Trapped saturated FFAs in the mitochondrial matrix cause ROS production, lipid peroxidation, and mitochondrial dysfunction.[26] Our previous study confirmed that excessive mitochondrial fission leading to abnormal activation of RA‐FLS.[27] To investigate the impact of FASN and PA on mitochondrial function, we first examined ROS production in RA‐FLSs cultured with exogenous palmitate using flow cytometry. This evidence concerns the gene FASN and rheumatoid arthritis.