Serum resistin level is associated with radiographic changes in hand osteoarthritis: cross-sectional study

Immobilization by 21-days of bed rest causes changes in biomarkers of cartilage homeostasis in healthy individuals

Objective

To investigate the effects of 21 days bed rest immobilization (with and without exercise and nutrition intervention) on serum concentrations of cartilage homeostasis biomarkers in healthy individuals.

Design

Twelve male volunteers (age 34.2 ​± ​8.3 years; BMI 22.4 ​± ​1.7 ​kg/m2) participated in 6 days of baseline data collection (BDC), 21 days of 6° head-down-tilt (HDT) bed rest (CON) ​+ ​interventions HDT ​+ ​resistive vibration exercise (RVE; 2 times/week; 25 ​min) and HDT ​+ ​RVE ​+ ​nutrition (NeX; 0.6 ​g/kg body weight/day whey protein and 90 ​mmol KHCO3/day bicarbonate supplementation), and 6 days of recovery (R) in a cross-over designed study. The starting HDT condition was randomized (CON-RVE-NeX, RVE-NeX-CON, NeX-CON-RVE). Blood samples were collected before, during and after HDT. Serum concentrations of COMP, MMP-3, MMP-9, YKL-40 and resistin were analyzed.

Results

The main effect of time was significant for all biomarkers tested (p ​< ​0.001). While COMP (-36 ​% at HDT5, p ​< ​0.001) and MMP-3 (-36 ​% at HDT21, p ​< ​0.001) decreased during HDT bed rest, MMP-9 (+18 ​% at HDT5, p ​< ​0.001) and resistin (+13 ​% at HDT21, p ​< ​0.001) increased during HDT bed rest. Interestingly, during recovery, YKL-40 levels increased (+13 ​% at R1, p ​= ​0.022), while MMP-9 levels decreased (-19 ​% at R6, p ​= ​0.035). We identified correlations between COMP and MMP-3 (rrm ​= ​0.58, p ​< ​0.001) as well as between MMP-9 and resistin (rrm ​= ​0.58, p ​< ​0.001).

Conclusions

Immobilization affects serum concentrations of cartilage homeostasis biomarkers suggesting changes in cartilage metabolism that do not completely recover during re-ambulation. Both interventions had only minimal effects.

Hand Osteoarthritis: Molecular Mechanisms, Randomized Controlled Trials, and the Future of Targeted Treatment

Hand osteoarthritis (OA) is a prevalent and disabling condition, yet its pathogenesis remains less studied than OA in large weight-bearing joints. Emerging genetic, epigenetic, and microbiome research suggests that hand OA might be biologically distinct, involving joint-specific pathways not shared by knee or hip OA. This review integrates genome-wide association studies specific to hand OA, highlighting key molecular contributors such as inflammatory cytokines. These genetic insights, together with emerging data on epigenetic alterations and gut microbial dysbiosis, point to broader systemic and regulatory influences on hand OA onset and progression. We also assess pharmacologic interventions tested in randomized controlled trials that have attempted to target these pathways. While agents such as TNF and IL-6 inhibitors, hydroxychloroquine, and corticosteroids have shown limited success, emerging evidence supports the potential of methotrexate in synovitis-positive general hand OA, platelet-rich plasma in thumb carpometacarpal (CMC) OA, and prolotherapy in interphalangeal (IP) OA. These findings illustrate the persistent gap between mechanistic understanding and therapeutic success. Future work must prioritize multifactorial strategies for addressing pain and translational frameworks that link molecular mechanisms to treatment response. In summary, this review offers an update on hand OA and identifies key opportunities for more targeted and effective therapy.

Comparing Five Major Knee Osteoarthritis Cohort Studies: Similarities, Differences, and Unique Aspects of CHECK, OAI, FNIH, IMI-APPROACH, and MOST

ObjectiveTo analyze and synthesize the information available from five pivotal, large-scale, multicenter, observational studies (CHECK, OAI, FNIH Biomarkers Consortium, IMI-APPROACH, and MOST) focusing on knee osteoarthritis (OA), which can be used to elucidate disease progression, risk factors, and the effectiveness of potential interventions.DesignFor this narrative review, a comprehensive literature search and data extraction from official web pages and scientific databases were conducted to compare methodologies, in- and exclusion criteria, outcomes, and cohort characteristics across the studies. Thematic, comparative, and qualitative analyses were employed to identify trends, commonalities, and disparities among the findings.ResultsThe studies collectively enhanced understanding of the onset and progression of knee OA, and in several of the studies, hip OA, emphasizing the importance of both systemic and local risk factors. Advanced imaging and biomarkers are important components in all the cohorts, with the goal of aiding early diagnosis and tracking disease progression. All cohorts evaluated unique markers generally not available in the other cohorts, while other factors overlap, suggesting possibilities for combining or cross-validating between cohorts.ConclusionsThe collaborative efforts of major OA research significantly advance our understanding of knee OA. These studies highlight the importance of a multifaceted approach, integrating advanced imaging, biomarkers, and longitudinal data to tackle the complexities of OA. By synthesizing findings and addressing knowledge gaps such as heterogeneity of patients and used measurements, and use of novel pain measures, future research can develop more effective diagnostic tools and treatments, ultimately enhancing the quality of life for OA patients.

Biochemical markers in hand osteoarthritis: a path to precision medicine

Hand osteoarthritis (HOA) is a heterogeneous joint disease with high radiographic and symptomatic prevalence. The diagnosis of HOA is based on clinical and radiographic features. The identification of potential biomarkers for diagnosis, prognosis, disease severity assessment, and therapeutic efficacy evaluation of НОА remains an active area of research. To summarize the eligible biomarker data, a comprehensive narrative review was performed using the PubMed and Scopus databases covering publications from inception to December 2024. Our search uncovered five distinct groups of biomarkers associated with HOA, categorized based on their origin and involvement in distinct biological processes: (1) cartilage synthesis and catabolism, (2) bone remodeling, (3) inflammation, (4) adipokines, and (5) others classified separately. Each biomarker was evaluated in accordance with the Burden of disease, Investigative, Prognostic, Efficacy of intervention, and Diagnostic (BIPED) criteria. In conclusion, no biomarker has yet demonstrated sufficient sensitivity, specificity, or reproducibility to meet the BIPED criteria for classification. The early diagnosis and treatment of HOA require the development of more sensitive assays, advanced platforms, and rigorous bio-clinical trials to stratify previously studied biomarkers and identify novel ones. Precision medicine in HOA demands reliable biomarkers, cost-effective assays, and standardized, reproducible methodologies for global applicability.

The Role of Adipokines between Genders in the Pathogenesis of Osteoarthritis

Osteoarthritis (OA) is a chronic, progressive, degenerative joint disease characterized by joint pain, stiffness, and limited movement. It presents significant intra- and inter-individual variability-in particular, between genders. Recent research has increasingly focused on the role of adipokines-especially leptin, adiponectin, and resistin-in the development of OA. Adipokines, peptide hormones primarily secreted by adipose tissue, are involved in crucial physiological processes related to metabolism and immunity. They can also impact bone and cartilage turnover by interacting with joint cells such as osteoblasts, osteoclasts, chondrocytes, and mesenchymal stem cells, thereby linking inflammation with bone cartilage homeostasis. This review aims to elucidate the structure and functions of various adipokines, their serum and synovial levels, and their association with clinical presentation and radiographic progression in OA patients, with a focus on differences between sexes. A narrative literature review was conducted using three databases specifically analyzing sex differences. OA patients generally show elevated serum and synovial levels of leptin, chemerin, and visfatin, as well as high plasma levels of resistin and visfatin. In contrast, synovial levels of adiponectin and omentin are reduced in OA patients compared to healthy individuals, with an inverse relationship to disease severity, suggesting a potential protective role. Resistin and leptin were positively correlated with pain severity and radiographic progression, while adiponectin's role in OA remains controversial. Regarding sex differences, male OA patients exhibited higher serum levels of leptin, chemerin, and omentin compared to healthy controls, with a positive correlation to the BMI and estrogen levels, potentially explaining the sexual dimorphism observed in this condition. Studies on visfatin and lipocalin did not reveal significant differences in synovial or serum levels between the sexes. The role of resistin remains controversial. Adipokines influence the joint microenvironment and contribute to the progression of osteoarthritis (OA). However, the precise biological mechanisms are not yet fully understood due to the complex interactions between the metabolic, mechanical, and immune systems. Further research is needed to clarify their roles in OA and to identify targeted therapies for managing this degenerative disease.

Resistin - A Plausible Therapeutic Target in the Pathogenesis of Psoriasis

Resistin, a cytokine hormone predominantly secreted by adipose tissue, is elevated in various metabolic disorders such as obesity, type 2 diabetes, and cardiovascular disease. In addition to its involvement in metabolic regulation, resistin has been implicated in the pathogenesis of psoriasis, a chronic inflammatory skin disorder. Numerous studies have reported increased resistin levels in psoriatic skin lesions, suggesting a possible association between resistin and psoriasis. Recent studies have suggested the potential involvement of resistin in the development and progression of certain cancers. Resistin is overexpressed in breast, colorectal, and gastric cancers. This suggests that it may play a role in the development of these cancers, possibly by inducing inflammation and cell growth. The link between resistin and cancer raises the possibility of shared underlying mechanisms driving the pathogenesis of psoriasis. Chronic inflammation, one such mechanism, is a hallmark of psoriasis and cancer. Further research is needed to fully understand the relationship between resistin and psoriasis. Identifying potential therapeutic targets is crucial for effective management of psoriasis. By doing so, we may be able to develop more effective treatment options for individuals living with psoriasis and ultimately improve their quality of life. Ultimately, a more comprehensive understanding of the mechanisms underlying the impact of resistin on psoriasis is essential for advancing our knowledge and finding new ways to treat and manage this challenging condition.

Gut-Derived Endotoxin and Telomere Length Attrition in Adults with and without Type 2 Diabetes

Premature aging, as denoted by a reduced telomere length (TL), has been observed in several chronic inflammatory diseases, such as obesity and type 2 diabetes mellitus (T2DM). However, no study to date has addressed the potential inflammatory influence of the gut-derived Gram-negative bacterial fragments lipopolysaccharide, also referred to as endotoxin, and its influence on TL in low-grade inflammatory states such as type 2 diabetes mellitus (T2DM). The current study therefore investigated the influence of endotoxin and inflammatory factors on telomere length (TL) in adults with (T2DM: n = 387) and without (non-diabetic (ND) controls: n = 417) obesity and T2DM. Anthropometric characteristics were taken, and fasted blood samples were used to measure biomarkers, TL, and endotoxin. The findings from this study highlighted across all participants that circulating endotoxin (r = -0.17, p = 0.01) was inversely associated with TL, noting that endotoxin and triglycerides predicted 18% of the variance perceived in TL (p < 0.001). Further stratification of the participants according to T2DM status and sex highlighted that endotoxin significantly predicted 19% of the variance denoted in TL among male T2DM participants (p = 0.007), where TL was notably influenced. The influence on TL was not observed to be impacted by anti-T2DM medications, statins, or anti-hypertensive therapies. Taken together, these results show that TL attrition was inversely associated with circulating endotoxin levels independent of the presence of T2DM and other cardiometabolic factors, suggesting that low-grade chronic inflammation may trigger premature biological aging. The findings further highlight the clinical relevance of mitigating the levels of circulating endotoxin (e.g., manipulation of gut microbiome) not only for the prevention of chronic diseases but also to promote healthy aging.

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.

Increased adiponectin levels are associated with higher radiographic scores in the knee joint, but not in the hand joint

Several studies have evaluated the association between serum adiponectin levels and knee and hand osteoarthritis (OA); mixed results have been reported. We investigated the relationship between OA and serum adiponectin levels according to the radiographic features of knee and hand OA. A total of 2402 subjects was recruited from the Dong-gu Study. Baseline characteristics were collected via a questionnaire, and X-rays of knee and hand joints were scored using a semi-quantitative grading system. The relationship between serum adiponectin levels and radiographic severity was evaluated by linear and logistic regression analysis. Subjects in the higher serum adiponectin levels tertiles were older and had a lower body mass index (BMI) than those in the lower tertiles. Regarding knee joint scores, serum adiponectin levels was positively associated with the total (P < 0.001), osteophyte (P = 0.003), and joint space narrowing (JSN) scores (P < 0.001) after adjustment for age, sex, BMI, smoking, alcohol consumption, education, and physical activity. In terms of hand joint scores, no association was found between serum adiponectin levels and the total, osteophyte, JSN, subchondral cyst, sclerosis, erosion, or malalignment score after the above-mentioned adjustments. Similarly, subjects with serum adiponectin levels above the median had higher total radiographic scores in the knee joints, but not in the hand joints, after adjustment. An increased serum adiponectin levels was associated with a higher radiographic score in the knee joint, but not in the hand joint, suggesting the involvement of different pathophysiologic mechanisms in the development of OA between those joints.

Resistin concentrations in serum and stifle synovial fluid from normal and cruciate deficient dogs with osteoarthritis

OBJECTIVE

To compare synovial fluid (SF) resistin concentrations in healthy dogs to dogs with osteoarthritis (OA) secondary to cranial cruciate ligament (CrCL) injury and to correlate resistin concentrations with body condition score (BCS) and evaluate resistin release from peripheral blood mononuclear cells (PBMC) and adipocytes.

STUDY DESIGN

Controlled, prospective, clinical study ANIMALS: Thirty-nine client-owned dogs, 13 healthy and 26 with secondary OA, were enrolled. Blood was collected from six healthy purpose-bred dogs for PBMC culture. An additional six mixed-breed dogs were used for adipocyte collection and culture.

METHODS

Resistin concentrations were measured with a canine-specific enzyme-linked immunoabsorbent assay. Resistin was compared between healthy SF and OA SF with Student's t test. Correlation of resistin concentrations to BCS was performed. Peripheral blood mononuclear cells and adipocytes were cultured under three conditions: negative control, lipopolysaccharide, and concanavalin A (Con A). A linear mixed model was used to determine differences in resistin concentrations among treatments.

RESULTS

Resistin concentrations in OA SF were comparable to healthy SF. Neither serum nor SF resistin was correlated with BCS. Cultured PBMC stimulated with Con A released resistin, while adipocytes did not.

CONCLUSION

Neither serum nor SF resistin were altered in dogs with OA secondary to CrCL insufficiency. In addition, resistin was not correlated with canine body fat and did not appear to function as adipocytokine in the dog.

CLINICAL SIGNIFICANCE

Resistin may not be involved in the pathogenesis of OA. However, resistin may be important in inflammation because it is released from inflammatory cells.

The role of adipose tissue secretion in the creation and pain level in osteoarthritis

Objectives. With increasing evidence regarding the metabolic basis of osteoarthritis (OA), we studied the relationship between adipose tissue and OA.

Methods. This study is part of an OA registry in the eastern part of Fars Province, Iran. Overall, 150 patients with OA and 300 sex matched individuals were selected as a control group. They were compared regarding adipokine concentration (leptin, adiponectin, resistin and visfatin), anthropo-metric indices, the Western Ontario and McMaster universities arthritis index score (WOMAC).

Results. All adipokine levels were higher among OA patients (p<0.001). After adjusting for age, sex, and body mass index (BMI), adipokines showed a significant and positive association with OA (B: 14.12, B: 9.92, B: 24.71 and B: 12.29 for leptin, adiponectin, visfatin, and resistin, respectively; p<0.001). Except the adiponectin that had a negative relationship with BMI in the OA group (r=–0.570, p<0.001), other adipokines had positive relationships with BMI (r=0.781, p<0.001; r=0.530, p<0.001; r=0.549, p<0.001 for leptin, visfatin, and resistin, respectively). Only leptin and adiponectin levels were correlated with pain (B: 0.045, –0.079 and p<0.05).

Conclusion. The present study shows that aside to the well-known role of mechanical stress in OA pathogenesis (weight load), leptin, adiponectin, visfatin, and resistin, which represent the adi-pose tissue independent on the weight, may play a chemical role in OA pathogenesis. In addition, leptin and adiponectin may be involved in the pain levels among patients with OA.

Relationship between serum resistin, body fat and inflammatory markers in females with clinical knee osteoarthritis

OBJECTIVES

Adipokines have gained much interest in osteoarthritis (OA) pathogenesis studies over the past years in that they play crucial roles in bone and cartilage homeostasis. Obesity is known to be one of the well-recognized and modifiable causes of OA burden. Key mediators in this metabolic link between obesity and OA could be resistin, among other cytokines secreted by the adipose tissue. We aimed to evaluate the association of serum resistin with obesity, and inflammation in female patients with knee OA.

METHODS

One hundred female participants, aged above 40 years, with symptomatic primary knee OA were matched for age with 100 apparently healthy females in a case-control study design. All study participants were subjected to clinical examination, laboratory investigations and radiological examination.

RESULTS

Patients with primary knee OA had elevated levels of serum resistin compared with healthy controls. We demonstrated that elevated serum resistin positively correlated with adiposity measures, inflammatory markers and WOMAC index. High sensitivity C reactive protein was found to be an independent predictor of serum resistin levels after adjustment for confounder factors.

CONCLUSIONS

These results indicate that resistin may play an important role in the progression of knee OA and may serve as a novel and reliable biomarker for reflecting disease severity, with the potential to contribute to the fundamental processes underlying the pathogenesis of knee OA.

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

OBJECTIVES

To investigate associations of leptin and adiponectin levels with knee and hand osteoarthritis, and explore whether these mediate the association between adiposity and osteoarthritis.

METHODS

This is a cross-sectional analysis of baseline data from the population-based Netherlands Epidemiology of Obesity study. Adiposity was assessed with body mass index (BMI) and percentage total body fat (%TBF). Osteoarthritis, defined as hand or knee osteoarthritis, was determined using American College of Rheumatology criteria. Fasting serum adipokine levels were measured using immunoassays. Associations between adiposity and osteoarthritis were examined with logistic regression, adjusted for age, sex, ethnicity and education, and additionally for leptin and adiponectin as potential mediators.

RESULTS

In 6408 participants (56% women, median age 56 years), prevalence of osteoarthritis was 22% (10% isolated knee and 8% isolated hand osteoarthritis). Leptin levels were positively associated with osteoarthritis, while adiponectin levels were not. Leptin partially mediated the association of adiposity with osteoarthritis (OR 1.40 (95%CI 1.30; 1.52) attenuated to 1.38 (1.24; 1.54) per 5 units BMI and OR 1.25 (1.17; 1.35) to 1.20 (1.10; 1.32) per 5 units %TBF, representing 4% and 17% mediation, respectively). Larger proportion mediation by leptin was found in knee (13%/27%) than in hand osteoarthritis (9%/18%). Sex-stratified analyses generally showed stronger associations between adiposity, leptin and osteoarthritis in women than in men.

CONCLUSIONS

Serum leptin levels were associated with osteoarthritis, and partially mediated the association between adiposity and osteoarthritis, while adiponectin levels were not associated with osteoarthritis. These findings provide evidence for systemic effects of adipose tissue in osteoarthritis.

Role of resistin genetic variations in knee osteoarthritis pathogenesis, a cross sectional study

Osteoarthritis (OA) is a serious health concern globally and is recognized by degradation of articular cartilage, bone remodeling and synovial inflammation. Resistin is an adipokine that shown to be involved in inflammatory process associated with OA. Aim of the current study was to estimate the link of resistin gene polymorphisms (- 420 C>G, + 299 G>A) with genetic susceptibility of knee OA in a Pakistani population. 280 patients and 308 age and sex matched controls were recruited in this case-control study. Genotype and allele frequencies were evaluated by Polymerase chain reaction-Restriction Fragment Length Polymorphism. Resistin concentration was measured by immunoassay. A significant difference in allele and genotype frequency was observed for both study groups. Resistin - 420 mutant genotype was associated with an increased susceptibility to OA (p = 0.001). Similarly, resistin + 299 GA + AA genotypes showed a relation with an elevated risk of knee OA compared to GG genotype (p = 0.01). Moreover, the mutant alleles frequency was significantly high in patient group as compared to healthy individuals for both loci (p < 0.01). Resistin - 420/+ 299 alleles haplotype analysis demonstrated that mutant alleles were more prevalent in OA affected individuals compared to healthy subjects (p < 0.05). The serum resistin levels were not remarkably different in patient vs. control group (p = 0.9). Further, the circulating resistin level was not found to be influenced by - 420G and + 299A alleles and non significant differences were observed in resistin concentration in mutant vs. wild type genotypes for both SNPs (p > 0.05). Our data suggest an association between investigated resistin genetic variants and knee OA susceptibility in our population. This is the first report to show association between investigated single nucleotide polymorphisms and OA among any population.

An Update on the Emerging Role of Resistin on the Pathogenesis of Osteoarthritis

Background

Resistin may be involved in the pathogenesis of osteoarthritis (OA), but a systematic understanding of the role of resistin in OA is lacking.

Methods

We reviewed studies that evaluated the role of resistin in OA. The expression levels of resistin in vitro experiments and OA/rheumatoid arthritis (RA) patients were analyzed. We also studied potential resistin receptors and the signaling pathways that these receptors activate, ultimately leading to cartilage degeneration.

Results

Resistin levels in both the serum and synovial fluid were higher in OA and RA patients than in healthy subjects. Overall, resistin levels are much higher in serum than in synovial fluid. In human cartilage, resistin induces the expression of proinflammatory factors such as degradative enzymes, leading to the inhibition of cartilage matrix synthesis, perhaps by binding to Toll-like receptor 4 and the adenylyl cyclase-associated protein 1 receptor, which then activates the p38-mitogen-activated phosphate kinase, protein kinase A–cyclic AMP, nuclear factor-κB, and C/enhancer-binding protein β signaling pathways.

Conclusion

Resistin levels are higher in OA patients than in healthy controls; however, the precise role of resistin in the pathogenesis of OA needs to be studied further. Resistin may be a novel therapeutic target in OA in the future.

A Complex Relationship between Visfatin and Resistin and microRNA: An In Vitro Study on Human Chondrocyte Cultures

Growing evidence indicates the important role of adipokines and microRNA (miRNA) in osteoarthritis (OA) pathogenesis. The purpose of the present study was to investigate the effect of visfatin and resistin on some miRNA (34a, 140, 146a, 155, 181a, let-7e), metalloproteinases (MMPs), and collagen type II alpha 1 chain (Col2a1) in human OA chondrocytes and in the T/C-28a2 cell line. The implication of nuclear factor (NF)-κB in response to adipokines was also assessed. Chondrocytes were stimulated with visfatin (5 or 10 μg/mL) and resistin (50 or 100 ng/mL) with or without NF-κB inhibitor (BAY-11-7082, 1 μM) for 24 h. Viability and apoptosis were detected by MMT and cytometry, miRNA, MMP-1, MMP-13, and Col2a1 by qRT-PCR and NF-κB activation by immunofluorescence. Visfatin and resistin significantly reduced viability, induced apoptosis, increased miR-34a, miR-155, miR-181a, and miR-let7e, and reduced miR-140 and miR-146a gene expression in OA chondrocytes. MMP-1, MMP-13, and Col2a1 were significantly modulated by treatment of OA chondrocytes with adipokines. Visfatin and resistin significantly increased NF-κB activation, while the co-treatment with BAY11-7082 did not change MMPs or Col2a1 levels beyond that caused by single treatment. Visfatin and resistin regulate the expression levels of some miRNA involved in OA pathogenesis and exert catabolic functions in chondrocytes via the NF-κB pathway. These data confirm the complex relationship between adipokines and miRNA.

High in vivo levels of adipsin lead to increased knee tissue degradation in osteoarthritis: data from humans and animal models

Objective

This study explored the role of the adipokine adipsin in OA.

Methods

Control and OA articular tissues, cells and serum were obtained from human individuals. Serum adipsin levels of human OA individuals were compared with cartilage volume loss as assessed by MRI at 48 months. Human adipsin expression was determined by PCR, its production in tissues by immunohistochemistry, and in SF and serum by a specific assay. OA was surgically induced in wild-type (Df+/+) and adipsin-deficient (Df-/-) mice, and synovial membrane and cartilage processed for histology and immunohistochemistry.

Results

Adipsin levels were significantly increased in human OA serum, SF, synovial membrane and cartilage compared with controls, but the expression was similar in chondrocytes, synoviocytes and osteoblasts. Multivariate analysis demonstrated that human serum adipsin levels were significantly associated (P = 0.045) with cartilage volume loss in the lateral compartment of the knee. Destabilization of the medial meniscus-Df-/- mice showed a preservation of the OA synovial membrane and cartilage lesions (P ⩽ 0.026), the latter corroborated by the decreased production of cartilage degradation products and proteases (P ⩽ 0.047). The adipsin effect is likely due to a deficient alternative complement pathway (P ⩽ 0.036).

Conclusion

In human OA, higher serum adipsin levels were associated with greater cartilage volume loss in the lateral compartment, and adipsin deficiency led to a preservation of knee structure. Importantly, we documented an association between adipsin and OA synovial membrane and cartilage degeneration through the activation of the complement pathway. This study highlights the clinical relevance of adipsin as a valuable biomarker and potential therapeutic target for OA.

Leptin and the intervertebral disc: a biochemical link exists between obesity, intervertebral disc degeneration and low back pain-an in vitro study in a bovine model

PURPOSE

The aim of this study was to identify the effects of leptin upon the intervertebral disc (IVD) and to determine whether these responses are potentiated within an environment of existing degeneration. Obesity is a significant risk factor for low back pain (LBP) and IVD degeneration. Adipokines, such as leptin, are novel cytokines produced primarily by adipose tissue and have been implicated in degradative and inflammatory processes. Obese individuals are known to have higher concentrations of serum leptin, and IVD cells express leptin receptors. We hypothesise that adipokines, such as leptin, mediate a biochemical link between obesity, IVD degeneration and LBP.

METHODS

The bovine intervertebral disc was used as a model system to investigate the biochemical effects of obesity, mediated by leptin, upon the intervertebral disc. Freshly isolated cells, embedded in 3D alginate beads, were subsequently cultured under varying concentrations of leptin, alone or together with the pro-inflammatory cytokines TNF-α, IL-1β or IL-6. Responses in relation to production of nitric oxide, lactate, glycosaminoglycans and expression of anabolic and catabolic genes were analysed.

RESULTS

Leptin influenced the cellular metabolism leading particularly to greater production of proteases and NO. Addition of leptin to an inflammatory environment demonstrated a marked deleterious synergistic effect with greater production of NO, MMPs and potentiation of pro-inflammatory cytokine production.

CONCLUSIONS

Leptin can initiate processes involved in IVD degeneration. This effect is potentiated in an environment of existing degeneration and inflammation. Hence, a biochemical mechanism may underlie the link between obesity, intervertebral disc degeneration and low back pain. These slides can be retrieved under Electronic Supplementary Material.

Association of osteoarthritis and circulating adiponectin levels: a systematic review and meta-analysis

BACKGROUND

The objective of this study was to perform a meta-analysis to investigate the specific relationship between the expression level of circulating adiponectin and osteoarthritis (OA).

METHOD

Multiple databases were searched to estimate the high quality of studies relevant to adiponectin and OA. We extracted the data from the eligible studies and included them in the meta-analysis using a random effects model. Subgroup analysis and meta-regression were further performed to explore the potential sources of heterogeneity.

RESULTS

Ten articles consisting of thirteen case-control studies that contained a combined total of 1255 subjects. Our results revealed that the OA patients displayed higher adiponectin levels than the healthy controls (SMD = 0.327, 95% CI: 0.11-0.55, P = 0.003). The ethnicity-stratified subgroup analysis indicated that the adiponectin was a sensitive biomarker in both Caucasians (P = 0.021) and Asians (P = 0.037). Moreover, the meta-regression analysis suggested that the sample size (P = 0.03) and nationality (p = 0.01) could account for a part of heterogeneity in our study.

CONCLUSION

Taken together, the current study indicated that the adiponectin expression levels were higher in the OA patients than in the healthy controls and might be associated with OA prevalence.

Biomechanics, obesity, and osteoarthritis. The role of adipokines: When the levee breaks

Osteoarthritis is a high-incidence painful and debilitating disease characterized by progressive degeneration of articular joints, which indicates a breakdown in joint homeostasis favoring catabolic processes. Biomechanical loading, associated with inflammatory and metabolic imbalances of joint, strongly contributes to the initiation and progression of the disease. Obesity is a primary risk factor for disease onset, and mechanical factors increased the risk for disease progression. Moreover, inflammatory mediators, in particular, adipose tissue-derived cytokines (better known as adipokines) play a critical role linking obesity and osteoarthritis. The present article summarizes the knowledge about the role of adipokines in cartilage and bone function, highlighting their contribution to the imbalance of joint homeostasis and, consequently, pathogenesis of osteoarthritis. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:594-604, 2018.

Can adipokines serum levels be used as biomarkers of hand osteoarthritis?

PURPOSE

To evaluate serum levels of visfatin, resistin and adiponectin in patients with erosive (E) and non-erosive (NE) osteoarthritis (OA) of the hand (HOA) compared to normal controls (NC).

METHODS

94 outpatients with E HOA and NE HOA and 21 NC were enrolled. The radiological assessment of both hands was performed according to the Kellgren-Lawrence and Kallman score. Patients were divided into two subsets (lone HOA or generalized OA) based on clinically OA involvement of knee and hip. Serum visfatin, resistin and adiponectin levels were determined by ELISA assay.

RESULTS

Visfatin was significantly higher in E HOA patients in comparison to NC and NE HOA group. Resistin showed a significant increase in both E HOA and NE HOA groups versus NC, in particular in generalized OA. No significant differences among groups were found in adiponectin. The Kallman score was more severe in the two subsets of E HOA patients compared to NE HOA.

CONCLUSIONS

This study showed increased levels of resistin in erosive and non-erosive HOA, and higher visfatin levels in E HOA in comparison to NE HOA. These data suggest the adipokines possible role in the pathogenesis of HOA and their potential usefulness as biomarkers of the disease.

Adipokine Contribution to the Pathogenesis of Osteoarthritis

Recent studies have shown that overweight and obesity play an important role in the development of osteoarthritis (OA). However, joint overload is not the only risk factor in this disease. For instance, the presence of OA in non-weight-bearing joints such as the hand suggests that metabolic factors may also contribute to its pathogenesis. Recently, white adipose tissue (WAT) has been recognized not only as an energy reservoir but also as an important secretory organ of adipokines. In this regard, adipokines have been closely associated with obesity and also play an important role in bone and cartilage homeostasis. Furthermore, drugs such as rosuvastatin or rosiglitazone have demonstrated chondroprotective and anti-inflammatory effects in cartilage explants from patients with OA. Thus, it seems that adipokines are important factors linking obesity, adiposity, and inflammation in OA. In this review, we are focused on establishing the physiological mechanisms of adipokines on cartilage homeostasis and evaluating their role in the pathophysiology of OA based on evidence derived from experimental research as well as from clinical-epidemiological studies.

Serum levels of resistin and interleukin-17 are associated with increased cartilage defects and bone marrow lesions in patients with knee osteoarthritis

OBJECTIVES

To investigate cross-sectional associations between serum levels of resistin and interleukin-17 (IL-17) and cartilage defects and bone marrow lesions (BMLs) in patients with knee symptomatic osteoarthritis (OA).

METHODS

One hundred and ninety-four consecutively-selected patients with knee symptomatic OA (mean 55.4 years, range 34-74, 87% females) were included in Anhui Osteoarthritis (AHOA) Study. Knee cartilage defects and BMLs were determined at different sites using T2-weighted fat-suppressed fast spin echo MRI. Serum resistin, IL-17, and high-sensitivity C-reactive protein (hs-CRP) levels were measured using ELISA.

RESULTS

In multivariable analyses, serum resistin was positively associated with cartilage defects at lateral femoral, lateral tibial, and medial tibial (all p < 0.05) sites. The significant associations were also present with BMLs at lateral femoral and tibial sites (ORs: 1.13-1.19, both p < 0.05). In patients with the highest quartile of hs-CRP (>2.45 pg/ml), IL-17 was positively and significantly associated with cartilage defect score at nearly all sites (ORs: 1.33-1.44, all p < 0.05), and BMLs at lateral and medial femoral sites (ORs: 1.26-1.51, both p < 0.05).

CONCLUSIONS

Serum levels of resistin were positively and independently associated with cartilage defects and BMLs in patients with knee OA. Serum IL-17 was significantly associated with cartilage defects and BMLs in patients with an increased inflammatory status. These suggest that metabolic and inflammatory mechanisms may have a role to play in knee OA.

Adipokines induce catabolism of newly synthesized matrix in cartilage and meniscus tissues

PURPOSE

Altered synovial levels of various adipokines (factors secreted by fat as well as other tissues) have been associated with osteoarthritis (OA) onset and progression. However, the metabolic effects of adipokines on joint tissues, in particular the fibrocartilaginous menisci, are not well understood. This study investigated effects of several adipokines on release of recently synthesized extracellular matrix in bovine cartilage and meniscus tissue explants.

MATERIALS AND METHODS

After labeling newly synthesized proteins and sulfated glycosaminoglycans (sGAGs) with ³H-proline and ³⁵S-sulfate, respectively; bovine cartilage and meniscus tissue explants were cultured for 6 days in basal medium (control) or media supplemented with adipokines (1 µg/ml of leptin, visfatin, adiponectin, or resistin) or 20 ng/ml interleukin-1 (IL-1). Release of radiolabel and sGAG to the media during culture and the final explant water, DNA, sGAG, and retained radiolabel were measured. Matrix metalloproteinase (MMP-2) and MMP-3 activities were assessed using gelatin and casein zymography, respectively.

RESULTS

Water and DNA contents were not significantly altered by any treatment. Visfatin, adiponectin, resistin, and IL-1 stimulated sGAG release from meniscus, whereas only IL-1 stimulated sGAG release from cartilage. Release of ³H and ³⁵S was stimulated not only by resistin and IL-1 in meniscus but also by IL-1 in cartilage. Retained ³H was unaltered by any treatment, while retained ³⁵S was reduced by visfatin, resistin, and IL-1 in meniscus and by only IL-1 in cartilage. Resistin and IL-1 elevated active MMP-2 and total MMP-3 in meniscus, whereas cartilage MMP-3 activity was elevated by only IL-1.

CONCLUSIONS

Resistin stimulated rapid and extensive catabolism of meniscus tissue, similar to IL-1, whereas adipokines minimally affected cartilage. Release of newly synthesized matrix was similar to overall release in both tissues. These observations provide further indications that meniscal tissue is more sensitive to pro-inflammatory factors than cartilage and also suggest further study of resistin's role in OA.

Correlations between serum adipocytokine concentrations, disease stage, radiological status and total body fat content in the patients with primary knee osteoarthritis

PURPOSE

The study was designed to investigate whether serum concentrations of leptin, resistin and adiponectin in obese and normal-weight patients with primary knee osteoarthritis (OA) correlate with clinical and radiological stages of the disease and percentage of total body fat.

METHODS

Seventy-three patients with knee OA, divided into obese and normal-weight groups, were clinically evaluated according to the Knee Society Score (KSS), and radiologically assessed using Kellgren and Lawrence scale. The percentage of total body fat and some anthropometric data were also given. Serum leptin, resistin and adiponectin concentrations were measured by Elisa and were correlated with the clinical, radiological and anthropometric parameters.

RESULTS

Leptin concentrations were significantly higher (p = 0.001) in the obese patients and positively correlated (R = 0.63) with radiologically assessed OA grade, but only in the normal-weight group. Resistin and adiponectin concentrations were identical in obese and normal-weight patients and negatively correlated (R = -0.41) with the clinical status of obese patients. In both groups, percentage of total body fat positively correlated (R = 0.29 and R = 0.53 for obese and normal-weight respectively) with radiologically assessed OA grade. However, no correlations were found with clinical status of the patients.

CONCLUSIONS

It was found that in the obese patients with knee OA, increased percentage of total body fat and elevated serum leptin concentration might favour the advancement of clinical but not radiologically assessed changes in the joint structures, while in normal-weight patients it correlates only with radiologically assessed changes but does not affect to an appreciable extent the clinical status of the patients.

Serum levels of interleukin-17 and adiponectin are associated with infrapatellar fat pad volume and signal intensity alteration in patients with knee osteoarthritis

BACKGROUND

In the present study, we sought to generate hypotheses regarding the associations of serum levels of interleukin (IL)-17, adiponectin, and resistin with magnetic resonance imaging-measured infrapatellar fat pad (IPFP) size and signal intensity alterations in patients with knee osteoarthritis (OA).

METHODS

A total of 170 subjects with symptomatic knee OA (mean age 55.4 years, range 34-74, 88.2 % females) were included. IPFP volume was measured on T1-weighted spoiled gradient-recalled acquisition in the steady state images and was computed by using a software program. IPFP high signal intensity (grades 0-3) was assessed on T2-weighted fast spin echo images. Serum IL-17, adiponectin, and resistin levels were measured using an enzyme-linked immunosorbent assay.

RESULTS

In multivariable analyses, serum IL-17 was negatively associated with IPFP volume (β = -0.185, 95 % CI -0.337 to -0.034) but positively associated with the severity of IPFP signal intensity alteration (OR 1.23, 95 % CI 1.06-1.42) after adjustment for age, sex, weight, and height. Serum adiponectin was positively associated with IPFP volume (β = 0.016, 95 % CI 0.001-0.032) but negatively associated with IPFP signal intensity alteration (OR 0.99, 95 % CI 0.98-1.00) after adjustment for covariates. Resistin was positively associated with IPFP signal intensity alteration (OR 1.13, 95 % CI 1.04-1.23) but not with IPFP volume. The significant associations of adiponectin or resistin disappeared after further adjustment for IL-17; in contrast, the significant associations of IL-17 remained after further adjustment for adiponectin.

CONCLUSIONS

While serum IL-17 and resistin were associated with reduced IPFP volume and/or increased abnormal signal intensity alteration, serum adiponectin had opposite associations that were largely through IL-17. These findings suggest that serum adipocytokines may have a role to play in IPFP changes of knee OA.

Serum Resistin Levels May Contribute to an Increased Risk of Acute Cerebral Infarction

The objective of this study was to investigate the association between serum resistin levels and acute cerebral infarction (ACI). PubMed, SpringerLink, Wiley, EBSCO, Ovid, Web of Science, Wanfang, China National Knowledge Infrastructure, and VIP databases (last updated search in October 2014) were exhaustively searched, and data from the eligible studies were extracted and analyzed to assess the association between serum resistin levels and ACI. STATA software (version 12.0, Stata Corporation, College Station, TX, USA) was utilized for data analysis. Ten studies including 1829 ACI patients and 1557 healthy controls were eligible for inclusion in the meta-analysis. Our major result revealed that ACI patients exhibited higher serum resistin levels compared with healthy controls. Asubgroup analysis based on ethnicity showed a significant association between serum resistin levels and ACI in Asians, but surprisingly not in Caucasians. The results of our meta-analysis suggest that serum resistin levels are associated with an increased risk of ACI.

Pathophysiology of obesity on knee joint homeostasis: contributions of the infrapatellar fat pad

Osteoarthritis (OA) is a debilitating condition characterized by inflammation, breakdown, and consequent loss of cartilage of the joints. Epidemiological studies indicate obesity is an important risk factor involved in OA initiation and progression. Traditional views propose OA to be a biomechanical consequence of excess weight on weight-bearing joints; however, emerging data demonstrates that systemic and local factors released from white adipose depots play a role. Hence, current views characterize OA as a condition exacerbated by a metabolic link related to adipose tissue, and not solely related to redistributed/altered weight load. Factors demonstrated to influence cartilage and bone homeostasis include adipocyte-derived hormones (“adipokines”) and adipose depot released cytokines. Epidemiological studies demonstrate a positive relation between systemic circulating cytokines, leptin, and resistin with OA types, while the association with adiponectin is controversial. Local factors in joints have also been shown to play a role in OA. In particular, this includes the knee, a weight-bearing joint that encloses a relatively large adipose depot, the infrapatellar fat pad (IFP), which serves as a source of local inflammatory factors. This review summarizes the relation of obesity and OA as it specifically relates to the IFP and other integral supporting structures. Overall, studies support the concept that metabolic effects associated with systemic obesity also extend to the IFP, which promotes inflammation, pain, and cartilage destruction within the local knee joint environment, thus contributing to development and progression of OA.

Racial Differences in Serum Adipokine and Insulin Levels in a Matched Osteoarthritis Sample: A Pilot Study

BACKGROUND

In an attempt to correlate biomarkers with disease, serum-based biomarkers often are compared between individuals with osteoarthritis (OA) and control subjects. However, variable results have been reported. Some studies have suggested an association between certain adipokines and insulin and OA. We know that there are racial differences in OA prevalence and incidence, and from general population-based studies, those of Asian race consistently demonstrate a unique adipokine/insulin serum concentration profile as compared to Caucasians. Whether similar racial differences exist within OA samples is unknown and may have implications for selecting appropriate controls in comparative studies.

METHODS

Serum levels of adipokines, leptin, and adiponectin, along with insulin, were determined by ELISA in patients scheduled for total hip or knee replacement surgery for OA. Fifteen Asian patients were matched 1 : 1 on age (±2 years), gender, body mass index (±1.5 kg/m(2)), and surgical joint with Caucasian patients. Differences in serum concentrations were tested using paired t-tests.

RESULTS

Serum leptin and insulin levels were significantly higher in Asians compared to Caucasians (p < 0.05). While serum adiponectin levels were lower among Asians, the difference did not reach statistical significance (p = 0.12).

CONCLUSION

Findings from this work suggest that when studying serum biomarker concentrations in OA versus controls, race may be an important factor to consider. Our findings warrant confirmation in larger studies.

Possible Involvement of Serum and Synovial Fluid Resistin in Knee Osteoarthritis: Cartilage Damage, Clinical, and Radiological Links

BACKGROUND

Resistin is an adipocytokine associated with inflammation and insulin resistance. Recent studies have shown that resistin plays an important role in the pathogenesis and progression in osteoarthritis (OA) patients. The current study was aimed at investigating the relationship between resistin in serum and synovial fluid (SF) and disease severity in patients with knee osteoarthritis.

METHOD

Seventy-four patients diagnosed with knee OA and 79 healthy controls receiving regular body check in our hospital were recruited in the study. The Noyes score method was used to assess articular cartilage damage arthroscopically. The symptomatic severity was evaluated according to the Western Ontario McMaster University Osteoarthritis (WOMAC) scores. The radiographic disease severity of OA was assessed by the Kellgren-Lawrence (K-L) grading system. The resistin levels in serum and SF were determined by enzyme-linked immunosorbent assay. Cartilage degradation marker CTX-II in SF was also examined.

RESULTS

SF but not serum resistin levels are positively associated with Noyes scores, K-L grading scores WOMAC pain scores, physical functional scores and WOMAC total scores. In addition, SF resistin correlated positively with CTX-II.

CONCLUSION

Resistin in SF might serve as a potential biomarker for reflecting the disease severity and cartilage degenerative extent of knee OA.

Is osteoarthritis a metabolic disorder?

BACKGROUND

Obesity is associated with an increased risk of developing osteoarthritis (OA), even in non-weight bearing joints. High levels of adipose tissue-associated inflammation may explain this association.

SOURCES OF DATA AND AREAS OF DEBATE

Published evidence looking at the associations between components of Metabolic Syndrome (MetS) and knee, hip or hand OA and the higher mortality described with knee OA.

EMERGING POINTS

Development of MetS and OA shares a relationship with adipose tissue-associated inflammation. This review supports this inflammatory pathway being part of the shared mechanism behind obesity as a risk factor for OA and the recently described OA-associated increased mortality.

TIMELY AREAS FOR DEVELOPMENT

In an era of an obesity epidemic, this review identifies a need for well-designed cohort studies assessing early metabolic changes in populations at high risk of OA and MetS, and to identify risk factors for increased mortality in patients with OA.

Meniscus is more susceptible than cartilage to catabolic and anti-anabolic effects of adipokines

OBJECTIVE

This study compared the effects on cartilage and meniscus matrix catabolism and biosynthesis of several adipokines implicated in osteoarthritis (OA).

DESIGN

Bovine cartilage and meniscus explants were cultured for 1 or 9 days in serum-free medium alone or with 0.02, 0.2, or 2 μg/ml of leptin, visfatin, adiponectin, or resistin. Media were supplemented with (3)H-proline or (35)S-sodium sulfate to evaluate protein and sulfated glycosaminoglycan (sGAG) accumulation on the last day of culture. Explants were assayed for radiolabel, sGAG, and DNA contents. Cultured media were assayed for sGAG, nitrite and lactate dehydrogenase.

RESULTS

Cartilage tissue was minimally affected by adipokines, with only the highest resistin dose increasing sGAG release and nitrite production compared to controls. In sharp contrast, meniscus tissue was responsive to several adipokines, with elevated sGAG and nitrite release following treatment with resistin, leptin, or visfatin. Cartilage sGAG content was unaltered by adipokine treatment whereas meniscal sGAG content significantly decreased with resistin dosage. Protein ((3)H) incorporation was unaffected by adipokine treatment in both tissues. sGAG ((35)S) incorporation did not significantly vary with adipokine treatment in cartilage but was inhibited by treatment with leptin, visfatin, and resistin in meniscus.

CONCLUSION

Our results indicate that meniscal tissue is more susceptible to adipokine-stimulated catabolism than is cartilage. Resistin had the strongest effect of the adipokines tested, inducing sGAG release in both tissues and depleting sGAG content in meniscus. These results suggest that increased adipokine levels due to obesity or joint injury may alter the mechanical integrity of the knee joint through biological pathways.

Increased serum resistin levels correlate with psoriasis: a meta-analysis

Background

Recent studies implicate adipokines in the pathogenesis of inflammatory diseases, including psoriasis. In this study we evaluated the significance of serum resistin levels in psoriasis patients using a meta-analysis approach.223

Methods

Relevant articles were retrieved by searching the following English and Chinese databases: Cochrane Library, PubMed, Springer Link, Chinese Biomedical Database (CBM) and Chinese National Knowledge Infrastructure (CNKI). The retrieved studies were subjected to a thorough screening procedure to identify case–control studies that contained the required data. Data was extracted from each study and Version 12.0 STATA statistical software was employed for statistical analyses.

Results

Nine case–control studies, containing 421 psoriasis patients and 348 healthy controls, were included in this study. The major result of the meta-analysis revealed a statistically significant association between serum resistin levels and psoriasis (SMD = 2.22, 95%CI: 1.14-3.29, P < 0.001). Subgroup analysis based on ethnicity showed that, compared to the healthy controls, serum resistin levels were markedly higher in psoriasis patients in both Asian and Caucasian populations (Asians: SMD = 3.27, 95%CI = 1.62 ~ 4.91, P < 0.001; Caucasians: SMD = 0.91, 95%CI = 0.28 ~ 1.54, P < 0.001).

Conclusions

Based on our results, we conclude that serum resistin level in psoriasis patients is higher than healthy controls, and raises the possibility that elevated serum resistin levels may be a novel diagnostic marker in psoriasis and may predict the occurrence of co-morbidities in psoriasis patients.

Obesity and osteoarthritis, more than just wear and tear: pivotal roles for inflamed adipose tissue and dyslipidaemia in obesity-induced osteoarthritis

OA is a degenerative joint disease characterized by articular cartilage degradation, osteophyte formation, synovitis, and subchondral bone sclerosis. One of OAs main risk factors is obesity. To date, it is not fully understood how obesity results in OA. Historically, this link was ascribed to excessive joint loading as a result of increased body weight. However, the association between obesity and OA in non-weight-bearing joints suggests a more complex aetiology for obesity-induced OA. In the present review, the link between obesity and OA is discussed. First, the historical view of altered joint loading leading to wear and tear of the joint is addressed. Subsequently, the effects of a disturbed lipid metabolism, low-grade inflammation, and adipokines on joint tissues are discussed and linked to OA. Taken together, inflamed adipose tissue and dyslipidaemia play pivotal roles in obesity-induced OA. It becomes increasingly clear that the link between obesity and OA transcends excessive loading.

Clinical significance of resistin expression in osteoarthritis: a meta-analysis

Background. The objective of this study was to conduct a systematic review of literature evaluating human resistin expression as a diagnostic factor in osteoarthritis development and to quantify the overall diagnostic effect. Method. Relevant studies were identified and evaluated for quality through multiple search strategies. Studies analyzing resistin expression in the development of OA were eligible for inclusion. Data from eligible studies were extracted and included into the meta-analysis using a random-effects model. Results. Four case-control studies consisting of a total of 375 OA patients and 214 controls as well as three sex-stratified analyses composed of 53 males and 104 females were incorporated into our meta-analysis. Our results revealed that resistin levels were significantly higher in male OA subjects and OA patients overall. Country-stratified analysis yielded significantly different estimates in resistin levels between male OA subjects and female OA subjects in the Canadian subgroup but not among the French and USA subgroups. Based on the resistin levels in OA cases and controls, resistin levels were heightened in OA patients in the Dutch population. Conclusion. These results support the hypothesis that high expression of resistin represents a significant and reproducible marker of poor progression in OA patients, especially in males.

Adipokines: Biomarkers for osteoarthritis?

Osteoarthritis (OA) is one of the most common degenerative joint diseases in aging population. Obesity is an important risk factor for initiation and progression of OA. It is accepted that excess body weight may lead to cartilage degeneration by increasing the mechanical forces across weight-bearing joints. However, emerging data suggest that additional metabolic factors released mainly by white adipose tissue may also be responsible for the high prevalence of OA among obese people. Adipocyte-derived molecules ‘‘adipokines’’ have prompt much interest in OA pathophysiological research over the past decade since they play an important role in cartilage and bone homeostasis. Therefore, the aim of this review is to summarize the current knowledge on the role of adipokines including leptin, adiponectin, visfatin and resistin in OA and their potential to be used as biomarkers for earlier diagnosis, classifying disease severity, monitoring disease progression, and testing pharmacological interventions for OA. In OA patients, leptin, visfatin and resistin showed increased production whereas adiponectin showed decreased production. Leptin and adiponectin are far more studied than visfatin and resistin. Importantly, altered adipokine levels also contribute to a wide range of diseases. Further experiments are still crucial for understanding the relationship between adipokines and OA.

Adipokines as predictors of recovery from upper extremity soft tissue disorders

OBJECTIVES

To study the associations of adipokines with recovery from upper extremity soft tissue disorders (UESTDs) and to explore whether overweight or obesity modify these associations.

METHODS

In this follow-up study, patients seeking medical advice due to incipient upper extremity symptoms with symptom duration <1 month were included (n = 163). The outcome of the study was full or substantial recovery from UESTDs, assessed at 2, 8 and 12 weeks of follow-up. We studied the associations of four adipokines (leptin, adiponectin, resistin and visfatin) with recovery using the generalized estimating equation.

RESULTS

Of the study population, 27.5% reported full or substantial recovery at the 8-week follow-up and 32% at 12 weeks. Higher levels of resistin [odds ratio (OR) = 1.58, 95% CI 1.18, 2.11 for 1 s.d. increase] and visfatin (OR = 1.29, 95% CI 0.94, 1.78 for 1 s.d. increase) at baseline predicted a higher recovery rate at the 8-week follow-up. Moreover, higher levels of leptin predicted a lower rate of recovery (OR = 0.73, 95% CI 0.51, 1.02 for 1 s.d. increase). Adipokines did not predict recovery at 12 weeks. In subgroup analyses, high levels of resistin and visfatin at baseline predicted a higher recovery rate during follow-up in non-overweight patients.

CONCLUSION

The adipokines resistin and visfatin predicted recovery from UESTDs and the associations may be related to stimulation of anti-inflammatory response mechanisms. A higher level of leptin may prevent recovery from UESTDs.

Resistin as a factor in osteoarthritis: synovial fluid resistin concentrations correlate positively with interleukin 6 and matrix metalloproteinases MMP-1 and MMP-3

OBJECTIVES

Resistin is an adipocytokine that has been related to inflammation and insulin resistance. Following knee injury, elevated levels of resistin have been found in synovial fluid (SF) while very little is known about the role of resistin in osteoarthritis (OA). The aim of the present study was to investigate resistin levels in OA joints and to determine if it is associated with inflammatory and catabolic factors in the joints.

METHOD

SF, plasma, and cartilage samples were collected from 88 OA patients undergoing knee replacement surgery. Resistin levels were measured by enzyme-linked immunosorbent assay (ELISA) in SF, plasma, and cartilage culture media.

RESULTS

Significant levels of resistin [0.75 (0.67) ng/mL; median (IQR)] were found in SF from OA patients. Resistin correlated positively with interleukin (IL)-6 (r = 0.39, p < 0.001) and with matrix metalloproteinases MMP-1 (r = 0.31, p = 0.004) and MMP-3 (r = 0.24, p = 0.024) in SF. Resistin was also released from cultured OA cartilage and it correlated with resistin levels in SF (r = 0.39, p < 0.001). In addition, resistin levels in plasma correlated positively with those in SF (r = 0.44, p < 0.001). There were no differences in SF or plasma resistin concentrations between females and males or between non-diabetic and diabetic patients, and resistin did not correlate with body mass index (BMI).

CONCLUSIONS

Resistin is present in OA joints and is released from OA cartilage. Levels of resistin in SF are associated with inflammatory and catabolic factors, suggesting that resistin has a role to play in the pathogenesis of, and as a possible drug target in, OA.

Plasma Adipokine Levels and Their Association with Overall Burden of Painful Joints among Individuals with Hip and Knee Osteoarthritis

Objective.

To investigate the association between plasma adipokine levels and the burden of painful joints among individuals with hip and knee osteoarthritis (OA).

Methods.

Adipokines (leptin, adiponectin, adipsin, resistin) were determined by ELISA (n = 78). Individuals reported painful joints on a homunculus. Associations were examined by sex-stratified Poisson analyses.

Results.

Adjusted for age, body mass index, and hip/knee OA, higher leptin and adiponectin and lower adipsin levels were associated with greater painful joint burden (i.e., counts) among women (p < 0.01). Among men, higher resistin levels were associated with lower counts (p = 0.03).

Conclusion.

Findings support the likelihood of a systemic-dependent sex-specific pain burden among individuals with OA.

Rheumatic diseases and obesity: adipocytokines as potential comorbidity biomarkers for cardiovascular diseases

Inflammation has been recognized as a common trait in the pathogenesis of multifactorial diseases including obesity, where a low-grade inflammation has been established and may be responsible for the cardiovascular risk related to the disease. Obesity has also been associated with the increased incidence and a worse outcome of rheumatoid arthritis (RA) and osteoarthritis (OA). RA is characterized by systemic inflammation, which is thought to play a key role in accelerated atherosclerosis and in the increased incidence of cardiovascular disease, an important comorbidity in patients with RA. The inflammatory process underlying the cardiovascular risk both in obesity and RA may be mediated by adipocytokines, a heterogeneous group of soluble proteins mainly secreted by the adipocytes. Many adipocytokines are mainly produced by white adipose tissue. Adipocytokines may also be involved in the pathogenesis of OA since a positive association with obesity has been found for weight-bearing and nonweight-bearing joints, suggesting that, in addition to local overload, systemic factors may contribute to joint damage. In this review we summarize the current knowledge on experimental models and clinical studies in which adipocytokines were examined in obesity, RA, and OA and discuss the potential of adipocytokines as comorbidity biomarkers for cardiovascular risk.

Osteoarthritis and osteoporosis: what is the overlap?

Osteoarthritis (OA) and osteoporosis (OP) are highly prevalent health problems, associated with considerable morbidity. In the past, attention was focused on a supposed inverse relationship between OA and OP, since both disorders usually affect the elderly, but were regarded to rarely coexist in a single person. However, recent studies have revealed several factors which contribute to the pathogenesis of both disorders. These insights might contribute to the development of shared new treatment options in the near future. Increased subchondral bone loss is a characteristic feature of OP and the early stage of OA, and this finding is the rationale for studies on the effect of anti-osteoporotic drugs in OA. In addition, inflammation and unfavourable body composition have been recognized as contributing factors for both disorders. Underweight is a risk factor for OP, while obesity stimulates the development of OA, by mechanical overloading of weight-bearing joints but also by supposed unfavourable effects of adipokines.

Role of inflammation in the pathogenesis of osteoarthritis: latest findings and interpretations

Osteoarthritis (OA) has traditionally been classified as a noninflammatory arthritis; however, the dichotomy between inflammatory and degenerative arthritis is becoming less clear with the recognition of a plethora of ongoing immune processes within the OA joint and synovium. Synovitis is defined as inflammation of the synovial membrane and is characteristic of classical inflammatory arthritidies. Increasingly recognized is the presence of synovitis in a significant proportion of patients with primary OA, and based on this observation, further studies have gone on to implicate joint inflammation and synovitis in the pathogenesis of OA. However, clinical OA is not one disease but a final common pathway secondary to many predisposing factors, most notably age, joint trauma, altered biomechanics, and obesity. How such biochemical and mechanical processes contribute to the progressive joint failure characteristic of OA is tightly linked to the interplay of joint damage, the immune response to perceived damage, and the subsequent state of chronic inflammation resulting in propagation and progression toward the phenotype recognized as clinical OA. This review will discuss a wide range of evolving data leading to our current hypotheses regarding the role of immune activation and inflammation in OA onset and progression. Although OA can affect any joint, most commonly the knee, hip, spine, and hands, this review will focus primarily on OA of the knee as this is the joint most well characterized by epidemiologic, imaging, and translational studies investigating the association of inflammation with OA.