Clinical assessment of fracture risk and novel therapeutic strategies to combat osteoporosis

Associated Factors for Osteoporosis and Fracture in Chinese Elderly

Background

The factors associated with osteoporosis are poorly understood in the Chinese population. This study aimed to examine the factors associated with osteoporosis and with fractures in a Chinese elderly population.

Material/Methods

This was a cross-sectional study of elderly people living in Tianjin between 2012 and 2014. Bone mineral density was measured by dual X-ray absorptiometry. The subjects completed a questionnaire about lifestyle habits, personal and family medical history, calcium intake, and exercising. Data were gathered on occurrence of fracture at 5 years or August 2018, whichever occurred first.

Results

There were 298 individuals with osteoporosis (18.5% male, median age 67 years) and 397 without (46.3% male, median age 62 years). Male sex (OR=0.051, 95% CI: 0.021–0.126), age (OR=1.049, 95% CI: 1.099–1.202), being divorced/widowed (OR=2.445, 95% CI: 1.219-4.904), digestive ulcer history (OR=3.805, 95% CI: 1.539–9.405), family history of hunchback (OR=2.659, 95% CI: 1.145–6.175), family history of osteoarthropathy (OR=4.222, 95% CI: 2.128–8.375), fracture history (OR=2.138, 95% CI: 1.307–3.496), drinking green tea (OR=0.352, 95% CI: 0.217–0.574), and exercising (OR=0.303, 95% CI: 0.193–0.475) were independently associated with osteoporosis. Digestive ulcer history (OR=3.183, 95% CI: 1.178–8.5992), exercising (OR=0.354, 95% CI: 0.139–0.903), and taking calcium supplements during follow-up (OR=0.262, 95% CI: 0.112–0.611) were independently associated with fractures in patients with osteoporosis.

Conclusions

Female sex, age, marital status, history of digestive ulcer and fracture, and family history of hunchback and osteoarthropathy are associated with osteoporosis among elderly subjects, while drinking green tea and exercising are inversely associated. Among the patients with osteoporosis, a history of digestive ulcer is associated with fractures, while exercising and taking calcium supplements are inversely associated.

Glucocorticoid induced osteoporosis

INTRODUCTION

Glucocorticoid-induced osteoporosis is the most common secondary cause of osteoporosis. Despite this, many patients receiving glucocorticoids are not evaluated for their skeletal health.

AREAS COVERED

Glucocorticoids have profound effects on bone cells, resulting in increases in bone resorption and impairments in bone formation. Bone loss and subsequent increases in fracture risk occur early after the administration of glucocorticoids. Incidence of fractures is highest within the first 6 months of glucocorticoid treatment, and declines with longer exposure. Decreases in bone mass follow a dose-dependent relationship with glucocorticoid dosage. Pharmacologic prevention and treatment for osteoporosis are recommended for all patients receiving glucocorticoids. Oral bisphosphonates, with concomitant vitamin D and calcium supplementation, are considered as the first-line treatment option. However, a number of alternative treatment options, including intravenous bisphosphonates, anabolic agents, and denosumab have all proven efficacy in increasing lumbar spine or hip bone mineral density. The mechanism of action and recent controlled trials for these therapies are reviewed. The literature search was conducted within PubMed in November 2018. 492 articles were found and 45 were included.

EXPERT OPINION

Future studies will likely evaluate the safety profiles of alternative treatments, while focusing on its ability to reduce fracture risk.

TGF-β inhibits osteogenesis by upregulating the expression of ubiquitin ligase SMURF1 via MAPK-ERK signaling

High incidence of osteoporotic fractures emphasizes the necessity of developing effective measures to promote osteogenesis. In our study, we investigated a possible role of MAPK-ERK signaling in the TGF-β-mediated osteoblastic differentiation. Our results indicated that TGF-β activated the MAPK-ERK pathway and inhibited osteogenesis in mesenchymal pluripotent cell line, C3H10T1/2, and preosteoblastic cell line, MC3T3 cells. And the downregulation of MAPK-ERK signaling using pharmacological inhibitor U0126 and RNA interference rescued osteoblast differentiation suppressed by TGF-β, which was confirmed by Alkaline phosphatase (ALP) staining and alizarrn red staining, and the enhanced expression of osteogenesic markers. Western blotting analysis indicated that TGF-β induced protein expression of E3 ubiquitin-protein ligase SMURF1, which contributed to the degradation of RUNX2 and SMAD1 as evidenced by SMURF1 inhibition using RNA interference and proteasome inhibitor MG132. Moreover, we observed that the expression of SMURF1 was decreased, while that of SMAD1 and RUNX2 increased by MAPK-ERK inhibitor U0126 in TGF-β-treated differentiating preosteoblasts, suggesting that MAPK-ERK regulated the transcription of osteogenesis-related genes. Furthermore, a synergistic effect between U0126 and bone morphogenic protein (BMP)-2 on osteoblast differentiation and bone formation was observed both in cell cultures and experimental animals. In conclusion, our results revealed that TGF-β inhibited osteoblastic differentiation by inducing the MAPK-ERK pathway which upregulated the expression of ubiquitin ligase SMURF1 and resulted in reduced presence of osteogenic proteins. In addition, the potentiation of BMP-2 on osteogenic activity by ERK1/2 inhibitor U0126 suggests that it may have potential clinical utility for promoting osteogenesis in bone fracture repair.

Ethanol Extract of Cissus quadrangularis Enhances Osteoblast Differentiation and Mineralization of Murine Pre-Osteoblastic MC3T3-E1 Cells

Traditional medicinal literature and previous studies have reported the possible role of Cissus quadrangularis (CQ) as an anti-osteoporotic agent. This study examines the effectiveness of CQ in promoting osteoblast differentiation of the murine pre-osteoblast cell line, MC3T3-E1. Ethanolic extract of CQ (CQ-E) was found to affect growth kinetics of MC3T3-E1 cells in a dosage-dependent manner. High concentrations of CQ-E (more than 10 μg/ml) have particularly adverse effects, while lower concentrations of 0.1 and 1 µg/ml were non-toxic and did not affect cell viability. Notably, cell proliferation was significantly increased at the lower concentrations of CQ-E. CQ-E treatment also augmented osteoblast differentiation, as reflected by a substantial increase in expression of the early osteoblast marker ALP activity, and at later stage, by mineralization of extracellular matrix compared to the control group. These findings suggest dose-dependent effect of CQ-E with lower concentrations exhibiting anabolic and osteogenic properties. J. Cell. Physiol. 232: 540-547, 2017. © 2016 Wiley Periodicals, Inc.

Live imaging of osteoclast inhibition by bisphosphonates in a medaka osteoporosis model

Osteoclasts are bone-resorbing cells derived from the monocyte/macrophage lineage. Excess osteoclast activity leads to reduced bone mineral density, a hallmark of diseases such as osteoporosis. Processes that regulate osteoclast activity are therefore targeted in current osteoporosis therapies. To identify and characterize drugs for treatment of bone diseases, suitable in vivo models are needed to complement cell-culture assays. We have previously reported transgenic medaka lines expressing the osteoclast-inducing factor receptor activator of nuclear factor κB ligand (Rankl) under control of a heat shock-inducible promoter. Forced Rankl expression resulted in ectopic osteoclast formation, as visualized by live imaging in fluorescent reporter lines. This led to increased bone resorption and a dramatic reduction of mineralized matrix similar to the situation in humans with osteoporosis. In an attempt to establish the medaka as an in vivo model for osteoporosis drug screening, we treated Rankl-expressing larvae with etidronate and alendronate, two bisphosphonates commonly used in human osteoporosis therapy. Using live imaging, we observed an efficient, dose-dependent inhibition of osteoclast activity, which resulted in the maintenance of bone integrity despite an excess of osteoclast formation. Strikingly, we also found that bone recovery was efficiently promoted after inhibition of osteoclast activity and that osteoblast distribution was altered, suggesting effects on osteoblast-osteoclast coupling. Our data show that transgenic medaka lines are suitable in vivo models for the characterization of antiresorptive or bone-anabolic compounds by live imaging and for screening of novel osteoporosis drugs.

Genetic factors influencing bone mineral content in a black South African population

Bone mass differs according to ethnic classification, with individuals of African ancestry attaining the highest measurements across numerous skeletal sites. Elevated bone mass is even maintained in those individuals exposed to adverse environmental factors, suggesting a prominent genetic effect that may have clinical or therapeutic value. Using a candidate gene approach, we investigated associations of six candidate genes (ESR1, TNFRSF11A, TNFRSF11B, TNFSF11, SOST and SPP1) with bone mass at the hip and lumbar spine amongst pre-pubertal black South African children (mean age 10.6 years) who formed part of the longitudinal Birth to Twenty cohort. 151 black children were genotyped at 366 polymorphic loci, including 112 previously associated and 254 tagging single nucleotide polymorphisms (SNPs). Linear regression was used to highlight significant associations whilst adjusting for height, weight, sex and bone area. Twenty-seven markers (8 previously associated and 19 tag SNPs; P < 0.05) were found to be associated with either femoral neck (18) or lumbar spine (9) bone mineral content. These signals were derived from three genes, namely ESR1 (17), TNFRSF11B (9) and SPP1 (1). One marker (rs2485209) maintained its association with the femoral neck after correction for multiple testing (P = 0.038). When compared to results amongst Caucasian adults, we detected differences with respect to associated skeletal sites. Allele frequencies and linkage disequilibrium patterns were also significantly different between populations. Hence, our results support the existence of a strong genetic effect acting at the femoral neck in black South African children, whilst simultaneously highlighting possible causes that account for inter-ethnic bone mass diversity.

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.

The utility and limitations of FRAX: A US perspective

The FRAX calculator is a major achievement in terms of our understanding of measuring fracture risk. Along with being an easily accessible web-based tool, it is the only model based on extensive data on multiple cohorts. FRAX will help clinicians identify individuals who need osteoporosis treatments, while also screening out those who do not require osteoporosis treatments. However, FRAX is limited by a number of factors. Although it is web based, few physicians have the means to access it. It also assumes that body mass index and mortality are constant across different racial and ethnic groups. FRAX is further limited by the exclusion of variables known to be associated with fracture risk, lack of dose-response relationships for variables, increased subsequent fracture risk after initial fracture, restriction to only one bone mineral density site, racial and ethnic differences that may influence fracture risk, and availability of racial and ethnic fracture risk data to be used in the FRAX calculator. Finally, the values obtained from FRAX should not take the place of good clinical judgment.

Current, new and future treatments of osteoporosis

Osteoporosis as a common chronic disease is challenging human health. Although different therapeutic options are routinely used for prevention/treatment of osteoporosis, their side effects and benefits are under question. Increasing our knowledge about signaling pathways in bone and osteocytes as well as osteoblasts and osteoclasts will help us in designing new therapeutic modalities for osteoporosis. In the present study, all new therapeutic measures of osteoporosis have been reviewed. For this purpose, search engines like Pubmed, Web of Science, Scopus, Google Scholar were searched and all relevant articles were found. The study was limited to the year 1998-2010. Bisphosphonates are the cornerstone of osteoporosis treatment, but there are not enough relevant studies that investigated their equivalencies in comparison with each other or the other medications. Therefore, medication selection is empirical and subjective. Furthermore, no eminent study has compared certain combinations. There are new hopes for treatment of osteoporosis, which are more specific with less harm. Our results show that new and emerging therapies are more potent and target specified which more individualize osteoporosis treatment; however, more investigations on their safety and efficacy in comparison with current medications are highly recommended.

Bone fractures after menopause

BACKGROUND

Every year 30% of individuals above age 65 fall, and falls are the principal cause of bone fractures. To reduce fracture incidence requires both prevention of falls and maintenance of bone strength.

METHODS

PubMed searches were performed, for studies of the epidemiology of fractures, bone physiology, endocrine effects, osteoporosis measurement, genetics, prevention and effectiveness. Topic summaries were presented to the Workshop Group and omissions or disagreements were resolved by discussion.

RESULTS

Ageing reduces bone strength in post-menopausal women because estrogen deficiency causes accelerated bone resorption. Bone mineral density (BMD) decreased more than 2.5 standard deviation below the mean of healthy young adults defines osteoporosis, a condition associated with an increased risk of fractures. Risk factors such as age and previous fracture are combined with BMD for a more accurate prediction of fracture risk. The most widely used assessment tool is FRAX™ which combines clinical risk factors and femoral neck BMD. General preventive measures include physical exercise to reduce the risk of falling and vitamin D to facilitate calcium absorption. Pharmacological interventions consist mainly in the administration of inhibitors of bone resorption. Randomized controlled trials show treatment improves BMD, and may reduce the relative fracture risk by about 50% for vertebral, 20-25% for non-vertebral and up to 40% for hip fractures although the absolute risk reductions are much lower.

CONCLUSIONS

Although diagnosis of osteoporosis is an important step, the threshold for treatment to prevent fractures depends on additional clinical risk factors. None of the presently available treatment options provide complete fracture prevention.