Type I collagen racemization and isomerization and the risk of fracture in postmenopausal women: the OFELY prospective study

Intersecting Paths: Unraveling the Complex Journey of Cancer to Bone Metastasis

The phenomenon of bone metastases presents a significant challenge within the context of advanced cancer treatments, particularly pertaining to breast, prostate, and lung cancers. These metastatic occurrences stem from the dissemination of cancerous cells into the bone, thereby interrupting the equilibrium between osteoblasts and osteoclasts. Such disruption results in skeletal complications, adversely affecting patient morbidity and quality of life. This review discusses the intricate interplay between cancer cells and the bone microenvironment, positing the bone not merely as a passive recipient of metastatic cells but as an active contributor to cancer progression through its distinctive biochemical and cellular makeup. A thorough examination of bone structure and the dynamics of bone remodeling is undertaken, elucidating how metastatic cancer cells exploit these processes. This review explores the genetic and molecular pathways that underpin the onset and development of bone metastases. Particular emphasis is placed on the roles of cytokines and growth factors in facilitating osteoclastogenesis and influencing osteoblast activity. Additionally, this paper offers a meticulous critique of current diagnostic methodologies, ranging from conventional radiography to advanced molecular imaging techniques, and discusses the implications of a nuanced understanding of bone metastasis biology for therapeutic intervention. This includes the development of targeted therapies and strategies for managing bone pain and other skeletal-related events. Moreover, this review underscores the imperative of ongoing research efforts aimed at identifying novel therapeutic targets and refining management approaches for bone metastases. It advocates for a multidisciplinary strategy that integrates advancements in medical oncology and radiology with insights derived from molecular biology and genetics, to enhance prognostic outcomes and the quality of life for patients afflicted by this debilitating condition. In summary, bone metastases constitute a complex issue that demands a comprehensive and informed approach to treatment. This article contributes to the ongoing discourse by consolidating existing knowledge and identifying avenues for future investigation, with the overarching objective of ameliorating patient care in the domain of oncology.

Night shift work and serum markers of bone turnover in male shift workers

Night shift work is related to sleep disorders, disruption of circadian rhythm and low serum levels of vitamin D. It is known that all these conditions can adversely affect bone mass. The rate of bone turnover can be assessed through the measurement of molecules called bone turnover markers, including C-terminal telopeptide fragment of type I collagen (CTX) and procollagen type I N-terminal propeptide (P1NP). In this study, we evaluated the serum levels of CTX, P1NP and 25-Hydroxy Vitamin D in 82 male subjects (42 daytime workers and 40 night shift workers) to assess the possible risk of osteoporosis in male shift workers. Serum levels of CTX and P1NP were found to be higher in night shift workers than in daytime workers. No significant difference was found in vitamin D levels between night shift and daytime workers. The increased CTX and P1NP levels reveal a higher rate of bone turnover in night shift workers and thus a possible increased risk of osteoporosis in this category of workers compared with daytime workers. In view of this, our results highlight the importance of further studies investigating the bone health in male night shift workers.

Clinical application of the fracture risk assessment tool in the general population and its correlation with bone turnover markers

Objective: To compare the risk of osteoporotic fractures between the urban and urban-rural fringe populations in southern China and to explore the effect of bone turnover markers on fracture risk. Methods: Epidemiological investigations were conducted in the urban and urban-rural fringe areas of southern China in June 2018. Residents aged 40 years and over who signed informed consent forms were included. Physical examination and questionnaire collection were completed. Bone turnover markers (BTMs) including osteocalcin (OC) and beta cross-linked C-telopeptide of type 1 collagen (β-CTX) were tested. Bone mineral density (BMD) of the femoral neck and lumbar vertebrae 1-4 were measured using dual energy X-ray absorptiometry. Fracture risk assessment tool (FRAX) values were calculated to show the probability of major osteoporotic fracture (PMOF) and probability of hip fracture (PHF) over the next 10 years. Results: A total of 1,051 participants were included in this study, including 553 in the urban areas and 498 in the urban-rural fringe areas. The average PMOF and PHF were 3.4 (2.3-5.4) % and .6 (.3-1.5) %, respectively. Compared with that in the urban populations, the femoral neck BMD in the urban-rural fringe populations was lower and FRAX values were generally higher, especially for women. FRAX values in various populations were mainly negatively correlated with lumbar and femoral neck BMD and were positively correlated with β-CTX; meanwhile, only PHF was negatively correlated with OC. After adjusting for sex, elevated β-CTX levels significantly increased the risk of high PMOF in various populations and increased the risk of high PHF in the urban-rural fringe populations. In particular, the risks of increased PMOF and PHF could increase by as much as 33 times and 19.5 times, respectively, in the urban-rural fringe areas. Conclusion: The urban-rural fringe populations in Southern China may be at risk of osteoporotic fracture. In addition to being related to BMD, the FRAX value also correlates with some BTMs. Combining FRAX with BMD, and BTMs may better predict the fracture risk.

Bone Quality in Relation to HIV and Antiretroviral Drugs

PURPOSE OF REVIEW

People living with HIV (PLWH) are at an increased risk for osteoporosis, a disease defined by the loss of bone mineral density (BMD) and deterioration of bone quality, both of which independently contribute to an increased risk of skeletal fractures. While there is an emerging body of literature focusing on the factors that contribute to BMD loss in PLWH, the contribution of these factors to bone quality changes are less understood. The current review summarizes and critically reviews the data describing the effects of HIV, HIV disease-related factors, and antiretroviral drugs (ARVs) on bone quality.

RECENT FINDINGS

The increased availability of high-resolution peripheral quantitative computed tomography has confirmed that both HIV infection and ARVs negatively affect bone architecture. There is considerably less data on their effects on bone remodeling or the composition of bone matrix. Whether changes in bone quality independently predict fracture risk, as seen in HIV-uninfected populations, is largely unknown. The available data suggests that bone quality deterioration occurs in PLWH. Future studies are needed to define which factors, viral or ARVs, contribute to loss of bone quality and which bone quality factors are most associated with increased fracture risk.

Potential of biomarkers during pharmacological therapy setting for postmenopausal osteoporosis: a systematic review

Background

Biochemical markers of bone turnover (BTMs), such as the bone alkaline phosphatase (bALP), procollagen type I N propeptide (PINP), serum cross-linked C-telopeptides of type I collagen (bCTx), and urinary cross-linked N-telopeptides of type I collagen (NTx), are used to manage therapy monitoring in osteoporotic patients. This systematic review analyzed the potential of these BMTs in predicting the clinical outcomes in terms of BMD, t-score, rate of fractures, and adverse events during the therapy setting in postmenopausal osteoporosis.

Methods

All randomized clinical trials (RCTs) reporting data on biomarkers for postmenopausal osteoporosis were accessed. Only articles reporting quantitative data on the level of biomarkers at baseline and on the outcomes of interest at the last follow-up were eligible.

Results

A total of 36,706 patients were retrieved. Greater values of bALP were associated with a greater rate of vertebral (P = 0.001) and non-vertebral fractures (P = 0.0001). Greater values of NTx at baseline were associated with a greater rate of adverse events at the last follow-up (P = 0.02). Greater values of CTx at baseline were associated with a greater rate of adverse events leading to discontinuation (P = 0.04), gastrointestinal adverse events (P = 0.0001), musculoskeletal adverse events (P = 0.04), and mortality (P = 0.04). Greater values of PINP at baseline were associated with greater rates of gastrointestinal adverse events (P = 0.02) at the last follow-up.

Conclusion

The present analysis supports the adoption of BMTs during pharmacological therapy setting of patients suffering from osteoporosis.

Level of evidence

I, systematic review of RCTs

Biomarkers as therapy monitoring for postmenopausal osteoporosis: a systematic review

Background

Biochemical markers of bone turnover (BTMs), such as bone alkaline phosphatase (bALP), procollagen type I N propeptide (PINP), serum cross-linked C-telopeptides of type I collagen (bCTx), and urinary cross-linked N-telopeptides of type I collagen (NTx), are commonly used for therapy monitoring purposes for osteoporotic patients. The present study evaluated the potential role of BTMs as therapy monitoring.

Methods

All randomized clinical trials (RCTs) comparing two or more pharmacological treatments for postmenopausal osteoporosis were accessed. Only studies that reported the value of bALP, PINP, bCTx, and NTx at last follow-up were included. A multivariate analysis was performed to assess associations between these biomarkers and clinical outcomes and rate of adverse events in patients with postmenopausal osteoporosis. A multiple linear model regression analysis through the Pearson product-moment correlation coefficient was used.

Results

A total of 16 RCTs (14,446 patients) were included. The median age was 67 years, and the median BMI 25.4 kg/m². The median vertebral BMD was 0.82, hip BMD 0.79, and femur BMD 0.64 g/cm². The ANOVA test found optimal within-group variance concerning mean age, body mass index, and BMD. Greater bALP was associated with lower femoral BMD (P = 0.01). Greater NTx was associated with a greater number of non-vertebral fractures (P = 0.02). Greater NTx was associated with greater rate of therapy discontinuation (P = 0.04). No other statistically significant associations were detected.

Conclusion

Our analysis supports the adoption of BTMs in therapy monitoring of osteoporotic patients.

Level of evidence

Level I, systematic review of RCTs.

The Association between Fast Increase in Bone Turnover During the Menopause Transition and Subsequent Fracture

CONTEXT

Bone turnover increases rapidly during the menopause transition (MT) and plateaus above premenopausal levels in early postmenopause. It is uncertain whether higher bone turnover is associated with fracture in midlife women with near-normal bone mineral density (BMD).

OBJECTIVE

Examine whether faster increases in bone turnover during the MT (2 years before to 2 years after the final menstrual period [FMP]), and greater bone turnover during early postmenopause (≥2 years after the FMP) are risk factors for subsequent fracture, accounting for BMD.

DESIGN AND SETTING

The Study of Women's Health Across the Nation, a longitudinal cohort study of the MT.

PARTICIPANTS

A total of 484 women (initially pre- or early perimenopausal, who transitioned to postmenopause) with bone turnover (urine collagen type I N-telopeptide), BMD, and fracture data.

MAIN OUTCOME MEASURE

Incident fracture after the MT.

RESULTS

Adjusting for age, race/ethnicity, fracture before the MT, cigarette use, body mass index, and study site in Cox proportional hazards regression, each SD increment in the rate of increase in bone turnover during the MT was associated with 24% greater hazard of incident fracture in postmenopause (P = .008). Accounting for the same covariates, each SD increment in bone turnover during early postmenopause was associated with a 27% greater hazard of fracture (P = .01). Associations remained significant after controlling for MT rate of change and early postmenopausal level of BMD.

CONCLUSION

Faster increases in bone turnover during the MT and greater bone turnover in early postmenopause forecast future fractures.

Potential Biomarkers to Improve the Prediction of Osteoporotic Fractures

Osteoporotic fracture (OF) is associated with high disability and morbidity rates. The burden of OF may be reduced by early identification of subjects who are vulnerable to fracture. Although the current fracture risk assessment model includes clinical risk factors (CRFs) and bone mineral density (BMD), its overall ability to identify individuals at high risk for fracture remains suboptimal. Efforts have therefore been made to identify potential biomarkers that can predict the risk of OF, independent of or combined with CRFs and BMD. This review highlights the emerging biomarkers of bone metabolism, including sphongosine-1-phosphate, leucine-rich repeat-containing 17, macrophage migration inhibitory factor, sclerostin, receptor activator of nuclear factor-κB ligand, and periostin, and the importance of biomarker risk score, generated by combining these markers, in enhancing the accuracy of fracture prediction.

Position Statement on the Use of Bone Turnover Markers for Osteoporosis Treatment

Current evidences continue to support the clinical application of bone turnover markers (BTMs) in the management of postmenopausal osteoporosis. The limitations of bone mineral density measured by dual energy X-ray absorptiomet especially emphasize the beneficial roles of BTMs, such as serum C-terminal telopeptide of type I collagen and serum procollagen type I N-propeptide, as monitoring tools to assess the responses to treatment. Therefore, the proper application and assessment of BTM in clinical practice is very important. However, their use in Korea is still insufficient. Therefore, the BTM committee has set up by the Korean Society for Bone and Mineral Research have been constituted and provided a position statement which will suggest on the clinical application of BTM for the management of postmenopausal osteoporosis in Korea.

Paleoproteomics of Mesozoic Dinosaurs and Other Mesozoic Fossils

Molecular studies have contributed greatly to our understanding of evolutionary processes that act upon virtually every aspect of living organisms. However, these studies are limited with regard to extinct organisms, particularly those from the Mesozoic because fossils pose unique challenges to molecular workflows, and because prevailing wisdom suggests no endogenous molecular components can persist into deep time. Here, the power and potential of a molecular approach to Mesozoic fossils is discussed. Molecular methods that have been applied to Mesozoic fossils-including iconic, non-avian dinosaurs- and the challenges inherent in such analyses, are compared and evaluated. Taphonomic processes resulting in the transition of living organisms from the biosphere into the fossil record are reviewed, and the possible effects of taphonomic alteration on downstream analyses that can be problematic for very old material (e.g., molecular modifications, limitations of on comparative databases) are addressed. Molecular studies applied to ancient remains are placed in historical context, and past and current studies are evaluated with respect to producing phylogenetically and/or evolutionarily significant data. Finally, some criteria for assessing the presence of endogenous biomolecules in very ancient fossil remains are suggested as a starting framework for such studies.

Combining information from multiple bone turnover markers as diagnostic indices for osteoporosis using support vector machines

CONTEXT

Osteoporosis (OP) is a progressive systemic bone disease. Dual-energy X-ray absorptiometry (DXA) is routinely employed and is considered the gold standard method for the diagnosis of OP.

OBJECTIVE

We aimed to investigate the potential use of combined information from multiple bone turnover markers (BTMs) as a clinical diagnostic tool for OP.

MATERIALS AND METHODS

A total of 9053 Chinese postmenopausal women (2464 primary OP patients and 6589 healthy controls) were recruited. Serum levels of six common BTMs, including BAP, BSP, CTX, OPG, OST and sRANKL were assayed. Models based on support vector machine (SVM) were constructed to explore the efficiency of different combinations of multiple BTMs for OP diagnosis.

RESULTS

Increasing the number of BTMs used in generating the models increased the predictive power of the SVM models for determining the disease status of study subjects. The highest kappa coefficient for the model with one BTM (BAP) compared to DXA was 0.7783. The full model incorporating all six BTMs resulted in a high kappa coefficient of 0.9786.

CONCLUSION

Our findings showed that although single BTMs were not sufficient for OP diagnosis, appropriate combinations of multiple BTMs incorporated into the SVM models showed almost perfect agreement with the DXA.

Efficacy and safety of alfacalcidol in Chinese postmenopausal women aged over 65 with osteoporosis or osteopenia: An open label, non-comparative, post marketing observational study

This study aimed to explore the therapeutic efficacy and safety of alfacalcidol among Chinese postmenopausal women (age >65 years) with osteoporosis or osteopenia.A total of 62 postmenopausal women with osteoporosis or osteopenia (>65 years) were recruited from urban residential community of Beijing. The patients daily took oral calcium and alfacalcidol (Alpha D3, 1 μg) for 9 months. Safety and efficacy assessments were performed at baseline and regular intervals. Alfacalcidol was adjusted to a daily dose of 0.5 μg in case of hypercalcemia or hypercalciuria.A significant improvement in "timed up and go test" and "chair rising test" was achieved 3 months after treatment. Significant decreases in bone turnover markers were observed 3 months after the treatment and lasted throughout the study. Nineteen patients discontinued due to adverse events (17 hypercalciuria, 1 hydronephrosis, and 1 stomach ache), while alfacalcidol was adjusted to a daily dose of 0.5 μg in 18 patients (29.0%). Increased serum creatinine was observed when compared to baseline (P <.001), but all the values were in normal range.The treatment with 1 μg alfacalcidol can significantly improve muscle function and bone metabolism. Regular monitoring of urine calcium and timely dosage-adjustments are very important to guarantee the safety of alfacalcidol treatment in Chinese menopausal women.

Clinical Utility of Biochemical Marker of Bone Turnover: Fracture Risk Prediction and Bone Healing

Bone turnover markers (BTMs) are released during bone remodeling and are thought to reflect the metabolic activity of bone at the cellular level. This review examines BTM as a biological response marker for monitoring future fracture prediction and fracture healing processes. Substantial evidence has been of high value to investigate the use of BTM in fracture risk prediction; nevertheless, the conclusions of some studies are inconsistent due to their large variability. BTM is promising for fracture risk prediction for adopting international reference standards or providing absolute risks, such as 10-year fracture probabilities. There are uncertainties over their clinical use for monitoring osteoporotic fracture healing. More rigorous evidence is needed that can provide more detailed insights for fracture healing and for ascertaining the progression of fracture healing.

High Plasma Sphingosine 1-phosphate Levels Predict Osteoporotic Fractures in Postmenopausal Women: The Center of Excellence for Osteoporosis Research Study

Background

Higher sphingosine 1-phosphate (S1P) plasma levels are associated with decreased bone mineral density (BMD), and increased risk of prevalent vertebral fracture. So, we hypothesized that postmenopausal women with increased baseline plasma S1P levels have a greater risk for future incident fracture (osteoporosis-related fractures [ORFs]).

Methods

This study was conducted in a prospective longitudinal cohort of 707 women recruited in 2004 and followed up annually for a mean period of 5.2±1.3 years. They were postmenopausal (aged ≥50 years). The primary outcome measure was the time to the first confirmed ORF event using radiographs and/or a surgical report.

Results

The plasma S1P levels (µmol/L) were significantly higher in the women with incident fracture (7.23±0.79) than in those without ORFs (5.02±0.51; P<0.001). High S1P levels were strongly associated with increased fracture risk. After adjustment for age and other confounders, the hazard ratio (HR) was 6.12 (95% confidence interval [CI], 4.92−7.66) for each 1-standard deviation increase in plasma S1P levels. The women in the highest quartile of S1P levels had a significant increase in fracture risk (HR, 9.89; 95% CI, 2.83−34.44). Results were similar when we compared plasma S1P levels at the 1-year visit.

Conclusions

The associations between plasma S1P levels and fracture risk were independent of BMD and other confounders. These findings demonstrate that high plasma S1P level at baseline and at years 1 to 5 is a strong and independent risk factor for future [ORFs] among postmenopausal women and could be a useful biomarker for fracture risk assessment in this population.

Clinical guidelines for the prevention and treatment of osteoporosis: summary statements and recommendations from the Italian Society for Orthopaedics and Traumatology

BACKGROUND

The Italian Society for Orthopaedics and Traumatology conceived this guidance-which is primarily addressed to Italian orthopedic surgeons, but should also prove useful to other bone specialists and to general practitioners-in order to improve the diagnosis, prevention, and treatment of osteoporosis and its consequences.

MATERIALS AND METHODS

Literature reviews by a multidisciplinary team.

RESULTS

The following topics are covered: the role of instrumental, metabolic, and genetic evaluations in the diagnosis of osteoporosis; appraisal of the risk of fracture and thresholds for intervention; general strategies for the prevention and treatment of osteoporosis (primary and secondary prevention); the pharmacologic treatment of osteoporosis; the setting and implementation of fracture liaison services for tertiary prevention. Grade A, B, and C recommendations are provided based on the main levels of evidence (1-3). Toolboxes for everyday clinical practice are provided.

CONCLUSIONS

The first up-to-date Italian guidelines for the primary, secondary, and tertiary prevention of osteoporosis and osteoporotic fractures are presented.

Measurement and Clinical Utility of βCTX in Serum and Plasma

Biochemical markers of bone turnover (BTM) are released during bone remodeling and can be measured in blood or urine as noninvasive surrogate markers for the bone remodeling rate. The C-terminal cross-linked telopeptide of type I collagen (βCTX) is released during bone resorption and is specific to bone tissue. Assays have been developed to measure βCTX in blood and in urine; most current use of βCTX measurement for research and in clinical practice is performed on a blood sample. Method-specific differences for serum and plasma βCTX have led to initiatives to standardize or harmonize βCTX commercial assays. βCTX demonstrates significant biological variation due to circadian rhythm and effect of food which can be minimized by standardized sample collection in the fasting state in the morning. While βCTX predicts fracture risk independent of bone mineral density, lack of data has precluded its inclusion in fracture risk calculators. The changes seen in βCTX with antiresorptive therapies have been well characterized and this has led to its widespread use for monitoring therapy in osteoporosis. However, more fracture-based data on appropriate treatment goals for monitoring need to be developed. Evidence is lacking for the use of βCTX in managing "drug holidays" of bisphosphonate treatment in osteoporosis or risk stratifying those at increased risk of developing osteonecrosis of the jaw. βCTX is useful as an adjunct to imaging techniques for the diagnosis of Paget's disease of bone and for monitoring therapy and detecting recurrence. βCTX also shows promise in the management of metastatic bone disease.

Biochemical Markers of Bone Turnover and Fracture Prediction

Low bone mineral density is a strong risk factor for fractures in the older woman. Biochemical markers of bone turnover may predict fracture risk independently of bone mineral density. High levels of bone resorption markers are associated with increased risk of fracture in both retrospective and prospective studies, although the evidence for bone formation markers and fracture risk is equivocal. For example, the risk of fracture is increased up to two-fold in women with elevated levels of several markers of bone resorption. Prediction models have been developed to predict the 10–year risk of fracture using bone mineral density and biochemical markers of bone turnover and these could prove very useful in clinical practice.

The role of biochemical of bone turnover markers in osteoporosis and metabolic bone disease: a consensus paper of the Belgian Bone Club

The exact role of biochemical markers of bone turnover in the management of metabolic bone diseases remains a topic of controversy. In this consensus paper, the Belgian Bone Club aimed to provide a state of the art on the use of these biomarkers in different clinical or physiological situations like in postmenopausal women, osteoporosis in men, in elderly patients, in patients suffering from bone metastasis, in patients with chronic renal failure, in pregnant or lactating women, in intensive care patients, and in diabetics. We also gave our considerations on the analytical issues linked to the use of these biomarkers, on potential new emerging biomarkers, and on the use of bone turnover biomarkers in the follow-up of patients treated with new drugs for osteoporosis.

The Role of Collagen Organization on the Properties of Bone

Bone is a complex tissue constituted by a collagen matrix filled in with crystal of hydroxyapatite (HAP). Bone mechanical properties are influenced by the collagen matrix which is organized into hierarchical structures from the individual type I collagen heterotrimer flanked by linear telopeptides at each end to the collagen fibrils that are interconnected by enzymatic and non-enzymatic cross-links. Although most studies focused on the role of collagen cross-links in bone strength, other organizational features may also play a role. At the molecular level it has been shown that homotrimer of type I collagen found in bone tissue of some patients with osteogenesis imperfecta (OI) is characterized by decreased mechanical competence compared to the regular heterotrimer. The state of C-telopeptide isomerization-which can be estimated by the measurement in body fluids of the native and isomerized isoforms-has also been shown to be associated with bone strength, particularly the post-yield properties independent of bone size and bone mineral density. Other higher hierarchical features of collagen organization have shown to be associated with changes in bone mechanical behavior in ex vivo models and may also be relevant to explain bone fragility in diseases characterized by collagen abnormalities e.g., OI and Paget's disease. These include the orientation of collagen fibrils in a regular longitudinal direction, the D-spacing period between collagen fibrils and the collagen-HAP interfacial bonding. Preliminary data indicate that some of these organizational features can change during treatment with bisphosphonate, raloxifene, and PTH suggesting that they may contribute to their anti-fracture efficacy. It remains however to be determined which of these parameters play a specific and independent role in bone matrix properties, what is the magnitude of mechanical strength explained by collagen organization, whether they are relevant to explain osteoporosis-induced bone fragility, and how they could be monitored non-invasively to develop efficient bone quality biomarkers.

Prior fracture as a risk factor for future fracture in an Australian cohort

SUMMARY

This study investigated the influence of prior fracture on the risk of subsequent fracture. There was a higher risk of subsequent fracture in both young and older adult age groups when Australian males or females had already sustained a prior fracture. Fracture prevention is important throughout life for both sexes.

INTRODUCTION

The purpose of this study was to determine the impact of prior fracture on the risk of subsequent fracture across the adult age range in Australian males and females.

METHODS

All-cause fractures were grouped into age categories for males and females enrolled in the Geelong Osteoporosis Study (Australia) using retrospective self-report data and prospective radiology-confirmed data. For all age categories, the relative risk (RR and 95% confidence interval (CI)) of subsequent fracture in a later age category was compared between those with prior fracture and those without.

RESULTS

For both sexes, childhood fracture increased the risk of subsequent fracture in adolescence (males: RR 21.7; 95% CI 16.0, 27.4; females: RR 8.1; 3.5, 12.8). Males with adolescent fracture had increased risk of subsequent fracture in early adulthood (RR 11.5; 5.7, 17.3) and mid-adulthood (RR 13.0; 6.3, 19.7). Additionally, males with young adulthood or mid-adulthood fracture had increased risk of subsequent fracture in the following age group (RR 11.2; 4.4, 17.9, and RR 6.2; 0.8, 11.7, respectively). Mid-adult fractures increased the risk of subsequent fracture in older adulthood (RR 6.2; 0.8, 11.7). Females with childhood or adolescent fracture had an increased risk of fracture in young adulthood (RR 4.3; 0.7, 7.9, and RR 10.5; 4.4, 16.6), and prior fracture in older adult life increased the risk of subsequent fracture in old age (RR 14.9; 6.4. 23.3).

CONCLUSIONS

Fracture prevention strategies may be more effective if attention is directed towards individuals with prior fracture at any age as they have a higher likelihood of sustaining a subsequent fracture later in life.

Age- and sex-related patterns of first fracture and fracture prevalence

There are few data documenting the pattern of prevalent fracture across the entire adult age range, so we aimed to address this gap by investigating the prevalence of fractures in an Australian cohort. All-cause (ever) fractures were identified for males and females enrolled in the Geelong Osteoporosis Study (Australia) using a combination of radiology-confirmed and self-reported data. First fractures were used to generate age-related frequencies of individuals who had ever sustained a fracture. Of 1,538 males and 1,731 females, 927 males and 856 females had sustained at least one fracture since birth. The proportion of all prevalent fractures in the 0-10 year age group was similar for both sexes (~10%). In males, the proportion with prevalent fracture increased to 34.1% for age 11-20 year. Smaller increases were observed into mid-life, reaching a plateau at ~50% from mid to late life. The age-related prevalence of fracture for females showed a more gradual increase until mid-life. For adulthood prevalent fractures, approximately 20% of males had sustained a first adulthood fracture in the 20-30 year age group, with a gradual increase up to the oldest age group (49.1%), while females showed an exponential pattern of increase from the 20-30 year age group (6.8%) to the oldest age group (60.4%). In both sexes, those who had not sustained a fracture in childhood or early adulthood generally appeared to remain fracture-free until at least the sixth decade. When considering the prevalence of adulthood fractures across the age groups, males showed a gradual increase while females showed an exponential increase.

Serum periostin is associated with fracture risk in postmenopausal women: a 7-year prospective analysis of the OFELY study

PURPOSE

Periostin (POSTN) is a secreted γ-carboxyglutamic acid-containing protein expressed mainly in the periosteum in adult individuals. POSNT deficient mice develop periodontis and osteoporosis with decreased bone strength. The relationship between serum POSTN and bone metabolism and fracture risk in postmenopausal women is unknown.

SUBJECTS AND METHODS

Serum POSTN was measured in 607 postmenopausal women (mean age 66.6 ± 8.4 y) from the Os des Femmes de Lyon cohort at the ninth annual follow-up visit (baseline visit of the current analysis). Nonvertebral and clinical vertebral incident fragility fractures were reported annually during 7 years. Areal bone mineral density (BMD; measured by dual energy X-ray absorptiometry) of the hip and bone markers (intact N-terminal propeptide of type I collagen, osteocalcin, and serum type I collagen C-telopeptide) were also measured.

RESULTS

At baseline, serum POSTN did not correlate with age, bone markers, and BMD. After a median of 7 years of follow-up, 75 women sustained an incident clinical vertebral or nonvertebral fragility fracture. The proportion of women who had an incident fracture was significantly higher in women with levels of POSTN in the highest quartile than that of women in the three other quartiles (19.5% vs 10.1%, P = .018) after adjustment for age and prevalent fracture. The highest quartile of POSTN was associated with an increased risk of incident fracture with a relative risk (95% confidence interval) of 1.88 (1.1-3.2) after adjustment for age, prevalent fracture, and hip BMD T-score. Patients with both low hip BMD (T-score < -2.5) and high levels of POSTN (fourth quartile) had a relative risk of fracture of 7.1 (95% confidence interval 2.4-21.8) after adjustment for age.

CONCLUSION

High serum POSTN levels are independently associated with increased fracture risk in postmenopausal women. These data suggest that serum POSTN could be useful to improve fracture risk assessment.

A meta-analysis of reference markers of bone turnover for prediction of fracture

The aim of this report was to summarize the clinical performance of two reference bone turnover markers (BTMs) in the prediction of fracture risk. We used an updated systematic review to examine the performance characteristics of serum procollagen type I N propeptide (s-PINP) and serum C-terminal cross-linking telopeptide of type I collagen (s-CTX) in fracture risk prediction in untreated individuals in prospective cohort studies. We excluded cross-sectional studies. Ten potentially eligible publications were identified and six included in the meta-analysis. There was a significant association between s-PINP and the risk of fracture. The hazard ratio per SD increase in s-PINP (gradient of risk [GR]) was 1.23 (95 % CI 1.09-1.39) for men and women combined unadjusted for bone mineral density. There was also a significant association between s-CTX and risk of fracture, GR = 1.18 (95 % CI 1.05-1.34) unadjusted for bone mineral density. For the outcome of hip fracture, the association between s-CTX and risk of fracture was slightly higher, 1.23 (95 % CI 1.04-1.47). Thus, there is a modest but significant association between BTMs and risk of future fractures.

Biochemical markers of bone turnover - uses and limitations

Bone turnover markers of resorption and formation are released during the process of bone remodelling. These markers have been extensively studied in a number of therapeutic trials of osteoporosis during the past decade. This has led to better understanding of their physiology, clinical applications and possible ways to optimize analytical techniques. Bone markers can complement the results of bone mineral density in the management of osteoporosis, but their use in clinical practice is challenged by pre-analytical and analytical variability. This review will discuss different types of bone markers, their limitations, use in different metabolic bone diseases and current recommendations from the International Osteoporosis Foundation and the International Federation of Clinical Chemistry and Laboratory Medicine bone marker standards working group.

The contribution of collagen crosslinks to bone strength

Collagen crosslinking is a major post-translational modification of collagen which has important roles in determining the biomechanical competence of bone. Crosslinks can be divided into enzymatic lysil oxidase-mediated and non-enzymatic glycation-induced (advanced glycation end products, AGE) molecules. In addition, collagen in bone can also undergo spontaneous isomerization and racemization of the aspartic acid residues with the C-telopeptide (CTX), leading to the formation of two isomers namely α (newly formed collagen) and β (matured isomerized collagen) CTX. Several in vitro and ex vivo studies, relating the bone content of these crosslinks with bone strength, have shown that they contributed to the mechanical competence of trabecular and cortical bone-mainly on the post-yield properties-in part independent of the bone mineral content. In addition, AGEs such as pentosidine have been reported to alter the formation and propagation of microdamage by making the bone more brittle. The bone content of AGEs and isomerization can also be modified by antiresorptive and anabolic therapies. They may thus explain part of the antifracture efficacy of these treatments. The main challenge consists in the transposition of these in vitro/ex vivo studies to clinical applications for the development of a non-invasive biomarker, as none of currently identified collagen crosslinks (both enzymatic and nonenzymatic) is bone specific. Nevertheless, serum or urine levels of pentosidine and the ratio of α/β CTX have been reported to predict fracture risk in postmenopausal women, in men and in patients with type 2 diabetes.

Cathepsin K preferentially solubilizes matured bone matrix

Bone collagen undergoes a series of enzymatic and nonenzymatic posttranslational modifications with maturation. The aim of this study was to analyze the collagenolytic efficiency of cathepsin K in relation to the extent of bone collagen age. Bone collagen posttranslational maturation was induced in vitro by preincubating bovine fetal cortical bone specimens at 37 °C for different times. The collagen enzymatic cross-links pyridinoline (PYD) and deoxypyridinoline (DPD), the advanced glycation end product pentosidine (PEN), and the native (α) and β-isomerized C-telopeptide (CTX) isomers were measured in each bone specimen. After extraction, bone collagen was incubated with human recombinant cathepsin K at different concentrations and its collagenolytic activity was measured by the release of hydroxyproline. To assess the affinity of cathepsin K for isomerized and nonisomerized CTX isomers, incubation with cathepsin K was also performed in the presence of various concentrations of a specific inhibitor. We showed that preincubation of bone collagen at 37 °C induces a marked increase in the bone concentration of PYD, DPD, and PEN and of CTX isomerization as reflected by the ratio of α-/βCTX. This increase was associated with a parallel increase in the efficiency of cathepsin K to solubilize bone collagen. When cathepsin K was incubated in the presence of an inhibitor, the β-isomerized form of collagen from 3-month- and 8-year-old bovine bone was more susceptible to degradation than the native α form. These results suggest that the collagenolytic activity of cathepsin K may be increased toward more matured bone collagen.

Bone turnover markers: use in osteoporosis

Biochemical markers of bone turnover (bone turnover markers, BTMs) can be used to study changes in bone remodelling in osteoporosis. Investigators and clinicians should be aware of the appropriate sample collection and storage conditions for optimum measurements of these markers. Improvements in the variability of BTM measurements have resulted from the development of assays for automated analysers, and from international consensus regarding their use. Appropriate reference intervals should be used for the optimum interpretation of results. BTMs can provide information that is useful for the management of patients with osteoporosis, for both the initial clinical assessment and for guiding and monitoring of treatment. BTMs are clinically useful to determine possible causes of secondary osteoporosis by identifying patients with high bone turnover and rapid bone loss. In the follow-up of treatment response, BTM levels respond rapidly to both anabolic and antiresorptive treatments. BTM changes can also be used for understanding the mechanism of action of drugs in development and identifying the correct dose; they are also potentially useful as surrogate biomarkers for fracture.

Measurement of C-terminal telopeptide of type I collagen (CTX) in serum

Serum CTX assays measure a fragment of the C-terminal telopeptide of type 1 collagen released during resorption of mature bone. Assay reagents are available in manual and automated formats and give good analytical performance. However their standardisation is not transparent and significant differences in results between methods have been demonstrated. CTX is most stable in EDTA plasma, although serum samples processed promptly would be satisfactory. sCTX shows a profound circadian rhythm, especially in non-fasting subjects; specimens should be collected from fasting patients at a well-defined time of day to minimise biological variation. Reference intervals in pre-menopausal women have been well studied but in other adult groups there is less information. Healthy children show the expected age-related variation corresponding to growth rate. Serum CTX fulfils or partially fulfils all the criteria of a reference bone turnover marker. Further studies aimed at reducing inter-method differences in results and establishing the relationships of sCTX with fracture risk and with fracture risk improvement with treatment are required.

Current recommendations for laboratory testing and use of bone turnover markers in management of osteoporosis

Osteoporosis is a major health problem worldwide, and is projected to increase exponentially due to the aging of the population. The absolute fracture risk in individual subjects is calculated by the use of algorithms which include bone mineral density (BMD), age, gender, history of prior fracture and other risk factors. This review describes the laboratory investigations into osteoporosis which include serum calcium, phosphate, creatinine, alkaline phosphatase and 25-hydroxyvitamin D and, additionally in men, testosterone. Parathyroid hormone (PTH) is measured in patients with abnormal serum calcium to determine its cause. Other laboratory investigations such as thyroid function testing, screening for multiple myeloma, and screening for Cushing's syndrome, are performed if indicated. Measurement of bone turnover markers (BTMs) is currently not included in algorithms for fracture risk calculations due to the lack of data. However, BTMs may be useful for monitoring osteoporosis treatment. Further studies of the reference BTMs serum carboxy terminal telopeptide of collagen type I (s-CTX) and serum procollagen type I N-terminal propeptide (s-PINP) in fracture risk prediction and in monitoring various treatments for osteoporosis may help expedite their inclusion in routine clinical practice.

The role of bone turnover markers in monitoring treatment in postmenopausal osteoporosis

Bone metabolism is assessed using biochemical bone turnover markers (BTM). BTM reflect the metabolic effect of drugs on bone turnover, help to establish the lowest dose inducing the largest change in the BTM, predict treatment-related reduction in fracture risk, and are helpful in bridging studies. Changes in BTM during anti-osteoporotic therapy depend on the cellular mechanism of action of the drug, degree of change in bone turnover rate and route of administration. BTM help to establish the optimal dose of anti-osteoporotic drugs because treatment-related changes in BTM are more rapid compared with change in BMD. A greater decrease in BTM levels during the first year of tantiresorptive treatment is associated with greater antifracture efficacy over 3 years. According to preliminary data, measurement of BTM can improve persistence with anti-resorptive treatment. The use of BTM to monitor anti-osteoporotic therapy in "real life" is limited at this stage.

Use of Bone Turnover Markers in Clinical Osteoporosis Assessment in Women: Current Issues and Future Options

Monitoring bone turnover of the adult and aging skeleton is essential for optimal treatment of bone metabolic diseases, such as postmenopausal osteoporosis. Diagnosis of osteoporosis is based solely on dual-emission x-ray absorptiometry-based measurements of bone mineral density. However, within the last 20 years, biochemical markers of bone turnover have been implemented to a larger degree, and especially within the field of drug development. Numerous clinical studies have underscored that the markers have promise in terms of predicting patients at high risk of losing bone, future fracture events and importantly also the fracture efficacy of drugs in development. Furthermore, while classical methods often require years to monitor the changes, the bone turnover markers do so within a shorter time span. The aims of this article are to provide an update on the different biochemical markers of bone turnover, and to give an overview of their applications in epidemiological and clinical research especially in women. The main emphasis will be on their utility in clinical trials testing the efficacy of drugs for the treatment of osteoporosis, and their ability to supplement bone mass measurements. Finally, recent evidence suggests that biochemical markers may provide information on bone age that may indirectly relate to bone quality, and this is discussed together with future possibilities for measuring bone quality using bone turnover markers. In summary, a more targeted use of biomarkers could assist in the identification of high-risk patients, the process of drug discovery and monitoring of the efficacy of osteoporosis treatment in clinical settings.

International Osteoporosis Foundation and International Federation of Clinical Chemistry and Laboratory Medicine position on bone marker standards in osteoporosis

The International Osteoporosis Foundation (IOF) and the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) Working Group on Bone Marker Standards (WG-BMS) has evaluated the clinical potential of bone turnover markers (BTMs) in the prediction of fracture risk and for monitoring treatment. Research evidence suggests that BTMs may provide information on fracture risk independently from BMD, so that fracture risk prediction might be enhanced by their inclusion in assessment algorithms. The potential use of BTMs to predict the response to treatments for osteoporosis in the individual patient is also of great interest. Treatment-induced changes in specific markers account for a substantial proportion of fracture risk reduction. However, there is still a need for stronger evidence on which to base practice in both situations. IOF/IFCC recommends one bone formation marker (serum procollagen type I N propeptide, s-PINP) and one bone resorption marker (serum C-terminal cross-linking telopeptide of type I collagen, s-CTX) to be used as reference markers and measured by standardised assays in observational and intervention studies in order to enlarge the international experience of the application of markers to clinical medicine and to help resolve uncertainties over their clinical use.

Biochemical markers of bone turnover as predictors of osteoporosis and osteoporotic fractures in men and women: 10-year follow-up of the Taiji cohort

We aimed to assess the capacity of biochemical markers of bone turnover (BTMs) to predict bone loss, osteoporosis (OP), and osteoporotic fractures. We randomly selected 400 individuals (age 40-79 years in 1993; 50 of each gender and age stratum) from a list of registered residents. In the years 1993, 1996, 2000, and 2003, bone mineral density (BMD) of the spine and hip were measured by dual-energy X-ray absorptiometry. The BTMs assessed at baseline were serum intact osteocalcin (OC), total OC, bone-specific alkaline phosphatase, C-terminal propeptide of type I procollagen, N-terminal propeptide of type I procollagen (PINP), C-terminal cross-linking telopeptide of type I collagen generated by matrix metalloproteinase, C-terminal cross-linking telopeptide of type I collagen (beta-CTX), N-terminal cross-linking telopeptide of type I collagen (NTX), urinary pyridinoline, and deoxypyridinoline (DPD). For 307 completers, multivariate analysis after adjusting for confounders revealed that serum PINP levels in men [hazard ratio (HR) 2.80, P < 0.05] and serum PINP (HR 1.65, P < 0.05), beta-CTX (HR 1.80, P < 0.001), NTX (HR 1.96, P < 0.01), and urinary DPD levels (HR 1.40, P < 0.05) in women were significantly related to the occurrence of spinal OP. In addition to adjustment for the baseline status of BMD, i.e., osteopenia or normal range, PINP, beta-CTX, and NTX in women could significantly predict the future occurrence of spinal OP. BTMs were not significant predictors of bone loss, femoral OP, or osteoporotic fractures. In conclusion, various BTMs in women can predict the occurrence of spinal OP.

Markers of bone turnover for the prediction of fracture risk and monitoring of osteoporosis treatment: a need for international reference standards

The International Osteoporosis Foundation (IOF) and the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) recommend that a marker of bone formation (serum procollagen type I N propeptide, s-PINP) and a marker of bone resorption (serum C-terminal telopeptide of type I collagen, s-CTX) are used as reference analytes for bone turnover markers in clinical studies.

INTRODUCTION

Bone turnover markers (BTM) predict fracture risk, and treatment-induced changes in specific markers account for a substantial proportion of fracture risk reduction. The aims of this report were to determine their clinical potential in the prediction of fracture risk and for monitoring the treatment of osteoporosis and to set an appropriate research agenda.

METHODS

Evidence from prospective studies was gathered through literature review of the PUBMED database between the years 2000 and 2010 and the systematic review of the Agency for Healthcare Research and Quality up to 2001.

RESULTS

High levels of BTMs may predict fracture risk independently from bone mineral density in postmenopausal women. They have been used for this purpose in clinical practice for many years, but there is still a need for stronger evidence on which to base practice. BTMs provide pharmacodynamic information on the response to osteoporosis treatment, and as a result, they are widely used for monitoring treatment in the individual. However, their clinical value for monitoring is limited by inadequate appreciation of the sources of variability, by limited data for comparison of treatments using the same BTM and by inadequate quality control. IOF/IFCC recommend one bone formation marker (s-PINP) and one bone resorption marker (s-CTX) to be used as reference markers and measured by standardised assays in observational and intervention studies in order to compare the performance of alternatives and to enlarge the international experience of the application of markers to clinical medicine.

CONCLUSION

BTM hold promise in fracture risk prediction and for monitoring treatment. Uncertainties over their clinical use can be in part resolved by adopting international reference standards.

Bone markers in osteoporosis

Current biological markers of bone turnover have proven useful in improving fracture risk assessment and monitoring treatment efficacy in postmenopausal osteoporosis. Recent developments in the field of bone markers include 1) identification of new biochemical markers providing additional information on the complex pathways leading to bone fragility; 2) application of novel technologies such as proteomics for the discovery of novel markers; 3) automation and multiplexing for improving analytical performance and convenience; and 4) refinement of the clinical interpretation of markers. Currently, however, for the management of individual patients, their most established application is to monitor treatment efficacy and possibly to improve fracture risk assessment. The role of bone markers for improving adherence to therapy will need to be investigated in further studies. This brief review discusses these novel technological developments and the recent clinical data on the use of established and new markers in postmenopausal osteoporosis.

Is bone quality associated with collagen age?

The World Health Organization defines osteoporosis as a systemic disease characterized by decreased bone tissue mass and microarchitectural deterioration, resulting in increased fracture risk. Since this statement, a significant amount of data has been generated showing that these two factors do not cover all risks for fracture. Other independent clinical factors, such as age, as well as aspects related to qualitative changes in bone tissue, are believed to play an important role. The term "bone quality" encompasses a variety of parameters, including the extent of mineralization, the number and distribution of microfractures, the extent of osteocyte apoptosis, and changes in collagen properties. The major mechanism controlling these qualitative factors is bone remodeling, which is tightly regulated by the osteoclast/osteoblast activity. We focus on the relationship between bone remodeling and changes in collagen properties, especially the extent of one posttranslational modification. In vivo, measurements of the ratio between native and isomerized C-telopeptides of type I collagen provides an index of bone matrix age. Current preclinical and clinical studies suggests that this urinary ratio provides information about bone strength and fracture risk independent of bone mineral density and that it responds differently according to the type of therapy regulating bone turnover.

Bone turnover markers: understanding their value in clinical trials and clinical practice

While bone mineral density (BMD) by dual-energy X-ray absorptiometry is the primary method of determining fracture risk, assessing bone turnover may add valuable information for the management of patients with low bone mass. Bone turnover markers (BTMs) are used in clinical trials where they can provide essential information on the biological efficacy of osteoporosis treatments. In such population-based studies, BTMs can predict fracture risk independent of BMD. When combined with BMD, they improve the fracture risk estimate above and beyond BMD alone in postmenopausal osteoporotic women. Since changes in bone turnover after the initiation of therapy with bone resorption inhibitors occur much more rapidly than changes in BMD, treatment efficacy could, in theory, be determined within weeks of using BTMs. However, such predictive value is limited by the large biological variability of these biochemical markers, even though newer automated methods have reduced their analytical variability. Consequently, widespread adoption as a means of predicting treatment efficacy in fracture prevention for individual patients cannot yet be recommended. BTMs may be useful for monitoring adherence to antiresorptive therapy and may aid in identifying patients for whom antiresorptive therapy is most appropriate. Thus, although BTMs are currently confined to clinical research applications, further improvement in assay precision may extend their diagnostic value in clinical settings.

2008 Santa Fe Bone Symposium: update on osteoporosis

The Ninth Annual Santa Fe Bone Symposium was held on August 1-2, 2008, in Santa Fe, New Mexico, USA. The symposium faculty presented the current best evidence on selected topics of clinical relevance in the fields of osteoporosis, metabolic bone disease, and assessment of skeletal health. The educational venues were in the form of didactic presentations, panel discussions, challenging cases, and numerous interactive discussions. Knowledge of basic science and clinical trials was applied to real-world patient scenarios that were discussed by faculty experts and clinician participants. Topics included an update on the rationale and development of new agents for the treatment of osteoporosis, the use of bone turnover markers in clinical practice, hospital-based pathways for the management of hip fracture patients, injectable bisphosphonates for the treatment of osteoporosis, combination therapy with anabolic and antiresorptive agents, and assessment of skeletal health with devices other than central dual-energy X-ray absorptiometry. This is a collection of scientific essays based on presentations and discussions at the 2008 Santa Fe Bone Symposium.

Bone turnover and type I collagen C-telopeptide isomerization in adult osteogenesis imperfecta: associations with collagen gene mutations

INTRODUCTION

Increased bone fragility in osteogenesis imperfecta (OI) is not totally accounted for by decreased bone mineral density (BMD), and alterations of type I collagen (Col I) are believed to play a role. Newly synthesized Col I comprises non isomerized C-telopeptide (alphaCTX), but with bone matrix maturation alphaCTX is converted to its isomerized beta form (betaCTX). Urinary alpha/betaCTX ratio has been proposed to reflect collagen maturation. We investigated changes in bone turnover and Col I isomerization in adult patients with OI and their relationship with Col I gene mutations.

PATIENTS AND METHODS

Sixty four adult patients [25 women, 39 men mean age (SD): 36.2 (11.6) years] with OI participating in a randomized study and 64 healthy controls of similar age and gender distribution were investigated. In patients with OI and controls, we measured the following biochemical markers of bone metabolism: serum type I collagen N-propeptide (PINP) an index of Col I synthesis, osteocalcin a marker of osteoblastic activity, urinary Col I helical peptide, a marker reflecting the degradation of the helical portion of Col I, urinary alphaCTX and urinary and serum betaCTX. Based on the putative functional effects of Col I gene mutations which were identified in 56 OI subjects, patients were divided in those with haploinsufficiency (n=29), patients presenting with helical domain alterations (n=17) and others (n=10).

RESULTS

Compared to healthy controls, patients with OI had decreased levels of PINP (-22.7%, p<0.0001), increased osteocalcin (+73%, p<0.0001) and increased Col I helical peptide (+58%, p=0.0007). Urinary alphaCTX was increased (+31%, p=0.03) whereas urinary (-15%, p=0.022) and serum (-9.9%, p=0.0056) betaCTX were significantly decreased, resulting in a 49% (p<0.001) higher urinary alpha/betaCTX ratio. Patients with Col I gene mutations resulting in haploinsufficiency had lower PINP levels than patients with helical domain alterations (26.4+/-15.3 vs 41.6+/-27.4 ng/ml, p=0.0043) and controls (p<0.01).

CONCLUSION

Adults with OI are characterized by decreased Col I synthesis - especially those with haploinsufficiency mutations - increased Col I degradation and decreased Col I C-telopeptide isomerization.

Effects of ovariectomy on bone turnover, porosity, and biomechanical properties in ovine compact bone 12 months postsurgery

Compact bone makes up approximately 80% of the human skeleton by mass; but there are little data available on the effects of increased bone turnover on compact bone mechanical and material properties. This study addresses this question by measuring intracortical remodeling, resorption cavity number, and porosity in an ovariectomized (OVX) sheep model, and measures changes in biomechanical properties. Thirty-eight sheep were divided into two groups. Group 1 were controls (n = 19), and Group 2 were ovariectomized (OVX; n = 19). Fluorochrome dyes were administered intravenously to both groups at five time points over 12 months post-OVX to label sites of bone turnover. At 12 months post-OVX all animals were euthanized. Samples were harvested from the left metatarsal and were analyzed for intracortical bone turnover at five time points, the number of resorption cavities, and the level of intracortical porosity. The effects of these parameters on bone biomechanical properties were then measured. Bone turnover was increased in the OVX group at 6, 9, and 12 months (p < 0.05). Resorption was also higher in the OVX group at 12 months (p < 0.05). Furthermore, porosity was significantly increased in the OVX group at 12 months (p < 0.05). Stiffness and yield strength were reduced in the OVX group compared to controls (p = 0.05). Ultimate compressive strength and work to fracture did not differ between groups. These findings provide new insights into the mechanisms and effects of increased bone turnover on bone material and microstructural properties.

Biochemical markers of bone turnover: potential use in the investigation and management of postmenopausal osteoporosis

INTRODUCTION

The aim was to analyse data on the use of biochemical bone turnover markers (BTM) in postmenopausal osteoporosis.

METHODS

We carried out a comparative analysis of the most important papers concerning BTM in postmenopausal osteoporosis that have been published recently.

RESULTS

The BTM levels are influenced by several factors. They are moderately correlated with BMD and subsequent bone loss. Increased levels of bone resorption markers are associated with a higher risk of fracture. Changes in the BTM during the anti-osteoporotic treatment (including combination therapy) reflect the mechanisms of action of the drugs and help to establish their effective doses. Changes in the BTM during the anti-resorptive treatment are correlated with their anti-fracture efficacy.

CONCLUSION

Biological samples should be obtained in a standardised way. BTM cannot be used for prediction of the accelerated bone loss at the level of the individual. BTM help to detect postmenopausal women who are at high risk of fracture; however, adequate practical guidelines are lacking. BTM measurements taken during the anti-resorptive therapy help to identify non-compliers. They may improve adherence to the anti-resorptive therapy and the fall in the BTM levels that exceeds the predefined threshold improves patients' persistence with the treatment. There are no guidelines concerning the use of BTM in monitoring anti-osteoporotic therapy in postmenopausal women.