Table 2 indicates that the serum levels of apelin in the model group increased more sharply than those in the control group. However, the serum levels of apelin decreased significantly in the rats with PIO gastric perfusion compared with the rats in the model group. To the best of our knowledge, the results reported in the present study showed that for the first time the serum levels of apelin could be reduced by PIO in T2DM rats. Here, APLN is linked to type 2 diabetes mellitus.