The transcription factors PPAR-γ and C/EBPα play key roles in the complex transcriptional cascade of adipocyte differentiation that will eventually activate and express adipocyte-specific genes such as fatty acid synthetase, fatty acid binding protein, leptin, adiponectin and etc., which closely related to obesity disease such as diabetes and non-alcoholic fatty liver disease [30]. Here, LEP is linked to obesity due to melanocortin 4 receptor deficiency.