The present study concludes that expression levels of adiponectin were higher in the OA patients as compared to the healthy controls and might be associated with OA prevalence.

Osteoarthritis is a painful degenerative joint disease which includes cartilage loss, subchondral bone remodelling, osteophyte formation and soft tissue damage. It leads to ongoing disability in older adults due to irreversible outcomes. About 6–17% and 2–10%of people suffer from knee and hip OA respectively. It is most prevalent in women over 60 years of age. It is the leading cause of total joint arthroplasty (TJA) and therefore creates a considerable economic burden. The aetiology of osteoarthritis [OA] is not clearly understood, and most of the evidence suggests that OA is a systemic disorder with a multifactorial origin. The risk factors include age, gender, obesity, injury, the risk of genetic bias.

Moreover, increasing evidence suggests that obesity is an integral element in the pathogenesis of OA. Sowers et al. indicated that an increase in mechanical burden on joints might be a proposed mechanism for the involvement of obesity in OA. However, Gabay et al. reported that obesity induces high inflammatory and metabolic environments that may play a crucial role in the onset of OA. Several early studies have suggested an association between OA and some adipokines in serum or synovial fluid. One of the mediators of interest is adiponectin that might be related with OA.

Adiponectin, a 28–30 kDa collagen-like protein, is one of the most abundantly secreted adipose tissue proteins and the only adipokine which is negatively correlated with obesity. Adiponectin poses various effects in many metabolic conditions such as atherosclerosis, insulin resistance, atherosclerosis, and myocardial infarction as well as in inflammatory and anti-inflammatory processes have been intensely studied for many years. However, the effects of adiponectin in OA pathogenesis are still controversial. On the other hand, evidence has shown that human and murine chondrocytes express function adiponectin receptors (AdipoR1 and AdipoR2). It was also found that adiponectin treatment can lead to a dose-dependent increase in pro-inflammatory factors such as interleukin -6 (IL-6), inducible nitric oxide synthase (iNOS), metalloproteases (MMPs) in cultured chondrocytes. All of these determinants can lead to the degradation of the matrix, articular cartilage and results in OA. The higher levels of adiponectin were observed in both plasma and synovial fluid of OA patients compared with the healthy controls. A recent study shows a positive association between adiponectin concentration and the Kellgren-Lawrence (KL) grading scores.

On the other hand, few studies failed to determine a statistical association between adiponectin and OA. Moreover, another study data indicates a negative correlation between with radiographic severity of OA that might play a preventive role in OA. The present study conducted a meta-analysis to determine a relationship between the expression levels of adiponectin and prevalence of OA.

Rationale behind research:

The effects of adiponectin in the pathogenesis of OA are controversial as the previous studies provide no sufficient evidence to suggest a correlation between the association of adiponectin and OA. Therefore, the present study conducted a meta-analysis to determine a relationship between the expression levels of adiponectin and prevalence of OA.

Objective:

The goal of the meta analysis was to perform a meta-analysis to determine the specific association between the expression level of adiponectin and osteoarthritis (OA).

Study outcomes:

• Patient demographic characteristics were evaluated at baseline
• Other outcomes include the evaluation of expression of adiponectin levels in various types and stages of OA progression

Time Points: NA

Outcomes:

Baseline: There were no significant differences observed at baseline

Study outcomes:

• There was an incidence of higher expression levels of adiponectin in the OA patients compared with that in the healthy groups {Fig 2.}

• The higher expression level of adiponectin was observed in the patients with knee OA as compared to subjects with the hand OA or knee and hip OA

• An association was found between adiponectin expression levels in patients who entered later stages of OA rather than in patients with early O A phase 

The present meta-analysis revealed that expression levels of adiponectin were significantly higher in OA patients than in healthy patients. The findings support the results of previous studies that indicated that adipose tissue metabolism was a key factor for the development of OA and thereby, adiponectin may be closely related to the pathogenesis of OA. Pooled analysis also indicated that levels of adiponectin were significantly upregulated in the middle and late stage of OA compared to healthy control. The adiponectin levels might be down-regulated in response to the elevating level of lipid metabolism.

The results also indicated that adiponectin association was stronger in patients with knee OA but not with knee or hip OA. Furthermore, the ethnicity stratified analysis showed that adiponectin expression levels were higher in both Caucasian and Asian OA subjects than in the controls suggesting that ethnic differences not affect the outcomes. Therefore, the expression of adiponectin can be used as a pivotal biomarker in the diagnosis of OA progression.