HPGDS and obesity due to melanocortin 4 receptor deficiency: To study the roles of L-PGDS and PGD2 in obesity, we generated the experimental mice by breeding the L-PGDSflox/flox mice with either of two distinct types of adipose-specific L-PGDS gene knockout (KO) mice: aP2-Cre/L-PGDSflox/flox and AdipoQ-Cre/L-PGDSflox/flox mice (Fig. 2a).