FASN and obesity due to melanocortin 4 receptor deficiency: It is thus likely that β3-AR’s lipid-accumulative effects on differentiating 3T3-L1 cells are also attributable to the increased expression of FASN and perilipin A. Accordingly, adipocytes express and secrete an array of adipokines, such as leptin, that involve in the pathogenesis of obesity and type 2 diabetes [32].