The OD values of NPY mRNA expression for the DIO4W, DIO8W and T2DM groups were 1.15 ± 0.16, 1.51 ± 0.14 and 1.78 ± 0.14, respectively, all of which were significantly higher than that of the control group (0.86 ± 0.14, P < 0.01) (Fig. 3). Here, NPY is linked to type 2 diabetes mellitus.