Finally, the organism must take care to limit their plasma concentration, taking into account their potential central effects [24], namely their influence on the synthesis of neuromediators (via glutamate synthesis, or by competition with the cerebral transport of aromatic amino acids via LAT1/2 [8]) or because of their neurotoxicity, with the ultimate situation of maple syrup urine disease (MSUD, a BCKD deficiency) [25]. This evidence concerns the gene SLC7A5 and maple syrup urine disease.