FABP4 and obesity due to melanocortin 4 receptor deficiency: In terms of the inflammatory contribution of the IFP/SC to OA, Clockaerts et al. [7] and others [64, 65] have reported that this adipose depot, particularly in cases of obesity, can cumulatively secrete cytokines, interferons, adipokines such as fatty acid binding protein 4 (FABP4) [66–68], and growth factors, all of which exert local signaling effects on articular cartilage and synovial cells [7, 64, 65].