APLN and type 2 diabetes mellitus: Apelin has recently been identified as a polypeptide hormone reportedly linked to IR.[13] A previous study showed elevated apelin levels in patients with T2DM, but it did not refer to the patients with DPN.[24] Our study shows that the fasting plasma apelin level of patients with DPN is increased, while the correlation analysis shows that the apelin level are significantly correlated with FBG and TNF-α levels.