RBP4 and type 2 diabetes mellitus: As shown in Table 5, the presence of LEAD in T2DM patients was used as the dependent variable, while 25(OH)D, TC, TG, HDL, LDL, BMI, RBP4, HOMA-IR, SBP, FINS, FPG, WHR, age, sex, duration, and smoking were used as the independent variables.