An update on biomarkers of bone turnover and their utility in biomedical research and clinical practice

Daily supplement of sesame oil prevents postmenopausal osteoporosis via maintaining serum estrogen and aromatase levels in rats

Estrogen deficiency is one of the main causes of postmenopausal osteoporosis in elderly women. Hormone replacement therapy has been employed to manage postmenopausal osteoporosis; however, it has raised concerns related to heart attacks and breast cancer. Sesame oil has been reported to affect sex hormone status. The aim of the present study is to evaluate the effect of sesame oil supplement on postmenopausal osteoporosis in rats. We used female Sprague Dawley rats that underwent bilaterally ovariectomy (OVX) as an experimental postmenopausal osteoporosis animal model. These rats were orally administrated sesame oil (0.25 or 0.5 mL/kg/day) for four months as the therapeutic group. We assessed bone mineral density (BMD) and the levels of osteocalcin, procollagen-I C-terminal propeptide (PICP), collagen cross-linked N-telopeptide (NTx), estradiol, and aromatase in the sera. The daily supplementation of sesame oil significantly increased BMD, serum osteocalcin levels, and trabecular areas in the OVX-treated rats. Sesame oil also elevated serum PICP levels and decreased NTx levels in these rats. Furthermore, sesame oil effectively maintained serum estradiol and aromatase levels in the OVX-induced osteoporosis rats. In conclusion, daily supplementation of sesame oil prevents postmenopausal osteoporosis by maintaining serum estrogen and aromatase levels, while also modulating the imbalance between bone formation and resorption in osteoporosis rats.

From biochemical markers to molecular endotypes of osteoarthritis: a review on validated biomarkers

INTRODUCTION

Osteoarthritis (OA) affects over 500 million people worldwide. OA patients are symptomatically treated, and current therapies exhibit marginal efficacy and frequently carry safety-risks associated with chronic use. No disease-modifying therapies have been approved to date leaving surgical joint replacement as a last resort. To enable effective patient care and successful drug development there is an urgent need to uncover the pathobiological drivers of OA and how these translate into disease endotypes. Endotypes provide a more precise and mechanistic definition of disease subgroups than observable phenotypes, and a panel of tissue- and pathology-specific biochemical markers may uncover treatable endotypes of OA.

AREAS COVERED

We have searched PubMed for full-text articles written in English to provide an in-depth narrative review of a panel of validated biochemical markers utilized for endotyping of OA and their association to key OA pathologies.

EXPERT OPINION

As utilized in IMI-APPROACH and validated in OAI-FNIH, a panel of biochemical markers may uncover disease subgroups and facilitate the enrichment of treatable molecular endotypes for recruitment in therapeutic clinical trials. Understanding the link between biochemical markers and patient-reported outcomes and treatable endotypes that may respond to given therapies will pave the way for new drug development in OA.

First Ecuadorian statement consensus for the evaluation and treatment of osteoporosis

Osteoporosis management has become more relevant as the life expectancy increases. In Ecuador, approximately 19% of adults over 65 years of age have been diagnosed with osteoporosis. There is no national consensus for the management and prevention of the disease being this proposal the first Ecuadorian consensus.

INTRODUCTION

In Ecuador, it is estimated that around 19% of adults over 65 years of age have osteoporosis. Due to the increase in life expectancy in the world population, the evaluation and management of osteoporosis has become more relevant. Currently, there is no national consensus for the management and prevention of the disease. The Ecuadorian Society of Rheumatology presented the project for the elaboration of the first Ecuadorian consensus for the management and prevention of osteoporosis.

METHODS

A panel of experts in multiple areas and extensive experience was invited to participate. The consensus was carried out using the Delphi method. Six working dimensions were created: definition and epidemiology of osteoporosis, fracture risk prediction tools, non-pharmacological treatment, pharmacological treatment, calcium and vitamin D, and glucocorticoid-induced osteoporosis.

RESULTS

The first round was held in December 2021, followed by the second round in February 2022 and the third round in March 2022. The data was shared with the specialists at the end of each round. After three rounds of work, a consensus was reached for the management and prevention of osteoporosis.

CONCLUSION

This is the first Ecuadorian consensus for the management and treatment of postmenopausal osteoporosis.

Calcium status assessment at the population level: Candidate approaches and challenges

Inadequate dietary calcium intake is a global public health problem that disproportionately affects low- and middle-income countries. However, the calcium status of a population is challenging to measure, and there are no standard methods to identify high-risk communities even in settings with an elevated prevalence of a disease caused or exacerbated by low calcium intake (e.g., rickets). The calcium status of a population depends on numerous factors, including intake of calcium-rich foods; the bioavailability of the types of calcium consumed in foods and supplements; and population characteristics, including age, sex, vitamin D status, and genetic attributes that influence calcium retention and absorption. The aim of this narrative review was to assess candidate indicators of population-level calcium status based on a range of biomarkers and measurement methods, including dietary assessment, calcium balance studies, hormonal factors related to calcium, and health outcomes associated with low calcium status. Several promising approaches were identified, but there was insufficient evidence of the suitability of any single indicator to assess population calcium status. Further research is required to develop and validate specific indicators of calcium status that could be derived from the analysis of data or samples that are feasibly collected in population-based surveys.

A Comparative Study of Bone Tissue Morphology and Bone Turnover Markers in Different Stages of Kümmell's Disease

Although the incidence of Kümmell's disease (KD) has increased significantly in recent years, its pathological mechanism is still unclear. The aim of this study is to investigate the histomorphological characteristics and the kinetics of bone turnover markers following KD. This study involves 82 patients with KD, and fasting blood samples were collected to detect the serum concentration of bone turnover markers. A transpedicular bone biopsy was performed to collect bone biopsy specimens during vertebroplasty surgery. According to Li's staging system for KD, all cases were divided into 3 stages. Comparisons of the 3 stages and their kinetics were conducted. 19 (23.2%) patients were classified as Stage I, 39 (47.5%) as Stage II, 24 (29.2%) as Stage III. Bone histomorphological analysis showed that the ratios of WBV and FV reached a peak value (14.23 ± 0.62 and 54.63% ± 3.52%; p = 0.001 and 0.001) at Stage I. The ratios of NBV remained low (4.81% ± 2.61%) in Stage I, but reached a peak value (18.50% ± 2.77%; p = 0.001) in Stage III. Bone metabolism index level showed that the serum concentration of OST and β-CTX continued to rise after fracture, reaching a peak value of (38.15 ± 3.84 and 1.31 ± 0.16 ng/Ml; p = 0.073 and 0.026), while PINP reached its valley value (48.57 ± 7.25 ng/Ml; p = 0.069) in Stage III. A significant and negative correlation was found between the ratio of β-CTX and EBV/TV (p= 0.0194, r = -0.2037), and FV/TV (p= 0.0001, r = -0.5368). At the same time, β-CTX had a positive significant correlation with the NBV/TV (p= 0.0001, r = 0.6218). Bone histomorphometric analysis and bone turnover markers showed that KD has a possibility of healing in the early stage.

Clinical monitoring in osteoarthritis: Biomarkers

OBJECTIVE

The purpose of this overview of osteoarthritis (OA) biomarkers is to provide the non-specialist with a toolbox, based on experience acquired by biomarker researchers over many years, to understand biomarkers in general and their use in the OA field.

METHODS

We provide an update on this subject since the OARSI Primer on osteoarthritis (OA) nearly a decade ago.

RESULTS

Since the last update, the importance of molecular biomarkers has been increasingly recognized in the field, but no OA-related biomarkers have been adopted for routine use in clinical practice. The current lack of chondroprotective treatments for OA impairs the assessment, validation and qualification of the potential role of biomarkers as tools for monitoring disease status and patient responses to treatment of OA. Yet there is no lack of an evolving compendium of OA-related biomarkers, ever more fit-for-purpose, that could currently facilitate drug development for OA. We provide an abbreviated update and overview of specific soluble OA-related biomarkers for this new OARSI Primer on OA with OA-relevant examples encompassing the concepts of biomarker nomenclature, qualification, interpretation, measurement, reporting requirements, application to research, drug discovery and clinical care, and future needs for biomarker advancement.

CONCLUSION

Appropriate biomarkers should play a role at all stages of OA diagnosis, prognosis, drug development, and treatment. The future of OA biomarker research and development holds great promise as its foundation is increasingly robust.

Dietary supplementation of 25-hydroxycholecalciferol as an alternative to cholecalciferol in swine diets: A review

25-hydroxycholecalciferol (25-OHD₃ ) formed via hepatic hydroxylation from vitamin D, cholecalciferol, represents the precursor of the biologically active vitamin D hormone, 1,25-dihydroxyvitamin D. Due to a higher absorption rate and the omission of one hydroxylation, dietary supplementation of 25-OHD₃ instead of vitamin D₃ is considered to be more efficient as plasma concentrations of 25-OHD₃ are increased more pronounced. The present review summarises studies investigating potential beneficial effects on mineral homeostasis, bone metabolism, health status and performance in sows, piglets and fattening pigs. Results are inconsistent. While most studies could not demonstrate any or only a slight impact of partial or total replacement of vitamin D₃ by 25-OHD₃ , some experiments indicated that 25-OHD₃ might alter physiological processes when animals are challenged, for example, by a restricted mineral supply.

An MMP-degraded and cross-linked fragment of type III collagen as a non-invasive biomarker of hepatic fibrosis resolution

BACKGROUND AND AIMS

Liver fibrosis results from a prolonged wound healing response to continued injury with excessive production of extracellular proteins. In patients with chronic liver disease, the monitoring of liver fibrosis dynamics is of high interest. Whilst markers of fibrogenesis exist, markers of hepatic fibrosis resolution remain an unmet clinical need. Thus, we sought to develop an assay quantifying a circulating proteolytic fragment of cross-linked type III collagen as a biomarker of fibrolysis, testing its utility in two clinical cohorts of liver fibrosis of distinct aetiology and regressing endotype METHODS: We used a monoclonal antibody targeting the C-telopeptide of type III collagen following C-proteinase cleavage to develop and validate a neo-epitope-specific enzyme-linked immunosorbent assay (CTX-III). A potential fibrosis resolution marker, CTX-III, was measured in two clinical cohorts of patients with obesity-associated non-alcoholic fatty liver disease undergoing bariatric surgery or hepatitis C virus infection from a clinical trial study evaluating the anti-fibrotic effect of farglitazar.

RESULTS

CTX-III was robust and specific for the targeted neo-epitope with good reproducibility in EDTA plasma. We assessed type III collagen remodelling using a panel of biomarkers, including a type III collagen formation marker (PRO-C3), degradation (C3M), and CTX-III (fibrolysis). Net fibrolysis was increased in patients with non-alcoholic fatty liver disease following bariatric surgery (p < .001). Moreover, net fibrolysis identified spontaneous fibrotic regressors from stable and progressors (p < .05 and p < .001) among hepatitis C virus infection patients.

CONCLUSION

Circulating CTX-III as a marker of fibrolysis indicates the biomarker's beneficial use in assessing hepatic fibrosis resolution.

Bone microarchitecture and metabolism in elderly male patients with signs of intravertebral cleft on MRI

OBJECTIVES

Intravertebral cleft (IVC) is a common but not unique imaging manifestation in Kümmell's disease. To date, great controversy exists regarding the specific mechanisms of IVC. In this study, we aimed to investigate the characteristics of microarchitecture and metabolism in patients with IVC and to analyse the correlations between degree of vertebral collapse and risk factors.

METHODS

A total of 79 elderly men were included in this study. We divided all patients into two groups: the IVC group (30 patients) and the non-IVC group (49 patients). We compared the differences in microarchitecture and bone turnover marker (BTM) serum concentrations between the groups and analysed risk factors affecting vertebral collapse by using the Mann-Whitney U test and Spearman's correlation test.

RESULTS

Quantitative analysis of the microarchitecture showed higher content of necrotic bone (p < 0.001) and lower content of lamellar bone (p < 0.001) in the IVC group. Analysis of BTMs identified lower concentration of N-terminal propeptide of type I collagen (PINP, p = 0.002) and higher concentration of β-isomerized C-terminal telopeptide (β-CTX, p < 0.001) in the IVC group. The correlation analysis showed that lamellar bone content (p < 0.001) and spine T-score (p = 0.011) were significantly correlated with the degree of vertebral collapse.

CONCLUSIONS

IVC is a radiological feature of excessive bone resorption by higher activities of osteoclasts and decreased bone remodelling ability by lower activities of osteoblasts. Histomorphological feature in patients with IVC is delayed callus mineralisation, which may increase the risk of vertebral collapse.

KEY POINTS

• A key histomorphological feature in patients with IVC is delayed callus mineralisation, which may aggravate the degree of vertebral collapse. • We investigated bone metabolism in patients with IVC to evaluate the activities of osteoclasts and osteoblasts directly. • We propose a novel hypothesis for the pathogenesis of IVC: bone resorption by higher activity of osteoclasts and decreased callus mineralisation ability by lower activity of osteoblasts are the main mechanisms leading to IVC.

Biochemical Markers of Bone Turnover in Older Adults With Type 1 Diabetes

CONTEXT

Type 1 diabetes (T1D) is characterized by high fracture risk, yet little is known regarding diabetes-related mechanisms or risk factors.

OBJECTIVE

Determine whether glycemic control, advanced glycation end products (AGEs), and microvascular complications are associated with bone turnover markers among older T1D adults.

DESIGN

Cross-sectional.

SETTING

Epidemiology of Diabetes Interventions and Complications study (6 of 27 clinical centers).

PARTICIPANTS

232 T1D participants followed for >30 years.

EXPOSURES

Glycemic control ascertained as concurrent and cumulative hemoglobin A1c (HbA1c); kidney function, by estimated glomerular filtration rates (eGFR); and AGEs, by skin intrinsic fluorescence.

MAIN OUTCOME MEASURES

Serum procollagen 1 intact N-terminal propeptide (PINP), bone-specific alkaline phosphatase (bone ALP), serum C-telopeptide (sCTX), tartrate-resistant acid phosphatase 5b (TRACP5b), and sclerostin.

RESULTS

Mean age was 59.6 ± 6.8 years, and 48% were female. In models with HbA1c, eGFR, and AGEs, adjusted for age and sex, higher concurrent HbA1c was associated with lower PINP [β -3.4 pg/mL (95% CI -6.1, -0.7), P = 0.015 for each 1% higher HbA1c]. Lower eGFR was associated with higher PINP [6.9 pg/mL (95% CI 3.8, 10.0), P < 0.0001 for each -20 mL/min/1.73 m2 eGFR], bone ALP [1.0 U/L (95% CI 0.2, 1.9), P = 0.011], sCTX [53.6 pg/mL (95% CI 32.6, 74.6), P < 0.0001], and TRACP5b [0.3 U/L (95% CI 0.1, 0.4), P = 0.002]. However, AGEs were not associated with any bone turnover markers in adjusted models. HbA1c, eGFR, and AGEs were not associated with sclerostin levels.

CONCLUSIONS

Among older adults with T1D, poor glycemic control is a risk factor for reduced bone formation, while reduced kidney function is a risk factor for increased bone resorption and formation.

Between-subject and within-subject variability in measures of biochemical markers of bone turnover in cynomolgus and rhesus macaques

Development of optimal bone mass during early adulthood is determined by the balance between bone formation and resorption. The utility of minimally invasive biomarkers for monitoring bone turnover balance in maturing non-human primates has received limited attention. This study evaluated the biological variation of osteocalcin (a marker of bone formation), carboxyterminal cross-linking telopeptide of type 1 collagen (CTX, a marker of bone resorption), and the ratio of osteocalcin to CTX (reflecting bone turnover balance), in 136 rhesus and cynomolgus macaques aged 3.8-11.6 years. In a subsample of the animals (n = 28), blood samples were collected at monthly intervals over 4 months. Between-subject analysis revealed that there were no sex or species differences for CTX. Osteocalcin and the ratio of osteocalcin to CTX were higher in males than in females, and in rhesus macaques than in cynomolgus macaques. There were no changes in osteocalcin, CTX, or the ratio of osteocalcin to CTX across 4 months for any of the groups. In contrast, there was considerable within-subject variation in osteocalcin and CTX concentrations. However, differences in values exhibited no discernible pattern, suggesting that within-subject variation can be reduced by averaging repeat measurements. In summary, the data provide reference values for male and female rhesus and cynomolgus macaques and support the utility of osteocalcin and CTX as biomarkers to monitor bone turnover at the population level.

Considerations for understanding protein measurements: Identification of formation, degradation and more pathological relevant epitopes

OBJECTIVES

There is a need for precision medicine and an unspoken promise of an optimal approach for identification of the right patients for value-based medicine based on big data. However, there may be a misconception that measurement of proteins is more valuable than measurement of fewer selected biomarkers. In population-based research, variation may be somewhat eliminated by quantity. However, this fascination of numbers may limit the attention to and understanding of the single. This review highlights that protein measurements (with collagens as examples) may mean different things depending on the targeted epitope - formation or degradation of tissues, and even signaling potential of proteins.

DESIGN AND METHODS

PubMed was searched for collagen, neo-epitope, biomarkers.

RESULTS

Ample examples of assays with specific epitopes, either pathological such as HbA1c, or domain specific such as pro-peptides, which total protein arrays would not have identified were evident.

CONCLUSIONS

We suggest that big data may be considered as the funnel of data points, in which most important parameters will be selected. If the technical precision is low or the biological accuracy is limited, and we include suboptimal quality of biomarkers, disguised as big data, we may not be able to fulfill the promise of helping patients searching for the optimal treatment. Alternatively, if the technical precision of the total protein quantification is high, but we miss the functional domains with the most considerable biological meaning, we miss the most important and valuable information of a given protein. This review highlights that measurements of the same protein in different ways may provide completely different meanings. We need to understand the pathological importance of each epitope quantified to maximize protein measurements.

The Impact of Bone Mineral Density on Bone Metabolism and the Fracture Healing Process in Elderly Chinese Patients With Osteoporotic Vertebral Compression Fractures

BACKGROUND

The aim of this study was to investigate the effect of bone mineral density (BMD) on bone histomorphological parameters and bone turnover markers (BTMs) following osteoporotic vertebral compression fracture (OVCF) and to determine the correlation between BMD and the percentage of middle height compression during the healing process.

METHODS

A total of 206 patients with OVCFs were included in this study. Bone biopsy specimens were acquired during surgery. Blood samples were obtained to determine the serum concentrations of BTMs. The patients were divided into 2 groups according to BMD.

RESULTS

The concentrations of N-terminal propeptide of type I collagen (PINP) in the T-score ≤ -2.5 group (50.92 ± 12.78 ng/ml) were significantly lower than those in the T-score > -2.5 group (68.75 ± 28.66 ng/ml, p = 0.025) 3-6 mo after fracture. Moreover, the volume of necrotic bone in the T-score ≤ -2.5 group (15.15 ± 5.44%) was higher than that (1.67 ± 0.79%, p < 0.001) in the T-score > -2.5 group during the same period. BMD was statistically correlated with cancellous bone content (R_S = 0.761, p <0.001), PMHC (R_S = 0.85, p < 0.001), fibrous tissue volume (R_S = -0.376, p < 0.001), and necrotic bone content (R_S = -0.487, p < 0.001).

CONCLUSIONS

The healing process of OVCFs in the setting of low bone mass frequently occurs in the presence of decreased bone formation abilities, severe vertebral body height loss and a large amount of necrotic bone.

Evaluation of hematology, general serum biochemistry, bone turnover markers and bone marrow cytology in a glucocorticoid treated ovariectomized sheep model for osteoporosis research

Osteoporosis is a metabolic disorder characterized by a loss of bone mass and structure and increasing the risk of fragility fractures, mostly among postmenopausal women. Sheep is a recognized large animal model for osteoporosis research. An experimental group of ewes (3-4 years old) was subjected to ovariectomy (OVX) and weekly glucocorticoid (GC) application for 24 weeks and compared with a sham control group. Blood and bone marrow parameters were analyzed before and 24 weeks after OVX and GC administration. Osteopenia was confirmed through micro-computed tomography and histomorphometric analysis of L4 vertebra in the study end. A statistically significant increase was observed in mean corpuscular volume, mean cell hemoglobin and monocytes and a decrease in red blood count and eosinophils (p<0.05). Alkaline phosphatase (ALP), gamma-glutamyl transpeptidase, magnesium and α1-globulin increased, and creatinine, albumin, sodium and estradiol decreased (p<0.05). A slight decrease of bone formation markers (bone ALP and osteocalcin) and an increase of bone resorption markers (C-terminal telopeptides of collagen type 1 and tartrate-resistant acid phosphatase) were observed, but without statistical significance. This study aims to contribute to better knowledge of sheep as a model for osteoporosis research and the consequences that a performed induction protocol may impose on organic metabolism.

Metabolomic Associations with Serum Bone Turnover Markers

Bone is a dynamic tissue that is in a constant state of remodeling. Bone turnover markers (BTMs), procollagen type I N-terminal propeptide (P1NP) and C-terminal telopeptides of type I collagen (CTX), provide sensitive measures of bone formation and resorption, respectively. This study used ultra-high-resolution metabolomics (HRM) to determine plasma metabolic pathways and targeted metabolites related to the markers of bone resorption and formation in adults. This cross-sectional clinical study included 34 adults (19 females, mean 27.8 years), without reported illnesses, recruited from a US metropolitan area. Serum BTM levels were quantified by an ELISA. Plasma HRM utilized dual-column liquid chromatography and mass spectrometry to identify metabolites and metabolic pathways associated with BTMs. Metabolites significantly associated with P1NP (p < 0.05) were significantly enriched in pathways linked to the TCA cycle, pyruvate metabolism, and metabolism of B vitamins important for energy production (e.g., niacin, thiamin). Other nutrition-related metabolic pathways associated with P1NP were amino acid (proline, arginine, glutamate) and vitamin C metabolism, which are important for collagen formation. Metabolites associated with CTX levels (p < 0.05) were enriched within lipid and fatty acid beta-oxidation metabolic pathways, as well as fat-soluble micronutrient pathways including, vitamin D metabolism, vitamin E metabolism, and bile acid biosynthesis. P1NP and CTX were significantly related to microbiome-related metabolites (p < 0.05). Macronutrient-related pathways including lipid, carbohydrate, and amino acid metabolism, as well as several gut microbiome-derived metabolites were significantly related to BTMs. Future research should compare metabolism BTMs relationships reported here to aging and clinical populations to inform targeted therapeutic interventions.

Changes of Bone Turnover Markers and Bone Tissue Content After Severe Osteoporotic Vertebral Compression Fracture

Background

The incidence of osteoporotic vertebral fractures (OVCFs) has increased significantly in recent years. In order to assess osteoporotic fracture healing process, it is necessary to study the characteristics after this type of vertebral fracture. However, there are few researches on fracture healing process in severe OVCFs. We aim to investigate the histological healing process and the kinetics of bone turnover markers following severe OVCFs.

Material/Methods

There were 149 patients with severe OVCFs included in this study. Fasting blood samples were obtained to detect bone turnover markers levels. A transpedicular bone biopsy was performed to collect bone biopsy specimens during vertebroplasty surgery. Stratification of healing process was performed: stage I (1–3 days), stage II (4–10 days), stage III (11–20 days), stage IV (21–30 days), stage V (1–3 months), stage VI (3–6 months).

Results

Quantitative analysis of bone histomorphometry showed that a large amount of necrotic bone tissue was observed in stage VI (12.92±3.66%). Bone turnover markers showed the concentration of β-isomerized C-terminal telopeptide (β-CTX) which reflects activity in osteoclast continued to increase in stage VI (0.9±0.33 ng/mL). These results differed from previous reports of other type vertebral fractures.

Conclusions

Bone histomorphometric analysis and bone turnover markers showed that severe osteoporotic vertebral compression fractures often associated with delayed union and nonunion during the healing process.

Role of Secreted Frizzled-Related Protein 1 and Tumor Necrosis Factor-α (TNF-α) in Bone Loss of Patients with Rheumatoid Arthritis

Bone loss is one of the emerging extra-articular manifestations of rheumatoid arthritis. TNF-α is the main inflammatory cytokine that can directly increase bone resorption. However, its role in bone formation is still unknown, especially related to secreted frizzled-related protein 1 (SFRP-1), an osteoblast inhibitor. This study examines the correlation between TNF-α and SFRP-1, with a bone turn over marker (CTX and P1NP). This is a cross-sectional study with 38 subjects of premenopausal female patients with RA. This study found that 60.6% of the patients were in remission or low disease activity. The median of TNF-α was 10.6 pg/mL, mean of SFRP-1 was 9.29 ng/mL, mean of CTX was 2.74 ng/mL, and the median of P1NP was 34.04 pg/ml. There is positive correlation between TNF-α and P1NP (r = 0.363, p = 0.026), also between SFRP-1 and P1NP (r = 0.341; p = 0.036). A low level of TNF-𝛼, high level of SFRP-1, high level of CTX, and low level of P1NP in this study indicate a high bone turn over process, with dominant resorption activity in premenopausal female patients with RA.

Molecular taxonomy of osteoarthritis for patient stratification, disease management and drug development: biochemical markers associated with emerging clinical phenotypes and molecular endotypes

PURPOSE OF REVIEW

This review focuses on the molecular taxonomy of osteoarthritis from the perspective of molecular biomarkers. We discuss how wet biochemical markers may be used to understand disease pathogenesis and progression and define molecular endotypes of osteoarthritis and how these correspond to clinical phenotypes.

RECENT FINDINGS

Emerging evidence suggests that osteoarthritis is a heterogeneous and multifaceted disease with multiple causes, molecular endotypes and corresponding clinical phenotypes. Biomarkers may be employed as tools for patient stratification in clinical trials, enhanced disease management in the primary care centres of the future and for directing more rational and targeted osteoarthritis drug development. Proximal molecular biomarkers (e.g synovial fluid) are more likely to distinguish between molecular endotypes because there is less interference from systemic sources of biomarker noise, including comorbidities.

SUMMARY

In this review, we have focused on the molecular biomarkers of four distinct osteoarthritis subtypes including inflammatory, subchondral bone remodelling, metabolic syndrome and senescent age-related endotypes, which have corresponding phenotypes. Progress in the field of osteoarthritis endotype and phenotype research requires a better understanding of molecular biomarkers that may be used in conjunction with imaging, pain and functional assessments for the design of more effective, stratified and individualized osteoarthritis treatments.

Metabolomics analysis in adults with high bone mass identifies a relationship between bone resorption and circulating citrate which replicates in the general population

OBJECTIVE

Bone turnover, which regulates bone mass, may exert metabolic consequences, particularly on markers of glucose metabolism and adiposity. To better understand these relationships, we examined cross-sectional associations between bone turnover markers (BTMs) and metabolic traits in a population with high bone mass (HBM, BMD Z-score ≥+3.2).

DESIGN

β-C-terminal telopeptide of type-I collagen (β-CTX), procollagen type-1 amino-terminal propeptide (P1NP) and osteocalcin were assessed by electrochemiluminescence immunoassays. Metabolic traits, including lipids and glycolysis-related metabolites, were measured using nuclear magnetic resonance spectroscopy. Associations of BTMs with metabolic traits were assessed using generalized estimating equation linear regression, accounting for within-family correlation, adjusting for potential confounders (age, sex, height, weight, menopause, bisphosphonate and oral glucocorticoid use).

RESULTS

A total of 198 adults with HBM had complete data, mean [SD] age 61.6 [13.7] years; 77% were female. Of 23 summary metabolic traits, citrate was positively related to all BTMs: adjusted ββ-CTX  = 0.050 (95% CI 0.024, 0.076), P = 1.71 × 10-4 , βosteocalcin  = 6.54 × 10-4 (1.87 × 10-4 , 0.001), P = .006 and βP1NP  = 2.40 × 10-4 (6.49 × 10-5 , 4.14 × 10-4 ), P = .007 (β = increase in citrate (mmol/L) per 1 µg/L BTM increase). Inverse relationships of β-CTX (β = -0.276 [-0.434, -0.118], P = 6.03 × 10-4 ) and osteocalcin (-0.004 [-0.007, -0.001], P = .020) with triglycerides were also identified. We explored the generalizability of these associations in 3664 perimenopausal women (age 47.9 [4.4] years) from a UK family cohort. We confirmed a positive, albeit lower magnitude, association between β-CTX and citrate (adjusted βwomen  = 0.020 [0.013, 0.026], P = 1.95 × 10-9 ) and an inverse association of similar magnitude between β-CTX and triglycerides (β = -0.354 [-0.471, -0.237], P = 3.03 × 10-9 ).

CONCLUSIONS

Bone resorption is positively related to circulating citrate and inversely related to triglycerides. Further studies are justified to determine whether plasma citrate or triglyceride concentrations are altered by factors known to modulate bone resorption, such as bisphosphonates.

Biomarkers of collagen synthesis predict progression in the PROFILE idiopathic pulmonary fibrosis cohort

Idiopathic pulmonary fibrosis (IPF) is characterised by excessive extracellular matrix (ECM) deposition and remodelling. Measuring this activity provides an opportunity to develop tools capable of identifying individuals at-risk of progression. Longitudinal change in markers of ECM synthesis was assessed in 145 newly-diagnosed individuals with IPF.Serum levels of collagen synthesis neoepitopes, PRO-C3 and PRO-C6 (collagen type 3 and 6), were elevated in IPF compared with controls at baseline, and progressive disease versus stable disease during follow up, (PRO-C3 p < 0.001; PRO-C6 p = 0.029). Assessment of rate of change in neoepitope levels from baseline to 3 months (defined as 'slope to month 3': HIGH slope, slope > 0 vs. LOW slope, slope < =0) demonstrated no relationship with mortality for these markers (PRO-C3 (HR 1.62, p = 0.080); PINP (HR 0.76, p = 0.309); PRO-C6 (HR 1.14, p = 0.628)). As previously reported, rising concentrations of collagen degradation markers C1M, C3M, C6M and CRPM were associated with an increased risk of overall mortality (HR = 1.84, CI 1.03-3.27, p = 0.038, HR = 2.44, CI 1.39-4.31, p = 0.002; HR = 2.19, CI 1.25-3.82, p = 0.006; HR = 2.13 CI 1.21-3.75, p = 0.009 respectively).Elevated levels of PRO-C3 and PRO-C6 associate with IPF disease progression. Collagen synthesis and degradation biomarkers have the potential to enhance clinical trials in IPF and may inform prognostic assessment and therapeutic decision making in the clinic.

Serum C-terminal cross-linking telopeptide level as a predictive biomarker of osteonecrosis after dentoalveolar surgery in patients receiving bisphosphonate therapy: Systematic review and meta-analysis

BACKGROUND

The authors' aim in this systematic review was to evaluate the validity of using preoperative serum C-terminal cross-linking telopeptide (CTX) levels as a predictive factor of increased risk of developing medication-related osteonecrosis of the jaw (MRONJ) in patients receiving bisphosphonate (BP) therapy who underwent invasive dental procedures.

TYPES OF STUDIES REVIEWED

The authors searched PubMed, MEDLINE, and Web of Science and followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines and the Cochrane Handbook for Systematic Reviews of Interventions. The authors conducted a meta-analysis on the risk ratio. The authors used the methodological index for nonrandomized studies and Quality Appraisal of Reliability Studies checklist to assess quality.

RESULTS

The authors included 18 clinical trials involving 2,301 patients. Most patients received alendronate or risedronate for an average of 62.14 months. The average serum CTX level in patients who received BP before surgery was 198.25 picograms per milliliter. Meta-analysis results showed that the cutoff in CTX level (150 pg/mL) was not predictive of MRONJ risk. The sensitivity of CTX values lower than 150 pg/mL was 34.26%, and the specificity was 77.08%.

CONCLUSIONS AND PRACTICAL IMPLICATIONS

The use of CTX levels to diagnose MRONJ risk after dental procedures in patients receiving BP is not justified. The cutoff of 150 pg/mL in serum CTX levels is not predictive of MRONJ. Further studies are needed to develop other reliable biomarkers.

Pharmacology of bisphosphonates

The biological effects of the bisphosphonates (BPs) as inhibitors of calcification and bone resorption were first described in the late 1960s. In the 50 years that have elapsed since then, the BPs have become the leading drugs for the treatment of skeletal disorders characterized by increased bone resorption, including Paget's disease of bone, bone metastases, multiple myeloma, osteoporosis and several childhood inherited disorders. The discovery and development of the BPs as a major class of drugs for the treatment of bone diseases is a paradigm for the successful journey from "bench to bedside and back again". Several of the leading BPs achieved "blockbuster" status as branded drugs. However, these BPs have now come to the end of their patent life, making them highly affordable. The opportunity for new clinical applications for BPs also exists in other areas of medicine such as ageing, cardiovascular disease and radiation protection. Their use as inexpensive generic medicines is therefore likely to continue for many years to come. Fifty years of research into the pharmacology of bisphosphonates have led to a fairly good understanding about how these drugs work and how they can be used safely in patients with metabolic bone diseases. However, while we seemingly know much about these drugs, a number of key aspects related to BP distribution and action remain incompletely understood. This review summarizes the existing knowledge of the (pre)clinical and translational pharmacology of BPs, and highlights areas in which understanding is lacking.

Regulatory Perspectives in Pharmacometric Models of Osteoporosis

Osteoporosis is a disorder of the bones in which they are weakened to the extent that they become more prone to fracture. There are various forms of osteoporosis: some of them are induced by drugs, and others occur as a chronic progressive disorder as an individual gets older. As the median age of the population rises across the world, the chronic form of the bone disease is drawing attention as an important worldwide health issue. Developing new treatments for osteoporosis and comparing them with existing treatments are complicated processes due to current acceptance by regulatory authorities of bone mineral density (BMD) and fracture risk as clinical end points, which require clinical trials to be large, prolonged, and expensive to determine clinically significant impacts in BMD and fracture risk. Moreover, changes in BMD and fracture risk are not always correlated, with some clinical trials showing BMD improvement without a reduction in fractures. More recently, bone turnover markers specific to bone formation and resorption have been recognized that reflect bone physiology at a cellular level. These bone turnover markers change faster than BMD and fracture risk, and mathematically linking the biomarkers via a computational model to BMD and/or fracture risk may help in predicting BMD and fracture risk changes over time during the progression of a disease or when under treatment. Here, we discuss important concepts of bone physiology, osteoporosis, treatment options, mathematical modeling of osteoporosis, and the use of these models by the pharmaceutical industry and the Food and Drug Administration.

Fast and sensitive near-infrared fluorescent probes for ALP detection and 3d printed calcium phosphate scaffold imaging in vivo

Alkaline phosphatase (ALP) is a critical biological marker for osteoblast activity during early osteoblast differentiation, but few biologically compatible methods are available for its detection. Here, we describe the discovery of highly sensitive and rapidly responsive novel near-infrared (NIR) fluorescent probes (NIR-Phos-1, NIR-Phos-2) for the fluorescent detection of ALP. ALP cleaves the phosphate group from the NIR skeleton and substantially alters its photophysical properties, therefore generating a large "turn-on" fluorescent signal resulted from the catalytic hydrolysis on fluorogenic moiety. Our assay quantified ALP activity from 0 to 1.0UmL^-1 with a 10^-5-10^-3UmL^-1 limit of detection (LOD), showing a response rate completed within 1.5min. A potentially powerful approach to probe ALP activity in biological systems demonstrated real-time monitoring using both concentration- and time-dependent variations of endogenous ALP in live cells and animals. Based on high binding affinity to bone tissue of phosphate moiety, bone-like scaffold-based ALP detection in vivo was accessed using NIR probe-labeled three-dimensional (3D) calcium deficient hydroxyapatite (CDHA) scaffolds. They were subcutaneously implanted into mice and monitored ALP signal changes using a confocal imaging system. Our results suggest the possibility of early-stage ALP detection during neo-bone formation inside a bone defect, by in vivo fluorescent evaluation using 3D CDHA scaffolds.

Tartrate-resistant acid phosphate as biomarker of bone turnover over the lifespan and different physiologic stages in sheep

Background

Currently, the best resources for assessment of bone tissue using imaging techniques are expensive and available in few medical facilities, thus serum or urinary bone turnover biomarkers could be useful as early indicators of prognosis. However, there is a wide range of variability in bone turnover markers due to several factors, such as different ages and metabolic stages, thus it is important to have as much data published on the subject as possible. The aim of this study was therefore to generate a reference range for alkaline phosphatase (ALP) and tartrate-resistant acid phosphatase (TRAP) and validate the already published data.

Results

Serum alkaline phosphatase decreased with age, with statistical difference between the 1 month old and the other groups and between the over 8 years and the 6 months old groups. There was also a statistical difference in the ALP levels between the 3 to 5 years old gestation and lactation groups. For serum tartrate-resistant acid phosphatase, there was a statistical difference mainly between the 1 month old and the 6 months old, 6–8 years old, and above 8 years old groups.

Conclusions

The results obtained could represent a useful tool for future studies using sheep as an animal model for orthopedic research. The different groups presented a wide variation of serum ALP and TRAP levels, however, these variations are entirely explained by known physiology. Therefore, this detailed study confirms the prediction that unexplained changes in these bone turnover markers do not occur during the lifespan of sheep.

Changes of Bone Turnover Markers in Long Bone Nonunions Treated with a Regenerative Approach

In this clinical trial, we investigated if biochemical bone turnover markers (BTM) changed according to the progression of bone healing induced by autologous expanded MSC combined with a biphasic calcium phosphate in patients with delayed union or nonunion of long bone fractures. Bone formation markers, bone resorption markers, and osteoclast regulatory proteins were measured by enzymatic immunoassay before surgery and after 6, 12, and 24 weeks. A satisfactory bone healing was obtained in 23 out of 24 patients. Nine subjects reached a good consolidation already at 12 weeks, and they were considered as the “early consolidation” group. We found that bone-specific alkaline phosphatase (BAP), C-terminal propeptide of type I procollagen (PICP), and beta crosslaps collagen (CTX) changed after the regenerative treatment, BAP and CTX correlated to the imaging results collected at 12 and 24 weeks, and BAP variation along the healing course differed in patients who had an “early consolidation.” A remarkable decrease in BAP and PICP was observed at all time points in a single patient who experienced a treatment failure, but the predictive value of BTM changes cannot be determined. Our findings suggest that BTM are promising tools for monitoring cell therapy efficacy in bone nonunions, but studies with larger patient numbers are required to confirm these preliminary results.

Bone turnover markers in sheep and goat: A review of the scientific literature

Bone turnover markers (BTMs) are product of bone cell activity and are generally divided in bone formation and bone resorption markers. The purpose of this review was to structure the available information on the use of BTMs in studies on small ruminants, especially for monitoring their variations related to diet, exercise, gestation and metabolic lactation state, circadian and seasonal variations, and also during skeletal growth. Pre-clinical and translational studies using BTMs with sheep and goats as animal models in orthopaedic research studies to help in the evaluation of the fracture healing process and osteoporosis research are also described in this review. The available information from the reviewed studies was systematically organized in order to highlight the most promising BTMs in small ruminant research, as well as provide a wide view of the use of sheep and goat as animal models in orthopaedic research, type of markers and commercial assay kits with cross-reactivity in sheep and goat, method of sample and storage of serum and urine for bone turnover markers determination and the usefulness and limitations of bone turnover markers in the different studies, therefore an effective tool for researchers that seek answers to different questions while using BTMs in small ruminants.

Metabolomics and Its Application in the Development of Discovering Biomarkers for Osteoporosis Research

Osteoporosis is a progressive skeletal disorder characterized by low bone mass and increased risk of fracture in later life. The incidence and costs associated with treating osteoporosis cause heavy socio-economic burden. Currently, the diagnosis of osteoporosis mainly depends on bone mineral density and bone turnover markers. However, these indexes are not sensitive and accurate enough to reflect the osteoporosis progression. Metabolomics offers the potential for a holistic approach for clinical diagnoses and treatment, as well as understanding of the pathological mechanism of osteoporosis. In this review, we firstly describe the study subjects of osteoporosis and bio-sample preparation procedures for different analytic purposes, followed by illustrating the biomarkers with potentially predictive, diagnosis and pharmaceutical values when applied in osteoporosis research. Then, we summarize the published metabolic pathways related to osteoporosis. Furthermore, we discuss the importance of chronological data and combination of multi-omics in fully understanding osteoporosis. The application of metabolomics in osteoporosis could provide researchers the opportunity to gain new insight into the metabolic profiling and pathophysiological mechanisms. However, there is still much to be done to validate the potential biomarkers responsible for the progression of osteoporosis and there are still many details needed to be further elucidated.

Protein degradation fragments as diagnostic and prognostic biomarkers of connective tissue diseases: understanding the extracellular matrix message and implication for current and future serological biomarkers

The aim of this review is to discuss the potential usefulness of novel biochemical markers of connective tissues: neo-epitopes of extracellular matrix proteins generated by post-translational modifications by tissue proteinases. As each modification results from a specific local physiological or pathobiological process, the identification of specific proteinase-mediated cleavage products of tissue-specific proteins may produce a unique disease-specific biochemical marker. The authors present a novel interpretation of the process of tissue degradation described by neo-epitope fragments of the interstitial and basement membrane matrix in fibrotic disease, and the diagnostic and prognostic potential of such markers. Moreover, the authors highlight the importance of matrix protein fragments not only as markers of tissue remodeling, but also as players in tissue remodeling, due to their signaling properties.

Diagnostic accuracy of bone turnover markers as a screening tool for aseptic loosening after total hip arthroplasty

Aseptic loosening is the most common cause of prosthesis failure after total hip arthroplasty (THA). We measured serum cross-linked carboxyterminal telopeptide of type I collagen (ICTP), tartrate-resistant acid phosphatase 5b (TRAP5b), dickkopf-1 (dkk-1) and sclerostin; and urinary α isomer of C-terminal cross-linked telopeptide of type I collagen (αCTX-I) to investigate their potential diagnostic value detecting aseptic loosening after THA. Biomarkers were measured in 24 subjects with aseptic loosening of THA versus 26 control subjects without loosening after THA. Serum ICTP in the loose group (7.04 ng/mL) was higher than controls (5.15 ng/mL), (p = 0.0007). ROC analysis demonstrated that a serum ICTP >5.5 ng/L had a sensitivity of 91% and specificity of 69% for detecting aseptic loosening (area under ROC curve = 0.77, p = 0.0001), resulting in a positive predictive value (PPV) of 73% and a negative predictive value (NPV) of 90%. Serum TRAP5b in the aseptic loosening group (4.17U/L) was higher than controls (3.44 U/L), (p = 0.03). A serum TRAP5b >2.46 U/L had sensitivity of 100% and a specificity of 31% to detect aseptic loosening (AUC 0.67, p = 0.031), resulting in a PPV of 57% and a NPV of 100%. Serum dkk-1, serum sclerostin and urinary αCTX-I were not elevated in subjects with aseptic loosening (p>0.05). Serum ICTP and TRAP5b show potential utility as screening biomarkers for excluding aseptic loosening, because of their ability to discriminate individuals without disease. Our finding of elevated ICTP, generated by the action of matrix metalloproteinases, suggests a role for this group of endopeptidases in aseptic loosening.

The efficacy and safety of tenofovir alafenamide versus tenofovir disoproxil fumarate in antiretroviral regimens for HIV-1 therapy: Meta-analysis

BACKGROUND

To date, a definite conclusion about efficiency and safety of tenofovir alafenamide for patients with HIV-1 is not available. The aim of the study was to investigate the efficacy and safety of TAF versus TDF in antiretroviral regimens for patients with HIV-1.

METHODS

PUBMED, MEDLINE, and EMBASE database were searched in March 2016, with no language restriction, for randomized controlled trials (RCTs).

RESULTS

Six RCTs (n = 5888) met entry criteria. At week 48, viral suppression rates were similar between TAF and TDF group (90.2% vs 89.5%) for the naive patients. Interestingly, the rate was higher in patients who switched to TAF regimens compared with patients who continued previous TDF regimens (96.4% vs 93.1%). Both groups were generally well tolerated with high barrier to resistance. As compared to TDF, TAF had significantly smaller reductions in eGFR-CG, smaller changes in RBP/Cr and urineβ-2 M/Cr ratio, and less reduction in spine and hip BMD for the treatment-naive patients. Moreover, the switched group had significant efficacy advantages of improving renal function and BMD, including significant decreases in urine albumin/Cr, urine protein/Cr, urine RBP/Cr, and urine β-2 M/Cr ratios, and increases in hip and spine BMD by 1.47% and 1.56%,respectively, as compared with continued TDF regimens.

CONCLUSIONS

TAF has a similar tolerability, safety, and effectiveness to TDF and probably less adverse events related to renal and bone density outcomes in the treatment of naive and experienced patients with HIV-1.

Early changes in blood-based joint tissue destruction biomarkers are predictive of response to tocilizumab in the LITHE study

Background

Rheumatoid arthritis (RA) is characterized by gradual joint destruction. Tocilizumab (TCZ) significantly suppresses symptoms, however not all patients are protected from joint damage. We investigated whether early measurement of specific biomarkers could predict early joint protection response to tocilizumab.

Method

Serum biomarkers (CRPM, VICM, C1M, C2M, C3M (MMP-degraded CRP, vimentin type I, II and III collagen), CTX-I/OC (bone turnover), and CRP) were measured in 740 RA patients (the LITHE study) treated with Placebo, or 4 or 8 mg/kg TCZ. Early responders were those with ≥20 % improvement in SJC or TJC by week 16. The biomarkers' predictability of response was investigated by AUROC and classification regression tree analysis.

Results

The best biomarker predictability for identification of TCZ responders were; baseline CTX-I/OC (AUC 0.66, p = 0.0005) and changes in C1M (AUC 0.67, p = 0.0072), C2M (AUC 0.72, p = 0.0002), C3M (AUC 0.63, p = 0.018) and the combination of biomarkers (AUC 0.81, p = 0.0025). Patients with high bone turnover (CTX-I/OC) and low C2M were 6.8-fold (p = 0.003) more likely to have an early response to TCZ.

Conclusion

This enhanced pharmacodynamic (PD) response enabled identification of early responders with a superior TCZ clinical benefit. This biomarker model may assist in the identification of TCZ responsive RA patients and thus potentially benefit individual patients.

Trial registration

Clinicaltrials.gov: NCT00106535. JAN 2005

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-015-0913-x) contains supplementary material, which is available to authorized users.

A semi-mechanistic model of bone mineral density and bone turnover based on a circular model of bone remodeling

Development of novel therapies for bone diseases can benefit from mathematical models that predict drug effect on bone remodeling biomarkers. Therefore, a bone cycle model (BCM) was developed that takes into consideration the concept of the basic multicellular unit and the dynamic equilibrium of bone remodeling. The model is a closed form cyclical model with four compartments representing resorption, formation, primary mineralization, and secondary mineralization. Equations describing the time course of bone turnover biomarkers were developed using the flow rate of bone cycle units (BCU) between the compartments or the amount of BCU in each compartment. A disease progression model representing bone loss in osteoporosis, a vitamin D and calcium supplementation (placebo) model, and a drug model for antiresorptive treatments were added to the model. Initial model parameter values were derived from published bone turnover data. The BCM accurately described biomarker-time profiles in postmenopausal women receiving either placebo or bisphosphonate treatment. The slow continual increase in bone mineral density (BMD) observed after 1 year of treatment was accurately described when changes in bone turnover were combined with increases in mineralization. For this purpose, the secondary mineralization compartment was replaced by three catenary chain compartments representing increasing mineral content. The refined BCM satisfactorily predicted biomarker profiles after long-term (10-year) bisphosphonate treatment. Furthermore, the model successfully described individual bone turnover markers and BMD results following treatment with denosumab in postmenopausal women. Analyses with this model could be used to optimize dosing regimens and to predict effects of novel osteoporotic treatments.

Bone turnover markers for early detection of fracture healing disturbances: A review of the scientific literature

Imaging techniques are the standard method for assessment of fracture healing processes. However, these methods are perhaps not entirely reliable for early detection of complications, the most frequent of these being delayed union and non-union. A prompt diagnosis of such disorders could prevent prolonged patient distress and disability. Efforts should be directed towards the development of new technologies for improving accuracy in diagnosing complications following bone fractures. The variation in the levels of bone turnover markers (BTMs) have been assessed with regard to there ability to predict impaired fracture healing at an early stage, nevertheless the conclusions of some studies are not consensual. In this article the authors have revised the potential of BTMs as early predictors of prognosis in adult patients presenting traumatic bone fractures but who did not suffer from osteopenia or postmenopausal osteoporosis. The available information from the different studies performed in this field was systematized in order to highlight the most promising BTMs for the assessment of fracture healing outcome.

Chronic kidney disease and the skeleton

Fractures across the stages of chronic kidney disease (CKD) could be due to osteoporosis, some form of renal osteodystrophy defined by specific quantitative histomorphometry or chronic kidney disease-mineral and bone disorder (CKD-MBD). CKD-MBD is a systemic disease that links disorders of mineral and bone metabolism due to CKD to either one or all of the following: abnormalities of calcium, phosphorus, parathyroid hormone or vitamin D metabolism; abnormalities in bone turnover, mineralization, volume, linear growth or strength; or vascular or other soft-tissue calcification. Osteoporosis, as defined by the National Institutes of Health, may coexist with renal osteodystrophy or CKD-MBD. Differentiation among these disorders is required to manage correctly the correct disorder to reduce the risk of fractures. While the World Health Organization (WHO) bone mineral density (BMD) criteria for osteoporosis can be used in patients with stages 1-3 CKD, the disorders of bone turnover become so aberrant by stages 4 and 5 CKD that neither the WHO criteria nor the occurrence of a fragility fracture can be used for the diagnosis of osteoporosis. The diagnosis of osteoporosis in stages 4 and 5 CKD is one of the exclusion-excluding either renal osteodystrophy or CKD-MBD as the cause of low BMD or fragility fractures. Differentiations among the disorders of renal osteodystrophy, CKD-MBD or osteoporosis are dependent on the measurement of specific biochemical markers, including serum parathyroid hormone (PTH) and/or quantitative bone histomorphometry. Management of fractures in stages 1-3 CKD does not differ in persons with or without CKD with osteoporosis assuming that there is no evidence for CKD-MBD, clinically suspected by elevated PTH, hyperphosphatemia or fibroblast growth factor 23 due to CKD. Treatment of fractures in persons with osteoporosis and stages 4 and 5 CKD is not evidence-based, with the exception of post-hoc analysis suggesting efficacy and safety of specific osteoporosis therapies (alendronate, risedronate and denosumab) in stage 4 CKD. This review also discusses how to diagnose and manage fragility fractures across the five stages of CKD.

1H-NMR analysis of the human urinary metabolome in response to an 18-month multi-component exercise program and calcium–vitamin-D3supplementation in older men

The musculoskeletal benefits of calcium and vitamin-D3supplementation and exercise have been extensively studied, but the effect on metabolism remains contentious. Urine samples were analyzed by1H-NMR spectroscopy from participants recruited for an 18-month, randomized controlled trial of a multi-component exercise program and calcium and vitamin-D3fortified milk consumption. It was shown previously that no increase in musculoskeletal composition was observed for participants assigned to the calcium and vitamin-D3intervention, but exercise resulted in increased bone mineral density, total lean body mass, and muscle strength. Retrospective metabolomics analysis of urine samples from patients involved in this study revealed no distinct changes in the urinary metabolome in response to the calcium and vitamin-D3intervention, but significant changes followed the exercise intervention, notably a reduction in creatinine and an increase in choline, guanidinoacetate, and hypoxanthine (p < 0.001, fold change > 1.5). These metabolites are intrinsically involved in anaerobic ATP synthesis, intracellular buffering, and methyl-balance regulation. The exercise intervention had a marked effect on the urine metabolome and markers of muscle turnover but none of these metabolites were obvious markers of bone turnover. Measurement of specific urinary exercise biomarkers may provide a basis for monitoring performance and metabolic response to exercise regimes.

Effect of folic acid on bone metabolism: a randomized double blind clinical trial in postmenopausal osteoporotic women

BACKGROUND

In spite of several studies, the impact of homocysteine level and folic acid supplementation on bone metabolism is yet to be recognized. In this registered clinical trial (IRCT2014042217385N1), we aimed to find out the power of 6-month folic acid supplementation on homocysteine level and bone metabolism.

METHODS

Forty postmenopausal osteoporotic women (50 to 87 years) were enrolled in the study. All participants were randomized to receive folic acid 1 mg (n = 17) or placebo (n = 14). At baseline, 3 months, and finally 6 months post intervention, the level of homocysteine, vitamin B12, and bone biomarkers were measured.

RESULTS

Both groups were similar at baseline. The homocysteine decreased in both groups but statistically non-significant (P > 0.05). The changes of the serum level of vitamin B12, osteocalcin, and β cross laps were significant between groups after 6 months (P ≤ 0.05).

CONCLUSION

The trend of changes of bone biomarkers after 6 months folic acid supplementation shows that homocysteine concentration and/or folic acid supplementation have impact on the rate of bone metabolism. However, further investigations by larger sample size and differentiating age and gender are still needed to clarify the exact role of folate, homocysteine and vitamin B12.

Chronic kidney disease and osteoporosis: evaluation and management

Fractures across the stages of chronic kidney disease (CKD) could be due to osteoporosis, some form of renal osteodystrophy defined by specific quantitative histomorphometry or chronic kidney disease-mineral and bone disorder (CKD-MBD). CKD-MBD is a systemic disease that links disorders of mineral and bone metabolism due to CKD to either one or all of the following: abnormalities of calcium, phosphorus, parathyroid hormone or vitamin D metabolism; abnormalities in bone turnover, mineralization, volume, linear growth or strength; or vascular or other soft-tissue calcification. Osteoporosis, as defined by The National Institutes of Health, may coexist with renal osteodystrophy or CKD-MBD. Differentiation among these disorders is required to manage correctly the correct disorder to reduce the risk of fractures. While the World Health Organization (WHO) BMD criteria for osteoporosis can be used in patients with stages 1-3 CKD, the disorders of bone turnover become so aberrant by stages 4 and 5 CKD that neither the WHO criteria nor the occurrence of a fragility fracture can be used for the diagnosis of osteoporosis. The diagnosis of osteoporosis in stages 4 and 5 CKD is one of the exclusion-excluding either renal osteodystrophy or CKD-MBD as the cause of low BMD or fragility fractures. Differentiations among the disorders of renal osteodystrophy, CKD-MBD or osteoporosis are dependent on the measurement of specific biochemical markers, including serum parathyroid hormone (PTH) and/or quantitative bone histomorphometry. Management of fractures in stages 1-3 CKD does not differ in persons with or without CKD with osteoporosis assuming there is no evidence for CKD-MBD, clinically suspected by elevated PTH, hyperphosphatemia or fibroblast growth factor 23 due to CKD. Treatment of fractures in persons with osteoporosis and stages 4 and 5 CKD is not evidence based, with the exception of post hoc analysis suggesting efficacy and safety of specific osteoporosis therapies (alendronate, risedronate and denosumab) in stage 4 CKD. This review also discusses how to diagnose and manage fragility fractures across the five stages of CKD.

A meta-analysis of reference markers of bone turnover for prediction of fracture

The aim of this report was to summarize the clinical performance of two reference bone turnover markers (BTMs) in the prediction of fracture risk. We used an updated systematic review to examine the performance characteristics of serum procollagen type I N propeptide (s-PINP) and serum C-terminal cross-linking telopeptide of type I collagen (s-CTX) in fracture risk prediction in untreated individuals in prospective cohort studies. We excluded cross-sectional studies. Ten potentially eligible publications were identified and six included in the meta-analysis. There was a significant association between s-PINP and the risk of fracture. The hazard ratio per SD increase in s-PINP (gradient of risk [GR]) was 1.23 (95 % CI 1.09-1.39) for men and women combined unadjusted for bone mineral density. There was also a significant association between s-CTX and risk of fracture, GR = 1.18 (95 % CI 1.05-1.34) unadjusted for bone mineral density. For the outcome of hip fracture, the association between s-CTX and risk of fracture was slightly higher, 1.23 (95 % CI 1.04-1.47). Thus, there is a modest but significant association between BTMs and risk of future fractures.

Low bone turnover phenotype in Rett syndrome: results of biochemical bone marker analysis

BACKGROUND

Patients with Rett syndrome (RTT) are at risk of having low bone mass and low-energy fractures.

METHODS

We characterized bone metabolism by both bone formation and resorption markers in blood in a RTT population of 61 girls and women and 122 well-matched healthy controls. Levels of N-terminal propeptides of collagen type 1 (P1NP), C-terminal telopeptide cross links (CTX), osteocalcin (OC), and bone-specific alkaline phosphatase (B-ALP) were compared between RTT patients and controls in regression models adjusted for BMI, vitamin D status, volumetric bone mineral apparent density of the lumbar spine (vBMAD spine), and femoral neck (vBMAD neck). We examined biochemical bone marker levels overall and stratified to persons younger than age 25 y or equal to or older than age 25 y.

RESULTS

The RTT patients had reduced levels of all biochemical bone markers (P < 0.05), which remained significant in persons younger than 25 y (P ≤ 0.001) regarding P1NP, CTX, and OC. Bone marker levels were not significantly associated to methyl-CpG-binding protein 2 (MECP2) mutation group, walking ability, or previous low-energy fractures.

CONCLUSION

Our findings of a low bone turnover state in girls with RTT suggest critical attention to medical treatment of low bone mass in young RTT patients.

Isolation and characterization of human osteoblasts from needle biopsies without in vitro culture

SUMMARY

We isolate and characterize osteoblasts from humans without in vitro culture. These techniques should be broadly applicable to studying the pathogenesis of osteoporosis and other bone disorders.

INTRODUCTION

There is currently no data regarding the expression of specific genes or pathways in human osteoblasts that have not been subjected to extensive in vitro culture. Thus, we developed methods to rapidly isolate progressively enriched osteoblast populations from humans and characterized these cells.

METHODS

Needle bone biopsies of the posterior iliac crest were subjected to sequential collagenase digests. The cells from the second digest were stained with an alkaline phosphatase (AP) antibody, and the AP+ cells were isolated using magnetic cell sorting.

RESULTS

Relative to AP- cells, the AP+ cells contained virtually all of the mineralizing cells and were enriched for key osteoblast marker genes. The AP+ cells were further purified by depletion of cells expressing CD45, CD34, or CD31 (AP+/CD45/34/31- cells), which represented a highly enriched human osteoblast population devoid of hematopoietic/endothelial cells. These cells expressed osteoblast marker genes but very low to undetectable levels of SOST. We next used high-throughput RNA sequencing to compare the transcriptome of the AP+/CD45/34/31- cells to human fibroblasts and identified genes and pathways expressed only in human osteoblasts in vivo, but not in fibroblasts, including 448 genes unique to human osteoblasts.

CONCLUSIONS

We provide a detailed characterization of highly enriched human osteoblast populations without in vitro culture. These techniques should be broadly applicable to studying the pathogenesis of osteoporosis and other bone disorders.