The<unk>  phosphate system is needed for the storage and transmission of phosphate-bound energy in the brain and muscle. The brain and muscle have particularly high metabolic demands, therefore, making<unk>  a necessary molecule in ATP homeostasis. In regard to the brain, in order for<unk>  to reach the brain, it must first pass through the blood–brain barrier (BBB). The BBB separates blood from brain interstitial fluid and is, therefore, able to regulate the transfer of nutrients to the brain from the blood. In order to pass through the BBB,<unk>  utilizes<unk><unk>  (CRT). When present at the BBB, CRT mediates the passage of<unk>  from the blood to the brain. When being<unk>  from the blood to the brain,<unk>  has to constantly move against the<unk>  concentration gradient that is present at the border between the brain and circulating blood.
Creatine transporter defect
N-Acetylglutamate synthase deficiency
Cerebral creatine deficiency
Mitochondrial complex II deficiency
Lysosomal storage disease
D-bifunctional protein deficiency
Mitochondrial trifunctional protein deficiency
Trinucleotide repeat disorder