Evidence for a protective role for adiponectin in osteoarthritis

Adipokines as potential pharmacological targets for immune inflammatory rheumatic diseases: Focus on rheumatoid arthritis, osteoarthritis, and intervertebral disc degeneration

Adipokines are a heterogeneous group of signalling molecules secreted prevalently by adipose tissue. Initially considered as regulators of energy metabolism and appetite, adipokines have been recognized for their substantial involvement in musculoskeletal disorders, including osteoarthritis, rheumatoid arthritis, and many others. Understanding the role of adipokines in rheumatic inflammatory and autoimmune diseases, as well as in other musculoskeletal diseases such as intervertebral disc degeneration, is crucial for the development of novel therapeutic strategies. Targeting adipokines, or their signalling pathways, may offer new opportunities for the treatment and management of these conditions. By modulating adipokines levels or activity, it may be possible to regulate inflammation, to maintain bone health, and preserve muscle mass, thereby improving the outcomes and quality of life for individuals affected by musculoskeletal diseases. The aim of this review article is to update the reader on the multifaceted role of adipokines in the main rheumatic diseases such as osteoarthritis and rheumatoid arthritis and to unravel the complex interplay among adipokines, cartilage metabolism, bone remodelling and muscles, which will pave the way for innovative therapeutic intervention in the future. For completeness, the role of adipokines in intervertebral disc degeneration will be also addressed.

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.

Visceral adipose tissue and osteoarthritis, a two-sample Mendelian randomized study

Background

The relationship between visceral adipose tissue and osteoarthritis is not clear. The purpose of our study was to explore the relationship between visceral adipose tissue and osteoarthritis.

Methods

We used a two-sample Mendelian randomization method to select single-nucleotide polymorphisms (SNPs) significantly associated with visceral adipose tissue as instrumental variables to explore the relationship between visceral adipose tissue and all osteoarthritis, hand osteoarthritis, hip osteoarthritis, knee osteoarthritis, and spine osteoarthritis. The reliability of the results was tested using sensitivity analysis.

Results

Our findings indicated that visceral adipose tissue was associated with all osteoarthritis, hip osteoarthritis, knee osteoarthritis, and spine osteoarthritis (all osteoarthritis: OR = 1.399, 95% CI: 1.335-1.467, p = 7.95e-44; hip osteoarthritis: OR = 1.399, 95% CI: 1.284-1.524, p = 1.41e-14; knee osteoarthritis: OR = 1.794, 95% CI: 1.662-1.937, p = 1.33e-50; and spine osteoarthritis: OR = 1.445, 95% CI: 1.314-1.589, p = 2.89e-14). Sensitivity analysis demonstrated the reliability of these results.

Conclusion

Our study suggests that genetically predicted visceral adipose tissue is associated with osteoarthritis. Reducing the accumulation of visceral adipose tissue could potentially have an impact on the incidence of osteoarthritis.

Risk of metabolic abnormalities in osteoarthritis: a new perspective to understand its pathological mechanisms

Although aging has traditionally been viewed as the most important risk factor for osteoarthritis (OA), an increasing amount of epidemiological evidence has highlighted the association between metabolic abnormalities and OA, particularly in younger individuals. Metabolic abnormalities, such as obesity and type II diabetes, are strongly linked to OA, and they affect both weight-bearing and non-weight-bearing joints, thus suggesting that the pathogenesis of OA is more complicated than the mechanical stress induced by overweight. This review aims to explore the recent advances in research on the relationship between metabolic abnormalities and OA risk, including the impact of abnormal glucose and lipid metabolism, the potential pathogenesis and targeted therapeutic strategies.

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

Objectives

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

Design

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

Results

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

Conclusion

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

Anti-Inflammatory Effects of Adiponectin Receptor Agonist AdipoRon against Intervertebral Disc Degeneration

Adiponectin, a hormone secreted by adipocytes, has anti-inflammatory effects and is involved in various physiological and pathological processes such as obesity, inflammatory diseases, and cartilage diseases. However, the function of adiponectin in intervertebral disc (IVD) degeneration is not well understood. This study aimed to elucidate the effects of AdipoRon, an agonist of adiponectin receptor, on human IVD nucleus pulposus (NP) cells, using a three-dimensional in vitro culturing system. This study also aimed to elucidate the effects of AdipoRon on rat tail IVD tissues using an in vivo puncture-induced IVD degeneration model. Analysis using quantitative polymerase chain reaction demonstrated the downregulation of gene expression of proinflammatory and catabolic factors by interleukin (IL)-1β (10 ng/mL) in human IVD NP cells treated with AdipoRon (2 μM). Furthermore, western blotting showed AdipoRon-induced suppression of p65 phosphorylation (p < 0.01) under IL-1β stimulation in the adenosine monophosphate-activated protein kinase (AMPK) pathway. Intradiscal administration of AdipoRon was effective in alleviating the radiologic height loss induced by annular puncture of rat tail IVD, histomorphological degeneration, production of extracellular matrix catabolic factors, and expression of proinflammatory cytokines. Therefore, AdipoRon could be a new therapeutic candidate for alleviating the early stage of IVD degeneration.

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

Osteoarthritis (OA) is a prevalent progressive disease that frequently coexists with obesity. For several decades, OA was thought to be the result of ageing and mechanical stress on cartilage. Researchers' perspective has been greatly transformed when cumulative findings emphasized the role of adipose tissue in the diseases. Nowadays, the metabolic effect of obesity on cartilage tissue has become an integral part of obesity research; hoping to discover a disease-modifying drug for OA. Recently, several adipokines have been reported to be associated with OA. Particularly, metrnl (meteorin-like) and retinol-binding protein 4 (RBP4) have been recognized as emerging adipokines that can mediate OA pathogenesis. Accordingly, in this review, we will summarize the latest findings concerned with the metabolic contribution of obesity in OA pathogenesis, with particular emphasis on dyslipidemia, insulin resistance and adipokines. Additionally, we will discuss the most recent adipokines that have been reported to play a role in this context. Careful consideration of these molecular mechanisms interrelated with obesity and OA will undoubtedly unveil new avenues for OA treatment.

Correlation analysis of differentially expressed long non-coding RNA HOTAIR with PTEN/PI3K/AKT pathway and inflammation in patients with osteoarthritis and the effect of baicalin intervention

OBJECTIVE

This study aims to investigate the correlation of long non-coding RNA HOX transcript antisense RNA (lncRNA HOTAIR) with the PTEN/PI3K/AKT pathway and clinical-related indicators in osteoarthritis (OA) and determine the effect of baicalin intervention.

METHODS

The levels of clinical lipid metabolism indexes and immune-inflammatory indexes in OA patients and normal controls was detected. OA chondrocytes (OA-CHs) were induced with peripheral blood mononuclear cells (PBMCs), followed by baicalin treatment (50 ug/mL). RT-qPCR was performed to measure lncRNA HOTAIR expression. The levels of inflammatory cytokines and adiponectin were detected using ELISA kits. CCK-8 assay was used to assess the viability of CHs. The related protein expression was measured using Western blot analysis.

RESULTS

LncRNA HOTAIR might act as a biomarker of OA in vivo. LncRNA HOTAIR was positively correlated with TC, hs-CRP, IgA, TNF-α, and VAS score. Overexpression of lncRNA HOTAIR in vitro inhibited cell proliferation, reduced IL-10 and PTEN expression, but augmented TNF-α, p-PI3K, and p-AKT proteins in OA-CHs stimulated by OA-PBMCs. The changes of above indexes were also observed in OA-CHs stimulated by OA-PBMCs treated with si-lncRNA HOTAIR or baicalin, implying the synergistic effects of baicalin and lncRNA HOTAIR silencing on OA.

CONCLUSIONS

Conclusively, lncRNA HOTAIR was highly expressed in OA-CHs, which facilitated OA inflammatory responses by orchestrating inflammatory cytokines and the PTEN/PI3K/AKT pathway. Baicalin exerted therapeutic effects by inhibiting the expression of lncRNA HOTAIR, decreasing the protein levels of p-PI3K and p-AKT, and increasing the protein levels of PTEN, APN, and ADIPOR1.

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

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

Adipokines as targets in musculoskeletal immune and inflammatory diseases

Adipokines are the principal mediators in adipose signaling. Nevertheless, besides their role in energy storage, these molecules can be produced by other cells, such as immune cells or chondrocytes. Given their pleiotropic effects, research over the past few years has also focused on musculoskeletal diseases, showing that these adipokines might have relevant roles in worsening the disease or improving the treatment response. In this review, we summarize recent advances in our understanding of adipokines and their role in the most prevalent musculoskeletal immune and inflammatory disorders.

Source and hub of inflammation: The infrapatellar fat pad and its interactions with articular tissues during knee osteoarthritis

Knee osteoarthritis, the most prevalent degenerative joint disorder worldwide, is driven by chronic low-grade inflammation and subsequent cartilage degradation. Clinical data on the role of the Hoffa or infrapatellar fat pad in knee osteoarthritis are, however, scarce. The infrapatellar fat pad is a richly innervated intracapsular, extrasynovial adipose tissue, and an abundant source of adipokines and proinflammatory and catabolic cytokines, which may contribute to chronic synovial inflammation, cartilage destruction, and subchondral bone remodeling during knee osteoarthritis. How the infrapatellar fat pad interacts with neighboring tissues is poorly understood. Here, we review available literature with regard to the infrapatellar fat pad's interactions with cartilage, synovium, bone, menisci, ligaments, and nervous tissue during the development and progression of knee osteoarthritis. Signaling cascades are described with a focus on immune cell populations, pro- and anti-inflammatory cytokines, adipokines, mesenchymal stromal cells, and molecules derived from conditioned media from the infrapatellar fat pad. Understanding the complex interplay between the infrapatellar fat pad and its neighboring articular tissues may help to better understand and treat the multifactorial pathogenesis of osteoarthritis.

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

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

Inhibition of Pathological Increased Matrix Metalloproteinase (MMP) Activity for Improvement of Bone Regeneration in Diabetes

Patients with diabetes suffer from poor fracture healing. Molecular reasons are not fully understood and our previous gene expression microarray analyses of regenerating bones from mice with type 2 diabetes (db⁻/db⁻) revealed accelerated activation of pathways concerning matrix metalloproteases (MMPs). Thus, we picked out the pathological MMP acceleration as a target for profound gene expression analyses and additional therapeutic intervention in the present study. In the first part, gene expression of ECM degrading proteinases and inhibitors was investigated three and seven days postoperatively. Mmp3, Mmp9, Mmp13 and gene expression of MMP inhibitor Timp2 was significantly higher in regenerating bone fractures of db⁻/db⁻ compared to wild type animals. Timp1 and metalloproteinase AdamTS4 showed no differences. In the second part, we locally applied a single dose (1 µL of 5 µM solution) of the broad-spectrum molecular MMP inhibitor Marimastat on tibial defects in db⁻/db⁻. We performed immunohistochemical and histological stainings seven days post operation. Impaired bone healing, collagen content, angiogenesis, and osteoclast invasion in db⁻/db⁻ were restored significantly by application of Marimastat compared to PBS controls (n = 7/group). Hence, local intervention of bone defects by the molecular MMP inhibitor Marimastat might be an alternative therapeutic intervention for bone healing in diabetes.

Adiponectin, May Be a Potential Protective Factor for Obesity-Related Osteoarthritis

Osteoarthritis (OA) is the most common joint disease in elderly individuals and seriously affects quality of life. OA has often been thought to be caused by body weight load, but studies have increasingly shown that OA is an inflammation-mediated metabolic disease. The current existing evidence suggests that OA is associated with obesity-related chronic inflammation as well as abnormal lipid metabolism in obesity, such as fatty acids (FA) and triglycerides. Adiponectin, a cytokine secreted by adipose tissue, can affect the progression of OA by regulating obesity-related inflammatory factors. However, the specific molecular mechanism has not been fully elucidated. According to previous research, adiponectin can promote the metabolism of FA and triglycerides, which indicates that it is a potential protective factor for OA through many mechanisms. This article aims to review the mechanisms of chronic inflammation, FA and triglycerides in OA, as well as the potential mechanisms of adiponectin in regulating chronic inflammation and promoting FA and triglyceride metabolism. Therefore, adiponectin may have a protective effect on obesity-related OA, which could provide new insight into adiponectin and the related mechanisms in OA.

Chondrocytes from osteoarthritic cartilage of obese patients show altered adiponectin receptors expression and response to adiponectin

Obesity and osteoarthritis (OA) are well-known comorbidities and their precise molecular interactions are still unidentified. Adiponectin, a major adipokine, known to have an anti-inflammatory effect in atherosclerosis or Type 2 Diabetes Mellitus (T2DM), has also been postulated to be pro-inflammatory in OA. This dual role of adiponectin is still not explained. The precise mechanism by which adiponectin affects cartilage and chondrocytes remains to be elucidated. In the present observational study chondrocytes from 30 patients with OA (18 females and 12 males) undergoing total knee replacement (TKR) were isolated. Expression of adiponectin receptors 1 and 2 (ADIPOR1 and ADIPOR2) was examined both at gene and protein levels in chondrocytes. The difference in adiponectin receptor expression between lean and obese patients with OA and the role of adiponectin in regulating pro-inflammatory genes (MCP-1, IL-6, and VCAM-1, MMP-1, MMP-2, and TIMP-1) has been investigated. We found that ADIPOR1 represented the most abundant adiponectin receptor in primary OA chondrocytes. ADIPOR1 and ADIPOR2 genes and ADIPOR1 protein were differently expressed in OA chondrocytes obtained from obese compared with lean patients with OA. Adiponectin induced gene expression of MCP-1, IL-6, and MMP-1 in all OA patients' chondrocytes. In contrast, VCAM-1 and MMP-2 were differently regulated by adiponectin depending on the patient's body mass index. This study suggests that adiponectin and ADIPOR1 may have important roles in the pathogenesis of cartilage degeneration in OA of obese subjects.

Association of urinary phthalate metabolites with osteoarthritis in American adults: Results from the national health and nutrition examination survey 2003-2014

Phthalates have extensive existence in the living environment of human, probably tightly associated with multiple human diseases. The present study aimed to exploratorily investigate the association of urinary phthalate metabolites with osteoarthritis (OA) in American adults by exploiting the data extracted from National Health and Nutrition Examination Survey (NHANES) 2003-2014 with levels of eleven urinary phthalate metabolites as exposure. The multivariable logistic regression models were performed after controlling for urinary creatinine, age, gender, race/ethnicity, education level, marital status, smoking, body mass index, physical activity in recreational time, family poverty income ratio, diabetes, hypertension, as well as survey cycle. Compared with those in the lowest quantile, we observed higher prevalence of OA in the maximal quantile of MCOP (OR = 1.55, 95% CI = 1.06-2.27) in adjusted model. A one-unit increase in log-transformed phthalate metabolites was significantly associated with higher OA prevalence, including MCOP (OR = 1.13, 95% CI = 1.02-1.26) and MBzP (OR = 1.12, 95% CI = 1.00-1.26) in adjusted model. In subgroup analysis, the positive associations between phthalate metabolites and OA prevalence remained robust both in males and females. In brief, this study first presented positive evidence for the association of urinary level of phthalate metabolites with OA prevalence in American adults. Additional causal research is required to confirm the finding from our analysis and elucidate the potential underlying mechanisms of phthalates exposure on OA.

Therapeutic Applications of Type 2 Diabetes Mellitus Drug Metformin in Patients with Osteoarthritis

Type 2 diabetes mellitus (T2DM) and osteoarthritis (OA) are common chronic diseases that frequently co-exist. The link between OA and T2DM is attributed to common risk factors, including age and obesity. Several reports suggest that hyperglycemia and accumulated advanced glycosylation end-products might regulate cartilage homeostasis and contribute to the development and progression of OA. Metformin is used widely as the first-line treatment for T2DM. The drug acts by regulating glucose levels and improving insulin sensitivity. The anti-diabetic effects of metformin are mediated mainly via activation of adenosine monophosphate (AMP)-activated protein kinase (AMPK), which is an energy sensing enzyme activated directly by an increase in the AMP/ATP ratio under conditions of metabolic stress. Dysregulation of AMPK is strongly associated with development of T2DM and metabolic syndrome. In this review, we discuss common risk factors, the association between OA and T2DM, and the role of AMPK. We also address the adaptive use of metformin, a known AMPK activator, as a new drug for treatment of patients with OA and T2DM.

Anti-Osteoarthritic Mechanisms of Chrysanthemum zawadskii var. latilobum in MIA-Induced Osteoarthritic Rats and Interleukin-1β-Induced SW1353 Human Chondrocytes

Background and objectives: Chrysanthemum zawadskii var. latilobum (CZ), which has traditionally been used as a oriental tea in Asia, is known to have anti-inflammatory effects in osteoarthritis (OA). But the mechanism of these effects has not been made clear and it needs to be elucidated specifically for the clinical use of CZE in OA. Materials and Methods: To reveal this mechanism, we first identified which biomarkers were expressed in the joints of rats in which OA had been induced with monosodium iodoacetate and determined whether CZ extract (CZE) could normalize these biomarkers in the progression of OA. The anti-osteoarthritis effect of CZE was evaluated for its capability to inhibit levels of extracellular matrix (ECM)-degrading enzymes and enhance ECM synthesis. We also sought to identify whether the marker compound of CZE, linarin, has anti-osteoarthritic effects in the human chondrosarcoma cell line SW1353. Results: The changes in matrix metalloproteinases (MMPs) were remarkable: among them, MMP-1, MMP-3, MMP-9 and MMP-13 were most strongly induced, whereas their expressions were inhibited by CZE dose dependently. The expressions of the ECM synthetic genes, COL2A1 and ACAN, and the transcription factor SOX9 of these genes were reduced by OA induction and significantly normalized by CZE dose dependently. SOX9 is also a repressor of ECM-degrading aggrecanases, ADAMTS-4 and ADAMTS-5, and CZE significantly reduced the levels of these enzymes dose dependently. Similar results were obtained using the human chondrosarcoma cell line SW1353 with linarin, the biologically active compound of CZE. Conclusions: These anti-osteoarthritic effects suggest that CZE has mechanisms for activating ECM synthesis with SOX9 as well as inhibiting articular ECM-degrading enzymes.

Purinergic System Signaling in Metainflammation-Associated Osteoarthritis

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

Therapeutic Manipulation of Macrophages Using Nanotechnological Approaches for the Treatment of Osteoarthritis

Osteoarthritis (OA) is the most common joint pathology causing severe pain and disability. Macrophages play a central role in the pathogenesis of OA. In the joint microenvironment, macrophages with an M1-like pro-inflammatory phenotype induce chronic inflammation and joint destruction, and they have been correlated with the development and progression of the disease, while the M2-like anti-inflammatory macrophages support the recovery of the disease, promoting tissue repair and the resolution of inflammation. Nowadays, the treatment of OA in the clinic relies on systemic and/or intra-articular administration of anti-inflammatory and pain relief drugs, as well as surgical interventions for the severe cases (i.e., meniscectomy). The disadvantages of the pharmacological therapy are related to the chronic nature of the disease, requiring prolonged treatments, and to the particular location of the pathology in joint tissues, which are separated anatomical compartments with difficult access for the drugs. To overcome these challenges, nanotechnological approaches have been investigated to improve the delivery of drugs toward macrophages into the diseased joint. This strategy may offer advantages by reducing off-target toxicities and improving long-term therapeutic efficacy. In this review, we describe the nanomaterial-based approaches designed so far to directly or indirectly manipulate macrophages for the treatment of osteoarthritis.

Metabolomic Signature of Amino Acids, Biogenic Amines and Lipids in Blood Serum of Patients with Severe Osteoarthritis

Metabolomic analysis is an emerging new diagnostic tool, which holds great potential for improving the understanding of osteoarthritis (OA)-caused metabolomic shifts associated with systemic inflammation and oxidative stress. The main aim of the study was to map the changes of amino acid, biogenic amine and complex lipid profiles in severe OA, where the shifts should be more eminent compared with early stages. The fasting serum of 70 knee and hip OA patients and 82 controls was assessed via a targeted approach using the AbsoluteIDQ™ p180 kit. Changes in the serum levels of amino acids, sphingomyelins, phoshatidylcholines and lysophosphatidylcholines of the OA patients compared with controls suggest systemic inflammation in severe OA patients. Furthermore, the decreased spermine to spermidine ratio indicates excessive oxidative stress to be associated with OA. Serum arginine level was positively correlated with radiographic severity of OA, potentially linking inflammation through NO synthesis to OA. Further, the level of glycine was negatively associated with the severity of OA, which might refer to glycine deficiency in severe OA. The current study demonstrates significant changes in the amino acid, biogenic amine and low-molecular weight lipid profiles of severe OA and provides new insights into the complex interplay between chronic inflammation, oxidative stress and OA.

Serum adipokines/related inflammatory factors and ratios as predictors of infrapatellar fat pad volume in osteoarthritis: Applying comprehensive machine learning approaches

OBJECTIVE

The infrapatellar fat pad (IPFP) has been associated with knee osteoarthritis onset and progression. This study uses machine learning (ML) approaches to predict serum levels of some adipokines/related inflammatory factors and their ratios on knee IPFP volume of osteoarthritis patients.

METHODS

Serum and MRI were from the OAI at baseline. Variables comprised the 3 main osteoarthritis risk factors (age, gender, BMI), 6 adipokines, 3 inflammatory factors, and their 36 ratios. IPFP volume was assessed on MRI with a ML methodology. The best variables and models were identified in Total-cohort (n = 678), High-BMI (n = 341) and Low-BMI (n = 337), using a selection approach based on ML methods.

RESULTS

The best model for each group included three risk factors and adipsin/C-reactive protein combined for Total-cohort, adipsin/chemerin; High-BMI, chemerin/adiponectin HMW; and Low-BMI, interleukin-8. Gender separation improved the prediction (13-16%) compared to the BMI-based models. Reproducibility with osteoarthritis patients from a clinical trial was excellent (R: female 0.83, male 0.95). Pseudocodes based on gender were generated.

CONCLUSION

This study demonstrates for the first time that the combination of the serum levels of adipokines/inflammatory factors and the three main risk factors of osteoarthritis could predict IPFP volume with high reproducibility, with the superior performance of the model accounting for gender separation.

Osteoarthritis and type 2 diabetes: From pathogenetic factors to therapeutic intervention

Over the last decades, osteoarthritis (OA) and type 2 diabetes (T2D) prevalence increased due to the global ageing population and the pandemic obesity. They currently affect a substantial part of the Western world population and are characterized by enhancing the risk of disability and reduction of quality of life. OA is a multifactorial condition whose development derives from the interaction between individual and environmental factors: The best known primarily include age, female gender, genetic determinants, articular biomechanics, and obesity (OB). Given the high prevalence of OA and T2D and their association with OB and inflammation, several studies have been conducted to investigate the causative role of biological characteristics proper to T2D on the development of OA. This review aims to analyse the relationship between of OA and T2D, in order to explain the pathophysiological drivers of the degenerative process and to delineate possible targets to which appropriate treatments may be addressed in the near future.

Urinary biomarkers in lupus nephritis

Systemic lupus erythematosus (SLE) is the prototypical autoimmune disease that can affect any organ of the body. Multiple mechanisms may contribute to the pathophysiology of systemic lupus, including failure to remove apoptotic bodies, hyperactivity of self-reactive B and T lymphocytes, abnormal exposure to autoantigens, and increased levels of B-cell stimulatory cytokines. The involvement of the kidney, called lupus nephritis (LN), during the course of the disease affects between 30% and 60% of adult SLE patients, and up to 70% of children. LN is an immune-mediated glomerulonephritis that is a common and serious finding in patients with SLE. Nowadays, renal biopsy is considered the gold standard for classifying LN, besides its degree of activity or chronicity. Nevertheless, renal biopsy lacks the ability to predict which patients will respond to immunosuppressive therapy and is a costly and risky procedure that is not practical in the monitoring of LN because serial repetitions would be necessary. Consequently, many serum and urinary biomarkers have been studied in SLE patients for the complementary study of LN, existing conventional biomarkers like proteinuria, protein/creatinine ratio in spot urine, 24 ​h urine proteinuria, creatinine clearance, among others and non-conventional biomarkers, like Monocyte chemoattractant protein-1 (MCP-1), have been correlated with the histological findings of the different types of LN. In this article, we review the advances in lupus nephritis urinary biomarkers. Such markers ideally should be capable of predicting early sub-clinical flares and could be used to follow response to therapy. In addition, some of these markers have been found to be involved in the pathogenesis of lupus nephritis.

Association of Circulating COMP and YKL-40 as Markers of Metabolic Changes of Cartilage with Adipocytokines in Juvenile Idiopathic Arthritis

The aim of this study was to evaluate the association of circulating cartilage oligomeric matrix protein (COMP) and human cartilage glycoprotein-39 (YKL-40) as markers of metabolic changes of cartilage, with leptin, adiponectin, and resistin in juvenile idiopathic arthritis (JIA) patients before and after treatment. A significant decrease of COMP and an increase of YKL-4 were found in blood of untreated patients. JIA treatment leading to clinical improvement resulted in normalization of COMP levels only. Concentrations of both markers in treated patients, while showing no clinical improvement, differed from those in controls and patients with remission. The leptin level decreased (p < 0.05) in untreated patients; however, concentrations of adiponectin and resistin increased (p < 0.05) as compared to controls. JIA treatment resulted in normalization of adipocytokine levels in remissive patients but not those with active JIA. Untreated patients showed a correlation between COMP and leptin, adiponectin, and body mass index (BMI) and between YKL-40 and leptin, adiponectin, BMI, C-reactive protein (CRP), and erythrocyte sedimentation rate (ESR). In inactive JIA, a correlation between YKL-40 and leptin was shown. Treated patients with an active JIA demonstrated a correlation between COMP and adiponectin and between YKL-40 and leptin, adiponectin, BMI, CRP, and ESR. The results of this work indicate that leptin and adiponectin but not resistin may be involved in the development and progression of joint dysfunction in JIA. Additionally, we suggest that YKL-40 may be a useful biomarker of disease activity and may be used to assess treatment towards remission, as compared to COMP.

In vivo protective effect of adipsin-deficiency on spontaneous knee osteoarthritis in aging mice

The adipokine adipsin is an emerging mediator of human osteoarthritis (OA) progression. Here, we investigated its in vivo role in the development of spontaneous OA in aging mice. We compared articular knee joint morphology, histology in knee cartilage, synovial membrane, subchondral bone, meniscus, and anterior cruciate ligament (ACL); and chondrogenesis in the ACL from adipsin-deficient (Df^-/-) and wild-type (Df^+/+) 20-week- and 20-month-old mice. Serum levels of a panel of adipokines, inflammatory factors, and metalloproteases known to be implicated in OA were investigated. Data first revealed that the early manifestation of OA appeared in the ACL of 20-week-old mice, progressing to severe alterations in the 20 month-old wild-type mice. Further results demonstrated that adipsin-deficiency protected the articular tissues from spontaneous OA progression and triggered significantly higher serum levels of the adipokines adiponectin and FGF-21 while lowering levels of the inflammatory factor interleukin 6 (IL-6) in both young and old mice. This work further underlines the clinical relevance of adipsin as a novel therapeutic approach of human OA. Moreover, this study shows the potential beneficial effect of the adipokine FGF-21 against OA, and provides support for this factor to be a new biomarker and/or target of primary OA therapeutic avenues.

Role of Adiponectin in Cervical Cancer

BACKGROUND

Cervical Cancer (CC) is the most common leading cancer in women globally. This is considered to be the type of cancer that is restricted to women. Any women in the reproductive age range can develop CC. However, women between the ages of 25 and 39 are at a higher risk.

OBJECTIVE

In comparison with developed countries, the screening and awareness of CC in developing countries are significantly low. Infection with Human papillomavirus (HPV) is the main cause of CC, especially HPV-16 and HPV-18. Other than HPV, there are other factors that can contribute to CC, such as Human simplex virus (HSV) infection and immunocompromised patients with HIV.

CONCLUSION

Cervical cancer can be detected by molecular techniques such as (1) PCR, (2) visual acetic acid method, (3) DNA Hybrid II test, (4) liquid-based cytology, (5) Pap-Smear techniques, and (6) colposcopy techniques. Early detection of CC is very much needed; cryotherapy or LEEP (Loop electro surgical excision procedure) can be conducted during the pre-invasive stage of CC. Some metabolic changes in the human body such as fluctuating levels of insulin and triglycerides and increased activity of adiponectin may lead to CC. These contributing factors, such as adipokines, can be used as biomarkers for CC detection.

Adiponectin receptor agonist AdipoRon attenuates calcification of osteoarthritis chondrocytes by promoting autophagy

Cartilage calcification contributes to the development and progression of osteoarthritis (OA). It has been well-investigated adiponectin regulates vascular calcification. The purpose of this study is to investigate the therapeutic value and the molecular mechanism of AdipoRon, an adiponectin receptor agonist, on the chondrocytes calcification. Primary chondrocytes were isolated and cultured from normal cartilage and OA cartilage. The calcification in tissues was evaluated by inductively coupled plasma/atomic emission spectroscopy and alizarin red S staining. The calcification in chondrocytes was determined using the alkaline phosphatase (ALP) staining and an ALP assay kit. The cellular effects of AdipoRon were assessed by immunofluorescence staining and Western blot analysis. We found that calcification was significantly increased in OA cartilage tissues and cells. Importantly, the degree of calcification and ALP activity of the OA chondrocytes was decreased upon the treatment with AdipoRon. The AdipoRon-induced cellular effects, including the reduction of the calcification of chondrocytes and improvement of autophagy, were blocked by dorsomorphin, an 5'-adenosine monophosphate-activated protein kinase (AMPK) inhibitor. Moreover, autophagy activation by AdipoRon was mediated by the AMPK-mammalian target of rapamycin (mTOR) signaling pathway. Our results suggest that AdipoRon significantly alleviates the calcification of OA chondrocytes via activating AMPK-mTOR signaling to promote autophagy. Therefore, AdipoRon could be a potential therapeutic agent for the prevention and treatment of OA.

Chronic inflammation during osteoarthritis is associated with an increased expression of CD161 during advanced stage

Increasing evidence suggests a role of inflammation during the pathogenesis of osteoarthritis (OA). The local and systemic inflammation was studied in 33 patients of different KL grades, grade2 (n = 11), grade3 (n = 6) and grade4 (n = 16). The levels of cytokines, adipokines and matrix metalloproteinases (MMPs) were measured in serum and synovial fluid (SF) by flow cytometry and ELISA, respectively. The frequency of T cells and CD161 expression was measured by flow cytometry. The levels of IL-1β, IL-6 and IL-10 were significantly higher in sera and SF of patients with OA as compared to healthy control's serum. Higher levels of MMP9 and leptin and lower levels of adiponectin were observed in SF as compared to serum. The MMP9 in SF and MMP13 levels in serum and SF decreased in KL grade 4 cases. In these patients, higher levels of leptin and lower levels of adiponectin were observed in SF versus patients of lower grades. There was increased infiltration of CD8+ T cells in SF of OA cases with decreased frequency in grade 4 cases. The expression of CD161 on T cells was significantly higher in SF than peripheral blood with significant upregulation in grade 4 patients. The CD161 expression had significant positive correlation with IL-17 in the serum of patients. The ROC curves of CD161 expression significantly distinguished grade 2 and grade 4 patients. Collectively, an elevated CD161 expression on T cells in circulation and synovial compartment clearly distinguished lower and higher grade patients warranting studies to assess its role as a contributing factor towards OA progression.

Pro-inflammatory cytokines: The link between obesity and osteoarthritis

Osteoarthritis (OA), characterized by joint malfunction and chronic disability, is the most common form of arthritis. Clinical and animal experiments reveal that age-related OA is associated with many factors such as age, sex, trauma, and obesity. One of the most influential and modifiable risk factors is obesity. Obesity not only increases mechanical stress on the tibiofemoral cartilage, but also leads to a higher prevalence of OA in non-weight-bearing areas. There is a link between obesity and inflammation. Adipose tissues play a crucial role in this context because they are the major source of cytokines, chemokines, and metabolically-active mediators named adipokines. The adipokines, including adiponectin and leptin, have been demonstrated to regulate inflammatory immune responses in cartilage. Obese people and animals show a higher level of serum tumor necrosis factor-alpha (TNF-α), interleukin-1 beta (IL)-1β and IL-6, all of which are produced by macrophages derived from adipose tissue. These pro-inflammatory cytokines regulate the proliferation and apoptosis of adipocytes, promote lipolysis, inhibit lipid synthesis and decrease blood lipids through autocrine and paracrine mechanisms. Elevated levels of TNF-α, IL-1 and IL-6 have been found in the synovial fluid, synovial membrane, subchondral bone and cartilage of OA patients, confirming their important roles in OA pathogenesis. TNF-α, IL-6 and IL-1 are the factors released by fat to negatively regulate cartilage directly. Moreover, TNF-α, IL-1 and IL-6 can induce the production of other cytokines, matrix metalloproteinases (MMPs) and prostaglandins and inhibit the synthesis of proteoglycans and type II collagen; thus, they play a pivotal role in cartilage matrix degradation and bone resorption in OA. Activated chondrocytes also produce MMP-1, MMP-3, MMP-13, and aggrecanase 1 and 2 (ADAMTS-4, ADAMTS-5). In addition, IL-1, TNF-α and IL-6 may cause OA indirectly by regulating release of adiponectin and leptin from adipocytes. In this review, we first summarize the relationship between obesity and inflammation. Then we summarize the roles of IL-1, TNF-α and IL-6 in OA. We further discuss how IL-1, TNF-α and IL-6 regulate the communication between fat and OA, and their pathological roles in obesity-related OA. Lastly, we discuss the possibility of using the pro-inflammatory signaling pathway as a therapeutic target to develop drugs for obesity-related OA.

Associations between knee structural measures, circulating inflammatory factors and MMP13 in patients with knee osteoarthritis

OBJECTIVE

To investigate cross-sectional associations between serum level of Matrix metalloproteinase (MMP)13 and knee structural measures and circulating inflammatory factors in patients with symptomatic knee osteoarthritis (OA).

DESIGN

A total of 149 subjects with symptomatic knee OA were included. Magnetic resonance imaging was used to measure infrapatellar fat pad (IPFP) volume, IPFP signal intensity alternation, cartilage volume and cartilage defects. Knee radiography was used to assess radiographic OA using the Kellgren-Lawrence (K-L) grading system. Enzyme-linked immunosorbent assay was used to measure the serum levels of inflammatory factors and MMP13.

RESULTS

In multivariable analyses, serum MMP13 was negatively associated with cartilage volume at patellar site (β: -32.94 mm³ per 10 ng/ml, P < 0.05), and positively associated with cartilage defect at medial femoral site (OR: 1.13 per 10 ng/ml, P < 0.05). Also, MMP13 was positively associated with K-L grading and IPFP signal intensity alteration (OR: 1.14 and 1.15 per 10 ng/ml, respectively, both P < 0.05), and negatively associated with IPFP volume (β: -0.34 cm³ per 10 ng/ml, P < 0.05). Furthermore, serum level of adiponectin was negatively associated serum MMP13 quartiles (OR: 0.66 per 10 μg/ml, P < 0.05), and serum levels of tumor necrosis factor (TNF)-α, interleukin (IL)-8 and IL-18 were positively associated with serum MMP13 quartiles (ORs: 1.01-1.18 per 10 pg/ml, all P < 0.05).

CONCLUSIONS

Serum level of MMP13 was associated with knee structural abnormalities as well as serum inflammatory factors. These suggest that systemic MMP13 may play a role in knee OA, and could be regulated by inflammatory factors.

Adiponectin Downregulates TNF-α Expression in Degenerated Intervertebral Discs

STUDY DESIGN

Given the results of previous in vitro investigations of the expression patterns of adiponectin and its receptors in healthy and degenerated intervertebral discs (IVDs), we studied the effects of adiponectin on tumor necrosis factor-alpha (TNF-α) production in degenerated nucleus pulposus (NP) cells and analyzed the association between adiponectin levels in IVD tissues and IVD Pfirrmann grades.

OBJECTIVE

The aim of this study was to investigate the potential role of adiponectin in the pathogenesis of IVD degeneration.

SUMMARY OF BACKGROUND DATA

Adiponectin has been reported to be involved in physiologic and pathologic processes associated with bone and cartilage diseases. However, the expression profiles of adiponectin and its receptors in human IVD tissues and the function of adiponectin in the pathogenesis of IVD degeneration remain unknown.

METHODS

Real-time polymerase chain reaction, immunohistochemistry, and western blotting were performed to examine the expression levels of adiponectin, adiponectin receptors, and TNF-α in IVD tissues and isolated NP cells. The effects of adiponectin on TNF-α production in degenerated NP cells were detected by enzyme linked immunosorbent assay.

RESULTS

Adiponectin expression levels were downregulated, while adiponectin receptor 1 (adipoR1) and adipoR2 expression levels were upregulated in degenerated IVD tissues and degenerated NP cells compared with those in healthy IVD tissues and healthy NP cells. Moreover, we confirmed that TNF-α production by degenerated NP cells was downregulated by adiponectin administration in a dose- and time-dependent manner. Furthermore, our data showed that adiponectin levels in degenerated IVD tissues were inversely correlated with IVD Pfirrmann grades.

CONCLUSION

These results indicated that adiponectin may play an anti-inflammatory role with respect to the maintenance of IVD homeostasis by downregulating TNF-α production.

LEVEL OF EVIDENCE

N/A.

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.

Expression of adiponectin in the subchondral bone of lumbar facet joints with different degrees of degeneration

BACKGROUND

Osteoarthritis research has been most commonly performed in the setting of the articular cartilage of the knee. To the best of our knowledge, no studies have evaluated the role of adiponectin in osteoarthritis of the lumbar facet joint (FJOA). Therefore, in this study, we explored whether adiponectin was expressed in the lumbar facet joints and evaluated the role of adiponectin in FJOA.

METHODS

We enrolled patients who underwent lumbar computed tomography (CT) and magnetic resonance imaging (MRI) at the Orthopedic Department of the First Affiliated Hospital of Nanchang from May 2015 to June 2016. Lumbar facet joints were obtained from 135 patients at the time of lumbar fusion surgery and divided into three groups according to the Weishaupt grade. Cytokine levels in the subchondral bones were evaluated by enzyme-linked immunosorbent assays (ELISAs), and adiponectin levels were determined by immunohistochemistry, western blotting, and quantitative polymerase chain reaction (qPCR).

RESULTS

By ELISA, adiponectin levels were examined in the subchondral bone for lumbar facet joint, and adiponectin was found to be negatively correlated with BMI in 52 patients (p < 0.001, r = -0.861). By immunohistochemistry analysis, adiponectin was found to be expressed in the subchondral bone of the lumbar facet, whereas the cartilage area was negative for adiponectin expression. Immunostaining intensity and area was related to the degeneration of the lumbar facet joint, and, in our research, considerably decreased staining intensity and area were observed in more severely degenerated lumbar facet joints. Furthermore, the expression of adiponectin was also reduced in degenerated lumbar facet joints, and the level of decline corresponded to degeneration detected by western blotting and qPCR analysis (n = 27, p < 0.0001).

CONCLUSIONS

Adiponectin expression was observed in the subchondral bone of the lumbar facet joint and decreased as the degree of degeneration increased. Thus, the results of this study provide new insights into the relationship between adiponectin and osteoarthritis.

Infrapatellar fat pad features in osteoarthritis: a histopathological and molecular study

OBJECTIVE

The infrapatellar fat pad (IFP) is considered a local producer of adipocytokines, suggesting a potential role in OA. The objective of this study was to evaluate the histopathological and molecular characteristics of OA IFPs compared with controls.

METHODS

The histopathological characteristics of IFPs were evaluated in patients undergoing total knee replacements and in control patients (without OA), considering the following parameters: presence of inflammatory cells, vascularization, adipose lobules dimension and thickness of the interlobular septa. Immunohistochemistry was performed to evaluate VEGF, monocyte chemotactic protein 1 (MCP-1) and IL-6 proteins. Quantitative real time PCR was performed to evaluate the expression levels of adipocytokines in the OA IFPs.

RESULTS

OA IFPs showed an increase in inflammatory infiltration, vascularization and thickness of the interlobular septa compared with controls. VEGF, MCP-1 and IL-6 proteins were higher in OA IFPs compared with in controls. Inflammatory infiltration, hyperplasia, vascularization and fibrosis were increased in OA IFP synovial membranes compared with in those of controls. VEGF protein levels were associated with an increased number of vessels in the OA IFPs, while MCP-1 and IL-6 protein levels were associated with higher grades of inflammatory infiltration. Leptin levels were positively correlated with adiponectin and MCP-1expression, while adiponectin positively correlated with peroxisome proliferative activated receptor gamma, MCP-1 and IFP vascularity. MCP-1 showed a positive correlation with peroxisome proliferative activated receptor gamma. IFP lobules dimensions were positively correlated with IL-6 expression and negatively with thickness of interlobular septa. VEGF mRNA levels were positively correlated with increased synovial vascularity.

CONCLUSIONS

OA IFPs and synovial membranes are more inflamed, vascularized and fibrous compared with those of control patients (without OA).

Therapeutic Effects of Olive and Its Derivatives on Osteoarthritis: From Bench to Bedside

Osteoarthritis is a major cause of morbidity among the elderly worldwide. It is a disease characterized by localized inflammation of the joint and destruction of cartilage, leading to loss of function. Impaired chondrocyte repair mechanisms, due to inflammation, oxidative stress and autophagy, play important roles in the pathogenesis of osteoarthritis. Olive and its derivatives, which possess anti-inflammatory, antioxidant and autophagy-enhancing activities, are suitable candidates for therapeutic interventions for osteoarthritis. This review aimed to summarize the current evidence on the effects of olive and its derivatives, on osteoarthritis and chondrocytes. The literature on animal and human studies has demonstrated a beneficial effect of olive and its derivatives on the progression of osteoarthritis. In vitro studies have suggested that the augmentation of autophagy (though sirtuin-1) and suppression of inflammation by olive polyphenols could contribute to the chondroprotective effects of olive polyphenols. More research and well-planned clinical trials are required to justify the use of olive-based treatment in osteoarthritis.

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.

ADIPONECTIN CORRELATION WITH BIOCLINICAL BENEFITS OF USING NATURAL THERAPEUTIC FACTORS IN KNEE OSTEOARTHRITIS

Context and objective

The new insights in the pathogenesis of osteoarthritis (OA) reveal the implications of adipocytokines. This study aims to analyze the correlations between the serum value of adiponectin and the clinical rehabilitation effects in patients diagnosed with knee OA, admitted and treated in the complex balneal resort of Techirghiol lake.

Subjects and methods

The prospective randomized clinical study included 23 patients in the study group, diagnosed with knee OA according to ACR criteria, and a matching control group of 23 subjects. Serum level of adiponectin (using ELISA technique), uric acid, triglycerides, cholesterol, HDL-cholesterol and clinical response using a visual analog scale (VAS) were evaluated in all patients on their admission day and after 10 days of balneal treatment. Control group benefited from the same procedures except for cold mud therapy and mineral water baths.

Results

Plasma adiponectin levels (23.73±6.44 ng/dL) were statistically higher (p<0.05) in the study group compared to the control group (18.15±6.49 ng/dL). The mean VAS in both groups was decreased (p<0.005) compared to the initial moment.

Conclusions

Cold peloidotherapy combined with physical therapy and balneal factors induces serum adiponectin elevation and improves knee pain in OA. Therapeutic properties of Techirghiol mud still need further research.

Regional Differences Between Perisynovial and Infrapatellar Adipose Tissue Depots and Their Response to Class II and Class III Obesity in Patients With Osteoarthritis

OBJECTIVE

Obesity is associated with an increased risk of developing osteoarthritis (OA), which is postulated to be secondary to adipose tissue-dependent inflammation. Periarticular adipose tissue depots are present in synovial joints, but the association of this tissue with OA has not been extensively explored. The aim of this study was to investigate differences in local adipose tissue depots in knees with OA and characterize the changes related to class II and class III obesity in patients with end-stage knee OA.

METHODS

Synovium and the infrapatellar fat pad (IPFP) were collected during total knee replacement from 69 patients with end-stage OA. Histologic changes, changes in gene and protein expression of adiponectin, peroxisome proliferator-activated receptor γ (PPARγ), and Toll-like receptor 4 (TLR-4), and immune cell infiltration into the adipose tissue were investigated.

RESULTS

IPFP and synovium adipose tissue depots differed significantly and were influenced by the patient's body mass index. Compared to adipocytes from the IPFP and synovium of lean patients, adipocytes from the IPFP of obese patients were significantly larger and the synovium of obese patients displayed marked fibrosis, increased macrophage infiltration, and higher levels of TLR4 gene expression. The adipose-related markers PPARγ in the IPFP and adiponectin and PPARγ in the synovium were expressed at lower levels in obese patients compared to lean patients. Furthermore, there were increased numbers of CD45+ hematopoietic cells, CD45+CD14+ total macrophages, and CD14+CD206+ M2-type macrophages in both the IPFP and synovial tissue of obese patients.

CONCLUSION

These differences suggest that IPFP and synovium may contain 2 different white adipose tissue depots and support the theory of inflammation-induced OA in patients with class II or III obesity. These findings warrant further investigation as a potentially reversible, or at least suppressible, cause of OA in obese patients.

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.

Systemic and Local Adipose Tissue in Knee Osteoarthritis

Osteoarthritis is a common chronic joint disorder affecting older people. The knee is the major joint affected. The symptoms of osteoarthritis include limited range of motion, joint swelling, and pain causing disability. There are no disease modifying drugs available, and treatments are mainly focused on pain management. Total knee replacement performed at the end stage of the disease is considered the only cure available. It has been found that obese people have an increased risk to develop not only knee but also hand osteoarthritis. This supports the concept that adipose tissue might be related to osteoarthritis not only through overloading. As matter of fact, obesity induces a low grade systemic inflammatory state characterized by the production and secretion of several adipocytokines that may have a role in osteoarthritis development. Furthermore, hypertension, impaired glucose, and lipid metabolism, which are comorbidities associated with obesity, have been shown to alter the joint tissue homeostasis. Moreover, infrapatellar fat pad in the knee has been demonstrated to be a local source of adipocytokines and potentially contribute to osteoarthritis pathogenesis. Here, we discuss the role of systemic and local adipose tissue in knee osteoarthritis. J. Cell. Physiol. 232: 1971-1978, 2017. © 2016 Wiley Periodicals, Inc.

Local effects of adipose tissue in psoriasis and psoriatic arthritis

The structure and physiological state of the local white adipose tissue (WAT) located underneath the lesional psoriatic skin and inside of the joints affected by psoriatic arthritis play an important role in the pathophysiology of these diseases. WAT pads associated with inflammatory sites in psoriasis and psoriatic arthritis are, correspondingly, dermal WAT and articular adipose tissue; these pads demonstrate inflammatory phenotypes in both diseases. Such local WAT inflammation could be the primary effect in the pathophysiology of psoriasis leading to the modification of the local expression of adipokines, a change in the structure of the basement membrane and the release of keratinocytes with consequent epidermal hyperproliferation during psoriasis. Similar articular adipose tissue inflammation can lead to the induction of structural modifications and synovial inflammation in the joints of patients with psoriatic arthritis.

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.