LEP and obesity due to melanocortin 4 receptor deficiency: Next, we determined whether β3-AR knockdown alters expression levels of FASN, an enzyme responsible for fatty acid synthesis [24], perilipin A, a lipid droplet-binding and stabilizing protein, and leptin, adipokines, such as leptin, that involve in the pathogenesis of obesity and type 2 diabetes [25], during 3T3-L1 preadipocyte differentiation.