Response of biochemical markers of bone turnover to hormone replacement therapy: impact of biological variability

Bone Metabolism Defects in Children With Idiopathic Hypercalciuria: An Update

Idiopathic hypercalciuria (IH) in adults is considered to be the most common identifiable metabolic risk factor for calcium nephrolithiasis, also contributing to osteopenia and osteoporosis. Data on children and adolescents associating IH with bone metabolism show that up to one-third of such patients present with lower bone mineral density (BMD), increasing the risk of osteopenia, osteoporosis, and bone fractures in adulthood. Several factors, such as the degree of hypercalciuria and the presence of calcium urolithiasis, seem to affect the severity of bone metabolism abnormalities in children with IH. In order to follow these patients, BMD has traditionally been estimated by dual-energy X-ray absorptiometry (DXA) scan. In children, chronological age should be taken into account when measuring BMD, as well as weight, height, and BMI. In addition, biochemical bone turnover markers provide surrogate indices of bone turnover and complement the static measurements of BMD. They respond rapidly to changes in bone physiology, and their measurement can be repeated more frequently. However, since children's bone mass increases constantly until after puberty, age, sex, and pubertal stage have to be taken into consideration when assessing these markers. In addition, relevant studies in children and adolescents have shown conflicting results. Regarding the management of patients with IH, identification and appropriate treatment are of great importance in order to prevent the formation of kidney stones, as well as to improve bone metabolism defects and decrease fracture risk. Such treatment measures include dietary interventions, potassium citrate supplementation and/or thiazide diuretics, and bisphosphonates in resistant cases. This review summarizes the latest data on bone metabolism defects in children and adolescents with IH, the possible pathomechanisms involved, the biochemical markers that could be used together with DXA to follow these patients, and the available treatment options.

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).

METHODS

This 18-year longitudinal analysis of a community-based cohort from the Study of Women's Health Across the Nation included 541 women (126 Black, 90 Chinese, 87 Japanese, 238 White) who transitioned from pre- to postmenopause. 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 < .0001) and 7.5% (P < .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 < .0001) and 2.9% (P < .0001) per year, respectively. Compared with the White participants, during the MT, Chinese participants had larger gains in CTX (P = .01), and Japanese women experienced greater increases in CTX (P < .0001) and PINP (P = .02). In postmenopause, CTX (P = .01) and PINP (P = .01) rose more in Japanese relative to White women.

CONCLUSION

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.

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.

Follicle-stimulating hormone is associated with low bone mass in postmenopausal women

We evaluated the influence of two endogenous hormones on bone health in older women. Higher FSH was associated with bone disease, especially in lower estradiol environments. FSH attenuated the relationship between estradiol and bone. This may provide a mechanism through which future clinical research intervenes on bone loss.

INTRODUCTION/PURPOSE

Despite preclinical evidence for an inverse association of follicle-stimulating hormone (FSH) and bone mineral density (BMD), no large epidemiologic studies have evaluated the separate and joint influences of FSH and estradiol on bone in postmenopausal women.

METHODS

In a cross-sectional study of 675 postmenopausal women, we evaluated associations of serum FSH and dual X-ray absorptiometry (DXA)-classified areal BMD as well as low bone mass or osteoporosis (T-score <  - 1.0) of the femoral neck and total hip. We stratified this analysis by serum estradiol (cut at the median). We tested whether FSH mediates the association of estradiol and BMD using the Sobel test.

RESULTS

In linear regression models, there was a significant inverse association of serum FSH with both femoral neck and total hip BMD (both p < 0.01) when adjusted for age, hormone therapy (HT) use, and diabetes. In fully adjusted logistic regression models, women in the highest FSH tertile had higher odds of low bone mass/osteoporosis at the femoral neck (OR = 2.98; 95% CI = 1.86-4.77) and at the total hip (OR = 1.74; 95% CI = 1.06-2.84) compared to those in the lowest FSH tertile. We report evidence of effect modification by estradiol in stratified models and an interaction term. FSH met all criteria of a mediator, including an estimated 70% attenuation of the estradiol-BMD relationship (Sobel p value < 0.001).

CONCLUSIONS

FSH is associated with higher odds of having low bone mass/osteoporosis even after accounting for HT use. FSH is a mediator of the relationship between estradiol and BMD in healthy postmenopausal women. Larger, prospective studies of FSH concentrations and bone health are needed.

Menopausal Transition: Prospective Study of Estrogen Status, Circulating MicroRNAs, and Biomarkers of Bone Metabolism

OBJECTIVE

Osteoporosis is associated with an impaired balance between bone resorption and formation, which in turn leads to bone loss and fractures. Many recent studies have underlined the regulatory role of microRNAs (miRNAs) in bone remodeling processes and their potential as biomarkers of osteoporosis. The purpose of this study was to prospectively examine the association of circulating miRNAs and bone biomarkers with estrogen status in women before and after oophorectomy, as well as in oophorectomized women on estrogen therapy.

METHODS

In this prospective study, we included 11 women before oophorectomy and hysterectomy and at 201 ± 24 days after the surgery. Another 11 women were evaluated 508 ± 127 days after oophorectomy and hysterectomy and after an additional 203 ± 71 days of estradiol treatment. Serum miRNAs were profiled by sequencing. Estrogen status and biomarkers of bone metabolism were quantified. Bone mineral density was assessed in the lumbar spine.

RESULTS

Our analysis revealed 17 miRNAs associated with estrogen levels. Of those miRNAs that were upregulated with estrogen deficiency and downregulated after estrogen therapy, miR-422a correlated with serum beta-carboxy-terminal type I collagen crosslinks (β-CTX) and procollagen 1 N-terminal propeptide (P1NP); and miR-1278 correlated with serum β-CTX, P1NP, osteocalcin, sclerostin, and Dickkopf-1(Dkk1). In contrast, we found an inverse association of miR-24-1-5p with estrogen status and a negative correlation with serum β-CTX, P1NP, osteoprotegerin, and sclerostin levels.

CONCLUSION

The reported miRNAs associated with estrogen status and bone metabolism could be potential biomarkers of bone pathophysiology and would facilitate studies on the prevention of postmenopausal osteoporosis. Our findings require validation in an extended cohort.

Shatavari Supplementation in Postmenopausal Women Improves Handgrip Strength and Increases Vastus lateralis Myosin Regulatory Light Chain Phosphorylation but Does Not Alter Markers of Bone Turnover

Shatavari has long been used as an Ayurvedic herb for women's health, but empirical evidence for its effectiveness has been lacking. Shatavari contains phytoestrogenic compounds that bind to the estradiol receptor. Postmenopausal estradiol deficiency contributes to sarcopenia and osteoporosis. In a randomised double-blind trial, 20 postmenopausal women (68.5 ± 6 years) ingested either placebo (N = 10) or shatavari (N = 10; 1000 mg/d, equivalent to 26,500 mg/d fresh weight shatavari) for 6 weeks. Handgrip and knee extensor strength were measured at baseline and at 6 weeks. Vastus lateralis (VL) biopsy samples were obtained. Data are presented as difference scores (Week 6-baseline, median ± interquartile range). Handgrip (but not knee extensor) strength was improved by shatavari supplementation (shatavari +0.7 ± 1.1 kg, placebo -0.4 ± 1.3 kg; p = 0.04). Myosin regulatory light chain phosphorylation, a known marker of improved myosin contractile function, was increased in VL following shatavari supplementation (immunoblotting; placebo -0.08 ± 0.5 a.u., shatavari +0.3 ± 1 arbitrary units (a.u.); p = 0.03). Shatavari increased the phosphorylation of Akt^ser473 (Akt^ser473 (placebo -0.6 ± 0.6 a.u., shatavari +0.2 ± 1.3 a.u.; p = 0.03) in VL. Shatavari supplementation did not alter plasma markers of bone turnover (P1NP, β-CTX) and stimulation of human osteoblasts with pooled sera (N = 8 per condition) from placebo and shatavari supplementation conditions did not alter cytokine or metabolic markers of osteoblast activity. Shatavari may improve muscle function and contractility via myosin conformational change and further investigation of its utility in conserving and enhancing musculoskeletal function, in larger and more diverse cohorts, is warranted.

Advances in bone turnover markers

Bone fragility fractures remain an important worldwide health and economic problem due to increased morbidity and mortality. The current methods for predicting fractures are largely based on the measurement of bone mineral density and the utilization of mathematical risk calculators based on clinical risk factors for bone fragility. Despite these approaches, many bone fractures remain undiagnosed. Therefore, current research is focused on the identification of new factors such as bone turnover markers (BTM) for risk calculation. BTM are a group of proteins and peptides released during bone remodeling that can be found in serum or urine. They derive from bone resorptive and formative processes mediated by osteoclasts and osteoblasts, respectively. Potential use of BTM in monitoring these phenomenon and therefore bone fracture risk is limited by physiologic and pathophysiologic factors that influence BTM. These limitations in predicting fractures explain why their inclusion in clinical guidelines remains limited despite the large number of studies examining BTM.

Bone Biomarkers in Mucopolysaccharidoses

The accumulation of glycosaminoglycans (GAGs) in bone and cartilage leads to progressive damage in cartilage that, in turn, reduces bone growth by the destruction of the growth plate, incomplete ossification, and growth imbalance. The mechanisms of pathophysiology related to bone metabolism in mucopolysaccharidoses (MPS) include impaired chondrocyte function and the failure of endochondral ossification, which leads to the release of inflammatory cytokines via the activation of Toll-like receptors by GAGs. Although improvements in the daily living of patients with MPS have been achieved with enzyme replacement, treatment for the bone disorder is limited. There is an increasing need to identify biomarkers related to bone and cartilage to evaluate the progressive status and to monitor the treatment of MPS. Recently, new analysis methods, such as proteomic analysis, have identified new biomarkers in MPS. This review summarizes advances in clinical bone metabolism and bone biomarkers.

The Effects of Osteoporotic and Non-osteoporotic Medications on Fracture Risk and Bone Mineral Density

Osteoporosis is a highly prevalent bone disease affecting more than 37.5 million individuals in the European Union (EU) and the  United States of America (USA). It is characterized by low bone mineral density (BMD), impaired bone quality, and loss of structural and biomechanical properties, resulting in reduced bone strength. An increase in morbidity and mortality is seen in patients with osteoporosis, caused by the approximately 3.5 million new osteoporotic fractures occurring every year in the EU. Currently, different medications are available for the treatment of osteoporosis, including anti-resorptive and osteoanabolic medications. Bisphosphonates, which belong to the anti-resorptive medications, are the standard treatment for osteoporosis based on their positive effects on bone, long-term experience, and low costs. However, not only medications used for the treatment of osteoporosis can affect bone: several other medications are suggested to have an effect on bone as well, especially on fracture risk and BMD. Knowledge about the positive and negative effects of different medications on both fracture risk and BMD is important, as it can contribute to an improvement in osteoporosis prevention and treatment in general, and, even more importantly, to the individual's health. In this review, we therefore discuss the effects of both osteoporotic and non-osteoporotic medications on fracture risk and BMD. In addition, we discuss the underlying mechanisms of action.

The role of estrogens in osteosarcopenia: from biology to potential dual therapeutic effects

Osteoporosis and sarcopenia are two conditions associated with aging and characterized by a simultaneous decline in bone and muscle mass, respectively. These conditions share common risk factors (genetic, endocrine, nutritional and lifestyle factors) and biological pathways that often co-exist in a syndrome known as osteosarcopenia. Among the endocrine causes, estrogens play a critical role, especially in women. Estrogens have been demonstrated to exert a positive effect on bone and muscle development and maintenance. For this reason, menopause is characterized by a loss in bone mineral density and skeletal muscle quality and quantity. To date, studies indicate a positive effect of hormonal therapy on the prevention and management of osteoporosis, to the point that estrogen is prescribed as a first-line treatment for osteoporosis by the major international authorities. While results on sarcopenia are still disputable, such that estrogens are not recommended to prevent muscle loss in postmenopausal women, increased response to anabolic stimuli with estrogen therapy suggests similar beneficial effects on muscle as seen with bone, particularly when combined with resistance exercise.

Estrogen and bones after menopause: a reappraisal of data and future perspectives

Menopausal hormone therapy (MHT) is effective in preventing menopause-related bone loss and decreasing vertebral, non-vertebral and hip fracture risk. MHT contains estrogens that exert both antiosteoclastic and osteoanabolic effects. These effects are dose-dependent, as even ultra-low doses preserve or increase bone mineral density. The transdermal route of administration is effective on cancellous and cortical bone, although fracture data are still lacking. Hormone replacement therapy is the treatment of choice to preserve skeletal health in women with premature ovarian insufficiency and early menopause. MHT can be considered in women aged < 60 years or within 10 years since menopause as, in this population, benefits outweigh possible risks, such as breast cancer and cardiovascular events. Despite the ensuing bone loss after MHT discontinuation, a residual antifracture effect persists. However, in women at risk of fracture, subsequent antiosteoporotic therapy may be needed, either with an antiosteoclastic or osteoanabolic agent. In any case, longitudinal data from randomized controlled trials comparing different estrogen doses and routes of administration, as well as designating the optimal treatment strategy after MHT discontinuation, are needed to elucidate these issues further.

Gender-Affirming Hormone Therapy and Bone Health: Do Different Regimens Influence Outcomes in Transgender Adults? A Narrative Review and Call for Future Studies

BACKGROUND

Gender-affirming hormone therapy (GAHT) influences bone health in transgender individuals. Several hormone preparations and administration routes are available for GAHT, but no studies have compared clinical and laboratory bone health measures across different GAHT regimens.

CONTENT

We searched PubMed (MEDLINE), Embase, and Google Scholar for studies measuring bone turnover markers and bone mineral density before and during GAHT in transgender adults. We summarized bone health data by hormone type and administration route (estrogen or testosterone; oral, transdermal/percutaneous, intramuscular). Among trans women, we also examined outcomes among regimens containing different adjunctive agents (antiandrogens or gonadotropin-releasing hormone analogs).

SUMMARY

Most hormone preparations maintained or increased areal bone mineral density among trans adults taking GAHT for at least 12 months from baseline. Different bone turnover markers were measured across studies, and we were unable to compare or comment on the direct influence of selected hormone preparations on these clinical laboratory measures. Larger and uniformed studies are needed to measure volumetric bone mineral density and biomarkers of bone metabolism in trans adults taking standardized GAHT regimens.

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.

Estrogen effects on orthodontic tooth movement and orthodontically-induced root resorption

Estrogen is an essential regulator of the bone tissue. The remodeling of the alveolar bone and periodontal ligament is the basis of orthodontic tooth movement (OTM). There is a negative coregulation between physiological estrogen levels and the rate of OTM. As a possible inhibitory factor of OTM, estrogen suppresses bone resorption by inhibiting osteoclastic differentiation and restraining osteoclast lifespan though multiple pathways and cytokines, leading to the suppression of the initiation step of bone remodeling. On the other hand, estrogen stimulates osteoblastic differentiation and function. Estrogen receptor-α (ERα) involves in the osteogenic responses to mechanical stimulation, and the ERα expression is regulated positively by the levels of circulatory estrogen. Orthodontically induced root resorption (OIRR) is a common side-effect of orthodontic treatment. Estrogen may have some inhibitory effects on OIRR, but more studies are needed to get an effective conclusion.

The challenge of long-term adherence: The role of bone turnover markers in monitoring bisphosphonate treatment of osteoporosis

Oral Bisphosphonates (BPs) are the mainstay of osteoporotic treatment, however long-term adherence remains a challenge, primarily owing to the chronic character of the disease and the regimen complexity. Poor compliance has been shown to have a clear link to fracture risk. The role of bone turnover markers (BTMs) as a tool to ascertain adherence and response to therapy is supported by their rapid response to treatment; a decrease in values is witnessed within days or weeks of commencing treatment. A greater reduction of serum CTX and NTX is evidenced with alendronate and ibandronate compared to risedronate. A change in bone formation BTMs appears to be related to vertebral fracture risk reduction, whereas no significant relationship is evident for hip and non-vertebral fractures. The utility of BTMs as an adjunct for monitoring withdrawal of treatment with oral BP has also been suggested. Finally, studies evaluating BTMs as an intervention, failed to demonstrate any effect on adherence. This review explores the challenge of long-term adherence with bisphosphonates and provides an analytic framework with respect to the role of BTMs in monitoring bisphosphonate treatment, adherence and the offset of treatment effect.

Development and Evaluation of Novel ELISA for Determination of Urinary Pentosidine

Pentosidine is the most well-characterized advanced glycation end product (AGE). It has been measured by HPLC, although this approach cannot be adapted to analyze many clinical samples and is also time-consuming. Furthermore, the detection of pentosidine using a reported ELISA kit and HPLC system requires pretreatment by heating, which generates artificial pentosidine leading to overestimation. We developed a novel pentosidine ELISA system that don't require sample pretreatment for analyzing urine samples. We then analyzed the accuracy, precision, and reliability of this system. Urinary samples for analysis were obtained from healthy volunteers and stored urinary samples from the participants of the Nagano cohort study were also used. The LoB and LoD were 4.25 and 6.24 pmol/mL, respectively. Intra- and inter-assay coefficients of variation were less than 5%. The spiking and dilution recoveries were 101.4% and 100.5%, respectively. Analysis of the cross-reactivities against seven compounds representative of AGEs and structurally similar to pentosidine showed no significant cross-reactivity. The correlation coefficient between the concentrations of pentosidine obtained from HPLC and ELISA for the same urine samples was r=0.815. The urinary excretion of pentosidine upon overnight fasting was lower than that after a meal, suggesting the presence of diurnal variation in urinary pentosidine. In contrast, day-to-day variation was not observed. These results indicate that the ELISA system has sufficient reliability, accuracy, and precision for measuring urinary pentosidine. Sampling of fasting urine is suitable for minimizing variation. In conclusion, this ELISA system is promising to evaluate the effect of AGE on lifestyle-related diseases.

A multicenter study to evaluate harmonization of assays for N-terminal propeptide of type I procollagen (PINP): a report from the IFCC-IOF Joint Committee for Bone Metabolism

Background Biochemical bone turnover markers (BTM) are useful tools to assess bone remodeling at the cellular level. N-terminal propeptide of type I procollagen (PINP) has been recommended as a reference marker for bone formation in research studies. Methods We describe the results of a multicenter study for routine clinical laboratory assays for PINP in serum and plasma. Four centers (Athens, Greece [GR], Copenhagen, Denmark [DK], Liege, Belgium [BE] and Sheffield, United Kingdom [UK]) collected serum and plasma (EDTA) samples from 796 patients presenting to osteoporosis clinics. Specimens were analyzed in duplicate with each of the available routine clinical laboratory methods according to the manufacturers' instructions. Passing-Bablok regressions, Bland-Altman plots, V-shape evaluation method and the concordance correlation coefficient for PINP values between serum and plasma specimens and between methods were used to determine the agreement between results. A generalized linear model was employed to identify possible variables that affected the relationship between the methods. Results We showed that both EDTA plasma and serum were suitable for PINP determination. We observed a significant proportional bias between Orion radioimmunoassay and the automated methods for PINP (Roche Cobas and IDS iSYS), which both gave very similar results. The multivariate model did not improve the excellent correlation that was observed between the methods. Conclusions Harmonization of PINP assays is possible by applying a correction factor or correctly assigning the values of the calibrators. This work will benefit from further collaboration between assays manufacturers and clinical laboratory professionals.

Biochemical markers of bone turnover and risk of incident hip fracture in older women: the Cardiovascular Health Study

The relationships of osteocalcin (OC) and C-telopeptide of type I collagen (CTX) with long-term incidence of hip fracture were examined in 1680 post-menopausal women from a population-based study. CTX, but not OC, levels were associated with incident hip fracture in these participants, a relationship characterized by an inverted U-shape.

INTRODUCTION

We sought to investigate the relationships of OC, a marker of bone formation, and CTX, a marker of bone resorption, with long-term incidence of hip fracture in older women.

METHODS

We included 1680 women from the population-based Cardiovascular Health Study (mean [SD] age 74.5 [5.0] years). The longitudinal association of both markers with incidence of hip fracture was examined using multivariable Cox models.

RESULTS

During a median follow-up of 12.3 years, 288 incident hip fractures occurred. Linear spline analysis did not demonstrate an association between OC levels and incident hip fracture. By contrast, increasing levels of CTX up to the middle-upper range were associated with a significantly greater risk of hip fracture (HR = 1.52 per SD increment, 95% CI = 1.10-2.09), while further increases were associated with a marginally non-significant lower risk (HR = 0.80 per SD increment, 95% CI = 0.63-1.01), after full adjustment for potential confounders. In analyses of quartiles, CTX exhibited a similar inverted U-shaped relationship with incident fracture after adjustment, with a significant association observed only for the comparison of quartile 3 to quartile 1 (HR = 1.63, 95% CI = 1.10-2.43). In a subset with available measures, both OC and CTX were inversely associated with bone mineral density of the hip.

CONCLUSION

CTX, but not OC, levels were associated with incident hip fracture in post-menopausal women, a relationship characterized by an inverted U-shape. These findings highlight the complex relationship of bone turnover markers with hip fracture risk.

Impact of Route of Estrogen Administration on Bone Turnover Markers in Oligoamenorrheic Athletes and Its Mediators

OBJECTIVE

Transdermal, but not oral, estrogen replacement improves bone mineral density (BMD) in athletes with oligoamenorrhea (OA). Our objective was to determine mechanisms that may explain the impact of route of estrogen administration on bone outcomes.

METHODS

Seventy-three participants with OA between 14 and 25 years old received (i) a 17β-estradiol transdermal patch continuously with cyclic oral micronized progesterone (PATCH), (ii) a combined ethinyl estradiol and desogestrel pill (PILL), or (iii) no estrogen/progesterone (NONE) for 12 months. We evaluated morning fasting levels of a marker of bone formation [N-terminal propeptide of type 1 procollagen (P1NP)], a marker of bone resorption (N-telopeptide), IGF-1, insulinlike growth factor binding protein 3, total testosterone, estradiol, SHBG, sclerostin, preadipocyte factor-1 (Pref-1), brain-derived neurotrophic factor (BDNF), calcium, 25(OH) vitamin D, and PTH levels at baseline and 12 months.

RESULTS

Groups did not differ for age, weight, exercise activity, or markers of bone formation at baseline. Over 12 months, P1NP decreased the most in the PILL group (P = 0.03) associated with a decrease in IGF-1 levels (r = 0.37; P = 0.003). Sclerostin, Pref-1, and BDNF decreased in the PATCH group over 12 months. PATCH had the greatest increases in estradiol (P ≤ 0.0001), and estradiol increases were associated with increases in bone density.

CONCLUSION

Transdermal 17β-estradiol given over 12 months does not cause the decrease in IGF-1 observed with oral ethinyl estradiol. It also leads to decreases in sclerostin, Pref-1, and BDNF, which may mediate the beneficial effects of estrogen.

The Bromodomain Inhibitor N-Methyl pyrrolidone Prevents Osteoporosis and BMP-Triggered Sclerostin Expression in Osteocytes

(1) Background: In an adult skeleton, bone is constantly renewed in a cycle of bone resorption, followed by bone formation. This coupling process, called bone remodeling, adjusts the quality and quantity of bone to the local needs. It is generally accepted that osteoporosis develops when bone resorption surpasses bone formation. Osteoclasts and osteoblasts, bone resorbing and bone forming cells respectively, are the major target in osteoporosis treatment. Inside bone and forming a complex network, the third and most abundant cells, the osteocytes, have long remained a mystery. Osteocytes are responsible for mechano-sensation and -transduction. Increased expression of the osteocyte-derived bone inhibitor sclerostin has been linked to estrogen deficiency-induced osteoporosis and is therefore a promising target for osteoporosis management. (2) Methods: Recently we showed in vitro and in vivo that NMP (N-Methyl-2-pyrrolidone) is a bioactive drug enhancing the BMP-2 (Bone Morphogenetic Protein 2) induced effect on bone formation while blocking bone resorption. Here we tested the effect of NMP on the expression of osteocyte-derived sclerostin. (3) Results: We found that NMP significantly decreased sclerostin mRNA and protein levels. In an animal model of osteoporosis, NMP prevented the estrogen deficiency-induced increased expression of sclerostin. (4) Conclusions: These results support the potential of NMP as a novel therapeutic compound for osteoporosis management, since it preserves bone by a direct interference with osteoblasts and osteoclasts and an indirect one via a decrease in sclerostin expression by osteocytes.

Developing a toolkit for the assessment and monitoring of musculoskeletal ageing

The complexities and heterogeneity of the ageing process have slowed the development of consensus on appropriate biomarkers of healthy ageing. The Medical Research Council–Arthritis Research UK Centre for Integrated research into Musculoskeletal Ageing (CIMA) is a collaboration between researchers and clinicians at the Universities of Liverpool, Sheffield and Newcastle. One of CIMA’s objectives is to ‘Identify and share optimal techniques and approaches to monitor age-related changes in all musculoskeletal tissues, and to provide an integrated assessment of musculoskeletal function’—in other words to develop a toolkit for assessing musculoskeletal ageing. This toolkit is envisaged as an instrument that can be used to characterise and quantify musculoskeletal function during ‘normal’ ageing, lend itself to use in large-scale, internationally important cohorts, and provide a set of biomarker outcome measures for epidemiological and intervention studies designed to enhance healthy musculoskeletal ageing. Such potential biomarkers include: biochemical measurements in biofluids or tissue samples, in vivo measurements of body composition, imaging of structural and physical properties, and functional tests. This review assesses candidate biomarkers of musculoskeletal ageing under these four headings, details their biological bases, strengths and limitations, and makes practical recommendations for their use. In addition, we identify gaps in the evidence base and priorities for further research on biomarkers of musculoskeletal ageing.

Young female patients with multiple myeloma have low occurrence of osteolytic lesion

OBJECTIVE

Osteolytic lesion (OL) and bone damage are common complications in multiple myeloma (MM). This study aimed to analyze the occurrence of OL in MM patient groups of different ages and genders.

PATIENTS AND METHODS

We performed a retrospective study of 762 MM patients admitted to West China Hospital from 2009 to 2014 to investigate the association between OL occurrence with patients' ages and genders. The presence or absence of OL was confirmed by X-ray, computed tomography (CT) or magnetic resonance imaging (MRI) examination. We also downloaded MM patients' published gene expression profiles and performed microarray-based analyses to identify differentially regulated genes and signaling pathways. Finally, we examined target gene expressions in MM bone marrow (BM) biopsies through immunohistochemistry (IHC).

RESULTS

We calculated the frequency of OL in female and male MM patients with different age cut-offs. From West China Hospital data, we found that in young female MM patients aged under 55, the frequency of OL was 16.67%, significantly lower than the frequencies in other groups of patients (young males: 34.38%; old males: 31.04%; old females: 29.24%; p < .05). The same was true in another independent MM cohort. Microarray-based analyses showed that Microtubule Associated Serine/Threonine Kinase Family Member 4 (MAST4), an estrogen-responsive gene, expression was up-regulated in MM patients without OL and in young female MM patients (p < .05). The expression of MAST4 in MM BM was confirmed by IHC. The perspective of cell signaling network suggested that MAST4 might interact with phosphatase and tensin homolog (PTEN) and control the expression of a panel of osteoclast-regulatory cytokines, such as TNFSF11 and CCL2.

CONCLUSIONS

Young female (<55 years) MM patients have significantly lower OL frequency than other groups. MAST4 gene expression is thought to be associated with this phenomenon.

Bone Metabolism and Fracture Risk in Diabetes Mellitus

Individuals with Type 1 diabetes mellitus (T1DM) and type 2 diabetes mellitus (T2DM) are at increased risk for fragility fractures. Bone mineral density (BMD) is decreased in T1DM but often normal or even elevated in T2DM when compared with age-matched non-DM populations. However, bone turnover is decreased in both T1DM and T2DM. The pathophysiologic mechanisms leading to bone fragility is multifactorial, and potentially leads to reduced bone formation, altered bone microstructure and decreased bone strength. Interestingly, different antidiabetic treatments may influence fracture risk due to effects on glycemic control, triggering of hypoglycemic events or osteoblastogenesis.

The effect of estrogen on tendon and ligament metabolism and function

Tendons and ligaments are crucial structures inside the musculoskeletal system. Still many issues in the treatment of tendon diseases and injuries have yet not been resolved sufficiently. In particular, the role of estrogen-like compound (ELC) in tendon biology has received until now little attention in modern research, despite ELC being a well-studied and important factor in the physiology of other parts of the musculoskeletal system. In this review we attempt to summarize the available information on this topic and to determine many open questions in this field.

Cathepsin K Inhibitors for Osteoporosis: Biology, Potential Clinical Utility, and Lessons Learned

Cathepsin K is a cysteine protease member of the cathepsin lysosomal protease family. Although cathepsin K is highly expressed in osteoclasts, lower levels of cathepsin K are also found in a variety of other tissues. Secretion of cathepsin K from the osteoclast into the sealed osteoclast-bone cell interface results in efficient degradation of type I collagen. The absence of cathepsin K activity in humans results in pycnodysostosis, characterized by increased bone mineral density and fractures. Pharmacologic cathepsin K inhibition leads to continuous increases in bone mineral density for ≤5 years of treatment and improves bone strength at the spine and hip. Compared with other antiresorptive agents, cathepsin K inhibition is nearly equally efficacious for reducing biochemical markers of bone resorption but comparatively less active for reducing bone formation markers. Despite multiple efforts to develop cathepsin K inhibitors, potential concerns related to off-target effects of the inhibitors against other cathepsins and cathepsin K inhibition at nonbone sites, including skin and perhaps cardiovascular and cerebrovascular sites, prolonged the regulatory approval process. A large multinational randomized, double-blind phase III study of odanacatib in postmenopausal women with osteoporosis was recently completed. Although that study demonstrated clinically relevant reductions in fractures at multiple sites, odanacatib was ultimately withdrawn from the regulatory approval process after it was found to be associated with an increased risk of cerebrovascular accidents. Nonetheless, the underlying biology and clinical effects of cathepsin K inhibition remain of considerable interest and could guide future therapeutic approaches for osteoporosis.

Hormonal and systemic regulation of sclerostin

The Wnt/β-catenin signaling pathway plays an essential role in osteoblast biology. Sclerostin is a soluble antagonist of Wnt/β-catenin signaling secreted primarily by osteocytes. Current evidence indicates that sclerostin likely functions as a local/paracrine regulator of bone metabolism rather than as an endocrine hormone. Nonetheless, circulating sclerostin levels in humans often reflect changes in the bone microenvironment, although there may be exceptions to this observation. Using existing assays, circulating sclerostin levels have been shown to be altered in response to both hormonal stimuli and across a variety of normal physiological and pathophysiological conditions. In both rodents and humans, parathyroid hormone provided either intermittently or continuously suppresses sclerostin levels. Likewise, most evidence from both human and animal studies supports a suppressive effect of estrogen on sclerostin levels. Efforts to examine non-hormonal/systemic regulation of sclerostin have in general shown less consistent findings or have provided associations rather than direct interventional information, with the exception of mechanosensory studies which have consistently demonstrated increased sclerostin levels with skeletal unloading, and conversely decreases in sclerostin with enhanced skeletal loading. Herein, we will review the existent literature on both hormonal and non-hormonal/systemic factors which have been studied for their impact on sclerostin regulation.

International Osteoporosis Foundation and European Calcified Tissue Society Working Group. Recommendations for the screening of adherence to oral bisphosphonates

Adherence to oral bisphosphonates is low. A screening strategy is proposed based on the response of biochemical markers of bone turnover after 3 months of therapy. If no change is observed, the clinician should reassess the adherence to the treatment and also other potential issues with the drug.

INTRODUCTION

Low adherence to oral bisphosphonates is a common problem that jeopardizes the efficacy of treatment of osteoporosis. No clear screening strategy for the assessment of compliance is widely accepted in these patients.

METHODS

The International Osteoporosis Foundation and the European Calcified Tissue Society have convened a working group to propose a screening strategy to detect a lack of adherence to these drugs. The question to answer was whether the bone turnover markers (BTMs) PINP and CTX can be used to identify low adherence in patients with postmenopausal osteoporosis initiating oral bisphosphonates for osteoporosis. The findings of the TRIO study specifically address this question and were used as the basis for testing the hypothesis.

RESULTS

Based on the findings of the TRIO study, specifically addressing this question, the working group recommends measuring PINP and CTX at baseline and 3 months after starting therapy to check for a decrease above the least significant change (decrease of more than 38% for PINP and 56% for CTX). Detection rate for the measurement of PINP is 84%, for CTX 87% and, if variation in at least one is considered when measuring both, the level of detection is 94.5%.

CONCLUSIONS

If a significant decrease is observed, the treatment can continue, but if no decrease occurs, the clinician should reassess to identify problems with the treatment, mainly low adherence.

Bone turnover markers: Emerging tool in the management of osteoporosis

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

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

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

INTRODUCTION

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Short-Term Effect of Estrogen on Human Bone Marrow Fat

Bone marrow fat, an unique component of the bone marrow cavity increases with aging and menopause and is inversely related to bone mass. Sex steroids may be involved in the regulation of bone marrow fat, because men have higher bone marrow fat than women and clinical observations have suggested that the variation in bone marrow fat fraction is greater in premenopausal compared to postmenopausal women and men. We hypothesized that the menstrual cycle and/or estrogen affects the bone marrow fat fraction. First, we measured vertebral bone marrow fat fraction with Dixon Quantitative Chemical Shift MRI (QCSI) twice a week during 1 month in 10 regularly ovulating women. The vertebral bone marrow fat fraction increased 0.02 (95% CI, 0.00 to 0.03) during the follicular phase (p = 0.033), and showed a nonsignificant decrease of 0.02 (95% CI, -0.01 to 0.04) during the luteal phase (p = 0.091). To determine the effect of estrogen on bone marrow fat, we measured vertebral bone marrow fat fraction every week for 6 consecutive weeks in 6 postmenopausal women before, during, and after 2 weeks of oral 17-β estradiol treatment (2 mg/day). Bone marrow fat fraction decreased by 0.05 (95% CI, 0.01 to 0.09) from 0.48 (95% CI, 0.42 to 0.53) to 0.43 (95% CI, 0.34 to 0.51) during 17-β estradiol administration (p < 0.001) and increased again after cessation. During 17-β estradiol administration the bone formation marker procollagen type I N propeptide (P1NP) increased (p = 0.034) and the bone resorption marker C-terminal crosslinking telopeptides of collagen type I (CTx) decreased (p < 0.001). In conclusion, we described the variation in vertebral bone marrow fat fraction among ovulating premenopausal women. And among postmenopausal women, we demonstrated that 17-β estradiol rapidly reduces the marrow fat fraction, suggesting that 17-β estradiol regulates bone marrow fat independent of bone mass.

Safety of daily teriparatide treatment: a post hoc analysis of a Phase III study to investigate the possible association of teriparatide treatment with calcium homeostasis in patients with serum procollagen type I N-terminal propeptide elevation

OBJECTIVE

Serum procollagen type I N-terminal propeptide (PINP), a representative marker of bone anabolic action, is strongly related to bone mineral density during teriparatide therapy. This post hoc study analyzed data from a Phase III study (ClinicalTrials.gov identifier NCT00433160) to determine if there was an association between serum PINP elevation and serum calcium concentration or calcium metabolism-related disorders.

RESEARCH DESIGN AND METHODS

Japanese subjects with osteoporosis at high risk of fracture were randomized 2:1 to teriparatide 20 μg/day (n=137) or placebo (n=70) for a 12-month double-blind treatment period, followed by 12 months of open-label teriparatide treatment of all subjects.

MAIN OUTCOME MEASURES

Serum PINP levels were measured at baseline, and after 1, 3, 6, 12, 18, and 24 months of treatment. Serum calcium levels were measured at baseline, and after 1, 3, 6, 9, 12, 15, 18, 21, and 24 months of treatment.

RESULTS

Serum PINP increased from baseline to 1 month of treatment and then remained high through 24 months. Twenty-eight of 195 subjects experienced PINP elevations >200 μg/L during teriparatide treatment. Serum calcium concentration in both the teriparatide and placebo groups remained within the normal range. There was no clinically relevant difference in serum calcium concentration between subjects with PINP >200 μg/L and subjects with PINP ≤200 μg/L. Two subjects experienced hypercalcemia and recovered without altering teriparatide treatment. Adverse events possibly related to calcium metabolism disorders included periarthritis calcarea (one subject) and chondrocalcinosis pyrophosphate (two subjects), but neither was accompanied with a significant increase in PINP or serum calcium concentration.

CONCLUSION

Although the moderate size of this study prevented statistical analysis of any potential association between calcium metabolism-related disorders and elevated PINP, this analysis suggests that there was no association between serum PINP elevation during daily teriparatide treatment and serum calcium concentration or calcium metabolism-related disorders in Japanese subjects.

Estrogen Modulates Bone Morphogenetic Protein-Induced Sclerostin Expression Through the Wnt Signaling Pathway

Clinical data show that estrogen levels are inversely associated with the production of sclerostin, a Wnt antagonist that recently attracted great attention over the use of its antibody in the anabolic treatment of osteoporotic conditions. However, the molecular link between sclerostin expression and estrogen signaling is not yet known. We investigated the mechanisms by which estrogen modulates sclerostin (SOST) gene expression at the cellular level in human osteoblast cells in association with bone morphogenetic protein (BMP)2 signaling given that BMP2 is a potential inducer of SOST in human mesenchymal stromal cells (hMSCs). 17β-Estradiol (E2) alone had no effect on SOST expression, which was significantly induced by treatment with BMP2 in hMSCs and osteoblasts derived from the mandibles of female donors. However, E2 suppressed the induction of SOST and other BMP2 target genes by BMP2 in hMSCs. E2 signaling was independent of the Smad pathway, which plays a critical role in SOST induction mediated by BMP2. Instead, E2 increased the transcriptional expression of β-catenin and levels of its activated form. Silencing of the gene encoding estrogen receptor (ER)α decreased E2 activity in β-catenin activation and the suppression of SOST induction by BMP2, but had no influence on BMP2-mediated SOST induction in the same conditions. Similar results were obtained after treatment with ERα antagonist as a Wnt inhibitor. In human osteoblasts, the effect of E2 on SOST expression was either suppressive or absent, depending on the cell donor. Interestingly, the SOST expression pattern after treatment with BMP2 or BMP2/E2 in human osteoblasts showing a pattern of E2 suppression on SOST induction by BMP2 correlated with the ratio of receptor activator of nuclear factor kappa-B ligand (RANKL) to osteoprotegerin (OPG) expression. These results demonstrate that estrogen signaling in osteoblasts negatively regulates SOST expression in an indirect manner through interaction with BMP2 signaling and that this regulation involves the Wnt/ERα and β-catenin pathways. This study highlights several interactions between estrogen and BMP cascades in osteoblasts that may provide a basis for therapeutic intervention for the modification of bone mass density.

PINP as a biological response marker during teriparatide treatment for osteoporosis

Postmenopausal women with severe osteoporosis may require treatment with the bone anabolic drug teriparatide. While changes in bone mineral density (BMD) are one measure of response, BMD changes often require a minimum of one year to observe measureable changes. Biochemical markers of bone turnover change within 1 to 3 months of initiating osteoporosis therapy. Monitoring with a marker such as procollagen type I N propeptide (PINP), an osteoblast-derived protein, during teriparatide treatment may provide clinically useful information for managing patients with osteoporosis. Clinical trials have shown consistent increases in PINP within 3 months of initiating teriparatide, increases that are significantly greater than placebo and significantly different from baseline. Increases in PINP concentrations during teriparatide treatment correlate well with increases in skeletal activity assessed by radioisotope bone scans and quantitative bone histomorphometry parameters. Individuals treated with teriparatide in clinical trials usually experienced an increase in PINP > 10 mcg/L from baseline, while those given placebo usually did not. In the clinical setting, patients experiencing a significant increase in PINP > 10 mcg/L after initiating teriparatide therapy may receive an earlier confirmation of anabolic effect, while those who do not may be assessed for adherence, proper injection technique, or undetected secondary conditions that might mitigate an anabolic response. PINP monitoring may provide information supplemental to BMD monitoring and be a useful aid in managing patients receiving anabolic osteoporosis treatment in the same way that biochemical markers of bone resorption are useful in monitoring antiresorptive therapy. This review examines PINP as a biological response marker during teriparatide treatment for osteoporosis.

Procollagen type 1 amino-terminal propeptide (P1NP) and risk of hip fractures in elderly Norwegian men and women. A NOREPOS study

The current study aimed to assess a possible association between the bone turnover marker procollagen type 1 amino-terminal propeptide (P1NP) and future hip fractures in elderly Norwegian men and women and to elucidate the relation between P1NP, bone mineral density and 25-hydroxyvitamin D (25(OH)D). Men and women aged 71 to 77 from two population based health studies in Norway (1999-2001) were followed for a median period of 7.3 years with respect to hip fractures. The study was designed as a case-cohort study. P1NP and 25(OH)D were analysed in frozen serum samples obtained at baseline in hip fracture patients (n=340) and in randomly selected sex stratified sub-cohorts. Bone mineral density was measured by dual-energy X-ray absorptiometry (DXA) in a subset of participants. Cox proportional hazards regression with inverse probability weighting and robust variance was performed. No significant correlation between 25(OH)D and P1NP was found. A negative correlation between P1NP and BMD was observed in women (Rho=-0.36, p=0.001). A similar trend was observed in men. No association between quartiles of P1NP and rate of subsequent hip fractures was found. Spline analyses suggested a higher rate of hip fracture at P1NP levels above 60 μg/L in both men and women. A higher hip fracture rate, which was independent of BMD, was also indicated in women with very low levels of P1NP.

TGFβ inducible early gene-1 plays an important role in mediating estrogen signaling in the skeleton

TGFβ Inducible Early Gene-1 (TIEG1) knockout (KO) mice display a sex-specific osteopenic phenotype characterized by low bone mineral density, bone mineral content, and overall loss of bone strength in female mice. We, therefore, speculated that loss of TIEG1 expression would impair the actions of estrogen on bone in female mice. To test this hypothesis, we employed an ovariectomy (OVX) and estrogen replacement model system to comprehensively analyze the role of TIEG1 in mediating estrogen signaling in bone at the tissue, cell, and biochemical level. Dual-energy X-ray absorptiometry (DXA), peripheral quantitative computed tomography (pQCT), and micro-CT analyses revealed that loss of TIEG1 expression diminished the effects of estrogen throughout the skeleton and within multiple bone compartments. Estrogen exposure also led to reductions in bone formation rates and mineralizing perimeter in wild-type mice with little to no effects on these parameters in TIEG1 KO mice. Osteoclast perimeter per bone perimeter and resorptive activity as determined by serum levels of CTX-1 were differentially regulated after estrogen treatment in TIEG1 KO mice compared with wild-type littermates. No significant differences were detected in serum levels of P1NP between wild-type and TIEG1 KO mice. Taken together, these data implicate an important role for TIEG1 in mediating estrogen signaling throughout the mouse skeleton and suggest that defects in this pathway are likely to contribute to the sex-specific osteopenic phenotype observed in female TIEG1 KO mice.

Effects of estrogen on bone mRNA levels of sclerostin and other genes relevant to bone metabolism in postmenopausal women

CONTEXT

Studies in postmenopausal women have shown that estrogen reduces circulating sclerostin levels, but effects of estrogen on skeletal sclerostin mRNA levels are unknown.

OBJECTIVE

The objective of the study was to evaluate the effects of short-term estrogen treatment on bone mRNA levels of sclerostin and other genes relevant to bone metabolism.

DESIGN, SETTING, AND PATIENTS

Needle bone biopsies were obtained from 20 postmenopausal women treated with transdermal estrogen for 3 weeks and 20 untreated controls. Quantitative PCR analyses were used to examine the expression of sclerostin and other genes related to bone metabolism, including 71 additional genes linked to bone density/fracture from genome-wide association studies.

RESULTS

Estrogen treatment was associated with lower bone sclerostin mRNA levels (by 48%, P<.05) and with lower (by 54%, P<.01) mRNA levels of the sclerostin-related protein, sclerostin domain-containing protein 1 (SOSTDC1), which is also a Wnt/bone morphogenetic protein inhibitor. Consistent with studies in mice showing that ovariectomy increased nuclear factor-κB (NF-κB) activation, we found that estrogen treatment was associated with a significant reduction in inflammatory genes as a group (P=.028), with bone mRNA levels of NFKB2 and RELB (both encoding proteins in the NF-κB transcription factor complex) being significantly reduced individual genes. Eight of the 71 genome-wide association study-related genes examined were modulated by estrogen (P<.05, false discovery rate<0.10).

CONCLUSION

In humans, estrogen-induced decreases in two key inhibitors of Wnt/bone morphogenetic protein signaling, sclerostin and SOSTDC1, along with reductions in NF-κB signaling, may be responsible for at least part of the protective effects of estrogen on bone.

Nitrates and bone turnover (NABT) - trial to select the best nitrate preparation: study protocol for a randomized controlled trial

Background

Organic nitrates uncouple bone turnover, improve bone mineral density, and improve trabecular and cortical components of bone. These changes in turnover, strength and geometry may translate into an important reduction in fractures. However, before proceeding with a large fracture trial, there is a need to identify the nitrate formulation that has both the greatest efficacy (with regards to bone turnover markers) and gives the fewest headaches. Ascertaining which nitrate formulation this may be is the purpose of the current study.

Methods and design

This will be an open-label randomized, controlled trial conducted at Women’s College Hospital comparing five formulations of nitrates for their effects on bone turnover markers and headache. We will recruit postmenopausal women age 50 years or older with no contraindications to nitroglycerin. Our trial will consist of a run-in phase and a treatment phase. We will enroll 420 women in the run-in phase, each to receive all of the 5 potential treatments in random order for 2 days, each with a 2-day washout period between treatments. Those who tolerate all formulations will enter the 12-week treatment phase and be randomly assigned to one of five groups: 0.3 mg sublingual nitroglycerin tablet, 0.6 mg of the sublingual tablet, a 20 mg tablet of isosorbide mononitrate, a 160 mg nitroglycerin transdermal patch (used for 8 h), and 15 mg of nitroglycerin ointment as used in a previous trial by our group. We will continue enrolment until we have randomized 210 women or 35 women per group. Concentrations of bone formation (bone-specific alkaline phosphatase and procollagen type I N-terminal propeptide) and bone resorption (C-telopeptides of collagen crosslinks and N-terminal crosslinks of collagen) agents will be measured in samples taken at study entry (the start of the run in phase) and 12 weeks. Subjects will record the frequency and severity of headaches daily during the run-in phase and then monthly after that. We will use the ‘multiple comparisons with the best’ approach for data analyses, as this strategy allows practical considerations of ease of use and tolerability to guide selection of the preparation for future studies.

Discussion

Data from this protocol will be used to develop a randomized, controlled trial of nitrates to prevent osteoporotic fractures.

Trial registration

ClinicalTrials.gov Identifier: NCT01387672. Controlled-Trials.com: ISRCTN08860742.

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.

The effects of soy isoflavone on bone density in north region of climacteric Chinese women

Only a few investigations were based on limb bone density. This study evaluated the efficacy of soy isoflavone in the treatment of the principal menopausal disorders, limb bone density and the role of pathway. The research protocol involved the random subdivision of the enrolled sample into two groups of 40 women, who were to receive treatment for 6 months with isoflavone (90 mg/day) and with placebo. All of the patients were asked to fill in a questionnaire concerning their complaints. BMD of the radius and tibia were measured using quantitative ultrasound. Bone metabolism indexes calcium, phosphorus and alkaline phosphatase (ALP) were examined regularly. Serum cytokines interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) examined by ELISA. The results of the score of Kupperman table showed that the isoflavone can lead to a significant reduction in some of the disorders. Compared with placebo, the tibia bone density in isoflavone group increased obviously against the base value before trail. Isoflavone led to a stronger descent of the concentration of ALP and a decrease of IL-6 and TNF-α level than placebo. For climacteric women, soy isoflavone in the dose of 90 mg/day could improve some menopausal syndromes and was effective on increasing limb bone density, which maybe had the relationship with the levels of IL-6, TNF-α and ALP in serum.

Limited utility of tartrate-resistant acid phosphatase isoform 5b in assessing response to therapy in osteoporosis

BACKGROUND

Tartrate-resistant acid phosphatase isoform 5b (TRACP5b) is a serum bone resorption marker. Our aim was to investigate its utility in monitoring metabolic bone disease.

METHODS

Serum TRACP5b, C-terminal cross-linking telopeptide of type I collagen, urine N-terminal cross-linking telopeptide of type I collagen and free deoxypyridinoline were measured pre- and post-treatment with a parathyroid hormone analogue [PTH (1-34)] (n = 14) or a bisphosphonate (N-BP) (n = 8). TRACP5b, bone alkaline phosphatase (bone ALP), 25-hydroxyvitamin D (25OHD) and parathyroid hormone (PTH) were measured in 100 osteoporosis patients on prolonged bisphosphonate therapy.

RESULTS

Changes in TRACP5b were smaller in magnitude but mimicked those of other bone resorption markers. Absolute changes in TRACP5b and the other resorption markers correlated significantly (p < 0.001). In patients on long-term bisphosphonates, TRACP5b and bone ALP levels were not suppressed. Vitamin D status was consistent with the level of supplementation.

CONCLUSION

TRACP5b has limited utility as a single marker of metabolic bone disease treatment.

Reference intervals for serum osteocalcin concentrations in adult men and women from the study of health in Pomerania

BACKGROUND

Osteocalcin (OC) is a bone-specific protein produced primarily by osteoblasts during bone formation. Besides its role in bone formation, osteocalcin may play a role in the regulation of energy metabolism and male fertility. To interpret serum OC data, reference intervals adapted to a specific laboratory method are needed.

METHODS

A healthy reference population was selected from the first follow-up of the Study of Health in Pomerania. Serum OC concentrations were measured with the IDS-iSYS N-Mid Osteocalcin assay on the IDS-iSYS Automated System (Immunodiagnostic Systems, Frankfurt am Main, Germany). The reference interval was defined as the central 95% range (2.5th-97.5th percentile). Age-specific reference intervals were calculated by quantile regression for 1107 men (25-79 years) and 545 premenopausal women (25-54 years). The reference interval for 498 postmenopausal women (50-79 years) was calculated irrespective of age.

RESULTS

Median (1st-3rd quartile) serum OC concentrations were 15.4 ng/mL (12.0-19.4 ng/mL) in men, 14.4 ng/mL (11.3-18.5 ng/mL) in premenopausal women, and 18.6 ng/mL (13.6-25.6 ng/mL) in postmenopausal women. Serum OC concentrations were highest in men and premenopausal women aged 25-29 years, were stable during midlife, and rose again after 65 years of age in men and at transition to menopause in women. Serum OC concentrations were lower in women taking oral contraceptives or who were under hormone replacement therapy after menopause and in subjects with diabetes mellitus or with body mass index < 18 or > 30 kg/m2 than in subjects without these conditions.

CONCLUSIONS

We established sex-specific adult reference intervals for the serum OC concentration measured by the IDS-iSYS N-Mid Osteocalcin assay.

Osteocalcin is associated with testosterone in the general population and selected patients with bone disorders

Research in the last decade has revealed that bone is not only a target tissue for numerous circulating hormones but functions as an endocrine organ itself. As a recent study demonstrated a stimulatory effect of the osteoblast-derived hormone osteocalcin (OCN) on testosterone production in mice, we investigated whether such an association can be replicated in humans. We used data from 1338 men (25-86 years) in the population-based epidemiological Study of Health in Pomerania and from 110 male outpatients with bone disorders (18-85 years) for the study. We analysed cross-sectional associations between OCN and total testosterone serum concentrations (TT), as well as associations between further markers of bone turnover [bone-specific alkaline phosphatase (BAP), serum C-terminal telopeptides of Type I collagen (CTX), urinary deoxypyridinoline] and TT using ordinary least square (OLS) regression models. Multivariable OLS models revealed a positive association between OCN and TT in the population-based (β coefficients for a one standard deviation increase, 0.590; standard error (SE), 0.175; p-value, <0.01) and patient-based (β coefficient, 0.575; SE, 0.132; p-value, <0.01) samples even after adjustment for age and body mass index (both samples), and time of blood sampling (population-based sample only). Furthermore, we observed positive associations between BAP and TT (β coefficient, 0.403; SE, 0.170; p-value, 0.02) as well as between CTX and TT (β coefficient, 0.733; SE, 0.172; p-value, <0.01) in men from the general population. The present investigation shows that OCN is associated with TT in the general population and in patients with bone disorders, and may thus indicate general male health status. Additional longitudinal observational studies are warranted to confirm our findings and future experimental research is necessary to elucidate potential mechanisms underlying the observed associations.

Estrogen and the skeleton

Estrogen is the major hormonal regulator of bone metabolism in women and men. Therefore, there is considerable interest in unraveling the pathways by which estrogen exerts its protective effects on bone. Although the major consequence of the loss of estrogen is an increase in bone resorption, estrogen deficiency is associated with a gap between bone resorption and formation, indicating that estrogen is also important for maintaining bone formation at the cellular level. Direct estrogen effects on osteocytes, osteoclasts, and osteoblasts lead to inhibition of bone remodeling, decreased bone resorption, and maintenance of bone formation, respectively. Estrogen also modulates osteoblast/osteocyte and T-cell regulation of osteoclasts. Unraveling these pleiotropic effects of estrogen may lead to new approaches to prevent and treat osteoporosis.

National Bone Health Alliance Bone Turnover Marker Project: current practices and the need for US harmonization, standardization, and common reference ranges

This position paper reviews how the National Bone Health Alliance (NBHA) will execute a project to help assure health professionals of the clinical utility of bone turnover markers; the current clinical approaches concerning osteoporosis and the status and use of bone turnover markers in the USA; the rationale for focusing this effort around two specific bone turnover markers; the need to standardize bone marker sample collection procedures, reference ranges, and bone turnover marker assays in clinical laboratories; and the importance of harmonization for future research of bone turnover markers.

INTRODUCTION

Osteoporosis is a major global health problem, with the prevalence and incidence of osteoporosis for at-risk populations estimated to be 44 million Americans. The potential of bone markers as an additional tool for health care professionals to improve patient outcomes and impact morbidity and mortality is crucial in providing better health care and addressing rising health care costs. This need to advance the field of bone turnover markers has been recognized by a number of organizations, including the International Osteoporosis Foundation (IOF), National Osteoporosis Foundation, International Federation of Clinical Chemistry, and Laboratory Medicine (IFCC), and the NBHA.

METHODS

This position paper elucidates how this project will standardize bone turnover marker sample collection procedures in the USA, establish a USA reference range for one bone formation (serum procollagen type I N propeptide, s-PINP) and one bone resorption (serum C-terminal telopeptide of type I collagen, s-CTX) marker, and standardize bone turnover marker assays used in clinical laboratories. This effort will allow clinicians from the USA to have confidence in their use of bone turnover markers to help monitor osteoporosis treatment and assess future fracture risk. This project builds on the recommendations of the IOF/IFCC Bone Marker Standards Working Group by developing USA reference standards for s-PINP and s-CTX, the markers identified as most promising for use as reference markers.

RESULTS

The goals of this project will be realized through the NBHA and will include its governmental, academic, for-profit, and non-profit sector stakeholders as well as major academic and commercial laboratories. Upon completion, a parallel effort will be pursued to make bone turnover marker measurements reliable and accepted by all health care professionals for facilitating treatment decisions and ultimately be reimbursed by all health insurance payers.

CONCLUSIONS

Successful completion of this project will help assure health professionals from the USA of the clinical utility of bone turnover markers and ties in with the parallel effort of the IOF/IFCC to develop worldwide bone turnover reference ranges.

Pathogenesis of age-related bone loss in humans

BACKGROUND

Although data from rodent systems are extremely useful in providing insights into possible mechanisms of age-related bone loss, concepts evolving from animal models need to ultimately be tested in humans.

METHODS

This review provides an update on mechanisms of age-related bone loss in humans based on the author's knowledge of the field and focused literature reviews.

RESULTS

Novel imaging, experimental models, biomarkers, and analytic techniques applied directly to human studies are providing new insights into the patterns of bone mass acquisition and loss as well as the role of sex steroids, in particular estrogen, on bone metabolism and bone loss with aging in women and men. These studies have identified the onset of trabecular bone loss at multiple sites that begins in young adulthood and remains unexplained, at least based on current paradigms of the mechanisms of bone loss. In addition, estrogen appears to be a major regulator of bone metabolism not only in women but also in men. Studies assessing mechanisms of estrogen action on bone in humans have identified effects of estrogen on RANKL expression by several different cell types in the bone microenvironment, a role for TNF-α and IL-1β in mediating effects of estrogen deficiency on bone, and possible regulation of the Wnt inhibitor, sclerostin, by estrogen.

CONCLUSIONS

There have been considerable advances in our understanding of age-related bone loss in humans. However, there are also significant gaps in knowledge, particularly in defining cell autonomous changes in bone in human studies to test or validate concepts emerging from studies in rodents. Decision Editor: Luigi Ferrucci, MD, PhD.

The usefulness of high pre-operative levels of serum type I collagen bone markers for the prediction of changes in bone mineral density after parathyroidectomy

BACKGROUND

Amino-terminal procollagen propeptide of type I collagen (P1NP) and cross-linked C-terminal telopeptide of type I collagen (βCTX) are two of the more sensitive bone markers for reflecting and monitoring patients with an increased bone turnover as observed in primary hyperparathyroidism (PHPT) patients.

AIM

The present study was performed to evaluate the trend of type I collagen markers one year after parathyroidectomy (PTX) and to examine the relationships between serum P1NP and βCTX levels and bone mineral density (BMD) change after PTX in PHPT Spanish patients.

MATERIALS AND METHODS

Fifty-three PHPT patients were enroled and were followed for one year by measuring lumbar BMD, lumbar t-score, lumbar z-score, PTH, calcium, phosphorus, P1NP and βCTX.

RESULTS

Pre-surgery concentrations of both markers were elevated (P1NP: 90.71±5.03; βCTX: 1.52±0.44). A significant decrease was observed in mean post-operative βCTX and P1NP concentrations (p<0.0001). Levels of BMD, t-score and z-score at lumbar spine were relatively low (BMD: 0.75±0.16; z-score -0.90±0.23; t-score -2.51±0.32); after PTX a significant increase was observed in the levels of these three parameters. P1NP and βCTX were correlated with lumbar BMD change one year after PTX (P1NP: r=0.79, p=0.016; βCTX: r=0.89, p=0.003).

CONCLUSIONS

Pre-surgery concentrations of both bone markers were elevated and a significant decrease after PTX was found. Serum βCTX and P1NP levels were potently related to lumbar BMD changes over one year after PTX. The measurement of βCTX and P1NP would be useful to predict long-term changes in lumbar BMD after PTX.

Postmenopausal osteoporosis treatment with antiresorptives: effects of discontinuation or long-term continuation on bone turnover and fracture risk--a perspective

Osteoporosis may be a lifelong condition. Robust data regarding the efficacy and safety of both long-term osteoporosis therapy and therapy discontinuation are therefore important. A paucity of clinical trial data regarding the long-term antifracture efficacy of osteoporosis therapies necessitates the use of surrogate endpoints in discussions surrounding long-term use and/or discontinuation. Long-term treatment (beyond 3-4 years) may produce further increases in bone mineral density (BMD) or BMD stability, depending on the specific treatment and the skeletal site. Bisphosphonates, when discontinued, are associated with a prolonged reduction in bone turnover markers (BTMs), with a very gradual increase to pretreatment levels within 3 to 60 months of treatment cessation, depending on the bisphosphonate used and the prior duration of therapy. In contrast, with nonbisphosphonate antiresorptive agents, such as estrogen and denosumab, BTMs rebound to above pretreatment values within months of discontinuation. The pattern of BTM change is generally mirrored by a more or less rapid decrease in BMD. Although the prolonged effect of some bisphosphonates on BTMs and BMD may contribute to residual benefit on bone strength, it may also raise safety concerns. Adequately powered postdiscontinuation fracture studies and conclusive evidence on maintenance or loss of fracture benefit is lacking for bisphosphonates. Similarly, the effects of rapid reversal of bone turnover upon discontinuation of denosumab on fracture risk remain unknown. Ideally, studies evaluating the effects of long-term treatment and treatment discontinuation should be designed to provide head-to-head "offset" data between bisphosphonates and nonbisphosphonate antiresorptive agents. In the absence of this, a clinical recommendation for physicians may be to periodically assess the benefits/risks of continuation versus discontinuation versus alternative management strategies.

Patients with cirrhosis and ascites have false values of bone density: implications for the diagnosis of osteoporosis

The effect of ascites on bone densitometry has been assessed in 25 patients with advanced cirrhosis, and it was concluded that ascites over 4 l causes inaccuracy of BMD measurements, particularly at the lumbar spine. This fact must be considered when assessing bone mass in patients with decompensated cirrhosis.

INTRODUCTION

Bone mineral density (BMD) measured by dual-energy x-ray absorptiometry (DXA) is the best procedure for assessment of osteoporosis and fracture risk, but BMD values at the central skeleton may be influenced by changes in soft tissues. Therefore, we have studied the effect of ascites on BMD.

METHODS

BMD was measured by DXA at the lumbar spine, femoral neck and total hip, just before and shortly after therapeutic paracentesis in 25 patients with advanced liver cirrhosis. Changes in BMD, lean and fat mass, abdominal diameter and weight, as well as the amount of removed ascites were measured.

RESULTS

The amount of drained ascites was 6.6 ± 0.5 l (range: 3.0 to 12.7 l). After paracentesis, BMD increased at the lumbar spine (from 0.944 ± 0.035 to 0.997 ± 0.038 g/cm(2), p < 0.001) and at the total hip (from 0.913 ± 0.036 to 0.926 ± 0.036 g/cm(2), p < 0.01). Patients with a volume of drained ascites higher than 4 l showed a significant increase in lumbar BMD (7.0%), compared with patients with a lower amount (1.5%) (p < 0.03). The decrease in total soft tissue mass correlated with the amount of removed ascites (r = 0.951, p < 0.001). Diagnosis of osteoporosis or osteopenia changed after paracentesis in 12% of patients.

CONCLUSION

Ascites over 4 l causes inaccuracy of BMD measurements, particularly at the lumbar spine. This fact must be considered when assessing bone mass in patients with advanced cirrhosis.