Metformin limits osteoarthritis development and progression through activation of AMPK signalling

Fibroblast growth factor 8 (FGF8) induces mitochondrial remodeling in chondrocytes via ERK/AMPK signaling pathway

Osteoarthritis (OA) is a disease characterized by articular cartilage degeneration, and its pathogenic mechanisms are associated with mitochondrial homeostasis disorders. Fibroblast growth factor 8 (FGF8) is a multipotent protein ligand which is upregulated in OA cartilage. However, the molecular mechanisms by which FGF8 regulates mitochondria in chondrocytes are not yet fully understood. Here, we treated chondrocytes with FGF8 and detected the effects of FGF8 on mitochondrial morphology in the cytoplasm using transmission electron and confocal laser scanning microscopy. ATP levels were measured to determine the cellular energy status. Western blotting and immunofluorescence staining experiments were employed to detect the fusion-fission proteins mitofusin 1 (MFN1), mitofusin 2 (MFN2), optic atrophy 1 (OPA1), dynamin-related protein 1 (DRP1), mitochondrial fission 1 protein (FIS1), and related signaling pathways. The FGF receptor (FGFR) inhibitor, AZD4547, and the ERK inhibitor, U0126, were used to verify the specific effects of the FGFR and ERK pathways. We found that FGF8 regulated mitochondrial morphology and dynamics in chondrocytes by inducing mitochondrial elongation. While it upregulated fusion proteins MFN1, MFN2, and OPA1, FGF8 downregulated fission proteins DRP1 and FIS1. ERK and AMPK pathways were activated in chondrocytes after FGF8 treatment. In contrast, both AZD4547 and U0126 inhibitors abolished mitochondrial elongation as well as the alteration of fusion-fission proteins induced by FGF8, and U0126 also inhibited the FGF8-triggered activation of AMPK. This study is the first to reveal that FGF8 remodels mitochondria through ERK/AMPK signaling in chondrocytes, offering novel insights into the potential role of FGF8 in OA.

Sex differences in the orofacial antinociceptive effect of metformin and the role of transient receptor potential channels

Metformin is classified as a biguanide and is used in the treatment of type 2 diabetes. It is used worldwide and has been investigated in drug repositioning. The present study aims to investigate whether there is sexual dimorphism in the orofacial antinociceptive effect of metformin and the participation of TRP channels. Acute nociceptive behavior was induced by administering cinnamaldehyde or capsaicin to the upper lip. Nociceptive behavior was assessed through orofacial rubbing, and the effects of pre-treatment with metformin (125 or 250 mg/Kg) or vehicle (control) were tested on the behavior. Nociceptive behavior was also induced by formalin injected into the temporomandibular joint. The chronic pain model involved infraorbital nerve transection (IONX) was evaluated using Von Frey electronic filaments. Trpv1 gene expression was analyzed in the nerve ganglion. Docking experiments were performed. Metformin, but not the vehicle, produced antinociception (p < 0.0001) in all acute nociceptive behaviors in both sexes, and these effects were attenuated by the TRPV1 antagonist capsazepine and the TRPA1 antagonist HC-030031. In IONX with better (**p < 0.01, ****p < 0.0001 vs. control) results in females. TRPV1 gene expression was observed in the metformin treated group (*p < 0.05 vs. control). Docking experiments revealed that metformin may interact with TRPV1 and TRPA1 channels. Metformin promotes orofacial antinociception in both sexes in acute pain and is more effective in chronic pain in females than in males, through the modulation of TRPV1 and TRPA1 channels. These preclinical findings suggest a potential repositioning of metformin as an analgesic agent in acute and chronic orofacial pain states.

Metabolic Reprogramming in Stromal and Immune Cells in Rheumatoid Arthritis and Osteoarthritis: Therapeutic Possibilities

Metabolic reprogramming of stromal cells, including fibroblast-like synoviocytes (FLS) and chondrocytes, as well as osteoclasts (OCs), are involved in the inflammatory and degenerative processes underlying rheumatoid arthritis (RA) and osteoarthritis (OA). In RA, FLS exhibit mTOR activation, enhanced glycolysis and reduced oxidative phosphorylation, fuelling inflammation, angiogenesis, and cartilage degradation. In OA, chondrocytes undergo metabolic rewiring, characterised by mTOR and NF-κB activation, mitochondrial dysfunction, and increased glycolysis, which promotes matrix metalloproteinase production, extracellular matrix (ECM) degradation, and angiogenesis. Macrophage-derived immunometabolites, including succinate and itaconate further modulate stromal cell function, acting as signalling molecules that modulate inflammatory and catabolic processes. Succinate promotes inflammation whilst itaconate is anti-inflammatory, suppressing inflammatory joint disease in models. Itaconate deficiency also correlates inversely with disease severity in RA in humans. Emerging evidence highlights the potential of targeting metabolic processes as promising therapeutic strategies for connective tissue disorders.

Integrated bioinformatics and clinical data identify three novel biomarkers for osteoarthritis diagnosis and synovial immune

Osteoarthritis (OA) is a degenerative joint disease that can be aggravated by synovitis and synovial immune disorders (SID). However, the role of synovial SID-related genes in OA synovium remains poorly understood. OA synovial and peripheral blood datasets were obtained from the GEO database ( https://www.ncbi.nlm.nih.gov/ ). Immune-related genes ( https://reactome.org/ ) showing differential expression in peripheral blood were identified as immune disorder genes. Subsequently, differentially expressed immune disorder genes in OA synovium were further identified as SID genes. The Venn diagram, random forest, SVM-RFE algorithm, and multivariate analysis were employed to determine SID-related hub genes in OA synovium. Using the identified hub genes, we constructed and validated a diagnostic model for predicting OA occurrence. The correlation between hub gene expression and immune-related modules was explored using CIBERSORT and MCP-counter analyses. We identified three SID-related hub genes (ACAT1, SPHK1, and ACACB) in OA synovium. The diagnostic model incorporating these hub genes demonstrated reliable predictive accuracy (AUC = 0.939). Through qPCR analysis, we quantitated the expression levels of the hub genes and confirmed that three hub genes could serve as novel biomarkers for OA patients (AUC = 0.960). Furthermore, we observed a significant correlation between the expression of these hub genes and immune cell infiltration, as well as inflammatory cytokine levels in OA synovium. Our findings suggest that three SID-related hub genes have the potential to serve as diagnostic biomarkers for OA patients. These genes are associated with immune disorder and contribute to immune alterations within the OA synovium.

Metformin ameliorates osteoporosis by enhancing bone angiogenesis via the YAP1/TAZ-HIF1α axis

BACKGROUND

Osteoporosis, resulting from an imbalance between osteoclast-mediated bone resorption and osteoblast-mediated bone formation, affects millions globally. Recent studies have identified type H vessels (CD31hiEMCNhi) as a specialized subset of bone blood vessels that positively regulate bone formation. This study aims to investigate the effects of metformin on bone mass, strength, and angiogenesis in osteoporotic mice, and to elucidate the underlying molecular mechanisms, particularly focusing on the YAP1/TAZ-HIF1α axis.

METHODS

Osteoporotic mice were administered metformin, and bone mass and strength were measured. In vivo and in vitro angiogenesis assays were performed under hypoxic conditions. Expression levels of YAP1/TAZ and HIF1α were assessed in femoral metaphysis and hypoxia-cultured human microvascular endothelial cells (HMECs). Small interfering RNA was used to interfere with HIF1α or YAP1/TAZ expression in hypoxia-cultured HMECs. Additionally, we employed AAV-mediated overexpression of YAP1/TAZ in vivo to determine whether elevated YAP1/TAZ levels alter metformin's effects on bone mass and angiogenesis.

RESULTS

Metformin significantly enhanced bone mass and strength in osteoporotic mice. It also promoted angiogenesis under hypoxia conditions both in vivo and in vitro. Metformin reduced YAP1/TAZ expression while increasing HIF1α expression in both the femoral metaphysis of osteoporotic mice and hypoxia-cultured HMECs. Interference with HIF1α or YAP1/TAZ confirmed that metformin enhances HIF1α and its target genes primarily by inhibiting YAP1/TAZ. Furthermore, overexpression of YAP1/TAZ partially reversed the bone-protective effect of metformin, leading to reduced HIF1α levels and diminished type H vessel formation.

CONCLUSION

Our findings suggest that metformin holds promise as a therapeutic agent for osteoporosis by enhancing type H vessel formation through the inhibition of the YAP1/TAZ-HIF1α axis.

Hyaluronic acid composite hydrogel with enhanced lubrication and controllable drug release for the mitigation of osteoarthritis

Excessive inflammation, overexpressed reactive oxygen species (ROS), degradation of the extracellular matrix, and high friction aggravate osteoarthritis (OA). Intra-articular injection for local drug delivery in the joint cavity enhances drug retention duration for OA treatment. Nevertheless, it remains a challenge to attenuate OA by thoroughly modulating the joint microenvironment, achieving controlled drug release, and enhancing lubrication. This study develops hyaluronic acid (HA) composite hydrogels, infused with gelatin microspheres containing a drug, utilizing dynamic interactions between phenylboronic acid and catechol to modulate the microenvironment by scavenging ROS, facilitating controlled drug release, and improving lubrication to mitigate OA. The composite hydrogels can be injected by intra-articular injection due to the shear-thinning properties, demonstrating broad ROS scavenging capacity and matrix metalloproteinase-9 responsive drug release. Both the in vitro and in vivo experiments prove the protective efficacy of the composite hydrogels against the degradation of cartilage matrix. Additionally, the hydrogels can offer efficient lubrication and effectively attenuate OA. Thus, the injectable HA composite hydrogels demonstrated potential in the management of OA.

Implications of obesity-mediated cellular dysfunction and adipocytokine signaling pathways in the pathogenesis of osteoarthritis

Osteoarthritis (OA) is a degenerative joint disease characterized by cartilage degradation, bone sclerosis, and chronic low-grade inflammation. Aging and injury play key roles in OA pathogenesis by triggering the release of proinflammatory factors from adipose tissue and other sources. Obesity and aging impair the function of endoplasmic reticulum (ER) chaperones, leading to ER stress, protein misfolding, and cellular apoptosis. Obesity also induces mitochondrial dysfunction in OA through oxidative stress and disrupts mitochondrial dynamics, exacerbating chondrocyte damage. These factors contribute to inflammation, matrix imbalance, and chondrocyte apoptosis. Adipocytes, the primary source of adipokines, release inflammatory mediators that affect joint cells. Several adipocytokines have a central role in the regulation of many aspects of inflammation. Adiponectin and leptin are the two most abundant adipocytokines that are strongly associated with OA progression. This literature review suggests that adipokines activate many signaling pathways to exert downstream effects and play significant roles in obesity-induced OA. Understanding this rapidly growing family of mainly adipocyte-derived mediators and obesity-mediated cellular dysfunction may be important in the development of new therapies for obesity-associated OA management.

Metformin treatment for patients with hand osteoarthritis: protocol for the multicentre, randomised, placebo-controlled METRO trial

INTRODUCTION

Hand osteoarthritis (OA) is a prevalent joint disorder with limited treatment options. Accumulating evidence suggests that the antidiabetic drug metformin has beneficial effects on knee OA and may likewise be beneficial for hand OA. The objective of this randomised, double-blinded, placebo-controlled trial is to investigate the effect of metformin 1000 mg two times a day, or maximum tolerated dose, compared with placebo on reducing finger joint pain after 16 weeks of treatment.

METHODS AND ANALYSIS

The participants will be enrolled from the OA clinic at the Parker Institute at Copenhagen University Hospital - Bispebjerg and Frederiksberg, Copenhagen, Denmark and from the Department of Rheumatology, Hospitalsenhed Midt, Silkeborg, Denmark. 150 participants with painful hand OA according to the American College of Rheumatology criteria will be randomly allocated in a 1:1 ratio to receive either metformin or a matching placebo for 16 weeks. The initial dose of 500 mg of metformin or placebo once daily is increased by 500 mg every week until the target dose of 1000 mg two times a day, or the maximum tolerated dose, is reached. The participants will have clinical visits every 4 weeks, except the week 12 visit, which is by telephone. The primary endpoint is the between-group difference in least squares means for the change in the Visual Analogue Scale (VAS) finger joint pain scores between the metformin and placebo groups at 16 weeks. The main analysis will be conducted on the intention-to-treat population, comprising all participants assessed and randomly assigned at baseline. Least squares means and the differences between them, along with their respective 95% CIs, will be derived from a mixed-effects model for repeated measurements (outcomes collected at baseline and at weeks 4, 8, 12 and 16). Adverse events will be registered systematically.

ETHICS AND DISSEMINATION

Approval has been obtained from the European Medicines Agency (EudraCT: 2023-509181-38-00), which also includes approval from the local health research ethics committee. Written informed consent will be obtained from all participants. Study findings will be published in international peer-reviewed journals and will be presented in relevant media and at international scientific conferences.

TRIAL REGISTRATION NUMBER

EudraCT, 2023-509181-38-00; ClinicalTrials.gov, NCT06367283.

Gel@CAT-L hydrogel mediates mitochondrial unfolded protein response to regulate reactive oxygen species and mitochondrial homeostasis in osteoarthritis

OBJECTIVE

This study investigates the role of Gelatin-Catalase (Gel@CAT)-L hydrogel in mediating reactive oxygen species (ROS) production and maintaining mitochondrial homeostasis through SIRT3-mediated unfolded protein response (UPRmt), while exploring its involvement in the molecular mechanism of osteoarthritis (OA).

METHODS

Self-assembled Gel@CAT-L hydrogels were fabricated and characterized using transmission electron microscopy, mechanical testing, external release property evaluation, and oxygen production measurement. Biocompatibility was assessed via live/dead cell staining and CCK8 assays. An OA mouse model was established using destabilization of the medial meniscus (DMM) surgery. X-ray and micro-CT imaging were employed to evaluate the structural integrity of the mouse knee joints, while histological staining was used to assess cartilage degeneration. Immunohistochemistry was performed to analyze the expression of proteins including Col2a1, Aggrecan, MMP13, ADAMTS5, SIRT3, PINK1, and Parkin. Multi-omics analyses-encompassing high-throughput sequencing, proteomics, and metabolomics-were conducted to identify key genes and metabolic pathways targeted by Gel@CAT-L hydrogel intervention in OA. Immunofluorescence techniques were utilized to measure ROS levels, mitochondrial membrane potential, and the expression of SIRT3, PINK1, Parkin, LYSO, LC3B, Col2a1, and MMP13 in primary mouse chondrocytes and mouse knee joints. Flow cytometry was applied to quantify ROS-positive cells. RT-qPCR analysis was conducted to determine mRNA levels of Aggrecan, Col2a1, ADAMTS5, MMP13, SIRT3, mtDNA, HSP60, LONP1, CLPP, and Atf5 in primary mouse chondrocytes, mouse knee joints, and human knee joints. Western blotting was performed to measure protein expression levels of SIRT3, HSP60, LONP1, CLPP, and Atf5 in both primary mouse chondrocytes and mouse knee joints. Additionally, 20 samples each from the control (CON) and OA groups were collected for analysis. Hematoxylin and eosin staining was used to evaluate cartilage degeneration in human knee joints. The Mankin histological scoring system quantified the degree of cartilage degradation, while immunofluorescence analyzed SIRT3 protein expression in human knee joints.

RESULTS

In vitro experiments demonstrated that self-assembled Gel@CAT-L hydrogels exhibited excellent biodegradability and oxygen-releasing capabilities, providing a stable three-dimensional environment conducive to cell viability and proliferation while reducing ROS levels. Multi-omics analysis identified SIRT3 as a key regulatory gene in mitigating OA and revealed its central role in the UPRmt pathway. Furthermore, Gel@CAT-L was confirmed to regulate mitochondrial homeostasis. Both in vitro experiments and in vivo mouse model studies confirmed that Gel@CAT-L significantly reduced ROS levels and regulated mitochondrial autophagy by activating the SIRT3-mediated UPRmt pathway, thereby improving the pathological state of OA. Clinical trials indicated downregulation of SIRT3 and UPRmt-related proteins in OA patients.

CONCLUSION

Gel@CAT-L hydrogel activates SIRT3-mediated UPRmt to regulate ROS and mitochondrial homeostasis, providing potential therapeutic benefits for OA.

Metformin as a disease-modifying therapy in osteoarthritis: bridging metabolism and joint health

Background

Osteoarthritis (OA) and impaired glucose tolerance (IGT) frequently coexist, leading to compounded clinical and metabolic challenges. This study investigates the effects of metformin in improving both clinical outcomes (pain, stiffness, physical function) and metabolic parameters (inflammatory markers, lipid profile, BMI) in patients with knee OA and IGT.

Methods

The study included 60 patients diagnosed with knee OA and IGT. Participants were divided into two groups: 26 patients received standard OA treatment without metformin (Without Metf), while 34 received metformin (500 mg twice daily) for 3 months, in addition to standard treatment (With Metf). Clinical assessments (WOMAC, Lequesne Algofunctional Index, KOOS, VAS) and metabolic markers (CRP, NLR, SOD, lipid profile, BMI) were measured before treatment, after 1 month, and after 3 months.

Results

The With Metf group showed significantly greater improvements in pain, stiffness, physical function, and quality of life compared to the Without Metf group. Metformin also led to significant reductions in inflammatory markers and improvements in lipid profiles and metabolic health indicators. The With Metf group demonstrated enhanced BMI, waist-to-hip ratio, and waist-to-height ratio. Furthermore, the need for increased NSAID doses was predicted by factors such as pain severity and inflammatory markers.

Conclusion

Metformin effectively alleviates osteoarthritis symptoms and improves metabolic health in patients with both OA and IGT. Further research is needed to explore its long-term effects on joint health, inflammatory markers, and its potential role in OA management in patients without IGT.

Metformin-Loaded Tannic Acid Nanoparticles Attenuate Osteoarthritis by Promoting Chondrocyte Mitochondria Homeostasis Based on Mitocytosis

The oxidative stress microenvironment and mitochondrial dysfunction in chondrocytes are key mechanisms in the development of osteoarthritis (OA). Metformin (Met) has demonstrated multiple effects on mitochondria and is regarded as a potential therapeutic agent for OA. The low blood flow characteristics in the joint cavity make targeted local delivery of metformin crucial for its clinical application. In this study, tannic acid (TA), with its natural antioxidant and anti-inflammatory properties, was used to prepare self-assemble Met-loaded TA nanoparticles (NPs). The NPs exhibit excellent reactive oxygen scavenging capability, stability in various media, and an acid-responsive release of Met. In Vitro experiments showed that NPs possess excellent biocompatibility, effectively protecting chondrocyte viability in OA's pathological environment and preventing the senescence phenotype. In addition, NPs promoted the expression of antioxidant elements in chondrocytes, restored mitochondrial membrane potential, and enhanced mitocytosis to improve mitochondrial quality. In vivo experiments further confirmed that intra-articular injection of NPs in rats with post-traumatic OA improves cartilage matrix degradation, osteophyte formation, and subchondral bone sclerosis over 8 weeks. Tissue staining further confirmed the protective effects of NPs on chondrocyte mitochondria. Importantly, both in vivo and in vitro experiments revealed that NPs provided superior cellular protection compared to TA or Met alone. Overall, this study demonstrates that NPs effectively against OA cartilage degeneration, with the advantages of easy preparation, high efficiency, and biosafety.

The PIKASO trial (Preventing Injured Knees from Osteoarthritis: Severity Outcomes): Rationale and design features for a randomized controlled trial

Objective

Given the high burden and increasing prevalence of post-traumatic osteoarthritis (PTOA), identifying clinically beneficial strategies to prevent or delay its onset could improve the quality of life of those at high risk of developing the disease.

Methods

Preventing Injured Knees from OsteoArthritis: Severity Outcomes (PIKASO) is a multicenter blinded, parallel, two-arm randomized controlled trial of 512 individuals aged 18-45 years undergoing anterior cruciate ligament reconstruction (ACLR). This study is designed to evaluate the efficacy of a 12-month intervention of oral metformin vs. placebo in decreasing the rate of structural knee changes and pain. Participants will be asked to take up to 1500 ​mg/day of either metformin or placebo as tolerated. The primary outcomes are Knee injury and Osteoarthritis Outcome Score (KOOS) Pain subscale scores averaged between 12 and 24 months after randomization, and MRI derived cartilage structural change at 24 months. The trial will be deemed successful if at least one of the two primary outcomes reaches the preplanned effect size with sufficient statistical certainty. In this paper, we describe PIKASO elements according to the Standard Protocol Items: Recommendations for Interventional Trials (SPIRIT) guidelines.

Results

Our multidisciplinary team developed the methods and statistical analysis plan for a placebo controlled, randomized clinical trial to determine whether metformin alters pain and early osteoarthritic changes after ACLR.

Discussion

This manuscript outlines the rationale, study design, and implementation of the PIKASO trial aiming to prevent the onset of PTOA after ACLR.

Trial registration

clinicaltrials.gov NCT06096259.

Prospective Preference Assessment of a Pharmacological Clinical Trial to Alter the Progression of Posttraumatic Osteoarthritis After ACL Reconstruction

Background

Understanding the factors contributing to willingness to participate in randomized clinical trials (RCTs) after anterior cruciate ligament reconstruction (ACLR) is crucial to optimizing recruitment and understanding whether interested participants represent the patient population that may benefit from the studied treatment.

Purpose

To understand patients' willingness to participate in a future RCT of an oral medication to prevent posttraumatic osteoarthritis (PTOA) after ACLR.

Study Design

Cross-sectional study; Level of evidence, 3.

Methods

A total of 103 patients aged 18 to 45 years who were either planning to undergo ACLR in the next 4 months or had undergone ACLR within 1 year of the screening date were recruited from 2 institutions. The patients viewed a video explaining the trial and completed a questionnaire that included demographic characteristics, pain intensity, activity level, willingness to participate in the hypothetical trial, and their perceived risk (on a scale of 0%-100%) of developing knee PTOA (next 10 years or lifetime).

Results

Within the cohort, 31% stated they were "definitely willing," 38% were "probably willing," 17% were "unsure," and 14% were "unwilling" to participate in a hypothetical trial. Willingness did not differ by pain or activity level; however, younger patients stated they were less willing to participate. The most common reasons for unwillingness to participate included not wanting to take a medication daily (59%) and concerns about medication risks or side effects (59%). Respondents who indicated a definite willingness to participate in the trial had higher perceptions of their own PTOA risk over the next 10 years than those who indicated they would not participate (70% vs 50%).

Conclusion

In this prospective preference assessment, 69% of survey respondents expressed a willingness to participate in an RCT involving an oral medication to potentially alter the progression of PTOA after ACLR. The results suggest that an RCT in this study should include clear and concise information on the risk of developing PTOA after ACLR and the safety and tolerability of study medications in the recruitment materials.

Quercetin attenuates the symptoms of osteoarthritis in vitro and in vivo by suppressing ferroptosis via activation of AMPK/Nrf2/Gpx4 signaling

Osteoarthritis (OA) is a common joint disorder involving the cartilage and other joint tissues. Quercetin (QCT) serves a protective role in the development of OA. However, to the best of our knowledge, the regulatory mechanisms of QCT in the progression of OA have not yet been fully elucidated. In order to mimic a model of OA in vitro, IL‑1β was used to stimulate chondrocytes. Furthermore, an in vivo animal model of OA was induced by anterior cruciate ligament transection (ACLT). 5‑Ethynyl‑2'‑deoxyuridine assays, TUNEL assays, ELISAs, western blotting and immunohistochemical assays were conducted to assess the chondroprotective properties of QCT in the development of OA. The results revealed that 100 µM QCT significantly promoted the proliferation, reduced the apoptosis and inflammation, and inhibited the extracellular matrix (ECM) degradation in IL‑1β‑stimulated chondrocytes. Additionally, QCT attenuated the IL‑1β‑induced ferroptosis of chondrocytes, as demonstrated by the reduced lipid reactive oxygen species and Fe2+ levels. Conversely, the inhibitory effects of QCT on the apoptosis and inflammatory responses were reversed by the activation of ferroptosis by erastin in IL‑1β‑stimulated chondrocytes. Furthermore, QCT significantly elevated the level of phosphorylated (p‑)5' AMP‑activated protein kinase (AMPK) and the levels of two negative regulators of ferroptosis [nuclear factor erythroid 2‑related factor 2 (Nrf2) and glutathione peroxidase 4 (Gpx4)] in IL‑1β‑stimulated chondrocytes. The AMPK inhibitor compound C notably reversed the promoting effects of QCT on phosphorylated‑AMPK, Nrf2 and Gpx4 expression in IL‑1β‑stimulated chondrocytes. Additionally, QCT markedly ameliorated the destruction and degradation of articular cartilage, and elevated the p‑AMPK, Nrf2 and Gpx4 levels in the mouse model of ACLT‑induced OA. Overall, the present study demonstrated that QCT inhibited the development of OA by suppressing ferroptosis via the activation of the AMPK/Nrf2/Gpx4 signaling pathway. These findings provide novel insights into the regulatory mechanisms of QCT for the treatment of patients with OA.

Effect of glucagon-like peptide-1 receptor agonists in osteoarthritis: A systematic review of pre-clinical and human studies

Objective

There is significant interest in the potential of glucagon-like peptide 1 receptor agonists (GLP-1A) to improve outcomes in osteoarthritis. We systematically reviewed the evidence from pre-clinical and human studies for effect of glucagon-like peptide 1 receptor agonists (GLP-1A) in osteoarthritis.

Method

Ovid Medline, Embase and CINAHL were searched (inception to November 2024) using MeSH terms and key words to identify studies examining the association between GLP-1A use and outcomes related to osteoarthritis. Risk of bias assessment and data extraction were conducted by three reviewers independently. Qualitative evidence synthesis was performed and prospectively registered on PROSPERO (CRD42024522782 and CRD42024522787).

Results

This systematic review included 11 (7 pre-clinical; 4 human studies) studies. In pre-clinical studies, GLP-1A was assessed for its effect on structural (n ​= ​6); immunomodulation (n ​= ​7); analgesia (n ​= ​1) and molecular pathways in osteoarthritis (n ​= ​5). For human studies, GLP-1A were assessed for structural (n ​= ​1) and symptomatic (n ​= ​4) effects in osteoarthritis. Pre-clinical studies consistently demonstrated favourable chondroprotective and immunomodulatory effects of GLP-1A in osteoarthritis, with a dose-dependent effect, primarily driven by inhibition of NF-κB pathway. Limited human studies supported these findings in osteoarthritis.

Conclusion

There are consistent signals across limited pre-clinical and human studies to support a potential favourable structural protective, immunomodulatory and analgesic effects of GLP-1A in osteoarthritis. With the growing burden of obesity, high-quality trials are needed to determine the role of GLP-1A in osteoarthritis.

Zn2+-driven metformin conjugated with siRNA attenuates osteoarthritis progression by inhibiting NF-κB signaling and activating autophagy

Osteoarthritis (OA) is a type of joint disease that influences millions of individuals. Regrettably, effective treatment for OA is currently unavailable. The challenge lies in the deep location of chondrocytes within the dense cartilage matrix that hinders the delivery and efficiency of clinical OA drugs. To overcome this obstacle, the present study proposed a hybrid nanodrug by Zinc(II) metal-drug coordination-driven self-assembly as highly efficient delivery system. This nano-assembly formulations possessed the ability to deliver two types of drugs, namely metformin (Met) and therapeutic genes (p65 siRNA). Results showed that this nano-assembly not only exhibited positive charge-driven anchoring to the cartilage matrix and effective drug delivery capacity, but also synergistically inhibited NF-κB activity and activates autophagy of OA chondrocytes, thus safeguarding the cartilage. The successful achievement of this project not only contribute to the advancement of research on bio-nanomaterials for treating OA, but also establish a robust theoretical foundation for realizing promising and functional integration of nanomedicine targeting OA.

Metformin's Effects on Cognitive Function from a Biovariance Perspective: A Narrative Review

This study examines the effects of metformin on brain functions focusing on the variability of the results reported in the literature. While some studies suggest that metformin may have neuroprotective effects in diabetic patients, others report an insignificant impact of metformin on cognitive function, or even a negative effect. We propose that this inconsistency may be due to intrinsic cellular-level variability among individuals, which we term "biovariance". Biovariance persists even in demographically homogeneous samples due to complex and stochastic biological processes. Additionally, the complex metabolic actions of metformin, including its influence on neuroenergetics and neuronal survival, may produce different effects depending on individual metabolic characteristics.

Metformin-induced mitophagy suppresses auditory hair cell apoptosis via AMPK pathway

Hearing loss is a pervasive issue affecting numerous individuals, and its etiology and categorization are multifaceted. Among these, sensorineural hearing loss (SNHL) emerges as the most prevalent variant among these. The primary causative factor underlying SNHL resides in the depletion of auditory hair cells within the cochlea, yet the pursuit of efficacious therapeutic interventions remains an ongoing challenge. Previous investigations have illuminated the role of mitochondrial dysfunction in precipitating cellular apoptosis, and mitophagy has emerged as a promising mechanism to ameliorate such dysfunction. Additionally, it has been noted that metformin possesses the specific ability to induce mitophagy. Herein, our objective is to explore the protective effects of metformin-induced mitophagy against apoptosis in auditory hair cells (HEI-OC1 cells) and explore its potential mechanisms. Our results revealed that metformin effectively triggered mitophagy in HEI-OC1 cells. Moreover, metformin treatment showed the ability to prevent tert-butyl hydroperoxide (TBHP) induced mitochondrial dysfunction and intrinsic apoptotic pathways. Mechanistically, we discovered that metformin activates AMP-activated protein kinase (AMPK) signaling in HEI-OC1 cells stimulated by TBHP, thereby triggering mitophagy. Overall, our results suggest that metformin may represent a promising and innovative therapeutic strategy for mitigating the onset of hearing loss.

GelMA@APPA microspheres promote chondrocyte regeneration and alleviate osteoarthritis via Fgfr2 activation

BACKGROUND

In the context of osteoarthritis (OA), a condition marked by joint degeneration, there is a notable absence of efficacious approaches to promote regenerative healing in chondrocytes. Novel therapeutic strategies like nanomicelles-hydrogel microspheres loaded with Astragalus polysaccharide (GelMA@APPA) offer promising avenues for promoting chondrocyte regeneration and mitigating OA progression.

METHODS

Astragalus polysaccharide (APS) has been shown to induce chondrocyte proliferation and promote cartilage matrix secretion, demonstrating biological activity associated with chondrocyte regeneration. However, the clinical efficacy of APS remains uncertain. Therefore, this investigation validated the beneficial impact of APS on reducing knee joint damage severity induced by destabilization of the medial meniscus (DMM) in mice. The application of bioinformatics analysis and in vitro experimentation revealed that fibroblast growth factor receptor 2 (Fgfr2) in chondrocytes is a key target protein for APS in ameliorating OA-induced cartilage injury, as the deletion of chondrocyte Fgfr2 resulted in the complete loss of the therapeutic effect of APS. To enhance the efficacy of APS, we incorporated APS into nanoparticle-laden hydrogel microspheres to further bolster its potential in chondrocyte regeneration therapy. Subsequently, we developed GelMA@APPA, which exhibited no significant cytotoxic effects on normal chondrocytes in vitro and could be efficiently internalized by chondrocytes. Following subsequent in vitro and in vivo experiments, we affirmed the beneficial effects of GelMA@APPA on OA mice and cartilage cells damaged by OA, as well as its enhancement of the therapeutic effects of APS.

RESULTS

APS significantly improved knee joint injuries in OA mice. Bioinformatics and in vitro analyses identified Fgfr2 as a critical target protein for APS's regenerative effects. Disruption of Fgfr2 negated APS's benefits. GelMA@APPA demonstrated good biocompatibility, effective internalization by chondrocytes, and enhanced the therapeutic efficacy of APS in experiments conducted both in vitro and in vivo, improving chondrocyte proliferation and reducing apoptosis.

CONCLUSIONS

This study demonstrates that GelMA@APPA microspheres effectively promote chondrocyte regeneration and OA treatment by activating Fgfr2. These findings suggest a novel therapeutic mechanism for OA and lay the groundwork for future clinical utilization of GelMA@APPA in regenerative medicine.

Up IGF-I via high-toughness adaptive hydrogels for remodeling growth plate of children

The growth plate is crucial for skeletal growth in children, but research on repairing growth plate damage and restoring growth is limited. Here, a high-toughness adaptive dual-crosslinked hydrogel is designed to mimic the growth plate's structure, supporting regeneration and bone growth. Composed of aldehyde-modified bacterial cellulose (DBNC), methacrylated gelatin (GelMA) and sodium alginate (Alg), the hydrogel is engineered through ionic bonding and Schiff base reactions, creating a macroporous structure. This structure can transform into a denser form by binding with calcium ions. In vitro, the loose macroporous structure of the hydrogels can promote chondrogenic differentiation, and when it forms a dense structure by binding with calcium ions, it also can activate relevant chondrogenic signaling pathways under the influence of insulin-like growth factor I (IGF-1), further inhibiting osteogenesis. In vivo experiments in a rat model of growth plate injury demonstrated that the hydrogel promoted growth plate cartilage regeneration and minimized bone bridge formation by creating a hypoxic microenvironment that activates IGF-1-related pathways. This environment encourages chondrogenic differentiation while preventing the undesired formation of bone tissue within the growth plate area. Overall, the dual-crosslinked hydrogel not only mimics the growth plate's structure but also facilitates localized IGF-1 expression, effectively reshaping the growth plate's function. This approach represents a promising therapeutic strategy for treating growth plate injuries, potentially addressing challenges associated with skeletal growth restoration in pediatric patients.

Genetic Links Between Metabolic Syndrome and Osteoarthritis: Insights From Cross-Trait Analysis

CONTEXT

Previous observational studies have indicated a bidirectional association between metabolic syndrome (MetS) and osteoarthritis (OA). However, it remains unclear whether these bidirectional associations reflect causal relationships or shared genetic factors, and the underlying biological mechanisms of this association are not fully understood.

OBJECTIVE

We aimed to explore the genetic connection between MetS and OA using genome-wide association study (GWAS) summary data.

METHODS

Leveraging summary statistics from GWAS conducted by the UK Biobank and the Glucose and Insulin-related Traits Consortium (MAGIC), we performed global genetic correlation analyses, genome-wide cross-trait meta-analyses, and a bidirectional two-sample Mendelian randomization analyses using summary statistics from GWAS to comprehensively assess the relationship of MetS and OA.

RESULTS

We first detected an extensive genetic correlation between MetS and OA (rg = 0.393, P = 1.52 × 10-18), which was consistent in 4 MetS components, including waist circumference, triglycerides, hypertension, and high-density lipoprotein cholesterol and OA with rg ranging from -0.229 to 0.490. We then discovered 32 variants jointly associated with MetS and OA through Multi-Trait Analysis of GWAS (MTAG). Co-localization analysis found 12 genes shared between MetS and OA, with functional implications in several biological pathways. Finally, Mendelian randomization analysis suggested genetic liability to MetS significantly increased the risk of OA, but no reverse causality was found.

CONCLUSION

Our results illustrate a common genetic architecture, pleiotropic loci, as well as causality between MetS and OA, potentially enhancing our knowledge of high comorbidity and genetic processes that overlap between the 2 disorders.

M13, an anthraquinone compound isolated from Morinda officinalis alleviates the progression of the osteoarthritis via the regulation of STAT3

BACKGROUND

Osteoarthritis (OA) is characterized by the progressive deterioration of articular cartilage, leading to joint pain and functional impairment. OA severely impacts quality of life and presents a substantial societal burden. Currently, effective treatment options remain limited. Morinda officinalis (MO), a traditional Chinese herb, is commonly used to treat rheumatoid arthritis and alleviate joint pain. M13, an anthraquinone extracted from MO, has shown significant anti-inflammatory properties, making it a promising candidate for the treatment of OA. However, its role in inhibiting OA progression and the mechanisms involved remain poorly understood.

PURPOSE

The objective of this study is to examine the impact of M13 on osteoarthritis and uncover the mechanisms.

METHODS

The effects of M13 on OA were assessed using TNF-α induced chondrocyte models and mice with destabilization of the medial meniscus (DMM). Celecoxib was used as a positive control. We evaluated the expression of factors related to chondrocyte degeneration and inflammation through qRT-PCR, immunoblotting, and immunofluorescence. Chondrocyte viability was measured using CCK-8 assays, EdU staining, and flow cytometry. Molecular docking, molecular dynamics simulations and isothermal titration calorimetry (ITC) were performed to evaluate the binding efficacy of target proteins. Additionally, the therapeutic effects of M13 in OA mice were confirmed through in vivo experiments.

RESULTS

In primary murine chondrocytes, M13 rescued TNF-α-induced matrix degradation and loss of vitality while suppressing ROS generation. Mechanistically, STAT3 was identified as a target protein of M13, through which M13 mitigated OA by inhibiting the STAT3 signaling pathway. Further in vivo experiments demonstrated that M13 reduced the scores of the Osteoarthritis Research Society International (OARSI), alleviating cartilage impairment. M13 enhanced levels of collagen II and aggrecan in cartilage tissue while decreasing the amounts of cartilage-degrading proteins ADAMTS-5 and MMP13.

CONCLUSION

This is the first study to validate that M13 mitigates the inflammation and damage in cartilage tissue by blocking the STAT3 signaling pathway. These findings hold promise for enhancing innovative clinical interventions targeting OA.

Development of novel osteoarthritis therapy by targeting AMPK-β-catenin-Runx2 signaling

Osteoarthritis (OA) is a debilitating chronic joint disease affecting large populations of patients, especially the elderly. The pathological mechanisms of OA are currently unknown. Multiple risk factors are involved in OA development. Among these risk factors, alterations of mechanical loading in the joint leading to changes in biological signaling pathways have been known as a key event in OA development. The importance of AMPK-β-catenin-Runx2 signaling in the initiation and progression of OA has been recognized in recent years. In this review, we discuss the recent progress in understanding the role of this signaling pathway and the underlying interaction mechanisms during OA development. We also discuss the drug development aiming to target this signaling pathway for OA treatment.

The effect of Miya on skeletal muscle changes by regulating gut microbiota in rats with osteoarthritis through AMPK pathway

BACKGROUND

The study aimed to explore whether Miya (MY), a kind of Clostridium butyricum, regulated osteoarthritis (OA) progression through adenosine 5'-monophosphate-activated protein kinase (AMPK) pathway.

METHODS

The OA rats were orally given MY daily for 4 weeks and were intramuscularly injected with AMPK inhibitor once a week for 4 weeks. Hematoxylin eosin (HE) staining was used to observe the histological morphology of the knee joint. The levels of succinate dehydrogenase (SDH) and muscle glycogen (MG) in the tibia muscle of rats were detected by the corresponding kits, as well as the expression of related genes/proteins were assessed by real-time quantitative PCR (RT-qPCR) and western blot.

RESULTS

HE staining suggested that MY suppressed the symptoms of OA, which was abolished by AMPK inhibitor. Furthermore, the SDH and MG contents in the OA + MY + AMPK inhibitor group were lower than in the OA + MY group. At last, the levels of AMPK, PI3K, AKT1, Ldh, Myod, Chrna1, and Chrnd were notably decreased after AMPK inhibitor treatment, while the levels of Lcad and Mcad were up-regulated by AMPK inhibitor. Furthermore, their protein expression levels detected by western blot were consistent with those from RT-qPCR.

CONCLUSION

MY may partially regulate skeletal muscle changes and prevente OA development through the AMPK pathway.

Association between life's simple 7 (LS7) and arthritis: the mediating role of body fat percentage (BFP)

BACKGROUND

Life's Simple 7 (LS7), developed by the American Heart Association, addresses seven key health behaviors and relationship factors. Although LS7 has been studied in relation to various chronic diseases, its association with arthritis remains unclear. This study seeks to investigate the association between LS7 and arthritis, with particular emphasis on the mediating role of body fat percentage (BFP).

METHODS

Data from the 2011-2018 National Health and Nutrition Examination Survey (NHANES), including 16,332 adult participants, were analyzed. The connection between LS7 and arthritis was evaluated using multivariable logistic regression, smooth curve fitting, and subgroup analysis. Mediation analysis assessed the role of BFP in this relationship. Additionally, ROC curve analysis was used to assess the predictive performance of the model, and the Boruta algorithm identified the influential factors associated with arthritis.

RESULTS

After adjusting for relevant covariables, each standard deviation increase in LS7 was linked to a 13% lower likelihood of arthritis [OR = 0.87, 95% CI: 0.84, 0.89]. Participants in the highest LS7 tertile (T3) exhibited a 50% reduced likelihood of developing arthritis compared to those in the lowest tertile (T1) [OR = 0.50, 95% CI: 0.43, 0.60]. Mediation analysis confirmed that BFP significantly mediated the LS7-arthritis relationship. Furthermore, the Boruta algorithm identified LS7 and BFP as key variables associated with arthritis.

CONCLUSION

Elevated LS7 scores were associated with a lower likelihood of arthritis, with BFP serving as a mediating factor. Improving LS7 scores and managing body fat may help prevent arthritis. Due to the study's cross-sectional design, causality cannot be confirmed. Future research should use longitudinal studies to verify these findings and target high-risk groups.

Metformin and fibromyalgia pathophysiology: current insights and promising future therapeutic strategies

Fibromyalgia (FM) is a complex, chronic pain syndrome characterized by widespread musculoskeletal pain, fatigue, and cognitive disturbances. Despite its prevalence, the pathophysiology of FM remains poorly understood, with current treatments often providing limited relief. Recent studies have suggested that metformin, a widely used antidiabetic drug, may have potential therapeutic benefits for chronic pain conditions, including FM. This review aims to provide current insights into the role of metformin in FM pathophysiology, focusing on its neurotransmitter-modulating and anti-inflammatory effects. Metformin has been shown to mitigate neuroinflammation, protect neural tissues, and modulate key neurotransmitters involved in pain and mood regulation. These effects are particularly evident in animal models, where metformin has been observed to reduce pain sensitivity, improve mood-related behaviors, and decrease levels of pro-inflammatory cytokines like interleukin 1-beta (IL-1β). Additionally, the ability of metformin to influence serotonin, norepinephrine, and glutamate levels suggests a potential mechanism for its analgesic and mood-stabilizing effects. However, the current evidence is largely preclinical, and further research is needed to confirm these findings in human studies. This review aims to encourage researchers to explore the association between metformin and FM more deeply, with the hope of uncovering new therapeutic strategies that could offer relief to FM patients.

Ferroptosis and its role in osteoarthritis: mechanisms, biomarkers, and therapeutic perspectives

Osteoarthritis (OA) is one of the leading causes of disability worldwide, characterized by a complex pathological process involving cartilage degradation, synovial inflammation, and subchondral bone remodeling. In recent years, ferroptosis, a form of programmed cell death driven by iron-dependent lipid peroxidation, has been recognized as playing a critical role in the onset and progression of OA. Investigating the molecular mechanisms of ferroptosis and its involvement in OA may offer novel strategies for diagnosing and treating this disease. This review first outlines the core mechanisms of ferroptosis, with a particular focus on the roles of critical molecules such as Glutathione Peroxidase 4 (GPX4), Transferrin Receptor 1 (TfR1), and Nuclear Receptor Coactivator 4 (NCOA4). Subsequently, this study examines the specific impacts of ferroptosis on the pathophysiology of OA. Building on this, the potential of ferroptosis-related biomarkers for OA diagnosis and treatment is highlighted, along with proposed therapeutic strategies targeting ferroptosis regulation. This review aims to deepen the understanding of ferroptosis mechanisms and advance the clinical application of regulatory therapies for OA.

Cellular and molecular mechanisms underlying obesity in degenerative spine and joint diseases

Degenerative spine and joint diseases, including intervertebral disc degeneration (IDD), ossification of the spinal ligaments (OSL), and osteoarthritis (OA), are common musculoskeletal diseases that cause pain or disability to the patients. However, the pathogenesis of these musculoskeletal disorders is complex and has not been elucidated clearly to date. As a matter of fact, the spine and joints are not independent of other organs and tissues. Recently, accumulating evidence demonstrates the association between obesity and degenerative musculoskeletal diseases. Obesity is a common metabolic disease characterized by excessive adipose tissue or abnormal adipose distribution in the body. Excessive mechanical stress is regarded as a critical risk factor for obesity-related pathology. Additionally, obesity-related factors, mainly including lipid metabolism disorder, dysregulated pro-inflammatory adipokines and cytokines, are reported as plausible links between obesity and various human diseases. Importantly, these obesity-related factors are deeply involved in the regulation of cell phenotypes and cell fates, extracellular matrix (ECM) metabolism, and inflammation in the pathophysiological processes of degenerative spine and joint diseases. In this study, we systematically discuss the potential cellular and molecular mechanisms underlying obesity in these degenerative musculoskeletal diseases, and hope to provide novel insights for developing targeted therapeutic strategies.

Sexually dimorphic metabolic effects of a high fat diet on knee osteoarthritis in mice

BACKGROUND

Women have a higher risk of developing osteoarthritis (OA) than men, including with obesity. To better understand this disparity, we investigated sex differences in metabolic and inflammatory factors associated with OA using a diet-induced mouse model of obesity. We hypothesized that 20 weeks of high-fat diet (HFD) would induce sexually dimorphic changes in both systemic and local risk factors of knee OA.

METHODS

Male and female C57BL/6J mice were fed Chow or HFD from 6 to 26 weeks of age (n = 12 per diet and sex). We performed broad metabolic phenotyping, 16 S gut microbiome analysis, targeted gene expression analysis of synovium-infrapatellar fat tissue, targeted gene expression and proteomic analysis of articular cartilage, chondrocyte metabolic profiling, and OA histopathology. Two-way ANOVA statistics were utilized to determine the contribution of sex and diet and their interaction on outcomes.

RESULTS

Mice fed HFD weighed 1.76-fold (p < 0.0001) and 1.60-fold (p < 0.0001) more than male and female Chow cohorts, respectively, with both sexes reaching similar body fat levels (male: 43.9 ± 2.2%; female: 44.1 ± 3.8%). HFD caused greater cartilage pathology (p < 0.024) and synovial hyperplasia (p < 0.038) versus Chow in both sexes. Cartilage pathology was greater in male versus female mice (p = 0.048), and only male mice developed osteophytes with HFD (p = 0.044). Both sexes exhibited metabolic inflexibility on HFD, but only male mice developed glucose intolerance (p < 0.0001), fatty liver (p < 0.0001), and elevated serum amylase (p < 0.0001) with HFD versus Chow. HFD treatment caused sex-dependent differences in gut microbiota beta diversity (p = 0.01) and alteration in specific microbiome clades, such as a HFD-dependent reduction in abundance of Bifidobacterium only in male mice. In knee synovium and infrapatellar fat tissue, HFD upregulated the expression of pro-inflammatory and pro-fibrotic genes predominantly in female mice. In cartilage, lipid metabolism proteins were more abundant with HFD in male mice, whereas proteins involved in glycolysis/gluconeogenesis and biosynthesis of amino acids were greater in cartilage of female mice. Sex-dependent metabolic differences were observed in cartilage from young, healthy mice prior to pubertal maturation, but not in primary juvenile chondrocytes studied in vitro.

CONCLUSIONS

HFD induced numerous sex differences in metabolic and inflammatory outcomes, especially in joint tissues, suggesting that sex-specific cellular processes are involved during development of early-stage OA with obesity.

Targeted non-invasive Metformin-Curcumin co-loaded nanohyaluosomes halt osteoarthritis progression and improve articular cartilage structure: A preclinical study

Osteoarthritis (OA) is a degenerative disease that affects the quality of life in elderly and young populations. Current therapies using corticosteroids and non-steroidal anti-inflammatory drugs via parenteral or oral routes show limited ability to retard progression of the disease and achieve long term effectiveness and safety. Herein, the potential of MT-Cur combinatorial nano-formulations in OA management was explored for the first time. MT-Cur loaded nanohyaluosomes (MT-Cur-HL1) were designed for topical administration of the combined therapy in OA. The optimized MT-Cur-HL1 showed particle size 247.7 ± 3.7 nm, zeta potential -37.3 ± 0.4 mV; and entrapment efficiency (%EE) 70.22 %±0.303 and 76.7 %±0.077 for MT and Cur, respectively. MT-Cur-HL1 exhibited sustained drug release over 24 h and were stable over 3 months at 4 °C in terms of P.S., ZP and %EE. A detailed preclinical study, using MIA-induced osteoarthritis rat model, revealed the most significant anti-arthritic effect and halted OA progression of MT-Cur-HL1. This was proved to be mainly through the potentiation of p-AMPK signaling that ultimately led to suppression of its downstream TLR4/ NF-κB signaling pathway with subsequent reduction in MMP13 and ADAMTS5 induced chondrocytes degeneration. This study proved that this trajectory effectively promotes a significant improvement in the articular cartilage structure and reinforcement of joint mobility with an efficient antinociceptive effect. In conclusion, the novel MT-Cur coloaded nanohyaluosomes offer a promising non-invasive approach for the local management of OA.

Berberine attenuates neuronal ferroptosis via the AMPK-NRF2-HO-1-signaling pathway in spinal cord-injured rats

Ferroptosis, characterized by iron-dependent accumulation of lipid peroxides, plays an important role in spinal cord injury (SCI). Berberine (BBR), as a lipid peroxide scavenger, has been widely used in treating other diseases; however, its role in ferroptosis has not been fully elucidated. Therefore, here, to test our hypothesis that BBR can reduce the severity of SCI and promote motor function recovery by inhibiting neuronal ferroptosis, we evaluated the changes in ferroptosis-related indicators after BBR administration by establishing a cellular ferroptosis model and an SCI contusion model. We found that BBR administration significantly reduces lipid peroxidation damage, maintains normal mitochondrial function, reduces excessive accumulation of iron ions, enhances antioxidant capacity, and activates the ferroptosis defense system in vivo and in vitro. Mechanistically, BBR alleviates neuronal ferroptosis by inducing adenosine monophosphate-activated protein kinase (AMPK) phosphorylation and up-regulating nuclear factor erythroid 2-related factor 2 (NRF2) and heme oxygenase-1 (HO-1) protein expression to promote glutathione production. BBR administration also significantly improves motor function recovery in SCI rats. Meanwhile, applying the AMPK inhibitor Compound C blocks the neuroprotective and all other effects of BBR. Collectively, our findings demonstrate that BBR can attenuate neuronal ferroptosis after SCI by activating the AMPK-NRF2-HO-1 pathway.

The cereblon-AMPK (AMP-activated protein kinase) axis in chondrocytes regulates the pathogenesis of osteoarthritis

OBJECTIVE

AMP-activated protein kinase (AMPK) dysregulation is implicated in osteoarthritis (OA), but the mechanisms underlying this dysregulation remain unclear. We investigated the role of cereblon, a substrate-recognition protein within the E3-ligase ubiquitin complex, in AMPK dysregulation and OA pathogenesis.

METHODS

Cereblon expression was examined in human (n = 5) and mouse (n = 10) OA cartilage. The role of cereblon was investigated through its adenoviral overexpression (n = 10) or knockout (KO, n = 15) in the destabilization of the medial meniscus (DMM)-operated mice. The therapeutic potentials of the chemical cereblon degrader, TD-165, and the AMPK activator, metformin, were assessed through intra-articular (IA) injection to mice (n = 15).

RESULTS

Immunostaining revealed that cereblon is upregulated in human and mouse OA cartilage. In DMM model mice, cartilage destruction was exacerbated by overexpression of cereblon in mouse joint tissues (OARSI grade; 1.11 [95% CI: 0.50 to 2.75]), but inhibited in global (-2.50 [95% CI: -3.00 to -1.17]) and chondrocyte-specific (-2.17 [95% CI: -3.14 to -1.06]) cereblon KO mice. The inhibitory effects were more pronounced in mice fed a high-fat diet compared to a regular diet. The degradation of cereblon through IA injection of TD-165 inhibited OA cartilage destruction (-2.47 [95% CI: -3.22 to -1.56]). Mechanistically, cereblon exerts its catabolic effects by negatively modulating AMPK activity within chondrocytes. Consistently, activation of AMPK by IA injection of metformin inhibited posttraumatic OA cartilage destruction (-1.20 ([95% CI: -1.89 to -0.45]).

CONCLUSIONS

The cereblon-AMPK axis acts as a catabolic regulator of OA pathogenesis and seems to be a promising therapeutic target in animal models of OA.

Rheumatic diseases and metabolism: where centre and periphery meet

Over the past few decades, the connection between metabolism and various inflammatory and rheumatic diseases has been an area of active investigation. Nonetheless, the precise mechanisms underlying these relationships remain a topic of ongoing debate, owing in part to conflicting data. This discrepancy can be attributed to the predominant focus on peripheral mechanisms in research into the metabolic consequences of rheumatic diseases. However, a wealth of evidence supports the notion that the central nervous system, specifically the hypothalamus, has an important influence on metabolic homeostasis. Notably, links have been established between crucial hypothalamic mechanisms responsible for regulating energy balance (including food intake, thermogenesis, and glucose and lipid metabolism), such as AMP-activated protein kinase, and the pathophysiology of rheumatoid arthritis. This Review aims to comprehensively examine the current understanding of central metabolic control in rheumatic diseases and explore potential therapeutic options that target this pathophysiological mechanism.

The Antinociceptive Effects and Sex-Specific Neurotransmitter Modulation of Metformin in a Mouse Model of Fibromyalgia

Fibromyalgia (FM) is a chronic and debilitating condition characterized by diffuse pain, often associated with symptoms such as fatigue, cognitive disturbances, and mood disorders. Metformin, an oral hypoglycemic agent, has recently gained attention for its potential benefits beyond glucose regulation. It has shown promise in alleviating neuropathic and inflammatory pain, suggesting that it could offer a novel approach to managing chronic pain conditions like FM. This study aimed to further explore metformin's analgesic potential by evaluating its effects in an experimental FM model induced by reserpine in both male and female mice. After the administration of 200 mg/kg metformin to male and female mice, the FM-related symptoms were assessed, including mechanical allodynia, thermal hyperalgesia, and depressive-like behaviors. A histological examination of the thalamus, hippocampus, and spinal cord was conducted using haematoxylin and eosin staining. The neurotransmitter and proinflammatory cytokines levels were measured in the brains and spinal cords. Our results have shown that metformin treatment for seven days significantly reversed these FM-like symptoms, reducing pain sensitivity and improving mood-related behaviors in both the male and female mice. Additionally, metformin exhibited neuroprotective effects, mitigating reserpine-induced damage in the hippocampus, thalamus, and spinal cord. It also significantly lowered the levels of the proinflammatory cytokine interleukin 1-beta (IL-1β) in the brain and spinal cord. Notably, metformin modulated the neurotransmitter levels differently between the sexes, decreasing glutamate and increasing serotonin and norepinephrine in the male mice, but not in the females. These findings underscore metformin's potential as an alternative therapy for FM, with sex-specific differences suggesting distinct mechanisms of action.

Is there a genetic relationship between blood glucose and osteoarthritis? A mendelian randomization study

OBJECTIVE

The relationship between blood glucose levels and osteoarthritis (OA) is unclear. This study aimed to investigate the genetic causal relationship between blood glucose-related traits and OA.

METHODS

We first performed univariate Mendelian randomization (UVMR) analyses using published genome-wide association study (GWAS) datasets with fasting glucose (FG), 2 h-glucose post-challenge glucose (2hGlu), and glycosylated hemoglobin (HbA1c) as exposures, and hip osteoarthritis (HOA) and knee osteoarthritis (KOA) as outcomes; then, we performed inverse analyses of them. We used Inverse-variance weighted (IVW) analysis as the primary analysis, and sensitivity analyses were performed. Moreover, we performed multivariate Mendelian randomization (MVMR) to estimate the independent effect of exposure on outcome after adjusting for body mass index (BMI). Summarized data for blood glucose-related traits were obtained from the MAGIC Consortium study of the glucose trait genome and for OA from the UK Biobank and arcOGEN. Summarized data for BMI were obtained from the GIANT Consortium meta-analysis of individuals of European ancestry. A two-sided p value < 0.05 in UVMR was considered suggestive of significance when p < 0.0167 (Bonferroni correction p = 0.05/3 exposures) was considered statistically significant.

RESULTS

We found significant negative genetic causality of FG for HOA and KOA, and these associations remained significant after we adjusted for the effect of BMI [odds ratios (ORs) of 0.829 (0.687-0.999, p = 0.049) and 0.741 (0.570-0.964, p = 0.025)]. HbA1c also had an independent negative genetic causal effect on HOA after adjustment for BMI [0.665 (0.463-0.954, p = 0.027)]. At the same time, there was no evidence of reverse genetic causality of OA on blood glucose-related traits.

CONCLUSION

We further elucidated the relationship between blood glucose-related traits and OA by adjusting for the effect of BMI from a genetic causal perspective. This study provides new insights to further clarify the relationship between blood glucose levels and OA, as well as the pathogenesis, etiology and genetics of OA.

Acacetin targets STING to alleviate the destabilization of the medial meniscus-induced osteoarthritis in mice

Osteoarthritis (OA) is a common joint disorder affecting about 7% of the global population, primarily characterized by the gradual loss of articular cartilage. This degeneration results from local inflammation, matrix depletion, and direct cartilage damage. A critical element in this process is the activation of the stimulator of the interferon genes (STING) pathway. Emerging evidence highlights its potential as a therapeutic target, with natural products showing promise as inhibitors. Our study centers on Acacetin, a basic unit of polyketides known for its anti-inflammatory properties. Prior research has highlighted its potential interaction with STING based on the structure. Thus, this study aimed to assess the effectiveness of Acacetin as a STING inhibitor and its protective role against OA. In vitro experiments showed that Acacetin pretreatment not only mitigated interleukin-1β (IL-1β)-induced cytotoxicity but also decreased the inflammatory response and degeneration in chondrocytes stimulated IL-1β. In vivo studies revealed that Acacetin administration significantly reduced articular cartilage destruction, abnormal bone remodeling, and osteophyte formation in a model of OA induced by destabilization of the medial meniscus (DMM). Mechanistically, Acacetin was found to interact directly with STING, and inhibit IL-1β-induced activation of STING, along with the subsequent phosphorylation of the TBK1/NF-κB pathway in chondrocytes. In conclusion, our findings establish Acacetin as an effective inhibitor of STING that protects chondrocytes from IL-1β-induced damage and slows the progression of OA in mice.

Deapi-platycodin D3 attenuates osteoarthritis development via suppression of PTP1B

Dysregulated chondrocyte metabolism is an essential risk factor for osteoarthritis (OA) progression. Maintaining cartilage homeostasis represents a promising therapeutic strategy for the treatment of OA. However, no effective disease-modifying therapy is currently available to OA patients. To discover potential novel drugs for OA, we screened a small-molecule natural product drug library and identified deapi-platycodin D3 (D-PDD3), which was subsequently tested for its effect on extracellular matrix (ECM) properties and on OA progression. We found that D-PDD3 promoted the generation of ECM components in cultured chondrocytes and cartilage explants and that intra-articular injection of D-PDD3 delayed disease progression in a trauma-induced mouse model of OA. To uncover the underlying molecular mechanisms supporting these observed functions of D-PDD3, we explored the targets of D-PDD3 via screening approach integrating surface plasmon resonance with liquid chromatography-tandem mass spectrometry. The results suggested that D-PDD3 targeted tyrosine-protein phosphatase non-receptor type 1 (PTP1B), deletion of which restored chondrocyte homeostasis and markedly attenuated destabilization of the medial meniscus induced OA. Further cellular and molecular analyses showed that D-PDD3 maintained cartilage homeostasis by directly binding to PTP1B and consequently suppressing the PKM2/AMPK pathway. These findings demonstrated that D-PDD3 was a potential therapeutic drug for the treatment of OA and that PTP1B served as a protein target for the development of drugs to treat OA. This study provided significant insights into the development of therapeutics for OA treatment, which, in turn, helped to improve the quality of life of OA patients and to reduce the health and economic burden.

lncRNA OIP5-AS1 promotes mitophagy to alleviate osteoarthritis by upregulating PPAR-γ to activate the AMPK/Akt/mTOR pathway

OBJECTIVES

Osteoarthritis (OA) is the most common chronic joint degenerative disease. Herein, we investigated long non-coding RNA Opa-interacting protein 5-antisense transcript 1's (OIP5-AS1) in regulating mitophagy during OA.

METHODS

RNA immunoprecipitation and RNA pull-down verified the relationship between molecules. Cell counting kit-8 detected cell viability. Enzyme-linked immunosorbent assay evaluated inflammatory cytokines secretion. Flow cytometry measured the contents of reactive oxygen species (ROS) and calcium. Immunofluorescence staining analysed TOMM20 and LC3B levels. JC-1 staining was adopted to measure mitochondrial membrane potential. The changes of mitophagy were analysed by transmission electron microscopy.

RESULTS

Lipopolysaccharide (LPS) treatment contributed to the decrease of chondrocyte viability, and calcium level and inhibited mitochondrial membrane potential, while elevating the secretion of inflammatory factors, ROS, and TOMM20 expression. OIP5-AS1 overexpression inhibited LPS-induced chondrocyte injury and activated mitophagy. OIP5-AS1 upregulated the peroxisome proliferator-activated receptor-γ (PPAR-γ) mRNA level to regulate adenosine monophosphate-activated protein kinase (AMPK)/v-akt murine thymoma viral oncogene homolog (Akt)/mammalian target of rapamycin (mTOR) signalling by interacting with FUS. PPAR-γ overexpression alleviated LPS-induced chondrocyte injury by activating AMPK/Akt/mTOR signalling. PPAR-γ knockdown reversed the promotion of OIP5-AS1 upregulation on mitophagy.

CONCLUSIONS

OIP5-AS1 promotes PPAR-γ expression to activate the AMPK/Akt/mTOR signalling, thereby enhancing mitophagy and alleviating OA progression.

Ginger-derived nanovesicles attenuate osteoarthritis progression by inhibiting oxidative stress via the Nrf2 pathway

Aim: Osteoarthritis (OA) is a common degenerative joint disease. Previous studies demonstrated ginger-derived exosome-like nanovesicles (GDN) showed therapeutic effects in degenerative diseases. However, it remains unknown whether GDN could alleviate OA progression.Materials & methods: In this study, GDN were obtained and characterized. Then we evaluated the effects of GDN in tert-butyl hydroperoxide (TBHP)-induced chondrocytes, posttraumatic OA rat model and ex vivo cultured human OA cartilage explants.Results: We demonstrated GDN promoted cartilage anabolism and alleviated oxidative stress in TBHP-induced chondrocytes and OA rat. Our results also showed GDN exhibited protective effects in cultured cartilage explants. Furthermore, we verified the Nrf2 pathway was associated with protective effects of GDN.Conclusion: Altogether, our findings demonstrated GDN hold great potential for OA treatment.

Advances in targeted therapies for age-related osteoarthritis: A comprehensive review of current research

Osteoarthritis (OA) is a common degenerative joint disease that disproportionately impacts the elderly population on a global scale. As aging is a significant risk factor for OA, there is a growing urgency to develop specific therapies that target the underlying mechanisms of aging associated with this condition. This summary seeks to offer a thorough introduction of ongoing research efforts aimed at developing therapies to combat senescence in the context of OA. Cellular senescence plays a pivotal role in both the deterioration of cartilage integrity and the perpetuation of chronic inflammation and tissue remodeling. Consequently, targeting SnCs has emerged as a promising therapeutic approach to alleviate symptoms and hinder the progression of OA. This review examines a range of approaches, including senolytic drugs targeting SnCs, senomorphics that modulate the senescence-associated secretory phenotype (SASP), and interventions that enhance immune system clearance of SnCs. Novel methodologies, such as utilizing novel materials for exosome delivery and administering anti-aging medications with precision, offer promising avenues for the precise treatment of OA. Accumulating evidence underscores the potential of targeting senescence in OA management, potentially facilitating the development of more effective and personalized therapeutic interventions.

Mitochondrial quality control dysfunction in osteoarthritis: Mechanisms, therapeutic strategies & future prospects

Osteoarthritis (OA) is a prevalent chronic joint disease characterized by articular cartilage degeneration, pain, and disability. Emerging evidence indicates that mitochondrial quality control dysfunction contributes to OA pathogenesis. Mitochondria are essential organelles to generate cellular energy via oxidative phosphorylation and regulate vital processes. Impaired mitochondria can negatively impact cellular metabolism and result in the generation of harmful reactive oxygen species (ROS). Dysfunction in mitochondrial quality control mechanisms has been increasingly linked to OA onset and progression. This review summarizes current knowledge on the role of mitochondrial quality control disruption in OA, highlighting disturbed mitochondrial dynamics, impaired mitochondrial biogenesis, antioxidant defenses and mitophagy. The review also discusses potential therapeutic strategies targeting mitochondrial Quality Control in OA, offering future perspectives on advancing OA therapeutic strategies.

Interplay of Glucose Metabolism and Hippo Pathway in Chondrocytes: Pathophysiology and Therapeutic Targets

In this review, we explore the intricate relationship between glucose metabolism and mechanotransduction pathways, with a specific focus on the role of the Hippo signaling pathway in chondrocyte pathophysiology. Glucose metabolism is a vital element in maintaining proper chondrocyte function, but it has also been implicated in the pathogenesis of osteoarthritis (OA) via the induction of pro-inflammatory signaling pathways and the establishment of an intracellular environment conducive to OA. Alternatively, mechanotransduction pathways such as the Hippo pathway possess the capacity to respond to mechanical stimuli and have an integral role in maintaining chondrocyte homeostasis. However, these mechanotransduction pathways can be dysregulated and potentially contribute to the progression of OA. We discussed how alterations in glucose levels may modulate the Hippo pathway components via a variety of mechanisms. Characterizing the interaction between glucose metabolism and the Hippo pathway highlights the necessity of balancing both metabolic and mechanical signaling to maintain chondrocyte health and optimal functionality. Furthermore, this review demonstrates the scarcity of the literature on the relationship between glucose metabolism and mechanotransduction and provides a summary of current research dedicated to this specific area of study. Ultimately, increased research into this topic may elucidate novel mechanisms and relationships integrating mechanotransduction and glucose metabolism. Through this review we hope to inspire future research into this topic to develop innovative treatments for addressing the clinical challenges of OA.

Pip5k1γ promotes anabolism of nucleus pulposus cells and intervertebral disc homeostasis by activating CaMKII-Ampk pathway in aged mice

Degenerative disc disease (DDD) represents a significant global health challenge, yet its underlying molecular mechanisms remain elusive. This study aimed to investigate the role of type 1 phosphatidylinositol 4-phosphate 5-kinase (Pip5k1) in intervertebral disc (IVD) homeostasis and disease. All three Pip5k1 isoforms, namely Pip5k1α, Pip5k1β, and Pip5k1γ, were detectable in mouse and human IVD tissues, with Pip5k1γ displaying a highest expression in nucleus pulposus (NP) cells. The expression of Pip5k1γ was significantly down-regulated in the NP cells of aged mice and patients with severe DDD. To determine whether Pip5k1γ expression is required for disc homeostasis, we generated a Pip5k1γfl/fl; AggrecanCreERT2 mouse model for the conditional knockout of the Pip5k1γ gene in aggrecan-expressing IVD cells. Our findings revealed that the conditional deletion of Pip5k1γ did not affect the disc structure or cellular composition in 5-month-old adult mice. However, in aged (15-month-old) mice, this deletion led to several severe degenerative disc defects, including decreased NP cellularity, spontaneous fibrosis and cleft formation, and a loss of the boundary between NP and annulus fibrosus. At the molecular level, the absence of Pip5k1γ reduced the anabolism of NP cells without markedly affecting their catabolic or anti-catabolic activities. Moreover, the loss of Pip5k1γ significantly dampened the activation of the protective Ampk pathway in NP cells, thereby accelerating NP cell senescence. Notably, Pip5k1γ deficiency blunted the effectiveness of metformin, a potent Ampk activator, in activating the Ampk pathway and mitigating lumbar spine instability (LSI)-induced disc lesions in mice. Overall, our study unveils a novel role for Pip5k1γ in promoting anabolism and maintaining disc homeostasis, suggesting it as a potential therapeutic target for DDD.

The role of obesity and adipose tissue dysfunction in osteoarthritis pain

Obesity has a pivotal and multifaceted role in pain associated with osteoarthritis (OA), extending beyond the mechanistic influence of BMI. It exerts its effects both directly and indirectly through various modifiable risk factors associated with OA-related pain. Adipose tissue dysfunction is highly involved in OA-related pain through local and systemic inflammation, immune dysfunction, and the production of pro-inflammatory cytokines and adipokines. Adipose tissue dysfunction is intricately connected with metabolic syndrome, which independently exerts specific effects on OA-related pain, distinct from its association with BMI. The interplay among obesity, adipose tissue dysfunction and metabolic syndrome influences OA-related pain through diverse pain mechanisms, including nociceptive pain, peripheral sensitization and central sensitization. These complex interactions contribute to the heightened pain experience observed in individuals with OA and obesity. In addition, pain management strategies are less efficient in individuals with obesity. Importantly, therapeutic interventions targeting obesity and metabolic syndrome hold promise in managing OA-related pain. A deeper understanding of the intricate relationship between obesity, metabolic syndrome and OA-related pain is crucial and could have important implications for improving pain management and developing innovative therapeutic options in OA.

Injectable porous microspheres for articular cartilage regeneration through in situ stem cell recruitment and macrophage polarization

In situ mesenchymal stem cells (MSCs) regenerative therapy holds promising potential for treating osteoarthritis. However, MSCs engraftment and intra-articular inflammation limit the therapeutic efficacy of this approach. This study introduces porous microspheres (PMs) composed of aldehyde-modified poly(lactic-co-glycolic acid), that encapsulate platelet derived growth factor-AB and kartogenin. Metformin (Met) is also incorporated onto the microsphere through a Schiff base reaction to create PMs@Met. In vitro, in vivo and ex experiments revealed that PMs@Met can be injected into the joint cavity, effectively recruiting endogenous MSCs in situ. This approach creates a favorable environment for MSCs proliferation. It also controls the intra-articular inflammatory environment by modulating the polarization of synovial macrophages, ultimately promoting cartilage repair. In summary, our study presents an innovative tissue engineering strategy for the treatment of osteoarthritis-induced articular cartilage injuries. STATEMENT OF SIGNIFICANCE: Cell therapy using autologous mesenchymal stem cells (MSCs) has potential to slow the progression of osteoarthritis (OA). Nonetheless, there are some disadvantages to adopting in situ MSCs therapy, including difficulties with MSC engraftment into cartilage-deficient regions, the effect of intra-articular inflammation on MSC therapeutic efficacy, and attaining selective chondrogenic MSC differentiation. We created injectable PLGA microspheres (PMs) that were loaded with PDGF-AB and KGN. Metformin was bonded to the surface of microspheres using a Schiff base reaction. The microspheres can recruit intra-articular MSCs and encourage their development into chondrocytes. The microspheres actively modulate the inflammatory joint environment by altering synovial macrophage polarization, thereby supporting MSCs in effective cartilage treatment. To summarize, microspheres hold great potential in the treatment of OA.

Exploring antidiabetic drug targets as potential disease-modifying agents in osteoarthritis

BACKGROUND

Osteoarthritis is a leading cause of disability, and disease-modifying osteoarthritis drugs (DMOADs) could represent a pivotal advancement in treatment. Identifying the potential of antidiabetic medications as DMOADs could impact patient care significantly.

METHODS

We designed a comprehensive analysis pipeline involving two-sample Mendelian Randomization (MR) (genetic proxies for antidiabetic drug targets), summary-based MR (SMR) (for mRNA), and colocalisation (for drug-target genes) to assess their causal relationship with 12 osteoarthritis phenotypes. Summary statistics from the largest genome-wide association meta-analysis (GWAS) of osteoarthritis and gene expression data from the eQTLGen consortium were utilised.

FINDINGS

Seven out of eight major types of clinical antidiabetic medications were identified, resulting in fourteen potential drug targets. Sulfonylurea targets ABCC8/KCNJ11 were associated with increased osteoarthritis risk at any site (odds ratio (OR): 2.07, 95% confidence interval (CI): 1.50-2.84, P < 3 × 10-4), while PPARG, influenced by thiazolidinediones (TZDs), was associated with decreased risk of hand (OR: 0.61, 95% CI: 0.48-0.76, P < 3 × 10-4), finger (OR: 0.50, 95% CI: 0.35-0.73, P < 3 × 10-4), and thumb (OR: 0.49, 95% CI: 0.34-0.71, P < 3 × 10-4) osteoarthritis. Metformin and GLP1-RA, targeting GPD1 and GLP1R respectively, were associated with reduced risk of knee and finger osteoarthritis. In the SMR analyses, gene expression of KCNJ11, GANAB, ABCA1, and GSTP1, targeted by antidiabetic drugs, was significantly linked to at least one osteoarthritis phenotype and was replicated across at least two gene expression datasets. Additionally, increased KCNJ11 expression was related to decreased osteoarthritis risk and co-localised with at least one osteoarthritis phenotype.

INTERPRETATION

Our findings suggest a potential therapeutic role for antidiabetic drugs in treating osteoarthritis. The results indicate that certain antidiabetic drug targets may modify disease progression, with implications for developing targeted DMOADs.

FUNDING

This study was funded by the Shanghai Municipal Education Commission-Gaofeng Clinical Medicine Grant (2022), the Shanghai Municipal Health Commission Health Industry Clinical Research Project (Grant No. 20224Y0139), Beijing Natural Science Foundation (Grant No. 7244458), and the Postdoctoral Fellowship Program (Grade C) of China Postdoctoral Science Foundation (Grant No. GZC20230130).

Causal factors for osteoarthritis risk revealed by mendelian randomization analysis

Osteoarthritis (OA), a prevalent chronic disease among the elderly, presents a complex pathogenesis and currently lacks effective treatment. Traditional observational studies are time-consuming, labor-intensive, susceptible to confounding factors, and cannot establish causal relationships. Mendelian randomization (MR) analysis, leveraging genetic variation to assess causal associations between exposures and outcomes, offers a cost-effective and efficient alternative. Over the past decade, large-scale genome-wide association studies have identified numerous genetic variants linked to OA risk factors, facilitating MR study design. In this review, we systematically identified 52 MR studies meeting specific criteria and evaluated their quality, exploring the impact of lifestyle, nutrition, comorbidities, circulating metabolites, plasma proteins, and other health factors on OA risk. We discuss the results and potential mechanisms of MR findings, addressing conflicting evidence based on existing literature and our prior research. With the ongoing expansion of genome-wide association data, we anticipate MR's role in future OA studies to broaden, particularly in drug development research using targeted MR approaches. We thus aim for this paper to offer valuable insights for researchers and clinicians in related fields.

Metformin relieves bone cancer pain by reducing TGFβRI-TRPV1 signaling in rats

Common cancer complications include bone cancer pain (BCP), which was not sufficiently alleviated by traditional analgesics. More safe and effective therapy was urgent needed. Metformin relieved osteoarthritis pain, but the analgesia of Metformin in BCP was not well studied. The study aimed to explore the Metformin-mediated analgesic effect and its molecular mechanisms in BCP rats. We demonstrated that Walker 256 cell transplantation into the medullary cavity of the tibia worsened mechanical allodynia in BCP rats, increased the expression of TGFβ1 in the metastatic bone tissue, and raised the expression of TGFβRI and TRPV1 in the L4-6 dorsal root ganglion (DRG) of BCP rats. While, selectively blockade of TGFβRI by SD208 could obviously elevated the paw withdraw threshold (PWT) of BCP rats, together with decreased TRPV1 expression in L4-6 DRG. Notably, continuous Metformin treatment reduced TGFβ1, TGFβRI and TRPV1 expression, and relieved mechanical allodynia of BCP rats in a long-term effect. In conclusion, these results illustrated that Metformin ameliorated bone cancer pain, and the downregulation of TGFβ1-TGFβRI-TRPV1 might be a potential mechanism of Metformin-mediated analgesia in BCP.

A Novel BD2-Selective Inhibitor of BRDs Mitigates ROS Production and OA Pathogenesis

Bromodomain and extra-terminal domain (BET) family proteins regulate transcription and recognize lysine residues in histones. Selective BET inhibitors targeting one domain have attracted attention because they maintain normal physiological activities, whereas pan (nonselective) BET inhibitors do not. Osteoarthritis (OA) is a joint disorder characterized by cartilage degeneration for which no treatment currently exists. Here, we investigated whether the selective inhibition of BET proteins is an appropriate therapeutic strategy for OA. We focused on the development and characterization of 2-(4-(2-(dimethylamino)ethoxy)-3,5-dimethylphenyl)-5,7-dimethoxyquinazolin-4(3H)-one (BBC0906), a novel bromodomain 2 (BD2)-specific inhibitor designed to suppress OA progression. Using a DNA-encoded chemical library (DEL) screening approach, BBC0906 was identified because of its high affinity with the BD2 domain of BET proteins. BBC0906 effectively reduced reactive oxygen species (ROS) production and suppressed catabolic factor expression in chondrocytes in vitro. Moreover, in an OA mouse model induced by the destabilization of the medial meniscus (DMM), BBC0906 intra-articular injection attenuated cartilage degradation and alleviated OA. Importantly, BBC0906 selectively inhibits the BD2 domain, thus minimizing its potential side effects. We highlighted the therapeutic potential of targeting BET proteins to modulate oxidative stress and suppress cartilage degradation in OA. BBC0906 is a promising candidate for OA treatment, offering improved safety and efficacy.