Abstract: AIM To investigate whether irisin exerts endothelial protection in response to high-glucose/high-fat damage through reducing reactive oxygen species (ROS) formation. METHODS Cultured human umbilical vein endothelial cells (HUVECs) were randomly divided into control group (5 mmol/L glucose and 20 mmol/L mannitol), high-glucose/high-fat group (25 mmol/L glucose and 500 μmol/L sodium palmitate, 24 h incubation) and high-glucose/high-fat+irisin group (25 mmol/L glucose, 500 μmol/L sodium palmitate and 1 μg/ml irisin, 24 h incubation). Cells from these groups were harvested for evaluation of cell viability, ROS formation, NADPH oxidase gp91phox expression and apoptosis rate. RESULTS Compared with those in the control group, cell viability decreased, whereas gp91phox expression, ROS formation and apoptosis rate increased in high-glucose/high-fat group (all P<0.05). These changes were all reversed by irisin (all P<0.05). CONCLUSION High-glucose/high-fat leads to oxidative stress in HUVECs and irisin can protect HUVECs by alleviating oxidative stress and endothelial apoptosis.