Clinical use of bone markers: a challenge to variability

Bone markers are a group of substances released into circulation during bone formation and/or resorption. These substances can be measured in blood and urine to obtain information about metabolic bone disorders. This review provides an insight into factors influencing bone marker variability and describes different approaches to minimize variability and interpret results appropriately. Variability in bone marker concentrations results from biological and analytical variability across assays. Other influencing factors include gender, age, physical exercise, circadian rhythm, and diet. The multiplicity of influencing factors hinders the establishment of accurate reference values. Gaining a deep understanding of bone marker variability is the first step to ascertain their clinical usefulness. Bone marker variability can be minimized by controlling as many variables as it is possible and through the standardization of patient preparation and sample collection and handling.

Signs of a Glucose- and Insulin-Independent Gut-Bone Axis and Aberrant Bone Homeostasis in Type 1 Diabetes

CONTEXT

Gut hormones seem to play an important role in postprandial bone turnover, which also may be affected by postprandial plasma glucose excursions and insulin secretion.

OBJECTIVE

To investigate the effect of an oral glucose tolerance test (OGTT) and an isoglycemic intravenous glucose infusion (IIGI) on bone resorption and formation markers in individuals with type 1 diabetes and healthy controls.

METHODS

This observational case-control study, conducted at the Center for Clinical Metabolic Research, Gentofte Hospital, Hellerup, Denmark, included 9 individuals with C-peptide negative type 1 diabetes and 8 healthy controls matched for gender, age, and body mass index. Subjects underwent an OGTT and a subsequent IIGI. We analyzed changes in bone resorption assessed by measurements of carboxy-terminal type I collagen crosslinks (CTX) and in bone formation as assessed by procollagen type I N-terminal propeptide (PINP) concentrations.

RESULTS

Baseline CTX and PINP levels were similar in the 2 groups. Both groups exhibited significantly greater suppression of CTX during OGTT than IIGI. PINP levels were unaffected by OGTT and IIGI, respectively, in healthy controls. Participants with type 1 diabetes displayed impaired suppression of CTX-assessed bone resorption and inappropriate suppression of PINP-assessed bone formation during OGTT.

CONCLUSION

Our data suggest the existence of a gut-bone axis reducing bone resorption in response to oral glucose independently of plasma glucose excursions and insulin secretion. Subjects with type 1 diabetes showed impaired suppression of bone resorption and reduced bone formation during OGTT, which may allude to the reduced bone mineral density and increased fracture risk characterizing these individuals.

The Effect of Effervescent and Buffered Alendronate Compared to Conventional Alendronate on Markers of Bone Turnover: A Randomized Non-inferiority Trial

Buffered and effervescent alendronate (ALN-EFF) increases gastric pH and is reported to decrease the risk of gastrointestinal side effects compared to conventional formulations of alendronate (ALN). The clinical effectiveness of ALN-EFF, however, has not been investigated. This study aims to investigate if ALN-EFF is non-inferior to ALN in suppressing bone turnover markers (BTM). We conducted a 16-week prospective, randomized, open-label study comprising 64 postmenopausal women with BMD T-score < -1 naïve to osteoporosis treatment. Participants were randomized 1:1 to ALN or ALN-EFF. We collected blood samples at 0, 4, 8, and 16 weeks. Non-inferiority margin was determined as 12% (80% of efficacy retained), and an SD of 15% on change in CTx. CTx decreased by 58.2% ± 24.1% in the ALN group and by 46.9% ± 23.3% (CI - 38.42:- 55.35) in the ALN-EFF group (p = 0.08). The non-inferiority limit was 46.6%. With ALN-EFF the CI crosses the non-inferiority limit thus the test for non-inferiority was indeterminate. PINP decreased by 45.7 ± 22.6% in the ALN group and by 35.1 ± 20.7% in the ALN-EFF group (p = 0.07). Changes over time in the BTMs were not significantly different between the groups, p > 0.10 for both CTx and PINP. There was no difference in frequency of AEs or compliance between the two groups, but rate of discontinuation was lower with ALN-EFF. In conclusion, suppression of BTMs was not significantly different between the groups but formal non-inferiority could not be established.

Impact of vitamin D supplementation on markers of bone turnover: Systematic review and meta-analysis of randomised controlled trials

AIM

The effects of vitamin D administration on bone turnover markers (BTMs) in adults are controversial. Thus, we carried out a meta-analysis of available randomised controlled trials (RCTs) to examine the impact of vitamin D supplementation on BTMs.

METHODS

To identify relevant RCTs, we searched the PubMed/MEDLINE, Web of Science, Scopus, Cochrane Library and Embase databases for manuscripts published up to July 2022. The present study was conducted in agreement with the PRISMA guidelines. Weighed mean difference (WMD) and 95% confidence intervals (CI) were used to calculate the magnitude of the effect of the intervention.

RESULTS

A total of 42 RCTs were included in the meta-analysis. The age of the participants enrolled in the RCTs ranged from 19.4 to 84 years. The pooled results depicted a decrease in deoxypyridinoline (DPD) concentrations (WMD: -1.58 nmol/mmol, 95% CI: -2.55, -.61, p = .001) following vitamin D supplementation. In addition, subgroup analyses demonstrated that vitamin D administration notably reduced procollagen type I N-terminal propeptide (PINP) levels in individuals aged >50 years and led to a pronounced decrease in alkaline phosphatase (ALP) values when the intervention lasted >12 weeks. No significant effect was observed on other BTMs, for example, collagen type 1 cross-linked C-telopeptide (CTX) and osteocalcin (OC) levels.

CONCLUSION

Vitamin D administration decreases DPD, PINP and ALP levels, indicating a reduced bone turnover following the intervention. Other BTMs, for example, CTX or OC values, were not affected by vitamin D prescription. Vitamin D supplementation may exert a positive effect on some important BTMs.

Metabolic Imbalances and Bone Remodeling Agents in Adolescent Idiopathic Scoliosis: A Study in Postmenarcheal Girls

The causes and mechanisms underlying adolescent idiopathic scoliosis (AIS) remain unclear, and the available information regarding metabolic imbalances in AIS is still insufficient. This investigation aimed to evaluate the concentrations of specific bone remodeling-related agents in postmenarcheal girls diagnosed with AIS. The study encompassed thirty-six scoliosis patients and eighteen age-matched healthy individuals assigned to the control group. The patients underwent clinical and radiological examinations to assess the degree of the spinal deformity, type of curvature, and skeletal maturity. Blood and urine samples were collected from all participants and serological markers were measured using an enzyme-linked immunosorbent assay. Our study results demonstrated that the balance of phosphate-calcium and parathormone levels seems normal in individuals with AIS. Furthermore, no statistically significant differences were observed in the content of Klotho protein, osteocalcin, osteoprotegerin, C-terminal telopeptide of type I collagen (CTX), sclerostin, and alkaline phosphatase. Nevertheless, the serum levels of vitamin D (25-OH-D) were lowered, while N-terminal propeptide of type I procollagen (PINP), and fibroblast growth factor-23 (FGF23) were increased in the AIS group, with p-values of 0.044, 0.001, and 0.022, respectively. This finding indicates the potential involvement of these factors in the progression of AIS, which necessitates further studies to uncover the fundamental mechanisms underlying idiopathic scoliosis.

Low Bone Turnover Associates With Lower Insulin Sensitivity in Newly Diagnosed Drug-Naïve Persons With Type 2 Diabetes

CONTEXT

Bone turnover markers (BTMs) are lower in type 2 diabetes mellitus (T2D). The relationships between bone turnover, β-cell function, and insulin sensitivity in T2D are uncertain.

OBJECTIVE

To investigate if fasting levels of BTMs in persons with T2D are associated with β-cell function or insulin sensitivity.

METHODS

We defined three T2D phenotypes, the insulinopenic (low β-cell function, high insulin sensitivity), the classical (low β-cell function, low insulin sensitivity), and the hyperinsulinemic (high β-cell function, low insulin sensitivity) phenotypes, in the Danish Centre for Strategic Research T2D cohort using the homeostatic model assessment. We selected age- and gender-matched subgroups to represent the three T2D phenotypes, yielding 326 glucose-lowering treatment-naïve persons with T2D. Median values of BTMs between the three T2D phenotypes were compared. Regression models were applied to assess the association between BTMs, β-cell function, and insulin sensitivity adjusted for potential confounders.

RESULTS

Median serum levels of procollagen type I N-terminal propeptide, C-terminal telopeptide of type I collagen, and osteocalcin were higher in the insulinopenic phenotype (52.3 μg/L, IQR 41.6, 63.3; 259.4 ng/L, IQR 163.4, 347.7; and 18.0 μg/L, IQR 14.4, 25.2, respectively) compared with the classical (41.4, IQR 31.0, 51.4; 150.4 IQR 103.5, 265.1; 13.1, IQR 10.0, 17.6, respectively) and the hyperinsulinemic (43.7, IQR 32.3, 57.3; 163.3, IQR 98.9, 273.1; 15.7 IQR 10.2, 20.8, respectively) phenotypes (all P < .01). These differences persisted after adjustment for age, sex, waist to hip ratio, or fasting plasma glucose (P < .01).

CONCLUSION

BTMs are lower in newly diagnosed persons with T2D characterized by low insulin sensitivity.

Bone Turnover Markers in Children: From Laboratory Challenges to Clinical Interpretation

Bone turnover markers (BTMs) have been developed many years ago to study, in combination with imaging techniques, bone remodeling in adults. In children and adolescents, bone metabolism differs from adults since it implies both growth and bone remodeling, suggesting an age- and gender-dependent BTM concentration. Therefore, specific studies have evaluated BTMs in not only physiological but also pathological conditions. However, in pediatrics, the use of BTMs in clinical practice is still limited due to these many children-related specificities. This review will discuss about physiological levels of BTMs as well as their modifications under pathological conditions in children and adolescents. A focus is also given on analytical and clinical challenges that restrain BTM usefulness in pediatrics.

Baseline bone turnover marker levels can predict change in bone mineral density during antiresorptive treatment in osteoporotic patients: the Copenhagen bone turnover marker study

Anti-resorptive osteoporosis treatment might be more effective in patients with high bone turnover. In this registry study including clinical data, high pre-treatment bone turnover measured with biochemical markers was correlated with higher bone mineral density increases. Bone turnover markers may be useful tools to identify patients benefitting most from anti-resorptive treatment.

INTRODUCTION

In randomized, controlled trials of bisphosphonates, high pre-treatment levels of bone turnover markers (BTM) were associated with a larger increase in bone mineral density (BMD). The purpose of this study was to examine this correlation in a real-world setting.

METHODS

In this registry-based cohort study of osteoporosis patients (n = 158) receiving antiresorptive therapy, the association between pre-treatment levels of plasma C-telopeptide of type I Collagen (CTX) and/or N-terminal propeptide of type I procollagen (PINP) and change in bone mineral density (BMD) at lumbar spine, total hip, and femoral neck upon treatment was examined. Patients were grouped according to their pre-treatment BTM levels, defined as values above and below the geometric mean for premenopausal women.

RESULTS

Pre-treatment CTX correlated with annual increase in total hip BMD, where patients with CTX above the geometric mean experienced a larger annual increase in BMD (p = 0.008) than patients with CTX below the geometric mean. The numerical pre-treatment level of CTX showed a similar correlation at all three skeletal sites (total hip (p = 0.03), femoral neck (p = 0.04), and lumbar spine (p = 0.0003)). A similar association was found for PINP where pre-treatment levels of PINP above the geometric mean correlated with a larger annual increase in BMD for total hip (p = 0.02) and lumbar spine (p = 0.006).

CONCLUSION

Measurement of pre-treatment BTM levels predicts osteoporosis patients' response to antiresorptive treatment. Patients with high pre-treatment levels of CTX and/or PINP benefit more from antiresorptive treatment with larger increases in BMD than patients with lower pre-treatment levels.

Broad application prospects of bone turnover markers in pediatrics

BACKGROUND

Bone turnover markers (BTMs) have been studied for application in clinical medicine. However, BTMs in children are challenging, and few studies explore these BTMs in children. The application of BTMs is complicated mainly due to pre-analytical factors, variable reference intervals of age- and sex-related BTMs for adolescents and children in different regions and laboratories. Therefore, laboratory testing of BTMs is critical for understanding pediatric bone development and metabolism, which provides additional information about bone development and diseases.

METHODS

Literature search was conducted using the MeSH term "child" combined with the terms that bone turnover markers such as "osteocalcin," "Procollagen type I N-terminal propeptide," "procollagen type I C-terminal propeptide," "osteocalcin," "N-terminal cross-linked telopeptide," and "C-terminal cross-linked telopeptide," Several databases including Web of Science, Google Scholar, and PubMed were searched to obtain the relevant studies.

RESULTS

BTMs represent the combined effects of skeletal development, growth, and remodeling in children, which can be used in clinical pediatrics to assist in the diagnosis and prognosis of bone metabolic disorders.

CONCLUSION

BTMs are clearly helpful for diagnosis and monitoring of bone growth and development as well as bone metabolic disorders.

Fluctuations in Metabolites and Bone Markers Across the Menstrual Cycle in Eumenorrheic Women and Oral Contraceptive Users

CONTEXT

Little is known about changes in circulating metabolites during the menstrual cycle and how use of oral contraceptives (OCs) affects these changes.

OBJECTIVES

To study fluctuations in circulating metabolite and bone marker levels during the menstrual/pill cycle in eumenorrheic women and OC users.

METHODS

Plasma samples were collected from 28 eumenorrheic women and 10 OC users at 7 to 9 time points across a menstrual/pill cycle. Longitudinal and cross-sectional analyses were performed to examine the cycle- and OC-induced variations in the plasma metabolite and bone turnover marker levels.

RESULTS

In eumenorrheic women, plasma levels of alanine, glutamine, threonine, and tyrosine varied significantly across the menstrual cycle, and all dropped to the lowest level around day 21 of the menstrual cycle. These amino acid concentrations were negatively correlated with fluctuations in progesterone and/or estrogen levels. A between-group analysis showed that plasma levels of alanine, glutamine, glycine, proline, and tyrosine were lower in OC users than in nonusers. Concomitantly, plasma C-terminal telopeptide of type I collagen (CTX) and N-terminal propeptide of type I procollagen (PINP) levels were lower in OC users. Intriguingly, when all data were pooled, variations in CTX and PINP levels were positively correlated with fluctuations in proline and glycine concentrations (r > 0.5 or 0.3 < r < 0.5, P < 0.05).

CONCLUSIONS

The menstrual cycle and the use of OCs alter plasma levels of metabolites and bone turnover markers in young women. While the impact of these findings remains to be established, the lower glycine level among OC users and the accompanying lower CTX level supports that the use of OCs lowers collagen turnover in young women and may thereby have long-term implications for bone health among OC users.

Utility of PINP to monitor osteoporosis treatment in primary care, the POSE study (PINP and Osteoporosis in Sheffield Evaluation)

PURPOSE

In Sheffield (UK), we introduced the PINP monitoring algorithm for the management of osteoporosis treatment delivered in primary care. Our aims were to evaluate whether this algorithm was associated with better osteoporosis outcomes and was cost-effective compared to standard care.

METHODS

Inclusion criteria were referral from Sheffield GPs, BMD scans performed between 2012 and 2013 and a report advising initiation of oral bisphosphonate and PINP monitoring. 906 patients were identified and retrospectively divided into Group A (intention to monitor, with baseline PINP, n = 588) and Group B (no intention to monitor, without baseline PINP, n = 318). The model described by Davis and colleagues was used to extrapolate life-time costs and quality-adjusted life-years (QALYs).

RESULTS

No differences were found in baseline characteristics between groups (age, gender, BMI, BMD and major risk factors for fractures). More patients in Group A started oral treatment (77.4% vs 49.1%; p < 0.001), but there were no differences between groups in the presence of a gap in treatment >3 months or in treatment duration. Patients in Group A were more likely to have follow-up DXA scan at 4-6 years from baseline (46.9% vs 29.2%; p < 0.000) and had a greater increase in total hip BMD (+2.74% vs + 0.42%; p value = 0.003). Fewer new fractures occurred in Group A but this was not statistically significant, but the numbers of fractures were small. Patients in Group A were more likely to change management (p = 0.005) including switching to zoledronate (p = 0.03). The PINP measurement and increased prescribing in Group A resulted in increases in both costs (£30.19) and QALYs (0.0039) relative to Group B, giving an incremental cost effectiveness ratio (ICER) of £7660 in the probabilistic sensitivity analysis.

CONCLUSIONS

Patients monitored with PINP are more likely to start oral bisphosphonate treatment, switch to zoledronate, have follow-up DXA scans and a greater increase of hip BMD. PINP monitoring has the potential to be cost-effective in a UK NHS setting given that interventions with an ICER under £20,000 are generally considered to be cost-effective.

Age-related trends and reference intervals of cross-linked C-telopeptide of type I collagen and procollagen type I N-propeptide from a reference population of Sri Lankan adult women

Refer ence values of bone turnover markers (BTMs) are determined by factors that are country-specific. In Sri Lanka, unavailability of BTM reference data has led to their non-use in management of osteoporosis. The results of this study can be used as reference data for women in Sri Lanka.

INTRODUCTION

This study was performed to establish age-related reference intervals for bone resorption marker; cross-linked C-telopeptide of type I collagen (CTX) and bone formation marker; procollagen type I N-propeptide (PINP) in a group of Sri Lankan adult women.

METHODS

Adult women (n = 347) aged 20-70 years were recruited using age-stratified random sampling technique and categorized into age groups by decades. Serum CTX and PINP concentration were measured using enzyme-linked immunosorbent assay (ELISA). The geometric mean (95% confidence interval) and 2.5th and 97.5th percentiles were calculated. ANOVA was used to compare the means between groups.

RESULTS

Mean CTX levels were relatively low and remained unchanged between 20 and 49 years. After the age of 49 years, mean CTXconcentration elevated significantly until the age of 70 years (43%, p < 0.001). Mean PINP concentrations were not significantly different between age categories (p > 0.05). Reference intervals of CTX and PINP were based on 2.5th and 97.5th percentile values. Reference intervals of CTX for the age groups of 20-29, 30-39, 40-49, 50-59, and 60-70 years were 0.19-0.97 ng/mL, 0.18-0.95 ng/mL, 0.20-1.29 ng/mL, 0.17-2.20 ng/mL, and 0.17-2.85 ng/mL respectively. Reference intervals of PINP for the same age groups were 118-810 pg/mL, 119-772 pg/mL, 116-645 pg/mL, 108-684 pg/mL, and 108-715 pg/mL respectively.

CONCLUSION

In Sri Lanka, bone turnover markers are not used in evaluating patients mainly due to lack of normative data. These values can be used as reference data for women in this age group.

Age-related changes and reference intervals of RANKL, OPG, and bone turnover markers in Indian women

RANKL and OPG are cytokines involved in bone remodeling that makes them potential bone biomarkers. The reference interval for these cytokines, their ratio, and bone turnover markers CTX and PINP were established in Indian women, which may serve in diagnosis and management of osteoporosis.

PURPOSE

The aim of the study was to establish reference interval for RANKL, OPG, RANKL/OPG, and bone turnover markers CTX and PINP in healthy Indian women.

METHODS

This was a cross-sectional study on 374 healthy Indian women in the age group of 20-65 years. Serum levels of total RANKL, OPG, CTX, PINP, and estradiol were determined by commercial ELISA kits. The reference intervals for these cytokines and bone turnover markers were based on the 95% centrally distributed data.

RESULTS

Median RANKL (245.6 pmol/L vs. 149 pmol/L) and RANKL/OPG (38.7 vs. 20.4) were higher, while sCTX (380 ng/L vs. 551 ng/L) and OPG levels (6.1 pmol/L vs. 7.4 pmol/L) were lower in premenopausal women than those in postmenopausal women. PINP levels were comparable in both groups. Women were classified into 5 groups according to decades of age and the reference intervals for RANKL, OPG, RANKL/OPG ratio, and CTX and PINP in each group were reported.

CONCLUSION

We reported menopausal status-based and age-related reference intervals for serum RANKL, OPG, RANKL/OPG ratio, and CTX and PINP in healthy Indian women.

Bone Metabolism and RANKL/OPG Ratio in Rheumatoid Arthritis Women Treated with TNF-α Inhibitors

The aim of this study was to evaluate the effect of anti-tumor necrosis factor α (anti-TNF-α) therapy in combination with methotrexate on bone remodeling and osteoclastogenesis in female patients with RA. Serum levels of bone turnover markers (i.e., C- and N-terminal propeptides of type I procollagen (PICP and PINP), C- and N-terminal cross-linking telopeptides of type I collagen (CTX-I and NTX-I), and soluble receptor activator of nuclear factor κB ligand (sRANKL) and osteoprotegerin (OPG)) were determined by immunoassay at baseline and 15 months after initiation of treatment. Bone mineral density was measured by dual-energy x-ray absorptiometry. We found a significant decrease in serum PINP levels, a biomarker of bone formation, and higher levels of CTX-I and sRANKL indicative of increased bone resorption in RA patients prior to TNFαI treatment compared to the controls. Anti-TNF-α therapy was effective in improving bone metabolism in RA patients as reflected in a decrease in CTX-I (at least partially due to the RANKL/OPG reduction) and a concomitant increase in PINP levels. The bone metabolism changes were independent of the type of TNFαI used. PINP and CTX-I were found to be useful markers of bone metabolism, which may prove the effectiveness of TNF-α therapy earlier than the bone density assessment.

Assessing bone formation in patients with chronic kidney disease using procollagen type I N-terminal propeptide (PINP): The choice of assay makes a difference

BACKGROUND

Measurement of procollagen type I N-terminal propeptide (PINP) concentration in serum reflects the rate of type I collagen synthesis and can therefore be used as a bone formation marker. There are two methods of PINP quantification; the first measures the trimeric propeptide (intact PINP) and the second measures both the trimeric and monomeric propeptides (total PINP). Trimeric PINP is excreted via hepatic endothelial cells, whereas monomeric PINP is cleared renally. Therefore, in renal failure, the total assay has a positive bias with respect to the intact assay, due to monomeric PINP accumulation. The aim of this study was to compare the performance of both assays across all stages of chronic kidney disease.

METHODS

Serum was taken from male (n = 111) and female (n = 105) patients attending a metabolic bone clinic, and these were partitioned into stages of chronic kidney disease 1-5. Each serum sample was analysed using the Roche electrochemiluminescence immunoassay for total PINP and the Immunodiagnostic Systems chemiluminescence immunoassay for intact PINP.

RESULTS

Passing-Bablok regression analysis comparing both methods showed that with advancing chronic kidney disease there was a proportional positive bias affecting the total assay when compared with the intact assay. This proportional positive bias was statistically significant for chronic kidney disease stages 3b, 4 and 5.

CONCLUSIONS

Based on this method comparison study, usage of the total PINP assay should be avoided in chronic kidney disease stages 3b, 4 and 5 (eGFR ≤44 mL/min/1.73 m²) and instead an intact assay used as the total assay overestimates PINP concentrations due to monomeric PINP accumulation.

Role of Bone Turnover Markers in Osteoporosis Therapy

Bone turnover markers fill a clinical need that improves comprehensive care of metabolic bone health and osteoporosis. Creating a standard process for drawing them that reduces modifiable variability improves their precision and clinical usefulness. Creating a standard process for interpreting them by applying statistical significance improves their clinical applicability. Understanding what causes them to increase and decrease can help elucidate secondary causes of osteoporosis. Monitoring them can assess patient adherence to therapy for a silent disease that will progressively become louder with an aging global population.

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

Comparison of Bone Turnover Biomarkers in Serum and Urine Measured on an Automated Analytical Platform

BACKGROUND

Matched serum and urine samples from patients who had total hip replacement were used to assess serum-validated immunoassay reagents for use in urine.

METHODS

Samples were evaluated by an automated electrochemiluminescent immunoassay (cobas e411; Roche Diagnostics) for C-terminal telopeptide of type I collagen isoform β (β-Crosslaps), osteocalcin N-terminal midfragment (N-MID OC), N-terminal propeptide of type I collagen (PINP), and interleukin 6 (IL-6). Spike and recovery experiments were utilized to assess urinary matrix effects. Correlations between serum and both raw and creatinine-corrected urinary measures were assessed. Short-term precision was assessed.

RESULTS

Spike and recovery experiments indicated minimal matrix effects of urine for the β-Crosslaps assay. Potential matrix effects were observed for the other analytes because N-MID OC and IL-6 tended to be slightly overrecovered, whereas PINP was underrecovered. There were strong correlations between serum β-Crosslaps and raw (Spearman ρ [rs] = 0.725, P < 0.0001) and creatinine-corrected (rs = 0.793, P < 0.0001) urinary measures and moderate correlations between serum N-MID OC and raw (rs = 0.582, P < 0.0001) and creatinine-corrected (rs = 0.482, P < 0.0001) urinary measures. PINP was not detected in urine, and no significant serum-urine correlations were found for IL-6. Short-term precision for urinary levels of β-Crosslaps, N-MID OC, and IL-6 were 1.6%, 6.3% and 14.4%, respectively.

CONCLUSIONS

Urinary measurements of β-Crosslaps and N-MID OC assays were correlated with serum measurements and had good short-term precision. Urinary PINP was not detectable. IL-6 can be measured in urine using this technology, but the levels did not correlate with serum levels, and the short-term precision was variable.

Serum levels of bone formation and resorption markers in relation to vitamin D status in professional gymnastics and physically active men during upper and lower body high-intensity exercise

Purpose/introduction

To compare serum levels of bone turnover markers in athletes and non-athletes, and to evaluate the relationship between serum levels of vitamin D metabolites and exercise-induced changes in biomarker levels.

Methods

Sixteen elite male artistic gymnasts (EG; 21.4 ± 0.8 years-old) and 16 physically active men (the control group, PAM; 20.9 ± 1.2 years-old) performed lower and upper body 30-s Wingate anaerobic tests (LBWT and UBWT, respectively). For biomarker analysis, blood samples were collected before, and 5 and 30 min after exercise. Samples for vitamin D levels were collected before exercise. N-terminal propeptide of type I collagen (PINP) was analysed as a marker of bone formation. C-terminal telopeptide of type I collagen (CTX) was analysed as a marker of bone resorption.

Results

UBWT fitness readings were better in the EG group than in the PAM group, with no difference in LBWT readings between the groups. UBWT mean power was 8.8% higher in subjects with 25(OH)D₃ levels over 22.50 ng/ml and in those with 24,25(OH)₂D₃ levels over 1.27 ng/ml. Serum CTX levels increased after both tests in the PAM group, with no change in the EG group. PINP levels did not change in either group; however, in PAM subjects with 25(OH)D₃ levels above the median, they were higher than those in EG subjects.

Conclusion

Vitamin D metabolites affect the anaerobic performance and bone turnover markers at rest and after exercise. Further, adaptation to physical activity modulates the effect of anaerobic exercise on bone metabolism markers.

Analytical considerations and plans to standardize or harmonize assays for the reference bone turnover markers PINP and β-CTX in blood

Procollagen type I N-propeptide (PINP) and the C-terminal telopeptide of type I collagen (β-CTX) in blood have been designated as reference bone turnover markers in osteoporosis by the International Osteoporosis Foundation (IOF) and International Federation of Clinical Chemistry and Laboratory Medicine (IFCC). The IFCC Committee on Bone Metabolism (C-BM) has examined current commercial assays and performed a multicentre study to examine the agreement between assays for PINP and β-CTX in serum and plasma. The results of these studies will inform our work towards the harmonization of PINP assays and the standardization of β-CTX assays in blood, with the development of common calibrators and reference measurement procedures in collaboration with the reagent manufacturing industry. Successful achievement of these goals will help develop universally acceptable practice guidelines for the management of osteoporosis with the inclusion of common reference intervals and treatment targets for PINP and β-CTX.

Age- and sex-specific concentrations of bone remodeling markers in healthy Indian adults with and without vitamin D deficiency

Bone remodeling markers exhibit marked inter-ethnic variation; hence, population-specific data are required. Herein, we have established age- and sex-specific concentrations of serum PINP and CTX in healthy Indian adults with and without vitamin D deficiency that can be used in clinical practice for monitoring response to anti-osteoporotic therapy.

OBJECTIVE

The present study was undertaken to generate data on age- and sex-specific concentrations of serum procollagen type I N-propeptide (PINP) and type I collagen C-telopeptide (CTX) in healthy Indian adults with and without vitamin D deficiency.

METHODS

Apparently, healthy subjects aged ≥ 20 years with no prior co-morbidities were recruited from the community by door-to-door surveys. Provisionally eligible participants underwent blood sampling after overnight fast. Individuals with biochemical abnormalities that could potentially affect bone remodeling were excluded. However, subjects with vitamin D deficiency were not excluded. Serum total PINP and β-CrossLaps (CTX) were measured using electro-chemiluminescence immunoassay.

RESULTS

After exclusion, 677 subjects were enrolled (M:F = 2.5:4.2, mean age = 45.0 years). Median serum PINP and CTX were 55.78 ng/ml (40.27-71.70) and 0.356 ng/ml (0.238-0.499), respectively. There was no difference in PINP/CTX between men and women or between premenopausal and postmenopausal women. Decade-wise distribution of PINP/CTX showed that maximum values were attained in 3rd decade; subsequently, in men, levels declined with age while in women, there was a peak in the 6th decade coinciding with the early years of menopause. Vitamin D deficiency and severe vitamin D deficiency were seen in 417 (61.5%) and 259 subjects (38.2%), respectively. There was no significant difference in PINP/CTX in subjects with and without vitamin D deficiency.

CONCLUSIONS

The present study has allowed us to generate data on serum concentrations of PINP/CTX in a diverse group of healthy community-dwelling Indian adults with varying serum vitamin D levels. It might aid in monitoring response to anti-osteoporotic therapy amongst native Indians.

Tocilizumab controls bone turnover in early polymyalgia rheumatica

OBJECTIVES

This study explores changes in the bone homeostasis by testing the N-terminal collagen type I extension propeptide (PINP) marker for osteo-formation and the carboxy-terminal region of collagen type I (CTX-I) marker for osteo-resorption in patients taking tocilizumab for polymyalgia rheumatica (PMR).

METHODS

Twenty patients were included in the prospective open-label TENOR study (Clinicaltrials.gov NCT01713842) and received three monthly tocilizumab infusions, followed by corticosteroids starting at week (W) 12. PINP and CTX-I were tested at inclusion (W0), after tocilizumab but before steroid initiation (W12), at the end of the protocol (W24) and were compared to healthy controls. Information regarding disease activity, bone mineral density using scanographic bone attenuation correlation (SBAC), inflammatory parameters and interleukin (IL)-6 levels were collected during the follow-up of the patients.

RESULTS

PMR patients were characterised by a reduction in bone mineral density and a higher level of CTX-I relative to healthy controls matched in age and sex at baseline. PINP levels increased at W12 (P< 0.001, versus W0) following tocilizumab introduction and CTX-I levels decreased at W24 and after steroid initiation (P=0.001, versus W0). Such modifications explain the altered correlation observed between PINP and CTX-I at W0 (r=0.255 at W0 versus r=0.641 in healthy controls) and its correction after treatment (r=0.760 at W12 and r=0.767 at W24). Finally, greater changes in PINP were observed in patients whose circulating IL-6 levels decreased after tocilizumab therapy.

CONCLUSIONS

Control of bone turnover, in part through the inhibition of the IL-6 axis, is observed during tocilizumab and subsequent steroid treatment of PMR.

Bone Marrow Metabolism Is Impaired in Insulin Resistance and Improves After Exercise Training

CONTEXT

Exercise training improves bone mineral density, but little is known about the effects of training on bone marrow (BM) metabolism. BM insulin sensitivity has been suggested to play an important role in bone health and whole-body insulin sensitivity.

OBJECTIVE

To study the effects of exercise training on BM metabolism.

DESIGN

Randomized controlled trial.

SETTING

Clinical research center.

PARTICIPANTS

Sedentary healthy (n = 28, 40-55 years, all males) and insulin resistant (IR) subjects (n = 26, 43-55 years, males/females 16/10).

INTERVENTION

Two weeks of sprint interval training or moderate-intensity continuous training.

MAIN OUTCOME MEASURES

We measured femoral, lumbar, and thoracic BM insulin-stimulated glucose uptake (GU) and fasting free fatty acid uptake (FFAU) using positron-emission tomography and bone turnover markers from plasma.

RESULTS

At baseline, GU was highest in lumbar, followed by thoracic, and lowest in femoral BM (all Ps < 0.0001). FFAU was higher in lumbar and thoracic than femoral BM (both Ps < 0.0001). BM FFAU and femoral BM GU were higher in healthy compared to IR men and in females compared to males (all Ps < 0.05). Training increased femoral BM GU similarly in all groups and decreased lumbar BM FFAU in males (all Ps < 0.05). Osteocalcin and PINP were lower in IR than healthy men and correlated positively with femoral BM GU and glycemic status (all Ps < 0.05).

CONCLUSIONS

BM metabolism differs regarding anatomical location. Short-term training improves BM GU and FFAU in healthy and IR subjects. Bone turnover rate is decreased in insulin resistance and associates positively with BM metabolism and glycemic control.

CLINICAL TRIAL REGISTRATION NUMBER

NCT01344928.

Galectin-3, N-terminal Propeptides of Type I and III Procollagen in Patients with Atrial Fibrillation and Metabolic Syndrome

The aim of this study was to determine the concentration of galectin-3, PINP and PIIINP in patients with metabolic syndrome (MS) and atrial fibrillation (AF) with an assessment of the relationship with severity of left atrium fibrosis. A total of 480 subjects were included in the case-control study: MS patients (n = 337), 176 of whom had AF, 72 patients with AF without MS and 71 healthy subjects. Galectin-3, PINP and PIIINP blood concentrations and metabolic parameters were compared with the severity of left atrium fibrosis, measured by CARTO3. Galectin-3 in AF and MS patients is higher than in MS without AF and in healthy subjects (10.3 (4.8–15.4), 5.1 (4.3–8.8), 3.2 (2.4–4.2) ng/mL, p < 0.0001). Galectin-3 serum concentration in AF patients with MS is higher than in patients without MS: 10.3 (4.8–15.4), 6.8 (5.2–8.1) ng/mL, p = 0.0001. PINP and PIIINP concentration were higher in patients with AF and MS than in MS without AF: 3499.1 (2299.2–4567.3), 2130.9 (1425.3–2861.8) pg/mL, p < 0.0001, 94.9 (64.8–123.5), 57.6 (40.5–86.9) ng/mL, p < 0.0001. Galectin-3 correlates with PINP (r = 0.496, p < 0.001) and PIIINP concentration (r = 0.451, p < 0.0001). The correlation between galectin-3, PINP and the severity of left atrium fibrosis was found (r = 0.410, p < 0.001; r = 0.623, p < 0.001). Galectin-3 higher than 12.6 ng/mL increased the risk of AF more than five-fold. High galectin-3, PINP and PIIINP concentrations were associated with heart remodeling in MS patients and increased the risk of AF.

European Biological Variation Study (EuBIVAS): within- and between-subject biological variation estimates of β-isomerized C-terminal telopeptide of type I collagen (β-CTX), N-terminal propeptide of type I collagen (PINP), osteocalcin, intact fibroblast growth factor 23 and uncarboxylated-unphosphorylated matrix-Gla protein-a cooperation between the EFLM Working Group on Biological Variation and the International Osteoporosis Foundation-International Federation of Clinical Chemistry Committee on Bone Metabolism

We have calculated the biological variation (BV) of different bone metabolism biomarkers on a large, well-described cohort of subjects. BV is important to calculate reference change value (or least significant change) which allows evaluating if the difference observed between two consecutive measurements in a patient is biologically significant or not.

INTRODUCTION

Within-subject (CV_I) and between-subject (CV_G) biological variation (BV) estimates are essential in determining both analytical performance specifications (APS) and reference change values (RCV). Previously published estimates of BV for bone metabolism biomarkers are generally not compliant with the most up-to-date quality criteria for BV studies. We calculated the BV and RCV for different bone metabolism markers, namely β-isomerized C-terminal telopeptide of type I collagen (β-CTX), N-terminal propeptide of type I collagen (PINP), osteocalcin (OC), intact fibroblast growth factor 23 (iFGF-23), and uncarboxylated-unphosphorylated Matrix-Gla Protein (uCuP-MGP) using samples from the European Biological Variation Study (EuBIVAS).

METHODS

In the EuBIVAS, 91 subjects were recruited from six European laboratories. Fasting blood samples were obtained weekly for ten consecutive weeks. The samples were run in duplicate on IDS iSYS or DiaSorin Liaison instruments. The results were subjected to outlier and variance homogeneity analysis before CV-ANOVA was used to obtain the BV estimates.

RESULTS

We found no effect of gender upon the CV_I estimates. The following CV_I estimates with 95% confidence intervals (95% CI) were obtained: β-CTX 15.1% (14.4-16.0%), PINP 8.8% (8.4-9.3%), OC 8.9% (8.5-9.4%), iFGF23 13.9% (13.2-14.7%), and uCuP-MGP 6.9% (6.1-7.3%).

CONCLUSIONS

The EuBIVAS has provided updated BV estimates for bone markers, including iFGF23, which have not been previously published, facilitating the improved follow-up of patients being treated for metabolic bone disease.

Effects of post exercise protein supplementation on markers of bone turnover in adolescent swimmers

BACKGROUND

This study examined the effects of whey protein supplementation, compared with an isocaloric carbohydrate beverage and water, consumed immediately following an intense swimming trial on bone turnover in adolescent swimmers.

METHODS

Fifty-eight (31 female, 27 male) swimmers (14.1 ± 0.4 years) were stratified into three groups matched for age, sex and body mass. The protein and carbohydrate groups consumed two isocaloric post-exercise beverages each containing 0.3 g^.kg^- 1 of whey protein (with ~ 6 mg of calcium) or maltodextrin while the control group consumed water. Participants provided a morning, fasted, resting blood sample, then performed an intense swimming trial consisting of a maximal 200 m swim followed by a high intensity interval swimming protocol (5x100m, 5x50m and 5x25m; 1:1 work-to-rest ratio). Following swimming, they consumed their first respective post-exercise beverage, and 2 h later, they performed a second maximal swim immediately followed by the second beverage. Approximately 3 h after the second beverage, two post-consumption blood samples were collected at 8 h and 24 h from baseline. Procollagen type 1 intact N-terminal propeptide (PINP) and carboxy-terminal collagen crosslinks (CTXI) were measured in serum. The multiples of medians of PINP and CTXI were also used to calculate bone turnover rate and balance.

RESULTS

No significant changes were observed in PINP. CTXI increased (+ 11%) at 8 h in all groups, but then significantly decreased (- 22%) at 24 h in the protein group only. The protein group also had a significantly higher calculated rate of bone turnover at 8 h and 24 h compared to baseline, which was not observed in the other groups.

CONCLUSIONS

These results shed light on the potential importance of protein consumed shortly after intense swimming in promoting positive bone turnover responses up to 24 h following exercise in adolescent athletes.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov PRS; NCT04114045. Registered 1 October 2019 - Retrospectively registered.

Harmonization of commercial assays for PINP; the way forward

International Federation of Clinical Chemistry and Laboratory Medicine and The International Osteoporosis Foundation Joint Committee on Bone Metabolism believes that the harmonization of PINP assays is an achievable and practical goal.

INTRODUCTION

In order to examine the agreement between current commercial assays, a multi-center study was performed for PINP in serum and plasma.

METHODS

The automated methods for PINP (Roche Cobas and IDS iSYS) gave similar results. A significant proportional bias was observed between the two automated assays and the Orion radioimmunoassay (RIA) for PINP.

RESULTS

Results from other published studies comparing PINP values among these three assays broadly support our findings. Taken together, these results confirm that harmonized PINP measurements exist between the two automated assays (Roche Cobas and IDS iSYS) when the eGFR is > 30 mL/min/1.73m², but a significant bias exists between the Orion RIA and the two automated assays.

CONCLUSION

Therefore, in subjects with normal renal function, PINP results reported by the Roche Cobas and IDS iSYS assays are similar and may be used interchangeably, and similar reference intervals and treatment targets could be applied for the two automated assays. Harmonization between the automated assays and the RIA is potentially possible with the use of common calibrators and the development of a reference method for PINP. This should also help ensure that any new commercial assay developed in the future will attain similar results. IOF and IFCC are committed to working together towards this goal with the cooperation of the reagent manufacturing industry.

Association between glycosylated hemoglobin A1c and bone biochemical markers in type 2 diabetic postmenopausal women: a cross-sectional study

BACKGROUND

type 2 diabetes mellitus (T2DM) is a complicated disease that can affect bone health, but the change in bone biochemical markers caused by T2DM was controversial, so the aim of this study was to investigate whether there was a discrepancy in the levels of bone biochemical markers between postmenopausal women with T2DM and non-diabetic women and to explore the relationship between the level of glycosylated hemoglobin A1c (HbA1c) and bone biochemical markers in these subjects.

METHODS

A total of 237 type 2 diabetic postmenopausal women visiting the First Affiliated Hospital of Anhui Medical University from January 2017 to October 2018 and 93 healthy postmenopausal women were retrospectively enrolled. The differences in the levels of bone biochemical markers between patients and controls were analyzed by one-way ANOVA or chi-square test. The relationship between HbA1c and bone biochemical markers was analyzed by multivariate regression, forest plot and fitted curve.

RESULTS

Bone formation markers including N-MID osteocalcin and procollagen type 1 amino-terminal pro-peptide (PINP) were decreased in postmenopausal women with T2DM compared to controls (17.42 ± 9.50 vs 23.67 ± 7.58, p < 0.001; 48.47 ± 27.27 vs 65.86 ± 21.06, p < 0.001, respectively), but the bone resorption markers β-crossLaps (β-CTX) was no difference between the two groups (0.57 ± 0.28 vs 0.55 ± 0.21, p = 0.868). Multivariate regression showed that HbA1c was inversely associated with N-MID osteocalcin and PINP after adjusting for age, BMI, menopause^'s years, diabetic duration, TC, TG, HDL-c, LDL-c, creatinine, UA and eGFR. The adjusted coefficients for N-MID osteocalcin and PINP per 1% HbA1c decrease were - 0.71 (- 1.19, - 0.22) and - 1.79 (- 3.30, - 0.28), respectively. A segmentation effect was seen in the fitted curve between HbA1c and β-CTX with an inflection point at 7.4% of HbA1c, the highest quartile of β-CTX (> = 0.74 ng/ml) showed a significantly negative with HbA1c. No significant association was seen between HbA1c and other biochemical markers.

CONCLUSIONS

Our study found that bone formation was inhibited in postmenopausal women with T2DM, but bone resorption was not affected, and poor glycemic control was related to lower levels of bone formation, may increase the risk of bone fracture in postmenopausal women with T2DM.

Reference markers of bone turnover for prediction of fracture: a meta-analysis

OBJECTIVE

To explore whether bone turnover biomarkers (BTMs), i.e., C-terminal telopeptide of type I collagen (CTX) and procollagen type I aminoterminal propeptide (PINP), are associated with fracture.

METHODS

We searched electronic database including PubMed, Embase and Cochrane Library, and the reference lists of relevant articles published from inception to August 22, 2018. An updated meta-analysis was performed to assess the prediction value of CTX and PINP in fracture.

RESULTS

Nine articles met our inclusion criteria and were included in the meta-analysis. The crude and adjusted effect size between PINP and fracture were extracted from two and five studies, respectively. PINP was not associated with fracture incidence without adjusting covariates (crude GR, 1.03; 95% CI, 0.91-1.17). After adjusting for potential confounders, PINP demonstrated a significant positive association with fracture (adjusted GR, 1.28; 95% CI, 1.15-1.42). In the subgroup analysis of studies after adjusting covariates, there were significant associations in women. Both the crude (1.16, 95%CI, 1.04-1.20) and adjusted GR (1.20, 95%CI, 1.05-1.37) shown positive relationships between CTX and fracture, which were extracted from four and six studies, separately. The sensitivity analysis confirmed the stability of the results. In the subgroup analysis of studies after adjusting covariates, there were significant associations in the subgroups of elderly, female, and hip fracture patients.

CONCLUSIONS

Our results indicate a statistically significant but modest association between BTMs (s-PINP or s-CTX) and future fracture risk after adjusting for BMD and clinical risk factors. The causal relationship between the two clinical conditions requires future validation with more standardized studies.

REGISTRATION NUMBER

CRD42018107879.

Contribution of bone turnover markers to the variation in bone mineral density: a study in Vietnamese men and women

The present cross-sectional study constructed reference ranges for bone resorption marker beta isomerized form of C-terminal crosslinking telopeptides of type I collagen (beta-CTX) and bone formation marker procollagen type 1 N-terminal propeptide (PINP) for the Vietnamese population. We have further shown that for a given age and weight, higher levels of beta-CTX were significantly associated with bone mineral density in men and women.

INTRODUCTION

Normal bone is constantly renewed by two opposing processes of resorption and formation which can be reflected by bone turnover markers (BTMs). This study sought to define the contribution of BTMs to the variation in bone mineral density (BMD) in normal individuals.

METHODS

The study involved 205 men and 432 women aged between 18 and 87, who were randomly selected from various districts within Ho Chi Minh City, Vietnam. Fasting serum levels of PINP and beta-CTX were determined by electrochemiluminescence (Roche, ECLIA). BMD at the lumbar spine (LS) and femoral neck (FN) was measured by dual-energy x-ray absorptiometry (Hologic, Waltham, MA, USA).

RESULTS

Among those aged < 50 years, women had lower PINP and beta-CTX levels than men, but among those aged > 50 years, women had higher PINP and beta-CTX levels than men. In the multiple linear regression analysis, beta-CTX-but not PINP-was significantly associated with both femoral neck (P = 0.008) and lumbar spine BMD (P = 0.008) and the association was independent of gender, age, and body weight. The proportion of variance in BMD attributable to beta-CTX was 1% for femoral neck BMD and 2% for lumbar spine BMD.

CONCLUSION

The elevation in bone formation marker PINP and bone resorption marker beta-CTX in postmenopausal women was greater than in elderly men. However, only beta-CTX was modestly but significantly associated with BMD.

Clinical utility of bone markers in various diseases

Measurements of bone markers (BMs) in peripheral blood or urine are a pivotal part of bone research within modern clinical medicine. In recent years the use of BMs increased substantially as they can be useful either to diagnose bone (related) disease and to follow its natural history, but also to monitor the effects of interventions. However, the use of BMs is still complicated mainly due to (pre)analytical variability of these substances, limited accessibility of assays, variable cut-off values in different countries and laboratories and heterogeneous results with regard to clinical implications of measuring BMs in several studies. This review will provide the clinician with a practical guide, based on current evidence, in which circumstances to test which bone markers for optimal diagnostic purposes, in order to improve patient care in different areas of bone diseases including Paget's disease, primary osteoporosis, tumor induced osteomalacia, hypophosphatemic rickets, van Buchem disease, chronic kidney disease, rheumatoid arthritis, neoplasma/multiple myeloma, type 2 diabetes mellitus and primary hyperparathyroidism. The clinician should consider fasting state, recent fractures, aging, menopausal status, concomitant liver and kidney disease when ordering and interpreting BM measurements as these factors might result in misleading BM concentrations. We found that BMs are clearly useful in the current diagnosis of tumor induced osteomalacia, van Buchem disease, Paget's disease and hypophosphatemic rickets. In addition, BMs are useful to monitor disease activity in chronic kidney disease, Paget's disease and are useful to monitor treatment adherence in osteoporosis.

Bone Turnover Markers Are Not Associated With Hip Fracture Risk: A Case-Control Study in the Women's Health Initiative

Current guidelines recommend that serum C-terminal telopeptide of type I collagen (CTX) and serum procollagen type 1 aminoterminal propeptide (PINP), measured by standardized assays, be used as reference markers in observational and interventional studies. However, there are limited data to determine whether serum CTX and PINP are associated with hip fracture risk among postmenopausal women. We determined the associations of serum CTX and serum PINP with hip fracture risk among postmenopausal women aged 50 to 79 years at baseline. We performed a prospective case-control study (400 cases, 400 controls) nested in the Women's Health Initiative Observational Study, which enrolled participants at 40 US clinical centers. Cases were women with incident hip fracture not taking osteoporosis medication; hip fractures were confirmed using medical records. Untreated controls were matched by age, race/ethnicity, and date of blood sampling. Serum CTX and serum PINP were analyzed on 12-hour fasting blood samples. The main outcome measure was incident hip fracture risk (mean follow-up 7.13 years). After adjustment for body mass index, smoking, frequency of falls, history of fracture, calcium and vitamin D intake, and other relevant covariates, neither serum CTX level nor serum PINP level was statistically significantly associated with hip fracture risk (CTX p_trend  = 0.22, PINP p_trend  = 0.53). Our results do not support the utility of serum CTX level or PINP level to predict hip fracture risk in women in this age group. These results will inform future guidelines regarding the potential utility of these markers in fracture prediction. © 2018 American Society for Bone and Mineral Research.

Periostin and sclerostin levels in juvenile Paget's disease

Juvenile Paget's disease (JPD) is a rare, autosomal recessive disorder featuring markedly increased serum alkaline phosphatase activity, indicative of greatly accelerated bone turnover throughout the skeleton. The main aim of this study was to evaluate circulating periostin and sclerostin levels in two adult patients with mild JPD (due to "Balkan" mutation). We measured periostin and sclerostin levels in a previously described woman and a newly diagnosed man with JPD, and 10 apparently healthy individuals, matched (1:5) to JPD patients for gender, age and body mass index. Sclerostin levels were similar between JPD patients and controls. Periostin levels were about 2.5 times higher in JPD patients. Periostin and sclerostin levels were negatively correlated (rs= -0.63; p=0.03). In conclusion, a trend towards higher periostin levels was observed in JPD patients, whereas sclerostin levels were similar to controls.

Improvement of cancellous bone microstructure in patients on teriparatide following alendronate pretreatment

An increase in procollagen type I amino-terminal propeptide (PINP) early after teriparatide initiation was shown to correlate with increased lumbar spine areal BMD and is a good predictor of the anabolic response to teriparatide. Few data exist correlating PINP and bone microstructure, and no data exist in patients on teriparatide following prior potent antiresorptive treatment. This exploratory analysis aimed to investigate the effects of teriparatide on cancellous bone microstructure and correlations of bone markers with microstructure in alendronate-pretreated patients. This was a post hoc analysis of changes in bone markers and three-dimensional indices of bone microstructure in paired iliac crest biopsies from a prospective teriparatide treatment study in postmenopausal women with osteoporosis who were either treatment-naïve (TN, n=16) or alendronate-pretreated (ALN, n=29) at teriparatide initiation. Teriparatide (20μg/day) was given for 24months; biopsies were taken at baseline and endpoint, and serum concentrations of PINP and type 1 collagen cross-linked C-telopeptide (βCTX) were measured at intervals up to 24months. In the TN and ALN groups, respectively, mean (SD) increases in three-dimensional bone volume/tissue volume were 105 (356)% (P=0.039) and 55 (139)% (P<0.005) and trabecular thickness 30.4 (30)% (P<0.001) and 30.8 (53)% (P<0.001). No significant changes were observed in trabecular number or separation. In the ALN patients, 3-month change of neither PINP nor βCTX correlated with indices of cancellous bone microstructure. However, 12-month changes in biochemical bone markers correlated significantly with improvements in bone volume/tissue volume, r=0.502 (P<0.01) and r=0.378 (P<0.05), trabecular number, r=0.559 (P<0.01) and r=0.515 (P<0.01), and reduction of trabecular separation, r=-0.432 (P<0.05) and r=-0.530 (P<0.01), for PINP and βCTX, respectively. We conclude that cancellous bone microstructure improved with teriparatide therapy irrespective of prior antiresorptive use.

Effects of immobilization and whole-body vibration on rat serum Type I collagen turnover

Objective

The aim of this study was to investigate the effects of short-term, high-magnitude whole-body vibration (WBV) on serum type I collagen turnover in immobilized rats.

Materials and Methods

Thirty Wistar albino rats were randomly divided into the following 5 groups: immobilization (IS), immobilization + remobilization (IR), immobilization + WBV (IV), control (C), and WBV control (CV). Immobilization was achieved by casting from the crista iliaca anterior superior to the lower part of the foot for 2 weeks. The applied WBV protocol involved a frequency of 45 Hz and amplitude of 3 mm for 7 days starting a day after the end of the immobilization period. Serum type I collagen turnover markers were measured by using ELISA kits.

Results

Serum NH2-terminal propeptide of type I collagen (PINP) levels were significantly lower in the immobilization groups (p < 0.02) compared with the control groups. Although WBV improved PINP levels in the control groups, there were no differences in PINP levels among the immobilization groups. Similarly, serum COOH-terminal telopeptide of type I collagen (CTX) levels were higher in the WBV controls than their own controls (p < 0,05). Immobilization led to deterioration of tendon tissue, as observed by histopathological analysis with a transmission electron microscope.

Conclusion

Although 1 week of WBV had a positive effect on type I collagen turnover in controls, it is not an efficient method for repairing tissue damage in the early stage following immobilization.

Clinical usefulness of bone turnover marker concentrations in osteoporosis

Current evidence continues to support the potential for bone turnover markers (BTM) to provide clinically useful information particularly for monitoring the efficacy of osteoporosis treatment. Many of the limitations identified earlier remain, principally in regard to the relationship between BTM and incident fractures. Important data are now available on reference interval values for CTX and PINP across a range of geographic regions and for individual clinical assays. An apparent lack of comparability between current clinical assays for CTX has become evident indicating the possible limitations of combining such data for meta-analyses. Harmonization of units for reporting serum/plasma CTX (ng/L) and PINP (μg/L) is recommended. The development of international collaborations continues with an important initiative to combine BTM results from clinical trials in osteoporosis in a meta-analysis and an assay harmonization program are likely to be beneficial. It is possible that knowledge derived from clinical studies can further enhance fracture risk estimation tools with inclusion of BTM together with other independent risk factors. Further data of the relationships between the clinical assays for CTX and PINP as well as physiological and pre-analytical factors contributing to variability in BTM concentrations are required.

Treatment of osteoporosis with eldecalcitol, a new vitamin D analog: a comprehensive review and meta-analysis of randomized clinical trials

OBJECTIVE

Eldecalcitol (ELD) is an active form of vitamin D analog that has been approved for the treatment of osteoporosis in Japan. Over recent years, a number of multicenter, randomized controlled clinical trials have been conducted. Our goal is to comprehensively summarize the results from these studies.

METHODS

We searched the databases MEDLINE, EMBASE, and Cochrane Central Register of Controlled Trials up to February 28, 2015. Each database was searched using search terms "Eldecalcitol" and "ED-71" and the results were combined. The retrieved data from three independent clinical trials included a total of 1,332 patients with osteoporosis. After the data were pooled from three trials, RevMan software was used to conduct meta-analyses to determine the effects of ELD on bone mineral density (BMD) and bone turnover marker (BTM) type I collagen amino-terminal telopeptide (NTX). Effects of ELD on some of the bone formation and bone resorption parameters, incidence of vertebral fractures at the lower spine, and health-related quality of life (HRQOL) in patients with osteoporosis were also summarized.

RESULTS

With a test for overall effect Z=6.35, ELD could increase lumbar BMD (P<0.00001). In comparison with alphacalcidol, ELD suppressed the NTX level to a greater degree (test for overall effect Z=3.82,P<0.0001). ELD was also found to suppress bone alkaline phosphatase (BALP) by 19% (P<0.01) and osteocalcin by 19% (P<0.01) at the dose of 0.75 μg/day. Compared to alfacalcidol, ELD showed higher potency in suppressing serum BALP (26±9 vs 32±11 U/L,P<0.05) and amino-terminal propeptide of procollagen I (PINP) (42±15 vs 59±23 ng/mL,P<0.05). In addition, ELD was found to be more effective in reducing the incidence of vertebral fractures at the lower spine (P=0.029).

CONCLUSION

Our meta-analysis showed that ELD was more potent than alphacalcidol in reducing BTM (NTX). Clinical data together suggest that ELD is efficient in treating osteoporosis by increasing lumbar BMD; suppressing BTMs, including NTX, BALP, osteocalcin, and PINP; resulting in the reduction in the incidence of vertebral fractures at the lower spine; and increasing the HRQOL in patients with osteoporosis.

Associations between frailty and serum N-terminal propeptide of type I procollagen and 25-hydroxyvitamin D in older Spanish women: The Toledo Study for Healthy Aging

Frail older people are at high risk for fractures and falls increasing the rates of institutionalization and mortality. Bone markers have been related to both aging and fractures. However, no previous reports have shown a potential relationship between serum bone markers such as N-terminal propeptide of type I procollagen (PINP), C-terminal telopeptide of type I collagen (β-CTX) and parathyroid hormone (PTH) with frailty in elderly female populations. This study is aimed at examining the associations of bone metabolism markers and frailty in older Spanish women through a descriptive cross-sectional analysis based on a cohort of the Toledo Study for Healthy Aging (TSHA). The levels of serum PINP, β-CTX, PTH and 25-hydroxyvitamin D (25(OH)D) were assessed in 592 participants (median age 74years) who were defined as robust, prefrail and frail according to Fried's approach. Frail subjects had significantly high levels of PINP, β-CTX and PTH and low production of 25(OH)D. After adjustment for confounders, high PINP levels (defined by the upper quartile) and low levels of 25(OH)D (lower quartile) remained significantly associated to frailty [OR for PINP: 2.19 (95% CI, 1.15-4.18; P=0.017); OR for 25(OH)D: 1.65 (95% CI, 1.02-2.67; P=0.042)]. Women with both high PINP levels and low 25(OH)D levels presented a 5.85-fold increased frailty risk (95% CI, 1.64-20.93; P=0.007). The main contribution of this paper is the novel definition of PINP and 25(OH)D markers as potential biomarkers of frailty and targets for intervention.

Relationship between pretreatment rate of bone loss and bone density response to once-yearly ZOL: HORIZON-PFT extension study

Several studies have shown that high bone turnover is associated with greater rates of bone loss and greater bone mineral density (BMD) response to antiresorptive therapy in postmenopausal osteoporosis. However, it is not known whether greater rates of bone loss before therapy are associated with greater BMD response to antiresorptive therapy. In the HORIZON-PFT study and its extension, one group of women who were randomized to receive placebo for 3 years (years 1, 2, and 3) were then switched to zoledronic acid (ZOL) 5 mg annually for up to three injections (years 4, 5, and 6, P3Z3 arm) (n = 1223). We measured total hip BMD at baseline, 1, 2, and 3 years on placebo and at 4.5 and 6 years on ZOL. The procollagen type I N-terminal propeptide (PINP) was measured at 3, 4.5, and 6 years. By design, not all subjects were followed for as long as 6 years, so this analysis focused on the results at 4.5 years. Those with the largest loss in total hip BMD on placebo in years 0 to 3 had the largest gain during ZOL (years 3 to 4.5): (r = -0.39, p < 0.0001). The change in total hip BMD in years 0 to 3 on placebo was related to the serum PINP at the end of the 3-year period (r = -0.24, p < 0.0001). The change in total hip BMD on ZOL from year 3 to 4.5 was related to the serum PINP at the end of the 3-year period (r = 0.26, p < 0.0001). We conclude that BMD response to ZOL is greater in postmenopausal women who had larger loss before treatment. This association may result from higher bone turnover being associated with both greater bone loss on placebo and greater BMD response to ZOL.

Determinants associated with bone mineral density increase in response to daily teriparatide treatment in patients with osteoporosis

INTRODUCTION

Several factors associated with bone mineral density (BMD) increase are reported with daily teriparatide treatment, but there has been no systematic analysis to summarize these associations. The purpose of this study was to investigate the clinical determinants associated with BMD increase to daily teriparatide treatment.

METHODS

This was a retrospective study. We performed an analysis of 306 patients diagnosed with osteoporosis. Teriparatide was administered at 20μg/day for 12months. The primary efficacy measure was a change in lumbar spine (LS) BMD from baseline at 12months. To determine the response variables of BMD changes, we investigated the clinical determinants using univariate and multivariate analyses.

RESULTS

There was a 9.8±8.2% increase in LS BMD after 12months. Prior bisphosphonate treatment and baseline procollagen type I N-terminal propeptide (PINP) concentration were significantly associated with LS BMD absolute response by univariate analyses. In the multiple regression model, patients with higher baseline PINP concentration had a significantly greater LS BMD absolute increase. Prior bisphosphonate use lost its correlation in the multiple regression models.

CONCLUSION

Our results showed that baseline PINP concentration was a useful predictor of LS BMD absolute increase regardless of prior treatment.

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.

The association between insulin-like growth factor I and bone turnover markers in the general adult population

OBJECTIVES

Growth hormone (GH) and its main mediator, insulin-like growth factor I (IGF-I), play a fundamental role in human metabolism. Previous epidemiological studies investigating the association of IGF-I and bone turnover markers (BTMs) yielded conflicting results and were limited by study design or sample size. Therefore, we aimed to investigate the associations between serum levels of IGF-I or the IGF-I/IGF binging protein 3 (IGFBP-3) ratio and levels of BTMs including procollagen type 1 N-terminal propeptide (PINP), C-terminal telopeptides of type 1 collagen (CTX), and bone-specific alkaline phosphatase (BAP).

METHODS

Data from 1463 men and 1481 women who participated in the first follow-up of the Study of Health in Pomerania were used. IGF-I and IGFBP-3 levels were measured using chemiluminescent immunometric assays on an Immulite 2500 analyzer. BTM levels were measured on the IDS-iSYS Multi-Discipline Automated Analyser. Analyses of variance (ANOVA) and quantile regression models were calculated.

RESULTS

In men <55 years and premenopausal women ANOVA and quantile regression analyses revealed positive associations between IGF-I or even stronger the IGF-I/IGFBP-3 ratio and PINP [per unit increase in IGF-I/IGFBP-3 ratio in men: beta (95%-CI) 2.33 ng/ml (0.91; 3.75), p < 0.01; women: 3.63 ng/ml (2.31; 4.95), p < 0.01] or CTX [men: 20.8 ng/l (3.5; 38.0), p = 0.02; women: 12.0 ng/l (-1.2; 25.2), p = 0.07]. Furthermore in postmenopausal women, IGF-I and the IGF-I/IGFBP-3 ratio were inversely related with CTX levels, whereas an inverse U-shaped relation between IGF-I/IGFBP-3 ratio and PINP was found. Regarding BAP, we observed borderline significant associations with IGF-I or the IGF-I/IGFBP-3 ratio in older subjects only.

CONCLUSION

IGF-I levels and particularly free IGF-I, estimated by the IGF-I/IGFBP-3 ratio, are positively related with PINP as a bone formation marker and CTX as a bone resorption marker in healthy adult men younger than 55 years and premenopausal women. In older subjects the found positive as well as negative relations with BTMs have to be further investigated.

Peripubertal female athletes in high-impact sports show improved bone mass acquisition and bone geometry

OBJECTIVE

Intensive physical training may have a sport-dependent effect on bone mass acquisition. This cross-sectional study evaluated bone mass acquisition in girls practicing sports that put different mechanical loads on bone.

MATERIALS/METHODS

Eighty girls from 10.7 to 18.0 years old (mean 13.83 ± 1.97) were recruited: 20 artistic gymnasts (AG; high-impact activity), 20 rhythmic gymnasts (RG; medium-impact activity), 20 swimmers (SW, no-impact activity), and 20 age-matched controls (CON; leisure physical activity <3h/wk). Areal bone mineral density (aBMD) was determined using DEXA. Hip structural analysis applied at the femur evaluated cross-sectional area (CSA, cm(2)), section modulus (Z, cm(3)), and buckling ratio. Bone turnover markers and OPG/RANKL levels were analyzed.

RESULTS

AG had higher aBMD than SW and CON at all bone sites and higher values than RG in the lumbar spine and radius. RG had higher aBMD than SW and CON only in the femoral region. CSA and mean cortical thickness were significantly higher and the buckling ratio was significantly lower in both gymnast groups compared with SW and CON. In RG only, endocortical diameter and width were reduced, while Z was only increased in AG compared with SW and CON. Reduced bone remodeling was observed in RG compared with AG only when groups were subdivided according to menarcheal status. All groups showed similar OPG concentrations, while RANKL concentrations increased with age and were decreased in SW.

CONCLUSION

High-impact activity clearly had a favorable effect on aBMD and bone geometry during the growth period, although the bone health benefits seem to be more marked after menarche.

Carboxy-terminal telopeptide (CTX) and amino-terminal propeptide (PINP) of type I collagen as markers of bone metastases in patients with non-small cell lung cancer

The early diagnosis of non-small cell lung carcinoma (NSCLC) is difficult, and 30-40% of patients with NSCLC develop bone metastases (BMs) during the course of their disease. Because the delayed demonstration of skeletal involvement may seriously affect survival, there is a need for early diagnosis of BMs. Unfortunately, the sensitivity of common serum tumor markers is low and they are used mainly for monitoring the efficacy of therapy and detection of recurrence. The aim of this study was to evaluate the utility of a panel of serum biomarkers in patients with NSCLC and BMs. Sixteen patients (11 males, 5 females; median age=64 years, range 54-68 years) with NSCLC and BMs (cases), and 18 age- and stage-matched patients without BMs (controls) underwent measurement of serum carboxy-terminal telopeptide of type I collagen (CTX), tartrate-resistant acid phosphatase isoform type 5b (TRAP5b) and amino-terminal propeptide of type I collagen (PINP), carcinoembryonic antigen (CEA) and fragments of cytokeratin 19 (CYFRA 21-1. CTX (443.7 ± 945.1 vs. 402.7 ± 28.4 pg/ml, p=0.003) and PINP (75.9 ± 11.4 vs. 64.1 ± 7.5 μg/l, p=0.001) were significantly higher in patients with BMs, while the mean value of the other markers did not differ (p=NS) between cases and controls. The sensitivity, specificity and accuracy were 73.3%, 86.7% and 79.4% for CTX; 55.5%, 62.5% and 58.8% for CEA; 65.0%, 78.6% and 70.6% for CYFRA; 30.4%, 76.2% and 67.6% for TRAP5b; and 72.2%, 81.2% and 76.5% for PINP, respectively. The area under the receiver operating characteristic curve (AUC) for CTX was 0.68. In conclusion, CTX and PINP measurement can be useful in monitoring patients with NSCLC during follow-up, with the aim of detecting BMs early.

Clinical Chemistry and Other Laboratory Tests on Mouse Plasma or Serum

Besides hematological analyses, many other parameters, including clinical chemistry and endocrinological values, can be determined from mouse blood samples. For most of these tests, plasma or serum samples are used. Data obtained by these investigations provide indications of genotype effects on metabolism and organ functions. Here we describe in detail the considerations that have to be taken into account to get adequate samples for plasma or serum analyses and the recommended sample processing for different investigations. Furthermore, we describe established methods used in the German Mouse Clinic (GMC) to determine clinical chemical parameters; for more in-depth analysis of specific classes of biomarkers, we provide instructions for ELISAs (sandwich and competitive) as well as LC-MS/MS, focusing on markers associated with bone or steroid metabolism in the mouse as working examples. Curr. Protoc. Mouse Biol. 3:69-100 © 2013 by John Wiley & Sons, Inc.