Beyond mechanical loading: The metabolic contribution of obesity in osteoarthritis unveils novel therapeutic targets

Obesity and hyperlipidemia were associated with more severe synovitis and structural abnormalities as well as inferior functional outcomes in knee osteoarthritis: a retrospective comparative study

BACKGROUND

Considering that the respective effects of obesity and hyperlipidemia on knee osteoarthritis (OA) have not been fully investigated, the purpose of this study was to determine the relationship of obesity or hyperlipidemia with the synovitis and structural abnormalities of knee OA, and the effect of obesity and hyperlipidemia on functional outcomes of total knee arthroplasty.

METHODS

There were 99 OA patients without obesity and hyperlipidemia in Group 1, 100 OA patients only with obesity in Group 2, 98 OA patients only with hyperlipidemia in Group 3, and 97 OA patients with both obesity and hyperlipidemia in Group 4. Semi-quantitative synovial inflammatory markers were measured including effusion-synovitis, size and intensity of infrapatellar fat pad abnormality, and synovial proliferation score. The structural abnormalities of knee OA were evaluated using Whole-Organ Magnetic Resonance Imaging Score (WORMS). Functional outcomes were evaluated before surgery and at 2 years follow-up.

RESULTS

There were significantly higher effusion-synovitis, size and intensity of infrapatellar fat pad abnormality, and synovial proliferation score, as well as higher cartilage, bone marrow edema, meniscus, and total WORMS scores in Group 2, Group 3, and Group 4 (P < 0.05), but with no significant difference between Group 2 and Group 3 (P > 0.05). Group 2, Group 3, Group 4 had significantly worse Western Ontario and McMaster Universities Osteoarthritis Index, Forgotten Joint Score, Oxford Knee Score, Knee Society Score at baseline and 2 years follow-up (P < 0.05), but with no significant difference between Group 2 and Group 3 (P > 0.05). There were significant associations of obesity or hyperlipidemia with all synovial inflammatory markers and cartilage, bone marrow edema, meniscus, and total WORMS scores as well as functional outcomes (P < 0.05).

CONCLUSIONS

Obesity and hyperlipidemia were associated with more severe synovitis and structural abnormalities of knee OA, as well as inferior preoperative and postoperative functional outcomes. The negative effects of obesity and hyperlipidemia on knee OA could be mutually enhanced. The findings emphasized the negative effects of obesity and hyperlipidemia on the symptoms and outcomes of knee OA, and highlighted the association of obesity and hyperlipidemia with synovitis.

Association of blood vitamin A with osteoarthritis: a nationally representative cross-sectional study

Objectives

Vitamin A plays an important role in health, especially regarding its impact on bone tissue. Vitamin A can lead to bone damage and deformity, thus becoming an important causative factor in osteoarthritis. In this study, we aimed to evaluate the association of serum vitamin A with osteoarthritis.

Methods

We included participants who self-reported whether they had OA in NHANES 2001-2006 and NHANES 2017-2018 to explore the association and dose-response relationship between vitamin A concentration and risk of osteoarthritis through weighted multivariate logistic models and restricted cubic splines. Sensitivity and stratification analyses were also used to assess the robustness of the results.

Results

A total of 18,034 participants were included in this study, and a linear association between serum vitamin A concentration and osteoarthritis risk was observed. The OR of osteoarthritis was 1.22 (95% CI: 0.98, 1.52), 1.40 (95% CI: 1.05,1.85), and 1.47 (95% CI: 1.14, 1.91) for participants in the second, third, and fourth quartiles, respectively, compared with the lowest vitamin A reference group. Similar results were obtained when sensitivity and stratification analyses were performed.

Conclusion

Serum vitamin A is positively associated with osteoarthritis risk. Within a certain range of vitamin A concentrations, vitamin A is a protective factor against osteoarthritis, beyond which it becomes a causative factor for osteoarthritis.

The association between ADAMTS14/rs4747096 gene polymorphism and some risk factors and knee osteoarthritis

Knee osteoarthritis (KOA) is an important cause of disability in the world and it denotes a public health defiance of the upcoming years.Aim To examine the connection between ADAMTS14 gene rs4747096 polymorphism and KOA and to assess risk factors associated with KOA.Methods A case control study was conducted on 158 patients with KOA and 120 controls with comparable age and sex randomly recruited from National Research Centre employees. All participants were subjected to full history taking, assessment of KOA severity using WOMAC scoring system, and thorough clinical examination. Blood sample was collected for detection of ADAMTS14/rs4747096 gene polymorphism.Results The frequency of ADAMTS14 gene rs4747096 genotypes among patients with KOA was 73.5% for AA, 25.7% for AG, and 0.7% for GG compared to controls 963%, 31.3%, and 5.6% respectively and the frequency of alleles among patients was 86.4% for A and 78.7% for G compared to controls (78.7% and 21.3% respectively, P < 0.05. The study found that the median levels of total WOMAC score and its domains were significantly higher among KOA patients than controls. The logistic regression analysis revealed that age ≥ 50 years, BMI ≥ 35, and long standing at work were predictive factors for KOA (P < 0.05). Regarding different genetic patterns, only the A recessive pattern of inheritance was found to be a predictive risk factor for KOA.Conclusion For ADAMTS14 rs4747096 genotype, the AA and AG genotypes significantly increased the risk of KOA. The recessive pattern of inheritance, older age, morbid obesity, and prolonged standing at work were the predictive risk factors for KOA. Further studies with larger sample size are encouraged to investigate the mechanism by which this genotype can affect the development of KOA.

Association between body roundness index and risk of osteoarthritis: a cross-sectional study

BACKGROUND

The link between body roundness index (BRI) and osteoarthritis (OA) has yet to be validated. Our aim was to explore this connection between BRI and OA risk.

METHODS

This cross-sectional study utilized the 1999-2018 National Health and Nutrition Examination Survey retrieved data. To assess the association between BRI and OA risk, we performed weighted multivariable regression analysis (MVRA), with smooth curve fitting for potential nonlinear association and subgroup analysis and interaction tests for relationships in specific subgroups. A 7:3 ratio was adopted for the random division of the acquired data into training and validation sets. Subsequently, least absolute shrinkage and selection operator regression, along with MVRA, were conducted for the training set to isolate variables for a prediction model. This model was visualized using the nomogram and was followed by evaluation. Finally, the validation set was utilized to validate the model.

RESULTS

This study enrolled 12,946 individuals. Following the adjustment for all covariables, OA risk increased by 18% with every unit rise in BRI (odd ratio [OR] = 1.18; 95% confidence interval [CI]: 1.13-1.23; P < 0.0001). Upon regarding BRI as a categorical variable, it was divided into quartiles for subsequent analysis. In comparison to quartile 1, the risk of OA was increased in quartile 2 (OR = 1.58; 95% CI: 1.22-2.03; P = 0.0006), quartile 3 (OR = 1.83; 95% CI: 1.40-2.40; P < 0.0001) and quartile 4 (OR = 2.70; 95% CI: 1.99-3.66; P < 0.0001). Smooth curve fitting revealed no non-linear relationships. None of the subgroups showed a statistically significant interaction (all P > 0.05). After selecting the variables, a prediction model was developed. The prediction model exhibited favorable discriminatory power, high accuracy, and potential clinical benefits in training and validation sets.

CONCLUSIONS

The BRI was positively associated with OA risk. Our predictive model demonstrated that combining BRI with other easily accessible factors was helpful in assessing and managing high-risk OA groups.

Enhancement of Intracellular Cholesterol Efflux in Chondrocytes Leading to Alleviation of Osteoarthritis Progression

OBJECTIVE

Osteoarthritis (OA) is the most common degenerative disease worldwide, with no practical means of prevention and limited treatment options. Recently, our group unveiled a novel mechanism contributing to OA pathogenesis in association with abnormal cholesterol metabolism in chondrocytes. In this study, we aimed to establish a clinical link between lipid profiles and OA in humans, assess the effectiveness of cholesterol-lowering drugs in suppressing OA development in mice, and uncover the cholesterol-lowering mechanisms that effectively impede OA progression.

METHODS

Five clinically approved cholesterol-lowering drugs (fenofibrate, atorvastatin, ezetimibe, niacin, and lomitapide) were injected into the knee joints or administered with diet to mice with OA who underwent destabilization of the medial meniscus induction and were fed a 2% high-cholesterol diet. Gene expression linked to cholesterol metabolism was determined using microarray analysis. Furthermore, the in vivo functions of these genes were explored through intra-articular injection of either its inhibitor or adenovirus.

RESULTS

Logistic regression analysis confirmed a close relationship between the diagnostic criteria of hyperlipidemia based on serum lipid levels and OA incidence. Among the cholesterol-lowering drugs examined, fenofibrate exerted the most significant protective effect against cartilage destruction, which was attributed to elevated levels of high-density lipoprotein cholesterol that are crucial for cholesterol efflux. Notably, cholesterol efflux was suppressed during OA progression via down-regulation of apolipoprotein A1-binding protein (AIBP) expression. Overexpression of AIBP effectively inhibits OA progression.

CONCLUSION

Our results suggest that restoration of cholesterol homeostasis to a normal state through administration of fenofibrate or AIBP overexpression, both of which induce cholesterol efflux, offers an effective therapeutic option for patients with OA.

Leptin protects chondrocytes by inhibiting autophagy via phosphoinositide 3 kinase/protein kinase B/mammalian target of rapamycin signaling pathway

Leptin has been widely studied and found to have a significant impact on the development of osteoarthritis (OA). However, there are conflicting findings regarding the impact of leptin on chondrocytes. The study aimed to examine the impact of leptin on human chondrocytes and rats with OA. In the in vitro experiment, cartilage tissue obtained from patients hospitalized for knee replacement due to OA was collected for primary culture of chondrocytes. The proliferation and apoptosis of chondrocytes were assessed using cell counting kit-8 and flow cytometry. Autophagy levels were evaluated through monodansylcadaverine staining, mRFP-GFP-LC3 fluorescence, and transmission electron microscopy. Additionally, the expression of autophagy-related genes and proteins was analyzed using qRT-PCR and western blotting. In the in vivo experiment, an OA rat model was established. Following treatment with leptin and leptin antagonists, the cartilage tissues were examined using histology analysis (hematoxylin-eosin and Safranin O/fast green staining) and immunohistochemical. Mankin's score was utilized to assess the severity of OA, while qRT-PCR and western blotting were employed to detect the expression of autophagy-related genes and proteins in the cartilage. The ability of leptin to protect chondrocytes is achieved through the inhibition of autophagy via phosphoinositide 3 kinase/protein kinase B/mammalian target of rapamycin signaling pathway.

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.

Obesity, Metabolic Syndrome, and Osteoarthritis Require Integrative Understanding and Management

Osteoarthritis (OA) is a progressive chronic disease affecting the articular joints, leading to pain and disability. Unlike traditional views that primarily link OA to aging, recent understanding portrays it as a multifactorial degenerative disease of the entire joint. Emerging research highlights metabolic and immune dysregulation in OA pathogenesis, emphasizing the roles of obesity, dyslipidemia, and insulin resistance in altering joint homeostasis. Recent studies have increasingly focused on the complex role of white adipose tissue (WAT) in OA. WAT not only serves metabolic functions but also plays a critical role in systemic inflammation through the release of various adipokines. These adipokines, including leptin and adiponectin, have been implicated in exacerbating cartilage erosion and promoting inflammatory pathways within joint tissues. The overlapping global crises of obesity and metabolic syndrome have significantly impacted joint health. Obesity, now understood to contribute to mechanical joint overload and metabolic dysregulation, heightens the risk of developing OA, particularly in the knee. Metabolic syndrome compounds these risks by inducing chronic inflammation and altering macrophage activity within the joints. The multifaceted effects of obesity and metabolic syndrome extend beyond simple joint loading. These conditions disrupt normal joint function by modifying tissue composition, promoting inflammatory macrophage polarization, and impairing chondrocyte metabolism. These changes contribute to OA progression, highlighting the need for targeted therapeutic strategies that address both the mechanical and biochemical aspects of the disease. Recent advances in understanding the molecular pathways involved in OA suggest potential therapeutic targets. Interventions that modulate macrophage polarization, improve chondrocyte function, or normalize adipokine levels could serve as preventative or disease-modifying therapies. Exploring the role of diet, exercise, and pharmacological interventions in modulating these pathways offers promising avenues for reducing the burden of OA. Furthermore, such methods could prove cost-effective, avoiding the increase in access to healthcare.

[Relationship between hypercholesterolemia and osteoarthritis (preliminary results)]

AIM

To evaluate the relationship of hypercholesterolemia (HCE) with clinical, instrumental, and laboratory parameters in osteoarthritis (OA) in a multicenter, cross-sectional study.

MATERIALS AND METHODS

The study included 183 patients aged 40-75 years, with a confirmed diagnosis of stage I-III OA (ACR) of the knee joints, who signed an informed consent. The mean age was 55.6±10.7 years (40 to 75), body mass index was 29.3±6.3 kg/m2, and disease duration was 5 [1; 10] years. For each patient, a case record form was filled out, including anthropometric indicators, medical history, clinical examination data, an assessment of knee joint pain according to VAS, WOMAC, KOOS and comorbidities. All patients underwent standard radiography and ultrasound examination of the knee joints and laboratory tests.

RESULTS

HCE was detected in 59% of patients. Depending on its presence or absence, patients were divided into two groups. Patients were comparable in body mass index, waist and hip measurement, and disease duration but differed significantly in age. Individuals with elevated total cholesterol levels had higher VAS pain scores, total WOMAC and its components, an overall assessment of the patient's health, a worse KOOS index, and ultrasound findings (reduced cartilage tissue). HCE patients showed high levels of cholesterol, low-density lipoproteins, triglycerides, STX-II, and COMP (p<0.05). However, after stratification by age, many initial intergroup differences became insignificant, and differences in the WOMAC pain score persisted.

CONCLUSION

The results of the study confirmed the high prevalence of HCE in OA patients (59%). Patients with OA and increased total cholesterol have more intense pain in the knee joints.

Surgical Interventions for the Management of Obesity-Related Joint Pain: A Narrative Review

Obesity-related joint pain is a common and debilitating condition that significantly impacts the quality of life, primarily due to the excess weight straining the joints. This results in inflammation and degeneration, which can cause pain, stiffness, and difficulty moving. We aimed to comprehensively review the literature discussing surgical interventions for obesity-related joint pain. We searched across databases (PubMed, Scopus, and Cochrane Library) to identify studies published between 2000 and 2023 that assessed surgical interventions for obesity-related joint pain. This review highlights the complex interplay of mechanical, inflammatory, and metabolic factors contributing to joint pain in obese individuals, highlighting both surgical and non-surgical interventions. Non-surgical interventions include weight loss, exercise, physical therapy, and medications. Surgical interventions include bariatric surgery and joint replacement surgery. Bariatric surgery significantly reduces body weight and improves the quality of life outcomes; however, multiple studies have found no improvement or worsening of joint pain post-surgery. Total joint arthroplasty has demonstrated good improvement in pain and function outcomes based on recent meta-analyses, although risks of complications are higher in obese patients. The treatment choice for obesity-related joint pain depends on the individual patient's circumstances. Non-surgical interventions are usually the first line of treatment. However, if these interventions are not effective, surgical interventions may be an option.

The Function and Mechanism of Anti-Inflammatory Factor Metrnl Prevents the Progression of Inflammatory-Mediated Pathological Bone Osteolytic Diseases

Metrnl, recently identified as an adipokine, is a secreted protein notably expressed in white adipose tissue, barrier tissues, and activated macrophages. This adipokine plays a pivotal role in counteracting obesity-induced insulin resistance. It enhances adipose tissue functionality by promoting adipocyte differentiation, activating metabolic pathways, and exerting anti-inflammatory effects. Extensive research has identified Metrnl as a key player in modulating inflammatory responses and as an integral regulator of muscle regeneration. These findings position Metrnl as a promising biomarker and potential therapeutic target in treating inflammation-associated pathologies. Despite this, the specific anti-inflammatory mechanisms of Metrnl in immune-mediated osteolysis and arthritis remain elusive, warranting further investigation. In this review, we will briefly elaborate on the role of Metrnl in anti-inflammation function in inflammation-related osteolysis, arthritis, and pathological bone resorption, which could facilitate Metrnl's clinical application as a novel therapeutic strategy to prevent bone loss. While the pathogenesis of elbow stiffness remains elusive, current literature suggests that Metrnl likely exerts a pivotal role in its development.

Association between lipid accumulation products and osteoarthritis among adults in the United States: A cross-sectional study, NHANES 2017-2020

OBJECTIVE

Using cross-sectional data from the 2017-2020 National Health and Nutrition Examination Survey (NHANES) for American, the aim of this research is to investigate the potential association between Lipid Accumulation Products (LAP) and the risk of osteoarthritis (OA).

METHODS

Data from the NHANES (2017-2020) were downloaded and further analyzed. The participants between 20 and 80 years reported having OA, and other relevant variables and information on LAP were included. The linear and non-linear associations between LAP and OA were evaluated using multivariable logistic regression analysis and smoothed curve fitting methods. A two-part linear regression model was also used to estimate threshold effects.

RESULTS

The increased risk of OA was shown to have a nonlinear relationship with higher LAP, showing a solid threshold impact with a saturation value of 120.00 cm × mmol/L, according to our data. The two variables showed a positive relationship to the left of the saturation point but no significant association to the right, pointing to a complicated nonlinear relationship between OA prevalence and LAP.

CONCLUSIONS

Our findings revealed that LAP was an independent risk factor for OA when it was <120.00 cm × mmol/L. The LAP index may serve as a valuable method for predicting and diagnosed OA. To validate our results, further large-scale prospective research are required.

Pathogenic Mechanisms and Therapeutic Approaches in Obesity-Related Knee Osteoarthritis

The knee is the joint most frequently involved in osteoarthritis, a common joint disorder in the adult population that is associated with significant chronic joint pain, reduced mobility and quality of life. Recent studies have established an association between obesity and the development of knee osteoarthritis that goes beyond the increased mechanical load on the knees as weight-bearing joints. This link is based on the maintenance of a chronic low-grade inflammation, altered secretion of adipokines by the adipose tissue and development of sarcopenia. Major adipokines involved in the pathogenesis of obesity-related knee osteoarthritis include adiponectin, which appears to have a protective effect, as well as leptin, resistin and visfatin, which are associated with higher pain scores and more severe structural damage. Joint pain in knee osteoarthritis may be both nociceptive and neuropathic and is the result of complex mechanisms driven by nerve growth factor, calcitonin gene-related peptide and pro-inflammatory cytokines. The role of endogenous cannabinoids and gut microbiota in common mechanisms between obesity and knee pain has recently been studied. The aim of the present review is to highlight major pathogenic mechanisms in obesity-related knee osteoarthritis with special attention on pain and to comment on possible therapeutic approaches.

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.