SLC6A15 and obesity due to melanocortin 4 receptor deficiency: Other lines of evidence that support the role of SLC6A15 in obesity related phenotypes include a prior linkage study for individual differences in carbohydrate and protein consumption that identified a 12q23.3 locus near the SLC6A15[12] and the associations between obesity and haplotypes in a related neutral amino acid transporter, SLC6A14 [31],[32].