SLC7A9 and obesity due to melanocortin 4 receptor deficiency: In line with obesity-associated upregulation of Slc7a9, an amino acid transporter (Table S2A), targeted metabolomics analysis revealed significant increases in the levels of most amino acids in the colonic epithelium of young obese mice (Table S3A), reminiscent of a metabolic trait observed in human colon cancer (Hirayama et al., 2009).