Henning W. Woitge

Supplementation With Oral Vitamin D3 and Calcium During Winter Prevents Seasonal Bone Loss: A Randomized Controlled Open-Label Prospective Trial†

Bone metabolism follows a seasonal pattern with high bone turnover and bone loss during the winter. In a randomized, open‐label 2‐year sequential follow‐up study of 55 healthy adults, we found that supplementation with oral vitamin D3 and calcium during winter abolished seasonal changes in calciotropic hormones and markers of bone turnover and led to an increase in BMD. Supplementation with oral vitamin D3 and calcium during the winter months seems to counteract the effects of seasonal changes in vitamin D and thus may be beneficial as a primary prevention strategy for age‐related bone loss.

Novel serum markers of bone resorption: clinical assessment and comparison with established urinary indices.

Although urinary measurements of collagen degradation provide valid estimates of bone resorption, their clinical application is hampered by pronounced analytical and biological variability. Therefore, immunoassays for the determination of such parameters in serum have been developed. In this study, we assessed the performance of three new serum markers of bone turnover, i.e., C‐terminal and N‐terminal telopeptides of type I collagen (S‐CTX and S‐NTX) and bone sialoprotein. Results were compared with urinary total pyridinoline, total deoxypyridinoline, and urinary C‐terminal telopeptides of type I collagen (U‐CTX) and urinary N‐terminal telopeptides of type I collagen (U‐NTX). The study population included healthy men (n = 27), premenopausal (n = 30) and postmenopausal (n = 31) women, patients with hepatic dysfunction (HF, n = 24), renal failure (RF, n = 30), breast cancer without (BC–, n = 24) and with (BC+, n = 30) bone metastases, primary vertebral osteoporosis (OPO, n = 27), primary hyperparathyroidism (PHPT, n = 16), active Pagets disease of bone (n = 18), multiple myeloma (MM, n = 18), and patients with hypercalcemia of malignancy before and after treatment with pamidronate (HOM, n = 28). Changes in urinary and serum markers were similar in most metabolic bone diseases. However, differentiation between healthy controls and OPO, or PHPT, was improved by the serum markers. In MM, all serum and urinary markers were elevated (p < 0.05 vs. controls). In BC+, skeletal involvement was reflected by significant increments in all indices (p < 0.01 vs. BC–), except U‐CTX and S‐CTX. In HOM, pamidronate‐induced changes in biomarkers were most pronounced for U‐CTX and S‐CTX and S‐NTX. HF and RF were associated with elevated levels of all serum markers (p < 0.05 vs. controls). In conclusion, measurements in serum reflect bone resorption to the same extent as the urinary indices. Since serum markers circumvent some of the limitations of urinary measurements, their use potentially improves the assessment of skeletal disorders.

Circannual Rhythms and Interactions of Vitamin D Metabolites, Parathyroid Hormone, and Biochemical Markers of Skeletal Homeostasis: A Prospective Study

Recent studies suggest a circannual pattern of bone turnover. To further investigate the underlying mechanisms, 41 healthy subjects (25‐80 years old) living in a southwestern German city were studied prospectively over a period of 18 months. Participants were examined every 4 weeks, and blood and urine samples were obtained on each visit. The following parameters were measured: serum 25‐hydroxyvitamin D3 [25(OH)D3], 1,25‐dihydroxyvitamin D3 [1,25(OH)2D3], and parathyroid hormone (PTH), as regulators, and serum total alkaline phosphatase (TAP), bone‐specific alkaline phosphatase (BAP), urinary total pyridinoline (PYD), deoxypyridinoline (DPD), and the aminoterminal telopeptide of collagen type I (NTX), as biochemical markers of bone turnover. The presence of significant circannual rhythms for the various markers was tested using the Pharmfit method. In the total group, 25(OH)D3, 1,25(OH)2D3, and PTH as well as BAP, PYD, DPD, and NTX showed a significant seasonal variation. 25(OH)D3 revealed the highest amplitude (38.0%) with an acrophase in August. Levels of the biochemical markers and of PTH were highest in winter with amplitudes of up to 17.7% (DPD). Results were most pronounced in premenopausal women, in subjects <50 years of age, and in subjects who did show a significant individual rhythm in 25(OH)D3 levels. No differences were found regarding other anthropometric or life style factors. Correlation analyses revealed strongest associations between the amplitudes of a vitamin D metabolite and a biochemical marker in premenopausal women. We conclude that specific markers of bone turnover show significant circannual rhythms. These changes are related directly to variations in the hormonal regulation of skeletal homeostasis. In postmenopausal women and in men, other effects may superimpose the circannual variation of biomarkers of bone turnover.

Changes in Bone Turnover Induced by Aerobic and Anaerobic Exercise in Young Males

Physical activity is considered an important factor in attaining bone mass. However, the mechanisms by which exercise affects bone metabolism are not completely understood. The present study was performed to investigate the effects of aerobic and anaerobic exercise on bone turnover. Twenty healthy young males (aged 20–29 years) were followed through an 8‐week program of aerobic (n = 10) and anaerobic training (n = 10). Ten age‐matched individuals served as controls. Serum bone‐specific alkaline phosphatase (BAP), serum osteocalcin (OC), and urinary pyridinoline (Pyd) and deoxypyridinoline (Dpd) were determined as indices of bone metabolism. After 4 weeks of aerobic training, serum BAP and OC (p < 0.01), and urinary Pyd (p < 0.001) and Dpd (p < 0.01) were significantly reduced. After 8 weeks, BAP and OC levels had returned to baseline values, whereas the urinary cross‐link excretion remained low. In the anaerobic training group, elevated levels of BAP (p < 0.05 vs. week 4), OC (p < 0.05 vs. week 4), and Pyd (p < 0.01 vs. week 0) were observed after 8 weeks of exercise. Changes in urinary Pyd and Dpd (week 0 vs. week 8) were positively correlated with changes in the mean power level in the Wingate test, a parameter of the anaerobic performance capacity (r = 0.50 and r = 0.55, p < 0.01, respectively). In the controls, no significant changes in biochemical markers were observed. We conclude that aerobic and anaerobic training excert different effects on bone metabolism. While aerobic training led to changes compatible with reduced bone resorption activity, anaerobic training seems to result in an overall accelerated bone turnover. Therefore, the impact of physical activity on bone turnover may depend on the kind of exercise performed.

Basic Principles and Clinical Applications of Biochemical Markers of Bone Metabolism: Biochemical and Technical Aspects

The interest in and the need for effective measures to be used in the screening, diagnosis, and follow-up of disorders of connective tissue, bone, and mineral metabolism has markedly grown. Next to clinical and imaging techniques, indices of bone turnover have come to play an important role in the assessment of metabolic bone disease. In osteoporosis, recent research has shown that bone markers may also be used to predict future bone loss and hip fractures (in larger cohorts of older patients), identify individuals at risk for osteoporosis, select therapy, and predict and monitor the therapeutic response in individual patients. The development of new markers of bone metabolism has greatly enriched the spectrum of serum and urine analytes used in the assessment of skeletal pathologies. Besides total alkaline phosphatase, other markers such as bone-specific alkaline phosphatase, osteocalcin, or the collagen propeptides are being used to measure bone formation. Bone resorption, previously assessed only by the measurement of urinary calcium and hydroxyproline, may now be detected more precisely by a number of new serum and urine markers. Among these, the pyridinium crosslinks and the telopeptides of collagen type I are presently considered the most specific markers of bone resorption. More recently, bone sialoprotein has also been suggested as a marker of bone resorption in serum. Tartrate-resistant acid phosphatase is now measurable by immunoassay. This article surveys the biochemistry and relevant technical aspects of the currently available markers of bone metabolism.

Serum bone sialoprotein as a marker of tumour burden and neoplastic bone involvement and as a prognostic factor in multiple myeloma

To test the potential of immunoreactive BSP, a non-collagenous bone matrix component, as a clinical guide in patients with plasma cell dyscrasias, serum BSP concentrations were measured in 62 patients with newly diagnosed multiple myeloma (MM) followed over a period of 4 years, in 46 patients with monoclonal gammopathy of undetermined significance (MGUS), in 71 patients with untreated benign vertebral osteoporosis (OPO), and in 139 healthy adults. Results were compared with clinical and laboratory data, including serum osteocalcin (OC), and urinary pyridinoline (PYD) and deoxypyridinoline (DPD) as markers of bone turnover. In MM, serum BSP, and urinary PYD and DPD were higher than in healthy controls and in MGUS or OPO (P< 0.001). BSP levels correlated with the bone marrow plasma cell content (r = 0.40, P< 0.001), and serum β2-microglobulin (r = 0.31, P < 0.01). The differentiation of MM from healthy controls and from MGUS or OPO was highest for BSP. After chemotherapy, BSP reflected the response to treatment and correlated with the change in monoclonal protein (r = 0.55, P< 0.001). MM patients with normal baseline BSP levels survived longer than patients with initially elevated BSP values (P< 0.001, logrank test). Only serum monoclonal protein and BSP were independent predictors of survival. We conclude that in MM, BSP levels are associated with skeletal involvement and tumour cell burden. The quantification of serum BSP may be a non-invasive method for the diagnosis and follow-up, and may improve the prognostic value of conventional staging in MM.

Cloning and in Vitro Characterization ofα 1(I)-Collagen 11β-Hydroxysteroid Dehydrogenase Type 2 Transgenes as Models for Osteoblast-Selective Inactivation of Natural Glucocorticoids1

The NAD-dependent enzyme, 11β-hydroxysteroid dehydrogenase type II (11βHSD2), catalyzes the unidirectional conversion of biologically active glucocorticoids to inactive metabolites. In vivo, 11βHSD2 protects the mineralocorticoid receptor from activation by glucocorticoids in mineralocorticoid target tissues such as kidney. The goal of the present study was to use targeted overexpression of 11βHSD2 as a novel means of disrupting glucocorticoid signaling in osteoblastic cells. Rat 11βHSD2 complementary DNA was cloned downstream of a 2.3- and 3.6-kb α1(I)-collagen (Col1a1) promoter fragment to produce the expression plasmids Col2.3-HSD2 and Col3.6-HSD2, respectively, which were transiently and/or stably transfected in osteoblastic ROS 17/2.8 and MC3T3-E1 cells. Transgene messenger RNA and protein were detected in transfected cells by Northern blot analysis and immunostaining, respectively. Transfection of 11βHSD2 led to higher rates of conversion of[ 3H]corticosterone to[ 3H]dehydrocorticosterone and reduce...

Calvariae from Fetal Mice with a Disrupted Igf1 Gene Have Reduced Rates of Collagen Synthesis but Maintain Responsiveness to Glucocorticoids

The goals of this study were to examine the role of insulin‐like growth factor I (IGF‐I) on bone formation and to test the hypothesis that the inhibitory effects of glucocorticoids on bone formation are independent of the IGF‐I pathway. In serum‐free organ cultures of 18‐day fetal mouse calvariae derived from Igf1 null mice (Igf1−/−) and their wild‐type (Igf1+/+) and heterozygous (Igf1+/−) littermates, we measured the incorporation of [3H]proline into collagenase‐digestible protein (CDP) and noncollagen protein (NCP), percent collagen synthesis (PCS), the incorporation of [3H]thymidine into DNA, and messenger RNA (mRNA) levels of osteoblast markers in the presence or absence of dexamethasone. After 24 h of culture, calvariae of all genotypes had similar levels of PCS. However, after 48–96 h of culture, PCS was significantly lower in Igf1−/− calvariae compared with Igf1+/+ calvariae. Treatment of calvariae with 100 nM of dexamethasone for 48–96 h decreased PCS in all genotypes. After 72 h of culture, [3H]thymidine incorporation was similar in all genotypes and 100 nM dexamethasone caused a significant reduction in [3H]thymidine incorporation in all genotypes. Dexamethasone at 100 nM decreased α1(I)‐collagen (Col1a1) mRNA and increased alkaline phosphatase, bone sialoprotein, and osteopontin mRNA in all genotypes after 72 h of culture. Type I IGF receptor mRNA levels were highest in Igf1−/− calvarial cultures. Dexamethasone at 100 nM increased Igf2 and type I IGF receptor mRNA levels in all genotypes. We conclude that one intact allele for Igf1 is sufficient to maintain normal rates of collagen synthesis in fetal mouse calvarial cultures. Moreover, the inhibitory effects of glucocorticoids on collagen synthesis and cell replication are at least partially independent of the IGF‐I pathway in this model.

Biochemical Markers to Survey Bone Turnover

Molecular markers of bone turnover have gained increasing relevance in the evaluation of patients with metabolic bone diseases. Their clinical applications include the assessment of future osteoporotic fracture risk, complementation of bone density measurements, diagnosis of certain metabolic osteopathies, therapeutic decision making, and monitoring of therapeutic efficacy and patient compliance. One should be aware, however, that the results from large epidemiologic or clinical trials are sometimes difficult to translate into the everyday clinical situation. The individual patient often has more than one disease that might affect either bone turnover or the handling of the parameters mentioned (or both). Analytic and biologic variability of bone markers can be significant and also needs to be considered when using these indices. In the scientific setting, conventional and new markers of bone turnover can help to elucidate formerly unknown mechanisms and pathways. Because the development of ever more specific and sensitive markers of bone metabolism is progressing rapidly, we are likely to witness new insights into the pathophysiology of bone diseases in the near future.

Molecular markers of bone and cartilage metabolism.

Molecular markers of bone and cartilage metabolism are increasingly used as helpful tools in the diagnosis and early detection of joint disease. Their quantification may help to improve the ability for therapeutic monitoring and follow-up of patients affected with rheumatic or degenerative cartilage disorders. The biochemical background and the functional properties of markers of bone, cartilage, and synovial tissue turnover are described. Current clinical applications and the diagnostic and prognostic validity of these metabolites are presented with special emphasis on recent research activities. Finally, molecular aspects of bone and joint diseases are discussed, highlighting genetic contributions to the development of joint disease.