When C57BL/6 mice on a 16-week high fat diet (HFD) were administered with hUC MSC EVs weekly (120 μg/mouse, i.v.), the mice showed corrected body weights, liver weights, blood glucose and insulin, and serum AST or ALT, reduced HFD-mediated steatosis, hepatocyte ballooning, macrophage inflammation, a reduced production or expression of ROS, TNFα, IL-6, ACCα, FASN, SCD1, PPARγ, NOX2, NOX4, TNF-α, IL-6, IL-1β and CCL2, and restored levels of antioxidant SOD and CAT. The gene discussed is IL1B; the disease is steatosis.