tissue-to-bone ratio (SBR) to their peers with normal weight or overweight.

STUDY DESIGN

A total of 219 male and female pediatrics (mean age=12.3±2.5 years) participated in this study. Body composition was assessed with a total body dual X-ray absorptiometry. The MBR was calculated by dividing lean mass by bone mineral content. The SBR was determined by dividing the soft tissue mass (i.e., lean mass+fat mass) by bone mineral content. Differences in total and regional body composition measures between body mass index (BMI) percentile groups was assessed by ANOVA.

RESULTS

The obesity group had significantly higher MBR compared to the normal weight group for total (19.24±1.56 vs. 18.26±1.64), arm (17.11±1.67 vs. 15.88±1.81), and leg (18.41±1.68 vs. 16.62±1.55). Similarly, the obesity group had significantly higher MBR in the leg (18.41±1.68) compared to the overweight group (17.24±1.45). However, the overweight group was not significantly different from the normal weight or the obesity group for total and arm MBR. The total, arm, and leg SBR was significantly different between all BMI groups. Across the entire sample, MBR and SBR were negatively associated with high-density lipoprotein. SBR was positively associated with insulin, HOMA-IR, low-density lipoprotein, very low-density lipoprotein, triglycerides, and systolic blood pressure.

CONCLUSIONS

Children with obesity had a higher MBR and SBR compared to their normal weight peers. In addition, there were significant associations between SBR, higher levels of insulin, atherogenic lipoproteins, and increased systolic blood pressure. Thus, SBR may be useful as a marker for increased cardiometabolic disease risk, though more research in this area is warranted.

New Insights into Calorie Restriction Induced Bone Loss

Caloric restriction (CR) is now a popular lifestyle choice due to its ability in experimental animals to improve lifespan, reduce body weight, and lessen oxidative stress. However, more and more emerging evidence suggests this treatment requires careful consideration because of its detrimental effects on the skeletal system. Experimental and clinical studies show that CR can suppress bone growth and raise the risk of fracture, but the specific mechanisms are poorly understood. Reduced mechanical loading has long been thought to be the primary cause of weight loss-induced bone loss from calorie restriction. Despite fat loss in peripheral depots with calorie restriction, bone marrow adipose tissue (BMAT) increases, and this may play a significant role in this pathological process. Here, we update recent advances in our understanding of the effects of CR on the skeleton, the possible pathogenic role of BMAT in CR-induced bone loss, and some strategies to mitigate any potential side effects on the skeletal system.

Twelve weeks of a diet and exercise intervention alters the acute bone response to exercise in adolescent females with overweight/obesity

Introduction: Exercise and consumption of dairy foods have been shown to improve bone mineralization. However, little is known about the magnitude and timing of their synergistic effects on markers and regulators of bone metabolism in response to acute exercise in adolescent females with obesity, a population susceptible to altered bone metabolism and mineral properties. This study examined the influence of twelve weeks of exercise training and nutritional counselling on the bone biochemical marker response to acute exercise and whether higher dairy consumption could further influence the response. Methods: Thirty adolescent females (14.3 ± 2.0 years) with overweight/obesity (OW/OB) completed a 12-week lifestyle modification intervention involving exercise training and nutritional counselling. Participants were randomized into two groups: higher dairy intake (RDa; 4 servings/day; n = 14) or low dairy intake (LDa; 0-2 servings/d; n = 16). Participants performed one bout of plyometric exercise (5 circuits; 120 jumps) both pre- and post-intervention. Blood samples were taken at rest, 5 min and 1 h post-exercise. Serum sclerostin, osteocalcin (OC), osteoprotegerin (OPG), receptor activator nuclear factor kappa B ligand (RANKL), and C-terminal telopeptide of type 1 collagen (βCTX) concentrations were measured. Results: While there was an overall increase in sclerostin pre-intervention from pre to 5 min post-exercise (+11% p = 0.04), this response was significantly decreased post-intervention (-25%, p = 0.03) independent of dairy intake. The OPG:RANKL ratio was unresponsive to acute exercise pre-intervention but increased 1 h post-exercise (+2.6 AU; p < 0.001) post-intervention. Dairy intake did not further influence these absolute responses. However, after the 12-week intervention, the RDa group showed a decrease in the relative RANKL post-exercise response (-21.9%; p < 0.01), leading to a consistent increase in the relative OPG:RANKL ratio response, which was not the case in the LDa group. There was no influence of the intervention or dairy product intake on OC, OPG, or βCTX responses to acute exercise (p > 0.05). Conclusion: A lifestyle modification intervention involving exercise training blunts the increase in sclerostin and can augment the increase in OPG:RANKL ratio to acute exercise in adolescent females with OW/OB, while dairy product consumption did not further influence these responses.

Associations between physical physique/fitness in children and bone development during puberty: a 4-year longitudinal study

Bone growth is most remarkable during puberty. This study aimed to clarify the effects of physique and physical strength on bone mineral density and bone metabolism markers during puberty to help improve bone growth during puberty and prevent future osteoporosis. There were 277 pubertal participants (125 boys and 152 girls) in this survey from 2009 to 2015, all aged 10/11 and 14/15 years. The measures included physical fitness/physique indices (such as muscle ratio etc.), grip strength, bone density (osteo sono-assessment index, OSI), and bone metabolism markers (bone-type alkaline phosphatase and type I collagen cross-linked N-telopeptide). At 10/11-years-old for girls, a positive correlation was found between body size/grip strength and OSI. At 14/15-year-old for boys, all body size factors/grip strength were positively correlated with OSI. The change in body muscle ratio was positively correlated with change in OSI for both sexes. The height, body muscle ratio and grip strength at 10/11-year-old were significantly associated with OSI (positively) and bone metabolism markers (negatively) at 14/15-year-old for both sexes. Adequate physique building after 10/11 years for boys and before 10/11 years for girls may be effective in increasing peak bone mass.

Forearm Fractures in Overweight-Obese Children and Adolescents: A Matter of Bone Density, Bone Geometry or Body Composition?

Forearm fractures in children and adolescents are associated with increased body mass index (BMI). This bone site is non-weight-bearing and therefore is appropriate to explore the effect of BMI on bone mineral density (BMD) and bone geometry, avoiding the confounding effect of increased weight-associated mechanical loading. The aim of this review was to summarize available evidence on bone indices and body composition assessed by peripheral quantitative computed tomography (pQCT) or dual X-ray absorptiometry (DXA) at the forearm level in overweight (Ow) or obese (Ob) subjects. We conducted a review of the literature according to the PICOS model. A total of 46 studies were identified following the literature search. A final number of 12 studies were included in this review. pQCT studies evidenced that Ow and Ob children typically have normal or increased volumetric BMD (vBMD), total bone area and cortical area, with normal or reduced cortical thickness at the forearm. Outcomes from DXA evaluations are less conclusive. In almost all the studies fat mass and lean mass area at the forearm are increased. A higher fat-to-lean mass ratio has been observed in few studies. Bone strength was reported as normal or increased compared to normal weight peers. In Ow or Ob children-adolescents, vBMD, bone size and bone strength are not reduced compared to normal weight peers. The local higher fat-to-lean mass ratio may give a mismatch between bone strength and the load experienced by the distal forearm during a fall, resulting in increased risk of forearm fractures.

Subcutaneous adipose tissue is a positive predictor for bone mineral density in prepubertal children with Prader-Willi syndrome independent of lean mass

OBJECTIVES

Emerging evidence suggests a fat depot-specific relationship with bone mineral density (BMD) in children, particularly in those who are overweight/obese. However, this has not yet been investigated in detail in children with Prader-Willi syndrome (PWS), a genetic syndrome characterized by a decreased lean mass (LM) and increased fat mass (FM). The objective of this study is to investigate the relationships of LM and FM, particularly fat distribution, with bone mineral parameters.

METHODS

This is a retrospective and cross-sectional study. Forty-seven prepubertal Japanese children with PWS (22 males, mean age: 6.86 years) were included. No subjects had type 2 diabetes mellitus or osteoporotic medications. LM, FM, and BMD and bone mineral content in the total body less head and the lumbar spine were measured using dual-energy x-ray absorptiometry, in addition to subcutaneous/visceral adipose tissue (SAT/VAT), and the ratio of VAT to SAT (V/S) by computed tomography at the umbilical level. Bone mineral apparent density was calculated to correct for bone size.

RESULTS

LM positively correlated with bone mineral parameters after controlling for age, sex, growth hormone (GH) treatment, and FM. Although FM did not correlate with bone mineral parameters, compartment-specific analysis revealed that SAT positively and V/S negatively correlated with bone mineral parameters after controlling for age, sex, GH treatment and LM.

CONCLUSIONS

A compartment-specific effect of FM on bone mineral parameters was noted such that SAT was a positive predictor for BMD independent of LM in prepubertal children with PWS.

Effect of physical activity and BMI SDS on bone metabolism in children and adolescents

OBJECTIVE

Children with obesity are known to have reduced bone density and are at a higher risk for fractures. This may be caused by decreased physical activity or a metabolic phenomenon. In this study, we evaluated associations of physical activity with bone metabolism in children and adolescents with and without obesity.

METHODS

Results from 574 visits of 397 subjects, 191 girls and 206 boys aged five to 18 years (mean: 11.7 ± 2.8) representing 180 children with (mean BMI SDS 2.5 ± 0.4) and 217 without obesity (mean BMI SDS 0.2 ± 1.0) from the LIFE Child study, a population-based cohort of children/adolescents with normal weight and with obesity were analyzed for the impact of their daily physical activity (MET/day, SenseWear Accelerometer) on serum SDS levels for bone formation (alkaline phosphatase, osteocalcin, procollagen type I N propeptide [P1NP]), bone resorption (beta-crosslaps), and calcium homeostasis (parathormone, OH-25-vitamin D) by a linear regression model adjusted for gender- and age-based differences.

RESULTS

For male subjects, BMI SDS significantly influenced the association of physical activity to PTH, vitamin D, and beta-crosslaps SDS levels. A higher physical activity was accompanied by increased PTH but decreased vitamin D SDS levels in children with normal weight. In males with obesity, all levels remained unaltered. In females, BMI SDS significantly impacted the association of physical activity to PTH, vitamin D, P1NP, beta-crosslaps, and osteocalcin SDS levels. In females with obesity, higher physical activity was related to higher SDS levels of vitamin D, P1NP, and beta-crosslaps. In contrast, in normal weight females, only PTH SDS was higher.

CONCLUSIONS

The effect of daily physical activity on bone metabolic markers and calciotropic hormones depends significantly on gender and BMI SDS. However, higher levels of physical activity were associated with increased bone turnover for female subjects with obesity only. Thus, motivating especially girls with obesity to be physically active may help improve their bone health.

The effects of home confinement on pediatric fractures during the COVID 19 outbreak

OBJECTIVE

To control the transmission of coronavirus disease 2019 (COVID-19), the Chinese government encouraged people to stay at home. This study aimed to evaluate the effects of home confinement on the occurrence of fractures among children.

STUDY DESIGN

We retrospectively reviewed children admitted to Children's Hospital of Chongqing Medical University, for traumatic injury from January 24 to March 10, 2020, and the same time period in 2017, 2018 and 2019. At the same time, children with fracture were screened out and the date for the past 4 years was compared in terms of etiology, location of fracture, sex and age to evaluate the effects of home confinement on the epidemiology of pediatric fractures during the COVID-19 outbreak.

RESULTS

There were 6066 fractures in5,346 patients in 2017-2019, and 1034 fractures in 862 patients in 2020; the number of patients in all years reached a peak at the age of 2 to 4 years. The patients were slightly younger in 2020 than in 2017-2019 (t = 9.953, 95% CI: 0.846-1.262), and the proportion of boys in 2017-2019 is higher than in 2020 (X² = 6.944, P = 0.008). Home confinement and traffic restriction resulted in a reduction in traffic accidents-associated fractures among children (X² = 16.399, P < 0.001).

CONCLUSION

Home confinement lead to the significant reduction in the number of pediatric fractures, especially in male children, but the number of patients under 4 years old was still considerable, and the proportion of younger patients even increased. Therefore, the perspective of children should not be relaxed during home isolation.

Relationship Between Bone Mineral Density and Body Composition According to Obesity Status in Children

OBJECTIVE

To analyze the relationship between body composition, metabolic parameters, and bone mineral density (BMD) according to sex and the degree of obesity in children and adolescents.

METHODS

A total of 236 subjects with obesity, aged 10 to 15 years (36.9% girls), were enrolled. Obesity was classified into simple (SmOb) and extreme (ExOb) forms. The BMD of the total body, less head, was measured by dual energy x-ray absorptiometry, and the BMD z-score was used to evaluate the relationship of body composition with metabolic parameters.

RESULTS

BMD z-scores were higher in subjects with ExOb than in those with SmOb. Lean mass index (LMI), body mass index z-score, and vitamin D intake showed positive relationships, whereas percentage of body fat and serum leptin level showed negative relationships with BMD z-scores in boys. In girls, LMI and body mass index z-score showed positive relationships with BMD z-scores. In multivariable linear regressions, serum leptin level showed negative relationships with BMD z-score, only in boys. In addition, positive relationships of LMI and negative relationships of percentage of body fat with BMD z-scores were observed in subjects with SmOb. However, positive relationships of LMI with BMD z-scores were attenuated in subjects with ExOb.

CONCLUSION

High BMD appears to be positively associated with lean mass in children and adolescents with obesity, which might be a natural protective mechanism to withstand the excess weight. However, excessive body fat appears to be negatively associated with BMD, which might attenuate the positive relationship between lean mass and BMD in subjects with ExOb.

Influence of weight status on bone mineral content measured by DXA in children

INTRODUCTION

Childhood obesity is a public health problem with repercussions in later life. As tissue formation peaks in childhood we determined how weight status influences bone mineral content.

MATERIAL AND METHODS

We studied 553 children aged 4-18 years over 10 years (46.8% girls). We measured age, weight, height and through bone densitometry (DXA), bone mineral content (BMC), bone mineral density (BMD), and waist, arm and hip circumferences. The patients were divided into groups using the body mass index z-score: underweight, normal weight, overweight, obese and very obese.

RESULTS

BMC and BMD values were highest in the normal-weight and overweight groups. Logistic regression showed bone mineralization was inversely associated with waist circumference, the association being positive for weight and age. No differences were found according to sex.

DISCUSSION

Studies of the relationship between weight and bone mineralization report contradictory results, often because of different study designs. Moreover, studies in children are either few or with small samples. Our findings in a large sample show the importance of weight status in bone mineralization given the risk of bone fractures or osteoporosis.

CONCLUSIONS

Weight status influenced bone mineralization. BMC and BMD decreased in children with a higher degree of obesity. Waist circumference correlated negatively with bone mineralization.

PCA-based GRS analysis enhances the effectiveness for genetic correlation detection

Genetic risk score (GRS, also known as polygenic risk score) analysis is an increasingly popular method for exploring genetic architectures and relationships of complex diseases. However, complex diseases are usually measured by multiple correlated phenotypes. Analyzing each disease phenotype individually is likely to reduce statistical power due to multiple testing correction. In order to conquer the disadvantage, we proposed a principal component analysis (PCA)-based GRS analysis approach. Extensive simulation studies were conducted to compare the performance of PCA-based GRS analysis and traditional GRS analysis approach. Simulation results observed significantly improved performance of PCA-based GRS analysis compared to traditional GRS analysis under various scenarios. For the sake of verification, we also applied both PCA-based GRS analysis and traditional GRS analysis to a real Caucasian genome-wide association study (GWAS) data of bone geometry. Real data analysis results further confirmed the improved performance of PCA-based GRS analysis. Given that GWAS have flourished in the past decades, our approach may help researchers to explore the genetic architectures and relationships of complex diseases or traits.

Association between Visceral Fat and Bone Mineral Density in Both Male and Female Patients with Adult Growth Hormone Deficiency

Aim

Adult growth hormone deficiency (AGHD) is associated with an increased risk of fractures. The interactions between various body composition and bone are known to be complex in nature. However, very few studies have examined this crosstalk in AGHD. In this study, we sought to investigate the relationship between various parameters of body composition and bone mineral density (BMD) as well as determine the role of visceral fat in determining the bone mass in patients with AGHD.

Methods

We conducted a cross-sectional study on 57 patients with AGHD. Anthropometry, biochemistry, and analysis of body composition and BMD were performed according to standard protocols. Male and female patients were classified into those with osteoporosis and those without osteoporosis (normal subjects and patients with osteopenia). Further, we analyzed the correlation between the BMD and measurements obtained for various body composition parameters in male and female AGHD patients.

Results

Our findings indicated that among female AGHD patients, those with osteoporosis had a significantly higher levels of fat mass (FM) and visceral adipose tissue mass (VATM) (both, P < 0.05) than those without osteoporosis. Further, Pearson correlation analysis showed that the values of age, body mass index (BMI), FM, and VATM correlated negatively with BMD in women with AGHD (all P < 0.05); however, this association was not noted in men. After adjusting for the other covariates, VATM was found to be independently correlated with the BMD in female patients with AGHD.

Conclusions

A close correlation was noted between VATM and BMD in female patients with AGHD.

Bone Mineral Density of Femur and Lumbar and the Relation between Fat Mass and Lean Mass of Adolescents: Based on Korea National Health and Nutrition Examination Survey (KNHNES) from 2008 to 2011

It is most important to reach the maximum bone density in the childhood period to prevent developing osteoporosis; it is widely known that increased body weight has a positive correlation with bone density and that even though both the fat mass and lean mass have a significant impact on bone density, the latter mass has more importance for adults. Therefore, the study analyzed to identify the relationship between bone density and both fat mass and lean mass of Korean adolescents. Subjects were chosen among 21,303 people from the Korea National Health and Nutrition Examination Survey (KNHNES) between 2008 and 2011 that took a bone density checkup; as a result, 1454 teenagers aged between 12 and 18 were selected. Data analysis was performed in SAS ver. 9.4 (SAS Institute Inc., Cary, NC, USA) following the KNHNES and the weighted complex sample analysis was conducted; body fat mass and lean mass were divided into quintile groups, and to figure out the differences in bone density that were analyzed in six models adjusted by body weight (kg) and walking (yes/no), muscle strengthening exercises (yes/no), nutrition (intake of ca (g), and serum vitamin D (ng/mL)). Then, the generalized linear model (GLM) and trend test were conducted for each gender with a significance level of 0.05. The bone density differences of fat mass and lean mass were analyzed. The result of Model 6 considering all correction variables is as follows; in the case of male adolescents, the total femur and lumbar spine showed a significant difference (F = 13.120, p < 0.001; F = 12.900, p < 0.001) for fat mass, and the trend test showed that the figures significantly decreased (β = −0.030, p < 0.001; −0.035, p < 0.001). Meanwhile, for lean mass, the total femur and lumbar spine had a significant difference (F = 16.740, p < 0.001; F = 20.590, p < 0.001) too, but the trend test showed a significant increase (β = 0.054, p < 0.001; 0.057, p < 0.001). In the case of female adolescents, the lumbar spine (F = 3.600, p < 0.05) for lean mass showed a significant difference, and it also significantly rose in the trend test too (β = 0.020, p < 0.01). To sum up the results, for male adolescents, the bone density differences for fat mass (FM) and lean mass (LM) all had significant differences, but for female adolescents, only the lumbar spine for LM showed such a result. Meanwhile, both genders showed that LM had a more positive impact on bone density than FM.

Leptin signaling and the intervertebral disc: Sex dependent effects of leptin receptor deficiency and Western diet on the spine in a type 2 diabetes mouse model

Type 2 diabetes and obesity are associated with back pain in juveniles and adults and are implicated in intervertebral disc (IVD) degeneration. Hypercaloric Western diets are associated with both obesity and type 2 diabetes. The objective of this study was to determine if obesity and type 2 diabetes result in spinal pathology in a sex-specific manner using in vivo diabetic and dietary mouse models. Leptin is an appetite-regulating hormone, and its deficiency leads to polyphagia, resulting in obesity and diabetes. Leptin is also associated with IVD degeneration, and increased expression of its receptor was identified in degenerated IVDs. We used young, leptin receptor deficient (Db/Db) mice to mimic the effect of diet and diabetes on adolescents. Db/Db and Control mice were fed either Western or Control diets, and were sacrificed at 3 months of age. Db/Db mice were obese, while only female mice developed diabetes. Female Db/Db mice displayed altered IVD morphology, with increased intradiscal notochordal band area, suggesting delayed IVD cell proliferation and differentiation, rather than IVD degeneration. Motion segments from Db/Db mice exhibited increased failure risk with decreased torsional failure strength. Db/Db mice also had inferior bone quality, which was most prominent in females. We conclude that obesity and diabetes due to impaired leptin signaling contribute to pathological changes in vertebrae, as well as an immature IVD phenotype, particularly of females, suggesting a sex-dependent role of leptin in the spine.

Cytokines, Adipokines, and Bone Markers at Rest and in Response to Plyometric Exercise in Obese vs Normal Weight Adolescent Females

BACKGROUND

In adults, excess adiposity has been associated with low-grade, chronic inflammation and compromised bone health, but less is known about these linkages in children. The purpose of this study was to compare the circulating levels of inflammatory cytokines, adipokines, osteokines, and bone markers at rest and in response to plyometric exercise between obese and normal weight adolescent females.

METHODS

Ten normal weight (BMI = 21.3 ± 2) and 10 obese (BMI = 32.9 ± 4), postmenarcheal females, aged 13-17 years, performed one bout of plyometric exercise (5 circuits; 120 jumps). Blood samples were taken at rest, 5 min, 1 h, and 24 h post-exercise. Tumor necrosis factor alpha (TNF-α), interleukin 6 (IL-6), insulin, leptin, osteocalcin, carboxy-terminal telopeptide (CTX), sclerostin, and parathyroid hormone (PTH) were measured in serum.

RESULTS

Cytokines were not different between groups at rest or over time with IL-6 increasing (+31%; p = 0.04) 5 min post-exercise and TNF-α decreasing (-9%; p = 0.001) 1 h post-exercise. Insulin and leptin were higher in the obese compared to the normal weight females. In both groups, insulin significantly increased 5 min post-exercise but remained elevated 1 h post-exercise only in the obese group. Leptin did not change in response to exercise. Osteocalcin was lower in the obese group across time and increased (+12%; p = 0.02) 24 h post-exercise in both groups. CTX was similar between groups at rest and decreased (-24%; p < 0.001) 1 h post-exercise. Sclerostin was similar between groups at rest, but there was a significant interaction reflecting a significant increase (+29%; p = 0.04) 5 min post-exercise in the obese group and a non-significant decrease (-13%; p = 0.08) in normal weight controls. PTH increased 5 min post-exercise, dropped 1 h post-exercise to lower than pre-exercise, and returned to baseline 24 h post-exercise in both groups.

CONCLUSION

Obese adolescent females from our study had no evidence of resting inflammation or differences in bone resorption but show blunted bone formation when compared to normal weight controls. The direction and temporal changes in inflammatory cytokines, adipokines, and bone turnover markers to exercise were similar in both groups, reflecting an overall bone anabolic response for most biomarkers, except sclerostin, which increased only in the obese females immediately post-exercise, suggesting a different systemic regulation of sclerostin depending on adiposity.

The role of PPARγ in childhood obesity-induced fractures

Globally, obesity is on the rise with ~ 30% of the world’s population now obese, and childhood obesity is following similar trends. Childhood obesity has been associated with numerous chronic conditions, including musculoskeletal disorders. This review highlights the effects of childhood adiposity on bone density by way of analyzing clinical studies and further describing two severe skeletal conditions, slipped capital femoral epiphysis and Blount’s disease. The latter half of this review discusses bone remodeling and cell types that mediate bone growth and strength, including key growth factors and transcription factors that help orchestrate this complex pathology. In particular, the transcriptional factor peroxisome proliferator-activated receptor gamma (PPARγ) is examined as it is a master regulator of adipocyte differentiation in mesenchymal stem cells (MSCs) that can also influence osteoblast populations. Obese individuals are known to have higher levels of PPARγ expression which contributes to their increased adipocyte numbers and decreased bone density. Modulating PPAR*gamma* signaling can have significant effects on adipogenesis, thereby directing MSCs down the osteoblastogenesis pathway and in turn increasing bone mineral density. Lastly, we explore the potential of PPARγ as a druggable target to decrease adiposity, increase bone density, and be a treatment for children with obesity-induced bone fractures.

Body Weight and Body Mass Index Influence Bone Mineral Density in Late Adolescence in a Two-Year Follow-Up Study. The Tromsø Study: Fit Futures

Determinants of bone acquisition in late adolescence and early adulthood are not well‐described. This 2‐year follow‐up study explored the associations of body weight (BW), body mass index (BMI), and changes in weight status with adolescent bone accretion in a sample of 651 adolescents (355 girls and 296 boys) between 15 and 19 years of age from The Tromsø Study: Fit Futures. This Norwegian population‐based cohort study was conducted from 2010 to 2011 and was repeated from 2012 to 2013. We measured femoral neck, total hip, and total body bone mineral content and areal bone mineral density (aBMD) by dual‐energy X‐ray absorptiometry. We measured height, BW, calculated BMI (kg/m ²), and collected information on lifestyle at both surveys. Mean BMI (SD) at baseline was 22.17 (3.76) and 22.18 (3.93) in girls and boys, respectively. Through multiple linear regression, baseline BW and BMI were positively associated with ∆aBMD over 2 years of follow‐up at all skeletal sites in boys ( p < 0.05), but not in girls. ∆BW and ∆BMI predicted ∆aBMD and ∆BMC in both sexes, but the strength of the associations was moderate. Individuals who lost weight during follow‐up demonstrated a slowed progression of aBMD accretion compared with those gaining weight, but loss of BW or reduction of BMI during 2 years was not associated with net loss of aBMD. In conclusion, our results confirm that adequate BW for height in late adolescence is important for bone health. Associations between change in weight status and bone accretion during follow‐up were moderate and unlikely to have any clinical implication on adolescents of normal weight. Underweight individuals, particularly boys, are at risk of not reaching optimal peak bone mass and could benefit from an increase in BMI. © 2019 The Authors. JBMR Plus is published by Wiley Periodicals, Inc. on behalf of the American Society for Bone and Mineral Research.

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.

Long-term childhood body mass index and adult bone mass are linked through concurrent body mass index and body composition

Body mass plays a crucial role in the bone growth and development, but few studies have examined the association of long-term cumulative impact and trajectory patterns of childhood body mass index (BMI) with adult bone mass, and the mediation effect of adult BMI and body composition on these associations. A total of 397 Chinese adults (54.4%) who had been examined for BMI 4-8 times during childhood (6-19 years) and bone mass in adulthood (29-37 years), were included for analysis. Adult bone mineral content (BMC), areal bone mineral density (aBMD) and body composition were assessed via dual-energy x-ray absorptiometry. Childhood BMI growth curves were constructed using a random-effects mixed model. The area under the curve (AUC) was calculated to represent the long-term impact of childhood BMI. At baseline, 24.4%, 66.2%, 7.6% and 1.8% of the participants were underweight, normal weight, overweight and obese, respectively. Quadratic curve parameters of childhood BMI differed significantly between groups of adult whole body (WB) BMC, lumbar spine (LS) aBMD and femoral neck (FN) aBMD, with low BMC/aBMD groups having lower childhood BMI than the normal groups. AUC of childhood BMI was significantly and positively related to adult WB BMC and aBMD at each site, irrespective of sex. Significant mediation effects of adult BMI were shown on the association of childhood BMI AUC with adult WB BMC in males (52.0%) and FN aBMD in both sexes (males: 65.4%; females: 64.3%). Additionally, mediation effect of fat mass index was only noted on the association of childhood BMI AUC with adult WB BMC (41.3%), with a positive total indirect effect estimated at 0.118. The adult lean mass index, by contrast, mediated the childhood BMI-adult BMC/aBMD association positively at all sites in males (71.5%~89.2%) and at WB BMC in females (45.0%). These findings suggest that the impact of body weight on adult bones originates from childhood, which is mediated by concurrent BMI and body composition.

Mechanisms Involved in Childhood Obesity-Related Bone Fragility

Childhood obesity is one of the major health problems in western countries. The excessive accumulation of adipose tissue causes inflammation, oxidative stress, apoptosis, and mitochondrial dysfunctions. Thus, obesity leads to the development of severe co-morbidities including type 2 diabetes mellitus, liver steatosis, cardiovascular, and neurodegenerative diseases which can develop early in life. Furthermore, obese children have low bone mineral density and a greater risk of osteoporosis and fractures. The knowledge about the interplay bone tissue and between adipose is still growing, although recent findings suggest that adipose tissue activity on bone can be fat-depot specific. Obesity is associated to a low-grade inflammation that alters the expression of adiponectin, leptin, IL-6, Monocyte Chemotactic Protein 1 (MCP1), TRAIL, LIGHT/TNFSF14, OPG, and TNFα. These molecules can affect bone metabolism, thus resulting in osteoporosis. The purpose of this review was to deepen the cellular mechanisms by which obesity may facilitate osteoporosis and bone fractures.

Fat and bone in children - where are we now?

The risk of fracture secondary to low-impact trauma is greater in obese children, suggesting obese children are at risk of skeletal fragility. However, despite this finding, there is a lack of agreement about the impact of excessive adiposity on skeletal development. The combination of poor diet, sedentary lifestyle, greater force generated on impact through falls, and greater propensity to falls may in part explain the increased risk of fracture in obese children. To date, evidence suggests that in early childhood years, obesity confers a structural advantage to the developing skeleton. However, in time, this relationship attenuates and then reverses, such that there is a critical period during skeletal development when obesity has a detrimental effect on skeletal structure and strength. Fat mass may be important to the developing cortical and trabecular bone compartments, provided that gains in fat mass are not excessive. However, when fat accumulation reaches excessive levels, unfavorable metabolic changes may impede skeletal development. Evidence from studies examining bone microstructure suggests skeletal adaption to excessive load fails, and bone strength is relatively diminished in relation to body size in obese children. Mechanisms that may explain these changes include changes in the hormonal environment, particularly in relation to alterations in adipokines and fat distribution. Given the concomitant rise in the prevalence of childhood obesity and fractures, as well as adult osteoporosis, further work is required to understand the relationship between obesity and skeletal development.

The effect of weight loss on body composition, serum bone markers, and adipokines in prepubertal obese children after 1-year intervention

Purpose/Aim: The influence of weight loss on bone turnover and bone quality in childhood remains controversial, but it may implicate interactions between adiposity and bone metabolism. Therefore, we studied the relationships between bone markers and adipokines during weight loss in obese children.

MATERIALS AND METHODS

We determined serum leptin, soluble leptin receptor, adiponectin, bone alkaline phosphatase (BALP), C-terminal telopeptide of type I collagen (CTX-I), osteocalcin (OC), carboxylated-OC (Gla-OC), undercarboxylated-OC (Glu-OC), sclerostin, body composition, and bone mineral density (BMD) in 40 obese prepubertal children before and after therapy. The control group, matched for sex and age, consisted of 40 non-obese children.

RESULTS

We found that values of the total body less head-bone mineral content (TBLH-BMC) and TBLH-BMD were significantly increased, but TBLH-BMD Z-score was decreased by 25% (p = 0.002) in obese children with weight loss after therapy. We observed increases of CTX-I to OC ratio (p = 0.009), and Gla-OC concentrations (p = 0.049). Changes in TBLH-BMD Z-score in patients were positively correlated with changes in BMI Z-score (p = 0.001), percentage of fat mass (p = 0.004), and BALP activity (p = 0.01). Changes in BALP activity were negatively correlated (p < 0.001) with changes in adiponectin concentrations, while changes in sclerostin levels were positively correlated (p = 0.001) with leptin changes.

CONCLUSIONS

We suggest that alterations in adipokines metabolism were associated with a lower rate of bone mineral accrual as a result of decreased bone formation rather than increased bone resorption. The lower rate of bone mass accrual in weight losing children may be an effect of reduced BALP levels related to increase in adiponectin levels.

Bone mineral density is compromised in very long-term survivors of irradiated childhood brain tumor

INTRODUCTION

The increase in the number of childhood brain tumor survivors warrants detailed research to increase our knowledge regarding the possible physical and psychosocial adverse outcomes of tumor and tumor therapy. The aim of this study was to evaluate the current bone health by measuring the bone mineral density (BMD) in irradiated, adult long-term survivors of childhood brain tumors.

MATERIAL AND METHODS

We studied a national cohort of 74 adult survivors of childhood brain tumors treated with irradiation in Finland between 1970 and 2008. Dual X-ray absorptiometry (DXA) was performed for the femoral necks, total hips, and lumbar spine. Laboratory tests were conducted for evaluating the pituitary, thyroid, and gonadal functions. The participants were interviewed, examined clinically, and the disease and treatment related data were retrieved from the patient files.

RESULTS

One fourth of the patients (23.6%) had sex- and age-normalized z-scores below the expected range for age (z-score ≤ -2.0). Mean BMD scores were decreased in all the DXA measurement sites. Male sex was associated with low BMD (p < .05), while body mass index (BMI) had a significant positive association with BMD (p < .01). Mode of irradiation (with or without spinal irradiation) or inclusion of chemotherapy in the treatment did not affect BMD significantly. However, patients with a ventriculoperitoneal shunt had lower BMD than those without a shunt (p < .05). Follicle stimulating hormone (FSH) and luteinizing hormone (LH) were negatively associated with BMD in women (p < .05). However, a higher cumulative dose of glucocorticoids during treatment was not associated with lower BMD, while low BMD was significantly associated with previous fractures in long bones.

DISCUSSION

Low BMD should be taken in consideration in treatment of irradiated childhood brain tumor survivors especially in those with previous fractures in long bones.

Effects of interventions with a physical activity component on bone health in obese children and adolescents: a systematic review and meta-analysis

Given the rise in pediatric obesity, clarifications on the relationship between obesity and bone health and on the impact of structured intervention on this relationship are needed. This systematic review and meta-analysis investigated the effect of obesity on bone health and assessed the effect of structured intervention in children and adolescents with obesity. Medline complete, OVID, CINAHL, EMBASE and PubMed databases were searched for studies on obesity and bone health variables up to September 2016, then an update occurred in March 2016. Search items included obesity, childhood, dual energy X-ray absorptiometry and peripheral quantitative computed tomography. Twenty-three studies (14 cross-sectional and nine longitudinal) matched the inclusion criteria. Results from the meta-analysis (cross-sectional studies) confirmed that children and adolescents with obesity have higher bone content and density than their normal weight peers. Results from longitudinal studies remain inconclusive as only 50% of the included studies reported a positive effect of a structured intervention program on bone health. As such, the meta-analysis reported that structured intervention did not influence bone markers despite having beneficial effects on general health in youth with obesity.

Increased levels of sodium chloride directly increase osteoclastic differentiation and resorption in mice and men

To better understand the association between high salt intake and osteoporosis, we investigated the effect of sodium chloride (NaCl) on mice and human osteoclastogenesis. The results suggest a direct, activating role of NaCl supplementation on bone resorption.

INTRODUCTION

High NaCl intake is associated with increased urinary calcium elimination and parathyroid hormone (PTH) secretion which in turn stimulates the release of calcium from the bone, resulting in increased bone resorption. However, while calciuria after NaCl loading could be shown repeatedly, several studies failed to reveal a significant increase in PTH in response to a high-sodium diet. Another possible explanation that we investigated here could be a direct effect of high-sodium concentration on bone resorption.

METHODS

Mouse bone marrow macrophage and human peripheral blood mononuclear cells (PBMC) driven towards an osteoclastogenesis pathway were cultivated under culture conditions mimicking hypernatremia environments.

RESULTS

In this study, a direct effect of increased NaCl concentrations on mouse osteoclast differentiation and function was observed. Surprisingly, in a human osteoclast culture system, significant increases in the number of tartrate-resistant acid phosphatase (TRAP)-positive osteoclasts, calcitonin receptor (CTR)-positive osteoclasts, nuclear factor-activated T cells c1 (NFATc1) gene expression, and areal and volumetric resorptions were observed for increasing concentrations of NaCl. This suggests a direct, activating, cell-mediated effect of increased concentrations of NaCl on osteoclasts.

CONCLUSIONS

The reported that enhanced bone resorption after high-sodium diets may not only be secondary to the urinary calcium loss but may also be a direct, cell-mediated effect on osteoclastic resorption. These findings allow us to suggest an explanation for the clinical findings independent of a PTH-mediated regulation.

Obesity status influences the relationship among serum osteocalcin, iron stores and insulin sensitivity

BACKGROUND & AIMS

Increased iron stores significantly influence the clinical course of several chronic metabolic diseases. Recent studies have shown that iron overload decreases osteocalcin. We aimed to explore the relationship among osteocalcin, iron stores and insulin sensitivity.

METHODS

Extensive clinical and laboratory measurements, including serum ferritin, cross-linked C-telopeptide of type I collagen (CTX) and osteocalcin (OC) concentrations, were analyzed in 250 adult consecutive Caucasian men. Insulin sensitivity was evaluated through frequently sampled intravenous glucose tolerance tests with minimal model analysis.

RESULTS

Circulating serum ferritin were negatively associated with serum OC and CTX (p = 0.004 and p = 0.045 respectively). In all subjects as a whole, BMI and ferritin contributed to explain 5.2% of OC variance after controlling for age and smoking status. However, the association between OC and insulin sensitivity remained significant only in lean subjects (BMI < 25 kg/m², r = 0.468; p = 0.006) whereas the link between serum ferritin concentration and OC and CTX were significant only in overweight/obese subjects (BMI ≥ 25 kg/m², r = -0.229; p = 0.002 and r = -0.196; p = 0.008, respectively).

CONCLUSIONS

The association of circulating osteocalcin with parameters of insulin sensitivity and iron stores were dependent on obesity status. Increased iron stores could contribute to the detrimental metabolic effects of overweight and obesity on bone.

Intragastric balloon as an adjunct to lifestyle programme in severely obese adolescents: impact on biomedical outcomes and skeletal health

Intragastric Balloons are a temporary, reversible and safer option compared to bariatric surgery to promote significant weight loss, leading to improved metabolic outcomes. However, due to subsequent weight regain, alternative procedures are now preferred in adults. In adolescents, more amenable to lifestyle change, balloons may be an alternative to less reversible procedures. Our aim was to assess the tolerability and efficacy of the intragastric balloon in severely obese adolescents and the impact of associated weight loss on biomedical outcomes (glucose metabolism, blood pressure, lipid profiles) and bone density. A 2-year cohort study of 12 adolescents (BMI >3.5 s.d., Tanner stage >4) following 6 months intragastric balloon placement was carried out. Subjects underwent anthropometry, oral glucose tolerance test, and DEXA scans at 0, 6 and 24 months. The results showed clinically relevant improvements in blood pressure, insulin: glucose metabolism, liver function and sleep apnoea at 6 months. Changes were not sustained at 2 years though some parameters (Diastolic BP, HBA1c, insulin AUC) demonstrated longer-term improvement despite weight regain. Despite weight loss, bone mass accrual showed age appropriate increases. In conclusion, the intragastric balloon was safe, well tolerated and effective in supporting short-term weight loss and clinically relevant improvement in obesity-related complications, which resolved in some individuals. Benefits were not sustained in the majority at 2 years.

Do bone mineral content and density determine fracture in children? A possible threshold for physical activity

BackgroundRelations between bone parameters, physical exertion, and childhood fractures are complex. We aimed to estimate the associations between fracture history and bone mineral content (BMC) and areal bone mineral density (aBMD) at 7 years of age, by levels of physical activity, as a proxy for trauma frequency.MethodsWe used data collected from 2,261 children of the Generation XXI birth cohort, assembled in 2005/6 in Porto, Portugal. At the age of 7 years (2012/4), fracture history, time spent per week in active play, and sports practice were reported by parents. Subtotal and lumbar spine (LS) BMC and aBMD were measured using whole-body dual-energy X-ray absorptiometry.ResultsBoys and girls in the highest categories of time spent in sports practice or active play generally had higher BMC and aBMD. Among girls, BMC and aBMD were protective of fracture only in the highest quarter of active play (>660 min/week)-odds ratios (OR; 95% confidence interval (95% CI)) for subtotal BMC=0.27 (0.11-0.67), subtotal aBMD=0.18 (0.06-0.49), and LS aBMD=0.41 (0.22-0.75). For boys in the highest quarter of sports practice (>240 min/week), subtotal and LS BMC were protective of fracture-OR=0.39 (0.16-0.98) and 0.51 (0.27-0.96), respectively.ConclusionIn prepubertal children, BMC and aBMD predicted fracture history only in the highest levels of physical activity.

The Impact of Fat and Obesity on Bone Microarchitecture and Strength in Children

A complex interplay of genetic, environmental, hormonal, and behavioral factors affect skeletal development, several of which are associated with childhood fractures. Given the rise in obesity worldwide, it is of particular concern that excess fat accumulation during childhood appears to be a risk factor for fractures. Plausible explanations for this higher fracture risk include a greater propensity for falls, greater force generation upon fall impact, unhealthy lifestyle habits, and excessive adipose tissue that may have direct or indirect detrimental effects on skeletal development. To date, there remains little resolution or agreement about the impact of obesity and adiposity on skeletal development as well as the mechanisms underpinning these changes. Limitations of imaging modalities, short duration of follow-up in longitudinal studies, and differences among cohorts examined may all contribute to conflicting results. Nonetheless, a linear relationship between increasing adiposity and skeletal development seems unlikely. Fat mass may confer advantages to the developing cortical and trabecular bone compartments, provided that gains in fat mass are not excessive. However, when fat mass accumulation reaches excessive levels, unfavorable metabolic changes may impede skeletal development. Mechanisms underpinning these changes may relate to changes in the hormonal milieu, with adipokines potentially playing a central role, but again findings have been confounding. Changes in the relationship between fat and bone also appear to be age and sex dependent. Clearly, more work is needed to better understand the controversial impact of fat and obesity on skeletal development and fracture risk during childhood.

A randomized controlled trial of dance exergaming for exercise training in overweight and obese adolescent girls

BACKGROUND

Structured exergaming with prescribed moderate intensity physical activity has reduced adiposity among adolescents. The extent to which adolescents reduce adiposity when allowed to self-select intensity level is not known.

OBJECTIVE

The objective of the study was to examine the influence of exergaming on adolescent girls' body composition and cardiovascular risk factors.

METHODS

This randomized controlled trial assigned 41 overweight and obese girls aged 14 to 18 years to group-based dance exergaming (36 h over 3 months) or to a self-directed care control condition. Body size and composition were measured by anthropometry, dual-energy X-ray absorptiometry [%fat and bone mineral density {BMD}] and magnetic resonance imaging. Cardiovascular risk factors included blood pressure, cholesterol, triglycerides, glucose and insulin.

RESULTS

Attrition was 5%. Using analysis of covariance controlling for baseline value, age and race, there were no significant condition differences. Per protocol (attended >75%), the intervention group significantly decreased abdominal subcutaneous adiposity and increased trunk and spine BMD (ps < 0.05). Per protocol (>2600 steps/session), the intervention group significantly decreased leg %fat and decreased abdominal subcutaneous and total adiposity (ps < 0.05).

CONCLUSION

Exergaming reduced body fat and increased BMD among those adolescent girls who adhered. Further research is required before exergaming is recommended in clinical settings.

Chronic High Dose Alcohol Induces Osteopenia via Activation of mTOR Signaling in Bone Marrow Mesenchymal Stem Cells

Chronic consumption of excessive alcohol results in reduced bone mass, impaired bone structure, and increased risk of bone fracture. However, the mechanisms underlying alcohol-induced osteoporosis are not fully understood. Here, we show that high dose chronic alcohol consumption reduces osteogenic differentiation and enhances adipogenic differentiation of bone marrow mesenchymal stem cells (BMMSCs), leading to osteopenia in a mouse model. Mechanistically, impaired osteo/adipogenic lineage differentiation of BMMSCs is due to activation of a phosphatidylinositide 3-kinase/AKT/mammalian target of rapamycin (mTOR) signaling cascade, resulting in downregulation of runt-related transcription factor 2 and upregulation of peroxisome proliferator-activated receptor gamma via activation of p70 ribosomal protein S6 kinase. Blockage of the mTOR pathway by rapamycin treatment ameliorates alcohol-induced osteopenia by rescuing impaired osteo/adipogenic lineage differentiation of BMMSCs. In this study, we identify a previously unknown mechanism by which alcohol impairs BMMSC lineage differentiation and reveal a potential rapamycin-based drug therapy for alcohol-induced osteoporosis. Stem Cells 2016;34:2157-2168.

Fructose consumption does not worsen bone deficits resulting from high-fat feeding in young male rats

Dietary-induced obesity (DIO) resulting from high-fat (HF) or high-sugar diets produces a host of deleterious metabolic consequences including adverse bone development. We compared the effects of feeding standard rodent chow (Control), a 30% moderately HF (starch-based/sugar-free) diet, or a combined 30%/40% HF/high-fructose (HF/F) diet for 12weeks on cancellous/cortical bone development in male Sprague-Dawley rats aged 8weeks. Both HF feeding regimens reduced the lean/fat mass ratio, elevated circulating leptin, and reduced serum total antioxidant capacity (tAOC) when compared with Controls. Distal femur cancellous bone mineral density (BMD) was 23-34% lower in both HF groups (p<0.001) and was characterized by lower cancellous bone volume (BV/TV, p<0.01), lower trabecular number (Tb.N, p<0.001), and increased trabecular separation versus Controls (p<0.001). Cancellous BMD, BV/TV, and Tb.N were negatively associated with leptin and positively associated with tAOC at the distal femur. Similar cancellous bone deficits were observed at the proximal tibia, along with increased bone marrow adipocyte density (p<0.05), which was negatively associated with BV/TV and Tb.N. HF/F animals also exhibited lower osteoblast surface and reduced circulating osteocalcin (p<0.05). Cortical thickness (p<0.01) and tissue mineral density (p<0.05) were higher in both HF-fed groups versus Controls, while whole bone biomechanical characteristics were not different among groups. These results demonstrate that "westernized" HF diets worsen cancellous, but not cortical, bone parameters in skeletally-immature male rats and that fructose incorporation into HF diets does not exacerbate bone loss. In addition, they suggest that leptin and/or oxidative stress may influence DIO-induced alterations in adolescent bone development.

Fat and Sucrose Intake Induces Obesity-Related Bone Metabolism Disturbances: Kinetic and Reversibility Studies in Growing and Adult Rats

Metabolic and bone effects were investigated in growing (G, n = 45) and mature (M, n = 45) rats fed a high-fat/high-sucrose diet (HFS) isocaloric to the chow diet of controls (C, n = 30 per group). At week 19, a subset of 15 rats in each group (HFS or C, at both ages) was analyzed. Then one-half of the remaining 30 HFS rats in each groups continued HFS and one-half were shifted to C until week 27. Although no serum or bone marrow inflammation was seen, HFS increased visceral fat, serum leptin and insulin at week 19 and induced further alterations in lipid profile, serum adiponectin, and TGFβ1, TIMP1, MMP2, and MMP9, suggesting a prediabetic phenotype and cardiovascular dysfunction at week 27 more pronounced in M than G. These events were associated with dramatic reduction of osteoclastic and osteoid surfaces with accelerated mineralizing surfaces in both HFS age groups. Mineral metabolism and its major regulators were disturbed, leading to hyperphosphatemia and hypocalcemia. These changes were associated with bone alterations in the weight-bearing tibia, not in the non-weight-bearing vertebra. Indeed in fat rats, tibia trabecular bone accrual increased in G whereas loss of trabecular bone in M was alleviated. At diaphysis cortical porosity increased in G and even more in M at week 27. After the diet switch, metabolic and bone cellular disturbances fully reversed in G, but not in M. Trabecular benefit of the obese was preserved in both age groups and in M the age-related bone loss was even lighter after the diet switch than in prolonged HFS. At the diaphysis, cortical porosity normalized in G but not in M. Hypocalcemia in G and M was irreversible. Thus, the mild metabolic syndrome induced by isocaloric HFS is able to alter bone cellular activities and mineral metabolism, reinforce trabecular bone, and affect cortical bone porosity in an irreversible manner in older rats.

Bone-adiposity cross-talk: implications for pediatric obesity. A narrative review of literature

The rising prevalence of overweight and obesity among pediatric populations has become a major global concern. The objective of this review is to demonstrate potential interactions between the products released by fat tissue and the hormonal production of bone tissue in obese children and adolescents. Advancing the understanding of the complex interactions between adipocyte and osteocyte activities may contribute to the mechanistic understanding of the body's responses to weight loss during adolescence. This knowledge could also reveal any side effects encountered with these interventions. Currently, the concept of bone-adiposity crosstalk has not been fully elucidated, and the mechanisms remain controversial. Understanding the local interactions between the released products by fat tissue and hormones produced in bone tissue requires further investigations.

Windows of opportunity for physical activity in the prevention of obesity

Tackling increasing rates of obesity is likely to be a defining feature of health care over the next several decades. Adult obesity is a persistent and treatment-resistant problem. Consequently, an emerging theme in the literature is to commence prevention efforts earlier in the developmental time course. This view is based primarily on epidemiological data demonstrating a link between traits manifesting early during development and increased obesity risk in adulthood. Physical activity is a perennial factor in discussions of obesity prevention. However, the optimal timing and type of physical activity interventions to commence remains unclear. Critical developmental windows of plasticity may afford time-limited opportunities to shape body composition across the life course; however, physical activity has not been explicitly considered in these discussions. Although animal models suggest that physical activity commenced earlier in development has differential effects on obesity onset compared to physical activity commenced in adulthood, human research is lacking. In this conceptual review, we consider physical activity during critical developmental periods as a way to mitigate obesity risk later in life.

Effects of Combined Exposure to Lead and High-Fat Diet on Bone Quality in Juvenile Male Mice

BACKGROUND

Lead (Pb) exposure and obesity are co-occurring risk factors for decreased bone mass in the young, particularly in low socioeconomic communities.

OBJECTIVES

The goal of this study was to determine whether the comorbidities of Pb exposure and high-fat diet-induced obesity amplify skeletal deficits independently associated with each of these risk factors, and to explore associated mechanisms of the observed deficiencies.

METHODS

Five-week-old male C57BL/6J mice were placed on low-fat (10% kcal, LFD) or high-fat (60% kcal, HFD) diets for 12 weeks. Mice were exposed to lifetime Pb (50 ppm) through drinking water.

RESULTS

HFD was associated with increased body mass and glucose intolerance. Both HFD and Pb increased fasting glucose and serum leptin levels. Pb and HFD each reduced trabecular bone quality and together had a further detrimental effect on these bone parameters. Mechanical bone properties of strength were depressed in Pb-exposed bones, but HFD had no significant effect. Both Pb and HFD altered progenitor cell differentiation, promoting osteoclastogenesis and increasing adipogenesis while suppressing osteoblastogenesis. In support of this lineage shift being mediated through altered Wnt signaling, Pb and non-esterified fatty acids in MC3T3 cells increased in vitro PPAR-γ activity and inhibited β-catenin activity. Combining Pb and non-esterified fatty acids enhanced these effects.

CONCLUSIONS

Pb and HFD produced selective deficits in bone accrual that were associated with alterations in progenitor cell activity that may involve reduced Wnt signaling. This study emphasizes the need to assess toxicants together with other risk factors relevant to human health and disease.