C1QTNF9 and atherosclerosis: Second, CTRP9 reduced the number of lipid droplets, lowered the levels of cholesteryl ester, promoted cholesterol efflux in ox-LDL-induced THP1 macrophages, suggesting that CTRP9 protects against atherosclerosis by promoting cholesterol efflux to reduce the formation of foam cells (Zhang L. et al., 2018).