Causal association of adipokines with osteoarthritis: a Mendelian randomization study

Risk factors for the development of knee osteoarthritis across the lifespan: A systematic review and meta-analysis

OBJECTIVE

To identify and quantify risk factors for incident knee osteoarthritis (KOA) across the lifespan.

METHODS

This systematic review and meta-analysis identified eligible studies from seven electronic databases and three registries. Longitudinal cohort studies or randomised controlled trials evaluating participants who developed incident symptomatic and/or radiographic KOA were included. Two independent reviewers completed data screening and extraction. Estimates were pooled using a random effects model and reported as odds ratio (OR), hazard ratio, or risk ratio and corresponding 95% confidence intervals (95% CI). Grading of Recommendations, Assessment, Development and Evaluation was used to determine the certainty of evidence. Population attributable fractions were calculated, including risk factors significantly associated with radiographic KOA based on the pooled meta-analysis and where we could determine communality scores using existing clinical datasets.

RESULTS

We identified 131 studies evaluating > 150 risk factors. Previous knee injury, older age and high bone mineral density were associated with an increased risk of incident radiographic KOA based on the pooled analysis [OR (95% CI): 2.67 (1.41, 5.05), 1.15 (1.00, 1.33) and 1.82 (1.12, 2.94), respectively], with moderate-to-high certainty. Two risk factors (overweight/obesity and previous knee injury) accounted for 14% of incident radiographic KOA. Other modifiable risk factors, including occupational physical activity, also contribute to radiographic or symptomatic KOA.

CONCLUSION

Novel strategies addressing known modifiable risk factors including overweight/obesity, knee injuries and occupational physical activity are needed to reduce overall burden of KOA.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO ID: CRD42023391187.

The Impact of Ketogenic Nutrition on Obesity and Metabolic Health: Mechanisms and Clinical Implications

The ketogenic diet (KD) has recently gained increasing popularity. This high-fat, adequate-protein, and carbohydrate-poor eating pattern leads to nutritional ketosis. The KD has long been known for its antidiabetic and antiepileptic effects and has been used therapeutically in these contexts. Recently, the KD, due to its effectiveness in inducing weight loss, has also been proposed as a possible approach to treat obesity. Likewise, a KD is currently explored as a supporting element in the treatment of obesity-associated metabolic disorders and certain forms of cancer. Here, we discuss the metabolic and biochemical mechanisms at play during the shift of metabolism to fatty acids and fatty acid-derived ketone bodies as main fuel molecules, in the substitution of carbohydrates, in ketogenic nutrition. Different sources of ketone bodies and KDs as alternatives to glucose and carbohydrates as main energy substrates are discussed, together with an attempt to weigh the benefits and risks posed by the chronic use of a KD in the context of weight loss, and also considering the molecular effects that ketone bodies exert on metabolism and on the endocrine system.

Polyunsaturated fatty acids may not be helpful for people with osteoarthritis: a two-sample Mendelian randomization analysis

In recent years, researchers have examined the use of polyunsaturated fatty acids (PUFA) or a low omega-6/3 ratio to protect the knee joint. The current study is based on genome-wide association study (GWAS) analysis and uses the Mendelian randomization (MR) method to evaluate the effect of total PUFA, omega-3, omega-6, and omega-6/3 ratios on osteoarthritis (OA). First, we downloaded the latest PUFA and OA GWAS data. The PUFA data were divided into four groups: total PUFA, omega-3, omega-6, and omega-6/3 ratios. The OA data were split into nine groups: hip OA (total, males, and females), knee OA (total, males, and females), and hand OA (total, males, and females). Then, qualified SNPs were selected as instrumental variables. Inverse variance weighting (IVW), weighted median, and the MR‒Egger method were used for MR analysis. Finally, MR‒Egger, MR-Presso, and Cochran's Q statistical methods were used to evaluate the heterogeneity and pleiotropy. Thirty-six IVW results showed that total PUFA, omega-3, omega-6, and omega-6/3 ratios did not significantly increase or decrease the risk of knee, hip, and hand OA. The IVW results of the effect of PUFA on OA (male and female) were as follows: total PUFA-knee OA (OR: 0.97, 95% CI: 0.92-1.02, P = 0.283); total PUFA-hip OA (OR: 1.01, 95% CI: 0.93-1.08, P = 0.806); total PUFA-hand OA (OR: 0.99, 95% CI: 0.91-1.07, P = 0.896). There was no obvious horizontal polytropy in all the analyses, and there was heterogeneity in some analyses. Our study does not indicate that total PUFA, mega-3, and low omega-6/3 ratios are helpful for people with OA, nor does it indicate that omega-6 increases the risk of OA. The dietary management of PUFA in OA patients needs to be performed cautiously.

Extracecellulr vesicles (EVs) microRNAs (miRNAs) derived from mesenchymal stem cells (MSCs) in osteoarthritis (OA); detailed role in pathogenesis and possible therapeutics

The primary cause of pain and disability in the world is osteoarthritis (OA), a common joint disease characterized by the primary pathological alteration in articular cartilage deterioration. The general outcome of treatment is not acceptable despite current interventions. Therefore, joint replacement surgery is frequently needed by patients with severe OA. Mesenchymal stem cells (MSCs) have become a practical treatment choice for preclinical and clinical OA palliation in recent years, mainly due to their unique immunomodulatory attributes. Further, attractive candidates for cell-free therapy for OA are MSC-derived extracecellulr vesicles (EVs) that convey bioactive molecules of the original cells, such as microRNAs. These EVs have been shown to significantly influence the regulation of various physiological activities of cells in the joint cavity. Dysregulated miRNAs upregulate the synthesis of enzymes that degrade cartilage, downregulate the expression of components in the cartilage matrix, promote the production of proinflammatory cytokines, induce programmed cell death in chondrocytes, inhibit the process of autophagy in chondrocytes, and participate in pathways related to pain. MiRNAs are also found in extracellular membranous vesicles (EVs), such as exosomes, and play a role in intercellular communication in osteoarthritic joints. Thus, the biosynthesis, chemical makeup, and mechanism of action of miRNAs-enriched EVs in OA are all thoroughly covered in this review. We additionally discussed how miRNA-enriched MSC-EVs might be used therapeutically to change intercellular interaction in OA.

Metabolism-Related Adipokines and Metabolic Diseases: Their Role in Osteoarthritis

Osteoarthritis (OA) affects several joints but tends to be more prevalent in those that are weight-bearing, such as the knees, which are the most heavily loaded joints in the body. The incidence and disability rates of OA have continued to increase and seriously jeopardise the quality of life of middle-aged and older adults. However, OA is more than just a wear and tear disease; its aetiology is complex, and its pathogenesis is poorly understood. Metabolic syndrome (MetS) has emerged as a critical driver of OA development. This condition contributes to the formation of a distinct phenotype, termed metabolic syndrome-associated osteoarthritis (MetS-OA),which differs from other metabolically related diseases by its unique pathophysiological mechanisms and clinical presentation. As key mediators of MetS, metabolic adipokines such as leptin, lipocalin, and resistin regulate inflammation and bone metabolism through distinct or synergistic signaling pathways. Their modulation of inflammatory responses and bone remodeling processes plays a critical role in the pathogenesis and progression of OA. Due to their central role in regulating inflammation and bone remodeling, metabolic adipokines not only deepen our understanding of MetS-OA pathogenesis but also represent promising targets for novel therapeutic strategies that could slow disease progression and improve clinical outcomes in affected patients.

The impact of coffee consumption on osteoarthritis: insights from NHANES and Mendelian randomization analysis

Background

Osteoarthritis (OA) is a prevalent degenerative joint condition, and emerging evidence suggests that dietary factors, such as coffee consumption, may influence its risk. However, the relationship between coffee consumption and the risk of developing OA remains ambiguous. This study aims to explore the association between coffee intake and OA complemented by Mendelian randomization (MR) to infer causality.

Materials and methods

We analyzed data from 32,439 participants across 10 NHANES cycles (1999-2018), including 3,676 individuals diagnosed with OA. Osteoarthritis was diagnosed through a structured questionnaire, while coffee consumption was assessed via 24-h dietary recalls. Participants were categorized based on reported coffee intake: 0 cups, <2 cups, 2-4 cups, and >4 cups per day. We employed weighted multivariable logistic regression to examine associations between coffee consumption and OA by using data from the NHANES 1999-2018, adjusting for various covariates. Subsequently, a MR analysis was conducted using genetic variants as instrumental variables to infer causal relationships, with multiple methods including inverse-variance weighted (IVW) analysis, MR-Egger regression, and weighted median techniques to assess the robustness, heterogeneity, and potential pleiotropy of our findings.

Results

Our regression models indicated an increased risk of OA with rising coffee consumption, with significant associations noted particularly for those consuming more than 4 cups daily (OR = 1.19, 95% CI: 1.00-1.41, p = 0.049). In MR analysis, coffee intake was causally linked to OA types, demonstrating increased risk for knee OA (KOA: OR = 1.60, 95% CI: 1.08-2.35, p = 0.018), hip OA (HOA: OR = 1.85, 95% CI: 1.06-3.25, p = 0.031), and combined KOA and HOA (KHOA: OR = 1.66, 95% CI: 1.18-2.33, p = 0.003). Sensitivity analyses confirmed the stability of results across multiple evaluation methods.

Conclusion

Our findings highlight a significant association between coffee consumption and an increased risk of OA, suggesting that higher intake levels may contribute to OA morbidity. These results warrant further exploration into the underlying biological mechanisms and implications for dietary guidelines in populations at risk for OA.

Regulating lipid metabolism in osteoarthritis: a complex area with important future therapeutic potential

BACKGROUND

Osteoarthritis (OA), which is characterized by pain, inflammation and pathological changes, is associated with abnormal lipid metabolism. Extensive studies have been conducted on the potential functions of lipids including cholesterol, fatty acids (FAs) and adipokines.

MATERIALS AND METHODS

By searching and screening the literature included in the PubMed and Web of Science databases from 1 January 2019 to 1 January 2024, providing an overview of research conducted on lipid metabolism and OA in the last 5 years.

RESULTS

In addition to adiponectin, several studies on the effects of lipid metabolism on OA have been consistent and complementary. Total cholesterol, triglycerides, low-density lipoprotein cholesterol, adipsin, leptin, resistin, saturated FAs, monounsaturated FAs, FA-binding protein 4 and the ratios of the FAs hexadecenoylcarnitine (C16:1) to dodecanoylcarnitine and C16:1 to tetradecanoylcarnitine induced mostly deleterious effects, whereas high-density lipoprotein cholesterol and apolipoprotein A/B/D had a positive impact on the health of joints. The situation for polyunsaturated FAs may be more complicated, as omega-3 increases the genetic susceptibility to OA, whereas omega-6 does the opposite.

Alterations in lipid or adipokine levels and the resulting pathological changes in cartilage and other tissues (such as bone and synovium) ultimately affect joint pain, inflammation and cartilage degradation. Lipid or adipokine regulation has potential as a future direction for the treatment of OA, this potential avenue of OA treatment requires high-quality randomized controlled trials of combined lipid regulation therapy, and more in-depth in vivo and in vitro studies to confirm the underlying mechanism.

Associations between folate intake and knee pain, inflammation mediators and comorbid conditions in patients with symptomatic knee osteoarthritis

BACKGROUND

To investigate the associations between folate intake and changes in knee pain, inflammation mediators and comorbid conditions over 2 years in patients with symptomatic knee osteoarthritis (OA).

METHODS

A post-hoc analysis was performed based on data from the VIDEO study, a multicenter, randomized, double-blind, placebo-controlled clinical trial aimed at assessing the impact of vitamin D supplementation on patients with knee OA who were also vitamin D deficient. The original trial's design and inclusion and exclusion criteria were integrated into this subsequent post-hoc analysis. The average daily folate intake was evaluated using the Dietary Questionnaire for Epidemiological Studies version 2 over two years. The progression of knee symptoms was monitored at the baseline and then at months 3, 6, 12, and 24, utilizing the Western Ontario and McMaster Universities Index alongside a 100-mm visual analog scale. Levels of serum inflammatory mediators were quantified using ELISA techniques. Assessments of knee joint structures, leg muscle strength, depressive symptoms, feet pain, and low back pain were treated at both baseline and follow-up intervals.

RESULTS

Folate intake was correlated with reductions in overall knee pain, dysfunction, and stiffness, as well as decreased levels of Leptin and Apelin. Additionally, it was associated with enhanced leg muscle strength and diminished feet and low back pain. However, there is no association between folate intake and alterations in serum cytokine levels or knee joint structural changes. Within the subsets of overall knee pain, a significant relationship was identified between folate intake and the reduction of pain experienced when ascending or descending stairs and standing for two years.

CONCLUSIONS

Folate intake was linked with reduced knee pain, lower levels of adipokines, and a decreased prevalence of comorbid conditions in individuals with knee OA, implying that folate consumption may be associated with an improvement in knee OA symptoms, but further research is needed to verify this association.

Association of lipid levels, adipokines and multiple myeloma: a two-sample multivariate Mendelian randomization study

Many observational studies and experiments have found a strong association between lipid levels and adipokines and multiple myeloma (MM), but the causal relationship between lipid levels, adipokines and MM remains to be determined. We performed a two-sample and multivariate MR analysis to investigate the causal relationship between lipid levels, adipokines and MM. Total cholesterol(TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), and triglycerides (TG) were used to represent lipid levels, and adiponectin, leptin, and resistin were used to represent adipokines. Genetic data for each index and MM were obtained from the Integrated Epidemiology Unit (IEU) Genome-Wide Association Study (GWAS) database, and two-sample MR analyses were performed, as well as multivariate MR analyses of adipokines for causality of MM using BMI as an adjusting factor. In the analyzed results, no significant causal association was found between adipokines, lipid levels and multiple myeloma, and after adjusting for BMI, an association between adipokines and MM was still not found. The results of this MR study do not support an association between genetically predicted adipokines, lipid levels, and risk of MM, but we cannot rule out the existence of a weak association. The mechanisms need to be further investigated.

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.

Exploring the causal association between frailty index with the common types of arthritis: a Mendelian randomization analysis

BACKGROUND

Previous observational studies indicated a complex association between frailty and arthritis.

AIMS

To investigate the genetic causal relationship between the frailty index and the risk of common arthritis.

METHODS

We performed a large-scale Mendelian randomization (MR) analysis to assess frailty index associations with the risk of common arthritis in the UK Biobank (UKB), and the FinnGen Biobank. Summary genome-wide association statistics for frailty, as defined by the frailty index, and common arthritis including rheumatoid arthritis (RA), osteoarthritis (OA), psoriatic arthritis (PSA), and ankylosing spondylitis (AS). The inverse-variance weight (IVW) method served as the primary MR analysis. Heterogeneity testing and sensitivity analysis were also conducted.

RESULTS

Our results denoted a genetic association between the frailty index with an increased risk of OA, the odds ratio (OR)IVW in the UKB was 1.03 (95% confidence interval [CI]: 1.01-1.05; P = 0.007), and ORIVW was 1.55 (95% CI: 1.16-2.07; P = 0.003) in the FinnGen. For RA, the ORIVW from UKB and FinnGen were 1.03 (1.01-1.05, P = 0.006) and 4.57 (1.35-96.49; P = 0.025) respectively. For PSA, the frailty index was associated with PSA (ORIVW = 4.22 (1.21-14.67), P = 0.023) in FinnGen, not in UKB (P > 0.05). However, no association was found between frailty index and AS (P > 0.05). These results remained consistent across sensitivity assessments.

CONCLUSION

This study demonstrated a potential causal relationship that genetic predisposition to frailty index was associated with the risk of arthritis, especially RA, OA, and PSA, not but AS. Our findings enrich the existing body of knowledge on the subject matter.

Proteomic and lipidomic landscape of the infrapatellar fat pad and its clinical significance in knee osteoarthritis

Osteoarthritis (OA) is a prevalent joint disease that can be exacerbated by lipid metabolism disorders. The intra-articular fat pad (IFP) has emerged as an active participant in the pathological changes of knee OA (KOA). However, the proteomic and lipidomic differences between IFP tissues from KOA and control individuals remain unclear. Samples of IFP were collected from individuals with and without OA (n = 6, n = 6). Subsequently, these samples underwent liquid chromatography/mass spectrometry-based label-free quantitative proteomic and lipidomic analysis to identify differentially expressed proteins (DEPs) and lipid metabolites (DELMs). The DEPs were further subjected to enrichment analysis, and hub DEPs were identified using multiple algorithms. Additionally, an OA diagnostic model was constructed based on the identified hub DEPs or DELMs. Furthermore, CIBERSORT was utilized to investigate the correlation between hub protein expression and immune-related modules in IFP of OA. Our results revealed the presence of 315 DEPs and eight DELMs in IFP of OA patients compared to the control group. Enrichment analysis of DEPs highlighted potential alterations in pathways related to coagulation, complement, fatty acid metabolism, and adipogenesis. The diagnostic model incorporating four hub DEPs (AUC = 0.861) or eight DELMs (AUC = 0.917) exhibited excellent clinical validity for diagnosing OA. Furthermore, the hub DEPs were found to be associated with immune dysfunction in IFP of OA. This study presents a distinct proteomic and lipidomic landscape of IFP between individuals with OA and those without. These findings provide valuable insights into the molecular changes associated with potential mechanisms underlying OA.

Circulating cytokines levels and osteoarthritis: A Mendelian randomization study

BACKGROUND

Previous traditional observational studies have suggested the contribution of several cytokines and growth factors to the development of osteoarthritis (OA). This study aimed to determine the association of circulating cytokine and growth factor levels with OA.

METHODS

We used two-sample Mendelian randomization (MR) to explore the causality between circulating cytokine and growth factor levels and OA [including knee or hip OA (K/HOA), knee OA (KOA), and hip OA (HOA)]. Summary level data for circulating cytokine and growth factor levels were sourced from a genome-wide association study (GWAS) involving 8,293 participants of Finnish ancestry. Single-nucleotide polymorphisms related to K/HOA (39,427 cases and 378,169 controls), KOA (24,955 cases and 378,169 controls), and HOA (15,704 cases and 378,169 controls) were obtained from a previous GWAS. The inverse variance weighted (IVW) method was primarily used for our MR analysis. For exposures to only one relevant SNP as IV, we used the Wald ratio as the major method to assess causal effects. We also conducted a series of sensitivity analyses to improve the robustness of the results.

RESULTS

Circulating vascular endothelial growth factor levels were suggestively associated with an increased risk of K/HOA (odds ratio (OR) = 1.034; 95 % confidence interval (CI) = 1.013-1.055; P = 0.001), KOA (OR = 1.034; 95 % CI = 1.014-1.065; P = 0.002), and HOA (OR = 1.039; 95 % CI = 1.003-1.067; P = 0.034). Circulating interleukin (IL)-12p70 levels was suggestively associated with K/HOA (OR = 1.047; 95 % CI = 1.018-1.077; P = 0.001), KOA (OR = 1.058; 95 % CI = 1.022-1.095; P = 0.001), and HOA (OR = 1.044; 95 % CI = 1.000-1.091; P = 0.048). Circulating IL-18 levels were suggestively associated with HOA (OR = 1.068; 95 % CI = 1.014-1.125; P = 0.012). However, limited evidence exists to support causal genetic relationships between other circulating cytokines, growth factor levels and K/HOA, KOA, and HOA.

CONCLUSIONS

Our MR analysis provides suggestive evidence of causal relationships between circulating cytokines and growth factors levels and OA, providing new insights into the etiology of OA.

Diabetes and osteoporosis: a two-sample mendelian randomization study

BACKGROUND

The effects on bone mineral density (BMD)/fracture between type 1 (T1D) and type 2 (T2D) diabetes are unknown. Therefore, we aimed to investigate the causal relationship between the two types of diabetes and BMD/fracture using a Mendelian randomization (MR) design.

METHODS

A two-sample MR study was conducted to examine the causal relationship between diabetes and BMD/fracture, with three phenotypes (T1D, T2D, and glycosylated hemoglobin [HbA1c]) of diabetes as exposures and five phenotypes (femoral neck BMD [FN-BMD], lumbar spine BMD [LS-BMD], heel-BMD, total body BMD [TB-BMD], and fracture) as outcomes, combining MR-Egger, weighted median, simple mode, and inverse variance weighted (IVW) sensitivity assessments. Additionally, horizontal pleiotropy was evaluated and corrected using the residual sum and outlier approaches.

RESULTS

The IVW method showed that genetically predicted T1D was negatively associated with TB-BMD (β = -0.018, 95% CI: -0.030, -0.006), while T2D was positively associated with FN-BMD (β = 0.033, 95% CI: 0.003, 0.062), heel-BMD (β = 0.018, 95% CI: 0.006, 0.031), and TB-BMD (β = 0.050, 95% CI: 0.022, 0.079). Further, HbA1c was not associated with the five outcomes (β ranged from - 0.012 to 0.075).

CONCLUSIONS

Our results showed that T1D and T2D have different effects on BMD at the genetic level. BMD decreased in patients with T1D and increased in those with T2D. These findings highlight the complex interplay between diabetes and bone health, suggesting potential age-specific effects and genetic influences. To better understand the mechanisms of bone metabolism in patients with diabetes, further longitudinal studies are required to explain BMD changes in different types of diabetes.

Causal Factors for Osteoarthritis: A Scoping Review of Mendelian Randomization Studies

OBJECTIVE

Mendelian randomization (MR) has increasingly been utilized as a tool for establishing causal relations between modifiable exposures and osteoarthritis (OA). The goal of this review was to summarize available MR studies of OA that evaluate the causal role of modifiable risk factors on OA.

METHODS

This review was performed following the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) Extension for Scoping Reviews model. We performed a literature search for relevant studies published before December 2021 across multiple databases using the search terms "osteoarthritis" and ("Mendelian randomization" or "polygenic risk score"). We reported the MR estimates of causal associations between exposures and OA and then assessed methodologic quality of abstracted studies according to their efforts to validate the three key MR assumptions.

RESULTS

Our search identified 45 studies reporting on 141 exposure-association analyses. All studies performed a formal instrumental variable analysis to estimate the causal effect of exposure on OA. Causal associations (P < 0.05) were reported in 60 of these analyses representing 36 unique publications, and MR-Egger sensitivity analyses were performed in 45 of these analyses. MR studies provided support for causal associations of OA with increased levels of adiposity, coffee consumption, bone mineral density, and sleep disturbance, and decreased levels of serum calcium and low-density lipoprotein cholesterol.

CONCLUSION

These results highlight the potential benefits of weight reduction and improvement of sleep quality to reduce the risk of OA and call for a better understanding of the relations of coffee consumption and serum calcium to OA risk.

Does Walking Have an Association with Osteoarthritis? A Two-Sample Mendelian Randomization Analysis

Objective

Osteoarthritis (OA) is one of the major disabling human diseases. The related studies indicate a potential correlation between walking and OA. However, there is still a lack of evidence in genetics to support the correlation between walking and OA. Therefore, this study aimed to explore the relationship between walking and OA at the genetic level.

Methods

The publicly available Genome Wide Association Study (GWAS) data were used, with inverse variance weighting (IVW, the random-effects model) as the main analysis method, whereas MR-Egger, Weighted median, Simple mode, and Weighted mode as the secondary analysis methods. In addition, Cochran's Q test, pleiotropy test, and MR-Egger intercept test were conducted to examine the heterogeneity and pleiotropy of the outcome.

Results

In the MR analysis, IVW results showed a negative correlation between types of physical activity in last 4 weeks: Walking for pleasure (not as a means of transport) and OA (KOA or HOA) (odds ratio (OR) = 0.3224, 95% confidence interval (CI): 0.1261 to 0.8243), and the difference was of statistical significance (P = 0.0181). Moreover, IVW results also revealed a negative correlation between types of physical activity in last 4 weeks: Walking for pleasure (not as a means of transport) and KOA (OR = 0.1396, 95% CI: 0.0484 to 0.4026), and the difference was statistically significant (P = 0.0003). However, IVW results did not demonstrate any statistical significance types of physical activity in last 4 weeks: Walking for pleasure (not as a means of transport) and HOA (OR = 1.2075, 95% CI: 0.1978 to 7.3727, P = 0.8381).

Conclusion

From genetic studies, types of physical activity in last 4 weeks: Walking for pleasure (not as a means of transport) is negatively correlated with knee osteoarthritis (KOA), but there is no clear evidence supporting its correlation with hip osteoarthritis (HOA).

The causal relationship between osteoarthritis and bladder cancer: A Mendelian randomization study

OBJECTIVE

The causal association between osteoarthritis (OA) and bladder cancer remains unclear. This Mendelian randomization (MR) study was carried out to assess the potential causal effects of any OA, knee OA and hip OA, and bladder cancer.

METHOD

Genome-wide association study (GWAS) summary data for OA and bladder cancer were obtained in GWAS CATALOG, UK Biobank, and FinnGen Consortium. Inverse-variance weighted (IVW) approach was primarily conducted to evaluate the causal relationships between OA and bladder cancer, and MR-Egger intercept and Cochran's Q test were mainly used to estimate heterogeneity and pleiotropy. MR-PRESSO was used to test the presence of horizontal outliers. Leave-one-out analysis was utilized to ensure the reliability of the results.

RESULTS

A higher genetic predisposition to any OA has a causal association with bladder cancer risk, while neither knee OA nor hip OA is causally linked to bladder cancer. MR-Egger intercept analysis exhibited that any OA and knee OA had no pleiotropic effect on the risk of bladder cancer, and Cochran's Q test showed that any OA, knee OA and hip OA had no heterogeneity on bladder cancer risk. Neither MR PRESSO analysis nor leave-one-out analysis revealed any outlier SNPs.

CONCLUSIONS

This MR study exhibited a positive cause-and-effect relationship between any type of OA and bladder cancer risk, but not between site-specific OA, knee OA and hip OA, and bladder cancer. Attention should be paid to the screening and prevention of bladder cancer in OA patients at any site.

Osteoporosis and osteoarthritis: a bi-directional Mendelian randomization study

OBJECTIVE

To investigate the causal relationship between low bone mineral density (BMD) and osteoarthritis (OA) using Mendelian randomization (MR) design.

METHODS

Two-sample bi-directional MR analyses were performed using summary-level information on OA traits from UK Biobank and arcOGEN. Sensitivity analyses including MR-Egger, simple median, weighted median, MR pleiotropy residual sum, and outlier approaches were utilized in conjunction with inverse variance weighting (IVW). Gene ontology (GO) enrichment analyses and expression quantitative trait locus (eQTL) colocalization analyses were used to investigate the potential mechanism and shared genes between osteoporosis (OP) and OA.

RESULTS

The IVW method revealed that genetically predicted low femoral neck BMD was significantly linked with hip (β = 0.105, 95% CI: 0.023-0.188) and knee OA (β = 0.117, 95% CI: 0.049-0.184), but not with other site-specific OA. Genetically predicted low lumber spine BMD was significantly associated with OA at any sites (β = 0.048, 95% CI: 0.011-0.085), knee OA (β = 0.101, 95% CI: 0.045-0.156), and hip OA (β = 0.150, 95% CI: 0.077-0.224). Only hip OA was significantly linked with genetically predicted reduced total bone BMD (β = 0.092, 95% CI: 0.010-0.174). In the reverse MR analyses, no evidence for a causal effect of OA on BMD was found. GO enrichment analysis and eQTL analysis illustrated that DDN and SMAD-3 were the most prominent co-located genes.

CONCLUSIONS

These findings suggested that OP may be causally linked to an increased risk of OA, indicating that measures to raise BMD may be effective in preventing OA. More research is required to determine the underlying processes via which OP causes OA.

Articular Cartilage Regeneration via Induced Chondrocyte Autophagy by Sustained Release of Leptin Inhibitor from Thermo-Sensitive Hydrogel through STAT3/REDD1/mTORC1 Cascade

The pathophysiology of osteoarthritis (OA) is closely linked to autophagy abnormalities in articular chondrocytes, the sole mature cell type in healthy cartilage. Nevertheless, the precise molecular mechanism remains uncertain. Previous research has demonstrated that leptin activates mTORC1 , thereby inhibiting chondrocyte autophagy during the progression of OA. In this study, it is demonstrated that the presence of leptin induces a substantial increase in the expression of STAT3, leading to a notable decrease in REDD1 expression and subsequent phosphorylation of p70S6K, a recognized downstream effector of mTORC1. Conversely, inhibition of leptin yields contrasting effects. Additionally, the potential advantages of utilizing a sustained intra-articular release of a leptin inhibitor (LI) via an injectable, thermosensitive poly(D,L-lactide)-poly(ethylene glycol)-poly(D,L-lactide) (PDLLA-PEG-PDLLA: PLEL) hydrogel delivery system for the purpose of investigating its impact on cartilage repair are explored. The study conducted on LI-loaded PLEL (PLEL@LI) demonstrates remarkable efficacy in inhibiting OA and displays encouraging therapeutic advantages in the restoration of subchondral bone and cartilage. These findings establish a solid foundation for the advancement of a pioneering treatment approach utilizing PLEL@LI for OA.

Genetic Association of Circulating Adipokines with Risk of Idiopathic Pulmonary Fibrosis: A Two-Sample Mendelian Randomization Study

PURPOSE

The causal relationships between circulating adipokines and idiopathic pulmonary fibrosis (IPF) are yet to be established. We performed a two-sample Mendelian randomization (MR) study to investigate the causal roles of adipokines on IPF risk.

METHODS

We analyzed the summary data from genome-wide association studies (GWAS), including adiponectin, leptin, resistin and monocyte chemoattractant protein-1 (MCP-1) and IPF. The inverse-variance weighted (IVW) method was considered as the major method and the MR-Egger, weighted median, simple mode and weighted mode were utilized as complementary methods. We also performed the sensitivity analyses, including heterogeneity test, horizontal pleiotropy test and leave-one-out analysis.

RESULTS

The selected number of single nucleotide polymorphisms (SNPs) was 13 for adiponectin, 6 for leptin,12 for resistin, and 6 for MCP-1, respectively. The results showed a causal effect of the circulating adiponectin levels on the risk of IPF (OR 0.645, 95% CI 0.457-0.911, P = 0.013). However, we did not observe significant associations of genetic changes in serum leptin (OR 1.018, 95% CI 0.442-2.346, P = 0.967), resistin (OR 1.002, 95% CI 0.712-1.408, P = 0.993), and MCP-1 (OR 1.358, 95% CI 0.891-2.068, P = 0.155) with risk of developing IPF. There was no evidence of heterogeneity or horizontal pleiotropy. The sensitivity analyses confirmed that our results were stable and reliable.

CONCLUSIONS

The increase in serum adiponectin was associated causally with a decreased risk of developing IPF. There is no evidence to support a causal association between leptin, resistin or MCP-1 with risk of IPF. Further studies are needed to confirm our findings.

Association Between Metabolically Different Adiposity Subtypes and Osteoarthritis: A Mendelian Randomization Study

OBJECTIVE

In this Mendelian randomization (MR) study, the objective was to investigate the causal effect of metabolically different adiposity subtypes on osteoarthritis.

METHODS

We performed 2-sample MR using summary-level data for osteoarthritis (10,083 cases and 40,425 controls) from a genome-wide association using the UK Biobank, and for site-specific osteoarthritis from the Arthritis Research UK Osteoarthritis Genetics consortium. We used 3 classes of genetic instruments, which all increase body mass index but are associated with different metabolic profiles (unfavorable, neutral, and favorable). Primary analysis was performed using inverse variance weight (IVW), with additional sensitivity analysis from different MR methods. We further applied a nonlinear MR using UK Biobank data to understand the nature of the adiposity-osteoarthritis relationship.

RESULTS

Greater metabolically unfavorable and metabolically neutral adiposity were associated with higher odds of osteoarthritis (IVW odds ratio [OR] 1.56 [95% confidence interval (95% CI) 1.31, 1.85] and OR 1.60 [95% CI 1.15, 2.23], respectively). The estimate for the association between metabolically favorable adiposity and osteoarthritis was similar, although with notable imprecision (OR 1.55 [95% CI 0.70, 3.41]). Using site-specific osteoarthritis, metabolically unfavorable, neutral, and favorable adiposity were all associated with higher odds of knee osteoarthritis (OR 1.44 [95% CI 1.04, 1.98], OR 2.28 [95% CI 1.04, 4.99], and OR 6.80 [95% CI 2.08, 22.19], respectively). We found generally consistent estimates with a wider confidence interval crossing the null from other MR methods. The nonlinear MR analyses suggested a nonlinear relationship between metabolically unfavorable adiposity and osteoarthritis (Pnonlinear  = 0.003).

CONCLUSION

Metabolic abnormalities did not explain the association between greater adiposity and the risk of osteoarthritis, which might suggest that the association is largely due to a mechanical effect on the joints.

Exploratory analysis of the effect of a controlled lifestyle intervention on inflammatory markers - the Healthy Lifestyle Community Programme (cohort 2)

BACKGROUND

Chronic low-grade inflammation is associated with an increased risk of chronic disease and mortality. The objective of the study was to test the effect of a healthy lifestyle intervention on biomarkers of inflammation (among other risk markers).

METHODS

We conducted a non-randomized controlled trial with mostly middle-aged and elderly participants from the general population in rural northwest Germany (intervention: n = 114; control: n = 87). The intervention consisted of a 1-year lifestyle programme focusing on diet (largely plant-based; strongest emphasis), physical activity, stress management, and social support. High-sensitivity C-reactive protein (hs-CRP) was assessed at baseline, 10 weeks, 6 months, and 1 year. Homocysteine (Hcy) was assessed at baseline, 10 weeks, and 1 year. Adiponectin (Apn) was assessed at baseline and 10 weeks. An exploratory analysis of these inflammatory markers assessing the between-group differences with ANCOVA was conducted.

RESULTS

The 1-year trajectory of hs-CRP was significantly lower in the intervention group compared to control (between-group difference: -0.8 (95% CI -1.2, -0.3) mg/l; p = 0.001; adjusted for baseline). The 1-year trajectory of Hcy was non-significantly higher in the intervention compared to control (between-group difference: 0.2 (95% CI -0.3, 0.7) µmol/l; p = 0.439; adjusted for baseline). From baseline to 10 weeks, Apn decreased significantly more in the intervention group compared to control (between-group difference: -1.6 (95% CI -2.7, -0.5) µg/ml; p = 0.004; adjusted for baseline).

CONCLUSIONS

Our study shows that healthy lifestyle changes can lower hs-CRP and Apn levels and are unlikely to significantly affect Hcy levels within 1 year.

TRIAL REGISTRATION

German Clinical Trials Register (DRKS; reference: DRKS00018775 , registered 12 Sept 2019; retrospectively registered; www.drks.de ).

No Evidence to Support a Causal Relationship between Circulating Adiponectin Levels and Ankylosing Spondylitis: A Bidirectional Two-Sample Mendelian Randomization Study

Based on previous observational studies, the causal association between circulating adiponectin (CA) levels and ankylosing spondylitis (AS) risk remains unclear. Therefore, this study aims to investigate whether CA levels are related to the risk of AS. We carried out a bidirectional two-sample Mendelian randomization (MR) analysis to examine the causal correlation between CA levels and AS via published genome-wide association study (GWAS) datasets. Single-nucleotide polymorphisms (SNPs) related to CA levels were derived from a large GWAS that included 39,883 individuals of European descent. SNPs related to AS were obtained from the FinnGen consortium (2252 cases and 227,338 controls). The random-effects inverse variance weighted (IVW) method was the primary method utilized in our research. We also used four complementary approaches to improve the dependability of this study (MR-Egger regression, Weighted median, Weighted mode, and Simple mode). Random-effects IVW (odds ratio [OR], 1.00; 95% confidence interval [CI], 0.79-1.27, p = 0.984) and four complementary methods all indicated that genetically predicted CA levels were not causally related to the risk of AS. In reverse MR analysis, there is little evidence to support the genetic causality between the risk of AS and CA levels.

Epidemiologic Opportunities and Challenges in Studying Environmental Risk Factors for Rheumatic Diseases

Most rheumatic diseases have a stronger environmental than hereditary etiology. This article summarizes the key environmental risk factors for rheumatic diseases, the data sources that generated these findings, and the key pitfalls with existing research that every rheumatology clinician should know. Emerging research opportunities hold promise to revolutionize this field, and soon.

Mendelian Randomization Studies of Lifestyle-Related Risk Factors for Osteoarthritis: A PRISMA Review and Meta-Analysis

Risk factors for osteoarthritis (OA) often exert effects over protracted time-courses. Mendelian randomization (MR) studies therefore have an advantage over conventional observational studies when studying the causal effect of long-term lifestyle-related risk factors on OA. However, given the heterogeneous design of existing MR studies on OA, the reported causal estimates of these effects remain inconsistent, thus obscuring the true extent of the biological effects of OA lifestyle-risk factors. We conducted a PRISMA systematic review and specifically included MR studies that investigated the causal effect between lifestyle-related risk factors and OA, where causal estimates for various lifestyle factors were pooled for meta-analysis. Quality of studies was assessed according to STROBE-MR guidelines. A total of 1576 studies were evaluated and 23 were included. Overall, the studies included were of high quality and had a low risk of bias. Our meta-analysis demonstrates the positive causal effect of BMI (ORIVW-random effects 1.49 [1.23-1.80]) and negative causal effects of serum calcium (ORIVW-random effects 0.69 [0.57-0.83]) and LDL levels (ORIVW-random effects 0.93 [0.90-0.96]) on OA. Despite the heterogeneous designs and estimates of causal effects provided by various MR studies, our meta-analysis suggests that lifestyle-related risk factors in the form of BMI, serum calcium, and LDL have true biological effects on the development of OA.

Beef intake and risk of rheumatoid arthritis: Insights from a cross-sectional study and two-sample Mendelian randomization

Background

Beef is common in daily diet, but its association with the risk of rheumatoid arthritis (RA) remains uncertain. The objective of this study is to explore the relationship between beef intake and the risk of RA.

Materials and methods

We investigated the association between beef intake and risk of RA by multivariate logistic regression, based on the National Health and Nutrition Examination Survey (NHANES) 1999–2016 involving 9,618 participants. The dose–response relationship between beef intake and RA was explored as well. Furthermore, we performed Mendelian randomization (MR) analysis to examine the causal effect of beef intake on RA. Genetic instruments for beef intake were selected from a genome-wide association study (GWAS) including 335,576 individuals from the UK Biobank study, and summary statistics relating to RA were obtained from a GWAS meta-analysis of 14,361 RA patients and 43,923 controls. The inverse-variance weighted (IVW) approach was used to estimate the causal association, and MR-Egger regression and Mendelian randomization pleiotropy residual sum and outlier (MR-PRESSO) test were applied to evaluate the pleiotropy and outliers.

Results

Compared with the lowest quintile (0 to ≤33.50 g/d), beef intake was found to be significantly associated with the risk of RA [odds ratio (OR): 1.94; 95% confidence interval (CI): 1.20–3.12] in the third quintile (50.26 to ≤76.50 g/d). Moreover, a reversed “U” dose–response relationship between beef and RA (Pnon–linearity = 0.023) was found. In the MR analysis, beef intake was associated with an increased risk of RA (OR: 3.05; 95% CI: 1.11–8.35; P = 0.030) by the IVW method. The results from MR-Egger regression and MR-PRESSO test showed that there were no pleiotropic variations and outliers.

Conclusion

This study indicated that there is suggestive evidence to support the causal effect of beef intake on the risk of RA, while further studies are warranted to elucidate the exact association.

Interplay of retinol binding protein 4 with obesity and associated chronic alterations (Review)

Obesity is a multifactorial disease, defined as excessive fat deposition in adipose tissue. Adipose tissue is responsible for the production and secretion of numerous adipokines that induce metabolic disorders. Retinol‑binding protein 4 (RBP4) is an adipokine that transports vitamin A or retinol in the blood. High levels of RBP4 are associated with development of metabolic disease, including obesity, insulin resistance (IR), metabolic syndrome, and type 2 diabetes (T2D). The present review summarizes the role of RBP4 in obesity and associated chronic alterations. Excessive synthesis of RBP4 contributes to inflammatory characteristic of obesity by activation of immune cells and release of proinflammatory cytokines, such as TNFα and ILs, via the Toll‑like receptor/JNK pathway. The retinol‑RBP4 complex inhibits insulin signaling directly in adipocytes by activating Janus kinase 2 (JAK2)/STAT5/suppressor of cytokine signaling 3 signaling. This mechanism is retinol‑dependent and requires vitamin A receptor stimulation by retinoic acid 6 (STRA6). In muscle, RBP4 is associated with increased serine 307 phosphorylation of insulin receptor substrate‑1, which decreases its affinity to PI3K and promotes IR. In the liver, RBP4 increases hepatic expression of phosphoenolpyruvate carboxykinase, which increases production of glucose. Elevated serum RBP4 levels are associated with β‑cell dysfunction in T2D via the STRA6/JAK2/STAT1/insulin gene enhancer protein 1 pathway. By contrast, RBP4 induces endothelial inflammation via the NF‑κB/nicotinamide adenine dinucleotide phosphate oxidase pathway independently of retinol and STRA6, which stimulates expression of proinflammatory molecules, such as vascular cell adhesion molecule 1, E‑selectin, intercellular adhesion molecule 1, monocyte chemoattractant protein 1 and TNFα. RBP4 promotes oxidative stress by decreasing endothelial mitochondrial function; overall, it may serve as a useful biomarker in the diagnosis of obesity and prognosis of associated disease, as well as a potential therapeutic target for treatment of these diseases.

Genetically Predicted Longer Telomere Length May Reduce Risk of Hip Osteoarthritis

Objective: This two-sample Mendelian randomization (MR) study aimed to examine the potential causal association of telomere length (TL) with the risk of osteoarthritis (OA).

Method: The summary-level data for OA was derived from the United Kingdom Biobank cohort, including 50,508 individuals of European descent. Eighteen single nucleotide polymorphisms associated with TL were identified as instrumental variables from the most up-to-date TL genome-wide association study (GWAS) involving over 78,592 individuals of European descent. Based on the GWASs data, MR was performed using established statistical analysis methods including the inverse variance weighted, weighted median, MR-Egger, and MR pleiotropy residual sum and outlier.

Results: Genetically determined TL was not associated with the risk of total OA (IVW odds ratio [OR] = 1.00, 95% confidence interval [CI] = 0.83, 1.21). In subgroup analyses stratified by OA site, no evidence in favor of association between genetically determined TL and knee OA was found (IVW OR = 1.18, 95% CI = 0.89, 1.58). However, using WM method, we observed a limited protective effect of longer TL on the risk of hip OA (OR = 0.60, 95% CI = 0.36–0.99), whereas the results of the IVW (p = 0.931) and MR-PRESSO (p = 0.932) showed that TL had no effect on hip OA.

Conclusions: This study does not support a causal association between TL and total OA. A potential protective association between longer TL and hip OA, though possible, remains less certain.