Gut microbiota and intervertebral disc degeneration: a bidirectional two-sample Mendelian randomization study

Exploring the role of gut microbiota in intervertebral disc degeneration: insights from bidirectional Mendelian randomization analysis

OBJECTIVE

Although previous studies have indicated a potential association between the gut microbiota and intervertebral disc degeneration (IVDD), the precise nature of this relationship remains unclear. The objective of this study is to further explore the potential causal relationship between gut microbiota and IVDD using a bidirectional Mendelian randomization approach, with the aim of identifying potential microbial characteristics associated with IVDD.

METHODS

Using the data from genome-wide association studies (GWAS) involving 412 gut microbiota species and 227,388 controls and 29,508 cases of IVDD. Inverse variance weighted (IVW) was used as the primary Mendelian randomization (MR) analysis, complemented by weighted median, MR-Egger regression, weighted mode and simple mode methods. Extensive sensitivity analyses were performed to confirm the robustness of the results and to assess heterogeneity and horizontal pleiotropy.

RESULTS

This study revealed a positive genetic predisposition between 6 types of gut microbiota and IVDD through the IVW method, indicating that increased levels of these microbiota may lead to a higher risk of IVDD. Conversely, 6 types of gut microbiota were found to have negative effects on IVDD, suggesting that increased levels of these microbiota may have a protective effect against IVDD. Reverse MR analysis results revealed such possibilities as 1 positive and 5 negative causal relationships between IVDD and gut microbiota. The results of Cochran's Q test, MR-Egger regression, and MR-PRESSO analysis from the bidirectional Mendelian randomization all yielded p-values greater than 0.05, indicating that there is no significant heterogeneity or pleiotropy in the genetic effect analysis between gut microbiota and IVDD.

CONCLUSION

We used a bidirectional Mendelian randomization approach to identify various gut microbiota associated with IVDD. Our findings lay the foundation for further exploration of the pathogenesis and treatment strategies of gut microbiota and IVDD, and provide new possibilities for research on biomarkers of IVDD-related metabolic microbiota.

Guiqi Huoxue capsule alleviates cervical spondylosis in rats: Insights from 16S rRNA sequencing, lipidomics, and network pharmacology

ETHNOPHARMACOLOGICAL RELEVANCE

Cervical spondylosis (CS) is a common condition primarily caused by intervertebral disc degeneration (IVDD), adversely affecting quality of life. Traditional Chinese medicine believes that Qi deficiency and blood stasis are the main pathogenesis of CS. Guiqi Huoxue capsule (GQHX) has the effect of beneficial Qi tonifying kidneys and promoting blood circulation, which is mainly used in the clinical treatment of CS (Qi deficiency and blood stasis syndrome). However, the underlying mechanism of action has not been reported and clarified.

AIM OF THE STUDY

The aim of this study was to investigate the efficacy and underlying mechanisms of GQHX in CS rats.

MATERIALS AND METHODS

The CS rat model (Qi deficiency and blood stasis syndrome) was established by using IVDD and Ovariectomy (OVX) surgeries, along with qi deficiency and blood stasis modeling. The effects of GQHX on CS rats were evaluated by behavioral tests, blood indexes, H&E staining, and other means. Fatty acid profiles and gut microbiota were analyzed using lipidomics and 16S rRNA sequencing. The mechanism of action of GQHX was investigated by network pharmacology and western blotting.

RESULTS

GQHX reduced the symptoms of CS rats as confirmed by behavioral indicators, serum markers, and other measures of efficacy. Meanwhile, 16S rRNA sequencing and lipidomics results showed that GQHX regulated the abundance of Blautia and Muribaculaceae, influencing the production of various fatty acids (e.g. isobutyric, isovaleric, and linoleic acids). More importantly, network pharmacology and Western blot results suggested that GQHX could alleviate the clinical symptoms of CS by regulating the abnormal expression of AGE-RAGE, MAPK, and HIF-1 signaling pathways.

CONCLUSION

This study elucidated the role of GQHX in alleviating CS and highlighted the mechanisms involved, particularly the regulation of gut microbiota and lipid metabolism, as well as the AGE-RAGE, MAPK, and HIF-1 signaling pathways.

A Mendelian randomization study to reveal gut-disc axis: causal associations between gut microbiota with intervertebral disc diseases

PURPOSE

Emerging evidence suggests a link between gut microbiota and intervertebral disc diseases (IDDs); however, the causal relationships remain unclear. This study aimed to evaluate the causal effects of gut microbiota on the risk of cervical disc disorders (CDD), other intervertebral disc disorders (OIDD), pyogenic intervertebral disc infections, and discitis, shedding light on the potential "gut-disc axis".

METHODS

Genetic variation data for 202 gut microbiota taxa were obtained from the Dutch Microbiome Project, and disease outcome data were sourced from the FinnGen consortium. A Mendelian Randomization (MR) approach was employed to assess causal relationships, using genetic variants as instrumental variables. Sensitivity analyses, including tests for pleiotropy, heterogeneity, and reverse causation, ensured robust findings.

RESULTS

The study identified 20 gut microbial taxa with significant associations to IDDs. Notably, taxa within the Erysipelotrichaceae family showed consistent protective effects against OIDD after Bonferroni correction (P < 0.05). Associations between several species and specific diseases, such as Alistipes senegalensis with CDD and Ruminococcus lactaris with discitis, were also observed. Sensitivity analyses confirmed no evidence of confounding or reverse causation.

CONCLUSION

This study provides evidence of causal relationships between specific gut microbiota and IDDs, supporting the existence of a "gut-disc axis." The findings suggest that microbial dysbiosis may influence spinal health through systemic inflammation and immune regulation. These insights open new possibilities for microbiota-targeted interventions, such as probiotics or dietary modifications, to prevent or manage IDDs. However, further research is required to validate these therapeutic strategies.

Causal Correlations Between Plasma Metabolites, Inflammatory Proteins, and Chronic Obstructive Pulmonary Disease: A Mendelian Randomization and Bioinformatics-Based Investigation

Background

An increasing number of studies have demonstrated a strong correlation between metabolism, inflammation, and chronic obstructive pulmonary disease (COPD). However, it remains unclear if there is a causal relationship between these factors. This study employed the Mendelian randomization (MR) approach to investigate the associations between these factors and explore the mediating roles of key inflammatory proteins.

Methods

MR was used to assess the causal associations between plasma metabolites, inflammatory proteins, and COPD. Sensitivity analyses were performed to verify the robustness of the findings. Mediation analysis was conducted to explore the roles of inflammatory proteins in the metabolism-COPD pathway. We constructed protein-protein interaction (PPI) network and explored the potential mechanism through gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment. Single-cell sequencing and transcriptome datasets were used for auxiliary validation. Finally, experimental validation was performed using human lung tissue.

Results

This study identified 63 metabolites, 10 metabolite ratios, and 48 inflammatory proteins that were associated with COPD, all of which exhibited potential causal relationships. Furthermore, three proteins were identified as mediators in the metabolite-to-COPD pathway. PPI network, GO and KEGG enrichment analysis revealed the biological pathways in which they were involved. Validation of the expression of these three intermediary proteins in lung tissue demonstrated that NRXN3 was expressed in pulmonary endothelial cells and exerted a protective effect against COPD development.

Conclusion

The MR analysis revealed causal associations among metabolism, inflammation, and COPD. These findings offer novel insights into metabolism-inflammation-COPD mechanisms, suggesting that interventions targeting metabolic processes may represent a promising strategy for preventing the onset or progression of COPD.

Genetic Causal Association Between Skin Microbiota and Biological Aging: Evidence From a Mendelian Randomization Analysis

BACKGROUND

The skin microbiota, a complex community of microorganisms residing on the skin, plays a crucial role in maintaining skin health and overall homeostasis. Recent research has suggested that alterations in the composition and function of the skin microbiota may influence the aging process. However, the causal relationships between specific skin microbiota and biological aging remain unclear. Mendelian randomization (MR) analysis provides a powerful tool to explore these causal links by utilizing genetic variants as instrumental variables, thereby minimizing confounding factors and reverse causality that often complicate observational studies.

METHODS

We utilized a two-sample MR approach with population-based cross-sectional data from two German cohorts, KORA FF4 (n = 324) and PopGen (n = 273). In total, GWAS summary data from 1656 skin samples and datasets on accelerated biological age were analyzed to investigate the causal relationship between skin microbiota and accelerated biological aging. The primary analysis was performed using the inverse variance weighted (IVW) method with random effects and was further supported by MR-Egger regression, Cochran's Q test, and a range of sensitivity analyses.

RESULTS

The MR analysis revealed that for biological age acceleration (BioageAccel), the IVW analysis identified protective effects from certain skin microbiota, including Alphaproteobacteria_Dry (p = 0.046), Asv033_sebaceous (p = 0.043), Burkholderiales_Moist (p = 0.008), and Proteobacteria_Moist (p = 0.042). Similar protective effects were observed for Burkholderiales_Moist (p = 0.045) and Proteobacteria_Moist (p = 0.012) in the weighted median analysis. In contrast, Paracoccus_Moist (p = 0.013) and Proteobacteria_Sebaceous (p = 0.005) were associated with accelerated aging. When using PhenoAge acceleration as the outcome, the IVW analysis linked skin microbiota like Asv005_Dry (p = 0.026), ASV039_Dry (p = 0.003), Betaproteobacteria_Sebaceous (p = 0.038), and Chryseobacterium_Moist (p = 0.013) with accelerated aging. The weighted median analysis supported these findings and also identified protective effects from ASV011_Dry (p = 0.021), ASV023_Dry (p = 0.040), Bacteroidales_Dry (p = 0.022), Enhydrobacter_Moist (p = 0.038), Proteobacteria_Moist (p = 0.002), and Rothia_Moist (p = 0.038).

CONCLUSIONS

This two-sample MR study reveals potential causal relationships between skin microbiota and aging. However, to confirm these findings, further randomized controlled trials (RCTs) are necessary.

Bone morphogenetic proteins, DNA methylation, and gut microbiota interaction in lumbar disc degeneration: A multi-omics Mendelian randomization study

Background

Lumbar disc degeneration (LDD) is a ubiquitous finding in low back pain. Many different etiology factors may explain the LDD process, such as bone morphogenetic proteins (BMPs), DNA methylation, and gut microbiota. Until recently the mechanisms underlying the LDD process have been elusive.

Methods

BMP-related genes were extracted from the GeneCards database. The LDD transcriptome dataset was obtained from the Gene Expression Omnibus. We used linear regression and meta-analysis to screen and integrate the differentially expressed genes associated with BMPs in LDD. Genome-wide association studies (GWASs) of LDD were from FinnGen and UKBB. The expression quantitative trait loci (eQTLs) and DNA methylation quantitative trait loci from the blood were identified via the summary data-based Mendelian randomization (SMR) method, and the possible blood BMP genes and their regulatory elements associated with the risk of LDD were prioritized. Intestinal eQTLs and fecal microbial QTLs (mbQTLs) were integrated, and the potential interactions between BMP gene expression in host intestinal tissue and the gut microbiota were revealed through SMR and colocalization analysis. The GWAS catalog (GCST90246169) was used to validate SMR results.

Results

A meta-analysis of five datasets revealed that 113 BMP genes were differentially expressed between LDD and control tissues. Seven genes were selected as candidate pathogenic genes of LDD via the three-step SMR method: CREB1, BMP6, PTCH1, GLI1, MEG3, GALNS, and NF1. SMR analysis also revealed five possible gut genes: HFE, MET, MAPK3, NPC1, and GDF5. The correlation between the gut microbiota and BMP gene expression in intestinal tissues was verified by eQTL-mbQTL colocalization.

Conclusion

This multi-omics study revealed that the BMP genes associated with LDD are regulated by DNA methylation. There are genetic differences between gut gene expression and the gut microbiota. These findings provide evidence for new therapeutic targets in the future.

Gut microbiome dysbiosis is associated with lumbar degenerative spondylolisthesis in symptomatic patients

Background

Lumbar degenerative spondylolisthesis (LDS), characterized as degeneration of the intervertebral disc and structural changes of the facet joints, is a condition with varying degrees of instability that may lead to pain, canal stenosis, and subsequent surgical intervention. However, the etiology of LDS remains inconclusive. Gut microbiome dysbiosis may stimulate systemic inflammation in various disorders. However, the role of such dysbiosis upon spine health remains under-studied. The current study assessed the association of gut microbiome dysbiosis in symptomatic patients with or without LDS.

Methods

A cross-sectional analysis within the framework of a prospective study was performed. DNA was extracted from fecal samples collected from adult symptomatic patients with (n = 21) and without LDS (n = 12). Alpha and beta diversity assessed differences in fecal microbial community between groups. Taxon-by-taxon analysis identified microbial features with differential relative abundance between groups. Subject demographics and imaging parameters were also assessed.

Results

There was no significant group differences in age, sex, race, body mass index, smoking/alcohol history, pain profiles, spinopelvic alignment, and Modic changes (p >0.05). LDS subjects had significantly higher disc degeneration severity (p = 0.018) and alpha diversity levels compared to non-LDS subjects (p = 0.002-0.003). Significant differences in gut microbial community structure were observed between groups (p = 0.046). Subjects with LDS exhibited distinct differences at the phylum level, with a significantly higher Firmicutes to Bacteroidota ratio compared to non-LDS (p = 0.003). Differential relative abundance analysis identified six taxa with significant differences between the two groups, with LDS demonstrating an increase in putative pro-inflammatory bacteria (Dialister, CAG-352) and a decrease in anti-inflammatory bacteria (Slackia, Escherichia-Shigella).

Conclusion

This study is the first to report a significant association of gut microbiome dysbiosis and LDS in symptomatic patients, noting pro-inflammatory bacterial taxa. This work provides a foundation for future studies addressing the role of the gut microbiome in association with spine health and disease.

A new target for treating intervertebral disk degeneration: gut microbes

Intervertebral disk degeneration (IDD) is a common clinical spinal disease and one of the main causes of low back pain (LBP). Generally speaking, IDD is considered a natural degenerative process with age. However, with the deepening of research, people have discovered that IDD is not only related to age, but also has many factors that can induce and accelerate its progression. In addition, the pathogenesis of IDD remains unclear, resulting in limited traditional treatment methods that cannot effectively prevent and treat IDD. Conservative treatment may lead to patients' dependence on drugs, and the pain relief effect is not obvious. Similarly, surgical treatment is highly invasive, with a longer recovery time and a higher recurrence rate. With the deepening of exploration, people have discovered that intestinal microorganisms are an important symbiotic microbial community in the human body and are closely related to the occurrence and development of various diseases. Changes in intestinal microorganisms and their metabolites may affect the body's inflammatory response, immune regulation, and metabolic processes, thereby affecting the health of the intervertebral disk. In this context, the gut microbiota has received considerable attention as a potential target for delaying or treating IDD. This article first introduces the impact of gut microbes on common distal organs, and then focuses on three potential mechanisms by which gut microbes and their metabolites influence IDD. Finally, we also summarized the methods of delaying or treating IDD by interfering with intestinal microorganisms and their metabolites. Further understanding of the potential mechanisms between intestinal microorganisms and IDD will help to formulate reasonable IDD treatment strategies to achieve ideal therapeutic effects.

Causal effects of specific gut microbiota on spinal stenosis diseases: a two-sample mendelian randomization study

Background

Although recent observational studies and clinical trials have indicated a strong association between the gut microbiota and spinal stenosis diseases, the causal relationship between them remains unclear.

Methods

Based on large-scale genome-wide association studies, we employed two-sample Mendelian randomization (MR) to analyse the causal relationships between the gut microbiota (GM) and 3 spinal stenosis diseases: adolescent idiopathic scoliosis (AIS), lumbar spondylolisthesis (LS), and spinal stenosis (SS). MR analysis was performed using the inverse variance weighting (IVW) method as the primary approach, supplemented by MR‒Egger regression, weighted median, and weighted mode analyses. MR-PRESSO and MR‒Egger regression were employed to assess horizontal pleiotropy. Cochran's Q test was used to evaluate heterogeneity. Further leave-one-out sensitivity analysis was conducted to ascertain the reliability of the causal relationships.

Results

The IVW method identified 9 gut microbiota taxa (9 genera) that were causally related to AIS, 14 taxa (4 phyla, 2 classes, 2 orders, 1 family, and 5 genera) to LS, and 4 taxa (2 classes, 1 order, and 1 genus) to SS. The Cochrane Q test results did not indicate heterogeneity. Moreover, both the MR‒Egger intercept test and the MR-PRESSO global test demonstrated that our findings were robust against potential horizontal pleiotropy. Furthermore, leave-one-out analysis provided additional evidence supporting the reliability of our identified causal relationships.

Conclusion

Our findings have substantiated the potential causal impact of specific GM taxa on AIS, LS, and SS, thereby offering novel insights into the mechanisms mediated by the gut microbiota in these three diseases and laying the foundation for targeted preventive measures in further research.

Association between gut microbiota and spinal stenosis: a two-sample mendelian randomization study

Introduction

Considerable evidence has unveiled a potential correlation between gut microbiota and spinal degenerative diseases. However, only limited studies have reported the direct association between gut microbiota and spinal stenosis. Hence, in this study, we aimed to clarify this relationship using a two-sample mendelian randomization (MR) approach.

Materials and Methods

Data for two-sample MR studies was collected and summarized from genome-wide association studies (GWAS) of gut microbiota (MiBioGen, n = 13, 266) and spinal stenosis (FinnGen Biobank, 9, 169 cases and 164, 682 controls). The inverse variance-weighted meta-analysis (IVW), complemented with weighted median, MR-Egger, weighted mode, and simple mode, was used to elucidate the causality between gut microbiota and spinal stenosis. In addition, we employed mendelian randomization pleiotropy residual sum and outlier (MR-PRESSO) and the MR-Egger intercept test to assess horizontal multiplicity. Cochran's Q test to evaluate heterogeneity, and "leave-one-out" sensitivity analysis to determine the reliability of causality. Finally, an inverse MR analysis was performed to assess the reverse causality.

Results

The IVW results indicated that two gut microbial taxa, the genus Eubacterium fissicatena group and the genus Oxalobacter, have a potential causal relationship with spinal stenosis. Moreover, eight potential associations between genetic liability of the gut microbiota and spinal stenosis were implied. No significant heterogeneity of instrumental variables or horizontal pleiotropy were detected. In addition, "leave-one-out" sensitivity analysis confirmed the reliability of causality. Finally, the reverse MR analysis revealed that no proof to substantiate the discernible causative relationship between spinal stenosis and gut microbiota.

Conclusion

This analysis demonstrated a possible causal relationship between certain particular gut microbiota and the occurrence of spinal stenosis. Further studies focused on the mechanism of gut microbiota-mediated spinal stenosis can lay the groundwork for targeted prevention, monitoring, and treatment of spinal stenosis.

Roles of organokines in intervertebral disc homeostasis and degeneration

The intervertebral disc is not isolated from other tissues. Recently, abundant research has linked intervertebral disc homeostasis and degeneration to various systemic diseases, including obesity, metabolic syndrome, and diabetes. Organokines are a group of diverse factors named for the tissue of origin, including adipokines, osteokines, myokines, cardiokines, gastrointestinal hormones, and hepatokines. Through endocrine, paracrine, and autocrine mechanisms, organokines modulate energy homeostasis, oxidative stress, and metabolic balance in various tissues to mediate cross-organ communication. These molecules are involved in the regulation of cellular behavior, inflammation, and matrix metabolism under physiological and pathological conditions. In this review, we aimed to summarize the impact of organokines on disc homeostasis and degeneration and the underlying signaling mechanism. We focused on the regulatory mechanisms of organokines to provide a basis for the development of early diagnostic and therapeutic strategies for disc degeneration.