ANGPTL8 and obesity due to melanocortin 4 receptor deficiency: ANGPTL8 is closely associated with metabolic disorder-related diseases, such as type 2 diabetes mellitus (T2DM) (Zou et al., 2020a; Zou et al., 2020b), nonalcoholic fatty liver disease (NAFLD) (von Loeffelholz et al., 2017), obesity and metabolic syndrome (Mele et al., 2017; Wang et al., 2016).