RBP4 and type 2 diabetes mellitus: In this study, the levels of LDL and RBP4 reduced in T2DM group after the intervention of vitamin D, and, simultaneously, the incidence rate of LEAD in T2DM group also decreased after the intervention of vitamin D. Therefore, vitamin D supplementation can protect T2DM patients from being complicated with LEAD ultimately by improving IR and lipid metabolism and inhibiting inflammation.