Bone health and osteoporosis in postmenopausal women

Bone health and menopause: Osteoporosis prevention and treatment

A continuous process of bone turnover is central to bone health and strength. If bone resorption exceeds bone formation, bone strength deteriorates with resultant fractures. Osteoporosis is defined by a fracture or bone mineral density. The lack of ovarian estrogen after menopause causes a significant loss in bone strength, placing women at higher risk of osteoporosis. The probability of future fractures can be calculated by identifying risk factors in all menopausal women. Preventive action starts with a bone-friendly lifestyle. The need for and type of interventive medication can best be determined by classifying fracture risk as low, high, or very high using a combination of fracture history, bone mineral density, 10-year fracture probability or country-specific values. As osteoporosis is an incurable disease, treatment should be seen as a lifelong strategy consisting of the correct sequencing of available bone-specific drugs and appropriate drug-free periods when applicable.

RANK signaling in osteoclast precursors results in a more permissive epigenetic landscape and sexually divergent patterns of gene expression

Background

Sex is an important risk factor in the development of osteoporosis and other bone loss disorders, with women often demonstrating greater susceptibility than men. While variation in sex steroids, such as estradiol, accounts for much of the risk, there are likely additional non-endocrine factors at transcriptional and epigenetic levels that result in a higher rate of bone loss in women. Identification of these factors could improve risk assessment and therapies to preserve and improve bone health.

Methods

Osteoclast precursors were isolated male and female C57Bl/6 mice and cultured with either MCSF alone or MCSF and RANKL. Following the culture period RNA was isolated for RNA sequencing and DNA was isolated for tagmentation and ATAC sequencing. RNA-Seq and ATAC-seq were evaluated via pathway analysis to identify sex- and RANKL-differential transcription and chromatin accessibility.

Results

Osteoclasts demonstrated significant alterations in gene expression compared to macrophages with both shared and differential pathways between the sexes. Transcriptional pathways differentially regulated between male and female cells were associated with immunological functions with evidence of greater sensitivity in male macrophages and female osteoclasts. ATAC-Seq revealed a large increase in chromatin accessibility following RANKL treatment with few alterations attributable to sex. Comparison of RNA-Seq and ATAC-seq data revealed few common pathways suggesting that many of the transcriptional changes of osteoclastogenesis occur independently of chromatin remodeling.

Prediction of compounds with antiosteoporosis activity in Chrysophyllum cainito L. leaves through in silico approach

OBJECTIVES

Estrogen deficiency causes various health problems in postmenopausal women, including osteoporosis. Phytoestrogen emerged as a potential alternative of estrogen with minimum side effects. The aims of this study were to analyze the metabolite profiling results of various extract of Chyrsophyllum cainito L. leaves, which contain phytoestrogen, through in silico study against 3OLS protein, an X-ray protein of ERβ, so it can predict the types of the phytoestrogen contents which have antiosteoporosis property.

METHODS

In silico analysis was carried out for the compounds from the metabolite profiling data of C. cainito leaves from our previous study. The structure compounds from metabolite profiling results of various extract of C. cainito leaves were prepared with Avogadro 1.0.1 software, molecular docking was done using PyRx 0.8 software, and Biovia Discovery Studio Visualizer 2016 software was used to visualize the structure of compounds against 3OLS protein. The physicochemical characteristics of the compounds were analyzed using the SwissADME web tool.

RESULTS

From in silico studies, it was known that there were total 11 compounds in C. cainito leaves that predicted as phytoestrogens which have ERβ agonist properties against 3OLS protein. The ERβ agonist was a compound that has parameters similar to 17β-estradiol in its interaction with 3OLS protein, which has a pharmacophore distance of 10.862 Å, and binding to amino acids His 475 and Glu 305 or Arg 346 at receptor-ligand docking simulation.

CONCLUSIONS

C. cainito leaves contain 11 compounds that are predicted to be phytoestrogens with ERβ agonist properties, which is responsible for antiosteoporosis activity.

Water extract of Cnidii Rhizoma suppresses RANKL-induced osteoclastogenesis in RAW 264.7 cell by inhibiting NFATc1/c-Fos signaling and prevents ovariectomized bone loss in SD-rat

Background

Cnidii Rhizoma is the dried root stem of Cnidium officinale Makino. Cnidii Rhizoma (CR) has been used to treat menstrual irregularity, menstrual pain, and menopause in Korea. However, the effects and mechanisms of CR on RANKL-induced osteoclastogenesis pathway remain to be elucidated. In this study, we investigated the effects of CR on the inhibition of bone resorption of osteoclast and its mechanism RANK signaling pathway.

Methods

The anti-osteoclastogenesis of water extract of CR was measured using RAW 264.7 cell. Tartrate-resistant acid phosphatase (TRAP) assay, pit assay, reverse transcription polymerase chain reaction (RT-PCR) and western blot were performed. Moreover, the effects of CR were determined with an in vivo model using ovariectomized (OVX) rats.

Results

CR extract suppressed osteoclastogenesis, its activity and bone resorption activity through decreasing gene of osteoclast-related such as nuclear factor of activated T-cells, cytoplasmic 1 (NFATc1), c-Fos, etc. Moreover, CR extract prevented the bone loss in OVX rats.

Conclusion

These results show that CR has a positive effect on menopausal osteoporosis by suppressing osteoclastogenesis.

Electronic supplementary material

The online version of this article (10.1186/s12906-019-2611-8) contains supplementary material, which is available to authorized users.

Eurycoma longifolia, a promising suppressor of RANKL-induced differentiation and activation of osteoclasts: An in vitro mechanistic evaluation

Background

Eurycoma longifolia (E. longifolia) has gained remarkable recognition due to its promising efficacy of stimulating bone formation in androgen-deficient osteoporosis. Numerous in vivo studies have explored the effects of E. longifolia on osteoporosis; however, the in vitro cellular mechanism was not discovered yet.

Objectives

The present study was aimed to investigate the effect of E. longifolia on the proliferation, differentiation and maturation of osteoclasts and the translational mechanism of inhibition of osteoclastogenesis using RAW 264.7 cells as an in vitro osteoclastic model.

Materials and methods

Having assessed cytotoxicity, the cell viability, cell proliferation rate and osteoclastic differentiation capacity of E. longifolia was investigated by evaluating the tartrate-resistant acid phosphatase (TRAP) activity in receptor activator of nuclear factor-κB (NF-κB) ligand (RANKL)-induced osteoclasts. Taken together, the time-mannered expression of osteoclast-related protein biomarkers such as matrix metallopeptidase-9 (MMP-9), cathepsin-K, TRAP, nuclear factor of activated T-cells cytoplasmic 1 (NFATc1), superoxide (free radicals) generation and superoxide dismutase activity were also measured to comprehend the mechanism of osteoclastogenesis.

Results

E. longifolia did not show significant effects on cytotoxicity and cell proliferation of RAW 264.7 cells; however, a significant inhibition of cells differentiation and maturation of osteoclasts was observed. Moreover, a significant down-regulation of RANKL-induced TRAP activity and expression of MMP-9, cathepsin-K, TRAP, NFATc1 and generation of superoxide and enhanced superoxide dismutase activity was observed in E. longifolia treated cell cultures.

Conclusion

We anticipated that E. longifolia that enhances bone regeneration on the one hand and suppresses osteoclast’s maturation on the other hand may have great therapeutic value in treating osteoporosis and other bone-erosive diseases such as rheumatoid arthritis and metastasis associated with bone loss.

Gadolinium Tagged Osteoprotegerin-Mimicking Peptide: A Novel Magnetic Resonance Imaging Biospecific Contrast Agent for the Inhibition of Osteoclastogenesis and Osteoclast Activity

The control of osteoblast/osteoclast cross-talk is crucial in the bone remodelling process and provides a target mechanism in the development of drugs for bone metabolic diseases. Osteoprotegerin is a key molecule in this biosignalling pathway as it inhibits osteoclastogenesis and osteoclast activation to prevent run-away bone resorption. This work reports the synthesis of a known osteoprotegerin peptide analogue, YCEIEFCYLIR (OP3-4), and its tagging with a gadolinium chelate, a standard contrast agent for magnetic resonance imaging. The resulting contrast agent allows the simultaneous imaging and treatment of metabolic bone diseases. The gadolinium-tagged peptide was successfully synthesised, showing unaltered magnetic resonance imaging contrast agent properties, a lack of cytotoxicity, and dose-dependent inhibition of osteoclastogenesis in vitro. These findings pave the way toward the development of biospecific and bioactive contrast agents for the early diagnosis, treatment, and follow up of metabolic bone diseases such as osteoporosis and osteosarcoma.

Pulsed electromagnetic fields (PEMF) attenuate changes in vertebral bone mass, architecture and strength in ovariectomized mice

Pulsed electromagnetic fields (PEMF) has been investigated as a noninvasive alternative method to prevent bone loss for postmenopausal osteoporosis (OP), and the bone tissue involved in these studies are usually long bones such as femur and tibia in OP patients or rat models. However, few studies have investigated the effects of PEMF on the vertebral bone in mice with OP. This study aimed to investigate whether PEMF preserve lumbar vertebral bone mass, microarchitecture and strength in ovariectomized (OVX) mouse model of OP and its associated mechanisms. Thirty 3-month-old female BALB/c mice were randomly divided into three groups (n=10): sham-operated control (Sham), ovariectomy (OVX), and ovariectomy with PEMF treatment (OVX+PEMF). The OVX+PEMF group was exposed to 15Hz, 1.6 mT PEMF for 8h/day, 7days/week. After 8weeks, the mice were sacrificed. The OVX+PEMF group showed lower body weight gain of mice induced by estrogen deficiency compared with OVX group. Biochemical analysis of serum demonstrated that serum bone formation markers including bone specific alkaline phosphatase (BALP), serum osteocalcin (OCN), osteoprotegerin (OPG) and N-terminal propeptide of type I procollagen (P1NP) were markedly higher in OVX+PEMF group compared with OVX group. Besides, serum bone resorption markers including tartrate-resistant acid phosphatase 5b (TRAP-5b) and C-terminal crosslinked telopeptides of type I collagen (CTX-I) were markedly lower in OVX+PEMF group compared with OVX group. Biomechanical test observed that OVX+PEMF group showed higher compressive maximum load and stiffness of the lumbar vertebrae compared with OVX group. Micro-computed tomography (μCT) and histological analysis of lumbar vertebrae revealed that PEMF partially prevented OVX-induced decrease of trabecular bone mass and deterioration of trabecular bone microarchitecture in lumbar vertebrae. Real-time PCR showed that the canonical Wnt signaling pathway of the lumbar vertebrae, including Wnt3a, LRP5 and β-catenin were markedly up-regulated in OVX+PEMF group compared with OVX group. Moreover, the mRNA expressions of RANKL and OPG were markedly up-regulated in OVX+PEMF group compared with OVX group, whereas no statistical difference in RANKL/OPG mRNA ratio was found between OVX+PEMF group and OVX group. Besides, our study also found that the RANK mRNA expression was down-regulated in OVX+PEMF group compared with OVX group. Taken together, we reported that long-term stimulation with PEMF treatment was able to alleviate lumbar vertebral OP in postmenopausal mice through a combination of increased bone formation and suppressed bone resorption related to regulating the skeletal gene expressions of Wnt3a/LRP5/β-catenin and OPG/RANKL/RANK signaling pathways.

Molecular mechanisms of the inhibitory effects of jiangu granule‑containing serum on RANKL‑induced osteoclastogenesis

Postmenopausal osteoporosis (PMOP) is characterized by increased bone loss due to enhanced osteoclastogenesis and bone resorption. A Chinese herbal formula, jiangugranule (JG), exhibited great efficacy in the clinical treatment of PMOP. However, the molecular mechanisms underlying the therapeutic effects remain unclear. The present study aimed to examine the effects of JG‑containing serum on receptor activator of nuclear factor‑κB (NF‑κB) ligand (RANKL)‑induced osteoclastogenesis. Osteoclast precursor RAW264.7 cells were cultured and treated with JG‑containing serum in the presence of RANKL. Following 6 days of culture, the cells were stained with tartrate‑resistant acid phosphatase and the rate of differentiation was calculated. In addition, cells were treated with JG‑containing serum for 24, 48 and 96 h and total RNA and proteins were extracted for reverse transcription‑quantitative polymerase chain reaction and western blot analysis to detect mRNA and protein expression, respectively, of key molecules in the RANK/RANKL signaling pathway, including RANK, tumor necrosis factor receptor‑associated factor 6, NF‑κB (p50 and p52 subunits), c‑Fos and nuclear factor of activated T cells, cytoplasmic 1 (NFATc1). The results revealed that JG‑containing serum inhibited RANKL‑induced osteoclastogenesis and reduced mRNA and protein expression of RANK, c‑Fos and NFATc1. The results suggested that JG may regulate osteoclast differentiation through the RANK/RANKL signaling pathway, which may be a possible mechanism for the therapeutic effects of JG on PMOP.

Effects of four kinds of electromagnetic fields (EMF) with different frequency spectrum bands on ovariectomized osteoporosis in mice

Electromagnetic fields (EMF) was considered as a non-invasive modality for treatment of osteoporosis while the effects were diverse with EMF parameters in time domain. In present study, we extended analysis of EMF characteristics from time domain to frequency domain, aiming to investigate effects of four kinds of EMF (LP (1–100 Hz), BP (100–3,000 Hz), HP (3,000–50,000 Hz) and AP (1–50,000 Hz)) on ovariectomized (OVX) osteoporosis (OP) in mice. Forty-eight 3-month-old female BALB/c mice were equally assigned to Sham, OVX, OVX + LP, OVX + BP, OVX + HP and OVX + AP groups (n = 8). After 8-week exposure (3 h/day), LP and BP significantly increased serum bone formation markers and osteogenesis-related gene expressions compared with OVX. Bedsides, LP and BP also slightly increased bone resorption activity compared with OVX, evidenced by increased RANKL/OPG ratio. HP sharply decreased serum bone formation and resporption markers and osteogenesis and osteoclastogenesis related gene expressions compared with OVX. AP had accumulative effects of LP, BP and HP, which significantly increased bone formation and decreased bone resporption activity compared with OVX. As a result, LP, BP and HP exposure did not later deterioration of bone mass, microarchitecture and mechanical strength in OVX mice with OP. However, AP stimulation attenuated OVX-induced bone loss.

The effects of Lycii Radicis Cortex on RANKL-induced osteoclast differentiation and activation in RAW 264.7 cells

Post-menopausal osteoporosis is a serious age-related disease. After the menopause, estrogen deficiency is common, and excessive osteoclast activity causes osteoporosis. Osteoclasts are multinucleated cells generated from the differentiation of monocyte/macrophage precursor cells such as RAW 264.7 cells. The water extract of Lycii Radicis Cortex (LRC) is made from the dried root bark of Lycium chinense Mill. and is termed 'Jigolpi' in Korea. Its effects on osteoclastogenesis and post‑menopausal osteoporosis had not previously been tested. In the present study, the effect of LRC on receptor activator of nuclear factor-κB (NF-κB) ligand (RANKL)-induced osteoclast differentiation was demonstrated using a tartrate-resistant acid phosphatase (TRAP) assay and pit formation assay. Moreover, in order to analyze molecular mechanisms, we studied osteoclastogenesis-related markers such as nuclear factor of activated T-cells cytoplasmic 1 (NFATc1), c-Fos, receptor activator of NF-κB (RANK), TRAP, cathepsin K (CTK), matrix metallopeptidase-9 (MMP-9), calcitonin receptor (CTR) and carbonic anhydrase Ⅱ (CAII) using RT-qPCR and western blot analysis. Additionally, we also determined the effect of LRC on an ovariectomized (OVX) rat model. We noted that LRC inhibited RANKL-induced osteoclast differentiation via suppressing osteoclastogenesis-related markers. It also inhibited osteoporosis in the OVX rat model by decreasing loss of bone density and trabecular area. These results suggest that LRC exerts a positive effect on menopausal osteoporosis.

Biochemical Predictors of Low Bone Mineral Density and Fracture Susceptibility in Maltese Postmenopausal Women

Osteoporosis and fractures are complex conditions influenced by an interplay of genetic and environmental factors. The aim of the study was to investigate three biochemical parameters including total serum calcium, total serum alkaline phosphatase (sALP) and albumin in relation to bone mineral density (BMD) at the lumbar spine and femoral neck (FN), and with all-type of low-trauma fractures in Maltese postmenopausal women. Levels were also correlated with age and physical activity. A case-control study of 1045 women was performed. Women who suffered a fracture were classified as cases whereas women without a fracture history were included as controls subdivided into normal, osteopenic, or osteoporotic according to their BMD measurements. Blood specimens were collected following good standard practice and testing was performed by spectrophotometry. Calcium and sALP levels were weakly correlated with FN BMD levels (calcium: r = -0.111, p = 0.002; sALP: r = 0.089, p = 0.013). Fracture cases had the lowest serum levels of calcium, sALP and albumin relative to all other control groups, which decreased with increasing age, possibly increasing fracture risk. Biochemical levels were lowest in women who sustained a hip fracture and more than one fracture. Biochemical parameters decreased with reduced physical activity; however, this was most evident for fracture cases. Reduced physical activity was associated with lower BMD levels at the hip, and to a lower extent at the spine. In conclusion, results suggest that levels of serum calcium and albumin could be indicative of fracture risk, whereas calcium levels and to lower extent sALP levels could be indicators of hip BMD.

Combination therapy of Chinese herbal medicine Fructus Ligustri Lucidi with high calcium diet on calcium imbalance induced by ovariectomy in mice

CONTEXT

Our previous biological study demonstrated that Fructus Ligustri Lucidi (FLL), the fruit of Ligustrum lucidum Ait. (Oleaceae), could be used to maintain calcium balance and prevent age-related osteoporosis since it effectively decreased calcium loss and increased calcium retention in rats.

OBJECTIVE

This study investigates the combination effect of the Chinese herbal medicine FLL and a high calcium diet on calcium imbalance induced by ovariectomy in mice.

MATERIALS AND METHODS

The ovariectomized (OVX) mice were orally treated with vehicle, FLL extract (700 mg/kg), milk powder (5 g/mice) fortified with calcium (1.0% Ca) and the combination of FLL with milk powder. After 6 weeks of treatment, urine, serum, and tibia were preserved for biochemical analysis and kidneys were taken for gene expression analysis.

RESULTS

The combination treatment of FLL and a high calcium diet significantly increased bone calcium content (6.80 ± 0.34 mg) by 22% (p < 0.05) and decreased urine calcium excretion (0.099 ± 0.009 mg/mg) by 62% (p < 0.01) as compared with those of the OVX group (bone Ca, 5.57 ± 0.31 mg; urine Ca/Cr, 0.261 ± 0.017 mg/mg). The mRNA expression of renal calcium-binding protein-9k (CaBP-9k) and calcium-sensing receptor (CaSR) in combination treatment group was significantly up-regulated and down-regulated, respectively, as compared with those of the OVX group.

CONCLUSION

The beneficial effects of this combination therapy on calcium balance of OVX mice were, at least partially, attributed to its regulation on mRNA expression of CaBP-9k and CaSR in kidney.

Breast size, thoracic kyphosis & thoracic spine pain - association & relevance of bra fitting in post-menopausal women: a correlational study

BACKGROUND

Menopause would seem to exist as a period of accelerated changes for women and their upper torso mechanics. Whether these anthropometric changes reflect changes in pain states remains unclear. Plausible mechanisms of pain exist for the independent and combined effect of increasing breast size and thoracic kyphosis. Bra fit has the potential to change when the anthropometric measures (chest circumference and bust circumference) used to determine bra size change, such as postmenopausally.Identifying an association between breast size, thoracic kyphosis and thoracic spine pain in postmenopausal women and identifying the relevance of bra fit to this association may be of importance to the future management and education of post-menopausal women presenting clinically with thoracic spine pain.

METHODS

A cross-sectional study design. Fifty-one postmenopausal bra-wearing women were recruited. Measures included breast size (Triumph International), thoracic kyphosis (flexible curve), bra fitted (Y/N) and pain (Short Form McGill Pain Questionnaire) and tenderness on palpation (posteroanterior pressure testing). These measures were collected in one session at a physiotherapy clinic.

RESULTS

The majority of the women in this study were overweight or obese and wearing an incorrect sized bra. Pain was significantly related to breast size, body weight and BMI at mid thoracic levels (T7-8). In contrast self-reported thoracic pain was not correlated with age or index of kyphosis (thoracic kyphosis). Women with thoracic pain were no more likely to have their bra professionally fitted whereas women with a higher BMI and larger breasts were more likely to have their bra professionally fitted.

CONCLUSION

The findings of this study show that larger breasts and increased BMI are associated with thoracic pain in postmenopausal women. This is unrelated to thoracic kyphosis. Increasing breast size and how a bra is worn may have biomechanical implications for the loaded thoracic spine and surrounding musculature. Post-menopause women present with a spectrum of anthropometrical changes that have the potential to contribute to altered biomechanics and affect pain states in the thoracic spine.

Quercetin-6-C-β-D-glucopyranoside isolated from Ulmus wallichiana planchon is more potent than quercetin in inhibiting osteoclastogenesis and mitigating ovariectomy-induced bone loss in rats

OBJECTIVE

The aim of this study was to determine the skeletal effect of quercetin-6-C-β-D-glucopyranoside (QCG) isolated from the extract of Ulmus wallichiana and compare this effect with quercetin (Q) in a rat model of postmenopausal bone loss.

METHODS

Murine bone marrow cells were used to study the effect of QCG or Q on osteoclast differentiation. QCG or Q (1.0 and 5.0 mg kg(-1) d(-1) doses) was administered orally to ovarietomized (OVx) rats for 12 weeks. Sham-operated + vehicle and OVx + vehicle groups served as positive and negative controls, respectively. Bone mineral density, bone microarchitecture, biomechanical strength, bone turnover markers, and uterotrophic effect were studied. One-way analysis of variance was used to test significance of effects.

RESULTS

QCG at 1.0 nM significantly inhibited differentiation of multinucleated osteoclasts and expression of osteoclastogenic genes from bone marrow cells, whereas Q at 10.0 μM had comparable results. OVx rats treated with QCG exhibited significantly higher bone mass and better microarchitecture in trabecular and cortical bones compared with OVx + vehicle. QCG treatment of OVx rats had better functional impact than did Q-treated OVx rats, evident from increased bone biomechanical strength. Serum osteocalcin and urinary fragments of type 1 collagen were significantly lower in QCG-treated OVx rats compared with OVx + vehicle group. The protective effect of QCG under ovariectomy-induced bone loss setting was found to be significantly better than Q. Uterine histomorphometry parameters of OVx rats did not change with QCG treatment.

CONCLUSIONS

QCG improves bone biomechanical quality more effectively than Q through positive modifications of bone mineral density and bone microarchitecture without a hyperplastic effect on the uterus.

The Fracture Risk Assessment Tool (FRAX®): applications in clinical practice

Osteoporosis is a serious health concern affecting millions of Americans, with many patients going undiagnosed and untreated. Fractures due to osteoporosis and fracture-related complications are the most clinically relevant and costly consequences of this disorder. The Fracture Risk Assessment Tool (FRAX®), released by the World Health Organization (WHO) in February 2008, is a major achievement in helping determine which patients may be candidates for pharmacological therapy for osteoporosis. This Web-based algorithm, which has been incorporated into some dual x-ray absorptiometry (DXA) reporting software, calculates the 10-year probability of major osteoporotic fracture (clinical vertebral, hip, forearm, or humerus) and the 10-year probability of hip fracture in men and women based on easily obtained clinical risk factors and bone mineral density (BMD) of the femoral neck (optional). The National Osteoporosis Foundation updated its U.S. guidelines in February 2008 to incorporate FRAX and recommends that all postmenopausal women and men aged ≥50 years with a hip or vertebral fracture, a T-score ≤-2.5 at the femoral neck or spine (excluding secondary causes), or low bone mass (T-score between -1.0 and -2.5) and a 10-year probability of hip fracture ≥3% or of major osteoporosis-related fracture ≥20% (based on FRAX) should be considered candidates for drug therapy. Despite its demonstrated clinical utility, FRAX has limitations and should not be used in all situations. Acceptance and clinical use of FRAX may help identify men and women at increased risk for osteoporotic fracture, but implementing the tool into clinical practice may be a challenge for busy physicians.

Bone Turnover Markers

Bone turnover markers (BTM) provide useful data to titrate the optimal dosing regimes for patients within 3–6 months as compared to 1–2 years using bone mineral density (BMD). Serum obtained under standardised conditions (fasting, early morning) should be tested using a precise automated immunoassay for a panel of bone markers that includes a resorption marker — C-terminal cross-linked telopeptide of bone collagen (CTX) — and formation markers — Procollagen Type 1 N-terminal Propeptide (P1NP) and Osteocalcin (OC).

The discovery of MK-0674, an orally bioavailable cathepsin K inhibitor

MK-0674 is a potent and selective cathepsin K inhibitor from the same structural class as odanacatib with a comparable inhibitory potency profile against Cat K. It is orally bioavailable and exhibits long half-life in pre-clinical species. In vivo studies using deuterated MK-0674 show stereoselective epimerization of the alcohol stereocenter via an oxidation/reduction cycle. From in vitro incubations, two metabolites could be identified: the hydroxyleucine and the glucuronide conjugate which were confirmed using authentic synthetic standards.