Chapter 67 Chapter 67 Biochemical Markers of Bone Turnover in Osteoporosis Copyright © 2013 Elsevier Inc. All rights reserved.

FIGURE 67.1 Molecular basis of the biochemical markers of bone collagen degradation used currently as markers of bone resorption. CTx: C-terminal cross-linking telopeptide; DPD: deoxypyridinoline; NTx: N-terminal cross-linking telopeptide; PYD: pyridinoline. Source: reproduced from Seibel (2000), with permission from Springer Verlag [70]. 2

Copyright © 2013 Elsevier Inc. All rights reserved. FIGURE 67.2 Racemization and isomerization of type I collagen C-telopeptides. An attack by a peptide backbone nitrogen on the side chain carbonyl group of an adjacent aspartyl residue can result in the formation of a succinimide ring (A: B). The succinimide ring is prone to hydrolysis and racemization producing peptides and β-aspartyl peptides in both the D and L configurations. Racemization is thought to proceed primarily through the succinimide pathway (B: E), but other pathways as direct proton abstraction (A D) and (C F) may also contribute to the formation of D -aspartyl. Throughout the figure, the peptide backbone is shown as a bold line. The four types of C-telopeptides are present in bone matrix, the native form (αL) and three age-related forms: An isomerized (βL), a racemized (αD), and an isomerized/racemized (βD) form. With increasing age of type I collagen molecules, the proportion of β-isomerized and D racemized form within bone matrix increases. Degradation products of these four CTx forms of type I collagen can be measured in urine independently by immunoassays using specific conformational monoclonal antibodies. Source: reprinted from Cloos and Fledelius (2000), with permission from Porland Press Ltd [114]. 3

Copyright © 2013 Elsevier Inc. All rights reserved. FIGURE 67.3 Combination of the assessment of bone mineral density (BMD) at the hip and of bone resorption rate to predict hip fracture risk in elderly women followed prospectively for 2 years: The EPIDOS study. Low BMD was defined according to the World health organization guidelines, i.e. by a value lower than 2.5 SD below the young adult mean (T score < 2.5). High bone resorption was defined by urinary CTx (cross-linking telopeptide of type I collagen) or free DPD (deoxypyridinoline) values higher than the upper limit (mean + 2 standard deviations) of the premenopausal range. Source: reprinted from Garnero et al., with permission [251]. 4

Copyright © 2013 Elsevier Inc. All rights reserved. FIGURE 67.4 Percent change from baseline in serum: (A) CTx (cross-linking telopeptide of type I collagen), (B) PINP (N-terminal collagen type I extension propeptides), (C) TRACP 5b (subform b of the isoenzyme 5), and (D) bone ALP (alkaline phosphatase) over 36 months in the postmenopausal osteoporotic women treated with denosumab 60 mg subcutaneously every 6 months for 3 years (FREEDOM (Future REvascularization Evaluation in patients with Diabetes mellitus: optimal management of Multivessel disease) trial). The horizontal line shows the line of no change, and each point and error bar represent the median percent change and interquartile range, respectively. Samples were measured prior to the next injection, except for the month 1 and month 36 time points, at which a dose was not administered. * P < Source: reproduced from Eastell R et al. (2011), with permission from John Wiley & Sons [40]. 5

Copyright © 2013 Elsevier Inc. All rights reserved. FIGURE 67.5 Mean percent change from baseline in bone turnover markers in postmenopausal osteoporotic women treated with risedronate 75 mg on two consecutive days of each month or risedronate 5 mg daily. 2CDM: Two consecutive days each month; sBAP: Bone-specific alkaline phosphatase; uNTx: Urinary type 1 collagen N- telopeptide. Source: reproduced from Delmas et al. (2008), with permission from Springer Verlag [330]. 6

Copyright © 2013 Elsevier Inc. All rights reserved. FIGURE 67.6 Serum TRACP5b (subform b of the isoenzyme 5) (A) and serum ICTP (B) in a group of postmenopausal women with low bone mineral density treated with odanacatib 50 mg weekly for 3 years (50 mg/50 mg), with odanacatib 50 mg weekly for 2 years and then with placebo for 1 year (50 mg/placebo) or with placebo for 3 years (Placebo/Placebo). (Per-protocol extension population from previous study described in detail in Bone et al. (2010) [332]. Graphic presentation of the geometric mean percentage change from baseline over 3 years, backtransformed from log-transformed fraction from baseline. Source: reproduced from Eisman et al. (2011), with permission from John Wiley & Sons [69]. 7

Copyright © 2013 Elsevier Inc. All rights reserved. FIGURE 67.7 Median absolute changes for serum bone-specific alkaline phosphatase (BALP), serum procollagen type I C-terminal extension propeptide (PICP), urinary N-terminal cross-linking telopeptide of type I collagen (NTx), and urinary free deoxypyridinoline (DPD) from baseline at 1, 3, 6, and 12 months. Bars represent the 25th and 75th percentiles. TPTD20, teriparatide 20 μg/day; TPTD40, teriparatide 40 μg/day (*p < 0.05, **p < 0.01 vs. placebo). Source: reproduced from Chen et al. (2005), with permission from John Wiley & Sons [43]. 8

Copyright © 2013 Elsevier Inc. All rights reserved. FIGURE 67.8 Logistic regression analysis curves of the percentage change in serum type I procollagen N- terminal propeptide (PINP) at 1 year, and the risk of new vertebral fractures at 3 years with 95% confidence intervals (CI) as indicated, in the placebo group (circles with CI as dotted lines) and in the raloxifene group (squares with CI as dashed lines). Source: reproduced from Reginster et al. (2004), with permission from Elsevier [372]. 9

Copyright © 2013 Elsevier Inc. All rights reserved. FIGURE 67.9 Median (interquartile range) levels of biochemical bone turnover markers during the first daily teriparatide course administered with alendronate (solid line) and during second daily teriparatide course (dotted line) over 15 months. There were no differences in the changes of osteocalcin (OC) or N-terminal cross-linking telopeptide (NTx) between the first teriparatide course and teriparatide retreatment, but the increment for PINP was slightly lower during the teriparatide retreatment versus the first teriparatide course (p = 0.04). BCE: Bone collagen equivalents. Source: reproduced from Cosman et al. (2009), with permission from John Wiley & Sons [404]. 10

Copyright © 2013 Elsevier Inc. All rights reserved. FIGURE Risk of hip fracture over 5 years of follow-up (n = 72) in 1005 older men from the MrOS cohort by quartile of baseline bone turnover marker, adjusted for age and clinic. Source: reproduced from Bauer et al. (2009), with permission from John Wiley & Sons [432]. 11

Copyright © 2013 Elsevier Inc. All rights reserved. FIGURE Effect of once monthly ibandronate 150 mg on bone turnover markers in men with low bone mineral density. BSAP, bone-specific alkaline phosphatase; SCTx, serum levels of C-terminal cross-linking telopeptide of type I collagen. SCTx:. Source: reproduced from Orwoll et al. (2010), with permission from Elsevier [451]. 12