FABP4 and obesity due to melanocortin 4 receptor deficiency: Among FABPs, fatty acid-binding protein 4 (FABP4), also referred to as adipocyte FABP (A-FABP) or aP2, is mainly expressed in both adipocytes and macrophages and plays an important role in the development of obesity, insulin resistance, type 2 diabetes mellitus and atherosclerosis [4–6].