FASN and obesity due to melanocortin 4 receptor deficiency: To clarify the effects of hepatic FASN deficiency on NAFLD and diabetes in obese mice in the setting of NCD overfeeding without leptin deficiency, we next studied Mc4r-KO mice as an alternative mouse model of hyperphagic obesity associated with hepatic FASN upregulation and hyperleptinemia (49–51).