Recently, administration of 2-aminoisobutyrate and non-physiological amino acids such as DL-norleucine, 2-aminonorbornane, and N-methyl-aminoisobutyrate acting as inhibitors for various brain amino acid transporters have been shown to reduce brain phenylalanine concentrations up to 56% in PKU mice [67]. This evidence concerns the gene SLC38A7 and phenylketonuria.