Differential Effects of Dabigatran and Warfarin on Bone Volume and Structure in Rats with Normal Renal Function

Outcomes of Unicompartmental Knee Arthroplasty in Patients Receiving Long-Term Anticoagulation Therapy: A Propensity-Matched Cohort Study

BACKGROUND

Although total knee arthroplasty has been considered the gold-standard treatment for severe osteoarthritis of the knee, unicompartmental knee arthroplasty (UKA) has become an increasingly favorable alternative for single-compartment osteoarthritis of the knee. Few studies have examined potential high-risk populations undergoing this procedure. The purpose of this study was to investigate the outcomes of UKA in patients receiving long-term anticoagulation therapy.

METHODS

In this study, a large administrative database was queried to identify patients undergoing UKA between 2009 and 2019, who were then divided into a cohort receiving long-term anticoagulation and a control cohort. Propensity scores were utilized to match these patients. Multivariable logistic regression was utilized to compare 90-day and 2-year complication rates between cohorts.

RESULTS

Patients who were on long-term anticoagulation had significantly increased odds of extended length of stay, surgical site infection, wound complication, transfusion, deep vein thrombosis, pulmonary embolism, and readmission at 90-day follow-up. The long-term anticoagulation cohort also experienced significantly higher odds of periprosthetic joint infection and mechanical complications at 2-year follow-up; however, odds of conversion to total knee arthroplasty were not increased.

CONCLUSIONS

This study demonstrated that long-term anticoagulation use was associated with poorer medical and surgical outcomes at both 90 days and 2 years postoperatively in patients undergoing UKA, even after rigorous adjustment for confounders.

Effects of sodium dehydroacetate on broiler chicken bones

Sodium dehydroacetate (DHA-Na) is a fungicidal preservative widely used in food and animal feed. DHA-Na can induce coagulation disorders in rats and poultry by inhibiting carboxylation of vitamin K-dependent proteins; it can also impair bone development in zebrafish. However, the effects of DHA-Na on broiler chicken bones remain unknown. Here, we assessed whether DHA-Na impairs bone development in broiler chickens. We administered Suji yellow chickens with 200 to 800 mg/kg DHA-Na, 2 mg/kg vitamin K, or both for 2 mo. Bone metabolite-related serum indicators, tissue micromorphology, and relevant protein expression were monitored during the treatment period. We also assessed primary chicken osteoblast activity, differentiation, and bone metabolite-related proteins after treatment with DHA-Na, vitamin K, or both. The results demonstrated that DHA-Na reduced bone index values and serum and bone osteoblast differentiation marker levels but blocked bone vitamin K cycle. DHA-Na also increased serum osteoclast differentiation marker levels, as well as the bone ratio of receptor activator of nuclear factor kappa-Β ligand to osteoprotegerin ratio. Moreover, DHA-Na reduced bone trabecular number, thickness, and area and increased trabecular separation considerably. In general, compared with the control group, the DHA-Na group demonstrated impairments in osteoblast activity and differentiation, as well as in the vitamin K cycle. By contrast, vitamin K supplementation led to considerable attenuation of the DHA-Na-induced decrease in osteogenic marker levels, along with a considerable increase in serum bone absorption marker levels and restoration of DHA-Na-induced bone microstructure damage. Vitamin K also attenuated DHA-Na-induced impairment in osteoclasts. In conclusion, the results indicated that in broiler chickens, DHA-Na supplementation can damage bones by inhibiting osteoblast function and increasing osteoclast activity; this damage can be prevented through vitamin K supplementation.

How I treat pediatric venous thromboembolism in the DOAC era

ABSTRACT

The direct oral anticoagulants (DOACs) rivaroxaban and dabigatran are newly licensed for the treatment and prevention of venous thromboembolism (VTE) in children and mark a renaissance in pediatric anticoagulation management. They provide a convenient option over standard-of-care anticoagulants (heparins, fondaparinux, and vitamin K antagonists) because of their oral route of administration, child-friendly formulations, and significant reduction in monitoring. However, limitations related to therapeutic monitoring when needed and the lack of approved reversal agents for DOACs in children raise some safety concerns. There is accumulating experience of safety and efficacy of DOACs in adults for a broad scope of indications; however, the cumulative experience of using DOACs in pediatrics, specifically for those with coexisting chronic illnesses, is sparse. Consequently, clinicians must often rely on their experience for treating VTE and extrapolate from data in adults while using DOACs in children. In this article, the authors share their experience of managing 4 scenarios that hematologists are likely to encounter in their day-to-day practice. Topics addressed include (1) appropriateness of indication; (2) use for special populations of children; (3) considerations for laboratory monitoring; (4) transition between anticoagulants; (5) major drug interactions; (6) perioperative management; and (7) anticoagulation reversal.

Effect of direct oral anticoagulant dabigatran on early bone healing: An experimental study in rats

Background

Dabigatran belongs to the new generation of direct oral anticoagulants (DOACs). Its advantages are oral administration and no need for international normalized ratio (INR) monitoring. Although its use has increased, its potential side effects on bone healing and remodeling have not been fully investigated. The present study aimed to evaluate the possible effects of dabigatran on early bone healing.

Methods

Sixteen male Wistar rats were divided into two groups; in group A, 20-mg/kg dabigatran dose was administered orally daily for 15 days, while group B served as a control. Two circular bone defects (d=6 mm) were created on either side of the parietal bones. Two weeks after surgery and euthanasia of the animals, tissue samples (parietal bones that contained the defects) were harvested for histological and histomorphometric analysis. Statistical analysis was performed with a significance level of α=0.5.

Results

No statistically significant differences were found between the two groups regarding the regenerated bone (21.9% vs. 16.3%, P=0.172) or the percentage of bone bridging (63.3% vs. 53.5%, P=0.401).

Conclusion

Dabigatran did not affect bone regeneration, suggesting that it might be a safer drug compared to older anticoagulants known to lead to bone healing delay.

Risk of osteoporosis in patients treated with direct oral anticoagulants vs. warfarin: an analysis of observational studies

Aims

Evidence on the association between the risk of new-onset osteoporosis and oral anticoagulants remains controversial. We aimed to compare the risk of osteoporosis associated with the use of direct oral anticoagulants (DOACs) with that associated with warfarin use.

Methods

Studies published up to 15 March 2023 that investigated the association between the use of DOACs and warfarin and the incidence of osteoporosis were identified by online searches in PubMed, Embase, the Cochrane Library, and Web of Science conducted by two independent investigators. Random-effects or fixed-effect models were employed to synthesize hazard ratios (HRs)/relative ratios (RRs) with 95% confidence intervals (CIs) for estimating the risk of osteoporosis correlated with DOAC and warfarin prescriptions (PROSPERO No. CRD42023401199).

Results

Our meta-analysis ultimately included four studies involving 74,338 patients. The results suggested that DOAC use was associated with a significantly lower incidence of new-onset osteoporosis than warfarin use (pooled HR: 0.71, 95% CI: 0.57 to 0.88, p < 0.001, I 2: 85.1%). Subanalyses revealed that rivaroxaban was associated with a lower risk of osteoporosis than both warfarin and dabigatran. In addition, DOACs were associated with a lower risk of developing osteoporosis than warfarin in both male and female patients, in patients with atrial fibrillation (AF), and in patients who underwent therapy for > 365 days.

Conclusion

DOAC users experienced a lower incidence of osteoporosis than warfarin users. This study may give us insight into safe anticoagulation strategies for patients who are at high risk of developing osteoporosis.

Systematic review registration

https://www.crd.york.ac.uk/PROSPERO, identifier CRD42023401199.

Pharmaceutical treatment of bone loss: From animal models and drug development to future treatment strategies

Animal models are fundamental to advance our knowledge of the underlying pathophysiology of bone loss and to study pharmaceutical countermeasures against it. The animal model of post-menopausal osteoporosis from ovariectomy is the most widely used preclinical approach to study skeletal deterioration. However, several other animal models exist, each with unique characteristics such as bone loss from disuse, lactation, glucocorticoid excess, or exposure to hypobaric hypoxia. The present review aimed to provide a comprehensive overview of these animal models to emphasize the importance and significance of investigating bone loss and pharmaceutical countermeasures from perspectives other than post-menopausal osteoporosis only. Hence, the pathophysiology and underlying cellular mechanisms involved in the various types of bone loss are different, and this might influence which prevention and treatment strategies are the most effective. In addition, the review sought to map the current landscape of pharmaceutical countermeasures against osteoporosis with an emphasis on how drug development has changed from being driven by clinical observations and enhancement or repurposing of existing drugs to today's use of targeted anti-bodies that are the result of advanced insights into the underlying molecular mechanisms of bone formation and resorption. Moreover, new treatment combinations or repurposing opportunities of already approved drugs with a focus on dabigatran, parathyroid hormone and abaloparatide, growth hormone, inhibitors of the activin signaling pathway, acetazolamide, zoledronate, and romosozumab are discussed. Despite the considerable progress in drug development, there is still a clear need to improve treatment strategies and develop new pharmaceuticals against various types of osteoporosis. The review also highlights that new treatment indications should be explored using multiple animal models of bone loss in order to ensure a broad representation of different types of skeletal deterioration instead of mainly focusing on primary osteoporosis from post-menopausal estrogen deficiency.

Dysbiosis in Patients with Chronic Kidney Disease: Let Us Talk About Vitamin K

PURPOSE OF REVIEW

This narrative review aimed to summarize the current evidence on the connection between dysbiosis and vitamin K deficiency in patients with chronic kidney disease (CKD). The presence of dysbiosis (perturbations in the composition of the microbiota) has been described in several non-communicable diseases, including chronic kidney disease, and it has been hypothesized that dysbiosis may cause vitamin K deficiency. Patients with CKD present both vitamin K deficiency and gut dysbiosis; however, the relationship between gut dysbiosis and vitamin K deficiency remains to be addressed.

RECENT FINDINGS

Recently, few studies in animals have demonstrated that a dysbiotic environment is associated with low production of vitamin K by the gut microbiota. Vitamin K plays a vital role in blood coagulation as well as in the cardiovascular and bone systems. It serves as a cofactor for γ-glutamyl carboxylases and thus is essential for the post-translational modification and activation of vitamin K-dependent calcification regulators, such as osteocalcin, matrix Gla protein, Gla-rich protein, and proteins C and S. Additionally, vitamin K executes essential antioxidant and anti-inflammatory functions. Dietary intake is the main source of vitamin K; however, it also can be produced by gut microbiota. This review discusses the effects of uremia on the imbalance in gut microbiota, vitamin K-producing bacteria, and vitamin K deficiency in CKD patients, leading to a better understanding and raising hypothesis for future clinical studies.

The association of non-vitamin K antagonist oral anticoagulants vs. warfarin and the risk of fractures for patients with atrial fibrillation: a systematic review and meta-analysis

BACKGROUND

The fracture risks of non-vitamin K antagonist oral anticoagulants (NOACs) vs. warfarin in patients with atrial fibrillation (AF) remain controversial.

METHODS

PubMed, Cochrane Library, EMBASE, Clinical Trials.gov databases for RCTs, and cohort studies were systematically searched from inception to 10 June 2021.

RESULTS

Twelve-two studies met the inclusion criteria and 477,821 patients were included. Warfarin increased the risk of fracture in AF patients compared with NOACs in overall any fracture (RR = 0.79; 95% CI = 0.70-10.88; p = 0.00), osteoporotic fracture (RR = 0.746; 95% CI = 0.630-0.883; p = 0.001). No significant difference was observed in the hip or pelvic fracture, vertebral fracture, extremity fracture, wrist fracture, femoral neck fracture, and ankle fracture. In subgroup analyses based on several aspects, NOACs were associated with a significant reduction in any fracture (standard dosage NOACs, cohort studies, elderly patients, rivaroxaban in RCTs, dabigatran, rivaroxaban, and apixaban in cohort studies), in the hip/pelvic fracture (follow-up time ≤1 year, cohort studies), and osteoporotic fracture (cohort studies).

CONCLUSION

NOACs were associated with a significantly lower risk of any fracture and osteoporotic fracture compared to warfarin. This benefit was also observed in specific NOACs types of dabigatran, rivaroxaban, and apixaban. However, whether NOACs had a less fracture risk than warfarin on the other risk of fractures was still uncertain.

Comparative Risks of Fracture Among Direct Oral Anticoagulants and Warfarin: A Systematic Review and Network Meta-Analysis

Importance

Previous studies have shown the effectiveness and safety of direct oral anticoagulants (DOACs), including lower fracture risks, compared to warfarin. However, direct or indirect comparisons between different DOACs are scarce in the literature.

Objective

This study aims to compare fracture risks among different DOACs and warfarin, including apixaban, rivaroxaban, dabigatran, and edoxaban, in patients with non-valvular atrial fibrillation (NVAF) or venous thromboembolism (VTE).

Methods

We searched PubMed/MEDLINE, Embase, Cochrane CENTRAL, and Web of Science for randomized controlled trials and cohort studies comparing the fracture risks among patients who used warfarin or DOACs, up to March 2021. Two authors extracted data and appraised the risk of bias of included studies. The primary outcome was fracture risk. We performed pairwise meta-analyses to compare differences between medications and network meta-analyses using frequentist random-effects models to compare through indirect evidence. We used surface under the cumulative ranking curve (SUCRA) and mean ranks to determine the probability of a DOAC ranking best in terms of fracture risk.

Results

Thirty-one studies were included in the final analysis. Twenty-four randomized controlled trials and seven cohort studies with 455,343 patients were included in the systematic review and network meta-analysis. Compared to warfarin, the risk of any fractures was lowest with apixaban [relative risk (RR) = 0.59; 95% confidence interval (CI): 0.48-0.73], followed by rivaroxaban (RR: 0.72; 95% CI: 0.60-0.86), edoxaban (RR: 0.88; 95% CI: 0.62-1.23), and dabigatran (RR = 0.90; 95% CI: 0.75-1.07). No substantial inconsistency between direct and indirect evidence was detected for all outcomes.

Conclusions

All DOACs were safer than warfarin concerning the risk of fracture; however, apixaban had the lowest relative risk of fracture within the class of DOACs. Further head-to-head prospective studies should confirm the comparative safety profiles of DOACs regarding fractures.

Hip fractures risks in edoxaban versus warfarin users: A propensity score-matched population-based cohort study with competing risk analyses

OBJECTIVE

The three direct oral anticoagulants (DOAC), rivaroxaban, apixaban and dabigatran have been associated with lower risks of fractures compared to warfarin. However, no large scale studies have explored the associations with the newest DOAC, edoxaban, with fracture risk. The present study aims to elucidate the effects of edoxaban on the risk of hip fracture amongst elderly patients by comparing the incidence of new onset hip fracture between edoxaban and warfarin users in a Chinese population.

METHODS

This was a retrospective population-based cohort study of patients with edoxaban or warfarin use between January 1st, 2016 and December 31st, 2019 in Hong Kong, China. Patients with less than one-month exposure, medication switching between warfarin and edoxaban, those who died within 30 days after drug exposure, prior human immunodeficiency virus infection, age <50 years old, and those with prior hip fractures were excluded. Propensity score matching (1:2) between edoxaban and warfarin users using the nearest neighbour method was performed based on demographics, prior comorbidities, and use of different medications. The study outcomes were new onset hip fractures, medically attended falls and all-cause mortality.

RESULTS

A total of 5014 patients including 579 edoxaban users and 4435 warfarin users (median age: 70 years old [interquartile range (IQR): 62-79], 56.66% males) with a median follow-up of 637.5 (IQR: 320-1073) days were included. In the matched cohort, edoxaban users had significantly lower rates of new onset hip fractures, medically attended falls and all-cause mortality. The protective value of edoxaban use against new onset hip fracture (hazard ratio [HR]: 0.13, 95% confidence interval [CI]: [0.03-0.54], p = 0.0051), medically attended falls (HR: 0.47, [0.29-0.75], p = 0.0018) and all-cause mortality (HR: 0.61, [0.42-0.87], p = 0.0059) in comparison to warfarin use persisted after matching. The significant relationship between edoxaban use and lower fracture risk was preserved in all sensitivity analyses using different approaches using the propensity score.

CONCLUSIONS

Edoxaban use is associated with lower risks of new onset hip fractures, medically attended falls and mortality risks compared to warfarin after propensity score matching.

The Role of Vitamin K in CKD-MBD

PURPOSE OF REVIEW

We describe the mechanism of action of vitamin K, and its implication in cardiovascular disease, bone fractures, and inflammation to underline its protective role, especially in chronic kidney disease (CKD).

RECENT FINDINGS

Vitamin K acts as a coenzyme of y-glutamyl carboxylase, transforming undercarboxylated in carboxylated vitamin K-dependent proteins. Furthermore, through the binding of the nuclear steroid and xenobiotic receptor, it activates the expression of genes that encode proteins involved in the maintenance of bone quality and bone remodeling. There are three main types of K vitamers: phylloquinone, menaquinones, and menadione. CKD patients, for several conditions typical of the disease, are characterized by lower levels of vitamin K than the general populations, with a resulting higher prevalence of bone fractures, vascular calcifications, and mortality. Therefore, the definition of vitamin K dosage is an important issue, potentially leading to reduced bone fractures and improved vascular calcifications in the general population and CKD patients.

Bone density and quality in patients treated with direct-acting oral anticoagulants versus warfarin

INTRODUCTION

Direct-acting oral anticoagulants (DOACs) are therapeutic alternatives to warfarin that act independently of vitamin K, thus not affecting bone matrix formation. The aim of this study was to compare bone mineral density (BMD) and microarchitecture in patients treated with DOACs versus warfarin.

METHODS

Cross-sectional, observational study in patients using oral anticoagulants for >1 year and a paired control group (CG). Based on the type of anticoagulant used, the patients were grouped into a DOAC (DOACG) or warfarin (WG) group. All patients filled out a questionnaire and underwent BMD evaluation and trabecular bone score (TBS) measurement.

RESULTS

In all, 150 patients were included (50 patients in each group). The mean age was 60.49 ± 7.48 years, and most participants were men (64%). The most frequent comorbidities were hypertension, dyslipidemia, and hyperglycemia (comparison between groups p > 0.05). Low bone mass was diagnosed in 42%, 50%, and 66% of the patients in the CG, DOACG, and WG, respectively (p = 0.012). On logistic regression analysis, BMD was associated with body mass index (BMI; odds ratio [OR] 0.846, 95% confidence interval [CI] 0.763-0.926, p = 0.001), creatinine level (OR 0.024, 95%CI 0.001-0.434, p = 0.017), and TBS value (OR 17.777, 95%CI 4.526-96.903, p = 0.000). The mean TBS decreased progressively from the CG to the DOACG and WG (1.328 ± 0.112, 1.264 ± 0.138, and 1.203 ± 0.112, respectively, p < 0.001). On multivariate linear regression, negative predictors of TBS included warfarin use (-0.06, 95%CI -0.11 to -0.02, p = 0.006), BMI (-0.01, 95%CI -0.01 to -0.00, p < 0.001), and hyperglycemia (-0.07, 95%CI -0.11 to -0.03, p = 0.003), while positive predictors were an active IPAQ classification (0.06, 95%CI 0.01-0.11, p = 0.029) and family history of hip fracture (0.07, 95%CI 0.01-0.14, p = 0.029).

CONCLUSION

Patients using anticoagulants have lower BMD and TBS values compared with controls. This negative effect on bone was more pronounced with warfarin, but was also seen with DOACs.

Non-vitamin K oral anticoagulants and risk of fractures: a systematic review and meta-analysis

AIMS

Comparative fracture risk for non-vitamin K antagonist oral anticoagulants (NOACs) and vitamin K antagonists (VKAs) among patients with atrial fibrillation (AF) remains unclear. This study aimed to provide summary relative risk (RR) estimates for associations between NOACs vs. VKAs and fracture risk.

METHODS AND RESULTS

PubMed, EMBASE, and Cochrane Library were searched from 2010 to 26 May 2020. Observational studies investigating the association between NOACs vs. VKAs and fracture risk in patients with AF were included. The adjusted effect estimates were pooled using the DerSimonian-Laird random effects models. The Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) and the Meta-analysis of Observational Studies in Epidemiological (MOOSE) guidelines were followed. Five observational studies comprising 269 922 patients and 4289 fractures were included. Non-vitamin K antagonist oral anticoagulants use was associated with a lower risk of any fractures compared to VKAs use, with moderate heterogeneity [pooled RR = 0.83, 95% confidence interval (CI): 0.75-0.92, P < 0.001, I2 = 73.0%]. When comparing individual NOAC to VKAs, a statistically significant lower risk of any fractures was found for rivaroxaban (pooled RR = 0.79, 95% CI: 0.71-0.88, P < 0.001, I2 = 55.2%) and apixaban (pooled RR = 0.75, 95% CI: 0.60-0.92, P = 0.007, I2 = 54.5%), but not dabigatran (pooled RR = 0.87, 95% CI: 0.74-1.01, P = 0.061, I2 = 74.6%). No differences were observed in all head-to-head comparisons between NOACs.

CONCLUSION

This large meta-analysis suggests that NOACs use was associated with a lower risk of fractures compared with VKAs. Fracture risks were similar between NOACs. These findings may help inform the optimal anticoagulant choice for patients with AF at high risk of fracture.

Association of Direct Oral Anticoagulants vs. Vitamin K Antagonists With Fractures in Atrial Fibrillation Patients: A Systematic Review and Meta-Analysis

Background: Current evidence regarding the application of direct oral anticoagulants (DOACs) vs. vitamin K antagonists (VKAs) on the fracture risk is inconsistent. Therefore, we conducted a meta-analysis to evaluate the fracture risk of DOACs vs. VKAs in patients with atrial fibrillation (AF).

Methods: The PubMed and Embase databases were systematically searched until June 2021 for all the studies that reported oral anticoagulants in AF patients. The random-effect model with an inverse variance method was selected to pool the risk ratios (RRs) and 95% confidence intervals (CIs).

Results: A total of 10 studies were included in this meta-analysis. Among AF patients receiving anticoagulants, DOAC users showed a reduced risk of any fracture compared to those with VKAs (RR = 0.80; 95% CI: 0.70–0.91) regardless of gender [males (RR = 0.79; 95% CI: 0.67–0.92) and females (RR = 0.71; 95% CI: 0.57–0.89)]. Apixaban (RR = 0.75; 95% CI: 0.60–0.92) and rivaroxaban (RR = 0.73; 95% CI: 0.61–0.88), but not dabigatran and edoxaban, were associated with a decreased risk of any fracture compared with VKAs. DOAC users had decreased risks of osteoporotic fractures (RR = 0.63; 95% CI: 0.47–0.84) and hip/pelvic fractures (RR = 0.88; 95% CI: 0.79–0.97) compared to those treated with VKAs.

Conclusions: Our meta-analysis suggested that the use of DOACs was associated with a reduced risk of any fracture compared with VKAs. Further studies should confirm our findings.

A Network Meta-Analysis Comparing Osteoporotic Fracture among Different Direct Oral Anticoagulants and Vitamin K Antagonists in Patients with Atrial Fibrillation

Background

There are limited studies comparing the risk of osteoporosis and fractures between different direct oral anticoagulants (DOACs) and vitamin K antagonists (VKA) in non-valvular atrial fibrillation (AF). Using a network meta-analysis (NMA), we compared osteoporotic fractures among 5 different treatment arms, viz. dabigatran, rivaroxaban, apixaban, edoxaban, and VKA.

Methods

Ten studies, including 5 randomized control trials and 5 population-based studies, with a total of 321,844 patients (148,751 and 173,093 in the VKA and DOAC group, respectively) with a median follow-up of 2 years, were included. A Bayesian random-effects NMA model comparing fractures among the treatment arms was performed using MetInsight V3. Sensitivity analysis excluded studies with the highest residual deviances from the NMA model.

Results

The mean age of the patients was 70 years. The meta-analysis favored DOACs over VKA with significantly lower osteoporotic fracture (odds ratio [OR], 0.77; 95% credible interval [CrI], 0.70–0.86). The NMA demonstrated that fractures were significantly lower with apixaban compared with dabigatran (OR, 0.64; 95% CrI, 0.44–0.95); however, fractures were statistically similar between apixaban and rivaroxaban (OR, 0.84; 95% CrI, 0.58–1.24) and dabigatran and rivaroxaban (OR, 1.32; 95% CrI, 0.90–1.87). Based on the Bayesian model of NMA, the probability of osteoporotic fracture was highest with VKA and lowest with apixaban, followed by rivaroxaban, edoxaban, and dabigatran.

Conclusions

The decision to prescribe anticoagulants in elderly patients with AF should be made not only based on thrombotic and bleeding risks but also on the risk of osteoporotic fracture; these factors should be considered and incorporated in contemporary cardiology practice.

Fracture risks among patients with atrial fibrillation receiving different oral anticoagulants: a real-world nationwide cohort study

AIMS

To evaluate the fracture risk among patients with atrial fibrillation (AF) treated with non-vitamin K antagonist oral anticoagulants (NOACs) or warfarin.

METHODS AND RESULTS

We conducted a real-world nationwide retrospective cohort study using Taiwan's National Health Insurance Research Database. All adult patients in Taiwan newly diagnosed with AF between 2012 and 2016 who received NOACs or warfarin were enrolled and followed up until 2017. Patients treated with NOACs were sub-grouped according to the NOAC used (dabigatran, rivaroxaban, and apixaban). Propensity score matching was performed for each head-to-head comparison. Cox regression analysis, with a shared frailty model, was used to calculate the adjusted hazard ratios (aHRs) for hip, vertebral, and humerus/forearm/wrist fractures. After matching, 19 414 patients were included (9707 in each NOAC and warfarin groups). The median follow-up time was 2.4 years. Compared with warfarin, NOACs were associated with a reduced fracture risk [aHR = 0.84, 95% confidence interval (CI) = 0.77-0.93; P < 0.001]. Sub-analyses revealed that each NOAC, namely dabigatran (aHR = 0.88, 95% CI = 0.78-0.99; P = 0.027), rivaroxaban (aHR = 0.81, 95% CI = 0.72-0.90; P < 0.001), and apixaban (aHR = 0.67, 95% CI = 0.52-0.87; P = 0.003), had a reduced fracture risk. Analyses including all eligible patients, without propensity score matching, generated similar results.

CONCLUSION

Compared with warfarin, NOAC was associated with a reduced fracture risk among AF patients. Therefore, if oral anticoagulants are indicated, NOACs rather than warfarin should be considered to lower the risk of fractures. However, further studies are needed to investigate the underlying mechanisms and elucidate causality.

Off-target effects of oral anticoagulants - vascular effects of vitamin K antagonist and non-vitamin K antagonist oral anticoagulant dabigatran etexilate

INTRODUCTION

Vitamin K antagonists (VKA) and non-vitamin K oral antagonist anticoagulants (NOAC) are used in the clinic to reduce risk of thrombosis. However, they also exhibit vascular off-target effects. The aim of this study is to compare VKA and NOAC on atherosclerosis progression and calcification in an experimental setup.

MATERIAL AND METHODS

Female Apoe-/- mice (age 12 weeks) were fed Western-type diet as control or supplemented with dabigatran etexilate or warfarin for 6 or 18 weeks. Vascular calcification was measured in whole aortic arches using µCT and [18 F]-NaF. Atherosclerotic burden was assessed by (immuno)histochemistry. Additionally, in vitro effects of warfarin, thrombin, and dabigatran on primary vascular smooth muscle cells (VSMC) were assessed.

RESULTS

Short-term treatment with warfarin promoted formation of atherosclerotic lesions with a pro-inflammatory phenotype, and more rapid plaque progression compared with control and dabigatran. In contrast, dabigatran significantly reduced plaque progression compared with control. Long-term warfarin treatment significantly increased both presence and activity of plaque calcification compared with control and dabigatran. Calcification induced by warfarin treatment was accompanied by increased presence of uncarboxylated matrix Gla protein. In vitro, both warfarin and thrombin significantly increased VSMC oxidative stress and extracellular vesicle release, which was prevented by dabigatran.

CONCLUSION

Warfarin aggravates atherosclerotic disease activity, increasing plaque inflammation, active calcification, and plaque progression. Dabigatran lacks undesired vascular side effects and reveals beneficial effects on atherosclerosis progression and calcification. The choice of anticoagulation impacts atherosclerotic disease by differential off target effect. Future clinical studies should test whether this beneficial effect also applies to patients.

Fracture Risks in Patients Treated With Different Oral Anticoagulants: A Systematic Review and Meta-Analysis

Background Evidence on the differences in fracture risk associated with non-vitamin K antagonist oral anticoagulants (NOAC) and warfarin is inconsistent and inconclusive. We conducted a systematic review and meta-analysis to assess the fracture risk associated with NOACs and warfarin. Methods and Results We searched PubMed, Embase, Cochrane Library, Scopus, Web of Science, and ClinicalTrials.gov from inception until May 19, 2020. We included studies presenting measurements (regardless of primary/secondary/tertiary/safety outcomes) for any fracture in both NOAC and warfarin users. Two or more reviewers independently screened relevant articles, extracted data, and performed quality assessments. Data were retrieved to synthesize the pooled relative risk (RR) of fractures associated with NOACs versus warfarin. Random-effects models were used for data synthesis. We included 29 studies (5 cohort studies and 24 randomized controlled trials) with 388 209 patients. Patients treated with NOACs had lower risks of fracture than those treated with warfarin (pooled RR, 0.84; 95% CI, 0.77-0.91; P<0.001) with low heterogeneity (I²=38.9%). NOACs were also associated with significantly lower risks of hip fracture than warfarin (pooled RR, 0.89; 95% CI, 0.81-0.98; P=0.023). A nonsignificant trend of lower vertebral fracture risk in NOAC users was also observed (pooled RR, 0.74; 95% CI, 0.54-1.01; P=0.061). Subgroup analyses for individual NOACs demonstrated that dabigatran, rivaroxaban, and apixaban were significantly associated with lower fracture risks. Furthermore, the data synthesis results from randomized controlled trials and real-world cohort studies were quite consistent, indicating the robustness of our findings. Conclusions Compared with warfarin, NOACs are associated with lower risks of bone fracture.

Clinical Risk Factors and Prognostic Impact of Osteoporosis in Patients With Chronic Heart Failure

BACKGROUND

The clinical significance of osteoporosis in chronic heart failure (CHF) remains unclear.Methods and Results:A total of 303 CHF patients (75 years, [interquartile range (IQR) 66-82 years]; 41% female) were retrospectively examined. Bone mineral densities (BMDs) at the lumbar spine, femoral neck, and total femur were measured by using dual-energy X-ray absorptiometry (DEXA), and osteoporosis was diagnosed when the BMD at any of the 3 sites was <70% of the Young Adult Mean percentage (%YAM). The prevalence of osteoporosis in CHF patients was 40%. Patients with osteoporosis were older (79 [IQR, 74-86] vs. 72 [IQR, 62-80] years), included a large percentage of females, had slower gait speed and had a lower body mass index. Multivariate logistic regression analysis indicated that sex, BMI, gait speed, loop diuretics use and no use of direct oral anticoagulants (DOACs) were independently associated with osteoporosis. Kaplan-Meier survival curves showed that the rate of death and heart failure hospitalization was higher in patients with osteoporotic BMD at 2 or 3 sites than in patients without osteoporosis (hazard ratio 3.45, P<0.01). In multivariate Cox regression analyses, osteoporotic BMD at 2 or 3 sites was an independent predictor of adverse events after adjustment for prognostic markers.

CONCLUSIONS

Loop diuretics use and no DOACs use are independently associated with osteoporosis in CHF patients. Osteoporosis is a novel predictor of worse outcome in patients with CHF.

Effects of Long-term Thrombin Inhibition (Dabigatran Etexilate) on Spontaneous Thrombolytic Activity during the Progression of Atherosclerosis in ApoE-/--LDLR-/- Double-Knockout Mice

Background and Objectives

Atherosclerosis is characterized by a hypercoagulable state, during which coagulation and fibrinolytic factors are activated simultaneously. However, details regarding the thrombolytic pathway in this context remain unknown. Here we investigated how direct long-term inhibition of thrombin influenced spontaneous thrombolytic activity during atherosclerotic progression in apolipoprotein E (ApoE)^–/^––low density lipoprotein receptor (LDLR)^–/^– double-knockout mice.

Methods

All mice received either standard chow (placebo group) or dabigatran-containing chow for 22 weeks, after which we evaluated them. The amount of atherosclerosis was estimated as the ratio of the atherosclerotic area to the total aortic intimal area. In addition, we used immunohistochemistry to analyze the expression of tissue plasminogen activator (t-PA), plasminogen activator inhibitor-1 (PAI-1), thrombin activatable fibrinolysis inhibitor (TAFI), and endothelial nitric oxide synthase (eNOS) in atherosclerotic regions. To evaluate thrombolysis, we used a He–Ne laser to induce thrombosis in vessels of the cremaster muscle and then measured the thrombus volume over time.

Results

The atherosclerotic area was smaller and thrombolytic activity greater in the dabigatran-treated group than in the placebo group. Furthermore, according to the thrombolysis model, spontaneous thrombolytic activity was increased in the dabigatran-treated mice compared with the placebo mice. In support of these results, immunohistochemistry demonstrated decreased expression of PAI-1 and TAFI but increased expression of eNOS in the dabigatran group compared with the placebo group. However, t-PA expression did not differ between groups.

Conclusions

Direct long-term inhibition by dabigatran etexilate of thrombin led to an increase in spontaneous thrombolytic activity decreasing the expression of PAI-1 and TAFI.

Trabecular bone score (TBS) and bone mineral density in patients with long-term therapy with warfarin

In this study, we compared patients using the anticoagulant warfarin for more than a year with a control group with similar characteristics but without using the drug. We demonstrated worse BMD and bone quality by trabecular bone score (TBS) in patients using warfarin for more than 1 year.

PURPOSE

Evaluate the bone mineral density (BMD) and the trabecular bone score (TBS) of patients taking warfarin for more than 1 year compared with a control group.

METHODS

Male patients aged 25-65 years in warfarin use for more than 1 year were included. Patients answered a questionnaire regarding lifestyle habits and realized a dual X-ray densitometry (DXA) (lumbar spine and hip), and TBS was evaluated.

RESULTS

From the 96 patients invited, 33 patients accepted to participate and comprised the warfarin group (WG), and 3 were excluded. The control group (CG) was composed of 21 individuals matched by age and race. The mean age of WG was 57.0 ± 7.6 and in the CG 54.0 ± 10.6 years (p = 0.095). The BMD in WG was lower than that in the CG in all sites (spine p < 0.001, total hip p = 0.001, and femoral neck p = 0.005). A longer time of warfarin use increased the likelihood of having low BMD (OR = 1.239, CI 1.064-1.674, p = 0.01), whereas high BMI decreased it (OR = 0.732, CI 0.533-0.918, p = 0.03). The TBS was lower in WG than the CG (p = 0.04). Lower TBS was associated with hypertension in both groups and to the hip BMD (neck and total) (p < 0.005) in the WG. In the multivariate analysis, only hypertension (- 0.10, CI - 0.17 to - 0.03, p = 0.008) and total hip BMD ( 0.26, CI 0.07-0.46, p = 0.009) influenced TBS.

CONCLUSION

We demonstrated an association between worsening of BMD and bone quality in patients taking warfarin for more than 1 year.

Warfarin-induced impairment of bone material quality in a patient undergoing maintenance hemodialysis: A case report

INTRODUCTION

The use of warfarin in patients undergoing hemodialysis is associated with decreased bone mineral density and an increased incidence of bone fracture. However, no studies to date have directly estimated bone quality with bone histomorphometry in patients with bone abnormalities who are taking warfarin and undergoing hemodialysis.

PATIENT CONCERNS

A 47-year-old female with Noonan syndrome presented with progressive bilateral lower extremity pain on walking, and skin sclerosis. She had been undergoing maintenance hemodialysis for 25 years following 2 years of peritoneal dialysis for chronic glomerulonephritis. She had been taking warfarin as an anticoagulant agent for 13 years after she underwent an aortic valve replacement.

DIAGNOSIS

Warfarin-induced impairment of bone material quality.

INTERVENTIONS AND OUTCOMES

Histomorphometric analysis of the bone biopsy specimens showed impairment in bone calcification processes, a high turnover of bone remodeling, low bone volume, and mild fibrosis. The bone abnormality could not be categorized into any type of representative bone disease classification such as osteitis fibrosa, osteomalacia, adynamic bone disease, uremic osteodystrophy, or hyperparathyroidism, but was consistent with warfarin-induced impairment of bone material quality.

CONCLUSION

Warfarin can induce impairment of bone material quality in a patient undergoing hemodialysis.

Osteoporotic Fractures in Patients With Atrial Fibrillation Treated With Conventional Versus Direct Anticoagulants

BACKGROUND

Elderly patients in long-term treatment with vitamin K antagonists (VKAs) are at high risk of osteoporotic fractures compared with the background population. It has been speculated that the choice of oral anticoagulant (OAC) may affect the risk of osteoporotic fractures.

OBJECTIVES

The risk of osteoporotic fractures was evaluated among patients with atrial fibrillation treated with VKA or direct oral anticoagulants (DOACs).

METHODS

Patients were identified using the Danish national registries. Patients were included only if they had no prior use of osteoporosis medication and they had undergone 180 days of OAC treatment. Outcomes were hip fracture, major osteoporotic fracture, any fracture, initiation of osteoporosis medication, and a combined endpoint.

RESULTS

Overall, 37,350 patients were included. The standardized absolute 2-year risk of any fracture was low among DOAC-treated patients (3.1%; 95% CI: 2.9% to 3.3%) and among VKA-treated patients (3.8%; 95% CI: 3.4% to 4.2%). DOAC was associated with a significantly lower relative risk of any fracture (hazard ratio [HR]: 0.85; 95% CI: 0.74 to 0.97), major osteoporotic fractures (HR: 0.85; 95% CI: 0.72 to 0.99), and initiating osteoporotic medication (HR: 0.82; 95% CI: 0.71 to 0.95). A combined endpoint showed that patients treated with DOAC had a significantly lower relative risk of experiencing any fracture or initiating osteoporosis medication (HR: 0.84; 95% CI: 0.76 to 0.93).

CONCLUSIONS

In a nationwide population, the absolute risk of osteoporotic fractures was low among patients with atrial fibrillation on OAC, but DOAC was associated with a significantly lower risk of osteoporotic fractures compared with VKA.

Systematic DOACs oral anticoagulation in patients with atrial fibrillation and chronic kidney disease: the nephrologist's perspective

Atrial fibrillation (AF) is highly prevalent among patients with chronic kidney disease (CKD), and also associated with unfavorable outcome. Anticoagulant therapy is the mainstep of management in such patients, aimed at reducing the high risk of systemic thromboembolism and especially of ischemic stroke, which is reportedly associated with increased mortality in CKD patients. Even though new direct oral anticoagulant agents (DOACs) proved to be effective in patients with non valvular chronic AF, and are therefore recommended by recent guidelines for their treatment, warfarin is currently used in more than one-half of subjects needing oral anticoagulation, and only 30% of them are converted from a vitamin K antagonist- to a DOAC-based regimen. The main reason for not prescribing DOACs is often a reduction in renal function, even if mild. Aim of this review was therefore to evaluate the impact of DOAC therapy in the setting of CKD, from a nephrological perspective, by comparing available evidence on the role of DOACs in patients with CKD and AF with that emerging from traditional warfarin-based therapy. Both the pathogenesis of AF in CKD, and available findings of renal, cardiovascular and bone effects of DOACs in CKD are discussed, leading to the conclusion that DOAC therapy should be considered as the first line therapy for non valvular AF in patients with mild and moderate reduction of renal function, and could also be adopted for patients with severe CKD not on hemodialysis treatment, whereas there is insufficient evidence for ESRD patients on dialysis.

Association of Anticoagulant Therapy With Risk of Fracture Among Patients With Atrial Fibrillation

IMPORTANCE

Warfarin is prescribed to patients with atrial fibrillation (AF) for the prevention of cardioembolic complications. Whether warfarin adversely affects bone health is controversial. The availability of alternate direct oral anticoagulant (DOAC) options now make it possible to evaluate the comparative safety of warfarin in association with fracture risk.

OBJECTIVE

To test the hypothesis that, among patients with nonvalvular AF, use of DOACs vs warfarin is associated with lower risk of incident fracture.

DESIGN, SETTING, AND PARTICIPANTS

This comparative effectiveness cohort study used the MarketScan administrative claims databases to identify patients with nonvalvular AF and who were prescribed oral anticoagulants from January 1, 2010, through September 30, 2015. To reduce confounding, patients were matched on age, sex, CHA2DS2-VASc (congestive heart failure, hypertension, age [>65 years = 1 point; >75 years = 2 points], diabetes, and previous stroke/transient ischemic attack [2 points], vascular disease) score, and high-dimensional propensity scores. The final analysis included 167 275 patients with AF. Data were analyzed from February 27, 2019 to September 18, 2019.

EXPOSURES

Warfarin and DOACs (dabigatran etexilate, rivaroxaban, and apixaban).

MAIN OUTCOMES AND MEASURES

Incident hip fracture, fracture requiring hospitalization, and all clinical fractures (identified using inpatient or outpatient claims) defined by International Classification of Diseases, Ninth Revision, Clinical Modification codes.

RESULTS

In the study population of 167 275 patients with AF (38.0% women and 62.0% men; mean [SD] age, 68.9 [12.5] years), a total of 817 hip fractures, 2013 hospitalized fractures, and 7294 total fractures occurred during a mean (SD) follow-up of 16.9 (13.7) months. In multivariable-adjusted, propensity score-matched Cox proportional hazards regression models, relative to new users of warfarin, new users of DOACs tended to be at lower risk of fractures requiring hospitalization (hazard ratio [HR], 0.87; 95% CI, 0.79-0.96) and all clinical fractures (HR, 0.93; 95% CI, 0.88-0.98), whereas the association with hip fractures (HR, 0.91; 95% CI, 0.78-1.07) was not statistically significant. When comparing individual DOACs with warfarin, the strongest findings were for apixaban (HR for hip fracture, 0.67 [95% CI, 0.45-0.98]; HR for fractures requiring hospitalization, 0.60 [95% CI, 0.47-0.78]; and HR for all clinical fractures, 0.86 [95% CI, 0.75-0.98]). In subgroup analyses, DOACs appeared more beneficial among patients with AF who also had a diagnosis of osteoporosis than among those without a diagnosis of osteoporosis.

CONCLUSIONS AND RELEVANCE

In this real-world population of 167 275 patients with AF, use of DOACs-particularly apixaban-compared with warfarin use was associated with lower fracture risk. These associations were more pronounced among patients with a diagnosis of osteoporosis. Given the potential adverse effects of warfarin on bone health, these findings suggest that caution should be used when prescribing warfarin to patients with AF at high risk of fracture.

Risk of Osteoporosis in Patients With Atrial Fibrillation Using Non-Vitamin K Antagonist Oral Anticoagulants or Warfarin

Background Warfarin, a vitamin K antagonist, has been shown to affect bone mineral density and cause osteoporosis. However, studies investigating the relationship between non-vitamin K antagonist oral anticoagulants (NOACs) and osteoporosis are limited. We thus compared the risk of osteoporosis in patients with atrial fibrillation treated with either NOACs or warfarin. Methods and Results This nationwide, retrospective cohort study used Taiwan's National Health Insurance Research Database. All adult patients in Taiwan who were newly diagnosed with atrial fibrillation and treated with NOACs or warfarin between January 2012 and December 2015 were included and classified into their respective cohorts. Patients who received NOACs were subcategorized into the rivaroxaban, dabigatran, and apixaban subgroups. Propensity score matching was performed for each head-to-head comparison. Adjusted hazard ratios (aHRs) for the risk of osteoporosis were calculated using Cox proportional hazards regression models, with adjustment for confounders. Overall, 17 008 patients were included, with 8504 in each cohort. NOACs were associated with a lower osteoporosis risk than warfarin (aHR=0.82; 95% CI=0.68-0.97). A subgroup effect of treatment duration was identified (namely, the lower osteoporosis risk with NOAC compared with warfarin became stronger in those with longer treatment duration [P for interaction <0.001]). Furthermore, significantly lower risks of osteoporosis were observed in the rivaroxaban (aHR=0.68; 95% CI=0.55-0.83) and apixaban (aHR=0.38; 95% CI=0.22-0.66) subgroups, but not in the dabigatran subgroup (aHR=1.04; 95% CI=0.85-1.27). Conclusions Compared with warfarin, rivaroxaban and apixaban were associated with a significantly lower risk of osteoporosis in patients with atrial fibrillation.

Association between oral anticoagulants and osteoporosis: Real-world data mining using a multi-methodological approach

Introduction: Warfarin and direct oral anticoagulants (DOACs) have been widely used in antithrombotic therapy. Although warfarin use has been suspected to be associated with osteoporosis risk, several studies have shown otherwise. Conversely, a few reports have found an association between DOACs and osteoporosis. This study therefore clarifies the association between oral anticoagulants and osteoporosis by analyzing real-world data using different methodologies, algorithms, and databases. Methods: Real-world data from the US Food and Drug Administration Adverse Event Reporting System (FAERS; 2004-2016) and Japanese administrative claims database (2005-2017; JMDC Inc., Tokyo) were used. Reporting odds ratio (ROR) and information component (IC) were calculated through disproportionality analysis (DPA) using reports recorded in the FAERS. Sequence symmetry analysis (SSA) was employed to calculate the adjusted sequence ratio (SR) using the JMDC Claims Database. For the adjusted SR and ROR, a significant signal was detected when the lower limit of the two-sided 95% confidence interval (CI) was more than 1. For the IC, a significant signal was detected when the lower limit of the 95% CI was more than 0. Results: DPA for warfarin found significant signals for osteoporosis in ROR (1.43, 95% CI: 1.32-1.54) and IC (0.50, 95% CI: 0.39-0.61). SSA showed a significant association between warfarin use and osteoporosis or bisphosphonate use. Moreover, a significant association was observed in males and females, albeit only for warfarin. Conclusion: Multi-methodological data mining revealed that warfarin use, not DOACs, is significantly associated with osteoporosis regardless of sex difference.

Vitamin K and Bone Health: A Review on the Effects of Vitamin K Deficiency and Supplementation and the Effect of Non-Vitamin K Antagonist Oral Anticoagulants on Different Bone Parameters

Although known for its importance in the coagulation cascade, vitamin K has other functions. It is an essential vitamin for bone health, taking part in the carboxylation of many bone-related proteins, regulating genetic transcription of osteoblastic markers, and regulating bone reabsorption. Vitamin K deficiency is not uncommon, as deposits are scarce and dependent upon dietary supplementation and absorption. Vitamin K antagonist oral anticoagulants, which are prescribed to many patients, also induce vitamin K deficiency. Most studies find that low serum K1 concentrations, high levels of undercarboxylated osteocalcin (ucOC), and low dietary intake of both K1 and K2 are associated with a higher risk of fracture and lower BMD. Studies exploring the relationship between vitamin K supplementation and fracture risk also find that the risk of fracture is reduced with supplements, but high quality studies designed to evaluate fracture as its primary endpoint are needed. The reduction in risk of fracture with the use of non-vitamin K antagonist oral anticoagulants instead of warfarin is also of interest although once again, the available evidence offers disparate results. The scarce and limited evidence, including low quality studies reaching disparate conclusions, makes it impossible to extract solid conclusions on this topic, especially concerning the use of vitamin K supplements.

Inhibitory effects of dabigatran etexilate, a direct thrombin inhibitor, on osteoclasts and osteoblasts

INTRODUCTION

Anticoagulants are widely used in orthopedic surgery to decrease the risk of deep vein thrombosis. While significant bone impairment is induced by long-term heparin therapy, little is known about the effects of direct oral anticoagulants (DOACs). Herein, we investigated the effects of dabigatran etexilate (Pradaxa®), a DOAC inhibitor of thrombin, on bone cells using in vitro and ex vivo cell culture models.

MATERIALS AND METHODS

Osteoblasts and osteoclasts exposed to different concentrations of dabigatran etexilate and untreated cells were assayed for cell differentiation and activity. Favorable osteogenic conditions for osteoblasts were tested using titanium with nanotopography (Ti-Nano). In addition, mice treated with a dabigatran etexilate solution had bone marrow cells analyzed for the ability to generate osteoclasts.

RESULTS

Dabigatran etexilate at concentrations of 1 μg/mL and 2 μg/mL did not impact osteoclast or osteoblast viability. The drug inhibited osteoclast differentiation and activity as observed by the reduction of TRAP+ cells, resorption pits and gene and protein expression of cathepsin K. Consistently, osteoclasts from mice treated with dabigatran showed decreased area, resorptive activity, as well as gene and protein expression of cathepsin K. In osteoblast cultures, grown both on polystyrene and Ti-Nano, dabigatran etexilate reduced alkaline phosphatase (ALP) activity, matrix mineralization, gene expression of ALP and osteocalcin.

CONCLUSIONS

Dabigatran etexilate inhibited osteoclast differentiation in ex vivo and in vitro models in a dose-dependent manner. Moreover, the drug reduced osteoblast activity even under optimal osteogenic conditions. This study provides new evidence regarding the negative overall impact of DOACs on bone cells.

Drug-induced Reduction of Gamma Carboxylation in Osteocalcin: What is the Fallback?

Osteoporosis is a medical condition in which bone becomes fragile and weak. In this condition, the quality and density of the bone are reduced. Vitamin K is vital for bone mineralization as it plays a vital role in the gamma-carboxylation of osteocalcin. Therefore, if there is a deficiency of vitamin K, it can lead to osteoporosis due to undercarboxylated osteocalcin. Warfarin is the most widely used anticoagulant in the elderly. In this article, we reviewed how Warfarin, an inhibitor of vitamin K, affects bone remodeling and leads to osteoporosis.

The effect of oral dabigatran etexilate on bone density, strength, and microstructure in healthy mice

Thrombin is a key component in the coagulation cascade where it converts factor V, VIII, XI, and fibrinogen. In addition to the abundant production of thrombin in the liver, osteoclasts synthesize and secrete thrombin as well. Osteoblasts express thrombin receptors, and it has been reported that thrombin stimulates the expression of RANKL relatively to OPG, resulting in greater osteoclast activation and bone degradation. Pradaxa (dabigatran etexilate, DE) is a new anticoagulant, which has recently been approved for clinical use. DE is a direct thrombin inhibitor with potential to modulate the RANKL/OPG ratio and thereby limit osteoclast activation and bone degradation. The purpose of the study was to investigate whether DE can increase bone density, bone strength, and bone microstructure in healthy male and female mice and to investigate whether the effect of DE is sex-dependent. Twenty-eight 14-week-old male C57BL/6 mice were stratified by weight into 4 groups: 1. Control 3 weeks; 2. DE 3 weeks; 3. Control 6 weeks; 4. DE 6 weeks. An identical study design was applied to twenty-four 14-week-old female C57BL/6 mice. Chow mixed with DE was offered ad libitum, resulting in a dose of 1.70 mg DE/g body weight and 1.52 mg DE/g body weight, to female and male mice, respectively. The animals were euthanized after 3 or 6 weeks. Bone mineral density (aBMD) and bone mineral content (BMC) were evaluated with DEXA, 3D microstructural properties were determined with μCT, bone strength was determined with mechanical testing, and bone formation and resorption was evaluated with bone histomorphometry. In female mice, DE resulted in significant higher tibial aBMD values after 6 weeks of intervention. Furthermore, DE significantly increased tibial diaphyseal cortical bone area and tissue area, which was accompanied by significantly increased strength of the tibial shaft. DE had no effect on femoral cortical bone or on femoral and vertebral trabecular 3D microstructure. Finally, bone histomorphometry showed that DE had no effect on MS/BS or Oc.S/BS. In male mice, no bone positive effects of DE were found in any of the parameters investigated. In conclusion, intervention with DE may result in a weak positive site specific effect at tibial cortical bone in female mice, and importantly, no major deleterious effects of DE on bone tissue were seen in either female or male mice despite the relatively high dose of DE used.

Non-vitamin K Antagonist Oral Anticoagulants vs. Warfarin at Risk of Fractures: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Warfarin is a traditional oral anticoagulant for preventing thrombotic events in patients with atrial fibrillation (AF) and venous thromboembolism. Along with the widespread clinical use, the potential association between warfarin use and fracture risk have been addressed gradually. Non-vitamin K antagonist oral anticoagulants (NOACs), targeting thrombin or Xa factor, have been recommended as an optimal alternative due to their favorable property of thromboembolism prophylaxis and reduced bleeding risk. However, evidence of the fracture risk with NOACs use is limited. Therefore, the present study investigated this issue by a meta-analysis. Medline, Embase, Cochrane Library and the ClinicalTrials.gov Website were searched for randomized controlled trials (RCTs) that reported the fracture data of NOACs and warfarin. The primacy outcome was a composite of any fracture. Summary relative risks (RRs) and 95% confidence intervals (CIs) were calculated using random- or fixed-effects models according to between-study heterogeneity. Heterogeneity was assessed through I² test and Q statistic, and the number of patients needed to treat (NNT) was calculated based on fracture incidence. Subgroup analyses were conducted according to individual NOACs, indications, and duration of follow up. Finally, 12 RCTs involving 89,549 patients were included, among which 44,816 (50%) receiving NOACs and 44,733 (50%) receiving warfarin. Overall, 1,139 (1.3%) patients including 515 NOACs users (1.1%) and 624 warfarin users (1.4%) developed fracture. Risk of fracture was significantly lower in NOACs compared to warfarin (RR: 0.82, 95%CI: 0.73–0.93, P = 0.001), with a NNT of 333. No significantly decreased risk was detected according to fracture sites. Subgroup analysis confirmed that the estimate of decreased fracture risk was derived mainly from AF patients receiving long-term anticoagulation treatment. The meta-regression did not detect any potential confounding on fracture risk. No heterogeneity between the studies (I² = 15.0%) and no publication bias was identified. In conclusion, the use of NOACs was associated with a lower risk of fracture compared to warfarin, but with a relatively low absolute risk reduction. Therefore, screening for the fracture risk should be considered before initiating anticoagulation treatment. For patients who are at high risk of fracture or expected long-term treatment of anticoagulation, NOACs may represent a preferable alternative to warfarin.

Vitamin K plasma levels determination in human health

Vitamin K (phylloquinone or vitamin K1 and menaquinones or vitamin K2) plays an important role as a cofactor in the synthesis of hepatic blood coagulation proteins, but recently has also aroused an increasing interest for its action in extra-hepatic tissues, in particular in the regulation of bone and vascular metabolism. The accurate measurement of vitamin K status in humans is still a critical issue. Along with indirect assays, such as the undercarboxylated fractions of vitamin K-dependent proteins [prothrombin, osteocalcin (OC), and matrix gla protein], the direct analysis of blood levels of phylloquinone and menaquinones forms might be considered a more informative and direct method for assessing vitamin K status. Different methods for direct quantification of vitamin K serum levels are available. High-performance liquid chromatography (HPLC) methods coupled with post-column reduction procedures and fluorimetric or electrochemical detection are commonly used for food and blood analysis of phylloquinone, but they show some limitations when applied to the analysis of serum menaquinones because of interferences from triglycerides. Recent advancements include liquid chromatography tandem mass spectrometry (LCMS/MS) detection, which assures higher specificity. The optimization and standardization of these methods requires specialized laboratories. The variability of results observed in the available studies suggests the need for further investigations to obtain more accurate analytical results.

Vitamin K and bone

Vitamin K is mainly known as an agent involved in blood coagulation, maintaining the activity of coagulation factors in the liver. In addition, epidemiological studies suggested that a lack of vitamin K is associated with several diseases, including osteoporosis and vascular calcification. There are two main kinds of vitamin K: Phylloquinone (or PK) and Menaquinones (MKn), both act as co-enzyme of y-glutamyl carboxylase (GGCX) transforming under-carboxylated in carboxylated vitamin K dependent proteins, such as Bone Gla Protein (or Osteocalcin) and Matrix Gla Protein. Recently, Vitamin K was also identified as a ligand of the nuclear steroid and xenobiotic receptor (SXR) (in murine species Pregnane X Receptor: PXR), expressed in osteoblasts. The purpose of this literature review is to evaluate the protective role of Vitamin K in bone and vascular health.

Does Anticoagulant Medication Alter Fracture-Healing? A Morphological and Biomechanical Evaluation of the Possible Effects of Rivaroxaban and Enoxaparin Using a Rat Closed Fracture Model

Low molecular weight heparin (LMWH) is routinely used to prevent thromboembolism in orthopaedic surgery, especially in the treatment of fractures or after joint-replacement. Impairment of fracture-healing due to increased bone-desorption, delayed remodelling and lower calcification caused by direct osteoclast stimulation is a well-known side effect of unfractioned heparin. However, the effect of LMWH is unclear and controversial. Recent studies strongly suggest impairment of bone-healing in-vitro and in animal models, characterized by a significant decrease in volume and quality of new-formed callus. Since October 2008, Rivaroxaban (Xarelto) is available for prophylactic use in elective knee- and hip-arthroplasty. Recently, some evidence has been found indicating an in vitro dose independent reduction of osteoblast function after Rivaroxaban treatment. In this study, the possible influence of Rivaroxaban and Enoxaparin on bone-healing in vivo was studied using a standardized, closed rodent fracture-model. 70 male Wistar-rats were randomized to Rivaroxaban, Enoxaparin or control groups. After pinning the right femur, a closed, transverse fracture was produced. 21 days later, the animals were sacrificed and both femora harvested. Analysis was done by biomechanical testing (three-point bending) and micro CT. Both investigated substances showed histomorphometric alterations of the newly formed callus assessed by micro CT analysis. In detail the bone (callus) volume was enhanced (sign. for Rivaroxaban) and the density reduced. The bone mineral content was enhanced accordingly (sign. for Rivaroxaban). Trabecular thickness was reduced (sign. for Rivaroxaban). Furthermore, both drugs showed significant enlarged bone (callus) surface and degree of anisotropy. In contrast, the biomechanical properties of the treated bones were equal to controls. To summarize, the morphological alterations of the fracture-callus did not result in functionally relevant deficits.

Warfarin and Vascular Calcification

The vitamin K antagonist, warfarin, is the most commonly prescribed oral anticoagulant. Use of warfarin is associated with an increase in systemic calcification, including in the coronary and peripheral vasculature. This increase in vascular calcification is due to inhibition of the enzyme matrix gamma-carboxyglutamate Gla protein (MGP). MGP is a vitamin K-dependent protein that ordinarily prevents systemic calcification by scavenging calcium phosphate in the tissues. Warfarin-induced systemic calcification can result in adverse clinical effects. In this review article, we highlight some of the key translational and clinical studies that associate warfarin with vascular calcification.

Real Data on Effectiveness, Tolerability and Safety of New Oral Anticoagulant Agents: Focus on Dabigatran

Vitamin K-dependent antagonists (VKAs) are the most commonly used oral anticoagulants. Non-VKA oral anticoagulants (NOACs), directly target factor IIa (dabigatran) or Xa (rivaroxaban, apixaban, and edoxaban) have predictable pharmacological effects and relatively few drug and food interactions compared with VKA. Among NOACs, dabigatran has been extensively tested for stroke prevention in patients with non-valvular atrial fibrillation eligible for oral anticoagulation with VKA. Dabigatran is at least as effective as warfarin at preventing stroke with advantages of less serious bleeding except for gastrointestinal bleeding, which occurs more often than with warfarin. The findings of dabigatran use in randomized trials, post market registries and specific clinical settings are discussed in this article.