The role of leptin and adiponectin as mediators in the relationship between adiposity and hand and knee osteoarthritis

PLOD2 gene expression in infrapatellar fat pad is correlated with fat mass in obese patients with end-stage knee osteoarthritis

Objective

To investigate associations between obesity-linked systemic factors and gene expression indicative for the inflammatory and fibrotic processes in the infrapatellar fat pad (IFP), in a population of obese patients with end-stage knee osteoarthritis (KOA).

Methods

We collected human IFPs from 48 patients with a mean body mass index (BMI) of 35.44 ​kg/m2 during total knee replacement procedures. These patients were part of a randomized controlled trial and met the criteria of having OA and a BMI of ≥30 ​kg/m2. Blood samples were collected to assess serum levels of glucose, total cholesterol, HDL cholesterol, LDL cholesterol, triglycerides, and leptin. Total body composition was measured using dual-energy X-ray absorptiometry. Gene expressions of IL6, TNFA, COL1A1, IL1B, ASMA, PLOD2 in the IFP were analyzed.

Results

Univariate analysis resulted in a positive correlation between BMI and procollagen-lysine,2-oxoglutarate 5-dioxygenase 2 (PLOD2) expression (r2 ​= ​0.13). In univariate analyses of obesity-linked systemic factors and PLOD2, significant correlations were found for lean mass (r2 ​= ​0.20), fat mass (r2 ​= ​0.20), serum cholesterol (r2 ​= ​0.17), serum triglycerides (r2 ​= ​0.19) and serum leptin (r2 ​= ​0.10). A multiple linear regression model indicated fat mass to be a strong predictor of PLOD2 production in the IFP (r2 ​= ​0.22, P ​= ​0.003).

Conclusion

Our study demonstrates the positive association between fat mass and PLOD2 expression in the IFP of obese end-stage knee OA patients. This may indicate that within this patient population the fibrotic process in the IFP is influenced by systemic adipose tissue, next to local inflammatory processes.

The effect of plasma cytokines on the expression of adiponectin and its receptors in the synovial membrane of joints and the infrapatellar fat pad in patients with rheumatoid arthritis and osteoarthritis

BACKGROUND

Rheumatoid arthritis (RA) is an autoimmune inflammatory disease that leads to joint destruction. Numerous pro-inflammatory mediators, including adipokines, play an important role in the pathogenesis of RA.

OBJECTIVE

The aim of the study was to investigate the relationships between selected plasma cytokines and expression of adiponectin and its receptors in the synovium and the infrapatellar fat pad in patients with RA and osteoarthritis (OA).

METHODS

Blood, synovium and fat pad samples from 18 patients with RA and 18 with OA were collected during joint replacement surgery. Spearman rank correlations between plasma concentrations of selected cytokines (IL-1β, IL-2, IL-4, IL-6, IL-7, IL-8, IL-10, IL-12 p40, IL-13, IL-17, G-CSF and GM-CSF) and the expression of adiponectin and its receptors were determined. Plasma levels of cytokines were determined using a magnetic bead-based multiplex assay, mRNA expression of adiponectin and its receptors were determined by real-time PCR.

RESULTS

In OA patients, there were significant positive correlations between adiponectin expression in the synovial membrane and plasma levels of IL-1β, IL-4, G-CSF and GM-CSF, as well as a significant positive correlation between adiponectin expression in the fat pad and plasma levels of GM-CSF. In addition, OA patients showed significant negative correlations between AdipoR1 and AdipoR2 expression in the synovial membrane and plasma IL-6 levels, as well as between AdipoR2 expression in the synovial membrane and plasma MCP-1 and TNF-α levels. In patients with RA, there were no significant correlations between adiponectin expression in the synovial membrane and infrapatellar fat pad and plasma levels of the cytokines studied. In addition, RA patients showed a statistically significant negative correlation between AdipoR1 expression in the synovial membrane and plasma levels of TNF-α, IL-7, IL-12 and IL-13, and a significant negative correlation between AdipoR1 expression in the infrapatellar fat pad and plasma levels of IL-1β.

CONCLUSIONS

Adiponectin and its receptors showed the correlations with several plasma cytokines, however, a thorough understanding of the role of adiponectin in RA and OA requires further investigation.

Effects of weight loss through dietary intervention on pain characteristics, functional mobility, and inflammation in adults with elevated adiposity

Background

The relationship between adiposity and pain is complex. Excess weight increases the risk for chronic musculoskeletal pain (CMP), driven by increased biomechanical load and low-grade systemic inflammation. Pain limits physical function, impacting energy balance contributing to weight gain. The primary aims of this study were to profile pain characteristics in participants with overweight or obesity and determine if weight loss through dietary-induced energy restriction, and presence of CMP, or magnitude of weight loss, was associated with changes in adiposity, pain, functional mobility, and inflammation.

Methods

This was a secondary analysis of data from adults (25-65 years) with overweight or obesity (BMI 27.5-34.9 kg/m2) enrolled in a 3-month, 30% energy-restricted dietary intervention to induce weight loss (January 2019-March 2021). Anthropometric measures (weight, waist circumference and fat mass), pain prevalence, pain severity (McGill Pain Questionnaire, MPQ), pain intensity (Visual Analog Scale, VAS), functional mobility (timed up and go, TUG) and inflammation (high sensitivity C-Reactive Protein, hsCRP) were assessed at baseline and 3-months.

Results

One hundred and ten participants completed the intervention and had weight and pain assessed at both baseline and 3-months. Participants lost 7.0 ± 0.3 kg, representing 7.9% ± 3.7% of body mass. At 3-months, functional mobility improved (TUG -0.2 ± 0.1 s, 95% CI -0.3, -0.1), but there was no change in hsCRP. Compared to baseline, fewer participants reported CMP at 3-months (n = 56, 51% to n = 27, 25%, p < 0.001) and presence of multisite pain decreased from 22.7% to 10.9% (p < 0.001). Improvements in anthropometric measures and functional mobility did not differ between those presenting with or without CMP at baseline. Improvements in pain were not related to the magnitude of weight loss.

Conclusion

Weight loss was effective in reducing pain prevalence and improving functional mobility, emphasizing the importance of considering weight-loss as a key component of pain management.

Clinical trial registration

identifier, ACTRN12618001861246.

Osteoarthritis, adipokines and the translational research potential in small animal patients

Osteoartritis (OA) is a debilitating disease affecting both humans and animals. In the early stages, OA is characterized by damage to the extracellular matrix (ECM) and apoptosis and depletion of chondrocytes. OA progression is characterized by hyaline cartilage loss, chondrophyte and osteophyte formation, thickening of the joint capsule and function loss in the later stages. As the regenerative potential of cartilage is very limited and osteoarthritic changes are irreversible, prevention of OA, modulation of existing osteoarthritic joint inflammation, reducing joint pain and supporting joint function are the only options. Progression of OA and pain may necessitate surgical intervention with joint replacement or arthrodesis as end-stage procedures. In human medicine, the role of adipokines in the development and progression of OA has received increasing interest. At present, the known adipokines include leptin, adiponectin, visfatin, resistin, progranulin, chemerin, lipocalin-2, vaspin, omentin-1 and nesfatin. Adipokines have been demonstrated to play a pivotal role in joint homeostasis by modulating anabolic and catabolic balance, autophagy, apoptosis and inflammatory responses. In small animals, in terms of dogs and cats, naturally occurring OA has been clearly demonstrated as a clinical problem. Similar to humans, the etiology of OA is multifactorial and has not been fully elucidated. Humans, dogs and cats share many joint related degenerative diseases leading to OA. In this review, joint homeostasis, OA, adipokines and the most common joint diseases in small animals leading to naturally occurring OA and their relation with adipokines are discussed. The purpose of this review is highlighting the translational potential of OA and adipokines research in small animal patients.

Assessing the association of epigenetic age acceleration with osteoarthritis in the Multicenter Osteoarthritis Study (MOST)

PURPOSE

Advancing age is one of the strongest risk factors for osteoarthritis (OA). DNA methylation-based measures of epigenetic age acceleration may provide insights into mechanisms underlying OA.

METHODS

We analyzed data from the Multicenter Osteoarthritis Study in a subset of 671 participants ages 45-69 years with no or mild radiographic knee OA. DNA methylation was assessed with the Illumina Infinium MethylationEPIC 850K array. We calculated predicted epigenetic age according to Hannum, Horvath, PhenoAge, and GrimAge epigenetic clocks, then regressed epigenetic age on chronological age to obtain the residuals. Associations between the residuals and knee, hand, and multi-joint OA were assessed using logistic regression, adjusted for chronological age, sex, clinical site, smoking status, and race.

RESULTS

Twenty-three percent met criteria for radiographic hand OA, 25% met criteria for radiographic knee OA, and 8% met criteria for multi-joint OA. Mean chronological age (SD) was 58.4 (6.7) years. Mean predicted epigenetic age (SD) according to Horvath, Hannum, PhenoAge, and GrimAge epigenetic clocks was 64.9 (6.4), 68.6 (5.9), 50.5 (7.7), and 67.0 (6.2), respectively. Horvath epigenetic age acceleration was not associated with an increased odds of hand OA, odds ratio (95% confidence intervals) = 1.03 (0.99-1.08), with similar findings for knee and multi-joint OA. We found similar magnitudes of associations for Hannum epigenetic age, PhenoAge, and GrimAge acceleration compared to Horvath epigenetic age acceleration.

CONCLUSIONS

Epigenetic age acceleration as measured by various well-validated epigenetic clocks based on DNA methylation was not associated with increased risk of knee, hand, or multi-joint OA independent of chronological age.

Current evidence for non-pharmaceutical, non-surgical treatments of canine osteoarthritis

Osteoarthritis is a progressive degenerative disease process that affects a significant proportion of the canine population, impacting these animals' quality of life. Currently, there is no cure and treatment consists of managing the clinical signs of pain and reduced mobility. There are many treatments for canine osteoarthritis and in this review we discuss the evidence base behind non-pharmaceutical, non-surgical treatments of this disease. These treatments include weight management, nutraceuticals, acupuncture, physiotherapies such as therapeutic exercise, hydrotherapy as well as other therapeutic modalities including photobiomodulation therapy, electromagnetic field therapy and others.

Fatty acid binding protein 4 (FABP4) induces chondrocyte degeneration via activation of the NF-κb signaling pathway

The pathogenesis of osteoarthritis (OA) is still unclear. Fatty acid binding protein 4 (FABP4), a novel adipokine, has been found to play a role in OA. This study aimed to explore the role of NF-κB in FABP4-induced OA. In the in vivo study, four pairs of 12-week-old male FABP4 knockout (KO) and wild-type (WT) mice were included. The activation of NF-κB was assessed. In parallel, 24 6-week-old male C57/Bl6 mice were fed a high-fat diet (HFD) and randomly allocated to four groups: daily oral gavage with (1) PBS solution; (2) QNZ (NF-κB-specific inhibitor, 1 mg/kg/d); (3) BMS309403 (FABP4-specific inhibitor, 30 mg/kg/d); and (4) BMS309403 (30 mg/kg/d) + QNZ (1 mg/kg/d). The diet and treatment were sustained for 4 months. The knee joints were obtained to assess cartilage degradation, NF-κB activation, and subchondral bone sclerosis. In the in vitro study, a mouse chondrogenic cell line (ATDC5) was cultured. FABP4 was supplemented to stimulate chondrocytes, and the activation of NF-κB was investigated. In parallel, QNZ and NF-κB-specific siRNA were used to inhibit NF-κB. In vivo, the FABP4 WT mice had more significant NF-κB activation than the KO mice. Dual inhibition of FABP4 and NF-κB alleviated knee OA in mice. FABP4 has no significant effect on the activation of the JNK signaling pathway. In vitro, FABP4 directly activated NF-κB in chondrocytes. The use of QNZ and NF-κB-siRNA significantly alleviated the expression of catabolic markers of chondrocytes induced by FABP4. FABP4 induces chondrocyte degeneration by activating the NF-κB pathway.

Association of adipokines with severity of knee osteoarthritis assessed clinically and on magnetic resonance imaging

Objectives

We aimed to evaluate the association between the adipokines: Leptin, Adiponectin, Resistin, and high sensitive-C-reactive protein (hs-CRP) with clinical, radiographical and magnetic resonance imaging (MRI) assessment of knee osteoarthritis (OA) severity.

Design

We performed a cross-sectional study in participants with earlier knee OA. Demographics, clinical (WOMAC), radiographical and MRI (BLOKS scoring) severity of knee OA were assessed. Serum leptin, adiponectin, resistin and hs-CRP were measured. Association of adipokines and hs-CRP with clinical, radiographic and MRI severity outcomes were evaluated using regression models with adjustment with age, sex, and body mass index (BMI).

Results

137 participants with earlier knee OA (82% women, mean ​± ​SD age: 55.5 ​± ​7.8 years) were included. Participants had moderate knee OA symptoms, mean WOMAC pain and function were 30.6 ​± ​18.0, and 31.7 ​± ​19.8 respectively. Mean BMI was 27.0 ​± ​5.9 ​kg/m2. After adjustment with age, sex and BMI, serum leptin was positively associated with osteophyte size, cartilage integrity, infrapatellar synovitis and effusion. While hs-CRP was associated with meniscus extrusion and adiponectin was associated with WOMAC pain and function.

Conclusion

Serum adipokines, particularly leptin was associated with severity of various structural defects of the knee joint on MRI beyond age, sex and BMI in earlier knee OA.

Leptin and interleukin-1β levels associated with osteoarthritis in Vietnamese patients: a cross-sectional analysis

Leptin and interleukin-1 beta (IL-1β) are two extensively studied biomarkers associated with metabolic syndrome (MetS) and osteoarthritis (OA). Previous studies have mostly focused on either MetS or OA alone, with no available data on Vietnamese patients. This study aimed to investigate the levels of leptin and IL-1β in this patient population and explore their association with clinical parameters of MetS and OA. The study included 164 patients with primary knee OA, who were classified into two categories based on the presence of MetS, and 78 healthy controls. The plasma leptin and IL-1β levels were quantified by ELISA and correlated with clinical parameters. Leptin levels were higher in patients with OA (11.50±10.04 ng/mL) than in healthy controls (0.54±0.37 ng/mL) and increased in patients with MetS compared to those without MetS. IL-1β levels were also significantly higher in OA patients (14.63±15.87 pg/mL) than in controls (7.79±5.11 pg/mL), but were not significantly different between the MetS and non-MetS groups. Leptin levels were positively correlated with body mass index, waist-to-hip ratio, visual analogue scale scores, HbA1c and insulin levels, and HOMA-IR index, whereas IL-1β levels were only correlated with insulin levels and HOMA-IR index. ROC curve analysis revealed that leptin and IL-1β levels could distinguish individuals with and without OA (AUC=0.96; 0.88, respectively), and individuals with and without MetS (AUC=0.82; 0.71, respectively). Our findings suggested that both leptin and IL-1β levels were associated with both MetS and OA and may play a critical role in the pathogenesis of MetS-related OA.

Obesity, Metabolic Syndrome, and Osteoarthritis-An Updated Review

PURPOSE OF REVIEW

Metabolic syndrome (MetS), also called the 'deadly quartet' comprising obesity, diabetes, dyslipidemia, and hypertension, has been ascertained to have a causal role in the pathogenesis of osteoarthritis (OA). This review is aimed at discussing the current knowledge on the contribution of metabolic syndrome and its various components to OA pathogenesis and progression.

RECENT FINDINGS

Lately, an increased association identified between the various components of metabolic syndrome (obesity, diabetes, dyslipidemia, and hypertension) with OA has led to the identification of the 'metabolic phenotype' of OA. These metabolic perturbations alongside low-grade systemic inflammation have been identified to inflict detrimental effects upon multiple tissues of the joint including cartilage, bone, and synovium leading to complete joint failure in OA. Recent epidemiological and clinical findings affirm that adipokines significantly contribute to inflammation, tissue degradation, and OA pathogenesis mediated through multiple signaling pathways. OA is no longer perceived as just a 'wear and tear' disease and the involvement of the metabolic components in OA pathogenesis adds up to the complexity of the disease. Given the global surge in obesity and its allied metabolic perturbations, this review aims to throw light on the current knowledge on the pathophysiology of MetS-associated OA and the need to address MetS in the context of metabolic OA management. Better regulation of the constituent factors of MetS could be profitable in preventing MetS-associated OA. The identification of key roles for several metabolic regulators in OA pathogenesis has also opened up newer avenues in the recognition and development of novel therapeutic agents.

Associations between chronic widespread pain, pressure pain thresholds, leptin, and metabolic factors in individuals with knee pain

OBJECTIVE

The aim was to study associations between chronic widespread pain, widespread pain sensitivity, leptin, and metabolic factors in individuals with knee pain. A secondary aim was to study these associations in a subgroup of individuals with normal BMI.

METHOD

This cross-sectional study included 265 individuals. The participants were categorised into three different pain groups: Chronic widespread pain (CWP), chronic regional pain (ChRP), or no chronic pain (NCP). The pressure pain thresholds (PPTs) were assessed using computerised pressure algometry. Low PPTs were defined as having PPTs in the lowest third of all tender points. Leptin and metabolic factors such as BMI, visceral fat area (VFA), lipids, and glucose were also assessed.

RESULT

Sixteen per cent reported CWP, 15% had low PPTs, and 4% fulfilled both criteria. Those who fulfilled the criteria for CWP were more often women, more obese, and had increased leptin levels. In logistic regression, adjusted for age and gender, leptin was associated with fulfilling criteria for CWP, OR 1.015 (95% CI 1.004-1.027, p = 0.008). In logistic regression, adjusted for age and gender, leptin was associated with low PPTs, OR 1.016 (95% CI 1.004-1.029, p = 0.012). Leptin was also associated with fulfilling both criteria, adjusted for age, sex, and visceral fat area (VFA), OR 1.030 (95% CI 1.001-1.060), p = 0.040.

CONCLUSION

Leptin was associated with fulfilling the combined criteria for chronic widespread pain and low PPTs, even after adjusting for the visceral fat area (VFA). Longitudinal studies are needed to study the causal relationships between leptin and the development of widespread pain.

TRIAL REGISTRATION

clinicalTrials.gov Identifier: NCT04928170.

Obesity-Related Knee Osteoarthritis-Current Concepts

The knee is the joint most frequently involved in osteoarthritis and represents a significant contributor to patient morbidity and impaired functional status. Major risk factors include genetics, age, sex, mechanical load and obesity/metabolic syndrome. Recent studies highlighted the role of obesity and metabolic syndrome in the pathogenesis of knee osteoarthritis not simply through increased mechanical loading but the systemic effects of obesity-induced inflammation. The current concept of knee osteoarthritis is that of a 'whole joint disease', which highlights the involvement not only of articular cartilage but also the synovium, subchondral bone, ligaments and muscles. Obesity and metabolic syndrome are associated with higher levels of pro-inflammatory cytokines, increased production of adipokines with both protective and destructive effects on articular cartilage, an up-regulation of proteolytic enzymes such as matrix metalloproteinases and aggrecanases and an increase in free fatty acids and reactive oxygen species induced by dyslipidemia. These findings underscore that the adequate management of knee osteoarthritis needs to include an optimization of body weight and a beneficial mobility regimen. The possible introduction of pharmacological therapy targeting specific molecules involved in the pathogenesis of obesity-related osteoarthritis will likely also be considered in future therapeutic strategies, including personalized treatment approaches.

The Mediation and Moderation Effect Association among Physical Activity, Body-Fat Percentage, Blood Pressure, and Serum Lipids among Chinese Adults: Findings from the China Health and Nutrition Surveys in 2015

Physical activity (PA) is of benefit and particularly important for cardiovascular disease risk factors as being sedentary becomes a lifestyle habit. Research into Chinese complex association among physical activity, body-fat percentage (BF%), blood pressure, and serum lipids is limited. The present study is based on an observational study among adults (>18 years old) residing in fifteen provinces in China. Data of 10,148 adult participants in the 2015 China Health and Nutrition Survey (CHNS) were analyzed. The simple mediation effect models with covariates were utilized to assess the association among PA and blood pressure or serum lipids, and BF% was played as a mediator. The serial multiple-mediator models with covariates were constructed to the further analysis of the relationship between PA and blood pressure, and BF% was the mediator 1 and blood lipids were the mediator 2. Based on the above hypothesis, the moderated mediation models with covariates were used to analyze the association among PA, BF%, and blood pressure; in addition, BF% was used as the mediator and blood lipids played as the moderator. In the simple mediation models, the model with a dependent variable was high-density lipoprotein cholesterol (HDL-C) or low-density lipoprotein cholesterol (LDL-C); BF% was played as the partly mediation effect and the proportion of contribution was 0.23 and 0.25, respectively. In the serial multiple-mediator models, blood lipids, as the second mediator, played the mediation effect; however, the effect was smaller than the BF%. In the moderated mediation model, blood lipids had the moderation effect as the moderator variable. HDL-C played a moderating role in the latter pathway of the "PA→BF%→SBP/DBP" mediation model, and LDL-C/TC played a moderating role in the direct effect of the "PA→BF%→DBP". In conclusion, BF% played a mediating role in the relationship between PA and blood pressure. HDL-C, LDL-C, and TC were more likely to act as moderating variables in the mediation model "PA→BF%→SBP/DBP". PA could directly and indirectly benefit to control the CVD risk factors simultaneously.

Effects of Leptin and Body Weight on Inflammation and Knee Osteoarthritis Phenotypes in Female Rats

Leptin is a proinflammatory adipokine that contributes to obesity-associated osteoarthritis (OA), especially in women. However, the extent to which leptin causes knee OA separate from the effect of increased body weight is not clear. We hypothesized that leptin is necessary to induce knee OA in obese female rats but not sufficient to induce knee OA in lean rats lacking systemic metabolic inflammation. The effect of obesity without leptin signaling was modeled by comparing female lean Zucker rats to pair fed obese Zucker rats, which possess mutant fa alleles of the leptin receptor gene. The effect of leptin without obesity was modeled in female F344BN F1 hybrid rats by systemically administering recombinant rat leptin versus saline for 23 weeks via osmotic pumps. Primary OA outcomes included cartilage histopathology and subchondral bone micro-computed tomography. Secondary outcomes included targeted cartilage proteomics, serum inflammation, and synovial fluid inflammation following an acute intra-articular challenge with interleukin-1β (IL-1β). Compared to lean Zucker rats, obese Zucker rats developed more severe tibial osteophytes and focal cartilage lesions in the medial tibial plateau, with modest changes in proximal tibial epiphysis trabecular bone structure. In contrast, exogenous leptin treatment, which increased plasma leptin sixfold without altering body weight, caused mild generalized cartilage fibrillation and reduced Safranin O staining compared to vehicle-treated animals. Leptin also significantly increased subchondral and trabecular bone volume and bone mineral density in the proximal tibia. Cartilage metabolic and antioxidant enzyme protein levels were substantially elevated with leptin deficiency and minimally suppressed with leptin treatment. In contrast, leptin treatment induced greater changes in systemic and local inflammatory mediators compared to leptin receptor deficiency, including reduced serum IL-6 and increased synovial fluid IL-1β. In conclusion, rat models that separately elevate leptin or body weight develop distinct OA-associated phenotypes, revealing how obesity increases OA pathology through both leptin-dependent and independent pathways. © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Sex-specific effects of calving season on joint health and biomarkers in Montana ranchers

BACKGROUND

Agricultural workers have a higher incidence of osteoarthritis (OA), but the etiology behind this phenomenon is unclear. Calving season, which occurs in mid- to late-winter for ranchers, includes physical conditions that may elevate OA risk. Our primary aim was to determine whether OA biomarkers are elevated at the peak of calving season compared to pre-season, and to compare these data with joint health survey information from the subjects. Our secondary aim was to detect biomarker differences between male and female ranchers.

METHODS

During collection periods before and during calving season, male (n = 28) and female (n = 10) ranchers completed joint health surveys and provided samples of blood, urine, and saliva for biomarker analysis. Statistical analyses examined associations between mean biomarker levels and survey predictors. Ensemble cluster analysis identified groups having unique biomarker profiles.

RESULTS

The number of calvings performed by each rancher positively correlated with plasma IL-6, serum hyaluronic acid (HA) and urinary CTX-I. Thiobarbituric acid reactive substances (TBARS), a marker of oxidative stress, was significantly higher during calving season than pre-season and was also correlated with ranchers having more months per year of joint pain. We found evidence of sexual dimorphism in the biomarkers among the ranchers, with leptin being elevated and matrix metalloproteinase-3 diminished in female ranchers. The opposite was detected in males. WOMAC score was positively associated with multiple biomarkers: IL-6, IL-2, HA, leptin, C2C, asymmetric dimethylarginine, and CTX-I. These biomarkers represent enzymatic degradation, inflammation, products of joint destruction, and OA severity.

CONCLUSIONS

The positive association between number of calvings performed by each rancher (workload) and both inflammatory and joint tissue catabolism biomarkers establishes that calving season is a risk factor for OA in Montana ranchers. Consistent with the literature, we found important sex differences in OA biomarkers, with female ranchers showing elevated leptin, whereas males showed elevated MMP-3.

Causal Relationships of General and Abdominal Adiposity on Osteoarthritis: A Two-Sample Mendelian Randomization Study

Background: Adiposity is closely related to osteoarthritis, but the causal effects of different types of adiposity on osteoarthritis are indistinct. This study conducted a Mendelian Randomization (MR) analysis for the causal effects of general adiposity and abdominal adiposity on knee osteoarthritis (KOA) and hip osteoarthritis (HOA). Methods: The general adiposity was assessed by body mass index (BMI), while the abdominal adiposity was evaluated with waist circumference (WC), hip circumference (HC), and waist-to-hip ratio (WHR). The data used in this two-sample MR analysis originated from genome-wide association studies (GWAS). Significant (p < 5 × 10−8) and independent (r2 < 0.01) single-nucleotide polymorphisms were selected as instrumental variables for the MR analysis. Subsequently, this study used the inverse variance weighted, weighted median, and other methods for the causal inference, and the results were presented as odds ratios (OR). Moreover, sensitivity analyses were conducted to assess the stability and reliability of the results. Results: The MR results revealed positive causal effects of BMI on KOA (OR: 1.694; 95% CI: from 1.492 to 1.923; p = 3.96 × 10−16) and HOA (OR: 1.412; 95% CI: from 1.196 to 1.666; p = 4.58 × 10−5). Additionally, WC and HC both positively and causally related to KOA (WC: OR: 1.827; 95% CI: from 1.564 to 2.134; p = 2.68 × 10−14; HC: OR: 1.610; 95% CI: from 1.357 to 1.912; p = 5.03 × 10−8) and HOA (WC: OR: 1.491; 95% CI: from 1.254 to 1.772; p = 5.85 × 10−6; HC: OR: 1.439; 95% CI: from 1.205 to 1.719; p = 5.82 × 10−5). However, no causal relationship existed between WHR and obesity. These results were robust according to the sensitivity analyses. Conclusions: This study indicated that both general and abdominal obesity had positive causal effects on knee osteoarthritis and hip osteoarthritis.

Research progress on the mechanism of interleukin-1β on epiphyseal plate chondrocytes

Epiphyseal plate injury, a common problem in pediatric orthopedics, may result in poor bone repair or growth defects. Epiphyseal plate, also known as growth plate is a layer of hyaline cartilage tissue between the epiphysis and metaphyseal and has the ability to grow longitudinally. Under normal physiological conditions, the epiphyseal plate has a certain axial resistance to stress, but it is fragile in growth phase and can be damaged by excessive stress, leading to detachment or avulsion of the epiphysis, resulting in life-long devastating consequences for patients. There is an obvious inflammatory response in the phase of growth plate injury, the limited physiological inflammatory response locally favors tissue repair and the organism, but uncontrolled chronic inflammation always leads to tissue destruction and disease progression. Interleukin-1β (IL-1β), as representative inflammatory factors, not only affect the inflammatory phase response to bone and soft tissue injury, but have a potentially important role in the later repair phase, though the exact mechanism is not fully understood. At present, epiphyseal plate injuries are mainly treated by corrective and reconstructive surgery, which is highly invasive with limited effectiveness, thus new therapeutic approaches are urgently needed, so a deeper understanding and exploration of the pathological mechanisms of epiphyseal plate injuries at the cellular molecular level is an entry point. In this review, we fully introduced the key role of IL-1 in the progression of epiphyseal plate injury and repair, deeply explored the mechanism of IL-1 on the molecular transcript level and endocrine metabolism of chondrocytes from multiple aspects, and summarized other possible mechanisms to provide theoretical basis for the clinical treatment and in-depth study of epiphyseal plate injury in children.

Relationship Between Body Mass Index and Osteoarthritis for Single and Multisite Osteoarthritis of the Hand, Hip, or Knee: Findings From a Canadian Longitudinal Study on Aging

OBJECTIVE

To determine whether an apparent association between hand osteoarthritis (OA) and adiposity is explained by the presence of OA at other joint sites.

METHODS

Data from the Canadian Longitudinal Study on Aging, first cycle, comprehensive cohort, were used. Respondents age 45-85 years (n = 18,279) were asked separate questions about doctor-diagnosed OA in the hand, hip, or knee. Multinomial logistic regression was used to investigate the relationship between all combinations of hand, hip, and knee OA and body mass index (BMI) and waist-to-height ratio (WHtR).

RESULTS

OA was reported by 34.6% of respondents, 28.0% with OA at >1 joint site. Hand OA was not significantly associated with BMI after accounting for OA at other joint sites, with similar findings for WHtR. All joint site combinations containing the knee were strongly associated with BMI, with odds ratios (ORs) ranging from OR 2.92 (95% confidence interval [95% CI] 2.53-3.37) for knee OA only with obesity class I to OR 9.98 (95% CI 7.12-13.88) for multi-joint knee, hip, hand OA with obesity class II/III. BMI distributions including knee OA were broader and shifted to higher BMI levels than those for hand or hip OA.

CONCLUSION

Apparent associations between hand OA and BMI may be explained by concurrent OA at other joint sites. Recognizing that OA is a multi-joint disease is crucial for studies of the associations of adiposity with OA in a particular joint, especially the hand. The association between knee OA and BMI appears to be distinct from those for OA at other joint sites.

The association of the lipid profile with knee and hand osteoarthritis severity: the IMI-APPROACH cohort

OBJECTIVE

To investigate the association of the lipidomic profile with osteoarthritis (OA) severity, considering the outcomes radiographic knee and hand OA, pain and function.

DESIGN

We used baseline data from the Applied Public-Private Research enabling OsteoArthritis Clinical Headway (APPROACH) cohort, comprising persons with knee OA fulfilling the clinical American College of Rheumatology classification criteria. Radiographic knee and hand OA severity was quantified with Kellgren-Lawrence sum scores. Knee and hand pain and function were assessed with validated questionnaires. We quantified fasted plasma higher order lipids and oxylipins with liquid chromatography with tandem mass spectrometry (LC-MS/MS)-based platforms. Using penalised linear regression, we assessed the variance in OA severity explained by lipidomics, with adjustment for clinical covariates (age, sex, body mass index (BMI) and lipid lowering medication), measurement batch and clinical centre.

RESULTS

In 216 participants (mean age 66 years, mean BMI 27.3 kg/m², 75% women) we quantified 603 higher order lipids (triacylglycerols, diacylglycerols, cholesteryl esters, ceramides, free fatty acids, sphingomyelins, phospholipids) and 28 oxylipins. Lipidomics explained 3% and 2% of the variance in radiographic knee and hand OA severity, respectively. Lipids were not associated with knee pain or function. Lipidomics accounted for 12% and 6% of variance in hand pain and function, respectively. The investigated OA severity outcomes were associated with the lipidomic fraction of bound and free arachidonic acid, bound palmitoleic acid, oleic acid, linoleic acid and docosapentaenoic acid.

CONCLUSIONS

Within the APPROACH cohort lipidomics explained a minor portion of the variation in OA severity, which was most evident for the outcome hand pain. Our results suggest that eicosanoids may be involved in OA severity.

Obesity, Inflammation, and Immune System in Osteoarthritis

Obesity remains the most important risk factor for the incidence and progression of osteoarthritis (OA). The leading cause of OA was believed to be overloading the joints due to excess weight which in turn leads to the destruction of articular cartilage. However, recent studies have proved otherwise, various other factors like adipose deposition, insulin resistance, and especially the improper coordination of innate and adaptive immune responses may lead to the initiation and progression of obesity-associated OA. It is becoming increasingly evident that multiple inflammatory cells are recruited into the synovial joint that serves an important role in pathological changes in the synovial joint. Polarization of macrophages and macrophage-produced mediators are extensively studied and linked to the inflammatory and destructive responses in the OA synovium and cartilage. However, the role of other major innate immune cells such as neutrophils, eosinophils, and dendritic cells in the pathogenesis of OA has not been fully evaluated. Although cells of the adaptive immune system contribute to the pathogenesis of obesity-induced OA is still under exploration, a quantity of literature indicates OA synovium has an enriched population of T cells and B cells compared with healthy control. The interplay between a variety of immune cells and other cells that reside in the articular joints may constitute a vicious cycle, leading to pathological changes of the articular joint in obese individuals. This review addresses obesity and the role of all the immune cells that are involved in OA and summarised animal studies and human trials and knowledge gaps between the studies have been highlighted. The review also touches base on the interventions currently in clinical trials, different stages of the testing, and their shortcomings are also discussed to understand the future direction which could help in understanding the multifactorial aspects of OA where inflammation has a significant function.

Associations of Body Mass Index With Pain and the Mediating Role of Inflammatory Biomarkers in People With Hand Osteoarthritis

OBJECTIVE

To examine the association of body mass index (BMI) with pain in people with hand osteoarthritis (OA), and explore whether this association, if causal, is mediated by systemic inflammatory biomarkers.

METHODS

In 281 Nor-Hand study participants, we estimated associations between BMI and hand pain, as measured by the Australian/Canadian Osteoarthritis Hand Index (AUSCAN; range 0-20) and Numerical Rating Scale (NRS; range 0-10); foot pain, as measured by NRS (range 0-10); knee/hip pain, as measured by the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC; range 0-20); painful total body joint count; and pain sensitization. We fit natural-effects models to estimate natural direct and natural indirect effects of BMI on pain through inflammatory biomarkers.

RESULTS

Each 5-unit increase in BMI was associated with more severe hand pain (on average increased AUSCAN by 0.64 [95% confidence interval (95% CI) 0.23, 1.08]), foot pain (on average increased NRS by 0.65 [95% CI 0.36, 0.92]), knee/hip pain (on average increased WOMAC by 1.31 [95% CI 0.87, 1.73]), generalized pain, and pain sensitization. Mediation analyses suggested that the effects of BMI on hand pain and painful total body joint count were partially mediated by leptin and high-sensitivity C-reactive protein (hsCRP), respectively. Effect sizes for mediation by leptin were larger for the hands than for the lower extremities, and were statistically significant for the hands only.

CONCLUSION

In people with hand OA, higher BMI is associated with greater pain severity in the hands, feet, and knees/hips. Systemic effects of obesity, measured by leptin, may play a larger mediating role for pain in the hands than in the lower extremities. Low-grade inflammation, measured by hsCRP, may contribute to generalized pain in overweight/obese individuals.

Fundamentals of OA. An initiative of Osteoarthritis and Cartilage. Obesity and metabolic factors in OA

OBJECTIVE

Obesity was once considered a risk factor for knee osteoarthritis (OA) primarily for biomechanical reasons. Here we provide an additional perspective by discussing how obesity also increases OA risk by altering metabolism and inflammation.

DESIGN

This narrative review is presented in four sections: 1) metabolic syndrome and OA, 2) metabolic biomarkers of OA, 3) evidence for dysregulated chondrocyte metabolism in OA, and 4) metabolic inflammation: joint tissue mediators and mechanisms.

RESULTS

Metabolic syndrome and its components are strongly associated with OA. However, evidence for a causal relationship is context dependent, varying by joint, gender, diagnostic criteria, and demographics, with additional environmental and genetic interactions yet to be fully defined. Importantly, some aspects of the etiology of obesity-induced OA appear to be distinct between men and women, especially regarding the role of adipose tissue. Metabolomic analyses of serum and synovial fluid have identified potential diagnostic biomarkers of knee OA and prognostic biomarkers of disease progression. Connecting these biomarkers to cellular pathophysiology will require future in vivo studies of joint tissue metabolism. Such studies will help reveal when a metabolic process or a metabolite itself is a causal factor in disease progression. Current evidence points towards impaired chondrocyte metabolic homeostasis and metabolic-immune dysregulation as likely factors connecting obesity to the increased risk of OA.

CONCLUSIONS

A deeper understanding of how obesity alters metabolic and inflammatory pathways in synovial joint tissues is expected to provide new therapeutic targets and an improved definition of "metabolic" and "obesity" OA phenotypes.

Leptin in Osteoarthritis and Rheumatoid Arthritis: Player or Bystander?

White adipose tissue (WAT) is a specialized tissue whose main function is lipid synthesis and triglyceride storage. It is now considered as an active organ secreting a plethora of hormones and cytokines namely adipokines. Discovered in 1994, leptin has emerged as a key molecule with pleiotropic functions. It is primarily recognized for its role in regulating energy homeostasis and food intake. Currently, further evidence suggests its potent role in reproduction, glucose metabolism, hematopoiesis, and interaction with the immune system. It is implicated in both innate and adaptive immunity, and it is reported to contribute, with other adipokines, in the cross-talking networks involved in the pathogenesis of chronic inflammation and immune-related diseases of the musculo-skeletal system such as osteoarthritis (OA) and rheumatoid arthritis (RA). In this review, we summarize the most recent findings concerning the involvement of leptin in immunity and inflammatory responses in OA and RA.

Adiponectin in Osteoarthritis: Pathophysiology, Relationship with Obesity and Presumptive Diagnostic Biomarker Potential

Osteoarthritis (OA) is a multifactorial, irreversible age- and obesity-induced joint degenerative disease, with an increasing incidence in developed countries. With a pathophysiology and etiology that are currently under-investigated, the only available disease-modifying treatment relies solely on total joint arthroplasty, which entails major economic burdens. Recently, the research focus has shifted towards the evaluation of metabolically active mediators secreted by the adipose tissue, which could be potential targets for a better understanding of the mechanisms involved in OA onset and development. Of note, adiponectin has drawn a great deal of attention, since it is the most abundant type of circulating adipokine and has been highly associated with OA occurrence. Thus far, studies have been controversial in establishing whether adiponectin possesses a destructive or protective role in OA development. Therefore, we critically and systematically reviewed, herein, the roles of adiponectin in the pathophysiology of OA, the link between obesity, adiponectin expression and the progression of OA, as well as its potential role as a future biomarker for a more optimized and reliable diagnosis of this degenerative disorder.

Effects of body weight and fat mass on back pain - direct mechanical or indirect through inflammatory and metabolic parameters?

BACKGROUND

While reports indicate the association between obesity and back pain, its mechanism is still unclear. Thus, we aimed to investigate the effects of weight and its components on back pain in middle-aged women while considering direct mechanical and indirect effects via inflammatory and metabolic parameters.

METHODS

We used data from the Chingford 1000 Women Study, two follow-ups seven years apart. We assessed effects of weight, body mass index (BMI), total fat mass (TFM), total lean mass (TLM) and total bone mineral density (TBMD), measured by dual-energy X-ray absorptiometry, on back pain episode. We used inflammatory (C-reactive protein, interleukin-6, and tumour necrosis factor-alpha) and metabolic parameters (systolic and diastolic blood pressure, triglyceride, high-density lipoprotein cholesterol, and fasting blood glucose) as mediators of indirect effects. We investigated associations of interest cross-sectionally and longitudinally using binary logistic regression and parallel mediation model.

RESULTS

We included 826 Chingford middle-aged women (mean age=60.7, SD=5.9) from the first used follow-up in cross-sectional and mediation analyses and 645 women that attended the follow-up seven years later, in longitudinal analyses. We found that increased weight was directly associated with increased odds of having back pain episode (OR=1.02; 95% CI 1.01-1.03), similarly as BMI (OR=1.05; 95% CI 1.02-1.08) and TFM (OR=1.03; 95% CI 1.01-1.04) consistently across the cross-sectional and longitudinal models, but not TLM or TBMD. However, we did not find consistent indirect effects of weight or its components through measured inflammatory or metabolic parameters on back pain.

CONCLUSIONS

Our results show that in middle-aged women, weight, BMI and TFM are directly related to back pain, indicating prominence of mechanical loading effect.

Molecular Classification of Knee Osteoarthritis

Knee osteoarthritis (KOA) is the most common form of joint degeneration with increasing prevalence and incidence in recent decades. KOA is a molecular disorder characterized by the interplay of numerous molecules, a considerable number of which can be detected in body fluids, including synovial fluid, urine, and blood. However, the current diagnosis and treatment of KOA mainly rely on clinical and imaging manifestations, neglecting its molecular pathophysiology. The mismatch between participants' molecular characteristics and drug therapeutic mechanisms might explain the failure of some disease-modifying drugs in clinical trials. Hence, according to the temporal alteration of representative molecules, we propose a novel molecular classification of KOA divided into pre-KOA, early KOA, progressive KOA, and end-stage KOA. Then, progressive KOA is furtherly divided into four subtypes as cartilage degradation-driven, bone remodeling-driven, inflammation-driven, and pain-driven subtype, based on the major pathophysiology in patient clusters. Multiple clinical findings of representatively investigated molecules in recent years will be reviewed and categorized. This molecular classification allows for the prediction of high-risk KOA individuals, the diagnosis of early KOA patients, the assessment of therapeutic efficacy, and in particular, the selection of homogenous patients who may benefit most from the appropriate therapeutic agents.

Serum Leptin and Resistin Levels in Knee Osteoarthritis-Clinical and Radiologic Links: Towards Precise Definition of Metabolic Type Knee Osteoarthritis

Obesity is considered a major risk factor for the development and progression of knee osteoarthritis (OA). Apart from the mechanical effect of obesity via increase in mechanical overload of weight-bearing joints, an association with hand OA has been observed. There has been increasing interest in the role of adipokines in the pathogenesis of OA in the recent years. It has been suggested that their systemic effects link obesity and OA. In this regard, the aim of the current study was measurement and analysis of serum levels of leptin and resistin in patients with knee OA with different body mass index (BMI). Seventy-three patients with primary symptomatic knee OA at the age between 35 and 87 years (mean age 66 years) were included in the study (67 women and 6 men). The patients were from 2nd to 4th radiographic stage according to Kellgren–Lawrence scale. 43 patients were with concomitant obesity (BMI ≥ 30 kg/m², mean values 38.34 ± 8.20) and 30 patients with BMI < 30 kg/m² (mean values 25.07 ± 2.95). Eleven individuals with different BMIs, including cases with obesity but without radiographic knee OA, were examined as a control group. Serum levels of leptin and resistin were measured via ELISA method. In patients with knee OA and BMI ≥ 30 kg/m², serum levels of leptin (39.546 ± 12.918 ng/mL) were significantly higher as compared with healthy individuals (15.832 ± 16.531 ng/mL, p < 0.05) and the patients with low BMI (p < 0.05). In patients with BMI < 30 kg/m² the levels of leptin (13.010 ± 10.94 ng/mL) did not differ significantly from the respective values in the control group (p = 0.48). Serum levels of resistin were also higher in knee OA patients in comparison with healthy controls, but the difference was statistically significant only for patients with high BMI (2.452 ± 1.002 ng/mL in the group with BMI ≥ 30 kg/m²; 2.401 ± 1.441 ng/mL in patients with BMI < 30 kg/m²; 1.610 ± 1.001 ng/mL in the control group, p < 0.05). A correlation was found between the serum levels of leptin and radiographic stage of OA, i.e., higher leptin levels were present in the more advanced 3rd and 4th radiographic stage, while for resistin a correlation was observed in the patient subgroup with BMI < 30 kg/m². Serum leptin and resistin levels and clinical characteristics were analyzed in patients with different clinical forms of OA. Novel clinical correlations have been found in the current study in patients with isolated knee OA vs. cases with presence of other disease localizations. It has been observed that patients with isolated knee OA were significantly younger and had higher BMI as compared with cases in whom OA is combined with other localizations i.e., spondyloarthritis ± presence of hip OA and with generalized OA. This supports the hypothesis that presence of obesity promotes earlier development of knee OA as an isolated localization of the disease in younger patients before appearance of osteoarthritic changes at other sites. The levels of leptin and resistin in isolated knee OA were also higher. Serum levels of leptin and resistin in combination with patients’ clinical characteristics suggest existence of different clinical and laboratory profile through which more precise definition of metabolic phenotype of knee OA would be possible. Considering the fact that obesity is a modifiable risk factor that has an impact on progression of knee OA, different approaches to influence obesity may offer potential for future disease-modifying therapeutic interventions.

Current Epidemiology and Risk Factors for the Development of Hand Osteoarthritis

PURPOSE OF REVIEW

Hand osteoarthritis (hand OA), the most common peripheral arthritis in the world, is less studied than osteoarthritis (OA) of the knee and hip. However, it is uniquely situated to offer novel insight into OA as a disease process by removing weight-bearing as a confounder of systemic disease mechanisms. Here we review the epidemiology of hand OA and key risk factors for its development.

RECENT FINDINGS

Mounting evidence points to obesity as an important risk factor for hand OA development, with new evidence implicating a role for leptin and serum fatty acids. Disease progression in hand OA and specifically the erosive OA subtype may be associated with diabetes. New evidence supports an association between cardiovascular disease progression and symptomatic hand OA. Alcohol use may be associated with increased synovitis and erosive hand OA. Differences in ethnical distributions of hand OA have become more apparent, with a lower prevalence in Black patients compared to White patients. Novel genetic insights implicating the WNT gene pathway and IL-1β have led to novel potential targets in hand OA pathogenesis. Hand OA is a heterogeneous disease with many modifiable and non-modifiable risk factors that can determine disease severity and shed light on disease pathogenesis.

Clinical and Genetic Risk Factors Associated With the Presence of Lupus Nephritis

Objective

To elucidate whether clinical features and the weighted genetic risk score (wGRS) were associated with the presence of lupus nephritis (LN).

Methods

We retrospectively divided patients with systemic lupus erythematosus (SLE, n=1,078) into biopsy-proven LN (n=507) and non-LN groups (non-LN, n=571) Baseline clinical features, serologic markers, and the wGRS were collected The wGRS was calculated from 112 non-human leukocyte antigen (non-HLA) loci and HLA-DRβ1 amino acid haplotypes for SLE Associations among clinical features, wGRS, and the presence of LN were identified.

Results

In the multivariate analysis, patients with LN were younger at diagnosis (odds ratio [OR]=0.97, p<0.001), had more pleuritis (OR=2.44, p<0.001) and pericarditis (OR=1.62, p=0.029), had a higher detection rate of anti-double stranded deoxyribonucleic acid (anti-dsDNA antibodies, OR=2.22, p<0.001), anti-Smith antibodies (anti-Sm antibodies, OR=1.70, p=0.002), low level of complement (OR=1.37, p=0.043) and absence of antiphospholipid antibodies (aPL antibodies, OR=1.60, p=0.002), and had higher wGRS (OR=1.16, p=0.012) Mediation analysis suggested that anti-Sm antibodies and low complement could be mediators in the relationship between high wGRS and the presence of LN.

Conclusion

Onset age, pleuritis, pericarditis, several serologic markers, and wGRS were associated with the presence of LN Anti-Sm antibodies and low complement appeared to mediate the indirect relationship between wGRS and the presence of LN.

Association of serum levels of inflammatory markers and adipokines with joint symptoms and structures in participants with knee osteoarthritis

OBJECTIVE

To investigate the longitudinal associations of serum inflammatory markers and adipokines with joint symptoms and structures in participants with knee osteoarthritis (OA).

METHODS

Two hundred participants (46.5% female, mean age 63.1 years, mean BMI 29.5 kg/m2) from Tasmania part of the VIDEO (Vitamin D Effect on OA) study were randomly selected in the current study. Serum levels of 19 biomarkers, scores of Western Ontario and McMaster Universities Index (WOMAC), and magnetic resonance imaging-assessed knee structures were evaluated at baseline and month 24. The patterns of biomarkers were derived from principal component analysis and their association with knee symptoms and structures were examined using adjusted generalized estimating equations.

RESULTS

Five components explained 78% of the total variance. Interleukin (IL)-1β, -2, -4, -6, -8, -17A, -17F, -21, -22 and -23 loaded the highest on the first component, which was associated with increased bone marrow lesions (BMLs) and WOMAC dysfunction score. IL-10, -12 and granulocyte-macrophage colony-stimulating factor loaded on the second component, which was associated with increased cartilage volume, and decreased effusion-synovitis and WOMAC scores. Leptin, adipsin and C-reactive protein loaded on the third component, which was positively associated with WOMAC scores. Resistin loaded on the fourth component, which was associated with increased BMLs and cartilage defects. Apelin-36 and adiponectin loaded on the fifth component, which was associated with increased BMLs.

CONCLUSION

Various inflammatory and metabolic components were associated differently with joint symptoms and structural changes in knee OA, suggesting a complex inflammatory and metabolic inter-relationship in the pathogenesis of knee OA.

Reduced Muscle Strength Is Associated With Insulin Resistance in Type 2 Diabetes Patients With Osteoarthritis

CONTEXT

Type 2 diabetes is associated with a greater risk for musculoskeletal disorders, yet its impact on joint function remains unclear.

OBJECTIVE

We hypothesized that patients with type 2 diabetes and osteoarthritis would exhibit musculoskeletal impairment, which would associate with insulin resistance and distinct microRNA profiles.

METHODS

Participants of the German Diabetes Study with type 2 diabetes (T2D, n = 39) or normal glucose tolerance (CON, n = 27), both with (+OA) or without osteoarthritis (-OA) underwent intravenous glucose tolerance and hyperinsulinemic-euglycemic clamp tests. Musculoskeletal function was assessed by isometric knee extension strength (KES), grip strength, range of motion (ROM), and balance skills, while neural function was measured by nerve conductance velocity (NCV). Arthritis-related symptoms were quantified using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) questionnaire, serum arthritis-related microRNA using quantitative polymerase chain reaction.

RESULTS

Insulin sensitivity was lower in T2D+OA vs T2D-OA (4.4 ± 2.0 vs 5.7 ± 3.0 mg* kg-1*min-1) and in CON+OA vs CON-OA (8.1 ± 2.0 vs 12.0 ± 2.6 mg*kg-1,*min-1, both P < .05). In T2D+OA, KES and ROM were 60% and 22% lower than in CON+OA, respectively (both P < .05). Insulin sensitivity correlated positively with KES (r = 0.41, P < .05) among T2D, and negatively with symptom severity in CON and T2D (r = -0.60 and r = -0.46, respectively, P < .05). CON+OA and T2D+OA had inferior balance skills than CON-OA, whereas NCV was comparable in T2D+OA and T2D-OA. Expression of arthritis-related microRNAs was upregulated in T2D compared to CON, but downregulated in CON+OA compared to CON-OA (P < .05), and did not differ between T2D+OA and T2D-OA.

CONCLUSION

Musculoskeletal impairment and osteoarthritis-related symptoms are associated with insulin resistance. Type 2 diabetes can mask changes in arthritis-related microRNA profiles.

Acteoside Counteracts Interleukin-1β-Induced Catabolic Processes through the Modulation of Mitogen-Activated Protein Kinases and the NFκB Cellular Signaling Pathway

Osteoarthritis (OA) is the most common degenerative joint disease with chronic joint pain caused by progressive degeneration of articular cartilage at synovial joints. Acteoside, a caffeoylphenylethanoid glycoside, has various biological activities such as antimicrobial, anti-inflammatory, anticancer, antioxidative, cytoprotective, and neuroprotective effect. Further, oral administration of acteoside at high dosage does not cause genotoxicity. Therefore, the aim of present study is to verify the anticatabolic effects of acteoside against osteoarthritis and its anticatabolic signaling pathway. Acteoside did not decrease the viabilities of mouse fibroblast L929 cells used as normal cells and primary rat chondrocytes. Acteoside counteracted the IL-1β-induced proteoglycan loss in the chondrocytes and articular cartilage through suppressing the expression and activation of cartilage-degrading enzyme such as matrix metalloproteinase- (MMP-) 13, MMP-1, and MMP-3. Furthermore, acteoside suppressed the expression of inflammatory mediators such as inducible nitric oxide synthase, cyclooxygenase-2, nitric oxide, and prostaglandin E2 in the primary rat chondrocytes treated with IL-1β. Subsequently, the expression of proinflammatory cytokines was decreased by acteoside in the primary rat chondrocytes treated with IL-1β. Moreover, acteoside suppressed not only the phosphorylation of mitogen-activated protein kinases in primary rat chondrocytes treated with IL-1β but also the translocation of NFκB from the cytosol to the nucleus through suppression of its phosphorylation. Oral administration of 5 and 10 mg/kg acteoside attenuated the progressive degeneration of articular cartilage in the osteoarthritic mouse model generated by destabilization of the medial meniscus. Our findings indicate that acteoside is a promising potential anticatabolic agent or supplement to attenuate or prevent progressive degeneration of articular cartilage.

Biomarkers of Joint Damage in Osteoarthritis: Current Status and Future Directions

Osteoarthritis (OA) is a disease of the whole joint organ, characterized by the loss of cartilage, and structural changes in bone including the formation of osteophytes, causing disability and loss of function. It is also associated with systemic mediators and low-grade inflammation. Currently, there is negligible/no availability of specific biomarkers that can be used to facilitate the diagnosis and treatment of OA. The most unmet clinical need is, however, related to the monitoring of disease progression over a short period that can be used in clinical trials. In this review, the value of biomarkers identified over the past decade has been highlighted. These biomarkers are associated with the synthesis and breakdown of cartilage, including collagenous and noncollagenous biomarkers, inflammatory and anti-inflammatory biomarkers, expressed in the biological fluid such as serum, synovial fluid, and urine. Broad validation of novel and clinically applicable biomarkers and their involvement in the pathways are particularly needed for early-stage diagnosis, monitoring disease progression, and severity and examining new drugs to mitigate the effects of this highly prevalent and debilitating condition.

Joint-adjacent Adipose Tissue by MRI is Associated With Prevalence and Progression of Knee Degenerative Changes: Data from the Osteoarthritis Initiative

BACKGROUND

Adipose tissue has recently gained interest as an independent imaging biomarker for osteoarthritis.

PURPOSE

To explore 1) cross-sectional associations between local subcutaneous fat (SCF) thickness at the knee and the extent of degenerative changes in overweight and obese individuals and 2) associations between local fat distribution and progression of osteoarthritis over 4 years.

STUDY TYPE

Retrospective cohort study.

POPULATION

338 obese and overweight participants from the Osteoarthritis Initiative cohort without radiographic evidence of osteoarthritis.

FIELD STRENGTH

3T: 3D-FLASH-WE; 3D-DESS-WE; T1w-SE; MSME.

ASSESSMENT

Baseline SCF thickness was measured in standardized locations medial, lateral and anterior to the knee and the average joint-adjacent SCF (ajSCF) was calculated. Right thigh SCF cross-sectional area was assessed. Quantitative cartilage T₂ relaxation times and semi-quantitative whole organ MRI scores (WORMS) were obtained at baseline and 4-year follow-up. WORMS_sum was calculated as sum of cartilage, bone marrow edema, subchondral cyst, and meniscal scores.

STATISTICAL TESTS

Associations of SCF measures with baseline, and 4-year change in T₂ and WORMS were analyzed using regression models. SCF measurements were standardized using the equation Value Participant - Mean Cohort Standard deviation . Analyses were adjusted for age, sex, physical activity, and BMI.

RESULTS

Cross-sectionally, significant associations between lateral SCF, lateral compartment WORMS and T₂ were found ( Δ WORMS sum 1 SD change in lateral SCF , [95% CI]: 0.53, [0.12-0.95], P < 0.05; ΔT₂ : 0.50, [0.02-0.98], P < 0.05). Moreover, greater lateral SCF was associated with faster progression of lateral WORMS_sum gradings (OR = 1.50, [1.05-2.15], P < 0.05). No significant positive associations were found for thigh SCF and WORMS_sum (P = 0.44) or T₂ measurements (medial: P = 0.15, lateral: 0.39, patellar: P = 0.75).

DATA CONCLUSION

Joint-adjacent SCF thickness was associated with imaging parameters of knee osteoarthritis, both cross-sectionally and longitudinally, while thigh SCF was not, suggesting a spatial association of SCF and knee osteoarthritis. Based on these findings, joint-adjacent SCF may play a role in the development and progression of knee osteoarthritis.

LEVEL OF EVIDENCE

4 TECHNICAL EFFICACY: Stage 5.

An Update on the Role of Leptin in the Immuno-Metabolism of Cartilage

Since its discovery in 1994, leptin has been considered as an adipokine with pleiotropic effects. In this review, we summarize the actual information about the impact of this hormone on cartilage metabolism and pathology. Leptin signalling depends on the interaction with leptin receptor LEPR, being the long isoform of the receptor (LEPRb) the one with more efficient intracellular signalling. Chondrocytes express the long isoform of the leptin receptor and in these cells, leptin signalling, alone or in combination with other molecules, induces the expression of pro-inflammatory molecules and cartilage degenerative enzymes. Leptin has been shown to increase the proliferation and activation of immune cells, increasing the severity of immune degenerative cartilage diseases. Leptin expression in serum and synovial fluid are related to degenerative diseases such as osteoarthritis (OA), rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE). Inhibition of leptin signalling showed to have protective effects in these diseases showing the key role of leptin in cartilage degeneration.

Gender-Specific Response in Pain and Function to Biologic Treatment of Knee Osteoarthritis: A Gender-Bias-Mitigated, Observational, Intention-to-Treat Study at Two Years

Knee osteoarthritis is a major cause of disability worldwide. Newer modalities of treatment with less morbidity, such as intra-articular injection of microfragmented fat (MFAT), are showing promise. We report on our novel observation that women show a greater improvement in pain and function to MFAT than men. Traditionally, women have been underrepresented in studies and studies with both sexes regularly fail to analyze the results by sex. To mitigate for this bias and quantify it, we describe a technique using reproducible statistical analysis and replicable results with Open Access statistical software R to calculate the magnitude of this difference. Genetic, hormonal, environmental, and age factors play a role in our observed difference between the sexes. There is a need for further studies to identify the molecular basis for this difference and be able to utilize it to improve outcome for both women and men.

Cartilage tissue engineering for obesity-induced osteoarthritis: Physiology, challenges, and future prospects

Osteoarthritis (OA) is a multifactorial joint disease with pathological changes that affect whole joint tissue. Obesity is acknowledged as the most influential risk factor for both the initiation and progression of OA in weight-bearing and non-weight-bearing joints. Obesity-induced OA is a newly defined phenotypic group in which chronic low-grade inflammation has a central role. Aside from persistent chronic inflammation, abnormal mechanical loading due to increased body weight on weight-bearing joints is accountable for the initiation and progression of obesity-induced OA. The current therapeutic approaches for OA are still evolving. Tissue-engineering-based strategy for cartilage regeneration is one of the most promising treatment breakthroughs in recent years. However, patients with obesity-induced OA are often excluded from cartilage repair attempts due to the abnormal mechanical demands, altered biomechanical and biochemical activities of cells, persistent chronic inflammation, and other obesity-associated factors. With the alarming increase in the number of obese populations globally, the need for an innovative therapeutic approach that could effectively repair and restore the damaged synovial joints is of significant importance for this sub-population of patients. In this review, we discuss the involvement of the systemic and localized inflammatory response in obesity-induced OA and the impact of altered mechanical loading on pathological changes in the synovial joint. Moreover, we examine the current strategies in cartilage tissue engineering and address the critical challenges of cell-based therapies for OA. Besides, we provide examples of innovative ways and potential strategies to overcome the obstacles in the treatment of obesity-induced OA.

THE TRANSLATIONAL POTENTIAL OF THIS ARTICLE

Altogether, this review delivers insight into obesity-induced OA and offers future research direction on the creation of tissue engineering-based therapies for obesity-induced OA.

L-PGDS deficiency accelerated the development of naturally occurring age-related osteoarthritis

Osteoarthritis (OA) is the most common musculoskeletal disorder among the elderly. It is characterized by progressive cartilage degradation, synovial inflammation, subchondral bone remodeling and pain. Lipocalin prostaglandin D synthase (L-PGDS) is responsible for the biosynthesis of PGD₂, which has been implicated in the regulation of inflammation and cartilage biology. This study aimed to evaluate the effect of L-PGDS deficiency on the development of naturally occurring age-related OA in mice.

OA-like structural changes were assessed by histology, immunohistochemistry, and micro–computed tomography. Pain related behaviours were assessed using the von Frey and the open-field assays.

L-PGDS deletion promoted cartilage degradation during aging, which was associated with enhanced expression of extracellular matrix degrading enzymes, matrix metalloprotease 13 (MMP-13) and a disintegrin and metalloproteinase with thrombospondin motifs 5 (ADAMTS-5), and their breakdown products, C1,2C, VDIPEN and NITEG. Moreover, L-PGDS deletion enhanced subchondral bone changes, but had no effect on its angiogenesis. Additionally, L-PGDS deletion increased mechanical sensitivity and reduced spontaneous locomotor activity. Finally, we showed that the expression of L-PGDS was elevated in aged mice. Together, these findings indicate an important role for L-PGDS in naturally occurring age-related OA. They also suggest that L-PGDS may constitute a new efficient therapeutic target in OA.

Pain in women with knee and/or hip osteoarthritis is related to systemic inflammation and to adipose tissue dysfunction: Cross-sectional results of the KHOALA cohort

BACKGROUND

Considering the role of metabolic diseases in osteoarthritis (OA), we investigated whether biomarkers of adipose tissue dysfunction could be associated with OA-related pain.

DESIGN

We cross-sectionally analyzed patients with knee and/or hip OA at inclusion in the KHOALA cohort. We used visual analogic scale (VAS) for pain, the Western Ontario and McMaster Universities Arthritis Index (WOMAC) and Osteoarthritis Knee and Hip Quality of Life (OAKHQOL) pain subscores. At inclusion, we measured ultra-sensitive CRP (usCRP), leptin and adiponectin for calculation of leptin:adiponectin ratio (LAR), a marker of adipose tissue dysfunction associated with central adiposity, high-molecular-weight adiponectin, visfatin and apolipoproteins. Univariate and multivariable analyses using stepwise linear regression models were performed to search for correlation between pain assessments and these biomarkers, with systematic adjustment on age.

RESULTS

In 596 women with hip and/or knee OA, multivariable analyses indicated that higher pain intensity was associated with higher LAR (VAS pain: β=0.49; p = 0.0001, OAKHQOL pain: β=-0.46; p = 0.0002, WOMAC pain: β=0.30; p = 0.001) in the whole group as well as in hip or knee OA patients considered separately. Pain intensity correlated also with usCRP level (VAS pain: β= 0.27; p = 0.02, OAKHQOL pain: β =-0.30; p = 0.01) and Kellgren-Lawrence score. In 267 men, no correlation between biomarkers and pain was found.

CONCLUSION

Serum LAR and usCRP level are associated with pain level, independently of radiographic structural severity in women with hip and/or knee OA, emphasizing the role of adipose tissue dysfunction and of meta-inflammation in pain experience in the female population.

Of mice and men: converging on a common molecular understanding of osteoarthritis

Despite an increasing burden of osteoarthritis in developed societies, target discovery has been slow and there are currently no approved disease-modifying osteoarthritis drugs. This lack of progress is due in part to a series of misconceptions over the years: that osteoarthritis is an inevitable consequence of ageing, that damaged articular cartilage cannot heal itself, and that osteoarthritis is driven by synovial inflammation similar to that seen in rheumatoid arthritis. Molecular interrogation of disease through ex-vivo tissue analysis, in-vitro studies, and preclinical models have radically reshaped the knowledge landscape. Inflammation in osteoarthritis appears to be distinct from that seen in rheumatoid arthritis. Recent randomised controlled trials, using treatments repurposed from rheumatoid arthritis, have largely been unsuccessful. Genome-wide studies point to defects in repair pathways, which accords well with recent promise using growth factor therapies or Wnt pathway antagonism. Nerve growth factor has emerged as a robust target in osteoarthritis pain in phase 2-3 trials. These studies, both positive and negative, align well with those in preclinical surgical models of osteoarthritis, indicating that pathogenic mechanisms identified in mice can lead researchers to valid human targets. Several novel candidate pathways are emerging from preclinical studies that offer hope of future translational impact. Enhancing trust between industry, basic, and clinical scientists will optimise our collective chance of success.

Setting up distinctive outcome measures for each osteoarthritis phenotype

Osteoarthritis (OA) is an evolving chronic joint disease with a huge global impact. Given the intricate nature of the etiopathogenesis and subsequent high heterogeneity in the clinical course of OA, it is crucial to discriminate between etiopathogenic endotypes and clinical phenotypes, especially in the early stages of the disease. In this sense, we propose that an OA phenotype should be properly assessed with a set of outcome measures including those specifically related to the main underlying pathophysiological mechanisms. Thus, each OA phenotype can be related to different and clinically meaningful outcomes. OA phenotyping would lead to an adequate patient stratification in well-designed clinical trials and the discovery of precise therapeutic approaches. A significant effort will be required in this field in light of inconclusive results of clinical trials of tissue-targeting agents for the treatment of OA.

Purinergic System Signaling in Metainflammation-Associated Osteoarthritis

Inflammation triggered by metabolic imbalance, also called metainflammation, is low-grade inflammation caused by the components involved in metabolic syndrome (MetS), including central obesity and impaired glucose tolerance. This phenomenon is mainly due to excess nutrients and energy, and it contributes to the pathogenesis of osteoarthritis (OA). OA is characterized by the progressive degeneration of articular cartilage, which suffers erosion and progressively becomes thinner. Purinergic signaling is involved in several physiological and pathological processes, such as cell proliferation in development and tissue regeneration, neurotransmission and inflammation. Adenosine and ATP receptors, and other members of the signaling pathway, such as AMP-activated protein kinase (AMPK), are involved in obesity, type 2 diabetes (T2D) and OA progression. In this review, we focus on purinergic regulation in osteoarthritic cartilage and how different components of MetS, such as obesity and T2D, modulate the purinergic system in OA. In that regard, we describe the critical role in this disease of receptors, such as adenosine A2A receptor (A2AR) and ATP P2X7 receptor. Finally, we also assess how nucleotides regulate the inflammasome in OA.

Mediation analysis for the relationship between dyslipidemia and coronary artery disease via hypersensitive C-reactive protein in a case-control study

BACKGROUND

The pathological basis of coronary artery disease (CAD) is atherosclerosis which is associated with inflammation and dyslipidemia. However, the involvement of hypersensitive C-reactive protein (hs-CRP) in lipid metabolism and how it affects the pathogenesis of CAD is uncertain.

OBJECTIVE

To explore whether the relationship between dyslipidemia and CAD is partly mediated by hs-CRP levels.

METHODS

Three hundred fifteen pairs of randomly sexand age-matched CAD and non-CAD subjects collected from Zhongda Hospital Affiliated to Southeast University were involved in the final analysis. We gathered information about each subjects clinical history as well as their results of detected hs-CRP and lipid levels. Linear regression analysis was used to determine the association between dyslipidemia and hs-CRP levels in which univariate and multivariate logistic regression analyzes were performed to determine the relationship between hs-CRP levels and CAD as well as dyslipidemia and CAD. Mediation analysis was used to evaluate whether hs-CRP levels act as a mediator of the relationship between dyslipidemia and CAD.

RESULTS

Dyslipidemia and hs-CRP levels were significantly associated with an increased risk of CAD, with β = 0.594 (P = 0.001) and β = 0.016 (P = 0.024), respectively, and there was a correlation between dyslipidemia and hs-CRP levels (β = 3.273, P = 0.004). Mediation analysis results revealed that the correlation between dyslipidemia and CAD was 8.27% mediated by hs-CRP levels with a direct effect of 0.621 and an indirect effect of 0.056.

CONCLUSION

Hs-CRP levels played a partial mediation role in the association between dyslipidemia and CAD.

An update on the association between metabolic syndrome and osteoarthritis and on the potential role of leptin in osteoarthritis

Metabolic syndrome (MetS) has been associated with osteoarthritis (OA). Leptin, which is one of the markers of MetS, has been associated with OA pathophysiology. This study aimed to provide an update on the association between MetS and OA and on the potential role of leptin in OA. In this review, we summarized the current knowledge of the association between MetS and OA and updated the evidence on the potential role of leptin in OA. Clinical studies have investigated the epidemiologic association between MetS or its components and OA. Results suggested strong epidemiologic associations between MetS and OA, especially in the Asian population. Animal studies also indicated that metabolic dysregulation may lead to OA pathogenesis. The systemic role of MetS in OA pathophysiology is associated with obesity-related inflammation, the beneficial role of n-3 polyunsaturated fatty acids and deleterious role of cholesterol, physical inactivity, hypertension-induced subchondral ischemia, dyslipidemia-induced ectopic lipid deposition in chondrocytes, hyperglycemia-induced local effects of oxidative stress and advanced glycation end-products, low-grade systemic inflammation, and obesity-related adipokines by inducing the expression of proinflammtory factors. Leptin levels in serum/plasma and synovial fluid were associated with joint pain, radiographic progression, bone formation biomarkers, cartilage volume, knee OA incidence, and total joint arthroplasty in OA patients. Elevated leptin expression and increased effect of leptin on infrapatellar fat pad, synovium, articular cartilage, and bone were also involved in the pathogenesis of OA. Current knowledge indicates a convincing epidemiologic association between MetS and OA, especially in the Asian population. Animal studies have also shown that metabolic dysregulation may lead to OA pathogenesis. Accumulating evidence suggests that leptin may play a potential role in OA pathogenesis. Therefore, leptin and its receptor may be an emerging target for intervention in metabolic-associated OA.

Metabolic Score for Insulin Resistance Is Correlated to Adipokine Disorder and Inflammatory Activity in Female Knee Osteoarthritis Patients in a Chinese Population

PURPOSE

This study was to evaluate the metabolic score for insulin resistance (METS-IR) in female knee osteoarthritis (KOA) patients in a Chinese population. The associations between METS-IR and adipokines, erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP) were investigated.

PATIENTS AND METHODS

This study included 4686 women from the 2011 China Health and Retirement Longitudinal Study (CHARLS) and 108 women who underwent arthroplasty of KOA at a university hospital. The clinical data were collected, and adipokines were evaluated. METS-IR was calculated in the KOA patients and compared with the national baseline. Logistic regression analyses were applied to explore the associations of METS-IR with adipokines, ESR, and CRP.

RESULTS

Receiver operating characteristic curve analysis of METS-IR and metabolic syndrome (MetS) in national baseline showed an area under the curve value of 0.851, with sensitivity of 0.777 and specificity of 0.772. The METS-IR of KOA was higher than the national baseline level (40.29 ± 6.98 vs 36.20 ± 8.50, P < 0.01), even after adjusting age. In addition, the METS-IR was higher in patients with KOA who had MetS than in those without metabolic syndrome (nMetS), even after adjusting body mass index (BMI). After adjusting for age and BMI, METS-IR was associated with CRP (OR 1.238, 95% confidence interval (CI) 1.088, 1.409, P < 0.01), ESR (OR 1.124, 95% CI 1.008, 1.254, P = 0.036), plasma leptin (OR 1.123, 95% CI 1.052, 1.199, P < 0.01), plasma resistin (OR 1.134, 95% CI 1.011, 1.271, P = 0.031), and plasma adiponectin (OR 0.865, 95% CI 0.771, 0.971, P = 0.014).

CONCLUSION

METS-IR in female KOA was higher than that of the national baseline. The METS-IR was related to adipokine disorder and inflammatory activity. These findings suggest that METS-IR can be used to evaluate the degree of involvement of MetS in KOA.