Creatinine is a low-molecular-weight uremic solute and breakdown product of creatine phosphate in muscle, often used as a clinical marker of renal function (altered serum creatinine clearance levels can indicate pathophysiology in various diseases). Arginine from the diet is absorbed into systemic circulation and enters hepatocytes through an amino acid transporter, where it undergoes a series of metabolic reactions. First, it forms guanidinoacetic acid in a reaction catalysed by glycine amidinotransferase, then undergoes a reaction catalysed by guanidinoacetate N-methyltransferase to form creatine. Creatine is non-enzymatically converted into creatinine, which can exit the liver via the solute carrier family 22 member 2 transporter to enter the bloodstream. If not cleared, it can reduce cardiomyocyte contractility and weaken cardiac efficiency, leading to systolic dysfunction and heart failure.

Metabolism and Physiological Effects of Creatinine References