Background By secreting numerous adipocytokines adipose tissue contributes to the development of cardiovascular diseases (CVD) and diabetes while its role in rheumatoid arthritis (RA) and osteoarthritis (OA) is less known. The secretory activity of adipose tissue varies according to anatomical location. Data concerning functional characteristics and the role of abdominal subcutaneous adipose tissue (ScAAT) in RA and OA patients are missing.
Objectives To characterise secretory activity of ScAAT in RA and OA patients and search for relationship with clinical data.
Methods ScAAT explants, obtained by needle biopsy from 91 (68F/23M) RA and 39 (26F/13M) OA patients of similar age, were cultured in vitro (100 mg/ml) and spontaneous and interleukin (IL)-1β-triggered (1ng/ml/) release of select adipocytokines and their serum levels were measured by specific ELISA. Body mass composition, i.e. fat free mass (FFM), total (tFM) and visceral fat mass (vFM), was measured by bioelectric impendance. Basic demographic and clinical information were collected and routine blood tests were done. Study was approved by the Ethics Committee. Data were analysed using the Wilcoxon signed-rank test to evaluate the effect of IL-1β, the Mann-Whitney U test to compare RA and OA groups, and Spearman test to assess the correlation (r value is shown); p values <0.05 were considered significant.
Results Correlation between serum levels and spontaneous tissue release of leptin (r=0.513) and adiponectin (Adn) (r=0.49) in OA and macrophage migration inhibitory factor (MIF) (r=0.231) in RA patients suggests that ScAAT supports circulating pool of these adipocytokines. Compared with OA, RA patients were characterised by significantly lower tFM, vFM and FFM contents, higher systemic inflammation indices (ESR, CRP), higher spontaneous (Adn, IL-6, IL-10, MIF) and IL-1β-triggered (Adn, IL-6, IL-10, MIF, TNF) release of several adipocytokines by ScAAT. In OA and RA patients spontaneous tissue secretion of leptin correlated with tFM (r=0.367, r=0.337). Only in RA patients TNF release was inversely correlated with vFM (r=-0.484) and FFM (r=-0.426), while Adn secretion with vFM (r=-0.42). Moreover, in OA patients Adn and IL-6 secretion was correlated in opposite way (r=-0.384 and r=0.346) with atherogenic index (AI = total cholesterol/HDL-cholesterol). In RA patients Adn secretion was similarly associated with AI (r=-0.234) but release of hepatocyte growth factor (HGF) correlated positively (r=0.249) with serum levels of triglycerides. Importantly, in OA patients tissue secretion of MIF correlated with the presence of CVD (r=0.4) and diabetes (r=0.376) while in RA secretion of HGF was associated with the presence of amyloidosis (r=0.244).
Conclusions Secretory activity of ScAAT has an impact on RA and OA clinical manifestation. In RA patients TNF released by ScAAT seems to contribute to cachexia. Higher spontaneous secretory activity and reactivity of ScAAT to IL-1β suggest that in RA patients this tissue is activated by proinflammatory stimuli. In RA and OA patients different adipocytokines released by ScAAT are related to lipid metabolism and comorbidity.
Disclosure of Interest None declared