VIP and type 2 diabetes mellitus: Moreover, our previous studies have observed less neurons that express proopiomelanocortin in the infundibular nuclei, fewer oxytocin neurons in the paraventricular nuclei, as well as reduced arginine vasopressin and vasoactive intestinal polypeptide in the suprachiasmatic nuclei [11, 23, 31], suggesting that T2DM does affect neuronal function in various brain regions.