Investigating the causal relationship between ankylosing spondylitis and osteoporosis in the European population: a bidirectional Mendelian randomization study

Urolithiasis Causes Osteoporosis in Asians: Genetic Evidence from Mendelian Randomization and Pathway Analysis

BACKGROUND

It is an indisputable fact that patients with urolithiasis are prone to osteoporosis (OP), but the specific mechanism of their association is unclear. Previous studies have focused on the mediation of environmental factors such as diet; however, the potential of urolithiasis itself to induce OP remains uncertain.

METHODS

In this study, we used data from the Japan BioBank (6638 urolithiasis and 7788 OP cases) to investigate the direct causal relationship and mechanism between urolithiasis and OP, applying Mendelian randomization, genetic correlation analysis, colocalization, and pathway analysis. We selected 10 genetic variants as instrumental variables for urolithiasis.

RESULTS

The results showed a positive association between genetically predicted urolithiasis and OP, with significant direct effects persisting after adjusting for OP-associated factors in 4 models. Reverse analysis revealed no significant causal effect of genetically predicted OP on urolithiasis. While genetic correlation analysis and colocalization did not find conclusive evidence, mediation analysis identified estimated glomerular rate as a significant contributor. Co-risk factor analysis unveiled cardiovascular elements as common risks for both conditions. Bioanalysis implicates that cytokine, metabolic, and calcium signaling pathways may bridge urolithiasis and OP, with BCAS3, DGKH, TBX2, and TBX2-AS1 identified as potential causal genes.

CONCLUSION

In conclusion, the study establishes a direct causal link between urolithiasis and OP, independent of environmental factors. Regardless of lifestyle, urolithiasis patients should remain vigilant about the risk of OP and consider regular OP screening. The biological mechanism of urolithiasis combined with OP and related drugs still needs to be further explored.

Efficacy and Mechanism of Highly Active Umbilical Cord Mesenchymal Stem Cells in the Treatment of Osteoporosis in Rats

BACKGROUND

Osteoporosis increases bone brittleness and the risk of fracture. Umbilical cord mesenchymal stem cell (UCMSC) treatment is effective, but how to improve the biological activity and clinical efficacy of UCMSCs has not been determined.

METHODS

A rat model of osteoporosis was induced with dexamethasone sodium phosphate. Highly active umbilical cord mesenchymal stem cells (HA-UCMSCs) and UCMSCs were isolated, cultured, identified, and infused intravenously once at a dose of 2.29 × 106 cells/kg. In the 4th week of treatment, bone mineral density (BMD) was evaluated via cross-micro-CT, tibial structure was observed via HE staining, osteogenic differentiation of bone marrow mesenchymal stem cells (BMMSCs) was examined via alizarin red staining, and carboxy-terminal cross-linked telopeptide (CTX), nuclear factor-κβ ligand (RANKL), procollagen type 1 N-terminal propeptide (PINP) and osteoprotegerin (OPG) levels were investigated via enzyme-linked immunosorbent assays (ELISAs). BMMSCs were treated with 10-6 mol/L dexamethasone and cocultured with HA-UCMSCs and UCMSCs in transwells. The osteogenic and adipogenic differentiation of BMMSCs was subsequently examined through directional induction culture. The protein expression levels of WNT, β-catenin, RUNX2, IFN-γ and IL-17 in the bone tissue were measured via Western blotting.

RESULTS

The BMD in the healthy group was higher than that in the model group. Both UCMSCs and HA-UCMSCs exhibited a fusiform morphology; swirling growth; high expression of CD73, CD90 and CD105; and low expression of CD34 and CD45 and could differentiate into adipocytes, osteoblasts and chondrocytes, while HA-UCMSCs were smaller in size; had a higher nuclear percentage; and higher differentiation efficiency. Compared with those in the model group, the BMD increased, the bone structure improved, the trabecular area, number, and perimeter increased, the osteogenic differentiation of BMMSCs increased, RANKL expression decreased, and PINP expression increased after UCMSC and HA-UCMSC treatment for 4 weeks. Furthermore, the BMD, trabecular area, number and perimeter, calcareous nodule counts, and OPG/RANKL ratio were higher in the HA-UCMSC treatment group than in the UCMSC treatment group. The osteogenic and adipogenic differentiation of dexamethasone-treated BMMSCs was enhanced after the coculture of UCMSCs and HA-UCMSCs, and the HA-UCMSC group exhibited better effects than the UCMSC coculture group. The protein expression of WNT, β-catenin, and runx2 was upregulated, and IFN-γ and IL-17 expression was downregulated after UCMSC and HA-UCMSC treatment.

CONCLUSION

HA-UCMSCs have a stronger therapeutic effect on osteoporosis compared with that of UCMSCs. These effects include an improved bone structure, increased BMD, an increased number and perimeter of trabeculae, and enhanced osteogenic differentiation of BMMSCs via activation of the WNT/β-catenin pathway and inhibition of inflammation.

The mediating role of the genetically predicted N6, N6, N6-trimethyllysine levels in the association between HLA DR on CD14- CD16+ monocytes and ankylosing spondylitis

This study explores the hidden connection between HLA DR on CD14- CD16+ monocytes and ankylosing spondylitis (AS), with a particular emphasis on investigating and measuring the impact of 1091 blood metabolites as potential mediators. We harnessed the power of summary-level data extracted from a comprehensive genome-wide association study to delve into the intricate relationship between genetically predicted HLA DR on CD14- CD16+ monocytes (3621 cases) and AS (1193 cases and 374,621 controls). Furthermore, we employed a two-step Mendelian randomization (MR) methodology to elucidate the extent to which blood metabolites contribute to the effects observed in CD14- CD16+ monocytes, ultimately influencing the development of AS. This methodological approach provides a comprehensive and rigorous exploration of the interplay between blood metabolites and AS, shedding light on the underlying mechanisms governing this intricate association. Through MR analysis, our investigation revealed an increase in HLA DR on CD14- CD16+ monocytes within plasma, which correspondingly led to a reduction in the incidence of AS. The primary MR analysis yielded an odds ratio of 0.64 with a 95% confidence interval spanning from 0.53 to 0.78, underscoring the protective effect of elevated HLA DR on CD14- CD16+ monocytes against the development of AS. Furthermore, our study found no compelling evidence to suggest that AS exerts any discernible influence on HLA DR on CD14- CD16+ monocytes. Instead, our investigation identified N6, N6, N6-trimethyllysine levels (TML), a blood metabolite, as the sole mediator in the relationship between HLA DR on CD14- CD16+ monocytes and AS. Notably, the genetic prediction of AS mediated by TML accounted for a substantial -2.98% proportion of the observed variance. Our investigation has delineated a causal association between HLA DR on CD14- CD16+ monocytes and AS. Specifically, HLA DR on CD14- CD16+ monocytes exhibited a protective effect against the development of AS. Conversely, AS mediated by TML emerged as a risk factor, though the precise impact of HLA DR on CD14- CD16+ monocytes on AS pathogenesis remains enigmatic. It is imperative to embark on further investigations into potential mediators. In a clinical setting, it is imperative to carefully monitor the patient's HLA DR on CD14- CD16+ monocytes levels.

The Paradox of Osteoporosis in Spondyloarthropathies

Introduction

Spondyloarthropathies (SpA) are a family of inflammatory disorders that affect the spine and peripheral joints. The most common representatives are axial Spondylarthritis (axSpA) and Psoriatic Arthritis (PsA). Despite the fact that SpA are characterised by new bone formation, paradoxically, total Bone Mineral Density (BMD) may be decreased.

Methods

An electronic search was conducted on Medline in order to explore the prevalence, risk factors and pathophysiology of Osteoporosis (OP) in SpA patients.

Results

The prevalence of OP globally is reported to be 18.3%. The prevalence of OP in Axial Spondylarthritis (axSpA) patients ranges from 11.7% to 34.4%, while in Psoriatic Arthritis (PsA) patients seems to be similar to the general population. Several factors have been proposed for the development of OP in SpA, such as corticosteroid use and physical inactivity. Moreover, systemic inflammation appears to participate in the pathophysiology of OP with inflammatory cytokines such as Tumour Necrosis Factor (TNF) and Interleukin (IL)-23/IL-17 potentially having a key role in the pathogenesis of bone loss.

Discussion

The current literature points to the direction that OP is an established comorbidity in axSpA. Local or/and systemic inflammation is possibly the main pathway contributing to bone loss in axSpA patients. However, it remains unclear whether OP is an established comorbidity in PsA patients, as it seems that OP is a treatment-associated adverse event.

Mendelian randomization studies in ankylosing spondylitis: A systematic review

INTRODUCTION

Previous research has revealed connections between ankylosing spondylitis (AS) and comorbid conditions. However, observational studies frequently encounter difficulties in establishing definitive causal links between potential risk factors and AS. In contrast, Mendelian randomization (MR) offers a more robust approach to exploring causality by leveraging the random allocation of alleles at birth, thereby minimizing confounding factors.

METHODS

The PubMed, Web of Science, and Cochrane databases were searched for MR studies related to AS with a time frame of database creation to May 2024. Information on authors, exposures, outcomes, data sources, SNPs, MR analysis methods, ORs (95% CIs), and p-values was extracted. Quality assessment was performed using the Critical Appraisal Skills Program (CASP) checklist.

RESULTS

We systematically reviewed 42 MR studies in AS. Health behaviors, comorbidities, and serum markers were involved. Overall, physical activity, inflammatory bowel disease, and specific intestinal flora with serum markers as exposures were causally associated with AS, which leads to an increased risk with several comorbidities.

CONCLUSIONS

MR is a powerful tool for assessing causal relationships between risk factors and outcomes. Specific intestinal flora and inflammatory bowel disease appear to be uncontroversial risk factors that increase the risk of AS. Reliable and robust MR findings may provide a more comprehensive health management strategy for patients with AS.

A Displaced Atypical Femoral Fracture Healed Without Anti-osteoporotic Agents in a Case of Ankylosing Spondylitis

Bone loss leading to osteoporosis is a well-known feature in patients with ankylosing spondylitis (AS), with the prevalence of osteoporosis varying widely across different studies. However, there is still no consensus on the treatment of osteoporosis in AS patients. A 67-year-old male, a case of AS under medication control, had taken oral bisphosphonate for about seven years for suspected osteoporosis due to compression fracture at T12 and discontinued for disproportionately high dual-energy X-ray absorptiometry T-score (11.0 SD). He had been well until his right hip painful disability developed after a fall at home with a resultant right subtrochanteric transverse fracture with medial cortical spike, fulfilling features of atypical femoral fractures five months later. Open reduction and internal fixation with a cephalomedullary femoral nail were performed smoothly on the same day, and the fracture healed slowly and eventually one year later with only supplementation of calcium with vitamin D.

Hounsfield units in assessing bone mineral density in ankylosing spondylitis patients with cervical fracture-dislocation

BACKGROUND

Cervical spine fracture-dislocations in patients with ankylosing spondylitis (AS) are mostly unstable and require surgery. However, osteoporosis, one of the comorbidities for AS, could lead to detrimental prognoses. There are few accurate assessments of bone mineral density in AS patients.

AIM

To analyze Hounsfield units (HUs) for assessing bone mineral density in AS patients with cervical fracture-dislocation.

METHODS

The HUs from C2 to C7 of 51 patients obtained from computed tomography (CT) scans and three-dimensional reconstruction of the cervical spine were independently assessed by two trained spinal surgeons and statistically analyzed. Inter-reader reliability and agreement were assessed by interclass correlation coefficient.

RESULTS

The HUs decreased gradually from C2 to C7. The mean values of the left and right levels were significantly higher than those in the middle. Among the 51 patients, 25 patients (49.02%) may be diagnosed with osteoporosis, and 16 patients (31.37%) may be diagnosed with osteopenia.

CONCLUSION

The HUs obtained by cervical spine CT are feasible for assessing bone mineral density with excellent agreement in AS patients with cervical fracture-dislocation.

Is sarcopenia a real concern in ankylosing spondylitis? A systematic literature review

PURPOSE

Sarcopenia is a condition defined as loss of muscle mass and strength, associated with poor functional performance and disability. Sarcopenia can be exacerbated or worsened in presence of inflammation, sedentary lifestyle and cytokine imbalance, thus it frequently occurs in people affected by rheumatic diseases. This systematic literature review aims to explore the association between sarcopenia and spondyloarthritis (SpA) and its most frequent manifestation, i.e. ankylosing spondylitis (AS).

METHODS

The Scopus, PubMed, and Web of Science databases were searched for articles on muscle mass, muscle strength and axial SpA, from any date to November 2023. Only studies written in English were considered. The methodological quality of the studies included in the review was evaluated using the Newcastle-Ottawa Scales for observational studies and for case-control studies.

RESULTS

190 papers were retrieved from the searches, 14 of which met the inclusion criteria. Rather than diagnosis of sarcopenia, pre-sarcopenia or probable sarcopenia were frequent in people with AS, with a great reduction especially of muscle strength. The pre-sarcopenia status appears to be related to high AS disease activity, suggesting that chronic inflammation resulting in pain, less movement and decreased physical activity could play a role in the muscle heath of AS patients.

CONCLUSIONS

Our review confirms the existence of an association between AS and loss of muscle strength-likely sarcopenia-already at a young age. Preventive and early strategies should be adopted to ensure successful aging for individuals with AS.

Potential association of rheumatic diseases with bone mineral density and fractures: a bi-directional mendelian randomization study

BACKGROUND

Previous studies have implicated rheumatoid arthritis as an independent risk factor for bone density loss. However, whether there is a causal relationship between rheumatic diseases and bone mineral density (BMD) and fractures is still controversial. We employed a bidirectional Mendelian analysis to explore the causal relationship between rheumatic diseases and BMD or fractures.

METHODS

The rheumatic diseases instrumental variables (IVs) were obtained from a large Genome-wide association study (GWAS) meta-analysis dataset of European descent. Analyses were performed for the three rheumatic diseases: ankylosing spondylitis (AS) (n = 22,647 cases, 99,962 single nucleotide polymorphisms [SNPs]), rheumatoid arthritis (RA) (n = 58,284 cases, 13,108,512 SNPs), and systemic lupus erythematosus (SLE) (n = 14,267 cases, 7,071,163 SNPs). Two-sample Mendelian randomization (MR) analyses were carried out by using R language TwoSampleMR version 0.5.7. The inverse-variance weighted (IVW), MR-Egger, and weighted median methods were used to analyze the causal relationship between rheumatic diseases and BMD or fracture.

RESULTS

The MR results revealed that there was absence of evidence for causal effect of AS on BMD or fracture. However, there is a positive causal relationship of RA with fracture of femur (95% CI = 1.0001 to 1.077, p = 0.046), and RA and fracture of forearm (95% CI = 1.015 to 1.064, p = 0.001). SLE had positive causal links for fracture of forearm (95% CI = 1.004 to 1.051, p = 0.020). Additionally, increasing in heel bone mineral density (Heel-BMD) and total bone mineral density (Total-BMD) can lead to a reduced risk of AS without heterogeneity or pleiotropic effects. The results were stable and reliable. There was absence of evidence for causal effect of fracture on RA (95% CI = 0.929 to 1.106, p = 0.759), and fracture on SLE (95% CI = 0.793 to 1.589, p = 0.516).

CONCLUSIONS

RA and SLE are risk factors for fractures. On the other hand, BMD increasing can reduce risk of AS. Our results indicate that rheumatic diseases may lead to an increased risk of fractures, while increased BMD may lead to a reduced risk of rheumatic diseases. These findings provide insight into the risk of BMD and AS, identifying a potential predictor of AS risk as a reduction in BMD.

Osteoporosis and coronary heart disease: a bi-directional Mendelian randomization study

Background

Osteoporosis (OP) and cardiovascular disease (CVD) are major global public health issues, especially exacerbated by the challenges of an aging population. As these problems intensify, the associated burden on global health is expected to increase significantly. Despite extensive epidemiological investigations into the potential association between OP and CVD, establishing a clear causal relationship remains elusive.

Methods

Instrumental variables were selected from summary statistics of the IEU GWAS database. Five different components of BMD (heel BMD, LS BMD, FA BMD, FN BMD, and TB BMD) were used as OP phenotypes. CHD, MI, and stroke were selected to represent CVD. Multiple analysis methods were used to evaluate the causal relationship between CVD and OP comprehensively. In addition, sensitivity analyses(Cochran's Q test, MR-Egger intercept test, and "leave one out" analysis) were performed to verify the reliability of the results.

Results

The MR showed a significant causal relationship between CHD on heel BMD and TB BMD; in the reverse analysis, there was no evidence that OP has a significant causal effect on CVD. The reliability of the results was confirmed through sensitivity analysis.

Conclusion

The study results revealed that CHD was causally associated with Heel BMD and TB BMD, while in the reverse MR analysis, the causal relationship between OP and CVD was not supported. This result posits CHD as a potential etiological factor for OP and prompts that routine bone density assessment at traditional sites (forearm, femoral neck, lumbar spine) using DAX may inadequately discern underlying osteoporosis issues in CHD patients. The recommendation is to synergistically incorporate heel ultrasound or DAX for total body bone density examinations, ensuring clinical diagnostics are both precise and reliable. Moreover, these findings provide valuable insights for public health, contributing to the development of pertinent prevention and treatment strategies.