Table 1.

Selected studies investigating the association of adiponectin and rheumatoid arthritis in humans, cell cultures, and animals.

Authors	Study Design	Subjects	Results/Outcomes
Su et al. 2015 [72]	Observation of the effect of adiponectin on the expression of oncostatin M (OSM), a pro-inflammatory cytokine, in human osteoblastic cells.	Human osteoblastic cells.	Adiponectin increased OSM expression via the PI3K, Akt, and NF-κB signaling pathways in osteoblastic cells, suggesting that adiponectin is a novel target for arthritis treatment.
Bustos Rivera-Bahena et al. (2015) [73]	Cross-sectional study evaluating the correlation between adipokine levels and disease activity.	121 RA patients	No correlation between serum adiponectin and clinical activity of RA, but a negative correlation with TNFα and positive correlation with IL-1β.
Chennareddy et al. (2016) [74]	Cross-sectional study evaluating the serum concentrations of adiponectin and its impact on disease activity and radiographic joint damage.	43 RA patients 25 controls	Increased levels of serum adiponectin in RA, but no correlation with erosive and non-erosive disease, disease duration, BMI, waist-to-hip ratio and disease activity.
Krumbholz et al. (2017) [69]	Adiponectin and its receptors were examined in bone tissue. Primary human osteoblasts and osteoclasts were stimulated with adiponectin and analyzed using real-time polymerase chain-reaction and immunoassays. Effects on matrix-production by osteoblasts and differentiation and resorptive activity of osteoclasts were examined.	Cell cultures	Adiponectin expression in key cells of bone remodeling. Adiponectin altered gene expression and cytokine release in osteoblasts and increased IL-8 secretion by osteoclasts. Adiponectin inhibited osterix and induced osteoprotegerin mRNA in osteoblasts. In osteoclasts, MMP-9 and tartrate resistant acid phosphatase expression was increased. Accordingly, the mineralization capacity of osteoblasts decreased, whereas the resorptive activity of osteoclasts increased.
Lee et al. (2018) [49]	Meta-analyses on serum/plasma adiponectin or visfatin levels in patients with RA and controls and the correlation coefficients between circulating adiponectin and visfatin levels and Disease Activity Score of 28 joints (DAS28) in RA patients.	813 RA patients 684 controls	Adiponectin levels were significantly higher in the RA group than in the control group. Circulating adiponectin levels were not associated with RA activity based on DAS28 and C-reactive protein (CRP) levels.
Liu (2020) [17]	Investigation whether AD exerts effect on Tfh cells in RA.	Human RA FLS Mice	AD-stimulated RA FLSs promote Tfh cell generation, which is mainly mediated by the secretion of soluble factor IL-6.
Zhang Y et al. (2020) [75]	Report determining the effect of baseline serum adiponectin levels in predicting the development of rheumatoid arthritis (RA).	3693 subjects with obesity followed-up for up to 29 years.	In this cohort of subjects with obesity, high serum adiponectin levels at baseline were associated with an increased risk of RA. Moreover, subjects with both high adiponectin and CRP levels at baseline were at particular risk of developing RA.