AB0135 LEVELS OF MYOKINES AND RADIOGRAPHIC PROGRESSION IN PATIENTS WITH RHEUMATOID ARTHRITIS

Abstract

Objectives: Myokines are mainly expressed in the skeletal muscle, which is also their primary target tissue, and then released into circulation promoting crosstalk among different tissues. Considering that myokines, such as irisin and myostatin, have a role in bone tissue homeostasis, our aim was to investigate whether myokines serum levels can predict one‐year radiographic progression in patients with rheumatoid arthritis (RA). Methods: Forty female patients with RA, according to ACR/EULAR 2010 classification criteria, were included in the study. Thirty healthy subjects paired by sex, age and body mass index (BMI) were enrolled as the control group. Blood samples were collected, and ELISA was used to measure serum levels of irisin and myostatin. Radiographs of hands and feet, taken within three months of the blood collection and a year later, were evaluated using the Sharp‐van der Heijde (SvH) score to verify the one‐year radiographic progression in RA patients. The RA ac‐tivity was assessed by disease activity score based on evaluation of 28 joints (DAS28‐ESR). Statistical analysis included Mann‐Whitney U test and Spearman correlation. A value of p<0.05 was considered significant. Results: The mean age of the RA patients was 53 years, mean DAS28‐ESR was 4.09, mean disease duration was 11.2 years and mean BMI was 27.33 kg/m2. The serum levels of irisin and myostatin were significantly lower in RA patients (25,61 ± 8,25; 3011,28 ± 1271,11) than in control subjects (30,36 ± 10,95; 4049,08 ± 1610,01). Considering radiographic progression, the mean values of SvH score were 28,3 and 31,3 in the first and in the second evaluation, re‐spectively, resulting in a mean ΔSvH of 3. Over one year, 81,5% of the patients presented radiographic progression (ΔSvH score >0), and 21% presented rapid progression (ΔSvH score >5). Irisin and myostatin serum levels were not corre‐lated with the radiographic progression. Conclusions: The serum levels of irisin and myostatin were significantly lower in RA patients in comparison with control individuals and were not correlated with the radiographic progression. Irisin is known to retrieve disuse‐induced bone loss by stimulating the osteoblast pathways, while myostatin was demon‐strated to be highly expressed in the synovial tissues of RA subjects, with direct role in osteoclastogenesis. Based on our results, it is likely that the amount of irisin and myostatin that reaches the joint, or is produced in the joint environment, may differ from the circulating concentration.