Preanalytical variability of biochemical markers of bone turnover

A non-invasive measure of bone growth in mammals: Validating urinary CTX-I as a bone resorption marker through long-bone growth velocity in bonobos

Assessing bone growth trajectories in mammals is crucial for understanding life history dynamics, but the quantification of bone growth in natural settings can be challenging. Bone resorption markers that can be measured in urine, such as C-telopeptide of type I collagen (CTX-I), offer a non-invasive solution to assess bone growth. Although measurement of urinary CTX-I levels has been applied extensively in human studies, its use in other species is so far limited to a few clinical studies. To validate urinary CTX-I as a bone resorption marker under less controlled conditions, we investigated within-individual day-to-day variation, diurnal patterns, and sex and age-specific variation in zoo-housed bonobos (Pan paniscus). We then also correlated urinary CTX-I levels with forearm growth velocity measures. We found a day-to-day variability in urinary CTX-I levels of around 25%, comparable to human variation. Diurnally, CTX-I levels decreased, aligning with observations in humans and other species. Both sexes showed an age-related decline in urinary CTX-I levels, with a steady decrease after the age of 10 years. Additionally, we found a positive correlation between forearm growth velocity and urinary CTX-I levels across age in female, but not in male, bonobos. Our results demonstrate that urinary CTX-I levels are a meaningful measure of bone growth and highlight its potential to examine bone growth trajectories also in wild populations to investigate life history dynamics.

Comparative analysis of bone turnover markers in bone marrow and peripheral blood: implications for osteoporosis

INTRODUCTION

This study examines bone turnover marker (BTM) variations between bone marrow and peripheral blood in osteoporotic and non-osteoporotic patients. BTMs offer insights into bone remodeling, crucial for understanding osteoporosis.

METHODS

A total of 133 patients were categorized into osteoporotic and non-osteoporotic cohorts. BTMs-C-telopeptide cross-linked type 1 collagen (β-CTX), serum osteocalcin (OC), Procollagen type I N-propeptide (P1NP), 25(OH)D-were measured in bone marrow and peripheral blood. Lumbar spine bone mineral density (BMD) was assessed.

RESULTS

Osteoporotic patients exhibited elevated β-CTX and OC levels in peripheral blood, indicating heightened bone resorption and turnover. β-CTX levels in osteoporotic bone marrow were significantly higher. Negative correlations were found between peripheral blood β-CTX and OC levels and lumbar spine BMD, suggesting their potential as osteoporosis severity indicators. No such correlations were observed with bone marrow markers. When analyzing postmenopausal women separately, we obtained consistent results.

CONCLUSIONS

Elevated β-CTX and OC levels in osteoporotic peripheral blood highlight their diagnostic significance. Negative β-CTX and OC-BMD correlations underscore their potential for assessing osteoporosis severity. Discrepancies between peripheral blood and bone marrow markers emphasize the need for further exploration. This research advances our understanding of BTM clinical applications in osteoporosis diagnosis and treatment.

Recent advances in the identification of related factors and preventive strategies of hip fracture

Hip fracture is the most devastating type of osteoporosis-related fracture, and is a major worldwide public health problem with a high socioeconomic burden, morbidity rate, and mortality rate. Thus, it is crucial to uncover the risk factors and protective factors to create a hip fracture prevention strategy. In addition to a briefly review of some well accepted risk and protective factors of hip fracture, this review mainly summarized the recent advances in the identification of emerging risk or protective factors for hip fracture, in terms of regional differences in medical services, diseases, drugs, mechanical load, neuromuscular mass, genes, blood types, cultural differences. This review provides a comprehensive review of the associated factors and effective prevention measures for hip fracture, and discusses issues that need further investigation. These issues include the determination of the influencing mechanism of risk factors triggering hip fracture and their interlinked correlation with other factors, as well as the confirmation or correction of emerging factors associated with hip fracture, particularly those that are still controversial. These recent findings will aid in optimizing the strategy for preventing hip fracture.

Advancement in the Treatment of Osteoporosis and the Effects on Bone Healing

Osteoporosis (OP) is a major global health concern, with aging being one of the most important risk factors. Osteoarthritis (OA) is also an age-related disorder. Patients with OP and/or OA may be treated surgically for fractures or when their quality of life is impaired. Poor bone quality due to OP can seriously complicate the stability of a bone fixation construct and/or surgical fracture treatment. This review summarizes the current knowledge on the pathophysiology of normal and osteoporotic bone healing, the effect of a bone fracture on bone turnover markers, the diagnosis of a low bone mineral density (BMD) before surgical intervention, and the effect of available anti-osteoporosis treatment. Interventions that improve bone health may enhance the probability of favorable surgical outcomes. Fracture healing and the treatment of atypical femoral fractures are also discussed.

Bone Turnover Markers: Basic Biology to Clinical Applications

Bone turnover markers (BTMs) are used widely, in both research and clinical practice. In the last 20 years, much experience has been gained in measurement and interpretation of these markers, which include commonly used bone formation markers bone alkaline phosphatase, osteocalcin, and procollagen I N-propeptide; and commonly used resorption markers serum C-telopeptides of type I collagen, urinary N-telopeptides of type I collagen and tartrate resistant acid phosphatase type 5b. BTMs are usually measured by enzyme-linked immunosorbent assay or automated immunoassay. Sources contributing to BTM variability include uncontrollable components (e.g., age, gender, ethnicity) and controllable components, particularly relating to collection conditions (e.g., fasting/feeding state, and timing relative to circadian rhythms, menstrual cycling, and exercise). Pregnancy, season, drugs, and recent fracture(s) can also affect BTMs. BTMs correlate with other methods of assessing bone turnover, such as bone biopsies and radiotracer kinetics; and can usefully contribute to diagnosis and management of several diseases such as osteoporosis, osteomalacia, Paget's disease, fibrous dysplasia, hypophosphatasia, primary hyperparathyroidism, and chronic kidney disease-mineral bone disorder.

Long-Term Selenium-Yeast Supplementation Does Not Affect Bone Turnover Markers: A Randomized Placebo-Controlled Trial

Higher selenium status has been associated with lower bone turnover markers (BTM) in epidemiological studies. However, the long-term impact of selenium supplementation on BTMs has not been studied. We investigated the effects of selenium supplementation on BTMs including osteocalcin (OC), procollagen type I N-terminal propeptide (PINP), collagen type I cross-linked C-telopeptide (CTX), and bone alkaline phosphatase (BALP) in the short (6 months) and long term (5 years). A total of 481 Danish men and women (60-74 years) were randomized to receive placebo-yeast versus 100, 200, or 300 μg selenium as selenium-enriched yeast daily for 5 years. Plasma selenium concentration was measured using inductively coupled plasma mass spectrometry, and BTMs were measured in nonfasted samples at baseline, 6 months, and 5 years. Data were analyzed by ANCOVA to investigate the shape of the dose-response relationships. Covariates included age, body mass index, baseline selenium status, baseline BTM, smoking, alcohol, supplement use, and medication. Plasma selenium concentration (mean 86.5 μg/d at baseline) increased significantly with increasing selenium supplementation to 152.6, 209.1, and 253.7 μg/L after 6 months and remained elevated at 5 years (158.4, 222.4, and 275.9 μg/L for 100, 200, and 300 μg supplemental selenium/d, respectively (p < 0.001)). There was no change in plasma selenium concentration in the placebo-treated group. There was no significant effect of selenium supplementation on OC (6 months p = 0.37; 5 years p = 0.63), PINP (6 months p = 0.37; 5 years p = 0.79), CTX (6 months p = 0.91; 5 years p = 0.58) or BALP (6 months p = 0.17; 5 years p = 0.53). The relatively replete baseline selenium status in the study participants may explain this lack of effect. Testing in more deficient populations may provide further insights into the impact of selenium supplementation on bone health. © 2022 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Short-Term Carbohydrate Restriction Impairs Bone Formation at Rest and During Prolonged Exercise to a Greater Degree than Low Energy Availability

Bone stress injuries are common in athletes, resulting in time lost from training and competition. Diets that are low in energy availability have been associated with increased circulating bone resorption and reduced bone formation markers, particularly in response to prolonged exercise. However, studies have not separated the effects of low energy availability per se from the associated reduction in carbohydrate availability. The current study aimed to compare the effects of these two restricted states directly. In a parallel group design, 28 elite racewalkers completed two 6-day phases. In the Baseline phase, all athletes adhered to a high carbohydrate/high energy availability diet (CON). During the Adaptation phase, athletes were allocated to one of three dietary groups: CON, low carbohydrate/high fat with high energy availability (LCHF), or low energy availability (LEA). At the end of each phase, a 25-km racewalk was completed, with venous blood taken fasted, pre-exercise, and 0, 1, 3 hours postexercise to measure carboxyterminal telopeptide (CTX), procollagen-1 N-terminal peptide (P1NP), and osteocalcin (carboxylated, gla-OC; undercarboxylated, glu-OC). Following Adaptation, LCHF showed decreased fasted P1NP (~26%; p < 0.0001, d = 3.6), gla-OC (~22%; p = 0.01, d = 1.8), and glu-OC (~41%; p = 0.004, d = 2.1), which were all significantly different from CON (p < 0.01), whereas LEA demonstrated significant, but smaller, reductions in fasted P1NP (~14%; p = 0.02, d = 1.7) and glu-OC (~24%; p = 0.049, d = 1.4). Both LCHF (p = 0.008, d = 1.9) and LEA (p = 0.01, d = 1.7) had significantly higher CTX pre-exercise to 3 hours post-exercise but only LCHF showed lower P1NP concentrations (p < 0.0001, d = 3.2). All markers remained unchanged from Baseline in CON. Short-term carbohydrate restriction appears to result in reduced bone formation markers at rest and during exercise with further exercise-related increases in a marker of bone resorption. Bone formation markers during exercise seem to be maintained with LEA although resorption increased. In contrast, nutritional support with adequate energy and carbohydrate appears to reduce unfavorable bone turnover responses to exercise in elite endurance athletes. © 2022 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Change in Bone Mineral Density in Stroke Patients with Osteoporosis or Osteopenia

We aimed to investigate the correlation between changes in bone mineral density (BMD) of the lumbar spine (LS) and femoral neck (FN) and osteoporosis-related factors in stroke patients with osteoporosis or osteopenia, and we suggest the need for active rehabilitation treatment. This study included 63 osteoporosis and 34 osteopenia patients who underwent a BMD test following primary stroke onset. The osteoporosis group was followed up with a BMD test after 12 months of bisphosphonate treatment, and the osteopenia group was followed up without medication. The correlation between BMD changes and functional factors was analyzed, biochemical markers were measured, and hematology tests were performed. In the osteoporosis group, a significant increase was observed in LS BMD (p < 0.05), and in the osteopenia group, there was a significant decrease in FN BMD (p < 0.05). The group with a functional ambulatory category of 1 or more showed a significant improvement in BMD (p < 0.05). Comparative analysis was performed on various indicators, but no significant correlation was found between any variable. In stroke patients with osteoporosis or osteopenia, early appropriate drug treatment is important to prevent bone loss and reduce the risk of fractures, and comprehensive rehabilitation treatment, such as appropriate education and training to prevent falls, is essential.

The impact of acute fracture on interpretation of bone turnover marker measurements for patients starting anti-resorptive therapies

INTRODUCTION

Bone turnover markers (BTM) are used in evaluating patients' response to anti-resorptive agents (ARA). Fracture and its healing process, however, can influence the measurements, which might make their interpretation difficult in patients with a recent fracture. We aimed to evaluate the effect of oral ARA on changes in BTM levels in patients with a recent distal radius fracture (DRF).

METHODS

In 143 women who had a new DRF and then received oral ARA including selective estrogen receptor modulator (SERM, n = 101), and bisphosphonate (n = 42), we measured serum cross-linked C-telopeptides of type I collagen (CTXI) and osteocalcin, at baseline and six months, as well as lumbar and total hip bone mineral density (BMD) at baseline and one year after fracture. We determined the predictive value of BTM at six months in determining one-year responses in BMD.

RESULTS

Both BTM levels decreased significantly at six months, with the average decrease of 27 ± 63% for CTX-I and 11% ± 37% for osteocalcin. The percent changes of BTM at six months were independent predictors of the BMD change. Cutoff points of 50.0% CTX-I decrease and 23.5% for osteocalcin decrease had the highest sensitivities and specificities for detecting BMD responders for bisphosphonate users, but cutoffs could not be found for SERM users.

CONCLUSION

Although a fresh fracture can influence BTM, ARA therapy significantly reduced their levels and their percent change at six months could predict BMD improvement at one year. However, adjusted cutoff points can be necessary to increase sensitivity for detecting patients responsive to ARA treatment after a new DRF.

Bone turnover markers in gingival crevicular fluid and blood serum of patients with fixed orthodontic appliances

AIM

Bone remodelling can be followed through the bone turnover markers (BTMs). Aim of the present study was to record the fluctuation of an osteoclastic and an osteoblastic BTM [C-terminal telopeptide of type I collagen (CTX) and N-terminal pro-peptide of type I pro-collagen (PINP), respectively] in both the gingival crevicular fluid (GCF) and the serum of orthodontic patients before and after the initial application of orthodontic forces.

MATERIALS AND METHODS

Twenty-one Caucasian patients were prospectively evaluated. GCF and blood samples were collected in order to measure the selected biomarkers by ELISA at three time-points: exactly before, 5 days, and 14 days after bonding of the appliances. Standardized sample handling and patient preparation procedures were adopted in order to reduce pre-analytical variability.

RESULTS

GCF and serum CTX levels were found to be independent of age, although higher in the serum of female subjects. PINP levels were found higher in the serum of patients ≥25 years old, as well as in the GCF of males. A positive correlation between serum and GCF baseline PINP levels was observed.

LIMITATIONS

The effect of orthodontic treatment on bone remodelling might not be absolutely representative of the local bone microenvironment as the levels of the specific BTMs where measured within the GCF of the lower front teeth.

CONCLUSIONS

This is the first time PINP and CTX have been evaluated in the GCF and serum of orthodontic patients with fixed appliances. No statistically significant alterations of CTX and PINP levels in the GCF and the serum of patients were recorded over time during the initial stages of orthodontic treatment.

Identification of Potential Osteoporosis miRNA Biomarkers Using Bioinformatics Approaches

Osteoporosis is a degenerative osteoarthropathy commonly found in old people and postmenopausal women. Many studies showed that microRNAs (miRNAs) can regulate the expression of osteoporosis-related genes and are abnormally expressed in patients with osteoporosis. miRNAs therefore have the potential to serve as biomarkers of osteoporosis. In this study, the limma package was used for the differential expression analysis of mRNA expression profiles and 357 significantly differentially expressed genes (DEGs) were obtained. Metascape was used for functional enrichment analysis of DEGs. The result revealed that DEGs were mainly enriched in signaling pathways like MAPK6/MAPK4. Based on the STRING database, the protein-protein interaction (PPI) network of DEGs was constructed. MCODE was used to analyze the functional subsets, and a key functional subset composed of 9 genes was screened out. In addition, the miRNA-mRNA regulatory interaction network (RegIN) was analyzed by the CyTargetLinker plugin, which generated 55 miRNA-mRNA regulatory interactions. Through literature searching, the osteoporosis-related gene FOXO1 in the key functional subset was determined to be the main object of the study. In qRT-PCR assay, the expression of the predicted miRNAs was tested in peripheral blood mononuclear cells of mice with osteoporosis, in which 13 miRNAs were remarkably highly expressed. All in all, this study, based on bioinformatics analysis and testing assay of miRNA expression, determined the potential biomarkers of osteoporosis.

Durability and delayed treatment effects of zoledronic acid on bone loss after spinal cord injury: a randomized, controlled trial

A single infusion of zoledronic acid (ZOL) after acute spinal cord injury (SCI) attenuates bone loss at the hip (proximal femur) and knee (distal femur and proximal tibia) for at least 6 months. The objective of this study was to examine the effects of timing and frequency of ZOL over 2 years. In this double-blind, placebo-controlled trial, we randomized 60 individuals with acute SCI (<120 days of injury) to receive either ZOL 5-mg infusion (n = 30) or placebo (n = 30). After 12 months, groups were again randomized to receive ZOL or placebo, resulting in four treatment groups for year 2: (i) ZOL both years; (ii) ZOL year 1, placebo year 2; (iii) placebo year 1, ZOL year 2; and (iv) placebo both years. Our primary outcome was bone loss at 12 months; compared to placebo, a single infusion of ZOL attenuated bone loss at the proximal femur, where median changes relative to baseline were -1.7% to -2.2% for ZOL versus -11.3% to -12.8% for placebo (p < 0.001). Similarly, the distal femur and proximal tibia showed changes of -4.7% to -9.6% for ZOL versus -8.9% to -23.0% for placebo (p ≤ 0.042). After 24 months, differences were significant at the proximal femur only (-3.2% to -6.0% for ZOL vs. -16.8% to -21.8% for placebo; p ≤ 0.018). Although not statistically significant, median bone density losses suggested some benefit from two annual infusions compared to a single baseline infusion, as well as from a single infusion 12 months after baseline compared to 2 years of placebo; therefore, further investigation in the 12-month to 24-month treatment window is warranted. No unanticipated adverse events associated with drug treatment were observed. In summary, ZOL 5-mg infusion after acute SCI was well-tolerated and may provide an effective therapeutic approach to prevent bone loss in the first few years following SCI. © 2021 American Society for Bone and Mineral Research (ASBMR).

Fragility Fractures: Risk Factors and Management in the Elderly

Given the progressive ageing of Western populations, the fragility fractures market has a growing socioeconomic impact. Fragility fractures are common in the elderly, negatively impacting their quality of life, limiting autonomy, increasing disability, and decreasing life expectancy. Different causes contribute to the development of a fractures in frail individuals. Among all, targeting fragile patients before the development of a fracture may represent the greatest challenge, and current diagnostic tools suffer from limitations. This study summarizes the current evidence on the management of fragility fractures, discussing risk factors, prevention, diagnosis, and actual limitations of the clinical therapeutic options, putting forward new ideas for further scientific investigation.

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.

Uncovering the Bone-Muscle Interaction and Its Implications for the Health and Function of Older Adults (the Wellderly Project): Protocol for a Randomized Controlled Crossover Trial

BACKGROUND

Bone and muscle are closely linked anatomically, biochemically, and metabolically. Acute exercise affects both bone and muscle, implying a crosstalk between the two systems. However, how these two systems communicate is still largely unknown. We will explore the role of undercarboxylated osteocalcin (ucOC) in this crosstalk. ucOC is involved in glucose metabolism and has a potential role in muscle maintenance and metabolism.

OBJECTIVE

The proposed trial will determine if circulating ucOC levels in older adults at baseline and following acute exercise are associated with parameters of muscle function and if the ucOC response to exercise varies between older adults with low muscle quality and those with normal or high muscle quality.

METHODS

A total of 54 men and women aged 60 years or older with no history of diabetes and warfarin and vitamin K use will be recruited. Screening tests will be performed, including those for functional, anthropometric, and clinical presentation. On the basis of muscle quality, a combined equation of lean mass (leg appendicular skeletal muscle mass in kg) and strength (leg press; one-repetition maximum), participants will be stratified into a high or low muscle function group and randomized into the controlled crossover acute intervention. Three visits will be performed approximately 7 days apart, and acute aerobic exercise, acute resistance exercise, and a control session (rest) will be completed in any order. Our primary outcome for this study is the effect of acute exercise on ucOC in older adults with low muscle function and those with high muscle function.

RESULTS

The trial is active and ongoing. Recruitment began in February 2018, and 38 participants have completed the study as of May 26, 2019.

CONCLUSIONS

This study will provide novel insights into bone and muscle crosstalk in older adults, potentially identifying new clinical biomarkers and mechanistic targets for drug treatments for sarcopenia and other related musculoskeletal conditions.

TRIAL REGISTRATION

Australia New Zealand Clinical Trials Registry ACTRN12618001756213; https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=375925.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

DERR1-10.2196/18777.

Serum and Urinary Osteocalcin in Healthy 7- to 19-Year-Old Finnish Children and Adolescents

Children and adolescents have high bone turnover marker (BTM) levels due to high growth velocity and rapid bone turnover. Pediatric normative values for BTMs reflecting bone formation and resorption are vital for timely assessment of healthy bone turnover, investigating skeletal diseases, or monitoring treatment outcomes. Optimally, clinically feasible measurement protocols for BTMs would be validated and measurable in both urine and serum. We aimed to (a) establish sex- and age-specific reference intervals for urinary and serum total and carboxylated osteocalcin (OC) in 7- to 19-year-old healthy Finnish children and adolescents (n = 172), (b) validate these against standardized serum and urinary BTMs, and (c) assess the impact of anthropometry, pubertal status, and body composition on the OC values. All OC values in addition to other BTMs increased with puberty and correlated with pubertal growth, which occurred and declined earlier in girls than in boys. The mean serum total and carboxylated OC and urinary OC values and percentiles for sex-specific age categories and pubertal stages were established. Correlation between serum and urinary OC was weak, especially in younger boys, but improved with increasing age. The independent determinants for OC varied, the urinary OC being the most robust while age, height, weight, and plasma parathyroid hormone (PTH) influenced serum total and carboxylated OC values. Body composition parameters had no influence on any of the OC values. In children and adolescents, circulating and urinary OC reflect more accurately growth status than bone mineral density (BMD) or body composition. Thus, validity of OC, similar to other BTMs, as a single marker of bone turnover, remains limited. Yet, serum and urinary OC similarly to other BTMs provide a valuable supplementary tool when assessing longitudinal changes in bone health with repeat measurements, in combination with other clinically relevant parameters.

Bone turnover and metabolite responses to exercise in people with and without long-duration type 1 diabetes: a case-control study

INTRODUCTION

Exercise acutely alters markers of bone resorption and formation. As risk of fracture is increased in patients with type 1 diabetes, understanding if exercise-induced bone turnover is affected within this population is prudent. We assessed bone turnover responses to acute exercise in individuals with long-duration type 1 diabetes and matched controls.

RESEARCH DESIGN AND METHODS

Participants with type 1 diabetes (n=15; age: 38.7±13.3; glycosylated hemoglobin: 60.5±6.7 mmol/mol; diabetes duration: 19.3±11.4 years) and age-matched, fitness-matched, and body mass index-matched controls (n=15) completed 45 min of incline walking (60% peak oxygen uptake). Blood samples were collected at baseline and immediately, 30 min, and 60 min postexercise. Markers of bone resorption (β-C-terminal cross-linked telopeptide of type 1 collagen, β-CTx) and formation (procollagen type-1 amino-terminal propeptide, P1NP), parathyroid hormone (PTH), phosphate, and calcium (albumin-adjusted and ionized) were measured. Data (mean±SD) were analyzed by a mixed-model analysis of variance.

RESULTS

Baseline concentrations of P1NP and β-CTx were comparable between participants with type 1 diabetes and controls. P1NP did not change with exercise (p=0.20) but β-CTx decreased (p<0.001) in both groups, but less so in participants with type 1 diabetes compared with controls (-9.2±3.7%; p=0.02). PTH and phosphate increased immediately postexercise in both groups; only PTH was raised at 30 min postexercise (p<0.001), with no between-group differences (p>0.39). Participants with type 1 diabetes had reduced albumin and ionized calcium at all sample points (p<0.01).

CONCLUSIONS

Following exercise, participants with type 1 diabetes displayed similar time-course changes in markers of bone formation and associated metabolites, but an attenuated suppression in bone resorption. The reduced albumin and ionized calcium may have implications for future bone health. Further investigation of the interactions between type 1 diabetes, differing modalities and intensities of exercise, and bone health is warranted.

Associations between the serum levels of selected bone turnover markers and biological traits in nursing home women aged 80+ without inflammation. A pilot study

BACKGROUND

Bone turnover markers (BTM) reflect the status of bone remodeling processes responsible for bone mineral density. The existing body of evidence that osseous tissue can interact with many other body tissues and organs suggests that the cross-talks can lead to different relationships. The biological traits associated with BTMs have not been thoroughly studied in the elderly despite bone turnover being known to increase with age.

OBJECTIVE

To determine whether the C-terminal crosslinking telopeptides of type I collagen (CTXI) and the serum levels of total (TAP) and bone-specific (BAP) alkaline phosphatase are associated with the biological traits in nursing home women aged 80-92 years without inflammation and, if so, to indicate the best predictors of these BTM's blood concentrations.

METHODS

A group of 64 female volunteers aged 80 years and older, the residents of nursing homes, were screened for the study. Fifty two women were ineligible as they met the exclusion criteria. As a result, the study group consisted of 12 participants (85.1 ± 3.9 years; 58.1 ± 8.7 kg; 1.52 ± 0.06 m), all having blood C-reactive protein (CRP) levels below 3 mg/l. Also assessed were the participants' morphology, glucose and insulin levels, lipid profiles, CTXI, TAP, and BAP. Other measured parameters included body composition, resting heart rate and arterial blood pressure, isometric knee extension peak torque (IKEPT), and walking capacity (6-min walk test). The statistical analysis was performed using Pearson's correlation coefficients, the Benjamini-Hochberg procedure, and a stepwise multiple regression analysis with backward elimination.

RESULTS

Inverse correlations were found between CTX-I and hemoglobin concentration (HGB) (r = -0.680; p = .015), red blood cells count (RBC) (r = -0.664; p = .019), fat-free mass (r = -0.633; p = .027), body weight (r = -0.589; p = .044), and total cholesterol (r = -0.581; p = .048). The multiple regression analysis of CTX-I showed that body weight was the only independent variable that was statistically significant (r2 = 0.346; p < .05; SEE = 0.347 ng/ml). BAP was positively correlated with double product (DP) (r = 0.742; p = .006), RBC (r = 0.650; p = .022), HGB (r = 0.637; p = .026), mean arterial pressure (MAP) (r = 0.622; p = .031), diastolic blood pressure (DBP) (r = 0.612; p = .034), body height (r = 0.603; p = .038), IKEPT (r = 0.565; p = .056), and systolic blood pressure (SBP) (r = 0.538; p = .071). BAP, a dependent variable, was the most closely correlated with DP (r² = 0.550; p < .01; SEE = 9.161 U/l). TAP was also significantly associated with DP (r = 0.775; p = .003), with the association being stronger than between BAP and DP (r² = 0.600; p < .01; SEE = 1000.5 beats/min*mm Hg).

CONCLUSIONS

In relatively healthy the oldest-old nursing home women without inflammation, total body weight was the best predictor of bone resorption shown by the CTX-I concentration, whereas the rate pressure product (DP) turned out to best predict osteoblastic activity determinable from serum alkaline phosphatase activity. The results of the study suggest that the activity of serum TAP and BAP can be enhanced by different mechanisms.

Biological variation in serum bone turnover markers

Background

Serum total N-terminal propeptide of type I collagen (P1NP) and serum C-terminal telopeptide of type I collagen (CTX) are used as reference analytes of bone turnover in clinical application. Biological variation is important for clinical application of these biomarkers. However, the biological variation data of these biomarkers are not consistent. The present study determined biological variations of total P1NP and CTX and their confidence intervals in China using electrochemiluminescence.

Methods

We collected samples from 25 healthy individuals (17 women and 8 men, ranging from 22 to 49 years of age) at weekly intervals for six weeks. Samples were analysed in a single run in duplicate. Biological variations and their related parameters, such as reference change value and index of individuality (II) were calculated. The results were compared with individual studies in the EFLM database.

Results

Within-subject and between-subject biological variations were 8.0% and 32.5% for total P1NP and 11.4% and 38.7% for CTX, respectively. The index of individuality for total P1NP and CTX was 0.25 and 0.30, while the reference change value for P1NP values and CTX was 22.4% and 31.9%, respectively.

Conclusions

No difference was found in weekly biological variation of bone turnover markers between men and premenopausal women. Compared with daily and monthly variation, the present study based on weekly variation provided additional support for clinical application.

Use of Bone Turnover Markers in Clinical Practice for the Management of Osteoporosis in Korea: From the Survey on the Prescription Pattern of Bone Turnover Markers

Background

There has been interest in the clinical potential of bone turnover markers (BTMs) as tools both for assessing fracture risk and for monitoring treatment. However, the practical use of BTMs has been limited by their biological variability and difficulties in the interpretation of results. We investigated the current situation of application of BTMs by clinicians in Korea for the management of osteoporosis through a survey asking the patterns of BTMs prescription in clinical practice.

Methods

The survey was conducted online using the “google survey” by the BTM committee authorized by the Korean Society for Bone and Mineral Research.

Results

Total 108 clinicians responded the survey. Most of the respondents prescribed BTMs (80.6%) when they prescribed anti-osteoporotic medications (AOMs). The most frequently prescribed bone resorption and formation markers were serum C-terminal telopeptide of type I collagen (90.7%) and osteocalcin (65.1%), respectively. BTMs were mostly prescribed before starting AOMs (90.8%) and used for the purpose of evaluating treatment response (74.4%). Treatment response and compliance to AOMs were evaluated according to the change of absolute value of BTMs (55.1%). The respondents complained difficulties in the interpretation of BTMs (33.3%), the choice of proper BTMs (17.2%), and the proper sample preparation and handling (13.8%).

Conclusions

In Korea, most of clinicians recognized the benefit of BTMs in the management of osteoporosis. However, there are limitations in the broad use of these markers in clinical practice. Therefore, a clear recommendation for BTM in Korea enhances their use in clinical practice.

Update on the Comprehensive Approach to Fragility Fractures

The prevention and treatment of fragility fractures continuously evolve. Adequate fracture care should involve treating the fracture itself and the underlying bone disease. Although effective treatments of osteoporosis are available, a large proportion of patients with fragility fractures are not prescribed antiosteoporotic medications after their injury. Recent advances in diagnostic tools, medications, and implementation of Fracture Liaison Services allow for more effective and comprehensive treatment or fragility fractures. In the Fracture Liaison Service model, a physician and physician extenders coordinate care. This includes a thorough medical and surgical history, metabolic bone disease laboratory testing, dual-energy x-ray absorptiometry screening, treatment, and long-term follow-up. Treatment options include nonpharmacologic treatment with calcium and vitamin D and antiresorptive and anabolic agents. Antiresorptive agents such as bisphosphonates and denosumab are first-line treatments for osteoporosis and anabolic agents such as teriparatide are effective in reducing bone density loss and have implications in fracture healing. In addition, new anabolic agents including antisclerostin antibodies and parathyroid hormone-related protein show promise as potential treatments to increase bone density.

Bone markers in polycystic ovary syndrome: A multicentre study

OBJECTIVE

Hyperandrogenism, hyperinsulinaemia and obesity, known characteristics of polycystic ovary syndrome (PCOS), may influence bone mineral density and biochemical markers of bone turnover (BTMs) can provide a noninvasive assessment of bone turnover. To this end, the serum concentrations of BTMs and 25-hydroxyvitamin D (25OHD) were analysed in women with PCOS, and their possible associations with metabolic parameters of PCOS were determined.

SUBJECTS AND METHODS

Bone formation markers procollagen type I amino-terminal propeptide (PINP) and osteocalcin (OC), and bone resorption marker carboxy-terminal cross-linking telopeptide of type I collagen (CTX), along with 25OHD, were measured in 298 women with PCOS and 194 healthy controls.

RESULTS

Serum levels of PINP (47.0 ± 20.2 vs 58.1 ± 28.6 μg/L, P < .001) and OC (18.2 ± 7.5 vs 20.6 ± 9.8 μg/L, P < .001) were decreased in women with PCOS compared with controls, whereas no significant differences were found in CTX and 25OHD levels. Age-stratified analyses suggested that PINP (50.5 ± 21.7 vs 68.2 ± 26.6 μg/L, P < .001) and OC levels (20.4 ± 7.6 vs 25.5 ± 9.6 μg/L, P < .001) were decreased only in the younger age group (≤30 years) women with PCOS compared with controls. The formation markers and resorption marker decreased with age in both study groups.

CONCLUSIONS

Bone formation markers were decreased in younger women with PCOS when compared with healthy women, which may affect bone mass in these women.

Use of CTX-I and PINP as bone turnover markers: National Bone Health Alliance recommendations to standardize sample handling and patient preparation to reduce pre-analytical variability

The National Bone Health Alliance (NBHA) recommends standardized sample handling and patient preparation for C-terminal telopeptide of type I collagen (CTX-I) and N-terminal propeptide of type I procollagen (PINP) measurements to reduce pre-analytical variability. Controllable and uncontrollable patient-related factors are reviewed to facilitate interpretation and minimize pre-analytical variability.

INTRODUCTION

The IOF and the International Federation of Clinical Chemistry (IFCC) Bone Marker Standards Working Group have identified PINP and CTX-I in blood to be the reference markers of bone turnover for the fracture risk prediction and monitoring of osteoporosis treatment. Although used in clinical research for many years, bone turnover markers (BTM) have not been widely adopted in clinical practice primarily due to their poor within-subject and between-lab reproducibility. The NBHA Bone Turnover Marker Project team aim to reduce pre-analytical variability of CTX-I and PINP measurements through standardized sample handling and patient preparation.

METHODS

Recommendations for sample handling and patient preparations were made based on review of available publications and pragmatic considerations to reduce pre-analytical variability. Controllable and un-controllable patient-related factors were reviewed to facilitate interpretation and sample collection.

RESULTS

Samples for CTX-I must be collected consistently in the morning hours in the fasted state. EDTA plasma is preferred for CTX-I for its greater sample stability. Sample collection conditions for PINP are less critical as PINP has minimal circadian variability and is not affected by food intake. Sample stability limits should be observed. The uncontrollable aspects (age, sex, pregnancy, immobility, recent fracture, co-morbidities, anti-osteoporotic drugs, other medications) should be considered in BTM interpretation.

CONCLUSION

Adopting standardized sample handling and patient preparation procedures will significantly reduce controllable pre-analytical variability. The successful adoption of such recommendations necessitates the close collaboration of various stakeholders at the global stage, including the laboratories, the medical community, the reagent manufacturers and the regulatory agencies.

Association between the metabolome and bone mineral density in pre- and post-menopausal Chinese women using GC-MS

The present study describes for the first time, a metabolic profile reflecting the osteoporosis progression in 364 pre- and postmenopausal Chinese women using GC-MS. In order to accurately evaluate the dynamic changes of metabolites along with estrogen deficiency and osteoporosis progression, we divided these subjects into the following four groups: premenopausal women with normal bone mass density (BMD, group I), postmenopausal women with normal BMD (group II), postmenopausal women with osteopenia (group III) and postmenopausal women with osteoporosis (group IV), according to their menopause or low BMD status. Principal component analysis (PCA) and Partial least squares-discriminant analysis (PLS-DA) were used to evaluate the associations of metabolic changes with low BMD or estrogen deficiency. Twelve metabolites identified by the PLS-DA model were found to be able to differentiate low BMD groups from normal BMD groups. Of the 12 metabolites, five free fatty acids (LA, oleic acid, AA and 11,14-eicosadienoic acid) have the most potential to be used as osteoporosis biomarkers due to their better correlations with BMD, and high sensitivity and specificity in distinguishing the low BMD groups from the normal BMD groups calculated by the receiver operating characteristic curve (ROC). The lipid profile may be useful for osteoporosis prediction and diagnosis.

Reduced Bone Material Strength is Associated with Increased Risk and Severity of Osteoporotic Fractures. An Impact Microindentation Study

The aim of the study was to test, whether bone material strength differs between different subtypes of osteoporotic fracture and assess whether it relates to vertebral fracture severity. Cortical bone material strength index (BMSi) was measured by impact microindentation in 66 women with osteoporotic fracture and 66 age- and sex-matched controls without fracture. Bone mineral density (BMD) and bone turnover markers were also assessed. Vertebral fracture severity was graded by semiquantitative (SQ) grading. Receiver operator characteristic (ROC) curves were used to examine the ability of BMSi to discriminate fractures. Subjects with osteoporotic fractures exhibited lower BMSi than controls (71.5 ± 7.3 vs. 76.4 ± 6.2, p < 0.001). After adjusting for age and hip BMD, a significant negative correlation was seen between BMSi and vertebral fracture severity (r ² = 0.19, p = 0.007). A decrease of one standard deviation (SD) in BMSi was associated with increased risk of fracture (OR 2.62; 95% CI 1.35, 5.10, p = 0.004). ROC curve areas under the curve (AUC) for BMSi in subjects with vertebral fracture (VF), hip fracture (HF), and non-vertebral non-hip fracture (NVNHFx), (mean; 95% CI) were 0.711 (0.608; 0.813), 0.712 (0.576; 0.843), 0.689 (0.576; 0.775), respectively. Combining BMSi and BMD provided further improvement in the discrimination of fractures with AUC values of 0.777 (0.695; 0.858), 0.789 (0.697; 0.882), and 0.821 (0.727; 0.914) for VFx, HFx, and NVNHFx, respectively. Low BMSi of the tibial cortex is associated with increased risk of all osteoporotic fractures and severity of vertebral fractures.

Ankylosing Spondylitis Patients Have Impaired Osteoclast Gene Expression in Circulating Osteoclast Precursors

INTRODUCTION

Ankylosing spondylitis (AS) is typically characterized by focal bone overgrowth and also by systemic bone loss. We hypothesize that the increased osteoproliferation found in AS might be partially due to reduced ability of osteoclast precursors (OCPs) to differentiate into osteoclasts (OCs). Therefore, our aim was to characterize bone remodeling and pro-osteoclastogenesis inflammatory environment, monocytes' phenotype, and in vitro osteoclast differentiation in AS patients.

METHODS

Patients with active AS without any ongoing therapy and age- and gender-matched healthy donors were recruited. Receptor activator of nuclear factor-κβ (RANKL) surface expression on circulating leukocytes and frequency and phenotype of monocyte subpopulations were assessed. Quantification of serum levels of bone turnover markers and cytokines, in vitro OC differentiation assay and quantitative reverse transcription real-time PCR for OC-specific genes were performed.

RESULTS

Pro- and anti-inflammatory cytokine serum levels were higher in AS patients than in controls. RANKL neutrophil expression was higher in AS patients when compared to healthy donors, but CD51/CD61 expression was lower in the classical monocyte subpopulation. Concerning osteoclastogenesis, we found no differences in the in vitro osteoclast differentiating potential of these cells when compared to healthy donors. However, we observed low expression of CSF1R, RANK, and NFATc1 in AS OCPs.

CONCLUSION

Despite the high levels of pro-inflammatory cytokines present in AS patients, no differences in the number of OC or resorbed area were found between AS patients and healthy donors. Moreover, we observed that OCPs have low OC-specific gene expression. These findings support our hypothesis of an impaired response of OCPs to pro-osteoclastogenic stimuli in vivo in AS patients.

Bone turnover markers: Emerging tool in the management of osteoporosis

Bone is a dynamic tissue which undergoes constant remodeling throughout the life span. Bone turnover is balanced with coupling of bone formation and resorption at various rates leading to continuous remodeling of bone. A study of bone turnover markers (BTMs) provides an insight of the dynamics of bone turnover in many metabolic bone disorders. An increase in bone turnover seen with aging and pathological states such as osteoporosis leads to deterioration of bone microarchitecture and thus contributes to an increase in the risk of fracture independent of low bone mineral density (BMD). These microarchitectural alterations affecting the bone quality can be assessed by BTMs and thus may serve as a complementary tool to BMD in the assessment of fracture risk. A systematic search of literature regarding BTMs was carried out using the PubMed database for the purpose of this review. Various reliable, rapid, and cost-effective automated assays of BTMs with good sensitivity are available for the management of osteoporosis. However, BTMs are subjected to various preanalytical and analytical variations necessitating strict sample collection and assays methods along with utilizing ethnicity-based reference standards for different populations. Estimation of fracture risk and monitoring the adherence and response to therapy, which is a challenge in a chronic, asymptomatic disease such as osteoporosis, are the most important applications of measuring BTMs. This review describes the physiology of bone remodeling, various conventional and novel BTMs, and BTM assays and their role in the assessment of fracture risk and monitoring response to treatment with antiresorptive or anabolic agents.

The clinical contribution of cortical porosity to fragility fractures

Cortical bone is not compact; rather it is penetrated by many Haversian and Volkmann canals for blood supply. The lining of these canals are the intracortical bone surfaces available for bone remodeling. Increasing intracortical bone remodeling increases cortical porosity. However, cortical bone loss occurs more slowly than trabecular loss due to the fact that less surface per unit of bone matrix volume is available for bone remodeling. Nevertheless, most of the bone loss over time is cortical because cortical bone constitutes 80% of the skeleton, and the relative proportion of trabecular bone diminishes with advancing age. Higher serum levels of bone turnover markers are associated with higher cortical porosity of the distal tibia and the proximal femur. Greater porosity of the distal radius is associated with higher odds for forearm fracture, and greater porosity of the proximal femur is associated with higher odds for non-vertebral fracture in postmenopausal women. Measurement of cortical porosity contributes to fracture risk independent of areal bone mineral density and Fracture Risk Assessment Tool. On the other hand, antiresorptive treatment reduces porosity at the distal radius and at the proximal femoral shaft. Thus, porosity is a substantial determinant of the bone fragility that underlies the risk of fractures and may be a target for fracture prevention.

Bone turnover marker reference intervals in young females

Background

The use of bone turnover markers in clinical practice and research in younger people is limited by the lack of normative data and understanding of common causes of variation in bone turnover marker values in this demographic. To appropriately interpret bone turnover markers, robust reference intervals specific to age, development and sex are necessary. This study aimed to determine reference intervals of bone turnover markers in females aged 16–25 years participating in the Safe-D study.

Methods

Participants were recruited through social networking site Facebook and were asked to complete an extensive, online questionnaire and attend a site visit. Participants were tested for serum carboxy-terminal cross-linking telopeptide of type 1 collagen and total procollagen type 1 N-propeptide using the Roche Elecsys automated analyser. Reference intervals were determined using the 2.5th to 97.5th percentiles of normalized bone turnover marker values.

Results

Of 406 participants, 149 were excluded due to medical conditions or medication use (except hormonal contraception) which may affect bone metabolism. In the remaining 257 participants, the reference interval was 230–1000 ng/L for serum carboxy-terminal cross-linking telopeptide of type 1 collagen and 27–131  µg/L for procollagen type 1 N-propeptide. Both marker concentrations were inversely correlated with age and oral contraceptive pill use. Therefore, intervals specific to these variables were calculated.

Conclusions

We defined robust reference intervals for cross-linking telopeptide of type 1 collagen and procollagen type 1 N-propeptide in young females grouped by age and contraceptive pill use. We examined bone turnover markers’ relationship with several lifestyle, clinical and demographic factors. Our normative intervals should aid interpretation of bone turnover markers in young females particularly in those aged 16 to 19 years where reference intervals are currently provisional.

Response of bone turnover markers to raloxifene treatment in postmenopausal women with osteopenia

We used two methods of identifying women who reached the target for raloxifene treatment with bone turnover markers. Both approaches identified women that responded to treatment but did not fully agree and may be complementary.

INTRODUCTION

The change in bone turnover markers (BTMs) in response to osteoporosis therapy can be assessed by a decrease beyond the least significant change (LSC) or below the mean of the reference interval (RI). We compared the performance of these two approaches in women treated with raloxifene.

METHODS

Fifty postmenopausal osteopenic women (age 51-72 years) were randomised to raloxifene or no treatment for 2 years. Blood samples were collected for the measurement of BTM. The LSC for each marker was calculated from the untreated women and the RI obtained from healthy premenopausal women (age 35-40 years). Bone mineral density (BMD) was measured at the spine and hip.

RESULTS

There was a decrease in BTM in response to raloxifene treatment, percentage change at 12 weeks: C terminal telopeptide of type I collagen (CTX) -39 % (95 % CI -48 to -28) and N terminal propeptide of type I procollagen (PINP) -32 % (95 % CI -40 to -23) P < 0.001. The proportion of women classified as responding to treatment using LSC at 12 weeks was as follows: CTX 38 % and PINP 52 % and at 48 weeks CTX 60 % and PINP 65 %. For the RI approach, the proportion of women classified as responding to treatment at 12 weeks was CTX and PINP 38 % and at 48 weeks CTX 40 % and PINP 45 %. There was a significant difference in the change in spine BMD in the raloxifene-treated group compared to the no-treatment group at week 48: difference 0.031 g/cm(2) (95 % CI 0.016 to 0.046, P < 0.001).

CONCLUSIONS

The two approaches identified women that reached the target for treatment using BTM. Both LSC and RI criteria appear useful in identifying treatment response, but the two approaches do not fully overlap and may be complementary.

Assessing the utility of serum C-telopeptide cross-link of type 1 collagen as a predictor of bisphosphonate-related osteonecrosis of the jaw: A systematic review and meta-analysis

BACKGROUND

The authors of this systematic review and meta-analysis assessed the utility of serum C-telopeptide cross-link of type 1 collagen (sCTX), a biomarker of bone resorption, as a predictor of the development of bisphosphonate-related osteonecrosis of the jaw (BRONJ).

TYPES OF STUDIES REVIEWED

The authors searched for studies involving adult participants, written in English, and published through January 20, 2016, using the following electronic databases: the Cochrane Library, MEDLINE via PubMed, and Web of Science. They also searched Google Scholar and the reference lists of all eligible trials and reviews. They identified 16 articles that met their inclusion criteria (9 controlled studies and 7 case series). They applied the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines for systematic reviews and meta-analyses. They independently extracted data in duplicate, including the characteristics of study participants, risk factors, control groups, and outcomes. They assessed risk of bias, and they resolved any disagreements between review authors through discussion.

RESULTS

A meta-analysis with 9 controlled studies revealed no significant difference in mean sCTX values between patients with BRONJ and control participants (difference in means, -31.417; 95% confidence interval [CI], -91.560 to 28.726; P = .306). A second meta-analysis with 4 studies showed no significant difference in risk of having an sCTX value below 150 picograms per milliliter for patients with BRONJ compared with control participants (risk ratio, 1.892; 95% CI, 0.636-5.626; P = .251).

CONCLUSIONS AND PRACTICAL IMPLICATIONS

A systematic review of the literature with meta-analysis does not support the use of sCTX levels as a predictor of the development of BRONJ. Further prospective large sample studies are needed to understand the role of sCTX as a predictor for BRONJ.

Response of bone turnover markers to three oral bisphosphonate therapies in postmenopausal osteoporosis: the TRIO study

We used bone turnover markers to identify women who responded to bisphosphonate treatment for osteoporosis. Response was more likely with alendronate and ibandronate than risedronate. There was a greater decrease in bone markers if baseline bone turnover markers were higher and if the patient took more than 80 % of her medication.

INTRODUCTION

Biochemical response to bisphosphonate therapy can be assessed using either a decrease in bone turnover marker beyond the least significant change (LSC) or a reduction to within a reference interval (RI). We compared the performance of these target responses and determined whether response was related to the type of bisphosphonate, compliance and baseline bone turnover markers.

METHODS

Biochemical responses to three oral bisphosphonates were assessed in an open, controlled trial comprising 172 postmenopausal osteoporotic women (age 53-84 years), randomised to alendronate, ibandronate or risedronate, plus calcium and vitamin D supplementation for 2 years. The LSC for each marker was derived within the study population, whereas RIs were obtained from a control group of healthy premenopausal women (age 35-40 years).

RESULTS

Over 70 % of women achieved a target response for serum CTX and PINP, irrespective of the approach used. The percentage decrease at 12 weeks was greater for women with baseline PINP above the RI -63 % (difference 13 %, 95 % CI 0 to 27.1, P = 0.049) and good compliance -67 % (difference 15.9 %, 95 % CI 6.3 to 25.5, P = 0.001). Responders had a greater increase in spine bone density compared to nonresponders; for example 6.2 vs. 2.3 % (difference 3.9 %, 95 % CI 1.6 to 6.3, P = 0.0011) for PINP LSC. The magnitude of change in bone markers was greater with ibandronate and alendronate than risedronate.

CONCLUSIONS

Both approaches to response identified similar proportions of women as responders. Nonresponders had smaller increases in BMD, and we suggest that biochemical assessment of response is a useful tool for the management of women with postmenopausal osteoporosis.

Bone turnover markers are associated with higher cortical porosity, thinner cortices, and larger size of the proximal femur and non-vertebral fractures

Bone turnover markers (BTM) predict bone loss and fragility fracture. Although cortical porosity and cortical thinning are important determinants of bone strength, the relationship between BTM and cortical porosity has, however, remained elusive. We therefore wanted to examine the relationship of BTM with cortical porosity and risk of non-vertebral fracture. In 211 postmenopausal women aged 54-94 years with non-vertebral fractures and 232 age-matched fracture-free controls from the Tromsø Study, Norway, we quantified femoral neck areal bone mineral density (FN aBMD), femoral subtrochanteric bone architecture, and assessed serum levels of procollagen type I N-terminal propeptide (PINP) and C-terminal cross-linking telopeptide of type I collagen (CTX). Fracture cases exhibited higher PINP and CTX levels, lower FN aBMD, larger total and medullary cross-sectional area (CSA), thinner cortices, and higher cortical porosity of the femoral subtrochanter than controls (p≤0.01). Each SD increment in PINP and CTX was associated with 0.21-0.26 SD lower total volumetric BMD, 0.10-0.14 SD larger total CSA, 0.14-0.18 SD larger medullary CSA, 0.13-0.18 SD thinner cortices, and 0.27-0.33 SD higher porosity of the total cortex, compact cortex, and transitional zone (all p≤0.01). Moreover, each SD of higher PINP and CTX was associated with increased odds for fracture after adjustment for age, height, and weight (ORs 1.49; 95% CI, 1.20-1.85 and OR 1.22; 95% CI, 1.00-1.49, both p<0.05). PINP, but not CTX, remained associated with fracture after accounting for FN aBMD, cortical porosity or cortical thickness (OR ranging from 1.31 to 1.39, p ranging from 0.005 to 0.028). In summary, increased BTM levels are associated with higher cortical porosity, thinner cortices, larger bone size and higher odds for fracture. We infer that this is produced by increased periosteal apposition, intracortical and endocortical remodeling; and that these changes in bone architecture are predisposing to fracture.

Effect of age and sex on bone markers in Chlorocebus aethiops raised in captivity

BACKGROUND

The objective was to evaluate the procollagen type I N-propeptide (PINP), osteocalcin (OC), β-crosslaps (β-CTX), and parathyroid hormone (PTH) in relation to age and sex of Chlorocebus aethiops in captivity.

METHODS

Seventy-three monkeys were divided into four age groups: AG1 (juvenile); AG2 (young adult); AG3 (adult); and AG4 (senile). An electrochemiluminescence immunoassay with an Elecsys 2010 analyzer was used to determine the serum markers of bone.

RESULTS AND CONCLUSIONS

Sex did not influence the results of the markers. However, the variables PINP, OC, and β-CTX were negatively correlated with age (r = -0.643; r = -0.711; r = -0.488; P < 0.001, respectively), and PTH was correlated positively with age (r = 0.418, P < 0.001). The data obtained can be used as biomarkers of bone metabolism reference intervals in healthy C. aethiops in captivity.

Evaluating and mitigating fracture risk in established rheumatoid arthritis

Patients with rheumatoid arthritis are predisposed to systemic bone loss, and they are at an increased risk of fractures. Although there are similarities in the patient demographics between rheumatoid arthritis patients and the general population of osteoporosis patients, there are factors, particularly the use of glucocorticoids, which are specific to rheumatoid arthritis. These factors can lead to an increased risk of bone loss and fracture. Given that fractures are often very debilitating, especially in elderly patients, it is of paramount importance for the practicing rheumatologist to be aware of ways to reduce the risk of fracture in patients with rheumatoid arthritis. This review discusses currently available modalities for fracture risk assessment as well as pharmacologic and lifestyle interventions available to treat and prevent bone loss in rheumatoid arthritis patients.

Type I collagen degradation during tissue repair: comparison of mechanisms following fracture and acute coronary syndromes

There is turnover of type I collagen during tissue repair. The degradation of type I collagen by matrix metalloproteinases (MMPs) is reflected by serum ICTP and that by cathepsins by CTX-I. There is evidence for increases in ICTP after acute coronary syndromes (ACS) and in CTX-I during fracture repair. The involvement of the MMP pathway in fracture repair and cathepsins after myocardial infarction is unclear. We studied 74 men; 22 were admitted to the hospital on the day of their ACS (ST or non-ST elevation myocardial infarction) (mean age 56 years, range 39 to 82) and 9 attended hospital on the day of their tibial shaft fracture (mean age 33 years, range 21 to 79); we had 43 age-matched controls (mean age 54 years, range 20 to 82). Subjects with ACS and tibial shaft fracture were followed up for up to one year; control subjects were used to establish a reference interval. We measured serum ICTP by ELISA (reference interval 1.1 to 17.6 ng/mL) and CTX-I by chemiluminescence (reference interval 0.094 to 0.991 ng/mL). After ACS, the mean ICTP increased from 5.41 to 6.60 ng/mL within one day of admission (p<0.05); the mean CTX-I increased from 0.263 to 0.414 ng/mL (p<0.05). In two cases, the CTX increased to above the reference interval. After tibial shaft fracture, the mean ICTP increased from 5.51 to maximum of 8.71 ng/mL within 28 days of admission (p<0.01); the mean CTX increased from 0.200 to 0.374 ng/mL (p<0.001). In four cases, the CTX increased to above the reference interval. We conclude that the MMP and cathepsin pathways are both implicated in tissue repair in the bone and heart. This may have clinical implications; drugs that block either pathway (TIMPs, cathepsin K inhibitors) may affect the repair of both tissues.

Monitoring of osteoporosis therapy

Over the past two decades, major advances have been made in the number and range of agents available for the treatment of osteoporosis, all with proven anti-fracture efficacy. Unfortunately, compliance with these treatments is not optimal, and a number of patients could be considered as non-responders. Consequently, monitoring anti-osteoporotic therapy could be part of successful osteoporosis management. Currently, no formal well-accepted clinical practice guidelines are available for monitoring anti-osteoporosis therapies. Changes in bone mineral density and bone turnover markers, while on therapy, have potential value in monitoring treatment but their assessment and, consequently, their benefits could be limited by metrological and clinical issues. Moreover, their effectiveness is probably drug dependant. Recommendation for the standardisation of the methodology when analysing the potential relevance of tools for the monitoring of osteoporosis therapy is needed.

Bone turnover markers in serum and urine as diagnostic, prognostic and monitoring biomarkers of bone metastasis

Bone metastases are characterized by increased osteoblastic and/or osteolytic processes depending on the tumor type. The altogether destructive effect of metastasis formation promoted by increased metabolic activity raises the release of components from the osseous metabolism into the blood stream. These components are either enzymes directly involved in the alteration processes, metabolites/proteins that develop during this or bone matrix proteins released during this. These biomarkers are categorized in relation to their involvement in the bone formation or resorption as bone formation and resorption markers. Based on a PubMed literature search, a critical appraisal of the various biomarkers for diagnostic, prognostic, and monitoring purposes is given for patients with skeletal metastases caused by breast, prostate, lung, or renal cell carcinomas.

Differences in peripartal plasma parameters related to calcium homeostasis of dairy sheep and goats in comparison with cows

Recently it has been demonstrated that there are differences between sheep and goats in respect to adaptation to a calcium-restricted diet. It was the aim of the present study to evaluate whether species-specific peculiarities also occur when calcium homoeostasis is challenged by lactation. Therefore, we investigated the time courses of plasma parameters related to calcium homoeostasis (calcium, phosphate, calcitriol, the bone resorption marker CrossLaps® and the bone formation marker osteocalcin) during the transition period in multiparous animals of both species and compared the results to data from a former study carried out with dairy cows. As in cows, plasma calcium and the ratio of bone formation to bone resorption decreased at parturition in goats while plasma calcitriol increased. On day 10 post partum the bone parameters of goats reached prepartum values again, which was not the case in cows. Sheep were found to experience a challenge of calcium homoeostasis already 10 d before parturition, reflected by a very low ratio of bone formation to bone resorption, which was not accompanied by an increase in plasma calcitriol. Additionally, sheep and goats which had been in milk for 3 months were sampled, dried-off and sampled again 6 weeks later. In dried-off animals there were no detectable differences in parameters of bone metabolism. In conclusion we could show that the contribution of bone mobilisation to the compensation for the enhanced calcium demand due to lactation differs between the three ruminant species.

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.

Diurnal variation of plasma bone markers in Japanese black calves

To evaluate diurnal variation of plasma bone markers, blood samples were collected from five calves at 2-hr intervals throughout a 24-hr period. Tartrate-resistant acid phosphatase isoform 5b (TRAP5b), carboxy-terminal collagen crosslinks of type-I collagen (CTX), hydroxyproline, bone specific alkaline phosphatase (BALP) and osteocalcin were measured. Cosinor analysis showed a significant rhythm in all bone markers. The acrophase of each bone marker appeared from the early to late morning. The percentage ratio of the amplitude to mesor and the within-subject variability for CTx and osteocalcin were significantly larger than those for TRAP5b and BALP. This marked diurnal variation in five bone markers suggested that the time of blood sampling should be fixed when studying bone marker concentrations in bovine plasma.

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.

Update on long-term treatment with bisphosphonates for postmenopausal osteoporosis: a systematic review

INTRODUCTION

Osteoporosis is a progressive skeletal disorder that requires long-term treatment. However, there is little guidance regarding optimal treatment duration and what the treatment discontinuation and retreatment criteria should be. Given that bisphosphonates are the most commonly prescribed class of agent for the treatment of osteoporosis, we reviewed the long-term data relating to these therapies and discussed the considerations for using bisphosphonates in postmenopausal women with osteoporosis.

METHODS

A PubMed search, using the search terms 'bisphosphonate', 'postmenopausal osteoporosis' and 'long term' and/or 'extension' was conducted in January 2013. Results from nine controlled studies that prospectively assessed alendronate, risedronate, ibandronate or zoledronic acid in women with postmenopausal osteoporosis were reviewed.

FINDINGS

Clinical studies in postmenopausal women with osteoporosis showed that long-term use of bisphosphonates resulted in persistent antifracture and bone mineral density (BMD) increasing effects beyond 3 years of treatment. No unexpected adverse events were identified in these studies and the long-term tolerability profiles of bisphosphonates remain favorable. Data from the withdrawal extension studies of alendronate and zoledronic acid also showed that residual fracture benefits were seen in patients who discontinued treatment for 3 to 5 years after an initial 3- to 5-year treatment period. BMD monitoring and fracture risk assessments should be conducted regularly to determine whether treatment could be stopped or should be reinitiated. Patients exhibiting T-scores<-2.5 or who have suffered a new fracture while on treatment should continue treatment, while patients with T-scores>-2.5 could be considered for discontinuation of active treatment while undergoing continued monitoring of their bone health. The duration and potential discontinuation of treatment should be personalized for individual patients based on their response to treatment, fracture risk and comorbidities.

Reference intervals for serum concentrations of three bone turnover markers for men and women

OBJECTIVE

Bone turnover markers (BTMs) reflect the metabolic activity of bone tissue and can be used to monitor osteoporosis therapy. To adequately interpret BTMs, method-specific reference intervals are needed. We aimed to determine reference intervals for serum concentrations of intact amino-terminal propeptide of type I procollagen (PINP), bone-specific alkaline phosphatase (BAP) and carboxy-terminal telopeptide of type I collagen (CTX).

MATERIAL AND METHODS

We established a healthy reference population of 1107 men as well as 382 pre- and 450 postmenopausal women, who participated in the first follow-up of the Study of Health in Pomerania. Serum PINP, BAP and CTX concentrations were measured on the IDS-iSYS Automated System (Immunodiagnostic Systems, Frankfurt am Main, Germany). The reference interval was defined as the central 95% range. We determined age-specific reference intervals for PINP, BAP, and CTX for men by quantile regression. Reference intervals for women were age-independent.

RESULTS

Reference intervals for men for PINP and CTX decreased with age (25-29year-old men: PINP 31.1-95.9ng/mL, CTX 0.12-0.83ng/mL; 75-79year-old men: PINP 15.7-68.1ng/mL, CTX 0.05-0.58ng/mL). The reference interval for men for BAP did not significantly change with age (25-29year-old men: 7.4-27.7ng/mL; 75-79year-old men: 7.6-24.4ng/mL). The reference intervals for 30-54year-old premenopausal women were: PINP 19.3-76.3ng/mL, BAP 6.0-22.7ng/mL, and CTX 0.05-0.67ng/mL. The reference intervals for 50-79year-old postmenopausal women were: PINP 18.2-102.3ng/mL, BAP 8.1-31.6ng/mL, and CTX 0.09-1.05ng/mL.

CONCLUSION

An intensively characterized, large reference population free of bone-related diseases allowed us to determine robust reference intervals for serum concentrations of PINP, BAP and CTX. Our normative data may aid to interpret bone turnover in adult men and pre- and postmenopausal women.