Old BAT showed decreased gene expression related to the lipid metabolism, such as stearoyl-CoA desaturase 2 (Scd2) and angiopoietin-like 8 (Angptl8), and increased gene expression related to obesity in WAT, such as Peg3 [30]. The gene discussed is PEG3; the disease is obesity due to melanocortin 4 receptor deficiency.