FGF21 and obesity due to melanocortin 4 receptor deficiency: Indeed, additional RAR-dependent and -independent mechanisms have also been identified that may contribute to the therapeutic effect of fenretinide in obesity-related pathologies, including enhanced mitochondrial and peroxisomal β-oxidation [184,185,186,187,188], ER-stress-mediated degradation of SCD1 [189], inhibition of ceramide synthesis, enhanced reactive oxygen species (ROS) production [184,190], enhanced retinoid signaling [191], and inhibition of hepatic FGF21 expression [192].