PIK3CD and obesity due to melanocortin 4 receptor deficiency: Mgat1 is associated with lipid metabolism and obesity (Jacobsson et al., 2012; Johansson et al., 2010), Tkt regulates glucose metabolism (Bartáková et al., 2016; Kang et al., 2018), and Pik3cd is involved in lipid metabolism and diabetes (Hood et al., 2019; Wójcik et al., 2014).