GLUL and chronic liver failure: Hyperammonemia and inflammation seem to play an important role in the pathophysiology of HE.25, 26, 27, 28Ammonia, a toxic molecule, is turned into urea by the liver and is excreted by the kidneys.28During acute or chronic liver failure, the urea cycle is impaired, leading to increased levels of serum ammonia, well known as hyperammonemia.29In the CNS, ammonia neutralization occurs through the conjugation of this molecule with glutamate by the glutamine synthase (GS) enzyme.