The bone marker plot: an innovative method to assess bone turnover in women

Vitamin D and Calcium in Osteoporosis, and the Role of Bone Turnover Markers: A Narrative Review of Recent Data from RCTs

Osteoporosis is a common disease, defined primarily by a low measured bone density, which is associated with an increased risk of fragility fractures. Low calcium intake and vitamin D deficiency seem to be positively correlated with the prevalence of osteoporosis. Although they are not suitable for the diagnosis of osteoporosis, the biochemical markers of bone turnover can be measured in serum and/or urine, enabling the assessment of the dynamic bone activity and the short-term effectiveness of the osteoporosis treatment. Calcium and vitamin D are essential for maintaining bone health. The aim of this narrative review is to summarize the effects of vitamin D and calcium supplementation separately and in combination, on bone density and circulating serum and blood plasma vitamin D, calcium, parathyroid hormone levels, markers of bone metabolism concentrations, and clinical outcomes, such as falls and osteoporotic fractures. We searched the PubMed online database to find clinical trials from the last five years (2016-April 2022). A total of 26 randomized clinical trials (RCTs) were included in this review. The present reviewed evidence suggests that vitamin D alone or in combination with calcium increases circulating 25(OH)D. Calcium with concomitant vitamin D supplementation, but not vitamin D alone, leads to an increase in BMD. In addition, most studies did not detect significant changes in circulating levels of plasma bone metabolism markers, nor in the incidence of falls. Instead, there was a decrease in blood serum PTH levels in the groups receiving vitamin D and/or Ca supplementation. The plasma vitamin D levels at the beginning of the intervention, and the dosing regimen followed, may play a role in the observed parameters. However, further study is needed to determine an appropriate dosing regimen for the treatment of osteoporosis and the role of bone metabolism markers.

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.

The effect of bisphosphosphonates on bone turnover and bone balance in postmenopausal women with osteoporosis: The T-score bone marker approach in the TRIO study

Postmenopausal osteoporosis is characterised by increased bone turnover and an imbalance between bone resorption and formation. Bisphosphonate treatment reduces bone turnover but their effect on bone balance is yet to be fully investigated. Using the T-score approach our aims were to: i) investigate the effects of oral nitrogen-containing bisphosphonates on bone balance and turnover in postmenopausal women with osteoporosis and ii) determine the relationship of the change in bone balance and turnover with the change in BMD at the lumbar spine and total hip. Women were recruited, mean age 67 years, and randomised to receive: ibandronate (n = 55, 150 mg/month), alendronate (n = 54, 70 mg/week) or risedronate (n = 56, 35 mg/week). They also received calcium and vitamin D daily. A fasting serum sample was collected at baseline and weeks 1, 2, 4, 12, 13, 48 and 96. The control group were 226 healthy premenopausal women receiving no treatments. PINP and CTX were measured using the iSYSIDS analyser and BMD (in g/cm2) of the lumbar spine and total hip were measured by DXA (Hologic Inc). PINP and CTX values were log10-transformed and normalised. T-scores were calculated using the mean and standard deviation from the premenopausal group. Bone turnover and bone balance were calculated from the T-scores. Mean levels (95% CI) of balance and turnover are shown in the table. The change in turnover at weeks 4, 12 and 48 was inversely correlated with the change in lumbar spine and total hip BMD at weeks 48 and 96, (p < .01 to p < .001). The change in balance at week 4 positively correlated with the change in total hip BMD at weeks 48, (p < .01). Bisphosphonates resulted in an initial positive balance and a reduction in turnover. Some of these changes were associated with increases in BMD. Bone turnover is a better predictor of BMD than bone balance.

Consumption of Greek yogurt during 12 weeks of high-impact loading exercise increases bone formation in young, adult males – a secondary analysis from a randomized trial

Exercise combined with protein and calcium has been shown to benefit bone turnover and bone metabolism. Greek yogurt (GY) contains important nutrients that support bone but has yet to be studied with exercise for this purpose. Thirty untrained, university-aged, males were randomized to 2 groups (n = 15/group): GY (20 g protein, 208 mg calcium/dose) or placebo pudding (PP; 0 g protein, 0 g calcium/dose) consumed 3×/day on training days and 2×/day on nontraining days. Both groups underwent a resistance/plyometric training program for 12 weeks. Blood was obtained at weeks 0, 1, and 12 to measure procollagen-type-I-N-terminal-propeptide (P1NP) and C-terminal-telopeptide (CTX). After outlier treatment, P1NP increased more over time in GY versus PP (p = 0.002; interaction). Both groups decreased CTX over time (p = 0.046; time effect). Following 1 week of training, there was a trend towards a significant increase in CTX in PP with no change in GY (p = 0.062; interaction). P1NP changed more in GY than PP (baseline to week 12; p = 0.029) as did the P1NP/CTX ratio (p = 0.015) indicating a greater increase in formation with GY. Thus, GY added to a high-load, high-impact exercise program positively shifted bone turnover towards increased formation while attenuating resorption. GY could be a plausible postexercise food to support bone health in young adult males.

Novelty Greek yogurt, with exercise, increased bone formation in young adult males over 12 weeks. After 1 week of an osteogenic exercise program, Greek yogurt tended to blunt a rise in bone resorption seen with the placebo. Greek yogurt is a plausible postexercise food that supports bone.

Energy Deficiency Suppresses Bone Turnover in Exercising Women With Menstrual Disturbances

CONTEXT

In exercising women, energy deficiency can disrupt the balance of bone formation and resorption, resulting in bone loss and an altered rate of bone turnover, which may influence future bone mineral density and fracture risk.

OBJECTIVE

To assess the effects of energy status and estrogen status on bone turnover.

DESIGN

Cross-sectional.

SETTING

The Women's Health and Exercise Laboratory at Pennsylvania State University.

PARTICIPANTS

Exercising women (n = 109) operationally defined as energy deficient or replete based on total triiodothyronine concentration and as estrogen deficient or replete based on menstrual cycle history and reproductive hormone metabolites.

MAIN OUTCOME MEASURES

Bone formation index [procollagen type I N-terminal propeptide (P1NP) concentration corrected for average P1NP concentration in healthy reference group, i.e., [P1NP]i/median [P1NP]ref], bone resorption index [serum C-terminal telopeptide (sCTx) concentration corrected for average sCTx concentration in healthy reference group, i.e., [sCTx]i/median [sCTx]ref], bone balance (ratio of bone formation index to bone resorption index to indicate which process predominates), and bone turnover rate (collective magnitude of bone formation index and bone resorption index to indicate overall amount of bone turnover).

RESULTS

The combination of energy and estrogen deficiency resulted in less bone formation and a lower rate of bone turnover compared with women who were estrogen deficient but energy replete. Regardless of estrogen status, energy deficiency was associated with decreased bone resorption as well. No main effects of estrogen status were observed.

CONCLUSIONS

The results highlight the critical role that adequate energy plays in the regulation of bone turnover, especially bone formation, in exercising women with menstrual disturbances.

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.

Effect of isolated vitamin D supplementation on bone turnover markers in younger postmenopausal women: a randomized, double-blind, placebo-controlled trial

Vitamin D (VD) plays an important role in bone mineralization. The present study investigates the effect of VD supplementation alone on bone turnover markers in younger postmenopausal women. It has been shown that VD supplementation in postmenopausal women with hypovitaminosis D is associated with a reduction in bone turnover markers.

PURPOSE

The purpose of this study is to evaluate the effect of VD supplementation alone on bone turnover markers in younger postmenopausal women.

METHODS

In this double-blind, placebo-controlled trial, 160 women were randomized into the VD group (supplementation with 1000 IU of vitamin D3/day, orally; n = 80) or placebo group (n = 80). Women aged 50-65 years with amenorrhea ≥ 12 months and normal bone mineral density were included. The intervention lasted 9 months, and the participants were assessed at the beginning and end of treatment. Serum levels of total calcium, parathormone (PTH), alkaline phosphatase (AP), and 24-h urine calcium were determined. Serum C-terminal telopeptide of type I collagen (s-CTX) and procollagen type 1 N-terminal propeptide (P1NP) were measured by immunoassay as markers of bone resorption and formation, respectively. Plasma 25-hydroxyvitamin-D [25(OH)D] concentrations were measured by HPLC. Intention-to-treat analysis was performed using ANOVA, Student's t test, Tukey's test, and gamma distribution.

RESULTS

Over the period of 9 months, 25(OH)D concentrations increased from 15.0 ± 7.5 to 27.5 ± 10.4 ng/mL (+ 45.4%) in the VD group and decreased from 16.9 ± 6.7 to 13.8 ± 6.0 ng/mL (- 18.5%) in the placebo group (p < 0.001). There was a decrease (- 21.3%) of PTH levels in the VD group with a significant difference between groups at the end of the study (p < 0.001). No significant differences were observed in the other laboratory parameters (total calcium, AP, and calciuria) in either group (p > 0.05). A comparison of bone turnover markers showed a significant reduction in of s-CTX (- 24.2%, p < .0001) and P1NP (- 13.4%, p = 0.003) levels in the VD group. No significant variations in bone turnover markers were observed in the placebo group (s-CTX, - 6.9%, p = 0.092 and P1NP, - 0.6%, p = 0.918).

CONCLUSION

In younger postmenopausal women with VD deficiency, isolated supplementation with 1000 IU of vitamin D3 for 9 months is associated with a reduction in bone turnover markers. However, any between-group differences was not observed in bone turnover markers.

Effect of osteoporosis medication on changes in bone mineral density and bone turnover markers after 24-month administration of daily teriparatide: comparison among minodronate, raloxifene, and eldecalcitol

This study reveals the changes in bone mineral density (BMD), the turnover rate, and the balance [multiple of median formation/multiple of median resorption (MoMf/MoMr)] affected by the selection of different bone resorption inhibitors after 24-month daily teriparatide (20 µg/day) administration. The turnover rate was calculated as √(MoMf² + MoMr²), where MoMf = bone-specific alkaline phosphatase (BAP) value/18.6 and MoMr = tartrate-resistant acid phosphatase 5b (TRACP-5b) value/463. One hundred and twenty-one osteoporotic women (mean age 82.4 years) were randomly administered minodronate (50 mg/28 days), raloxifene (60 mg/day), or eldecalcitol (0.75 µg/day) after teriparatide discontinuation. BMD was measured at 0, 24, and 48 weeks; BAP values and TRACP-5b were measured at 0, 12, 24, 36, and 48 weeks after administration of bone resorption inhibitors. In the minodronate group, BMD increased significantly from week 0 to weeks 24 and 48. The turnover rate was significantly reduced at week 12, and remained so over the entire course in all three groups. The speed of change of turnover rate was greatest in the minodronate group. The balance in the minodronate group shifted significantly toward formation dominance at week 12 (to 0.97 from 0.87) and then again toward resorption dominance (to 0.84) at week 24. However, no further advancement in resorption dominance was observed until week 48. Conversely, the balance in the raloxifene and eldecalcitol groups shifted toward resorption dominance gradually over the entire course. In conclusion, the BMD-increasing effect was greatest with minodronate administration and depends not only on the decrease in turnover rate but also on changes in balance after teriparatide discontinuation.

Bone Turnover Markers as a New Predicting Factor for Nonunion After Spinal Fusion Surgery

STUDY DESIGN

Retrospective observational study.

OBJECTIVE

We investigated whether bone turnover markers could be a useful indicator for prediction of nonunion.

SUMMARY OF BACKGROUND DATA

Nonunion is a major complication of lumbar spinal fusion surgery. The involvement of bone turnover in the process of bony union in spinal fusion surgery is, however, poorly understood.

METHODS

Of the 74 patients analyzed, 13 were diagnosed with nonunion. We evaluated the significance of the following risk factors: age, sex, number of fused segments, serum levels of total alkaline phosphatase, procollagen type 1 amino-terminal propeptide (P1NP), tartrate-resistant acid phosphatase 5b (TRACP-5b), and albumin, and history of diabetes mellitus, cigarette smoking, or alcohol use. We also defined the bone turnover ratio (BTR) as a value that equals serum TRACP-5b concentration divided by serum P1NP concentration to evaluate patients' individual bone turnover balance and investigated the significance of BTR as a risk factor.

RESULTS

Univariate analysis showed that older age, malnutrition, and lower P1NP are risk factors for nonunion. Stepwise logistic regression analysis revealed that in the presence of lower P1NP, higher TRACP-5b becomes a risk factor. Furthermore, we identified BTR as the most significant risk factor for nonunion. The optimum cut-off value of BTR by receiver-operating characteristic curve was 11.74.

CONCLUSION

These findings show a relation between bone turnover and nonunion after spinal fusion surgery. The measurement of bone turnover markers could potentially be used to predict nonunion after spinal fusion surgery.

LEVEL OF EVIDENCE

4.

Bone Turnover Status: Classification Model and Clinical Implications

Aim: To develop a practical model for classification bone turnover status and evaluate its clinical usefulness. Methods: Our classification of bone turnover status is based on internationally recommended biomarkers of both bone formation (N-terminal propeptide of type1 procollagen, P1NP) and bone resorption (beta C-terminal cross-linked telopeptide of type I collagen, bCTX), using the cutoffs proposed as therapeutic targets. The relationships between turnover subtypes and clinical characteristic were assessed in1223 hospitalised orthogeriatric patients (846 women, 377 men; mean age 78.1±9.50 years): 451(36.9%) subjects with hip fracture (HF), 396(32.4%) with other non-vertebral (non-HF) fractures (HF) and 376 (30.7%) patients without fractures. Resalts: Six subtypes of bone turnover status were identified: 1 - normal turnover (P1NP>32 μg/L, bCTX≤0.250 μg/L and P1NP/bCTX>100.0[(median value]); 2- low bone formation (P1NP ≤32 μg/L), normal bone resorption (bCTX≤0.250 μg/L) and P1NP/bCTX>100.0 (subtype2A) or P1NP/bCTX<100.0 (subtype 2B); 3- low bone formation, high bone resorption (bCTX>0.250 μg/L) and P1NP/bCTX<100.0; 4- high bone turnover (both markers elevated ) and P1NP/bCTX>100.0 (subtype 4A) or P1NP/bCTX<100.0 (subtype 4B). Compared to subtypes 1 and 2A, subtype 2B was strongly associated with nonvertebral fractures (odds ratio [OR] 2.0), especially HF (OR 3.2), age>75 years and hyperparathyroidism. Hypoalbuminaemia and not using osteoporotic therapy were two independent indicators common for subtypes 3, 4A and 4B; these three subtypes were associated with in-hospital mortality. Subtype 3 was associated with fractures (OR 1.7, for HF OR 2.4), age>75 years, chronic heart failure (CHF), anaemia, and history of malignancy, and predicted post-operative myocardial injury, high inflammatory response and length of hospital stay (LOS) above10 days. Subtype 4A was associated with chronic kidney disease (CKD), anaemia, history of malignancy and walking aids use and predicted LOS>20 days, but was not discriminative for fractures. Subtype 4B was associated with fractures (OR 2.1, for HF OR 2.5), age>75 years, CKD and indicated risks of myocardial injury, high inflammatory response and LOS>10 days. Conclusions: We proposed a classification model of bone turnover status and demonstrated that in orthogeriatric patients altered subtypes are closely related to presence of nonvertebral fractures, comorbidities and poorer in-hospital outcomes. However, further research is needed to establish optimal cut points of various biomarkers and improve the classification model.

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.

Bone turnover rate and bone formation/resorption balance during the early stage after switching from a bone resorption inhibitor to denosumab are predictive factors of bone mineral density change

Objectives

This study aimed to investigate the correlation between bone mineral density (BMD) and the turnover rate [√(MoMf² + MoMr²), multiple of median formation (MoMf) was calculated as bone-specific alkaline phosphatase (BAP) value/18.6 and multiple of median resorption (MoMr) as tartrate-resistant acid phosphatase 5b (TRACP-5b) value/463] and the balance (MoMf/MoMr) and to compare differences in therapeutic effects evoked by differences in previous treatments.

Methods

In 51 osteoporotic women treated with bisphosphonates (BPs) or selective estrogen receptor modulators (SERMs), BMD was measured at 0, 24, and 48 weeks after denosumab administration. The values of BAP and TRACP-5b were measured at 0, 4, 12, 24, 36, and 48 weeks.

Results

The turnover rate decreased at week 4 and decreased further at week 12. The balance indicated a relative predominantly formative state at week 4. This balance became higher in the SERM group than in the BP group at week 4. A correlation was observed between the rate of BMD change and turnover rate at weeks 0 and 4.

Conclusions

It is necessary to evaluate the turnover rate and balance to determine the therapeutic effect of denosumab, which induces dissociation between the trends in the bone turnover markers. Turnover rate and balance during the early stages of denosumab treatment may be predictive factors of BMD. When switching from bone resorption inhibitors to denosumab, it was necessary to consider the beginning values that were affected by the previous treatment. The state of relative anabolism is greater at 4 weeks when the previous treatment involved SERMs rather than BPs.

Quantifying the Balance Between Total Bone Formation and Total Bone Resorption: An Index of Net Bone Formation

CONTEXT

Bone gain vs loss across the skeleton loss depends on the balance between total bone formation and total bone resorption.

OBJECTIVE

The objective of the study was to determine whether resorption and formation markers can be combined to gauge net bone formation across the skeleton.

DESIGN

The study included a cohort followed up across menopause transition (Study of Women's Health Across the Nation).

SETTING AND PARTICIPANTS

Community-dwelling women, 42-52 years old, premenopausal or early perimenopausal at baseline, participated in the study.

OUTCOME

The study included the following measures: 1) bone balance index (BBI) created by estimating the relationship between resorption (urinary N-telopeptide) and formation (osteocalcin) markers when the total formation equals the total resorption in 685 women with stable bone mineral density (BMD) (>5 y before the final menstrual period [FMP]) and applying this relationship to measured bone turnover markers in 216 women beginning to lose bone (≤2 y from FMP); and 2) annualized percentage declines over the following 3-4 years in the lumbar spine (LS) and femoral neck (FN) BMD.

RESULTS

Adjusted for covariates, the BBI was greater (more favorable) in women with a greater body mass index (P = .03) and lower (less favorable) in women closer to the FMP (P = .007). Each SD decrement in BBI was associated with 0.27%/y faster LS BMD decline (P 0.04) and a 38% higher odds of faster-than-average loss of LS bone mass (P = .008, c-statistic 0.76). BBI was not associated with decline in FN BMD. Urinary N-telopeptide alone was not associated with either LS or FN BMD decline.

CONCLUSIONS

An index that quantifies net bone formation vs resorption can be created from bone turnover markers and may help identify individuals at high risk for LS bone loss.

The importance of assessing the rate of bone turnover and the balance between bone formation and bone resorption during daily teriparatide administration for osteoporosis: a pilot study

This study aimed to examine the importance of simultaneously measuring bone formation and resorption markers during daily teriparatide administration. In 135 women with osteoporosis, bone mineral density (BMD) was measured at 0, 24, and 48 weeks after teriparatide administration. Bone-specific alkaline phosphatase and tartrate-resistant acid phosphatase 5b were measured at 0, 4, 12, 24, 36, and 48 weeks. Subanalyses were performed in groups divided according to the BMD change at 48 weeks (increased and decreased groups), history of fragility fracture (acute and chronic groups), and treatment prior to teriparatide administration (alendronate, raloxifene, and naïve groups). The scatter diagram of multiple of median formation (MoMf) and multiple of median resorption (MoMr) showed that the distribution gradually spread to a high turnover by week 24. A significant correlation was observed between the rate of change in BMD at week 48 and the turnover rate [√(MoMf(2) + MoMr(2))] at week 0. Significant differences were observed in the turnover rate between the acute and chronic groups at weeks 0 and 4 and between the groups divided according to prior treatment from week 0 to 24. Because the assessment of either bone formation markers or bone resorption markers may result in erroneous data, it is necessary to assess them together during teriparatide treatment. The turnover rate at treatment initiation is a useful indicator to predict changes in BMD. When evaluating the turnover rate and balance (MoMf/MoMr), one should consider patient characteristics, including history of fragility fracture and prior treatment.

Co-administration of antiresorptive and anabolic agents: a missed opportunity

Co-administration of antiresorptive and anabolic therapies has appeal because these treatments target the two main abnormalities in bone remodeling responsible for bone loss and microstructural deterioration. Antiresorptives reduce the number of basic multicellular units (BMUs) remodeling bone and reduce the volume of bone each BMU resorbs. Intermittent parathyroid hormone (PTH) increases the volume of bone formed by existing BMUs and those generated by PTH administration. PTH also increases bone formation by stimulating the differentiation, maturation, and longevity of osteoblast lineage cells residing upon quiescent bone surfaces. Despite these rationally targeted actions, enthusiasm for this approach waned when combined therapy blunted the increase in areal bone mineral density (aBMD) relative to that produced by PTH. Although many studies have since reported additive effects of combined therapy, whatever the aBMD result (blunting, additive, or null), these outcomes give little, if any, insight into changes in bone's material composition or microstructure and give misleading information concerning the net effects on bone strength. Combined therapy remains a potentially valuable approach to therapy. Because studies of antifracture efficacy comparing combined with single therapy are unlikely to be performed in humans, efforts should be directed toward improving methods of quantifying the net effects of combined therapy on bone's material composition, microarchitecture, and strength.

Radon balneotherapy and physical activity for osteoporosis prevention: a randomized, placebo-controlled intervention study

Low-dose radon hyperthermia balneo treatment (LDRnHBT) is applied as a traditional measure in the non-pharmacological treatment of rheumatic diseases in Europe. During the last decades, the main approach of LDRnHBT was focused on the treatment of musculoskeletal disorders, but scientific evidence for the biological background of LDRnHBT is weak. Recently, evidence emerged that LDRnHBT influences bone metabolism. We investigated, whether combined LDRnHBT and exercise treatment has an impact on bone metabolism and quality of life in a study population in an age group at risk for developing osteoporosis. This randomized, double-blind, placebo-controlled trial comprised guided hiking tours and hyperthermia treatment in either radon thermal water (LDRnHBT) or radon-free thermal water (PlaceboHBT). Markers of bone metabolism, quality of life and somatic complaints were evaluated. Statistics was performed by linear regression and a linear mixed model analysis. Significant changes over time were observed for most analytes investigated as well as an improvement in self-assessed health in both groups. No significant impact from the LDRnHBT could be observed. After 6 months, the LDRnHBT group showed a slightly stronger reduction of the osteoclast stimulating protein receptor activator of nuclear kB-ligand compared to the PlaceboHBT group, indicating a possible trend. A combined hyperthermia balneo and exercise treatment has significant immediate and long-term effects on regulators of bone metabolism as well as somatic complaints. LDRnHBT and placeboHBT yielded statistically equal outcomes.

The clinical utility of bone marker measurements in osteoporosis

Osteoporosis is characterised by low bone mass and structural deterioration of bone tissue, resulting in increased fragility and susceptibility to fracture. Osteoporotic fractures are a significant cause of morbidity and mortality. Direct medical costs from such fractures in the UK are currently estimated at over two billion pounds per year, resulting in a substantial healthcare burden that is expected to rise exponentially due to increasing life expectancy. Currently bone mineral density is the WHO standard for diagnosis of osteoporosis, but poor sensitivity means that potential fractures will be missed if it is used alone. During the past decade considerable progress has been made in the identification and characterisation of specific biomarkers to aid the management of metabolic bone disease. Technological developments have greatly enhanced assay performance producing reliable, rapid, non-invasive cost effective assays with improved sensitivity and specificity. We now have a greater understanding of the need to regulate pre-analytical sample collection to minimise the effects of biological variation. However, bone turnover markers (BTMs) still have limited clinical utility. It is not routinely recommended to use BTMs to select those at risk of fractures, but baseline measurements of resorption markers are useful before commencement of anti-resorptive treatment and can be checked 3–6 months later to monitor response and adherence to treatment. Similarly, formation markers can be used to monitor bone forming agents. BTMs may also be useful when monitoring patients during treatment holidays and aid in the decision as to when therapy should be recommenced. Recent recommendations by the Bone Marker Standards Working Group propose to standardise research and include a specific marker of bone resorption (CTX) and bone formation (P1NP) in all future studies. It is hoped that improved research in turn will lead to optimised markers for the clinical management of osteoporosis and other bone diseases.

Influence of age and gender on associations of body mass index with bone mineral density, bone turnover markers and circulating calcium-regulating and bone-active sex hormones

Although it is well known that body mass index (BMI) and bone mineral density (BMD) are positively correlated, the mechanisms by which adiposity reduces the risk of osteoporotic fractures are not fully understood. The present study was initiated to gain deeper insight into the mechanisms underlying the osteoprotective effect of adiposity, and to assess particularly the relevance that BMI-associated changes in circulating hormone levels could have for the build-up of additional bone mineral density. Using data from a previous study on a large cohort of healthy adult Austrians, we analyzed correlations of BMI with (i) BMD at sites in the lumbar spine and hip region, (ii) bone resorption and formation markers, (iii) circulating levels of vitamin D, parathyroid hormone, testosterone and estrogen, and (iv) rates of daily vitamin D and calcium intake. After adjustment for age, positive correlations between BMI and BMD were highly significant (P<0.0001) at all skeletal sites across the entire study cohort. Associations were stronger in post-menopausal women than in pre-menopausal women and in men. In absolute values, the gain in BMD at the lumbar spine from an incremental rise of BMI in post-menopausal women was 1.5-fold higher than in pre-menopausal women, and three times of that observed in men (P<0.05). Inverse relations between BMI and β-crosslaps were consistently found in men (P<0.01) and in women before and after menopause (P<0.01 and P<0.05, respectively), suggesting that inhibition of osteoclastic bone resorption is responsible at least in part for the positive effect of high BMI on BMD. Sub-group analysis revealed that increasing BMI was associated with a significant fall of testosterone in men (P<0.05), and of 25-(OH)D in pre- and post-menopausal women (P<0.001 and P<0.05, respectively), but with a significant rise in PTH (P<0.01) in women before menopause. Since all these hormonal changes would cause bone loss, this excludes their playing any role in the osteoprotective effect of adiposity.

Calcium supplementation attenuates citrate-related changes in bone metabolism: a placebo-controlled crossover study in healthy volunteers

BACKGROUND

Citrate is the anticoagulation of choice in apheresis procedures. Citrate anticoagulation results in a short-term increase in serological markers of bone turnover, with uncertain clinical significance.

AIM

To understand the effect of calcium supplementation on serological bone turnover markers during an acute citrate load as a mimic of citrate anticoagulation during apheresis procedures.

METHODS

A placebo-controlled, crossover study was conducted in 22 healthy volunteers. Volunteers received a standardized citrate load at a fixed dose of 1.5 mg/kg of body weight/min for 80 min for three times and a single placebo infusion as a control. Each intervention was separated by a wash-out interval of 2 to 3 weeks. During two citrate infusions, volunteers received an additional calcium supplementation, consisting of either oral administration of calcium carbonate or an i.v. bypass infusion of calcium gluconate. Serial blood samples were collected for the determination of ionized calcium (iCa), intact parathyroid hormone (iPTH) and markers of bone remodeling, C-telopeptide of type 1 collagen (CTX) and osteocalcin (OC).

RESULTS

The infusion of citrate without calcium supplementation resulted in an increase in the bone formation marker OC and the bone resorption marker CTX, in addition to the changes in iPTH and iCa. The administration of calcium by either oral administration or as an i.v. bypass infusion attenuated the observed changes in CTX, but showed no effects on the elevation of the bone formation marker OC. There was no difference in the attenuation of CTX between the two calcium formulations. However, the i.v. application of calcium gluconate had a superior effect in reducing the change of serum iPTH and iCa as compared to the oral administration of calcium carbonate.

CONCLUSIONS

Calcium supplementation is an effective method in damping the citrate-related transient increase of the serological bone resorption marker CTX. As a mimic for the citrate-based apheresis procedure, our data may enforce the prophylactic application of calcium supplementation to attenuate the short-term elevation of bone resorption related to an acute citrate load.

Changes in osteopontin and in biomarkers of bone turnover during human endotoxemia

Systemic infection and inflammation in men are associated with bone loss. Rodent studies have elucidated the pathways mediating the effects of bacterial lipopolysaccharide (LPS), activated immune cells and hormones on bone. Here we investigate the changes in biochemical parameters of bone turnover following human endotoxemia, an experimental model of self-limiting systemic infection and inflammation. Ten healthy men received in a randomised, placebo-controlled, cross-over trial once placebo and once 2 ng/kg Escherichia coli endotoxin (LPS). During the following 6 h we monitored parathyoid hormone (PTH) and osteopontin (OPN), a multifunctional protein related to bone pathophysiology, as well as biochemical markers of bone turnover: C-terminal telopeptide of type I collagen (CTX), N-terminal propeptide of type I collagen (P1NP) and osteocalcin (OC). In LPS sessions there was a transient fall in PTH at 3 h (p=0.009) and a nearly two-fold increase in OPN levels after 6 h (LPS: 155+/-19 pg/ml; placebo: 85+/-13 pg/ml, p<0.001). LPS gradually reduced CTX levels (LPS: 0.44+/-0.4 pg/ml; placebo: 0.59+/-0.06 pg/ml, p=0.003), P1NP showed a peak at 4 h (LPS: 89.9+/-14.7 pg/ml; placebo: 75+/-9.7 pg/ml, p=0.028) and circulating OC did not change. The early human response to systemic endotoxemia boosts osteopontin levels and modifies bone biomarkers, indicating a decrease in the lytic activity of osteoclasts, accompanied by an increase in the activity of immature osteoblasts. These changes might present the acute phase response of immune and bone cells to bacterial stimuli in men.