The effects of denosumab on osteoclast precursors in postmenopausal women: a possible explanation for the overshoot phenomenon after discontinuation.

Upon denosumab discontinuation, an observed overshoot phenomenon in bone turnover may occur, potentially leading to a reduction in bone mineral density and the occurrence of vertebral fractures. Several theories have been proposed to explain this phenomenon, one of which is that osteoclast precursors might be accumulating during treatment. Our aim was to study the effects of denosumab on osteoclast precursors in postmenopausal women. This cross-sectional observational study included 30 postmenopausal women with osteopenia or osteoporosis, divided into two groups: 15 treated with denosumab (mean duration 4 years, range 6 months-9 years) and 15 treatment-naïve controls. Peripheral blood mononuclear cells (PBMCs) were isolated from whole blood and were stained for CD14, MCSFR, CD11b and TNFRII. Osteoclast precursors (CD14+/MCSFR+, CD14+/CD11b + OR CD14+/TNFRII+) were identified with fluorescent activated cell sorting (FACS). The proportion of osteoclasts was determined by calculating their percentage of the total cell population in each whole blood sample. To confirm the expected suppression of bone turnover in the subjects treated with denosumab, we measured serum PINP, CTX and TRACP5b. Denosumab-treated patients exhibited a significantly higher count of CD14+/CD11b + osteoclast precursors compared to controls (median 4% vs 0.75%, P=.011). There was no correlation with the duration of treatment. Bone turnover markers were significantly lower in the group treated with denosumab than controls. Our findings indicate an increase in osteoclast precursors, which could explain the overshoot phenomenon observed after discontinuing denosumab.

Denosumab is an anti-osteoporotic medication that has proven effective in preventing bone loss and reducing the incidence of fractures. When it is discontinued, there is a risk of overshoot in markers of bone turnover, which may lead to a reduction in bone mineral density and new vertebral fractures. Whilst we suspect the mechanism underlying this phenomenon, we do not know the process in any detail in terms of the cells involved, particularly the role of the progenitors of bone cells that break down bone tissue (osteoclast precursors). We found that in postmenopausal women treated with denosumab, there is an increase in one of the populations of osteoclast precursors. On denosumab discontinuation, accumulated cells can mature into osteoclasts, which remove bone and lead to the overshoot of bone turnover and decreased bone density.

The impact of androgen deprivation therapy on bone microarchitecture in men with prostate cancer: A longitudinal observational study (The ANTELOPE Study).

Introduction: Androgen Deprivation Therapy (ADT) for prostate cancer (PC) has substantial negative impacts on the musculoskeletal system and body composition. Many studies have focused on the effects of ADT on areal bone mineral density (aBMD), but aBMD does not capture key determinants of bone strength and fracture risk, for example volumetric bone density (vBMD), geometry, cortical thickness and porosity, trabecular parameters and rate of remodelling. More specialist imaging techniques such as high-resolution peripheral quantitative computed tomography (HR-pQCT) have become available to evaluate these parameters. Although it has previously been demonstrated that bone microarchitectural deterioration occurs in men undergoing ADT, the aim of the ANTELOPE study was to examine longitudinal changes in bone microstructure alongside a range of musculoskeletal parameters and frailty, comparing men with PC receiving ADT alone or ADT plus chemotherapy for metastatic disease, with a healthy age-matched population. Methods: We used HR-pQCT to investigate effects of 12 months of ADT on vBMD and microstructural parameters, complemented by assessment of changes in aBMD, serum bone turnover markers, sex hormones, body composition, grip strength, physical and muscle function, frailty and fracture risk. We studied three groups: Group A - men with localised/locally advanced PC due to commence ADT; Group B - men with newly diagnosed hormone-sensitive, metastatic PC, starting ADT alongside docetaxel chemotherapy and steroids; Group C - healthy, age-matched men. The primary endpoint was change in vBMD (Group A vs Group C) at the distal radius. Results: Ninety-nine participants underwent baseline study assessments (Group A: n = 38, Group B: n = 30 and Group C: n = 31). Seventy-five participants completed all study assessments (Group A (29), Group B (18), Group C (28). At baseline, there were no significant differences between Groups A and C in any of the BMD or bone microstructure outcomes of interest. After 12 months of ADT treatment, there was a significantly greater decrease in vBMD (p < 0.001) in Group A (mean 12-month change = -13.7 mg HA/cm3, -4.1 %) compared to Group C (mean 12-month change = -1.3 mg HA/cm3, -0.4 %), demonstrating achievement of primary outcome. Similar effects were observed when comparing the change in vBMD between Group B (mean 12-month change = -13.5 mg HA/cm3, -4.3 %) and Group C. These changes were mirrored in aBMD. ADT resulted in microstructural deterioration, a reduction in estimated bone strength and an increase in bone turnover. There was evidence of increase in total fat mass and trunkal fat mass in ADT-treated patients, with marked loss in upper limb mass, along with BMI gain. Frailty increased and physical performance and strength deteriorated in both ADT groups, relative to the healthy control group. Conclusion: The study showed that ADT has profound effects on vBMD, aBMD, bone microstructure and strength and body composition, and important impacts on frailty and physical performance. Whilst DXA remains a valuable tool (changes in aBMD are of the same magnitude as those observed for vBMD), HR-pQCT should be considered for assessing the effects of anti-androgens and other newer PC therapies on bone, as well as potential mitigation by bone-targeted agents.

Week-by-week changes in serum levels of bone-related circulating microRNAs and bone turnover markers.

MicroRNAs are involved in post-transcriptional regulation of gene expression. Due to their regulatory role, microRNAs are differently expressed during specific conditions in healthy and diseased individuals, so microRNAs circulating in the blood could be used as diagnostic and prognostic biomarkers for various diseases and conditions. We want to investigate the variability of circulating microRNAs and bone turnover markers in weekly time intervals in older women. In a single-site longitudinal study, a panel of 19 bone-related miRNAs was measured using the osteomiR RT-qPCR assay in serum samples of 35 postmenopausal women divided into 3 groups: healthy controls (n = 12), low BMD (n = 14), and vertebral fractures (n = 9). Blood samples for measurement of CTX, PINP, OC, and bone ALP were collected once per week for 8 weeks at 9:00 AM after overnight fasting. Serum samples from all participants were analyzed for 19 microRNA bone biomarkers and 4 bone turnover markers over 8 weeks. We analyzed the data using a mixed model analysis of variance and found no significant changes between week-by-week time points in any of the groups. To estimate intraindividual variability between weekly time points, we have calculated the median coefficient of variation (CV). This was between 28.4% and 80.2% for microRNA, with an assay CV of 21.3%. It was between 8.5% and 15.6% for bone turnover markers, with an assay CV of 3.5% to 6.5%. The intraindividual variability was similar between groups. Circulating microRNAs measured in serum had a higher weekly intraindividual variability than bone turnover markers due in part to a higher assay CV.

Changes in collagen type I C-telopeptide and procollagen type I N-terminal propeptide during the menopause transition.

CONTEXT: Collagen type I C-telopeptide (CTX) and procollagen type I N-terminal propeptide (PINP) are reference bone resorption and formation markers, respectively. OBJECTIVE: To characterize CTX and PINP trajectories across the menopause transition (MT). DESIGN: 18-year longitudinal analysis from the Study of Women's Health Across the Nation. SETTING: Community-based cohort. PARTICIPANTS: 541 women (126 Black, 90 Chinese, 87 Japanese, 238 White) who transitioned from pre- to postmenopause. MAIN OUTCOME MEASURES: CTX and PINP. RESULTS: Multivariable mixed effects regression fit piecewise linear models of CTX or PINP relative to years from final menstrual period (FMP); covariates were race/ethnicity, body mass index (BMI), and age at FMP. In the referent participant (White, 52.46 years at FMP, BMI 27.12 kg/m2), CTX and PINP were stable until 3 years pre- FMP (premenopause). During the MT (3 years before to 3 years after the FMP), CTX and PINP increased 10.3% (p<0.0001) and 7.5% (p<0.0001) per year, respectively; MT-related gains totaled 61.9% for CTX and 45.2% for PINP. Starting 3 years post-FMP (postmenopause), CTX and PINP decreased 3.1% (p<0.0001) and 2.9% (p<0.0001) per year, respectively. Compared to White women, during the MT, Chinese participants had larger gains in CTX (p=0.01), and Japanese women experienced greater increases in CTX (p<0.0001) and PINP (p=0.02). In postmenopause, CTX (p=0.01) and PINP (p=0.01) rose more in Japanese relative to White women. CONCLUSIONS: CTX and PINP are stable in premenopause, increase during the MT, and decrease in postmenopause. During the MT and postmenopause, bone turnover change rates vary by race/ethnicity.

Effect of age and gender on serum growth differentiation factor 15 and its relationship to bone density and bone turnover.

Senescent cells and senescence-associated secretory phenotype (SASP) proteins are involved in age-related bone loss. Growth differentiation factor 15 (GDF 15), a stress-responsive cytokine member of the transforming growth factor-ß (TGF-ß) superfamily, is one of the key SASP proteins. It is strongly associated with age and higher levels correlate with frailty and are detected in several conditions and diseases. It also modulates appetite and body weight through the binding to its receptor glial cell- derived neurotrophic factor family receptor alpha- like (GFRAL) in the brainstem. The GDF 15 involvement in bone metabolism has been studied in several murine models, however, it is still unclear in humans. Therefore, this study aims to determine whether GDF 15 is associated with bone mineral density (BMD) and bone turnover, and to establish the effect of age and gender on its levels. Serum GDF 15 was measured with an ELISA from R&D Systems in 180 healthy women and men from the "XtremeCT study", divided into three age groups which represent different stages of skeletal development (16-18, 30-32, over 70 years). We also measured bone resorption marker C-terminal telopeptide of type I collagen (CTX) and bone formation markers N-terminal propeptide of type I collagen (PINP), osteocalcin (OC) and bone alkaline phosphatase (BAP) using iSYS-IDS analyser. Parathyroid hormone (PTH), 25hydroxyvitamin D (25OH-vitamin D), Insulin-like Growth Factor I (IGF-1), estradiol and testosterone were measured using the Cobas automated analyser (Roche Diagnostics). We assessed BMD at spine and total hip by dual-energy x-ray absorptiometry (DXA) and high resolution peripheral quantitative computed tomography (HRpQCT) of the radius and tibia. Univariate analysis of variance with the post-hoc Sheffe test and multiple linear regression has been used to assess the effect of age and gender. Spearman's rank correlation was used to evaluate the associations between GDF 15 and the other variables. We found GDF 15 levels significantly associated with age (p < 0.001) and gender (p = 0.008), with a significant gender ∗ age interaction (p < 0.001). Significantly higher levels of GDF 15 were found in subjects aged over 70 compared with the younger people (p < 0.001) and significantly higher levels were detected in men. We did not find any significant correlation between GDF 15 and bone turnover markers (BTMs), BMD, HRpQCT measures and hormones in any of the age groups. In conclusion, age and gender are determinants of GDF15 and much higher levels are found in older people and in men. Since no association was found between GDF 15 and bone health measures, we hypothesize that the effect of GDF 15 on bone might be exert by other tissue, such as muscle.

11ß-HSD1 inhibition in men mitigates prednisolone-induced adverse effects in a proof-of-concept randomised double-blind placebo-controlled trial.

Glucocorticoids prescribed to limit inflammation, have significant adverse effects. As 11ß-hydroxysteroid dehydrogenase type 1 (11ß-HSD1) regenerates active glucocorticoid, we investigated whether 11ß-HSD1 inhibition with AZD4017 could mitigate adverse glucocorticoid effects without compromising their anti-inflammatory actions. We conducted a proof-of-concept, randomized, double-blind, placebo-controlled study at Research Unit, Churchill Hospital, Oxford, UK (NCT03111810). 32 healthy male volunteers were randomized to AZD4017 or placebo, alongside prednisolone treatment. Although the primary endpoint of the study (change in glucose disposal during a two-step hyperinsulinemic, normoglycemic clamp) wasn't met, hepatic insulin sensitivity worsened in the placebo-treated but not in the AZD4017-treated group. Protective effects of AZD4017 on markers of lipid metabolism and bone turnover were observed. Night-time blood pressure was higher in the placebo-treated but not in the AZD4017-treated group. Urinary (5aTHF+THF)/THE ratio was lower in the AZD4017-treated but remained the same in the placebo-treated group. Most anti-inflammatory actions of prednisolone persisted with AZD4017 co-treatment. Four adverse events were reported with AZD4017 and no serious adverse events. Here we show that co-administration of AZD4017 with prednisolone in men is a potential strategy to limit adverse glucocorticoid effects.

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 factors (eg, age, gender, ethnicity) and controllable factors, particularly relating to collection conditions (eg, 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).

Development of the Bone Phenotype and microRNA Profile in Adults With Low-Density Lipoprotein Receptor-Related Protein 5-High Bone Mass (LRP5-HBM) Disease.

Pathogenic variants in the Wnt-pathway co-receptor low-density lipoprotein (LDL) receptor-related protein 5 (LRP5) cause high bone mass (LRP5-HBM) due to insensitivity to the endogenous antagonist of Wnt-signaling. Although indicating incessant progression of BMD and biomarkers reflecting bone formation, this has not been confirmed in individuals with LRP5-HBM. We investigated how the LRP5-HBM bone phenotype changes with age in adults and is associated with quantitative changes of bone turnover markers and bone-related microRNAs (miRNAs) in the circulation. Whole body, lumbar spine, total hip, and femoral neck areal BMD (aBMD) and radial and tibial bone microarchitecture and geometry were assessed using DXA and HR-pQCT scans of 15 individuals with LRP5-HBMT253I (11 women; median age 51 years; range, 19 to 85 years) with a time interval between scans of 5.8 years (range, 4.9 to 7.6 years). Fasting P1NP and CTX were measured in 14 LRP5-HBMT253I individuals and age-, sex-, and body mass index (BMI)-matched controls, and 187 preselected miRNAs were quantified using qPCR in 12 individuals and age-, sex-, and BMI-matched controls. DXA and HR-pQCT scans were assessed in subjects who had reached peak bone mass (aged >25 years, n = 12). Femoral neck aBMD decreased by 0.8%/year (p = 0.01) and total hip by 0.3%/year, and radial volumetric BMD (vBMD) increased 0.3%/year (p = 0.03). Differences in bone turnover markers at follow-up were not observed. Compared to controls, 11 of the 178 detectable miRNAs were downregulated and none upregulated in LRP5-HBM individuals, and five of the downregulated miRNAs are reported to be involved in Wnt-signaling. Bone loss at the hip in LRP5-HBM individuals demonstrates that the bone phenotype does not uniformly progress with age. Differentially expressed miRNAs may reflect changes in the regulation of bone turnover and balance in LRP5-HBM individuals. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC. on behalf of American Society for Bone and Mineral Research.

Bone turnover in pregnancy, measured by urinary CTX, is influenced by vitamin D supplementation and is associated with maternal bone health: findings from the Maternal Vitamin D Osteoporosis Study (MAVIDOS) trial.

BACKGROUND: The pattern of change in maternal bone turnover throughout pregnancy is poorly characterized. OBJECTIVES: We investigated changes across pregnancy in a marker of maternal bone resorption, urinary C-terminal telopeptide of type I collagen (CTX), the influence of gestational vitamin D supplementation, and associations between CTX and maternal postnatal bone indices. METHODS: MAVIDOS (the Maternal Vitamin D Osteoporosis Study) is a randomized, double-blind, placebo-controlled trial of 1000 IU cholecalciferol/d compared with placebo from 14 weeks of gestation to birth. Maternal second-void urinary α- and ß-CTX were measured (ELISA) at 14 and 34 weeks of gestation; DXA was performed within 2 wk postpartum. The Mann-Whitney Rank Sum test, Spearman's rank correlation, and linear regression were used to compare median CTX values within and between groups from early to late pregnancy, and associations with maternal bone outcomes. RESULTS: In total, 372 women had CTX and 25-hydroxyvitamin D [25(OH)D] measured in early and late pregnancy. CTX at 14 and 34 weeks of gestation were correlated in both placebo (r = 0.31) and cholecalciferol (r = 0.45) groups (P < 0.0001). Median CTX increased from 14 to 34 weeks of gestation in both groups (n = 372 total) [placebo (n = 188): from 223.6 to 449.7 µg/mmol creatinine; cholecalciferol (n = 184): from 222.3 to 419.3 µg/mmol creatinine; P = 0.03 for placebo compared with cholecalciferol difference in CTX at 34 weeks of gestation]. The conditional mean ± SD increase in CTX [z-score (SD)] from early to late pregnancy was greater in the placebo group (n = 188) than in the cholecalciferol group (n = 184) (placebo: 0.16 ± 0.92; cholecalciferol: -0.16 ± 1.06; P-difference < 0.01). Higher CTX at 34 weeks of gestation was associated, similarly in both groups, with lower maternal total hip and lumbar spine bone mineral content and bone mineral density (BMD) (e.g., lumbar spine BMD: ß = -0.02 g · cm-2 · SD-1 increase in CTX; 95% CI: -0.027, -0.002 g · cm-2 · SD-1; P = 0.02, n = 283). CONCLUSIONS: Maternal urinary CTX, a bone resorption marker, rises through pregnancy, although to a lesser degree with gestational cholecalciferol supplementation, and is inversely associated with maternal bone mass postpartum.This trial was registered at www.isrctn.com as ISRCTN 82927713 and eudract.ema.europa.eu as EudraCT 2007-001716-23.

Vascular calcification relationship to vascular biomarkers and bone metabolism in advanced chronic kidney disease.

BACKGROUND: Vascular calcification (VC) and renal osteodystrophy are important complications of advanced chronic kidney disease (CKD). High resolution peripheral quantitative computed tomography (HRpQCT) is able to assess bone microstructure in renal osteodystrophy and lower leg arterial calcification (LLAC) is usually seen as an incidental finding. LLAC can be a useful quantitative assessment of VC in CKD but the relationship between LLAC and vascular biomarkers and bone is unknown. We aimed to assess the relationship between LLAC and biomarkers, bone turnover and microstructure. METHODS: In this cross-sectional study, fasting blood samples were taken from 69 CKD stages 4-5D patients and 68 healthy controls. HRpQCT of distal tibia and radius were performed. 43 CKD patients had trans-iliac bone biopsy after tetracycline labelling. RESULTS: LLAC was more severe in CKD than controls (median [IQR] 1.043 [0.05-16.52] vs 0 [0-0.55] mgHA, p < 0.001). CKD patients with diabetes (28%) had significantly higher LLAC compared to non-diabetic CKD (median [IQR] 24.07 [3.42-61.30] vs 0.23 [0-3.78] mgHA, p < 0.001). LLAC mass in CKD correlated with serum phosphate (rho = 0.29, p < 0.05), calcium x phosphate product (rho = 0.31, p < 0.05), intact parathyroid hormone (rho = 0.38, p < 0.01), intact fibroblast growth factor-23 (iFGF23) (rho = 0.40, p = 0.001), total alkaline phosphatase (rho = 0.41, p < 0.001), bone alkaline phosphatase (rho = 0.29, p < 0.05), osteocalcin (rho = 0.32, p < 0.05), osteoprotegerin (rho = 0.40, p = 0.001) and dephosphorylated-uncarboxylated matrix Gla protein (rho = 0.31, p < 0.05). LLAC in CKD also correlated with worse distal tibia cortical bone mineral density, thickness and porosity. No association was found between LLAC and bone turnover, mineralization or volume on biopsy in CKD. In multivariate analysis, only age, diabetes, iPTH and iFGF23 were independently associated with LLAC in CKD. CONCLUSIONS: High levels of PTH and FGF23, along with older age and the presence of diabetes may all play independent roles in the development of LLAC in advanced CKD.

Clinical and biochemical characteristics of adults with hypophosphatasia attending a metabolic bone clinic.

OBJECTIVES: This study sought to identify the clinical and biochemical characteristics that would help distinguish hypophosphatasia (HPP) from other metabolic bone diseases in adult patients attending a metabolic bone clinic by comparing patients who have genetically confirmed HPP with a group of patients with low bone mineral density (BMD) in the osteoporotic or osteopenic range. METHODS: Data were collected from February 2016 to October 2018 for 41 patients (n = 20 in the HPP group, n = 21 in the low-BMD group) attending the metabolic bone clinic at Sheffield, United Kingdom (UK) or who were recruited via the Rare UK Diseases Study (RUDY) platform during the same period. A study questionnaire was administered to all patients, and assessments were conducted for laboratory values, physical functions, BMD, and spine imaging. RESULTS: Patients with HPP were characterized as being younger, more likely to have metatarsal or femoral shaft fractures, and less likely to have vertebral fractures compared with patients in the low-BMD group. The HPP group had lower total and bone-specific alkaline phosphatase, higher pyridoxal 5'-phosphate (PLP), and lower, albeit sufficient, 25-hydroxyvitamin D. Low-BMD group had lower C-terminal telopeptide and tartrate-resistant acid phosphatase 5b (61.9% were on bisphosphonates at enrollment). Dual X-ray absorptiometry (DXA) analysis found that the HPP group had higher total hip and lumbar BMD T- and Z-scores compared with the low-BMD group. There were no differences found between the two groups with physical functional assessments. Results of receiver operating characteristic analysis indicated strong diagnostic accuracy of these biomarkers for HPP. Thresholds of total alkaline phosphatase (ALP) activity of 43 IU/L or less and PLP level of 120 nmol/L or more were determined to be potentially clinically useful for distinguishing HPP from other metabolic bone diseases. CONCLUSION: This study supported the use of ALP and PLP measurements as predictive of HPP diagnosis along with certain demographic and clinical characteristics (younger age, metatarsal or femoral fractures without low mean BMD T- and Z-scores on a DXA scan) that can aid in recognizing adults who should be further evaluated for HPP. The critical values identified need to be applied to an independent sample to be tested for diagnostic accuracy.

Effect of vitamin D supplementation on free and total vitamin D: A comparison of Asians and Caucasians.

OBJECTIVES: It is well established that UK Asians typically have lower vitamin D levels than Caucasians. It is also known that vitamin D binding protein (DBP) is lower in some races than Caucasians. To investigate how ethnicity, skin colour and genetic variation affect the response to vitamin D (15000 IU) administered to young Asian and Caucasian men. DESIGN: Prospective, single-centre clinical trial. PARTICIPANTS: Sixty young men (18-25 year) of Asian (n = 30) and Caucasian (n = 30) origin. MEASUREMENTS: We measured serum calcium, phosphate, magnesium, alkaline phosphatase, albumin, parathyroid hormone; total 25 hydroxyvitamin D (25OHD); calculated and directly measured free 25OHD; DBP at baseline and 4 weeks; DBP genotype, skin colour (Fitzpatrick scale), dietary vitamin D and calcium intake at baseline; and urine calcium:creatinine ratio at baseline, 1 and 4 weeks. RESULTS: At baseline, Asians had lower serum total 25OHD (26.4 [13.7] vs 34.1 [12.3] nmol/L P = 0.0272) and DBP (6.7 [3.4] vs 9.6 [4.4] nmol/L; P = 0.0065) but similar free 25OHD (16.7 [10.4] vs 17.8 [7.5] pmol/L P = 0.6530). After dosing, total 25OHD rose similarly in each group (≈56 nmol/L), but measured free 25OHD rose more in Asians (18.1 [9.4] vs 12.2 [13.3] pmol/L P = 0.0464). Lower DBP at baseline, possibly reflecting genotype differences, was associated with a greater change in measured free 25OHD in Caucasians, but not in Asians. CONCLUSIONS: Asian compared with Caucasian males had a larger increment in measured free 25OHD following 150 000 units vitamin D3, possibly reflecting differences in DBP affinity for 25OHD. Ethnicity should be considered when devising guidelines for the treatment of vitamin D deficiency.

Diagnostic Accuracy of Biomarkers and Imaging for Bone Turnover in Renal Osteodystrophy.

Background Renal osteodystrophy is common in advanced CKD, but characterization of bone turnover status can only be achieved by histomorphometric analysis of bone biopsy specimens (gold standard test). We tested whether bone biomarkers and high-resolution peripheral computed tomography (HR-pQCT) parameters can predict bone turnover status determined by histomorphometry.Methods We obtained fasting blood samples from 69 patients with CKD stages 4-5, including patients on dialysis, and 68 controls for biomarker analysis (intact parathyroid hormone [iPTH], procollagen type 1 N-terminal propeptide [PINP], bone alkaline phosphatase [bALP], collagen type 1 crosslinked C-telopeptide [CTX], and tartrate-resistant acid phosphatase 5b [TRAP5b]) and scanned the distal radius and tibia of participants by HR-pQCT. We used histomorphometry to evaluate bone biopsy specimens from 43 patients with CKD.Results Levels of all biomarkers tested were significantly higher in CKD samples than control samples. For discriminating low bone turnover, bALP, intact PINP, and TRAP5b had an areas under the receiver operating characteristic curve (AUCs) of 0.82, 0.79, and 0.80, respectively, each significantly better than the iPTH AUC of 0.61. Furthermore, radius HR-pQCT total volumetric bone mineral density and cortical bone volume had AUCs of 0.81 and 0.80, respectively. For discriminating high bone turnover, iPTH had an AUC of 0.76, similar to that of all other biomarkers tested.Conclusions The biomarkers bALP, intact PINP, and TRAP5b and radius HR-pQCT parameters can discriminate low from nonlow bone turnover. Despite poor diagnostic accuracy for low bone turnover, iPTH can discriminate high bone turnover with accuracy similar to that of the other biomarkers, including CTX.

Bone turnover markers after the menopause: T-score approach.

Bone turnover increases at the menopause and is associated with accelerated bone loss. However, it is not known to what extent there is an imbalance between the processes of bone resorption and bone formation, nor whether it is the rate of bone turnover or the bone balance that is most closely associated with the rate of bone loss. We studied 657 healthy women ages 20 to 79 from five European cities (the OPUS Study) and divided them into two premenopausal age groups, 20 to 29 (n=129), 30 to 39years (n=183), and three postmenopausal groups 1 to 10years (n=91), 11 to 20years (n=131) and 21+ years since menopause (n=123). We measured collagen type I C-telopeptide (CTX, a marker of bone resorption) and procollagen I N-propeptide (PINP, a marker of bone formation). We used these two markers to calculate the overall bone turnover and the difference between bone formation and resorption (bone balance) using the results from the women ages 30 to 39years to calculate a standardised score (T-score). We found that the CTX and PINP levels were higher in the women ages 20 to 29 and in the women in the three menopausal groups as compared to women ages 30 to 39years (p<0.001). For example, the CTX and PINP levels were 80 and 33% higher in women 1 to 10years since menopause as compared to women ages 30 to 39years. In this group of postmenopausal women, the bone turnover expressed as a T-score was 0.72 (0.57 to 0.88, 95%CI) and the bone balance was -0.37 (-0.59 to -0.16). There was greater rate of bone loss from the total hip in all the groups of women after the menopause compared to women before the menopause. We conclude that the bone loss after the menopause is associated with both an increase in bone turnover and a negative bone balance and that bone loss was most clearly associated with overall bone turnover.

Associations Between Serum Bone Biomarkers in Early Breast Cancer and Development of Bone Metastasis: Results From the AZURE (BIG01/04) Trial.

Background: Adjuvant therapies can prevent/delay bone metastasis development in breast cancer. We investigated whether serum bone turnover markers in early disease have clinical utility in identifying patients with a high risk of developing bone metastasis. Methods: Markers of bone formation (N-terminal propeptide of type-1 collagen [P1NP]) and bone resorption (C-telopeptide of type-1 collagen [CTX], pyridinoline cross-linked carboxy-terminal telopeptide of type-1 collagen [1-CTP]) were measured in baseline (pretreatment blood samples from 872 patients from a large randomized trial of adjuvant zoledronic acid (AZURE-ISRCTN79831382) in early breast cancer. Cox proportional hazards regression and cumulative incidence functions (adjusted for factors having a statistically significant effect on outcome) were used to investigate prognostic and predictive associations between recurrence events, bone marker levels, and clinical variables. All statistical tests were two-sided. Results: When considered as continuous variables (log transformed), P1NP, CTX, and 1-CTP were each prognostic for future bone recurrence at any time (P = .006, P = .009, P = .008, respectively). Harrell's c-indices were a P1NP of 0.57 (95% confidence interval [CI] = 0.51 to 0.63), CTX of 0.57 (95% CI = 0.51 to 0.62), and 1-CTP of 0.57 (95% CI = 0.52 to 0.63). In categorical analyses based on the normal range, high baseline P1NP (>70 ng/mL) and CTX (>0.299 ng/mL), but not 1-CTP (>4.2 ng/mL), were also prognostic for future bone recurrence (P = .03, P = .03, P = .10, respectively). None of the markers were prognostic for overall distant recurrence; that is, they were bone metastasis specific, and none of the markers were predictive of treatment benefit from zoledronic acid. Conclusions: Serum P1NP, CTX, and 1-CTP are clinically useful, easily measured markers that show good prognostic ability (though low-to-moderate discrimination) for bone-specific recurrence and are worthy of further study.

Effect of Teriparatide Treatment on Circulating Periostin and Its Relationship to Regulators of Bone Formation and BMD in Postmenopausal Women With Osteoporosis.

Context: Treatment of postmenopausal osteoporosis with teriparatide parathyroid hormone amino terminal 1-34 increases bone formation and improves bone microarchitecture. A possible modulator of action is periostin. In vitro experiments have shown that periostin might regulate osteoblast differentiation and bone formation through Wnt signaling. The effect of teriparatide on periostin is not currently known. Objectives: To determine the effect of teriparatide treatment on circulating levels of periostin and other regulators of bone formation and investigate how changes in periostin relate to changes in bone turnover markers, regulators of bone formation, and bone mineral density (BMD). Participants and Design: Twenty women with osteoporosis; a 2-year open-label single-arm study. Intervention: Teriparatide 20 µg was administered by subcutaneous injection daily for 104 weeks. Periostin, sclerostin, and Dickkopf-related protein 1, procollagen type I N-terminal propeptide (PINP), and C-telopeptide of type I collagen were measured in fasting serum collected at baseline (two visits) and then at weeks 1, 2, 4, 12, 26, 52, 78, and 104. BMD was measured at the lumbar spine, total hip, and femoral neck using dual energy x-ray absorptiometry. Results: Periostin levels increased by 6.6% [95% confidence interval (CI), -0.4 to 13.5] after 26 weeks of teriparatide treatment and significantly by 12.5% (95% CI, 3.3 to 21.0; P < 0.01) after 52 weeks. The change in periostin correlated positively with the change in the lumbar spine BMD at week 52 (r = 0.567; 95% CI, 0.137 to 0.817; P < 0.05) and femoral neck BMD at week 104 (r = 0.682; 95% CI, 0.261 to 0.885; P < 0.01). Conclusions: Teriparatide therapy increases periostin secretion; it is unclear whether this increase mediates the effect of the drug on bone.

DIAGNOSIS OF ENDOCRINE DISEASE: Bone turnover markers: are they clinically useful?

Bone turnover markers (BTMs) are useful in clinical practice as they are inexpensive, and they have proven useful for treatment monitoring and identification of poor adherence. BTMs cannot be used in individual patients for identifying accelerated bone loss or an increase in fracture risk or in deciding on the optimal therapy. They are useful for monitoring both anti-resorptive and anabolic treatment. Response can be defined as a result that exceeds an absolute target, or by a change greater than the least significant change; if such a response is not present, then poor compliance or secondary osteoporosis are likely causes. A baseline BTM measurement is not always made; in that case, a value of BTM on anti-resorptive treatment that is low or low normal or above the reference interval for anabolic therapy may be taken to indicate a satisfactory response. We provide an approach to using these bone turnover markers in clinical practice by describing algorithms for anti-resorptive and anabolic therapy and describing the changes we observe in the clinical practice setting.

Bone Turnover Markers: Use in Fracture Prediction.

Bone turnover markers (BTMs) provide us with a noninvasive approach to studying bone turnover and they can be measured easily and with good precision, especially using automated analyzers. BTMs increase at menopause, and these higher levels are associated with more rapid bone loss. In some but not all studies, they are also associated with greater risk of fracture. However, the evidence base for use as predictors of fracture is not robust, and so BTMs have not been included in fracture prediction models. Further research is needed, and this might include (1) use of reference analytes such as C-telopeptide of type I collagen and procollagen I N-propeptide, measured using automated analyzers in subjects in the fasting state on more than 1 occasion; (2) careful collection of vertebral fractures, which would be the primary endpoint; and (3) common approach to statistical analyses with results expressed as hazard ratio per standard deviation of increase in BTM. We believe that by improving our approach to studying the relationship between BTMs and fracture risk, any association will become clearer and that in the future we might then be able to include BTMs in our fracture prediction models.

Effect of age and gender on serum periostin: Relationship to cortical measures, bone turnover and hormones.

Periostin is an extracellular matrix protein, and in bone is expressed most highly in the periosteum. It increases bone formation through osteoblast differentiation, cell adhesion, Wnt signalling and collagen cross-linking. We hypothesised that serum periostin would be high at times of life when cortical modeling is active, in early adulthood and in older age, and that it would correlate with cortical bone measures, bone turnover and hormones that regulate cortical modeling. We conducted a cross-sectional observational study of 166 healthy men and women at three skeletal stages; the end of longitudinal growth (16-18years), peak bone mass (30-32years) and older age (over 70years). We measured serum periostin with a new ELISA optimised for human serum and plasma which recognises all known splice variants (Biomedica). We measured the distal radius and distal tibia with HR-pQCT, and measured serum PINP, CTX, sclerostin, PTH, IGF-1, estradiol and testosterone. Periostin was higher at age 16-18 than age 30-32 (1253 vs 842pmol/l, p<0.001), but not different between age 30-32 and over age 70. Periostin was inversely correlated with tibia cortical thickness and density (R -0.229, -0.233, both p=0.003). It was positively correlated with PINP (R 0.529, p<0.001), CTX (R 0.427, p<0.001) and IGF-1 (R 0.440, p<0.001). When assessed within each age group these correlations were only significant at age 16-18, except for PINP which was also significant over age 70. We conclude that periostin may have a role in IGF-1 driven cortical modeling and consolidation in young adults, but it may not be an important mediator in older adults.