106,679 research outputs found
Quantitative Ultrasound of Cortical Bone in the Femoral Neck Predicts Femur Strength: Results of a Pilot Study
No full textArticle first published online: 15 JAN 2013 Pour consulter la version éditeur DOI: 10.1002/jbmr.1742A significant risk of femoral neck (FN) fracture exists for men and women with an areal bone mineral density (aBMD) higher than the osteoporotic range, as measured with dual-energy X-ray absorptiometry (DXA). Separately measuring the cortical and trabecular FN compartments and combining the results would likely be a critical aspect of enhancing the diagnostic capabilities of a new technique. Because the cortical shell determines a large part of FN strength a novel quantitative ultrasound (QUS) technique that probes the FN cortical compartment was implemented, aimed at testing the sensitivity of the method to variations of FN cortical properties and FN strength. Nine femurs (women, mean age 83 years) were subjected to QUS to measure the through transmission time-of-flight (TOF) at the FN and mechanical tests to assess strength. Quantitative computed tomography (QCT) scans were performed to enable analysis of the dependence of TOF on bone parameters. DXA was also performed for reference. An ultrasound wave propagating circumferentially in the cortical shell, which TOF was not influenced by the properties of the trabecular compartment Q3, was measured in all specimens. Averaged TOF for nine FN measurement positions/orientations was significantly correlated to strength (R² = 0.79) and FN cortical QCT variables: total BMD (R² = 0.54); regional BMD in the inferoanterior (R² = 0.90) and superoanterior (R² = 0.57) quadrants; and moment of inertia (R² = 0.71). The results of this study demonstrate that QUS can perform a targeted measurement of the FN cortical compartment. Because the method involves mechanical guided waves, the QUS variable is related to the geometric and material properties of the cortical shell (cortical thickness, tissue elasticity, and porosity). This work opens the way to a multimodal QUS assessment of the proximal femur, combining our approach targeting the cortical shell with the existing modality sensitive to the trabecular compartment. In vivo feasibility of our approach has to be confirmed with experimental data in patients
Low vitamin D status adversely affects bone health parameters in adolescents
No full textBackground: The effects of subclinical vitamin D deficiency on bone mineral density (BMD) and bone turnover in adolescents, especially in boys, are unclear.Objective: We aimed to investigate the relations of different stages of vitamin D status and BMD and bone turnover in a representative sample of adolescent boys and girls.Design: BMD was measured by dual-energy X-ray absorptiometry at the nondominant forearm and dominant heel in a random sample of 12- (n = 260) and 15-y-old (n = 239) boys and 12- (n = 266) and 15-y-old (n = 250) girls. Serum 25-hydroxyvitamin D, parathyroid hormone, osteocalcin, and type I collagen cross-linked C-telopeptide were assessed by using enzyme-linked immunoassays. Relations between vitamin D status and bone health indexes were assessed by using regression modeling.Results: Using multivariate regression to adjust for potential physical, lifestyle, and dietary confounding factors, we observed that 12-and 15-y-old girls with high vitamin D status (>= 74.1 nmol/L) had significantly greater forearm (but not heel) BMD (beta = 0.018; SE = 0.008; P < 0.05 for each age group) and lower serum parathyroid hormone concentrations and bone turnover markers than did those with low vitamin D status. These associations were evident in subjects sampled throughout the year and in winter only. There was no significant relation between vitamin D status and BMD in boys.Conclusions: Maintaining serum 25-hydroxyvitamin D concentrations above approximate to 50 nmol/L throughout the year may be a cost-effective means of improving bone health. Increased emphasis on exploring strategies for improving vitamin D status in adolescents is needed.</p
Bone fractures after menopause
No full textEvery year 30% of individuals above age 65 fall, and falls are the principal cause of bone fractures. To reduce fracture incidence requires both prevention of falls and maintenance of bone strength.PubMed searches were performed, for studies of the epidemiology of fractures, bone physiology, endocrine effects, osteoporosis measurement, genetics, prevention and effectiveness. Topic summaries were presented to the Workshop Group and omissions or disagreements were resolved by discussion.Ageing reduces bone strength in post-menopausal women because estrogen deficiency causes accelerated bone resorption. Bone mineral density (BMD) decreased more than 2.5 standard deviation below the mean of healthy young adults defines osteoporosis, a condition associated with an increased risk of fractures. Risk factors such as age and previous fracture are combined with BMD for a more accurate prediction of fracture risk. The most widely used assessment tool is FRAX (TM) which combines clinical risk factors and femoral neck BMD. General preventive measures include physical exercise to reduce the risk of falling and vitamin D to facilitate calcium absorption. Pharmacological interventions consist mainly in the administration of inhibitors of bone resorption. Randomized controlled trials show treatment improves BMD, and may reduce the relative fracture risk by about 50% for vertebral, 20-25% for non-vertebral and up to 40% for hip fractures although the absolute risk reductions are much lower.Although diagnosis of osteoporosis is an important step, the threshold for treatment to prevent fractures depends on additional clinical risk factors. None of the presently available treatment options provide complete fracture prevention.</p
The Longitudinal Effect of Impaired Kidney Function on Bone Mineral Density and the Association of Body Composition on Biomarkers of Kidney Function Among Afro-Caribbean Men of West African Ancestry
No full textBackground: Chronic kidney disease (CKD) is a rising global health problem. African Americans bear a greater proportion of CKD burden compared to Caucasians. Little is known about the relationship of CKD with bone loss and body composition distribution with biomarkers of CKD in blacks.
Objective: The prevalence of CKD among Tobago black, African American and Caucasian men, aged 40 years and older were determined and compared. The risk factors of CKD, the association of body composition with biomarkers of CKD and the effect of CKD on longitudinal bone loss were examined among Tobago black males.
Methods: Tobago men were recruited from Tobago Island in 2004-2007. Counterparts from U.S were obtained from the National Health and Nutrition Examination Survey (NHANES) 2003-2006. Standardized serum creatinine, cystatin C and urinary albumin were measured using Jaffè reaction, Dade Behring nephelometer and fluorescent immunoassay respectively. Longitudinal Bone Mineral Density changes in trochanter, femoral neck and total hip from 2004/2007-2012 were measured using Dual X-Ray Absorptiomertry (DXA). Body composition was measured using DXA and Peripheral Quantitative Computed Tomography (PQCT). Covariates were assessed from questionnaires in 2004-2007.
Results: The prevalence of CKD was 19.7%, 23.4% and 19.7% in Tobago black, African American and Caucasian men respectively. Age, hypertension and diabetes were significantly associated with CKD in Tobago men. Lean body mass and calf muscle area were positively associated with serum creatinine. All adiposity measures were positively associated with cystatin C, but not with calf muscle area. There was consistent greater decline in BMD across quartiles of ACR, serum creatinine and cystatin C in trochanter, femoral neck and total hip bones. The rate of bone loss in Tobago men was similar to that in Caucasian men.
Public Health Significance: The biomarkers used for assessing CKD (serum creatinine and cystatin C) are influenced by body composition. Future CKD screening among blacks with high lean or muscle mass should include cystatin C assessment due to the influence of muscle mass on serum creatinine.
CKD is associated with bone loss. Proper management of bone minerals and DXA screenings are necessary in order to reduce bone loss among individuals with CKD
Evidence-based policy on dietary calcium and vitamin D
No full textCopyright © 2011 American Society for Bone and Mineral Research.Peer reviewe
Vitamin D metabolism in human osteoblasts
No full textCirculating 1 α ,25-dihydroxyvitamin D₃ (1,25D) derives from conversion of 25-hydroxyvitamin D₃ (25D) by the kidney 1 α -hydroxylase (CYP27B1). 1,25D exerts a number of effects on human osteoblasts, including inhibition of proliferation and differentiation, and effects on gene expression, including stimulation of RANKL, osteocalcin (OCN) and bone sialoprotein (BSP). We have examined vitamin D₃ metabolism in human osteoblastic cells, and found that primary normal human osteoblasts (NHBC) and human osteosarcoma cell lines, including MG-63, SaOS-2, HOS, G-292, all up-regulate the negative regulator of 1,25D, the 24-hydroxylase (CYP24), in response to 1,25D exposure. Additionally, all of these cell types expressed CYP27B1 mRNA, implying that human osteoblasts are capable of metabolising 25D into 1,25D. We have investigated this possibility and found that NHBC exposed to physiological concentrations of 25D (10 - 100 nM) in the absence of serum, exhibit up-regulated transcription of the downstream genes RANKL and OCN. Unlike 1,25D, 25D did not elicit a vigorous CYP24 response except at high concentrations (10⁻⁷ - 10⁻⁶ M). Consistent with this, NHBC treated with high concentrations of 25D secreted detectable 1,25D into the culture supernatant. We also found that NHBC express the 25-hydroxylase, and treatment with 1-hydroxyvitamin D₃ (1D), resulted in a gene expression response qualitatively similar to 25D. Inhibition of CYP activity using ketoconazole (10 μ M) resulted in an elevated response to 1,25D, probably due to inhibition of the catabolic activity of CYP24. Results to date indicate that the activity of 1D is CYP-dependent, since ketoconazole abolished its effects. However, 25D effects at low concentrations were unaffected by ketoconazole, indicating that 25D may have direct effects in osteoblasts independent of its conversion to 1,25D. Our results suggest that vitamin D₃ metabolism represents an intrinsic autocrine/paracrine pathway in these cells. Thus, vitamin D metabolites may regulate key functions in human osteoblasts independently of circulating levels of 1,25D
Adjusting bone mass for differences in projected bone area and other confounding variables: an allometric perspective.
No full textThe traditional method of assessing bone mineral density (BMD; given by bone mineral content [BMC] divided by projected bone area [Ap], BMD = BMC/Ap) has come under strong criticism by various authors. Their criticism being that the projected bone "area" (Ap) will systematically underestimate the skeletal bone "volume" of taller subjects. To reduce the confounding effects of bone size, an alternative ratio has been proposed called bone mineral apparent density [BMAD = BMC/(Ap)3/2]. However, bone size is not the only confounding variable associated with BMC. Others include age, sex, body size, and maturation. To assess the dimensional relationship between BMC and projected bone area, independent of other confounding variables, we proposed and fitted a proportional allometric model to the BMC data of the L2-L4 vertebrae from a previously published study. The projected bone area exponents were greater than unity for both boys (1.43) and girls (1.02), but only the boy's fitted exponent was not different from that predicted by geometric similarity (1.5). Based on these exponents, it is not clear whether bone mass acquisition increases in proportion to the projected bone area (Ap) or an estimate of projected bone volume (Ap)3/2. However, by adopting the proposed methods, the analysis will automatically adjust BMC for differences in projected bone size and other confounding variables for the particular population being studied. Hence, the necessity to speculate as to the theoretical value of the exponent of Ap, although interesting, becomes redundant
The Warwick Hip Trauma Evaluation – an abridged protocol for the WHiTE Study : a multiple embedded randomised controlled trial cohort study
No full textFractures of the proximal femur are one of the greatest challenges facing the medical community, constituting a heavy socioeconomic burden worldwide. The National Hip Fracture Audit currently provides a framework for service evaluation. This evaluation is based upon the assessment of process rather than assessment of patient-centred outcome and therefore it fails to provide meaningful data regarding the clinical effectiveness of treatments. This study aims to capture data from the cohort of patients who present with a fracture of the proximal femur at a single United Kingdom Major Trauma Centre. Patient-centred outcomes will be recorded and provide a baseline cohort within which to test the clinical effectiveness of experimental interventions
Effect of calcitriol on bone turnover and osteocalcin in recent-onset type 1 diabetes
No full textContains fulltext :
125353.pdf (Publisher’s version ) (Open Access)BACKGROUND: Vitamin D supplementation in childhood improves the achievement of peak bone mass. We investigated the effect of supplementation with calcitriol on bone turnover in recent-onset type 1 diabetes (T1D). Moreover, the association between osteocalcin and parameters of beta-cell function and metabolic control was examined. METHODOLOGY/PRINCIPAL FINDINGS: We conducted a post-hoc analysis of a double-blind, placebo-controlled study of calcitriol supplementation to preserve beta-cell function. 27 recent-onset T1D subjects, mean age 22 years, were randomized to 0.25 microg calcitriol per day or placebo (1:1) and followed up for one year. Changes in bone formation (osteoclacin) and resorption (beta-CrossLaps) markers, and differences between placebo and calcitriol-treated group were evaluated. At baseline, osteocalcin levels were significantly lower in female than in male patients (P<0.01) while no other metabolic parameters as HbA1c and C-peptide differed between gender. No significant correlations were found in relation to HbA1c, insulin requirement and C-peptide. At 1 year follow-up, no significant differences were observed between calcitriol and placebo groups for osteocalcin and beta-CrossLaps. In the placebo group osteocalcin levels were unrelated with parameters of metabolic control, such as C-peptide, insulin requirement or HbA1c. Changes of C-peptide, insulin requirement and HbA1c were not related to osteocalcin levels. CONCLUSIONS: Supplementation with 0.25 microg calcitriol per day to patients with new-onset T1D does not affect circulating markers of bone turnover. OC levels were unrelated to beta-cell function and other metabolic parameters suggesting that OC is ineffective to control pancreatic function in presence of aggressive autoimmune destruction
Correlations between cancellous bone architecture and its dynamic behaviour
No full textPrevious studies showed that in vivo evaluation of the fracture risk of cancellous bone can be assessed by identifying the relationships between its microarchitecture description extracted from clinical imaging and its mechanical properties. The mechanical properties under dynamic loadings (with and without confinement) were obtained and compared to quasi-static ones. The architectural parameters of each specimen were extracted from pQCT images and split into four groups: geometry, topology, connectivity and anisotropy. Results show that architectural parameters are strong determinants of mechanical behaviour for the different applied boundary conditions.http://icills2014.org/wp-content/uploads/2014/01/Marrianne-Prot.pd
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