Comparison of percentile tables and algorithm-based calculators for classification of blood pressures in children and adolescents with obesity: A secondary analysis of a clinical trial.

AIM: Obesity as a major risk factor for childhood hypertension necessitates careful blood pressure (BP) monitoring of those affected. This study aimed to compare BP classification in a cohort of children affected by obesity using tables versus digital calculations in two sets of guidelines. METHODS: This study was a secondary analysis of data collected from a randomised clinical trial of a multidisciplinary life-style assessment and intervention program. Baseline data from 237 children with a body mass index >99th percentile or >91st percentile with weight-related comorbidities and available BP measurements were analysed. We assessed agreement between tables and algorithms in classification of elevated BP/pre-hypertension and hypertension based on the American Academy of Paediatrics (AAP) clinical practice guidelines (CPG) and the older Fourth Report using Cohen's weighted kappa. The prevalence of hypertensive diagnoses was also compared between the two guidelines. RESULTS: Agreement between BP tables and algorithmic calculation of percentiles was discordant, though improved in the AAP CPG compared to the Fourth Report (Cohen's kappa = 0.70 vs. 0.57, respectively). None (0%) were missed diagnoses, and 59 (24.9%) were false positives for the Fourth Report, and 0 (0%) were missed diagnoses, and 49 (20.9%) were false positives for the AAP CPG. Under the recent guidelines, there was an increase in prevalence of 6.0% (95% confidence interval (CI) 2.5-9.4%; P = 0.0001) for BP ≥90th percentile, and of 3.0% (95% CI 0.4-5.6%; p = 0.016) for hypertension (BP ≥ 95th percentile) in the cohort (18.0% and 6.8%, respectively, increased from 12.0% and 3.8%). CONCLUSIONS: Digital calculators over tables in clinical practice are recommended where possible to improve the accuracy of paediatric BP classification. Substantial rates of elevated BP/Hypertension were found in this cohort of children and adolescents with overweight and obesity.

External validation of a prediction model for estimating fat mass in children and adolescents in 19 countries: individual participant data meta-analysis.

OBJECTIVE: To evaluate the performance of a UK based prediction model for estimating fat-free mass (and indirectly fat mass) in children and adolescents in non-UK settings. DESIGN: Individual participant data meta-analysis. SETTING: 19 countries. PARTICIPANTS: 5693 children and adolescents (49.7% boys) aged 4 to 15 years with complete data on the predictors included in the UK based model (weight, height, age, sex, and ethnicity) and on the independently assessed outcome measure (fat-free mass determined by deuterium dilution assessment). MAIN OUTCOME MEASURES: The outcome of the UK based prediction model was natural log transformed fat-free mass (lnFFM). Predictive performance statistics of R2, calibration slope, calibration-in-the-large, and root mean square error were assessed in each of the 19 countries and then pooled through random effects meta-analysis. Calibration plots were also derived for each country, including flexible calibration curves. RESULTS: The model showed good predictive ability in non-UK populations of children and adolescents, providing R2 values of >75% in all countries and >90% in 11 of the 19 countries, and with good calibration (ie, agreement) of observed and predicted values. Root mean square error values (on fat-free mass scale) were <4 kg in 17 of the 19 settings. Pooled values (95% confidence intervals) of R2, calibration slope, and calibration-in-the-large were 88.7% (85.9% to 91.4%), 0.98 (0.97 to 1.00), and 0.01 (-0.02 to 0.04), respectively. Heterogeneity was evident in the R2 and calibration-in-the-large values across settings, but not in the calibration slope. Model performance did not vary markedly between boys and girls, age, ethnicity, and national income groups. To further improve the accuracy of the predictions, the model equation was recalibrated for the intercept in each setting so that country specific equations are available for future use. CONCLUSION: The UK based prediction model, which is based on readily available measures, provides predictions of childhood fat-free mass, and hence fat mass, in a range of non-UK settings that explain a large proportion of the variability in observed fat-free mass, and exhibit good calibration performance, especially after recalibration of the intercept for each population. The model demonstrates good generalisability in both low-middle income and high income populations of healthy children and adolescents aged 4-15 years.

Genetic variants and physical activity interact to affect bone density in Hispanic children.

BACKGROUND: Our aim was to investigate if moderate to vigorous physical activity (MVPA), calcium intake interacts with bone mineral density (BMD)-related single nucleotide polymorphisms (SNPs) to influence BMD in 750 Hispanic children (4-19y) of the cross-sectional Viva La Familia Study. METHODS: Physical activity and dietary intake were measured by accelerometers and multiple-pass 24 h dietary recalls, respectively. Total body and lumbar spine BMD were measured by dual energy X-ray absorptiometry. A polygenic risk score (PRS) was computed based on SNPs identified in published literature. Regression analysis was conducted with PRSs, MVPA and calcium intake with total body and lumbar spine BMD. RESULTS: We found evidence of statistically significant interaction effects between the PRS and MVPA on total body BMD and lumbar spine BMD (p < 0.05). Higher PRS was associated with a lower total body BMD (ß = - 0.040 ± 0.009, p = 1.1 × 10- 5) and lumbar spine BMD (ß = - 0.042 ± 0.013, p = 0.0016) in low MVPA group, as compared to high MVPA group (ß = - 0.015 ± 0.006, p = 0.02; ß = 0.008 ± 0.01, p = 0.4, respectively). DISCUSSION: The study indicated that calcium intake does not modify the relationship between genetic variants and BMD, while it implied physical activity interacts with genetic variants to affect BMD in Hispanic children. Due to limited sample size of our study, future research on gene by environment interaction on bone health and functional studies to provide biological insights are needed. CONCLUSIONS: Bone health in Hispanic children with high genetic risk for low BMD is benefitted more by MVPA than children with low genetic risk. Our results may be useful to predict disease risk and tailor dietary and physical activity advice delivery to people, especially children.

Characterization of the Robinow syndrome skeletal phenotype, bone micro-architecture, and genotype-phenotype correlations with the osteosclerotic form.

Robinow syndrome (RS) is a genetically heterogeneous skeletal dysplasia with recent reports suggesting an osteosclerotic form of the disease. We endeavored to investigate the full spectrum of skeletal anomalies in a genetically diverse cohort of RS patients with a focus on the bone micro-architecture. Seven individuals with molecularly confirmed RS, including four with DVL1 variants and single individuals with variants in WNT5A, ROR2, and GPC4 underwent a musculoskeletal focused physical examination, dual-energy X-ray absorptiometry (DEXA) scan, and high-resolution peripheral quantitative computed tomography (HR-pQCT). Skeletal examination revealed variability in limb shortening anomalies consistent with recent reports. DEXA scan measures revealed increased total body bone mineral density (BMD) (3/7), cranial BMD (5/7), and non-cranial BMD (1/7). Cranial osteosclerosis was only observed in DVL1-RS (4/4) and GPC4-RS (1/1) subjects and in one case was complicated by choanal atresia, bilateral conductive hearing loss, and cranial nerve III, VI, and VII palsy. HR-pQCT revealed a unique pattern of low cortical BMD, increased trabecular BMD, decreased number of trabeculations, and increased thickness of the trabeculations for the DVL1-RS subjects. The spectrum of skeletal anomalies including the micro-architecture of the bones observed in RS has considerable variability with some osteosclerosis genotype-phenotype correlations more frequent with DVL1 variants.

Fat and fat-free mass index references in children and young adults: assessments along racial and ethnic lines.

BACKGROUND: Fat-free mass index (FFMI) and fat mass index (FMI) are superior to BMI and fat percentage in evaluating nutritional status. However, existing references fail to account for racial/ethnic differences in body composition among children. OBJECTIVES: Our goal was to produce age-based normative references for FFMI and FMI in children for specific racial/ethnic groups. METHODS: Body composition, weight, and height were measured in 1122 normal healthy children aged 2-21 y. Bone mineral content measured by DXA, total body water by deuterium dilution, and total body potassium by whole-body γ counting were combined to calculate fat-free mass (FFM) and fat mass (FM) using equations based on the Reference Child and Adolescent models. FFMI and FMI were calculated by dividing FFM and FM by height squared, respectively. After outlier removal, the LMS (Lambda-Mu-Sigma) function within R's GAMLSS package was used to produce age-based FFMI and FMI growth curves for black (B), white (W), and Hispanic (H) children for each sex. Combined models were produced in cases where outcomes did not differ by race/ethnicity. Resulting models were compared with previously published FFMI and FMI models. RESULTS: FFMI and FMI models based on 1079 children, aged 2-21 y, were created for both sexes. FFMI models for B children showed higher values throughout. W and H children were combined to produce FFMI models for each sex. H boys were modeled individually for FMI, whereas W and B boys were combined. FMI models for girls were created for each race/ethnicity. Models agreed well with those based on children from the United Kingdom of comparable race/ethnicity. CONCLUSIONS: Race/ethnicity-specific references for FFMI and FMI will increase the accuracy of health and nutrition status assessment in children over race/ethnicity-generic references. The models allow the calculation of SD scores to assess health and nutrition status in children.

Genetic variants affecting bone mineral density and bone mineral content at multiple skeletal sites in Hispanic children.

CONTEXT: Osteoporosis is a major public health burden with significant economic costs. However, the correlates of bone health in Hispanic children are understudied. OBJECTIVE: We aimed to identify genetic variants associated with bone mineral density (BMD) and bone mineral content (BMC) at multiple skeletal sites in Hispanic children. METHODS: We conducted a cross-sectional genome-wide linkage analysis, genome-wide and exome-wide association analysis of BMD and BMC. The Viva La Familia Study is a family-based cohort with a total of 1030 Hispanic children (4-19 years old at baseline) conducted in Houston, TX. BMD and BMC were measured by Dual-energy X-ray absorptiometry. RESULTS: Significant heritability were observed for BMC and BMD at multiple skeletal sites ranging between 44 and 68% (P < 2.8 × 10-9). Significant evidence for linkage was found for BMD of pelvis and left leg on chromosome 7p14, lumbar spine on 20q13 and left rib on 6p21, and BMC of pelvis on chromosome 20q12 and total body on 14q22-23 (logarithm of odds score > 3). We found genome-wide significant association between BMC of right arm and rs762920 at PVALB (P = 4.6 × 10-8), and between pelvis BMD and rs7000615 at PTK2B (P = 7.4 × 10-8). Exome-wide association analysis revealed novel association of variants at MEGF10 and ABRAXAS2 with left arm and lumber spine BMC, respectively (P < 9 × 10-7). CONCLUSIONS: We identified novel loci associated with BMC and BMD in Hispanic children, with strongest evidence for PTK2B. These findings provide better understanding of bone genetics and shed light on biological mechanisms underlying BMD and BMC variation.

Validity of Body Mass Index as a Measure of Adiposity in Infancy.

OBJECTIVES: To assess the validity of body mass index (BMI) and age- and sex-standardized BMI z-score (BMIZ) as surrogates for adiposity (body fat percentage [BF%], fat mass, and fat mass index [kg/m2]) at 3 time points in infancy (1, 4, and 7 months) and to assess the extent to which the change in BMIZ represents change in adiposity. STUDY DESIGN: We performed a secondary analysis of 447 full-term infants in a previous trial of maternal vitamin D supplementation during lactation. Study staff measured infant anthropometrics and assessed body composition with dual-energy x-ray absorptiometry at 1, 4, and 7 months of age. We calculated Spearman correlations (rs) among BMI, BMIZ, and adiposity at each time point, and between change in BMIZ and change in adiposity between time points. RESULTS: Infants (N = 447) were 52% male, 38% white, 31% black, and 29% Hispanic. The BMIZ was moderately correlated with BF% (rs = 0.43, 0.55, 0.48 at 1, 4, and 7 months of age, respectively). BMIZ correlated more strongly with fat mass and fat mass index, particularly at 4 and 7 months of age (fat mass rs = 0.72-0.76; fat mass index rs = 0.75-0.79). Changes in BMIZ were moderately correlated with adiposity changes from 1 to 4 months of age (rs = 0.44 with BF% change; rs = 0.53 with fat mass change), but only weakly correlated from 4 to 7 months of age (rs = 0.21 with BF% change; rs = 0.27 with fat mass change). CONCLUSIONS: BMIZ is moderately correlated with adiposity in infancy. Changes in BMIZ are a poor indicator of adiposity changes in later infancy. BMI and BMIZ are limited as surrogates for adiposity and especially adiposity changes in infancy. TRIAL REGISTRATION: ClinicalTrials.gov: NCT00412074.

Associations of infant feeding with trajectories of body composition and growth.

Background: The extent to which breastfeeding is protective against later-life obesity is controversial. Little is known about differences in infant body composition between breastfed and formula-fed infants, which may reflect future obesity risk.Objective: We aimed to assess associations of infant feeding with trajectories of growth and body composition from birth to 7 mo in healthy infants.Design: We studied 276 participants from a previous study of maternal vitamin D supplementation during lactation. Mothers used monthly feeding diaries to report the extent of breastfeeding. We measured infants' anthropometrics and used dual-energy X-ray absorptiometry to assess body composition at 1, 4, and 7 mo. We compared changes in infant size (z scores for weight, length, and body mass index [BMI (in kg/m2)]) and body composition (fat and lean mass, body fat percentage) between predominantly breastfed and formula-fed infants, adjusting in linear regression for sex, gestational age, race/ethnicity, maternal BMI, study site, and socioeconomic status.Results: In this study, 214 infants (78%) were predominantly breastfed (median duration: 7 mo) and 62 were exclusively formula fed. Formula-fed infants had lower birth-weight z scores than breastfed infants (-0.22 ± 0.86 and 0.16 ± 0.88, respectively; P < 0.01) but gained more in weight and BMI through 7 mo of age (weight z score difference: 0.37; 95% CI: 0.04, 0.71; BMI z score difference: 0.35; 95% CI: 0, 0.69), with no difference in linear growth (z score difference: 0.05; 95% CI: -0.24, 0.34). Formula-fed infants gained more lean mass (difference: 303 g; 95% CI: 137, 469 g) than breastfed infants, but not fat mass (difference: -42 g; 95% CI: -299, 215 g).Conclusions: Formula-fed infants gained weight more rapidly and out of proportion to linear growth than did predominantly breastfed infants. These differences were attributable to greater accretion of lean mass, rather than fat mass. Any later obesity risk associated with infant feeding does not appear to be explained by differential adiposity gains in infancy.

Energetic adaptations persist after bariatric surgery in severely obese adolescents.

OBJECTIVE: Energetic adaptations induced by bariatric surgery have not been studied in adolescents or for extended periods postsurgery. Energetic, metabolic, and neuroendocrine responses to Roux-en-Y gastric bypass (RYGB) surgery were investigated in extremely obese adolescents. METHODS: At baseline and at 1.5, 6, and 12 months post-baseline, 24-h room calorimetry, body composition, and fasting blood biochemistries were measured in 11 obese adolescents relative to five matched controls. RESULTS: In the RYGB group, mean weight loss was 44 ± 19 kg at 12 months. Total energy expenditure (TEE), activity EE, basal metabolic rate (BMR), sleep EE, and walking EE significantly declined by 1.5 months (P = 0.001) and remained suppressed at 6 and 12 months. Adjusted for age, sex, fat-free mass, and fat mass, EE was still lower than baseline (P = 0.001). Decreases in serum insulin, leptin, and triiodothyronine (T3), gut hormones, and urinary norepinephrine (NE) paralleled the decline in EE. Adjusted changes in TEE, BMR, and/or sleep EE were associated with decreases in insulin, homeostatic model assessment, leptin, thyroid stimulating hormone, total T3, peptide YY3-36, glucagon-like peptide-2, and urinary NE and epinephrine (P = 0.001-0.05). CONCLUSIONS: Energetic adaptations in response to RYGB-induced weight loss are associated with changes in insulin, adipokines, thyroid hormones, gut hormones, and sympathetic nervous system activity and persists 12 months postsurgery.

Solid anthropomorphic infant whole-body DXA phantom: design, evaluation, and multisite testing.

BACKGROUND: Dual-energy X-ray absorptiometry (DXA) requires phantoms for quality control and cross-calibration. No commercially available phantoms are designed specifically for whole-body scanning of infants. METHODS: We fabricated a phantom closely matching a 7-kg human infant in body habitus using polyvinyl chloride (PVC), nylon mix, and polyethylene for bone, lean tissue, and fat, respectively, for evaluating the comparability of instruments used in studies on infant body composition. We scanned the phantom multiple times for short- and long-term repeatability and then shipped it to six other sites for comparison scans. All instruments were Hologic Delphi or Discovery models. Scan analyses were in-house procedures (Hologic V12.1). RESULTS: Short- and long-term results were not significantly different. Nylon mix underrepresented expected lean mass values by 5%, PVC underrepresented bone by 12%, and polyethylene overrepresented fat by 30%. Precision values were as follows: lean mass ≈ 3%; bone ≈ 3.5%; and fat = 5.5-7.5%. Instruments differed significantly for bone mineral content and density results in most instances. Three instruments differed in fat and lean mass. The two Hologic models differed significantly in all compartments except bone density. CONCLUSION: The phantom design came close to emulating bone, lean tissue, and fat and showed good reproducibility. Significant differences among various DXA instruments highlight the necessity of cross-calibration for any multicenter studies.

A residential summer camp can reduce body fat and improve health-related quality of life in obese children.

In an earlier report, we showed that a 2-week, residential summer camp (Kamp K'aana) led to improved body weight, body mass index, body mass index z score, and self-esteem among obese children. To assess whether improvements in body weight and self-esteem translate into improvement in body fat and weight-related quality of life, we measured the changes in body fat by bioimpedance and quality of life by Impact of Weight on Quality of Life instrument on 42 multiethnic obese children who took part in our Kamp K'aana program. Significant reduction in body fat was detected with significant improvements in the weight-related quality of life scores.

Effect of soy isoflavone supplementation on menopausal quality of life.

OBJECTIVE: The purpose of this study was to assess the effect of soy isoflavone supplementation on quality of life in postmenopausal women. METHODS: A multicenter, randomized, double-blind, placebo-controlled 24-month trial was conducted to assess the effect of 80 or 120 mg of daily aglycone hypocotyl soy isoflavone supplementation on quality of life in 403 postmenopausal women using a validated Menopause-Specific Quality of Life questionnaire. RESULTS: Menopause-Specific Quality of Life domain scores at 1 year and 2 years were similar to baseline. There were no differences in domain scores among treatment groups. CONCLUSIONS: Soy isoflavone supplementation offers no benefit to quality of life in postmenopausal women.

Assessment of bone mineral status in children with Marfan syndrome.

Marfan syndrome (MFS) is an autosomal dominant connective tissue disorder with skeletal involvement. It is caused by mutations in fibrillin1 (FBN1) gene resulting in activation of TGF-ß, which developmentally regulates bone mass and matrix properties. There is no consensus regarding bone mineralization in children with MFS. Using dual-energy X-ray absorptiometry (DXA), we evaluated bone mineralization in 20 children with MFS unselected for bone problems. z-Scores were calculated based on age, gender, height, and ethnicity matched controls. Mean whole body bone mineral content (BMC) z-score was 0.26±1.42 (P=0.41). Mean bone mineral density (BMD) z-score for whole body was -0.34±1.4 (P=0.29) and lumbar spine was reduced at -0.55±1.34 (P=0.017). On further adjusting for stature, which is usually higher in MFS, mean BMC z-score was reduced at -0.677±1.37 (P=0.04), mean BMD z-score for whole body was -0.82±1.55 (P=0.002) and for lumbar spine was -0.83±1.32 (P=0.001). An increased risk of osteoporosis in MFS is controversial. DXA has limitations in large skeletons because it tends to overestimate BMD and BMC. By adjusting results for height, age, gender, and ethnicity, we found that MFS patients have significantly lower BMC and BMD in whole body and lumbar spine. Evaluation of diet, exercise, vitamin D status, and bone turnover markers will help gain insight into pathogenesis of the reduced bone mass. Further, larger longitudinal studies are required to evaluate the natural history, incidence of fractures, and effects of pharmacological therapy.

Clinical outcomes of a 2-y soy isoflavone supplementation in menopausal women.

BACKGROUND: Soy isoflavones are naturally occurring phytochemicals with weak estrogenic cellular effects. Despite numerous clinical trials of short-term isoflavone supplementation, there is a paucity of data regarding longer-term outcomes and safety. OBJECTIVE: Our aim was to evaluate the clinical outcomes of soy hypocotyl isoflavone supplementation in healthy menopausal women as a secondary outcome of a trial on bone health. DESIGN: A multicenter, randomized, double-blind, placebo-controlled 24-mo trial was conducted to assess the effects of daily supplementation with 80 or 120 mg aglycone equivalent soy hypocotyl isoflavones plus calcium and vitamin D on the health of 403 postmenopausal women. At baseline and after 1 and 2 y, clinical blood chemistry values were measured and a well-woman examination was conducted, which included a mammogram and a Papanicolaou test. A cohort also underwent transvaginal ultrasound measurements to assess endometrial thickness and fibroids. RESULTS: The baseline characteristics of the groups were similar. After 2 y of daily isoflavone exposure, all clinical chemistry values remained within the normal range. The only variable that changed significantly was blood urea nitrogen, which increased significantly after 2 y (P = 0.048) but not after 1 y (P = 0.343) in the supplementation groups. Isoflavone supplementation did not affect blood lymphocyte or serum free thyroxine concentrations. No significant differences in endometrial thickness or fibroids were observed between the groups. Two serious adverse events were detected (one case of breast cancer and one case of estrogen receptor-negative endometrial cancer), which was less than the expected population rate for these cancers. CONCLUSION: Daily supplementation for 2 y with 80-120 mg soy hypocotyl isoflavones has minimal risk in healthy menopausal women. This trial was registered at clinicaltrials.gov as NCT00665860.

A comparison of the growth responses following intramuscular GHRH plasmid administration versus daily growth hormone injections in young pigs.

The efficacy of daily porcine growth hormone (GH) injections versus plasmid-driven porcine GH-releasing hormone (pGHRH) production to promote growth was assessed. Ten-day-old piglets were injected intramuscularly with 0.1, 1, or 3 mg pGHRH, or a control plasmid followed by electroporation. Plasmid constructs were driven by a synthetic muscle-specific promoter. A fifth group received daily injections of GH [0.15 mg/(kg.day)]. Control and pGHRH-treated pigs were pair-fed to GH-treated pigs. Body composition was assessed by dual-energy X-ray absorptiometry (DXA). Weight gains of GH- and pGHRH-treated pigs were greater than of controls (P < 0.001) due to greater lean mass accretion; fat accretion was similar across all treatments. Weight gain of pGHRH- and GH-treated pigs was similar for 6 weeks, but over the final 10 days, only pigs administered the highest plasmid dose maintained higher growth rates. Serum insulin-like growth factor-I (IGF-I) levels were two- to threefold higher in GH- and pGHRH-treated pigs than in controls after 4 weeks (P = 0.05), but subsequently decreased to control levels in the pGHRH-treated group. Organ weights were greater in GH- than pGHRH-treated and control piglets (P < 0.02). These results demonstrate that pGHRH transfer is effective for promoting growth and avoids the need for the frequent injections necessitated with peptide hormone use.

Soy isoflavone supplementation and bone mineral density in menopausal women: a 2-y multicenter clinical trial.

BACKGROUND: Isoflavones are naturally occurring plant estrogens that are abundant in soy. Although purported to protect against bone loss, the efficacy of soy isoflavone supplementation in the prevention of osteoporosis in postmenopausal women remains controversial. OBJECTIVE: Our aim was to test the effect of soy isoflavone supplementation on bone health. DESIGN: A multicenter, randomized, double-blind, placebo-controlled 24-mo trial was conducted to assess the effects of daily supplementation with 80 or 120 mg of soy hypocotyl aglycone isoflavones plus calcium and vitamin D on bone changes in 403 postmenopausal women. Study subjects were tested annually and changes in whole-body and regional bone mineral density (BMD), bone mineral content (BMC), and T scores were assessed. Changes in serum biochemical markers of bone metabolism were also assessed. RESULTS: After study site, soy intake, and pretreatment values were controlled for, subjects receiving a daily supplement with 120 mg soy isoflavones had a statistically significant smaller reduction in whole-body BMD than did the placebo group both at 1 y (P < 0.03) and at 2 y (P < 0.05) of treatment. Smaller decreases in whole-body BMD T score were observed among this group of women at 1 y (P < 0.03) but not at 2 y of treatment. When compared with the placebo, soy isoflavone supplementation had no effect on changes in regional BMD, BMC, T scores, or biochemical markers of bone metabolism. CONCLUSION: Daily supplementation with 120 mg soy hypocotyl isoflavones reduces whole-body bone loss but does not slow bone loss at common fracture sites in healthy postmenopausal women. This trial was registered at clinicaltrials.gov as NCT00665860.

DXA: can it be used as a criterion reference for body fat measurements in children?

OBJECTIVE: Dual-energy X-ray absorptiometry (DXA) is often cited as a criterion method for body composition measurements. We have previously shown that a new DXA software version (Hologic Discovery V12.1) will affect whole-body bone mineral results for subjects weighing <40 kg. We wished to reanalyze pediatric whole-body scans in order to assess the impact of the new software on pediatric soft-tissue body composition estimates. METHODS AND PROCEDURES: We reanalyzed 1,384 pediatric scans (for ages 1.7-17.2 years) using Hologic software V12.1, previously analyzed using V11.2. Regression analysis and ANCOVA were used to compare body fat (total body fat (TBF), percentage fat (%BF)), and non-bone lean body mass (LBM) for the two versions, adjusting for gender, age and weight. RESULTS: Software V12.1 yielded values that were higher for TBF, lower for LBM, and unchanged for DXA-derived weight in subjects weighing <40 kg. Body composition values for younger, smaller subjects were most affected, and girls were more affected than boys. Using the new software, 14% of the girls and 10% of the boys were reclassified from the "normal" %BF range to "at risk of obesity," while 7 and 5%, respectively, were reclassified as obese. DISCUSSION: Hologic's newest DXA software has a significant effect on soft-tissue results for children weighing <40 kg. The effect is greater for girls than boys. Comparison of TBF estimates with previous studies that use older DXA instruments and software should be done with caution. DXA has not yet achieved sufficient reliability to be considered a "gold standard" for body composition assessment in pediatric studies.

Body-composition assessment in infancy: air-displacement plethysmography compared with a reference 4-compartment model.

BACKGROUND: A better understanding of the associations of early infant nutrition and growth with adult health requires accurate assessment of body composition in infancy. OBJECTIVE: This study evaluated the performance of an infant-sized air-displacement plethysmograph (PEA POD Infant Body Composition System) for the measurement of body composition in infants. DESIGN: Healthy infants (n = 49; age: 1.7-23.0 wk; weight: 2.7-7.1 kg) were examined with the PEA POD system. Reference values for percentage body fat (%BF) were obtained from a 4-compartment (4-C) body-composition model, which was based on measurements of total body water, bone mineral content, and total body potassium. RESULTS: Mean (+/- SD) reproducibility of %BF values obtained with the PEA POD system was 0.4 +/- 1.3%. Mean %BF obtained with the PEA POD system (16.9 +/- 6.5%) did not differ significantly from that obtained with the 4-C model (16.3 +/- 7.2%), and the regression between %BF for the 4-C model and that for the PEA POD system (R2 = 0.73, SEE = 3.7%BF) did not deviate significantly from the line of identity (y = x). CONCLUSIONS: The PEA POD system provided a reliable, accurate, and immediate assessment of %BF in infants. Because of its ease of use, good precision, minimum safety concerns, and bedside accessibility, the PEA POD system is highly suitable for monitoring changes in body composition during infant growth in both the research and clinical settings.

Vitamin D receptor Fok1 polymorphisms affect calcium absorption, kinetics, and bone mineralization rates during puberty.

UNLABELLED: Few studies of the VDR polymorphisms have looked at calcium metabolism or long-term effects. We measured bone mineralization and calcium metabolic parameters longitudinally in a group of 99 adolescents. We found a significant relationship between calcium absorption and skeletal calcium accretion and the Fok1, but not other VDR or related, genetic polymorphisms. It seems that the Fok1 polymorphism directly affects bone mineralization during pubertal growth through an effect on calcium absorption. INTRODUCTION: There are few data regarding the relationship between genetic markers for low bone mass and changes in calcium metabolism in childhood or adolescence. We sought to identify the effects of polymorphisms of the vitamin D receptor (VDR) on calcium and bone mineral metabolism in a longitudinal study of pubertal adolescents. MATERIALS AND METHODS: Adolescents (n = 99) received comprehensive stable isotope studies of calcium absorption, bone calcium kinetics, and bone mineralization. Studies were repeated 12 months later. Polymorphisms of putative genetic markers were determined and related to bone mineralization and calcium metabolic finding. Results were analyzed by ANOVA in which changes over time were determined using the initial value as a covariate. RESULTS: Polymorphisms of the Fok1 gene of the VDR were significantly related to calcium absorption (p = 0.008) and whole body BMC (p = 0.03) and BMD (p = 0.006). The Fok1 effect on whole body BMD was significant for those with Ca intake >800 mg/day (p < 0.001), whereas for those with Ca intake < or = 800 mg/day, the Fok1 genotype did not have a significant effect on whole body BMD (p = 0.40). The Fok1 genotype was significantly related to the changes during the year in whole body calcium accretion, with the ff genotype having a 63 +/- 20 mg/day deficit compared with the FF genotype (p = 0.008). CONCLUSIONS: The Fok1 polymorphism of the VDR receptor seems to directly affect bone mineral accretion during pubertal growth through an effect on calcium absorption. The relationship between different genetic polymorphisms and bone mineral metabolism may vary by life stage as well as diet.