Bone geometry and density in the skeleton of pre-pubertal gymnasts and school children.
ABSTRACT We have studied the differences between the peripheral and axial skeleton of pre-pubertal gymnasts and controls. We hypothesised that compared to controls, gymnasts would have larger and stronger radius and tibia diaphyses with greater bone mineral content and larger cross-sectional muscle area. At the distal metaphyseal sites of the radius and tibia, gymnasts would have greater bone cross-sectional area and total and trabecular volumetric bone mineral density (vBMD). Differences between the lumbar spine, total body and body composition in gymnasts versus controls were also studied. Peripheral quantitative computed tomography (pQCT) was used to measure bone geometry, density and muscle of the peripheral skeleton; dual energy X-ray absorptiometry (DXA) for total body and axial measurements. Eighty-six pre-pubertal children, 44 gymnasts (mean age 9.0 years, range 5.4-11.9 years) and 42 controls (mean age 8.8 years, range 5.6-11.9 years) were studied. Eighty-four children were Caucasian, one child was mixed race, one Chinese. Data were adjusted for age, sex and height. Differences in the effect size between sexes were also tested. At the 50% radius diaphysis gymnasts had larger bones (9.2%, p = 0.0054) with greater cortical area (8.2%, p = 0.022) and stress strain index (surrogate measure of bone strength) than controls (13.6%, p = 0.015). The effect size was different between males and females for cortical thickness (p = 0.03). At the 65% tibia diaphysis, gymnasts had greater cortical area (5.3%, p = 0.057) and thickness (6.2%, p = 0.068) than controls; consequently, bone strength was 5.4% higher (p = 0.14). There were no significant differences in cortical volumetric bone mineral density (vBMD) at the radius or tibia diaphysis between the groups. There was a difference in effect size for tibia muscle cross-sectional area between the sexes (p = 0.035). At the distal radius and tibia total and trabecular vBMD was greater (Total: radius 17%, p < 0.0001, tibia: 5.7%, p = 0.0053; trabecular: radius 21%, p < 0.0001, tibia 4.5%, p = 0.11). Bone size was not different in gymnasts compared to controls Lumbar spine BMC (12.3%, p = 0.0007), areal bone mineral density (aBMD) (9.1%, p = 0.0006) and bone mineral apparent density (BMAD) (7.6%, p = 0.0047) were greater in gymnasts but vertebral size was not significantly different. Likewise, total body BMD (3.5%, p = 0.0057) and BMC (4.78%, p = 0.085) were greater in gymnasts but there were no differences in skeletal size. These data suggest site-specific differences in how the pre-pubertal skeleton develops in response to the repetitive loading it experiences when participating in regular gymnastics. At diaphyseal sites these differences are predominantly in the bone and muscle geometry and not density. Conversely, at trabecular sites, the differences are increased density rather than geometry. In conclusion, the present study has demonstrated skeletal differences between gymnasts and controls. These differences appear to be site and sex specific.
Article: Associations of physical activity duration, frequency, and load with volumetric BMD, geometry, and bone strength in young girls.[show abstract] [hide abstract]
ABSTRACT: More efficacious physical activity (PA) prescriptions for optimal bone development are needed. This study showed that PA duration, frequency, and load were all independently associated with bone parameters in young girls. Increased PA duration, frequency, and load are all important osteogenic stimuli that should be incorporated into future PA interventions. This study evaluated the associations of physical activity (PA) duration, frequency, load, and their interaction (total PA score = duration × frequency × load) with volumetric bone mineral density, geometry, and indices of bone strength in young girls. Four hundred sixty-five girls (aged 8-13 years) completed a past year physical activity questionnaire (PYPAQ) which inquires about the frequency (days per week) and duration (average minutes per session) of leisure-time PA and sports. Load (peak strain score) values were assigned to each activity based on ground reaction forces. Peripheral quantitative computed tomography was used to assess bone parameters at metaphyseal and diaphyseal sites of the femur and tibia of the non-dominant leg. Correlations across all skeletal sites between PA duration, frequency, load and periosteal circumference (PC), bone strength index (BSI), and strength-strain index (SSI) were significant (p ≤ 0.05), although low (0.10-0.17). A 2.7-3.7% greater PC across all skeletal sites was associated with a high compared to a low PYPAQ score. Also, a high PYPAQ score was associated with greater BSI (6.5-8.7%) at metaphyseal sites and SSI (7.5-8.1%) at diaphyseal sites of the femur and tibia. The effect of a low PYPAQ score on bone geometric parameters and strength was greater than a high PYPAQ score. PA duration, frequency, and load were all associated with bone geometry and strength, although their independent influences were modest and site specific. Low levels of PA may compromise bone development whereas high levels have only a small benefit over more average levels.Osteoporosis International 05/2011; 22(5):1419-30. · 4.58 Impact Factor
Article: Ibandronate does not reduce the anabolic effects of PTH in ovariectomized rat tibiae: a microarchitectural and mechanical study.[show abstract] [hide abstract]
ABSTRACT: Osteoporosis remains a challenging problem. Understanding the regulation on osteoclast and osteoblast by drugs has been of great interest. Both anabolic and anti-resorptive drugs yield positive results in the treatment of osteoporosis. However, whether the concurrent administration of parathyroid hormone (1-34) and ibandronate may offer an advantage over monotherapy is still unknown. This study, therefore, attempts to compare the efficacy of two therapeutical approaches and to investigate the beneficial effects in concurrent therapy in a rat model using three-point bending, pQCT and μCT analysis. A total of 60 female Sprague-Dawley rats of age 10 to 12 weeks were divided into 5 groups (SHAM, OVX+VEH, OVX+PTH, OVX+IBAN, OVX+PTH+IBAN) and subjected to ovariectomy or sham surgery accordingly. Low-dose parathyroid hormone (PTH) and/or ibandronate or its vehicle were administered subcutaneously to the respective groups starting from 4th week post-surgery at weekly intervals. Three rats from each group were euthanized every 2 weeks and their tibiae were harvested. The tibiae were subjected to metaphyseal three-point bending, pQCT and μCT analysis. Serum biomarkers for both bone formation (P1NP) and resorption (CTX) were studied. A total of 11 indices showed a significant difference between SHAM and OVX+VEH groups, suggesting the successful establishment of osteoporosis in the rat model. Compared to the previous studies which showed impedance from bisphosphonates in combination therapy with PTH, our study revealed that ibandronate does not block the anabolic effects of PTH in ovariectomized rat tibiae. Maximum load, strength-strain indices and serum bone formation markers of OVX+PTH+IBAN group are significantly higher than both monotherapy groups. With the proper ratio of anabolic and anti-resorptive drugs, the effect could be more pronounced.Bone 02/2011; 48(5):1154-63. · 4.02 Impact Factor
Article: Influence of polymorphisms in the RANKL/RANK/OPG signaling pathway on volumetric bone mineral density and bone geometry at the forearm in men.[show abstract] [hide abstract]
ABSTRACT: We sought to determine the influence of single-nucleotide polymorphisms (SNPs) in RANKL, RANK, and OPG on volumetric bone mineral density (vBMD) and bone geometry at the radius in men. Pairwise tag SNPs (r (2) ≥ 0.8) for RANKL (n = 8), RANK (n = 44), and OPG (n = 22) and five SNPs near RANKL and OPG strongly associated with areal BMD in genomewide association studies were previously genotyped in men aged 40-79 years in the European Male Ageing Study (EMAS). Here, these SNPs were analyzed in a subsample of men (n = 589) who had peripheral quantitative computed tomography (pQCT) performed at the distal (4%) and mid-shaft (50%) radius. Estimated parameters were total and trabecular vBMD (mg/mm(3)) and cross-sectional area (mm(2)) at the 4% site and cortical vBMD (mg/mm(3)); total, cortical, and medullary area (mm(2)); cortical thickness (mm); and stress strain index (SSI) (mm(3)) at the 50% site. We identified 12 OPG SNPs associated with vBMD and/or geometric parameters, including rs10505348 associated with total vBMD (β [95% CI] = 9.35 [2.12-16.58], P = 0.011), cortical vBMD (β [95% CI] = 5.62 [2.10-9.14], P = 0.002), cortical thickness (β [95% CI] = 0.08 [0.03-0.13], P = 0.002), and medullary area (β [95% CI] = -2.90 [-4.94 to -0.86], P = 0.005) and rs2073618 associated with cortical vBMD (β [95% CI] = -4.30 [-7.78 to -0.82], P = 0.015) and cortical thickness (β [95% CI] = -0.08 [-0.13 to -0.03], P = 0.001). Three RANK SNPs were associated with vBMD, including rs12956925 associated with trabecular vBMD (β [95% CI] = -7.58 [-14.01 to -1.15], P = 0.021). There were five RANK SNPs associated with geometric parameters, including rs8083511 associated with distal radius cross-sectional area (β [95% CI] = 8.90 [0.92-16.88], P = 0.029). No significant association was observed between RANKL SNPs and pQCT parameters. Our findings suggest that genetic variation in OPG and RANK influences radius vBMD and geometry in men.Calcified Tissue International 10/2011; 89(6):446-55. · 2.38 Impact Factor