Carnitine palmitoyl transferase 1 (CPT1) constitutes a rate-limiting step of FAO by shuttling long-chain fatty acids into mitochondria [19], in order to investigate the role of FAO in RA-FLS, we treated FLS with RA serum in the presence or absence of irreversible CPT1 inhibitor etomoxir (ETO) and detected the changes of proinflammatory phenotypes in RA-FLS. This evidence concerns the gene CPT1A and rheumatoid arthritis.