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

Intraarticular injection of liposomal adenosine reduces cartilage damage in established murine and rat models of osteoarthritis

Osteoarthritis (OA) affects nearly 10% of the population of the United States and other industrialized countries and, at present, short of surgical joint replacement, there is no therapy available that can reverse the progression of the disease. Adenosine, acting at its A2A receptor (A2AR), is a critical autocrine factor for maintenance of cartilage homeostasis and here we report that injection of liposomal suspensions of either adenosine or a selective A2AR agonist, CGS21680, significantly reduced OA cartilage damage in a murine model of obesity-induced OA. The same treatment also improved swelling and preserved cartilage in the affected knees in a rat model of established post-traumatic OA (PTOA). Differential expression analysis of mRNA from chondrocytes harvested from knees of rats with PTOA treated with liposomal A2AR agonist revealed downregulation of genes associated with matrix degradation and upregulation of genes associated with cell proliferation as compared to liposomes alone. Studies in vitro and in affected joints demonstrated that A2AR ligation increased the nuclear P-SMAD2/3/P-SMAD1/5/8 ratio, a change associated with repression of terminal chondrocyte differentiation. These results strongly suggest that targeting the A2AR is an effective approach to treat OA.

Vitamin D supplementation and inflammatory and metabolic biomarkers in patients with knee osteoarthritis: post hoc analysis of a randomised controlled trial

The aim of this study was to determine whether vitamin D supplementation and maintaining vitamin D sufficiency are associated with changes in inflammatory and metabolic biomarkers in patients with knee osteoarthritis (OA) and vitamin D deficiency. A total of 413 participants with symptomatic knee OA and vitamin D deficiency were enrolled in a randomised, placebo-controlled trial and received 1·25 mg vitamin D3 or placebo monthly for 24 months across two sites. In this post hoc analysis, 200 participants from one site (ninety-four from the placebo group and 106 from the vitamin D group; mean age 63·1 (sd 7·3) years, 53·3 % women) were randomly selected for measurement of serum levels of inflammatory and metabolic biomarkers at baseline and 24 months using immunoassays. In addition, participants were classified into two groups according to serum 25-hydroxyvitamin D (25(OH)D) levels at months 3 and 24: (1) not consistently sufficient (25(OH)D≤50 nmol/l at either month 3 or 24, n 61), and (2) consistently sufficient (25(OH)D>50 nmol/l at both months 3 and 24, n 139). Compared with placebo, vitamin D supplementation had no significant effect on change in serum high-sensitive C-reactive protein, IL-6, IL-8, IL-10, leptin, adiponectin, resistin, adipsin and apelin. Being consistently vitamin D sufficient over 2 years was also not associated with changes in these biomarkers compared with not being consistently sufficient. Vitamin D supplementation and maintaining vitamin D sufficiency did not alter serum levels of inflammatory and metabolic biomarkers over 2 years in knee OA patients who were vitamin D insufficient, suggesting that they may not affect systemic inflammation in knee OA patients.

The Adipokine Network in Rheumatic Joint Diseases

Rheumatic diseases encompass a diverse group of chronic disorders that commonly affect musculoskeletal structures. Osteoarthritis (OA) and rheumatoid arthritis (RA) are the two most common, leading to considerable functional limitations and irreversible disability when patients are unsuccessfully treated. Although the specific causes of many rheumatic conditions remain unknown, it is generally accepted that immune mechanisms and/or uncontrolled inflammatory responses are involved in their etiology and symptomatology. In this regard, the bidirectional communication between neuroendocrine and immune system has been demonstrated to provide a homeostatic network that is involved in several pathological conditions. Adipokines represent a wide variety of bioactive, immune and inflammatory mediators mainly released by adipocytes that act as signal molecules in the neuroendocrine-immune interactions. Adipokines can also be synthesized by synoviocytes, osteoclasts, osteoblasts, chondrocytes and inflammatory cells in the joint microenvironment, showing potent modulatory properties on different effector cells in OA and RA pathogenesis. Effects of adiponectin, leptin, resistin and visfatin on local and systemic inflammation are broadly described. However, more recently, other adipokines, such as progranulin, chemerin, lipocalin-2, vaspin, omentin-1 and nesfatin, have been recognized to display immunomodulatory actions in rheumatic diseases. This review highlights the latest relevant findings on the role of the adipokine network in the pathophysiology of OA and RA.

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.

The effect of a garlic supplement on the pro-inflammatory adipocytokines, resistin and tumor necrosis factor-alpha, and on pain severity, in overweight or obese women with knee osteoarthritis

BACKGROUND

Osteoarthritis (OA) is a prevalent degenerative joint disease, which is associated with chronic and disabling pain. The adipocytokines, resistin and tumor necrosis factor-alpha (TNF-α), might play a role in OA pathogenesis and outcomes.

PURPOSE

The aim of this study was, therefore, to assess the anti-inflammatory and analgesic effects of a garlic supplement on serum resistin and TNF-α concentrations and on pain severity in overweight or obese women with knee OA.

STUDY DESIGN

Randomized, double-blind, placebo-controlled, parallel-design trial.

METHODS

In this study, 80 post-menopausal overweight or obese women (25 ≤ BMI ≤ 40 kg/m², age 50-75 years) with mild to moderate knee OA were enrolled. Patients were randomly divided into two groups to receive twice-daily either garlic tablets (total: 1000 mg) or placebo for 12 weeks. The primary outcome measures were fasting serum concentrations of resistin and TNF-α, and pain severity (assessed using 0-10 point visual analogue scale (VAS)).

RESULTS

At week 12, resistin concentrations were significantly decreased in the garlic group (6.41 ± 2.40 to 5.56 ± 2.16 ng/ml; P = 0.008). Serum TNF-α levels did not change significantly within or between the two groups. Pain scores were significantly reduced in the garlic (6.8 ± 2 to 5.3 ± 2.3; P = 0.002), but not in the placebo (6.7 ± 2.4 to 6.2 ± 2.5; P = 0.674), group. Pain scores were also significantly lower in the garlic, compared with the placebo, group following supplementation (5.3 ± 2.3 vs. 6.2 ± 2.5; P = 0.043).

CONCLUSIONS

The findings suggest that garlic supplementation for 12 weeks might reduce pain severity in overweight or obese women with knee OA, which may, at least in part, be mediated via a reduction in the pro-inflammatory adipocytokine, resistin.

Adiposity Measures and Plasma Adipokines in Females with Rheumatoid and Osteoarthritis

The objective of this study was to examine the relationship between adipokines and adiposity in individuals with rheumatoid and osteoarthritis in the Atlantic PATH cohort. Using a nested case-control analysis, participants in the Atlantic PATH cohort with rheumatoid or osteoarthritis were matched for measures of adiposity with participants without a history of arthritis. Both measured and self-reported data were used to examine disease status, adiposity, and lifestyle factors. Immunoassays were used to measure plasma markers. BMI was positively correlated with percentage body fat, fat mass index (FMI), and a change in BMI from 18 years of age in all 3 groups. There were no statistical differences between levels of plasma adipokines; adiponectin levels were 6.6, 7.9, and 8.2 μg/ml, leptin levels were 10.3, 13.7, and 11.5 ng/ml, and resistin levels were 10.0, 12.1, and 10.8 ng/ml in participants without arthritis, with rheumatoid arthritis, and with osteoarthritis, respectively. Those with higher levels of adiponectin were more likely to have osteoarthritis (but not rheumatoid arthritis). No association was found between arthritis types and leptin or resistin. This study demonstrates differences in measures of adiposity and adipokines in specific types of arthritis and highlights the need for more research targeting specific adipokines during arthritic disease progression.

Adipokine genes and radiographic hand osteoarthritis in Finnish women: a cross-sectional study

OBJECTIVES

Available evidence suggests that genetic factors and overweight play major roles in the aetiology of osteoarthritis (OA). We analysed the association of 18 single-nucleotide polymorphisms (SNPs) from nine adipokine and adipokine receptor genes (LEP, LEPR, ADIPOQ, RETN, NAMPT, SERPINA12, ITLN1, RARRES2, and APLN) with radiographic hand OA.

METHOD

The study design was cross-sectional. Bilateral hand radiographs of 542 occupationally active Finnish female dentists and teachers aged 45-63 years were examined and classified for the presence of hand OA using reference images. Hand OA was defined as at least three finger joints with radiographic OA of grade 2-4. The genotypes were determined using polymerase chain reaction-based methods. Body mass index (BMI) was calculated based on self-reported height and measured weight. Associations of the individual SNPs and their haplotypes with hand OA were tested using logistic regression analysis.

RESULTS

The minor allele of RETN rs10401670 was associated with a decreased [odds ratio (OR) = 0.73, 95% confidence interval (CI) 0.55-0.97, p = 0.03] and RARRES2 rs4721 with an increased (OR 1.41, 95% CI 1.07-1.87, p = 0.01) prevalence of hand OA. Also, LEPR AC (OR 1.54, 95% CI 1.01-2.35, p = 0.05) and RETN GGTT (OR 0.58, 95% CI 0.37-0.93, p = 0.02) haplotypes were associated with hand OA. These associations were modified by BMI when comparing normal and overweight women. However, the associations lost their statistical significance after adjusting for multiple testing.

CONCLUSION

Our results suggest weak associations between the studied variations in LEPR, RARRES2, and RETN genes and hand OA in Finnish women, and that the associations are modified by BMI. However, these associations could not be verified in the current study.