Finally, the development of the new agents [112], or, possibly, mentioned peptides application (i.e., amylin [97], cholecystokinin [98,99] leptin [101] and stable gastric pentadecapeptide BPC 157 [102,103,104,105,106,107,108,110,113,114,115,116,117] likely acting mediator of the dopamine brain-gut axis [107]) may likely approach the original gastroduodenal ulcer-Parkinson’s disease-schizophrenia circle [7,13,109]. Here, IAPP is linked to duodenal ulcer.