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Biomedical subjects

J Dequeker

Publications and source records attributed to J Dequeker.

At least 127 records · Page 7Linked to original sources
PubMed1996

Relationship between baseline insulin-like growth factor-I (IGF-I) and femoral bone density in women aged over 70 years: potential implications for the prevention of age-related bone loss.

OBJECTIVE: To test the hypothesis that the decline in femoral bone mass associated with healthy aging is partially accounted for by deficiency of the growth hormone-insulin-like growth factor-I (IGF-I) axis. DESIGN: Cross-sectional study. STUDY PARTICIPANTS: A sample of 245 community-dwelling healthy women aged 70 and older. Exclusion criteria were diseases or medications known to affect the musculoskeletal system or the somatotrophic axis. MEASUREMENTS: Serum levels of IGF-I, calcitriol, and osteocalcin were determined by radioimmunoassay; serum calcidiol was measured by competitive binding assay, and serum parathyroid hormone (PTH) was assessed immunochemically. Urinary pyridinium crosslinks were measured by fluorescent detection after high-pressure liquid chromatography. Isometric and isokinetic quadriceps strength was evaluated using an isokinetic dynamometer. Bone density (BMD) was assessed by dual-energy X-ray absorptiometry at the proximal femur. Multiple regression was used to adjust for potential confounders. RESULTS: At the proximal femur, BMD declined by 0.59-0.84% per year. In addition to body mass index and muscle strength, serum IGF-I was found to be an independent predictor of BMD at all femoral sites. CONCLUSION: The data support the hypothesis that circulating IGF-I not only reflects the integrated growth hormone secretion but also has a direct role in the endocrine regulation of bone remodeling. The present findings support the need for further studies to assess the potential of IGF-I in attenuating age-related femoral bone loss.

Age Factors↗
PubMed1996

Deficiency of the growth hormone-insulin-like growth factor-I axis potentially involved in age-related alterations in body composition.

Because the body composition effects of growth hormone and insulin-like growth factor-I (IGF-I) are opposite to those of advancing age, it has been hypothesized that the decreased activity of the growth hormone-IGF-I axis is partly responsible for the loss of bone and muscle mass that characterizes normal human aging. The aim of the present cross-sectional analysis was to test this hypothesis in a well-defined community-based sample of 245 healthy elderly women. Dual-energy X-ray absorptiometry was used to measure body composition. To establish the major determinants of total bone mineral content (TBBMC), we assessed the relationships between TBBMC and age, height, weight, body mass index, muscle strength and serum concentrations of IGF-I, calcidiol, calcitriol, parathyroid hormone and sex hormone-binding globulin. Total body lean mass (TBLM), an indication of muscle mass, was related to the following potential determinants: age, habitual physical activity and serum IGF-I. Multiple regression was used to adjust for potential confounders. A significant relationship between circulating IGF-I and TBLM was not apparent in this study. On the other hand, serum IGF-I was found to be an independent predictor of TBBMC, despite the inclusion of established determinants of bone mass. These findings suggest that the demineralization of the skeleton in aging women is in part due to a deficiency of the somatotrophic axis.

Absorptiometry, Photon↗
PubMed1996

Effect of 1alpha-vitamin D3 and estrogen therapy on cortical bone mechanical properties in the ovariectomized rat model.

It is well documented that both bone mass and size of ovariectomized rats can be increased by 1alpha-vitamin D3 therapy. The repercussion of this therapy on bone mechanical competence is far less clear. Therefore, the objective of this study was to examine the mechanical properties of the shaft femur in ovariectomized rats (3 months old) receiving estrogen (0.25 mg/kg-week) and /or 1alpha-vitamin D3 (0.5 microgram/kg-day). The medication was given during 6 months starting immediately after ovariectomy or starting 3 months later. Torsional testing was performed from which the parameters strength, stiffness, maximum angular displacement, and energy-absorbing capacity (toughness) were derived. Multiple regression models were generated to estimate the relative importance of the therapies on bone mechanical properties. Bone stiffness increased with age. Ovariectomy improved bone mechanical parameters until 6 months postovariectomy, whereas estrogen treatment resulted in similar mechanical properties as those in intact age-matched controls. A significant improvement of all mechanical parameters was observed after 1alpha-vitamin D3 therapy. The combined therapy of 1alpha-vitamin D3 and estrogen was less effective than 1alpha-vitamin D3 alone, but better than estrogen therapy alone, suggesting interactive effects between both therapies. We conclude that 1alpha-vitamin D3 treatment of ovariectomized rats improves bone mechanical competence, which might be partially related to alterations in both bone mass and size.

Aging↗
PubMed1996

Age-related endocrine deficiencies and fractures of the proximal femur. I implications of growth hormone deficiency in the elderly.

Growth hormone activates osteoblasts to increase local synthesis of IGF-I, which acts in an autocrine or paracrine way to enhance bone matrix apposition, suggesting a role in the preservation of bone mass. Growth hormone deficiency in the elderly may therefore be of pathogenetic significance in senile osteoporosis. However, critical evidence does not yet support the concept that the decreased activity of the growth hormone-IGF-I axis alters bone remodelling, and the extent to which geriatric hyposomatotropism contributes to the age-related femoral bone loss remains to be elucidated. Despite the fact that biochemical estimates of bone turnover indicate that (short-term) administration of rhGH and IGF-I stimulates bone metabolism in non-osteoporotic older people, no significant changes have been observed in bone mineral density at the proximal femur. Additional studies are needed to assess the therapeutic potential for rhGH in attenuating or reversing bone loss in elderly people. Moreover, data on long-term adverse side effects of rhGH therapy are not yet available. Because of the known mitogenic action of IGF-I, the neoplastic potential of long-term rhGH therapy needs to be considered.

Age Factors↗
PubMed1996

Age-related endocrine deficiencies and fractures of the proximal femur. II implications of vitamin D deficiency in the elderly.

In the United Kingdom, as many as 60% of institutionalized people who are not taking vitamin D supplements may be deficient. Both impaired mineralization and a hyperparathyroidism-related increase in bone turnover have been identified in the presence of vitamin D deficiency. Recent interventional data have confirmed the role of vitamin D deficiency in the pathogenesis of senile osteoporosis and indicated the need to maintain serum cholecalciferol levels within the normal range in elderly people.

Aged↗
PubMed1996

Age-related factors in the pathogenesis of senile (Type II) femoral neck fractures.

A variety of age-related factors may affect the two ultimate determinants of hip fracture: propensity to trauma and femoral bone quality. The decline in muscle function that occurs with aging increases the incidence and impact of falls. Vitamin D deficiency, common in the elderly, causes impaired mineralization and a hyper-parathyroidism-related increase in bone turnover, reducing bone quality. Skeletal growth factors, essential regulators of bone-cell replication and differentiation, may mediate the maintenance of normal bone mass; the age-related deficiency of these factors may contribute to senile osteoporosis as well. In elderly women, these age-related factors add to estrogen-deficiency-related bone loss, leading to a lifetime risk of hip fracture of approximately 16%. The relative clinical importance of these potential pathogenetic factors remains to be elucidated.

Accidental Falls↗
PubMed1996

Methotrexate osteopathy, does it exist?

We describe 2 postmenopausal women with rheumatoid arthritis (RA). They developed fractures during their treatment with weekly low dose methotrexate (MTX). The adverse effect of longterm low dose regimens of MTX on bone metabolism has been described as "methotrexate osteopathy," an analogy of the syndrome known in pediatric oncology. MTX may be an additional risk factor for osteoporosis and fractures in RA. This therapy should be relatively contraindicated in patients with multiple risk factors for osteoporosis.

Antirheumatic Agents↗
PubMed1995

Effect of oral alendronate on bone mineral density and the incidence of fractures in postmenopausal osteoporosis. The Alendronate Phase III Osteoporosis Treatment Study Group.

BACKGROUND: Postmenopausal osteoporosis is a serious health problem, and additional treatments are needed. METHODS: We studied the effects of oral alendronate, an aminobisphosphonate, on bone mineral density and the incidence of fractures and height loss in 994 women with postmenopausal osteoporosis. The women were treated with placebo or alendronate (5 or 10 mg daily for three years, or 20 mg for two years followed by 5 mg for one year); all the women received 500 mg of calcium daily. Bone mineral density was measured by dual-energy x-ray absorptiometry. The occurrence of new vertebral fractures and the progression of vertebral deformities were determined by an analysis of digitized radiographs, and loss of height was determined by sequential height measurements. RESULTS: The women receiving alendronate had significant, progressive increases in bone mineral density at all skeletal sites, whereas those receiving placebo had decreases in bone mineral density. At three years, the mean (+/- SE) differences in bone mineral density between the women receiving 10 mg of alendronate daily and those receiving placebo were 8.8 +/- 0.4 percent in the spine, 5.9 +/- 0.5 percent in the femoral neck, 7.8 +/- 0.6 percent in the trochanter, and 2.5 +/- 0.3 percent in the total body (P < 0.001 for all comparisons). The 5-mg dose was less effective than the 10-mg dose, and the regimen of 20 mg followed by 5 mg was similar in efficacy to the 10-mg dose. Overall, treatment with alendronate was associated with a 48 percent reduction in the proportion of women with new vertebral fractures (3.2 percent, vs. 6.2 percent in the placebo group; P = 0.03), a decreased progression of vertebral deformities (33 percent, vs. 41 percent in the placebo group; P = 0.028), and a reduced loss of height (P = 0.005) and was well tolerated. CONCLUSIONS: Daily treatment with alendronate progressively increases the bone mass in the spine, hip, and total body and reduces the incidence of vertebral fractures, the progression of vertebral deformities, and height loss in postmenopausal women with osteoporosis.

Aged↗
PubMed1995

Dual X-ray absorptiometry of the proximal femur: normal European values standardized with the European Spine Phantom.

Measurements of the proximal femur by dual X-ray absorptiometry (DXA) are assuming increasing importance in clinical and epidemiological studies. However, different DXA manufacturers have adopted varying approaches to measuring the femoral neck and trochanter regions with the result that there is as yet no agreement on normal ranges and how to cross-calibrate between different machines. In this Concerted Action (of the EU's 2nd Framework Programme), 12 clinical centers in eight countries recruited a total of 855 female and 517 male Caucasian subjects who were judged to be free of conditions known to cause secondary osteoporosis and who had not been treated with drugs known to affect bone mass. The DXA machines used were made by Hologic, Lunar, and Norland. Each machine was cross-calibrated with the European Spine Phantom prototype designed by Kalender. All femoral neck and trochanter results were expressed as standardized values and were first examined for possible bias due to between-brand differences in choice of areas for measurement. On average, trochanter areas were similar between brands but Norland chose a narrower neck region for analysis. Bone mineral density (BMA or BMD g/cm2) was log-normally distributed for all groups at the femoral neck but normally distributed at the trochanter in men and postmenopausal women. There were substantial between-center differences after cross-calibration in age-adjusted mean values at both sites and also in the rates of apparent bone loss with age and the amounts of scatter within populations about mean age-adjusted values. With the proviso that locally derived normal ranges would allow more accurate comparisons for clinical purposes, European normal ranges were derived for both neck and trochanter. Data obtained with the three individual brands of machine fitted these overall ranges well. Bone loss was apparent in premenopausal women at the femoral neck but not the trochanter. Postmenopausal women's data was somewhat better fitted by reference to years since menopause than to chronological age. This work provides a basis for conducting future epidemiological and clinical studies with more than one brand of machine as long as each individual subject, if measured consecutively, is measured on the same machine throughout.

Absorptiometry, Photon↗
PubMed1995

Risk factors for hip fracture in European women: the MEDOS Study. Mediterranean Osteoporosis Study.

The aims of this study were to determine common international risk factors for hip fracture in women aged 50 years or more. We studied women aged 50 years or more who sustained a hip fracture in 14 centers from Portugal, Spain, France, Italy, Greece, and Turkey over a 1-year period. Women aged 50 years or more selected from the neighborhood or population registers served as controls. Cases and controls were interviewed using a structured questionnaire on work, physical activity, exposure to sunlight, reproductive, history and gynecologic status, height, weight, mental score, and consumption of tobacco, alcohol, calcium, coffee, and tea. Significant risk factors identified by univariate analysis included low body mass index (BMI), short fertile period, low physical activity. lack of sunlight exposure, low milk consumption, no consumption of tea, and a poor mental score. No significant adverse effects of coffee or smoking were observed. Moderate intake of spirits was a protective factor in young adulthood, but otherwise no significant effect of alcohol intake was observed. For some risks, a threshold effect was observed. A low BMI and milk consumption were significant risks only in the lowest 50% and 10% of the population, respectively. A late menarche, poor mental score, low BMI and physical activity, low exposure to sunlight, and a low consumption of calcium and tea remained independent risk factors after multivariate analysis, accounting for 70% of hip fractures. Excluding mental score and age at menarche (not potentially reversible), the attributable risk was 56%. Thus, about half of the hip fractures could be explained on the basis of the potentially reversible risk factors sought. In contrast, the use of risk factors to "predict" hip fractures had moderate sensitivity and specificity. We conclude that variations in lifestyle factors are associated with significant differences in the risk of hip fracture, account for a large component of the total risk, and may be of some value in selecting individuals at high risk.

Aged↗
PubMed1995

Measurement of femoral geometry in type I and type II osteoporosis: differences in hip axis length consistent with heterogeneity in the pathogenesis of osteoporotic fractures.

The epidemiologic patterns of vertebral and femoral fractures are sufficiently different to suggest that they represent distinct disorders (type I versus type II osteoporosis) although osteopenia is common in both. To determine whether differences in femoral geometry, one of the main determinants of bone quality, might contribute to the heterogeneity in osteoporotic fractures, we obtained dual energy X-ray absorptiometry scans on 210 women age 60 or older, including 105 type I fracture cases, 30 type II patients, and 75 controls. Hip axis length, measured on the scan printout, was significantly increased (p < 0.01) in hip fracture patients compared with women with postmenopausal osteoporosis, whereas femoral neck density (BMD) was equal in both groups. The best discrimination between both fracture types was obtained by a logistic regression model based on age and axis length. Adding BMD to the model did not improve the discriminative power (p = 0.67). These data provide further evidence that geometric characteristics may be implicated in hip fracture risk. Furthermore, these findings suggest that an increase in hip axis length may predispose osteopenic subjects to a femoral localization of fragility fractures, consistent with the postulated heterogeneity in the pathogenesis of osteoporotic fractures.

Absorptiometry, Photon↗
PubMed1995

Timing and quantification of bone loss in cardiac transplant recipients.

To evaluate osteopenic bone disease in heart transplant patients, we prospectively measured bone mineral density (BMD) in 33 consecutive male recipients before hospital discharge and 1 year later, using dual photon absorptiometry. At hospital discharge BMD measurement at the lumbar spine was 90% of that expected in healthy age- and sex-matched controls (p = 0.005). One year later BMD had further decreased by 8.5% at the lumber spine and by 10.4% at the femoral neck (P = 0.0001). Five patients suffered vertebral compression fractures during the 1st postoperative year. Our results indicate that osteopenia of the lumbar spine is already present at the time of hospital discharge after transplantation and that further bone loss occurs at considerable rate during the 1st postoperative year at the lumber spine and at the femoral neck.

Adult↗
PubMed1995

European semi-anthropomorphic spine phantom for the calibration of bone densitometers: assessment of precision, stability and accuracy. The European Quantitation of Osteoporosis Study Group.

Up to now it has not been possible to reliably cross-calibrate dual-energy X-ray absorptiometry (DXA) densitometry equipment made by different manufacturers so that a measurement made on an individual subject can be expressed in the units used with a different type of machine. Manufacturers have adopted various procedures for edge detection and calibration, producing various normal ranges which are specific to each individual manufacturer's brand of machine. In this study we have used the recently described European Spine Phantom (ESP, prototype version), which contains three semi-anthropomorphic "vertebrae" of different densities made of stimulated cortical and trabecular bone, to calibrate a range of DXA densitometers and quantitative computed tomography (QCT) equipment used in the measurement of trabecular bone density of the lumbar vertebrae. Three brands of QCT equipment and three brands of DXA equipment were assessed. Repeat measurements were made to assess machine stability. With the large majority of machines which proved stable, mean values were obtained for the measured low, medium and high density vertebrae respectively. In the case of the QCT equipment these means were for the trabecular bone density, and in the case of the DXA equipment for vertebral body bone density in the posteroanterior projection. All DXA machines overestimated the projected area of the vertebral bodies by incorporating variable amounts of transverse process. In general, the QCT equipment gave measured values which were close to the specified values for trabecular density, but there were substantial differences from the specified values in the results provided by the three DXA brands. For the QCT and Norland DXA machines (posteroanterior view), the relationships between specified densities and observed densities were found to be linear, whereas for the other DXA equipment (posteroanterior view), slightly curvilinear, exponential fits were found to be necessary to fit the plots of observed versus specified densities. From these plots, individual calibration equations were derived for each machine studied. For optimal cross-calibration, it was found to be necessary to use an individual calibration equation for each machine. This study has shown that it is possible to cross-calibrate DXA as well as QCT equipment for the measurement of axial bone density. This will be of considerable benefit for large-scale epidemiological studies as well as for multi-site clinical studies depending on bone densitometry.

Absorptiometry, Photon↗
PubMed1995

Bone mass in Zaireans: radiogrammetric determination.

Bone mass was measured in 230 subjects with ages ranging from 15 to 54 years (110 males and 120 females), using the radiogrammetric method on the second metacarpal bone. Results of the study show that bone mass increases with age up to 34 years and then decreases, both in males and females, although males have significantly higher values than females. The decrease is however more marked in females than in males.

Adolescent↗
PubMed1995

Age-related bone loss and senile osteoporosis: evidence for both secondary hyperparathyroidism and skeletal growth factor deficiency in the elderly.

Aging is characterized by a decrease in bone volume, implying that net bone resorption exceeds net bone formation. This age-related bone loss can be regarded as the main determinant of hip fracture risk in the elderly. In the concept of senile osteoporosis, a key role has been attributed to vitamin D deficiency. Lack of vitamin D activity may affect femoral strength through impaired mineralization as well as through a hyperparathyroidism-mediated increase in bone resorption. In addition to vitamin D-related mechanisms, recent evidence has indicated a decline in the skeletal content of anabolic growth factors--such as insulin-like growth factor-I (IGF-I)--in femoral (cortical) bone, suggesting that skeletal growth factor deficiency may contribute to the age-related bone loss in the proximal femur as well. It is tempting to speculate that skeletal IGF-I loss might, at least partially, be accounted for by growth hormone deficiency. However, critical evidence does not yet support the concept that the decreased activity of the growth hormone-IGF-I-axis alters bone remodeling, and the extent to which serum concentrations of growth factors are reflective of skeletal activity remains to be clarified.

Aged↗