Compared to the day workers without T2DM, the shift workers without T2DM showed a 51.7% (31.50 ± 1.28 μg/mL vs. 20.77 ± 1.14 μg/mL) elevation in RBP4 concentration, and that of day workers with T2DM was 21.0% (25.12 ± 1.37 μg/mL vs. 20.77 ± 1.14 μg/mL). This evidence concerns the gene RBP4 and type 2 diabetes mellitus.