Correlation of plasma and synovial fluid adiponectin with knee osteoarthritis severity

The effect of plasma cytokines on the expression of adiponectin and its receptors in the synovial membrane of joints and the infrapatellar fat pad in patients with rheumatoid arthritis and osteoarthritis

BACKGROUND

Rheumatoid arthritis (RA) is an autoimmune inflammatory disease that leads to joint destruction. Numerous pro-inflammatory mediators, including adipokines, play an important role in the pathogenesis of RA.

OBJECTIVE

The aim of the study was to investigate the relationships between selected plasma cytokines and expression of adiponectin and its receptors in the synovium and the infrapatellar fat pad in patients with RA and osteoarthritis (OA).

METHODS

Blood, synovium and fat pad samples from 18 patients with RA and 18 with OA were collected during joint replacement surgery. Spearman rank correlations between plasma concentrations of selected cytokines (IL-1β, IL-2, IL-4, IL-6, IL-7, IL-8, IL-10, IL-12 p40, IL-13, IL-17, G-CSF and GM-CSF) and the expression of adiponectin and its receptors were determined. Plasma levels of cytokines were determined using a magnetic bead-based multiplex assay, mRNA expression of adiponectin and its receptors were determined by real-time PCR.

RESULTS

In OA patients, there were significant positive correlations between adiponectin expression in the synovial membrane and plasma levels of IL-1β, IL-4, G-CSF and GM-CSF, as well as a significant positive correlation between adiponectin expression in the fat pad and plasma levels of GM-CSF. In addition, OA patients showed significant negative correlations between AdipoR1 and AdipoR2 expression in the synovial membrane and plasma IL-6 levels, as well as between AdipoR2 expression in the synovial membrane and plasma MCP-1 and TNF-α levels. In patients with RA, there were no significant correlations between adiponectin expression in the synovial membrane and infrapatellar fat pad and plasma levels of the cytokines studied. In addition, RA patients showed a statistically significant negative correlation between AdipoR1 expression in the synovial membrane and plasma levels of TNF-α, IL-7, IL-12 and IL-13, and a significant negative correlation between AdipoR1 expression in the infrapatellar fat pad and plasma levels of IL-1β.

CONCLUSIONS

Adiponectin and its receptors showed the correlations with several plasma cytokines, however, a thorough understanding of the role of adiponectin in RA and OA requires further investigation.

Analysis of the Level of Adiponectin and Selected Cytokines in Patients with Knee Osteoarthritis

Background and Objectives: Knee osteoarthritis (KOA) is a degenerative disease that is continuously targeting people of different ages, but especially the elderly population, the number of which tends to increase continuously at the global level. Apart from age, excess weight can influence the evolution of the disease, with obesity being associated with a weak inflammation stage and an imbalance between pro-inflammatory and anti-inflammatory cytokines. The present work aimed to analyze specific biomarkers, namely ACRP-30, IL-10, TNF-α, and IL-6, in knee synovial fluid, and correlate them with KOA patients' clinical data, radiographic changes, and functional and pain scores. Materials and Methods: 24 subjects with KOA and over 50 years of age participate in the present study. Synovial fluid was harvested using ultrasound guidance from the target knees of the enrolled KOA patients, and the levels of ACRP-30, IL-10, TNF-α, and IL-6 were measured using enzyme-linked immunosorbent assays (ELISA). All patients underwent a supine X-ray at the target knee and were classified using Kellgren-Lawrence (K-L) grading. The Western Ontario and McMaster University Osteoarthritis Index (WOMAC) was used to assess self-reported physical function, pain, and stiffness. Results: The obtained results highlighted a significant correlation between age and adiponectin level (p = 0.0451, r = -0.412). Also, the IL-10 values are lower in cases where the intensity of the pain is more pronounced (p = 0.0405, r = -0.421). In addition, analyzing the data by gender, it was observed that in the case of males, stiffness is more related to age (p = 0.0079, r = 0.7993), compared to women (p = 0.0203, r = 0.6223). In the case of women, the progression of the disease tends to increase more intensively the WOMAC score's total values (p = 0.00031, r = 0.8342), compared with men (p = 0.0289, r = 7013). Regarding interleukins and BMI, significant correlations were observed only in the case of men. Conclusions: A significant correlation between age and adiponectin, and adiponectin and IL-6, suggests that advanced age may contribute to adiponectin reduction. Comparing men with women, it was observed that men's age is more related to rigidity, and IL-6 and IL-10 are directly correlated to BMI; in addition, women seem to be more sensitive to pain and stiffness.

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.

Exerkines and osteoarthritis

Osteoarthritis (OA) is the most prevalent chronic joint disease, with physical exercise being a widely endorsed strategy in its management guidelines. Exerkines, defined as cytokines secreted in response to acute and chronic exercise, function through endocrine, paracrine, and/or autocrine pathways. Various tissue-specific exerkines, encompassing exercise-induced myokines (muscle), cardiokines (heart), and adipokines (adipose tissue), have been linked to exercise therapy in OA. Exerkines are derived from these kines, but unlike them, only kines regulated by exercise can be called exerkines. Some of these exerkines serve a therapeutic role in OA, such as irisin, metrnl, lactate, secreted frizzled-related protein (SFRP), neuregulin, and adiponectin. While others may exacerbate the condition, such as IL-6, IL-7, IL-15, IL-33, myostatin, fractalkine, follistatin-like 1 (FSTL1), visfatin, activin A, migration inhibitory factor (MIF), apelin and growth differentiation factor (GDF)-15. They exerts anti-/pro-apoptosis/pyroptosis/inflammation, chondrogenic differentiation and cell senescence effect in chondrocyte, synoviocyte and mesenchymal stem cell. The modulation of adipokine effects on diverse cell types within the intra-articular joint emerges as a promising avenue for future OA interventions. This paper reviews recent findings that underscore the significant role of tissue-specific exerkines in OA, delving into the underlying cellular and molecular mechanisms involved.

Epigenetic Regulation of Chondrocytes and Subchondral Bone in Osteoarthritis

The aim of this review is to provide an updated review of the epigenetic factors involved in the onset and development of osteoarthritis (OA). OA is a prevalent degenerative joint disease characterized by chronic inflammation, ectopic bone formation within the joint, and physical and proteolytic cartilage degradation which result in chronic pain and loss of mobility. At present, no disease-modifying therapeutics exist for the prevention or treatment of the disease. Research has identified several OA risk factors including mechanical stressors, physical activity, obesity, traumatic joint injury, genetic predisposition, and age. Recently, there has been increased interest in identifying epigenetic factors involved in the pathogenesis of OA. In this review, we detail several of these epigenetic modifications with known functions in the onset and progression of the disease. We also review current therapeutics targeting aberrant epigenetic regulation as potential options for preventive or therapeutic treatment.

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.

Evaluation of aggrecan and adipokine levels in temporomandibular joint synovial fluid

The aim of this study was to investigate the effect various mediators in synovial fluid (SF) on the pathogenesis of temporomandibular disorders (TMD) and to evaluate the relationship between clinical and radiological features of temporomandibular joint (TMJ) diseases. Patients who had received SF sample during arthrocentesis because of TMD were included in this study. Clinical and radiological records were evaluated retrospectively. Enzyme-Linked ImmunoSorbent Assay (ELISA) method was used for analysis of aggrecan, adiponectin, resistin, apelin, Vascular Endothelial Growth Factor (VEGF) and Prostaglandin E2 (PGE2) in SFs. 59 joints of 41 patients were included in the study. Anterior disc displacement with reduction (ADDwR) was detected in 22 joints, anterior disc displacement without reduction (ADDwoR) was detected in 29 joints and osteoarthritis (OA) in 8. In OA group, PGE2 level was significantly higher than the other groups (p = 0.029). Aggrecan and PGE2 levels were statistically higher in joints with localized pain (p = 0.030, p = 0.029). The aggrecan level was statistically significant higher in patients who had degenerative changes in radiological examinations (p = 0.044). Resistin was correlated with PGE2 and aggrecan (p = 0.011), and apelin showed positive correlation with VEGF (p˂0.001). The detection of aggrecan and adipokines in SF may be a precursor of degenerative joint disease and it should be taken into account that the presence of localized pain in the joint area may be an early sign of degenerative changes.

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.

Level of Adiponectin, Leptin and Selected Matrix Metalloproteinases in Female Overweight Patients with Primary Gonarthrosis

The aim of this study was to assess levels of adiponectin (ACRP-30) and leptin in serum and synovial fluid (SF) of overweight females with primary gonarthrosis (GOA) and to look for their correlations with clinical status and the level of biochemical OA biomarkers: matrix metalloproteinase (MMP) 1, MMP-9 and tissue inhibitor of metalloproteinase (TIMP-1). The studied group consisted of 39 overweight females undergoing primary total knee arthroplasty as a result of GOA. The stage of GOA was evaluated according to Knee Society Score (KSS), Ahlbäck and Kellgren–Lawrence (K-L) scores. Peripheral blood and SF were obtained. Levels of selected biomarkers were assessed using ELISA kits. The mean level of ACRP-30 in serum valued were 8393.80 ng/mL and in SF, 774.33 ng/mL, the mean concentration of leptin in serum was 32,040.74 pg/mL and in SF, 27,332.12 pg/mL. Levels of leptin in serum and SF correlated with body mass index (BMI), (p = 0.0005, and p = 0.0002, respectively). Levels of ACRP-30 in serum was correlated with clinical scores (Ahlbäck: p = 0.0214; K-L: p = 0.0146). ACRP-30 in SF correlated with ACRP-30 in serum (p = 0.0003), tended to negatively correlate with MMP-1 in serum (p = 0.0598) and positively correlate with pro-MMP-1 in SF (p = 0.0600). To conclude, this study confirms the correlations between concentrations of both, leptin and ACRP-30, comparing serum and SF. In overweight females, leptin levels increase with BMI and ACRP-30 serum level increase in more advanced GOA stages. Finally, leptin levels were correlated with TIMP-1 serum concentration, one of the biochemical markers of GOA.

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

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

Miconia albicans and Curcuma longa herbal medicines positively modulate joint pain, function and inflammation in patients with osteoarthritis: a clinical study

This study aims to evaluate the analgesic and modulating effect of Curcuma longa and Miconia albicans herbal medicines in knee's osteoarthritis (OA) treatment. This longitudinal study evaluated 24 patients with OA. The patients were divided into three groups: ibuprofen (1200 mg/day), C. longa (1000 mg/day) and M. albicans (1000 mg/day). The medications were applied orally for 30 days. The synovial fluid of the knee joint was collect at the first (day 0) and the last medical (day 30) consultation. The groups treated with herbal medicines presented the same results when compared to Ibuprofen. The comparison of the means of Total WOMAC for M. albicans before and after treatment presented a statistically significant difference (mean day 0 = 57.19; mean day 30 = 31.02) as well as variation of Total WOMAC for C. longa (mean day 0 = 54.79; mean day 30 = 37.08). The WOMAC Total and the VASP were compared, it was found that there was a significant decrease in the means in the C. longa and M. albicans groups, as well as in the Ibuprofen group after treatment. The study demonstrated that the treatment of knee OA with C. longa or M. albicans positively interferes with patients pain and functionality, decreased WOMAC and VASP scores, leading to functional improvement of these patients. This is the first clinical study demonstrating the analgesic and anti-inflammatory effect on knee osteoarthritis from M. albicans comparable to Ibuprofen drug.

Detection of synovitis in early knee osteoarthritis by MRI and serum biomarkers in Japanese general population

To investigate synovitis' influence on early knee osteoarthritis (EKOA) by serum biomarkers and magnetic resonance imaging (MRI) findings in Japanese women. We enrolled 255 women aged 30-70 without radiographic abnormalities (Kellgren-Lawrence grade ≥ 2). Knee injury, OA outcome scores (KOOS), clinical examinations, and standing radiograph were used for classification criteria of EKOA. Participants were classified into normal knee group and EKOA group. All participants underwent MRIs of their right knee. The amount of effusion-synovitis volume was quantified. We compared serum matrix metalloproteinases-3 levels (MMP-3), high-sensitivity C-reactive protein, interleukin-6, and adiponectin between the groups. The relationship between synovitis and EOKA was investigated using multiple linear regression. Fifty-four participants (21%) were classified as EKOA. Serum MMP-3 concentration and effusion-synovitis volume were higher in patients with EKOA (p = 0.025 and p = 0.001, respectively). Effusion-synovitis volume negatively correlated with all KOOS subscales and positively correlated with serum MMP-3 concentration. Serum MMP-3 concentration was associated with effusion-synovitis volume β = 0.60, p < 0.001). There was mildly active but definitive synovitis in EKOA. This was an observational study so that no conclusions can be drawn regarding cause-effect for synovitis and symptoms. Future studies should conduct follow-up of participants with synovitis to assess the progression of knee OA.

Decreased Serum Adiponectin Reflects Low Vitamin D, High Interleukin 6, and Poor Physical Performance in Knee Osteoarthritis

Obesity is a major contributor to deterioration of physical function toward sarcopenia in knee osteoarthritis (OA) due to its effect mediated through adipokines-derived molecules that have pro-/anti-inflammatory properties. This study aimed to investigate relationships of serum adiponectin, 25-hydroxyvitamin D (25(OH)D), interleukin (IL)-6, and physical performance in knee OA patients. A total of 175 knee OA patients and 52 healthy controls were recruited. Serum adiponectin, 25(OH)D, IL-6, biochemical markers, knee pain and functional scores, muscle strength, physical performance, metabolic parameters, and body composition were evaluated. Serum adiponectin levels were significantly higher in knee OA patients than that in controls, while its serum levels were significantly decreased in obese patients, especially those with sarcopenia. Furthermore, there were independent relationships of serum adiponectin with body composition parameters, knee pain scores, physical function tests, and metabolic parameters in knee OA patients. Besides, serum adiponectin levels were positively associated with 25(OH)D levels, and negatively correlated with C-reactive protein and IL-6 levels in knee OA. Additionally, low serum adiponectin could be used to distinguish knee OA patients with sarcopenic obesity from those without sarcopenic obesity. Circulating adiponectin levels may serve as a possible surrogate biomarker for exacerbated physical function in knee OA patients-particularly sarcopenic obesity.

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.

Metabolic Score for Insulin Resistance Is Correlated to Adipokine Disorder and Inflammatory Activity in Female Knee Osteoarthritis Patients in a Chinese Population

PURPOSE

This study was to evaluate the metabolic score for insulin resistance (METS-IR) in female knee osteoarthritis (KOA) patients in a Chinese population. The associations between METS-IR and adipokines, erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP) were investigated.

PATIENTS AND METHODS

This study included 4686 women from the 2011 China Health and Retirement Longitudinal Study (CHARLS) and 108 women who underwent arthroplasty of KOA at a university hospital. The clinical data were collected, and adipokines were evaluated. METS-IR was calculated in the KOA patients and compared with the national baseline. Logistic regression analyses were applied to explore the associations of METS-IR with adipokines, ESR, and CRP.

RESULTS

Receiver operating characteristic curve analysis of METS-IR and metabolic syndrome (MetS) in national baseline showed an area under the curve value of 0.851, with sensitivity of 0.777 and specificity of 0.772. The METS-IR of KOA was higher than the national baseline level (40.29 ± 6.98 vs 36.20 ± 8.50, P < 0.01), even after adjusting age. In addition, the METS-IR was higher in patients with KOA who had MetS than in those without metabolic syndrome (nMetS), even after adjusting body mass index (BMI). After adjusting for age and BMI, METS-IR was associated with CRP (OR 1.238, 95% confidence interval (CI) 1.088, 1.409, P < 0.01), ESR (OR 1.124, 95% CI 1.008, 1.254, P = 0.036), plasma leptin (OR 1.123, 95% CI 1.052, 1.199, P < 0.01), plasma resistin (OR 1.134, 95% CI 1.011, 1.271, P = 0.031), and plasma adiponectin (OR 0.865, 95% CI 0.771, 0.971, P = 0.014).

CONCLUSION

METS-IR in female KOA was higher than that of the national baseline. The METS-IR was related to adipokine disorder and inflammatory activity. These findings suggest that METS-IR can be used to evaluate the degree of involvement of MetS in KOA.

The ratio adipsin/MCP-1 is strongly associated with structural changes and CRP/MCP-1 with symptoms in obese knee osteoarthritis subjects: data from the Osteoarthritis Initiative

OBJECTIVE

There is a need to identify reliable biomarkers that can predict knee osteoarthritis (OA) progression. We investigated a panel of adipokines and some related inflammatory factors alone and their ratios for their associative value at assessing cartilage volume loss over time and symptoms in obese [High body mass index (BMI)] and non-obese (Low BMI) OA subjects.

DESIGN

Human OA serum was from the Osteoarthritis Initiative Progression subcohort. Baseline levels of adiponectin (high and low molecular weight forms), adipsin, chemerin, leptin, visfatin, C-reactive protein (CRP), interleukin-8 (IL-8) and monocyte chemoattractant protein-1 (MCP-1) were evaluated with specific assays. Cartilage volume was assessed at baseline and 48 months by quantitative magnetic resonance imaging (MRI), and symptoms using baseline Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) scores. Data were analysed by linear regression with confounding factors at baseline, followed by multiple comparison adjustment.

RESULTS

The levels of the nine biomarkers and their ratios (36) were studied. Among High BMI subjects, only the ratio adipsin/MCP-1 was associated with cartilage volume loss over time in the lateral compartment [β, -2.95; 95% confidence interval (CI), -4.42, -1.49; P = 0.010], whereas MCP-1 was associated with WOMAC pain (-1.74; -2.75, -0.73; P = 0.030) and the ratio CRP/MCP-1 with WOMAC pain (0.76; 0.37, 1.14; P = 0.023), function (2.43; 1.20, 3.67; P = 0.020) and total (3.29; 1.58, 5.00; P = 0.027). No associations were found for biomarkers or ratios in Low BMI OA.

CONCLUSION

In this study, the ratio adipsin/MCP-1 was found to be associated with the knee structural changes and that of CRP/MCP-1 with symptoms in obese OA subjects. Our data further underline the relevance of ratios as biomarkers to a stronger association to OA progression and symptoms.

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.

Adiponectin as a novel biomarker for liver fibrosis

Adiponectin is known to play primary roles in the regulation of systemic glucose homeostasis and lipid metabolism. Interestingly, emerging evidence indicates beneficial effects of adiponectin on liver fibrosis; however, the exact mechanisms of this action remain unclear. Herein, we aimed to summarize the recent findings regarding the role of adiponectin in liver fibrogenesis and update the current comprehensive knowledge regarding usefulness of adiponectin-based treatments in liver fibrosis. Adiponectin has been demonstrated to have an anti-fibrotic action in the liver by blocking the activation of hepatic stellate cell-mediated adenosine monophosphate-activated protein kinase and peroxisome proliferator-activated receptor-alpha pathways, which in turn diminish the expression of pro-fibrotic genes. In addition, hyperadiponectinemia was noted in patients with various chronic liver diseases (CLDs)-related liver fibrosis. An increase in circulating adiponectin levels was also found to be associated with the development of liver fibrosis, indicating a role of adiponectin as a non-invasive biomarker for predicting the progression of liver fibrosis. It is therefore reasonable to speculate that adiponectin may be developed as a new therapeutic candidate for the treatment of liver fibrosis. Nonetheless, future observations are still necessary to fully elucidate the extent of the effects of adiponectin on liver fibrotic outcomes, in order to modify adiponectin as an anti-fibrotic therapy that would speed up fibrosis reversal in patients with CLD.

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

BACKGROUND

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

METHOD

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

RESULTS

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

CONCLUSION

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

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.

DNA Methylation in Osteoarthritis: Current Status and Therapeutic Implications

Background:

Primary Osteoarthritis (OA) is a multifactorial disease in which genetic factors are strongly associated with its development; however, recently it has been observed that epigenetic modifications are also involved in the pathogenesis of OA. DNA methylation is related to gene silencing, and several studies have investigated its role in the loci of different pathways or molecules associated to OA.

Objective:

This review is focused on the current status of DNA methylation studies related to OA pathogenesis.

Method:

A review of the literature was conducted on searching in PUBMED for original papers on DNA methylation in OA.

Conclusion:

The DNA methylation research of loci related to OA pathogenesis has shown a correlation between methylation and gene repression; however, there are some exceptions to this rule. Recently, the development of genome-wide methylation and genome-wide hydroxymethylation profiles has demonstrated that several genes previously associated with OA can have changes in their methylation status, favoring the development of the disease, and these have even shown the role of other epigenetic markers.

Obesity, Metabolic Syndrome, and Musculoskeletal Disease: Common Inflammatory Pathways Suggest a Central Role for Loss of Muscle Integrity

Inflammation can arise in response to a variety of stimuli, including infectious agents, tissue injury, autoimmune diseases, and obesity. Some of these responses are acute and resolve, while others become chronic and exert a sustained impact on the host, systemically, or locally. Obesity is now recognized as a chronic low-grade, systemic inflammatory state that predisposes to other chronic conditions including metabolic syndrome (MetS). Although obesity has received considerable attention regarding its pathophysiological link to chronic cardiovascular conditions and type 2 diabetes, the musculoskeletal (MSK) complications (i.e., muscle, bone, tendon, and joints) that result from obesity-associated metabolic disturbances are less frequently interrogated. As musculoskeletal diseases can lead to the worsening of MetS, this underscores the imminent need to understand the cause and effect relations between the two, and the convergence between inflammatory pathways that contribute to MSK damage. Muscle mass is a key predictor of longevity in older adults, and obesity-induced sarcopenia is a significant risk factor for adverse health outcomes. Muscle is highly plastic, undergoes regular remodeling, and is responsible for the majority of total body glucose utilization, which when impaired leads to insulin resistance. Furthermore, impaired muscle integrity, defined as persistent muscle loss, intramuscular lipid accumulation, or connective tissue deposition, is a hallmark of metabolic dysfunction. In fact, many common inflammatory pathways have been implicated in the pathogenesis of the interrelated tissues of the musculoskeletal system (e.g., tendinopathy, osteoporosis, and osteoarthritis). Despite these similarities, these diseases are rarely evaluated in a comprehensive manner. The aim of this review is to summarize the common pathways that lead to musculoskeletal damage and disease that result from and contribute to MetS. We propose the overarching hypothesis that there is a central role for muscle damage with chronic exposure to an obesity-inducing diet. The inflammatory consequence of diet and muscle dysregulation can result in dysregulated tissue repair and an imbalance toward negative adaptation, resulting in regulatory failure and other musculoskeletal tissue damage. The commonalities support the conclusion that musculoskeletal pathology with MetS should be evaluated in a comprehensive and integrated manner to understand risk for other MSK-related conditions. Implications for conservative management strategies to regulate MetS are discussed, as are future research opportunities.

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.

Differential involvement of synovial adipokines in pain and physical function in female patients with knee osteoarthritis. A cross-sectional study

OBJECTIVE

Adipokines have been reported to play a role in the development, progression and severity of knee osteoarthritis but the influence of the different adipokines are not well known. The aim of this study was to evaluate the association between different synovial fluid adipokines with pain and disability knee osteoarthritis patients.

METHODS

Cross-sectional study with systematic inclusion of 115 symptomatic primary knee osteoarthritis female patients with ultrasound-confirmed joint effusion. Age, physical exercise, symptoms duration and different anthropometric measurements were collected. Radiographic severity was evaluated according to Kellgren-Lawrence scale. Pain and disability were assessed by WOMAC-total, -pain, -function subscales and Knee injury and Osteoarthritis Outcome Score (KOOS) pain and function scales. Seven adipokines and three inflammatory markers were measured by ELISA in synovial fluid. Partial Correlation Coefficient (PCC) and corresponding 95% confidence interval were used as a measure of association.

RESULTS

Leptin, osteopontin and inflammatory factors, especially TNF-alpha, were associated to pain and function. After adjustment for potential confounders including inflammatory factors and all adipokines, an association was found for adiponectin with pain (PCC 0.240 [0.012, 0.444]) and for resistin and visfatin with function (PCC 0.336 [0.117, 0.524] and -0.262 [-0.463, -0.036]). No other adipokines or inflammatory markers were statistically and independently associated. An association between physical exercise and pain and disability remained after adjustment, whereas an attenuation of the influence of anthropometric measurements was observed.

CONCLUSIONS

Different patterns of association between synovial fluid adipokines were observed regarding pain and disability in knee osteoarthritis patients. Specifically, adiponectin was associated to pain while resistin and visfatin were mainly related to function.

Associations between circulating adipokines and bone mineral density in patients with knee osteoarthritis: a cross-sectional study

Background

Associations between adipokines and bone mineral density (BMD) in knee osteoarthritis (OA) remain indistinct. The aim of this study was to investigate the cross-sectional associations between serum levels of adipokines and BMD in patients with knee OA.

Methods

This study included 164 patients with symptomatic knee OA from the Anhui Osteoarthritis study. Serum levels of leptin, adiponectin, and resistin were measured using an enzyme-linked immunosorbent assay (ELISA). BMD at total body, spine, hip, and femur were measured by dual-energy X-ray absorptiometry (DXA).

Results

In multivariable analyses, serum levels of leptin were significantly associated with reduced BMD at total body, hip, total femur, femoral neck, and femoral shaft (β = − 0.019, 95% CI -0.034 to − 0.005; β = − 0.018, 95% CI -0.034 to − 0.003; β = − 0.018, 95% CI -0.034 to − 0.002; β = − 0.016, 95% CI -0.032 to 0.000; β = − 0.026, 95% CI -0.046 to − 0.006; respectively). Serum levels of adiponectin were significantly and negatively associated with BMD at total femur and femoral shaft (β = − 0.007, 95% CI -0.013 to 0.000; β = − 0.011, 95% CI -0.018 to − 0.003; respectively). However, no significant associations were found between serum levels of resistin and BMD at any site measured.

Conclusions

Serum levels of leptin and adiponectin were significantly and negatively associated with BMD, suggesting potentially detrimental effects of leptin and adiponectin on BMD in knee OA patients.

Association of adiponectin gene polymorphisms with knee osteoarthritis

AIM

To investigate the possible relationship of adiponectin (ADIPOQ) gene polymorphisms, plasma adiponectin, and the risk of knee osteoarthritis (OA).

METHODS

A total of 398 subjects, 202 knee OA patients and 196 healthy individuals, were enrolled in the case-control study. Genotyping at +45T/G (rs2241766) and +276G/T (rs1501299) loci was performed using polymerase chain reaction-restriction fragment length polymorphism. Plasma adiponectin levels were assessed using enzyme-linked immunosorbent assay. OA severity was determined using the Kellgren-Lawrence (KL) grading system.

RESULTS

No significant associations were observed in the genotype distributions and allele frequencies at two loci of +45T/G and +276G/T polymorphisms in the ADIPOQ between knee OA patients and control subjects. There was a significant association between genotype distribution of +276G/T polymorphism and KL grade 2, 3 or 4 (P = 0.037, P = 0.046, P = 0.016, respectively). At +45T/G locus, the percentage of GG genotype was notably greater in control subjects (13.40%) compared with OA subjects (1.70%) (P = 0.023). Plasma adiponectin was markedly decreased in OA subjects compared with control subjects (P = 0.03). Likewise, circulating adiponectin in OA subjects was notably lesser than that in control subjects in GG genotype of +45T/G (P = 0.029) and +276G/T polymorphisms (P = 0.012).

CONCLUSION

Polymorphisms +45T/G and +276G/T of the ADIPOQ gene might not be responsible for OA susceptibility among Thais.

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.

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.

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.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

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

Background

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

Methods

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

Results

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

Conclusions

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

Obesity, Exercise and Orthopedic Disease

Osteoarthritis is common among aging canine and feline patients. The incidence and severity of clinical lameness are closely correlated to body condition in overweight and obese patients. Excessive adiposity may result in incongruous and excessive mechanical loading that worsens clinical signs in affected patients. Data suggest a potential link between adipokines, obesity-related inflammation, and a worsening of the underlying pathology. Similarly, abnormal physical stress and generalized systemic inflammation propagated by obesity contribute to neurologic signs associated with intervertebral disc disease. Weight loss and exercise are critical to ameliorating the pain and impaired mobility of affected animals.

Identification of upstream regulators for synovial expression signature genes in osteoarthritis

OBJECTIVES

The detection of transcription factors (TFs) for OA signature genes provides better clues to the underlying regulatory mechanisms and therapeutic applications.

METHODS

We searched GEO database for synovial expression profiling from different OA microarray studies to perform a systematic analysis. Functional annotation of DEGs was conducted, including gene ontology (GO) enrichment analysis and Kyoto encyclopedia of genes and genomes (KEGG) pathway enrichment analysis. Based on motif databases and the results from integrated analysis of current gene expression data, a global transcriptional regulatory network was constructed, and the upstream TFs were identified for OA signature genes.

RESULTS

Six GEO datasets were obtained. Totally, 805 genes across the studies were consistently differentially expressed in OA (469 up-regulated and 336 down-regulated genes) with FDR≤0.01. Supporting an involvement of ECM in the development of OA, we showed that ECM-receptor interaction was the most significant pathway in our KEGG analysis (P=5.92E-12). Sixty-one differentially expressed TFs were identified with FDR≤0.05. The constructed OA-specific regulatory networks consisted of 648 TF-target interactions between 51 TFs and 429 DEGs in the context of OA. The top 10 TFs covering the most downstream DEGs were identified as crucial TFs involved in the development of OA, including ARID3A, NFIC, ZNF354C, NR4A2, BRCA1, EHF, FOXL1, FOXC1, EGR1, and HOXA5.

CONCLUSION

This integrated analysis has identified the OA signature, providing clues to pathogenesis of OA at the molecular level, which may be also used as diagnostic markers for OA. Some crucial upstream regulators, such as NR4A2, EHF, and EGR1 may be considered as potential new therapeutic targets for OA.

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

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

Adiponectin: is it a biomarker for assessing the disease severity in knee osteoarthritis patients?

AIM

The results of previous studies regarding the role of adiponectin in the pathogenesis of osteoarthritis (OA) are controversial. The aim of this study is to investigate the relation of plasma adiponectin levels with clinical and radiological disease severity in knee OA patients.

METHOD

Sixty patients with knee OA and 25 healthy controls were included in the study. Patients were divided into two subgroups: lean (Group 1, n = 30) and obese (Group 2, n = 30). Healthy controls were accepted as Group 3 (n = 25). Pain intensity was measured with a visual analogue scale (VAS), functional disability with Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and Quality of Life (QoL) with Short Form-36 (SF-36). Also all patients were radiologically evaluated and graded according to Kellgren-Lawrence (KL) scale. Plasma concentrations of adiponectin levels were measured by enzyme-linked immune-sorbent assay (ELISA).

RESULTS

Serum adiponectin levels were higher in OA patient subgroups than those in the control group but the difference did not reach a significant level after adjustments for age, gender and body mass index (P = 0.078). There was a positive correlation between adiponectin concentration and KL grading scores. Additionally, there was a positive correlation between adiponectin levels and clinical variables (VAS and WOMAC total scores) in patient subgroups (r = 0.326 P = 0.012, r = 0.583 P < 0.001, respectively). SF-36 scores were inversely associated with adiponectin levels.

CONCLUSION

Plasma adiponectin concentrations were associated with both clinical and radiological disease severity in knee OA patients. Thus, adiponectin hormone might be a potential clinically useful biomarker while assessing disease severity in the future.

Association between circulating adipokines, radiographic changes, and knee cartilage volume in patients with knee osteoarthritis

OBJECTIVES

To explore the associations between serum adipokine levels, radiographic osteoarthritis (ROA) severity, and articular cartilage volume in patients with knee OA.

METHOD

A cross-sectional sample of 205 patients (aged 45-74 years) with knee OA were consecutively recruited to the Anhui Osteoarthritis (AHOA) study. ROA was assessed using the Kellgren-Lawrence (KL) grading system (grades 0-4). Knee cartilage volume was determined using fat-saturated T1-weighted magnetic resonance imaging (MRI). Serum levels of the adipokines leptin, adiponectin, and resistin were measured by using an enzyme-linked immunosorbent assay (ELISA).

RESULTS

Serum adiponectin, but not serum leptin or resitin, was significantly associated with reduced ROA severity in univariable analyses and this association remained significant after adjustment for age, sex, body mass index (BMI), and disease duration [β = -0.012, 95% confidence interval (CI) -0.021 to -0.002]. In ROA patients, leptin was significantly and positively associated with knee cartilage volume at patellar and medial tibial sites in both unadjusted and adjusted analyses (β = 0.006, 95% CI 0.02-0.010 for medial tibia and β = 0.009, 95% CI 0.001-0.018 for patella sites) but adiponectin and resistin had no significant associations with cartilage volume. In non-ROA patients, leptin, adiponectin, and resistin were not significantly associated with cartilage volume at any site.

CONCLUSIONS

Serum levels of leptin are independently associated with increased knee cartilage volume. In addition, serum adiponectin is significantly and negatively associated with ROA severity, suggesting a potentially protective effect.

Is osteoarthritis a metabolic disorder?

BACKGROUND

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

SOURCES OF DATA AND AREAS OF DEBATE

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

EMERGING POINTS

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

TIMELY AREAS FOR DEVELOPMENT

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

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

OBJECTIVE

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

DESIGN

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

RESULTS

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

CONCLUSION

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

Epigenetic Regulation of Chondrocyte Catabolism and Anabolism in Osteoarthritis

Osteoarthritis (OA) is one of the most prevalent forms of joint disorder, associated with a tremendous socioeconomic burden worldwide. Various non-genetic and lifestyle-related factors such as aging and obesity have been recognized as major risk factors for OA, underscoring the potential role for epigenetic regulation in the pathogenesis of the disease. OA-associated epigenetic aberrations have been noted at the level of DNA methylation and histone modification in chondrocytes. These epigenetic regulations are implicated in driving an imbalance between the expression of catabolic and anabolic factors, leading eventually to osteoarthritic cartilage destruction. Cellular senescence and metabolic abnormalities driven by OA-associated risk factors appear to accompany epigenetic drifts in chondrocytes. Notably, molecular events associated with metabolic disorders influence epigenetic regulation in chondrocytes, supporting the notion that OA is a metabolic disease. Here, we review accumulating evidence supporting a role for epigenetics in the regulation of cartilage homeostasis and OA pathogenesis.

A Prospective Follow-Up of Adipocytokines in Cohort Patients With Gout: Association With Metabolic Syndrome But Not With Clinical Inflammatory Findings: Strobe-Compliant Article

The aim of this study was to determine the levels of leptin (Lep) and adiponectin (AdipoQ) in patients with gout and its relationship with joint inflammatory data and/or with metabolic syndrome (MetS) variables, during 1 year follow-up.Forty-one patients (40 males) with gout diagnosis, attending for the first time to a rheumatology department, were included. Evaluations were performed baseline, at 6 and 12 months. Variables included the following: demographic, clinical and laboratory data related to gout and associated diseases. Lep and AdipoQ determinations by the ELISA method were performed in frozen serum from each visit. The pharmacological and no-pharmacological treatment for gout and associated diseases was individualized for each patient according to published guidelines. Statistical analysis included Mann-Whitney U test, Fisher test, x, ANOVA, Cochran Q, Pearson and Spearman correlation tests, as well as linear regression.In the baseline evaluation, 29.2% had MetS (hypertriglyceridemia 66%, hypertension 44% and obesity 37%); patients with MetS had higher C reactive protein (CRP) levels [34.1 ± 28.6 vs. 12.2 ± 11.2 mg/dL, P = 0.033]. Although not significant, also had higher Lep and lower AdipoQ levels (3.2 ± 3.0 vs. 1.9 ± 1.2 ng/mL, P = 0.142 and 40.5 ± 26.8 vs. 38.0 ± 24.9 ng/mL, P = 0.877, respectively). During follow-up, our patients had significant improvement in serum uric acid (sUA) levels and variables evaluating pain and joint swelling (P ≤ 0.05). Metabolic abnormalities tended to persist or even worsen during the monitoring period: significant increase in total cholesterol (P = 0.004), tendency to higher triglycerides (P = 0.883) and slight improvement in glycaemia (P = 0.052). Lep values increased significantly during follow-up (P = 0.001) while AdipoQ levels diminished slightly (P = 0.317). Neither Lep nor AdipoQ values showed important correlation (r > 0.5) with metabolic variables or joint swelling.This study suggests that in patients with gout, concentrations of Lep and AdipoQ are more in line with the metabolic state than with clinical disease activity.

Adipokines as potential prognostic biomarkers in patients with acute knee injury

This review considers adipokines as predictive biomarkers for early onset post-traumatic knee osteoarthritis (KOA). Serum concentrations of leptin and resistin can predict radiographic changes and are elevated in early KOA, with higher leptin concentrations independently associated with more severe knee changes. Plasma concentrations of resistin are chronically elevated after injury. Leptin, resistin, chemerin and vistfatin induce catabolic enzymes associated with cartilage degeneration. Available literature on adipokines in post-traumatic KOA pathogenesis suggests that they could contribute to risk prediction of early onset post-traumatic KOA. Further research is needed to further understand the association between adipokines, synovitis and long-term outcomes in this population.

Significance of increased leptin expression in osteoarthritis patients

OBJECTIVE

Alterations in leptin expression contributes to the progression of various diseases, including cancers. This meta-analysis investigated the clinical significance of leptin levels in osteoarthritis (OA) patients, with the goal of building a leptin-based diagnostic criterion for OA.

METHOD

Multiple scientific databases in English and Chinese languages, such as the Cochrane Library Database, CINAHL, Chinese Biomedical (CBM), EMBASE, PubMed, and Web of Science, were exhaustively searched, without any language restrictions, to identify high-quality studies relevant to leptin and OA. Version 12.0 STATA software was used for data analysis. We used odds ratios (OR) and 95% confidence intervals (CI) to test the correlation between serum leptin levels and OA progression.

RESULTS

A total of 11 clinical studies were finally selected for their high quality and relevance to the topic in this meta-analysis. The 11 case-control studies contained a combined total of 3,625 subjects. The meta-analysis results showed that leptin expression was significantly increased in OA patients, compared with the controls (SMD = 0.87, 95%CI: 0.72-1.02, P < 0.001), and there was also a strong association between leptin expression levels and gender (SMD = 8.55, 95%CI: 4.74-12.35, P < 0.001). In ethnicity-stratified subgroup analysis, all the study populations, irrespective of ethnicity, showed remarkably high leptin expression levels in females and in OA patients (all P < 0.05), compared to their respective counterparts.

CONCLUSION

The present study revealed that increased leptin expression levels are associated with disease severity in OA patients, especially among the female OA patients. Based on our results, we propose that leptin level may be a useful biomarker for the assessment of the clinical status in OA patients.