Fatty acid binding protein 4 (FABP4), also known as adipose fatty acid binding protein (AFABP), is a low-molecular weight protein that is abundantly expressed in mature adipocytes [14], and has previously been shown to be associated with several metabolic disease states such as obesity, metabolic syndrome, type 2 diabetes, and insulin resistance [17,18]. Here, FABP4 is linked to type 2 diabetes mellitus.