ABSTRACT
Creatine (Cr)—methylguanidino acetic acid-is a naturally occurring compound that was first described by Chevreul in 1832. Its name is derived from the Greek word kreas (flesh): Creatine is found in abundance in skeletal muscle (red meat) and fish. It is essential in energy transmission and storage via creatine kinase (CK). The daily Cr dosage is obtained by both endogenous synthesis and via nutritional intake, followed by absorption in the intestine.[1] Creatine supplementation is widespread among sportspersons because of its documented and=or presumed ergogenic effects.[2-4] In addition, supplementation with Cr has proven to be instrumental for the treatment of rare inborn errors of metabolism due to defects in Cr biosynthesis enzymes.[5-8]
Creatine is stored in high concentrations in skeletal and heart muscles and to a lesser extent in the brain. It exists in both free and phosphorylated form [phosphocreatine (PCr)], and is important for maintaining high adenosine triphosphate (ATP) : adenosine diphosphate (ADP) ratios. Upon increases in workload, ATP hydrolysis is initially buffered by PCr via the CK reaction. During high-intensity exercise, PCr in muscle is depleted within several seconds. Whether de novo Cr biosynthesis occurs in the brain, or whether Cr is taken up into the brain through the blood-brain barrier is currently a matter of debate.
