Scientists have revealed that the main factors that cause inflammation in diabetes mellitus are disorders of the following pathways: nuclear factor kappa ß (NF-κß), phosphoinositide 3-kinases (PI3Ks), adiponectin, fibroblast growth factor 21 (FGF-21), and fatty-acid-binding protein 4 (FABP4), which are presented in Figure 1 [18,23]. Here, FGF21 is linked to diabetes mellitus.