Adiponectin and leptin induce VCAM-1 expression in human and murine chondrocytes

Implications of obesity-mediated cellular dysfunction and adipocytokine signaling pathways in the pathogenesis of osteoarthritis

Osteoarthritis (OA) is a degenerative joint disease characterized by cartilage degradation, bone sclerosis, and chronic low-grade inflammation. Aging and injury play key roles in OA pathogenesis by triggering the release of proinflammatory factors from adipose tissue and other sources. Obesity and aging impair the function of endoplasmic reticulum (ER) chaperones, leading to ER stress, protein misfolding, and cellular apoptosis. Obesity also induces mitochondrial dysfunction in OA through oxidative stress and disrupts mitochondrial dynamics, exacerbating chondrocyte damage. These factors contribute to inflammation, matrix imbalance, and chondrocyte apoptosis. Adipocytes, the primary source of adipokines, release inflammatory mediators that affect joint cells. Several adipocytokines have a central role in the regulation of many aspects of inflammation. Adiponectin and leptin are the two most abundant adipocytokines that are strongly associated with OA progression. This literature review suggests that adipokines activate many signaling pathways to exert downstream effects and play significant roles in obesity-induced OA. Understanding this rapidly growing family of mainly adipocyte-derived mediators and obesity-mediated cellular dysfunction may be important in the development of new therapies for obesity-associated OA management.

Vitamin D Supplementation Effects on Markers Related with Endothelial Function and Coagulation in Obese Orthopedic Patients: Insights from Acute and Chronic Cases

Obesity is a risk factor for thrombosis-related diseases and a condition that leads to vitamin D deficiency. Furthermore, orthopedic conditions are also at risk for diseases associated with coagulation and endothelial function. This study aimed to assess whether vitamin D supplementation in patients with acute (AOCs) and chronic orthopedic conditions (COCs) and coexisting obesity could affect coagulation and endothelial function. Thirty-three obese individuals with AOCs or COCs were included in the study. Patients were supplemented with vitamin D at 4000 IU/day for 3 months. An enzyme-linked immunosorbent assay (ELISA) was used to measure the concentrations of alpha 2-antiplasmin (α2AP), vascular cell adhesion molecule 1 (VCAM-1), plasminogen activator inhibitor-1 (PAI-1), tissue factor pathway inhibitor (TFPI), and vitamin D, which were examined at two time points-before and after supplementation. Regardless of the increase in serum vitamin D levels in both groups after supplementation, there was a statistically significant increase in VCAM-1 and PAI-1 levels in the group with AOCs, whereas only VCAM-1 increased statistically significantly in the second group. For obese patients with COCs, vitamin D does not appear to have a potentially beneficial effect on coagulation and the endothelium.

Chromone components of Saposhnikovia divaricate attenuate rheumatoid arthritis development by inhibiting the inflammatory response

ETHNOPHARMACOLOGICAL RELEVANCE

Saposhnikovia divaricata (Turcz.) Schisck., a traditional Chinese medicine (TCM), has historically been utilized in the clinical treatment of RA. It was initially documented in the 'Shennong Ben Cao Jing' as a superior quality, with the text stating: 'The herb is widely renowned for its efficacy in alleviating whole-body discomfort, bone pain, malaise, and promoting long-lasting vitality. Chromones (CHR) were identified as the primary active components in Saposhnikovia divaricata. However, the specific molecular mechanisms by which CHR impacts RA remain incompletely understood.

AIM OF THE STUDY

To explore the therapeutic efficacy of CHR, a class of compound derived from Saposhnikovia divaricata, in alleviating arthropathy and immune hyperactivity in a collagen-induced arthritis (CIA) mouse model.

MATERIAL AND METHODS

Surface plasmon resonance (SPR) molecular fishing and UHPLC-QTOF/MS technology were used to identify CHR in Saposhnikovia divaricata as an active ingredient for treating RA. A CIA mouse model was used to verify the anti-RA effect of CHR in vivo. The anti-RA efficacy of CHR in vivo was evaluated by body weight change, joint swelling, arthritis index, immune organ index, ankle joint disease, and immunoglobulin G (IgG) content. The mechanism of improving RA was further analyzed by a protein chip assay and verified by Western blotting.

RESULTS

CHR treatment reduced swelling, arthritis index, and IgG, IgG1, IgG2a, and IgG2b levels in CIA mice. Protein microarray indicated that CHR mitigated CIA-induced joint inflammation by inhibiting immune cell activation, reducing the expression of inflammatory factors and chemokines, potentially by modulating the rheumatoid arthritis pathway involving tumor necrosis factor-α (TNF-α), interleukin-17 (IL-17), and chemokines. This hypothesis was supported by the upregulation of bone morphogenetic proteins 3 (BMP3) and phospho-Smad2 (p-Smad2) proteins, coupled with the downregulation of interleukin-6 (IL-6), interleukin-1β (IL-1β), TNF-α, and IL-17A proteins in the joints of CHR-treated mice.

CONCLUSION

CHR shows promise as a potential therapeutic agent for RA, exerting its effects through anti-inflammatory mechanisms.

Metabolism-Related Adipokines and Metabolic Diseases: Their Role in Osteoarthritis

Osteoarthritis (OA) affects several joints but tends to be more prevalent in those that are weight-bearing, such as the knees, which are the most heavily loaded joints in the body. The incidence and disability rates of OA have continued to increase and seriously jeopardise the quality of life of middle-aged and older adults. However, OA is more than just a wear and tear disease; its aetiology is complex, and its pathogenesis is poorly understood. Metabolic syndrome (MetS) has emerged as a critical driver of OA development. This condition contributes to the formation of a distinct phenotype, termed metabolic syndrome-associated osteoarthritis (MetS-OA),which differs from other metabolically related diseases by its unique pathophysiological mechanisms and clinical presentation. As key mediators of MetS, metabolic adipokines such as leptin, lipocalin, and resistin regulate inflammation and bone metabolism through distinct or synergistic signaling pathways. Their modulation of inflammatory responses and bone remodeling processes plays a critical role in the pathogenesis and progression of OA. Due to their central role in regulating inflammation and bone remodeling, metabolic adipokines not only deepen our understanding of MetS-OA pathogenesis but also represent promising targets for novel therapeutic strategies that could slow disease progression and improve clinical outcomes in affected patients.

Cellular and molecular mechanisms underlying obesity in degenerative spine and joint diseases

Degenerative spine and joint diseases, including intervertebral disc degeneration (IDD), ossification of the spinal ligaments (OSL), and osteoarthritis (OA), are common musculoskeletal diseases that cause pain or disability to the patients. However, the pathogenesis of these musculoskeletal disorders is complex and has not been elucidated clearly to date. As a matter of fact, the spine and joints are not independent of other organs and tissues. Recently, accumulating evidence demonstrates the association between obesity and degenerative musculoskeletal diseases. Obesity is a common metabolic disease characterized by excessive adipose tissue or abnormal adipose distribution in the body. Excessive mechanical stress is regarded as a critical risk factor for obesity-related pathology. Additionally, obesity-related factors, mainly including lipid metabolism disorder, dysregulated pro-inflammatory adipokines and cytokines, are reported as plausible links between obesity and various human diseases. Importantly, these obesity-related factors are deeply involved in the regulation of cell phenotypes and cell fates, extracellular matrix (ECM) metabolism, and inflammation in the pathophysiological processes of degenerative spine and joint diseases. In this study, we systematically discuss the potential cellular and molecular mechanisms underlying obesity in these degenerative musculoskeletal diseases, and hope to provide novel insights for developing targeted therapeutic strategies.

Novel perspectives on leptin in osteoarthritis: Focus on aging

Osteoarthritis (OA) is a common chronic joint disease characterized by articular cartilage degeneration, subchondral sclerosis, synovitis, and osteophyte formation. OA is associated with disability and impaired quality of life, particularly among the elderly. Leptin, a 16-kD non-glycosylated protein encoded by the obese gene, is produced on a systemic and local basis in adipose tissue and the infrapatellar fat pad located in the knee. The metabolic mechanisms employed by leptin in OA development have been widely studied, with attention being paid to aging as a corroborative risk factor for OA. Hence, in this review, we have attempted to establish a potential link between leptin and OA, by focusing on aging-associated mechanisms and proposing leptin as a potential diagnostic and therapeutic target in aging-related mechanisms of OA that may provide fruitful guidance and emphasis for future research.

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.

The microbiota-metabolic syndrome axis as a promoter of metabolic osteoarthritis

The relation between obesity and osteoarthritis (OA) development has been traditionally explained as consequence of the excessive joint effort derived of overweight. However, in the last two decades a metabolic OA has been suggested through diverse molecular mechanism implying metabolic syndrome, although more investigation must be conducted to elucidate it. Metabolic syndrome is responsible of the release of diverse inflammatory cytokines, specially the increased adipokine in obesity, causing a chronic low-grade inflammatory status that alters the joint homeostasis. In this scenario, the microbiota dysbiosis contribute by worsening the low-grade chronic inflammation or causing metabolic disorders mediated by endotoxemia generated by an increased lipopolysaccharides intake. This results in joint inflammation and cartilage degradation, which contributes to the development of OA. Also, the insulin resistance provoked by type 2 Diabetes contributes to the OA development. When intake patterns are considered, some coincidences can be pointed between the food patterns associated to the metabolic syndrome and the food patterns associated to OA development. Therefore, these coincidences support the idea of a molecular mechanism of the OA development caused by the molecular mechanism generated under the metabolic syndrome status. This review points the relation between metabolic syndrome and OA, showing the connected molecular mechanisms between both pathologies as well as the shared dietary patterns that promote or prevent both pathologies.

Concentration-dependent effects of leptin on osteoarthritis-associated changes in phenotype of human chondrocytes

Metabolic syndrome is a risk factor for osteoarthritis. Elevated leptin levels have been implicated as a potential cause of this association. Previous studies have shown that supra-physiological leptin concentrations can induce osteoarthritis-like changes in chondrocyte phenotype. Here, we tested the effects of leptin in the concentration range found in synovial fluid on chondrocyte phenotype. Chondrocytes isolated from macroscopically normal regions of cartilage within osteoarthritic joints from patients undergoing knee arthroplasty, all with body mass index >30 kg/m2 were treated with 2-40 ng/ml leptin for 24 h. Chondrocyte phenotype marker expression was measured by RT-qPCR and western blot. The role of HES1 in mediating the effects of leptin was determined by gene knockdown using RNAi and over-expression using adenoviral-mediated gene delivery. Treatment of chondrocytes with 20 or 40 ng/ml leptin resulted in decreased SOX9 levels and decreased levels of the SOX9-target genes COL2A1 and ACAN. Levels of HES1 were lower and ADAMTS5 higher in chondrocytes treated with 20 or 40 ng/ml leptin. HES1 knockdown resulted in increased ADAMTS5 expression whereas over-expression of HES1 prevented the leptin-induced increase in ADAMTS5. An increase in MMP13 expression was only evident in chondrocytes treated with 40 ng/ml leptin and was not mediated by HES1 activity. High concentrations of leptin can cause changes in chondrocyte phenotype consistent with those seen in osteoarthritis. Synovial fluid leptin concentrations of this level are typically observed in patients with metabolic syndrome and/or women, suggesting elevated leptin levels may form part of the multifactorial network that leads to osteoarthritis development in these patients.

Obesity, Metabolic Syndrome, and Osteoarthritis-An Updated Review

PURPOSE OF REVIEW

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

RECENT FINDINGS

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

Role of Leptin and Adiponectin in Carcinogenesis

Hormones produced by adipocytes, leptin and adiponectin, are associated with the process of carcinogenesis. Both of these adipokines have well-proven oncologic potential and can affect many aspects of tumorigenesis, from initiation and primary tumor growth to metastatic progression. Involvement in the formation of cancer includes interactions with the tumor microenvironment and its components, such as tumor-associated macrophages, cancer-associated fibroblasts, extracellular matrix and matrix metalloproteinases. Furthermore, these adipokines participate in the epithelial-mesenchymal transition and connect to angiogenesis, which is critical for cancer invasiveness and cancer cell migration. In addition, an enormous amount of evidence has demonstrated that altered concentrations of these adipocyte-derived hormones and the expression of their receptors in tumors are associated with poor prognosis in various types of cancer. Therefore, leptin and adiponectin dysfunction play a prominent role in cancer and impact tumor invasion and metastasis in different ways. This review clearly and comprehensively summarizes the recent findings and presents the role of leptin and adiponectin in cancer initiation, promotion and progression, focusing on associations with the tumor microenvironment and its components as well as roles in the epithelial-mesenchymal transition and angiogenesis.

Exploring the chondroprotective effect of Chaenomeles speciosa on Glucose-6-Phosphate Isomerase model mice using an integrated approach of network pharmacology and experimental validation

ETHNOPHARMACOLOGICAL RELEVANCE

Traditional Chinese medicine (TCM) has been used in China for a long time and is gradually gaining more and more recognition worldwide. Chaenomeles speciosa (CSP) (Chinese Pinyin: mugua) is a medicinal and food herb that has long been used as a folk medicine for rheumatic diseases, yet its bioactive components and therapeutic mechanisms are not clear.

AIM OF THE STUDY

Exploring anti-inflammatory and chondroprotective effects of CSP on rheumatoid arthritis (RA) and its possible targets of action.

MATERIALS AND METHODS

In this study, we performed an integrated approach of network pharmacology, molecular docking and experimental studies to explore the potential mechanism of action of CSP in the treatment of cartilage damage in RA.

RESULTS

Studies have shown that Quercetin, ent-Epicatechin and Mairin may be the main active compounds of CSP in the treatment of RA, while AKT1, VEGFA, IL-1β, IL-6, MMP9 etc. are considered as core target proteins to which the main active compounds in CSP bind, as further confirmed by molecular docking. In addition, the potential molecular mechanism of CSP for the treatment of cartilage damage in RA predicted by network pharmacology analysis was validated by in vivo experiments. CSP was found to downregulate the expression of AKT1, VEGFA, IL-1β, IL-6, MMP9, ICAM1, VCAM1, MMP3, MMP13 and TNF-α and increase the expression of COL-2 in the joint tissue of Glucose-6-Phosphate Isomerase (G6PI) model mice. Thus CSP contributes to the treatment of rheumatoid arthritis cartilage destruction.

CONCLUSION

This study showed that CSP has multi-component, multi-target and multi-pathway characteristics in treating cartilage damage in RA, which can achieve the effect of treating RA by inhibiting the expression of inflammatory factors, reducing neovascularization and alleviating the damage to cartilage caused by the diffusion of synovial vascular opacities, and reducing the degradation of cartilage by MMPs to play a protective role in RA cartilage damage. In conclusion, this study indicates that CSP is a candidate Chinese medicine for further research in treating cartilage damage in RA.

A novel visceral adiposity index predicts bone loss in female early rheumatoid arthritis patients detected by HR-pQCT

The purpose of this prospective study is to compare the Chinese visceral adiposity index (CVAI) between early rheumatoid arthritis (ERA) patients and healthy controls; and to assess the relationship between CVAI and the bone microstructure using high-resolution peripheral quantitative computed tomography (HR-pQCT) in ERA patients. 104 female ERA and 100 age-, gender- and BMI-matched healthy controls were recruited for the comparison of CVAI. All ERA patients were prospectively followed for 1 year. HR-pQCT scan of the distal radius, tibia and second metacarpal head were performed at baseline and after one-year. ERA patients were divided into two sub-groups according to the median CVAI value (65.73) (low CVAI and high CVAI groups). CVAI in the ERA group was significantly higher than the controls group (p = 0.01). At baseline, the high CVAI group had a higher ESR level (p = 0.004) while the cortical volumetric bone mineral density (vBMD) was lower (at both the distal radius and tibia, all p < 0.05) compared to the low CVAI group. Linear regression analysis revealed that a higher baseline CVAI was an independent predictor of a lower cortical vBMD at month 12 (distal radius: B = - 0.626, p = 0.022, 95%CI - 1.914  to  - 0.153; tibia: B = - 0.394, p = 0.003, 95%CI - 1.366 to - 0.290); and a greater reduction in trabecular vBMD (tibia: B = 0.444, p = 0.001, 95%CI 0.018-0.063; distal radius: B = 0.356, p = 0.008, 95%CI 0.403-0.063). In summary, CVAI is an independent predictor of trabecular bone loss in female patients with ERA, which may be augmented by a chronic inflammatory state in patients with visceral dysfunction of fat metabolism.Trial registration: http://Clinicaltrial.gov no: NCT01768923, 16/01/2013.

Obesity and Risk for Lymphoma: Possible Role of Leptin

Obesity, which is considered a pandemic due to its high prevalence, is a risk factor for many types of cancers, including lymphoma, through a variety of mechanisms by promoting an inflammatory state. Specifically, over the last few decades, obesity has been suggested not only to increase the risk of lymphoma but also to be associated with poor clinical outcomes and worse responses to different treatments for those diseases. Within the extensive range of proinflammatory mediators that adipose tissue releases, leptin has been demonstrated to be a key adipokine due to its pleotropic effects in many physiological systems and diseases. In this sense, different studies have analyzed leptin levels and leptin/leptin receptor expressions as a probable bridge between obesity and lymphomas. Since both obesity and lymphomas are prevalent pathophysiological conditions worldwide and their incidences have increased over the last few years, here we review the possible role of leptin as a promising proinflammatory mediator promoting lymphomas.

The Association of uPA, uPAR, and suPAR System with Inflammation and Joint Damage in Rheumatoid Arthritis: suPAR as a Biomarker in the Light of a Personalized Medicine Perspective

BACKGROUND

In recent years, the involvement of the soluble urokinase Plasminogen Activator Receptor (suPAR) in the pathophysiological modulation of Rheumatoid Arthritis (RA) has been documented, resulting in the activation of several intracellular inflammatory pathways.

METHODS

We investigated the correlation of urokinase Plasminogen Activator (uPA)/urokinase Plasminogen Activator Receptor (uPAR) expression and suPAR with inflammation and joint damage in RA, evaluating their potential role in a precision medicine context.

RESULTS

Currently, suPAR has been shown to be a potential biomarker for the monitoring of Systemic Chronic Inflammation (SCI) and COVID-19. However, the effects due to suPAR interaction in immune cells are also involved in both RA onset and progression. To date, the literature data on suPAR in RA endorse its potential application as a biomarker of inflammation and subsequent joint damage.

CONCLUSION

Available evidence about suPAR utility in the RA field is promising, and future research should further investigate its use in clinical practice, resulting in a big step forward for precision medicine. As it is elevated in different types of inflammation, suPAR could potentially work as an adjunctive tool for the screening of RA patients. In addition, a suPAR system has been shown to be involved in RA pathogenesis, so new data about the therapeutic response to Jak inhibitors can represent a possible way to develop further studies.

Adipokine Signaling Pathways in Osteoarthritis

Osteoarthritis (OA) is a debilitating joint disease that affects millions of individuals. The pathogenesis of OA has not been fully elucidated. Obesity is a well-recognized risk factor for OA. Multiple studies have demonstrated adipokines play a key role in obesity-induced OA. Increasing evidence show that various adipokines may significantly affect the development or clinical course of OA by regulating the pro/anti-inflammatory and anabolic/catabolic balance, matrix remodeling, chondrocyte apoptosis and autophagy, and subchondral bone sclerosis. Several signaling pathways are involved but still have not been systematically investigated. In this article, we review the cellular and molecular mechanisms of adipokines in OA, and highlight the possible signaling pathways. The review suggested adipokines play important roles in obesity-induced OA, and exert downstream function via the activation of various signaling pathways. In addition, some pharmaceuticals targeting these pathways have been applied into ongoing clinical trials and showed encouraging results. However, these signaling pathways are complex and converge into a common network with each other. In the future work, more research is warranted to further investigate how this network works. Moreover, more high quality randomised controlled trials are needed in order to investigate the therapeutic effects of pharmaceuticals against these pathways for the treatment of OA. This review may help researchers to better understand the pathogenesis of OA, so as to provide new insight for future clinical practices and translational research.

Micro- and nanotechnology in biomedical engineering for cartilage tissue regeneration in osteoarthritis

Osteoarthritis, which typically arises from aging, traumatic injury, or obesity, is the most common form of arthritis, which usually leads to malfunction of the joints and requires medical interventions due to the poor self-healing capacity of articular cartilage. However, currently used medical treatment modalities have reported, at least in part, disappointing and frustrating results for patients with osteoarthritis. Recent progress in the design and fabrication of tissue-engineered microscale/nanoscale platforms, which arises from the convergence of stem cell research and nanotechnology methods, has shown promising results in the administration of new and efficient options for treating osteochondral lesions. This paper presents an overview of the recent advances in osteochondral tissue engineering resulting from the application of micro- and nanotechnology approaches in the structure of biomaterials, including biological and microscale/nanoscale topographical cues, microspheres, nanoparticles, nanofibers, and nanotubes.

Leptin in Osteoarthritis and Rheumatoid Arthritis: Player or Bystander?

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

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

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

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.

Emerging role of leptin in joint inflammation and destruction

Rheumatoid arthritis (RA) is an autoimmune disease characterized by tumor-like hyperplasia and inflammation of the synovium, which causes synovial cell invasion into the bone and cartilage. In RA pathogenesis, various molecules in effector cells (i.e., immune cells and mesenchymal cells) are dysregulated by genetic and environmental factors. Consistent with the early stages of RA, these pathogenic cells cooperate and activate each other directly by cell-to-cell contact or indirectly via humoral factors. Recently, growing evidence has revealed essential role of adipokines, which are multifunctional signal transduction molecules, in the immune system. In this review, we summarize the current understanding of the cross-talk between leptin, one of the most well-known and best-characterized adipokines, and osteoimmunology. Furthermore, we discuss the contribution of leptin to the pathogenesis of RA and its potential mechanisms.

Causal association of adipokines with osteoarthritis: a Mendelian randomization study

OBJECTIVE

This two-sample Mendelian randomization study aimed to delve into the effects of genetically predicted adipokine levels on OA.

METHODS

Summary statistic data for OA originated from a meta-analysis of a genome-wide association study with an overall 50 508 subjects of European ancestry. Publicly available summary data from four genome-wide association studies were exploited to respectively identify instrumental variables of adiponectin, leptin, resistin, chemerin and retinol-blinding protein 4. Subsequently, Mendelian randomization analyses were conducted with inverse variance weighted (IVW), weighted median and Mendelian randomization-Egger regression. Furthermore, sensitivity analyses were then conducted to assess the robustness of our results.

RESULTS

The positive causality between genetically predicted leptin level and risk of total OA was indicated by IVW [odds ratio (OR): 2.40, 95% CI: 1.13-5.09] and weighted median (OR: 2.94, 95% CI: 1.23-6.99). In subgroup analyses, evidence of potential harmful effects of higher level of adiponectin (OR: 1.28, 95% CI: 1.01-1.61 using IVW), leptin (OR: 3.44, 95% CI: 1.18-10.03 using IVW) and resistin (OR: 1.18, 95% CI: 1.03-1.36 using IVW) on risk of knee OA were acquired. However, the mentioned effects on risk of hip OA were not statistically significant. Slight evidence was identified supporting causality of chemerin and retinol-blinding protein 4 for OA. The findings of this study were verified by the results from sensitivity analysis.

CONCLUSIONS

An association between genetically predicted leptin level and risk of total OA was identified. Furthermore, association of genetically predicted levels of adiponectin, leptin and resistin with risk of knee OA were reported.

VCAM-1 as a predictor biomarker in cardiovascular disease

The vascular cellular adhesion molecule-1 (VCAM-1) is a protein that canonically participates in the adhesion and transmigration of leukocytes to the interstitium during inflammation. VCAM-1 expression, together with soluble VCAM-1 (sVCAM-1) induced by the shedding of VCAM-1 by metalloproteinases, have been proposed as biomarkers in immunological diseases, cancer, autoimmune myocarditis, and as predictors of mortality and morbidity in patients with chronic heart failure (HF), endothelial injury in patients with coronary artery disease, and arrhythmias. This revision aims to discuss the role of sVCAM-1 as a biomarker to predict the occurrence, development, and preservation of cardiovascular disease.

Cartilage Protective and Immunomodulatory Features of Osteoarthritis Synovial Fluid-Treated Adipose-Derived Mesenchymal Stem Cells Secreted Factors and Extracellular Vesicles-Embedded miRNAs

Intra-articular administration of adipose-derived mesenchymal stem cells (ASCs), either in vitro expanded or within adipose tissue-based products obtained at point-of-care, has gained popularity as innovative regenerative medicine approach for osteoarthritis (OA) treatment. ASCs can stimulate tissue repair and immunomodulation through paracrine factors, both soluble and extracellular vesicles (EV) embedded, collectively defining the secretome. Interaction with the degenerative/inflamed environment is a crucial factor in understanding the finely tuned molecular message but, to date, the majority of reports have described ASC-secretome features in resting conditions or under chemical stimuli far from the in vivo environment of degenerated OA joints. In this report, the secretory profile of ASCs treated with native synovial fluid from OA patients was evaluated, sifting 200 soluble factors and 754 EV-embedded miRNAs. Fifty-eight factors and 223 EV-miRNAs were identified, and discussed in the frame of cartilage and immune cell homeostasis. Bioinformatics gave a molecular basis for M2 macrophage polarization, T cell proliferation inhibition and T reg expansion enhancement, as well as cartilage protection, further confirmed in an in vitro model of OA chondrocytes. Moreover, a strong influence on immune cell chemotaxis emerged. In conclusion, obtained molecular data support the regenerative and immunomodulatory properties of ASCs when interacting with osteoarthritic joint environment.

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

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

Mini-Review: The Contribution of Adipokines to Joint Inflammation in Inflammatory Rheumatic Diseases

Inflammatory rheumatic diseases (IRD) are complex disorders characterized by chronic inflammation of the joints and related skeletal structures. The most common forms of IRD are rheumatoid arthritis (RA) and spondyloarthritis (SpA), including axial SpA (axSpA) and psoriatic arthritis (PsA). Obesity is a frequent comorbidity in RA and PsA, and to a lesser extend in axial SpA. The association between obesity and IRD may be explained by the release from fat tissue of several bioactive proteins, namely adipokines. Adipokines are involved in the regulation of various processes such as lipid or glucose metabolism, but also inflammation. Adipokines are interrelated with the immune system, with both innate and adaptive immune cell connections. Several adipokines with pro-inflammatory effects have been identified such as leptin, visfatin or resistin. Conversely, adiponectin and more specifically its low molecular weight isoform, is considered to have antiinflammatory properties. In this review, we discuss the contribution of adipokines to the joint inflammation of IRD, the relation they have with immune pathways of these diseases, their links with the structural impact on peripheral joints and/or axial skeleton, and also the influence they may have on the cardiometabolic risk of IRD.

Hip preservation surgery and the acetabular fossa

As our understanding of hip function and disease improves, it is evident that the acetabular fossa has received little attention, despite it comprising over half of the acetabulum’s surface area and showing the first signs of degeneration. The fossa’s function is expected to be more than augmenting static stability with the ligamentum teres and being a templating landmark in arthroplasty. Indeed, the fossa, which is almost mature at 16 weeks of intrauterine development, plays a key role in hip development, enabling its nutrition through vascularization and synovial fluid, as well as the influx of chondrogenic stem/progenitor cells that build articular cartilage. The pulvinar, a fibrofatty tissue in the fossa, has the same developmental origin as the synovium and articular cartilage and is a biologically active area. Its unique anatomy allows for homogeneous distribution of the axial loads into the joint. It is composed of intra-articular adipose tissue (IAAT), which has adipocytes, fibroblasts, leucocytes, and abundant mast cells, which participate in the inflammatory cascade after an insult to the joint. Hence, the fossa and pulvinar should be considered in decision-making and surgical outcomes in hip preservation surgery, not only for their size, shape, and extent, but also for their biological capacity as a source of cytokines, immune cells, and chondrogenic stem cells.

Cite this article: Bone Joint Res 2020;9(12):857–869.

Role of Adiponectin in the Pathogenesis of Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a systemic chronic inflammatory autoimmune joint disease, characterized by progressive articular damage and joint dysfunction. One of the symptoms of this disease is persistent inflammatory infiltration of the synovial membrane, the principle site of inflammation in RA. In the affected conditions, the cells of the synovial membrane, fibroblast-like synoviocytes and macrophage-like synovial cells, produce enzymes degrading cartilage and underlining bone tissue, as well as cytokines increasing the infiltration of immune cells. In patients with RA, higher levels of adiponectin are measured in the serum and synovial fluid. Adiponectin, a secretory product that is mainly white adipose tissue, is a multifunctional protein with dual anti-inflammatory and pro-inflammatory properties. Several studies underline the fact that adiponectin can play an important pro-inflammatory role in the pathophysiology of RA via stimulating the secretion of inflammatory mediators. This narrative review is devoted to the presentation of recent knowledge on the role played by one of the adipokines produced by adipose tissue—adiponectin—in the pathogenesis of rheumatoid arthritis.

Adipokines: New Potential Therapeutic Target for Obesity and Metabolic, Rheumatic, and Cardiovascular Diseases

Besides its role as an energy storage organ, adipose tissue can be viewed as a dynamic and complex endocrine organ, which produces and secretes several adipokines, including hormones, cytokines, extracellular matrix (ECM) proteins, and growth and vasoactive factors. A wide body of evidence showed that adipokines play a critical role in various biological and physiological functions, among which feeding modulation, inflammatory and immune function, glucose and lipid metabolism, and blood pressure control. The aim of this review is to summarize the effects of several adipokines, including leptin, diponectin, resistin, chemerin, lipocalin-2 (LCN2), vaspin, omentin, follistatin-like 1 (FSTL1), secreted protein acidic and rich in cysteine (SPARC), secreted frizzled-related protein 5 (SFRP5), C1q/TNF-related proteins (CTRPs), family with sequence similarity to 19 member A5 (FAM19A5), wingless-type inducible signaling pathway protein-1 (WISP1), progranulin (PGRN), nesfatin-1 (nesfatin), visfatin/PBEF/NAMPT, apelin, retinol binding protein 4 (RPB4), and plasminogen activator inhibitor-1 (PAI-1) in the regulation of insulin resistance and vascular function, as well as many aspects of inflammation and immunity and their potential role in managing obesity-associated diseases, including metabolic, osteoarticular, and cardiovascular diseases.

Association Between Adiponectin and Clinical Manifestations in Rheumatoid Arthritis

Adiponectin (APN) belongs to adipokines. Previous studies showed contradictory results that have both proinflammatory and anti-inflammatory effects in rheumatoid arthritis (RA). We set out to detect the levels of APN and the correlations between APN and the clinical manifestations in RA patients. Sera of 60 newly diagnosed patients with RA and 29 age- and gender-matched healthy subjects were collected. Clinical parameters, including C-reactive protein (CRP), erythrocyte sedimentation rate, rheumatoid factor (RF), antibodies to cyclic citrullinated peptide, disease activity score 28, and bone erosion conditions, were collected. The serum levels of total APN and high-molecular-weight APN (HMW-APN) were detected by enzyme-linked immunosorbent assay. As a result, total APN and HMW-APN levels were all lower in patients with RA compared with healthy controls. The levels of APN and HMW-APN were all positively correlated with CRP levels. There was also positive correlation between HMW-APN levels and RF levels. Moreover, patients with higher disease activities had higher HMW-APN levels; patients with more severe synovial thickening had higher APN and HMW-APN levels. Therefore, APN, especially HMW-APN, may play a regulatory role in RA.

Inhibition of BMP3 increases the inflammatory response of fibroblast-like synoviocytes in rheumatoid arthritis

Rheumatoid arthritis (RA) is a persistent autoimmune disease. Fibroblast-like synoviocytes (FLS) are a key component of invasive pannus and a pathogenetic mechanism in RA. Expression of bone morphogenetic protein 3 (BMP3) mRNA is reportedly decreased in the arthritic synovium. We previously showed that BMP3 expression is significantly downregulated in the synovial tissues of RA patients and models of adjuvant-induced arthritis (AIA). In the present study, we explored the association between BMP3 and FLS migration and secretion of proinflammatory factors in RA. We found that inhibition of BMP3 expression using BMP3 siRNA increased the proinflammatory chemokines and migration of FLS stimulated with TNF-α. Inhibition of BMP3 expression also increased expression of IL-6, IL-1β, IL-17A, CCL-2, CCL-3, VCAM-1, MMP-3, and MMP-9, but not TIMP-1, in AIA and RA FLS. Correspondingly, induction of BMP3 overexpression through intra-articular injection of ad-BMP3 diminished arthritis severity in AIA rats. We also found that BMP3 may inhibit activation of TGF-β1/Smad signaling. These data indicate that BMP3 may suppress the proliferation and migration of FLS via the TGF-β1/Smad signaling pathway.

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

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

Inflammatory priming enhances mesenchymal stromal cell secretome potential as a clinical product for regenerative medicine approaches through secreted factors and EV-miRNAs: the example of joint disease

BACKGROUND

Mesenchymal stromal cell (MSC)-enriched products showed positive clinical outcomes in regenerative medicine, where tissue restoration and inflammation control are needed. GMP-expanded MSCs displayed an even higher potential due to exclusive secretion of therapeutic factors, both free and conveyed within extracellular vesicles (EVs), collectively termed secretome. Moreover, priming with biochemical cues may influence the portfolio and biological activities of MSC-derived factors. For these reasons, the use of naive or primed secretome gained attention as a cell-free therapeutic option. Albeit, at present, a homogenous and comprehensive secretome fingerprint is still missing. Therefore, the aim of this work was to deeply characterize adipose-derived MSC (ASC)-secreted factors and EV-miRNAs, and their modulation after IFNγ preconditioning. The crucial influence of the target pathology or cell type was also scored in osteoarthritis to evaluate disease-driven potency.

METHODS

ASCs were isolated from four donors and cultured with and without IFNγ. Two-hundred secreted factors were assayed by ELISA. ASC-EVs were isolated by ultracentrifugation and validated by flow cytometry, transmission electron microscopy, and nanoparticle tracking analysis. miRNome was deciphered by high-throughput screening. Bioinformatics was used to predict the modulatory effect of secreted molecules on pathologic cartilage and synovial macrophages based on public datasets. Models of inflammation for both macrophages and chondrocytes were used to test by flow cytometry the secretome anti-inflammatory potency.

RESULTS

Data showed that more than 60 cytokines/chemokines could be identified at varying levels of intensity in all samples. The vast majority of factors are involved in extracellular matrix remodeling, and chemotaxis or motility of inflammatory cells. IFNγ is able to further increase the capacity of the secretome to stimulate cell migration signals. Moreover, more than 240 miRNAs were found in ASC-EVs. Sixty miRNAs accounted for > 95% of the genetic message that resulted to be chondro-protective and M2 macrophage polarizing. Inflammation tipped the balance towards a more pronounced tissue regenerative and anti-inflammatory phenotype. In silico data were confirmed on inflamed macrophages and chondrocytes, with secretome being able to increase M2 phenotype marker CD163 and reduce the chondrocyte inflammation marker VCAM1, respectively. IFNγ priming further enhanced secretome anti-inflammatory potency.

CONCLUSIONS

Given the portfolio of soluble factors and EV-miRNAs, ASC secretome showed a marked capacity to stimulate cell motility and modulate inflammatory and degenerative processes. Preconditioning is able to increase this ability, suggesting inflammatory priming as an effective strategy to obtain a more potent clinical product which use should always be driven by the molecular mark of the target pathology.

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.

Novel adipokine associated with OA: retinol binding protein 4 (RBP4) is produced by cartilage and is correlated with MMPs in osteoarthritis patients

Objective

Retinol binding protein 4 (RBP4) is a member of the lipocalin family and a vitamin A carrier in the blood. More recently, RBP4 has been described as an adipokine that is involved in insulin resistance and metabolic syndrome (MetS). As obesity, MetS and some adipokines contribute to the pathogenesis of osteoarthritis (OA), we investigated RBP4 in patients with OA.

Materials and methods

Cartilage, synovial fluid and blood samples were collected from 100 OA patients undergoing total knee replacement surgery. Primary chondrocytes and cartilage tissue were cultured to measure the RBP4 expression. The concentrations of RBP4, other adipokines (adipsin, adiponectin, leptin and resistin) and biomarkers of OA (COMP, MMP-1, MMP-3 and YKL-40) were measured by immunoassay, and gene expression was measured by next-generation RNA sequencing.

Results

The OA cartilage samples released RBP4 into the culture medium, and the levels correlated positively with the expression of the adipokines adipsin, adiponectin, leptin and resistin. RBP4 was the most prominently expressed of these adipokines in the OA chondrocytes, and the expression of the RBP4 receptors STRA6 (stimulated by retinoic acid gene homologue 6) and TLR4 (Toll-like receptor 4) was also detected. Within the cartilage culture medium, RBP4 showed a positive correlation with MMP-1, MMP-3 and YKL-40. RBP4 was also present in the synovial fluid from the OA patients and correlated positively with the concentrations of RBP4 found in the plasma and the cartilage culture medium. Plasma RBP4 concentrations also showed a positive correlation with MMP-3 and adipsin.

Conclusions

We show here, for the first time, that RBP4 is produced within OA joints and that it is associated with increased levels of adipokines and MMPs. The results suggest a role for RBP4 in the pathogenesis of OA and as a possible target for the disease-modifying drugs for the treatment of OA.

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.

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.

Plasma levels of CTRP-3, CTRP-9 and apelin in women with multiple sclerosis

BACKGROUND

Recently, adipocytokines have been shown to play a pivotal role in autoimmune and inflammatory-related disease. The purpose of this study was to compare the levels of CTRP3, CTRP9, adiponectin and apelin- in Multiple Sclerosis (MS) patients with healthy subjects and their relationship with clinical parameters and the levels of pro-inflammatory mediators.

METHODS

Plasma levels of CTRP3, CTRP9, apelin, TNF-α, hs-CRP, and adiponectin were evaluated in 24 healthy women and 26 women with relapsing-remitting MS using immunoassay methods.

RESULTS

The plasma apelin level of the MS patients was significantly lower than that of healthy controls. The concentration of TNF-α and adiponectin were significantly higher in MS patients compared to the healthy controls. Plasma CTRP3, CTRP9 and hs-CRP levels were not significantly different between the two groups. There was no correlation between these adipokines and inflammatory mediators. A statistically significant negative correlation was observed between plasma concentrations of apelin with expanded disability status scale (EDSS) scores and number of relapse.

CONCLUSIONS

Our findings suggest that adipokines, particularly apelin and adiponectin, may contribute to the pathogenesis of MS and can be considered as a biomarker or as a therapeutic target for the treatment of this disease.

Natural Molecules for Healthy Lifestyles: Oleocanthal from Extra Virgin Olive Oil

Extra virgin olive oil (EVOO) is the main source of fat in the Mediterranean diet. Phenolic compounds of EVOO, in particular, secoiridoids, are minor components that have generated special interest due to their positive effects on human health, supported by several clinical trials. This review summarizes the most recent findings on the pharmacological properties and action's mechanisms of secoiridoid oleocanthal, focusing attention on inflammation, oxidative stress, cancer, neurodegenerative processes, and rheumatic diseases. Being of relevance to the clinical effects of EVOO intake, the bioavailability and biotransformation of EVOO polyphenols are addressed. Moreover, this review summarizes the factors that may influence the oleocanthal concentration in EVOO. With the growing incidence of age- and lifestyle-related diseases, the current data indicated that the administration of EVOO rich in secoiridoids may be helpful in the prevention or treatment of different pathologies with an inflammatory component. Although promising, the future raises several questions and challenges, which are discussed here. The real beneficial effects of olive oil phenols on human health need to be clarified in new, well-designed clinical studies.

Associations between Adipokines in Arthritic Disease and Implications for Obesity

Secretion from adipose tissue of adipokines or adipocytokines, comprising of bioactive peptides or proteins, immune molecules and inflammatory mediators, exert critical roles in inflammatory arthritis and obesity. This review considers the evidence generated over the last decade regarding the effects of several adipokines including leptin, adiponectin, visfatin, resistin, chemerin and apelin, in cartilage and bone homeostasis in the pathogenesis of rheumatoid arthritis and osteoarthritis, which has important implications for obesity.

Obesity, Fat Mass and Immune System: Role for Leptin

Obesity is an epidemic disease characterized by chronic low-grade inflammation associated with a dysfunctional fat mass. Adipose tissue is now considered an extremely active endocrine organ that secretes cytokine-like hormones, called adipokines, either pro- or anti-inflammatory factors bridging metabolism to the immune system. Leptin is historically one of most relevant adipokines, with important physiological roles in the central control of energy metabolism and in the regulation of metabolism-immune system interplay, being a cornerstone of the emerging field of immunometabolism. Indeed, leptin receptor is expressed throughout the immune system and leptin has been shown to regulate both innate and adaptive immune responses. This review discusses the latest data regarding the role of leptin as a mediator of immune system and metabolism, with particular emphasis on its effects on obesity-associated metabolic disorders and autoimmune and/or inflammatory rheumatic diseases.

uPA/uPAR signaling in rheumatoid arthritis: Shedding light on its mechanism of action

Rheumatoid arthritis (RA) is a systemic and chronic autoimmune inflammatory disorder affecting multiple joints. Various cytokines, chemokines and growth factors synergistically modulate the joint physiology leading to bone erosion and cartilage degradation. Other than these conventional mediators that are well established in the past, the newly identified plasminogen activator (PA) family of proteins have been witnessed to possess a multifactorial approach in mediating RA pathogenesis. One such family of proteins comprises of the urokinase-type plasminogen activator (uPA) and its receptor (uPAR)/soluble-type plasminogen activator receptor (suPAR). PA family of proteins are classified into two types namely: uPA and tissue type plasminogen activator (tPA). Both these subtypes have been implicated to play a key role in RA disease progression. However during RA pathogenesis, uPA secreted by neutrophils, chondrocytes, and monocytes are designated to interact with uPAR expressed on macrophages, fibroblast-like synoviocytes (FLS), chondrocytes and endothelial cells. Interaction of uPA/uPAR promotes the disease progression of RA through secretion of several cytokines, chemokines, growth factors and matrix metalloproteinases (MMPs). Moreover, uPA/uPAR initiates inflammatory responses in macrophages and FLS through activation of PI3K/Akt signaling pathways. Furthermore, uPAR plays a dual role in osteoclastogenesis under the presence/absence of growth factors like monocyte-colony stimulating factor (M-CSF). Overall, this review emphasizes the role of uPA/uPAR on various immune cells, signaling pathways and osteoclastogenesis involved in RA pathogenesis.

Adipokines and inflammation: is it a question of weight?

Obesity has reached epidemic proportions in the Western society and is increasing in the developing world. It is considered as one of the major contributors to the global burden of disability and chronic diseases, including autoimmune, inflammatory and degenerative diseases. Research conducted on obesity and its complications over the last two decades has transformed the outdated concept of white adipose tissue (WAT) merely serving as an energy depot. WAT is now recognized as an active and inflammatory organ capable of producing a wide variety of factors known as adipokines. These molecules participate through endocrine, paracrine, autocrine or juxtacrine crosstalk mechanisms in a great variety of physiological or pathophysiological processes, regulating food intake, insulin sensitivity, immunity and inflammation. Although initially restricted to metabolic activities (regulation of glucose and lipid metabolism), adipokines currently represent a new family of proteins that can be considered key players in the complex network of soluble mediators involved in the pathophysiology of immune/inflammatory diseases. However, the complexity of the adipokine network in the pathogenesis and progression of inflammatory diseases has posed, since the beginning, the important question of whether it may be possible to target the mechanism(s) by which adipokines contribute to disease selectively without suppressing their physiological functions. Here, we explore in depth the most recent findings concerning the involvement of adipokines in inflammation and immune responses, in particular in rheumatic, inflammatory and degenerative diseases. We also highlight several possible strategies for therapeutic development and propose that adipokines and their signalling pathways may represent innovative therapeutic strategies for inflammatory disorders.

The role of leptin in osteoarthritis

BACKGROUND

The pathogenesis of osteoarthritis (OA) is not clear; leptin may be related to its pathogenesis.

METHODS

We reviewed articles on leptin in OA, chondrocytes, and in vitro experiments. It is concluded that leptin may lead to OA via some signaling pathways. At the same time, the concentration of leptin in vitro experiments and OA/rheumatoid arthritis (RA) patients was summarized.

RESULTS

Leptin levels in serum and synovial fluid of OA/RA patients were higher than normal person. In the condition of infection and immunity, serum leptin levels in the peripheral blood significantly increase. Because of the close relationship between obesity, leptin, and OA, it is crucial to study the effects of weight loss and exercise intervention on serum leptin levels to improve the symptoms of OA patients.

CONCLUSION

Treatment for leptin-increased obesity may be a treatment for OA. The role of leptin in OA cannot be ignored and needs to be further studied.

The Unexplored Role of Intra-articular Adipose Tissue in the Homeostasis and Pathology of Articular Joints

Intra-articular adipose tissue deposits known as articular fat pads (AFPs) are described to exist within synovial joints. Their assumed role in normal joint biomechanics is increasingly objectivized by means of advanced methods of functional imaging. AFPs possess structural similarity with body subcutaneous white adipose tissue (WAT), however, seems to be regulated by independent metabolic loops. AFP dimension are conserved during extreme WAT states: obesity, metabolic syndrome, lipodystrophy, and cachexia. Hoffa fat pad (HFP) in the knee is increasingly recognized as a major player in pathological joint states such as anterior knee pain and osteoarthritis. HFP contains numerous population of mesenchymal and endothelial progenitors; however, the possible role of mature adipocytes in the maintenance of stem cell niche is unknown. We propose that AFP is an active component of the joint organ with multifunctional roles in the maintenance of joint homeostasis. Endowed with a rich network of sensitive nervous fibbers, AFPs may act as a proprioceptive organ. Adipokines and growth factors released by AFP-resident mature adipocytes could participate in the maintenance of progenitor stem cell niche as well as in local immune regulation. AFP metabolism may be locally controlled, correlated with but independent of WAT homeostasis. The identification of AFP role in normal joint turnover and its possible implication in pathological states could deliver diagnostic and therapeutic targets. Drug and/or cell therapies that restore AFP structure and function could become the next step in the design of disease modifying therapies for disabling joint conditions such as osteoarthritis and inflammatory arthritis.